Resin composition, molded body, and film

Abstract

A resin composition according to the present invention contains a polyimide and an acrylic resin. The polyimide has a tetracarboxylic dianhydride component and a diamine component and may be a polyamideimide having an amide structural unit formed by bonding a diamine component and a polybasic acid component. The polyimide constituting the resin composition contains, as the diamine component, a benzidine derivative in which at least one hydrogen atom on the two benzene rings of benzidine is substituted with a difluoromethyl group. A molded article such as a film formed from the resin composition has high transparency.

Description

Resin compositions, molded articles, and films

[0001] The present invention relates to a resin composition containing polyimide and an acrylic resin, and to molded articles such as films.

[0002] Display devices such as liquid crystal displays, organic EL displays, and electronic paper, as well as electronic devices such as solar cells and touch panels, are required to be thinner, lighter, and more flexible. By replacing the glass materials used in these devices with film materials, flexibility, thinning, and weight reduction can be achieved. Transparent polyimide film has been developed as a glass substitute material and is used in display substrates and cover films, etc.

[0003] Although transparent polyimide has superior heat resistance compared to general-purpose transparent resins, higher transparency is required when used in display cover films and the like. As a method to improve the transparency of transparent polyimide films, Patent Document 1 proposes using a resin composition that mixes polyimide and an acrylic resin. Patent Document 2 discloses a resin composition that mixes polyamide-imide and an acrylic resin.

[0004] International Publication No. 2023 / 026982, International Publication No. 2023 / 132310

[0005] Patent documents 1 and 2 use solvent-soluble polyimides containing fluoroalkyl-substituted benzidines such as 2,2'-bis(trifluoromethyl)benzidine (TFMB) as the diamine of the poly(amide)imide. Polyimides using fluorine-containing compounds as the diamine and / or tetracarboxylic dianhydride exhibit excellent transparency and solvent solubility.

[0006] On the other hand, in recent years, the environmental persistence of organofluorine compounds (PFAS) has become a problem. Generally, the carbon-fluorine bonds contained in organofluorine compounds have high bond energy and are not easily decomposed in the environment. In particular, structures 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, including C, have low biodegradability in the environment, and their effects on the human body have also been pointed out.

[0007] In view of these issues, the present invention aims to provide molded articles such as films containing polyimide, which are environmentally safe and highly transparent, and resin compositions used in their production.

[0008] The present invention relates to a resin composition comprising polyimide and an acrylic resin, and a molded article such as a film comprising the resin composition. The resin composition may contain polyimide and acrylic resin in a weight ratio in the range of 98:2 to 2:98.

[0009] In the resin composition of the present invention, the polyimide contains a benzidine derivative as a diamine component, in which at least one hydrogen atom on the two benzene rings of benzidine is substituted with a difluoromethyl group. Examples of such benzidine derivatives include 2,2'-bis(difluoromethyl)benzidine, 3,3'-bis(difluoromethyl)benzidine, and 2,3'-bis(difluoromethyl)benzidine. The amount of the benzidine derivative relative to the total amount of the diamine component of the polyimide is preferably 10 mol% or more.

[0010] The polyimide may contain, 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, and bis(trimellitic anhydride) esters.

[0011] Preferred examples of specific acid dianhydrides 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-fluorene-9-ylidenebis(2-methyl-4,1-phenylene)]bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate], and 5,5'-spiro[9H-fluorene-9,9'-[9H Examples include xanthene-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofuran carboxylate), 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.

[0012] The total amount of diamine components in polyimide is CF at the carbon atoms of the aromatic ring. ３ - or -C (CF ３ ) ２ The amount of diamine having a structure to which a negative charge is directly bonded is preferably less than 0.5 mol%. The amount of CF at the carbon atom of the aromatic ring relative to the total amount of the tetracarboxylic dianhydride component of the polyimide is preferably less than 0.5 mol%. ３ - or -C (CF ３ ) ２ The amount of tetracarboxylic dianhydride having a structure to which a negative charge is directly bonded is preferably less than 0.5 mol%.

[0013] The above polyimide may also be a polyamideimide that contains a polybasic acid component in addition to a diamine component and a tetracarboxylic dianhydride, and has an amide structural unit formed by the bonding of the diamine component and the polybasic acid component.

[0014] The molded article such as a film formed from the resin composition of the present invention has a high light transmittance and excellent transparency. Further, since the polyimide contains a specific diamine as a diamine component, it has lower environmental persistence and excellent environmental safety compared to polyamide-imide using an organic fluorine compound such as fluoroalkyl-substituted benzidine.

[0015] One embodiment of the present invention is a resin composition containing a polyimide and an acrylic resin. Since the polyimide and the acrylic resin are compatible, the molded article such as a film formed from the resin composition exhibits transparency.

[0016] [Polyimide] <Structure of Polyimide> In this specification, the term "polyimide" refers to polyimide in a broad sense including polyamide-imide.

[0017] "Polyimide" in a narrow sense is a polymer obtained by dehydrating and cyclizing a polyamic acid obtained by an addition polymerization of a tetracarboxylic dianhydride (hereinafter sometimes referred to as "acid dianhydride") and a diamine, and having an imide structural unit represented by the general formula (I).

[0018] Polyamide-imide is a polymer having an imide structural unit represented by the general formula (I) and an amide structural unit represented by the general formula (II) and / or an amide-imide structural unit represented by the general formula (III).

[0019]

[0020] In general formulas (I) to (III), X is a tetravalent organic group, Y and Z are divalent organic groups, and W is a trivalent organic group. Y is a diamine residue, which is an organic group obtained by removing two amino groups from the diamine represented by general formula (V) below. X is a tetracarboxylic dianhydride (hereinafter sometimes referred to as "acid dianhydride") residue, which is an organic group obtained by removing two anhydrous carboxyl groups from the tetracarboxylic dianhydride represented by general formula (IV) below. Z is a dicarboxylic acid residue, which is an organic group obtained by removing two carboxyl groups from the dicarboxylic acid represented by general formula (VI) below. W is a tricarboxylic acid anhydride residue, which is an organic group obtained by removing anhydrous carboxyl groups from the tricarboxylic acid anhydride represented by general formula (VII) below.

[0021]

[0022] In other words, polyamide-imide includes a diamine-derived structure represented by the following general formula (Va) and a tetracarboxylic dianhydride-derived structure represented by the following general formula (IVa), and further includes one or more structures selected from the group consisting of a dicarboxylic acid-derived structure represented by the following general formula (VIa) and a tricarboxylic acid anhydride-derived structure represented by the following general formula (VIIa). The diamine-derived structure (Va) and the tetracarboxylic dianhydride-derived structure (IVa) form an imide bond to constitute an imide structural unit represented by general formula (I), the diamine-derived structure (Va) and the dicarboxylic acid-derived structure (VIa) form an amide bond to constitute an amide structural unit represented by general formula (II), and the anhydride carboxyl group portion and carboxyl group portion of the tricarboxylic acid anhydride-derived structure (VIIa) form an imide bond and an amide bond, respectively, with the diamine-derived structure (Va), to constitute an amide-imide structural unit represented by general formula (III).

[0023]

[0024] As will be described in detail later, polyimide is generally obtained by synthesizing polyamic acid using diamine and tetracarboxylic dianhydride as monomers and dehydrating and cyclizing the amic acid at the bonding portion between the tetracarboxylic acid and the diamine. Polyimide can also be synthesized by condensation by decarboxylation of tetracarboxylic dianhydride and diisocyanate, etc. In any synthesis method, the obtained polyimide has an acid dianhydride-derived structure (tetracarboxylic dianhydride residue) X obtained by removing four carboxy groups from the tetracarboxylic dianhydride and a diamine-derived structure (diamine residue) Y obtained by removing two amino groups from the diamine. Therefore, even when the starting materials used for the synthesis of polyimide are not tetracarboxylic dianhydride or diamine, the structure corresponding to the tetracarboxylic dianhydride residue contained in the polyimide is expressed as the "acid dianhydride component", and the structure corresponding to the diamine residue is expressed as the "diamine component".

