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

Abstract

A polyamic acid composition comprises a plasticizer and polyamic acid containing the structural unit given by general formula (1). A polyimide is an imidized product from polyamic acid containing the structural unit given by general formula (1). A polyimide film contains an imidized product from polyamic acid containing the structural unit given by general formula (1). A laminate has a support and a polyimide film that contains an imidized product from polyamic acid containing the structural unit given by general formula (1). An electronic device has: a polyimide film that contains an imidized product from polyamic acid containing the structural unit given by general formula (1), and an electronic element disposed on the polyimide film.　

Description

[Technical Field]

[0001] The present invention relates to a polyamic acid composition, a polyimide, a polyimide film, a laminate, a method for producing the laminate, and an electronic device. The present invention also 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. [Background technology]

[0002] Rapid advances in electronic devices, such as displays (LCDs, OLEDs, electronic paper, etc.), solar cells, and touch panels, have led to devices becoming thinner, lighter, and more flexible. In these devices, polyimide is being used as the substrate material instead of glass.

[0003] These devices require various electronic elements, such as thin-film transistors and transparent electrodes, to be formed on the 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 close 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 displays, 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 LCD displays, or when sensors or camera modules are placed on the back of the substrate to make smartphones and other devices full-screen (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] To reduce the coloration of polyimides, there are known techniques for suppressing the formation of CT complexes using aliphatic monomers (Patent Documents 1 and 2), and a technique for increasing transparency using monomers containing fluorine atoms or sulfur atoms (Patent Document 3).

[0007] The polyimides described in Patent Documents 1 and 2 have high transparency and low CTE, but because they have an aliphatic structure, they have a low thermal decomposition temperature, making them difficult to apply to high-temperature processes when forming electronic devices. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-29177 [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-41530 [Patent Document 3] Japanese Patent Application Laid-Open No. 2014-70139 Summary of the Invention [Problem to be solved by the invention]

[0009] The inventors have found through their investigations that the polyimide described in Patent Document 3 contains fluorine atoms, and therefore may generate hydrogen fluoride during high-temperature processes. The generation of hydrogen fluoride may result in poor adhesion between the polyimide and a barrier film or the like, or may cause corrosion of electronic elements provided on the polyimide film.

[0010] The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a polyimide and a polyamic acid composition as its precursor that exhibit reduced coloration, excellent transparency, high heat resistance, and suppresses the generation of hydrogen fluoride during high-temperature processes. Another aim is to provide a product or component that requires heat resistance and transparency and is manufactured using the polyimide and polyamic acid composition. In particular, the present invention aims to provide a product or component in which the polyimide film of the present invention is formed on the surface of an inorganic material such as glass, metal, metal oxide, or single-crystal silicon. [Means for solving the problem]

[0011] As a result of extensive research, the present inventors have found that a polyimide obtained from a composition containing a specific polyamic acid and a plasticizer exhibits reduced coloration, excellent transparency, and high heat resistance, and is capable of suppressing the generation of hydrogen fluoride during high-temperature processes, thereby completing the present invention.

[0012] The polyamic acid composition according to the present invention contains a polyamic acid containing a structural unit represented by the following general formula (1) and a plasticizer.

[0013] [ka]

[0014] In the general formula (1), R 1 and R 2 each independently represents a hydrogen atom, a monovalent aliphatic group, or a monovalent aromatic group, and X represents a tetravalent organic group.

[0015] In the polyamic acid composition according to one embodiment of the present invention, R 1 and R 2 Both represent hydrogen atoms.

[0016] In the polyamic acid composition according to one embodiment of the present invention, X in the general formula (1) is at least one selected from the group consisting of 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), and a tetravalent organic group represented by the following chemical formula (5):

[0017] [ka]

[0018] In the polyamic acid composition according to one embodiment of the present invention, the content of the structural unit represented by the general formula (1) is 50 mol % or more and 100 mol % or less based on all structural units of the polyamic acid.

[0019] In the polyamic acid composition according to one embodiment of the present invention, the amount of the plasticizer is 20 parts by weight or less based on 100 parts by weight of the polyamic acid.

[0020] In the polyamic acid composition according to one embodiment of the present invention, the plasticizer is at least one selected from the group consisting of phosphorus-containing compounds, polyalkylene glycols, and aliphatic dibasic acid esters.

[0021] The polyamic acid composition according to one embodiment of the present invention further contains an organic solvent.

[0022] The polyimide according to the present invention is an imidized product of the polyamic acid contained in the polyamic acid composition according to the present invention.

[0023] The polyimide according to the present invention preferably has a 1% weight loss temperature of 500° C. or higher.

[0024] The polyimide film according to the present invention contains the polyimide according to the present invention.

[0025] The polyimide film according to the present invention preferably has a yellowness index of 20 or less.

[0026] The laminate according to the present invention has a support and the polyimide film according to the present invention.

[0027] The method for producing a laminate according to the present invention comprises applying the polyamic acid composition according to one embodiment of the present invention onto a support to form a coating film containing a polyamic acid and a plasticizer, and then heating the coating film to imidize the polyamic acid.

[0028] An electronic device according to the present invention comprises the polyimide film according to the present invention and an electronic element disposed on the polyimide film. [Effects of the Invention]

[0029] The polyimide produced using the polyamic acid composition of the present invention exhibits reduced coloration, excellent transparency and heat resistance, and can suppress the generation of hydrogen fluoride during high-temperature processes. Therefore, the polyimide produced using the polyamic acid composition of the present invention is suitable as a material for electronic devices that require low coloration, transparency, and heat resistance and are manufactured through high-temperature processes. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a graph showing the results obtained by analyzing the polyimide films according to Example 18 and Comparative Example 5 using a quadrupole mass spectrometer. DETAILED DESCRIPTION OF THE INVENTION

[0031] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited to these.

[0032] 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 (6) (hereinafter, sometimes referred to as "structural unit (6)"). In this specification, not only polyamic acid but also polyamic acid esters (polyamic acid alkyl esters, polyamic acid aryl esters, etc.) are referred to as "polyamic acid."

[0033] [ka]

[0034] In general formula (6), R 3 and R 4 each independently represents a hydrogen atom, a monovalent aliphatic group, or a monovalent aromatic group; A 1 represents, for example, a tetracarboxylic dianhydride residue (a tetravalent organic group derived from a tetracarboxylic dianhydride), and A 2 represents, for example, a diamine residue (a divalent organic group derived from a diamine).

[0035] The content of the structural unit (6) 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%.

[0036] The "1% weight loss temperature" is the temperature measured when the weight of the polyimide at a measurement temperature of 150°C is reduced by 1% by weight relative to the reference weight (100% by weight). The 1% weight loss temperature is measured by the same method as in the examples described below or a method equivalent thereto.

[0037] "m / z" is a measurement value that can be read from the horizontal axis of a mass spectrum, which is the measurement result of mass spectrometry. It is "a dimensionless quantity obtained by dividing the mass of an ion by the unified atomic mass unit (Dalton), and then dividing that quantity by the absolute value of the charge on the ion."

[0038] "Plasticizer" refers to a material that exists in liquid form during imidization of at least a portion of the polyamic acid.

[0039] Hereinafter, the compound name may be followed by "system" to refer to the compound and its derivatives collectively. When the compound name is followed by "system" to refer to the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, tetracarboxylic dianhydrides may be referred to as "acid dianhydrides."

[0040] The polyamic acid composition according to this embodiment contains a polyamic acid containing a structural unit represented by the following general formula (1) (hereinafter, sometimes referred to as "structural unit (1)") and a plasticizer.

[0041] [ka]

[0042] In general formula (1), R 1 and R 2 each independently represents a hydrogen atom, a monovalent aliphatic group, or a monovalent aromatic group, and X represents a tetravalent organic group. 1 and R 2 are each independently preferably a hydrogen atom, a methyl group or an ethyl group, and R 1 and R 2 However, it is more preferable that both represent a hydrogen atom. 1 and R 2 However, the structural unit that represents a hydrogen atom in both cases is called structural unit (1).

[0043] The polyamic acid composition according to the present embodiment contains a polyamic acid containing the structural unit (1) and a plasticizer. Therefore, when a polyimide is produced using the polyamic acid composition according to the present embodiment, a polyimide can be obtained that is reduced in coloration, has excellent transparency and heat resistance, and is capable of suppressing the generation of hydrogen fluoride during high-temperature processes.

