Polyimide, resin composition, molded object, and film

Abstract

The present invention relates to a polyimide and a resin composition comprising the polyimide and an acrylic resin. The polyimide includes: a diamine component comprising a diamine having one or more structures selected from among CF3-O-, -(CF2-O)n-, and -O-(CF2-CF2-O)n- (wherein n is an integer of 1-20); and a tetracarboxylic acid dianhydride component comprising one or more tetracarboxylic acid dianhydrides selected from the group consisting of tetracarboxylic acid dianhydrides having an ether bond, tetracarboxylic acid dianhydrides having a fluorene structure, tetracarboxylic acid dianhydrides having a xanthene structure, and bis(trimellitic anhydride) esters.

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 resin that is soluble in organic solvents 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 Document 2 describes that the transparency and other properties of a transparent polyimide film can be improved by mixing a soluble polyimide with an acrylic resin.

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

[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 a polyimide and an acrylic resin. The polyimide contains CF as a diamine component. ３ -O-, -(CF ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ -(CF), 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 fluorene structure, tetracarboxylic dianhydrides having a xanthene structure, and bis(trimellitic anhydride) esters. ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ In the -, n is an integer of 1 to 20.

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

[0010] 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], 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, spiro[fluorene-9,9'xanthene]-2',3',6',7'-tetracarboxylic dianhydride, and 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate.

[0013] The tetracarboxylic acid dianhydride other than the specific acid dianhydride may be an alicyclic tetracarboxylic acid dianhydride. Examples of the alicyclic tetracarboxylic acid dianhydride include 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetracarboxylic acid dianhydride, 1,2,4,5-cyclohexanetetracarboxylic acid dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic acid anhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic acid dianhydride, and 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride. The amount of the alicyclic tetracarboxylic dianhydride relative to the total amount of the tetracarboxylic dianhydride components in the polyimide may be 1 to 80 mol %.

[0014] 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 %.

[0015] The polyimide is preferably soluble in dimethylformamide at 23°C.

[0016] The resin composition of the present invention contains the above-mentioned polyamide and acrylic resin. The resin composition may contain the polyimide and acrylic resin in a weight ratio ranging from 98:2 to 2:98.

[0017] The polyimide and resin composition described above can be applied to molded articles such as films.

[0018] The polyimide of the present invention, which contains a specific diamine as a diamine component and a specific acid dianhydride as a tetracarboxylic dianhydride component, has excellent solubility in organic solvents and transparency. Furthermore, since the specific diamine has lower environmental persistence than organic fluorine compounds such as fluoroalkyl-substituted benzidine, the polyimide of the present invention has excellent environmental safety.

[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 CF as a diamine component. ３ -O-, -(CF ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ -, wherein n is an integer of 1 to 20. Hereinafter, these diamines will be referred to as "specific diamines."

[0021] In certain diamines, a trifluoromethyl group (-CF ３ ) or a difluoromethylene group (—CF ２ The carbon atom of the alkyl group (-C-CF) is bonded to an oxygen atom, and a trifluoromethyl group is bonded to the carbon atom. ３ ) and a structure in which carbon atoms are bonded to both ends of a difluoromethylene group (—C—CF ２ As a result, polyimides containing specific diamines as diamine components are superior in environmental safety to conventional soluble polyimides containing organic fluorine compounds such as fluoroalkyl-substituted benzidine as diamine components.

[0022] Among the specific diamines, CF does not fall under the category of "specific fluorine structure" described below.３ -O-, or -(CF ２ -O) ｎ From the viewpoint of the polymerizability and mechanical strength of the polyimide, it is preferable to use a trifluoromethoxy group (CF ３ -O-) is preferred, and among them, diamines in which the oxygen atom of the trifluoromethoxy group is bonded to a carbon atom of an aromatic ring are preferred. From the viewpoint of reactivity, diamines in which a trifluoromethoxy group is bonded to a carbon atom of an aromatic ring are preferably those which do not have a fluorine atom directly bonded to the aromatic ring to which the trifluoromethoxy group is bonded, and particularly preferred are those which do not contain fluorine atoms other than the trifluoromethoxy group. Examples of specific diamines in which a trifluoromethoxy group is bonded to a carbon atom of an aromatic ring include trifluoromethoxy-substituted benzidine and trifluoromethoxy-substituted phenylenediamine.