[0025] For the synthesis of polyamideimide, in addition to diamine and tetracarboxylic dianhydride, polybasic acid derivatives such as dicarboxylic acid dichloride and tricarboxylic acid anhydride chloride are used. The obtained polyamideimide has a structure Z (dicarboxylic acid residue) obtained by removing two carboxy groups from the dicarboxylic acid or a structure W (tricarboxylic acid residue) obtained by removing three carboxy groups from the tricarboxylic acid. Therefore, even when the starting material used for the synthesis of polyamideimide is a polybasic acid derivative, the structure corresponding to the polybasic acid residue is expressed as the "polybasic acid component".

[0026] Hereinafter, the diamine component, the tetracarboxylic dianhydride component, and the polybasic acid component as monomer units constituting the polyimide will be described with examples.

[0027] <Diamine> (Benzidine having a difluoromethyl group) In the resin composition of the present invention, the polyimide contains, as a diamine component, a benzidine derivative in which at least one of the hydrogen atoms on the two benzene rings of benzidine is substituted with a difluoromethyl group (-CF ２ H). This benzidine derivative (hereinafter referred to as "benzidine having a difluoromethyl group") is a compound represented by the following general formula (4).

[0028]

[0029] In general formula (4), the two n are each an independent integer between 0 and 4, and at least one of the n is 1 or greater.

[0030] The method for synthesizing benzidine having a difluoromethyl group is not particularly limited. For example, it can be obtained by applying the method for synthesizing benzidine from nitrobenzene, but instead of nitrobenzene, using nitrobenzene in which at least one hydrogen atom on the benzene ring is substituted with a difluoromethyl group as the starting material.

[0031] Specifically, in the presence of a reduction catalyst, nitrobenzene having a difluoromethyl group is reacted to synthesize 1,2-diphenylhydrazine having a difluoromethyl group, either directly or via azobenzene having a difluoromethyl group. Benzidine having a difluoromethyl group is then obtained by contacting it with a strong acid to perform a benzidine transition.

[0032]

[0033] Benzidines having a difluoromethyl group are trifluoromethyl (-CHF ３ ) and difluoromethylene (-CF ２ It does not possess any of the above characteristics and is therefore not subject to the definition of per- and polyfluoroalkyl substances (PFAS) as defined by the OECD. For this reason, polyimides containing benzidine with a difluoromethyl group as the diamine component tend to be more degradable and less persistent in the environment compared to conventional soluble polyimides containing compounds with perfluoroalkyl groups such as TFMB as the diamine component, and thus have superior environmental safety.

[0034] Benzidines having a difluoromethyl group may have substituents other than the difluoromethyl group on the benzene ring, but from the viewpoint of reactivity, it is preferable that they do not have a fluorine atom directly bonded to the carbon atom of the benzene ring. Benzidines having a difluoromethyl group are preferably free of fluorine atoms other than the difluoromethyl group, and difluoromethyl-substituted benzidines that do not have substituents other than the difluoromethyl group are particularly preferred.

[0035] Examples of difluoromethyl-substituted benzidines include those having a difluoromethyl group on one benzene ring of the benzidine, such as 2-(difluoromethyl)benzidine, 3-(difluoromethyl)benzidine, 2,3-bis(difluoromethyl)benzidine, 2,5-bis(difluoromethyl)benzidine, 2,6-bis(difluoromethyl)benzidine, 2,3,5-tris(difluoromethyl)benzidine, 2,3,6-tris(difluoromethyl)benzidine, and 2,3,5,6-tetrakis(difluoromethyl)benzidine; and 2,2'-bis(difluoromethyl)benzidine (DFMB), 3,3'-bis(difluoromethyl)benzidine, and 2,3'-bis(difluoromethyl Examples include benzidine, 2,2',3-tris(difluoromethyl)benzidine, 2,3,3'-tris(difluoromethyl)benzidine, 2,2',5-tris(difluoromethyl)benzidine, 2,2',6-tris(difluoromethyl)benzidine, 2,3',5-tris(difluoromethyl)benzidine, 2,3',6-tris(difluoromethyl)benzidine, 2,2',3,3'-tetrakis(difluoromethyl)benzidine, 2,2',5,5'-tetrakis(difluoromethyl)benzidine, and 2,2',6,6'-tetrakis(difluoromethyl)benzidine, in which each of the two benzene rings of the benzidine has at least one difluoromethyl group.

[0036] From the viewpoint of polymerizability and mechanical strength of the polyimide, it is preferable that the benzidine having a difluoromethyl group has at least one difluoromethyl group on each of the two benzene rings of the benzidine. From the viewpoint of solubility of the polyimide in organic solvents, it is preferable that the biphenyl has a difluoromethyl group at the 2nd or 3rd position. Specifically, 2,2'-bis(difluoromethyl)benzidine (hereinafter referred to as "DFMB"), 3,3'-bis(difluoromethyl)benzidine, and 2,3'-bis(difluoromethyl)benzidine are preferred, with DFMB being particularly preferred.

[0037] By having a difluoromethyl group at the 2 or 3 position of biphenyl, the electron-withdrawing properties of the difluoromethyl group reduce the π electron density, and the steric hindrance of the difluoromethyl group inhibits π-π stacking between the benzene rings. This causes a shorter wavelength shift in the absorption edge wavelength, reducing the coloration of the polyimide. Furthermore, in DFMB, the steric hindrance between the difluoromethyl groups at the 2 and 2' positions of biphenyl causes the bond between the two benzene rings of biphenyl to twist, reducing the planarity of the π-conjugated bond. This also causes a shorter wavelength shift in the absorption edge wavelength, further reducing the coloration of the polyimide.

[0038] The amount of benzidine having a difluoromethyl group relative to the total amount of 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%. In particular, it is preferable that the amount of difluoromethyl group-containing diamine be within this range, and especially preferable that the amount of difluoromethyl-substituted benzidine be within this range. The higher the proportion of benzidine having a difluoromethyl group, the more the discoloration is suppressed, and the mechanical strength of the film, such as pencil hardness, elastic modulus, breaking strength, and elongation at break, may improve.

[0039] (Other diamines) Polyimides may contain diamines other than benzidine having a difluoromethyl group as a diamine component. From the viewpoint of the environmental safety of polyimides, -C-CF ３ and -C-CF ２Materials that do not contain -C- are preferred, and materials that do not contain fluorine atoms are particularly preferred.

[0040] Examples of diamines that do not contain a fluorine atom include 2,2'-dimethylbenzidine, p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, and 3,3'-diaminodi Phenylsulfone, 3,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis[4-(4-aminophenoxy)phenyl]fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 2,2-di(3-aminophenyl)propane, 2,2-di(4-aminophenyl)propane, 2-(3-aminophenyl)-2-(4-aminophenyl)propane, 1,1-di(3-aminophenyl)-1-phenylethane, 1,1-di(4-aminophenyl)-1-phenylethane, 1-(3-aminophenyl)-1-(4-aminophenyl)-1-phenylethane n, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminobenzoyl)benzene, 1,3-bis(4-aminobenzoyl)benzene, 1,4-bis(3-aminobenzoyl)benzene, 1,4-bis(4-aminobenzoyl)benzene, 1,3-bis(3-amino-α α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene, 2,6-bis(3-aminophenoxy)benzonitrile, 2,6-bis(3-aminophenoxy)pyridine, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-Bis(4-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfone, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 2,2-bis[4-( 3-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)-α,α-dimethyl [Benzyl]benzene, 1,4-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 4,4'-bis[4-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenylsulfone, 4,4'-bis[4-(4-aminophenoxy)phenoxy]diphenyl Lusulfone, 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis(3-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirovindan, 6,6'-bis(4-aminophenoxy)-3,3,3',3'-tetramethyl-1,1'-spirovindan, 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-(2-aminomethoxy)ethyl] ether, bis[2-(2-aminoethoxy)ethyl] ether, bis[2-(3-aminopropoxy)ethyl] ether, 1,2-bis(aminomethoxy)ethane, 1,2-bis(2-aminoethoxy)ethane, 1,2-bis[2-(aminomethoxy)ethoxy]ethane, 1,2-bis[2-(2-aminoethoxy)ethoxy]ethane, ethylene glycol bis(3-aminopropyl) ether, diethylene glycol bis(3-aminopropyl) ether, triethylene glycol bis(3-aminopropyl (L) 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-diaminocyclohex Examples include san, 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, etc.

