JP2021088626A - Optical film - Google Patents

Abstract

To provide an optical film that is low in haze and yellowness even after stored in a bent state for a long time under a high-temperature and high-humidity environment.SOLUTION: An optical film has a yield point strain of 1.5% or more, and a haze of 1.5% or less, which is represented by Hza after a mandrel test in which it is bent one time at a bending radius of 1 mm at the room temperature and then returned into a planar shape.SELECTED DRAWING: None

Description

The present invention relates to an optical film used as a material for a flexible display device and the like, and the optical film is used for a flexible display device.

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. Glass has been used as the front plate of such a display device, but it is difficult to use it as a front plate material of a flexible display device because the glass is very rigid and easily broken. As one of the alternative materials to glass, an optical film using a polymer such as a polyimide resin and having high heat resistance has been studied (for example, Patent Document 1).

Japanese Patent Publication No. 2014-528490

A flexible display device using such an optical film as a material may be exposed to a high temperature and high humidity environment in a bent state. However, according to the study of the present inventor, it has been found that when the conventional optical film is exposed to such harsh durable conditions, the optical characteristics are deteriorated and the haze and yellowness can be increased.

Therefore, an object of the present invention is to provide an optical film having low haze and yellowness and a flexible display device including the optical film even after being stored in a bent state in a high temperature and high humidity environment for a long time.

As a result of diligent studies to solve the above problems, the present inventor adjusts the yield point distortion of the optical film to 1.50% or more, and bends the optical film once at a bending radius of 1 mm to return it to a flat state at room temperature. We have found that the above problems can be solved by adjusting the haze after the test to 1.5% or less, and have completed the present invention. That is, the present invention includes the following preferred embodiments.

［式（１）中、Ｘは２価の有機基を表し、Ｙは４価の有機基を表し、＊は結合手を表す］
で表される構成単位、及び式（２）：

［式（２）中、Ｘ及びＺは、互いに独立に、２価の有機基を表し、＊は結合手を表す］
で表される構成単位
を含む、［２］に記載の光学フィルム。
［４］前記マンドレル試験前のＨｚ_ｂで表されるヘーズは１．０％以下である、［１］〜［３］のいずれかに記載の光学フィルム。
［５］フィラーの含有量は、光学フィルムの質量に対して、３０質量％以下である、［１］〜［４］のいずれかに記載の光学フィルム。
［６］厚さは、２０〜１００μｍである、［１］〜［５］のいずれかに記載の光学フィルム。
［７］弾性率は、１．０ＧＰａ以上である、［１］〜［６］のいずれかに記載の光学フィルム。
［８］［１］〜［７］のいずれかに記載の光学フィルムを備える、フレキシブル表示装置。
［９］さらに、タッチセンサを備える、［８］に記載のフレキシブル表示装置。
［１０］さらに、偏光板を備える、［８］又は［９］に記載のフレキシブル表示装置。 _{[1] The yield point strain is 1.50% or more, and the haze represented by Hz a} after the mandrel test of bending once at a bending radius of 1 mm to return to a flat surface at room temperature is 1.5% or less. , Optical film.
[2] The optical film according to [1], which contains a polyamide-imide resin.
[3] The polyamide-imide resin has the formula (1):

[In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, and * represents a bond]
The structural unit represented by and the formula (2):

[In formula (2), X and Z represent divalent organic groups independently of each other, and * represents a bond]
The optical film according to [2], which comprises a structural unit represented by.
[4] The optical film according to any one of [1] to [3], _{wherein the haze represented by Hz b} before the mandrel test is 1.0% or less.
[5] The optical film according to any one of [1] to [4], wherein the content of the filler is 30% by mass or less with respect to the mass of the optical film.
[6] The optical film according to any one of [1] to [5], which has a thickness of 20 to 100 μm.
[7] The optical film according to any one of [1] to [6], which has an elastic modulus of 1.0 GPa or more.
[8] A flexible display device including the optical film according to any one of [1] to [7].
[9] The flexible display device according to [8], further comprising a touch sensor.
[10] The flexible display device according to [8] or [9], further comprising a polarizing plate.

The optical film of the present invention has low haze and yellowness even after being stored in a bent state in a high temperature and high humidity environment for a long time. Therefore, it can be suitably used as a material for flexible display devices.

[Optical film]
The optical film of the present invention has a yield point strain of 1.50% or more, and has a haze represented by _{Hz a} of 1.5 after a mandrel test in which the film is bent once at a bending radius of 1 mm and returned to a flat state at room temperature. % Or less. According to the present inventor, when the yield point distortion of the optical film is 1.50% or more and Hz _a is 1.5% or less, even after the optical film is stored for a long time in a high temperature and high humidity environment in a bent state. , It was found that the haze and yellowness of the optical film (hereinafter, may be referred to as YI value) are low. This is because when the optical film is bent under high temperature and high humidity, the optical film is easily deformed, and the color is easily changed by absorbing moisture and deforming, but the haze after the mandrel test is low. That is, it is presumed that when the bending resistance is high and the yield point strain is high, the haze and the increase in the YI value due to the deformation can be suppressed. In the present specification, the haze or YI value after long-term storage or exposure in a high-temperature and high-humidity environment in a bent state may be referred to as a hertz or YI value after storage, and the bending radius at room temperature. _{The haze represented by Hz a} after the mandrel test, which is bent once at 1 mm and returned to a flat surface, may be simply referred to as the hertz after the mandrel test or Hz _a.

The yield point strain in the optical film of the present invention is 1.50% or more, preferably 1.60% or more, more preferably 1.70%, still more preferably 1.80% or more, and particularly preferably 1.90%. That is all. When the yield point strain is equal to or higher than the above lower limit, the YI value after storage can be easily reduced. The yield point strain is usually 3.0% or less. The yield point strain is an index indicating rubberiness, etc., and the slope of the region according to Young's law measured using a tensile tester and the strain value at the intersection of the strain axis intercept and the SS curve are used. Shown, for example, can be obtained by the method described in Examples. The yield point strain is a value at 30 ° C. and a relative humidity of 50%.

Hz _a is 1.5% or less, preferably 1.3% or less, more preferably 1.0% or less, still more preferably 0.8% or less, and usually 0% or more. When Hz _a is not more than the above upper limit, it is easy to reduce the hertz and YI values after storage. The mandrel test is a test in which the bent optical film is returned to a flat surface immediately after the optical film is evenly bent along a cylindrical mandrel having a bending radius of 1 mm at room temperature (25 ° C.). Further, Hz _a can be obtained by measuring the bent portion in the mandrel test using a haze computer or the like, and can be obtained by, for example, the method described in Examples.

_{The haze represented by Hz b} before the mandrel test of the optical film of the present invention is preferably 1.0% or less, more preferably 0.8% or less, still more preferably 0.5% or less, and usually 0%. That is all. When Hz _b is not more than the above upper limit, Hz _a and the haze after storage tend to be low. Further, the transparency of the optical film is increased, and high visibility can be exhibited when used for, for example, the front plate of a display device. In addition, Hz _b can be measured using a haze computer or the like, and can be measured by, for example, the method described in Examples.

The YI value of the optical film of the present invention before the mandrel test is preferably 2.0 or less, more preferably 1.9 or less, usually -5 or more, and preferably -2 or more. When the YI value before the mandrel test is not more than the above upper limit, the YI value after storage tends to be low. Further, the transparency of the optical film is high, and it can contribute to high visibility when used for a front plate or the like of a display device. The YI value was measured by measuring the transmittance of light at 300 to 800 nm using an ultraviolet-visible near-infrared spectrophotometer, and the tristimulus values (X, Y, Z) were obtained, and YI = 100 × (1.2769X−). It can be calculated based on the formula of 1.0592Z) / Y. For example, it can be calculated by the method described in Examples.

The total light transmittance of the optical film of the present invention is preferably 85% or more, more preferably 88% or more, further preferably 90% or more, particularly preferably 91% or more, and usually 100% or less. When the total light transmittance is at least the above lower limit, the transparency becomes high, and when used for, for example, the front plate of a display device, high visibility can be exhibited. Further, the total light transmittance can be measured by using a haze computer in accordance with JIS K 7105: 1981, and can be measured by, for example, the method described in Examples. Further, in the present specification, the total light transmittance and the haze can be the total light transmittance and the haze in the range of the thickness of the optical film of the present invention.

The elastic modulus of the optical film of the present invention is preferably 1.0 GPa or more, more preferably 2.0 GPa or more, still more preferably 3.0 GPa or more, still more preferably 4.0 GPa or more, and particularly preferably 5.0 GPa or more. Yes, usually 100 GPa or less. When the elastic modulus is equal to or higher than the above lower limit, a force for returning to the original shape acts strongly when the optical film is deformed. Therefore, when a predetermined yield point strain is satisfied, the temperature and humidity are higher. It does not easily deteriorate even when bent for a long time, and the haze and YI value after storage are likely to decrease. The elastic modulus can be measured using a tensile tester, for example, by the method described in Examples. The elastic modulus is a value at a temperature of 25 ° C. and a relative humidity of 50%.

Since the optical film of the present invention can suppress an increase in haze and YI values even after long-term exposure or storage in a high-temperature and high-humidity environment, the haze and YI values are kept low even after the storage. can do. Therefore, when it is used in a flexible display device or the like, it can have high transparency even when it is placed in a bent state under harsh conditions, and is useful as an optical film. The optical film of the present invention has a haze of preferably 1.5% or less, more preferably 1. It is 3% or less, more preferably 1.0% or less, particularly preferably 0.8% or less, and the YI value after storage is preferably 2.3 or less, more preferably 2.1 or less, still more preferably. It is 1.9 or less, particularly preferably 1.8 or less. The haze and YI values after storage are the haze and YI values of the bent portion after the folded optical film is returned to a flat surface after storage for 24 hours and allowed to stand at a temperature of 30 ° C. and a relative humidity of 50% for 30 minutes. The haze and YI values are measured by the same method as described above, and can be measured by, for example, the method described in Examples.

The thickness of the optical film of the present invention is appropriately adjusted according to the intended use, but is preferably 20 μm or more, more preferably 25 μm or more, still more preferably 30 μm or more, still more preferably 35 μm or more, and particularly preferably 40 μm or more. Yes, preferably 100 μm or less, more preferably 80 μm or less, still more preferably 60 μm or less. When the thickness of the optical film is within the above range, it is easy to reduce the haze and YI value after storage. The thickness of the optical film can be measured with a film thickness meter or the like, and can be measured by, for example, the method described in Examples.

<Resin>
The optical film of the present invention preferably contains a resin. The resin is preferably a transparent resin, and examples thereof include polyester resins such as polyethylene terephthalate, polycarbonate resins, polyarylate resins, polyether sulfone resins, polyimide resins, and acrylic resins. And so on. These resins can be used alone or in combination of two or more. Among these _{, a polyimide resin is preferable from the viewpoint that Hz a} is easily reduced and the yield point distortion is likely to be high.
The polyimide-based resin means a polyimide resin and a polyamide-imide resin. The polyimide resin indicates a polymer containing a repeating structural unit containing an imide group, and the polyamide-imide resin indicates a polymer containing a repeating structural unit containing an imide group and a repeating structural unit containing an amide group. The optical film of the present invention more preferably contains a polyamide-imide resin as a resin from the viewpoint _{that Hz a is easily reduced and the yield point distortion is likely to be high.}

［式（１）中、Ｘは２価の有機基を表し、Ｙは４価の有機基を表し、＊は結合手を表す］
で表される構成単位を含むことが好ましい。 The polyimide resin contained in the optical film of the present invention _{can easily reduce the Hz a} of the optical film, and can easily increase the yield point strain and the elastic modulus.

[In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, and * represents a bond]
It is preferable to include a structural unit represented by.

［式（２）中、Ｘ及びＺは、互いに独立に、２価の有機基を表し、＊は結合手を表す］
で表される構成単位を含むことが好ましい。 The polyamide-imide resin has the formulas (1) and (2):

[In formula (2), X and Z represent divalent organic groups independently of each other, and * represents a bond]
It is preferable to include a structural unit represented by.

The structural unit represented by the formula (1) is a structural unit formed by reacting a tetracarboxylic acid compound and a diamine compound, and the structural unit represented by the formula (2) is a dicarboxylic acid compound and a diamine compound. Is a structural unit formed by the reaction of and.

［式（２０）〜式（２９）中、
Ｗ^１は、単結合、−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−又は−Ａｒ−ＳＯ_２−Ａｒ−を表し、ここで、Ａｒは、互いに独立に、水素原子がフッ素原子で置換されていてもよい炭素数６〜２０のアリーレン基（例えばフェニレン基）を表し、＊は結合手を表す］
で表される基の結合手のうち、隣接しない２つが水素原子に置き換わった基及び炭素数６以下の２価の鎖式炭化水素基が例示され、Ｚのヘテロ環構造としてはチオフェン環骨格を有する基が例示される。光学フィルムのＹＩ値を低減しやすい観点から、式（２０）〜式（２７）で表される基、及び、チオフェン環骨格を有する基が好ましい。 In the above formula (2), Z is a divalent organic group, preferably substituted with a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms substituted with fluorine. It is a good divalent organic group having 4 to 40 carbon atoms, and more preferably it may be substituted with a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms substituted with fluorine. It represents a divalent organic group having a cyclic structure and having 4 to 40 carbon atoms. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure. As the organic group of Z, the formula (20), the formula (21), the formula (22), the formula (23), the formula (24), the formula (25), the formula (26), the formula (27), the formula (28). And equation (29):

[In equations (20) to (29),
W ¹ represents a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) 2 -, -Ar-, -SO _2- , -CO-, -O-Ar-O-, -Ar-O-Ar- _{, -Ar-CH 2} -Ar-, -Ar-C (CH ₃ ) _2-Ar- Or -Ar-SO _2- Ar-, where Ar represents an arylene group having 6 to 20 carbon atoms (for example, a phenylene group) in which a hydrogen atom may be substituted with a fluorine atom independently of each other. * Represents a bond]
Of the group bonds represented by, a group in which two non-adjacent groups are replaced with hydrogen atoms and a divalent chain hydrocarbon group having 6 or less carbon atoms are exemplified, and the heterocyclic structure of Z is a thiophene ring skeleton. The group having is exemplified. From the viewpoint of easily reducing the YI value of the optical film, groups represented by the formulas (20) to (27) and groups having a thiophene ring skeleton are preferable.

［式中、Ｗ^１及び＊は、式（２０）〜（２９）において定義した通りである］
で表される２価の有機基がより好ましい。なお、式（２０）〜式（２９）及び式（２０’）〜式（２９’）における環上の水素原子は、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基で置換されていてもよい。炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基及び炭素数６〜１２のアリール基としては、それぞれ、後述の式（３）において例示のものが挙げられる。 Examples of the organic group of Z include the formula (20'), the formula (21'), the formula (22'), the formula (23'), the formula (24'), the formula (25'), the formula (26'), and the formula. (27'), equation (28') and equation (29'):

[In the formula, W ¹ and * are as defined in the formulas (20) to (29)]
The divalent organic group represented by is more preferable. The hydrogen atom on the ring in the formulas (20) to (29) and the formulas (20') to (29') is an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. It may be substituted with an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified in the formula (3) described later.

