JP2023182123A - Resin composition and film - Google Patents

Abstract

To provide: a transparent film that has high transparency and sufficient mechanical strength; and a resin composition that is used in the production of the transparent film.SOLUTION: A resin composition includes a polyimide and an acrylic resin. The polyimide has a structure derived from a tetracarboxylic acid dianhydride and a structure derived from a diamine. The diamine-derived structure includes a fluoroalkyl-substituted benzidine. The tetracarboxylic acid dianhydride-derived structure includes a structure derived from 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride and/or a bis(trimellitic anhydride) ester. The resin composition is soluble in an amide solvent.SELECTED DRAWING: None

Description

The present invention relates to resin compositions and films.

Display devices such as liquid crystals, organic EL, and electronic paper, and electronic devices such as solar cells and touch panels are required to be thinner, lighter, and more flexible. By replacing the glass material used in these devices with a film material, they can be made more flexible, thinner, and lighter. Transparent polyimide film has been developed as a glass substitute material and is used for display substrates, cover films, etc.

A typical polyimide film is obtained by coating a polyamic acid solution, which is a polyimide precursor, on a support in the form of a film, treating it at high temperature, and simultaneously removing the solvent and performing thermal imidization. However, the heating temperature for thermal imidization is high (e.g. 300°C or higher), and coloration (increase in yellowness) is likely to occur due to heating, making it difficult to apply to applications that require high transparency, such as cover films for displays. Have difficulty.

As a method for producing a polyimide film having high transparency, a method using a polyimide resin that is soluble in organic solvents and does not require imidization at high temperatures after film formation has been proposed. For example, Patent Document 1 proposes a method for producing polyimide containing bistrimellitic anhydride as a tetracarboxylic dianhydride component, and the polyimide obtained by this method is heated in a low boiling point solvent such as dichloromethane. It is described that it is soluble and has excellent transparency and mechanical strength.

International Publication No. 2020/004236

Introducing a rigid structure to polyimide improves its mechanical strength, but it also causes a decrease in solubility in organic solvents and transparency. Conventional transparent polyimide resins cannot achieve high mechanical strength while maintaining transparency. It is not easy to have it. In view of such problems, the present invention aims to provide a transparent film that has high transparency, can reduce coloring, and has sufficient mechanical strength, and a resin composition used for producing the same.

As a result of intensive studies, the present inventors have found that the above problems can be solved by using the following resin composition. The present invention has the following configuration.

1). A resin composition containing a polyimide and an acrylic resin, wherein the polyimide has a structure derived from a tetracarboxylic dianhydride and a structure derived from a diamine, and a structure derived from a fluoroalkyl-substituted benzidine is added to the diamine-derived structure. The structure derived from the tetracarboxylic dianhydride includes a structure derived from 4,4'-(4,4'-isopropylidene diphenoxy) diphthalic anhydride and/or bis(trimellitic anhydride) ester, A resin composition that is soluble in amide solvents.

2). In addition to the structure derived from the tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 3,4'-oxydiphthalic anhydride, pyromellitic dianhydride, merophanic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride , 9,9-bis(3,4-dicarboxyphenyl)fluorene dioic anhydride, 5,5'-dimethylmethylenebis(phthalic anhydride), 3,3',4,4'-diphenylsulfone tetracarboxylic acid anhydride The resin composition according to 1), which is composed of one or more selected from acid dianhydrides.

3). The resin composition according to 1) or 2), wherein the bis(trimellitic anhydride) ester is represented by the following general formula (1). (However, X in general formula (1) is a divalent organic group selected from the following (A) to (K), and R ¹ to R ³ are a hydrogen atom, a fluorine atom, and a carbon atom number of 20 alkyl group or a fluoroalkyl group having 1 to 20 carbon atoms, m is an integer of 1 to 4, n is an integer of 0 to 4, p is an integer of 1 to 10, and q is an integer of 0 to 4. )

4). The resin composition according to any one of 1) to 3), wherein the fluoroalkyl-substituted benzidine is 2,2'-bis(trifluoromethyl)benzidine.

5). The resin composition according to any one of 1) to 4), wherein the content of the fluoroalkyl-substituted benzidine is 55 to 100 mol%.

6). The resin composition according to any one of 1) to 5), wherein the acrylic resin contains methyl methacrylate in an amount of 60% by weight or more based on the total amount of monomer components.

7). The resin composition according to any one of 1) to 6), wherein the acrylic resin has a glass transition temperature of 80° C. or higher.

8). The resin composition according to any one of 1) to 7), comprising the polyimide and the acrylic resin in a weight ratio in the range of 2:98 to 98:2.

9). A film comprising the resin composition according to any one of 1) to 8).

10). The film according to 9), which has a thickness of 5 μm or more and 300 μm or less.

11). When the thickness is 50 μm, the total light transmittance is 90% or more, the haze is 3% or less, the yellowness is 5.0 or less, the tensile modulus is 2.8 GPa or more, and the pencil hardness is F or more, 9) or 10 ).

According to the present invention, it is possible to provide a transparent film that has high transparency, can reduce coloring, and has sufficient mechanical strength, and a resin composition used for producing the transparent film.

[Resin composition]
One embodiment of the present invention is a compatible resin composition containing a polyimide resin and an acrylic resin, wherein the polyimide has a structure derived from a tetracarboxylic dianhydride and a structure derived from a diamine, and the polyimide has a structure derived from a tetracarboxylic dianhydride and a structure derived from a diamine; The structure derived from diamine includes a structure derived from fluoroalkyl-substituted benzidine, and the structure of the tetracarboxylic dianhydride contains 4,4'-(4,4'-isopropylidene diphenoxy) diphthalic anhydride and/or bis( Contains a structure derived from trimellitic anhydride (trimellitic anhydride) ester and is soluble in amide solvents.

Further, as a structure derived from tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, or 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4 , 4'-oxydiphthalic anhydride or 3,4'-oxydiphthalic anhydride, pyromellitic dianhydride, merophanic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dioic anhydride, 5,5'-dimethylmethylenebis(phthalic anhydride), 3,3',4,4'-diphenylsulfone tetracarboxylic acid It may contain one or more selected from dianhydrides.

