WO2020138042A1

WO2020138042A1 - Optical film, flexible display device and polyamide-imide resin

Info

Publication number: WO2020138042A1
Application number: PCT/JP2019/050538
Authority: WO
Inventors: 建太朗増井; 皓史宮本; 勝紀望月; 拓志畔見; 坂本　宏
Original assignee: 住友化学株式会社
Priority date: 2018-12-28
Filing date: 2019-12-24
Publication date: 2020-07-02

Abstract

Provided is an optical film having a high modulus of elasticity and surface hardness. The optical film comprises a polyamide-imide resin containing a structural unit represented by formula (1): (In formula (1), R1 and R2 independently represent a C1-12 alkyl group, a C1-12 alkoxy group, a C6-12 aryl group, a C6-12 aryloxy group, a C1-12 carbonyl group, a C1-12 oxycarbonyl group or a halogen group, where the hydrogen atoms contained in R1 and R2 are may each be independently substituted with a halogen atom, a C1-4 alkyl group, a C1-4 alkoxy group, a hydroxyl group, or a carboxyl group, and V represents a single bond, -O-, a diphenylmethylene group, a C1-12 linear, branched or alicyclic divalent hydrocarbon group, -SO2-, -S-, -CO-, -PO-, PO2-, -N(R30)- or -Si(R31)2-, where the hydrogen atoms contained in said hydrocarbon group may each be independently substituted with a halogen atom, and R30 and R31 each independently represent hydrogen atoms or C1-12 alkyl groups which may be substituted with halogen atoms, m represents an integer of 0-2, n represents an integer of 1-4, p represents an integer of 0-4, and q represents an integer of 0-4) and a structural unit represented by formula (2): (in formula (2) X represents a divalent organic group and Y represents a tetravalent organic group).

Description

Optical film, flexible display device, and polyamide-imide resin

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

Currently, display devices such as liquid crystal display devices and organic EL display devices are widely used in various applications such as mobile phones and smart watches as well as televisions. 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 extremely rigid and easily broken, so that it is difficult to use it as a front plate material of a flexible display device.

Therefore, the use of polymer materials is being considered as an alternative to glass. Since a front plate made of a polymer material easily exhibits flexible properties, it is expected to be used for various purposes. As one of the polymer materials having flexibility, an optical film using, for example, a polyamide-imide resin has been studied (Patent Documents 1 and 2).

Japanese Patent Publication No. 2015-521686 Japanese Patent Laid-Open No. 2018-119132

However, when an optical film 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. The present inventor has studied various means for improving the above, and found that defects such as scratches in the optical film can be effectively prevented by increasing the elastic modulus and surface hardness of the optical film.

Therefore, an object of the present invention is to provide an optical film having high elastic modulus and surface hardness.

In order to solve the above-mentioned problems, the inventors of the present invention have focused their attention on the structure of the monomer that constitutes the polyamide-imide-based resin contained in the optical film and have conducted earnest studies. As a result, they have found that an optical film containing a polyamide-imide resin having at least a specific structural unit has both high elastic modulus and surface hardness, and have completed the present invention.

That is, the present invention includes the following preferred embodiments.
[1] Formula (1):

[In the formula (1),
R ¹ and R ² are, independently of each other, 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, an aryloxy group having 6 to 12 carbon atoms, and a carbon number. Represents a carbonyl group having 1 to 12 carbon atoms, an oxycarbonyl group having 1 to 12 carbon atoms, or a halogeno group, wherein hydrogen atoms contained in R ¹ and R ² are, independently of each other, a halogen atom, a hydrogen atom having 1 to 4 carbon atoms. It may be substituted with an alkyl group, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group,
V is a single bond, —O—, a diphenylmethylene group, a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, —SO ₂ —, —S—, —CO Represents ——, —PO—, —PO ₂ —, —N(R ³⁰ )—, or —Si(R ³¹ ) ₂ —, wherein hydrogen atoms contained in the hydrocarbon group, independently of each other, are halogen atoms. R ³⁰ and R ³¹ each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, which may be substituted with a halogen atom.
m represents an integer of 0 to 2, n represents an integer of 1 to 4, p represents an integer of 0 to 4, and q represents an integer of 0 to 4]
And a structural unit represented by the formula (2):

[In Formula (2), X represents a divalent organic group and Y represents a tetravalent organic group]
An optical film containing a polyamide-imide resin having a structural unit represented by.
[2] R ¹ in the formula (1) independently represents an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms or a halogeno group, and hydrogen atoms contained in R ¹ are mutually The optical film according to the above [1], which may be independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group.
[3] V in the formula (1) represents a single bond, —O—, a diphenylmethylene group or a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, Here, the hydrogen atom contained in this hydrocarbon group is mutually independently, The optical film as described in said [1] or [2] which may be substituted by the halogen atom.
[4] The polyamide-imide-based resin has the following formula (4) as a constitutional unit represented by the formula (1):

[In formula (4), R ¹ and V are, independently of each other, as defined for R ¹ and V in formula (1), and R ¹⁹ and R ²⁰ are independently of each other a hydrogen atom or a formula ( Represents the groups described for R ^{2 in} 1)]
The optical film as described in any of [1] to [3] above, which comprises a structural unit represented by:
[5] The optical film as described in [4] above, wherein R ¹ in the formula (4) is a fluoroalkyl group having 1 to 12 carbon atoms.
[6] The optical film as described in any of [1] to [5] above, which has a thickness of 10 to 200 μm.
[7] A flexible display device including the optical film according to any one of [1] to [6].
[8] The flexible display device according to [7], further including a touch sensor.
[9] The flexible display device according to [7] or [8], further including a polarizing plate.
[10] Formula (1):

[In the formula (1),
R ¹ and R ² are, independently of each other, 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, an aryloxy group having 6 to 12 carbon atoms, and a carbon number. It represents a carbonyl group having 1 to 12 carbon atoms, an oxycarbonyl group having 1 to 12 carbon atoms or a halogeno group, wherein the hydrogen atoms contained in R ¹ and R ² are, independently of each other, a halogen atom or a carbon atom having 1 to 12 carbon atoms. 4 may be substituted with an alkyl group, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group,
V is a single bond, —O—, a diphenylmethylene group or a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, —SO ₂ —, —S—, —CO Represents ——, —PO—, —PO ₂ —, —N(R ³⁰ )—, or —Si(R ³¹ ) ₂ —, wherein the hydrogen atoms contained in the hydrocarbon group are halogen atoms independently of each other. R ³⁰ and R ³¹ each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, which may be substituted with a halogen atom.
m represents an integer of 0 to 2, n represents an integer of 1 to 4, p represents an integer of 0 to 4, and q represents an integer of 0 to 4]
And a structural unit represented by the formula (2):

[In Formula (2), X represents a divalent organic group and Y represents a tetravalent organic group]
A polyamide-imide resin having a structural unit represented by:

The optical film of the present invention has high elastic modulus and surface hardness.

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.

The optical film of the present invention has the formula (1):

[In Formula (2), X represents a divalent organic group and Y represents a tetravalent organic group]
A polyamide-imide resin having a structural unit represented by The constitutional unit represented by the formula (1) is a constitutional unit formed by reacting a dicarboxylic acid compound and a diamine compound, and the constitutional unit represented by the formula (2) is a tetracarboxylic acid compound and a diamine compound. And are structural units formed by reaction. The polyamide-imide resin contained in the optical film of the present invention may have one type of structural unit represented by the formula (1), or two or more types of structural unit represented by the formula (1). May have. Similarly, the polyamide-imide resin may have one type of structural unit represented by the formula (2) or two or more types of structural unit represented by the formula (2). May be. The polyamide-imide resin may include a further structural unit which 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.

In the optical film of the present invention containing the polyamide-imide resin having the structural unit (1) and the structural unit (2) as described above, the reason why the elastic modulus and the surface hardness are improved is not clear. When the structural unit (1) and the structural unit (2) are included, the skeleton thereof has appropriate rigidity and side chains have appropriate mobility. As a result, it is considered that, surprisingly, both the elastic modulus and the surface hardness of the optical film containing such a polyamide-imide resin are improved.

The polyamide-imide resin contained in the optical film of the present invention has the structural unit (1) and the structural unit (2). From the viewpoint of easily improving the elastic modulus and surface hardness 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 proportion of is preferably 20 to 99 mol %, more preferably 40 to 98 mol %, further preferably 50 to 95 mol %, and particularly preferably 60 to 93 mol %. When the ratio of the structural unit (1) is at least the above lower limit, it is easy to improve the elastic modulus and surface hardness of the optical film. Moreover, when the ratio of the structural unit (1) is at most the above upper limit, it is easy to secure the solubility in a solvent. 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). It is 5 mol or more, more preferably 1.0 mol or more, particularly preferably 1.5 mol or more, preferably 15 mol or less, more preferably 12 mol or less, and further preferably 10 mol or less. When the content of the constituent unit represented by the formula (1) is at least the above lower limit, the elastic modulus and surface hardness 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 (1) is suppressed, and the processability of the optical film is improved. Easy to make.

R ¹ and R ² in the formula (1) are, independently of each other, (i) an alkyl group having 1 to 12 carbon atoms, (ii) an alkoxy group having 1 to 12 carbon atoms, and (iii) having 6 to 12 carbon atoms. An aryl group, (iv) an aryloxy group having 6 to 12 carbon atoms, (v) a carbonyl group having 1 to 12 carbon atoms, (vi) an oxycarbonyl group having 1 to 12 carbon atoms, or (vii) a halogeno group Here, the hydrogen atoms contained in R ¹ and R ² are independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. May be. The structural unit (1) has at least one type of R ¹ . The structural unit (1) may have one type of R ¹ or two or more types of R ¹ . The structural unit (1) may have one type of R ² , two or more types of R ² , or may not have R ² .

