JP7632280B2 - Laminate - Google Patents

Description

The present invention relates to a laminate, and more particularly to a laminate in which a polyimide film is adhered to a glass substrate or a silicon substrate, and a metal film or an oxide semiconductor film is further laminated on the polyimide film.

Various applications of polyimide resins are being considered in the fields of electric and electronic components, etc. For example, it is desirable to replace glass substrates used in image display devices such as liquid crystal displays and OLED displays with plastic substrates in order to make the devices lighter and more flexible, and research into polyimide films suitable for such plastic substrates is being conducted.
In an image display device, when light emitted from a display element is emitted through a plastic substrate, the plastic substrate is required to be colorless and transparent. Furthermore, when light passes through a retardation film or a polarizing plate (for example, a liquid crystal display, a touch panel, etc.), in addition to being colorless and transparent, the plastic substrate is also required to have high optical isotropy (i.e., low Rth).

When a polyimide film is used as a substrate, the desired electronic circuit is created on the polyimide film through various processes, such as a sputtering process and an etching process for creating an oxide semiconductor film such as an indium tin oxide (ITO) film, depending on the application. When creating the desired electronic circuit on the polyimide film, the polyimide film is adhered to a hard support such as a glass plate to ensure the flatness of the polyimide film. If the polyimide film is not adhered to the support, problems will occur in the process. In addition, after these processes, a process is required to peel the polyimide film from the support. This peeling process is carried out after the molded body on the substrate is cooled to room temperature to about 50°C.

Methods for adhering a polyimide film to a support include adding an adhesive to the polyimide itself, as well as a method in which a layer known as a release layer is placed between the polyimide film and the support to ensure adhesion during processing.

As a method for peeling off a polyimide film from a support, for example, the following method is known.
(1) A method in which a structure containing a polyimide resin/support is obtained, and then a laser is irradiated from the support side to ablate the polyimide resin interface, thereby peeling off the polyimide resin (see, for example, Patent Document 1). The type of laser used is a solid (YAG) laser or a gas (UV excimer) laser, and a spectrum of 308 nm or the like is used.
(2) A method in which a release layer is formed on a support before applying a resin composition to the support, and then a structure including a polyimide resin film/release layer/support is obtained, and the polyimide resin film is mechanically peeled off (see, for example, Patent Document 2). As the release layer, there are methods using Parylene (registered trademark, manufactured by Nippon Parylene LLC) and tungsten oxide, and methods using vegetable oil-based, silicone-based, fluorine-based, and alkyd-based release agents. In addition, the laser irradiation described in (1) above may also be used in combination.

Furthermore, Patent Document 3 discloses a method for fixing a resin substrate to a support substrate via an adhesive layer, forming an electronic element on the resin substrate, and peeling an electronic device including the electronic element and the resin substrate from the support substrate, in which an adhesive layer containing a material whose adhesive strength with the support substrate decreases upon contact with moisture is used as a main component.

On the other hand, Patent Document 4 discloses that the moisture content in a resin composition containing a polyimide precursor and an organic solvent is reduced from the viewpoint of imidization of polyamic acid and storage stability of the resin composition. That is, it is believed that moisture causes the acid anhydride groups of some acid dianhydride monomers to hydrolyze and become carboxyl groups, which remain in a low molecular weight state without becoming high molecular weight. It is also believed that moisture is involved in the decomposition and recombination of the polyimide precursor, which affects the viscosity stability of the resin composition during storage.

Special Publication No. 2007-512568 JP 2010-067957 A JP 2016-021384 A JP 2018-145440 A

The method according to (1) above has a problem in that the resin substrate formed on the base body may be damaged during laser irradiation, and also has a cost problem in that an expensive laser irradiation device must be introduced.
In the method (2) above, a laser irradiation device is not necessary, but depending on the type of polyimide, the release layer may not fully exhibit its function.
In the method of Patent Document 3, when forming an electronic element, it was necessary to form a sealing layer to seal the exposed portion of the adhesive layer in order to prevent the adhesive layer from contacting moisture so as not to reduce the adhesive strength. On the other hand, when peeling off the electronic device after forming the electronic element, it was necessary to remove the sealing layer before peeling off in order to bring the adhesive layer into contact with moisture. Therefore, the method of Patent Document 3 was a complicated process overall. Furthermore, it was necessary to place the device in a high humidity environment of 90% or more in order to contact moisture, and there was a problem that it was difficult to control the moisture content and ensure stable peelability.

The present invention has been made in consideration of these circumstances, and aims to provide a laminate in which a polyimide film is adhered to a glass substrate or a silicon substrate, and a metal film or an oxide semiconductor film is further laminated on the polyimide film, in which the polyimide film is excellent in colorless transparency and optical isotropy, and in which the polyimide film can be easily and stably peeled off from the glass substrate or the silicon substrate.

The inventors have surprisingly found that the above-mentioned problems can be solved by intentionally incorporating an optimal amount of moisture in the film, a content that was previously required to be reduced. The present invention was completed based on this finding.

That is, the present invention relates to the following.
<1> A laminate comprising a polyimide film adhered to a glass substrate or a silicon substrate, and a metal film or an oxide semiconductor film further laminated on the polyimide film, wherein the metal film or the oxide semiconductor film has a thickness of 1 to 400 nm, and the polyimide film has a moisture content of 1,000 to 35,000 ppm by mass.
<2> The laminate according to <1> above, wherein the polyimide film has a peel strength from a glass substrate or a silicon substrate of 20 gf/cm or less.
<3> The laminate according to <1> or <2> above, wherein the polyimide film has a film thickness of 3 to 20 μm.
<4> The laminate according to any one of <1> to <3> above, wherein the oxide semiconductor film is at least one selected from the group consisting of indium tin oxide, amorphous silicon, indium gallium zinc oxide, and low-temperature polysilicon.
<5> A conductive film obtained by peeling and removing the glass substrate or the silicon substrate from the laminate according to any one of <1> to <4> above.
<6> A step of laminating a polyimide film on a glass substrate or a silicon substrate;
adjusting the moisture content of the polyimide film to 1,000 to 35,000 ppm by mass;
A method for producing a conductive film, comprising: laminating a metal film or an oxide semiconductor film having a thickness of 1 to 400 nm on a polyimide film; and peeling off the glass substrate or the silicon substrate.
<7> The method for producing a conductive film according to the above <6>, wherein the step of adjusting the moisture content of the polyimide film is a step of maintaining the polyimide film in a temperature and humidity environment of 10 to 40° C. and 40 to 80% RH for 20 hours or more.
<8> The method for producing a conductive film according to <6> or <7> above, wherein the step of laminating a metal film or an oxide semiconductor film on the polyimide film is performed by a physical vapor deposition method or a chemical vapor deposition method.

The laminate of the present invention allows the polyimide film to be easily and stably peeled off from the glass substrate or silicon substrate even when the polyimide film is mechanically peeled off from the glass substrate or silicon substrate, and therefore the laminate of the present invention can contribute to simplifying the manufacturing process of flexible electronic devices having resin substrates and improving the yield thereof.
Furthermore, polyimide films are excellent in colorless transparency and optical isotropy, and therefore, when peeled off from a glass substrate or a silicon substrate, the film is suitable as a resin substrate for a flexible electronic device.

An embodiment of the present invention will be described below, but the content of the present invention is not limited to the embodiment described below.
In this specification, the term "A to B" in relation to numerical values means "A or more and B or less" (when A<B) or "A or less and B or more" (when A>B). In addition, in the present invention, a combination of preferred embodiments is a more preferred embodiment.

The laminate of the present invention is a laminate in which a polyimide film is adhered to a glass substrate or a silicon substrate, and a metal film or an oxide semiconductor film is further laminated on the polyimide film, the metal film or the oxide semiconductor film having a thickness of 1 to 400 nm, and the moisture content of the polyimide film being 1,000 to 35,000 ppm by mass.

(Glass substrate or silicon substrate)
The glass substrate or silicon substrate is not particularly limited, and it is sufficient if it has a strength sufficient to support a polyimide film when manufacturing an electronic device (conductive film) using the polyimide film as a substrate. The type of glass is also not particularly limited, and non-alkali glass (borosilicate glass), alkali glass, soda glass, non-fluorescent glass, phosphate glass, borate glass, quartz, etc. can be used.
In order to improve adhesion to the polyimide film, it is preferable that the upper surface of the glass substrate or silicon substrate is highly flat. Specifically, the surface roughness Rmax is preferably 10 μm or less, and more preferably 1 μm or less.

(Polyimide film)
In the laminate of the present invention, a polyimide film is adhered to a glass substrate or a silicon substrate. The polyimide film is preferably directly adhered to the glass substrate or the silicon substrate, and it is preferable that no adhesive layer or the like is interposed between the glass substrate or the silicon substrate and the polyimide film.

The moisture content of the polyimide film in the present invention is 1,000 to 35,000 ppm by mass, preferably 3,000 to 30,000 ppm by mass, and more preferably 5,000 to 25,000 ppm by mass. If the moisture content of the polyimide film is within this range, the polyimide film can be stably peeled off from the glass substrate or silicon substrate after the electronic device is manufactured.

The thickness of the polyimide film is preferably 3 to 20 μm, more preferably 4 to 15 μm, and even more preferably 5 to 10 μm. If the thickness of the polyimide film is within this range, the polyimide film will not be damaged during the manufacture of the electronic device, the electronic device will be easily manufactured, and the electronic device can be stably peeled off from the glass substrate or silicon substrate after the electronic device is manufactured. The thickness of the polyimide film can be physically measured using a micrometer or the like, or it can be obtained by optically observing the film using a laser microscope or the like and measuring the height between the top surface of the film and the surface that contacts the glass.

The peel strength of the polyimide film from the glass substrate or silicon substrate is preferably 20 gf/cm or less, more preferably 15 gf/cm or less, and even more preferably 10 gf/cm or less. If the peel strength is within this range, the polyimide film adheres closely to the glass substrate or silicon substrate during the manufacture of the electronic device and does not peel off, and can be stably peeled off from the glass substrate or silicon substrate after the manufacture of the electronic device.

The polyimide film of the present invention is excellent in colorless transparency and optical isotropy. The preferred physical properties of the polyimide film of the present invention are as follows:

The total light transmittance is preferably 88% or more, more preferably 88.5% or more, and even more preferably 89% or more when the film is 10 μm thick. The yellow index (YI) is preferably 4.0 or less, more preferably 2.5 or less, and even more preferably 2.0 or less when the film is 10 μm thick. b ^* is preferably 2.0 or less, more preferably 1.2 or less, and even more preferably 1.0 or less when the film is 10 μm thick.

The absolute value of the thickness retardation (Rth) is preferably 100 nm or less, more preferably 60 nm or less, and even more preferably 35 nm or less, when the film has a thickness of 10 μm. When the thickness is within this range, the film has excellent optical isotropy.

The tensile strength is preferably 60 MPa or more, more preferably 70 MPa or more, and even more preferably 80 MPa or more. The tensile modulus is preferably 2.0 GPa or more, more preferably 2.5 GPa or more, and even more preferably 3.0 GPa or more.

The glass transition temperature (Tg) of the polyimide resin constituting the polyimide film in the present invention is preferably 230°C or higher, more preferably 250°C or higher, and even more preferably 270°C or higher.

A preferred example of a polyimide resin that can be used in the present invention is shown below, but the present invention is not limited to this.

[Polyimide resin 1]
Polyimide resin 1 has a structural unit A1 derived from a tetracarboxylic dianhydride and a structural unit B1 derived from a diamine, in which the structural unit A1 includes a structural unit (A-11) derived from a compound represented by formula (a-11) below, and a structural unit (A-12) derived from a compound represented by formula (a-12) below, and the structural unit B1 includes a structural unit (B-11) derived from a compound represented by formula (b-11) below, and a structural unit (B-12) derived from a compound represented by formula (b-12) below.

<Structural Unit A1>
The structural unit A1 is a structural unit derived from a tetracarboxylic dianhydride contained in the polyimide resin 1, and includes a structural unit (A-11) derived from a compound represented by the following formula (a-11) and a structural unit (A-12) derived from a compound represented by the following formula (a-12).

