JP2020109154A - Polyamide-imide resin, optical film and flexible display device - Google Patents

Abstract

To provide a polyamide-imide resin that makes it possible to produce an optical film having a high elastic modulus while maintaining a high light transmittance, and an optical film containing the resin.SOLUTION: A polyamide-imide resin has at least a constitutional unit represented by formula (1), and a constitutional unit represented by formula (2) [where Y is an optionally substituted tetravalent aromatic group, X, Z each denote a divalent organic group].SELECTED DRAWING: None

Description

The present invention relates to a polyamide-imide resin, an optical film containing the resin, and a flexible display device including the optical film.

Currently, 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 smart watches. Conventionally, glass has been used as the front plate of such a display device. However, while glass has high transparency and can exhibit high hardness depending on the type, it is very rigid and easily broken, so that it is difficult to use it as a front plate material of a flexible display device.

Therefore, utilization of polymer materials is being studied as a material to replace glass. Since a front plate made of a polymer material easily exhibits flexible properties, it is expected to be used in various applications. As one of flexible polymer materials, optical films using, for example, a polyamide-imide resin have been studied (Patent Documents 1 and 2).

Japanese Patent Publication No. 2015-521686 JP, 2008-119132, A

When an optical film produced using a polyamide-imide resin is used in a flexible display device or the like, defects such as scratches and wrinkles may occur in the optical film due to bending and contact with external factors. As a method of suppressing the occurrence of such defects, it is considered to increase the elastic modulus of the optical film, but depending on the type of the polyamide-imide resin, the elastic modulus of the obtained optical film may not be sufficiently increased. there were.

Therefore, an object of the present invention is to provide a polyamide-imide resin capable of producing an optical film having a high elastic modulus while maintaining a high transmittance, and an optical film containing the resin.

In order to solve the above-mentioned problems, the present inventors have paid attention to the structure of the monomer that constitutes the polyamideimide-based resin contained in the optical film, and have conducted earnest studies. As a result, it has been found that a polyamide-imide 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, and has completed the present invention. ..

［式（１）中、Ｙは、置換基を有していてもよい４価の芳香族基を表し、
Ｘは、式（３）：

〔式（３）中、Ｒ^１は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^１に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ｖは、−Ｏ−、ジフェニルメチレン基、炭素数１〜１２の直鎖状、分枝状又は脂環式の２価の炭化水素基、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^１２）−を表し、ここで、該炭化水素基に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、Ｒ^１２は、水素原子、又はハロゲン原子で置換されていてもよい炭素数１〜１２のアルキル基を表す〕
で表される２価の有機基を表す］
で表される構成単位、及び、式（２）：

［式（２）中、Ｚは２価の有機基を表し、
Ｘは前記式（１）において定義した通りである］
で表される構成単位を少なくとも有するポリアミドイミド系樹脂。
〔２〕式（３）中のＶは炭素数１〜１２の直鎖状、分枝状又は脂環式の２価の炭化水素基を表し、ここで、該炭化水素基に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよい、前記〔１〕に記載のポリアミドイミド系樹脂。
〔３〕式（１）で表される構成単位は、Ｙとして、式（４）で表される４価の芳香族基及び／又は式（５）で表される４価の芳香族基：

［式（４）及び式（５）中、Ｒ^２及びＲ^３は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^２及びＲ^３に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
ｎは０〜２の整数を表す］
を含む、前記〔１〕又は〔２〕に記載のポリアミドイミド系樹脂。
〔４〕式（４）は式（４ａ）：

で表される、前記〔３〕に記載のポリアミドイミド系樹脂。
〔５〕式（５）は式（５ａ）：

で表される、前記〔３〕に記載のポリアミドイミド系樹脂。
〔６〕式（３）は式（３ａ）：

で表される、前記〔１〕〜〔５〕のいずれかに記載のポリアミドイミド系樹脂。
〔７〕ポリアミドイミド系樹脂は、少なくともＺにおいて互いに異なる２種以上の式（２）で表される構成単位を有する、少なくともＸにおいて互いに異なる２種以上の式（２）で表される構成単位を有する、及び／又は、式（７）：

［式（７）中、Ｚは式（１）において定義した通りであり、
Ｘ’は、式（２）中のＸに該当しない２価の有機基を表す］
で表される構成単位をさらに有する、前記〔１〕〜〔６〕のいずれかに記載のポリアミドイミド系樹脂。
〔８〕式（７）中のＸ’は式（８）：

［式（８）中、Ａｒ^２は置換基を有していてもよい２価の芳香族基を表し、
Ｖは、単結合を表し、ｍは０〜３の整数を表し、＊は結合手を表す］
で表される、前記〔７〕に記載のポリアミドイミド系樹脂。
〔９〕式（２）で表される構成単位及び式（７）で表される構成単位の合計を１００モル％としたときに、式（２）で表される構成単位の割合は１〜５０モル％である前記〔７〕又は〔８〕に記載のポリアミドイミド系樹脂。
〔１０〕式（２）で表される構成単位は、Ｚとして、置換基を有していてもよい２価の芳香族基を含む、前記〔１〕〜〔９〕のいずれかに記載のポリアミドイミド系樹脂。
〔１１〕前記〔１〕〜〔１０〕のいずれかに記載のポリアミドイミド系樹脂を含む光学フィルム。
〔１２〕前記〔１１〕に記載の光学フィルムを備えるフレキシブル表示装置。
〔１３〕タッチセンサをさらに備える、前記〔１２〕に記載のフレキシブル表示装置。
〔１４〕偏光板をさらに備える、前記〔１２〕又は〔１３〕に記載のフレキシブル表示装置。 That is, the present invention includes the following preferred embodiments.
[1] Formula (1):

[In the formula (1), Y represents a tetravalent aromatic group which may have a substituent,
X is the formula (3):

In [Formula (3), ^{R 1,} independently of one another, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group or an aryl group having 6 to 12 carbon atoms having 1 to 6 carbon atoms, the ^{R 1} The contained hydrogen atoms may be independently substituted with a halogen atom,
V is, -O-, diphenylmethylene group, the number 1 to 12 linear, divalent hydrocarbon radical of branched or _{cycloaliphatic,} -SO 2 -, - S -, - CO- or - N(R ¹² )-, wherein the hydrogen atoms contained in the hydrocarbon group may be independently substituted with a halogen atom, and R ¹² is a hydrogen atom or a halogen atom. Represents an optionally substituted alkyl group having 1 to 12 carbon atoms]
Represents a divalent organic group represented by]
And a structural unit represented by the formula (2):

[In Formula (2), Z represents a divalent organic group,
X is as defined in the above formula (1)]
A polyamide-imide resin having at least a structural unit represented by:
[2] V in the formula (3) represents a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, wherein the hydrogen atom contained in the hydrocarbon group. Are independently of each other, may be substituted with a halogen atom, the polyamide-imide resin according to the above [1].
[3] The constitutional unit represented by the formula (1) is, as Y, a tetravalent aromatic group represented by the formula (4) and/or a tetravalent aromatic group represented by the formula (5):

[In the formulas (4) and (5), R ² and R ³ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 6 to 12 carbon atoms. The hydrogen atom, which represents an aryl group and is contained in R ² and R ³ , may be independently substituted with a halogen atom,
n represents an integer of 0 to 2]
The polyamide-imide resin according to the above [1] or [2], which comprises:
[4] Formula (4) is Formula (4a):

The polyamide-imide resin according to the above [3], represented by:
[5] Formula (5) is Formula (5a):

The polyamide-imide resin according to the above [3], represented by:
[6] Formula (3) is Formula (3a):

The polyamide-imide resin according to any one of [1] to [5] above.
[7] The polyamide-imide resin has at least two types of structural units represented by formula (2) different from each other in Z, and at least two types of structural units represented by formula (2) different from each other in X. And/or formula (7):

[In the formula (7), Z is as defined in the formula (1),
X′ represents a divalent organic group which does not correspond to X in the formula (2)]
The polyamide-imide resin according to any one of [1] to [6], further including a structural unit represented by:
[8] X′ in formula (7) is formula (8):

[In the formula (8), Ar ² represents a divalent aromatic group which may have a substituent,
V represents a single bond, m represents an integer of 0 to 3, and * represents a bond.]
The polyamide-imide resin according to the above [7], represented by:
[9] When the total of the constitutional unit represented by the formula (2) and the constitutional unit represented by the formula (7) is 100 mol %, the ratio of the constitutional unit represented by the formula (2) is 1 to The polyamide-imide resin according to the above [7] or [8], which is 50 mol%.
[10] The constitutional unit represented by the formula (2) contains, as Z, a divalent aromatic group which may have a substituent, and is represented by any one of the above [1] to [9]. Polyamide-imide resin.
[11] An optical film containing the polyamide-imide resin according to any one of [1] to [10].
[12] A flexible display device including the optical film according to [11].
[13] The flexible display device according to [12], further including a touch sensor.
[14] The flexible display device according to [12] or [13], further including a polarizing plate.

According to the polyamide-imide resin of the present invention, it is possible to provide an optical film having a high elastic modulus while maintaining a high transmittance. Further, the optical film of the present invention has a high elastic modulus while maintaining a high transmittance.

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

［式（１）中、Ｙは、置換基を有していてもよい４価の芳香族基を表し、
Ｘは、後述する式（３）で表される２価の有機基を表す］
で表される構成単位、及び、式（２）：

［式（２）中、Ｚは２価の有機基を表し、
Ｘは式（１）において定義した通りである］
で表される構成単位を少なくとも有する。式（１）で表される構成単位は、テトラカルボン酸化合物とジアミン化合物とが反応して形成される構成単位であり、式（２）で表される構成単位は、ジカルボン酸化合物とジアミン化合物とが反応して形成される構成単位である。本発明のポリアミドイミド系樹脂は、式（１）で表される１種類の構成単位を有していてもよいし、式（１）で表される２種類以上の構成単位を有していてもよい。同様に、該ポリアミドイミド系樹脂は、式（２）で表される１種類の構成単位を有していてもよいし、式（２）で表される２種類以上の構成単位を有していてもよい。なお、該ポリアミドイミド系樹脂は、式（１）で表される構成単位にも式（２）で表される構成単位にも該当しない、さらなる構成単位を含んでいてもよい。本明細書において、式（１）で表される構成単位を「構成単位（１）」とも称し、式（２）で表される構成単位を「構成単位（２）」とも称する。なお、式（１）及び式（２）中、点線で表される結合は、隣接する構成単位と結合する結合手を表す。本明細書において、他の化学構造式中の点線で表される結合も、同様に、隣接する構成単位又は基と結合する結合手を表す。 The polyamide-imide resin of the present invention has the formula (1):

[In the formula (1), Y represents a tetravalent aromatic group which may have a substituent,
X represents a divalent organic group represented by the formula (3) described below]
And a structural unit represented by the formula (2):

[In Formula (2), Z represents a divalent organic group,
X is as defined in formula (1)]
It has at least a structural unit represented by. The structural unit represented by the formula (1) is a structural unit formed by reacting a tetracarboxylic acid compound and a diamine compound, and the structural unit represented by the formula (2) is a dicarboxylic acid compound and a diamine compound. And are structural units formed by reaction. The polyamide-imide resin of the present invention may have one type of structural unit represented by the formula (1), or may have two or more types of structural unit represented by the formula (1). Good. Similarly, the polyamide-imide-based resin may have one type of constitutional unit represented by the formula (2), or may have two or more types of constitutional unit represented by the formula (2). May be. The polyamide-imide resin may include a further structural unit that does not correspond to the structural unit represented by the formula (1) or the structural unit represented by the formula (2). In the present specification, the constitutional unit represented by the formula (1) is also referred to as “constitutional unit (1)”, and the constitutional unit represented by the formula (2) is also referred to as “constitutional unit (2)”. In addition, in Formula (1) and Formula (2), the bond represented by the dotted line represents a bond that bonds to an adjacent structural unit. In the present specification, a bond represented by a dotted line in other chemical structural formulas similarly represents a bond that bonds to an adjacent structural unit or group.

When an optical film is produced using the polyamide-imide resin having the above structural unit (1) and structural unit (2), an optical film having a high elastic modulus and a light transmittance can be obtained. Although the reason is not clear, when the polyamide-imide resin has the structural unit (1) and the structural unit (2), the polyamide-imide resin is contained in the structural portion derived from the tetracarboxylic acid in the structural unit (1). Has rigidity, and in the structural portion derived from the diamine in the structural unit (1) and the structural unit (2), the polyamide-imide-based resin has flexibility, and the interaction between molecules is reduced. Will be done. It has been surprisingly found that when the polyamide-imide resin has such a structure, it is easy to improve the elastic modulus and the light transmittance of the optical film containing the polyamide-imide resin.

The polyamide-imide resin of the present invention has the structural unit (1) and the structural unit (2). From the viewpoint of easily improving the elastic modulus and light transmittance of the optical film, when the total of the structural unit (1) and the structural unit (2) contained in the polyamide-imide resin is 100 mol %, the structural unit (1 The ratio of) 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%. When the ratio of the structural unit (1) is at least the above lower limit, it is easy to improve the elastic modulus of the optical film. Moreover, when the ratio of the structural unit (1) is at most the above upper limit, it is easy to improve the light transmittance. The contents of the structural unit (1) and the structural unit (2) can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of the raw materials.

In the polyamide-imide resin, the content of the structural unit represented by the formula (1) is preferably 0.1 mol or more, more preferably 0.1 mol or less with respect to 1 mol of the structural unit represented by the formula (2). The amount is 2 mol or more, more preferably 0.3 mol or more, preferably 5 mol or less, more preferably 3 mol or less, further preferably 2 mol or less, and particularly preferably 1 mol or less. When the content of the structural unit represented by the formula (1) is at least the above lower limit, the elastic modulus of the optical film can be easily improved. Further, when the content of the constitutional unit represented by the formula (1) is at most the above upper limit, thickening due to hydrogen bonds between amide bonds in the formula (2) is suppressed, and the processability of the optical film is improved. Easy to make.

Y in the formula (1) represents a tetravalent aromatic group which may have a substituent. In addition, in the present specification, the tetravalent aromatic group is a group in which four hydrogen atoms of a monocyclic aromatic ring, a condensed polycyclic aromatic ring or a ring-assembled aromatic ring are replaced with a bond, Preferably, in a monocyclic aromatic ring, a condensed polycyclic aromatic ring or a ring-assembled aromatic ring, two hydrogen atoms adjacent to each other and two hydrogen atoms adjacent to each other different from the hydrogen atom Is a group in which a total of four hydrogen atoms are replaced with a bond. The tetravalent aromatic group may include an aromatic ring in which a ring (monocycle, condensed polycycle or ring assembly) is formed only by carbon atoms, or a ring formed by including atoms other than carbon atoms. The heteroaromatic ring may be included. Examples of atoms other than carbon atoms include nitrogen atoms, sulfur atoms and oxygen atoms. 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 further preferably 5 to 13.

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

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

Examples of the ring-assembled aromatic ring include a structure in which two or more monocyclic aromatic rings and/or condensed polycyclic aromatic rings are linked by a single bond, and examples thereof include a monocyclic aromatic ring. Alternatively, a group in which two or more of the rings described above as examples of the condensed polycyclic aromatic ring are linked by a single bond, for example, biphenyl, terphenyl, quaterphenyl, binaphthyl, 1-phenylnaphthalene, 2-phenylnaphthalene, Bipyridine etc. are mentioned.

From the viewpoint of easily improving the elastic modulus and light transmittance of the optical film, the tetravalent aromatic group which may have a substituent preferably has four hydrogen atoms of the aromatic hydrocarbon ring as a bond. A group in which four hydrogen atoms of benzene, biphenyl, terphenyl or quaterphenyl are replaced by a bond, more preferably a group in which four hydrogen atoms of benzene or biphenyl are replaced by a bond. ..

