JP7699063B2 - Hard coat film and its manufacturing method - Google Patents

Description

The present invention relates to a hard coat film having a hard coat layer which is a cured product of a hard coat composition containing a polyorganosiloxane compound.

Rapid advances in electronic devices such as displays, touch panels, and solar cells have created a demand for thinner, lighter, and more flexible devices. In response to these demands, the replacement of glass materials used in substrates, cover windows, and the like with plastic film materials is being considered. For these applications, plastic films are required to have high heat resistance, dimensional stability at high temperatures, and high mechanical strength. In addition, curved displays (flexible displays, foldable displays) have been developed in recent years, and plastic films used in cover windows, in particular, are required to have excellent transparency and flexibility (flexibility) in addition to the above characteristics.

As a material for forming a hard coat layer, Patent Document 1 discloses a polyorganosiloxane compound having an epoxy group as a photopolymerizable functional group.

JP 2019-143161 A

Although the hard coat layer obtained by curing the polyorganosiloxane compound disclosed in Patent Document 1 has high hardness, when the hard coat film is folded with a small radius of curvature, the hard coat layer is prone to breakage and cracks, making it difficult to apply to flexible displays, foldable displays, etc. Furthermore, when the hard coat film is used as a cover window material for a display, high transparency is required, and there is also room for improvement in transparency (light transmittance).

In view of the above, the present invention aims to provide a hard-coated film having high transparency and hardness as well as excellent flexural resistance, and a curable material for forming the hard-coat layer of the hard-coated film.

The inventors have discovered that a polyorganosiloxane compound obtained by condensing a silane compound having a hydrocarbon group with a specific chain length between a Si atom and an epoxy group has excellent transparency and surface hardness after photocuring, as well as excellent flex resistance.

The polyorganosiloxane compound according to one embodiment of the present invention is a condensate of a silane compound represented by general formula (A). The weight average molecular weight of the polysiloxane compound is preferably 500 to 20,000.
Q-(Si(OR ² ) _x R ³ _3-x ) …(A)

In general formula (A), ^R2 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and ^R3 is a hydrogen atom or a monovalent hydrocarbon group selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. x is 2 or 3.

By using the silane compound represented by the general formula (1) as the silane compound, a polyorganosiloxane compound having a structure represented by the following general formula (5) can be obtained.
Y−R ¹ −(Si(OR ² ) _x R ³ _3−x )…(1)
[Y-R ¹ -Si]...(5)

In the general formula (1), R ² , R ³ and x are the same as those in the general formula (A). R ¹ is a chain alkylene group having a main chain carbon number of 4 to 16. Y is a glycidyloxy group represented by the following formula:

The ratio of the structure represented by the general formula (5) to the total number of Si atoms in the polyorganosiloxane compound may be 30% or more. The polyorganosiloxane compound may further contain a structure represented by the general formula (6).
[X-Si]…(6)

By using a silane compound represented by the following general formula (2) in addition to the silane compound represented by general formula (1) as the above silane compound, a polyorganosiloxane compound having a structure represented by formula (6) in addition to the structure represented by formula (5) can be obtained.
X-(Si(OR ² ) _x R ³ _3-x ) …(2)

In general formula (2) and general formula (6), X is a monovalent organic group containing an alicyclic epoxy group. In general formula (2), R ² , R ³ and x are the same as those in general formula (A).

The polyorganosiloxane compound may contain a structural unit (T3 structure) represented by general formula (3) and a structural unit (T2 structure) represented by general formula (4). The ratio of the content of the T3 structure to the content of the T2 structure, T3/T2, is preferably less than 5.
[Q-SiO _3/2 ] …(3)
[Q-SiO2 _/2 -Z]...(4)

Q in general formula (3) and general formula (4) is the same as in general formula (A). In general formula (4), Z is a hydrogen atom or a monovalent organic group selected from the group consisting of an alkoxy group having an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms.

A polyorganosiloxane compound is obtained by hydrolysis and condensation reaction of a silane compound. By using a compound represented by general formula (1) as part or all of the silane compound, a polyorganosiloxane compound having a structure of formula (5) is obtained.

The hydrolysis and condensation reaction of the silane compound may be carried out in the presence of a neutral salt catalyst. The polyorganosiloxane compound obtained by the reaction in the presence of a neutral salt catalyst tends to have a small T3/T2 ratio, so that a compound having a T3/T2 ratio of less than 5 can be easily obtained.

As a neutral salt catalyst, a salt consisting of a combination of an ion of an element selected from the group consisting of alkali metal elements and Group 2 elements and a halide ion selected from the group consisting of chloride ions, bromide ions, and iodide ions is preferred.

The polyorganosiloxane compound obtained by the hydrolysis and condensation reaction of the silane compound may contain the above-mentioned neutral salt. The polyorganosiloxane compound may contain about 1 to 10,000 ppm of neutral salt.

The above polyorganosiloxane compound has photocurability and is suitable for use in forming a hard coat layer. One aspect of the present invention is a hard coat composition containing the above polyorganosiloxane compound. The hard coat composition may contain a photocationic polymerization initiator in addition to the polyorganosiloxane compound. The photocationic polymerization initiator may be a non-antimony photocationic polymerization initiator that does not contain antimony.

One aspect of the present invention is a hard coat film having a hard coat layer made of a cured product of the above-mentioned hard coat composition on at least one main surface of a transparent resin substrate. The thickness of the hard coat layer may be 0.5 to 100 μm. Examples of resin materials for the transparent resin substrate include polyester, polycarbonate, polyamide, polyimide, cyclic polyolefin, acrylic resin, and cellulose-based resin.

The above-mentioned hard coat composition is applied onto a transparent resin substrate, and the hard coat composition (the above-mentioned polyorganosiloxane compound) is cured by irradiating it with active energy rays to form a hard coat film.

The cured film (hard coat layer) formed by curing the above polysiloxane compound has high surface hardness and transparency, as well as excellent bending resistance. A hard coat film having the cured film on a transparent resin substrate is less likely to crack even when bent with a small radius of curvature, and can be suitably used for flexible displays and foldable displays.

One aspect of the present invention is a polyorganosiloxane compound having cationic polymerization properties and a method for producing the same. Another aspect of the present invention is a hard coat film having a hard coat layer made of a hard coat composition containing the silane compound and a method for producing the same. Below, preferred forms of the polyorganosiloxane compound, the hard coat composition for forming the hard coat layer, and the hard coat film will be described in order. In addition, the components and functional groups exemplified in this specification may be used alone or in combination (coexistence) of two or more types, unless otherwise specified.

[Polyorganosiloxane compound]
<Silane Compound>
The polyorganosiloxane compound of one embodiment of the present invention is a condensation product of a silane compound represented by the following general formula (A).
Q-(Si(OR ² ) _x R ³ _3-x ) …(A)

^R2 is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. Specific examples of the alkyl group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an isopropyl group, an isobutyl group, a cyclohexyl group, and an ethylhexyl group.

The silane compound represented by the general formula (A) has two or three (-OR ² ) in one molecule. Since Si-OR ² is hydrolyzable, a polyorganosiloxane compound is obtained by condensation of the silane compound. From the viewpoint of hydrolysis, the carbon number of R ² is preferably 3 or less, and it is particularly preferable that R ² is a methyl group.

^R3 is a hydrogen atom or a monovalent hydrocarbon group selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. Specific examples of the hydrocarbon group include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decyl group, an isopropyl group, an isobutyl group, a cyclohexyl group, an ethylhexyl group, a benzyl group, a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a phenethyl group.

In the general formula (A), x is 2 or 3, and when x=3 (i.e., when three alkoxy groups (or hydroxy groups) ^-OR2 are bonded to a Si atom), the silane compound does not have ^R3 . From the viewpoint of forming a network-like polysiloxane compound and increasing the number of epoxy groups contained in the polysiloxane compound to increase the hardness of the cured film, it is preferable that x=3 in the general formula (A). A silane compound in which x=2 and a silane compound in which x=3 may be used in combination. In addition, for the purpose of adjusting the molecular weight of the polysiloxane compound obtained by condensation, a silane compound in which x is 1 may be used in addition to a silane compound in which x is 2 or 3.

In general formula (A), Q is any monovalent organic group. When Q contains an epoxy group, the polyorganosiloxane compound obtained by condensation of the silane compound has photocationic polymerizability.

