Resin composition and film

Abstract

To provide a transparent film having high transparency and sufficient mechanical strength, and a resin composition used for producing the same.SOLUTION: The resin composition contains a polyimide and an acrylic resin. The polyimide contains an alicyclic tetracarboxylic acid dianhydride such as 1,2,3,4-cyclobutane tetracarboxylic acid dianhydride as a tetracarboxylic acid dianhydride component. The polyimide may contain a fluoroalkyl-substituted benzidine such as 2,2'-bis(trifluoromethyl)benzidine as a diamine component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition and a film. [Background technology]

[0002] There is a demand for thinner, lighter, and more flexible electronic devices, including display devices such as liquid crystal displays, organic electroluminescence displays, and electronic paper, as well as solar cells and touch panels. By replacing the glass materials used in these devices with film materials, these devices can be made more flexible, thinner, and lighter. Transparent polyimide films have been developed as glass replacement materials and are used in display substrates, cover films, and other applications.

[0003] Conventional polyimide films are obtained by applying a polyamic acid solution, which is a polyimide precursor, to a support in the form of a film and then treating it at high temperature to remove the solvent and simultaneously perform thermal imidization. However, the heating temperature for thermal imidization is high (e.g., 300°C or higher), and coloring (increased yellowness) due to heating is likely to occur, making it difficult to apply to applications requiring high transparency, such as display cover films.

[0004] As a method for producing a highly transparent polyimide film, a method using a polyimide resin that is soluble in organic solvents and does not require high-temperature imidization after film formation has been proposed. For example, Patent Document 1 describes that a polyimide containing a bis(trimellitic anhydride) ester as a tetracarboxylic dianhydride component is soluble in a low-boiling point solvent such as dichloromethane and has excellent transparency and mechanical strength. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2020 / 004236 Summary of the Invention [Problem to be solved by the invention]

[0006] Although the introduction of a rigid structure into polyimide improves its mechanical strength, it also reduces its solubility in organic solvents and its transparency, and conventional transparent polyimide resins have not easily achieved both transparency and high mechanical strength while maintaining their transparency. In view of this problem, the present invention aims to provide a transparent film having high transparency and sufficient mechanical strength, and a resin composition for use in producing the same. [Means for solving the problem]

[0007] The present inventors have discovered that polyimides having specific chemical structures are compatible with acrylic resins, and that a resin composition obtained by mixing these can produce a highly transparent film without impairing the excellent mechanical strength of polyimides, thereby solving the above-mentioned problems.

[0008] One aspect of the present invention relates to a film and a resin composition containing a polyimide resin and an acrylic resin. The resin composition may contain the polyimide resin and the acrylic resin in a weight ratio ranging from 98:2 to 2:98.

[0009] The polyimide contains an alicyclic tetracarboxylic dianhydride such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride as a tetracarboxylic dianhydride component. The polyimide may contain, as a tetracarboxylic dianhydride component, one or more compounds selected from the group consisting of fluorine-containing aromatic tetracarboxylic dianhydrides and bis(trimellitic anhydride) esters in addition to the alicyclic tetracarboxylic dianhydride.

[0010] The amount of the alicyclic tetracarboxylic dianhydride relative to the total amount of the tetracarboxylic dianhydride components of the polyimide is preferably 1 to 80 mol %. The total content of the alicyclic tetracarboxylic dianhydride, the fluorine-containing aromatic tetracarboxylic dianhydride, and the bis(trimellitic anhydride) ester relative to the total amount of the tetracarboxylic dianhydride components of the polyimide may be 50 mol % or more.

[0011] The polyimide may contain a fluoroalkyl-substituted benzidine such as 2,2'-bis(trifluoromethyl)benzidine as a diamine component. The amount of the fluoroalkyl-substituted benzidine relative to the total amount of the diamine components of the polyimide may be 50 mol % or more.

[0012] A film according to one embodiment of the present invention has a thickness of 5 μm or more and 300 μm or less, a haze of 10% or less, a yellowness index of 2.0 or less, a tensile modulus of elasticity of 3.5 GPa or more, and a pencil hardness of F or more. The film may be a stretched film that is stretched in at least one direction. [Effects of the Invention]

[0013] The compatibility of the polyimide resin and acrylic resin contained in the resin composition allows for the production of a transparent film with low haze. Furthermore, the compatibility of the polyimide resin and acrylic resin allows for the reduction of coloration without significantly reducing the excellent mechanical strength of the polyimide, making it possible to produce a transparent film suitable for use as a cover film for displays. [Brief explanation of the drawings]

[0014] [Figure 1] 1A and 1B are transmission electron microscope images of the plan and cross sections of films of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0015] [Resin composition] One embodiment of the present invention is a compatible resin composition containing a polyimide resin and an acrylic resin.

[0016] <Polyimide> Polyimide is obtained by cyclodehydration of polyamic acid obtained by addition polymerization of tetracarboxylic dianhydride (hereinafter sometimes referred to as "acid dianhydride") and diamine. That is, polyimide is a polycondensation product of tetracarboxylic dianhydride and diamine, and has a structure derived from the acid dianhydride (acid dianhydride component) and a structure derived from the diamine (diamine component).

[0017] (acid dianhydride) The polyimide used in this embodiment contains an alicyclic tetracarboxylic dianhydride as an acid dianhydride component. When the acid dianhydride component has an alicyclic structure, the compatibility between the polyimide resin and the acrylic resin tends to be improved. The alicyclic tetracarboxylic dianhydride only needs to have at least one alicyclic structure, and may have both an alicyclic ring and an aromatic ring in one molecule. The alicyclic ring may be polycyclic or may have a spiro structure.

