Resin composition, molded body, and film

Abstract

This resin composition includes a polyimide and a polyester. The polyester has a weight-average molecular weight of more than 10,000. The polyimide includes, as a diamine component, a diamine having at least one structure selected from CF3-O-, -(CF2-O)n-, and -O-(CF2-CF2-O)n- (where n is an integer of 1-20), and the diamine is preferably 2,2'-bis(trifluoromethoxy)benzidine, 3,3'-bis(trifluoromethoxy)benzidine, 2,3'-bis(trifluoromethoxy)benzidine, or the like.

Description

Resin composition, molded article and film

[0001] The present invention relates to a resin composition, a molded article, and a film.

[0002] There is a demand for thinner, lighter, and more flexible electronic devices, such as display devices (e.g., liquid crystal displays, organic electroluminescence displays, and electronic paper), 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 for display substrates, cover films, and the like.

[0003] Although transparent polyimide has superior heat resistance compared to general-purpose transparent resins, higher transparency is required when used as a cover film for a display, etc. As a method for improving the transparency of a transparent polyimide film, the use of a resin composition in which polyimide is mixed with another resin has been proposed. Patent Document 1 proposes a resin composition in which polyimide is mixed with an acrylic resin, and Patent Document 2 proposes a resin composition in which polyimide is mixed with polycarbonate or polyarylate.

[0004] International Publication No. 2023 / 026982 International Publication No. 2021 / 132279

[0005] In Patent Documents 1 and 2, a solvent-soluble polyimide containing a fluoroalkyl-substituted benzidine such as 2,2'-bis(trifluoromethyl)benzidine (TFMB) as a diamine is used. Polyimides using fluorine-containing compounds as diamines and / or tetracarboxylic dianhydrides have excellent transparency and solvent solubility.

[0006] On the other hand, in recent years, the environmental persistence of organic fluorine compounds (PFAS) has become a problem. In general, the carbon-fluorine bond contained in organic fluorine compounds has high bond energy and is difficult to decompose in the environment. In particular, the structure in which a trifluoromethyl group is bonded to a carbon atom (-C-CF ３ ), or a structure in which carbon atoms are bonded to both ends of a difluoromethylene group (—C—CF ２Organic fluorine compounds containing fluorine atoms (C) have low decomposition properties in the environment and have been reported to have adverse effects on the human body.

[0007] In view of the above problems, the present invention aims to provide a molded article such as a film containing a polyimide that is environmentally safe and highly transparent, and a resin composition used for producing the same.

[0008] The present invention relates to a resin composition containing a polyimide and a polyester, and a molded article such as a film containing the resin composition. ３ -O-, -(CF ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ - (CF ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ In the -, n is an integer of 1 to 20.

[0009] Preferred examples of the specific diamine that is a fluorine atom-containing diamine include 2,2'-bis(trifluoromethoxy)benzidine, 3,3'-bis(trifluoromethoxy)benzidine, and 2,3'-bis(trifluoromethoxy)benzidine.

[0010] The polyimide preferably contains, as a tetracarboxylic acid dianhydride component, one or more tetracarboxylic acid dianhydrides (specific acid dianhydrides) selected from the group consisting of bisphenol-type tetracarboxylic acid dianhydrides, bis(trimellitic anhydride) esters, and tetracarboxylic acid dianhydrides having a fluorene structure.

[0011] Preferred examples of the specific acid dianhydride include 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride, 1,4-phenylenebis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diylbis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), bisphenol Z bis(trimellitic anhydride), 5,5'-[cyclododecylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate), 9,9-bis(3,4-dicarboxylic anhydride), ...1,4-phenylenebis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), 1,4-phenylenebis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), 1,4-phenylenebis(1,3-dioxo-1,3-dihydroiso and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-fluorene]-1,3,7,9-tetraone.

[0012] The polyimide may contain an alicyclic tetracarboxylic dianhydride as a tetracarboxylic dianhydride component in addition to the specific acid dianhydride. The amount of the alicyclic tetracarboxylic dianhydride relative to the total amount of the tetracarboxylic dianhydride components of the polyimide may be 1 to 80 mol %.

[0013] Polyimide is a compound in which the carbon atoms of the aromatic ring are bonded with CF ３ - or -C(CF ３ ) ２ The amount of diamine having a structure in which - is directly bonded is less than 0.5 mol %, and the amount of CF on the carbon atom of the aromatic ring is less than 0.5 mol % based on the total amount of the tetracarboxylic dianhydride component. ３ - or -C(CF ３ ) ２The amount of tetracarboxylic dianhydride having a structure in which - is directly bonded is preferably less than 0.5 mol %.

[0014] The weight-average molecular weight of the polyester is greater than 10,000. The polyester preferably contains, as a diol component, at least one selected from the group consisting of diols having a chain alkylene group having 3 or more carbon atoms which may be branched, diols having a chain alkenylene group having 3 or more carbon atoms which may be branched, polyalkylene glycols, and diols having a cyclic structure.

[0015] Among the above diols, diols having a fluorene structure and diols having a bisphenol derivative structure are preferred. Examples of diols having a bisphenol derivative structure include bisphenol alkylene oxide adducts such as bisphenol EO adducts and bisphenol PO adducts.

[0016] The resin composition may contain polyimide and polyester in a weight ratio ranging from 98:2 to 2:98.

[0017] Molded articles such as films formed from the resin composition of the present invention have high light transmittance and excellent transparency. In addition, since the polyimide contains a specific diamine as a diamine component, it has low environmental residual properties and excellent environmental safety compared to polyimides using organic fluorine compounds such as fluoroalkyl-substituted benzidine.

[0018] [Resin Composition] One embodiment of the present invention is a compatible resin composition containing polyimide and polyester. Due to the compatibility between polyimide and polyester, a molded article such as a film formed from the resin composition exhibits transparency.

[0019] [Polyimide] Polyimide is a polymer having a structural unit represented by general formula (I) and is obtained by dehydrating and cyclizing a polyamic acid obtained by addition polymerization of a tetracarboxylic dianhydride (hereinafter sometimes referred to as "acid dianhydride") and a diamine. That is, polyimide is a polycondensation product of a tetracarboxylic dianhydride and a diamine, and has a structure derived from the tetracarboxylic dianhydride (acid dianhydride component) and a structure derived from the diamine (diamine component). Note that polyimide can also be synthesized by condensation via decarboxylation of a diisocyanate and a tetracarboxylic dianhydride.

[0020]

[0021] In general formula (I), X is a tetravalent organic group, and Y is a divalent organic group. X is a tetracarboxylic dianhydride residue, which is an organic group obtained by removing two carboxy anhydride groups from a tetracarboxylic dianhydride represented by the following general formula (II). Y is a diamine residue, which is an organic group obtained by removing two amino groups from a diamine represented by the following general formula (III). When synthesizing a polyimide using a diisocyanate, Y is an organic group obtained by removing two isocyanate groups from a diisocyanate compound, and in this case too, the divalent organic group Y is referred to as a "diamine residue."

[0022]

[0023] In other words, the polyimide contains a structural unit represented by the following general formula (IIa) and a structural unit represented by the following general formula (IIIa), and the tetracarboxylic dianhydride-derived structure (IIa) and the diamine-derived structure (IIIa) form an imide bond, thereby having the structural unit represented by general formula (I).

[0024]

[0025] The polyimide may contain multiple types of tetracarboxylic dianhydride residues X, or multiple types of diamine residues Y. Hereinafter, the diamine component and the acid dianhydride component as monomer units constituting the polyimide will be described with reference to examples.

[0026] <Diamine> The polyimide according to an embodiment of the present invention contains CF as a diamine component. ３ -O-, -(CF ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ -, wherein n is an integer of 1 to 20. Hereinafter, these diamines will be referred to as "specific diamines."