[0041] In addition to benzidine having a difluoromethyl group, using diaminodiphenylsulfone as the diamine may improve the solubility and transparency of the polyimide in the solvent. Among diaminodiphenylsulfones, 3,3'-diaminodiphenylsulfone (3,3'-DDS) and 4,4'-diaminodiphenylsulfone (4,4'-DDS) are preferred, and these may be used in combination.

[0042] When diaminodiphenylsulfone is used in addition to benzidine having a difluoromethyl group, the amount of diaminodiphenylsulfone relative to the total amount of diamine components may be 1 to 40 mol%, 3 to 30 mol%, or 5 to 25 mol%.

[0043] In addition to benzidine having a difluoromethyl group, using a diamine having a fluorene structure may improve the solubility, transparency, and mechanical strength of the polyimide. Preferred fluorene-containing diamines include 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.

[0044] When a diamine having a fluorene structure is used in addition to benzidine having a difluoromethyl group, the amount of the diamine having a fluorene structure relative to the total amount of the diamine component may be 1 to 80 mol%, 3 to 60 mol%, or 5 to 30 mol%.

[0045] In addition to benzidine having a difluoromethyl group, using alicyclic diamines as diamines may improve the transparency of polyimides. Among alicyclic diamines, isophorone diamine and 1,4-diaminocyclohexane are preferred, and these may be used in combination.

[0046] When using an alicyclic diamine in addition to benzidine having a difluoromethyl group, the amount of alicyclic diamine relative to the total amount of 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%.

[0047] The total amount of benzidine having a difluoromethyl group, 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, even more preferably 90 mol% or more, and may be 95 mol% or more or 99 mol% or more, or even 100 mol%.

[0048] Polyimides may contain fluorine-containing diamines other than benzidine having a difluoromethyl group as a diamine component. However, from the viewpoint of environmental safety of polyimides, the amount of fluorine-containing diamines other than benzidine having a difluoromethyl group relative to the total amount of diamine components of polyimides 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. Polyimides may also not contain fluorine-containing diamines other than benzidine having a difluoromethyl group as a diamine component.

[0049] Among fluorine atom-containing diamines, there is a 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 Polyimides containing -C- have low degradability and raise environmental safety concerns. From the perspective of improving the transparency and solubility of polyimides in solvents, general soluble polyimides use CF as the diamine component at the carbon atom of the aromatic ring. ３ - or -C (CF ３ ) ２ Although it contains diamines having a structure in which a hyphen 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 the environmental safety of polyimides, it is preferable that these diamines are substantially absent. The total amount of diamine components in the polyimide is such that CF is attached to the carbon atoms of the aromatic ring. ３ - or -C (CF ３ ) ２ The amount of diamine directly bonded to the negative sign 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 even 0.

[0050] CF at the carbon atoms of the aromatic ring ３ - or -C (CF ３ ) ２Examples of fluorine-containing diamines that do not have a structure to which a hyphen is directly bonded include, in addition to the benzidine having a difluoromethyl group mentioned above, 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, and 2,3,5,6-tetrakis(trifluoro Methoxy)benzidine, 2,2'-bis(trifluoromethoxy)benzidine, 3,3'-bis(trifluoromethoxy)benzidine, 2,3'-bis(trifluoromethoxy)benzidine, 2,2',3-tris(trifluoromethoxy)benzidine, 2,3,3'-tris(trifluoromethoxy)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, 2,2',6,6'-tetrakis(trifluoromethoxy)benzidine, 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) C) Benzene, 1,4-diamino-2,6-bis(trifluoromethoxy)benzene, 1,4-diamino-2,3,5-tris(trifluoromethoxy)benzene, 1,4-diamino-2,3,5,6-tetrakis(trifluoromethoxy)benzene, 1,4-bis(4-aminophenoxy)tetrafluorobenzene, 1,4-bis(4-amino-3-methylphenoxy)tetrafluorobenzene, 1,4-bis(4-amino-3,5-dimethylphenoxy)tetrafluorobenzene, 2,2',3,3',5,5',6,6'-octafluoro4,Examples include 4'-bis(4-aminophenoxy)-1,1'-biphenyl, 2,2',3,3',5,5',6,6'-octafluoro4,4'-bis(4-amino-3-methylphenoxy)-1,1'-biphenyl, 2,2',3,3',5,5',6,6'-octafluoro4,4'-bis(4-amino-3,5-dimethylphenoxy)-1,1'-biphenyl, etc.

[0051] <Tetracarboxylic acid dianhydride> The acid dianhydride component of the polyimide is not particularly limited, and various tetracarboxylic acid dianhydrides can be used without any particular restrictions.

[0052] (Specific Acid Dianhydrides) From the viewpoint of improving the solubility of polyimide in solvents, the compatibility of polyimide with acrylic resins, transparency, and mechanical strength, it is preferable that polyimide contains one or more acid dianhydrides selected from acid dianhydrides having ether bonds, bis(trimellitic anhydride) esters, and acid dianhydrides having a fluorene structure as an acid dianhydride component. Hereinafter, these acid dianhydrides will be referred to as "specific acid dianhydrides."

[0053] Examples of dianhydrides containing an ether bond include those in which two phthalic anhydrides are linked via an ether bond (-O-) or a functional group containing an ether bond. Examples of dianhydrides in which two phthalic anhydrides are linked via an ether bond include 3,4'-oxydiphthalic anhydride (a-ODPA) and 4,4'-oxydiphthalic anhydride (s-ODPA).

[0054] Examples of functional groups containing ether bonds include bisphenol derivative structures. Examples of acid dianhydrides in which two phthalic anhydrides are linked via a bisphenol derivative structure include compounds represented by the following general formula (5).

[0055]

[0056] In general formula (5), A is any divalent organic group, and p is 1 or 2. １ａ , R １ｂ , R ２ａ and R ２ｂEach of the substituents is independently an arbitrary substituent, m1 and m2 are independently integers from 0 to 3, and n1 and n2 are independently integers from 0 to 4.

[0057] Examples of divalent organic group A are shown below (a), (b), and (c). R in (a) ３ａ and R ３ｂ Each of these is independently a hydrogen atom, a C1-C10 alkyl group, or a phenyl group. (b) R ４ R is an alkyl group having 1 to 10 carbon atoms, and k is an integer from 0 to 10. If k is 2 or greater, multiple R ４ They may be the same or they may be different.

[0058]

[0059] Substituent R １ａ and R １ｂ , and substituent R ２ａ and R ２ｂ Examples include alkyl groups having 1 to 10 carbon atoms, alkoxy groups having 1 to 10 carbon atoms, phenyl groups, and halogens.

[0060] From the viewpoint of polyimide solubility, as an acid dianhydride having an ether bond, one in general formula (5) where A is represented by (a) is preferred, and among these, 4,4'-(4,4'-isopropylidene diphenoxy)diphthalic acid anhydride (BPADA) is particularly preferred.

[0061] Bis(trimellitic anhydride) esters are represented by the following general formula (1).

[0062]

[0063] In general formula (1), X is any divalent organic group, with carboxyl groups bonded to the carbon atoms of X at both ends. The carbon atoms bonded to the carboxyl groups may form a ring structure. Specific examples of divalent organic groups X are listed below (A) to (K).

[0064]

[0065] R in equation (A) １m is an alkyl group having 1 to 20 carbon atoms or a fluorine atom, and m is an integer from 0 to 4. The group represented by formula (A) is a hydroquinone which may have substituents on the benzene ring, with two hydroxyl groups removed. Examples of hydroquinone derivatives having substituents on the benzene ring include tert-butylhydroquinone, 2,5-di-tert-butylhydroquinone, and 2,5-di-tert-amylhydroquinone.

