JP7547792B2 - Laminate, display surface material, touch panel member, liquid crystal display device, and organic electroluminescence display device - Google Patents

Description

The present invention relates to a laminate, a surface material for a display, a touch panel member, a liquid crystal display device, and an organic electroluminescence display device.

Thin sheet glass has excellent hardness and heat resistance, but it is difficult to bend, easily breaks when dropped, has problems with workability, and is heavy compared to plastic products. For this reason, in recent years, resin products such as resin substrates and resin films have begun to replace glass products in terms of workability and weight reduction, and research is being conducted into resin products that can replace glass.

For example, with the rapid advancement of electronics such as liquid crystal and organic electroluminescence displays and touch panels, there is a demand for devices to be thinner, lighter and more flexible. Conventionally, these devices have various electronic elements, such as thin transistors and transparent electrodes, formed on a thin sheet of glass, but by changing this thin sheet glass to a resin film, the impact resistance of the panel itself can be strengthened and it can be made more flexible, thinner and lighter.

Generally, polyimide is a highly heat-resistant resin obtained by dehydrating and ring-closing polyamic acid obtained by condensation reaction of aromatic tetracarboxylic anhydride and aromatic diamine. However, polyimide generally shows yellow or brown coloration, so it has been difficult to use it in fields that require transparency, such as display applications and optical applications. Therefore, application of polyimide with improved transparency to display components has been considered. For example, Patent Document 1 discloses a polyimide resin with high heat resistance, high transparency, and low water absorption, which is obtained by reacting at least one acyl-containing compound selected from the group consisting of 1,2,4,5-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, and reactive derivatives thereof with at least one imino-forming compound selected from compounds having at least one phenylene group and isopropylidene group represented by a specific formula, and describes that it is suitable for use as a substrate material for flat panel displays, mobile phone devices, etc.

Furthermore, Patent Document 2 discloses a transparent polyimide film that contains a unit structure derived from an aromatic dianhydride and an aromatic diamine, and further contains a unit structure derived from a tear strength improving additive or a monomer having a functional group selected from the group consisting of a hexafluoro group, a sulfone group, and an oxy group.

Patent Document 3 also discloses polyimides that have excellent transparency, high heat resistance, a low coefficient of linear thermal expansion, and solvent processability in low hygroscopic solvents, such as polyimides obtained by reacting tetracarboxylic dianhydride obtained by esterifying trimellitic anhydride chloride with 2,2',3,3',5,5'-hexamethyl-biphenyl-4,4'-diol with 2,2-bis(trifluoromethyl)benzidine to obtain polyamic acid, and imidizing the obtained polyamic acid. It is described that the polyimide in Patent Document 3 achieves low thermal expansion properties, solvent solubility, and high transparency at the same time by introducing parabiphenylene groups with a large twisted dihedral angle via ester bonds in order to increase solvent solubility while making the main chain skeleton as linear and rigid as possible.

JP 2006-199945 A Special table 2014-501301 publication International Publication No. WO 2014/046180

Resin products that can be used as glass replacements require transparency and durability.
Moreover, mobile devices with foldable screens are folded when carried and unfolded when used. Therefore, flexible displays mounted on mobile devices are required to be able to withstand repeated bending without causing display defects, and surface materials for flexible displays are required to have a good balance between bending resistance when repeatedly bent (hereinafter sometimes referred to as dynamic bending resistance) and elasticity.
However, for example, the polyimide film described in Patent Document 3 is easily discolored and has insufficient durability.

The present invention has been made in consideration of the above problems, and has as its main object to provide a laminate having a good balance between bending resistance and elastic modulus, and also having durability.
Another object of the present invention is to provide a surface material for a display which is the laminate, and a touch panel member, a liquid crystal display device, and an organic electroluminescence display device each including the laminate.

The present invention comprises a polyimide film and
a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound, and an ultraviolet absorber;
The polyimide film contains 10 mol % or more and 100 mol % or less of a structural unit represented by the following general formula (1) and (100-x) mol % (wherein x is the mol % of the structural unit represented by the general formula (1)) of a structural unit represented by the following general formula (2), and has a weight average molecular weight of 100,000 or more as measured by gel permeation chromatography in terms of polystyrene:
the yellowness index (YI) of the laminate calculated in accordance with JIS K7373-2006 divided by the total film thickness (μm) of the polyimide film and the hard coat layer is less than 0.12;
a value obtained by dividing a yellowness index change ΔYI of the laminate before and after the following weather resistance test by a total film thickness (μm) of the polyimide film and the hard coat layer is less than 0.11;
The laminate has a color change ΔE before and after the following weather resistance test, the color change ΔE being less than 0.09 when divided by the total film thickness (μm) of the polyimide film and the hard coat layer.
(Weather resistance test)
Using a weather resistance tester conforming to JIS K5600-7-8, the laminate is irradiated for 96 hours using a UVA (340) lamp with a spectral distribution similar to sunlight from 365 nm to 295 nm, with the output set at 0.63 W/m ² /nm.
The laminate before and after the weather resistance test is measured for yellowness index (YI) calculated in accordance with JIS K7373-2006, and L ^* , a ^* , and b ^* in the CIE L ^* a ^* b ^* color system using light source C.
ΔYI = YI after test - YI before test
ΔE={(L ^* after test−L ^* before test) ² +(a ^* after test−a ^* before test) ² +(b ^* after test−b ^* before test) ² } ^1/2

（一般式（１）及び（２）において、Ｒ^１～Ｒ^４はそれぞれ独立に、水素原子又は炭素原子数１～６のアルキル基を表し、Ｒ^１及びＲ^２の少なくとも１つ、及びＲ^３及びＲ^４の少なくとも１つは、炭素原子数１～６のアルキル基を表す。Ａは芳香族環又は脂肪族環を有するテトラカルボン酸残基である４価の基を表し、Ｂは、芳香族環又は脂肪族環を有するジアミン残基である２価の基を表す。）

(In general formulas (1) and (2), R ¹ to R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and at least one of R ¹ and R ² , and at least one of R ³ and R ⁴ , represents an alkyl group having 1 to 6 carbon atoms. A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.)

The present invention also relates to a polyimide film and
a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound, and an ultraviolet absorber;
the polyimide film contains 10 mol % or more and 100 mol % or less of the structural unit represented by the general formula (1) and (100-x) mol % (wherein x is the mol % of the structural unit represented by the general formula (1)) of the structural unit represented by the general formula (2), and has a weight average molecular weight of 100,000 or more as calculated in terms of polystyrene by gel permeation chromatography;
the yellowness index (YI) of the laminate calculated in accordance with JIS K7373-2006 divided by the film thickness (μm) of the polyimide film is less than 0.15;
a value obtained by dividing the yellowness index change ΔYI of the laminate before and after the weather resistance test by the film thickness (μm) of the polyimide film is less than 0.13;
The laminate has a color change ΔE before and after the weather resistance test, the color change ΔE being less than 0.11 when divided by the film thickness (μm) of the polyimide film.

In the laminate of the present invention, it is preferable that the ultraviolet absorber is one or more ultraviolet absorbers selected from the group consisting of hydroxybenzophenone-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers, in terms of improving durability.

In the laminate of the present invention, it is preferable that the transmittance of the laminate at a wavelength of 380 nm is 8% or less in order to improve durability.

In the laminate of the present invention, it is preferable that the polyimide film contains 1 ppm or more and 2000 ppm or less of dichloromethane, since this improves the film thickness uniformity, appearance, and bending resistance.

In the laminate of the present invention, the diamine residue having an aromatic ring or an aliphatic ring in B in the general formulas (1) and (2) of the polyimide is a trans-cyclohexanediamine residue, a trans-1,4-bismethylenecyclohexanediamine residue, a 4,4'-diaminodiphenylsulfone residue, a 3,4'-diaminodiphenylsulfone residue, a 2,2-bis(4-aminophenyl)propane residue, a 3,3'-bis(trifluoromethyl)-4,4'-[(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(4,1-phenyleneoxy)]dianiline residue, a 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1 , 1,3,3,3-hexafluoropropane residue, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, and at least one divalent group represented by the following general formula (3), and may further contain at least one divalent group selected from the group consisting of N,N'-bis(4-aminophenyl)terephthalamide residue, 4-aminophenyl-4-aminobenzoate residue, (2-phenyl-4-aminophenyl)-4-aminobenzoate residue, and bis(4-aminophenyl)terephthalate residue, are preferred in terms of the balance between light transmittance, bending resistance, and elastic modulus.

（一般式（３）において、Ｒ^５及びＲ^６はそれぞれ独立に、水素原子、アルキル基、またはパーフルオロアルキル基を表す。）

(In formula (3), ^R5 and ^R6 each independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)

In the laminate of the present invention, the tetracarboxylic acid residue having an aromatic ring or an aliphatic ring in A of the general formula (2) of the polyimide is a cyclohexanetetracarboxylic acid dianhydride residue, a cyclopentanetetracarboxylic acid dianhydride residue, a dicyclohexane-3,4,3',4'-tetracarboxylic acid dianhydride residue, a cyclobutanetetracarboxylic acid dianhydride residue, a pyromellitic acid dianhydride residue, a 3,3',4,4'-biphenyltetracarboxylic acid dianhydride residue, or a 2,2',3,3'-biphenyltetracarboxylic acid dianhydride residue. From the viewpoint of the balance between light transmittance, bending resistance, and elastic modulus, it is preferable that the tetravalent group is at least one selected from the group consisting of 2,3,3',4'-biphenyltetracarboxylic dianhydride residue, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene)diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride residue, and 3,4'-oxydiphthalic anhydride residue.

The laminate of the present invention preferably further has a glass substrate having a thickness of 100 μm or less, since this makes it less likely to develop creases.

The present invention also provides a display surface material that is the laminate of the present invention. The display surface material can be used for flexible displays.

The present invention also relates to a laminate of the present invention,
A transparent electrode including a plurality of conductive portions disposed on one surface side of the laminate;
and a plurality of lead wires electrically connected to at least one side of an end of the conductive portion.

The present invention also relates to a laminate of the present invention,
and a liquid crystal display section disposed on one surface side of the laminate and having a liquid crystal layer between opposing substrates.

The present invention also relates to a laminate of the present invention,
and an organic electroluminescence display section disposed on one surface side of the laminate and having an organic electroluminescence layer between opposing substrates, the organic electroluminescence display device having the organic electroluminescence display section being provided.

According to the present invention, it is possible to provide a laminate having a good balance between bending resistance and elastic modulus, and also having durability.
The present invention can also provide a surface material for a display, which is the laminate, and a touch panel member, a liquid crystal display device, and an organic electroluminescence display device, each of which includes the laminate.

1 is a schematic cross-sectional view showing an example of a laminate of the present invention. FIG. 1 is a diagram for explaining a method of a dynamic bending test. 1 is a schematic plan view of one surface of an example of a touch panel member of the present invention. 4 is a schematic plan view of the other surface of the touch panel member shown in FIG. 3. 5 is a cross-sectional view of the touch panel member shown in FIG. 3 and FIG. 4 along line A-A'. 1 is a schematic plan view showing an example of a conductive member including a laminate of the present invention. FIG. 2 is a schematic plan view showing another example of a conductive member including a laminate of the present invention. FIG. 4 is a schematic cross-sectional view showing another example of the touch panel member of the present invention. FIG. 1 is a schematic cross-sectional view showing an example of a liquid crystal display device of the present invention. FIG. 4 is a schematic cross-sectional view showing another example of a liquid crystal display device of the present invention. 1 is a schematic cross-sectional view showing an example of an organic electroluminescence display device of the present invention. FIG. 2 is a schematic cross-sectional view showing another example of an organic electroluminescence display device of the present invention.

Hereinafter, the laminate, the surface material for a display, the touch panel member, the liquid crystal display device, and the organic electroluminescence display device according to the present invention will be described in detail.
In addition, terms used in this specification that specify shapes, geometric conditions, and the degree thereof, such as "parallel,""orthogonal," and "same," as well as values of length and angle, are not to be bound by strict meanings, but are to be interpreted to include a range within which similar functions can be expected.
In this specification, when describing a mode in which another component is disposed on a certain component, the term "above" or "below" is used, unless otherwise specified, to include both a case in which another component is disposed directly above or below a certain component so as to be in contact with the component, and a case in which another component is disposed above or below a certain component with another component interposed therebetween. Also, in this specification, when describing a mode in which another component is disposed on the surface of a certain component, the term "on the surface side" or "on the surface" is used, unless otherwise specified, to include both a case in which another component is disposed directly above or below a certain component so as to be in contact with the component, and a case in which another component is disposed above or below a certain component with another component interposed therebetween.
In this specification, (meth)acrylic means both acrylic and methacrylic.
In addition, in this specification, "light" means actinic rays or radiation, and includes, for example, the bright line spectrum of a mercury lamp, far ultraviolet rays represented by excimer lasers, extreme ultraviolet rays (EUV light), X-rays, electron beams, and the like.
In the drawings attached to this specification, the scale and aspect ratios may be appropriately changed and exaggerated from those of the actual objects for the convenience of illustration and ease of understanding.
In addition, in this specification, the use of "to" indicating a range of values is used to mean that the values before and after it are included as the lower limit and upper limit.
In this specification, "ppm" used as a unit of the content of an organic solvent in a polyimide film represents mass ppm.

I. Laminate The laminate of the present invention comprises a polyimide film and
a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound, and an ultraviolet absorber;
The polyimide film contains 10 mol % or more and 100 mol % or less of a structural unit represented by the following general formula (1) and (100-x) mol % (wherein x is the mol % of the structural unit represented by the general formula (1)) of a structural unit represented by the following general formula (2), and has a weight average molecular weight of 100,000 or more as calculated using polystyrene standards by gel permeation chromatography:
the yellowness index (YI) of the laminate calculated in accordance with JIS K7373-2006 divided by the total film thickness (μm) of the polyimide film and the hard coat layer is less than 0.12;
a value obtained by dividing a yellowness index change ΔYI of the laminate before and after the following weather resistance test by a total film thickness (μm) of the polyimide film and the hard coat layer is less than 0.11;
The color change ΔE of the laminate before and after the weather resistance test described below is divided by the total film thickness (μm) of the polyimide film and the hard coat layer, and the value is less than 0.09.
(Weather resistance test)
Using a weather resistance tester conforming to JIS K5600-7-8, the laminate is irradiated for 96 hours using a UVA (340) lamp with a spectral distribution similar to sunlight from 365 nm to 295 nm, with the output set at 0.63 W/m ² /nm.
The laminate before and after the weather resistance test is measured for yellowness index (YI) calculated in accordance with JIS K7373-2006, and L ^* , a ^* , and b ^* in the CIE L ^* a ^* b ^* color system using light source C.
ΔYI = YI after test - YI before test
ΔE={(L ^* after test−L ^* before test) ² +(a ^* after test−a ^* before test) ² +(b ^* after test−b ^* before test) ² } ^1/2

（一般式（１）及び（２）において、Ｒ^１～Ｒ^４はそれぞれ独立に、水素原子又は炭素原子数１～６のアルキル基を表し、Ｒ^１及びＲ^２の少なくとも１つ、及びＲ^３及びＲ^４の少なくとも１つは、炭素原子数１～６のアルキル基を表す。Ａは芳香族環又は脂肪族環を有するテトラカルボン酸残基である４価の基を表し、Ｂは、芳香族環又は脂肪族環を有するジアミン残基である２価の基を表す。）

(In general formulas (1) and (2), R ¹ to R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and at least one of R ¹ and R ² , and at least one of R ³ and R ⁴ , represents an alkyl group having 1 to 6 carbon atoms. A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.)

The laminate of the present invention further comprises a polyimide film and
a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound, and an ultraviolet absorber;
the polyimide film contains 10 mol % or more and 100 mol % or less of the structural unit represented by the general formula (1) and (100-x) mol % (wherein x is the mol % of the structural unit represented by the general formula (1)) of the structural unit represented by the general formula (2), and has a weight average molecular weight of 100,000 or more as calculated in terms of polystyrene by gel permeation chromatography;
the yellowness index (YI) of the laminate calculated in accordance with JIS K7373-2006 divided by the film thickness (μm) of the polyimide film is less than 0.15;
a value obtained by dividing the yellowness index change ΔYI of the laminate before and after the weather resistance test by the film thickness (μm) of the polyimide film is less than 0.13;
The color change ΔE of the laminate before and after the weather resistance test divided by the film thickness (μm) of the polyimide film is less than 0.11.

1 is a schematic cross-sectional view showing an example of the laminate of the present invention. The laminate 10 of the present invention has a polyimide film 1 and a hard coat layer 2 containing an ultraviolet absorber.
According to the present invention, the polyimide film contains a polyimide having a tetracarboxylic acid residue with a specific structure including a parabiphenylene group with a twisted dihedral angle via an ester bond in the main chain, and a diamine residue having an aromatic ring or an aliphatic ring, and is selected to have a specific weight-average molecular weight, so that it is easy to achieve a good balance between bending resistance and elastic modulus. However, the specific polyimide is easily colored depending on the manufacturing method, and has insufficient durability. It has been considered to add an ultraviolet absorber to the polyimide film, but it is difficult to simultaneously color the polyimide film and suppress color change before and after weather resistance testing.
In contrast, the laminate of the present invention is a combination of the specific polyimide film and a hard coat layer containing an ultraviolet absorber, selected so that the coloring degree of the laminate and the yellowness change and color change during weather resistance testing are within specific ranges. By using such a specific hard coat layer positioned on the surface or light incidence side of the polyimide film, the laminate of the present invention has good transparency, can appropriately suppress changes over time, has a good balance between bending resistance and elastic modulus, and has durability.
The polyimide film and the hard coat layer used in the present invention will be described below in order.

I-1. Polyimide film The polyimide film used in the present invention contains the specific polyimide described above. It may further contain other components or have other structures as long as the effects of the present invention are not impaired.

1. Polyimide Polyimide is obtained by reacting a tetracarboxylic acid component with a diamine component. It is preferable to obtain a polyamic acid by polymerization of the tetracarboxylic acid component and the diamine component, and then imidize the polyamic acid. The imidization may be performed by chemical imidization, thermal imidization, or a combination of chemical imidization and thermal imidization.
The polyimide used in the present invention contains 10 mol % or more and 100 mol % or less of a constitutional unit represented by the following general formula (1) and (100-x) mol % (wherein x is the mol % of the constitutional unit represented by the general formula (1)) of a constitutional unit represented by the following general formula (2), and has a weight average molecular weight of 100,000 or more as calculated using polystyrene standards by gel permeation chromatography:

（一般式（１）及び（２）において、Ｒ^１～Ｒ^４はそれぞれ独立に、水素原子又は炭素原子数１～６のアルキル基を表し、Ｒ^１及びＲ^２の少なくとも１つ、及びＲ^３及びＲ^４の少なくとも１つは、炭素原子数１～６のアルキル基を表す。Ａは芳香族環又は脂肪族環を有するテトラカルボン酸残基である４価の基を表し、Ｂは、芳香族環又は脂肪族環を有するジアミン残基である２価の基を表す。）

(In general formulas (1) and (2), R ¹ to R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and at least one of R ¹ and R ² , and at least one of R ³ and R ⁴ , represents an alkyl group having 1 to 6 carbon atoms. A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.)

Here, the tetracarboxylic acid residue refers to a residue obtained by removing four carboxyl groups from a tetracarboxylic acid, and has the same structure as the residue obtained by removing the acid dianhydride structure from a tetracarboxylic dianhydride.
The diamine residue refers to a residue obtained by removing two amino groups from a diamine.

In general formula (1), at least one of ^R1 and ^R2 , and at least one of ^R3 and ^R4 , represents an alkyl group having 1 to 6 carbon atoms.
The alkyl group having 1 to 6 carbon atoms may be a linear or branched alkyl group, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, an n-pentyl group, and an n-hexyl group.
From the viewpoint of solvent solubility, an alkyl group having 1 to 4 carbon atoms is preferable, an alkyl group having 1 to 2 carbon atoms is more preferable, and a methyl group is even more preferable.
Among these, it is preferable that R ¹ and R ² , and R ³ and R ⁴ each represent a methyl group from the viewpoint of solvent solubility.

In formula (1), B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.
The diamine residue having an aromatic ring or an aliphatic ring can be a residue obtained by removing two amino groups from a diamine having an aromatic ring or a diamine having an aliphatic ring. The diamine residue having an aromatic ring or an aliphatic ring may have at least an aromatic ring or an aliphatic ring, and may have both an aromatic ring and an aliphatic ring.
Examples of diamines having an aromatic ring include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzanilide, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenone, nylmethane, 3,4'-diaminodiphenylmethane, 2,2-di(3-aminophenyl)propane, 2,2-di(4-aminophenyl)propane, 2-(3-aminophenyl)-2-(4-aminophenyl)propane, 2,2-di(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-di(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2-(3-aminophenyl)-2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 1,1-di(3-aminophenyl)-1-phenylethane, 1,1-di(4-aminophenyl)-1-phenylethane, 1-(3-aminophenyl)-1-(4-aminophenyl)-1-phenylethane, 1,3-biphenyl bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminobenzoyl)benzene, 1,3-bis(4-aminobenzoyl)benzene, 1,4-bis(3-aminobenzoyl)benzene, 1,4-bis(4-aminobenzoyl)benzene, 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(3-amino-α,α-ditrifluoromethyl)benzene, 1,3-bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene, 1,4-bis(3-amino-α,α-ditrifluoromethylbenzyl)benzene, 1,4-bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene, 2,6-bis(3-aminophenoxy)benzonitrile, 2,6-bis(3-aminophenoxy)pyridine, N,N'-bis(4-aminophenyl)terephthalamide, 4-aminophenyl-4-aminobenzoate, (2-phenyl-4-aminophenyl)-4-aminobenzoate, bis(4-aminophenyl)terephthalate, 9,9-bis(4-aminophenyl)fluorene, 2,2'-dimethyl-4,4'-diaminobiphenyl, 2,2'-ditrifluorophenyl 4,4'-diaminobiphenyl (2,2-bis(trifluoromethyl)benzidine), 3,3'-dichloro-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfide sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(4- 4,4'-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 4,4'-bis[4-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, 4,4'-bis[4-(4-aminophenoxy )phenoxy]diphenylsulfone, 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, and the like, and diamines in which some or all of the hydrogen atoms on the aromatic ring of the above diamines are substituted with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group can also be used.

The diamine residue having an aromatic ring preferably contains a diamine residue of a diamine represented by the following general formula (5), including the above-mentioned N,N'-bis(4-aminophenyl)terephthalamide, 4-aminophenyl-4-aminobenzoate, (2-phenyl-4-aminophenyl)-4-aminobenzoate, and bis(4-aminophenyl)terephthalate, from the viewpoint of improving the elastic modulus. By introducing a diamine residue in which two or three phenylene groups are bonded by at least one of an amide bond and an ester bond, the planarity of the molecular chain can be increased, promoting π-π intermolecular interactions between the molecular chains, and further, when an amide bond is contained, the intermolecular force due to the formation of hydrogen bonds between the amide bond site and the ester bond site of the tetracarboxylic acid residue of general formula (1) can be increased, which is believed to improve the elastic modulus.

（式（５）において、Ｒ^７はそれぞれ独立に、ハロゲン化アルキル基、アルキル基、シクロアルキル基、又はアリール基を表し、Ｚ^１及びＺ^２はそれぞれ独立に、－ＮＨＣＯ－、－ＣＯＮＨ－、－ＯＣＯ－、又は－ＣＯＯ－の２価の基を表し、Ｚ^２はアミノ基に対してパラ位又はメタ位に結合し、Ｚ^１はＺ^２に対してパラ位又はメタ位に結合し、ｋは０又は１の整数を表し、ｊ１、ｊ２及びｊ３はそれぞれ独立に０～４の整数を表す。）

(In formula (5), R ⁷ each independently represents a halogenated alkyl group, an alkyl group, a cycloalkyl group, or an aryl group; Z ¹ and Z ² each independently represent a divalent group of -NHCO-, -CONH-, -OCO-, or -COO-; Z ² is bonded at the para or meta position relative to the amino group; Z ¹ is bonded at the para or meta position relative to Z ² ; k represents an integer of 0 or 1; and j1, j2, and j3 each independently represent an integer of 0 to 4.)