[0044] The structural unit (1) has a partial structure derived from 2,2'-bis(trifluoromethyl)benzidine (hereinafter, sometimes referred to as "TFMB"). That is, the structural unit (1) is A in the above-mentioned general formula (6). 2 It has TFMB residues as a

[0045] TFMB has a rigid structure and is suitable as a raw material (monomer) for polyimides with a high glass transition temperature (excellent heat resistance). In addition, TFMB contains a trifluoromethyl group, making it suitable as a raw material (monomer) for polyimides with reduced coloration and high transparency.

[0046] When synthesizing a polyamic acid containing the structural unit (1) (hereinafter, sometimes referred to as "polyamic acid (1)"), diamines other than TFMB may be used as monomers as long as the performance of the polyamic acid is not impaired. Examples of diamines other than TFMB include 4-aminophenyl-4-aminobenzoate (hereinafter, sometimes referred to as "4-BAAB"), 1,4-diaminocyclohexane, p-phenylenediamine, m-phenylenediamine, 9,9-bis(4-aminophenyl)fluorene, 4,4'-oxydianiline, 3,4'-oxydianiline, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, and N,N'-bis(4-aminophenyl). Examples of the methylaminobenzoic acid include 4,4'-diamino-3,3'-dihydroxybiphenyl, 4,4'-methylenebis(cyclohexaneamine), 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 4,4'-diamino-3,3'-dihydroxybiphenyl, 4,4'-methylenebis(cyclohexaneamine), 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and derivatives thereof, and these may be used alone or in combination of two or more.

[0047] From the viewpoint of improving heat resistance, 4-BAAB is preferred as a diamine other than TFMB. Therefore, from the viewpoint of improving heat resistance, it is preferred that polyamic acid (1) has a 4-BAAB residue. 4-BAAB has a rigid structure, so it is suitable as a raw material (monomer) for polyimides with excellent heat resistance. Furthermore, 4-BAAB, which has a rigid structure, is also suitable as a raw material (monomer) for polyimides with high mechanical strength while suppressing the generation of internal stress.

[0048] In order to obtain a polyimide having reduced coloration, excellent heat resistance, and higher transparency, it is preferable that the polyamic acid (1) has only TFMB residues as diamine residues, or has only TFMB residues and 4-BAAB residues as diamine residues.

[0049] In order to obtain a polyimide with reduced coloration and superior heat resistance, the content of TFMB residues relative to all diamine residues constituting the polyamic acid (1) is preferably 30 mol% or more, more preferably 40 mol% or more, even more preferably 50 mol% or more, even more preferably 60 mol% or more, and may be 70 mol% or more, 80 mol% or more, or 90 mol% or more, or even 100 mol%.

[0050] In order to obtain a polyimide having reduced coloration and superior heat resistance, the content of the structural unit (1) is preferably 30 mol% or more and 100 mol% or less, more preferably 40 mol% or more and 100 mol% or less, even more preferably 50 mol% or more and 100 mol% or less, and even more preferably 60 mol% or more and 100 mol% or less, and may be 70 mol% or more and 100 mol% or less, 80 mol% or more and 100 mol% or less, or 90 mol% or more and 100 mol% or less, based on all structural units of the polyamic acid (1).

[0051] When the polyamic acid (1) has 4-BAAB residues, in order to obtain a polyimide having superior heat resistance, the content of 4-BAAB residues relative to all diamine residues constituting the polyamic acid (1) is preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more. Furthermore, when the polyamic acid (1) has 4-BAAB residues, in order to obtain a polyimide having reduced coloration, the content of 4-BAAB residues relative to all diamine residues constituting the polyamic acid (1) is preferably 70 mol% or less, more preferably 60 mol% or less, even more preferably 50 mol% or less, and even more preferably 40 mol% or less.

[0052] When the polyamic acid (1) contains TFMB residues and 4-BAAB residues, in order to obtain a polyimide with reduced coloration, better heat resistance, and higher transparency, the total content of TFMB residues and 4-BAAB residues relative to all diamine residues constituting the polyamic acid (1) is preferably 50 mol % or more, more preferably 60 mol % or more, even more preferably 70 mol % or more, and even more preferably 80 mol % or more, and may be 90 mol % or more, or even 100 mol %.

[0053] Examples of tetracarboxylic dianhydrides (acid dianhydrides that provide X in general formula (1)) for synthesizing polyamic acid (1) include pyromellitic dianhydride (hereinafter sometimes referred to as "PMDA"), 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes referred to as "BPDA"), p-phenylenebis(trimellitate anhydride), 2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (hereinafter sometimes referred to as "BPAF"). Examples of suitable dianhydrides include 4,4'-oxydiphthalic anhydride (hereinafter sometimes referred to as "ODPA"), 4,4'-(hexafluoroisopropylidene)diphthalic anhydride, 9,9-bis(trifluoromethyl)xanthenetetracarboxylic dianhydride, 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, and derivatives thereof, and these may be used alone or in combination.

[0054] In order to obtain a polyimide that can further suppress the generation of hydrogen fluoride during a high-temperature process, the acid dianhydride that provides X in general formula (1) is preferably an acid dianhydride that does not contain a fluorine atom. In other words, in order to obtain a polyimide that can further suppress the generation of hydrogen fluoride during a high-temperature process, it is preferable that the acid dianhydride residue that constitutes polyamic acid (1) does not contain a fluorine atom.

[0055] The acid dianhydride that provides X in general formula (1) is preferably one or more selected from the group consisting of PMDA, BPDA, BPAF, and ODPA. That is, the polyamic acid (1) preferably has, as X in general formula (1), one or more selected from the group consisting of a PMDA residue, a BPDA residue, a BPAF residue, and an ODPA residue.

[0056] The PMDA residue is a tetravalent organic group represented by the following chemical formula (2). The BPDA residue is a tetravalent organic group represented by the following chemical formula (3). The BPAF residue is a tetravalent organic group represented by the following chemical formula (4). The ODPA residue is a tetravalent organic group represented by the following chemical formula (5).

[0057] [ka]

[0058] To obtain a polyimide having excellent heat resistance, reduced internal stress, and high mechanical strength, the polyamic acid (1) preferably contains one or more residues selected from the group consisting of PMDA residues and BPDA residues.To obtain a polyimide having higher transparency, the polyamic acid (1) preferably contains one or more residues selected from the group consisting of BPAF residues and ODPA residues.

[0059] When polyamic acid (1) contains one or more selected from the group consisting of PMDA residues, BPDA residues, BPAF residues, and ODPA residues, the total content of PMDA residues, BPDA residues, BPAF residues, and ODPA residues relative to all dianhydride residues constituting polyamic acid (1) is preferably 60 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, and may even be 100 mol%. When the total content of PMDA residues, BPDA residues, BPAF residues, and ODPA residues relative to all dianhydride residues constituting polyamic acid (1) is 60 mol% or more, a polyimide can be obtained that is excellent in transparency and heat resistance, can reduce internal stress, and has high mechanical strength.

[0060] When the polyamic acid (1) has a PMDA residue, in order to obtain a polyimide having excellent heat resistance, reduced internal stress, and high mechanical strength, the content of the PMDA residue is preferably 30 mol % or more and 100 mol % or less, more preferably 40 mol % or more and 90 mol % or less, and even more preferably 50 mol % or more and 80 mol % or less, based on the total acid dianhydride residues constituting the polyamic acid (1).

[0061] When the polyamic acid (1) has BPDA residues, in order to obtain a polyimide having excellent heat resistance, reduced internal stress, and high mechanical strength, the content of BPDA residues is preferably 10 mol % or more and 100 mol % or less, and more preferably 10 mol % or more and 90 mol % or less, based on the total acid dianhydride residues constituting the polyamic acid (1).

[0062] When the polyamic acid (1) has BPAF residues, in order to obtain a polyimide with higher transparency, the content of BPAF residues is preferably 1 mol % or more, more preferably 3 mol % or more, even more preferably 5 mol % or more, and may even be 10 mol % or more, based on the total acid dianhydride residues constituting the polyamic acid (1). Furthermore, when the polyamic acid (1) has BPAF residues, in order to reduce internal stress, the content of BPAF residues is preferably 50 mol % or less, more preferably 40 mol % or less, and even more preferably 30 mol % or less, based on the total acid dianhydride residues constituting the polyamic acid (1).

[0063] When the polyamic acid (1) has ODPA residues, in order to obtain a polyimide with higher transparency, the content of ODPA residues is preferably 1 mol % or more, more preferably 3 mol % or more, and even more preferably 5 mol % or more, based on the total acid dianhydride residues constituting the polyamic acid (1). Furthermore, when the polyamic acid (1) has ODPA residues, in order to reduce internal stress, the content of ODPA residues is preferably 50 mol % or less, more preferably 40 mol % or less, and even more preferably 30 mol % or less, based on the total acid dianhydride residues constituting the polyamic acid (1).