Soluble in amide solvents means selected from N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N,N'-diethylacetamide, and N-methyl-2-pyrrolidone (NMP). This means that 5% by weight or more of the polyimide is dissolved in the amide solvent at 25°C.

<Polyimide>

Polyimide refers to something that has a structure as shown in general formula (2), and is obtained by addition polymerization of diamine and tetracarboxylic dianhydride (hereinafter sometimes referred to as "acid dianhydride"). It can be synthesized by cyclodehydration of polyamic acid, condensation of diisocyanate and acid dianhydride through decarboxylation, and the like. However, in the general formula (2), X represents a tetravalent organic group, and Y represents a divalent organic group.

In the present invention, even if the starting material for synthesizing polyimide is not an acid dianhydride, if it has a structure corresponding to the part surrounded by a straight line in the imide general formula (3), it can be considered as an acid dianhydride-derived structure. do. Furthermore, even if the starting material for synthesizing polyimide is not a diamine, if it has a structure corresponding to the part surrounded by the dotted line in general formula (3), it is expressed as a diamine-derived structure. However, in the general formula (3), X represents a tetravalent organic group, and Y represents a divalent organic group.

(Diamine)
The polyimide used in this embodiment includes fluoroalkyl-substituted benzidine as a diamine-derived structure. When the diamine-derived structure has a fluoroalkyl-substituted benzidine, there is a tendency to achieve both solubility and transparency of the polyimide resin.

Examples of fluoroalkyl-substituted benzidine include 2-(trifluoromethyl)benzidine, 3-(trifluoromethyl)benzidine, 2,3-bis(trifluoromethyl)benzidine, 2,5-bis(trifluoromethyl)benzidine , 2,6-bis(trifluoromethyl)benzidine, 2,3,5-tris(trifluoromethyl)benzidine, 2,3,6-tris(trifluoromethyl)benzidine, 2,3,5,6-tetrakis (trifluoromethyl)benzidine, 2,2'-bis(trifluoromethyl)benzidine, 3,3'-bis(trifluoromethyl)benzidine, 2,3'-bis(trifluoromethyl)benzidine, 2,2' , 3-tris(trifluoromethyl)benzidine, 2,3,3'-tris(trifluoromethyl)benzidine, 2,2',5-tris(trifluoromethyl)benzidine, 2,2',6-tris( trifluoromethyl)benzidine, 2,3',5-tris(trifluoromethyl)benzidine, 2,3',6,-tris(trifluoromethyl)benzidine, 2,2',3,3'-tetrakis(trifluoromethyl)benzidine, Examples thereof include fluoromethyl)benzidine, 2,2',5,5'-tetrakis(trifluoromethyl)benzidine, and 2,2',6,6'-tetrakis(trifluoromethyl)benzidine.

Among these, fluoroalkyl-substituted benzidine having a fluoroalkyl group at the 2-position of biphenyl is preferred, and 2,2'-bis(trifluoromethyl)benzidine (hereinafter referred to as "TFMB") is particularly preferred. By having fluoroalkyl groups at the 2- and 2'-positions of biphenyl, in addition to reducing the π-electron density due to the electron-withdrawing property of the fluoroalkyl group, the steric hindrance of the fluoroalkyl group causes the two benzene rings of biphenyl to Since the bonds between are twisted and the planarity of the π-conjugation is reduced, the absorption edge wavelength is shifted to a shorter wavelength, and coloring of the polyimide can be reduced.

When the diamine-derived structure includes a condensed structure of a fluoroalkyl-substituted benzidine and a dicarboxylic acid, the diamine-derived structure also includes a fluoroalkyl-substituted benzidine.

General formula (4) can be exemplified as a preferable example of the diamine containing the condensed structure of the fluoroalkyl-substituted benzidine and dicarboxylic acid. However, R ¹ and R ² in general formula (4) are independently a halogen, a methyl group, or a trifluoromethyl group, and m is an integer of 0 to 3, but either R ¹ or R ² m is not 0. R ³ is an unsubstituted benzene ring or biphenyl, a benzene ring substituted with a halogen, a methyl group, or a trifluoromethyl group, or biphenyl.

In general formula (4), the structure of a diamine in which two fluoroalkyl-substituted benzidines and one dicarboxylic acid are condensed is exemplified. Even if the resulting polyimide is a diamine condensed with four dicarboxylic acids and three dicarboxylic acids, a diamine condensed with five fluoroalkyl-substituted benzidines and four dicarboxylic acids, etc., the resulting polyimide tends to exhibit high elasticity and high transparency. It is preferable because it is.

A structure corresponding to general formula (4) can also be introduced into a polyimide by a method of condensing a fluoroalkyl-substituted benzidine-terminated polyamic acid oligomer or a fluoroalkyl-substituted benzidine-terminated polyimide oligomer with a dicarboxylic acid or a dichloride of a dicarboxylic acid. Can be done.

From the viewpoint of exhibiting transparency and high elasticity, general formula (4) preferably has a condensation structure of 2,2'-bis(trifluoromethyl)benzidine and dicarboxylic acid, and the dicarboxylic acid is terephthalic acid or Biphenyl-4,4'-dicarboxylic acid is more preferred because it exhibits a higher elastic modulus.

From the viewpoint of exhibiting solubility in a solvent, the dicarboxylic acid is preferably isophthalic acid.

The content of diamine containing a condensed structure of fluoroalkyl-substituted benzidine and dicarboxylic acid based on 100 mol% of the total amount of diamine components is preferably 55 to 100 mol%, more preferably 57 to 95 mol%, and may be 59 to 90 mol%. A large content of diamine containing a condensed structure of a fluoroalkyl-substituted benzidine and a dicarboxylic acid tends to suppress discoloration of the film and increase mechanical strength such as pencil hardness and elastic modulus. Although the general formula (4) has two fluoroalkyl-substituted benzidines, when calculating the content of the fluoroalkyl-substituted benzidine based on 100 mol% of the total amount of diamine components, it is calculated as one diamine.

