CN111378279A

CN111378279A - Optical film

Info

Publication number: CN111378279A
Application number: CN201911360991.3A
Authority: CN
Inventors: 增井建太朗; 宫本皓史; 望月胜纪; 杉山纮子; 池内淳一; 片宝蓝
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-12-28
Filing date: 2019-12-24
Publication date: 2020-07-07
Also published as: CN111378130A

Abstract

The present invention addresses the problem of providing an optical film that exhibits excellent elastic modulus while maintaining yield point strain. The solution of the present invention is an optical film comprising a polyamideimide resin having at least structural units represented by the formulae (1) and (2). In the formulas (1) and (2), X represents a 2-valent organic group, Y represents a 4-valent organic group, and Z represents a 2-valent aromatic group having at least 1 substituent selected from the group consisting of an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, and an aryloxy group having 6 to 12 carbon atoms which may have a substituent.

Description

Optical film

Technical Field

The present invention relates to an optical film that can be used as a front panel material of a flexible display device or the like, a flexible display device provided with the optical film, and a polyamideimide resin capable of forming the optical film.

Background

Display devices such as liquid crystal display devices and organic EL display devices have been widely and flexibly used for various applications such as mobile phones and smartwatches. Glass has been conventionally used as a front panel of such a display device, but glass is very rigid and easily broken, and therefore, for example, it is difficult to use the glass as a front panel material of a flexible display device or the like. As one of materials replacing glass, an optical film formed of a polyamideimide resin has been studied (for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2015-521687

Disclosure of Invention

Problems to be solved by the invention

Optical films that can be used as front panel materials for such display devices, particularly flexible display devices, are required to have hard and high rubber properties so as not to cause sagging, cracking, or breaking upon collision with an object, and such properties can be evaluated by the elastic modulus and the yield point strain. However, it has been found through studies by the present inventors that there is generally a trade-off relationship between the elastic modulus and the yield point strain (trade off), and particularly in an optical film comprising a polyamideimide-based resin, the elastic modulus and the yield point strain cannot be sufficiently achieved at the same time.

Accordingly, an object of the present invention is to provide an optical film exhibiting excellent elastic modulus while maintaining yield point strain, a flexible display device including the optical film, and a polyamideimide resin capable of forming the optical film.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above problems can be solved if an optical film contains a polyamideimide resin having at least a structural unit represented by formula (1) and a structural unit represented by formula (2), and have completed the present invention. That is, the present invention includes the following preferred embodiments.

[1] An optical film includes a polyamideimide resin having at least a structural unit represented by formula (1) and a structural unit represented by formula (2).

[ in the formula (1), X represents a 2-valent organic group and Y represents a 4-valent organic group ]

[ in the formula (2), X represents a 2-valent organic group, Z represents a 2-valent aromatic group having at least 1 substituent selected from the group consisting of an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent and an aryloxy group having 6 to 12 carbon atoms which may have a substituent ]

[2] The optical film according to [1], wherein the structural unit represented by the formula (2) contains a group represented by the formula (3) as Z.

[ in the formula (3), R¹Independently represent an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, k and n independently represent an integer of 1 to 4, and when k is 2 or more, R substituted on different aromatic groups¹May be the same or different and represent a chemical bond]

[3] The optical film according to [2], wherein 2 chemical bonds are located at para positions to each other in formula (3).

[4] The optical film according to any one of [1] to [3], wherein the structural unit represented by formula (1) contains a group represented by formula (4) as Y.

[ in the formula (4), R²～R⁷Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R²～R⁷Wherein the hydrogen atoms contained in (A) may be substituted independently of each other by halogen atoms, table VRepresents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁸)-，R⁸Represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and represents a bond]

[5]Such as [4]]Wherein, in the formula (4), V represents a single bond, -O-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-。

[6] The optical film according to any one of [1] to [5], wherein the structural unit represented by formula (1) and/or the structural unit represented by formula (2) contains a group represented by formula (5) as X.

[ in the formula (5), R⁹～R¹⁶Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R⁹～R¹⁶The hydrogen atoms contained in (A) may be substituted independently of each other by halogen atoms, representing a chemical bond]

[7]Such as [2]]～[6]The optical film according to any one of the above items, wherein R in the formula (3)¹Independently represents an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and k and n independently represent 1 or 2.

[8]Such as [2]]～[6]The optical film according to any one of the above items, wherein R in the formula (3)¹Independently of each other, an alkoxy group having 1 to 6 carbon atoms, k represents 1, and n represents 1 or 2.

[9]Such as [2]]～[6]The optical film according to any one of the above items, wherein R in the formula (3)¹Independently of each other, an alkyl group having 1 to 6 carbon atoms, k represents 1, and n represents 1 or 2.

[10] The optical film according to any one of [6] to [9], wherein the formula (5) is represented by formula (6).

[ in formula (6),' represents a chemical bond ]

[11] The optical film according to any one of [1] to [10], having a thickness of 10 to 200 μm.

[12] A flexible display device comprising the optical film according to any one of [1] to [11 ].

[13] The flexible display device according to [12], further comprising a touch sensor.

[14] The flexible display device according to [12] or [13], further comprising a polarizing plate.

[15] A polyamideimide resin having at least a structural unit represented by formula (1) and a structural unit represented by formula (2),

the structural unit represented by formula (2) contains a group represented by formula (3) as Z.

[ in the formula (3), R¹Independently represent an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituentOr an aryl group having 6 to 12 carbon atoms which may have a substituent, wherein k and n independently represent an integer of 1 to 4, and when k is 2 or more, R is substituted on different aromatic groups¹May be the same or different and represent a chemical bond]

ADVANTAGEOUS EFFECTS OF INVENTION

The optical film of the present invention not only maintains yield point strain, but also exhibits excellent elastic modulus. Therefore, the optical film of the present invention can be used for a front panel of a flexible display device or the like.

Detailed Description

[ optical film ]

The optical film of the present invention contains a polyamideimide resin having at least a specific structural unit.

< Polyamide-imide resin >

The polyamide-imide resin contained in the optical film of the present invention has at least a structural unit represented by formula (1) and a structural unit represented by formula (2).

In the optical film of the present invention, since the polyamideimide resin has such a specific structural unit, particularly, the structural unit represented by formula (2) in which Z is a specific 2-valent aromatic group having an electron-donating group, the elastic modulus and the yield point strain can be increased, and an excellent elastic modulus and an excellent yield point strain can be simultaneously achieved.

In the formulae (1) and (2), X independently represents a 2-valent organic group, preferably a 2-valent organic group having 4 to 40 carbon atoms, and more preferably a 2-valent organic group having 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. The organic group may have hydrogen atoms substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. The polyamideimide resin according to an embodiment of the present invention may include a plurality of kinds of X, and the plurality of kinds of X may be the same or different. Examples of X may include groups represented by formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); a group obtained by substituting a hydrogen atom in the groups represented by the formulae (10) to (18) with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In the formulae (10) to (18), represents a bond,

V¹、V²and V³Independently of each other, represents a single bond, -O-, -S-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -CO-or-N (Q) -. Wherein Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methylbutyl group, 3-methylbutyl group, 2-ethylpropyl group, n-hexyl group, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group, and the like, which may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

1 is provided withExamples are: v¹And V³Is a single bond, -O-or-S-, and, V²is-CH₂-、-C(CH₃)₂-、-C(CF₃)₂-or-SO₂-。V¹And V²Bonding position with respect to each ring, and V²And V³The bonding position to each ring is preferably meta-or para-position, more preferably para-position, to each ring.

Among the groups represented by formulae (10) to (18), the groups represented by formulae (13), (14), (15), (16) and (17) are preferable, and the groups represented by formulae (14), (15) and (16) are more preferable, from the viewpoint of easily improving the elastic modulus, optical characteristics, surface hardness and bending resistance of the optical film. In addition, from the viewpoint of easily improving the elastic modulus, yield point strain, surface hardness and bending resistance of the optical film, V¹、V²And V³Independently of one another, are preferably single bonds, -O-or-S-, more preferably single bonds or-O-.

In a preferred embodiment of the present invention, the structural unit represented by formula (1) and/or the structural unit represented by formula (2) contains a group represented by formula (5) as X.

That is, in the plurality of xs in the formula (1) and/or the formula (2), at least a part of xs is a group represented by the formula (5). In this manner, the optical film easily exhibits excellent elastic modulus, optical characteristics, surface hardness, and bending resistance. The structural unit represented by formula (1) and/or the structural unit represented by formula (2) may contain 1 or more groups represented by formula (5) as X.

In the formula (5), R⁹、R¹⁰、R¹¹、R¹²、R¹³、R¹⁴、R¹⁵And R¹⁶Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 2-ethylpropyl group, and an n-hexyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy, ethoxy, propyloxy, isopropyloxy, butoxy, isobutyloxy, tert-butoxy, pentyloxy, hexyloxy, cyclohexyloxy, and the like. 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. In these, R⁹～R¹⁶Independently of each other, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R⁹～R¹⁶The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. R is a group of values which facilitate improvement in the elastic modulus, optical characteristics, surface hardness and bending resistance of the optical film⁹～R¹⁶Further preferred are, independently of one another, a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; even more preferably R⁹、R¹⁰、R¹²、R¹⁴、R¹⁵And R¹⁶Is a hydrogen atom, R¹¹And R¹³Is hydrogen atom, methyl, fluoro, chloro or trifluoromethyl; among them, R is preferred¹¹And R¹³Is methyl or trifluoromethyl.

In a preferred embodiment of the present invention, formula (5) is represented by formula (6).

[ in formula (6),' represents a chemical bond ]

That is, the structural unit represented by formula (1) and/or the structural unit represented by formula (2) (preferably, the structural unit represented by formula (1) and the structural unit represented by formula (2)) contains a group represented by formula (6) as X. In this manner, the optical film easily exhibits excellent elastic modulus, optical characteristics, surface hardness, and bending resistance. Further, the fluorine-containing skeleton can improve the solubility of the resin in a solvent, and the viscosity of the resin varnish can be reduced to a low level, thereby facilitating the processing of the optical film. The structural unit represented by formula (1) and/or the structural unit represented by formula (2) may contain 1 or more groups represented by formula (6) as X.

In a preferred embodiment of the present invention, the proportion of the group represented by formula (5), particularly formula (6), which is contained as X in formula (1) and/or formula (2) is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, and preferably 100 mol% or less, relative to the molar amount of the structural unit represented by formula (1) and/or the structural unit represented by formula (2). When the ratio of the group represented by formula (5), particularly formula (6), included as X in formula (1) and/or formula (2) is in the above range, excellent elastic modulus, yield point strain, optical characteristics, surface hardness, and bending resistance are easily exhibited, and the solubility of the resin in a solvent can be improved by the fluorine element-containing skeleton, the viscosity of the resin varnish can be suppressed to a low level, and the optical film can be easily processed. The ratio of the group represented by the formula (5), particularly the formula (6) contained as X in the formula (1) and/or the formula (2) can be, for example, used¹H-NMR was measured, or it was calculated from the charge ratio of the raw materials.

In the formula (1), Y independently represents a 4-valent organic group, preferably a 4-valent organic group having 4 to 40 carbon atoms, and more preferably a 4-valent organic group having 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. The organic group is an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. The polyamideimide resin according to one embodiment of the present invention may include a plurality of kinds of Y, and the plurality of kinds of Y may be the same or different. Examples of Y include groups represented by the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29); a group obtained by substituting a hydrogen atom in the group represented by the formulae (20) to (29) with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having a valence of 4 and 6 or less carbon atoms.

In the formulae (20) to (29),

the symbol represents a chemical bond,

W¹represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-Ar-、-SO₂-、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂-Ar-、-Ar-C(CH₃)₂-Ar-or-Ar-SO₂-Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and specific examples thereof include phenylene groups.

Among the groups represented by formulae (20) to (29), the group represented by formula (26), formula (28) or formula (29) is preferable, and the group represented by formula (26) is more preferable, from the viewpoint of easily improving the elastic modulus, yield point strain, optical characteristics, surface hardness and bending resistance of the optical film. In addition, from the viewpoint of easily improving the elastic modulus, optical characteristics, surface hardness and bending resistance of the optical film, W¹Independently of one another, are preferably single bonds, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-, more preferably a single bond, -O-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-is more preferably a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-。

In a preferred embodiment of the present invention, the structural unit represented by formula (1) contains a group represented by formula (4) as Y.

[ in the formula (4), R²～R⁷Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R²～R⁷Wherein the hydrogen atoms contained in (A) may be substituted independently by halogen atoms, and V represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁸)-，R⁸Represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and represents a bond]

That is, at least a part of Y in the plurality of Y in the formula (1) is a group represented by the formula (4). In this manner, the optical film easily exhibits excellent elastic modulus, optical characteristics, surface hardness, and bending resistance. The structural unit represented by formula (1) may contain 1 or more groups represented by formula (4) as Y.