(Silane Compounds Having Long Chain Spacers)
The polyorganosiloxane compound of one embodiment of the present invention contains, as the silane compound, a silane compound represented by the following general formula (1).
Y−R ¹ −(Si(OR ² ) _x R ³ _3−x )…(1)

In the general formula (1), R ² , R ³ and x are the same as those in the general formula (A). R ¹ is a chain alkylene group having a main chain carbon number of 4 to 16. Y is a glycidyloxy group represented by the following formula:

The number of carbon atoms in the main chain refers to the number of carbon atoms contained in the straight chain connecting the Si atom and the oxygen atom of the glycidyloxy group Y in general formula (1), and when R ¹ is a straight-chain alkylene group, the number of carbon atoms in the main chain is equal to the number of carbon atoms in R ^1. That is, the silane compound of general formula (1) (hereinafter sometimes referred to as "silane compound (1)") is a compound in which a Si atom and a glycidyloxy group Y are bonded to each other via 4 to 16 carbon atoms.

Specific examples of linear alkylene groups having 4 to 16 carbon atoms include tetramethylene, pentamethylene, hexamethylene, heptamethylene, octamethylene, decamethylene, dodecamethylene, tetradecamethylene, and hexadecamethylene. ^R1 may be a methylene ( _-CH2- ) group in which some or all of the hydrogen atoms have been substituted with a substituent having 1 to 6 carbon atoms. Examples of the substituent having 1 to 6 carbon atoms include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a cyclohexyl group, and a phenyl group.

The polyorganosiloxane compound obtained by condensation of the silane compound (1) has a specific chain length between the epoxy group, which is a polymerizable functional group, and ^the Si atom, and therefore has a flexible molecular structure even after being cured by the reaction of the epoxy group. Therefore, the hard coat layer formed by the cured product of the polyorganosiloxane compound shows excellent flexibility (flexibility).

The greater the distance between the Si atom and the epoxy group, that is, the greater the number of carbon atoms in the main chain of the spacer alkylene group R ¹ and the longer the chain length, the more the bending resistance of the hard coat layer tends to improve. As described above, the number of carbon atoms in the main chain of R ¹ is 4 or more, preferably 6 or more, and may be 8 or more. On the other hand, if the number of carbon atoms in the main chain of R ¹ is excessively large, the hardness of the hard coat layer tends to be insufficient. Therefore, the number of carbon atoms in the main chain of R ¹ is 16 or less, preferably 14 or less, more preferably 12 or less, and may be 10 or less.

Specific examples of silane compound (1) include 4-glycidyloxybutyltrimethoxysilane, 4-glycidyloxybutylmethyldimethoxysilane, 4-glycidyloxybutyltriethoxysilane, 4-glycidyloxybutylmethyldiethoxysilane, 5-glycidyloxypentyltrimethoxysilane, 5-glycidyloxypentylmethyldimethoxysilane, 5-glycidyloxypentyltriethoxysilane, 5-glycidyloxypentylmethyldiethoxysilane, 6-glycidyloxyhexyltrimethoxysilane, 6-glycidyloxyhexylmethyldimethoxysilane, 6-glycidyloxyhexyltriethoxysilane, 6-glycidyloxyhexylmethyldiethoxysilane, 7-glycidyloxyheptyltrimethoxysilane, 7-glycidyloxyhexyltriethoxy ... glycidyloxyheptylmethyldimethoxysilane, 7-glycidyloxyheptyltriethoxysilane, 7-glycidyloxyheptylmethyldiethoxysilane, 8-glycidyloxyoctyltrimethoxysilane, 8-glycidyloxyoctylmethyldimethoxysilane, 8-glycidyloxyoctyltriethoxysilane, 8-glycidyloxyoctylmethyldiethoxysilane, 9-glycidyloxynonyltrimethoxysilane, 9-glycidyloxynonylmethyldimethoxysilane, 9-glycidyloxynonyltriethoxysilane, 9-glycidyloxynonylmethyldiethoxysilane, 10-glycidyloxydecyltrimethoxysilane, 10-glycidyloxydecylmethyldimethoxysilane, 10-glycidyloxydecyltriethoxysilane, 10- glycidyloxydecylmethyldiethoxysilane, 11-glycidyloxyundecyltrimethoxysilane, 11-glycidyloxyundecylmethyldimethoxysilane, 11-glycidyloxyundecyltriethoxysilane, 11-glycidyloxyundecylmethyldiethoxysilane, 12-glycidyloxydodecyltrimethoxysilane, 12-glycidyloxydodecylmethyldimethoxysilane, 12-glycidyloxydodecyltriethoxysilane, 12-glycidyloxydodecylmethyldiethoxysilane, 13-glycidyloxytridecyltrimethoxysilane, 13-glycidyloxytridecylmethyldimethoxysilane, 13-glycidyloxytridecyltriethoxysilane, 13-glycidyloxytridecylmethyldiethoxysilane, Examples of the glycidyloxytetradecyltrimethoxysilane include 14-glycidyloxytetradecylmethyldimethoxysilane, 14-glycidyloxytetradecyltriethoxysilane, 14-glycidyloxytetradecylmethyldiethoxysilane, 15-glycidyloxypentadecyltrimethoxysilane, 15-glycidyloxypentadecylmethyldimethoxysilane, 15-glycidyloxypentadecyltriethoxysilane, 15-glycidyloxypentadecylmethyldiethoxysilane, 16-glycidyloxyhexadecyltrimethoxysilane, 16-glycidyloxyhexadecylmethyldimethoxysilane, 16-glycidyloxyhexadecyltriethoxysilane, and 16-glycidyloxyhexadecylmethyldiethoxysilane.

(Other silane compounds)
When obtaining a polyorganosiloxane compound by condensation of a silane compound, other silane compounds may be used as the silane compound in addition to the above-mentioned silane compound (1). For example, a compound represented by the following general formula (2) may be used as the silane compound.
X-(Si(OR ² ) _x R ³ _3-x ) …(2)

In formula (2), R ² , R ³ and x are the same as those in formula (A), and X is a monovalent organic group containing an alicyclic epoxy group.

Examples of X include an alicyclic epoxy group, an alkyl group having an alicyclic epoxy group as a substituent, and an ethylene glycol group having an alicyclic epoxy group as a substituent. A specific example of an alicyclic epoxy group for X is a 3,4-epoxycyclohexyl group.

From the viewpoint of the heat resistance and bending resistance of the hard coat layer, X is preferably an alkyl group having an alicyclic epoxy group as a substituent. In general formula (2), when X is an alkyl group having an alicyclic epoxy group as a substituent, the alkylene group between the Si atom and the epoxy group may be linear or branched, but a linear alkylene group is preferred, a linear alkylene group having 1 to 5 carbon atoms is preferred, and ethylene is particularly preferred.

Specific examples of silane compounds of general formula (2) (hereinafter sometimes referred to as "silane compound (2)") include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyldimethylmethoxysilane, 3-(3,4-epoxycyclohexyl)propyltrimethoxysilane, 3-(3,4-epoxycyclohexyl)propylmethyldimethoxysilane, 3-(3,4-epoxycyclohexyl)propyldimethylmethoxysilane, etc.

By using the compound (1) in combination with the silane compound (2) containing an alicyclic epoxy group, the surface hardness of the hard coat layer formed by curing the hard coat composition containing the polyorganosiloxane compound may be improved. In addition, since the alicyclic epoxy group has a higher curing rate in photocationic polymerization than the glycidyl group, the curing rate of the hard coat layer is increased by using the silane compound containing an alicyclic epoxy group in combination, the tackiness of the surface is reduced (the tack-free property is increased), and the sticking (blocking) of the hard coat film tends to be suppressed.

When a polyorganosiloxane compound is obtained by condensation of a silane compound, the ratio of silane compound (2) to the total of silane compound (1) and silane compound (2) may be 1% or more, 3% or more, 5% or more, 7% or more, or 10% or more by molar ratio. When compound (1) and compound (2) are used as silane compounds containing epoxy groups, the ratio of compound (2) is approximately equal to the ratio of alicyclic epoxy groups to the total amount of epoxy groups in the polyorganosiloxane compound.

The polyorganosiloxane compound has an alicyclic epoxy group derived from the silane compound (2), which tends to increase the hardness and tack-free property of the hard coat layer. However, if the content of the alicyclic epoxy group is excessively large, the flexibility of the hard coat layer may be low and the bending resistance may be reduced. Therefore, the ratio of the silane compound (2) to the total of the silane compound (1) and the silane compound (2) is preferably 40% or less, more preferably 30% or less, and may be 25% or less, 20% or less, or 15% or less, in terms of molar ratio.

As a silane compound other than silane compound (1), a silane compound not containing an epoxy group may be used. Examples of silane compounds not containing an epoxy group include those in which Q in the general formula (A) is a monovalent organic group selected from the group consisting of substituted or unsubstituted alkyl groups having 1 to 10 carbon atoms, alkenyl groups, aryl groups having 6 to 25 carbon atoms, and aralkyl groups having 7 to 12 carbon atoms. When Q is an alkyl group having a substituent, examples of the substituent include a thiol group, an amino group, a (meth)acryloyl group, a phenyl group, a cyclohexyl group, a halogen, and the like.

