CN113227209A

CN113227209A - Polyamide-imide resin, optical film, and flexible display device

Info

Publication number: CN113227209A
Application number: CN201980085963.7A
Authority: CN
Inventors: 增井建太朗; 宫本皓史; 金成民; 池内淳一; 杉山纮子; 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: 2021-08-06
Also published as: TW202030231A; TW202031733A; CN113227210A; KR20210110648A; KR20210110643A; TW202031734A

Abstract

The invention provides a polyamide-imide resin capable of manufacturing an optical film having a high elastic modulus while maintaining a high light transmittance, and an optical film comprising the same. The polyamide-imide resin has at least a structural unit represented by formula (1) and a structural unit represented by formula (2). In the formula (1), Y represents a 4-valent aromatic group which may have a substituent, and X represents a 2-valent organic group represented by the formula (3). In the formula (3), R¹Independently 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, R¹The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms; v represents-O-, diphenylmethylene, straight chain, branched chain or alicyclic 2-valent hydrocarbon group having 1-12 carbon atoms, -SO₂-, -S-, -CO-or-N (R)¹²) -, wherein the hydrogen atoms contained in the hydrocarbon group independently of each other may be substituted by halogen atoms, R¹²Represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom. In the formula (2), Z represents a 2-valent organic group, and X is as defined in the formula (1).

Description

Polyamide-imide resin, optical film, and flexible display device

Technical Field

The present invention relates to a polyamideimide resin, an optical film including the resin, and a flexible display device including the optical film.

Background

At present, display devices such as liquid crystal display devices and organic EL display devices are widely used not only for televisions but also for various applications such as mobile phones and smartwatches. Conventionally, glass has been used as a front panel of such a display device. However, glass has high transparency and can exhibit high hardness depending on the type, but on the other hand, it is very rigid and easily broken, and therefore, it is difficult to use it as a front panel material for a flexible display device.

Therefore, studies have been made on flexible use of polymer materials as materials replacing glass. A front panel made of a polymer material is expected to be used for various applications because it is easy to exhibit flexibility. As one of polymer materials having flexibility, for example, an optical film using a polyamideimide resin has been studied (patent documents 1 and 2).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2015-521686

Patent document 2: japanese patent laid-open publication No. 2018-119132

Disclosure of Invention

Problems to be solved by the invention

When an optical film produced using a polyamideimide resin is used for a flexible display device or the like, the optical film may be damaged or wrinkled due to bending or contact with an external factor. As a method for suppressing the occurrence of such defects, it is conceivable to increase the elastic modulus of the optical film, but depending on the type of the polyamideimide resin, the elastic modulus of the optical film obtained may not be sufficiently increased.

Accordingly, an object of the present invention is to provide a polyamideimide resin capable of producing an optical film having a high elastic modulus while maintaining a high transmittance, and an optical film comprising the same.

Means for solving the problems

In order to solve the above problems, the present inventors have made intensive studies focusing on the structure of a monomer constituting a polyamideimide resin contained in an optical film. As a result, they have found that a polyamideimide resin having at least a specific structural unit is suitable for producing an optical film having a high elastic modulus while maintaining a high transmittance, thereby completing the present invention.

That is, the present invention includes the following preferred embodiments.

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

[ chemical formula 1]

[ in the formula (1), Y represents a 4-valent aromatic group which may have a substituent,

x represents a 2-valent organic group represented by the formula (3),

[ chemical formula 2]

[ in formula (3), R¹Independently 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, R¹The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

v represents-O-, diphenylmethylene, straight chain, branched chain or alicyclic 2-valent hydrocarbon group having 1-12 carbon atoms, -SO₂-, -S-, -CO-or-N (R)¹²) -, wherein the hydrogen atoms contained in the hydrocarbon group independently of each other may be substituted by halogen atoms, R¹²Represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom ]]

[ chemical formula 3]

[ in the formula (2), Z represents a 2-valent organic group,

x is as defined in the above formula (1) ]

[ 2] the polyamideimide resin according to the above [ 1], wherein V in the formula (3) represents a linear, branched or alicyclic 2-valent hydrocarbon group having 1 to 12 carbon atoms, and wherein hydrogen atoms contained in the hydrocarbon group may be independently substituted by a halogen atom.

[ 3] the polyamideimide resin according to the above [ 1] or [ 2], wherein the structural unit represented by the formula (1) contains a 4-valent aromatic group represented by the formula (4) and/or a 4-valent aromatic group represented by the formula (5) as Y.

[ chemical formula 4]

[ formula (4) and formula (5) wherein R²And R³Independently 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, R²And R³The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

n represents an integer of 0 to 2]

[ 4] the polyamideimide resin according to the above [ 3], wherein the formula (4) is represented by the formula (4 a).

[ chemical formula 5]

[ 5] the polyamideimide resin according to the above [ 3], wherein the formula (5) is represented by the formula (5 a).

[ chemical formula 6]

[ 6] the polyamideimide resin according to any one of [ 1] to [ 5] above, wherein the formula (3) is represented by the formula (3 a).

[ chemical formula 7]

[ 7] the polyamideimide resin according to any one of the above [ 1] to [ 6], wherein the polyamideimide resin has at least 2 or more structural units represented by the formula (2) in which Z is different from each other, and/or has at least 2 or more structural units represented by the formula (2) in which X is different from each other, and/or further has a structural unit represented by the formula (7).

[ chemical formula 8]

[ in formula (7), Z is as defined for formula (1),

x' represents a 2-valent organic group not belonging to X in the formula (2) ]

[ 8] the polyamideimide resin according to the above [ 7], wherein X' in the formula (7) is represented by the formula (8).

[ chemical formula 9]

[ formula (8) wherein Ar is²Represents a 2-valent aromatic group which may have a substituent,

v represents a single bond, m represents an integer of 0 to 3, and

[ 9] the polyamideimide resin according to the above [ 7] or [ 8], wherein the proportion of the structural unit represented by the formula (2) is 1 to 50 mol% based on 100 mol% of the total of the structural unit represented by the formula (2) and the structural unit represented by the formula (7).

[ 10] the polyamideimide resin according to any one of [ 1] to [ 9] above, wherein Z in the structural unit represented by formula (2) contains a 2-valent aromatic group which may have a substituent.

An optical film comprising the polyamideimide resin according to any one of [ 1] to [ 10 ].

A flexible display device comprising the optical film according to [ 11 ].

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

The flexible display device according to any one of the above [ 12] and [ 13], further comprising a polarizing plate.

ADVANTAGEOUS EFFECTS OF INVENTION

The polyamide-imide resin of the present invention can provide an optical film having a high elastic modulus while maintaining a high transmittance. In addition, the optical film of the present invention has a high elastic modulus while maintaining a high transmittance.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described herein, and various modifications can be made without departing from the spirit of the present invention.

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

[ chemical formula 10]

x represents a 2-valent organic group represented by the formula (3) described later

[ chemical formula 11]

[ in the formula (2), Z represents a 2-valent organic group,

x is as defined in formula (1) ]

The structural unit represented by formula (1) is a structural unit formed by reacting a tetracarboxylic acid compound with a diamine compound, and the structural unit represented by formula (2) is a structural unit formed by reacting a dicarboxylic acid compound with a diamine compound. The polyamideimide resin of the present invention may have 1 kind of structural unit represented by formula (1), or may have 2 or more kinds of structural units represented by formula (1). Similarly, the polyamideimide resin may have 1 kind of structural unit represented by formula (2), or may have 2 or more kinds of structural units represented by formula (2). The polyamideimide resin may contain other structural units that do not belong to either the structural unit represented by formula (1) or the structural unit represented by formula (2). In the present specification, the structural unit represented by formula (1) is also referred to as "structural unit (1)", and the structural unit represented by formula (2) is also referred to as "structural unit (2)". In the formulae (1) and (2), the bond represented by a dotted line represents a chemical bond with an adjacent structural unit. In the present specification, the bond represented by a dotted line in the other chemical structural formulae also represents a chemical bond to an adjacent structural unit or group.

When an optical film is produced using the polyamideimide resin having the structural unit (1) and the structural unit (2) as described above, an optical film having a high elastic modulus and a high light transmittance can be obtained. The reason for this is not clear, but in the case where the polyamideimide resin has the structural unit (1) and the structural unit (2), the polyamideimide resin has rigidity in the structural part derived from tetracarboxylic acid in the structural unit (1), and the polyamideimide resin has flexibility in the structural part derived from diamine in the structural unit (1) and the structural unit (2), and interaction between molecules is reduced. When the polyamideimide resin has such a structure, it has been surprisingly found that the elastic modulus of an optical film containing the polyamideimide resin can be easily increased and the light transmittance can be easily increased.

The polyamide-imide resin of the present invention has a structural unit (1) and a structural unit (2). From the viewpoint of easily improving the elastic modulus and the light transmittance of the optical film, the proportion of the structural unit (1) is preferably 5 to 90 mol%, more preferably 10 to 80 mol%, further preferably 20 to 80 mol%, and particularly preferably 30 to 70 mol%, based on 100 mol% of the total of the structural unit (1) and the structural unit (2) contained in the polyamideimide resin. When the ratio of the structural unit (1) is not less than the lower limit, the elastic modulus of the optical film is easily increased. When the proportion of the structural unit (1) is not more than the above upper limit, the light transmittance is easily improved. The contents of the structural units (1) and (2) may be, for example, those used¹H-NMR, or the ratio of the raw materials charged may be calculated.

In the polyamide imide resin, the content of the structural unit represented by formula (1) is preferably 0.1 mol or more, more preferably 0.2 mol or more, further preferably 0.3 mol or more, preferably 5mol or less, more preferably 3 mol or less, further preferably 2 mol or less, and particularly preferably 1mol or less, relative to 1mol of the structural unit represented by formula (2). When the content of the structural unit represented by formula (1) is not less than the above lower limit, the elastic modulus of the optical film is easily increased. When the content of the structural unit represented by formula (1) is not more than the upper limit, the thickening due to the hydrogen bond between the amide bonds in formula (2) is easily suppressed, and the processability of the optical film is improved.

Y in the formula (1) represents a 4-valent aromatic group which may have a substituent. In the present specification, the 4-valent aromatic group is a group in which 4 hydrogen atoms of a monocyclic aromatic ring, a condensed polycyclic aromatic ring, or a ring-assembled aromatic ring are replaced with chemical bonds, and preferably a group in which 4 hydrogen atoms in total, that is, 2 hydrogen atoms adjacent to each other in a monocyclic aromatic ring, a condensed polycyclic aromatic ring, or a ring-assembled aromatic ring, and 2 hydrogen atoms adjacent to each other which are different from the hydrogen atom, are replaced with chemical bonds. The 4-valent aromatic group may include an aromatic ring having a ring (a single ring, a condensed multiple ring, or a ring assembly) formed only of carbon atoms, or may include an aromatic heterocyclic ring having a ring formed so as to contain an atom other than carbon atoms. Examples of the atom other than carbon atoms include a nitrogen atom, a sulfur atom and an oxygen atom. The total number of carbon atoms and atoms other than carbon atoms forming the aromatic ring is not particularly limited, but is preferably 5 to 18, more preferably 5 to 14, and still more preferably 5 to 13.

Examples of the monocyclic aromatic ring include benzene, furan, pyrrole, thiophene, pyridine, imidazole, pyrazole, oxazole, thiazole, imidazoline, and the like.

Examples of the fused polycyclic aromatic ring include naphthalene, anthracene, phenanthrene, indole, benzothiazole, benzoxazole, benzimidazole, and the like.

The ring-assembled aromatic ring may have a structure in which 2 or more monocyclic aromatic rings and/or condensed polycyclic aromatic rings are connected by a single bond, and examples thereof include: examples of the monocyclic aromatic ring or the condensed polycyclic aromatic ring include those in which 2 or more of the above-described rings are connected by a single bond, such as biphenyl, terphenyl, quaterphenyl, binaphthyl, 1-phenylnaphthalene, 2-phenylnaphthalene, and bipyridine (bipyridine).

From the viewpoint of easily improving the elastic modulus and the light transmittance of the optical film, the 4-valent aromatic group which may have a substituent is preferably a group in which 4 hydrogen atoms of an aromatic hydrocarbon ring are replaced with chemical bonds, more preferably a group in which 4 hydrogen atoms of benzene, biphenyl, terphenyl, or quaterphenyl are replaced with chemical bonds, and even more preferably a group in which 4 hydrogen atoms of benzene or biphenyl are replaced with chemical bonds.