In the formula (4), R²、R³、R⁴、R⁵、R⁶And R⁷Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include those exemplified above as the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms in the formula (5). R²～R⁷Independently of each other, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R²～R⁷The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. Examples of the halogen atom include a fluorine atomChlorine atom, bromine atom, iodine atom. V represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁸)-，R⁸Represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom include V in the formulae (14) to (16)¹、V²And V³Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom are as exemplified above. Among these, V is preferably a single bond, -O-, -CH-from the viewpoint of easily improving the elastic modulus, optical characteristics, surface hardness and bending resistance of the optical film₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-, more preferably a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-, more preferably a single bond or-C (CF)₃)₂-。

In a preferred embodiment of the present invention, formula (4) is represented by formula (7a) or formula (7 b).

That is, the structural unit represented by formula (1) includes the structural unit represented by formula (7a) and/or the structural unit represented by formula (7b) as Y. In this manner, the optical film tends to exhibit excellent elastic modulus, yield point strain, optical characteristics, surface hardness, and bending resistance. Further, the fluorine-containing skeleton can improve the solubility of the resin in a solvent, and the viscosity of the resin varnish can be reduced to a low level, thereby facilitating the processing of the optical film. The plural Y in the formula (1) may contain 1 or more kinds of the structural units represented by the formula (7a) or the formula (7 b).

In a preferred embodiment of the present invention, the ratio of the group represented by formula (4), particularly formula (7a) and/or formula (7b), contained as Y in formula (1) is relative to the junction represented by formula (1)The molar amount of the constituent unit is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more, and preferably 100 mol% or less. When the ratio of the group represented by formula (4), particularly formula (7a) and/or formula (7b), included as Y in formula (1) is in the above range, the optical film tends to exhibit excellent elastic modulus, yield point strain, optical characteristics, surface hardness, and bending resistance. Further, the fluorine-containing skeleton can improve the solubility of the resin in a solvent, and the viscosity of the resin varnish can be reduced to a low level, thereby facilitating the processing of the optical film. The proportion of the group represented by the formula (4) contained as Y in the formula (1) can be, for example, used¹H-NMR was measured, or it was calculated from the charge ratio of the raw materials.

In the formula (2), Z represents a 2-valent aromatic group having at least 1 substituent selected from the group consisting of an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent and an aryloxy group having 6 to 12 carbon atoms which may have a substituent. In the optical film of the present invention, Z in the structural unit constituting the polyamideimide resin, particularly in the formula (2), is such a specific 2-valent aromatic group having an electron donating group, and therefore, the elastic modulus and the yield point strain can be improved. The 2-valent aromatic group means a 2-valent monocyclic aromatic group, a 2-valent condensed polycyclic aromatic group, or a 2-valent ring-assembled aromatic group. The 2-valent aromatic group is preferably a 2-valent aromatic group having 5 to 40 carbon atoms. The polyamideimide resin in one embodiment of the present invention may include 1 or more kinds of Z, and the plural kinds of Z may be the same or different from each other.

The 2-valent monocyclic aromatic group includes a 2-valent group obtained by removing 2 hydrogen atoms from carbon atoms constituting a monocyclic aromatic hydrocarbon ring such as a benzene ring, preferably a monocyclic aromatic hydrocarbon ring having 6 to 15 carbon atoms; and 2-valent groups obtained by removing 2 hydrogen atoms directly bonded to carbon atoms or heteroatoms constituting a monocyclic aromatic heterocyclic ring containing at least 1 heteroatom selected from a sulfur atom, a nitrogen atom and an oxygen atom (preferably a monocyclic aromatic heterocyclic ring having 5 to 15 carbon and heteroatoms, for example, a pyridine ring, a diazepine ring, a triazine ring, a furan ring, a thiophene ring, a pyrrole ring, a diazole ring, a triazole ring, an oxazole ring, an oxadiazole ring, a thiazole ring, a thiadiazole ring, etc.).

Examples of the 2-valent condensed polycyclic aromatic group include 2-valent groups obtained by removing 2 hydrogen atoms from carbon atoms constituting a condensed polycyclic aromatic hydrocarbon ring such as a naphthalene ring, an anthracene ring, or a phenanthrene ring, preferably a condensed polycyclic aromatic hydrocarbon ring having 10 to 25 carbon atoms; and 2-valent groups obtained by removing 2 hydrogen atoms directly bonded to carbon atoms or hetero atoms constituting a condensed polycyclic aromatic heterocycle containing at least 1 hetero atom selected from a sulfur atom, a nitrogen atom and an oxygen atom (preferably a condensed polycyclic aromatic heterocycle having 8 to 25 carbon and hetero atoms, for example, an azanaphthalene ring, a naphthyridine ring, a carbazole ring, a dibenzofuran ring, a dibenzothiophene ring, a dibenzosilacyclopentadiene ring (dibenzosilole), a phenoxazine ring, a phenothiazine ring, an acridine ring, a dihydroacridine ring, etc.). The monocyclic aromatic hydrocarbon ring and the monocyclic aromatic heterocyclic ring are collectively referred to as a monocyclic aromatic ring, and the condensed polycyclic aromatic hydrocarbon ring and the condensed polycyclic aromatic heterocyclic ring are collectively referred to as a condensed polycyclic aromatic ring.

The 2-valent ring-aggregated aromatic group represents a 2-valent group obtained by removing 2 hydrogen atoms directly bonded to a carbon atom or a heteroatom constituting a ring-aggregated aromatic ring (preferably a ring-aggregated aromatic ring having 10 to 40 carbon and heteroatom atoms) formed by connecting monocyclic aromatic rings and/or condensed polycyclic aromatic rings by a single bond. The 2-valent ring-aggregated aromatic group may be composed of 1 or more monocyclic aromatic rings, 1 or more condensed polycyclic aromatic rings, or a combination of these groups. Specifically, the 2-valent ring-aggregated aromatic group includes a 2-valent group obtained by removing 2 hydrogen atoms directly bonded to a carbon atom or a heteroatom constituting a ring-aggregated aromatic ring such as a biphenyl ring, a bipyridine ring, a phenylnaphthyl ring, a terphenyl ring, or a terpyridine ring.

Among the aromatic groups having a valence of 2, from the viewpoint of easy improvement in elastic modulus, yield strain, optical properties, surface hardness and water resistance, a monocyclic aromatic group having a valence of 2 or a ring-assembled aromatic group having a valence of 2 is preferable, and a monocyclic aromatic group having a valence of 2 such as a phenylene group is more preferable.

The 2-valent aromatic group in Z in the formula (2) has at least 1 substituent (sometimes referred to as substituent A) selected from the group consisting of an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent, and an aryloxy group having 6 to 12 carbon atoms which may have a substituent. When the 2-valent aromatic group has a plurality of substituents a, the aromatic group may have a plurality of the same or different substituents a. It is preferable to have a plurality of the same substituent groups a from the viewpoint of easily improving the elastic modulus, yield point strain, optical characteristics, surface hardness and water resistance of the optical film, and solubility in a solvent. The number of the substituent A contained in the 2-valent aromatic group may be appropriately selected depending on the kind of the aromatic group, and is, for example, 1 to 8, preferably 1 to 6, more preferably 1 to 4, further preferably 1 to 3, and particularly preferably 1 or 2, from the viewpoint of easily improving the elastic modulus, yield strain, optical characteristics, surface hardness, and water resistance of the optical film.

Examples of the alkyl group having 1 to 12 carbon atoms in Z in formula (2) include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methylbutyl, 3-methylbutyl, 2-ethylpropyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, and n-decyl groups. The alkyl group having 1 to 12 carbon atoms may have a substituent (sometimes referred to as substituent B). The substituent B is not particularly limited, and examples thereof include a halogen atom such as a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom; cycloalkyl groups such as cyclopentyl and cyclohexyl; an aryl group exemplified as an aryl group having 6 to 12 carbon atoms described later; an aryloxy group having 6 to 12 carbon atoms described later; aralkyl groups such as benzyl; an alkoxy group exemplified by an alkoxy group having 1 to 12 carbon atoms described later; aralkyloxy such as benzyloxy; alkylthio groups such as methylthio and ethylthio; cycloalkylthio groups such as cyclohexylthio; arylthio groups such as phenylthio (thiophenoxy); aralkylthio groups such as benzylthio; acyl groups such as acetyl; a nitro group; cyano, and the like. Among the alkyl groups having 1 to 12 carbon atoms which may have the substituent(s) B, the alkyl groups having 1 to 6 carbon atoms which may have a substituent(s) are preferable, the alkyl groups having 1 to 4 carbon atoms which may have a substituent(s) are more preferable, and the methyl or ethyl groups which may have a substituent(s) are even more preferable, from the viewpoint of easily improving the elastic modulus, yield strain, optical characteristics, surface hardness and water resistance of the optical film. The alkyl group having 1 to 12 carbon atoms which may have a substituent may be used alone or in combination of two or more.

In Z in formula (2), examples of the alkoxy group having 1 to 12 carbon atoms include methoxy, ethoxy, propyloxy, isopropyloxy, butoxy, isobutyloxy, tert-butoxy, pentyloxy, hexyloxy, octyloxy, 2-ethylhexyloxy, nonyloxy, decyloxy, undecyloxy, dodecyloxy, cyclohexyloxy, and the like. The alkoxy group having 1 to 12 carbon atoms may have a substituent. The substituent is not particularly limited, and examples thereof include the alkyl group having 1 to 12 carbon atoms; the same examples as those of the substituent B are given. Among the alkoxy groups having 1 to 12 carbon atoms which may have a substituent, from the viewpoint of easily improving the elastic modulus, yield strain, optical characteristics, surface hardness and water resistance of the optical film, the alkoxy group having 1 to 6 carbon atoms which may have a substituent is preferable, the alkoxy group having 1 to 4 carbon atoms which may have a substituent is more preferable, and the methoxy group or the ethoxy group which may have a substituent is further preferable. The alkoxy group having 1 to 12 carbon atoms which may have a substituent may be used alone or in combination of two or more.

In Z in the formula (2), examples of the aryl group having 6 to 12 carbon atoms include phenyl, naphthyl, biphenyl and the like. The aryl group having 6 to 12 carbon atoms may have a substituent. The substituent is not particularly limited, and examples thereof include the alkyl group having 1 to 12 carbon atoms; examples of the substituents other than the aryl group having 6 to 12 carbon atoms in the substituent B are the same as those of the substituents described above. Among aryl groups having 6 to 12 carbon atoms which may have a substituent, a phenyl group is preferable from the viewpoint of easily improving the elastic modulus, yield strain, optical characteristics, surface hardness, and water resistance of the optical film. The aryl group having 6 to 12 carbon atoms which may have a substituent may be used alone or in combination of two or more.

In Z in the formula (2), examples of the aryloxy group having 6 to 12 carbon atoms include phenoxy and the like. The aryloxy group having 6 to 12 carbon atoms may have a substituent. The substituent is not particularly limited, and examples thereof include the alkyl group having 1 to 12 carbon atoms; the same examples as those of the substituent B are given. The aryloxy group having 6 to 12 carbon atoms which may have a substituent may be used alone or in combination of two or more.

Z in formula (2) is preferably a 2-valent monocyclic aromatic group or a 2-valent ring-aggregated aromatic group having an alkyl group having 1 to 12 carbon atoms which may have a substituent or an alkoxy group having 1 to 12 carbon atoms which may have a substituent, from the viewpoint of easily obtaining an optical film having excellent elastic modulus, yield strain, optical properties, surface hardness, and water resistance; more preferably a monocyclic aromatic group having a valence of 2, which has an alkoxy group having 1 to 6 carbon atoms which may have a substituent, or an alkyl group having 1 to 6 carbon atoms which may have a substituent.

In a preferred embodiment of the present invention, the structural unit represented by formula (2) contains a group represented by formula (3) as Z.

[ in the formula (3), R¹Independently represent an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, k and n independently represent an integer of 1 to 4, and when k is 2 or moreR substituted on different aromatic groups¹May be the same or different and represent a chemical bond]

That is, in the plural Z in the formula (2), at least a part of Z is a group represented by the formula (3). In this manner, the optical film easily exhibits excellent elastic modulus, yield strain, optical characteristics, surface hardness, and water resistance. The structural unit represented by formula (2) may contain 1 or more groups represented by formula (3) as Z.

R in the formula (3)¹Independently represent an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent. Examples of the alkyl group having 1 to 12 carbon atoms which may have a substituent, the alkoxy group having 1 to 12 carbon atoms which may have a substituent, and the aryl group having 6 to 12 carbon atoms which may have a substituent include the alkyl group having 1 to 12 carbon atoms which may have a substituent, the alkoxy group having 1 to 12 carbon atoms which may have a substituent, and the aryl group having 6 to 12 carbon atoms which may have a substituent, which are exemplified above as Z in the formula (2). Among these, R in the formula (3) is R from the viewpoint of easily improving the elastic modulus, yield point strain, optical characteristics, surface hardness and water resistance of the optical film¹Independently of each other, an alkyl group having 1 to 12 carbon atoms which may have a substituent or an alkoxy group having 1 to 12 carbon atoms which may have a substituent is preferable, and an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms is more preferable.

In the formula (3), k and n independently represent an integer of 1 to 4, and when k is 2 or more, R is substituted on different aromatic groups¹May be the same or different. From the viewpoint of easily improving the elastic modulus, yield point strain, optical characteristics, surface hardness, and water resistance of the optical film, k is preferably an integer of 1 to 3, more preferably 1 or 2, even more preferably 1, and n is preferably an integer of 1 to 3, and more preferably 1 or 2.

