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

Abstract

To provide a polyamic acid composition high in defoaming property, having excellent coating property, excellent also in heat resistance, adhesion and optical characteristics, by using a solvent with high safety.SOLUTION: A polyamic acid solution containing polyamic acid, which is a reaction product of a dianhydride and a diamine compound, an amide-based solvent, and a surfactant, wherein the amide-based solvent is 3-methoxy-N,N-dimethylpropanamide, the polyamic acid comprises at least 80% of 3,3',4,4'-biphenyltetracarboxylic dianhydride based on the total dianhydride, and at least 80% or more in the total diamine compound is p-phenylenediamine, and wherein the surface tension at 23°C of a 1 wt% solid content surfactant solution obtained by diluting the surfactant with the amide-based solvent is between 25 mN / m and 34 mN / m, and the time-dependent increase rate of the contact angle is 10% or less, and the above problems can be solved using the polyamic acid solution.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyamic acid solution, a polyimide film, a laminate, an electronic device, a method for producing a polyimide film, and a method for producing an electronic device.

[0002] The present invention further relates to polyimide-based electronic device materials, thin-film transistor (TFT) substrates, flexible display substrates, color filters, printed materials, optical materials, image display devices (more specifically, liquid crystal display devices, organic EL, electronic paper, etc.), 3D displays, solar cells, touch panels, transparent conductive film substrates, and alternative materials for components currently using glass. [Background technology]

[0003] 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.

[0004] 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 linear expansion (CTE) is similar to that of glass substrates and electronic elements, making it less susceptible to internal stress and suitable for use as a substrate material for flexible displays and other applications.

[0005] Polyimides obtained from polyamic acid solutions containing polyamic acid and organic solvents are used as substitutes for glass substrates in electronic devices, insulating films used in semiconductor devices, protective coating agents, and also as planarizing films for TFT substrates for display devices (see, for example, Patent Document 1). It is also known that materials such as acrylic resins, siloxanes, and photosensitive polyimides are used as planarizing films for TFT substrates (see, for example, Patent Documents 2 and 3). Generally, N-methyl-2-pyrrolidone (NMP), a solvent with a high boiling point and high dissolving power, is often used in the synthesis of polyamic acid. However, due to concerns about the impact of NMP on living organisms and the environment, the use of alternative solvents such as 3-methoxy-N,N-dimethylpropanamide (hereinafter sometimes referred to as MPA) as an alternative solvent to NMP has been investigated (see Patent Document 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2021-34578 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-178436 [Patent Document 3] Japanese Patent Publication No. 2022-34533 [Patent Document 4] Japanese Patent Application Laid-Open No. 2024-13698 Summary of the Invention [Problem to be solved by the invention]

[0007] In recent years, in order to improve the barrier properties of substrates, SiO x N y is increasingly being used as a passivation layer, but the traditional SiO x Compared with passivation layers such as those described above, the wettability of the polyamic acid solution to the substrate tends to be lower, and the coatability of the polyamic acid solution tends to be poor. Furthermore, when using an alternative solvent such as MPA, which is a highly safe solvent, MPA has a lower surface tension and a higher boiling point than NMP, which increases the fluidity of the polyamic acid solution during application, causing the coating film to shrink from the edge of the substrate, further worsening the coatability of the polyamic acid solution.

[0008] The present invention was made in view of the above circumstances, and aims to provide a polyamic acid composition that uses a solvent that is safer than NMP, has high defoaming properties, has good coating properties even on passivation layers with high barrier properties, and is also excellent in heat resistance, adhesion, and optical properties. Another aim of the present invention is to provide polyimides, polyimide films, laminates, and electronic devices produced using the polyamic acid composition. Furthermore, the present invention also aims to provide methods for producing polyimides, laminates, and electronic devices using the polyamic acid composition. [Means for solving the problem]

[0009] <Aspects of the present invention> The present invention includes the following aspects.

