Optical film

Abstract

To provide an optical film which has excellent mechanical characteristics in addition to excellent weather resistance.SOLUTION: An optical film is provided which includes 0.5-3 parts of an ultraviolet absorber with respect to 100 pts.wt. of a polyimide resin, wherein the polyimide resin is soluble in methylene chloride, an SP value of the polyimide resin is 88.6-9.9, an SP value of the ultraviolet absorber is 7.3-9.7, and a difference between the SP value of the polyimide resin and the SP value of the ultraviolet absorber is less than 2.0. (wherein the SP value of the polyimide resin is a value obtained by multiplying an SP value determined by an evaporation enthalpy of each monomer with a composition ratio, and adding them, and the SP value of the ultraviolet absorber is a value determined by evaporation enthalpy.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to an optical film.

Background Art

[0002] In recent years, with the rapid progress of electronic devices, there has been a demand for thinner, lighter, and more flexible devices. In particular, for applications that require high heat resistance, dimensional stability at high temperatures, and high mechanical strength, the application of polyimide films as alternative materials to glass used in substrates, cover windows, etc. has been studied. In particular, as an alternative material for cover glass for foldable displays, a transparent polyimide film having excellent transparency, that is, low haze and yellowness, and high mechanical strength, that is, high elastic modulus and yield stress, is required. (Patent Document 1)

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, a highly transparent polyimide film obtained from a polyimide resin as in Patent Document 1 has problems such as weak interaction between polymer chains, resulting in low mechanical strength such as elastic modulus and yield stress, and poor weather resistance, and yellowing when irradiated with ultraviolet rays.

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide an optical film having excellent weather resistance and excellent mechanical properties.

Means for Solving the Problems

[0006] As a result of intensive studies, the inventors have found that the above problems can be solved by the optical film shown below. The present invention has the following configuration.

[0007] 1). An optical film containing 0.5 to 3 parts of an ultraviolet absorber with respect to 100 parts by weight of a polyimide resin, wherein the polyimide resin is soluble in methylene chloride, the SP value of the polyimide resin is 8.6 to 9.9, the SP value of the ultraviolet absorber is 7.3 to 9.7, and the difference between the SP value of the polyimide resin and the SP value of the ultraviolet absorber is less than 2.0. (However, the SP value of the polyimide resin is a value obtained by multiplying the SP value determined by the evaporation enthalpy of each monomer by the composition ratio and adding them, and the SP value of the ultraviolet absorber is a value determined by the evaporation enthalpy.)

[0008] 2). The polyimide resin is a polyimide resin having a diamine-derived structure and an acid dianhydride-derived structure, and at least one or more of the acid dianhydrides and at least one or more of the diamines constituting the polyimide resin are selected from the following group. The optical film according to 1), wherein the group of acid dianhydrides is 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)propane dianhydride (BPADA), 3,3’,4,4’-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3’,4’-biphenyltetracarboxylic dianhydride (a-BPDA), 4,4’-oxydiphthalic dianhydride (ODPA), 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA), dicyclohexyl-3,4,3’,4’-tetracarboxylic dianhydride (H-BPDA), the acid dianhydride represented by formula (1), and the group of diamines is 2,2’-bis(trifluoromethyl)benzidine, 2,2’-dimethylbenzidine, isophoronediamine, 3,3’-diaminodiphenylsulfone, 4,4’-diaminodiphenylsulfone, 9,9-bis(4-aminophenyl)fluorene, 3,3’-diaminodiphenyl ether, 3,4’-diaminodiphenyl ether, 4,4’-diaminodiphenyl ether, 2,2-bis(4-(4-aminophenoxy)phenyl)propane. n in formula (1) is 1 or 2, and R 1 ~R 4 are each a hydrogen atom, an alkyl group having 1 to 20 carbon atoms or a fluoroalkyl group, and at least one of them is an alkyl group having 1 to 20 carbon atoms or a fluoroalkyl group.)

Chemical formula

[0009] 3) The polyimide resin contains 40 mol% or more and 100 mol% or less of fluoroalkyl-substituted benzidine as the diamine, based on 100 mol% of the total amount of diamine. As the acid dianhydride, it has a structure containing 10 mol% or more and 65 mol% or less of an acid dianhydride having an ester structure represented by the formula (1), based on 100 mol% of the total amount of acid dianhydride. The optical film according to 1) or 2) is characterized by this. (However, n in the formula (1) is 1 or 2, and R 1 ~R 4 are each a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a fluoroalkyl group, and at least one of them is an alkyl group having 1 to 20 carbon atoms or a fluoroalkyl group.) [Chemical formula]

[0010] 4) When the relationship between the elastic modulus of the optical film (Film 1) containing 0.5 to 3 parts of an ultraviolet absorber per 100 parts by weight of the polyimide resin and the elastic modulus of the film (Film 2) when the ultraviolet absorber is 0 part per 100 parts by weight of the polyimide resin is expressed as ([Elastic modulus of Film (Film 1)] / [Elastic modulus of Film (Film 2)]), it is 1.02 to 1.10. The optical film according to any one of 1) to 3) is characterized by this. [Advantages of the Invention]

