CN112778522A

CN112778522A - Polyamide-imide resin, optical film, and flexible display device

Info

Publication number: CN112778522A
Application number: CN202011217347.3A
Authority: CN
Inventors: 增井希望; 宫本皓史; 池内淳一
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2019-11-07
Filing date: 2020-11-04
Publication date: 2021-05-11

Abstract

The invention relates to a polyamide-imide resin, an optical film and a flexible display device. The invention provides an optical film with excellent quality stability and suppressed degradation of optical and mechanical properties over time, and a polymer capable of forming the optical filmAn amide imide resin. The solution is that the polyamide-imide resin is obtained by using deuterated dimethyl sulfoxide solution of the polyamide-imide resin as a measuring sample¹H‑¹³An integral value (int) of a peak existing in a region (A) in which a chemical shift of a proton is 8.06 to 8.14ppm and a chemical shift of carbon is 129.6 to 130.3ppm in a C HSQC spectrum_A) And an integral value (int) of a peak present in a region (B) having a chemical shift from proton of 7.26 to 7.85ppm and a chemical shift from carbon of 132.4 to 134.0ppm_B) Ratio of (int)_A/int_B) Is 1.5% or less.

Description

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

Technical Field

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

Background

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 smartwatches. Conventionally, glass has been used as a front panel of such a display device. However, glass has high transparency and can exhibit high hardness depending on the kind, but on the other hand, it is very rigid and easily broken, and thus it is difficult to use it as a front panel material of a flexible display device.

Therefore, the application of polymer materials has been studied as materials replacing glass. A front panel made of a polymer material is expected to be used for various applications because it is easy to exhibit flexibility. As one of polymer materials having flexibility, for example, an optical film using a polyamide-imide resin has been studied (patent document 1).

Documents of the prior art

Patent document

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

Disclosure of Invention

Problems to be solved by the invention

When an optical film containing a polyamideimide resin is used in, for example, a flexible display device, it is required to satisfy various properties such as optical properties and mechanical properties. However, it is known that when a flexible display device including the optical film is used for a long period of time, the optical film may deteriorate and optical and mechanical properties may deteriorate with time depending on the environment in which the flexible display device is placed.

Accordingly, an object of the present invention is to provide an optical film having excellent quality stability in which deterioration of optical properties and mechanical properties with time is suppressed, and a polyamideimide resin capable of forming the optical film.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems and as a result, have found that a polyamide-imide resin is obtained¹H-¹³When the peak volume of a specific peak in the C HSQC spectrum satisfies a specific relationship, the quality stability of an optical film containing the polyamideimide resin can be improved, thereby completing the present invention.

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

[ 1] Polyamide-imide resin obtained by using a deuterated dimethyl sulfoxide solution of polyamide-imide resin as a measurement sample¹H-¹³An integral value (int) of a peak existing in a region (A) in which a chemical shift of a proton is 8.06 to 8.14ppm and a chemical shift of carbon is 129.6 to 130.3ppm in a C HSQC spectrum_A) And an integral value (int) of a peak present in a region (B) having a chemical shift from proton of 7.26 to 7.85ppm and a chemical shift from carbon of 132.4 to 134.0ppm_B) Ratio of (int)_A/int_B) Is 1.5% or less.

[ 2] the polyamideimide resin according to the above [ 1], which has at least a structural unit represented by the formula (1) and a structural unit represented by the formula (2),

[ chemical formula 1]

[ in the formula (1), Y represents a tetravalent organic group,

x represents a divalent organic group, and X represents a divalent organic group,

showing a connecting bond

[ chemical formula 2]

[ in the formula (2), Z and X independently represent a divalent organic group,

it represents a bond.

[ 3] the polyamideimide 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] the polyamideimide resin according to any one of the above [ 1] to [ 3], wherein X in the formula (1) or X in the formula (2) has at least a structure represented by the formula (4),

[ chemical formula 3]

[ formula (4) is H^4aAnd H^4bRepresents a hydrogen atom, and is represented by,

R^4a～R^4dindependently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R^4a～R^4dThe hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

it represents a bond.

[ 5] the polyamideimide resin according to any one of [ 1] to [ 4] above, wherein Z in the formula (2) has at least a structure represented by the formula (3),

[ chemical formula 4]

[ in the formula (3), R^3aAnd R^3bIndependently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R^3aAnd R^3bThe hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

w independently of one another represent a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹)-，R⁹Represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom,

s is an integer of 0 to 4,

t is an integer of 0 to 4,

u is an integer of 0 to 4,

it represents a bond.

An optical film comprising the polyamideimide resin according to any one of [ 1] to [ 5] above.

An optical film comprising a polyamideimide resin, wherein the rate of change in weight average molecular weight of the optical film before and after a storage test at a temperature of 85 ℃ and a humidity of 85% for 1 week is 26% or less.

The optical film according to the above [ 7], wherein a rate of change in weight average molecular weight before and after the storage test is 25% or less.

A front panel for a flexible display device, comprising the optical film according to any one of [ 6] to [ 8] above.

A flexible display device comprising the front panel according to the above [ 9 ].

The flexible display device according to [ 11] above [ 10], further comprising a touch sensor.

The flexible display device according to [ 10] or [ 11] above, further comprising a polarizing plate.

The process for producing a polyamideimide resin according to any one of [ 1] to [ 5] above, which is a process for producing a polyamideimide resin by reacting a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compound, 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 more than 1.000.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, an optical film having excellent quality stability in which deterioration of optical properties and mechanical properties with time is suppressed, and a polyamideimide resin capable of forming the optical film can be provided.

Detailed Description

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

[ polyamideimide resin ]

The polyamideimide resin of the present invention is obtained by using a deuterated dimethyl sulfoxide solution of the polyamideimide resin as a measurement sample¹H-¹³An integral value (int) of a peak existing in a region (A) in which a chemical shift of a proton is 8.06 to 8.14ppm and a chemical shift of carbon is 129.6 to 130.3ppm in a C HSQC spectrum_A) And an integral value (int) of a peak present in a region (B) having a chemical shift from proton of 7.26 to 7.85ppm and a chemical shift from carbon of 132.4 to 134.0ppm_B) Ratio of (int)_A/int_B) Is 1.5% or less.

¹H-¹³The C HSQC (Heteronuclear Single Quantum coherence) spectrum is an NMR spectrum showing Heteronuclear coupling between protons and carbons, and in general, the vertical axis represents the chemical shift of carbon and the horizontal axis represents the chemical shift of protons. The inventors of the present application have found that the integral value (int) of a peak existing in a region (A) where a proton chemical shift is 8.06 to 8.14ppm and a carbon chemical shift is 129.6 to 130.3ppm is used_A) And an integral value (int) of a peak present in a region (B) having a chemical shift from proton of 7.26 to 7.85ppm and a chemical shift from carbon of 132.4 to 134.0ppm_B) Ratio of (int)_A/int_B) The polyamide-imide resin content of 1.5% or less can provide an optical film having excellent quality stability in which deterioration of optical properties and mechanical properties with time is suppressed. Ratio (int)_A/int_B) If the content exceeds 1.5%, the optical properties and mechanical properties of the optical film containing the resin tend to deteriorate with time. From the viewpoint of facilitating further improvement of the effect of suppressing deterioration of optical properties and mechanical properties, the ratio (int)_A/int_B) Preferably 1.2% or less, more preferably 1.0% or less, still more preferably 0.8% or less, and particularly preferably 0.6% or less. Ratio (int)_A/int_B) The lower limit is not particularly limited, but is usually 0% or more, for example, 0.01% or more.

Ratio (int)_A/int_B) When the content is 1.5% or less, the optical properties of the optical film obtained can be suppressed andthe reason why the mechanical properties are deteriorated with time is not clear, but is considered to be based on the following reason. The polyamideimide resin is generally obtained by polymerization using a tetracarboxylic acid compound, a dicarboxylic acid compound and a diamine compound as monomers. Depending on the ratio of monomers to be polymerized and the polymerization conditions of the polymer, carboxylic acid moieties derived from dicarboxylic acids may remain at the terminals of the resulting polymer. Herein, it is considered to be¹H-¹³In a region (A) in which the chemical shift of a proton is 8.06 to 8.14ppm and the chemical shift of carbon is 129.6 to 130.3ppm in the C HSQC spectrum, there is a peak of a proton corresponding to the amount of a carboxylic acid moiety derived from a dicarboxylic acid and present at the terminal of a polyamideimide resin. Therefore, it is considered that when the integral value of the peak present in the region (a) (volume of the peak) which relatively indicates the amount of the carboxylic acid moiety derived from the dicarboxylic acid present at the terminal is a predetermined value or less with respect to the integral value of the peak present in the region (B) corresponding to the proton of the other portion of the polyamideimide resin, it indicates that the amount of the carboxylic acid moiety present at the terminal of the polyamideimide resin is extremely small, and the deterioration of the optical properties and mechanical properties of the optical film obtained with time can be suppressed. It is considered that when an optical film is used for a long period of time, particularly, corrosion due to an external environment or the like occurs from the surface of the optical film, and thus optical properties and mechanical properties are deteriorated with time. When the amount of the carboxylic acid moiety present at the terminal of the polyamideimide resin contained in the optical film is small, the corrosion of the surface of the optical film under, for example, high-temperature and high-humidity conditions can be reduced, and it is considered that such reduction of corrosion is one of the causes of suppressing the deterioration of the optical properties and mechanical properties over time. For the same reason, the ratio (int) is_A/int_B) An optical film obtained from a resin having a weight average molecular weight of 1.5% or less can also be inhibited from decreasing with time.

As described above, if the amount of the terminal carboxylic acid moiety of the dicarboxylic acid present at the terminal of the polyamideimide resin is increased, the ratio (int)_A/int_B) Int of (1)_ABecomes larger. Therefore, the above-mentioned polyamide-imide resin can be synthesized by reducing the terminal carboxylic acid moiety derived from the dicarboxylic acid as much as possibleThe ratio is adjusted to be within a range of 1.5% or less. As an example of a method for synthesizing a polyamideimide resin in such a manner that the amount of the carboxylic acid moiety at the terminal is reduced as much as possible, it is conceivable that, in synthesizing a polyamideimide resin, a compound which is low in reactivity among dicarboxylic acid compounds and is likely to become a terminal carboxylic acid is first added, or 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 to obtain the polyamideimide resin, the ratio (int) is easy to adjust when 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), hereinafter also referred to as "amine ratio") is adjusted so that the molar amount of the diamine compound is preferably 1.000 or more, more preferably 1.003 or more, further preferably 1.005 or more, still more preferably 1.008 or more, and particularly preferably 1.01 or more, where the total molar amount of the tetracarboxylic acid compound and the dicarboxylic acid compound is 1_A/int_B) Adjusted to the above range. From the viewpoint of easily increasing the weight average molecular weight of the polyamideimide resin, the upper limit of the amine ratio is preferably 1.05 or less, more preferably 1.03 or less, and still more preferably 1.02 or less.

Further, the ratio (int) may be adjusted by adjusting the amount of water in the solvent used in synthesizing the polyamideimide resin_A/int_B) Adjusted to the above range. Specifically, when a certain amount of water is present in the solvent, a part of the dicarboxylic acid compound in the synthesis solvent is deactivated, and is not easily introduced into the polyamideimide resin. As a result, it is considered that when a certain amount of water is present in the solvent, the amount of carboxylic acid moiety derived from dicarboxylic acid present at the terminal of the polyamideimide resin can be reduced, and the ratio (int) can be easily adjusted_A/int_B) Adjusted to the above range. From easy to scale (int)_A/int_B) From the viewpoint of adjusting the content to the above range, the water content in the solvent used for synthesizing the polyamideimide resin is preferably 400ppm or more, more preferably 500ppm or more, and from the viewpoint of suppressing decomposition of the polyamideimide resin, the water content is preferably 400ppm or moreIs 1,000ppm or less, more preferably 800ppm or less.

Further, the ratio (int) may be adjusted by adjusting the temperature increase rate of imidization_A/int_B) Adjusted to the above range. Specifically, when the temperature rise rate of imidization is too high in synthesizing the polyamideimide resin, the imidization catalyst cannot sufficiently capture hydrochloric acid in the synthesis solvent, and the hydrochloric acid decomposes the polyamideimide resin, so that carboxylic acid moieties derived from the dicarboxylic acid compound are likely to be present at the terminal of the polyamideimide resin. Therefore, the ratio (int) can be adjusted by adjusting the temperature increase rate at the time of imidization to suppress decomposition of the polyamideimide resin_A/int_B) Adjusted to the above range. From easy to scale (int)_A/int_B) From the viewpoint of adjusting the temperature to the above range, it is preferable to decrease the temperature increase rate at the time of imidization, and it is more preferable that the temperature increase from 10 ℃ to 50 ℃ takes 30 minutes or more.