The polyimide may contain a diamine other than fluoroalkyl-substituted benzidine as a diamine-derived structure. Examples of diamines other than fluoroalkyl-substituted benzidine include 2-fluorobenzidine, 3-fluorobenzidine, 2,3-difluorobenzidine, 2,5-difluorobenzidine, 2,6-difluorobenzidine, 2,3,5-trifluorobenzidine, Fluorobenzidine, 2,3,6-trifluorobenzidine, 2,3,5,6-tetrafluorobenzidine, 2,2'-difluorobenzidine, 3,3'-difluorobenzidine, 2,3'-difluorobenzidine, 2 ,2',3-trifluorobenzidine, 2,3,3'-trifluorobenzidine, 2,2',5-trifluorobenzidine, 2,2',6-trifluorobenzidine, 2,3',5- Trifluorobenzidine, 2,3',6,-trifluorobenzidine, 2,2',3,3'-tetrafluorobenzidine, 2,2',5,5'-tetrafluorobenzidine, 2,2',6 , 6'-tetrafluorobenzidine, 2,2', 3,3', 6,6'-hexafluorobenzidine, 2,2', 3,3', 5,5', 6,6'-octafluorobenzidine , 2,4-diaminotoluene, 2,5-diaminotoluene, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4' -diaminodiphenyl ether, 3,3'-diaminodiphenylsulfide, 3,4'-diaminodiphenylsulfide, 4,4'-diaminodiphenylsulfide, 3,3'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 4 , 4'-diaminodiphenylsulfone, 9,9-bis(4-aminophenyl)fluorene, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'- Diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 2,2-di(3-aminophenyl)propane, 2,2-di(4-aminophenyl)propane, 2-(3- aminophenyl)-2-(4-aminophenyl)propane, 1,1-di(3-aminophenyl)-1-phenylethane, 1,1-di(4-aminophenyl)-1-phenylethane, 1- (3-aminophenyl)-1-(4-aminophenyl)-1-phenylethane, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4 -Bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminobenzoyl)benzene, 1,3-bis(4-aminobenzoyl)benzene, 1 , 4-bis(3-aminobenzoyl)benzene, 1,4-bis(4-aminobenzoyl)benzene, 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis( 4-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene , 2,6-bis(3-aminophenoxy)benzonitrile, 2,6-bis(3-aminophenoxy)pyridine, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(4 -aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[ 4-(4-aminophenoxy)phenyl] sulfide, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy) phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy) phenyl]propane, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3 -aminophenoxy)benzoyl]benzene, 1,4-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1, 4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 4,4'-bis[4-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4- (4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenylsulfone, 4,4'-bis[4 -(4-aminophenoxy)phenoxy]diphenylsulfone, 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 3,3'-diamino -4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'- Spirobiindane, 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane , 1,3-bis(4-aminobutyl)tetramethyldisiloxane, α,ω-bis(3-aminopropyl)polydimethylsiloxane, α,ω-bis(3-aminobutyl)polydimethylsiloxane, bis(aminobutyl) methyl)ether, bis(2-aminoethyl)ether, bis(3-aminopropyl)ether, bis(2-aminomethoxy)ethyl]ether, bis[2-(2-aminoethoxy)ethyl]ether, bis[2 -(3-aminoprotoxy)ethyl]ether, 1,2-bis(aminomethoxy)ethane, 1,2-bis(2-aminoethoxy)ethane, 1,2-bis[2-(aminomethoxy)ethoxy] Ethane, 1,2-bis[2-(2-aminoethoxy)ethoxy]ethane, ethylene glycol bis(3-aminopropyl) ether, diethylene glycol bis(3-aminopropyl) ether, triethylene glycol bis(3-aminopropyl) ) Ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9 -Diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, trans-1,4 -Diaminocyclohexane, 1,2-di(2-aminoethyl)cyclohexane, 1,3-di(2-aminoethyl)cyclohexane, 1,4-di(2-aminoethyl)cyclohexane, bis(4-aminocyclohexane) xyl)methane, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane, 1,4-diamino-2- Fluorobenzene, 1,4-diamino-2,3-difluorobenzene, 1,4-diamino-2,5-difluorobenzene, 1,4-diamino-2,6-difluorobenzene, 1,4-diamino-2, 3,5-trifluorobenzene, 1,4-diamino, 2,3,5,6-tetrafluorobenzene, 1,4-diamino-2-(trifluoromethyl)henzene, 1,4-diamino-2,3 -bis(trifluoromethyl)benzene, 1,4-diamino-2,5-bis(trifluoromethyl)benzene, 1,4-diamino-2,6-bis(trifluoromethyl)benzene, 1,4-diamino -2,3,5-tris(trifluoromethyl)benzene, 1,4-diamino, 2,3,5,6-tetrakis(trifluoromethyl)benzene, 2,2'-bis[4-(4-amino) phenoxy)phenyl]hexafluoropropane (HFBAPP), 2,2'-bis[4-(4-aminophenoxy)phenyl]propane (BAPP), 2,2'-dimethylbenzidine (m-Tol), 3,3' -dimethylbenzidine, 2,3'-dimethylbenzidine, 3,3',5,5'-tetramethylbenzidine, 2,2',3,3',5,5'-hexamethylbenzidine, 2,2'- Examples include dichloro-3,3',5,5'-tetramethylbenzidine, 3,3'-dichlorobenzidine, and benzidine.

For example, by using diaminodiphenylsulfone, 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane in addition to fluoroalkyl-substituted benzidine as the diamine, the solubility of the polyimide resin in the solvent can be improved. and transparency may be improved. Among the diaminodiphenylsulfones, 3,3'-diaminodiphenylsulfone (3,3'-DDS) and 4,4'-diaminodiphenylsulfone (4,4'-DDS) are preferred. 3,3'-DDS and 4,4'-DDS may be used together.

The content of diaminodiphenylsulfone or 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane based on 100 mol% of the total amount of diamine is 1 to 45 mol%, 3 to 30 mol%, or 5 to 25 mol%. It may be mol%.

(acid dianhydride)
The polyimide used in this embodiment has a structure derived from tetracarboxylic dianhydride, such as 4,4'-(4,4'-isopropylidene diphenoxy) diphthalic anhydride and/or bis(trimellitic anhydride) ester. Contains the structure of origin. When polyimide contains these structures, it tends to be soluble in solvents and improve its compatibility with acrylic resins.

The structure of the bis(trimellitic anhydride) ester is represented by the following general formula (1). (However, X in general formula (1) is a divalent organic group selected from the following (A) to (K).)

