JP2021075702A - Polyamide-imide resin, optical film and flexible display device - Google Patents

Abstract

To provide an optical film which suppresses deterioration in optical characteristics and mechanical characteristics with time and is excellent in quality stability, and a polyamide-imide resin providing the optical film.SOLUTION: In a polyamide-imide resin, in a 1H-13C HSQC spectrum in which a deuterated dimethyl sulfoxide solution of a polyamide-imide resin is obtained as a measurement sample, a ratio (intA/intB) of an integral value (intA) of a peak present in a region (A) where a chemical shift of proton is 8.06-8.14 ppm and a chemical shift of carbon is 129.6-130.3 ppm to an integral value (intB) of a peak present in a region (B) where a chemical shift of proton is 7.26-7.85 ppm and a chemical shift of carbon is 132.4-134.0 ppm is 1.5% or less.SELECTED DRAWING: None

Description

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

Currently, display devices such as liquid crystal display devices and organic EL display devices are widely used not only in televisions but also in various applications such as mobile phones and smart watches. Conventionally, glass has been used as the front plate of such a display device. However, while glass has high transparency and can exhibit high hardness depending on the type, it is very rigid and easily broken, so that it is difficult to use it as a front plate material for a flexible display device.

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

Special Table 2015-521686

When an optical film containing a polyamide-imide resin is used, for example, in a flexible display device, it is required to satisfy various properties such as optical properties and mechanical properties. However, when the flexible display device provided with the optical film is used for a long period of time, the optical film may deteriorate and the optical characteristics and mechanical characteristics may deteriorate over time depending on the environment in which the flexible display device is placed. I understood.

Therefore, it is an object of the present invention to provide an optical film having excellent quality stability in which deterioration of optical properties and mechanical properties with time is suppressed, and a polyamide-imide resin that gives the optical film.

As a result of diligent studies to solve the above problems, the present inventors have made a ^{case where the peak volume of a specific peak in the 1} H- ¹³ C HSQC spectrum of the polyamide-imide resin satisfies a specific relationship, the polyamide-imide resin. We have found that the quality stability of the optical film containing the above can be improved, and have completed the present invention.

［式（１）中、Ｙは４価の有機基を表し、
Ｘは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、及び、式（２）：

［式（２）中、Ｚ及びＸ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少なくとも有する、前記〔１〕に記載のポリアミドイミド樹脂。
〔３〕２００，０００以上１，０００，０００以下の重量平均分子量を有する、前記〔１〕又は〔２〕に記載のポリアミドイミド樹脂。
〔４〕式（１）中のＸ又は式（２）中のＸとして、式（４）：

［式（４）中、Ｈ^４ａ及びＨ^４ｂは水素原子を表し、
Ｒ^４ａ〜Ｒ^４ｄ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^４ａ〜Ｒ^４ｄ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］
で表される構造を少なくとも有する、前記〔１〕〜〔３〕のいずれかに記載のポリアミドイミド樹脂。
〔５〕式（２）中のＺとして、式（３）：

［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］
で表される構造を少なくとも有する、前記〔１〕〜〔４〕のいずれかに記載のポリアミドイミド樹脂。
〔６〕前記〔１〕〜〔５〕のいずれかに記載のポリアミドイミド樹脂を含む光学フィルム。
〔７〕ポリアミドイミド樹脂を含む光学フィルムであって、該光学フィルムを温度８５℃、湿度８５％の条件で１週間保管する保管試験の前後の重量平均分子量の変化率が２６％以下である、光学フィルム。
〔８〕前記保管試験の前後の重量平均分子量の変化率が２５％以下である、前記〔７〕に記載の光学フィルム。
〔９〕前記〔６〕〜〔８〕のいずれかに記載の光学フィルムを有するフレキシブル表示装置の前面板。
〔１０〕前記〔９〕に記載の前面板を備えるフレキシブル表示装置。
〔１１〕タッチセンサをさらに備える、前記〔１０〕に記載のフレキシブル表示装置。
〔１２〕偏光板をさらに備える、前記〔１０〕又は〔１１〕に記載のフレキシブル表示装置。
〔１３〕ジアミン化合物、テトラカルボン酸化合物及びジカルボン酸化合物を反応させるポリアミドイミド樹脂の製造方法であって、該テトラカルボン酸化合物及び該ジカルボン酸化合物の合計モル数に対する該ジアミン化合物のモル数の割合が１．０００を超える、前記〔１〕〜〔５〕のいずれかに記載のポリアミドイミド樹脂の製造方法。 That is, the present invention includes the following preferred embodiments.
^{[1] In the 1} H- ¹³ C HSQC spectrum obtained by using a deuterated dimethylsulfoxide solution of a polyamide-imide resin as a measurement sample, the chemical shift of protons is 8.06 to 8.14 ppm, and the chemical shift of carbon is _{The integrated value (int A} ) of the peak existing in the region (A) of 129.6 to 130.3 ppm, the chemical shift of the proton is 7.26 to 7.85 ppm, and the chemical shift of carbon is 132. integral value of peaks present in the region (B) is a 4~134.0ppm ratio between _{(int B) (int a /} int B) is 1.5% or less, a polyamide-imide resin.
[2] Equation (1):

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

[In formula (2), Z and X represent divalent organic groups independently of each other.
* Represents a bond]
The polyamide-imide resin according to the above [1], which has at least the structural unit represented by.
[3] The polyamide-imide resin according to the above [1] or [2], which has a weight average molecular weight of 200,000 or more and 1,000,000 or less.
[4] As X in the formula (1) or X in the formula (2), the formula (4):

[In formula (4), H ^4a and H ^4b represent hydrogen atoms.
R ^{4a to} R ^4d independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and are included in ^{R 4a to} R ^4d. Hydrogen atoms may be substituted with halogen atoms independently of each other.
* Represents a bond]
The polyamide-imide resin according to any one of the above [1] to [3], which has at least the structure represented by.
[5] As Z in the equation (2), the equation (3):

[In the formula (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 R ^3a. And the ^{hydrogen atoms contained in R 3b} 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]
The polyamide-imide resin according to any one of [1] to [4] above, which has at least the structure represented by.
[6] An optical film containing the polyamide-imide resin according to any one of the above [1] to [5].
[7] An optical film containing a polyamide-imide resin, wherein the rate of change in weight average molecular weight before and after a storage test in which the optical film is stored at a temperature of 85 ° C. and a humidity of 85% for one week is 26% or less. Optical film.
[8] The optical film according to the above [7], wherein the rate of change in the weight average molecular weight before and after the storage test is 25% or less.
[9] A front plate of a flexible display device having the optical film according to any one of the above [6] to [8].
[10] A flexible display device including the front plate according to the above [9].
[11] The flexible display device according to the above [10], further comprising a touch sensor.
[12] The flexible display device according to the above [10] or [11], further comprising a polarizing plate.
[13] A method for producing a polyamideimide resin in which a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compound are reacted, and the ratio of the number of moles of the diamine compound to the total number of moles of the tetracarboxylic acid compound and the dicarboxylic acid compound. The method for producing a polyamideimide resin according to any one of [1] to [5] above, wherein the amount exceeds 1.000.

According to the present invention, it is possible to provide an optical film having excellent quality stability in which deterioration of optical properties and mechanical properties with time is suppressed, and a polyamide-imide resin that gives the optical film.

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

[Polyamide-imide resin]
^{The polyamide-imide resin of the present invention has a chemical shift of protons of 8.06 to 8.14 ppm in a 1} H- ¹³ C HSQC spectrum obtained by using a deuterated dimethyl sulfoxide solution of the polyamide-imide resin as a measurement sample, and has a chemical shift of 8.06 to 8.14 ppm. _{The integrated value (int A} ) of the peak existing in the region (A) where the chemical shift of carbon is 129.6 to 130.3 ppm, and the chemical shift of protons are 7.26 to 7.85 ppm, and the carbon integral value of the peak chemical shift is present in the region (B) is a 132.4~134.0ppm ratio between _{(int B) (int a /} int B) is 1.5% or less.

¹ H- ¹³ C HSQC (Heteronuclear Single Quantum Correlation) spectrum is an NMR spectrum showing heteronuclear coupling between protons and carbon, and in the spectrum, the vertical axis usually represents the chemical shift of carbon. The horizontal axis represents the chemical shift of protons. _{The present inventor has an integral value (int A} ) of peaks existing in the region (A) in which the chemical shift of protons is 8.06 to 8.14 ppm and the chemical shift of carbon is 129.6 to 130.3 ppm. _{) And the integral value (int B} ) of the peak existing in the region (B) where the chemical shift of the proton is 7.26 to 7.85 ppm and the chemical shift of the carbon is 132.4 to 134.0 ppm. By using a polyamide-imide resin having a ratio (int _A / int _B ) of 1.5% or less, it is possible to provide an optical film having excellent quality stability in which deterioration of optical properties and mechanical properties over time is suppressed. I found. When the ratio (int _A / int _B ) exceeds 1.5%, the optical film containing the resin tends to deteriorate in optical properties and mechanical properties with time. The ratio (int _A / int _B ) is preferably 1.2% or less, more preferably 1.0% or less, still more preferably 0, from the viewpoint of easily improving the effect of suppressing deterioration of optical properties and mechanical properties. It is 8.8% or less, particularly preferably 0.6% or less. The smaller the ratio (int _A / int _B ), the more preferable, and the lower limit thereof is not particularly limited, and is usually 0 or more, for example 0.01% or more.

When the ratio (int _A / int _B ) is 1.5% or less, the reason why the deterioration of the optical properties and mechanical properties of the obtained optical film with time can be suppressed is not clear, but according to the reason described later. Conceivable. The polyamide-imide resin is usually obtained by polymerizing a tetracarboxylic acid compound, a dicarboxylic acid compound, and a diamine compound as monomers. Then, depending on the proportion of the monomer to be polymerized and the polymerization conditions of the polymer, a carboxylic acid moiety derived from a dicarboxylic acid may remain at the end of the obtained polymer. Here, ^{in the region (A) in the 1} H- ¹³ C HSQC spectrum, where the chemical shift of protons is 8.06 to 8.14 ppm and the chemical shift of carbon is 129.6 to 130.3 ppm, It is considered that there is a proton peak corresponding to the amount of the carboxylic acid moiety present at the end of the polyamide-imide resin derived from the dicarboxylic acid. Therefore, the integral value (volume of the peak) of the peak existing in the region (A), which relatively represents the abundance of the carboxylic acid portion derived from the terminal dicarboxylic acid, corresponds to the proton of the other portion of the polyamide-imide resin. When it is equal to or less than a predetermined value with respect to the integral value of the peak existing in the region (B), it means that the amount of the carboxylic acid moiety present at the end of the polyamide-imide resin is very small, and the optical of the obtained optical film It is considered that the deterioration of the characteristics and the mechanical characteristics with time can be suppressed. It is considered that when the optical film is used for a long period of time, the optical characteristics and the mechanical characteristics may deteriorate with time, especially due to erosion from the surface of the optical film due to the external environment or the like. When the amount of the carboxylic acid moiety present at the end of the polyamide-imide resin contained in the optical film is small, erosion of the surface of the optical film under, for example, high temperature and high humidity conditions can be reduced, and such reduction of erosion can be achieved. It is considered to be one of the factors that suppress the deterioration of optical properties and mechanical properties over time. Further, for the same reason, _{an optical film obtained from a resin having a ratio (int A} / int _B ) of 1.5% or less can suppress a decrease in weight average molecular weight with time.

_{As described above, int A} in the ratio (int _A / int _B ) increases as the amount of the terminal carboxylic acid portion of the dicarboxylic acid present at the end of the polyamide-imide resin increases. Therefore, the above ratio can be adjusted to the range of 1.5% or less by synthesizing the polyamide-imide resin so that the terminal carboxylic acid portion derived from the dicarboxylic acid is as small as possible. As an example of a method for synthesizing a polyamide-imide resin so that the terminal carboxylic acid portion is as small as possible, when synthesizing a polyamide-imide resin, among the dicarboxylic acid compounds, the compound having low reactivity and easily becoming a terminal carboxylic acid is first selected. In addition, it is conceivable that the molar amount of the diamine monomer is higher than the total molar amount of the dicarboxylic acid and the tetracarboxylic acid. Specifically, for example, when the tetracarboxylic acid compound, the dicarboxylic acid compound and the diamine compound are copolymerized in order to obtain a polyamideimide resin, the total molar amount of the tetracarboxylic acid compound and the dicarboxylic acid compound is set to 1. The ratio of the molar amount of the diamine compound (the molar amount of the diamine compound / (the total molar amount of the tetracarboxylic acid compound and the dicarboxylic acid compound), this ratio is also referred to as “amine ratio” below) is preferably 1.000 or more. _{When the ratio (int A} / int _B ) is adjusted to be more preferably 1.003 or more, still more preferably 1.005 or more, still more preferably 1.008 or more, and particularly preferably 1.01 or more, the above-mentioned ratio (int A / int B) is adjusted. Easy to adjust to the range of. The upper limit of the amine ratio is preferably 1.05 or less, more preferably 1.03 or less, still more preferably 1.02 or less, from the viewpoint of easily increasing the weight average molecular weight of the polyamide-imide resin.