The tetravalent aromatic group represented by Y in the 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, and (iv) having 6 to carbon atoms. And 12 aryloxy groups, (v) carbonyl groups having 1 to 12 carbon atoms, (vi) oxycarbonyl groups having 1 to 12 carbon atoms, or (vii) halogeno groups. In addition, the hydrogen atom contained in the said substituent is mutually independently substituted by the halogen atom, the C1-C4 alkyl group, the C1-C4 alkoxy group, the hydroxyl group, or the carboxyl group. Good. The tetravalent aromatic group represented by Y in the formula (1) is at least one kind of the above-mentioned substituents (i) to (vii) and/or the above-mentioned substituents (i) to (vii). The contained hydrogen atoms may independently have 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 group further substituted with a carboxyl group. However, it does not have to have a substituent. From the viewpoint of easy production of an optical film having a high elastic modulus, the tetravalent aromatic group represented by Y in the formula (1) preferably has no substituent.

(I) C1-C12 alkyl groups include C1-C12 linear, branched or alicyclic alkyl groups. Examples of the linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert- Butyl group, n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group , N-decyl group, cyclopentyl group, cyclohexyl group 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 containing an alicyclic hydrocarbon structure. The carbon number 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 has at least one hydrogen atom independently of each other, 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. It may be a group substituted with. 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 It is not included in the number of carbon atoms of the alkyl group of the numbers 1 to 12. For example, a group in which an alkyl group having 1 to 12 carbon atoms is substituted with an alkyl group having 1 to 4 carbon atoms has an alkyl group having 1 to 12 carbon atoms as a main chain, and at least one hydrogen atom of the alkyl group Is a group substituted with an alkyl group having 1 to 4 carbon atoms. If the carbon number of the alkyl group portion forming the main chain is 1 to 12, the carbon number of the alkyl group as a whole may exceed 12. In the case where the total number of carbon atoms in the alkyl group does not exceed 12, a group in which an alkyl group having 1 to 12 carbon atoms is substituted with an alkyl group having 1 to 4 carbon atoms has 1 to 12 carbon atoms. It is a group included in the definition of a branched alkyl group.

(Ii) Examples of the alkoxy group having 1 to 12 carbon atoms include methoxy group, ethoxy group, propyloxy group, isopropyloxy group, n-butoxy group, isobutoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, Examples thereof include cyclohexyloxy group, heptyloxy group, octyloxy group, nonyloxy group and decyloxy group. The alkyl group portion and/or alkylene group portion in the alkoxy group having 1 to 12 carbon atoms may be linear, branched, or alicyclic. The carbon number of the alkoxy group having 1 to 12 carbon atoms is preferably 1 to 6, more preferably 1 to 4, and further preferably 1 to 3. In the above alkoxy group having 1 to 12 carbon atoms, at least one hydrogen atom is independently 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. It may be a group substituted with. Examples of the halogen atom include the atoms described above. Here, 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 equal to the carbon number of the alkoxy group having 1 to 12 carbon atoms. exclude.

(Iii) Examples of the aryl group having 6 to 12 carbon atoms include phenyl group, tolyl group, xylyl group, naphthyl group and biphenyl group. The aryl group having 6 to 12 carbon atoms preferably has 6 or 10 or 12 carbon atoms. In the aryl group having 6 to 12 carbon atoms, at least one hydrogen atom is independently 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. It may be a group substituted with. Examples of the halogen atom include the atoms described above. Here, 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 the same as the carbon number of the aryl group having 6 to 12 carbon atoms. exclude.

(Iv) Examples of 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 aryloxy group having 6 to 12 carbon atoms preferably has 6 or 10 or 12 carbon atoms. In the aryloxy group having 6 to 12 carbon atoms, at least one hydrogen atom is, independently of each other, 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. It may be a group substituted with a 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 the number of carbon atoms of the aryloxy group having 6 to 12 carbon atoms. Not included in.

(V) a carbonyl group having 1 to 12 carbon atoms, * - is ^{CO-R a} or ^* -R b ^{-CO-R a} group represented by. Examples of R ^a include the groups described for the (i) C 1-12 alkyl group, and examples of R ^b include at least one hydrogen atom of the group described for the (i) C 1-12 alkyl group. A divalent alkylene group having 1 to 12 carbon atoms in which is replaced by a bond. In the carbonyl group having 1 to 12 carbon atoms, at least one hydrogen atom is independently 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. It may be a group substituted with. Examples of the halogen atom include the atoms described above. Here, 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 equal to the carbon number of the carbonyl group having 1 to 12 carbon atoms. exclude.

(Vi) oxycarbonyl group having 1 to 12 carbon ^{atoms, * - CO-O-R} a, * - R b -CO-O-R a, * - O-CO-R a, or, -R ^b - a group represented by ^{O-CO-R a.} Examples of R ^a include the groups described for the (i) C 1-12 alkyl group, and examples of R ^b include at least one hydrogen atom of the group described for the (i) C 1-12 alkyl group. A divalent alkylene group having 1 to 12 carbon atoms in which is replaced by a bond. In the oxycarbonyl group having 1 to 12 carbon atoms, at least one hydrogen atom is, independently of each other, 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. It may be a group substituted with a 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 the number of carbon atoms of the oxycarbonyl group having 1 to 12 carbon atoms. Not included in.

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

［式（４）及び式（５）中、Ｒ^２及びＲ^３は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、
Ｒ^２及びＲ^３に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
ｎは０〜２の整数を表す］
を含む。構成単位（１）が、Ｙとして、式（４）で表される４価の芳香族基及び／又は式（５）で表される４価の芳香族基を含む場合、ポリアミドイミド系樹脂を用いて製造した光学フィルムの弾性率及び光線透過率を高めやすい。ポリアミドイミド系樹脂における構成単位（１）が、Ｙとして、式（４）で表される４価の芳香族基及び／又は式（５）で表される４価の芳香族基を含む場合、ポリアミドイミド系樹脂は、Ｙとして式（４）で表される１種類の４価の芳香族を含む構成単位を含んでいてもよいし、Ｙとして式（４）で表される２種類以上の４価の芳香族を含む構成単位を含んでいてもよい。また、ポリアミドイミド系樹脂は、Ｙとして式（５）で表される１種類の４価の芳香族を含む構成単位を含んでいてもよいし、Ｙとして式（５）で表される２種類以上の４価の芳香族を含む構成単位を含んでいてもよい。さらに、ポリアミドイミド系樹脂は、Ｙとして、式（４）で表される１種類以上の４価の芳香族基を含む構成単位と、式（５）で表される１種以上の４価の芳香族を含む構成単位の、両方を含んでいてもよい。なお、ポリアミドイミド系樹脂は、Ｙとして式（４）にも式（５）にも該当しない芳香族基を有する構成単位（１）をさらに含んでいてもよい。 In a preferred embodiment of the present invention, the structural unit (1) contained in the polyamide-imide resin is represented by Y as a tetravalent aromatic group represented by the formula (4) and/or a formula (5). Tetravalent aromatic group:

[In the formulas (4) and (5), R ² and R ³ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 6 to 12 carbon atoms. Represents an aryl group,
The hydrogen atoms contained in R ² and R ³ may be independently substituted with a halogen atom,
n represents an integer of 0 to 2]
including. When the structural unit (1) contains, as Y, a tetravalent aromatic group represented by the formula (4) and/or a tetravalent aromatic group represented by the formula (5), a polyamideimide resin is used. It is easy to increase the elastic modulus and light transmittance of the optical film produced by using the optical film. When the structural unit (1) in the polyamide-imide resin contains, as Y, a tetravalent aromatic group represented by the formula (4) and/or a tetravalent aromatic group represented by the formula (5), The polyamide-imide-based resin may contain, as Y, one structural unit containing a tetravalent aromatic represented by the formula (4), or may contain two or more types represented by the formula (4) as Y. You may include the structural unit containing a tetravalent aromatic. In addition, the polyamide-imide resin may include one structural unit containing a tetravalent aromatic represented by the formula (5) as Y, or two types represented by the formula (5) as Y. You may include the structural unit containing the above tetravalent aromatic. Furthermore, the polyamide-imide-based resin includes, as Y, a structural unit containing one or more tetravalent aromatic groups represented by the formula (4) and one or more tetravalent aromatic groups represented by the formula (5). Both of the constituent units containing an aromatic may be included. The polyamide-imide resin may further include a structural unit (1) having an aromatic group that does not correspond to formula (4) or formula (5) as Y.

The polyamide-imide-based 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) and a plurality of structural units (2). ) And optionally other structural units. In the present specification, that the structural unit (1) contains a tetravalent aromatic group represented by the formula (4) as Y means that at least one of the plural structural units (1) included in the polyamide-imide resin. It means that Y in the structural unit (1) of the part is represented by the formula (4). The above statements apply to other similar statements herein.

The constituent unit (1) contained in the polyamide-imide resin of the present invention is, as Y, a tetravalent aromatic group represented by the formula (4) and/or a tetravalent aromatic group represented by the formula (5). In a preferred embodiment of the present invention containing a group, from the viewpoint of easily improving the elastic modulus of the optical film, when the total of the constituent units (1) contained in the polyamide-imide resin is 100 mol%, the formula (1) A structural unit in which Y is a tetravalent aromatic group represented by formula (4) and a structural unit in which Y in the formula (1) is a tetravalent aromatic group represented by formula (5) The total ratio is preferably 70 to 100 mol%, more preferably 80 to 100 mol%, and further preferably 90 to 100 mol%, and in all the structural units represented by formula (1), Y is It may be a tetravalent aromatic group represented by (4) and/or a tetravalent aromatic group represented by the formula (5). From the viewpoint of easily increasing the surface hardness (pencil hardness) of the obtained optical film, the constitutional unit represented by the formula (1) contains, as Y, a tetravalent aromatic group represented by the formula (4). Is preferred. The content of the structural unit (1) and the structural unit (1) in which Y is a tetravalent aromatic group represented by the formula (4) or (5) is measured by using, for example, ¹ H-NMR. Alternatively, it can be calculated from the charging ratio of the raw materials. In the above description, Y in the structural unit (1) is a tetravalent aromatic group represented by the formula (4a) described below and/or a tetravalent aromatic group represented by the formula (5a). The same applies if

R ² and R ³ in the formulas (4) and (5) are, independently of each other, at least one kind of the above-mentioned substituents (i) to (vii), and/or the above-mentioned (i) to (vii). The hydrogen atoms contained in the substituents independently of each other represent 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 group further substituted with a carboxyl group. Good. In one preferred embodiment of the present invention, R ² and R ³ in formula (4) and formula (5) are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. Alternatively, a hydrogen atom which represents an aryl group having 6 to 12 carbon atoms and is included in R ² and R ³ may be independently substituted with a halogen atom. When R ² and/or R ³ represents an alkyl group having 1 to 6 carbon atoms, the alkyl group having 1 to 6 carbon atoms is the above-mentioned (i) carbon number as a substituent which the tetravalent aromatic group may have. Among the groups described for the alkyl group of 1 to 12, those having 1 to 6 carbon atoms can be mentioned. When R ² and/or R ³ represents an alkoxy group having 1 to 6 carbon atoms, the group includes (ii) the carbon number described above as a substituent that the tetravalent aromatic group may have. Among the groups described for the alkoxy groups 1 to 12, those having 1 to 6 carbon atoms can be mentioned. When R ² and/or R ³ represents an aryl group having 6 to 12 carbon atoms, the group may be a substituent which a tetravalent aromatic group may have (iii) carbon number described above. The groups described for 6 to 12 aryl groups can be mentioned. When R ² and/or R ³ is a hydrogen atom or the above group, the hydrogen atoms contained in R ² and/or R ³ may be independently substituted with a halogen atom. In a preferred embodiment of the present invention, R ² and R ³ are preferably hydrogen atoms from the viewpoint of easily increasing the elastic modulus of the optical film obtained by using the polyamideimide resin.

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

で表され、及び／又は、上記式（５）は、式（５ａ）：

で表される。なお、式（４ａ）は、式（４）中のＲ^２が水素原子であり、かつ、ｎが０である芳香族基に相当し、式（５ａ）は、式（５）中のＲ^３が水素原子である芳香族基に相当する。 In a preferred embodiment of the present invention, from the viewpoint of easily increasing the elastic modulus and light transmittance of the optical film, the above formula (4) is the formula (4a):

And/or the above formula (5) is represented by the formula (5a):

It is represented by. Note that the formula (4a) corresponds to an aromatic group in which R ² in the formula (4) is a hydrogen atom and n is 0, and the formula (5a) corresponds to R ³ in the formula (5). Corresponds to an aromatic group in which is a hydrogen atom.

〔式（３）中、Ｒ^１は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、
Ｒ^１に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ｖは、−Ｏ−、ジフェニルメチレン基、炭素数１〜１２の直鎖状、分枝状又は脂環式の２価の炭化水素基、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^１２）−を表し、ここで、該炭化水素基に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ｒ^１２は、水素原子、又はハロゲン原子で置換されていてもよい炭素数１〜１２のアルキル基を表す〕
で表される２価の有機基である。 X in Formula (1) and Formula (2) is Formula (3):

[In the formula (3), R ^1's each independently 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;
The hydrogen atoms contained in R ¹ may be independently substituted with a halogen atom,
V is, -O-, diphenylmethylene group, the number 1 to 12 linear, divalent hydrocarbon radical of branched or _{cycloaliphatic,} -SO 2 -, - S -, - CO- or - N(R ¹² )-, wherein the hydrogen atoms contained in the hydrocarbon group may be independently substituted with a halogen atom,
R ¹² represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom.
It is a divalent organic group represented by.

R ^1's each independently 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, and the hydrogen atoms contained in R ¹ are mutually Independently, it may be substituted with a halogen atom. When R ¹ represents 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, the alkyl group having 1 to 6 carbon atoms is a tetravalent aromatic group. Among the groups described above for (i) the alkyl group having 1 to 12 carbon atoms as the substituent which may have, a group having 1 to 6 carbon atoms can be mentioned, and 1 to 6 carbon atoms can be mentioned. Examples of the alkoxy group include a group having 1 to 6 carbon atoms among groups described in (ii) an alkoxy group having 1 to 12 carbon atoms, and examples of the aryl group having 6 to 12 carbon atoms include (iii) ) The groups described in the aryl group having 6 to 12 carbon atoms can be mentioned.

V in the formula (3) is, -O-, diphenylmethylene group, having 1 to 12 carbon atoms linear, divalent hydrocarbon radical of branched or cycloaliphatic, _-SO 2 -, - S- , -CO- or -N(R< ¹² >)-, wherein the hydrogen atoms contained in the hydrocarbon group may be independently substituted with a halogen atom, and R< ¹² > is a hydrogen atom, Alternatively, it represents 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 the groups described for (i) the alkyl group having 1 to 12 carbon atoms of R ¹ in formula (1). ..

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

Regarding V in the formula (3), the straight-chain, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbons includes straight-chain, branched or 1 to 12 carbons. Examples thereof include a group in which at least one hydrogen atom of an alicyclic alkyl group is replaced with a bond. Examples of the linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms include, for example, methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group and sec-butyl group. , Tert-butyl group, n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n -Nonyl group, n-decyl group, cyclopentyl group, cyclohexyl group and the like can be mentioned. The divalent hydrocarbon group having 1 to 12 carbon atoms may be a linear alkylene group, a branched alkylene group, or an alicyclic alkylene group containing an alicyclic hydrocarbon structure. The divalent hydrocarbon group having 1 to 12 carbon atoms preferably has 1 to 6 carbon atoms, more preferably 1 to 4 carbon atoms, and further preferably 1 to 3 carbon atoms. The divalent hydrocarbon group having 1 to 12 carbon atoms may be a group in which at least one 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 at least one hydrogen atom of a linear, branched or alicyclic alkylene group having 1 to 12 carbon atoms, which is substituted with a halogen atom (preferably a fluorine atom). Group (preferably a fluoroalkylene group having 1 to 12 carbon atoms), and even more preferably all hydrogen atoms of a linear, branched or alicyclic alkylene group having 1 to 12 carbon atoms are halogen atoms. A group (preferably fluorine atom) substituted (preferably a perfluoroalkylene group having 1 to 12 carbon atoms, particularly preferably a ditrifluoromethylmethylene group).