[0010] [1] A polyamic acid solution containing a polyamic acid (A) which is a reaction product of an acid dianhydride and a diamine compound, an amide solvent (B), and a surfactant (C), The amide solvent (B) is 3-methoxy-N,N-dimethylpropanamide represented by chemical formula (1), The polyamic acid (A) contains 3,3',4,4'-biphenyltetracarboxylic dianhydride in an amount of 80% or more of all dianhydrides, and contains p-phenylenediamine in an amount of 80% or more of all diamine compounds, the surface tension of a surfactant solution having a solid content concentration of 1% by weight obtained by diluting the surfactant (C) with the amide solvent (B) at 23°C is 24 mN / m or more and 34 mN / m or less; 600 nm SiO2 formed on a 0.7 mm thick glass substrate conditioned at 23 °C x N y 2 μL of a polyamic acid solution at 23°C is dropped onto the surface of the film, and the contact angle is measured after 2 and 4 minutes. The polyamic acid solution has an increase in the contact angle over time of 10% or less (where, the increase in the contact angle over time = (contact angle after 4 minutes / contact angle after 2 minutes - 1) × 100 [%]).

[0011] [ka]

[0012] [2] The polyamic acid solution according to [1], wherein the content of the surfactant (C) is 5 ppm or more and 500 ppm or less based on the total of (A), (B), and (C).

[0013] [3] The polyamic acid solution according to [1] or [2], wherein the weight average molecular weight (Mw) of the polyamic acid (A) is 30,000 or more and 200,000 or less.

[0014] [4] The polyamic acid solution according to any one of [1] to [3] above, wherein the surfactant (C) is a polyether-modified siloxane surfactant or a poly(meth)acrylate surfactant.

[0015] [5] The polyamic acid solution according to any one of [1] to [4] above, which is for slit coating.

[0016] [6] A polyimide film which is an imidized product of the polyamic acid solution according to any one of [1] to [5] above.

[0017] [7] The polyimide film according to [6] above, which has a 1% weight loss temperature of 450°C or higher.

[0018] [8] A method for producing a polyimide film, comprising the steps of applying the polyamic acid solution according to any one of [1] to [5] above to a substrate and heating the solution at a temperature of 300° C. or higher.

[0019] [9] A laminate of the polyimide film according to [6] or [7] above and a substrate.

[0020]

[10] A method for producing an electronic device, comprising forming an electronic element on or under the polyimide film according to [6] or [7] above.

[0021]

[11] An electronic device comprising an electronic element formed on or under the polyimide film according to [6] or [7] above. [Effects of the Invention]

[0022] The present invention provides a polyamic acid solution that uses a solvent that is safer than NMP, has high defoaming properties, and has good coating properties even on passivation layers with high barrier properties, and is also excellent in heat resistance, adhesion, and optical properties. The present invention also provides polyimides, polyimide films, laminates, and electronic devices produced using the polyamic acid solution. Furthermore, the present invention also provides methods for producing polyimides, laminates, and electronic devices using the polyamic acid composition. DETAILED DESCRIPTION OF THE INVENTION

[0023] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited thereto. In addition, all academic and patent documents described in this specification are incorporated herein by reference.

[0024] 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 (3) (hereinafter, sometimes referred to as "structural unit (3)").

[0025] [ka]

[0026] In general formula (3), A 1 represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from a tetracarboxylic dianhydride), and A 2 represents a diamine residue (a divalent organic group derived from a diamine).

[0027] The content of the structural unit (3) relative to all structural units constituting the polyamic acid is, for example, 50 mol% to 100 mol%, preferably 60 mol% to 100 mol%, more preferably 70 mol% to 100 mol%, even more preferably 80 mol% to 100 mol%, still more preferably 90 mol% to 100 mol%, and may even be 100 mol%. Furthermore, a portion of the structural unit (3) may undergo dehydration ring closure to become an imide structural unit. Considering the solubility of the polyamic acid in a solvent, the content of the imide structural unit is preferably 50% or less of all structural units.

[0028] 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.