The compound represented by formula (a-11) is 1,2,4,5-cyclohexanetetracarboxylic dianhydride.
The compound represented by formula (a-12) is 4,4'-oxydiphthalic anhydride.
When the structural unit A1 contains both the structural unit (A-11) and the structural unit (A-12), the colorless transparency, optical isotropy, and chemical resistance of the film can be improved. The structural unit (A-11) particularly contributes greatly to improving the colorless transparency and optical isotropy, and the structural unit (A-12) particularly contributes greatly to improving the chemical resistance.

The proportion of the structural unit (A-11) in the structural unit A1 is preferably from 5 to 95 mol %, more preferably from 15 to 95 mol %, even more preferably from 20 to 90 mol %, and particularly preferably from 50 to 90 mol %.
The proportion of the structural unit (A-12) in the structural unit A1 is preferably from 5 to 95 mol %, more preferably from 5 to 85 mol %, even more preferably from 10 to 80 mol %, and particularly preferably from 10 to 50 mol %.
The total ratio of the structural units (A-11) and (A-12) in the structural unit A1 is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit for the total ratio of the structural units (A-11) and (A-12), that is, it is 100 mol%. The structural unit A1 may be composed only of the structural unit (A-11) and the structural unit (A-12).

The structural unit A1 may contain structural units other than the structural units (A-11) and (A-12). The tetracarboxylic dianhydride that gives such a structural unit is not particularly limited, and examples thereof include aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride, and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (excluding the compound represented by formula (a-12)); alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-cyclobutane tetracarboxylic dianhydride and norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride (excluding the compound represented by formula (a-11)); and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butane tetracarboxylic dianhydride.
In this specification, the term "aromatic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more aromatic rings, the term "alicyclic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing one or more alicyclic rings but no aromatic rings, and the term "aliphatic tetracarboxylic acid dianhydride" refers to a tetracarboxylic acid dianhydride containing neither an aromatic ring nor an alicyclic ring.
The structural units optionally contained in the structural unit A1 (that is, structural units other than the structural units (A-11) and (A-12)) may be of one type, or of two or more types.

<Structural Unit B1>
The structural unit B1 is a structural unit derived from a diamine contained in a polyimide resin, and includes a structural unit (B-11) derived from a compound represented by the following formula (b-11), and a structural unit (B-12) derived from a compound represented by the following formula (b-12).

The compound represented by formula (b-11) is 3,3'-diaminodiphenyl sulfone.
When the structural unit B1 contains the structural unit (B-11), the optical isotropy and chemical resistance of the film can be improved.
The compound represented by formula (b-12) is bis[4-(4-aminophenoxy)phenyl]sulfone.
When the structural unit B1 contains the structural unit (B-12), the tensile elongation of the film can be improved.

The proportion of the structural unit (B-11) in the structural unit B1 is preferably from 5 to 95 mol %, more preferably from 15 to 95 mol %, even more preferably from 20 to 90 mol %, and particularly preferably from 50 to 90 mol %.
The proportion of the structural unit (B-12) in the structural unit B1 is preferably from 5 to 95 mol %, more preferably from 5 to 85 mol %, even more preferably from 10 to 80 mol %, and particularly preferably from 10 to 50 mol %.
The total proportion of the structural units (B-11) and (B-12) in the structural unit B1 is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit to the total proportion of the structural units (B-11) and (B-12), that is, it is 100 mol%. The structural unit B1 may be composed only of the structural unit (B-11) and the structural unit (B-12).

The structural unit B1 may contain a structural unit other than the structural units (B-11) and (B-12). Diamines that provide such structural units are not particularly limited, but include 1,4-phenylenediamine, p-xylylenediamine, 3,5-diaminobenzoic acid, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-inden-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, and the like. aromatic diamines (excluding the compounds represented by formula (b-11) or (b-12)) such as benzenediamine, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, and 4,4'-diamino-2,2'-bistrifluoromethyldiphenyl ether; alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.
In this specification, an aromatic diamine means a diamine containing one or more aromatic rings, an alicyclic diamine means a diamine containing one or more alicyclic rings but no aromatic rings, and an aliphatic diamine means a diamine containing neither an aromatic ring nor an alicyclic ring.
The structural units optionally contained in the structural unit B1 (that is, structural units other than the structural units (B-11) and (B-12)) may be of one type, or of two or more types.

As the diamine that provides the structural unit optionally contained in the structural unit B1, a compound represented by the following formula (b-13-1), a compound represented by the following formula (b-13-2), a compound represented by the following formula (b-13-3), and a compound represented by the following formula (b-13-4) are preferred. That is, in the polyimide resin of one embodiment of the present invention, the structural unit B1 may further include at least one structural unit (B-13) selected from the group consisting of a structural unit (B-13-1) derived from a compound represented by the following formula (b-13-1), a structural unit (B-13-2) derived from a compound represented by the following formula (b-13-2), a structural unit (B-13-3) derived from a compound represented by the following formula (b-13-3), and a structural unit (B-13-4) derived from a compound represented by the following formula (b-13-4).

（式（ｂ－１３－２）中、Ｒはそれぞれ独立して、水素原子、フッ素原子又はメチル基である。）

(In formula (b-13-2), each R is independently a hydrogen atom, a fluorine atom, or a methyl group.)

The compound represented by formula (b-13-1) is 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (6FODA).
When the structural unit B1 contains the structural unit (B-13-1), the colorless transparency of the film can be improved.

In formula (b-13-2), R is independently selected from the group consisting of a hydrogen atom, a fluorine atom, and an alkyl group having 1 to 5 carbon atoms, and is a hydrogen atom, a fluorine atom, or a methyl group, and is preferably a hydrogen atom. Examples of the compound represented by formula (b-13-2) include 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(3-fluoro-4-aminophenyl)fluorene, and 9,9-bis(3-methyl-4-aminophenyl)fluorene, and at least one selected from the group consisting of these three compounds is preferred, and 9,9-bis(4-aminophenyl)fluorene is preferred.
When the structural unit B1 contains the structural unit (B-13-2), the optical isotropy and heat resistance of the film can be improved.

The compound represented by formula (b-13-3) is 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane.
When the structural unit B1 contains the structural unit (B-13-3), the colorless transparency of the film can be improved.

The compound represented by formula (b-13-4) is 2,2'-bis(trifluoromethyl)benzidine.
When the structural unit B1 contains the structural unit (B-13-4), the colorless transparency, chemical resistance, and mechanical properties of the film can be improved.

When the structural unit B1 contains the structural unit (B-11), the structural unit (B-12), and the structural unit (B-13), the total proportion of the structural units (B-11) and (B-12) in the structural unit B1 is preferably 70 to 95 mol%, more preferably 75 to 95 mol%, and even more preferably 75 to 90 mol%, and the proportion of the structural unit (B-13) in the structural unit B1 is preferably 5 to 30 mol%, more preferably 5 to 25 mol%, and even more preferably 10 to 25 mol%.
The total ratio of the structural units (B-11), (B-12), and (B-13) in the structural unit B1 is preferably 75 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit to the total ratio of the structural units (B-11), (B-12), and (B-13), that is, it is 100 mol%. The structural unit B1 may be composed only of the structural units (B-11), (B-12), and (B-13).

The structural unit (B-13) may be only the structural unit (B-13-1), only the structural unit (B-13-2), only the structural unit (B-13-3), or only the structural unit (B-13-4).
In addition, the structural unit (B-13) may be a combination of two or more structural units selected from the group consisting of the structural units (B-13-1) to (B-13-4).

The number average molecular weight of polyimide resin 1 is preferably 5,000 to 200,000 from the viewpoint of the mechanical strength of the resulting polyimide film. The number average molecular weight of polyimide resin can be determined, for example, from a standard polymethyl methacrylate (PMMA) equivalent value measured by gel filtration chromatography.

The polyimide resin 1 may contain a structure other than a polyimide chain (a structure in which the structural unit A1 and the structural unit B1 are bonded by an imide bond). Examples of structures other than a polyimide chain that can be contained in the polyimide resin include a structure containing an amide bond.
It is preferable that the polyimide resin 1 contains a polyimide chain (a structure formed by imide bonding between the structural unit A1 and the structural unit B1) as a main structure. Therefore, the ratio of the polyimide chain in the polyimide resin 1 is preferably 50 mass % or more, more preferably 70 mass % or more, even more preferably 90 mass % or more, and particularly preferably 99 mass % or more.

[Method of producing polyimide resin 1]
Polyimide resin 1 can be produced by reacting a tetracarboxylic acid component containing a compound that provides the above-mentioned structural unit (A-11) and a compound that provides the above-mentioned structural unit (A-12) with a diamine component containing a compound that provides the above-mentioned structural unit (B-11) and a compound that provides the above-mentioned structural unit (B-12).

Compounds that provide the structural unit (A-11) include, but are not limited to, compounds represented by formula (a-11), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a-11) (i.e., 1,2,4,5-cyclohexanetetracarboxylic acid) and alkyl esters of the tetracarboxylic acid. Compounds that provide the structural unit (A-11) are preferably compounds represented by formula (a-11) (i.e., dianhydrides).
Similarly, examples of compounds that provide the structural unit (A-12) include, but are not limited to, compounds represented by formula (a-12), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a-12) and alkyl esters of the tetracarboxylic acid. Compounds that provide the structural unit (A-12) are preferably compounds represented by formula (a-12) (i.e., dianhydrides).

The tetracarboxylic acid component contains a compound that provides the structural unit (A-11) in an amount of preferably 5 to 95 mol %, more preferably 15 to 95 mol %, even more preferably 20 to 90 mol %, and particularly preferably 50 to 90 mol %.
The tetracarboxylic acid component contains a compound that provides the structural unit (A-12) in an amount of preferably 5 to 95 mol %, more preferably 5 to 85 mol %, even more preferably 10 to 80 mol %, and particularly preferably 10 to 50 mol %.
The tetracarboxylic acid component preferably contains at least 50 mol %, more preferably at least 70 mol %, even more preferably at least 90 mol %, and particularly preferably at least 99 mol %, of the compound that provides the structural unit (A-11) and the compound that provides the structural unit (A-12) in total. There are no particular limitations on the upper limit of the total content of the compound that provides the structural unit (A-11) and the compound that provides the structural unit (A-12), and this is 100 mol %. The tetracarboxylic acid component may consist only of the compound that provides the structural unit (A-11) and the compound that provides the structural unit (A-12).

The tetracarboxylic acid component may contain a compound other than the compound that provides the structural unit (A-11) and the compound that provides the structural unit (A-12). Examples of such compounds include the above-mentioned aromatic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid dianhydrides, as well as derivatives thereof (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.).
The compound optionally contained in the tetracarboxylic acid component (i.e., compounds other than the compound that provides the structural unit (A-11) and the compound that provides the structural unit (A-12)) may be one type, or two or more types.

Compounds that provide the structural unit (B-11) include, but are not limited to, compounds represented by formula (b-11), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include diisocyanates corresponding to the diamines represented by formula (b-11). Compounds that provide the structural unit (B-11) are preferably compounds represented by formula (b-11) (i.e., diamines).
Compounds that provide the structural unit (B-12) include, but are not limited to, compounds represented by formula (b-12), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include diisocyanates corresponding to the diamines represented by formula (b-12). Compounds that provide the structural unit (B-12) are preferably compounds represented by formula (b-12) (i.e., diamines).

The diamine component contains the structural unit (B-11) in an amount of preferably 5 to 95 mol %, more preferably 15 to 95 mol %, even more preferably 20 to 90 mol %, and particularly preferably 50 to 90 mol %.
The diamine component contains the structural unit (B-12) in an amount of preferably 5 to 95 mol %, more preferably 5 to 85 mol %, even more preferably 10 to 80 mol %, and particularly preferably 10 to 50 mol %.
The diamine component contains the structural units (B-11) and (B-12) in total, preferably at least 50 mol%, more preferably at least 70 mol%, even more preferably at least 90 mol%, and particularly preferably at least 99 mol%. There is no particular upper limit on the total proportion of the structural units (B-11) and (B-12), that is, it is 100 mol%. The diamine component may be composed only of the structural unit (B-11) and the structural unit (B-12).

The diamine component may contain a compound other than the compound that provides the structural unit (B-11) and the compound that provides the structural unit (B-12). Examples of such compounds include the above-mentioned aromatic diamines, alicyclic diamines, and aliphatic diamines, as well as derivatives thereof (diisocyanates, etc.).
The compound optionally contained in the diamine component (i.e., compounds other than the compound that provides the structural unit (B-11) and the compound that provides the structural unit (B-12)) may be one type, or two or more types.