[0027] In certain diamines, a trifluoromethyl group (-CF ３ ) or a difluoromethylene group (—CF ２ The carbon atom of the alkyl group (-C-CF) is bonded to an oxygen atom, and a trifluoromethyl group is bonded to the carbon atom. ３ ) and a structure in which carbon atoms are bonded to both ends of a difluoromethylene group (—C—CF ２ As a result, polyimides containing specific diamines as diamine components are superior in environmental safety to conventional soluble polyimides containing organic fluorine compounds such as fluoroalkyl-substituted benzidine as diamine components.

[0028] Among the specific diamines, CF does not fall under the category of "specific fluorine structure" described below. ３ -O-, or -(CF ２ -O) ｎ From the viewpoint of the polymerizability and mechanical strength of the polyimide, it is preferable to use a trifluoromethoxy group (CF ３-O-) is preferred, and among them, diamines in which the oxygen atom of the trifluoromethoxy group is bonded to a carbon atom of an aromatic ring are preferred. From the viewpoint of reactivity, diamines in which a trifluoromethoxy group is bonded to a carbon atom of an aromatic ring are preferably those which do not have a fluorine atom directly bonded to the aromatic ring to which the trifluoromethoxy group is bonded, and particularly preferred are those which do not contain fluorine atoms other than the trifluoromethoxy group. Examples of specific diamines in which a trifluoromethoxy group is bonded to a carbon atom of an aromatic ring include trifluoromethoxy-substituted benzidine and trifluoromethoxy-substituted phenylenediamine.

[0029] Examples of trifluoromethoxy-substituted benzidines include 2-(trifluoromethoxy)benzidine, 3-(trifluoromethoxy)benzidine, 2,3-bis(trifluoromethoxy)benzidine, 2,5-bis(trifluoromethoxy)benzidine, 2,6-bis(trifluoromethoxy)benzidine, 2,3,5-tris(trifluoromethoxy)benzidine, 2,3,6-tris(trifluoromethoxy)benzidine, 2,3,5,6-tetrakis(trifluoromethoxy)benzidine, 2,2'-bis(trifluoromethoxy)benzidine (TFMOB), 3,3'-bis(trifluoromethoxy)benzidine, 2,3'-bis(trif 2,2',3-tris(trifluoromethoxy)benzidine, 2,3,3'-tris(trifluoromethoxyl)benzidine, 2,2',5-tris(trifluoromethoxy)benzidine, 2,2',6-tris(trifluoromethoxy)benzidine, 2,3',5-tris(trifluoromethoxy)benzidine, 2,3',6-tris(trifluoromethoxy)benzidine, 2,2',3,3'-tetrakis(trifluoromethoxy)benzidine, 2,2',5,5'-tetrakis(trifluoromethoxy)benzidine, and 2,2',6,6'-tetrakis(trifluoromethoxy)benzidine.

[0030] Examples of trifluoromethoxy-substituted phenylenediamines include 1,2-diamino-4-(trifluoromethoxy)benzene, 1,3-diamino-4-(trifluoromethoxy)benzene, 1,4-diamino-2-(trifluoromethoxy)benzene, 1,4-diamino-2,3-bis(trifluoromethoxy)benzene, 1,4-diamino-2,5-bis(trifluoromethoxy)benzene, 1,4-diamino-2,6-bis(trifluoromethoxy)benzene, 1,4-diamino-2,3,5-tris(trifluoromethoxy)benzene, and 1,4-diamino-2,3,5,6-tetrakis(trifluoromethoxy)benzene.

[0031] From the viewpoint of the polymerizability of the polyimide and compatibility with polyester, trifluoromethoxy-substituted benzidine is preferred as the specific diamine. Among them, from the viewpoint of the solubility of the polyimide in organic solvents and compatibility with other resins, those having a trifluoromethoxy group at the 2- or 3-position of the biphenyl are preferred, with 2,2'-bis(trifluoromethoxy)benzidine (hereinafter referred to as "TFMOB"), 3,3'-bis(trifluoromethoxy)benzidine, and 2,3'-bis(trifluoromethoxy)benzidine being more preferred, and TFMOB being particularly preferred. By having a trifluoromethoxy group at the 2- or 3-position of the biphenyl, in addition to a decrease in π electron density due to the electron-withdrawing properties of the trifluoromethoxy group, the steric hindrance of the trifluoromethoxy group inhibits π-π stacking between benzene rings, thereby shifting the absorption edge wavelength to shorter wavelengths and reducing coloration of the polyimide. Furthermore, in the case of TFMOB, the steric hindrance between the trifluoromethoxy groups at the 2- and 2'-positions of the biphenyl causes a twist in the bond between the two benzene rings of the biphenyl, reducing the planarity of the π-conjugation, thereby shifting the absorption edge wavelength to shorter wavelengths and reducing the coloration of the polyimide.

[0032] The amount of the specific diamine relative to the total amount of the diamine components of the polyimide is preferably 10 mol% or more, more preferably 30 mol% or more, even more preferably 50 mol% or more, and may be 60 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more, or even 100 mol%. Among these, the amount of the trifluoromethoxy group-containing diamine is preferably within this range, and the amount of the trifluoromethoxy-substituted benzidine is particularly preferably within this range. The higher the ratio of the specific diamine, the more suppressed the coloration and the mechanical strength of the film, such as pencil hardness, elastic modulus, breaking strength, and breaking elongation, may be improved.

[0033] (Diamines other than the specific diamines) The polyimide may contain diamines other than the specific diamines as the diamine component. ３ and -C-CF ２ Those which do not contain —C— are preferred, and those which do not contain a fluorine atom are particularly preferred.

[0034] Examples of diamines not containing fluorine atoms include 2,2'-dimethylbenzidine, 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. 9,9-bis(4-aminophenyl)fluorene, 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene, 9,9-bis(4-amino-3-methylphenyl)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'-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(4-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-aminopropoxy)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 Examples of suitable cyclohexanes include cyclohexane, 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, isophoronediamine, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, and 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane.

[0035] The use of diaminodiphenyl sulfone as the diamine in addition to the specific diamine may improve the solubility in solvents and transparency of the polyimide. Among diaminodiphenyl sulfones, 3,3'-diaminodiphenyl sulfone (3,3'-DDS) and 4,4'-diaminodiphenyl sulfone (4,4'-DDS) are preferred, and these may be used in combination.

[0036] When diaminodiphenyl sulfone is used in addition to the specific diamine, the amount of diaminodiphenyl sulfone relative to the total amount of the diamine components may be 1 mol% or more, 3 mol% or more, 5 mol% or more, 10 mol% or more, 12 mol% or more, or 15 mol% or more, or may be 50 mol% or less, 30 mol% or less, 20 mol% or less, or 10 mol% or less.

[0037] The use of a diamine having a fluorene structure in addition to the specific diamine as the diamine may improve the solubility in solvents, transparency, and mechanical strength of the polyimide. Preferred fluorene-containing diamines are 9,9-bis(4-aminophenyl)fluorene, 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene, 9,9-bis(3-amino-4-hydroxyphenyl)fluorene, and 9,9-bis(4-amino-3-methylphenyl)fluorene, and these may be used in combination.

[0038] When a diamine having a fluorene structure is used in addition to the specific diamine, the amount of the diamine having a fluorene structure relative to the total amount of the diamine components may be 1 mol% or more, 3 mol% or more, 5 mol% or more, 10 mol% or more, 15 mol% or more, or 30 mol% or more, or may be 90 mol% or less, 70 mol% or less, 50 mol% or less, or 30 mol% or less.

[0039] The transparency of the polyimide may be improved by using an alicyclic diamine in addition to the specific diamine. Among the alicyclic diamines, isophoronediamine and 1,4-diaminocyclohexane are preferred, and these may be used in combination.

[0040] When an alicyclic diamine is used in addition to the specific diamine, the amount of the alicyclic diamine relative to the total amount of the diamine components may be 1 mol% or more, 3 mol% or more, 5 mol% or more, 10 mol% or more, 12 mol% or more, or 15 mol% or more, and may be 50 mol% or less, 30 mol% or less, or 20 mol% or less.