Further, the ratio (int) can be adjusted by adjusting the heating conditions during the reaction_A/int_B) Adjusted to the above range. Specifically, it was found that hydrolysis of the terminal carboxylic acid is easily progressed while suppressing decomposition of the main chain of the polyamideimide resin by locally heating the reaction vessel in the case of synthesizing the polyamideimide resin, as compared with the case of heating the entire reaction vessel in order to achieve the same temperature rise rate. The ratio (int) can be adjusted by releasing the terminal carboxylic acid to expose the amine terminal instead of releasing it_A/int_B) Adjusted to the above range. This is considered to be because, when the entire reaction vessel is heated with a heat medium in synthesizing the polyamideimide resin, the amount of the reaction solution which is excessively heated increases, and not only hydrolysis of the carboxylic acid at the terminal of the resin proceeds, but also decomposition of the main chain proceeds. As a result, it is difficult to adjust the ratio (int)_A/int_B) Adjusted to the above range, and also a decrease in molecular weight is liable to occur. It is considered that when the reaction vessel is locally heated, decomposition of the main chain of the polyamideimide resin is reduced, hydrolysis of the carboxylic acid terminal, which has higher reactivity than that of the main chain, occurs preferentially, and the polyamide imide resin is easily decomposedRatio (int)_A/int_B) Adjusted to the above range.

In a preferred embodiment of the present invention, the polyamideimide resin has at least a structural unit represented by the formula (1) and a structural unit represented by the formula (2),

[ chemical formula 5]

[ in the formula (1), Y represents a tetravalent organic group,

showing a connecting bond

[ chemical formula 6]

[ in the formula (2), Z and X independently represent a divalent organic group,

it represents a bond.

The structural unit represented by formula (1) is a structural unit formed by reacting a tetracarboxylic acid compound with a diamine compound, and the structural unit represented by formula (2) is a structural unit formed by reacting a dicarboxylic acid compound with a diamine compound. When the polyamideimide resin has the structural unit represented by the formula (1) and the structural unit represented by the formula (2), the polyamideimide resin usually has a plurality of structural units represented by the formula (1) and a plurality of structural units represented by the formula (2). The plurality of structural units represented by formula (1) may be one structural unit or two or more structural units. The plurality of structural units represented by formula (2) may be one structural unit or two or more structural units. The polyamideimide resin may have other structural units than those of the formula (1) and the formula (2).

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 beSubstituted with a halogen atom, preferably a fluorine atom), and more preferably represents a4 to 40 carbon atom divalent organic group having a cyclic structure which may be substituted with a 1 to 6 carbon atom alkyl group, a 1 to 6 carbon atom alkoxy group, or a 6 to 12 carbon atom aryl group (the hydrogen atom in these groups may be substituted with a halogen atom, preferably a fluorine atom). 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 are the same as those of R in the formula (3) described later^3aAnd R^3bThe relevant examples apply as well. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. Examples of the organic group of Z include a group in which two non-adjacent connecting bonds of the groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28), and formula (29) are replaced with a hydrogen atom, and a 2-valent chain hydrocarbon group having 6 or less carbon atoms, and examples of the heterocyclic structure of Z include a group having a thiophene ring skeleton.

[ chemical formula 7]

In [ formula (20) to formula (29), W¹Represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-Ar-、-SO₂-、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂-Ar-、-Ar-C(CH₃)₂-Ar-or-Ar-SO₂Ar-wherein Ar independently of each other represents an arylene group having 6 to 20 carbon atoms in which hydrogen atoms may be substituted with fluorine atoms, such as a phenylene group, and represents a connecting bond]

From the viewpoint of easily reducing the yellow index (hereinafter, may be simply referred to as YI value) of the optical film, Z is preferably a group represented by formulae (20) to (29) or a group having a thiophene ring skeleton.

More preferred as the organic group of Z is a divalent organic group represented by formula (20 '), formula (21'), formula (22 '), formula (23'), formula (24 '), formula (25'), formula (26 '), formula (27'), formula (28 ') and formula (29'):

[ chemical formula 8]

In [ formulae (20 ') to (29'), W¹And as defined in formulae (20) to (29)]。

The hydrogen atom on the ring in the formulae (20) to (29) and (20 ') to (29') may be substituted by an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, in which the hydrogen atom may be substituted by a halogen atom, preferably a fluorine atom.

In the case where the polyamideimide resin has a structural unit wherein Z in the formula (2) is represented by any one of the above-mentioned formulae (20 ') to (29 '), particularly in the case where Z in the formula (2) is represented by the formula (3 ') described later, it is preferable that the polyamideimide resin has, in addition to the structural unit, a structural unit derived from a carboxylic acid represented by the following formula (d1) from the viewpoint of easily improving the film-forming property of a varnish containing the resin and easily improving the uniformity of an optical film to be obtained:

[ chemical formula 9]

[ in the formula (d1), R²⁴Represents R in the formula (3) described later^3aAnd a group or a hydrogen atom as defined,

R²⁵represents R²⁴or-C (═ O) -,

it represents a bond.

Specific examples of the structural unit (d1) include R²⁴And R²⁵Structural units each of which is a hydrogen atom, i.e., structural units derived from a dicarboxylic acid compound, R²⁴Are all hydrogen atoms and R²⁵To representA structural unit of-C (═ O) -, that is, a structural unit derived from a tricarboxylic acid compound, and the like.

The polyamideimide resin of the present invention may contain a plurality of kinds of Z as Z in the formula (2), and the plurality of kinds of Z may be the same as or different from each other. Among them, from the viewpoint of easily improving the impact resistance of the optical film obtained using the polyamideimide resin of the present invention and easily improving the optical characteristics, it is preferable that at least Z in the formula (2) has a structural unit represented by the formula (3) preferably, and more preferably, by the formula (3'):

[ chemical formula 10]

s is an integer of 0 to 4,

t is an integer of 0 to 4,

u is an integer of 0 to 4,

showing a connecting bond

[ chemical formula 11]

[ formula (3') wherein R^3a、R^3bS, t, u, W and x are as defined in formula (3)]。

In the present specification, the phrase "the polyamideimide resin has a structural unit wherein Z in the formula (2) is represented by the formula (3)" has the same meaning as "the polyamideimide resin has a structure represented by the formula (3) as Z in the formula (2)", and means that Z in at least a part of the structural units in the plurality of structural units represented by the formula (2) contained in the polyamideimide resin is represented by the formula (3). This description is also applicable to other similar descriptions.

In the formulae (3) and (3'), W independently represents a single bond, -O-, -CH₂-、-CH₂-CH2-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹) From the viewpoint of the bending resistance of the optical film, the compound preferably represents-O-or-S-, and more preferably represents-O-.

R^3aAnd R^3bIndependently 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, a 2-methylbutyl group, a 3-methylbutyl group, a 2-ethylpropyl group, and an n-hexyl group. Examples of the alkoxy group having 1 to 6 carbon atoms include a methoxy group, an ethoxy group, a propoxy group, an isopropoxy group, an n-butoxy group, an isobutoxy group, a sec-butoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, and a cyclohexyloxy group. Examples of the aryl group having 6 to 12 carbon atoms include a phenyl group, a tolyl group, a xylyl group, a naphthyl group, and a biphenyl group. From the viewpoint of surface hardness and flexibility of the optical film, R^3aAnd R^3bIndependently of each other, the alkyl group preferably has 1 to 6 carbon atoms, and more preferably has 1 to 3 carbon atoms. Here, R^3aAnd R^3bThe hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other.

R⁹Represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl and 2-methylbutylA group such as a phenyl group, a 3-methylbutyl group, a 2-ethylpropyl group, a n-hexyl group, a n-heptyl group, a n-octyl group, a tert-octyl group, a n-nonyl group, a n-decyl group and the like, which may be substituted with a halogen atom. Examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, an iodine atom and the like.

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

When s in the formulae (3) and (3') is an integer in the range of 0 to 4, and s is in this range, the impact resistance, elastic modulus and bending resistance of the optical film obtained using the polyamideimide resin of the present invention are easily improved. From the viewpoint of facilitating further improvement in impact resistance, elastic modulus and bending resistance of the optical film obtained, s in the formulae (3) and (3') is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, further preferably 0 or 1, and particularly preferably 0. The structural unit containing a structure represented by formula (3) or formula (3 ') in which s is 0 as the structural unit of Z in formula (2) is, for example, a structural unit derived from terephthalic acid or isophthalic acid, and the structural unit is particularly preferably a structural unit containing a structure in which s is 0 and u is 0 in formula (3) or formula (3'). The polyamideimide resin preferably contains a structural unit derived from terephthalic acid from the viewpoint of easily improving impact resistance, elastic modulus and bending resistance of the optical film. The polyamideimide resin may include one or two or more kinds of structural units wherein Z is represented by formula (3) or formula (3'). From the viewpoint of improving the impact resistance, elastic modulus and bending resistance of the optical film, and lowering the YI value, the polyamideimide resin preferably contains two or more structures having different values of s in formula (3) or formula (3 ') as Z in formula (2), and more preferably contains two or three structures having different values of s in formula (3) or formula (3') as Z in formula (2). In this case, from the viewpoint of easily improving the impact resistance, elastic modulus, and bending resistance of the optical film and from the viewpoint of easily lowering the YI value of the optical film, it is particularly preferable that the polyamideimide resin contains a structure represented by formula (3) in which s is 0 as Z in the structural unit represented by formula (2), and contains a structural unit including a structure represented by formula (3) in which s is 1 in addition to the structural unit containing the structure. It is also preferable that the functional group has a structural unit represented by the above formula (d1) in addition to a structural unit represented by the formula (2) having Z represented by the formula (3) in which s is 0.

In a preferred embodiment of the present invention, the polyamideimide resin has a structure in which s is 0 and u is 0 as a structure (divalent group) represented by formula (3) or formula (3'). In a more preferred embodiment of the present invention, the polyamideimide resin has a structure in which s is 0 and u is 0, and a structure represented by formula (3 ″) as a structure represented by formula (3) or formula (3').

[ chemical formula 12]

In this case, the optical film obtained using the polyamideimide resin is likely to have improved impact resistance, elastic modulus and bending resistance, and the YI value is likely to be lowered.

When the polyamideimide resin of the present invention has a structural unit represented by formula (3) or formula (3') as Z in formula (2), the proportion thereof is preferably 20 mol% or more, more preferably 30 mol% or more, further preferably 40 mol% or more, still more preferably 50 mol% or more, particularly preferably 60 mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, and further preferably 80 mol% or less, when the total of the structural unit represented by formula (1) and the structural unit represented by formula (2) of the polyamideimide resin is 100 mol%. When the ratio of the structural unit represented by formula (3) or formula (3') for Z in formula (2) is not less than the above lower limit, the impact resistance, elastic modulus, and bending resistance of the optical film are easily improved. When the ratio of the structural unit represented by formula (3) or formula (3') for Z in formula (2) is not more than the above upper limit, the viscosity increase of the varnish containing the resin due to the hydrogen bond between the amide bonds derived from formula (3) is easily suppressed, and the processability of the film is improved.

The polyamideimide resin has an E-value of from 1 to EIn the case where the structure represented by the formula (3) or the formula (3 ') of 4 is Z in the formula (2), the proportion of the structural unit represented by the formula (2) having Z represented by the formula (3) or the formula (3') having s of 1 to 4 is preferably 3 mol% or more, more preferably 5 mol% or more, further preferably 7 mol% or more, particularly preferably 9 mol% or more, preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, particularly preferably 30 mol% or less, when the total of the structural unit represented by the formula (1) and the structural unit represented by the formula (2) in the polyamideimide resin is 100 mol%. When the ratio of the structural unit represented by formula (2) having Z represented by formula (3) or formula (3') in which s is 1 to 4 is not less than the above lower limit, the impact resistance, elastic modulus, and bending resistance of the optical film are easily improved. When the ratio of the structural unit represented by formula (2) having Z represented by formula (3) or formula (3 ') in which s is 1 to 4 is not more than the upper limit, it is easy to suppress an increase in viscosity of the varnish containing the resin due to hydrogen bonds between amide bonds derived from the structure represented by formula (3) or formula (3'), thereby improving the processability of the film. The proportion of the structural unit represented by formula (3) or formula (3 ') in formula (1), formula (2) or formula (2) wherein Z is represented by formula (3) or formula (3') can be used, for example¹H-NMR, or the ratio of the charged raw materials.

In a preferred embodiment of the present invention, 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 of Z in the polyamideimide resin of the present invention is represented by formula (3) or formula (3') wherein s is 0 to 4. When the above lower limit or more of Z is represented by formula (3) or formula (3') where s is 0 to 4, the impact resistance, elastic modulus and bending resistance of the optical film are easily improved. In addition, in the polyamide-imide resin, the 100 mol% or less of Z may be represented by formula (3) or formula (3') wherein s is 0 to 4. The proportion of the structural unit represented by formula (2) having Z represented by formula (3) or formula (3') wherein s is 0 to 4 in the resin can be used, for example¹H-NMR, or the ratio of the charged raw materials.

One preferred embodiment of the inventionIn the formula, preferably 5 mol% or more, more preferably 8 mol% or more, further preferably 10 mol% or more, and particularly preferably 12 mol% or more of Z in the polyamideimide resin of the present invention is represented by formula (3) or formula (3') wherein s is 1 to 4. When the above lower limit or more of Z in the polyamideimide resin is represented by formula (3) or formula (3') wherein s is 1 to 4, the impact resistance, elastic modulus and bending resistance of the optical film are easily improved. In addition, preferably 90 mol% or less, more preferably 70 mol% or less, further preferably 50 mol% or less, and particularly preferably 30 mol% or less of Z is represented by formula (3) or formula (3') with s of 1 to 4. When the upper limit of Z is 1 to 4 or less, represented by formula (3), the viscosity of the varnish containing the resin is easily inhibited from increasing due to hydrogen bonds between amide bonds derived from the structural unit represented by formula (3) or formula (3') wherein s is 1 to 4, and the processability of the film is improved. The proportion of the structural unit represented by the formula (3) or (3') wherein s is 1 to 4 in the resin can be used, for example¹H-NMR, or the ratio of the charged raw materials.