As the compound optionally contained in the diamine component, a compound which provides the structural unit (B-13) (i.e., a compound which provides the structural unit (B-13-1), a compound which provides the structural unit (B-13-2), a compound which provides the structural unit (B-13-3), and a compound which provides the structural unit (B-13-4)) is preferred.
Compounds that provide the structural unit (B-13) include, but are not limited to, compounds represented by formula (b-13-1), compounds represented by formula (b-13-2), compounds represented by formula (b-13-3), and compounds represented by formula (b-13-4). Derivatives thereof may be used as long as they can form the same structural unit. Examples of such derivatives include diisocyanates corresponding to the diamines represented by formulas (b-13-1) to (b-13-4). Compounds that provide the structural unit (B-13) are preferably compounds represented by formulas (b-13-1) to (b-13-4) (i.e., diamines).

When the diamine component contains a compound that provides the structural unit (B-11), a compound that provides the structural unit (B-12), and a compound that provides the structural unit (B-13), the diamine component preferably contains a total of 70 to 95 mol %, more preferably 75 to 95 mol %, and even more preferably 75 to 90 mol %, of the compound that provides the structural unit (B-11) and the compound that provides the structural unit (B-12), and preferably contains 5 to 30 mol %, more preferably 5 to 25 mol %, and even more preferably 10 to 25 mol % of the compound that provides the structural unit (B-13).
The diamine component contains the compound that gives the structural unit (B-11), the compound that gives the structural unit (B-12), and the compound that gives the structural unit (B-13) in a total amount of preferably 75 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. The upper limit of the total content ratio of the compound that gives the structural unit (B-11), the compound that gives the structural unit (B-12), and the compound that gives the structural unit (B-13) is not particularly limited, that is, it is 100 mol%. The diamine component may be composed only of the compound that gives the structural unit (B-11), the compound that gives the structural unit (B-12), and the compound that gives the structural unit (B-13).

The compound that provides the structural unit (B-13) may be only compounds that provide the structural unit (B-13-1), may be only compounds that provide the structural unit (B-13-2), may be only compounds that provide the structural unit (B-13-3), or may be only compounds that provide the structural unit (B-13-4).
Furthermore, the compound which provides the structural unit (B-13) may be a combination of two or more compounds selected from the group consisting of compounds which provide the structural units (B-13-1) to (B-13-4).

The ratio of the amounts of the tetracarboxylic acid component and the diamine component used in the production of polyimide resin 1 is preferably 0.9 to 1.1 moles of the diamine component per mole of the tetracarboxylic acid component.

In addition to the tetracarboxylic acid component and diamine component described above, a terminal blocking agent may be used in the production of polyimide resin 1. Monoamines or dicarboxylic acids are preferred as terminal blocking agents. The amount of terminal blocking agent introduced is preferably 0.0001 to 0.1 moles per mole of the tetracarboxylic acid component, and more preferably 0.001 to 0.06 moles. As monoamine terminal blocking agents, for example, methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, etc. are recommended. Of these, benzylamine and aniline are preferably used. As dicarboxylic acid terminal blocking agents, dicarboxylic acids are preferred, and a part of them may be ring-closed. For example, phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2,3-benzophenonedicarboxylic acid, 3,4-benzophenonedicarboxylic acid, cyclopentane-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, etc. are recommended. Of these, phthalic acid and phthalic anhydride are preferably used.

The method for reacting the tetracarboxylic acid component and the diamine component is not particularly limited, and any known method can be used.
Specific reaction methods include: (1) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the mixture is stirred at room temperature to 80° C. for 0.5 to 30 hours, and then the temperature is raised to carry out the imidization reaction; (2) a method in which a diamine component and a reaction solvent are charged into a reactor and dissolved, and then a tetracarboxylic acid component is charged, and the mixture is stirred at room temperature to 80° C. for 0.5 to 30 hours as necessary, and then the temperature is raised to carry out the imidization reaction; and (3) a method in which a tetracarboxylic acid component, a diamine component, and a reaction solvent are charged into a reactor, and the temperature is immediately raised to carry out the imidization reaction.

The reaction solvent used in the production of polyimide resin 1 may be any solvent that does not inhibit the imidization reaction and can dissolve the resulting polyimide resin. Examples of such solvents include aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

Specific examples of aprotic solvents include amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,3-dimethylimidazolidinone, and tetramethylurea; lactone-based solvents such as γ-butyrolactone and γ-valerolactone; phosphorus-containing amide-based solvents such as hexamethylphosphoric amide and hexamethylphosphine triamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone-based solvents such as acetone, cyclohexanone, and methylcyclohexanone; amine-based solvents such as picoline and pyridine; and ester-based solvents such as 2-methoxy-1-methylethyl acetate.

Specific examples of phenol-based solvents include phenol, o-cresol, m-cresol, p-cresol, 2,3-xylenol, 2,4-xylenol, 2,5-xylenol, 2,6-xylenol, 3,4-xylenol, and 3,5-xylenol.
Specific examples of ether solvents include 1,2-dimethoxyethane, bis(2-methoxyethyl)ether, 1,2-bis(2-methoxyethoxy)ethane, bis[2-(2-methoxyethoxy)ethyl]ether, tetrahydrofuran, and 1,4-dioxane.
Specific examples of carbonate solvents include diethyl carbonate, methyl ethyl carbonate, ethylene carbonate, and propylene carbonate.
Among the above reaction solvents, amide-based solvents and lactone-based solvents are preferred. The above reaction solvents may be used alone or in combination of two or more.

In the imidization reaction, it is preferable to carry out the reaction while removing the water generated during production using a Dean-Stark apparatus or the like. By carrying out such an operation, it is possible to further increase the degree of polymerization and the imidization rate.

In the above imidization reaction, a known imidization catalyst can be used, such as a base catalyst or an acid catalyst.
Examples of the base catalyst include organic base catalysts such as pyridine, quinoline, isoquinoline, α-picoline, β-picoline, 2,4-lutidine, 2,6-lutidine, trimethylamine, triethylamine, tripropylamine, tributylamine, triethylenediamine, imidazole, N,N-dimethylaniline, and N,N-diethylaniline; and inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogencarbonate, and sodium hydrogencarbonate.
Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, oxybenzoic acid, terephthalic acid, benzenesulfonic acid, paratoluenesulfonic acid, naphthalenesulfonic acid, etc. The above imidization catalysts may be used alone or in combination of two or more kinds.
Among the above, from the viewpoint of handleability, it is preferable to use a base catalyst, more preferably an organic base catalyst, further preferably triethylamine, and particularly preferably a combination of triethylamine and triethylenediamine.

The temperature of the imidization reaction is preferably 120 to 250°C, more preferably 160 to 200°C, from the viewpoint of the reaction rate and suppression of gelation, etc. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

The solid content concentration during the imidization reaction is preferably 30 to 60% by mass, more preferably 35 to 58% by mass, and particularly preferably 40 to 56% by mass. When the solid content concentration during the imidization reaction is within this range, the imidization reaction proceeds well and water generated during the reaction can be easily removed, thereby increasing the degree of polymerization and the imidization rate.
The solid content concentration during the imidization reaction is a value calculated from the following formula based on the masses of the tetracarboxylic acid component added to the reaction system, the diamine component in the reaction system, and the reaction solvent.
Solid content concentration during imidization reaction (mass %)=(total mass of tetracarboxylic acid component and diamine component)/(total mass of tetracarboxylic acid component, diamine component, and reaction solvent)×100

Another preferred example of a polyimide resin that can be used in the present invention is shown below, but the present invention is not limited to this.

[Polyimide resin 2]
Polyimide resin 2 has a structural unit A2 derived from a tetracarboxylic dianhydride and a structural unit B2 derived from a diamine, in which the structural unit A2 contains a structural unit (A-21) derived from a compound represented by formula (a-21) below and a structural unit (A-22) derived from a compound represented by formula (a-22) below, the structural unit B2 contains a structural unit (B-21) derived from a compound represented by formula (b-21) below, and the ratio of the structural unit (B-21) in the structural unit B2 is 70 mol % or more.

<Structural Unit A2>
The structural unit A2 is a structural unit derived from a tetracarboxylic dianhydride contained in the polyimide resin 2, and includes a structural unit (A-21) derived from a compound represented by formula (a-21) and a structural unit (A-22) derived from a compound represented by formula (a-22). The compound represented by formula (a-21) is the same as the compound represented by formula (a-11) described above. In addition, the compound represented by formula (a-22) is the same as the compound represented by formula (a-12) described above.
When the structural unit A2 contains both the structural unit (A-21) and the structural unit (A-22), the colorless transparency, optical isotropy, and chemical resistance of the film can be improved. The structural unit (A-21) particularly contributes greatly to improving the colorless transparency and optical isotropy, and the structural unit (A-22) particularly contributes greatly to improving the chemical resistance.

The proportion of the structural unit (A-21) in the structural unit A2 is preferably from 5 to 95 mol %, more preferably from 15 to 95 mol %, even more preferably from 20 to 90 mol %, and particularly preferably from 50 to 90 mol %.
The proportion of the structural unit (A-22) in the structural unit A2 is preferably from 5 to 95 mol %, more preferably from 5 to 85 mol %, even more preferably from 10 to 80 mol %, and particularly preferably from 10 to 50 mol %.
The total proportion of the structural units (A-21) and (A-22) in the structural unit A2 is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit for the total proportion of the structural units (A-21) and (A-22), that is, it is 100 mol%. The structural unit A2 may be composed only of the structural unit (A-21) and the structural unit (A-22).

The structural unit A2 may include a structural unit other than the structural units (A-21) and (A-22). The tetracarboxylic dianhydride that gives such a structural unit is not particularly limited, and examples thereof include aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride, and 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (excluding the compound represented by formula (a-22)); alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-cyclobutane tetracarboxylic dianhydride and norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride (excluding the compound represented by formula (a-21)); and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butane tetracarboxylic dianhydride.
The structural units optionally contained in the structural unit A2 (that is, structural units other than the structural units (A-21) and (A-22)) may be of one type, or of two or more types.

<Structural Unit B2>
The structural unit B2 is a structural unit derived from a diamine contained in a polyimide resin, and includes a structural unit (B-21) derived from a compound represented by formula (b-21). The compound represented by formula (b-21) is the same as the compound represented by formula (b-11) described above.
When the structural unit B2 contains the structural unit (B-21), the optical isotropy and chemical resistance of the film can be improved.

The ratio of structural unit (B-21) in structural unit B2 is 70 mol% or more. This ratio is preferably 75 mol% or more, and more preferably 80 mol% or more. The upper limit of the ratio of structural unit (B-21) may be 90 mol%, 95 mol%, 99 mol%, or 100 mol%. Structural unit B2 may consist only of structural unit (B-21).

The structural unit B2 may contain a structural unit other than the structural unit (B-21). Diamines that provide such a structural unit are not particularly limited, but include 1,4-phenylenediamine, p-xylylenediamine, 3,5-diaminobenzoic acid, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzanilide, 1-(4-aminophenyl)-2,3-dihydro-1,3,3-trimethyl-1H-inden-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropyl aromatic diamines (excluding the compound represented by formula (b-21)) such as diphenylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 9,9-bis(4-aminophenyl)fluorene, and 4,4'-diamino-2,2'-bistrifluoromethyldiphenyl ether; alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.
The structural unit optionally contained in the structural unit B2 (that is, the structural unit other than the structural unit (B-21)) may be of one type, or of two or more types.

（式（ｂ－２２－２）中、Ｒはそれぞれ独立して、水素原子、フッ素原子又はメチル基である。） As the diamine that provides the structural unit optionally contained in the structural unit B2, a compound represented by the following formula (b-22-1), a compound represented by the following formula (b-22-2), a compound represented by the following formula (b-22-3), and a compound represented by the following formula (b-22-4) are preferred. That is, in the polyimide resin of one embodiment of the present invention, the structural unit B2 may further include at least one structural unit (B-22) selected from the group consisting of a structural unit (B-22-1) derived from a compound represented by the following formula (b-22-1), a structural unit (B-22-2) derived from a compound represented by the following formula (b-22-2), a structural unit (B-22-3) derived from a compound represented by the following formula (b-22-3), and a structural unit (B-22-4) derived from a compound represented by the following formula (b-22-4).