[0041] The total amount of the specific diamine, diaminodiphenyl sulfone, diamine having a fluorene structure, and alicyclic diamine relative to the total amount of diamine components in the polyimide is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, and may be 95 mol% or more, 99 mol% or more, or even 100 mol%.

[0042] Among aromatic diamines other than those mentioned above, p-phenylenediamine, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, etc. can contribute to improving the mechanical strength of the polyimide. The amount of these aromatic diamines may be 1 mol% or more, 3 mol% or more, 5 mol% or more, 10 mol% or more, 12 mol% or more, or 15 mol% or more, or 50 mol% or less, 30 mol% or less, 20 mol% or less, or 10 mol% or less, based on the total amount of the diamine components.

[0043] The polyimide may contain a fluorine atom-containing diamine other than the specific diamine as a diamine component, but from the viewpoint of environmental safety of the polyimide, the amount of the fluorine atom-containing diamine other than the specific diamine relative to the total amount of the diamine components of the polyimide is preferably 30 mol % or less, more preferably 20 mol % or less, even more preferably 10 mol % or less, and may be 5 mol % or less, 1 mol % or less, or 0.5 mol % or less. The polyimide may not contain a fluorine atom-containing diamine other than the specific diamine as a diamine component.

[0044] Among fluorine atom-containing diamines, the structure in which a trifluoromethyl group is bonded to a carbon atom (-C-CF ３ ) and / or a structure in which carbon atoms are bonded to both ends of a difluoromethylene group (—C—CF ２ In order to improve the transparency and solubility of polyimides in solvents, general soluble polyimides contain CF4 as a diamine component on the carbon atom of the aromatic ring. ３ - or -C(CF ３ ) ２Although it contains diamines having a structure in which - is directly bonded (for example, trifluoromethyl-substituted benzidines such as 2,2'-bis(trifluoromethyl)benzidine, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis(3-amino-4-hydroxyphenyl)hexafluoropropane), from the viewpoint of environmental safety of polyimides, it is preferable that these diamines are not substantially contained. ３ - or -C(CF ３ ) ２ The amount of diamine to which - is directly bonded is preferably less than 0.5 mol %, and may be 0.3 mol % or less, 0.1 mol % or less, or 0.05 mol % or less, or may be 0.

[0045] <Tetracarboxylic acid dianhydride> (Specific acid dianhydride) The acid dianhydride component of the polyimide is not particularly limited, but from the viewpoint of improving environmental safety and providing solubility in organic solvents, it is preferable that the acid dianhydride component contains one or more tetracarboxylic acid dianhydrides selected from the group consisting of bisphenol-type tetracarboxylic acid dianhydrides, bis(trimellitic anhydride) esters, and tetracarboxylic acid dianhydrides having a fluorene structure. Hereinafter, these tetracarboxylic acid dianhydrides will be referred to as "specific acid dianhydrides."

[0046] The bisphenol tetracarboxylic dianhydride is a compound represented by the following general formula (1), and can be obtained, for example, by reacting two hydroxy groups of a bisphenol with iodoisobenzofuran-1,3-dione or the like.

[0047]

[0048] In general formula (1), A is any divalent organic group, and at both ends of A, a phenyl group is bonded to a carbon atom of A. p is 1 or 2. １ａ , R １ｂ , R ２ａ and R ２ｂare each independently an arbitrary substituent, and from the viewpoint of the solubility of the polyimide, are preferably an alkyl group having 1 to 10 carbon atoms, a phenyl group, an alkoxy group, or a halogen. m1 and m2 are each independently an integer of 0 to 3, and n1 and n2 are each independently an integer of 0 to 4.

[0049] Examples of the divalent organic group A include the following (a), (b), and (c). ３ａ and R ３ｂ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group. ４ is an alkyl group having 1 to 10 carbon atoms, and k is an integer of 0 to 10. When k is 2 or more, multiple R ４ may be the same or different.

[0050]

[0051] From the viewpoint of the solubility of the polyimide, 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (BPADA) is particularly preferred as the bisphenol tetracarboxylic dianhydride.

[0052] The bis(trimellitic anhydride) ester is represented by the following general formula (2).

[0053]

[0054] In general formula (2), B is any divalent organic group, and carboxy groups are bonded to carbon atoms of B at both ends of B. Specific examples of the divalent organic group B include the following (i) to (viii).

[0055]

[0056] The groups represented by formulas (i) to (viii) are groups obtained by removing two hydroxyl groups from a diol. For example, the group represented by formula (i) is a group obtained by removing two hydroxyl groups from a hydroquinone derivative which may have a substituent on the benzene ring.

[0057] In formulas (i) and (ii), R １ , R ２ａ and R ２ｂare each independently an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a halogen atom, and m, n1, and n2 are each independently an integer of 0 to 4. In formulas (iii), (iv), and (v), R ３ａ and R ３ｂ are each independently an arbitrary substituent, and from the viewpoint of the solubility of the polyimide, an alkyl group having 1 to 10 carbon atoms, a phenyl group, an alkoxy group, or a halogen atom is preferred. k1 and k2 are each independently an integer of 0 to 4. R ４ is an alkyl group, an alkoxy group, or a halogen; and j is an integer of 0 to 10.

[0058] The bis(trimellitic anhydride) ester is preferably an aromatic ester, and among the above (i) to (viii), (i) to (v) are preferred as B in the general formula (2), with (i) to (iv) being preferred, and (i) and (ii) being particularly preferred.

[0059] When B is a group represented by general formula (i), from the viewpoint of the mechanical properties of the resin composition, the bis(trimellitic anhydride) ester of general formula (2) is preferably 1,4-phenylenebis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) (TMHQ) represented by the following formula (2-1):

[0060]

[0061] When B is a group represented by formula (ii), from the viewpoint of the solubility of the polyimide, the bis(trimellitic anhydride) ester of general formula (2) is preferably 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diylbis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) (TAHMBP) represented by the following formula (2-2):

[0062]

[0063] When B is a group represented by formula (iii), from the viewpoint of the solubility of the polyimide, the bis(trimellitic anhydride) ester of general formula (2) is preferably bisphenol Z bis(trimellitic anhydride) (BPZ-TME) represented by the following formula (2-3):

[0064]

[0065] When B is a group represented by formula (iv), from the viewpoint of the solubility of the polyimide, the bis(trimellitic anhydride) ester of general formula (2) is preferably 5,5'-[cyclododecylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) (TBIS-DMPN) represented by the following formula (2-4):

[0066]

[0067] A tetracarboxylic acid dianhydride having a fluorene structure is a compound having a fluorene structure between two acid anhydride groups. When the bisphenol tetracarboxylic acid dianhydride of the general formula (1) or the bis(trimellitic anhydride) ester of the general formula (2) has a fluorene structure, the acid dianhydride is treated as a tetracarboxylic acid dianhydride having a fluorene structure.

[0068] Examples of tetracarboxylic dianhydrides having a fluorene structure include the acid dianhydrides represented by the following group (A) and N,N'-(9H-fluoren-9-ylidene-di-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxamide].

[0069]

[0070] (A) R in group １ａ , R １ｂ , R ２ａ , R ２ｂ , R ３ａ , R ３ｂ , R ４ａ and R ４ｂare each independently an arbitrary substituent, and from the viewpoint of the solubility of the polyimide, an alkyl group having 1 to 10 carbon atoms, a phenyl group, an alkoxy group, or a halogen is preferred. m1 and m2 are each independently an integer of 0 to 3. n1 and n2 are each independently an integer of 0 to 4. k1 and k2 are each independently an integer of 0 to 2. j1 and j2 are each independently an integer of 0 to 4.

[0071] R ５ａ and R ５ｂ is an alkylene group, and R ５ａ and R ５ｂ may be the same or different. p1 and p2 each independently represent 0 or 1. R ６ represents a carbonyl group; q1 and q2 each independently represent 0 or 1.

