Resin compositions, molded articles, and films

Abstract

The resin composition comprises a polyimide and a polyester. The polyester has a weight average molecular weight greater than 10,000. As a diamine component, the polyimide comprises a diamine having one or more structures selected from CF3-O-, -(CF2-O)n- and -O-(CF2-CF2-O)n- (where n is an integer from 1 to 20). The diamine is preferably 2,2'-bis(trifluoromethoxy)benzidine, 3,3'-bis(trifluoromethoxy)benzidine, or 2,3'-bis(trifluoromethoxy)benzidine.

Description

Technology Field

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

[0002] In display devices such as liquid crystals, organic ELs, and electronic paper, as well as in electronic devices such as solar cells and touch panels, there is a demand for thinning, lightweighting, and further flexibility. By replacing the glass materials used in these devices with film materials, flexibility, thinning, and lightweighting can be achieved. As a glass substitute material, transparent polyimide films have been developed and are being used as display substrates and cover films.

[0003] Although transparent polyimide has superior heat resistance compared to general-purpose transparent resins, higher transparency is required when used in cover films for displays, etc. As a method to improve the transparency of transparent polyimide films, it has been proposed to use a resin composition in which polyimide is mixed with other resins. 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 a polycarbonate or a polyarylate. Prior art literature

[0004] International Release No. 2023 / 026982 International Release No. 2021 / 132279 The problem to be solved

[0005] In Patent Documents 1 and 2, solvent-soluble polyimides comprising fluoroalkyl-substituted benzidines such as 2,2'-bis(trifluoromethyl)benzidine (TFMB) as the diamine are used. Polyimides using a fluorine-containing compound as the diamine and / or tetracarboxylic acid dianhydride have excellent transparency and solvent solubility.

[0006] Meanwhile, in recent years, the environmental persistence of organic fluorine compounds (PFAS) has become a problem. Generally, the carbon-fluorine bonds contained in organic fluorine compounds have high bond energies, making them difficult to decompose in the environment. In particular, organic fluorine compounds containing structures in which a trifluoromethyl group is bonded to a carbon atom (-C-CF3) or carbon atoms are bonded to both ends of a difluoromethylene group (-C-CF2-C-) have low decomposition rates in the environment, and their impact on the human body has also been pointed out.

[0007] In light of these challenges, the present invention aims to provide a molded body, such as a film, comprising a polyimide having excellent environmental safety and high transparency, and a resin composition used in the production of the same. means of solving the problem

[0008] The present invention relates to a resin composition comprising a polyimide and a polyester, and a molded article such as a film comprising said resin composition. The polyimide is, as a diamine component, CF3-O-, -(CF2-O) n - and -O-(CF2-CF2-O) n It includes a fluorine atom-containing diamine (specific diamine) having one or more structures selected from -(CF2-O) n - and -O-(CF2-CF2-O) n - n is an integer from 1 to 20.

[0009] Preferred examples of specific diamines containing fluorine atoms include 2,2'-bis(trifluoromethoxy)benzidine, 3,3'-bis(trifluoromethoxy)benzidine, and 2,3'-bis(trifluoromethoxy)benzidine.

[0010] It is preferable that the polyimide comprises 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, as tetracarboxylic acid dianhydrides.

[0011] Preferred examples of specific acid dianhydrides include 4,4'-(4,4'-isopropylidene diphenoxy)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), and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride. Examples include 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, 5,5'-[9H-fluorene-9-ylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate), 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthen]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate), and spiro[11H-diplo[3,4-b: 3',4'-i]xanthen-11,9'-fluorene]-1,3,7,9-tetraone.

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

[0013] It is preferable that the polyimide has a structure in which CF3- or -C(CF3)2- is directly bonded to a carbon atom of an aromatic ring with less than 0.5 mol% relative to the total amount of the diamine component, and a structure in which CF3- or -C(CF3)2- is directly bonded to a carbon atom of an aromatic ring with less than 0.5 mol% relative to the total amount of the tetracarboxylic acid dianhydride component.

[0014] The weight average molecular weight of the polyester is greater than 10,000. The polyester preferably comprises, as a diol component, one or more selected from the group consisting of a diol having a chain-like alkylene group having three or more carbon atoms that may have branches, a diol having a chain-like alkenylene group having three or more carbon atoms that may have branches, polyalkylene glycol, and a diol having a cyclic structure.

[0015] Among the above-mentioned 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 include polyimide and polyester in a weight ratio ranging from 98:2 to 2:98. Effects of the invention

[0017] The molded article, such as a film, formed by the resin composition of the present invention has high light transmittance and excellent transparency. In addition, since the polyimide contains a specific diamine as a diamine component, it has lower environmental persistence compared to polyimides using organic fluorine compounds such as fluoroalkyl-substituted benzidine, and thus has excellent environmental safety. Specific details for implementing the invention

[0018] [Resin Composition]

[0019] One embodiment of the present invention is a commercial resin composition comprising polyimide and polyester. Since the polyimide and polyester are commercially compatible, a molded body, such as a film, formed by the resin composition exhibits transparency.

[0020] [Polyimide]

[0021] Polyimide is a polymer having a structural unit represented by general formula (I), and is obtained by dehydrating a polyamic acid obtained by addition polymerization of a tetracarboxylic acid dianhydride (hereinafter referred to as "acid dianhydride") and a diamine. That is, polyimide is a polycondensation product of a tetracarboxylic acid dianhydride and a diamine, and has a structure derived from the tetracarboxylic acid dianhydride (acid dianhydride component) and a structure derived from the diamine (diamine component). In addition, polyimide can also be synthesized by condensation of a diisocyanate and a tetracarboxylic acid dianhydride through decarboxylation.

[0022]

[0023] In general formula (I), X is a tetravalent organic group and Y is a divalent organic group. X is a tetracarboxylic acid dianhydride residue and is an organic group from which two anhydrous carboxyl groups have been removed from the tetracarboxylic acid dianhydride represented by the following general formula (II). Y is a diamine residue and is an organic group from which two amino groups have been removed from the diamine represented by the following general formula (III). Additionally, when synthesizing polyimide using diisocyanate, Y is an organic group from which two isocyanate groups have been removed from the diisocyanate compound, but in that case as well, the divalent organic group Y is referred to as a "diamine residue."

[0024]

[0025] In other words, the polyimide comprises a structural unit represented by the following general formula (IIa) and a structural unit represented by the following general formula (IIIa), and has a structural unit represented by the general formula (I) by the tetracarboxylic acid dianhydride-derived structure (IIa) and the diamine-derived structure (IIIa) forming an imide bond.

[0026]

[0027] The polyimide may contain multiple tetracarboxylic acid dianhydride residues X and multiple diamine residues Y. Below, the diamine component and the acid dianhydride component as monomer units constituting the polyimide will be explained by example.

[0028] Diamine

[0029] The polyimide in an embodiment of the present invention is, as a diamine component, CF3-O-, -(CF2-O) n - and -O-(CF2-CF2-O) n It includes one or more diamines having a structure selected from -. n is an integer from 1 to 20. Hereinafter, such diamines are described as “specific diamines.”

[0030] In certain diamines, the carbon atom of the trifluoromethyl group (-CF3) or the carbon atom of the difluoromethylene group (-CF2-) is bonded to the oxygen atom, and compared to the structure in which the trifluoromethyl group is bonded to the carbon atom (-C-CF3) or the structure in which carbon atoms are bonded to both ends of the difluoromethylene group (-C-CF2-C-), there is a tendency for higher degradability and lower environmental persistence. Therefore, polyimides containing the specific diamine as the diamine component have superior environmental safety compared to conventional soluble polyimides containing organic fluorine compounds such as fluoroalkyl-substituted benzidine as the diamine component.

