Polyamic acid composition, polyimide, polyimide film, laminate, electronic device, and method for producing polyamic acid composition

Abstract

This polyamic acid composition contains a polyamic acid, an organic solvent, aminophenol, and methyl aminobenzoate. The polyamic acid has a 4-aminophenyl-4-aminobenzoate residue as a diamine residue. The content of the 4-aminophenyl-4-aminobenzoate residue is 70% by mol or more with respect to the total mass of all diamine residues constituting the polyamic acid. When the content of the aminophenol is determined by gas chromatography mass spectrometry using a sample obtained by dilution the polyamic acid composition to a polyamic acid concentration of 1% by mass, the content of the aminophenol is 1 ppm by mass to 30 ppm by mass inclusive with respect to the whole mass of the sample. When the content of the methyl aminobenzoate is determined by gas chromatography mass spectrometry using a sample obtained by dilution the polyamic acid composition to a polyamic acid concentration of 1% by mass, the content of the methyl aminobenzoate is 0.01 ppm by mass to 0.10 ppm by mass inclusive with respect to the whole mass of the sample.

Description

Polyamic acid composition, polyimide, polyimide film, laminate, electronic device, and method for producing polyamic acid composition

[0001] The present invention relates to a polyamic acid composition, a polyimide, a polyimide film, a laminate, an electronic device, and a method for producing the polyamic acid composition.The present invention further relates to an electronic device material using the polyimide, a thin film transistor (TFT) substrate, a flexible display substrate, a color filter, a printed matter, an optical material, an image display device (more specifically, a liquid crystal display device, an organic electroluminescence (EL) display, an electronic paper, etc.), a 3D display, a solar cell, a touch panel, a transparent conductive film substrate, and a substitute material for a component currently using glass.

[0002] Rapid advances in electronic devices, such as displays (liquid crystal displays, organic electroluminescence (EL) displays, electronic paper displays), solar cells, and touch panels, have led to devices becoming thinner, lighter, and more flexible. Polyimide is being used as a substrate material in place of glass substrates in these devices.

[0003] These devices require various electronic elements, such as thin-film transistors and transparent electrodes, to be formed on a substrate, and high-temperature processes are required to form these electronic elements. Polyimide has sufficient heat resistance to be applicable to high-temperature processes, and its coefficient of thermal expansion (CTE) is similar to that of glass substrates and electronic elements, making it less susceptible to internal stress and suitable for use as a substrate material for flexible displays and other applications.

[0004] Aromatic polyimides are generally colored yellowish-brown due to intramolecular conjugation and the formation of charge-transfer (CT) complexes, but in top-emission organic electroluminescence (OLED) and other devices, where light is extracted from the opposite side of the substrate, transparency is not required for the substrate, and conventional aromatic polyimides have been used. However, in cases where light emitted from the display element is emitted through the substrate, such as in transparent displays, bottom-emission organic electroluminescence (OLED) and liquid crystal displays, or when sensors or camera modules are placed on the back of the substrate to make smartphones and other devices full-screen displays (notchless), high optical properties (more specifically, transparency, etc.) are now required for the substrate as well.

[0005] In light of this, there is a demand for materials that have heat resistance equivalent to that of existing aromatic polyimides, but that are less colored and have excellent transparency.

[0006] Known techniques for reducing the coloration of polyimides include a technique for suppressing the formation of CT complexes using aliphatic monomers (Patent Documents 1 and 2), a technique for increasing transparency by using a monomer having a fluorine atom (Patent Document 3), and a technique for increasing transparency by using a monomer having a fluorene structure (Patent Document 4).

[0007] Japanese Patent Publication No. 2016-29177 Japanese Patent Publication No. 2012-41530 Taiwan Patent Application Publication No. 201713726 International Publication No. 2019 / 195148

[0008] As a result of investigations conducted by the present inventors, it was found that when the polyamic acid compositions described in Patent Documents 1 to 4 are applied to a support and the polyamic acid is imidized, the internal stress generated at the interface between the polyimide film and the support tends to increase. Hereinafter, the internal stress generated at the interface between the polyimide film and the support may be simply referred to as "internal stress." If the internal stress increases, it may become difficult to apply the composition to electronic devices.

[0009] Furthermore, the techniques described in Patent Documents 1 to 4 still have room for improvement in terms of increasing the transparency of polyimide.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a polyimide having excellent transparency while reducing internal stress, as well as a polyimide film, a laminate, and an electronic device containing the polyimide. Another aim of the present invention is to provide a polyamic acid composition containing a polyamic acid as a precursor of the polyimide, and a method for producing the same.

[0011] <Aspects of the Present Invention> The present invention includes the following aspects.

[0012] [1] A polyamic acid composition comprising a polyamic acid, an organic solvent, an aminophenol, and methyl aminobenzoate, wherein the polyamic acid has a 4-aminophenyl-4-aminobenzoate residue as a diamine residue, and the content of the 4-aminophenyl-4-aminobenzoate residue is 70 mol % or more relative to all diamine residues constituting the polyamic acid, the content of the aminophenol obtained by diluting the polyamic acid composition to a polyamic acid concentration of 1% by mass and measuring it by gas chromatography-mass spectrometry is 1 ppm by mass or more and 30 ppm by mass or less relative to the total amount of the sample, and the content of the methyl aminobenzoate obtained by diluting the polyamic acid composition to a polyamic acid concentration of 1% by mass and measuring it by gas chromatography-mass spectrometry is 0.01 ppm by mass or more and 0.10 ppm by mass or less relative to the total amount of the sample.

[0013] [2] The polyamic acid composition according to [1] above, wherein a sample obtained by diluting the polyamic acid composition to a polyamic acid concentration of 1% by mass has a Gardner color index and a Hazen color index of 0.3 or less and 10 or less, respectively, measured in a cell having an optical path length of 1 cm.

[0014] [3] The polyamic acid composition according to [1] or [2], wherein the polyamic acid has, as a tetracarboxylic dianhydride residue, one or more selected from the group consisting of a tetravalent organic group represented by the following chemical formula (1), a tetravalent organic group represented by the following chemical formula (2), a tetravalent organic group represented by the following chemical formula (3), a tetravalent organic group represented by the following chemical formula (4), a tetravalent organic group represented by the following chemical formula (5), a tetravalent organic group represented by the following chemical formula (6), a tetravalent organic group represented by the following chemical formula (7), a tetravalent organic group represented by the following chemical formula (8), a tetravalent organic group represented by the following chemical formula (9), and a tetravalent organic group represented by the following chemical formula (10).

[0015]

[0016] [4] A polyimide which is an imidized product of the polyamic acid contained in the polyamic acid composition according to any one of [1] to [3] above.

[0017] [5] A polyimide film containing the polyimide according to [4] above.

[0018] [6] The polyimide film according to [5] above, having a yellowness index of 20 or less.

[0019] [7] The polyimide film according to [5] or [6] above, which has a transmittance of 8% or more for light with a wavelength of 400 nm.

[0020] [8] A laminate having a support and the polyimide film according to any one of [5] to [7] above.

[0021] [9] The laminate according to [8], wherein the support is a glass substrate, and an internal stress between the polyimide film and the glass substrate is 30 MPa or less.

[0022]

[10] An electronic device comprising the polyimide film according to any one of [5] to [7] above and an electronic element disposed on the polyimide film.

[0023]

[11] A method for producing a polyamic acid composition according to any one of [1] to [3] above, comprising a step S1 of reacting a diamine with a tetracarboxylic dianhydride in an organic solvent, wherein the diamine contains 4-aminophenyl-4-aminobenzoate, the content of the 4-aminophenyl-4-aminobenzoate being 70 mol % or more based on the total amount of the diamine, the 4-aminophenyl-4-aminobenzoate being supplied to the step S1 as a raw material monomer containing impurities, the impurities including aminophenol and methyl aminobenzoate, and the Gardner color index and the Hazen color index, measured using a 1 mass % N-methyl-2-pyrrolidone solution of the raw material monomer in a cell with an optical path length of 1 cm, are 3.0 or less and 200 or less, respectively.

[0024]

[12] The method for producing a polyamic acid composition according to

[11] above, wherein the content of the aminophenol in the raw material monomers is 0.60% by mass or less, based on the total amount of the 4-aminophenyl-4-aminobenzoate, and the content of the methyl aminobenzoate in the raw material monomers is 0.60% by mass or less, based on the total amount of the 4-aminophenyl-4-aminobenzoate.

[0025] According to the present invention, it is possible to provide a polyimide having excellent transparency while reducing internal stress, a polyimide film, a laminate, and an electronic device containing the polyimide. Furthermore, according to the present invention, it is also possible to provide a polyamic acid composition containing a polyamic acid as a precursor of the polyimide, and a method for producing the same.

[0026] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited thereto. In addition, all academic and patent documents described in this specification are incorporated herein by reference.

[0027] First, the terms used in this specification will be explained. A "structural unit" refers to a repeating unit that constitutes a polymer. A "polyamic acid" is a polymer containing a structural unit represented by the following general formula (11) (hereinafter, sometimes referred to as "structural unit (11)").

[0028]

[0029] In general formula (11), A １ represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from a tetracarboxylic dianhydride), A ２ represents a diamine residue (a divalent organic group derived from a diamine).

[0030] The content of the structural unit (11) relative to all structural units constituting the polyamic acid is, for example, 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, even more preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%.

[0031] Hereinafter, the compound name may be followed by "based" to refer to the compound and its derivatives in a comprehensive manner. Furthermore, when the compound name is followed by "based" to represent the name of a polymer, unless otherwise specified, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, tetracarboxylic acid dianhydrides may be referred to as "acid dianhydrides."

[0032] Unless otherwise specified, the components and functional groups exemplified in this specification may be used alone or in combination of two or more kinds.