R ¹ in formula (A) is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, or a fluoroalkyl group having 1 to 20 carbon atoms, and m is an integer of 1 to 4. The group represented by formula (A) is a group obtained by removing two hydroxyl groups from a hydroquinone derivative having a substituent on the benzene ring. Examples of the hydroquinone having a substituent on the benzene ring include tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and 2,5-di-tert-amylhydroquinone.

R ² in formula (B) is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, or a fluoroalkyl group having 1 to 20 carbon atoms, and n is an integer of 0 to 4. The group represented by formula (B) is a group obtained by removing two hydroxyl groups from biphenol which may have a substituent on the benzene ring. Examples of biphenol derivatives having a substituent on the benzene ring include 2,2'-dimethylbiphenyl-4,4'-diol, 3,3'-dimethylbiphenyl-4,4'-diol, 3,3',5, Examples include 5'-tetramethylbiphenyl-4,4'-diol, 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diol, and the like.

The group represented by formula (C) is a group obtained by removing two hydroxyl groups from 4,4'-isopropylidene diphenol (bisphenol A). The group represented by formula (D) is a group obtained by removing two hydroxyl groups from resorcinol.

p in formula (E) is an integer from 1 to 10. The group represented by formula (E) is a group obtained by removing two hydroxyl groups from a linear diol having 1 to 10 carbon atoms. Examples of linear diols having 1 to 10 carbon atoms include ethylene glycol and 1,4-butanediol.

The group represented by formula (F) is a group obtained by removing two hydroxyl groups from 1,4-cyclohexanedimethanol.

R ³ in formula (G) is a hydrogen atom, a fluorine atom, an alkyl group having 1 to 20 carbon atoms, or a fluoroalkyl group having 1 to 20 carbon atoms, and q is an integer of 0 to 4. The group represented by formula (G) is a group obtained by removing two hydroxyl groups from bisphenolfluorene which may have a substituent on the benzene ring having a phenolic hydroxyl group. Examples of bisphenol fluorene derivatives which may have a substituent on the benzene ring having a phenolic hydroxyl group include biscresol fluorene and the like.

When X is a group represented by general formula (B), from the viewpoint of solubility of the polyimide resin, X is 2,2',3,3',5, 5'-hexamethylbiphenyl-4,4'-diyl is preferred.

In general formula (1), the acid dianhydride in which X is a group represented by formula (B1) is bis(1,3-dioxo-1,3-dihydroisobenzofuran) represented by formula (5) below. -5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'diyl (abbreviation: TAHMBP).

In addition to the above-mentioned TAHMBP, examples of bis(trimellitic anhydride) esters include p-phenylene bis(trimellitate anhydride) (TAHQ), p-biphenylene bis(trimellitate anhydride) (BP-TME), and 2,2-bis(trimellitate anhydride) (BP-TME). Also included are 4-hydroxyphenyl)propane dibenzoate-3,3',4,4'-tetracarboxylic dianhydride.

The polyimide may contain a tetracarboxylic dianhydride other than the above-mentioned tetracarboxylic dianhydride as a structure derived from tetracarboxylic dianhydride. Examples of these tetracarboxylic dianhydrides include pyromellitic dianhydride, merophanic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride or 2,2',3, 3'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride or 3,4'-oxydiphthalic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride , 5,5'-dimethylmethylenebis(phthalic anhydride), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, fluorine-containing aromatic tetracarboxylic dianhydride, alicyclic tetra Examples include carboxylic dianhydrides.

Examples of the fluorine-containing aromatic tetracarboxylic dianhydride include 4,4'-(hexafluoroisopropylidene) diphthalic anhydride, 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]hexafluoro Propane dianhydride, 1,4-difluoropyromellitic dianhydride, 1,4-bis(trifluoromethyl)pyromellitic dianhydride, 4-(trifluoromethyl)-1H,3H-benzo[1, 2-c:4,5-c'] difuran-1,3,5,7-tetrone, 3,6-di[3',5'-bis(trifluoromethyl)phenyl]pyromellitic dianhydride, 1 -(3',5'-bis(trifluoromethyl)phenyl)pyromellitic dianhydride and the like.

Examples of the alicyclic tetracarboxylic dianhydride include 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,1'- Bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4,3',4'-dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2”- Examples include norbornane-5,5'',6,6''-tetracarboxylic dianhydride, 2,2'-vinorbornane-5,5',6,6'tetracarboxylic dianhydride, etc. Among them, From the viewpoint of transparency and mechanical strength of polyimide, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, or 1,2,4 ,5-cyclohexanetetracarboxylic dianhydride is preferred, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride is particularly preferred.

The content of 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride and/or bis(trimellitic anhydride) ester based on 100 mol% of the total amount of acid dianhydride components is From the viewpoint of solubility and compatibility with the acrylic resin, the total content of both acid dianhydrides is preferably 30 mol% or more, more preferably 35 mol% or more, and even more preferably 40 mol% or more.

From the viewpoint of obtaining a polyimide resin that has both solubility in organic solvents and compatibility with acrylic resins, 4,4'-(4,4'-isopropylidene diphenoxy ) Diphthalic anhydride and/or bis(trimellitic anhydride) ester, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride Acid dianhydride, 3,4'-oxydiphthalic anhydride, 4,4'-oxydiphthalic anhydride, pyromellitic dianhydride, merophanic dianhydride, 3,3',4,4'-benzophenone tetra Carboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 5,5'-dimethylmethylenebis(phthalic anhydride), 3,3',4,4' - One or more types selected from diphenylsulfone tetracarboxylic dianhydride, 2,2-bis(4-hydroxyphenyl)propane dibenzoate-3,3',4,4'-tetracarboxylic dianhydride The content is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol%. It may be more than that.