［式（ｄ１）中、Ｒ^２４は、互いに独立に、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^２５は、Ｒ^２４又は−Ｃ（＝Ｏ）−＊を表し、＊は結合手を表す］
で表されるカルボン酸由来の構成単位をさらに有することができ、ワニスの流動性の観点から好ましい。 When the polyimide resin has a structural unit in which Z in the formula (2) is represented by any of the above formulas (20') to (29'), Z in the formula (2) will be described later. When it has a structural unit represented by the formula (3'), the polyimide resin is added to the structural unit and has the following formula (d1):

[In the formula (d1), R ²⁴ represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and R ²⁵ is R ^24. Or -C (= O)-*, * represents a bond]
It is possible to further have a structural unit derived from a carboxylic acid represented by, which is preferable from the viewpoint of fluidity of the varnish.

In R ²⁴ , examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms are given in the formula (3) described later, respectively. Specifically, as the structural unit (d1), R ²⁴ and R ²⁵ are both hydrogen atoms (constituent units derived from a dicarboxylic acid compound), and R ²⁴ is a hydrogen atom and R ^25. Examples thereof include a structural unit (a structural unit derived from a tricarboxylic acid compound) representing −C (= O) − *.

［式（３）中、
Ｒ^３ａ及びＲ^３ｂは、互いに独立に、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基、又は炭素数６〜１２のアリール基を表し、Ｒ^３ａ及びＲ^３ｂに含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ｗは、互いに独立に、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^９）−を表し、Ｒ^９は水素原子、ハロゲン原子で置換されていてもよい炭素数１〜１２の１価の炭化水素基を表し、
ｓは０〜４の整数であり、
ｔは０〜４の整数であり、
ｕは０〜４の整数であり、
＊は結合手を表す］
で表され、より好ましくは式（３’）：

［式（３’）中、Ｒ^３ａ、Ｒ^３ｂ、ｓ、ｔ、ｕ、Ｗ及び＊は、式（３）において定義した通りである］
で表される、式（２）で表される構成単位を少なくとも有することが好ましい。 The polyimide-based resin of the present invention may contain a plurality of types of Z as Z in the formula (2), and the plurality of types of Z may be the same as or different from each other. In particular, Z in the formula (2) is preferable from the viewpoint of easily reducing _{the Hz a of the optical film and easily increasing the yield point strain and the elastic modulus.}

[In equation (3),
R ^3a and R ^3b independently represent 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 hydrogen contained in ^{R 3a} and R ^3b. Atoms may be substituted with halogen atoms independently of each other.
W, independently of one another, a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) _{2 -, - SO 2 -,} - S -, - CO- or -N ^{(R 9)} - represents, ^{R 9} is a hydrogen atom, monovalent 1-12 carbon atoms which may be substituted with a halogen atom Represents a hydrocarbon group
s is an integer from 0 to 4
t is an integer from 0 to 4
u is an integer from 0 to 4
* Represents a bond]
It is represented by, more preferably the formula (3') :.

[In equation (3'), R ^3a , R ^3b , s, t, u, W and * are as defined in equation (3)]
It is preferable to have at least the structural unit represented by the formula (2) represented by.

In formulas (3) and (3 '), W, independently of one another, a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C ( CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- , -S-, -CO- or -N (R ⁹ )-, preferably from the viewpoint of bending resistance of the optical film. It represents −O− or −S−, more preferably −O−.
R ^3a and R ^3b independently represent an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of alkyl groups having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group and 2-methyl-. Butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl group and the like can be mentioned. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group and a cyclohexyloxy group. Can be mentioned. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xsilyl group, a naphthyl group, a biphenyl group and the like. From the viewpoint of easily reducing the Hz _a of the optical film and easily increasing the breakdown point strain and the elastic coefficient, R ^3a and R ^3b are independent of each other, preferably an alkyl group having 1 to 6 carbon atoms or 1 to 6 carbon atoms. Represents the alkoxy group of, more preferably an alkyl group having 1 to 3 carbon atoms or an alkoxy group having 1 to 3 carbon atoms. Here, the ^{hydrogen atoms contained in R 3a} and R ^3b may be substituted with halogen atoms independently of each other.
R ⁹ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group and an n-pentyl group. 2-Methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group and the like. These may be substituted with halogen atoms. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

T and u in the formula (3) and the formula (3') are independently integers of 0 to 4, preferably an integer of 0 to 2, and more preferably 0 or 1.

S in the formula (3) is an integer in the range of 0 to 4, and when s is in this range, it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. The s in the formulas (3) and (3') is preferably an integer in the range of 0 to 3, from the viewpoint of easily reducing _{the Hz a of the optical film and easily increasing the yield point strain and the elastic modulus, more preferably.} It is an integer in the range of 0 to 2. The structural unit represented by the formula (3) or the formula (3') in which s is 0 is, for example, a structural unit derived from terephthalic acid or isophthalic acid, and the structural unit is particularly the formula (3) or the formula (3'). In 3'), s and u are 0, respectively, or s is 0 and u is 1 or 2 (preferably R ^3b is an alkyl group having 1 to 3 carbon atoms or a fluorinated alkyl group or an alkoxy having 1 to 3 carbon atoms. It is preferably a structural unit which is a group, more preferably an alkoxy group having 1 to 3 carbon atoms. From the viewpoint of easily reducing the Hz _a of the optical film and easily increasing the yield point strain and elastic modulus, the polyimide resin preferably contains a structural unit derived from terephthalic acid. The polyimide resin may contain one or more structural units represented by the formula (3) or the formula (3') in Z.

Further, from the viewpoint of reducing the YI value of the optical film, the polyimide resin may contain two or more kinds of structural units having different values of s in the formula (3) or the formula (3') in Z. For example, two or three types of structural units having different values of s in the formula (3) or the formula (3') may be included. In this case, from the viewpoint of reducing the YI value of the optical film, the polyimide resin contains the structural unit represented by the formula (3) in which s is 0 as Z in the structural unit represented by the formula (2). In addition to the structural unit, a structural unit represented by the formula (3) in which s is 1 may be further contained.

In a preferred embodiment of the present invention, the polyimide-based resin has s and u of 0 as structural units represented by the formula (3) or formula (3'), or s and u, respectively. It has a structural unit of 0 and where R ^3b is a methyl group, a methoxy group or a trifluoromethyl group (preferably a methoxy group). In such an embodiment, it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus.

When the polyimide-based resin of the present invention has a structural unit represented by the formula (3) or the formula (3'), the ratio thereof is the structural unit represented by the formula (1) and the formula (2) of the polyimide-based resin. ) Is 100 mol%, preferably 5 mol% or more, more preferably 10 mol% or more, still more preferably 15 mol% or more, and particularly preferably 20 mol% or more. It is preferably 90 mol% or less, more preferably 85 mol% or less, still more preferably 80 mol% or less, and particularly preferably 70 mol% or less. When the ratio of the structural units represented by the formula (3) or the formula (3') is equal to or higher than the above lower limit, the Hz _a of the optical film can be easily reduced, and the yield point strain and the elastic modulus can be easily increased. When the ratio of the structural units represented by the formula (3) or the formula (3') is not more than the above upper limit, the increase in the viscosity of the resin-containing varnish due to the hydrogen bond between the amide bonds derived from the formula (3) is suppressed, and the film is formed. It is easy to improve the workability of.

In a preferred embodiment of the present invention, Z in the polyimide resin of the present invention is preferably 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, and particularly preferably 50 mol% or more. Is a structural unit represented by the formula (3) or the formula (3'). When the above lower limit of Z or more is the structural unit represented by the formula (3) or the formula (3'), it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. Further, 100 mol% or less of Z in the polyimide resin may be a structural unit represented by the formula (3) or the formula (3'). The proportion of the structural unit represented by the formula (3) or the formula (3') in the resin ^{can be measured using, for example, 1 1} H-NMR, or can be calculated from the raw material charging ratio. it can.

In the formula (1), Y represents a tetravalent organic group independently of each other, preferably a tetravalent organic group having 4 to 40 carbon atoms, and more preferably having a cyclic structure having 4 to 40 carbon atoms. Represents a tetravalent organic group. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure. The organic group is an organic group in which the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case the hydrocarbon group and the fluorine-substituted hydrocarbon group The number of carbon atoms is preferably 1-8. The polyimide resin according to one embodiment of the present invention may contain a plurality of types of Y, and the plurality of types of Y may be the same as or different from each other. As Y, the formula (20), the formula (21), the formula (22), the formula (23), the formula (24), the formula (25), the formula (26), the formula (27), the formula (28) and the formula Groups represented by (29); groups in which the hydrogen atom in the groups represented by the formulas (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; A chain hydrocarbon group having a tetravalent carbon number of 6 or less is exemplified.

In the formula (20) to (29), * represents a bond, ^{W 1} is 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) represents a 2 -Ar- or _-Ar-SO 2 -Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and specific examples thereof include a phenylene group. Even if the hydrogen atom on the ring in the formulas (20) to (29) is substituted with 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. Good. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms are exemplified in the formula (3).

Among the groups represented by the formulas (20) to (29), the formula (26), the formula (28) or the formula (28) or the formula (28) from the viewpoint of easily reducing _{the Hz a of the optical film and easily increasing the yield point strain and the elastic modulus.} The group represented by the formula (29) is preferable, and the group represented by the formula (26) is more preferable. Further, ^{W 1} is easy to reduce the Hz _a of the optical film, and the yield point strain and elastic modulus from the enhanced easily standpoint, independently of one another, preferably a single _{bond, -O -, - CH 2 -} , - CH 2 -CH _2- , -CH (CH ₃ )-, -C (CH ₃ ) _2- or -C (CF ₃ ) _2- , more preferably single bond, -O-, -CH _2- , -CH (CH) ₃ )-, -C (CH ₃ ) ₂ -or-C (CF ₃ ) _2- , more preferably single bond, -C (CH ₃ ) _2- or -C (CF ₃ ) _2- , even more preferably. Single bond or -C (CF ₃ ) _2- , especially preferably -C (CF ₃ ) _2- .

［式（４ａ）中、Ｒ^２〜Ｒ^７は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^２〜Ｒ^７に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、Ｖは、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^８）−を表し、Ｒ^８は、水素原子、又はハロゲン原子で置換されていてもよい炭素数１〜１２の一価の炭化水素基を表し、＊は結合手を表す］
で表される基（又は構造）、及び／又は、式（４ｂ）

［式（４ｂ）中、Ｒ^９及びＲ^１０は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^９及びＲ^１０に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、＊は結合手を表す］
で表される基（又は構造）を含む。すなわち、複数の式（１）中のＹの少なくとも一部は、式（４ａ）及び／又は式（４ｂ）で表される。このような態様であると、光学フィルムのＨｚ_ａを低減し、かつ降伏点歪を高めやすいため、保管後のヘーズ及びＹＩ値を低減しやすい。 In a preferred embodiment of the present invention, the structural unit represented by the formula (1) is Y, and the formula (4a):

[In formula (4a), R ^{2 to} R ⁷ 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 independently of each other. hydrogen atoms contained in R ² to R ^7, independently of each other, may be substituted with a halogen atom, V is a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - Represents CH (CH ₃ )-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- , -S-, -CO- or -N (R ⁸ )-, and R ⁸ Represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom, and * represents a bond.]
Group (or structure) represented by and / or formula (4b)

[In formula (4b), R ⁹ and R ¹⁰ 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 9} and R ¹⁰ may be substituted with halogen atoms independently of each other, and * represents a bond.]
Includes a group (or structure) represented by. That is, at least a part of Y in the plurality of formulas (1) is represented by the formulas (4a) and / or the formula (4b). In such an embodiment, the Hz _a of the optical film is easily reduced and the yield point distortion is easily increased, so that the hertz and YI value after storage are easily reduced.

In formula (4a), R ² , R ³ , R ⁴ , R ⁵ , R ⁶ and R ⁷ are independent of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an alkoxy group having 1 to 6 carbon atoms. Represents an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified above in the formula (3). R ² to R ^7, independently of one another, preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, more preferably a hydrogen atom Represent. Here, the ^{hydrogen atoms contained in R 2 to} R ⁷ may be substituted with halogen atoms independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

V in the formula (4a) is a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF _{3) 2 -, - SO 2} -, - S -, - CO- or -N ^{(R 8)} - represents, ^{R 8} is a hydrogen atom or a halogen atom carbon atoms which may be substituted with 1 to 12 Represents a monovalent hydrocarbon group. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group and a tert. -Butyl 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 Examples include a group and an n-decyl group, which may be substituted with a halogen atom. Examples of the halogen atom include those exemplified above. Among these, _{from the viewpoint of reducing the Hz a} of the optical film and easily increasing the yield point strain and elastic modulus, V is a single bond, −O−, −CH ₂₋ , −CH (CH ₃ ) −, −. C _{(CH 3) 2} - or -C _{(CF 3) 2} - is preferably a single bond, -C _{(CH 3) 2} - or -C _{(CF 3) 2} - and more preferably, single It is more preferably bonded or −C (CF ₃ ) ₂ −, and most preferably _{−C (CF 3} ) _{2 −.}

In formula (4b), R ⁹ and R ¹⁰ 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. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include those exemplified above in the formula (3), respectively. Among these, _{from the viewpoint of reducing the Hz a} of the optical film and easily increasing the breakdown point strain and the elastic coefficient, R ⁹ and R ¹⁰ are independent of each other, 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, and even more preferably a hydrogen atom. Here, the ^{hydrogen atoms contained in R 9} and R ¹⁰ may be substituted with halogen atoms independently of each other. Examples of the halogen atom include those exemplified above.

In a preferred embodiment of the present invention, in formula ^(4a), R 2 ~R ⁷ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, V is a single bond, -C (CH ₃ ) ₂ -or-C (CF ₃ ) _2- . In such an embodiment, it is _{easy to reduce the Hz a} of the optical film and increase the yield point strain and the elastic modulus.

In a preferred embodiment of the present invention, in formula (4b), R ⁹ and R ¹⁰ are hydrogen atoms or alkyl groups having 1 to 3 carbon atoms independently of each other. In such an embodiment, it is _{easy to reduce the Hz a} of the optical film and increase the yield point strain and the elastic modulus.

で表され、式（４ｂ）は、式（７ｃ）

で表される。すなわち、複数のＹの少なくとも一部は、式（７ａ）、式（７ｂ）又は式（７ｃ）で表される。このような態様であると、光学フィルムのＨｚ_ａを低減し、かつ降伏点歪及び弾性率を高めやすい。また、複数のＹの少なくとも一部が式（７ａ）で表される場合、フッ素元素を含有する骨格により樹脂の溶媒への溶解性を向上し、樹脂ワニスの粘度を低く抑制することができ、光学フィルムの加工性を向上しやすい。また、フッ素元素を含有する骨格により、ヘーズ及びＹＩ値等の光学特性を低減しやすい。 In a more preferred embodiment of the invention, formula (4a) is formula (7a) or formula (7b) :.

The formula (4b) is represented by the formula (7c).

It is represented by. That is, at least a part of the plurality of Ys is represented by the formula (7a), the formula (7b) or the formula (7c). In such an embodiment, it is _{easy to reduce the Hz a} of the optical film and increase the yield point strain and the elastic modulus. Further, when at least a part of the plurality of Y is represented by the formula (7a), the solubility of the resin in the solvent can be improved by the skeleton containing the fluorine element, and the viscosity of the resin varnish can be suppressed to be low. It is easy to improve the workability of the optical film. Further, the skeleton containing a fluorine element makes it easy to reduce optical characteristics such as haze and YI value.