[0018] Examples of alicyclic tetracarboxylic dianhydrides include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, meso-butane-1,2,3,4-tetracarboxylic dianhydride, 1,1'-Bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid dianhydride, 2,2'-binorbornane-5,5',6,6'tetracarboxylic acid dianhydride, 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic acid 1,4:2,3-dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 4 -(2,5-Dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid anhydride, cyclohexane-1,4-diylbis(methylene)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride, 5,5'-[cyclohexylidenebis(4,1-phenyleneoxy)]bis-1,3-isobenzofurandione, 5-isobenzyl Benzofurancarboxylic acid, 1,3-dihydro-1,3-dioxo-,5,5'-[1,4-cyclohexanediylbis(methylene)] ester, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride, 3,5,6-tricarboxynorbornane-2-acetic acid 2,3:5,6-dianhydride, decahydro-1,4,5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic dianhydride, tricyclo[6.4.0.0(2,7)]dodecane-1,8:2,7-tetracarboxylic dianhydride, octahydro-1H,3H,8H,10H-biphenyleno[4a,4b-c:8a,8b-c']difuran-1,3,8,10-tetrone, ethylene glycol bis(hydrogenated trimellitic anhydride) ester, decahydro[2]benzopyrano[6,5,4,-def][2]benzopyran-1,3,6,8-tetrone, etc.

[0019] Among alicyclic tetracarboxylic dianhydrides, from the viewpoint of the transparency and mechanical strength of the polyimide, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA) or 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride (H-BPDA) are preferred, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride is particularly preferred.

[0020] From the viewpoint of improving compatibility between the polyimide resin and the acrylic resin, the content of the alicyclic tetracarboxylic dianhydride relative to 100 mol% of the total amount of the dianhydride components is preferably 1 mol% or more, more preferably 3 mol% or more, and even more preferably 5 mol% or more, and may be 6 mol% or more, 7 mol% or more, 8 mol% or more, 9 mol% or more, 10 mol% or more, 12 mol% or more, or 15 mol% or more. The amount of alicyclic tetracarboxylic dianhydride required to ensure compatibility with the acrylic resin may vary depending on the type of acrylic resin and the amount of alicyclic tetracarboxylic dianhydride. For example, when the alicyclic tetracarboxylic dianhydride is 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), the content of CBDA relative to 100 mol% of the total amount of the dianhydride components is preferably 6 mol% or more, more preferably 8 mol% or more, and even more preferably 10 mol% or more.

[0021] From the viewpoint of ensuring the solubility of the polyimide resin in organic solvents, the content of the alicyclic tetracarboxylic dianhydride relative to the total amount of the acid dianhydride components (100 mol%) is preferably 80 mol% or less, more preferably 78 mol% or less, and even more preferably 76 mol% or less, and may be 74 mol% or less, 72 mol% or less, 70 mol% or less, 65 mol% or less, 60 mol% or less, 55 mol% or less, or 50 mol% or less. To make the polyimide resin soluble in a low-boiling halogen-based solvent such as methylene chloride, the content of the alicyclic tetracarboxylic dianhydride is preferably 45 mol% or less, more preferably 40 mol% or less, and may be 35 mol% or less.

[0022] From the viewpoint of making the polyimide resin soluble in an organic solvent, it is preferable that the acid dianhydride component contains a fluorine-containing aromatic tetracarboxylic acid dianhydride and / or a bis(trimellitic anhydride) ester in addition to an alicyclic tetracarboxylic acid dianhydride.

[0023] Examples of the fluorine-containing aromatic tetracarboxylic dianhydride include 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride and 2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}-1,1,1,3,3,3-hexafluoropropane dianhydride.

[0024] The bis(trimellitic anhydride) ester is represented by the following general formula (1).

[0025] [ka]

[0026] In general formula (1), X is any divalent organic group, and at both ends of X, a carboxy group and a carbon atom of X are bonded. The carbon atoms bonded to the carboxy group may form a ring structure. Specific examples of the divalent organic group X include the following (A) to (K).

[0027] [ka]

[0028] R in formula (A) 1 is 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 hydroquinones having a substituent on the benzene ring include tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and 2,5-di-tert-amylhydroquinone.

[0029] R in formula (B) 2 is 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 from 0 to 4. The group represented by formula (B) is a group obtained by removing two hydroxyl groups from a 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',5,5'-tetramethylbiphenyl-4,4'-diol, and 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diol.

[0030] The group represented by formula (C) is a group obtained by removing two hydroxyl groups from 4,4'-isopropylidenediphenol (bisphenol A). The group represented by formula (D) is a group obtained by removing two hydroxyl groups from resorcinol.

[0031] In formula (E), p is an integer of 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.

[0032] The group represented by formula (F) is a group in which two hydroxyl groups have been removed from 1,4-cyclohexanedimethanol.

[0033] R in formula (G) 3 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 bisphenolfluorene derivatives having a substituent on the benzene ring having a phenolic hydroxyl group include biscresolfluorene.

[0034] The bis(trimellitic anhydride) ester is preferably an aromatic ester, and among the above (A) to (K), X is preferably (A), (B), (C), (D), (G), (H), or (I). Among these, (A) to (D) are preferred, and the group having a biphenyl skeleton of (B) is particularly preferred. When X is a group represented by general formula (B), from the viewpoint of the solubility of the polyimide resin, X is preferably 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diyl represented by the following formula (B1).

[0035] [ka]

[0036] The acid dianhydride in which X is a group represented by formula (B1) in general formula (1) is bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'diyl (abbreviation: TAHMBP) represented by the following formula (3).