[0023] Examples of trifluoromethoxy-substituted benzidines include 2-(trifluoromethoxy)benzidine, 3-(trifluoromethoxy)benzidine, 2,3-bis(trifluoromethoxy)benzidine, 2,5-bis(trifluoromethoxy)benzidine, 2,6-bis(trifluoromethoxy)benzidine, 2,3,5-tris(trifluoromethoxy)benzidine, 2,3,6-tris(trifluoromethoxy)benzidine, 2,3,5,6-tetrakis(trifluoromethoxy)benzidine, 2,2'-bis(trifluoromethoxy)benzidine (TFMOB), 3,3'-bis(trifluoromethoxy)benzidine, 2,3'-bis(trif 2,2',3-tris(trifluoromethoxy)benzidine, 2,3,3'-tris(trifluoromethoxyl)benzidine, 2,2',5-tris(trifluoromethoxy)benzidine, 2,2',6-tris(trifluoromethoxy)benzidine, 2,3',5-tris(trifluoromethoxy)benzidine, 2,3',6-tris(trifluoromethoxy)benzidine, 2,2',3,3'-tetrakis(trifluoromethoxy)benzidine, 2,2',5,5'-tetrakis(trifluoromethoxy)benzidine, and 2,2',6,6'-tetrakis(trifluoromethoxy)benzidine.

[0024] 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.

[0025] From the viewpoint of the polymerizability and mechanical strength of the polyimide, trifluoromethoxy-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 trifluoromethoxy group at the 2- or 3-position of the biphenyl are preferred, with 2,2'-bis(trifluoromethoxy)benzidine (hereinafter referred to as "TFMOB"), 3,3'-bis(trifluoromethoxy)benzidine, and 2,3'-bis(trifluoromethoxy)benzidine being more preferred, and TFMOB being particularly preferred. By having a trifluoromethoxy group at the 2- or 3-position of the biphenyl, in addition to a decrease in π electron density due to the electron-withdrawing properties of the trifluoromethoxy group, the steric hindrance of the trifluoromethoxy group inhibits π-π stacking between benzene rings, thereby shifting the absorption edge wavelength to shorter wavelengths and reducing coloration of the polyimide. Furthermore, in the case of TFMOB, the steric hindrance between the trifluoromethoxy groups at the 2- and 2'-positions of the biphenyl causes a twist in the bond between the two benzene rings of the biphenyl, reducing the planarity of the π-conjugation, thereby shifting the absorption edge wavelength to shorter wavelengths and reducing the coloration of the polyimide.

[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, the amount of the trifluoromethoxy group-containing diamine is preferably within this range, and the amount of the trifluoromethoxy-substituted benzidine is particularly preferably within this range. The higher the ratio of the specific diamine, the more suppressed the 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 Those which do not contain —C— are preferred, and those which do not contain a fluorine atom are particularly preferred.

[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 fluorene structure in addition to the specific diamine as the diamine may improve the solubility in solvents, transparency, and mechanical strength of the polyimide resin. Preferred fluorene-containing diamines 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 fluorene structure is used in addition to the specific diamine, the amount of the diamine having a fluorene structure relative to the total amount of the diamine components may be 1 to 80 mol %, 3 to 60 mol %, or 5 to 30 mol %.

[0033] The transparency of the polyimide may be improved by using an alicyclic diamine in addition to the specific diamine. Among the alicyclic diamines, isophoronediamine and 1,4-diaminocyclohexane are preferred, and these may be used in combination.

[0034] When an alicyclic diamine is used in addition to the specific diamine, the amount of the alicyclic diamine relative to the total amount of the diamine components may be 1 to 70 mol %, 3 to 50 mol %, 5 to 40 mol %, 10 to 30 mol %, or 12 to 25 mol %.

[0035] The total amount of the specific diamine, diaminodiphenylsulfone, diamine having a fluorene structure, and alicyclic diamine relative to the total amount of diamine components in the polyimide is preferably 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more, and may be 95 mol% or more, 99 mol% or more, or even 100 mol%.

[0036] 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.

[0037] Among fluorine atom-containing diamines, the structure in which a trifluoromethyl group is bonded to a carbon atom (—C—CF ３ ) and / or a structure in which carbon atoms are bonded to both ends of a difluoromethylene group (—C—CF ２ In order to improve the transparency and solubility 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, trifluoromethoxy-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.