[0031] Among certain diamines, CF3-O- or -(CF2-O) in that they do not correspond to the "certain fluorine structure" described below n It is desirable to have a trifluoromethoxy group (CF3-O-) and, from the perspective of the polymerization and mechanical strength of the polyimide, a diamine having a trifluoromethoxy group is preferred, and among them, a diamine in which the oxygen atom of the trifluoromethoxy group is bonded to the carbon atom of the aromatic ring is preferred. From the perspective of reactivity, it is desirable that the diamine in which the trifluoromethoxy group is bonded to the carbon atom of the aromatic ring does not have a fluorine atom that is directly bonded to the aromatic ring to which the trifluoromethoxy group is bonded, and it is particularly desirable that it does not contain a fluorine atom other than the trifluoromethoxy group. Examples of specific diamines in which the trifluoromethoxy group is bonded to the carbon atom of the aromatic ring include trifluoromethoxy-substituted benzidine and trifluoromethoxy-substituted phenylenediamine.

[0032] 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(trifluoromethoxy)benzidine, 2,2',3-tris(trifluoromethoxy)benzidine, Examples include 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.

[0033] 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.

[0034] From the perspective of the polymerization of polyimide and compatibility with polyester, trifluoromethoxy-substituted benzidine is preferred as a specific diamine. Among these, from the perspective of the solubility of polyimide in organic solvents and compatibility with other resins, it is preferable to have a trifluoromethoxy group at the 2nd or 3rd position of the biphenyl, and 2,2'-bis(trifluoromethoxy)benzidine (hereinafter referred to as "TFMOB"), 3,3'-bis(trifluoromethoxy)benzidine, and 2,3'-bis(trifluoromethoxy)benzidine are more preferable, and TFMOB is particularly preferred. By having a trifluoromethoxy group at the 2nd or 3rd position of the biphenyl, in addition to the reduction in π-electron density due to the electron-attracting properties of the trifluoromethoxy group, π-π stacking between benzene rings is inhibited by the steric hindrance of the trifluoromethoxy group, so the absorption end wavelength is shifted to a shorter wavelength, which can reduce the coloration of the polyimide. In addition, TFMOB can reduce the coloration of polyimide because the bond between the two benzene rings of biphenyl is twisted due to steric hindrance between the 2nd and 2' trifluoromethoxy groups of biphenyl, thereby reducing the planarity of the π-conjugation and causing the absorption end wavelength to shift to a shorter wavelength.

[0035] The amount of a specific diamine relative to the total amount of the diamine component of the polyimide is preferably 10 mol% or more, more preferably 30 mol% or more, more preferably 50 mol% or more, 60 mol% or more, 70 mol% or more, 80 mol% or more, or 90 mol% or more, and may be 100 mol%. Among these, it is preferable that the amount of the trifluoromethoxy group-containing diamine be within the said range, and particularly preferable that the amount of the trifluoromethoxy-substituted benzidine be within the said range. As the proportion of the specific diamine increases, discoloration is suppressed, and mechanical strengths such as pencil hardness, elastic modulus, breaking strength, and breaking elongation of the film may be improved.

[0036] (Diamines other than specific diamines)

[0037] The polyimide may include diamines other than specific diamines as diamine components. From the perspective of the environmental safety of the polyimide, it is preferable not to include -C-CF3 and -C-CF2-C-, and it is particularly preferable not to include fluorine atoms.

[0038] Examples of diamines that do not contain a fluorine atom 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'-diaminodiphenylsulfone, 3,4'-diaminodiphenyl sulfone, 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-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-Bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-Bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-Bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 4,4'-Bis[4-(4-aminophenoxy)benzoyl]diphenylether, 4,4'-Bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-Bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenylsulfone, 4,4'-Bis[4-(4-aminophenoxy)phenoxy]diphenylsulfone, 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3'-Diamino-4,4'-Dibiphenoxybenzophenone, 3,3'-Diamino-4-phenoxybenzophenone, 3,3'-Diamino-4-Biphenoxybenzophenone, 6,6'-Bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, 6,6'-Bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, 1,3-Bis(3-aminopropyl)tetramethyldisiloxane, 1,3-Bis(4-aminobutyl)tetramethyldisiloxane, α,ω-Bis(3-aminopropyl)polydimethylsiloxane, α,ω-Bis(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, trans-1,4-diaminocyclohexane, 1,2-di(2-aminoethyl)cyclohexane, 1,3-di(2-aminoethyl)cyclohexane, Examples include 1,4-di(2-aminoethyl)cyclohexane, bis(4-aminocyclohexyl)methane, isophoronediamine, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane, etc.

[0039] As a diamine, the solubility or transparency of the polyimide in a solvent may be improved by using diaminodiphenylsulfone in addition to a specific diamine. Among diaminodiphenylsulfones, 3,3'-diaminodiphenylsulfone (3,3'-DDS) and 4,4'-diaminodiphenylsulfone (4,4'-DDS) are preferred, and these may be used in combination.

[0040] In the case where diaminodiphenylsulfone is used in addition to a specific diamine, the amount of diaminodiphenylsulfone relative to the total amount of the diamine component 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.

[0041] As a diamine, in addition to a specific diamine, using a diamine having a fluorene structure may improve the solubility, transparency, and mechanical strength of the polyimide in solvents. As diamines containing fluorene, 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 are preferred, and these may be used in combination.

[0042] In addition to a specific diamine, when a diamine having a fluorene structure is used, the amount of the diamine having a fluorene structure relative to the total amount of the diamine component 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 90 mol% or less, 70 mol% or less, 50 mol% or less, or 30 mol% or less.

[0043] As a diamine, the transparency of the polyimide may be improved by using a diamine alicyclic in addition to a specific diamine. Among diamines alicyclic, isophorone diamine and 1,4-diaminocyclohexane are preferred, and these may be used in combination.

[0044] In addition to a specific diamine, when a cycloaliphatic diamine is used, the amount of the cycloaliphatic diamine relative to the total amount of the diamine component 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.

[0045] The total amount of specific diamines, diaminodiphenylsulfone, diamines having a fluorene structure, and alicyclic diamines relative to the total amount of diamine components of the polyimide is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, may be 95 mol% or more or 99 mol% or more, and may be 100 mol%.

[0046] Among aromatic diamines other than those mentioned above, p-phenylenediamine, 4,4'-diaminodiphenyl ether, and 3,4'-diaminodiphenyl ether, etc., may 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 with respect to the total amount of the diamine component, or 50 mol% or less, 30 mol% or less, 20 mol% or less, or 10 mol% or less.

[0047] The polyimide may include a fluorine atom-containing diamine other than a specific diamine as a diamine component, but from the perspective 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 polyimide diamine component 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 include a fluorine atom-containing diamine other than a specific diamine as a diamine component.

[0048] Among fluorine-containing diamines, those having a structure in which a trifluoromethyl group is bonded to a carbon atom (-C-CF3) and / or a structure in which a carbon atom is bonded to both ends of a difluoromethylene group (-C-CF2-C-) have low degradability, raising concerns regarding environmental safety. In order to increase the transparency or solubility of polyimides in solvents, general soluble polyimides contain, as a diamine component, a diamine having a structure in which CF3- or -C(CF3)2- is directly bonded to a carbon atom of an aromatic ring (e.g., 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), but from the perspective of environmental safety of polyimides, it is desirable not to substantially contain these diamines. The amount of diamine in which CF3- or -C(CF3)2- is directly bonded to a carbon atom of an aromatic ring relative to the total amount of diamine components of the polyimide is preferably less than 0.5 mol%, may be 0.3 mol% or less, 0.1 mol% or less, or 0.05 mol% or less, or 0.