In one preferable embodiment of the present invention, X in the formula (1) and the formula (2) is such that R ¹ in the formula (3) is a hydrogen atom, and V is preferably a straight chain having 1 to 12 carbon atoms. A group in which at least one hydrogen atom of a chain, branched or alicyclic divalent hydrocarbon group is substituted with a halogen atom (preferably a fluorine atom) (preferably a fluoroalkylene group having 1 to 12 carbon atoms). , More preferably a group (preferably a fluorine atom) in which all the hydrogen atoms of a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms are substituted with a halogen atom (preferably a fluorine atom). It is preferably a divalent organic group represented by the formula (3), which is a perfluoroalkylene group having 1 to 12 carbon atoms, and more preferably a ditrifluoromethylmethylene group.

で表される。本発明のポリアミドイミド系樹脂に含まれる構成単位（１）及び構成単位（２）が、Ｘとして、式（３ａ）で表される２価の有機基を含む場合、ポリアミドイミド系樹脂に含まれる構成単位（１）及び構成単位（２）の合計を１００モル％としたときに、式（１）中のＸが式（３ａ）で表される構成単位及び式（２）中のＸが式（３ａ）で表される構成単位の合計の割合は、光学フィルムの加工性及び光線透過率を向上させやすい観点から、好ましくは１〜５０モル％、より好ましくは３〜４０モル％、さらに好ましくは５〜３０モル％である。構成単位（１）及び構成単位（２）、並びに、Ｘが式（３ａ）で表される構成単位（１）及び構成単位（２）の含有量は、例えば^１Ｈ−ＮＭＲを用いて測定することができ、又は原料の仕込み比から算出することもできる。 In a preferred embodiment of the present invention, the formula (3) is represented by the formula (3a) from the viewpoint of easily improving the processability and light transmittance of the optical film obtained by using the polyamideimide resin.

It is represented by. When the structural unit (1) and the structural unit (2) contained in the polyamide-imide resin of the present invention contain, as X, a divalent organic group represented by the formula (3a), they are contained in the polyamide-imide resin. When the total of the structural unit (1) and the structural unit (2) is 100 mol %, X in the formula (1) is the structural unit represented by the formula (3a) and X in the formula (2) is the formula. The total ratio of the structural units represented by (3a) is preferably 1 to 50 mol%, more preferably 3 to 40 mol%, and further preferably from the viewpoint of easily improving the processability and light transmittance of the optical film. Is 5 to 30 mol %. The content of the structural unit (1) and the structural unit (2), and the content of the structural unit (1) and the structural unit (2) in which X is represented by the formula (3a) is measured by using, for example, ¹ H-NMR. Alternatively, it can be calculated from the charging ratio of raw materials.

で表される基の結合手のうち、隣接しない２つが水素原子に置き換わった２価の有機基及び炭素数６以下の２価の鎖式炭化水素基が例示され、Ｚのヘテロ環構造としてはチオフェン環骨格を有する２価の有機基が例示される。光学積層体の黄色度（以下、ＹＩ値とも称する）を低減しやすい観点から、式（２０）〜式（２９）で表される基の結合手のうち、隣接しない２つが水素原子に置き換わった２価の有機基、及び、チオフェン環骨格を有する２価の有機基が好ましい。 Z in the formula (2) is a divalent organic group, and may preferably be substituted with a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms which is fluorine-substituted. , A divalent organic group having 4 to 40 carbon atoms, and more preferably a hydrocarbon group having 1 to 8 carbon atoms or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms, It is a C4-C40 bivalent organic group which has a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring and heterocyclic structures. As Z, formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29):

Examples of the bond of the group represented by are a divalent organic group in which two non-adjacent hydrogen atoms are replaced by hydrogen atoms and a divalent chain hydrocarbon group having 6 or less carbon atoms, and the heterocyclic structure of Z is A divalent organic group having a thiophene ring skeleton is exemplified. From the viewpoint of easily reducing the yellowness (hereinafter, also referred to as YI value) of the optical laminate, two non-adjacent bonds of the groups represented by the formulas (20) to (29) are replaced with hydrogen atoms. A divalent organic group and a divalent organic group having a thiophene ring skeleton are preferable.

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

［式（２０’）〜式（２９’）中、Ｗ^１及び＊は、式（２０）〜式（２９）において定義する通りである］
で表される２価の有機基がより好ましい。なお、式（２０）〜式（２９）及び式（２０’）〜式（２９’）における環上の水素原子は、炭素数１〜８の炭化水素基、フッ素置換された炭素数１〜８の炭化水素基、炭素数１〜６のアルコキシ基、フッ素置換された炭素数１〜６のアルコキシ基で置換されていてもよい。 Examples of the divalent organic group represented by Z in the formula (2) include formula (20′), formula (21′), formula (22′), formula (23′), formula (24′), and formula (25′). ), formula (26′), formula (27′), formula (28′) and formula (29′):

[In the formulas (20′) to (29′), W ¹ and * are as defined in the formulas (20) to (29)]
A divalent organic group represented by is more preferable. In addition, the hydrogen atom on the ring in Formula (20)-Formula (29) and Formula (20')-Formula (29') is a C1-C8 hydrocarbon group, the fluorine-substituted C1-C8. May be substituted with a hydrocarbon group, a C1-6 alkoxy group, or a fluorine-substituted C1-6 alkoxy group.

［式（ｄ１）中、Ｒ^ｅは、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、
Ｒ^ｆは、Ｒ^ｅ又は−Ｃ（＝Ｏ）−＊を表し、＊は結合手を表す］
で表されるカルボン酸由来の構成単位をさらに有することが、ワニスの成膜性を高めやすく、光学フィルムの均一性を得やすい観点から好ましい。 When the polyamide-imide-based resin has a structural unit represented by any one of the above formulas (20′) to (29′) in the formula (2), Z in the formula (2) will be described later. When it has a constitutional unit represented by the formula (6), the polyamide-imide-based resin has the following formula (d1) in addition to the constitutional unit:

[In the formula (d1), R ^e independently of each other 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 ^f represents ^Re or -C(=O)-*, and * represents a bond]
It is preferable to further include a carboxylic acid-derived structural unit represented by from the viewpoints that the film-forming property of the varnish is easily enhanced and the uniformity of the optical film is easily obtained.

In R ^e , 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 each have 1 carbon atom in R ^{4 to} R ¹¹ in the formula (6). Examples of the alkyl group having 6 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms can be given. As the structural unit (d1), specifically, a structural unit in which R ^e and R ^f are both hydrogen atoms (a structural unit derived from a dicarboxylic acid compound), R ^e is both a hydrogen atom, and R ^f A structural unit (a structural unit derived from a tricarboxylic acid compound) and the like represent -C(=O)-*.

In one embodiment of the present invention, the polyamide-imide-based resin may contain one kind of divalent organic group as Z in the formula (2), or may contain two or more kinds of divalent organic groups. You can leave. When the polyamide-imide-based resin contains two or more kinds of divalent organic groups as Z in the formula (2), the divalent organic groups may be the same as or different from each other.

［式（６ａ）中、Ｒ^ｇ及びＲ^ｈは、互いに独立に、ハロゲン原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基を表し、
Ａ、ｍ’及び＊は式（６）中のＡ、ｍ’及び＊と同じであり、
ｔ及びｕは互いに独立に０〜４の整数である］
で表される２価の有機基を含むことが好ましく、式（６）：

［式（６）中、Ｒ^４〜Ｒ^１１は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基を表し、
Ｒ^４〜Ｒ^１１に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ａは、互いに独立に、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^１２）−を表し、
Ｒ^１２は水素原子、ハロゲン原子で置換されていてもよい炭素数１〜１２の１価の炭化水素基を表し、
ｍ’は０〜４の整数であり、
＊は結合手を表す］
で表される２価の有機基を含むことがより好ましい。 In one embodiment of the present invention, the polyamide-imide-based resin is represented by the formula (2) from the viewpoint of easily increasing the surface hardness of an optical film produced using the polyamide-imide-based resin of the present invention and easily improving the optical properties. As Z in formula (6a):

[In the formula (6a), R ^g and R ^h each independently represent 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 * are the same as A, m′ and * in the formula (6),
t and u are each independently an integer of 0 to 4]
A divalent organic group represented by the formula (6):

[In formula (6), R< ⁴ >-R< ¹¹ > represents a hydrogen atom, a C1-C6 alkyl group, a C1-C6 alkoxy group, or a C6-C12 aryl group mutually independently. ,
The hydrogen atoms contained in R ^{4 to} R ¹¹ may be independently substituted with a halogen atom,
A is, independently of one another, a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) _{2 -, - SO 2 -,} - S -, - CO- or -N ^{(R 12)} - represents,
R ¹² represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom,
m'is an integer from 0 to 4,
* Represents a bond]
It is more preferable to include a divalent organic group represented by

In the formula (6a), the bond of each benzene ring may be bonded to any of the ortho position, the meta position or the para position with respect to -A-, and is preferably bonded to the meta position or the para position. May be. R ^g and R ^{h in} formula (6a) each independently represent 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. In the formula (6a), t and u are preferably 0, but when t and/or u is 1 or more, R ^g and R ^h preferably represent an alkyl group having 1 to 6 carbon atoms, More preferably, it represents an alkyl group having 1 to 3 carbon atoms. In R ^g and R ^h in the formula (6a), 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 are respectively represented by the formula (6 ), the halogen atom, the 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 are exemplified.

In formula (6a), t and u are each independently an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

The A in the formula (6) and (6a), a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 - _{, -C (CF 3) 2 -} , - SO 2 -, - S -, - CO- or -N ^{(R 12)} - represents, in terms of flex resistance of the optical film, preferably -O- or - Represents S-, and more preferably represents -O-.
In formula (6), R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ⁸ , R ⁹ , R ¹⁰ , and R ¹¹ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a carbon number 1 Represents an alkoxy group having 6 to 6 or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl- group. A butyl group, a 3-methylbutyl group, a 2-ethyl-propyl group, an n-hexyl group and the like can be mentioned. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, propyloxy group, isopropyloxy group, butoxy group, isobutoxy group, tert-butoxy group, pentyloxy group, hexyloxy group and cyclohexyloxy group. Can be mentioned. Examples of the aryl group having 6 to 12 carbon atoms include phenyl group, tolyl group, xylyl group, naphthyl group and biphenyl group. From the viewpoint of surface hardness and flexibility of the optical film, R ^{4 to} R ¹¹ each independently represent preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom or 1 to 3 carbon atoms. Represents an alkyl group, more preferably represents a hydrogen atom. Here, the hydrogen atoms contained in R ^{4 to} R ¹¹ may be independently substituted with a halogen atom.
R ¹² represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group and the like. And these may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

M'in Formula (6a) and Formula (6) is an integer in the range of 0 to 4, and when m'is in this range, the bending resistance and elastic modulus of the optical film are likely to be good. Further, m'in the formulas (6a) and (6) is preferably an integer in the range of 0 to 3, more preferably 0 to 2, still more preferably 0 or 1, and most preferably 0. When m'is within this range, the bending resistance and elastic modulus of the optical film can be easily improved. The structural unit (2) may contain, as Z, one or more divalent organic groups represented by the formula (6), and improves the elastic modulus and bending resistance of the optical film. From the viewpoint of reducing the YI value, the structural unit (2) includes, as Z, two or more divalent organic groups having different m′ values, preferably two divalent organic groups having different m′ values. It may contain an organic group. In that case, from the viewpoint of easily exhibiting a high elastic modulus, bending resistance and a low YI value of the optical film, the structural unit (2) included in the polyamide-imide resin has a formula (6a) in which m′ is 0 as Z. Alternatively, it preferably contains a divalent organic group represented by the formula (6), and in addition to the divalent organic group, the formula (6a) or the formula (6) in which m′ is 1 It is more preferable to further contain a valent organic group. In this case, the polyamide-imide-based resin contains at least two types of structural units (2) in which Z in formula (2) is different from each other.

で表される２価の有機基である構成単位（２）とを有する。この場合、光学フィルムの表面硬度及び耐屈曲性を向上させやすく、ＹＩ値を低減しやすい。 In a preferred embodiment of the present invention, the polyamide-imide resin is a divalent organic group represented by the formula (6a) or the formula (6) as Z in the formula (2), and m′=0. And t in formula (6a) is 0, or R ^{8 to} R ¹¹ in formula (6) have an organic group which is a hydrogen atom. In a more preferred embodiment of the present invention, in the polyamide-imide resin, Z in the formula (2) is a divalent organic group represented by the formula (6a) or the formula (6), and m′=0. And t in formula (6a) is 0 or R ^{8 to} R ¹¹ in formula (6) are hydrogen atoms (2) (more preferably Z in formula (2)). Is a divalent organic group represented by the formula (6), m′=0, and structural units (2) in which R ^{8 to} R ¹¹ are hydrogen atoms, and Z in the formula (2). Is equation (6'):

And a structural unit (2) which is a divalent organic group represented by. In this case, the surface hardness and flex resistance of the optical film are easily improved, and the YI value is easily reduced.

When the polyamide-imide-based resin of the present invention contains a divalent organic group represented by the formula (6a) or the formula (6) as Z in the formula (2), a constituent unit ( When the total of 1) and the structural unit (2) is 100 mol %, the ratio of the structural unit (2) in which Z is a divalent organic group represented by the formula (6a) or the formula (6) is: Preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, even more preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 95 mol% or less, and more preferably It is preferably 90 mol% or less, more preferably 85 mol% or less. When the ratio of the structural unit (2), which is a divalent organic group represented by formula (6a) or formula (6), is not less than the above lower limit, it is easy to increase the surface hardness of the optical film, and the bending resistance is high. It is easy to increase the elasticity and elasticity. When the ratio of the constitutional unit (2) in which Z is a divalent organic group represented by the formula (6a) or the formula (6) is at most the above upper limit, hydrogen bonds between amide bonds derived from the constitutional unit It suppresses the increase in viscosity of the resin-containing varnish and easily improves the processability of the film.

When the polyamide-imide resin has a structural unit (2) having Z as a divalent organic group represented by the formula (6a) or the formula (6) in which m′=1 to 4, the polyamide-imide resin is The divalent organic group represented by the formula (6a) or the formula (6) in which m′ is 1 to 4, when the total of the contained structural unit (1) and structural unit (2) is 100 mol %. The proportion of the structural unit (2) having Z as Z is preferably 3 mol% or more, more preferably 5 mol% or more, further preferably 7 mol% or more, particularly preferably 9 mol% or more, and preferably 90 mol% or more. % Or less, more preferably 70 mol% or less, further preferably 50 mol% or less, and particularly preferably 30 mol% or less. When the proportion of the structural unit (2) having, as Z, a divalent organic group represented by the formula (6a) or the formula (6) in which m′ is 1 to 4 is at least the above lower limit, the surface of the optical film Easy to increase hardness and bending resistance. When the proportion of the structural unit (2) having as a Z a divalent organic group represented by the formula (6a) or the formula (6) in which m′ is 1 to 4 is at most the above upper limit, the formula (6a) Alternatively, it is easy to improve the processability of the film by suppressing the viscosity increase of the resin-containing varnish due to the hydrogen bond between amide bonds derived from the structural unit (2) having a divalent organic group represented by the formula (6) as Z. .. The content of the structural unit (1), the structural unit (2), and the structural unit (2) having a divalent organic group represented by the formula (6a) or the formula (6) as Z is, for example, ¹ It can be measured using 1 H-NMR, or can be calculated from the charging ratio of raw materials.