[0066] R in equation (B) ２ n is an alkyl group having 1 to 20 carbon atoms or a fluorine atom, and n is an integer from 0 to 4. The group represented by formula (B) is a biphenol which may have substituents on the benzene ring, with two hydroxyl groups removed. Examples of biphenol derivatives having substituents 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.

[0067] The group represented by formula (C) is the group obtained by removing two hydroxyl groups from 4,4'-isopropylidenediphenol (bisphenol A). The group represented by formula (D) is the group obtained by removing two hydroxyl groups from resorcinol.

[0068] In formula (E), p is an integer between 1 and 10. The group represented by formula (E) is a straight-chain diol having 1 to 10 carbon atoms from which two hydroxyl groups have been removed. Examples of straight-chain diols having 1 to 10 carbon atoms include ethylene glycol and 1,4-butanediol.

[0069] The group represented by formula (F) is a group obtained by removing two hydroxyl groups from 1,4-cyclohexanedimethanol.

[0070] R in equation (G) ３X is a hydrogen atom, a fluorine atom, and 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 bisphenol fluorene, which may have substituents on a benzene ring having a phenolic hydroxyl group. Examples of bisphenol fluorene derivatives having substituents on a benzene ring having a phenolic hydroxyl group include biscresol fluorene. When X has the structure of formula (G), it falls under both acid dianhydrides having a fluorene structure and bis(trimellitic anhydride) esters, but for the classification of specific acid dianhydrides, it is classified as a bis(trimellitic anhydride) ester. Also, a compound in formula (1) where X has the structure of formula (J) falls under both acid dianhydrides having a fluorene structure and bis(trimellitic anhydride) esters, but for the classification of specific acid dianhydrides, it is classified as a bis(trimellitic anhydride) ester.

[0071] 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 as X. Among these, (A) to (D) are preferred, and the group having a biphenyl skeleton of (B) is particularly preferred. When X is a group represented by general formula (B), from the viewpoint of polyimide solubility, X is preferably biphenylene or 2,2',3,3',5,5'-hexamethylbiphenyl-4,4'-diyl represented by the following formula (B1).

[0072]

[0073] The dianhydride in general formula (1) where X is biphenylene is bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylic acid)-biphenyl-4,4'diyl (BP-TME). The dianhydride in general formula (1) where X is 3,3'-dimethylbiphenylene is 5,5'-(3,3'-dimethyl[1,1'-biphenyl]-4,4'-diyl)bis(1,3-dihydro-1,3-dioxo-5-isobenzofuran carboxylate) (OCBP-TME). In general formula (1), the acidic dianhydride in which X is the 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).

[0074]

[0075] Preferred bis(trimellitic anhydride) esters in which X in general formula (1) is a structure other than that of formula (B) include p-phenylenebis(trimellitic monoester anhydride) (TMHQ), tert-butylhydroquinonebis(trimellitate anhydride) (TA.BHQ), and trimethylhydroquinonebis(trimellitate anhydride) (TA.TMHQ).

[0076] From the viewpoint of the mechanical properties of polyimide, BP-TME, TMHQ, TAHMBP, OCBP-TME, TA.BHQ, and TA.TMHQ are preferred as bis(trimellitic anhydride) esters. Among these, TMHQ, TAHMBP, and OCBP-TME are particularly preferred from the viewpoint of polyimide solubility.

[0077] 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-fluorene-9-ylidenedi-4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxamide] (FDA-ATA), and 5,5'-[9H-fluorene-9-ylidenebis(2-meth Examples include 4,1-phenylene)bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate] (TBIS.MPN), 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate) (TBIS.RXN), spiro[fluorene-9,9'xanthene]-2',3',6',7'-tetracarboxylic dianhydride (SFDA), etc. From the viewpoint of polyimide solubility, BPAF, BPF-PA, or TBIS.MPN are preferred, and among these, BPAF or TBIS.MPN are particularly preferred.

[0078] Polyimides containing benzidine having the aforementioned difluoromethyl group as the diamine component and a specific acid dianhydride as the acid dianhydride component tend to be soluble in organic solvents and possess high transparency and mechanical strength.

[0079] From the viewpoint of solubility in organic solvents and transparency, among specific acid dianhydrides, 4,4'-(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-fluorene-9-ylidenebis(2-methyl-4,1-phenylene)]bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate] (TBIS.MPN), 5,5'-spiro[9H-fluorene] Oren-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofuran carboxylate) (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) are preferred.

[0080] From the viewpoint of the UV resistance of polyimide, among specific dianhydrides, dianhydrides having ether bonds and 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 dianhydrides do not have ester bonds and do not undergo fleece transition due to UV light, so discoloration of polyimide when exposed to UV light is less likely to occur.

[0081] In terms of compatibility between polyimide and acrylic resins, among specific acid dianhydrides, acid dianhydrides having a fluorene structure and bis(trimellitic anhydride) esters are preferred, with BPAF and TAHMBP being particularly preferred.

[0082] From the viewpoint of improving the solubility of polyimide in organic solvents and compatibility with acrylic resins, the total amount of specific acid dianhydrides relative to the total amount of acid dianhydrides 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 specific acid dianhydrides relative to the total amount of acid dianhydrides may be 100 mol%, and may be 95 mol% or less, 90 mol% or less, 85 mol% or less, 80 mol% or less, 75 mol% or less, or 70 mol% or less.

[0083] (Acid dianhydrides other than specified acid dianhydrides) Polyimides may contain acid dianhydrides other than specified acid dianhydrides as acid dianhydrides components. Examples of such acid dianhydrides include alicyclic tetracarboxylic dianhydrides and aromatic tetracarboxylic dianhydrides. From the viewpoint of the environmental safety of polyimides, -C-CF ３ and -C-CF ２ Materials that do not contain -C- are preferred, and materials that do not contain fluorine atoms are particularly preferred.

[0084] Alicyclic tetracarboxylic dianhydrides only need to have at least one alicyclic structure, and may have both an alicyclic and an aromatic ring in one molecule. The alicyclic may be polycyclic and may have a spiro structure. Examples of alicyclic tetracarboxylic dianhydrides include 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,3-dimethylcyclobutane-1,2,3,4-tetracarboxylic dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, and 1,1'-bicyclohexane-3,3',4,4'tetracarboxylic acid-3,4:3',4'-di Anhydride, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride, 2,2'-binorbornane-5,5',6,6'tetracarboxylic dianhydride, 3-(carboxymethyl)-1,2,4-cyclopentanetricarboxylic acid-1,4:2,3-dianhydride, bicyclo[2.2.2]octa-7-en-2,3,5,6-tetracarboxylic dianhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-1,2,3,4 -Tetrahydronaphthalene-1,2-dicarboxylic acid anhydride, cyclohexane-1,4-diylbis(methylene)bis(1,3-dioxo-1,3-dihydroisobenzofuran-5-carboxylate), 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride, 5,5'-[cyclohexylidenebis(4,1-phenyleneoxy)]bis-1,3-isobenzofrandione, 5-isobenzofurancarboxylic acid, 1,3-dihydro-1,3-di Xo-,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 include 7-tetracarboxylic dianhydride, octahydro-1H,3H,8H,10H-biphenyleno[4a,4b-c:8a,8b-c']difuran-1,3,8,10-tetraone, ethylene glycol bis(hydrogenated trimellitic anhydride) ester, decahydro[2]benzopyrano[6,5,4-def][2]benzopyran-1,3,6,8-tetraone, etc. The inclusion of alicyclic tetracarboxylic dianhydride as an acid dianhydride component tends to improve the mechanical strength of the polyimide.

[0085] Among alicyclic tetracarboxylic dianhydrides, 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]octa-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-3,4:3',4'-dianhydride (H-BPDA) are preferred from the viewpoint of polyimide transparency and mechanical strength. In particular, from the viewpoint of mechanical strength, tetracarboxylic anhydrides in which two acid anhydride groups are bonded to one alicyclic ring are preferred, and CBDA is especially preferred.