[0037] [ka]

[0038] From the viewpoint of making the polyimide resin soluble in an organic solvent, the total content of the fluorine-containing aromatic tetracarboxylic acid dianhydride and the bis(trimellitic anhydride) ester relative to 100 mol% of the total amount of the dianhydride components is preferably 15 mol% or more, more preferably 20 mol% or more, even more preferably 25 mol% or more, and may be 30 mol% or more, 35 mol% or more, 40 mol% or more, 45 mol% or more, or 50 mol% or more. The total content of the fluorine-containing aromatic tetracarboxylic acid dianhydride and the bis(trimellitic anhydride) ester relative to 100 mol% of the total amount of the dianhydride components is preferably 99 mol% or less, more preferably 95 mol% or less, even more preferably 90 mol% or less, and may be 85 mol% or less, 80 mol% or less, 75 mol% or less, or 70 mol% or less.

[0039] From the viewpoint of obtaining a polyimide resin that is both soluble in organic solvents and compatible with acrylic resins, the total content of the alicyclic tetracarboxylic acid dianhydride, the fluorine-containing aromatic tetracarboxylic acid dianhydride, and the bis(trimellitic anhydride) ester relative to 100 mol% of the total amount of the acid dianhydride components is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 65 mol% or more, and may be 70 mol% or more, 75 mol% or more, 80 mol% or more, 85 mol% or more, 90 mol% or more, or 95 mol% or more.

[0040] The polyimide may contain, as the acid dianhydride component, an acid dianhydride other than the alicyclic tetracarboxylic dianhydride, the fluorine-containing aromatic tetracarboxylic dianhydride, and the bis(trimellitic anhydride) ester. Examples of the acid dianhydride other than the above include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyl tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, and the like. 1,3-bis[(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 1,3-bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 1,4 -Bis[(3,4-dicarboxy)benzoyl]benzene dianhydride, 2,2-bis{4-[4-(1,2-dicarboxy)phenoxy]phenyl}propane dianhydride, 2,2-bis{4-[4-(3,4-dicarboxy)phenoxy]phenyl}propane dianhydride, 2,2-bis{4-[3-(1,2-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 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,Examples of suitable dianhydrides include bis(4-[4-(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, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic 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, and bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid)-1,4-phenylene ester.

[0041] (diamine) The diamine component of the polyimide used in this embodiment is not particularly limited. From the viewpoint of solubility, the diamine of the polyimide resin preferably has one or more selected from the group consisting of a fluorine group, a trifluoromethyl group, a sulfone group, a fluorene structure, and an alicyclic structure. In particular, from the viewpoint of achieving both solubility and transparency of the polyimide resin, it is preferable that the polyimide contains a fluoroalkyl-substituted benzidine as the diamine component.

[0042] Examples of fluoroalkyl-substituted benzidines 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, tri(trifluoromethyl)benzidine, 2,2',3-bis(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, 2,2',5,5'-tetrakis(trifluoromethyl)benzidine, 2,2',6,6'-tetrakis(trifluoromethyl)benzidine, and the like.

[0043] Among these, fluoroalkyl-substituted benzidines having a fluoroalkyl group at the 2-position of the biphenyl are preferred, with 2,2'-bis(trifluoromethyl)benzidine (hereinafter referred to as "TFMB") being particularly preferred. By having fluoroalkyl groups at the 2- and 2'-positions of the biphenyl, the π-electron density is reduced due to the electron-withdrawing properties of the fluoroalkyl groups, and the steric hindrance of the fluoroalkyl groups causes the bond between the two benzene rings of the biphenyl to twist, reducing the planarity of the π-conjugation. This shifts the absorption edge wavelength to shorter wavelengths, thereby reducing the coloration of the polyimide.

[0044] The content of the fluoroalkyl-substituted benzidine relative to the total amount of the diamine components (100 mol%) is preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more, and may be 80 mol% or more, 85 mol% or more, or 90 mol% or more. A high content of the fluoroalkyl-substituted benzidine tends to suppress coloration of the film and increase mechanical strength such as pencil hardness and elastic modulus.

[0045] The polyimide may contain a diamine other than fluoroalkyl-substituted benzidine as a diamine component. Examples of the diamine other than fluoroalkyl-substituted benzidine include p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl sulfone. Diphenyl sulfone, 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-( 1,3-bis[4-(4-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-dimethyl benzyl]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]diphenyl sulfone, 4,4'-bis[4-(4-aminophenoxy)phenoxy]diphenyl sulfone, 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'-spirobiindan, 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindan, 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(aminomethyl)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 cyclohexane, 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-aminocyclohexyl)methane, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane butane, 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)benzene, 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'-dimethylbenzidine, 2-fluorobenzidine, 3-fluorobenzidine, 2,3-difluorobenzidine, 2,5-difluorobenzidine, 2,6-difluorobenzidine, 2,3,5-trifluorobenzidine, 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.

[0046] For example, the use of diaminodiphenyl sulfone in addition to fluoroalkyl-substituted benzidine as a diamine can improve the solubility in solvents and transparency of polyimide resins. Among diaminodiphenyl sulfones, 3,3'-diaminodiphenyl sulfone (3,3'-DDS) and 4,4'-diaminodiphenyl sulfone (4,4'-DDS) are preferred. 3,3'-DDS and 4,4'-DDS may also be used in combination.

[0047] The content of diaminodiphenylsulfone relative to 100 mol % of the total amount of diamines may be 1 to 40 mol %, 3 to 30 mol %, or 5 to 25 mol %.