[0064] Polyamic acid (1) can be synthesized by a known general method, for example, by reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. A specific example of a method for synthesizing polyamic acid (1) will be described. First, a diamine is dissolved or dispersed in a slurry state in an organic solvent in an inert gas atmosphere such as argon or nitrogen to prepare a diamine solution. Then, tetracarboxylic dianhydride is added to the diamine solution after being dissolved or dispersed in a slurry state in the organic solvent, or in a solid state.

[0065] When synthesizing polyamic acid (1) using a diamine and a tetracarboxylic dianhydride, the desired polyamic acid (1) (a polymer of diamine and 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 polyamic acid (1) corresponds, for example, to the molar fraction of each monomer (diamine and tetracarboxylic dianhydride) used in synthesizing polyamic acid (1). Furthermore, blending two polyamic acids can also produce polyamic acid (1) containing multiple tetracarboxylic dianhydride residues and multiple diamine residues. The temperature conditions for the reaction between diamine and tetracarboxylic dianhydride, i.e., the synthesis reaction of polyamic acid (1), 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 polyamic acid (1) is, for example, in the range of 10 minutes to 30 hours.

[0066] The organic solvent used in the synthesis of polyamic acid (1) is preferably a solvent capable of dissolving the tetracarboxylic dianhydride and diamine used, and more preferably a solvent capable of dissolving the polyamic acid (1) produced. Examples of organic solvents that can be used in the synthesis of polyamic acid (1) include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea; sulfoxide-based solvents such as dimethyl sulfoxide; sulfone-based solvents such as diphenyl sulfone and tetramethyl sulfone; amide-based solvents such as N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), and hexamethylphosphoric triamide; ester-based solvents such as γ-butyrolactone; alkyl halide-based solvents such as chloroform and methylene chloride; aromatic hydrocarbon-based solvents such as benzene and toluene; phenol-based solvents such as phenol and cresol; ketone-based solvents such as cyclopentanone; and ether-based solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, and p-cresol methyl ether. These solvents are usually used alone, but two or more may be used in combination as needed. In order to enhance the solubility and reactivity of polyamic acid (1), the organic solvent used in the synthesis reaction of polyamic acid (1) is preferably one or more solvents selected from the group consisting of amide solvents, ketone solvents, ester solvents, and ether solvents, and more preferably amide solvents (more specifically, DMF, DMAC, NMP, etc.). The synthesis reaction of polyamic acid (1) is preferably carried out under an inert gas atmosphere such as argon or nitrogen.

[0067] The weight-average molecular weight of polyamic acid (1) varies depending on its intended use, 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 facilitates the formation of coating films or polyimide films from polyamic acid (1) or polyimides obtained using polyamic acid (1). On the other hand, a weight-average molecular weight of 1,000,000 or less exhibits sufficient solubility in solvents, allowing the use of a polyamic acid composition described below to produce coating films or polyimide films with smooth surfaces and uniform thicknesses. The weight-average molecular weight used here refers to a polyethylene oxide-equivalent value measured using gel permeation chromatography (GPC).

[0068] Methods for controlling the molecular weight of polyamic acid (1) 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 polyamic acid (1) is between 0.95 and 1.05. The molar ratio is the ratio of the total amount of diamines used to synthesize polyamic acid (1) to the total amount of dianhydrides used to synthesize polyamic acid (1) (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 polyamic acid (1).

[0069] Next, the effect of the plasticizer (hereinafter sometimes simply referred to as "plasticizer") contained in the polyamic acid composition according to this embodiment will be described. Generally, to obtain a transparent polyimide film, it is only necessary, in principle, to design a polyimide with a large HOMO-LUMO band gap. Therefore, TFMB, which has low electron donating properties, is effective for obtaining a transparent polyimide film. On the other hand, TFMB with low electron donating properties is expected to have a slow reaction rate and a slow imidization rate due to its low nucleophilicity. The inventors of the present invention have investigated the imidization rate and have obtained the following findings. In other words, when the imidization rates of a typical colored polyimide obtained from BPDA and p-phenylenediamine were compared with those of transparent polyimides obtained from PMDA or BPDA and TFMB, the colored polyimide was over 90% imidized at an imidization reaction temperature of 300°C and nearly 100% imidized at an imidization reaction temperature of 350°C, whereas the transparent polyimide was only about 75% imidized at an imidization reaction temperature of 300°C and only about 80% imidized even at an imidization reaction temperature of 350°C, showing a clear difference in the imidization rate.

[0070] Generally, the driving forces for the dehydration ring closure of polyamic acid to polyimide during thermal imidization are largely due to thermal molecular motion and the plasticizing effect of the solvent. Therefore, for complete imidization, it is desirable to treat the polyimide at temperatures above its glass transition temperature. However, when a rigid dianhydride such as PMDA is combined with TFMB, the resulting polyimide has a glass transition temperature exceeding 400 °C, which may be higher than the heat treatment temperature used for film formation. Therefore, imidization may not be complete during the imidization reaction between a rigid dianhydride such as PMDA and TFMB. This can lead to imidization of unreacted sites in the polyimide film during high-temperature processes (e.g., annealing of TFTs), which can lead to outgassing (e.g., hydrogen fluoride) due to the formation of low-molecular-weight components from the polyimide film, potentially resulting in barrier film peeling and TFT corrosion. In contrast, in the polyamic acid composition according to the present embodiment, the use of a plasticizer imparts sufficient molecular motion to the polyamic acid (1) during imidization, thereby not only ensuring complete imidization but also suppressing depolymerization of the polyamic acid (1) and suppressing the generation of outgassing (particularly hydrogen fluoride). Furthermore, in the polyamic acid composition according to the present embodiment, the molecular motion imparted to the polyamic acid (1) facilitates solvent removal, reducing the amount of solvent remaining in the film (polyimide film) and reducing film discoloration.

[0071] The inventors' investigations have revealed that imidization in the presence of a plasticizer reduces the amount of residual solvent in the film and significantly reduces the amount of outgassing. In particular, when TFMB is used as a monomer, imidization in the presence of a plasticizer has been found to suppress the generation of hydrogen fluoride gas when the resulting polyimide is used in a high-temperature process. The polyamic acid composition according to this embodiment contains a plasticizer, thereby suppressing the generation of hydrogen fluoride during high-temperature processes. Therefore, the polyamic acid composition according to this embodiment can, for example, suppress corrosion of the barrier film formed on the polyimide film and the glass supporting substrate during the manufacturing process of a flexible display, thereby improving the reliability (resistance to failure) of the flexible display. Furthermore, the polyamic acid composition according to this embodiment provides sufficient molecular motion during the imidization of polyamic acid (1) by using a plasticizer, thereby accelerating imidization and producing a polyimide with excellent heat resistance. The plasticizer may remain in the polyimide film, or it may be decomposed and removed from the polyimide film during the imidization process. When the plasticizer remains in the polyimide film, in order to obtain a polyimide film having superior heat resistance, the content of the plasticizer relative to the total amount of the polyimide film is preferably 0.01% by weight or less, more preferably 0.001% by weight or less, and even more preferably 0.0001% by weight or less.

[0072] Furthermore, since the polyamic acid composition according to the present embodiment contains a plasticizer, even if the content of TFMB residues is high (for example, even if it is 50 mol % or more relative to all diamine residues), generation of hydrogen fluoride can be suppressed when the resulting polyimide is used in a high-temperature process.

[0073] The detection intensity obtained from mass spectrometry can be used as an indicator of the amount of hydrogen fluoride gas generated when an imidized product of polyamic acid (1) (the polyimide according to the present embodiment) is used in a high-temperature process. Specifically, the polyimide is first heated in a helium gas flow from an ambient temperature of 60°C at a heating rate of 10°C / min until the ambient temperature reaches 470°C. The gas generated from the polyimide is analyzed using a quadrupole mass spectrometer. The detection intensity of the m / z=20 peak (hereinafter sometimes referred to as the "20 peak intensity"), which is presumed to be due to hydrogen fluoride, is then read from the resulting mass spectrum (specifically, a mass spectrum showing the results of analyzing the components of the gas generated from the polyimide when the ambient temperature reaches 470°C). The 20 peak intensity tends to increase as the amount of hydrogen fluoride generated increases. The flow rate of helium gas when analyzing with a quadrupole mass spectrometer may be set so that the gas generated from the polyimide can be analyzed in real time by the quadrupole mass spectrometer, and is, for example, in the range of 50 mL / min to 150 mL / min, preferably in the range of 80 mL / min to 120 mL / min.