In a preferred embodiment of the present invention, Z in the structural unit (2) included in the polyamideimide resin is preferably 30 mol% or more, more preferably 40 mol% or more, further preferably 45 mol% or more, More preferably, 50 mol% or more, and particularly preferably 70 mol% or more is a divalent organic group represented by formula (6a) or formula (6) in which m′ is 0 to 4. When the above lower limit of Z is a divalent organic group represented by the formula (6a) or the formula (6) in which m′ is 0 to 4, it is easy to increase the surface hardness of the optical film and the flex resistance The elasticity and elastic modulus are also easily increased. Further, 100 mol% or less of Z in the structural unit (2) included in the polyamide-imide resin is a divalent organic group represented by the formula (6a) or the formula (6) in which m′ is 0 to 4. If The proportion of the structural unit (2), which is a divalent organic group represented by the formula (6a) or the formula (6) in which m is 0 to 4, is ¹ H-NMR. It can be measured or can be calculated from the charging ratio of raw materials.

In a preferred embodiment of the present invention, Z in the structural unit (2) contained in the polyamideimide resin is preferably 5 mol% or more, more preferably 8 mol% or more, still more preferably 10 mol% or more, and especially Preferably, 12 mol% or more is a divalent organic group represented by the formula (6a) or the formula (6) in which m′ is 1 to 4. When the above lower limit of Z in the structural unit (2) is a divalent organic group represented by the formula (3) in which m′ is 1 to 4, it is easy to increase the surface hardness of the optical film, and Easy to increase bending resistance and elastic modulus. Further, Z in the structural unit (2) is preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, particularly preferably 30 mol% or less, and m′ is 1 to 4 Is preferably a divalent organic group represented by the formula (6a) or the formula (6). When the above upper limit of Z is a divalent organic group represented by formula (6a) or formula (6) in which m′ is 1 to 4, formula (6a) in which m′ is 1 to 4 Alternatively, it is possible to suppress an increase in the viscosity of the resin-containing varnish due to hydrogen bonds between amide bonds derived from the structural unit (2) having a divalent organic group represented by the formula (6) as Z, and easily improve the processability of the film. The proportion of the structural unit (2), which is a divalent organic group represented by the formula (6a) or the formula (6) in which Z is 1 to 4, is ¹ H-NMR, for example. It can be measured or can be calculated from the charging ratio of raw materials.

［式（７）中、Ｚは式（１）において定義した通りであり、
Ｘ’は、式（２）中のＸに該当しない２価の有機基を表す］
で表される構成単位をさらに有する。なお、以下において、式（７）で表される構成単位を、構成単位（７）とも称する。上記の態様においては、ポリアミドイミド系樹脂は、式（２）中の少なくともＺ部分において互いに異なる２種類以上の構成単位（２）を含むか、式（２）中の少なくともＸ部分において互いに異なる２種類以上の構成単位（２）を含むか、及び／又は、少なくともＸ部分において式（２）に該当しないさらなる構成単位（７）を有してよい。 In a preferred embodiment of the present invention, the polyamide-imide resin is a formula in which at least Z in formula (2) is different from each other from the viewpoint of easily increasing the elastic modulus and light transmittance of the optical film produced using the polyamide-imide resin. Has at least two types of structural units represented by formula (2), has at least two types of structural units represented by formula (2) in which at least X in formula (2) are different from each other, and/or Formula (7):

[In the formula (7), Z is as defined in the formula (1),
X′ represents a divalent organic group which does not correspond to X in the formula (2)]
Further has a structural unit represented by. In addition, below, the structural unit represented by Formula (7) is also called a structural unit (7). In the above aspect, the polyamide-imide-based resin contains two or more kinds of structural units (2) different from each other in at least the Z portion of the formula (2) or different from each other in at least the X portion of the formula (2). It may comprise more than one type of structural unit (2) and/or may have additional structural unit (7) which does not correspond to formula (2) at least in the X part.

In a preferred embodiment of the present invention in which the polyamide-imide resin further has a structural unit (7), X′ in the formula (7) is X in the formula (1) (a divalent group represented by the formula (3)). It is not particularly limited as long as it represents a divalent organic group that does not correspond to (organic group), but from the viewpoint of easily increasing the elastic modulus and light transmittance of the optical film produced using the polyamideimide resin, it is preferably the formula (3) A divalent organic group having 4 to 40 carbon atoms which does not correspond to the divalent organic group represented by, and more preferably a carbon number 4 having a cyclic structure which does not correspond to the divalent organic group represented by the formula (3). Represents a divalent organic group of -40. Examples of the cyclic structure include alicyclic, aromatic ring and heterocyclic structures. The organic group, the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case, the carbon number of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably Is 1-8. In one embodiment of the present invention, the structural unit (7) that may be contained in the polyamide-imide resin may include one type of organic group as X′, or may include two or more types of organic groups. Good.

［式（８）中、Ａｒ^２は置換基を有していてもよい２価の芳香族基を表し、
Ｖは、単結合を表し、ｍは０〜３の整数を表し、＊は結合手を表す］
で表される。構成単位（７）におけるＸ’が式（８）で表される２価の有機基である場合、構成単位（７）は、Ｘ’として、式（８）で表される１種類又は２種類以上の２価の有機基を含んでよい。 In a preferred embodiment of the present invention, X′ in the formula (7) is preferably a divalent organic group which may have a substituent, from the viewpoint of easily improving the elastic modulus and light transmittance of the optical film. And more preferably formula (8):

[In the formula (8), Ar ² represents a divalent aromatic group which may have a substituent,
V represents a single bond, m represents an integer of 0 to 3, and * represents a bond.]
It is represented by. When X′ in the structural unit (7) is a divalent organic group represented by the formula (8), the structural unit (7) may be one or two types represented by the formula (8) as X′. It may contain the above divalent organic groups.

Ar ² in the formula (8) represents a divalent aromatic group which may have a substituent. The divalent aromatic group is a group in which two hydrogen atoms of a monocyclic aromatic ring, a condensed polycyclic aromatic ring or a ring-assembled aromatic ring are replaced by a bond. The divalent aromatic group may include an aromatic ring in which a ring (monocycle, condensed polycycle or ring assembly) is formed only by carbon atoms, or a ring including atoms other than carbon atoms is formed. It may contain a heteroaromatic ring. Examples of atoms other than carbon atoms include nitrogen atoms, sulfur atoms and oxygen atoms. 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 further preferably 5 to 12. Specific examples of the monocyclic aromatic ring, the condensed polycyclic aromatic ring and the ring-assembled aromatic ring include the monocyclic aromatic ring and the condensed polycyclic aromatic ring described for Y in the formula (1). And ring-assembled aromatic rings. When m in the formula (8) is 1 or more, a plurality of Ar ^2's may be the same or different.

From the viewpoint of easily improving the elastic modulus and light transmittance of the optical film, the divalent aromatic group which may have a substituent is preferably an aromatic hydrocarbon which may have a substituent. A group in which two hydrogen atoms in the ring are replaced by a bond, more preferably a group in which two hydrogen atoms of benzene, biphenyl, terphenyl or quaterphenyl, which may have a substituent, are replaced by a bond, More preferably, it is a group in which two hydrogen atoms of benzene or biphenyl which may have a substituent are replaced by a bond.

The substituent in Ar ^2, 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, and, a halogeno group, and a halogen is a hydrogen atom contained in these Examples include groups substituted with atoms. Specific examples of an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, an aryl group having 6 to 12 carbon atoms, a halogeno group, and a group in which a hydrogen atom contained therein is substituted with a halogen atom. Examples include (i) an alkyl group having 1 to 12 carbon atoms and (ii) an alkoxy group having 1 to 12 carbon atoms as a substituent that the tetravalent aromatic group represented by Y in the formula (1) may have. Group, (iii) the aryl group having 6 to 12 carbon atoms, and the groups described for the (vii) halogeno group.

The substituent in Ar ² is preferably a halogen group, or an alkyl group having 1 to 12 carbon atoms in which a hydrogen atom may be replaced by a halogen atom, and a methyl group, a fluoro group, a chloro group or a trifluoromethyl group. More preferable.

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

The polyamide-imide resin of the present invention includes, in addition to the structural unit (1) and the structural unit (2), a structural unit (7) (preferably X′ is represented by formula (7) represented by formula (8)). In a preferred embodiment of the present invention containing a structural unit), the proportion of the structural unit (2) is 100% by mol of the total of the structural unit (2) and the structural unit (7) contained in the polyamide-imide resin. 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 elastic modulus and light transmittance of the optical film.

［式（８ａ）中、Ｒ^１５は、炭素数１〜１２のフルオロアルキル基を表し、
ｐ及びｑは、互いに独立に、１〜４の整数を表し、ただし、ｐ及び／又はｑが２〜４の整数を表す場合に複数存在するＲ^１５は、互いに同一であってもよいし、異なっていてもよく、
＊は結合手を表す］
で表される。構成単位（７）が、Ｘ’として式（８ａ）で表される２価の有機基を含む場合、構成単位（７）は、Ｘ’として、式（８ａ）で表される１種類又は２種類以上の２価の有機基を含んでよい。構成単位（７）は、Ｘ’として、式（８ａ）で表される２価の有機基の他に、式（８ａ）で表される２価の有機基にも、式（８）で表される２価の有機基にも該当しない、他の２価の有機基を含んでいてもよい。 In a preferable embodiment of the present invention, the formula (8) is represented by the formula (8a):

[In the formula (8a), R ¹⁵ represents a fluoroalkyl group having 1 to 12 carbon atoms,
p and q each independently represent an integer of 1 to 4, provided that when p and/or q represents an integer of 2 to 4, a plurality of R ^15's may be the same as each other, Can be different,
* Represents a bond]
It is represented by. When the structural unit (7) contains a divalent organic group represented by the formula (8a) as X′, the structural unit (7) may be one type or the two represented by the formula (8a) as X′. It may contain two or more kinds of divalent organic groups. The structural unit (7) has, as X′, a divalent organic group represented by the formula (8a) as well as a divalent organic group represented by the formula (8a). The other divalent organic group which does not correspond to the above-mentioned divalent organic group may be contained.

R ¹⁵ in the formula (8a) represents a fluoroalkyl group having 1 to 12 carbon atoms. The group is a group in which at least one 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 methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group and n- Examples thereof include groups in which at least one hydrogen atom in a decyl group or the like 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, and a heptafluoro group. Examples thereof include a propyl group and a nonafluorobutyl group. The carbon number 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 1 to 12 carbon atoms, from the viewpoint of easily improving the elastic modulus, light transmittance and durability of the optical film. A perfluoroalkyl group having 6 carbon atoms, more preferably a perfluoroalkyl group having 1 to 4 carbon atoms, and particularly preferably a trifluoromethyl group or a pentafluoroethyl group.

p and q represent the integer of 1-4 independently of each other. p is preferably an integer of 1 or 2, and more preferably 2 from the viewpoint of easily improving the elastic modulus, light transmittance and durability of the optical film. q is preferably an integer of 1 or 2, and more preferably 1 from the viewpoint of easily improving the elastic modulus, light transmittance and durability of the optical film. Here, when p and/or q represents an integer of 2 to 4, a plurality of R ^{4 s} may be the same or different, but a plurality of R ^{4 s} are the same as each other. It is preferable to have.

The positions of the two bonds in the formula (8a) are not particularly limited and may be any of the ortho position, the meta position and the para position, but the elastic modulus, light transmittance and durability of the optical film. From the viewpoint of easily improving the above, the bonds are preferably located in the para position relative to each other.

As a preferred example of the divalent aromatic group represented by the formula (8a), R ² in the formula (8a) represents a perfluoroalkyl group having 1 to 12 carbon atoms, p is 2, q is 1 Or 2 and/or an aromatic group in which the two bonds are in the para position relative to each other.

［式（８ｂ）中、Ｒ^１６〜Ｒ^２３は、互いに独立に、水素原子又は炭素数１〜１２のフルオロアルキル基を表し、＊は結合手を表す］
で表される。なお、式（８ｂ）は、式（８ａ）中の結合手が互いにパラ位に位置し、ｐが２である式に相当する。光学フィルムの弾性率及び光線透過率、並びに耐久性を向上させやすい観点から、式（８ｂ）中、Ｒ^１６〜Ｒ^２３の少なくとも２つが炭素数１〜１２のフルオロアルキル基を表すことが好ましく、少なくともＲ^１８及びＲ^２０が炭素数１〜１２のフルオロアルキル基を表すことがより好ましく、Ｒ^１８及びＲ^２０が炭素数１〜１２のフルオロアルキル基を表し、Ｒ^１６、Ｒ^１７、Ｒ^１９、Ｒ^２１、Ｒ^２２及びＲ^２３が水素原子を表すことがさらに好ましい。また、上記態様において、炭素数１〜１２のフルオロアルキル基は、好ましくは炭素数１〜１２のパーフルオロアルキル基、より好ましくは炭素数１〜６のパーフルオロアルキル基、さらに好ましくは炭素数１〜４のパーフルオロアルキル基、さらにより好ましくはトリフルオロメチル基又はペンタフルオロエチル基、とりわけ好ましくはトリフルオロメチル基である。 In a preferred embodiment of the present invention, formula (8a) is represented by formula (8b):

[In the formula (8b), R ^{16 to} R ²³ each independently represent a hydrogen atom or a fluoroalkyl group having 1 to 12 carbon atoms, and * represents a bond]
It is represented by. The formula (8b) corresponds to a formula in which the bonds in the formula (8a) are located in the para positions with respect to each other and p is 2. From the viewpoint of easily improving the elastic modulus and light transmittance of the optical film, and durability, in the formula (8b), it is preferable that at least two of R ^{16 to} R ²³ represent a fluoroalkyl group having 1 to 12 carbon atoms, It is more preferable that at least R ¹⁸ and R ²⁰ represent a fluoroalkyl group having 1 to 12 carbon atoms, R ¹⁸ and R ²⁰ represent a fluoroalkyl group having 1 to 12 carbon atoms, and R ¹⁶ , R ¹⁷ , R ¹⁹ , It is further preferred that R ²¹ , R ²² and R ²³ represent 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, and further preferably 1 carbon atom. A perfluoroalkyl group of 4 to 4, even more preferably a trifluoromethyl group or a pentafluoroethyl group, and particularly preferably a trifluoromethyl group.

［式（８ｃ）中、＊は結合手を表す］
で表される。なお、式（８ｃ）は、式（８ｂ）中のＲ^１８及びＲ^２０がトリフルオロメチル基を表し、Ｒ^１６、Ｒ^１７、Ｒ^１９、Ｒ^２１、Ｒ^２２及びＲ^２３が水素原子を表す式に相当する。 In a preferred embodiment of the present invention, formula (8b) is represented by formula (8c):

[In the formula (8c), * represents a bond]
It is represented by. In the formula (8c), R ¹⁸ and R ²⁰ in the formula (8b) represent a trifluoromethyl group, and R ¹⁶ , R ¹⁷ , R ¹⁹ , R ²¹ , R ²² and R ²³ represent a hydrogen atom. Equivalent to.

The polyamide-imide resin is represented by the formula (30) in addition to the constitutional unit represented by the formula (1), the constitutional unit represented by the formula (2), and optionally the constitutional unit represented by the formula (7). And/or a structural unit represented by the formula (31).

In formula (30), Y ¹ is a tetravalent 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. Examples of Y ¹ include the groups described as Y in the formula (1). In one embodiment of the present invention, the polyamide-imide-based resin may include a plurality of types of Y ¹ , and the plurality of types of Y ¹ may be the same as or different from each other.

In formula (31), Y ² is a trivalent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Examples of Y ² include a group in which any one of the bonds of the group described as Y in the formula (1) is replaced by a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyamide-imide-based resin may include a plurality of types of Y ² , and the plurality of types of Y ² may be the same as or different from each other.

In formulas (30) and (31), X ¹ and X ² are independently of each other a divalent organic group, and preferably a hydrogen atom in the organic group is a hydrocarbon group or a hydrocarbon group in which fluorine is substituted. Is an organic group which may be substituted with. Examples of X ¹ and X ² include the group described as X in the formula (2) and the group described as X′ in the formula (7).

