CN113272361A

CN113272361A - Method for producing polyimide resin

Info

Publication number: CN113272361A
Application number: CN201980085770.1A
Authority: CN
Inventors: 大久保绘美; 西山奈津美; 宫本皓史
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-12-26
Filing date: 2019-12-20
Publication date: 2021-08-17
Also published as: JP2020105496A; TW202033616A; KR20210107761A; TWI834786B

Abstract

The invention provides a method for producing a polyimide resin capable of forming a film with excellent bending resistance. A method for producing a polyimide resin, comprising: a step (I) for obtaining an intermediate (K), said step (I) comprising a step (A) for reacting a diamine compound with a carboxylic acid compound having 3 or more carbonyl groups; and a step (II) for further reacting the intermediate (K) with a diamine compound.

Description

Method for producing polyimide resin

Technical Field

The present invention relates to a method for producing a polyimide resin which can be used as a material for a flexible display device or the like.

Background

Display devices such as liquid crystal display devices and organic EL display devices have been widely and flexibly used for various applications such as mobile phones and smartwatches. Glass has been conventionally used as a front panel of such a display device, but since glass is very rigid and easily broken, it is difficult to use the glass as a front panel material of a flexible display device. As one of materials replacing glass, there is a polyimide-based resin, and films using the polyimide-based resin are being studied (patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2017-203984

Disclosure of Invention

Problems to be solved by the invention

When such a film is applied to a flexible display device, the film is required to have a bending resistance capable of withstanding breakage and the like even when repeatedly bent. However, according to the study of the inventors of the present application, it was found that the film formed of the polyimide-based resin may have insufficient bending resistance.

Accordingly, an object of the present invention is to provide a method for producing a polyimide resin capable of forming a film having excellent bending resistance.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have found that the above problems can be solved by reacting a diamine compound 2 or more times in the production process of a polyimide resin, and have completed the present invention. That is, the present invention includes the following preferred embodiments.

[1] A method for producing a polyimide resin, comprising:

a step (I) for obtaining an intermediate (K), said step (I) comprising a step (A) for reacting a diamine compound with a carboxylic acid compound having 3 or more carbonyl groups; and

and (II) further reacting the intermediate (K) with a diamine compound.

[2] The production process according to [1], wherein the diamine compound to be reacted in the step (I) is used in an amount of 80 to 99.99 mol, based on 100 mol of the total amount of the diamine compounds to be reacted in the step (I) and the step (II).

[3] The production method according to [1] or [2], wherein the step (I) further comprises a step (B) of reacting a dicarboxylic acid compound after the step (A).

ADVANTAGEOUS EFFECTS OF INVENTION

According to the production method of the present invention, a polyimide resin capable of forming a film having excellent bending resistance can be obtained.

Detailed Description

[ method for producing polyimide resin ]

The manufacturing method of the present invention includes: a step (I) for obtaining an intermediate (K), said step (I) comprising a step (A) for reacting a diamine compound with a carboxylic acid compound having 3 or more carbonyl groups; and a step (II) for further reacting the intermediate (K) with a diamine compound. The polyimide resin obtained by the production method of the present invention is a polyimide resin, a polyamideimide resin, a polyimide resin precursor, or a polyamideimide resin precursor. The polyimide resin precursor and the polyamideimide resin precursor may be collectively referred to as a polyimide resin precursor. The polyimide resin is a polymer containing a repeating structural unit containing an imide group, and is, for example, a resin containing a repeating structural unit derived from a diamine compound and a repeating structural unit derived from a carboxylic acid compound having 3 or more carbonyl groups (for example, a repeating structural unit derived from a tetracarboxylic acid compound). The polyamideimide resin is a polymer containing both a repeating structural unit including an imide group and a repeating structural unit including an amide group, and is, for example: a resin containing a repeating structural unit derived from a diamine compound and a repeating structural unit derived from a carboxylic acid compound having 3 or more carbonyl groups (for example, a repeating structural unit derived from a tricarboxylic acid compound); a resin comprising a repeating structural unit derived from a diamine compound, a repeating structural unit derived from a carboxylic acid compound having 3 or more carbonyl groups (for example, a repeating structural unit derived from a tetracarboxylic acid compound), and a repeating structural unit derived from a dicarboxylic acid compound. The polyimide resin precursor means a precursor before the polyimide resin is produced by imidization, and the polyamideimide resin precursor means a precursor before the polyamideimide resin is produced by imidization. In the present specification, a "repeating structural unit" may be referred to as a "structural unit". A structural unit derived from a compound may be simply referred to as a "unit", and for example, a structural unit derived from a compound may be referred to as a compound unit.

< Process (I) >

The step (I) is a step of obtaining an intermediate (K), and includes a step (a) of reacting a diamine compound with a carboxylic acid compound having 3 or more carbonyl groups.

(step A)

Examples of the diamine compound used in step a include an aliphatic diamine such as an acyclic or cyclic aliphatic diamine, an aromatic diamine, and a mixture thereof. In this 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. 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. The diamine compound may be used alone or in combination of two or more.

In one embodiment of the present invention, the diamine compound preferably contains, for example, a compound represented by the formula (1) (sometimes referred to as a diamine compound (1)).

[ chemical formula 1]

H₂N-X-NH₂ (1)

When two or more kinds of diamine compounds are used, two or more kinds of diamine compounds different from each other in the kind of X in the diamine compound (1) may be used.

In the formula (1), X represents a 2-valent organic group, preferably a 2-valent organic group having 4 to 40 carbon atoms, and more preferably a 2-valent 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. The organic group may have hydrogen atoms substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. Examples of X may include groups represented by formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and formula (18); a group obtained by substituting a hydrogen atom in the groups represented by the formulae (10) to (18) 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 2]

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

V¹、V²and V³Independently of each other, 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 C1-12 hydrocarbon group which may be substituted with a halogen atom.

An 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, to each ring.

A film comprising a polyimide-based resin, wherein the group represented by the formula (10) to the formula (18) is easily improvedFrom the viewpoint of the elastic modulus, the bending resistance and the surface hardness of (a), the groups represented by formula (13), formula (14), formula (15), formula (16) and formula (17) are preferable, and the groups represented by formula (14), formula (15) and formula (16) are more preferable. In addition, from the viewpoint of easily improving the elastic modulus, flexibility, bending resistance and surface hardness of a film comprising a polyimide resin, 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, X in formula (1) is a group represented by formula (2).

[ chemical formula 3]

[ in the formula (2), R¹～R⁸Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R¹～R⁸Wherein the hydrogen atoms contained in (A) independently of one another may be replaced by halogen atoms, represent a chemical bond]

When the compound containing the group represented by the formula (2) as X in the formula (1) is used as the diamine compound, an optical film containing a polyimide-based resin tends to exhibit high elastic modulus, bending resistance and optical characteristics.

In the formula (2), R¹、R²、R³、R⁴、R⁵、R⁶、R⁷And R⁸Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms.

Examples of the alkyl group having 1 to 6 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, a 2-methyl-butyl group, a 3-methylbutyl group, a 2-ethyl-propyl 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 propyloxy group, an isopropyloxy group, a butoxy group, an isobutoxy group, a tert-butoxy group, a pentyloxy group, a hexyloxy group, a cyclohexyloxy group, and the like.

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. R¹～R⁸Independently 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 R¹～R⁸The 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 compounds capable of easily improving the surface hardness, optical properties, elastic modulus and bending resistance of a film comprising a polyimide resin¹～R⁸Independently of each other, further preferably represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and further more preferably R¹、R²、R³、R⁴、R⁵And R⁶Represents a hydrogen atom, R⁷And R⁸Represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and R is particularly preferred⁷And R⁸Represents a methyl group or a trifluoromethyl group.

In a preferred embodiment of the present invention, formula (2) is represented by formula (2').

[ chemical formula 4]

When a compound containing a group represented by the formula (2') as X in the formula (2) is used as the diamine compound, the film containing the polyimide-based resin tends to have reduced haze and yellowness (hereinafter, may be referred to as YI value), and the optical properties tend to be improved. Further, the fluorine-containing skeleton can improve the solubility of the polyimide resin in a solvent, and easily suppress the viscosity of the resin varnish to a low level.

Specific examples of the aliphatic diamine include acyclic aliphatic diamines such as 1, 6-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 ' -diaminodiphenyl methane, 4 ' -diaminodiphenyl propane, 4 ' -diaminodiphenyl ether, 3,4 ' -diaminodiphenyl ether, 4-diaminodiphenyl sulfone, 3 ' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-amino-phenoxy) benzene, bis (4-phenylene) sulfone, bis (4-phenylene) benzene, bis (4-phenylene) benzene, bis (bis) benzene) sulfone, bis (4-phenylene) benzene, bis (4-phenylene) benzene, bis (p) benzene, bis (4-phenylene) benzene, bis (p-phenylene) benzene, bis (2, bis (p-phenylene) benzene, 2, bis (p-phenylene) benzene, 2, bis (p-phenylene) benzene, bis (p-phenylene) benzene, 2, bis (bis) benzene, 2, bis (p) benzene, 2, bis (p-phenylene) benzene, 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 (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 2 or more.

The aromatic diamine is preferably 4,4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 3' -diaminodiphenylether, 4 '-diaminodiphenylsulfone, 3' -diaminodiphenylsulfone, 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, 2' -bis (trifluoromethyl) -4,4 '-diaminobiphenyl (TFMB), 4' -bis (4-aminophenoxy) biphenyl, more preferably 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, 2' -bis (trifluoromethyl) -4,4 '-diaminobiphenyl (TFMB), 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 surface hardness, high transparency, high elastic modulus, high flexibility, high bending resistance, and low coloring of a film comprising a polyimide-based resin, it is preferable to use 1 or more selected from the group consisting of aromatic diamines having a biphenyl structure. More preferably, 1 or more 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, 2 '-bis (trifluoromethyl) -4, 4' -diaminobiphenyl (TFMB) is used.