Examples of the structure of the carboxylic acid terminal moiety derived from the dicarboxylic acid compound in the polyamideimide resin of the present invention include a structure represented by the following formula (32):

[ chemical formula 13]

[ in the formula (32), R^32aAnd R^32bIndependently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R^32aAnd R^32bThe hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

R^32crepresents a hydrogen atom (in this case, -OR)^32cis-OH), an alkali metal atom, a halogen atom, or an alkyl group having 1 to 3 carbon atoms,

p is an integer of 0 to 4,

r is an integer of 0 to 4, preferably 0 to 2, more preferably 0,

a independently of one another represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)⁹)-，R⁹Represents a hydrogen atom, a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom,

q is an integer of 0 to 4,

it represents a bond.

When the structure of the carboxylic acid terminal moiety is represented by formula (32) (preferably, r ═ 0, q ═ 0, and the substitution position of the carboxylic acid group is para to the amide group), it is considered to be classified as having a carboxylic acid group (-C (═ O) OR^32c) The peak of the hydrogen atom bonded to the carbon atom on the benzene ring in (a) is detected in the region (a). The structure of the carboxylic acid terminal moiety represented by formula (32) is derived from dicarboxylic acid and diamine which provide the structural unit represented by formula (3) wherein Z in formula (2) is represented by the above formula, and is a part of the diamine and a structure of dicarboxylic acid. Therefore, when the polyamideimide resin has a structural unit in which Z in formula (2) is represented by formula (3) above, the terminal structure represented by formula (32) may be contained in the polyamideimide resin. Thus, R in formula (3)^3a、R^3bW, s, t and u can be respectively related to R in the formula (32)^32a、R^32bA, p, q and r correspond.

In the formulas (1) and (2), X independently represents a divalent organic group, preferably represents a divalent organic group having 4 to 40 carbon atoms, and more preferably represents a divalent organic group having 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. In the above organic group, the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. In one embodiment of the present invention, the polyamideimide resin of the present invention may contain a plurality of kinds of X, and the plurality of kinds of X may be the same as or different from each other. As X, there can be exemplified: a group represented by formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) or formula (18); a group represented by the formulae (10) to (18) wherein a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

[ chemical formula 14]

In the formulae (10) to (18), the bond is represented by,

V¹、V²and V³Independently of one another, represents a single bond, -O-, -S-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -CO-or-N (Q) -. Wherein 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 those mentioned above for R⁹The groups described.

1 example is: v¹And V³Is a single bond, -O-or-S-, and, V²is-CH₂-、-C(CH₃)₂-、-C(CF₃)₂-or-SO₂-。V¹And V²Bonding position with respect to each ring, and V²And V³The bonding position to each ring is preferably meta-or para-position, more preferably para-position, independently of each other, to each ring.

Among the groups represented by formulae (10) to (18), the groups represented by formulae (13), (14), (15), (16) and (17) are preferable, and the groups represented by formulae (14), (15) and (16) are more preferable, from the viewpoint of easily improving the impact resistance, elastic modulus and bending resistance of the optical film. In addition, from the viewpoint of easily improving the impact resistance, elastic modulus and flexibility of the optical film, V¹、V²And V³Independently of one another, are preferably single bonds, -O-or-S-, more preferably single bonds or-O-.

In a preferred embodiment of the present invention, the polyamideimide resin of the present invention has a structure represented by formula (4) as X in formula (1) or X in formula (2):

[ chemical formula 15]

[ formula (4) is H^4aAnd H^4bRepresents a hydrogen atom, R^4a～R^4dIndependently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R^4a～R^4dThe hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

it represents a bond.

When the polyamideimide resin has a structure represented by the formula (4) as X in the formula (1) or X in the formula (2), it is considered that H in the formula (4) is ascribed to^4aAnd H^4bThe peak of (B) is detected in the region (B). The structural unit represented by the formula (1) and the structural unit represented by the formula (2) are present in a plurality in the polyamideimide resin. When X in the formulae (1) and (2) is represented by the formula (4) in at least a part of these structural units, the impact resistance, elastic modulus and transparency of the optical film are easily improved.

In a preferred embodiment of the present invention, the structural unit represented by formula (4) is a structural unit represented by formula (4').

[ chemical formula 16]

That is, at least a part of X among the structural units represented by formulas (1) and (2) is a structural unit represented by formula (4'). In this case, the fluorine element-containing skeleton improves the solubility of the polyamideimide resin in a solvent, and the storage stability of the varnish containing the resin is easily improved, and the viscosity of the varnish is easily lowered, and the processability of the optical film is easily improved. Further, the optical properties of the optical film are easily improved by the skeleton containing the fluorine element. The polyamideimide resin contains a structure represented by the formula (4) or the formula (4')When the structure is X in the formula (1) or (2), it is considered that H in the formula (4)^4aAnd H^4bThe peaks of the hydrogen atoms represented by the formula (4 ') or the hydrogen atoms at the same positions in the formula (4') are detected in the region (B).

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 50 mol% or more, and still more preferably 70 mol% or more of X in the polyamideimide resin is represented by formula (4), particularly formula (4'). When X in the above range in the polyamideimide resin is represented by formula (4), particularly formula (4'), the solubility of the resin in a solvent is improved by the skeleton containing a fluorine element in the obtained optical film, the storage stability of a varnish containing the resin is easily improved, the viscosity of the varnish is easily lowered, and the processability of the optical film is easily improved. Further, the optical properties of the optical film are also easily improved by the skeleton containing the fluorine element. In the polyamideimide resin, 100 mol% or less of X is preferably represented by formula (4), particularly (4'). X in the above resin may be formula (4), particularly formula (4'). The proportion of the structural unit represented by formula (4) in X in the resin can be used, for example¹H-NMR, or the ratio of the charged raw materials.

As the structural unit in which X in formula (1) or formula (2) is represented by another structural formula, which is contained in addition to or instead of the structural unit in formula (1) or formula (2) in which X is represented by formula (4) or formula (4'), for example, a structural unit in which X in formula (1) or formula (2) is represented by formula (6):

[ chemical formula 17]

[ in the formula (6), R¹⁰～R¹⁷Independently 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, R¹⁰～R¹⁷May be substituted independently of one another by halogen atoms, with the exclusion ofR¹¹And R¹²Any one of (1), and R¹⁴And R¹⁷When any of the above groups is a trifluoromethyl group,

it represents a bond.

When at least a part of the plurality of xs in the formulae (1) and (2) is a group represented by the formula (6), the impact resistance, elastic modulus, and transparency of the optical film are also easily improved.

R in the formula (4)^4a、R^4b、R^4cAnd R^4dAnd R in the formula (6)¹⁰、R¹¹、R¹²、R¹³、R¹⁴、R¹⁵、R¹⁶And R¹⁷Independently 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 alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, or aryl groups having 6 to 12 carbon atoms in the formula (3). R^4a～R^4dAnd R¹⁰～R¹⁷Independently of each other, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R^4a～R^4dAnd R¹⁰～R¹⁷The hydrogen atoms contained in (a) may be substituted by 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 is R from the viewpoint of impact resistance, elastic modulus, transparency and bending resistance of the optical film^4a～R^4dAnd R¹⁰～R¹⁷Further preferred are, independently of one another, a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and R is particularly preferred^4a～R^4dIs a hydrogen atom, R¹⁰、R¹²、R¹³、R¹⁴、R¹⁵And R¹⁶Is a hydrogen atom, and R¹¹And R¹⁷Is hydrogen atom, methyl, fluoro, chloro or trifluoromethyl. Wherein R in the formula (6) is excluded¹¹And R¹²Any one of (1), and R¹⁴And R¹⁷Becomes three in any one ofIn the case of fluoromethyl groups.

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 4 to 40 carbon atoms and having a cyclic structure. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure, and preferred examples thereof include an aromatic ring from the viewpoint of easily improving impact resistance and elastic modulus. The organic group is an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. In one embodiment of the present invention, the polyamideimide resin may include a plurality of kinds of Y, and the plurality of kinds of Y may be the same as or different from each other. As Y, there can be exemplified: a group represented by the following formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29); a group represented by the formulae (20) to (29) wherein a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having a valence of 4 and a carbon number of 6 or less.

[ chemical formula 18]

In the formulae (20) to (29), W represents a connecting bond¹Represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-Ar-、-SO₂-、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂-Ar-、-Ar-C(CH₃)₂-Ar-or-Ar-SO₂-Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and specific examples thereof include phenylene groups.

Among the groups represented by formulae (20) to (29), the group represented by formula (26), formula (28) or formula (29) is preferable, and the group represented by formula (26) is more preferable, from the viewpoint of easily improving the impact resistance, elastic modulus and bending resistance of the optical film. In addition, the optical film is easily improvedIn view of the fact that the optical film is likely to have low YI value, the optical film has impact resistance, elastic modulus and bending resistance, and W¹Independently of one another, are preferably single bonds, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂-, more preferably a single bond, -O-, -CH₂-、-CH(CH₃)-、-C(CH₃₎₂-or-C (CF)₃)₂-is more preferably a 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, and still more preferably 70 mol% or more of Y in the polyamideimide resin is represented by the formula (26). Y in the above range in the polyamideimide resin is represented by the formula (26), preferably W¹Is a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-formula (26), more preferably W¹Is a single bond or-C (CF)₃)₂When the formula (26) represents, the impact resistance, elastic modulus and bending resistance of the optical film are easily improved, and the YI value of the optical film is easily lowered. The proportion of the structural unit represented by the formula (26) for Y in the polyamideimide resin can be used, for example¹H-NMR, or the ratio of the charged raw materials.

In a preferred embodiment of the present invention, at least a part of Y in the plurality of formulas (1) is represented by formula (5) and/or formula (9):

[ chemical formula 19]

[ in the formula (5), R¹⁸～R²⁵Independently 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, R¹⁸～R²⁵The hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

showing a connecting bond

[ chemical formula 20]

[ formula (9) wherein R³⁵～R⁴⁰Independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R³⁵～R⁴⁰Wherein the hydrogen atoms contained in (A) may be substituted independently of each other by halogen atoms, represent a connecting bond]。

When at least a part of Y in the plurality of formulae (1) is represented by formula (5) and/or formula (9), the impact resistance, elastic modulus, and optical characteristics of the optical film are easily improved.

In the formula (5), R¹⁸、R¹⁹、R²⁰、R²¹、R²²、R²³、R²⁴And R²⁵Independently 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 those exemplified above as the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms or the aryl group having 6 to 12 carbon atoms in the formula (3). R¹⁸～R²⁵Independently of each other, preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein R¹⁸～R²⁵The hydrogen atoms contained in (a) may be substituted by 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 is a group of R which is easy to improve the impact resistance, elastic modulus and bending resistance of the optical film and is easy to improve the transparency and maintain the transparency¹⁸～R²⁵Further preferred are, independently of each other, a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and further preferred is R¹⁸、R¹⁹、R²⁰、R²³、R²⁴And R²⁵Is a hydrogen atom, and R²¹And R²²Is a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and R is particularly preferred²¹And R²²Is methyl or trifluoromethyl.

In the formula (9), R is R from the viewpoint of easily improving the impact resistance, elastic modulus and bending resistance of the optical film, and from the viewpoint of easily improving the transparency and easily maintaining the transparency³⁵～R⁴⁰Preferably 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 still more preferably a hydrogen atom. Here, R³⁵～R⁴⁰The hydrogen atoms contained in (a) may be independently substituted with a halogen atom, and examples of the halogen atom include a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom. As R³⁵～R⁴⁰In the above-mentioned examples, the alkyl group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms are each as exemplified above.

In a preferred embodiment of the present invention, formula (5) is represented by formula (5 '), and formula (9) is represented by formula (9').

[ chemical formula 21]

That is, at least a part of the plurality of Y is represented by formula (5 ') and/or formula (9'). In this case, the impact resistance, elastic modulus, and bending resistance of the optical film are easily improved. In the case where the formula (5) is represented by the formula (5'), the solubility of the polyamideimide resin in a solvent is improved by the fluorine element-containing skeleton, so that the storage stability of the varnish containing the resin is easily improved, the viscosity of the varnish is easily lowered, and the processability of the optical film is easily improved. Further, the optical properties of the optical film are easily improved by the skeleton containing the fluorine element.

In a preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, and still more preferably 70 mol% or more of Y in the polyamideimide resin is represented by formula (5), particularly formula (5'). Within the above range in the polyamideimide resinWhen Y is represented by the formula (5), particularly the formula (5'), the solubility of the polyamideimide resin in a solvent is improved by the fluorine element-containing skeleton, and the viscosity of the varnish containing the resin is easily lowered, thereby easily improving the processability of the optical film. Further, the optical properties of the optical film are easily improved by the skeleton containing the fluorine element. Preferably, 100 mol% or less of Y in the polyamideimide resin is represented by formula (5), particularly formula (5'). Y in the polyamideimide resin may be formula (5), especially formula (5'). The proportion of the structural unit represented by the formula (5) in Y in the polyamideimide resin can be used, for example¹H-NMR, or the ratio of the charged raw materials.