[0033] <Preferred Embodiment of the Present Invention> The polyamic acid composition according to this embodiment contains a polyamic acid (hereinafter sometimes referred to as "specific polyamic acid"), an organic solvent, an aminophenol, and methyl aminobenzoate. The specific polyamic acid has 4-aminophenyl-4-aminobenzoate residues as diamine residues. In the specific polyamic acid, the content of 4-aminophenyl-4-aminobenzoate residues is 70 mol% or more relative to the total diamine residues (100 mol%) constituting the specific polyamic acid. The polyamic acid composition according to this embodiment is diluted to a specific polyamic acid concentration of 1 mass%, and the aminophenol content measured by gas chromatography-mass spectrometry is 1 ppm by mass or more and 30 ppm by mass or less relative to the total amount of the sample. The polyamic acid composition according to this embodiment is diluted to a specific polyamic acid concentration of 1 mass%, and the methyl aminobenzoate content measured by gas chromatography-mass spectrometry is 0.01 ppm by mass or more and 0.10 ppm by mass or less relative to the total amount of the sample.

[0034] Examples of dilution solvents for preparing the above samples (specifically, samples used to determine the aminophenol content and the methyl aminobenzoate content) include organic solvents of the same type as the organic solvent contained in the polyamic acid composition.

[0035] Hereinafter, gas chromatography-mass spectrometry may be referred to as "GC / MS analysis." Furthermore, the aminophenol content (percentage of the total amount of the sample) obtained by GC / MS analysis using a sample obtained by diluting a polyamic acid composition so that the polyamic acid concentration is 1% by mass may be simply referred to as the "aminophenol content in the polyamic acid composition." Furthermore, the methyl aminobenzoate content (percentage of the total amount of the sample) obtained by GC / MS analysis using a sample obtained by diluting a polyamic acid composition so that the polyamic acid concentration is 1% by mass may be simply referred to as the "methyl aminobenzoate content in the polyamic acid composition." The methods for measuring the aminophenol content in the polyamic acid composition and the methyl aminobenzoate content in the polyamic acid composition are both the same as or similar to the methods described in the Examples below. Furthermore, 4-aminophenyl-4-aminobenzoate may be referred to as "4-BAAB."

[0036] Polyimides obtained from polyamic acids having 4-BAAB residues have a relatively low CTE due to the rigid structure of the 4-BAAB residues, and therefore can reduce internal stress. Since the specific polyamic acid has 4-BAAB residues in a content of 70 mol % or more relative to all diamine residues, polyimides obtained using the polyamic acid composition according to this embodiment can reduce internal stress.

[0037] Furthermore, since the carbonyl group of the ester bond of 4-BAAB exhibits electron-withdrawing properties, it can suppress the formation of CT complexes, making it suitable as a monomer component for polyimides with excellent transparency.

[0038] On the other hand, commercially available 4-BAAB (raw material monomer) for synthesizing polyamic acid typically contains aminophenol and methyl aminobenzoate as impurities. Examples of aminophenols include one or more selected from the group consisting of p-aminophenol, m-aminophenol, and o-aminophenol. Examples of methyl aminobenzoate include one or more selected from the group consisting of methyl 2-aminobenzoate, methyl 3-aminobenzoate, and methyl 4-aminobenzoate.

[0039] Hereinafter, a raw material (usually a powdered raw material) containing 4-BAAB and impurities for synthesizing polyamic acid may be referred to as a "4-BAAB composition." The aminophenol and methyl aminobenzoate in the polyamic acid composition according to this embodiment are, for example, residual impurity components in the 4-BAAB composition. The inventors' studies have revealed that when a 4-BAAB composition containing a large amount of impurities is dissolved in a polymerization solvent, the solution turns yellow or brown, and the transparency of the polyimide film after polymerization decreases.

[0040] GC / MS analysis of the 4-BAAB composition containing many impurities revealed that the impurities thought to be the cause of the coloration were aminotoluene, aminophenol (specifically, p-aminophenol, etc.), 2,4,4-trimethyl-1,3-pentanediol-1-isobutyrate, methyl aminobenzoate (specifically, methyl 4-aminobenzoate, etc.), ethyl aminobenzoate (specifically, ethyl 4-aminobenzoate, etc.), 4-aminobenzohydrazide, 4-(1H-benzimidazole-2- Examples of such compounds include N-(4-(2-(3-phenylpropanoyl)hydrazino]carbonyl)aniline derivatives (estimated molecular weight: 209), p-aminobenzoic acid, 4-aminophenol derivatives (estimated molecular weight: 213), 4-amino-N-(2-ethoxyphenyl)benzamide derivatives (estimated molecular weight: 256), 4-(dimethylamino)-N-(2-ethoxyphenyl)benzamide derivatives (estimated molecular weight: 256), N-(4-{[2-(3-phenylpropanoyl)hydrazino]carbonyl}phenyl)propanamide derivatives (estimated molecular weight: 284), and structures similar thereto.

[0041] As a result of extensive investigations by the present inventors, it has become clear that the transparency of the resulting polyimide film decreases as the content of monoamines as impurities increases, and in particular, the transparency of the resulting polyimide film decreases significantly as the amounts of aminophenol and methyl aminobenzoate in the 4-BAAB composition increase.

[0042] In this embodiment, the content of aminophenol in the polyamic acid composition is 30 ppm by mass or less, and the content of methyl aminobenzoate in the polyamic acid composition is 0.10 ppm by mass or less, so that the decrease in transparency of the obtained polyimide film is suppressed, and the inherent function of 4-BAAB (the transparency-improving function by suppressing the formation of CT complexes) is fully exhibited. Thus, the polyimide obtained using the polyamic acid composition according to this embodiment has excellent transparency.

[0043] When the content of aminophenol in the polyamic acid composition is in the range of 1 ppm by mass to 30 ppm by mass, a trace amount of aminophenol tends to function as an accelerator for the imidization reaction.When the content of methyl aminobenzoate in the polyamic acid composition is in the range of 0.01 ppm by mass to 0.10 ppm by mass, a trace amount of methyl aminobenzoate tends to function as an accelerator for the imidization reaction.

[0044] In the present embodiment, in order to obtain a polyimide having excellent transparency while further reducing internal stress, the content of 4-BAAB residues is preferably 80 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more, relative to all diamine residues constituting the specific polyamic acid, and may be 100 mol %.

[0045] In this embodiment, in order to obtain a polyimide having excellent transparency, the content of aminophenol in the polyamic acid composition is preferably 28 ppm by mass or less, more preferably 25 ppm by mass or less. In addition, in this embodiment, in order to obtain a polyimide having excellent transparency, the content of methyl aminobenzoate in the polyamic acid composition is preferably 0.08 ppm by mass or less, more preferably 0.05 ppm by mass or less.

[0046] The aminophenol content in the polyamic acid composition and the methyl aminobenzoate content in the polyamic acid composition can both be adjusted by changing the preparation conditions of the 4-BAAB composition. Specifically, they can be adjusted by changing at least one of the purification methods (e.g., recrystallization, activated carbon treatment, etc.) of the raw material for 4-BAAB (4-nitrophenyl-4-nitrobenzoate) and the purification methods (e.g., activated carbon treatment, recrystallization, etc.) of the resulting 4-BAAB composition. Furthermore, when multiple purification methods are employed, the above contents can also be adjusted by changing the order in which the purification methods are performed. The activated carbon treatment method is effective in reducing aminophenol. On the other hand, the recrystallization method is effective in reducing methyl aminobenzoate.

[0047] In this embodiment, in order to obtain a polyimide having excellent transparency, the Gardner color number measured in a cell having an optical path length of 1 cm using a sample obtained by diluting a polyamic acid composition so that the concentration of the specific polyamic acid is 1% by mass is preferably 0.3 or less, more preferably 0.2 or less. Furthermore, in this embodiment, in order to obtain a polyimide having excellent transparency, the Hazen color number measured in a cell having an optical path length of 1 cm using a sample obtained by diluting a polyamic acid composition so that the concentration of the specific polyamic acid is 1% by mass is preferably 10 or less, more preferably 8 or less.

[0048] Hereinafter, the Hazen color number may be referred to as "APAH." The Gardner color number measured in a cell with an optical path length of 1 cm using a sample obtained by diluting a polyamic acid composition to a polyamic acid concentration of 1% by mass may be simply referred to as the "Gardner color number of the polyamic acid composition." The APAH measured in a cell with an optical path length of 1 cm using a sample obtained by diluting a polyamic acid composition to a polyamic acid concentration of 1% by mass may be simply referred to as the "APAH of the polyamic acid composition." Examples of dilution solvents used to prepare the samples (specifically, samples used to determine the Gardner color number and APAH of the polyamic acid composition) include organic solvents of the same type as those contained in the polyamic acid composition.

[0049] The method for measuring the Gardner color number of a polyamic acid composition and the method for measuring the APAH of a polyamic acid composition are both the same as or similar to the methods described in the Examples below. The Gardner color number and the APAH of a polyamic acid composition tend to decrease as the aminophenol content and the methyl aminobenzoate content in the polyamic acid composition decrease. The lower limits of the Gardner color number and the APAH of a polyamic acid composition are not limited and may be 0.

[0050] The specific polyamic acid contained in the polyamic acid composition according to this embodiment has a tetracarboxylic dianhydride residue and a diamine residue.