[0011] According to the present invention, in addition to excellent weather resistance, a transparent polyimide film having a high elastic modulus and a method for producing the same can be provided. Furthermore, since the transparent polyimide film of the present invention has excellent transparency and high mechanical strength, it is useful as an optical film and can also be used as a cover window material for a foldable display. [Embodiments for Carrying Out the Invention]

[0012] [(Transparent) Polyimide Resin] Polyimide is generally obtained by dehydrating and cyclizing a polyamic acid obtained by the reaction of a diamine and a tetracarboxylic dianhydride (hereinafter sometimes simply referred to as "dianhydride"). That is, polyimide has a structure derived from a diamine and a structure derived from a dianhydride. The polyimide resin of the present invention is soluble in methylene chloride, and is characterized in that the SP value of the polyimide resin is 8.6 to 9.9.

[0013] The polyimide resin of the present invention is a polyimide resin having a structure derived from a diamine and a structure derived from a dianhydride, and at least one or more of the dianhydrides constituting the polyimide resin and at least one or more of the diamines are selected from the following groups. (However, the group of dianhydrides is 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 2,2-bis(4-(3,4-dicarboxyphenoxy)phenyl)propane dianhydride (BPADA), 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 4,4'-oxydiphthalic dianhydride (ODPA), 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride (6FDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA), dicyclohexyl-3,4,3‘,4’-tetracarboxylic dianhydride (H-BPDA), the dianhydride represented by formula (1), and the group of diamines is 2,2'-bis(trifluoromethyl)benzidine, 2,2'-dimethylbenzidine, isophoronediamine, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 9,9-bis(4-aminophenyl)fluorene, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2-bis(4-(4-aminophenoxy)phenyl)propane. However, n in formula (1) is 1 or 2, and R 1 ~R 4Each is a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a fluoroalkyl group, and at least one of them is an alkyl group having 1 to 20 carbon atoms or a fluoroalkyl group.)

Chemical formula

[0014] (Fluoroalkyl-substituted benzidine) As the diamine, based on 100 mol% of the total amount of the diamine, it contains 40 mol% or more and 100 mol% or less of fluoroalkyl-substituted benzidine. Among them, 50 mol% or more is preferable, and 60 mol% or more is more preferable. By setting it to 40 mol% or more, a decrease in mechanical strength such as elastic modulus and yield stress can be suppressed.)

[0015] Examples of fluoroalkyl-substituted benzidine include 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-tris(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',5,5'-tetrakis(trifluoromethyl)benzidine, 2,2',6,6'-tetrakis(trifluoromethyl)benzidine, etc.)

[0016] Among them, fluoroalkyl-substituted benzidine having a fluoroalkyl group at the 2-position of biphenyl is preferable, and 2,2'-bis(trifluoromethyl)benzidine (hereinafter referred to as "TFMB") is particularly preferable. By having fluoroalkyl groups at the 2- and 2'-positions of biphenyl, in addition to the decrease in π-electron density due to the electron-withdrawing property of the fluoroalkyl group, the steric hindrance of the fluoroalkyl group causes the bond between the two benzene rings of biphenyl to twist and the planarity of π-conjugation to decrease. Therefore, the absorption edge wavelength undergoes a short-wavelength shift, and the coloring of the polyimide can be reduced.

[0017] (Other diamines) Outside the above, diamines other than the above may be used in combination as long as the solubility in low-boiling solvents such as dichloromethane is not impaired and the properties such as transparency and mechanical strength are not impaired. Examples of diamines other than the above include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 2-(3-aminophenyl)-2-(4-aminophenyl)propane, 1,1-bis(3-aminophenyl)-1-phenylethane, 1,1-bis(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-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminobenzoyl)benzene, 1,3-bis(4-aminobenzoyl)benzene, 1,4-bis(3-aminobenzoyl)benzene, 1,4-bis(4-aminobenzoyl)benzene, 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene, 2,6-bis(3-aminophenoxy)benzonitrile, 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)phenyl]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, 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-dimethylbenzyl]benzene, 1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 4,4'-bis[4-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, 4,4'-bis[4-(4-aminophenoxy)phenoxy]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'-spirobiindane, 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 1,3-bis(4-aminobutyl)tetramethyldisiloxane, α,ω-bis(3-aminopropyl)polydimethylsiloxane, α,ω-bis(3-aminobutyl)polydimethylsiloxane, bis(aminomethyl)ether, bis(2-aminoethyl)ether, bis(3-aminopropyl)ether, bis(2-aminomethoxy)ethyl]ether, bis[2-(2-aminoethoxy)ethyl]ether, bis[2-(3-aminopropoxy)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-diaminocyclohexane, 1,2-di(2-aminoethyl)cyclohexane, 1,3-di(2-aminoethyl)cyclohexane, 1,4-di(2-aminoethyl)cyclohexane, bis(4-aminocyclohexyl)methane, 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)benzene, 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,Examples include 5-tris(trifluoromethyl)benzene, 1,4-diamino, 2,3,5,6-tetrakis(trifluoromethyl)benzene. Among them, 3,3'-diaminodiphenyl sulfone is preferably used from the viewpoint of solubility in solvents. For example, by using 3,3'-diaminodiphenyl sulfone (hereinafter referred to as "3,3'-DDS") in addition to fluoroalkyl-substituted benzidine as the diamine, the solubility and transparency of the polyimide resin in the solvent may be improved. The content of 3,3'-DDS relative to 100 mol% of the total amount of diamine is preferably 5 mol% or more, more preferably 10 mol% or more. The content of 3,3'-DDS may be 15 mol% or more, 20 mol% or more, or 25 mol% or more. From the viewpoint of the mechanical strength of the polyimide resin, the content of 3,3'-DDS relative to 100 mol% of the total amount of diamine is preferably 50 mol% or less, more preferably 40 mol% or less, and even more preferably 35 mol% or less.,