From the viewpoint of increasing the surface hardness of the hard coat layer, the number of epoxy groups contained in one molecule of the polyorganosiloxane compound is preferably as large as possible. When a polyorganosiloxane compound is obtained by condensation of a silane compound of the general formula (A), the ratio of the silane compound not containing an epoxy group to the epoxy group-containing silane compound such as silane compound (1) and silane compound (2) is preferably 2 or less in molar ratio, more preferably 1 or less, even more preferably 0.4 or less, particularly preferably 0.2 or less, and may be 0. In addition, the ratio of the silane compound not containing an epoxy group to the silane compound (1) is preferably 2 or less in molar ratio, more preferably 1 or less, even more preferably 0.4 or less, particularly preferably 0.2 or less, and may be 0.

<Characteristics of polyorganosiloxane compounds>
(molecular weight)
By hydrolysis and condensation of the Si-OR ² portion of the silane compound, a Si-O-Si bond is formed between the silane compounds, and a polyorganosiloxane compound is generated. From the viewpoint of increasing the hardness of the cured film (hard coat layer), the weight average molecular weight of the polyorganosiloxane compound is preferably 500 or more. Also, from the viewpoint of suppressing volatilization, the weight average molecular weight of the polyorganosiloxane compound is preferably 500 or more. On the other hand, if the molecular weight is excessively large, cloudiness may occur due to a decrease in compatibility with other compositions. Therefore, the weight average molecular weight of the polyorganosiloxane compound is preferably 20,000 or less. The weight average molecular weight of the polyorganosiloxane compound is more preferably 1,000 to 18,000, more preferably 1,500 to 16,000, and may be 2,000 to 14,000, or 2,800 to 12,000.

The weight average molecular weight of a polyorganosiloxane compound can be controlled by appropriately selecting the amount of water and the type and amount of catalyst used in the reaction. For example, the more water is charged together with the catalyst during the hydrolysis reaction, the higher the weight average molecular weight tends to be.

(T3/T2 ratio)
The polyorganosiloxane compound produced by hydrolysis and condensation of the silane compound of general formula (A) contains a structural unit represented by the following formula (3) and a structural unit represented by the following formula (4).

[Q-SiO _3/2 ] …(3)
[Q-SiO2 _/2 -Z]...(4)

In the general formulas (3) and (4), Q is the same as in the general formula (A). In the polyorganosiloxane compound produced by condensation of the silane compound (1), Q- is the above-mentioned Y-R ¹ -. In the formula (4), Z is a hydrogen atom or a monovalent organic group selected from the group consisting of an alkoxy group having an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms.

Specific examples of monovalent organic groups Z include methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, isopropyl, isobutyl, cyclohexyl, ethylhexyl, benzyl, phenyl, tolyl, xylyl, naphthyl, and phenethyl groups.

The structural unit represented by formula (3): [SiO _3/2 body] has a structure in which three alkoxy groups (Si-OR ² ) of a silane compound having a T unit structure where x=3 in general formula (A) are all subjected to a condensation reaction to form a Si-O-Si bond, and is referred to as a "T3 structure". The structural unit represented by formula (4): [SiO _2/2 body] has a structure in which two of three alkoxy groups of a silane compound having a T unit structure where x=3 in general formula (A) are subjected to a condensation reaction to form a Si-O-Si bond, and is referred to as a "T2 structure".

The polyorganosiloxane compound according to the embodiment of the present invention preferably has a ratio [SiO _{3/2 body]/[SiO 2/2 body] of the SiO 3/2 body} (T3 structure) represented by formula (3) and the SiO _2/2 body (T2 structure) represented by formula (4) of less than 5. In addition to the polyorganosiloxane compound having a long-chain spacer structure derived from the alkylene group R ¹ of the silane compound (1), the ratio of the T3 structure to the T2 structure (hereinafter sometimes referred to as the "T3/T2 ratio") is less than 5, which tends to improve the bending resistance of the hard coat layer formed by curing the polyorganosiloxane compound. In addition, the T3/T2 ratio being less than 5 tends to improve the adhesion of the hard coat layer to the transparent resin substrate.

The T3/T2 ratio of the polyorganosiloxane compound is preferably 4 or less, more preferably 3.5 or less, and may be 3 or less or 2.5 or less. The smaller the T3/T2 ratio, the higher the bending resistance of the hard coat layer, and the more likely it is that cracks or breakage of the hard coat layer will be suppressed when the hard coat film is bent.

The higher the ratio of SiO3 _/2 body (T3 structure), the easier it is to form a three-dimensionally grown dense network-like polysiloxane skeleton, and the hardness tends to be increased, but on the other hand, the flexibility of the molecular structure decreases, so it is considered that the bending resistance is insufficient when the ratio of T3 structure is 5 or more. As described above, it is considered that a hard coat layer having high surface hardness and excellent bending resistance is formed because the balance between excellent mechanical strength due to the formation of the polysiloxane skeleton and the flexibility (bending resistance) due to the SiO2 _/2 body (T2 structure) is excellent when the T3/T2 ratio is less than 5.

The polyorganosiloxane compound may not contain SiO3 _/2 form (i.e., the T3/T2 ratio is 0). From the viewpoint of increasing the surface hardness of the hard coat layer, the T3/T2 ratio is preferably 0.5 or more, more preferably 1 or more, and may be 1.5 or more or 2 or more.

In the polyorganosiloxane compound obtained by condensation of the compound (1), the ratio [SiO _3/2 body]/[SiO 2/2 body] of the SiO _{3/2 body (T3 structure) represented by the following formula (3') and the SiO 2/2 body} ( _T2 structure) represented by the following formula (4') is preferably less than 5, more preferably 4 or less, even more preferably 3.5 or less, and may be 3 or less or 2.5 or less. The ratio of the two may be 0, but is preferably 0.5 or more, more preferably 1 or more, and may be 1.5 or more or 2 or more.

[Y-R ¹ -SiO _3/2 ]...(3')
[Y-R ¹ -SiO _2/2 -Z]...(4')

Y and ^R1 in the general formula (3') and the general formula (4') are the same as those in the general formula (1). Z in the general formula (4') is the same as that in the general formula (4).

In the polyorganosiloxane compound obtained by condensation of the silane compound (1) with another silane compound (e.g., the silane compound (2) or a silane compound not containing an epoxy group), the ratio of the SiO _3/2 unit of the formula (3') to the SiO _2/2 unit of the formula (4') is preferably within the above range.

The content and ratio of SiO _3/2 and SiO _2/2 in the polyorganosiloxane compound can be calculated by ²⁹ Si-NMR measurement. In ²⁹ Si-NMR, the Si atoms of the SiO _3/2 and SiO _2/2 bodies show different chemical shifts, so the integral values of the respective signals in the NMR spectrum are obtained, and the T3/T2 ratio can be calculated from the ratio of the two.

The T3/T2 ratio can be controlled by adjusting the amount of water, the type of catalyst, and the amount of catalyst used in the hydrolysis condensation reaction of the silane compound. For example, the greater the amount of catalyst, the greater the T3/T2 ratio tends to be. As described below, the use of a neutral salt catalyst tends to reduce T3/T2.

<Hydrolysis and condensation of silane compounds>
By reacting the silane compound with water, the Si- ^OR2 portion of the silane compound is hydrolyzed, and the hydrolyzate is condensed to obtain a polysiloxane compound. The amount of water required for the hydrolysis and condensation reaction is preferably 0.3 to 3 equivalents, more preferably 0.5 to 2 equivalents, per equivalent of the ^-OR2 group bonded to the Si atom. If the amount of water is too small, many ^OR2 groups remain unhydrolyzed, and the molecular weight of the polyorganosiloxane compound is small, so the hardness of the hard coat layer tends to be insufficient. If the amount of water is too large, the reaction rate of the hydrolysis and condensation reaction is high, a high molecular weight condensate is generated, and the transparency and flexibility of the hard coat layer tend to decrease.

In the hydrolysis and condensation reactions of the silane compounds, it is preferable to suppress deactivation due to ring opening of the epoxy groups contained in the silane compounds (1) and (2). From the viewpoint of suppressing the ring opening of the epoxy groups, it is preferable to carry out the reaction under neutral or basic conditions. In particular, from the viewpoint of reducing the T3/T2 ratio of the polyorganosiloxane compound obtained as the condensation product of the silane compounds, it is preferable to carry out the hydrolysis and condensation reactions in the presence of a neutral salt catalyst.