[0051] Examples of acid dianhydrides (monomers) that can be used when synthesizing the specific polyamic acid include pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as "s-BPDA"), 2,3,3',4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as "a-BPDA"), 2,2',3,3'-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as "i-BPDA"), p-phenylenebis(trimellitate anhydride), 2,3,6,7-naphthalenetetracarboxylic dianhydride, and the like. carboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride (hereinafter sometimes referred to as "ODPA"), 3,4'-oxydiphthalic anhydride (hereinafter sometimes referred to as "a-ODPA"), spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone (hereinafter sometimes referred to as "SFDA"), 9,9-bis(3,4-dicarboxyphenoxy) dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 2'-oxodispiro[bicyclo[2.2.1]heptane-2,1'-cyclopentane-3',2''-bicyclo[2.2.1]heptane]-5,6:5'',6''-tetracarboxylic dianhydride, 5,5'-bis-2-norbornene-5,5',6,6'-tetracarboxylic acid Examples of suitable dianhydrides include norbornane-5,5',6,6'-tetracarboxylic acid dianhydride (hereinafter, may be referred to as "BNBDA"), decahydro-1H,3H-4,10:5,9-dimethanonaphtho[2,3-c:6,7-c']difuran-1,3,6,8-tetraone (hereinafter, may be referred to as "DNDA"), norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid dianhydride (hereinafter, may be referred to as "CpODA"), and derivatives thereof, and these may be used alone or in combination of two or more.

[0052] In order to obtain a polyimide having excellent transparency while further reducing internal stress, the specific polyamic acid preferably has, as the tetracarboxylic dianhydride residue, one or more selected from the group consisting of s-BPDA residue, a-BPDA residue, i-BPDA residue, ODPA residue, a-ODPA residue, SFDA residue, BPAF residue, DNDA residue, BNBDA residue, and CpODA residue, and more preferably has one or more selected from the group consisting of s-BPDA residue, a-BPDA residue, SFDA residue, BPAF residue, and ODPA residue.

[0053] The s-BPDA residue is a tetravalent organic group represented by the following chemical formula (1). The a-BPDA residue is a tetravalent organic group represented by the following chemical formula (2). The i-BPDA residue is a tetravalent organic group represented by the following chemical formula (3). The ODPA residue is a tetravalent organic group represented by the following chemical formula (4). The a-ODPA residue is a tetravalent organic group represented by the following chemical formula (5). The SFDA residue is a tetravalent organic group represented by the following chemical formula (6). The BPAF residue is a tetravalent organic group represented by the following chemical formula (7). The DNDA residue is a tetravalent organic group represented by the following chemical formula (8). The BNBDA residue is a tetravalent organic group represented by the following chemical formula (9). The CpODA residue is a tetravalent organic group represented by the following chemical formula (10).

[0054]

[0055] In order to obtain a polyimide capable of further reducing internal stress, the specific polyamic acid preferably has an s-BPDA residue as a tetracarboxylic dianhydride residue. In order to obtain a polyimide capable of further reducing internal stress, the content of the s-BPDA residue is preferably 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more, relative to the total tetracarboxylic dianhydride residues (100 mol %) constituting the specific polyamic acid, and may be 100 mol %.

[0056] In order to obtain a polyimide having superior transparency, the specific polyamic acid preferably has, as a tetracarboxylic dianhydride residue, one or more selected from the group consisting of a-BPDA residues, SFDA residues, BPAF residues, and ODPA residues. In order to obtain a polyimide having even superior transparency, the content of one or more residues selected from the group consisting of a-BPDA residues, SFDA residues, BPAF residues, and ODPA residues is preferably 1 mol % or more and 50 mol % or less, more preferably 5 mol % or more and 40 mol % or less, and even more preferably 10 mol % or more and 30 mol % or less, relative to all tetracarboxylic dianhydride residues (100 mol %) constituting the specific polyamic acid.

[0057] In order to obtain a polyimide having even more excellent transparency while further reducing internal stress, the content of one or more residues selected from the group consisting of s-BPDA residues, a-BPDA residues, SFDA residues, BPAF residues, and ODPA residues is preferably 60 mol % or more, more preferably 70 mol % or more, even more preferably 80 mol % or more, and even more preferably 90 mol % or more, relative to all tetracarboxylic dianhydride residues constituting the specific polyamic acid (100 mol %), and may be 100 mol %.

[0058] When synthesizing the specific polyamic acid, diamine monomers other than 4-BAAB can also be used. Examples of diamines (monomers) that can be used other than 4-BAAB include p-phenylenediamine, 1,3-bis(3-aminopropyl)tetramethyldisiloxane (hereinafter sometimes referred to as "PAM-E"), 9,9-bis(4-aminophenyl)fluorene, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzanilide, m-phenylenediamine, and 4,4'-oxygen. Examples thereof include dianiline, 3,4'-oxydianiline, N,N'-bis(4-aminophenyl)terephthalamide, m-tolidine, o-tolidine, 4,4'-bis(4-aminophenoxy)biphenyl, 2-(4-aminophenyl)-6-aminobenzoxazole, 3,5-diaminobenzoic acid, 4,4'-diamino-3,3'-dihydroxybiphenyl, 4,4'-methylenebis(cyclohexanamine), and derivatives thereof, and these may be used alone or in combination.

[0059] In order to improve the adhesion between the resulting polyimide film and the substrate, it is preferable to use PAM-E as the diamine (monomer). In order to further improve the adhesion between the resulting polyimide film and the substrate, the content of PAM-E residues is preferably 0.01 mol % or more and 1 mol % or less relative to the total diamine residues (100 mol %) constituting the specific polyamic acid.

[0060] In order to suppress the generation of hydrogen fluoride in a high-temperature atmosphere and thereby enhance the adhesion between the polyimide film and the substrate in a high-temperature process, the content of fluorine atoms in the specific polyamic acid is preferably less than 5% by mass, more preferably less than 1% by mass, and even more preferably less than 0.5% by mass, relative to the total amount (100% by mass) of the specific polyamic acid.

[0061] The weight-average molecular weight of the specific polyamic acid varies depending on its application, but is preferably in the range of 10,000 to 1,000,000, more preferably 20,000 to 500,000, and even more preferably 30,000 to 200,000. A weight-average molecular weight of 10,000 or more allows the viscosity of the polyamic acid composition to be easily adjusted to a range suitable for coating (e.g., 0.5 to 10 Pa·s). On the other hand, a weight-average molecular weight of 1,000,000 or less allows the polyamic acid composition to exhibit sufficient solubility in solvents, thereby enabling the production of a coating film or polyimide film with a smooth surface and uniform thickness. The weight-average molecular weight used here refers to a polyethylene oxide equivalent value measured using gel permeation chromatography (GPC).

[0062] The polyamic acid composition according to this embodiment may also contain an imidization accelerator and / or a dehydration catalyst in order to shorten the heating time and to develop properties.

[0063] The imidization accelerator is not particularly limited, but a tertiary amine can be used. The tertiary amine is preferably a heterocyclic tertiary amine. Specific preferred examples of heterocyclic tertiary amines include pyridine, picoline, quinoline, isoquinoline, and imidazoles. Specific preferred examples of the dehydration catalyst include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride.

[0064] From the viewpoints of shortening the heating time and of expressing the properties, the amount of the imidization accelerator is preferably from 0.1 to 20 parts by mass, and more preferably from 0.5 to 20 parts by mass, per 100 parts by mass of the specific polyamic acid. Also, from the viewpoints of shortening the heating time and of expressing the properties, the amount of the dehydration catalyst is preferably from 0.1 to 10 parts by mass, and more preferably from 0.5 to 5 parts by mass, per 100 parts by mass of the specific polyamic acid.

[0065] As the imidization accelerator, imidazoles are preferred. In this specification, the term "imidazoles" refers to compounds having a 1,3-diazole ring (1,3-diazole ring structure). Imidazoles that can be added to the polyamic acid composition according to this embodiment are not particularly limited, but examples include 1H-imidazole, 2-methylimidazole, 2-undecylimidazole, 2-heptadecylimidazole, 1,2-dimethylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 2-phenyl-4-methylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole. Of these, 1,2-dimethylimidazole, 1-benzyl-2-methylimidazole, and 1-benzyl-2-phenylimidazole are preferred, and 1,2-dimethylimidazole and 1-benzyl-2-methylimidazole are more preferred.

[0066] The content of imidazoles is preferably 0.005 mol or more and 0.1 mol or less, more preferably 0.01 mol or more and 0.08 mol or less, and even more preferably 0.015 mol or more and 0.050 mol or less, per mol of amide group in the specific polyamic acid. By incorporating 0.005 mol or more of imidazoles, the film strength and transparency of the polyimide can be improved, and by limiting the content of imidazoles to 0.1 mol or less, the heat resistance of the specific polyamic acid can be improved while maintaining its storage stability. In this specification, the term "amide group of the specific polyamic acid" refers to an amide group formed by the polymerization reaction of a diamine and a tetracarboxylic dianhydride.

[0067] The method for mixing the specific polyamic acid and the imidazole is not particularly limited. From the viewpoint of ease of molecular weight control of the specific polyamic acid, it is preferable to add the imidazole to the specific polyamic acid after polymerization. In this case, the imidazole may be added directly to the specific polyamic acid, or the imidazole may be dissolved in a solvent in advance and this solution may be added to the specific polyamic acid; the addition method is not particularly limited. The polyamic acid composition according to this embodiment may be prepared by adding the imidazole to a solution containing the specific polyamic acid after polymerization (post-reaction solution).

[0068] The polyamic acid composition according to this embodiment may contain various organic or inorganic low-molecular-weight compounds or polymeric compounds as additives. Examples of additives that can be used include plasticizers, antioxidants, dyes, surfactants, leveling agents, silicones, fine particles, and sensitizers. Examples of fine particles include organic fine particles made of polystyrene, polytetrafluoroethylene, and the like, and inorganic fine particles made of colloidal silica, carbon, layered silicates, and the like, which may have a porous or hollow structure. The function and form of the fine particles are not particularly limited, and they may be, for example, pigments, fillers, or fibrous particles.

[0069] Furthermore, the polyamic acid composition according to this embodiment may contain a silane coupling agent in order to achieve appropriate adhesion to the support. Known silane coupling agents can be used without particular limitation. To achieve good adhesion to the support, usable silane coupling agents are preferably compounds containing an amino group, more preferably one or more compounds selected from the group consisting of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyldiethoxymethylsilane, 3-(ethoxydimethylsilyl)propylamine, N-2-(aminoethyl)-3-aminopropyltrimethoxysilane, N-2-(aminoethyl)-3-aminopropylmethyldimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane, even more preferably one or more compounds selected from the group consisting of 3-aminopropyltriethoxysilane and 3-aminopropyldiethoxymethylsilane, with 3-aminopropyltriethoxysilane being particularly preferred.