[0018] (Ester group-containing acid dianhydride) As the acid dianhydride, based on 100 mol% of the total amount of acid dianhydrides, it contains 10 mol% or more and 65 mol% or less of an acid dianhydride having an ester structure represented by the formula (1). Among them, 15 mol% or more and 60 mol% or less are preferable, and 20 mol% or more and 50% or less are more preferable. When it is 10 mol% or more, it is preferable because the mechanical strength such as elastic modulus and yield stress becomes high. Also, when it is 65 mol% or less, it is possible to suppress the increase in yellowness and suppress problems such as significant thickening, solidification, and gelation during the polymerization reaction. (However, n in the formula (1) is 1 or 2, and R 1 ~R 4 are each a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a fluoroalkyl group, and at least one of them is an alkyl group having 1 to 20 carbon atoms or a fluoroalkyl group.)

Chemical formula

[0019] The acid dianhydride represented by the general formula (1) is an ester of trimellitic anhydride and an aromatic diol (bis trimellitic anhydride ester). When the aromatic diol is a hydroquinone, a bis trimellitic anhydride ester with n = 1 in the general formula (1) can be obtained. When the aromatic diol is a biphenol, a bis trimellitic anhydride ester with n = 2 in the general formula (1) can be obtained.

[0020] Substituent R in the general formula (1) 1 ~R 4 is each independently a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, or a perfluoroalkyl group having 1 to 20 carbon atoms. When n is 2 or more, the substituents R 1 ~R 4 bonded to each benzene ring may be the same or different. Specific examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a t-butyl group, a cyclobutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a cyclopentyl group, an n-hexyl group, a cyclohexyl group, etc. Specific examples of the perfluoroalkyl group include a trifluoromethyl group, etc.

[0021] In the general formula (1), n is preferably 1 or 2, and R 1 ~R 4 is each independently preferably a hydrogen atom, a methyl group or a trifluoromethyl group. Preferred examples of the acid dianhydride with n = 1 in the general formula (1) include p-phenylenebis(trimellitic acid monoester anhydride) (hereinafter referred to as "TMHQ") represented by the following formula (2).

Chemical formula

[0022] In the general formula (1), preferred examples of the acid dianhydride where n = 2 include bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid) 2,2’,3,3’,5,5’-hexamethylbiphenyl-4,4’-diyl (hereinafter referred to as "TAHMBP") represented by the following formula (3). [Chemical formula]

[0023] As the acid dianhydride, polyimides containing these bisanhydride trimellitic acid esters show high solubility in low-boiling alkyl halides such as dichloromethane, and the polyimide film tends to show high transparency and mechanical strength. TAHMBP represented by the formula (3) has a highly rigid biphenyl skeleton, and due to the steric hindrance of the methyl group, the bond between the two benzene rings of biphenyl is twisted and the planarity of the π-conjugation is reduced, so that the absorption edge wavelength is shifted to a shorter wavelength, and the coloring of the polyimide can be reduced.

[0024] (Other acid dianhydrides) It is also possible to use in combination an acid dianhydride component and a diamine component other than the above acid dianhydride component and diamine component, as long as the solubility in the solvent is not impaired and the properties such as haze, yellowness, and mechanical strength are not impaired.

[0025] Examples of the acid dianhydride components that can be used in combination include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 3,3’,4,4’-benzophenone tetracarboxylic dianhydride, 2,2’,3,3’-benzophenone tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 1,3-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 1,4-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 2,2-bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, 4,4’-bis[4-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, 4,4’-bis[3-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, 2,2-bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}-1,1,1,3,3,3-propane dianhydride, 2,3,6,7-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,Examples include 1,10 - perylene tetracarboxylic dianhydride, 2,3,6,7 - anthracene tetracarboxylic dianhydride, 1,2,7,8 - phenanthrene tetracarboxylic dianhydride, etc., and these can be used alone or in combination of two or more.

