WO2022085735A1 - Hard coating film, method for producing same, and image display device - Google Patents

Abstract

This hard coating film (10) is provided with a hard coating layer (2) on at least one surface of a base material film (1). The base material film is a polyimide film that contains a polyimide resin; and the hard coating layer is formed of a cured product of a photocurable resin composition. Since both of the hard coating layer and the polyimide film contain an ultraviolet absorbent, the hard coating film has high hardness and excellent light resistance. This hard coating film is applicable to a surface protective material that is arranged on the viewing-side surface of an image display panel, or the like.

Description

Hardcourt film and its manufacturing method, and image display device

The present invention relates to a hard coat film having a hard coat layer on at least one surface of the transparent polyimide film, a method for manufacturing the same, and an image display device provided with the hard coat film.

Mobile terminal devices are becoming thinner and lighter, and terminal devices such as smartphones are becoming widespread. In recent years, a flexible display, particularly a foldable mobile terminal device equipped with an organic EL panel using a flexible substrate, has been proposed as a method for achieving both a large screen size and portability.

In flexible devices, not only the display substrate but also the surface protective material such as the cover window must have flexibility, and the surface of the polyimide film having excellent transparency, surface hardness, and bending durability is hard coated. It has been proposed to use a hard coat film provided with a layer (for example, Patent Document 1 and Patent Document 2). Patent Document 1 discloses that a hard coat layer is formed by using a photocurable resin composition containing a reactive urethane acrylate, a photoradical polymerization initiator and an ultraviolet absorber.

Japanese Unexamined Patent Publication No. 2017-226712 International Publication No. 2020/040209

Since the surface protective material of the display device is located in the outermost layer, it is easily exposed to external light. Therefore, the hard coat film used as a surface protective material is required to have high light resistance with little change in optical characteristics and mechanical strength even when exposed to ultraviolet rays or the like.

One aspect of the present invention is a hard-coated film in which a hard-coat layer is provided on at least one surface of the base film. The base film is a polyimide film containing a polyimide resin, and the hard coat layer is made of a cured product of a photocurable resin composition. Each of the hardcoat layer and the polyimide film contains an ultraviolet absorber.

As the ultraviolet absorber contained in the polyimide film and the hard coat layer, a benzotriazole compound or a triazine compound is preferable. The content of the ultraviolet absorber in the polyimide film is preferably 0.1 to 4.5% by weight. The content of the ultraviolet absorber in the hard coat layer is preferably 0.1 to 4.5% by weight.

The thickness of the hard coat layer is, for example, 0.5 to 100 μm. The thickness of the polyimide film is, for example, 5 to 100 μm.

The polyimide resin of the polyimide film is preferably soluble in dichloromethane. For example, a polyimide film containing an ultraviolet absorber can be obtained by applying a solution containing a polyimide resin soluble in dichloromethane and an ultraviolet absorber onto a substrate and removing the solvent. A photocurable resin composition (hard coat composition) containing a photocurable resin and a photopolymerization initiator is applied to the surface of the polyimide film and photocured to provide a hard coat layer on the surface of the polyimide film. A hard coat film can be produced.

The hardcoat composition may be photocationically polymerizable. An example of a photocurable resin having photocationic polymerizable properties is a polysiloxane compound having an epoxy group. The hard coat composition contains, for example, a photocurable resin having photocationic polymerizable properties, a photocationic polymerization initiator (photoacid generator), and an ultraviolet absorber.

The hard coat film can be used as a surface protective material arranged on the visible side surface of the image display panel, for example, in an image display device. The image display device may be bendable.

Since the hard coat film contains an ultraviolet absorber in both the polyimide film and the hard coat layer, photodegradation of the polyimide is suppressed, so that the optical characteristics and mechanical strength change even when exposed to ultraviolet rays or the like. It is small and has excellent light resistance.

It is sectional drawing which shows the structural example of a hard coat film.

FIG. 1 is a cross-sectional view of a hard coat film 10 provided with a hard coat layer 2 on one main surface of the polyimide film 1. The hard coat layer 2 is formed by applying the hard coat composition to the main surface of the polyimide film 1 as a film base material and curing it. The hard coat layer may be provided only on one main surface of the polyimide film, or may be provided on both sides of the polyimide film.

Both the polyimide film 1 and the hard coat layer 2 contain an ultraviolet absorber. Since both the polyimide film and the hard coat layer contain an ultraviolet absorber, the light resistance is improved, and the yellowing of the hard coat film tends to be suppressed even after long-term exposure to ultraviolet rays.

Examples of the ultraviolet absorber contained in the polyimide film and the hard coat layer include triazine-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, benzophenone-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, hydroxybenzoate-based ultraviolet absorbers, and the like. Be done. Among them, a benzotriazole-based ultraviolet absorber and a triazine-based ultraviolet absorber are preferable because they absorb less visible light and can obtain good light resistance.

Specific examples of the benzotriazole-based ultraviolet absorber include 2- (2H-benzotriazole-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (ADEKA "Adecastab LA-24"). ), 2- (2H-benzotriazole-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol ("Adecastab LA-29" manufactured by ADEKA), 2,2'-methylenebis [6 -(2H-benzotriazole-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol] (ADEKA "Adecastab LA-31G" and "Adecastab LA-31RG"), 2- ( 2H-benzotriazole-2-yl) -p-cresol (ADEKA "Adecastab LA-32"), 2- (2H-benzotriazole-2-yl) -6-dodecyl-4-methylphenol (BASF "TINUVIN571") ”), 2- (2H-benzotriazole-2-yl) -p-cresol (BASF“ TINUVIN P ”), 2- (2-hydroxy-5-tert-butylphenyl) -2H-benzotriazole (BASF) "TINUVIN PS"), 2- (2H-benzotriazole-2-yl) -4-6-bis (1-methyl-1-phenylethyl) phenol (BASF "TINUVIN 234"), 2- [5-chloro (2H) -benzotriazole-2-yl] -4-methyl-6- (tert-butyl) phenol (BASF "TINUVIN 326,"), 2- (2H-benzotriazole-2-yl) -4,6 -Di-tert-pentylphenol (BASF "TINUVIN 328"), 2- (2H-benzotriazole-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol (BASF "TINUVIN") 329 "), 2- (2H-benzotriazole-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol (BASF's" TINUVIN 900 "), 2- (2H-benzotriazole-" 2-yl) -6- (1-methyl-1-phenylethyl) -4- (1,1,3,3-tetramethylbutyl) phenol (BASF "TINUVIN 928"), 2- [2-hydroxy- 3- (3,4,5,6-tetrahydrophthalimide-methyl) -5-methylphenyl] benzotriazole (Sumitomo Chemical's "Sumis" orb250 ") and the like.

Specific examples of the triazine-based ultraviolet absorber include 2- (4,6-diphenyl-1,3,5-triazine-2-yl) -5- [2- (2-ethylhexanoyloxy) ethoxy] -phenol. (ADEKA "Adecastab LA-46"), 2,4,6-Tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-triazine (ADEKA "Adecastab LA-F70") , 2- (4,6-bis (2,4-dimethylphenyl) -1,3,5-triazine-2-yl) -5-hydroxyphenyl and [(alkyloxy) methyl] oxylan reaction product ( BASF "TINUVIN 400"), 2- (2,4-dihydroxyphenyl) -4,6-bis- (2,4-dimethylphenyl) -1,3,5-triazine and (2-ethylhexyl) -glycidic acid Reaction product with ester (BASF "TINUVIN 405"), (2,4-bis [2-hydroxy-4-butoxyphenyl] -6- (2,4-dibutoxyphenyl) -1,3,5- Triazine (BASF "TINUVIN 460"), 2- (2-hydroxy-4- [1-octyloxycarbonylethoxy] phenyl) -4,6-bis (4-phenylphenyl) -1,3,5-triazine ( BASF "TINUVIN 479"), 2- (4,6-diphenyl-1,3,5-triazine-2-yl) -5-[(hexyl) oxy] -phenol (BASF "TINUVIN 577"), bis Ethylhexyloxyphenol methoxyphenyltriazine (“Tinosorb S” manufactured by BASF) and the like can be mentioned.

Hereinafter, preferable forms of the polyimide film and the hard coat layer will be described in order. Unless otherwise specified, the compounds exemplified in this specification may be used alone or in combination (coexistence) of two or more.

[Polyimide film]
<Polyimide composition>
The polyimide film 1 contains a polyimide resin. Polyimide is generally obtained by dehydration cyclization of a polyamic acid obtained by reacting a tetracarboxylic acid dianhydride (hereinafter, may be simply referred to as "acid dianhydride") with a diamine. That is, the polyimide has an acid dianhydride-derived structure and a diamine-derived structure.