(I) Examples of the alkyl group having 1 to 12 carbon atoms include linear, branched or alicyclic alkyl groups having 1 to 12 carbon atoms. Examples of the linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group and tert-group. 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 alkyl 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 or 2 carbon atoms. At least one hydrogen atom of the alkyl group having 1 to 12 carbon atoms 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 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, the above-mentioned 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 number of carbon atoms in the main chain alkyl group portion is 1 to 12, the total number of carbon atoms in the alkyl group may exceed 12. When the number of carbon atoms in the alkyl group as a whole 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 a cyclohexyloxy group, a heptyloxy group, an octyloxy group, a nonyloxy group and a 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 alkoxy 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 or 2 carbon atoms. 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, and more preferably has 6 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 smaller than that of the aryl group having 6 to 12 carbon atoms. exclude.

(Iv) Examples of the aryloxy group having 6 to 12 carbon atoms include phenoxy group, tolyloxy group, xylyloxy group, naphthyloxy group and biphenyloxy group. The aryloxy group having 6 to 12 carbon atoms preferably has 6 or 10 or 12 carbon atoms, and more preferably has 6 carbon atoms. In the aryloxy 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 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 same as that 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 (i) an alkyl group having 1 to 12 carbons, and examples of R ^b include at least one hydrogen atom of the group described for (i) an alkyl group having 1 to 12 carbons. And 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 independently of each other is 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 - It is a group represented by O—CO—R ^a . Examples of R ^a include the groups described for (i) an alkyl group having 1 to 12 carbons, and examples of R ^b include at least one hydrogen atom of the group described for (i) an alkyl group having 1 to 12 carbons. And a divalent alkylene group having 1 to 12 carbon atoms in which is replaced by a bond. In the above-mentioned oxycarbonyl group having 1 to 12 carbon atoms, at least one hydrogen atom independently of one another is 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.

In a preferred embodiment of the present invention, R ¹ and R ^{2 in} formula (1) are, independently of each other, (i) an alkyl group having 1 to 12 carbon atoms, (ii) an alkoxy group having 1 to 12 carbon atoms, or , (Vii) a halogeno group, wherein the hydrogen atoms of R ¹ and R ² are, 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 , May be substituted with a carboxyl group.

More preferably, R ¹ and R ² in the formula (1) are (i) a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms, and at least one hydrogen atom of the alkyl group. Independently of each other, a group substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group (preferably a halogen atom), or (vii) A halogeno group, more preferably a group in which at least one hydrogen atom of a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms is substituted with a halogen atom (preferably fluorine atom). Represents a fluoroalkyl group), and particularly preferably, all hydrogen atoms of a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms are substituted with halogen atoms (preferably fluorine atoms). Represents a group (preferably a perfluoroalkyl group). The carbon number of these groups is preferably 1 to 6, more preferably 1 to 4, and further preferably 1 or 2.

V in the formula (1) is a single bond, —O—, a diphenylmethylene group or a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, —SO ₂ —, Represents —S—, —CO—, —PO—, —PO ₂ —, —N(R ³⁰ )— or —Si(R ³¹ ) ₂ —, wherein the hydrogen atom contained in the hydrocarbon group is They may be independently substituted with a halogen atom, and R ³⁰ and R ³¹ each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom. As the linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, the description is made of (i) the alkyl group having 1 to 12 carbon atoms of R ¹ in the formula (1). In the group, a divalent alkylene group having 1 to 12 carbon atoms in which at least one hydrogen atom is replaced with a bond is mentioned.

V in the formula (1) is preferably a single bond, a divalent hydrocarbon group having 1 to 12 carbon atoms, or a hydrogen atom contained in the divalent hydrocarbon group having 1 to 12 carbon atoms is a halogen atom. It represents a substituted group, and more preferably represents a group in which a hydrogen atom contained in a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms is substituted with a halogen atom.

When V represents a divalent hydrocarbon group having 1 to 12 carbon atoms, or a hydrogen atom contained in the divalent hydrocarbon group having 1 to 12 carbon atoms is substituted with a halogen atom, the number of carbon atoms is 1 Examples of the divalent hydrocarbon group having 12 to 12 include groups in which at least one hydrogen atom of a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms 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 Examples thereof include nonyl group, n-decyl group, cyclopentyl group and cyclohexyl group. 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.

In one preferable embodiment of the present invention, V in the formula (1) is preferably a single bond or at least one hydrogen atom of a linear, branched or alicyclic alkylene group having 1 to 12 carbon atoms. Is a group (preferably fluoroalkylene group) substituted with a halogen atom (preferably a fluorine atom), more preferably a single bond, or a straight chain, branched or alicyclic group having 1 to 12 carbon atoms. It is a group (preferably a perfluoroalkylene group, more preferably a ditrifluoromethylmethylene group) in which all hydrogen atoms of the alkylene group are substituted with halogen atoms (preferably fluorine atoms).

In the formula (1), m represents an integer of 0 to 2, n represents an integer of 1 to 4, p represents an integer of 0 to 4, and q represents an integer of 0 to 4. M in the formula (1) is preferably 0 or 1, and more preferably 0. N in the formula (1) is preferably 1 or 2, and more preferably 1. P in the formula (1) is preferably an integer of 0 to 2, and more preferably 0 or 1. Q in the formula (1) is preferably an integer of 0 to 2, and more preferably 0 or 1.

In one preferred embodiment of the present invention, V and q in the formula (1), V represents a single bond, and q is 1 or 2 (preferably 1), or V has 1 to 2 carbon atoms. 12 linear, branched or alicyclic alkylene groups (more preferably fluoroalkylene groups, further preferably perfluoroalkylene groups, particularly preferably difluoromethylmethylene groups), and q is 0 or 1 (Preferably 0).

In a preferred embodiment of the present invention, the polyamide-imide-based resin has the following formula (1a) as a structural unit represented by formula (1) from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film.

[In Formula (1a),
R ³ to R ¹⁰ each independently represent a hydrogen atom or a group described for R ¹ in the formula (1), provided that at least one of R ³ to R ¹⁰ is the same as R ¹ in the formula (1). Is the listed group,
R ² , q and V are as defined for R ² , q and V in formula (1) respectively]
Including a structural unit represented by. Hereinafter, the constitutional unit represented by the formula (1a) is also referred to as “constitutional unit (1a)”.

When the polyamide-imide resin contains the structural unit (1a) as the structural unit (1), the polyamide-imide resin contains one structural unit represented by the formula (1a) as the structural unit (1). And may include two or more types of structural units represented by formula (1a), and may correspond to formula (1) in addition to the structural unit represented by formula (1a). It may further include a structural unit which does not correspond to the formula (1a).

The polyamide-imide resin contained in the optical film of the present invention has at least the structural unit (1) and the structural unit (2) as described above, and the resin is usually a plurality of structural units (1) and a plurality of structural units. The structural unit (2) and optionally other structural units. In the present specification, that the polyamide-imide resin contains a constitutional unit represented by the formula (1a) as the constitutional unit (1) means that at least a part of a plurality of constitutional units (1) included in the polyamide-imide resin. It means that the structural unit (1) is a structural unit represented by the formula (1a). The above statements also apply to other similar statements herein.

In a preferred embodiment of the present invention, the polyamide-imide resin contained in the optical film of the present invention contains the constitutional unit represented by the formula (1a) as the constitutional unit (1). When (1) is 100 mol %, the proportion of the structural unit represented by the formula (1a) is preferably 70 to 100 mol %, from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film. It is preferably 80 to 100 mol %, more preferably 90 to 100 mol %, and all the structural units (1) may be structural units represented by the formula (1a). The content of the structural unit (1) and the structural unit (1a) can be measured by using, for example, ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

In a preferred embodiment of the present invention, the polyamide-imide-based resin has the following formula (1aa) as a constitutional unit represented by formula (1a) from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film.

[In the formula (1aa),
R ³ to R ¹⁰ are, independently of each other, as defined for R ³ to R ^{10 in} formula (1a),
R ¹¹ to R ¹⁸ each independently represent a hydrogen atom or a group described for R ² in the formula (1), provided that at least one of R ¹¹ to R ¹⁸ is the same as R ² in the formula (1). It is the stated group]
And/or the formula (1ab):

[In the formula (1ab),
R ³ to R ¹⁰ independently of each other are as defined for R ³ to R ^{10 in} formula (1a), and V is as defined for V in formula (1)].
Including a structural unit represented by. Hereinafter, the constitutional unit represented by the formula (1aa) is also referred to as “constitutional unit (1aa)”, and the constitutional unit represented by the formula (1ab) is also referred to as “constitutional unit (1ab)”.

When the polyamide-imide resin includes the structural unit (1aa) and/or the structural unit (1ab) as the structural unit (1a), the polyamide-imide resin is represented by the formula (1aa) as the structural unit (1a). May include one type of structural unit represented by the formula (1aa), may include two or more types of structural units represented by the formula (1aa), and may include one type of structural unit represented by the formula (1ab). It may contain, or may contain two or more types of structural units represented by the formula (1ab), both one or more types of structural units (1aa) and one or more types of structural units (1ab) May be included. In addition, in this aspect, the polyamide-imide-based resin includes, in addition to the structural unit (1aa) or the structural unit (1ab), a structural unit that corresponds to the formula (1a) but does not correspond to the formula (1aa) or the formula (1ab). It may further include.

In a preferred embodiment of the present invention, the polyamideimide-based resin contained in the optical film of the present invention contains the structural unit represented by the formula (1aa) as the structural unit (1a). When (1a) is 100 mol %, the ratio of the structural unit represented by the formula (1aa) is preferably 70 to 100 from the viewpoint of easily improving the elastic modulus, surface hardness and flex resistance of the optical film. It is mol%, more preferably 80 to 100 mol%, further preferably 90 to 100 mol%, and all the structural units (1a) may be structural units represented by the formula (1aa). The content of the structural unit (1a) and the structural unit (1aa) can be measured by using, for example, ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

The polyamide-imide resin contained in the optical film of the present invention may contain a structural unit represented by the formula (1ab) as the structural unit (1a). In this aspect, when the constituent unit (1a) contained in the polyamide-imide resin is 100 mol %, the ratio of the constituent unit represented by the formula (1ab) is from the viewpoint of flex resistance and solubility in a solvent. Therefore, it is preferably 0 to 100 mol %, more preferably 0 to 50 mol %, and further preferably 0 to 30 mol %. When the proportion of the structural unit represented by the formula (1ab) is at most the above upper limit, the elastic modulus and bending resistance of the optical film can be more easily improved. The content of the structural unit (1a) and the structural unit (1ab) can be measured by using, for example, ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

In one embodiment of the present invention, the polyamideimide resin included in the optical film includes both a structural unit represented by the formula (1aa) and a structural unit represented by the formula (1ab) as the structural unit (1a). You can leave. In this aspect, when the constituent unit (1a) contained in the polyamide-imide resin is 100 mol %, the total ratio of the constituent unit (1aa) and the constituent unit (1ab) is the elastic modulus and surface hardness of the optical film. From the viewpoint of easily improving the ratio, it is preferably 70 to 100 mol %, more preferably 80 to 100 mol %, further preferably 90 to 100 mol %, and all the structural units (1a) are structural units (1aa) and It may be the structural unit (1ab). In this case, the content of the structural unit (1aa) is preferably 1 mol or more, more preferably 4 mol or more, further preferably 6 mol or more, and particularly preferably 8 mol or more, relative to 1 mol of the structural unit (1ab). Is. When the content of the structural unit represented by the formula (1aa) is at least the above lower limit, the bending resistance, elastic modulus and surface hardness of the optical film can be easily improved.