[0072] Among the (A) group, tetracarboxylic dianhydrides having a fluorene structure include 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride, 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, spiro[11H-difuro[3,4-b:3',4'-i]ky]fluorene dianhydride, and tetracarboxylic dianhydrides having a fluorene structure, because they have a small molecular weight, a relatively high proportion of a fluorene structure, and can improve the solubility and transparency of polyimide and compatibility with polyester. Santhene-11,9'-fluorene]-1,3,7,9-tetraone, 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate), and 5,5'-[9H-fluoren-9-ylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) are preferred.

[0073] Polyimides containing the above-mentioned specific diamine as the diamine component and the specific acid dianhydride as the acid dianhydride component tend to exhibit solubility in organic solvents, as well as high transparency and compatibility with polyesters.

[0074] Among the specific acid dianhydrides, from the viewpoints of solubility in organic solvents, transparency, and compatibility with polyester, 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (BPADA), 1,4-phenylenebis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) (TMHQ), 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diylbis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) (TAHMBP), bisphenol Z bis(trimellitic anhydride) (BPZ-TME), 5,5'-[cyclododecylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) (TBIS-DMP), and the like are preferred. N), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride (BPF-PA), 5,5'-[9H-fluoren-9-ylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) (TBIS-MPN), 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) (TBIS-RXN), and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-fluorene]-1,3,7,9-tetraone are preferred.

[0075] From the viewpoint of the UV resistance of the polyimide, among the specific acid dianhydrides, bisphenol-type tetracarboxylic acid dianhydrides and acid dianhydrides having a fluorene structure (excluding those having an ester structure) are preferred. From the viewpoints of solubility in solvents and mechanical strength, BPADA, BPAF, and BPF-PA are particularly preferred. These acid dianhydrides do not have an ester bond and do not undergo Friess transition due to UV light, so that the polyimide is less likely to discolor when exposed to UV light. Furthermore, from the viewpoint of compatibility with polyester, bisphenol-type tetracarboxylic acid dianhydrides such as BPADA and acid dianhydrides having a fluorene structure such as BPAF and BPF-PA are preferred as the specific acid dianhydrides.

[0076] From the viewpoint of the solubility of the polyimide in organic solvents and the compatibility with polyesters, the total amount of the specific acid dianhydrides relative to the total amount of the acid dianhydride components is preferably 15 mol% or more, more preferably 30 mol% or more, and even more preferably 50 mol% or more, and may be 60 mol% or more, 70 mol% or more, 80 mol% or more, 90 mol% or more, 95 mol% or more, or 100 mol%. The total amount of the specific acid dianhydrides relative to the total amount of the acid dianhydride components may be 95 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, or 70 mol% or less.

[0077] (Tetracarboxylic acid dianhydride other than the specific acid dianhydride) The polyimide may contain an acid dianhydride other than the specific acid dianhydride as the acid dianhydride component. Examples of such an acid dianhydride include alicyclic tetracarboxylic acid dianhydrides, aromatic tetracarboxylic acid dianhydrides, and linear aliphatic tetracarboxylic acid dianhydrides. From the viewpoint of environmental safety of the polyimide, -C-CF ３ and -C-CF ２ Those which do not contain —C— are preferred, and those which do not contain a fluorine atom are particularly preferred.

[0078] The alicyclic tetracarboxylic acid dianhydride may 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. Examples of the alicyclic tetracarboxylic acid dianhydride include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic acid dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid 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 anhydride, 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 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 1,3,6,7-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-tetraone, ethylene glycol bis(hydrogenated trimellitic anhydride) ester, decahydro[2]benzopyrano[6,5,4,-def][2]benzopyran-1,3,6,8-tetraone, and the like.The inclusion of an alicyclic tetracarboxylic dianhydride as an acid dianhydride component in addition to a specific acid dianhydride tends to improve the mechanical strength of the polyimide. In addition, the inclusion of an alicyclic tetracarboxylic dianhydride as an acid dianhydride component in the polyimide may improve the compatibility between the polyimide and polyester.

[0079] Among alicyclic tetracarboxylic dianhydrides, from the viewpoint of transparency and mechanical strength of polyimide, 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA), 1,2,4,5-cyclohexanetetracarboxylic dianhydride (H-PMDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride (TDA-100), bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BEDA), bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride (BODA), and 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride (H-BPDA) are preferred. Among these, from the viewpoint of mechanical strength, tetracarboxylic dianhydrides in which two acid anhydride groups are bonded to one alicyclic ring are preferred, and CBDA is particularly preferred.

[0080] When an alicyclic tetracarboxylic dianhydride is used in addition to the specific acid dianhydride, the amount of the alicyclic tetracarboxylic dianhydride relative to the total amount of the acid dianhydride components may be 1 mol% or more, 3 mol% or more, 5 mol% or more, 10 mol% or more, 12 mol% or more, or 15 mol% or more. The greater the amount of the alicyclic tetracarboxylic dianhydride, the higher the transparency tends to be. From the viewpoint of ensuring the solubility of the polyimide in organic solvents, the amount of the alicyclic tetracarboxylic dianhydride relative to the total amount of the acid dianhydride components is preferably 80 mol% or less, more preferably 60 mol% or less, and even more preferably 50 mol% or less, and may be 40 mol% or less, 30 mol% or less, or 20 mol% or less.

[0081] Examples of aromatic tetracarboxylic dianhydrides other than the specific acid dianhydrides include pyromellitic dianhydride, mellophanic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 3,4'-oxydiphthalic anhydride (3,4'-ODPA), 4,4'-oxydiphthalic anhydride (4,4'-ODPA), 3,3'-oxydiphthalic anhydride (3,3'-ODP), A), 5,5'-dimethylmethylenebis(phthalic anhydride), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, terphenyltetracarboxylic dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 2,2-bis(4-hydroxyphenyl)propanedibenzoate-3,3',4,4'-tetracarboxylic dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic dianhydride, and the like.

[0082] Among these aromatic tetracarboxylic acid dianhydrides, 4,4'-oxydiphthalic anhydride is preferred from the viewpoint of solubility of polyimide, and pyromellitic dianhydride and mellophanic dianhydride are preferred from the viewpoint of mechanical strength, with pyromellitic dianhydride being particularly preferred.

[0083] When an aromatic tetracarboxylic dianhydride other than the specific acid dianhydride is used in addition to the specific acid dianhydride, the amount of the aromatic tetracarboxylic dianhydride other than the specific acid dianhydride relative to the total amount of the acid dianhydride components may be 1 mol% or more, 3 mol% or more, 5 mol% or more, 10 mol% or more, 12 mol% or more, or 15 mol% or more. From the viewpoint of ensuring the solubility of the polyimide in organic solvents, the amount of the aromatic tetracarboxylic dianhydride other than the specific acid dianhydride relative to the total amount of the acid dianhydride components is preferably 80 mol% or less, more preferably 60 mol% or less, even more preferably 50 mol% or less, and may be 40 mol% or less, 30 mol% or less, or 20 mol% or less.

[0084] Examples of the chain aliphatic tetracarboxylic dianhydride include ethylene tetracarboxylic dianhydride, 1,2,3,4-butane tetracarboxylic dianhydride, and meso-butane-1,2,3,4-tetracarboxylic dianhydride.

[0085] The amount of the fluorine atom-containing acid dianhydride relative to the total amount of the acid dianhydride components of the polyimide is preferably 30 mol % or less, more preferably 20 mol % or less, and even more preferably 10 mol % or less, and may be 5 mol % or less, 1 mol % or less, or 0.5 mol % or less. The polyimide may not contain a fluorine atom-containing acid dianhydride as an acid dianhydride component.