The 4-valent aromatic group represented by Y in formula (1) may have a substituent. Examples of the substituent include (i) an alkyl group having 1 to 12 carbon atoms, (ii) an alkoxy group having 1 to 12 carbon atoms, (iii) an aryl group having 6 to 12 carbon atoms, (iv) an aryloxy group having 6 to 12 carbon atoms, (v) a carbonyl group having 1 to 12 carbon atoms, (vi) an oxycarbonyl group having 1 to 12 carbon atoms, and (vii) a halogeno group. The hydrogen atoms contained in the above-mentioned substituents may be independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. The 4-valent aromatic group represented by Y in formula (1) may have at least 1 of the substituents (i) to (vii) described above, and/or a group in which a hydrogen atom contained in the substituents (i) to (vii) described above is independently substituted by a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group, or may have no substituent. The 4-valent aromatic group represented by Y in formula (1) preferably has no substituent from the viewpoint of ease of manufacturing an optical film having a high elastic modulus.

Examples of the (i) alkyl group having 1 to 12 carbon atoms include a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms. Examples of the linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, n-decyl, cyclopentyl, cyclohexyl and the like. The alkyl group having 1 to 12 carbon atoms may be a linear alkyl group, a branched alkyl group, or an alicyclic alkyl group having an alicyclic hydrocarbon structure. The number of carbon atoms of the alkyl group having 1 to 12 carbon atoms is preferably 1 to 6, more preferably 1 to 4, and further preferably 1 to 3. The alkyl group having 1 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. Here, when the alkyl group having 1 to 12 carbon atoms is substituted with a substituent containing a carbon atom (for example, an alkyl group having 1 to 4 carbon atoms), the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the alkyl group having 1 to 12 carbon atoms. For example, the group in which the alkyl group having 1 to 12 carbon atoms is substituted with an alkyl group having 1 to 4 carbon atoms is a group in which the alkyl group having 1 to 12 carbon atoms is the main chain and at least 1 hydrogen atom of the alkyl group is substituted with an alkyl group having 1 to 4 carbon atoms. When the number of carbon atoms of the alkyl moiety which becomes the main chain is 1 to 12, the number of carbon atoms of the alkyl group as a whole may be more than 12. In the case where the number of carbon atoms of the alkyl group exceeds 12, the group in which an alkyl group having 1 to 12 carbon atoms is substituted with an alkyl group having 1 to 4 carbon atoms is also included in the definition of a branched alkyl group having 1 to 12 carbon atoms.

Examples of the (ii) alkoxy group having 1 to 12 carbon atoms include methoxy, ethoxy, propyloxy, isopropyloxy, n-butoxy, i-butoxy, t-butoxy, pentyloxy, hexyloxy, cyclohexyloxy, heptyloxy, octyloxy, nonyloxy, decyloxy and the like. The alkyl moiety and/or the alkylene moiety in the C1-12 alkoxy group may be any of linear, branched, or alicyclic. The alkoxy group having 1 to 12 carbon atoms preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and still more preferably 1 to 3 carbon atoms. The alkoxy group having 1 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include the atoms described above. When the alkoxy group having 1 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the alkoxy group having 1 to 12 carbon atoms.

Examples of (iii) 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. The number of carbon atoms of the aryl group having 6 to 12 carbon atoms is preferably 6, 10 or 12. The above-mentioned aryl group having 6 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include the atoms described above. When the aryl group having 6 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the aryl group having 6 to 12 carbon atoms.

Examples of (iv) the aryloxy group having 6 to 12 carbon atoms include a phenoxy group, a tolyloxy group, a xylyloxy group, a naphthyloxy group, and a biphenyloxy group. The number of carbon atoms of the aryloxy group having 6 to 12 carbon atoms is preferably 6, 10 or 12. The aryloxy group having 6 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted by a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include the atoms described above. Here, when the aryloxy group having 6 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the aryloxy group having 6 to 12 carbon atoms.

(v) The carbonyl group having 1 to 12 carbon atoms is onium-CO-R^aOr (iii) R^b-CO-R^aThe group shown. As R^aExamples of the group include (i) a group described for an alkyl group having 1 to 12 carbon atoms as R^bExamples of the alkylene group include (i) a 2-valent alkylene group having 1 to 12 carbon atoms, in which at least 1 hydrogen atom of the group described in the alkyl group having 1 to 12 carbon atoms is replaced with a chemical bond. The carbonyl group having 1 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include the atoms described above. When the carbonyl group having 1 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the carbonyl group having 1 to 12 carbon atoms.

(vi) The oxycarbonyl group having 1 to 12 carbon atoms is O-CO-O-R^a、＊-R^b-CO-O-R^a、＊-O-CO-R^aor-R^b-O-CO-R^aThe group shown. As R^aExamples of the group include (i) a group described for an alkyl group having 1 to 12 carbon atoms as R^bExamples of the alkylene group include (i) a 2-valent alkylene group having 1 to 12 carbon atoms, in which at least 1 hydrogen atom of the group described in the alkyl group having 1 to 12 carbon atoms is replaced with a chemical bond. The oxycarbonyl group having 1 to 12 carbon atoms may be a group in which at least 1 hydrogen atom is independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. Examples of the halogen atom include the atoms described above. Here, when the oxycarbonyl group having 1 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is not included in the number of carbon atoms of the oxycarbonyl group having 1 to 12 carbon atoms.

Examples of the (vii) halogeno group include a fluoro group, a chloro group, a bromo group and an iodo group.

In a preferred embodiment of the present invention, Y in the structural unit (1) contained in the polyamideimide resin contains a 4-valent aromatic group represented by the formula (4) and/or a 4-valent aromatic group represented by the formula (5).

[ chemical formula 12]

[ formula (4) and formula (5) wherein R²And R³Independently represents 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,

R²and R³The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

n represents an integer of 0 to 2]

When the structural unit (1) contains a 4-valent aromatic group represented by the formula (4) and/or a 4-valent aromatic group represented by the formula (5) as Y, the elastic modulus and the light transmittance of an optical film produced using a polyamideimide resin can be easily improved. When the structural unit (1) in the polyamideimide resin contains a 4-valent aromatic group represented by formula (4) and/or a 4-valent aromatic group represented by formula (5) as Y, the polyamideimide resin may contain a structural unit containing 1 kind of 4-valent aromatic group represented by formula (4) as Y, or may contain a structural unit containing 2 or more kinds of 4-valent aromatic group represented by formula (4) as Y. The polyamideimide resin may contain a structural unit containing 1 kind of 4-valent aromatic group represented by formula (5) as Y, or may contain a structural unit containing 2 or more kinds of 4-valent aromatic groups represented by formula (5) as Y. The polyamideimide resin may contain both a structural unit containing 1 or more kinds of 4-valent aromatic groups represented by the formula (4) as Y and a structural unit containing 1 or more kinds of 4-valent aromatic groups represented by the formula (5). The polyamideimide resin may further include a structural unit (1) having an aromatic group as Y, which does not belong to either formula (4) or formula (5).

The polyamideimide resin of the present invention has at least the structural unit (1) and the structural unit (2) as described above, and the resin usually has a plurality of structural units (1), a plurality of structural units (2), and any other structural unit. In the present specification, the structural unit (1) containing a 4-valent aromatic group represented by the formula (4) as Y means that Y in at least a part of the structural units (1) in the plurality of structural units (1) of the polyamideimide resin is represented by the formula (4). The above description is also applicable to other descriptions in the present specification.

In a preferred embodiment of the present invention in which the structural unit (1) contained in the polyamideimide resin of the present invention contains a 4-valent aromatic group represented by formula (4) and/or a 4-valent aromatic group represented by formula (5) as Y, the total ratio of the structural unit in which Y in formula (1) is a 4-valent aromatic group represented by formula (4) and the structural unit in which Y in formula (1) is a 4-valent aromatic group represented by formula (5) is preferably 70 to 100 mol%, more preferably 80 to 100 mol%, further preferably 90 to 100 mol%, and also may be the structural unit in which Y in formula (1) is a 4-valent aromatic group represented by formula (5), from the viewpoint of easily improving the elastic modulus of the optical film, when the total of the structural units (1) contained in the polyamideimide resin is 100 mol%) Y in all the structural units is a 4-valent aromatic group represented by the formula (4) and/or a 4-valent aromatic group represented by the formula (5). The structural unit represented by formula (1) preferably contains a 4-valent aromatic group represented by formula (4) as Y from the viewpoint of easily improving the surface hardness (pencil hardness) of the optical film obtained. The content of the structural unit (1) and the structural unit (1) in which Y is a 4-valent aromatic group represented by the formula (4) or the formula (5) can be used, for example¹H-NMR, or the ratio of the raw materials charged may be calculated. The same applies to the case where Y described above in the structural unit (1) is a 4-valent aromatic group represented by formula (4a) and/or a 4-valent aromatic group represented by formula (5a) described later.

R in the formulae (4) and (5)²And R³Independently of each other, at least 1 of the substituents (i) to (vii) above, and/or a group in which a hydrogen atom contained in the substituents (i) to (vii) above is further substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. In a preferred embodiment of the present invention, R in the formulae (4) and (5)²And R³Independently 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, R²And R³The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. R²And/or R³When the alkyl group having 1 to 6 carbon atoms is represented, examples of the group include groups having 1 to 6 carbon atoms among the groups described for (i) alkyl groups having 1 to 12 carbon atoms, which are described above as substituents that the 4-valent aromatic group may have. R²And/or R³When the alkoxy group having 1 to 6 carbon atoms is represented, examples of the group include groups having 1 to 6 carbon atoms among the groups described for (ii) the alkoxy group having 1 to 12 carbon atoms, which are described above as substituents that the 4-valent aromatic group may have. R²And/or R³When the aryl group has 6 to 12 carbon atoms, examples of the group include substituents which may be contained as a 4-valent aromatic group and are described above(iv) the group described for (iii) an aryl group having 6 to 12 carbon atoms. R²And/or R³In the case of a hydrogen atom or the above-mentioned group, R²And/or R³The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. In a preferred embodiment of the present invention, R is R from the viewpoint of easily improving the elastic modulus of an optical film obtained using a polyamideimide resin²And R³Preferably a hydrogen atom.

N in formula (4) represents an integer of 0 to 2, and is preferably 0 or 1, and more preferably 0, from the viewpoint of easily improving the elastic modulus of an optical film obtained using a polyamideimide resin.

In a preferred embodiment of the present invention, from the viewpoint of easily improving the elastic modulus and the light transmittance of the optical film, the formula (4) is represented by formula (4a), and/or the formula (5) is represented by formula (5 a).

[ chemical formula 13]

[ chemical formula 14]

The formula (4a) corresponds to R in the formula (4)²An aromatic group in which n is 0 and the formula (5a) corresponds to R in the formula (5)³An aromatic group which is a hydrogen atom.

X in the formula (1) and the formula (2) is a 2-valent organic group represented by the formula (3).

[ chemical formula 15]

[ in formula (3), R¹Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or a carbon atomAn aryl group having 6 to 12 atomic numbers,

R¹the hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

v represents-O-, diphenylmethylene, straight chain, branched chain or alicyclic 2-valent hydrocarbon group having 1-12 carbon atoms, -SO₂-, -S-, -CO-or-N (R)¹²) Wherein the hydrogen atoms contained in the hydrocarbon group, independently of each other, may be substituted by halogen atoms,

R¹²represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom ]

R¹Independently 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, R¹The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. R¹When 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 is used, examples of the alkyl group having 1 to 6 carbon atoms include a group having 1 to 6 carbon atoms among the groups described above for (i) an alkyl group having 1 to 12 carbon atoms as a substituent that the 4-valent aromatic group may have, examples of the alkoxy group having 1 to 6 carbon atoms include a group having 1 to 6 carbon atoms among the groups described for (ii) an alkoxy group having 1 to 12 carbon atoms, and examples of the aryl group having 6 to 12 carbon atoms include a group described for (iii) an aryl group having 6 to 12 carbon atoms.

V in the formula (3) represents-O-, diphenylmethylene, straight chain, branched chain or alicyclic 2-valent hydrocarbon group with 1-12 carbon atoms and-SO₂-, -S-, -CO-or-N (R)¹²) -, wherein the hydrogen atoms contained in the hydrocarbon group independently of each other may be substituted by halogen atoms, R¹²Represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms include those for R in the formula (1)¹The (i) alkyl group having 1 to 12 carbon atoms.