[0049] Tetracarboxylic acid dianhydride

[0050] (Specific acidic amurous substance)

[0051] The acid dianhydride component of the polyimide is not particularly limited, but from the perspective of enhancing environmental safety and ensuring solubility in organic solvents, it is preferable to include 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 as the acid dianhydride component. Hereinafter, these tetracarboxylic acid dianhydrides are referred to as "specific acid dianhydrides."

[0052] Bisphenol-type tetracarboxylic acid dianhydrides are compounds represented by the following general formula (1), and are obtained, for example, by reacting two hydroxyl groups of bisphenols with iodoisobenzofuran-1,3-dione, etc.

[0053]

[0054] 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. R 1a , R 1b , R 2a and R 2b Each is independently any substituent, and from the perspective 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 integers from 0 to 3, and n1 and n2 are each independently integers from 0 to 4.

[0055] Examples of a divalent organic group A include the following (a), (b), and (c). R in (a). 3a and R 3b is, each independently, a hydrogen atom, a C1 to C10 alkyl group, or a phenyl group. R in (b) 4 is an alkyl group having 1 to 10 carbon atoms, and k is an integer from 0 to 10. If k is 2 or more, multiple R 4 It can be the same or different.

[0056]

[0057] In terms of the solubility of polyimide, 4,4'-(4,4'-isopropylidene diphenoxy)diphthalic anhydride (BPADA) is particularly preferred as a bisphenol-type tetracarboxylic acid dianhydride.

[0058] Bis(anhydrous trimellitic acid) ester is represented by the following general formula (2).

[0059]

[0060] In general formula (2), B is any divalent organic group, and at both ends of B, a carboxyl group and a carbon atom of B are bonded. Specific examples of the divalent organic group B include the following (i) to (viii).

[0061]

[0062] The groups represented by formulas (i) to (viii) are groups from diols with two hydroxyl groups removed, and for example, the group represented by formula (i) is a group from a hydroquinone derivative that may have a substituent on the benzene ring with two hydroxyl groups removed.

[0063] In equations (i) and (ii), R 1 , R 2a and R 2b is each independently an alkyl group having 1 to 4 carbon atoms, an alkoxy group, or a halogen, and m, n1, and n2 are each independently integers from 0 to 4. In formulas (iii), (iv), and (v), R 3a and R 3b Each is independently any substituent, and from the perspective 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. k1 and k2 are each independently integers from 0 to 4. R 4 is an alkyl group, an alkoxy group, or a halogen, and j is an integer from 0 to 10.

[0064] Bis(anhydrous trimellitic acid) ester is preferably an aromatic ester, and as B in general formula (2), among (i) to (viii) above, (i) to (v) are preferred, among (i) to (iv) are preferred, and (i) and (ii) are particularly preferred.

[0065] In the case where B is represented by general formula (i), from the perspective 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).

[0066]

[0067] In the case where B is represented by formula (ii), in terms 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).

[0068]

[0069] In the case where B is represented by formula (iii), in terms of the solubility of the polyimide, the bis(trimellitic anhydride) ester of general formula (2) is preferably bisphenol Zbis(trimellitic anhydride) (BPZ-TME) represented by the following formula (2-3).

[0070]

[0071] In the case where B is represented by formula (iv), in terms 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).

[0072]

[0073] A tetracarboxylic acid dianhydride having a fluorene structure is a compound having a fluorene structure between two acid anhydride groups. Additionally, if the bisphenol-type tetracarboxylic acid dianhydride of the above general formula (1) or the bis(trimellitic anhydride) ester of the above (2) has a fluorene structure, the acid dianhydride is treated as a tetracarboxylic acid dianhydride having a fluorene structure.

[0074] Examples of tetracarboxylic acid dianhydrides having a fluorene structure include acid dianhydrides represented by the following group (A) or N,N'-(9H-fluorene-9-ylidendi-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxamide].

[0075]

[0076] R in group (A) 1a , R 1b , R 2a , R 2b , R 3a , R 3b , R 4a and R 4b Each is independently any substituent, and from the perspective 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 integers from 0 to 3. n1 and n2 are each independently integers from 0 to 4. k1 and k2 are each independently integers from 0 to 2. j1 and j2 are each independently integers from 0 to 4.

[0077] R 5a and R 5b is an alkylene group, and R 5a and R 5b may be the same or different. p1 and p2 are each independently 0 or 1. R 6 represents a carbonyl group, and q1 and q2 are each independently 0 or 1.

[0078] Among group (A), tetracarboxylic acid 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-diplo[3,4-b: 3',4'-i]xanthene-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 in terms of having a small molecular weight, a relatively high proportion of fluorene structures, and high solubility and transparency of polyimide and compatibility with polyester. 5,5'-[9H-fluorene-9-ylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) is preferred.

[0079] Polyimides comprising the aforementioned specific diamine as a diamine component and a specific acid dianhydride as an acid dianhydride component tend to exhibit solubility in organic solvents, as well as high transparency and compatibility with polyesters.

[0080] Among certain acid dianhydrides, in terms of solubility in organic solvents, transparency, and compatibility with polyesters, 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-DMPN), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride (BPF-PA), 5,5'-[9H-fluorene-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]xanthen]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) (TBIS-RXN) and spiro[11H-diplo[3,4-b: 3',4'-i]xanthen-11,9'-fluorene]-1,3,7,9-tetraone are preferred.

[0081] From the perspective of UV resistance of polyimide, among 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 perspective of solubility in solvents and mechanical strength, BPADA, BPAF, and BPF-PA are particularly preferred. Since these acid dianhydrides do not have ester bonds and do not undergo fleece transition due to UV light, discoloration is unlikely to occur when the polyimide is exposed to UV light. Furthermore, from the perspective 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 specific acid dianhydrides.

[0082] With respect to the solubility of the polyimide in organic solvents and compatibility with polyester, the total amount of a specific acid dianhydride relative to the total amount of acid dianhydride components is preferably 15 mol% or more, more preferably 30 mol% or more, 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 a specific acid dianhydride relative to the total amount of 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.

[0083] (Tetracarboxylic acid dianhydrides other than specific acid dianhydrides)

[0084] As an acid dianhydride component, the polyimide may include acid dianhydrides other than specific acid dianhydrides. Examples of such acid dianhydrides include alicyclic tetracarboxylic acid dianhydrides, aromatic tetracarboxylic acid dianhydrides, and chain-like aliphatic tetracarboxylic acid dianhydrides. From the perspective of environmental safety of the polyimide, it is preferable not to include -C-CF3 and -C-CF2-C-, and it is particularly preferable not to include fluorine atoms.