_{Further, the ratio (int A} / int _B ) can be adjusted within the above range by adjusting the amount of water in the solvent used when synthesizing the polyamide-imide resin. Specifically, when a certain amount of water is present in the solvent, a part of the dicarboxylic acid compound in the synthetic solvent is inactivated, and it becomes difficult to introduce the dicarboxylic acid compound into the polyamide-imide resin. As a result, when a certain amount of water is present in the solvent, the abundance of the dicarboxylic acid-derived carboxylic acid moiety present at the end of the polyamide-imide resin can be reduced, and the ratio (int _A / int _B ) can be set as described above. It is thought that it will be easier to adjust to the range of. From the viewpoint that the ratio (int _A / int _B ) can be easily adjusted to the above range, the water content in the solvent used when synthesizing the polyamide-imide resin is preferably 400 ppm or more, more preferably 500 ppm or more, and the polyamide. From the viewpoint of suppressing the decomposition of the imide resin, it is preferably 1,000 ppm or less, more preferably 800 ppm or less.

The ratio (int _A / int _B ) can also be adjusted within the above range by adjusting the imidization heating rate. Specifically, when synthesizing a polyamide-imide resin, if the imidization heating rate is too fast, the imidization catalyst cannot sufficiently trap the hydrochloric acid in the synthesis solvent, and this hydrochloric acid decomposes the polyamide-imide resin. As a result, a carboxylic acid moiety derived from the dicarboxylic acid compound is likely to be present at the end of the polyamide-imide resin. _{Therefore, the ratio (int A} / int _B ) can be adjusted within the above range by adjusting the rate of temperature rise during imidization and suppressing the decomposition of the polyamide-imide resin. From the viewpoint that the ratio (int _A / int _B ) can be easily adjusted to the above range, it is preferable to lower the heating rate at the time of imidization, and it is possible to take 30 minutes or more to raise the temperature from 10 ° C to 50 ° C. More preferred.

_{The ratio (int A} / int _B ) can also be adjusted within the above range by adjusting the heating conditions during the reaction. Specifically, when synthesizing a polyamide-imide resin, the main chain of the polyamide-imide resin is formed by locally heating the reaction vessel rather than heating the entire reaction vessel in order to achieve the same heating rate. It was found that the hydrolysis of the terminal carboxylic acid can be easily promoted while suppressing the decomposition of the resin. By desorbing the terminal carboxylic acid, the amine terminal is exposed instead, so that the ratio (int _A / int _B ) can be adjusted to the above range. This is because when the entire reaction vessel is heated with a heat medium when synthesizing a polyamide-imide resin, the amount of the reaction solution that is overheated increases, and not only the hydrolysis of the carboxylic acid at the resin terminal but also the decomposition of the main chain Also progresses. As a result, _{it is considered that it becomes difficult to adjust the ratio (int A} / int _B ) to the above range, and the molecular weight tends to decrease. When the reaction vessel is locally heated, hydrolysis of the carboxylic acid terminal, which is more reactive than decomposition of the main chain, occurs preferentially while reducing decomposition of the main chain of the polyamide-imide resin, and the ratio (int _A). It is considered that / int _B ) can be easily adjusted to the above range.

［式（１）中、Ｙは４価の有機基を表し、
Ｘは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及び式（２）：

［式（２）中、Ｚ及びＸ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少なくとも有する。 In one preferred embodiment of the present invention, the polyamide-imide resin is represented by the formula (1):

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

[In equation (2), Z and X are independent of each other.
Represents a divalent organic group
* Represents a bond]
It has at least a structural unit represented by.

The structural unit represented by the formula (1) is a structural unit formed by reacting a tetracarboxylic acid compound and a diamine compound, and the structural unit represented by the formula (2) is a dicarboxylic acid compound and a diamine compound. Is a structural unit formed by the reaction of and. When the polyamide-imide resin has a structural unit represented by the formula (1) and a structural unit represented by the formula (2), the polyamide-imide resin usually has a plurality of structural units represented by the formula (1) and a plurality of structural units. It has a plurality of structural units represented by the formula (2). The plurality of structural units represented by the formula (1) may be one type of structural unit or two or more types of structural units. Further, the plurality of structural units represented by the formula (2) may also be one type of structural unit or two or more types of structural units. Furthermore, the polyamide-imide resin may have additional structural units different from those of the formulas (1) and (2).

［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。Ｚとしては、光学フィルムの黄色度（以下、ＹＩ値と略すことがある）を低減しやすい観点から、式（２０）〜式（２９）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 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 atom in these groups may be substituted with a halogen atom, preferably a fluorine atom), and is a divalent organic group having 4 to 40 carbon atoms, more preferably carbon atoms. Substituted with an alkyl group of 1 to 6, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms (the hydrogen atom in these groups may be substituted with a halogen atom, preferably a fluorine atom). It represents a divalent organic group having a cyclic structure and having 4 to 40 carbon atoms. Examples of 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 include examples relating to ^{R 3a} and R ^{3b in the formula (3) described later.} The same applies. 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):

Wherein (20) to Formula (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-, Represents -Ar-C (CH ₃ ) _2- Ar- or -Ar-SO _2- Ar-, where Ar has 6 to 6 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom independently of each other. Represents 20 arylene groups, such as phenylene groups, where * 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. Z is a group represented by the formulas (20) to (29) and a group having a thiophene ring skeleton from the viewpoint of easily reducing the yellowness of the optical film (hereinafter, may be abbreviated as YI value). Is preferable.

［式（２０’）〜式（２９’）中、Ｗ^１及び＊は、式（２０）〜式（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（これらの基における水素原子はハロゲン原子、好ましくはフッ素原子で置換されていてもよい）で置換されていてもよい。 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 formula (20 ') to formula (29'), ^{W 1} and * are as defined in formula (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 (the hydrogen atom in these groups may be substituted with a halogen atom, preferably a fluorine atom).

［式（ｄ１）中、Ｒ^２４は後述する式（３）中のＲ^３ａについて定義する基又は水素原子を表し、
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、該樹脂を含むワニスの成膜性を高めやすく、得られる光学フィルムの均一性を高めやすい観点から好ましい。構成単位（ｄ１）としては、具体的には、Ｒ^２４及びＲ^２５がいずれも水素原子である構成単位、すなわちジカルボン酸化合物に由来する構成単位、Ｒ^２４がいずれも水素原子であり、Ｒ^２５が−Ｃ（＝Ｏ）−＊を表す構成単位、すなわちトリカルボン酸化合物に由来する構成単位等が挙げられる。 When the polyamide-imide resin has a structural unit in which Z in the formula (2) is represented by any of the above formulas (20') to (29'), the Z in the formula (2) will be described later. When having a structural unit represented by the formula (3'), the polyamide-imide resin is added to the structural unit and has the following formula (d1):

[In the formula (d1), R ²⁴ represents a group or a hydrogen atom defining ^{R 3a} in the formula (3) described later.
R ²⁵ represents R ²⁴ or -C (= O)-*,
* Represents a bond]
It is preferable to further have a carboxylic acid-derived structural unit represented by (1) from the viewpoint of easily improving the film-forming property of the varnish containing the resin and easily improving the uniformity of the obtained optical film. Specifically, as the structural unit (d1), R ²⁴ and R ²⁵ are both hydrogen atoms, that is, a structural unit derived from a dicarboxylic acid compound, and R ²⁴ is a hydrogen atom and R ^25. A structural unit representing −C (= O) − *, that is, a structural unit derived from a tricarboxylic acid compound and the like can be mentioned.

［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］
、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］
で表される構成単位を少なくとも有することが好ましい。なお、本明細書において、ポリアミドイミド樹脂が式（２）中のＺが式（３）で表される構成単位を有することと、ポリアミドイミド樹脂が式（２）中のＺとして式（３）で表される構造を有することとは、同様の意味を有し、ポリアミドイミド樹脂に含まれる複数の式（２）で表される構成単位のうち、少なくとも一部の構成単位におけるＺが式（３）で表されることを意味する。当該記載は、他の同様の記載にもあてはまる。 The polyamide-imide 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. Above all, Z in the formula (2) is preferably used from the viewpoint that the impact resistance of the optical film obtained by using the polyamide-imide resin of the present invention can be easily enhanced and the optical characteristics can be easily enhanced.

[In the formula (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 R ^3a. And the ^{hydrogen atoms contained in R 3b} 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]
, More preferably equation (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 a structural unit represented by. In the present specification, the polyamide-imide resin has a structural unit in which Z in the formula (2) is represented by the formula (3), and the polyamide-imide resin has the Z in the formula (2) as the formula (3). Having a structure represented by (2) has the same meaning, and among the plurality of structural units represented by the formula (2) contained in the polyamide-imide resin, Z in at least a part of the structural units is represented by the formula (. It means that it is represented by 3). This statement also applies to other similar statements.

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 the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an 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, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group and a hexyloxy group. Groups, cyclohexyloxy groups and the like 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 the surface hardness and flexibility of the optical film, R ^3a and R ^3b independently represent an alkyl group having 1 to 6 carbon atoms, and more preferably an alkyl 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 monovalent hydrocarbon groups having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group and 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 Etc., and these may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom.

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, more preferably 0 or 1, and even more preferably 0. is there.

S in the formulas (3) and (3') is an integer in the range of 0 to 4, and when s is in this range, the impact resistance of the optical film obtained by using the polyamide-imide resin of the present invention. , Elastic modulus and bending resistance are likely to be improved. The s in the formula (3) and the formula (3') is preferably an integer in the range of 0 to 3, more preferably, from the viewpoint of easily improving the impact resistance, elastic modulus and bending resistance of the obtained optical film. Is an integer in the range 0-2, more preferably 0 or 1, and particularly preferably 0. The structural unit including the structure represented by the formula (3) or the formula (3') in which s is 0 as Z in the formula (2) is, for example, a structural unit derived from terephthalic acid or isophthalic acid. The unit is particularly preferably a structural unit including a structure in which s is 0 and u is 0 in the formula (3) or the formula (3'). From the viewpoint of easily improving the impact resistance, elastic modulus and bending resistance of the optical film, the polyamide-imide resin preferably contains a structural unit derived from terephthalic acid. The polyamide-imide resin may contain one or more structural units in which Z is represented by the formula (3) or the formula (3'). From the viewpoint of improving the impact resistance, elastic modulus and bending resistance of the optical film, and reducing the YI value, the polyamide-imide resin is designated as Z in the formula (2) and s in the formula (3) or the formula (3'). It is preferable to include two or more types of structures having different values of, and more preferably to include two or three types of structures having different values of s in the formula (3) or the formula (3'). In this case, the polyamide-imide resin is used in the structural unit represented by the formula (2) from the viewpoint of easily increasing the impact resistance, elastic modulus and bending resistance of the optical film and easily reducing the YI value of the optical film. Z includes a structure represented by the formula (3) in which s is 0, and in addition to the structural unit including the structure, a structural unit including the structure represented by the formula (3) in which s is 1 is further added. It is particularly preferable to contain it. Further, in addition to the structural unit represented by the formula (2) having Z represented by the formula (3) in which s is 0, it is also preferable to further have the structural unit represented by the above formula (d1). ..

で表される構造を有する。この場合、該ポリアミドイミド樹脂を用いて得られる光学フィルムの耐衝撃性、弾性率及び耐屈曲性を向上させやすいと共に、ＹＩ値を低減しやすい。 In a preferred embodiment of the present invention, the polyamide-imide resin has a structure (divalent group) represented by the formula (3) or the formula (3') in which s = 0 and u = 0. Has. In a more preferred embodiment of the present invention, the polyamide-imide resin has a structure represented by the formula (3) or the formula (3'), in which s = 0 and u = 0, and a structure represented by the formula (3'). "):

It has a structure represented by. In this case, it is easy to improve the impact resistance, elastic modulus and bending resistance of the optical film obtained by using the polyamide-imide resin, and it is easy to reduce the YI value.

When the polyamideimide resin of the present invention has a structural unit in which Z in the formula (2) is represented by the formula (3) or the formula (3'), the ratio thereof is represented by the formula (1) of the polyamideimide resin. When the total of the structural units to be used and the structural units represented by the formula (2) is 100 mol%, it is preferably 20 mol% or more, more preferably 30 mol% or more, still more preferably 40 mol% or more, and further. It is more preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, still more preferably 80 mol% or less. When the ratio of the structural unit represented by the formula (3) or the formula (3') in the formula (2) is equal to or more than the above lower limit, the impact resistance, elastic modulus and bending resistance of the optical film are enhanced. Cheap. When Z in the formula (2) is equal to or less than the above upper limit of the proportion of the structural unit represented by the formula (3) or the formula (3'), the resin-containing varnish due to the hydrogen bond between the amide bonds derived from the formula (3). It is easy to improve the processability of the film by suppressing the increase in viscosity of the film.