[0026] Among these, examples of acid dianhydride monomers that can be particularly preferably used include 1,2,3,4 - cyclobutane tetracarboxylic dianhydride (hereinafter referred to as "CBDA") and 3,3',4,4' - biphenyltetracarboxylic dianhydride (hereinafter referred to as "BPDA"). A polyimide having both a high elastic modulus and transparency can be obtained while maintaining solubility in a solvent. The acid dianhydride component used in combination is preferably 50 mol% or less, more preferably 30 mol% or less, based on 100 mol% of the total amount of the acid dianhydride component.

[0027] (Composition of polyimide resin) The polyimide resin in the present invention includes a polyimide resin containing an ester group - containing acid dianhydride represented by the formula (1) as an acid dianhydride component and fluoroalkyl - substituted benzidine [also referred to as TFMB] as a diamine component. Among them, as the ester group - containing acid dianhydride, it is preferable to use bis(1,3 - dihydro - 1,3 - dioxo - 5 - isobenzofurancarboxylic acid) - 1,4 - phenylene ester [also referred to as TMHQ] represented by the formula (2) or bis(1,3 - dihydro - 1,3 - dioxo - 5 - isobenzofurancarboxylic acid) - (2,2',3,3',5,5' - hexamethyl[1,1' - biphenyl] - 4,4' - diyl) ester [also referred to as TAHMBP] represented by the formula (3). Further, 3,3',4,4' - biphenyltetracarboxylic dianhydride [also referred to as BPDA] or 1,2,3,4 - cyclobutane tetracarboxylic dianhydride [also referred to as CBDA] can be used as the acid dianhydride component. Furthermore, it is more preferable to use 3,3' - diaminodiphenyl sulfone [also referred to as 3,3' - DDS] as the diamine.

[0028] As the polyimide resin in the present invention, it preferably contains 20 mol% or more and 65 mol% or less of an ester group-containing acid dianhydride represented by the formula (1) as the acid dianhydride component, and 40 mol% or more and 100 mol% or less of TFMB as the diamine component. Among them, as the ester group-containing acid dianhydride, it is preferable to use 20 mol% or more and 65 mol% or less of TAHMBP or TMHQ. Further, as the acid dianhydride component, 10 mol% or more and 40 mol% or less of BPDA or CBDA may be used. When using TAHMBP or TMHQ as the ester group-containing acid dianhydride, it is preferable to use 10 mol% or more and 40 mol% or less of BPDA or CBDA. Furthermore, from the viewpoint of improving the solubility in the solvent and the transparency of the film as the diamine component, it is preferable to contain 60 mol% or less of 3,3'-DDS.

[0029] That is, as the polyimide resin, it is preferable to use the following (a) or (b).

[0030] (a) The polyimide resin preferably contains 20 mol% or more and 65 mol% or less of TMHQ and 50 mol% or less of BPDA as the acid dianhydride component, and 40 mol% or more and 100 mol% or less of TFMB and 50 mol% or less of 3,3'-DDS as the diamine component. It is more preferable to contain 20 mol% or more and 50 mol% or less of TMHQ, 10 mol% or more and 40 mol% or less of BPDA, and 60 mol% or more and 80 mol% or less of TFMB and 20 mol% or more and 40 mol% or less of 3,3'-DDS as the diamine component. It is still more preferable to contain 20 mol% or more and 50 mol% or less of TMHQ, 10 mol% or more and 40 mol% or less of BPDA, and 10 mol% or more and 70 mol% or less of 6FDA, and 60 mol% or more and 80 mol% or less of TFMB and 20 mol% or more and 40 mol% or less of 3,3'-DDS as the diamine component. The SP value of the polyimide resin with a more preferable composition is 8.6 to 9.4.

[0031] In addition, (b) the polyimide resin preferably contains 20 mol% or more and 65 mol% or less of TAHMBP as the acid dianhydride component and 50 mol% or less of CBDA, and 40 mol% or more and 100 mol% or less of TFMB and 50 mol% or less of 3,3'-DDS as the diamine component. More preferably, it contains 30 mol% or more and 60 mol% or less of TAHMBP and 40 mol% or less of CBDA, and 60 mol% or more and 95 mol% or less of TFMB and 5 mol% or more and 40 mol% or less of 3,3'-DDS as the diamine component. Even more preferably, it contains 30 mol% or more and 60 mol% or less of TAHMBP, 5 mol% or more and 40 mol% or less of CBDA, and 5 mol or more and 40 mol or less of ODPA, and 60 mol% or more and 95 mol% or less of TFMB and 5 mol% or more and 40 mol% or less of 3,3'-DDS as the diamine component. The SP value of the polyimide resin with a more preferable composition is 8.6 to 9.9.

[0032] As the (b) polyimide resin, in order to achieve the same effect, a-BPDA, s-BPDA, etc. may be used instead of ODPA.

[0033] By using the above material combinations and setting each acid dianhydride component and diamine component within the above ranges, it is possible to easily reduce the amount of residual solvent because it dissolves in a low-boiling solvent, and a polyimide resin excellent in transmittance, yellowness, and mechanical strength can be obtained.