[0029] Hereinafter, the compound name may be followed by "based" to refer to the compound and its derivatives in a comprehensive manner. Furthermore, when the compound name is followed by "based" to represent the name of a polymer, unless otherwise specified, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, tetracarboxylic acid dianhydrides may be referred to as "acid dianhydrides."

[0030] Unless otherwise specified, the components, functional groups, etc. exemplified in this specification may be used alone or in combination of two or more kinds.

[0031] <Preferred embodiment of the present invention> A polyamic acid solution containing a polyamic acid (A) which is a reaction product of an acid dianhydride and a diamine compound, an amide solvent (B), and a surfactant (C), wherein the amide solvent (B) is 3-methoxy-N,N-dimethylpropanamide represented by chemical formula (1), the polyamic acid (A) contains 3,3',4,4'-biphenyltetracarboxylic dianhydride in an amount of 80% or more of the total acid dianhydride, and p-phenylenediamine in an amount of 80% or more of the total diamine compounds, and the surfactant (C) is the amide solvent (B) represented by chemical formula (1). A polyamic acid solution in which the surface tension of a surfactant solution diluted with system solvent (B) and having a solids concentration of 1% by weight at 23°C is 24 mN / m or more and 34 mN / m or less, and when 2 μL of the polyamic acid solution at 23°C is dropped onto the surface of a 600 nm SiOxNy film formed on a 0.7 mm thick glass substrate prepared at 23°C and the contact angle is measured after 2 and 4 minutes, the increase in the contact angle over time is 10% or less (where the increase in the contact angle over time = (contact angle after 4 minutes / contact angle after 2 minutes - 1) × 100 [%]).

[0032] [ka]

[0033] In the present invention, the SiO 2 film is a highly hydrophobic inorganic oxide film. x N y It was found that when a highly fluid polyamic acid solution using a solvent such as MPA is applied to a passivation layer, if the increase in contact angle over time exceeds 10%, the coating shrinks from the edge of the substrate, deteriorating the coatability of the polyamic acid solution. Therefore, by using a surfactant (C) with a specific surface tension to suppress the increase in contact angle over time to 10% or less, it is possible to provide a polyamic acid solution that uses a solvent that is safer than NMP, has good coatability even on high-barrier passivation layers, and also has excellent heat resistance, adhesion, and optical properties. (Note that the increase in contact angle over time = (contact angle after 4 minutes / contact angle after 2 minutes - 1) × 100 [%].)

[0034] The polyamic acid solution according to this embodiment contains a polyamic acid (A), an amide solvent (B), and a surfactant (C). The polyamic acid is a reaction product of a tetracarboxylic dianhydride and a diamine compound. Examples of tetracarboxylic dianhydrides and diamine compounds preferred for the polyamic acid of this embodiment are shown below.

[0035] Examples of tetracarboxylic dianhydrides include 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), 4,4'-oxydiphthalic dianhydride (ODPA), norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic dianhydride (CpODA), 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic anhydride (6FDA), 5-(2,5-dioxotetrahydrofuran)- ... 1,2-Dimethyl-3-furanyl)-3-methyl-cyclohexene-1,2-dicarboxylic acid anhydride, 1,2,3,4-benzenetetracarboxylic acid dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic acid dianhydride, methylene-4,4'-diphthalic dianhydride, 1,1-ethylidene-4,4'-diphthalic dianhydride, 2,2-propylidene-4,4'-diphthalic dianhydride, 1,2-ethylene-4,4'-diphthalic dianhydride, 1,3-trimethylene-4,4'-diphthalic dianhydride, 1,4-tetramethylene-4,4'-diphthalic dianhydride, 1,5-pentane Tamethylene-4,4'-diphthalic dianhydride, 4,4'-oxydiphthalic dianhydride, p-phenylenebis(trimellitate anhydride), thio-4,4'-diphthalic dianhydride, sulfonyl-4,4'-diphthalic dianhydride, 1,3-bis(3,4-dicarboxyphenyl)benzene dianhydride, 1,3-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)benzene dianhydride, 1,3-bis[2-(3,4-dicarboxyphenyl)-2-propyl]benzene dianhydride, 1,4-bis[2-(3,4 -dicarboxyphenyl)-2-propyl]benzene dianhydride, bis[3-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, bis[4-(3,4-dicarboxyphenoxy)phenyl]methane dianhydride, 2,2-bis[3-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride, bis(3,4-dicarboxyphenoxy)dimethylsilane dianhydride, 1,3-bis(3,4-dicarboxyphenyl)-1,1,3,3-tetramethyldisiloxane dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,The polyimide may include those selected from the group consisting of 7-anthracenetetracarboxylic dianhydride, 1,2,7,8-phenanthrenetetracarboxylic dianhydride, bicyclohexyl-3,3',9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone (SFDA), p-phenylenebis(trimellitic acid monoester anhydride) (TMHQ), (1,3-dioxoisobenzofuran-5-yl)1,3-dioxoisobenzofuran-5-carboxylate (8CI), and combinations thereof. The appropriate tetracarboxylic dianhydride residue can be selected and used depending on the required physical properties of the polyimide application field.