In formula (5), R ⁷ independently represents a halogenated alkyl group, an alkyl group, a cycloalkyl group, or an aryl group. Examples of the alkyl group include an alkyl group having 1 to 10 carbon atoms, and preferably an alkyl group having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, and a propyl group. Examples of the halogenated alkyl group include a halogenated alkyl group having 1 to 10 carbon atoms, and preferably an alkyl group having 1 to 3 carbon atoms, such as a trifluoromethyl group, a tetrafluoroethyl group, a heptafluoropropyl group, a monofluoromethyl group, and a difluoromethyl group. Examples of the cycloalkyl group include a cycloalkyl group having 5 to 7 carbon atoms, such as a cyclopentyl group, a cyclohexyl group, and a cycloheptyl group. Examples of the aryl group include an aryl group having 6 to 12 carbon atoms, and preferably an aryl group having 6 to 10 carbon atoms, such as a phenyl group, a naphthyl group, and a biphenyl group.

As ^R7 , a halogenated alkyl group is preferably used from the viewpoint of transparency, an alkyl group is preferably used from the viewpoint of imparting solubility in a solvent, a cycloalkyl group is preferably used from the viewpoint of imparting solubility without impairing the planarity of the molecular chain, and an aryl group is preferably used from the viewpoint of increasing the planarity and rigidity of the molecular chain and improving the elastic modulus.

Each of j1, j2, and j3, which indicate the number of substituents ^R7 , independently represents an integer of 0 to 4. Each of j1, j2, and j3 independently represents an integer of 0 to 2, and more preferably an integer of 0 to 1. Furthermore, j1+j2+j3 is preferably an integer of 0 to 6, and more preferably an integer of 0 to 3.

k represents an integer of 0 or 1, and when k is 0, two phenylene groups are linked together.
When k is 0, it is preferable from the viewpoint of obtaining the effect of the substituent that at least one of j1 or j2 represents an integer of 1 or more. That is, when k is 0, it is preferable that at least one substituent ^R7 is contained in the diamine residue.
When k is 0, j1+j2 is preferably 1 to 4, and more preferably 1 or 2.
The substituent ^R7 when k is 0 may be appropriately selected from the above-mentioned viewpoints, but among them, from the viewpoint of enhancing the planarity and rigidity of the molecular chain, an aryl group is preferably used, and it is preferable that the substituent R7 contains at least one aryl group.

^Z1 and ^Z2 each independently represent a divalent group of -NHCO-, -CONH-, -OCO-, or -COO-, ^Z2 is bonded at the para or meta position relative to the amino group, and ^Z1 is bonded at the para or meta position relative to ^Z2 .
From the viewpoint of bonding to an aromatic ring directly bonded to the diamine raw material via -NH- and making the aromatic ring electron-rich to enhance reactivity, when k=0, Z ¹ is preferably -NHCO- or -CONH-, and when k=1, it is more preferable that Z ² is -NHCO- and Z ¹ is -CONH-.
From the viewpoint of bonding to an aromatic ring directly bonded to the diamine raw material via -O- and making the aromatic ring electron-rich to enhance reactivity, when k=0, Z ¹ is preferably -OCO- or -COO-, and when k=1, it is more preferable that Z ² is -OCO- and Z ¹ is -COO-.
In addition, in order to increase the elastic modulus by making the main skeleton of the molecular chain have a linear structure and facilitating stacking, it is preferable that ^Z2 is bonded to the amino group at the para position and ^Z1 is bonded to ^Z2 at the para position.

Examples of the diamine represented by formula (5) include, but are not limited to, the diamines having the following structures:

The diamine residue of the structural unit represented by the formula (5) may be a diamine residue of at least one diamine selected from the group consisting of the formulae (DA1), (DA4), (DA7), and (DA29), since it is necessary to select a highly reactive diamine to obtain a high molecular weight polymer.

Examples of diamines having an aliphatic ring include 1,4-cyclohexanediamine, trans-1,4-bismethylenecyclohexanediamine, 2,6-bis(aminomethyl)bicyclo[2,2,1]heptane, and 2,5-bis(aminomethyl)bicyclo[2,2,1]heptane.
The diamine residues having an aromatic ring or an aliphatic ring may be used alone or in combination of two or more kinds.

The polyimide used in the present invention contains (100-x) mol % (where x is the mol % of the structural unit represented by the general formula (1)) of the structural unit represented by the general formula (2). When the polyimide used in the present invention contains 100 mol % of the structural unit represented by the general formula (1), the structural unit represented by the general formula (2) is 0 mol %, i.e., no structural unit is contained.

In the general formula (2), A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.
B in the general formula (2) may be the same as B in the general formula (1), and therefore the explanation here is omitted. B in the general formula (1) and B in the general formula (2) may be the same or different.

The tetracarboxylic acid residue in A of the general formula (2) can be a residue obtained by removing an acid dianhydride structure from a tetracarboxylic acid dianhydride having an aromatic ring, or a residue obtained by removing an acid dianhydride structure from a tetracarboxylic acid dianhydride having an aliphatic ring.
Examples of tetracarboxylic dianhydrides having an aromatic ring include pyromellitic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetracarboxylic dianhydride, 2,3,3',4'-biphenyl tetracarboxylic dianhydride residue, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2, 3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 1,4-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride, 2,2-bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, 4,4'-bis[4-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, 4,4'-bis[3-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride phenoxy]phenyl}sulfide dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3'-(hexafluoroisopropylidene)diphthalic anhydride, 4,4'-oxydiphthalic anhydride, 3,4'-oxydiphthalic anhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, and the like.
Examples of tetracarboxylic dianhydrides having an aliphatic ring include cyclohexanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, dicyclohexane-3,4,3',4'-tetracarboxylic dianhydride, and cyclobutanetetracarboxylic dianhydride.
These may be used alone or in combination of two or more.

The polyimide film used in the present invention contains 10 mol % or more and 100 mol % or less of the constitutional unit represented by the general formula (1).
From the viewpoint of solubility in a solvent, the polyimide film used in the present invention preferably contains 15 mol % or more of the structural unit represented by the general formula (1), more preferably 25 mol % or more, even more preferably 50 mol % or more, and even more preferably 60 mol % or more.
On the other hand, from the viewpoint of improving surface hardness and light transmittance, a copolymerization component may be contained, and the polyimide film used in the present invention may contain 95 mol % or less of the constitutional unit represented by the general formula (1), further may contain 90 mol % or less, and further may contain 80 mol % or less.

The polyimide film used in the present invention contains the constitutional unit represented by the general formula (2) in an amount of (100-x) mol % (where x is the mol % of the constitutional unit represented by the general formula (1)).
From the viewpoint of solubility in a solvent, in the polyimide film used in the present invention, the constitutional unit represented by the general formula (2) is preferably 85 mol % or less, more preferably 75 mol % or less, even more preferably 50 mol % or less, and even more preferably 40 mol % or less.
In the polyimide film used in the present invention, the constitutional unit represented by the general formula (2) may be 0 mol %, but may be contained as a copolymerization component from the viewpoint of improving surface hardness and light transmittance. The polyimide film used in the present invention may contain the constitutional unit represented by the general formula (2) in an amount of 5 mol % or more, further may contain 10 mol % or more, and further may contain 20 mol % or more.

From the viewpoint of improving light transmittance and surface hardness, it is preferable that at least one of the tetravalent group which is a tetracarboxylic acid residue of A and the divalent group which is a diamine residue of B contains an aromatic ring and at least one selected from the group consisting of (i) a fluorine atom, (ii) an aliphatic ring, and (iii) a structure in which aromatic rings are linked together by an alkylene group which may be substituted with a sulfonyl group or fluorine.
The polyimide used in the present invention contains at least one selected from a tetracarboxylic acid residue having an aromatic ring and a diamine residue having an aromatic ring, and thus the molecular skeleton becomes rigid, the orientation is enhanced, and the surface hardness is improved. However, the rigid aromatic ring skeleton tends to extend the absorption wavelength to longer wavelengths, and the transmittance in the visible light region tends to decrease.
On the other hand, when the polyimide contains (i) fluorine atoms, the electronic state in the polyimide skeleton is made difficult to transfer charges, and thus the light transmittance is improved.
When the polyimide contains (ii) an aliphatic ring, the conjugation of π electrons in the polyimide skeleton can be broken, thereby inhibiting the movement of charges in the skeleton, and thus improving the light transmittance.
When the polyimide contains (iii) a structure in which aromatic rings are linked together via a sulfonyl group or an alkylene group which may be substituted with fluorine, the conjugation of π electrons in the polyimide skeleton can be broken, thereby inhibiting the movement of charges in the skeleton, and thus improving the light transmittance.
In particular, from the viewpoints of improving light transmittance and surface hardness, it is preferable that at least one of the tetravalent group which is the tetracarboxylic acid residue of A and the divalent group which is the diamine residue of B contains an aromatic ring and a fluorine atom, and it is preferable that the divalent group which is the diamine residue of B contains an aromatic ring and a fluorine atom.

The polyimide used in the present invention is such that the diamine residue having an aromatic ring or an aliphatic ring in B in the general formulas (1) and (2) is a trans-cyclohexanediamine residue, a trans-1,4-bismethylenecyclohexanediamine residue, a 4,4'-diaminodiphenylsulfone residue, a 3,4'-diaminodiphenylsulfone residue, a 2,2-bis(4-aminophenyl)propane residue, a 3,3'-bis(trifluoromethyl)-4,4'-[(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(4,1-phenyl)propane residue, From the viewpoints of light transmittance, bending resistance, and surface hardness, it is preferable that the divalent group contains at least one selected from the group consisting of a 2,2-bis[3-(3-aminophenoxy)phenyl]dianiline residue, a 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, and a divalent group represented by the following general formula (3), and further contains at least one diamine residue of a diamine represented by the general formula (5).
The polyimide used in the present invention is such that the diamine residue having an aromatic ring or an aliphatic ring in B in the general formulas (1) and (2) is a trans-cyclohexanediamine residue, a trans-1,4-bismethylenecyclohexanediamine residue, a 4,4'-diaminodiphenylsulfone residue, a 3,4'-diaminodiphenylsulfone residue, a 2,2-bis(4-aminophenyl)propane residue, a 3,3'-bis(trifluoromethyl)-4,4'-[(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)bis(4,1-phenyleneoxy)]dianiline residue, a 2,2-bis At least one selected from the group consisting of [3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, and a divalent group represented by the following general formula (3), and further at least one selected from the group consisting of N,N'-bis(4-aminophenyl)terephthalamide residue, 4-aminophenyl-4-aminobenzoate residue, (2-phenyl-4-aminophenyl)-4-aminobenzoate residue, and bis(4-aminophenyl)terephthalate residue. From the viewpoints of light transmittance, bending resistance, and surface hardness, it is preferable that the divalent group contains at least one selected from the group consisting of a 4,4'-diaminodiphenylsulfone residue, a 3,4'-diaminodiphenylsulfone residue, a 2,2-bis(4-aminophenyl)propane residue, and a divalent group represented by the following general formula (3), and further contains an N,N'-bis(4-aminophenyl)terephthalamide residue, a 4-aminophenyl-4-aminobenzoate residue, a (2-phenyl-4-aminophenyl)-4-aminobenzoate residue, It is preferable that the divalent group may contain at least one selected from the group consisting of N,N'-bis(4-aminophenyl)terephthalamide residue, 4-aminophenyl-4-aminobenzoate residue, (2-phenyl-4-aminophenyl)-4-aminobenzoate residue, and bis(4-aminophenyl)terephthalate residue, and more preferably a divalent group containing at least one selected from the group consisting of N,N'-bis(4-aminophenyl)terephthalamide residue, 4-aminophenyl-4-aminobenzoate residue, (2-phenyl-4-aminophenyl)-4-aminobenzoate residue, and bis(4-aminophenyl)terephthalate residue. As the divalent group represented by the following general formula (3), R ⁵ and R ⁶ are more preferably perfluoroalkyl groups, among which perfluoroalkyl groups having 1 to 3 carbon atoms are preferred, and trifluoromethyl groups or perfluoroethyl groups are more preferred. In addition, as the alkyl groups in R ⁵ and R ⁶ in the following general formula (3), alkyl groups having 1 to 3 carbon atoms are preferred, and more preferably methyl groups or ethyl groups.

（一般式（３）において、Ｒ^５及びＲ^６はそれぞれ独立に、水素原子、アルキル基、またはパーフルオロアルキル基を表す。）

(In formula (3), ^R5 and ^R6 each independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.)

In the polyimide used in the present invention, from the viewpoints of light transmittance, bending resistance and surface hardness, in particular, the tetracarboxylic acid residue having an aromatic ring or an aliphatic ring in A in the general formula (2) is a cyclohexanetetracarboxylic acid dianhydride residue, a cyclopentanetetracarboxylic acid dianhydride residue, a dicyclohexane-3,4,3',4'-tetracarboxylic acid dianhydride residue, a cyclobutanetetracarboxylic acid dianhydride residue, a pyromellitic acid dianhydride residue, a 3,3',4,4'-biphenyltetracarboxylic acid dianhydride residue, a 2, It is preferably at least one tetravalent group selected from the group consisting of 2',3,3'-biphenyltetracarboxylic dianhydride residue, 2,3,3',4'-biphenyltetracarboxylic dianhydride residue, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene)diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride residue, and 3,4'-oxydiphthalic anhydride residue.
In A in the general formula (2), the total amount of these suitable residues is preferably 50 mol % or more, more preferably 70 mol % or more, and even more preferably 90 mol % or more.

In terms of improving surface hardness, A in the general formula (2) preferably includes at least one tetracarboxylic acid residue group (Group A) suitable for improving rigidity, such as at least one selected from the group consisting of pyromellitic dianhydride residue, 3,3',4,4'-biphenyltetracarboxylic dianhydride residue, and 2,2',3,3'-biphenyltetracarboxylic dianhydride residue, and from the viewpoint of improving light transmittance, it is preferable that A includes at least one tetracarboxylic acid residue group (Group A) suitable for improving rigidity, such as at least one selected from the group consisting of cyclohexanetetracarboxylic dianhydride residue, cyclopentanetetracarboxylic dianhydride residue, dicyclohexane-3,4,3',4'-tetracarboxylic dianhydride residue, cyclobutanetetracarboxylic dianhydride residue, It is preferable that the tetracarboxylic acid dianhydride group contains at least one tetracarboxylic acid residue group (Group B) suitable for improving light transmittance, such as at least one selected from the group consisting of tetracarboxylic acid dianhydride residues, 2,3,3',4'-biphenyltetracarboxylic acid dianhydride residues, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride residues, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride residues, 3,3'-(hexafluoroisopropylidene)diphthalic anhydride residues, 4,4'-oxydiphthalic anhydride residues, and 3,4'-oxydiphthalic anhydride residues, and the Group A and Group B may be used in combination. In the case of mixing Group A and Group, the content ratio of the tetracarboxylic acid residue group suitable for improving the rigidity (Group A) to the tetracarboxylic acid residue group suitable for improving the light transmittance (Group B) is preferably 0.05 mol or more and 9 mol or less, more preferably 0.1 mol or more and 5 mol or less, and even more preferably 0.3 mol or more and 4 mol or less, of the tetracarboxylic acid residue group suitable for improving the rigidity (Group A) per 1 mol of the tetracarboxylic acid residue group suitable for improving the light transmittance (Group B).
Among these, it is preferable that Group B contains at least one selected from the group consisting of 4,4'-(hexafluoroisopropylidene)diphthalic anhydride residues, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride residues, and cyclobutane tetracarboxylic dianhydride residues in terms of improving surface hardness and light transmittance, and it is more preferable that Group B contains cyclobutane tetracarboxylic dianhydride residues in terms of a high effect of reducing yellowness and excellent elastic modulus.

The content ratio of each repeating unit in the polyimide and the content ratio (mol %) of each tetracarboxylic acid residue and each diamine residue can be determined from the molecular weight of the feed when the polyimide is produced. The content ratio (mol %) of each tetracarboxylic acid residue and each diamine residue in the polyimide can be determined by using high performance liquid chromatography, gas chromatography mass spectrometry, NMR, elemental analysis, XPS/ESCA, and TOF-SIMS for the decomposition product of the polyimide. The decomposition product of the polyimide can be obtained, for example, by decomposing the sample with an alkaline aqueous solution or supercritical methanol.

The polyimide used in the present invention is selected from those having a weight average molecular weight of 100,000 or more as calculated on a polystyrene basis by gel permeation chromatography, because of its excellent flexural resistance.
From the viewpoint of flex resistance, the weight average molecular weight may be 120,000 or more, further 140,000 or more, and further 160,000 or more. On the other hand, from the viewpoint of preventing bubble defects from occurring, the weight average molecular weight is preferably 270,000 or less, and from the viewpoint of solubility, the weight average molecular weight may be 250,000 or less, further 230,000 or less, and further 210,000 or less.
The weight average molecular weight of polyimide can be measured by gel permeation chromatography (GPC). Specifically, polyimide is dissolved in N-methylpyrrolidone (NMP) at a concentration of 0.1% by mass, and a 30 mmol% LiBr-NMP solution with a water content of 500 ppm or less is used as the developing solvent. Measurement is performed using a Tosoh GPC device (HLC-8120, column used: GPC LF-804 manufactured by SHODEX) under conditions of sample injection amount of 50 μL, solvent flow rate of 0.4 mL/min, and 37° C. The weight average molecular weight is determined based on a polystyrene standard sample having the same concentration as the sample.

2. Additives The polyimide film used in the present invention may further contain additives, if necessary, in addition to the polyimide, so long as the effects of the present invention are not impaired. Examples of the additives include inorganic particles, silica filler for facilitating winding, surfactants for improving film-forming properties and defoaming properties, and ultraviolet absorbers.

3. Characteristics of Polyimide Film The polyimide film used in the present invention preferably further has the characteristics described below.
(1) Residual Solvent The polyimide film used in the present invention is preferably produced using an organic solvent containing dichloromethane in an amount of 90 mass % or more based on the total organic solvent, as described below, in that a polyimide film is easily obtained which is less susceptible to bubble defects, has good film thickness uniformity, and has good bending resistance.
Therefore, the polyimide film used in the present invention preferably contains dichloromethane as a residual solvent in an amount of 1 ppm or more and 2000 ppm or less, in view of being less susceptible to bubble defects, having good film thickness uniformity, and having good bending resistance.
In the polyimide film used in the present invention, the dichloromethane content is preferably 1000 ppm or less, more preferably 800 ppm or less, more preferably 400 ppm or less, and even more preferably 100 ppm or less, from the viewpoint of improving the static bending resistance and the dynamic bending resistance, and the dichloromethane content is preferably as small as possible, and may be about 1 ppm, which is the detection limit described later.
In addition, in order to improve the bending resistance of the polyimide film of the present invention, the content of an organic solvent having a boiling point of 70° C. or more, particularly 100° C. or more, at 1 atmospheric pressure is preferably 1,000 ppm or less, more preferably 800 ppm or less, even more preferably 400 ppm or less, and even more preferably 100 ppm or less.

The amount of residual solvent in the polyimide film can be measured as follows.
[Identification of types of residual solvents]
First, the type of residual solvent is identified using a GC-MS connected to a purge and trap device (thermal desorption device).
A sample tube containing 10 mg of polyimide film was placed in a purge and trap device (product name JTD505-III, Japan Analytical Industry Co., Ltd.) and heated at 200°C for 30 minutes to generate gas, which was then collected in a trap tube at -60°C. The collected gas was then heated at 315°C to remove the gas and sent to a GC-MS for qualitative analysis of the components of the generated organic gas.
(Purge and trap device conditions)
Total split ratio (intake volume/exhaust volume) 1:10,
Carrier gas: Helium 1.0 ml/min Quantitative (GC-MS conditions)
Device name: GC-MS device (Agilent, 6890/5973 GC/MS)
Column: UA-5, inner diameter 250 μm × length 30 m × film thickness 0.25 μm (manufactured by Frontier Labs), temperature rise conditions: 50°C (hold for 5 minutes) → 10°C/min (heat rise) → 320°C (hold for 3 minutes)

[Quantitative determination of residual solvent]
A polyimide film is added to N,N-dimethylformamide (DMF) so that the concentration of the polyimide film is 5% by mass, to prepare a polyimide film/N,N-dimethylformamide (DMF) solution, and an internal standard solution (0.2% by mass anisole/DMF solution) is added to this solution to prepare a sample solution. The sample solution is subjected to GC-MS measurement under the following conditions using a GC-MS device (e.g., Agilent, 6890/5973 GC/MS). The GC-MS measurement is performed three times, and the measurement result is the average value of the three measurements.
(GC conditions)
Column: InertCapWax inner diameter 250 μm × length 30 m × film thickness 0.25 μm (GL Sciences),
Sample injection amount: 0.2 uL; split ratio (introducing amount/exhausting amount): 1:50; carrier gas: helium 94.3 kPa constant pressure; injection port temperature: 250°C; heating conditions: 40°C (5 min hold) → 5°C/min → 120°C → 20°C/min → 240°C (6 min hold); transfer line temperature: 250°C
(MS conditions)
Ionization method: EI, measurement mode: SIM, ion source temperature: 250°C, quadrupole temperature: 150°C, ionization voltage: 70 eV

A calibration curve is prepared for each of the residual solvents identified as above, and the amount of each residual solvent is quantified based on the calibration curve.
For example, when the residual solvent contained is dichloromethane, a calibration curve is created by adding an internal standard solution to each of dichloromethane (target compound)/DMF solutions prepared so that the dichloromethane content is, for example, 0.01 mass%, 0.05 mass%, or 0.1 mass%, in the same manner as in the above-mentioned sample solution, and then performing GC-MS measurement on each calibration curve. The GC-MS measurement is performed three times, and the measurement result is the average value of the three measurements.
The content of dichloromethane is calculated as a mass ratio to the polyimide film based on the calibration curve. The calibration curve is appropriately reconstructed depending on the amount detected.
When two or more types of residual solvents are contained, a calibration curve solution is prepared for each residual solvent as in the case of dichloromethane, and a calibration curve created from the measurement results of GC-MS measurement for each calibration curve solution is used as the standard.
When N,N-dimethylformamide (DMF) is contained as a residual solvent, a sample solution is prepared using a good solvent for polyimide that does not contain DMF as a residual solvent, such as N-methyl-2-pyrrolidone.

(2) Total light transmittance
From the viewpoint of transparency, the polyimide film used in the present invention preferably has a total light transmittance measured in accordance with JIS K7361-1 of 85.0% or more, more preferably 88.0% or more, and even more preferably 89.0% or more.

The total light transmittance measured in accordance with JIS K7361-1 can be measured, for example, by a haze meter (e.g., HM150 manufactured by Murakami Color Research Laboratory). Note that the total light transmittance at a different thickness can be calculated from the measured value of the total light transmittance at a certain thickness according to the Beer-Lambert law, and this can be used.
Specifically, according to the Beer-Lambert law, the transmittance T is given by
Log ₁₀ (1/T)=kcb
(k=constant specific to the material, c=concentration, b=optical path length).
In the case of the transmittance of a film, if it is assumed that the density is constant even if the film thickness changes, c is also a constant, so the above formula can be expressed as Log ₁₀ (1/T) = fb
(f = kc). Here, if the transmittance at a certain film thickness is known, the constant f specific to each material can be found. Therefore, by using the formula T = 1/10 ^{f b} , substituting a specific constant for f and the target film thickness for b, the transmittance at a desired film thickness can be found.

(3) Yellowness The polyimide film used in the present invention preferably has a yellowness index (YI value) calculated in accordance with JIS K7373-2006 of 12.0 or less. A low yellowness index is preferable in that yellow coloring is suppressed and light transmittance is improved. The yellowness index (YI value) calculated in accordance with JIS K7373-2006 is more preferably 10.0 or less, even more preferably 7.0 or less, even more preferably 5.0 or less, and particularly preferably 4.5 or less.
The yellowness index (YI value) can be calculated in accordance with JIS K7373-2006 by using an ultraviolet-visible-near infrared spectrophotometer (for example, V-7100 manufactured by JASCO Corporation) and a spectrophotometric method using auxiliary illuminant C and a 2-degree visual field, based on the transmittance measured at 1 nm intervals in the range of 250 nm to 800 nm, and tristimulus values X, Y, and Z in the XYZ color system are determined based on the transmittance. The YI value can then be calculated from the X, Y, and Z values according to the following formula.
YI=100(1.2769X-1.0592Z)/Y
In addition, from the measured value of yellowness at a certain thickness, the yellowness at a different thickness can be calculated and used by calculating the conversion value of each transmittance at each wavelength at different thicknesses using Lambert-Beer's law for each transmittance at each wavelength measured at 1 nm intervals between 250 nm and 800 nm of a sample of a certain film thickness, in the same manner as for the total light transmittance.