In a preferred embodiment of the present invention, in formula (3), R¹Independently of one another represent carbonAn alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and k and n independently represent 1 or 2. In a more preferred embodiment of the present invention, in formula (3), R¹Independently of each other, an alkoxy group having 1 to 6 carbon atoms, k represents 1, and n represents 1 or 2. In a preferred embodiment of the present invention, in formula (3), R¹Independently of each other, an alkyl group having 1 to 6 carbon atoms, k represents 1, and n represents 1 or 2. In this manner, an optical film having further improved water resistance, surface hardness, yield strain, optical characteristics, surface hardness, and water resistance can be easily obtained.

In formula (3), the 2 chemical bonds may be located at the ortho, meta, or para positions with respect to each other, and preferably at the para position with respect to each other. When 2 chemical bonds are in alignment with each other, the elastic modulus and pencil hardness are advantageous, and the polymerizability and the molecular weight are easily improved.

In a preferred embodiment of the present invention, the proportion of the group represented by formula (3) contained as Z in formula (2) is preferably 50 mol% or more, more preferably 60 mol% or more, further preferably 70 mol% or more, and preferably 100 mol% or less, relative to the molar amount of the structural unit represented by formula (2). When the proportion of the structural unit represented by formula (3) is in the above range, the optical film tends to exhibit excellent elastic modulus, yield strain, optical characteristics, surface hardness, and water resistance. The ratio of the groups represented by the formula (3) can be used, for example¹H-NMR was measured, or it was calculated from the charge ratio of the raw materials.

The proportion of the group represented by formula (3) included as Z in formula (2) is preferably 5 mol% or more, more preferably 20 mol% or more, further preferably 40 mol% or more, further more preferably 60 mol% or more, particularly preferably 70 mol% or more, particularly more preferably 80 mol% or more, preferably 99 mol% or less, and more preferably 95 mol% or less, based on the total molar amount of the structural unit represented by formula (1) and the structural unit represented by formula (2). When the proportion of the structural unit represented by formula (2) is not less than the above-described lower limit, the elastic modulus, yield point strain, optical characteristics, surface hardness, and water resistance of the optical film are easily improved, and when it is not more than the above-described upper limit, thickening due to hydrogen bonds between amide bonds in formula (2) is suppressed, the viscosity of the resin varnish can be reduced, and the optical film can be easily produced.

In the polyamideimide resin of the present invention, the proportion of the structural unit represented by the formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol or more, further preferably 1.0 mol or more, particularly preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, further preferably 4.5 mol or less based on 1mol of the structural unit represented by the formula (1). When the proportion of the structural unit represented by formula (2) is not less than the above-described lower limit, the elastic modulus, yield point strain, optical characteristics, surface hardness, and water resistance of the optical film are easily improved, and when it is not more than the above-described upper limit, thickening due to hydrogen bonds between amide bonds in formula (2) is suppressed, the viscosity of the resin varnish can be reduced, and the optical film can be easily produced.

In one embodiment of the present invention, the polyamideimide resin of the present invention may include a structural unit represented by formula (8).

[ in the formula (8), K and L independently represent a 2-valent organic group ]

In formula (8), L is independently a 2-valent organic group, and can be selected from the same groups as the 2-valent organic group of X in formula (1) and/or formula (2).

In the formula (8), K is independently a 2-valent organic group, preferably a 2-valent organic group having 4 to 40 carbon atoms which may be substituted by a hydrocarbon group having 1 to 8 carbon atoms or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms, and more preferably a 2-valent organic group having 4 to 40 carbon atoms which may be substituted by a hydrocarbon group having 1 to 8 carbon atoms or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms and has a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. Examples of the organic group of K include a group obtained by replacing 2 nonadjacent hydrogen atoms in the chemical bonds of the groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29), and a 2-valent chain hydrocarbon group having 6 or less carbon atoms, and examples of the heterocyclic structure of Z include a group having a thiophene ring skeleton, and from the viewpoint of easily suppressing the yellowness (hereinafter, sometimes referred to as YI value) of the optical film, preferred examples include groups represented by formula (20) to formula (28) and a group having a thiophene ring skeleton.

The organic group of K is more preferably a 2-valent organic group represented by formula (20 '), formula (21'), formula (22 '), formula (23'), formula (24 '), formula (25'), formula (26 '), formula (27'), formula (28 ') and formula (29').

In [ formulae (20 ') to (29'), W¹And as defined in formulas (20) to (29)]

The hydrogen atoms on the ring in the formulae (20) to (29) and (20 ') to (29') may be substituted with a hydrocarbon group having 1 to 8 carbon atoms, a hydrocarbon group having 1 to 8 carbon atoms and substituted with fluorine, an alkoxy group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms and substituted with fluorine.

In the polyamideimide resin, when K in the formula (8) has a structural unit represented by any one of the above-mentioned formulae (20 ') to (29'), particularly when K in the formula (8) has a structural unit represented by the formula (9a) described later, it is preferable that the polyamideimide resin has a structural unit derived from a carboxylic acid represented by the following formula (d1) in addition to the structural unit, from the viewpoint of easily improving the film-forming property of the varnish.

[ in the formula (d1), R^cIndependently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R^dRepresents R^cor-C (═ O) -, denotes a bond]

R^cIn the formula (5), examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms and aryl groups having 6 to 12 carbon atoms. Specific examples of the structural unit (d1) include R^cAnd R^dStructural units each of which is a hydrogen atom (structural units derived from a dicarboxylic acid compound), R^cAre all hydrogen atoms and R^dA structural unit (structural unit derived from a tricarboxylic acid compound) representing — C (═ O) -, and the like.

The polyamideimide resin of the present invention may contain a plurality of K's as K in the formula (8), and the plurality of K's may be the same as or different from each other. Among them, from the viewpoint of easily improving the elastic modulus, yield point strain, optical characteristics, surface hardness and bending resistance of the optical film, it is preferable that the structural unit represented by formula (8) preferably contains a group represented by formula (9a) as K,

[ in the formula (9a), R^aAnd R^bIndependently represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R^aAnd R^bWherein the hydrogen atoms contained in (a) are independently substituted with halogen atoms, A, m and are the same as A, m and x in formula (9), t is an integer of 0 to 4, and u is an integer of 0 to 4]

More preferably, a group represented by the formula (9).

[ formula (9) wherein R¹⁷～R²⁴Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or a C6 to 12 carbon atomAryl of (A), R¹⁷～R²⁴Wherein the hydrogen atoms contained in (A) may be substituted independently by halogen atoms, and A represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)²⁵)-，R²⁵Represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and m is an integer of 0 to 4]

That is, at least a part of the plurality of K in formula (8) is preferably a group represented by formula (9a), more preferably a group represented by formula (9).

In the formula (9a), the chemical bond of each benzene ring may be bonded to any of the ortho-position, meta-position or para-position, preferably may be bonded to the meta-position or para-position, based on-a-. R^aAnd R^bIndependently represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. T and u in the formula (9a) are preferably 0, and when t and/or u is 1 or more, R^aAnd R^bIndependently of each other, the alkyl group preferably has 1 to 6 carbon atoms, and more preferably has 1 to 3 carbon atoms. R in the formula (9a)^aAnd R^bIn the above formula (5), examples of the halogen atom, the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms and an aryl group having 6 to 12 carbon atoms.

T and u in formula (9a) are independently an integer of 0 to 4, preferably an integer of 0 to 2, and more preferably 0 or 1.

In the formulae (9) and (9a), A independently represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)²⁵) From the viewpoint of easily improving the yield point strain, optical characteristics, surface hardness and bending resistance of the optical film, it is preferable to represent-O-or-S-, more preferably-O-. The polyamideimide resin according to one embodiment of the present invention may include a plurality of kinds of a, and the plurality of kinds of a may be the same or different.

In the formula (9), R¹⁷～R²⁴Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include R in the formula (5)⁹～R¹⁶The above examples are exemplified by C1-6 alkyl groups, C1-6 alkoxy groups and C6-12 aryl groups. R is the ratio of the surface hardness to the yield point strain of the optical film, the optical characteristics, and the bending resistance¹⁷～R²⁴Independently of each other, the alkyl group preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a hydrogen atom. Here, R¹⁷～R²⁴The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. R²⁵Represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom include V in the formulae (14) to (16)¹、V²And V³Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom are as exemplified above. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

In the formulae (9) and (9a), when m is an integer of 0 to 4, preferably an integer in the range of 1 to 4, and m is within the above range, the optical film is excellent in elastic modulus, yield strain, optical characteristics, surface hardness, and bending resistance. In the formulae (9) and (9a), when m is preferably an integer in the range of 1 to 3, more preferably 1 or 2, and further preferably 1, and m is in the above range, the optical film is excellent in elastic modulus, yield strain, optical characteristics, surface hardness, and bending resistance, and the raw material availability is excellent. When m is 0, in the formula (9a)u is preferably 0, R in the formula (9)²¹～R²⁴Preferably a hydrogen atom. In addition, the structural unit represented by formula (8) may contain 1 or 2 or more groups represented by formula (9) or formula (9a) as K.

In a preferred embodiment of the present invention, the formula (9) is represented by formula (9') in view of easily improving the elastic modulus, yield point strain, optical characteristics, surface hardness, and bending resistance of the optical film.

That is, the structural unit represented by formula (8) contains the group represented by formula (9') as K.

In one embodiment of the present invention, the proportion of the group represented by formula (9a) or formula (9), particularly formula (9'), which is contained as K in formula (8) is preferably 50 mol% or more, more preferably 60 mol% or more, further preferably 70 mol% or more, and preferably 100 mol% or less, relative to the molar amount of the structural unit represented by formula (8). When the proportion of the structural unit represented by formula (8) is in the above range, the optical film tends to exhibit excellent elastic modulus, yield point strain, optical characteristics, surface hardness, and bending resistance.

In one embodiment of the present invention, when the polyamideimide resin contains the structural unit represented by formula (8), the proportion of the group represented by formula (9a) or formula (9), particularly formula (9'), contained as K in formula (8) is preferably 5 mol% or more, more preferably 8 mol% or more, still more preferably 10 mol% or more, particularly preferably 12 mol% or more, preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, and particularly preferably 30 mol% or less, relative to the total molar amount of the structural unit represented by formula (2) and the structural unit represented by formula (8). When the ratio of the group represented by the formula (9a) or the formula (9), particularly the formula (9') is not less than the above lower limit, the optical film tends to exhibit excellent elastic modulus, yield point strain, optical characteristics, surface hardness and bending resistance, and when the ratio is not more than the above upper limit, the optical film can be inhibited from exhibiting excellent elastic modulus, yield point strain, optical characteristics, surface hardness and bending resistanceThe thickening due to the hydrogen bond between the amide bonds in the formula (8) can reduce the viscosity of the resin varnish, and the optical film can be easily produced. The ratio of the group represented by the formula (9a) or the formula (9) can be used, for example¹H-NMR was measured, or it was calculated from the charge ratio of the raw materials.

In one embodiment of the present invention, when the polyamideimide resin contains the structural unit represented by formula (8), the proportion of the structural unit represented by formula (8) is preferably 0.01 mol or more, more preferably 0.5 mol or more, further preferably 0.1 mol or more, preferably 1mol or less, more preferably 0.5 mol or less, and further preferably 0.3 mol or less, based on 1mol of the total of the structural unit represented by formula (1) and the structural unit represented by formula (2). When the proportion of the structural unit represented by formula (8) is not less than the above-described lower limit, the optical film tends to exhibit excellent elastic modulus, yield point strain, optical characteristics, surface hardness, and bending resistance, and further, thickening due to hydrogen bonds between amide bonds in formula (8) can be suppressed, the viscosity of the resin varnish can be reduced, and the optical film can be easily produced. The proportion of the structural unit represented by the formula (8) can be used, for example¹H-NMR was measured, or it was calculated from the charge ratio of the raw materials.

The polyamideimide resin of the present invention may contain a structural unit represented by formula (30) and/or a structural unit represented by formula (31) in addition to the structural units represented by formulae (1) to (3).

In the formula (30), Y¹Is a 4-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y¹Examples thereof may include groups represented by the formulae (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29), groups in which a hydrogen atom in the groups represented by the formulae (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and chain hydrocarbon groups having 4-valent carbon atoms of 6 or less. As an originalThe polyamideimide resin of one embodiment of the present invention may include a plurality of Y' s¹Plural kinds of Y¹May be the same or different from each other.

In the formula (31), Y²Is a 3-valent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y²Examples thereof include a group obtained by replacing any of the chemical bonds of the groups represented by the above-mentioned formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29) with a hydrogen atom, and a chain hydrocarbon group having 3-valent carbon atoms of 6 or less. The polyamideimide resin, which is one embodiment of the present invention, may include a plurality of Y' s²Plural kinds of Y²May be the same or different from each other.