[0070] The blending ratio of the silane coupling agent to 100 parts by mass of the specific polyamic acid is preferably 0.01 parts by mass or more and 0.50 parts by mass or less, more preferably 0.01 parts by mass or more and 0.30 parts by mass or less, and even more preferably 0.01 parts by mass or more and 0.20 parts by mass or less. By making the blending ratio of the silane coupling agent 0.01 parts by mass or more, the peeling suppression effect on the support is fully exerted, and by making the blending ratio of the silane coupling agent 0.50 parts by mass or less, the molecular weight reduction of the specific polyamic acid is suppressed, so that the embrittlement of the polyimide film can be suppressed.

[0071] In order to obtain a polyimide having even greater transparency while further reducing internal stress, the polyamic acid composition according to this embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, and even more preferably satisfies the following condition 3. Condition 1: The specific polyamic acid has one or more residues selected from the group consisting of s-BPDA residues, a-BPDA residues, SFDA residues, BPAF residues, and ODPA residues, and the content of the one or more residues selected from the group consisting of s-BPDA residues, a-BPDA residues, SFDA residues, BPAF residues, and ODPA residues is 80 mol % or more and 100 mol % or less, based on all tetracarboxylic dianhydride residues (100 mol %) constituting the specific polyamic acid. Condition 2: The above condition 1 is satisfied, and the content of 4-BAAB residues is 80 mol % or more and 100 mol % or less, based on all diamine residues (100 mol %) constituting the specific polyamic acid. Condition 3: The above condition 2 is satisfied, and the Gardner color number and APAH of the polyamic acid composition are 0.3 or less and 10 or less, respectively.

[0072] The method for producing a polyamic acid composition according to this embodiment includes step S1 of reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. The method for reacting a diamine with a tetracarboxylic dianhydride in an organic solvent can be a known, general method, as long as the following conditions A to F are met. Specific methods for reacting a diamine with a tetracarboxylic dianhydride in an organic solvent are described below. Condition A: At least 4-BAAB is used as the diamine (monomer). Condition B: The content of 4-BAAB in the diamine (monomer) is 70 mol % or more relative to the total amount of diamine (100 mol %). Condition C: 4-BAAB is supplied to step S1 as a raw material containing impurities (4-BAAB composition). Condition D: Impurities in the 4-BAAB composition include aminophenol and methyl aminobenzoate. Condition E: The Gardner color number measured using a 1% by mass NMP solution of the 4-BAAB composition in a cell with a 1 cm optical path length is 3.0 or less. Condition F: The APAH measured using a 1 mass % NMP solution of the 4-BAAB composition in a cell having an optical path length of 1 cm is 200 or less.

[0073] By satisfying the above conditions A to F, the polyamic acid composition according to the present embodiment can be easily produced.

[0074] Hereinafter, the Gardner color number measured using a 1% by mass NMP solution of a 4-BAAB composition in a cell with an optical path length of 1 cm may be simply referred to as the "Gardner color number of the 4-BAAB composition." Furthermore, the APAH measured using a 1% by mass NMP solution of a 4-BAAB composition in a cell with an optical path length of 1 cm may be simply referred to as the "APAH of the 4-BAAB composition." The method for measuring the Gardner color number of a 4-BAAB composition and the method for measuring the APAH of a 4-BAAB composition are both the same as or equivalent to the methods described in the Examples below. The Gardner color number of the 4-BAAB composition and the APAH of the 4-BAAB composition tend to decrease as the content of aminophenol and the content of methyl aminobenzoate in the 4-BAAB composition decrease. The lower limit of the Gardner color number of the 4-BAAB composition and the lower limit of the APAH of the 4-BAAB composition are not limited and may be 0.

[0075] In order to obtain a polyimide having excellent transparency while further reducing internal stress, the method for producing a polyamic acid composition according to this embodiment preferably satisfies the following conditions G and H. Condition G: The content of aminophenol in the 4-BAAB composition is 0.60% by mass or less, based on the total amount of 4-BAAB (100% by mass). Condition H: The content of methyl aminobenzoate in the 4-BAAB composition is 0.60% by mass or less, based on the total amount of 4-BAAB (100% by mass).

[0076] Hereinafter, the content of aminophenol in the 4-BAAB composition relative to the total amount of 4-BAAB may be simply referred to as the "content of aminophenol in the 4-BAAB composition." Furthermore, the content of methyl aminobenzoate in the 4-BAAB composition relative to the total amount of 4-BAAB may be simply referred to as the "content of methyl aminobenzoate in the 4-BAAB composition." The methods for measuring the "content of aminophenol in the 4-BAAB composition" and the "content of methyl aminobenzoate in the 4-BAAB composition" are both the same as or similar to the methods described in the Examples below.

[0077] In order to obtain a polyimide having even more excellent transparency while further reducing the internal stress, the content of aminophenol in the 4-BAAB composition is preferably 0.05% by mass or more and 0.60% by mass or less, more preferably 0.10% by mass or more and 0.58% by mass or less, and even more preferably 0.15% by mass or more and 0.56% by mass or less.

[0078] In order to obtain a polyimide having even more excellent transparency while further reducing the internal stress, the content of methyl aminobenzoate in the 4-BAAB composition is preferably 0.01% by mass or more and 0.60% by mass or less, more preferably 0.02% by mass or more and 0.40% by mass or less, and even more preferably 0.03% by mass or more and 0.20% by mass or less.

[0079] In order to obtain a polyimide having even more excellent transparency while further reducing the internal stress, the content of ethyl aminobenzoate in the 4-BAAB composition is preferably 0.15% by mass or less, more preferably 0.01% by mass or more and 0.15% by mass or less, still more preferably 0.02% by mass or more and 0.10% by mass or less, and particularly preferably 0.02% by mass or more and 0.05% by mass or less, relative to the total amount (100% by mass) of 4-BAAB.

[0080] An example of a method (synthesis method) for reacting a diamine and a tetracarboxylic dianhydride in an organic solvent will be described. A first method involves dissolving or dispersing a diamine in an organic solvent in a slurry-like state in an inert gas atmosphere such as argon or nitrogen to prepare a diamine solution. Then, after the tetracarboxylic dianhydride has been dissolved or dispersed in a slurry-like state in the organic solvent, or after the tetracarboxylic dianhydride has been dissolved or dispersed in a slurry-like state in the organic solvent, the tetracarboxylic dianhydride is added to the diamine solution in a solid state. A second method involves dissolving or dispersing a tetracarboxylic dianhydride in an organic solvent in a slurry-like state in an inert gas atmosphere such as argon or nitrogen to prepare a tetracarboxylic dianhydride solution. Then, after the diamine has been dissolved or dispersed in a slurry-like state in the organic solvent, the diamine is added to the tetracarboxylic dianhydride solution in a solid state.

[0081] When synthesizing a specific polyamic acid using a diamine and a tetracarboxylic dianhydride, the desired specific polyamic acid (a polymer of a diamine and a tetracarboxylic dianhydride) can be obtained by adjusting the molar amount of the diamine (or, if multiple diamines are used, the molar amount of each diamine) and the molar amount of the tetracarboxylic dianhydride (or, if multiple tetracarboxylic dianhydrides are used, the molar amount of each tetracarboxylic dianhydride). The molar fraction of each residue in the specific polyamic acid corresponds, for example, to the molar fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the specific polyamic acid. Furthermore, a specific polyamic acid containing multiple tetracarboxylic dianhydride residues and multiple diamine residues can also be obtained by blending two types of polyamic acid. The temperature conditions for the reaction between the diamine and the tetracarboxylic dianhydride, i.e., the synthesis reaction of the specific polyamic acid, are not particularly limited, but are, for example, in the range of 20°C to 150°C. The reaction time for the synthesis reaction of the specific polyamic acid is, for example, in the range of 10 minutes to 30 hours.

[0082] Methods for controlling the molecular weight of specific polyamic acids include using an excess of either the acid dianhydride or the diamine, or quenching the reaction by reacting with a monofunctional acid anhydride or amine, such as phthalic anhydride or aniline. When polymerizing with an excess of either the acid dianhydride or the diamine, a polyimide film with sufficient strength can be obtained if the molar ratio of the diamines used to synthesize the specific polyamic acid is between 0.95 and 1.05. The molar ratio is the ratio of the total amount of diamines used to synthesize the specific polyamic acid to the total amount of dianhydrides used to synthesize the specific polyamic acid (total amount of diamines / total amount of dianhydrides). Furthermore, end-capping with phthalic anhydride, maleic anhydride, aniline, or the like can further reduce the coloration of polyimides obtained using specific polyamic acids.

[0083] The organic solvent used in the synthesis of the specific polyamic acid is preferably a solvent capable of dissolving the tetracarboxylic dianhydride and diamine used, and more preferably a solvent capable of dissolving the specific polyamic acid to be produced. Examples of organic solvents used in the synthesis of the specific polyamic acid include urea-based solvents such as N,N-dimethylethyl urea, sulfoxide-based solvents such as dimethyl sulfoxide, sulfone-based solvents such as tetramethyl sulfone, amide-based solvents such as N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), N,N-diethylformamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), N-butyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropanamide (MPA), and hexamethylphosphoric triamide, ester-based solvents such as γ-butyrolactone, halogenated alkyl solvents such as chloroform, aromatic hydrocarbon solvents such as toluene, phenol-based solvents such as phenol, ketone-based solvents such as cyclopentanone, and ether-based solvents such as tetrahydrofuran. Usually, these solvents are used alone, but two or more of them may be used in appropriate combination as needed. The organic solvent used for the synthesis of the specific polyamic acid is preferably one or more solvents selected from the group consisting of amide solvents, ketone solvents, ester solvents, and ether solvents, and more preferably an amide solvent (more specifically, DMF, DMAC, NMP, MPA, etc.). In addition, the synthesis reaction of the specific polyamic acid is preferably carried out under an inert gas atmosphere such as argon or nitrogen.