The proportion of the diamine compound in which X in formula (1) is a group represented by formula (2), for example, the proportion of the diamine compound in which X in formula (1) is a group represented by formula (2'), in the diamine compounds used in step a, is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, particularly preferably 80 mol% or more, and preferably 100 mol% or less, relative to the total molar amount of the diamine compounds used in step a. When the ratio of the diamine compound in which X in the formula (1) is a group represented by the formula (2) is within the above range, the solubility of the resin in a solvent can be improved by the skeleton containing a fluorine element in the film comprising the polyimide-based resin, the viscosity of the resin varnish can be suppressed to a low level, and the YI value, the haze, and the like of the film can be reduced, thereby easily improving the optical characteristics. The ratio of the diamine compound in which X in the formula (1) is a group represented by the formula (2) and the like can be calculated from the charge ratio of the raw materials.

The carboxylic acid compound having 3 or more carbonyl groups used in step a is preferably a tricarboxylic acid compound or a tetracarboxylic acid compound, and more preferably a tetracarboxylic acid compound.

The tetracarboxylic acid compound represents a tetracarboxylic acid or a tetracarboxylic acid derivative. Examples of the tetracarboxylic acid derivative include anhydrides and acid chlorides of tetracarboxylic acids, and preferable examples thereof include dianhydrides of tetracarboxylic acids.

Examples of the tetracarboxylic acid compound include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic acid and anhydride thereof, preferably dianhydride thereof; aliphatic tetracarboxylic acid and anhydride thereof, preferably aliphatic tetracarboxylic acid compounds such as dianhydride thereof. These tetracarboxylic acid compounds may be used alone or in combination of two or more.

In one embodiment of the present invention, the tetracarboxylic acid compound is preferably a tetracarboxylic dianhydride. The tetracarboxylic dianhydride is preferably a compound represented by the formula (3) (hereinafter, may be referred to as a tetracarboxylic acid compound (3)).

[ chemical formula 5]

The tetracarboxylic acid compound may be used alone or in combination of two or more, and when two or more tetracarboxylic acid compounds are used, two or more tetracarboxylic acid compounds different from each other in the kind of Y of the tetracarboxylic acid compound (3) may be used.

In the formula (3), Y independently represents a 4-valent organic group, preferably a 4-valent organic group having 4 to 40 carbon atoms, and more preferably a 4-valent 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. 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 in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. Examples of Y include groups represented by the following formulae (20), (21), (22), (23), (24), (25), (26), (27), (28) and (29); a group obtained by substituting a hydrogen atom in the group represented by the formulae (20) to (29) 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 6 or less carbon atoms.

[ chemical formula 6]

In the formulae (20) to (29),

it represents a chemical bond,

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-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 elastic modulus, bending resistance and surface hardness of the film. In addition, from the viewpoint of easily improving the elastic modulus, bending resistance and surface hardness of the film and easily improving the optical characteristics, W¹Preferably represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂A group represented by-more preferably a single bond, -O-, -CH₂-、-CH(CH₃)-、-C(CH₃)₂-or-C (CF)₃)₂A group represented by-further preferably a single bond, -C (CH)₃)₂-or-C (CF)₃)₂-a group represented by (a).

In a preferred embodiment of the present invention, Y in formula (3) is a group represented by formula (4).

[ chemical formula 7]

[ in the formula (4), R⁹～R¹⁶Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkyl group having 1 to 6 carbon atomsAlkoxy or aryl with 6-12 carbon atoms, R⁹～R¹⁶Wherein the hydrogen atoms contained in (A) independently of one another may be replaced by halogen atoms, represent a chemical bond]

When a compound containing a group represented by formula (4) as Y in formula (3) is used as a tetracarboxylic acid compound, the elastic modulus, optical characteristics, bending resistance and surface hardness of a film containing a polyimide-based resin can be easily improved. In addition, the solubility of the resin in the solvent can be improved, the viscosity of the resin varnish can be suppressed to a low level, and the film production becomes easy.

In the formula (4), R is preferred⁹、R¹⁰、R¹¹、R¹²、R¹³、R¹⁴、R¹⁵And R¹⁶Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms 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 (2). R⁹～R¹⁶Independently 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 R⁹～R¹⁶The 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 compounds capable of easily improving the elastic modulus, optical properties, bending resistance and surface hardness of a film comprising a polyimide resin⁹～R¹⁶Independently of each other, further preferably represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and further preferably R⁹、R¹⁰、R¹¹、R¹²、R¹³And R¹⁴Represents a hydrogen atom, R¹⁵And R¹⁶Represents a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and R is particularly preferred¹⁵And R¹⁶Represents a methyl group or a trifluoromethyl group.

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

[ chemical formula 8]

When a compound containing a group represented by formula (4') as Y in formula (4) is used as a tetracarboxylic acid compound, the elastic modulus, optical characteristics, bending resistance and surface hardness of a film containing a polyimide-based resin can be easily improved. Further, the fluorine-containing skeleton can improve the solubility of the resin in a solvent, and the viscosity of the resin varnish can be reduced to a low level, thereby facilitating the production of a film.

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 (4,4 ' -oxydiphthalic dianhydride), 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 (4,4 ' - (hexafluoroisopropylidene) dicarboxylic anhydride, which is sometimes referred to as 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 ' - (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.

Of 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, 4, 4' - (hexafluoroisopropylidene) diphthalic anhydride (6FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4,4 '- (terephthaloxy) bisphthalic anhydride and 4, 4' - (m-phenylenedioxy) bisphthalic anhydride, more preferably 4,4 '-oxydiphthalic anhydride, 3, 3', 4,4 '-biphenyltetracarboxylic dianhydride, 2', 3,3 '-biphenyltetracarboxylic dianhydride, 4, 4' - (hexafluoroisopropylidene) bisphthalic anhydride (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 2 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 2 or more. In addition, a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

Among the tetracarboxylic dianhydrides, from the viewpoint of high surface hardness, high transparency, high flexibility, high elastic modulus, high bending resistance and low coloring property of the film, preferred are 4,4 ' -oxydiphthalic dianhydride, 3,3 ', 4,4 ' -benzophenone tetracarboxylic dianhydride, 3,3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride, 2 ', 3,3 ' -biphenyl tetracarboxylic dianhydride, 3,3 ', 4,4 ' -diphenylsulfone tetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 4,4 ' - (hexafluoroisopropylidene) diphthalic anhydride and mixtures thereof, more preferred are 3,3 ', 4,4 ' -biphenyl tetracarboxylic dianhydride and 4,4 ' - (hexafluoroisopropylidene) diphthalic anhydride and mixtures thereof, further preferred is 4, 4' - (hexafluoroisopropylidene) diphthalic anhydride (6 FDA).

In the tetracarboxylic acid compound used in step a, the proportion of the tetracarboxylic acid compound in which Y in formula (3) is a group represented by formula (4), for example, the tetracarboxylic acid compound in which Y in formula (3) is a group represented by formula (4'), is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, particularly preferably 80 mol% or more, and preferably 100 mol% or less, relative to the total molar amount of the tetracarboxylic acid compound used in step a. When the ratio of the tetracarboxylic acid compound in which Y in formula (3) is a group represented by formula (4) is within the above range, the elastic modulus, optical characteristics, bending resistance, and surface hardness of a film comprising a polyimide-based resin can be easily improved. Further, the fluorine-containing skeleton can improve the solubility of the resin in a solvent, and the viscosity of the resin varnish can be reduced to a low level, thereby facilitating the production of a film. The ratio of the tetracarboxylic acid compound in which Y in formula (3) is a group represented by formula (4) and the like can be calculated from the charge ratio of the raw materials.

In addition, as the tetracarboxylic acid compound, tetracarboxylic dianhydride is preferable, but tetracarboxylic monoanhydride may also be used. Examples of the tetracarboxylic monoanhydride include a compound represented by formula (5) (hereinafter, may be referred to as a tetracarboxylic acid compound (5)).

[ chemical formula 9]

The tetracarboxylic acid compound (5) may be used alone or in combination of two or more, and when two or more tetracarboxylic acid compounds (5) are used, Y of the tetracarboxylic acid compound (5) may be used¹Two or more kinds of tetracarboxylic acid compounds (5) different from each other.

In the formula (5), Y¹Is a 4-valent 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 of the group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) include a group in which a hydrogen atom in the group represented by formula (20) to formula (29) is substituted with a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and a chain hydrocarbon group having a valence of 4 and a carbon number of 6 or less. In addition, R¹⁷And R¹⁸Independently of one another, -OH, -OMe, -OEt, -OPr, -OBu or-Cl, preferably-Cl.

The tricarboxylic acid compound represents a tricarboxylic acid or a tricarboxylic acid derivative, and examples of the tricarboxylic acid derivative include an acid chloride, an anhydride, and an ester of the tricarboxylic acid.

In one embodiment of the present invention, examples of the tricarboxylic acid compound include a compound represented by the formula (8) (hereinafter, may be referred to as a tricarboxylic acid compound (8)), and the like.

[ chemical formula 10]

The tricarboxylic acid compounds may be used alone or in combination of two or more, and in the case of using two or more, Y of the tricarboxylic acid compound (8) may be used²Two or more tricarboxylic acid compounds (8) different from each other in kind. In the formula (8), R³⁴is-OH, -OMe, -OEt, -OPr, -OBu or-Cl, preferably-Cl.

In the formula (8), Y²Is a 3-valent organic radical, preferably havingThe hydrogen atom in the organic group may be an organic group substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. As Y²Examples thereof include a group in which any one of the chemical bonds of the group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) is replaced with a hydrogen atom, and a chain hydrocarbon group having 3-valent carbon atoms of 6 or less.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and derivatives thereof (for example, acid chlorides, acid anhydrides, and the like), and specific examples thereof include 1,3, 5-benzenetricarboxylic acid and acid chlorides thereof, and anhydrides of 1,2, 4-benzenetricarboxylic acid; 2,3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; by single bonds, -O-, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂Or phenylene linking phthalic anhydride to benzoic acid. These tricarboxylic acid compounds may be used alone or in combination of two or more.

