TW202239818A - Optical film and flexible display device provided with optical film - Google Patents

Abstract

The present invention relates to an optical film: which contains a polyimide resin having a structural unit derived from an aliphatic diamine; which has a 350 nm light transmittance of 10% or lower; and which has a photoelastic coefficient of no greater than 50*10-12Pa-1.

Description

Optical film and flexible display device having the optical film

The invention relates to an optical film and a flexible display device equipped with the optical film.

Optical films are used in various applications such as display devices such as liquid crystals and organic electroluminescence (EL), touch sensors, speakers, and semiconductors. For example, polyimide-based films having dimensional stability and the like are known as touch sensor substrate materials (for example, Patent Document 1 and Patent Document 2).

In recent years, the development of flexible display devices has been rapidly progressing. When used in such cutting-edge display applications, it is required to protect the display device not only from ultraviolet rays but also from oxygen or water vapor. An optical film excellent in both UV cut and gas barrier properties. [Prior art literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2005-336243 [Patent Document 2] International Publication No. 2019/156717 Handbook

[Problem to be Solved by the Invention] However, according to studies by the inventors of the present invention, the aromatic polyimide-based film described in Patent Document 1 does not necessarily have high gas barrier properties. In addition, the aliphatic polyimide-based film described in Patent Document 2 tends to have low ultraviolet cutoff properties and high water absorption, and it has been found that it is difficult to achieve both high ultraviolet cutoff properties and gas barrier properties.

Therefore, an object of the present invention is to provide an optical film excellent in ultraviolet cutoff properties and gas barrier properties, and a flexible display device including the optical film. [Means to solve the problem]

The inventors of the present invention conducted diligent research to solve the above-mentioned problems, and as a result found that by including a polyimide-based resin having a structural unit derived from an aliphatic diamine in an optical film, and converting 350 nm light The above problems can be solved by setting the transmittance to 10% or less and the photoelastic coefficient to 50×10 ^-12 Pa ^-1 or less, and thus completed the present invention. That is, the present invention includes the following preferred aspects.

[式（1）中，X表示二價有機基，Y表示四價有機基，*表示鍵結鍵] 且式（1）所表示的構成單元含有二價脂肪族基作為X。 〔9〕如〔8〕所述的光學膜，其中所述式（1）所表示的構成單元含有式（2）所表示的結構作為Y， [化2]

[式（2）中，R ²～R ⁷彼此獨立地表示氫原子、碳數1～6的烷基、碳數1～6的烷氧基或碳數6～12的芳基，R ²～R ⁷中所含的氫原子可彼此獨立地經鹵素原子取代，V表示單鍵、-O-、-CH ₂-、-CH ₂-CH ₂-、-CH(CH ₃)-、-C(CH ₃) ₂-、-C(CF ₃) ₂-、-SO ₂-、-S-、-CO-或-N(R ⁸)-，R ⁸表示氫原子、或可經鹵素原子取代的碳數1～12的一價烴基，*表示鍵結鍵]。 〔10〕如〔8〕或〔9〕所述的光學膜，其中所述聚醯亞胺系樹脂包含氟原子。 〔11〕一種柔性顯示裝置，具備如〔1〕至〔10〕中任一項所述的光學膜。 〔12〕如〔11〕所述的柔性顯示裝置，進而具備偏光板。 〔13〕如〔11〕或〔12〕所述的柔性顯示裝置，進而具備觸控感測器。 [發明的效果] [1] An optical film comprising a polyimide-based resin having a constituent unit derived from an aliphatic diamine, having a light transmittance at 350 nm of 10% or less, and a photoelastic coefficient of 50×10 ^-12 Pa ^-1 the following. [2] The optical film according to [1], wherein the coefficient of humidity expansion exceeds 10 ppm. [3] The optical film according to [1] or [2], wherein the water absorption at 60° C. is 2.5% or less. [4] The optical film according to any one of [1] to [3], wherein the solvent content is 7.0% by mass or less relative to the mass of the optical film. [5] The optical film according to any one of [1] to [4], wherein the light transmittance at 500 nm is 90% or more. [6] The optical film according to any one of [1] to [5], which contains a filler. [7] The optical film according to any one of [1] to [6], wherein the film thickness is not less than 10 μm and not more than 100 μm. [8] The optical film according to any one of [1] to [7], wherein the polyimide-based resin has a structural unit represented by formula (1), [Chem. 1]

[In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, and * represents a bonding bond] And the structural unit represented by formula (1) contains a divalent aliphatic group as X. [9] The optical film according to [8], wherein the structural unit represented by the formula (1) contains a structure represented by the formula (2) as Y, [Chem. 2]

[In formula (2), R ² to R ⁷ independently represent a hydrogen atom, an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or an aryl group with 6 to 12 carbons, and R ² to The hydrogen atoms contained in R ⁷ may be independently replaced by halogen atoms, and V represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C( CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁸ )-, R ⁸ represents a hydrogen atom, or a carbon that may be substituted by a halogen atom A monovalent hydrocarbon group with a number of 1 to 12, * means a bond]. [10] The optical film according to [8] or [9], wherein the polyimide-based resin contains fluorine atoms. [11] A flexible display device comprising the optical film according to any one of [1] to [10]. [12] The flexible display device according to [11], further comprising a polarizing plate. [13] The flexible display device according to [11] or [12], further comprising a touch sensor. [Effect of the invention]

According to the present invention, it is possible to provide an optical film excellent in ultraviolet cutoff properties and gas barrier properties, and a flexible display device including the optical film.

The optical film of the present invention contains a polyimide-based resin having constituent units derived from aliphatic diamine, has a light transmittance at 350 nm of 10% or less, and a photoelastic coefficient of 50×10 ^-12 Pa ^-1 or less.

Surprisingly, the inventors of the present invention found that in an optical film containing a polyimide-based resin having constituent units derived from aliphatic diamine, at a photoelastic coefficient of 50×10 ^-12 Pa ^-1 Excellent gas barrier properties can be achieved in the following cases. In addition, in this specification, the term "excellent gas barrier property or high gas barrier property" means that both water vapor permeability and oxygen permeability are low, and preferably satisfies water vapor permeability unless otherwise specified. The permeability is 100 g/m ² /24 hours/0.1 mm or less, and the oxygen permeability is 1000 cc (NTP)/m ² /24 hours/0.1 mm/atm.

[Polyimide resin] The polyimide-based resin refers to a polymer including a repeating structural unit (also referred to as a constitutional unit) containing an amide group, and may further contain a repeating structural unit containing an amide group.

In the present invention, the polyimide-based resin contains a structural unit derived from aliphatic diamine. The term "aliphatic diamine" means a diamine having an aliphatic group, which may contain other substituents in a part of its structure, but does not have an aromatic ring. When the polyimide-based resin contains a structural unit derived from an aliphatic diamine, the photoelastic coefficient of the optical film tends to decrease, and as a result, the gas barrier properties of the optical film tend to be improved. Examples of aliphatic diamines include acyclic aliphatic diamines and cyclic aliphatic diamines, and acyclic aliphatic diamines are preferred in terms of the ease of further improving the gas barrier properties of the optical film. . Examples of acyclic aliphatic diamines include: 1,2-diaminoethane, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane alkanes, 1,6-diaminohexane, 1,2-diaminopropane, 1,2-diaminobutane, 1,3-diaminobutane, 2-methyl-1,2- Linear or branched diaminoalkanes having 2 to 10 carbon atoms such as diaminopropane and 2-methyl-1,3-diaminopropane. Examples of cycloaliphatic diamines include 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, and 4, 4'-diaminodicyclohexylmethane, etc. These can be used alone or in combination of two or more. Among these, 1,2-diaminoethane, 1,3-diaminopropane, and 1,4-diaminobutane are preferable in terms of further improving the gas barrier properties of the optical film. (sometimes called 1,4-DAB), 1,5-diaminopentane, 1,6-diaminohexane, 1,2-diaminopropane, 1,2-diaminobutane , 1,3-diaminobutane, 2-methyl-1,2-diaminopropane, 2-methyl-1,3-diaminopropane and other diaminoalkanes with 2 to 10 carbon atoms, More preferably, it is a diaminoalkane having 2 to 6 carbon atoms, and still more preferably, it is 1,4-diaminobutane.

The polyimide-based resin may contain a structural unit derived from an aromatic diamine in addition to a structural unit derived from an aliphatic diamine. The term "aromatic diamine" means a diamine having an aromatic ring, and a part of its structure may contain an aliphatic group or other substituents. The aromatic ring may be a single ring or a condensed ring, and examples thereof include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring.

Examples of aromatic diamines include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2 , 6-diaminonaphthalene and other aromatic diamines with an aromatic ring, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diamino Amino diphenyl ether, 3,4'-diamino diphenyl ether, 3,3'-diamino diphenyl ether, 4,4'-diamino diphenyl ether, 3,4' -Diaminodiphenylphenoxide, 3,3'-diaminodiphenylphenoxide, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy Base) benzene, bis[4-(4-aminophenoxy)phenyl]pyridine, bis[4-(3-aminophenoxy)phenyl]pyridine, 2,2-bis[4-(4 -aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'- Bis(trifluoromethyl)-4,4'-diaminodiphenyl (sometimes called TFMB), 4,4'-(hexafluoropropylene)diphenylamine, 4,4'-bis(4 -aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene, 9,9-bis Aromatic diamines having two or more aromatic rings, such as (4-amino-3-chlorophenyl)fluorene and 9,9-bis(4-amino-3-fluorophenyl)fluorene. These can be used alone or in combination of two or more.

The polyimide-based resin may further contain a structural unit derived from a tetracarboxylic acid compound. When the structural unit derived from a tetracarboxylic-acid compound is contained, it becomes easy to improve solvent resistance, heat resistance, optical characteristics, and tensile strength. As a tetracarboxylic-acid compound, Aromatic tetracarboxylic-acid compound, such as an aromatic tetracarboxylic-acid dianhydride; Aliphatic tetracarboxylic-acid compound, such as an aliphatic tetracarboxylic-acid dianhydride, etc. are mentioned. Tetracarboxylic acid compounds may be used alone or in combination of two or more. The tetracarboxylic acid compound may be tetracarboxylic acid compound analogues, such as an acid chloride compound, other than a dianhydride.