[0074] The inventors' investigations revealed that there is a very high correlation between the 20 peak intensity and the adhesion between the barrier film and the polyimide film after a heating test. Furthermore, the inventors' investigations revealed that a laminate consisting of a polyimide film and an inorganic film or glass lowers the temperature at which hydrogen fluoride begins to generate and increases the amount of hydrogen fluoride generated compared to a single-layer structure consisting of a polyimide film. This is presumably because the laminate prevents components containing radicals generated by heat from volatilizing, accelerating the autoxidation cycle of the polyimide.

[0075] The plasticizer used in this embodiment is preferably a material that dissolves in the solvent used during imidization of the polyamic acid (1). Furthermore, the plasticizer preferably does not volatilize at low temperatures, so as to impart sufficient molecular mobility to the polyamic acid (1) during imidization. Therefore, the boiling point of the plasticizer is preferably 50°C or higher, more preferably 100°C or higher, and even more preferably 150°C or higher. Furthermore, the plasticizer preferably does not have a decomposition temperature below its boiling point, so as to impart sufficient molecular mobility to the polyamic acid (1) during imidization.

[0076] The amount of the plasticizer is preferably 20 parts by weight or less per 100 parts by weight of polyamic acid (1) from the viewpoint of avoiding decomposition of the plasticizer itself while imparting sufficient molecular mobility to the polyamic acid (1). The amount of the plasticizer is preferably 0.001 to 20 parts by weight, more preferably 0.01 to 15 parts by weight, even more preferably 0.05 to 10 parts by weight, and even more preferably 0.05 to 5 parts by weight, per 100 parts by weight of polyamic acid (1) from the viewpoint of avoiding decomposition of the plasticizer itself while imparting sufficient molecular mobility to the polyamic acid (1).

[0077] The plasticizer not only improves molecular motion when the polyamic acid (1) undergoes dehydration ring closure to form a polyimide, but also can impart functions such as adjusting the glass transition temperature and providing flame retardancy, etc. As the plasticizer, for example, one or more types can be appropriately selected and used from known plasticizers.

[0078] In order to further suppress the generation of hydrogen fluoride when used in a high-temperature process, the plasticizer is preferably at least one selected from the group consisting of phosphorus-containing compounds, polyalkylene glycols, and aliphatic dibasic acid esters.

[0079] Examples of the phosphorus-containing compound include compounds represented by the following general formulas (7-1) to (7-10). In the following general formulas (7-1) to (7-10), R 5 , R 6 and R 7each independently represents a hydrogen atom, a monovalent organic group, or a polyvalent organic group; R 8 represents a polyvalent organic group, and n represents the degree of polymerization.

[0080] [ka]

[0081] Preferred examples of phosphorus-containing compounds include phosphoric acid compounds, phosphorous acid compounds, phosphonic acid compounds, phosphinic acid compounds, phosphine compounds, phosphine oxide compounds, phosphorane compounds, and phosphazene compounds. The phosphorus-containing compounds may be esters of the above-listed compounds or condensates thereof, may contain a cyclic structure, or may form a salt with an amine or the like. Furthermore, some of these phosphorus-containing compounds are in a tautomeric relationship, such as phosphorous acid compounds and phosphonic acid compounds, and may exist in either state.

[0082] Specific examples of phosphoric acid compounds include trimethyl phosphate, triethyl phosphate, tributyl phosphate, tri(2-ethylhexyl) phosphate, tributoxyethyl phosphate, triphenyl phosphate, tricresyl phosphate, trixylenyl phosphate, tris(isopropylphenyl) phosphate, trinaphthyl phosphate, cresyl diphenyl phosphate, xylenyl diphenyl phosphate, diphenyl(2-ethylhexyl) phosphate, di(isopropylphenyl)phenyl phosphate, monoisodecyl phosphate, 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, diphenyl-2-acryloyloxyethyl phosphate, diphenyl-2-methacryloyloxyethyl phosphate, melamine phosphate, dimelamine phosphate, bisphenol A bis(diphenyl phosphate), and tris(β-chloropropyl) phosphate.

[0083] Specific examples of phosphorous compounds include triphenyl phosphite, trisnonylphenyl phosphite, tricresyl phosphite, triethyl phosphite, triisobutyl phosphite, tris(2-ethylhexyl) phosphite, tridecyl phosphite, trilauryl phosphite, tris(tridecyl) phosphite, diphenyl phosphite, diethyl phosphite, dibutyl phosphite, dimethyl phosphite, diphenyl mono(2-ethylhexyl) phosphite, diphenyl monodecyl phosphite, diphenyl mono(tridecyl) phosphite, trilauryl trithio phosphite, diethyl hydrogen phosphite, bis(2-ethylhexyl) phosphite, Hydrogen phosphite, dilauryl hydrogen phosphite, dioleyl hydrogen phosphite, diphenyl hydrogen phosphite, tetraphenyl dipropylene glycol diphosphite, bis(decyl)pentaerythritol diphosphite, bis(tridecyl)pentaerythritol diphosphite, tristearyl phosphite, distearyl pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, triisodecyl phosphite, 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane, and the like.

[0084] The condensate may be a condensed phosphate ester. Specific examples of the condensed phosphate ester include trialkyl polyphosphate, resorcinol polyphenyl phosphate, resorcinol poly(di-2,6-xylyl) phosphate, and hydroquinone poly(2,6-xylyl) phosphate. Commercially available condensed phosphate esters include "CR-733S" and "CR-741" manufactured by Daihachi Chemical Industry Co., Ltd., and "FP-600" manufactured by ADEKA Corporation.

[0085] Specific examples of the phosphazene compound include phenoxycyclophosphazene ("FP-110" manufactured by Fushimi Pharmaceutical Co., Ltd.), cyclic cyanophenoxyphosphazene ("FP-300" manufactured by Fushimi Pharmaceutical Co., Ltd.), and the like.

[0086] Examples of polyalkylene glycols include polypropylene glycol represented by the following general formula (8-1) and polyethylene glycol represented by the following general formula (8-2): In the following general formulas (8-1) and (8-2), n represents the degree of polymerization.

[0087] [ka]

[0088] In order to improve compatibility with the polyamic acid (1), the number average degree of polymerization of the polyalkylene glycol is preferably 10 or more and 10,000 or less, more preferably 10 or more and 6,000 or less, and even more preferably 10 or more and 4,000 or less.

[0089] Specific examples of aliphatic dibasic acid esters include dibutyl adipate, diisobutyl adipate, bis(2-ethylhexyl) adipate, diisononyl adipate, diisodecyl adipate, bis[2-(2-butoxyethoxy)ethyl]adipate, bis(2-ethylhexyl)azelate, dibutyl sebacate, bis(2-ethylhexyl) sebacate, and diethyl succinate.

[0090] The plasticizer may be a low-molecular-weight organic compound or a thermoplastic resin, as long as it exhibits a plasticizing effect. Examples of the low-molecular-weight organic compound include organic compounds having a molecular weight of about 1,000 or less, such as phenolic compounds; phthalimide compounds such as phthalimide, N-phenylphthalimide, N-glycidylphthalimide, N-hydroxyphthalimide, and cyclohexylthiophthalimide; and maleimide compounds such as N,Np-phenylenebismaleimide and 2,2-(ethylenedioxy)bis(ethylmaleimide). Examples of the thermoplastic resin include polyimides and polyamides having an asymmetric structure.

[0091] In order to further suppress the generation of hydrogen fluoride when used in a high-temperature process, the plasticizer is preferably a phosphorous-based compound, more preferably a phosphorous ester, and even more preferably triphenyl phosphite.

[0092] In order to obtain a polyimide that exhibits even less coloration, even more excellent transparency and heat resistance, and that can further suppress the generation of hydrogen fluoride during high-temperature processes, the polyamic acid composition according to the present embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, even more preferably satisfies the following condition 3, and even more preferably satisfies the following condition 4. Condition 1: The content of TFMB residues relative to all diamine residues constituting the polyamic acid (1) is 50 mol % or more and 100 mol % or less, and the polyamic acid (1) contains one or more residues selected from the group consisting of PMDA residues, BPDA residues, BPAF residues, and ODPA residues. Condition 2: The above condition 1 is satisfied, and the polyamic acid (1) has only TFMB residues as diamine residues, or has only TFMB residues and 4-BAAB residues as diamine residues. Condition 3: The above condition 2 is satisfied, and the total content of PMDA residues, BPDA residues, BPAF residues, and ODPA residues relative to all acid dianhydride residues constituting the polyamic acid (1) is 100 mol %. Condition 4: The above condition 3 is satisfied, and the plasticizer is a phosphorous compound.