In a preferred embodiment of the present invention, V in formula (3) preferably represents-O-, a diphenylmethylene group, a linear, branched or alicyclic 2-valent hydrocarbon group having 1 to 12 carbon atoms, or a group in which a hydrogen atom contained in the 2-valent hydrocarbon group having 1 to 12 carbon atoms is substituted with a halogen atom, and more preferably represents a 2-valent hydrocarbon group having 1 to 12 carbon atoms, or a group in which a hydrogen atom contained in the 2-valent hydrocarbon group having 1 to 12 carbon atoms is substituted with a halogen atom.

The V in the formula (3) is a group in which at least 1 hydrogen atom of a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms is replaced by a chemical bond, as the linear, branched or alicyclic 2-valent hydrocarbon group having 1 to 12 carbon atoms. Examples of the linear, branched or alicyclic alkyl group having 1 to 12 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-methyl-butyl group, a 3-methylbutyl group, a 2-ethyl-propyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, a tert-octyl group, an n-nonyl group, an n-decyl group, a cyclopentyl group, a cyclohexyl group and the like. The C1-12 divalent hydrocarbon group may be a linear alkylene group, a branched alkylene group, or an alicyclic alkylene group having an alicyclic hydrocarbon structure. The number of carbon atoms of the 2-valent hydrocarbon group having 1 to 12 carbon atoms is preferably 1 to 6, more preferably 1 to 4, and further preferably 1 to 3. The above-mentioned C1-12 hydrocarbon group having a valence of 2 may be a group in which at least 1 hydrogen atom is independently substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom.

V in the formula (3) is more preferably a group in which at least 1 hydrogen atom of a linear, branched or alicyclic alkylene group having 1 to 12 carbon atoms is substituted with a halogen atom (preferably a fluorine atom) (preferably a fluoroalkylene group having 1 to 12 carbon atoms), and still more preferably a group in which all hydrogen atoms of a linear, branched or alicyclic alkylene group having 1 to 12 carbon atoms are substituted with a halogen atom (preferably a fluorine atom) (preferably a perfluoroalkylene group having 1 to 12 carbon atoms, and particularly preferably a bistrifluoromethylmethylene group).

One advantage of the inventionIn an alternative embodiment, X in formula (1) and formula (2) is preferably: r in the formula (3)¹And V is preferably a 2-valent organic group represented by the formula (3), wherein V is a hydrogen atom and is preferably a group (preferably a fluoroalkylene group having 1 to 12 carbon atoms) in which at least 1 hydrogen atom of a linear, branched or alicyclic 2-valent hydrocarbon group having 1 to 12 carbon atoms is substituted with a halogen atom (preferably a fluorine atom), more preferably a group (preferably a perfluoroalkylene group having 1 to 12 carbon atoms, further preferably a bistrifluoromethylmethylene group) in which all hydrogen atoms of a linear, branched or alicyclic 2-valent hydrocarbon group having 1 to 12 carbon atoms are substituted with a halogen atom (preferably a fluorine atom).

In a preferred embodiment of the present invention, the formula (3) is represented by formula (3a) in view of easily improving the processability and light transmittance of an optical film obtained using the polyamideimide resin.

[ chemical formula 16]

When the structural unit (1) and the structural unit (2) contained in the polyamideimide resin of the present invention contain the 2-valent organic group represented by the formula (3a) as X, the total ratio of the structural unit represented by the formula (3a) as X in the formula (1) and the structural unit represented by the formula (3a) as X in the formula (2) is preferably 1 to 50 mol%, more preferably 3 to 40 mol%, and further preferably 5 to 30 mol%, from the viewpoint of easily improving the processability and light transmittance of the optical film, when the total of the structural unit (1) and the structural unit (2) contained in the polyamideimide resin is 100 mol%. The contents of the structural unit (1) and the structural unit (2), and the structural unit (1) and the structural unit (2) in which X is represented by the formula (3a) can be used, for example¹H-NMR, or the ratio of the raw materials charged may be calculated.

Z in the formula (2) is 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 hydrocarbon group having 1 to 8 carbon atoms substituted with fluorine, 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 hydrocarbon group having 1 to 8 carbon atoms substituted with fluorine and has a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. Examples of Z include a 2-valent organic group obtained by replacing non-adjacent 2 of 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) with a hydrogen atom, and a 2-valent chain hydrocarbon group having 6 or less carbon atoms, and an example of Z includes a 2-valent organic group having a thiophene ring skeleton as a heterocyclic structure of Z. From the viewpoint of easily reducing the yellowness (hereinafter, also referred to as YI value) of the optical layered body, a 2-valent organic group in which 2 nonadjacent groups among the chemical bonds of the groups represented by formulae (20) to (29) are replaced with hydrogen atoms, and a 2-valent organic group having a thiophene ring skeleton are preferable.

[ chemical formula 17]

In the formulae (20) to (29), the bond is represented by,

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.

The 2-valent organic group of Z in formula (2) 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').

[ chemical formula 18]

In [ formulae (20 ') to (29'), W¹And the same as defined in formula (20) to formula (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 substituted with fluorine, an alkoxy group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms substituted with fluorine.

In the case where the polyamideimide resin has a structural unit wherein Z in the formula (2) is represented by any one of the formulae (20 ') to (29'), particularly in the case where Z in the formula (2) is represented by the formula (6) 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 and easily obtaining the uniformity of the optical film.

[ chemical formula 19]

[ in the formula (d1), R^eIndependently represents 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^frepresents R^eor-C (═ O) -, represents a chemical bond]

R^eIn the formula (6), 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 R⁴～R¹¹The alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms. Specific examples of the structural unit (d1) include R^eAnd R^fStructural units each of which is a hydrogen atom (structural units derived from a dicarboxylic acid compound), R^eAre all hydrogen atoms and R^fA structural unit (a structural unit derived from a tricarboxylic acid compound) representing-C (═ O) -, and the like.

In one embodiment of the present invention, the polyamideimide resin may contain 1 type of 2-valent organic group, or may contain 2 or more types of 2-valent organic groups as Z in formula (2). When the polyamideimide resin contains 2 or more kinds of 2-valent organic groups as Z in formula (2), the 2-valent organic groups may be the same or different from each other.

In one embodiment of the present invention, from the viewpoint of easily improving the surface hardness and the optical characteristics of an optical film produced using the polyamideimide resin of the present invention, the polyamideimide resin preferably contains a 2-valent organic group represented by formula (6a), and more preferably contains a 2-valent organic group represented by formula (6) as Z in formula (2).

[ chemical formula 20]

[ in the formula (6a), R^gAnd R^hIndependently 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, A, m 'and A, m' and the same as those in the formula (6),

t and u are each independently an integer of 0 to 4]

[ chemical formula 21]

[ in the formula (6), R⁴～R¹¹Independently 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, R⁴～R¹¹The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

a independently of each other represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)¹²)-，

R¹²Represents a hydrogen atom, a C1-valent hydrocarbon group which may be substituted with a halogen atom and has 1 to 12 carbon atoms,

m' is an integer of 0 to 4,

denotes a chemical bond

In the formula (6a), the chemical bond of each benzene ring may be bonded to any of the ortho-position, meta-position or para-position based on-a-, and preferably may be bonded to the meta-position or para-position. R in the formula (6a)^gAnd R^hIndependently 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 (6a) are preferably 0, but when t and/or u is 1 or more, R^gAnd R^hPreferably represents an alkyl group having 1 to 6 carbon atoms, and more preferably represents an alkyl group having 1 to 3 carbon atoms. R in the formula (6a)^gAnd R^hIn the formula (6), 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 in the formula (6).

T and u in formula (6a) are independently an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0.

A in the formulas (6) and (6a) represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)¹²) From the viewpoint of the bending resistance of the optical film, the compound preferably represents-O-or-S-, and more preferably represents-O-.

In the formula (6), R⁴、R⁵、R⁶、R⁷、R⁸、R⁹、R¹⁰、R¹¹Independently represent a hydrogen atom or carbonAn 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-methyl-butyl group, a 3-methylbutyl group, a 2-ethyl-propyl group, and an n-hexyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a cyclohexyloxy group, 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. From the viewpoint of surface hardness and flexibility of the optical film, R⁴～R¹¹Independently 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, R⁴～R¹¹The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other.

R¹²Represents a hydrogen atom, a C1-valent hydrocarbon group which may be substituted with a halogen atom and has 1 to 12 carbon atoms. Examples of the 1-valent hydrocarbon group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, and n-decyl groups, 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.

In the formulae (6a) and (6), m 'is an integer in the range of 0 to 4, and when m' is in this range, the optical film tends to have good bending resistance and good elastic modulus. In the formulae (6a) and (6), m' is preferably an integer in the range of 0 to 3, more preferably 0 to 2, still more preferably 0 or 1, and particularly preferably 0. When m' is within this range, the bending resistance and the elastic modulus of the optical film are easily improved. In addition, the structural unit (2) may contain 1 or 2 or more kinds of the 2-valent organic groups represented by the formula (6) as Z, and in particular, the structural unit (2) may contain 2 or more kinds of the 2-valent organic groups having different values of m ', and preferably 2 or more kinds of the 2-valent organic groups having different values of m', from the viewpoint of improving the elastic modulus and the bending resistance of the optical film and reducing the YI value. In this case, from the viewpoint of easily exhibiting a high elastic modulus, high bending resistance, and a low YI value of the optical film, Z in the structural unit (2) of the polyamideimide resin preferably contains a 2-valent organic group represented by formula (6a) or formula (6) in which m 'is 0, and more preferably contains a 2-valent organic group represented by formula (6a) or formula (6) in which m' is 1 in addition to the 2-valent organic group. In this case, the polyamideimide resin includes 2 or more kinds of structural units (2) different from each other in at least Z in formula (2).

In a preferred embodiment of the present invention, in the polyamideimide resin, Z in formula (2) has a 2-valent organic group represented by formula (6a) or formula (6), m' is 0, and t in formula (6a) is 0 or R in formula (6)⁸～R¹¹An organic group which is a hydrogen atom. In a more preferred embodiment of the present invention, the polyamideimide resin has: wherein Z in formula (2) is a 2-valent organic group represented by formula (6a) or formula (6), and m' is 0, and t in formula (6a) is 0, or R in formula (6)⁸～R¹¹A structural unit (2) which is a hydrogen atom (more preferably, in formula (2), Z is a 2-valent organic group represented by formula (6), and m' is 0 and R is⁸～R¹¹A structural unit (2) which is a hydrogen atom); and Z in formula (2) is a structural unit (2) of a 2-valent organic group represented by formula (6'). In this case, the surface hardness and the bending resistance of the optical film are easily improved, and the YI value is easily reduced.

[ chemical formula 22]

When the polyamideimide resin of the present invention contains the 2-valent organic group represented by formula (6a) or formula (6) as Z in formula (2), the proportion of the structural unit (2) in which Z is the 2-valent organic group represented by formula (6a) or formula (6) is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, further more preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 95 mol% or less, more preferably 90 mol% or less, further preferably 85 mol% or less, when the total of the structural unit (1) and the structural unit (2) contained in the polyamideimide resin is taken as 100 mol%. When the ratio of the structural unit (2) in which Z is a 2-valent organic group represented by formula (6a) or formula (6) is not less than the lower limit, the surface hardness of the optical film is easily increased, and the bending resistance and the elastic modulus are easily increased. When the proportion of the structural unit (2) in which Z is a 2-valent organic group represented by formula (6a) or formula (6) is not more than the upper limit, the viscosity of the varnish containing the resin is easily inhibited from increasing due to hydrogen bonds between amide bonds derived from the structural unit, and the processability of the film is improved.

In addition, when the polyamideimide resin contains the structural unit (2) having Z as a 2-valent organic group represented by the formula (6a) or the formula (6) in which m 'is 1 to 4, the proportion of the structural unit (2) having Z as a 2-valent organic group represented by the formula (6a) or the formula (6) in which m' is 1 to 4 is preferably 3 mol% or more, more preferably 5 mol% or more, further preferably 7 mol% or more, particularly preferably 9 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, when the total of the structural unit (1) and the structural unit (2) contained in the polyamideimide resin is taken as 100 mol%. When the ratio of the structural unit (2) having a 2-valent organic group represented by formula (6a) or formula (6) wherein m' is 1 to 4 as Z is not less than the lower limit, the surface hardness and the bending resistance of the optical film can be easily improved. When the proportion of the structural unit (2) having Z as a 2-valent organic group represented by formula (6a) or formula (6) wherein m' is 1 to 4 is not more than the upper limit, the viscosity of the varnish containing the resin is easily inhibited from increasing due to hydrogen bonding between amide bonds derived from the structural unit (2) having Z as a 2-valent organic group represented by formula (6a) or formula (6), thereby improving the processability of the film. The structural unit (1), the structural unit (2), and the structure having a 2-valent organic group represented by formula (6a) or formula (6) as ZThe content of the unit (2) may be used, for example¹H-NMR, or the ratio of the raw materials charged may be calculated.