The polyimide may contain acid dianhydrides other than those mentioned above as the acid dianhydride component. Examples of acid dianhydrides other than those listed above include ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2 -bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, Bis(3,4-dicarboxyphenyl)methane dianhydride, 1,3-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 1,4-bis[(3,4-dicarboxy) benzoyl]benzene dianhydride, 2,2-bis[4-(3,4-dicarboxy)phenoxy]phenylpropane dianhydride, 2,2-bis(4-(2,3-dicarboxy)phenoxy]phenyl }Propane dianhydride, bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone Dianhydride, 4,4'-bis[4-(1,2-dicarboxy)phenoxy]biphenyl dianhydride, 4,4'-bis[3-(1,2-dicarboxy)phenoxy]biphenyl dianhydride bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}ketone dianhydride, Bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfone dianhydride, bis{ 4-[4-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, bis{4-[3-(1,2-dicarboxy)phenoxy]phenyl}sulfide dianhydride, 1,2, 5,6-naphthalenetetracarboxylic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6, 7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid)-1, 4-phenylene ester, 2,3,6,7-naphthalenetetracarboxylic acid 2,3:6,7-dianhydride, 11,11-dimethyl-1H-difuro[3,4-b:3',4' -i] , 5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride, ethylene glycol bis(trimellitic anhydride), naphthalene-1 , 4,5,8-tetracarboxylic dianhydride, N,N'-(9H-fluorene-9-ylidene-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5- isobenzofurancarboxamide], N,N'-[[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis(6-hydroxy-3,1-phenylene)]bis[1,3-dihydro -1,3-dioxo-5-isobenzofurancarboxamide].
can be mentioned.

(Preparation of polyimide)
A polyamic acid as a polyimide precursor is obtained by the reaction of an acid dianhydride and a diamine, and a polyimide is obtained by cyclodehydration (imidization) of the polyamic acid. As mentioned above, by adjusting the composition of polyimide, that is, the type and ratio of acid dianhydride and diamine, polyimide has transparency and solubility in organic solvents, as well as compatibility with acrylic resin. show.

The method for preparing polyamic acid is not particularly limited, and any known method can be applied. For example, a polyamic acid solution can be obtained by dissolving an acid dianhydride and a diamine in approximately equimolar amounts (molar ratio of 95:100 to 105:100) in an organic solvent and stirring. The concentration of the polyamic acid solution is usually 5 to 35% by weight, preferably 10 to 30% by weight. When the concentration is within this range, the polyamic acid obtained by polymerization has an appropriate molecular weight, and the polyamic acid solution has an appropriate viscosity.

When polymerizing polyamic acid, it is preferable to add an acid dianhydride to the diamine in order to suppress ring opening of the acid dianhydride. When adding multiple types of diamines or multiple types of acid dianhydrides, they may be added at once or may be added in multiple portions. Various physical properties of polyimide can also be controlled by adjusting the order of addition of monomers.

The organic solvent used in the polymerization of polyamic acid is not particularly limited as long as it does not react with diamines and acid dianhydrides and can dissolve polyamic acid. Examples of organic solvents include urea-based solvents such as methylurea and N,N-dimethylethylurea, sulfoxide or sulfone-based solvents such as dimethylsulfoxide, diphenylsulfone, and tetramethylsulfone, N,N-dimethylacetamide (DMAc), N, Amide solvents such as N-dimethylformamide (DMF), N,N'-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, hexamethylphosphoric triamide, etc., halogenation of chloroform, methylene chloride, etc. Examples include alkyl solvents, aromatic hydrocarbon solvents such as benzene and toluene, and ether solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. Generally, these solvents are used alone or in combination of two or more as necessary. From the viewpoint of solubility and polymerization reactivity of polyamic acid, DMAc, DMF, NMP, etc. are preferably used.

Polyimide is obtained by cyclodehydration of polyamic acid. A method for preparing polyimide from a polyamic acid solution includes a method in which a dehydrating agent, an imidization catalyst, etc. are added to the polyamic acid solution, and imidization is allowed to proceed in the solution. In order to promote the progress of imidization, the polyamic acid solution may be heated. By mixing a solution containing polyimide produced by imidization of polyamic acid with a poor solvent, a polyimide resin is precipitated as a solid. By isolating the polyimide resin as a solid, impurities generated during the synthesis of polyamic acid, residual dehydrating agents, imidization catalysts, etc. can be washed and removed with a poor solvent, resulting in increased coloration and yellowness of the polyimide. etc. can be prevented. Furthermore, by isolating the polyimide resin as a solid, a solvent suitable for film formation, such as a low boiling point solvent, can be applied when preparing a solution for producing a film.

The molecular weight of the polyimide (weight average molecular weight in terms of polyethylene oxide measured by gel filtration chromatography (GPC)) is preferably from 10,000 to 400,000, more preferably from 20,000 to 300,000, and from 40,000 to 250,000 is more preferred. If the molecular weight is too low, the strength of the film may be insufficient. On the other hand, if the molecular weight is excessively large, the compatibility with the acrylic resin may be poor.

From the viewpoint of thermal stability and optical stability of the resin composition and film, it is preferable that the polyimide has a low acid value and a high imidization rate. The acid value of the polyimide is preferably 0.4 mmol/g or less, more preferably 0.3 mmol/g or less, and even more preferably 0.2 mmol/g or less. The acid value of the polyimide may be 0.1 mmol/g or less, 0.05 mmol/g or less, or 0.03 mmol/g or less. The imidization rate of polyimide is preferably 95% or more, more preferably 96% or more, even more preferably 97% or more, and may be 98% or more, or 99% or more. A low acid value and a high imidization rate tend to increase the stability of polyimide and improve its compatibility with acrylic resins.

<Acrylic resin>
Acrylic resins include poly(meth)acrylic esters such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylic ester copolymers, and methyl methacrylate- Examples include acrylic ester-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer, and the like. The acrylic resin may have a glutarimide structural unit or a lactone ring structural unit introduced through modification. There is no particular restriction on the configuration of the ester group in the side chain, and it may be an atactic acrylic resin with an irregular configuration, an isotactic acrylic resin or a syndiotactic acrylic resin with regularity.

From the viewpoint of transparency and compatibility with polyimide, the acrylic resin preferably has methyl methacrylate as its main structural unit. The amount of methyl methacrylate based on the total amount of monomer components in the acrylic resin is preferably 60% by weight or more, and may be 70% by weight or more, 80% by weight or more, or 90% by weight or more. The acrylic resin may be a homopolymer of methyl methacrylate.

From the viewpoint of heat resistance of the film, the glass transition temperature of the acrylic resin is preferably 80°C or higher, preferably 90°C or higher, preferably 100°C or higher, 105°C or higher, 110°C or higher, 115°C or higher, or 120°C or higher. There may be.