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

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

[ chemical formula 22]

In the formula (30), Y¹Is a tetravalent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y¹Examples thereof include groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29), groups represented by formula (20) to formula (29) wherein a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a tetravalent chain hydrocarbon group having 6 or less carbon atoms. One embodiment of the inventionIn the above embodiment, the polyamideimide resin may contain plural kinds of Y¹Plural kinds of Y¹May be the same or different from each other.

In the formula (31), Y²Is a trivalent organic group, preferably an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a hydrocarbon group substituted with fluorine. As Y²Examples of the chain hydrocarbon group include a group in which any one of the connecting bonds of the groups represented by the above formulae (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29) is replaced with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. In one embodiment of the present invention, the polyamideimide resin may include a plurality of Y' s²Plural kinds of Y²May be the same or different from each other.

In the formulae (30) and (31), X¹And X²Independently of one another, are divalent organic groups, preferably organic groups in which the hydrogen atoms of the organic group may be replaced by hydrocarbon groups or fluorine-substituted hydrocarbon groups. As X¹And X²The following can be exemplified: groups represented by the above-mentioned formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); a group represented by the formulae (10) to (18) wherein a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In one embodiment of the present invention, the polyamideimide resin includes a structural unit represented by formula (1) and formula (2), and optionally a structural unit represented by formula (30) and/or formula (31). In addition, from the viewpoint of easily improving the optical properties, impact resistance, elastic modulus, and bending resistance of the optical film, the proportion of the structural unit represented by formula (1) and formula (2) based on all the structural units represented by formula (1) and formula (2) and, in some cases, formula (30) and formula (31) in the polyamideimide resin is preferably 80 mol% or more, more preferably 90 mol% or more, and still more preferably 95 mol% or more. In the polyamideimide resin, the structural units represented by the formulae (1) and (2) are based on all the structural units represented by the formulae (1) and (2) and, in some cases, the formulae (30) and/or (31)The ratio of (B) is usually 100% or less. The above ratio can be used, for example¹H-NMR, or the ratio of the charged raw materials.

In the polyamide-imide resin, the content of the structural unit represented by formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol or more, further 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, and further preferably 4.5 mol or less, relative to 1mol of the structural unit represented by formula (1). When the content of the structural unit represented by formula (2) is not less than the above lower limit, the impact resistance and elastic modulus of the optical film are easily improved. When the content of the structural unit represented by formula (2) is not more than the upper limit, the thickening due to the hydrogen bond between the amide bonds in formula (2) is easily suppressed, and the processability of the optical film is improved.

In a preferred embodiment of the present invention, the polyamideimide resin of the present invention may contain, for example, a halogen atom such as a fluorine atom, which can be introduced through the above-mentioned fluorine-containing substituent or the like. When the polyamideimide resin contains a halogen atom, the elastic modulus of the optical film is easily increased and the YI value is easily decreased. When the elastic modulus of the optical film is high, the occurrence of scratches, wrinkles, and the like is easily suppressed. In addition, when the YI value of the optical film is low, the transparency and visibility of the film are easily improved. The halogen atom is preferably a fluorine atom. Examples of the fluorine-containing substituent preferred for the purpose of containing a fluorine atom in the polyamideimide resin include a fluorine group and a trifluoromethyl group.

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

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

The weight average molecular weight of the polyamideimide resin is preferably 200,000 or more, more preferably 230,000 or more, further preferably 250,000 or more, further preferably 270,000 or more, and particularly preferably 280,000 or more, in terms of standard polystyrene, from the viewpoint of easily improving the impact resistance, elastic modulus, and bending resistance of the optical film. The weight average molecular weight of the polyamideimide resin is preferably 1,000,000 or less, more preferably 800,000 or less, even more preferably 700,000 or less, and particularly preferably 500,000 or less, from the viewpoint of easily improving the solubility of the resin in a solvent and easily improving the stretchability and processability of the optical film. The weight average molecular weight can be determined by GPC measurement or conversion to standard polystyrene, and can be calculated by the method described in examples.

[ method for producing Polyamide-imide resin ]

The polyamideimide resin and the polyamideimide precursor resin can be produced, for example, from a tetracarboxylic acid compound, a dicarboxylic acid compound and a diamine compound as main raw materials.

Examples of the diamine compound used for producing the resin include aliphatic diamines, aromatic diamines, and mixtures thereof. In the present embodiment, the "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or other substituent in a part of the structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited thereto. Among these, benzene rings are preferred. The "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituent in a part of the structure.

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

Examples of the aromatic diamine include aromatic diamines having 1 aromatic ring such as p-phenylenediamine, m-phenylenediamine, 2, 4-tolylenediamine, m-xylylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene and 2, 6-diaminonaphthalene, 4 ' -diaminodiphenylmethane, 4 ' -diaminodiphenylpropane, 4 ' -diaminodiphenyl ether, 3 ' -diaminodiphenyl ether, 4 ' -diaminodiphenyl sulfone, 3 ' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, p-phenylenediamine, m-phenylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene, 2, 6-diaminonaphthalene, etc., 4 ' -, Bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 ' -dimethylbenzidine, 2 ' -bis (trifluoromethyl) -4,4 ' -diaminobiphenyl (hereinafter, sometimes referred to as TFMB), aromatic diamines having 2 or more aromatic rings, such as 4, 4' -bis (4-aminophenoxy) biphenyl, 9-bis (4-aminophenyl) fluorene, 9-bis (4-amino-3-methylphenyl) fluorene, 9-bis (4-amino-3-chlorophenyl) fluorene, and 9, 9-bis (4-amino-3-fluorophenyl) fluorene. These may be used alone or in combination of two or more.

The aromatic diamine is preferably 4,4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenyl ether, 3' -diaminodiphenyl ether, 4 '-diaminodiphenyl sulfone, 3' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, TFMB, 4' -bis (4-aminophenoxy) biphenyl, more preferred are 4,4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenyl ether, 4' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, TFMB, and 4, 4' -bis (4-aminophenoxy) biphenyl. These may be used alone or in combination of two or more.

Among the diamine compounds, from the viewpoint of high elastic modulus, high transparency, high flexibility, high bending resistance, and low coloring of the optical film, it is preferable to use at least one selected from the group consisting of aromatic diamines having a biphenyl structure. More preferably, at least one selected from the group consisting of 2,2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) benzidine, 4 '-bis (4-aminophenoxy) biphenyl, and 4, 4' -diaminodiphenyl ether is used, and still more preferably, TFMB is used.

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

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples of the non-condensed polycyclic aromatic tetracarboxylic acid dianhydride include 4,4 '-oxydiphthalic anhydride, 3, 3', 4,4 '-benzophenonetetracarboxylic acid dianhydride, 2', 3,3 '-benzophenonetetracarboxylic acid dianhydride, 3, 3', 4,4 '-biphenyltetracarboxylic acid dianhydride, 2', 3,3 '-biphenyltetracarboxylic acid dianhydride, 3, 3', 4,4 '-diphenylsulfonetetracarboxylic acid dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4, 4' - (hexafluoroisopropylidene) diphthalic anhydride (hereinafter, sometimes referred to as "6 FDA"), (a-co-aromatic tetracarboxylic acid dianhydride), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4 '- (p-phenylenedioxy) diphthalic anhydride, 4' - (m-phenylenedioxy) diphthalic anhydride. Examples of the monocyclic aromatic tetracarboxylic acid dianhydride include 1,2,4, 5-benzenetetracarboxylic acid dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic acid dianhydride include 2,3,6, 7-naphthalenetetracarboxylic acid dianhydride.

Among these, preferred examples include 4,4 ' -oxydiphthalic anhydride, 3,3 ', 4,4 ' -benzophenonetetracarboxylic dianhydride, 2 ', 3,3 ' -benzophenonetetracarboxylic dianhydride, 3,3 ', 4,4 ' -biphenyltetracarboxylic dianhydride, 2 ', 3,3 ' -biphenyltetracarboxylic dianhydride, 3,3 ', 4,4 ' -diphenylsulfonetetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 6FDA, 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4,4 '- (p-phenylenedioxy) diphthalic anhydride and 4, 4' - (m-phenylenedioxy) diphthalic anhydride, and more preferably 4,4 '-oxydiphthalic anhydride, 3, 3', 4,4 '-biphenyltetracarboxylic dianhydride, 2', 3,3 '-biphenyltetracarboxylic dianhydride, 6FDA, bis (3, 4-dicarboxyphenyl) methane dianhydride and 4, 4' - (p-phenylenedioxy) diphthalic anhydride. These may be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic and acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkanetetracarboxylic dianhydrides such as 1,2,4, 5-cyclohexanetetracarboxylic dianhydride, 1,2,3, 4-cyclobutanetetracarboxylic dianhydride and 1,2,3, 4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3,5, 6-tetracarboxylic dianhydride, dicyclohexyl-3, 3 ', 4, 4' -tetracarboxylic dianhydride and positional isomers thereof. These may be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic acid dianhydride include 1,2,3, 4-butanetetracarboxylic acid dianhydride, and 1,2,3, 4-pentanedicarboxylic acid dianhydride, and these can be used alone or in combination of two or more. In addition, cyclic aliphatic tetracarboxylic dianhydride and acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

Among the tetracarboxylic dianhydrides, 4,4 ' -oxydiphthalic anhydride, 3 ', 4,4 ' -benzophenonetetracarboxylic dianhydride are preferable from the viewpoint of high impact resistance, high elastic modulus, high surface hardness, high transparency, high flexibility, high bending resistance, and low coloring property of the optical film, 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride, 2 ', 3, 3' -biphenyltetracarboxylic dianhydride, 3,3 ', 4, 4' -diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 6FDA and mixtures thereof, more preferably 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride and 6FDA and mixtures thereof, and still more preferably 6FDA and 3,3 ', 4, 4' -biphenyltetracarboxylic dianhydride.

As the dicarboxylic acid compound used for producing the resin, terephthalic acid, isophthalic acid, 4' -oxybis benzoic acid, or an acid chloride compound thereof is preferably used. In addition to terephthalic acid, isophthalic acid, 4' -oxybis benzoic acid or their acid chloride compounds, other dicarboxylic acid compounds may also be used. Examples of the other dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and acid chloride compounds and acid anhydrides which are analogues thereof, and two or more of them may be used in combination. Specific examples thereof include: isophthalic acid; naphthalenedicarboxylic acid; 4, 4' -biphenyldicarboxylic acid; 3, 3' -LinPhthalic acid; dicarboxylic acid compound of chain hydrocarbon having 8 or less carbon atoms and single bond, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene groups, each of which is formed by linking 2 benzoic acids, and acid chloride compounds thereof. Specifically, 4' -oxybis (benzoyl chloride) (hereinafter, may be referred to as OBBC), terephthaloyl chloride (hereinafter, may be referred to as TPC) or isophthaloyl chloride is preferable, and OBBC and TPC are more preferably used in combination.

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

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

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and acid chloride compounds and acid anhydrides which are analogues thereof, and two or more of them may be used in combination. Specific examples thereof include: 1,2, 4-benzenetricarboxylic acid anhydride, 1,3, 5-benzenetricarboxylic acid anhydride; 2,3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; by single bonds, -O-, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂Or a compound in which phthalic anhydride is bonded to benzoic acid by phenylene group.

In the production of the resin, the amount of the diamine compound, the tetracarboxylic acid compound and/or the dicarboxylic acid compound to be used may be appropriately selected depending on the ratio of the respective structural units of the desired polyamideimide resin, and as described above, the ratio (int) can be adjusted by synthesizing the polyamideimide resin so that the amount of the dicarboxylic acid present at the terminal of the polyamideimide resin is as small as possible_A/int_B) Adjusted to within the 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, the dicarboxylic acid compound and the diamine compound is preferably more than 1.000, more preferably 1.0The amount of each monomer used is adjusted so as to be 03 or more, more preferably 1.005 or more, still more preferably 1.008 or more, and particularly preferably 1.01 or more.

The present invention also provides a method for producing a polyamideimide resin, which comprises reacting a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compound, 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 (amine ratio) is 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, and is, for example, 5 to 350 ℃, preferably 20 to 200 ℃, and more preferably 25 to 100 ℃. From easy to scale (int)_A/int_B) From the viewpoint of adjusting the reaction temperature to a desired range, the production may be carried out by adjusting the reaction temperature to the above reaction temperature by locally heating the reaction vessel, or the amount of the imidization catalyst described later and the amount of an acid anhydride such as acetic anhydride may be adjusted simultaneously with the local heating. The reaction time is also not particularly limited, and is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out in an inert atmosphere or under reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or in an inert gas atmosphere while stirring. The reaction is preferably carried out in a solvent inactive to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include: alcohol solvents such as water, methanol, ethanol, ethylene glycol, isopropanol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ -butyrolactone (hereinafter, sometimes referred to as GBL), γ -valerolactone, propylene glycol methyl ether acetate, and ethyl lactate; ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, and methyl isobutyl ketone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; acetonitrileNitrile solvents; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as N, N-dimethylacetamide (hereinafter, sometimes referred to as DMAc) and N, N-dimethylformamide (hereinafter, sometimes referred to as DMF); sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; combinations thereof, and the like. Among these, an amide solvent is preferably used from the viewpoint of solubility. From easy to scale (int)_A/int_B) From the viewpoint of adjusting the amount to the desired range, the amount of water in the solvent to be used is preferably 400ppm or more, more preferably 500ppm or more. From the viewpoint of suppressing decomposition of the polyamideimide resin, the water content in the solvent is preferably 1,000ppm or less, and more preferably 800ppm or less.