[0038] <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, bis(trimellitic anhydride) esters, acid dianhydrides having a fluorene structure, and acid dianhydrides having a xanthene structure. Hereinafter, these acid dianhydrides will be referred to as "specific acid dianhydrides."

[0039] Examples of acid dianhydrides having an ether bond include those in which two phthalic anhydrides are bonded via an ether bond (—O—) or a functional group containing an ether bond. Examples of acid dianhydrides in which two phthalic anhydrides are bonded via an ether bond include 3,4′-oxydiphthalic anhydride (a-ODPA) and 4,4′-oxydiphthalic anhydride (s-ODPA).

[0040] An example of a functional group containing an ether bond is a bisphenol derivative structure. An example of an acid dianhydride in which two phthalic anhydrides are bonded via a bisphenol derivative structure is a compound represented by the following general formula (5):

[0041]

[0042] In general formula (5), A is any divalent organic group, and p is 1 or 2. １ａ , R １ｂ , R ２ａ and R ２ｂ are each independently an arbitrary substituent, m1 and m2 are each independently an integer of 0 to 3, and n1 and n2 are each independently an integer of 0 to 4.

[0043] Examples of the divalent organic group A include the following (a), (b), and (c). ３ａ and R ３ｂ are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or a phenyl group. ４ is an alkyl group having 1 to 10 carbon atoms, and k is an integer of 0 to 10. When k is 2 or more, multiple R ４ may be the same or different.

[0044]

[0045] Substituent R １ａ and R １ｂ , and the substituent R ２ａ and R ２ｂ Examples of the alkyl group include an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a phenyl group, and halogens.

[0046] From the viewpoint of solubility of the polyimide resin, the acid dianhydride having an ether bond is preferably one represented by general formula (1), and among these, 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (BPADA) is particularly preferred.

[0047] The bis(trimellitic anhydride) ester is represented by the following general formula (1).

[0048]

[0049] In general formula (1), X is any divalent organic group, and at both ends of X, a carboxy group and a carbon atom of X are bonded. The carbon atoms bonded to the carboxy group may form a ring structure. Specific examples of the divalent organic group X include the following (A) to (K).

[0050]

[0051] R in formula (A) １ is an alkyl group having 1 to 20 carbon atoms or a fluorine atom, and m is an integer of 0 to 4. The group represented by formula (A) is a group obtained by removing two hydroxyl groups from hydroquinone which may have a substituent on the benzene ring. Examples of hydroquinone derivatives having a substituent on the benzene ring include tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and 2,5-di-tert-amylhydroquinone.

[0052] R in formula (B) ２is an alkyl group having 1 to 20 carbon atoms or a fluorine atom, and n is an integer of 0 to 4. The group represented by formula (B) is a group obtained by removing two hydroxyl groups from a biphenol which may have a substituent on the benzene ring. Examples of biphenol derivatives having a substituent on the benzene ring include 2,2'-dimethylbiphenyl-4,4'-diol, 3,3'-dimethylbiphenyl-4,4'-diol, 3,3',5,5'-tetramethylbiphenyl-4,4'-diol, and 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diol.

[0053] The group represented by formula (C) is a group obtained by removing two hydroxyl groups from 4,4'-isopropylidenediphenol (bisphenol A). The group represented by formula (D) is a group obtained by removing two hydroxyl groups from resorcinol.

[0054] In formula (E), p is an integer of 1 to 10. The group represented by formula (E) is a group obtained by removing two hydroxyl groups from a linear diol having 1 to 10 carbon atoms. Examples of the linear diol having 1 to 10 carbon atoms include ethylene glycol and 1,4-butanediol.

[0055] The group represented by formula (F) is a group obtained by removing two hydroxyl groups from 1,4-cyclohexanedimethanol.

[0056] R in formula (G) ３is a hydrogen atom, a fluorine atom, or an alkyl group having 1 to 20 carbon atoms, and q is an integer from 0 to 4. The group represented by formula (G) is a group obtained by removing two hydroxyl groups from bisphenolfluorene, which may have a substituent on the benzene ring having a phenolic hydroxyl group. Examples of bisphenolfluorene derivatives having a substituent on the benzene ring having a phenolic hydroxyl group include biscresolfluorene. When X has the structure of formula (G), the compound falls under both acid dianhydrides and bis(trimellitic anhydride) esters having a fluorene structure, but is classified as a bis(trimellitic anhydride) ester in terms of the specific acid dianhydride category. Furthermore, a compound in which X in formula (1) has the structure of formula (J) falls under both acid dianhydrides having a fluorene structure, acid dianhydrides having a xanthene structure, and bis(trimellitic anhydride) esters, but is classified as a bis(trimellitic anhydride) ester in terms of the specific acid dianhydride category.