[0084] When the specific polyamic acid is obtained by the above-described method, the reaction solution (the solution after the reaction) itself may be used as the polyamic acid composition according to the present embodiment. In this case, the organic solvent in the polyamic acid composition is the organic solvent used in the synthesis reaction. Alternatively, the solid specific polyamic acid obtained by removing the solvent from the reaction solution may be dissolved in an organic solvent to prepare the polyamic acid composition according to the present embodiment.

[0085] The concentration of the specific polyamic acid in the polyamic acid composition according to the present embodiment is not particularly limited and is, for example, 5% by mass or more and 40% by mass or less, and preferably 8% by mass or more and 30% by mass or less, relative to the total amount (100% by mass) of the polyamic acid composition.

[0086] The polyimide according to this embodiment is an imidized product of the specific polyamic acid described above. The polyimide according to this embodiment can be obtained by known methods, and its manufacturing method is not particularly limited. An example of a method for obtaining the polyimide according to this embodiment by imidizing the specific polyamic acid is described below. Imidization is performed by dehydration ring-closing the specific polyamic acid. This dehydration ring-closing can be performed by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method. Furthermore, the imidization of the specific polyamic acid to polyimide can be any ratio between 1% and 100%. In other words, a partially imidized specific polyamic acid may be synthesized. In particular, when imidization is performed by heating, the ring-closing reaction from the specific polyamic acid to polyimide and the hydrolysis of the specific polyamic acid proceed simultaneously, which may result in a polyimide with a lower molecular weight than the specific polyamic acid. Therefore, from the perspective of improving mechanical properties, it is preferable to partially imidize the specific polyamic acid in the polyamic acid composition before forming the polyimide film described below. In this specification, partially imidized polyamic acid may also be referred to as "polyamic acid."

[0087] The dehydration ring closure of the specific polyamic acid can be carried out by heating the specific polyamic acid. The method for heating the specific polyamic acid is not particularly limited. For example, the polyamic acid composition according to the present embodiment described above can be applied to a support such as a glass substrate, a metal plate, or a PET film (polyethylene terephthalate film), followed by heat treatment of the specific polyamic acid at a temperature ranging from 40°C to 500°C. This method can produce a laminate according to the present embodiment, which has a support and a polyimide film (more specifically, a polyimide film containing an imidized product of the specific polyamic acid) disposed on the support. Alternatively, the dehydration ring closure of the specific polyamic acid can be carried out by directly placing the polyamic acid composition in a container that has been subjected to a release treatment, such as coating with a fluorine-based resin, and then heating and drying the polyamic acid composition under reduced pressure. Polyimides can be obtained by dehydration ring closure of the specific polyamic acid using these methods. The heating time for each of the above treatments varies depending on the amount of polyamic acid composition to be treated and the heating temperature, but it is generally preferred that the heating time be in the range of 1 minute to 300 minutes after the treatment temperature reaches the maximum temperature.

[0088] The polyimide film according to this embodiment (specifically, a polyimide film containing an imidized product of a specific polyamic acid) is colorless, transparent, and has a low yellowness and a glass transition temperature (heat resistance) that can withstand the TFT fabrication process, making it suitable as a transparent substrate material for flexible displays. The content of polyimide (specifically, an imidized product of a specific polyamic acid) in the polyimide film according to this embodiment is, for example, 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and may even be 100% by mass, based on the total amount of the polyimide film. Examples of components other than polyimide in the polyimide film include the additives described above (more specifically, fine particles, etc.).

[0089] An electronic device according to this embodiment (more specifically, a flexible device, etc.) includes the polyimide film according to this embodiment and electronic elements disposed directly or indirectly on the polyimide film. When manufacturing an electronic device according to this embodiment for use in a flexible display, a polyimide film is first formed on an inorganic substrate such as glass as a support. Electronic elements such as TFTs are then disposed (formed) on the polyimide film to form an electronic device on the support. The process of forming TFTs is generally carried out over a wide temperature range of 150°C or higher and 650°C or lower, but in order to actually achieve the desired performance, an oxide semiconductor layer or a-Si layer is formed at 300°C or higher, and in some cases, the a-Si or the like may be further crystallized using a laser or the like.

[0090] In this case, if the thermal decomposition temperature of the polyimide film is low, outgassing may occur during electronic device formation, and the outgassing may adhere to the oven as sublimate, causing furnace contamination or peeling of inorganic films (such as the barrier film described below) and electronic devices formed on the polyimide film. Therefore, the 1% weight loss temperature of the polyimide is preferably 500°C or higher. The upper limit of the 1% weight loss temperature of the polyimide is preferably as high as possible, but is, for example, 600°C. The 1% weight loss temperature can be adjusted, for example, by changing the content of residues having a rigid structure (more specifically, s-BPDA residues, etc.). More specifically, before TFT formation, an inorganic film such as a silicon oxide film (SiOx film) or a silicon nitride film (SiNx film) is formed as a barrier film on the polyimide film. In this case, if the polyimide has low heat resistance, if imidization has not progressed completely, or if there is a large amount of residual solvent, peeling between the polyimide and the inorganic film may occur due to volatile components such as polyimide decomposition gas during the high-temperature process after lamination of the inorganic film. For this reason, it is desirable that the polyimide film and the inorganic film do not peel off when the laminate after the inorganic film has been formed is held for 1 hour at a temperature of 400° C. Since the performance of TFTs improves as the processing temperature increases, it is desirable that the polyimide film and the inorganic film do not peel off when the laminate after the inorganic film has been formed is held for 1 hour at a temperature of 430° C., and it is even more desirable that the polyimide film and the inorganic film do not peel off when the laminate after the inorganic film has been formed is held for 1 hour at a temperature of 470° C.

[0091] Furthermore, if the glass transition temperature (Tg) of the polyimide is significantly lower than the process temperature, misalignment or the like may occur during the formation of electronic elements. Therefore, the Tg of the polyimide is preferably 400°C or higher, more preferably 420°C or higher, even more preferably 430°C or higher, and even more preferably 450°C or higher. The upper limit of the Tg of the polyimide is preferably as high as possible, for example, 500°C. Furthermore, since the thermal expansion coefficient of a glass substrate is generally smaller than that of a resin, internal stress occurs between the glass substrate and the polyimide film. If the internal stress of a laminate of a glass substrate or electronic element used as a support and a polyimide film is high, the laminate including the polyimide film will expand during the high-temperature TFT formation process and then shrink when cooled to room temperature, resulting in problems such as warping or breakage of the glass substrate and peeling of the polyimide film from the glass substrate. Therefore, in a laminate (laminate according to this embodiment) having a glass substrate (support) and a polyimide film, the internal stress between the polyimide film and the glass substrate is preferably 30 MPa or less, more preferably 20 MPa or less, and even more preferably 10 MPa or less. The lower limit of the internal stress is the better, and may be 0 MPa. The method for measuring the internal stress is the same as or similar to the method described in the examples below.

[0092] The polyimide according to this embodiment can be suitably used as a material for display substrates such as TFT substrates and touch panel substrates. When using polyimide for the above applications, a method is often adopted in which an electronic device (specifically, an electronic device having electronic elements formed on a polyimide film) is formed on a support as described above, and then the polyimide film is peeled off from the support. Furthermore, alkali-free glass is suitably used as the support material. An example of a method for producing a laminate of a polyimide film and a support will be described in detail below.

[0093] First, the polyamic acid composition according to this embodiment is applied (cast) onto a support to form a coating film-containing laminate consisting of a coating film containing the specific polyamic acid and the support. Next, the coating film-containing laminate is heated, for example, at a temperature of 40°C to 200°C. The heating time is, for example, 3 minutes to 120 minutes. A multi-stage heating process may be performed, for example, by heating the coating film-containing laminate at 50°C for 30 minutes and then at 100°C for 30 minutes. Next, to promote imidization of the specific polyamic acid in the coating film, the coating film-containing laminate is heated, for example, at a maximum temperature of 200°C to 500°C. The heating time (heating time at the maximum temperature) is, for example, 1 minute to 300 minutes. It is preferable to gradually increase the temperature from a low temperature to the maximum temperature. The heating rate is preferably 2°C / min to 10°C / min, more preferably 4°C / min to 10°C / min. The maximum temperature is preferably in the range of 250°C or higher and 450°C or lower. If the maximum temperature is 250°C or higher, imidization proceeds sufficiently, while if the maximum temperature is 450°C or lower, thermal degradation and discoloration of the polyimide can be suppressed. The reaction may be maintained at any temperature for any time until the maximum temperature is reached. The imidization reaction can be carried out under air, reduced pressure, or an inert gas such as nitrogen. However, to achieve higher transparency, it is preferable to carry out the reaction under reduced pressure or an inert gas such as nitrogen. Known heating devices such as hot air ovens, infrared ovens, vacuum ovens, inert ovens, and hot plates can be used. Through these steps, the specific polyamic acid in the coating film is imidized, and a laminate (i.e., the laminate according to this embodiment) of the support and the polyimide film (a film containing an imidized product of the specific polyamic acid) can be obtained.

[0094] The polyimide film can be peeled from the resulting laminate of the support and the polyimide film by known methods. For example, the film may be peeled by hand, or by using a mechanical device such as a drive roll or a robot. Furthermore, a method of providing a peeling layer between the support and the polyimide film, or a method of forming a silicon oxide film on a substrate having a large number of grooves, forming a polyimide film using the silicon oxide film as an underlayer, and then peeling the polyimide film by infiltrating a silicon oxide etchant between the substrate and the silicon oxide film can also be employed. Another method of separating the polyimide film by irradiation with laser light can also be employed.