[0086] Among fluorine atom-containing acid dianhydrides, the structure in which a trifluoromethyl group is bonded to a carbon atom (-C-CF ３ ) and / or a structure in which carbon atoms are bonded to both ends of a difluoromethylene group (—C—CF ２ -C-) has low decomposition properties and is a concern for environmental safety. ３ - or -C(CF ３ ) ２Acid dianhydrides having a structure in which - is directly bonded (for example, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 9,9-bis(trifluoromethyl)xanthenetetracarboxylic dianhydride, 9-trifluoromethylxanthenetetracarboxylic dianhydride, 2,2'-bis(trifluoromethyl)-4,4',5,5'-biphenyltetracarboxylic dianhydride) are poorly degradable in the environment, and therefore, from the viewpoint of environmental safety of polyimides, it is preferable that these acid dianhydrides are substantially not contained. ３ - or -C(CF ３ ) ２ The amount of acid dianhydride to which - is directly bonded is preferably less than 0.5 mol %, and may be 0.3 mol % or less, 0.1 mol % or less, or 0.05 mol % or less, or may be 0.

[0087] <Content of specific fluorine structure in polyimide> As described above, the diamine component is CF ３ -O-, -(CF ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ The polyimide containing one or more diamines (specific diamines) having the structure selected from -C-CF ３ , -C-CF ２ It is substantially free of structures such as --C-- and exhibits solubility in organic solvents and compatibility with polyesters.

[0088] In order to reduce the environmental persistence of fluorine-containing compounds, it is preferable that the polyimide contains a small amount of monomers (diamines and acid dianhydrides) having a specific fluorine structure. The specific fluorine structure is a trifluoromethyl group (CF ３ -), excluding those containing only the components of the following structural formula (i), and a difluoromethylene group (-CF ２ -), excluding those having only the components of the following structural formula (ii): CF ３ -X (i) X-CF ２ -X' (ii)

[0089] X in formula (i) and (ii) is —OR or —NRR′, and X′ in formula (ii) is —H, —CH ３ , aromatic, —C(O)—, —OR″, —SR″, and NR″R′″. R, R′, R″, and R′″ each independently represent —H, —CH ３ , -CH ２ -, aromatic, or -C(O)-.

[0090] From the viewpoint of improving environmental degradability, the amount of fluorine atoms contained in the specific fluorine structure per 1 kg of polyimide is preferably less than 500 mg, more preferably less than 300 mg, even more preferably less than 100 mg, and particularly preferably less than 50 mg.

[0091] <Preparation of Polyimide> Polyamic acid, which serves as a polyimide precursor, is obtained by the reaction of a diamine with an acid dianhydride, and polyimide is obtained by cyclodehydration (imidization) of the polyamic acid. 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 90:100 to 110:100) in an organic solvent and stirring the mixture.

[0092] 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.

[0093] 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.

[0094] The organic solvent used in the polymerization of polyamic acid is not particularly limited, as long as it does not react with the diamine and the acid dianhydride and can dissolve the polyamic acid. Examples of organic solvents include urea solvents such as methylurea and N,N-dimethylethylurea; sulfoxide or sulfone solvents such as dimethyl sulfoxide, diphenyl sulfone, and tetramethyl sulfone; amide 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 dichloromethane; 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. 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.

[0095] Polyimides are obtained by dehydration cyclization of polyamic acid. One method for preparing polyimides from polyamic acid solutions is to add a dehydrating agent, an imidization catalyst, etc. to the polyamic acid solution and allow imidization to proceed in the solution. The polyamic acid solution may be heated to accelerate the imidization process. By mixing a solution containing polyimide produced by imidization of polyamic acid with a poor solvent, a polyimide resin precipitates 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 the poor solvent, preventing discoloration of the polyimide and increased yellowness. Furthermore, by isolating the polyimide resin as a solid, solvents suitable for film formation, such as low-boiling point solvents, can be used when preparing a solution for film production.

[0096] The molecular weight of the polyimide (weight average molecular weight in terms of polystyrene measured by gel permeation chromatography (GPC)) is preferably 10,000 to 1,000,000, more preferably 20,000 to 500,000, and even more preferably 40,000 to 300,000. If the molecular weight is too small, the strength of the film may be insufficient. If the molecular weight is too large, the solubility of the polyimide and its compatibility with polyester may be poor.

[0097] The polyimide is preferably soluble in an organic solvent. Specifically, the polyimide is preferably soluble in dimethylformamide (DMF) at 23°C at a concentration of 1% by weight or more. In addition to being soluble in amide solvents such as DMF, the polyimide is preferably soluble in non-amide solvents. Examples of non-amide solvents include ketone solvents such as acetone and methyl ethyl ketone, alkyl halide solvents such as chloroform and dichloromethane, and ester solvents such as ethyl acetate and γ-butyrolactone. Non-amide solvents have a lower boiling point than amide solvents, making it easier to remove residual solvent during film production. Therefore, polyimides soluble in non-amide solvents are expected to improve film productivity. The polyimide is particularly preferably soluble in dichloromethane.

[0098] From the viewpoint of the thermal stability and light stability of the resin composition and molded articles such as films, the polyimide preferably 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, the polyimide preferably has a high imidization rate. A low acid value enhances the stability of the polyimide.

[0099] [Polyester] The polyester is a condensate of a dicarboxylic acid and a glycol, and has a structure derived from a dicarboxylic acid and a structure derived from a diol. From the viewpoint of ensuring the mechanical strength of a molded article such as a film formed from the resin composition, a polyester having a weight average molecular weight (Mw, polystyrene equivalent) of more than 10,000 is used. The weight average molecular weight of the polyester is preferably 15,000 or more, more preferably 20,000 or more, and may be 30,000 or more. From the viewpoint of ensuring compatibility with polyimide and moldability of the resin composition into a film or the like, the weight average molecular weight of the polyester is preferably 200,000 or less, more preferably 150,000 or less, even more preferably 100,000 or less, and may be 80,000 or less.

[0100] Polyethylene terephthalate (PET), a typical polyester, is a condensation product of ethylene glycol and terephthalic acid, and has high crystallinity and low solubility in organic solvents. In this embodiment, a polyester soluble in organic solvents is used. The polyester is preferably soluble in organic solvents common to polyimides, and is particularly preferably soluble in highly polar solvents such as amide-based solvents.

[0101] The polyester may have a weight average molecular weight of more than 10,000 and be soluble in an organic solvent, and the dicarboxylic acid component and the diol component are not particularly limited. From the viewpoint of solubility in an organic solvent, amorphous polyesters are preferred.

[0102] <Diol> From the viewpoint of imparting solubility to the polyester in organic solvents, the diol component of the polyester is preferably a diol having a chain alkylene group having 3 or more carbon atoms which may be branched, a diol having a chain alkenylene group having 3 or more carbon atoms which may be branched, a polyalkylene glycol, or a diol having a cyclic structure. Hereinafter, these diols will be referred to as "specific diols."

[0103] Examples of diols having a chain alkylene structure of 3 or more carbon atoms which may have a branch include propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, etc. Among these, diols having a chain alkylene structure of 5 or more carbon atoms are preferred, and diols having an alkylene group with a branched structure such as neopentyl glycol are particularly preferred. Examples of diols having a chain alkenylene group of 3 or more carbon atoms which may have a branch include 2-butene-1,4-diol, etc.

[0104] Examples of polyalkylene glycols include diethylene glycol, triethylene glycol, dipropylene glycol, and polytetramethylene ether glycol.

[0105] Examples of diols having a cyclic structure include diols having a cycloalkylene structure such as 1,4-cyclohexanediol and 1,4-cyclohexanedimethanol; diols having a cyclic ether structure such as isosorbide; diols having a fluorene structure; and diols having a bisphenol derivative structure.

[0106] Among these, butanediol, neopentyl glycol, polytetramethylene ether glycol, diols having a fluorene structure, and diols having a bisphenol derivative structure are preferred from the viewpoint of the solubility of the polyester and the compatibility with the polyimide.

[0107] The diol having a fluorene structure has a fluorene skeleton between two hydroxy groups and is represented by the following general formula (3).