[0057] The bis(trimellitic anhydride) ester is preferably an aromatic ester. Of the above (A) to (K), (A), (B), (C), (D), (G), (H), and (I) are preferred for X. Of these, (A) to (D) are preferred, with (B) being the group having a biphenyl skeleton being particularly preferred. When X is a group represented by general formula (B), from the viewpoint of the solubility of the polyimide resin, X is preferably biphenylene or 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diyl represented by the following formula (B1):

[0058]

[0059] In the general formula (1), the acid dianhydride in which X is biphenylene is bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-biphenyl-4,4'-diyl. In the general formula (1), the acid dianhydride in which X is a group represented by formula (B1) is 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 (3).

[0060]

[0061] As the bis(trimellitic anhydride) ester in which X in the general formula (1) is a structure other than formula (B), p-phenylenebis(trimellitic acid monoester anhydride) (TMHQ), bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-biphenyl-4,4'-diyl (OCBP-TME), 5,5'-(3,3'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) (BP-TME), tert-butylhydroquinone bis(trimellitate anhydride) (TA.BHQ), trimethylhydroquinone bis(trimellitate anhydride) (TA.TMHQ), are preferred.

[0062] From the viewpoint of the solubility of the polyimide, TMHQ, TAHMBP, and OCBP-TME are particularly preferred as the bis(trimellitic anhydride) ester.

[0063] Examples of acid dianhydrides having a fluorene 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-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate] (TBIS.MPN), and the like. From the viewpoint of the solubility of the polyimide, BPAF, BPF-PA, or TBIS.MPN is preferred, and among these, BPAF or TBIS.MPN is particularly preferred.

[0064] Examples of acid dianhydrides having a xanthene structure include 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate (TBIS.RXN) and spiro[fluorene-9,9'xanthene]-2',3',6',7'-tetracarboxylic dianhydride (SFDA). These exemplary compounds contain a xanthene structure and a fluorene structure, but are classified as acid dianhydrides having a xanthene structure.

[0065] 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.

[0066] 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- p-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate] (TBIS.MPN), 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) are preferred.

[0067] From the viewpoint of UV resistance of the polyimide, among the specific acid dianhydrides, acid dianhydrides having an ether bond and acid dianhydrides having a fluorene structure are preferred. From the viewpoint of solubility in solvents and mechanical strength, BPADA, a-ODPA, s-ODPA, BPAF, and BPF-PA are particularly preferred. These acid dianhydrides do not have an ester bond and do not undergo Friess transition due to UV light, so that the polyimide is less likely to become discolored when exposed to UV light. Furthermore, from the viewpoint of compatibility with the acrylic resin described below, acid dianhydrides having an ether bond and acid dianhydrides having a fluorene structure are preferred as the specific acid dianhydrides.

[0068] 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.

[0069] (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.

[0070] 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 acrylic resins tends to be enhanced.

[0071] 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.

[0072] 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. Furthermore, polyimides containing an alicyclic tetracarboxylic dianhydride within the above range as the acid dianhydride component tend to have excellent compatibility with acrylic resins.

[0073] 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] Among fluorine atom-containing acid dianhydrides, the structure in which a trifluoromethyl group is bonded to a carbon atom (-C-CF ３ ) and / or a structure in which carbon atoms are bonded to both ends of a difluoromethylene group (—C—CF ２ -C-) has low decomposition properties and is a concern for environmental safety. ３ - or -C(CF ３ ) ２Acid dianhydrides having a structure in which - is directly bonded (for example, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 9,9-bis(trifluoromethyl)xanthenetetracarboxylic dianhydride, 9-trifluoromethylxanthenetetracarboxylic dianhydride) 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.