[0034] [Polyimide Film] An example of a method for producing a polyimide resin constituting a polyimide film useful for the optical film of the present invention will be described below. First, in an organic solvent, a diamine component and an acid dianhydride component are polymerized to obtain a polyamic acid solution which is a polyimide precursor. Next, an imidization catalyst and a dehydrating agent are added and dehydration ring closure is carried out to obtain a polyimide resin solution. By adding a poor solvent for the polyimide resin to the polyimide resin solution, the polyimide resin is precipitated, and the polyimide resin is obtained by solid-liquid separation. It is preferable to use the acid dianhydride component and the diamine component in equimolar amounts (95:105 to 105:95). When either component is in excess, a high molecular weight product cannot be obtained and the mechanical strength of the polyimide film decreases.

[0035] In the polymerization of the acid dianhydride component and the diamine component, the organic solvent that can be used is not particularly limited as long as the acid dianhydride component, the diamine component, and the polyamic acid which is the polymerization product are dissolved.

[0036] Specific examples of the organic solvent include urea solvents such as methyl urea and N,N-dimethylethyl urea; sulfone solvents such as dimethyl sulfoxide, diphenyl sulfone, and tetramethyl sulfone; amide solvents such as N,N-dimethylacetamide, N,N-dimethylformamide, N,N'-diethylacetamide, N-methyl-2-pyrrolidone, γ-butyrolactone, and hexamethylphosphoric triamide; alkyl halide solvents such as chloroform and methylene chloride; aromatic hydrocarbon solvents such as benzene and toluene; and ether solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. These solvents may be used alone or, if necessary, two or more of them may be appropriately combined and used. Among these, dimethylacetamide, dimethylformamide, or N-methylpyrrolidone is preferably used because of its excellent polymerization reactivity and solubility of the polyamic acid.

[0037] In the polymerization of the acid dihydrate component and the diamine component, the reaction temperature 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. By setting the temperature to 0°C or higher, a decrease in the reaction rate can be suppressed, and the polymerization reaction can be carried out in a relatively short time. Also, by setting the temperature to 80°C or lower, a decrease in the degree of polymerization due to ring opening of the acid dianhydride component can be suppressed.

[0038] As the imidization catalyst in the imidization reaction, a tertiary amine compound is used. As the tertiary amine, a heterocyclic tertiary amine is preferred. Specific preferred examples of the heterocyclic tertiary amine include pyridine, picoline, quinoline, isoquinoline, and the like. As the dehydrating agent, a carboxylic acid anhydride is used, and specific preferred examples include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, trifluoroacetic anhydride, and the like. The addition amount of the imidizing agent and the dehydration catalyst is such that, based on the amide group of the polyamic acid, the imidization catalyst is 0.5 to 5.0 molar equivalents, more preferably 0.7 to 2.5 molar equivalents, and particularly preferably 0.8 to 2.0 molar equivalents. Also, the dehydrating agent is 0.5 to 10.0 molar equivalents, more preferably 0.7 to 5.0 molar equivalents, and particularly preferably 0.8 to 3.0 molar equivalents.

[0039] As the poor solvent for precipitating the polyimide resin from the polyimide resin solution, a poor solvent for the polyimide resin that is miscible with the solvent in which the polyimide resin is dissolved is preferred, and examples include water and alcohols. Examples of the 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. Since ring opening of the polyimide is less likely to occur, alcohols such as isopropyl alcohol, 2-butyl alcohol, 2-pentyl alcohol, phenol, cyclopentyl alcohol, cyclohexyl alcohol, and t-butyl alcohol are preferred, and isopropyl alcohol is particularly preferred.

[0040] The optical film containing the polyimide resin of the present invention is an optical film containing 0.5 to 3 parts of an ultraviolet absorber with respect to 100 parts by weight of the polyimide resin, wherein the polyimide resin is soluble in methylene chloride, the SP value of the polyimide resin is 8.6 to 9.9, the SP value of the ultraviolet absorber is 7.3 to 9.7, and the difference between the SP value of the polyimide resin and the SP value of the ultraviolet absorber is less than 2.0.

[0041] The following steps will be described. (Coating step) The organic solvent for dissolving the polyimide resin is not particularly limited as long as it can dissolve the above polyimide resin. For example, the urea-based solvent, sulfone-based solvent, amide-based solvent, alkyl halide-based solvent, aromatic hydrocarbon-based solvent, ether-based solvent, etc. exemplified above as the organic solvent used for the polymerization of polyamic acid can be mentioned. In addition to these, ketone-based solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diethyl ketone, cyclopentanone, cyclohexanone, and methyl cyclohexanone are also preferably used as the solvent for the polyimide resin composition. These may be used alone or in combination.

[0042] Among these, an alkyl halide-based solvent, an amide-based solvent, an aromatic hydrocarbon-based solvent, or a ketone-based solvent is preferred.