In one embodiment of the present invention, the polyamide-imide resin is a structural unit represented by the formula (1), a structural unit represented by the formula (2), and optionally a structural unit represented by the formula (7). , And/or a structural unit represented by formula (31). From the viewpoint of easily improving the elastic modulus, light transmittance, optical characteristics, and surface hardness of the optical film, the constitutional units represented by the formulas (1) and (2) in the polyamideimide resin are represented by the formula (1) And based on the formula (2), and optionally all the structural units represented by formula (7), formula (30) and formula (31), preferably 80 mol% or more, more preferably 90 mol% or more, It is preferably 95 mol% or more. In the polyamide-imide resin, the constitutional units represented by the formulas (1) and (2) are represented by the formulas (1) and (2), and in some cases, the formulas (7), (30) and/or It is usually 100% or less based on all the structural units represented by formula (31). The above ratio can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

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, and further preferably 50 parts by mass with respect to 100 parts by mass of the optical film. It is at least 9 parts by mass, preferably at most 99.5 parts by mass, more preferably at most 95 parts by mass. When the content of the polyamide-imide resin is within the above range, the optical properties, elastic modulus and light transmittance of the optical film can be easily improved.

The weight average molecular weight of the polyamide-imide resin is, in terms of standard polystyrene, preferably 200,000 or more, more preferably 250,000 or more, still more preferably from the viewpoint of easily increasing the elastic modulus, surface hardness and bending resistance of the optical film. Is 270,000 or more, particularly preferably 300,000 or more. In addition, the weight average molecular weight of the resin is preferably 1,000,000 or less, from the viewpoint of easily improving the solubility of the polyamide-imide resin in a solvent and easily improving the stretchability and processability of the optical film. It is preferably 800,000 or less, more preferably 700,000 or less, particularly preferably 600,000 or less. The weight average molecular weight can be determined, for example, by performing GPC measurement and converting into standard polystyrene, and may be calculated by the method described in Examples, for example.

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

The total light transmittance (and/or light transmittance for light of 300 to 800 nm) of the optical film of the present invention is preferably 80% or more, more preferably 85% or more, even more preferably 88% or more, even more preferably It is 89% or more, particularly preferably 90% or more, and usually 100% or less. When the total light transmittance is not less than the above lower limit, it is easy to improve the visibility when the optical film is incorporated into a display device, particularly as a front plate. Since the optical film of the present invention usually exhibits a high total light transmittance, for example, as compared with the case of using a film having a low transmittance, the emission intensity of a display element or the like necessary for obtaining a constant brightness is suppressed. It becomes possible. Therefore, power consumption can be reduced. For example, when the optical film of the present invention is incorporated in a display device, bright display tends to be obtained even if the light amount of the backlight is reduced, which can contribute to energy saving. The total light transmittance can be measured by using a haze computer according to JIS K 7361-1:1997, for example. The total light transmittance may be the total light transmittance in the range of the thickness of the optical film described below.

The haze of the optical film of the present invention is preferably 5% or less, more preferably 4% or less, even more preferably 3% or less, even more preferably 2.5% or less, particularly preferably 2% or less, and particularly preferably It is 1% or less, particularly preferably 0.5% or less, and usually 0.01% or more. When the haze of the optical film is equal to or less than the above upper limit, the visibility is likely to be improved when the optical film is incorporated into a display device, particularly as a front plate. The haze can be measured using a haze computer according to JIS K 7136:2000.

The YI value of the optical film of the present invention is preferably 3.5 or less, more preferably 3.0 or less, still more preferably 2.5 or less, and usually -5 or more, preferably -2 or more. When the YI value of the optical film is less than or equal to the above upper limit, the transparency becomes good, and when used for the front plate of the display device, it can contribute to high visibility. The YI value is measured by using an ultraviolet-visible-near-infrared spectrophotometer to measure transmittance for light of 300 to 800 nm, and tristimulus values (X, Y, Z) are calculated, and YI=100×(1.2769X− It can be calculated based on the formula 1.0592Z)/Y. In the present specification, that the optical film has excellent optical properties means that the light transmittance is high.

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. The following is particularly preferable, and the thickness is 60 μm or less, and a combination of these upper and lower limits may be used. When the thickness of the optical film is within the above range, the elastic modulus of the optical film can be easily increased. The thickness of the optical film can be measured by using a micrometer, for example, 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 higher, and more preferably F or higher. When the pencil hardness of at least one surface of the optical film is not less than the above hardness, it is easy to prevent scratches and the like on the surface of the optical film. The pencil hardness can be measured according to JIS K 5600-5-4:1999, and can be measured, for example, by the method described in Examples.

The imidization ratio of the polyamide-imide resin is preferably 90% or higher, more preferably 93% or higher, even more preferably 96% or higher, and usually 100% or lower. From the viewpoint of easily improving the optical properties of the optical film, the imidization ratio is preferably at least the above lower limit. The imidization ratio indicates the ratio of the molar amount of imide bonds in the polyamideimide resin to the double value of the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyamideimide resin. When the polyamide-imide-based resin contains a tricarboxylic acid compound, the value of twice the molar amount of the constitutional unit derived from the tetracarboxylic acid compound in the polyamide-imide-based resin and the constitutional unit derived from the tricarboxylic acid compound The ratio of the molar amount of the imide bond in the polyamide-imide resin to the total of the molar amount is shown. Further, the imidization ratio can be obtained by IR method, NMR method, or the like.

The content of halogen atoms in the polyamideimide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and further preferably 5 to 30% by mass, based on the mass of the polyamideimide resin. When the content of halogen atoms is at least the above lower limit, the elastic modulus, surface hardness, transparency and visibility of the optical film can be more easily improved. When the content of halogen atoms is at most the above upper limit, the resin will be easily synthesized.

<Resin manufacturing method>
The polyamide-imide resin can be produced using, for example, a tetracarboxylic acid compound, a dicarboxylic acid compound and a diamine compound as main raw materials. Here, the constitutional unit represented by the above formula (1) is a constitutional unit formed by the reaction of a tetracarboxylic acid compound and a diamine compound, and the constitutional unit represented by the above formula (2) and The constitutional unit represented by the formula (7) is a constitutional unit formed by reacting a dicarboxylic acid compound and a diamine compound. Therefore, a dicarboxylic acid compound, a tetracarboxylic acid compound and a diamine compound are used so that the constitutional units represented by the above formulas (1) and (2), and optionally the constitutional unit represented by the formula (7) are used. Thus, a polyamide-imide resin may be manufactured.

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

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydride, monocyclic aromatic tetracarboxylic dianhydride and condensed polycyclic aromatic tetracarboxylic dianhydride. Examples thereof include carboxylic acid dianhydride. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride include 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, and 2,2'. ',3,3'-Benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2',3,3'-biphenyltetracarboxylic acid Dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,2 3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (with 6FDA May be mentioned), 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis( 2,3-dicarboxyphenyl)methane dianhydride, 4,4′-(p-phenylenedioxy)diphthalic acid dianhydride, 4,4′-(m-phenylenedioxy)diphthalic acid dianhydride. To be Examples of monocyclic aromatic tetracarboxylic dianhydrides include 1,2,4,5-benzenetetracarboxylic dianhydride (pyromellitic dianhydride (PMDA)), which is a condensed polycondensate. Examples of the cyclic aromatic tetracarboxylic dianhydride include 2,3,6,7-naphthalene tetracarboxylic dianhydride.

Among these, 4,4'-oxydiphthalic acid dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2',3,3'-benzophenone tetracarboxylic acid dianhydride is preferable. Anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), 2,2',3 3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2 ,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 1,2-bis(2,3-dicarboxy) Phenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-( p-phenylenedioxy)diphthalic acid dianhydride and 4,4′-(m-phenylenedioxy)diphthalic acid dianhydride are mentioned, and more preferably 4,4′-oxydiphthalic acid dianhydride, 3,3. ',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride , 4,4′-(p-phenylenedioxy)diphthalic dianhydride and 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA). These may be used alone or in combination of two or more.

Among the above-mentioned tetracarboxylic acid dianhydrides, 4,4′-oxydiphthalic acid dianhydride is preferably used from the viewpoint of easily increasing the elastic modulus, light transmittance, surface hardness, transparency and bending resistance of the optical film and reducing the colorability. Substance, 3,3′,4,4′-benzophenone tetracarboxylic dianhydride, 3,3′,4,4′-biphenyltetracarboxylic dianhydride, 2,2′,3,3′-biphenyltetra Carboxylic dianhydride, 3,3′,4,4′-diphenylsulfone tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 4,4′-( Hexafluoroisopropylidene)diphthalic dianhydride, 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), and mixtures thereof are preferred, and 3,3′,4,4′-biphenyltetracarboxylic More preferred are acid dianhydride (BPDA) and 1,2,4,5-benzenetetracarboxylic dianhydride (PMDA), and mixtures thereof.

Examples of the dicarboxylic acid compound used in the production of the polyamide-imide resin include aromatic dicarboxylic acids, aliphatic dicarboxylic acids and their related acid chloride compounds, acid anhydrides, and the like, and two or more of these dicarboxylic acid compounds. May be used in combination. As the dicarboxylic acid compound, terephthalic acid, 4,4′-oxybisbenzoic acid or their acid chloride compounds are preferably used. In addition to terephthalic acid, 4,4′-oxybisbenzoic acid or their acid chloride compounds, other dicarboxylic acid compounds may be used. Specific examples of other dicarboxylic acid compounds include isophthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; dicarboxylic acids having a chain structure of 8 or less carbon atoms. acid compound and the two benzoate single _{bond, -CH 2 -, - C (} CH 3) 2 -, - C (CF 3) 2 -, - SO 2 - or compounds linked phenylene radicals and of their Acid chloride compounds may be mentioned. As a specific example, 4,4′-oxybis(benzoyl chloride) and terephthaloyl chloride are preferable, and 4,4′-oxybis(benzoyl chloride) and terephthaloyl chloride are more preferably used in combination.

Examples of the diamine compound used for producing the polyamide-imide resin of the present invention include aromatic diamines. In addition, in this embodiment, the "aromatic diamine" represents a diamine in which an amino group is directly bonded to an aromatic ring, and may have an aliphatic group or other substituents as part of its structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring and a fluorene ring, but are not limited thereto. Of these, a benzene ring is preferable.

Examples of the aromatic diamine include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, and the like. , An aromatic diamine having one aromatic ring, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 3,3′- Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4 -Aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl] Propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB and May be described), 4,4'-bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene , 9,9-bis(4-amino-3-chlorophenyl)fluorene, 9,9-bis(4-amino-3-fluorophenyl)fluorene, and other aromatic diamines having two or more aromatic rings. These may be used alone or in combination of two or more.

The aromatic diamine is preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone. ,3′-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2 ,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2′-dimethylbenzidine, 2,2′-bis( Trifluoromethyl)-4,4′-diaminodiphenyl (TFMB), 4,4′-bis(4-aminophenoxy)biphenyl, 4,4′-(hexafluoropropylidene)dianiline (6FDAM), and more preferably Is 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, bis[ 4-(4-aminophenoxy)phenyl] sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2′-dimethylbenzidine, 2,2′-bis(trifluoromethyl)- 4,4'-diaminodiphenyl (TFMB), 4,4'-bis(4-aminophenoxy)biphenyl and 4,4'-(hexafluoropropylidene)dianiline (6FDAM). These may be used alone or in combination of two or more.

As the diamine compound used for producing the polyamide-imide resin of the present invention, an aliphatic diamine may be further used in addition to the aromatic diamine. In addition, "aliphatic diamine" represents a diamine in which an amino group is directly bonded to an aliphatic group, and an aromatic ring or other substituent may be included in a part of its structure. Examples of the aliphatic diamine include acyclic aliphatic diamine such as hexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine and 4,4′. Examples thereof include cycloaliphatic diamines such as diaminodicyclohexylmethane.

Among the above diamine compounds, one or more selected from the group consisting of aromatic diamines having a biphenyl structure is selected from the viewpoint of high surface hardness, high transparency, high flexibility, high bending resistance and low colorability of the optical film. It is preferable to use. 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl and 4,4'-diaminodiphenyl ether, 4,4'-(hexa It is more preferable to use one or more selected from the group consisting of fluoropropylidene)dianiline, and 2,2′-bis(trifluoromethyl)-4,4′-diaminodiphenyl (TFMB) and/or 4,4′ It is even more preferred to use -(hexafluoropropylidene)dianiline (6FDAM).

The polyamide-imide resin is a resin obtained by further reacting a tetracarboxylic acid and a 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. It may be.

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

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and related acid chloride compounds, acid anhydrides, and the like, and two or more kinds may be used in combination. Specific examples include 1,2,4-benzenetricarboxylic acid anhydride; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthalic anhydride and benzoic acid are single bonds, -O- _{, -CH 2 -, - C (} CH 3) 2 -, - C (CF 3) 2 -, - SO 2 - or compounds linked phenylene group.

In the production of the resin, the amount of the diamine compound, the tetracarboxylic acid compound and/or the dicarboxylic acid compound used can be appropriately selected according to the ratio of each constituent unit of the desired polyamide-imide resin.

The method for producing the polyamide-imide resin having at least the structural unit (1) and the structural unit (2) is not particularly limited as long as the polyamide-imide resin can be obtained, but the elastic modulus and surface hardness of the optical film are increased. From an easy viewpoint, it is a production method of reacting a diamine compound, a tetracarboxylic acid compound, and a dicarboxylic acid compound, and it is preferable to produce a polyamide-imide resin by a production method of dividing and adding a dicarboxylic acid compound, and a diamine compound. And a tetracarboxylic acid compound to produce an intermediate (A), and a step (II) of reacting the intermediate (A) with a dicarboxylic acid compound. In (), it is more preferable to produce the polyamide-imide resin by the method of adding the dicarboxylic acid compound in portions.

The polyamideimide resin of the present invention having at least the structural unit (1) and the structural unit (2) is produced by a method of dividing and adding a dicarboxylic acid compound to improve the transmittance and elastic modulus of the optical film. Considered easy. In addition, the weight average molecular weight of the resin can be easily adjusted to a desired range by producing the dicarboxylic acid compound in a divided manner.

Therefore, the polyamideimide-based resin contained in the optical film of the present invention, and the polyamideimide-based resin of the present invention is a production method of reacting a diamine compound, a tetracarboxylic acid compound, and a dicarboxylic acid compound, and a dicarboxylic acid compound It is preferable that the resin is produced by a production method in which the diamine compound is added in portions, a step (I) of reacting a diamine compound and a tetracarboxylic acid compound to produce an intermediate (A), and the intermediate (A) It is more preferable that the resin is produced by a production method including a step (II) of reacting the dicarboxylic acid compound with a dicarboxylic acid compound, wherein the dicarboxylic acid compound is dividedly added in the step (II).

In the case of producing a polyamide-imide resin by a production method including the above steps (I) and (II), the step (I) of reacting a diamine compound with a tetracarboxylic acid compound to produce an intermediate (A) The reaction temperature is not particularly limited, but may be, for example, 5 to 200°C, preferably 5 to 100°C, more preferably 5 to 50°C, and further preferably 5°C to room temperature (about 25°C). 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 in an atmosphere of an inert gas such as nitrogen or argon while stirring, and may be carried out under normal pressure, under pressure or under reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or the inert gas atmosphere while stirring.

In the step (I), the diamine compound and the tetracarboxylic acid compound react with each other to produce an intermediate (A), that is, a 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), it is preferable that the intermediate (A) is reacted with the dicarboxylic acid compound, and the dicarboxylic acid compound is dividedly added here. The dicarboxylic acid compound is dividedly added to the reaction solution obtained in the step (I) to react the intermediate (A) with the dicarboxylic acid compound. It is easy to adjust the molecular weight of the polyamide-imide resin within the above preferable range by adding the dicarboxylic acid compound in portions instead of adding it all at once. In the present specification, the divided addition means that the dicarboxylic acid compound to be added is divided and added in several times, more specifically, the dicarboxylic acid to be added is divided into specific amounts, and each is separated by a predetermined interval or a predetermined time. Means to add. Since the predetermined interval or predetermined time includes a very short interval or time, the divided addition also includes continuous addition or continuous feed.