In addition, since the polyimide film used in the present invention is suppressed from being yellowed and has improved light transmittance, and can be suitably used as a glass replacement material, the value obtained by dividing the yellowness index (YI value) calculated in accordance with JIS K7373-2006 by the film thickness (μm) (YI value/film thickness (μm)) is preferably less than 0.16, more preferably less than 0.12, even more preferably less than 0.11, and even more preferably less than 0.10.
In the present invention, the value obtained by dividing the yellowness index (YI value) by the film thickness (μm) (YI value/film thickness (μm)) is rounded to two decimal places in accordance with Rule B of JIS Z8401:1999.

(4) Haze Value The haze value of the polyimide film used in the present invention is preferably 1.0 or less, more preferably 0.5 or less, from the viewpoint of light transmittance. The haze value can be preferably achieved when the polyimide film has a thickness of 5 μm or more and 100 μm or less.
The haze value can be measured by a method in accordance with JIS K-7136, for example, by using a haze meter HM150 manufactured by Murakami Color Research Laboratory.

(5) Tensile modulus
The polyimide film used in the present invention preferably has a tensile modulus of 3.3 GPa or more at 25°C measured on a 10mm x 150mm test piece in accordance with JIS K7127 at a tensile speed of 50mm/min and a chuck distance of 100mm. Thus, when the tensile modulus at 25°C (room temperature) is high, the film can maintain a sufficient surface hardness as a protective film even at room temperature, and can be used as a surface material or a substrate. The tensile modulus is more preferably 4.0 GPa or more, even more preferably 4.5 GPa or more, and even more preferably 5.0 GPa or more. On the other hand, the tensile modulus may be 8.0 GPa or less from the viewpoint of improving bending resistance.
The tensile modulus can be measured by cutting a test piece having a width of 10 mm and a length of 150 mm from a polyimide film using a tensile tester (e.g., Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN) at 25° C., a pulling speed of 50 mm/min, and a chuck distance of 100 mm. The thickness of the polyimide film when determining the tensile modulus is preferably 30 μm±5 μm to 100 μm±5 μm.

(6) tan δ curve The polyimide film used in the present invention is preferably one that has a peak apex only in a temperature range of 150° C. or more in a tan δ curve, which is a value obtained by dividing the loss modulus by the storage modulus. If the peak apex in the tan δ curve is below 150° C., the molecular chains of the polyimide are likely to move and are likely to be plastically deformed, which may result in poor flex resistance. On the other hand, if the peak apex is not below 150° C., the mobility of the molecular chains is suppressed, making it difficult to undergo plastic deformation, and the flex resistance can be improved.
In addition, when the tan δ curve has a peak only in a temperature region of 150° C. or higher, the bending resistance is prevented from being impaired by thermal deformation even in a high-temperature environment, such as inside a car in summer, and therefore the bending resistance is improved even in a high-temperature environment.
Furthermore, if the tan δ curve has peaks only in a temperature range of 150° C. or higher, the tensile modulus tends to be high and the surface hardness tends to be high.
From the viewpoint of improving bending resistance and surface hardness, the polyimide film used in the present invention preferably has a peak apex in the tan δ curve only in a temperature range of 200° C. or higher, even more preferably only in a temperature range of 250° C. or higher, and even more preferably only in a temperature range of 300° C. or higher. On the other hand, from the viewpoint of reducing the bake temperature, it is preferable that the peak apex in the tan δ curve be in a temperature range of 380° C. or lower.
The tan δ curve is obtained from the relationship between temperature and tan δ (tan δ=loss modulus (E″)/storage modulus (E′)) by dynamic viscoelasticity measurement, and the temperature at the apex of the peak where the maximum value of the peak is the largest can be used as an index of the glass transition temperature. The dynamic viscoelasticity measurement can be performed, for example, by a dynamic viscoelasticity measuring device RSA-G2 (TA Instruments Japan Co., Ltd.) with a measurement range of −150° C. to 490° C., a frequency of 1 Hz, and a temperature rise rate of 5° C./min. The measurement can also be performed with a sample width of 5 mm and a chuck distance of 20 mm. When analyzing the peaks and inflection points, the data is digitized and analyzed from the numerical values without visual evaluation.
In the curve of temperature (horizontal axis) and tan δ (tan δ=loss modulus (E″)/storage modulus (E′)) (vertical axis), a peak refers to a curve having a tan δ value of 0.2 or more, preferably 0.3 or more, having a maximum value, and having a peak width between the valleys of the peak of 3° C. or more. Small upward and downward fluctuations in the curve resulting from measurement noise or the like are not observed as peaks at the apex of the peak.
The sample for measuring the tan δ curve is a polyimide film that has been left to stand for 24 hours in an environment of 23°C ± 2°C and RH 30-50%, and then a sample of 10 cm square or more is taken. The central part of the sample is cut into a size of 5 mm wide x 50 mm long (so that the sample length is 20 mm when chucked) using a cutting tool with a 5 mm wide slit made with a razor or scalpel. The width is measured three times at different positions using a caliper, and the average value is recorded. If there is a variation of 3% or more from the average value in any part of the width measurement, do not use that sample.

(7) Pencil Hardness The polyimide film used in the present invention preferably has a pencil hardness of 2B or more, more preferably B or more, and even more preferably HB or more.
The pencil hardness of the polyimide film can be measured by subjecting a measurement sample to a temperature of 25° C. and a relative humidity of 60% for 2 hours, and then subjecting the film surface to a pencil hardness test (load of 0.98 N) according to JIS K5600-5-4 (1999) using a test pencil according to JIS-S-6006, and evaluating the highest pencil hardness that does not cause scratches. For example, a pencil scratch coating hardness tester manufactured by Toyo Seiki Co., Ltd. can be used.

4. Structure of polyimide film The thickness of the polyimide film used in the present invention may be appropriately selected depending on the application, but may be 1 μm or more, preferably 10 μm or more, more preferably 20 μm or more, even more preferably 30 μm or more, and may be 35 μm or more. On the other hand, it is preferably 200 μm or less, more preferably 150 μm or less, even more preferably 100 μm or less, and even more preferably 90 μm or less.
If the thickness is too thin, the strength decreases, whereas if the thickness is too thick, the difference between the inner diameter and the outer diameter when bent increases, which increases the load on the film and may decrease the bending resistance.

The polyimide film used in the present invention may also be subjected to surface treatments such as saponification, glow discharge, corona discharge, ultraviolet light, and flame treatment.

5. Method for Producing Polyimide Film There are no particular limitations on the method for producing the polyimide film used in the present invention, so long as it is a method capable of producing the polyimide film used in the present invention.
When the polyimide has good solubility in an organic solvent, it is preferable to use the first polyimide production method, in which the polyimide is dissolved in an organic solvent, and then dried using a polyimide varnish containing an additive as necessary, to produce a polyimide film.
The polyimide used in the present invention has a tetracarboxylic acid residue having a specific structure including a parabiphenylene group with a twisted dihedral angle via an ester bond in the main chain, and is therefore easily soluble in an organic solvent. When the polyimide has a solvent solubility such that it is dissolved in the organic solvent at 25° C. in an amount of 6 mass % or more, the first production method can be suitably used.

The first method for producing a polyimide film includes the steps of:
A step of preparing a polyimide varnish containing the polyimide used in the present invention and an organic solvent, the polyimide content in the polyimide varnish being 6% by mass or more and 15% by mass or less, and having a viscosity of 1,000 to 10,000 cps at 25°C as measured by a rotational viscometer;
applying the polyimide varnish to a substrate, drying the polyimide varnish at a temperature of 100° C. or less, and peeling the coating film from the substrate after drying;
It is preferable to have a process of fixing the ends of the dried coating film peeled off from the support and then heating the dried coating film at a temperature of 150°C or higher, since this makes it difficult for air bubble defects to occur and makes it easy to reduce the amount of residual solvent.
In particular, by drying the organic solvent at two or more drying temperatures below 100°C, it is possible to suppress skinning on the coating surface and to suppress bubbles due to bumping of the organic solvent in the coating. Skinning refers to a state in which the coating surface is more dried than the interior, a concentration gradient occurs in the coating thickness direction, and solvent diffusion is hindered in the outermost skin layer, resulting in drying rate-limiting. Skinning can cause the evaporated solvent in the coating to expand, generating bubble defects.
Heating the peeled, dried coating film to 150°C or higher is also preferably performed at a temperature of 150°C or higher in two or more heating stages, since this makes it difficult for bubble defects to occur and makes it easier to reduce the amount of residual solvent.
For example, when the thickness of the coating film after drying is less than 50 μm, it is preferable to set the holding time at each stage to 10 minutes or more and less than 60 minutes, and when the thickness of the coating film after drying is 50 μm or more and 100 μm or less, it is preferable to set the holding time at each stage to 30 minutes or more and less than 90 minutes.
Examples of the organic solvent used in the polyimide varnish include aprotic polar solvents and water-soluble alcohol solvents. Specific examples include N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, 1,3-dimethyl-2-imidazolidinone, γ-butyrolactone, and dichloromethane.

Among these, the following production method is preferred from the viewpoint of easily obtaining a polyimide film which is less prone to coloration, is less prone to bubble defects, has good film thickness uniformity, and has good bending resistance.
The method for producing the polyimide film used in the present invention includes the steps of:
A polyimide varnish containing a polyimide and an organic solvent,
The polyimide contains 10 mol % or more and 100 mol % or less of the constitutional unit represented by the general formula (1) and (100-x) mol % (wherein x is the mol % of the constitutional unit represented by the general formula (1)) of the constitutional unit represented by the general formula (2), and has a weight average molecular weight of 100,000 or more as calculated in terms of polystyrene by gel permeation chromatography;
The organic solvent contains dichloromethane in an amount of 90% by mass or more based on the total amount of the organic solvent,
preparing a polyimide varnish having a polyimide content of 6% by mass or more and 15% by mass or less in the polyimide varnish and a viscosity of 1,000 to 10,000 cps at 25° C. as measured by a rotational viscometer;
applying the polyimide varnish to a support, drying the polyimide varnish at a temperature of 40° C. or less, and peeling the coating film from the support after drying;
It is preferable to have a step of fixing the end portion of the dried coating film peeled from the support, and then heating the dried coating film at a temperature of 150° C. or higher.

According to this manufacturing method, the polyimide content in the varnish can be increased to a sufficient concentration, and the varnish can be adjusted to a desired viscosity range, so that even polyimide films with a thickness of 30 μm or more can be easily manufactured, and films with good thickness uniformity can be obtained without bubble defects. Since an organic solvent containing 90 mass % or more of dichloromethane with a boiling point of 40° C. in the total organic solvent is used, there is no need to heat at a high temperature or perform forced drying with hot air during drying, and foaming, uneven thickness, yellowing, etc. of the film can be suppressed, the amount of residual solvent can be reduced, and bending resistance can be improved.
Hereinafter, a detailed description will be given of a preferred production method among the first production method, but the following description can be applied to the first production method in general, except for the organic solvent and drying temperature.

(1) Step of preparing polyimide varnish The varnish used in the present invention is a polyimide varnish containing a polyimide and an organic solvent,
The polyimide contains 10 mol % or more and 100 mol % or less of the constitutional unit represented by the general formula (1) and (100-x) mol % (wherein x is the mol % of the constitutional unit represented by the general formula (1)) of the constitutional unit represented by the general formula (2), and has a weight average molecular weight of 100,000 or more as calculated in terms of polystyrene by gel permeation chromatography;
The organic solvent contains dichloromethane in an amount of 90% by mass or more based on the total amount of the organic solvent,
The content of the polyimide in the polyimide varnish is preferably adjusted to 6% by mass or more and 15% by mass or less, and the viscosity at 25° C. measured with a rotational viscometer is preferably adjusted to 1,000 to 10,000 cps.

(1-1) Polyimide The polyimide containing 10 mol % or more and 100 mol % or less of the constitutional unit represented by the general formula (1) and (100-x) mol % (wherein x is the mol % of the constitutional unit represented by the general formula (1)) of the constitutional unit represented by the general formula (2) and having a weight average molecular weight of 100,000 or more as calculated in terms of polystyrene by gel permeation chromatography may be the same as the polyimide described in the polyimide film used in the present invention, and therefore description thereof will be omitted here.
The method for producing the polyimide is not particularly limited. For example, the polyimide can be produced by reacting one or more tetracarboxylic dianhydrides, including a tetracarboxylic dianhydride represented by the following general formula (4) and a tetracarboxylic dianhydride having an aromatic ring or an aliphatic ring as necessary, with a diamine having one or more aromatic rings or aliphatic rings, through a process of obtaining a polyimide precursor (polyamic acid) containing 10 mol % or more and 100 mol % or less of a structural unit represented by the following general formula (1') and (100-x) mol % (where x is the mol % of the structural unit represented by the general formula (1')) of a structural unit represented by the following general formula (2'), and a process of imidizing the obtained polyimide precursor (polyamic acid).

（一般式（４）において、Ｒ^１～Ｒ^４は、前記一般式（１）と同様である。）

(In the general formula (4), R ¹ to R ⁴ are the same as those in the general formula (1).)

（一般式（１’）及び（２’）において、Ｒ^１～Ｒ^４、Ａ、及びＢは、それぞれ、前記一般式（１）及び（２）と同様である。）

(In general formulas (1') and (2'), R ¹ to R ⁴ , A, and B are the same as those in general formulas (1) and (2), respectively.)

The tetracarboxylic dianhydride represented by the general formula (4) can be obtained by a known esterification reaction using the corresponding biphenyl 4,4'-diol and trimellitic acid. Examples of the trimellitic acid include trimellitic anhydride and trimellitic anhydride halide.
The tetracarboxylic acid dianhydride having an aromatic ring or an aliphatic ring and the diamine having one or more aromatic rings or aliphatic rings, which are used as necessary, may be the same as those described in the polyimide film.

The polyimide precursor is obtained by reacting the above-mentioned tetracarboxylic dianhydride with the above-mentioned diamine in a solvent. The solvent used in the synthesis of the polyimide precursor (polyamic acid) is not particularly limited as long as it can dissolve the above-mentioned tetracarboxylic dianhydride and diamine, and for example, an aprotic polar solvent or a water-soluble alcohol solvent can be used. In the present invention, it is preferable to use organic solvents containing nitrogen atoms such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, and 1,3-dimethyl-2-imidazolidinone; γ-butyrolactone, etc. It should be noted that an organic solvent is a solvent containing carbon atoms.

The polymerization reaction procedure can be appropriately selected from known methods.
For example, a diamine is first dissolved in a polymerization solvent in a reaction vessel, and an acid dianhydride in an amount substantially equimolar to the diamine is gradually added to the solution, followed by stirring using a mechanical stirrer or the like at a temperature in the range of 0 to 100° C., preferably 20 to 60° C., for 0.5 to 150 hours, preferably 1 to 48 hours. In this case, the monomer concentration is usually in the range of 5 to 50% by mass, preferably 10 to 40% by mass.

In addition, when the polyimide precursor solution is prepared by combining at least two kinds of acid dianhydrides, the acid dianhydride may be added to a polymerization solvent in which a diamine is dissolved to synthesize a polyamic acid, or at least two kinds of acid dianhydrides may be added in a stepwise manner in an appropriate molar ratio to a reaction solution to control to some extent the sequence in which each raw material is incorporated into a polymer chain.
For example, a tetracarboxylic dianhydride represented by general formula (4) may be added to a reaction solution in which a diamine has been dissolved, and reacted to synthesize an amic acid in which the tetracarboxylic dianhydride represented by general formula (4) reacts with a diamine, and then a tetracarboxylic dianhydride different from the tetracarboxylic dianhydride represented by general formula (4) may be added thereto, and further diamine may be added as necessary to polymerize a polyamic acid. When polymerized by this method, the tetracarboxylic dianhydride represented by general formula (4) is introduced into the polyamic acid in a linked form via one diamine.
Polymerizing polyamic acid by such a method is preferable because it allows the positional relationship of tetracarboxylic acid residues having a specific structure containing a para-biphenylene group with a twisted dihedral angle via an ester bond in the main chain to be specified to a certain extent, and makes it easy to obtain a polyimide film having good surface hardness and excellent bending resistance.

When the number of moles of diamine in the polyimide precursor solution (polyamic acid solution) is a and the number of moles of tetracarboxylic dianhydride is b, it is preferable that b/a is 0.9 or more and 1.1 or less, more preferably 0.95 or more and 1.05 or less, even more preferably 0.97 or more and 1.03 or less, and particularly preferably 0.99 or more and 1.01 or less. By setting it in such a range, the molecular weight (degree of polymerization) of the obtained polyamic acid can be appropriately adjusted.

In order to prepare a polyimide having a weight average molecular weight of 100,000 or more as calculated by polystyrene equivalent using gel permeation chromatography, it is preferable to gradually add an acid dianhydride to a reaction solution in which a diamine is dissolved in the preparation of the polyimide precursor, and carry out the reaction while measuring by gel permeation chromatography that the molecular weight reaches the desired range.

The polyimide precursor (polyamic acid) has a weight average molecular weight of preferably 50,000 or more, more preferably 80,000 or more. In addition, from the viewpoint of improving bending resistance, the polyimide precursor (polyamic acid) has a weight average molecular weight of preferably 100,000 or more, more preferably 120,000 or more, and even more preferably 140,000 or more. On the other hand, from the viewpoint of suppressing bubble defects, the polyimide precursor (polyamic acid) has a weight average molecular weight of preferably 350,000 or less, more preferably 300,000 or less, and even more preferably 270,000 or less.
The weight average molecular weight of the polyimide precursor can be measured by gel permeation chromatography (GPC).
The polyimide precursor is dissolved in N-methylpyrrolidone (NMP) at a concentration of 0.5% by mass, and a 10 mmol% LiBr-NMP solution with a water content of 500 ppm or less is used as the developing solvent, and the measurement is performed using a Tosoh GPC device (HLC-8120, column used: SHODEX GPC LF-804) under conditions of a sample injection amount of 50 μL, a solvent flow rate of 0.5 mL/min, and 40° C. The weight average molecular weight is determined based on a polystyrene standard sample of the same concentration as the sample.

As the polyimide precursor (polyamic acid) used for imidization, the polyimide precursor solution obtained by the synthesis reaction may be used as is, or the solvent of the polyimide precursor solution may be dried and dissolved in another solvent.

Methods for imidizing a polyimide precursor include thermal imidization, which involves a dehydration ring-closing reaction by heating, and chemical imidization, which involves a dehydration ring-closing reaction using a chemical imidization agent (a dehydration ring-closing agent). Of these, chemical imidization is preferred from the viewpoint of suppressing yellowing due to heating.
When chemical imidization is performed, known compounds such as amines such as pyridine and β-picolinic acid, carbodiimides such as dicyclohexylcarbodiimide, and acid anhydrides such as acetic anhydride may be used as the chemical imidization agent. The acid anhydride is not limited to acetic anhydride, but may include, but is not limited to, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, and the like. In addition, a tertiary amine such as pyridine or β-picolinic acid may be used in combination. However, since these amines reduce the optical properties, particularly the yellowness index (YI value), if they remain in the film, it is preferable to purify the reaction solution in which the polyimide precursor is reacted to form a polyimide by reprecipitation or the like, and remove the chemical imidization agent components other than the polyimide to 100 ppm or less of the total weight of the polyimide.

There are no particular limitations on the organic solvent used in the reaction solution for chemically imidizing the polyimide precursor, so long as it is capable of dissolving the polyimide precursor. For example, organic solvents containing nitrogen atoms, such as N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, hexamethylphosphoramide, and 1,3-dimethyl-2-imidazolidinone; γ-butyrolactone, etc., can be used.

A typical method for reprecipitating the reaction solution that has been reacted to form a polyimide is to drop the reaction solution into a large amount of poor solvent while stirring it. In terms of making it easier to reduce impurities, a preferred method for reprecipitating the reaction solution is to dilute the reaction solution that has been reacted to form a polyimide to an appropriate concentration as necessary, and then gradually add a poor solvent for the polyimide to the reaction solution to precipitate the polyimide.
When the poor solvent is dropped to precipitate a polyimide, the solids concentration of the reaction liquid (polyimide solution) is preferably 0.1% by mass or more and 30% by mass or less, and more preferably 1% by mass or more and 10% by mass or less, from the viewpoints of yield and efficient removal of impurities.
In order to obtain a solids concentration of the polyimide solution suitable for precipitation of the polyimide, the polyimide solution may be appropriately diluted with a good solvent for the polyimide.
As a guideline, a good solvent for polyimide can be appropriately selected from solvents in which the solubility of polyimide at 25° C. is 20 g/100 g or more.
The poor solvent for polyimide can be appropriately selected from solvents in which the solubility of polyimide at 25° C. is less than 20 g/100 g, as a guideline.

For example, an organic solvent that is a good solvent for polyimide, such as n-butyl acetate, is added to the reaction liquid that has been reacted to form polyimide, and the reaction liquid is diluted by stirring until it becomes uniform. Next, an alcohol-based organic solvent, such as t-butanol, methanol, ethanol, isopropyl alcohol, 2-butanol, cyclohexanol, or t-amyl alcohol, is gradually added to precipitate the polyimide, obtaining a white slurry, which is then filtered to obtain the polyimide. As the alcohol-based organic solvent, it is preferable to use secondary or tertiary alcohol, and it is more preferable to use tertiary alcohol, because these solvents provide excellent stability to the polyimide.

The polyimide obtained by reprecipitation as described above is preferably washed repeatedly with an organic solvent to remove residual solvent. By reducing the residual solvent having a boiling point of 70° C. or higher, particularly 100° C. or higher, at 1 atmospheric pressure in the polyimide material to 100 ppm or lower, the bending resistance is further improved.
For example, the polyimide obtained by reprecipitation is washed in an organic solvent for washing, and then filtered. This washing process is repeated, and the polyimide is dried at 100° C. to 120° C. using a vacuum dryer to obtain the polyimide.
The organic solvent for washing is selected from among organic solvents that are highly compatible with the residual solvent contained in the polyimide obtained by reprecipitation, are poor solvents for the polyimide, and have a boiling point lower than the drying temperature of a vacuum dryer so that they can be completely volatilized by drying at 100°C to 120°C using a vacuum dryer.
For example, when the residual solvent is N,N-dimethylacetamide, N-methyl-2-pyrrolidone, etc., which are used in preparing the polyimide precursor, isopropyl alcohol, methanol, etc. are preferably used as the cleaning organic solvent. As the cleaning organic solvent, one or more kinds can be used.

The content of the polyimide in the polyimide varnish is preferably adjusted to 6% by mass or more and 15% by mass or less. By adjusting the concentration in this manner, air bubble defects are unlikely to occur even if the film has a thickness of 30 μm or more.
It is preferable to appropriately select the content of the polyimide within this range so that the viscosity described below becomes appropriate.

(1-2) Organic Solvent in Varnish The organic solvent contained in the polyimide varnish is preferably an organic solvent containing dichloromethane in an amount of 90 mass % or more of the total organic solvent.
The organic solvent other than dichloromethane, which may be contained in an amount of 10 mass % or less in the total organic solvents, can be appropriately selected according to the application from within a range that does not impair the solubility of the polyimide in the solvent.
Examples of organic solvents different from dichloromethane that may be contained in an amount of 10 mass% or less in the total organic solvent include ethylene glycol monoethyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol mono-n-butyl ether, ethylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ortho-dichlorobenzene, xylene, cresol, chlorobenzene, i-butyl acetate, i-pentyl acetate, n-butyl acetate, n-propyl acetate, n-pentyl acetate, cyclohexanol, cyclohexanone, 1.4-dioxane, tetrachloroethylene, toluene, methyl isobutyl ketone, methylcyclohexanol, methylcyclohexanone, methyl-n-butyl ketone, dichloroethane, methanol, ethanol, n-propanol, i-propanol, n-butanol, s-butanol, t-butanol, and mixed solvents thereof.
For example, from the viewpoint of reducing the residual solvent in the film, it is preferable to use at least one of methanol and ethanol, and from the viewpoint of the solubility of polyimide, it is preferable to use at least one of dichloroethane and cyclohexanone.

The organic solvent contained in the polyimide varnish of the present invention preferably contains an organic solvent other than dichloromethane in an amount of 1 mass % or more, and more preferably 2 mass % or more, of the total organic solvent, in order to exhibit the function of the added organic solvent other than dichloromethane.
Therefore, from the viewpoint of exhibiting the function of the added organic solvent different from dichloromethane, the dichloromethane content in the total organic solvents may be 99% by mass or less, or 98% by mass or less.
From the viewpoint of reducing residual solvents, the dichloromethane content in the total organic solvents is preferably 95% by mass or more, and more preferably 97% by mass or more.