A neutral salt is a positive salt between a strong acid and a strong base, specifically, a salt between an ion (cation) of an element selected from the group consisting of alkali metal elements and group II elements and a halide ion (anion) selected from the group consisting of chloride ion, bromide ion, and iodide ion.

Specific examples of neutral salts include lithium chloride, sodium chloride, potassium chloride, beryllium chloride, magnesium chloride, calcium chloride, lithium bromide, sodium bromide, potassium bromide, beryllium bromide, magnesium bromide, calcium bromide, lithium iodide, sodium iodide, potassium iodide, beryllium iodide, magnesium iodide, calcium iodide, etc.

As described above, by using a neutral salt catalyst, polyorganosiloxane compounds with a small T3/T2 ratio can be obtained. In addition, whereas acid and base catalysts themselves react electrophilically and nucleophilically with various substances, neutral salts have the advantage of being less corrosive to the metal and resin materials of reaction vessels and storage containers, meaning there are fewer restrictions on the materials used for manufacturing and storage equipment.

If a basic catalyst that is generally used in the condensation reaction of a silane compound remains in the hard coat composition, it may quench the acid generated from the photocationic polymerization initiator (photoacid generator) and inhibit the polymerization reaction. In contrast, the use of a neutral salt catalyst can suppress polymerization inhibition. Therefore, the neutral salt catalyst may remain in the polyorganosiloxane compound obtained by condensation of the silane compound or in the hard coat composition, and steps such as removing the catalyst after the reaction and neutralizing it can be omitted. The use of a neutral salt catalyst can contribute to simplifying the manufacturing process and improving the yield.

The amount of the catalyst used is not particularly limited. The greater the amount of the catalyst used, the more the hydrolysis and condensation reaction of the silane compound tends to be accelerated. On the other hand, if the amount of the catalyst used is excessively large, the transparency of the condensate may be impaired and purification may become complicated. The amount of the neutral salt catalyst used is preferably 0.000001 to 0.1 mol, more preferably 0.000005 to 0.01 mol, per mol of the hydrolyzable silyl group (-OR ² ) of the silane compound.

As described above, the polyorganosiloxane compound obtained by the hydrolysis and condensation reaction of the silane compound may contain a neutral salt catalyst remaining. The amount of neutral salt (catalyst) remaining in the polyorganosiloxane compound may be 1 ppm or more, 10 ppm or more, 50 ppm or more, or 100 ppm or more. From the viewpoint of transparency of the hard coat layer, the amount of basic catalyst remaining in the polyorganosiloxane compound is preferably 10,000 ppm or less, more preferably 5,000 ppm or less, and even more preferably 3,000 ppm or less, and may be 1,000 ppm or less, 800 ppm or less, or 500 ppm or less.

In the hydrolysis and condensation reaction of the silane compound, the reaction may be carried out while refluxing the dilution solvent and the alcohol generated by hydrolysis. The dilution solvent is preferably one that is compatible with water, and water-soluble alcohol or ether compounds are preferred. Many silane compounds have low compatibility with neutral salts and the water used for hydrolysis, so it is preferable to react them as a compatible system in the form of a solution using a dilution solvent.

The boiling point of the diluting solvent is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. If the boiling point of the diluting solvent is excessively low, the diluting solvent may reflux at low temperatures, resulting in a slower reaction rate. From the viewpoint of the removability of the diluting solvent after the reaction, the boiling point of the diluting solvent is preferably 200°C or lower.

Specific examples of dilution solvents include methanol, ethanol, 1-propanol, 2-propanol, 2-butanol, 1-methoxy-2-propanol, ethylene glycol monomethyl ether, ethylene glycol dimethyl ether, propylene glycol monomethyl ether, propylene glycol dimethyl ether, etc.

The reaction temperature for the hydrolysis and condensation reaction of the silane compound is preferably 40°C or higher, more preferably 50°C or higher, and even more preferably 60°C or higher. If the reaction temperature is 40°C or higher, the catalytic activity of the neutral salt is high, so the reaction time can be shortened. From the viewpoint of suppressing side reactions of the organic groups of the silane compound, the reaction temperature is preferably 200°C or lower.

From the viewpoint of increasing the crosslinking density in the cured product (hard coat layer) and improving hardness, it is preferable that the polyorganosiloxane compound obtained by hydrolysis and condensation of the silane compound has a high residual epoxy group rate. The residual epoxy group rate, that is, the ratio of the number of moles of epoxy groups in the polyorganosiloxane compound obtained by condensation to the number of moles of epoxy groups contained in the silane compound as a raw material, is preferably 20% or more, more preferably 40% or more, even more preferably 60% or more, particularly preferably 80% or more, and may be 90% or more or 95% or more. The residual epoxy group rate is determined by ¹ H-NMR measurement.

As described above, a polyorganosiloxane compound is obtained by hydrolysis and condensation reaction of a silane compound represented by general formula (A). In the hydrolysis and condensation reaction, the monovalent organic group Q bonded to the Si atom does not react, except for side reactions such as ring-opening of the epoxy group, so that the structural portion of [Q-Si] in the silane compound is maintained in the polyorganosiloxane compound. Therefore, the polyorganosiloxane compound obtained by condensation of the silane compound (1) has a structure represented by the following general formula (5) (hereinafter, sometimes referred to as "structure (5)").
[Y-R ¹ -Si]...(5)

Y and R ¹ in the general formula (5) are the same as those in the general formula (1). The content of the structure (5) in the polyorganosiloxane compound is approximately equal to the sum of the content of the structure of the general formula (3 ') and the content of the structure of the general formula (4 ').

The ratio of the number of structures (5) to the total number of Si atoms in the polyorganosiloxane compound is preferably 30% or more, more preferably 50% or more, even more preferably 60% or more, particularly preferably 70% or more, and may be 80% or more, 85% or more, 90% or more, or 95% or more.

Since the silane compound represented by the general formula (A) has one Si per molecule, the polyorganosiloxane compound produced by condensation of N molecules of the silane compound contains N Si atoms. If the epoxy group remains unreacted during the hydrolysis and condensation reaction, n structures (5) are produced from n silane compounds (1). Therefore, in the polyorganosiloxane compound obtained by condensation of the silane compounds, the ratio of silane compound (1) in the silane compound used as the raw material (molar ratio: n/N) is approximately equal to the ratio of structure (5) to the number of Si atoms in the polyorganosiloxane compound.

When the silane compound (2) is used in addition to the silane compound (1) as the silane compound, the polyorganosiloxane compound has, in addition to the above structure (5), a structure represented by the following general formula (6) (hereinafter, sometimes referred to as "structure (6)").
[X-Si]…(6)
X in the general formula (6) is the same as in the general formula (2).

The ratio of the number of structures (6) to the total number of Si atoms in the polyorganosiloxane compound may be 1% or more, 3% or more, 5% or more, 7% or more, or 10% or more, and may be 40% or less, 30% or less, 25% or less, 20% or less, or 15% or less.

The ratio of the number of epoxy groups to the total number of Si atoms of the polyorganosiloxane compound is preferably 30% or more, more preferably 50% or more, even more preferably 60% or more, particularly preferably 70% or more, and may be 80% or more, 85% or more, 90% or more, or 95% or more. The ratio of the number of glycidyloxy groups to the total number of epoxy groups is preferably 60% or more, more preferably 70% or more, and may be 80% or more, 85% or more, 90% or more, 95% or more, or 100%. The ratio of the number of alicyclic epoxy groups to the total number of epoxy groups may be 1% or more, 3% or more, 5% or more, 7% or more, or 10% or more, and may be 40% or less, 30% or less, 25% or less, 20% or less, or 15% or less. These ratios can be adjusted to any range depending on the composition (ratio of compounds) of the silane compound used as a raw material for the polyorganosiloxane compound.

[Hard Coat Composition]
The hard coat composition according to one embodiment of the present invention is a composition containing the above-mentioned polyorganosiloxane compound as an essential component. In addition to the polyorganosiloxane compound, the hard coat composition preferably contains a photocationic polymerization initiator, and may contain other components.

From the viewpoint of forming a hard coat cured film having excellent mechanical strength, the content of the above polyorganosiloxane compound in the hard coat composition is preferably 40 parts by weight or more, more preferably 50 parts by weight or more, and even more preferably 60 parts by weight or more, per 100 parts by weight of the total solid content (non-volatile content).

<Photocationic Polymerization Initiator>
The photocationic polymerization initiator is a compound (photoacid generator) that generates an acid when irradiated with active energy rays. The acid generated from the photoacid generator promotes ring-opening and polymerization reaction of the epoxy group of the polyorganosiloxane compound, forming intermolecular crosslinks and curing the hard coat material.