Further, when the polyamideimide resin has a structure represented by the formula (3) or the formula (3') in which s = 1 to 4 as Z in the formula (2), the formula (3) in which s is 1 to 4 ) Or the ratio of the structural unit represented by the formula (2) having Z represented by the formula (3') is represented by the structural unit represented by the formula (1) and the formula (2) of the polyamide imide resin. When the total of the constituent units is 100 mol%, it is preferably 3 mol% or more, more preferably 5 mol% or more, further preferably 7 mol% or more, particularly preferably 9 mol% or more, preferably 90 mol% or more. It is mol% or less, more preferably 70 mol% or less, still more preferably 50 mol% or less, and particularly preferably 30 mol% or less. When the ratio of the structural unit represented by the formula (3) in which s is 1 to 4 or the formula (2) having Z represented by the formula (3') is equal to or more than the above lower limit, the impact resistance of the optical film is increased. It is easy to improve the property, elastic modulus and bending resistance. When the ratio of the structural unit represented by the formula (3) in which s is 1 to 4 or the formula (2) having Z represented by the formula (3') is equal to or less than the above upper limit, the formula (3) or the formula (3') It is easy to improve the processability of the film by suppressing the increase in viscosity of the resin-containing varnish due to the hydrogen bond between the amide bonds derived from the structure represented by the formula (3'). The ratio of the structural unit in which Z in the formula (1), the formula (2), and the formula (2) is represented by the formula (3) or the formula (3') is ^{measured by using, for example, 1 1} H-NMR. It can also be calculated from the raw material charging ratio.

In a preferred embodiment of the present invention, Z in the polyamide-imide 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 expressed by the formula (3) or the formula (3') in which s is 0 to 4. When the above lower limit of Z or more is represented by the formula (3) or the formula (3') in which s is 0 to 4, the impact resistance, elastic modulus and bending resistance of the optical film can be easily enhanced. Further, 100 mol% or less of Z in the polyamide-imide resin may be represented by the formula (3) or the formula (3') in which s is 0 to 4. The ratio of the structural unit represented by the formula (3) in which s is 0 to 4 or the formula (2) having Z represented by the formula (3') in the resin is, for example, ^{1 1} H-NMR. It can be measured using it, or it can be calculated from the charging ratio of raw materials.

In a preferred embodiment of the present invention, Z in the polyamide-imide resin of the present invention is preferably 5 mol% or more, more preferably 8 mol% or more, still more preferably 10 mol% or more, and particularly preferably 12 mol% or more. Is expressed by the formula (3) or the formula (3') in which s is 1 to 4. When the above lower limit or more of Z of the polyamide-imide resin is represented by the formula (3) or the formula (3') in which s is 1 to 4, the impact resistance, elastic modulus and bending resistance of the optical film are enhanced. Cheap. Further, the formula (3) or formula (3) or formula in which s is 1 to 4, preferably 90 mol% or less, more preferably 70 mol% or less, still more preferably 50 mol% or less, and particularly preferably 30 mol% or less of Z. It is represented by (3'). When the above upper limit or less of Z is represented by the formula (3) in which s is 1 to 4, it is derived from the structural unit represented by the formula (3) or the formula (3') in which s is 1 to 4. It is easy to improve the processability of the film by suppressing the increase in viscosity of the resin-containing varnish due to the hydrogen bond between the amide bonds. The ratio of the structural units represented by the formula (3) or the formula (3') in which s is 1 to 4 in the resin ^{can be measured by using, for example, 1 1} H-NMR, or the raw material charging ratio. It can also be calculated from.

［式（３２）中、Ｒ^３２ａ及びＲ^３２ｂ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^３２ａ及びＲ^３２ｂに含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ｒ^３２ｃは、水素原子（この場合、−ＯＲ^３２ｃは−ＯＨである）、アルカリ金属原子、ハロゲン原子、又は炭素数１〜３のアルキル基を表し、
ｐは０〜４の整数であり、
ｒは０〜４の整数であり、好ましくは０〜２の整数、より好ましくは０であり、
Ａは、互いに独立に、単結合、−Ｏ−、−ＣＨ_２−、−ＣＨ_２−ＣＨ_２−、−ＣＨ（ＣＨ_３）−、−Ｃ（ＣＨ_３）_２−、−Ｃ（ＣＦ_３）_２−、−ＳＯ_２−、−Ｓ−、−ＣＯ−又は−Ｎ（Ｒ^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、
ｑは０〜４の整数であり、
＊は結合手を表す］
で表される構造が挙げられる。カルボン酸末端部分の構造が式（３２）で表される場合（好ましくはｒ＝０、ｑ＝０であり、カルボン酸基の置換位置がアミド基に対してパラ位である）、カルボン酸基（−Ｃ（＝Ｏ）ＯＲ^３２ｃ）を有するベンゼン環上の炭素原子に結合する水素原子に帰属されるピークが、領域（Ａ）に検出されると考えられる。式（３２）で表されるカルボン酸末端部分の構造は、式（２）中のＺが上記の式（３）で表される構成単位を与えるジカルボン酸及びジアミンにおける、該ジカルボン酸とジアミンの一部とに由来する構造である。そのため、ポリアミドイミド樹脂が、式（２）中のＺが上記の式（３）で表される構成単位を有する場合、式（３２）で表される末端構造がポリアミドイミド樹脂に含まれ得る。そのため、式（３）中のＲ^３ａ、Ｒ^３ｂ、Ｗ、ｓ、ｔ及びｕは、それぞれ、式（３２）中のＲ^３２ａ、Ｒ^３２ｂ、Ａ、ｐ、ｑ及びｒに対応し得る。 The structure of the carboxylic acid terminal portion derived from the dicarboxylic acid compound in the polyamide-imide resin of the present invention is, for example, the formula (32):

[In formula (32), R ^32a and R ^32b 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 R ^32a. And the ^{hydrogen atoms contained in R 32b} may be substituted with halogen atoms independently of each other.
R ^32c represents a hydrogen atom (in this case, -OR ^32c is -OH), an alkali metal atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms.
p is an integer from 0 to 4
r is an integer from 0 to 4, preferably an integer from 0 to 2, more preferably 0.
A is, independently of one another, a single _{bond, -O -, - CH 2 -} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) _{2 -, - SO 2 -,} - S -, - CO- or -N ^{(R 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
q is an integer from 0 to 4
* Represents a bond]
The structure represented by is mentioned. When the structure of the carboxylic acid terminal portion is represented by the formula (32) (preferably r = 0, q = 0, and the substitution position of the carboxylic acid group is the para position with respect to the amide group), the carboxylic acid group It is considered that the peak attributed to the hydrogen atom bonded to the carbon atom on the benzene ring having (-C (= O) OR ^{32c) is detected in the region (A).} The structure of the terminal portion of the carboxylic acid represented by the formula (32) is the structure of the dicarboxylic acid and the diamine in the dicarboxylic acid and the diamine in which Z in the formula (2) gives the structural unit represented by the above formula (3). It is a structure derived from a part. Therefore, when the polyamide-imide resin has a structural unit in which Z in the formula (2) is represented by the above formula (3), the terminal structure represented by the formula (32) can be contained in the polyamide-imide resin. ^{Therefore, R 3a} , R ^3b , W, s, t and u in the formula (3) ^{can correspond to R 32a} , R ^32b , A, p, q and r in the formula (32), respectively.

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 polyamide-imide 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 chain having 6 or less carbon atoms. The formula 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 the monovalent hydrocarbon group having 1 to 12 carbon atoms include the groups mentioned above for R ^9.
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, more preferably with respect to each ring. It is a para position.

Among the groups represented by the formulas (10) to (18), the formulas (13), (14), and (15) are used from the viewpoint of easily increasing the impact resistance, elastic modulus, and bending resistance of the optical film. , The groups represented by the formulas (16) and (17) are preferable, and the groups represented by the formulas (14), (15) and (16) are more preferable. Further, V ¹ , V ² and V ³ are independent of each other, preferably single bond, -O- or -S-, more preferably, from the viewpoint of easily increasing the impact resistance, elastic modulus and flexibility of the optical film. Single bond or -O-.

［式（４）中、Ｈ^４ａ及びＨ^４ｂは水素原子を表し、Ｒ^４ａ〜Ｒ^４ｄ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^４ａ〜Ｒ^４ｄ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］
で表される構造を有する。ポリアミドイミド樹脂が、式（１）中のＸ又は式（２）中のＸとして式（４）で表される構造を有する場合、式（４）中のＨ^４ａ及びＨ^４ｂに帰属されるピークが、領域（Ｂ）に検出されると考えられる。なお、式（１）で表される構成単位、及び、式（２）で表される構成単位は、ポリアミドイミド樹脂中に複数存在する。これらの構成単位の少なくとも一部において、式（１）及び式（２）中のＸが式（４）で表される場合、光学フィルムの耐衝撃性、弾性率及び透明性を高めやすい。 In a preferred embodiment of the present invention, the polyamide-imide resin of the present invention has the formula (4): X as X in the formula (1) or X in the formula (2).

[In the formula (4), H ^4a and H ^4b represent a hydrogen atom, and R ^{4a to} R ^4d are 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, respectively. A hydrogen atom representing an aryl group having 6 to 12 carbon ^{atoms and contained in R 4a to} R ^4d may be substituted with a halogen atom independently of each other.
* Represents a bond]
It has a structure represented by. When the polyamide-imide resin has a structure represented by the formula (4) as X in the formula (1) or X in the formula (2), the peaks assigned to ^{H 4a} and H ^{4b in the formula (4).} Is considered to be detected in the region (B). In addition, a plurality of structural units represented by the formula (1) and the structural unit represented by the formula (2) exist in the polyamide-imide resin. When X in the formulas (1) and (2) is represented by the formula (4) in at least a part of these constituent units, the impact resistance, elastic modulus and transparency of the optical film can be easily increased.

で表される構成単位であり、すなわち、式（１）及び式（２）で表される複数の構成単位中の複数のＸの少なくとも一部は、式（４’）で表される構成単位である。この場合、フッ素元素を含有する骨格によりポリアミドイミド樹脂の溶媒への溶解性を高め、該樹脂を含有するワニスの保管安定性を向上しやすいと共に、該ワニスの粘度を低減しやすく、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、光学フィルムの光学特性を向上しやすい。ポリアミドイミド樹脂が式（１）又は式（２）中のＸとして、式（４）又は式（４’）で表される構造を含む場合、式（４）中のＨ^４ａ及びＨ^４ｂで表される水素原子、又は、式（４’）中の同様の位置の水素原子に帰属されるピークが、領域（Ｂ）に検出されると考えられる。 In one preferred embodiment of the present invention, the structural unit represented by the formula (4) is the formula (4'):

That is, at least a part of the plurality of Xs in the plurality of structural units represented by the equations (1) and (2) is the structural unit represented by the equation (4'). Is. In this case, the skeleton containing a fluorine element enhances the solubility of the polyamide-imide resin in the solvent, and it is easy to improve the storage stability of the varnish containing the resin, and it is easy to reduce the viscosity of the varnish. Easy to improve workability. Further, the skeleton containing a fluorine element makes it easy to improve the optical characteristics of the optical film. When the polyamide-imide resin contains a structure represented by the formula (4) or the formula (4') as X in the formula (1) or the formula (2), it is represented by H ^4a and H ^{4 b} in the formula (4). It is considered that the hydrogen atom to be generated or the peak assigned to the hydrogen atom at a similar position in the formula (4') is detected in the region (B).

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more of X in the above-mentioned polyamide-imide resin is the formula (4), particularly the formula (4). It is represented by'). When X in the above range in the polyamide-imide resin is represented by the formula (4), particularly the formula (4'), the obtained optical film has a skeleton containing a fluorine element to enhance the solubility of the resin in the solvent. It is easy to improve the storage stability of the varnish containing the resin, it is easy to reduce the viscosity of the varnish, and it is easy to improve the processability of the optical film. Further, the skeleton containing a fluorine element makes it easy to improve the optical characteristics of the optical film. It should be noted that preferably, 100 mol% or less of X in the above-mentioned polyamide-imide resin is represented by the formula (4), especially (4'). X in the resin may be of the formula (4), particularly of the formula (4'). The ratio of the structural unit represented by the formula (4) of X in the resin ^{can be measured by using, for example, 1 1} H-NMR, or can be calculated from the charging ratio of the raw materials.

［式（６）中、Ｒ^１０〜Ｒ^１７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^１０〜Ｒ^１７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、ただし、Ｒ^１１及びＲ^１２のいずれか一方と、Ｒ^１４及びＲ^１７のいずれか一方とがトリフルオロメチル基となる場合を除く、
＊は結合手を表す］
で表される構成単位が挙げられる。式（１）及び式（２）中の複数のＸの少なくとも一部が式（６）で表される基である場合にも、光学フィルムの耐衝撃性、弾性率及び透明性を高めやすい。 Formula (1) or formula (1) or in which X in formula (1) or formula (2) is contained in addition to or in place of the structural unit represented by formula (4) or formula (4'). As a structural unit in which X in the formula (2) is represented by another structural formula, for example, X in the formula (1) or the formula (2) is the formula (6) :.