[0085] A cycloaliphatic tetracarboxylic acid dianhydride may have at least one cycloaliphatic structure, and may have both a cycloaliphatic and an aromatic ring in one molecule. The cycloaliphatic may be polycyclic or may have a spiro structure. As alicyclic tetracarboxylic acid dianhydrides, 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, norbornan-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornan-5,5'',6,6''-tetracarboxylic acid Dehydrogenate, 2,2'-vinorbornan-5,5',6,6'-tetracarboxylic acid dehydrogenate, 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic acid-1,4: 2,3-dehydrogenate, bicyclo[2.2.2]oct-7-en-2,3,5,6-tetracarboxylic acid dehydrogenate, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid dehydrogenate, 5-(2,5-dioxotetrahydropril)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid dehydrogenate, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic acid dehydrogenate, Bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid dianhydride, 3,5,6-tricarboxynorrbornan-2-acetic acid 2,3: 5,6-dianhydride, decahydro-1,4,5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic acid dianhydride, tricyclo[6.4.0.0(2,7)]dodecane-1,8: 2,7-tetracarboxylic acid dianhydride, octahydro-1H,3H,8H,0H-biphenyleno[4a,4b-c: 8a,8b-c']difuran-1,3,8,10-tetraone, ethylene glycolbis(hydrogenated trimellitic anhydride)ester, Examples include decahydro[2]benzopyrano[6,5,4,-def][2]benzopyran-1,3,6,8-tetraone.The mechanical strength of polyimide tends to improve by including alicyclic tetracarboxylic acid dianhydride in addition to a specific acid dianhydride as an acid dianhydride component. In addition, the compatibility between polyimide and polyester may be improved when the polyimide includes alicyclic tetracarboxylic acid dianhydride as an acid dianhydride component.

[0086] Among alicyclic tetracarboxylic acid dianhydrides, with respect to the transparency and mechanical strength of polyimides, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride (CPDA), 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride (H-PMDA), 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid anhydride (TDA-100), bicyclo[2.2.2]oct-7-en-2,3,5,6-tetracarboxylic acid dianhydride (BEDA), bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid dianhydride (BODA), 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride (H-BPDA) is preferred. Among these, from the perspective of mechanical strength, a tetracarboxylic acid dianhydride in which two acid anhydride groups are bonded to one ring is preferred, and CBDA is particularly preferred.

[0087] In the case where alicyclic tetracarboxylic acid dianhydride is used in addition to a specific acid dianhydride, the amount of alicyclic tetracarboxylic acid dianhydride relative to the total amount of 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. Transparency tends to increase as the amount of alicyclic tetracarboxylic acid dianhydride increases. From the perspective of ensuring the solubility of polyimide in organic solvents, the amount of alicyclic tetracarboxylic acid dianhydride relative to the total amount of 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.

[0088] Aromatic tetracarboxylic acid dianhydrides other than specific acid dianhydrides include pyromellitic acid dianhydride, melophanate dianhydride, 3,3',4,4'-benzophenone tetracarboxylic acid dianhydride, 2,2',3,3'-benzophenone tetracarboxylic acid dianhydride, 2,2',3,3'-biphenyl tetracarboxylic acid dianhydride, 3,3',4,4'-biphenyl tetracarboxylic acid dianhydride, 3,3',4,4'-diphenylsulfone tetracarboxylic acid dianhydride, 3,4'-oxydiphthalic anhydride (3,4'-ODPA), 4,4'-oxydiphthalic anhydride (4,4'-ODPA), 3,3'-oxydiphthalic anhydride (3,3'-ODPA), and 5,5'-dimethylmethylenebis(phthalate) Examples include anhydrides), 2,3,6,7-naphthalene tetracarboxylic acid dianhydride, 1,4,5,8-naphthalene tetracarboxylic acid dianhydride, 1,2,5,6-naphthalene tetracarboxylic acid dianhydride, terphenyl tetracarboxylic acid dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 2,2-bis(4-hydroxyphenyl)propanedibenzoate-3,3',4,4'-tetracarboxylic acid dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid dianhydride, etc.

[0089] Among these aromatic tetracarboxylic acid dianhydrides, 4,4'-oxydiphthalic anhydride is preferred in terms of polyimide solubility, pyromellitic anhydride and melopanoic anhydride are preferred in terms of mechanical strength, and pyromellitic anhydride is particularly preferred.

[0090] In addition to a specific acid dianhydride, when an aromatic tetracarboxylic acid dianhydride other than the specific acid dianhydride is used, the amount of the aromatic tetracarboxylic acid dianhydride other than the specific acid dianhydride relative to the total amount of the acid dianhydride component 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 perspective of ensuring the solubility of the polyimide in organic solvents, the amount of the aromatic tetracarboxylic acid dianhydride other than the specific acid dianhydride relative to the total amount of the acid dianhydride component 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.

[0091] Examples of chain-like aliphatic tetracarboxylic acid dianhydrides include ethylenetetracarboxylic acid dianhydride, 1,2,3,4-butanetetracarboxylic acid dianhydride, and meso-butane-1,2,3,4-tetracarboxylic acid dianhydride.

[0092] The amount of fluorine atom-containing acid dianhydride relative to the total amount of the acid dianhydride component 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 include fluorine atom-containing acid dianhydride as an acid dianhydride component.

[0093] Among fluorine-containing acid dianhydrides, those having a structure in which a trifluoromethyl group is bonded to a carbon atom (-C-CF3) and / or a structure in which a carbon atom is bonded to both ends of a difluoromethylene group (-C-CF2-C-) have low degradability, raising concerns regarding environmental safety. In particular, acid dianhydrides having a structure in which CF3- or -C(CF3)2- is directly bonded to a carbon atom of an aromatic ring (e.g., 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 9,9-bis(trifluoromethyl)xanthene tetracarboxylic acid dianhydride, 9-trifluoromethylxanthene tetracarboxylic acid dianhydride, 2,2'-bis(trifluoromethyl)-4,4',5,5'-biphenyltetracarboxylic acid dianhydride) have low degradability in the environment; therefore, from the perspective of environmental safety of polyimides, it is desirable not to substantially include these acid dianhydrides. The amount of acid dianhydride in which CF3- or -C(CF3)2- is directly bonded to a carbon atom of an aromatic ring relative to the total amount of acid dianhydride components of the polyimide is preferably less than 0.5 mol%, may be 0.3 mol% or less, 0.1 mol% or less, or 0.05 mol% or less, or 0.

[0094] Content of specific fluorine structures in polyimide

[0095] As mentioned above, as a diamine component, CF3-O-, -(CF2-O) n - and -O-(CF2-CF2-O) n A polyimide comprising a diamine (specific diamine) having one or more structures selected from - exhibits solubility in organic solvents and compatibility with polyester without substantially including structures such as -C-CF3, -C-CF2-C-.

[0096] To reduce the environmental persistence of fluorine-containing compounds, it is desirable for the polyimide to have a low amount of monomers (diamines and acid anhydrides) having specific fluorine structures. Specific fluorine structures are structures having a trifluoromethyl group (CF3-) except those containing only the components of structural formula (i) below, and structures having a difluoromethylene group (-CF2-) except those containing only the components of structural formula (ii) below.

[0097]

[0098] In equations (i) and (ii), X is -OR or -NRR', and in equation (ii), X' is any of -H, -CH3, aromatic, -C(O)-, -OR'', -SR'' and NR''R'''. R, R', R'' and R''' are each independently any of -H, -CH3, -CH2-, aromatic, and -C(O)-.

[0099] In terms of improving biodegradability in the environment, the amount of fluorine atoms included in a 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.

[0100] Preparation of Polyimide

[0101] Polyamic acid as a polyimide precursor is obtained by the reaction of a diamine and an acid dianhydride, and polyimide is obtained by the dehydration (imidization) of the polyamic acid. The method of preparing polyamic acid is not particularly limited, and any known method can be applied. For example, a polyamic acid solution is obtained by dissolving an acid dianhydride and a diamine in an organic solvent in roughly equimolar amounts (molar ratio of 90:100 to 110:100) and stirring.