[0078] <Content of specific fluorine structure in polyimide> As described above, the diamine component is CF ３ -O-, -(CF ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ and a polyimide containing, as an acid dianhydride component, one or more acid dianhydrides (specific acid dianhydrides) selected from the group consisting of acid dianhydrides having an ether bond, bis(trimellitic anhydride) esters, acid dianhydrides having a fluorene structure, and acid dianhydrides having a xanthene structure, is -C-CF ３ , -C-CF ２ It is substantially free of structures such as —C— and exhibits solubility in organic solvents.

[0079] 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 trifluoromethyl group (CF ３ -), excluding those containing only the components of the following structural formula (i), and a difluoromethylene group (-CF ２-), excluding those having only the components of the following structural formula (ii): CF ３ -X (i) X-CF ２ -X' (ii)

[0080] X in formula (i) and (ii) is —OR or —NRR′, and X′ in formula (II) is —H, —CH ３ , aromatic, —C(O)—, —OR″, —SR″, and NR″R′″. R, R′ , R″, and R′″ each independently represent —H, —CH ３ , -CH ２ -, aromatic, or -C(O)-.

[0081] 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.

[0082] <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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] From the viewpoint of the thermal stability and light stability of polyimide resins and molded articles such as films, it is preferable that the polyimide has low reactivity. The acid value of the polyimide is preferably 0.4 mmol / g or less, more preferably 0.3 mmol / g or less, and even more preferably 0.2 mmol / g or less. The acid value of the polyimide may be 0.1 mmol / g or less, 0.05 mmol / g or less, or 0.03 mmol / g or less. From the viewpoint of reducing the acid value, it is preferable that the polyimide has a high imidization rate. A low acid value enhances the stability of the polyimide.

[0090] [Resin Composition] The polyimide of the present invention contains a specific diamine and a specific acid dianhydride, and therefore exhibits solubility in organic solvents and compatibility with other resins. The polyimide of the present invention is particularly compatible with acrylic resins and can be used as a resin composition containing the polyimide and the acrylic resin. Furthermore, the polyimide of the present invention can be made into a resin composition by adding various additives.

[0091] <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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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 ３The 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.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] <Preparation of Resin Composition Containing Polyimide and Acrylic Resin> The polyimide resin and acrylic resin are mixed to prepare a resin composition. The polyimide resin and acrylic resin can be compatible at any ratio, so the ratio of the polyimide resin to the acrylic resin in the resin composition is not particularly limited. The mixing ratio (weight ratio) of the polyimide resin to the acrylic resin may be 98:2 to 2:98, 95:5 to 10:90, or 90:10 to 15:85. The higher the ratio of the polyimide resin, the higher the elastic modulus of the film and the greater the mechanical strength. The higher the ratio of the acrylic resin, the less coloring there is and the greater the transparency of the film.

[0101] In order to fully exert the effect of improving transparency by mixing polyimide and acrylic resin, the ratio of the acrylic resin to the total of polyimide and acrylic resin is preferably 10% by weight or more, and may be 15% by weight or more, 20% by weight or more, 25% by weight or more, 30% by weight or more, 35% by weight or more, 40% by weight or more, 45% by weight or more, or 50% by weight or more.

[0102] 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.

[0103] A resin composition containing a polyimide resin and an acrylic resin preferably has a single glass transition temperature in differential scanning calorimetry (DSC) and / or dynamic mechanical analysis (DMA). When the resin composition has a single glass transition temperature, the polyimide resin and the acrylic resin can be considered to be completely compatible with each other. A film containing a polyimide resin and an acrylic resin also preferably has a single glass transition temperature.

[0104] The resin composition may be a simple mixture of a polyimide resin precipitated as a solid content and an acrylic resin, or a mixture of a polyimide and an acrylic resin. Furthermore, when a polyimide solution is mixed with a poor solvent to precipitate a polyimide resin, an acrylic resin may be mixed with the solution, and the resin composition obtained by mixing the polyimide and the acrylic resin may be precipitated as a solid (powder).

[0105] The resin composition may be a mixed solution containing a polyimide resin and an acrylic resin. The method for mixing the resins is not particularly limited, and the resins may be mixed in a solid state or in a liquid state to form a mixed solution. A polyimide resin solution and an acrylic resin solution may be prepared separately, and then the two may be mixed to prepare a mixed solution of the polyimide resin and the acrylic resin.