[0095] The transparency of a polyimide film can be evaluated, for example, by the total light transmittance (TT) according to JIS K7361-1:1997 and the haze according to JIS K7136-2000. When a polyimide film is used in an application requiring high transparency, the total light transmittance of the polyimide film is preferably 75% or more, more preferably 80% or more. When a polyimide film is used in an application requiring high transparency, the haze of the polyimide film is preferably 1.5% or less, more preferably 1.2% or less, even more preferably 1.0% or less, and may even be 0%. In applications requiring high transparency, the polyimide film is required to have high transmittance over the entire wavelength range, but polyimide films tend to easily absorb light on the short wavelength side, and the film itself often becomes yellow-colored. In order to use a polyimide film in an application requiring high transparency, it is preferable that the coloration of the polyimide film be reduced. Specifically, in order to use a polyimide film in applications requiring high transparency, the yellowness index (YI) of the polyimide film is preferably 25 or less, more preferably 20 or less, and may even be 0. The YI can be measured in accordance with JIS K7373-2006. The YI can be adjusted, for example, by changing the contents of aminophenol and methyl aminobenzoate in the polyamic acid composition. A polyimide film with reduced coloration and transparency is thus suitable for transparent substrates used as glass replacements, etc., and for substrates on the back surface of which a sensor or camera module is provided.

[0096] Furthermore, in applications requiring transparency, from the viewpoint of color reproducibility, etc., high transmittance is particularly required for blue light (light with a wavelength of around 470 nm), and practically, high transmittance for light with a wavelength of 400 nm (400 nm transmittance) is required. From the viewpoint of color reproducibility, etc., the 400 nm transmittance of the polyimide film is preferably 8% or more. The upper limit of the 400 nm transmittance of the polyimide film is not particularly limited and may be 100%. The 400 nm transmittance can be adjusted, for example, by changing the content of aminophenol and methyl aminobenzoate in the polyamic acid composition.

[0097] Furthermore, there are two types of light extraction methods for flexible displays: a top-emission method in which light is extracted from the front surface side of the TFT, and a bottom-emission method in which light is extracted from the back surface side of the TFT. The top-emission method is characterized by the fact that light is not blocked by the TFT, making it easy to increase the aperture ratio and obtain high-definition image quality. The bottom-emission method is characterized by the ease of alignment between the TFT and the pixel electrode, making it easy to manufacture. If the TFT is transparent, the aperture ratio can also be improved in the bottom-emission method, so the bottom-emission method, which is easy to manufacture, tends to be adopted for large displays. The polyimide film according to this embodiment has a low YI and excellent heat resistance, making it applicable to both of the above light extraction methods.

[0098] Furthermore, in a batch-type device production process in which a polyamic acid composition is applied to a support such as a glass substrate, heated to imidize, and then electronic elements or the like are formed, followed by peeling off the polyimide film, excellent adhesion between the support and the polyimide film is preferred. Here, adhesion refers to adhesion strength. In a production process in which electronic elements or the like are formed on the polyimide film on the support, and then the polyimide film on which the electronic elements or the like are formed is peeled off from the support, excellent adhesion between the polyimide film and the support allows for more accurate formation or mounting of electronic elements or the like. In a production process in which electronic elements or the like are arranged on a support via a polyimide film, the higher the peel strength between the support and the polyimide film, the better, from the viewpoint of improving productivity. Specifically, the peel strength is preferably 0.05 N / cm or more, and more preferably 0.1 N / cm or more.

[0099] In the above-described manufacturing process, when peeling a polyimide film from a laminate of a support and a polyimide film, the polyimide film is often peeled from the support by laser irradiation. In this case, since the polyimide film needs to absorb the laser light, the cutoff wavelength of the polyimide film is required to be longer than the wavelength of the laser light used for peeling. Since a XeCl excimer laser with a wavelength of 308 nm is often used for laser peeling, the cutoff wavelength of the polyimide film is preferably 312 nm or more, more preferably 330 nm or more. On the other hand, if the cutoff wavelength is long, the polyimide film tends to be colored yellow, so the cutoff wavelength of the polyimide film is preferably 390 nm or less. From the viewpoint of achieving both transparency (low yellowness) and laser peeling processability, the cutoff wavelength of the polyimide film is preferably 320 nm or more and 390 nm or less, more preferably 330 nm or more and 390 nm or less. In this specification, the cut-off wavelength means a wavelength at which the transmittance is 0.1% or less as measured by an ultraviolet-visible spectrophotometer.

[0100] The polyamic acid composition and polyimide according to the present embodiment may be used as they are in coating or molding processes for producing products or components, or may be used as materials for further coating or other treatments on molded articles formed into films. For use in coating or molding processes, the polyamic acid composition or polyimide may be dissolved or dispersed in an organic solvent as needed, and further blended with a photocurable component, a thermosetting component, a non-polymerizable binder resin, and other components as needed to prepare a composition containing the specific polyamic acid or polyimide.

[0101] On the surface of the polyimide film according to this embodiment, various inorganic thin films such as a metal oxide thin film, a transparent electrode, etc. The method for forming these inorganic thin films is not particularly limited, and examples thereof include PVD methods such as sputtering, vacuum deposition, and ion plating, and CVD methods.

[0102] The polyimide film according to the present embodiment is heat-resistant, has low thermal expansion, and is transparent. Furthermore, it generates little internal stress when laminated with a glass substrate, ensuring good adhesion to inorganic materials during high-temperature processes. Therefore, it is preferably used in fields and products where these properties are valuable. For example, the polyimide film according to the present embodiment is preferably used in image display devices such as liquid crystal displays, organic electroluminescence displays, and electronic paper, printed materials, color filters, flexible displays, optical films, 3D displays, touch panels, transparent conductive film substrates, solar cells, and the like. It is even more preferable to use the polyimide film as a replacement material for glass. In these applications, the thickness of the polyimide film is, for example, from 1 μm to 200 μm, and preferably from 5 μm to 100 μm. The thickness of the polyimide film can be measured using a laser hologram.

[0103] The polyamic acid composition according to this embodiment can be suitably used in a method for producing a polyimide film, which involves applying the polyamic acid composition to a support, heating it to imidize it, and then peeling the polyimide film from the support. The polyamic acid composition according to this embodiment can also be suitably used in a batch-type device production process, which involves applying the polyamic acid composition to a support, heating it to imidize it, forming electronic elements or the like on the formed polyimide film, and then peeling the polyimide film with the electronic elements or the like formed on it from the support. Therefore, this embodiment also includes a method for producing an electronic device, which includes the steps of applying the polyamic acid composition to a support, heating it to imidize it, and then forming electronic elements or the like on the polyimide film formed on the support. Such an electronic device production method may further include the step of peeling the polyimide film with the electronic elements or the like formed on it from the support.

[0104] Examples of the present invention will be described below, but the scope of the present invention is not limited to the following examples. In the following, compounds and reagents are abbreviated as follows: NMP: N-methyl-2-pyrrolidone s-BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride a-BPDA: 2,3,3',4'-biphenyltetracarboxylic dianhydride SFDA: spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride ODPA: 4,4'-oxydiphthalic anhydride 4-BAAB: 4-aminophenyl-4-aminobenzoate

[0105] <Methods for Measuring Physical Properties> First, methods for measuring the physical properties of the 4-BAAB composition, polyamic acid composition, and polyimide (polyimide film) will be described.

[0106] [Gardner Color Index] First, using a petroleum product color tester ("OME-2000" manufactured by Nippon Denshoku Industries Co., Ltd.), the Gardner color index of distilled water was measured in a cell with an optical path length of 1 cm in accordance with ISO 4630, and it was confirmed that the measured value was 0.0. Next, the Gardner color index of each sample (1 mass % NMP solution of each 4-BAAB composition, or each polyamic acid composition diluted with NMP to a polyamic acid concentration of 1 mass %) was measured in the same manner as for distilled water. The Gardner color index of the NMP itself used was measured in the same manner as for distilled water, and it was confirmed that the Gardner color index of NMP was 0.0.

[0107] [APAH] First, using a petroleum product color tester ("OME-2000" manufactured by Nippon Denshoku Industries Co., Ltd.), the APAH of distilled water was measured in a cell with an optical path length of 1 cm in accordance with ISO 2211, and it was confirmed that the measured value was 0. Next, the APAH of each sample (1 mass % NMP solution of each 4-BAAB composition, or each polyamic acid composition diluted with NMP to a polyamic acid concentration of 1 mass %) was measured in the same manner as for distilled water. The APAH of the NMP itself used was also measured in the same manner as for distilled water, and it was confirmed that the APAH of NMP was 0.

[0108] [Internal Stress] Each polyamic acid composition prepared in the following Examples and Comparative Examples was applied using a spin coater to a Corning glass substrate (trade name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm) whose warpage had been measured in advance. The substrate was then heated in air at 120°C for 30 minutes, and then heated in a nitrogen atmosphere at 430°C for 30 minutes to obtain a laminate comprising a 10 μm-thick polyimide film on the glass substrate. To eliminate the influence of water absorption by the polyimide film, the laminate was dried at 120°C for 10 minutes, and the warpage of the laminate was measured at 25°C in a nitrogen atmosphere using a thin film stress measurement device ("FLX-2320-S" manufactured by KLA-Tencor Corporation). The internal stress generated between the glass substrate and the polyimide film was calculated using the Stoney equation from the warpage of the glass substrate before the polyimide film was formed and the warpage of the laminate. When the internal stress was 30 MPa or less, it was evaluated as "internal stress was reduced." On the other hand, when the internal stress was more than 30 MPa, it was evaluated as "internal stress was not reduced."