[0102] The concentration of the polyamic acid solution is typically 5 to 35 weight%, and preferably 10 to 30 weight%. At this concentration range, the polyamic acid obtained by polymerization has an appropriate molecular weight, and the polyamic acid solution has an appropriate viscosity.

[0103] When polymerizing polyamide acids, it is preferable to add acid dianhydrides to diamines to suppress ring opening of acid dianhydrides. When adding multiple types of diamines or multiple types of acid dianhydrides, they may be added all at once or in multiple stages. By adjusting the order of monomer addition, various properties of the polyimide can be controlled.

[0104] The organic solvent used for the polymerization of polyamide acid is not particularly limited, as long as it is a solvent that does not react with diamines and acid dianhydrides and can dissolve polyamide acid. Examples of organic solvents include urea-based solvents such as methyl urea and N,N-dimethylethylurea; sulfoxide or sulfone-based solvents such as dimethyl sulfoxide, diphenylsulfone, and tetramethylsulfone; amide-based solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N,N'-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, and hexamethylphosphate triamide; alkyl halide-based solvents such as chloroform and dichloromethane; aromatic hydrocarbon-based 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-cresolmethyl ether. Typically, these solvents are used individually or, if necessary, in an appropriate combination of two or more types. In terms of the solubility and polymerization reactivity of polyamide acids, DMAc, DMF, NMP, etc. are preferably used.

[0105] Polyimide is obtained by the dehydration and cyclization of polyamic acid. As a method for preparing polyimide from a polyamic acid solution, a dehydrating agent, an imidation catalyst, etc., can be added to the polyamic acid solution, and imidation can be carried out within the solution. To promote the progress of imidation, the polyamic acid solution may be heated. By mixing a solution containing the polyimide produced by the imidation of polyamic acid with a non-solvent, the polyimide resin precipitates as a solid. By isolating the polyimide resin as a solid, impurities generated during the synthesis of polyamic acid, as well as residual dehydrating agents and imidation catalysts, can be washed and removed using the non-solvent, thereby preventing discoloration of the polyimide or an increase in yellowness. Furthermore, by isolating the polyimide resin as a solid, solvents suitable for film formation, such as low-boiling point solvents, can be applied when preparing a solution for film production.

[0106] The molecular weight of the polyimide (weight-average molecular weight equivalent to polystyrene measured by gel filtration 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 excessively small, the strength of the film may be insufficient. If the molecular weight is excessively large, the solubility of the polyimide or its compatibility with polyester may be reduced.

[0107] It is preferable that the polyimide be soluble in organic solvents. Specifically, it is preferable that the polyimide dissolves in dimethylformamide (DMF) at 23°C at a concentration of 1 wt% or more. In addition to being soluble in amide-based solvents such as DMF, it is preferable that the polyimide be soluble in non-amide-based solvents. Examples of non-amide-based solvents include ketone-based solvents such as acetone and methyl ethyl ketone, alkyl halide-based solvents such as chloroform and dichloromethane, and ester-based solvents such as ethyl acetate and γ-butyrolactone. Since non-amide-based solvents have lower boiling points compared to amide-based solvents and allow for easy removal of residual solvent during film production, polyimides soluble in non-amide-based solvents can be expected to improve film productivity. It is particularly preferable that the polyimide be soluble in dichloromethane.

[0108] From the perspective of thermal stability and light stability of resin compositions and molded articles such as films, it is desirable for the polyimide to have 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 perspective of reducing the acid value, it is desirable for the polyimide to have a high imidization rate. By having a low acid value, the stability of the polyimide is increased.

[0109] [Polyester]

[0110] Polyester is a condensation product of a dicarboxylic acid and a glycol, and has a structure derived from the dicarboxylic acid and a structure derived from the diol. From the perspective of securing mechanical strength of a molded article, such as a film, formed by a resin composition, a polyester with a weight average molecular weight (Mw, equivalent to polystyrene) greater 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 perspective of securing compatibility with polyimide and moldability of the resin composition for films, etc., 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.

[0111] Polyethylene terephthalate (PET), a representative polyester, is a condensation product of ethylene glycol and terephthalic acid, has high crystallinity, and low solubility in organic solvents. In the present embodiment, a polyester soluble in organic solvents is used. It is preferable that the polyester be soluble in organic solvents common to polyimide, and particularly preferable that it be soluble in highly polar solvents such as amide-based solvents.

[0112] The polyester has a weight average molecular weight greater than 10,000 and is soluble in organic solvents, and the dicarboxyl and diol components are not particularly limited. It is preferable that it be amorphous from the perspective of solubility in organic solvents.

[0113] Dior

[0114] In terms of making the polyester soluble in organic solvents, as the diol component of the polyester, a diol having a chain-like alkylene group having three or more carbon atoms that may have branches, a diol having a chain-like alkenylene group having three or more carbon atoms that may have branches, a polyalkylene glycol, and a diol having a cyclic structure are preferred. Hereinafter, these diols are referred to as "specific diols."

[0115] Examples of diols having a chain alkylene structure with 3 or more carbon atoms that may have branches include propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, etc. Among these, a diol having a chain alkylene structure with 5 or more carbon atoms is preferred, and among these, a diol having an alkylene group having a branched structure, such as neopentyl glycol, is preferred. Examples of diols having a chain alkenylene group with 3 or more carbon atoms that may have branches include 2-butene-1,4-diol, etc.

[0116] Examples of polyalkylene glycols include diethylene glycol, triethylene glycol, dipropylene glycol, polytetramethylene ether glycol, etc.

[0117] 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.

[0118] Among these, butanediol, neopentyl glycol, polytetramethylene ether glycol, diols having a fluorene structure; and diols having a bisphenol derivative structure are preferred in terms of the solubility of polyester and compatibility with polyimide.

[0119] A diol having a fluorene structure is one that has a fluorene backbone between two hydroxyl groups and is represented by the following general formula (3).

[0120]

[0121] In general formula (3), Ar1 and Ar2 are aromatic hydrocarbon rings. R 1a and R 1b is, each independently, an alkyl group having 1 to 10 carbon atoms or a phenyl group, and n1 and n2 are each independently integers greater than or equal to 0. R2a and R 2b is each independently an alkyl group having 1 to 10 carbon atoms or a phenyl group, and n1 and n2 are each independently integers from 0 to 4. R 3a and R 3b is an alkylene group, and R 5a and R 5b may be the same or different. p1 and p2 are each independently greater than or equal to 0 integers. q1 and q2 are 1.

[0122] Specific examples of diols 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, 9,9-bis{4-[2-(2-hydroxyethoxy)ethoxy]-3-phenylphenyl}fluorene, etc. Among these, 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 in terms of improving heat resistance.

[0123] Diols having a bisphenol derivative structure are those in which an alkylene oxide is added to two phenolic hydroxyl groups of bisphenol (bisphenol-alkylene oxide adducts), and ethylene oxide (EO) adducts and propylene oxide (PO) adducts of bisphenol are preferred. In addition, diols having a fluorene structure of the above general formula (3) include diols having a bisphenol derivative structure, but diols having a fluorene backbone are treated as diols having a fluorene structure even if they have a bisphenol derivative structure.

[0124] Examples of bisphenols that do not have a fluorene backbone 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), 2,2-bis(4-hydroxy-3-isopropylphenyl)propane (Bisphenol G), 1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene (Bisphenol M), and bis(4-hydroxyphenyl)sulfone (Bisphenol Examples include 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), etc.

[0125] Among bisphenol-alkylene oxide adducts, ethylene oxide adducts of bisphenol A, ethylene oxide adducts of bisphenol S, and ethylene oxide adducts of bisphenol Z are preferred in terms of the solubility of polyester.