[0048] (Preparation of Polyimide) The reaction of an acid dianhydride with a diamine yields a polyamic acid as a polyimide precursor, and the polyamic acid is then cyclized (imidized) to obtain a polyimide. As described above, by adjusting the composition of the polyimide, i.e., the types and ratios of the acid dianhydride and diamine, the polyimide has transparency and solubility in organic solvents, and is compatible with acrylic resins.

[0049] The method for preparing polyamic acid is not particularly limited, and any known method can be used. For example, a polyamic acid solution can be obtained by dissolving an acid dianhydride and a diamine in approximately equimolar amounts (a molar ratio of 95:100 to 105:100) in an organic solvent and stirring the mixture. The concentration of the polyamic acid solution is usually 5 to 35% by weight, and 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.

[0050] In the polymerization of polyamic acid, it is preferable to add the 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 all at once or in multiple portions. The physical properties of the polyimide can also be controlled by adjusting the order of addition of the monomers.

[0051] The organic solvent used in the polymerization of polyamic acid is not particularly limited as long as it does not react with diamines and 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 dimethyl sulfoxide, diphenyl sulfone, and tetramethyl sulfone; amide-based solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N,N'-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, and hexamethylphosphoric triamide; alkyl halide solvents such as chloroform and methylene chloride; aromatic hydrocarbon solvents such as benzene and toluene; and ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. These solvents are typically used alone or in combination as needed. From the viewpoint of the solubility and polymerization reactivity of polyamic acid, DMAc, DMF, NMP, etc. are preferably used.

[0052] Polyimides are obtained by the dehydration and cyclization of polyamic acid. One method for preparing polyimides from polyamic acid solutions involves adding a dehydrating agent, an imidization catalyst, etc. to the polyamic acid solution and allowing imidization to proceed in the solution. Heating the polyamic acid solution can be used to accelerate the imidization process. Mixing a solution containing the polyimide produced by imidization of polyamic acid with a poor solvent results in the precipitation of a polyimide resin as a solid. Isolating the polyimide resin as a solid allows for the removal of impurities generated during polyamic acid synthesis, as well as residual dehydrating agents and imidization catalysts, by washing with a poor solvent, thereby preventing discoloration and increased yellowness of the polyimide. Furthermore, isolating the polyimide resin as a solid allows for the use of solvents suitable for film formation, such as low-boiling point solvents, when preparing a solution for film production.

[0053] The molecular weight of the polyimide (weight average molecular weight in terms of polyethylene oxide measured by gel permeation chromatography (GPC)) is preferably 10,000 to 300,000, more preferably 20,000 to 250,000, and even more preferably 40,000 to 200,000. If the molecular weight is too small, the strength of the film may be insufficient. If the molecular weight is too large, the compatibility with the acrylic resin may be poor.

[0054] The polyimide is preferably soluble in a low-boiling-point solvent such as a ketone solvent or an alkyl halide solvent. The term "solubility of a polyimide in a solvent" means that the polyimide is soluble in a concentration of 5% by weight or more. In one embodiment, the polyimide is soluble in methylene chloride. Methylene chloride has a low boiling point, making it easy to remove residual solvent during film production. Therefore, the use of a polyimide resin soluble in methylene chloride is expected to improve film productivity.

[0055] From the viewpoint of the thermal stability and light stability of the resin composition and film, it is preferable that the polyimide has low reactivity. 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. From the viewpoint of reducing the acid value, it is preferable that the polyimide has a high imidization rate. A low acid value tends to increase the stability of the polyimide and improve its compatibility with acrylic resins.

[0056] <Acrylic resin> Examples of acrylic resins include poly(meth)acrylic acid esters such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylic acid ester copolymers, methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymers, methyl (meth)acrylate-styrene copolymers, etc. The acrylic resins may be modified to introduce glutarimide structural units or lactone ring structural units.

[0057] From the viewpoints of transparency, compatibility with polyimide, and mechanical strength of molded articles such as films, the acrylic resin is preferably one having methyl methacrylate as the main structural unit. The amount of methyl methacrylate relative to 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, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The acrylic resin may be a homopolymer of methyl methacrylate. Alternatively, the acrylic resin may be an acrylic polymer having a methyl methacrylate content within the above range, into which a glutarimide structure or a lactone ring structure has been introduced.

[0058] From the viewpoint of heat resistance of the film, the glass transition temperature of the acrylic resin is preferably 100°C or higher, more preferably 110°C or higher, and may be 115°C or higher or 120°C or higher.

[0059] From the viewpoints of solubility in organic solvents, compatibility with the polyimide, and film strength, the weight average molecular weight (polystyrene equivalent) of the acrylic resin is preferably 5,000 to 500,000, more preferably 10,000 to 300,000, and even more preferably 15,000 to 200,000.

[0060] From the viewpoint of the thermal and light stability of the resin composition and film, it is preferable that the acrylic resin have 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 even more preferably 5.08 g / 100 g (0.2 mmol / g) or less. 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 small acid value tends to increase the stability of the acrylic resin and improve its compatibility with polyimide.

[0061] <Preparation of Resin Composition> The polyimide resin and the acrylic resin are mixed to prepare a resin composition. The polyimide resin and the acrylic resin can be compatible at any ratio, so the ratio of the polyimide resin to the acrylic resin in the resin composition is not particularly limited. The mixing ratio (weight ratio) of the polyimide resin to the acrylic resin may be 98:2 to 2:98, 95:5 to 10:90, or 90:10 to 15:85. The higher the ratio of the polyimide resin, the higher the elastic modulus and pencil hardness of the film, and the better the mechanical strength. The higher the ratio of the acrylic resin, the less coloring the film tends to have and the higher its transparency. To fully utilize the transparency-improving effect of mixing the polyimide and the acrylic resin, the ratio of the acrylic resin to the total of the polyimide and the acrylic resin is preferably 10% by weight or more, and may be 15% by weight or more, 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, 45% by weight or more, or 50% by weight or more.