In the formulae (30) and (31), X¹And X²Independently of one another, are 2-valent organic groups, preferably organic groups in which the hydrogen atoms of the organic groups can be replaced by hydrocarbon groups or fluorine-substituted hydrocarbon groups. As X¹And X²Examples of the "substituent" may include groups represented by the above-mentioned formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); a group obtained by substituting a hydrogen atom in the groups represented by the formulae (10) to (18) with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In one embodiment of the present invention, the polyamideimide resin is composed of the structural units represented by the formulae (1) and (2) and optionally at least 1 structural unit selected from the group consisting of the structural units represented by the formulae (8), (30) and (31). In the polyamideimide resin, the total molar amount of the structural unit represented by formula (1) and the structural unit represented by formula (2) is preferably 80 mol% or more, and more preferably 100 mol% or less, based on the total molar amount of all the structural units represented by formula (1), formula (2), formula (8), formula (30) and formula (31), from the viewpoint of easily improving the elastic modulus, yield point strain, optical characteristics, surface hardness and water resistance of the optical film. The above ratio can be used, for example¹H-NMR measurement, or calculation from the charge ratio of the raw materials。

The weight average molecular weight of the polyamideimide resin is preferably 150,000 or more, more preferably 200,000 or more, further preferably 250,000 or more, further more preferably 300,000 or more, particularly preferably 350,000 or more, preferably 1,000,000 or less, more preferably 800,000 or less, further preferably 700,000 or less, particularly preferably 500,000 or less in terms of polystyrene. When the weight average molecular weight of the polyamideimide resin is not less than the above lower limit, the elastic modulus, yield point strain, surface hardness and bending resistance of the optical film are easily improved, and when it is not more than the above upper limit, the viscosity of the resin varnish can be suppressed to a low level, and the film formation of the optical film is easily performed, and therefore, the processability is good. The weight average molecular weight can be determined by GPC measurement, for example, in terms of standard polystyrene, and can be determined by the method described in examples, for example.

In one embodiment of the present invention, the polyamideimide resin contains a halogen atom. When the polyamideimide resin contains a halogen atom, the YI value of the optical film may be reduced, and high flexibility and high bending resistance tend to be simultaneously achieved. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom, and the like, and a fluorine atom is preferable from the viewpoint of a reduction in the YI value of the optical film, that is, an improvement in transparency, a reduction in water absorption rate, and bending resistance. Specific examples of the fluorine-containing substituent in the polyamideimide resin include a fluorine group and a trifluoromethyl group.

The content of the halogen atom in the polyamideimide resin is preferably 1 to 40% by mass, more preferably 3 to 35% by mass, and even more preferably 5 to 32% by mass, based on the mass of the polyamideimide resin, from the viewpoints of a reduction in YI value, that is, an improvement in transparency, a reduction in water absorption, and bending resistance of the optical film.

In one embodiment of the present invention, the imidization ratio of the polyamideimide resin is preferably 95 to 100%, more preferably 97 to 100%, and still more preferably 98 to 100%. The imidization ratio is preferably not less than the above-described lower limit from the viewpoint of stability of the resin varnish and mechanical properties of the optical film to be obtained. The imidization ratio can be determined by an IR method, an NMR method, or the like.

In one embodiment of the present invention, the polyamideimide resin is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, further preferably 60 parts by mass or more, and preferably 100 parts by mass or less, per 100 parts by mass of the optical film.

In one embodiment of the present invention, the polyamideimide resin can be obtained by reacting (polycondensing) a diamine compound, a tetracarboxylic acid compound, a dicarboxylic acid compound, and, if necessary, a tricarboxylic acid compound. The structural units represented by the formulae (1) and (30) are generally derived from a diamine compound and a tetracarboxylic acid compound. The structural units represented by the formulae (2) and (8) are generally derived from a diamine compound and a dicarboxylic acid compound. The structural unit represented by formula (31) is usually derived from a diamine compound and a tricarboxylic acid compound.

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples of the non-condensed polycyclic aromatic tetracarboxylic acid dianhydride include 4, 4 ' -oxydiphthalic anhydride (4, 4 ' -oxydiphthalic dianhydride), 3, 3 ', 4, 4 ' -benzophenonetetracarboxylic acid dianhydride, 2 ', 3, 3 ' -benzophenonetetracarboxylic acid dianhydride, 3, 3 ', 4, 4 ' -biphenyltetracarboxylic acid dianhydride (sometimes referred to as BPDA), 2 ', 3, 3 ' -biphenyltetracarboxylic acid dianhydride, 3, 3 ', 4, 4 ' -diphenylsulfonetetracarboxylic acid dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4, 4 ' - (hexafluoroisopropylidene) diphthalic anhydride (4, 4 ' - (hexafluoroisopropylidene) dicarboxylic anhydride, which is sometimes referred to as 6FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4 ' - (p-phenylenedioxy) diphthalic anhydride, 4 ' - (m-phenylenedioxy)) diphthalic anhydride. Examples of the monocyclic aromatic tetracarboxylic acid dianhydride include 1, 2, 4, 5-benzenetetracarboxylic acid dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic acid dianhydride include 2, 3, 6, 7-naphthalenetetracarboxylic acid dianhydride.

Of these, preferred examples include 4, 4 '-oxydiphthalic anhydride, 3, 3', 4, 4 '-benzophenonetetracarboxylic dianhydride, 2', 3, 3 '-benzophenonetetracarboxylic dianhydride, 3, 3', 4, 4 '-biphenyltetracarboxylic dianhydride, 2', 3, 3 '-biphenyltetracarboxylic dianhydride, 3, 3', 4, 4 '-diphenylsulfonetetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4, 4' - (hexafluoroisopropylidene) diphthalic anhydride (6FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4, 4 '- (terephthaloxy) bisphthalic anhydride and 4, 4' - (m-phenylenedioxy) bisphthalic anhydride, more preferably 4, 4 '-oxydiphthalic anhydride, 3, 3', 4, 4 '-biphenyltetracarboxylic dianhydride (BPDA), 2', 3, 3 '-biphenyltetracarboxylic dianhydride, 4, 4' - (hexafluoroisopropylidene) bisphthalic anhydride (6FDA), bis (3, 4-dicarboxyphenyl) methane dianhydride and 4, 4' - (p-phenylenedioxy) diphthalic anhydride. These can be used alone or in combination of 2 or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic and acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkanetetracarboxylic dianhydrides such as 1, 2, 4, 5-cyclohexanetetracarboxylic dianhydride, 1, 2, 3, 4-cyclobutanetetracarboxylic dianhydride and 1, 2, 3, 4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3, 5, 6-tetracarboxylic dianhydride, dicyclohexyl-3, 3 ', 4, 4' -tetracarboxylic dianhydride and positional isomers thereof. These may be used alone, or 2 or more of them may be used in combination. Specific examples of the acyclic aliphatic tetracarboxylic acid dianhydride include 1, 2, 3, 4-butanetetracarboxylic acid dianhydride, and 1, 2, 3, 4-pentanedicarboxylic acid dianhydride, and these can be used alone or in combination of 2 or more. In addition, cyclic aliphatic tetracarboxylic dianhydrides and acyclic aliphatic tetracarboxylic dianhydrides may be used in combination.

Among the tetracarboxylic dianhydrides, from the viewpoint of easily improving the elastic modulus, optical characteristics, surface hardness, bending resistance and water resistance of the optical film, preferred are 4, 4 ' -oxydiphthalic dianhydride, 3, 3 ', 4, 4 ' -benzophenone tetracarboxylic dianhydride, 3, 3 ', 4, 4 ' -biphenyl tetracarboxylic dianhydride, 2 ', 3, 3 ' -biphenyl tetracarboxylic dianhydride, 3, 3 ', 4, 4 ' -diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 4, 4 ' - (hexafluoroisopropylidene) diphthalic anhydride and mixtures thereof, and more preferred are 3, 3 ', 4, 4 ' -biphenyl tetracarboxylic dianhydride (BPDA) and 4, 4 ' - (hexafluoroisopropylidene) diphthalic anhydride (6FDA), And mixtures thereof.

Examples of the dicarboxylic acid compound that can be used for the synthesis of the polyamideimide resin include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and the like, and acid chloride compounds and acid anhydrides thereof, and 2 or more kinds thereof may be used in combination. Specific examples thereof include terephthalic acid; isophthalic acid; 2-methoxy terephthalic acid; 2-methyl terephthalic acid; 2, 5-dimethyl terephthalic acid; 2, 5-dimethoxyterephthalic acid; naphthalenedicarboxylic acid; 4, 4' -biphenyldicarboxylic acid; 3, 3' -biphenyldicarboxylic acid; by single bonds, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂Or a compound in which a dicarboxylic acid compound of a chain hydrocarbon having 8 or less carbon atoms and 2 benzoic acids are linked to each other through a phenylene group, and an acid chloride compound thereof. Among these dicarboxylic acid compounds, from the viewpoint of easily improving the elastic modulus, optical properties, surface hardness, bending resistance and water resistance of the optical film,preferred are 4, 4' -oxybis benzoic acid, terephthalic acid, 2-methoxy terephthalic acid, 2-methyl terephthalic acid, 2, 5-dimethyl terephthalic acid, 2, 5-dimethoxy terephthalic acid and their acid chlorides, more preferred are 2-methoxy terephthaloyl chloride (OMTPC), 2, 5-dimethyl terephthaloyl chloride (DMTPC) and 2, 5-dimethoxy terephthaloyl chloride (DMTPC).

The polyamideimide resin may be a product obtained by further reacting tetracarboxylic acid and tricarboxylic acid, their anhydrides and derivatives thereof, in addition to the tetracarboxylic acid compound usable in the synthesis of the polyamideimide resin, within a range that does not impair various physical properties of the optical film.

Examples of the other tetracarboxylic acid include water adducts of anhydrides of the above tetracarboxylic acid compounds.

Examples of the tricarboxylic acid compound include an aromatic tricarboxylic acid, an aliphatic tricarboxylic acid, and a similar acid chloride compound or acid anhydride thereof, and 2 or more kinds thereof may be used in combination. Specific examples thereof include 1, 3, 5-benzenetricarboxylic acid and acid chlorides thereof, anhydrides of 1, 2, 4-benzenetricarboxylic acid; 2, 3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; by single bonds, -O-, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂Or phenylene linking phthalic anhydride to benzoic acid.

Examples of the diamine compound that can be used for synthesizing the polyamideimide resin include aliphatic diamines, aromatic diamines, and mixtures thereof. In this embodiment, the "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or another substituent in a part of the structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited thereto. Of these, benzene rings are preferred. The "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituent in a part of the structure.

Examples of the aliphatic diamine include acyclic aliphatic diamines such as 1, 6-hexamethylenediamine, and cyclic aliphatic diamines such as 1, 3-bis (aminomethyl) cyclohexane, 1, 4-bis (aminomethyl) cyclohexane, norbornanediamine, and 4, 4' -diaminodicyclohexylmethane. These may be used alone, or 2 or more of them may be used in combination.

Examples of the aromatic diamine include aromatic diamines having 1 aromatic ring such as p-phenylenediamine, m-phenylenediamine, 2, 4-tolylenediamine, m-xylylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene and 2, 6-diaminonaphthalene, 4 ' -diaminodiphenylmethane, 4 ' -diaminodiphenylpropane, 4 ' -diaminodiphenyl ether, 3 ' -diaminodiphenyl ether, 4 ' -diaminodiphenyl sulfone, 3 ' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene, 2, 6-diaminonaphthalene, etc., 4 ' -, Bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 ' -dimethylbenzidine, 2 ' -bis (trifluoromethyl) -4, 4 ' -diaminobiphenyl (sometimes referred to as TFMB), aromatic diamines having 2 or more aromatic rings, such as 4, 4' -bis (4-aminophenoxy) biphenyl, 9-bis (4-aminophenyl) fluorene, 9-bis (4-amino-3-methylphenyl) fluorene, 9-bis (4-amino-3-chlorophenyl) fluorene, and 9, 9-bis (4-amino-3-fluorophenyl) fluorene. These can be used alone or in combination of 2 or more.

The aromatic diamine is preferably 4, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 3' -diaminodiphenylether, 4 '-diaminodiphenylsulfone, 3' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4, 4 '-diaminobiphenyl (TFMB), 4' -bis (4-aminophenoxy) biphenyl, more preferably 4, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenyl ether, 4' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4, 4 '-diaminobiphenyl (TFMB), 4' -bis (4-aminophenoxy) biphenyl. These can be used alone or in combination of 2 or more.

Among the diamine compounds, 1 or more selected from the group consisting of aromatic diamines having a biphenyl structure is preferably used from the viewpoint of easily improving the elastic modulus, optical properties, surface hardness, bending resistance, and water resistance of the optical film. More preferably, 1 or more selected from the group consisting of 2, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) benzidine, 4 '-bis (4-aminophenoxy) biphenyl, and 4, 4' -diaminodiphenyl ether is used, and still more preferably, 2 '-bis (trifluoromethyl) -4, 4' -diaminobiphenyl (TFMB) is used.

In the production of the polyamideimide resin, the amount of the diamine compound, the tetracarboxylic acid compound and the dicarboxylic acid compound to be used may be appropriately selected depending on the ratio of each structural unit of the desired polyamideimide resin.