In the step (II), the number of divisions when the dicarboxylic acid compound is dividedly added can be appropriately selected depending on the reaction scale, the type of raw material, etc., and is preferably 2 to 20 times, more preferably 3 to 10 times, and further preferably 3 times. ~ 6 times. When the number of divisions is within the above range, it is considered that the structure is likely to be optimal for increasing the elastic modulus while maintaining the transmittance of the optical film. Further, it is considered that the weight average molecular weight of the polyamide-imide resin can be easily adjusted to the above preferable range.

The dicarboxylic acid compound may be divided and added in an equal amount, or may be divided and added in an uneven amount. The time between each addition (sometimes referred to as an addition interval) may be the same or different. When two or more dicarboxylic acid compounds are added, the term “divided addition” means that the total amount of all dicarboxylic acid compounds is divided and added, and the method of dividing each dicarboxylic acid compound is not particularly limited. However, for example, each dicarboxylic acid compound may be added separately or batchwise, each dicarboxylic acid compound may be dividedly added together, or a combination thereof may be used.

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

The reaction temperature of step (II) is not particularly limited, but may be, for example, 5 to 200°C, preferably 5 to 100°C, more preferably 5 to 50°C, and further preferably 5 to room temperature (about 25°C). .. The reaction may be carried out in air or in an atmosphere of an inert gas such as nitrogen or argon while stirring, and may be carried out under normal pressure, under pressure or under reduced pressure. In a preferred embodiment, step (II) is carried out under normal pressure and/or an inert gas atmosphere with stirring.

In the step (II), after the dicarboxylic acid compound is dividedly added, the mixture is stirred for a predetermined time and reacted to obtain a polyamideimide precursor. The polyamide-imide precursor can be isolated by, for example, adding a large amount of water or the like to a reaction liquid containing the polyamide-imide precursor to precipitate the polyamide-imide precursor, and performing filtration, concentration, drying and the like.

In the step (II), the intermediate (A) reacts with the dicarboxylic acid compound to obtain a polyamideimide precursor. Therefore, the polyamide-imide precursor refers to a polyamide-imide before imidization (before ring closure) having at least a constitutional unit derived from a diamine compound, a constitutional unit derived from a tetracarboxylic acid, and a constitutional unit derived from a dicarboxylic acid compound.

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, but is, for example, 5 to 350°C, preferably 5 to 200°C, more preferably 5 to 100°C. The reaction time is not particularly limited, but is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out under the conditions of an inert atmosphere or reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or an inert gas atmosphere with stirring. Further, the reaction is preferably carried out in a solvent inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, for example, water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, Alcohol solvents such as 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, methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; toluene, xylene An aromatic hydrocarbon solvent such as acetonitrile; a nitrile solvent such as acetonitrile; an ether solvent such as tetrahydrofuran and dimethoxyethane; a chlorine-containing solvent such as chloroform and chlorobenzene; an amide such as N,N-dimethylacetamide and N,N-dimethylformamide. Examples include system solvents; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations (mixed solvents) thereof. Among these, amide solvents can be preferably used from the viewpoint of solubility.

The method for producing a polyamideimide resin may further include a step (III) of imidizing a polyamideimide precursor in the presence of an imidization catalyst. By subjecting the polyamide-imide precursor obtained in the step (II) to the step (III), the structural unit portion having a polyamic acid structure in the constitutional unit of the polyamide-imide precursor is imidized (closed), and the formula ( It is possible to obtain a polyamide-imide resin containing the structural unit represented by 1) and the structural unit represented by the formula (2). Examples of the imidization catalyst include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydro. Alicyclic amine (monocyclic) such as azepine; azabicyclo[2.2.1]heptane, azabicyclo[3.2.1]octane, azabicyclo[2.2.2]octane, and azabicyclo[3.2. 2] Alicyclic amine (polycyclic) such as nonane; and 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 Aromatic amines such as isoquinoline may be mentioned. From the viewpoint of facilitating the imidization reaction, it is preferable to use an acid anhydride together with the imidization catalyst. Examples of the acid anhydride include conventional acid anhydrides used for imidization reaction, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, and aromatics such as phthalic acid. Examples thereof include acid anhydrides.

The polyamide-imide resin may be isolated (separated and purified) by a conventional method, for example, separation means such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a combination of these separation means. In a preferred embodiment, a large amount of alcohol such as methanol is added to a reaction liquid containing a polyamide-imide resin to precipitate the resin, which can be isolated by concentration, filtration and drying.

<Filler>
The present invention also provides an optical film containing the above polyamide-imide resin. The optical film of the present invention may include at least one filler. Examples of the filler include organic particles and inorganic particles, and preferably inorganic particles. The inorganic particles include silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, metal oxide particles such as cerium oxide, magnesium fluoride, fluorine. Examples thereof include metal fluoride particles such as sodium fluoride, and among these, from the viewpoint of increasing the elastic modulus and/or tear strength of the optical film and easily improving impact resistance, silica particles, zirconia particles, and alumina particles are preferable. And more preferably silica particles. These fillers can be used alone or in combination of two or more.

The average primary particle size of the filler, preferably silica particles, is usually 1 nm or more, preferably 5 nm or more, more preferably 10 nm or more, further preferably 15 nm or more, particularly preferably 20 nm or more, preferably 100 nm or less, more preferably It is 90 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, particularly preferably 60 nm or less, particularly preferably 50 nm or less, particularly preferably 40 nm or less. When the average primary particle diameter of the silica particles is within the above range, aggregation of the silica particles is 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 with 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, and more preferably 100 parts by mass of the optical film. It is 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 60 parts by mass or less. When the content of the filler is at least the above lower limit, the elastic modulus of the obtained optical film can be easily improved. Further, when the content of the filler is not more than the above upper limit, the optical characteristics of the optical film are likely to be improved.

<Ultraviolet absorber>
The optical film of the present invention may include at least one UV absorber. The ultraviolet absorber can be appropriately selected from those usually used as an ultraviolet absorber in the field of resin materials. The ultraviolet absorber may include a compound that absorbs light having a wavelength of 400 nm or less. Examples of the ultraviolet absorber include at least one compound selected from the group consisting of benzophenone compounds, salicylate compounds, benzotriazole compounds, and triazine compounds. The ultraviolet absorbers can be used alone or in combination of two or more. Since the optical film contains the ultraviolet absorber, the deterioration of the resin is suppressed, so that the visibility can be enhanced when the optical film of the present invention is applied to a display device or the like. In the present specification, the “system compound” refers to a derivative of the compound to which the “system compound” is attached. For example, “benzophenone-based compound” refers to a compound having benzophenone as a base 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, and more preferably, the mass of the polyamideimide-based resin contained in the optical film. It is 1 to 8 parts by mass, more preferably 2 to 7 parts by mass. When the content of the ultraviolet absorber is at least the above lower limit, it is easy to improve the ultraviolet absorptivity. When the content of the ultraviolet absorber is not more than the above upper limit, decomposition of the ultraviolet absorber due to heat at the time of manufacturing the base material can be suppressed, optical characteristics can be easily improved, and haze, for example, can be easily reduced.

<Other additives>
The optical film of the present invention may further contain an additive other than the filler and the ultraviolet absorber. Examples of other additives include antioxidants, release agents, stabilizers, coloring agents such as bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, and leveling agents. Can be mentioned. When containing other additives, the content thereof is 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 with respect to the mass of the optical film. It may be 10 parts by mass.

(Method for producing optical film)
The method for producing an optical film using the polyamideimide-based resin of the present invention is not particularly limited, for example, the following steps:
(A) a step of preparing a polyamide-imide resin composition containing at least the polyamide-imide resin and a solvent (hereinafter, also referred to as “varnish”) (varnish preparation step),
(B) a step of applying a varnish to a support material to form a coating film (application step), and (c) a step of drying the applied liquid (coating film) to form an optical film (optical film forming step) )
It may be a manufacturing method including.

In the varnish preparation step, a polyamide-imide resin is dissolved in a solvent, and if necessary, additives such as the filler and the ultraviolet absorber are added and mixed with stirring to prepare a varnish. When silica particles are used as the filler, a dispersion liquid of silica sol containing silica particles may be added to the resin with a solvent in which the resin can be dissolved, for example, a silica sol obtained by substituting with a solvent used for preparing the varnish described below. ..

The solvent used for preparing the varnish is not particularly limited as long as it can dissolve the resin. Examples of such a solvent include amide solvents such as N,N-dimethylacetamide and N,N-dimethylformamide; lactone solvents such as γ-butyrolactone and γ-valerolactone; sulfur-containing dimethyl sulfone, dimethyl sulfoxide, sulfolane and the like. Examples include system solvents; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvent). Among these, amide solvents or lactone solvents are preferable. These solvents may be used alone or in combination of two or more. Further, the varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, or the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 20% by mass, and further preferably 5 to 15% by mass.

In the coating step, a varnish is coated on the support material to form a coating film by a known coating method. As a known coating method, for example, wire bar coating method, reverse coating, roll coating method such as gravure coating, die coating method, comma coating method, lip coating method, spin coating method, screen coating method, fountain coating method, dipping method, The spray method, the spout molding method and the like can be mentioned.

In the film forming process, the optical film can be formed by drying the coating film and peeling it from the support material. A step of drying the optical film may be further provided after the peeling. The coating film can be dried usually at a temperature of 50 to 350°C. If necessary, the coating film may be dried under an inert atmosphere or a reduced pressure condition.

Examples of the support material include a SUS plate if it is a metal system, a PET film, a PEN film, a polyamide resin film, a polyimide resin film, a cycloolefin polymer (COP) film, an acrylic film if it is a resin system. Are listed. 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 with an optical film and cost.

The application of the optical film of the present invention is not particularly limited and may be used for various applications. The optical film of the present invention may be a single layer or a laminate as described above, and the optical film of the present invention may be used as it is, or a laminate with another film. May be used as. When the optical film is a laminated body, all layers laminated on one side or both sides of the optical film are referred to as an optical film.

(Functional layer)
One or more functional layers may be laminated on at least one surface of the optical film of the present invention. 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 layer can be used alone or in combination of two or more kinds.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays, for example, a main material selected from a transparent resin of an ultraviolet curable type, a transparent resin of an electron beam curable type, and a transparent resin of a thermosetting type, and a main material thereof. It is composed of dispersed ultraviolet absorbers.

A hard coat layer may be provided on at least one surface 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 ensured, bending resistance is unlikely to decrease, and a problem of curling due to curing shrinkage tends not to occur. ..
The hard coat layer can be formed by curing a hard coat composition containing a reactive material capable of forming a crosslinked structure by irradiation with active energy rays or application of thermal energy, and irradiation with active energy rays is preferable. Active energy rays are defined as energy rays capable of decomposing compounds that generate active species to generate active species, and include visible light, ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays and electron rays. And the like, and preferably ultraviolet rays. The hard coat composition contains at least one polymer of a radically polymerizable compound and a cationically polymerizable compound.

The radically polymerizable compound is a compound having a radically polymerizable group. The radical polymerizable group contained in the radical polymerizable compound may be any functional group capable of causing a radical polymerization reaction, and examples thereof include a group containing a carbon-carbon unsaturated double bond, and specifically, a vinyl group. And (meth)acryloyl group. When the radical-polymerizable compound has two or more radical-polymerizable groups, these radical-polymerizable groups may be the same as or different from each other. The number of radically polymerizable groups contained in one molecule of the radically polymerizable compound is preferably 2 or more from the viewpoint of improving the hardness of the hard coat layer. From the viewpoint of high reactivity, the radical-polymerizable compound is preferably a compound having a (meth)acryloyl group. Specifically, 2 to 6 (meth)acryloyl groups are included in one molecule. A compound called a polyfunctional acrylate monomer, an epoxy (meth)acrylate, a urethane (meth)acrylate, or a polyester (meth)acrylate, which has several (meth)acryloyl groups in its molecule, has a molecular weight of from several hundred. Thousands of oligomers may be mentioned, preferably one or more selected from 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 oxetanyl group and a vinyl ether group. The number of cationically polymerizable groups contained in one 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.

In addition, as the cationically polymerizable compound, among others, a compound having at least one of an epoxy group and an oxetanyl group as a cationically polymerizable group is preferable. A cyclic ether group such as an epoxy group or an oxetanyl group is preferable from the viewpoint that the shrinkage accompanying the polymerization reaction is small. In addition, compounds having an epoxy group among cyclic ether groups are easily available as compounds having various structures, do not adversely affect the durability of the obtained hard coat layer, and easily control the compatibility with the radically polymerizable compound. There is an advantage that. In addition, the oxetanyl group of the cyclic ether group tends to have a higher degree of polymerization than the epoxy group, accelerates the network formation rate obtained from the cationically polymerizable compound of the obtained hard coat layer, and is mixed with the radically polymerizable compound. Even in the region to be formed, there is an advantage that an independent network is formed without leaving unreacted monomer in the film.

As the cationically polymerizable compound having an epoxy group, for example, polyglycidyl ether of a polyhydric alcohol having an alicyclic ring, or cyclohexene ring, a cyclopentene ring-containing compound, hydrogen peroxide, with a suitable oxidizing agent such as peracid Alicyclic epoxy resin obtained by epoxidation; polyglycidyl ether of aliphatic polyhydric alcohol or alkylene oxide adduct thereof, polyglycidyl ester of aliphatic long-chain polybasic acid, homopolymer of glycidyl (meth)acrylate, Aliphatic epoxy resins such as copolymers; glycidyl ethers produced by the reaction of bisphenols such as bisphenol A, bisphenol F and hydrogenated bisphenol A, or derivatives thereof 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 hard coat composition may further include a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, etc., which are 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 to promote radical polymerization and cation polymerization.
The radical polymerization initiator may be any substance that can release a substance that initiates radical polymerization by at least one of irradiation with active energy rays and heating. Examples of thermal radical polymerization initiators include hydrogen peroxide, organic peroxides such as perbenzoic acid, and azo compounds such as azobisbutyronitrile.
As the active energy ray radical polymerization initiator, a Type 1 type radical polymerization initiator that generates a radical by decomposition of a molecule and a Type 2 type radical polymerization initiator that coexists with a tertiary amine to generate a radical by a hydrogen abstraction type reaction Yes, they are used alone or in combination.
The cationic polymerization initiator may be any one that can release a substance that initiates cationic polymerization by at least one of irradiation with active energy rays and heating. As the cationic polymerization initiator, an aromatic iodonium salt, an aromatic sulfonium salt, a cyclopentadienyl iron(II) complex or the like can be used. These can initiate cationic polymerization either by irradiation with active energy rays or by heating, or both, depending on the difference in structure.

The polymerization initiator may be included in an amount of preferably 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 in the above range, curing can be sufficiently advanced, and the mechanical properties and adhesion of the finally obtained coating film can be in a good range, and Poor adhesion due to curing shrinkage, cracking and curling tend to occur less easily.

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

The adhesive layer is a layer having an adhesive function and has a function of adhering the optical film to another member. A commonly known material can be used as the material for forming the adhesive layer. For example, a thermosetting resin composition or a photocurable resin composition can be used. In this case, the resin composition can be polymerized and cured by supplying energy afterwards.

The pressure-sensitive adhesive layer may be a layer called a pressure sensitive adhesive (Pressure Sensitive Adhesive, PSA) that is attached to an object by pressing. The pressure-sensitive adhesive may be an adhesive that is "a substance that has adhesiveness at room temperature and adheres to an adherend with a light pressure" (JIS K 6800), and may be a "protective coating (microcapsule containing specific components). ), which is capable of maintaining stability until the coating is broken by an appropriate means (pressure, heat, etc.) (JIS K 6800).