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 40 mol% or more, further preferably 45 mol% or more, further more preferably 50 mol% or more, and particularly preferably 70 mol% or more of Z in the structural unit (2) of the polyamideimide resin is a 2-valent organic group represented by formula (6a) or formula (6) in which m' is 0 to 4. When the lower limit of Z is a 2-valent organic group represented by formula (6a) or formula (6) in which m' is 0 to 4, the surface hardness of the optical film is easily increased, and the bending resistance and the elastic modulus are also easily increased. Further, the polyamideimide resin may have a structure in which 100 mol% or less of Z in the structural unit (2) is a 2-valent organic group represented by formula (6a) or formula (6) in which m' is 0 to 4. The proportion of the structural unit (2) in which Z is a 2-valent organic group represented by the formula (6a) or the formula (6) in which m' is 0 to 4 can be used, for example¹H-NMR, or the ratio of the raw materials charged may be calculated.

In a preferred embodiment of the present invention, preferably 5 mol% or more, more preferably 8 mol% or more, further preferably 10 mol% or more, and particularly preferably 12 mol% or more of Z in the structural unit (2) of the polyamideimide resin is a 2-valent organic group represented by formula (6a) or formula (6) in which m' is 1 to 4. When the lower limit of Z in the structural unit (2) is a 2-valent organic group represented by formula (3) in which m' is 1 to 4, the surface hardness of the optical film is easily increased, and the bending resistance and the elastic modulus are easily increased. In addition, the content of Z in the structural unit (2) is preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, and particularly preferably 30 mol% or less, and is preferably a 2-valent organic group represented by formula (6a) or formula (6) in which m' is 1 to 4. When the above upper limit or less of Z is a 2-valent organic group represented by formula (6a) or formula (6) in which m 'is 1 to 4, the viscosity of the varnish containing the resin is easily inhibited from increasing due to hydrogen bonding between amide bonds derived from the 2-valent organic group represented by formula (6a) or formula (6) in which m' is 1 to 4 as the structural unit (2) of Z, thereby improving the viscosityProcessability of the film. The proportion of the structural unit (2) in which Z is a 2-valent organic group represented by the formula (6a) or the formula (6) in which m' is 1 to 4 can be used, for example¹H-NMR, or the ratio of the raw materials charged may be calculated.

In a preferred embodiment of the present invention, from the viewpoint of easily improving the elastic modulus and the light transmittance of an optical film produced using a polyamideimide resin, the polyamideimide resin has 2 or more kinds of structural units represented by formula (2) in which at least Z is different from each other in formula (2), or 2 or more kinds of structural units represented by formula (2) in which at least X is different from each other in formula (2), and/or further has a structural unit represented by formula (7).

[ chemical formula 23]

[ in formula (7), Z is as defined for formula (1),

x' represents a 2-valent organic group not belonging to X in the formula (2) ]

Hereinafter, the structural unit represented by formula (7) is also referred to as structural unit (7). In the above-described embodiment, the polyamideimide resin may contain 2 or more kinds of structural units (2) different from each other in at least the Z portion in formula (2), or 2 or more kinds of structural units (2) different from each other in at least the X portion in formula (2), and/or may have another structural unit (7) that does not belong to formula (2) at least in the X portion.

In a preferred embodiment of the present invention in which the polyamideimide resin further has a structural unit (7), X' in formula (7) is not particularly limited as long as it represents a 2-valent organic group that does not belong to X in formula (1) (the 2-valent organic group represented by formula (3)), and from the viewpoint of easily improving the elastic modulus and the light transmittance of an optical film produced using the polyamideimide resin, it preferably represents a 2-valent organic group having 4 to 40 carbon atoms that does not belong to the 2-valent organic group represented by formula (3), and more preferably represents a 2-valent organic group having 4 to 40 carbon atoms that has a cyclic structure that does not belong to the 2-valent organic group represented by formula (3). 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. In one embodiment of the present invention, the structural unit (7) that the polyamideimide resin may contain 1 kind of organic group or 2 or more kinds of organic groups as X'.

In a preferred embodiment of the present invention, X' in formula (7) is preferably a 2-valent organic group which may have a substituent, and more preferably represented by formula (8), from the viewpoint of easily improving the elastic modulus and the light transmittance of the optical film.

[ chemical formula 24]

v represents a single bond, m represents an integer of 0 to 3, and

when X 'in the structural unit (7) is a 2-valent organic group represented by formula (8), 1 or 2 or more 2-valent organic groups represented by formula (8) may be contained as X' in the structural unit (7).

Ar in formula (8)²Represents a 2-valent aromatic group which may have a substituent. The 2-valent aromatic group is a group in which 2 hydrogen atoms of a monocyclic aromatic ring, a condensed polycyclic aromatic ring, or a ring-assembly aromatic ring are replaced with a chemical bond. The 2-valent aromatic group may include an aromatic ring having a ring (a single ring, a condensed multiple ring, or a ring assembly) formed only of carbon atoms, or may include an aromatic heterocyclic ring having a ring formed so as to contain an atom other than carbon atoms. Examples of the atom other than carbon atoms include a nitrogen atom, a sulfur atom and an oxygen atom. The total number of carbon atoms and atoms other than carbon atoms forming the aromatic ring is not particularly limited, but is preferably 5 to 18, more preferably 5 to E14, and more preferably 5 to 12. Specific examples of the monocyclic aromatic ring, the condensed polycyclic aromatic ring, and the ring-aggregated aromatic ring include the monocyclic aromatic ring, the condensed polycyclic aromatic ring, and the ring-aggregated aromatic ring described with respect to Y in formula (1). In the formula (8), when m is 1 or more, Ar is present in plural²May be the same or different from each other.

From the viewpoint of easily improving the elastic modulus and the light transmittance of the optical film, the 2-valent aromatic group which may have a substituent is preferably a group in which 2 hydrogen atoms of an aromatic hydrocarbon ring which may have a substituent are replaced with chemical bonds, more preferably a group in which 2 hydrogen atoms of benzene, biphenyl, terphenyl, or quaterphenyl which may have a substituent are replaced with chemical bonds, and even more preferably a group in which 2 hydrogen atoms of benzene or biphenyl which may have a substituent are replaced with chemical bonds.

As Ar²Examples of the substituent in (3) include an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogeno group, and a group in which a hydrogen atom contained in the above groups is substituted with a halogen atom. Specific examples of the alkyl group having 1 to 12 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, the aryl group having 6 to 12 carbon atoms, and the halogeno group, and the group in which a hydrogen atom contained in them is substituted with a halogen atom include groups described for (i) the alkyl group having 1 to 12 carbon atoms, (ii) the alkoxy group having 1 to 12 carbon atoms, (iii) the aryl group having 6 to 12 carbon atoms, and (vii) the halogeno group, which may be a substituent that the 4-valent aromatic group represented by Y in the formula (1) may have.

As Ar²The substituent(s) in (1) is preferably a halogen group or an alkyl group having 1 to 12 carbon atoms in which a hydrogen atom may be substituted with a halogen atom, and more preferably a methyl group, a fluoro group, a chloro group or a trifluoromethyl group.

V in the formula (8) represents a single bond. In the formula (8), m represents an integer of 0 to 3, and is preferably 0 to 2, more preferably 0 or 1, from the viewpoint of easily improving the elastic modulus, the light transmittance and the durability of the optical film.

In a preferred embodiment of the present invention in which the polyamideimide resin of the present invention further comprises a structural unit (7) (preferably, a structural unit represented by formula (7) in which X' is represented by formula (8)) in addition to the structural unit (1) and the structural unit (2), the proportion of the structural unit (2) is preferably 1 to 50 mol%, more preferably 3 to 40 mol%, and still more preferably 5 to 30 mol%, from the viewpoint of easily improving the elastic modulus and the light transmittance of the optical film, when the total of the structural unit (2) and the structural unit (7) contained in the polyamideimide resin is taken as 100 mol%.

In a preferred embodiment of the present invention, from the viewpoint of easily improving the elastic modulus and the light transmittance of the optical film, the formula (8) is represented by formula (8 a).

[ chemical formula 25]

[ in the formula (8a), R¹⁵Represents a fluoroalkyl group having 1 to 12 carbon atoms,

p and q independently represent an integer of 1 to 4, wherein when p and/or q represents an integer of 2 to 4, a plurality of R exist¹⁵May be the same as, or different from,

denotes a chemical bond

When the structural unit (7) contains a 2-valent organic group represented by the formula (8a) as X ', 1 or 2 or more 2-valent organic groups represented by the formula (8a) may be contained in the structural unit (7) as X'. In the structural unit (7), as X', in addition to the 2-valent organic group represented by the formula (8a), another 2-valent organic group that does not belong to either the 2-valent organic group represented by the formula (8a) or the 2-valent organic group represented by the formula (8) may be contained.

R in the formula (8a)¹⁵Represents a fluoroalkyl group having 1 to 12 carbon atoms. The group is a group in which at least 1 hydrogen atom of a linear or branched alkyl group having 1 to 12 carbon atoms is substituted with a fluorine atom. Examples of the linear or branched fluoroalkyl group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl groupButyl group, n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group, n-heptyl group, n-octyl group, t-octyl group, n-nonyl group, n-decyl group, and the like, in which at least 1 hydrogen atom is substituted with a fluorine atom. Specific examples of the fluoroalkyl group having 1 to 12 carbon atoms include a fluoromethyl group, a difluoromethyl group, a trifluoromethyl group, a fluoroethyl group, a difluoroethyl group, a trifluoroethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a nonafluorobutyl group, and the like. The number of carbon atoms of the fluoroalkyl group is preferably 1 to 6, more preferably 1 to 4, and further preferably 1 or 2.

The fluoroalkyl group having 1 to 12 carbon atoms is preferably a perfluoroalkyl group having 1 to 12 carbon atoms, more preferably a perfluoroalkyl group having 1 to 6 carbon atoms, still more preferably a perfluoroalkyl group having 1 to 4 carbon atoms, and particularly preferably a trifluoromethyl group or a pentafluoroethyl group, from the viewpoint of easily improving the elastic modulus, light transmittance, and durability of the optical film.

p and q independently represent an integer of 1 to 4. From the viewpoint of easily improving the elastic modulus, the light transmittance and the durability of the optical film, p is preferably an integer of 1 or 2, and more preferably 2. From the viewpoint of easily improving the elastic modulus, the light transmittance and the durability of the optical film, q is preferably an integer of 1 or 2, and more preferably 1. Where p and/or q represents an integer of 2 to 4, a plurality of R's are present⁴May be the same or different from each other, but a plurality of R's are present⁴Preferably identical to each other.

The 2 chemical bonds in the formula (8a) may be located at any of the ortho, meta, and para positions, but are preferably located at the para position from the viewpoint of easily improving the elastic modulus, light transmittance, and durability of the optical film.

Preferred examples of the 2-valent aromatic group represented by the formula (8a) include: r in the formula (8a)²An aromatic group having 1 to 12 carbon atoms, p is 2, q is 1 or 2, and/or 2 bonds are para to each other.

In a preferred embodiment of the present invention, formula (8a) is represented by formula (8 b).

[ chemical formula 26]

[ in the formula (8b), R¹⁶～R²³Independently represent a hydrogen atom or a fluoroalkyl group having 1 to 12 carbon atoms, and represent a chemical bond]

The formula (8b) corresponds to a formula in which the bonds in the formula (8a) are in alignment with each other and p is 2. In the formula (8b), R is preferably R from the viewpoint of easily improving the elastic modulus, the light transmittance and the durability of the optical film¹⁶～R²³At least two of them represent fluoroalkyl groups having 1 to 12 carbon atoms, more preferably at least R¹⁸And R²⁰Represents a fluoroalkyl group having 1 to 12 carbon atoms, and more preferably R¹⁸And R²⁰Represents a fluoroalkyl group having 1 to 12 carbon atoms and R¹⁶、R¹⁷、R¹⁹、R²¹、R²²And R²³Represents a hydrogen atom. In the above aspect, the fluoroalkyl group having 1 to 12 carbon atoms is preferably a perfluoroalkyl group having 1 to 12 carbon atoms, more preferably a perfluoroalkyl group having 1 to 6 carbon atoms, still more preferably a perfluoroalkyl group having 1 to 4 carbon atoms, yet still more preferably a trifluoromethyl group or a pentafluoroethyl group, and particularly preferably a trifluoromethyl group.