From the viewpoints of solubility in organic solvents, compatibility with the above-mentioned polyimide, and film strength, the weight average molecular weight (in terms of polystyrene) of the acrylic resin is preferably from 5,000 to 2,000,000, and from 10,000 to It is more preferably 500,000, even more preferably 15,000 to 300,000, and may be 20,000 to 200,000.

From the viewpoint of thermal stability and optical stability of the resin composition and film, it is preferable that the acrylic resin has a low content of reactive functional groups such as ethylenically unsaturated groups and carboxyl groups. The iodine value of the acrylic resin is preferably 10.16 g/100 g (0.4 mmol/g) or less, more preferably 7.62 g/100 g (0.3 mmol/g) or less, and 5.08 g/100 g (0.2 mmol/g) or less. /g) or less is more preferable. The iodine value of the acrylic resin may be 2.54 g/100 g (0.1 mmol/g) or less or 1.27 g/100 g (0.05 mmol/g) or less. The acid value of the acrylic resin is preferably 0.4 mmol/g or less, more preferably 0.3 mmol/g or less, and even more preferably 0.2 mmol/g or less. The acid value of the acrylic resin may be 0.1 mmol/g or less, 0.05 mmol/g or less, or 0.03 mmol/g or less. A low acid value tends to increase the stability of the acrylic resin and improve its compatibility with polyimide.

<Preparation of resin composition>
A resin composition is prepared by mixing the above polyimide resin and acrylic resin. Since the above polyimide resin and acrylic resin can exhibit compatibility at any ratio, the ratio of the polyimide resin and acrylic resin in the resin composition is not particularly limited. The mixing ratio (weight ratio) of polyimide resin and acrylic resin may be 98:2 to 20:80. The higher the proportion of polyimide resin, the higher the elastic modulus of the film, which tends to be superior in mechanical strength. The higher the ratio of acrylic resin, the less coloring the film tends to have and the higher the transparency. In order to fully exhibit the effect of improving transparency by mixing polyimide and acrylic resin, the ratio of acrylic resin to the total of polyimide and acrylic resin is preferably 10% by weight or more, 15% by weight or more, It may be 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, or 45% by weight or more.

The resin composition containing polyimide and acrylic resin preferably has a single glass transition temperature in suggested scanning calorimetry (DSC) and/or dynamic rheology (DMA). When the resin composition has a single glass transition temperature, it can be considered that the polyimide and the acrylic resin are completely compatible. Preferably, the film containing polyimide and acrylic resin also has a single glass transition temperature.

The resin composition may be a mixed solution containing a polyimide resin and an acrylic resin. The method of mixing the resins is not particularly limited, and the resins may be mixed in a solid state, or may be mixed in a liquid to form a mixed solution. A polyimide resin solution and an acrylic resin solution may be prepared separately and then mixed to prepare a mixed solution of a polyimide resin and an acrylic resin.

The solvent for the solution containing the polyimide resin and the acrylic resin is not particularly limited as long as it exhibits solubility in both the polyimide resin and the acrylic resin. Examples of solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; ether solvents such as tetrahydrofuran and 1,4-dioxane; acetone, methyl ethyl ketone, Ketone solvents such as methylpropylketone, methylisopropylketone, methylisobutylketone, diethylketone, cyclopentanone, cyclohexanone, methylcyclohexanone; chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chlorobenzene, Examples include halogenated alkyl solvents such as dichlorobenzene and methylene chloride. Among these, amide solvents, ketone solvents, and halogenated alkyl solvents are preferred because they have excellent solubility in both polyimide resins and acrylic resins.

A resin composition containing polyimide and an acrylic resin has a solution viscosity lower than that of polyimide alone when compared at the same solid content concentration. By lowering the viscosity of a mixed solution containing a polyimide resin, an acrylic resin, and a solvent, there are advantages in that unevenness in film thickness becomes smaller and film formation becomes easier. Furthermore, since the melt viscosity of the resin composition is lower than that of polyimide alone, there is an advantage that it can be used in transfer molding, compression molding, and injection molding.

An organic or inorganic low-molecular or high-molecular compound may be added to the resin composition (solution) for the purpose of improving processability of the film or imparting various functions. An example of a polymer compound is an epoxy resin. The resin composition may contain flame retardants, ultraviolet absorbers, crosslinking agents, dyes, pigments, surfactants, leveling agents, plasticizers, fine particles, fiber reinforcing materials, sensitizers, and the like. The fine particles include organic fine particles such as polystyrene and polytetrafluoroethylene, inorganic fine particles such as colloidal silica, carbon, and layered silicates, and may have a porous or hollow structure. Fiber reinforcement materials include carbon fiber, glass fiber, aramid fiber, and the like.

[film]
A film is obtained by applying a solution containing the above polyimide resin and acrylic resin onto a support and drying and removing the solvent.

As a method for coating the resin solution on the support, a known method using a bar coater, a comma coater, etc. can be applied. As the support, a glass substrate, a metal substrate such as SUS, a metal drum, a metal belt, a plastic film, etc. can be used. From the viewpoint of improving productivity, it is preferable to manufacture the film by roll-to-roll using an endless support such as a metal drum or a metal belt, or a long plastic film as the support. When using a plastic film as a support, a material that does not dissolve in the solvent of the film-forming dope may be appropriately selected.

It is preferable to heat the solvent when drying it. The heating temperature is not particularly limited as long as the solvent can be removed and the resulting film can be inhibited from coloring, and is appropriately set between room temperature and about 250°C, preferably between 50°C and 230°C. The heating temperature may be increased in steps. In order to increase the efficiency of solvent removal, the resin film may be peeled off from the support and dried after drying has progressed to a certain extent, or heating may be performed under reduced pressure to promote solvent removal. .

A film made of acrylic resin alone may have low toughness, but the strength of the film may be improved by employing a compatible system of polyimide and acrylic resin. Stretching may be performed in one direction or in multiple directions for the purpose of improving the mechanical strength of the film. When a film is stretched, the polymer chains are oriented in the stretching direction, so that the strength in the stretching direction and/or the direction orthogonal to the stretching is improved, and the occurrence of cracks and cracks in the film tends to be suppressed. From the viewpoint of increasing the strength in any in-plane direction, it is preferable to biaxially stretch the film.