The hue adjusting layer is a layer having a function of adjusting hue, and is a layer capable of adjusting the laminate including the optical film to a desired hue. The hue adjustment layer is, for example, a layer containing a resin and a colorant. Examples of the colorant include titanium oxide, zinc oxide, rouge, titanium oxide-based calcined pigment, ultramarine blue, cobalt aluminate, and inorganic pigments such as carbon black; azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, Organic pigments such as perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, slene compounds, and diketopyrrolopyrrole compounds; extender pigments such as barium sulfate and calcium carbonate; and basic dyes, Examples include acid dyes and mordant dyes.

The refractive index adjusting layer is a layer having a refractive index adjusting function, and has a refractive index different from that of the optical film, for example, and is a layer capable of imparting 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 optionally a pigment, or a metal thin film. 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 passing through the refractive index adjusting layer can be prevented, and a decrease in transparency can be prevented. Examples of the metal used for the refractive index adjusting layer include metals 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. An oxide or a metal nitride is mentioned.

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

In one embodiment of the present invention, the optical film may have a protective film on at least one surface (one surface or both surfaces). For example, when it has a functional layer on one side of the optical film, the protective film may be laminated on the surface of the optical film side or the surface of the functional layer side, and is laminated on both the optical film side and the functional layer side. May be. When the optical film has functional layers on both sides, the protective film may be laminated on one surface of the functional layer side or on both surfaces of the functional layer side. The protective film is a film for temporarily protecting the surface of the optical film or the functional layer, and is not particularly limited as long as it is a peelable film capable of protecting 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; polyolefin resin films such as polyethylene and polypropylene films; acrylic resin films; polyolefin resin films, polyethylene. It is preferably selected from the group consisting of a terephthalate resin film and an acrylic resin film. When the optical film has two protective films, each protective film may be the same as 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, more preferably 20 to 100 μm. When the optical film has two protective films, the thickness of each protective film 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 plate of a display device, particularly as a front plate of a flexible display device (hereinafter sometimes referred to as a window film). The flexible display device has, for example, a flexible functional layer and an optical film that is superposed on the flexible functional layer and functions as a front plate. That is, the front plate of the flexible display device is arranged on the visible side above the flexible functional layer. This front plate has a function of protecting the flexible functional layer.

Examples of the display device include TVs, smartphones, mobile phones, car navigations, tablet PCs, portable game machines, electronic paper, indicators, bulletin boards, watches, and wearable devices such as smart watches. Examples of the flexible display device include all display devices having flexible characteristics.

[Flexible display device]
The present invention also provides a flexible display device comprising the optical film of the present invention. The optical film of the present invention is preferably used as a front plate in a flexible display device, and the front plate is sometimes referred to as a window film. The flexible display device includes a flexible display device laminate and an organic EL display panel. The flexible display device laminate is arranged 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. The order of laminating them is arbitrary, but the window film, the polarizing plate, It is preferable that the touch sensor or the window film, the touch sensor, and the polarizing plate are laminated in this order. 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 visible and the visibility of the display image is improved. Each member can be laminated using an adhesive, a pressure-sensitive adhesive or the like. Further, a light-shielding pattern formed on at least one surface of any one of the window film, the polarizing plate, and the touch sensor may be provided.

[Polarizer]
The flexible display device of the present invention may further include a polarizing plate, preferably a circularly polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only a right circularly polarized light component or a left circularly polarized light component by laminating a λ/4 retardation plate on a linearly polarizing plate. For example, by converting the external light into right circularly polarized light, blocking the external light reflected by the organic EL panel to become left circularly polarized light, and transmitting only the luminescent component of the organic EL, the effect of reflected light is suppressed and the image is displayed. It is used to make it easier to see. In order to achieve the circular polarization function, the absorption axis of the linear polarizing plate and the slow axis of the λ/4 retardation plate need to be theoretically 45°, but they are practically 45±10°. The linearly polarizing plate and the λ/4 retardation plate are not necessarily required to be laminated adjacent to each other, and it is sufficient that the relationship between the absorption axis and the slow axis satisfies the above range. It is preferable to achieve perfect circularly polarized light at all wavelengths, but this is not always necessary in practice, so the circularly polarizing plate in the present invention includes an elliptically polarizing plate. It is also preferable to further laminate a λ/4 retardation film on the visible side of the linear polarizing plate to make the emitted light circularly polarized light and thereby improve the visibility in the state of wearing polarized sunglasses.

The linearly polarizing plate is a functional layer having a function of transmitting light oscillating in the transmission axis direction but blocking polarized light of an oscillating component perpendicular to the light. The linear polarizing plate may have a configuration including a linear polarizer alone or a linear polarizer and a protective film attached to at least one surface thereof. The thickness of the linear polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness is in the above range, flexibility tends to be difficult to decrease.
The linear polarizer may be a film-type polarizer produced by dyeing and stretching a polyvinyl alcohol (PVA) film. A dichroic dye such as iodine is adsorbed on a PVA-based film oriented by stretching or is stretched in a state of being adsorbed on PVA, whereby the dichroic dye is oriented and exhibits polarization performance. The production of the film-type polarizer may include other steps such as swelling, crosslinking with boric acid, washing with an aqueous solution, and drying. The stretching and dyeing steps may be performed on the PVA-based film alone, or may be performed in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA-based film used is preferably 10 to 100 μm, and the stretching ratio is preferably 2 to 10 times.
Further, 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 has only to have a property of exhibiting a liquid crystal state, and it is preferable to have a higher order alignment state such as a smectic phase because high polarization performance can be exhibited. It is also preferable that the liquid crystal compound has a polymerizable functional group.

The dichroic dye is a dye that is aligned with the liquid crystal compound and exhibits dichroism, and the dichroic dye itself may have liquid crystallinity or has a polymerizable functional group. You can also 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 cross-linking agent, a silane coupling agent and the like.
The liquid crystal polarizing layer is manufactured by applying a liquid crystal polarizing composition on the alignment film to form a liquid crystal polarizing layer.
The liquid crystal polarizing layer can be formed thinner than the film-type polarizer. The thickness of the liquid crystal polarizing layer may be preferably 0.5 to 10 μm, more preferably 1 to 5 μm.
The alignment film can be produced, for example, by applying the composition for forming an alignment film on a substrate and imparting the alignment property by rubbing, irradiation with polarized light, or the like. The composition for forming an alignment film may contain a solvent, a cross-linking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent and the like in addition to the alignment agent. As the alignment agent, for example, polyvinyl alcohols, polyacrylates, polyamic acids, and polyimides can be used. When applying photo-alignment, it is preferable to use an aligning agent containing a cinnamate group. The weight average molecular weight of the polymer used as the aligning agent may be about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000 nm, more preferably 10 to 500 nm from the viewpoint of the alignment control force. The liquid crystal polarizing layer can be peeled from the base material and transferred to be laminated, or the base material can be laminated as it is. It is also preferable that the base material plays a role as a transparent base material of a protective film, a retardation plate or a window.

The protective film may be a transparent polymer film, and the materials and additives used for the transparent substrate can be used. Cellulose type films, olefin type films, acrylic films and polyester type films are preferable. It may be a coating type protective film obtained by applying and curing a cationically curable composition such as an epoxy resin or a radical curable composition such as an acrylate. If necessary, plasticizers, ultraviolet absorbers, infrared absorbers, colorants such as pigments and dyes, optical brighteners, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants, lubricants, solvents, etc. 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 does not easily deteriorate. The protective film can also serve as the transparent base material of the window.

The λ/4 retardation plate is a film that gives a λ/4 retardation in a direction (in-plane direction of the film) orthogonal to the traveling direction of incident light. The λ/4 retardation plate may be a stretchable retardation plate produced by stretching a polymer film such as a cellulose film, an olefin film, a polycarbonate film. If necessary, retarder, plasticizer, ultraviolet absorber, infrared absorber, colorant such as pigment or dye, fluorescent whitening agent, dispersant, heat stabilizer, light stabilizer, antistatic agent, antioxidant. , A lubricant, a solvent, etc. may be contained. The thickness of the stretchable retardation plate may be 200 μm or less, and preferably 1 to 100 μm. When the thickness is in the above range, the flexibility of the film tends to be less likely to decrease.
Further, another example of the λ/4 retardation plate may be a liquid crystal coating type retardation plate formed by applying a liquid crystal composition. The liquid crystal composition contains a liquid crystal compound having a property of exhibiting a liquid crystal state such as nematic, cholesteric, or smectic. Any of the compounds including the liquid crystal compound in the liquid crystal composition has a polymerizable functional group. The liquid crystal coated retardation plate may further contain an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a cross-linking agent, a silane coupling agent and the like. The liquid crystal coating type retardation plate can be manufactured by coating and curing the liquid crystal composition on the alignment film to form a liquid crystal retardation layer as in the case of the liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed thinner than the stretched 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 coating type retardation plate can be peeled from the base material and transferred to be laminated, or the base material can be laminated as it is. It is also preferable that the base material plays a role as a transparent base material of a protective film, a retardation plate or a window.

In general, many materials exhibit large birefringence at shorter wavelengths and smaller birefringence at longer wavelengths. In this case, since a phase difference of λ/4 cannot be achieved in the entire visible light region, an in-plane phase difference of 100 to 180 nm, preferably 130, which is λ/4 near 560 nm where the visibility is high. Often designed to be ~150 nm. It is preferable to use an inverse dispersion λ/4 retardation plate made of a material having a birefringence wavelength dispersion characteristic opposite to the usual one because the visibility can be improved. As such a material, those described in JP-A-2007-232873 in the case of a stretched retardation plate and those disclosed in JP-A-2010-30979 in the case of a liquid crystal coated retardation plate may be used. preferable.
As another method, there is also known a technique of obtaining a broadband λ/4 retardation plate by combining with a λ/2 retardation plate (Japanese Patent Laid-Open No. 10-90521). The λ/2 retardation plate is also manufactured by the same material method as that of the λ/4 retardation plate. The combination of the stretched retardation plate and the liquid crystal coating type retardation plate is arbitrary, but it is preferable to use the liquid crystal coating type retardation plate for both of them because the thickness can be reduced.
There is also known a method of laminating a positive C plate on the circularly polarizing plate in order to enhance visibility in an oblique direction (Japanese Patent Laid-Open No. 2014-224837). The positive C plate may be a liquid crystal coating type retardation plate or a stretching type retardation plate. The retardation 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 is used as an input means. As the touch sensor, various types such as a resistance film type, a surface acoustic wave type, an infrared type, an electromagnetic induction type, and a capacitance type have been proposed, and any type may be used. Of these, the capacitance method is preferable. The capacitive touch sensor is divided into an active region and a non-active region located outside the active region. The active area is an area corresponding to a display area where a screen is displayed on the display panel and is an area where a user's touch is sensed, and the inactive area is a non-display area where the screen is not displayed on the display device. Is an area corresponding to the area. The touch sensor has a flexible substrate; a sensing pattern formed in an active region of the substrate; a non-active region of the substrate and connected to an external driving circuit through the sensing pattern and a pad. Each sensing line can be included. As the substrate having flexible characteristics, the same material as the transparent substrate for the window can be used. The toughness of the substrate of the touch sensor is preferably 2,000 MPa% or more from the viewpoint of suppressing cracks in the touch sensor. More preferably, the toughness may be 2,000 to 30,000 MPa%. Here, toughness is defined as the area under the curve up to the breaking point in a stress (MPa)-strain (%) curve (Stress-strain curve) obtained through a tensile test of a polymer material.

The sensing pattern may include a first pattern formed in the first direction and a second pattern formed in the second direction. The first pattern and the second pattern are arranged in different directions. The first pattern and the second pattern are formed on the same layer, and the respective patterns must be electrically connected in order to detect a touched point. The first pattern has a structure in which the unit patterns are connected to each other through a joint, but the second pattern has a structure in which the unit patterns are separated from each other in an island shape. A separate bridge electrode is required to make the connection. A known transparent electrode material can be applied to the sensing pattern. For example, 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, metal wire and the like can be mentioned, and these can be used alone or in combination of two or more. Preferably ITO can be used. The metal used for the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, and chromium. These may be used alone or in combination of two or more.

The bridge electrode may be formed on the insulating layer on the sensing pattern via an insulating layer. The bridge electrode is formed on the substrate, and the insulating layer and the sensing pattern may be formed on the bridge electrode. The bridge electrode may be formed of the same material as the sensing pattern, and may be formed of a metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of two or more of these. You can also do it. Since the first pattern and the second pattern must be electrically insulated, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the joint of the first pattern and the bridge electrode, or may be formed in the layer structure covering the sensing pattern. In the latter case, the bridge electrode can connect the second pattern through a contact hole formed in the insulating layer. The touch sensor has a difference in transmittance between a pattern area where a pattern is formed and a non-pattern area where a pattern is not formed, specifically, a light transmittance induced by a difference in refractive index in these areas. An optical adjustment layer may be further included between the substrate and the electrode as a means for appropriately compensating the difference, and the optical adjustment layer may include an inorganic insulating material or an organic insulating material. The optical adjustment layer may be formed by coating a photocurable composition containing a photocurable organic binder and a solvent on a substrate. The photocurable composition may further include inorganic particles. The inorganic particles can increase the refractive index of the optical adjustment layer.
The photo-curable organic binder may include a copolymer of each monomer such as an acrylate-based monomer, a styrene-based monomer, and a carboxylic acid-based monomer. The photocurable organic binder may be, for example, a copolymer containing different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.
The inorganic particles can include, for example, zirconia particles, titania particles, alumina particles, and the like. The photocurable composition may further include additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

[Adhesive layer]
Each layer such as a window film, a polarizing plate, a touch sensor and the like, which forms the laminate for a flexible display device, and a linear polarizing plate and a film member such as a λ/4 retardation plate, which constitute each layer, may be bonded with an adhesive. it can. As the adhesive, a water-based adhesive, an organic solvent-based adhesive, a solvent-free adhesive, a solid adhesive, a solvent volatile adhesive, a water-based solvent volatile adhesive, a moisture-curable adhesive, a heat-curable adhesive, Anaerobic curable adhesives, active energy ray curable adhesives, curing agent mixed adhesives, hot melt adhesives, pressure sensitive adhesives, pressure sensitive adhesives, rewet adhesives, etc. are widely used. Things can be used. Of these, water-based solvent volatilizing adhesives, active energy ray-curing adhesives, and pressure-sensitive adhesives are often used. The thickness of the adhesive layer can be appropriately adjusted according to the required adhesive force and the like, and is, for example, 0.01 to 500 μm, preferably 0.1 to 300 μm. A plurality of adhesive layers may be present in the laminate for flexible display device, but the thickness of each and the type of adhesive used may be the same or different.

As the water-based solvent volatilizing adhesive, a polyvinyl alcohol-based polymer, a water-soluble polymer such as starch, a water-dispersed polymer such as an ethylene-vinyl acetate emulsion and a styrene-butadiene-based emulsion can be used as a main polymer. In addition to water and the main polymer, a cross-linking agent, a silane compound, an ionic compound, a cross-linking 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 water-based solvent volatilization type adhesive, the water-based solvent volatilization type adhesive may be injected between the adhered layers to bond the adhered layers and then dried to impart adhesiveness. The thickness of the adhesive layer when the water-based solvent volatilizing adhesive is used may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the water-based 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 that is irradiated with an active energy ray to form an adhesive layer. The active energy ray-curable composition may contain at least one polymer of a radically polymerizable compound and a cationically polymerizable compound, which are similar to those of the hard coat composition. The radical-polymerizable compound is the same as the hard coat composition, and the same kind as the hard coat composition can be used. The radically polymerizable compound used in the adhesive layer is preferably a compound having an acryloyl group. It is also preferable to include a monofunctional compound in order to reduce the viscosity of the adhesive composition.