In a preferred embodiment of the present invention, formula (8b) is represented by formula (8 c).

[ chemical formula 27]

[ in the formula (8c), denotes a chemical bond ]

The formula (8c) corresponds to R in the formula (8b)¹⁸And R²⁰Represents a trifluoromethyl group, and R¹⁶、R¹⁷、R¹⁹、R²¹、R²²And R²³Represents a chemical formula of a hydrogen atom.

The polyamideimide resin may contain a structural unit represented by formula (30) and/or a structural unit represented by formula (31) in addition to the structural unit represented by formula (1), the structural unit represented by formula (2), and, if necessary, the structural unit represented by formula (7).

[ chemical formula 28]

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 include groups described as Y in the formula (1). In one embodiment of the present invention, the polyamideimide-based resin 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 may include a group obtained by replacing a hydrogen atom with any one of the chemical bonds of the group represented by Y in the formula (1), and a chain hydrocarbon group having 6 or less carbon atoms and having a valence of 3. In one embodiment of the present invention, the polyamideimide-based resin 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 thereof may include a group represented by X in the formula (2) and a group represented by X' in the formula (7).

In one embodiment of the present invention, the polyamideimide resin is formed of a structural unit represented by formula (1), a structural unit represented by formula (2), and optionally a structural unit represented by formula (7), a structural unit represented by formula (30), and/or a structural unit represented by formula (31). Easily increase the modulus of elasticity of an optical filmIn the polyamideimide resin, the structural unit represented by formula (1) and formula (2) is preferably 80 mol% or more, more preferably 90 mol% or more, and even more preferably 95 mol% or more, based on all the structural units represented by formula (1) and formula (2) and, if necessary, formula (7), formula (30), and formula (31). In the polyamideimide resin, the structural units represented by the formulae (1) and (2) are usually 100% or less based on all the structural units represented by the formulae (1) and (2) and, if necessary, the formulae (7), (30) and/or (31). The above ratio can be used, for example¹H-NMR, or the ratio of the raw materials charged may be calculated.

In one embodiment of the present invention, the content of the polyamideimide resin in the optical film is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, further preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, more preferably 95 parts by mass or less, per 100 parts by mass of the optical film. When the content of the polyamideimide resin is within the above range, the optical properties, elastic modulus and light transmittance of the optical film are easily improved.

The weight average molecular weight of the polyamideimide resin is preferably 200,000 or more, more preferably 250,000 or more, even more preferably 270,000 or more, and particularly preferably 300,000 or more, in terms of standard polystyrene, from the viewpoint of easily improving the elastic modulus, surface hardness, and bending resistance of the optical film. In addition, from the viewpoint of easily improving the solubility of the polyamideimide resin in a solvent and easily improving the stretchability and processability of the optical film, the weight average molecular weight of the resin is preferably 1,000,000 or less, more preferably 800,000 or less, even more preferably 700,000 or less, and particularly preferably 600,000 or less. The weight average molecular weight can be determined by GPC measurement and conversion to standard polystyrene, for example, and can be calculated by the method described in examples.

From the viewpoint of easily preventing wrinkles, scratches, and the like of the optical film, the elastic modulus of the optical film of the present invention is preferably 5.2GPa or more, more preferably 5.5GPa or more, further preferably 5.8GPa or more, particularly preferably 6.0GPa or more, and usually 100GPa or less. The elastic modulus can be measured using a tensile tester (the distance between chucks is 50mm, and the tensile speed is 10 mm/min), and can be measured, for example, by the method described in examples.

The optical film of the present invention has a total light transmittance (and/or a light transmittance with respect to light of 300 to 800 nm) of preferably 80% or more, more preferably 85% or more, further preferably 88% or more, further more preferably 89% or more, particularly preferably 90% or more, and usually 100% or less. When the total light transmittance is not less than the lower limit, visibility is easily improved when the optical film, particularly, the front panel is incorporated into a display device. The optical film of the present invention generally exhibits a high total light transmittance, and therefore, for example, the light emission intensity of a display element or the like required to obtain a certain luminance can be suppressed as compared with the case of using a film having a low transmittance. Therefore, power consumption can be reduced. For example, when the optical film of the present invention is incorporated into a display device, bright display tends to be obtained even when the amount of light from a backlight is reduced, and this contributes to energy saving. The total light transmittance may be, for example, a value in accordance with JIS K7361-1: 1997. the haze was determined using a haze computer. The total light transmittance may be a total light transmittance within a range of a thickness of an optical film to be described later.

The haze of the optical film of the present invention is preferably 5% or less, more preferably 4% or less, further preferably 3% or less, further more preferably 2.5% or less, particularly preferably 2% or less, particularly preferably 1% or less, particularly preferably 0.5% or less, and usually 0.01% or more. When the haze of the optical film is not more than the above upper limit, the visibility is easily improved when the optical film is incorporated into a display device, particularly as a front panel. The haze may be measured according to JIS K7136: 2000. the haze was determined using a haze computer.

The YI value of the optical film of the present invention is preferably 3.5 or less, more preferably 3.0 or less, further preferably 2.5 or less, and usually-5 or more, preferably-2 or more. When the YI value of the optical film is not more than the above upper limit, the transparency becomes good, and when the optical film is applied to a front panel of a display device, high visibility can be contributed. The YI value can be calculated based on the formula of YI × (1.2769X-1.0592Z)/Y by measuring the transmittance to light of 300 to 800nm using an ultraviolet-visible near-infrared spectrophotometer to obtain the tristimulus value (X, Y, Z). In the present specification, the optical film having excellent optical properties means a high light transmittance.

The thickness of the optical film of the present invention is preferably 10 μm or more, more preferably 20 μm or more, further preferably 25 μm or more, particularly preferably 30 μm or more, preferably 200 μm or less, more preferably 100 μm or less, further preferably 80 μm or less, particularly preferably 60 μm or less, and may be a combination of these upper and lower limits. When the thickness of the optical film is within the above range, the elastic modulus of the optical film is more easily increased. The thickness of the optical film can be measured using a micrometer, and can be measured, for example, by the method described in examples.

The pencil hardness of at least one surface of the optical film of the present invention is preferably HB or more, and more preferably F or more. When the pencil hardness of at least one surface of the optical film is equal to or higher than the above hardness, damage or the like on the surface of the optical film can be easily prevented. The pencil hardness may be measured in accordance with JIS K5600-5-4: 1999, it can be measured, for example, by the method described in examples.

The imidization ratio of the polyamide imide resin is preferably 90% or more, more preferably 93% or more, further preferably 96% or more, and usually 100% or less. The imidization ratio is preferably not less than the above-described lower limit from the viewpoint of easily improving the optical properties of the optical film. The imidization ratio represents a ratio of a molar amount of imide bonds in the polyamideimide resin to a value 2 times as large as a molar amount of a structural unit derived from a tetracarboxylic acid compound in the polyamideimide resin. When the polyamideimide resin contains a tricarboxylic acid compound, it means a ratio of a molar amount of imide bonds in the polyamideimide resin relative to a total of a value 2 times as large as a molar amount of a structural unit derived from a tetracarboxylic acid compound in the polyamideimide resin and a molar amount of a structural unit derived from a tricarboxylic acid compound. The imidization ratio can be determined by an IR method, an NMR method or the like.

The content of the halogen atom in the polyamideimide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and still more preferably 5 to 30% by mass, based on the mass of the polyamideimide resin. When the content of the halogen atom is not less than the above lower limit, the elastic modulus, the surface hardness, the transparency, and the visibility of the optical film are more easily improved. When the content of the halogen atom is not more than the above upper limit, the synthesis of the resin becomes easy.

< method for producing resin >

The polyamideimide resin can be produced, for example, from a tetracarboxylic acid compound, a dicarboxylic acid compound, and a diamine compound as main raw materials. Here, the structural unit represented by the above formula (1) is a structural unit formed by reacting a tetracarboxylic acid compound and a diamine compound, and the structural unit represented by the above formula (2) and the structural unit represented by the above formula (7) are structural units formed by reacting a dicarboxylic acid compound and a diamine compound. Accordingly, the polyamideimide resin can be produced by using a dicarboxylic acid compound, a tetracarboxylic acid compound and a diamine compound which form the structural units represented by the above formulae (1) and (2) and, if necessary, the structural unit represented by the formula (7).

Examples of the tetracarboxylic acid compound that can be used for producing the resin include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride. The tetracarboxylic acid compound may be used alone or in combination of 2 or more. The tetracarboxylic acid compound may be a tetracarboxylic acid compound analog such as an acid chloride compound, in addition to the dianhydride.

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 (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 (pyromellitic dianhydride (PMDA)), 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 (BPDA), 1,2,4, 5-benzenetetracarboxylic dianhydride (PMDA), 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, 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, bis (3, 4-dicarboxyphenyl) methane dianhydride, 4, 4' - (terephthaloxy) bisphthalic anhydride and 1,2,4, 5-benzenetetracarboxylic dianhydride (PMDA). These may be used alone or in combination of 2 or more.

Among the tetracarboxylic dianhydrides, from the viewpoint of easily improving the elastic modulus, light transmittance, surface hardness, transparency, bending resistance, and easily decreasing the coloring property of the optical film, 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, 1,2,4, 5-benzenetetracarboxylic dianhydride (PMDA), and mixtures thereof are preferable, and 3,3 ', 4, 4' -biphenyl tetracarboxylic dianhydride (BPDA) and 1 are more preferable, 2,4, 5-benzenetetracarboxylic dianhydride (PMDA), and mixtures thereof.

Examples of the dicarboxylic acid compound that can be used for producing 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 of these dicarboxylic acid compounds may be used in combination. As the dicarboxylic acid compound, terephthalic acid, 4' -oxybis-benzoic acid or an acid chloride compound thereof is preferably used. In addition to terephthalic acid, 4' -oxybis-benzoic acid or their acid chloride compounds, other dicarboxylic acid compounds may also be used. Examples of the other dicarboxylic acid compounds include isophthalic acid; naphthalenedicarboxylic acid; 4, 4' -biphenyldicarboxylic acid; 3, 3' -biphenyldicarboxylic acid; a dicarboxylic acid compound of chain hydrocarbon having 8 or less carbon atoms and 2 benzoic acids via a single bond, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂Examples of the compound in which-or phenylene groups are bonded to each other and the acid chloride compound thereof are mentioned. Specific examples thereof are preferably 4, 4' -oxybis (benzoyl chloride) and p-phenylene bisThe formyl chloride is more preferably used in combination with 4, 4' -oxybis (benzoyl chloride) and terephthaloyl chloride.

Examples of the diamine compound that can be used for producing the polyamideimide resin of the present invention include aromatic diamines. In the present 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 other 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. Among these, benzene rings are preferred.

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 ' -diaminodiphenyl methane, 4 ' -diaminodiphenyl propane, 4 ' -diaminodiphenyl ether, 3,4 ' -diaminodiphenyl ether, 4-diaminodiphenyl sulfone, 3 ' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-amino-phenoxy) benzene, bis (4-phenylene) sulfone, bis (4-phenylene) benzene, bis (4-phenylene) benzene, bis (bis) benzene) sulfone, bis (4-phenylene) benzene, bis (4-phenylene) benzene, bis (p) benzene, bis (4-phenylene) benzene, bis (p-phenylene) benzene, bis (2, bis (p-phenylene) benzene, 2, bis (p-phenylene) benzene, 2, bis (p-phenylene) benzene, bis (p-phenylene) benzene, 2, bis (bis) benzene, 2, bis (p) benzene, 2, bis (p-phenylene) benzene, 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 may 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), 4,4 '-bis (4-aminophenoxy) biphenyl, 4' - (hexafluoropropylidene) diphenylamine (6FDAM), 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, 4 ' - (hexafluoropropylidene) diphenylamine (6 FDAM). These may be used alone or in combination of 2 or more.

The diamine compound that can be used for producing the polyamideimide resin of the present invention may be an aliphatic diamine in addition to an aromatic diamine. 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.

Among the diamine compounds, 1 or more selected from the group consisting of aromatic diamines having a biphenyl structure are preferably used from the viewpoints of high surface hardness, high transparency, high flexibility, high bending resistance, and low coloring of the optical film. More preferably, at least one selected from the group consisting of 2,2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) benzidine, 4 '-bis (4-aminophenoxy) biphenyl, 4' -diaminodiphenyl ether, and 4,4 '- (hexafluoropropylidene) diphenylamine is used, and still more preferably, 2' -bis (trifluoromethyl) -4,4 '-diaminobiphenyl (TFMB) and/or 4, 4' - (hexafluoropropylidene) diphenylamine (6FDAM) is used.