In the production of a transparent polyimide film, a method (solution casting method) in which a solution of a polyimide resin dissolved in an organic solvent is applied onto a substrate and the solvent is dried and removed by heating is preferably adopted. Therefore, in addition to being transparent, polyimide is preferably soluble in organic solvents. From the viewpoint of productivity of the polyimide film, it is preferable to use a low boiling point such as dichloromethane for the solution casting method. Therefore, the polyimide resin is preferably soluble in dichloromethane.

As an example of polyimide soluble in dichloromethane, the acid dianhydride component includes a tetracarboxylic acid dianhydride represented by the general formula (1) and a tetracarboxylic acid dianhydride having a cyclobutane structure, and as a diamine component. Polyimides containing fluoroalkyl substituted benzidine can be mentioned.

In the general formula (1), n is 1 or 2. R ¹ to R ⁴ are independently hydrogen atoms, fluorine atoms, alkyl groups having 1 to 20 carbon atoms or fluoroalkyl groups, and at least one of R ¹ to R ⁴ has 1 to 1 carbon atoms. 20 alkyl or fluoroalkyl groups.

As an example of the composition of the polyimide, the fluoroalkyl-substituted benzidine is contained in an amount of 40 mol% or more and 100 mol% or less with respect to 100 mol% of the total amount of the diamine component, and the formula (1) is used with respect to 100 mol% of the total amount of the acid dianhydride component. Examples thereof include an acid dianhydride having an ester structure represented by 40 mol% or more and 85 mol% or less, and an acid dianhydride having a cyclobutane structure containing 15 mol% or more and 60 mol% or less.

(Acid dianhydride having an ester structure)
The compound represented by the above general formula (1) is an acid dianhydride having an ester structure. Examples of the alkyl group when R ¹ to R ⁴ are an alkyl group or a fluoroalkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group and a t-butyl group. Cyclobutyl group, n-pentyl group, isopentyl group, neopentyl group, cyclopentyl group, n-hexyl group, cyclohexyl group and the like can be mentioned. Examples of the fluoroalkyl group include a monofluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a pentafluoroethyl group and the like.

Since a polyimide showing high solubility in dichloromethane can be obtained, among the compounds represented by the general formula (1), the bis (1,3-dioxo-1,3-dihydroiso) represented by the following formula (2) Benzofuran-5-carboxylic acid) -2,2', 3,3', 5,5'-hexamethylbiphenyl-4,4'diyl (TAHMBP) is preferred.

(Acid dianhydride having a cyclobutane structure)
Specific examples of the acid dianhydride having a cyclobutane structure include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride and 1,3-dimethyl-1,2-2,3,4-cyclobutanetetracarboxylic acid dianhydride. 1,4-dimethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride , 1,3-Dipropyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,4-dipropyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, cyclobutane-1,2 : 3,4-Bis (tetramethylene) -1,2,3,4-tetracarboxylic acid dianhydride and the like can be mentioned. Of these, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA) is preferable.

(Fluoroalkyl substituted benzidine)
Specific examples of the fluoroalkyl substituted benzidine include 2-fluorobenzidine, 3-fluorobenzidine, 2,3-difluorobenzidine, 2,5-difluorobenzidine, 2,6-difluorobenzidine, and 2,3,5-trifluorobenzidine. , 2,3,6-trifluorobenzidine, 2,3,5,6-tetrafluorobenzidine, 2,2'-difluorobenzidine, 3,3'-difluorobenzidine, 2,3'-difluorobenzidine, 2,2 ', 3-trifluorobenzidine, 2,3,3'-trifluorobenzidine, 2,2', 5-trifluorobenzidine, 2,2', 6-trifluorobenzidine, 2,3', 5-trifluoro Benzidine, 2,3', 6,-trifluorobenzidine, 2,2', 3,3'-tetrafluorobenzidine, 2,2', 5,5'-tetrafluorobenzidine, 2,2', 6,6 '-Tetrafluorobenzidine, 2,2', 3,3', 6,6'-hexafluorobenzidine, 2,2', 3,3', 5,5', 6,6'-octafluorobenzidine, 2 -(Trifluoromethyl) benzidine, 3- (trifluoromethyl) benzidine, 2,3-bis (trifluoromethyl) benzidine, 2,5-bis (trifluoromethyl) benzidine, 2,6-bis (trifluoromethyl) ) Benzidine, 2,3,5-tris (trifluoromethyl) benzidine, 2,3,6-tris (trifluoromethyl) benzidine, 2,3,5,6-tetrakis (trifluoromethyl) benzidine, 2,2 '-Bis (trifluoromethyl) benzidine, 3,3'-bis (trifluoromethyl) benzidine, 2,3'-bis (trifluoromethyl) benzidine, 2,2', 3-bis (trifluoromethyl) benzidine , 2,3,3'-tris (trifluoromethyl) benzidine, 2,2', 5-tris (trifluoromethyl) benzidine, 2,2', 6-tris (trifluoromethyl) benzidine, 2,3' , 5-tris (trifluoromethyl) benzidine, 2,3', 6,-tris (trifluoromethyl) benzidine, 2,2', 3,3'-tetrakis (trifluoromethyl) benzidine, 2,2', Examples thereof include 5,5'-tetrakis (trifluoromethyl) benzidine, 2,2', 6,6'-tetrakis (trifluoromethyl) benzidine and the like.

Among them, a fluoroalkyl-substituted benzidine having a fluoroalkyl group at the 2-position of the biphenyl skeleton is preferable, and 2,2'-bis (trifluoromethyl) benzidine is more preferable. By having a fluoroalkyl group at the 2-position of the biphenyl skeleton, the aromatic ring of the biphenyl skeleton is twisted due to steric hindrance of the fluoroalkyl group, and coloring is reduced due to the electron attractiveness of the fluoroalkyl group.

(Other acid dianhydrides and diamines)
The polyimide may contain an acid dianhydride component and a diamine component other than the above, as long as the solubility in a low boiling point solvent such as dichloromethane is not impaired and the transparency and mechanical strength are not impaired.

Examples of acid dianhydride components that can be used in combination are pyromellitic acid dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane. Acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 9,9-bis (3,4-dicarboxyphenyl) fluorene dianhydride, ethylenetetracarboxylic acid dianhydride, Butanetetracarboxylic acid dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexane Tetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid dianhydride, 1,1'-bicyclohexane-3,3', 4,4'-tetracarboxylic acid-3,4: 3', 4'- Dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2', 3,3'-benzophenone tetracarboxylic acid dianhydride, 2,2-bis (3,4-bis) Dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) Carboxyphenyl) sulfonate dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) Phenyl) methane dianhydride, 1,3-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2 , 2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} Propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride Anhydride, 4,4'-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4,4'-bis [3- (1,2-dicarboxy) phenoxy] biphenyl dianhydride , Bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] Fe Nyl} sulfonate dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} sulfonate dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} Sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] Phenyl} -1,1,1,3,3,3-propane dianhydride, 2,3,6,7-naphthalenetetracarboxylic acid dianhydride, 1,4,5,8-naphthalenetetracarboxylic acid dianhydride , 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 1,2,3,4-benzenetetracarboxylic acid dianhydride, 3,4,9,10-perylenetetracarboxylic acid dianhydride, Examples thereof include 2,3,6,7-anthracenetetracarboxylic acid dianhydride and 1,2,7,8-phenanthrentetracarboxylic acid dianhydride.