[0093] The polyamic acid composition according to the present embodiment may further contain an organic solvent in addition to the polyamic acid (1) and the plasticizer. Examples of the organic solvent contained in the polyamic acid composition include those listed above as organic solvents usable in the synthesis reaction of the polyamic acid (1). Preferred are one or more solvents selected from the group consisting of amide solvents, ketone solvents, ester solvents, and ether solvents, with amide solvents (more specifically, DMF, DMAC, NMP, etc.) being more preferred. When the polyamic acid (1) is obtained by the above-described method, the reaction solution (post-reaction solution) to which a plasticizer has been added may itself be used as the polyamic acid composition according to the present embodiment. Alternatively, the polyamic acid composition according to the present embodiment may be prepared by dissolving the solid polyamic acid (1) and plasticizer obtained by removing the solvent from the reaction solution in an organic solvent. The content of the polyamic acid (1) in the polyamic acid composition according to the present embodiment is not particularly limited, but is, for example, 1% by weight to 80% by weight based on the total weight of the polyamic acid composition.

[0094] The polyimide according to this embodiment is an imidized product of the polyamic acid (1). The polyimide according to this embodiment can be obtained by a known method, and its manufacturing method is not particularly limited. An example of a method for obtaining the polyimide according to this embodiment by imidizing the polyamic acid (1) is described below. The imidization is performed by dehydrating and cyclizing the polyamic acid (1). This dehydrating and cyclizing can be performed by an azeotropic method using an azeotropic solvent, a thermal method, or a chemical method. Furthermore, the imidization ratio of the polyamic acid (1) to the polyimide can be any ratio between 1% and 100%. In other words, a partially imidized polyamic acid (1) may be synthesized. In particular, when imidizing by heating, the cyclization reaction from the polyamic acid (1) to the polyimide and the hydrolysis of the polyamic acid (1) proceed simultaneously, which may result in a polyimide having a lower molecular weight than the polyamic acid (1). Therefore, from the viewpoint of improving mechanical properties, it is preferable to pre-imidize a portion of the polyamic acid (1) in the polyamic acid composition before forming the polyimide film described below. In this specification, partially imidized polyamic acids may also be referred to as "polyamic acids."

[0095] The dehydration ring closure of the polyamic acid (1) can be carried out by heating the polyamic acid (1). The method for heating the polyamic acid (1) is not particularly limited. For example, the polyamic acid composition according to the present embodiment (preferably a polyamic acid composition containing the polyamic acid (1), a plasticizer, and an organic solvent) 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 polyamic acid (1) at a temperature ranging from 40°C to 500°C. This method produces a laminate according to the present embodiment, which comprises a support and a polyimide film (specifically, a polyimide film containing an imidized product of the polyamic acid (1)) disposed on the support. Alternatively, the dehydration ring closure of the polyamic acid (1) 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 the dehydration ring closure of the polyamic acid (1) using these methods. The heating time for each of the above treatments varies depending on the treatment amount and heating temperature of the polyamic acid composition to be subjected to dehydration ring closure, but is generally preferably in the range of 1 minute to 300 minutes after the treatment temperature reaches the maximum temperature. To shorten the heating time or to enhance the properties, an imidizing agent and / or a dehydration catalyst may be added to the polyamic acid composition, and the polyamic acid composition to which the imidizing agent and / or dehydration catalyst has been added may be heated by the above method to be imidized.

[0096] The imidizing agent is not particularly limited, but a tertiary amine can be used. The tertiary amine is preferably a heterocyclic tertiary amine. Specific preferred examples of the heterocyclic tertiary amine include pyridine, picoline, quinoline, isoquinoline, and 1,2-dimethylimidazole. Specific preferred examples of the dehydration catalyst include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride.

[0097] The amount of the imidizing agent added is preferably 0.5 to 5.0 molar equivalents, more preferably 0.7 to 2.5 molar equivalents, and even more preferably 0.8 to 2.0 molar equivalents, relative to the amide groups in the polyamic acid (1). The amount of the dehydration catalyst added is preferably 0.5 to 10.0 molar equivalents, more preferably 0.7 to 5.0 molar equivalents, and even more preferably 0.8 to 3.0 molar equivalents, relative to the amide groups in the polyamic acid (1). In this specification, the term "amide groups in the polyamic acid (1)" refers to the amide groups formed by the polymerization reaction of the diamine and the tetracarboxylic dianhydride. The imidizing agent and / or dehydration catalyst may be added directly to the polyamic acid composition without dissolving them in an organic solvent, or may be added after dissolving them in an organic solvent. If the imidizing agent and / or dehydration catalyst are added directly without dissolving them in an organic solvent, the reaction may proceed too quickly before the imidizing agent and / or dehydration catalyst can diffuse, resulting in the formation of a gel. Therefore, it is preferable to add a solution obtained by dissolving the imidizing agent and / or dehydration catalyst in an organic solvent to the polyamic acid composition.

[0098] The polyimide film according to this embodiment (specifically, a polyimide film containing an imidized product of polyamic acid (1)) is colorless, transparent, and has a low yellowness index 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 polyamic acid (1)) in the polyimide film according to this embodiment is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may even be 100% by weight, based on the total weight of the polyimide film. Examples of components other than polyimide in the polyimide film include additives (more specifically, nanosilica particles, etc.) described below.

[0099] The electronic device according to this embodiment includes the polyimide film according to this embodiment and electronic elements disposed on the polyimide film. When manufacturing the 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 the electronic device on the support. The TFT formation process is generally carried out over a wide temperature range of 150°C to 650°C, but to actually achieve the desired performance, the oxide semiconductor layer and a-Si layer are formed at 300°C or higher, and in some cases, the a-Si layer may be further crystallized using a laser or the like.

[0100] If the thermal decomposition temperature of the polyimide film is low, outgassing may occur during the formation of electronic devices. This may result in sublimate deposits inside the oven, causing furnace contamination and possibly peeling off 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 520°C, although the higher the upper limit, the better. The 1% weight loss temperature can be adjusted, for example, by changing the content of residues with rigid structures (more specifically, TFMB residues, PMDA residues, 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 on the polyimide film as a barrier film. If the polyimide has low heat resistance, is not fully imidized, or contains a large amount of residual solvent, volatile components such as polyimide decomposition gases may cause peeling between the polyimide and the inorganic film during the high-temperature process after lamination of the inorganic film. Therefore, it is desirable that the 1% weight loss temperature of the polyimide is 500°C or higher, and that the weight loss rate when the polyimide is isothermally maintained at a temperature in the range of 400°C to 450°C is less than 1%.

[0101] Furthermore, if the glass transition temperature (Tg) of the polyimide is significantly lower than the process temperature, misalignment or other issues may occur during the formation of electronic elements. Therefore, the Tg of the polyimide is preferably 300°C or higher, more preferably 350°C or higher, and even more preferably 400°C or higher. The upper limit of the Tg of the polyimide is preferably as high as possible, for example, 450°C. Furthermore, because the thermal expansion coefficient of a glass substrate is generally lower than that of a resin, internal stress occurs between the glass substrate and the polyimide film. If the internal stress of a laminate formed by a glass substrate or electronic element used as a support and a polyimide film is high, the laminate containing 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, the internal stress generated in the laminate formed by the polyimide film and the glass substrate is preferably 30 MPa or lower, more preferably 25 MPa or lower, and even more preferably 20 MPa or lower.

[0102] 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 in which electronic elements are formed on a polyimide film) is formed on a support as described above, and then the polyimide film is peeled off from the support. In addition, alkali-free glass is suitably used as the material for the support. An example of a method for producing a laminate of a polyimide film and a support will be described in detail below.