The thickness of the film is not particularly limited, and may be appropriately set depending on the application. The thickness of the film can be, for example, 5 to 300 μm. From the viewpoint of achieving both self-support and flexibility and a highly transparent film, the thickness of the film is preferably 20 μm to 100 μm, and may be 30 μm to 90 μm, 40 μm to 85 μm, or 50 μm to 80 μm. . The thickness of the film used as a display cover film is preferably 50 μm or more.

The haze of the film is preferably 5% or less, more preferably 4% or less, even more preferably 3.5% or less, and may be 3% or less, 2% or less, or 1% or less. The lower the haze of the optical film, the better. As mentioned above, since polyimide and acrylic resin are compatible, a film with low haze and high transparency can be obtained. It is preferable that the resin composition, which is a mixture of polyimide and acrylic resin, has a haze of 3% or less when a film having a thickness of 50 μm is produced.

The total light transmittance (TT) of the film when the thickness is 50 μm is preferably 85% or more, more preferably 87% or more, even more preferably 89% or more, particularly preferably 90% or more, and 91% or more. Good too. The higher the TT of the film, the better. As mentioned above, since polyimide and acrylic resin are compatible, a film with high TT and high transparency can be obtained.

The resin composition obtained by mixing polyimide and acrylic resin preferably has a yellowness index (YI) of 5.0 or less, more preferably 4.0 or less, and 3.5 or less when a film with a thickness of 50 μm is produced. is more preferable, 3.0 or less is particularly preferable, and may be 2.5 or less or 2.0 or less. As described above, by mixing a polyimide resin and an acrylic resin, a film having a smaller YI, that is, less colored, can be obtained than when a polyimide resin is used alone.

From the viewpoint of strength, the tensile modulus of the film when the thickness is 50 μm is preferably 2.7 GPa or more, more preferably 2.8 GPa or more, even more preferably 2.9 GPa or more, and may be 3.0 GPa or more. Further, the pencil hardness is preferably F or higher, and may be H or higher or 2H or higher. In a compatible system of polyimide and acrylic resin, pencil hardness does not easily decrease even if the ratio of acrylic resin is increased. Furthermore, the pencil hardness tends to be higher than that of polyimide alone. Therefore, it is possible to provide a film that is less colored and has excellent transparency without significantly reducing the excellent mechanical strength characteristic of polyimide.

Hereinafter, embodiments of the present invention will be described in more detail with reference to Examples. Note that the present invention is not limited to the following examples.

[Production example of polyimide resin]
N,N-dimethylformamide (DMF) was charged into a separable flask and stirred under a nitrogen atmosphere. Diamine and acid dianhydride were added therein at the ratio (mol%) shown in Table 1, and the reaction was stirred for 5 to 10 hours under a nitrogen atmosphere to form a polyamic acid solution with a solid content concentration of 18% by weight. Obtained.

After adding 6.0 g of pyridine as an imidization catalyst to 100 g of polyamic acid solution and completely dispersing it, 8 g of acetic anhydride was added and stirred at 90° C. for 3 hours. After cooling to room temperature, while stirring the solution, 100 g of 2-propyl alcohol (hereinafter referred to as IPA) was added at a rate of 2 to 3 drops/second to precipitate polyimide. Furthermore, 150 g of IPA was added, and after stirring for about 30 minutes, suction filtration was performed using a Kiriyama funnel. After washing the obtained solid with IPA, it was dried in a vacuum oven set at 120° C. for 12 hours to obtain a polyimide resin.
In Comparative Examples 2 to 5 and Comparative Examples 11 to 15, the polyimide solidified during addition of the imidization catalyst and during heating.

[Film production example]
<Examples 1 to 16, Comparative Examples 1, 6 to 10>
Polyimide (PI) obtained in the above production example and polymethyl methacrylate resin were mixed in DMF at the ratio shown in Table 1 to prepare a DMF solution with a resin content of 20% by weight. This solution was applied on a non-alkali glass plate, heated and dried in an air atmosphere for 15 minutes at 60°C, 15 minutes at 90°C, 15 minutes at 120°C, 15 minutes at 150°C, and 15 minutes at 180°C. A film with a thickness of about 50 μm was produced.

<Reference examples 1 and 2>
In Reference Example 1, a methylene chloride solution of acrylic resin 1 was prepared, and dried by heating at 60°C for 30 minutes, at 80°C for 30 minutes, at 100°C for 30 minutes, and at 110°C for 30 minutes in an air atmosphere to a thickness of approx. A 51 μm film was produced.

<Reference example 3>
In Reference Example 3, a methylene chloride solution of PI obtained in the above production example was prepared and heated at 60°C for 15 minutes, at 90°C for 15 minutes, at 120°C for 15 minutes, at 150°C for 15 minutes, and at 180°C for 15 minutes. The film was dried by heating at 200° C. for 15 minutes in an air atmosphere to produce a film with a thickness of about 56 μm.

[evaluation]
<Haze and total light transmittance>
The film was cut into 3 cm square pieces, and the haze and total light transmittance (TT) were measured using a haze meter "HZ-V3" manufactured by Suga Test Instruments in accordance with JIS K7136 and JIS K7361-1. For those with haze exceeding 20%, total light transmittance, transmittance at 400 nm, and the following yellowness, tensile modulus, and pencil hardness were not measured (in Table 1, indicated as "-") ).

<Transmittance>
The film was cut into 3 cm square pieces, and the light transmittance was measured using a UV-visible spectrophotometer (V-770, manufactured by JASCO Corporation).

<Yellowness>
The film was cut into 3 cm square pieces, and the yellowness index (YI) was measured according to JIS K7373 using a spectrophotometer "SC-P" manufactured by Suga Test Instruments.

<Tensile modulus>
The film was cut into strips with a width of 10 mm, left to stand at 23°C/55% RH for one day to condition the humidity, and then the tensile modulus was measured using Shimadzu's "AUTOGRAPH AGS-X" under the following conditions. It was measured.
Distance between grips 100mm
Tensile speed: 20.0mm/min
Measurement temperature: 23℃

<Pencil hardness>
The pencil hardness of the film was measured according to JIS K5600-5-4 "Pencil scratch test".

<Bending resistance>
The film was cut into a strip of 20 mm x 100 mm and bent at 180° at the center in the longitudinal direction, and the film was rated "O" if the film did not break, and the film was rated "x" if the film cracked.