[0086] When using alicyclic tetracarboxylic dianhydrides, the amount of alicyclic tetracarboxylic dianhydrides relative to the total amount of acid dianhydride components may be 1 mol% or more, 3 mol% or more, 5 mol% or more, 10 mol% or more, 12 mol% or more, or 15 mol% or more. There is a tendency for the mechanical strength to increase as the amount of alicyclic tetracarboxylic dianhydrides increases. From the viewpoint of ensuring the solubility of polyimide in organic solvents, the amount of alicyclic tetracarboxylic dianhydrides relative to the total amount of acid dianhydride components is preferably 80 mol% or less, more preferably 60 mol% or less, even more preferably 50 mol% or less, and may also be 40 mol% or less, 30 mol% or less, or 20 mol% or less.

[0087] Aromatic tetracarboxylic dianhydrides other than specific acid dianhydrides include pyromellitic acid dianhydride (PMDA), 1,2,3,4-benzenetetracarboxylic dianhydride (MPDA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA), 2,3,3',4'-biphenyltetracarboxylic dianhydride (a-BPDA), and 2,2',3,3'-biphenyltetracarboxylic dianhydride. Examples include aqueous (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.

[0088] When using aromatic tetracarboxylic dianhydrides other than specified acid dianhydrides, the amount of aromatic tetracarboxylic dianhydrides other than specified acid dianhydrides relative to the total amount of acid dianhydrides 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 polyimide in organic solvents, the amount of aromatic tetracarboxylic dianhydrides other than specified acid dianhydrides relative to the total amount of acid dianhydrides is preferably 80 mol% or less, more preferably 60 mol% or less, even more preferably 50 mol% or less, and may also be 40 mol% or less, 30 mol% or less, or 20 mol% or less.

[0089] Polyimide may contain linear aliphatic tetracarboxylic dianhydrides as acid dianhydride components, such as ethylenetetracarboxylic dianhydride, 1,2,3,4-butanetetracarboxylic dianhydride, and meso-butane-1,2,3,4-tetracarboxylic dianhydride.

[0090] The amount of fluorine-containing dianhydride relative to the total amount of dianhydride components in the polyimide is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, and may also be 5 mol% or less, 1 mol% or less, or 0.5 mol% or less. The polyimide may also not contain fluorine-containing dianhydride as its dianhydride component.

[0091] Among fluorine atom-containing acid dianhydrides, there is a structure in which the 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 Those containing -C-) have low decomposability and raise environmental safety concerns. In particular, those with CF at the carbon atom of the aromatic ring. ３ - or -C (CF ３ ) ２ Acidic dianhydrides having a structure in which a negative (-) is directly bonded (e.g., 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 9,9-bis(trifluoromethyl)xanthenetetracarboxylic dianhydride, 9-trifluoromethylxanthenetetracarboxylic dianhydride) have low environmental degradation; therefore, from the viewpoint of the environmental safety of polyimides, it is preferable that polyimides substantially do not contain these acidic dianhydrides. The total amount of acidic dianhydride components in polyimides is such that CF is attached to the carbon atoms of the aromatic ring. ３ - or -C (CF ３ ) ２ The amount of acid dianhydride to which the negative charge 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 even 0.

[0092] <Polybasic Acids> As mentioned above, when the polyimide is a polyamideimide, by using a dicarboxylic acid and / or a tricarboxylic acid anhydride as a polybasic acid component in addition to the diamine and tetracarboxylic dianhydride, a polyamideimide containing a dicarboxylic acid-derived structure represented by general formula (VIa) and / or a tricarboxylic acid anhydride-derived structure represented by general formula (VIIa) can be obtained.

[0093] Examples of dicarboxylic acids include aliphatic dicarboxylic acids such as adipic acid, suberic acid, azelaic acid, sebacic acid, and dodecanedioic acid; aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 5-methylisophthalic acid, 2,6-naphthalenedicarboxylic acid, 4,4'-oxybisbenzoic acid, 4,4'-biphenyldicarboxylic acid, and 2-fluoroterephthalic acid; alicyclic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-hexahydroterephthalic acid, hexahydroisophthalic acid, 1,3-cyclopentanedicarboxylic acid, and bi(cyclohexyl)-4,4'-dicarboxylic acid; and heterocyclic dicarboxylic acids such as 2,5-thiophenedicarboxylic acid and 2,5-franzicarboxylic acid.

[0094] Examples of tricarboxylic acid anhydrides include trimellitic anhydride, 2-fluorotrimellitic anhydride, 5-fluorotrimellitic anhydride, 6-fluorotrimellitic anhydride, 2,5-difluorotrimellitic anhydride, 2,6-difluorotrimellitic anhydride, 5,6-difluorotrimellitic anhydride, and 2,5,6-trifluorotrimellitic anhydride, as well as other trimellitic anhydride derivatives.

[0095] From the viewpoint of polyamide-imide solubility, preferred polybasic acids are aromatic dicarboxylic acids, alicyclic dicarboxylic acids, and trimellitic anhydride, with aromatic dicarboxylic acids being particularly preferred. Among aromatic dicarboxylic acids, terephthalic acid, isophthalic acid, 4,4'-biphenyldicarboxylic acid, and 4,4'-oxybisbenzoic acid are preferred, with terephthalic acid and isophthalic acid being particularly preferred, and terephthalic acid being particularly preferred. Among alicyclic dicarboxylic acids, 1,4-cyclohexanedicarboxylic acid and bi(cyclohexyl)-4,4'-dicarboxylic acid are preferred, with 1,4-cyclohexanedicarboxylic acid being particularly preferred.

[0096] In the preparation of polyamide-imides and polyamic acids as precursors, polybasic acid derivatives such as dicarboxylic acid dichlorides, dicarboxylic acid esters, dicarboxylic acid anhydrides, and tricarboxylic acid anhydride chlorides may be used instead of polybasic acids.

[0097] Preferably, the polyamide-imide contains 90 to 110 mole parts of the total structure derived from a tetracarboxylic dianhydride represented by general formula (IVa), a dicarboxylic acid represented by general formula (VIa), and a tricarboxylic acid anhydride represented by general formula (VIIa) relative to 100 mole parts of the diamine-derived structure represented by general formula (Va). The total of the structure of general formula (IVa), general formula (VIa), and general formula (VIIa) may be 93 to 107 mole parts, 95 to 105 mole parts, 97 to 103 mole parts, or 99 to 101 mole parts relative to 100 mole parts of the structure of general formula (Va).

[0098] The ratio of the structure of general formula (VIa) to the sum of the structures of general formula (VIIa) is between 1 and 99 mol%. The ratio of the structure of general formula (IVa) to the structure of general formula (VIa) is approximately equal to the ratio of the imide structure of general formula (I) to the amide structure of general formula (II), and the ratio of the structure of general formula (IVa) to the structure of general formula (VIIa) is approximately equal to the ratio of the imide structure of general formula (I) to the amide-imide structure of general formula (III). The ratio of the total structure of general formula (VIa) to the total structure of general formula (VIIa) to the total structure of general formula (VIIa) may be 5 mol% or more, 10 mol% or more, 20 mol% or more, 30 mol% or more, 40 mol% or more, or 50 mol% or more, and may be 80 mol% or less, 75 mol% or less, 70 mol% or less, 65 mol% or less, or 60 mol% or less.

[0099] The higher the proportion of structures of general formulas (VIa) and (VIIa), that is, the higher the proportion of amide structures, the more likely it is that the solubility of polyamide-imides in organic solvents will improve.

[0100] The amount of polybasic acid relative to the diamine component of polyamide-imide, that is, the total ratio of structural units of general formula (VI) and general formula (VII) to structural unit of general formula (V), may be 1 mol% or more, 5 mol% or more, 10 mol% or more, 20 mol% or more, 30 mol% or more, 40 mol% or more, or 50 mol% or more, and may be 80 mol% or less, 75 mol% or less, 70 mol% or less, 65 mol% or less, or 60 mol% or less.