[0108]

[0109] In general formula (3), Ar1 and Ar2 are aromatic hydrocarbon rings. １ａ and R １ｂ are each independently an alkyl group having 1 to 10 carbon atoms or a phenyl group, and n1 and n2 are each independently an integer of 0 or more. ２ａ and R２ｂ are each independently an alkyl group having 1 to 10 carbon atoms or a phenyl group, and n1 and n2 are each independently an integer of 0 to 4. ３ａ and R ３ｂ is an alkylene group, and R ５ａ and R ５ｂ may be the same or different. p1 and p2 each independently represent an integer of 0 or more. q1 and q2 are 1.

[0110] Specific examples of the diol represented by general formula (3) include 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene, 9,9-bis[4-(2-hydroxypropoxy)phenyl]fluorene, 9,9-bis[4-[2-(2-hydroxyethoxy)ethoxy]phenyl]-9H-fluorene, 2,2'-[(9H-fluorene-9,9-diyl)bis(naphthalene-6,2-diyloxy)]diethanol, 9,9-bis[4-(2-hydroxyethoxy)-3-phenylphenyl]fluorene, 9,9-bis[4-(2-hydroxypropoxy)-3-phenylphenyl]fluorene, and 9,9-bis{4-[2-(2-hydroxyethoxy)ethoxy]-3-phenylphenyl}fluorene. Among these, from the viewpoint of improving heat resistance, 9,9-bis[4-(2-hydroxyethoxy)phenyl]fluorene, 9,9-bis[4-(2-hydroxypropoxy)phenyl]fluorene, and 9,9-bis[4-(2-hydroxyethoxy)-3-phenylphenyl]fluorene are preferred.

[0111] The diol having bisphenol derivative structure is the one in which alkylene oxide is added to two phenolic hydroxyl groups of bisphenol (bisphenol alkylene oxide adduct), and preferably the ethylene oxide (EO) adduct and propylene oxide (PO) adduct of bisphenol.In addition, the diol having fluorene structure of the above general formula (3) includes the diol having bisphenol derivative structure, but the diol having fluorene skeleton is treated as the diol having fluorene structure even if it has bisphenol derivative structure.

[0112] Examples of bisphenols without a fluorene skeleton include 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), 1,1-bis(4-hydroxyphenyl)-1-phenylethane (bisphenol AP), 2,2-bis(4-hydroxyphenyl)butane (bisphenol B), bis(4-hydroxyphenyl)diphenylmethane (bisphenol BP), 2,2-bis(3-methyl-4-hydroxyphenyl)propane (bisphenol C), 1,1-bis(4-hydroxyphenyl)ethane (bisphenol E), bis(4-hydroxyphenyl)methane (bisphenol F), and 2,2-bis(4-hydroxy-3-isopropyl bisphenol G), 1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene (bisphenol M), bis(4-hydroxyphenyl)sulfone (bisphenol S), 1,4-bis(2-(4-hydroxyphenyl)-2-propyl)benzene (bisphenol P), 5,5'-(1-methylethylidene)-bis[1,1'(bisphenyl)-2-ol]propane (bisphenol PH), 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane (bisphenol TMC), 1,1-bis(4-hydroxyphenyl)cyclohexane (bisphenol Z), and the like.

[0113] Among the bisphenol alkylene oxide adducts, from the viewpoint of solubility in polyester, ethylene oxide adducts of bisphenol A, ethylene oxide adducts of bisphenol S, and ethylene oxide adducts of bisphenol Z are preferred.

[0114] The polyester may contain a diol other than the above-mentioned specific diol as a diol component. An example of a diol other than the specific diol is ethylene glycol. When the specific diol and ethylene glycol are used in combination, the molar ratio of the specific diol to ethylene glycol is preferably 90:10 to 10:90, and may be 80:20 to 20:80, or 60:40 to 40:60, from the viewpoint of compatibility between the polyester and the polyimide. In other words, the amount of the specific diol relative to the total amount of the diol component is preferably 10 mol% or more, and may be 20 mol% or more, or 40 mol% or more.

[0115] <Dicarboxylic Acid> The dicarboxylic acid component of the polyester is not particularly limited, and various aromatic dicarboxylic acids and aliphatic dicarboxylic acids can be used. As the dicarboxylic acid, an aliphatic dicarboxylic acid and an aromatic dicarboxylic acid can be used in combination.

[0116] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and biphenyldicarboxylic acid.Further examples of aromatic dicarboxylic acids include dicarboxylic acids having a fluorene structure, such as 9,9-bis(carboxymethyl)fluorene and 9,9-bis(2-carboxyethyl)fluorene.

[0117] From the viewpoint of improving the solubility and mechanical strength of the polyester, terephthalic acid and isophthalic acid are preferred. Terephthalic acid and isophthalic acid may be used alone or in combination. When terephthalic acid and isophthalic acid are used in combination, from the viewpoint of the solubility of the polyester, the molar ratio of terephthalic acid to isophthalic acid is preferably 90:10 to 10:90, and may be 25:75 to 75:25 or 60:40 to 40:60. From the viewpoint of the solubility and mechanical strength of the polyester, the total amount of terephthalic acid and isophthalic acid relative to the total amount of dicarboxylic acid components of the polyester is preferably 30 mol% or more, more preferably 40 mol% or more, even more preferably 60 mol% or more, and may be 80 mol% or more.

[0118] Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, fumaric acid, maleic acid, itaconic acid, citraconic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, and tetrahydrophthalic acid.

[0119] Inclusion of an aliphatic dicarboxylic acid as the dicarboxylic acid component of the polyester may improve the compatibility between the polyester and the polyimide. From the viewpoint of improving compatibility with the polyimide, the aliphatic dicarboxylic acid is preferably a dicarboxylic acid having 6 to 12 carbon atoms, particularly 6 to 10 carbon atoms, and among these, adipic acid, pimelic acid, suberic acid, azelaic acid, and sebacic acid are preferred because they can also contribute to improving the solubility of the polyester.

[0120] <Other Components> Monomers other than diols and dicarboxylic acids may be used as monomer components constituting the polyester, as long as the effects of the present invention are not impaired. Examples of monomers other than diols and dicarboxylic acids include polyols having three or more hydroxy groups (e.g., trimethylolpropane, glycerin), monoalcohols (e.g., octyl alcohol, decyl alcohol, lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, 2-phenoxyethanol), polycarboxylic acids having three or more carboxy groups (e.g., 1,3,4-benzenetricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, pyromellitic acid, trimellitic acid, tetrahydrophthalic acid), monocarboxylic acids (e.g., lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid, p-tert-butylbenzoic acid, cyclohexanoic acid), and hydroxycarboxylic acids (e.g., methyl methyl esters). Examples of such an acid include compounds having one or more hydroxy groups and / or one or more carboxy groups, such as lactic acid, glycolic acid, 2-hydroxybutyric acid, 3-hydroxybutyric acid, 4-hydroxybutyric acid, 2-hydroxyisobutyric acid, 2-hydroxy-2-methylbutyric acid, 2-hydroxyvaleric acid, 3-hydroxyvaleric acid, 4-hydroxyvaleric acid, 5-hydroxyvaleric acid, 6-hydroxycaproic acid, 10-hydroxystearic acid, 4-hydroxyphenylstearic acid, and 4-(β-hydroxy)ethoxybenzoic acid), lactones (e.g., β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, and ε-caprolactone), and oxiranes (e.g., ethylene oxide), as well as compounds that generate one or more hydroxy groups and / or one or more carboxy groups upon hydrolysis.

[0121] <Preparation of Polyester> The polymerization method for the polyester is not particularly limited, and various known methods can be used, such as a method in which an oligomer is obtained by a transesterification method or a direct esterification method, and then melt polymerization or solid-phase polymerization is performed. In the polymerization of the polyester, a dicarboxylic acid derivative such as an acid anhydride may be used as the dicarboxylic acid component.

[0122] From the viewpoint of the heat resistance and moldability of the resin composition and the molded article, the glass transition temperature (Tg) of the polyester is preferably −25 to 200° C., more preferably 15 to 180° C., still more preferably 40 to 150° C., and may be about 60 to 130° C.