The amount of the carboxylic acid compound having 3 or more carbonyl groups to be reacted in the step (a) may be appropriately selected depending on the ratio of the structural units in the desired polyimide resin, and is preferably 1 mole or more, more preferably 5 moles or more, further preferably 10 moles or more, preferably 150 moles or less, more preferably 100 moles or less, further preferably 80 moles or less, and particularly preferably 50 moles or less, when the total amount of the diamine compounds to be reacted in the steps (I) and (II) is 100 moles. When the amount of the carboxylic acid compound having 3 or more carbonyl groups is within the above range, the imide skeleton is appropriately introduced, and the bending resistance of the film after film formation is easily improved.

When the total amount of the diamine compounds reacted in the step (I) and the step (II) is 100 moles, the amount of the diamine compound reacted in the step (I) is preferably 80 moles or more, more preferably 85 moles or more, further preferably 90 moles or more, further more preferably 95 moles or more, particularly preferably 98 moles or more, and preferably 99.99 moles or less. When the amount of the diamine compound to be reacted in the step (I) is within the above range, the bending resistance of the film comprising the polyimide-based resin can be more easily improved.

The reaction in step (I) is preferably carried out in a solvent which is inert 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, isopropyl alcohol, 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, 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; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as N, N-dimethylacetamide and N, N-dimethylformamide; 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 can be preferably used from the viewpoint of solubility of the diamine compound and the tetracarboxylic acid compound.

The amount of the solvent used is preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, and still more preferably 5 to 15 parts by mass, based on 1 part by mass of the total amount of the diamine compound and the carboxylic acid compound having 3 or more carbonyl groups. The content of the solvent is preferably not less than the lower limit described above from the viewpoint of suppressing an increase in viscosity of the reaction system, and preferably not more than the upper limit described above from the viewpoint of the polymerization reaction.

In the case of using a solvent, either one of the diamine compound and the carboxylic acid compound having 3 or more carbonyl groups may be dissolved in the solvent to obtain a solution, the other one may be added to the solution, and the solution may be reacted by stirring or the like, or the diamine compound and the carboxylic acid compound having 3 or more carbonyl groups may be dissolved in the solvent to obtain solutions, and then the solutions may be mixed and stirred to react, or both may be added to the solvent and stirred to react.

The reaction temperature in the step (A) is not particularly limited, and may be, for example, -5 to 100 ℃, preferably 0 to 50 ℃, and more preferably 5 to 30 ℃. The reaction time may be, for example, 1 minute to 72 hours, preferably 10 minutes to 24 hours, and more preferably 30 minutes to 10 hours. The reaction may be carried out in air or an inert gas atmosphere such as nitrogen or argon while stirring, or may be carried out under normal pressure, increased pressure or reduced pressure. In a preferred embodiment, the stirring is carried out under normal pressure and/or under the inert gas atmosphere.

When the step (I) is constituted by the step (a), the obtained intermediate (K) has a structural unit derived from a diamine compound and a structural unit derived from a carboxylic acid compound having 3 or more carbonyl groups. In a preferred embodiment of the present invention, the intermediate (K) contains a repeating structural unit represented by the formula (a) obtained by reacting the diamine compound (1) with the tetracarboxylic acid compound (3).

[ chemical formula 11]

[ in the formula (A), G¹Same as Y in the formula (3), X¹Same as X in the formula (1)]

When two or more kinds of the diamine compound (1) and/or the tetracarboxylic acid compound (3) are present, the intermediate (K) has two or more kinds of repeating structural units represented by the formula (a). The intermediate (K) having a structural unit derived from a diamine compound and a structural unit derived from a tetracarboxylic acid compound may be referred to as an intermediate (K-1).

In one embodiment of the present invention, the step (I) may further include a step (B) of reacting a dicarboxylic acid compound after the step (a).

(step B)

The dicarboxylic acid compound used in the step (B) represents a dicarboxylic acid or a dicarboxylic acid derivative, and examples of the dicarboxylic acid derivative include an acid chloride and an ester of the dicarboxylic acid. In one embodiment of the present invention, the dicarboxylic acid compound is preferably a compound represented by formula (6) (hereinafter, may be referred to as dicarboxylic acid compound (6)).

[ chemical formula 12]

The dicarboxylic acid compound may be used alone or in combination of two or more, and when two or more dicarboxylic acid compounds are used, two or more dicarboxylic acid compounds (6) having different W types from each other in the dicarboxylic acid compound (6) may be used. In the formula (6), R¹⁹And R²⁰Independently of one another, -OH, -OMe, -OEt, -OPr, -OBu or-Cl, preferably-Cl.

In the formula (6), W is a 2-valent organic group, preferably a 2-valent organic group having 4 to 40 carbon atoms which may be substituted by a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms substituted with fluorine, more preferably a 2-valent organic group having 4 to 40 carbon atoms which may be substituted by a hydrocarbon group having 1 to 8 carbon atoms or a hydrocarbon group having 1 to 8 carbon atoms substituted with fluorine and has a cyclic structure. Examples of the cyclic structure include alicyclic, aromatic ring, and heterocyclic structure. Examples of the organic group of W include a group in which non-adjacent 2 groups among the chemical 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 hydrogen atoms, and a 2-valent chain hydrocarbon group having 6 or less carbon atoms. From the viewpoint of easily reducing the YI value of a film comprising a polyimide-based resin, the groups represented by formulae (20) to (27) are preferred.

The organic group of W is more preferably a 2-valent 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 13]

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

The hydrogen atoms on the ring in the formulae (20) to (29) and (20 ') to (29') may be substituted with a hydrocarbon group having 1 to 8 carbon atoms, a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or a fluorine-substituted alkoxy group having 1 to 6 carbon atoms.

When the dicarboxylic acid compound contains a compound represented by any one of the above-described formulae (20 ') to (29') wherein W in formula (6) is contained, particularly when the compound represented by formula (6a) wherein W in formula (6) is contained, it is preferable that the dicarboxylic acid compound contains a compound represented by the following formula (d1) (hereinafter, sometimes referred to as compound (d1)) in addition to the compound represented by formula (6a) wherein W in formula (6) is contained, from the viewpoint of easily improving the film-forming property of the varnish and easily improving the uniformity of a film containing the polyimide-based resin.

[ chemical formula 14]

[ in the formula (d1), R^cIndependently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R^dRepresents R^cor-C (═ O) R^e，R^eIndependently of one another, -OH, -OMe, -OEt, -OPr, -OBu or-Cl]

R^cIn the formula (2), examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms and aryl groups having 6 to 12 carbon atoms. Specific examples of the compound (d1) include R^cAnd R^dCompounds all of which are hydrogen atoms,R^cAre all hydrogen atoms and R^dis-C (═ O) R^eAnd the like.

In the dicarboxylic acid compound of the present invention, W in the formula (6) may include a plurality of kinds of W, and the plurality of kinds of W may be the same or different. Among them, W in formula (6) is preferably represented by formula (6a), more preferably represented by formula (7a), from the viewpoint of easily improving the surface hardness, water resistance, optical characteristics, elastic modulus, yield strain and bending resistance of the optical film.

[ chemical formula 15]

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

a and b are the same as A and b in formula (7b),

m is an integer of 0 to 4,

t is an integer of 0 to 4,

u is an integer of 0 to 4]

[ chemical formula 16]

[ in the formula (7a), R²¹～R²⁴Independently 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,

R²¹～R²⁴the hydrogen atoms contained in (a) may be substituted independently of each other by halogen atoms,

m2 is an integer of 1 to 4,

denotes a chemical bond

When a compound containing a group represented by formula (7a) as W in formula (6) is used as the dicarboxylic acid compound, a film containing a polyimide-based resin tends to exhibit excellent elastic modulus, bending resistance, and optical characteristics. The compound of formula (6) in which W is a group represented by formula (7a) and the compound of formula (6) in which W is a group represented by formula (6a) may be referred to as a dicarboxylic acid compound (7a) and a dicarboxylic acid compound (6a), respectively.

In the formula (6a), the chemical bond of each benzene ring may be bonded to any of the ortho-position, meta-position or para-position based on-a-, and preferably may be bonded to the meta-position or para-position. R^aAnd R^bIndependently represents a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. T and u in the formula (6a) are preferably 0, but when t and/or u is 1 or more, R^aAnd R^bIndependently of each other, the alkyl group preferably has 1 to 6 carbon atoms, and more preferably has 1 to 3 carbon atoms. R in the formula (6a)^aAnd R^bIn the formula (2), examples of the halogen atom, the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms and the aryl group having 6 to 12 carbon atoms include a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms and an aryl group having 6 to 12 carbon atoms.

T and u in formula (6a) are independently an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1, and still more preferably 0.

In the formula (6a), when m is an integer in the range of 0 to 4, and m is within the range, the film comprising the polyimide resin has good bending resistance and elastic modulus. In the formula (6a), m 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. When m is within this range, the film comprising the polyimide-based resin is excellent in bending resistance and elastic modulus, and the availability of the raw material is relatively good. The compound represented by the formula (6a) wherein m is 0 is, for example, terephthalic acid or isophthalic acid or a derivative thereof, and the compound is preferably a compound in which m is 0 and u is 0 in the formula (6 a). The dicarboxylic acid compound may contain 1 or 2 or more compounds represented by the formula (6a) in which W in the formula (6) is represented by the formula (6a), and from the viewpoint of improving the elastic modulus and the bending resistance and reducing the YI value of a film containing a polyimide-based resin, 2 or more compounds having different m values, preferably 2 compounds having different m values, may be contained.

From the viewpoint of improving the elastic modulus and the bending resistance of a film comprising a polyimide-based resin and reducing the yellowness (YI value), it is preferable to include a compound represented by formula (6a) in which m is 0 in formula (6a), and it is more preferable to include a compound represented by formula (6a) in which m is 1 in addition to the compound.

In the formula (7a), R²¹、R²²、R²³And R²⁴Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms 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 (2). R is a group of compounds capable of easily improving the surface hardness, flexibility and bending resistance of a film comprising a polyimide resin²¹～R²⁴Independently of each other, the alkyl group preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a hydrogen atom. Here, R²¹～R²⁴The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other.

In the formula (7a), m2 is preferably an integer of 1 to 3, more preferably 1 or 2, and even more preferably 1, from the viewpoint of easily improving the bending resistance and the elastic modulus of a film comprising a polyimide-based resin. R²¹～R²⁴When all of the hydrogen atoms are present, the film containing the polyimide-based resin is advantageous in that the elastic modulus and the bending resistance of the film are improved.