In the production of the resin, the reaction temperature of the diamine compound, the tetracarboxylic acid compound and the dicarboxylic acid compound is not particularly limited, and is, for example, 5 to 350 ℃, preferably 20 to 200 ℃, and more preferably 25 to 100 ℃. The reaction time is also not particularly limited, and is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out in an inert atmosphere or under reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or in an inert gas atmosphere while stirring. The reaction is preferably carried out in a solvent inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include alcohol solvents such as water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ -butyrolactone, γ -valerolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl 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 solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvents). Among these, an amide solvent can be suitably used from the viewpoint of solubility.

The method for producing a polyamideimide resin having at least the above-mentioned structural unit (1) and structural unit (2) is not particularly limited as long as the polyamideimide resin can be obtained, and from the viewpoint of easily improving the elastic modulus and yield strain of the optical film, it is preferable to produce a polyamideimide resin by a production method in which a dicarboxylic acid compound is added in portions and a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compound are reacted, and it is more preferable to produce a polyamideimide resin by a method comprising a step (I) of reacting a diamine compound and a tetracarboxylic acid compound to produce an intermediate (a), a step (II) of reacting the intermediate (a) and a dicarboxylic acid compound, and adding the dicarboxylic acid compound in portions in the step (II). In the case of using the method of adding the dicarboxylic acid compound in portions, although the reason is not clear, it is considered that a resin optimal for improving the elastic modulus and yield strain of the optical film can be obtained. In addition, the weight average molecular weight of the polyamideimide resin can be easily adjusted to the above range.

Therefore, the polyamideimide resin contained in the optical film of the present invention and the polyamideimide resin of the present invention are preferably resins obtained by a production method of reacting a diamine compound and a tetracarboxylic acid compound by adding a dicarboxylic acid compound thereto in divided portions, and more preferably resins obtained by a production method of adding a dicarboxylic acid compound to the step (II) in divided portions, wherein the step (II) includes a step (I) of reacting a diamine compound and a tetracarboxylic acid compound to produce an intermediate (a) and a step (II) of reacting the intermediate (a) and a dicarboxylic acid compound.

When the polyamideimide resin is produced by the production method comprising the above-mentioned step (I) and step (II), the reaction temperature of the step (I) of reacting the diamine compound with the tetracarboxylic acid compound to produce the intermediate (a) is not particularly limited, and may be, for example, 5 to 200 ℃, preferably 5 to 100 ℃, more preferably 5 to 50 ℃, and still more preferably 5 to 25 ℃. The reaction time may be, for example, 1 minute to 72 hours, preferably 10 minutes to 24 hours. The reaction may be carried out in air or under an inert gas atmosphere (e.g., nitrogen, argon, etc.) with stirring, or may be carried out under normal pressure, under increased pressure, or under reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or in an inert gas atmosphere while stirring.

In the step (I), the diamine compound reacts with the tetracarboxylic acid compound to produce the intermediate (a), i.e., polyamic acid. Therefore, the intermediate (a) has at least a structural unit derived from a diamine compound and a structural unit derived from a tetracarboxylic acid compound.

Next, in the step (II), the intermediate (a) is reacted with a dicarboxylic acid compound, and here, the dicarboxylic acid compound is preferably added in portions. The intermediate (a) is reacted with a dicarboxylic acid compound by adding the dicarboxylic acid compound to the reaction solution obtained in the step (I) in portions. The weight average molecular weight of the polyamideimide resin can be easily adjusted to the above-mentioned preferred range by adding the dicarboxylic acid compound in divided portions rather than in one portion. In the present specification, the term "divided addition" means that the dicarboxylic acid compound to be added is added in several divided portions, and more specifically, the dicarboxylic acid to be added is divided into specific amounts and added separately at predetermined intervals or for predetermined time. Since the prescribed interval or prescribed time also includes a very short interval or time, the divided addition also includes continuous addition or continuous feeding.

In the step (II), the number of times of adding the dicarboxylic acid compound in portions may be appropriately selected depending on the scale of the reaction, the kind of the raw material, and the like, and is preferably 2 to 20 times, more preferably 3 to 10 times, and still more preferably 3 to 6 times.

The dicarboxylic acid compound may be added in an equal amount or in an unequal amount. The time between the addition behaviors (hereinafter, sometimes referred to as an addition interval) may be the same or different. In addition, in the case of adding two or more dicarboxylic acid compounds, the term "divided addition" means adding all the dicarboxylic acid compounds in a divided manner, and the dividing manner of each dicarboxylic acid compound is not particularly limited, and for example, each dicarboxylic acid compound may be added together or divided, or a combination thereof may be used.

In the step (II), the dicarboxylic acid compound is preferably added in an amount of 1 to 40 mol%, more preferably 2 to 25 mol%, based on the total molar amount of the dicarboxylic acid compound to be added, at a time point when the weight average molecular weight of the polyamideimide resin is preferably 10% or more, more preferably 15% or more, based on the weight average molecular weight of the polyamideimide resin to be obtained.

The reaction temperature in the step (II) is not particularly limited, and may be, for example, 5 to 200 ℃, preferably 5 to 100 ℃, more preferably 5 to 50 ℃, and still more preferably 5 to 25 ℃. The reaction may be carried out in air or an inert gas atmosphere such as nitrogen or argon while stirring, or may be carried out under normal pressure, under increased pressure or under reduced pressure. In a preferred embodiment, the step (II) is performed under normal pressure and/or under the inert gas atmosphere while stirring.

In the step (II), the dicarboxylic acid compound is added in portions, and then the mixture is reacted by stirring for a predetermined time, whereby a polyamideimide precursor can be obtained. The polyamideimide precursor may be isolated, for example, by: the polyamideimide precursor is precipitated by adding a large amount of water or the like to a reaction liquid containing the polyamideimide precursor, followed by filtration, concentration, drying, and the like.

In the step (II), the intermediate (A) is reacted with a dicarboxylic acid compound to obtain a polyamideimide precursor. Accordingly, the polyamideimide precursor means a polyamideimide having at least a structural unit derived from a diamine compound, a structural unit derived from a tetracarboxylic acid, and a structural unit derived from a dicarboxylic acid compound before imidization (before ring closure).

The method for producing a polyamideimide resin may further include the step (III) of imidizing the polyamideimide precursor in the presence of an imidization catalyst. By subjecting the polyamideimide precursor obtained in the step (II) to the step (III), a structural unit having a polyamic acid structure in a structural unit of the polyamideimide precursor can be partially imidized (ring-closed), and a polyamideimide resin containing a structural unit represented by the formula (1) and a structural unit represented by the formula (2) can be obtained. Examples of the imidization catalyst include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; n-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepino

Alicyclic amines (monocyclic); azabicyclo [2.2.1]Heptane, azabicyclo [3.2.1]Octane, azabicyclo [2.2.2]Octane, and azabicyclo [3.2.2]Alicyclic amines (polycyclic) such as nonane; and aromatic amines such as pyridine, 2-methylpyridine (2-picoline), 3-methylpyridine (3-picoline), 4-methylpyridine (4-picoline), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-dimethylpyridine, 2, 4, 6-trimethylpyridine, 3, 4-cyclopentenopyridine, 5, 6, 7, 8-tetrahydroisoquinoline, and isoquinoline. In addition, from the viewpoint of facilitating the imidization reaction, it is preferable to use not only the imidization catalyst but also an acid anhydride. Examples of the acid anhydride include conventional acid anhydrides usable in the imidization reaction, 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.

The polyamide-imide resin can be separated (separated and purified) by a conventional method, for example, separation means such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or separation means combining these, and in a preferred embodiment, the separation can be carried out by: a large amount of an alcohol such as methanol is added to a reaction solution containing a polyamideimide resin to precipitate the resin, followed by concentration, filtration, drying, and the like.

< additives >

The optical film of the present invention may contain additives. The additive is appropriately selected depending on the application of the optical film, and examples thereof include a filler such as silica particles, a leveling agent, an antioxidant, an ultraviolet absorber, a bluing agent, a plasticizer, and a surfactant. These additives may be used alone or in combination of two or more. When the optical film contains the additive, the content of the additive is, for example, about 0.001 to 60 parts by mass, preferably about 0.1 to 40 parts by mass, and more preferably about 0.2 to 20 parts by mass, per 100 parts by mass of the optical film.

< optical film >

The optical film of the present invention comprises the structural unit represented by formula (1) and the structural unit represented by formula (2), and particularly the structural unit represented by formula (2) in which Z is a 2-valent aromatic group having a specific electron-donating group, and therefore, the elastic modulus and the yield point strain can be improved. Thus, a high elastic modulus and a high yield point strain can be obtained, and therefore, even if an impact is applied to the object, for example, the occurrence of a sink defect, a crack, a fracture, or the like can be effectively suppressed. In addition, the optical film of the present invention has excellent optical characteristics. Therefore, the optical film of the present invention can be suitably used as a flexible display device. In the present specification, the optical properties include, for example, total light transmittance (hereinafter, sometimes referred to as Tt), YI value, haze and the like, and the optical properties are optically evaluated, and the "optical property improvement" includes, for example: tt becomes higher, YI value becomes lower, and haze becomes lower.

The thickness of the optical film of the present invention can be suitably adjusted depending on the application, and is preferably 10 μm or more, more preferably 20 μm or more, further preferably 30 μm or more, preferably 100 μm or less, more preferably 80 μm or less, further preferably 65 μm or less, and particularly preferably 55 μm or less. The thickness of the optical film can be measured by a film thickness meter or the like, and can be measured by the method described in examples, for example.

In one embodiment of the present invention, the optical film of the present invention has a Tt of preferably 80% or more, more preferably 85% or more, further preferably 90% or more, and usually 100% or less. When Tt is equal to or higher than the above lower limit, transparency becomes good, and it can contribute to high visibility when applied to a front panel of a display device, for example. Tt may be within the above thickness range of the optical film. Further, Tt may be measured according to JIS K7105: 1981. the haze can be measured by using a haze computer, for example, by the method described in examples.

In one embodiment of the present invention, the haze of the optical film of the present invention is preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% or less, particularly preferably 0.5% or less, particularly more preferably 0.3% or less, and usually 0.01% or more. When the haze of the optical film is not more than the above upper limit, the transparency becomes good, and for example, when the optical film is applied to a front panel of a display device, the optical film can contribute to high visibility. The haze can be measured, for example, according to JIS K7136: 2000. the haze can be measured by using a haze computer, for example, by the method described in examples.

In one embodiment of the present invention, the YI value of the optical film of the present invention is preferably 8 or less, more preferably 5 or less, further preferably 3 or less, particularly preferably 2.5 or less, particularly preferably 2 or less, and usually-5 or more, preferably-2 or more, and when the YI value of the optical film is not more than the above upper limit, the optical film has good transparency and contributes to high visibility when applied to a front panel of a display device, for example, and the YI value can be calculated by measuring the transmittance to light of 300 to 800nm using an ultraviolet-visible near infrared spectrophotometer according to JIS K7373: 2006 to obtain the tristimulus value (X, Y, Z) and calculating the YI value based on the formula of YI 100 × (1.2769X-1.0592Z)/Y, for example, by the method described in examples.

In one embodiment of the present invention, the elastic modulus at 25 ℃ of the optical film of the present invention is preferably 5.0GPa or more, more preferably 5.5GPa or more, further preferably 6.0GPa or more, particularly preferably 6.5GPa or more, and usually 15GPa or less. When the elastic modulus is not less than the above lower limit, the occurrence of a sink defect or the like in the optical film is easily suppressed. The elastic modulus can be measured using a tensile tester, and can be measured, for example, by the method described in examples.

In one embodiment of the present invention, the optical film of the present invention has a yield strain at 25 ℃ of preferably 0.5% or more, more preferably 1.0% or more, still more preferably 1.50% or more, particularly preferably 1.60% or more, particularly preferably 1.62% or more, and usually 5.0% or less. When the yield point strain is not less than the above lower limit, the rubber property is high, and the occurrence of cracking, breaking, or the like of the optical film is easily suppressed. The yield point strain is an index indicating rubber properties or the like, and is a value indicating the strain at the intersection of the stress-strain curve (hereinafter, sometimes referred to as S-S curve) and the intercept of the strain axis with the slope of the region following young' S law measured using a tensile tester, and can be obtained, for example, by the method described in examples.

The use of the optical film of the present invention is not particularly limited, and the optical film can be used for various purposes. As described above, 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 may be used in the form of a laminate with another film. When the optical film is a laminate, all layers including the optical film laminated on one surface or both surfaces thereof are referred to as optical films.

When the optical film of the present invention is a laminate, it is preferable that at least one surface of the optical film has 1 or more functional layers. Examples of the functional layer include an ultraviolet absorbing layer, a hard coat layer, a primer layer, a gas barrier layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer. The functional layers may be used alone or in combination of two or more.

The ultraviolet absorbing layer is a layer having an ultraviolet absorbing function, and is composed of a main material selected from an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, and an ultraviolet absorber dispersed in the main material.