Examples of photoacid generators include strong acids such as toluenesulfonic acid or boron tetrafluoride; onium salts such as sulfonium salts, ammonium salts, phosphonium salts, iodonium salts, and selenium salts; iron-arene complexes; silanol-metal chelate complexes; sulfonic acid derivatives such as disulfones, disulfonyldiazomethanes, disulfonylmethanes, sulfonylbenzoylmethanes, imidosulfonates, and benzoin sulfonates; and organic halogen compounds.

Among the above photoacid generators, aromatic sulfonium salts or aromatic iodonium salts are preferred because of their high stability in hard coat compositions containing polyorganosiloxane compounds having epoxy groups. Examples of counter anions include fluorophosphate anions, fluoroantimonate anions, and fluoroborate anions. When a photoacid generator containing these counter anions is used, it is easy to obtain a hard coat layer that has a high photocuring speed and excellent adhesion to a transparent resin substrate.

Among them, fluorophosphate-based anions and fluoroborate-based anions are preferred as counter anions that have a lower environmental load and less impact on the environment and human body than antimony-based anions such as _SbF6 . When a photoacid generator containing these non-antimony-based counter anions is used, the hardness of the hard coat layer tends to improve. In addition, even if the hard coat layer (hard coat film) is exposed to a high-temperature and high-humidity environment, the residual photoacid generator is less likely to bleed out, and the decrease in transparency due to the increase in haze tends to be suppressed.

Specific examples of non-antimony photoacid generators that have a high photocuring speed and do not contain antimony compounds include diphenyl(4-phenylthiophenyl)sulfonium hexafluorophosphate, hexafluorophosphate derivatives in which some or all of the fluorine atoms of hexafluorophosphate are replaced with perfluoroalkyl groups, and triphenylsulfonium tetrakispentafluorophenylborate.

The content of the photocationic polymerization initiator in the hard coat composition is preferably 0.05 to 10 parts by weight, more preferably 0.1 to 5 parts by weight, and even more preferably 0.2 to 2 parts by weight, per 100 parts by weight of the polyorganosiloxane compound.

<Reactive Diluent>
The hard coat composition may contain a reactive diluent. The reactive diluent may contain, for example, a cationic polymerizable compound other than the polyorganosiloxane compound. A compound having a cationic polymerizable functional group is used as the reactive diluent for photo-cationic polymerization. Examples of the cationic polymerizable functional group of the reactive diluent include an epoxy group, a vinyl ether group, an oxetane group, and an alkoxysilyl group. Among them, the reactive diluent having an epoxy group is preferred because it has high reactivity with the epoxy group of the polyorganosiloxane compound.

The content of reactive diluent in the hard coat composition is preferably 100 parts by weight or less, and more preferably 50 parts by weight or less, per 100 parts by weight of polyorganosiloxane compound.

<Photosensitizer>
The hard coat composition may contain a photosensitizer for the purpose of improving the photosensitivity of the photocationic polymerization initiator (photoacid generator). The photosensitizer is preferably one that has little overlap with the absorption wavelength range of the photoacid generator, since it is more efficient to use a photosensitizer that can absorb light in a wavelength range that the photoacid generator itself cannot absorb. Examples of the photosensitizer include anthracene derivatives, benzophenone derivatives, thioxanthone derivatives, anthraquinone derivatives, and benzoin derivatives.

The content of the photosensitizer in the hard coat composition is preferably 50 parts by weight or less per 100 parts by weight of the above-mentioned photoacid generator, more preferably 30 parts by weight or less, and even more preferably 10 parts by weight or less.

<Particle>
The hard coat composition may contain particles for the purpose of adjusting the film properties such as surface hardness and bending resistance, suppressing curing shrinkage, etc. As the particles, organic particles, inorganic particles, organic-inorganic composite particles, etc. may be appropriately selected and used. Examples of the organic particle material include poly(meth)acrylic acid alkyl ester, crosslinked poly(meth)acrylic acid alkyl ester, crosslinked styrene, nylon, silicone, crosslinked silicone, crosslinked urethane, crosslinked butadiene, etc. Examples of the inorganic particle material include metal oxides such as titania , alumina, tin oxide, zirconia, zinc oxide, and antimony oxide; metal nitrides such as silicon nitride and boron nitride; and metal salts such as calcium carbonate, calcium hydrogen phosphate, calcium phosphate, and aluminum phosphate. Examples of the organic-inorganic composite filler include those in which an inorganic layer is formed on the surface of organic particles, and those in which an organic layer or organic fine particles is formed on the surface of inorganic particles.

The particle shapes include spherical, powdery, fibrous, needle-like, scaly, etc. Spherical particles are not anisotropic and are less likely to cause uneven distribution of stress, which reduces distortion and can contribute to suppressing warping of the film caused by curing shrinkage, etc.

The average particle diameter of the particles is, for example, about 5 nm to 10 μm. From the viewpoint of increasing the transparency of the hard coat layer, the average particle diameter is preferably 1000 nm or less, more preferably 500 nm or less, even more preferably 300 nm or less, and particularly preferably 100 nm or less. The particle diameter can be measured by a laser diffraction/scattering type particle size distribution measuring device, and the volume-based median diameter is taken as the average particle diameter.

The hard coat composition may contain surface-modified particles. By surface-modifying the particles, the dispersibility of the particles in the polyorganosiloxane compound tends to improve. In addition, when the particle surface is modified with a polymerizable functional group capable of reacting with an epoxy group, the functional group on the particle surface reacts with the epoxy group of the polyorganosiloxane compound to form a chemical crosslink, which is expected to improve the film strength.

Examples of polymerizable functional groups that can react with epoxy groups include vinyl groups, (meth)acrylic groups, hydroxyl groups, phenolic hydroxyl groups, carboxyl groups, acid anhydride groups, amino groups, epoxy groups, and oxetane groups. Among these, epoxy groups are preferred. In particular, particles surface-modified with epoxy groups are preferred because they can form chemical crosslinks between the particles and the polyorganosiloxane compound when the hard coat composition is cured by photocationic polymerization.

Examples of particles having reactive functional groups on their surfaces include surface-modified inorganic particles and core-shell polymer particles.

<Solvent>
The hard coat composition may be solvent-free or may contain a solvent. When a solvent is contained, it is preferable that the solvent does not dissolve the transparent resin substrate. On the other hand, by using a solvent having a degree of solubility that swells the transparent resin substrate, the adhesion between the transparent resin substrate and the hard coat layer may be improved. The content of the solvent is preferably 500 parts by weight or less, more preferably 300 parts by weight or less, and even more preferably 100 parts by weight or less, relative to 100 parts by weight of the polyorganosiloxane compound.

<Additives>
The hard coat composition may contain additives such as inorganic pigments, organic pigments, surface conditioners, surface modifiers, plasticizers, dispersants, wetting agents, thickeners, and defoamers. The hard coat composition may also contain thermoplastic or thermosetting resin materials other than the polyorganosiloxane compounds. When the polyorganosiloxane compound and/or the resin material other than the polyorganosiloxane compound has radical polymerizability, the hard coat composition may contain a radical polymerization initiator in addition to the photocationic polymerization initiator.

[Hard coat film]
A hard coat composition is applied onto a transparent resin substrate, and the solvent is removed by drying as necessary, and then the hard coat composition is cured by irradiating with active energy rays to obtain a hard coat film. The hard coat layer may be formed on only one main surface of the transparent resin substrate, or may be formed on both main surfaces of the transparent resin substrate.

<Transparent resin base material>
The transparent resin substrate is a film substrate that serves as a base for forming a hard coat layer. The total light transmittance of the transparent resin substrate is preferably 80% or more, more preferably 85% or more, and even more preferably 90% or more. The haze of the transparent resin substrate is preferably 2% or less, and more preferably 1% or less.

The thickness of the transparent resin substrate is not particularly limited and is, for example, 1 to 1000 μm, preferably 5 to 500 μm, more preferably 10 to 200 μm, and even more preferably 15 to 150 μm.

The resin material constituting the transparent resin substrate is not particularly limited as long as it is a transparent resin. Examples of transparent resins include polyesters such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polycarbonates, polyamides, transparent polyimides, cyclic polyolefins, acrylic resins such as polymethyl methacrylate (PMMA), and cellulose-based resins such as triacetyl cellulose (TAC).