[0036] Examples of diamine compounds include p-phenylenediamine (PDA), m-phenylenediamine, 4,4'-diamino-2,2'-bis(trifluoromethyl)biphenyl, 4,4'-diamino-2,2'-dimethylbiphenyl, 4,4'-diaminodiphenyl ether, 4-aminophenyl 4-aminobenzoate, 4,4'-diaminobenzanilide, diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, and 3,3'-diaminodiphenyl Phenyl sulfide, 4,4'-diaminobiphenyl, 3,4'-diaminobiphenyl, 3,3'-diaminobiphenyl, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy) )benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, 4,4-bis(4-aminophenoxy)biphenyl, 4,4-bis(3-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ether, bis[4-(3-aminophenoxy)phenyl]ether, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 9,10-bis(4-aminophenyl)anthracene, 2,2-bis(4-aminophenyl)propane The diamine residue may be selected from the group consisting of benzene, 2,2-bis(4-aminophenyl)hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 1,4-bis(3-aminopropyldimethylsilyl)benzene, 9,9-bis(4-aminophenyl)fluorene (BAFL), 4-aminophenyl-4-aminobenzoate (4-BAAB), etc., and combinations thereof. An appropriate diamine residue can be selected and used depending on the required physical properties of the application field of the polyimide.

[0037] In particular, in the polyamic acid and the method for producing the polyamic acid, it is preferred that the tetracarboxylic dianhydride residues contain BPDA in an amount of 80 mol % or more, preferably 90 mol % or more, and the diamine residues contain PDA in an amount of 80 mol % or more, preferably 90 mol % or more.

[0038] The polyamic acid of the present invention can be synthesized by a known general method. For example, a polyamic acid solution can be obtained by reacting (addition polymerization) a diamine with a tetracarboxylic dianhydride in MPA. Furthermore, the synthesis reaction of the polyamic acid is preferably carried out under an inert gas atmosphere such as argon or nitrogen.

[0039] When synthesizing polyamic acid using diamines and tetracarboxylic dianhydrides, the desired polyamic acid (a polymer of diamines and tetracarboxylic dianhydrides) can be obtained by adjusting the molar amount of diamine (or, if multiple diamines are used, the molar amount of each diamine) and the molar amount of tetracarboxylic dianhydride (or, if multiple tetracarboxylic dianhydrides are used, the molar amount of each tetracarboxylic dianhydride). The molar fraction of each residue in the polyamic acid corresponds, for example, to the molar fraction of each monomer (diamine and tetracarboxylic dianhydride) used in the synthesis of the polyamic acid. Furthermore, blending two polyamic acids can also produce polyamic acids containing multiple tetracarboxylic dianhydride residues and multiple diamine residues. The temperature conditions for the reaction between diamines and tetracarboxylic dianhydrides, i.e., the polyamic acid synthesis reaction, are not particularly limited, but are, for example, in the range of 20°C to 150°C. The reaction time for the polyamic acid synthesis reaction is, for example, in the range of 10 minutes to 30 hours.