The pressure-sensitive adhesive layer is a layer having a pressure-sensitive adhesive function and has a function of bonding the optical film to another member. As a material for forming the adhesive layer, a generally known material can be used. For example, a thermosetting resin composition or a photocurable resin composition can be used. In this case, the thermosetting resin composition or the photocurable resin composition can be polymerized and cured by supplying energy after the polymerization.

The Pressure-Sensitive Adhesive layer may be a layer called a Pressure-Sensitive Adhesive (PSA) that is pressed and attached to an object. The pressure-sensitive adhesive may be a capsule adhesive as "a substance having adhesiveness at normal temperature and adhering to an adherend under light pressure" (JIS K6800) or as "an adhesive which contains a specific component in a protective film (microcapsule) and can maintain stability until the film is broken by an appropriate means (pressure, heat, or the like)".

The hue adjustment layer is a layer having a hue adjustment function and is a layer capable of adjusting the optical film to a target hue. The hue adjustment layer is, for example, a layer containing a resin and a colorant. Examples of the colorant include inorganic pigments such as titanium oxide, zinc oxide, red iron oxide, titanium oxide-based calcined pigments, ultramarine blue, cobalt aluminate, and carbon black; organic pigments such as azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, perylene-based compounds, isoindolinone-based compounds, phthalocyanine-based compounds, quinophthalone-based compounds, threne-based compounds, and diketopyrrolopyrrole-based compounds; bulk pigments such as barium sulfate and calcium carbonate; and basic dyes, acid dyes, mordant dyes, and the like.

The refractive index adjustment layer is a layer having a function of adjusting the refractive index, and is, for example, a layer having a refractive index different from that of a single optical film and capable of providing a predetermined refractive index to the optical film. The refractive index adjusting layer may be, for example, a resin layer containing an appropriately selected resin and, in some cases, a pigment, or may be a thin film of a metal. Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle diameter of the pigment may be 0.1 μm or less. By setting the average primary particle diameter of the pigment to 0.1 μm or less, diffuse reflection of light transmitted through the refractive index adjustment layer can be prevented, and deterioration in transparency can be prevented. Examples of the metal usable for the refractive index adjustment layer include metal oxides and metal nitrides such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride.

In one embodiment of the present invention, the optical film may have a protective film on at least one side (one side or both sides). For example, in the case where one surface of the optical film has a functional layer, the protective film may be laminated on the surface of the optical film side or the surface of the functional layer side, or may be laminated on both the optical film side and the functional layer side. When the optical film has functional layers on both surfaces thereof, the protective film may be laminated on the surface on one functional layer side or may be laminated on the surfaces on both functional layers. 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 is a peelable film that can protect the surface of the optical film or the functional layer. Examples of the protective film include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; the resin film is preferably selected from the group consisting of polyolefin resin films, polyethylene, polypropylene films and the like, and acrylic resin films. When the optical film has 2 protective films, the protective films may be the same or different.

The thickness of the protective film is not particularly limited, but is usually 10 to 120 μm, preferably 15 to 110 μm, and more preferably 20 to 100 μm. When the optical film has 2 protective films, the thicknesses of the respective protective films may be the same or different.

[ method for producing optical film ]

The optical film of the present invention is not particularly limited, and can be produced, for example, by a method including the following steps:

(a) a step (varnish preparation step) of preparing a liquid (sometimes referred to as a resin varnish) containing the polyamideimide resin;

(b) a step (coating step) of applying a resin varnish to a base material to form a coating film; and the number of the first and second groups,

(c) and a step of drying the applied liquid (coating film) to form an optical film (optical film forming step).

In the varnish preparation step, the polyamide imide resin is dissolved in a solvent, and the additive is added as needed, and stirred and mixed to prepare a varnish.

The solvent that can be used in the preparation of the varnish is not particularly limited as long as the polyamideimide resin can be dissolved. Examples of the solvent include amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; lactone solvents such as γ -butyrolactone (GBL) and γ -valerolactone; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, amide solvents or lactone solvents are preferable. These solvents may be used alone or in combination of two or more. The resin varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The solid content concentration of the varnish is preferably 1 to 25 mass%, more preferably 5 to 15 mass%. In the present specification, the solid content of the varnish refers to the total amount of components remaining after the solvent is removed from the varnish.

In the coating step, a varnish is applied to a 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, comma coating, lip coating, spin coating, screen coating, spray coating, dipping, spraying, and casting.

In the optical film forming step, the coating film is dried and peeled from the substrate, whereby an optical film can be formed. After the peeling, a drying step of drying the optical film may be further performed. The drying of the coating film can be carried out at a temperature of 50 to 350 ℃. If necessary, the coating film may be dried in an inert atmosphere or under reduced pressure.

Examples of the substrate include a PET film, a PEN film, another polyimide resin, a polyamide resin film, and the like. Among them, a PET film, a PEN film, and the like are preferable from the viewpoint of excellent heat resistance, and a PET film is more preferable from the viewpoint of adhesion to an optical film and cost.

[ Flexible display device ]

The present invention includes a flexible display device provided with the optical film of the present invention. The optical film of the present invention is preferably used as a front panel in a flexible display device, and the front panel is sometimes referred to as a window film. The flexible display device includes a laminate for flexible display device and an organic EL display panel, and the laminate for flexible display device is disposed on the viewing side of the organic EL display panel and is configured to be bendable. The laminate for a flexible display device may further include a polarizing plate and a touch sensor, and the lamination order thereof is arbitrary, and it is preferable that a window film, a polarizing plate and a touch sensor are laminated in this order or a window film, a touch sensor and a polarizing plate are laminated in this order from the viewing side. If the polarizing plate is present on the viewing side of the touch sensor, the pattern of the touch sensor is less likely to be observed, and the visibility of the display image is improved, which is preferable. The members may be laminated using an adhesive, or the like. Further, the light-shielding film may include a light-shielding pattern formed on at least one surface of any one of the window film, the polarizing plate, and the touch sensor.

[ polarizing plate ]

As described above, the flexible display device of the present invention preferably further includes a polarizing plate, particularly a circular polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only a right-handed circularly polarized light component or a left-handed circularly polarized light component by laminating a λ/4 phase difference plate on a linearly polarizing plate. For example, can be used for: the external light is converted into right-handed circularly polarized light, the external light reflected by the organic EL panel to become left-handed circularly polarized light is blocked, and only the light emitting component of the organic EL is transmitted, thereby suppressing the influence of reflected light and facilitating the viewing of images. In order to achieve the circularly polarized light function, the absorption axis of the linear polarizer and the slow axis of the λ/4 phase difference plate need to be 45 ° in theory, and 45 ± 10 ° in practical application. The linear polarizing plate and the λ/4 phase difference plate do not have to be laminated adjacent to each other as long as the relationship between the absorption axis and the slow axis satisfies the aforementioned range. It is preferable to completely circularly polarize light at all wavelengths, but it is not essential in practical use, and therefore, the circularly polarizing plate in the present invention also includes an elliptically polarizing plate. It is also preferable that a λ/4 retardation film is further laminated on the viewing side of the linear polarizing plate to convert the emitted light into circularly polarized light, thereby improving visibility in a state where the polarized sunglasses are worn.

The linear polarizing plate is a functional layer having a function of transmitting light vibrating in the transmission axis direction, but blocking polarized light of a vibration component perpendicular thereto. The linear polarizer may be a single linear polarizer or a structure having a linear polarizer and a protective film attached to at least one surface of the linear polarizer. The thickness of the linearly polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness of the linear polarizer is within the above range, the flexibility of the linear polarizer tends to be less likely to decrease.

The linear polarizer may be a film-type polarizer produced by dyeing and stretching a polyvinyl alcohol (hereinafter, abbreviated as PVA) film. Polarizing performance can be exhibited by adsorbing a dichroic dye such as iodine to a PVA-based film that has been oriented by stretching, or by orienting a dichroic dye by stretching the film in a state of being adsorbed to PVA. The film-type polarizer may be produced by swelling, crosslinking with boric acid, washing with an aqueous solution, and drying. The stretching and dyeing step may be performed on the PVA-based film alone or in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA film to be used is preferably 10 to 100 μm, and the stretching ratio is preferably 2 to 10 times.

In addition, another example of the polarizer is a liquid crystal coating type polarizer formed by coating a liquid crystal polarizing composition. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic pigment compound. The liquid crystalline compound may have a property of exhibiting a liquid crystal state, and is preferably capable of exhibiting high polarizing performance if it has a high-order alignment state such as a smectic phase. The liquid crystalline compound preferably has a polymerizable functional group.

The dichroic pigment compound is a pigment which exhibits dichroism by being aligned with the liquid crystal compound, and may have a polymerizable functional group, and the dichroic pigment itself may have liquid crystallinity.

Any of the compounds contained in the liquid crystal polarizing composition has a polymerizable functional group. The liquid crystal polarizing composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like.

The liquid crystal polarizing layer may be manufactured by applying a liquid crystal polarizing composition on an alignment film to form a liquid crystal polarizing layer. The liquid crystal polarizing layer can be formed thinner than the film type polarizer, and the thickness thereof is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

The alignment film can be produced by, for example, applying an alignment film-forming composition to a base material, and imparting alignment properties by rubbing, polarized light irradiation, or the like. The alignment film-forming composition may contain an alignment agent, and may further contain a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like. Examples of the orientation agent include polyvinyl alcohols, polyacrylates, polyamide acids, and polyimides. When an alignment agent that imparts alignment properties by polarized light irradiation is used, an alignment agent containing a cinnamate group (cinnamate group) is preferably used. The weight average molecular weight of the polymer that can be used as the orientation agent is, for example, about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000nm, and more preferably 10 to 500nm in view of sufficiently developing an alignment controlling force.

The liquid crystal polarizing layer may be laminated by being peeled off from a substrate and transferred, or the substrate may be directly laminated. The substrate preferably functions as a transparent substrate for a protective film, a retardation plate, and a window film.

The protective film may be a transparent polymer film, and may be made of the same material or additive as that used for the transparent base material of the window film. Further, the coating-type protective film may be obtained by applying and curing a cationically curable composition such as an epoxy resin or a radically curable composition such as an acrylate. The protective film may contain a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like, as necessary. The thickness of the protective film is preferably 200 μm or less, and more preferably 1 to 100 μm. When the thickness of the protective film is within the above range, the flexibility of the film tends not to be easily reduced.

The λ/4 retardation plate is a film that imparts a retardation of λ/4 in a direction perpendicular to the traveling direction of incident light, that is, in the in-plane direction of the film. The λ/4 retardation plate may be a stretched retardation plate produced by stretching a polymer film such as a cellulose film, an olefin film, or a polycarbonate film. The λ/4 retardation plate may contain a retardation regulator, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like, as required.

The thickness of the stretched phase difference plate is preferably 200 μm or less, and more preferably 1 to 100 μm. When the thickness of the stretched retardation film is within the above range, the flexibility of the stretched retardation film tends to be less likely to decrease.

Another example of the λ/4 retardation plate is a liquid crystal coating type retardation plate formed by coating a liquid crystal composition.

The liquid crystal composition contains a liquid crystalline compound that exhibits a liquid crystal state such as a nematic state, a cholesteric state, or a smectic state. The liquid crystalline compound has a polymerizable functional group.

The aforementioned liquid crystal composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like.

The liquid crystal coated retardation plate can be produced by coating a liquid crystal composition on a substrate and curing the coating to form a liquid crystal retardation layer, as in the liquid crystal polarizing layer. The liquid crystal coated retardation plate can be formed to a smaller thickness than the stretched retardation plate. The thickness of the liquid crystal polarizing layer is preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

The liquid crystal coated retardation plate may be laminated by being peeled from a substrate and transferred, or the substrate may be directly laminated. The substrate preferably functions as a transparent substrate for a protective film, a retardation plate, and a window film.

In general, the birefringence is large as the wavelength is shorter, and the birefringence is small as the wavelength is longer. In this case, since a retardation of λ/4 cannot be achieved in all visible light regions, the in-plane retardation is designed to be preferably 100 to 180nm, more preferably 130 to 150nm so as to be λ/4 in the vicinity of 560nm, which is high in visibility. The inverse dispersion λ/4 phase difference plate using a material having a wavelength dispersion characteristic of birefringence opposite to that of ordinary use is preferable in view of good visibility. As such a material, for example, as for the stretched phase difference plate, the stretched phase difference plate described in japanese patent application laid-open No. 2007-232873 and the like can be used, and as for the liquid crystal coated phase difference plate, the liquid crystal coated phase difference plate described in japanese patent application laid-open No. 2010-30979 and the like can be used.

As another method, a technique of obtaining a wide-band λ/4 phase difference plate by combining with a λ/2 phase difference plate is also known (for example, japanese patent application laid-open No. h 10-90521). The λ/2 phase difference plate can be manufactured by the same material method as the λ/4 phase difference plate. The combination of the stretching type retardation plate and the liquid crystal coating type retardation plate is arbitrary, and the thickness can be made thin by using the liquid crystal coating type retardation plate.

For the circularly polarizing plate, a method of laminating a positive C plate is known in order to improve visibility in an oblique direction (for example, japanese patent application laid-open No. 2014-224837). The positive C plate may be a liquid crystal coated retardation plate or a stretched retardation plate. The retardation in the thickness direction of the retardation plate is preferably from-200 to-20 nm, more preferably from-140 to-40 nm.