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

Examples of the 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 anhydrides of 1,2, 4-benzenetricarboxylic acid; 2,3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; phthalic anhydride and benzoic acid through single bond, -O-, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene groups.

In the production of the resin, the amount of the diamine compound, the tetracarboxylic acid compound and/or the dicarboxylic acid compound to be used may be appropriately selected depending on the ratio of the respective constituent units of the desired polyamideimide resin.

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 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, from the viewpoint of easily improving the elastic modulus and the surface hardness of an optical film; more preferably, the polyamideimide resin is produced by a method comprising the step (I) of reacting a diamine compound with a tetracarboxylic acid compound to produce an intermediate (a), and the step (II) of reacting the intermediate (a) with a dicarboxylic acid compound, wherein the dicarboxylic acid compound is added in portions in the step (II).

It is considered that the transmittance and elastic modulus of the optical film can be easily improved by producing the polyamideimide resin of the present invention having at least the structural unit (1) and the structural unit (2) by the method of adding the dicarboxylic acid compound in a batch. Further, the weight average molecular weight of the resin can be easily adjusted to a desired range by using a method of adding the dicarboxylic acid compound in portions.

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 in a batch, and more preferably resins obtained by a production method of adding a dicarboxylic acid compound in a batch in the step (II) by 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 including 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 further preferably 5 to room temperature (about 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 an inert gas atmosphere such as nitrogen or argon while stirring, or may be carried out under normal pressure, increased pressure or reduced pressure. In a preferred embodiment, the stirring is carried out under normal pressure and/or under the inert gas atmosphere.

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 molecular weight of the polyamideimide resin can be easily adjusted to the above-mentioned preferred range by adding the dicarboxylic acid compound in portions rather than all at once. In the present specification, the batch addition means: the dicarboxylic acid compound to be added is added in several 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. The prescribed interval or prescribed time also includes a very short interval or time, and therefore the batch addition also includes continuous addition or continuous feeding.

In the step (II), the number of times of addition of 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. When the number of batches is within the above range, it is considered that the transmittance of the optical film is easily maintained and the structure optimal for increasing the elastic modulus is formed. It is also considered that the weight average molecular weight of the polyamideimide resin can be easily adjusted to the above-mentioned preferred range.

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

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, when the weight average molecular weight of the polyamide resin is preferably 10% or more, more preferably 15% or more, based on the weight average molecular weight of the polyamide 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 room temperature (about 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, increased pressure or reduced pressure. In a preferred embodiment, the step (II) is performed under normal pressure and/or in an 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 solution 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).

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 5 to 200 ℃, and more preferably 5 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. In addition, the reaction is preferably carried out in a solvent which is inactive 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 is preferably used from the viewpoint of solubility.

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 is partially imidized (ring-closed), and a polyamideimide resin including 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 an acid anhydride together with an imidization catalyst. The acid anhydride may be a conventional acid anhydride used in the imidization reaction, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride and butyric anhydrideAromatic acid anhydrides such as aliphatic acid anhydrides and phthalic acid.

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

< Filler >

The present invention also provides an optical film comprising the above polyamideimide resin. The optical film of the present invention may comprise at least 1 filler. Examples of the filler include organic particles and inorganic particles, and preferably inorganic particles. Examples of the inorganic particles include silicon dioxide, zirconium dioxide, aluminum oxide, titanium dioxide, zinc oxide, germanium oxide, indium oxide, tin oxide, Indium Tin Oxide (ITO), metal oxide particles such as antimony oxide and cerium oxide, and metal fluoride particles such as magnesium fluoride and sodium fluoride, and among these, from the viewpoint of easily improving the elastic modulus and/or tear strength of the optical film and easily improving the impact resistance, silicon dioxide particles, zirconium dioxide particles and aluminum oxide particles are preferable, and silicon dioxide particles are more preferable. These fillers may be used alone or in combination of 2 or more.

The average primary particle diameter of the filler, preferably the silica particles, is usually 1nm or more, preferably 5nm or more, more preferably 10nm or more, further preferably 15nm or more, particularly preferably 20nm or more, preferably 100nm or less, more preferably 90nm or less, further preferably 80nm or less, further preferably 70nm or less, particularly preferably 60nm or less, particularly preferably 50nm or less, and particularly preferably 40nm or less. When the average primary particle size of the silica particles is within the above range, aggregation of the silica particles is easily suppressed, and the optical properties of the obtained optical film are easily improved. The average primary particle diameter of the filler can be measured by the BET method. The average primary particle size may be measured by image analysis using a transmission electron microscope or a scanning electron microscope.

When the optical film of the present invention contains a filler, preferably silica particles, the content of the filler is usually 0.1 part by mass or more, preferably 1 part by mass or more, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, further preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 60 parts by mass or less, per 100 parts by mass of the optical film. When the content of the filler is not less than the above lower limit, the elastic modulus of the optical film to be obtained is easily increased. When the content of the filler is not more than the upper limit, the optical properties of the optical film are easily improved.

< ultraviolet absorber >

The optical film of the present invention may comprise at least 1 ultraviolet absorber. The ultraviolet absorber can be appropriately selected from those generally used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400nm or less. Examples of the ultraviolet absorber include at least 1 compound selected from the group consisting of benzophenone-based compounds, salicylate-based compounds, benzotriazole-based compounds, and triazine-based compounds. The ultraviolet absorber may be used alone or in combination of two or more. Since the optical film contains the ultraviolet absorber, deterioration of the resin can be suppressed, and thus, when the optical film of the present invention is applied to a display device or the like, visibility can be improved. In the present specification, the term "related compound" refers to a derivative of a compound to which the "related compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a matrix skeleton and a substituent bonded to benzophenone.

When the optical film of the present invention contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 0.01 to 10 parts by mass, more preferably 1 to 8 parts by mass, and still more preferably 2 to 7 parts by mass, based on the mass of the polyamideimide resin contained in the optical film. When the content of the ultraviolet absorber is not less than the above lower limit, the ultraviolet absorbability is easily improved. When the content of the ultraviolet absorber is not more than the above upper limit, decomposition of the ultraviolet absorber by heat during production of the substrate can be suppressed, and optical characteristics, for example, haze can be easily improved.

< other additives >

The optical film of the present invention may further contain other additives besides the filler and the ultraviolet absorber. Examples of the other additives include colorants such as antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, and leveling agents. When other additives are contained, the content thereof may be preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and still more preferably 0.1 to 10 parts by mass, relative to the mass of the optical film.

(method for producing optical film)

The method for producing an optical film using the polyamideimide resin of the present invention is not particularly limited, and for example, a production method including the following steps can be used.

(a) A step of preparing a polyamideimide resin composition (hereinafter also referred to as "varnish") containing at least the polyamideimide resin and a solvent (varnish preparation step),

(b) a step of applying a varnish to a support material to form a coating film (coating step), and

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

In the varnish preparation step, the polyamide imide resin is dissolved in a solvent, and if necessary, the above-mentioned additives such as the filler and the ultraviolet absorber are added and stirred and mixed to prepare a varnish. When silica particles are used as the filler, a silica sol obtained by replacing a dispersion of a silica sol containing silica particles with a solvent capable of dissolving the resin, for example, a solvent usable in the preparation of a varnish described below, may be added to the resin.

The solvent used in the preparation of the varnish is not particularly limited as long as the 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 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 (mixed solvents). Among these, amide solvents or lactone solvents are preferable. These solvents may be used alone or in combination of two or more. The 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 20 mass%, and still more preferably 5 to 15 mass%.

In the coating step, a varnish is applied to the support material 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 film forming step, the coating film is dried and peeled from the support material, whereby an optical film can be formed. After the peeling, a step of drying the optical film may be further provided. The drying of the coating film may 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 support material include a metal-based SUS plate, and a resin-based PET film, a PEN film, a polyamide-based resin film, a polyimide-based resin film, a cycloolefin-based polymer (COP) film, and an acrylic film. Among them, a PET film, a COP film, and the like are preferable from the viewpoint of excellent smoothness and heat resistance, and a PET film is more preferable from the viewpoint of adhesion to an optical film and cost.

The application of the optical film of the present invention is not particularly limited, and the optical film can be used for various applications. 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, the optical film is referred to as an optical film including all layers laminated on one or both surfaces of the optical film.

(functional layer)

At least one surface of the optical film of the present invention may have 1 or more functional layers stacked thereon. 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.

A hard coat layer may be provided on at least one side of the optical film of the present invention. The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100 μm. When the thickness of the hard coat layer is within the above range, sufficient scratch resistance can be secured, and the flex resistance is less likely to be lowered, and the problem of curling due to curing shrinkage is less likely to occur.

The aforementioned hard coat layer may be formed by: curing the hard coating composition including the reactive material capable of forming a cross-linked structure by irradiating active energy rays or imparting thermal energy; preferably by irradiation with active energy rays. The active energy ray is defined as an energy ray that can decompose a compound that generates an active species to generate an active species, and examples thereof include visible light, ultraviolet light, infrared light, X-ray, α -ray, β -ray, γ -ray, and electron beam, and preferable examples thereof include ultraviolet light. The hard coat composition contains at least 1 polymer selected from the group consisting of a radically polymerizable compound and a cationically polymerizable compound.

The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group of the radical polymerizable compound may be a functional group capable of undergoing a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond, specifically, a vinyl group and a (meth) acryloyl group. When the radical polymerizable compound has 2 or more radical polymerizable groups, the radical polymerizable groups may be the same or different from each other. The number of radical polymerizable groups in 1 molecule of the radical polymerizable compound is preferably 2 or more in terms of increasing the hardness of the hard coat layer. The radical polymerizable compound preferably includes a compound having a (meth) acryloyl group in view of high reactivity, specifically, a compound called a polyfunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in 1 molecule, an oligomer called epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate having several (meth) acryloyl groups in a molecule and having a molecular weight of several hundred to several thousand, and preferably 1 or more selected from the group consisting of epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate.

The cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an oxetane group, or a vinyl ether group. The number of the cationically polymerizable groups contained in 1 molecule of the cationically polymerizable compound is preferably 2 or more, and more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.

Among the above cationically polymerizable compounds, preferred are compounds having at least 1 of an epoxy group and an oxetanyl group as a cationically polymerizable group. A cyclic ether group such as an epoxy group or an oxetane group is preferable in that shrinkage accompanying the polymerization reaction is small. In addition, the compound having an epoxy group in a cyclic ether group has the following advantages: it is easy to obtain compounds having various structures, to exert no adverse effect on the durability of the obtained hard coat layer, and to control the compatibility with the radical polymerizable compound. In addition, the oxetanyl group in the cyclic ether group has the following advantages as compared with the epoxy group: the polymerization degree is easily increased, the forming speed of the network obtained by the cationic polymerizable compound of the obtained hard coat layer is increased, and even in the area mixed with the radical polymerizable compound, the unreacted monomer is not remained in the film, and the independent network is formed; and so on.

Examples of the cationically polymerizable compound having an epoxy group include: polyglycidyl ethers of polyhydric alcohols having an alicyclic ring or alicyclic epoxy resins obtained by epoxidizing compounds containing a cyclohexene ring or cyclopentene ring with an appropriate oxidizing agent such as hydrogen peroxide or a peroxy acid; aliphatic epoxy resins such as polyglycidyl ethers of aliphatic polyols or alkylene oxide adducts thereof, polyglycidyl esters of aliphatic long-chain polybasic acids, homopolymers and copolymers of glycidyl (meth) acrylate; glycidyl ethers produced by the reaction of bisphenols such as bisphenol a, bisphenol F and hydrogenated bisphenol a, or their derivatives such as alkylene oxide adducts and caprolactone adducts with epichlorohydrin, and glycidyl ether type epoxy resins derived from bisphenols such as Novolac epoxy resins.

The aforementioned hard coating composition may further comprise 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 are decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, and radical polymerization and cationic polymerization are performed.

The radical polymerization initiator may be a substance that can release and initiate radical polymerization by at least one of irradiation with active energy rays and heating. Examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, and azo compounds such as azobisbutyronitrile.

The active energy ray radical polymerization initiator includes a Type1 radical polymerization initiator which generates radicals by decomposition of molecules and a Type2 radical polymerization initiator which generates radicals by hydrogen abstraction reaction in the coexistence of a tertiary amine, and they can be used alone or in combination.

The cationic polymerization initiator may be a substance which can release a substance for initiating cationic polymerization by at least one of irradiation with active energy rays and heating. As the cationic polymerization initiator, aromatic iodonium salts, aromatic sulfonium salts, cyclopentadienyl iron (II) complexes, and the like can be used. Depending on the difference in structure, they can initiate cationic polymerization by either or both of irradiation with active energy rays or heating.