(1-3) Additives The varnish may contain additives as necessary. The additives may be the same as those that may be contained as necessary in the description of the polyimide film.

(1-4) Viscosity of Varnish The polyimide varnish used in the method for producing a polyimide film used in the present invention is preferably selected so that the polyimide content in the polyimide varnish is in the range of 6% by mass to 15% by mass, and the viscosity at 25° C. measured with a rotational viscometer is 1,000 to 10,000 cps.
When the polyimide film is produced, if the viscosity of the polyimide varnish is less than 1,000 cps, the thickness uniformity of the polyimide film may deteriorate.
On the other hand, when the polyimide film is produced, if the viscosity of the polyimide varnish exceeds 10,000 cps, air bubble defects may easily occur in the polyimide film.
The viscosity of the polyimide varnish can be measured at 25° C. using a single cylinder type rotational viscometer (for example, TVB-10 type viscometer manufactured by Toki Sangyo Co., Ltd.) according to the method described in JIS K7117-1.

(2) Pre-drying Step Next, the pre-drying step includes a step of applying the polyimide varnish to a support, drying the polyimide varnish at a temperature of 40° C. or less, and peeling the coating film from the support after drying.
(2-1) Step of applying the polyimide varnish to a support In the step of applying the polyimide varnish to a support, the support to be used is not particularly limited as long as it has a smooth surface and is heat-resistant and solvent-resistant. Examples of the support include inorganic materials such as glass plates and metal plates with mirror-finished surfaces. The shape of the support is selected depending on the application method, and may be, for example, a plate, a drum, a belt, or a sheet that can be wound up on a roll.

The coating means is not particularly limited as long as it is a method capable of coating at a desired thickness, and known means such as a die coater, comma coater, roll coater, gravure coater, curtain coater, spray coater, and lip coater can be used.
The coating may be performed by a sheet-type coating apparatus or a roll-to-roll type coating apparatus.
The step of applying the polyimide varnish to the support may be carried out in a closed space in order to reduce air bubble defects, and may be followed by a preliminary drying step.

(2-2) Pre-drying step After the polyimide varnish is applied to the support, it is preferable to dry the varnish at a temperature of 40° C. or less to evaporate the organic solvent in the varnish to 15% by mass or less, thereby forming a coating film after drying.
If the initial drying temperature for evaporating the organic solvent in the varnish is more than 40° C., the coating film is likely to foam and bubble defects are likely to occur. In addition, blowing heated air during the initial drying tends to deteriorate the film thickness uniformity.
In contrast, in the present production method, the organic solvent in the varnish contains 90% by mass or more of dichloromethane having a boiling point of 40°C. Therefore, dichloromethane in the varnish can be evaporated at a temperature of 40°C or less without blowing heated air or heating to a temperature above 40°C. This makes it difficult for air bubble defects to occur in the film, and improves film thickness uniformity and the appearance of the film surface.

Drying at a temperature of 40°C or less is preferably carried out at 30°C or less, more preferably at 15°C to 25°C.
Among them, from the viewpoint of reducing bubble defects, it is preferable to leave the support coated with the polyimide varnish in an enclosed space, and evaporate dichloromethane while creating a dichloromethane atmosphere in the enclosed space. The enclosed space can be controlled so that the dichloromethane in the space has a saturated vapor pressure, and examples of the enclosed space include a method using a glove bag, a method using a glove box, and an industrial method using a continuous drying furnace to control the atmosphere immediately after coating so that the dichloromethane vapor pressure is 50% to 100% of the saturated vapor pressure, gradually reducing the dichloromethane vapor concentration, and finally removing the product from the furnace.
In the final stage of the pre-drying process in which the organic solvent in the varnish is evaporated, the dichloromethane atmosphere in the sealed space may be replaced with an inert gas atmosphere or air atmosphere to evaporate the organic solvent, in view of the mechanical strength of the film.

The pre-drying time may be adjusted as appropriate depending on the thickness of the polyimide varnish coating, the type of organic solvent other than dichloromethane, the drying temperature, etc., but is usually set to 5 to 60 minutes, preferably 10 to 40 minutes.

(2-3) Step of Peeling Off the Dried Coating Film Next, the dried coating film is peeled off from the support.
By peeling the dried coating film from the support before carrying out the main drying at high temperatures described below, the organic solvent can be evaporated from both surfaces of the film in the main drying described below, making it possible to sufficiently reduce the residual solvent.

(3) Main drying step Next, the method includes a step of fixing the end of the dried coating film peeled off from the support, and then heating the dried coating film at a temperature of 150° C. or higher. In the step of heating at a temperature of 150° C. or higher, it is preferable to remove as much residual solvent in the film as possible.

The dried coating film peeled off from the support is preferably heated after fixing the ends of the dried coating film in order to prevent shrinkage during heating at a temperature of 150° C. or higher and to improve the appearance and film thickness uniformity. If the ends of the dried coating film are not fixed, waviness is likely to occur in the polyimide film.
As a method for fixing the ends of the dried coating film peeled off from the support, for example, when the dried coating film is in the form of a single sheet, the dried coating film is sandwiched between two metal frames having roughly the same outer dimensions as the dried coating film and appropriate inner dimensions, and the two metal frames and the dried coating film are fixed with a fixing jig.
In addition, for example, when the dried coating film is in a roll shape, a method can be used in which the ends of the dried coating film are fixed using an apparatus capable of conveying a film by holding both left and right ends of a continuous film with fixing jigs such as clips.

The drying means for the dried coating film peeled off from the support is not particularly limited as long as it is possible to dry the organic solvent in a heating process at a temperature of 150° C. or higher, and for example, an oven, a drying furnace, a hot plate, infrared heating, etc. can be used.
When high-level control of optical properties is required, the solvent is preferably dried in an inert gas atmosphere. The inert gas atmosphere is preferably a nitrogen atmosphere, and the oxygen concentration is preferably 100 ppm or less, more preferably 50 ppm or less. If the heat treatment is performed in air, the film may be oxidized, resulting in coloration and a decrease in performance.

The dried coating film peeled off from the support may be heated to a maximum temperature of 150° C. or higher.
The heating temperature does not need to be as high as the heating temperature for imidization, and may be appropriately adjusted depending on the type and amount of organic solvent and residual solvent in the varnish, and the thickness of the coating film. Under normal pressure, the maximum temperature is preferably in the range of 250° C. or less, and more preferably in the range of 220° C. or less. Under reduced pressure, the maximum temperature is preferably in the range of 200° C. or less, and more preferably in the range of 180° C. or less.
The dried coating film peeled off from the support is preferably heated stepwise from room temperature to the maximum temperature. The heating rate is, for example, within the range of 3 to 50° C./min, and preferably within the range of 5 to 20° C./min. Examples of the stepwise heating include heating at 140° C. for 1 to 3 minutes, heating at 170° C. for 1 to 3 minutes, and heating at 200° C. for 5 to 20 minutes.
Even in the main drying step in which heating is performed at a maximum temperature of 150° C. or higher, the stepwise drying temperature and drying time may be appropriately adjusted depending on the type and amount of organic solvent and residual solvent in the varnish and the film thickness of the coating film.

(4) Stretching Step After the step of heating the dried coating film peeled off from the support at a temperature of 150° C. or higher, a stretching step of stretching the resulting polyimide resin coating film may be included.

In the stretching step, the stretching step of stretching from 101% to 10,000% is preferably performed while heating at 80° C. or higher, assuming that the initial dimension before stretching is 100%.
The heating temperature during stretching is preferably within the range of the glass transition temperature of the polyimide ±50° C., more preferably within the range of the glass transition temperature ±40° C. If the stretching temperature is too low, the film may not deform and sufficient orientation may not be induced. On the other hand, if the stretching temperature is too high, the orientation obtained by stretching may be relaxed by the temperature, and sufficient orientation may not be obtained.

The stretch ratio of the polyimide film is preferably 101% or more and 10,000% or less, and more preferably 101% or more and 500% or less. By stretching within the above range, the surface hardness of the resulting polyimide film can be further improved.

There are no particular limitations on the method of fixing the polyimide film during stretching, and it is selected according to the type of stretching device, etc. Also, there are no particular limitations on the stretching method, and it is possible to use a stretching device having a conveying device such as a tenter, and stretch the film while passing it through a heating furnace. The polyimide film may be stretched in only one direction (longitudinal or transverse stretching), or may be stretched in two directions by simultaneous biaxial stretching, sequential biaxial stretching, diagonal stretching, etc.

Alternatively, the polyimide film used in the present invention can be produced by the steps of obtaining a polyimide precursor (polyamic acid) in the same manner as described above, and preparing a polyimide precursor resin composition containing the polyimide precursor and an organic solvent;
applying the polyimide precursor resin composition to a support to form a polyimide precursor resin coating film;
The polyimide film may be produced by a second method for producing a polyimide film, the method including a step of imidizing the polyimide precursor by heating.

I-2. Hard Coat Layer The hard coat layer used in the present invention contains at least one polymer of a radically polymerizable compound and a cationic polymerizable compound, and an ultraviolet absorber.
Here, the "hard coat layer" refers to a layer for improving the surface hardness, and specifically refers to a layer that exhibits a hardness of "H" or more in the pencil hardness test specified in JIS 5600-5-4 (1999).
The hard coat layer used in the laminate of the present invention may further contain optional additive components as required, so long as the effects of the present invention are not impaired.

1. UV absorber For the hard coat layer used in the laminate of the present invention, as described below, a UV absorber is selected and contained in an appropriate amount in the hard coat layer so that the yellowness index (YI) of the laminate divided by the total thickness of the polyimide film and the hard coat layer, the yellowness change ΔYI of the laminate before and after the weather resistance test described below divided by the total thickness of the polyimide film and the hard coat layer, and the color change ΔE of the laminate before and after the weather resistance test described below divided by the total thickness of the polyimide film and the hard coat layer are within a specific range, or the yellowness index (YI) of the laminate divided by the thickness of the polyimide film, the yellowness change ΔYI of the laminate before and after the weather resistance test described below divided by the thickness of the polyimide film, and the color change ΔE of the laminate before and after the weather resistance test described below divided by the thickness of the polyimide film are within a specific range.

The ultraviolet absorbent used in the hard coat layer of the laminate of the present invention preferably has a peak absorption wavelength in absorbance measurement of 300 nm to 390 nm, more preferably 320 to 370 nm, and even more preferably 330 nm to 370 nm. This is because such an ultraviolet absorbent can efficiently absorb ultraviolet rays in the UVA region, and can form a hard coat layer having ultraviolet absorbing ability without causing inhibition of curing of the hard coat layer by shifting the peak wavelength from the absorption wavelength of 250 nm of the initiator for curing the hard coat layer.
The ultraviolet absorbent used in the hard coat layer used in the laminate of the present invention is preferably one having an absorption wavelength peak of 380 nm or less, since coloring due to the ultraviolet absorbent can be suppressed.
The absorbance of the ultraviolet absorbent can be measured, for example, by using an ultraviolet-visible-near infrared spectrophotometer (for example, V-7100 manufactured by JASCO Corporation).

In addition, the content of the ultraviolet absorber used in the hard coat layer used in the laminate of the present invention is preferably adjusted to 10 parts by mass or less, more preferably 7 parts by mass or less, per 100 parts by mass of the solid content of the hard coat layer, in order to suppress haze caused by mixing.

As the ultraviolet absorber used in the hard coat layer used in the laminate of the present invention, it is preferable to use one or more ultraviolet absorbers selected from the group consisting of hydroxybenzophenone-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers, because, when combined with the polyimide film, the value obtained by dividing the yellowness index (YI) of the laminate by the specific film thickness, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the weather resistance test described below by the specific film thickness, and the value obtained by dividing the color change ΔE of the laminate before and after the weather resistance test described below by the specific film thickness tend to fall within a specific range. It is further preferable to use one or more ultraviolet absorbers selected from the group consisting of hydroxybenzophenone-based ultraviolet absorbers.

The hydroxybenzophenone-based ultraviolet absorber refers to an ultraviolet absorber having a benzophenone skeleton substituted with a hydroxy group, such as 2-hydroxybenzophenone, 4-hydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octyloxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxy-4'-chlorobenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2' -dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-diallyloxybenzophenone, 2,2'-dihydroxy-4,4'-diallylbenzophenone, 2,4-dihydroxy-4-methoxy-5-sulfobenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonic acid hydrate, etc. The above hydroxybenzophenone-based ultraviolet absorbers may be of one type or of two or more types.

Among the hydroxybenzophenone-based UV absorbers, 2-hydroxybenzophenone-based UV absorbers are preferred, and one or more selected from the group consisting of benzophenone-based UV absorbers having the following general formula (A) are preferred because, when combined with the polyimide film, the value obtained by dividing the yellowness index (YI) of the laminate by the specific film thickness, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the weather resistance test described below by the specific film thickness, and the value obtained by dividing the color change ΔE of the laminate before and after the weather resistance test described below by the specific film thickness are reduced, and durability is easily improved.

（一般式（Ａ）において、Ｘ^１及びＸ^２はそれぞれ独立に、水酸基、－ＯＲ^ａ、又は炭素原子数１～１５の炭化水素基を表し、Ｒ^ａは炭素原子数１～１５の炭化水素基を表す。）

(In general formula (A), ^X1 and ^X2 each independently represent a hydroxyl group, -OR ^a , or a hydrocarbon group having 1 to 15 carbon atoms, and R ^a represents a hydrocarbon group having 1 to 15 carbon atoms.)

In the general formula (A), examples of the hydrocarbon group having 1 to 15 carbon atoms in X ¹ , X ² and R ^a include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a dodecyl group, an allyl group, and a benzyl group. The aliphatic hydrocarbon groups having 3 or more carbon atoms may each be linear or branched. The hydrocarbon group preferably has 1 to 12 carbon atoms, and more preferably has 1 to 8 carbon atoms. In terms of facilitating improvement in light transmittance, the hydrocarbon group is preferably an aliphatic hydrocarbon group, and among these, at least one of a methyl group and an allyl group is preferably used.
From the viewpoint of easily improving durability, it is preferable that X ¹ and X ² each independently represent a hydroxyl group or -OR ^a .
The one or more selected from the group consisting of benzophenone-based ultraviolet absorbers having the general formula (A) is preferably one or more selected from the group consisting of 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and 2,2'-dihydroxy-4,4'-diallyloxybenzophenone, and more preferably one or more selected from the group consisting of 2,2',4,4'-tetrahydroxybenzophenone and 2,2'-dihydroxy-4,4'-dimethoxybenzophenone.

The benzotriazole-based ultraviolet absorber refers to an ultraviolet absorber having a benzotriazole skeleton, such as 2-(2-hydroxy-4-octyloxyphenyl)-2H-benzotriazole, 2-(2,4-dihydroxyphenyl)-2H-benzotriazole, 2-(2-hydroxy-5-methylphenyl)-2H-benzotriazole, 5-chloro-2-(3,5-di-tert-butyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(3 -tert-butyl-2-hydroxy-5-methylphenyl)-5-chloro-2H-benzotriazole, 2-(3,5-di-tert-pentyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(3,5-di-tert-butyl-2-hydroxyphenyl)-2H-benzotriazole, 2-(2-hydroxy-5-tert-octylphenyl)-2H-benzotriazole and other 2-(2-hydroxyphenyl)benzotriazoles.

Among the benzotriazole-based UV absorbers, 2-(2-hydroxyphenyl)benzotriazole-based UV absorbers are preferred, and one or more selected from the group consisting of benzotriazole-based UV absorbers having the following general formula (B) are preferred because, when combined with the polyimide film, the value obtained by dividing the yellowness index (YI) of the laminate by the specific film thickness, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the weather resistance test described below by the specific film thickness, and the value obtained by dividing the color change ΔE of the laminate before and after the weather resistance test described below by the specific film thickness are reduced, and durability is easily improved.

（一般式（Ｂ）において、Ｙ^１、Ｙ^２、及びＹ^３はそれぞれ独立に、水素原子、水酸基、－ＯＲ^ｂ、又は炭素原子数１～１５の炭化水素基を表し、Ｒ^ｂは炭素原子数１～１５の炭化水素基を表し、Ｙ^１、Ｙ^２、及びＹ^３の少なくとも１つは、水酸基、－ＯＲ^ｂ、又は炭素原子数１～１５の炭化水素基を表す。Ｙ^４は、水素原子又はハロゲン原子を表す。）

(In general formula (B), Y ¹ , Y ² , and Y ³ each independently represent a hydrogen atom, a hydroxyl group, -OR ^b , or a hydrocarbon group having 1 to 15 carbon atoms, R ^b represents a hydrocarbon group having 1 to 15 carbon atoms, and at least one of Y ¹ , Y ² , and Y ³ represents a hydroxyl group, -OR ^b , or a hydrocarbon group having 1 to 15 carbon atoms. ^{Y 4} represents a hydrogen atom or a halogen atom.)

In the general formula (B), examples of the hydrocarbon group having 1 to 15 carbon atoms in Y ¹ , Y ² , and Y ³ and R ^b include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, and a dodecyl group. The aliphatic hydrocarbon group having 3 or more carbon atoms may each be linear or branched. The hydrocarbon group preferably has 1 to 12 carbon atoms, and more preferably has 1 to 8 carbon atoms. In terms of facilitating improvement in light transmittance, the hydrocarbon group is preferably an aliphatic hydrocarbon group, and is preferably a linear or branched alkyl group, and among these, a methyl group, a t-butyl group, a t-pentyl group, a n-octyl group, or a t-octyl group is preferable.

In formula (B), examples of the halogen atom in ^Y4 include a chlorine atom, a fluorine atom, and a bromine atom, and among these, a chlorine atom is preferable.

In general formula (B), in particular, when combined with the polyimide film, the value obtained by dividing the yellowness index (YI) of the laminate by the specific film thickness, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the weather resistance test described below by the specific film thickness, and the value obtained by dividing the color change ΔE of the laminate before and after the weather resistance test described below by the specific film thickness are reduced, and durability is likely to be improved. Therefore, it is preferable that Y ¹ and Y ³ represent a hydrogen atom and Y ² represents a hydroxyl group or -OR ^b , and in particular, it is preferable that Y 1 and Y 3 represent one or more selected from the group consisting of 2-(2-hydroxy-4-octyloxyphenyl)-2H-benzotriazole and 2-(2,4-dihydroxyphenyl)-2H-benzotriazole.

The content of the ultraviolet absorber may be appropriately adjusted so that, when combined with the polyimide film, the value obtained by dividing the yellowness index (YI) of the laminate by the specific film thickness, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the weather resistance test described below by the specific film thickness, and the value obtained by dividing the color change ΔE of the laminate before and after the weather resistance test described below by the specific film thickness are within a specific range. The content of the ultraviolet absorber is preferably 1 to 6 parts by mass relative to 100 parts by mass of the solid content of the hard coat layer, since it is easy to fall within the specific range. The more preferred lower limit of the content of the ultraviolet absorber is 2 parts by mass, and the more preferred upper limit is 5 parts by mass. The solid content refers to all components other than the solvent.
The content of the ultraviolet absorber is preferably 0.010 g/m 2 to 1.200 g/m 2, more preferably 0.030 g/m 2 to 0.950 g/m 2, and even more preferably 0.180 g/m 2 to 0.800 g/m 2, because when combined with the polyimide film, the value obtained by dividing the yellowness index (YI) of the laminate by the specific film thickness, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the weather resistance test described below by the specific film thickness, and the value obtained by dividing the color change ΔE of the laminate before and after the weather ^resistance test ^described below by the specific film thickness tend ^to fall within ^{specific ranges .}

2. Polymer of at least one kind of radical polymerizable compound and cationic polymerizable compound The polymer of at least one kind of radical polymerizable compound and cationic polymerizable compound can be obtained by polymerizing at least one kind of radical polymerizable compound and cationic polymerizable compound by a known method, using a polymerization initiator as necessary.

The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound is not particularly limited as long as it is a functional group capable of causing a radical polymerization reaction, but examples thereof include groups containing a carbon-carbon unsaturated double bond, and specific examples thereof include a vinyl group and a (meth)acryloyl group. Note that when the radical polymerizable compound has two or more radical polymerizable groups, these radical polymerizable groups may be the same or different.

The number of radically polymerizable groups that the radically polymerizable compound has in one molecule is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.
As the radical polymerizable compound, from the viewpoint of high reactivity, a compound having a (meth)acryloyl group is preferable. For example, polyfunctional (meth)acrylate monomers and oligomers having several (meth)acryloyl groups in the molecule and a molecular weight of several hundred to several thousand, such as urethane (meth)acrylate, polyester (meth)acrylate, epoxy (meth)acrylate, melamine (meth)acrylate, polyfluoroalkyl (meth)acrylate, silicone (meth)acrylate, etc., can be preferably used. Also, polyfunctional (meth)acrylate polymers having two or more (meth)acryloyl groups in the side chain of an acrylate polymer can be preferably used. Among them, polyfunctional (meth)acrylate monomers having two or more (meth)acryloyl groups in one molecule can be preferably used. By including a polymer of the polyfunctional (meth)acrylate monomer in the hard coat layer, the hardness of the hard coat layer can be improved, and further, the adhesion can be improved. In addition, a polyfunctional (meth)acrylate oligomer or polymer having two or more (meth)acryloyl groups in one molecule can also be preferably used. By including a polymer of the polyfunctional (meth)acrylate oligomer or polymer in the hard coat layer, the hardness and bending resistance of the hard coat layer can be improved, and further, the adhesion can be improved.
In this specification, (meth)acryloyl refers to each of acryloyl and methacryloyl, and (meth)acrylate refers to each of acrylate and methacrylate.

Examples of the polyfunctional (meth)acrylate monomer include trimethylolpropane tri(meth)acrylate, tripropylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, dipropylene glycol di(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, 1,6-hexanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, isocyanuric acid tri(meth)acrylate, isocyanuric acid di(meth)acrylate, polyester tri(meth)acrylate, polyester di(meth)acrylate, bisphenol di(meth)acrylate, diglycerin tetra(meth)acrylate, adamantyl di(meth)acrylate, isobornyl di(meth)acrylate, dicyclopentane di(meth)acrylate, tricyclodecane di(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, and those modified with PO, EO, caprolactone, etc. Among these, from the viewpoints of high reactivity, improving the hardness of the hard coat layer, and adhesion, those having 3 to 6 (meth)acryloyl groups in one molecule are preferred. For example, pentaerythritol triacrylate (PETA), dipentaerythritol hexaacrylate (DPHA), pentaerythritol tetraacrylate (PETTA), dipentaerythritol pentaacrylate (DPPA), trimethylolpropane tri(meth)acrylate, tripentaerythritol octa(meth)acrylate, tetrapentaerythritol deca(meth)acrylate, etc. can be preferably used. In particular, at least one selected from pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, and dipentaerythritol hexaacrylate, and those modified with PO, EO, or caprolactone are preferred.

In the present disclosure, the radical polymerizable compound may contain a monofunctional (meth)acrylate monomer for adjusting the hardness or viscosity of the composition for the hard coat layer, improving adhesion, etc. Examples of the monofunctional (meth)acrylate monomer include hydroxyethyl acrylate (HEA), glycidyl methacrylate, methoxypolyethylene glycol (meth)acrylate, isostearyl (meth)acrylate, 2-acryloyloxyethyl succinate, acryloylmorpholine, N-acryloyloxyethylhexahydrophthalimide, cyclohexyl acrylate, tetrahydrofuryl acrylate, isobornyl acrylate, phenoxyethyl acrylate, and adamantyl acrylate.

A cationic polymerizable compound is a compound having a cationic polymerizable group. The cationic polymerizable group of the cationic polymerizable compound is not particularly limited as long as it is a functional group capable of causing a cationic polymerization reaction, and examples thereof include an epoxy group, an oxetanyl group, and a vinyl ether group. When the cationic polymerizable compound has two or more cationic polymerizable groups, these cationic polymerizable groups may be the same or different.