[In formula (6), R ^{10 to} R ¹⁷ 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 10 to} R ¹⁷ may be substituted with halogen atoms independently of each other, except that one of R ¹¹ and R ¹² and one of R ¹⁴ and R ¹⁷ are used. Except when it becomes a trifluoromethyl group,
* Represents a bond]
The structural unit represented by is mentioned. Even when at least a part of the plurality of Xs in the formulas (1) and (2) is a group represented by the formula (6), the impact resistance, elastic modulus and transparency of the optical film can be easily improved.

^{R 4a} , R ^4b , R ^4c and R ^4d in formula (4) ^{, and R 10} , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ and R ¹⁷ in formula (6) are mutually exclusive. Independently, it represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms include the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms in the formula (3). Examples thereof include groups exemplified as groups or aryl groups having 6 to 12 carbon atoms. R ^{4a to} R ^4d and R ^{10 to} R ¹⁷ represent independent of each other, preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Here, the ^{hydrogen atoms contained in R 4a to} R ^4d and R ^{10 to} R ¹⁷ 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. R ^{4a to} R ^4d and R ^{10 to} R ¹⁷ are more preferably hydrogen atoms, methyl groups, fluoro groups, and chloros, independently of each other, from the viewpoint of impact resistance, elasticity, transparency, and bending resistance of the optical film. Groups or trifluoromethyl groups, most preferably R ^{4a to} R ^4d are hydrogen atoms, R ¹⁰ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are hydrogen atoms, R ¹¹ and R ¹⁷ is a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group. However, in the formula (6), the case where either one of ^{R 11} and R ^{12 and one of R 14} and R ^{17 form} a trifluoromethyl group is excluded.

In the formula (1), Y represents a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms, and more preferably a tetravalent organic group having a cyclic structure and having 4 to 40 carbon atoms. Represents a group. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure, and an aromatic ring is preferably used from the viewpoint of easily increasing impact resistance and elastic modulus. 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. In one embodiment of the present invention, the polyamide-imide resin 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 following formulas (20), formulas (21), formulas (22), formulas (23), formulas (24), formulas (25), formulas (26), formulas (27), formulas (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; In addition, a chain hydrocarbon group having 4 or less valences of 6 carbon atoms 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.

Among the groups represented by the formulas (20) to (29), the formula (26), the formula (28) or the formula (29) from the viewpoint of easily increasing the impact resistance, elastic modulus and bending resistance of the optical film. The group represented by the formula (26) is preferable, and the group represented by the formula (26) is more preferable. Further, W ¹ is independent of each other, preferably single bond, −O−, − from the viewpoint of easily increasing the impact resistance, elastic modulus and bending resistance of the optical film and easily reducing the YI value of the optical film. 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- , particularly preferably a single bond or -C (CF ₃ ) _2- .

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 polyamide-imide resin is represented by the formula (26). Y is the formula within the above range in the polyamide-imide resin (26), preferably ^{W 1} is a single bond, -C _{(CH 3) 2} - or -C _{(CF 3) 2} - a is the formula (26), more preferably When W ¹ is represented by the equation (26) of single bond or −C (CF ₃ ) ₂₋ , the impact resistance, elastic modulus and bending resistance of the optical film can be easily increased, and the YI value of the optical film can be increased. Easy to reduce. The ratio of the structural unit in which Y is represented by the formula (26) in the polyamide-imide resin ^{can be measured using, for example, 1} H-NMR, or can be calculated from the charging ratio of the raw materials.

［式（５）中、Ｒ^１８〜Ｒ^２５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^１８〜Ｒ^２５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］
及び／又は式（９）：

［式（９）中、Ｒ^３５〜Ｒ^４０は、互いに独立に、水素原子、炭素数１〜６のアルキル基又は炭素数６〜１２のアリール基を表し、Ｒ^３５〜Ｒ^４０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。複数の式（１）中のＹの少なくとも一部が式（５）で表される、及び／又は、式（９）で表されると、光学フィルムの耐衝撃性、弾性率及び光学特性を向上させやすい。 In a preferred embodiment of the present invention, at least a part of Y in the plurality of formulas (1) is the formula (5) :.

[In formula (5), R ^{18 to} R ²⁵ 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 18 to} R ²⁵ may be substituted with halogen atoms independently of each other.
* Represents a bond]
And / or equation (9):

[In the formula (9), R ^{35 to} R ⁴⁰ represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and hydrogen contained in ^{R 35 to} R ^40. Atoms may be substituted with halogen atoms independently of each other, with * representing a bond]
It is represented by. When at least a part of Y in the plurality of formulas (1) is represented by the formula (5) and / or the formula (9), the impact resistance, elastic modulus and optical characteristics of the optical film are determined. Easy to improve.

In formula (5), R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ and R ²⁵ are independent of each other, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, and 1 carbon atom. Represents an alkoxy group of ~ 6 or an aryl group of 6-12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, or the aryl group having 6 to 12 carbon atoms include the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms in the formula (3). Examples of groups or aryl groups having 6 to 12 carbon atoms can be mentioned above. R ^{18 to} R 25 represent independently 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 here, R ¹⁸ to ^{R 25.} The ^{hydrogen atom contained in R 25} may be substituted with a halogen atom independently of each other. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom. R ^{18 to} R ²⁵ are more preferable from the viewpoint of easily increasing the impact resistance, elasticity and bending resistance of the optical film, and easily increasing the transparency and maintaining the transparency independently of each other. Is a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and even more preferably R ¹⁸ , R ¹⁹ , R ²⁰ and R ²³ , R ²⁴ and R ²⁵ are hydrogen atoms, R ²¹ and R ^22. Is a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and particularly preferably R ²¹ and R ²² are a methyl group or a trifluoromethyl group.

^{In the formula (9), R 35 to} R ⁴⁰ are described from the viewpoints of easily increasing the impact resistance, elastic coefficient and bending resistance of the optical film, and easily increasing the transparency and maintaining the transparency. It is 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 further preferably a hydrogen atom. Here, the ^{hydrogen atoms contained in R 35 to} R ⁴⁰ may be substituted with halogen atoms independently of each other, and examples of the halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. .. Examples of the alkyl group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms in R ^{35 to} R ^{40 are exemplified above.}

で表される。すなわち、複数のＹの少なくとも一部は、式（５’）及び／又は式（９’）で表される。この場合、光学フィルムの耐衝撃性、弾性率及び耐屈曲性を高めやすい。さらに、式（５）が式（５’）で表される場合、フッ素元素を含有する骨格によりポリアミドイミド樹脂の溶媒への溶解性を高め、該樹脂を含有するワニスの保管安定性を向上しやすいと共に、該ワニスの粘度を低減しやすく、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、光学フィルムの光学特性を向上しやすい。 In a preferred embodiment of the present invention, formula (5) is represented by formula (5'), and formula (9) is represented by formula (9') :.

It is represented by. That is, at least a part of the plurality of Y is represented by the formula (5') and / or the formula (9'). In this case, it is easy to improve the impact resistance, elastic modulus and bending resistance of the optical film. Further, when the formula (5) is represented by the formula (5'), the skeleton containing a fluorine element enhances the solubility of the polyamide-imide resin in the solvent and improves the storage stability of the varnish containing the resin. In addition to being easy, it is easy to reduce the viscosity of the varnish and improve the processability of the optical film. Further, the skeleton containing a fluorine element makes it easy to improve the optical characteristics of the optical film.

In a preferred embodiment of the present invention, Y in the polyamide-imide resin is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more, according to the formula (5), particularly the formula (5). It is represented by'). When Y in the above range in the polyamide-imide resin is represented by the formula (5), particularly the formula (5'), the skeleton containing a fluorine element enhances the solubility of the polyamide-imide resin in a solvent and contains the resin. It is easy to reduce the viscosity of the varnish, and it is easy to improve the workability of the optical film. Further, the skeleton containing a fluorine element makes it easy to improve the optical characteristics of the optical film. It should be noted that preferably, 100 mol% or less of Y in the above-mentioned polyamide-imide resin is represented by the formula (5), particularly the formula (5'). Y in the polyamide-imide resin may be of the formula (5), particularly of the formula (5'). The ratio of the structural units represented by the formula (5) of Y in the polyamide-imide resin ^{can be measured using, for example, 1 1} H-NMR, or can be calculated from the charging ratio of the raw materials.

In a preferred embodiment of the present invention, the plurality of structural units represented by the formula (1) are the structural units in which Y is represented by the formula (9) in addition to the structural units in which Y is represented by the formula (5). It is preferable to further include. When Y further includes the structural unit represented by the formula (9), the impact resistance and elastic modulus of the optical film can be further improved.

The polyamide-imide resin may contain a structural unit represented by the formula (30) and / or a structural unit represented by the formula (31), and may be represented by the formula (1) and optionally the formula (2). In addition to the structural unit represented by the formula (30), the structural unit represented by the formula (30) and / or the structural unit represented by the formula (31) may be included.

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, the polyamide-imide 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, the polyamide-imide 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 polyamide-imide resin is derived from 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 improving the optical characteristics, impact resistance, elastic modulus and bending resistance of the optical film, the ratio of the structural units represented by the formulas (1) and (2) in the above-mentioned polyamide-imide resin is expressed by the formula. Based on (1) and the formula (2), and optionally all the structural units represented by the formulas (30) and (31), preferably 80 mol% or more, more preferably 90 mol% or more, still more preferably. It is 95 mol% or more. In the polyamide-imide 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 based on all the constituent 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 polyamide imide resin, the content of the structural unit represented by the formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol or more, with respect to 1 mol of the structural unit represented by the formula (1). It is mol or more, more preferably 1.0 mol or more, particularly preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, still more preferably 4.5 mol or less. .. When the content of the structural unit represented by the formula (2) is at least the above lower limit, the impact resistance and elastic modulus of the optical film can be easily increased. Further, when the content of the structural unit represented by the formula (2) is not more than the above upper limit, the thickening due to the hydrogen bond between the amide bonds in the formula (2) is suppressed and the processability of the optical film is improved. Easy to make.

In a preferred embodiment of the present invention, the polyamide-imide 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 polyamide-imide resin contains a halogen atom, it is easy to improve the elastic modulus of the optical film and reduce the YI value. 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 polyamide-imide resin include, for example, a fluoro group and a trifluoromethyl group.

The content of halogen atoms in the polyamide-imide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, still more preferably 5 to 30% by mass, based on the mass of the polyamide-imide resin. When the content of the halogen atom is at least the above lower limit, the elastic modulus of the optical film is further improved, the water absorption rate is lowered, the YI value is further reduced, and the transparency and visibility are more likely to be improved. When the content of halogen atoms is not more than the above upper limit, synthesis becomes easy.

The imidization ratio of the polyamide-imide resin is preferably 90% or more, more preferably 93% or more, still more preferably 96% or more, and usually 100% or less. 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 imidization ratio indicates the ratio of the molar amount of imide bond in the polyamide-imide resin to the value twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyamide-imide resin. When the polyamide-imide 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 polyamide-imide 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 polyamide-imide 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 polyamide-imide resin is preferably 200,000 or more, more preferably 230,000 or more, still more preferably 230,000 or more, in terms of standard polystyrene, from the viewpoint of easily increasing the impact resistance, elastic modulus and bending resistance of the optical film. Is 250,000 or more, even more preferably 270,000 or more, and particularly preferably 280,000 or more. The weight average molecular weight of the polyamide-imide resin is preferably 1,000,000 or less, more preferably from the viewpoint of easily improving the solubility of the resin in a solvent and improving the stretchability and processability of the optical film. Is 800,000 or less, 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.

[Manufacturing method of polyamide-imide resin]
The polyamide-imide resin and the polyamide-imide precursor resin can be produced, for example, using a tetracarboxylic acid compound, a dicarboxylic acid compound and a diamine compound as main raw materials.

Examples of the diamine compound used in the production 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. , 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'- Diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4) -Aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] Propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) -4,4'-diaminodiphenyl (hereinafter, TFMB), 4,4'-bis (4-aminophenoxy) biphenyl, 9,9-bis (4-aminophenyl) fluorene, 9,9-bis (4-amino-3-methylphenyl) ) Aromatic diamines having two or more aromatic rings, such as fluorene, 9,9-bis (4-amino-3-chlorophenyl) fluorene, 9,9-bis (4-amino-3-fluorophenyl) fluorene, etc. Be done. These can be used alone or in combination of two or more.

The aromatic diamines are 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, TFMB, 4,4'- Bis (4-aminophenoxy) biphenyl, more preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethylbenzidine , TFMB, 4,4'-bis (4-aminophenoxy) biphenyl. These can be used alone or in combination of two or more.

Among the above diamine compounds, one or more selected from the group consisting of aromatic diamines having a biphenyl structure are selected from the viewpoints of high elastic modulus, high transparency, high flexibility, high bending resistance and low coloring property of the optical film. It is preferable to use it. One selected from the group consisting of 2,2'-dimethylbenzidine, 2,2'-bis (trifluoromethyl) benzidine, 4,4'-bis (4-aminophenoxy) biphenyl and 4,4'-diaminodiphenyl ether. It is more preferable to use the above, and it is even more preferable to use TFMB.