In one embodiment of the present invention, when the polyimide-based resin of the present invention has a structural unit in which Y in the formula (1) is represented by the formulas (4a) and / or (4b), the proportion thereof is polyimide-based. When the total of the structural units represented by the resin formula (1) and the structural units represented by the formula (2) is 100 mol%, it is preferably 10 mol% or more, more preferably 20 mol% or more, and further. It is preferably 30 mol% or more, particularly preferably 35 mol% or more, preferably 95 mol% or less, more preferably 90 mol% or less, still more preferably 85 mol% or less. When the ratio of the structural units represented by the formulas (4a) and / or (4b) is not more than the above lower limit, it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. When the ratio of the structural units represented by the formulas (4a) and / or (4b) is not more than the above upper limit, the increase in viscosity of the resin-containing varnish due to the hydrogen bond between the amide bonds derived from the formula (3) is suppressed, and the film is formed. It is easy to improve the workability of.

In a preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more of Y in the polyimide resin of the present invention is the formula (4a) and /. Alternatively, it is a structural unit represented by (4b). When the above lower limit of Y or more is a structural unit represented by the formulas (4a) and / or (4b), it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. Further, 100 mol% or less of Z in the polyimide resin may be a structural unit represented by the formulas (4a) and / or (4b). The proportion of the structural unit represented by the formula (4a) or (4b) in the resin ^{can be measured using, for example, 1 1} H-NMR, or can be calculated from the raw material charging ratio.

In a preferred embodiment of the present invention, V in formula (4a) 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 8)} - the group of the formula (4a ') which is represented by a polyimide resin of the present invention , When Y in the formula (1) has a structural unit represented by the formula (4a'), the ratio thereof is represented by the structural unit represented by the formula (1) and the formula (2) of the polyimide resin. When the total of the constituent units is 100 mol%, it is preferably 35 mol% or more, more preferably 40 mol% or more. When the above lower limit of Y or more is a structural unit represented by the equation (4a'), it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. The proportion of the structural unit in which Y in the formula (1) is represented by the formula (4a') is the structural unit represented by the formula (1) and the structural unit represented by the formula (2) of the polyimide resin. When the total of is 100 mol% or less, it is preferably 95 mol% or less, more preferably 90 mol% or less, still more preferably 85 mol% or less. The ratio of the structural unit represented by the formula (4a') in the resin ^{can be measured using, for example, 1 1} H-NMR, or can be calculated from the charging ratio of the raw materials.

In the formulas (1) and (2), X represents a divalent organic group independently of each other, preferably a divalent organic group having 4 to 40 carbon atoms, and more preferably 4 carbon atoms having a cyclic structure. Represents a divalent organic group of ~ 40. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure. In the organic group, the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine, in which case the number of carbon atoms of the hydrocarbon group and the hydrocarbon group substituted with fluorine is preferable. Is 1 to 8. In one embodiment of the present invention, the polyimide-based resin of the present invention may contain a plurality of types of X, and the plurality of types of X may be the same as or different from each other. X is represented by the formula (10), the formula (11), the formula (12), the formula (13), the formula (14), the formula (15), the formula (16), the formula (17) and the formula (18). Groups; Groups in which the hydrogen atom in the groups represented by the formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a group having 6 or less carbon atoms. A chain hydrocarbon group is exemplified.

In equations (10) to (18),
* Represents a bond
V ^{1, V 2} and ^{V 3} independently of one another, a single _{bond, -O -, - S -,} - CH 2 -, - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH ₃ ) _{Represents 2-} , -C (CF ₃ ) _2- , -SO _2- , -CO- or -N (Q)-. Here, Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms include those exemplified above.
In one example, V ¹ and V ³ are single bonds, -O- or -S-, and V ² is -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2. -Or -SO _2- . The ^{bonding positions of V 1} and V ² with respect to each ring and the bonding positions of V ² and V ³ with respect to each ring are independent of each other, preferably in the meta position or para position with respect to each ring, and more preferably in the para position. It is a place.

［式（３４）中、Ａｒ^１及びＡｒ^２は、互いに独立に、置換基を有していてもよい２価の芳香族基を表し、Ｗは、互いに独立に、単結合、−Ｏ−、ジフェニルメチレン基、−ＳＯ_２−、−Ｓ−、−ＣＯ−、―ＰＯ−、―ＰＯ_２−、−Ｎ（Ｒ^１５）−、−Ｓｉ（Ｒ^１６）_２−、又は炭素数１〜１２の二価の炭化水素基を表し、該炭化水素基に含まれる水素原子は、互いに独立に、ハロゲン原子に置換されていてもよく、２つの水素原子に代わって環を形成してもよく、Ｒ^１５及びＲ^１６は、互いに独立に、水素原子、又はハロゲン原子で置換されていてもよい炭素数１〜１２の一価の炭化水素基を表し、ｑは０〜４の整数を表す］
で表される基（又は構造）を含む。すなわち、式（１）及び／又は式（２）中の複数のＸの少なくとも一部は式（３４）で表される基である。このような態様であると、光学フィルムのＨｚ_ａを低減しやすく、かつ降伏点歪及び弾性率を高めやすい。 In a preferred embodiment of the present invention, the structural unit represented by the formula (1) and / or the structural unit represented by the formula (2) is represented by the formula (34) as X.

[In formula (34), Ar ¹ and Ar ² represent divalent aromatic groups which may have substituents independently of each other, and W represents a single bond, −O−, independently of each other. Diphenylmethylene group, -SO _2- , -S-, -CO-, -PO-, -PO _2- , -N (R ¹⁵ )-, -Si (R ¹⁶ ) _2- , or 1 to 12 carbon atoms Representing a divalent hydrocarbon group, the hydrogen atoms contained in the hydrocarbon group may be independently substituted with halogen atoms or may form a ring in place of the two hydrogen atoms, R. ¹⁵ and R ¹⁶ represent a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom independently of each other, and q represents an integer of 0 to 4].
Includes a group (or structure) represented by. That is, at least a part of the plurality of Xs in the formula (1) and / or the formula (2) is a group represented by the formula (34). In such an embodiment, it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus.

^{Ar 1} and Ar ² in the formula (34) represent a divalent aromatic group which may have a substituent independently of each other. The divalent aromatic group refers to a divalent monocyclic aromatic group, a divalent fused polycyclic aromatic group, or a divalent ring-assembled aromatic group. The divalent aromatic group is preferably a divalent aromatic group having 5 to 20 carbon atoms.

The divalent monocyclic aromatic group includes, for example, a monocyclic aromatic hydrocarbon ring such as a benzene ring, preferably among carbon atoms constituting a monocyclic aromatic hydrocarbon ring having 6 to 15 carbon atoms. A divalent group excluding two hydrogen atoms; a monocyclic aromatic heterocycle containing at least one heteroatom selected from sulfur, nitrogen and oxygen atoms, preferably carbon and heteroatoms 5 to 15. It constitutes a monocyclic aromatic heterocycle, for example, a pyridine ring, a diazabenzene ring, a triazine ring, a furan ring, a thiophene ring, an azole ring, a diazole ring, a triazole ring, an oxazole ring, an oxaziazole ring, a thiazole ring, a thiazazole ring, and the like. Examples thereof include a divalent group excluding two hydrogen atoms that are directly bonded to a carbon atom or a hetero atom.

Examples of the divalent condensed polycyclic aromatic group include a condensed polycyclic aromatic hydrocarbon ring such as a naphthalene ring, an anthracene ring, and a phenanthrene ring, preferably a condensed polycyclic aromatic hydrocarbon having 10 to 20 carbon atoms. Of the carbon atoms constituting the ring, a divalent group excluding two hydrogen atoms; a fused polycyclic aromatic heterocycle containing at least one heteroatom selected from a sulfur atom, a nitrogen atom and an oxygen atom, preferably. Is a fused polycyclic aromatic heterocycle having 8 to 20 carbon and heteroatoms, such as azanaphthalene ring, diazanaphthalene ring, carbazole ring, dibenzofuran ring, dibenzothiophene ring, dibenzosilol ring, phenoxazine ring, phenothiazine ring, Examples thereof include a divalent group excluding two hydrogen atoms directly bonded to a carbon atom or a hetero atom constituting an aromatic ring or the like. The monocyclic aromatic hydrocarbon ring and the monocyclic aromatic heterocycle are collectively referred to as a monocyclic aromatic ring, and the fused polycyclic aromatic hydrocarbon ring and the condensed polycyclic aromatic heterocycle are referred to as a monocyclic aromatic ring. Collectively, they are referred to as fused polycyclic aromatic rings.

The divalent ring-assembled aromatic group is a ring-assembled aromatic ring in which a monocyclic aromatic ring and / or a fused polycyclic aromatic ring is linked by a single bond, preferably carbon and a heteroatom number of 10 to 40. Ring assembly Indicates a divalent group from which two hydrogen atoms directly bonded to a carbon atom or a heteroatom constituting an aromatic ring have been removed. The divalent ring-assembled aromatic group may be composed of one or more monocyclic aromatic rings, or may be composed of one or more fused polycyclic aromatic rings, and these groups. May be configured in combination. Specifically, the divalent ring-assembled aromatic group is directly bonded to a carbon atom or a hetero atom constituting a ring-assembled aromatic ring such as a biphenyl ring, a bipyridine ring, a phenylnaphthyl ring, a terphenyl ring, or a terpyridine ring. A divalent group from which two hydrogen atoms have been removed can be mentioned.

Among the divalent aromatic groups, _a divalent monocyclic aromatic group or a divalent ring-assembled aromatic group from the viewpoint of easily reducing the Hz a of the optical film and increasing the yield point strain and the elastic coefficient. Is preferable, and a divalent monocyclic aromatic ring such as a phenylene group is preferable.

Examples of the alkyl group having 1 to 12 carbon atoms include a linear, branched or alicyclic alkyl group having 1 to 12 carbon atoms. Examples of linear, branched or alicyclic alkyl groups having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group and tert-. Butyl group, n-pentyl group, 2-methyl-butyl group, 3-methylbutyl group, 2-ethyl-propyl group, n-hexyl, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group , N-decyl group, cyclopentyl group, cyclohexyl group and the like. The alkyl group having 1 to 12 carbon atoms may be a linear alkyl group, a branched alkyl group, or an alicyclic alkyl group containing an alicyclic hydrocarbon structure. The number of carbon atoms of the alkyl group having 1 to 12 carbon atoms is preferably 1 to 6, more preferably 1 to 4, and further preferably 1 or 2. In the above alkyl 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 a group. Examples of the halogen atom include those exemplified above. The alkyl group having 1 to 12 carbon atoms is preferably a group in which at least one hydrogen atom is substituted with a halogen atom (sometimes referred to as an alkyl halide group), more preferably a fluoroalkyl group, and even more preferably. Is a perfluoroalkyl group. Here, when an 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 carbon. It is not included in the carbon number of the alkyl group of numbers 1-12. For example, the above-mentioned alkyl group having 1 to 12 carbon atoms is replaced with an alkyl group having 1 to 4 carbon atoms, the main chain of which is an alkyl group having 1 to 12 carbon atoms, and at least one hydrogen atom of the alkyl group. Is a group substituted with an alkyl group having 1 to 4 carbon atoms. As long as the number of carbon atoms in the alkyl group portion of the main chain is 1 to 12, the total number of carbon atoms in the alkyl group may exceed 12. In the case where the total number of carbon atoms of the alkyl group does not exceed 12, the group in which the alkyl group having 1 to 12 carbon atoms is replaced with the alkyl group having 1 to 4 carbon atoms has 1 to 12 carbon atoms. It is a group that is also included in the definition of a branched alkyl group.

Examples of the alkoxy group having 1 to 12 carbon atoms include a methoxy group, an ethoxy group, a propyloxy group, an isopropyloxy group, an n-butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group and a cyclohexyloxy group. , Heptyloxy group, octyloxy group, nonyloxy group, decyloxy group and the like. The alkylene moiety in the alkoxy group having 1 to 12 carbon atoms may be linear, branched, or alicyclic. The number of carbon atoms of the alkoxy group having 1 to 12 carbon atoms is preferably 1 to 6, more preferably 1 to 4, and further preferably 1 or 2. In the above-mentioned alkoxy 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 those described above. Here, when an 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 the same as the number of carbon atoms of the alkoxy group having 1 to 12 carbon atoms. exclude.

Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a naphthyl group, a biphenyl group and the like. The aryl group having 6 to 12 carbon atoms preferably has 6, 10 or 12, more preferably 6 or 12. In the above aryl group having 6 to 12 carbon atoms, at least one hydrogen atom has 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 independently of each other. It may be a group substituted with. Examples of the halogen atom include those described above. Here, when an aryl group having 6 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is the same as the carbon number of the aryl group having 6 to 12 carbon atoms. exclude.

Examples of the aryloxy group having 6 to 12 carbon atoms include a phenoxy group, a naphthyloxy group, and a biphenyloxy group. The aryloxy group having 6 to 12 carbon atoms preferably has 6, 10 or 12, more preferably 6 or 12. In the above aryloxy group having 6 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 a group. Examples of the halogen atom include those described above. Here, when an aryloxy group having 6 to 12 carbon atoms is substituted with a substituent containing a carbon atom, the number of carbon atoms contained in the substituent is the number of carbon atoms of the aryloxy group having 6 to 12 carbon atoms. Not included in.

A carbonyl-containing group having 1 to 12 carbon atoms indicates a group containing a carbonyl group, for example, * -CO-R ^a , * -R ^b- CO-R ^a , * ^{-CO-OR a} , * -R ^{b-. CO-O-R a, *} - O-CO-R a, ^or a group (* represents a bond) represented by ^{-R b -O-CO-R a} . The R ^a, include the groups described above for an alkyl group having 1 to 12 carbon atoms, and R ^b, binding at least one hydrogen atom of the groups described above for alkyl groups having 1 to 12 carbon atoms Examples thereof include a divalent alkylene group having 1 to 12 carbon atoms which has been replaced by a hand.

Examples of the halogeno group include a fluoro group, a chloro group, a bromo group or an iodine group.

Among these, _{from the viewpoint of easily reducing the Hz a} of the optical film and easily increasing the breakdown point strain and the elastic coefficient, the substituent is an alkyl group having 1 to 12 carbon atoms; an alkyl halide having 1 to 12 carbon atoms. A group (preferably a fluoroalkyl group, more preferably a perfluoroalkyl group); and at least one selected from an alkoxy group having 1 to 12 carbon atoms, preferably an alkyl halide group having 1 to 12 carbon atoms. Is more preferable. The carbon atoms of these groups are preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 or 2.

^{Ar 1} and Ar ² in the formula (34) are divalent phenylene having no substituents independently of each other from the viewpoint of easily reducing the Hz _{a of the optical film and easily increasing the breakdown point strain and the elastic coefficient.} A divalent phenylene group having a group or an alkyl halide group having 1 to 12 carbon atoms (preferably a fluoroalkyl group, more preferably a perfluoroalkyl group) is preferable.