In a preferred embodiment of the present invention, the dicarboxylic acid compound includes an aromatic dicarboxylic acid compound in which 2 or more aromatic hydrocarbon rings are connected by a single bond or a divalent group other than an aromatic group, from the viewpoint that a film including a polyimide resin easily exhibits good bending resistance. Examples of the aromatic hydrocarbon ring include monocyclic hydrocarbon rings such as benzene rings; polycyclic hydrocarbon rings such as fused bicyclic hydrocarbon rings such as naphthalene and ring-aggregated hydrocarbon rings such as biphenyl are preferably benzene rings.

Specifically, an aromatic dicarboxylic acid compound in which 2 or more aromatic hydrocarbon rings are connected by a single bond or a divalent group other than an aromatic group is a compound in which W in formula (6) is a group represented by formula (7 b).

[ chemical formula 17]

[ in the formula (7b), R²⁵～R³²Independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, R²⁵～R³²Wherein the hydrogen atoms contained in (A) may be substituted independently by halogen atoms, and A represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)³³)-，R³³Represents a hydrogen atom, a C1-12 valent hydrocarbon group which may be substituted with a halogen atom, and m¹Is an integer of 1 to 4, represents a chemical bond]

When the compound containing the group represented by the formula (7b) as W in the formula (6) is used as the dicarboxylic acid compound, a film containing a polyimide-based resin tends to exhibit excellent elastic modulus, bending resistance and optical characteristics. In the formula (6), a compound in which W is a group represented by the formula (7b) may be referred to as a dicarboxylic acid compound (7 b).

In the formulae (7b) and (6a), A represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-, -S-, -CO-or-N (R)³³) Easy to extractFrom the viewpoint of high elastic modulus and high bending resistance of a film comprising a polyimide resin, the film preferably represents-O-or-S-, and more preferably represents-O-. 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 (2). R is a group of compounds capable of easily improving the surface hardness, flexibility and bending resistance of a film comprising a polyimide resin²⁵～R³²Independently of each other, the alkyl group preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and still more preferably represents a hydrogen atom. Here, R²⁵～R³²The hydrogen atoms contained in (a) may be substituted by halogen atoms independently of each other. R³³Represents a hydrogen atom, a C1-valent hydrocarbon group which may be substituted with a halogen atom and has 1 to 12 carbon atoms. Examples of the 1-valent hydrocarbon group having 1 to 12 carbon atoms include methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-pentyl, 2-methyl-butyl, 3-methylbutyl, 2-ethyl-propyl, n-hexyl, n-heptyl, n-octyl, tert-octyl, n-nonyl, and n-decyl groups, 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. m is¹In the case of 2 to 4, A may be the same or different.

In the formula (7b), m¹Is an integer of 1 to 4, m¹When the amount is within this range, the film comprising the polyimide resin tends to have good bending resistance and good elastic modulus. In the formula (7b), m¹Preferably an integer of 1 to 3, more preferably 1 or 2, and still more preferably 1, m¹When the amount is within this range, the film tends to have good bending resistance and good elastic modulus.

From the viewpoint of improving the elastic modulus and the bending resistance of the film comprising the polyimide-based resin and lowering the YI value, the dicarboxylic acid compound (7a) or (7B) is preferably used as the dicarboxylic acid compound in the step (B), and the dicarboxylic acid compound (7a) and the dicarboxylic acid compound (7B) are more preferably used in combination.

In a more preferred embodiment of the present invention, formula (7a) is represented by formula (7 a'). The formula (7b) is represented by formula (7 b').

[ chemical formula 18]

[ chemical formula 19]

When the compound represented by the formula (6) wherein W is a group represented by the formula (7a '), the compound represented by the formula (7 b'), or both of them is used as the dicarboxylic acid compound, a film having further improved elastic modulus and bending resistance can be easily obtained.

Specific examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their analogous acid chloride compounds and acid anhydrides, and 2 or more kinds thereof can be used in combination. Specific examples thereof include terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4, 4' -biphenyldicarboxylic acid; 3, 3' -biphenyldicarboxylic acid; a dicarboxylic acid compound of chain hydrocarbon having 8 or less carbon atoms and 2 benzoic acids via a single bond, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene group, and acid chloride compounds thereof. Among these dicarboxylic acid compounds, from the viewpoint of easily improving the elastic modulus and bending resistance of a film comprising a polyimide-based resin, 4 ' -oxybis benzoic acid, terephthalic acid, or acid chlorides thereof are preferable, and as described above, 4 ' -oxybis (benzoyl chloride) and terephthalic acid chloride are more preferable, and 4,4 ' -oxybis (benzoyl chloride) and terephthalic acid chloride are further preferably used in combination.

When the step (I) includes the step (B), the intermediate (K-1) obtained in the step (a) may be isolated and then supplied to the step (B), but the step (B) is usually continuously carried out without isolation.

In a preferred embodiment of the present invention, the amount of the dicarboxylic acid compound to be reacted in the step (B) may be appropriately selected depending on the ratio of the structural units of the desired polyimide-based resin, and for example, when the total amount of the diamine compounds to be reacted in the steps (I) and (II) is 100 moles, the amount is preferably 5 moles or more, more preferably 20 moles or more, further preferably 30 moles or more, further more preferably 40 moles or more, particularly preferably 50 moles or more, particularly preferably 60 moles or more, preferably 95 moles or less, more preferably 90 moles or less, further preferably 85 moles or less, and particularly preferably 80 moles or less. When the amount of the dicarboxylic acid compound used is within the above range, the elastic modulus and the bending resistance of the film comprising the polyimide-based resin are easily improved.

In a preferred embodiment of the present invention, the proportion of the dicarboxylic acid compound (6a) in the dicarboxylic acid compound used in the step (I) (step (B)) is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, particularly preferably 80 mol% or more, and preferably 100 mol% or less, based on the total molar amount of the dicarboxylic acid compound used in the step (B). When the proportion of the dicarboxylic acid compound (6a) is within the above range, the elastic modulus, optical characteristics, bending resistance and surface hardness of the film comprising the polyimide-based resin are easily improved. Further, the fluorine-containing skeleton can improve the solubility of the resin in a solvent, and the viscosity of the resin varnish can be reduced to a low level, thereby facilitating the production of a film. The ratio of the dicarboxylic acid compound (6a) can be calculated from the charge ratio of the raw materials.

In a preferred embodiment of the present invention, the total proportion of the dicarboxylic acid compounds (7a) and (7B) in the dicarboxylic acid compound used in step (B) is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, particularly preferably 80 mol% or more, and preferably 100 mol% or less, based on the total molar amount of the dicarboxylic acid compounds used in step (B). When the total ratio of the dicarboxylic acid compounds (7a) and (7b) is within the above range, the elastic modulus, optical characteristics, bending resistance, and surface hardness of the film comprising the polyimide-based resin are easily improved. Further, the fluorine-containing skeleton can improve the solubility of the resin in a solvent, and the viscosity of the resin varnish can be reduced to a low level, thereby facilitating the production of a film. The total ratio of the dicarboxylic acid compounds (7a) and (7b) can be calculated from the charge ratio of the raw materials.

In a preferred embodiment of the present invention, the dicarboxylic acid compounds (7a) and (7b) are preferably used in combination. The amount of the dicarboxylic acid compound (7b) used is preferably 0.01 mol or more, more preferably 0.05 mol or more, further preferably 0.1 mol or more, preferably 20 mol or less, more preferably 15 mol or less, further preferably 10 mol or less, further more preferably 1 mol or less, particularly preferably 0.5 mol or less, and particularly preferably 0.3 mol or less based on 1 mol of the dicarboxylic acid compound (7 a). When the amount of the dicarboxylic acid compound (7b) is within the above range, the film after film formation can easily achieve both the bending resistance and the elastic modulus.

In one embodiment of the present invention, a solvent may be further added in step (B). By adding the solvent in the step (B), a rapid increase in the viscosity of the reaction system can be suppressed, and a state in which uniform stirring is possible can be maintained for a long time. Therefore, the polymerization reaction can be sufficiently performed, and the molecular weight of the polyimide resin and the bending resistance of the obtained film can be easily improved. Examples of the solvent to be added include the solvents exemplified in (step (a)), and these solvents may be used alone or in combination of two or more. An amide solvent is preferably used from the viewpoint of good solubility, easy improvement of the molecular weight of the polyimide resin, and easy improvement of the bending resistance of the resulting film. The solvent to be added in step (B) may be the same as or different from the solvent used in step (a), but is preferably the same from the viewpoint of improving the molecular weight and bending resistance of the resin. The solvent may be added at once or in portions.

The amount of the solvent added in step (B) is preferably 1 part by mass or more, more preferably 5 parts by mass or more, further preferably 10 parts by mass or more, particularly preferably 20 parts by mass or more, preferably 300 parts by mass or less, more preferably 200 parts by mass or less, further preferably 100 parts by mass or less, and particularly preferably 50 parts by mass or less, relative to 1 part by mass of the dicarboxylic acid compound used in step (B). When the amount of the solvent to be added in the step (B) is within the above range, the molecular weight of the polyimide resin and the bending resistance of the film obtained are easily improved.

In the step (B), the dicarboxylic acid compound may be added together or may be added in portions. When the reaction mixture is added in portions, the rapid increase in the viscosity of the reaction system is easily suppressed, and a uniformly stirrable state is easily maintained for a long period of time. Therefore, the polymerization reaction is easily carried out, and the molecular weight of the resulting polyimide resin and the bending resistance of the resulting film are easily improved.

In the step (B), the number of times of addition of the dicarboxylic acid compound in portions may be appropriately selected depending on the scale of the reaction, the kind of the raw material, and the like, and is preferably 2 to 20 times, more preferably 2 to 10 times, and still more preferably 2 to 6 times. When the number of times of the batch is within the above range, the molecular weight of the polyimide resin and the bending resistance of the film obtained are easily improved.