Examples of the tetracarboxylic acid compound used in the production of the resin include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. Be done. 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, 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-di) Carboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4'-(hexafluoroisopropylidene) diphthalic acid dianhydride (hereinafter referred to as 6FDA). (May be), 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis ( 3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2) , 3-Dicarboxyphenyl) methanedianhydride, 4,4'-(p-phenylenedioxy) diphthalic acid dianhydride, 4,4'-(m-phenylenedioxy) diphthalic acid dianhydride, and examples thereof. .. Examples of the monocyclic aromatic tetracarboxylic dianhydride include 1,2,4,5-benzenetetracarboxylic dianhydride, and the condensed polycyclic aromatic dianhydride dianhydride. Examples thereof include 2,3,6,7-naphthalenetetracarboxylic dianhydride.

Among these, preferably 4,4'-oxydiphthalic acid dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, 2,2', 3,3'-benzophenonetetracarboxylic dianhydride. Anhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-diphenyl Sulfontetracarboxylic 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, 6FDA, 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ) Etan dianhydride, 1,2-bis (3,4-dicarboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-) Dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxyphenyl) methane dianhydride, 4,4'-(p-phenylenedioxy) diphthalic acid dianhydride and 4,4'-(m-) Phenylenedioxy) diphthalic acid dianhydride is mentioned, more preferably 4,4'-oxydiphthalic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2',. Examples thereof include 3,3'-biphenyltetracarboxylic dianhydride, 6FDA, bis (3,4-dicarboxyphenyl) methane dianhydride and 4,4'-(p-phenylenedioxy) diphthalic acid dianhydride. .. 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, 4,4'from the viewpoints of high impact resistance, high elasticity, high surface hardness, high transparency, high flexibility, high bending resistance, and low coloring property of the optical film. -Oxydiphthalic dianhydride, 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) propanedianhydride, 6FDA , And a mixture thereof, preferably 3,3', 4,4'-biphenyltetracarboxylic dianhydride and 6FDA, and a mixture thereof, more preferably 6FDA and 3,3', 4,4'-biphenyltetra. A carboxylic dianhydride is more preferred.

As the dicarboxylic acid compound used in the production of the resin, terephthalic acid, isophthalic acid, 4,4'-oxybis benzoic acid or an acid chloride compound thereof is preferably used. In addition to terephthalic acid, isophthalic acid, 4,4'-oxybis benzoic acid or their acid chloride compounds, other dicarboxylic acid compounds may be used. Examples of other dicarboxylic acid compounds include aromatic dicarboxylic acids, aliphatic dicarboxylic 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 a dicarboxylic acid compound of isophthalic acid; naphthalenedicarboxylic acid; 4,4'-biphenyldicarboxylic acid; 3,3'-biphenyldicarboxylic acid; a chain hydrocarbon having 8 or less carbon atoms, and two benzoic acids. Examples thereof include compounds in which is single-bonded, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- or phenylene groups, and their acid chloride compounds. Specific examples thereof are 4,4'-oxybis (benzoyl chloride) (hereinafter, may be referred to as OBBC), terephthalic acid chloride (hereinafter, which may be referred to as TPC) or isophthaloyl chloride, and OBBC and TPC are preferable. It is more preferable to use in combination with.

The polyamide-imide resin is obtained by further reacting tetracarboxylic acid and tricarboxylic acid and their anhydrides and derivatives in addition to the tetracarboxylic acid compound as long as the various physical properties of the optical film are not impaired. May be good.

Examples of the tetracarboxylic acid include a water adduct of the anhydride of the tetracarboxylic acid compound.

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 anhydride of 1,3,5-benzenetricarboxylic acid; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthalic acid. A compound in which an anhydride and benzoic acid are single-bonded, -O-, -CH _2- , -C (CH ₃ ) _2- , -C (CF ₃ ) _2- , -SO _2- or a phenylene group is linked. Can be mentioned.

In the production of the resin, the amount of the diamine compound, the tetracarboxylic acid compound and / or the dicarboxylic acid compound used may be appropriately selected according to the ratio of each structural unit of the desired polyamide-imide resin, but as described above, By synthesizing the polyamide-imide resin so that the amount of dicarboxylic acid present at the end of the polyamide-imide resin is as small as possible, the ratio (int _A / int _B ) can be adjusted to a desired range. Therefore, as described above, the amine ratio (molar amount of diamine compound / (total molar amount of tetracarboxylic acid compound and dicarboxylic acid compound)) when copolymerizing the tetracarboxylic acid compound, dicarboxylic acid compound and diamine compound is preferable. Adjusted the amount of each monomer used so that It is preferable to do so.

The present invention is a method for producing a polyamide-imide resin in which a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compound are reacted, and the molar amount of the diamine compound is based on the total number of moles of the tetracarboxylic acid compound and the dicarboxylic acid compound. Also provided is a method for producing a polyamide-imide resin having a number ratio (amine ratio) of more than 1.000.

In the production of the resin, the reaction temperature of the diamine compound, the tetracarboxylic acid compound and the dicarboxylic acid compound is not particularly limited, but is, for example, 5 to 350 ° C., preferably 20 to 200 ° C., and more preferably 25 to 100 ° C. From the viewpoint that the ratio (int _A / int _B ) can be easily adjusted to a desired range, the reaction vessel may be locally heated in some cases to adjust the reaction temperature to the above-mentioned reaction temperature. Often, the amount of acid anhydride such as acetic anhydride may be adjusted together with the amount of the imidization catalyst described below at the same time as local heating. 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; ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone (hereinafter sometimes referred to as GBL), γ-valerolactone, propylene glycol methyl ether Ester solvents such as acetate and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane and heptane; ethylcyclohexane and the like. Alicyclic hydrocarbon solvent; aromatic hydrocarbon solvent such as toluene and xylene; nitrile solvent such as acetonitrile; ether solvent such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvent such as chloroform and chlorobenzene; N, N-dimethylacetamide Amid-based solvents such as (hereinafter, may be referred to as DMAc) and N, N-dimethylformamide (hereinafter, may be referred to as DMF); sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane; ethylene carbonate, Carbonated solvents such as propylene carbonate; and combinations thereof may be mentioned. Among these, an amide-based solvent can be preferably used from the viewpoint of solubility. From the viewpoint that the ratio (int _A / int _B ) can be easily adjusted to a desired range, the amount of water in the solvent used is preferably adjusted to 400 ppm or more, more preferably 500 ppm or more. From the viewpoint of suppressing the decomposition of the polyamide-imide resin, the water content in the solvent is preferably 1,000 ppm or less, more preferably 800 ppm or less.

In the imidization step in the production of the polyamide-imide resin, imidization can be performed in the presence of an imidization catalyst. 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. From the viewpoint that the ratio (int _A / int _B ) can be easily adjusted to a desired range, it is preferable to lower the heating rate in the imidization step, and it is possible to take 30 minutes or more to raise the temperature from 10 ° C. to 50 ° C. More preferred.

The polyamide-imide resin may be 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, which is preferable. In the embodiment, it can be isolated by adding a large amount of alcohol such as methanol to a reaction solution containing a transparent polyamide-imide resin, precipitating the resin, and performing concentration, filtration, drying, and the like.

[Optical film]
The present invention also provides an optical film containing the above-mentioned polyamide-imide resin of the present invention. In one embodiment of the present invention, the content of the polyamide-imide resin of the present invention in the optical film of the present invention is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, based on 100 parts by mass of the optical film. It is more preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, and more preferably 95 parts by mass or less. When the content of the polyamide-imide resin is within the above range, it is easy to improve the optical properties, impact resistance and elastic coefficient of the optical film, and it is easy to suppress the deterioration of the optical properties and mechanical properties of the optical film with time. , It is easy to improve the quality stability of the optical film.

The optical film of the present invention may contain at least one filler in addition to the polyamide-imide resin of the present invention. 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 increasing the elasticity and / or tear strength of the optical film and easily improving the impact resistance. , 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 11 nm or more, particularly preferably 13 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 filler, preferably silica particles, is within the above range, aggregation of the filler, preferably silica particles is suppressed, and the optical characteristics of the obtained optical film can be easily improved. 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 TEM or a scanning electron microscope SEM.

When the optical film of the present invention contains a filler, preferably silica particles, the content of the filler is usually 0.1 part by mass or more, preferably 1 part by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the optical film. It is 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 60 parts by mass or less. When the content of the filler is at least the above lower limit, the elastic modulus of the obtained optical film can be easily improved. Further, when the content of the filler is not more than the above upper limit, the optical characteristics of the optical film can be easily improved.

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 obtained 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 part by mass or more, more preferably 2 parts by mass or more, still more preferably 3 parts by mass or more with respect to 100 parts by mass of the optical film. It is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 6 parts 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 fillers and ultraviolet absorbers. Other additives include, for example, antioxidants, mold release agents, stabilizers, bluing 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 parts by mass, more preferably 0.01 to 15 parts by mass, and further preferably 0.1 with respect to 100 parts by mass of the optical film. It may be 10 parts by mass.

In a preferred embodiment of the present invention, the optical film of the present invention containing the above-mentioned polyamide-imide resin of the present invention can easily suppress deterioration of optical properties and mechanical properties over time, and can easily improve quality stability. The rate of change in the weight average molecular weight before and after the storage test in which the product is stored for one week under the conditions of a temperature of 85 ° C. and a humidity of 85% is preferably 26% or less. Further, in a more preferable aspect of the present invention, the optical film of the present invention containing the above-mentioned polyamide-imide resin of the present invention is likely to suppress deterioration of optical properties and mechanical properties over time, and is likely to enhance quality stability. From the viewpoint, it is preferable that the rate of change in the weight average molecular weight before and after the storage test of storing for one week under the conditions of a temperature of 85 ° C. and a humidity of 85% is 25% or less. When the rate of change in weight average molecular weight under the above conditions exceeds 26% or 25%, the polyamide resin contained in the optical film depends on the storage conditions in the optical film and the storage conditions of the display device incorporating the optical film. It is considered that some reaction may occur and the optical property and / or the mechanical property may be easily deteriorated with time. The rate of change in weight average molecular weight is more preferably 25% or less, even more preferably 23% or less, and even more preferably 22% or less. In the present invention, the rate of change in the weight average molecular weight before and after the storage test of storing for one week under the conditions of a temperature of 85 ° C. and a humidity of 85%, which is unlikely to cause a decrease in optical properties and / or mechanical properties over time, is preferably 26%. Hereinafter, a polyamide-imide resin-containing optical film, which is more preferably 25% or less, is also provided. The rate of change in the weight average molecular weight before and after the storage test is preferably 26% or less, more preferably 25% or less, still more preferably 23% or less, still more preferably 22% or less. The rate of change in the weight average molecular weight can be calculated by, for example, the method described in Examples. Regarding the above-mentioned polyamide-imide resin-containing optical film in which the rate of change in weight average molecular weight before and after the above storage test is preferably 26% or less, more preferably 25% or less, the rate of change in weight average molecular weight is set to the above upper limit or less. ^{The method is not particularly limited, but for example, in the 1} H- ¹³ C HSQC spectrum obtained by using a dehydrohydride dimethyl sulfoxide solution of the polyamide-imide resin contained in the optical film as a measurement sample, the chemical shift of protons is 8.06 to _{The integrated value (int A} ) of the peak existing in the region (A) where the chemical shift of carbon is 12.14 ppm and the chemical shift of carbon is 129.6 to 130.3 ppm, and the chemical shift of protons are 7.26 to 7. is 85 ppm, and the integral value of the peak carbon chemical shift is present in the region (B) is a 132.4~134.0ppm the proportion between the _{(int B) (int a /} int B) 1.5% In the following cases, it is easy to adjust the rate of change in weight average molecular weight to the above upper limit or less. By setting the ratio (int _A / int _B ) to a specific range or less, the rate of change in the weight average molecular weight can be easily adjusted to a specific range, but the decrease in optical properties and mechanical properties over time is suppressed. From the viewpoint, it is not essential to set the rate of change of the weight average molecular weight within a specific range, and it is important to keep _{the ratio (int A} / int _{B) below the specific range.}

The elastic modulus of the optical film of the present invention is preferably 4.5 GPa or more, more preferably 4.8 GPa or more, still more preferably 5.0 GPa or more, and even more, from the viewpoint of easily preventing wrinkles and scratches of the optical film. It is preferably 5.1 GPa or more, particularly preferably 5.2 GPa or more, and usually 100 GPa or less. The elastic modulus can be measured using a tensile tester (distance between chucks 50 mm, tensile speed 10 mm / min), for example, by the method described in Examples.