The polymerization initiator may be preferably contained in an amount of 0.1 to 10% by mass based on 100% by mass of the entire hard coat composition. When the content of the polymerization initiator is within the above range, the curing can be sufficiently advanced, the mechanical properties and the adhesion of the finally obtained coating film can be in a good range, and poor adhesion, a crack phenomenon, and a curl phenomenon due to curing shrinkage tend to be less likely to occur.

The hard coating composition may further include one or more selected from the group consisting of a solvent and an additive. The solvent may be used in a range that does not impair the effects of the present invention, as long as it is a solvent that can dissolve or disperse the polymerizable compound and the polymerization initiator and is known as a solvent for a hard coat composition in the art. The aforementioned additives may further include inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, and the like.

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 resin composition can be cured by converting the polymer into a polymer by supplying energy after the curing.

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 a laminate including an 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 the optical film and capable of providing a predetermined refractive index to the optical laminate. 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.

The optical film of the present invention may be a single layer or a laminate, and for example, the optical film produced as described above may be used as it is, or may be used in the form of a laminate with another film.

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, when one surface of the optical film has a functional layer, the protective film may be laminated on the surface of the optical film or the surface of the functional layer, or may be laminated on both the optical film and the functional layer. 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 not particularly limited as long as it is a peelable film that can temporarily 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, acrylic resin films and the like. When the optical film has 2 protective films, the protective films may be the same or different from each other.

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.

In a preferred embodiment of the present invention, the optical film of the present invention is useful as a front panel of a display device, particularly a front panel of a flexible display device (hereinafter, may be referred to as a window film). The flexible display device includes, for example, a flexible functional layer and an optical film laminated on the flexible functional layer and functioning as a front panel. That is, the front panel of the flexible display device is arranged on the viewing side on the flexible functional layer. The front panel has the function of protecting the flexible functional layer.

Examples of the display device include wearable devices such as televisions, smartphones, mobile phones, car navigation systems, tablet PCs, portable game machines, electronic paper, indicators, bulletin boards, clocks, and smartwatches. As the flexible display device, all display devices having a flexible characteristic can be cited.

[ Flexible display device ]

The invention also provides a flexible display device provided with the optical film. The optical film of the present invention is preferably used as a front panel in a flexible display device, which is sometimes referred to as a window film. The flexible display device is formed of 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 contain a window film, a polarizing plate (preferably a circularly polarizing plate), and a touch sensor, and the lamination order thereof is arbitrary, and it is preferable that the window film, the polarizing plate, and the touch sensor are laminated in this order or the window film, the touch sensor, and the polarizing plate are laminated in this order from the viewing side. The presence of the polarizing plate on the viewing side of the touch sensor is preferable because the pattern of the touch sensor is less likely to be observed and the visibility of the display image is good. The members may be laminated using an adhesive, a bonding agent, 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 ]

The flexible display device of the present invention may further include a polarizing plate, preferably 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 which is reflected by the organic EL panel and becomes left-handed circularly polarized light is blocked, only the light-emitting component of the organic EL is transmitted, and therefore the influence of reflected light is inhibited, and the image can be easily viewed. 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, but in practical applications, 45 ± 10 °. The linear polarizing plate and the λ/4 phase difference plate do not necessarily have to be stacked adjacent to each other, and the relationship between the absorption axis and the slow axis may satisfy the above range. It is preferable to achieve completely circularly polarized light at all wavelengths, but this is not necessarily the case in practical applications, and therefore, the circularly polarizing plate in the present invention also includes an elliptically polarizing plate. It is also preferable to further laminate a λ/4 retardation film 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 the following functions: light vibrating in the direction of the transmission axis is passed through, and polarized light of a vibration component perpendicular to the light is blocked. The linear polarizing plate may be a single linear polarizer or a structure including 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 is within the above range, the flexibility tends not to be lowered easily.

The linear polarizer may be a film-type polarizer manufactured by dyeing and stretching a polyvinyl alcohol (PVA) film. The polarizing performance can be exhibited by adsorbing a dichroic dye such as iodine to a PVA film that has been stretched to be oriented, or by stretching the PVA film in a state of being adsorbed to the dichroic dye to orient the dichroic dye. The film-type polarizer may be produced by steps such as swelling, crosslinking with boric acid, washing with an aqueous solution, and drying. The stretching and dyeing step may be performed as a PVA 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 stretch ratio is preferably 2 to 10 times.

In addition, as another example of the polarizer, a liquid crystal coating type polarizer formed by coating a liquid crystal polarizing composition may be used. The liquid crystal polarizing composition may include a liquid crystal compound and a dichroic dye compound. The liquid crystalline compound is preferably used because it has a property of exhibiting a liquid crystal state, and when it has a high-order alignment state such as a smectic state, it can exhibit high polarizing performance. The liquid crystalline compound preferably has a polymerizable functional group.

The dichroic dye may have liquid crystallinity or may have a polymerizable functional group, and may be aligned with the liquid crystal compound to exhibit dichroism. Any of the compounds 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 is produced by applying a liquid crystal polarizing composition to an alignment film to form a liquid crystal polarizing layer.

The liquid crystal polarizing layer can be formed to a thinner thickness than the film type polarizer. The thickness of the liquid crystal polarizing layer may be preferably 0.5 to 10 μm, and more preferably 1 to 5 μm.

The foregoing alignment film can be produced, for example, by: the alignment film-forming composition is applied to a substrate, and alignment properties are imparted by rubbing, polarized light irradiation, or the like. The alignment film forming composition may contain a solvent, a crosslinking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like in addition to the alignment agent. Examples of the orientation agent include polyvinyl alcohols, polyacrylates, polyamide acids, and polyimides. In the case of applying photo-alignment, 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 may be about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000nm, more preferably 10 to 500nm, from the viewpoint of alignment regulating force. The liquid crystal polarizing layer may be laminated by being peeled off from the substrate and then transferred, or the substrate may be directly laminated. The substrate preferably functions as a protective film, a retardation plate, or a transparent substrate for a window.

The protective film may be a transparent polymer film, and a material and an additive that can be used for the transparent base material may be used. Cellulose-based films, olefin-based films, acrylic films, and polyester films are preferable. The protective film may be a coating type protective film obtained by coating and curing a cationically curable composition such as an epoxy resin or a radically curable composition such as an acrylate. If necessary, 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, or the like may be included. The thickness of the protective film may be 200 μm or less, preferably 1 to 100 μm. When the thickness of the protective film is within the above range, the flexibility of the protective film is not easily lowered. The protective film may also function as a transparent substrate for the window.

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 (i.e., 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. If necessary, a phase difference adjusting agent, 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 may be included. The thickness of the stretched retardation film may be 200 μm or less, preferably 1 to 100 μm. When the thickness is within the above range, the flexibility of the film tends not to be easily lowered.

Further, another example of the λ/4 retardation plate may be a liquid crystal coating type retardation plate formed by coating a liquid crystal composition. The liquid crystal composition contains a liquid crystalline compound having a property of exhibiting a liquid crystal state such as a nematic state, a cholesteric state, or a smectic state. Any compound including a liquid crystalline compound in the liquid crystal composition has a polymerizable functional group. The liquid crystal coating type retardation plate may further contain 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 an alignment film and curing the coating to form a liquid crystal retardation layer, as described in the liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed to a smaller thickness than the stretching type retardation plate. The thickness of the liquid crystal polarizing layer may be usually 0.5 to 10 μm, preferably 1 to 5 μm. The liquid crystal coated retardation film may be laminated by being peeled from a substrate and then transferred, or the substrate may be directly laminated. The substrate preferably functions as a protective film, a retardation plate, or a transparent substrate for a window.

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 it is not possible to achieve a retardation of λ/4 in all visible light regions, it is often designed so that an in-plane retardation of λ/4 is 100 to 180nm, preferably 130 to 150nm, in the vicinity of 560nm, which is high in visibility. The use of an inverse dispersion λ/4 phase difference plate using a material having a birefringence wavelength dispersion characteristic opposite to that of the usual one is preferable because it can improve visibility. As such a material, the material described in japanese patent application laid-open No. 2007-232873 and the like is preferably used also in the case of a stretched phase difference plate, and the material described in japanese patent application laid-open No. 2010-30979 is preferably used also in the case of a liquid crystal coated phase difference plate.

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 (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 use of the liquid crystal coating type retardation plate is preferable because the thickness can be reduced.

For the circularly polarizing plate, a method of laminating a positive C plate is also known in order to improve visibility in an oblique direction (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 phase difference in the thickness direction is-200 to-20 nm, preferably-140 to-40 nm.

[ touch sensor ]

The flexible display device of the present invention may further include a touch sensor. The touch sensor may be used as an input mechanism. As the touch sensor, 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 have been proposed, and any type may be used. Among them, the electrostatic capacitance system is preferable. The capacitive touch sensor may be divided into an active region and an inactive region located at a peripheral portion of the active region. The active region is a region corresponding to a region of the display unit on the display panel, which is a display screen, and is a region in which a user's touch is sensed, and the inactive region is a region corresponding to a region of the display unit, which is a non-display unit on the display device, which is not a display screen. 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) portion. As the substrate having the flexible property, the same material as the transparent substrate of the window can be used. The substrate of the touch sensor preferably has a toughness of 2,000 MPa% or more in terms of suppressing cracks in the touch sensor. The toughness may be more preferably 2,000 to 30,000 MPa%. Here, the toughness is defined as the area of the lower part of a Stress (MPa) -strain (%) curve (Stress-strain curve) obtained by a tensile test of a polymer material up to a failure point.

The sensing pattern may include a 1 st pattern formed along a 1 st direction and a 2 nd pattern formed along a 2 nd direction. The 1 st pattern and the 2 nd pattern are arranged in mutually different directions. The 1 st pattern and the 2 nd pattern are formed in the same layer, and in order to sense a touched position, the patterns must be electrically connected. The 1 st pattern is a form in which the unit patterns are connected to each other via a terminal, and the 2 nd pattern is a structure in which the unit patterns are separated from each other into islands, and therefore, in order to electrically connect the 2 nd pattern, a separate bridge electrode is required. The sensing pattern may use a known transparent electrode material. Examples thereof 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)), Carbon Nanotube (CNT), graphene, and a metal wire, and these may be used alone or in combination of 2 or more. Preferably, ITO can be used. The metal usable for the wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, chromium, and the like. These 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 sensor pattern, or may be formed of a metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of 2 or more of these metals. The 1 st pattern and the 2 nd pattern must be electrically insulated, and thus, an insulating layer is 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 in a structure of a layer covering the sensing pattern. In the latter case, 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 means for appropriately compensating for a difference in transmittance between a pattern region where a pattern is formed and a non-pattern region where no 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, and the optical adjustment layer may include an inorganic insulating substance or an organic insulating substance. The optical adjustment layer can be formed by applying a photocurable composition containing 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 inorganic particles.

The photocurable organic binder may include, for example, a copolymer of monomers such as an acrylate monomer, a styrene monomer, and a carboxylic acid monomer. 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.

The inorganic particles may include, for example, zirconium dioxide particles, titanium dioxide particles, aluminum oxide particles, and the like. 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 polarizing plate, and a touch sensor, and the film members of the layers, such as a linear polarizing plate and a λ/4 retardation plate, may be bonded together 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, and a rewetting adhesive can be used. Among them, water-based solvent-volatile adhesives, active energy ray-curable adhesives, and adhesives are generally used. The thickness of the adhesive layer can be adjusted as appropriate according to the required adhesive strength, and is, for example, 0.01 to 500. mu.m, preferably 0.1 to 300. mu.m. The adhesive layer may be present in a plurality of layers in the laminate for a flexible display device, and the thickness of each layer and the type of the adhesive used may be the same or different.

As the aqueous solvent volatile adhesive, 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 can be used as a main polymer. In addition to water and the main agent polymer, 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, the aqueous solvent volatile adhesive may be injected between the layers to be bonded, and the layers to be bonded may be bonded and then dried to impart adhesiveness. The thickness of the adhesive layer when the aqueous solvent-based volatile adhesive is used may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the aqueous solvent-volatile adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive 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 capable of forming an 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 radical polymerizable compounds and cationic polymerizable compounds, which are similar to the hard coat composition. The radical polymerizable compound may be the same type of radical polymerizable compound as used in the hard coat composition, as used in the hard coat composition. As the radical polymerizable compound that can be used in the adhesive layer, a compound having an acryloyl group is preferable. In order to reduce the viscosity of the adhesive composition, a monofunctional compound is preferably contained.