[0101] <Content of specific fluorine structures in polyimides> In order to reduce the environmental persistence of fluorine-containing compounds, it is preferable that polyimides use a small amount of monomers having specific fluorine structures. A specific fluorine structure is at least one fully fluorinated methyl (CF) group. ３ -) or methylene (-CF ２ -) A structure obtained by excluding structures containing only the components of structural formula (i) or (ii) below from structures that include carbon atoms (not bonded to H / Cl / Br / I). CF ３-X (i) X-CF ２ -X' (ii)

[0102] In equations (i) and (ii), X is -OR or -NRR', and in equation (ii), X' is -CH ３ It is one of the following: aromatic, -C(O)-, -OR'', -SR'', and NR''R''''. R, R', R'', and R''' are each independently -H, -CH ３ ,-CH ２ It is either -, aromatic, or -C(O)-.

[0103] 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.

[0104] <Preparation of Polyimide> As described above, by adjusting the types and ratios of monomers that make up the polyimide, a polyimide exhibiting solubility in organic solvents and compatibility with acrylic resins can be obtained.

[0105] Polyamic acid, a precursor to polyimide, is obtained by the reaction of an acidic dianhydride with a diamine, and polyimide (polyimide in the narrow sense) is obtained by dehydration cyclization (imidization) of the polyamic acid. In addition to diamines and tetracarboxylic dianhydrides, polybasic acids or their derivatives (acid chlorides, acid anhydrides, etc.) are used as monomers to prepare polyamic acid, and polyamideimide is obtained by dehydration cyclization (imidization) of the polyamic acid.

[0106] The method for preparing polyamic acid is not particularly limited, and any known method can be applied. For example, a polyamic acid solution can be obtained by dissolving an acidic dianhydride and a polybasic acid or its derivative in an organic solvent such that the total amount is approximately equimolar to the diamine (molar ratio of 90:100 to 110:100), and then stirring. The concentration of the polyamic acid solution is usually 5 to 35% by weight, preferably 10 to 30% by weight. When the concentration is within this range, the polyamic acid obtained by polymerization has an appropriate molecular weight, and the polyamic acid solution has an appropriate viscosity.

[0107] In the polymerization of polyamic acids, it is preferable to add the dianhydride to the diamine to suppress ring-opening of the dianhydride. When adding multiple types of diamines or dianhydrides, they may be added all at once or in multiple steps. The properties of the polyimide can also be controlled by adjusting the order of monomer addition.

[0108] The organic solvent used for polymerization of polyamic acid is not particularly limited, as long as it does not react with diamines and acidic dianhydrides and can dissolve polyamic acid. Examples of organic solvents include urea-based solvents such as methylurea and N,N-dimethylethylurea; sulfoxide or sulfone-based solvents such as dimethyl sulfoxide, diphenyl sulfone, and tetramethyl sulfone; amide-based solvents such as N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), N,N'-diethylacetamide, N-methyl-2-pyrrolidone (NMP), γ-butyrolactone, and hexamethylphosphate triamide; alkyl halogenated solvents such as chloroform and methylene chloride; aromatic hydrocarbon solvents such as benzene and toluene; and ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, and p-cresol methyl ether. These solvents are usually used individually or in appropriate combinations of two or more as needed. From the viewpoint of polyamic acid solubility and polymerization reactivity, DMAc, DMF, NMP, etc., are preferably used.

[0109] Polyimides can be obtained by the dehydration and cyclization of polyamic acids. One method for preparing polyimides from a polyamic acid solution is to add a dehydrating agent, an imidation catalyst, etc., to the polyamic acid solution and allow imidation to proceed in the solution. The polyamic acid solution may be heated to accelerate the progression of imidation. By mixing the solution containing the polyimide produced by the imidation of polyamic acid with a poor solvent, the polyimide resin precipitates as a solid. By isolating the polyimide resin as a solid, impurities generated during the synthesis of polyamic acid, as well as residual dehydrating agents and imidation catalysts, can be washed and removed with the poor solvent, preventing discoloration and increased yellowness of the polyimide. Furthermore, by isolating the polyimide resin as a solid, solvents suitable for film formation, such as low-boiling point solvents, can be applied when preparing the solution for film production.

[0110] The molecular weight of the polyimide (weight-average molecular weight in polystyrene equivalent, measured by gel filtration chromatography (GPC)) is preferably 10,000 to 1,000,000, more preferably 20,000 to 500,000, and even more preferably 40,000 to 300,000. If the molecular weight is excessively low, the strength of the film may be insufficient. If the molecular weight is excessively high, the solubility of the polyimide and its compatibility with acrylic resins may be poor.

[0111] It is preferable that the polyimide is soluble in organic solvents. Specifically, it is preferable that the polyimide dissolves 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, it is preferable that the polyimide is 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 lower boiling points compared to amide solvents, and residual solvents are easily removed during film production, so polyimides soluble in non-amide solvents can be expected to improve film productivity. It is particularly preferable that the polyimide is soluble in methylene chloride.

[0112] [Acrylic Resin] The above polyimide contains a specific diamine and a specific acid dianhydride, which allows it to be soluble in organic solvents and compatible with acrylic resins. The acrylic resin is preferably soluble in DMF at 23°C at a concentration of 1% by weight or more, similar to the polyimide.

[0113] 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, and methyl (meth)acrylate-styrene copolymers. The stereoregularity of the polymer is not particularly limited and may be isotactic, syndiotactic, or atactic.

[0114] From the viewpoint of transparency, compatibility with polyimide, and mechanical strength of molded articles such as films, acrylic resins that primarily use methyl methacrylate as a structural unit are preferred. 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 also be a homopolymer of methyl methacrylate.

[0115] The acrylic resin may have imide structures or lactone ring structures introduced into it. Such modified polymers are preferably acrylic polymers in which methyl methacrylate content is within the above range, and imide structures or lactone ring structures are introduced into them. That is, in acrylic resins modified by the introduction of imide structures or lactone ring structures, the total amount of methyl methacrylate and the modified methyl methacrylate structure 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 a homopolymer of methyl methacrylate in which imide structures or lactone ring structures are introduced.

[0116] Introducing an imide structure into acrylic polymers such as methyl methacrylate tends to improve the glass transition temperature of the acrylic resin. Furthermore, because the acrylic resin contains an imide structure, its compatibility with polyimides may improve. For example, a particular polyimide resin may not be compatible with polymethyl methacrylate, but it may be compatible with an acrylic resin containing a glutarimide structure.

[0117] Acrylic resins having a glutarimide structure can be obtained, for example, by heating and melting polymethyl methacrylate resin and treating it with an imidizing agent, as described in Japanese Patent Application Publication No. 2010-261025. Commercially available products such as EVONIK's "PLEXIMID TT70" and "PLEXIMID 8805" can also be used as imide-modified polymethyl methacrylate.

[0118] 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. The glutarimide content of the acrylic resin １ The introduction rate of the glutarimide structure (imidization rate) is determined from the 1H-NMR spectrum, and the imidization rate is calculated by converting it to weight. For example, in methyl methacrylate to which the glutarimide structure has been introduced, the O-CH group of methyl methacrylate is formed. ３ Area A of the proton-derived peak (around 3.5–3.8 ppm) and the N-CH of glutarimide. ３ The imidization rate Im = B / (A + B) can be determined from the area B of the proton-derived peak (around 3.0–3.3 ppm).

[0119] From the viewpoint of heat resistance of the resin composition and 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.

[0120] From the viewpoint of solubility in organic solvents, compatibility with the above-mentioned polyimide, and strength of the molded article, 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 also be 30,000 to 1,000,000 or 50,000 to 500,000. If the molecular weight of the acrylic resin is too low, the durability of the resulting film may decrease. If the molecular weight of the acrylic resin is too high, the film-forming properties may be poor.