[0106] The solvent for the solution containing the polyimide resin and the acrylic resin is not particularly limited as long as it can dissolve both the polyimide resin and the acrylic resin. Examples of the solvent include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; ether solvents such as tetrahydrofuran and 1,4-dioxane; ketone solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diethyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone; and alkyl halide solvents such as chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chlorobenzene, dichlorobenzene, and methylene chloride.

[0107] From the viewpoints of the solubility of polyimide and the compatibility of polyimide with acrylic resin in solution, amide 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 solvents are preferred, and ketone solvents and alkyl halide solvents are preferred because they have excellent solubility in both polyimide and acrylic resin and a low boiling point, making it easy to remove the remaining solvent when producing a film.

[0108] 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.

[0109] Resin compositions containing polyimide and acrylic resin tend to have lower melt viscosities than polyimide alone, and are excellent in moldability in injection molding, transfer molding, press molding, melt extrusion molding, and the like. Furthermore, solutions of resin compositions containing polyimide and acrylic resin tend to have lower solution viscosities than solutions of polyimide alone with the same solids concentration. Therefore, they are easy to handle, such as during solution transportation, and have high coatability, which is advantageous in reducing unevenness in film thickness.

[0110] A molded article molded from a solution of a resin composition containing a polyimide and an acrylic resin has a lower glass transition temperature than a molded article molded from a solution of the same polyimide alone, and therefore tends to have a lower amount of residual solvent in the molded article when treated under the same heating conditions. In particular, when an amide-based high-boiling point solvent is used, high-temperature heating at 250°C or higher or 300°C or higher may be required to remove the solvent, which may result in a decrease in the transparency of the resulting molded article. However, when a resin composition containing a polyimide and an acrylic resin is used, the amount of residual solvent can be reduced by heating for a shorter period of time, thereby suppressing coloration during heating and making it easier to obtain a molded article with high transparency.

[0111] [Molded Articles and Films] The polyimides and resin compositions containing polyimides and acrylic resins can be used to form various molded articles, including melt processes such as injection molding, transfer molding, press molding, blow molding, inflation molding, calendar molding, and melt extrusion molding.

[0112] 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 and the acrylic resin are compatible in solution, a highly transparent film can be produced by the solution method by using the polyimide and the acrylic resin in combination.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] The conditions for stretching the film are not particularly limited. For example, the stretching temperature is the glass transition temperature of the film ±40°C. The stretching temperature for polyimide films may be about 120 to 350°C, 150 to 300°C, or 180 to 250°C. The stretching temperature for films containing polyimide and acrylic resins may be about 120 to 300°C, 150 to 250°C, or 180 to 230°C.

[0118] The stretching ratio is about 1 to 200%, and may be 5 to 150%, 10 to 120%, or 20 to 100%. The stretching ratio (%) is 100×(L １ -L ０ ) / L ０ and L ０ is the length in the stretching direction of the film before stretching (original length), and L １ is the length of the stretched film in the stretching direction. The larger the stretching ratio, the larger the tensile modulus in the stretching direction tends to be. In particular, in a compatible system of polyimide and acrylic resin, the tensile modulus in the stretching direction tends to be larger, and as a result, the flex resistance tends to be improved. The higher the ratio of methyl methacrylate in the monomer components of the acrylic resin, the more pronounced the tendency for the tensile modulus in the stretching direction to increase. If the stretching ratio is excessively large, the mechanical strength in the direction perpendicular to the stretching direction tends to decrease, and the handleability of the film may be reduced.

[0119] 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.

[0120] 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.

[0121] 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 and acrylic resin are compatible, so a film containing polyimide and acrylic resin has low haze and excellent transparency, similar to a film made of polyimide alone.

[0122] The total light transmittance of the film is not particularly limited, but is preferably 87% or more, more preferably 88% or more, and may be 89% or more or 90% or more. A film containing polyimide and an acrylic resin has a higher total light transmittance than a film made of polyimide alone, and can exhibit a total light transmittance of 90% or more.

[0123] The yellowness index (YI) of the film is not particularly limited, but is preferably 10 or less, 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. A film containing polyimide and an acrylic resin has a lower YI than a film containing polyimide alone, and even if the YI of a film containing polyimide alone exceeds 10, it is possible to reduce the YI by adopting a mixed system with an acrylic resin. A film containing polyimide and an acrylic resin can achieve a low YI of 1.0 or less.

[0124] 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, still 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.

[0125] 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.