[0126] The polyester may include a diol other than the specific diol mentioned above as a diol component. Ethylene glycol may be cited as an example of a diol other than the specific diol. When the specific diol and ethylene glycol are used in combination, from the perspective of compatibility between the polyester and the polyimide, the ratio of the specific diol to the ethylene glycol is preferably 90:10 to 10:90 in molar ratio, and may be 80:20 to 20:80 or 60:40 to 40:60. 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.

[0127] Dicarboxylic acid

[0128] The dicarboxylic acid component of the polyester is not particularly limited, and various aromatic dicarboxylic acids and aliphatic dicarboxylic acids are used. As the dicarboxylic acid, aliphatic dicarboxylic acids and aromatic dicarboxylic acids may be used in combination.

[0129] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and biphenyldicarboxylic acid. Additionally, dicarboxylic acids having a fluorene structure, such as 9,9-bis(carboxymethyl)fluorene or 9,9-bis(2-carboxyethyl)fluorene, can also be exemplified as aromatic dicarboxylic acids.

[0130] From the perspective of improving the solubility and mechanical strength of polyester, terephthalic acid and isophthalic acid are preferred. Terephthalic acid and isophthalic acid may each be used alone or in combination. When terephthalic acid and isophthalic acid are used in combination, from the perspective of the solubility of 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 perspective of the solubility and mechanical strength of polyester, the total amount of terephthalic acid and isophthalic acid relative to the total amount of the dicarboxylic acid component of 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.

[0131] Examples of aliphatic dicarboxylic acids include oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimetic acid, souveric acid, azelaic acid, sebacic acid, undecane diacid, dodecane diacid, fumaric acid, maleic acid, itaconic acid, citraconic acid, 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, tetrahydrophthalic acid, etc.

[0132] In some cases, the compatibility between the polyester and the polyimide is improved by including an aliphatic dicarboxylic acid as the dicarboxylic acid component of the polyester. In terms of improving compatibility with the polyimide, as an aliphatic dicarboxylic acid, a dicarboxylic acid having 6 to 12 carbon atoms, particularly 6 to 10 carbon atoms, is preferred, and among these, adipic acid, pimelic acid, souveric acid, azelaic acid, and sebacic acid are preferred in that they can also contribute to improving the solubility of the polyester.

[0133] Other ingredients

[0134] As monomer components constituting the polyester, monomers other than diols and dicarboxylic acids may be used within a range that does not impair the effects of the present invention. Monomers other than diols and dicarboxylic acids include polyols having three or more hydroxyl 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 carboxyl 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., lactic acid, One or more hydroxyl groups such as 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, 4-(β-hydroxy)ethoxybenzoic acid), lactones (e.g., β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone), and oxiranes (e.g., ethylene oxide). Examples include compounds having one or more carboxyl groups and / or compounds that produce one or more hydroxyl groups and / or one or more carboxyl groups by hydrolysis.

[0135] Preparation of Polyester

[0136] The polymerization method of polyester is not particularly limited, and various known methods may be employed, such as obtaining an oligomer by an ester exchange reaction or a direct esterification method, followed by melt polymerization or additional solid-state polymerization. In the polymerization of polyester, a dicarboxylic acid derivative, such as an acid anhydride, may be used as the dicarboxylic acid component.

[0137] In terms 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, more preferably 40 to 150°C, and may be around 60 to 130°C.

[0138] Polyester resins that are commercially available as polyester may be used. Examples of commercially available polyester resins containing a diol having a fluorene structure as a diol component include OKP4HT (manufactured by Osaka Gas Chemical, Mw: 38,000, Tg: 142°C) and OKP4 (manufactured by Osaka Gas Chemical, 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 Erytel UE3600 (Uniticase, Mw: 60,000, Tg: 75°C), Erytel UE3690 (Uniticase, Mw: 46,000, Tg: 90°C), Erytel UE9100 (Uniticase, Mw: 77,000, Tg: 19°C), and Byron 290 (Toyobo, Mw: 61,000, Tg: 72°C).

[0139] Examples of commercially available polyester resins comprising specific diols other than those mentioned above as diol components include Erytel UE3200G (Uniticase, Mw: 43,000, Tg: 65℃), Erytel UE3210 (Uniticase, Mw: 62,000, Tg: 45℃), Erytel UE3240 (Uniticase, Mw: 50,000, Tg: 40℃), Erytel UE3500 (Uniticase, Mw: 83,000, Tg: 15℃), Erytel UE3510 (Uniticase, Mw: 63,000, Tg: -25℃), Erytel UE9200 (Uniticase, Mw: 39,000, Tg: 65℃), and Erytel UE9800 (Uniticase, Mw: Examples include 40,000 (Tg: 85℃), Byron 200 (Toyobo, Mw: 42,000, Tg: 67℃), Byron 240 (Toyobo, Mw: 35,000, Tg: 60℃), and Byron 600 (Toyobo, Mw: 38,000, Tg: 47℃).

[0140] [Preparation of resin composition]

[0141] A resin composition is prepared by mixing the aforementioned polyimide and polyester. Although polyimide generally does not exhibit compatibility with other polymers, as described above, a polyimide containing a specific diamine as a diamine component exhibits compatibility with a solvent-soluble polyester.

[0142] Whether a specific polyimide and a specific polyester are compatible is determined by producing a film with a thickness of 10 μm containing the polyimide and the polyester. If the film is transparent and the haze is 10% or less, it is determined that the polyimide and the polyester exhibit compatibility, and if the haze of the film exceeds 10%, it is determined that the polyimide and the polyester do not exhibit compatibility.

[0143] The ratio of polyimide to polyester in the resin composition is not particularly limited. The compositional 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. As the proportion of polyimide increases, the mechanical strength of the molded article, such as a film, tends to increase. As the proportion of polyester increases, the coloration of the molded article, such as a film, tends to decrease and the transparency tends to increase.

[0144] In order to fully exhibit the effect of improving transparency through the mixing of 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.

[0145] The resin composition may simply be a mixture of a polyimide resin and a polyester resin precipitated as a solid, or it may be a mixture of a polyimide resin and a polyester resin. Additionally, when precipitating the polyimide resin by mixing a polyimide solution with a non-solvent, a polyester resin may be mixed into the solution, and the resin composition of the mixture of polyimide and polyester may be precipitated as a solid (powder).

[0146] The resin composition may be a mixed solution containing polyimide and polyester. The method of mixing the resins is not particularly limited; they may be mixed in a solid state or mixed in a liquid to form a mixed solution. A polyimide solution and a polyester solution may be prepared separately, and the two may be mixed to prepare a mixed solution of polyimide and polyester.

[0147] As a solvent for a solution containing polyimide and polyester, it is not particularly limited as long as it exhibits solubility for both polyimide and polyester. Examples of solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; ether solvents such as tetrahydrofuran and 1,4-dioxane; 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.

[0148] Generally, polyimides have low solubility in solvents and are often soluble only in highly polar solvents. Therefore, amide-based solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone are preferred in terms of the solubility of polyimides and the compatibility of polyimides and polyesters in solution, whereas non-amide-based solvents with a low boiling point are preferred in terms of the ability to remove solvents when producing molded articles such as films. Furthermore, ketone-based solvents and alkyl halide-based solvents are preferred because they have excellent solubility for both polyimides and polyesters, and because they have a low boiling point, they facilitate the removal of residual solvents during film production.