In the imidization step in the production of the polyamideimide resin, imidization may be performed in the presence of an imidization catalyst. Examples of the imidization catalyst include: aliphatic amines such as tripropylamine, dibutylpropylamine and ethyldibutylamine; n-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepino

Alicyclic amines (monocyclic); azabicyclo [2.2.1]Heptane, azabicyclo [3.2.1]Octane, azabicyclo [2.2.2]Octane, and azabicyclo [3.2.2]Alicyclic amines (polycyclic) such as nonane; and aromatic amines such as pyridine, 2-methylpyridine (2-picoline), 3-methylpyridine (3-picoline), 4-methylpyridine (4-picoline), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-dimethylpyridine, 2,4, 6-trimethylpyridine, 3, 4-cyclopentenopyridine, 5,6,7, 8-tetrahydroisoquinoline, and isoquinoline. In addition, from the viewpoint of facilitating the imidization reaction, it is preferable to use not only the imidization catalyst but also an acid anhydride. The acid anhydride includes a conventional acid anhydride used in the imidization reaction, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic acid anhydrides such as phthalic anhydrideAcid anhydrides, and the like. From easy to scale (int)_A/int_B) From the viewpoint of adjusting the temperature to a desired range, the temperature increase rate in the imidization step is preferably low, and more preferably, it takes 30 minutes or more to increase the temperature from 10 ℃ to 50 ℃.

The polyamideimide resin can be isolated by separation and purification by a conventional method, for example, separation means such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a combination thereof, and among the preferred methods, the separation can be carried out by: a large amount of an alcohol such as methanol is added to a reaction solution containing a transparent polyamideimide resin to precipitate the resin, followed by concentration, filtration, drying, and the like.

[ optical film ]

The present invention also provides an optical film comprising the polyamideimide resin of the present invention described above. In one embodiment of the present invention, the content of the polyamideimide 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, further preferably 50 parts by mass or more, preferably 99.5 parts by mass or less, more preferably 95 parts by mass or less, per 100 parts by mass of the optical film. When the content of the polyamideimide resin is within the above range, it is easy to improve the optical properties, impact resistance and elastic modulus of the optical film, and to suppress deterioration of the optical properties and mechanical properties of the optical film with time, thereby improving the quality stability of the optical film.

The optical film of the present invention may further contain at least one filler in addition to the polyamideimide resin of the present invention. Examples of the filler include organic particles and inorganic particles, and preferably inorganic particles. The inorganic particles include silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, Indium Tin Oxide (ITO), metal oxide particles such as antimony oxide and cerium oxide, and metal fluoride particles such as magnesium fluoride and sodium fluoride, among which silica particles, zirconia particles and alumina particles are preferable, and silica particles are more preferable, from the viewpoint of improving the elastic modulus and/or tear strength of the optical film and easily improving the impact resistance. These fillers may be used alone or in combination of two or more.

The average primary particle diameter of the filler (preferably silica particles) is usually 1nm or more, preferably 5nm or more, more preferably 10nm or more, further preferably 11nm or more, particularly preferably 13nm or more, preferably 100nm or less, more preferably 90nm or less, further preferably 80nm or less, further preferably 70nm or less, particularly preferably 60nm or less, particularly preferably 50nm or less, and particularly preferably 40nm or less. When the average primary particle diameter of the filler (preferably, silica particles) is within the above range, aggregation of the filler (preferably, silica particles) is suppressed, and the optical properties of the obtained optical film are easily improved. The average primary particle diameter of the filler can be measured by the BET method. The average primary particle size may be measured by image analysis using 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 5 parts by mass or more, further preferably 10 parts by mass or more, further preferably 20 parts by mass or more, particularly preferably 30 parts by mass or more, and preferably 60 parts by mass or less, per 100 parts by mass of the optical film. When the content of the filler is not less than the above lower limit, the elastic modulus of the optical film to be obtained is easily increased. When the content of the filler is not more than the upper limit, the optical properties of the optical film are easily improved.

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

When the optical film contains the ultraviolet absorber, the content of the ultraviolet absorber is preferably 1 part by mass or more, more preferably 2 parts by mass or more, further preferably 3 parts by mass or more, preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and further preferably 6 parts by mass or less, relative to 100 parts by mass of the optical film. The appropriate content varies depending on the ultraviolet absorber used, and when the content of the ultraviolet absorber is adjusted so that the light transmittance at 400nm becomes about 20 to 60%, the light resistance of the optical film can be improved and the transparency can be easily improved.

The optical film of the present invention may further contain other additives besides the filler and the ultraviolet absorber. Examples of the other additives include an antioxidant, a mold release agent, a stabilizer, a bluing agent, a flame retardant, a pH adjuster, a silica dispersant, a lubricant, a thickener, and a leveling agent. When other additives are contained, the content thereof may be preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and still more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of the optical film.

In a preferred embodiment of the present invention, the optical film of the present invention containing the polyamideimide resin of the present invention described above preferably has a change rate of the weight average molecular weight of 26% or less before and after a storage test at a temperature of 85 ℃ and a humidity of 85% for 1 week, from the viewpoint of easily suppressing deterioration of optical properties and mechanical properties with time and easily improving quality stability. In a more preferred embodiment of the present invention, the optical film of the present invention comprising the polyamideimide resin of the present invention described above is easily inhibited from deterioration in the optical properties and mechanical properties with timeFrom the viewpoint of reducing and easily improving the quality stability, the rate of change in weight average molecular weight before and after a storage test at a temperature of 85 ℃ and a humidity of 85% for 1 week is preferably 25% or less. When the change rate of the weight average molecular weight under the above conditions is considered to exceed 26% or 25%, the following may occur: depending on the storage conditions of the optical film and the storage conditions of the display device incorporating the optical film, some reaction occurs in the polyamide resin included in the optical film, and the optical properties and/or mechanical properties are likely to be degraded with time. The rate of change in the weight average molecular weight is more preferably 25% or less, still more preferably 23% or less, and still more preferably 22% or less. The present invention also provides an optical film containing a polyamideimide resin, which is less likely to suffer degradation of optical properties and/or mechanical properties over time, and which has a rate of change in weight average molecular weight of preferably 26% or less, more preferably 25% or less, before and after a storage test at a temperature of 85 ℃ and a humidity of 85% for 1 week. 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, and still more preferably 22% or less. The rate of change in the weight average molecular weight can be calculated, for example, by the method described in examples. The method for adjusting the change rate of the weight average molecular weight of the optical film containing the polyamideimide resin to be not more than the upper limit is not particularly limited, and for example, the change rate of the weight average molecular weight of the optical film is adjusted to be not more than 26%, more preferably not more than 25% before and after the storage test, by using a deuterated dimethyl sulfoxide solution of the polyamideimide resin contained in the optical film as a measurement sample¹H-¹³In the C HSQC spectrum, the integral value (int) of the peak existing in the area (A) with the chemical shift of the proton of 8.06-8.14 ppm and the chemical shift of the carbon of 129.6-130.3 ppm_A) And an integral value (int) of a peak present in a region (B) having a chemical shift from proton of 7.26 to 7.85ppm and a chemical shift from carbon of 132.4 to 134.0ppm_B) Ratio of (int)_A/int_B) When the content is 1.5% or less, the rate of change in the weight average molecular weight can be easily adjusted to the upper limit or less. Note that, though, by making the ratio (int)_A/int_B) The rate of change of the weight average molecular weight is not necessarily in a specific range from the viewpoint of suppressing deterioration of optical properties and mechanical properties with time, but it is important to set the ratio (int) to a specific range_A/int_B) Below a specific range.

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

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

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

The YI value of the optical film of the present invention is preferably 3.0 or less, more preferably 2.0 or less, further preferably 1.9 or less, particularly preferably 1.8 or less, usually-5 or more, preferably-2 or more. When the YI value of the optical film is not more than the above upper limit, the transparency becomes good, and when the optical film is applied to a front panel of a display device, high visibility can be contributed. The YI value is preferably within the above range even after storage for 1 week under conditions of 85 ℃ and 85% humidity, from the viewpoint of improving quality stability. The YI value can be calculated based on the formula YI of 100 × (1.2769X-1.0592Z)/Y by measuring the transmittance to light of 300 to 800nm using an ultraviolet-visible near-infrared spectrophotometer to obtain the tristimulus value (X, Y, Z). The optical film preferably has a YI value within the above range even after a storage test in which the optical film is stored at a temperature of 85 ℃ and a humidity of 85% for 1 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, further preferably 80 μm or less, particularly preferably 60 μm or less, and the range of the thickness may be a combination of these upper and lower limits. When the thickness of the optical film is within the above range, the elastic modulus of the optical film is more easily increased. The thickness of the optical film can be measured using a micrometer, and can be measured, for example, by the method described in examples.

The pencil hardness of at least one surface of the optical film of the present invention is preferably HB or more, and more preferably F or more. When the pencil hardness of at least one surface of the optical film is equal to or higher than the above hardness, damage or the like to the surface of the optical film can be easily prevented. The pencil hardness may be measured in accordance with JIS K5600-5-4: 1999, the measurement was carried out.

The optical film of the present invention has excellent bending resistance. The optical film of the present invention preferably has a bending resistance of 50,000 or more, more preferably 60,000 or more, and further preferably 70,000 or more in the MIT bending fatigue test in compliance with ASTM standard D2176-16. When the number of times of bending resistance is equal to or more than the above lower limit, damage or the like due to bending when used as a front panel material of a flexible display or the like can be prevented. The MIT bending fatigue test can be performed using an MIT bending fatigue tester, and can be performed by the method described in examples, for example. It is preferable that the optical film satisfies the above-mentioned number of times of bending resistance of preferably 35,000 times or more, more preferably 40,000 times or more, and further preferably 50,000 times or more even after a storage test in which the optical film is stored at a temperature of 85 ℃ and a humidity of 85% for 1 week.

The optical film of the present invention has excellent quality stability in which deterioration of optical properties and mechanical properties with time is suppressed. Specifically, the optical film was stored at 85 ℃ and 85% relative humidity for 1 week, and the number of times of bending resistance of the optical film before the storage test (N1) and the number of times of bending resistance of the optical film after the storage test (N2) were each allowed to stand at 25 ℃ and 50% humidity for 24 hours or more, and then measured using an MIT bending fatigue tester under the conditions described in examples, for example. The smaller the change (%) in the number of times of bending resistance calculated according to the following formula is, the better the obtained number of times of bending resistance is, the more preferably 40% or less, the more preferably 35% or less, the more preferably 30% or less, the still more preferably 25% or less, and the particularly preferably 20% or less.

Change rate (%) of bending resistance number { (N1-N2)/N1} × 100

Further, 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 calculated by the method described in examples using an ultraviolet-visible near-infrared spectrophotometer, for example. The smaller the change rate (%) of the YI value calculated according to the following formula from the obtained YI value is, the better, it is preferably 25% or less, more preferably 20% or less, and further preferably 15% or less.

Change rate (%) of YI value { (Y2-Y1)/Y1} × 100

[ method for producing optical film ]

The method for producing the optical film of the present invention is not particularly limited, and for example, a production method including at least the following steps:

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

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

(c) and a step of drying the coating film to form an optical film (optical film forming step).

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

The solvent used for the preparation of the varnish is not particularly limited as long as it can dissolve the resin. Examples of the solvent include: amide solvents such as DMAc and DMF; lactone solvents such as GBL and gamma valerolactone; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, an amide solvent or a lactone solvent is preferable. These solvents may be used alone or in combination of two or more. The varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The solid content concentration of the varnish is preferably 1 to 25 mass%, more preferably 5 to 20 mass%, and still more preferably 5 to 15 mass%.

In the coating step, a varnish is applied to the support material by a known coating method to form a coating film. Examples of known coating methods include roll coating methods such as wire bar coating, reverse coating, and gravure coating, die coating, comma coating, lip coating, spin coating, screen coating, spray coating, dipping, spraying, and casting.

In the film forming step, the coating film is dried and peeled from the support material, whereby an optical film can be formed. A step of drying the optical film may be further provided after the peeling. The drying of the coating film may be carried out at a temperature of 50 to 350 ℃. If necessary, the coating film may be dried in an inert atmosphere or under reduced pressure.

Examples of the support material include a metal-based support material, an SUS plate, and a resin-based support material, a PET film, a PEN film, a polyamide-based resin film, another polyimide-based resin film, a cycloolefin-based polymer film, and an acrylic film. Among them, a PET film, a cycloolefin 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 the optical film can be used in various applications. The optical film of the present invention may be a single layer or a laminate, and the optical film of the present invention may be used as it is or may be further used as a laminate with another film. When the optical film is a laminate, all layers laminated on one surface or both surfaces of the optical film are referred to as optical films.

(functional layer)

At least one functional layer of 1 or more 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, an undercoat layer, a gas barrier layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer. The functional layers may be used alone or in combination of two or more.

A hard coat layer may be provided on at least one side of the optical film of the present invention. The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100 μm. When the thickness of the hard coat layer is within the above range, the impact resistance can be further improved, the bending resistance is less likely to be lowered, and the problem of occurrence of curling 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 which can form a crosslinked structure by irradiation with active energy rays or application of thermal energy, and is preferably obtained by irradiation with active energy rays. The active energy ray is defined as an energy ray that can decompose a compound capable of generating an active species to generate an active species, and examples thereof include visible light, ultraviolet ray, infrared ray, X-ray, α -ray, β -ray, γ -ray, and electron ray, and preferable examples thereof include ultraviolet ray. The hard coat composition contains a polymer of at least one of a radical polymerizable compound and a cation polymerizable compound.