Examples of diamines that can be used in combination are p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3, 3'-Diaminodiphenylsulfide, 3,4'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenyl Sulfon, 9,9-bis (4-aminophenyl) fluorene, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4 '-Diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-Aminophenyl) Propane, 1,1-di (3-aminophenyl) -1-phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-Aminophenyl) -1-phenylethane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-amino) Phenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1,3-bis (4-aminobenzoyl) benzene, 1,4-bis (3) -Aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (4-amino-α,) α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (4-amino-α, α-dimethylbenzyl) benzene, 2,6-bis (3-Aminophenoxy) Benzenenitrile, 2,6-bis (3-aminophenoxy) pyridine, 4,4'-bis (3-aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) biphenyl, Bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) pheni Le] Sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-Aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-Aminophenoxy) phenyl] propane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,4- Bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-aminophenoxy) -α, α -Dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -α, α-dimethyl Benzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4'-bis [4- (4-aminophenoxy) benzoyl] diphenyl ether, 4,4 '-Bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4'-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] diphenyl sulfone, 4, 4'-bis [4- (4-aminophenoxy) phenoxy] diphenyl sulfone, 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 3,3'-Diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis (3-aminophenoxy) -3,3,3', 3'-tetramethyl -1,1'-spirobiindan, 6,6'-bis (4-aminophenoxy) -3,3,3', 3'-tetramethyl-1,1'-spirobiindan, 1,3-bis (3-amino) Propyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis (3-aminopropyl) polydimethylsiloxane, α, ω-bis (3-aminobutyl) poly Dimethylsiloxane, bis (aminomethyl) A Tel, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis (2-aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- ( 3-Aminoprotoxy) ethyl] ether, 1,2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2-aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether , Ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane , 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, trans-1,4-diamino Cyclohexane, 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2-aminoethyl) cyclohexane, bis (4-aminocyclohexyl) Methan, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 1,4-diamino-2-fluorobenzene , 1,4-Diamino-2,3-difluorobenzene, 1,4-diamino-2,5-difluorobenzene, 1,4-diamino-2,6-difluorobenzene, 1,4-diamino-2,3 5-Trifluorobenzene, 1,4-diamino, 2,3,5,6-tetrafluorobenzene, 1,4-diamino-2- (trifluoromethyl) henzen, 1,4-diamino-2,3-bis (Trifluoromethyl) benzene, 1,4-diamino-2,5-bis (trifluoromethyl) benzene, 1,4-diamino-2,6-bis (trifluoromethyl) benzene, 1,4-diamino-2 , 3,5-Tris (trifluoromethyl) benzene, 1,4-diamino, 2,3,5,6-tetrakis (trifluoromethyl) benzene.

(Specific example of polyimide composition)
As described above, the polyimide of one embodiment contains, as an acid dianhydride component, an acid dianhydride having an ester structure represented by the general formula (1) and an acid dianhydride having a cyclobutane structure, and as a diamine component. Includes fluoroalkyl substituted benzidine.

The amount of the acid dianhydride represented by the general formula (1) is preferably 40 to 85 mol%, more preferably 45 to 80 mol%, and 50 to 70 with respect to 100 mol% of the total amount of the acid dianhydride component. Mol% is more preferred. Within this range, a polyimide showing high solubility in a low boiling point solvent such as dichloromethane and having excellent mechanical strength can be obtained. As described above, among the acid dianhydrides represented by the general formula (1), TAHMBP represented by the formula (2) is particularly preferable.

The amount of acid dianhydride having a cyclobutane structure is preferably 15 to 60 mol%, more preferably 20 to 55 mol%, still more preferably 25 to 50 mol%, based on 100 mol% of the total amount of acid dianhydride components. .. Within this range, a polyimide having solubility in a low boiling point solvent such as dichloromethane, less coloring, and excellent mechanical strength can be obtained. As described above, among the acid dianhydrides having a cyclobutane structure, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA) is particularly preferable.

When an acid dianhydride represented by the general formula (1) and an acid dianhydride other than the acid dianhydride having a cyclobutane structure are used in combination, the amount thereof is based on 100 mol% of the total amount of the acid dianhydride component. 45 mol% or less is preferable, and 30 mol% or less is more preferable. From the viewpoint of obtaining a polyimide having excellent solubility, transparency and mechanical strength, preferred examples of the acid dianhydride used in combination are 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (s-BPDA). , 4,4'-oxydiphthalic acid dianhydride (s-ODPA), 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropanedianhydride (6FDA) and the like.

The amount of the fluoroalkyl-substituted benzidine is preferably 40 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more, based on 100 mol% of the total diamine component. Within this range, a polyimide having excellent transparency and solubility can be obtained without impairing the mechanical strength. As mentioned above, among the fluoroalkyl-substituted benzidines, 2,2'-bis (trifluoromethyl) benzidine (TFMB) is particularly preferable.

When a diamine other than the fluoroalkyl-substituted benzidine is used in combination, the amount thereof is preferably 60 mol% or less, more preferably 40% or less, still more preferably 30 mol% or less, based on 100 mol% of the total amount of the diamine component. From the viewpoint of transparency and solubility of polyimide, fluoroalkyl substituted benzidine such as TFMB and 3,3'-diaminodiphenyl sulfone (3,3'-DDS) or 4,4'-diaminodiphenyl sulfone (3,3') -It is preferable to use DDS) together. The amount of diaminodiphenyl sulfone with respect to 100 mol% of the total amount of the diamine component is preferably 5 to 40 mol%, more preferably 10 to 30 mol%.

As described above, the polyimide preferably contains 40 to 85 mol% of TAHMBP and 15 to 60 mol% of CBDA as an acid dianhydride component, and 40 to 100 mol% of TFMB as a diamine component. Further, from the viewpoint of improving the solubility in a solvent and the transparency of the film, 5 to 40 mol% of diaminodiphenyl sulfone (3,3'-DDS and / and 4,4'-DDS) is contained as a diamine component. Is preferable, and 6FDA, s-BPDA, s-ODPA and the like may be contained as the acid dianhydride.

<Manufacturing of polyimide resin>
The method for producing the polyimide resin is not particularly limited, but a method in which a diamine and an acid dianhydride are reacted in a solvent to prepare a polyamic acid as a polyimide precursor and imidized by dehydration cyclization of the polyamic acid is preferable. For example, a polyimide solution can be obtained by adding an imidization catalyst and a dehydrating agent to the polyamic acid solution to dehydrate and close the polyamic acid. A polyimide resin can be obtained by mixing a polyimide solution and a poor solvent of polyimide to precipitate a polyimide resin and then solid-liquid separation.

(Synthesis of polyamic acid)
A polyamic acid solution is obtained by reacting the acid dianhydride with the diamine in a solvent. It is preferable to use substantially equal molar amounts of acid dianhydride and diamine. That is, the molar ratio of the acid dianhydride component to the diamine is preferably in the range of 95: 105 to 105: 95.

In the polymerization of acid dianhydride and diamine, the organic solvent that can be used is not particularly limited, and the acid dianhydride and diamine, and the polyamic acid that is a polymerization product may be dissolved. Specific examples of the organic solvent include urea-based solvents such as methyl urea, N, N-dimethylethyl urea; and sulfone-based solvents such as dimethyl sulfoxide, diphenyl sulfone, and tetramethyl sulfone; N, N-dimethylacetamide, N, N-. Amid solvents such as dimethylformamide, N, N'-diethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, hexamethylphosphate triamide; alkyl halide solvents such as chloroform and dichloromethane; benzene, toluene and the like. Examples thereof include aromatic hydrocarbon solvents, ether solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. Among these, N, N-dimethylacetamide, N, N-dimethylformamide, or N-methylpyrrolidone is preferable because of its excellent polymerization reactivity and solubility of polyamic acid.

The reaction temperature in the polymerization of acid dianhydride and diamine is not particularly limited, but is preferably 0 ° C. or higher and 80 ° C. or lower, and more preferably 20 ° C. or higher and 45 ° C. or lower. When the temperature is 0 ° C. or higher, the decrease in the reaction rate is suppressed, and when the temperature is 80 ° C. or lower, the decrease in the degree of polymerization due to ring-opening of the acid dianhydride tends to be suppressed.

(Imidization)
Polyimide is obtained by dehydration cyclization of polyamic acid. For imidization in solution, a chemical imidization method in which a dehydrating agent, an imidization catalyst, or the like is added to the polyamic acid solution is suitable. The polyamic acid solution may be heated to accelerate the progress of imidization.

A tertiary amine is used as the imidization catalyst. As the tertiary amine, a heterocyclic tertiary amine is preferable. Specific examples of the heterocyclic tertiary amine include pyridine, picoline, quinoline, isoquinoline and the like. As the dehydrating agent, carboxylic acid anhydride is used, and specific examples thereof include acetic anhydride, propionic acid anhydride, n-butyric acid anhydride, benzoic acid anhydride, and trifluoroacetic anhydride.

The amount of the imidization catalyst added is preferably 0.5 to 5.0 times the molar equivalent, more preferably 0.7 to 2.5 times the molar equivalent, and 0.8 to 2. A 0-fold molar equivalent is more preferred. The amount of the dehydrating agent added is preferably 0.5 to 10.0 times the molar equivalent, more preferably 0.7 to 5.0 times the molar equivalent, and 0.8 to 3.0 times the amide group of the polyamic acid. Double molar equivalents are more preferred.