[0109] [Yellowness Index (YI)] The transmittance of light with a wavelength of 200 nm or more and 800 nm or less was measured for the polyimide film in each laminate obtained in the Examples and Comparative Examples described below using an ultraviolet-visible-near-infrared spectrophotometer ("V-650" manufactured by JASCO Corporation), and the yellowness index (YI) of the polyimide film was calculated using the formula described in JIS K7373-2006. When the YI was 20 or less, the film was evaluated as having "excellent transparency." On the other hand, when the YI was more than 20, the film was evaluated as having "not excellent transparency."

[0110] [400 nm Transmittance and 450 nm Transmittance] The polyimide film in each laminate obtained in the examples and comparative examples described below was measured for the transmittance of light with a wavelength of 400 nm (400 nm transmittance) and the transmittance of light with a wavelength of 450 nm (450 nm transmittance) using an ultraviolet-visible-near-infrared spectrophotometer ("V-650" manufactured by JASCO Corporation).

[0111] [GC / MS Analysis of 4-BAAB Compositions] Each sample (1 mass % NMP solution of each 4-BAAB composition) was analyzed by GC / MS under the following conditions using a GC / MS analyzer combining a gas chromatograph (Agilent Technologies "6890N") and a mass spectrometer (Agilent Technologies "5975inert"). From the obtained GC / MS chart, the area S of the peaks (peaks derived from aminophenols) within the retention time (RT) range of 11.405 to 11.603 minutes was determined. １ and the area S of the peaks (peaks derived from methyl aminobenzoate) in the RT range of 13.196 to 13.256 minutes. ２ and the area S of the peaks (peaks derived from ethyl aminobenzoate) in the RT range of 13.652 to 13.704 minutes. ３ and the area S of the peaks (peaks derived from 4-BAAB) in the RT range of 18.303 to 18.803 minutes. ４ Then, the formula "100 x S １ / S ４ The aminophenol content (unit: mass%) in the 4-BAAB composition was calculated based on the formula "100 × S ２ / S ４ The content of methyl aminobenzoate in the 4-BAAB composition (unit: mass%) was calculated based on the formula "100 × S ３ / S ４ The content of ethyl aminobenzoate in the 4-BAAB composition (unit: mass%) was calculated based on the above.

[0112] (GC / MS analysis conditions) Column: Agilent Technologies "DB-5MS" (0.25 mm ID x 30 m, film thickness 0.25 μm) Carrier gas: Helium gas (1 mL / min) Oven temperature: Set to 40°C and heated to 320°C at 20°C / min Injection port temperature: 280°C Interface temperature: 280°C Ionization chamber temperature: 250°C EM voltage: 1500 eV Measurement mass range: m / z = 29 to 800 Injected sample: 2 wt% acetonitrile solution of sample (1 mass% NMP solution of 4-BAAB composition) (acetonitrile solution containing 2 g of sample in a total volume of 100 mL) Sample injection amount: 1 μL

[0113] [GC / MS Analysis of Polyamic Acid Compositions] GC / MS analysis of each polyamic acid composition was carried out in the same manner as in the above [GC / MS Analysis of 4-BAAB Compositions], except that for each sample (each polyamic acid composition diluted with NMP to a polyamic acid concentration of 1% by mass), a 2 wt. % acetonitrile solution of each polyamic acid composition diluted with NMP to a polyamic acid concentration of 1% by mass was used as the injection sample. The content (unit: ppm by mass) of each impurity relative to the total amount of each sample was calculated from the area values ​​of the peaks in the obtained GC / MS chart.

[0114] <Method of Preparing 4-BAAB Compositions> The methods of preparing 4-BAAB compositions M1 to M7 used in the examples and comparative examples are described below. The raw material, 4-nitrophenyl-4-nitrobenzoate, was synthesized by the method shown below.

[0115] [Method for synthesizing 4-nitrophenyl-4-nitrobenzoate] In a round three-neck flask, 14 g of 4-nitrophenol ("N0220" manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 300 mL of methyl ethyl ketone, and then 15.5 mL of triethylamine was added to obtain Solution S. ｐｈ Separately, 18.6 g of 4-nitrobenzoyl chloride ("N0176" manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 150 mL of 1,4-dioxane to obtain solution S. ｂｅ Then, the solution S in the flask was ｐｈ After cooling to a temperature of 0°C, solution S ｐｈWhile stirring, solution S ｂｅ Solution S ｐｈ The solution was added dropwise to the flask over a period of 1 hour. The contents of the flask were then stirred for 3 hours in an atmosphere at 23°C, and the precipitated salt was filtered off to obtain a homogeneous solution. The solvent was then removed from the obtained solution using an evaporator to obtain a powder. The obtained powder was then washed twice with a 5% by mass aqueous solution of sodium hydrogen carbonate, then washed twice with distilled water, and dried under reduced pressure at 80°C for 12 hours to obtain 4-nitrophenyl-4-nitrobenzoate.

[0116] [Preparation of 4-BAAB Composition M7] 15 g of FeSO was placed in a round, three-necked flask. ４ The heptahydrate, 30 g of methanol, and 30 g of distilled water were added to the flask, and the contents were stirred. Then, 5 g of 4-nitrophenyl-4-nitrobenzoate was added to the flask. The contents of the flask were refluxed for 30 minutes while stirring under an atmosphere at 100°C. Then, 25 g of KOH (potassium hydroxide) was added to the flask, and the contents of the flask were stirred for another 30 minutes. The contents of the flask were then transferred to a separatory funnel, and 100 g of toluene was added to the separatory funnel to extract the organic layer. This process was repeated three times. The toluene in the resulting organic layer was evaporated, and the mixture was dried under reduced pressure at 70°C for 12 hours to obtain powder P1. The resulting powder P1 was recrystallized using a mixed solvent of chloroform and ethanol (mass ratio: chloroform / ethanol = 70 / 30). The resulting precipitate was then washed with ethanol and dried under reduced pressure at 70°C for 12 hours to obtain 4-BAAB composition M7.

[0117] [Preparation of 4-BAAB Composition M5] Powder P1 was obtained in the same manner as in [Preparation of 4-BAAB Composition M7] above, and then the obtained powder P1 was dissolved in dimethylacetamide in a round three-neck flask. Next, a small amount of activated carbon was added to the obtained dimethylacetamide solution (solid content concentration: 10% by mass), and the contents of the flask were stirred for 3 hours under an atmosphere at a temperature of 50°C. Next, the activated carbon was filtered from the contents of the flask, and the solvent was distilled off from the obtained dimethylacetamide solution, followed by drying under reduced pressure at a temperature of 70°C for 12 hours to obtain 4-BAAB Composition M5.

[0118] [Preparation of 4-BAAB Composition M6] The 4-BAAB Composition M5 obtained by the above procedure was recrystallized using a mixed solvent of chloroform and ethanol (mass ratio: chloroform / ethanol = 70 / 30). The resulting precipitate was then washed with ethanol and dried under reduced pressure at 70°C for 12 hours to obtain 4-BAAB Composition M6.

[0119] [Preparation of 4-BAAB Composition M4] 4-Nitrophenyl-4-nitrobenzoate was dissolved in dimethylacetamide in a round three-neck flask. Next, a small amount of activated carbon was added to the obtained dimethylacetamide solution (solid content concentration: 10% by mass), and the contents of the flask were stirred for 3 hours under an atmosphere at a temperature of 50°C. Next, the activated carbon was filtered out from the contents of the flask, and the solvent was distilled off from the obtained dimethylacetamide solution, followed by drying under reduced pressure at a temperature of 70°C for 12 hours to obtain powder P2. Next, 15 g of FeSO was added to the round three-neck flask. ４ The heptahydrate, 30 g of methanol, and 30 g of distilled water were added to the flask, and the contents were stirred. Then, 5 g of powder P2 was added to the flask. The contents of the flask were refluxed for 30 minutes while stirring in an atmosphere at 100°C, after which 25 g of KOH (potassium hydroxide) was added to the flask, and the contents of the flask were stirred for an additional 30 minutes. The contents of the flask were then transferred to a separatory funnel, and 100 g of toluene was added to the separatory funnel to extract the organic layer. This process was repeated three times. The toluene in the resulting organic layer was evaporated, and the mixture was dried under reduced pressure at 70°C for 12 hours to obtain 4-BAAB composition M4.

[0120] [Preparation of 4-BAAB Composition M3] The 4-BAAB composition M4 obtained by the above procedure was recrystallized using a mixed solvent of chloroform and ethanol (mass ratio: chloroform / ethanol = 70 / 30). The resulting precipitate was then washed with ethanol and dried under reduced pressure at 70°C for 12 hours to obtain 4-BAAB composition M3.

[0121] [Preparation of 4-BAAB Composition M2] 4-Nitrophenyl-4-nitrobenzoate was recrystallized using a mixed solvent of chloroform and ethanol (mass ratio: chloroform / ethanol = 70 / 30). The resulting precipitate was then washed with ethanol and dried under reduced pressure at 70°C for 12 hours to obtain powder P3. The resulting powder P3 was then dissolved in dimethylacetamide in a round three-neck flask. A small amount of activated carbon was then added to the resulting dimethylacetamide solution (solid content concentration: 10% by mass), and the contents of the flask were stirred for 3 hours under an atmosphere at 50°C. The activated carbon was then filtered from the flask contents, and the solvent was then distilled off from the resulting dimethylacetamide solution. The solution was then dried under reduced pressure at 70°C for 12 hours to obtain powder P4. Next, 15 g of FeSO was added to the round three-neck flask. ４ The heptahydrate, 30 g of methanol, and 30 g of distilled water were added to the flask, and the contents were stirred. Then, 5 g of powder P4 was added to the flask. The contents of the flask were refluxed for 30 minutes while stirring in an atmosphere at 100°C. Then, 25 g of KOH (potassium hydroxide) was added to the flask, and the contents of the flask were stirred for another 30 minutes. The contents of the flask were then transferred to a separatory funnel, and 100 g of toluene was added to the separatory funnel to extract the organic layer. This process was repeated three times. The toluene in the resulting organic layer was evaporated, and the mixture was dried under reduced pressure at 70°C for 12 hours to obtain 4-BAAB composition M2.