[0062] Polyimide is a polymer having a unique molecular structure, and generally has low solubility in organic solvents and is not compatible with other polymers. In this embodiment, the polyimide contains an alicyclic tetracarboxylic dianhydride as an acid anhydride component, and thus exhibits high solubility in organic solvents and compatibility with acrylic resins.

[0063] A resin composition containing a polyimide and an acrylic resin preferably has a single glass transition temperature in differential scanning calorimetry (DSC) and / or dynamic mechanical analysis (DMA). When a resin composition has a single glass transition temperature, the polyimide and the acrylic resin can be considered to be completely compatible. A film containing a polyimide and an acrylic resin also preferably has a single glass transition temperature.

[0064] The resin composition may be a mixed solution containing a polyimide resin and an acrylic resin. The method for mixing the resins is not particularly limited, and the resins may be mixed in a solid state or in a liquid state to form a mixed solution. A polyimide resin solution and an acrylic resin solution may be prepared separately, and then the two may be mixed to prepare a mixed solution of the polyimide resin and the acrylic resin.

[0065] 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 the solvent 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; ketone solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diethyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone; and alkyl halide solvents such as chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chlorobenzene, dichlorobenzene, and methylene chloride. Among these, ketone solvents and alkyl halide solvents are preferred because they have excellent solubility in both the polyimide resin and the acrylic resin, a low boiling point, and allow for easy removal of residual solvent during film production.

[0066] For the purpose of improving the processability of the film or imparting various functions, the resin composition (solution) may contain organic or inorganic low molecular weight compounds, polymeric compounds (e.g., epoxy resins), etc. The resin composition may contain flame retardants, ultraviolet absorbers, crosslinking agents, dyes, pigments, surfactants, leveling agents, plasticizers, fine particles, sensitizers, etc. The fine particles include organic fine particles such as polystyrene and polytetrafluoroethylene, and inorganic fine particles such as colloidal silica, carbon, and layered silicates, and may have a porous or hollow structure. The fiber reinforcing material includes carbon fiber, glass fiber, aramid fiber, etc.

[0067] [Molded products and films] The above composition can be used to form various molded articles. Molding methods include melt methods such as injection molding, transfer molding, press molding, blow molding, inflation molding, calendar molding, and melt extrusion molding. Resin compositions containing polyimide and acrylic resin tend to have lower melt viscosity than polyimide alone, and are excellent in moldability in injection molding, transfer molding, press molding, melt extrusion molding, and the like.

[0068] Furthermore, a solution of a resin composition containing a polyimide and an acrylic resin tends to have a lower solution viscosity than a solution of a polyimide alone at the same solid content concentration, which is advantageous in terms of ease of handling during transportation and the like, high coatability, and reduction of unevenness in film thickness.

[0069] In one embodiment, the molded article is a film. The film molding method may be either a melting method or a solution method, but the solution method is preferred from the viewpoint of producing a film excellent in transparency and uniformity. In the solution method, a solution containing the above-mentioned polyimide resin and acrylic resin is applied to a support, and the solvent is dried and removed to obtain a film.

[0070] The resin solution can be applied to a support by a known method using a bar coater, a comma coater, or the like. Examples of the support that can be used include a glass substrate, a metal substrate such as SUS, a metal drum, a metal belt, and a plastic film. From the viewpoint of improving productivity, it is preferable to use an endless support such as a metal drum or a metal belt, or a long plastic film as the support and produce the film by a roll-to-roll method. When using a plastic film as the support, it is sufficient to appropriately select a material that is insoluble in the solvent of the film-forming dope.

[0071] It is preferable to heat the film when drying the solvent. The heating temperature is not particularly limited as long as it can remove the solvent and prevent the resulting film from becoming discolored, and is appropriately set between room temperature and about 250°C, preferably between 50°C and 220°C. The heating temperature may be increased stepwise. 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. Heating may be performed under reduced pressure to promote solvent removal.

[0072] Although acrylic films may have low toughness, the strength of the film may be improved by using a compatible system of polyimide and acrylic resin. Stretching may be performed in one or more directions to improve the mechanical strength of the film. Stretching a film orients the polymer chains in the stretching direction, improving the strength of the film in the in-plane direction and tending to suppress the occurrence of breakage or cracks in the film.

[0073] In particular, in a compatible system of polyimide and acrylic resin, the tensile modulus in the stretching direction tends to increase, and as a result, the flex resistance tends to improve. The higher the ratio of methyl methacrylate in the monomer components of the acrylic resin, the more pronounced the tendency for the tensile modulus in the stretching direction to increase.

[0074] For example, films used as cover films or substrate materials for foldable displays are repeatedly folded along the folding axis at the same location, and therefore are required to have high mechanical strength in a direction perpendicular to the folding axis. Therefore, by arranging the film so that the stretching direction is perpendicular to the folding axis, the film is less likely to break or crack at the folding location even when repeatedly folded, and a device with high bending resistance can be provided.

[0075] The conditions for stretching the film are not particularly limited. For example, the stretching temperature is about ±40°C of the glass transition temperature of the film, and may be about 120 to 300°C, 150 to 250°C, or 180 to 230°C. The stretching ratio is about 1 to 200%, and may be 5 to 150%, 10 to 120%, or 20 to 100%. The higher the stretching ratio, the higher the tensile modulus in the stretching direction tends to be. On the other hand, if the stretching ratio is too high, the mechanical strength in the direction perpendicular to the stretching direction tends to decrease, and the handleability of the film may be reduced.