The dicarboxylic acid compound may be added in an equal amount or in an unequal amount. The time between each addition (hereinafter, sometimes referred to as an addition interval) may be the same or different. In addition, in the case of adding two or more dicarboxylic acid compounds, the term "adding in portions" means adding all the dicarboxylic acid compounds in portions, and the method of adding the dicarboxylic acid compounds in portions is not particularly limited, and for example, the dicarboxylic acid compounds may be added together or in portions, or the dicarboxylic acid compounds may be added in portions, or a combination thereof.

In one embodiment of the present invention, when the dicarboxylic acid compound is two (hereinafter, referred to as the 1 st dicarboxylic acid compound and the 2 nd dicarboxylic acid compound, respectively), for example, the 1 st dicarboxylic acid compound may be added together and the 2 nd dicarboxylic acid compound may be added together, the 1 st dicarboxylic acid compound and the 2 nd dicarboxylic acid compound may be added separately in portions, the 1 st dicarboxylic acid compound and the 2 nd dicarboxylic acid compound may be added together in portions, the remaining portions may be added separately or one of the remaining portions may be added after the simultaneous addition in portions, or the remaining portions may be added together or one of the remaining portions may be added after the separate addition in portions. From the viewpoint of increasing the molecular weight of the polyimide resin and improving the bending resistance of the film obtained, it is preferable to add the 1 st dicarboxylic acid compound and the 2 nd dicarboxylic acid compound in portions together, or to add the remaining portion after adding them in portions together.

In the case where the solvent is further added in step (B), the solvent may be added together with the dicarboxylic acid compound, may be added separately from the dicarboxylic acid, or may be a combination thereof in the case where the dicarboxylic acid is added in portions.

The reaction temperature in the step (B) is not particularly limited, and may be, for example, -5 to 100 ℃, preferably 0 to 50 ℃, and more preferably 5 to 30 ℃. The reaction time may be, for example, 1 minute to 72 hours, preferably 10 minutes to 24 hours, and more preferably 30 minutes to 10 hours. The reaction may be carried out in air or in an inert gas atmosphere (e.g., nitrogen, argon, etc.) with stirring, or may be carried out under normal pressure, under increased pressure, 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.

In the step (B), the intermediate (K) can be obtained by adding the dicarboxylic acid compound and then reacting the mixture with stirring for a predetermined time.

When the step (I) is composed of the steps (a) and (B), the intermediate (K) has a structural unit derived from a diamine compound, a structural unit derived from a carboxylic acid compound having 3 or more carbonyl groups, and a structural unit derived from a dicarboxylic acid compound. In a preferred embodiment of the present invention, the intermediate (K) comprises a repeating structural unit represented by the formula (a) obtained by reacting the diamine compound (1) with the tetracarboxylic acid compound (3), and a repeating structural unit represented by the formula (B) obtained by reacting the diamine compound (a) with the dicarboxylic acid compound (6).

[ chemical formula 20]

[ formula (A) and formula (B) wherein G²In the same manner as W in the formula (6),

G¹in the same manner as Y in the formula (3),

X¹and X²Each is the same as X in the formula (1), X¹And X²May be the same or different]

When at least one selected from the diamine compound (1), the tetracarboxylic acid compound (3) and the dicarboxylic acid compound (5) is two or more, the intermediate (K) has two or more kinds of repeating structural units represented by the formula (a) and/or two or more kinds of repeating structural units represented by the formula (B). The intermediate (K) having a structural unit derived from a diamine compound, a structural unit derived from a tetracarboxylic acid compound, and a dicarboxylic acid compound may be referred to as an intermediate (K-2).

In the case of producing a polyimide resin, the intermediate (K) may be separated and then supplied to the step (II) described later, but from the viewpoint of the bending resistance of a film containing a polyimide resin and the viewpoint of production efficiency, the intermediate (K) is directly supplied to the step (II) without separation.

< Process (II) >

The step (II) is a step of further reacting the intermediate (K) with a diamine compound. The present invention is characterized by comprising the step (II) of reacting a diamine compound at 2 or more times (batch reaction). The inventors of the present application have surprisingly found that when the step (II) is included in the production process of a polyimide-based resin, the bending resistance of the resulting film can be improved, and a polyimide-based resin having excellent bending resistance can be obtained. In the present specification, the bending resistance means a characteristic that can suppress or prevent occurrence of a crack or the like even when bending is repeated. In a preferred embodiment of the present invention, the film made of the polyimide resin of the present invention does not break even when repeatedly bent, for example, 15 ten thousand or more, preferably 20 ten thousand or more.

The diamine compound reacted in the step (II) includes the diamine compounds exemplified above as the diamine compound reacted in the step (a). The diamine compound may be used alone or in combination of two or more.

In the diamine compound reacted in the step (II), the proportion of the diamine compound in which X in the formula (1) is a group represented by the formula (2), for example, the diamine compound in which X in the formula (1) is a group represented by the formula (2'), is preferably 30 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, particularly preferably 80 mol% or more, and preferably 100 mol% or less, relative to the total molar amount of the diamine compound used in the step (II). When the ratio of the diamine compound in which X in the formula (1) is a group represented by the formula (2) is within the above range, the solubility of the resin in a solvent can be improved by the skeleton containing a fluorine element in the film comprising the polyimide-based resin, the viscosity of the resin varnish can be suppressed to a low level, and the YI value, the haze, and the like of the film can be reduced, thereby easily improving the optical characteristics. The ratio of the diamine compound in which X in the formula (1) is a group represented by the formula (2) and the like can be calculated from the charge ratio of the raw materials.

In one embodiment of the present invention, at least 1 of the diamine compound reacted in the step (I) and the diamine compound reacted in the step (II) is preferably the same compound, from the viewpoint of more easily improving the bending resistance of the film comprising the polyimide-based resin. When the diamine compound reacted in the step (I) is the diamine compound (I) and the diamine compound reacted in the step (II) is the diamine compound (II), "at least 1 species is the same compound", when the diamine compound (I) is 1 species and the diamine compound (II) is 1 species, it means that the diamine compounds (I) and (II) are the same, and when the diamine compound (I) is 1 species and the diamine compound (II) is 2 or more species, it means that 1 or more species of the diamine compound (II) is the same as the diamine compound (I). In addition, when the diamine compound (I) is 2 or more and the diamine compound (II) is 1, it means that 1 or more of the diamine compound (I) is the same as the diamine compound (II), and when the diamine compound (I) is 2 or more and the diamine compound (II) is 2 or more, it means that 1 or more are the same as each other. In a more preferred embodiment, the diamine compound reacted in the step (I) and the diamine compound reacted in the step (II) are preferably all the same, from the viewpoint of more easily improving the bending resistance of the film comprising the polyimide-based resin.

In the step (II), the diamine compound may be added together or may be added in portions. In the present specification, the batch addition means: the compound to be added is added in several portions, and more specifically, the compound to be added is divided into specific amounts and added separately at predetermined intervals or for predetermined times. The prescribed interval or prescribed time also includes a very short interval or time, and therefore, the batch addition also includes continuous addition or continuous feeding.

In the case where the diamine compound is added in portions in the step (II), examples of the number of times of dividing, the amount of dividing, and the method of adding in portions include the number of times of dividing, the amount of dividing, and the method of adding in portions of the dicarboxylic acid compound in the step (B).

In the step (II), a solvent may be further added. When the solvent is further added, the diamine compound may be added together with the diamine compound, or may be added separately from the diamine compound, or when the diamine compound is added in portions, a combination thereof may be used.

Examples of the solvent to be added include the solvents exemplified in (step (a)), and these solvents may be used alone or in combination of two or more. The solvent to be added may be the same as or different from the solvent used in the step (a), but is preferably the same as the solvent used in the step (a) from the viewpoint of improving the molecular weight of the polyimide resin and the bending resistance of the film. The solvent may be added at once or in portions.

When the total amount of the diamine compounds reacted in the step (I) and the step (II) is 100 moles, the amount of the diamine compound reacted in the step (II) is preferably 0.01 or more, preferably 20 moles or less, more preferably 15 moles or less, further preferably 10 moles or less, further more preferably 5 moles or less, and particularly preferably 2 moles or less. When the amount of the diamine compound to be reacted in the step (II) is within the above range, the bending resistance of the film comprising the polyimide-based resin can be more easily improved.

When the amount of the carboxylic acid compound reacted in the step (I) is 100 moles, the total amount of the diamine compound reacted in the steps (I) and (II) is preferably 10.0 to 1,000 moles, more preferably 50.0 to 150 moles, still more preferably 80.0 to 120 moles, still more preferably 90.0 to 110 moles, particularly preferably 95.0 to 100 moles, particularly preferably 97.0 to 99.9 moles, and particularly preferably 98.0 to 99.9 moles. When the total amount of the diamine compounds reacted in the steps (I) and (II) is within the above range, the bending resistance of the film comprising the polyimide-based resin is more easily improved. The carboxylic acid compound is a carboxylic acid compound including a dicarboxylic acid compound, a tetracarboxylic acid compound, and a tricarboxylic acid compound used in the steps (I) and (II).

The reaction temperature in the step (II) is not particularly limited, and may be, for example, -5 to 100 ℃, preferably 0 to 50 ℃, and more preferably 5 to 30 ℃. The reaction time may be, for example, 1 minute to 72 hours, preferably 10 minutes to 24 hours, and more preferably 30 minutes to 10 hours. The reaction may be carried out in air or an inert gas atmosphere such as nitrogen or argon while stirring, or may be carried out under normal pressure, increased pressure or reduced pressure. In a preferred embodiment, the stirring is carried out under normal pressure and/or under the inert gas atmosphere.

In the step (II), a polyimide resin precursor or a polyamideimide resin precursor can be obtained. More specifically, the polyimide resin precursor is obtained by further reacting the intermediate (K-1) obtained in the step (a) in the step (I) with a diamine compound in the step (II). Therefore, the polyimide resin precursor contains a structural unit derived from a diamine compound and a structural unit derived from a tetracarboxylic acid compound, and in a preferred embodiment, contains a repeating structural unit represented by formula (a). The polyamideimide precursor is obtained by further reacting the intermediate (K-2) obtained in the step (B) in the step (I) with a diamine compound in the step (II). Therefore, the polyamideimide resin preferably contains a structural unit derived from a diamine compound, a structural unit derived from a tetracarboxylic acid compound and a structural unit derived from a dicarboxylic acid compound, and preferably contains a repeating structural unit represented by the formula (a) and a repeating structural unit represented by the formula (B). The polyimide resin precursor or the polyamideimide precursor can be separated by adding a large amount of water, methanol, or the like to a reaction solution containing the resin precursor, precipitating the resin precursor, and then filtering, concentrating, drying, or the like.