[0103] First, a polyamic acid composition according to the present embodiment (preferably a polyamic acid composition containing polyamic acid (1), a plasticizer, and an organic solvent) is applied onto a support to form a coating film containing the polyamic acid (1) and the plasticizer, and a coating film-containing laminate consisting of the support. Next, the coating film-containing laminate is heated, for example, at a temperature of 40°C or higher and 200°C or lower. The heating time is, for example, 3 minutes or longer and 120 minutes or shorter. Note that a multi-stage heating process may be performed, for example, by heating the coating film-containing laminate at a temperature of 50°C for 30 minutes and then at a temperature of 100°C for 30 minutes. Next, in order to promote imidization of the polyamic acid (1) in the coating film, the coating film-containing laminate is heated, for example, at a maximum temperature of 200°C or higher and 500°C or lower. The heating time (heating time at the maximum temperature) is, for example, 1 minute or longer and 300 minutes or shorter. At this time, it is preferable to gradually increase the temperature from a low temperature to the maximum temperature. The temperature rise rate is preferably 2°C / min to 10°C / min, more preferably 4°C / min to 10°C / min. The maximum temperature is preferably 250°C to 450°C. A maximum temperature of 250°C or higher allows for sufficient imidization, while a maximum temperature of 450°C or lower can prevent thermal degradation and discoloration of the polyimide. The reaction may be maintained at any temperature for any length of time before reaching the maximum temperature. The imidization reaction can be carried out under air, reduced pressure, or an inert gas such as nitrogen. To achieve higher transparency, the reaction is preferably carried out under reduced pressure or an inert gas such as nitrogen. Known heating devices, such as a hot air oven, infrared oven, vacuum oven, inert oven, or hot plate, can be used. Through these steps, the polyamic acid (1) in the coating film is imidized, resulting in the production of a laminate (i.e., the laminate according to the present embodiment) of the support and the polyimide film (a film containing the imidized product of polyamic acid (1)). In order to shorten the heating time and to develop desired properties, an imidizing agent or a dehydration catalyst may be added to the polyamic acid composition, and the resulting solution may be heated by the above-mentioned method to effect imidization.

[0104] 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.

[0105] If there is floating at the interface between the polyimide film and the support (e.g., a glass substrate), the polyimide film may peel off during the formation of electronic devices, or the yield may decrease when the polyimide film is peeled off after the formation of electronic devices. The term "floating" refers to a state in which poor adhesion occurs between the polyimide film and other material layers (more specifically, a glass substrate, a barrier film, etc.) due to secondary components (more specifically, hydrogen fluoride, etc.) generated during imidization or residual solvents. Specific examples of "floating" include a state in which the polyimide film floats up from the glass substrate, a state in which a portion of the polyimide film is destroyed, causing interlayer delamination between the polyimide film and other material layers, and a state in which a barrier film floats up from the polyimide film. The polyamic acid composition according to this embodiment can suppress the generation of hydrogen fluoride when the resulting polyimide is used in a high-temperature process, thereby suppressing the occurrence of floating.

[0106] The transparency of a polyimide film can be evaluated 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 less than 1.0%, and may even be 0%. In applications requiring high transparency, the polyimide film is required to have high transmittance across the entire wavelength range, but polyimide films tend to absorb light on the short wavelength side, and the film itself often becomes yellow. To use a polyimide film in an application requiring high transparency, it is preferable that the coloration of the polyimide film be reduced. Specifically, to use a polyimide film in applications requiring high transparency, the yellowness index (YI) of the polyimide film is preferably 20 or less, more preferably 18 or less, even more preferably 15 or less, even more preferably 12 or less, particularly preferably 8 or less, and may even be 0. The YI can be measured according to JIS K7373-2006. The YI can be adjusted, for example, by changing the content of TFMB residues in the polyamic acid (1). Polyimide films with reduced coloration and transparency are thus suitable for transparent substrates, such as those used as glass replacements, and for substrates on which sensors or camera modules are provided on the back surface.

[0107] Furthermore, there are two types of light extraction methods for flexible displays: a top-emission method in which light is extracted from the TFT side, and a bottom-emission method in which light is extracted from the back side of the TFT. The top-emission method is characterized by its ease of increasing the aperture ratio because light is not blocked by the TFT, resulting in high-definition image quality. The bottom-emission method is characterized by its ease of manufacturing, as it simplifies the alignment of the TFT and pixel electrode. Since the aperture ratio can be improved even in the bottom-emission method if the TFT is transparent, 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.

[0108] 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 this 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.

[0109] In the manufacturing process described above, 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 longer, and more preferably 330 nm or longer. On the other hand, since a longer cutoff wavelength tends to cause the polyimide film to turn yellow, the cutoff wavelength of the polyimide film is preferably 390 nm or shorter. From the viewpoint of achieving both transparency (low yellowness) and ease of laser peeling, the cutoff wavelength of the polyimide film is preferably 320 nm or longer to 390 nm or shorter, and more preferably 330 nm or longer to 380 nm or shorter. In this specification, the cutoff wavelength means a wavelength at which the transmittance is 0.1% or less as measured by an ultraviolet-visible spectrophotometer.

[0110] 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 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 polyamic acid (1) or polyimide.

[0111] In order to impart processing properties and various functionalities to the polyamic acid composition and polyimide according to this embodiment, various organic or inorganic low-molecular-weight compounds or high-molecular-weight compounds may be blended as additives. Examples of additives that can be used include dyes, surfactants, leveling agents, plasticizers, 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. Furthermore, the function and form of the fine particles are not particularly limited, and they may be, for example, pigments, fillers, or fibrous particles.

[0112] In order to improve the heat resistance while maintaining the transparency of the polyimide film, nanosilica particles may be used as the additive to composite the polyamic acid (1) with the nanosilica particles. From the viewpoint of maintaining the transparency of the polyimide film, the average primary particle diameter of the nanosilica particles is preferably 200 nm or less, more preferably 100 nm or less, even more preferably 50 nm or less, and may be 30 nm or less. On the other hand, from the viewpoint of ensuring dispersibility in the polyamic acid (1), the average primary particle diameter of the nanosilica particles is preferably 5 nm or more, more preferably 10 nm or more. As a method for composite the polyamic acid (1) with the nanosilica particles, known methods can be used, such as a method using an organosilica sol in which nanosilica particles are dispersed in an organic solvent. As a method for compounding polyamic acid (1) and nanosilica particles using an organosilica sol, a method may be used in which polyamic acid (1) is synthesized and then the synthesized polyamic acid (1) is mixed with an organosilica sol. However, in order to more highly disperse the nanosilica particles in polyamic acid (1), it is preferable to synthesize polyamic acid (1) in an organosilica sol.

[0113] Furthermore, to enhance the interaction with the polyamic acid (1), the nanosilica particles can be surface-treated with a surface treatment agent. Known surface treatment agents, such as silane coupling agents, can be used. Silane coupling agents include alkoxysilane compounds having functional groups such as amino groups or glycidyl groups, and these can be selected appropriately. To further enhance the interaction with the polyamic acid (1), amino group-containing alkoxysilanes are preferred. Examples of amino group-containing alkoxysilanes include 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, 3-(2-aminoethyl)aminopropyltrimethoxysilane, 3-phenylaminopropyltrimethoxysilane, 2-aminophenyltrimethoxysilane, and 3-aminophenyltrimethoxysilane. However, from the viewpoint of raw material stability, 3-aminopropyltriethoxysilane is preferred. A surface treatment method for nanosilica particles includes stirring a mixture of a dispersion (organosilica sol) and a silane coupling agent at an ambient temperature of 20°C to 80°C. The stirring time is, for example, 1 hour to 10 hours. A catalyst or the like may be added to accelerate the reaction.

[0114] A nanosilica-polyamic acid composite obtained by combining polyamic acid (1) and nanosilica particles preferably contains 1 to 30 parts by weight, and more preferably 1 to 20 parts by weight, of nanosilica particles per 100 parts by weight of polyamic acid (1). When the content of nanosilica particles is 1 part by weight or more, the heat resistance of the nanosilica particle-containing polyimide can be improved and internal stress can be sufficiently reduced, and when the content of nanosilica particles is 30 parts by weight or less, adverse effects on the mechanical properties and transparency of the nanosilica particle-containing polyimide can be suppressed.

[0115] Imidazoles may also be added to the polyamic acid composition of this embodiment as additives for imparting the aforementioned functionality. In this specification, imidazoles refer to compounds having a 1,3-diazole ring (1,3-diazole ring structure). The imidazoles added to the polyamic acid composition of 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.

[0116] The content of imidazoles is preferably 0.005 mol to 0.1 mol, more preferably 0.01 mol to 0.08 mol, and even more preferably 0.015 mol to 0.050 mol per mole of amide group in polyamic acid (1). Incorporating 0.005 mol or more of imidazoles can improve the film strength and transparency of the polyimide, while keeping the imidazole content at 0.1 mol or less can improve the Tg and heat resistance of polyamic acid (1) while maintaining its storage stability. Regarding the improvement in transparency, polymerization solvents such as NMP are known to form complexes with the carboxyl groups of polyamic acid (1) through hydrogen bonding. Therefore, if the imidization rate is slow, NMP or the like may remain in the polyimide film and oxidize or decompose, potentially causing discoloration. The addition of imidazoles coordinates with the carboxyl groups of polyamic acid (1) and promotes imidization, making it difficult for NMP and the like to remain in the polyimide film, while also suppressing decomposition of polyamic acid (1) during the thermal imidization process, which is thought to improve transparency. In the polyamic acid composition according to this embodiment, the use of a plasticizer provides sufficient molecular motion during imidization of polyamic acid (1), so imidazoles are not necessary in this embodiment.