The total light transmittance (hereinafter, may be abbreviated as Tt) of the optical film of the present invention is preferably 80% or more, more preferably 85% or more, still more preferably 88% or more, still more preferably 89% or more. Particularly preferably, it is 90% or more, and usually 100% or less. When the total light transmittance is equal to or higher than the above lower limit, it is easy to improve the visibility when the optical film is incorporated into the display device as the front plate. Since the optical film of the present invention usually exhibits a high total light transmittance, the emission intensity of a display element or the like required to obtain a constant brightness is suppressed as compared with the case where a film having a low transmittance is used, for example. It becomes possible. Therefore, power consumption can be reduced. For example, when the optical film of the present invention is incorporated into a display device, a bright display tends to be obtained even if the amount of light from the backlight is reduced, which can contribute to energy saving. The total light transmittance can be measured using a haze computer in accordance with, for example, JIS K 7361-1: 1997. The total light transmittance may be the total light transmittance in the range of the thickness of the optical film described later. In the present specification, when the optical film is excellent in optical characteristics, it means that the total light transmittance is high and / or the haze is low and / or the YI is low.

The haze of the optical film of the present invention is preferably 5% or less, more preferably 4% or less, still more preferably 3% or less, even more preferably 2.5% or less, particularly preferably 2% or less, and particularly more preferably. It is 1% or less, more preferably 0.5% or less, and usually 0.01% or more. When the haze of the optical film is not more than the above upper limit, it is easy to improve the visibility when the optical film is incorporated into the display device as the front plate. The haze can be measured using a haze computer in accordance with JIS K 7136: 2000.

The YI value of the optical film of the present invention is preferably 3.0 or less, more preferably 2.0 or less, still more preferably 1.9 or less, particularly preferably 1.8 or less, and usually -5 or more. It is preferably -2 or more. When the YI value of the optical film is not more than the above upper limit, the transparency becomes good, and when it is used for the front plate of the display device, it can contribute to high visibility. From the viewpoint of enhancing quality stability, the YI value is preferably within the above range even after being stored for one week under the conditions of a temperature of 85 ° C. and a humidity of 85%. This YI value is measured by measuring the transmittance for light of 300 to 800 nm using an ultraviolet-visible near-infrared spectrophotometer, and the tristimulus values (X, Y, Z) are obtained, and YI = 100 × (1.2769X-1). It can be calculated based on the formula of .0592Z) / Y. The optical film preferably has a YI value in the above range even after a storage test in which the optical film is stored at a temperature of 85 ° C. and a humidity of 85% for one week.

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

The pencil hardness of at least one surface of the optical film of the present invention is preferably HB or higher, more preferably F or higher. When the pencil hardness of at least one surface of the optical film is equal to or higher than the above hardness, it is easy to prevent scratches or the like on the surface of the optical film. The pencil hardness can be measured according to JIS K 5600-5-4: 1999.

The optical film of the present invention has excellent bending resistance. The number of bending resistances of the optical film of the present invention in the MIT folding fatigue resistance test according to ASTM standard D2176-16 is preferably 50,000 times or more, more preferably 60,000 times or more, still more preferably 70,000 times or more. Is. When the bending resistance is not more than the above lower limit, it is possible to prevent scratches due to bending when used as a front plate material for a flexible display or the like. The MIT fold resistance fatigue test can be measured using a MIT fold resistance fatigue tester, for example, by the method described in Examples. The optical film is preferably stored 35,000 times or more, more preferably 40,000 times or more, and further preferably 50,000 times even after a storage test in which the optical film is stored at a temperature of 85 ° C. and a humidity of 85% for one week. It is preferable to satisfy the above bending resistance times.

The optical film of the present invention is an optical film having excellent quality stability in which deterioration of optical properties and mechanical properties with time is suppressed. Specifically, the optical film is stored in an environment of a temperature of 85 ° C. and a relative humidity of 85% for one week, and the number of times the optical film is bent (N1) before the storage test and the number of times the optical film is bent after the storage test. (N2) is allowed to stand at a temperature of 25 ° C. and a humidity of 50% for 24 hours or more, and then measured using a MIT folding fatigue tester under the conditions described in, for example, Examples. From the obtained number of bending resistances, the following formula:
Rate of change in bending resistance (%) = {(N1-N2) / N1} x 100
The smaller the rate of change (%) of the bending resistance calculated by the above, the smaller the better, but it is preferably 40% or less, more preferably 35% or less, still more preferably 30% or less, still more preferably 25% or less, in particular. It is preferably 20% or less.

Further, the YI value (Y1) of the optical fill before the storage test and the YI value (Y2) of the optical film after the storage test are measured by using an ultraviolet-visible near-infrared spectrophotometer, for example, the method described in Examples. Calculate with. From the obtained YI value, the following formula:
Rate of change of YI value (%) = {(Y2-Y1) / Y1} × 100
The smaller the rate of change (%) of the YI value calculated according to the above, the smaller the better, but it is preferably 25% or less, more preferably 20% or less, and further preferably 15% or less.

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

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

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 DMAc and DMF; lactone solvents such as GBL and γ-valerolactone; sulfur-containing solvents such as dimethyl sulfoxide, dimethyl sulfoxide and sulfolane; and carbonate solvents such as ethylene carbonate and propylene carbonate. Solvents; and combinations thereof. 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 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 20% by mass, and further preferably 5 to 15% by mass.

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

Examples of the support material include a SUS plate for a metal-based material, a PET film, a PEN film, a polyamide-based resin film for a resin-based material, another polyimide-based resin film, a cycloolefin-based polymer film, an acrylic-based film, and the like. Be done. Among them, a PET film, a cycloolefin-based polymer film and the like are preferable from the viewpoint of excellent smoothness and heat resistance, and a PET film is more preferable from the viewpoint of adhesion to an optical film and cost.

The use of the optical film of the present invention is not particularly limited, and it may be used for various purposes. 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 may be used as a laminated body with another film. .. 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.

(Functional layer)
One or more functional layers may be laminated on at least one surface of the optical film of the present invention. Examples of the functional layer include an ultraviolet absorbing layer, a hard coat layer, a primer layer, a gas barrier layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer. The functional layer can be used alone or in combination of two or more.

A hard coat layer may be provided on at least one surface of the optical film of the present invention. The thickness of the hard coat layer is not particularly limited and may be, for example, 2 to 100 μm. When the thickness of the hard coat layer is within the above range, the impact resistance can be further enhanced, the bending resistance is less likely to be lowered, 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 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 and has low toxicity, accelerates the network formation rate obtained from the cationically polymerizable compound of the obtained hard coat layer, and is a radical. Even in the region mixed with the polymerizable compound, there are advantages such as forming an independent network without leaving unreacted monomers in the film.
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 their alkylene oxide adducts and caprolactone adducts with epichlorohydrin. And novolak epoxy resin and the like, and glycidyl ether type epoxy resin derived from bisphenols and the like can be mentioned.

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 reaction. 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 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 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 (sometimes referred to as 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 broken by an appropriate means such as pressure or heat" (specified in JIS K 6800).

The hue adjusting layer is a layer having a hue adjusting function, and is a layer capable of adjusting a laminate containing 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 an optical film and capable of imparting a predetermined refractive index to the optical laminate. The refractive index adjusting layer may be, for example, a resin layer 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.

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

In a preferred embodiment of the present invention, the optical film of the present invention is a front plate of an image display device, particularly a front plate of a flexible display device (hereinafter, may be referred to as a window film), a rollable display or a foldable display. Very useful as a front plate. The flexible display device has, for example, a flexible functional layer and an optical film that is superposed on the flexible functional layer and functions as a front plate. That is, the front plate of the flexible display device is arranged on the visual side on the flexible functional layer. This front plate has a function of protecting a flexible functional layer, for example, an image display element in a flexible display. The flexible display device is a display device that is used with operations such as repeatedly bending and repeatedly winding the image display device. High bending resistance is required for the front plate of a flexible display device used with such repeated bending operations. The front plate is also required to have high visibility. Compared with the film for the substrate of the image display device used inside the image display device, the front plate of the image display device, particularly the film for the front plate of the flexible display device, is required to have high visibility and high visibility. High bending resistance is required. For example, the film of the present invention preferably has the total light transmittance, haze and / or YI value as described above from the viewpoint of easily enhancing visibility when used for the front plate of a flexible display device. Further, from the viewpoint of easily increasing the bending resistance when used as the front plate of the flexible display device, it is preferable to satisfy the bending resistance number of times in the MIT folding resistance test as described above.

Examples of the image display device 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 device include all image display devices having flexible characteristics, and examples thereof include the rollable display and the foldable display as described above. The rollable display is an image display device in which an image display portion including a front plate is wound in a roll shape, and the image display portion is pulled out to form a flat surface or a curved surface, and is wound in a roll shape. It is an image display device in which operations such as taking are performed each time it is used. A foldable display is an image display device in which an image display portion including a front plate is bent and is used in a state where the image display portion is opened to form a flat surface or a curved surface, and an operation such as folding is used. It is an image display device that is performed every time. An image display device in which such operations such as winding and bending are repeatedly performed is referred to as a flexible image display device.

[Flexible display device]
The present invention also provides a flexible display device including 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. The flexible display device includes a laminated body for a flexible display device and an organic EL display panel, and the laminated body 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 a flexible display device may contain a window film, a polarizing plate, and a touch sensor, which are the optical films of the present invention, and the stacking order thereof is arbitrary, but from the visual side, the window film, the polarizing plate, and the polarizing plate, It is preferable that the touch sensor or window film, the touch sensor, and the polarizing plate are laminated in this order. The presence of the polarizing plate on the visual side of the touch sensor is preferable because the pattern of the touch sensor is less likely to be visually recognized 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]
The flexible display device of the present invention may further include a polarizing plate, preferably 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. If the thickness is within the above range, the flexibility 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, a liquid crystal coating type polarizer formed by coating a liquid crystal polarizing composition may be used. 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 it is preferable that the liquid crystal compound has a higher-order orientation state such as a smectic phase because it can exhibit high polarization performance. It is also preferable that the liquid crystal compound has a polymerizable functional group.

The dichroic dye is a dye that is oriented together with the liquid crystal compound to exhibit dichroism, and the dichroic dye itself may have liquid crystal properties or has a polymerizable functional group. You can also do it. Any compound 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. The thickness of the liquid crystal polarizing layer may be preferably 0.5 to 10 μm, more preferably 1 to 5 μm.

The alignment film can be produced, for example, by applying an alignment film forming composition on a substrate and imparting orientation by rubbing, polarized light irradiation, or the like. The alignment film forming composition may contain a solvent, a cross-linking agent, an initiator, a dispersant, a leveling agent, a silane coupling agent, and the like in addition to the alignment agent. As the alignment agent, for example, polyvinyl alcohols, polyacrylates, polyamic acids, and polyimides can be used. When applying photo-orientation, 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 may be 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 from the viewpoint of orientation regulating force. 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.

The protective film may be a transparent polymer film, and specifically, the polymer film used has a unit of a monomer containing polyethylene, polypropylene, polymethylpentene, norbornene or cycloolefin. Polyolefins such as cycloolefin derivatives, (modified) celluloses such as diacetyl cellulose, triacetyl cellulose, propionyl cellulose, acrylics such as methyl methacrylate (co) polymer, polystyrenes such as styrene (co) polymer, acrylonitrile -Butadiene-styrene copolymers, acrylonitrile-styrene copolymers, ethylene-vinyl acetate copolymers, polyvinyl chlorides, polyvinylidene chlorides, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, poly Films such as polyesters such as allylate, polyamides such as nylon, polyimides, polyamideimides, polyetherimides, polyethersulfones, polysulfones, polyvinyl alcohols, polyvinylacetals, polyurethanes, epoxy resins, etc. In terms of excellent transparency and heat resistance, preferred examples include polyamide, polyamideimide, polyimide, polyester, olefin, acrylic or cellulose-based films. Each of these polymers can be used alone or in combination of two or more. These films are used unstretched or as uniaxially or biaxially stretched films. Cellulose-based films, olefin-based films, acrylic films, and polyester-based films are preferable. 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. If necessary, plasticizers, UV absorbers, infrared absorbers, colorants such as pigments and dyes, optical brighteners, dispersants, heat stabilizers, light stabilizers, antistatic agents, antioxidants, lubricants, solvents, etc. May include. The thickness of the protective film may be 200 μm or less, preferably 1 to 100 μm. When the thickness of the protective film is within the above range, the flexibility of the protective film is unlikely 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. Phase difference adjusters, plasticizers, UV absorbers, infrared absorbers, colorants such as pigments and dyes, optical brighteners, dispersants, heat stabilizers, light stabilizers, antioxidants, antioxidants as needed , Lubricants, solvents and the like may be contained. The thickness of the stretchable retardation plate may be 200 μm or less, preferably 1 to 100 μm. When the thickness is in the above range, the flexibility of the film tends to be difficult to decrease.
Further, as another example of the λ / 4 retardation plate, a liquid crystal coating type retardation plate formed by coating a liquid crystal composition may be used. The liquid crystal composition contains a liquid crystal compound having a property of exhibiting a liquid crystal state such as nematic, cholesteric, and smectic. Any compound, including the liquid crystal compound in the liquid crystal composition, has a polymerizable functional group. The liquid crystal coating type retardation plate 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 coating and curing a liquid crystal composition on an alignment film to form a liquid crystal retardation layer in the same manner as described in 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 may be usually 0.5 to 10 μm, 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 greater 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, an in-plane phase difference of λ / 4 with respect to the vicinity of 560 nm having high visual sensitivity, that is, 100 to 180 nm is preferable. Is often designed to be 130-150 nm. It is preferable to use a reverse dispersion λ / 4 retardation plate using a material having a birefringence wavelength dispersion characteristic opposite to the usual one because visibility can be improved. As such a material, those described in JP-A-2007-232873 for stretch-type retardation plates and those described in JP-A-2010-30979 for liquid crystal-coated retardation plates may be used. preferable.
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 and 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 it is preferable to use the liquid crystal coating type retardation plate in both cases because the thickness can be reduced.
A method of laminating a positive C plate on the circularly polarizing plate in order to improve visibility in an oblique direction is also 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 is usually −200 to −20 nm, preferably −140 to −40 nm.