[0121] From the viewpoint of thermal and photostability 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 carboxyl groups. The iodine value of the acrylic resin is preferably 10.16 g / 100 g (0.4 mmol / g) or less, more preferably 7.62 g / 100 g (0.3 mmol / g) or less, and even more preferably 5.08 g / 100 g (0.2 mmol / g) or less. The iodine value of the acrylic resin may also 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 also be 0.1 mmol / g or less, 0.05 mmol / g or less, or 0.03 mmol / g or less. A low acid value enhances the stability of acrylic resins and tends to improve their compatibility with polyimides.

[0122] [Preparation of Resin Composition] The resin composition is prepared by mixing the above polyimide and acrylic resin. The above polyimide and acrylic resin can be compatible in any ratio. Therefore, the ratio of resin in the resin composition is not particularly limited. The mixing ratio (weight ratio) of polyimide and acrylic resin may be 98:2 to 2:98, 95:5 to 5:90, 95:5 to 10:90, 90:10 to 10:90, or 90:10 to 15:85.

[0123] The higher the proportion of polyimide, the higher the elastic modulus of the film tends to be, resulting in superior mechanical strength. Conversely, the higher the proportion of acrylic, the less coloration the film tends to have, and the higher its transparency tends to be.

[0124] In order to fully realize the effect of improving transparency by mixing polyimide and acrylic resin, the ratio of 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.

[0125] Polyimides are polymers with a unique molecular structure. Generally, they have low solubility in organic solvents and are incompatible with other polymers. However, as mentioned above, polyimides containing specific diamine and acid dianhydride components exhibit high solubility in organic solvents and compatibility with acrylic resins.

[0126] Resin compositions containing polyimide and acrylic resins preferably have a single glass transition temperature in differential scanning calorimetry (DSC) and / or dynamic viscoelasticity measurement (DMA). When a resin composition has a single glass transition temperature, the polyimide and acrylic resin can be considered to be perfectly miscible. Films containing polyimide and acrylic resins also preferably have a single glass transition temperature.

[0127] The resin composition may simply be a mixture of polyimide resin and acrylic resin precipitated as solid components, or it may be a mixture of polyimide and acrylic resin. Alternatively, when precipitating the polyimide resin by mixing the polyimide solution with a poor solvent, the acrylic resin may be mixed into the solution to precipitate the resin composition of polyimide and acrylic resin as a solid (powder).

[0128] The resin composition may be a mixed solution containing polyimide and an acrylic resin. The method of mixing the resins is not particularly limited; they may be mixed in a solid state or mixed in a liquid state to form a mixed solution. A polyimide solution and an acrylic resin solution may be prepared separately, and then the two may be mixed to prepare a mixed solution of polyimide and acrylic resin.

[0129] The solvent for a solution containing polyimide and acrylic resin is not particularly limited as long as it is soluble in both polyimide and acrylic resin. Examples of solvents include amide solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, and N-methyl-2-pyrrolidone; ether solvents such as tetrahydrofuran and 1,4-dioxane; ketone solvents such as acetone, methyl ethyl ketone, methyl propyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, diethyl ketone, cyclopentanone, cyclohexanone, and methylcyclohexanone; and alkyl halogen solvents such as chloroform, 1,2-dichloroethane, 1,1,2,2-tetrachloroethane, chlorobenzene, dichlorobenzene, and methylene chloride.

[0130] In terms of the solubility of polyimide and the compatibility of polyimide with acrylic resins in solution, amide solvents are preferred. On the other hand, in terms of the ease of solvent removal when producing molded articles such as films, low-boiling non-amide solvents are preferred. Ketone solvents and alkyl halogen solvents are preferred because they have excellent solubility for both polyimide and acrylic resins, have low boiling points, and allow for easy removal of residual solvent during film production.

[0131] The resin composition may contain organic or inorganic low-molecular-weight compounds, high-molecular-weight compounds (e.g., epoxy resins), etc. The resin composition may also contain flame retardants, ultraviolet absorbers, crosslinking agents, dyes, pigments, surfactants, leveling agents, plasticizers, fine particles, sensitizers, etc. The fine particles may include organic fine particles such as polystyrene and polytetrafluoroethylene, and inorganic fine particles such as colloidal silica, carbon, and layered silicates, and may have a porous or hollow structure. The fiber reinforcing material may include carbon fibers, glass fibers, aramid fibers, etc.

[0132] [Molded articles and films] The above compositions can be used to form various molded articles. Molding methods include injection molding, transfer molding, press molding, blow molding, inflation molding, calendering, and melt extrusion molding. Resin compositions containing polyimide and acrylic resins tend to have a lower melt viscosity than polyimide alone and exhibit excellent moldability in injection molding, transfer molding, press molding, and melt extrusion molding.

[0133] In one embodiment, the molded body 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 film is obtained by coating a solution containing the above-mentioned polyimide resin and acrylic resin onto a support and drying off the solvent. Since the above-mentioned polyimide is compatible with acrylic resin, it is possible to produce a highly transparent film by the solution method by using a composition containing polyimide and acrylic resin.

[0134] As a method for applying the resin solution onto the support, known methods using bar coaters, comma coaters, etc., can be applied. As the support, glass substrates, metal substrates such as SUS, metal drums, metal belts, plastic films, etc., can be used. From the viewpoint of improving productivity, it is preferable to use an endless support such as a metal drum or metal belt, or a long plastic film, as the support and manufacture the film by roll-to-roll. When using a plastic film as the support, a material that does not dissolve in the film-forming doping solvent should be appropriately selected.

[0135] Heating is preferable when drying the solvent. The heating temperature is not particularly limited as long as it can remove the solvent and suppress discoloration of the resulting film, and can be appropriately set between room temperature and approximately 250°C, with 50°C to 220°C being preferred. The heating temperature may be increased in stages. To improve the efficiency of solvent removal, the resin film may be peeled from the support and dried after a certain degree of drying has progressed. Heating may be performed under reduced pressure to promote solvent removal.

[0136] The above-mentioned composition containing polyimide and acrylic resin is a compatible system, resulting in a lower glass transition temperature compared to polyimide alone. This allows for molding and processing at low temperatures and reduces the coloration of molded products such as films.

[0137] The film may be stretched in one or more directions for purposes such as improving its mechanical strength. When a film is stretched, the polymer chains orient themselves in the stretching direction, which tends to improve the in-plane strength of the film and suppress the occurrence of cracks and fissures. In compatible systems of polyimide and acrylic resin, the tensile modulus in the stretching direction increases, and consequently, the flexibility tends to improve.

[0138] For example, films used as cover films or substrate materials for foldable displays require high mechanical strength in the direction perpendicular to the bending axis because they are repeatedly folded along the bending axis at the same point. Therefore, by arranging the film so that its stretching direction is perpendicular to the bending axis, cracks and breaks are less likely to occur at the bending point even after repeated folding, providing a device with high bending resistance.

[0139] The stretching conditions for the film are not particularly limited. For example, the stretching temperature is approximately ±40°C of the film's glass transition temperature, and may be around 120-300°C, 150-250°C, or 180-230°C. The stretching ratio is approximately 1-200%, and may be 5-150%, 10-120%, or 20-100%. The larger the stretching ratio, the greater the tensile modulus in the stretching direction tends to be. On the other hand, if the stretching ratio is excessively large, the mechanical strength in the direction perpendicular to the stretching direction tends to decrease, which may reduce the handling properties of the film.

[0140] From the viewpoint of increasing strength in any direction within the plane, the film may be biaxially stretched. Biaxial stretching may be simultaneous biaxial stretching or sequential biaxial stretching. In biaxial stretching, the stretching ratio in one direction and the stretching ratio in the direction perpendicular to it may be the same or different. If there is a difference in the stretching ratio, the mechanical strength tends to be relatively higher in the direction with the larger stretching ratio. When using a biaxially stretched film with anisotropic stretching ratio in a foldable device, it is preferable to position the direction with the larger stretching ratio perpendicular to the folding axis.