[0076] The film may be biaxially stretched to increase the strength in any in-plane direction. The biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. In biaxial stretching, the stretching ratio in one direction and the stretching ratio in the perpendicular direction may be the same or different. When a difference in stretching ratio is made, the mechanical strength in the direction with the larger stretching ratio tends to be relatively larger. When a biaxially stretched film with anisotropic stretching ratio is used in a foldable device, it is preferable to arrange it so that the direction with the larger stretching ratio is perpendicular to the folding axis.

[0077] The thickness of the film is not particularly limited and may be appropriately set depending on the application. The thickness of the film is, for example, 5 to 300 μm. From the viewpoint of obtaining a film that is both self-supporting and flexible and has high transparency, 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 cover film for a display is preferably 50 μm or more. When the film is stretched, the thickness after stretching is preferably within the above range.

[0078] The haze of the film is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, and may be 3.5% or less, 3% or less, 2% or less, or 1% or less. The lower the haze of the film, the better. As described 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 obtained by mixing polyimide and acrylic resin has a haze of 10% or less when a film with a thickness of 50 μm is produced.

[0079] The yellowness index (YI) of the film is preferably 2.0 or less, and may be 1.5 or less, or 1.0 or less. As described above, by mixing a polyimide resin with an acrylic resin, a film with less coloration and a small YI can be obtained compared to when a polyimide resin is used alone.

[0080] From the viewpoint of strength, the tensile modulus of the film is preferably 3.5 GPa or more, and may be 4.0 GPa or more. As described above, the tensile modulus may be anisotropic, and the tensile modulus in at least one direction may be 4.5 GPa or more, 5.0 GPa or more, 5.5 GPa or more, 6.0 GPa or more, 6.5 GPa or more, or 7.0 GPa or more. The pencil hardness of the film is preferably F or more, and may be H or more or 2H or more. In a compatible system of polyimide and acrylic resin, the pencil hardness is unlikely to decrease even if the ratio of acrylic resin is increased. Therefore, a film with little coloration and excellent transparency can be provided without significantly decreasing the excellent mechanical strength unique to polyimide.

[0081] Films formed from resin compositions containing polyimide and acrylic resins are suitable for use as display materials because they have little coloring and high transparency. In particular, films with high mechanical strength can be applied to surface components such as display cover windows. When used in practice, the film of the present invention may be provided on its surface with an antistatic layer, an easy-adhesion layer, a hard coat layer, an antireflection layer, or the like. [Example]

[0082] The following examples will be used to further explain the present invention, but the present invention is not limited to these examples.

[0083] [Example of polyimide resin production] Dimethylformamide was placed in a separable flask and stirred under a nitrogen atmosphere. Diamine and acid dianhydride were then added in the ratios (mol %) shown in Table 1, and the mixture was stirred under a nitrogen atmosphere for 5 to 10 hours to react, yielding a polyamic acid solution with a solids concentration of 18 wt %.

[0084] 5.5 g of pyridine was added as an imidization catalyst to 100 g of polyamic acid solution, and after complete dispersion, 8 g of acetic anhydride was added and stirred at 90°C for 3 hours. After cooling to room temperature, 100 g of 2-propyl alcohol (hereinafter referred to as IPA) was added at a rate of 2-3 drops per second while stirring the solution, causing polyimide to precipitate. 150 g of IPA was then added, and after stirring for approximately 30 minutes, the solution was subjected to suction filtration using a Kiriyama funnel. The resulting solid was washed with IPA and then dried for 12 hours in a vacuum oven set at 120°C to obtain a polyimide resin.

[0085] [Film production example] <Examples 1 to 10, 17 to 19, Comparative Examples 1 to 3> The polyimide (PI) obtained in the above Production Example and a commercially available polymethyl methacrylate resin ("Parapet HM1000" manufactured by Kuraray, glass transition temperature: 120°C, acid value: 0.0 mmol / g, hereafter referred to as "acrylic resin 1") were mixed in methylene chloride in the ratios shown in Table 1 to prepare a methylene chloride solution with a resin content of 11 wt%. This solution was applied to an alkali-free glass plate and dried by heating in air at 60°C for 15 minutes, 90°C for 15 minutes, 120°C for 15 minutes, 150°C for 15 minutes, 180°C for 15 minutes, and 200°C for 15 minutes to produce a film with a thickness of approximately 50 μm.

[0086] <Examples 11 to 16> Films were produced under the same conditions as above, except that acrylic resin 1 was replaced with the following acrylic resins 2 to 7 (all of which are acrylic copolymers or modified products thereof having methyl methacrylate as the main monomer component). Acrylic resin 2: Kuraray "Parapet HR-G", glass transition temperature 116°C, acid value 0.0 mmol / g Acrylic resin 3: Methyl methacrylate / methyl acrylate (monomer ratio 81 / 19) copolymer (Kuraray "Parapet GF"), glass transition temperature 102°C, acid value 0.0 mmol / g Acrylic resin 4: Methyl methacrylate / methyl acrylate (monomer ratio 87 / 13) copolymer (Kuraray "Parapet G"), glass transition temperature 109°C, acid value 0.0 mmol / g Acrylic resin 5: Methyl methacrylate / methyl acrylate (monomer ratio 96 / 4) copolymer (Kuraray "Parapet EH"), glass transition temperature 116°C, acid value 0.0 mmol / g Acrylic resin 6: Syndiotactic polymethyl methacrylate (Kuraray "Parapet SP-01"), glass transition temperature 130°C, acid value 0.0 mmol / g Acrylic resin 7: Acrylic resin having a glutarimide ring ("Acrylic resin (A2)" prepared according to "Acrylic resin production example 2" in JP 2018-70710 A), glutarimide content 4 wt%, glass transition temperature 125°C, acid value 0.4 mmol / g

[0087] Example 17 A film was prepared under the same conditions as above, except that methyl ethyl ketone was used as the solvent instead of methylene chloride.