(In formula (b-22-2), each R is independently a hydrogen atom, a fluorine atom, or a methyl group.)

The compound represented by formula (b-22-1) is the same as the compound represented by formula (b-13-1) described above.
When the structural unit B contains the structural unit (B-22-1), the colorless transparency of the film can be improved.

The compound represented by formula (b-22-2) is the same as the compound represented by formula (b-13-2) described above, and the preferred range is also the same.
When the structural unit B2 contains the structural unit (B-22-2), the optical isotropy and heat resistance of the film can be improved.

The compound represented by formula (b-22-3) is the same as the compound represented by formula (b-13-3) described above.
When the structural unit B2 contains the structural unit (B-22-3), the colorless transparency of the film can be improved.

The compound represented by formula (b-22-4) is the same as the compound represented by formula (b-13-4) described above.
When the structural unit B2 contains the structural unit (B-22-4), the colorless transparency, chemical resistance, and mechanical properties of the film can be improved.

When the structural unit B2 contains the structural unit (B-21) and the structural unit (B-22), the ratio of the structural unit (B-21) in the structural unit B2 is preferably 70 to 95 mol%, more preferably 75 to 95 mol%, and even more preferably 75 to 90 mol%, and the ratio of the structural unit (B-22) in the structural unit B2 is preferably 5 to 30 mol%, more preferably 5 to 25 mol%, and even more preferably 10 to 25 mol%.
The total proportion of the structural units (B-21) and (B-22) in the structural unit B2 is preferably 75 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit for the total proportion of the structural units (B-21) and (B-22), that is, it is 100 mol%. The structural unit B may be composed only of the structural units (B-21) and (B-22).

The structural unit (B-22) may be only the structural unit (B-22-1), only the structural unit (B-22-2), only the structural unit (B-22-3), or only the structural unit (B-22-4).
In addition, the structural unit (B-22) may be a combination of two or more structural units selected from the group consisting of structural units (B-22-1) to (B-22-4).

The number average molecular weight of polyimide resin 2 is preferably 5,000 to 200,000 from the viewpoint of the mechanical strength of the resulting polyimide film.

The polyimide resin 2 may contain a structure other than a polyimide chain (a structure formed by imide bonding between the structural unit A2 and the structural unit B2). Examples of structures other than polyimide chains that can be contained in the polyimide resin include structures containing amide bonds.
The polyimide resin 2 preferably contains a polyimide chain (a structure formed by imide bonding between the structural unit A2 and the structural unit B2) as a main structure. Therefore, the ratio of the polyimide chain in the polyimide resin 2 is preferably 50 mass % or more, more preferably 70 mass % or more, even more preferably 90 mass % or more, and particularly preferably 99 mass % or more.

[Method of manufacturing polyimide resin 2]
The polyimide resin can be produced by reacting a tetracarboxylic acid component containing a compound that provides the above-mentioned structural unit (A-21) and a compound that provides the above-mentioned structural unit (A-22) with a diamine component containing 70 mol % or more of a compound that provides the above-mentioned structural unit (B-21).

Compounds that provide the structural unit (A-21) include, but are not limited to, compounds represented by formula (a-21), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a-21) (i.e., 1,2,4,5-cyclohexanetetracarboxylic acid) and alkyl esters of the tetracarboxylic acid. Compounds that provide the structural unit (A-21) are preferably compounds represented by formula (a-21) (i.e., dianhydrides).
Similarly, examples of compounds that provide the structural unit (A-22) include, but are not limited to, compounds represented by formula (a-22), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride represented by formula (a-22) and alkyl esters of the tetracarboxylic acid. Compounds that provide the structural unit (A-22) are preferably compounds represented by formula (a-22) (i.e., dianhydrides).

The tetracarboxylic acid component contains a compound that provides the structural unit (A-21) in an amount of preferably 5 to 95 mol %, more preferably 15 to 95 mol %, even more preferably 20 to 90 mol %, and particularly preferably 50 to 90 mol %.
The tetracarboxylic acid component contains a compound that provides the structural unit (A-22) in an amount of preferably 5 to 95 mol %, more preferably 5 to 85 mol %, even more preferably 10 to 80 mol %, and particularly preferably 10 to 50 mol %.
The tetracarboxylic acid component preferably contains at least 50 mol %, more preferably at least 70 mol %, even more preferably at least 90 mol %, and particularly preferably at least 99 mol %, of the compound that provides the structural unit (A-21) and the compound that provides the structural unit (A-22). There are no particular limitations on the upper limit of the total content of the compound that provides the structural unit (A-21) and the compound that provides the structural unit (A-22), and this is 100 mol %. The tetracarboxylic acid component may consist only of the compound that provides the structural unit (A-21) and the compound that provides the structural unit (A-22).

The tetracarboxylic acid component may contain a compound other than the compound that provides the structural unit (A-21) and the compound that provides the structural unit (A-22). Examples of such compounds include the above-mentioned aromatic tetracarboxylic acid dianhydrides, alicyclic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid dianhydrides, as well as derivatives thereof (tetracarboxylic acids, alkyl esters of tetracarboxylic acids, etc.).
The compound optionally contained in the tetracarboxylic acid component (i.e., compounds other than the compound that provides the structural unit (A-21) and the compound that provides the structural unit (A-22)) may be one type, or two or more types.

Compounds that provide the structural unit (B-21) include, but are not limited to, compounds represented by formula (b-21), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include diisocyanates that correspond to the diamines represented by formula (b-21). Compounds that provide the structural unit (B-21) are preferably compounds represented by formula (b-21) (i.e., diamines).

The diamine component contains 70 mol% or more of the compound that provides the structural unit (B-21). The diamine component contains preferably 75 mol% or more, more preferably 80 mol% or more, of the compound that provides the structural unit (B-21). The upper limit of the content ratio of the compound that provides the structural unit (B-21) may be 90 mol%, 95 mol%, 99 mol%, or 100 mol%. The diamine component may consist only of the compound that provides the structural unit (B-21).

The diamine component may contain a compound other than the compound that provides the structural unit (B-21). Examples of such compounds include the above-mentioned aromatic diamines, alicyclic diamines, and aliphatic diamines, as well as their derivatives (diisocyanates, etc.).
The compound optionally contained in the diamine component (that is, a compound other than the compound that provides the structural unit (B-21)) may be one type, or two or more types.

As the compound optionally contained in the diamine component, a compound which provides the structural unit (B-22) (i.e., a compound which provides the structural unit (B-22-1), a compound which provides the structural unit (B-22-2), a compound which provides the structural unit (B-22-3), and a compound which provides the structural unit (B-22-4)) is preferred.
Compounds that provide the structural unit (B-22) include, but are not limited to, compounds represented by formula (b-22-1), compounds represented by formula (b-22-2), compounds represented by formula (b-22-3), and compounds represented by formula (b-22-4), and may be derivatives thereof as long as they can form the same structural unit. Examples of such derivatives include diisocyanates corresponding to the diamines represented by formulas (b-22-1) to (b-22-4). Compounds that provide the structural unit (B-22) are preferably compounds represented by formulas (b-22-1) to (b-22-4) (i.e., diamines).

When the diamine component contains a compound that provides the structural unit (B-21) and a compound that provides the structural unit (B-22), the diamine component preferably contains 70 to 95 mol %, more preferably 75 to 95 mol %, and even more preferably 75 to 90 mol % of the compound that provides the structural unit (B-21), and preferably contains 5 to 30 mol %, more preferably 5 to 25 mol %, and even more preferably 10 to 25 mol % of the compound that provides the structural unit (B-22).
The diamine component contains the compound that provides the structural unit (B-21) and the compound that provides the structural unit (B-22) in a total amount of preferably 75 mol % or more, more preferably 80 mol % or more, even more preferably 90 mol % or more, and particularly preferably 99 mol % or more. There is no particular upper limit on the total content of the compound that provides the structural unit (B-21) and the compound that provides the structural unit (B-22), that is, it is 100 mol %. The diamine component may consist only of the compound that provides the structural unit (B-21) and the compound that provides the structural unit (B-22).

The compound that provides the structural unit (B-22) may be only compounds that provide the structural unit (B-22-1), may be only compounds that provide the structural unit (B-22-2), may be only compounds that provide the structural unit (B-22-3), or may be only compounds that provide the structural unit (B-22-4).
Furthermore, the compound which provides the structural unit (B-22) may be a combination of two or more compounds selected from the group consisting of compounds which provide the structural units (B-22-1) to (B-22-4).

The ratio of the amounts of the tetracarboxylic acid component and the diamine component used in producing the polyimide resin 2 is preferably 0.9 to 1.1 moles of the diamine component per mole of the tetracarboxylic acid component.

In addition to the tetracarboxylic acid component and diamine component, a terminal blocking agent may be used in the production of polyimide resin 2. The terminal blocking agent is as described for polyimide resin 1, and the preferred range is also the same.

There are no particular limitations on the method for reacting the tetracarboxylic acid component and the diamine component, and any known method can be used. The specific reaction method is as described for polyimide resin 1.

The reaction solvent used in the production of polyimide resin 2 may be any solvent that does not inhibit the imidization reaction and can dissolve the resulting polyimide. Specific examples of reaction solvents are as described for polyimide resin 1, and the preferred ranges are also the same.

In the imidization reaction, it is preferable to carry out the reaction while removing the water generated during production using a Dean-Stark apparatus or the like. By carrying out such an operation, it is possible to further increase the degree of polymerization and the imidization rate.

In the above imidization reaction, a known imidization catalyst can be used. Specific examples of the imidization catalyst are as described for polyimide resin 1, and the preferred range is also the same.

The temperature of the imidization reaction is preferably 120 to 250°C, more preferably 160 to 200°C, from the viewpoint of the reaction rate and suppression of gelation, etc. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

Further, as another preferred example of a polyimide resin that can be used in the present invention, a polyimide resin obtained from the following copolymer can be mentioned, but the present invention is not limited thereto.

[Copolymer 3]
Copolymer 3 is a copolymer having a structural unit A3 derived from a tetracarboxylic dianhydride and a structural unit B3 derived from a diamine,
the structural unit A3 is composed of a structural unit (A-31) derived from an alicyclic tetracarboxylic dianhydride (a-31) and a structural unit (A-32) derived from a tetracarboxylic dianhydride (a-32) other than the alicyclic tetracarboxylic dianhydride (a-31);
The structural unit B3 includes a structural unit (B-31) derived from a compound represented by the following formula (b-31):
The structural unit (A-32) includes at least one selected from the group consisting of a structural unit (A-32-1) derived from a compound represented by the following formula (a-32-1), a structural unit (A-32-2) derived from a compound represented by the following formula (a-32-2), a structural unit (A-32-3) derived from a compound represented by the following formula (a-32-3), and a structural unit (A-32-4) derived from a compound represented by the following formula (a-32-4),
The copolymer has imide repeating structural units formed from a compound that provides the structural unit (A-31) and a compound that provides the structural unit (B-31), and has amic acid repeating structural units formed from a compound that provides the structural unit (A-32) and a compound that provides the structural unit B3.

<Structural Unit A3>
The structural unit A3 is a structural unit derived from a tetracarboxylic dianhydride contained in the copolymer 3, and is composed of a structural unit (A-31) derived from an alicyclic tetracarboxylic dianhydride (a-31) and a structural unit (A-32) derived from a tetracarboxylic dianhydride (a-32) other than the alicyclic tetracarboxylic dianhydride (a-31).

The structural unit (A-31) is a structural unit derived from an alicyclic tetracarboxylic dianhydride (a-31).
From the viewpoints of high transparency, high heat resistance, and low residual stress, the structural unit (A-31) preferably includes a structural unit (A-31-1) derived from a compound represented by the following formula (a-31-1): The compound represented by formula (a-31-1) is norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic acid dianhydride.

The ratio of the structural unit (A-31-1) in the structural unit (A-31) is preferably at least 45 mol%, more preferably at least 70 mol%, even more preferably at least 90 mol%, and particularly preferably at least 99 mol%. There is no upper limit to this ratio, and it is 100 mol%.
The structural unit (A-31) may have a structural unit derived from an alicyclic tetracarboxylic dianhydride other than the compound represented by formula (a-31-1). Examples of such alicyclic tetracarboxylic dianhydrides include 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, and dicyclohexyl tetracarboxylic dianhydride.
The alicyclic tetracarboxylic dianhydrides (a-31) may be used alone or in combination of two or more.