[0040] The amic acid solution of the present invention contains an amide solvent (B), which is 3-methoxy-N,N-dimethylpropanamide (MPA) represented by chemical formula (1). [ka] The purity of MPA in terms of the degree of polymerization and stability of the polyamic acid solution is preferably 99.95% or more, and more preferably 99.8% or more.

[0041] The polyamic acid solution of the present invention may contain an organic solvent other than the amide-based solvent (B). A solvent capable of dissolving the tetracarboxylic dianhydride and diamine used is preferred, and a solvent capable of dissolving the resulting polyamic acid is more preferred. Examples of organic solvents used in the synthesis of polyamic acid include amide-based solvents such as 3-methoxy-N,N-methylpropanamide (MMPA) and 3-butoxy-N,N-methylpropanamide (BPA), 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, N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), N,N-diethylacetamide (DEF), Examples of suitable solvents include ester solvents such as N-methyl-2-pyrrolidone (NMP) and γ-butyrolactone, halogenated alkyl solvents such as chloroform and methylene chloride, aromatic hydrocarbon solvents such as benzene and toluene, phenolic solvents such as phenol and cresol, ketone solvents such as cyclopentanone, and ether 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 typically used alone, but two or more may be used in combination as needed. However, from a safety standpoint, it is preferable not to use DMAC, DMF, or NMP, which may have adverse effects on living organisms and the environment.

[0042] When polyamic acid is obtained by the above-described method, the reaction solution (the solution after the reaction) itself may be used as the polyamic acid composition according to this embodiment. Alternatively, the solid polyamic acid obtained by removing the solvent from the reaction solution may be dissolved in an organic solvent to prepare the polyamic acid composition according to this embodiment. The content of polyamic acid in the polyamic acid composition according to this embodiment is not particularly limited, but is, for example, 1% by weight or more and 80% by weight or less based on the total amount of the polyamic acid composition.

[0043] The weight-average molecular weight of the polyamic acid varies depending on its application, but is preferably in the range of 10,000 to 500,000, more preferably 30,000 to 200,000, even more preferably 40,000 to 12,0000, and particularly preferably 50,000 to 100,000. A weight-average molecular weight of 10,000 or more facilitates the production of polyamic acid or polyimide films with high heat resistance. On the other hand, a weight-average molecular weight of 500,000 or less exhibits sufficient solubility in solvents and good coatability, allowing the production of coating films or polyimide films with smooth surfaces and uniform thicknesses using the polyamic acid composition described below. The weight-average molecular weight used here refers to a polyethylene oxide equivalent value measured using gel permeation chromatography (GPC).

[0044] Methods for controlling the molecular weight of polyamic acid 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. To obtain polyimides with superior adhesion to inorganic oxide films, polymerization with an excess of diamine is preferred. 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 in the synthesis of the polyamic acid is between 0.95 and 1.05. The molar ratio is the ratio of the total amount of diamines used in the synthesis of the polyamic acid to the total amount of acid dianhydrides used in the synthesis of the polyamic acid (total amount of diamines / total amount of acid dianhydrides). Furthermore, end-capping with phthalic anhydride, maleic anhydride, aniline, or the like can further reduce the coloration of polyimides obtained using polyamic acid.