[0123] Commercially available polyester resins may be used as the polyester. Examples of commercially available polyester resins containing a diol having a fluorene structure as a diol component include OKP4HT (manufactured by Osaka Gas Chemicals, Mw: 38,000, Tg: 142°C) and OKP4 (manufactured by Osaka Gas Chemicals, Mw: 40,000, Tg: 121°C). Examples of commercially available polyester resins containing a diol having a bisphenol derivative structure as a diol component include Elitel UE3600 (manufactured by Unitika, Mw: 60,000, Tg: 75°C), Elitel UE3690 (manufactured by Unitika, Mw: 46,000, Tg: 90°C), Elitel UE9100 (manufactured by Unitika, Mw: 77,000, Tg: 19°C), and Vylon 290 (manufactured by Toyobo, Mw: 61,000, Tg: 72°C).

[0124] Examples of commercially available polyester resins containing specific diols other than those mentioned above as diol components include Elitel UE3200G (manufactured by Unitika, Mw: 43,000, Tg: 65°C), Elitel UE3210 (manufactured by Unitika, Mw: 62,000, Tg: 45°C), Elitel UE3240 (manufactured by Unitika, Mw: 50,000, Tg: 40°C), Elitel UE3500 (manufactured by Unitika, Mw: 83,000, Tg: 15°C), Elitel UE3 510 (manufactured by Unitika, Mw: 63,000, Tg: -25°C), Elitel UE9200 (manufactured by Unitika, Mw: 39,000, Tg: 65°C), Elitel UE9800 (manufactured by Unitika, Mw: 40,000, Tg: 85°C), Vylon 200 (manufactured by Toyobo, Mw: 42,000, Tg: 67°C), Vylon 240 (manufactured by Toyobo, Mw: 35,000, Tg: 60°C), and Vylon 600 (manufactured by Toyobo, Mw: 38,000, Tg: 47°C).

[0125] [Preparation of Resin Composition] The polyimide and polyester are mixed to prepare a resin composition. Polyimides generally do not exhibit compatibility with other polymers, but as described above, polyimides containing specific diamines as diamine components exhibit compatibility with solvent-soluble polyesters.

[0126] Whether a specific polyimide and a specific polyester are compatible with each other is confirmed by preparing a 10 μm thick film containing the polyimide and the polyester. If the film is transparent and has a haze of 10% or less, the polyimide and the polyester are judged to be compatible with each other. If the film has a haze of more than 10%, the polyimide and the polyester are judged to be incompatible with each other.

[0127] The ratio of polyimide to polyester in the resin composition is not particularly limited. The composition ratio (weight ratio) of polyimide to polyester may be 2:98 to 98:2, 10:90 to 90:10, 25:75 to 75:25, or 40:60 to 60:40. The higher the polyimide ratio, the higher the mechanical strength of the molded product, such as a film. The higher the polyester ratio, the less coloring there is in the molded product, such as a film, and the higher the transparency.

[0128] In order to fully exert the effect of improving transparency by mixing polyimide and polyester, the ratio of polyester to the total of polyimide and polyester 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.

[0129] The resin composition may be a simple mixture of a polyimide resin and a polyester resin precipitated as solids, or a kneaded mixture of a polyimide resin and a polyester resin. Furthermore, when a polyimide solution is mixed with a poor solvent to precipitate a polyimide resin, a polyester resin may be mixed with the solution, and a resin composition obtained by mixing a polyimide and a polyester may be precipitated as a solid (powder).

[0130] The resin composition may be a mixed solution containing polyimide and polyester. 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 solution and a polyester solution may be prepared separately, and then the two may be mixed to prepare a mixed solution of polyimide and polyester.

[0131] The solvent for the solution containing the polyimide and polyester is not particularly limited as long as it can dissolve both the polyimide and the polyester. 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 dichloromethane.

[0132] Generally, polyimides have low solubility in solvents and are often soluble only in highly polar solvents. Therefore, from the viewpoints of polyimide solubility and compatibility between polyimide and polyester in solution, amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone are preferred. On the other hand, from the viewpoint of solvent removability when producing a molded product such as a film, low-boiling non-amide solvents are preferred. Ketone solvents and alkyl halide solvents are preferred because they have excellent solubility in both polyimide and polyester, have low boiling points, and allow easy removal of residual solvent when producing a film.

[0133] The resin composition 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.

[0134] [Molded Articles and Films] The above-mentioned compositions 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 polyester 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.

[0135] Furthermore, a solution of a resin composition containing a polyimide and a polyester 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.

[0136] 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 and polyester is applied to a support, and the solvent is dried and removed to obtain a film.

[0137] The resin solution can be applied to a support by a known method using a bar coater, a comma coater, or the like. The support may be a glass substrate, a metal substrate such as SUS, a metal drum, a metal belt, a plastic film, or the like. 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.

[0138] 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 can suppress coloration of the resulting film, and is appropriately set between room temperature and about 250°C, with 50°C to 220°C being preferred. The heating temperature may be increased in stages. 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. Heating may be performed under reduced pressure to promote solvent removal.

[0139] A resin composition containing polyimide and polyester has a lower glass transition temperature than polyimide alone because the polyimide and polyester are compatible with each other, and therefore can be molded or processed at low temperatures, making it possible to reduce coloration of molded products such as films.

[0140] The film may be stretched in one or more directions to improve its mechanical strength. Stretching the film orients the polymer chains in the stretching direction, improving the in-plane strength of the film and reducing the risk of breakage or cracking. In a compatible system of polyimide and polyester, the tensile modulus in the stretching direction increases, and the flex resistance tends to improve accordingly.

[0141] 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, even when the film is repeatedly folded, breakage or cracking of the film at the folding location is unlikely to occur, and a device with high bending resistance can be provided.

[0142] 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 excessively high, the mechanical strength in the direction perpendicular to the stretching direction tends to decrease, and the handleability of the film may be reduced.

[0143] 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.

[0144] The thickness of the film is not particularly limited and may be appropriately set depending on the application. The film thickness 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 film thickness is preferably 10 μm to 200 μm, and may be 30 μm to 150 μm, 40 μm to 100 μm, or 50 μm to 80 μm. The thickness of a film used as a cover film for a display is preferably 10 μm or more. When the film is stretched, the thickness after stretching is preferably within the above range.

[0145] 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. As described above, since polyimide and polyester are compatible with each other, a film with low haze and high transparency can be obtained. The resin composition obtained by mixing polyimide and polyester preferably has a haze of 10% or less when a film with a thickness of 10 μm is produced.

[0146] The total light transmittance of the film is preferably 85% or more, more preferably 86% or more, even more preferably 87% or more, particularly preferably 88% or more, and may be 89% or more or 90% or more. The resin composition obtained by mixing polyimide and polyester preferably has a total light transmittance of 85% or more when formed into a film having a thickness of 10 μm.

[0147] The yellowness index (YI) of the film is not particularly limited, but is preferably 20.0 or less, more preferably 10.0 or less, and even more preferably 5.0 or less, and may be 4.0 or less, 3.0 or less, 2.0 or less, 1.0 or less, or 0.0 or less. The resin composition obtained by mixing polyimide and polyester preferably has a yellowness index of 20.0 or less when a film having a thickness of 20 μm is produced. As described above, by mixing polyimide and polyester, a film with less coloration and a small YI can be obtained compared to when polyimide is used alone.

[0148] The tensile modulus of the film is not particularly limited, but from the viewpoint of strength, the tensile modulus of the film at room temperature is preferably 2.0 GPa or more, more preferably 3.0 GPa or more, and even more preferably 4.0 GPa or more. The tensile modulus may be anisotropic, and the tensile modulus in at least one direction may be 4.0 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 6B or more, preferably 4B or more, and may be 2B or more, F or more, or 2H or more. In a compatible system of polyimide and polyester, the pencil hardness is unlikely to decrease even if the ratio of polyester is increased. Therefore, a film with little coloration and excellent transparency can be provided without significantly reducing the excellent mechanical strength unique to polyimide.

[0149] Films formed from resin compositions containing polyimide and polyester 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.