[0088] <Reference examples 1~4> In Reference Examples 1, 3, and 4, a methylene chloride solution of a polyimide resin was prepared, and a film having a thickness of approximately 50 μm was produced under the same conditions as above. In Reference Example 2, a methylene chloride solution of acrylic resin 1 was prepared, and a film having a thickness of approximately 50 μm was produced under the same conditions as above, except that the heating conditions during drying were changed to 60°C for 30 minutes, 80°C for 30 minutes, 100°C for 30 minutes, and 110°C for 30 minutes.

[0089] [evaluation] <Haze and total light transmittance> The films were cut into 3 cm squares, and the haze and total light transmittance (TT) were measured using a Suga Test Instruments haze meter "HZ-V3" in accordance with JIS K7136 and JIS K7361-1. For films with a haze of more than 20%, the total light transmittance, yellowness index, tensile modulus, and pencil hardness measurements were not performed.

[0090] <Yellowness> The film was cut into 3 cm squares, and the yellowness index (YI) was measured according to JIS K7373 using a spectrophotometer "SC-P" manufactured by Suga Test Instruments.

[0091] <Tensile modulus> The film was cut into strips 10 mm wide and left to stand at 23°C / 55% RH for one day to condition the humidity. Then, the tensile modulus was measured using Shimadzu Corporation's "AUTOGRAPH AGS-X" under the following conditions. Grip distance: 100 mm Tensile speed: 20.0 mm / min Measurement temperature: 23℃

[0092] <Pencil hardness> The pencil hardness of the film was measured according to JIS K5600-5-4 "Pencil Scratch Test".

[0093] <Bending resistance> The film was cut into strips of 20 mm x 100 mm and folded 180° in the center of the lengthwise direction. Films that did not crack were marked "good", and films that cracked were marked "poor".

[0094] <Transmission electron microscope (TEM) observation> The planar (film surface) and cross-section of the films of Example 9 and Comparative Example 2 were observed using a transmission electron microscope (magnification: 10,000 times). TEM observation was also carried out on the stretched film of Example 53 described below. The TEM image is shown in Figure 1.

[0095] [Evaluation results] Table 1 shows the resin composition (polyimide composition, type of acrylic resin, and mixing ratio) and the evaluation results of the film.

[0096] In Table 1, the compounds are described by the following abbreviations: <Acid dianhydride> CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride H-PMDA: 1,2,4,5-cyclohexanetetracarboxylic dianhydride H-BPDA: 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride TAHMBP: bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diyl 6FDA: 2,2-bis(3,4-dicarboxyphenyl)-1,1,1,3,3,3-hexafluoropropane dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic dianhydride <Diamine> TFMB: 2,2'-bis(trifluoromethyl)benzidine 3,3'-DDS: 3,3'-diaminodiphenyl sulfone

[0097] [Table 1]

[0098] The polyimide film of Reference Example 1, which was produced using only polyimide resin, had a YI of more than 2 and was therefore insufficient in transparency. The same was true for the polyimide film of Reference Example 4. On the other hand, the acrylic film of Reference Example 2, which was produced using only acrylic resin 1, had a low tensile modulus and a pencil hardness of HB, and therefore was insufficient in mechanical strength. The acrylic film of Reference Example 2 also had insufficient bending resistance.

[0099] In Comparative Example 1, which used a resin composition obtained by mixing the same polyimide resin and acrylic resin 1 as in Reference Example 4, the haze of the film increased significantly. The same was true for Comparative Examples 2 to 4, and the films of Comparative Examples 1 to 4 had insufficient bending resistance, similar to the acrylic film of Reference Example 2. As shown in FIG. 1, a sea-island structure was confirmed in the TEM image of the film of Comparative Example 2, and therefore, it is believed that the transparency and mechanical strength of Comparative Examples 1 to 4 were low due to the low compatibility between the polyimide resin and the acrylic resin.

[0100] In Example 1, which used a resin composition obtained by mixing the same polyimide resin as in Reference Example 1 with acrylic resin 1, the YI was smaller and the total light transmittance was also increased compared to Reference Example 1. In Example 1, the increase in haze was suppressed compared to Comparative Examples 1 to 4. In Example 1, although the tensile modulus and pencil hardness were lower than in Reference Example 1, sufficient mechanical strength was exhibited and bending resistance was improved compared to Reference Example 2, which used an acrylic resin alone.

[0101] In Examples 2 to 10, and 17, which used polyimide resins different from Example 1, the increase in haze of the films was suppressed, the YI was small, and the mechanical strength was excellent, similar to Example 1. As shown in FIG. 1, the TEM image of the film of Example 9 did not confirm a sea-island structure, indicating that the polyimide resin and the acrylic resin were completely compatible. From these results, it is believed that in Examples 1 to 10, and 17, the polyimide contained CBDA, which has an alicyclic structure, as a tetracarboxylic dianhydride component, thereby improving the compatibility between the polyimide and the acrylic resin and suppressing the increase in haze.