[ touch sensor ]

As described above, the flexible display device of the present invention preferably further includes a touch sensor. A touch sensor is used as an input mechanism. The touch sensor includes various types such as a resistive film type, a surface acoustic wave type, an infrared ray type, an electromagnetic induction type, and a capacitance type, and preferably includes a capacitance type.

The capacitive touch sensor can be divided into an active region and an inactive region located at an outer periphery of the active region. The active region is a region corresponding to a display portion of a display screen on the display panel, and is a region in which a user's touch is sensed, and the inactive region is a region corresponding to a non-display portion of the display device in which the screen is not displayed. The touch sensor may include: a substrate having flexible properties; a sensing pattern formed on the active region of the substrate; and each sensing line formed in the inactive region of the substrate and used for connecting the sensing pattern with an external driving circuit through a pad (pad). As the substrate having a flexible property, the same material as the transparent substrate of the window film can be used.

The sensing pattern may include a 1 st pattern formed in a 1 st direction and a 2 nd pattern formed in a 2 nd direction. The 1 st pattern and the 2 nd pattern are arranged in different directions from each other. The 1 st pattern and the 2 nd pattern may be formed on the same layer, and in order to sense the touch position, the patterns must be electrically connected. The 1 st pattern is a form in which a plurality of cell patterns are connected to each other via a joint, and the 2 nd pattern has a structure in which a plurality of cell patterns are separated from each other in an island form, and therefore, in order to electrically connect the 2 nd pattern, an additional bridge electrode is required. As the electrode for connecting the 2 nd pattern, a known transparent electrode can be used. Examples of the material of the transparent electrode include Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), zinc oxide (ZnO), Indium Zinc Tin Oxide (IZTO), Indium Gallium Zinc Oxide (IGZO), Cadmium Tin Oxide (CTO), PEDOT (poly (3, 4-ethylenedioxythiophene), poly (3, 4-ethylenedioxythiophene)), Carbon Nanotube (CNT), graphene, and a metal wire, and ITO is preferably used. These can be used alone or in combination of 2 or more. The metal used in the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, chromium, and the like, and these metals may be used alone or in combination of 2 or more.

The bridge electrode may be formed on the insulating layer with an insulating layer interposed therebetween on the sensing pattern, the bridge electrode may be formed on the substrate, and the insulating layer and the sensing pattern may be formed thereon. The bridge electrode may be formed of the same material as the sensing pattern, or may be formed of molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of 2 or more of these.

The 1 st pattern and the 2 nd pattern must be electrically insulated, and thus, an insulating layer may be formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the tab of the 1 st pattern and the bridge electrode, or may be formed as a layer covering the entire sensing pattern. In the case of a layer covering the entire sensing pattern, the 2 nd pattern may be connected to the bridge electrode through a contact hole formed in the insulating layer.

In the touch sensor, as a means for appropriately compensating for a difference in transmittance between a pattern region where a sensing pattern is formed and a non-pattern region where no sensing pattern is formed, specifically, a difference in transmittance due to a difference in refractive index in these regions, an optical adjustment layer may be further included between the substrate and the electrode. The optical adjustment layer may contain an inorganic insulating substance or an organic insulating substance. The optical adjustment layer may be formed by applying a photocurable composition including a photocurable organic binder and a solvent onto a substrate. The aforementioned photocurable composition may further comprise inorganic particles. The refractive index of the optical adjustment layer can be increased by the aforementioned inorganic particles.

The photocurable organic binder may contain a copolymer of monomers such as an acrylate monomer, a styrene monomer, and a carboxylic acid monomer within a range not to impair the effects of the present invention. The photocurable organic binder may be, for example, a copolymer containing mutually different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.

Examples of the inorganic particles include zirconia particles, titania particles, and alumina particles.

The photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing assistant.

[ adhesive layer ]

The layers of the laminate for a flexible display device, such as a window film, a circularly polarizing plate, and a touch sensor, and the film members of the layers, such as a linearly polarizing plate and a λ/4 retardation plate, may be bonded to each other with an adhesive. As the adhesive, a commonly used adhesive such as an aqueous adhesive, an organic solvent adhesive, a solventless adhesive, a solid adhesive, a solvent volatile adhesive, an aqueous solvent volatile adhesive, a moisture curable adhesive, a heat curable adhesive, an anaerobic curable adhesive, an active energy ray curable adhesive, a curing agent hybrid adhesive, a hot melt adhesive, a pressure sensitive adhesive, a remoistenable adhesive, or the like can be used, and an aqueous solvent volatile adhesive, an active energy ray curable adhesive, or a bonding agent can be preferably used. The thickness of the adhesive layer can be adjusted as appropriate in accordance with the required adhesive strength, etc., and is preferably 0.01 to 500 μm, more preferably 0.1 to 300 μm. The laminate for a flexible display device has a plurality of adhesive layers, and the thickness and type of each layer may be the same or different.

The aqueous solvent-volatile adhesive may be a polyvinyl alcohol polymer, a water-soluble polymer such as starch, or a water-dispersed polymer such as an ethylene-vinyl acetate emulsion or a styrene-butadiene emulsion. In addition to the main polymer and water, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, and the like may be added. In the case of bonding with the aqueous solvent volatile adhesive, adhesiveness can be provided by injecting the aqueous solvent volatile adhesive between the layers to be bonded, and bonding the layers to be bonded together, followed by drying. When the aqueous solvent volatile adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.1 to 1 μm. When the aqueous solvent-volatile adhesive is used in a plurality of layers, the thickness and type of each layer may be the same or different.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material, which forms the adhesive layer, by irradiation with an active energy ray. The active energy ray-curable composition may contain at least 1 polymer selected from the group consisting of the same radical polymerizable compounds and cationic polymerizable compounds as those contained in the hard coat composition. The radical polymerizable compound may be the same as the radical polymerizable compound in the hard coat composition.

The cationic polymerizable compound may be the same compound as the cationic polymerizable compound in the hard coat composition.

As the cationically polymerizable compound which can be used in the active energy ray-curable composition, an epoxy compound is preferable. In order to reduce the viscosity as an adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

For the active energy ray composition, a monofunctional compound may be contained in order to reduce the viscosity. Examples of the monofunctional compound include an acrylate monomer having 1 (meth) acryloyl group in 1 molecule, a compound having 1 epoxy group or oxetanyl group in 1 molecule, and glycidyl (meth) acrylate.

The active energy ray composition may further include a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and they can be appropriately selected and used. These polymerization initiators can be decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, thereby allowing radical polymerization and cationic polymerization to proceed. An initiator capable of initiating at least either of radical polymerization or cationic polymerization by irradiation with active energy rays as described in the description of the hard coating composition may be used.

The active energy ray-curable composition may further contain an ion scavenger, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, an antifoaming agent, an additive, and a solvent. When 2 layers to be bonded are bonded with the active energy ray-curable adhesive, the following means may be used for bonding: the active energy ray-curable composition is applied to one or both of the adhesive layers, and then the adhesive layers are bonded to each other, and the adhesive layers are cured by irradiation with active energy rays. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used to form a plurality of adhesive layers, the thickness and type of each layer may be the same or different.

As the adhesive, any of those classified into acrylic adhesives, urethane adhesives, rubber adhesives, polysiloxane adhesives, and the like can be used depending on the base polymer. The pressure-sensitive adhesive may contain a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a tackifier, a plasticizer, a dye, a pigment, an inorganic filler, and the like in addition to the main polymer. The pressure-sensitive adhesive layer (adhesive layer) can be formed by dissolving and dispersing the components constituting the pressure-sensitive adhesive in a solvent to obtain a pressure-sensitive adhesive composition, applying the pressure-sensitive adhesive composition to a substrate, and drying the applied pressure-sensitive adhesive composition. The adhesive layer may be formed directly or by transferring an adhesive layer separately formed on the substrate. It is also preferable to use a release film for covering the pressure-sensitive adhesive surface before bonding. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.1 to 500 μm, more preferably 1 to 300 μm. When a plurality of the above-mentioned adhesives are used, the thickness and kind of each layer may be the same or different.

[ light-shielding pattern ]

The light-shielding pattern may be applied as at least a part of a bezel (bezel) or a housing of the flexible display device. The wiring disposed at the edge of the flexible display device is hidden by the light-shielding pattern and is not easily viewed, thereby improving visibility of an image. The light-shielding pattern may be in the form of a single layer or a plurality of layers. The color of the light-shielding pattern is not particularly limited, and may be various colors such as black, white, and metallic colors. The light-shielding pattern may be formed of a pigment for color, and a polymer such as an acrylic resin, an ester resin, an epoxy resin, polyurethane, or polysiloxane. They may be used alone or in the form of a mixture of 2 or more. The light-shielding pattern can be formed by various methods such as printing, photolithography, and inkjet. The thickness of the light-shielding pattern is preferably 1 to 100 μm, and more preferably 2 to 50 μm. Further, it is also preferable to provide a shape such as an inclination in the thickness direction of the light-shielding pattern.

[ polyamideimide resin ]

The present invention includes a polyamideimide resin having at least a structural unit represented by formula (1) and a structural unit represented by formula (2), wherein the structural unit represented by formula (2) contains a group represented by formula (3) as Z. The polyamideimide resin is the same as the polyamideimide resin described in the item < polyamideimide resin > which contains a group represented by the formula (3) as Z in the formula (2).

The polyamideimide resin of the present invention has a structural unit represented by formula (1) and a structural unit represented by formula (2), particularly a structural unit represented by formula (2) wherein Z is a specific 2-valent aromatic group having an electron donating group, and therefore, an optical film exhibiting excellent elastic modulus while maintaining yield point strain can be formed. In addition, the optical film can also have excellent optical characteristics.

[ examples ]

The present invention will be described in further detail below with reference to examples. In the examples, "%" and "part(s)" refer to% by mass and part(s) by mass unless otherwise specified. First, the evaluation method will be explained.

< measurement of elastic modulus and yield Point Strain >

The elastic modulus at 25 ℃ of the optical film obtained in each of examples and comparative examples was measured by using "AUTOGRAPH AG-IS" manufactured by Shimadzu corporation. More specifically, a film having a width of 10mm was produced, and an S-S curve was measured under conditions of an inter-chuck distance of 50mm and a stretching speed of 10 mm/min, and the elastic modulus was calculated from the slope thereof.

The yield point strain was calculated as follows.

Data collation of S-S curves

10 points are continuously sampled from the starting point of measurement in the S-S curve, and fitted to a quadratic function by using the least square method. Then, 1 point was excluded from the left side of the measurement starting point, and 1 point on the right side was added until a convex shape was formed by quadratic function fitting of 10 points in the sampling range. And finishing data sorting at the time point when the fitting function forms the upward projection.

Calculation of tangent equation of S-S curve

Based on the data n ═ i to j (j ═ 2 to 50) in the data of item 1, the slope and intercept were determined by the least square method. Then, for the slope of j-1, the K (K1 to 48) th to 49 th data were fitted to a 1-th order function by the least square method, and the slope at which strain became 0 was obtained by extrapolation. The median of the 48 points obtained was obtained and defined as the slope of the line at which the strain was 0 (S-S curve tangent). The intercept is calculated in the same manner, and an equation of a tangent to the S-S curve when the strain is 0 is obtained.

3. Calculation of yield point strain

The tangent line of the S-S curve obtained in the above 2, at which the strain is 0, was shifted in parallel by 0.2% in the strain direction. The yield point strain is defined as the strain value at which the measured stress exceeds the stress of the straight line after the parallel translation.

< measurement of Tt >

According to JIS K7105: in 1981, Tt of the optical films obtained in examples and comparative examples was measured by using a fully automatic direct haze computer HGM-2DP manufactured by Suga Test Instruments Co.

< Haze (Haze) >

The optical films obtained in examples and comparative examples were cut into a size of 30mm × 30mm according to JIS K7136: 2000, and the haze (%) was measured by a haze computer ("HGM-2 DP", manufactured by Suga Test Instruments Co., Ltd.).

< YI value >

According to JIS K7373: the YI value (Yellow Index) of the optical films obtained in examples and comparative examples was measured by using an ultraviolet-visible near-infrared spectrophotometer "V-670" manufactured by japan spectro-photometer. After background measurement was performed in a state where no sample was present, an optical film was placed on a sample holder, transmittance for light of 300 to 800nm was measured to obtain a tristimulus value (X, Y, Z), and a YI value was calculated based on the following formula.

YI＝100×(1.2769X-1.0592Z)/Y

< measurement of weight average molecular weight >

Gel Permeation Chromatography (GPC) measurement

(1) Pretreatment method

To the polyamideimide resins (samples) obtained in examples and comparative examples, a DMF eluent (10mmol/L lithium bromide solution) was added so that the concentration became 2mg/mL, and the mixture was heated under stirring at 80 ℃ for 30 minutes, cooled, and then filtered with a 0.45 μm membrane filter, and the obtained filtrate was used as a measurement solution.