[0141] The film thickness is not particularly limited and can be set appropriately depending on the application. For example, the film thickness is 5 to 300 μm. From the viewpoint of achieving both self-supporting properties and flexibility, and a highly transparent film, the film thickness is preferably 20 μm to 200 μm, but may also be 30 μm to 150 μm, 40 μm to 100 μm, or 50 μm to 80 μm. For use as a cover film for displays, the film thickness is preferably 10 μm or more. When stretching the film, it is preferable that the thickness after stretching is within the above range.

[0142] 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, since polyimide and acrylic resins are compatible, mixed resin films containing polyimide and acrylic resins have low haze and excellent transparency, similar to films made of polyimide alone. When a film with a thickness of 50 μm is made from a resin composition mixed with polyimide and acrylic resins, the haze is preferably 10% or less.

[0143] 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. Mixed resin films containing polyimide and acrylic resin tend to have less coloration and higher total light transmittance compared to films made of polyimide alone.

[0144] The yellowness (YI) of the film is not particularly limited, but is preferably 20 or less, more preferably 10 or less, even more preferably 5.0 or less, and may be 4.0 or less, 3.0 or less, 2.0 or less, 1.5 or less, or 1.0 or less. The yellowness of the film may be 0 or less (a negative value). As described above, mixed resin films containing polyimide and acrylic resin tend to have less coloration and a lower YI compared to films made of polyimide alone.

[0145] From the viewpoint of strength, the tensile modulus of the film is preferably 2.5 GPa or higher, more preferably 3.0 GPa or higher, even more preferably 3.5 GPa or higher, and may be 4.0 GPa or higher. The pencil hardness of the film is preferably 4B or higher, more preferably 2B or higher, even more preferably F or higher, and may be H or higher, 2H or higher, or 3H or higher. In compatible systems of polyimide and acrylic resin, increasing the proportion of acrylic resin tends not to significantly decrease the pencil hardness. Therefore, it is possible to provide a film with less discoloration and excellent transparency without significantly reducing the excellent mechanical strength characteristic of polyimide.

[0146] Films formed from resin compositions containing polyimide and acrylic resins 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 cover windows of displays. Furthermore, because polyimide substantially does not contain specific fluorine structures, it is highly biodegradable and environmentally safe. For practical use, the film of the present invention may be provided with an antistatic layer, an easy-adhesion layer, a hard coat layer, an anti-reflective layer, etc., on its surface.

[0147] The embodiments of the present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following embodiments.

[0148] [Preparation of Polyimide Resin] Dimethylformamide (DMF) was placed in a separable flask and stirred under a nitrogen atmosphere. Diamine, tetracarboxylic dianhydride, and polybasic acid derivatives were then added in the proportions shown in Table 2 and stirred under a nitrogen atmosphere for 5 to 48 hours to react and obtain a polyamic acid solution with a solid content of 18% by weight.

[0149] To 100 g of polyamic acid solution, 5.5 g of pyridine was added as an imidation catalyst and completely dispersed. Then, 8 g of acetic anhydride was added, and the mixture was stirred at 90°C for 3 hours to carry out imidation.

[0150] After cooling the imidized solution to room temperature, 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. Another 150 g of IPA was added, and after stirring for approximately 30 minutes, suction filtration was performed using a Kiriyama funnel. The obtained solid was washed with IPA and then dried in a vacuum oven set to 120°C for 12 hours to obtain polyimide resins 1-9 with the compositions shown in Table 2. Polyimide resins 7-9 are polyamide-imides containing polybasic acid components.

[0151] The obtained polyimide resin was dissolved in the eluent, and the weight-average molecular weight (Mw) was determined by gel permeation chromatography (GPC) under the conditions shown in Table 1.

[0152]

[0153] [Film Preparation] <Reference Example: Polyimide Film> Polyimide resins 1 to 9 were dissolved in DMF to prepare a polyimide solution with a solid content concentration of 10% by weight. The polyimide solution was applied to an alkali-free glass plate and heated and dried 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 produce films with the thicknesses shown in Table 2.

[0154] <Example: Mixed resin film of polyimide and acrylic resin> DMF was prepared by dissolving the above polyimide resins 1 to 9 and a commercially available polymethyl methacrylate resin (Kuraray's "Parapet G1000") in a 50:50 weight ratio to prepare a DMF solution with a solid content of 10 to 20% by weight. Using this solution, coating and drying were carried out in the same manner as above to produce films with the thicknesses shown in Table 2.

[0155] [Film Evaluation] <Haze and Total Light Transmittance> The film was cut into 3 cm squares, and the haze and total light transmittance (TT) were measured using a Suga Test Instruments HZ-V3 haze meter in accordance with JIS K7136 and JIS K7361-1.

[0156] <Yellowness> The film was cut into 3 cm squares, and the yellowness (YI) was measured according to JIS K7373 using a spectrophotometer "SC-P" manufactured by Suga Test Instruments.

[0157] [Evaluation Results] The evaluation results for polyimide-only films and polyimide / acrylic mixed resin films are shown in Table 2, along with the polyimide composition and Mw.

[0158] In Table 2, the composition of the polyimide (diamine, tetracarboxylic dianhydride, and polybasic acid derivative) is shown as a molar ratio where the total amount of tetracarboxylic dianhydride and the total amount of polybasic acid derivative is 100 mole parts, and the compounds are indicated by the following abbreviations.

[0159] <Diamines> DFMB: 2,2'-bis(difluoromethyl)benzidine DDS: 3,3'-diaminodiphenylsulfone <Acid dianhydrides> 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 acid dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic acid dianhydride PMDA: pyromellitic acid dianhydride <Polybasic acid derivatives> TPC: terephthalic acid dichloride TMAC: trimellitic anhydride chloride

[0160]

[0161] The mixed resin films of polyimides 1-9 and polymethyl methacrylate resin exhibited low haze similar to that of polyimide alone, and had higher total light transmittance compared to polyimide alone. These results indicate that by using a compatible resin composition of polyimide containing benzidine with a difluoromethyl group as a diamine component and an acrylic resin, a film with high environmental safety and excellent transparency can be obtained.

Claims

1. A resin composition comprising a polyimide and an acrylic resin, wherein the polyimide has a tetracarboxylic dianhydride component and a diamine component, and the diamine component comprises a benzidine derivative in which at least one hydrogen atom on two benzene rings of benzidine is substituted with a difluoromethyl group.

2. The resin composition according to claim 1, wherein the benzidine derivative is 2,2'-bis(difluoromethyl)benzidine, 3,3'-bis(difluoromethyl)benzidine, or 2,3'-bis(difluoromethyl)benzidine.

3. The resin composition according to claim 1, wherein the amount of the benzidine derivative relative to the total amount of the diamine component in the polyimide is 10 mol% or more.

4. The resin composition according to claim 1, wherein the polyimide comprises, as the 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, and bis(trimellitic anhydride) esters.

5. One or more tetracarboxylic dianhydrides selected from the group consisting of tetracarboxylic dianhydrides having an ether linkage, tetracarboxylic dianhydrides having a fluorene structure, and bis(trimellitic anhydride) esters are 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-fluorene-9-ylidenebis(2-methyl-4,1-phenylene)]bis[1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylate] The resin composition according to claim 4, wherein one or more are selected from the group consisting of ], 5,5'-spiro[9H-fluorene-9,9'-[9H]xanthene]-3',6'-diylbis(1,3-dihydro-1,3-dioxo-5-isobenzofuran carboxylate), 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.

6. The polyimide contains CF at the carbon atoms 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 to which a - is directly bonded is less than 0.5 mol%, and the amount of CF on the carbon atoms of the aromatic ring relative to the total amount of tetracarboxylic dianhydride components is less than 0.5 mol%. ３ - or -C (CF ３ ) ２ The resin composition according to claim 1, wherein the amount of tetracarboxylic dianhydride having a structure to which a - is directly bonded is less than 0.5 mol%.

7. The resin composition according to claim 1, wherein both the polyimide and the acrylic resin are soluble in dimethylformamide at 23°C.

8. The resin composition according to claim 1, comprising the polyimide and the acrylic resin in a weight ratio in the range of 98:2 to 2:

98.

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

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

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