(Precipitation of polyimide resin)
It is preferable to precipitate the polyimide resin as a solid substance from the polyimide solution obtained by imidizing the polyamic acid. By mixing the polyimide solution and the poor solvent, the polyimide resin is precipitated. The poor solvent is a poor solvent of the polyimide resin, preferably one that is mixed with a solvent in which the polyimide resin is dissolved, and examples thereof include water and alcohols. Examples of alcohols include methyl alcohol, ethyl alcohol, isopropyl alcohol, ethylene glycol, triethylene glycol, 2-butyl alcohol, 2-hexyl alcohol, cyclopentyl alcohol, cyclohexyl alcohol, phenol, t-butyl alcohol and the like. Alcohols such as isopropyl alcohol, 2-butyl alcohol, 2-pentyl alcohol, phenol, cyclopentyl alcohol, cyclohexyl alcohol, and t-butyl alcohol are preferable, and isopropyl alcohol is particularly preferable, because ring opening of the polyimide is unlikely to occur.

<Manufacturing of polyimide film>
A polyimide film can be produced by applying a polyimide solution (a dope for film formation) in which a polyimide resin is dissolved in an organic solvent onto a substrate and drying and removing the solvent. The organic solvent for dissolving the polyimide resin may be any solvent as long as it is soluble and soluble in the above-mentioned polyimide resin, and may be appropriately selected depending on the intended use of the polyimide resin. Dichloromethane, methyl acetate, tetrahydrofuran, acetone, and 1 A low boiling point solvent such as, 3-dioxolane is preferable, and dichloromethane is particularly preferable because the boiling point is low and the solvent can be easily removed by drying. By adjusting the composition ratios of the acid dianhydride component and the diamine component as described above, a polyimide showing high solubility in a low boiling point solvent such as dichloromethane can be obtained.

The solid content concentration of the polyimide solution may be appropriately set according to the molecular weight of the polyimide, the thickness of the film, the film forming environment, and the like. The solid content concentration is preferably 5 to 30% by weight, more preferably 6 to 20% by weight.

(UV absorber)
As mentioned above, the polyimide film contains an ultraviolet absorber. In the production of a polyimide containing an ultraviolet absorber, it is preferable to include the ultraviolet absorber in the polyimide solution. As described above, as the ultraviolet absorber, a benzotriazole-based ultraviolet absorber and a triazine-based ultraviolet absorber are preferable because they absorb less visible light and can obtain good light resistance. In particular, from the viewpoint of suppressing the volatilization of the ultraviolet absorber due to heating when the solvent is dried, the polyimide solution preferably contains a triazine-based ultraviolet absorber. The polyimide solution (and the polyimide film) may contain a triazine-based ultraviolet absorber and a benzotriazole-based ultraviolet absorber.

The acid dianhydride of the general formula (1) used as the acid dianhydride component of polyimide is an ester of phenol and trimellitic anhydride, and is easily deteriorated by light due to ultraviolet rays. It is presumed that this is because rearrangement reactions such as optical Fries rearrangement are likely to occur due to the structure. Since the polyimide film contains an ultraviolet absorber, the ultraviolet rays incident on the polyimide film are absorbed by the ultraviolet absorber, so that the polyimide is not easily affected by the ultraviolet rays and tends to suppress coloring (yellowing) due to light deterioration. be.

From the viewpoint of suppressing photodegradation of the polyimide, the amount of the ultraviolet absorber in the polyimide solution is preferably 0.1 part by weight or more, more preferably 0.3 part by weight or more, and 0 part by weight with respect to 100 parts by weight of the total solid content. It may be .5 parts by weight or more, 0.7 parts by weight or more, or 1 part by weight or more. The larger the amount of the ultraviolet absorber, the more the photodegradation of the polyimide tends to be suppressed. On the other hand, when the amount of the ultraviolet absorber is excessively large, the ultraviolet absorber may not be sufficiently compatible with the polyimide, which may cause the polyimide film to become cloudy or bleed out of the ultraviolet absorber to the surface. Therefore, the amount of the ultraviolet absorber in the polyimide solution is preferably 4.5 parts by weight or less, more preferably 4 parts by weight or less, and 3.5 parts by weight or less or 3 parts by weight or less with respect to 100 parts by weight of the total solid content. May be.

When the polyimide contains the acid dianhydride component represented by the general formula (1), it is easy to sufficiently suppress the photodegradation of the polyimide while suppressing the white turbidity of the film and the bleed-out of the ultraviolet absorber. is not. Therefore, as will be described later, it is preferable that the hard coat layer 2 provided on the surface of the polyimide film 1 contains an ultraviolet absorber to provide ultraviolet shielding properties and reduce the amount of ultraviolet rays reaching the polyimide film 1. ..

(Additive)
The polyimide solution may contain resin components and additives other than the polyimide resin and the ultraviolet absorber. Examples of the additive include a cross-linking agent, a dye, a surfactant, a leveling agent, a plasticizer, fine particles and the like. The content of the polyimide resin with respect to 100 parts by weight of the solid content of the polyimide resin composition is preferably 60 parts by weight or more, more preferably 70 parts by weight or more, still more preferably 80 parts by weight or more.

Specific examples of the above dyes include anthraquinone compounds, phthalocyanine compounds, indigo compounds and the like. Among these, the anthraquinone type is preferable from the viewpoint of heat resistance. The amount used is, for example, about 0.1 to 100 ppm based on the polyimide resin, and may be 1 to 90 ppm, 10 to 80 ppm, or 20 to 70 ppm. By including the dye, the color tone of the polyimide film can be adjusted. The polyimide and the ultraviolet absorber are slightly colored yellow because they absorb light in the short wavelength region of visible light, but the hue can be neutralized by adding a dye that functions as a brewing agent. As the bluing agent, known ones can be appropriately used, and commercially available products such as "Macrolex Blue RR", "Sumiplast Violet B", "Sumiplast Violet OR", "Plast Blue8580", "Plast Blue8590", and "Plast" can be used as appropriate. "Bluelet 8840" and the like.

(Applying and drying)
As a method of applying the polyimide solution to the substrate, a known method can be used, and for example, it can be applied by a bar coater or a comma coater. As the base material to which the polyimide solution is applied, a glass substrate, a metal substrate such as SUS, a metal drum, a metal belt, a plastic film, or the like can be used. From the viewpoint of improving productivity, it is preferable to use a metal drum, an endless support such as a metal belt, a long plastic film, or the like as the support, and to manufacture the film by roll-to-roll. When a plastic film is used as a support, a material that does not dissolve in the solvent of the film-forming dope may be appropriately selected, and as the plastic material, polyethylene terephthalate, polycarbonate, polyacrylate, polyethylene naphthalate or the like is used.

It is preferable to heat the solvent when it dries. The heating temperature is not particularly limited, but is preferably 200 ° C. or lower, more preferably 180 ° C. or lower, from the viewpoint of suppressing the coloring of the polyimide film and the volatilization of the ultraviolet absorber. When the solvent is dried, the heating temperature may be gradually increased. The solvent may be dried under reduced pressure. By using a polyimide resin soluble in dichloromethane and preparing a polyimide solution using dichloromethane as a solvent, the residual solvent can be easily reduced even by heating at 200 ° C. or lower, and coloring and volatilization of the ultraviolet absorber can be suppressed. The residual solvent amount of the polyimide film (mass of the solvent contained in the film with respect to the mass of the film) is preferably 1.5% or less, more preferably 1.0% or less. When the amount of residual solvent is in this range, the mechanical strength of the polyimide film tends to be improved.

The thickness of the polyimide film is not particularly limited and may be appropriately set according to the intended use. The thickness of the polyimide film is, for example, about 5 to 100 μm. From the viewpoint of achieving both mechanical strength and transparency, the thickness of the polyimide film is preferably 30 μm or more, more preferably 35 μm or more, still more preferably 40 μm or more. In particular, when used for applications requiring strength such as a cover window of a display, the thickness of the polyimide film is preferably 40 μm or more. The thickness of the polyimide film is preferably 90 μm or less, more preferably 85 μm or less.

From the viewpoint of preventing the film from being scratched due to contact with the roll during roll-to-roll transfer and contact between the films during winding, the pencil hardness of the polyimide film before forming the hard coat layer is preferably HB or higher. F or more is more preferable.

[Hard coat layer]
The hard coat layer 2 is formed by applying the hard coat composition on the polyimide film 1 and photo-curing it. The hardcourt composition contains a photocurable resin and a photopolymerization initiator. That is, the hard coat layer is a cured resin layer made of a cured product of the hard coat composition which is a photocurable resin composition. By including the UV absorber in the hardcoat composition, a hardcoat layer containing the UV absorber is formed.