(2) Measurement conditions

TSKgel α -2500 (7)7.8mm diameter × 300mm) × 1, α -M ((13)7.8mm diameter × 300mm) × 2 from Tosoh Corporation

Eluent: DMF (with addition of 10mmol/L lithium bromide)

Flow rate: 1.0 mL/min

A detector: RI detector

Column temperature: 40 deg.C

Sample introduction amount: 100 μ L

Molecular weight standard: standard polystyrene

< measurement of thickness >

The thickness of the optical films obtained in examples and comparative examples was measured using a micrometer (manufactured by Mitutoyo Corporation, "ID-C112 XBS").

< example 1>

[ preparation of polyamideimide resin (1) ]

2, 2' -bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylacetamide (DMAc) were added to a separable flask equipped with a stirring blade under a nitrogen atmosphere so that the solid content of TFMB became 5.28 mass%, and TFMB was dissolved in DMAc with stirring at room temperature. Next, 4' - (hexafluoroisopropylidene) diphthalic anhydride (6FDA) was added to the flask so that it became 40.20 mol% with respect to TFMB, and stirring was performed at room temperature for 3 hours. Then, after cooling to 10 ℃, 2, 5-dimethylterephthaloyl chloride (DMTPC) was added so that it became 27.14 mol% with respect to TFMB, and stirring was performed for 10 minutes, and then DMTPC was further added so that it became 27.14 mol% with respect to TFMB, and stirring was performed for 30 minutes. Then, DMAc was added in an amount equivalent to that of the first DMAc, and stirring was performed for 10 minutes, and then DMTPC was added so that the amount of DMTPC was 6.03 mol% with respect to TFMB, and stirring was performed for 2 hours. Subsequently, diisopropylethylamine and 4-methylpyridine at 60.30 mol% with respect to TFMB and acetic anhydride at 281.41 mol% with respect to TFMB were added to the flask, respectively, and stirred for 30 minutes, and then the internal temperature was raised to 70 ℃, and further stirred for 3 hours to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamideimide resin (1). The weight average molecular weight of the obtained polyamideimide resin (1) was 449,000.

[ production of optical film (1) ]

DMAc was added to the obtained polyamideimide resin (1) so that the concentration thereof became 10% by mass, thereby preparing a polyamideimide resin varnish (1). The obtained polyamide-imide resin varnish (1) was applied to a smooth surface of a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") using an applicator so that the thickness of the self-supporting film became 50 μm, and dried at 50 ℃ for 30 minutes and then at 140 ℃ for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 60 minutes to obtain an optical film (1) having a thickness of 45 μm.

< example 2>

[ preparation of polyamideimide resin (2) ]

TFMB and DMAc were added to a separable flask equipped with a stirring blade under a nitrogen atmosphere so that the solid content of TFMB became 5.63 mass%, and TFMB was dissolved in DMAc with stirring at room temperature. Then, 6FDA was added to the flask so that it became 20.20 mol% to TFMB, and stirring was performed at room temperature for 3 hours. Then, after cooling to 10 ℃, DMTPC was added so that the amount of DMTPC became 36.37 mol% with respect to TFMB, and stirring was performed for 10 minutes, and then 6FTPC was further added so that the amount of DMTPC became 36.37 mol% with respect to TFMB, and stirring was performed for 30 minutes. Then, DMAc was added in an amount equal to that of the first DMAc, and stirring was performed for 10 minutes, and then DMTPC was added so that the amount of DMTPC was 8.08 mol% with respect to TFMB, and stirring was performed for 2 hours. Subsequently, diisopropylethylamine and 4-methylpyridine in an amount of 80.81 mol% based on TFMB and acetic anhydride in an amount of 141.41 mol% based on TFMB were added to the flask, and the mixture was stirred for 30 minutes, and then the internal temperature was increased to 70 ℃.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamideimide resin (2). The weight average molecular weight of the obtained polyamideimide resin (2) was 482,000.

[ production of optical film (2) ]

DMAc was added to the obtained polyamideimide resin (2) so that the concentration thereof became 10% by mass, thereby producing a polyamideimide resin varnish (2). The obtained polyamide-imide resin varnish (2) was applied to a smooth surface of a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") using an applicator so that the thickness of the self-supporting film became 55 μm, and dried at 50 ℃ for 30 minutes and then at 140 ℃ for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 60 minutes to obtain an optical film (2) having a thickness of 50 μm.

< comparative example 1>

[ preparation of polyamideimide resin (3) ]

TFMB and DMAc were added to a separable flask equipped with a stirring blade under a nitrogen atmosphere so that the solid content of TFMB became 5.35 mass%, and TFMB was dissolved in DMAc with stirring at room temperature. Then, 6FDA was added to the flask so that it became 41.24 mol% based on TFMB, and stirring was performed at room temperature for 3 hours. Then, after cooling to 10 ℃, terephthaloyl chloride (TPC) was added so that it became 55.67 mol% with respect to TFMB, and stirring was performed for 130 minutes. Then, DMAc was added in an amount equivalent to that of the first DMAc, and stirring was performed for 10 minutes, and then TPC was added so that the amount of TPC was 6.19 mol% with respect to TFMB, and stirring was performed for 2 hours. Subsequently, diisopropylethylamine and 4-methylpyridine, each in an amount of 61.86 mol% based on TFMB, and acetic anhydride in an amount of 288.66 mol% based on TFMB were added to the flask, and the mixture was stirred for 30 minutes, and then the internal temperature was increased to 70 ℃.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamideimide resin (3). The weight average molecular weight of the obtained polyamideimide resin (3) was 174,000.

[ production of optical film (3) ]

DMAc was added to the obtained polyamideimide resin (3) so that the concentration thereof became 10% by mass, thereby preparing a polyamideimide resin varnish (3). The obtained polyamide-imide resin varnish (3) was applied to a smooth surface of a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") using an applicator so that the thickness of the self-supporting film became 55 μm, and dried at 50 ℃ for 30 minutes and then at 140 ℃ for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 60 minutes to obtain an optical film (3) having a thickness of 50 μm.

< example 3>

[ preparation of polyamideimide resin (4) ]

TFMB and DMAc were added to a separable flask equipped with a stirring blade under a nitrogen atmosphere so that the solid content of TFMB became 6.08 mass%, and TFMB was dissolved in DMAc with stirring at room temperature. Then, 6FDA was added to the flask so that it became 20.10 mol% to TFMB, and stirring was performed at room temperature for 3 hours. Then, after cooling to 10 ℃, 2-methoxy terephthaloyl chloride (OMTPC) was added so that it became 27.14 mol% with respect to TFMB, and stirring was performed for 10 minutes, and then, OMTPC was further added so that it became 36.37 mol% with respect to TFMB, and stirring was performed for 30 minutes. Then, DMAc was added in an amount equivalent to that of the first DMAc, followed by stirring for 10 minutes, and then, OMTPC was added so that the molar ratio of the resultant mixture to TFMB became 6.03 mol%, followed by stirring for 2 hours. Subsequently, diisopropylethylamine and 4-methylpyridine at 60.30 mol% with respect to TFMB and acetic anhydride at 140.70 mol% with respect to TFMB were added to the flask, respectively, and stirred for 30 minutes, and then the internal temperature was raised to 70 ℃, and further stirred for 3 hours to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamideimide resin (4). The weight average molecular weight of the obtained polyamideimide resin (4) was 441,000.

[ production of optical film (4) ]

DMAc was added to the obtained polyamideimide resin (4) so that the concentration thereof became 10% by mass, thereby preparing a polyamideimide resin varnish (4). The obtained polyamide-imide resin varnish (4) was applied to a smooth surface of a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") using an applicator so that the thickness of the self-supporting film became 55 μm, and dried at 50 ℃ for 30 minutes and then at 140 ℃ for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 60 minutes to obtain an optical film (4) having a thickness of 50 μm.

< example 4>

[ preparation of polyamideimide resin (5) ]

TFMB and DMAc were added to a separable flask equipped with a stirring blade under a nitrogen atmosphere so that the solid content of TFMB became 5.61 mass%, and TFMB was dissolved in DMAc with stirring at room temperature. Then, 6FDA was added to the flask so that it became 20.20 mol% to TFMB, and stirring was performed at room temperature for 3 hours. Then, after cooling to 10 ℃, 2-methoxy terephthaloyl chloride (OMTPC) was added so that it became 36.36 mol% with respect to TFMB, and stirring was performed for 10 minutes, and then, OMTPC was further added so that it became 36.37 mol% with respect to TFMB, and stirring was performed for 30 minutes. Then, DMAc was added in an amount equivalent to that of the initially added DMAc and stirred for 10 minutes, and then, OMTPC was added so that it became 8.08 mol% with respect to TFMB and stirred for 2 hours. Subsequently, diisopropylethylamine and 4-methylpyridine in an amount of 80.81 mol% based on TFMB and acetic anhydride in an amount of 141.41 mol% based on TFMB were added to the flask, and the mixture was stirred for 30 minutes, and then the internal temperature was increased to 70 ℃.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamideimide resin (5). The weight average molecular weight of the obtained polyamideimide resin (5) was 483,000.

[ production of optical film (5) ]

DMAc was added to the obtained polyamideimide resin (5) so that the concentration thereof became 10% by mass, thereby preparing a polyamideimide resin varnish (5). The obtained polyamide-imide resin varnish (5) was applied to a smooth surface of a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") using an applicator so that the thickness of the self-supporting film became 55 μm, and dried at 50 ℃ for 30 minutes and then at 140 ℃ for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 60 minutes to obtain an optical film (5) having a thickness of 50 μm.

The measurement results of the elastic modulus, yield strain, Tt, YI values, and haze (%) of the optical films obtained in examples 1 to 4 and comparative example 1 are shown in table 1.

[ Table 1]

As shown in table 1, it was confirmed that the optical films obtained in examples 1 to 4 have higher elastic modulus than the optical film obtained in comparative example 1. In addition, the optical films obtained in examples 1 and 2 had excellent yield point strain. Therefore, it is understood that the optical film of the present invention not only maintains the yield point strain, but also exhibits an excellent elastic modulus.

Claims

1. An optical film comprising a polyamideimide resin having at least a structural unit represented by formula (1) and a structural unit represented by formula (2),

in the formula (1), X represents a 2-valent organic group, Y represents a 4-valent organic group,

in the formula (2), X represents a 2-valent organic group, Z represents a 2-valent aromatic group having at least 1 substituent selected from the group consisting of an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent and an aryloxy group having 6 to 12 carbon atoms which may have a substituent.

2. The optical film according to claim 1, wherein the structural unit represented by formula (2) contains a group represented by formula (3) as Z,

in the formula (3), R¹Independently represent an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, or an aryl group having 6 to 12 carbon atoms which may have a substituent, k and n independently represent an integer of 1 to 4, and when k is 2 or more, R substituted on different aromatic groups¹May be the same or different, and represents a chemical bond.

3. The optical film according to claim 2, wherein 2 chemical bonds are located at para positions with respect to each other in formula (3).

4. The optical film according to any one of claims 1 to 3, wherein the structural unit represented by formula (1) contains a group represented by formula (4) as Y,

in the formula (4), R²～R⁷Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R²～R⁷Wherein the hydrogen atoms contained in (A) may be substituted independently by halogen atoms, and V represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁸)-，R⁸Represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom, and represents a bond.

5. The optical film according to claim 4, wherein in the formula (4), V represents a single bond, -O-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-。

6. The optical film according to any one of claims 1 to 5, wherein the structural unit represented by formula (1) and/or the structural unit represented by formula (2) contains a group represented by formula (5) as X,

in the formula (5), R⁹～R¹⁶Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R⁹～R¹⁶The hydrogen atoms contained in (a) may be substituted, independently of one another, by halogen atoms, representing a chemical bond.

7. The optical film according to any one of claims 2 to 6, wherein R in the formula (3)¹Independently represents an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms, and k and n independently represent 1 or 2.

8. Light according to any one of claims 2 to 6A membrane, wherein in the formula (3), R¹Independently of each other, an alkoxy group having 1 to 6 carbon atoms, k represents 1, and n represents 1 or 2.

9. The optical film according to any one of claims 2 to 6, wherein R in the formula (3)¹Independently of each other, an alkyl group having 1 to 6 carbon atoms, k represents 1, and n represents 1 or 2.

10. The optical film according to any one of claims 6 to 9, wherein formula (5) is represented by formula (6),

in formula (6), denotes a bond.

11. The optical film according to any one of claims 1 to 10, which has a thickness of 10 to 200 μm.

12. A flexible display device comprising the optical film according to any one of claims 1 to 11.

13. The flexible display device of claim 12, further provided with a touch sensor.

14. The flexible display device according to claim 12 or 13, further comprising a polarizing plate.

15. A polyamideimide resin having at least a structural unit represented by formula (1) and a structural unit represented by formula (2),

the structural unit represented by formula (2) contains a group represented by formula (3) as Z,

in the formula (2), X represents a 2-valent organic group, Z represents a 2-valent aromatic group having at least 1 substituent selected from the group consisting of an alkyl group having 1 to 12 carbon atoms which may have a substituent, an alkoxy group having 1 to 12 carbon atoms which may have a substituent, an aryl group having 6 to 12 carbon atoms which may have a substituent and an aryloxy group having 6 to 12 carbon atoms which may have a substituent,