Specific examples of aromatic tetracarboxylic dianhydrides include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Acid dianhydride. Examples of non-condensed polycyclic aromatic tetracarboxylic dianhydrides include 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic Acid dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (sometimes described as BPDA), 2,2',3,3'-Biphenyl tetracarboxylic dianhydride, 3,3',4,4'-Diphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-bis Carboxyphenyl) propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4 ,4'-(hexafluoroisopropylidene)diphthalic dianhydride (sometimes recorded as 6FDA), 1,2-bis(2,3-dicarboxyphenyl)ethanedianhydride, 1,1 -Bis(2,3-dicarboxyphenyl)ethanedianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethanedianhydride, 1,1-bis(3,4-dicarboxybenzene base) ethanedianhydride, bis(3,4-dicarboxyphenyl)methanedianhydride, bis(2,3-dicarboxyphenyl)methanedianhydride, 4,4'-(p-phenylenedioxy ) diphthalic dianhydride, 4,4'-(m-phenylenedioxy) diphthalic dianhydride. In addition, examples of monocyclic aromatic tetracarboxylic dianhydride include 1,2,4,5-benzenetetracarboxylic dianhydride, and examples of condensed polycyclic aromatic tetracarboxylic dianhydride include 2,3,6,7-Naphthalene tetracarboxylic dianhydride. These can be used alone or in combination of two or more.

As aliphatic tetracarboxylic dianhydride, a cyclic or acyclic aliphatic tetracarboxylic dianhydride is mentioned. The cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride and other cycloalkane tetracarboxylic dianhydride, bicyclo[2.2.2]octyl 7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride, and positional isomers thereof. These can be used alone or in combination of two or more. Specific examples of acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butane tetracarboxylic dianhydride and 1,2,3,4-pentane tetracarboxylic dianhydride etc., these can be used alone or in combination of two or more. Moreover, a cycloaliphatic tetracarboxylic dianhydride and a noncyclic aliphatic tetracarboxylic dianhydride can also be used in combination.

Among the tetracarboxylic dianhydrides, 4,4'-oxydiphthalic dianhydride, 3,3',4,4' -Benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3 ,3',4,4'-Diphenylphenyltetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene ) diphthalic dianhydride, and a mixture thereof, more preferably 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA).

In one embodiment of the present invention, the proportion of the constituent units derived from aliphatic diamine is preferably 30 mole % or more, more preferably It is 50 mol% or more, more preferably 70 mol% or more, particularly preferably 90 mol% or more, and more preferably 100 mol% or less. When the ratio of the structural unit derived from an aliphatic diamine is the said range, it becomes easy to become a thing with high gas barrier property of an optical film. The ratio of the constituent units can be measured using, for example, hydrogen spectrum nuclear magnetic resonance ( ¹ H-Nuclear Magnetic Resonance, ¹ H-NMR), or can also be calculated from the input ratio of raw materials.

Furthermore, the polyimide-based resin may further contain structural units derived from other tetracarboxylic acids in addition to the structural units derived from the tetracarboxylic acid compound within the range of not impairing the various physical properties of the optical film. A structural unit, a structural unit derived from a tricarboxylic acid, and a structural unit derived from these acid anhydrides and derivatives.

As another tetracarboxylic acid, the water adduct of the anhydride of the said tetracarboxylic-acid compound is mentioned.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and acyl chloride compounds and acid anhydrides similar to these, and two or more of them may be used in combination. Specific examples include: anhydride of 1,2,4-benzenetricarboxylic acid; 2,3-anhydride of 2,3,6-naphthalenetricarboxylic acid; phthalic anhydride and benzoic acid via a single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, or phenylene-linked compounds.

[式（1）中，X表示二價有機基，Y表示四價有機基，*表示鍵結鍵] 且式（1）所表示的構成單元含有二價脂肪族基作為X。若含有此種聚醯亞胺系樹脂，則容易成為光學膜的阻氣性高者。 In the present invention, it is preferable that the polyimide resin has a structural unit represented by formula (1), [Chem. 3]

[In Formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, and * represents a bonding bond] The structural unit represented by Formula (1) contains a divalent aliphatic group as X. When such a polyimide resin is contained, the optical film tends to have high gas barrier properties.

X in the formula (1) each independently represent a divalent organic group, preferably a divalent organic group having 2 to 40 carbon atoms. As a divalent organic group, a divalent aromatic group, a divalent aliphatic group, etc. are mentioned, for example. In addition, in this specification, a divalent aromatic group is a divalent organic group which has an aromatic group, and a part of its structure may contain an aliphatic group or other substituents. In addition, a divalent aliphatic group is a divalent organic group having an aliphatic group, and may contain other substituents in a part of its structure, but does not contain an aromatic group.

X in the formula (1) includes a divalent aliphatic group, and examples of the divalent aliphatic group include a divalent acyclic aliphatic group and a divalent cyclic aliphatic group. Among them, a divalent acyclic aliphatic group is preferable from the viewpoint of easily obtaining a dense structure with little stacking of molecules and easily reducing the photoelastic coefficient of the optical film.

In one embodiment of the present invention, examples of the divalent acyclic aliphatic group in X in formula (1) include ethylidene, trimethylene, tetramethylene, pentamethylene, Hexamethylene, propylene, 1,2-butanediyl, 1,3-butanediyl, 2-methyl-1,2-propanediyl, 2-methyl-1,3-propanediyl Such as linear or branched chain alkylene, etc. A hydrogen atom in the divalent acyclic aliphatic group may be substituted by a halogen atom, and a carbon atom may be substituted by a heteroatom (eg, oxygen atom, nitrogen atom, etc.). From the viewpoint of easily improving the gas barrier properties of the optical film, the carbon number of the linear or branched alkylene group is preferably 2 or more, more preferably 3 or more, further preferably 4 or more, and more preferably 10. or less, more preferably 8 or less, still more preferably 6 or less. Among the divalent acyclic aliphatic groups, ethylenyl, trimethylene, tetramethylene, pentamethylene, and hexamethylene are preferable from the viewpoint of easily improving the gas barrier properties of the optical film. An alkylene group having 2 to 6 carbon atoms such as a group, more preferably a tetramethylene group.

In one embodiment of the present invention, examples of the divalent aromatic group or divalent cycloaliphatic group in X in formula (1) include: formula (10), formula (11), formula (12) , the groups represented by formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); the groups represented by these formulas (10) ~ formula (18) A group in which the hydrogen atom in is substituted by methyl, fluorine, chlorine or trifluoromethyl; and a chain hydrocarbon group with 6 or less carbon atoms.

[chemical 4]

In formulas (10) to (18), * represents a bond, V ¹ , V ² and V ³ independently represent a single bond, -O-, -S-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -CO- or -N(Q)-. Here, Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted by a halogen atom. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms that may be substituted by halogen atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, second-butyl, third-butyl, n- Pentyl, 2-methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, third octyl, n-nonyl and n-decyl, etc. . As said halogen atom, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, etc. are mentioned. In one example, V ¹ and V ³ are single bonds, -O- or -S-, and V ² is -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ - or -SO ₂ -. The bonding positions of V ¹ and V ² to each ring, and the bonding positions of V ² and V ³ to each ring are independently from each other, preferably meta or para, more preferably para . Furthermore, the hydrogen atoms on the rings in the formulas (10) to (18) can also be substituted by an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons or an aryl group with 6 to 12 carbons. . Examples of the alkyl group having 1 to 6 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, second-butyl, third-butyl, n-pentyl, and 2-methyl -butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl and the like. Examples of the alkoxy group having 1 to 6 carbon atoms include: methoxy, ethoxy, propyloxy, isopropyloxy, butoxy, isobutoxy, tert-butoxy, pentyloxy, oxy, hexyloxy and cyclohexyloxy, etc. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. These divalent cycloaliphatic groups or divalent aromatic groups can be used alone or in combination of two or more.

In the present invention, the polyimide-based resin may contain multiple types of X, and the multiple types of X may be the same as or different from each other. For example, as X in formula (1), a divalent acyclic aliphatic group, a divalent aromatic group and/or a divalent cyclic aliphatic group may be contained.

In one embodiment of the present invention, the ratio of X in the formula (1) is a divalent aliphatic group, preferably a divalent acyclic aliphatic group, with respect to the constituent units represented by the formula (1) The total molar amount is preferably more than 30 mole%, more preferably more than 50 mole%, more preferably more than 70 mole%, especially preferably more than 90 mole%, and more preferably 100 mole% the following. When the proportion of constituent units in which X in formula (1) is a divalent aliphatic group, preferably a divalent acyclic aliphatic group falls within the above-mentioned range, the gas barrier properties of the optical film can be easily improved. The ratio of this structural unit can be measured using ¹ H-NMR, for example, or can also be calculated from the input ratio of a raw material.

In formula (1), Y independently represents a tetravalent organic group, preferably represents a tetravalent organic group with 4 to 40 carbon atoms, more preferably represents a tetravalent organic group with 4 to 40 carbon atoms having a ring structure . As a ring structure, an alicyclic ring, an aromatic ring, and a heterocyclic structure are mentioned. The organic group is an organic group in which hydrogen atoms in the organic group may be substituted by a hydrocarbon group or a fluorine-substituted hydrocarbon group. In this case, the carbon number of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1-8. The polyimide-based resin of the present invention may contain multiple types of Y, and the multiple types of Y may be the same as or different from each other. As Y, the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula ( 28) and the group represented by formula (29); the group in which the hydrogen atoms in the groups represented by these formulas (20) to (29) are replaced by methyl, fluorine, chlorine or trifluoromethyl; and A tetravalent chain hydrocarbon group having 6 or less carbon atoms.

[chemical 5]

In formulas (20) to (29), * represents a bond, W ¹ represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C (CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -Ar-, -SO ₂ -, -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH ₂ -Ar-, -Ar-C(CH ₃ ) ₂ -Ar-, or -Ar-SO ₂ -Ar-. Ar represents an arylylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted by a fluorine atom, and a specific example thereof includes a phenylene group.

Among the groups represented by the formulas (20) to (29), the groups represented by the formula (26), the formula (28) or the formula (29) are preferable in terms of easily improving the gas barrier properties of the optical film. , more preferably the group represented by formula (26). In addition, W ¹ is each independently preferably a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ ) in terms of easily improving the gas barrier properties of the optical film. -, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -, more preferably single bond, -O-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -, more preferably a single bond, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -.