[0043] Among them, low-boiling solvents such as methylene chloride, methyl acetate, tetrahydrofuran, acetone, and 1,3-dioxolane are preferred, and methylene chloride is more preferred because of its low boiling point and easy drying and removal of the solvent. As described above, by setting the composition ratio of the acid dianhydride component and the diamine component within a predetermined range, a polyimide resin showing high solubility in low-boiling solvents such as methylene chloride can be obtained.

[0044] The solid content concentration of the polyimide resin solution may be appropriately set according to the molecular weight of the polyimide resin, the film thickness, the film formation environment, etc. The solid content concentration is preferably 5 to 30 wt%, more preferably 8 to 20 wt%. The polyimide resin solution is characterized in that it contains 0.5 to 3 parts of an ultraviolet absorber having an SP value difference from the polyimide resin of less than 2.0 and an SP value of 7.3 to 9.7 per 100 parts by weight of the polyimide resin. By adding an ultraviolet absorber having an SP value difference from the polyimide resin of less than 2.0 and an SP value of 7.3 to 9.7, a transparent polyimide film having excellent weather resistance and excellent mechanical properties can be obtained.

[0045] The polyimide resin solution may contain a resin component other than the polyimide resin and an additive other than the above ultraviolet absorber. Examples of the additive include an ultraviolet absorber, a crosslinking agent, a dye, a surfactant, a leveling agent, a plasticizer, and fine particles. 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, and even more preferably 80 parts by weight or more.

[0046] As a method for applying the polyimide resin to a substrate, a known method can be used. For example, it can be applied by a bar coater, a comma coater, a die coater, or a gravure coater. As the substrate for applying the polyimide resin solution, a glass substrate, a metal substrate such as SUS, a metal drum, a metal belt, a plastic film, etc. can be used. From the viewpoint of improving productivity, it is preferable to use an endless support such as a metal drum or a metal belt, or a long plastic film as a support, and manufacture the film by roll-to-roll. When using a plastic film as a support, a material that is insoluble in the solvent of the film-forming dope can be appropriately selected. Examples of the plastic material include polyester-based polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose-based polymers such as diacetyl cellulose and triacetyl cellulose, or films made of polymers such as polycarbonate-based polymers and acrylic-based polymers such as polymethyl methacrylate.

[0047] (Drying Process 1) After applying the polyimide resin solution to the substrate, a coating film of the polyimide resin can be produced by drying the solvent. The drying temperature and drying time are not particularly limited, but it is preferable to dry so that the residual solvent in the coating film becomes 20% by weight or less, and it is more preferable to dry so that it becomes 10% by weight or less. By setting the residual solvent amount within the above range, a self-supporting film can be obtained. However, the residual solvent in the coating film indicates the amount of solvent contained in the coating film, and it may be quantified with an analytical instrument such as a gas chromatograph device by dissolving the coating film in a solvent, or it may be determined by the weight change before and after heating and removing the solvent from the coating film.

[0048] (Peeling Process) By peeling and removing the substrate from the coating film of the polyimide resin, a polyimide resin sheet (hereinafter referred to as a green sheet) with a residual solvent amount of 20% by weight or less can be produced. A peeling roll may be used for peeling and removing the substrate.

[0049] (Drying Process 2) A polyimide film can be produced by drying the residual solvent of the green sheet. The drying temperature and drying time are not particularly limited, but it is preferable to dry so that the residual solvent in the polyimide film becomes less than 900 ppm with respect to the weight of the polyimide film. By setting the residual solvent within the above range, the mechanical strength can be improved. Also, the drying temperature is not particularly limited, but from the viewpoint of suppressing coloring, 200°C or lower is preferable, and 180°C or lower is more preferable. When using a polyimide resin that is insoluble in low-boiling solvents such as methylene chloride, in order to bring the residual solvent amount into the desired range, it is necessary to perform high-temperature heating at 200°C or higher or long-time heating, and there are still problems from the viewpoint of productivity. However, since the polyimide resin in this specification is soluble in low-boiling solvents such as methylene chloride, the heating temperature can be lowered. Therefore, the residual solvent can be easily reduced and coloring can be suppressed.

[0050] The drying temperature can be increased to the maximum temperature all at once or the temperature can be increased step by step. Also, the atmosphere during drying can be an air atmosphere, an inert gas atmosphere such as nitrogen, or a vacuum (under reduced pressure).

[0051] The thickness of the polyimide film is not particularly limited and may be appropriately set according to the application. The thickness of the polyimide film is, for example, about 5 to 100 μm. From the viewpoint of achieving both impact resistance and transparency, the thickness of the polyimide film is preferably 30 μm or more, more preferably 35 μm or more, and particularly preferably 40 μm or more. In particular, when used for applications that require strength, such as the cover window of a display, 40 μm or more is preferable. The thickness of the polyimide film is preferably 90 μm or less, more preferably 85 μm or less. The polyimide film in this specification has excellent transparency even when the film thickness is as thick as 40 μm or more.