The structural unit (A-32) is a structural unit derived from a tetracarboxylic dianhydride (a-32) other than an alicyclic tetracarboxylic dianhydride (a-31). The tetracarboxylic dianhydride (a-32) may be one or more selected from the group consisting of aromatic tetracarboxylic dianhydrides and aliphatic tetracarboxylic dianhydrides, and preferably contains an aromatic tetracarboxylic dianhydride. In other words, the structural unit (A-32) preferably contains a structural unit derived from an aromatic tetracarboxylic dianhydride.
From the standpoint of high heat resistance and low residual stress, the structural unit (A-32) includes at least one selected from the group consisting of a structural unit (A-32-1) derived from a compound represented by the following formula (a-32-1), a structural unit (A-32-2) derived from a compound represented by the following formula (a-32-2), a structural unit (A-32-3) derived from a compound represented by the following formula (a-32-3), and a structural unit (A-32-4) derived from a compound represented by the following formula (a-32-4).

The compound represented by formula (a-32-1) is biphenyltetracarboxylic dianhydride (BPDA), and specific examples thereof include 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a-32-1s), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a-32-1a), and 2,2',3,3'-biphenyltetracarboxylic dianhydride (i-BPDA) represented by the following formula (a-32-1i). Among these, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a-32-1s) is preferred.

The compound represented by formula (a-32-2) is p-phenylenebis(trimellitate)dianhydride (TAHQ).

The compound represented by formula (a-32-3) is oxydiphthalic anhydride (ODPA), and specific examples thereof include 4,4'-oxydiphthalic anhydride (s-ODPA) represented by the following formula (a-32-3s), 3,4'-oxydiphthalic anhydride (a-ODPA) represented by the following formula (a-32-3a), and 3,3'-oxydiphthalic anhydride (i-ODPA) represented by the following formula (a-32-3i). Of these, 4,4'-oxydiphthalic anhydride (s-ODPA) represented by the following formula (a-32-3s) is preferred.

The compound represented by formula (a-32-4) is pyromellitic dianhydride (PMDA).

From the standpoint of high heat resistance and low residual stress, the structural unit (A-32) preferably includes at least one selected from the group consisting of the structural unit (A-32-1) and the structural unit (A-32-2).
The structural unit (A-32-1) is preferred from the viewpoints of improving the heat resistance and thermal stability of the film and further reducing residual stress, while the structural unit (A-32-2) is preferred from the viewpoints of reducing YI and achieving superior colorless transparency.

The tetracarboxylic dianhydride (a-32) may contain a tetracarboxylic dianhydride other than the compounds represented by formulae (a-32-1) to (a-32-4). Examples of such tetracarboxylic dianhydrides include aromatic tetracarboxylic dianhydrides such as 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, and the compound represented by the following formula (a-32-5); and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride. Among these, aromatic tetracarboxylic dianhydrides are preferred.
The tetracarboxylic dianhydrides (a-32) may be used alone or in combination of two or more.

The ratio of the structural units (A-32-1) to (A-32-4) in the structural unit (A-32) is preferably 45 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit to this ratio, that is, it is 100 mol%. The structural unit (A-32) may contain at least one selected from the structural units (A-32-1) to (A-32-4), and may be composed of only one selected from the structural units (A-32-1) to (A-32-4).
When the structural unit (A-32) contains two or more structural units selected from the structural units (A-32-1) to (A-32-4), there are no particular limitations on the ratio of the structural units in the structural unit (A-32), and any ratio can be used.

In the structural unit A3, the molar ratio of the structural unit (A-31) to the structural unit (A-32) [(A-31)/(A-32)] is preferably from 10/90 to 90/10, more preferably from 30/70 to 85/15, and even more preferably from 50/50 to 80/20.
The ratio of the aromatic tetracarboxylic dianhydride-derived structural units in the structural unit (A-32) is preferably 45 mol% or more, more preferably 60 mol% or more, and even more preferably 85 mol% or more. There is no particular upper limit to the total content, and it is 100 mol%.

<Structural Unit B3>
The structural unit B3 is a structural unit derived from a diamine contained in the copolymer of the present invention, and contains a structural unit (B-31) derived from a compound represented by the following formula (b-31): When the structural unit B contains the structural unit (B-31), it is possible to achieve both excellent transparency and the properties of low residual stress and low retardation.

The compound represented by formula (b-31) is the same as the compound represented by formula (b-13-1) described above.

It is preferable that the structural unit B3 further contains a structural unit (B-32) derived from a compound represented by the following general formula (b-32). When the structural unit B3 contains the structural unit (B-32), the residual stress is reduced.

In formula (b-32), ^Z1 and ^Z2 each independently represent a divalent aliphatic group or a divalent aromatic group, ^R1 and ^R2 each independently represent a monovalent aromatic group or a monovalent aliphatic group, ^R3 and ^R4 each independently represent a monovalent aliphatic group, ^R5 and ^R6 each independently represent a monovalent aliphatic group or a monovalent aromatic group, m and n each independently represent an integer of 1 or more, and the sum of m and n represents an integer of 2 to 1000. However, at least one of ^R1 and ^R2 represents a monovalent aromatic group.
In formula (b-32), two or more different repeating units described in parallel in brackets [ ] may be repeated in any form and order of random, alternating, or block.

In formula (b-32), the divalent aliphatic group or divalent aromatic group in ^Z1 and ^Z2 may be substituted with a fluorine atom. Examples of the divalent aliphatic group include divalent saturated or unsaturated aliphatic groups having 1 to 20 carbon atoms. The divalent aliphatic group preferably has 3 to 20 carbon atoms.
Examples of the divalent saturated aliphatic group include alkylene groups having 1 to 20 carbon atoms, such as a methylene group, an ethylene group, a propylene group, a trimethylene group, a tetramethylene group, a hexamethylene group, an octamethylene group, a decamethylene group, and a dodecamethylene group.
The divalent unsaturated aliphatic group may be an alkylene group having 2 to 20 carbon atoms, such as a vinylene group, a propenylene group, or an alkylene group having an unsaturated double bond at a terminal.
Examples of the divalent aromatic group include an arylene group having 6 to 20 carbon atoms and an aralkylene group having 7 to 20 carbon atoms. Specific examples of the arylene group having 6 to 20 carbon atoms in ^Z1 and ^Z2 include an o-phenylene group, an m-phenylene group, a p-phenylene group, a 4,4'-biphenylylene group, and a 2,6-naphthylene group.
Z ¹ and Z ² are preferably a trimethylene group or a p-phenylene group, and more preferably a trimethylene group.

In formula (b-32), the monovalent aliphatic groups for R ¹ to R ⁶ include monovalent saturated or unsaturated aliphatic groups. Examples of the monovalent saturated aliphatic groups include alkyl groups having 1 to 22 carbon atoms, such as a methyl group, an ethyl group, and a propyl group. Examples of the monovalent unsaturated aliphatic groups include alkenyl groups having 2 to 22 carbon atoms, such as a vinyl group and a propenyl group. These groups may be substituted with a fluorine atom.
Examples of the monovalent aromatic group for R ¹ , R ² , R ⁵ and R ⁶ in formula (b-32) include an aryl group having 6 to 20 carbon atoms, an aryl group having 7 to 30 carbon atoms and substituted with an alkyl group, and an aralkyl group having 7 to 30 carbon atoms. As the monovalent aromatic group, an aryl group is preferable, and a phenyl group is more preferable.
At least one of R ¹ and R ² represents a monovalent aromatic group, but it is preferable that both R ¹ and R ² are monovalent aromatic groups, and it is more preferable that both R ¹ and R ² are phenyl groups.
R ³ and R ⁴ are preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group.
^R5 and ^R6 are preferably a monovalent aliphatic group, more preferably a methyl group.

In formula (b-32), m represents the number of repeating siloxane units to which at least one monovalent aromatic group is bonded, and n represents the number of repeating siloxane units to which a monovalent aliphatic group is bonded.
m and n each independently represent an integer of 1 or more, and the sum of m and n (m+n) represents an integer of 2 to 1000. The sum of m and n preferably represents an integer of 3 to 500, more preferably an integer of 3 to 100, and even more preferably an integer of 3 to 50.
The ratio of m/n is preferably from 50/50 to 99/1, more preferably from 60/40 to 90/10, and even more preferably from 70/30 to 80/20.

The functional group equivalent of the compound represented by formula (b-32) is preferably 150 to 5,000 g/mol, more preferably 400 to 4,000 g/mol, and even more preferably 500 to 3,000 g/mol.
The functional group equivalent means the mass of the compound represented by formula (b-32) per mole of the functional group.

The content of the polyorganosiloxane unit relative to the total of the structural unit A3 and the structural unit B3 is preferably 5 to 45% by mass, more preferably 7 to 40% by mass, and even more preferably 10 to 35% by mass. When the content of the polyorganosiloxane unit is within the above range, low retardation and low residual stress can be more highly compatible.
The polyorganosiloxane unit has the same meaning as the structural unit (B-32), and the content of the polyorganosiloxane unit relative to the total of the structural units A3 and B3 is calculated from the mass ratio of the compound that provides the structural unit (B-32), preferably the compound represented by formula (b-32), to the total amount of the raw materials that provide the structural units A3 and B3.

Commercially available compounds represented by formula (b-32) include "X-22-9409" and "X-22-1660B-3" manufactured by Shin-Etsu Chemical Co., Ltd.

It is preferable that the structural unit B3 further contains a structural unit (B-33) derived from a compound represented by the following formula (b-33).

The compound represented by formula (b-33) is the same as the compound represented by formula (b-13-2) described above, and the preferred range is also the same.
The copolymer of the present invention has improved transparency and heat resistance due to the inclusion of the structural unit (B-33).

The proportion of the structural unit (B-31) in the structural unit B3 is preferably 45 mol% or more, more preferably 48 mol% or more, even more preferably 85 mol% or more, still more preferably 88 mol% or more, and is preferably 100 mol% or less, more preferably 99.5 mol% or less, and even more preferably 99.0 mol% or less. The structural unit B3 may be composed only of the structural unit (B-31).
When the structural unit B3 contains the structural unit (B-32), the proportion of the structural unit (B-32) in the structural unit B3 is preferably 0.01 to 15.0 mol %, more preferably 0.5 to 12.0 mol %, and even more preferably 1.0 to 8.0 mol %.
When the structural unit B3 includes the structural unit (B-33), from the viewpoint of low residual stress, the ratio of the structural unit (B-3) in the structural unit B3 is preferably 5 mol % or more, more preferably 10 mol % or more, even more preferably 25 mol % or more, and is preferably 65 mol % or less, more preferably 55 mol % or less, even more preferably 50 mol % or less.
When the structural unit B3 contains the structural unit (B-33), the total proportion of the structural units (B-31) and (B-33) in the structural unit B3 is preferably 85.0 to 100 mol%, more preferably 88.0 to 99.5 mol%, and even more preferably 92.0 to 99.0 mol%. When the structural unit B3 does not contain the structural unit (B-33), the proportion of the structural unit (B-31) in the structural unit B3 is preferably in the same range as above.
The total content of the structural units (B-31) to (B-33) in the structural unit B3 is preferably 45 to 100 mol %, more preferably 60 to 100 mol %, even more preferably 85 to 100 mol %, and particularly preferably 100 mol %.

The structural unit B3 may contain structural units other than the structural units (B-31) to (B-33).
Diamines that provide such structural units are not particularly limited, but include 1,4-phenylenediamine, p-xylylenediamine, 3,5-diaminobenzoic acid, 1,5-diaminonaphthalene, 2,2'-dimethylbiphenyl-4,4'-diamine, 2,2'-bis(trifluoromethyl)benzidine, 2,2'-dimethylbiphenyl-4,4'-diamine, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylmethane, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 2,2-bis(4-aminophenyl)hexafluoropropane, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzanilide, 3,4'-diaminodiphenyl ether, 1-(4-aminophenyl)-2,3-dihydro-1,3,3- Examples of the diamines include aromatic diamines such as trimethyl-1H-inden-5-amine, α,α'-bis(4-aminophenyl)-1,4-diisopropylbenzene, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane, and 1,4-bis(4-aminophenoxy)benzene; alicyclic diamines such as 1,3-bis(aminomethyl)cyclohexane and 1,4-bis(aminomethyl)cyclohexane; and aliphatic diamines such as ethylenediamine and hexamethylenediamine.
The structural units other than the structural units (B-31) to (B-33) optionally contained in the structural unit B3 may be of one type, or of two or more types.
It is preferable that the structural unit B3 does not contain any structural units other than the structural units (B-31) to (B-33). In particular, from the viewpoint of realizing low retardation, it is preferable that the structural unit B3 does not contain any structural units derived from 2,2'-bis(trifluoromethyl)benzidine.