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

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

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

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

The above hard coating composition may further comprise a polymerization initiator. Examples of the polymerization initiator include a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and they can be appropriately selected and used. These polymerization initiators are those which are decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, thereby causing radical polymerization and cationic polymerization.

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

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

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

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

The hard coating composition may further include one or more selected from the group consisting of a solvent and an additive.

The solvent is a solvent capable of dissolving or dispersing the polymerizable compound and the polymerization initiator, and any solvent known as a solvent for a hard coat composition in the art may be used as long as the effect of the present invention is not impaired.

The above additives may further contain inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, and the like.

The ultraviolet absorbing layer is a layer having a function of absorbing ultraviolet rays, and is composed of a main material selected from ultraviolet-curable transparent resins, electron beam-curable transparent resins, and thermosetting transparent resins, and an ultraviolet absorber dispersed in the main material.

The pressure-sensitive adhesive layer is a layer having a pressure-sensitive adhesive function and has a function of bonding the optical film to another member. As a material for forming the adhesive layer, a generally known material can be used. For example, a thermosetting resin composition or a photocurable resin composition may be used. In this case, the resin composition can be polymerized and cured by supplying energy afterwards.

The Pressure-Sensitive Adhesive layer may be a layer called a Pressure-Sensitive Adhesive (PSA) that is attached to an object by pressing. The pressure-sensitive adhesive may be a capsule adhesive as "an adhesive having adhesiveness at normal temperature and adhering to an adherend under light pressure" (JIS K6800), or as "an adhesive capable of maintaining stability until a protective film (microcapsule) is contained therein by a specific component and the film is broken by an appropriate means such as pressure and heat" (defined in JIS K6800).

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

The refractive index adjustment layer is a layer having a function of adjusting the refractive index, and is, for example, a layer having a refractive index different from that of the optical film and capable of providing a predetermined refractive index to the optical laminate. The refractive index adjusting layer may be, for example, a resin selected as appropriate, a resin layer containing a pigment as the case may be, or a thin film of a metal. Examples of the pigment for adjusting the refractive index include silica, alumina, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle diameter of the pigment may be 0.1 μm or less. By setting the average primary particle diameter of the pigment to 0.1 μm or less, diffuse reflection of light transmitted through the refractive index adjustment layer can be prevented, and a decrease in transparency can be prevented. Examples of the metal used for the refractive index adjustment layer include metal oxides and metal nitrides such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride.

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

In a preferred embodiment of the present invention, the optical film of the present invention is useful as a front panel of an image display device, particularly a front panel of a flexible display device (hereinafter, may be referred to as a window film), a front panel of a rollable display, or a front panel of a foldable display. Flexible display devices, for example, have flexible functional layers; and an optical film which is superposed on the flexible functional layer and functions as a front panel. That is, the front panel of the flexible display device is arranged on the viewing side on the flexible functional layer. The front panel has 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 used in association with operations such as repeated bending and repeated winding of the image display device. A front panel of a flexible display device used in association with such repeated bending operations is required to have high bending resistance. In addition, the front panel is required to have high visibility. A film used for a front panel of an image display device, particularly a front panel of a flexible display device, is required to have high visibility and high bending resistance as compared with a film used for a substrate of an image display device used inside an image display device. For example, the film of the present invention preferably has the total light transmittance, haze and/or YI value described above from the viewpoint of easily improving visibility when used for a front panel of a flexible display device, and preferably satisfies the number of times of bending resistance in the MIT bending fatigue test described above from the viewpoint of easily improving bending resistance when used as a front panel of a flexible display device.

Examples of the image display device include wearable devices such as a television, a smartphone, a mobile phone, a car navigation system, a tablet computer, a portable game machine, electronic paper, a pointer, a bulletin board, a clock, and a smart watch. Examples of the flexible display device include all image display devices having a flexible property, for example, the rollable display and the foldable display described above. By rollable display, it is meant: an image display device in which an image display portion including a front panel is wound in a roll shape and is used in a state where the image display portion is drawn out to form a flat surface or a curved surface is an image display device in which an operation such as winding in a roll shape is performed every time it is used. In addition, the foldable display means: an image display device used in a state in which an image display portion including a front panel is bent and the image display portion is opened to form a flat surface or a curved surface is an image display device in which an operation such as bending is performed every time the image display device is used. An image display device in which such operations such as winding and bending are repeated is referred to as a flexible image display device.

[ Flexible display device ]

The invention also provides a flexible display device provided with the optical film. The optical film of the present invention is preferably used as a front panel in a flexible display device. The flexible image display device is formed of a laminate for flexible display device and an organic EL display panel, and the laminate for flexible display device is disposed on the viewing side of the organic EL display panel and is configured to be foldable. The laminate for a flexible display device may contain a window film, a polarizing plate, and a touch sensor as the optical film of the present invention, and the lamination order thereof is arbitrary, and it is preferable to laminate the window film, the polarizing plate, and the touch sensor in this order or the window film, the touch sensor, and the polarizing plate in this order from the viewing side. The presence of the polarizing plate on the viewing side of the touch sensor is preferable because the pattern of the touch sensor is less likely to be observed and the visibility of the display image is good. The members may be laminated using an adhesive, a bonding agent, or the like. The touch panel may further include a light-shielding pattern formed on at least one surface of any one of the window film, the polarizing plate, and the touch sensor.

[ polarizing plate ]

The flexible display device of the present invention may further include a polarizing plate, preferably a circular polarizing plate. The circularly polarizing plate is a functional layer having a function of transmitting only a right-handed circularly polarized light component or a left-handed circularly polarized light component by laminating a λ/4 phase difference plate on a linearly polarizing plate. For example, can be used for: the external light is converted into right-handed circularly polarized light, the external light which is reflected by the organic EL panel and becomes left-handed circularly polarized light is blocked, only the light-emitting component of the organic EL is transmitted, and therefore the influence of reflected light is inhibited, and the image can be easily viewed. In order to achieve the circularly polarized light function, the absorption axis of the linear polarizer and the slow axis of the λ/4 phase difference plate need to be 45 ° in theory, but in practical applications, 45 ± 10 °. The linear polarizing plate and the λ/4 phase difference plate do not necessarily have to be stacked adjacent to each other, and the relationship between the absorption axis and the slow axis may satisfy the above range. It is preferable to achieve completely circularly polarized light at all wavelengths, but this is not necessarily the case in practical applications, and therefore, the circularly polarizing plate in the present invention also includes an elliptically polarizing plate. It is also preferable to further laminate a λ/4 retardation film on the viewing side of the linear polarizing plate to convert the emitted light into circularly polarized light, thereby improving visibility in a state where the polarized sunglasses are worn.

The linear polarizing plate is a functional layer having the following functions: light vibrating in the direction of the transmission axis is passed through, and polarized light of a vibration component perpendicular to the light is blocked. The linear polarizing plate may be a single linear polarizer or a structure including a linear polarizer and a protective film attached to at least one surface of the linear polarizer. The thickness of the linearly polarizing plate may be 200 μm or less, and preferably 0.5 to 100 μm. When the thickness is within the above range, the flexibility tends not to be easily lowered.

The linear polarizer may be a film-type polarizer manufactured by dyeing and stretching a polyvinyl alcohol (hereinafter, abbreviated as PVA) film. The polarizing performance can be exhibited by adsorbing a dichroic dye such as iodine to a PVA film that has been stretched to be oriented, or by stretching the PVA film in a state of being adsorbed to the dichroic dye to orient the dichroic dye. The film-type polarizer may be produced by steps such as swelling, crosslinking with boric acid, washing with an aqueous solution, and drying. The stretching and dyeing step may be performed as a PVA film alone or in a state of being laminated with another film such as polyethylene terephthalate. The thickness of the PVA film to be used is preferably 10 to 100 μm, and the stretch ratio is preferably 2 to 10 times.

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

The dichroic dye may be a dye that exhibits dichroism by being aligned with the liquid crystal compound, and may have liquid crystallinity or a polymerizable functional group. Any of the compounds in the liquid crystal polarizing composition has a polymerizable functional group.

The liquid crystal polarizing composition may further include an initiator, a solvent, a dispersant, a leveling agent, a stabilizer, a surfactant, a crosslinking agent, a silane coupling agent, and the like.

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

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

The protective film may be a transparent polymer film, and specific examples of the polymer film to be used include polyolefins such as polyethylene, polypropylene, polymethylpentene, cycloolefin derivatives of cycloolefin having a unit containing a norbornene or cycloolefin monomer, (modified) celluloses such as diacetylcellulose, triacetylcellulose and propionylcellulose, acrylics such as methyl methacrylate (co) polymers, polystyrenes such as styrene (co) polymers, acrylonitrile-butadiene-styrene copolymers, acrylonitrile-styrene copolymers, ethylene-vinyl acetate copolymers, polyvinyl chlorides, polyvinylidene chlorides, polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate and polyarylates, polyamides such as nylon, polyesters, polyamides, polyesters, polyamides, polyesters, films such as polyimides, polyamideimides, polyetherimides, polyethersulfones, polysulfones, polyvinyl alcohols, polyvinyl acetals, polyurethanes, and epoxy resins are preferably films of polyamides, polyamideimides, polyimides, polyesters, olefins, acrylic resins, or cellulose resins, from the viewpoint of excellent transparency and heat resistance. These polymers may be used alone or in combination of two or more. These films may be used in an unstretched state, or as uniaxially or biaxially stretched films. Cellulose-based films, olefin-based films, acrylic films, and polyester films are preferable. The protective film may be a coating type protective film obtained by applying and curing a cationically curable composition such as an epoxy resin or a radically curable composition such as an acrylate. If necessary, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, or the like may be included. The thickness of the protective film may be 200 μm or less, preferably 1 to 100 μm. When the thickness of the protective film is within the above range, the flexibility of the protective film is not easily reduced.

The λ/4 retardation plate is a film that imparts a retardation of λ/4 in a direction perpendicular to the traveling direction of incident light, in other words, in the in-plane direction of the film. The λ/4 retardation plate may be a stretched retardation plate produced by stretching a polymer film such as a cellulose film, an olefin film, or a polycarbonate film. If necessary, a phase difference adjusting agent, a plasticizer, an ultraviolet absorber, an infrared absorber, a pigment, a colorant such as a dye, a fluorescent brightener, a dispersant, a heat stabilizer, a light stabilizer, an antistatic agent, an antioxidant, a lubricant, a solvent, and the like may be included. The thickness of the stretched retardation film may be 200 μm or less, preferably 1 to 100 μm. When the thickness is within the above range, the flexibility of the film tends not to be easily lowered.

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

In general, the birefringence is large as the wavelength is shorter, and the birefringence is small as the wavelength is longer. In this case, since a retardation of λ/4 cannot be achieved in all visible light regions, it is often designed to have an in-plane retardation of λ/4 (i.e., 100 to 180nm, preferably 130 to 150nm) in the vicinity of 560nm, which has high visibility. The use of an inverse dispersion λ/4 phase difference plate using a material having a birefringence wavelength dispersion characteristic opposite to that of the usual one is preferable because it can improve visibility. As such a material, the material described in japanese patent application laid-open No. 2007-232873 and the like is preferably used also in the case of a stretched phase difference plate, and the material described in japanese patent application laid-open No. 2010-30979 is preferably used also in the case of a liquid crystal coated phase difference plate.

As another method, a technique of obtaining a wide-band λ/4 phase difference plate by combining with a λ/2 phase difference plate is also known (for example, japanese patent application laid-open No. h 10-90521). The λ/2 phase difference plate can be manufactured by the same material and method as the λ/4 phase difference plate. The combination of the stretching type retardation plate and the liquid crystal coating type retardation plate is arbitrary, and the use of the liquid crystal coating type retardation plate is preferable because the thickness can be reduced.

For the above-mentioned circularly polarizing plate, a method of laminating a positive C plate is also known in order to improve visibility in an oblique direction (for example, japanese patent application laid-open No. 2014-224837). The positive C plate may be a liquid crystal coated retardation plate or a stretched retardation plate. The phase difference in the thickness direction is usually from-200 to-20 nm, preferably from-140 to-40 nm.

[ touch sensor ]

The flexible display device of the present invention may further include a touch sensor. The touch sensor may be used as an input mechanism. As the touch sensor, various types such as a resistive film type, a surface acoustic wave type, an infrared ray type, an electromagnetic induction type, and a capacitance type have been proposed, and any type may be used. Among them, the electrostatic capacitance system is preferable. The capacitive touch sensor may be divided into an active region and an inactive region located at a peripheral portion of the active region. The active region is a region corresponding to a display portion, which is a region on the display panel where a screen is displayed, and is a region where a user's touch is sensed, and the inactive region is a region corresponding to a non-display portion, which is a region on the display device where a screen is not displayed. The touch sensor may include: a substrate having flexible properties; a sensing pattern formed in an active region of the substrate; and each sensing line formed in the inactive region of the substrate and used for connecting the sensing pattern with an external driving circuit through a pad (pad) portion. As the substrate having a flexible property, 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 in terms of suppressing cracks in the touch sensor. The toughness may be more preferably 2,000 to 30,000 MPa%. Here, the toughness is defined as the area of the lower part of a Stress (MPa) -strain (%) curve (Stress-strain curve) obtained by a tensile test of a polymer material up to a failure point.