The cationic polymerizable compound may be the same kind of cationic polymerizable compound as used in the hard coat composition, similarly to the hard coat composition. The cationically polymerizable compound used in the active energy ray-curable composition is preferably an epoxy compound. To reduce the viscosity of the adhesive composition, it is also preferable to include a monofunctional compound as a reactive diluent.

In the active energy ray composition, a polymerization initiator may be further contained. The polymerization initiator may be selected from a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and the like. These polymerization initiators are those which 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. The initiator described in the description of the hard coating composition, which can initiate at least either of radical polymerization or cationic polymerization by irradiation with active energy rays, 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 the bonding is performed by the active energy ray-curable adhesive, the bonding may be performed by: the active energy ray-curable composition is applied to one or both of the adhesive layers and then bonded thereto, and the adhesive layer or both of the adhesive layers is irradiated with active energy rays through the adhesive layer or both of the adhesive layers to be cured. The thickness of the adhesive layer when the active energy ray-curable adhesive is used may be 0.01 to 20 μm, preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive used may be the same or different.

The adhesive may be classified into an acrylic adhesive, a urethane adhesive, a rubber adhesive, a silicone adhesive, and the like according to the base polymer, and may be used. The binder may contain a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, an adhesion promoter, a plasticizer, a dye, a pigment, an inorganic filler, and the like in addition to the main polymer. The adhesive layer (adhesive layer) can be formed by dissolving and dispersing the components constituting the adhesive in a solvent to obtain an adhesive composition, applying the adhesive composition to a substrate, and then drying the adhesive composition. The adhesive layer may be formed directly or by transferring an adhesive layer separately formed on the substrate. A release film is also preferably used to cover the pressure-sensitive adhesive surface before bonding. The thickness of the adhesive layer when the adhesive is used may be 1 to 500. mu.m, preferably 2 to 300. mu.m. When the above-mentioned adhesive is used for forming a plurality of layers, the thickness of each layer and the kind of the adhesive used may be the same or different.

[ light-shielding pattern ]

The light-shielding pattern may be applied as at least a portion 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 have various colors such as black, white, metallic color, and the like. 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 usually 1 to 100 μm, preferably 2 to 50 μm. Further, it is preferable to provide a shape such as an inclination in the thickness direction of the light-shielding pattern.

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.

< determination of elastic modulus >

The elastic modulus of the polyamide-imide films obtained in examples and comparative examples was measured by using "AUTOGRAPH AG-IS" manufactured by Shimadzu corporation. A film having a width of 10mm was produced, and a stress-strain curve (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 of the curve.

< measurement of light transmittance >

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

< measurement of surface hardness >

The surface hardness of the polyamideimide films obtained in examples and comparative examples was measured in accordance with JIS K5600-5-4: 1999, pencil hardness of the film surface was used. The presence or absence of damage was evaluated under an environment of 4,000 lux with a load of 100g and a scanning speed of 60 mm/min, and the surface hardness (surface hardness represented by pencil hardness) was measured.

< determination of weight average molecular weight >

Gel Permeation Chromatography (GPC) measurement

(1) Pretreatment method

DMF eluent (10mmol/L lithium bromide solution) was added to the sample so that the concentration became 2mg/mL, and the mixture was heated at 80 ℃ for 30 minutes with stirring, cooled, and then filtered through a 0.45 μm membrane filter to obtain a filtrate as a measurement solution.

(2) Measurement conditions

Column: TSKgel α -2500 (7)7.8mm diameter. times.300 mm). times.1, and α -M ((13)7.8mm diameter. times.300 mm). times.2, manufactured by 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 polyamideimide films obtained in the examples and comparative examples was measured using a micrometer ("ID-C112 XBS" manufactured by Mitutoyo Co., Ltd.).

< example 1 >

[ preparation of polyamideimide resin (1) ]

In a separable flask equipped with a stirring fin, 2 '-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylacetamide (DMAc) were charged under a nitrogen atmosphere so that the solid content of TFMB became 5.39 mass%, and 4, 4' - (hexafluoropropylidene) diphenylamine (6FDAM) in an amount of 11.11 mol% relative to TFMB was further added, and TFMB and 6FDAM were dissolved in DMAc with stirring at room temperature. Next, 3 ', 4, 4' -biphenyltetracarboxylic dianhydride (BPDA) was added to the flask so that it became 33.50 mol% with respect to TFMB, and stirred at room temperature for 3 hours. Thereafter, after cooling to 10 ℃, 4' -oxybis (benzoyl chloride) (OBBC) was added in an amount of 5.59 mol% based on TFMB and terephthaloyl chloride (TPC) was added in an amount of 30.15 mol% based on TFMB, and after stirring for 10 minutes, OBBC was further added in an amount of 5.59m o l% based on TFMB and TPC was further added in an amount of 30.15m o l% based on TFMB, and the mixture was stirred for 30 minutes. Then, DMAc was added in an amount equivalent to that of the DMAc initially added, and after stirring for 10 minutes, TPC was added so as to be 6.70 mol% with respect to TFMB, and the mixture was stirred for 2 hours. Subsequently, diisopropylethylamine and 4-methylpyridine in an amount of 78.17 mol% based on TFMB, and acetic anhydride in an amount of 234.51 mol% based on TFMB were added to the flask, and the mixture was stirred for 30 minutes, then the internal temperature was increased to 70 ℃, and the mixture was 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 polyamideimide resin (1) is 583,000.

[ production of Polyamide-imide film (1) ]

DMAc was added to the obtained polyamideimide resin (1) so that the concentration thereof became 10% by mass, thereby preparing a polyamideimide varnish (1). The obtained polyamideimide 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 a polyamideimide film (1) having a thickness of 45 μm.

< example 2 >

[ preparation of polyamideimide resin (2) ]

In a nitrogen atmosphere, TFMB and DMAc were added to a separable flask equipped with a stirring blade so that the solid content of TFMB became 5.60 mass%, and 6FDAM was further added in an amount of 11.11 mol% relative to TFMB, and TFMB and 6FDAM were dissolved in DMAc with stirring at room temperature. Next, pyromellitic dianhydride (PMDA) was added to the flask so that it became 33.50 mol% with respect to TFMB, and the mixture was stirred at room temperature for 3 hours. Thereafter, after cooling to 10 ℃, OBBC at 5.59 mol% to TFMB and TPC at 30.15 mol% to TFMB were added, and after stirring for 10 minutes, OBBC at 5.59m o/l% to TFMB and TPC at 30.15m o/l% to TFMB were further added, and stirring was carried out for 30 minutes. Then, DMAc was added in an amount equivalent to that of the DMAc initially added, and after stirring for 10 minutes, TPC was added so as to be 6.70 mol% with respect to TFMB, and the mixture was stirred for 2 hours. Subsequently, diisopropylethylamine and 4-methylpyridine in an amount of 78.17 mol% based on TFMB, and acetic anhydride in an amount of 234.51 mol% based on TFMB were added to the flask, and the mixture was stirred for 30 minutes, then the internal temperature was increased to 70 ℃, and the mixture was 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 (2). The weight average molecular weight of the polyamideimide resin (2) is 436,000.

[ production of Polyamide-imide film (2) ]

DMAc was added to the obtained polyamideimide resin (2) so that the concentration thereof became 10% by mass, thereby preparing a polyamideimide varnish (2). The obtained polyamideimide 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 a polyamideimide 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 5.54 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 30.20 mol% with respect to TFMB, and the mixture was stirred at room temperature for 3 hours. Thereafter, the mixture was cooled to 10 ℃ and then, OBBC in an amount of 10.07 mol% based on TFMB and TPC in an amount of 54.35 mol% based on TFMB were added thereto, followed by stirring for 30 minutes. Then, DMAc was added in an amount equivalent to that of the initially added DMAc, and after stirring for 10 minutes, TPC was added so as to be 6.04 mol% with respect to TFMB, and stirring was carried out for 2 hours. Subsequently, diisopropylethylamine and 4-methylpyridine, each in an amount of 70.46 mol% based on TFMB, and acetic anhydride in an amount of 211.37 mol% based on TFMB were added to the flask, and the mixture was stirred for 30 minutes, then the internal temperature was increased to 70 ℃, and the mixture was 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 (3). The weight average molecular weight of the polyamideimide resin (3) is 402,000.

[ production of Polyamide-imide film (3) ]

DMAc was added to the obtained polyamideimide resin (3) so that the concentration thereof became 10% by mass, thereby preparing a polyamideimide varnish (3). The obtained polyamideimide 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 a polyamideimide film (3) having a thickness of 50 μm.

< comparative example 2 >

[ 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 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 the mixture was stirred at room temperature for 3 hours. Thereafter, after cooling to 10 ℃, TPC was added so as to be 55.67 mol% with respect to TFMB, and the mixture was stirred for 30 minutes. Then, DMAc was added in an amount equivalent to that of the DMAc initially added, and after stirring for 10 minutes, TPC was added so as to be 6.19 mol% with respect to TFMB, and the mixture was stirred 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, then the internal temperature was increased to 70 ℃, and the mixture was 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 polyamideimide resin (4) was 174,000.

[ production of Polyamide-imide film (4) ]

DMAc was added to the obtained polyamideimide resin (4) so that the concentration thereof became 10% by mass, thereby preparing a polyamideimide varnish (4). The obtained polyamideimide 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 a polyamideimide film (4) having a thickness of 50 μm.

The elastic modulus, light transmittance and surface hardness (pencil hardness) of the polyamideimide resin films (1) to (4) were measured in the manner described above. The obtained results are shown in table 1.

[ Table 1]

Claims

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

[ chemical formula 1]

In the formula (1), the reaction mixture is,

y represents a 4-valent aromatic group which may have a substituent,

x represents a 2-valent organic group represented by the formula (3),

[ chemical formula 2]

In the formula (3), R¹Independently 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, R¹The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

v represents-O-, diphenylmethylene, straight chain, branched chain or alicyclic 2-valent hydrocarbon group having 1-12 carbon atoms, -SO₂-, -S-, -CO-or-N (R)¹²) -, wherein the hydrogen atoms contained in the hydrocarbon group independently of each other may be substituted by halogen atoms, R¹²Represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom,

[ chemical formula 3]

In the formula (2), Z represents a 2-valent organic group,

x is as defined in the aforementioned formula (1).

2. The polyamideimide resin according to claim 1, wherein V in formula (3) represents a linear, branched or alicyclic 2-valent hydrocarbon group having 1 to 12 carbon atoms, wherein hydrogen atoms contained in the hydrocarbon group may be independently substituted with a halogen atom.

3. The polyamideimide resin according to claim 1 or 2, wherein Y in the structural unit represented by formula (1) comprises a 4-valent aromatic group represented by formula (4) and/or a 4-valent aromatic group represented by formula (5),

in the formulae (4) and (5), R²And R³Independently 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, R²And R³The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

n represents an integer of 0 to 2.

4. The polyamideimide-based resin according to claim 3, wherein the formula (4) is represented by formula (4a),

[ chemical formula 4]

5. The polyamideimide-based resin according to claim 3, wherein the formula (5) is represented by the formula (5a),

[ chemical formula 5]

6. The polyamideimide-based resin according to any one of claims 1 to 5, wherein the formula (3) is represented by the formula (3a),

[ chemical formula 6]

7. The polyamideimide-based resin according to any one of claims 1 to 6, wherein the polyamideimide-based resin has at least 2 or more structural units represented by formula (2) in which Z are different from each other and/or at least 2 or more structural units represented by formula (2) in which X are different from each other and/or further has a structural unit represented by formula (7),

[ chemical formula 7]

In the formula (7), Z is as defined in the formula (1),

x' represents a 2-valent organic group not belonging to X in the formula (2).

8. The polyamideimide-based resin according to claim 7, wherein X' in the formula (7) is represented by the formula (8),

[ chemical formula 8]

In the formula (8), Ar²Represents a 2-valent aromatic group which may have a substituent,

v represents a single bond, and V represents a single bond,

m represents an integer of 0 to 3,

it represents a chemical bond.

9. The polyamideimide resin according to claim 7 or 8, wherein the proportion of the structural unit represented by the formula (2) is 1 to 50 mol% when the total of the structural unit represented by the formula (2) and the structural unit represented by the formula (7) is 100 mol%.

10. The polyamideimide resin according to any one of claims 1 to 9, wherein Z in the structural unit represented by formula (2) comprises a 2-valent aromatic group which may have a substituent.

11. An optical film comprising the polyamideimide-based resin according to any one of claims 1 to 10.

12. A flexible display device comprising the optical film according to claim 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.