[0126] The following examples will be used to further explain the present invention, but the present invention is not limited to these examples.

[0127] [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 %.

[0128] 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 for 3 hours at 90° C. to carry out imidization. In Comparative Examples 1 to 10 in Table 2, the solubility of the polyimide in DMF was low, and gelation or precipitation occurred during the imidization process, so the subsequent operations were not carried out.

[0129] 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.

[0130] [Preparation of Polyimide Film] The polyimide resin was dissolved in a solvent to prepare a polyimide solution with a solids concentration of 10 wt%. The solvent used was DMF or methylene chloride (DCM). The polyimide solution was applied to an alkali-free glass plate and dried by heating 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 in an air atmosphere to prepare a film with a thickness of approximately 50 μm.

[0131] [Film Evaluation] <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.

[0132] <Total Light Transmittance> The film was cut into a 3 cm square, and the total light transmittance (TT) was measured using a haze meter "HZ-V3" manufactured by Suga Test Instruments in accordance with JIS K7136 and JIS K7361-1.

[0133] <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.

[0134] <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.

[0135] [Evaluation Results] The compositions of the polyimides in the Examples and Comparative Examples, as well as the solvents used to prepare the polyimide films in the Examples and the evaluation results of the films, 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.

[0136] In Tables 1 and 2, and Table 3 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. <Diamines> TFMOB: 2,2'-bis(trifluoromethoxy)benzidine 2,2-Bz: 2,2'-dimethylbenzidine 3,3'-DDS: 3,3'-diaminodiphenylsulfone 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 BPF-PA: 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride TBIS. MPN: 5,5'-(9H-fluoren-9-ylidenebis(2-methyl-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate] TBIS.RXN: 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) 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 acid-3,4:3',4'-dianhydride BT100: 1,2,3,4-butanetetracarboxylic acid dianhydride PMDA: pyromellitic dianhydride MPDA: 1,2,3,4-benzenetetracarboxylic acid dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride

[0137]

[0138]

[0139] The polyimides of Examples 1 to 25, 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.

[0140] These results demonstrate that by using a specific diamine that does not contain a specific fluorine structure as the diamine component and by appropriately selecting an acid dianhydride, a polyimide that is highly environmentally safe and has excellent solubility in organic solvents and transparency can be obtained.

[0141] [Preparation of Resin Composition of Polyimide and Acrylic Resin] The polyimides and acrylic resins of Examples 1, 6, 7, 8, 10, 12, 14-20, 22, 23, and 25 were dissolved in DMF at a 50:50 weight ratio to prepare a solution with a solids concentration of 10 wt%. The acrylic resins used were commercially available polymethyl methacrylate resin ("Parapet HM1000" manufactured by Kuraray, glass transition temperature: 120°C, acid value: 0.0 mmol / g, hereinafter referred to as "HM") and glutarimide-modified acrylic resin (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 polyimide and acrylic resin, the solutions were transparent, demonstrating compatibility between the polyimide and acrylic resin.

[0142] [Film Preparation and Evaluation] The polyimide resin and acrylic resin (HM) were dissolved in a solvent in a weight ratio of 50:50 to prepare a mixed resin solution with a solid content of 10 wt %. The mixed resin solution was applied to an alkali-free glass plate and dried by heating in an air atmosphere 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 prepare a film with a thickness of approximately 50 μm.

[0143] The resulting film was evaluated in the same manner as the polyimide film described above. The polyimide composition, the solvent used in preparing the film, and the evaluation results of the film are shown in Table 3.

[0144]

[0145] The films of Examples 101, 106, 107, 108, 110, 112, 114 to 120, 122, 123, and 125, which were mixed resin films of polyimide and acrylic resin, had mechanical strength (tensile modulus) equivalent to that of the polyimide films of Examples 1, 6, 7, 8, 10, 12, 14 to 20, 22, 23, and 25, which were polyimide films alone, and tended to have improved transparency compared to polyimide films alone. For example, while the polyimide film of Example 19 had a YI of over 10, the film of Example 119 had a YI reduced to 3.1 and a total light transmittance of over 90%, significantly improving transparency.

[0146] These results demonstrate that polyimides containing specific diamines as diamine components and appropriately selected acid dianhydrides exhibit solubility in organic solvents, excellent compatibility with acrylic resins, and can produce highly transparent films.