Among these, polyesters such as PET and transparent polyimides are preferred due to their high mechanical strength. When the hard coat film is used as a cover window for a display, the film substrate is required to have excellent heat resistance and mechanical strength, so transparent polyimides are particularly preferred as the resin material for the transparent resin substrate. While typical fully aromatic polyimides are colored yellow or brown, transparent polyimides with high visible light transmittance can be obtained by introducing an alicyclic structure, a bent structure, or a fluorine substituent.

The transparent resin substrate may be a single layer or a multilayer structure. For example, the transparent resin substrate may be a laminate in which a plurality of films are laminated together, and may have a functional layer such as an easy-adhesion layer, an antistatic layer, or an antireflection layer provided on the hard coat layer-forming surface and/or the non-hard coat layer-forming surface of the film substrate. The transparent resin substrate may also have a hard coat layer formed of a material other than the polyorganosiloxane compound on one of its main surfaces.

<Formation of hard coat layer>
As described above, the hard coat composition is applied onto the transparent resin substrate and cured to form a hard coat layer. Before applying the hard coat composition, the surface of the transparent resin substrate may be subjected to surface treatment such as corona treatment or plasma treatment. In addition, an easy-adhesion layer (primer layer) or the like may be provided on the surface of the transparent resin substrate. In addition, since the hard coat layer formed by curing the hard coat composition containing the above-mentioned polyorganosiloxane compound exhibits high adhesion to the transparent resin substrate, it is not necessary to provide an easy-adhesion layer or the like. That is, the hard coat film may be in contact with the transparent resin substrate and the hard coat layer.

When the hard coat composition is irradiated with active energy rays, an acid is generated from the photocationic polymerization initiator, and the epoxy groups of the polyorganosiloxane compound undergo ring-opening and cationic polymerization, thereby progressing the curing. When the hard coat composition contains a reactive diluent, in addition to the polymerization reaction between the polyorganosiloxane compounds themselves, a polymerization reaction also occurs between the epoxy groups of the polyorganosiloxane compound and the reactive diluent. Furthermore, when the hard coat composition contains particles having reactive functional groups on their surfaces, the functional groups on the particle surfaces may react with the epoxy groups of the polyorganosiloxane compound to form chemical crosslinks.

Examples of active energy rays irradiated during photocuring include visible light, ultraviolet light, infrared light, X-rays, α-rays, β-rays, γ-rays, and electron beams. UV light is preferred as the active energy ray because it has a high curing reaction rate and excellent energy efficiency. The cumulative dose of active energy rays is, for example, about 50 to 10,000 mJ/ ^cm2 , and may be set depending on the type and amount of photocationic polymerization initiator, the thickness of the hard coat layer, and the like. The curing temperature is not particularly limited, but is usually 100°C or less.

The thickness of the hard coat layer is preferably 0.5 μm or more, more preferably 2 μm or more, even more preferably 3 μm or more, particularly preferably 5 μm or more, and may be 10 μm or more, 20 μm or more, or 30 μm or more. The thicker the hard coat layer, the higher the surface hardness tends to be. On the other hand, from the viewpoint of transparency and bending resistance, the thickness of the hard coat layer is preferably 100 μm or less, more preferably 80 μm or less, and may be 70 μm or less.

The total thickness of the hard coat film is, for example, 1 to 1000 μm, preferably 10 to 500 μm, more preferably 15 to 250 μm, and even more preferably 20 to 200 μm. The ratio of the thickness of the hard coat layer to the thickness of the transparent resin substrate in the hard coat film (thickness of the hard coat layer/thickness of the transparent resin substrate) is not particularly limited and may be appropriately selected, for example, from between 1/10 and 10/1.

[Characteristics of hard coat film]
The hard coat layer formed by curing the above hard coat composition has excellent adhesion to the transparent resin substrate.In addition, the hard coat composition has a polymer matrix in which the polyorganosiloxane compound is crosslinked by the ring-opening and polymerization reaction of the epoxy group, so that it can achieve a surface hardness comparable to that of glass.The surface hardness (pencil hardness) of the hard coat layer-forming surface of the hard coat film is preferably HB or more, more preferably H or more, even more preferably 2H or more, and may be 3H or more or 4H or more.

As described above, the hard coat film has high surface hardness and excellent flex resistance. When a cylindrical mandrel test is performed with the hard coat layer surface facing outward, the mandrel diameter at which cracks occur in the hard coat layer is preferably 8 mm or less, more preferably 6 mm or less, and may be 4 mm or less, or 2 mm or less.

The total light transmittance of the hard coat film is preferably 80% or more, more preferably 85% or more, and even more preferably 88% or more. The haze of the hard coat film is preferably 1.5% or less, more preferably 0.9% or less, even more preferably 0.6% or less, and particularly preferably 0.5% or less.

When a hard coat film is subjected to a moist heat test in which the film is left to stand in an environment at a temperature of 60°C and a humidity of 90% for 24 hours, the change in haze, ΔHaze, is preferably 0.3% or less, more preferably 0.2% or less, and even more preferably 0.1% or less. As mentioned above, by using a non-antimony photocationic polymerization initiator (photoacid generator), bleeding out of residual materials is less likely to occur, and an increase in haze due to moist heat resistance tests tends to be suppressed.

[Applications of hard coat films]
The hard coat film may have various functional layers on the hard coat layer or on the non-hard coat layer surface of the transparent resin substrate. Examples of the functional layers include an anti-reflection layer, an anti-glare layer, an antistatic layer, a transparent electrode, etc. A transparent adhesive layer may also be provided on the hard coat film.

The hard coat film of the present invention has high transparency and excellent mechanical strength, and therefore can be suitably used for cover windows provided on the surface of image display panels, transparent substrates for displays, transparent substrates for touch panels, substrates for solar cells, etc. The hard coat film of the present invention has excellent flex resistance in addition to transparency and mechanical strength, and therefore can be suitably used particularly as cover windows and substrate films for curved displays, flexible displays, etc.

The present invention will be explained in more detail below by showing examples of producing a polyorganosiloxane compound and a hard coat film, but the present invention is not limited to the following examples.

[Synthesis of polyorganosiloxane compound]
<Synthesis Example 1>
In a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser, 67.4 g (220 mmol) of 8-glycidyloxyoctyltrimethoxysilane ("KBM-4803" manufactured by Shin-Etsu Chemical Co., Ltd.) and 11.6 g of methanol were charged and stirred uniformly. A solution of 0.010 g (0.11 mmol) of magnesium chloride dissolved in a mixture of 11.9 g (660 mmol) of water and 4.7 g of methanol was added dropwise to this mixture over 5 minutes and stirred until it became uniform. Thereafter, the temperature was raised to 70°C and a polycondensation reaction was carried out for 6 hours while stirring. After completion of the reaction, methanol and water were removed using a rotary evaporator to obtain a polyorganosiloxane compound 1 having an epoxy group.

<Synthesis Example 2>
In a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser, 69.0 g (225 mmol) of 8-glycidyloxyoctyltrimethoxysilane, 6.2 g (25 mmol) of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane ("SILQUEST A-186" manufactured by Momentive Performance Materials), and 15.3 g of 1-methoxy-2-propanol (PGME) were charged and stirred uniformly. A solution of 0.012 g (0.125 mmol) of magnesium chloride dissolved in a mixture of 13.5 g (750 mmol) of water and 5.4 g of methanol was added dropwise to this mixture over 5 minutes and stirred until it became uniform. Thereafter, the temperature was raised to 80°C and a polycondensation reaction was carried out for 6 hours while stirring. After completion of the reaction, the solvent was distilled off using a rotary evaporator to obtain a polyorganosiloxane compound 2 having an epoxy group.

<Synthesis Examples 3 to 5>
Polyorganosiloxane compounds 3 to 5 were obtained in the same manner as in Synthesis Example 2, except that the ratio of 8-glycidyloxyoctyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane was changed as shown in Table 1.

<Synthesis Example 6>
In a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser, 66.5 g (270 mmol) of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 16.5 g of PGME were charged and stirred uniformly. A solution of 0.039 g (0.405 mmol) of magnesium chloride dissolved in a mixture of 9.7 g (539 mmol) of water and 5.8 g of methanol was added dropwise to this mixture over 5 minutes and stirred until it became uniform. The mixture was then heated to 80°C and polycondensation reaction was carried out for 6 hours while stirring. After the reaction was completed, the solvent was removed using a rotary evaporator to obtain polyorganosiloxane compound 6.

<Synthesis Example 7>
In a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser, 63.8 g (270 mmol) of 3-glycidyloxypropyltrimethoxysilane ("KBM-403" manufactured by Shin-Etsu Chemical Co., Ltd.) and 16.5 g of PGME were charged and stirred uniformly. A solution of 0.013 g (0.135 mmol) of magnesium chloride dissolved in a mixture of 14.6 g (810 mmol) of water and 5.8 g of methanol was added dropwise to this mixture over 5 minutes and stirred until it became uniform. Thereafter, the temperature was raised to 80°C, and a polycondensation reaction was carried out for 6 hours while stirring. After completion of the reaction, the solvent was distilled off using a rotary evaporator to obtain polyorganosiloxane compound 7.