[0150] The following examples will be used to further explain the present invention, but the present invention is not limited to these examples.

[0151] [Preparation of Polyimide Resin] Dimethylformamide (DMF) was placed in a separable flask and stirred under a nitrogen atmosphere. Diamine and tetracarboxylic dianhydride were added in the ratios (mol %) shown in Table 1, followed by acetic acid, 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 13 wt %. Pyridine was added to the polyamic acid solution, and after complete dispersion, acetic anhydride was added and the mixture was stirred at 90°C for 3 hours to carry out imidization.

[0152] After the imidization, the solution was cooled to room temperature, and then 2-propyl alcohol (IPA) was added dropwise to the solution while stirring to precipitate a polyimide resin. Further IPA was added, and the solution was stirred for approximately 30 minutes, after which suction filtration was performed 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.

[0153] [Preparation of Resin Composition (Solution) and Film Fabrication] <Resin Composition of Polyimide (PI) and Polyester (PEs)> The above polyimide resin and the following commercially available polyester resin were dissolved in DMF in a weight ratio of 1:1 to prepare a resin solution with a solid content of 10 wt %.

[0154] PEs1: Eliter UE3600 (polyester containing a bisphenol alkylene oxide adduct as a diol component; manufactured by Unitika; weight average molecular weight: 60,000, glass transition temperature: 75°C) PEs2: Eliter UE9200 (polyester containing neopentyl glycol as a diol component; manufactured by Unitika; weight average molecular weight: 39,000, glass transition temperature: 65°C) PEs3: OKP4HT (polyester containing a diol having a fluorene structure as a diol component; manufactured by Osaka Gas Chemicals; weight average molecular weight: 38,000, glass transition temperature: 142°C)

[0155] The weight-average molecular weight of the polyester resin was measured using a gel permeation chromatography (HLC-8220GPC equivalent) manufactured by Tosoh Corporation under the following conditions: Eluent: LiBr (30 mM) + H3PO4 (30 mM) DMF solution Sample concentration: 0.15 wt% Flow rate: 0.6 mL / min Column configuration: From upstream, TSK guard column Super AW-H, TSK gel AWM-H, TSK gel AWM-H Column temperature: 40°C Detection conditions: RI, UV Molecular weight standard: Polystyrene (manufactured by Tosoh Corporation)

[0156] The above resin solution was applied to an alkali-free glass plate and heated and dried in air at 40°C, 60°C, 90°C, 120°C, 150°C, and 200°C in that order for 15 minutes at each temperature to produce a film with the thickness shown in Table 1.

[0157] [Evaluation] The films of the examples and comparative examples were cut into 3 cm squares and evaluated as follows: Films in which obvious cloudiness was visually confirmed (haze exceeding 10%) were not evaluated.

[0158] <Haze and Total Light Transmittance> 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.

[0159] <Yellowness Index> Yellowness index (YI) was measured according to JIS K7373 using a spectrophotometer "SC-P" manufactured by Suga Test Instruments.

[0160] [Evaluation Results] The polyimide compositions, the types of polyester resins, and the evaluation results of the films are shown in Table 1. In Table 1, the compounds are abbreviated as follows:

[0161] <Diamine> TFMOB: 2,2'-bis(trifluoromethoxy)benzidine BAFL: 9,9-bis(4-aminophenyl)fluorene DDS: 3,3'-diaminodiphenyl sulfone ODA: 4,4'-diaminodiphenyl ether

[0162] <Tetracarboxylic acid dianhydrides> BPADA: 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene anhydride TBIS-MPN: 5,5'-(9H-fluoren-9-ylidenebis(2-methyl-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate] TAHMBP: 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diylbis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate) CBDA: 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride BT-100: 1,2,3,4-butanetetracarboxylic acid dianhydride PMDA: pyromellitic dianhydride

[0163]

[0164] The compositions of Examples 1 to 17, which used polyimides containing the specific diamine TFMOB as the diamine component, were capable of producing films with a haze of 10% or less and a total light transmittance of 85% or more, and were therefore excellent in transparency. In Comparative Examples 1 to 6, which used polyimides containing ODA as the diamine, the polyimide and polyester were not compatible in solution, and transparent films could not be obtained.

Claims

1. A polymer comprising a polyimide and a polyester, the polyimide having a structure derived from a diamine and a structure derived from a tetracarboxylic dianhydride, and the diamine is CF ３ -O-, -(CF ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ - (where n is an integer of 1 to 20), and the weight average molecular weight of the polyester is greater than 10,000.

2. The resin composition according to claim 1, wherein the fluorine atom-containing diamine is 2,2'-bis(trifluoromethoxy)benzidine, 3,3'-bis(trifluoromethoxy)benzidine, or 2,3'-bis(trifluoromethoxy)benzidine.

3. The resin composition according to claim 1, wherein the polyimide contains, as the tetracarboxylic dianhydride, at least one selected from the group consisting of tetracarboxylic dianhydrides represented by general formula (1), tetracarboxylic dianhydrides represented by general formula (2), and tetracarboxylic dianhydrides having a fluorene structure: In the general formula (1), A is any divalent organic group, and at both ends of A, a phenyl group is bonded to a carbon atom of A, p is 1 or 2, and R １ａ , R １ｂ , R ２ａ and R ２ｂ are each independently any substituent, m1 and m2 are each independently an integer of 0 to 3, and n1 and n2 are each independently an integer of 0 to 4, and in general formula (2), B is any divalent organic group, and at both ends of B, a carboxy group and a carbon atom of B are bonded to each other.

4. The polyimide is a polyimide having a tetracarboxylic dianhydride selected from the group consisting of 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride, 1,4-phenylenebis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diylbis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), bisphenol Z bis(trimellitic anhydride), 5,5'-[cyclododecylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate), 9,9-bis(3,4-dicarboxyphenyl)furan, and the like. fluorene dianhydride, 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, 5,5'-[9H-fluoren-9-ylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate), 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate), and spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-fluorene]-1,3,7,9-tetraone. The resin composition according to claim 1, which comprises one or more selected from the group consisting of:

5. The resin composition according to claim 3, wherein the polyimide further contains an alicyclic tetracarboxylic dianhydride as the tetracarboxylic dianhydride, and the ratio of the structure derived from the alicyclic tetracarboxylic dianhydride to the total amount of structures derived from the tetracarboxylic dianhydride in the polyimide is 1 to 80 mol %.

6. The polyimide has a carbon atom of an aromatic ring having CF ３ - or -C(CF ３ ) ２ The ratio of the structure derived from the diamine having a structure in which - is directly bonded to the carbon atom of the aromatic ring is less than 0.5 mol % relative to the total amount of the structure derived from the tetracarboxylic dianhydride. ３ - or -C(CF ３ ) ２ The resin composition according to claim 1, wherein the ratio of a structure derived from a tetracarboxylic dianhydride having a structure in which - is directly bonded is less than 0.5 mol %.

7. The resin composition according to claim 1, wherein the polyester has a structure derived from a dicarboxylic acid and a structure derived from a diol, and the diol comprises at least one selected from the group consisting of a diol having a chain alkylene group having 3 or more carbon atoms which may be branched, a diol having a chain alkenylene group having 3 or more carbon atoms which may be branched, a polyalkylene glycol, and a diol having a cyclic structure.

8. The resin composition according to claim 1, wherein the polyester has a structure derived from a dicarboxylic acid and a structure derived from a diol, and the diol includes at least one selected from the group consisting of a diol having a fluorene structure and a diol having a bisphenol derivative structure.

9. The resin composition according to claim 1, wherein the polyester has a structure derived from a dicarboxylic acid and a structure derived from a diol, and the diol contains a bisphenol alkylene oxide adduct.

10. The resin composition according to claim 1, comprising said polyimide and said polyester in a weight ratio ranging from 2:98 to 98:

2.

11. A molded article comprising the resin composition according to any one of claims 1 to 10.

12. A film comprising the resin composition according to any one of claims 1 to 10.

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