The cationically polymerizable compound is the same as the hard coat composition, and the same kind as the hard coat composition can be used. As the cationically polymerizable compound used in the active energy ray-curable composition, an epoxy compound is more preferable. It is also preferable to include a monofunctional compound as a reactive diluent to reduce the viscosity of the adhesive composition.
The active energy ray composition may further include a polymerization initiator. As the polymerization initiator, there are radical polymerization initiators, cationic polymerization initiators, radical and cationic polymerization initiators, etc., which 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 to promote radical polymerization and cation polymerization. In the description of the hard coat composition, an initiator capable of initiating radical polymerization and/or cationic polymerization by irradiation with active energy rays can be used.

The active energy ray-curable composition is further an ion scavenger, an antioxidant, a chain transfer agent, an adhesion promoter, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, a defoaming agent solvent, an additive, a solvent. Can be included. In the case of adhering with the active energy ray-curable adhesive, the active energy ray-curable composition is applied to either or both of the adherend layers and then laminated, and activated through either adherent layer or both adherent layers. Adhesion can be achieved by irradiating with energy rays and curing. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer 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 adhesive used may be the same or different.

The pressure-sensitive adhesive may be classified into an acrylic pressure-sensitive adhesive, a urethane-based pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, etc. depending on the base polymer, and any of these may be used. In addition to the base polymer, the adhesive may contain a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a tackifier, a plasticizer, a dye, a pigment, an inorganic filler, and the like. A pressure-sensitive adhesive layer (adhesive layer) is formed by dissolving and dispersing each component constituting the pressure-sensitive adhesive in a solvent to obtain a pressure-sensitive adhesive composition, applying the pressure-sensitive adhesive composition on a substrate, and then drying. To be done. The adhesive layer may be directly formed, or may be separately formed on the substrate and transferred. It is also preferable to use a release film to cover the adhesive surface before adhesion. When the pressure-sensitive adhesive is used, the thickness of the adhesive layer may be 1 to 500 μm, preferably 2 to 300 μm. When the pressure-sensitive adhesive is used to form a plurality of layers, the thickness of each layer and the type of pressure-sensitive adhesive used may be the same or different.

[Shading pattern]
The light shielding pattern may be applied as at least a part of a bezel or a housing of the flexible display device. The visibility of the image is improved by hiding the wiring arranged at the peripheral portion of the flexible display device by the light-shielding pattern and making it difficult to see. The light shielding pattern may have a single-layer or multi-layer form. The color of the light-shielding pattern is not particularly limited, and may have various colors such as black, white and metallic colors. The light-shielding pattern can be formed of a pigment for realizing a color and a polymer such as acrylic resin, ester resin, epoxy resin, polyurethane or silicone. These may be used alone or as a mixture of two or more kinds. The light-shielding pattern can be formed by various methods such as printing, lithography and inkjet. The thickness of the light shielding pattern is usually 1 to 100 μm, preferably 2 to 50 μm. Further, it is also preferable to give a shape such as an inclination in the thickness direction of the light shielding pattern.

Hereinafter, the present invention will be described in more detail with reference to Examples. Unless otherwise specified, "%" and "parts" in the examples mean% by mass and parts by mass. First, the evaluation method will be described.

<Measurement of elastic modulus>
The elastic moduli of the polyamide-imide films obtained in Examples and Comparative Examples were measured using “Autograph AG-IS” manufactured by Shimadzu Corporation. A film having a width of 10 mm in length and width was produced, a stress-strain curve (SS curve) was measured under conditions of a chuck distance of 50 mm and a tensile speed of 10 mm/min, and the elastic modulus was calculated from the inclination.

<Measurement of light transmittance>
The total light transmittance Tt of the sample is measured according to JIS K 7105:1981 by the fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. to measure the optical films obtained in Examples and Comparative Examples. did.

<Measurement of surface hardness>
As the surface hardness of the polyamide-imide films obtained in Examples and Comparative Examples, the pencil hardness of the film surface was adopted according to JIS K 5600-5-4:1999. The load was 100 g, the scanning speed was 60 mm/min, the presence or absence of scratches was evaluated under the environment of 4,000 lux, and the surface hardness represented by the pencil hardness was measured.

<Measurement of weight average molecular weight>
Gel Permeation Chromatography (GPC) Measurement (1) Pretreatment Method DMF eluent (10 mmol/L lithium bromide solution) was added to the sample to a concentration of 2 mg/mL, and heated at 80° C. for 30 minutes with stirring. After cooling, it was filtered with a 0.45 μm membrane filter to obtain a measurement solution.
(2) Measurement condition column: TOSgel α-2500 ((7) 7.8 mm diameter × 300 mm) × 1, Tosoh Co., Ltd. α-M ((13) 7.8 mm diameter × 300 mm) × 2 eluents : DMF (10 mmol/L lithium bromide added)
Flow rate: 1.0 mL/min Detector: RI detector Column temperature: 40°C
Injection volume: 100 μL
Molecular weight standard: Standard polystyrene

<Measurement of thickness>
The thickness of the polyamide-imide films obtained in Examples and Comparative Examples was measured using a micrometer (“ID-C112XBS” manufactured by Mitutoyo Corporation).

<Example 1>
[Preparation of polyamide-imide resin (1)]
Under a nitrogen atmosphere, in a separable flask equipped with a stirring blade, 2,2′-bis(trifluoromethyl)benzidine (TFMB) and N,N-dimethylacetamide (DMAc) were added, and the solid content of TFMB was 5.39% by mass. Then, 11.4 mol% of 4,4′-(hexafluoropropylidene)dianiline (6FDAM) was added to TFMB, and TFMB and 6FDAM were dissolved in DMAc while stirring at room temperature. Next, 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) was added to the flask so as to be 33.50 mol% with respect to TFMB, and stirred at room temperature for 3 hours. Then, after cooling to 10° C., 4,4′ oxybis(benzoyl chloride) (OBBC) was adjusted to 5.59 mol% to TFMB and terephthalic acid chloride (TPC) was adjusted to 30.15 mol% to TFMB. After 10 minutes of stirring, OBBC was further added to TFMB in an amount of 5.59 mol% and TPC was 30.15 mol%, and the mixture was stirred for 30 minutes. Thereafter, the same amount of DMAc as the initially added DMAc was added, and after stirring for 10 minutes, TPC was added so as to be 6.70 mol% with respect to TFMB, and stirred for 2 hours. Next, 78.17 mol% of diisopropylethylamine and 4-picoline to TFMB and 234.51 mol% of acetic anhydride to TFMB were added to the flask, and after stirring for 30 minutes, the internal temperature was raised to 70°C. The mixture was stirred for 3 hours to obtain a reaction solution.
The obtained reaction liquid was cooled to room temperature, put into a large amount of methanol in a filament shape, the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60° C. to obtain a polyamideimide resin (1). The weight average molecular weight of the polyamide-imide resin (1) was 583,000.

[Production of Polyamideimide Film (1)]
DMAc was added to the obtained polyamide-imide resin (1) so that the concentration was 10% by mass to prepare a polyamide-imide varnish (1). The obtained polyamide-imide varnish (1) was applied on 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 was 50 μm, It was dried at 50°C for 30 minutes and then at 140°C for 15 minutes to obtain a free-standing film. The self-supporting film was fixed to a metal frame and further dried at 200° C. for 60 minutes to obtain a polyamideimide film (1) having a thickness of 45 μm.

<Example 2>
[Preparation of polyamide-imide resin (2)]
Under a nitrogen atmosphere, TFMB and DMAc were added to a separable flask equipped with a stirring blade so that the solid content of TFMB was 5.60% by mass, and 6FDAM was added 11.11 mol% to TFMB, and the mixture was stirred at room temperature. While TFMB and 6FDAM were dissolved in DMAc. Next, pyromellitic dianhydride (PMDA) was added to the flask at 33.50 mol% with respect to TFMB, and the mixture was stirred at room temperature for 3 hours. Then, after cooling to 10° C., OBBC was added at 5.59 mol% with respect to TFMB and TPC was added at 30.15 mol% with respect to TFMB, and after stirring for 10 minutes, OBBC was further added at 5.50 mol% with respect to TFMB. 59 mol% and TPC were added to 30.15 mol% and the mixture was stirred for 30 minutes. Thereafter, the same amount of DMAc as the initially added DMAc was added, and after stirring for 10 minutes, TPC was added so as to be 6.70 mol% with respect to TFMB, and stirred for 2 hours. Next, 78.17 mol% of diisopropylethylamine and 4-picoline to TFMB and 234.51 mol% of acetic anhydride to TFMB were added to the flask, and after stirring for 30 minutes, the internal temperature was raised to 70°C. The mixture was stirred for 3 hours to obtain a reaction solution.
The obtained reaction liquid was cooled to room temperature, put into a large amount of methanol in a filament shape, the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60° C. to obtain a polyamideimide resin (2). The weight average molecular weight of the polyamide-imide resin (2) was 436,000.

[Production of Polyamideimide Film (2)]
DMAc was added to the obtained polyamide-imide resin (2) so that the concentration was 10% by mass to prepare a polyamide-imide varnish (2). The obtained polyamide-imide varnish (2) was applied onto 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 was 55 μm, It was dried at 50°C for 30 minutes and then at 140°C for 15 minutes to obtain a free-standing film. The self-supporting film was fixed to a metal frame and further dried at 200° C. for 60 minutes to obtain a polyamideimide film (2) having a thickness of 50 μm.

<Comparative Example 1>
[Preparation of polyamide-imide resin (3)]
Under a nitrogen atmosphere, TFMB and DMAc were added to a separable flask equipped with a stirring blade so that the solid content of TFMB was 5.54% by mass, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 4,4′-(hexafluoroisopropylidene)diphthalic acid dianhydride (6FDA) was added to the flask at 30.20 mol% with respect to TFMB, and the mixture was stirred at room temperature for 3 hours. Then, after cooling to 10° C., OBBC was added to the TFMB at 10.07 mol% and TPC was added to the TFMB at 54.35 mol %, and the mixture was stirred for 30 minutes. Thereafter, the same amount of DMAc as the initially added DMAc was added, and the mixture was stirred for 10 minutes, then TPC was added so as to be 6.04 mol% with respect to TFMB, and the mixture was stirred for 2 hours. Next, to the flask were added diisopropylethylamine and 4-picoline in an amount of 70.46 mol% with respect to TFMB and 211.37 mol% of acetic anhydride with respect to TFMB, and after stirring for 30 minutes, the internal temperature was raised to 70°C. The mixture was stirred for 3 hours to obtain a reaction solution.
The obtained reaction liquid was cooled to room temperature, put into a large amount of methanol in a filament shape, the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60°C to obtain a polyamide-imide resin (3). The weight average molecular weight of the polyamide-imide resin (3) was 402,000.

[Production of Polyamideimide Film (3)]
DMAc was added to the obtained polyamide-imide resin (3) so that the concentration was 10% by mass to prepare a polyamide-imide varnish (3). The obtained polyamide-imide varnish (3) was applied on 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 was 55 μm, It was dried at 50°C for 30 minutes and then at 140°C for 15 minutes to obtain a free-standing film. The self-supporting film was fixed to a metal frame and further dried at 200° C. for 60 minutes to obtain a polyamideimide film (3) having a thickness of 50 μm.

<Comparative example 2>
[Preparation of polyamide-imide resin (4)]
Under a nitrogen atmosphere, TFMB and DMAc were added to a separable flask equipped with a stirring blade so that the solid content of TFMB was 5.35% by mass, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 6FDA was added to the flask at 41.24 mol% with respect to TFMB, and the mixture was stirred at room temperature for 3 hours. Then, after cooling to 10° C., TPC was added so as to be 55.67 mol% with respect to TFMB, and the mixture was stirred for 30 minutes. Thereafter, the same amount of DMAc as the initially added DMAc was added, and after stirring for 10 minutes, TPC was added so as to be 6.19 mol% with respect to TFMB, and stirred for 2 hours. Next, 61.86 mol% of diisopropylethylamine and 4-picoline to TFMB and 288.66 mol% of acetic anhydride to TFMB were added to the flask, and after stirring for 30 minutes, the internal temperature was raised to 70°C. The mixture was stirred for 3 hours to obtain a reaction solution.
The obtained reaction liquid was cooled to room temperature, put into a large amount of methanol in a filament shape, the deposited precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 60° C. to obtain a polyamideimide resin (4). The weight average molecular weight of the polyamide-imide resin (4) was 174,000.

[Production of Polyamideimide Film (4)]
DMAc was added to the obtained polyamide-imide resin (4) so that the concentration was 10% by mass to prepare a polyamide-imide varnish (4). The obtained polyamide-imide varnish (4) was coated on 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 was 55 μm, It was dried at 50°C for 30 minutes and then at 140°C for 15 minutes to obtain a free-standing film. The self-supporting film was fixed to a metal frame and further dried at 200° C. 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 polyamide-imide resin films (1) to (4) were measured according to the methods described above. The results obtained are shown in Table 1.

Claims (14)

Formula (1):

[In the formula (1),
Y represents a tetravalent aromatic group which may have a substituent,
X is the formula (3):

In [Formula (3), ^{R 1,} independently of one another, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group or an aryl group having 6 to 12 carbon atoms having 1 to 6 carbon atoms, the ^{R 1} The contained hydrogen atoms may be independently substituted with a halogen atom,
V is, -O-, diphenylmethylene group, the number 1 to 12 linear, divalent hydrocarbon radical of branched or _{cycloaliphatic,} -SO 2 -, - S -, - CO- or - N(R ¹² )-, wherein the hydrogen atoms contained in the hydrocarbon group may be independently substituted with a halogen atom, and R ¹² is a hydrogen atom or a halogen atom. Represents an optionally substituted alkyl group having 1 to 12 carbon atoms]
Represents a divalent organic group represented by]
And a structural unit represented by the formula (2):

[In Formula (2), Z represents a divalent organic group,
X is as defined in the above formula (1)]
A polyamide-imide resin having at least a structural unit represented by: V in the formula (3) represents a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, wherein hydrogen atoms contained in the hydrocarbon group are mutually The polyamide-imide resin according to claim 1, which may be independently substituted with a halogen atom. The constitutional unit represented by the formula (1) is, as Y, a tetravalent aromatic group represented by the formula (4) and/or a tetravalent aromatic group represented by the formula (5):

[In the formulas (4) and (5), R ² and R ³ are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkyl group having 6 to 12 carbon atoms. The hydrogen atom, which represents an aryl group and is contained in R ² and R ³ , may be independently substituted with a halogen atom,
n represents an integer of 0 to 2]
The polyamide-imide resin according to claim 1 or 2, which comprises: Formula (4) is Formula (4a):

The polyamide-imide resin according to claim 3, represented by: Formula (5) is Formula (5a):

The polyamide-imide resin according to claim 3, represented by: The formula (3) is the formula (3a):

The polyamide-imide resin according to any one of claims 1 to 5, represented by: The polyamide-imide resin has at least two different structural units represented by formula (2) in Z, and at least two different structural units represented by formula (2) in X, And/or equation (7):

[In the formula (7), Z is as defined in the formula (1),
X′ represents a divalent organic group which does not correspond to X in the formula (2)]
The polyamide-imide resin according to any one of claims 1 to 6, further comprising a structural unit represented by. X'in Formula (7) is Formula (8):

[In the formula (8), Ar ² represents a divalent aromatic group which may have a substituent,
V represents a single bond,
m represents an integer of 0 to 3,
* Represents a bond]
The polyamide-imide resin according to claim 7, which is represented by: When the total of the constitutional unit represented by the formula (2) and the constitutional unit represented by the formula (7) is 100 mol %, the ratio of the constitutional unit represented by the formula (2) is 1 to 50 mol %. The polyamide-imide resin according to claim 7 or 8. The polyamide-imide resin according to claim 1, wherein the structural unit represented by the formula (2) contains, as Z, a divalent aromatic group which may have a substituent. An optical film comprising the polyamide-imide resin according to claim 1. A flexible display device comprising the optical film according to claim 11. The flexible display device according to claim 12, further comprising a touch sensor. The flexible display device according to claim 12, further comprising a polarizing plate.