[式（2）中，R ²～R ⁷彼此獨立地表示氫原子、碳數1～6的烷基、碳數1～6的烷氧基或碳數6～12的芳基，R ²～R ⁷中所含的氫原子可彼此獨立地經鹵素原子取代，V表示單鍵、-O-、-CH ₂-、-CH ₂-CH ₂-、-CH(CH ₃)-、-C(CH ₃) ₂-、-C(CF ₃) ₂-、-SO ₂-、-S-、-CO-或-N(R ⁸)-，R ⁸表示氫原子、或可經鹵素原子取代的碳數1～12的一價烴基，*表示鍵結鍵] 若為此種實施方式，則容易提高光學膜的阻氣性。再者，式（1）所表示的構成單元亦可含有一種或多種式（2）所表示的結構作為Y。 In a preferred embodiment of the present invention, the structural unit represented by formula (1) contains a structure represented by formula (2) as Y. [chemical 6]

[In formula (2), R ² to R ⁷ independently represent a hydrogen atom, an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or an aryl group with 6 to 12 carbons, and R ² to The hydrogen atoms contained in R ⁷ may be independently replaced by halogen atoms, and V represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C( CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁸ )-, R ⁸ represents a hydrogen atom, or a carbon that may be substituted by a halogen atom A monovalent hydrocarbon group having a number of 1 to 12, * represents a bonding bond] According to such an embodiment, it is easy to improve the gas barrier properties of the optical film. Furthermore, the structural unit represented by formula (1) may contain one or more structures represented by formula (2) as Y.

In formula (2), R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ independently represent a hydrogen atom, an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or carbon The aryl group whose number is 6-12. Examples of the alkyl group having 1 to 6 carbons, the alkoxy group having 1 to 6 carbons, and the aryl group having 6 to 12 carbons include the above-mentioned exemplified alkyl group having 1 to 6 carbons, 6 alkoxy and 6-12 aryl. R ² to R ⁷ independently of each other preferably represent a hydrogen atom or an alkyl group with 1 to 6 carbons, more preferably represent a hydrogen atom or an alkyl group with 1 to 3 carbons. Here, R ² to R ⁷ represent The contained hydrogen atoms may be substituted independently of each other by halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. V represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁸ )-, R ⁸ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbons which may be substituted by a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom include those exemplified above as the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Among these, V is preferably a single bond, -O-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ - in terms of easily improving the gas barrier properties of the optical film. or -C(CF ₃ ) ₂ -, more preferably a single bond, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -, further preferably a single bond or -C(CF ₃ ) ₂ -.

[式（2'）中，*表示鍵結鍵] 若為此種實施方式，則容易進一步提高光學膜的阻氣性。另外，藉由包含氟元素的骨架來提升樹脂於溶媒中的溶解性，可將清漆的黏度抑制得低，可使光學膜的加工容易。 In a suitable embodiment of the present invention, formula (2) is represented by formula (2'). [chemical 7]

[In the formula (2′), * represents a bonding bond] According to such an embodiment, it is easy to further improve the gas barrier properties of the optical film. In addition, the solubility of the resin in the solvent is improved by including the skeleton of fluorine element, the viscosity of the varnish can be suppressed to be low, and the processing of the optical film can be facilitated.

In one embodiment of the present invention, when the structure represented by formula (2) is included as Y in formula (1), Y in formula (1) is the ratio of the constituent units represented by formula (2) Relative to the total molar amount of the constituent units represented by the formula (1), it is preferably at least 30 mole%, more preferably at least 50 mole%, further preferably at least 70 mole%, and most preferably at least 90 mole% % or more, and preferably less than 100 mol%. When Y in formula (1) is the ratio of the structural unit represented by formula (2) in the said range, it becomes easy to improve the gas barrier property of an optical film. Y in Formula (1) is the ratio of the structural unit represented by Formula (2), For example, it can measure using ¹ H-NMR, or can also calculate from the input ratio of a raw material.

In the present invention, the polyimide-based resin may contain, in addition to the structural unit represented by formula (1), a structural unit represented by formula (30) and/or a structural unit represented by formula (31). [chemical 8]

In formula (30), Y ¹ is a tetravalent organic group, preferably an organic group in which hydrogen atoms in the organic group may be substituted by hydrocarbon groups or hydrocarbon groups substituted with fluorine. Examples of Y ¹ include Formula (20), Formula (21), Formula (22), Formula (23), Formula (24), Formula (25), Formula (26), Formula (27), and Formula (28). ) and the group represented by formula (29), the group in which the hydrogen atoms in the groups represented by formula (20) to formula (29) are substituted by methyl, fluorine, chlorine or trifluoromethyl, and four A chain hydrocarbon group with a valence of 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may contain multiple Y ^{1 s} , and the multiple Y ^1s may be the same as or different from each other.

In formula (31), Y ² is a trivalent organic group, preferably an organic group in which hydrogen atoms in the organic group may be substituted by hydrocarbon groups or hydrocarbon groups substituted with fluorine. Examples of Y ² include: the formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and a group represented by formula (29) in which any one of the bonds of the groups represented by a hydrogen atom is substituted, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyimide-based resin may contain multiple types of Y ² , and the multiple types of Y ² may be the same as or different from each other.

In formula (30) and formula (31), X ¹ and X ² independently represent a divalent organic group, preferably a divalent organic group having 2 to 40 carbon atoms. As a divalent organic group, a divalent aromatic group, a divalent aliphatic group, etc. are mentioned, for example. As a divalent aliphatic group, a divalent acyclic aliphatic group or a divalent cycloaliphatic group is mentioned, for example. As the divalent cycloaliphatic group or divalent aromatic group in X1 and X2, can enumerate: said ^formula ( ¹⁰ ), formula (11), formula (12), formula (13), formula (14) ), formula (15), formula (16), formula (17) and formula (18); the hydrogen atoms in the groups represented by these formulas (10) to A group, a group substituted by a chlorine group or a trifluoromethyl group; and a chain hydrocarbon group with a carbon number of 6 or less. Examples of divalent acyclic aliphatic groups include ethylidene, trimethylene, tetramethylene, pentamethylene, hexamethylene, propylidene, 1,2-butanediyl, 1 , 3-butanediyl, 2-methyl-1,2-propanediyl, 2-methyl-1,3-propanediyl and other straight-chain or branched-chain alkylene groups with 2 to 10 carbons, etc. .

In one embodiment of the present invention, the polyimide-based resin includes a structural unit represented by formula (1), and optionally selected from a structural unit represented by formula (30) and a constituent represented by formula (31). At least one of the units constitutes a unit. In addition, in terms of improving the gas barrier properties of the optical film, in the polyimide-based resin, the ratio of the structural unit represented by formula (1) is based on all the components contained in the polyimide-based resin. The total molar amount of the structural unit, such as the structural unit represented by the formula (1), and at least one structural unit selected from the structural unit represented by the formula (30) and the structural unit represented by the formula (31) as the case may be , and preferably more than 80 mole%, more preferably more than 90 mole%, and more preferably more than 95 mole%. In addition, in polyimide-type resin, the upper limit of the ratio of the structural unit represented by formula (1) is 100 mol%. In addition, the said ratio can be measured using ¹ H-NMR, for example, or can also be calculated from the input ratio of a raw material. In addition, the polyimide-based resin in the present invention is preferably a polyimide resin at the point that it is easy to improve the gas barrier properties of the optical film.

In a preferred embodiment of the present invention, the polyimide resin may include, for example, a halogen atom, preferably a fluorine atom, which may be introduced through the halogen atom-containing substituent. When the polyimide-based resin contains a halogen atom, preferably a fluorine atom, the gas barrier properties of the optical film tend to be improved. As a preferable fluorine-containing substituent for making a polyimide-type resin contain a fluorine atom, a fluorine group and a trifluoromethyl group are mentioned, for example.

The content of the halogen atoms in the polyimide-based resin is preferably 1% by mass to 40% by mass, more preferably 5% by mass to 40% by mass based on the mass of the polyimide-based resin, and still more preferably 5% by mass to 30% by mass. There exists a tendency for the gas barrier property of an optical film to improve that content of a halogen atom is more than the said lower limit and below the said upper limit. Moreover, there exists a tendency for synthesis to become easy.

The imidization rate of the polyimide-based resin is preferably at least 90%, more preferably at least 93%, and still more preferably at least 95%. The imidization rate is preferably at least the above lower limit from the point of being easy to improve the gas barrier properties of the optical film. In addition, the upper limit of the imidization rate is 100%. The imidization rate represents the value of twice the molar amount of the imide bond in the polyimide-based resin relative to the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide-based resin proportion. Furthermore, in the case where the polyimide-based resin contains a tricarboxylic acid compound, it means the molar amount of the imide bond in the polyimide-based resin relative to the tetracarboxylic acid derived from the tetracarboxylic acid in the polyimide-based resin. The ratio of the value twice the molar amount of the structural unit of the acid compound to the total of the molar amount of the structural unit derived from the tricarboxylic acid compound. In addition, the imidization rate can be calculated|required by an infrared (infrared ray, IR) method, an NMR method, etc.

In one embodiment of the present invention, the content of the polyimide-based resin contained in the optical film is preferably at least 40% by mass, more preferably at least 50% by mass, based on the mass (100% by mass) of the optical film. , more preferably 60% by mass, particularly preferably 80% by mass or more, and more preferably 100% by mass or less. There exists a tendency for the gas barrier property of an optical film to improve that content of the polyimide-type resin contained in an optical film exists in the said range.

[Manufacturing method of polyimide resin] The said polyimide-type resin can use a commercial item, and can also manufacture by a usual method. The method for producing polyimide-based resins is not particularly limited. For example, polyimide-based resins containing structural units represented by formula (1) can be produced by a method including the following steps: making a diamine compound and tetra a step of obtaining polyamide acid by reacting a carboxylic acid compound; and a step of imidizing the polyamide acid. In addition, it is also possible to react a tricarboxylic acid compound other than a tetracarboxylic acid compound.