Ws in formula (34) are independent of each other, single-bonded, -O-, diphenylmethylene group, -SO _2- , -S-, -CO-, -PO-, -PO _2- , -N (R). ¹⁵ )-, -Si (R ¹⁶ ) _2- , or a divalent hydrocarbon group having 1 to 12 carbon atoms, and the hydrogen atom contained in the hydrocarbon group is substituted with a halogen atom independently of each other. A ring may be formed in place of two hydrogen atoms, and R ¹⁵ and R ¹⁶ may be substituted with a hydrogen atom or a halogen atom independently of each other. Represents the hydrocarbon group of. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms which may be substituted with halogen atoms in R ¹⁵ and R ^{16 include those exemplified above.}

As the divalent hydrocarbon group having 1 to 12 carbon atoms in W in the formula (34), among the monovalent hydrocarbon groups having 1 to 12 carbon atoms in V in the formula (4), a hydrogen atom is further added. Divalent groups, excluding one, may be mentioned, which may be substituted with a halogen atom. Examples of the halogen atom include those exemplified above. Further, among the hydrogen atoms contained in the divalent hydrocarbon group having 1 to 12 carbon atoms, a ring is formed in place of two hydrogen atoms, that is, the two hydrogen atoms are replaced with a bond and the two bonds are formed. The hands may be connected to form a ring, and examples of the ring include a cycloalkane ring having 3 to 12 carbon atoms. Among these Ws, _{from the viewpoint of easily reducing the Hz a} of the optical film and easily increasing the breakdown point strain and the elastic coefficient, a single bond or a divalent hydrocarbon group having 1 to 12 carbon atoms and their carbonization A group in which at least a part of the hydrogen atom contained in the hydrogen group is replaced with a halogen atom is preferable, and a single bond, −CH ₂ −, _{−CH 2} −CH ₂ −, _{−CH (CH 3} ) −, −C (CH ₃₎ ) ₂ − or −C (CF ₃ ) ₂ − is more preferred, single bond, −C (CH ₃ ) ₂ − or −C (CF ₃ ) ₂ − is even more preferred, single bond or −C (CF ₃ ) ₂ -Is particularly preferable.

Q in the formula (34) is an integer of 0 to 4, and is preferably an integer of 0 to 3 from the viewpoint of easily reducing _{the Hz a of the optical film and easily increasing the yield point distortion and the elastic modulus.} It is preferably an integer of 0 to 2, more preferably 0 or 1, and particularly preferably 1.

［式（３２）中、Ｒ^２６〜Ｒ^３３は、互いに独立に、水素原子、炭素数１〜６のアルキル基、炭素数１〜６のアルコキシ基又は炭素数６〜１２のアリール基を表し、Ｒ^２６〜Ｒ^３３に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、Ｗ^ａは、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、ジフェニルメチレン基、−ＳＯ_２−、−Ｓ−、−ＣＯ−、―ＰＯ−、―ＰＯ_２−、−Ｎ（Ｒ^３４）−又は−Ｓｉ（Ｒ^３５）_２−を表し、Ｒ^３４及びＲ^３５は、互いに独立に、水素原子、又はハロゲン原子で置換されていてもよい炭素数１〜１２の一価の炭化水素基を表す］
で表される。すなわち、式（１）で表される構成単位及び／又は式（２）で表される構成単位は、Ｘとして、式（３２）で表される基（又は構成単位）を含む。このような態様であると、光学フィルムのＨｚ_ａを低減しやすく、かつ降伏点歪及び弾性率を高めやすい。また、式（１）で表される構成単位及び／又は式（２）で表される構成単位は、Ｘとして式（３２）で表される基（又は構成単位）を１種又は複数種含んでいてもよい。 In a preferred embodiment of the present invention, formula (34) is represented by formula (32).

[In formula (32), R ^{26 to} R ³³ 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. hydrogen atoms contained in R ²⁶ to R ^33, independently of one another, it may be substituted with a halogen atom, ^{W a} represents a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, -CH (CH ₃ )-, -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , diphenylmethylene group, -SO _2- , -S-, -CO-, -PO-, -PO ₂ Represents −, −N (R ³⁴ ) − or −Si (R ³⁵ ) ₂ −, and R ³⁴ and R ³⁵ have 1 to 12 carbon atoms which may be substituted with hydrogen atoms or halogen atoms independently of each other. Represents a monovalent hydrocarbon group]
It is represented by. That is, the structural unit represented by the formula (1) and / or the structural unit represented by the formula (2) includes a group (or a structural unit) represented by the formula (32) as X. In such an embodiment, it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. Further, the structural unit represented by the formula (1) and / or the structural unit represented by the formula (2) includes one or more groups (or structural units) represented by the formula (32) as X. You may be.

R ^{26 to} R ³³ 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. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms are exemplified above in the formula (3). Here, the ^{hydrogen atoms contained in R 26 to} R ³³ may be substituted with halogen atoms independently of each other. Examples of the halogen atom include those exemplified above.

Among these, R ^{26 to} R ³³ are independent of each other, preferably hydrogen atoms and alkyl having 1 to 6 carbon atoms, from the viewpoints that the Hz _{a of the optical film can be easily reduced and the breakdown point strain and the elastic coefficient can be easily increased.} A group or an alkyl halide group having 1 to 6 carbon atoms, more preferably a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or a fluoroalkyl group having 1 to 6 carbon atoms (preferably a perfluoroalkyl group), still more preferably hydrogen. Atomic, methyl, chloro or trifluoromethyl groups, among which R ²⁶ , R ²⁸ , R ²⁹ , R ³⁰ , R ³¹ and R ³³ are hydrogen atoms, R ²⁷ and R ³² are hydrogen atoms, methyl groups, fluoro. It is more preferably a group, a chloro group or a trifluoromethyl group, ^{and it is particularly preferable that R 27} and R ³² are a hydrogen atom or a trifluoromethyl group.

^{W a} in the formula (32), independently of one another, a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 - , -C (CF ₃ ) _2- , diphenylmethylene group, -SO _2- , -S-, -CO-, -PO-, -PO _2- , -N (R ³⁴ )-or -Si (R ³⁵ ) _{Representing 2-} , R ³⁴ and R ³⁵ represent monovalent hydrocarbon groups having 1 to 12 carbon atoms which may be substituted with hydrogen atoms or halogen atoms independently of each other, and reduce _{the Hz a of the optical film.} From the viewpoint of easy yielding point strain and easy increase of elastic coefficient, preferably single bond, −CH ₂ −, _{−CH 2} −CH ₂ −, _{−CH (CH 3} ) −, −C (CH ₃ ) ₂ − Or -C (CF ₃ ) _2- , more preferably single bond, -C (CH ₃ ) _2- or -C (CF ₃ ) _2- , more preferably single bond or -C (CF ₃ ) _2-. .. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom include those exemplified above as V in the formula (4).

In a preferred embodiment of the present invention, in formula ^{(32), R} 26 ~R ^33, independently of one another, represent a hydrogen atom or a halogenated alkyl group having 1 to 6 carbon atoms, ^{W a} represents a single bond, -C Represents (CH ₃ ) _2- or −C (CF ₃ ) _2-.

で表される。すなわち、式（１）及び／又は式（２）中の複数のＸの少なくとも一部は、式（３５ａ）又は式（３５ｂ）で表される。このような態様であると、光学フィルムのＨｚ_ａを低減しやすく、かつ降伏点歪及び弾性率を高めやすい。なお、式（１）及び／又は式（２）で表される構成単位は、Ｘとして、式（３５ａ）又は（３５ｂ）で表される基を１種又は複数種含んでいてもよい。 In a preferred embodiment of the invention, formula (32) is formula (35a) or formula (35b).

It is represented by. That is, at least a part of the plurality of Xs in the formula (1) and / or the formula (2) is represented by the formula (35a) or the formula (35b). In such an embodiment, it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. The structural unit represented by the formula (1) and / or the formula (2) may contain one or more groups represented by the formula (35a) or (35b) as X.

In one embodiment of the present invention, when the polyimide-based resin of the present invention has a structural unit in which X in the formula (1) and / or the formula (2) is represented by the formula (34), among them, the formula (32) When it has a structural unit represented by, the ratio is calculated when the total of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) of the polyimide resin is 100 mol%. It is preferably 30 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more, and preferably 100 mol% or less. When the ratio of the structural unit in which X in the formula (1) and / or the formula (2) is represented by the formula (34) is in the above range, the Hz _a of the optical film can be easily reduced and the yield point of the optical film can be easily reduced. It is easy to increase strain and elastic modulus. The ratio of the structural unit in which X in the formula (1) and / or the formula (2) is represented by the formula (34) ^{can be measured using, for example, 1 1} H-NMR, or calculated from the charging ratio of the raw materials. You can also do it.

In one embodiment of the present invention, ^{W a} in the formula (32) _{is, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, -C (CF ₃ ) _2- , diphenylmethylene group, -SO _2- , -S-, -CO-, -PO-, -PO _2- , -N (R ³⁴ )-or -Si (R ³⁵⁾ ) When the _{group represented by 2} − is given by the formula (32'), the Y in the formula (1) is the structural unit represented by the formula (4a'), and the formula (1) and / or the formula (2). The ratio of at least one structural unit in which X is selected from the structural units represented by the formula (32') is the total molar amount of X, Y and Z in the formulas (1) and (2). When it is 100 mol%, it is preferably 17 mol% or more, more preferably 20 mol% or more, further preferably 25 mol% or more, particularly preferably 35 mol% or more, preferably 85 mol% or less, more preferably. Is 75 mol% or less. When the ratio of the structural units is equal to or higher than the above lower limit, it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. The ratio of the structural units ^{can be measured using, for example, 1 1} H-NMR, or can be calculated from the charging ratio of raw materials.

In the polyimide resin of the present invention, in addition to the structural units represented by the formulas (1) and (2), the structural units represented by the formula (30) and / or the structural units represented by the formula (31). May include.

In the formula (30), Y ¹ is a tetravalent organic group, preferably an organic group in which the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine. Examples of Y ¹ include formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and A group represented by the formula (29), a group in which the hydrogen atom in the groups represented by the formulas (20) to (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a group. A chain hydrocarbon group having a tetravalent carbon number of 6 or less is exemplified. In one embodiment of the present invention, a polyimide resin may include a plurality of kinds of Y ^1, Y ¹ of the plural kinds may being the same or different.

In the formula (31), Y ² is a trivalent organic group, preferably an organic group in which the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine. Examples of Y ² include the above equations (20), (21), (22), (23), (24), (25), (26), (27), and (28). ) And a group in which any one of the bonds of the group represented by the formula (29) is replaced with a hydrogen atom, and a chain hydrocarbon group having a trivalent carbon number of 6 or less are exemplified. In one embodiment of the present invention, a polyimide resin may include a plurality of kinds of Y ^2, Y ² a plurality of species may be be the same or different from each other.

In formulas (30) and (31), X ¹ and X ² are divalent organic groups independently of each other, and preferably a hydrocarbon group in which a hydrogen atom in the organic group is substituted with a hydrocarbon group or fluorine. It is an organic group that may be substituted with. Examples of X ¹ and X ² include the above equations (10), (11), (12), (13), (14), (15), (16), (17) and A group represented by the formula (18); a group in which a hydrogen atom in the groups represented by the formulas (10) to (18) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; A chain hydrocarbon group having 6 or less carbon atoms is exemplified.

In one embodiment of the present invention, the polyimide resin is composed of the structural units represented by the formulas (1) and (2) and, in some cases, the structural units represented by the formulas (30) and / or the formula (31). Become. Further, _{from the viewpoint of easily reducing the Hz a} of the optical film and easily increasing the breakdown point strain and the elastic modulus, the ratio of the structural units represented by the formulas (1) and (2) in the polyimide resin is determined. With respect to the total of the constituent units represented by the formulas (1) and (2) and, in some cases, the formulas (30) and (31), 80 mol% or more, more preferably 90 mol% or more, and further. It is preferably 95 mol% or more. In the polyimide resin, the proportions of the structural units represented by the formulas (1) and (2) are the formulas (1) and (2), and in some cases, the formulas (30) and / or the formula (31). It is usually 100% or less with respect to the total of the structural units represented by. The above ratio can be measured using, for example, ^{1 1} H-NMR, or can be calculated from the raw material charging ratio.

In the polyimide-based resin of the present invention, the ratio of the structural unit represented by the formula (2) is preferably 0.01 mol or more, more preferably 0, with respect to 1 mol of the structural unit represented by the formula (1). It is 0.05 mol or more, more preferably 0.1 mol or more, particularly preferably 0.2 mol or more, preferably 20 mol or less, more preferably 10 mol or less, still more preferably 5 mol or less, and particularly preferably 3 mol. It is as follows. When the ratio of the structural units represented by the formula (2) is not more than the above lower limit, it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. Further, when it is not more than the above upper limit, thickening due to hydrogen bonds between amide bonds in the formula (2) can be suppressed, the viscosity of the resin varnish can be reduced, and the production of an optical film is easy.

In a preferred embodiment of the present invention, the polyimide resin of the present invention may contain a halogen atom such as a fluorine atom which can be introduced by, for example, the above-mentioned fluorine-containing substituent or the like. When the polyimide resin contains halogen atoms, _{it is easy to reduce the Hz a} and YI values of the optical film, and it is easy to increase the yield point strain and the elastic modulus. Further, when the elastic modulus of the optical film is high, it is easy to suppress the occurrence of scratches and wrinkles. Further, when the YI value of the optical film is low, it becomes easy to improve the transparency and visibility of the film. The halogen atom is preferably a fluorine atom. Preferred fluorine-containing substituents for containing a fluorine atom in the polyimide resin include, for example, a fluoro group and a trifluoromethyl group.

The content of halogen atoms in the polyimide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, and further preferably 5 to 30% by mass, based on the mass of the polyimide resin. When the halogen atom content is at least the above lower limit, the Hz _a and YI values of the optical film can be easily reduced, and the yield point strain and elastic modulus can be easily increased. When the content of halogen atoms is not more than the above upper limit, synthesis becomes easy.

The imidization ratio of the polyimide resin is preferably 90% or more, more preferably 93% or more, still more preferably 96% or more. From the viewpoint of easily improving the optical characteristics of the optical film, the imidization ratio is preferably at least the above lower limit. The upper limit of the imidization rate is 100% or less. The imidization ratio indicates the ratio of the molar amount of the imide bond in the polyimide resin to twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin. When the polyimide resin contains a tricarboxylic acid compound, the value is twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin, and the molar amount of the structural unit derived from the tricarboxylic acid compound. The ratio of the molar amount of the imide bond in the polyimide resin to the total of the above is shown. The imidization rate can be determined by an IR method, an NMR method, or the like.

The weight average molecular weight of the resin is preferably 10,000 or more, more preferably 30,000 or more, in terms of standard polystyrene, from the viewpoint of easily reducing _{the Hz a of the optical film and increasing the yield point strain and elastic modulus.} It is more preferably 50,000 or more, still more preferably 100,000 or more, and particularly preferably 150,000 or more, and is preferably 1,000,000 or less from the viewpoint of easily improving the stretchability and processability of the optical film. , More preferably 800,000 or less, still more preferably 700,000 or less, and particularly preferably 500,000 or less. The weight average molecular weight can be determined by, for example, GPC measurement and standard polystyrene conversion, and may be calculated by, for example, the method described in Examples.

In one embodiment of the present invention, the resin contained in the optical film is preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass, particularly preferably 60% by mass, based on 100% by mass of the optical film. It is 80% by mass or more, preferably 100% by mass or less.

<Resin manufacturing method>
The method for producing the resin contained in the optical film of the present invention, preferably the polyimide resin, is not particularly limited. In one embodiment of the present invention, among the polyimide-based resins, the polyamide-imide resin undergoes a reaction such as polycondensation of a diamine compound, a tetracarboxylic acid compound, a dicarboxylic acid compound, and if necessary, a tricarboxylic acid compound or the like. Can be obtained. The polyimide resin can be obtained by subjecting a diamine compound and a tetracarboxylic acid compound to a reaction such as polycondensation.

The structural units represented by the formulas (1) and (30) are usually derived from a diamine compound and a tetracarboxylic acid compound. The structural unit represented by the formula (2) is usually derived from a diamine compound and a dicarboxylic acid compound. The structural unit represented by the formula (31) is usually derived from a diamine compound and a tricarboxylic acid compound.