The number of cationically polymerizable groups that the cationically polymerizable compound has in one molecule is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.
In addition, among the cationic polymerizable compounds, compounds having at least one of epoxy group and oxetanyl group as cationic polymerizable group are preferred, and compounds having at least two of epoxy group and oxetanyl group in one molecule are more preferred. Cyclic ether groups such as epoxy group and oxetanyl group are preferred because they are less likely to shrink during polymerization. In addition, compounds having epoxy group among cyclic ether groups have the advantage that compounds with various structures are easily available, they do not adversely affect the durability of the obtained hard coat layer, and the compatibility with radical polymerizable compounds is easily controlled. In addition, oxetanyl group among cyclic ether groups has a higher degree of polymerization and lower toxicity than epoxy group, and when the obtained hard coat layer is combined with a compound having epoxy group, it has the advantage of accelerating the network formation rate obtained from the cationic polymerizable compound in the coating film, and forming an independent network without leaving unreacted monomer in the film even in the region where it is mixed with the radical polymerizable compound.

Examples of cationic polymerizable compounds having an epoxy group include alicyclic epoxy resins obtained by epoxidizing polyglycidyl ethers of polyhydric alcohols having an alicyclic ring or compounds containing a cyclohexene ring or cyclopentene ring with a suitable oxidizing agent such as hydrogen peroxide or peracid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyhydric alcohols or their alkylene oxide adducts, polyglycidyl esters of aliphatic long-chain polybasic acids, and homopolymers and copolymers of glycidyl (meth)acrylate; glycidyl ethers produced by reacting bisphenols such as bisphenol A, bisphenol F, and hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts or caprolactone adducts, with epichlorohydrin, and novolac epoxy resins, etc., which are derived from bisphenols.

Examples of the alicyclic epoxy resins include 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate (UVR-6105, UVR-6107, UVR-6110) and bis-3,4-epoxycyclohexylmethyladipate (UVR-6128) (the names in parentheses are product names, all manufactured by Dow Chemical).

Examples of the glycidyl ether type epoxy resin include sorbitol polyglycidyl ether (Denacol EX-611, Denacol EX-612, Denacol EX-614, Denacol EX-614B, and Denacol EX-622), polyglycerol polyglycidyl ether (Denacol EX-512 and Denacol EX-521), pentaerythritol polyglycidyl ether (Denacol EX-411), diglycerol polyglycidyl ether (Denacol EX-421), and glycerol polyglycidyl ether (Denacol EX- 313, Denacol EX-314), trimethylolpropane polyglycidyl ether (Denacol EX-321), resortinol diglycidyl ether (Denacol EX-201), neopentyl glycol diglycidyl ether (Denacol EX-211), 1,6-hexanediol diglycidyl ether (Denacol EX-212), hydrodibisphenol A diglycidyl ether (Denacol EX-252), ethylene glycol diglycidyl ether (Denacol EX-810, Denacol EX-811), polyethylene glycol Coal diglycidyl ether (Denacol EX-850, Denacol EX-851, Denacol EX-821), propylene glycol glycidyl ether (Denacol EX-911), polypropylene glycol glycidyl ether (Denacol EX-941, Denacol EX-920), allyl glycidyl ether (Denacol EX-111), 2-ethylhexyl glycidyl ether (Denacol EX-121), phenyl glycidyl ether (Denacol EX-141), phenol glycidyl ether (Denacol EX-145) , butylphenyl glycidyl ether (Denacol EX-146), diglycidyl phthalate (Denacol EX-721), hydroquinone diglycidyl ether (Denacol EX-203), diglycidyl terephthalate (Denacol EX-711), glycidyl phthalimide (Denacol EX-731), dibromophenyl glycidyl ether (Denacol EX-147), dibromoneopentyl glycol diglycidyl ether (Denacol EX-221) (the names in parentheses are trade names, all of which are manufactured by Nagase ChemteX Corporation).
Other commercially available epoxy resins may also be used.

Examples of cationic polymerizable compounds having an oxetanyl group include 3-ethyl-3-hydroxymethyloxetane (OXT-101), 1,4-bis-3-ethyloxetan-3-ylmethoxymethylbenzene (OXT-121), bis-1-ethyl-3-oxetanyl methyl ether (OXT-221), 3-ethyl-3-2-ethylhexyloxymethyloxetane (OXT-212), 3-ethyl-3-phenoxymethyloxetane (OXT-211) (all of the above are trade names in parentheses, manufactured by Toa Gosei), and trade names Ethanacol EHO, Ethanacol OXBP, Ethanacol OXTP, and Ethanacol OXMA (all trade names, manufactured by Ube Industries).

The polymer of at least one of the radical polymerizable compound and the cationic polymerizable compound contained in the hard coat layer used in the present invention can be obtained, for example, by adding a polymerization initiator to at least one of the radical polymerizable compound and the cationic polymerizable compound as necessary, and polymerizing the compound by a known method.

The polymerization initiator can be appropriately selected from radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, etc. These polymerization initiators are decomposed by at least one of light irradiation and heating to generate radicals or cations, thereby promoting radical polymerization and cationic polymerization.
Therefore, there are cases where the polymerization initiator is completely decomposed and does not remain in the hard coat layer.

The radical polymerization initiator may be any one that can release a substance that initiates radical polymerization by at least one of light irradiation and heating. Examples of the photoradical polymerization initiator include imidazole derivatives, bisimidazole derivatives, N-arylglycine derivatives, organic azide compounds, titanocenes, aluminate complexes, organic peroxides, N-alkoxypyridinium salts, and thioxanthone derivatives. More specifically, examples of the photoradical polymerization initiator include 1,3-di(tert-butyldioxycarbonyl)benzophenone, 3,3',4,4'-tetrakis(tert-butyldioxycarbonyl)benzophenone, 3-phenyl-5-isoxazolone, 2-mercaptobenzimidazole, bis(2,4,5-triphenyl)imidazole, 2,2-dimethoxy-1,2-diphenyl Examples of the phenylethan-1-one (trade name Irgacure 651, manufactured by Ciba Japan Co., Ltd.), 1-hydroxy-cyclohexyl-phenyl-ketone (trade name Irgacure 184, manufactured by Ciba Japan Co., Ltd.), 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one (trade name Irgacure 369, manufactured by Ciba Japan Co., Ltd.), bis(η5-2,4-cyclopentadiene-1-yl)-bis(2,6-difluoro-3-(1H-pyrrol-1-yl)-phenyl)titanium) (trade name Irgacure 784, manufactured by Ciba Japan Co., Ltd.), and the like are not limited thereto.
In addition to the above, commercially available products can be appropriately selected and used.

The cationic polymerization initiator may be any that is capable of releasing a substance that initiates cationic polymerization by at least one of light irradiation and heating. Examples of the cationic polymerization initiator include sulfonic acid esters, imide sulfonates, dialkyl-4-hydroxysulfonium salts, arylsulfonic acid-p-nitrobenzyl esters, silanol-aluminum complexes, (η ⁶ -benzene)(η ⁵ -cyclopentadienyl)iron(II), and more specifically, benzoin tosylate, 2,5-dinitrobenzyl tosylate, N-tosiphthalic acid imide, but are not limited thereto.

Examples of initiators that can be used as both radical polymerization initiators and cationic polymerization initiators include aromatic iodonium salts, aromatic sulfonium salts, aromatic diazonium salts, aromatic phosphonium salts, triazine compounds, and iron arene complexes. More specifically, iodonium salts such as diphenyliodonium, ditolyliodonium, bis(p-tert-butylphenyl)iodonium, bis(p-chlorophenyl)iodonium chlorides, bromides, borofluorides, hexafluorophosphate salts, and hexafluoroantimonate salts, triphenylsulfonium, Examples of sulfonium salts include sulfonium chlorides, bromides, boron fluorides, hexafluorophosphate salts, and hexafluoroantimonate salts, such as 4-tert-butyltriphenylsulfonium and tris(4-methylphenyl)sulfonium, and 2,4,6-substituted-1,3,5-triazine compounds such as 2,4,6-tris(trichloromethyl)-1,3,5-triazine, 2-phenyl-4,6-bis(trichloromethyl)-1,3,5-triazine, and 2-methyl-4,6-bis(trichloromethyl)-1,3,5-triazine, but are not limited to these.

3. Optionally Added Components The hard coat layer used in the present invention may further contain optional added components, if necessary.
The optional added components are appropriately selected depending on the function to be imparted to the hard coat layer, and are not particularly limited. Examples of the optional added components include inorganic or organic fine particles for adjusting hardness or refractive index, infrared absorbing agents, antiglare agents, antifouling agents, antistatic agents, colorants such as blue pigments and purple pigments, and the like. Furthermore, the optional added components may include leveling agents, surfactants, lubricants, various sensitizers, flame retardants, adhesion promoters, polymerization inhibitors, antioxidants, light stabilizers, surface modifiers, and the like.

4. Structure of the Hard Coat Layer The thickness of the hard coat layer used in the present invention may be appropriately selected depending on the function of the hard coat layer and the application of the laminate while achieving the indicators of color tone and color change over time of the laminate described below. The thickness of the hard coat layer used in the present invention is preferably 2.0 μm or more, more preferably 3.0 μm or more, more preferably 5.0 μm or more, and even more preferably 6.0 μm or more, from the viewpoint of exerting the function of the hard coat layer, and from the viewpoint of the fact that, when combined with the polyimide film, the value obtained by dividing the yellowness index (YI) of the laminate by the specific film thickness, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the weather resistance test described below by the specific film thickness, and the value obtained by dividing the color change ΔE of the laminate before and after the weather resistance test described below by the specific film thickness tend to be within a specific range. On the other hand, from the viewpoint of the bending resistance of the laminate and the thinning, the thickness is preferably 50.0 μm or less, more preferably 30.0 μm or less, more preferably 20.0 μm or less, and even more preferably 10.0 μm or less.
The thickness of each layer in the laminate according to the present disclosure may be the average value of thicknesses at any 10 locations obtained by measuring a cross section in the thickness direction of the laminate observed with a transmission electron microscope (TEM), a scanning electron microscope (SEM), or a scanning transmission electron microscope (STEM).

Furthermore, the hard coat layer in the laminate of the present disclosure may be not only a single layer, but also a multilayer structure having two or more layers.
A preferred layer configuration in the case where the hard coat layer has two or more layers is, for example, a first hard coat layer located on the polyimide film side, and a second hard coat layer located on the opposite side of the first hard coat layer from the polyimide film side.
In the case of having two or more hard coat layers, the ultraviolet absorber may be contained in at least one layer as long as the value obtained by dividing the yellowness index (YI) of the laminate by the specific film thickness, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the weather resistance test described below by the specific film thickness, and the value obtained by dividing the color change ΔE of the laminate before and after the weather resistance test described below by the specific film thickness are within the specific ranges.
Among these, from the viewpoints of film thickness and ultraviolet absorbing ability, it is preferable that the first hard coat layer located on the polyimide film side contains an ultraviolet absorbing agent.

When the hard coat layer has two or more layers, in order to improve the surface hardness and to achieve a good balance between the bending resistance and the elastic modulus, it is preferable that the laminate structure of the hard coat layer includes a layer for satisfying the pencil hardness and a layer for satisfying the dynamic bending test (a layer for satisfying the abrasion resistance).
The layer for providing sufficient pencil hardness is preferably the first hard coat layer located on the polyimide film side.
The layer for improving the pencil hardness preferably has a Martens hardness of 500 MPa or more and 1000 MPa or less at the center of the cross section. If it is less than 500 MPa, the pencil hardness of the hard coat layer may be insufficient and the above-mentioned pencil hardness may not be satisfied, and if it exceeds 1000 MPa, the bending resistance of the laminate of the present invention may be insufficient. The more preferable lower limit of the Martens hardness at the center of the cross section of the layer for improving the pencil hardness is 600 MPa, and the more preferable upper limit is 950 MPa.

The layer for satisfying the dynamic bending test is preferably a second hard coat layer located on the opposite side of the first hard coat layer from the polyimide film side, i.e., located on the outermost surface on the opposite side from the polyimide film.
The layer for satisfying the dynamic bending test preferably has a Martens hardness of 375 MPa or more and 1000 MPa or less at the center of the cross section. If it is less than 375 MPa, the scratch resistance of the hard coat layer may be insufficient, and if it exceeds 1000 MPa, the bending resistance performance of the laminate of the present invention may be insufficient and the dynamic bending test described later may not be satisfied. The more preferred lower limit of the Martens hardness at the center of the cross section of the second hard coat layer is 450 MPa, and the more preferred upper limit is 575 MPa.

The Martens hardness of the layer for satisfying the pencil hardness is preferably greater than the Martens hardness of the layer for satisfying the dynamic bending test. By having such a relationship of Martens hardness, the laminate of the present invention has a particularly good surface hardness. This is because, when the laminate of the present invention is subjected to a pencil hardness test and pressed with a pencil under load, the deformation of the laminate of the present invention is suppressed, and scratches and dent deformation are reduced.
Examples of a method for making the Martens hardness of a layer for satisfying the pencil hardness test greater than the Martens hardness of a layer for satisfying the dynamic bending test include a method of controlling the content of silica fine particles so that more of them are contained on the first hard coat layer side.
The hard coat layer may have a single structure. In this case, it is preferable that the silica fine particles described later are unevenly distributed on the base film side of the hard coat layer, that is, the content of the silica fine particles in the hard coat layer is larger on the polyimide film side and decreases toward the side opposite to the polyimide film side.

In this specification, the term "Martens hardness" refers to the hardness measured by nanoindentation method when an indenter is pressed in to a depth of 500 nm.
In this specification, the measurement of the Martens hardness of the hard coat layer by the nanoindentation method was performed on a sample cut into 30 mm x 30 mm from the laminate of the present invention, using a "TI950 TriboIndenter" manufactured by HYSITRON. That is, a Berkovich indenter (triangular pyramid) was pressed 500 nm into the cross section of the hard coat layer of the laminate of the present invention, and the residual stress was relaxed by holding the indenter constant. The load was then removed to measure the max load after relaxation, and the Martens hardness was calculated by Pmax/A using the max load (Pmax (μN)) and the area of the indentation at a depth of 500 nm (A (nm ² )).

The layer for satisfying the pencil hardness, the first hard coat layer, preferably contains inorganic or organic fine particles, more preferably inorganic fine particles, from the viewpoint of improving hardness. In addition, as at least one polymer of a radical polymerizable compound and a cationic polymerizable compound, it is preferable to contain a polymer of the (meth)acrylate monomer.

Examples of inorganic fine particles include metal oxide fine particles such as silica (SiO ₂ ), aluminum oxide, zirconia, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide; metal fluoride fine particles such as magnesium fluoride and sodium fluoride; metal fine particles; metal sulfide fine particles; and metal nitride fine particles. Among these, metal oxide fine particles are preferred, and at least one selected from silica fine particles and aluminum oxide fine particles are more preferred, with silica fine particles being even more preferred.

The inorganic fine particles are preferably reactive inorganic fine particles having photoreactive reactive functional groups on at least a part of the particle surface that can form covalent bonds by crosslinking between the inorganic fine particles themselves or between at least one of the radical polymerizable compound and the cationic polymerizable compound. The hardness of the hard coat layer can be further improved by crosslinking between the reactive inorganic fine particles themselves or between the reactive inorganic fine particles and at least one of the radical polymerizable compound and the cationic polymerizable compound.

The reactive inorganic fine particles have at least a part of their surface coated with an organic component, and have reactive functional groups on the surface introduced by the organic component. As the reactive functional group, for example, a polymerizable unsaturated group is preferably used, more preferably a photocurable unsaturated group, and particularly preferably an ionizing radiation curable unsaturated group. Specific examples of the reactive functional group include ethylenically unsaturated bonds such as (meth)acryloyl groups, vinyl groups, and allyl groups, and epoxy groups.

The reactive silica fine particles are not particularly limited, and any conventionally known particles can be used, such as the reactive silica fine particles described in JP-A-2008-165040.
In addition, examples of commercially available reactive silica fine particles include MIBK-SD, MIBK-SDMS, MIBK-SDL, and MIBK-SDZL manufactured by Nissan Chemical Industries, Ltd., and V8802 and V8803 manufactured by JGC Catalysts and Chemicals, Ltd.

The silica fine particles may be spherical silica fine particles, but are preferably irregular silica fine particles. The spherical silica fine particles and irregular silica fine particles may be mixed. In this specification, the irregular silica fine particles refer to silica fine particles having a potato-like random unevenness on the surface.
The surface area of the above-mentioned irregular silica fine particles is larger than that of spherical silica fine particles, so by including such irregular silica fine particles, the contact area with the above-mentioned multifunctional (meth)acrylate etc. is increased, and the hardness (pencil hardness) of the above-mentioned hard coat layer can be made more excellent.Whether it is the above-mentioned irregular silica fine particles or not can be confirmed by observing the cross section of the above-mentioned first hard coat layer with an electron microscope.
The average particle size of the inorganic fine particles is preferably 5 nm or more, and more preferably 10 nm or more, from the viewpoint of improving hardness, while it is preferably 200 nm or less, more preferably 100 nm or less, and preferably 50 nm or less, from the viewpoint of transparency.
The average particle size of the inorganic fine particles can be measured by observing the cross section of the functional layer with an electron microscope, and the average particle size is the average of the particle sizes of 10 particles selected arbitrarily.The average particle size of the irregular silica fine particles is the average value of the maximum value (long axis) and the minimum value (short axis) of the distance between two points on the periphery of the irregular silica fine particles that appear in the cross section of the hard coat layer with a microscope.

The hardness (Martens hardness) of the hard coat layer can be controlled by controlling the size and amount of the inorganic fine particles. For example, when forming the first hard coat layer, the silica fine particles are preferably present in an amount of 25 to 60 parts by mass per 100 parts by mass of the resin component.

The layer for satisfying the dynamic bending test, the second hard coat layer, preferably contains at least the polymer of the (meth)acrylate monomer as at least one polymer of the radical polymerizable compound and the cationic polymerizable compound, and further preferably contains at least one polymer of the multifunctional (meth)acrylate oligomer and polymer. By containing at least one polymer of the multifunctional (meth)acrylate oligomer and polymer, the hard coat layer can improve the hardness and bending resistance, and further improve the adhesion.
As the polyfunctional (meth)acrylate oligomer, one or more polyfunctional (meth)acrylate oligomers selected from the group consisting of urethane (meth)acrylate, polyester (meth)acrylate, and epoxy (meth)acrylate can be preferably used, and among them, a polyfunctional (6 or more functional) urethane (meth)acrylate having a weight average molecular weight of 1000 to less than 10,000 is preferred. Also preferably used is a polyfunctional (meth)acrylate polymer having two or more (meth)acryloyl groups in the side chain of an acrylate polymer.

When the laminate according to the present disclosure has two or more hard coat layers, the total thickness of the hard coat layers may be similar to the thickness of the hard coat layers.
The thickness of the first hard coat layer is preferably 2.0 to 40.0 μm, and the thickness of the second hard coat layer is preferably 0.5 to 15.0 μm. If the thickness is less than the lower limit of each layer, the hardness of the hard coat layer may be significantly reduced, and if the thickness exceeds the upper limit of each layer, it becomes difficult to coat the coating liquid for forming the hard coat layer, and the processability may be deteriorated due to the thickness being too large.
The more preferred lower limit of the thickness of the first hard coat layer is 5.0 μm and the more preferred upper limit is 35.0 μm. The more preferred lower limit of the thickness of the second hard coat layer is 1.0 μm and the more preferred upper limit is 10.0 μm.

The polymers of at least one of the radically polymerizable compounds and the cationic polymerizable compounds contained in the hard coat layer used in the present invention can be analyzed using a Fourier transform infrared spectrophotometer (FTIR) or a pyrolysis gas chromatograph (GC-MS), and the decomposition products of the polymers can be analyzed using a combination of high performance liquid chromatography, a gas chromatograph mass spectrometer, NMR, elemental analysis, XPS/ESCA, and TOF-SIMS.

I-3. Structure of the Laminate The laminate of the present invention is not particularly limited as long as it has the polyimide film and the hard coat layer, and may be one in which the hard coat layer is laminated on one side of the polyimide film, or one in which the hard coat layer is laminated on both sides of the polyimide film from the viewpoint of preventing curling.
From the viewpoint of impact resistance, the laminate of the present invention may contain two or more layers of the polyimide film, for example, a composite film in which two of the polyimide films are laminated with an adhesive layer.
Furthermore, the laminate of the present invention may have, in addition to the polyimide film and the hard coat layer, another layer such as a primer layer for improving the adhesion between the polyimide film and the hard coat layer, as long as the effect of the present invention is not impaired. The laminate of the present invention may be one in which the polyimide film and the hard coat layer are laminated via another layer such as a primer layer, or one in which the polyimide film and the hard coat layer are adjacent to each other.

The laminate of the present invention may further include a glass substrate having a thickness of 100 μm or less.
When the laminate of the present invention further has a glass substrate having a thickness of 100 μm or less, it can be considered that a part of the thickness of a conventional glass substrate is replaced by the polyimide film and hard coat layer of the present invention. As glass becomes thinner, it becomes more fragile and its impact resistance is dramatically deteriorated, but such a laminate of the present invention has advantages such as hardness and optical properties of a flexible ultra-thin glass substrate, while suppressing the fracturing of the ultra-thin glass substrate and improving its impact resistance. Since such a laminate of the present invention is a laminate of the polyimide film and hard coat layer of the present invention described above on a flexible glass substrate having a thickness of 100 μm or less, it is a laminate having excellent surface hardness and impact resistance, good bending resistance, and durability.
When the laminate of the present invention further has a glass substrate having a thickness of 100 μm or less, the thickness of the polyimide film may be appropriately selected, but is preferably 5 μm to 60 μm, more preferably 10 μm to 50 μm, and even more preferably 15 μm to 40 μm. By making the thickness of the polyimide film relatively thin within the above range, the flexibility of the laminate can be increased while suppressing cracking of the glass substrate, and the bending resistance can be improved.

The glass constituting the glass substrate is not particularly limited, but is preferably chemically strengthened glass from the viewpoint of bending resistance. Chemically strengthened glass is preferable because it has excellent mechanical strength and can be made thinner accordingly. Chemically strengthened glass is typically glass whose mechanical properties have been strengthened by a chemical method by partially exchanging ion species, such as replacing sodium with potassium, near the surface of the glass, and has a compressive stress layer on the surface.
Examples of glasses constituting the chemically strengthened glass substrate include aluminosilicate glass, soda lime glass, borosilicate glass, lead glass, alkali barium glass, and aluminoborosilicate glass.
Commercially available chemically strengthened glass substrates include, for example, Gorilla Glass from Corning and Dragontrail from AGC. In addition, as the chemically strengthened glass substrate, for example, those described in JP-A-2019-194143 can also be used.
The thickness of the glass substrate can be preferably 15 μm or more and 100 μm or less, more preferably 20 μm or more and 90 μm or less, and even more preferably 25 μm or more and 80 μm or less, from the viewpoint of bending resistance. By making the thickness of the glass substrate thin in the above range, good flexibility can be obtained and sufficient hardness can be obtained. In addition, curling of the laminate can be suppressed. Furthermore, it is preferable in terms of weight reduction of the laminate.

When the laminate of the present invention further comprises a glass substrate having a thickness of 100 μm or less, it is preferable that the laminate comprises the glass substrate, the polyimide film, and the hard coat layer in this order.
When the laminate of the present invention further has a glass substrate having a thickness of 100 μm or less, in addition to the glass substrate, the polyimide film, and the hard coat layer, other layers such as a primer layer for improving the adhesion between the glass substrate and the polyimide film may be included within a range that does not impair the effects of the present invention. The laminate of the present invention may be one in which the glass substrate and the polyimide film are laminated via another layer such as a primer layer, or the glass substrate and the polyimide film are adjacent to each other.

The laminate of the present invention may further include an impact-resistant layer, a fingerprint prevention layer, an adhesive or pressure-sensitive adhesive layer, a protective layer, etc. As the other conventionally known functional layers such as the primer layer, the impact-resistant layer, the fingerprint prevention layer, the adhesive or pressure-sensitive adhesive layer, and the protective layer, conventionally known layers can be appropriately selected and used.
Alternatively, the laminate of the present invention may further comprise a metal foil.
In the laminate of the present invention, the adhesive layer and the primer layer may contain a colorant in order to adjust the YI.
In addition, in order to adjust the transmittance, the laminate of the present invention may further have a layer having a refractive index lower than that of the polyimide film on the side of the polyimide film on which the hard coat layer is not formed, and the low refractive index layer may contain inorganic fine particles. Furthermore, in order to adjust the YI, the laminate may contain a colorant including a blue pigment or a purple pigment.

The total thickness (film thickness) of the laminate of the present invention may be appropriately selected depending on the application, but from the viewpoint of strength, it is preferably 10 μm or more, and more preferably 40 μm or more. On the other hand, from the viewpoint of bending resistance, it is preferably 300 μm or less, and more preferably 250 μm or less.