As the tetracarboxylic acid compound, diamine compound and tricarboxylic acid compound used in the synthesis of polyimide resin, for example, the tetracarboxylic acid compound, The diamine compound and the tricarboxylic acid compound are the same.

In the production of polyimide-based resins, the usage-amount of a diamine compound, a tetracarboxylic-acid compound, and a tricarboxylic-acid compound can be suitably selected according to the ratio of each structural unit of a desired resin. In a suitable embodiment of the present invention, the usage amount of the diamine compound is preferably 0.94 mole or more, more preferably 0.96 mole or more, and more preferably 0.98 mole or more, relative to 1 mole of the tetracarboxylic acid compound. It is especially preferably at least 0.99 mol, more preferably at most 1.20 mol, more preferably at most 1.10 mol, still more preferably at most 1.05 mol, and most preferably at most 1.02 mol. When the usage-amount of a diamine compound with respect to a tetracarboxylic-acid compound exists in the said range, the gas barrier property of the optical film obtained will tend to improve.

The reaction temperature of the diamine compound and the tetracarboxylic acid compound is not particularly limited, for example, it may be 5° C. to 200° C., and the reaction time is not particularly limited, for example, it may be about 30 minutes to 72 hours. In a suitable embodiment of the present invention, the reaction temperature is preferably 5°C-50°C, more preferably 5°C-40°C, further preferably 5°C-25°C, and the reaction time is preferably 3 hours-24 hours, More preferably, it is 5 hours - 20 hours. Such reaction temperature and reaction time tend to improve the gas barrier properties of the obtained optical film.

The reaction between the diamine compound and the tetracarboxylic acid compound is preferably carried out in a solvent. The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1- Methoxy-2-propanol, 2-butoxyethanol, propylene glycol monomethyl ether and other alcohol solvents; phenol, cresol and other phenolic solvents; ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate , γ-butyrolactone, γ-valerolactone, propylene glycol methyl ether acetate, ethyl lactate and other ester solvents; acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl Ketone-based solvents such as isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile-based solvents such as acetonitrile Solvents; tetrahydrofuran and dimethoxyethane and other ether solvents; chloroform and chlorobenzene and other chlorine-containing solvents; N,N-dimethylacetamide, N,N-dimethylformamide and other amide-based solvents ; sulfur-containing solvents such as dimethylsulfone, dimethylsulfene, and cyclobutylene; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, from the viewpoint of solubility, phenol-based solvents and amide-based solvents can be suitably used. In a suitable embodiment of the present invention, the solvent used in the reaction is preferably a solvent that is strictly dehydrated until the water content is below 700 ppm. When such a solvent is used, the gas barrier properties of the obtained optical film tend to be improved.

The reaction between the diamine compound and the tetracarboxylic acid compound can be carried out under an inert atmosphere (nitrogen atmosphere, argon atmosphere, etc.) or under reduced pressure, preferably under an inert atmosphere (nitrogen atmosphere, argon atmosphere, etc.), The reaction is carried out with stirring in a carefully controlled dehydration vehicle. Under such conditions, the gas barrier properties of the obtained optical film tend to be improved.

In the imidization step, imidization may be performed using an imidization catalyst, imidization may be performed by heating, or a combination thereof may be used. Examples of the imidization catalyst used in the imidization step include: aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidine, Alicyclic amines (monocyclic) such as N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazidine; azabicyclo[2.2.1]heptane azabicyclo[3.2.1]octane, azabicyclo[2.2.2]octane, and azabicyclo[3.2.2]nonane and other alicyclic amines (polycyclic); and pyridine, 2 -Methylpyridine (2-Methylpyridine), 3-Methylpyridine (3-Methylpyridine), 4-Methylpyridine (4-Methylpyridine), 2-Ethylpyridine, 3-Ethylpyridine, 4-Ethylpyridine pyridine, 2,4-lutidine, 2,4,6-collidine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and isoquinoline Aromatic amines such as phylloline. In addition, it is preferable to use an acid anhydride together with an imidization catalyst from the viewpoint of facilitating the imidization reaction. As the acid anhydride, common acid anhydrides and the like used in imidization reaction may be mentioned, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic acid anhydrides such as phthalic acid.

In one embodiment of the present invention, in the case of imidization, the reaction temperature is preferably above 40°C, more preferably above 60°C, further preferably above 80°C, and preferably below 190°C, More preferably, it is 170 degreeC or less, More preferably, it is 150 degreeC or less. The reaction time of the imidization step is preferably 30 minutes to 24 hours, more preferably 1 hour to 12 hours. There exists a tendency for the gas barrier property of the optical film obtained to improve that reaction temperature and reaction time are in the said range.

In one embodiment of the present invention, the weight average molecular weight (Mw) of the polyimide resin is preferably 50,000 or more, more preferably 100,000 or more, further preferably 120,000 or more, particularly preferably 150,000 or more, very particularly preferably 200,000 or more, preferably 800,000 or less, more preferably 700,000 or less, still more preferably 600,000 or less. When the weight average molecular weight (Mw) is not less than the above-mentioned lower limit, the gas barrier properties of the obtained optical film tend to be improved, and if it is not more than the above-mentioned upper limit, the processability of the film is easily improved. The weight average molecular weight (Mw) can be measured by Gel Permeation Chromatography (GPC), and can be calculated in terms of standard polystyrene, for example, can be calculated by the method described in the Examples.

Polyimide-based resins can be isolated by conventional methods such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a combination of these separation means (separation and purification) , In a preferred aspect, the isolation can be carried out by the following method: add a large amount of alcohol such as methanol to the reaction solution containing the resin to precipitate the resin, and then concentrate, filter, and dry.

[Optical film] The optical film of the present invention contains a polyimide-based resin having constituent units derived from aliphatic diamine, has a light transmittance of 10% or less at 350 nm, and has a photoelastic coefficient of 50×10 ^-12 Pa ^-1 or less. If the optical film of the present invention contains a polyimide-based resin having constituent units derived from aliphatic diamine, and has a light transmittance of 10% or less at 350 nm, and a photoelastic coefficient of 50×10 ^-12 Pa ^-1 or less , the ultraviolet cutoff property and gas barrier property are excellent. Therefore, the optical film of the present invention has high barrier properties against ultraviolet rays, oxygen, and water vapor, and thus can be suitably used in flexible display devices that require high visibility under visible light and whose performance is easily degraded by water or oxygen.

The photoelastic coefficient of the optical film of the present invention is 50×10 ^-12 Pa ^-1 or less. When the photoelastic coefficient is 50×10 ^-12 Pa ^-1 or less, it becomes an optical film excellent in gas barrier properties. When the photoelastic coefficient exceeds 50×10 ^-12 Pa ^-1 , it may be difficult to obtain high gas barrier properties. The photoelastic coefficient is preferably at most 45×10 ^-12 Pa ^-1 , more preferably at most 35×10 ^-12 Pa ^-1 , still more preferably at most 30×10 ^-12 Pa ^-1 , ^and more preferably at most 5×10 -12 Pa -1 ¹² Pa ^-1 or more, more preferably 7.5×10 ^-12 Pa ^-1 or more, more preferably 10×10 ^-12 Pa ^-1 or more, still more preferably 12.5×10 ^-12 Pa ^-1 or more, most preferably 15 ×10 ^-12 Pa ^-1 or more, especially preferably 17.5×10 ^-12 Pa ^-1 or more, more preferably 20×10 ^-12 Pa ^-1 or more, and most preferably 22.5×10 ^-12 Pa ^-1 or more, Very particularly preferably at least 25×10 ^-12 Pa ^-1 . If the photoelastic coefficient is within the above range, the gas barrier properties, tensile strength, light transmittance at 500 nm, and glass transition temperature of the optical film are likely to be in the desired ranges, and therefore, it is easy to obtain a material that satisfies the gas barrier properties and mechanical properties at the same time. Optical film with strength, transparency and heat resistance. The photoelastic coefficient can be determined by the type or composition ratio of the constituent units of the resin contained in the optical film; the molecular weight of the resin; the solvent content of the optical film; the type or amount of the additive; the manufacturing conditions of the resin; the manufacture of the optical film Conditions, etc. are appropriately adjusted to be within the above-mentioned range, especially by adjusting the type or composition ratio of the constituent units of the resin contained in the optical film; the solvent content of the optical film; the production conditions of the optical film, etc. adjusted to be within the stated range. The photoelastic coefficient can be measured using a phase difference measuring device, for example, by the method described in Examples described later.

The light transmittance at 350 nm of the optical film of the present invention is 10% or less. When the light transmittance at 350 nm is 10% or less, it becomes an optical film excellent in ultraviolet cutoff properties. When the light transmittance at 350 nm exceeds 10%, the ultraviolet cutoff property tends to decrease. The light transmittance at 350 nm of the optical film of the present invention is preferably 8% or less, more preferably 5% or less. When the light transmittance at 350 nm is not more than the above-mentioned upper limit, the ultraviolet cut property can be improved. The lower limit of the light transmittance at 350 nm is 0%. The light transmittance at 350 nm is preferably within the range of the thickness (film thickness) of the optical film of the present invention. Furthermore, the light transmittance at 350 nm can be determined by the type or composition ratio of the constituent units constituting the resin contained in the optical film; the thickness of the optical film; the solvent content of the optical film; the type or amount of additives; The production conditions or the purity of the monomer; the production conditions of the optical film are appropriately adjusted to be within the above-mentioned range, for example, it is easy to adjust to the above-mentioned range by appropriately adjusting the type or amount of the ultraviolet absorber contained in the optical film. scope. The light transmittance at 350 nm can be measured using an ultraviolet-visible-near-infrared spectrophotometer, for example, by the method described in the examples.

The humidity expansion coefficient (hereinafter also referred to as "CME") of the optical film of the present invention is preferably 5 ppm or more, more preferably 10 ppm or more, still more preferably more than 10 ppm, still more preferably 20 ppm or more, and even more preferably It is preferably at least 27 ppm, more preferably at most 100 ppm, more preferably at most 80 ppm, and still more preferably at most 60 ppm. When the humidity expansion coefficient is within the above-mentioned range, it is easy to improve the gas barrier properties of the optical film. In the present invention, the humidity expansion coefficient refers to a value when measured by the method described in Examples described later under the conditions of 60° C. and 90% RH. The humidity expansion coefficient can be determined by adjusting the type or composition ratio of the constituent units of the resin contained in the optical film; the solvent content of the optical film; the type or amount of additives; the manufacturing conditions of the resin; the manufacturing conditions of the optical film, etc. adjusted to be within the stated range. The humidity expansion coefficient can be measured using a thermomechanical analyzer (thermomechanical analyzer (TMA)), for example, it can be measured by a method described in Examples described later.