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

Specific examples of aromatic tetracarboxylic dianhydrides include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetraides. Examples include carboxylic dianhydride. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride include 4,4'-oxydiphthalic acid dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride and 2,2. ', 3,3'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (sometimes referred to as BPDA), 2,2', 3,3 '-Biphenyltetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propanedianhydride, 2, 2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4'-(hexafluoroisopropyridene) diphthalic acid Dihydride (sometimes referred to as 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 Dihydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4'-(p-phenylenedioxy) diphthalic acid dianhydride, 4,4'-(m-phenylenedioxy) diphthal Acid dianhydride can be mentioned. Examples of the monocyclic aromatic tetracarboxylic dianhydride include 1,2,4,5-benzenetetracarboxylic dianhydride [pyromellitic dianhydride (PMDA)], which is polycondensed. Examples of the cyclic aromatic tetracarboxylic dianhydride include 2,3,6,7-naphthalenetetracarboxylic dianhydride.
Among these, preferably pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 3 , 3', 4,4'-diphenylsulfonetetracarboxylic 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'-(hexafluoroisopropyridene) diphthalic dianhydride (6FDA), 1,2- Bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethanedi Anhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride Examples thereof include 4,4'-(p-phenylenedioxy) diphthalic acid dianhydride and 4,4'-(m-phenylenedioxy) diphthalic acid dianhydride, more preferably 4,4'-. Oxydiphthalic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA), 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 4,4'- Examples include (hexafluoroisopropyridene) diphthalic dianhydride (6FDA), bis (3,4-dicarboxyphenyl) methane dianhydride, and 4,4'-(p-phenylenedioxy) diphthalic dianhydride. To be done. These can be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydride. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride. Cycloalkanetetracarboxylic dianhydride 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 their positional isomers are listed. Be done. These can 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, 1,2,3,4-pentanetetracarboxylic dianhydride and the like. These can be used alone or in combination of two or more. Further, a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

Among the above tetracarboxylic dianhydrides, pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic acid, from the viewpoint of easily reducing _{the Hz a of the optical film and easily increasing the breakdown point strain and the elastic ratio.} Dihydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'- Biphenyltetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 4,4' -(Hexafluoroisopropyridene) diphthalic dianhydride, and mixtures thereof are preferred, pyromellitic dianhydride (PMDA), 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA). And 4,4'-(hexafluoroisopropyridene) diphthalic acid dianhydride (6FDA), and mixtures thereof are more preferred, and 4,4'-(hexafluoroisopropyridene) diphthalic acid dianhydride (6FDA) is further preferred. preferable.

Examples of the dicarboxylic acid compound used in the synthesis of the resin include aromatic dicarboxylic acids, aliphatic dicarboxylic acids and their related acid chloride compounds, acid anhydrides, and the like, and two or more of them may be used in combination. Specific examples include terephthalic acid; 2,5-bis (trifluoromethyl) terephthalic acid; isophthalic acid; 2,5-dimethylterephthalic acid; 2,5-dimethoxyterephthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyl. Dicarboxylic acid; 3,3'-biphenyldicarboxylic acid; 2,2'-bis (trifluoromethyl) -4,4'-biphenyldicarboxylic acid; dicarboxylic acid compound of chain hydrocarbon having 8 or less carbon atoms and two Compounds in which benzoic acid is linked by a single bond, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- or a phenylene group, and their acid chloride compounds are listed. Be done. Among these dicarboxylic acid compounds, easily reduced Hz _a of the optical film, and the yield point strain and elastic modulus from the enhanced easily viewpoint, 4,4'-oxybis benzoic acid, terephthalic acid, isophthalic acid, 2,5 Dimethylterephthalic acid, 2,5-dimethoxyterephthalic acid, 2,5-bis (trifluoromethyl) terephthalic acid, 2,2'-bis (trifluoromethyl) -4,4'-biphenyldicarboxylic acid and their acid chlorides , 5,5-dimethylterephthalic acid chloride (DMTPC), 2,5-dimethoxyterephthalic acid chloride (MOTPC), 2,5-bis (trifluoromethyl) terephthalic acid chloride (6FTPC), terephthaloyl chloride (TPC). ), Isophthaloyl chloride is more preferable, and terephthaloyl chloride (TPC) and 2,5-dimethoxyterephthalic acid chloride (MOTPC) are further preferable.

The polyimide resin contains other tetracarboxylic acids and tricarboxylic acids, and their anhydrides and derivatives, in addition to the tetracarboxylic acid compounds used in the resin synthesis, as long as the various physical properties of the optical film are not impaired. It may be further reacted.

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

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, acid chloride compounds related thereto, acid anhydrides, and the like, and two or more of them may be used in combination. Specific examples include an anhydride of 1,2,4-benzenetricarboxylic acid; an acid chloride compound of 1,3,5-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthal. A compound in which an acid anhydride and a benzoic acid are single-bonded, -O-, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- or a phenylene group. Can be mentioned.

Examples of the diamine compound used in the synthesis of the resin include aliphatic diamines, aromatic diamines and mixtures thereof. In addition, in this embodiment, "aromatic diamine" represents a diamine in which an amino group is directly bonded to an aromatic ring, and an aliphatic group or other substituent may be contained in a part of the structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferable. Further, the "aliphatic diamine" represents a diamine in which an amino group is directly bonded to an aliphatic group, and an aromatic ring or other substituent may be contained as a part of the structure thereof.

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

Examples of the aromatic diamine include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylene diamine, p-xylylene diamine, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene and the like. , 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'-diaminodiphenylsulfone, 3,4′-diaminodiphenylsulfone, 3,3′-diaminodiphenylsulfone, 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 (with TFMB) (May be described), 4,4'-(hexafluoropropyridene) dianiline (may be described as 6FDAM), 4,4'-bis (4-aminophenoxy) biphenyl, 9,9-bis (4) -Aminophenyl) fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9,9-bis (4-amino-3) Examples thereof include aromatic diamines having two or more aromatic rings, such as −fluorophenyl) fluorene. These can be used alone or in combination of two or more.

As the aromatic diamine, preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,3'-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, more preferably 4,4'-diaminodiphenylmethane, 4,4'-diamino Diphenyl propane, 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' -(Hexafluoropropylidene) dianiline (6FDAM), 4,4'-bis (4-aminophenoxy) biphenyl. These can be used alone or in combination of two or more.

Among the above diamine compounds, 2,2'-dimethylbenzidine and 2,2'-bis (trifluoromethyl) -4 are easy to reduce _{the Hz a of the optical film and increase the yield point strain and elastic modulus.} , 4'-diaminodiphenyl (TFMB), 4,4'-bis (4-aminophenoxy) biphenyl, 4,4'-(hexafluoropropyridene) dianiline (6FDAM) and 4,4'-diaminodiphenyl ether It is more preferable to use one or more selected from 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl (TFMB) and / or 4,4'-(hexafluoropropyridene) dianiline. It is more preferable to use (6FDAM).

In the production of the polyimide resin, the amount of the diamine compound, the tetracarboxylic acid compound and the dicarboxylic acid compound used can be appropriately selected according to the ratio of each structural unit of the desired resin.

In the polyimide 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 10 to 200 ° C., and more preferably 20 to 100 ° C. .. The reaction time is also not particularly limited, but is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out under conditions of an inert atmosphere or reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and / or an atmosphere of an inert gas with stirring. The reaction is preferably carried out in a solvent inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, and for example, water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, etc. Alcohol-based solvents such as 2-butoxyethanol and propylene glycol monomethyl ether; ester-based 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 and heptane; alicyclic hydrocarbon solvents such as ethyl cyclohexane; toluene and xylene Aromatic hydrocarbon solvents such as; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amides such as N, N-dimethylacetamide and N, N-dimethylformamide. Examples thereof include sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvents). Among these, an amide-based solvent can be preferably used from the viewpoint of solubility.

In a preferred embodiment of the present invention, the method for producing a polyamide-imide resin containing the above-mentioned structural unit (1) and the above-mentioned structural unit (2) is not particularly limited as long as the above-mentioned polyamide-imide resin can be obtained, but the Hz _{a of the optical film is not particularly limited.} This is a production method in which a diamine compound, a tetracarboxylic acid compound, and a dicarboxylic acid compound are reacted from the viewpoint of easily reducing the yield point strain and increasing the elastic coefficient. It is preferable to produce a polyamide-imide resin, which is a step (I) of reacting a diamine compound with a tetracarboxylic acid compound to produce an intermediate (A), and a reaction between the intermediate (A) and a dicarboxylic acid compound. It is more preferable to produce a polyamide-imide resin by a method of dividing and adding the dicarboxylic acid compound in the step (II), which comprises the step (II) of causing the dicarboxylic acid compound to be added. When the method of adding the dicarboxylic acid compound in portions is used, the reason is not clear, but it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. Further, the weight average molecular weight of the polyamide-imide resin can be easily adjusted within the above range.

Therefore, the polyamideimide resin contained in the optical film of the present invention is a production method in which a diamine compound, a tetracarboxylic acid compound, and a dicarboxylic acid compound are reacted, and the resin is produced by a production method in which the dicarboxylic acid compound is separately added. The step (I) of reacting the diamine compound with the tetracarboxylic acid compound to produce the intermediate (A), and the step (II) of reacting the intermediate (A) with the dicarboxylic acid compound. ), The resin produced by the production method in which the dicarboxylic acid compound is divided and added in the step (II) is more preferable. Further, when the solvent is further added in the step (II), _{it is easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. Examples of the solvent include the above-exemplified solvents.

When the polyamide-imide resin is produced by the production method including the above steps (I) and (II), the reaction of the step (I) of reacting the diamine compound with the tetracarboxylic acid compound to produce the intermediate (A). The temperature is not particularly limited, but may be, for example, 5 to 200 ° C., preferably 10 to 100 ° C., more preferably 15 to 50 ° C., and even more preferably 20 to 30 ° C. The reaction time may be, for example, 1 minute to 72 hours, preferably 10 minutes to 24 hours. Further, the reaction may be carried out in the air or in an atmosphere of an inert gas such as nitrogen or argon with stirring, or may be carried out under normal pressure, pressure or reduced pressure. In a preferred embodiment, the operation is carried out under normal pressure and / or the atmosphere of the inert gas with stirring.

In step (I), the diamine compound and the tetracarboxylic acid compound react to form the intermediate (A), that is, the polyamic acid. Therefore, the intermediate (A) contains a structural unit derived from a diamine compound and a structural unit derived from a tetracarboxylic acid compound.

Next, in the step (II), it is preferable to react the intermediate (A) with the dicarboxylic acid compound, and here, the dicarboxylic acid compound is added in portions. The dicarboxylic acid compound is dividedly added to the reaction solution obtained in the step (I), and the intermediate (A) and the dicarboxylic acid compound are reacted. By adding the dicarboxylic acid compound in portions instead of adding them all at once, it is _{easy to reduce the Hz a} of the optical film, and it is easy to increase the yield point strain and the elastic modulus. In addition, the weight average molecular weight of the polyamide-imide resin can be easily adjusted to the above-mentioned preferable range. In the present specification, the divided addition means that the dicarboxylic acid compound to be added is added in several times, and more specifically, the dicarboxylic acid to be added is divided into specific quantities and separated by a predetermined interval or a predetermined time, respectively. Means to add. Since the predetermined interval or predetermined time also includes a very short interval or time, the divided addition also includes continuous addition or continuous feed.

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

The dicarboxylic acid compound may be added in equal amounts or in non-uniform amounts. The time between each addition (hereinafter, may be referred to as an addition interval) may be the same or different. When two or more kinds of 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 particularly limited. However, for example, each dicarboxylic acid compound may be added separately in a batch or in divided amounts, each dicarboxylic acid compound may be added in divided amounts together, or a combination thereof may be used.

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

The reaction temperature in step (II) is not particularly limited, but may be, for example, 5 to 200 ° C., preferably 10 to 100 ° C., more preferably 15 to 50 ° C., and even more preferably 20 to 30 ° C. Further, the reaction may be carried out in the air or in an atmosphere of an inert gas such as nitrogen or argon with stirring, or may be carried out under normal pressure, pressurization or reduced pressure. In a preferred embodiment, step (II) is carried out with stirring under normal pressure and / or the atmosphere of the inert gas.

In the step (II), the dicarboxylic acid compound is dividedly added and then reacted by stirring for a predetermined time or the like to obtain a polyamide-imide precursor. The polyamide-imide precursor can be isolated, for example, by adding a large amount of water or the like to a reaction solution containing the polyamide-imide precursor, precipitating 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 polyamide-imide precursor. Therefore, the polyamide-imide precursor indicates a pre-imidized (pre-ring ring) polyamide-imide containing 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.

The method for producing a polyamide-imide resin may further include a step (III) of imidizing the polyamide-imide precursor in the presence of an imidization catalyst. By subjecting the polyamide-imide precursor obtained in step (II) to step (III), the structural unit portion having a polyamic acid structure among the structural units of the polyamide-imide precursor is imidized (closed), and the formula ( A polyamide-imide resin containing a structural unit represented by 1) and a structural unit represented by the formula (2) can be obtained. Examples of imidization catalysts include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidin, N-propylpiperidin, N-butylpyrrolidin, N-butylpiperidin, and N-propylhexahydro. Alicyclic amines such as azepine (monocyclic); azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane, and azabicyclo [3.2. 2] Alicyclic amines such as nonane (polycyclic); and pyridine, 2-methylpyridine (2-picolin), 3-methylpyridine (3-picolin), 4-methylpyridine (4-picolin), 2- Ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and Examples include aromatic amines such as isoquinolin. Further, from the viewpoint of easily accelerating 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 the imidization reaction, and specific examples thereof include acetic anhydride, propionic anhydride, butyric anhydride and other aliphatic acid anhydrides, and phthalic acid and other aromatics. Acid anhydride and the like can be mentioned.

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

<Additives>
The optical film of the present invention may contain at least one filler in addition to the resin. Examples of the filler include organic particles and inorganic particles, and preferably inorganic particles. Examples of the inorganic particles include metal oxide particles such as silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (ITO), antimony oxide, and cerium oxide, magnesium fluoride, and foot. Examples thereof include metal fluoride particles such as sodium oxide. Among these, silica particles, zirconia particles, and alumina particles are preferable from the viewpoint of easily increasing the elasticity and bending resistance of the optical film _{and easily reducing Hz a.} , 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, still more preferably 15 nm or more, particularly preferably 20 nm or more, preferably 100 nm or less, more preferably. It is 90 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, particularly preferably 60 nm or less, particularly more preferably 50 nm or less, and particularly preferably 40 nm or less. When the average primary particle size of the silica particles is within the above range, the elastic modulus and bending resistance of the optical film can be easily increased, and Hz _a can be easily reduced. In addition, it is easy to suppress the aggregation of silica particles and improve the optical characteristics of the obtained optical film. The average primary particle size of the filler can be measured by the BET method. The average primary particle size may be measured by image analysis of a transmission electron microscope or a scanning electron microscope.

When the optical film of the present invention contains a filler, preferably silica particles, the content of the filler is preferably 30% by mass from the viewpoint of easily increasing the breakdown point distortion of the optical film with respect to 100% by mass of the mass of the optical film. % Or less, more preferably 20% by mass or less, still more preferably 10% by mass or less, preferably 0.1% by mass from the viewpoint of easily _{increasing the elastic modulus and bending resistance of the optical film and easily reducing Hz a.} % Or more, more preferably 1% by mass or more, still more preferably 5% by mass or more.