I-4. Properties of the Laminate The laminate of the present invention has a yellowness index (YI) calculated in accordance with JIS K7373-2006 divided by the total film thickness (μm) of the polyimide film and the hard coat layer of less than 0.12.
In addition, in the laminate of the present invention, the yellowness index (YI) of the laminate calculated in accordance with JIS K7373-2006 divided by the film thickness (μm) of the polyimide film is less than 0.15.
Since the yellowness index (YI) of the laminate of the present invention is small within the above-mentioned predetermined range, coloring during production is suppressed, and transparency can be increased.
It is more preferable that the laminate of the present invention has a yellowness index (YI) calculated in accordance with JIS K7373-2006 divided by the total film thickness (μm) of the polyimide film and the hard coat layer of less than 0.11.
In addition, the laminate of the present invention preferably has a yellowness index (YI) of the laminate calculated in accordance with JIS K7373-2006 divided by the film thickness (μm) of the polyimide film of 0.14 or less.
The yellowness index (YI) of the laminate calculated in accordance with JIS K7373-2006 can be measured in the same manner as the yellowness index (YI value) of the polyimide film calculated in accordance with JIS K7373-2006.
In the present invention, the values obtained by dividing the yellowness index (YI value), the yellowness change ΔYI, and the color change ΔE by the specific film thickness (μm) are rounded to two decimal places in accordance with Rule B of JIS Z8401:1999.

In the laminate of the present invention, a value obtained by dividing a yellowness change ΔYI of the laminate before and after the following weather resistance test by a total film thickness (μm) of the polyimide film and the hard coat layer is less than 0.11, and a value obtained by dividing a color change ΔE of the laminate before and after the following weather resistance test by a total film thickness (μm) of the polyimide film and the hard coat layer is less than 0.09.
In addition, in the laminate of the present invention, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the following weather resistance test by the film thickness (μm) of the polyimide film is less than 0.13, and the value obtained by dividing the color change ΔE of the laminate before and after the following weather resistance test by the film thickness (μm) of the polyimide film is less than 0.11.
In the laminate of the present invention, the yellowness index change ΔYI and color change ΔE before and after the weather resistance test described below are small within the above-mentioned specified ranges, and therefore deterioration of the polyimide film over time is suppressed, the balance between bending resistance and elastic modulus is maintained, and the laminate has high durability.
In the laminate of the present invention, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the following weather resistance test by the total film thickness (μm) of the polyimide film and the hard coat layer is preferably less than 0.10, and more preferably less than 0.09.
In the laminate of the present invention, the value obtained by dividing the color change ΔE of the laminate before and after the following weather resistance test by the total film thickness (μm) of the polyimide film and the hard coat layer is preferably less than 0.08, more preferably less than 0.07.
In addition, in the laminate of the present invention, the value obtained by dividing the yellowness change ΔYI of the laminate before and after the following weather resistance test by the film thickness (μm) of the polyimide film is preferably less than 0.12, and more preferably less than 0.11.
In the laminate of the present invention, the color change ΔE of the laminate before and after the following weather resistance test divided by the film thickness (μm) of the polyimide film is preferably less than 0.10, more preferably less than 0.09.
(Weather resistance test)
Using a weather resistance tester conforming to JIS K5600-7-8 (e.g., a QUV weather resistance tester (model number QUV) manufactured by Q-LAB), the laminate is irradiated for 96 hours using a UVA (340) lamp with a spectral distribution similar to sunlight from 365 nm to 295 nm, with the output set to 0.63 W/m ² /nm.
The laminate before and after the weather resistance test is measured for yellowness index (YI) calculated in accordance with JIS K7373-2006, and L ^* , a ^* , and b ^* in the CIE L ^* a ^* b ^* color system using light source C.
ΔYI = YI after test - YI before test
ΔE={(L ^* after test−L ^* before test) ² +(a ^* after test−a ^* before test) ² +(b ^* after test−b ^* before test) ² } ^1/2
L ^* , a ^* , and b ^* in the CIE L ^* a ^* b ^* color system using a C light source can be measured in accordance with JIS K7373-2006 using an ultraviolet-visible-near infrared spectrophotometer (e.g., V-7100 manufactured by JASCO Corporation) based on the transmittance measured at 1 nm intervals in the range of 250 nm to 800 nm using auxiliary illuminant C and a 2-degree visual field by a spectrophotometric colorimetric method.

The laminate of the present invention preferably has a pencil hardness of H or more on the surface on the hard coat layer side, more preferably 2H or more, and even more preferably 3H or more.
The pencil hardness of the laminate of the present invention can be measured in the same manner as in the above-mentioned method for measuring the pencil hardness of a polyimide film, except that the load is 9.8 N.

The laminate of the present invention has a total light transmittance measured in accordance with JIS K7361-1 of preferably 85.0% or more, more preferably 88.0% or more, and even more preferably 90.0% or more. Since the laminate has such a high transmittance, it has good transparency and can be used as a substitute for glass.
The total light transmittance of the laminate of the present invention can be measured in the same manner as the total light transmittance of the polyimide film, which is measured in accordance with JIS K7361-1.

The laminate of the present invention preferably has a transmittance of 8% or less, more preferably 6% or less, and even more preferably 4% or less, for light having a wavelength of 380 nm. If the transmittance exceeds 8%, when the laminate of the present invention is used as a display surface material, it may be easily deteriorated by exposure to ultraviolet rays.
The transmittance can be measured in accordance with JIS K7373-2006 using an ultraviolet-visible-near infrared spectrophotometer (V-7100 manufactured by JASCO Corporation), and is the arithmetic average value of values obtained by measuring three times.

The haze value of the laminate of the present invention is preferably 1.0 or less, and more preferably 0.5 or less, from the viewpoint of light transmittance.
The haze value of the laminate of the present invention can be measured in the same manner as the haze value of the polyimide film.

In addition, the laminate of the present invention preferably has a composite elastic modulus of 5.3 GPa or more of the laminated polyimide film. In this way, when the composite elastic modulus of the polyimide film is high, sufficient surface hardness can be maintained even at room temperature, and it can be used as a surface material or a substrate. The composite elastic modulus is more preferably 5.5 GPa or more, even more preferably 5.7 GPa or more, and even more preferably 6.0 GPa or more. On the other hand, the composite elastic modulus may be 10 GPa or less from the viewpoint of improving bending resistance.
The composite elastic modulus of the laminated polyimide film can be measured by the method described in the Examples section below.

I-5. Uses of the laminate The uses of the laminate of the present invention are not particularly limited, and it can be used as a surface material or other member where glass products such as thin plate glass have been used in the past. The laminate of the present invention has a good balance between bending resistance and elastic modulus, and has durability, so it can be suitably used as a display surface material that can accommodate curved surfaces.
Specifically, the laminate of the present invention can be suitably used, for example, as a substrate or surface material for flexible displays, such as a thin, bendable, flexible-type organic EL display, a mobile terminal such as a smartphone or a wristwatch-type terminal, a display device inside an automobile, a flexible panel used in a wristwatch, etc. The laminate of the present invention can also be applied to members for image display devices such as liquid crystal displays and organic EL displays, members for touch panels, flexible printed circuit boards, members for solar cell panels such as surface protective films and substrate materials, members for optical waveguides, other semiconductor-related members, etc.
Applications of the laminate of metal foil, polyimide film and hard coat layer include antennas, wiring, electromagnetic wave shielding materials and the like.

I-6. Method for Producing Laminate The method for producing the laminate of the present invention can be, for example,
forming a coating film of a hard coat layer-forming composition containing an ultraviolet absorber and at least one of a radical polymerizable compound and a cationic polymerizable compound on at least one surface of the polyimide film used in the present invention;
and forming a hard coat layer by curing the coating film.

As described above, the concentration of the ultraviolet absorber in the hard coat layer-forming composition and the thickness of the hard coat layer are adjusted so that the YI/specific film thickness, ΔYI/specific film thickness, and ΔE/specific film thickness of the laminate are within the specific ranges.

The composition for forming a hard coat layer contains at least one of a radically polymerizable compound and a cationic polymerizable compound, and an ultraviolet absorber, and may further contain a polymerization initiator, a solvent, an additive, and the like, as necessary.
Here, the ultraviolet absorber, the radical polymerizable compound, the cationic polymerizable compound, the polymerization initiator, and the additives contained in the hard coat layer forming composition can be the same as those described in the hard coat layer, and the solvent can be appropriately selected from known solvents.

As a method for forming a coating film of the composition for forming a hard coat layer on at least one surface of a polyimide film, for example, a method of coating the composition for forming a hard coat layer on at least one surface of a polyimide film by a known coating means can be mentioned.
The coating means is not particularly limited as long as it is a method capable of coating with a desired film thickness, and examples thereof include the same means as those for coating the polyimide varnish onto the support.

The coating film of the curable resin composition for the hard coat layer is dried as necessary to remove the solvent. Examples of drying methods include drying under reduced pressure, drying by heating, and a combination of these drying methods. When drying is performed under normal pressure, it is preferable to dry at 30°C or higher and 110°C or lower.

The hard coat layer curable resin composition is applied to a coating film, which is dried as necessary, and then cured by at least one of light irradiation and heating depending on the polymerizable groups of the radical polymerizable compound and the cationic polymerizable compound contained in the curable resin composition, to form a hard coat layer containing at least one polymer of the radical polymerizable compound and the cationic polymerizable compound on at least one surface of the polyimide film.

For light irradiation, ultraviolet light, visible light, electron beams, ionizing radiation, etc. are mainly used. For ultraviolet curing, ultraviolet light emitted from light beams of ultra-high pressure mercury lamps, high pressure mercury lamps, low pressure mercury lamps, carbon arcs, xenon arcs, metal halide lamps, etc. are used. The irradiation amount of the energy ray source is about 50 to 5000 mJ/ ^cm2 as the cumulative exposure amount at an ultraviolet wavelength of 365 nm.
When heating is performed, the treatment is usually performed at a temperature of 40° C. or higher and 120° C. or lower. Alternatively, the reaction may be performed by leaving the mixture at room temperature (25° C.) for 24 hours or more.

The configuration that may be further included in the laminate can be manufactured in the same manner as the conventionally known manufacturing method.

When the laminate of the present invention has a glass substrate, examples of the manufacturing method include a method of applying a polyimide varnish containing the specific polyimide and an organic solvent onto the glass substrate and drying it, and a method of applying a polyimide precursor composition containing a polyimide precursor (polyamic acid) and an organic solvent onto the glass substrate, and then imidizing the polyimide precursor by heat treatment.

In the case where the laminate of the present invention has the glass substrate, the manufacturing method includes the steps of:
Providing the glass substrate;
A step of preparing a polyimide varnish containing the polyimide used in the present invention and an organic solvent, the polyimide content in the polyimide varnish being 6% by mass or more and 15% by mass or less, and having a viscosity of 1,000 to 10,000 cps at 25°C as measured by a rotational viscometer;
It is preferable to have a step of applying the polyimide varnish onto the glass substrate, a first drying step of drying the coating film at a temperature of 100°C or less, and a second drying step of heating the dried coating film at a temperature of 150°C or more, since this makes it easy to obtain a laminate that is less susceptible to bubble defects and has good thickness uniformity, and makes it easy to reduce the amount of residual solvent.

In particular, when an organic solvent having a boiling point of 120° C. or higher is used, it is preferable to dry the organic solvent by providing two or more drying temperature stages at a temperature of 100° C. or lower, since this can suppress skinning on the coating film surface and suppress bubbles due to bumping of the organic solvent in the coating film. An example of an embodiment having two or more drying temperature stages at a temperature of 100° C. or lower is an embodiment in which the first stage is drying at 80° C. and the second stage is further drying at 100° C.
In addition, the heating at 150° C. or higher in the second drying step is preferably performed at two or more heating temperatures between 150° C. and 250° C., since this makes it difficult for bubble defects to occur and makes it easy to reduce the amount of residual solvent. An example of a mode in which two or more heating temperatures are performed at a temperature between 150° C. and 250° C. is a mode in which the first stage is drying at 150° C., the second stage is drying at 180° C., the third stage is drying at 230° C., and the fourth stage is further drying at 250° C.
For example, when the thickness of the coating film after drying is less than 50 μm, it is preferable to set the holding time at each stage to 10 minutes or more and less than 60 minutes, and when the thickness of the coating film after drying is 50 μm or more and 100 μm or less, it is preferable to set the holding time at each stage to 30 minutes or more and less than 90 minutes.

II. Display Surface Material The display surface material of the present invention includes the laminate of the present invention described above.
The display surface material of the present invention may be the laminate of the present invention described above.

The display surface material of the present invention is used, for example, as a display surface material by being arranged on the surface of various displays. As with the laminate of the present invention described above, the display surface material of the present invention has a good balance between bending resistance and elastic modulus, and is durable, so it can be particularly suitably used for flexible displays.

The display surface material of the present invention can be used in various known displays, and although there are no particular limitations, it can be used in, for example, the displays described in the applications of the laminate used in the present invention.

In the display surface material of the present invention, the surface that becomes the outermost surface after the laminate is placed on the surface of a display may be the surface on the polyimide film side or the surface on the hard coat layer side. In particular, it is preferable to place the display surface material of the present invention so that the surface on the hard coat layer side becomes the outermost surface. In addition, the display surface material of the present invention may have a fingerprint prevention layer on the outermost surface.

The method for placing the display surface material of the present invention on the surface of a display is not particularly limited, but may be, for example, a method using an adhesive layer. The adhesive layer may be any conventional adhesive layer that can be used to adhere a display surface material.

III. Touch Panel Member The touch panel member of the present invention comprises the laminate of the present invention described above,
A transparent electrode including a plurality of conductive portions disposed on one surface side of the laminate;
and a plurality of lead wires electrically connected to at least one end of the conductive portion.

Since the touch panel member of the present invention comprises the laminate of the present invention described above, it has excellent bending resistance and is particularly suitable for use in flexible displays, and also has excellent optical durability.
The laminate of the present invention used in the touch panel member of the present invention preferably has hard coat layers containing at least one polymer of a radically polymerizable compound and a cationic polymerizable compound adjacent to both sides of the polyimide film.
Furthermore, although there is no particular limitation, the touch panel member of the present invention is preferably one in which the transparent electrode is laminated in contact with one surface side of the laminate.
The touch panel member of the present invention can be used, for example, by being arranged on the surface of various displays. Also, the touch panel member of the present invention and the laminate of the present invention as a surface material can be arranged in this order on the surface of various displays.

FIG. 3 is a schematic plan view of one surface of an example of the touch panel member of the present invention, FIG. 4 is a schematic plan view of the other surface of the touch panel member shown in FIG. 3, and FIG. 5 is an A-A' cross-sectional view of the touch panel member shown in FIG. 3 and FIG. 4. The touch panel member 20 shown in FIG. 3, FIG. 4, and FIG. 5 includes the laminate 10 of the present invention, a first transparent electrode 4 arranged in contact with one surface of the laminate 10, and a second transparent electrode 5 arranged in contact with the other surface of the laminate 10. In the first transparent electrode 4, a plurality of first conductive parts 41, which are strip-shaped electrode pieces extending so as to extend in the x-axis direction, are arranged at predetermined intervals. A first take-out wire 7 electrically connected to the first conductive part 41 is connected to the first conductive part 41 at one of the ends in the longitudinal direction. It is preferable to provide a first terminal 71 for electrically connecting to an external circuit at the end of the first take-out wire 7 extended to the edge 21 of the laminate 10. The first conductive portion 41 and the first lead wire 7 are generally connected in a non-active area 23 that is located outside an active area 22 that is visible to a user of the touch panel.
3, a connection structure in which a connection portion 24 is interposed between the first conductive portion 41 and the first output wire 7 can be adopted. Specifically, the connection portion 24 can be formed by extending a layer of a conductive material from a longitudinal end of the first conductive portion 41 to a predetermined position within the inactive area 23. Furthermore, by overlapping at least a portion of the first output wire 7 on the connection portion 24, a connection structure between the first conductive portion 41 and the first output wire 7 can be formed.
The connection between the first conductive portion 41 and the first lead wire 7 is not limited to the structure forming the connection portion 24 as shown in Fig. 3. For example, although not shown, the longitudinal end of the first conductive portion 41 may be extended to the inactive area 23, and the first lead wire 7 may be caused to ride up onto the end of the first conductive portion 41 that has been extended to the inactive area 23 within the inactive area 23, thereby electrically connecting the two.
In addition, Figure 3 shows a configuration in which one of the longitudinal ends of the first conductive portion 41 is connected to the first output wire 7, but in the present invention, the first output wire 7 may be electrically connected to both longitudinal ends of one first conductive portion 41, respectively.

4, the touch panel member 20 includes a second transparent electrode 5 arranged in contact with the other surface of the laminate 10. In the second transparent electrode 5, second conductive portions 51, which are a plurality of rectangular electrode pieces extending so as to extend in the y-axis direction, are arranged at predetermined intervals in the x-axis direction.
A second output wire 8 is connected to the second conductive portion 51 at one of its longitudinal ends, and is electrically connected to the second conductive portion 51 .
The second output wire 8 is extended to a position on the edge 21 of the laminate 10 to which the above-mentioned first output wire 7 is extended, so as not to overlap with the first terminal 71 .
It is preferable to provide a second terminal 81 at the end of the second output wire 8 extending to the edge 21 of the laminate 10 for electrical connection to an external circuit.
The electrical connection between the second conductive portion 51 and the second output wire 8 can be made in the same manner as the electrical connection between the first output wire 7 and the first conductive portion 41 .

The pattern in which the first take-out wire 7 is a long wire and the second take-out wire 8 is a short wire as shown in Figures 3 and 4 is merely one embodiment of the touch panel member of the present invention. For example, it is also possible to have a pattern in which the first take-out wire 7 is a short wire and the second take-out wire 8 is a long wire. Furthermore, the extension direction of the first take-out wire 7 and the extension direction of the second take-out wire 8 are not limited to the directions shown in Figures 3 and 4, and can be designed arbitrarily.

The conductive portion of the touch panel member of the present invention can be appropriately selected and applied from those constituting the transparent electrode in the touch panel member, and the pattern of the conductive portion is not limited to those shown in Fig. 3 and Fig. 4. For example, a transparent electrode pattern capable of detecting a change in capacitance due to contact or a state close to contact with a finger or the like by a capacitance method can be appropriately selected and applied.
The material of the conductive portion is preferably a light-transmitting material, and examples thereof include, but are not limited to, indium oxide-based transparent electrode materials mainly composed of indium tin oxide (ITO), indium oxide, indium zinc oxide (IZO), etc., transparent conductive films mainly composed of tin oxide (SnO ₂ ), zinc oxide (ZnO), etc., conductive polymer compounds such as polyaniline and polyacetylene, etc. In addition, the first conductive portion 41 and the second conductive portion 51 may be formed using the same type of conductive material, or may be formed using different types of materials. In particular, forming the first conductive portion 41 and the second conductive portion 51 using the same type of conductive material is preferable from the viewpoint of more effectively suppressing the occurrence of warping and distortion of the touch panel member.
The thickness of the conductive portion is not particularly limited, but when the conductive portion is formed by photolithography, for example, it can generally be formed to be about 10 nm to 500 nm.

The conductive material constituting the take-out wire of the touch panel member of the present invention may or may not be optically transparent. In general, the take-out wire can be formed using a metal material such as silver or copper having high conductivity. Specifically, examples of the metal include a metal element, a metal complex, a metal and metal compound complex, and a metal alloy. Examples of the metal element include a metal element such as silver, copper, gold, chromium, platinum, or aluminum. Examples of the metal complex include MAM (a three-layer structure of molybdenum, aluminum, and molybdenum). Examples of the metal and metal compound complex include a laminate of chromium oxide and chromium. Examples of the metal alloy include silver alloy and copper alloy. Examples of the metal alloy include APC (an alloy of silver, palladium, and copper). In addition, the take-out wire may include the above-mentioned metal material mixed with an appropriate resin component.
In the touch panel member of the present invention, the terminals provided at the ends of the extraction lines can be formed, for example, using the same material as the extraction lines.
The thickness and width of the take-out wire are not particularly limited, but for example, when the take-out wire is formed by a photolithography method, the thickness is generally about 10 nm to 1000 nm, and the width is generally about 5 μm to 200 μm. On the other hand, when the take-out wire is formed by printing such as screen printing, the thickness is generally about 5 μm to 20 μm, and the width is generally about 20 μm to 300 μm.

The touch panel member of the present invention is not limited to the forms shown in Figures 3 to 5 and may be configured, for example, such that a first transparent electrode and a second transparent electrode are laminated on separate laminates.
6 and 7 are schematic plan views showing an example of a conductive member including a laminate of the present invention. A first conductive member 201 shown in FIG. 6 has a laminate 10 of the present invention and a first transparent electrode 4 arranged in contact with one surface of the laminate 10, and the first transparent electrode 4 has a plurality of first conductive parts 41. A second conductive member 202 shown in FIG. 7 has a laminate 10' of the present invention and a second transparent electrode 5 arranged in contact with one surface of the laminate 10', and the second transparent electrode 5 has a plurality of second conductive parts 51.
FIG. 8 is a schematic cross-sectional view showing another example of the touch panel member of the present invention, and the touch panel member 20' shown in FIG. 8 includes the first conductive member 201 shown in FIG. 6 and the second conductive member 202 shown in FIG. 7. In the touch panel member 20', the surface of the first conductive member 201 that does not have the first transparent electrode 4 and the surface of the second conductive member 202 that has the transparent electrode 5 are bonded together via an adhesive layer 6. In the present invention, for example, as an adhesive layer for bonding the laminate of the present invention and the touch panel member of the present invention, an adhesive layer for bonding the touch panel members of the present invention to each other, and an adhesive layer for bonding the touch panel member of the present invention and a display device, a conventionally known adhesive layer used in an optical member can be appropriately selected and used. In the conductive member used in the touch panel member of the present invention, the configurations and materials of the transparent electrodes, the take-out lines, and the terminals can be the same as those of the transparent electrodes, the take-out lines, and the terminals used in the touch panel member of the present invention described above.

IV. Liquid Crystal Display Device The liquid crystal display device of the present invention comprises the laminate of the present invention described above, and a liquid crystal display section disposed on one surface side of the laminate and having a liquid crystal layer between opposing substrates.

The liquid crystal display device of the present invention includes the above-mentioned laminate of the present invention, and therefore has excellent bending resistance and can be particularly suitably used for flexible displays, and also has excellent optical durability.
The laminate of the present invention used in the liquid crystal display device of the present invention preferably has hard coat layers containing at least one polymer of a radically polymerizable compound and a cationic polymerizable compound adjacent to both sides of the polyimide film.
The liquid crystal display device of the present invention may include the above-mentioned touch panel member of the present invention.
The counter substrate of the liquid crystal display device of the present invention may include the laminate of the present invention.

Figure 9 is a schematic cross-sectional view showing an example of a liquid crystal display device of the present invention. The liquid crystal display device 100 shown in Figure 9 has the laminate 10 of the present invention, a touch panel member 20 having a first transparent electrode 4 on one side of the laminate 10' of the present invention and a second transparent electrode 5 on the other side, and a liquid crystal display unit 30. In the liquid crystal display device 100, the laminate 10 is used as a surface material, and the laminate 10 and the touch panel member 20 are bonded together via an adhesive layer 6.

The liquid crystal display section used in the liquid crystal display device of the present invention has a liquid crystal layer formed between opposing substrates, and can adopt a configuration used in conventionally known liquid crystal display devices.
The driving method of the liquid crystal display device of the present invention is not particularly limited, and any driving method generally used in liquid crystal display devices can be adopted, such as the TN method, the IPS method, the OCB method, and the MVA method.
The counter substrate used in the liquid crystal display device of the present invention can be appropriately selected depending on the driving method of the liquid crystal display device, and may include the polyimide film or laminate used in the present invention.
As the liquid crystal constituting the liquid crystal layer, various liquid crystals having different dielectric anisotropy and mixtures thereof can be used according to the driving method of the liquid crystal display device of the present invention.
The liquid crystal layer can be formed by a method generally used for producing liquid crystal cells, such as a vacuum injection method, a liquid crystal dropping method, etc. After the liquid crystal layer is formed by the above method, the liquid crystal cell is gradually cooled to room temperature, whereby the enclosed liquid crystal can be aligned.
In the liquid crystal display device of the present invention, a colored layer of multiple colors or a light-shielding portion for defining pixels may be further provided between the opposing substrates. The liquid crystal display unit may have a backlight unit having light-emitting elements and phosphors on the outer side of the opposing substrates, opposite to the side where the touch panel member is located. The opposing substrates may each have a polarizing plate on their outer surfaces.