Generally, when the humidity expansion coefficient is high, the gas barrier property tends to be lowered because it is easily affected by moisture. However, in a preferred embodiment of the present invention, the optical film of the present invention can exhibit excellent gas barrier properties even though the coefficient of humidity expansion is relatively high, for example exceeding 10 ppm, preferably above 20 ppm. Since the optical film of the present invention has such properties, when the optical film of the present invention is used in a display device, etc., the display device is protected from water vapor or oxygen, and at the same time, it can be used in a normal (not low humidity environment) ) in a clean room for film processing, so it is advantageous.

The water absorption rate at 60° C. of the optical film of the present invention (hereinafter also simply referred to as “water absorption rate”) is preferably 2.5% or less, more preferably 2.1% or less, and still more preferably 1.9% or less. When the water absorption is not more than the above-mentioned upper limit, the barrier property against water vapor tends to be excellent. In addition, the lower limit of water absorption is usually 0%. The water absorption rate can be appropriately adjusted by the type or composition ratio of the constituent units of the resin contained in the optical film; the solvent content of the optical film; the type or amount of additives; the manufacturing conditions of the resin; the manufacturing conditions of the optical film, etc. and adjusted to be within the stated range. The water absorption rate can be measured using a thermal analysis device (TG/DTA6200) according to high temperature and high humidity standards, for example, it can be measured by a method described in Examples described later.

The solvent content (also called residual solvent amount) of the optical film of the present invention is preferably 7.0% by mass or less, more preferably 3.5% by mass or less, still more preferably 2.5% by mass or less, and still more preferably, with respect to the mass of the optical film 1.4% by mass or less. The gas barrier property of an optical film will improve easily that content of a solvent is below the said upper limit. In addition, the lower limit of the solvent content is usually 0.01% by mass. The solvent content can be adjusted within the above range by appropriately adjusting the type of solvent, the type of substrate, drying conditions (especially drying temperature and drying time, etc.) in the optical film production process described later. The solvent content can be measured, for example, by the method described in the Examples described later.

The 500 nm light transmittance of the optical film of the present invention is preferably at least 90.0%, more preferably at least 90.2%, still more preferably at least 90.3%, and most preferably at least 90.4%. When the light transmittance at 500 nm is more than the above-mentioned lower limit, it is easy to improve visibility when applied to a display device or the like. The upper limit of the light transmittance at 500 nm is 100% or less. Therefore, in a suitable embodiment of the present invention, the optical film may be not only good in the cutoff property in the ultraviolet region but also good in the transmittance in the visible light region. The light transmittance at 500 nm is preferably the light transmittance within the range of the thickness (film thickness) of the optical film of the present invention, more preferably the light transmittance at 25 μm. Furthermore, the light transmittance at 500 nm can be determined by the type or composition ratio of the constituent units constituting the resin contained in the optical film; the thickness of the optical film; the solvent content of the optical film; the type or amount of additives; Production conditions or the purity of a monomer; the production conditions of an optical film are adjusted suitably and adjusted so that it may exist in the said range. The light transmittance at 500 nm can be measured using an ultraviolet-visible-near-infrared spectrophotometer, for example, by the method described in Examples described later.

The film thickness (also referred to as thickness) of the optical film of the present invention is preferably at least 10 μm, more preferably at least 20 μm, and preferably at most 100 μm, more preferably at most 80 μm. When the film thickness of an optical film exists in the said range, it will become easy to improve the optical characteristic and handleability of an optical film. The film thickness can be adjusted within the above-mentioned range by, for example, appropriately adjusting the film-forming conditions at the time of producing the optical film. The film thickness of an optical film can be measured using a digital thickness meter etc., For example, it can measure by the method described in the Example mentioned later.

In a preferred embodiment of the present invention, the glass transition temperature (sometimes abbreviated as Tg) of the optical film of the present invention is preferably above 165°C, more preferably above 170°C, further preferably above 175°C, and further preferably above 175°C. More preferably above 180°C, particularly preferably above 180°C, especially preferably above 180.5°C, even more preferably above 181°C, most preferably above 182°C, preferably below 400°C, more preferably below 380°C , more preferably at most 350°C, particularly preferably at most 300°C. It is easy to improve heat resistance and gas barrier property as a glass transition temperature is more than the said minimum. Secondary processing becomes easy as glass transition temperature is below the said upper limit. The glass transition temperature is the glass transition temperature obtained by differential scanning calorimetry (DSC) (differential scanning calorimetry). The glass transition temperature can be determined by the type or composition ratio of the constituent units of the resin contained in the optical film; the solvent content of the optical film; the type or amount of the additive; the manufacturing conditions of the resin or the purity of the monomer; The production conditions are appropriately adjusted to be within the above-mentioned ranges. In particular, it is possible to adjust the solvent content of the optical film by using the above-mentioned preferred ones as the types or constitutional ratios of the constituent units constituting the resin, and to apply the optical film described later. Drying conditions and the like in the film production step are adjusted to the above-mentioned range. The glass transition temperature can be measured, for example, by DSC (Differential Scanning Calorimetry) using a thermal analysis device, under the conditions of a measurement sample amount: 5 mg, a temperature range: from room temperature to 400°C, and a heating rate: 10°C/min. .

In a suitable embodiment of the present invention, the tensile strength of the optical film of the present invention is preferably 70 MPa or more, more preferably 80 MPa or more, even more preferably 85 MPa or more, and even more preferably more than 86 MPa, especially It is preferably at least 87 MPa, more preferably at least 89 MPa, even more preferably at least 95 MPa, most preferably at least 100 MPa, more preferably at most 200 MPa, more preferably at most 180 MPa. When tensile strength is more than the said minimum, it will become easy to suppress damage|damage of an optical film etc., and when tensile strength is below the said upper limit, it will become easy to improve flexibility. Tensile strength can be measured using a tensile tester or the like under the conditions of a distance between chucks of 50 mm and a tensile speed of 20 mm/min, and can be measured, for example, by the method described in Examples. Furthermore, the tensile strength can be determined by the type or composition ratio of the constituent units of the resin contained in the optical film; the solvent content of the optical film; the molecular weight of the resin; the type or amount of additives; The purity of the body; the production conditions of the optical film are appropriately adjusted to be within the above range.

The optical film of the present invention may also contain an ultraviolet absorber. By including an ultraviolet absorber, the light absorption property of an ultraviolet region can be reduced easily. Therefore, in the optical film of the present invention having a photoelastic coefficient of 50×10 ⁻¹² Pa ⁻¹ or less, both the ultraviolet cutoff property and the gas barrier property can be improved. Examples of ultraviolet absorbers include triazine derivatives such as benzotriazole derivatives (benzotriazole-based ultraviolet absorbers) and 1,3,5-triphenyltriazine derivatives (triazine-based ultraviolet absorbers). agent), benzophenone derivatives (benzophenone-based ultraviolet absorbers), and salicylate derivatives (salicylate-based ultraviolet absorbers), and the group selected from these can be used at least one of . In terms of 300 nm to 400 nm, preferably near 320 nm to 360 nm, it has ultraviolet absorptivity, and can improve the ultraviolet cutoff property of the optical film without reducing the transmittance in the visible light region. Preferably, at least one selected from the group consisting of benzotriazole-based ultraviolet absorbers and triazine-based ultraviolet absorbers is used, more preferably a benzotriazole-based ultraviolet absorber.

As a specific example of a benzotriazole-based ultraviolet absorber, a compound represented by formula (I), a trade name manufactured by Sumitomo Chemical Co., Ltd.: Sumisorb (registered trademark) 250 (2-[ 2-Hydroxy-3-(3,4,5,6-tetrahydrophthalimidomethyl)-5-methylphenyl]benzotriazole), BASF Japan (share ) manufactured trade name: Tinuvin (registered trademark) 360 (2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-tertiary octylphenol ]) and the reaction of Tinuvin 213 (methyl 3-[3-(2H-benzotriazol-2-yl) 5-tert-butyl-4-hydroxyphenyl] propionate with PEG300 products), these can be used alone or in combination of two or more. Specific examples of the compound represented by formula (I) include: Sumisorb 200 (2-(2-hydroxy-5-methylphenyl)benzene) manufactured by Sumitomo Chemical Co., Ltd. and triazole), Smith Sobor (Sumisorb) 300 (2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chlorobenzotriazole), Smith Sobor ( Sumisorb) 340 (2-(2-hydroxy-5-tertoctylphenyl) benzotriazole), Smith Sobor (Sumisorb) 350 (2-(2-hydroxy 3,5-di-pentyl phenyl) benzotriazole), and the trade name manufactured by BASF Japan (Stock): Tinuvin 327 (2-(2'-hydroxy-3',5'-di-di Tributylphenyl)-5-chlorobenzotriazole), Tinuvin 571 (2-(2H-benzotriazol-2-yl)-6-dodecyl-4-methyl -phenol) and Tinuvin 234 (2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol) and Eddie ADEKA (stock) product name: Adekastab (registered trademark) LA-31 (2,2'-methylenebis[6-(2H-benzotriazol-2-yl )-4-(1,1,3,3-Tetramethylbutyl)phenol]). The ultraviolet absorber is preferably a compound represented by formula (I) and Tinuvin 213 (methyl 3-[3-(2H-benzotriazol-2-yl) 5-tert-butyl-4 -The reaction product of hydroxyphenyl] propionate and PEG300, more preferably the trade name that Sumitomo Chemical Co., Ltd. manufactures: Smith Suobo (Sumisorb) 200 (2-(2-hydroxyl-5-methylphenyl) Benzotriazole), Sumisorb 300 (2-(3-tert-butyl-2-hydroxy-5-methylphenyl)-5-chlorobenzotriazole), Sumisorb (Sumisorb) 340 (2-(2-hydroxy-5-tertiary octylphenyl) benzotriazole), Smith Sobor (Sumisorb) 350 (2-(2-hydroxy 3,5-di-tertiary Amylphenyl) benzotriazole), Adekastab (Adekastab) LA-31 (2,2'-methylenebis[6-(2H -Benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol]) and the trade name manufactured by BASF Japan (Stock): Dinubin ( Tinuvin) 327 (2-(2'-hydroxy-3',5'-di-tert-butylphenyl)-5-chlorobenzotriazole) and Tinuvin 571 (2-(2H- Benzotriazol-2-yl)-6-dodecyl-4-methyl-phenol), the best trade name manufactured by Sumitomo Chemical Co., Ltd.: Smith Suobo (Sumisorb) 340 (2-( 2-Hydroxy-5-tertiary octylphenyl) benzotriazole), Smith Sobor (Sumisorb) 350 (2-(2-hydroxy 3,5-di-tertiary pentylphenyl) benzotriazole azole), and ADEKA (stock) product name: Adekastab (Adekastab) LA-31 (2,2'-methylenebis[6-(2H-benzotriazole-2 -yl)-4-(1,1,3,3-tetramethylbutyl)phenol]).