R ³ to R ¹⁰ in formula (1a), formula (1aa) and formula (1ab) each independently represent a hydrogen atom or a group described for R ¹ in formula (1), provided that R ³ to At least one of R ¹⁰ is the group described for R ¹ in formula (1), preferably at least two of R ³ to R ¹⁰ are the groups described for R ¹ in formula (1). The preferred embodiments for the groups mentioned for R ¹ in formula (1) likewise apply to R ³ to R ¹⁰ in formula (1a), formula (1aa) and formula (1ab). From the viewpoint of easily improving the elastic modulus and surface hardness of the optical film, at least R ⁵ and R ⁷ in the formula (1a) are preferably the groups described for R ¹ in the formula (1), and more preferably the formula (1). R ⁵ and R ^{7 in} 1a) are the groups described for R ¹ in the formula (1), and R ³ , R ⁴ and R ⁶ , and R ⁸ to R ¹⁰ are hydrogen atoms.

The groups described for R ¹ in formula (1), which can be represented by R ³ to R ^{10 in} formula (1a), formula (1aa) and formula (1ab), include (i) alkyl having 1 to 12 carbons. Group, (ii) an alkoxy group having 1 to 12 carbon atoms, or (vii) a halogeno group, wherein the hydrogen atoms of R ¹ and R ² are, independently of each other, a halogen atom or a hydrogen atom having 1 to 4 carbon atoms. It may be substituted with an alkyl group, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. The group described for R ¹ in formula (1) is more preferably (i) an alkyl group having 1 to 12 carbon atoms, and at least one hydrogen atom of the alkyl group is independently a halogen atom or a carbon number. Examples thereof include an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, a group substituted with a carboxyl group (preferably a halogen atom), or (vii) a halogeno group, and more preferably a carbon number. Examples thereof include a group (preferably a fluoroalkyl group having 1 to 12 carbon atoms) in which at least one hydrogen atom of an alkyl group having 1 to 12 is substituted with a halogen atom (preferably fluorine atom), and particularly preferably 1 to 12 carbon atoms. A group (preferably a perfluoroalkyl group having 1 to 12 carbon atoms) in which all hydrogen atoms of 12 straight, branched or alicyclic alkyl groups are substituted with halogen atoms (preferably fluorine atoms) Can be mentioned.

In a preferred embodiment of the present invention, the polyamide-imide-based resin has the following formula (1b) as a structural unit represented by formula (1) from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film.

[In the formula (1b), R ¹ , R ² , q and V are as defined for R ¹ , R ² , q and V in the formula (1), respectively]
Including a structural unit represented by. Hereinafter, the constitutional unit represented by the formula (1b) is also referred to as “constitutional unit (1b)”. In the formula (1b), R ⁵ and R ⁷ in the formula (1a) are the groups described for R ¹ in the formula (1), and R ³ , R ⁴ , R ⁶ and R ⁸ to R ⁸ ¹⁰ corresponds to a structural unit in which a hydrogen atom is used.

When the polyamide-imide resin includes the structural unit (1b) as the structural unit (1), the polyamide-imide resin includes one type of structural unit represented by the formula (1b) as the structural unit (1). And may include two or more types of constitutional units represented by formula (1b), and in addition to the constitutional unit represented by formula (1b), It may further include a structural unit which does not correspond to the formula (1b).

In a preferred embodiment of the present invention, the polyamide-imide resin contained in the optical film of the present invention contains the constitutional unit represented by the formula (1b) as the constitutional unit (1). When (1) is 100 mol %, the ratio of the structural unit represented by the formula (1b) is preferably 70 to 100 mol %, more preferably from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film. It is preferably 80 to 100 mol %, more preferably 90 to 100 mol %, and all the structural units (1) may be structural units represented by the formula (1b). The contents of the structural unit (1) and the structural unit (1b) can be measured, for example, by ¹ H-NMR, or can be calculated from the charging ratio of the raw materials.

In a preferred embodiment of the present invention, the polyamide-imide-based resin has the following formula (1ba) as a structural unit represented by formula (1b) from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film.

[In the formula (1ba),
R ¹ is, independently of one another, as defined for R ¹ in formula (1),
R ¹¹ to R ¹⁸ each independently represent a hydrogen atom or a group described for R ² in the formula (1), provided that at least one of R ¹¹ to R ¹⁸ is the same as R ² in the formula (1). It is the stated group]
And/or the formula (1bb):

[In formula (1bb),
R ¹ is, independently of one another, as defined for R ¹ in formula (1),
V is as defined for V in formula (1)]
Including a structural unit represented by. Hereinafter, the constitutional unit represented by the formula (1ba) is also referred to as “constitutional unit (1ba)”, and the constitutional unit represented by the formula (1bb) is also referred to as “constitutional unit (1bb)”.

When the polyamide-imide resin includes the structural unit (1ba) and/or the structural unit (1bb) as the structural unit (1b), the polyamide-imide resin is represented by the formula (1ba) as the structural unit (1b). May be contained in one kind of constitutional unit, or may be contained in two or more kinds of constitutional unit represented by the formula (1ba), or as the constitutional unit (1b) is represented by the formula (1bb). 1 type of constitutional unit may be included, two or more types of constitutional units represented by the formula (1bb) may be included, and 1 or more types of constitutional units (1ba) and 1 or more types of Both of the structural units (1bb) may be included. In addition, in this aspect, the polyamide-imide-based resin includes, in addition to the structural unit (1ba) or the structural unit (1bb), a structural unit that corresponds to the formula (1b) but does not correspond to the formula (1ba) or the formula (1bb). It may further include.

In a preferred embodiment of the present invention, the polyamideimide-based resin contained in the optical film of the present invention contains the structural unit represented by the formula (1ba) as the structural unit (1b). When (1b) is 100 mol %, the ratio of the structural unit represented by the formula (1ba) is preferably 70 to 100 from the viewpoint of easily improving the elastic modulus, surface hardness and flex resistance of the optical film. Mol%, more preferably 80 to 100 mol%, still more preferably 90 to 100 mol%, and all of the structural units (1b) may be structural units represented by the formula (1ba). The content of the structural unit (1b) and the structural unit (1ba) can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

The polyamide-imide resin contained in the optical film of the present invention may contain a structural unit represented by the formula (1bb) as the structural unit (1b). In this aspect, when the constitutional unit (1a) contained in the polyamide-imide resin is 100 mol %, the ratio of the constitutional unit represented by the formula (1bb) is from the viewpoint of flex resistance and solubility in a solvent. Therefore, it is preferably 0 to 100 mol %, more preferably 0 to 50 mol %, and further preferably 0 to 30 mol %. When the proportion of the structural unit represented by the formula (1bb) is at most the above upper limit, the elastic modulus and bending resistance of the optical film can be more easily improved. The content of the structural unit (1b) and the structural unit (1bb) can be measured, for example, using ¹ H-NMR, or can be calculated from the charging ratio of the raw materials.

In one embodiment of the present invention, the polyamideimide resin included in the optical film includes both a structural unit represented by the formula (1ba) and a structural unit represented by the formula (1bb) as the structural unit (1b). You can leave. In this aspect, when the constituent unit (1b) contained in the polyamide-imide resin is 100 mol %, the total ratio of the constituent unit (1ba) and the constituent unit (1bb) is preferably 70 to 100 mol %, It is more preferably 80 to 100 mol %, further preferably 90 to 100 mol %, and all of the structural units (1b) may be either structural units (1ba) or structural units (1bb). In this case, the content of the structural unit (1ba) is preferably 1 mol or more, more preferably 4 mol or more, further preferably 6 mol or more, and particularly preferably 8 mol or more, relative to 1 mol of the structural unit (1bb). Is. When the content of the structural unit represented by the formula (1ba) is at least the above lower limit, the elastic modulus and surface hardness of the optical film can be easily improved.

R ¹ in formula (1b), formula (1ba) and formula (1bb) is the group described for R ¹ in formula (1), and the preferred descriptions for R ¹ in formula (1) also apply. .. That is, R ¹ in formula (1b), formula (1ba) and formula (1bb) is preferably (i) an alkyl group having 1 to 12 carbon atoms, (ii) an alkoxy group having 1 to 12 carbon atoms, or (Vii) a halogeno group, wherein the hydrogen atoms of R ¹ and R ² are, 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 It may be substituted with a carboxyl group. As such a group, more preferably, (i) an alkyl group having 1 to 12 carbon atoms, and at least one hydrogen atom of the alkyl group are independently a halogen atom, an alkyl group having 1 to 4 carbon atoms, or a carbon number. 1 to 4 alkoxy group, a hydroxyl group, a group substituted with a carboxyl group (preferably a halogen atom), or (vii) a halogeno group, and more preferably at least one alkyl group having 1 to 12 carbon atoms. And a group (preferably a fluoroalkyl group having 1 to 12 carbon atoms) in which one hydrogen atom is replaced by a halogen atom (preferably a fluorine atom), and particularly preferably a straight chain or branched chain having 1 to 12 carbon atoms. Examples thereof include groups (preferably perfluoroalkyl groups having 1 to 12 carbon atoms) in which all hydrogen atoms of a cyclic or alicyclic alkyl group are substituted with halogen atoms (preferably fluorine atoms).