[0149] The resin composition may incorporate organic or inorganic low-molecular-weight compounds, high-molecular-weight compounds (e.g., epoxy resin), etc. The resin composition may include flame retardants, ultraviolet absorbers, crosslinking agents, dyes, pigments, surfactants, leveling agents, plasticizers, fine particles, sensitizers, etc. The fine particles may include organic fine particles such as polystyrene and polytetrafluoroethylene, inorganic fine particles such as colloidal silica, carbon, and layered silicates, etc., and may have a porous or hollow structure. The fiber reinforcing material may include carbon fibers, glass fibers, aramid fibers, etc.

[0150] [Molded bodies and films]

[0151] The above-described composition can be used to form various molded articles. Molding methods include injection molding, transfer molding, press molding, blow molding, inflation molding, calendering, melt extrusion molding, and other melting methods. A resin composition containing polyimide and polyester tends to have a lower melt viscosity compared to polyimide alone, and exhibits excellent moldability in injection molding, transfer molding, press molding, melt extrusion molding, etc.

[0152] Furthermore, a solution of a resin composition containing polyimide and polyester tends to have a lower viscosity compared to a solution of polyimide alone at the same solid content concentration. Consequently, along with excellent handling properties such as transport, it offers high coating properties and is advantageous for reducing film thickness non-uniformity.

[0153] In one embodiment, the molded body is a film. The molding method of the film may be either a melt method or a solution method, but the solution method is preferred from the perspective of producing a film with excellent transparency and uniformity. In the solution method, a film is obtained by applying a solution containing the above-mentioned polyimide and polyester onto a support and drying and removing the solvent.

[0154] As a method for applying the resin solution onto a support, known methods using a bar coater or a comma coater can be applied. As the support, a glass substrate, a metal substrate such as SUS, a metal drum, a metal belt, a plastic film, etc., can be used. From the perspective of improving productivity, it is preferable to manufacture the film by roll-to-roll using a stepless support such as a metal drum or a metal belt, or a long plastic film, as the support. When using a plastic film as the support, a material that does not dissolve in the solvent of the film-forming dope should be appropriately selected.

[0155] It is preferable to perform heating when drying the solvent. The heating temperature is not particularly limited as long as it is a temperature capable of removing the solvent and suppressing discoloration of the resulting film, and is appropriately set to room temperature to about 250°C, and preferably 50°C to 220°C. The heating temperature may be increased in stages. 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. To promote the removal of the solvent, heating may be performed under reduced pressure.

[0156] A resin composition containing polyimide and polyester has a lower glass transition temperature compared to the case of polyimide alone because the polyimide and polyester are compatible. This enables molding or processing at low temperatures and reduces discoloration of molded articles such as films.

[0157] For the purpose of improving the mechanical strength of the film, stretching may be performed in one or multiple directions. When the film is stretched, the polymer chains are oriented in the stretching direction, which improves the strength in the in-plane direction of the film and tends to suppress the occurrence of cracking or splitting. In the case of a combination of polyimide and polyester, the tensile modulus in the stretching direction increases, and consequently, flexural strength tends to improve.

[0158] A film that can be used as a cover film or substrate material for a foldable display device requires high mechanical strength in a direction orthogonal to the bending axis, as the film is repeatedly bent along the bending axis at the same location. Therefore, by arranging the film so that its stretching direction is orthogonal to the bending axis, cracking or splitting of the film at the bending location is less likely to occur even when the film is repeatedly bent, thereby providing a device with high bending resistance.

[0159] The stretching conditions of the film are not particularly limited. For example, the stretching temperature is approximately ±40°C of the film's glass transition temperature, and may be approximately 120 to 300°C, 150 to 250°C, or 180 to 230°C. The stretching ratio is approximately 1 to 200%, and may be 5 to 150%, 10 to 120%, or 20 to 100%. As the stretching ratio increases, the tensile modulus in the stretching direction tends to increase. On the other hand, if the stretching ratio is excessively large, the mechanical strength in the direction perpendicular to the stretching direction tends to decrease, and the handling properties of the film may decrease.

[0160] The film may be biaxially stretched to increase strength in any direction within the plane. 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 direction orthogonal to it may be the same or different. If a difference in stretching ratios is provided, the mechanical strength in the direction with the larger stretching ratio tends to be relatively higher. When using a biaxially stretched film with anisotropy in stretching ratio in a foldable device, it is desirable to position the direction with the larger stretching ratio orthogonal to the bending axis.

[0161] The thickness of the film is not specifically limited and can be set appropriately according to the application. For example, the film thickness is 5 to 300 μm. From the perspective of achieving both self-supporting properties and flexibility, and also having 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. For use as a cover film for a display, the film thickness is preferably 10 μm or more. When stretching the film, it is preferable that the thickness after stretching be within the above range.

[0162] 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 exhibit compatibility, a film with low haze and high transparency is obtained. The resin composition mixed with polyimide and polyester preferably has a haze of 10% or less when a film with a thickness of 10 μm is produced.

[0163] The total light transmittance of the film is preferably 85% or higher, more preferably 86% or higher, even more preferably 87% or higher, particularly preferably 88% or higher, and may be 89% or higher or 90% or higher. The resin composition mixed with polyimide and polyester preferably has a total light transmittance of 85% or higher when a film with a thickness of 10 μm is produced.

[0164] The yellowness (YI) of the film is not particularly limited, but it is preferably 20.0 or less, more preferably 10.0 or less, 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 mixed with polyimide and polyester preferably has a yellowness of 20.0 or less when a film with a thickness of 20 μm is produced. As described above, by mixing polyimide and polyester, a film with less discoloration and a small YI is obtained compared to the case where polyimide is used alone.

[0165] The tensile modulus of the film is not particularly limited, but from the perspective of strength, the tensile modulus of the film at room temperature is preferably 2.0 GPa or higher, more preferably 3.0 GPa or higher, and even more preferably 4.0 GPa or higher. The tensile modulus may be anisotropic, and at least the unidirectional tensile modulus may be 4.0 GPa or higher, 5.0 GPa or higher, 5.5 GPa or higher, 6.0 GPa or higher, 6.5 GPa or higher, or 7.0 GPa or higher. The pencil hardness of the film is preferably 6B or higher, preferably 4B or higher, and may be 2B or higher, F or higher, or 2H or higher. In a commercial system of polyimide and polyester, it is difficult for the pencil hardness to decrease even if the proportion of polyester is increased. Therefore, it is possible to provide a film with low coloration and excellent transparency without significantly reducing the excellent mechanical strength characteristic of polyimide.

[0166] A film formed by a resin composition comprising polyimide and polyester is suitable for use as a display material due to its low coloration and high transparency. In particular, a film with high mechanical strength can be applied as a surface member, such as a cover window of a display. In practical use, the film of the present invention may be provided with an antistatic layer, an easy-to-adhesion layer, a hard coating layer, an anti-reflective layer, etc., on its surface.

[0167] Examples

[0168] The embodiments of the present invention will be described in more detail below by presenting examples. Furthermore, the present invention is not limited to the following examples.

[0169] [Preparation of Polyimide Resin]

[0170] Dimethylformamide (DMF) was added to a separable flask and stirred under a nitrogen atmosphere. Thereby, a diamine and a tetracarboxylic acid dianhydride were added in the ratios (mol%) shown in Table 1, and acetic acid was added. The mixture was then stirred under a nitrogen atmosphere for 5 to 10 hours to obtain a polyamic acid solution with a solid content of 13 wt%. Pyridine was added to the polyamic acid solution and completely dispersed, then acetic anhydride was added, and imidization was performed by stirring at 90°C for 3 hours.