<Imide repeating structural unit/Amic acid repeating structural unit>
Copolymer 3 has an imide repeating structural unit formed from a compound that provides the structural unit (A-31) and a compound that provides the structural unit (B-31), and an amic acid repeating structural unit formed from a compound that provides the structural unit (A-32) and a compound that provides the structural unit B3.
Copolymer 3 may have an imide repeating structural unit formed from a compound other than the compound that provides the structural unit (A-31) and a compound that provides the structural unit B3, or an imide repeating structural unit formed from a compound that provides the structural unit (A-31) and a compound other than the compound that provides the structural unit (B-31). Similarly, copolymer 3 may have an amic acid repeating structural unit formed from a compound other than the compound that provides the structural unit (A-32) and a compound that provides the structural unit B3.

[Production method of copolymer 3]
Copolymer 3 can be produced by reacting a tetracarboxylic acid component consisting of a compound that provides the structural unit (A-31) and a compound that provides the structural unit (A-32), with a diamine component that includes a compound that provides the structural unit B3, which contains the structural unit (B-31), and is preferably produced by a method having the following steps 1 and 2.
Step 1: reacting a compound that provides the structural unit (A-31) with a compound that provides the structural unit (B-31) to obtain an oligomer having imide repeating structural units. Step 2: reacting the oligomer obtained in step 1 with a compound that provides the structural unit (A-32) and a compound that provides the structural unit B3 to obtain a copolymer 3 having imide repeating structural units and amic acid repeating structural units. By using the production method including steps 1 and 2, it is possible to produce a copolymer 3 that is excellent in colorless transparency and heat resistance, as well as being capable of forming a film that has excellent low retardation and low residual stress.
The method for producing the copolymer 3 will be described below.

<Tetracarboxylic acid component>
Compounds that provide the structural unit (A-31) include, but are not limited to, alicyclic tetracarboxylic dianhydrides (a-31), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include alicyclic tetracarboxylic acids corresponding to the alicyclic tetracarboxylic dianhydrides (a-31) and alkyl esters of the alicyclic tetracarboxylic acids. As a compound that provides the structural unit (A-31), alicyclic tetracarboxylic dianhydrides (a-31) are preferred.
Similarly, examples of compounds that provide the structural unit (A-32) include, but are not limited to, tetracarboxylic dianhydride (a-32), and may be derivatives thereof as long as they provide the same structural unit. Examples of such derivatives include tetracarboxylic acids corresponding to the tetracarboxylic dianhydride (a-32) and alkyl esters of the tetracarboxylic acids. The compound that provides the structural unit (A-32) is preferably tetracarboxylic dianhydride (a-32).

In the tetracarboxylic acid component, the molar ratio of the compound that provides structural unit (A-31) to the compound that provides structural unit (A-32) [(A-31)/(A-32)] is preferably 10/90 to 90/10, more preferably 30/70 to 85/15, and even more preferably 50/50 to 80/20.

Compounds that provide the structural unit (A-31) are preferably compounds that provide the structural unit (A-31-1). The ratio of compounds that provide the structural unit (A-31-1) among the compounds that provide the structural unit (A-31) is preferably 45 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit to this ratio, and it is 100 mol%.
The compound that gives the structural unit (A-32) is preferably at least one selected from the group consisting of compounds that give the structural unit (A-32-1), compounds that give the structural unit (A-32-2), compounds that give the structural unit (A-32-3), and compounds that give the structural unit (A-32-4). The total ratio of the compounds that give the structural units (A-32-1) to (A-32-4) among the compounds that give the structural unit (A-32) is preferably 45 mol% or more, more preferably 70 mol% or more, even more preferably 90 mol% or more, and particularly preferably 99 mol% or more. There is no particular upper limit to this ratio, that is, it is 100 mol%.
The tetracarboxylic acid component may contain compounds other than the compounds that provide the structural unit (A-31-1), the structural unit (A-32-1), the structural unit (A-32-2), the structural unit (A-32-3), and the structural unit (A-32-4), and such compounds may be one type, or two or more types.

<Diamine component>
The compound that gives the structural unit B3 may be a diamine, but is not limited thereto, and may be a derivative thereof as long as it gives the same structural unit. The derivative may be a diisocyanate corresponding to the diamine. The compound that gives the structural unit B3 is preferably a diamine.
The compound that provides the structural unit (B-31) is preferably a compound represented by formula (b-31) (i.e., a diamine). Similarly, the compound that provides the structural unit (B-32) is preferably a compound represented by formula (b-32) (i.e., a diamine), and the compound that provides the structural unit (B-33) is preferably a compound represented by formula (b-33) (i.e., a diamine).

The diamine component contains a compound that provides the structural unit (B-31) in an amount of preferably 45 mol % or more, more preferably 48 mol % or more, even more preferably 85 mol % or more, and still more preferably 88 mol % or less, and preferably 100 mol % or less, more preferably 99.5 mol % or less, and even more preferably 99.0 mol % or less. The diamine component may consist solely of a compound that provides the structural unit (B-31).
When a compound that provides the structural unit (B-32) is contained as a diamine component, the compound that provides the structural unit (B-32) is preferably contained in an amount of 0.01 to 15.0 mol %, more preferably 0.5 to 12.0 mol %, and even more preferably 1.0 to 8.0 mol % of the total diamine components.
When a compound that provides the structural unit (B-33) is contained as a diamine component, the compound that provides the structural unit (B-33) is preferably contained in an amount of 5 to 65 mol %, more preferably 10 to 55 mol %, and even more preferably 25 to 50 mol % of the total diamine components.
The diamine component may be a combination of one or more compounds selected from the group consisting of a compound that provides the structural unit (B-31) and a compound that provides the structural unit (B-32) and a compound that provides the structural unit (B-33).

The total content ratio of the compound that provides the structural unit (B-31), the compound that provides the structural unit (B-32), and the compound that provides the structural unit (B-33) is preferably 45 mol% or more, more preferably 60 mol% or more, and even more preferably 85 mol% or more, of the total diamine components. There is no particular upper limit to the total content ratio, that is, it is 100 mol%.

The diamine component may contain a compound that provides the structural unit B3 other than the compound that provides the structural unit (B-31), the compound that provides the structural unit (B-32), and the compound that provides the structural unit (B-33). Examples of such compounds include the above-mentioned aromatic diamines, alicyclic diamines, and aliphatic diamines, as well as derivatives thereof (diisocyanates, etc.).
The compound other than the compound that gives the structural units (B-31) to (B-33) that is optionally contained in the diamine component may be one type, or two or more types.

The ratio of the tetracarboxylic acid component and diamine component used in the production of copolymer 3 is preferably 0.9 to 1.1 moles of diamine component per 1 mole of tetracarboxylic acid component.

<Solvent>
The solvent used in the production of copolymer 3 may be any solvent capable of dissolving the copolymer produced. Specific examples of the reaction solvent are as described for polyimide resin 1. Among the above reaction solvents, amide-based solvents or lactone-based solvents are preferred, amide-based solvents are more preferred, and N-methyl-2-pyrrolidone is even more preferred. The above reaction solvents may be used alone or in combination of two or more.

<Step 1>
Step 1 is a step in which a compound that provides the structural unit (A-31) is reacted with a compound that provides the structural unit (B-31) to obtain an oligomer having imide repeating structural units.
The tetracarboxylic acid component used in step 1 includes a compound that provides the structural unit (A-31). In cases where the structural unit (A-31) contains the structural unit (A-31-1), it is preferable to use the entire amount of the compound that provides the structural unit (A-31-1) in step 1.
The diamine component used in step 1 includes a compound that provides the structural unit (B-31), and may also include a diamine component other than the compound that provides the structural unit (B-31) as long as the effects of the present invention are not impaired. Examples of such compounds include compounds that provide the structural unit (B-33).
The ratio of the amounts of the components used in step 1 is preferably such that the diamine component used in step 1 is 0.9 to 1.1 mol, and more preferably 1.0 to 1.1 mol, relative to the compound that provides the structural unit (A-31).

There are no particular limitations on the method for reacting the tetracarboxylic acid component containing the compound that gives the structural unit (A-31) with the diamine component containing the compound that gives the structural unit (B-31) to obtain the oligomer in step 1, and any known method can be used. Specific reaction methods are as described for polyimide resin 1.

In the above imidization reaction, a known imidization catalyst can be used. Specific examples of the imidization catalyst are as described for polyimide resin 1, and the preferred range is also the same.

The temperature of the imidization reaction is preferably 120 to 250°C, more preferably 160 to 200°C, from the viewpoint of the reaction rate and suppression of gelation, etc. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

The oligomer obtained in step 1 has imide repeating structural units formed from the compound that provides the structural unit (A-31) and the compound that provides the structural unit (B-31).
The oligomer obtained in step 1 preferably has amino groups at both ends of the main molecular chain.
The above method provides a solution containing an oligomer dissolved in a solvent. The solution containing an oligomer obtained in step 1 may contain at least a portion of the components used as the tetracarboxylic acid component or the diamine component in step 1 as unreacted monomers, as long as the effects of the present invention are not impaired.

<Step 2>
Step 2 is a step of reacting the oligomer obtained in step 1 with a compound that provides the structural unit (A-32), and a compound that provides the structural unit B3, to obtain a copolymer having imide repeating structural units and amic acid repeating structural units.
The tetracarboxylic acid component used in step 2 contains a compound that provides the structural unit (A-32), and may also contain a compound that provides the structural unit (A-31) to the extent that the effects of the present invention are not impaired. However, it is preferable that the tetracarboxylic acid component used in step 2 does not contain a compound that provides the structural unit (A-31-1). It is also preferable that the entire amount of the compound that provides the structural unit (A-32) is used in step 2.
The diamine component used in step 2 is a compound that provides the structural unit B3. The diamine component used in step 2 refers to the compounds that provide the structural unit B3 in the raw material monomers in the copolymer of the present invention, excluding the diamine component that constitutes the oligomer obtained in step 1. The unreacted diamine component remaining in the solution containing the oligomer obtained in step 1 may be used as the diamine component in step 2. The diamine component used in step 2 preferably contains at least a compound that provides the structural unit (B-31). When a compound that provides the structural unit (B-32) is used, it is preferable to use the entire amount of the compound in step 2.

There are no particular limitations on the method for reacting a tetracarboxylic acid component containing a compound that provides the structural unit (A-32), a diamine component containing a compound that provides the structural unit B3, and the oligomer obtained in step 1 to obtain a copolymer in step 2, and any known method can be used.
Specific reaction methods include (1) a method in which the oligomer obtained in step 1, the tetracarboxylic acid component, the diamine component, and the solvent are charged into a reactor and stirred at 0 to 120° C., preferably 5 to 80° C., for 1 to 72 hours, and (2) a method in which the oligomer obtained in step 1, the diamine component, preferably a diamine component other than the compound that gives the structural unit (B-32), and the solvent are charged into a reactor and dissolved, and then the tetracarboxylic acid component is charged and stirred at 0 to 120° C., preferably 5 to 80° C., for 1 to 72 hours, and then the diamine component, preferably a compound that gives the structural unit (B-32), and the solvent are charged and stirred for 0.5 to 10 hours at 0 to 120° C., preferably 15 to 80° C., for example. When the diamine component contains a compound that gives the structural unit (B-32), the production method (2) is preferred among the above.
When the reaction is carried out at 80° C. or less, the molecular weight of the copolymer obtained in step 2 does not vary depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, so that the copolymer can be stably produced.