<Polyamide solvent solubility>
DMF was added to the polyimide resin so that the solid content concentration was 10 wt%, and the mixture was stirred at room temperature for 72 hours and the solution was visually confirmed. If solid content was confirmed, it was considered insoluble.

[Evaluation results]
Table 1 shows the resin composition (polyimide composition, type of acrylic resin, and mixing ratio) and the evaluation results of the film.

In Table 1, compounds are described by the following abbreviations.
<Acid dianhydride>
BPADA: 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride TAHMBP: Bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'diyl BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic anhydride TAHQ: p-phenylene bis (trimelitate anhydride)
BP-TME: p-biphenylene bis(trimelitate anhydride)
BTDA: 3,3',4,4'-benzophenone tetracarboxylic dianhydride PMDA: Pyromellitic dianhydride

<Diamine>
TFMB: 2,2'-bis(trifluoromethyl)benzidine HFBAPP: 2,2'-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane 3,3'-DDS: 3,3'-diaminodiphenyl Sulfone m-PDA: m-phenylenediamine m-Tol: 2,2'-dimethylbenzidine BAFL: 9,9-bis(4-aminophenyl)fluorene BAPP: 2,2'-bis[4-(4-aminophenoxy) ) phenyl] propane

<Acrylic resin>
Acrylic resin 1: "Parapet HM1000" manufactured by Kuraray, glass transition temperature: 120°C, acid value: 0.0 mmol/g, hereinafter "acrylic resin 1"
Acrylic resin 2: Copolymer of methyl methacrylate/methyl acrylate (monomer ratio 87/13) (“Parapet G” manufactured by Kuraray) Glass transition temperature 109°C, acid value 0.0 mmol/g
Acrylic resin 3: Acrylic resin having a glutarimide ring ("acrylic resin (A2)" produced according to "Acrylic resin production example 2" of JP 2018-70710A), glutarimide content 4% by weight, Glass transition temperature 125°C, acid value 0.4 mmol/g
Acrylic resin 4: Syndiotactic polymethyl methacrylate (Kuraray "Parapet SP-01"), glass transition temperature 130°C, acid value 0.0 mmol/g

The films of Reference Examples 1 and 2 prepared using only acrylic resin had excellent optical properties, but were insufficient in mechanical properties such as tensile modulus, pencil hardness, and bending resistance.

In Comparative Examples 1 and 6 to 10, which used a resin composition in which a polyimide resin composed of diamine and 50 mol% or less of TFMB was mixed with an acrylic resin, the haze of the film increased significantly, and The bending resistance was insufficient. This is considered to be because the polyimide resin and the acrylic resin were not compatible.

The polyimide resins of Comparative Examples 2 to 5 and 11 in which TFMB was not used as the diamine were insoluble in solvents. In addition, the polyimides shown in Comparative Examples 12 to 15 do not contain a total of 30 mol% or more of monomers constituting BPADA and/or TAHMBP, and are insoluble in solvents, making it difficult to synthesize resin compositions containing polyimide and acrylic resin. I couldn't.

It can be seen that in Example 4 made of polyimide and acrylic resin, yellowness, total light transmittance, transmittance at a wavelength of 400 nm, and pencil hardness are improved compared to Reference Example 3 made only of polyimide resin. .

From the above results, it was found that the diamine contains 55 mol% or more of fluoroalkyl-substituted benzidine, and the tetracarboxylic dianhydride contains BPADA and/or bis(trimellitic anhydride) ester, and at least BPDA, ODPA, BTDA, and PMDA. Polyimide composed of one or more acid dianhydrides is soluble in DMF and exhibits compatibility with acrylic resin. It can be seen that by using a resin composition in which this polyimide resin and acrylic resin are mixed, a film with high transparency and excellent mechanical strength can be obtained.

Claims (11)

A resin composition containing a polyimide and an acrylic resin, wherein the polyimide has a structure derived from a tetracarboxylic dianhydride and a structure derived from a diamine, and a structure derived from a fluoroalkyl-substituted benzidine is added to the diamine-derived structure. The structure derived from the tetracarboxylic dianhydride includes a structure derived from 4,4'-(4,4'-isopropylidene diphenoxy) diphthalic anhydride and/or bis(trimellitic anhydride) ester, A resin composition that is soluble in amide solvents. In addition to the structure derived from the tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4 , 4'-oxydiphthalic anhydride, 3,4'-oxydiphthalic anhydride, pyromellitic dianhydride, merophanic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dioic anhydride, 5,5'-dimethylmethylenebis(phthalic anhydride), 3,3',4,4'-diphenylsulfone tetracarboxylic acid The resin composition according to claim 1, containing one or more selected from dianhydrides. The resin composition according to claim 1, wherein the bis(trimellitic anhydride) ester is represented by the following general formula (1).
(However, X in general formula (1) is a divalent organic group selected from the following (A) to (K), and R ¹ to R ³ are a hydrogen atom, a fluorine atom, and a carbon atom number of 20 alkyl group or a fluoroalkyl group having 1 to 20 carbon atoms, m is an integer of 1 to 4, n is an integer of 0 to 4, p is an integer of 1 to 10, and q is an integer of 0 to 4. )
The resin composition according to claim 1, wherein the fluoroalkyl-substituted benzidine is 2,2'-bis(trifluoromethyl)benzidine. The resin composition according to claim 1, wherein the content of the fluoroalkyl-substituted benzidine is 55 to 100 mol%. 2. The resin composition according to claim 1, wherein the acrylic resin contains methyl methacrylate in an amount of 60% by weight or more based on the total amount of monomer components. The resin composition according to claim 1, wherein the acrylic resin has a glass transition temperature of 80°C or higher. The resin composition according to claim 1, wherein the polyimide and the acrylic resin are contained in a weight ratio in a range of 2:98 to 98:2. A film comprising the resin composition according to any one of claims 1 to 8. The film according to claim 9, having a thickness of 5 μm or more and 300 μm or less. Claim 9: When the thickness is 50 μm, the total light transmittance is 90% or more, the haze is 3% or less, the yellowness is 5.0 or less, the tensile modulus is 2.8 GPa or more, and the pencil hardness is F or more. The film mentioned.