The optical film of the present invention may further contain an ultraviolet 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 contain 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 UV absorber can be used alone or in combination of two or more. Since the optical film contains an ultraviolet absorber, deterioration of the resin is suppressed, so that visibility can be improved when the optical film is applied to an image display device or the like. As used herein, the term "system compound" refers to a derivative of a compound to which the "system compound" is attached. For example, the "benzophenone-based compound" refers to a compound having benzophenone as a maternal skeleton and a substituent attached to benzophenone.

When the optical film contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 3% by mass, based on 100% by mass of the optical film. % Or more, preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 6% by mass or less. The suitable content varies depending on the UV absorber used, but if the content of the UV absorber is adjusted so that the light transmittance at 400 nm is about 20 to 60%, the light resistance of the optical film is enhanced and the transparency is improved. Easy to increase.

The optical film of the present invention may further contain additives other than the filler and the ultraviolet absorber. Other additives include, for example, antioxidants, mold release agents, stabilizers, brewing agents, flame retardants, pH regulators, silica dispersants, lubricants, thickeners, leveling agents and the like. When other additives are contained, the content thereof is preferably 0.001 to 20% by mass, more preferably 0.01 to 15% by mass, still more preferably 0, based on 100% by mass of the optical film. It may be 1 to 10% by mass.

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

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

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, the impact resistance can be enhanced, the bending resistance is less likely to decrease, and the problem of curl generation due to curing shrinkage tends to be less likely 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 by applying thermal energy, and a hard coat layer is preferably formed by irradiation with active energy rays. Active energy rays are defined as energy rays that can generate active species by decomposing compounds that generate active species, and are visible light, ultraviolet rays, infrared rays, X-rays, α rays, β rays, γ rays, and electron beams. And the like, preferably ultraviolet rays. The hard coat composition contains at least one polymer of a radically polymerizable compound and a cationically polymerizable compound.

The radically polymerizable compound is a compound having a radically polymerizable group. The radically polymerizable group contained in the radically polymerizable compound may be a 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. , (Meta) acryloyl group and the like. When the radically polymerizable compound has two or more radically polymerizable groups, these radically polymerizable groups may be the same 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. Examples of the radically polymerizable compound include compounds having a (meth) acryloyl group, preferably from the viewpoint of high reactivity, and specifically, 2 to 6 (meth) acryloyl groups in one molecule. Compounds called polyfunctional acrylate monomers and epoxy (meth) acrylates, urethane (meth) acrylates, and polyester (meth) acrylates have a molecular weight of several hundreds of (meth) acryloyl groups in the molecule. Thousands of oligomers are mentioned, preferably one or more selected from epoxy (meth) acrylates, urethane (meth) acrylates and polyester (meth) acrylates.

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.
Further, as the cationically polymerizable compound, a compound having at least one of an epoxy group and an oxetanyl group as the cationically polymerizable group is preferable. A cyclic ether group such as an epoxy group or an oxetanyl group is preferable because the shrinkage associated with the polymerization reaction is small. Further, among the cyclic ether groups, compounds having an epoxy group are easily available, compounds having various structures are easily available, the durability of the obtained hard coat layer is not adversely affected, and compatibility with radically polymerizable compounds is easily controlled. There is an advantage. Further, among the cyclic ether groups, the oxetanyl 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. There are advantages such as forming an independent network without leaving unreacted monomers in the film even in the region where the polymer is formed.
Examples of the cationically polymerizable compound having an epoxy group include polyglycidyl ether of a polyhydric alcohol having an alicyclic ring, or a cyclohexene ring or cyclopentene ring-containing compound with an appropriate oxidizing agent such as hydrogen peroxide or peracid. Alicyclic epoxy resin obtained by epoxidation; polyglycidyl ether of aliphatic polyhydric alcohol or its alkylene oxide adduct, polyglycidyl ester of aliphatic long chain polybasic acid, homopolymer of glycidyl (meth) acrylate, An aliphatic epoxy resin such as a copolymer; a glycidyl ether produced by reacting bisphenols such as bisphenol A, bisphenol F and hydrogenated bisphenol A, or derivatives such as alkylene oxide adducts and caprolactone adducts thereof with epichlorohydrin. And glycidyl ether type epoxy resin which is a novolak epoxy resin and is derived from bisphenols and the like.

The hard coat composition may further contain a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and a cationic polymerization initiator, and the like, which are appropriately selected and used. These polymerization initiators are decomposed by at least one of activation energy ray irradiation and heating to generate radicals or cations to promote radical polymerization and cation polymerization.
The radical polymerization initiator may be any as long as it can release a substance that initiates radical polymerization by at least one of irradiation with active energy rays and heating. For example, examples of the thermal radical polymerization initiator include organic peroxides such as hydrogen peroxide and perbenzoic acid, and azo compounds such as azobisbutyronitrile.
Active energy ray radical polymerization initiators include Type 1 radical polymerization initiators, which generate radicals by decomposition of molecules, and Type 2 radical polymerization initiators, which coexist with tertiary amines and generate radicals by hydrogen abstraction type reactions. Yes, they are used alone or in combination.
The cationic polymerization initiator may be any one as long as it can release a substance that initiates cationic polymerization by at least one of activation energy ray irradiation and heating. As the cationic polymerization initiator, an aromatic iodonium salt, an aromatic sulfonium salt, a cyclopentadienyl iron (II) complex and the like can be used. These can initiate cationic polymerization by either irradiation with active energy rays or heating, depending on the difference in structure.

The polymerization initiator can preferably contain 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 proceed sufficiently, and the mechanical properties and adhesive strength of the finally obtained coating film can be in a good range. Poor adhesive strength due to curing shrinkage, cracking phenomenon, and curling phenomenon tend to be less likely to occur.

The hard coat composition may further comprise one or more selected from the group consisting of solvents and additives.
The solvent can dissolve or disperse the polymerizable compound and the polymerization initiator, and any solvent known as a solvent for hard coat compositions in the present art does not impair the effects of the present invention. In the range, it can be used.
The additive may further contain inorganic particles, a leveling agent, a stabilizer, a surfactant, an antistatic agent, a lubricant, an antifouling agent and the like.

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

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

The adhesive layer may be a layer called a pressure-sensitive adhesive (Pressure Sensitive Adhesive, PSA), which is attached to an object by pressing. The pressure-sensitive adhesive may be an adhesive that is "a substance that has adhesiveness at room temperature and adheres to an adherend with a light pressure" (JIS K 6800), and "protects a specific component (microcapsules). ), It may be a capsule type adhesive which is an adhesive which can maintain stability until the film is destroyed by an appropriate means (pressure, heat, etc.) ”(JIS K 6800).

The hue adjusting layer is a layer having a hue adjusting function, and is a layer capable of adjusting an optical film to a desired hue. The hue adjusting layer is, for example, a layer containing a resin and a colorant. Examples of this colorant include inorganic pigments such as titanium oxide, zinc oxide, petals, titanium oxide-based calcined pigments, ultramarine, cobalt aluminate, and carbon black; azo compounds, quinacridone compounds, anthracinone compounds, and the like. 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 thereof include dyes such as acidic dyes and medium dyes.

The refractive index adjusting layer is a layer having a function of adjusting the refractive index, for example, a layer having a refractive index different from that of a single-layer optical film and capable of imparting a predetermined refractive index to the optical film. The refractive index adjusting layer may be, for example, a resin layer appropriately selected and, in some cases, a resin layer further containing a pigment, or a thin film of metal. Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide and tantalum oxide. The average primary particle size of the pigment may be 0.1 μm or less. By setting the average primary particle size of the pigment to 0.1 μm or less, diffuse reflection of light transmitted through the refractive index adjusting layer can be prevented, and deterioration of 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. Oxides or metal nitrides can be mentioned.

In one embodiment of the present invention, the optical film may have a protective film on at least one side (one side or both sides). For example, when the functional layer is provided on one side of the optical film, the protective film may be laminated on the surface on the optical film side or the surface on the functional layer side, and is laminated on both the optical film side and the functional layer side. You may. When the optical film has functional layers on both sides, the protective film may be laminated on the surface on one functional layer side or on the surfaces on both functional layer sides. The protective film is a film for temporarily protecting the surface of the optical film or the functional layer, and is not particularly limited as long as it 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, and the like, and polyolefin resin films and polyethylene. It is preferable to select from the group consisting of a terephthalate resin film and an acrylic resin film. When the optical film has two protective films, each protective film may be the same or different.

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

[Manufacturing method of optical film]
The optical film of the present invention is not particularly limited, but for example, the following steps:
(A) A step of preparing a liquid containing the resin (sometimes referred to as a resin varnish) (varnish preparation step),
(B) A step of applying a resin varnish to a base material to form a coating film (coating step), and (c) a step of drying the applied liquid (coating film) to form an optical film (optical film formation). Process)
It can be manufactured by a method including.

In the varnish preparation step, the varnish is prepared by dissolving the resin in a solvent, adding the additive if necessary, and stirring and mixing.

The solvent used for preparing the varnish is not particularly limited as long as the resin can be dissolved. Examples of such a solvent include amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; lactone solvents such as γ-butyrolactone and γ-valerolactone; sulfur-containing solvents such as dimethyl sulfoxide, dimethyl sulfoxide and sulfolane. System solvents; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof can be mentioned. Among these, an amide solvent or a lactone solvent is preferable. These solvents can be used alone or in combination of two or more. Further, the resin varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent and the like. The solid content concentration of the varnish is preferably 1 to 25% by mass, more preferably 5 to 15% by mass. In the present specification, the solid content of the varnish indicates the total amount of the components of the varnish excluding the solvent.

In the coating step, a varnish is applied onto the substrate by a known coating method to form a coating film. Known coating methods include, 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, and the like. Examples include a spray method and a salivation molding method.

In the optical film forming step, the optical film can be formed by drying the coating film and peeling it from the base material. After the peeling, a drying step of further drying the optical film may be performed. The coating film can be dried at a temperature of usually 50 to 350 ° C. In order to obtain a film having a low YI value, the temperature is preferably 300 ° C. or lower, more preferably 250 ° C. or lower, and even more preferably 230 ° C. or lower. Further, from the viewpoint of reducing the haze and YI value of the bent portion in a high temperature and high humidity environment, the drying treatment time at 180 ° C. or higher is preferably 120 minutes or less, more preferably 90 minutes or less, 60. It is more preferably minutes or less, and particularly preferably 50 minutes or less. On the other hand, if the drying treatment is insufficient, the haze may increase in a high temperature and high humidity environment. From this point of view, the maximum drying temperature is preferably 100 ° C. or higher, more preferably 150 ° C. or higher, still more preferably 180 ° C. or higher. The drying time is preferably 10 minutes or longer, more preferably 20 minutes or longer, and even more preferably 30 minutes or longer. If necessary, the coating film may be dried under an inert atmosphere or under reduced pressure conditions.

Examples of the base material include PET film, PEN film, other polyimide-based resin, polyamide-based resin film, and the like. Among them, PET film, PEN film and the like are preferable from the viewpoint of excellent heat resistance, and PET film is more preferable from the viewpoint of adhesion to the optical film and cost.

In the present invention, the composition of the optical film, for example, the type and composition ratio of the repeating constituent units constituting the resin contained in the optical film; the production conditions of the resin; the thickness of the optical film; or the production conditions of the optical film, etc. are appropriately adjusted. In particular _{, the breakdown point distortion and Hz a} can be adjusted within the range of the present invention by appropriately combining the above-described embodiments as those that easily reduce _{the Hz a of the optical film and easily increase the breakdown point distortion.} For example, the structural units represented by the formulas (1) and (2) are used as the structural units of the resin, and the Hz _{a of the optical film is set particularly at X, Y and Z in the formulas (1) and (2). The yield point strain and Hz a} can be obtained by appropriately combining the above-mentioned ones as those described above as those that can be easily reduced and easily increase the yield point strain, or by adopting the divisional addition of a dicarboxylic acid or the like as a method for producing the resin. May be adjusted to the scope of the present invention.
Further, for example, Y in the formula (1) is a structural unit represented by the formula (4a) and / or the formula (4b), and Z in the formula (2) is the formula (3) and / or the formula (3'). The structural unit represented, when X in the formula (1) and / or the formula (2) uses the structural unit represented by the formula (34) (or the formula (32)), or when these structures are suitable as described above. When used in a range, the breakdown point distortion and Hz _a can be easily adjusted to the range of the present invention. In particular, among the structural units constituting the polyamide-imide resin, Y in the formula (1) is the structural unit represented by the formula (32'), and X in the formula (1) and / or the formula (2) is the formula ( _{The breakdown point strain and Hz a} may be adjusted to the range of the present invention by including the structural units having the structure represented by 32'), preferably by adjusting the ratio of these structural units to the above range. ..
Further, the optical film may contain a filler, preferably appropriately contained in the above range, _{to adjust Hz a} to the range of the present invention. As the filler content increases _{, both Hz a} and yield point strain tend to decrease, and conversely, as the filler content decreases _{, both Hz a} and yield point strain tend to increase. Therefore, when the optical film contains a filler, the filler content may be adjusted according to the _{Hz a and the yield point strain value of the optical film itself.}

The optical film of the present invention can be suitably used as a front plate (hereinafter, may be referred to as a window film) of a display device, particularly a flexible display device. The front plate has a function of protecting the display element of the flexible display device. Examples of display devices include wearable devices such as televisions, smartphones, mobile phones, car navigation systems, tablet PCs, portable game machines, electronic papers, indicators, bulletin boards, watches, and smart watches. Examples of the flexible display include display devices having flexible characteristics, such as televisions, smartphones, mobile phones, and smart watches.

[Flexible display device]
The present invention includes 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 may be referred to as a window film. The flexible display device includes a laminate for a flexible display device and an organic EL display panel, and the laminate for the flexible display device is arranged on the visual side with respect to the organic EL display panel and is configured to be bendable. The laminated body for the flexible display device may further contain a polarizing plate and a touch sensor, and the stacking order thereof is arbitrary, but from the visual side, a window film, a polarizing plate, a touch sensor or a window film, and a touch sensor. , It is preferable that the polarizing plates are laminated in this order. It is preferable that the polarizing plate is present on the visual side of the touch sensor because the pattern of the touch sensor is difficult to see and the visibility of the displayed image is improved. Each member can be laminated using an adhesive, an adhesive, or the like. Further, a light-shielding pattern formed on at least one surface of any layer of the window film, the polarizing plate, and the touch sensor can be provided.

〔Polarizer〕
As described above, the flexible display device of the present invention preferably further includes a polarizing plate, particularly a circular polarizing plate. The circular polarizing plate is a functional layer having a function of transmitting only a right circularly polarized light component or a left circularly polarized light component by laminating a λ / 4 retardation plate on a linear polarizing plate. For example, the external light is converted to right-handed circularly polarized light and reflected by the organic EL panel to block the left-handed circularly polarized light, and only the light emitting component of the organic EL is transmitted to suppress the influence of the reflected light. It is used to make it easier to see. In order to achieve the circularly polarized light function, the absorption axis of the linear polarizing plate and the slow axis of the λ / 4 retardation plate need to be theoretically 45 °, but practically, they are 45 ± 10 °. The linear polarizing plate and the λ / 4 retardation plate do not necessarily have to be laminated adjacent to each other, and the relationship between the absorption axis and the slow phase axis may satisfy the above range. It is preferable to achieve perfect circularly polarized light at all wavelengths, but it is not always necessary in practical use. Therefore, the circularly polarizing plate in the present invention also includes an elliptical polarizing plate. It is also preferable to further laminate a λ / 4 retardation film on the visible side of the linear polarizing plate to convert the emitted light into circularly polarized light to improve the visibility when wearing polarized sunglasses.