10 is a schematic cross-sectional view showing another example of the liquid crystal display device of the present invention. The liquid crystal display device 200 shown in FIG. 10 has the laminate 10 of the present invention, a first conductive member 201 having a first transparent electrode 4 on one side of the laminate 10' of the present invention, a touch panel member 20' having a second conductive member 202 having a second transparent electrode 5 on one side of the laminate 10" of the present invention, and a liquid crystal display unit 30. In the liquid crystal display device 200, the laminate 10 and the first conductive member 201, and the first conductive member 201 and the second conductive member 202 are each bonded together via an adhesive layer 6. The configuration of the touch panel member 20' can be the same as the configuration of the touch panel member 20' shown in FIG. 8, for example. The conductive member used in the liquid crystal display device of the present invention can be the same as the conductive member used in the touch panel member of the present invention.

V. Organic Electroluminescent Display Device The organic electroluminescent display device of the present invention comprises the laminate of the present invention described above, and an organic electroluminescent display unit disposed on one surface side of the laminate and having an organic electroluminescent layer between opposing substrates.

The organic electroluminescent display device of the present invention includes the laminate of the present invention described above, and therefore has excellent bending resistance, and is therefore particularly suitable for use as a flexible display, and has excellent optical properties.
The laminate of the present invention used in the organic electroluminescent display device of the present invention preferably has a hard coat layer containing at least one polymer of a radically polymerizable compound and a cationic polymerizable compound adjacent to both sides of the polyimide film.
The organic electroluminescent display device of the present invention may include the above-mentioned touch panel member of the present invention.
The counter substrate of the organic electroluminescent display device of the present invention may include the laminate of the present invention.

Figure 11 is a schematic cross-sectional view showing an example of an organic electroluminescent display device of the present invention. The organic electroluminescent display device 300 shown in Figure 11 has the laminate 10 of the present invention, a touch panel member 20 having a first transparent electrode 4 on one side of the laminate 10' of the present invention and a second transparent electrode 5 on the other side, and an organic electroluminescent display unit 40. In the organic electroluminescent display device 300, the laminate 10 is used as a surface material, and the laminate 10 and the touch panel member 20 are bonded together via an adhesive layer 6.

The organic electroluminescent display section (organic EL display section) used in the organic electroluminescent display device (organic EL display device) of the present invention has an organic electroluminescent layer (organic EL layer) formed between substrates arranged opposite each other, and may have a configuration used in conventionally known organic EL display devices.
The organic EL display unit may further include a support substrate, an organic EL element including an organic EL layer, an anode layer and a cathode layer sandwiching the organic EL layer, and a sealing base material sealing the organic EL element. The organic EL layer may include at least an organic EL light-emitting layer, and may include, for example, a layer having a structure in which a hole injection layer, a hole transport layer, an organic EL light-emitting layer, an electron transport layer and an electron injection layer are laminated in this order from the anode layer side.
The organic EL display device of the present invention can be applied to, for example, a passive driving organic EL display and an active driving organic EL display. The counter substrate used in the organic EL display device of the present invention can be appropriately selected depending on the driving method of the organic EL display device, and may include the laminate of the present invention.

12 is a schematic cross-sectional view showing another example of the organic electroluminescent display device of the present invention. The organic electroluminescent display device 400 shown in FIG. 12 has the laminate 10 of the present invention, a first conductive member 201 having a first transparent electrode 4 on one side of the laminate 10' of the present invention, a touch panel member 20' having a second conductive member 202 having a second transparent electrode 5 on one side of the laminate 10" of the present invention, and an organic electroluminescent display unit 40. In the organic electroluminescent display device 400, the laminate 10 and the first conductive member 201, and the first conductive member 201 and the second conductive member 202 are each bonded together via an adhesive layer 6. The configuration of the touch panel member 20' can be the same as the configuration of the touch panel member 20' shown in FIG. 7, for example. The conductive member used in the organic electroluminescent display device of the present invention can be the same as the conductive member used in the touch panel member of the present invention.

[Evaluation method]
Unless otherwise specified, measurements or evaluations were performed at 25°C.
The film specimens were cut near the center of the film.

<Weight average molecular weight of polyimide precursor>
The weight average molecular weight of the polyimide precursor was measured by dissolving the polyimide precursor in N-methylpyrrolidone (NMP) at a concentration of 0.5% by mass, filtering the solution through a syringe filter (pore size: 0.45 μm), and using a 10 mmol% LiBr-NMP solution with a water content of 500 ppm or less as a developing solvent, using a GPC apparatus (HLC-8120 manufactured by Tosoh, column used: GPC LF-804 manufactured by SHODEX), with a sample injection amount of 50 μL, a solvent flow rate of 0.5 mL/min, and 40° C. The weight average molecular weight of the polyimide precursor was measured using polystyrene standard samples (weight average molecular weights: 364,700, 204,000, 103,500, 44,360, 27,500, 13,030, 6,300, 3,070) of the same concentration as the sample as a standard polystyrene conversion value. The elution time was compared with a calibration curve to determine the weight average molecular weight.

<Weight average molecular weight of polyimide>
15 mg of polyimide powder was immersed in 15,000 mg of N-methylpyrrolidone (NMP), heated to 60 ° C. in a water bath, and stirred at a rotation speed of 200 rpm using a stirrer for 3 to 60 hours until dissolution was confirmed visually, thereby obtaining an NMP solution with a concentration of 0.1% by mass. The solution was filtered through a syringe filter (pore size: 0.45 μm), and a 30 mmol% LiBr-NMP solution with a water content of 500 ppm or less was used as a developing solvent. A GPC device (Tosoh, HLC-8120, detector: differential refractive index (RID) detector, column used: two SHODEX GPC LF-804s connected in series) was used, and the measurement was performed under the conditions of sample injection amount 50 μL, solvent flow rate 0.4 mL/min, column temperature 37 ° C., and detector temperature 37 ° C. The weight average molecular weight of the polyimide was calculated based on the weight average molecular weight of standard polystyrene measured using polystyrene standard samples of the same concentration as the sample (weight average molecular weights: 364,700, 204,000, 103,500, 44,360, 27,500, 13,030, 6,300, and 3,070). The elution time was compared with the calibration curve to determine the weight average molecular weight.

<Viscosity of Polyimide Varnish>
The viscosity of the polyimide varnish was measured at 25° C. using a single cylinder type rotational viscometer (for example, TVB-10 type viscometer, M4 rotor, manufactured by Toki Sangyo Co., Ltd.) according to the method described in JIS K7117-1, with a sample amount of 50 ml.

<Film thickness measurement method>
The thickness of a test piece of the laminate cut to a size of 10 cm x 10 cm was measured at five points, namely the four corners and the center, using a digital linear gauge (manufactured by Ozaki Seisakusho Co., Ltd., model PDN12 digital gauge), and the average of the measured values was regarded as the thickness of the laminate.
The thickness of the hard coat layer was determined as the average thickness of 10 arbitrary locations obtained by measuring a cross section of the laminate in the thickness direction observed with a scanning electron microscope.
The thickness of the polyimide film in the laminate was determined from the average thickness of 10 arbitrary points obtained by measuring the cross section of the laminate in the thickness direction observed with a scanning electron microscope.

<YI value (yellowness index)>
The YI value was calculated from the tristimulus values X, Y, and Z in the XYZ color system based on the transmittance measured at 1 nm intervals in the range of 250 nm to 800 nm inclusive using a spectrophotometric method using an ultraviolet-visible-near infrared spectrophotometer (JASCO Corporation V-7100) with auxiliary illuminant C and a 2-degree visual field in accordance with JIS K7373-2006, and the transmittance at 380 nm inclusive was also calculated from the measurement results.
YI=100(1.2769X-1.0592Z)/Y

<ΔYI>
The YI value (yellowness index) was measured before and after the weather resistance test described below in the same manner as described above, and the yellowness index was calculated from the difference between the YI values before and after the test.
ΔYI = YI after test - YI before test
(Weather resistance test)
Using a weather resistance tester conforming to JIS K5600-7-8 (QUV weather resistance tester, QUV, manufactured by Q-LAB), the laminate was irradiated for 96 hours using a UVA (340) lamp with a spectral distribution similar to sunlight from 365 nm to 295 nm, with the output set to 0.63 W/m ² /nm.

<ΔE>
For the laminate before and after the weather resistance test, in accordance with JIS K7373-2006, a UV-visible-near infrared spectrophotometer (for example, V-7100 manufactured by JASCO Corporation) was used to measure the transmittance at 1 nm intervals in the range of 250 nm to 800 nm using auxiliary illuminant C and a 2-degree visual field by spectrophotometric colorimetry. Based on the measured transmittance, L ^* , a ^* , and b ^* in the L ^* a ^* b ^* color system were determined, and ΔE was calculated from the following measurement formula.
ΔE={(L ^* after test−L ^* before test) ² +(a ^* after test−a ^* before test) ² +(b ^* after test−b ^* before test) ² } ^1/2

<Total light transmittance, haze value>
The total light transmittance was measured in accordance with JIS K7361-1 using a haze meter (HM150, manufactured by Murakami Color Research Laboratory).
The haze value was measured in accordance with JIS K-7136 using a haze meter (HM150, manufactured by Murakami Color Research Laboratory).

<Tensile modulus>
A test piece of the laminate (a laminate of a polyimide film and a hard coat layer) cut to 10 mm x 150 mm was subjected to measurement of the tensile modulus at 25°C at a temperature of 25°C in accordance with JIS K7127, at a tensile speed of 50 mm/min and a chuck distance of 100 mm. The tensile tester used was an Autograph AG-X 1N, load cell: SBL-1KN, manufactured by Shimadzu Corporation.

<Composite Elastic Modulus>
The composite elastic modulus of the polyimide film in the laminate containing the glass substrate was determined as follows.
First, the indentation hardness of the polyimide film was measured. The indentation hardness (H _IT ) was measured for the measurement sample using a "TI950 TriboIndenter" manufactured by BRUKER. Specifically, first, a block was prepared by embedding a laminate cut into 1 mm x 10 mm in embedding resin, and a uniform slice having a thickness of 50 nm to 100 nm without holes was cut out from this block by a general slice preparation method. The slice was cut in a direction perpendicular to the plane of the polyimide film. An "Ultramicrotome EM UC7" (manufactured by Leica Microsystems) was used to prepare the slice. The remaining block from which the uniform slice without holes was cut out was used as the measurement sample. Next, in the cross section obtained by cutting out the above-mentioned slice from such a measurement sample, a Berkovich indenter (triangular pyramid, TI-0039 manufactured by BRUKER) was pressed vertically into the center of the cross section of the polyimide film over 10 seconds until a maximum pressing load of 25 μN was reached under the following measurement conditions: In order to avoid the influence of the glass substrate and the side edges of the polyimide film, the Berkovich indenter was pressed into the interface between the glass substrate and the polyimide film, both side ends of the polyimide film, and into portions of the polyimide film 500 nm away from the center of the polyimide film from the surface of the polyimide film opposite the glass substrate. Thereafter, the residual stress was relaxed by holding the load constant, and then the load was removed over 10 seconds to measure the maximum load after relaxation. The indentation hardness ( _HIT ) was calculated from the maximum load _Pmax (μN) and the contact projected area _Ap ( ^nm2 ) by _Pmax / _Ap . The contact projected area was determined by correcting the indenter tip curvature by the Oliver-Pharr method using a standard sample of fused quartz (5-0098 manufactured by BRUKER). If any of the measured values deviated from the arithmetic mean value by ±20% or more, the measured value was excluded and remeasured.

(Measurement conditions)
・Loading speed: 2.5μN/sec ・Holding time: 5 seconds ・Unloading speed: 2.5μN/sec ・Measurement temperature: 25℃

Next, the composite elastic modulus was calculated from the above-mentioned contact projected area _Ap obtained when measuring the indentation hardness ( _HIT ) of the obtained polyimide film according to the following formula (1). The indentation hardness was measured at 10 points, and the composite elastic modulus was calculated each time, and the arithmetic average value of the composite elastic moduli obtained at the 10 points was used.

(In the above formula (1), A _p is the contact projected area, E _r is the composite elastic modulus of the polyimide film, and S is the contact stiffness.)

<Dynamic bending test>
The method of the dynamic bending test will be described below with reference to FIG.
Two movable metal plates 11 (100 mm x 30 mm) each having a movable portion 11a and a non-movable portion 11b were prepared and arranged in parallel such that the distance between the non-movable portions 11b of the two metal plates 11 was 60 mm. The movable portion 11a of the metal plate 11 was bent perpendicular to the non-movable portion 11b as shown in Fig. 2A, and a laminate test piece 10 cut to 20 mm x 100 mm was placed on the movable portion 11a. Both ends of the laminate test piece 10 were fixed to the movable portion 11a with Kapton (registered trademark) tape so that the center of the test piece 10 was located in the center of the distance between the metal plates. Next, the movable part 11a and the non-movable part 11b were arranged in a straight line to obtain the state shown in FIG. 2B, that is, the test piece 10 of the laminate curved at the half position of the long side was sandwiched between the metal plates 11 from both sides, and the metal plates 11 on both sides were arranged in parallel so that the distance between the metal plates 11 on both sides was 60 mm. This state and the state shown in FIG. 2C, in which the metal plates on both sides were arranged in parallel so that the distance between the metal plates 11 on both sides was 2.0 mm (in the case of a φ2 mm dynamic bending test) or 4.0 mm (in the case of a φ4 mm dynamic bending test), were repeatedly changed at a bending rate of 90 times per minute under an environment of 60° C. and 93% relative humidity (RH), and the bending was repeated 200,000 times. A constant temperature and humidity chamber durability test system (Yuasa System Equipment, planar body unloaded U-shaped expansion and contraction test jig DMX-FS) was used as the test jig.
(Evaluation Criteria)
A: No breakage or cracks were observed even after repeated bending 200,000 times.
B: Breaks or cracks occur during 200,000 repeated flexions.

<Change in elongation rate after weather resistance test>
A test piece of the laminate (a laminate of a polyimide film and a hard coat layer) cut to 15 mm x 40 mm was subjected to a tensile test at 25°C in accordance with JIS K7127 at a tensile speed of 10 mm/min and a chuck distance of 20 mm, and the tensile elongation until break was measured. The tensile test was performed using a tensile tester (Shimadzu Corporation: Autograph AG-X 1N, load cell: SBL-1KN).
The laminate before and after the weather resistance test were measured.
(Evaluation Criteria)
A: The elongation rate after the weather resistance test is 70% or more and 130% or less, when the elongation rate before the weather resistance test is 100%. B: The elongation rate after the weather resistance test is less than 70%, when the elongation rate before the weather resistance test is 100%.

<Changes in adhesion after weather resistance test>
Adhesion-cross-cut test was carried out according to the method of JIS K5400-8.5 (JIS D0202). Using a cutter knife, 11 cuts were made in the laminate from the hard coat layer side to the substrate, and then 11 cuts were made by turning 90°. Cellophane tape (registered trademark, (24 mm x 35 m CT405AP-24) manufactured by Nichiban) was attached to the cut coating surface, and the tape was attached to the coating by rubbing with an eraser. After 1 to 2 minutes, the edge of the tape was held at a right angle to the coating surface and instantly peeled off. The peeling of the coating in the cross-cut test according to JIS K5400-8.5 (JIS D0202) was evaluated as being 0 to 10 points.
The laminate before and after the weather resistance test were measured.
(Evaluation Criteria)
A: The classification is 10 points both before and after the weather resistance test.
B: The classification changes before and after the weather resistance test.

<Appearance (whiteness) after weather resistance test>
After the weather resistance test, the haze value of the laminate was measured in the same manner as above.
(Evaluation Criteria)
A: Haze value is 1.0 or less
B: Haze value exceeds 1.0

<Presence or Absence of Air Bubble Defects in Polyimide Film>
A total of five polyimide film test pieces cut into 100 mm x 200 mm, that is, test pieces with a total area of 100,000 ^mm2 , were collected and visually observed. When the polyimide film was in a roll form, the test pieces were collected at equal intervals over the entire width of the effective part of the remaining polyimide film roll after trimming and removing the ends of the film such as the part where the film was gripped for transportation. The polyimide film test pieces were visually observed under fluorescent lights to detect air bubbles. Furthermore, the diameter of the air bubbles detected by visual observation was measured at 100 times magnification using an optical microscope, and air bubbles with a diameter of 0.05 mm or more were counted as air bubble defects. The number of air bubbles generated per 20,000 ^mm2 was calculated as an average value from the total number of air bubble defects in ^100,000 mm2.
In the case of sheet test pieces, test pieces were taken so that the total area of the observed sheet test pieces was 100,000 ^mm2 , and the average number of bubbles generated per 20,000 ^mm2 was calculated in the same manner as above.
The table shows the number of bubbles generated per 20,000 ^mm2 .

<Polyimide film average thickness, thickness uniformity, and appearance>
For a polyimide film specimen cut to 100 mm x 200 mm, the two vertical and horizontal sides of the specimen were regarded as the x-axis and y-axis, and the coordinates of the four corners of the specimen were (0,0), (0,100), (200,0), and (200,100). The film thicknesses of a total of nine points located at (10,10), (10,50), (10,90), (100,10), (100,50), (100,90), (190,10), (190,50), and (190,90) were measured using a digital linear gauge (manufactured by Ozaki Manufacturing Co., Ltd., model PDN12 digital gauge), and the standard deviation σ of the measured film thicknesses was calculated.
The appearance was evaluated by checking for waviness and unevenness.
When the film had curl and was placed on a platen in a downward convex state, the film was evaluated as having undulations if any part of the film except for the four corners was floating 2 mm or more above the platen.
When the film was viewed with transmitted or reflected light, a state in which a streaky pattern was visually confirmed was evaluated as having an uneven appearance.
(Evaluation Criteria)
A: The film has no waviness or uneven appearance, and the film thickness uniformity is good with 3σ being 2 μm or less.
B: At least one of the following applies: the film is wavy, has an uneven appearance, and the film thickness uniformity is poor (3σ exceeds 2 μm).

(Synthesis Example 1)
With reference to Synthesis Example 1 of WO 2014/046180, a tetracarboxylic dianhydride represented by the following chemical formula (i) was synthesized.

A solution of dehydrated N,N-dimethylacetamide (DMAc) (1833.2 g) and 2,2'-bis(trifluoromethyl)benzidine (TFMB) (138.48 g) was placed in a 5 L separable flask, and the liquid temperature was controlled to 30°C. Tetracarboxylic acid dianhydride (TMPBPTME) (176.70 g) represented by the above chemical formula (i) was gradually added so that the temperature rise was 2°C or less, and the mixture was stirred with a mechanical stirrer for 30 minutes. Pyromellitic dianhydride (PMDA) (64.20 g) was gradually added in several portions so that the temperature rise was 2°C or less, synthesizing a polyimide precursor A solution (solid content 18% by mass) in which polyimide precursor A was dissolved. The molar ratio of the tetracarboxylic dianhydride TMPBPTME to PMDA (TMPBPTME:PMDA) used in polyimide precursor A was 90:10. The weight average molecular weight of polyimide precursor A was 75,000.

Under a nitrogen atmosphere, the above polyimide precursor A solution (2162 g) cooled to room temperature was added to a 5 L separable flask. Dehydrated N,N-dimethylacetamide (432 g) was added thereto and stirred until homogenous. Next, pyridine (6.622 g) and acetic anhydride (213.67 g) were added as catalysts and stirred at room temperature for 24 hours to synthesize a polyimide A solution.
N,N-dimethylacetamide (2000 g) was added to the obtained polyimide A solution and stirred until it became uniform. Next, polyimide solution A was divided into three equal parts and transferred to 5 L beakers, and isopropyl alcohol (3500 g) was gradually added to each beaker to obtain a white slurry. The above slurry was transferred onto a Buchner funnel and filtered, and then washed with isopropyl alcohol (total 9000 g) and filtered three times, and then dried at 110° C. using a vacuum dryer to obtain polyimide A1 (polyimide powder).
The weight average molecular weight of Polyimide A1 measured by GPC was 100,000.

(Synthesis Example 2)
Polyimide A2 was prepared in the same manner as in Synthesis Example 1, except that the molar ratio of diamine and acid dianhydride in Synthesis Example 1 was changed. Polyimide A2 had a weight average molecular weight of 174,000.

(Synthesis Example 3)
A 500 mL separable flask was purged with N ₂ , and 233.62 g of dehydrated dimethylacetamide (DMAc) and 19.22 g (60.0 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) were dissolved in a solution controlled to a liquid temperature of 30 ° C., and 2.34 g (11.9 mmol) of cyclobutane tetracarboxylic dianhydride (CBDA) and 28.84 g (46.6 mmol) of TMPBPTME were gradually added so that the temperature rise was 2 ° C. or less, and a polyamic acid solution was obtained by stirring with a mechanical stirrer for 3 hours. Next, 0.581 g (7.3 mmol) of pyridine and 18.75 g (183.7 mol) of acetic anhydride, which are catalysts, were added, and the solution was confirmed to be homogeneous by stirring at 25 ° C. for 240 minutes. After that, 134 g of 2-propyl alcohol (IPA) was gradually added to the solution cooled to room temperature, resulting in a slightly turbid solution. 223 g of IPA was added to the turbid solution all at once to obtain a white slurry. The slurry was filtered and washed five times with IPA, and then dried for six hours under reduced pressure in an oven heated to 100°C to obtain a powder of polyimide resin A3 (38.9 g).
The weight average molecular weight of the polyimide measured by GPC was 145,000.

(Synthesis Example 4)
A 500 mL separable flask was purged with N ₂ , and 219.23 g of dehydrated dimethylacetamide (DMAc), 16.62 g (51.9 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB), and 0.97 g (2.8 mmol) of diamine represented by the following formula (DA4) (N,N'-bis(4-aminophenyl)terephthalamide, DATA, manufactured by Wakayama Seika Kogyo Co., Ltd.) were dissolved in a solution controlled to a liquid temperature of 30 ° C., and 2.17 g (11.1 mmol) of cyclobutane tetracarboxylic dianhydride (CBDA) and 26.7 g (43.2 mmol) of TMPBPTME were gradually added so that the temperature rise was 2 ° C. or less, and the mixture was stirred with a mechanical stirrer for 3 hours to obtain a polyamic acid solution. Next, 0.814 g (10.3 mmol) of pyridine and 26.274 g (257.4 mol) of acetic anhydride as catalysts were added, and the mixture was stirred at 25° C. for 240 minutes to confirm that the solution was homogeneous. After that, 210 g of 2-propyl alcohol (IPA) was gradually added to the solution cooled to room temperature to obtain a slightly turbid solution. 420 g of IPA was added to the turbid solution at once to obtain a white slurry. The slurry was filtered and washed five times with IPA, and then dried in an oven heated to 100° C. under reduced pressure for six hours to obtain a powder of polyimide resin A4 (35.6 g).
The weight average molecular weight of the polyimide measured by GPC was 183,000.

(Synthesis Example 5)
Polyimide resin A5 was synthesized in the same manner as in Synthesis Example 4, except that in the synthesis of the polyimide resin in Synthesis Example 4, a diamine represented by the following formula (DA33) (4-aminophenyl-4-aminobenzoate, APAB, manufactured by Wakayama Seika Kogyo Co., Ltd.) was used instead of the diamine represented by the formula (DA4) above, and the composition ratio (molar ratio) of TFMB to APAB was changed to 90:10.
The weight average molecular weight of the polyimide measured by GPC was 189,000.

(Synthesis Example 6)
Polyimide resin A6 was synthesized in the same manner as in Synthesis Example 4, except that in the synthesis of the polyimide resin in Synthesis Example 4, a diamine represented by the following formula (DA10) ((2-phenyl-4-aminophenyl)-4-aminobenzoate, PHBAAB, manufactured by Nippon Junryo Chemical Co., Ltd.) was used instead of the diamine (DATA) represented by the formula (DA4) and the composition ratio (molar ratio) of TFMB to PHBAAB was changed to 90:10.
The weight average molecular weight of the polyimide measured by GPC was 160,000.

(Synthesis Example 7)
Polyimide resin A7 was synthesized in the same manner as in Synthesis Example 4, except that in the synthesis of the polyimide resin in Synthesis Example 4, the diamine represented by the formula (DA1) (bis(4-aminophenyl)terephthalate, BPTP: manufactured by Wakayama Seika Kogyo Co., Ltd.) was used instead of the diamine represented by the formula (DA4) (DATA), and the composition ratio (molar ratio) of TFMB to BPTP was changed to 90:10.
The weight average molecular weight of the polyimide measured by GPC was 147,000.