<Synthesis Example 8>
In a reaction vessel equipped with a thermometer, a stirrer and a reflux condenser, 46.0 g (150 mmol) of 8-glycidyloxyoctyltrimethoxysilane and 9.2 g of PGME were charged and stirred uniformly. A solution of 0.0052 g (0.0375 mmol) of potassium carbonate dissolved in a mixture of 8.1 g (450 mmol) of water and 3.2 g of methanol was added dropwise to this mixture over 5 minutes and stirred until it became uniform. The mixture was then heated to 80°C and polycondensation reaction was carried out for 6 hours while stirring. After the reaction was completed, the solvent was removed using a rotary evaporator to obtain a polyorganosiloxane compound 8 having an epoxy group.

<Synthesis Example 9>
A condensation reaction and solvent distillation were carried out in the same manner as in Synthesis Example 8, except that the amount of the condensation catalyst (potassium carbonate) was changed to 0.0104 g (0.075 mmol), to obtain Polyorganosiloxane Compound 9.

[Evaluation of Compounds]
The weight average molecular weight Mw, T3/T2 ratio, and residual rate of epoxy groups were measured by the following method for the polyorganosiloxane compounds 1 to 9 obtained in Synthesis Examples 1 to 9. The amount of remaining catalyst was calculated based on the amount of silane compound and catalyst charged in the reaction.

<Weight average molecular weight Mw>
Measurements were carried out using a Tosoh GPC apparatus "HLC-8220GPC" (columns: TSKgel GMHXL x 2, TSKgel G3000HXL, TSKgel G2000HXL) and THF as a solvent, and the weight average molecular weight in terms of polystyrene was calculated.

<T3/T2 ratio>
^{The 29} Si-NMR spectrum was measured using an Agilent NMR (600 MHz) to determine the ratio T3/T2 (molar ratio) of the SiO _3/2 body (T3 structure) to the SiO _2/2 body (T2 structure).

<Epoxy group residual ratio>
The amount of remaining epoxy groups was determined by measuring ¹ H-NMR spectrum using a Bruker NMR (400 MHz) and deuterated acetone as a solvent. The remaining rate of epoxy groups was 95% or more for all of the polyorganosiloxane compounds 1 to 9.

The amounts of raw materials (silane compounds) used in Synthesis Examples 1 to 9, the types of condensation catalysts, and the evaluation results of the polyorganosiloxane compounds (catalyst content, T3/T2 ratio, and weight average molecular weight Mw) are shown in Table 1.

The polyorganosiloxane compounds of Synthesis Examples 1 to 7 using magnesium chloride, a neutral salt catalyst, as the condensation catalyst had a T3/T2 ratio of less than 5, whereas the polyorganosiloxane compounds of Synthesis Examples 8 and 9 using potassium carbonate had a T3/T2 ratio of more than 5. From these results, it can be seen that a polyorganosiloxane compound having a small ratio of SiO3 _/2 bodies (T3 structure) can be obtained by performing a condensation reaction of a silane compound using a neutral salt catalyst.

[Preparation of hard coat composition]
<Hard Coat Composition 1>
The polyorganosiloxane compound 1 (100 parts by weight) obtained in Synthesis Example 1 was mixed with 0.5 parts by weight of a 50% propylene carbonate solution of triarylsulfonium.P(Rf) _{nF6 -n} salt (manufactured by San-Apro, "CPI-200K"), which is a non-antimony compound, as a photocationic polymerization initiator, and 0.125 parts by weight of a 52% xylene/isobutanol solution of polyether-modified polydimethylsiloxane (manufactured by BYK, "BYK-300"), as a leveling agent, to obtain a hard coat composition 1. The above blending amounts are the solid contents of each component.

<Hard Coat Compositions 2 to 5, 7 to 9>
Hard coat compositions were prepared by using polyorganosiloxane compounds 2 to 5 and 7 to 9 instead of polyorganosiloxane compound 1, and adding a photocationic polymerization initiator and a leveling agent. In preparing the compositions, PGME was added as a dilution solvent to adjust the viscosity of the solution (see Table 2 for the amount added).

<Hard Coat Composition 6>
The polyorganosiloxane compound 6 (100 parts by weight) obtained in Synthesis Example 6 was mixed with 0.2 parts by weight of a 50% propylene carbonate solution of diphenyl(4-phenylthiophenyl)sulfonium.SbF ₆ ("CPI-101A" manufactured by San-Apro) as a photocationic polymerization initiator, 0.25 parts by weight of a leveling agent ("BYK-300" manufactured by BYK), and 99.3 parts by weight of PGME as a dilution solvent to obtain a hard coat composition 6 having a total solids concentration of 50% by weight. The above blending amounts are the solids of each component.

<Hard Coat Composition 10>
A hard coat composition 10 having a total solids concentration of 80% by weight was obtained in the same manner as in the preparation of hard coat composition 1, except that a 50% propylene carbonate solution of diphenyl(4-phenylthiophenyl)sulfonium.SbF ₆ ("CPI-101A" manufactured by San-Apro) was used as the photocationic polymerization initiator, and 24.2 parts by weight of PGME was added as the dilution solvent.

[Preparation of hard coat film]
<Hard coat film 1>
Hard coat composition 1 was applied to one side of the transparent polyimide film (thickness 50 μm) of Example 12 of WO2020/004236 using a bar coater so that the film thickness after heating would be 10 μm, and heated for 10 minutes at 120° C. Thereafter, the hard coat composition was cured by irradiating ultraviolet light using a high-pressure mercury lamp so that the integrated light amount of wavelengths of 250 to 390 nm was 1000 mJ/cm ² , thereby obtaining hard coat film 1 having a hard coat layer having a thickness of 10 μm on one side of the transparent polyimide film.

<Hard Coat Films 2 to 5>
The coating thickness of the hard coat composition was changed so that the thickness of the hard coat (HC) layer was the value shown in Table 1. Otherwise, hard coat films 2 to 5 were produced in the same manner as in the production of hard coat film 1, by forming a hard coat layer on one side of a transparent polyimide film using hard coat composition 1.

<Hard Coat Film 6>
Hard coat composition 6 was applied using a bar coater so that the dry film thickness (film thickness after heating) was 50 μm, and heating and curing were performed in the same manner as in Preparation Example 1 to prepare a hard coat film having a hard coat layer of 50 μm thickness on one side of a transparent polyimide film. Hard coat composition 1 was applied using a bar coater to the non-hard coat layer side of this hard coat film so that the dry film thickness was 50 μm, and heating and curing were performed to prepare a hard coat film 6 having a hard coat layer of 50 μm thickness on both sides of a transparent polyimide film.

<Hard Coat Film 7>
Hard coat film 7 was prepared in the same manner as hard coat film 3, except that a 50 μm-thick polyethylene terephthalate (PET) film ("Lumirror 50U48" manufactured by Toray) was used instead of the transparent polyimide film. Hard coat film 7 had a 50 μm-thick hard coat layer on one side of the PET film.

<Hard Coat Film 8>
A hard coat film 8 having a hard coat layer having a thickness of 50 μm on one side of a transparent polyimide film was prepared in the same manner as in the preparation of the hard coat film 3, except that a hard coat composition 10 containing an antimony-based photocationic polymerization initiator was used instead of the hard coat composition 1.

<Hard Coat Films 9 to 16>
Hard coat films 9 to 16 were produced in the same manner as in the production of hard coat film 3, except that hard coat compositions 2 to 9 were used instead of hard coat composition 1, and each hard coat film had a hard coat layer having a thickness of 50 μm on one side of a transparent polyimide film.

[Evaluation of hard coat film]
The above hard coat films 1 to 16 were evaluated by the following methods.

<Surface hardness and adhesion>
According to JIS K5600-5-4:1999, the pencil hardness of the surface on which the hard coat layer was formed was measured under a load of 750 g. For the hard coat film 6 having hard coat layers on both sides, the surface on which the hard coat layer formed using the hard coat composition 1 (polyorganosiloxane compound 1) was evaluated. When the test was performed using a pencil with hardness H, those that did not peel off the hard coat layer were rated as having OK adhesion, and those that peeled off the hard coat layer were rated as having NG adhesion. For films 15 and 16 with NG adhesion, the surface hardness was not evaluated.