R ² , V and q in formulas (1a) and (1b) are, independently of each other, as defined for R ² , V and q in formula (1), and the preferred descriptions thereof also apply. For example, V represents a single bond and q is 1 or 2 (preferably 1), or V is a linear, branched or alicyclic alkylene group having 1 to 12 carbon atoms ( A fluoroalkylene group is more preferable, a perfluoroalkylene group is still more preferable, and a difluoromethylmethylene group is particularly preferable, and q is preferably 0 or 1 (preferably 0).

V in formulas (1ab) and (1bb) is as defined for V in formula (1), but is preferably a linear, branched or alicyclic alkylene group having 1 to 12 carbon atoms. Is more preferable, a fluoroalkylene group is more preferable, a perfluoroalkylene group is still more preferable, and a difluoromethylmethylene group is particularly preferable.

R ¹¹ to R ^{18 in} formulas (1aa) and (1ba) each independently represent a hydrogen atom or a group described for R ² in formula (1), provided that at least one of R ¹¹ to R ¹⁸ is present. is a group as described for ^{R 2} in the formula (1), preferably at least two ^R 11 ^{~ R 18} is as described for ^{R 2} in the formula (1) group. The preferred embodiments for the groups mentioned for R ² in formula (1) likewise apply to R ¹¹ to R ¹⁸ in formula (1aa) and formula (1ba). From the viewpoint of easily improving the elastic modulus and the surface hardness of the optical film, at least R ¹² and R ^{18 in} formula (1a) and formula (1ba) are preferably the groups described for R ² in formula (1), More preferably, R ¹² and R ¹⁸ in formula (1aa) and formula (1ba) are the groups described for R ² in formula (1), and R ¹¹ and R ¹³ to R ¹⁷ are hydrogen atoms. ..

The groups described for R ² in the formula (1), which can be represented by R ¹¹ to R ^{18 in the} formulas (1aa) and (1ba), include (i) an alkyl group having 1 to 12 carbon atoms, and (ii) a carbon atom. An alkoxy group having a number of 1 to 12 or (vii) a halogeno group is preferable, wherein the hydrogen atoms of R ¹ and R ² are, independently of each other, a halogen atom, an alkyl group having a carbon number of 1 to 4, and a carbon number of 1 It may be substituted with an alkoxy group of 4 to 4, a hydroxyl group or a carboxyl group. The group described for R ² in the formula (1) is more preferably (i) an alkyl group having 1 to 12 carbon atoms, and at least one hydrogen atom of the alkyl group is independently a halogen atom or a carbon atom. Examples thereof include an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a group substituted with a carboxyl group (preferably a halogen atom), or (vii) a halogeno group, and more preferably carbon. Examples thereof include a group (preferably a fluoroalkyl group having 1 to 12 carbon atoms) in which at least one hydrogen atom of an alkyl group having 1 to 12 atoms is substituted with a halogen atom (preferably a fluorine atom), and particularly preferably a carbon number 1 A group (preferably a perfluoroalkyl group having 1 to 12 carbon atoms) in which all hydrogen atoms of a linear, branched or alicyclic alkyl group of 1 to 12 are substituted with halogen atoms (preferably fluorine atoms), More preferably, it is a perfluoroalkyl group having 1 to 4 carbon atoms.

In a preferred embodiment of the present invention, the polyamide-imide-based resin has a formula (4) as a structural unit represented by the formula (1) from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film.

[In formula (4), R ¹ and V are, independently of each other, as defined for R ¹ and V in formula (1), and R ¹⁹ and R ²⁰ are independently of each other a hydrogen atom or a formula ( Represents the groups described for R ^{2 in} 1)]
Including a structural unit represented by. Hereinafter, the constitutional unit represented by the formula (4) is also referred to as “constitutional unit (4)”.

When the polyamide-imide resin contains the structural unit (4) as the structural unit (1), the polyamide-imide resin contains one structural unit represented by the formula (4) as the structural unit (1). And may include two or more types of constitutional units represented by formula (4), and in addition to the constitutional unit represented by formula (4), It may further include a structural unit which does not correspond to the formula (4).

In a preferred embodiment of the present invention, the polyamide-imide resin contained in the optical film of the present invention contains the constitutional unit represented by the formula (4) as the constitutional unit (1). When (1) is 100 mol %, the proportion of the structural unit represented by the formula (4) is preferably 70 to 100 mol %, from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film. It is preferably 80 to 100 mol %, more preferably 90 to 100 mol %, and all the structural units (1) may be structural units represented by the formula (4). The contents of the structural unit (1) and the structural unit (4) can be measured by using, for example, ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

^{R 1} in the formula (4) are each independently as defined for ^{R 1} in formula (1), ^{R 1} of the preferred described for ^{R 1} in formula (1) has the formula (4) The same applies to. That is, R ¹ in the formula (4) is preferably (i) an alkyl group having 1 to 12 carbon atoms, (ii) an alkoxy group having 1 to 12 carbon atoms, or (vii) a halogeno group, wherein , R ¹ and R ² may be independently substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group. As such a group, more preferably, (i) an alkyl group having 1 to 12 carbon atoms, and at least one hydrogen atom of the alkyl group are independently a halogen atom, an alkyl group having 1 to 4 carbon atoms, or a carbon number. 1 to 4 alkoxy group, a hydroxyl group, a group substituted with a carboxyl group (preferably a halogen atom), or (vii) a halogeno group, and more preferably at least one alkyl group having 1 to 12 carbon atoms. And a group (preferably a fluoroalkyl group having 1 to 12 carbon atoms) in which one hydrogen atom is replaced by a halogen atom (preferably a fluorine atom), and particularly preferably a straight chain or branched chain having 1 to 12 carbon atoms. Examples thereof include groups (preferably perfluoroalkyl groups having 1 to 12 carbon atoms) in which all hydrogen atoms of a cyclic or alicyclic alkyl group are substituted with halogen atoms (preferably fluorine atoms).

V in formula (4) is as defined for V in formula (1), and the preferred description regarding V in formula (1) also applies to V in formula (4).

R ¹⁹ and R ^{20 in} formula (4) each independently represent a hydrogen atom or a group described for R ² in formula (1). When at least one of R ¹⁹ and R ²⁰ in the formula (4) represents the group described for R ^{2 in} the formula (1), preferable description for R ² in the formula (1) is R ¹⁹ and R ^20. The same applies to at least one group of

R ¹⁹ , R ²⁰ and V in formula (4) are, in one preferred embodiment, V represents a single bond, and at least one of R ¹⁹ and R ²⁰ is the group described for R ² in formula (1). Or V is a linear, branched or alicyclic alkylene group having 1 to 12 carbon atoms (more preferably a fluoroalkylene group having 1 to 12 carbon atoms, further preferably 1 to 12 carbon atoms). Of the above, particularly preferably a difluoromethylmethylene group), and R ¹⁹ and R ²⁰ each represent a hydrogen atom.

X in the structural unit (2) represents a divalent organic group, preferably a C4-40 divalent organic group, and more preferably a C4-40 divalent organic group having a cyclic structure. Represents. Examples of the cyclic structure include an alicyclic structure, an aromatic ring structure, and a heterocyclic structure. 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 to 8. In one embodiment of the present invention, the structural unit (2) contained in the polyamide-imide resin may contain one type of organic group as X, or may contain two or more types of organic groups.

In a preferred embodiment of the present invention, the constitutional unit represented by the formula (2) is represented by the formula (1X) as X from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film:

[In the formula (1X), R ² , q and V are as defined for R ² , q and V in the formula (1), respectively, and * represents a bond]
Including a divalent organic group represented by. When the structural unit (2) contains a divalent organic group represented by the formula (1X) as X, the structural unit (2) may be one type or two or more types represented by the formula (1X) as X. The divalent organic group may be included. The structural unit (2) may contain, as X, a divalent organic group which does not correspond to the formula (1X), in addition to the divalent organic group represented by the formula (1X).

In the polyamide-imide-based resin contained in the optical film of the present invention, when the structural unit (2) has a divalent organic group represented by the formula (1X) as X, the structural unit ( When 2) is set to 100 mol %, the ratio of the constitutional unit in which X in the formula (2) is a divalent organic group represented by the formula (1X) improves the elastic modulus and surface hardness of the optical film. From the viewpoint of easy control, it is preferably 70 to 100 mol %, more preferably 80 to 100 mol %, further preferably 90 to 100 mol %, and in all the structural units of the structural unit (2), X is the formula (1X). It may be a divalent organic group represented by. The content of the structural unit (2) and the structural unit (2) in which X is represented by the formula (1X) can be measured, for example, by ¹ H-NMR, or from the charging ratio of raw materials. It can also be calculated.

R ² , q and V in formula (1X) are, independently of one another, as defined for R ² , q and V in formula (1), and relate to R ² , q and V in formula (1). The preferred statements likewise apply to R ² , q and V in formula (1X).

Y in the structural unit represented by the formula (2) represents a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms, and more preferably 4 to 4 carbon atoms having a cyclic structure. 40 tetravalent organic groups are represented. Examples of the cyclic structure include an alicyclic structure, an aromatic ring structure, and a heterocyclic structure. The organic group is an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case, a hydrocarbon group and a fluorine-substituted hydrocarbon group The carbon number is preferably 1-8. In one embodiment of the present invention, the structural unit (2) may have, as Y, one type of tetravalent organic group, or may have two or more types of tetravalent organic groups. Good. As Y, equation (20), equation (21), equation (22), equation (23), equation (24), equation (25), equation (26), equation (27), equation (28) and equation A group represented by (29); a group in which a hydrogen atom in the group represented by formula (20) to formula (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and 4 A chain hydrocarbon group having a valence of 6 or less is exemplified.

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- Alternatively, it represents —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. When there are a plurality of Ars, Ars may be the same or different from each other.