[chemical 9]

In formula (I), X ^I is a hydrogen atom, a fluorine atom, a chlorine atom, an alkyl group with 1 to 5 carbons, or an alkoxy group with 1 to 5 carbons, and R ^I1 and R ^I2 are each independently a hydrogen atom or a carbon A hydrocarbon group having 1 to 20 carbon atoms, at least one of R ^I1 and R ^I2 is a hydrocarbon group having 1 to 20 carbon atoms.

Examples of the alkyl group having ¹ to 5 carbon atoms in XI include methyl, ethyl, n-propyl, isopropyl, n-butyl, second-butyl, third-butyl, n-pentyl, 2 -Methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, etc. Examples of the alkoxy group having ¹ to 5 carbon atoms in XI include methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, second butoxy, and third butoxy. Oxy, n-pentyloxy, 2-methyl-butoxy, 3-methylbutoxy, 2-ethyl-propoxy and the like. ^XI is preferably a hydrogen atom, a fluorine atom, a chlorine atom or a methyl group, more preferably a hydrogen atom, a fluorine atom or a chlorine atom.

R ^I1 and R ^I2 are each independently a hydrogen atom or a hydrocarbon group having 1 to 20 carbons, and at least one of R ^I1 and R ^I2 is a hydrocarbon group. When each of R ^I1 and R ^I2 is a hydrocarbon group, it is preferably a hydrocarbon group having 1 to 12 carbons, more preferably a hydrocarbon group having 1 to 8 carbons. Specifically, a methyl group, a tertiary butyl group, a tertiary pentyl group, and a tertiary octyl group can be illustrated.

Another preferred aspect of the ultraviolet absorber is to use a triazine-based ultraviolet absorber in an optical film containing a polyimide-based resin. As a triazine type ultraviolet absorber, the compound represented by following formula (II) is mentioned. As its specific example, it can be cited: Adekastab (Adeka) LA-46 (2-(4,6-diphenyl-1,3,5- Triazin-2-yl)-5-[2-(2-ethylhexyloxy)ethoxy]phenol), trade name manufactured by BASF Japan Co., Ltd.: Tinuvin 400 (2-[4-[2-Hydroxy-3-tridecyloxypropyl]oxy]-2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)- 1,3,5-triazine), 2-[4-[2-hydroxy-3-didecyloxypropyl]oxy]-2-hydroxyphenyl]-4,6-bis(2,4- Dimethylphenyl)-1,3,5-triazine), Tinuvin 405 (2-[4-(2-hydroxy-3-(2'-ethyl)hexyl)oxy]- 2-hydroxyphenyl]-4,6-bis(2,4-dimethylphenyl)-1,3,5-triazine), Tinuvin 460 (2,4-bis(2- Hydroxy-4-butoxyphenyl)-6-(2,4-bis-butoxyphenyl)-1,3,5-triazine), Tinuvin 479 (hydroxyphenyltriazine UV absorber), and the product name of Chemipro Chemicals (stock): KEMISORB (registered trademark) 102 (2-[4,6-bis(2,4-dimethyl phenyl)-1,3,5-triazin-2-yl]-5-(n-octyloxy)phenol), etc., these may be used alone or in combination of two or more. The compound represented by formula (II) is preferably Adekastab LA-46 (2-(4,6-diphenyl-1,3,5-triazin-2-yl)-5- [2-(2-Ethylhexyloxy)ethoxy]phenol).

[chemical 10]

In formula (II), Y ^I1 to Y ^I4 are each independently a hydrogen atom, a fluorine atom, a chlorine atom, a hydroxyl group, an alkyl group with 1 to 20 carbons, or an alkoxy group with 1 to 20 carbons, preferably a hydrogen atom , an alkyl group having 1 to 12 carbons or an alkoxy group having 1 to 12 carbons, more preferably a hydrogen atom.

In formula (II), R ^I3 is a hydrogen atom, a hydrocarbon group with 1 to 20 carbons, an alkoxy group with 1 to 20 carbons containing one oxygen atom, or an alkyl ketone oxygen group with 1 to 12 carbons An alkoxy group with 1 to 4 carbons substituted by a radical, preferably an alkoxy group with 1 to 12 carbons containing an oxygen atom or an alkoxy group with 2 to 4 carbons substituted by an alkyl ketoneoxy group with 8 to 12 carbons an alkoxy group, more preferably an alkoxy group having 2 to 4 carbons substituted with an alkylketooxy group having 8 to 12 carbons.

Examples of alkyl groups having 1 to 20 carbon atoms in Y ^I1 to Y ^I4 include methyl, ethyl, n-propyl, isopropyl, n-butyl, second-butyl, third-butyl, n-pentyl Base, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl, n-dodecyl, n-undecyl. Examples of alkoxy groups having 1 to 20 carbon atoms include: methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, second butoxy, and third butoxy , n-pentyloxy, n-hexyloxy, n-heptyloxy, n-octyloxy, n-nonyloxy, n-decyloxy, n-dodecyloxy, n-undecyloxy base.

The ultraviolet absorber is preferably one having light absorption at 300 nm to 400 nm, more preferably one having light absorption at 320 nm to 360 nm, further preferably one having light absorption near 350 nm.

When the optical film of the present invention includes ultraviolet absorption, the content of the ultraviolet absorber is preferably at least 0.1 parts by mass, more preferably at least 0.5 parts by mass, and still more preferably at least 0.8 parts by mass relative to 100 parts by mass of the polyimide resin. It is at least 1 part by mass, particularly preferably at least 1 part by mass, more preferably at most 10 parts by mass, more preferably at most 8 parts by mass, still more preferably at most 5 parts by mass. When the content of the ultraviolet absorber is more than the above-mentioned lower limit, it is easy to improve the ultraviolet cut performance of the optical film, and when the content of the ultraviolet absorber is below the above-mentioned upper limit, it is easy to improve the transparency and mechanical properties of the optical film.

The optical film of the present invention may contain at least one filler. When the optical film contains a filler, the gas barrier property of the optical film, especially the oxygen transmission rate tends to decrease. As a filler, an organic particle, an inorganic particle etc. are mentioned, for example, Preferably an inorganic particle is mentioned. Examples of inorganic particles include metal oxides such as silicon dioxide, zirconia, aluminum oxide, titanium dioxide, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide. metal fluoride particles such as metal fluoride particles, magnesium fluoride, sodium fluoride, etc. Among them, from the viewpoint of easily improving the gas barrier properties of the optical film, silica particles, zirconia particles, and oxide particles are preferable. As the aluminum particles, silica particles are more preferable. These fillers may be used alone or in combination of two or more.

The average primary particle size of the filler, preferably silica particles, is usually more than 1 nm, preferably more than 5 nm, more preferably more than 10 nm, further preferably more than 15 nm, particularly preferably more than 20 nm, and more preferably The thickness is preferably at most 100 nm, more preferably at most 80 nm, further preferably at most 60 nm, and still more preferably at most 40 nm. When the average primary particle diameter of the silica particles is within the above range, the aggregation of the silica particles is suppressed, and the gas barrier properties of the obtained optical film are easily improved. The average primary particle size of the filler can be measured by the Brunauer-Emmett-Teller (BET) method. Furthermore, the average primary particle diameter can also be measured by image analysis of a transmission electron microscope or a scanning electron microscope.

When the optical film of the present invention contains a filler, preferably silica particles, the content of the filler is usually 0.1% by mass or more, preferably 1% by mass or more, more preferably 5% by mass relative to the mass of the optical film. % or more, more preferably 10 mass % or more, and preferably 60 mass % or less, more preferably 50 mass % or less, further preferably 40 mass % or less. When the content of the filler is within the above range, it is easy to maintain the transparency of the optical film, and it is easy to improve the gas barrier properties.

The optical film of the present invention may further contain other additives other than ultraviolet absorbers and fillers. Examples of other additives include antioxidants, release agents, stabilizers, blueing agents, flame retardants, pH regulators, silica dispersants, lubricants, tackifiers, and modifiers. Leveling agents, etc. When other additives are included, the content thereof is preferably 0.001% by mass to 20% by mass, more preferably 0.01% by mass to 15% by mass, and still more preferably 0.1% by mass to 10% by mass, based on the mass of the optical film. .

The application of the optical film of the present invention is not particularly limited, and can be used in various applications, such as substrates for touch sensors, materials for flexible display devices, protective films, films for frame printing, semiconductor applications, speaker diaphragms, and IR cut filters waiting. The optical film of the present invention may be a single layer or a laminate, and the optical film of the present invention may be used as it is or further may be used as a laminate with another film. In addition, when an optical film is a laminated body, it is called an optical film including all the layers laminated|stacked on one surface or both surfaces of an optical film.

When the optical film of the present invention is a laminate, it is preferable to have one or more functional layers on at least one surface of the optical film. As a functional layer, a hard coat layer, a primer layer, a gas barrier layer, an ultraviolet absorbing layer, an adhesive layer, a hue adjustment layer, a refractive index adjustment layer etc. are mentioned, for example. A functional layer can be used individually or in combination of 2 or more types.