In the case of producing a polyimide resin or a polyamideimide resin, the polyimide resin precursor or the polyamideimide resin precursor may be separated and then supplied to the step (III) described later, but from the viewpoint of production efficiency, it is preferable to supply the polyimide resin precursor or the polyamideimide resin precursor directly to the step (III) without separation.

< Process (III) >

The step (III) is a step of imidizing the polyimide-based resin precursor in the presence of an imidization catalyst. For example, a polyimide resin precursor containing a repeating structural unit represented by formula (a) is subjected to step (III), whereby the repeating structural unit represented by formula (a) is partially imidized (ring-closed), and a polyimide resin containing a repeating structural unit represented by formula (C) can be obtained. Further, for example, by subjecting a polyamideimide precursor comprising the repeating structural unit represented by the formula (a) and the repeating structural unit represented by the formula (B) to the step (III), the repeating structural unit represented by the formula (a) in the structural unit of the polyamideimide precursor is partially imidized (ring-closed), and a polyamideimide resin comprising the repeating structural unit represented by the formula (C) and the repeating structural unit represented by the formula (B) can be obtained.

[ chemical formula 21]

[ formula (B) and formula (C) wherein G¹Same as Y in the formula (3)，

G²In the same manner as W in the formula (6),

Examples of the imidization catalyst include aliphatic amines such as tripropylamine, diisopropylethylamine, 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. These imidization catalysts may be used alone or in combination of two or more.

The amount of the imidization catalyst used is preferably 0.1 to 10 moles, and more preferably 1 to 5 moles, based on 1 mole of the carboxylic acid compound having 3 or more carbonyl groups used in the step (a).

In the step (III), it is preferable to use an acid anhydride together with an imidization catalyst, from the viewpoint of facilitating the imidization reaction. Examples of the acid anhydride include conventional acid anhydrides usable 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 acid.

When an acid anhydride is used, the amount of the acid anhydride to be used is preferably 0.5 to 25 mol, more preferably 1 to 20 mol, and still more preferably 1 to 15 mol, based on 1 mol of the carboxylic acid compound having 3 or more carbonyl groups.

The reaction temperature in the step (III) is not particularly limited, and may be, for example, -5 to 100 ℃, preferably 0 to 90 ℃, and more preferably 5 to 80 ℃. The reaction time may be, for example, 1 minute to 72 hours, preferably 10 minutes to 24 hours, and more preferably 30 minutes to 10 hours. The reaction may be carried out in air or an inert gas atmosphere such as nitrogen or argon while stirring, or may be carried out under normal pressure, increased pressure or reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and/or under the inert gas atmosphere while stirring.

The polyimide-based resin obtained in step (III) can be isolated by a conventional method, for example, separation means such as filtration, concentration, extraction, crystallization, recrystallization, and column chromatography, or separation and purification by a separation means combining these, and in a preferred embodiment, the polyimide-based resin can be isolated by adding a large amount of water, methanol, or the like to the reaction solution containing the polyimide-based resin to precipitate the polyimide-based resin, and then concentrating, filtering, drying, or the like.

[ polyimide resin ]

The method of the present invention can provide a polyimide resin capable of forming a film having excellent bending resistance. Therefore, a film including the polyimide resin of the present invention can be preferably used as a front panel material of a display device such as a liquid crystal display device or an organic EL display device, particularly a flexible display device.

The weight average molecular weight (Mw) of the polyimide resin is preferably 150,000 or more, more preferably 200,000 or more, further preferably 250,000 or more, particularly preferably 300,000 or more, preferably 1,000,000 or less, more preferably 800,000 or less, further preferably 700,000 or less, and particularly preferably 500,000 or less in terms of standard polystyrene. When the weight average molecular weight is not less than the lower limit, the elastic modulus, the bending resistance and the surface hardness of the film comprising the polyimide-based resin are easily improved, and when the weight average molecular weight is not more than the upper limit, the gelation of the resin varnish is easily suppressed, and the optical properties of the film are easily improved. The weight average molecular weight can be determined by Gel Permeation Chromatography (GPC) measurement and conversion to standard polystyrene, for example, and can be determined by the method described in examples.

The viscosity at 25 ℃ when the polyimide resin is dissolved in N, N-dimethylacetamide at a concentration of 10 mass% is preferably 1,000mPa · s or more, more preferably 5,000mPa · s or more, further preferably 10,000mPa · s or more, particularly preferably 20,000mPa · s or more, preferably 70,000mPa · s or less, more preferably 60,000mPa · s or less, further preferably 50,000mPa · s or less, and particularly preferably 40,000mPa · s or less. When the viscosity of the polyimide resin is not lower than the lower limit, the intermolecular interaction becomes large, and the bending resistance and the mechanical strength are easily improved, and when the viscosity is not higher than the upper limit, the film forming property becomes good, and a uniform film is easily formed. The viscosity can be measured with a brookfield viscometer, for example, by the method described in examples.

In the polyimide-based resin obtained by the production method of the present invention, the polyimide resin preferably has at least a structural unit derived from a diamine compound and a structural unit derived from a tetracarboxylic acid compound, and in a preferred embodiment, contains a repeating structural unit represented by formula (C). The polyamideimide resin preferably has at least a structural unit derived from a diamine compound, a structural unit derived from a tetracarboxylic acid compound, and a structural unit derived from a dicarboxylic acid compound, and in a preferred embodiment, includes a repeating structural unit represented by formula (C) and a repeating structural unit represented by formula (B). The polyimide-based resin may be formed from a structural unit derived from a diamine compound and a structural unit derived from a tricarboxylic acid compound, and in the above preferred embodiment, the polyimide-based resin may further include a structural unit derived from a tricarboxylic acid compound. The polyimide-based resin containing a structural unit derived from a tetracarboxylic acid compound and a structural unit derived from a tricarboxylic acid compound can be produced, for example, by adding a tricarboxylic acid compound together with or separately from a tetracarboxylic acid compound in the step (a) or by adding a tricarboxylic acid compound together with or separately from a dicarboxylic acid compound in the step (B).

In one embodiment of the present invention, the polyimide resin having at least a structural unit derived from the diamine compound (1) and a structural unit derived from the tetracarboxylic acid compound (3) contains a repeating structural unit represented by formula (C). The polyamide-imide resin having at least a structural unit derived from the diamine compound (1), at least 1 structural unit selected from the group consisting of a structural unit derived from the tetracarboxylic acid compound (3) and a structural unit derived from the tricarboxylic acid compound (8), and a structural unit derived from the dicarboxylic acid compound (6) contains: a repeating structural unit represented by the formula (B), and at least 1 structural unit selected from the group consisting of a repeating structural unit represented by the formula (C) and a repeating structural unit represented by the formula (D).

[ chemical formula 22]

[ in the formula (D), G³And Y in the formula (8)²Same as X³Same as X in the formula (1)]

In one embodiment of the present invention, a polyamideimide resin having at least a structural unit derived from a diamine compound (1), at least 1 structural unit selected from the group consisting of a structural unit derived from a tetracarboxylic acid compound (3) and a structural unit derived from a tetracarboxylic acid compound (5), and a structural unit derived from a dicarboxylic acid compound (6) comprises: a repeating structural unit represented by the formula (B), and at least 1 structural unit selected from the group consisting of a repeating structural unit represented by the formula (C) and a repeating structural unit represented by the formula (E).

[ chemical formula 23]

[ in the formula (E), G⁴And Y in formula (5)¹Same as X⁴Same as X in the formula (1), R¹⁸And R in the formula (5)¹⁸Are identical to each other]

[ film ]

The polyimide resin in the present invention can be molded into a film, preferably an optical film. In the present invention, since the film particularly includes the step (II), a film having excellent bending resistance can be obtained. The film is not particularly limited, and can be produced, for example, by a method including the following steps.

(a) A step (varnish preparation step) of preparing a liquid (sometimes referred to as a resin varnish) containing the polyimide resin;

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

(c) a step of drying the applied liquid (coating film) to form a film (film-forming step)

In the varnish preparation step, the polyimide resin is dissolved in a solvent, and if necessary, an additive is added thereto, followed by stirring and mixing. Examples of the additives include fillers, ultraviolet absorbers, bluing agents, antioxidants, mold release agents, stabilizers, flame retardants, pH adjusters, dispersants, lubricants, thickeners, and leveling agents. The solvent that can be used for preparing the resin varnish is not particularly limited as long as it can dissolve the polyimide-based resin. Examples of the solvent include the solvents listed in (step (a)). Among these solvents, an amide solvent or a lactone solvent can be preferably used. These solvents may be used alone or in combination of two or more.

The solid content concentration of the resin varnish is preferably 1 to 25 mass%, more preferably 5 to 20 mass%. The solid content means a component obtained by removing the solvent from the resin varnish, and the solid content concentration means the mass of the solid content relative to the mass of the resin varnish.

In the coating step, a resin varnish is applied to the support material to form a coating film. Examples of the coating method 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 a film can be formed. After the peeling, a drying step of drying the film may be further performed. 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 tape such as SUS, and resin films such as a PET film, a PEN film, another polyimide film, a polyamide film, and a polyamideimide film. Among them, a PET film, a PEN film, and the like are preferable from the viewpoint of excellent heat resistance, and a PET film is more preferable from the viewpoint of adhesion to a film at the time of film formation, easy releasability, and cost.

The thickness of the film may be appropriately selected depending on the application, and is preferably 25 μm or more, more preferably 30 μm or more, preferably 100 μm or less, more preferably 80 μm or less, and further preferably 60 μm or less. The thickness of the film can be determined, for example, using a micrometer.