[0122] [Preparation of 4-BAAB Composition M1] 4-Nitrophenyl-4-nitrobenzoate was dissolved in dimethylacetamide in a round three-neck flask. A small amount of activated carbon was then added to the resulting dimethylacetamide solution (solid content: 10% by mass), and the contents of the flask were stirred for 3 hours under an atmosphere at 50°C. The activated carbon was then filtered from the flask contents, and the solvent was distilled off from the resulting dimethylacetamide solution. The solution was then dried under reduced pressure at 70°C for 12 hours to obtain Powder P5. The resulting Powder P5 was then recrystallized using a mixed solvent of chloroform and ethanol (mass ratio: chloroform / ethanol = 70 / 30). The resulting precipitate was then washed with ethanol and dried under reduced pressure at 70°C for 12 hours to obtain Powder P6. Next, 15 g of FeSO was added to a round three-neck flask. ４ The heptahydrate, 30 g of methanol, and 30 g of distilled water were added to the flask, and the contents were stirred. Then, 5 g of powder P6 was added to the flask. The contents of the flask were refluxed for 30 minutes while stirring in an atmosphere at 100°C. Then, 25 g of KOH (potassium hydroxide) was added to the flask, and the contents of the flask were stirred for another 30 minutes. The contents of the flask were then transferred to a separatory funnel, and 100 g of toluene was added to the separatory funnel to extract the organic layer. This process was repeated three times. The toluene in the resulting organic layer was evaporated, and the mixture was dried under reduced pressure at 70°C for 12 hours to obtain 4-BAAB composition M1.

[0123] For 4-BAAB compositions M1 to M7, the Gardner color number, APAH, the content of aminophenol in the 4-BAAB composition, the content of methyl aminobenzoate in the 4-BAAB composition, and the content of ethyl aminobenzoate in the 4-BAAB composition are shown in Table 1.

[0124]

[0125] <Preparation of Polyimide Film> The methods for preparing polyimide films (laminates) in Examples and Comparative Examples will be described below. Note that the preparation of the polyamic acid compositions used for preparing the polyimide films was carried out in a nitrogen atmosphere in all cases.

[0126] Example 1 56.6 g of NMP was placed in a 300 mL separable glass flask equipped with a stirrer equipped with a stainless steel stirring rod and a nitrogen inlet tube as the organic solvent for polymerization. Next, while stirring the contents of the flask, 4.393 g of 4-BAAB composition M1 was added to the flask and dissolved. Next, 5.607 g of s-BPDA was added to the contents of the flask, and the contents of the flask were stirred for 24 hours under an atmosphere at 23°C to obtain a polyamic acid composition. The obtained polyamic acid composition was applied to a Corning glass substrate (trade name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm) using a spin coater, heated in air at 80°C for 30 minutes, and then heated in a nitrogen atmosphere at 430°C for 30 minutes to obtain a laminate (the laminate of Example 1) comprising a 10 μm-thick polyimide film on the glass substrate.

[0127] [Examples 2 to 7 and Comparative Examples 1 to 6] Laminates of Examples 2 to 7 and Comparative Examples 1 to 6 were obtained in the same manner as in Example 1, except that the type and amount of acid dianhydride used, and the type and amount of 4-BAAB composition used were changed as shown in Table 2. In Examples 2 to 7 and Comparative Examples 1 to 6, the total amount of acid dianhydride used in preparing the polyamic acid composition was the same as the total amount of acid dianhydride used in preparing the polyamic acid composition in Example 1.

[0128] Table 2 shows the type and amount of acid dianhydride used, as well as the type and amount of 4-BAAB composition used, for Examples 1 to 7 and Comparative Examples 1 to 6. Table 3 also shows the Gardner color number of the polyamic acid composition used, the APAH of the polyamic acid composition used, the aminophenol content in the polyamic acid composition used, the methyl aminobenzoate content in the polyamic acid composition used, the ethyl aminobenzoate content in the polyamic acid composition used, the YI of the polyimide film, the 400 nm transmittance and 450 nm transmittance of the polyimide film, and the internal stress for Examples 1 to 7 and Comparative Examples 1 to 6.

[0129] In Table 2, "-" indicates that the component was not used. In Table 3, "-" indicates that the component was not measured. In Table 2, the values ​​in the "Acid Dianhydride" column indicate the content (unit: mol%) of each acid dianhydride relative to the total amount (100 mol%) of acid dianhydrides used. In Table 2, the values ​​in the "4-BAAB Composition" column indicate the charged ratio (unit: mol%) of 4-BAAB in the 4-BAAB composition used relative to the total amount (100 mol%) of acid dianhydrides used. In each of Examples 1 to 7 and Comparative Examples 1 to 6, the molar fraction of each polyamic acid residue in the prepared polyamic acid composition was consistent with the molar fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the polyamic acid.

[0130]

[0131]

[0132] In Examples 1 to 7, the content of 4-BAAB residues in the polyamic acid contained in the polyamic acid composition used was 70 mol % or more relative to all diamine residues constituting the polyamic acid. As shown in Table 3, in Examples 1 to 7, the content of aminophenol in the polyamic acid composition used was 1 ppm by mass or more and 30 ppm by mass or less. In Examples 1 to 7, the content of methyl aminobenzoate in the polyamic acid composition used was 0.01 ppm by mass or more and 0.10 ppm by mass or less.

[0133] As shown in Table 3, in Examples 1 to 7, the YI was 20 or less. Therefore, the polyimide films obtained in Examples 1 to 7 were excellent in transparency. In Examples 1 to 7, the internal stress was 30 MPa or less. Therefore, the laminates obtained in Examples 1 to 7 were able to reduce the internal stress.

[0134] As shown in Table 3, the aminophenol content in the polyamic acid compositions used exceeded 30 ppm by mass in Comparative Examples 3 to 6. In Comparative Examples 1 and 2, the methyl aminobenzoate content in the polyamic acid compositions used exceeded 0.10 ppm by mass.

[0135] As shown in Table 3, in Comparative Examples 1 to 6, the YI exceeded 20. Therefore, the polyimide films obtained in Comparative Examples 1 to 6 did not have excellent transparency.

[0136] The above results demonstrate that the present invention can provide a polyamic acid composition that can produce a polyimide having excellent transparency while reducing internal stress.

Claims

1. A polyamic acid composition comprising a polyamic acid, an organic solvent, an aminophenol, and methyl aminobenzoate, wherein the polyamic acid has a 4-aminophenyl-4-aminobenzoate residue as a diamine residue, and the content of the 4-aminophenyl-4-aminobenzoate residue is 70 mol % or more based on all diamine residues constituting the polyamic acid, the content of the aminophenol obtained by gas chromatography mass spectrometry using a sample obtained by diluting the polyamic acid composition to a polyamic acid concentration of 1% by mass is 1 ppm by mass or more and 30 ppm by mass or less based on the total amount of the sample, and the content of the methyl aminobenzoate obtained by gas chromatography mass spectrometry using a sample obtained by diluting the polyamic acid composition to a polyamic acid concentration of 1% by mass is 0.01 ppm by mass or more and 0.10 ppm by mass or less based on the total amount of the sample.

2. The polyamic acid composition according to claim 1, wherein the Gardner color number and the Hazen color number, measured in a cell having an optical path length of 1 cm using a sample obtained by diluting the polyamic acid composition to a polyamic acid concentration of 1% by mass, are 0.3 or less and 10 or less, respectively.

3. The polyamic acid composition according to claim 1, wherein the polyamic acid has, as a tetracarboxylic dianhydride residue, one or more selected from the group consisting of a tetravalent organic group represented by the following chemical formula (1), a tetravalent organic group represented by the following chemical formula (2), a tetravalent organic group represented by the following chemical formula (3), a tetravalent organic group represented by the following chemical formula (4), a tetravalent organic group represented by the following chemical formula (5), a tetravalent organic group represented by the following chemical formula (6), a tetravalent organic group represented by the following chemical formula (7), a tetravalent organic group represented by the following chemical formula (8), a tetravalent organic group represented by the following chemical formula (9), and a tetravalent organic group represented by the following chemical formula (10).

4. A polyimide which is an imidized product of the polyamic acid contained in the polyamic acid composition according to any one of claims 1 to 3.

5. A polyimide film comprising the polyimide according to claim 4.

6. The polyimide film according to claim 5, having a yellowness index of 20 or less.

7. The polyimide film according to claim 5, which has a transmittance of 8% or more for light with a wavelength of 400 nm.

8. A laminate comprising a support and the polyimide film according to claim 5.

9. The laminate according to claim 8, wherein the support is a glass substrate, and the internal stress between the polyimide film and the glass substrate is 30 MPa or less.

10. An electronic device comprising the polyimide film according to claim 5 and an electronic element disposed on said polyimide film.

11. A method for producing a polyamic acid composition according to any one of claims 1 to 3, comprising step S1 of reacting a diamine with a tetracarboxylic dianhydride in an organic solvent, wherein the diamine contains 4-aminophenyl-4-aminobenzoate, the content of the 4-aminophenyl-4-aminobenzoate being 70 mol % or more based on the total amount of the diamine, the 4-aminophenyl-4-aminobenzoate being supplied to step S1 as a raw monomer containing impurities, the impurities including aminophenol and methyl aminobenzoate, and the Gardner color number and Hazen color number, measured using a 1 mass % N-methyl-2-pyrrolidone solution of the raw monomer in a cell having an optical path length of 1 cm, are 3.0 or less and 200 or less, respectively.

12. The method for producing a polyamic acid composition according to claim 11, wherein the content of said aminophenol in said raw material monomers is 0.60 mass% or less based on the total amount of said 4-aminophenyl-4-aminobenzoate, and the content of said methyl aminobenzoate in said raw material monomers is 0.60 mass% or less based on the total amount of said 4-aminophenyl-4-aminobenzoate.

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