In one embodiment of the present invention, the optical film may have a protective film on at least one side (single side or both sides). For example, when there is a functional layer on one side of the optical film, the protective film may be laminated on the surface on the optical film side or the surface on the functional layer side, or may be laminated on both the optical film side and the functional layer side. When having a functional layer on both surfaces of an optical film, a protective film may be laminated|stacked on the surface of one functional layer side, and may be laminated|stacked on the surface of both functional layer sides. The protective film is a film for temporarily protecting the surface of the optical film or the functional layer, and is not particularly limited as long as it can protect the surface of the optical film or the functional layer and is peelable. Examples of protective films include: polyester-based resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin-based resin films such as polyethylene and polypropylene films; The resin film, the acrylic resin film, etc. are preferably selected from the group consisting of a polyolefin resin film, a polyethylene terephthalate resin film, and an acrylic resin film. When an optical film has two protective films, each protective film may be the same or different.

The thickness of the protective film is not particularly limited, but is usually 10 μm to 120 μm, preferably 15 μm to 110 μm, more preferably 20 μm to 100 μm. When an optical film has two protective films, the thickness of each protective film may be the same or different.

[Manufacturing method of optical film] In the present invention, the optical film is not particularly limited, for example, it can be produced by a method comprising the following steps: (a) A step of preparing a liquid (sometimes called a varnish) containing a polyimide-based resin (varnish preparation step); (b) a step of applying the varnish to the substrate to form a coating film (coating step); and (c) A step of drying the applied liquid (coating film) to form an optical film (optical film forming step).

In the varnish preparation step, the above-mentioned polyimide-based resin is dissolved in a solvent, and additives described later are added as necessary and stirred and mixed to prepare a varnish.

The solvent used for the preparation of the varnish is not particularly limited as long as it can dissolve the resin. Examples of the solvent include amides such as N,N-dimethylacetamide (N,N-Dimethylacetamide, DMAc) and N,N-dimethylformamide (N,N-Dimethylformamide, DMF). Amine-based solvents; γ-butyrolactone (GBL), γ-valerolactone and other lactone-based solvents; acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl Ketone-based solvents such as isobutyl ketone; sulfur-containing solvents such as dimethylsulfide, dimethylsulfoxide, and cyclobutylene; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations of these . Among these, an amide-based solvent, a lactone-based solvent, or a ketone-based solvent is preferable from the viewpoint of resin solubility. These solvents may be used alone or in combination of two or more. In addition, the varnish may contain water, alcohol-based solvents, acyclic ester-based solvents, ether-based solvents, and the like.

The solid content concentration of the varnish is preferably from 1% by mass to 30% by mass, more preferably from 5% by mass to 25% by mass, still more preferably from 10% by mass to 20% by mass. In addition, in this specification, the solid content of a varnish means the total amount of the component which removed the solvent from a varnish. In addition, the viscosity of the varnish is preferably from 5 Pa·s to 100 Pa·s, more preferably from 10 Pa·s to 50 Pa·s. When the viscosity of the varnish is in the above-mentioned range, it is easy to make the optical film uniform, and it is easy to obtain an optical film with a uniform film thickness. In addition, the viscosity of a varnish can be measured using a viscometer, for example, can be measured by the method described in an Example.

In the coating step, the varnish is applied to the substrate by a known coating method to form a coating film. Examples of known coating methods include roll coating methods such as wire bar coating, reverse coating, and gravure coating, die coating, chipped wheel coating, lip coating, and spin coating. Cloth method, screen coating method, fountain coating method, dipping method, spray method, salivation forming method, etc.

In the optical film forming step, the optical film can be formed by drying the coating film and peeling it off from the substrate. After peeling, you may further perform the drying process of drying an optical film. Drying of the coating film can be carried out at a temperature of usually 50°C to 350°C, preferably at a temperature of 50°C to 220°C. In a suitable embodiment, it is preferable to perform drying in stages. A varnish containing a high molecular weight resin tends to become highly viscous, and an optical film obtained from such a varnish tends to have a non-uniform thickness. In such an optical film, the gas barrier property tends to decrease locally. Therefore, by drying in stages, the varnish containing the high molecular weight resin can be dried uniformly, and an optical film excellent in gas barrier properties can be easily obtained. In a more suitable embodiment of the present invention, after heating at a relatively low temperature of 100°C to 170°C, it may be heated at 185°C to 220°C. The drying (or heating time) is preferably from 5 minutes to 5 hours, more preferably from 10 minutes to 1 hour. By heating stepwise from a low temperature to a high temperature within such a range, an optical film having a uniform thickness can be obtained, and an optical film having a higher gas barrier property can be easily obtained. Moreover, there exists a tendency for the external appearance of an optical film to become more favorable. If necessary, drying of the coating film may be performed under inert atmosphere conditions. In addition, if the drying of the optical film is performed under vacuum conditions, fine air bubbles may be generated and remain in the film, which may cause a decrease in transparency. Therefore, it is preferable to dry the optical film under atmospheric pressure.

Examples of substrates include glass substrates, polyethylene terephthalate (PET) films, polyethylene naphthalate (PEN) films, and other polyimide-based resins. Or a polyamide-based resin film or the like. Among these, glass, a PET film, a PEN film, etc. are preferable from the viewpoint of excellent heat resistance, and furthermore, a glass substrate or a PET film is more preferable from the viewpoint of adhesion to a polyimide-based film and cost. membrane.

The optical film of the present invention can be suitably used as a substrate for a display device, especially a touch sensor. In addition, examples of display devices include televisions, smart phones, mobile phones, car navigation, tablet personal computers (PCs), portable game machines, electronic paper, indicators (indicators), bulletin boards, Watches, smart watches and other wearable devices.

[Flexible display device] The invention includes flexible display devices comprising the optical film of the invention. Examples of the flexible display device include display devices with flexible characteristics, such as televisions, smart phones, mobile phones, smart watches, and the like. Although it does not specifically limit as a specific structure of a flexible display device, For example, the structure containing the laminated body for flexible display devices and an organic electroluminescence display panel is mentioned. Such a flexible display device of the present invention is preferably further provided with a polarizer and/or a touch sensor. A conventional one can be used as a polarizing plate or a touch sensor, and these may be contained in the said laminate for flexible display devices. Examples of polarizers include circular polarizers, and examples of touch sensors include resistive film systems, surface acoustic wave systems, infrared systems, electromagnetic induction systems, and capacitance systems. In a preferred embodiment of the present invention, the optical film of the present invention can be used as the substrate for the touch sensor (or the film for the touch sensor). In addition, in one embodiment of the present invention, the laminate for a flexible display device preferably further includes a window film on the viewing side. For example, a window film, a polarizing plate, a touch sensor, or Window films, touch sensors, polarizers. These members may be laminated using an adhesive or an adhesive, and may contain other members than these members. [Example]

Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

[Photoelastic Coefficient] The photoelastic coefficients of the optical films obtained in Examples and Comparative Examples were measured using the in-plane retardation measurement mode ( Calculated using a wavelength of 590 nm). Arrange the sample tensile fixture attached to the sample measurement site, and measure the phase difference change caused by the load change for the test piece of 15 mm × 150 mm, and obtain the slope by linear approximation of the result, and then use the following formula to find out. Photoelastic coefficient = slope × 1.5 × 10 ^-9 /9.8 (cm ² /dyn)

[Coefficient of Humidity Expansion (CME)] The humidity expansion coefficients of the optical films obtained in Examples and Comparative Examples were measured using a thermomechanical analyzer (TMA) equipped with a constant temperature and humidity chamber. With a certain load (20 mN) applied, the test piece is kept in a pair of clamps (clamps), and the constant temperature and humidity chamber is changed from a temperature of 60°C and a humidity of 0%RH to a temperature of 60°C and a humidity of 90%RH, measure the distance between clips that changes between 0% and 90%RH, calculate the amount of change, and set it as the value of the humidity expansion coefficient.

[water absorption] For the water absorption of the optical films obtained in Examples and Comparative Examples, the weight of the sample was measured in an air (AIR) atmosphere with controlled temperature and humidity, and the weight change rate was obtained from the amount of change from the weight before humidification. For the measurement, a thermal analysis device (TG/DTA6200) manufactured by Seiko Electronics Co., Ltd. with high-temperature and high-humidity specifications was used. Set two sample disks on the balance beam, and set a test piece (approximately 15 mm×15 mm) on one of the sample disks. The temperature of the sample is adjusted by using a circulating constant temperature bath for sample temperature control, and the humidity adjustment is performed by circulating dry air at 100 mL/min in a warm water circulating furnace. The measurement temperature is controlled at 25°C and 60°C step by step, and then the humidity is changed from 0%RH to 90%RH, and the sample weight is measured after standing under various temperature and humidity conditions until the sample weight is stable. Water absorption (weight change) % was calculated from the following formula. Water absorption (mg) = sample weight (mg) at each humidity - sample weight (mg) in a non-humidified state Water absorption (%) = water absorption (mg) ÷ sample weight (mg) without humidification × 100 From the formula, the water absorption rate at 60° C. and 90% RH was obtained.

[Solvent content] (Thermogravimetric-Differential Thermal Analysis (Thermogravimetric-Differential Thermal Analysis, TG-DTA)) measurement) Using a TG-DTA measuring device ("TG/DTA6300", manufactured by Hitachi High-Tech Science Co., Ltd.), the residual solvent amount (solvent content) of the optical films obtained in Examples and Comparative Examples was measured. A sample of about 20 mg was obtained from the optical film. The sample was heated from room temperature to 120°C at a rate of 10°C/min, and kept at 120°C for 5 minutes, then measured at a rate of 10°C/min to 400°C. quality changes. From the TG-DTA measurement results, the mass loss rate S (mass %) from 120° C. to 250° C. was calculated according to the following formula (1). S (mass%)=100-(W1/W0)×100 (1) [In formula (1), W0 is the mass of the sample after being kept at 120°C for 5 minutes, and W1 is the mass of the sample at 250°C] Let the calculated mass reduction rate S be the residual solvent amount S (mass %) in the optical film.

[Light transmittance at 350 nm and 500 nm] The light transmittance of 350 nm and 500 nm of the optical film obtained in the examples and comparative examples is obtained by the following method: use the ultraviolet-visible-near-infrared spectrophotometer V-670 that JASCO Co., Ltd. manufactures, measure relative Light transmittance of light from 200 nm to 800 nm.