<Hardcoat composition>
The photocurable resin of the hardcoat composition is a polyfunctional compound having two or more photopolymerizable functional groups. The polyfunctional compound may be a monomer or an oligomer. The photopolymerizable functional group may be radically polymerizable or cationically polymerizable. Examples of the radically polymerizable functional group include functional groups having an ethylenically unsaturated double bond such as a vinyl group and a (meth) acryloyl group. Examples of the cationically polymerizable functional group include a cyclic ether group such as an epoxy group and an oxetane group.

Among them, an epoxy group and an oxetane group are preferable as the photopolymerizable functional group of the photocurable resin because it can be cured by photocationic polymerization and the curing shrinkage is small. Examples of the photocationically polymerizable functional group containing an epoxy group include a glycidyl group and an alicyclic epoxy group. Of these, an alicyclic epoxy group is preferable because of its high reactivity with photocationic polymerization.

As described above, since the hard coat composition contains an ultraviolet absorber, ultraviolet rays as excitation light may be absorbed by the ultraviolet absorber during photocuring by irradiation with ultraviolet rays, which may cause curing failure (curing inhibition). be. Since photoradicals, which are active species of photoradical polymerization reactions, have a short life, they need to be continuously irradiated with ultraviolet rays during the curing reaction, and are easily affected by curing inhibition by ultraviolet absorbers.

On the other hand, the active species of the photocationic polymerization reaction is an acid generated by light irradiation, and the life of the active species is longer than that of photoradicals, and the curing reaction proceeds for a long time even after light irradiation. Therefore, the photocationic polymerization is less susceptible to the influence of the ultraviolet absorber than the photoradical polymerization, and even when the hard coat composition contains the ultraviolet absorber, curing failure is less likely to occur. Therefore, the hard coat composition is a photocationic polymerizable composition containing a photocurable resin having a photocationically polymerizable functional group such as an epoxy group, a photocationic polymerization initiator (photoacid generator), and an ultraviolet absorber. It is preferable to have.

Examples of the photocationically polymerizable hard coat composition include compositions containing polysiloxane compounds having an epoxy group disclosed in WO2018 / 096729, WO2014 / 204010, JP-A-2017-8142 and the like. Be done.

(Polysiloxane compound as a photocurable resin)
The polysiloxane compound having photocationic polymerizable has an epoxy group as a photocationically polymerizable functional group. The epoxy group is preferably an alicyclic epoxy group, and among them, a 3,4-epoxycyclohexyl group is preferable.

The polysiloxane compound having an alicyclic epoxy group is, for example, (A) condensation of a silane compound having an alicyclic epoxy group; or (B) a carbon-carbon double having a reactivity with a SiH group in one molecule. It is obtained by a hydrosilylation reaction between a compound having a bond and an alicyclic epoxy group (for example, vinylcyclohexene oxide) and a polysiloxane compound having at least two SiH groups in one molecule. Since a polysiloxane compound having a network structure having a large number of alicyclic epoxy groups in one molecule can be obtained, the polysiloxane compound is preferably formed by the method (A) above.

Examples of the silane compound used as a raw material for the condensation reaction of the above (A) include a compound represented by the following general formula (3).
Y-R ^5- (Si (OR ⁶ ) _x R ⁷ _3-x ) ... (3)

In the general formula (3), Y is an alicyclic epoxy group, and R5 is an alkylene group having 1 to ¹⁰ carbon atoms. R ⁶ is a monovalent hydrocarbon group selected from a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 25 carbon atoms, and an alkyl group having 7 to 12 carbon atoms. R ⁷ is a hydrogen atom or an alkyl group having 1 to 10 carbon atoms. x is an integer of 1 to 3. When x is 2 or more, the plurality of R ^6s may be the same or different. When (3-x) is 2 or more, the plurality of R ^7s may be the same or different.

As described above, the alicyclic epoxy group Y is preferably a 3,4-epoxycyclohexyl group. The alkylene group R ⁵ may be linear or has branches, but a linear alkylene group is preferable, a linear alkylene having 1 to 5 carbon atoms is preferable, and ethylene is particularly preferable. That is, the substituent Y-R5 ^- bonded to Si is preferably β- (3,4-epoxycyclohexyl) ethyl.

Specific examples of R ⁶ include hydrogen atom, methyl group, ethyl group, propyl group, butyl group, pentyl group, hexyl group, octyl group, nonyl group, decyl group, phenyl group, tolyl group, xylyl group and naphthyl group. Examples thereof include a benzyl group and a phenethyl group. From the viewpoint of enhancing the reactivity of the alicyclic epoxy group during photocationic polymerization of the polysiloxane compound, R6 is preferably an alkyl group having 1 to ⁴ carbon atoms, and particularly preferably an ethyl group or a propyl group.

Specific examples of R ⁷ include a hydrogen atom, a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, an octyl group, a nonyl group, a decyl group and the like. From the viewpoint of promoting the condensation of the silane compound, ^R7 is preferably an alkyl group having 1 to 3 carbon atoms, and particularly preferably a methyl group.

From the viewpoint of forming a mesh-like polysiloxane compound and increasing the number of alicyclic epoxy groups contained in the polysiloxane compound to increase the hardness of the cured film, x in the general formula (3) is preferably 2 or 3. A silane compound having x of 2 or 3 and a silane compound having x of 1 may be used in combination for the purpose of adjusting the molecular weight of the polysiloxane compound obtained by condensation.

Specific examples of the silane compound represented by the general formula (3) include β- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, β- (3,4-epoxycyclohexyl) ethylmethyldimethoxysilane, and β- ( 3,4-Epoxycyclohexyl) ethyldimethylmethoxysilane, γ- (3,4-epoxycyclohexyl) propyltrimethoxysilane, γ- (3,4-epoxycyclohexyl) propylmethyldimethoxysilane, γ- (3,4-epoxy) Cyclohexyl) propyldimethylmethoxysilane and the like can be mentioned.

By the reaction of the Si—OR ⁶ portion of the above silane compound, a Si—O—Si bond is formed to form a polysiloxane compound. Alicyclic epoxides such as epoxycyclohexyl groups have high electrophilic reactivity and low nucleophilic reactivity. Therefore, from the viewpoint of suppressing the ring-opening of the epoxy group, it is preferable to carry out the reaction under neutral or basic conditions.

Examples of the basic compound used to make the reaction system basic include alkali metals such as sodium hydroxide, lithium hydroxide and magnesium hydroxide, hydroxides of alkaline earth metals, and amines. When a basic compound is present during the formation of the hard coat layer (photocuring reaction), the acid generated from the photocationic polymerization initiator (photoacid generator) is quenched by the basic compound to form an alicyclic epoxy group. It may inhibit the photocationic polymerization reaction. Therefore, the basic compound used for forming the polysiloxane compound is preferably one that can be removed by volatilization. Further, from the viewpoint of suppressing the ring-opening of the epoxy group of the polysiloxane compound, the basic compound preferably has low nucleophilicity. Therefore, as the basic compound, a tertiary amine is preferable, and among them, a tertiary amine having a boiling point of 30 to 160 ° C. such as triethylamine, diethylmethylamine, tripropylamine, methyldiisopropylamine and diisopropylethylamine is preferable.

From the viewpoint of increasing the hardness of the cured film, the weight average molecular weight of the polysiloxane compound obtained by condensing the silane compound is preferably 500 or more. Further, from the viewpoint of suppressing the volatilization of the polysiloxane compound, the weight average molecular weight of the polysiloxane 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 polysiloxane compound is preferably 20000 or less. The weight average molecular weight of the polysiloxane compound is more preferably 1000 to 18000, more preferably 1500 to 16000, still more preferably 2000 to 14000, and particularly preferably 2800 to 12000.

The polysiloxane compound preferably has a plurality of alicyclic epoxy groups in one molecule. The larger the number of alicyclic epoxy groups contained in one molecule of the polysiloxane compound, the higher the crosslink density during photocuring, and the higher the mechanical strength of the cured film tends to be. The number of alicyclic epoxy groups in one molecule of the polysiloxane compound is preferably 3 or more, more preferably 4 or more, still more preferably 5 or more. On the other hand, if the number of alicyclic epoxy groups contained in one molecule becomes excessively large, the proportion of functional groups that do not contribute to cross-linking between molecules during curing may increase. Therefore, the number of alicyclic epoxy groups in one molecule of the polysiloxane compound is preferably 100 or less, more preferably 80 or less, further preferably 70 or less, and particularly preferably 60 or less.

From the viewpoint of increasing the crosslink point density and improving the hardness and scratch resistance of the cured product, the polysiloxane compound obtained by the condensation of the silane compound represented by the general formula (3) has the residual ratio of the alicyclic epoxy group. Is preferable. The ratio of the number of moles of the alicyclic epoxy group of the condensate (polysiloxane compound) to the number of moles of the alicyclic epoxy group contained in the silane compound is preferably 20% or more, more preferably 40% or more, and more preferably 60% or more. Is even more preferable.