[0117] The method for mixing the polyamic acid (1) with the imidazole is not particularly limited. From the viewpoint of ease of molecular weight control of the polyamic acid (1), it is preferable to add the imidazole to the polyamic acid (1) after polymerization. In this case, the imidazole may be added directly to the polyamic acid (1), or the imidazole may be dissolved in a solvent in advance and this solution may be added to the polyamic acid (1); the addition method is not particularly limited. The polyamic acid composition according to this embodiment may be prepared by adding the imidazole and a plasticizer to a solution containing the polyamic acid (1) after polymerization (post-reaction solution).

[0118] The polyamic acid composition according to the present embodiment may contain a silane coupling agent to achieve appropriate adhesion to the support. Any known silane coupling agent may be used without particular limitation, but compounds containing an amino group are particularly preferred in terms of reactivity with the polyamic acid (1).

[0119] The blending ratio of the silane coupling agent to 100 parts by weight of polyamic acid (1) is preferably 0.01 to 0.50 parts by weight, more preferably 0.01 to 0.10 parts by weight, and even more preferably 0.01 to 0.05 parts by weight. By making the blending ratio of the silane coupling agent 0.01 parts by weight or more, the effect of suppressing peeling from the support is sufficiently exhibited, and by making the blending ratio of the silane coupling agent 0.50 parts by weight or less, a decrease in the molecular weight of polyamic acid (1) is suppressed, thereby suppressing embrittlement of the polyimide film.

[0120] On the surface of the polyimide film according to this embodiment, various inorganic thin films such as metal oxide thin films, transparent electrodes, 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.

[0121] 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 preferable for use 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 (EL) displays, and electronic paper, as well as printed materials, color filters, flexible displays, optical films, 3D displays, touch panels, transparent conductive film substrates, solar cells, and more preferably as a replacement material for glass. In these applications, the thickness of the polyimide film is, for example, 1 μm to 200 μm, preferably 5 μm to 100 μm. The thickness of the polyimide film can be measured using a laser hologram.

[0122] Furthermore, the polyamic acid composition according to this embodiment can be suitably used in a batch-type device fabrication process in which the polyamic acid composition is applied to a support, heated to imidize, electronic elements, etc. are formed, and the polyimide film is then peeled off. Therefore, this embodiment also includes a method for fabricating an electronic device, which includes the steps of applying the polyamic acid composition to a support, heated to imidize, and forming electronic elements, etc. on the polyimide film formed on the support. Furthermore, this method for fabricating an electronic device may further include the step of peeling off the polyimide film on which the electronic elements, etc. are formed, from the support. [Example]

[0123] Examples of the present invention will be described below, but the scope of the present invention is not limited to the following examples.

[0124] <Methods for measuring physical properties and evaluating adhesion> First, methods for measuring the physical properties of polyimide (polyimide film) and methods for evaluating adhesion will be described.

[0125] [Yellowness (YI)] The polyimide film in each laminate obtained in the Examples and Comparative Examples described below was measured for transmittance of light with a wavelength of 200 nm or more and 800 nm or less 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, it was evaluated as "the coloration of the polyimide film was reduced." On the other hand, when the YI was more than 20, it was evaluated as "the coloration of the polyimide film was not reduced."

[0126] [Hayes] The haze of the polyimide film peeled from each laminate obtained in the Examples and Comparative Examples described below was measured using an integrating sphere haze meter ("HM-150N" manufactured by Murakami Color Research Laboratory Co., Ltd.) according to the method described in JIS K7136-2000. When the haze was less than 1.0%, it was evaluated as having "excellent transparency." On the other hand, when the haze was 1.0% or more, it was evaluated as having "poor transparency."

[0127] Internal Stress Each polyamic acid composition prepared in the following Examples and Comparative Examples was spin-coated onto a Corning glass substrate (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 in a nitrogen atmosphere at 430°C for 30 minutes to obtain a laminate with 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 analyzer (KLA-Tencor Corporation, "FLX-2320-S"). 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 formation and the warpage of the laminate.

[0128] [Glass transition temperature (Tg)] Polyimide films 3 mm wide and 10 mm long were sampled from each laminate obtained in the Examples and Comparative Examples described below and used as samples for Tg measurement. Using a thermal analyzer (Hitachi High-Tech Science Corporation, "TMA / SS7100"), a load of 98.0 mN was applied to the sample, and the temperature was raised from 20°C to 450°C at a rate of 10°C / min. The temperature and strain (elongation) were plotted to obtain a TMA curve. The inflection point temperature of the obtained TMA curve (the temperature corresponding to the peak in the differential curve of the TMA curve) was taken as the glass transition temperature (Tg). When the Tg was 350°C or higher, the sample was evaluated as having "excellent heat resistance." On the other hand, when the Tg was lower than 350°C, the sample was evaluated as having "poor heat resistance."

[0129] [1% weight loss temperature (TD1)] Each polyimide film obtained in the examples and comparative examples described below (specifically, a polyimide film sampled from each laminate so as to weigh 10 mg) was used as a measurement sample. Using a simultaneous differential thermal and thermogravimetric analyzer ("TG / DTA7200" manufactured by Hitachi High-Tech Science Corporation), the temperature was raised from 25°C to 650°C at a rate of 20°C / min in a nitrogen atmosphere. The measurement temperature at which the sample weight at a measurement temperature of 150°C was reduced by 1 wt% relative to this reference weight was defined as the 1% weight loss temperature (TD1).

[0130] [Whether or not there is a gap between the glass substrate and the polyimide film] Each polyamic acid composition prepared in the Examples and Comparative Examples described below was applied to a Corning glass substrate (material: alkali-free glass, thickness: 0.7 mm, size: 100 mm × 100 mm) using a spin coater, 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. The obtained laminate was visually inspected for any floating between the glass substrate and the polyimide film.

[0131] [Whether or not there is a gap between the SiOx film and the polyimide film] Each polyamic acid composition prepared in the Examples and Comparative Examples described below was applied to a Corning glass substrate (material: alkali-free glass, thickness: 0.7 mm, size: 100 mm × 100 mm) using a spin coater. 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 form a 10 μm-thick polyimide film on the glass substrate. Next, a SiOx film (thickness: 1 μm) was laminated on the resulting polyimide film by plasma CVD, and the resulting laminate was heated in a nitrogen atmosphere under the heating conditions shown in Table 4 described below. The laminate after heating was then visually inspected for the presence or absence of lift between the SiOx film and the polyimide film. The presence or absence of lift between the SiOx film and the polyimide film was confirmed for Examples 1 to 18, Comparative Examples 1 to 5, and Comparative Example 10 described below.

[0132] [Analysis of gas evolved from polyimide film] The gas generated from the polyimide film during heating was analyzed using an analytical device combining a thermogravimetric analyzer (NETZSCH "STA449 F5") and a quadrupole mass spectrometer (JEOL "JMS-Q1500GC"). The analytical procedure is described below.

[0133] First, using perfluorotributylamine as a standard substance, the voltage of the quadrupole mass spectrometer was adjusted so that the detection intensity of the peak at m / z=69 was 800,000. Next, using the thermogravimetric analyzer, each polyimide film obtained in the examples and comparative examples described below (specifically, a polyimide film sampled from each laminate to a mass of 140 mg) was heated from an ambient temperature of 60°C at a heating rate of 10°C / min under a helium gas flow at a flow rate of 100 mL / min. The gas generated from the polyimide film when the ambient temperature reached 470°C was analyzed with the quadrupole mass spectrometer. Note that by using the analyzer to heat the polyimide film under a helium gas flow, the helium gas served as a carrier gas, allowing the gas generated from the polyimide film to be analyzed in real time with the quadrupole mass spectrometer. The gas generated from the polyimide film when the ambient temperature reached 470°C was analyzed using the quadrupole mass spectrometer, and the detected intensity of the peak at m / z = 20 (20 peak intensity) was read from the resulting mass spectrum. If the 20 peak intensity was 60,000 or less, it was evaluated as "the generation of hydrogen fluoride was suppressed during the high-temperature process." On the other hand, if the 20 peak intensity was greater than 60,000, it was evaluated as "the generation of hydrogen fluoride was not suppressed during the high-temperature process."