The sensing pattern may include a 1 st pattern formed along a 1 st direction and a 2 nd pattern formed along a 2 nd direction. The 1 st pattern and the 2 nd pattern are arranged in mutually different directions. The 1 st pattern and the 2 nd pattern are formed in the same layer, and in order to sense a touched position, the patterns must be electrically connected. The 1 st pattern is a form in which the unit patterns are connected to each other via a terminal, and the 2 nd pattern is a structure in which the unit patterns are separated from each other into islands, and therefore, in order to electrically connect the 2 nd pattern, a separate bridge electrode is required. The sensing pattern may use a known transparent electrode material. Examples thereof include Indium Tin Oxide (ITO), Indium Zinc Oxide (IZO), zinc oxide (ZnO), Indium Zinc Tin Oxide (IZTO), Indium Gallium Zinc Oxide (IGZO), Cadmium Tin Oxide (CTO), PEDOT (poly (3, 4-ethylenedioxythiophene)), Carbon Nanotube (CNT), graphene, and a metal wire, and these may be used alone or in combination of 2 or more. Preferably, ITO can be used. The metal usable for the wire is not particularly limited, and examples thereof include silver, gold, aluminum, copper, iron, nickel, titanium, selenium, chromium, and the like. These can be used alone or in combination of 2 or more.

The bridge electrode may be formed on the insulating layer with an insulating layer interposed therebetween on the sensing pattern, the bridge electrode may be formed on the substrate, and the insulating layer and the sensing pattern may be formed thereon. The bridge electrode may be formed of the same material as the sensing pattern, or may be formed of a metal such as molybdenum, silver, aluminum, copper, palladium, gold, platinum, zinc, tin, titanium, or an alloy of 2 or more of these metals. The 1 st pattern and the 2 nd pattern must be electrically insulated, and thus, an insulating layer is formed between the sensing pattern and the bridge electrode. The insulating layer may be formed only between the tab of the 1 st pattern and the bridge electrode, or may be formed in a structure of a layer covering the sensing pattern. In the latter case, the 2 nd pattern may be connected to the bridge electrode through a contact hole formed in the insulating layer. In the touch sensor, as means for appropriately compensating for a difference in transmittance between a pattern region where a pattern is formed and a non-pattern region where no pattern is formed (specifically, a difference in transmittance due to a difference in refractive index in these regions), an optical adjustment layer may be further included between the substrate and the electrode, and the optical adjustment layer may include an inorganic insulating substance or an organic insulating substance. The optical adjustment layer can be formed by applying a photocurable composition containing a photocurable organic binder and a solvent onto a substrate. The above-mentioned photocurable composition may further comprise inorganic particles. The refractive index of the optical adjustment layer can be increased by the inorganic particles.

The photocurable organic binder may include, for example, a copolymer of monomers such as an acrylate monomer, a styrene monomer, and a carboxylic acid monomer. The photocurable organic binder may be, for example, a copolymer containing repeating units different from each other, such as repeating units containing an epoxy group, repeating units containing an acrylate, repeating units containing a carboxylic acid, and the like.

The inorganic particles may include, for example, zirconium dioxide particles, titanium dioxide particles, aluminum oxide particles, and the like. The photocurable composition may further contain various additives such as a photopolymerization initiator, a polymerizable monomer, and a curing assistant.

[ adhesive layer ]

Each layer of the laminate for a flexible display device, such as a window film, a polarizing plate, and a touch sensor, and a film member, such as a linear polarizing plate and a λ/4 retardation plate, constituting each layer may be bonded with an adhesive. As the adhesive, a commonly used adhesive such as an aqueous adhesive, an organic solvent adhesive, a solventless adhesive, a solid adhesive, a solvent-volatile adhesive, a moisture-curable adhesive, a heat-curable adhesive, an anaerobic curable adhesive, an aqueous solvent-volatile adhesive, an active energy ray-curable adhesive, a curing agent-mixed adhesive, a hot-melt adhesive, a pressure-sensitive adhesive, and a remoistenable adhesive can be used. Among them, water-based solvent-volatile adhesives, active energy ray-curable adhesives, and adhesives are generally used. The thickness of the adhesive layer can be adjusted as appropriate according to the required adhesive strength, and is, for example, 0.01 to 500. mu.m, preferably 0.1 to 300. mu.m. The laminate for a flexible image display device may have a plurality of adhesive layers, and the thickness and the type of the adhesive used may be the same or different.

The aqueous solvent-based volatile adhesive may be a polyvinyl alcohol polymer, a water-soluble polymer such as starch, or a water-dispersed polymer such as an ethylene-vinyl acetate emulsion or a styrene-butadiene emulsion. In addition to water and the above-mentioned main agent polymer, a crosslinking agent, a silane compound, an ionic compound, a crosslinking catalyst, an antioxidant, a dye, a pigment, an inorganic filler, an organic solvent, and the like may be blended. In the case of bonding with the aqueous solvent volatile adhesive, the aqueous solvent volatile adhesive may be injected between the layers to be bonded, and the layers to be bonded may be bonded and then dried to impart adhesiveness. The thickness of the adhesive layer when the aqueous solvent volatile adhesive is used may be 0.01 to 10 μm, preferably 0.1 to 1 μm. When the aqueous solvent-volatile adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive may be the same or different.

The active energy ray-curable adhesive can be formed by curing an active energy ray-curable composition containing a reactive material capable of forming an adhesive layer by irradiation with an active energy ray. The active energy ray-curable composition may contain at least 1 polymer selected from the group consisting of radical polymerizable compounds and cationic polymerizable compounds, which are similar to the hard coat composition. The radical polymerizable compound may be the same type of radical polymerizable compound as used in the hard coat composition, as used in the hard coat composition. As the radical polymerizable compound that can be used in the adhesive layer, a compound having an acryloyl group is preferable. In order to reduce the viscosity of the adhesive composition, a monofunctional compound is preferably contained.

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

In the active energy ray composition, a polymerization initiator may be further contained. The polymerization initiator may be a radical polymerization initiator, a cationic polymerization initiator, a radical or cationic polymerization initiator, and the like, and may be appropriately selected and used. These polymerization initiators are those which can be decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, thereby allowing radical polymerization and cationic polymerization to proceed. The initiator described in the description of the hard coating composition, which can initiate at least either of radical polymerization or cationic polymerization by irradiation with active energy rays, may be used.

The active energy ray-curable composition may further contain an ion scavenger, an antioxidant, a chain transfer agent, an adhesion-imparting agent, a thermoplastic resin, a filler, a flow viscosity modifier, a plasticizer, an antifoaming agent, an additive, and a solvent. When the bonding is performed by the active energy ray-curable adhesive, the bonding may be performed by: the active energy ray-curable composition is applied to one or both of the adhesive layers and then bonded thereto, and the adhesive layer or both of the adhesive layers is irradiated with an active energy ray through the adhesive layer or both of the adhesive layers to be cured. The thickness of the adhesive layer when the active energy ray-curable adhesive is used may be usually 0.01 to 20 μm, and preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of layers, the thickness of each layer and the type of the adhesive used may be the same or different.

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

[ light-shielding pattern ]

The light shielding pattern may be applied as at least a part of a bezel (bezel) or a housing of the flexible image display device. The wiring disposed at the edge of the flexible image display device is hidden by the light-shielding pattern and is not easily viewed, thereby improving visibility of an image. The light-shielding pattern may be in the form of a single layer or a plurality of layers. The color of the light-shielding pattern is not particularly limited, and may have various colors such as black, white, metallic color, and the like. The light-shielding pattern may be formed of a pigment for color, and polymers such as acrylic resin, ester resin, epoxy resin, polyurethane, silicone, and the like. They may be used alone or in the form of a mixture of 2 or more. The light-shielding pattern can be formed by various methods such as printing, photolithography, and inkjet. The thickness of the light-shielding pattern is usually 1 to 100 μm, preferably 2 to 50 μm. Further, it is preferable to provide a shape such as an inclination in the thickness direction of the light-shielding pattern.

Examples

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

< HSQC-NMR-based (int)_A/int_B) Measurement of

Based on HSQC-NMR (int)_A/int_B) The calculation is performed in the following manner.

(1) Method for preparing measurement sample

Dissolving the polyamide-imide resin in deuterated dimethyl sulfoxide (DMSO-d)₆) To prepare a 2 mass% solution, which was used as a measurement solution。

(2) Measurement conditions

A measuring device: 600MHzNMR apparatus AVANCE600 manufactured by Bruker

Temperature of the sample: 303K

The determination method comprises the following steps: HSQC

Chemical shift standard: DMSO (proton: 2.49ppm, carbon: 40.44ppm)

(3) Analytical method

In the obtained HSQC-NMR spectrum, the volume of a peak existing in a region A with a proton chemical shift of 8.06-8.14 ppm and a carbon chemical shift of 129.6-130.3 ppm is obtained by integration, and an integral value (int)_A). Further, the volume of a peak existing in a region B where the chemical shift of a proton is 7.26 to 7.85ppm and the chemical shift of carbon is 132.4 to 134.0ppm is obtained by integration, and the integral value (int) is obtained_B). Calculating an integral value (int)_A) Relative integral value (int)_B) Ratio of (int) is thus obtained_A/int_B)[％]。

< determination of weight average molecular weight (weight average molecular weight in terms of polystyrene) of Polyamide-imide resin >

Gel Permeation Chromatography (GPC) measurement

(1) Pretreatment method

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

(2) Measurement conditions

A chromatographic column: TSKgel α -2500 (7)7.8mm diameter. times.300 mm. times.1 pieces, and α -M ((13)7.8mm diameter. times.300 mm). times.2 pieces, manufactured by Tosoh corporation

Eluent: DMF (adding 10mmol/L lithium bromide)

Flow rate: 1.0 mL/min

A detector: RI detector

Column temperature: 40 deg.C

Sample introduction amount: 100 μ L

Molecular weight standard: standard polystyrene

< rate of change in weight average molecular weight >

The optical films obtained in examples and comparative examples were stored at 85 ℃ and 85% relative humidity for 1 week. Then, the weight average molecular weight (Mw1) of the polyamideimide resin contained in the optical film before the storage test and the weight average molecular weight (Mw2) of the polyamideimide resin contained in the optical film after the storage test were measured in the same manner as described above. From the obtained weight average molecular weight, the change rate (%) of the weight average molecular weight was calculated according to the following formula.

The change rate (%) of the weight average molecular weight { (Mw1-Mw2)/Mw1} × 100

< thickness >

The thickness of the optical films obtained in examples and comparative examples was measured using an ABS number dial gauge ("ID-C112 BS", manufactured by Mitutoyo Co., Ltd.).

< modulus of elasticity >

The elastic modulus of the optical films obtained in examples and comparative examples was measured at a temperature of 25 ℃ and a relative humidity of 50% by using "Autograph AG-IS" manufactured by Shimadzu corporation. More specifically, a film having a width of 10mm in width and width was produced, a stress-strain curve (S-S curve) was measured under conditions of a chuck-to-chuck distance of 50mm and a stretching speed of 20 mm/min, and the elastic modulus was calculated from the slope of the curve.

< Total light transmittance (Tt) >)

According to JIS K7105: 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-2 DP manufactured by Suga Test Instruments).

< haze >

According to JIS K7136: the optical films obtained in examples and comparative examples were cut into 30mm × 30mm pieces, and the haze (%) was measured using a fully automatic direct reading haze computer (HGM-2 DP manufactured by Suga Test Instruments, Ltd.).

< YI value >

The YI value was calculated by obtaining the tristimulus values (X, Y, Z) using an ultraviolet-visible near-infrared spectrophotometer (V-670, manufactured by JASCO corporation) and substituting the tristimulus values into the following equation.

YI＝100×(1.2769X-1.0592Z)/Y

< rate of change in YI value >

The optical films obtained in examples and comparative examples were subjected to a storage test in which the films were stored at 85 ℃ and 85% relative humidity for 1 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 in the same manner as described above. From the obtained YI values, the change rate (%) of YI values was calculated according to the following formula.

Change rate (%) 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 10mm × 100mm using a dumbbell cutter. The cut films were left to stand at a temperature of 25 ℃ and a humidity of 50% for 24 hours or more, and set in an MIT bending fatigue tester ("MIT-DA type: 0530 manufactured by toyoyo seiki corporation), bending tests were performed in both directions of the front and back surfaces under conditions of a test speed of 175cpm, a bending angle of 135 °, a load of 750g, and an R of a bending splint of 1.0mm, and the number of times of bending resistance, that is, the number of times of bending without breaking, of each film was measured.

< rate of change of bending resistance times >

The optical films obtained in examples and comparative examples were stored at 85 ℃ and 85% relative humidity for 1 week. Then, the number of times of bending resistance of the optical film before the storage test (N1) and the number of times of bending resistance of the optical film after the storage test (N2) were each allowed to stand at a temperature of 25 ℃ and a humidity of 50% for 24 hours or more, and then measured by the above-described method. From the obtained number of times of bending resistance, the change rate (%) of the number of times of bending resistance was calculated according to the following formula.

Change rate (%) of bending resistance number { (N1-N2)/N1} × 100

< amine ratio >

M represents the molar amount of a diamine compound used for the synthesis of a polyamideimide resin_AM represents the molar amount of the dicarboxylic acid compound_BM represents the molar amount of the tetracarboxylic acid compound_CThe amine ratio in the synthesis of the resin was calculated from the following formula.