From the viewpoint of suppressing side reactions during photocuring and from the viewpoint of the hardness of the cured product, it is preferable that the number of OR ⁶ groups remaining per silane compound unit in the polysiloxane compound is small. The number of OR ⁶ groups per Si atom in the polysiloxane compound is 2 or less. The average number of OR ⁶ units per Si atom is preferably 1.5 or less, and more preferably 1.0 or less. From the viewpoint of bending resistance of the cured product, the number of OR ⁶ units per Si atom in the polysiloxane compound may be 0.01 or more, 0.05 or more, or 0.3 or more on average.

When a polysiloxane compound is obtained by condensation of a silane compound, a silane compound having no alicyclic epoxy group may be used in addition to the silane compound having an alicyclic epoxy group. The silane compound having no alicyclic epoxy group is represented by, for example, the following general formula (4).
R ⁸ -Si (OR ⁶ ) ₃ ... (4)

R ⁸ of the general formula (4) is selected from the group consisting of substituted or unsubstituted alkyl groups having 1 to 10 carbon atoms, alkenyl groups, and substituted aryl groups, and is monovalent without an alicyclic epoxy group. It is a group. When R ⁸ is an alkyl group having a substituent, examples of the substituent include a glycidyl group, a thiol group, an amino group, a (meth) acryloyl group, a phenyl group, a cyclohexyl group, a halogen and the like. R ⁶ in the general formula (4) is the same as R ⁶ in the general formula (3).

As described above, from the viewpoint of increasing the mechanical strength of the cured film, it is preferable that the number of alicyclic epoxy groups contained in one molecule of the polysiloxane compound is large. Therefore, the polysiloxane compound obtained by the reaction of the silane compound is a silane compound having no alicyclic epoxy group (general formula) as opposed to a silane compound having an alicyclic epoxy group (compound represented by the general formula (3)). The compound represented by (4) is preferably condensed under the condition that the molar ratio is 2 or less. The molar ratio of the compound represented by the general formula (4) to the compound represented by the general formula (3) is preferably 1 or less, more preferably 0.6 or less, further preferably 0.4 or less, and 0.2. The following are particularly preferred. The molar ratio of the compound represented by the general formula (4) to the compound represented by the general formula (3) may be 0.

From the viewpoint of forming a hardcoat layer having excellent mechanical strength, the content of the polysiloxane compound in the hardcoat composition is preferably 40 parts by weight or more, preferably 50 parts by weight or more, based on 100 parts by weight of the total solid content. More preferably, 60 parts by weight or more is further preferable.

(Photocationic polymerization initiator)
The photocationically polymerizable hard coat composition preferably contains a photocationic polymerization initiator. The photocationic polymerization initiator is a compound (photoacid generator) that generates an acid by irradiation with active energy rays. The acid generated from the photoacid generator reacts with the alicyclic epoxy group of the polysiloxane compound to form intermolecular crosslinks and cure the hard coat material.

Examples of the photoacid generator include strong acids such as toluene sulfonic acid or boron tetrafluoride; onium salts such as sulfonium salt, ammonium salt, phosphonium salt, iodonium salt and selenium salt; iron-allene complexes; silanol-metal chelate complexes. Sulfonic acid derivatives such as disulfones, disulfonyldiazomethanes, disulfonylmethanes, sulfonylbenzoylmethanes, imidesulfonates, benzoinsulfonates; organic halogen compounds and the like.

Among the above photoacid generators, aromatic sulfonium salts or aromatic iodonium salts are preferable because they have high stability in a hard coat composition containing a polysiloxane compound having an alicyclic epoxy group. Above all, since a hard coat layer having fast photocuring and excellent adhesion to a polyimide film can be easily obtained, the counter anion of the aromatic sulfonium salt or the aromatic iodonium salt is a fluoroborate anion or a fluoroantimonate anion. , Or fluoroborate anions are preferred. In particular, as the counter anion, a fluorophosphate anion or a fluoroantimonate anion is preferable. Specific examples of such a photoacid generator include diphenyl (4-phenylthiophenyl) sulfonium hexafluorophosphate and hexafluoro, in which a part or all of the fluorine atom of hexafluorophosphate is substituted with a perfluoroalkyl group. Phenylfate derivatives, diphenyl (4-phenylthiophenyl) sulfonium / hexafluoroantimonate and the like can be mentioned.

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, based on 100 parts by weight of the above polysiloxane compound.

(UV absorber)
When the hard coat composition contains an ultraviolet absorber, a hard coat layer containing the ultraviolet absorber is formed. As described above, as the ultraviolet absorber, a benzotriazole-based ultraviolet absorber and a triazine-based ultraviolet absorber are preferable because they absorb less visible light and can obtain good light resistance. In particular, the benzotriazole-based ultraviolet absorber has a large absorption coefficient in the UVA region (wavelength 320 to 400 nm) and can effectively suppress deterioration due to the phototransfer reaction of polyimide. Therefore, the hard coat layer (hard coat composition) can be used. It is preferable to contain a benzotriazole-based ultraviolet absorber.

As described above, in the production of the polyimide film, high-temperature heating is required for drying and removing the solvent, so that the polyimide film preferably contains a triazine-based ultraviolet absorber having excellent heat resistance. If the hard coat layer 2 containing a benzotriazole ultraviolet absorber is formed on the polyimide film 1 containing a triazine-based ultraviolet absorber, ultraviolet rays in a wide wavelength range are absorbed, so that the light deterioration of the polyimide is efficient. Can be suppressed.

From the viewpoint of increasing the ultraviolet absorption (shielding property) of the hard coat layer and reducing the amount of ultraviolet rays reaching the polyimide film, the amount of the ultraviolet absorber in the hard coat composition is based on 100 parts by weight of the total solid content. 0.1 part by weight or more is preferable, 0.3 part by weight or more is more preferable, and 0.5 part by weight or more, 0.7 part by weight or more, or 1 part by weight or more may be used. The larger the amount of the UV absorber, the higher the UV shielding property of the hard coat layer tends to be. On the other hand, when the amount of the ultraviolet absorber is excessively large, the amount of ultraviolet rays absorbed by the ultraviolet absorber during the photocuring of the hard coat composition is large, and even if the hard coat composition is photocationically polymerizable, the light is emitted. Curing may be insufficient, and the mechanical strength (surface hardness) of the hard coat film may be insufficient. Therefore, the amount of the ultraviolet absorber in the hard coat composition is preferably 4.5 parts by weight or less, more preferably 4 parts by weight or less, and 3.5 parts by weight or less or 3 parts by weight, based on 100 parts by weight of the total solid content. It may be less than or equal to a part.

(solvent)
The hardcourt composition may be a solvent-free type or may contain a solvent. When a solvent is contained, it is preferable that the polyimide film is not dissolved. On the other hand, by using a solvent having a solubility enough to swell the polyimide film, the adhesion between the polyimide film base material 1 and the hard coat layer 2 may be improved. The amount of the solvent in the hardcoat composition is preferably 500 parts by weight or less, more preferably 300 parts by weight or less, still more preferably 100 parts by weight or less, based on 100 parts by weight of the curable resin (polysiloxane compound).

(Reactive diluent)
The hardcourt composition may contain a reactive diluent. As an example of the reactive diluent, for example, a cationically polymerizable compound other than the above-mentioned polysiloxane compound is used. Examples of the reactive diluent for the polymerization include compounds having a functional group such as an epoxy group, a vinyl ether group, an oxetane group, and an alkoxysilyl group.

(Photosensitizer)
The hard coat composition may contain a photosensitizer for the purpose of improving the photosensitivity of the photocationic polymerization initiator (photoacid generator). As the photosensitizer, those capable of absorbing light in a wavelength range that cannot be absorbed by the photoacid generator itself are more efficient, and therefore, those having less overlap with the absorption wavelength range of the photoacid generator are preferable. Examples of the photosensitizer include anthracene derivatives, benzophenone derivatives, thioxanthone derivatives, anthraquinone derivatives, benzoin derivatives and the like.

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

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

The particles may be surface-modified. The surface modification of the particles tends to improve the dispersibility of the particles. Further, 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 above polysiloxane compound to form a chemical crosslink. Improvement of film strength can be expected.

(Additive)
The hardcoat composition may contain additives such as inorganic pigments, organic pigments, surface modifiers, surface modifiers, plasticizers, dispersants, wetting agents, thickeners and defoaming agents. Further, the hard coat composition may contain a thermoplastic, thermosetting or photocurable resin material other than the above-mentioned polysiloxane compound.