In a preferred embodiment of the present invention, the film containing the polyimide-based resin of the present invention is an optical film. The optical film has excellent optical characteristics in addition to the bending resistance. In the present specification, the optical properties include optically evaluated properties including, for example, total light transmittance, YI and haze.

The optical film preferably has a total light transmittance of 80% or more, more preferably 85% or more, further preferably 88% or more, and particularly preferably 90% or more at a thickness of 50 μm. When the total light transmittance is not less than the above-described lower limit, the transparency becomes good, and for example, when the transparent member is used for a front panel of a display device, the transparent member can contribute to high visibility. The upper limit of the total light transmittance is usually 100% or less. The total light transmittance may be measured, for example, according to JIS K7361-1: 1997, haze computer determination was used.

The haze of the optical film is preferably 3.0% or less, more preferably 2.0% or less, further preferably 1.0% 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 transparency becomes good, and for example, when the optical film is used for a front panel of a display device, the optical film can contribute to high visibility. The haze can be measured according to JIS K7136: 2000, measured using a haze computer.

The YI value of the optical film is preferably 8 or less, more preferably 5 or less, further preferably 3 or less, particularly preferably 2 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 for example, when the optical film is used for a front panel of a display device, high visibility can be contributed. The YI value may be measured in accordance with JIS K7373: 2006, the tristimulus value (X, Y, Z) was obtained by measuring the transmittance for light of 300 to 800nm using an ultraviolet-visible near-infrared spectrophotometer, and calculated based on the formula YI of 100 × (1.2769X-1.0592Z)/Y.

The use of the film is not particularly limited, and the film can be used for various purposes. As described above, the film may be a single layer or a laminate, and the film may be used as it is, or may be used as a laminate with another film. When the film is a laminate, all layers including the film laminated on one surface or both surfaces of the film are referred to as a film.

When the film is a laminate, it is preferable that at least one surface of the film has 1 or more functional layers. Examples of the functional layer include an ultraviolet absorbing layer, a hard coat layer, a primer layer, a gas barrier layer, an adhesive layer, a hue adjusting layer, and a refractive index adjusting layer. The functional layers may be used alone or in combination of two or more.

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

The adhesive layer is a layer having an adhesive function, and has a function of bonding the 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 can be used. In this case, the thermosetting resin composition or the photocurable resin composition can be polymerized and cured by supplying energy after the polymerization.

The Pressure-Sensitive Adhesive layer may be a layer called a Pressure-Sensitive Adhesive (PSA) that is pressed and attached to an object. The pressure-sensitive adhesive may be a capsule adhesive as "a substance having adhesiveness at normal temperature and adhering to an adherend under light pressure" (JIS K6800) or as "an adhesive which contains a specific component in a protective film (microcapsule) and can maintain stability until the film is broken by an appropriate means (pressure, heat, or the like)".

The hue adjustment layer is a layer having a hue adjustment function and is a layer capable of adjusting the 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 adjusting 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 a single-layer film and capable of providing a film with a predetermined refractive index. The refractive index adjusting layer may be, for example, a resin layer containing an appropriately selected resin and, in some cases, a pigment, or may be a thin film of a metal. Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle 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 deterioration in transparency can be prevented. Examples of the metal usable 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 film may further comprise a protective layer (also referred to as a protective film). The protective layer may be laminated on one or both sides of the film. When a functional layer is provided on one surface of the film, the protective layer may be laminated on the surface on the film side or the surface on the functional layer side, or may be laminated on both the film side and the functional layer side. When the film has functional layers on both surfaces, the protective layer may be laminated on the surface on one functional layer side, or may be laminated on the surfaces on both functional layers. The protective layer is not particularly limited as long as it is a layer capable of temporarily protecting the surface of the film or the functional layer and being peelable to protect the surface of the film or the functional layer. Examples of the protective layer include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; the resin film is preferably selected from the group consisting of polyolefin resin films, polyethylene, polypropylene films and the like, acrylic resin films and the like. When the film has 2 protective layers, the protective layers may be the same or different.

The thickness of the protective layer is not particularly limited, but is usually 10 to 100. mu.m, preferably 10 to 80 μm, and more preferably 10 to 50 μm. When the optical film has 2 protective layers, the thicknesses of the respective protective layers may be the same or different.

The film comprising a polyimide-based resin obtained by the present invention has excellent bending resistance and optical properties, and therefore can be preferably used as a front plate (hereinafter, may be referred to as a window film) of a display device, particularly a flexible display device. The front panel has a function of protecting a display element of the flexible display device. Examples of the display device include wearable devices such as televisions, smartphones, mobile phones, car navigation systems, tablet PCs, portable game machines, electronic paper, indicators, bulletin boards, clocks, and smartwatches. Examples of the flexible display include display devices having flexible characteristics, such as televisions, smartphones, mobile phones, and smartwatches.

[ Flexible display device ]

The flexible 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 bendable. The laminate for a flexible display device may contain the window film, the polarizing plate, and the touch sensor in any order, but is preferably laminated in the order of the window film, the polarizing plate, and the touch sensor, or in the order of the window film, the touch sensor, and the polarizing plate 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. Further, the light-shielding film may 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.

[ Window film ]

The window film is disposed on the viewing side of the flexible display device, and plays a role in protecting other components from external impact or environmental changes such as temperature and humidity. Glass has been used as such a protective layer in the past, and a window film in a flexible display device has flexible characteristics, unlike glass, which is rigid and hard. The foregoing window film may comprise a hard coat layer on at least one side.

(hard coating)

The window film may be provided with a hard coat layer on at least one surface thereof. The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100 μm. When the thickness of the hard coat layer is within the above range, sufficient scratch resistance can be secured, and the flex resistance is less likely to be lowered, and the problem of curling due to curing shrinkage is less likely to occur.

The aforementioned hard coat layer may be formed by: curing the hard coating composition including the reactive material capable of forming a cross-linked structure by irradiating active energy rays or imparting thermal energy; preferably by irradiation with active energy rays. The active energy ray is defined as an energy ray that can decompose a compound that generates an active species to generate an active species, and examples thereof include visible light, ultraviolet light, infrared light, X-ray, α -ray, β -ray, γ -ray, and electron beam, and preferable examples thereof include ultraviolet light. The hard coat composition contains at least 1 polymer selected from the group consisting of a radically polymerizable compound and a cationically polymerizable compound.

The radical polymerizable compound is a compound having a radical polymerizable group. The radical polymerizable group 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 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 polyfunctional acrylate monomer having 2 to 6 (meth) acryloyl groups in 1 molecule, an oligomer called epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate having several (meth) acryloyl groups in a molecule and having a molecular weight of several hundred to several thousand, and preferably 1 or more selected from the group consisting of epoxy (meth) acrylate, urethane (meth) acrylate, and polyester (meth) acrylate.

The cationically polymerizable compound is a compound having a cationically polymerizable group such as an epoxy group, an 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 oxetanyl 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. In addition, the compound having an epoxy group in a cyclic ether group has 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. In addition, the oxetanyl group in the cyclic ether group has the following advantages as compared with the epoxy group: the polymerization degree is easily increased, the forming speed of the network obtained by the cationic polymerizable compound of the obtained hard coat layer is increased, and even in the area mixed with the radical polymerizable compound, the unreacted monomer is not remained in the film and the independent network is formed; and so on.

Examples of the cationically polymerizable compound having an epoxy group include: polyglycidyl ethers of polyhydric alcohols having an alicyclic ring or alicyclic epoxy resins obtained by epoxidizing compounds containing 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 their derivatives 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 aforementioned 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 decomposed by at least one of irradiation with active energy rays and heating to generate radicals or cations, and radical polymerization and cationic polymerization are performed.

The radical polymerization initiator may be a substance that can release and initiate 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 azobisbutyronitrile.

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 hydrogen abstraction reaction in the coexistence of a tertiary amine, and they can be used alone or in combination.

The cationic polymerization initiator may be a substance 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. Depending on the difference in structure, they can initiate cationic polymerization by either or both of irradiation with active energy rays or heating.

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 advanced, the mechanical properties and the adhesion of the finally obtained coating film can be in a good range, and poor adhesion, a crack phenomenon, and a curl phenomenon due to curing shrinkage tend to be less likely to occur.

In addition, the aforementioned hard coating composition may further comprise one or more selected from the group consisting of a solvent, an additive.

The solvent may be used in a range that does not impair the effects of the present invention, as long as it is a solvent that can dissolve or disperse the polymerizable compound and the polymerization initiator and is known as a solvent for a hard coat composition in the art.

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

[ polarizing plate ]

The flexible display device including the optical film of the present invention may further include a polarizing plate, preferably a circularly polarizing plate. The 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 linear 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 lowered easily.

The linear polarizer may be a film-type polarizer manufactured by dyeing and stretching a polyvinyl alcohol (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 used because it has a property of exhibiting a liquid crystal state, and when it has a high-order alignment state such as a smectic state, it can exhibit high polarizing performance. The liquid crystalline compound preferably has a polymerizable functional group.

The dichroic dye may have liquid crystallinity or may have a polymerizable functional group, and may be aligned with the liquid crystal compound to exhibit dichroism. 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 produced by applying a liquid crystal polarizing composition to 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 foregoing 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 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 base material preferably functions as a protective film, a retardation plate, or a window film.

The protective film may be a transparent polymer film, and specific examples of the polymer film that can be used include polyolefins such as polyethylene, polypropylene, polymethylpentene, cycloolefin derivatives having a unit of a norbornene or cycloolefin, (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, polycarbonates, and polyarylates, polyamides such as nylon, polyamides, and the like, Films of polyimides, polyamideimides, polyetherimides, polyethersulfones, polysulfones, polyvinyl alcohols, polyvinyl acetals, polyurethanes, epoxy resins, and the like 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 2 or more. These films may be used in an unstretched state or in the form of a uniaxially or biaxially stretched film. 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 coating 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 lowered.

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-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 coated 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 base material preferably functions as a protective film, a retardation plate, or 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 it is not possible to achieve a retardation of λ/4 in all visible light regions, it is often designed so that an in-plane retardation of λ/4 is 100 to 180nm, preferably 130 to 150nm, in the vicinity of 560nm, which is high in 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 (japanese patent application laid-open No. h 10-90521). The λ/2 phase difference plate can be manufactured by the same material 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 circularly polarizing plate, a method of laminating a positive C plate is also known in order to improve visibility in an oblique direction (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-200 to-20 nm, preferably-140 to-40 nm.