<Mandrel test>
According to JIS K5600-5-1:1999, a cylindrical mandrel test was performed using a type 1 testing machine with the hard coat layer formed on the outer side. For hard coat film 6, the test was performed with the surface on the side of the hard coat layer formed using hard coat composition 1 on the outer side. The smaller the mandrel diameter φ, the more excellent the bending resistance.

<Total Light Transmittance and Haze>
The haze was measured using a haze meter "HZ-V3" manufactured by Suga Test Instruments Co., Ltd., according to the methods described in JIS K7361-1: 1999 and JIS K7136: 2000. The measurement was performed using a D65 light source, and the total light transmittance was calculated as the ratio of the total transmitted light flux (parallel light component and diffuse light component) to the parallel incident light flux on the hard coat film.

<Haze change due to wet heat test>
The hard coat film was allowed to stand for 24 hours in a thermo-hygrostat set at a temperature of 60° C. and a humidity of 90%, and then the haze was measured by the above-mentioned method, and the amount of change in haze before and after the moist heat test, ΔHaze (= [haze of the hard coat film after the moist heat test] - [haze of the hard coat film before the moist heat test]) was calculated.

<Surface tackiness>
The hard coat film was placed on a horizontal desk with the surface on which the hard coat layer was formed facing up (in the case of hard coat film 6, the hard coat layer formed using hard coat composition 1 was facing up), and a PET film having a thickness of 75 μm was placed on the hard coat layer and pressed for 1 second with a load of 10 N/cm ^2. After removing the load, the presence or absence of sticking (blocking) between the hard coat layer and the PET film was visually confirmed, and those with no sticking at all were rated as A, those with sticking but within 30% of the area where the load was applied were rated as B, and those with sticking over an area greater than 30% were rated as C.

The compositions of the hard coat compositions used to prepare hard coat films 1 to 16, the thicknesses of the hard coat layers and hard coat films, and the evaluation results of the hard coat films are shown in Table 2. The compositions in Table 2 are expressed in parts by weight of the polymerization initiator, leveling agent, and solvent relative to 100 parts by weight of the polyorganosiloxane compound.

The hard coat film 14 has a hard coat layer formed using polyorganosiloxane compound 7, which is a condensate of a silane compound (3-glycidyloxypropyltrimethoxysilane) in which a silicon atom and a glycidyloxy group are bonded via a propylene group. The mandrel test result for this hard coat film 14 was 10 mm, indicating that the bending resistance of the hard coat layer was insufficient.

The hard coat film 13 has a hard coat layer formed using polyorganosiloxane compound 6, which is a condensation product of a silane compound (2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane) in which a silicon atom and an alicyclic epoxy group are bonded via an ethylene group. Although this hard coat film 13 had improved tackiness of the hard coat layer surface, the mandrel diameter was 32 mm and the bending resistance of the hard coat layer was poor.

Hardcoat films 1 to 5 have a hardcoat layer formed using polyorganosiloxane compound 1, which is a condensate of a silane compound (8-glycidyloxyoctyltrimethoxysilane) in which a Si atom and a glycidyloxy group are bonded via an octylene group. In these hardcoat films 1 to 5, the mandrel diameter tends to increase (flex resistance decreases) as the thickness of the hardcoat layer increases, but even when the thickness of the hardcoat layer is increased to 75 μm, the mandrel diameter is 6 mm, showing excellent flex resistance. Hardcoat film 6, which has hardcoat layers formed on both sides, and hardcoat film 7, which uses a PET film substrate, also showed excellent flex resistance, similar to hardcoat films 1 to 5.

In the hard coat films 15 and 16 in which the hard coat layer was formed using the polyorganosiloxane compounds 8 and 9 having a high ratio of T3 structure, the mandrel diameter was larger and the bending resistance was reduced compared to the hard coat film 3. In addition, in the hard coat films 15 and 16, the adhesion of the hard coat layer to the transparent polyimide film was poor.

From the above results, it can be seen that by using a polyorganosiloxane compound which is a condensation product of a silane compound in which a Si atom and a glycidyloxy group are bonded via an alkylene group having 4 or more carbon atoms and has a small ratio of T3 structures (T3/T2 ratio less than 5), a hard coat layer with excellent hardness, adhesion and flex resistance can be formed.

Hardcoat film 8, in which a hardcoat layer was formed using composition 10 using an antimony-based cationic photopolymerization initiator, exhibited a mandrel diameter (flex resistance) equivalent to that of hardcoat film 3, but had a lower surface hardness than hardcoat film 3 and showed an increase in haze after a moist heat test. These results show that the use of a non-antimony-based cationic photopolymerization initiator tends to improve the hardness and moist heat resistance (transparency after moist heat test) of the hardcoat layer compared to the use of an antimony-based photopolymerization initiator.

In the hard coat films 9 to 12, the hard coat layer was formed using polyorganosiloxane compounds 9 to 12, which were condensed with 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, a silane compound containing an alicyclic epoxy group, in addition to 8-glycidyloxyoctyltrimethoxysilane, as a silane compound. In these hard coat films 9 to 12, the tackiness of the hard coat layer surface was improved, and it is believed that the high photocationic polymerization of the alicyclic epoxy group is involved in the improvement of the tackiness. In the hard coat films 9 to 12, the bending resistance tended to decrease with an increase in the amount of 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane used. Therefore, from the viewpoint of the bending resistance of the hard coat layer, it can be said that it is preferable to reduce the ratio of the silane compound containing an alicyclic epoxy group within a range in which the tackiness can be improved.

Claims (9)

A hard coat film comprising a hard coat layer made of a cured product of a hard coat composition on at least one main surface of a transparent resin substrate,
The hard coat composition contains a polyorganosiloxane compound which is a condensation product of a silane compound represented by general formula (A),
Q-(Si(OR ² ) _x R ³ _3-x ) …(A)
The polyorganosiloxane compound is
The weight average molecular weight is 500 to 20,000,
It includes a T3 structure represented by general formula (3) and a T2 structure represented by general formula (4),
[Q-SiO _3/2 ] …(3)
[Q-SiO2 _/2 -Z]...(4)
the ratio T3/T2 of the content of the T3 structure to the content of the T2 structure is less than 5;
The ratio of the structure represented by the general formula (5) to the total number of Si atoms is 60% or more.
[Y-R ¹ -Si]...(5)
Hard coat film (excluding those in which the hard coat composition contains silica fine particles):
In the general formula (5), Y is a glycidyloxy group, R ¹ is a chain alkylene group having 4 to 16 carbon atoms in the main chain;
In general formula (A), R ² is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, R ³ is a hydrogen atom or a monovalent hydrocarbon group selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms, Q is a monovalent organic group, and x is 2 or 3;
In the silane compound represented by the general formula (A), the ratio of Q being a monovalent organic group containing an epoxy group is 90 mol % or more;
In the general formula (3) and the general formula (4), Q is the same as in the general formula (A) ;
In general formula (4), Z is a hydrogen atom or a monovalent organic group selected from the group consisting of an alkoxy group having an alkyl group having 1 to 10 carbon atoms, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an aralkyl group having 7 to 12 carbon atoms. The hard coat film according to claim 1 , wherein the polyorganosiloxane compound further contains a structure represented by general formula (6), and the ratio of the structure represented by general formula (6) to the total number of Si atoms is 1 to 40%:
[X-Si]…(6)
In general formula (6), X is a monovalent organic group containing an alicyclic epoxy group. the hard coat composition comprises a neutral salt comprising an ion of an element selected from the group consisting of an alkali metal element and a Group 2 element in combination with a halide ion selected from the group consisting of chloride ion, bromide ion, and iodide ion;
3. The hard coat film according to claim 1 , wherein the concentration of the neutral salt is 1 ppm to 10,000 ppm based on the polyorganosiloxane compound. The hard coat film according to any one of claims 1 to 3 , wherein the hard coat composition further contains a photocationic polymerization initiator. The hard coat film according to claim 4 , wherein the photocationic polymerization initiator does not contain antimony. The hardcoat film of any one of claims 1 to 5 , wherein the hardcoat composition is particle-free. The hard coat film according to any one of claims 1 to 6 , wherein the hard coat layer has a thickness of 0.5 to 100 µm. The hard coat film according to any one of claims 1 to 7 , wherein the transparent resin substrate comprises one or more resin materials selected from the group consisting of polyester, polycarbonate, polyamide, polyimide, cyclic polyolefin, acrylic resin, and cellulose-based resin. A method for producing the hard coat film according to any one of claims 1 to 8 ,
A method for producing a hard coat film, comprising applying the hard coat composition onto a transparent resin substrate, and irradiating the substrate with active energy rays to cure the hard coat composition, thereby forming the hard coat layer.