As described above, the hard coat composition contains a photopolymerization initiator and an ultraviolet absorber in addition to the polysiloxane compound as a curable resin, and further, as a solid content (nonvolatile content), a reactive diluent and a photosensitizer. , Particles and other additives may be included. From the viewpoint of forming a hardcoat layer having excellent mechanical strength, the content of the polysiloxane compound in the hardcoat composition is preferably 40 parts by weight or more, preferably 50 parts by weight or more, based on 100 parts by weight of the total solid content. Is more preferable, and 60 parts by weight or more is further preferable.

<Formation of hard coat layer>
A hard coat composition is applied onto the polyimide film, the solvent is dried and removed as necessary, and then the hard coat composition is cured by irradiating it with active energy rays such as ultraviolet rays to cure the hard coat composition on the polyimide film 1. A hard-coated film provided with the layer 2 is obtained.

The integrated irradiation amount of the active energy rays at the time of photocuring is, for example, about 50 to 10000 mJ / cm ² , and may be set according to the type and blending amount of the 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 lower.

The thickness of the hard coat layer is preferably 0.5 μm or more, more preferably 2 μm or more, further preferably 3 μm or more, and most preferably 5 μm or more. The thickness of the hard coat layer is preferably 100 μm or less, more preferably 80 μm or less. If the thickness of the hard coat layer is smaller than 0.5 μm, it may not be possible to sufficiently improve mechanical properties such as surface hardness. On the other hand, if the thickness of the hard coat layer is larger than 100 μm, the transparency and bending resistance may decrease.

[Characteristics of hard-coated film]
The total light transmittance of the hard coat film is preferably 80% or more, more preferably 85% or more, still more preferably 88% or more. The haze of the hard coat film is preferably 1.5% or less, more preferably 0.9% or less, further preferably 0.7% or less, and particularly preferably 0.5% or less.

The yellowness (YI) of the hard coat film is preferably 10 or less, more preferably 6 or less, further preferably 5 or less, and may be 4 or less, 3.5 or less, 3.0 or less, or 2.5 or less. ..

As described above, in the hard coat film of the present invention, both the polyimide film 1 and the hard coat layer 2 contain an ultraviolet absorber. Therefore, when external light is incident from the hard coat layer 2 side, the hard coat layer 2 absorbs (shields) the ultraviolet rays, the amount of the ultraviolet rays reaching the polyimide film 1 is small, and the ultraviolet rays reaching the polyimide film 1 are generated. It is absorbed by the ultraviolet absorber contained in the polyimide film 1. Therefore, the polyimide resin of the polyimide film 1 is not easily affected by ultraviolet rays, and discoloration (increase in yellowness) due to photodegradation is suppressed.

The content of the ultraviolet absorber in the polyimide film is preferably 0.1 to 4.5% by weight, more preferably 0.3 to 4% by weight, further preferably 0.5 to 3.5% by weight, and 0.7. It may be up to 3% by weight or 1.0 to 2.5% by weight. The content of the ultraviolet absorber in the hard coat layer is preferably 0.1 to 4.5% by weight, more preferably 0.3 to 4% by weight, further preferably 0.5 to 3.5% by weight, and 0. It may be 7 to 3% by weight or 1.0 to 2.5% by weight.

The amount of increase in yellowness of the hardcoat film when irradiated with ultraviolet rays for 48 hours under the conditions of an irradiance of 500 W / m ² and a black panel temperature of 63 ° C. from the hardcoat layer forming surface side is preferably 6 or less, preferably 5 or less. Is more preferable, and may be 4.5 or less or 4.0 or less.

The pencil hardness of the hard coat layer forming surface of the hard coat film is preferably HB or higher, more preferably H or higher, further preferably 2H or higher, particularly preferably 3H or higher, and may be 4H or higher. The tensile elastic modulus of the hard-coated film is preferably 3.5 GPa or more, more preferably 4.0 GPa or more, and even more preferably 5.0 GPa or more.

[Application of hard coat film]
As the hard coat film, various functional layers may be provided on the hard coat layer 2 or on the non-formed surface of the hard coat layer of the polyimide film 1. Examples of the functional layer include an antireflection layer, an antiglare layer, an antistatic layer, a transparent electrode and the like. Further, the hard coat film may be provided with a transparent adhesive layer.

Since the hard coat film of the present invention has high transparency and excellent mechanical strength, it can be used for a cover window arranged on the visible side surface of an image display panel, a transparent substrate for a display, a transparent substrate for a touch panel, a substrate for a solar cell, and the like. It is preferably used. Since the hard coat film of the present invention has excellent bending resistance and light resistance in addition to transparency and mechanical strength, it is a cover placed on the visible side surface of a curved display or a bendable display in particular. It can be suitably used as a window.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Manufacturing of transparent polyimide film]
(Preparation of polyimide resin)
In the reaction vessel, as diamine, 2,2'-bis (trifluoromethyl) benzidine (TFMB) 44.2 g (138.1 mmol), and 3,3'-diaminodiphenyl sulfone (3,3-DDS) 3.8 g. (15.3 mmol), as tetracarboxylic acid dianhydride, bis (1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid) -2,2', 3,3', 5,5'-Hexamethylbiphenyl-4,4'diyl (TAHMBP) 47.4 g (76.7 mmol), 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA) 9.0 g (46.0 mmol), and. 9.5 g (30.7 mmol) of 4,4'-oxydiphthalic acid dianhydride (ODA) and 800 g of N, N-dimethylformamide as a solvent are added, and the mixture is stirred under a nitrogen atmosphere for 12 hours to obtain a polyamic acid solution. rice field.

To the above polyamic acid solution, 36.4 g (460 mmol) of pyridine and acetic anhydride (7.0 g (460 mmol)) were added as imidization catalysts, and the mixture was stirred at 90 ° C. for 4 hours. The solution cooled to room temperature was stirred while stirring. 2000 g of 2-propyl alcohol (IPA) was added and suction filtration was performed using a Kiriyama funnel. The obtained solid was washed 6 times with 1000 g of IPA and then dried in a vacuum oven set at 120 ° C. for 8 hours. A white polyimide resin was obtained. The monomer composition of this polyimide resin was TFMB / 3,3'-DDS // TAHMBP / CBDA / ODA = 90/10 // 50/30/20 (molar ratio). there were.

(Preparation of polyimide film)
100 parts by weight of the above-mentioned polyimide resin, and an ultraviolet absorber (UVA) and a bluing agent (“PlastBlue 8590” manufactured by Arimoto Chemical Industry Co., Ltd.) shown in Table 1 are dissolved in dichloromethane, and a polyimide solution having a solid content concentration of 10% by weight is dissolved. Got In Comparative Examples 1, 5 and 6, no ultraviolet absorber was added. In Comparative Examples 4 and 6, no bluing agent was added.

The above polyimide solution is applied to non-alkali glass using a bar coater, and in an air atmosphere, 40 ° C. for 60 minutes, 80 ° C. for 30 minutes, 150 ° C. for 30 minutes, 170 ° C. for 30 minutes, 200 ° C. The solvent was removed by heating for 60 minutes with a transparent polyimide film having a thickness of 50 μm.

[Making a hard coat film]
(Synthesis of silsesquioxane compound)
66.5 g (270 mmol) of 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane (“SILQUEST A-186” manufactured by Momentive Performance Materials) in a reaction vessel equipped with a thermometer, agitator, and a reflux condenser. ) And 16.5 g of 1-methoxy-2-propanol (PGME) were added and stirred uniformly. A solution prepared by dissolving 0.039 g (0.405 mmol) of magnesium chloride in 9.7 g (539 mmol) of water and 5.8 g of methanol was added dropwise to this mixed solution over 5 minutes, and the mixture was stirred until uniform. Then, the temperature was raised to 80 ° C., and the polycondensation reaction was carried out for 6 hours with stirring. After completion of the reaction, decompression and concentration were carried out under reduced pressure using a rotary evaporator, and methanol and water in the condensate were removed to obtain a silsesquioxane compound.

(Preparation of hard coat composition)
A 50% propylene carbonate solution of diphenyl (4-phenylthiophenyl) and SbF ₆ salt as a photoacid generator (photocationic polymerization initiator) in 100 parts by weight of the above silsesquioxane compound (“CPI-101A” manufactured by San-Apro). ) And an ultraviolet absorber (UVA) were added in the blending amounts shown in Table 1 to prepare a hard coat composition. In Comparative Example 4 and Comparative Example 6, only the photoacid generator was added, and the ultraviolet absorber was not added.