[0134] <Preparation of polyimide film> The methods for producing polyimide films (laminates) in Examples and Comparative Examples are described below. In the following, compounds and reagents are abbreviated as follows. Furthermore, the polyamic acid solutions used for producing the polyimide films were all prepared under a nitrogen atmosphere. NMP: N-methyl-2-pyrrolidone PMDA: Pyromellitic dianhydride BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic anhydride 4-BAAB: 4-aminophenyl-4-aminobenzoate PDA: p-phenylenediamine TFMB: 2,2'-bis(trifluoromethyl)benzidine ODA: 4,4'-oxydianiline TPP: Triphenyl phosphate TMP: Trimethyl phosphate DEPi: Diethyl phosphite TPPi: Triphenyl phosphite PEP-36: 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3010: Triisodecyl phosphite PX-200: Resorcinol poly(di-2,6-xylyl) phosphate CR-741: Condensed phosphate ester (Daihachi Chemical Industry "CR-741") DBA: Dibutyl adipate BXA-N: Bis[2-(2-butoxyethoxy)ethyl]adipate PEG600: Polyethylene glycol (average molecular weight 560-640)

[0135] [Preparation of polyamic acid solution] (Preparation of Polyamic Acid Solution PA-2) A 300 mL glass separable flask equipped with a stainless steel stirrer and a nitrogen inlet tube was charged with 40.0 g of NMP as the polymerization organic solvent. Next, while stirring the contents of the flask, 5.453 g of TFMB was added and dissolved in the flask. Next, 2.439 g of PMDA, 0.788 g of BPAF, and 1.265 g of BPDA were added to the flask, and the contents were stirred for 24 hours at 25°C to obtain polyamic acid solution PA-2.

[0136] (Preparation of Polyamic Acid Solutions PA-1 and PA-3 to PA-10) Polyamic acid solutions PA-1 and PA-3 to PA-10 were each prepared in the same manner as polyamic acid solution PA-2, except that the acid dianhydrides used and their charging ratios, the diamines used and their charging ratios, and the ratio of the total substance amount of the diamines used to the total substance amount of the acid dianhydrides used were as shown in Table 1. Note that the total substance amount of the acid dianhydrides in each of polyamic acid solutions PA-1 and PA-3 to PA-10 was the same as that in polyamic acid solution PA-2.

[0137] In Table 1, "-" indicates that the component was not used. The values ​​in the "Acid Dianhydride" column in Table 1 indicate the content (unit: mol%) of each acid dianhydride relative to the total amount of acid dianhydrides used. The values ​​in the "Diamine" column in Table 1 indicate the content (unit: mol%) of each diamine relative to the total amount of diamines used. In Table 1, "Ratio" indicates the ratio of the total amount of diamines used to the total amount of acid dianhydrides used (total amount of diamines / total amount of acid dianhydrides). For each of the polyamic acid solutions PA-1 to PA-10, the molar fraction of each polyamic acid residue in the prepared polyamic acid solution matched the molar fraction of each monomer (diamine and tetracarboxylic dianhydride) used in the synthesis of the polyamic acid.

[0138] [Table 1]

[0139] [Example 1] Under a nitrogen atmosphere, TMP was added as a plasticizer to the polyamic acid solution PA-1, and the resulting mixture was stirred for 5 minutes to obtain a polyamic acid composition. The amount of TMP added was 1 part by weight per 100 parts by weight of polyamic acid in the polyamic acid solution PA-1. The resulting polyamic acid composition was applied to a glass substrate (manufactured by Corning Incorporated, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm x 100 mm) using a spin coater, 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.

[0140] [Examples 2 to 20 and Comparative Examples 1 to 10] A laminate having a 10 μm-thick polyimide film on a glass substrate was obtained in the same manner as in Example 1, except that the type of polyamic acid solution used and the type and amount of plasticizer used were as shown in Table 2. In Table 2, "-" indicates that no plasticizer was used. Therefore, in Comparative Examples 1 to 10, polyamic acid solutions PA-1 to PA-10 were used as the polyamic acid compositions, respectively. In Table 2, the amount of plasticizer added is the amount added (unit: parts by weight) relative to 100 parts by weight of polyamic acid in the polyamic acid solution used.

[0141] [Table 2]

[0142] <Physical properties and evaluation results> The physical properties and evaluation results for Examples 1 to 20 and Comparative Examples 1 to 10 are shown in Tables 3 and 4. In Table 3, "-" means that no measurement was performed. In Table 3, "presence or absence of lifting from glass substrate" refers to the presence or absence of lifting between the glass substrate and the polyimide film. In Table 4, "presence or absence of lifting from SiOx film" refers to the presence or absence of lifting between the SiOx film and the polyimide film.

[0143] FIG. 1 shows the results of analyzing the gas generated from the polyimide film using a quadrupole mass spectrometer in accordance with the method described above in "Analysis of gas generated from polyimide film" for Example 18 and Comparative Example 5. In FIG. 1, the vertical axis represents the detection intensity, and the horizontal axis represents the temperature (ambient temperature). In FIG. 1, the solid line represents the change in the detection intensity of the peak at m / z=20 in Comparative Example 5, and the dashed line represents the change in the detection intensity of the peak at m / z=20 in Example 18. As shown in FIG. 1, Example 18 exhibited a smaller detection intensity of the peak at m / z=20 at an ambient temperature of around 470°C than Comparative Example 5, demonstrating that generation of hydrogen fluoride can be suppressed when used in high-temperature processes.

[0144] [Table 3]

[0145] [Table 4]

[0146] As described above, in Examples 1 to 20, which used polyamic acid compositions containing a polyamic acid having the structural unit (1) and a plasticizer, all of the following conditions (1) to (6) were satisfied. (1) YI is 20 or less. (2) Haze is less than 1.0%. (3) The internal stress is 30 MPa or less. (4) Tg is 350°C or higher. (5) TD1 is 500°C or higher. (6) The 20 peak intensity is 60,000 or less.

[0147] In Comparative Examples 1 to 7, the 20 peak intensity exceeded 60,000. Therefore, the polyimide films obtained in Comparative Examples 1 to 7 were unable to suppress the generation of hydrogen fluoride during high-temperature processes. In Comparative Examples 8 and 9, the Tg was less than 350°C. Therefore, the polyimide films obtained in Comparative Examples 8 and 9 did not have excellent heat resistance. In Comparative Example 10, the YI exceeded 20. Therefore, the coloration of the polyimide film obtained in Comparative Example 10 was not reduced.

[0148] The above results demonstrate that the polyimide obtained from the polyamic acid composition according to the present invention is excellent in low coloration, transparency and heat resistance, and can suppress the generation of hydrogen fluoride during high-temperature processes.

Claims

1. A polyamic acid composition containing a polyamic acid having a structural unit represented by the following general formula (1) and a plasticizer, The polyamic acid has a 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride residue as X in the following general formula (1), The polyamic acid composition, wherein the plasticizer is at least one selected from the group consisting of phosphorus-containing compounds, polyalkylene glycols, and aliphatic dibasic acid esters. 【Chemical 1】 (In the general formula (1), R １ and R ２ each independently represents a hydrogen atom, a monovalent aliphatic group, or a monovalent aromatic group; X represents a tetravalent organic group.

2. In the general formula (1), R １ and R ２ and each represent a hydrogen atom.

3. The polyamic acid composition according to claim 1 or 2, wherein the polyamic acid further has, as X in the general formula (1), one or more selected from the group consisting of a tetravalent organic group represented by the following chemical formula (2), a tetravalent organic group represented by the following chemical formula (3), and a tetravalent organic group represented by the following chemical formula (5): 【Chemistry 2】

4. 4. The polyamic acid composition according to claim 1, wherein the content of the structural unit represented by general formula (1) is 50 mol % or more and 100 mol % or less, based on all structural units of the polyamic acid.

5. 5. The polyamic acid composition according to claim 1, wherein the amount of the plasticizer is 20 parts by weight or less based on 100 parts by weight of the polyamic acid.

6. The polyamic acid composition according to any one of claims 1 to 5, further comprising an organic solvent.

7. 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 6.

8. 8. The polyimide according to claim 7, which has a 1% weight loss temperature of 500°C or higher.

9. A polyimide film comprising the polyimide according to claim 7 or 8.

10. 10. The polyimide film according to claim 9, having a yellowness index of 20 or less.

11. A laminate comprising a support and the polyimide film according to claim 9 or 10.

12. A method for producing a laminate having a support and a polyimide film, comprising the steps of: A method for producing a laminate, comprising applying the polyamic acid composition according to claim 6 onto a support to form a coating film containing the polyamic acid and the plasticizer, and heating the coating film to imidize the polyamic acid.

13. An electronic device comprising the polyimide film according to claim 9 or 10 and an electronic element disposed on the polyimide film.

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