Among the groups represented by the formulas (20) to (29), they are represented by the formula (26), the formula (28) or the formula (29) from the viewpoint of the elastic modulus, surface hardness and bending resistance of the optical film. Group represented by formula (26) is more preferable. W ¹ is a single bond, —O—, independently of each other from the viewpoint of easily increasing the elastic modulus, surface hardness and bending resistance of the optical film, and easily reducing the yellowness (hereinafter also referred to as YI value). _{_{_{-CH 2 -, - CH 2 -CH}}} 2 -, - CH (CH 3) -, - C (CH 3) 2 - or -C _(CF _{3) 2} - is preferably a single bond, -O- , —CH ₂ —, —CH(CH ₃ )—, —C(CH ₃ ) ₂ — or —C(CF ₃ ) ₂ —, more preferably a single bond, —C(CH ₃ ) ₂ — or More preferably, it is —C(CF ₃ ) ₂ —.

In a preferred embodiment of the present invention, the structural unit represented by formula (2) is represented by formula (6):

[In the formula (6), R ²¹ to R ²⁸ 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 ²¹ to R ²⁸ may be independently substituted with a halogen atom,
* Represents a bond]
Including a tetravalent organic group represented by. When the structural unit (2) contains, as Y, a tetravalent organic group represented by the formula (6), it is easy to improve the elastic modulus and the surface hardness of the optical film. Further, in this case, the solubility of the polyamide-imide resin in the solvent is increased, the viscosity of the varnish containing the resin is easily reduced, and the processability of the optical film is easily improved. Furthermore, it is easy to improve the optical characteristics of the optical film.

In the formula (6), R ²¹ , R ²² , R ²³ , R ²⁴ , R ²⁵ , R ²⁶ , R ²⁷ and R ²⁸ are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or a carbon number 1 It represents an alkoxy group having 12 to 12 or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 12 carbon atoms, the alkoxy group having 1 to 12 carbon atoms and the aryl group having 6 to 12 carbon atoms include an alkyl group having 1 to 12 carbon atoms in R ¹ and R ² in the formula (1), Examples of the alkoxy group having 1 to 12 carbon atoms or the aryl group having 6 to 12 carbon atoms include those exemplified above. R ²¹ to R ²⁸ each independently represent, preferably, a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R ²¹ to R ²⁸ The hydrogen atoms contained in R ²⁸ may be 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. R ²¹ to R ²⁸ are, independently of each other, more preferably a hydrogen atom or a methyl group from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film, and easily improving the surface hardness, flex resistance and transparency. , A fluoro group, a chloro group or a trifluoromethyl group, and more preferably R ²¹ , R ²² , R ²³ , R ²⁶ , R ²⁷ and R ²⁸ are hydrogen atoms, and R ²⁴ and R ²⁵ are hydrogen atoms and a methyl group. , A fluoro group, a chloro group or a trifluoromethyl group, and particularly preferably R ²⁴ and R ²⁵ are a methyl group or a trifluoromethyl group.

In a preferred embodiment of the present invention, the structural unit (2) contained in the polyamide-imide resin contained in the optical film of the present invention contains, as Y, a tetravalent organic group represented by the formula (6). From the viewpoint of easily improving the elastic modulus and the surface hardness of Y, Y in the formula (2) is represented by the formula (6) when the total of the structural units (2) contained in the polyamide-imide resin is 100 mol %. The ratio of the structural unit which is a tetravalent organic group is preferably 70 to 100 mol %, more preferably 80 to 100 mol %, further preferably 90 to 100 mol %, and the total amount of the structural unit (2) is In the structural unit, Y may be a tetravalent organic group represented by the formula (6).

In a preferred embodiment of the present invention, the structural unit represented by formula (2) is represented by formula (6a) as Y:

Including a tetravalent organic group represented by. In addition, in the tetravalent organic group represented by the formula (6a), R ²⁴ and R ²⁵ in the formula (6) are triflufluoromethyl groups, and R ²¹ , R ²² , R ²³ , R ²⁶ , and R ^{27 are} And R ²⁸ corresponds to a group in which a hydrogen atom is present. When the structural unit (2) contains, as Y, a tetravalent organic group represented by the formula (6a), it is easy to improve the elastic modulus and surface hardness of the optical film. Further, in this case, the solubility of the polyamide-imide resin in the solvent is increased, the viscosity of the varnish containing the resin is easily reduced, and the processability of the optical film is easily improved. Furthermore, it is easy to improve the optical characteristics of the optical film.

In a preferred embodiment of the present invention, the structural unit (2) contained in the polyamide-imide resin contained in the optical film of the present invention contains, as Y, a tetravalent organic group represented by the formula (6a). From the viewpoint of easily improving the elastic modulus and surface hardness of Y, Y in the formula (2) is represented by the formula (6a) when the total of the structural units (2) contained in the polyamide-imide resin is 100 mol %. The ratio of the structural unit which is a tetravalent organic group is preferably 70 to 100 mol %, more preferably 80 to 100 mol %, further preferably 90 to 100 mol %, and the total amount of the structural unit (2) is In the structural unit, Y may be a tetravalent organic group represented by the formula (6a).

The polyamide-imide resin contained in the optical film of the present invention includes the structural unit (1) and the structural unit (2), as well as the formula (3) not corresponding to the formula (1):

[Z in Formula (3) is a divalent organic group, and X'represents a divalent organic group]
The constitutional unit represented by may be included. When the polyamide-imide resin contains the structural unit represented by the formula (3) in addition to the structural unit (1) and the structural unit (2), it is easy to improve the bending resistance and surface hardness of the optical film.

Z in the formula (3) is, for example, a cyclic structure (preferably an alicyclic structure, an aromatic group) which may be substituted with a hydrocarbon group having 1 to 8 carbon atoms or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms. And a divalent organic group having 4 to 40 carbon atoms including a ring structure or a heterocyclic structure). Examples of the divalent organic group having 4 to 40 carbon atoms including a cyclic structure include the above formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), Among the bonds of the groups represented by the formula (26), the formula (27), the formula (28) and the formula (29), two groups which are not adjacent to each other are replaced by hydrogen atoms, and a group having a thiophene ring structure is Can be mentioned. The constitutional unit represented by the formula (3) is different from the constitutional unit represented by the formula (1) at least in the portion Z, and does not correspond to the constitutional unit represented by the formula (1). Is.

Examples of the divalent organic group containing a cyclic structure and having 4 to 40 carbon atoms as Z in the formula (3) include formula (20′), formula (21′), formula (22′) and formula (23′). ), formula (24′), 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 the polyamide-imide resin, in addition to the constitutional unit represented by the formula (1), and/or Z in the formula (3) is represented by any one of the above formulas (20′) to (29′). In the case where Z has a structural unit represented by the following formula (7), in addition to the structural unit, the following formula (d1):

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

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 are respectively represented by R ¹ and R ² in the formula (1) having 1 carbon atom. Examples of the alkyl group having 12 to 12, the alkoxy group having 1 to 12 carbons, and the aryl group having 6 to 12 carbons include those exemplified above. 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)-*.

The constitutional unit represented by the formula (3) is represented by the formula (7a) as Z:

[In the formula (7a), 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, s and * are the same as A, s and * in the formula (7), t and u are each independently an integer of 0 to 4, provided that s is an integer of 1 to 4]
It is preferable that the divalent organic group represented by the formula (7):

[In the formula (7), R ³¹ to R ³⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms, or an aryl group having 6 to 12 carbon atoms. ,
A is, independently of one _{_{_{another, -O -, - CH 2 -}}} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) 2 -, Represents —SO ₂ —, —S—, —CO— or —N(R ³⁹ )—, wherein R ³⁹ represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom;
s is an integer from 0 to 4,
* Represents a bond]
It is more preferable to contain a divalent organic group represented by

In the formula (7a), 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-, preferably the meta position or the para position. May be. R ^g and R ^{h in} formula (7a) 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 (7a), 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 (7a), a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms and an aryl group having 6 to 12 carbon atoms are respectively represented by the formula (7 Examples of 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 in ).

In the formula (7a), 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.

In the formula (7) and (7a), A _{_{_{is, -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 ³⁹ )—, and from the viewpoint of flex resistance of the optical film, preferably —O— or —S—. Represents, more preferably -O-.
In formula (7), R ³¹ , R ³² , R ³³ , R ³⁴ , R ³⁵ , R ³⁶ , R ^37, and R ³⁸ are each independently a hydrogen atom, an alkyl group having 1 to 12 carbon atoms, or a carbon number 1 It represents an alkoxy group having 12 to 12 or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 12 carbon atoms, the alkoxy group having 1 to 12 carbon atoms and the aryl group having 6 to 12 carbon atoms include an alkyl group having 1 to 12 carbon atoms in R ¹ and R ² in the formula (1), Examples of the alkoxy group having 1 to 12 carbon atoms or the aryl group having 6 to 12 carbon atoms include those exemplified above. From the viewpoint of surface hardness and flexibility of the optical film, R ³¹ to R ³⁸ 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.
R ³⁹ represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the alkyl 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 and 2-methyl- group. Examples thereof include 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-decyl group. It 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. In the polyamide-imide resin, the structural unit represented by the formula (3) may contain, as Z, one kind of divalent organic group represented by the formula (7) or the formula (7a), Two or more types of organic groups represented by formula (7) or formula (7a) may be included.

In the formulas (7) and (7a), s is an integer in the range of 0 to 4, and when s is in this range, the bending resistance and elastic modulus of the optical film tend to be good. In the formulas (7) and (7a), s is preferably an integer in the range of 0 to 3, more preferably 0 to 2, even more preferably 0 or 1, and most preferably 0. When s is within this range, it is easy to improve the bending resistance and elastic modulus of the optical film. Examples of X′ in the formula (7) include the groups described above for X in the structural unit (2).

In the polyamide-imide resin included in the optical film of the present invention, the structural unit represented by the formula (3) is represented by the formula (3′):

It may have a structural unit 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.