[0147] [Preparation of Films with Different Mixing Ratios of Polyimide and Acrylic Resin] Examples 201 to 204 The polyimide of Example 14 and a commercially available acrylic resin (a copolymer of methyl methacrylate / methyl acrylate (monomer ratio 87 / 13): "Parapet G-1000" manufactured by Kuraray; glass transition temperature 109°C, acid value 0.0 mmol / g) were dissolved in methylene chloride at the weight ratios shown in Table 4 to prepare solutions with a solids concentration of 10 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 prepare films with a thickness of approximately 50 μm.

[0148] [Preparation of Stretched Films] Examples 205 to 208 Films with a thickness of approximately 60 μm were prepared by changing the mixing ratio of polyimide and acrylic resin as shown in Table 4. The films were cut into rectangles, and the short sides (both ends in the longitudinal direction) of the films were chucked, and both ends of the long sides were held and fixed with clips. In this state, the distance between the chucks was changed in an oven at the temperature shown in Table 4, and fixed-end uniaxial stretching was performed at the stretch ratio shown in Table 4.

[0149] [Evaluation] The films of Examples 201 to 208 were evaluated in the same manner as above. The tensile modulus of Examples 205 to 208 (stretched films) was measured in the stretching direction. The polyimide composition, the mixing ratio of polyimide to acrylic resin, the stretching conditions, and the evaluation results of the films are shown in Table 4, along with the evaluation result of Example 14 (film made of polyimide alone).

[0150]

[0151] In Examples 14 and 201 to 204, the total light transmittance increased, the YI decreased, and the transparency improved as the acrylic resin content increased. Although the tensile modulus tended to decrease as the acrylic resin content increased, the effect was slight.

[0152] A tendency for transparency to improve with an increase in the proportion of acrylic resin was also observed in the stretched films of Examples 205 to 208. Comparisons between Examples 202 and 205, and between Examples 203 and 206, show that stretching the film improves mechanical strength (tensile modulus) without impairing transparency.

Claims

1. A polyimide having a tetracarboxylic dianhydride component and a diamine component, wherein the diamine component is CF ３ -O-, -(CF ２ -O) ｎ -, and -O-(CF ２ -CF ２ -O) ｎ - (where n is an integer of 1 to 20) and containing, as a tetracarboxylic dianhydride component, one or more tetracarboxylic dianhydrides selected from the group consisting of tetracarboxylic dianhydrides having an ether bond, tetracarboxylic dianhydrides having a fluorene structure, tetracarboxylic dianhydrides having a xanthene structure, and bis(trimellitic anhydride) esters.

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

3. The one or more tetracarboxylic dianhydrides selected from the group consisting of tetracarboxylic dianhydrides having an ether bond, tetracarboxylic dianhydrides having a fluorene structure, tetracarboxylic dianhydrides having a xanthene 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 The polyimide according to claim 1, which is one or more selected from the group consisting of 1,2'-(9H-fluoren-9-ylidenebis(2-methyl-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate], 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 a 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, spiro[fluorene-9,9'xanthene]-2',3',6',7'-tetracarboxylic dianhydride, and 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate).

5. The polyimide according to claim 1, which contains an alicyclic tetracarboxylic dianhydride as the tetracarboxylic dianhydride component, and the amount of the alicyclic tetracarboxylic dianhydride relative to the total amount of the tetracarboxylic dianhydride component is 1 to 80 mol %.

6. The polyimide according to claim 5, wherein the alicyclic tetracarboxylic dianhydride is one or more selected from the group consisting of 1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4-tetrahydronaphthalene-1,2-dicarboxylic anhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, bicyclo[2.2.2]octane-2,3,5,6-tetracarboxylic dianhydride, and 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-dianhydride.

7. The amount of CF on 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 the diamine having a structure in which - is directly bonded is less than 0.5 mol %, and the amount of the diamine having a structure in which - is directly bonded to a carbon atom of an aromatic ring is less than 0.5 mol % based on 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 %.

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

9. A molded article comprising the polyimide according to any one of claims 1 to 8.

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

11. A resin composition comprising the polyimide according to any one of claims 1 to 8 and an acrylic resin.

12. The resin composition according to claim 11, comprising said polyimide and said acrylic resin in a weight ratio ranging from 98:2 to 2:

98.

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

14. A film comprising the resin composition according to claim 11.

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