Copolymer 3 is a copolymer having an amic acid repeating unit and an imide repeating unit, and is a product of a polyaddition reaction between the tetracarboxylic acid component in step 2, the diamine component in step 2, and the oligomer obtained in step 1.
Copolymer 3 has imide repeating structural units formed in step 1 from the compound that provides the structural unit (A-31) and the compound that provides the structural unit (B-31), and has amic acid repeating structural units formed in step 2 from the compound that provides the structural unit (A-32) and the compound that provides the structural unit B3.

By the above method, a copolymer solution containing the copolymer 3 dissolved in the solvent is obtained.
The concentration of the copolymer in the resulting copolymer solution is usually in the range of 1 to 50% by mass, preferably 3 to 35% by mass, and more preferably 10 to 30% by mass.

The number average molecular weight of copolymer 3 is preferably 5,000 to 500,000 from the viewpoint of the mechanical strength of the resulting polyimide film. The number average molecular weight of copolymer 3 can be determined, for example, from a standard polymethyl methacrylate (PMMA) equivalent value measured by gel filtration chromatography.

[Method of manufacturing polyimide film]
The method for producing the polyimide film of the present invention is not particularly limited, and a known method can be used, for example, a method in which a polyimide varnish is applied to a smooth support such as a glass plate, a metal plate, or a plastic plate, or formed into a film, and then organic solvents such as a reaction solvent and a dilution solvent contained in the varnish are removed by heating.

Examples of a method for applying the varnish include known application methods such as spin coating, slit coating, blade coating, etc. Among these, slit coating is preferred from the viewpoint of workability, since it controls intermolecular orientation and improves chemical resistance.
A preferred method for removing the organic solvent contained in the varnish by heating is to evaporate the organic solvent at a temperature of 150° C. or less to make the varnish tack-free, and then dry the varnish at a temperature equal to or higher than the boiling point of the organic solvent used (preferably 200 to 500° C., but not limited thereto). Drying is also preferred in an air atmosphere or a nitrogen atmosphere. The pressure of the drying atmosphere may be reduced pressure, normal pressure, or increased pressure.

<Polyimide varnish>
The polyimide varnish is prepared by dissolving a polyimide resin in an organic solvent. That is, the polyimide varnish contains a polyimide resin and an organic solvent, and the polyimide resin is dissolved in the organic solvent.
The organic solvent is not particularly limited as long as it dissolves the polyimide resin. However, it is preferable to use the above-mentioned compounds as reaction solvents used in the production of the polyimide resin, either alone or in combination of two or more kinds.
The polyimide varnish may be a polyimide solution itself in which a polyimide resin obtained by polymerization is dissolved in a reaction solvent, or may be a polyimide solution to which a dilution solvent is further added.

The polyimide resins 1 and 2 are soluble in solvents, and therefore can be made into a highly concentrated varnish that is stable at room temperature. The polyimide varnish preferably contains 5 to 40 mass % of polyimide resin 1 or 2, and more preferably contains 10 to 30 mass %. The viscosity of the polyimide varnish is preferably 1 to 200 Pa·s, more preferably 1.5 to 100 Pa·s, and even more preferably 2 to 100 Pa·s. The viscosity of the polyimide varnish is a value measured at 25°C using an E-type viscometer.
The polyimide varnish may also contain various additives, such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, defoamers, fluorescent brightening agents, crosslinking agents, polymerization initiators, and photosensitizers, within the scope of not impairing the required properties of the polyimide film.
The method for producing the polyimide varnish is not particularly limited, and any known method can be applied.

<Polyamic acid varnish>
The polyimide film can also be produced using a polyamic acid varnish prepared by dissolving polyamic acid in an organic solvent.
The polyamic acid contained in the polyamic acid varnish is preferably a precursor of polyimide resin 1 or 2. The polyamic acid, which is a precursor of polyimide resin 1, is a product of a polyaddition reaction between a tetracarboxylic acid component containing a compound that gives the above-mentioned structural unit (A-11) and a compound that gives the above-mentioned structural unit (A-12), and a diamine component containing a compound that gives the above-mentioned structural unit (B-11) and a compound that gives the above-mentioned structural unit (B-12). The polyamic acid, which is a precursor of polyimide resin 2, is a product of a polyaddition reaction between a tetracarboxylic acid component containing a compound that gives the above-mentioned structural unit (A-21) and a compound that gives the above-mentioned structural unit (A-22), and a diamine component containing 70 mol% or more of a compound that gives the above-mentioned structural unit (B-21). By imidizing (dehydrating and ring-closing) these polyamic acids, the final product polyimide resin 1 or 2 is obtained.
As the organic solvent contained in the polyamic acid varnish, an organic solvent contained in a polyimide varnish can be used.
In the present invention, the polyamic acid varnish may be a polyamic acid solution itself obtained by subjecting a tetracarboxylic acid component and a diamine component to a polyaddition reaction in a reaction solvent, or may be a polyamic acid solution to which a dilution solvent has been further added.

The method for producing a polyimide film using the polyamic acid varnish is not particularly limited, and a known method can be used.For example, the polyamic acid varnish is applied to a smooth support such as a glass plate, a metal plate, or a plastic plate, or formed into a film, and the organic solvent contained in the varnish, such as a reaction solvent or a dilution solvent, is removed by heating to obtain a polyamic acid film, and the polyamic acid in the polyamic acid film is imidized by heating, thereby producing a polyimide film.
The heating temperature when the polyamic acid varnish is dried to obtain a polyamic acid film is preferably 50 to 120° C. The heating temperature when the polyamic acid is imidized by heating is preferably 200 to 400° C.
The imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

<Copolymer varnish>
The polyimide film can also be produced by using a copolymer varnish obtained by dissolving the above-mentioned copolymer 3 in an organic solvent.
The copolymer varnish is obtained by dissolving the copolymer 3, which is a precursor of a polyimide resin, in an organic solvent. That is, the copolymer varnish contains the copolymer 3 and an organic solvent, and the copolymer 3 is dissolved in the organic solvent.
The organic solvent is not particularly limited as long as it dissolves copolymer 3. However, it is preferable to use the above-mentioned compounds alone or in a mixture of two or more kinds as the solvent used in the production of copolymer 3.
The copolymer varnish may be the above-mentioned copolymer solution itself, or may be the copolymer solution to which a dilution solvent has been further added.

The copolymer varnish may further contain an imidization catalyst and a dehydration catalyst from the viewpoint of efficiently proceeding with the imidization of the amide acid moiety in the copolymer 3. The imidization catalyst may be an imidization catalyst having a boiling point of 40° C. or more and 180° C. or less, and an amine compound having a boiling point of 180° C. or less is preferred. If the imidization catalyst has a boiling point of 180° C. or less, the film is not likely to be colored and its appearance is not likely to be impaired when dried at a high temperature after film formation. In addition, if the imidization catalyst has a boiling point of 40° C. or more, the possibility of volatilization before imidization has progressed sufficiently can be avoided.
Examples of the amine compound preferably used as the imidization catalyst include pyridine and picoline. The above imidization catalysts may be used alone or in combination of two or more kinds.
Examples of the dehydration catalyst include acid anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride; carbodiimide compounds such as dicyclohexylcarbodiimide; etc. These may be used alone or in combination of two or more kinds.

Since the copolymer 3 contained in the copolymer varnish has solvent solubility, a high concentration varnish can be obtained. The copolymer varnish preferably contains 5 to 40 mass % of the copolymer 3, more preferably 10 to 30 mass %. The viscosity of the copolymer varnish is preferably 0.1 to 100 Pa·s, more preferably 0.1 to 20 Pa·s. The viscosity of the copolymer varnish is a value measured at 25°C using an E-type viscometer.
In addition, the copolymer varnish may contain various additives such as inorganic fillers, adhesion promoters, release agents, flame retardants, UV stabilizers, surfactants, leveling agents, defoamers, fluorescent brightening agents, crosslinking agents, polymerization initiators, and photosensitizers, as long as the additives do not impair the required properties of the polyimide film.
The method for producing the varnish is not particularly limited, and any known method can be applied.

The heating temperature when the copolymer varnish is dried to obtain a copolymer film is preferably 50 to 150° C. The heating temperature when the copolymer 3 is imidized by heating can be selected from the range of preferably 200 to 500° C., more preferably 250 to 450° C., and even more preferably 300 to 400° C. The heating time is usually 1 minute to 6 hours, preferably 5 minutes to 2 hours, and more preferably 15 minutes to 1 hour.
Examples of the heating atmosphere include air gas, nitrogen gas, oxygen gas, hydrogen gas, and nitrogen/hydrogen mixed gas. In order to suppress coloration of the resulting polyimide resin, nitrogen gas having an oxygen concentration of 100 ppm or less and nitrogen/hydrogen mixed gas containing a hydrogen concentration of 0.5% or less are preferred.
The imidization method is not limited to thermal imidization, and chemical imidization can also be applied.

[Adjustment of Moisture Content of Polyimide Film]
The water content of the polyimide film in the present invention is 1,000 to 35,000 ppm by mass. The method for adjusting the water content of the polyimide film to fall within this range is not particularly limited, and the polyimide film may be produced by incorporating water when applying a polyimide varnish onto a glass substrate or a silicon substrate, but it is more preferable to allow the polyimide film to absorb moisture after production. Alternatively, after the polyimide film is produced, a metal film or an oxide semiconductor film may be laminated on the film, and the film may be allowed to absorb moisture after the production of various electronic devices.
To allow the polyimide film to absorb moisture, it is preferable to hold the film for a predetermined period of time in a temperature and humidity environment with a temperature of preferably 10 to 40° C., more preferably 15 to 35° C., and a humidity of 40 to 80% RH, more preferably 50 to 70% RH, and particularly preferably 55 to 65% RH. The holding time is affected by the temperature and humidity, but is preferably 20 hours or more, more preferably 40 hours or more, even more preferably 60 hours or more, and is usually within 170 hours. Here, RH indicates relative humidity.

(Metal Film or Oxide Semiconductor Film)
In the laminate of the present invention, a metal film or an oxide semiconductor film is further laminated on a polyimide film. By laminating a metal film or an oxide semiconductor film on a polyimide film, a target electronic device (conductive film) such as a touch sensor or an OLED can be produced on the polyimide film.
Preferable specific examples of the metal film include copper mesh and silver mesh.
A preferred example of the oxide semiconductor film is at least one selected from the group consisting of indium tin oxide (ITO), amorphous silicon, indium gallium zinc oxide (IGZO) and low temperature polysilicon (LTPS).
On the metal film or oxide semiconductor film, another metal film or oxide semiconductor film may be further stacked.
From the viewpoint of forming an electronic device on the polyimide film, the thickness of the metal film or oxide semiconductor film is 1 to 400 nm, preferably 10 to 300 nm, and more preferably 20 to 200 nm.

There are no particular limitations on the method for laminating a metal film or an oxide semiconductor film on a polyimide film, but physical vapor deposition or chemical vapor deposition is preferred. Examples of physical vapor deposition include vacuum vapor deposition, sputtering, and ion plating, while examples of chemical vapor deposition include plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

A conductive film can be obtained by peeling and removing the glass substrate or the silicon substrate from a laminate having a metal film or an oxide semiconductor film stacked thereon. That is, the method for producing a conductive film of the present invention includes a step of peeling and removing the glass substrate or the silicon substrate from the above-mentioned laminate.
After laminating a metal film or an oxide semiconductor film on a polyimide film to produce a conductive film, the glass substrate or silicon substrate may be peeled off immediately to obtain the conductive film, or the conductive film may be obtained by storing the conductive film in a laminated state and, if necessary, peeling off the glass substrate or silicon substrate. Storing the conductive film in a laminated state is preferable because it improves the handling properties of the conductive film during transportation.

There is no particular limitation on the method for peeling off the glass substrate or silicon substrate from the laminate, but since the laminate of the present invention allows the polyimide film to be easily and stably peeled off from the glass substrate or silicon substrate, it can be peeled off mechanically without laser irradiation.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to these examples in any way.

In the examples and comparative examples, the physical properties were measured by the methods shown below.
(1) Film Thickness The film thickness was measured using a laser microscope (manufactured by Keyence Corporation).

(2) Glass transition temperature (Tg)
Using a thermomechanical analyzer "TMA/SS6100" (manufactured by Hitachi High-Tech Science Corporation), the specimen was heated to a temperature sufficient to remove the residual stress under the conditions of a sample size of 2 mm x 20 mm, a load of 0.1 N, and a heating rate of 10°C/min in tensile mode, and then cooled to room temperature. Thereafter, the test piece elongation was measured under the same conditions as in the treatment for removing the residual stress, and the point at which an inflection point of elongation was observed was determined as the glass transition temperature.