Amine ratio of M_A/(M_B+M_C)

< example 1 >

313.57g of DMAc was charged into a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere, and a necessary amount of ion-exchanged water was charged so that the water content became 700 ppm. Then, 18.53g (57.86mmol) of TFMB was added thereto, and the solution was dissolved in DMAc while stirring at room temperature. Then, 7.64g (17.19mmol) of 6FDA was added to the flask, and the mixture was cooled to 10 ℃ and stirred for 16 hours. Then, 1.69g (5.73mmol) of OBBC was put into the flask, and then 6.28g (30.93mmol) of TPC was put into the flask, followed by stirring at 10 ℃ for 30 minutes. Then, 313.57g of DMAc adjusted to 700ppm in water content was added, and after stirring for 10 minutes, 0.70g (3.45 mm/l) of TPC was further added to the flask, and after stirring at 10 ℃ for 30 minutes, 0.0367g (0.115 mm/l) of TFMB was further added, and the mixture was stirred for 2 hours. Subsequently, 5.18g (40.11) of diisopropylethylamine, 3.74g (40.11mmol) of 4-methylpyridine and 12.29g (120.30mmol) of acetic anhydride were added to the flask, and the mixture was stirred at 10 ℃ for 30 minutes. Then, using an oil bath, the temperature was raised from 10 ℃ to 50 ℃ over 30 minutes, from 50 ℃ to 60 ℃ over 10 minutes, from 60 ℃ to 65 ℃ over 10 minutes, and then, in stages, from 65 ℃ to 70 ℃ over 10 minutes, from 70 ℃ to 75 ℃ over 10 minutes, and further, the temperature was maintained at 70 ℃ for 3 hours while stirring, to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamideimide resin (1).

The polyamideimide resin (1) was dissolved in DMAc to prepare a 10 mass% solution, the obtained polyamideimide varnish was filtered through a filter having a 10 μm opening, and then coated on a smooth surface of a polyester substrate (manufactured by tokyo corporation, trade name "a 4100") using an applicator so that the thickness of the self-supporting film became 55 μm, and after drying at 50 ℃ for 30 minutes and then at 140 ℃ for 15 minutes, the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 40 minutes under the atmosphere, to obtain an optical film 1 having a thickness of 50 μm.

< comparative example 1 >

313.57g of DMAc was charged into a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere, and a necessary amount of ion-exchanged water was charged so that the water content became 700 ppm. Then, 18.27g (57.05mmol) of TFMB was added thereto, and the solution was dissolved in DMAc while stirring at room temperature. Then, 7.76g (17.47mmol) of 6FDA was added to the flask, and the mixture was cooled to 10 ℃ and stirred for 16 hours. Then, 1.72g (5.85mmol) of OBBC was put into the flask, and then 6.38g (31.43mmol) of TPC was put into the flask, followed by stirring at 10 ℃ for 30 minutes. Then, 313.57g of DMAc adjusted to 700ppm in water content was added, and after stirring for 10 minutes, 0.71g (3.50mm o.l) of TPC was further added to the flask, and after stirring at 10 ℃ for 30 minutes, 0.186g (0.581mm o.l) of TFMB was further added, and after stirring for 30 minutes, 0.0932g (0.291mm o.l) of TFMB was further added, and stirring was carried out for 2 hours. Next, 5.27g (40.76mmol) of diisopropylethylamine, 3.80g (40.76mmol) of 4-methylpyridine and 12.48g (122.27mmol) of acetic anhydride were added to the flask, and the mixture was stirred at 10 ℃ for 30 minutes. Then, the reaction solution was stirred while being heated stepwise from 10 ℃ to 50 ℃ over 20 minutes, from 50 ℃ to 60 ℃ over 20 minutes, from 60 ℃ to 75 ℃ over 20 minutes, and then held at 75 ℃ for 3 hours by using an oil bath to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamideimide resin (2).

An optical film 2 having a thickness of 50 μm was obtained in the same manner as in example 1, except that the polyamideimide resin (2) was used.

< comparative example 2 >

313.57g of DMAc was charged into a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere. At this time, the water content in DMAc was 300 ppm. Then, 18.36g (57.33mmol) of TFMB was added thereto, and the solution was dissolved in DMAc while stirring at room temperature. Then, 7.72g (17.38mmol) of 6FDA was added to the flask, and the mixture was cooled to 10 ℃ and stirred for 16 hours. Then, 1.71g (5.81mmol) of OBBC was added to the flask, and then 6.35g (31.28mmol) of TPC was added to the flask, followed by stirring at 10 ℃ for 30 minutes. Then, 313.57g of DMAc having a water content of 300ppm was added, and after stirring for 10 minutes, 0.71g (3.48mm o/l) of TPC was further added to the flask, and the mixture was stirred for 2 hours. Next, 5.24g (40.54mmol) of diisopropylethylamine, 7.55g (81.08mmol) of 4-methylpyridine and 26.61g (260.60mmol) of acetic anhydride were added to the flask, and the mixture was stirred at 10 ℃ for 30 minutes. Then, the reaction solution was stirred while being heated stepwise from 10 ℃ to 55 ℃ over 20 minutes, from 55 ℃ to 65 ℃ over 20 minutes, from 65 ℃ to 85 ℃ over 20 minutes, and then held at 85 ℃ for 3 hours by using an oil bath to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamideimide resin (3).

An optical film 3 having a thickness of 50 μm was obtained in the same manner as in example 1, except that the polyamideimide resin (3) was used.

< example 2 >

Under nitrogen atmosphere, to 3m with stirring blades³In the reaction vessel of (3), 23.66kg of TFMB and DMAc having a water content adjusted to 300ppm were added so that the solid content concentration of TFMB in the reaction mixture became 5.54 mass%, and TFMB was dissolved in DMAc while stirring at room temperature. Then, 6FDA was added to the reaction vessel so that the concentration of TFMB was 30.21 mol%, and the mixture was stirred at 25 ℃ for 16 hours. Then, TPC and OBBC were made to be 60.42 mol% and 10.07 mol%, respectively, with respect to TFMBAdded as described above and stirred for 60 minutes. Next, 4-picoline 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 portion and the bottom portion of the reaction mixture was increased from 25 ℃ to 50 ℃ over 30 minutes, from 50 ℃ to 60 ℃ over 10 minutes, from 60 ℃ to 65 ℃ over 10 minutes, and then, stepwise, from 65 ℃ to 70 ℃ over 10 minutes, respectively. At this time, the wall surface of the reaction vessel was provided with a heating portion so as to be heated from 7 degrees above the liquid level of the reaction mixture, and the remaining bottom portion was made non-heating, so that the wall surface of the reaction vessel was heated to locally heat only the vicinity of the wall surface of the reaction mixture by setting a temperature difference between the wall surface and the bottom portion of the reaction vessel. The mixture was stirred in this state for 3 hours to obtain a reaction solution. At the end of the reaction, the unheated bottom was 65 ℃ and the partially heated wall surface was 81 ℃.

The obtained reaction solution was cooled to room temperature, and 1.6 times by weight of methanol and 0.55 times by weight of water were charged into the reaction solution while stirring, and the precipitated precipitate was taken out and washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamide resin (4). The weight average molecular weight of the obtained polyamideimide resin (4) was 429,000.

The polyamideimide resin (4) was dissolved in DMAc to prepare a 10 mass% solution, the obtained polyamideimide varnish was filtered with a filter having a pore opening of 10 μm, and then coated on a smooth surface of a polyester substrate (manufactured by tokyo corporation, trade name "a 4100") using an applicator so that the thickness of the self-supporting film became 55 μm, dried at 50 ℃ for 30 minutes, and then dried at 140 ℃ for 15 minutes, and the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 40 minutes under the atmosphere, to obtain an optical film 4 having a thickness of 50 μm.

< example 3 >

Under nitrogen atmosphere, to 3m with stirring blades³In the reaction vessel (a) of (b),23.66kg of TFMB and DMAc having a water content of 300ppm were added so that the solid content concentration of TFMB in the reaction mixture became 5.54 mass%, and TFMB was dissolved in DMAc while stirring at room temperature. Then, 6FDA was added to the reaction vessel so that the concentration of TFMB was 30.21 mol%, and the mixture was stirred at 25 ℃ for 16 hours. Then, TPC and OBBC were added to the mixture in amounts of 60.42 mol% and 10.07 mol% based on TFMB, respectively, and the mixture was stirred for 60 minutes. Next, 4-picoline 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 portion and the bottom portion of the reaction mixture was increased from 25 ℃ to 50 ℃ over 30 minutes, from 50 ℃ to 60 ℃ over 10 minutes, from 60 ℃ to 65 ℃ over 10 minutes, and then, stepwise, from 65 ℃ to 70 ℃ over 10 minutes, respectively. At this time, the wall surface of the reaction vessel was provided with a heating portion so as to be heated from 7 degrees above the liquid level of the reaction mixture, and the remaining bottom portion was made non-heating, so that the wall surface of the reaction vessel was heated to locally heat only the vicinity of the wall surface of the reaction mixture by setting a temperature difference between the wall surface and the bottom portion of the reaction vessel. The mixture was stirred in this state for 3 hours to obtain a reaction solution. At the end of the reaction, the unheated bottom was 68 ℃ and the locally heated wall surface was 78 ℃.

The obtained reaction solution was cooled to room temperature, and 1.6 times by weight of methanol and 0.55 times by weight of water were charged into the reaction solution while stirring, and the precipitated precipitate was taken out and washed with methanol. Then, the precipitate was dried under reduced pressure at 60 ℃ to obtain a polyamide resin (5). The weight average molecular weight of the obtained polyamideimide resin (5) was 410,000.

The polyamideimide resin (5) was dissolved in DMAc to prepare a 10 mass% solution, the obtained polyamideimide varnish was filtered with a filter having a pore opening of 10 μm, and then coated on a smooth surface of a polyester substrate (manufactured by tokyo corporation, trade name "a 4100") using an applicator so that the thickness of the self-supporting film became 55 μm, dried at 50 ℃ for 30 minutes, and then dried at 140 ℃ for 15 minutes, and the obtained coating film was peeled off from the polyester substrate to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 200 ℃ for 40 minutes under the atmosphere, to obtain an optical film 5 having a thickness of 50 μm.

In the examples and comparative examples, the weight average molecular weight of the polyamideimide resin, the elastic modulus of the optical film, the total light transmittance (Tt), the haze, and the YI value were measured. The weight average molecular weight, YI value and the number of times of bending resistance were measured in the same manner using the optical film after being stored for 1 week in an environment at a temperature of 85 ℃ and a relative humidity of 85%, and the rate of change thereof was calculated according to the above formula. The obtained results are shown in table 1 below. In the optical film of comparative example 1, the change rate of YI value was very large, and the film could not be used as an optical film, and therefore, the number of times of bending resistance was not evaluated.

[ Table 1]

Claims

1. Polyamideimide resin obtained by using deuterated dimethyl sulfoxide solution of polyamideimide resin as measurement sample¹H-¹³An integral value (int) of a peak existing in a region (A) in which a chemical shift of a proton is 8.06 to 8.14ppm and a chemical shift of carbon is 129.6 to 130.3ppm in a C HSQC spectrum_A) And an integral value (int) of a peak present in a region (B) having a chemical shift from proton of 7.26 to 7.85ppm and a chemical shift from carbon of 132.4 to 134.0ppm_B) Ratio of (int)_A/int_B) Is 1.5% or less.

2. The polyamideimide resin according to claim 1, which has at least a structural unit represented by formula (1) and a structural unit represented by formula (2),

in the formula (1), Y represents a tetravalent organic group,

it represents a connecting bond,

in the formula (2), Z and X independently represent a divalent organic group,

it represents a connecting bond.

3. The polyamideimide 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.

4. The polyamideimide resin according to any one of claims 1 to 3, wherein X in the formula (1) or X in the formula (2) has at least a structure represented by the formula (4),

in the formula (4), H^4aAnd H^4bRepresents a hydrogen atom, and is represented by,

it represents a connecting bond.

5. The polyamideimide resin according to any one of claims 1 to 4, wherein Z in the formula (2) has at least a structure represented by the formula (3),

in the formula (3), R^3aAnd R^3bIndependently represents an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R^3aAnd R^3bThe hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

s is an integer of 0 to 4,

t is an integer of 0 to 4,

u is an integer of 0 to 4,

it represents a connecting bond.

6. An optical film comprising the polyamideimide resin according to any one of claims 1 to 5.

7. An optical film comprising a polyamideimide resin, wherein the rate of change in weight average molecular weight of the optical film before and after a storage test at a temperature of 85 ℃ and a humidity of 85% for 1 week is 26% or less.

8. The optical film according to claim 7, wherein a rate of change in weight average molecular weight before and after the storage test is 25% or less.

9. A front panel of a flexible display device having the optical film according to any one of claims 6 to 8.

10. A flexible display device provided with the front panel according to claim 9.

11. The flexible display device of claim 10, further provided with a touch sensor.

12. The flexible display device according to claim 10 or 11, further comprising a polarizing plate.

13. The method for producing a polyamideimide resin according to any one of claims 1 to 5, which is a method for producing a polyamideimide resin by reacting a diamine compound, a tetracarboxylic acid compound and a dicarboxylic acid compound, 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 more than 1.000.