[0052] [Properties of Polyimide Film (Optical Film)] The yellowness index (YI) of the polyimide film is preferably 3.0 or less, more preferably 2.5 or less. When the yellowness index is 3.0 or less, the film can be suitably used as a film for displays and the like without being colored yellow.

[0053] The total light transmittance of the polyimide film is preferably 80% or more, more preferably 85% or more. Also, the haze of the polyimide film is preferably 2.0 or less, more preferably 1.0% or less, and still more preferably 0.5% or less. Furthermore, the tensile modulus of the polyimide film is preferably 4.0 GPa or more, more preferably 4.5 GPa or more, and still more preferably 5.0 GPa or more.

[0054] The polyimide film of the present invention has a low yellowness index, high transparency, and is suitably used as a display material. Furthermore, in addition to excellent weather resistance, it has excellent mechanical strength and even higher surface hardness, so it can be applied to surface members such as the cover window of a display.

Examples

[0055] Hereinafter, the present invention will be described more specifically based on Examples and Comparative Examples. Note that the present invention is not limited to the following Examples.

[0056] (Measurement of Elastic Modulus, Yield Stress, and Elongation) For the measurement, an autograph testing machine "AUTOGRAPH AGS-X" manufactured by Shimadzu Corporation was used, and the measurement was carried out under the following conditions. Sample measurement range: width 10 mm, distance between grips 100 mm, tensile speed: 12.5 mm / min, measurement temperature: 23°C. The samples were measured after being left standing for 1 day at 23°C / 55%RH for humidity conditioning.

[0057] (SP Value of Ultraviolet Absorbent) As a method for obtaining the SP value of the ultraviolet absorbent, it is calculated from the latent heat of vaporization per 1 cm as shown in the following formula. 3 Moreover, the evaporation enthalpy of each ultraviolet absorbent was the value calculated by Advanced Chemistry Development (ACD / Labs) Software V11.02 ((c)1994 - 2021 ACD / Labs). [Equation]

[0058] For LA-24, LA-31, LA-32, LA-36, and LA-F70 manufactured by ADEKA, which are the ultraviolet absorbents used in this study, the SP values were estimated from the evaporation enthalpy of each as shown in Table 1.

[0059]

Table 1

Table 1

[0060] (SP Value of Polyimide Resin) As a method for obtaining the SP value of the polyimide resin, it is calculated as the value obtained by multiplying the SP value calculated from the latent heat of vaporization per 1 cm of each monomer by the composition ratio and adding them as shown in the following formula. 3 It is calculated as the value obtained by multiplying the SP value calculated from the latent heat of vaporization per 1 cm of each monomer by the composition ratio and adding them. [Number]

[0061] In addition, the evaporation enthalpy of each monomer was the value calculated by Advanced Chemistry Development (ACD / Labs) Software V11.02 ((c)1994 - 2021 ACD / Labs).

[0062] (Polymerization of Polyimide Resin 1) Into a separable flask, 5.976 g (18.7 mmol) of TFMB, 1.986 g (8.00 mmol) of 3,3'-DDS, and 108.5 g of DMF were charged and stirred under a nitrogen atmosphere to obtain a diamine solution. To this, 4.582 g (6.7 mmol) of TMHQ, 8.883 g (13.3 mmol) of 6FDA, and 2.941 g (6.7 mmol) of BPDA were added and stirred under a nitrogen atmosphere for 12 hours to obtain a polyamic acid solution with a solid content concentration of 18% and a viscosity of 50 poises at 23°C.

[0063] To the above polyamic acid solution, 78.7 g of DMF and 9.5 g of pyridine as an imidization catalyst were added and completely dispersed. 12.2 g of acetic anhydride was added to the dispersed solution, stirred at 80°C for 4 hours, and then cooled to room temperature. While stirring the solution cooled to room temperature, a solution obtained by mixing 85 g of 2-propyl alcohol (hereinafter referred to as "IPA") and 15 g of DMF was dropped to precipitate polyimide. Further, 300 g of IPA was added, stirred for about 30 minutes, and then suction filtration was performed using a Kiriyama funnel. The obtained solid was washed with 100 g of IPA. After repeating the washing operation 6 times, it was dried in a vacuum oven set at 120°C for 8 hours to obtain polyimide resin 1. The SP value of this polyimide resin 1 was 8.9.

[0064] (Polymerization of Polyimide Resin 2) Into a separable flask, 10.998 g (34.3 mmol) of TFMB, 0.948 g (3.8 mmol) of 3,3'-DDS, and 108.5 g of DMF were added, and the mixture was stirred under a nitrogen atmosphere to obtain a diamine solution. Then, 11.792 g (19.1 mmol) of TAHMBP, 2.245 g (11.4 mmol) of CBDA, and 2.368 g (7.6 mmol) of s-ODPA were added thereto, and the mixture was stirred for 12 hours under a nitrogen atmosphere to obtain a polyamic acid solution having a solid content concentration of 18% and a viscosity of 50 poises at 23°C.