[Measurement of glass transition temperature] The glass transition temperature (Tg) by DSC (differential scanning calorimetry) of the optical film obtained in the Example and the comparative example was measured with the thermal analysis apparatus ("DSC Q200", manufactured by TA Instruments). The measurement conditions are: measurement sample amount: 5 mg, temperature range: from room temperature to 400° C., and temperature increase rate: 10° C./min.

[Measurement of tensile strength] The tensile strengths of the optical films obtained in Examples and Comparative Examples were measured as follows using a precision universal testing machine ("Autograph AG-IS", manufactured by Shimadzu Corporation). This optical film was cut into a width of 10 mm and a length of 100 mm to prepare an elongated test piece. Then, using this precision universal testing machine, a tensile test was performed under the conditions of a distance between chucks of 50 mm and a tensile speed of 20 mm/min to measure the tensile strength of the optical film.

[film thickness] The film thicknesses of the optical films obtained in Examples and Comparative Examples were measured three times using a contact-type digital thickness meter (manufactured by Mitutoyo Corporation), and the average value of the values obtained by the three measurements was taken as The film thickness of the optical film.

[Weight average molecular weight (Mw)] The weight average molecular weight (Mw) of the synthesized polyimide resin was measured using GPC under the following conditions. (GPC conditions) Device: Shimadzu LC-20A Column: TSKgel GMHHR-M (mixed column, exclusion limit molecular weight: 4 million) Guard column: TSKgel guardcolumn HHR-H Mobile phase: add N-methyl-2-pyrrolidinone (N-methyl-2-pyrrolidinone, NMP) 10 mM LiBr ※NMP uses high performance liquid chromatography (High Performance Liquid Chromatography, HPLC) grade, LiBr uses reagent grade (anhydride) Flow rate: 1 mL/min Measurement time: 20 minutes Column oven: 40°C Detection: UV 275 nm Cleaning solvent: NMP Sample concentration: 1 mg/mL (20 wt% reaction mass is analyzed after diluting to 5 mg/mL with mobile phase) Molecular weight calibration: Polymer Laboratories (Polymer Laboratories) manufactured standard polystyrene (17 molecular weight with a molecular weight of 5 to 4 million)

[Imidation Ratio] The imidization ratio of the synthesized polyimide resin was measured under the following conditions using NMR. (NMR conditions) 10 mg of polyimide-based resin was weighed, and 0.75 ml of deuterated dimethyl sulfoxide (DMSO) was added, followed by heating at 120° C. for 20 minutes to dissolve it. The solution was transferred to an NMR tube, and ¹ H NMR measurement was performed at 100° C. using an AV600 device manufactured by Bruker. From the ¹ H NMR spectrum, the protons derived from the amido group and the protons derived from the amido group were classified, and the imidization rate was calculated using the following formula. Amide imidization rate = {acyl imide group integral ratio/(acyl imide group integral ratio + amide imide group integral ratio)}×100

[viscosity] The viscosity of the varnish was measured using an E-type viscometer ("HBDV-II+P CP" manufactured by Brook Field) using 0.6 cc of the varnish as a sample at 25°C and 3 rpm .

[Water vapor permeability] The water vapor permeability of the optical films obtained in Examples and Comparative Examples was evaluated using a L80 series water vapor permeability meter manufactured by Lyssy. The measurement conditions are as follows. Test method: Humidity sensor method Temperature and humidity conditions: 25°C, 90%RH Measuring area: 1.3×10 ^-5 m ²

[Oxygen permeability] A differential pressure gas permeability measurement device (GTR-30AS type) manufactured by GTR tec Co., Ltd. was used, according to Japanese Industrial Standards (JIS) K 7126-1 ( differential pressure method) to evaluate the oxygen permeability of the optical films obtained in Examples and Comparative Examples. The measurement conditions are as follows. Measurement temperature: 30°C Permeation area: 15.2 cm ² (ϕ44 mm) Permeation gas: Oxygen (ultra-high purity) Supply gas pressure: 2 kgf/cm ² (Differential pressure: 223 cmHg)

[Synthesis Example 1] In a nitrogen gas atmosphere, 178.78 kg of m-cresol (manufactured by Honshu Chemical Industry Co., Ltd.), 7.940 kg of 1,4-DAB (manufactured by Thermo Fisher), and 6FDA (Yakuko Tsusho Co., Ltd.) 40.120 kg, and then, add 3.428 kg of isoquinoline (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.), raise the temperature to 158°C, stir for 5 hours, and then add 74.49 kg of m-cresol , and the obtained reaction solution was cooled to 50°C. While stirring, 118.97 kg of Solmix AP-1 (manufactured by Nippon Alcohol Sales Co., Ltd.) was added, and 356.91 kg of Solmix AP-1 was added, followed by filtration . Use Solmix (Solmix) AP-1 (70.62 kg) to wash the filtered precipitate, and then use Solmix (Solmix) AP-1 (141.23 kg) to carry out 4 times of suspension filtration, use drying Dry the precipitate at 70° C. for 96 hours to obtain 39.97 kg of polyimide-based resin. The weight average molecular weight (Mw) of the produced polyimide-type resin was 252,000, and the imidization rate was 99.9%.

(Example 1) The polyimide-based resin obtained in Synthesis Example 1 was dissolved in cyclohexanone so that the solid content concentration became 15% by mass, and 2 phr of Smithsonian was added as an ultraviolet absorber (ultraviolet light absorber, UVA). Sumisorb 340, preparation of varnishes. The viscosity of the varnish is 26 Pa·s. Next, the obtained varnish was coated on a glass substrate, heated at 140° C. for 10 minutes, and then heated at 200° C. for 30 minutes, and peeled off from the glass substrate to obtain an optical film with a thickness of 25 μm. The residual solvent amount of the obtained optical film was 1.2% by mass.

(Example 2) The polyimide-based resin obtained in Synthesis Example 1 was dissolved in cyclohexanone so that the solid content concentration became 15% by mass, and 2 phr of Sumisorb was added as an ultraviolet absorber (UVA) 340. Next, silica (product name: CHO-ST-M, manufacturer: Nissan Chemical Co., Ltd., average primary particle diameter: 22 nm) was added so as to become 20% by mass based on the polyimide resin, and prepared varnish. The viscosity of the varnish is 10 Pa·s. The obtained varnish was coated on a glass substrate, heated at 140° C. for 10 minutes, and then heated at 200° C. for 30 minutes, and peeled off from the glass substrate to obtain an optical film with a thickness of 25 μm. The residual solvent amount of the obtained optical film was 1.5% by mass. In addition, content of silicon dioxide was 16.4 mass % with respect to the mass of an optical film.

(comparative example 1) Polyimide resin (hereinafter also referred to as PI) (“KPI-MX300F”, manufactured by Kawamura Sangyo Co., Ltd.) was dissolved in DMAc so that the solid content concentration became 12% by mass to prepare a varnish. The varnish was coated on a glass substrate, heated at 140° C. for 10 minutes, and then heated at 200° C. for 20 minutes, and peeled off from the glass substrate to obtain an optical film with a thickness of 30 μm. The residual solvent amount of the obtained optical film was 1.5% by mass.

Table 1 shows the evaluation results of physical properties and gas barrier properties of the optical films obtained in Examples and Comparative Examples. [Table 1] resin Photoelastic coefficient (×10 ^-12 Pa ^-1 ) Light transmittance (%) CME (60℃90%RH/ppm) Water absorption (%) Solvent content (mass%) Tg (°C) Tensile strength (MPa) Film thickness (μm) Transparency 350 nm 500 nm Water vapor (g/m ² /24 hr/0.1 mm) Oxygen (cc(NTP)/m ² /24 h/0.1 mm/atm) Example 1 6FDA-DAB 39.4 1.1 90.5 26 1.9 1.2 181 90 25 37 850 Example 2 6FDA-DAB 26.6 1.1 90.7 28 1.9 1.5 200 110 25 37 690 Comparative example 1 Aromatic PI 58.8 1.0 90.5 10 1.1 1.5 >300 150 30 536.6 15,000

As shown in Table 1, the optical films of Example 1 and Example 2 having a small photoelastic coefficient had low water vapor permeability and oxygen permeability, and were excellent in gas barrier properties. In addition, the light transmittance at 350 nm is low, and the ultraviolet cutoff property is also excellent. Therefore, it turns out that the optical film of Example 1 and Example 2 is an optical film excellent in both ultraviolet cut property and gas barrier property.

Claims (13)

An optical film comprising a polyimide-based resin having constituent units derived from aliphatic diamine, having a light transmittance of 10% or less at 350 nm, and a photoelastic coefficient of 50×10 ^-12 Pa ^-1 or less. The optical film according to claim 1, wherein the coefficient of humidity expansion exceeds 10 ppm. The optical film according to claim 1 or 2, wherein the water absorption at 60°C is 2.5% or less. The optical film according to any one of claims 1 to 3, wherein the solvent content is 7.0% by mass or less relative to the mass of the optical film. The optical film according to any one of claims 1 to 4, wherein the light transmittance at 500 nm is above 90%. The optical film according to any one of claims 1 to 5, comprising a filler. The optical film according to any one of claims 1 to 6, wherein the film thickness is not less than 10 μm and not more than 100 μm. The optical film according to any one of claims 1 to 7, wherein the polyimide-based resin has a constituent unit represented by formula (1),

In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, * represents a bond, and the structural unit represented by formula (1) contains a divalent aliphatic group as X. The optical film according to claim 8, wherein the constituent unit represented by the formula (1) contains a structure represented by the formula (2) as Y,

In formula (2), R ² to R ⁷ independently represent a hydrogen atom, an alkyl group with 1 to 6 carbons, an alkoxy group with 1 to 6 carbons, or an aryl group with 6 to 12 carbons, and R ² to R The hydrogen atoms contained in ⁷ can be independently replaced by halogen atoms, and V represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁸ )-, R ⁸ represents a hydrogen atom, or a carbon number that may be substituted by a halogen atom A monovalent hydrocarbon group of 1 to 12, * represents a bond. The optical film according to claim 8 or 9, wherein the polyimide-based resin contains fluorine atoms. A flexible display device comprising the optical film according to any one of Claims 1 to 10. The flexible display device according to claim 11 further includes a polarizing plate. The flexible display device according to claim 11 or 12 further includes a touch sensor.