The polyamide-imide-based resin contained in the optical film of the present invention includes a structural unit (1) and a structural unit (2) as well as a structural unit represented by the formula (3) (hereinafter, “structural unit (3)”). Also referred to as “)”, the total of the structural unit (1), the structural unit (2) and the structural unit (3) contained in the polyamide-imide resin is 100, from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film. When it is defined as mol %, the total ratio of the structural unit (1) and the structural unit (2) is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably Is 85 mol% or more, particularly preferably 90 mol% or more. The upper limit of the ratio of the total of the structural unit (1) and the structural unit (2) may be less than 100 mol %. The content of the structural unit (1), the structural unit (2) or the structural unit (3) can be measured using, for example, ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

The polyamide-imide-based resin contained in the optical film of the present invention includes the structural unit (1) and the structural unit (2) as well as the structural unit represented by the formula (3) (hereinafter, “structural unit (3)”). Also referred to as “)”, from the viewpoint of easily improving the elastic modulus and surface hardness of the optical film, when the total of the structural unit (1) and the structural unit (3) contained in the polyamide-imide resin is 100 mol %. The proportion of the structural unit (1) is preferably 60 mol% or more, more preferably 70 mol% or more, still more preferably 80 mol% or more. The upper limit of the ratio of the structural unit (1) may be less than 100 mol%. The content of the structural unit (1), the structural unit (2) or the structural unit (3) can be measured using, for example, ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

The polyamide-imide resin contains a constitutional unit represented by the formula (30) and/or a constitutional unit represented by the formula (31) in addition to the constitutional units represented by the formulas (1) and (2). You can leave.

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 (2). 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 (2) is replaced with 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 each independently a divalent organic group, preferably a hydrocarbon group in which a hydrogen atom in the organic group is substituted or a fluorine-substituted hydrocarbon group. Is an organic group which may be substituted with. Examples of X ¹ and X ² include the groups described as X in the formula (2).

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 (3). , And/or a structural unit represented by the formula (31). From the viewpoint of easily improving the elastic modulus, optical characteristics, surface hardness and bending resistance of the optical film, in the polyamideimide resin, the constitutional unit represented by the formula (1) and the formula (2) is represented by the formula (1). And based on all the structural units represented by the formula (2), and optionally the formula (3), the formula (30) and the 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 optionally the formulas (3), (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 characteristics, elastic modulus and surface hardness of the optical film can be easily improved.

The weight average molecular weight (Mw) of the polyamide-imide resin is preferably 200,000 or more, more preferably 250,000 or more in terms of standard polystyrene, from the viewpoint of easily increasing the elastic modulus, surface hardness and flex resistance of the optical film. , More preferably 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 polyamideimide 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 by, for example, GPC measurement and standard polystyrene conversion, 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 4.5 GPa or more, more preferably 4.8 GPa or more, further preferably 5.0 GPa or more, and usually 100 GPa, from the viewpoint of easily preventing scratches and the like of the optical film. It is as follows. The elastic modulus can be measured by using a tensile tester (distance between chucks: 50 mm, pulling speed: 10 mm/min), and can be measured, for example, by the method described in 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, still more preferably 88% or more, even more preferably It is 89% or more, particularly preferably 90% or more, and particularly preferably 91% or more. 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 required to obtain 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 into 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 upper limit of the total light transmittance is usually 100% or less. Conventionally, in order to increase the elastic modulus of an optical film, for example, the optical film may be heated at a high temperature of more than 200° C. during production, but in this case, the light transmittance of the optical film is lowered and It is easy to get worse. Since the optical film of the present invention has a high elastic modulus without being heated at a high temperature exceeding 200° C., it is possible to suppress a decrease in total light transmittance. The total light transmittance can be measured by using a haze computer in accordance with 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, particularly preferably 0.2% 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 enhanced 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, and further preferably 2.5 or less. When the YI value of the optical film is less than or equal to the above upper limit, the transparency is good, and when used for the front plate of the display device, it is possible to contribute to high visibility. The YI value is usually -5 or more, preferably -2 or more. For the YI value, the transmittance for light of 300 to 800 nm is measured using an ultraviolet-visible near-infrared spectrophotometer, tristimulus values (X, Y, Z) are calculated, and YI=100×(1.2769X− It can be calculated based on the formula 1.0592Z)/Y. In addition, in this specification, that the optical film is excellent in optical characteristics 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, even more preferably It is 80 μm or less, particularly preferably 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 using a micrometer, for example, the method described in the examples.

The number of times of bending in the bending resistance test (bending radius R=1 mm) in the optical film of the present invention is preferably 90,000 times or more, more preferably 120,000 times or more, further preferably 150,000 times or more, and particularly It is preferably 180,000 times or more. When the number of times of bending is not less than the above lower limit, it has sufficient bending resistance as a front plate material for flexible display devices and the like. In addition, the number of times of bending in the bending resistance test is performed by repeatedly bending the optical film using a bending tester under the condition that the bending radius (curvature radius) R is 1 mm, and making a reciprocating motion until the film is cracked. The number of times of bending (one reciprocation is once) is shown.

The pencil hardness of at least one surface of the optical film of the present invention is preferably H or higher, more preferably 2H 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 the 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 characteristics of the optical film, it is preferable that the imidization ratio is not less than the above lower limit. The imidization ratio indicates the ratio of the molar amount of imide bonds in the polyamideimide-based resin to the double value of the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyamideimide-based 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. The imidization ratio can be determined by IR method, NMR method, or the like.

The present invention provides, in addition to the optical film containing the above polyamideimide resin, the above polyamideimide resin suitable for producing the optical film. Such a polyamide-imide resin has, for example, the formula (1):

[In the formula (1),
R ¹ and R ² are, independently of each other, 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, an aryloxy group having 6 to 12 carbon atoms, and a carbon number. It represents a carboxyl group of 1 to 12, an oxycarbonyl group of 1 to 12 carbon atoms or a halogeno group, wherein the hydrogen atoms contained in R ¹ and R ² may be independently substituted with a halogen atom. ,
V is a single bond, —O—, a diphenylmethylene group or a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, —SO ₂ —, —S—, —CO Represents ——, —PO—, —PO ₂ —, —N(R ³⁰ )—, or —Si(R ³¹ ) ₂ —, wherein the hydrogen atoms contained in the hydrocarbon group are halogen atoms independently of each other. R ³⁰ and R ³¹ each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, which may be substituted with a halogen atom.
m represents an integer of 0 to 2, n represents an integer of 1 to 4, p represents an integer of 0 to 4, and q represents an integer of 0 to 4]
And a structural unit represented by the formula (2):

[In Formula (2), X represents a divalent organic group and Y represents a tetravalent organic group]
A polyamide-imide resin having a structural unit represented by The above description regarding the polyamide-imide resin contained in the optical film of the present invention similarly applies to the examples of the types of respective symbols in the polyamide-imide resin and the proportions of the constituent units, and preferred embodiments.

The content of halogen atoms in the polyamideimide resin is preferably 1 to 60% by mass, more preferably 5 to 55% by mass, and further preferably 10 to 50% 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 reacting a dicarboxylic acid compound and a diamine compound, and the constitutional unit represented by the above formula (2) is It is a structural unit formed by the reaction of a tetracarboxylic acid compound and a diamine compound. Therefore, a polyamide-imide resin may be produced using a dicarboxylic acid compound, a tetracarboxylic acid compound, and a diamine compound, which are constituent units represented by the above formulas (1) and (2). From this viewpoint, the dicarboxylic acid compound preferably contains at least the compound represented by the formula (8).

[In formula (8), R ¹ , m, n, and p are respectively as defined for R ¹ , m, n, and p in formula (1), and R ^c and R ^d are independent of each other. , A hydroxyl group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group or a chlorine atom. ]

In one preferred embodiment of the present invention, the dicarboxylic acid compound is a compound represented by formula (8), wherein R ^c and R ^d are chlorine atoms. Moreover, you may use a diisocyanate compound instead of a diamine compound.

As the dicarboxylic acid compound used for producing the resin, an aromatic dicarboxylic acid having the structure represented by the formula (8) or an acid chloride compound thereof, for example, a biphenyldicarboxylic acid or an acid chloride compound thereof is preferably used. In addition to the aromatic dicarboxylic acid having the structure represented by formula (8) or the acid chloride compound thereof, other dicarboxylic acid compounds may be used. Examples of the other dicarboxylic acid compound include other aromatic dicarboxylic acids, aliphatic dicarboxylic acids and their related acid chloride compounds, acid anhydrides, and the like, and two or more kinds may be used in combination. As a specific example of the aromatic dicarboxylic acid having the structure represented by the formula (8), 2,2'-bis(trifluoromethyl)-4,4'-biphenyldicarboxylic acid chloride is preferable.

As the dicarboxylic acid compound, the compound represented by the formula (8) and another dicarboxylic acid compound may be used. Other dicarboxylic acid compounds include those represented by the formula (7′):

[In the formula (7′), R ³¹ to R ³⁸ 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 aryl group having 6 to 12 carbon atoms. The hydrogen atoms contained in R ³¹ to R ³⁸ may be independently substituted with a halogen atom,
A _{_{_{is, -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 ³⁹ )-,
R ³⁹ represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom,
s is an integer from 0 to 4,
R ^c and ^{R d} are as defined for ^{R c} and ^{R d} in the formula (8)]
The dicarboxylic acid compound represented by

In one embodiment of the present invention, the other dicarboxylic acid compound may be a compound represented by the formula (7′) in which s is 1 to 4 and A is an oxygen atom.

Examples of the diamine compound used for resin production include aliphatic diamines, aromatic diamines, and mixtures thereof. 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 another substituent in a 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. The "aliphatic diamine" represents a diamine in which an amino group is directly bonded to the aliphatic group, and may have an aromatic ring or other substituent in a part of its structure.

Examples of aliphatic diamines include acyclic aliphatic diamines such as hexamethylenediamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine and 4,4′. -Cyclic aliphatic diamines such as diaminodicyclohexylmethane and the like. These may be used alone or in combination of two or more.

Examples of aromatic diamines include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, and 2,6-diaminonaphthalene. , 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 mentioned), 4,4'-bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene And aromatic diamines having two or more aromatic rings, such as 9,9-bis(4-amino-3-chlorophenyl)fluorene and 9,9-bis(4-amino-3-fluorophenyl)fluorene. These may be used alone or in combination of 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 preferred 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.

Among the above diamine compounds, at least one 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 preferable to use -(hexafluoropropylidene)dianiline (6FDAM).