[ 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 region (display portion) 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 region (non-display portion) on the display device where a screen is not displayed. The touch sensor may include: a substrate having flexible properties; a sensing pattern formed on the 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 may 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 sensor 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 aforementioned 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 mutually different repeating units such as an epoxy group-containing repeating unit, an acrylate repeating unit, and a carboxylic acid repeating unit.

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 ]

The layers of the laminate for a flexible display device, such as a window film, a polarizing plate, and a touch sensor, and the film members of the layers, such as a linear polarizing plate and a λ/4 retardation plate, may be bonded together 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, an aqueous solvent volatile adhesive, a moisture curable adhesive, a heat curable adhesive, an anaerobic curable adhesive, an active energy ray curable adhesive, a curing agent hybrid adhesive, a hot melt adhesive, a pressure sensitive adhesive, and a rewetting 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 suitably adjusted depending on the required adhesive strength, and is, for example, 0.01 to 500. mu.m, preferably 0.1 to 300. mu.m, and the adhesive layer may be present in a plurality of layers in the laminate for a flexible display device, and the thickness of each layer and the kind of the adhesive used may be the same or different.

As the aqueous solvent volatile adhesive, 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 can be used as a main polymer. In addition to water and the 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 added. 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-based 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. In order to reduce the viscosity as an 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 selected from a radical polymerization initiator, a cationic polymerization initiator, a radical and cationic polymerization initiator, and the like. 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 active energy rays 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 0.01 to 20 μm, preferably 0.1 to 10 μm. When the active energy ray-curable adhesive is used for forming a plurality of layers, the thickness of each layer and the type of 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 pressure-sensitive adhesive layer/adhesive layer can be formed by dissolving and dispersing the components constituting the pressure-sensitive adhesive in a solvent to obtain a pressure-sensitive adhesive composition, applying the pressure-sensitive adhesive composition to a substrate, and drying the applied pressure-sensitive 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 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 portion of a bezel (bezel) or a housing of the flexible display device. The wiring disposed at the edge of the flexible 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 a polymer such as an acrylic resin, an ester resin, an epoxy resin, polyurethane, or polysiloxane. 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 more specifically below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Unless otherwise specified, "%" and "parts" in the examples refer to mass% and parts by mass. First, a measurement method will be described.

< determination of weight average molecular weight (Mw) >)

The measurement was performed using Gel Permeation Chromatography (GPC). The preparation method and the measurement conditions of the measurement sample are as follows.

(1) Sample preparation method

20mg of the polyimide-based resin was weighed out, and 10mL of DMF eluent (10mM lithium bromide solution) was added to completely dissolve the resin. The solution was filtered through a chromatography plate (pore size: 0.45 μm) to prepare a sample solution.

(2) Measurement conditions

The device comprises the following steps: HLC-8020GPC

Column: guard column + TSKgel alpha-M (300 mm. times.7.8 mm diameter). times.2 pieces + alpha-2500 (300 mm. times.7.8 mm diameter). times.1 pieces

Eluent: DMF (with addition of 10mM 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

< measurement of viscosity >

(1) Sample adjustment method

The polyimide-based resin was dissolved in DMAc to give 10 mass% to prepare a measurement sample.

(2) Measurement conditions

Device name: LVDV-II + Pro (manufactured by Bruker Filde Co., Ltd.)

Measuring temperature: 25 deg.C

A main shaft: CPE-52

Sample amount: 0.6mL

Rotor rotation speed: 3.0rpm

< measurement of film thickness >

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

< bending test >

The films obtained in examples and comparative examples were cut into a size of 10mm × 100mm using a dumbbell cutter. The cut films were set in a body of an MIT bending fatigue tester ("MIT-DA" model: 0530, manufactured by toyoyo seiki corporation), bending tests were performed in both the front and back directions under conditions of a test speed of 175cpm, a bending angle of 135 °, a weight of 750g, and a R of a bending splint of 1.0mm, and the number of times of bending resistance (the number of times of bending without breaking) of each film was measured.

The bending resistance was evaluated as good and indicated by good when the number of times of bending resistance was 15 ten thousand or more, and evaluated as poor and indicated by X when the number of times of bending resistance was less than 15 ten thousand. Good (o) indicates that the number of bending times in both the front and back directions is 15 ten thousand or more, and poor (x) indicates that the number of bending times in either or both of the front and back directions is less than 15 ten thousand.

Example 1: synthesis of polyimide resin

A fully dried reaction vessel equipped with a stirrer and a thermometer was purged with nitrogen to replace the inside of the vessel with nitrogen. The reaction vessel was cooled to 10 ℃ and 1907.2 parts of N, N-dimethylacetamide (DMAc) were charged into the vessel, 111.37 parts of 2,2 '-bis (trifluoromethyl) benzidine (TFMB) and 46.82 parts of 4, 4' - (hexafluoroisopropylidene) diphthalic anhydride (6FDA) were added, and the mixture was stirred for 3 hours.

Then, 10.37 parts of 4, 4' -oxybis (benzoyl chloride) (OBBC) and 38.54 parts of terephthaloyl chloride (TPC) were added thereto and stirred. To the resulting reaction solution were added DMAc1907.2 parts and TPC 4.28 parts, and the mixture was further stirred at 10 ℃ for 1 hour (step (I)). Further, 0.56 part of TFMB was added thereto and the mixture was stirred for 2 hours (step (II)).

Subsequently, 31.80 parts of diisopropylethylamine and 75.32 parts of acetic anhydride were added, and the mixture was stirred at 10 ℃ for 30 minutes, then 22.90 parts of 4-methylpyridine was added, and the temperature of the reaction vessel was raised to 75 ℃ and further stirred for 3 hours to obtain a reaction solution. The obtained reaction solution was cooled to 40 ℃ or lower, and 1147.1 parts of methanol was added thereto. Subsequently, nitrogen was introduced into a reaction vessel equipped with a stirrer and a thermometer to replace the inside of the vessel with nitrogen. The reaction solution was charged into the reaction vessel while stirring at 20 ℃. Further, 4575.1 parts of methanol and 2861.7 parts of ion-exchanged water were added dropwise to precipitate a white solid. The precipitated white solid was collected by centrifugal filtration and washed with methanol to obtain a wet cake containing a polyimide-based resin. The obtained wet cake was dried at 78 ℃ under reduced pressure to obtain a polyimide resin (powder) (step (III)).

As described above, the diamine compound used for producing the polyimide-based resin was TFMB, and the molar ratio of the amount of the diamine compound added in step (I) (the 1 st addition amount) to the amount of the diamine compound added in step (II) (the 2 nd addition amount) was 99.5: 0.5.

[ example 2]

A polyimide resin was obtained in the same manner as in example 1, except that the 1 st addition amount of the diamine compound was 110.26 parts and the 2 nd addition amount was 1.679 parts.

[ example 3]

A polyimide resin was obtained in the same manner as in example 1, except that the 1 st addition amount of the diamine compound was 111.60 parts and the 2 nd addition amount was 0.448 parts.

[ example 4]

A polyimide resin was obtained in the same manner as in example 1, except that the 1 st addition amount of the diamine compound was 110.60 parts and the 2 nd addition amount was 0.045 parts.

[ example 5]

A polyimide resin was obtained in the same manner as in example 1, except that the 1 st addition amount of the diamine compound was 110.60 parts and the 2 nd addition amount was 0.179 part.

[ example 6]

A polyimide resin was obtained in the same manner as in example 1, except that the 1 st addition amount of the diamine compound was 110.60 parts and the 2 nd addition amount was 0.067 parts.

Comparative example 1

A polyimide resin was obtained in the same manner as in example 1 except that the 1 st addition amount of the diamine compound was 111.37 parts and the step (II) was not performed (the 2 nd addition was not performed).

Comparative example 2

A polyimide resin was obtained in the same manner as in example 1 except that the 1 st addition amount of the diamine compound was 110.81 parts and the step (II) was not performed (the 2 nd addition was not performed).

In examples 1 to 6 and comparative examples 1 and 2, the molar ratios of the respective components (6FDA, TPC, OBBC, and TFMB) used for producing the polyimide resin are shown in table 1.

[ Table 1]

[ production of film ]

The polyimide resin prepared in examples 1 to 6 and comparative examples 1 and 2 was dissolved in DMAc to obtain a polyimide resin varnish having a concentration of 10% by mass of the polyimide resin. The obtained resin varnish was applied to a smooth surface of a polyester substrate (manufactured by Toyobo Co., Ltd., trade name "A4100") using an applicator so that the thickness of the self-supporting film became 55 μm, dried at 50 ℃ for 30 minutes, and then dried at 140 ℃ for 15 minutes, and then 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 a polyimide resin film having a thickness of 50 μm.

The obtained polyimide resin film was subjected to a bending resistance test. The molar ratio of amine in each component (referred to as the final amine ratio), the presence or absence of the 2 nd addition (step (II)), the molar ratio of the 1 st addition amount to the 2 nd addition amount, the weight average molecular weight (Mw) of the polyimide resin, the viscosity at 25 ℃ of the polyimide resin varnish, and the evaluation results of the bending resistance test are shown in table 2.

[ Table 2]

As shown in table 2, the films of examples 1 to 6 were evaluated well in the bending resistance test and were confirmed to have excellent bending resistance. On the other hand, it is found that the films of comparative examples 1 and 2, which were formed of the polyimide-based resin not produced in the step (II), were not evaluated in the bending resistance test.

Claims

1. A method for producing a polyimide resin, comprising:

and (II) further reacting a diamine compound with the intermediate (K).

2. The production process according to claim 1, wherein the amount of the diamine compound to be reacted in the step (I) is 80 to 99.99 mol, based on 100 mol of the total amount of the diamine compounds to be reacted in the steps (I) and (II).

3. The production process according to claim 1 or 2, wherein the step (I) further comprises a step (B) of reacting a dicarboxylic acid compound after the step (A).