[0171] After cooling the solution following imidization to room temperature, 2-propyl alcohol (IPA) was added dropwise while stirring the solution to precipitate the polyimide resin. Additionally, PA was added, and after stirring for about 30 minutes, suction filtration was performed using a Kiriyama funnel. The obtained solid was washed with IPA and dried in a vacuum oven set to 120°C for 12 hours to obtain the polyimide resin.

[0172] [Preparation of resin composition (solution) and production of film]

[0173] <Resin Composition of Polyimide (PI) and Polyester (PEs)>

[0174] 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% by weight.

[0175] PEs1: Erythel UE3600 (polyester containing a bisphenolalkylene oxide adduct as a diol component; uniticase, weight average molecular weight 60,000, glass transition temperature 75°C)

[0176] PEs2: Erythel UE9200 (polyester containing neopentyl glycol as a diol component; uniticase, weight average molecular weight 39,000, glass transition temperature: 65℃)

[0177] PEs3: OKP4HT (polyester containing a diol having a fluorene structure as a diol component; manufactured by Osaka Gas Chemical, weight average molecular weight 38,000, glass transition temperature 142℃)

[0178] The weight average molecular weight of the polyester resin was measured under the following conditions by gel permeation chromatography of the resin (HLC-8220 GPC equivalent).

[0179] Eluent: LiBr (30 mM) + H3PO4 (30 mM) DMF solution

[0180] Sample concentration: 0.15 wt%

[0181] Flow rate: 0.6 mL / min

[0182] Column composition: From upstream, TSK guard column Super AW-H, TSK gel AWM-H, TSK gel AWM-H

[0183] Column temperature: 40℃

[0184] Detection conditions: RI, UV

[0185] Molecular weight standard: Polystyrene (painting agent)

[0186] The above-mentioned resin solution was applied to an alkali-free glass plate and heated and dried in an atmospheric atmosphere at temperatures of 40°C, 60°C, 90°C, 120°C, 150°C, and 200°C for 15 minutes at each temperature to produce a film of the thickness shown in Table 1.

[0187] [evaluation]

[0188] The films of the examples and comparative examples were cut into squares with sides of 3 cm, and the following evaluations were performed. In addition, those in which clear opacity was confirmed by the naked eye (those with haze exceeding 10%) were not evaluated.

[0189] <Haze and Total Light Transmittance>

[0190] Haze and total light transmittance (TT) were measured using the Suga Shikenki haze meter “HZ-V3” in accordance with JIS K7136 and JIS K7361-1.

[0191] Yellowness

[0192] Yellowness (YI) was measured according to JIS K7373 using the Suga Shikenki spectrophotometer “SC-P”.

[0193] [Evaluation Results]

[0194] The composition of the polyimide, the type of polyester resin, and the evaluation results of the film are shown in Table 1. In Table 1, the compounds are described by the following abbreviations.

[0195] Diamine

[0196] TFMOB: 2,2'-bis(trifluoromethoxy)benzidine

[0197] BAFL: 9,9-bis(4-aminophenyl)fluoren

[0198] DDS: 3,3'-Diaminodiphenylsulfone

[0199] ODA: 4,4'-Diaminodiphenyl ether

[0200] Tetracarboxylic acid dianhydride

[0201] BPADA: 4,4'-(4,4'-isopropylidene diphenoxy)diphthalic anhydride

[0202] BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene anhydride

[0203] TBIS-MPN: 5,5'-(9H-fluorene-9-ylidenebis(2-methyl-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate]

[0204] TAHMBP: 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diylbis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate)

[0205] CBDA: 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride

[0206] BT-100: 1,2,3,4-butanetetracarboxylic acid dianhydride

[0207] PMDA: Pyromylic acid dianhydride

[0208]

[0209] The compositions of Examples 1 to 17, which used a polyimide containing TFMOB, a specific diamine, as the diamine component, were capable of producing a film having a haze of 10% or less and a total light transmittance of 85% or more, and had excellent transparency. In Comparative Examples 1 to 6, which used a polyimide in which the diamine was ODA, the polyimide and polyester were not compatible in solution, so a transparent film was not obtained.

Claims

Claim 1 The polyimide comprises a polyimide and a polyester, wherein the polyimide has a structure derived from a diamine and a structure derived from a tetracarboxylic acid dianhydride, and as the diamine, CF3-O-, -(CF2-O) n - and -O-(CF2-CF2-O) n A resin composition comprising a fluorine atom-containing diamine having one or more structures selected from (where n is an integer from 1 to 20), wherein the weight average molecular weight of the polyester is greater than 10,000. Claim 2 A 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. Claim 3 A resin composition according to claim 1, wherein the polyimide comprises one or more selected from the group consisting of a tetracarboxylic acid dianhydride represented by general formula (1), a tetracarboxylic acid dianhydride represented by general formula (2), and a tetracarboxylic acid dianhydride having a fluorene structure: In general formula (1), A is any divalent organic group, and at both ends of A, a carbon atom of A is bonded to a phenyl group, p is 1 or 2, and R 1a , R 1b , R 2a and R 2b Each is independently any substituent, m1 and m2 are each independently integers from 0 to 3, and n1 and n2 are each independently integers from 0 to 4, and in general formula (2), B is any divalent organic group, and at both ends of B, a carboxyl group and a carbon atom of B are bonded. Claim 4 In claim 1, the polyimide is, as the tetracarboxylic acid dianhydride, 4,4'-(4,4'-isopropylidene diphenoxy)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)fluorene A resin composition comprising one or more selected from the group consisting of dianhydrides, 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride, 5,5'-[9H-fluorene-9-ylidenebis(2-methyl-4,1-phenylene)]bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate), 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthen]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate), and spiro[11H-diplo[3,4-b: 3',4'-i]xanthen-11,9'-fluorene]-1,3,7,9-tetraone. Claim 5 A resin composition according to claim 3, wherein the polyimide further comprises an alicyclic tetracarboxylic acid dianhydride as the tetracarboxylic acid dianhydride, and the ratio of the structure derived from the alicyclic tetracarboxylic acid dianhydride to the total amount of the structure derived from the tetracarboxylic acid dianhydride of the polyimide is 1 to 80 mol%. Claim 6 A resin composition according to claim 1, wherein the polyimide has a ratio of a diamine-derived structure having a structure in which CF3- or -C(CF3)2- is directly bonded to a carbon atom of an aromatic ring relative to the total amount of a diamine-derived structure of less than 0.5 mol%, and a ratio of a tetracarboxylic acid dianhydride-derived structure having a structure in which CF3- or -C(CF3)2- is directly bonded to a carbon atom of an aromatic ring relative to the total amount of a tetracarboxylic acid dianhydride-derived structure of less than 0.5 mol%. Claim 7 A 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 one or more selected from the group consisting of a diol having a chain-like alkylene group having 3 or more carbon atoms that may have branches, a diol having a chain-like alkenylene group having 3 or more carbon atoms that may have branches, a polyalkylene glycol, and a diol having a cyclic structure. Claim 8 A 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 one or more selected from the group consisting of a diol having a fluorene structure and a diol having a bisphenol derivative structure. Claim 9 A 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 a bisphenolalkylene oxide adduct. Claim 10 A resin composition according to claim 1, comprising the polyimide and the polyester in a weight ratio ranging from 2:98 to 98:

2. Claim 11 A molded body comprising a resin composition described in any one of claims 1 to 10. Claim 12 A film comprising a resin composition described in any one of claims 1 to 10.

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