[0102] Examples 18 and 19, which used polyimides containing H-PMDA as the tetracarboxylic dianhydride having an alicyclic structure, and Example 20, which used polyimide containing H-BPDA as the tetracarboxylic dianhydride having an alicyclic structure, also produced films with excellent transparency and mechanical strength, similar to Examples 1 to 10. Furthermore, Examples 11 to 16, which used acrylic resins 2 to 7, also produced films with excellent transparency and mechanical strength, similar to Examples 1 to 10, etc.

[0103] The above results demonstrate that polyimides containing alicyclic tetracarboxylic dianhydrides as the tetracarboxylic dianhydride component are compatible with acrylic resins, and that the use of a resin composition containing these polyimides can provide films with high transparency and excellent mechanical strength.

[0104] [Preparation and evaluation of stretched films] <Examples 31, 41, 51 to 55, 61 to 67, Reference Examples 21 and 22> Films containing polyimide resin and acrylic resin were prepared in the same manner as in each of the above examples, and stretched films were obtained by free-end uniaxial stretching at the temperature and stretching ratio shown in Table 2. In Reference Examples 21 and 22, films of acrylic resin 1 were prepared in the same manner as in Reference Example 2 and stretched.

[0105] The obtained stretched film was evaluated in the same manner as above. The tensile modulus was evaluated in both the stretching direction (referred to as "MD") and the direction perpendicular to the stretching direction (referred to as "TD"). Furthermore, the following bending resistance test was carried out.

[0106] <Bending resistance test> The film was cut into strips measuring 20 mm in the TD and 120 mm in the MD. The short sides of the test specimens were attached to a U-shaped stretch test fixture (Yuasa System Instruments, "DMX-FS") and subjected to repeated bending tests at a temperature of 23°C and relative humidity of 55% using a tabletop durability tester (Yuasa System Instruments, "DMLHB") under conditions of a bending radius of 1.0 mm, a bending angle of 180°C, and a bending rate of 1 bending / second. The MD bending resistance (the number of bendings until the film broke) was measured. For stretched films, similar tests were performed on strip samples with the long side in the TD to measure the TD bending resistance. If the film did not break after 100,000 bending cycles, the TD bending resistance was determined to be 100,000 cycles.

[0107] Table 2 shows the resin compositions (polyimide compositions, types and mixing ratios of acrylic resins), stretching conditions, and film evaluation results for Examples 31, 41, 51 to 55, 61 to 67, and Reference Examples 21 and 22. Table 2 also shows data for Examples 7 to 16 and Reference Example 2. In the table, "ND" indicates that no evaluation was performed on the tensile modulus and flex endurance test.

[0108] [Table 2]

[0109] In Reference Examples 21 and 22, in which a resin film consisting of a single acrylic resin film was stretched, no clear difference was observed in the tensile modulus in MD and TD, and the tensile modulus was equivalent to that of the unstretched film of Reference Example 2. On the other hand, in Examples 51 to 55, the MD tensile modulus was higher than that of the unstretched film of Example 9, and the MD tensile modulus tended to increase with increasing stretch ratio. Furthermore, in Examples 51 to 55, the flex resistance in both MD and TD was improved compared to Example 9. As shown in Figure 1, the film of Example 53, like Example 9, did not exhibit a sea-island structure in the TEM image, indicating that the film maintained a completely compatible system even after stretching.

[0110] In Examples 31, 41, and 61 to 67, the tensile modulus in MD was larger than that of the unstretched film, and the bending resistance in both MD and TD was improved.

[0111] No clear difference in tensile modulus was observed in the unstretched films of Examples 9, and 12 to 16. On the other hand, among Examples 54, 63 to 67 in which films of the same composition were stretched at a stretch ratio of 90%, Examples 66 and 67, which used acrylic resins 1, 6, and 7 with a high ratio of methyl methacrylate in the acrylic resin monomer composition, had MD tensile moduli exceeding 7 GPa, indicating a tendency for the tensile modulus in the stretching direction to increase as the ratio of methyl methacrylate increases.

Claims

1. The polyimide and the acrylic resin are contained in a weight ratio ranging from 98:2 to 2:98, the polyimide contains, as a tetracarboxylic acid dianhydride component, one or more selected from the group consisting of an alicyclic tetracarboxylic acid dianhydride, a fluorine-containing aromatic tetracarboxylic acid dianhydride, and a bis(trimellitic anhydride) ester, and contains, as a diamine component, a fluoroalkyl-substituted benzidine; the amount of the alicyclic tetracarboxylic acid dianhydride is 1 to 80 mol % relative to the total amount of the tetracarboxylic acid dianhydride components of the polyimide, and the total content of the alicyclic tetracarboxylic acid dianhydride, the fluorine-containing aromatic tetracarboxylic acid dianhydride, and the bis(trimellitic anhydride) ester is 50 mol % or more; the amount of fluoroalkyl-substituted benzidine relative to the total amount of diamine components of the polyimide is 50 mol % or more; The acrylic resin has a total amount of methyl methacrylate and modified methyl methacrylate structures of 60% by weight or more based on the total amount of monomer components. Resin composition.

2. The alicyclic tetracarboxylic dianhydride is at least one selected from the group consisting of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, and 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride. The resin composition according to claim 1.

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

4. The resin composition according to any one of claims 1 to 3, wherein the acrylic resin has a glass transition temperature of 110°C or higher.

5. A film comprising the resin composition according to any one of claims 1 to 4.

6. 6. The film according to claim 5, having a thickness of 5 μm or more and 300 μm or less, a total light transmittance of 85% or more, a haze of 10% or less, a yellowness index of 2.0 or less, a tensile modulus of 3.5 GPa or more, and a pencil hardness of F or more.

7. 7. The film according to claim 5, which is a stretched film stretched in at least one direction.

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