[Touch sensor]
The flexible display device of the present invention may further include a touch sensor. The touch sensor is used as an input means. As the touch sensor, various types such as a resistive film method, a surface acoustic wave method, an infrared method, an electromagnetic induction method, and a capacitance method have been proposed, and any method may be used. Of these, the 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 the area where the screen is displayed on the display panel, that is, the area corresponding to the display unit, and the area where the user's touch is sensed, and the inactive area is the area where the screen is not displayed on the display device, that is, This is the area corresponding to the non-display part. The touch sensor is formed on a substrate having flexible characteristics; a sensing pattern formed in an active region of the substrate; and is formed in 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 properties, the same material as the polymer film can be used. The substrate of the touch sensor preferably has a toughness of 2,000 MPa% or more from the viewpoint of suppressing cracks in the touch sensor. More preferably, the toughness may be 2,000 to 30,000 MPa%. Here, toughness is defined as the lower area of the curve to the fracture point by the stress-strain curve obtained through the tensile experiment of the polymer material.

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 point to be touched. The first pattern is a form in which the unit patterns are connected to each other via a joint, but the second pattern has a structure in which the unit patterns are separated from each other into an island form, so that the second pattern is electrically connected. A separate bridge electrode is required for connection. A well-known transparent electrode material can be applied to the sensing pattern. For example, indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium zinc oxide oxide (IZTO), indium gallium zinc oxide (IGZO), cadmium tin oxide (CTO). , PEDOT (poly (3,4-ethylenedioxythiophene)), carbon nanotubes (CNT), graphene, metal wire and the like, and these can be used alone or in combination of two or more. ITO can be preferably used. The metal used for the metal wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, and chromium. These can be used alone or in combination of two or more.

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

[Adhesive layer]
Each layer such as a window film, a polarizing plate, and a touch sensor forming the flexible display device laminate, and a film member such as a linear polarizing plate and a λ / 4 retardation plate constituting each layer can be adhered with an adhesive. it can. Adhesives include water-based adhesives, organic solvent-based adhesives, solvent-free adhesives, solid adhesives, solvent volatilization adhesives, moisture-curable adhesives, heat-curable adhesives, anaerobic curable adhesives, and water-based adhesives. It is widely used in solvent volatilization adhesives, active energy ray-curable adhesives, hardener mixed adhesives, heat-melt adhesives, pressure-sensitive adhesives, pressure-sensitive adhesives, re-wet adhesives, etc. Things can be used. Of these, water-based solvent volatilization adhesives, active energy ray-curable adhesives, and adhesives are often used. The thickness of the adhesive layer can be appropriately adjusted according to the required adhesive force and the like, and is, for example, 0.01 to 500 μm, preferably 0.1 to 300 μm. A plurality of adhesive layers may be present in the laminated body for the flexible image display device, but the thickness of each adhesive layer and the type of adhesive used 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 water and the main polymer, a cross-linking agent, a silane compound, an ionic compound, a cross-linking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent and the like may be 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 aqueous solvent volatilization type adhesive is used, the thickness of the adhesive layer may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the water-based solvent volatilization type adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive may be the same or different.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material that is irradiated with 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 the hard coat composition. The radically polymerizable compound is the same as the hard coat composition, and the same kind as the hard coat composition can be used. As the radically polymerizable compound used for the adhesive layer, a compound having an acryloyl group is preferable. It is also preferable to include a monofunctional compound in order to reduce the viscosity of the adhesive composition.

The cationically polymerizable compound is the same as the hard coat composition, and the same kind as the hard coat composition can be used. As the cationically polymerizable compound used in the active energy ray-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 may further contain a polymerization initiator. The polymerization initiator includes a radical polymerization initiator, a cationic polymerization initiator, a radical or cationic polymerization initiator, and the like, and can be 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 adhering with the active energy ray-curable adhesive, the active energy ray-curable composition is applied to either or both of the adherend layers and then bonded, and is activated through either or both adherend layers. Adhesion can be achieved by irradiating with energy rays and curing. When the active energy ray-curable adhesive is used, the thickness of the adhesive layer may be usually 0.01 to 20 μm, preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of layers, the thickness of each layer and the type of adhesive used may be the same or different.

The pressure-sensitive adhesive may be classified into acrylic pressure-sensitive adhesives, urethane-based pressure-sensitive adhesives, rubber-based pressure-sensitive adhesives, silicone-based pressure-sensitive adhesives, and the like, depending on the main polymer. 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 and an adhesive layer are formed by dissolving and dispersing each component constituting the pressure-sensitive adhesive in a solvent to obtain a pressure-sensitive adhesive composition, applying the pressure-sensitive adhesive composition on a substrate, and then drying 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 pressure-sensitive adhesive is used, the thickness of the adhesive layer may be usually 1 to 500 μm, preferably 2 to 300 μm. When the pressure-sensitive adhesive is used for forming a plurality of layers, the thickness of each layer and the type of pressure-sensitive adhesive used may be the same or different.

[Shading pattern]
The shading pattern can be applied as at least a part of the bezel or housing of the flexible image display device. The light-shielding pattern hides the wiring arranged at the edge of the flexible image 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 can have 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 light-shielding pattern is usually 1 to 100 μm, 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 with reference to Examples. Unless otherwise specified, "%" and "part" in the example mean mass% and parts by mass. First, the evaluation method will be described.

<Measurement of _{(int A} / int _B ) by HSQC-NMR>
_{(Int A} / int _B ) by HSQC-NMR was obtained as follows.
(1) Method for preparing measurement sample A 2% by mass solution prepared by dissolving a polyamide-imide resin in deuterated dimethyl sulfoxide (DMSO-d _{6) was used as a measurement solution.}
(2) Measurement conditions Measuring device: Bruker 600 MHz NMR device AVANCE600
Sample temperature: 303K
Measurement method: HSQC
Chemical shift criteria: DMSO (proton 2.49 ppm, carbon 40.44 ppm)
(3) Analysis method In the obtained HSQC-NMR spectrum, the peak existing in the region A in which the chemical shift of protons is 8.06 to 8.14 ppm and the chemical shift of carbon is 129.6 to 130.3 ppm. The volume was obtained by integration to obtain the integrated value (int _A ). Further, the volume of the peak existing in the region B in which the chemical shift of protons is 7.26 to 7.85 ppm and the chemical shift of carbon is 132.4 to 134.0 ppm is obtained by integration, and the integrated value (int _{B) is obtained.} ) Was obtained. By calculating the ratio of the integrated value (int _A ) to the integrated value (int _B ), the ratio (int _A / int _B ) [%] was obtained.

<Measurement of weight average molecular weight of polyamide-imide resin (polystyrene equivalent weight average molecular weight)>
Gel Permeation Chromatography (GPC) Measurement (1) Pretreatment Method DMF eluent (10 mmol / L lithium bromide-added solution) was added to the polyamide-imide film to a concentration of 2 mg / mL, and the mixture was stirred at 80 ° C. for 30 minutes. After heating and cooling, the solution was filtered through a 0.45 μm membrane filter to prepare a measurement solution.
(2) Measurement condition Column: TSKgel α-2500 manufactured by Tosoh Corporation ((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

<Rate of change in weight average molecular weight>
The optical films obtained in Examples and Comparative Examples were stored for 1 week in an environment having a temperature of 85 ° C. and a relative humidity of 85%. Then, the weight average molecular weight (Mw1) of the polyamide-imide resin contained in the optical fill before the storage test and the weight average molecular weight (Mw2) of the polyamide-imide resin contained in the optical film after the storage test are measured according to the above method. did. From the obtained weight average molecular weight, the rate of change (%) of the weight average molecular weight was calculated according to the following formula.
Rate of change in weight average molecular weight (%) = {(Mw1-Mw2) / Mw1} × 100

<Thickness>
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.).

<Elastic modulus>
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.

<Total light transmittance (Tt)>
In accordance with JIS K 7105: 1981, the total light transmittance 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.).

<Haze>
In accordance with JIS K 7136: 2000, the optical films obtained in Examples and Comparative Examples were cut into a size of 30 mm × 30 mm, and a fully automatic direct reading haze computer (HGM-2DP manufactured by Suga Test Instruments Co., Ltd.) was used. Haze (%) was measured using.

<YI value>
The tristimulus values (X, Y, Z) were calculated using an ultraviolet-visible near-infrared spectrophotometer (V-670 manufactured by JASCO Corporation) and substituted into the following formula to calculate the YI value. ..
YI = 100 × (1.2769X-1.0592Z) / Y

<Rate of change in YI value>
A storage test was carried out in which the optical films obtained in Examples and Comparative Examples were stored in an environment of a temperature of 85 ° C. and a relative humidity of 85% for one week. The YI value (Y1) of the optical film before the storage test and the YI value (Y2) of the optical film after the storage test were measured according to the above method. From each of the obtained YI values, the rate of change (%) of the YI value was calculated according to the following formula.
Rate of change of YI value (%) = {(Y2-Y1) / Y1} × 100

<Number of bending resistance in MIT test>
The optical films obtained in Examples and Comparative Examples were each cut into a size of 10 mm × 100 mm using a dumbbell cutter. The cut film is allowed to stand at a temperature of 25 ° C. and a humidity of 50% for 24 hours or more, set in a MIT folding fatigue tester (“MIT-DA” format: 0530 manufactured by Toyo Seiki Seisakusho Co., Ltd.), and bent at a test speed of 175 cpm. A bending test was carried out in both the front and back directions under the conditions of an angle of 135 °, a load of 750 g, and a bending clamp R of 1.0 mm, and the number of times each film was bent, that is, the number of times it could be bent without breaking was measured.

<Rate of change in bending resistance>
The optical films obtained in Examples and Comparative Examples were stored for 1 week in an environment having a temperature of 85 ° C. and a relative humidity of 85%. Then, the bending resistance (N1) of the optical film before the storage test and the bending resistance (N2) of the optical film after the storage test are set to a temperature of 25 ° C. and a humidity of 50% for 24 hours or more. It was measured according to the above method. From the obtained number of bending resistances, the rate of change (%) of the number of bending resistances was calculated according to the following formula.
Rate of change in bending resistance (%) = {(N1-N2) / N1} x 100

<Amine ratio>
Used for the synthesis of the polyamide-imide resin, a molar amount of the diamine compound and M _A mole, the molar amount of the dicarboxylic acid compound and M _B moles, the molar amount of the tetracarboxylic acid compound and M _C mol, by the following equation, The amine ratio in the synthesis of the resin was calculated.
Amine ratio _{= M A / (M B +} M C)

<Example 1>
Under a nitrogen gas atmosphere, 313.57 g of DMAc was added to a 1 L separable flask equipped with a stirring blade, and a required amount of ion-exchanged water was added so that the water content became 700 ppm. Then, 18.53 g (57.86 mmol) of TFMB was added, and TFMB was dissolved in DMAc with stirring at room temperature. Next, 7.64 g (17.19 mmol) of 6FDA was added to the flask, the mixture was cooled to 10 ° C., and the mixture was stirred for 16 hours. Then 1.69 g (5.73 mmol) of OBBC and then 6.28 g (30.93 mmol) of TPC were added to the flask and stirred at 10 ° C. for 30 minutes. Next, 313.57 g of DMAc adjusted to a water content of 700 ppm was added, and the mixture was stirred for 10 minutes. Then, 0.70 g (3.45 mmоl) of TPC was added to the flask, and the mixture was stirred at 10 ° C. for 30 minutes, and then TFMB 0.0367 g. (0.115 mmоl) was added, and the mixture was stirred for 2 hours. Next, 5.18 g (40.11) of diisopropylethylamine, 3.74 g (40.11 mmol) of 4-methylpyridine, and 12.29 g (120.30 mmol) of acetic anhydride were added to the flask, and the mixture was stirred at 10 ° C. for 30 minutes. Then, using an oil bath, the temperature was raised from 10 ° C. to 50 ° C. for 30 minutes, from 50 ° C. to 60 ° C. for 10 minutes, and from 60 ° C. to 65 ° C. for 10 minutes, respectively, and then from 65 ° C. to 70 ° C. for 10 minutes. The temperature was gradually raised from 70 ° C. to 75 ° C. over 10 minutes, and the mixture was further stirred at 70 ° C. 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 60 ° C. to obtain a polyamide-imide resin (1).