Comparative Synthesis Example 1
Comparative polyimide CA1 was prepared in the same manner as in Synthesis Example 1, except that the molar ratio of diamine and acid dianhydride in Synthesis Example 1 was changed. The weight average molecular weight of the comparative polyimide CA1 was 75,000.

Comparative Synthesis Example 2
Comparative polyimide CA2 was prepared in the same manner as in the polymerization of the polyimide precursor and the chemical imidization reaction of Example 1 of WO 2014/046180. The weight average molecular weight of comparative polyimide CA2 was 288,000.

Example 1
(1) Production of Polyimide Film Polyimide A1 of Synthesis Example 1 was used to produce polyimide films having a thickness of 30 μm by carrying out the following procedures (P1) to (P3).
(P1) A mixed solvent of dichloromethane and methanol (dichloromethane:methanol=98:2 (mass ratio)) was added to polyimide A1 so that the solid content concentration of polyimide A1 was 10 mass %, to prepare a polyimide A1 varnish containing 10 mass % of polyimide in the varnish. The viscosity of the polyimide A1 varnish (solid content concentration 10 mass %) at 25 ° C. was 1200 cps.
(P2) Polyimide A1 varnish (solid content concentration 10% by mass) was applied to a sheet-like support (thickness 100 μm, SUS304, manufactured by Nisshin Steel Co., Ltd., SUS304 CSP-H-TA) so that the film thickness after drying in a circulation oven described below would be 30 μm. The varnish applied to the support was left to stand at 25° C. for 30 minutes in a dichloromethane atmosphere in a glove bag to dry, and then the glove bag was replaced with an air atmosphere and left to stand at 25° C. for 5 minutes to dry. The support and the dried coating film were removed from the glove bag, and the dried coating film was peeled off from the support.
(P3) The peeled dried coating film was cut into a size of 150 mm x 200 mm. The cut dried coating film was sandwiched between two metal frames (outer dimensions 150 mm x 200 mm, inner dimensions 130 mm x 180 mm), and the metal frames and the dried coating film were fixed with a fixing jig. The fixed dried coating film was heated in a circulation oven at a temperature increase rate of 5°C/min, and dried at 140°C for 2 minutes, 170°C for 2 minutes, and 200°C for 10 minutes to produce a polyimide film.
The evaluation results of the obtained polyimide film are shown in Reference Example 1 of Table 2. The optical properties, tensile modulus, and dynamic bending test were performed in the same manner as in the evaluation of the laminate. The residual solvent in the polyimide film was measured by the method described in the specification.

(2) Manufacture of Laminate Next, the hard coat layer composition 1 having the following composition was applied onto the polyimide film to form a coating film, and the formed coating film was heated at 70°C for 1 minute to evaporate the solvent in the coating film, and the coating film was half-cured by irradiating ultraviolet light in air to an integrated light amount of 100mJ/ ^cm2 using an ultraviolet irradiation device (manufactured by Fusion UV Systems Japan, light source H bulb), to form a hard coat layer with a thickness of 8μm, thereby manufacturing a laminate. The total thickness of the polyimide film and the hard coat layer was 38μm. The evaluation results of the laminate are shown in Table 1.

(Hardcoat layer composition 1)
Mixture of dipentaerythritol pentaacrylate and dipentaerythritol hexaacrylate (M403, manufactured by Toagosei Co., Ltd.) 25 parts by mass Dipentaerythritol EO-modified hexaacrylate (A-DPH-6E, manufactured by Shin-Nakamura Chemical Co., Ltd.) 25 parts by mass Non-standard silica fine particles (average particle size 25 nm, manufactured by JGC Catalysts and Chemicals Co., Ltd.) 50 parts by mass (solid equivalent)
Photopolymerization initiator (Irg184): 4 parts by mass Fluorine-based leveling agent (F568, manufactured by DIC Corporation): 0.2 parts by mass (solid equivalent)
UV absorber 1 (DAINSORB P6, manufactured by Daiwa Kasei) 3 parts by weight Solvent (MIBK) 150 parts by weight

(Examples 2 to 6)
The laminates of Examples 2 to 5 were produced in the same manner as in Example 1, except that in the production of the laminate of Example 1, the ultraviolet absorber 2, 3, 4, or 5 was used instead of the ultraviolet absorber 1 in the composition for hard coat layer 1 for forming the hard coat layer.
Moreover, a laminate of Example 6 was produced in the same manner as in Example 1, except that in the production of the laminate of Example 1, the thickness of the hard coat layer was changed to 5 μm.
The evaluation results are shown in Table 1.

(Examples 7 to 12)
The laminates of Examples 7 to 12 were produced in the same manner as in Example 1, except that in the production of the polyimide film in the production of the laminate of Example 1, polyimide A2, A3, A4, A5, A6, or A7 was used instead of polyimide A1, respectively.
However, the solid content concentration in the varnish of polyimide A3 was 12 mass %, and the solid content concentration in the varnishes of polyimides A4, A5, A6, and A7 was 15 mass %.
The evaluation results are shown in Table 1.

(Example 13)
In the production of the polyimide film in the production of the laminate of Example 1, the polyimide A2 of Synthesis Example 2 was used, and the following procedures (P1') to (P3') were carried out to produce a polyimide film having a thickness as shown in Table 1. The laminate of Example 13 was produced in the same manner as in Example 1, except that the polyimide film was produced using the polyimide A2 of Synthesis Example 2 and having a thickness as shown in Table 1.
(P1') DMAc was added to polyimide A2 so that the solid content concentration of polyimide A2 was 10 mass %, to prepare polyimide A2' varnish containing 10 mass % of polyimide in the varnish. The viscosity of polyimide A2' varnish (solid content concentration 10 mass %) at 25 ° C. was 7400 cps.
(P2') The polyimide A2' varnish (solid content concentration 10% by mass) was applied to a sheet-like support (thickness 100 μm, SUS304, manufactured by Nisshin Steel Co., Ltd., SUS304 CSP-H-TA) so that the film thickness after drying in a circulating oven described below would be the thickness shown in Table 1. The varnish applied to the support was heated from 25° C. to 80° C. over 10 minutes, dried at 80° C. for 30 minutes and then at 100° C. for 30 minutes, and the coating film was peeled off from the support.
(P3') The peeled dried coating film was cut into a size of 150 mm x 200 mm. Two metal frames (outer dimensions 150 mm x 200 mm, inner dimensions 130 mm x 180 mm) were used to hold the cut dried coating film, and the metal frames and the dried coating film were fixed with a fixing jig. The fixed dried coating film was heated in a circulation oven at a temperature increase rate of 5°C/min, and dried at 150°C for 10 minutes, 180°C for 10 minutes, 230°C for 10 minutes, and 250°C for 30 minutes to produce a polyimide film.

(Comparative Examples 1 to 15)
A laminate of Comparative Example 1 was produced in the same manner as in Example 1, except that in the production of the laminate of Example 1, the ultraviolet absorber 1 was not used in the composition for hard coat layer 1 for forming the hard coat layer.
Laminates of Comparative Examples 2 to 10 were produced in the same manner as in Example 1, except that in the production of the laminate of Example 1, the ultraviolet absorber 1 was used in the composition for hard coat layer 1 for forming the hard coat layer, and the thickness of the hard coat layer was changed to 5 μm, and the ultraviolet absorbers shown in Table 1 were used instead.
Laminates of Comparative Examples 11 to 15 were produced in the same manner as in Example 1, except that in the production of the laminate of Example 1, ultraviolet absorbers 6, 7, 8, 9, or 10 were used instead of ultraviolet absorber 1 in the composition for hard coat layer 1 for forming the hard coat layer.
The evaluation results are shown in Table 1.

The abbreviations in the table are as follows.
UV absorber 1: Benzophenone-based UV absorber (2,2',4,4'-tetrahydroxybenzophenone, trade name DAINSORB P6, manufactured by Daiwa Kasei)
UV absorber 2: Benzophenone-based UV absorber (2,2'-dihydroxy-4,4'-dimethoxybenzophenone, trade name DAINSORB P7, manufactured by Daiwa Kasei)
UV absorber 3: Benzophenone-based UV absorber (2,2'-dihydroxy-4,4'-diallyloxybenzophenone, trade name DAINSORB P61, manufactured by Daiwa Kasei)
Ultraviolet absorber 4: Benzotriazole-based ultraviolet absorber (2-(2-hydroxy-4-octyloxyphenyl)-2H-benzotriazole, trade name DAINSORB T-7, manufactured by Daiwa Kasei)
Ultraviolet absorber 5: Benzotriazole-based ultraviolet absorber (2-(2,4-dihydroxyphenyl)-2H-benzotriazole, trade name DAINSORB T-0, manufactured by Daiwa Kasei)
Ultraviolet absorber 6: Triazine-based ultraviolet absorber (product name Tinuvin 460, manufactured by BASF)
Ultraviolet absorber 7: Triazine-based ultraviolet absorber (product name Tinuvin 479, manufactured by BASF)
UV absorber 8: Triazine-based UV absorber (product name Tinuvin 477, manufactured by BASF)
Ultraviolet absorber 9: Triazine-based ultraviolet absorber (product name LA-F70, manufactured by ADEKA)
UV absorber 10: Triazine-based UV absorber (product name LA-46, manufactured by ADEKA)
HC: hard coat layer PI: polyimide film

(Comparative Examples 16 to 17)
Polyimide varnishes were prepared in the same manner as in Example 1, except that in step (P1) of Example 1, comparative polyimide CA1 was used instead of polyimide A1, and the polyimide concentration (mass%) in the varnish was changed as shown in Table 2.
Using each polyimide varnish, a polyimide film was produced in the same manner as in steps (P2) and (P3) of Example 1. The evaluation results of the obtained polyimide films of Comparative Examples 16 and 17 are shown in Table 2. The optical properties, elastic modulus, and dynamic bending test were performed in the same manner as in the evaluation of the laminate. The residual solvent in the polyimide film was measured by the method described in the specification.

(Comparative Example 18)
A polyimide film was produced in the same manner as in the preparation of a polyimide solution and the production of a polyimide film in Example 1 of WO 2014/046180, except that the comparative polyimide CA2 obtained in Comparative Synthesis Example 2 was used and applied so as to have a final film thickness of 30 μm.
The evaluation results of the polyimide film of Comparative Example 18 are shown in Table 2. The optical properties, elastic modulus, and dynamic bending test were performed in the same manner as in the evaluation of the laminate. The residual solvent in the polyimide film was measured by the method described in the specification, and the quantification ions of cyclopentanone were m/z = 55, 98.
The polyimide film of Comparative Example 18 was subjected to a weather resistance test in the same manner as the laminate of Example 1, and ΔYI/film thickness, ΔE/film thickness, and 380 nm transmittance were measured. These evaluation results are also shown in Table 1.

(Example 14)
(1) Preparation of Glass Substrate A chemically strengthened glass substrate (UTG) having a thickness of 30 μm was prepared, and the primer layer composition described below was applied to the glass substrate to a predetermined thickness, and dried at 80° C. for 3 minutes and at 150° C. for 60 minutes to form a primer layer having a thickness of 1 μm.
(Primer layer composition)
Bisphenol A type solid epoxy resin (jER1256B40 manufactured by Mitsubishi Chemical) 28 parts by mass Bisphenol A novolac type solid epoxy resin (jER157S65B80 manufactured by Mitsubishi Chemical) 5 parts by mass 2-ethyl-4-methylimidazole (manufactured by Tokyo Chemical Industry Co., Ltd.) 1 part by mass Solvent (MEK) 11 parts by mass

(2) Lamination of Polyimide Film Using the polyimide A1 of Synthesis Example 1, a polyimide film having a thickness as shown in Table 3 was laminated on the primer layer formed on the glass substrate by carrying out the following procedures (L1) to (L3).
(L1) A mixed solvent of dichloromethane and methanol (dichloromethane:methanol=98:2 (mass ratio)) was added to polyimide A1 so that the solid content concentration of polyimide A1 was 10 mass %, to prepare a polyimide A1 varnish containing 10 mass % of polyimide in the varnish. The viscosity of the polyimide A1 varnish (solid content concentration 10 mass %) at 25 ° C. was 1200 cps.
(L2) Polyimide A1 varnish (solid content concentration 10% by mass) was applied onto the primer layer formed on the glass substrate so that the film thickness after drying in a circulation oven described below would be the thickness shown in Table 3. The applied varnish was left to stand for 30 minutes at 25° C. in a dichloromethane atmosphere in a glove bag to dry, and then the atmosphere in the glove bag was replaced with an air atmosphere and left to stand for 5 minutes at 25° C. to dry. The glass substrate and the dried coating film were removed from the glove bag.
(L3) The glass substrate and the dried coating film were heated in a circulation oven at a temperature increase rate of 5°C/min, and dried at 140°C for 2 minutes, at 170°C for 2 minutes, and at 200°C for 10 minutes, to laminate a polyimide film on the glass substrate.

(3) Production of Laminate Next, a hard coat layer was formed on the polyimide film laminated on the glass substrate to produce a laminate in the same manner as in Example 1. The evaluation results of the laminate are shown in Table 3.

(Examples 15 to 19)
The laminates of Examples 15 to 18 were produced in the same manner as in Example 14, except that in the production of the laminate of Example 14, the ultraviolet absorber 2, 3, 4, or 5 was used instead of the ultraviolet absorber 1 in the composition for hard coat layer 1 for forming the hard coat layer.
Moreover, a laminate of Example 19 was produced in the same manner as in Example 14, except that in the production of the laminate of Example 14, the thickness of the hard coat layer was changed to 5 μm.
The evaluation results of the laminate are shown in Table 3.

(Examples 20 to 25)
The laminates of Examples 20 to 25 were produced in the same manner as in Example 14, except that in the production of the polyimide film in the production of the laminate of Example 14, polyimide A2, A3, A4, A5, A6, or A7 was used instead of polyimide A1, respectively.
However, the solid content concentration in the varnish of polyimide A3 was 12 mass %, and the solid content concentration in the varnishes of polyimides A4, A5, A6, and A7 was 15 mass %.
The evaluation results of the laminate are shown in Table 3.

(Example 26)
In the lamination of the polyimide film in the production of the laminate of Example 14, the polyimide A2 of Synthesis Example 2 was used, and the following procedures (L1') to (L3') were carried out to laminate a polyimide film having a thickness shown in Table 3. The laminate of Example 26 was produced in the same manner as in Example 14, except that.
(L1') DMAc was added to polyimide A2 so that the solid content concentration of polyimide A2 was 10 mass %, to prepare polyimide A2' varnish containing 10 mass % of polyimide in the varnish. The viscosity of polyimide A2' varnish (solid content concentration 10 mass %) at 25 ° C. was 7400 cps.
(L2') Onto the primer layer formed on the glass substrate, the polyimide A2' varnish (solid content concentration: 10% by mass) was applied so that the film thickness after drying in a circulation oven described below would be the thickness shown in Table 3. The applied varnish was heated from 25°C to 80°C over 10 minutes, and dried at 80°C for 30 minutes and then at 100°C for 30 minutes.
(L3') The glass substrate and the dried coating film were heated in a circulation oven at a temperature increase rate of 5°C/min, and dried at 150°C for 10 minutes, 180°C for 10 minutes, 230°C for 10 minutes, and 250°C for 30 minutes, to laminate a polyimide film on the glass substrate.
The evaluation results of the laminate are shown in Table 3.

(Comparative Examples 19 to 33)
A laminate of Comparative Example 19 was produced in the same manner as in Example 14, except that in the production of the laminate of Example 14, the ultraviolet absorber 1 was not used in the composition for hard coat layer 1 for forming the hard coat layer.
Laminates of Comparative Examples 20 to 28 were produced in the same manner as in Example 14, except that in the production of the laminate of Example 14, in the composition for hard coat layer 1 for forming the hard coat layer, the ultraviolet absorbers shown in Table 3 were used instead of the ultraviolet absorber 1, and further, the thickness of the hard coat layer was changed to 5 μm.
Laminates of Comparative Examples 29 to 33 were produced in the same manner as in Example 14, except that in the production of the laminate of Example 14, the ultraviolet absorber 6, 7, 8, 9 or 10 was used instead of the ultraviolet absorber 1 in the composition for hard coat layer 1 for forming the hard coat layer.
The evaluation results are shown in Table 3.

(Comparative Example 34)
Using the comparative polyimide CA2 obtained in Comparative Synthesis Example 2, a polyimide solution was prepared in the same manner as in Example 1 of WO 2014/046180, and the same glass substrate as in Example 14 (a primer layer was laminated on a chemically strengthened glass substrate (UTG) having a thickness of 30 μm) was prepared as a glass substrate, and the coating was applied so that the final film thickness was 30 μm. A polyimide film was produced in the same manner as in the film formation of the polyimide film in Example 1 of WO 2014/046180, except that the polyimide film was not peeled off from the glass substrate. A hard coat layer was not laminated.
The evaluation results are shown in Table 3.

In the table, "no data" means that no measurement was performed.

Claims (11)

A polyimide film;
a laminate having a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound, and an ultraviolet absorber;
The polyimide film contains 10 mol % or more and 100 mol % or less of a structural unit represented by the following general formula (1) and (100-x) mol % (wherein x is the mol % of the structural unit represented by the general formula (1)) of a structural unit represented by the following general formula (2), and has a weight average molecular weight of 100,000 or more as measured by gel permeation chromatography in terms of polystyrene:
the ultraviolet absorber is one or more ultraviolet absorbers selected from the group consisting of hydroxybenzophenone-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers , and the content of the ultraviolet absorber is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of a solid content of the hard coat layer;
the yellowness index (YI) of the laminate calculated in accordance with JIS K7373-2006 divided by the total film thickness (μm) of the polyimide film and the hard coat layer is less than 0.12;
a value obtained by dividing a yellowness index change ΔYI of the laminate before and after the following weather resistance test by a total film thickness (μm) of the polyimide film and the hard coat layer is less than 0.11;
a value obtained by dividing a color change ΔE of the laminate before and after the following weather resistance test by a total film thickness (μm) of the polyimide film and the hard coat layer is less than 0.09;
The thickness of the hard coat layer is 2.0 μm or more and 50.0 μm or less,
The laminate has a total thickness of 10 μm or more and 300 μm or less.
(Weather resistance test)
Using a weather resistance tester conforming to JIS K5600-7-8, the laminate is irradiated for 96 hours using a UVA (340) lamp with the output set at 0.63 W/m ² /nm.
The laminate before and after the weather resistance test is measured for yellowness index (YI) calculated in accordance with JIS K7373-2006, and L ^* , a ^* , and b ^* in the CIE L ^* a ^* b ^* color system using light source C.
ΔYI = YI after test - YI before test
ΔE={(L ^* after test−L ^* before test) ² +(a ^* after test−a ^* before test) ² +(b ^* after test−b ^* before test) ² } ^1/2

(In general formulas (1) and (2), R ¹ to R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and at least one of R ¹ and R ² , and at least one of R ³ and R ⁴ , represents an alkyl group having 1 to 6 carbon atoms. A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.) A polyimide film;
a laminate having a hard coat layer containing at least one polymer of a radical polymerizable compound and a cationic polymerizable compound, and an ultraviolet absorber;
The polyimide film contains 10 mol % or more and 100 mol % or less of a structural unit represented by the following general formula (1) and (100-x) mol % (wherein x is the mol % of the structural unit represented by the general formula (1)) of a structural unit represented by the following general formula (2), and has a weight average molecular weight of 100,000 or more as measured by gel permeation chromatography in terms of polystyrene:
the ultraviolet absorber is one or more ultraviolet absorbers selected from the group consisting of hydroxybenzophenone-based ultraviolet absorbers and benzotriazole-based ultraviolet absorbers , and the content of the ultraviolet absorber is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of a solid content of the hard coat layer;
the yellowness index (YI) of the laminate calculated in accordance with JIS K7373-2006 divided by the film thickness (μm) of the polyimide film is less than 0.15;
a value obtained by dividing the yellowness index change ΔYI of the laminate before and after the following weather resistance test by the film thickness (μm) of the polyimide film is less than 0.13;
the color change ΔE of the laminate before and after the following weather resistance test is divided by the film thickness (μm) of the polyimide film, and the value is less than 0.11;
The thickness of the hard coat layer is 2.0 μm or more and 50.0 μm or less,
The laminate has a total thickness of 10 μm or more and 300 μm or less.
(Weather resistance test)
Using a weather resistance tester conforming to JIS K5600-7-8, the laminate is irradiated for 96 hours using a UVA (340) lamp with the output set at 0.63 W/m ² /nm.
The laminate before and after the weather resistance test is measured for yellowness index (YI) calculated in accordance with JIS K7373-2006, and L ^* , a ^* , and b ^* in the CIE L ^* a ^* b ^* color system using light source C.
ΔYI = YI after test - YI before test
ΔE={(L ^* after test−L ^* before test) ² +(a ^* after test−a ^* before test) ² +(b ^* after test−b ^* before test) ² } ^1/2

(In general formulas (1) and (2), R ¹ to R ⁴ each independently represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and at least one of R ¹ and R ² , and at least one of R ³ and R ⁴ , represents an alkyl group having 1 to 6 carbon atoms. A represents a tetravalent group which is a tetracarboxylic acid residue having an aromatic ring or an aliphatic ring, and B represents a divalent group which is a diamine residue having an aromatic ring or an aliphatic ring.) The laminate according to claim 1 or 2, wherein the transmittance of the laminate at a wavelength of 380 nm is 8% or less. The laminate according to any one of claims 1 to 3, wherein the polyimide film contains 1 ppm or more and 2000 ppm or less of dichloromethane. The diamine residue having an aromatic ring or an aliphatic ring in B in the general formulas (1) and (2) is a trans-cyclohexanediamine residue, a trans-1,4-bismethylenecyclohexanediamine residue, a 4,4'-diaminodiphenylsulfone residue, a 3,4'-diaminodiphenylsulfone residue, a 2,2-bis(4-aminophenyl)propane residue, a 3,3'-bis(trifluoromethyl)-4,4'-[(1,1,1,3,3,3- a divalent group containing at least one selected from the group consisting of a 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, a 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane residue, and a divalent group represented by the following general formula (3):
The laminate according to any one of claims 1 to 4, wherein the diamine residue having an aromatic ring or an aliphatic ring may further contain at least one selected from the group consisting of an N,N'-bis(4-aminophenyl)terephthalamide residue, a 4-aminophenyl-4-aminobenzoate residue, a (2-phenyl-4-aminophenyl)-4-aminobenzoate residue, and a bis(4-aminophenyl)terephthalate residue.

(In formula (3), ^R5 and ^R6 each independently represent a hydrogen atom, an alkyl group, or a perfluoroalkyl group.) The tetracarboxylic acid residue having an aromatic ring or an aliphatic ring in A in the general formula (2) is a cyclohexanetetracarboxylic acid dianhydride residue, a cyclopentanetetracarboxylic acid dianhydride residue, a dicyclohexane-3,4,3',4'-tetracarboxylic acid dianhydride residue, a cyclobutanetetracarboxylic acid dianhydride residue, a pyromellitic acid dianhydride residue, a 3,3',4,4'-biphenyltetracarboxylic acid dianhydride residue, a 2,2',3,3'-biphenyltetracarboxylic acid dianhydride residue, a 2, The laminate according to any one of claims 1 to 5, which is at least one tetravalent group selected from the group consisting of 3,3',4'-biphenyltetracarboxylic dianhydride residue, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,4'-(hexafluoroisopropylidene)diphthalic anhydride residue, 3,3'-(hexafluoroisopropylidene)diphthalic anhydride residue, 4,4'-oxydiphthalic anhydride residue, and 3,4'-oxydiphthalic anhydride residue. The laminate according to any one of claims 1 to 6, further comprising a glass substrate having a thickness of 100 μm or less. A display surface material that is a laminate according to any one of claims 1 to 7. A laminate according to any one of claims 1 to 7;
A transparent electrode including a plurality of conductive portions disposed on one surface side of the laminate;
and a plurality of lead wires electrically connected to at least one side of an end of the conductive portion. A laminate according to any one of claims 1 to 7;
a liquid crystal display section disposed on one surface side of the laminate and having a liquid crystal layer between opposing substrates; A laminate according to any one of claims 1 to 7;
an organic electroluminescence display unit disposed on one surface side of the laminate and having an organic electroluminescence layer between opposing substrates;

Images