[0065] To the above polyamic acid solution, 78.7 g of DMF and 9.5 g of pyridine as an imidization catalyst were added and completely dispersed. 12.2 g of acetic anhydride was added to the dispersed solution, and the mixture was stirred at 80°C for 4 hours and then cooled to room temperature. While stirring the solution cooled to room temperature, a solution obtained by mixing 85 g of 2-propyl alcohol (hereinafter referred to as "IPA") and 15 g of DMF was dropped to precipitate polyimide. Further, 300 g of IPA was added, and after stirring for about 30 minutes, suction filtration was performed using a Kiriyama funnel. The obtained solid was washed with 100 g of IPA. After repeating the washing operation 6 times, it was dried in a vacuum oven set at 120°C for 8 hours to obtain polyimide resin 2. The SP value of this polyimide resin 2 was 9.2.

[0066] (Example 1) In Example 1, polyimide resin 1 was dissolved in methylene chloride so that the solid content concentration became 10%, and further, 1.0 part of LA-24 (manufactured by ADEKA), which is an ultraviolet absorber, was added to 100 parts by weight of polyimide resin to obtain a coating solution. The coating solution was applied to a polyethylene terephthalate film as a substrate so that the dry thickness became 45 to 55 μm to form a coating film. After drying the obtained coating film at 30°C or higher and 60°C or lower for 4 minutes, the polyethylene terephthalate film as a substrate was peeled off and removed, and dried at 90°C or higher and 200°C or lower for 90 minutes to produce polyimide film 1, and the elastic modulus in the MD direction was measured.

[0067] (Examples 2 to 7) In Examples 2 to 7, polyimide films 2 to 7 were prepared in the same manner as in Example 1, except that the type and amount of the ultraviolet absorber added were changed as shown in Table 2, and the elastic modulus in the MD direction was measured.

[0068] (Examples 8 to 16) In Examples 8 to 16, polyimide films 8 to 16 were prepared in the same manner as in Example 1, except that transparent polyimide resin 1 was changed to transparent polyimide resin 2, and the elastic modulus in the MD direction was measured.

[0069] (Comparative Examples 1 to 11) In Comparative Examples 1 to 11, polyimide films A to F were prepared in the same manner as in Example 1, except that the type of polyimide resin and the type and amount of the ultraviolet absorber were changed as shown in Table 2, and the elastic modulus in the MD direction was measured.

[0070] As shown in Table 2, the polyimide film of the present invention not only has excellent weather resistance but also has high mechanical strength, that is, a high elastic modulus.

Table 2

Claims

1. An optical film containing 0.5 to 3 parts by weight of an ultraviolet absorber with respect to 100 parts by weight of a polyimide resin, wherein the polyimide resin is soluble in methylene chloride, the SP value of the polyimide resin is 8.6 to 9.9, the SP value of the ultraviolet absorber is 7.3 to 9.7, and the difference between the SP value of the polyimide resin and the SP value of the ultraviolet absorber is less than 2.0, the ultraviolet absorber is a benzotriazole-based ultraviolet absorber, the polyimide resin contains 20 mol% or more and 65 mol% or less of bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid)-1,4-phenylene ester as an acid dianhydride component and 50 mol% or less of 3,3',4,4'-biphenyltetracarboxylic dianhydride, and as a diamine component, contains 40 mol% or more and 100 mol% or less of 2,2'-bis(trifluoromethyl)benzidine and 50 mol% or less of 3,3'-diaminodiphenyl sulfone, or contains 20 mol% or more and 65 mol% or less of bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid)-(2,2',3,3',5,5'-hexamethyl[1,1'-biphenyl]-4,4'-diyl)ester as an acid dianhydride component and 50 mol% or less of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and as a diamine component, contains 40 mol% or more and 100 mol% or less of 2,2'-bis(trifluoromethyl)benzidine and 50 mol% or less of 3,3'-diaminodiphenyl sulfone. (However, the SP value of the polyimide resin is a value obtained by multiplying the SP value determined by the evaporation enthalpy of each monomer by the composition ratio and adding them, and the SP value of the ultraviolet absorber is a value determined by the evaporation enthalpy.)

2. The optical film according to Claim 1, wherein the ultraviolet absorber is one or more ultraviolet absorbers selected from 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(2H-benzotriazol-2-yl)-p-cresol, and 2-(5-chloro-2H-benzotriazol-2-yl)-6-tert-butyl-4-methylphenol.

3. When the relationship between the elastic modulus of the optical film (Film 1) containing 0.5 to 3 parts of an ultraviolet absorber with respect to 100 parts by weight of the polyimide resin and the elastic modulus of the film (Film 2) when the amount of the ultraviolet absorber is 0 parts with respect to 100 parts by weight of the polyimide resin is expressed as ([Elastic modulus of Film (Film 1)] / [Elastic modulus of Film (Film 2)]), it is 1.02 to 1.

10. The optical film according to claim 1 or 2, characterized in that.

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