The linear polarizing plate is a functional layer having a function of transmitting light vibrating in the transmission axis direction but blocking polarization of a vibration component perpendicular to the linear polarizing plate. The linear polarizing plate may be configured to include a linear polarizing element alone or a linear polarizing element 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 of the linear polarizing plate is within the above range, the flexibility of the linear polarizing plate tends to be difficult to decrease.

The linear polarizer may be a film-type polarizer produced by dyeing and stretching a polyvinyl alcohol (hereinafter, may be abbreviated as PVA) -based film. A dichroic dye such as iodine is adsorbed on the PVA-based film oriented by stretching, or the dichroic dye is oriented in a state of being adsorbed on the PVA to exhibit polarization performance. In the production of the film-type polarizer, other steps such as swelling, cross-linking with boric acid, washing with an aqueous solution, and drying may be included. The stretching and dyeing steps may be performed on the PVA-based film alone, or may be performed in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA-based film used is preferably 10 to 100 μm, and the draw ratio is preferably 2 to 10 times.
Further, as another example of the polarizer, there is a liquid crystal coating type polarizing element formed by coating a liquid crystal polarizing composition. The liquid crystal polarizing composition may contain a liquid crystal compound and a dichroic dye compound. The liquid crystal compound may have a property of exhibiting a liquid crystal state, and is preferable if it has a higher-order orientation state such as a smectic phase because it can exhibit high polarization performance. Further, the liquid crystal compound preferably has a polymerizable functional group.
The dichroic dye compound is a dye that is oriented together with the liquid crystal compound and exhibits dichroism, and may have a polymerizable functional group, and the dichroic dye itself has a liquid crystal property. May be.
Any of the compounds contained in the liquid crystal polarizing composition has a polymerizable functional group. The liquid crystal polarizing composition can 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 polarizing layer is manufactured by applying a liquid crystal polarizing composition on an alignment film to form a liquid crystal polarizing layer. The liquid crystal polarizing layer can be formed to be thinner than the film-type polarizing element, and the thickness is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.

The alignment film is produced, for example, by applying an alignment film forming composition on a base material and imparting orientation by rubbing, polarized light irradiation, or the like. The alignment film forming composition contains an alignment agent, and may further contain a solvent, a cross-linking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like. Examples of the alignment agent include polyvinyl alcohols, polyacrylates, polyamic acids, and polyimides. When an orientation agent that imparts orientation by polarization irradiation is used, it is preferable to use an orientation agent containing a synnamate group. The weight average molecular weight of the polymer used as the alignment agent is, for example, about 10,000 to 1,000,000. The thickness of the alignment film is preferably 5 to 10,000 nm, and more preferably 10 to 500 nm in that the alignment regulating force is sufficiently exhibited.
The liquid crystal polarizing layer can be peeled off from the base material, transferred and laminated, or the base material can be laminated as it is. It is also preferable that the base material serves as a transparent base material for a protective film, a retardation plate, and a window film.

As the protective film, any transparent polymer film may be used, and the same materials and additives used for the transparent base material of the window film can be used. Further, it may be a coating type protective film obtained by applying a cationic curing composition such as an epoxy resin or a radical curing composition such as acrylate and curing the film. The protective film may be a plasticizer, an ultraviolet absorber, an infrared absorber, a colorant such as a pigment or a dye, a fluorescent whitening agent, a dispersant, a heat stabilizer, a light stabilizer, an antioxidant, an antioxidant, if necessary. , Lubricants, solvents and the like may be contained. The thickness of the protective film is preferably 200 μm or less, more preferably 1 to 100 μm. When the thickness of the protective film is in the above range, the flexibility of the film tends to be difficult to decrease.

The λ / 4 retardation plate is a film that gives a λ / 4 phase difference in a direction orthogonal to the traveling direction of incident light, in other words, in the in-plane direction of the film. The λ / 4 retardation plate may be a stretch-type retardation plate manufactured by stretching a polymer film such as a cellulose-based film, an olefin-based film, or a polycarbonate-based film. The λ / 4 retardation plate may be used as a retardation adjuster, a plastic agent, an ultraviolet absorber, an infrared absorber, a colorant such as a pigment or a dye, a fluorescent whitening agent, a dispersant, a heat stabilizer, and a light stabilizer. It may contain an agent, an antioxidant, an antioxidant, a lubricant, a solvent and the like.
The thickness of the stretched retardation plate is preferably 200 μm or less, more preferably 1 to 100 μm. When the thickness of the stretchable retardation plate is within the above range, the flexibility of the stretchable retardation plate tends to be difficult to decrease.
Further, as another example of the λ / 4 retardation plate, there is a liquid crystal coating type retardation plate formed by coating a liquid crystal composition.
The liquid crystal composition contains a liquid crystal compound exhibiting a liquid crystal state such as nematic, cholesteric, and smectic. The liquid crystal compound has a polymerizable functional group.
The liquid crystal composition can 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 applying a liquid crystal composition on a substrate and curing the liquid crystal composition to form a liquid crystal retardation layer, similarly to the liquid crystal polarizing layer. The liquid crystal coating type retardation plate can be formed to be thinner than the stretch type retardation plate. The thickness of the liquid crystal polarizing layer is preferably 0.5 to 10 μm, more preferably 1 to 5 μm.
The liquid crystal coating type retardation plate can be peeled off from the base material, transferred and laminated, or the base material can be laminated as it is. It is also preferable that the base material serves as a transparent base material for a protective film, a retardation plate, and a window film.

In general, there are many materials that exhibit larger birefringence at shorter wavelengths and smaller birefringence at longer wavelengths. In this case, since it is not possible to achieve a phase difference of λ / 4 in the entire visible light region, the in-plane phase difference is preferably 100 to 4 so that it becomes λ / 4 with respect to the vicinity of 560 nm, which has high visual sensitivity. It is designed to be 180 nm, more preferably 130-150 nm. An inversely dispersed λ / 4 retardation plate using a material having a double refractive index wavelength dispersion characteristic opposite to the usual one is preferable in that visibility is improved. As such a material, for example, a stretchable retardation plate can be used as described in JP-A-2007-232873, and a liquid crystal-coated retardation plate can be used as described in JP-A-2010-30979. ..
Further, as another method, a technique for obtaining a wideband λ / 4 retardation plate by combining with a λ / 2 retardation plate is also known (for example, Japanese Patent Application Laid-Open No. 10-90521). The λ / 2 retardation plate is also manufactured by the same material method as the λ / 4 retardation plate. The combination of the stretchable retardation plate and the liquid crystal coating type retardation plate is arbitrary, but the thickness can be reduced by using the liquid crystal coating type retardation plate in both cases.
A method of laminating a positive C plate on the circularly polarizing plate in order to improve visibility in an oblique direction is known (for example, Japanese Patent Application Laid-Open No. 2014-224738). The positive C plate may be a liquid crystal coating type retardation plate or a stretched retardation plate. The phase difference in the thickness direction of the retardation plate is preferably −200 to −20 nm, more preferably −140 to −40 nm.

[Touch sensor]
As described above, the flexible display device of the present invention preferably further includes a touch sensor. The touch sensor is used as an input means. Examples of the touch sensor include various types such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and a capacitance method, and a capacitance method is preferable.
The capacitive touch sensor is divided into an active region and an inactive region located outside the active region. The active area is an area corresponding to the area where the screen is displayed on the display panel, the area where the user's touch is sensed, and the inactive area is the non-display area where the screen is not displayed on the display device. It is an area corresponding to the area. The touch sensor is formed in a substrate having flexible characteristics, a sensing pattern formed in an active region of the substrate, and an inactive region of the substrate, and is connected to an external drive circuit via the sensing pattern and a pad portion. Each sensing line for can be included. As the substrate having flexible characteristics, the same material as the transparent substrate of the window film can be used.

The sensing pattern can 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 from each other. The first pattern and the second pattern are formed in the same layer, and each pattern must be electrically connected in order to sense the touched point. The first pattern is a form in which a plurality of unit patterns are connected to each other via a joint, but the second pattern has a structure in which a plurality of unit patterns are separated from each other in an island form, so that the second pattern is electrically operated. A separate bridge electrode is required for the connection. A well-known transparent electrode can be applied to the electrode for connecting the second pattern. Examples of the material of the transparent electrode include indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium zinc oxide (IZTO), and indium gallium zinc oxide (IGZO). , Cadmium tin oxide (CTO), PEDOT (poly (3,4-ethylenedioxythiophene)), carbon nanotubes (CNT), graphene, metal wire and the like, preferably ITO. These can be used alone or in combination of two or more. 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, and these may be used alone or in combination of two or more. Can be done.
The bridge electrode can be formed on the upper part of the insulating layer via the insulating layer on the upper part of the sensing pattern, the bridge electrode is formed on the substrate, and the insulating layer and the sensing pattern can be formed on the bridge electrode. The bridge electrode can be made of the same material as the sensing pattern, or it can be made of molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium or two or more alloys of these. it can.
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 as a layer covering the entire sensing pattern. In the case of a layer covering the entire sensing pattern, the bridge electrode can connect the second pattern through a contact hole formed in the insulating layer.

The touch sensor is induced by a difference in transmittance between a pattern region in which a sensing pattern is formed and a non-pattern region in which a sensing pattern is not formed, specifically, a difference in refractive index in these regions. An optical adjustment layer may be further included between the substrate and the electrode as a means for appropriately compensating for the difference in light transmittance. The optical control layer may contain an inorganic insulating material or an organic insulating material. The optical control layer can be formed by coating a photocurable composition containing a photocurable organic binder and a solvent on a substrate. The photocurable composition may further contain inorganic particles. The refractive index of the optical control layer can be increased by the inorganic particles.
The photocurable organic binder contains a copolymer of each monomer such as an acrylate-based monomer, a styrene-based monomer, and a carboxylic acid-based monomer, as long as the effects of the present invention are not impaired. be able to. 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.
Examples of the inorganic particles include zirconia particles, titania particles, alumina particles and the like.
The photocuring composition may further contain additives such as a photopolymerization initiator, a polymerizable monomer, and a curing aid.

[Adhesive layer]
Each layer of the window film, circularly polarizing plate, touch sensor, etc., which forms the laminated body for the flexible display device, and the film members such as the linear polarizing plate, λ / 4 retardation plate, etc., which form each layer, are joined by an adhesive. Can be done. Examples of the adhesive include water-based adhesives, organic solvent-based adhesives, solvent-free adhesives, solid adhesives, solvent volatilization adhesives, water-based solvent volatilization adhesives, moisture-curable adhesives, heat-curable adhesives, and anaerobic adhesives. Curable type, active energy ray curable type adhesive, hardener mixed type adhesive, heat melt type adhesive, pressure sensitive type adhesive, pressure sensitive type adhesive, re-wet type adhesive, etc. It can be used, and preferably an aqueous solvent volatilization type adhesive, an active energy ray-curable adhesive, and an adhesive can be used. The thickness of the adhesive layer can be appropriately adjusted according to the required adhesive force and the like, and is preferably 0.01 to 500 μm, more preferably 0.1 to 300 μm. The laminated body for a flexible display device has a plurality of adhesive layers, and the thickness and type of each may be the same or different.

As the water-based solvent volatilization type adhesive, a polyvinyl alcohol-based polymer, a water-soluble polymer such as starch, an ethylene-vinyl acetate-based emulsion, a styrene-butadiene-based emulsion, or the like in an aqueous-dispersed state can be used as the main component polymer. In addition to the main polymer and water, 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 blended. When adhering with the water-based solvent volatilization type adhesive, the water-based solvent volatilization type adhesive can be injected between the layers to be adhered, the adherend layers are bonded, and then dried to impart adhesiveness. When the water-based solvent volatilization type adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 10 μm, more preferably 0.1 to 1 μm. When the water-based solvent volatilization type adhesive is used in a plurality of layers, the thickness and type of each layer may be the same or different.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material that is irradiated with active energy rays to form an adhesive layer. The active energy ray-curable composition can contain at least one polymer of a radical-polymerizable compound and a cationically polymerizable compound similar to those contained in the hard coat composition. As the radically polymerizable compound, the same compound as the radically polymerizable compound in the hard coat composition can be used.
As the cationically polymerizable compound, the same compound as the cationically polymerizable compound in the hard coat composition can be used.
As the cationically polymerizable compound used in the active energy ray-curing composition, an epoxy compound is preferable. It is also preferable to include a monofunctional compound as a reactive diluent in order to reduce the viscosity of the adhesive composition.

The active energy ray composition can contain a monofunctional compound in order to reduce the viscosity. Examples of the monofunctional compound include an acrylate-based monomer having one (meth) acryloyl group in one molecule and a compound having one epoxy group or oxetanyl group in one molecule, for example, glycidyl (meth). ) Examples include acrylate.
The active energy ray composition can further contain a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, radicals and cationic polymerization initiators, and these are appropriately selected and used. These polymerization initiators are decomposed by at least one of activation energy ray irradiation and heating to generate radicals or cations to promote radical polymerization and cation polymerization. In the description of the hard coat composition, an initiator that can initiate at least one of radical polymerization or cationic polymerization by irradiation with active energy rays can be used.
The active energy ray-curing composition further comprises an ion trapping agent, an antioxidant, a chain transfer agent, an adhesion imparting agent, a thermoplastic resin, a filler, a fluid viscosity modifier, a plasticizer, a defoaming agent solvent, an additive, and a solvent. Can be included. When two layers to be adhered are bonded by the active energy ray-curable adhesive, the active energy ray-curable composition is applied to either or both of the layers to be adhered, and then bonded to each layer. Alternatively, both layers to be adhered can be adhered by irradiating them with active energy rays and curing them. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.01 to 20 μm, more preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of adhesive layers, the thickness and type of the respective layers may be the same or different.

The pressure-sensitive adhesive is 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, and the like according to the main polymer, and any of them can be used. In addition to the main polymer, the pressure-sensitive adhesive may contain a cross-linking agent, a silane compound, an ionic compound, a cross-linking catalyst, an antioxidant, a tackifier, a plasticizing agent, a dye, a pigment, an inorganic filler and the like. A pressure-sensitive 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 onto a substrate, and then drying the mixture. To. The adhesive layer may be directly formed, or a separately formed base material may be transferred. It is also preferable to use a release film to cover the adhesive surface before bonding. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer is preferably 0.1 to 500 μm, more preferably 1 to 300 μm. When a plurality of layers of the pressure-sensitive adhesive are used, the thickness and type of the respective layers may be the same or different.

[Shading pattern]
The shading pattern can be applied as at least part of the bezel or housing of the flexible display device. The light-shielding pattern hides the wiring arranged at the edge of the flexible display device to make it difficult to see, thereby improving the visibility of the image. The shading 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 be various colors such as black, white, and metallic. The light-shielding pattern can be formed of a pigment for embodying color and a polymer such as an acrylic resin, an ester resin, an epoxy resin, polyurethane, or silicone. They can also be used alone or in mixtures of two or more. The shading pattern can be formed by various methods such as printing, lithography, and inkjet. The thickness of the shading pattern is preferably 1 to 100 μm, more preferably 2 to 50 μm. It is also preferable to give a shape such as an inclination in the thickness direction of the light-shielding pattern.

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples, but the present invention is not limited to the following Examples. Unless otherwise specified, "%" and "part" in the example mean mass% and parts by mass. First, the measurement and evaluation methods will be described.