The polyamide-imide resin (1) was dissolved in DMAc to prepare a 10% by mass solution, and the obtained polyamide-imide varnish was filtered through a filter having an opening of 10 μm, and then a polyester substrate (manufactured by Toyo Boseki Co., Ltd., trade name “A4100”). ”) Is applied on the smooth surface of the self-supporting film using an applicator so that the thickness of the free-standing film is 55 μm, dried at 50 ° C. for 30 minutes, and then dried at 140 ° C. for 15 minutes, and then the obtained coating film is obtained from the polyester substrate. It was peeled off 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 1 having a thickness of 50 μm.

<Comparative example 1>
Under a nitrogen gas atmosphere, 313.57 g of DMAc was added to a 1 L separable flask equipped with a stirring blade, and a required amount of ion-exchanged water was added so that the water content became 700 ppm. Then 18.27 g (57.05 mmol) of TFMB was added and TFMB was dissolved in DMAc with stirring at room temperature. Next, 7.76 g (17.47 mmol) of 6FDA was added to the flask, the mixture was cooled to 10 ° C., and the mixture was stirred for 16 hours. Then 1.72 g (5.85 mmol) of OBBC and then 6.38 g (31.43 mmol) of TPC were added to the flask and stirred at 10 ° C. for 30 minutes. Next, 313.57 g of DMAc adjusted to a water content of 700 ppm was added and stirred for 10 minutes, then 0.71 g (3.50 mmоl) of TPC was further added to the flask, and the mixture was stirred at 10 ° C. for 30 minutes, and then 0.186 g of TFMB. (0.581 mmоl) was added, and the mixture was stirred for 30 minutes, then 0.0932 g (0.291 mmоl) of TFMB was further added, and the mixture was stirred for 2 hours. Next, 5.27 g (40.76) of diisopropylethylamine, 3.80 g (40.76 mmol) of 4-methylpyridine, and 12.48 g (122.27 mmol) of acetic anhydride were added to the flask, and the mixture was stirred at 10 ° C. for 30 minutes. .. Then, using an oil bath, the temperature is gradually raised from 10 ° C. to 50 ° C. for 20 minutes, from 50 ° C. to 60 ° C. for 20 minutes, and from 60 ° C. to 75 ° C. for 20 minutes, respectively, and then at 75 ° C. for 3 hours. The mixture was stirred while keeping warm 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 60 ° C. to obtain a polyamide-imide resin (2).

An optical film 2 having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyamide-imide resin (2) was used.

<Comparative example 2>
Under a nitrogen gas atmosphere, 313.57 g of DMAc was added to a 1 L separable flask equipped with a stirring blade. At this time, the amount of water in DMAc was 300 ppm. Then 18.36 g (57.33 mmol) of TFMB was added and TFMB was dissolved in DMAc with stirring at room temperature. Next, 7.72 g (17.38 mmol) of 6FDA was added to the flask, the mixture was cooled to 10 ° C., and the mixture was stirred for 16 hours. Then 1.71 g (5.81 mmol) of OBBC and then 6.35 g (31.28 mmol) of TPC were added to the flask and stirred at 10 ° C. for 30 minutes. Then, 313.57 g of DMAc having a water content of 300 ppm was added and stirred for 10 minutes, then 0.71 g (3.48 mmоl) of TPC was further added to the flask and stirred for 2 hours. Next, 5.24 g (40.54) of diisopropylethylamine, 7.55 g (81.08 mmol) of 4-methylpyridine, and 26.61 g (260.60 mmol) of acetic anhydride were added to the flask, and the mixture was stirred at 10 ° C. for 30 minutes. Then, using an oil bath, the temperature is gradually raised from 10 ° C. to 55 ° C. for 20 minutes, from 55 ° C. to 65 ° C. for 20 minutes, and from 65 ° C. to 85 ° C. for 20 minutes, respectively, and then at 85 ° C. for 3 hours. The mixture was stirred while keeping warm 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 60 ° C. to obtain a polyamide-imide resin (3).

An optical film 3 having a thickness of 50 μm was obtained in the same manner as in Example 1 except that the polyamide-imide resin (3) was used.

<Example 2>
Under a nitrogen atmosphere, 23.66 kg of TFMB and DMAc adjusted to a water content of 300 ppm were placed in ^{a 3 m 3} reaction vessel equipped with a stirring blade, and the solid content concentration of TFMB in the reaction mixture became 5.54% by mass. TFMB was dissolved in DMAc with stirring at room temperature. Next, 6 FDA was added to the reaction vessel so as to be 30.21 mol% with respect to TFMB, and the mixture was stirred at 25 ° C. for 16 hours. Then, TPC and OBBC were added to TFMB in an amount of 60.42 mol% and 10.07 mol%, respectively, and the mixture was stirred for 60 minutes. Next, 4-methylpyridine and acetic anhydride were added so as to be 35.25 mol% and 105.74 mol%, respectively, with respect to TFMB, and after stirring for 30 minutes, the average temperature of the wall surface and the bottom of the reaction mixture became high. It takes 30 minutes from 25 ° C to 50 ° C, 10 minutes from 50 ° C to 60 ° C, 10 minutes from 60 ° C to 65 ° C, and after raising the temperature, 10 from 65 ° C to 70 ° C. The temperature was gradually raised over a minute. At this time, a heating portion is provided on the wall surface of the reaction vessel so that about 70% of the height of the reaction mixture is heated, and the remaining bottom portion is a non-heating portion of the reaction vessel. The wall surface of the reaction vessel was heated by setting so that a temperature difference was generated between the wall surface and the bottom surface, and only the vicinity of the wall surface of the reaction mixture was locally heated. In this state, the mixture was stirred for 3 hours to obtain a reaction solution. At the end of the reaction, the unheated bottom was 65 ° C, while the locally heated wall was 81 ° C.
The obtained reaction solution is cooled to room temperature, 1.6 times by weight of methanol and 0.55 times by weight of water are added to the reaction solution with stirring, and the precipitated precipitate is taken out and washed with methanol. did. Next, the precipitate was dried under reduced pressure at 60 ° C. to obtain a polyamide resin (4). The weight average molecular weight of the obtained polyamide-imide resin (4) was 429000.

The polyamide-imide resin (4) was dissolved in DMAc to prepare a 10% by mass solution, and the obtained polyamide-imide varnish was filtered through a filter having an opening of 10 μm, and then a polyester substrate (manufactured by Toyo Boseki Co., Ltd., trade name “A4100”). ”) Is applied on the smooth surface of the self-supporting film using an applicator so that the thickness of the free-standing film is 55 μm, dried at 50 ° C. for 30 minutes, and then dried at 140 ° C. for 15 minutes, and then the obtained coating film is obtained from the polyester substrate. It was peeled off to obtain a self-supporting film. The free-standing film was fixed to a gold frame and further dried in the atmosphere at 200 ° C. for 40 minutes to obtain an optical film 4 having a thickness of 50 μm.

<Example 3>
Under a nitrogen atmosphere, 23.66 kg of TFMB and DMAc adjusted to a water content of 300 ppm were placed in ^{a 3 m 3} reaction vessel equipped with a stirring blade so that the solid content concentration of TFMB in the reaction mixture was 5.54% by mass. In addition, TFMB was dissolved in DMAc with stirring at room temperature. Next, 6 FDA was added to the reaction vessel so as to be 30.21 mol% with respect to TFMB, and the mixture was stirred at 25 ° C. for 16 hours. Then, TPC and OBBC were added to TFMB in an amount of 60.42 mol% and 10.07 mol%, respectively, and the mixture was stirred for 60 minutes. Next, 4-methylpyridine and acetic anhydride were added so as to be 35.25 mol% and 105.74 mol%, respectively, with respect to TFMB, and after stirring for 30 minutes, the average temperature of the wall surface and the bottom of the reaction mixture became high. The temperature was raised from 25 ° C to 50 ° C for 30 minutes, from 50 ° C to 60 ° C for 10 minutes, from 60 ° C to 65 ° C for 10 minutes, and then from 65 ° C to 70 ° C for 10 minutes. The temperature was raised stepwise. At this time, a heating portion is provided on the wall surface of the reaction vessel so that about 70% of the height of the reaction mixture is heated, and the remaining bottom portion is a non-heating portion of the reaction vessel. The wall surface of the reaction vessel was heated by setting so that a temperature difference was generated between the wall surface and the bottom surface, and only the vicinity of the wall surface of the reaction mixture was locally heated. In this state, the mixture was stirred for 3 hours to obtain a reaction solution. At the end of the reaction, the unheated bottom was 68 ° C, while the locally heated wall was 78 ° C.
The obtained reaction solution is cooled to room temperature, 1.6 times by weight of methanol and 0.55 times by weight of water are added to the reaction solution with stirring, and the precipitated precipitate is taken out and washed with methanol. did. Next, the precipitate was dried under reduced pressure at 60 ° C. to obtain a polyamide resin (5). The weight average molecular weight of the obtained polyamide-imide resin (5) was 410,000.

The polyamide-imide resin (5) was dissolved in DMAc to prepare a 10% by mass solution, and the obtained polyamide-imide varnish was filtered through a filter having an opening of 10 μm, and then a polyester substrate (manufactured by Toyo Boseki Co., Ltd., trade name “A4100”). ”) Is applied on the smooth surface of the self-supporting film using an applicator so that the thickness of the free-standing film is 55 μm, dried at 50 ° C. for 30 minutes, and then dried at 140 ° C. for 15 minutes, and then the obtained coating film is obtained from the polyester substrate. It was peeled off to obtain a self-supporting film. The free-standing film was fixed to a gold frame and further dried in the atmosphere at 200 ° C. for 40 minutes to obtain an optical film 5 having a thickness of 50 μm.

For Examples and Comparative Examples, the weight average molecular weight of the polyamide-imide resin, the elastic modulus of the optical film, the total light transmittance (Tt), the haze, and the YI value were measured. Further, using an optical film stored for one week in an environment of a temperature of 85 ° C. and a relative humidity of 85%, the weight average molecular weight, the YI value and the number of bending resistances were measured in the same manner, and these changes were made according to the above formula. The rate was calculated. The results obtained are shown in Table 1 below. Regarding the optical film of Comparative Example 1, the rate of change of the YI value was so large that it could not be used as an optical film, so the number of bending resistances was not evaluated.

Claims (13)

^{In the 1} H- ¹³ C HSQC spectrum obtained by using a deuterated dimethylsulfoxide solution of a polyamide-imide resin as a measurement sample, the chemical shift of protons was 8.06 to 8.14 ppm, and the chemical shift of carbon was 129.6. _{The integrated value (int A} ) of the peak existing in the region (A) of ~ 130.3 ppm, the chemical shift of the proton is 7.26 to 7.85 ppm, and the chemical shift of carbon is 132.4 to 134. integral value of peaks present in the region (B) is a .0ppm ratio between _{(int B) (int a /} int B) is 1.5% or less, a polyamide-imide resin. Equation (1):

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

[In formula (2), Z and X represent divalent organic groups independently of each other.
* Represents a bond]
The polyamide-imide resin according to claim 1, which has at least a structural unit represented by. The polyamide-imide resin according to claim 1 or 2, which has a weight average molecular weight of 200,000 or more and 1,000,000 or less. As X in the formula (1) or X in the formula (2), the formula (4):

[In formula (4), H ^4a and H ^4b represent hydrogen atoms.
R ^{4a to} R ^4d independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and are included in ^{R 4a to} R ^4d. Hydrogen atoms may be substituted with halogen atoms independently of each other.
* Represents a bond]
The polyamide-imide resin according to any one of claims 1 to 3, which has at least the structure represented by. As Z in equation (2), equation (3):

[In the formula (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 R ^3a. And the ^{hydrogen atoms contained in R 3b} 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]
The polyamide-imide resin according to any one of claims 1 to 4, which has at least the structure represented by. An optical film containing the polyamide-imide resin according to any one of claims 1 to 5. An optical film containing a polyamide-imide resin, wherein the rate of change in weight average molecular weight before and after a storage test in which the optical film is stored at a temperature of 85 ° C. and a humidity of 85% for one week is 26% or less. The optical film according to claim 7, wherein the rate of change in the weight average molecular weight before and after the storage test is 25% or less. A front plate of a flexible display device having the optical film according to any one of claims 6 to 8. A flexible display device including the front plate according to claim 9. The flexible display device according to claim 10, further comprising a touch sensor. The flexible display device according to claim 10 or 11, further comprising a polarizing plate. A method for producing a polyamideimide resin in which a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compound are reacted, wherein the ratio of the number of moles of the diamine compound to the total number of moles of the tetracarboxylic acid compound and the dicarboxylic acid compound is 1. The method for producing a polyamideimide resin according to any one of claims 1 to 5, which exceeds 000.