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

Specific examples of the aromatic tetracarboxylic dianhydride include a non-condensed polycyclic aromatic tetracarboxylic dianhydride, a monocyclic aromatic tetracarboxylic dianhydride and a condensed polycyclic aromatic tetraanhydride. Examples include carboxylic acid dianhydride. Examples of the non-condensed polycyclic aromatic tetracarboxylic acid dianhydride include 4,4′-oxydiphthalic acid dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride and 2,2 ',3,3'-Benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride ,3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-di) Carboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4′-(hexafluoroisopropylidene)diphthalic acid dianhydride (described as 6FDA , 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,3) 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. In addition, examples of the monocyclic aromatic tetracarboxylic dianhydride include 1,2,4,5-benzenetetracarboxylic dianhydride, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples thereof include 2,3,6,7-naphthalenetetracarboxylic dianhydride.

Among these, 4,4′-oxydiphthalic acid dianhydride, 3,3′,4,4′-benzophenone tetracarboxylic acid dianhydride and 2,2′,3,3′-benzophenone tetracarboxylic acid dianhydride are preferable. Anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl Sulfone tetracarboxylic acid 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, 4,4'-(hexafluoroisopropylidene)diphthalic acid dianhydride (6FDA), 1,2-bis(2,3-dicarboxyphenyl) Ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3 ,4-Dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p- Examples thereof include phenylenedioxy)diphthalic acid dianhydride and 4,4′-(m-phenylenedioxy)diphthalic acid dianhydride, and more preferably 4,4′-oxydiphthalic acid dianhydride, 3,3′, 4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA) , Bis(3,4-dicarboxyphenyl)methane dianhydride and 4,4′-(p-phenylenedioxy)diphthalic dianhydride. These may be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic acid dianhydride include cyclic or acyclic aliphatic tetracarboxylic acid dianhydride. The cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride. Compounds, cycloalkanetetracarboxylic dianhydrides such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo[2.2 .2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride and positional isomers thereof. To be These may be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,3,4-pentanetetracarboxylic dianhydride. These may be used alone or in combination of two or more. Moreover, you may use combining cycloaliphatic tetracarboxylic dianhydride and acyclic aliphatic tetracarboxylic dianhydride.

Among the above tetracarboxylic acid dianhydrides, 4,4′-oxydiphthalic acid dianhydride, 3,4′-oxydiphthalic acid dianhydride, in view of high surface hardness, high transparency, high flexibility, high bending resistance, and low colorability of the optical film. 3',4,4'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride ,3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene ) Diphthalic dianhydride, and mixtures thereof are preferable, and 3,3′,4,4′-biphenyltetracarboxylic dianhydride and 4,4′-(hexafluoroisopropylidene)diphthalic dianhydride, and These mixtures are more preferable, and 4,4'-(hexafluoroisopropylidene)diphthalic acid dianhydride (6FDA) is further preferable.

Incidentally, the polyamide-imide resin, in the range that does not impair the various physical properties of the optical laminate, in addition to the tetracarboxylic acid compound, tetracarboxylic acid and tricarboxylic acid and those anhydrides and derivatives thereof are further reacted. It may be.

Examples of the tetracarboxylic acid include water adducts of the above-mentioned tetracarboxylic acid compound anhydrides.

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 are 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 a compound linked by a 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 desired ratio of each constitutional unit of the polyamideimide resin.

The method for producing a 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 a viewpoint that is easy, 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 polyamideimide resin by a production method of dividing and adding a dicarboxylic acid compound. A step (I) of reacting a tetracarboxylic acid compound with an intermediate (A) to produce an intermediate (A), and the intermediate (A) and a dicarboxylic acid compound (preferably a compound represented by the formula (8)) It is more preferable to produce the polyamide-imide resin by a method including a step (II) of reacting, and in the step (II), the dicarboxylic acid compound is dividedly added. When the method of dividing and adding the dicarboxylic acid compound is used, the reason is not clear, but it is considered that an optimal resin can be obtained for improving the elastic modulus and surface hardness of the optical film. Further, it is easy to adjust the weight average molecular weight of the polyamide-imide resin within the above range.

Therefore, the polyamide-imide-based resin contained in the optical film of the present invention, and the polyamide-imide-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 and the tetracarboxylic acid compound are reacted to produce an intermediate (A), and the intermediate (A). A production method comprising a step (II) of reacting a dicarboxylic acid compound with a dicarboxylic acid compound (preferably a compound represented by the formula (8)), wherein the dicarboxylic acid compound is dividedly added in the step (II). More preferably, it is a resin produced by.

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 inert gas atmosphere (for example, nitrogen, argon, etc.) with stirring, and may be carried out under normal pressure, under pressure or under reduced pressure. In a preferred embodiment, it is carried out under normal pressure and/or an inert gas atmosphere with stirring.

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

In step (II), the number of divisions when the dicarboxylic acid compound is dividedly added can be appropriately selected depending on the reaction scale, the kind of the raw material, etc., and is preferably 2 to 20 times, more preferably 3 to 10 times, and further preferably 3 times. ~6 times.

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, each dicarboxylic acid compound may be added separately or collectively or in a divided manner, each dicarboxylic acid compound may be added in a divided manner together, or a combination thereof may be used.

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

The reaction temperature in step (II) is not particularly limited, but is, for example, 5 to 200° C., preferably 5 to 100° C., more preferably 5 to 50° C., further preferably 5° C. to room temperature (about 25° C.). Good. The reaction may be carried out in air or in an inert gas atmosphere (for example, nitrogen, argon, etc.) with 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, or the like.

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

In the production of 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. Although the reaction time is not particularly limited, it is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be performed under 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. In addition, the reaction is preferably carried out in a solvent inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, and 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 Aromatic hydrocarbon solvent such as acetonitrile; Nitrile solvent such as acetonitrile; Ether solvent such as tetrahydrofuran and dimethoxyethane; Chlorine-containing solvent such as chloroform and chlorobenzene; Amide such as N,N-dimethylacetamide, N,N-dimethylformamide Examples thereof 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 thereof (mixed solvent). Among these, amide solvents can be preferably used from the viewpoint of solubility.

The method for producing a polyamide-imide resin may further include a step (III) of imidizing a polyamide-imide 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 (ring 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 in 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 and column chromatography, or a separation means combining these. 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 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. Examples of 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, especially more preferably 50 nm or less, and even more 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. Moreover, 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 kinds. 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% by mass, and more preferably the mass of the polyamideimide resin contained in the optical film. It is 1 to 8% by mass, more preferably 2 to 7% 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 during manufacturing of 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. Other additives include, for example, 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 other additives are contained, their content is preferably 0.001 to 20% by mass, more preferably 0.01 to 15% by mass, and still more preferably 0.1 to 10% by mass based on the mass of the optical film. It may be 10% by weight.

(Method of manufacturing optical film)
The method for producing the optical film of the present invention is not particularly limited, but for example, the following steps:
(A) a step of preparing a polyamide-imide resin composition (hereinafter, also referred to as "varnish") containing at least the polyamide-imide resin and a solvent (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 by stirring to prepare a varnish. When silica particles are used as a filler, a dispersion of a silica sol containing silica particles may be added to the resin with a solvent capable of dissolving the resin, for example, a silica sol obtained by substituting with a solvent used for preparing a varnish described below. ..

The solvent used for preparing the varnish is not particularly limited as long as it can dissolve the resin. Examples of the solvent include amide solvents such as N,N-dimethylacetamide and N,N-dimethylformamide; lactone solvents such as γ-butyrolactone (GBL) and γ-valerolactone; dimethyl sulfone, dimethyl sulfoxide, sulfolane and the like. And a carbonate-based solvent such as ethylene carbonate and propylene carbonate; and a combination thereof (mixed solvent). Among these, amide solvents or lactone solvents are preferable. These solvents can 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 process, a varnish is coated on the support material by a known coating method to form a coating film. 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, A spray method, a spout molding method and the like can be mentioned.

In the film forming step, the optical film can be formed by drying the coating film and peeling it from the support material. You may provide the process of drying an optical film further after 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. Is mentioned. Among them, a PET film, a COP film and the like are preferable from the viewpoint of excellent smoothness and heat resistance, and further, a PET film is more preferable from the viewpoint of adhesion to an optical film and cost.

The use of the optical film of the present invention is not particularly limited and may be used for various purposes. The optical film of the present invention may be a single layer as described above, or may be a laminate, 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 the layers laminated on one side or both sides of the optical film are collectively 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 may 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, and 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 the main material 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 heat 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, such as 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 radical polymerizable compound is a compound having a radical 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 radically 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 the 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 area to be filled, 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, a polyglycidyl ether of a polyhydric alcohol having an alicyclic ring or a 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 bisphenol A, bisphenol F, bisphenols such as 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 one 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 produces a radical by decomposition of a molecule and a Type 2 type radical polymerization initiator that produces a radical by a hydrogen abstraction type reaction coexisting with a tertiary amine Yes, they are used alone or in combination.
Any cationic polymerization initiator may be used as long as it can release a substance that initiates cationic polymerization by irradiation with active energy rays and/or 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 preferably be contained in an amount of 0.1 to 10% by mass based on 100% by mass of the entire hard coat composition. When the content of the polymerization initiator is in the above range, curing can be sufficiently advanced, and the mechanical properties and adhesion of the finally obtained coating film can be set 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 additive may further include inorganic particles, a leveling agent, a stabilizer, a surfactant, an antistatic agent, a lubricant, an antifouling agent, 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 adhesive layer may be a layer called 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 that adheres to an adherend with a light pressure" (JIS K 6800), or "a protective film (microcapsule) for specific components. ), and a capsule type adhesive which is an adhesive (JIS K6800) capable of maintaining stability until the coating is broken by an appropriate means (pressure, heat, etc.).