<Hertz represented by _{Hz a} after the mandrel test at room temperature (25 ° C)>
The optical films obtained in Examples and Comparative Examples were cut into a size of 68 mm × 28 mm using a dumbbell cutter, and a mandrel test conforming to JIS K 5600-5: 1: 1999 was performed. In the mandrel test, it was bent evenly along a cylindrical mandrel with a bending radius of 1 mm at room temperature (25 ° C.). Immediately after that (1 to 2 seconds later), the bent optical film is returned to a flat surface, and a haze computer (mandrel test, "HGM-2DP") is used to remove the haze at the bent part in the mandrel test. It was measured.

<Haze after storage with a temperature of 85 ° C and a relative humidity of 85% in a bent state>
The optical films obtained in Examples and Comparative Examples were cut into a size of 68 mm × 28 mm using a dumbbell cutter, and the following durability test was performed. First, with a constant temperature and humidity constant environment durability tester (Yuasa System Equipment Co., Ltd., "CL09-type01D01-FSC90"), both ends of the bent optical film are held parallel and bent with a bending radius of 1 mm. It was stored for 24 hours in an environment with a temperature of 85 ° C. and a relative humidity of 85%. Then, the bent optical film was returned to a flat state and allowed to stand for 30 minutes in an environment of a temperature of 30 ° C. and a relative humidity of 50%. Then, the haze and YI value of the bent portion in the storage test were measured.

<Thickness of optical film>
The thickness of the optical film obtained in Examples and Comparative Examples was measured using an ABS digital indicator (“ID-C112BS” manufactured by Mitutoyo Co., Ltd.).

<Haze>
In accordance with JIS K 7136: 2000, the optical film after the mandrel test and after storage at a temperature of 85 ° C and a relative humidity of 85% in a bent state is cut into a size of 30 mm × 30 mm, and a haze computer (Suga Test Instruments Co., Ltd.) ), “HGM-2DP”) was used to measure the haze (%). In Examples 1 and 2, the hertz _{represented by Hz b} before the mandrel test was also measured.

<YI value>
Tristimulus values (V-670 manufactured by JASCO Corporation) were used for the optical film after the mandrel test and after storage at a temperature of 85 ° C and a relative humidity of 85% in a bent state. The YI value was calculated by obtaining X, Y, Z) and substituting it into the following formula.
YI = 100 × (1.2769X-1.0592Z) / Y
For Examples 1 and 2, the YI value before the mandrel test was also calculated.

<Total light transmittance>
In accordance with JIS K 7105: 1981, the total light transmittance (Tt) of the optical films obtained in Examples and Comparative Examples was measured by a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. ..

<Measurement of weight average molecular weight>
Gel Permeation Chromatography (GPC) Measurement (1) Pretreatment Method DMF eluent (10 mmol / L lithium bromide solution) is added to the polyamide-imide resin (sample) obtained in Examples and Comparative Examples to a concentration of 2 mg / mL. In addition, the solution was heated at 80 ° C. for 30 minutes with stirring, cooled, and filtered through a 0.45 μm membrane filter to prepare a measurement solution.
(2) Measurement condition Column: TSKgel α-2500 manufactured by Toso Co., Ltd. ((7) 7.8 mm diameter x 300 mm) x 1, α-M ((13) 7.8 mm diameter x 300 mm) x 2 eluent : 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 elastic modulus and yield point strain>
The elastic modulus of the optical films obtained in Examples and Comparative Examples at a temperature of 25 ° C. and a relative humidity of 50% was measured using "Autograph AG-IS" manufactured by Shimadzu Corporation. More specifically, a film having a width of 10 mm in length and width was produced, a stress-strain curve (SS curve) was measured under the conditions of a distance between chucks of 50 mm and a tensile speed of 20 mm / min, and the elastic modulus was calculated from the inclination.
The yield point strain was calculated as follows.
1. 1. Data arrangement of SS curve 10 consecutive points are sampled from the measurement start point on the SS curve and fitted to the quadratic function by the least squares method. After that, one point is excluded from the left side of the measurement start point and one point on the right side is added until the shape becomes convex upward by the quadratic function fitting of 10 points in the sampling range. Data organization ends when the fitting function becomes convex upward.
2. Calculation of tangent equations of SS curve 1. The slope and intercept are obtained by the least squares method from the n = i to jth (j = 2 to 50) data of the above data. After that, the kth (k = 1-48) to 49th data for the j-1 slopes are fitted to the linear function by the least squares method, and the slopes when the strain is 0 are obtained by extrapolation. The median value of the obtained 48 points is taken and defined as the slope of a straight line (tangent to the SS curve) when the strain is 0. The intercept is calculated in the same manner to obtain the tangent equation of the SS curve at zero strain.
3. 3. Calculation of yield point strain 2. The tangent line at strain 0 of the SS curve obtained in step 2 is translated by 0.2% in the strain direction. The strain value of the data in which the stress measurement data exceeds the stress of the translated straight line is defined as the yield point strain.

<Example 1>
Under a nitrogen gas atmosphere, 18.51 g (55.37 mmol) of 4,4'-(hexafluoroisopropyridene) dianiline (6FDAM) and 313.57 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and the mixture was stirred at room temperature. While doing so, 6FDAM was dissolved in DMAc. Next, 9.69 g (21.81 mmol) of 6FDA was added to the flask, and the mixture was stirred at room temperature for 3 hours. Then, 5.99 g (29.45 mmol) of TPC was added to the flask, and the mixture was stirred at room temperature for 30 minutes. Then, 313.57 g of DMAc was added and stirred for 10 minutes, then 0.66 g (3.27 mmоl) of TPC was further added to the flask, and the mixture was stirred at room temperature for 2 hours. Next, 3.05 g (32.72 mmol) of 4-methylpyridine and 15.59 g (152.69 mmol) of acetic anhydride were added, and the mixture was stirred at room temperature for 30 minutes, heated to 70 ° C. using an oil bath, and further 3 The mixture was stirred for a time to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of filaments, the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamide-imide resin (TPC / 6FDA / 6FDAM = 60/40/100 (molar ratio)). The weight average molecular weight of the polyamide-imide resin was 73,000.

The obtained polyamide-imide resin is dissolved in DMAc to prepare a 10% solution, and the obtained polyamide-imide varnish is filtered through a filter having an opening of 10 μm, and then a polyester base material (manufactured by Toyo Boseki Co., Ltd., trade name “A4100”). The self-supporting film was applied onto the smooth surface of the above using an applicator so as to have a thickness of 55 μm, dried at 50 ° C. for 30 minutes, and then dried at 140 ° C. for 15 minutes, and then the obtained coating film was peeled off from the polyester substrate. To obtain a self-supporting film. The free-standing film was fixed to a gold frame and further dried in the air at 200 ° C. for 40 minutes to obtain an optical film having a thickness of 50 μm. The Hz _b of the optical film was 0.3% and the YI was 1.7.
<Example 2>
Under a nitrogen gas atmosphere, 14.90 g (46.54 mmol) of TFMB and 250.00 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFBM was dissolved in DMAc while stirring at room temperature. Next, 4.16 g (9.35 mmol) of 6FDA was added to the flask, and the mixture was stirred at room temperature for 3 hours. Then, 7.85 g (33.68 mmol) of 2-methoxyterephthalic acid chloride (OMTPC) was added to the flask, and the mixture was stirred at room temperature for 30 minutes. Then, 313.57 g of DMAc was added and stirred for 10 minutes, then 0.87 g (3.74 mmоl) of OMTPC was further added to the flask, and the mixture was stirred at room temperature for 2 hours. Next, 3.49 g (37.42 mmol) of 4-methylpyridine and 6.69 g (65.48 mmol) of acetic anhydride were added, and the mixture was stirred at room temperature for 30 minutes, heated to 70 ° C. using an oil bath, and further 3 The mixture was stirred for a time to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of filaments, the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamide-imide resin (OMTPC / 6FDA / TFMB = 20/80/100 (molar ratio)). The weight average molecular weight of the polyamide-imide resin was 190,000.

The obtained polyamide-imide resin is dissolved in DMAc to prepare a 10% solution, and the obtained polyamide-imide varnish is filtered through a filter having an opening of 10 μm, and then a polyester base material (manufactured by Toyo Boseki Co., Ltd., trade name “A4100”). The self-supporting film was applied onto the smooth surface of the above using an applicator so as to have a thickness of 55 μm, dried at 50 ° C. for 30 minutes, and then dried at 140 ° C. for 15 minutes, and then the obtained coating film was peeled off from the polyester substrate. To obtain a self-supporting film. The free-standing film was fixed to a gold frame and further dried in the air at 200 ° C. for 40 minutes to obtain an optical film having a thickness of 50 μm. The Hz _b of the optical film was 0.3% and the YI was 1.9.

<Comparative example 1>
Under a nitrogen gas atmosphere, 40 g (124.91 mmol) of TFMB and 682.51 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 16.78 g (37.77 mmol) of 6FDA was added to the flask, and the mixture was stirred at room temperature for 3 hours. Then, 3.72 g (12.59 mmol) of OBBC and then 15.34 g (75.55 mmol) of TPC were added to the flask, and the mixture was stirred at room temperature for 1 hour. Next, 8.21 g (88.14 mmol) of 4-methylpyridine and 15.43 g (151.10 mmol) of acetic anhydride were added to the flask, and the mixture was stirred at room temperature for 30 minutes and then heated to 70 ° C. using an oil bath. The mixture was further stirred for 3 hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of filaments, the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamide-imide resin (TPC / OBBC / 6FDA / TFMB = 60/10/30/100 (molar ratio)). The weight average molecular weight of the polyamide-imide resin was 400,000.
The obtained polyamide-imide resin was diluted with GBL, GBL-substituted silica sol was added, and the mixture was sufficiently mixed to obtain a resin / silica particle mixed varnish having a resin: silica ratio of 6: 4. A mixed varnish was prepared so that the concentration of the resin and the silica particles was 11.0% by mass. After filtering the obtained polyamide-imide varnish with a filter having an opening of 10 μm, an applicator so that the thickness of the free-standing film is 55 μm on the smooth surface of a polyester base material (manufactured by Toyobo Co., Ltd., trade name “A4100”). After coating at 50 ° C. for 30 minutes and then drying at 140 ° C. for 15 minutes, the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The free-standing film was fixed to a gold frame and further dried in the air at 200 ° C. for 40 minutes to obtain an optical film having a thickness of 50 μm.

<Comparative example 2>
Under a nitrogen gas atmosphere, 53.05 g (165.66 mmol) of TFMB and 670.91 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, to the flask, 22.11 g (49.77 mmol) of 6FDA, 4.88 g (16.59 mmol) of 3,3', 4,4'-biphenyltetracarboxylic dianhydride (BPDA) was added, and then 20.21 g (99.54 mmol) of TPC was added, and the mixture was stirred at room temperature for 1 hour. Next, 10.53 g (133.08 mmol) of pyridine and 13.77 g (134.83 mmol) of acetic anhydride were added to the flask, and after stirring at room temperature for 30 minutes, the temperature was raised to 70 ° C. using an oil bath for another 3 hours. The mixture was stirred to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of filaments, the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamide-imide resin (TPC / BPDA / 6FDA / TFMB = 60/10/30/100 (molar ratio)). The weight average molecular weight of the polyamide-imide resin was 190,000.
The obtained polyamide-imide resin was diluted with DMAc to prepare a polyamide-imide varnish having a concentration of 22% by mass. After filtering the obtained polyamide-imide varnish with a filter having an opening of 10 μm, an applicator so that the thickness of the free-standing film is 55 μm on the smooth surface of a polyester base material (manufactured by Toyobo Co., Ltd., trade name “A4100”). After coating at 50 ° C. for 30 minutes and then drying at 140 ° C. for 15 minutes, the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The free-standing film was fixed to a gold frame and further dried in the air at 300 ° C. for 40 minutes to obtain an optical film having a thickness of 50 μm.

<Comparative example 3>
Under a nitrogen gas atmosphere, 40 g (124.91 mmol) of TFMB and 682.51 g of DMAc were added to a 1 L separable flask equipped with a stirring blade, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 16.78 g (37.77 mmol) of 6FDA was added to the flask, and the mixture was stirred at room temperature for 3 hours. Then, 3.72 g (12.59 mmol) of OBBC and then 15.34 g (75.55 mmol) of TPC were added to the flask, and the mixture was stirred at room temperature for 1 hour. Next, 8.21 g (88.14 mmol) of 4-methylpyridine and 15.43 g (151.10 mmol) of acetic anhydride were added to the flask, and the mixture was stirred at room temperature for 30 minutes and then heated to 70 ° C. using an oil bath. The mixture was further stirred for 3 hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of filaments, the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamide-imide resin (TPC / OBBC / 6FDA / TFMB = 60/10/30/100 (molar ratio)). The weight average molecular weight of the polyamide-imide resin was 400,000.
The obtained polyamide-imide resin is dissolved in DMAc to prepare a 10% solution, and the obtained polyamide-imide varnish is filtered through a filter having an opening of 10 μm, and then a polyester base material (manufactured by Toyo Boseki Co., Ltd., trade name “A4100”). The self-supporting film was applied onto the smooth surface of the above using an applicator so as to have a thickness of 55 μm, dried at 50 ° C. for 30 minutes, and then dried at 140 ° C. for 15 minutes, and then the obtained coating film was peeled off from the polyester substrate. To obtain a self-supporting film. The free-standing film was fixed to a gold frame and further dried in the air at 200 ° C. for 40 minutes to obtain a polyamide-imide film (optical film) having a thickness of 50 μm.

As shown in Table 1, the optical films obtained in Examples 1 and 2 and Comparative Examples 1 to 3 have elastic modulus (GPa), total light transmittance (Tt,%), Hz _a (%), and yield. The point strain (%) and the Hz (%) and YI values after storage at a temperature of 85 ° C. and a relative humidity of 85% in a bent state were measured.

As shown in Table 1, the optical films of Examples 1 and 2 having a yield point distortion of 1.5% or more and a Hz _a of 1.5% or less are in a bent state as compared with Comparative Examples 1 and 2. It was confirmed that the YI after storage at a temperature of 85 ° C. and a relative humidity of 85% was low, and the Hz after storage was lower than that of Comparative Examples 2 and 3.
Therefore, it was found that the optical films obtained in Examples 1 and 2 had low haze and yellow color even after being stored in a bent state in a high temperature and high humidity environment for a long time.

Claims (10)

_{The yield point strain is 1.50% or more, and the haze represented by Hz a} after the mandrel test in which the film is bent once at a bending radius of 1 mm and returned to a flat surface at room temperature is 1.5% or less. .. The optical film according to claim 1, which comprises a polyamide-imide resin. The polyamide-imide resin has the formula (1):

[In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, and * represents a bond]
The structural unit represented by and the formula (2):

[In formula (2), X and Z represent divalent organic groups independently of each other, and * represents a bond]
The optical film according to claim 2, further comprising a structural unit represented by. The optical film according to any one of claims 1 to 3, _{wherein the haze represented by Hz b} before the mandrel test is 1.0% or less. The optical film according to any one of claims 1 to 4, wherein the content of the filler is 30% by mass or less with respect to the mass of the optical film. The optical film according to any one of claims 1 to 5, wherein the thickness is 20 to 100 μm. The optical film according to any one of claims 1 to 6, wherein the elastic modulus is 1.0 GPa or more. A flexible display device comprising the optical film according to any one of claims 1 to 7. The flexible display device according to claim 8, further comprising a touch sensor. The flexible display device according to claim 8 or 9, further comprising a polarizing plate.