(3) Total light transmittance, yellow index (YI)
The total light transmittance and YI were measured in accordance with JIS K7105:1981 using a color/turbidity simultaneous measuring instrument "COH400" (manufactured by Nippon Denshoku Industries Co., Ltd.).

(4) Thickness Retardation (Rth)
The thickness retardation (Rth) was measured using an ellipsometer "M-220" (manufactured by JASCO Corporation). The thickness retardation value was measured at a measurement wavelength of 590 nm. Rth is expressed by the following formula, where the maximum in-plane refractive index of the polyimide film is nx, the minimum is ny, the refractive index in the thickness direction is nz, and the thickness of the film is d.
Rth=[{(nx+ny)/2}-nz]×d

(5) Moisture content of polyimide film The film was measured by the Karl Fischer method at 260° C. for 30 minutes using a trace moisture analyzer “CA-200” (manufactured by Mitsubishi Chemical Analytech Co., Ltd., moisture meter by Karl Fischer method) and a moisture vaporizer “VA-236S” (manufactured by Mitsubishi Chemical Analytech Co., Ltd., with sample changer) as the measuring instruments.

(6) Peel Strength A 90° peel test was carried out based on JIS K6854-1 to measure the peel strength between the polyimide film and the glass interface. The peel strength was measured five times, and the average value was taken as the peel strength.

The tetracarboxylic acid components, diamine components, other components, and their abbreviations used in the production examples are as follows:
<Tetracarboxylic acid component>
HPMDA: 1,2,4,5-cyclohexanetetracarboxylic dianhydride (manufactured by Mitsubishi Gas Chemical Company, Inc.; compounds represented by formulas (a-11) and (a-21))
ODPA: 4,4'-oxydiphthalic anhydride (manufactured by Manac Corporation; compounds represented by formulas (a-12) and (a-22))
CpODA: norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic dianhydride (manufactured by JX Nippon Oil & Energy Corporation; compound represented by formula (a-31-1))
s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride (manufactured by Mitsubishi Chemical Corporation, compound represented by formula (a-32-1s))
<Diamine component>
3,3'-DDS: 3,3'-diaminodiphenyl sulfone (manufactured by Seika Corporation; compounds represented by formulas (b-11) and (b-21))
BAPS: bis[4-(4-aminophenoxy)phenyl]sulfone (manufactured by Seika Corporation; compound represented by formula (b-12))
HFBAPP: 2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane (manufactured by Seika Corporation; compound represented by formula (b-22-3))
6FODA: 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether (manufactured by ChinaTech (Tianjin) Chemical Co., Ltd., a compound represented by formula (b-31))
X-22-1660B-3: silicone oil modified with amino at both ends (manufactured by Shin-Etsu Chemical Co., Ltd., compound represented by formula (b-32) (functional group equivalent: 2200 g/mol or 2170 g/mol)
＜Other＞
GBL: γ-butyrolactone (manufactured by Mitsubishi Chemical Corporation)
TEA: Triethylamine (Kanto Chemical Co., Ltd.)
NMP: N-methyl-2-pyrrolidone (manufactured by Mitsubishi Chemical Corporation)

Production Example 1
Into a 300 mL five-neck round-bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen inlet tube, a Dean-Stark equipped with a cooling tube, a thermometer, and a glass end cap, 13.845 g (0.056 mol) of 3,3′-DDS, 24.115 g (0.056 mol) of BAPS, and 41.903 g of GBL were placed, and the mixture was stirred at 200 rpm under a nitrogen atmosphere at an internal temperature of 70° C. to obtain a solution.
To this solution, 22.499 g (0.100 mol) of HPMDA, 3.459 g (0.011 mol) of ODPA, and 12.804 g of GBL were added all at once, and then 0.564 g of TEA was added as an imidization catalyst, and the mixture was heated with a mantle heater to raise the temperature in the reaction system to 190° C. over about 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190° C. and refluxed for about 5 hours while adjusting the rotation speed according to the increase in viscosity.
Thereafter, 175.981 g of GBL was added so that the solid content concentration was 20% by mass, and the temperature inside the reaction system was cooled to 100° C., and the mixture was further stirred for about 1 hour to be homogenized, thereby obtaining Polyimide Varnish 1.
Next, the obtained polyimide varnish 1 was applied onto a glass plate by spin coating, and held on a hot plate at 80°C for 20 minutes, and then heated in an air atmosphere in a hot air dryer at 260°C for 30 minutes to evaporate the solvent, thereby obtaining a film.

Production Example 2
23.530 g (0.094 mol) of 3,3′-DDS, 12.247 g (0.024 mol) of HFBAPP, and 62.820 g of GBL were placed in a 300 mL five-neck round-bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen inlet tube, a Dean-Stark equipped with a cooling tube, a thermometer, and a glass end cap, and the mixture was stirred at a system temperature of 70° C. under a nitrogen atmosphere at a rotation speed of 200 rpm to obtain a solution.
To this solution, 21.158 g (0.094 mol) of HPMDA, 7.313 g (0.024 mol) of ODPA, and 15.705 g of GBL were added all at once, and then 0.596 g of TEA was added as an imidization catalyst, and the mixture was heated with a mantle heater, and the temperature in the reaction system was raised to 190° C. over about 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190° C. and refluxed for 5 hours while adjusting the rotation speed according to the increase in viscosity.
Thereafter, 161.475 g of GBL was added so that the solid content concentration was 20% by mass, and the temperature inside the reaction system was cooled to 100° C., after which the mixture was further stirred for about 1 hour to be homogenized, thereby obtaining Polyimide Varnish 2.
Next, the obtained polyimide varnish 2 was applied onto a glass plate by spin coating, and held on a hot plate at 80°C for 20 minutes, and then heated in an air atmosphere in a hot air dryer at 260°C for 30 minutes to evaporate the solvent, thereby obtaining a film.

Production Example 3
26.953 g (0.0802 mol) of 6FODA and 56.000 g of NMP were placed in a 500 mL five-neck round-bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen inlet tube, a Dean-Stark equipped with a cooling tube, a thermometer, and a glass end cap, and the mixture was stirred at 200 rpm under a nitrogen atmosphere at an internal temperature of 70° C. to obtain a solution.
To this solution, 19.231 g (0.050 mol) of CpODA and 14.000 g of NMP were added all at once, and then 0.253 g of TEA was added as an imidization catalyst, and the mixture was heated with a mantle heater, and the temperature in the reaction system was raised to 190° C. over about 20 minutes. The components distilled off were collected, and the temperature in the reaction system was maintained at 190° C. and refluxed for 1 hour while adjusting the rotation speed according to the increase in viscosity. Then, 85.806 g of NMP was added, and the temperature in the reaction system was cooled to 50° C., to obtain a solution containing an oligomer having an imide repeating structural unit.
To the obtained solution, 9.814 g (0.033 mol) of s-BPDA and 7.527 g of NMP were added all at once and stirred at 50 ° C. for 5 hours. Then, 100.000 g of NMP was added and homogenized, and then a mixed solution in which 14.002 g (0.003 mol) of X-22-1660B-3 was dissolved in 16.667 g of NMP was added and stirred for about 1 hour, and varnish 3 containing a copolymer (PI-b-PAA) with a solid content concentration of about 20 mass % was obtained. Here, the copolymer having an imide repeating structural unit and an amic acid repeating structural unit is referred to as "PI-b-PAA".
Next, the obtained varnish 3 was applied onto a glass plate by spin coating, and held on a hot plate at 80°C for 20 minutes, and then heated in an air atmosphere in a hot air dryer at 350°C for 30 minutes to evaporate the solvent, thereby obtaining a polyimide film.

The above measurements were carried out on the polyimide films obtained in Production Examples 1 to 3. The results are shown in Tables 1 and 2.

Examples 1 to 2 and Comparative Example 1
The polyimide varnish 1 obtained in Production Example 1 was applied by spin coating onto a glass plate, held at 80°C for 20 minutes on a hot plate, and then heated at 260°C for 30 minutes in a hot air dryer under an air atmosphere to evaporate the solvent, obtaining a two-layer laminate (glass/polyimide film). Furthermore, a 30 nm thick _SiO2 film was formed on the polyimide film of the laminate by sputtering, and a 120 nm thick ITO film was formed thereon to obtain a four-layer laminate (glass/polyimide film/ _SiO2 film/ITO film). The obtained four-layer laminate was held under the conditions described in Table 3 to adjust the moisture content of the polyimide film in the four-layer laminate.

Examples 3 to 4 and Comparative Example 2
The polyimide varnish 2 obtained in Production Example 2 was applied by spin coating onto a glass plate, held at 80°C for 20 minutes on a hot plate, and then heated at 260°C for 30 minutes in a hot air dryer under an air atmosphere to evaporate the solvent, obtaining a two-layer laminate (glass/polyimide film). Furthermore, a 30 nm thick _SiO2 film was formed on the polyimide film of the laminate by sputtering, and a 120 nm thick ITO film was formed thereon to obtain a four-layer laminate (glass/polyimide film/ _SiO2 film/ITO film). The obtained four-layer laminate was held under the conditions described in Table 3 to adjust the moisture content of the polyimide film in the four-layer laminate.

Examples 5 to 6
The varnish 3 obtained in Production Example 3 was applied by spin coating onto a glass plate, held at 80°C for 20 minutes on a hot plate, and then heated at 350°C for 30 minutes in a hot air dryer under an air atmosphere to evaporate the solvent, obtaining a two-layer laminate (glass/polyimide film). Furthermore, a 30 nm thick _SiO2 film was formed on the polyimide film of the laminate by sputtering, and a 120 nm thick ITO film was formed thereon to obtain a four-layer laminate (glass/polyimide film/ _SiO2 film/ITO film). The obtained four-layer laminate was held under the conditions described in Table 3 to adjust the moisture content of the polyimide film in the four-layer laminate.

The laminate obtained above was subjected to the above peel test. The results are shown in Table 3.
For the laminate of Comparative Example 1, the film could not be peeled off from the glass, and the peel strength could not be measured. For the laminate of Comparative Example 2, the film broke when peeled off from the glass, and the peel strength could not be measured.

From the results in Table 3, it can be seen that the laminate of the present invention in which the moisture content of the polyimide film is adjusted to fall within a predetermined range has a relatively low peel strength, and the polyimide film can be easily and stably peeled off from the glass substrate or silicon substrate.
It is apparent from the results in Tables 1 and 2 that all of the polyimide films of Production Examples 1 to 3 are excellent in colorless transparency and optical isotropy.

Claims (7)

A laminate comprising a polyimide film adhered to a glass substrate , and a metal film or an oxide semiconductor film further laminated on the polyimide film, wherein the metal film or the oxide semiconductor film has a thickness of 1 to 400 nm, the water content of the polyimide film is 1,000 to 35,000 ppm by mass, and the peel strength of the polyimide film from the glass substrate is 20 gf/cm or less. The laminate according to claim 1, wherein the polyimide film has a film thickness of 3 to 20 μm. The laminate according to claim 1 or 2, wherein the oxide semiconductor film is at least one selected from the group consisting of indium tin oxide, amorphous silicon, indium gallium zinc oxide, and low-temperature polysilicon. A conductive film obtained by peeling and removing the glass substrate from the laminate according to any one of claims 1 to 3. laminating a polyimide film on a glass substrate ;
adjusting the moisture content of the polyimide film to 1,000 to 35,000 ppm by mass;
The method includes a step of laminating a metal film or an oxide semiconductor film having a thickness of 1 to 400 nm on a polyimide film, and a step of peeling off and removing the glass substrate ,
The method for producing a conductive film, wherein the polyimide film has a peel strength from a glass substrate of 20 gf/cm or less. The method for producing a conductive film according to claim 5, wherein the step of adjusting the moisture content of the polyimide film is a step of holding the film in a temperature and humidity environment of 10 to 40°C and 40 to 80% RH for 20 hours or more. The method for producing a conductive film according to claim 5 or 6, wherein the step of laminating a metal film or an oxide semiconductor film on the polyimide film is a physical vapor deposition method or a chemical vapor deposition method.