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, for example, a layer having a refractive index different from that of the optical film and 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 terephthalate resin films and acrylic resin films. 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 display devices include TVs, smartphones, mobile phones, car navigations, tablet PCs, portable game consoles, 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, and 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, and a touch sensor, and the order of laminating them is arbitrary, but the window film, the polarizing plate, the touch sensor or the window film, and the touch from the viewing side. It is preferable that the 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 may include a polarizing plate, and preferably includes a circular polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only the right circularly polarized light component or the 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 and 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 influence 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 are theoretically required to be 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 as long as 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 necessary in practice, so the circularly polarizing plate in the present invention also includes an elliptically polarizing plate. It is also preferable to further laminate a λ/4 retardation film on the visible side of the linearly polarizing plate to make the emitted light circularly polarized light to 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 thereto. The linear polarizing plate may be configured to include 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, preferably 0.5 to 100 μm. When the thickness is in the above range, the flexibility tends to be difficult to decrease.
The linear polarizer may be a film-type polarizer manufactured 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 further include 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 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 is only required 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 a 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 of 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 photo-alignment is applied, 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 regulating 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 any 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 orthogonal to the traveling direction of incident light (in-plane direction of the film). The λ/4 retardation plate may be a stretchable retardation plate produced by stretching a polymer film such as a cellulose-based film, an olefin-based film, or a polycarbonate-based film. If necessary, retarder, plasticizer, ultraviolet absorber, infrared absorber, colorant such as pigment or dye, fluorescent brightening 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, 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 compound in the liquid crystal composition, including the liquid crystal compound, 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 the 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 type retardation plate. The thickness of the liquid crystal polarizing layer may be usually 0.5 to 10 μm, preferably 1 to 5 μm. The liquid crystal 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 using 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 coating retardation plate may be used. preferable.
As another method, there is also known a technique for obtaining a broadband λ/4 retardation plate by combining it 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 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 includes a substrate having flexible characteristics; a sensing pattern formed in an active region of the substrate; formed in an inactive region of the substrate and connected to an external driving circuit through the sensing pattern and a pad unit. 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, the toughness is defined as the area under the curve 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, and these may 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 sensing layer via an insulating layer, and the bridge electrode may be 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 structure of the layer 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 the 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 photocurable organic binder may include, for example, 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 various 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, and a touch sensor, which forms the laminate for a flexible display device, and a film member such as a linear polarizing plate and a λ/4 retardation plate, which constitutes 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 volatilization type adhesive, a water-based solvent volatilization type adhesive, a moisture-curable adhesive, a heat-curable adhesive, Anaerobic curable adhesives, active energy ray curable adhesives, hardener 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 strength 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 a 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, polyvinyl alcohol-based polymer, water-soluble polymer such as starch, water-dispersed polymer such as ethylene-vinyl acetate emulsion, styrene-butadiene emulsion can be used as the main polymer. In addition to water and the base 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 volatile adhesive, the water-based solvent volatile 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 to form 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 irradiates an active energy ray to form an adhesive layer. The active energy ray-curable composition can contain at least one polymer of a radically polymerizable compound and a cationically polymerizable compound similar to 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. As the radically polymerizable compound used in the adhesive layer, a compound having an acryloyl group is preferable. 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 that used in 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 contain a polymerization initiator. Examples of the polymerization initiator include 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. It can be adhered by irradiating it with an energy ray and curing it. The thickness of the adhesive layer when the active energy ray-curable adhesive is used may be 0.01 to 20 μm, preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used to form 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 it. To be done. The adhesive layer may be directly formed, or may be separately formed on a 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 for forming 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 be in the form of a single layer or multiple layers. 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 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 provide 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 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 and a width of 10 mm was prepared, an SS curve was measured under conditions of a chuck distance of 50 mm and a pulling speed of 10 mm/min, and the elastic modulus was calculated from the inclination.

<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, and the presence or absence of scratches was evaluated under the environment of 4000 lux to measure the pencil hardness.

<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: TSKgel α-2500 ((7) 7.8 mm diameter × 300 mm) × 1 column, α-M ((13) 7.8 mm diameter × 300 mm) × 2 column eluent manufactured by Tosoh Corporation : 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 film 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 at a solid content of TFMB of 2.36% by mass. And TFMB were dissolved in DMAc with stirring at room temperature. Next, 4,4′-(hexafluoroisopropylidene)diphthalic acid dianhydride (6FDA) was added to the flask at 30.30 mol% with respect to TFMB, and the mixture was stirred at room temperature for 3 hours. Then, after cooling to 10° C., 4,4′ oxybis(benzoyl chloride) (OBBC) was added to 5.05 mol% with respect to TFMB, 2,2′-bis(trifluoromethyl)-4,4′-biphenyldicarboxylic acid. Acid chloride (6FBPDOC) was added to TFMB so as to be 27.28 mol%, and after stirring for 10 minutes, OBBC was further added at 5.05 mol% and 6FBPDOC to 27.28 mol% to TFMB, and 30 Stir for minutes. Thereafter, the same amount of DMAc as the initially added DMAc was added, and the mixture was stirred for 10 minutes, then, 6FBPDOC was added so as to be 6.06 mol% with respect to TFMB, and stirred for 2 hours. Next, add 70.71 mol% of diisopropylethylamine and 4-picoline to TFMB and 212.12 mol% of acetic anhydride to TFMB, and stir for 30 minutes, and then raise the internal temperature 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 form, the deposited precipitate was taken out, immersed in methanol for 6 hours, and 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 363,000.

[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 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 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 4.20% by mass, and 4,4′-(hexafluoropropylidene)dianiline (6FDAM) was added. 11.11 mol% was added to TFMB, and TFMB and 6FDAM were dissolved in DMAc while stirring at room temperature. Next, 6FDA was added to the flask at a concentration of 5.59 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 TFMB at 10.17 mol% and 6FBPDOC to 40.21 mol% to TFMB, and after stirring for 10 minutes, OBBC was further added to TFMB at 5. 59 mol% and 6FBPDOC were added to 40.21 mol% and 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 6FBDPOC was added so as to be 8.93 mol% with respect to TFMB, and stirred for 2 hours. Next, 100.50 mol% of diisopropylethylamine and 4-picoline to TFMB and 78.17 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 form, the deposited precipitate was taken out, immersed in methanol for 6 hours, and 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 227,000.

[Production of Polyamideimide Film (2)]
DMAc was added to the obtained polyamideimide resin (2) so that the concentration was 10% by mass, to prepare a polyamideimide 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 5.35 wt %, 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 the mixture was stirred for 10 minutes, then TPC was added so as to be 6.19 mol% with respect to TFMB, and stirred for 2 hours. Then, 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 stirred for 30 minutes, and then 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 form, the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 60° C. to obtain a polyamideimide resin (3). The weight average molecular weight of the polyamide-imide resin (4) was 174,000.

[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.

The elastic modulus and surface hardness (pencil hardness) of the polyamide-imide resin films (1) to (3) were measured according to the above method. The results obtained are shown in Table 1.

Claims

Formula (1):

[In the formula (1),
R 1 and R 2 are, independently of each other, 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, an aryloxy group having 6 to 12 carbon atoms, and a carbon number. Represents a carbonyl group having 1 to 12 carbon atoms, an oxycarbonyl group having 1 to 12 carbon atoms, or a halogeno group, wherein hydrogen atoms contained in R 1 and R 2 are, independently of each other, a halogen atom, a hydrogen atom having 1 to 4 carbon atoms. It may be substituted with an alkyl group, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group,
V is a single bond, —O—, a diphenylmethylene group, a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, —SO 2 —, —S—, —CO Represents ——, —PO—, —PO 2 —, —N(R 30 )—, or —Si(R 31 ) 2 —, wherein hydrogen atoms contained in the hydrocarbon group, independently of each other, are halogen atoms. R 30 and R 31 each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, which may be substituted with a halogen atom.
m represents an integer of 0 to 2, n represents an integer of 1 to 4, p represents an integer of 0 to 4, and q represents an integer of 0 to 4]
And a structural unit represented by the formula (2):

[In Formula (2), X represents a divalent organic group and Y represents a tetravalent organic group]
An optical film containing a polyamide-imide resin having a structural unit represented by.
R 1 in formula (1) independently represents an alkyl group having 1 to 12 carbon atoms, an alkoxy group having 1 to 12 carbon atoms or a halogeno group, and hydrogen atoms contained in R 1 independently of each other, The optical film according to claim 1, which may be substituted with a halogen atom, an alkyl group having 1 to 4 carbon atoms, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group, or a carboxyl group.
V in the formula (1) represents a single bond, —O—, a diphenylmethylene group or a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, wherein The optical film according to claim 1, wherein the hydrogen atoms contained in the hydrocarbon group may be independently substituted with a halogen atom.
The polyamide-imide resin has the following formula (4) as a constitutional unit represented by the formula (1):

[In formula (4), R 1 and V are, independently of each other, as defined for R 1 and V in formula (1), and R 19 and R 20 are independently of each other a hydrogen atom or a formula ( Represents the groups described for R 2 in 1)]
The optical film according to any one of claims 1 to 3, which comprises a structural unit represented by:
The optical film according to claim 4, wherein R 1 in the formula (4) is a fluoroalkyl group having 1 to 12 carbon atoms.
The optical film according to any one of claims 1 to 5, which has a thickness of 10 to 200 µm.
A flexible display device comprising the optical film according to any one of claims 1 to 6.
The flexible display device according to claim 7, further comprising a touch sensor.
The flexible display device according to claim 7 or 8, further comprising a polarizing plate.
Formula (1):

[In the formula (1),
R 1 and R 2 are, independently of each other, 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, an aryloxy group having 6 to 12 carbon atoms, and a carbon number. It represents a carbonyl group having 1 to 12 carbon atoms, an oxycarbonyl group having 1 to 12 carbon atoms or a halogeno group, wherein the hydrogen atoms contained in R 1 and R 2 are, independently of each other, a halogen atom or a carbon atom having 1 to 12 carbon atoms. 4 may be substituted with an alkyl group, an alkoxy group having 1 to 4 carbon atoms, a hydroxyl group or a carboxyl group,
V represents a single bond, —O—, a diphenylmethylene group, or a linear, branched or alicyclic divalent hydrocarbon group having 1 to 12 carbon atoms, which is included in the hydrocarbon group. Hydrogen atoms which are independently of each other may be substituted with a halogen atom,
m represents an integer of 0 to 2, n represents an integer of 1 to 4, p represents an integer of 0 to 4, and q represents an integer of 0 to 4]
And a structural unit represented by the formula (2):

[In Formula (2), X represents a divalent organic group and Y represents a tetravalent organic group]
A polyamide-imide resin having a structural unit represented by: