Polyimide, resin composition, molded body, and film

Abstract

The present invention relates to: a polyimide; and a resin composition comprising the polyimide and another resin. The polyimide comprises: as a diamine component, a diamine having a difluoromethoxy group; and as a tetracarboxylic acid dianhydride component, at least one tetracarboxylic acid dianhydride that is selected from the group consisting of a tetracarboxylic acid dianhydride having an ether bond, a tetracarboxylic acid dianhydride having a cardo structure, and a bis(trimellitic acid anhydride) ester. Examples of other resins that constitute the resin composition include acrylic resins and polyester resins.

Description

Polyimide, resin composition, molded article and film

[0001] The present invention relates to a polyimide, a resin composition containing the polyimide, and a molded article such as 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] As a method for producing a highly transparent polyimide film, a method using a polyimide that is soluble in an organic solvent and does not require high-temperature imidization after film formation has been proposed. From the viewpoint of balancing transparency and mechanical properties, such soluble polyimides use fluorine-containing compounds as diamines and / or tetracarboxylic dianhydrides as monomers, and many soluble polyimides have been proposed that use fluoroalkyl-substituted benzidines such as 2,2′-bis(trifluoromethyl)benzidine (TFMB) as the diamine (see, for example, Patent Document 1).

[0004] Patent Documents 2 and 3 describe that the transparency and other properties of a transparent polyimide film can be improved by mixing a soluble polyimide with another resin.

[0005] International Publication No. 2020 / 004236 International Publication No. 2023 / 026982 International Publication No. 2021 / 132279

[0006] 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, an object of the present invention is to provide a polyimide that is environmentally safe, soluble in organic solvents, and highly transparent, as well as a resin composition containing the polyimide, and a molded article such as a film.

[0008] The present invention relates to a polyimide and a resin composition containing the polyimide and another resin. The polyimide contains, as a diamine component, a diamine (specific diamine) having a difluoromethoxy group, and, as a tetracarboxylic dianhydride component, one or more tetracarboxylic dianhydrides (specific acid dianhydrides) selected from the group consisting of tetracarboxylic dianhydrides having an ether bond, tetracarboxylic dianhydrides having a cardo structure, and bis(trimellitic anhydride) esters.

[0009] Preferred examples of diamines having a difluoromethoxy group include 2,2'-bis(difluoromethoxy)benzidine, 3,3'-bis(difluoromethoxy)benzidine, and 2,3'-bis(difluoromethoxy)benzidine.

[0010] Preferred examples of the specific acid dianhydride include 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride, 3,4'-oxydiphthalic anhydride, 4,4'-oxydiphthalic anhydride, 9,9-bis(3,4-dicarboxyphenyl)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'-[9 H[xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate, spiro[fluorene-9,9'xanthene]-2',3',6',7'-tetracarboxylic dianhydride, p-phenylenebis(trimellitic acid monoester anhydride), bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-biphenyl-4,4'diyl, and bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'diyl.

[0011] The polyimide may contain a diamine other than the specific diamine as the diamine component, and may contain a tetracarboxylic acid dianhydride other than the specific acid dianhydride as the tetracarboxylic acid dianhydride component.

[0012] Examples of tetracarboxylic dianhydrides other than the specific acid dianhydrides include 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3',-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride.

[0013] Polyimide is a compound in which CF is bonded to the carbon atom of the aromatic ring relative to the total amount of the diamine component. 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 ) ２ The amount of tetracarboxylic dianhydride having a structure in which - is directly bonded is preferably less than 0.5 mol %.

[0014] The polyimide is preferably soluble in dimethylformamide at 23°C.

[0015] The resin composition of the present invention contains the above-described polyimide and another resin. Examples of the other resin include an acrylic resin and a polyester resin. The resin composition may contain the polyimide and the other resin in a weight ratio ranging from 98:2 to 2:98.

[0016] The polyimide and resin composition described above can be applied to molded articles such as films.

[0017] The polyimide containing the specific diamine as the diamine component and the specific acid dianhydride as the tetracarboxylic dianhydride component has excellent solubility in organic solvents and transparency. Furthermore, since the specific diamine has a lower environmental persistence than organic fluorine compounds such as fluoroalkyl-substituted benzidine, the polyimide of the present invention has excellent environmental safety.

[0018] Furthermore, the polyimide is compatible with acrylic resins and polyesters. Mixed resin films of polyimide and other resins can reduce coloration without significantly reducing the excellent mechanical strength of polyimide.

[0019] [Polyimide] Polyimide is obtained by cyclodehydration of polyamic acid obtained by addition polymerization of tetracarboxylic dianhydride (hereinafter sometimes referred to as "acid dianhydride") and diamine. That is, polyimide is a polycondensation product of tetracarboxylic dianhydride and diamine, and has a structure derived from the acid dianhydride (acid dianhydride component) and a structure derived from the diamine (diamine component).

[0020] <Diamine> (Specific diamine) The polyimide of the present invention contains a diamine component having a difluoromethoxy group (—O—CHF ２ Hereinafter, such diamines may be referred to as "specific diamines."

[0021] Monohydrodifluoromethyl (-CHF) in specific diamines ２ ) is trifluoromethyl (-CHF ３ ) tend to be more degradable in the environment than carbon atoms bonded to fluorine atoms (-CHF ２ The structure in which a carbon atom to which a fluorine atom is bonded is bonded to a carbon atom (e.g., CF ３ Therefore, polyimides containing specific diamines as diamine components are expected to have significantly reduced environmental persistence compared to conventional soluble polyimides containing organic fluorine compounds such as fluoroalkyl-substituted benzidines as diamine components.

[0022] From the viewpoint of reactivity, the specific diamine is preferably one having a structure in which a difluoromethoxy group is bonded to a carbon atom of an aromatic ring, and among these, one having a structure in which a difluoromethoxy group is bonded to a carbon atom of an aromatic ring and having no fluorine atom directly bonded to the aromatic ring to which the difluoromethoxy group is bonded is preferred, and one not containing any fluorine atom other than the difluoromethoxy group is particularly preferred. Examples of the specific diamine in which a difluoromethoxy group is bonded to a carbon atom of an aromatic ring include difluoromethoxy-substituted benzidine and difluoromethoxy-substituted phenylenediamine.

[0023] Examples of difluoromethoxy-substituted benzidines include 2-(difluoromethoxy)benzidine, 3-(difluoromethoxy)benzidine, 2,3-bis(difluoromethoxy)benzidine, 2,5-bis(difluoromethoxy)benzidine, 2,6-bis(difluoromethoxy)benzidine, 2,3,5-tris(difluoromethoxy)benzidine, 2,3,6-tris(difluoromethoxy)benzidine, 2,3,5,6-tetrakis(difluoromethoxy)benzidine, 2,2'-bis(difluoromethoxy)benzidine (DFMOB), 3,3'-bis(difluoromethoxy)benzidine, 2,3'-bis(difluoromethoxy)benzidine, 2,2',3-tris(difluoromethoxy)benzidine, 2,3,3'-tris(difluoromethoxyl)benzidine, 2,2',5-tris(difluoromethoxy)benzidine, 2,2',6-tris(difluoromethoxy)benzidine, 2,3',5-tris(difluoromethoxy)benzidine, 2,3',6-tris(difluoromethoxy)benzidine, 2,2',3,3'-tetrakis(difluoromethoxy)benzidine, 2,2',5,5'-tetrakis(difluoromethoxy)benzidine, and 2,2',6,6'-tetrakis(difluoromethoxy)benzidine.

[0024] Examples of difluoromethoxy-substituted phenylenediamines include 1,2-diamino-4-(difluoromethoxy)benzene, 1,3-diamino-4-(difluoromethoxy)benzene, 1,4-diamino-2-(difluoromethoxy)benzene, 1,4-diamino-2,3-bis(difluoromethoxy)benzene, 1,4-diamino-2,5-bis(difluoromethoxy)benzene, 1,4-diamino-2,6-bis(difluoromethoxy)benzene, 1,4-diamino-2,3,5-tris(difluoromethoxy)benzene, and 1,4-diamino-2,3,5,6-tetrakis(difluoromethoxy)benzene.

[0025] From the viewpoint of the polymerizability and mechanical strength of the polyimide, difluoromethoxy-substituted benzidine is preferred as the specific diamine. Among them, from the viewpoint of the solubility of the polyimide resin in organic solvents and the compatibility with other resins, those having a difluoromethoxy group at the 2- or 3-position of the biphenyl are preferred, with 2,2'-bis(difluoromethoxy)benzidine (hereinafter referred to as "DFMOB"), 3,3'-bis(difluoromethoxy)benzidine, and 2,3'-bis(difluoromethoxy)benzidine being more preferred, and DFMOB being particularly preferred. By having a difluoromethoxy 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 difluoromethoxy group, the steric hindrance of the difluoromethoxy 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 DFMOB, the steric hindrance between the difluoromethoxy 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.

[0026] The amount of the specific diamine relative to the total amount of the diamine components 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, it is particularly preferable that the amount of difluoromethoxy-substituted benzidine is within this range. The higher the ratio of the specific diamine, the more suppressed the coloring and the mechanical strength of the film, such as pencil hardness, elastic modulus, breaking strength, and breaking elongation, may be improved.

[0027] (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 It is preferable that it does not contain —C—. ３ and -C-CF ２Examples of fluorine atom-containing diamines that do not contain —C— include diamines having a structure in which the oxygen atom of a trifluoromethoxy group is bonded to a carbon atom of an aromatic ring, such as 2,2′-bis(trifluoromethoxy)benzidine, 3,3′-bis(trifluoromethoxy)benzidine, and 2,3′-bis(trifluoromethoxy)benzidine.

[0028] 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, and 3,4'-diaminodiphenyl sulfone. 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-amino phenyl)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-amino 2,2-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]benz benzene, 1,4-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 4 ,4'-bis[4-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, 4,4'-bis[4-(4-aminophenoxy)phenoxy]diphenyl sulfone, 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3 '-Diamino-4,4'-diviphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirobiindane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 1,3-bis(4-aminobutyl)tetramethyldisiloxane, α,ω-bis(3-aminopropyl)polydimethylsiloxane, α,ω-bis(3-aminobutyl)polydimethylsiloxane, bis(aminomethyl)ether, bis(2-aminoethyl)ether, bis(3-aminopropyl)ether, bis(2-aminomethoxy)ethyl]ether, bis[2-(2-aminoethoxy)ethyl]ether, bis[2-(3-aminoprotoxy)ethyl]ether, 1,2-bis(aminomethoxy)ethane, 1,2-bis(2-aminoethoxy)ethane, 1,2-bis[2-(aminomethoxy)ethoxy]ethane, 1,2-bis[2-(2-aminoethoxy)ethoxy]ethane, ethylene glycol bis(3-aminopropyl)ether, diethylene glycol bis(3-aminopropyl)ether, triethylene glycol bis(3-aminopropyl)ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohexane, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, trans 1,4-diaminocyclohexane, 1,2-di(2-aminoethyl)cyclohexane, 1,3-di(2-aminoethyl)cyclohexane, 1,4-di(2-aminoethyl)cyclohexane, bis(4-aminocyclohexyl)methane, isophoronediamine, 2,6-bis(aminomethyl)bicyclo[2.2.1]heptane, 2,5-bis(aminomethyl)bicyclo[2.2.1]heptane, and the like.

[0029] 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 resin. 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.

[0030] 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 to 40 mol %, 3 to 30 mol %, or 5 to 25 mol %.

[0031] The use of a diamine having a cardo structure in addition to a specific diamine as the diamine may improve the solubility in solvents, transparency, and mechanical strength of the polyimide resin. A cardo structure is a structure in which four aromatic rings are bonded to the carbon atom at the 9th position of fluorene. Preferred diamines having a cardo structure are 9,9-bis(4-aminophenyl)fluorene, 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene, and 9,9-bis(4-amino-3-methylphenyl)fluorene, and these may be used in combination.

[0032] When a diamine having a cardo structure is used in addition to the specific diamine, the amount of the diamine having a cardo structure relative to the total amount of the diamine components may be 1 to 80 mol %, 3 to 60 mol %, or 5 to 30 mol %.

[0033] The total amount of the specific diamine, diaminodiphenylsulfone, and diamine having a cardo structure relative to the total amount of diamine components in the polyimide is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, and may be 95 mol% or more, 99 mol% or more, or even 100 mol%.

[0034] 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.

[0035] Among fluorine atom-containing diamines, the structure in which a trifluoromethyl group is bonded to a carbon atom (—C—CF３ ) 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 in solvents of polyimides, general soluble polyimides contain CF4 as a diamine component on the carbon atom of the aromatic ring. ３ - or -C(CF ３ ) ２ Although 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.

[0036] <Tetracarboxylic acid dianhydride> (Specific acid dianhydride) The polyimide of the present invention contains, as an acid dianhydride component, one or more acid dianhydrides selected from the group consisting of acid dianhydrides having an ether bond, acid dianhydrides having a cardo structure, and bis(trimellitic anhydride) esters. Hereinafter, these acid dianhydrides will be referred to as "specific acid dianhydrides."

[0037] The use of an acid dianhydride having an ether bond tends to improve the solubility of the polyimide resin in a solvent. Examples of acid dianhydrides having an ether bond include 3,4'-oxydiphthalic anhydride (a-ODPA), 4,4'-oxydiphthalic anhydride (s-ODPA), and 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (BPADA). From the viewpoints of the solubility of the polyimide resin and compatibility with other resins, BPADA is particularly preferred.

[0038] The use of an acid dianhydride having a cardo structure tends to improve the solubility in solvents, mechanical properties, and heat resistance of the polyimide resin. Furthermore, polyimides containing an acid dianhydride having a cardo structure as the specific acid dianhydride tend to have excellent compatibility with other resins.

[0039] Acid dianhydrides having a cardo structure include 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride (BPF-PA), N,N'-(9H-fluoren-9-ylidene-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxamide] (FDA-ATA), 5,5'-(9H-fluoren-9-ylidenebis(2-methyl) 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(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), spiro[fluorene-9,9'xanthene]-2',3',6',7'-tetracarboxylic dianhydride (SFDA), and the like.

[0040] The bis(trimellitic anhydride) ester is represented by the following general formula (1).

[0041]

[0042] In the general formula (1), X is any divalent organic group, and at both ends of X, a carboxy group is bonded to a carbon atom of X. The divalent organic group X is difluoromethylene (-CF ２ Specific examples of the divalent organic group X include the following (i) to (viii):

[0043]

[0044] 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 or a phenyl group is preferable. 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.

[0045] The bis(trimellitic anhydride) ester is preferably an aromatic ester, and among the above (i) to (viii), (i) to (viii) are preferred as X in the general formula (1), with (i) to (iv) being preferred and (i) and (ii) being particularly preferred.

[0046] When X is a group represented by general formula (i), from the viewpoint of the mechanical properties of a molded product such as a film, the bis(trimellitic anhydride) ester of general formula (1) is preferably p-phenylene bis(trimellitic acid monoester acid anhydride) (TMHQ) represented by the following formula (2-1):

[0047]

[0048] When X is a group represented by formula (ii), from the viewpoint of the solubility of the polyimide, the bis(trimellitic anhydride) ester of general formula (1) is preferably bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diyl (TAHMBP) represented by the following formula (2-2):

[0049]

[0050] Specific examples of bis(trimellitic anhydride) esters other than those of the above formulas (2-1) and (2-2) include bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-biphenyl-4,4′-diyl (BP-TME), bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-3,3′-dimethylbiphenyl-4,4′-diyl (OCBP-TME), tert-butylhydroquinone bis(trimellitic anhydride) (TA.BHQ), trimethylhydroquinone bis(trimellitic anhydride) (TA.TMHQ), and the like.

[0051] From the viewpoint of the solubility of the polyimide, TMHQ and TAHMBP are particularly preferred as the bis(trimellitic anhydride) ester.

[0052] 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 and have high transparency and mechanical strength.

[0053] Among the specific acid dianhydrides, from the viewpoint of solubility in organic solvents and transparency, 4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (BPADA), 3,4'-oxydiphthalic anhydride (a-ODPA), 4,4'-oxydiphthalic anhydride (s-ODPA), 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[ ... Preferred are fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate (TBIS.RXN), spiro[fluorene-9,9'xanthene]-2',3',6',7'-tetracarboxylic dianhydride (SFDA), p-phenylenebis(trimellitic acid monoester anhydride) (TMHQ), bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-biphenyl-4,4'diyl (OCBP-TME), and bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'diyl (TAHMBP).

[0054] From the viewpoint of making the polyimide soluble in an organic solvent, the total amount of the specific acid dianhydride relative to the total amount of the acid dianhydride components is preferably 15 mol% or more, more preferably 20 mol% or more, even more preferably 25 mol% or more, and may be 30 mol% or more, 35 mol% or more, 40 mol% or more, 45 mol% or more, or 50 mol% or more. The total amount of the specific acid dianhydride relative to the total amount of the acid dianhydride components may be 100 mol%, or 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.

[0055] (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 acid dianhydrides include alicyclic tetracarboxylic acid dianhydrides and aromatic 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.

[0056] The alicyclic tetracarboxylic 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 dianhydride include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride, and 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride. hydrate, 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, cyclohexane-1,4-diylbis(methylene)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic anhydride, 5,5'-[cyclohexylidenebis(4,1-phenyleneoxy)]bis-1,3-isobenzofurandione, 5-isobenzofurancarboxylic acid, 1,3-dihydro-1,3-di Oxo-,5,5'-[1,4-cyclohexanediylbis(methylene)]ester, bicyclo[2.2.1]heptane-2,3,5,6-tetracarboxylic dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride, 3,5,6-tricarboxynorbornane-2-acetic acid 2,3:5,6-dianhydride, decahydro-1,4,5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic dianhydride, tricyclo[6.4.0.0(2,7)]dodecane-1,8:2,Examples of suitable dianhydrides include 7-tetracarboxylic acid 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, and decahydro[2]benzopyrano[6,5,4,-def][2]benzopyran-1,3,6,8-tetraone. By including an alicyclic tetracarboxylic acid dianhydride as the dianhydride component in addition to a specific dianhydride, the mechanical strength of the polyimide tends to be improved. Furthermore, by including an alicyclic tetracarboxylic acid dianhydride as the dianhydride component in the polyimide, the compatibility of the polyimide with other resins may be improved.

[0057] 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 acid anhydrides in which two acid anhydride groups are bonded to one alicyclic ring are preferred, and CBDA is particularly preferred.

[0058] 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 alicyclic tetracarboxylic dianhydride, the higher the mechanical strength 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. Polyimides containing an alicyclic tetracarboxylic dianhydride within the above range as the acid dianhydride component tend to have excellent compatibility with other resins. In particular, when an acid dianhydride having an ether bond and / or a bis(trimellitic anhydride) ester is used as the specific acid dianhydride, the compatibility of the polyimide with other resins tends to be improved by using an alicyclic tetracarboxylic acid dianhydride in addition to the specific acid dianhydride.

[0059] Examples of aromatic tetracarboxylic dianhydrides other than the specific acid dianhydrides include pyromellitic dianhydride (PMDA), 1,2,3,4-benzenetetracarboxylic dianhydride (MPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4' 2,3,3',4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), 2,2',3,3',-biphenyltetracarboxylic dianhydride (i-BPDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride (DSDA), 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, and bis(3,4-dicarboxyphenyl)sulfone dianhydride. Among these aromatic tetracarboxylic dianhydrides, a-BPDA, s-BPDA, i-BPDA, PMDA, MPDA, and DSDA are preferred from the viewpoint of improving mechanical strength.

[0060] 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.

[0061] The polyimide may contain, as an acid dianhydride component, a chain aliphatic tetracarboxylic dianhydride such as ethylene tetracarboxylic dianhydride, 1,2,3,4-butane tetracarboxylic dianhydride, or meso-butane-1,2,3,4-tetracarboxylic dianhydride.

[0062] 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.

[0063] 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 there are concerns about environmental safety. ３ - or -C(CF ３ ) ２ Acid 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) are poorly degradable in the environment, and therefore, from the viewpoint of environmental safety of polyimides, it is preferable that these acid dianhydrides are not substantially 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.

[0064] <Content of specific fluorine structure in polyimide> As described above, a polyimide containing a diamine (specific diamine) having a difluoromethoxy group as a diamine component and one or more acid dianhydrides (specific acid dianhydrides) selected from the group consisting of an acid dianhydride having an ether bond, an acid dianhydride having a cardo structure, and a bis(trimellitic anhydride) ester as an acid dianhydride component is -C-CF ３ , -C-CF ２ It is substantially free of structures such as —C— and exhibits solubility in organic solvents.

[0065] In order to reduce the environmental persistence of fluorine-containing compounds, it is preferable that the polyimide contains a small amount of a diamine component having a specific fluorine structure and an acid dianhydride component having a specific fluorine structure. The specific fluorine structure is a structure in which at least one completely fluorinated methyl group (CF ３ -) or methylene (-CF ２ -) A structure containing a carbon atom (not bonded to any of H, Cl, Br, or I) excluding those having only the components of the following structural formula (i) or (ii): CF ３ -X (i) X-CF ２ -X' (ii)

[0066] X in formula (i) and (ii) is —OR or —NRR′, and X′ in formula (II) is —CH ３ , -CH ２ R, R', R'' and R''' are each independently -H, -CH ３ , -CH ２ -, aromatic, or -C(O)-.

[0067] 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.

[0068] <Preparation of Polyimide> Polyamic acid as a polyimide precursor is obtained by the reaction of an acid dianhydride with a diamine, and polyimide is obtained by cyclodehydration (imidization) of the polyamic acid. As described above, by adjusting the monomer composition constituting the polyimide, i.e., the types and ratios of the acid dianhydride and diamine, a polyimide having solubility in organic solvents and transparency can be obtained.

[0069] 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 (molar ratio of 90:100 to 110:100) in an organic solvent and stirring the mixture. The concentration of the polyamic acid solution is usually 5 to 35 wt %, preferably 10 to 30 wt %. With a concentration within this range, the polyamic acid obtained by polymerization has an appropriate molecular weight and the polyamic acid solution has an appropriate viscosity.

[0070] 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.

[0071] For example, when a specific acid dianhydride and an acid dianhydride other than the specific acid dianhydride are used as the acid dianhydride component, a polyimide having a block property can be obtained by first mixing the specific acid dianhydride with the entire amount of diamine and reacting them, and then adding and reacting the acid dianhydride other than the specific acid dianhydride. Such a polyimide having a block property may have excellent compatibility with acrylic resins and polyesters.

[0072] 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 methylene chloride; 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.

[0073] 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. To accelerate the imidization process, the polyamic acid solution may be heated. By mixing a solution containing polyimide produced by imidization of polyamic acid with a poor solvent, a polyimide resin 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.

[0074] The molecular weight of the polyimide (weight average molecular weight in terms of polyethylene oxide measured by gel permeation chromatography (GPC)) is preferably 10,000 to 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 resin and its compatibility with other resins may be poor.

[0075] 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 methylene chloride.

[0076] [Resin Composition] The polyimide of the present invention contains a specific diamine and a specific acid dianhydride, and thus exhibits solubility in organic solvents and compatibility with other resins. The polyimide of the present invention is particularly compatible with acrylic resins and polyesters, and can be used as a resin composition containing the polyimide and these resins. Furthermore, the polyimide of the present invention can be made into a resin composition by adding various additives.

[0077] <Acrylic Resin> Examples of acrylic resins include poly(meth)acrylic acid esters such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymers, methyl methacrylate-(meth)acrylic acid ester copolymers, methyl methacrylate-acrylic acid ester-(meth)acrylic acid copolymers, methyl (meth)acrylate-styrene copolymers, etc. The stereoregularity of the polymer is not particularly limited, and may be any of isotactic, syndiotactic, and atactic.

[0078] From the viewpoints of transparency, compatibility with polyimide, and mechanical strength of molded articles such as films, the acrylic resin is preferably one having methyl methacrylate as a main structural unit. The amount of methyl methacrylate relative to the total amount of monomer components in the acrylic resin is preferably 60% by weight or more, and may be 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The acrylic resin may be a homopolymer of methyl methacrylate.

[0079] The acrylic resin may be one into which an imide structure or a lactone ring structure has been introduced. Such modified polymers are preferably those into which an imide structure or a lactone ring structure has been introduced into an acrylic polymer having a methyl methacrylate content within the above range. That is, in the acrylic resin modified by the introduction of an imide structure or a lactone ring structure, the total amount of methyl methacrylate and the modified structure of methyl methacrylate is preferably 60% by weight or more, and may be 70% by weight or more, 80% by weight or more, 85% by weight or more, 90% by weight or more, or 95% by weight or more. The modified polymer may be one into which an imide structure or a lactone ring structure has been introduced into a methyl methacrylate homopolymer.

[0080] Introducing an imide structure into an acrylic polymer such as methyl methacrylate tends to increase the glass transition temperature of the acrylic resin. Furthermore, since the acrylic resin contains an imide structure, its compatibility with polyimides may be improved. For example, even if a specific polyimide resin is not compatible with polymethyl methacrylate, it may be compatible with an acrylic resin having a glutarimide structure.

[0081] Acrylic resins having a glutarimide structure can be obtained by heating and melting polymethyl methacrylate resin and treating it with an imidizing agent, as described in, for example, JP 2010-261025 A. Commercially available imide-modified polymethyl methacrylates, such as "PLEXIMID TT70" and "PLEXIMID 8805" manufactured by EVONIK, can also be used.

[0082] When the acrylic resin has a glutarimide structure, the glutarimide content may be 3% by weight or more, 10% by weight or more, 20% by weight or more, 30% by weight or more, or 50% by weight or more. １ The introduction rate of the glutarimide structure (imidization rate) is determined from the H-NMR spectrum, and the imidization rate is calculated by converting it into weight. For example, in the case of methyl methacrylate into which a glutarimide structure has been introduced, the O—CH ３ The area A of the peak due to protons (around 3.5 to 3.8 ppm) and the N-CH ３ The imidization rate Im=B / (A+B) can be calculated from the area B of the peak (around 3.0 to 3.3 ppm) derived from protons.

[0083] From the viewpoint of the heat resistance of the resin composition and the molded article, the glass transition temperature of the acrylic resin is preferably 100°C or higher, more preferably 110°C or higher, and may be 115°C or higher or 120°C or higher.

[0084] From the viewpoints of solubility in organic solvents, compatibility with the polyimide, and strength of molded articles, the weight-average molecular weight (polystyrene equivalent) of the acrylic resin is preferably 5,000 to 5,000,000, more preferably 10,000 to 2,000,000, and may be 30,000 to 1,000,000 or 50,000 to 500,000. If the molecular weight of the acrylic resin is too small, the durability of the resulting film may be reduced. If the molecular weight of the acrylic resin is too high, film formability may be poor.

[0085] From the viewpoint of the thermal stability and light stability of the resin composition and film, it is preferable that the acrylic resin has a low content of reactive functional groups such as ethylenically unsaturated groups and carboxy groups. The iodine value of the acrylic resin is preferably 10.16 g / 100 g (0.4 mmol / g) or less, more preferably 7.62 g / 100 g (0.3 mmol / g) or less, and even more preferably 5.08 g / 100 g (0.2 mmol / g) or less. The iodine value of the acrylic resin may be 2.54 g / 100 g (0.1 mmol / g) or less or 1.27 g / 100 g (0.05 mmol / g) or less. The acid value of the acrylic resin is preferably 0.4 mmol / g or less, more preferably 0.3 mmol / g or less, and even more preferably 0.2 mmol / g or less. The acid value of the acrylic resin may be 0.1 mmol / g or less, 0.05 mmol / g or less, or 0.03 mmol / g or less. A small acid value tends to increase the stability of the acrylic resin and improve its compatibility with polyimide.

[0086] <Polyester> Polyester is a condensation product of dicarboxylic acid and diol, and has a structure derived from dicarboxylic acid and a structure derived from diol. The dicarboxylic acid component and diol component of the polyester are not particularly limited, but from the viewpoint of solubility in organic solvents, they are preferably amorphous. Polyethylene terephthalate (PET), a typical polyester, is a condensation product of ethylene glycol and terephthalic acid, and is highly crystalline and has low solubility in organic solvents, whereas amorphous polyester is soluble in organic solvents and exhibits high compatibility with the above-mentioned polyimide.

[0087] (Diol) From the viewpoint of imparting solubility to the polyester in an organic solvent, 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."

[0088] 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.

[0089] Examples of polyalkylene glycols include diethylene glycol, triethylene glycol, dipropylene glycol, and polytetramethylene ether glycol.

[0090] 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 cardo structure; and diols having a bisphenol derivative structure.

[0091] Among these, butanediol, neopentyl glycol, polytetramethylene ether glycol, diols having a cardo 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.

[0092] Specific examples of diols having a cardo structure 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.

[0093] The diol having a bisphenol derivative structure is a diol in which an alkylene oxide is added to two phenolic hydroxy groups of a bisphenol (a bisphenol alkylene oxide adduct), and an ethylene oxide (EO) adduct or a propylene oxide (PO) adduct of a bisphenol is preferred. Note that the diol having a cardo structure includes diols having a bisphenol derivative structure, but even if a diol having a cardo structure has a bisphenol derivative structure, it is still considered to be a diol having a cardo structure.

[0094] Examples of bisphenols that do not have a cardo structure 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 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.

[0095] 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.

[0096] 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.

[0097] (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.

[0098] 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 skeleton, such as 9,9-bis(carboxymethyl)fluorene and 9,9-bis(2-carboxyethyl)fluorene.

[0099] From the viewpoint of improving the solubility and mechanical strength of the polyester, terephthalic acid and isophthalic acid are preferred as aromatic dicarboxylic acids. 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.

[0100] 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.

[0101] 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.

[0102] (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.

[0103] (Preparation of Polyester) The polymerization method for 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, interfacial polymerization, or further solid-phase polymerization. In the polymerization of polyester, a dicarboxylic acid derivative such as an acid anhydride may be used as the dicarboxylic acid component.

[0104] From the viewpoint of ensuring the mechanical strength of a molded article such as a film formed from the resin composition, the weight-average molecular weight of the polyester is preferably greater than 10,000, more preferably 15,000 or more, even 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.

[0105] 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.

[0106] Commercially available polyester resins may be used as the polyester. Examples of commercially available polyester resins containing a specific diol as a diol component include OKP4HT (manufactured by Osaka Gas Chemicals, Mw: 38,000, Tg: 142°C), OKP4 (manufactured by Osaka Gas Chemicals, Mw: 40,000, Tg: 121°C), 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 UE3510 (manufactured by Unitika, Mw: 63,000, Tg: -25°C), Elitel UE3 600 (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), Elitel UE9200 (manufactured by Unitika, Mw: 39,000, Tg: 65°C), Elitel UE980 ...800 (manufactured by Unitika, Mw: 46,000, Tg: 90°C), Elitel UE9800 (manufactured by Unitika, Mw: 46,000, Tg: 90°C), Elitel UE9800 (manufactured by Unitika, Mw: Examples of such copolymers include Vylon 200 (manufactured by Nichika, 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), Vylon 290 (manufactured by Toyobo, Mw: 61,000, Tg: 72°C), and Vylon 600 (manufactured by Toyobo, Mw: 38,000, Tg: 47°C).

[0107] <Preparation of Resin Composition Containing Polyimide and Other Resins> The above polyimide is mixed with other resins to prepare a resin composition. The above polyimide and acrylic resin may be compatible with each other at any ratio. Furthermore, the above polyimide and polyester may be compatible with each other at any ratio. Therefore, the ratio of resins in the resin composition is not particularly limited. The mixing ratio (weight ratio) of the polyimide resin to the other resin may be 98:2 to 2:98, 95:5 to 10:90, or 90:10 to 15:85.

[0108] The higher the proportion of polyimide, the higher the elastic modulus of the film and the greater its mechanical strength.The higher the proportion of other resins (acrylic resin or polyester), the less coloring there is in the film and the greater its transparency.

[0109] In order to fully exert the effect of improving transparency by mixing polyimide with other resins, the ratio of the other resins to the total of polyimide and other resins 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.

[0110] Polyimides are polymers with a special molecular structure, and generally have low solubility in organic solvents and are not compatible with other polymers. However, as described above, polyimides containing specific diamine components and acid dianhydride components exhibit high solubility in organic solvents and are compatible with acrylic resins and polyesters.

[0111] A resin composition containing a polyimide and another resin preferably has a single glass transition temperature in differential scanning calorimetry (DSC) and / or dynamic mechanical analysis (DMA). When a resin composition has a single glass transition temperature, the polyimide and the other resin can be considered to be completely compatible with each other. A film containing a polyimide and another resin also preferably has a single glass transition temperature.

[0112] The resin composition may be a simple mixture of a polyimide resin precipitated as a solid content with another resin, or may be a mixture of polyimide and another resin. Alternatively, when a polyimide solution is mixed with a poor solvent to precipitate a polyimide resin, another resin may be mixed into the solution, and a resin composition obtained by mixing polyimide and another resin may be precipitated as a solid (powder).

[0113] The resin composition may be a mixed solution containing polyimide and other resin. The method for mixing the resins is not particularly limited, and the resins may be mixed in a solid state or in a liquid state to form a mixed solution. A polyimide solution and a polyester solution may be prepared separately, and then the two may be mixed to prepare a mixed solution of polyimide and other resin.

[0114] The solvent for the solution containing the polyimide and the other resin is not particularly limited as long as it can dissolve both the polyimide and the other resin. Examples of the solvent include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; ether solvents such as tetrahydrofuran and 1,4-dioxane; ketone solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diethyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone; and alkyl halide solvents such as chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chlorobenzene, dichlorobenzene, and methylene chloride.

[0115] From the viewpoints of the solubility of polyimide and the compatibility of polyimide with other resins in the solution, amide-based solvents are preferred, while from the viewpoint of the removability of the solvent when producing a molded product such as a film, low-boiling non-amide-based solvents are preferred, and ketone-based solvents and alkyl halide-based solvents are preferred because they have excellent solubility in both polyimide and other resins, and have low boiling points that make it easy to remove the remaining solvent when producing a film.

[0116] 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.

[0117] [Molded Articles and Films] The above-mentioned polyimides and resin compositions containing polyimides and other resins 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.

[0118] In one embodiment, the molded article is a film. The film may be molded by either a melting method or a solution method, but the solution method is preferred from the viewpoint of producing a film with excellent transparency and uniformity. In the solution method, a solution containing the polyimide is applied to a support, and the solvent is then dried and removed to obtain a film. Since the polyimide is compatible with acrylic resins and polyesters, it is possible to produce a highly transparent film by the solution method by using the polyimide in combination with other resins.

[0119] 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.

[0120] 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.

[0121] The film may be stretched in one or more directions for the purpose of improving the mechanical strength, etc. When the film is stretched, the polymer chains are oriented in the stretching direction, which tends to improve the strength of the film in the in-plane direction and suppress the occurrence of breakage or cracks in the film.

[0122] 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.

[0123] The conditions for stretching the film are not particularly limited. For example, the stretching temperature is approximately ±40°C of the glass transition temperature of the film. The stretching temperature for polyimide films may be approximately 120 to 350°C, 150 to 300°C, or 180 to 250°C. The stretching temperature for Empress resin films containing polyimide and other resins 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 also 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, which may reduce the handleability of the film.

[0124] 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.

[0125] 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 20 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.

[0126] The haze of the film is not particularly limited, but is preferably 10% or less, more preferably 5% or less, even more preferably 4% or less, and may be 3.5% or less, 3% or less, 2% or less, or 1% or less. The lower the haze of the film, the better. As described above, polyimide, acrylic resin, and polyester are compatible with each other, so a mixed resin film containing polyimide and other resins has low haze and excellent transparency, similar to a film made of polyimide alone.

[0127] The total light transmittance of the film is not particularly limited, but is preferably 60% or more, more preferably 80% or more, even more preferably 85% or more, and may be 87% or more, 88% or more, 89% or more, or 90% or more. A mixed resin film containing polyimide and another resin has a higher total light transmittance than a film containing polyimide alone, and can exhibit a total light transmittance of 90% or more.

[0128] The yellowness index (YI) of the film is not particularly limited, but is preferably 20 or less, more preferably 10 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, 1.5 or less, or 1.0 or less. The yellowness index of the film may be 0 or less (a negative value). A mixed resin film containing polyimide and another resin tends to have a smaller YI than a film of polyimide alone.

[0129] From the viewpoint of strength, the tensile modulus of the film is preferably 2.5 GPa or more, more preferably 3.0 GPa or more, even more preferably 3.5 GPa or more, and may be 4.0 GPa or more. The pencil hardness of the film is preferably 4B or more, more preferably 2B or more, and even more preferably F or more, and may be H or more, 2H or more, or 3H or more.

[0130] Films containing the polyimide of the present invention are suitable for use as display materials due to their low coloration and high transparency. In particular, films with high mechanical strength can be applied to surface components such as display cover windows. Furthermore, since the polyimide is substantially free of specific fluorine structures, they are highly degradable and environmentally safe. When used in practice, the film of the present invention may be provided with an antistatic layer, an easy-adhesion layer, a hard coat layer, an antireflection layer, or the like on its surface.

[0131] The following examples will be used to further explain the present invention, but the present invention is not limited to these examples.

[0132] [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 shown in Tables 1 and 2, and the mixture was stirred under a nitrogen atmosphere for 5 to 48 hours to react, yielding a polyamic acid solution with a solids concentration of 18 wt %.

[0133] To 100 g of the polyamic acid solution, 5.5 g of pyridine was added as an imidization catalyst, and after complete dispersion, 8 g of acetic anhydride was added and the mixture was stirred at 90° C. for 3 hours to carry out imidization.

[0134] After the imidization, the solution was cooled to room temperature, and then 100 g of 2-propyl alcohol (hereinafter referred to as IPA) was added at a rate of 2-3 drops / second while stirring to precipitate polyimide. 150 g of IPA was then added, and after stirring for approximately 30 minutes, the solution was subjected to suction filtration using a Kiriyama funnel. The resulting solid was washed with IPA and then dried for 12 hours in a vacuum oven set at 120°C to obtain a polyimide resin.

[0135] [Preparation of Polyimide Film] The above polyimide resin was dissolved in DMF to prepare a polyimide solution with a solids concentration of 5 to 30 wt %. In Comparative Examples 1 to 10 in Table 2, the polyimide was insoluble in DMF, and films could not be prepared, so further evaluations were not performed. The polyimide solution was applied to a non-alkali glass plate and dried by heating in the air for 15 minutes at 60°C, 15 minutes at 90°C, 15 minutes at 120°C, 150°C, 15 minutes at 180°C, and 15 minutes at 200°C to prepare a film with a thickness of approximately 50 μm.

[0136] [Evaluation] <Molecular Weight> The weight-average molecular weight (Mw) of the polyimide resins of Examples 1 to 10 was measured using a gel permeation chromatograph (HLC-8420GPC) manufactured by Tosoh Corporation under the following conditions: Eluent: LiBr (30 mM) + H3PO4 (30 mM) DMF solution sample concentration: 0.1 wt % Injection pressure: Approximately 1.3 to 1.7 MPa Injection volume: 10 μL Flow rate: 0.6 mL / min Guard column: TSK guard column Super AW-H Column: TSK gel AWM-H × 2 Column temperature: 40°C Detection conditions: RI, UV Molecular weight standard sample: Polystyrene (manufactured by Tosoh Corporation) Calibration curve order: 1st dimension

[0137] <Haze and Total Light Transmittance> The film was cut into a 3 cm square, and the haze and total light transmittance (TT) were measured using a haze meter "HZ-V3" manufactured by Suga Test Instruments in accordance with JIS K7136 and JIS K7361-1.

[0138] <Yellowness Index> The film was cut into a 3 cm square, and the yellowness index (YI) was measured according to JIS K7373 using a spectrophotometer "SC-P" manufactured by Suga Test Instruments.

[0139] <Tensile modulus> The film was cut into a 10 mm wide strip and allowed to stand at 23°C / 55% RH for 1 day to condition the humidity. The tensile modulus was then measured using an AUTOGRAPH AGS-X manufactured by Shimadzu Corporation under the following conditions: Grip distance: 100 mm, Pulling speed: 20.0 mm / min, Measurement temperature: 23°C.

[0140] [Evaluation Results] The compositions of the polyimides in the Examples and Comparative Examples, and the evaluation results of the polyimide films in the Examples, are shown in Tables 1 and 2. In Comparative Examples 1 to 10, solvent-soluble polyimides were not obtained, so Table 2 shows only the compositions.

[0141] In Tables 1 and 2, and Tables 3 and 4 described later, the polyimide compositions (amounts of diamine and tetracarboxylic dianhydride) are shown as molar ratios, with the total amount of tetracarboxylic dianhydride being 100 parts by mole, and the compounds are described by the following abbreviations.

[0142] <Diamines> DFMOB: 2,2'-bis(difluoromethoxy)benzidine 2,2-Bz: 2,2'-dimethylbenzidine 3,3'-DDS: 3,3'-diaminodiphenyl sulfone BAFL: 9,9-bis(4-aminophenyl)fluorene 3,4'-ODA: 3,4'-diaminodiphenyl ether <Acid dianhydrides> BPADA: 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride TAHMBP: bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'diyl CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride H-BPDA: 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic-3,4:3',4'-dianhydride PMDA: pyromellitic dianhydride MPDA: 1,2,3,4-benzenetetracarboxylic dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride

[0143]

[0144]

[0145] The polyimides of Examples 1 to 9, which contained a specific diamine as the diamine component and a specific acid dianhydride as the acid dianhydride component, were soluble in organic solvents and could be used to prepare transparent films. On the other hand, the polyimides of Comparative Examples 1 to 3, which contained a specific diamine but not a specific acid dianhydride, and Comparative Examples 4 to 10, which contained a specific acid dianhydride but not a specific diamine, were insoluble in organic solvents.

[0146] These results demonstrate that by using a difluoromethoxy group-containing diamine, which is a diamine that does not contain a specific fluorine structure, as the diamine component and by appropriately selecting an acid dianhydride, it is possible to obtain a polyimide that is highly environmentally safe and has excellent solubility in organic solvents and transparency.

[0147] [Preparation of Resin Compositions of Polyimides and Acrylic Resins and Film Fabrication] The polyimides of Examples 1 to 5, 8, and 9 and the acrylic resins shown in Table 3 were dissolved in DMF at a weight ratio of 50:50 to prepare solutions with solids concentrations of 10 to 20 wt%. The acrylic resins used were commercially available polymethyl methacrylate resins ("Parapet HM1000" manufactured by Kuraray Co., Ltd., glass transition temperature: 120°C, acid value: 0.0 mmol / g, hereinafter referred to as "HM"), or glutarimide-modified acrylic resins (hereinafter referred to as "HGI") with a glutarimide content of 33 wt% and a glass transition temperature of 131°C prepared according to "Acrylic Resin Production Example 3" in JP 2018-70710 A. In all combinations of polyimides and acrylic resins, the solutions were transparent, demonstrating compatibility between the polyimides and acrylic resins.

[0148] The polyimide resin and acrylic resin were dissolved in DMF in a weight ratio of 50:50 to prepare a mixed resin solution with a solid content of 10 to 20 wt %. The mixed resin solution was applied to an alkali-free glass plate and dried by heating in the air at 60°C for 15 minutes, 90°C for 15 minutes, 120°C for 15 minutes, 150°C for 15 minutes, 180°C for 15 minutes, and 200°C for 15 minutes to produce a film with a thickness of approximately 50 μm.

[0149] The mixed resin film of polyimide and acrylic resin was evaluated in the same manner as the polyimide film. The polyimide composition, the type of acrylic resin, and the evaluation results of the film are shown in Table 3.

[0150]

[0151] The films of Examples 101, 102, 103, 104, 105, 108, and 109, which are mixed resin films of polyimide and acrylic resin, tended to have improved transparency compared to the films of polyimide alone, Examples 1, 2, 3, 4, 5, 8, and 9. For example, the polyimide films of Examples 3 and 9 had a YI of over 10, whereas the films of Examples 103 and 109 had a YI of less than 10, and it can be seen that the total light transmittance was improved compared to the films of polyimide alone, and transparency was significantly improved.

[0152] [Preparation of Polyimide and Polyester Resin Compositions and Film Fabrication] The polyimides of Examples 3, 4, and 8 and a commercially available polyester resin ("Elitel UE3200" manufactured by Unitika, weight average molecular weight: 16,000, glass transition temperature: 65°C; copolymer of terephthalic acid, isophthalic acid, neopentyl glycol, and ethylene glycol) were dissolved in DFM at a weight ratio of 50:50 to prepare solutions with solid concentrations of 10 to 20 wt%. In all combinations of polyimide and polyester resin, the solutions were transparent, indicating compatibility between the polyimide and polyester resin.

[0153] The polyimide resin and polyester resin were dissolved in a solvent in a weight ratio of 50:50 to prepare a mixed resin solution with a solids concentration of 10 to 20 wt %. The mixed resin solution was applied to an alkali-free glass plate and dried by heating in air at 60°C for 15 minutes, 90°C for 15 minutes, 120°C for 15 minutes, 150°C for 15 minutes, 180°C for 15 minutes, and 200°C for 15 minutes to produce a film with a thickness of approximately 30 μm. The film was then evaluated in the same manner as the polyimide film described above. The polyimide composition, polyester resin type, and film evaluation results are shown in Table 4.

[0154]

[0155] The films of Examples 203, 204, and 208, which are mixed resin films of polyimide and polyester resin, have smaller YI, higher total light transmittance, and significantly improved transparency compared to the films of Examples 3, 4, and 8, which are films of polyimide alone.

[0156] From the evaluation results of the mixed resin films of polyimide and acrylic resin in Examples 101, 102, 103, 104, 105, 108, and 109, and the mixed resin films of polyimide and polyester resin in Examples 203, 204, and 208, it is clear that polyimides that use a difluoromethoxy group-containing diamine as the diamine component and that have an appropriately selected acid dianhydride exhibit solubility in organic solvents, have excellent compatibility with acrylic resins and polyesters, and can produce films with high transparency.

Claims

1. A polyimide having a tetracarboxylic dianhydride component and a diamine component, wherein the diamine component contains a diamine having a difluoromethoxy group, and the tetracarboxylic dianhydride component contains one or more tetracarboxylic dianhydrides selected from the group consisting of tetracarboxylic dianhydrides having an ether bond, tetracarboxylic dianhydrides having a cardo structure, and bis(trimellitic anhydride) esters.

2. The polyimide according to claim 1, wherein the diamine having a difluoromethoxy group is 2,2'-bis(difluoromethoxy)benzidine, 3,3'-bis(difluoromethoxy)benzidine, or 2,3'-bis(difluoromethoxy)benzidine.

3. The one or more tetracarboxylic dianhydrides selected from the group consisting of tetracarboxylic dianhydrides having an ether bond, tetracarboxylic dianhydrides having a cardo structure, and bis(trimellitic anhydride) esters are selected from the group consisting of 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride, 3,4'-oxydiphthalic anhydride, 4,4'-oxydiphthalic anhydride, 9,9-bis(3,4-dicarboxyphenyl)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, spiro[fluorene-9,9'xanthene]-2',3',6',7'-tetracarboxylic dianhydride, p-phenylenebis(trimellitic acid monoester anhydride), bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-biphenyl-4,4'diyl, and bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-2,2',3,3',5,5'-hexamethylbiphenyl-4,4'diyl.

4. The polyimide according to claim 1, further comprising, as the tetracarboxylic dianhydride component, one or more tetracarboxylic dianhydrides selected from the group consisting of 2,3,3',4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride.

5. The amount of CF on the carbon atom of the aromatic ring relative to the total amount of diamine components 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 bonded to a carbon atom of an aromatic ring is less than 0.5 mol % relative to the total amount of the tetracarboxylic dianhydride component. ３ - or -C(CF ３ ) ２ 2. The polyimide according to claim 1, wherein the amount of the tetracarboxylic dianhydride having a structure in which - is directly bonded is less than 0.5 mol %.

6. The polyimide of claim 1, which is soluble in dimethylformamide at 23°C.

7. A molded article comprising the polyimide according to any one of claims 1 to 6.

8. A film comprising the polyimide according to any one of claims 1 to 6.

9. A resin composition comprising the polyimide according to any one of claims 1 to 6 and an acrylic resin.

10. The resin composition according to claim 9, wherein the polyimide and the acrylic resin are contained in a weight ratio ranging from 98:2 to 2:

98.

11. A molded article comprising the resin composition according to claim 9.

12. A film comprising the resin composition according to claim 9.

13. A resin composition comprising the polyimide according to any one of claims 1 to 6 and a polyester resin.

14. The resin composition according to claim 13, wherein the polyimide and polyester resin are contained in a weight ratio ranging from 98:2 to 2:

98.

15. A molded article comprising the resin composition according to claim 13.

16. A film comprising the resin composition of claim 13.

Images