(Formation of hard coat layer)
The hardcourt composition was applied to the main surface of a transparent polyimide substrate having a thickness of 50 μm using a bar coater so that the thickness after curing was 50 μm, and heated at 120 ° C. for 10 minutes. Using a high-pressure mercury lamp, ultraviolet rays are irradiated so that the integrated light amount at a wavelength of 365 nm is 1000 mJ / cm ² , and then heated at 80 ° C. for 2 hours to cure the hard coat composition and hard on the polyimide film substrate. A hardcourt film with a coat (HC) layer was obtained. In Example 2, Comparative Example 5 and Comparative Example 6, a hard coat (HC) layer having a thickness of 50 μm was formed on both surfaces of the transparent polyimide film substrate. In Comparative Examples 1 to 4, the hard coat layer was not formed.

[Evaluation of hard-coated film]
The following evaluations were carried out on the hard-coated films of Examples and Comparative Examples (Comparative Examples 1 to 4 are polyimide films on which a hard-coat layer was not formed).

(exterior)
When the hard-coated film was visually observed, white turbidity was observed in Comparative Example 4. The haze of the hard-coated film of Comparative Example 4 was measured by the method described in JIS K7361-1 using a haze meter "HZ-V3" manufactured by Suga Test Instruments Co., Ltd. and found to be 41.0%. The haze of the hard-coated films of Examples 1 to 8 was less than 0.5%.

The hard-coated films of Comparative Example 8 and Comparative Example 9 had wrinkles on the film surface. Therefore, in Comparative Examples 8 and 9, the subsequent evaluation was not carried out.

(Yellowness)
The film was cut into a size of 3 cm square, and the yellowness (YI) was measured using a spectrocolorimeter (“SC-P” manufactured by Suga Test Instruments Co., Ltd.). Then, using a fade meter (“U48-HB” manufactured by Suga Testing Machine), one side of the film (Examples 1 and 3 to 8 and Comparative Examples 7 to 9) under the conditions of an irradiance of 500 W / m ² and a black panel temperature of 63 ° C. , The hard coat layer forming surface) was irradiated with ultraviolet rays for 48 hours. The yellowness of the film after irradiation with ultraviolet rays was measured, and the amount of change in yellowness before and after irradiation ΔYI was calculated from the yellowness YI ₀ before irradiation and the yellowness YI ₁ after irradiation according to the following formula. "
ΔYI = YI ₁ -YI ₀

(Pencil hardness)
The pencil hardness of the film was measured by the JIS K-5600-5-4 pencil scratch test. In Examples 1 and 3 to 8 and Comparative Examples 7 to 9, the pencil hardness of the hard coat layer forming surface was evaluated.

Types and contents of polyimide film additives in Examples and Comparative Examples, hard coat layer forming surface, amount of photoacid generator added in hard coat composition, type and content of UV absorber in hard coat composition , And the evaluation results of the film are shown in Table 1.

In Table 1, ultraviolet absorbers (UVA) are described by the following abbreviations.
LA-31RG: "ADEKA STAB LA-31RG" manufactured by ADEKA: 2,2'-methylenebis [6- (2H-benzotriazole-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol]
LA-F70: ADEKA "ADEKA STUB LA-F70": 2,4,6-tris (2-hydroxy-4-hexyloxy-3-methylphenyl) -1,3,5-triazine Tin 326: BASF "Tinvin 326" 2- [5-Chloro (2H) -benzotriazole-2-yl] -4-methyl-6- (tert-butyl) phenol LA-29: "ADEKA STAB LA-29" manufactured by ADEKA; 2- (2H-) Benzotriazole-2-yl) -4- (1,1,3,3-tetramethylbutyl) phenol LA-32: "ADEKA STAB LA-32" manufactured by ADEKA; 2- (2H-benzotriazole-2-yl)- p-cresol LA-24: "ADEKA STAB LA-24" manufactured by ADEKA; 2- (2H-benzotriazole-2-yl) -4,6-bis (1-methyl-1-phenylethyl) phenol

As shown in Table 1, the hard coat film containing an ultraviolet absorber in both the polyimide film and the hard coat layer shows high pencil hardness due to the formation of the hard coat layer, and ΔYI after light irradiation by a fade test. It can be seen that the size is small and the light resistance is excellent.

From the comparison of Examples 3 and 4, the comparison of Examples 5 and 6, and the comparison of Examples 7 and 8, the larger the amount of the ultraviolet absorber contained in the hard coat layer, the smaller the ΔYI tends to be. I understand. On the other hand, in Comparative Examples 8 and 9 in which 5 parts by weight of the ultraviolet absorber was blended with 100 parts by weight of the resin content of the hard coat composition, wrinkles were observed on the surface of the hard coat layer after curing. It is considered that this is due to insufficient curing due to the large amount of the ultraviolet absorber.

In Comparative Examples 1 to 4 in which the hard coat layer was not provided, the pencil hardness of the film was lower than that of the examples, and the hardness was insufficient. In addition, ΔYI was large and the light resistance was insufficient regardless of the presence or absence of the ultraviolet absorber of the polyimide film. In Comparative Example 4 in which 5 parts by weight of the ultraviolet absorber was blended with 100 parts by weight of the polyimide resin, remarkable cloudiness was observed due to insufficient compatibility.

In Comparative Example 5 in which neither the polyimide film nor the hard coat layer contained an ultraviolet absorber, ΔYI was large and the light resistance was insufficient. In Comparative Example 6 in which the ultraviolet absorber was blended only in the hard coat layer and Comparative Example 7 in which the UV absorber was blended only in the polyimide film, ΔYI was smaller than that of Comparative Example 5, but the light resistance was insufficient. ..

From the above results, it can be seen that a hard coat film having excellent transparency, light resistance and surface hardness can be obtained by including an ultraviolet absorber in both the polyimide film and the hard coat layer.

1 Polyimide film 2 Hardcourt layer 10 Hardcourt film

Claims (12)

1. A hard coat film comprising a base film and a hard coat layer provided on at least one surface of the base film.
   The base film is a polyimide film containing a polyimide resin.
   The hard coat layer is made of a cured product of a photocurable resin composition.
   A hard coat film in which each of the hard coat layer and the polyimide film contains an ultraviolet absorber.
2. The polyimide resin
   As a diamine component, 40 mol% or more and 100 mol% or less of fluoroalkyl-substituted benzidine is contained with respect to 100 mol% of the total amount of diamine.
   As the tetracarboxylic acid dianhydride component, 40 mol% or more and 85 mol% or less of the acid dianhydride having the ester structure represented by the formula (1) is contained with respect to 100 mol% of the total amount of the tetracarboxylic acid dianhydride component. , Contains 15 mol% or more and 60 mol% or less of acid dianhydride having a cyclobutane structure.
   The hard-coated film according to claim 1:
   

   

   In the formula (1), n is 1 or 2, and ^R1 to ^R4 are independently hydrogen atoms, alkyl groups having 1 to 20 carbon atoms, or fluoroalkyl groups, and among ^R1 to ^R4 . At least one of the above is an alkyl group or a fluoroalkyl group having 1 to 20 carbon atoms.
3. The hardcoat film according to claim 1 or 2, wherein the hardcoat layer contains a cured product of a polysiloxane compound having an epoxy group.
4. The hard coat film according to any one of claims 1 to 3, wherein the ultraviolet absorber is a benzotriazole compound or a triazine compound.
5. The hard coat film according to any one of claims 1 to 4, wherein the content of the ultraviolet absorber in the polyimide film is 0.1 to 4.5% by weight.
6. The hard coat film according to any one of claims 1 to 5, wherein the content of the ultraviolet absorber in the hard coat layer is 0.1 to 4.5% by weight.
7. 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.
8. The hard-coated film according to any one of claims 1 to 7, wherein the polyimide film has a thickness of 5 to 100 μm.
9. The method for producing a hardcourt film according to any one of claims 1 to 8.
   A dichloromethane solution containing a polyimide resin and an ultraviolet absorber was applied onto a substrate, and the solvent was removed to prepare a polyimide film containing an ultraviolet absorber.
   A method for producing a hard coat film, wherein a photocurable resin composition containing a photocurable resin and a photopolymerization initiator is applied to the surface of the polyimide film and photocured to form a hard coat layer.
10. The method for producing a hard coat film according to claim 9, wherein the photocurable resin is a polysiloxane compound having an epoxy group, and the photopolymerization initiator is a photocationic polymerization initiator.
11. An image display device provided with the hard coat film according to any one of claims 1 to 8 on the visible side surface of the image display panel.
12. The image display device according to claim 11, which is foldable.
    
    

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