[0045] The polyamic acid solution of the present invention contains a surfactant (C). The surfactant solution, diluted with an amide-based solvent (B) to a solids concentration of 1% by weight, has a surface tension at 23°C of 24 mN / m to 34 mN / m, preferably 25 mN / m to 33 mN / m, more preferably 27 mN / m to 33 mN / m, and even more preferably 28 mN / m to 33 mN / m. Adding a surfactant with a specific surface tension to the polyamic acid solution containing the amide-based solvent (B) improves the coatability of the polyamic acid. By selecting a surfactant that provides a surface tension of 25 mN / m to 34 mN / m at 23°C to a surfactant solution diluted with the amide-based solvent (B) to a solids concentration of 1% by weight, the surfactant is appropriately oriented at the interface between the amide-based solvent (B)-containing amide-based solvent and air, controlling the fluidity of the amide-based solvent. This improves coatability and prevents deterioration of the defoaming properties of the amide-based solvent. Examples of surfactants include silicone surfactants, polyether-modified siloxane surfactants, poly(meth)acrylate surfactants, fluorine-containing surfactants, polyalkylene oxide surfactants, anionic surfactants such as ammonium lauryl sulfate and polyoxyethylene alkyl ether triethanolamine sulfate, cationic surfactants such as stearylamine acetate and lauryl trimethylammonium chloride, amphoteric surfactants such as lauryl dimethylamine oxide and lauryl carboxymethyl hydroxyethyl imidazolium betaine, and nonionic surfactants such as polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, and sorbitan monostearate. Two or more of these surfactants may be used. Among these, surfactant (C) is preferably a polyether-modified siloxane surfactant or a poly(meth)acrylate surfactant having a specific surface tension, from the viewpoint of compatibility with the polyamic acid solution of the present invention.

[0046] Preferred examples of commercially available polyether-modified siloxane surfactants having a specific surface tension include DOWSIL (registered trademark) 8032 (manufactured by Dow-Toray Industries, Inc.) and LE-302N (manufactured by Kyoeisha Chemical Co., Ltd.). Preferred examples of commercially available poly(meth)acrylate surfactants having a specific surface tension include BYK-361N (manufactured by BYK Japan KK).

[0047] The content of the surfactant in the polyamic acid solution, in other words, the total amount of the polyamic acid (A), the amide solvent (B), and the surfactant (C), is preferably 1 ppm to 500 ppm, more preferably 5 ppm to 500 ppm, even more preferably 5 ppm to 300 ppm, and particularly preferably 10 ppm to 150 ppm. By including 1 ppm or more of the surfactant, the coatability of the polyamic acid solution can be improved, and by keeping the surfactant content at 500 ppm or less, deterioration of film properties such as heat resistance and adhesion can be suppressed.

[0048] In order to impart processing properties and various functionalities to the polyamic acid solution and polyimide according to this embodiment, various organic or inorganic low-molecular-weight compounds or high-molecular-weight compounds other than surfactants may be blended into the polyamic acid composition as additives. Examples of additives that can be used include dyes, 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.

[0049] Imidazoles may also be added to the polyamic acid solution 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). Examples of imidazoles include, but are not limited to, 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.

[0050] The content of the imidazoles is preferably 0.005 mol or more and 0.1 mol or less, more preferably 0.01 mol or more and 0.08 mol or less, and even more preferably 0.015 mol or more and 0.050 mol or less, per mol of amide group in the polyamic acid. By including 0.005 mol or more of the imidazoles, the film strength and transparency of the polyimide can be improved, and by including the imidazoles in an amount of 0.1 mol or less, the storage stability of the polyamic acid can be maintained while the Tg and heat resistance can be improved.

[0051] The polyimide according to this embodiment is an imidized product of the polyamic acid described above. The polyimide according to this embodiment can be obtained by a known method, and the manufacturing method is not particularly limited. An example of a method for obtaining the polyimide according to this embodiment by imidizing the polyamic acid will be described below. The imidization is performed by dehydrating and cyclizing the polyamic acid. 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 of the polyamic acid to the polyimide can be at any ratio of 1% to 100%. In other words, a partially imidized polyamic acid may be synthesized.

[0052] The dehydration ring closure of the polyamic acid can be carried out by heating the polyamic acid. The method for heating the polyamic acid is not particularly limited. For example, the polyamic acid composition according to the present embodiment described above can be applied to a support such as a glass substrate, an inorganic oxide film such as a silicon oxide film, a metal plate, or a PET (polyethylene terephthalate) film, followed by heat treatment of the polyamic acid 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 polyamic acid) disposed on the support. Alternatively, the polyamic acid composition can be directly placed in a container that has been subjected to a release treatment, such as a fluorine-based resin coating, and then heated and dried under reduced pressure to carry out the dehydration ring closure of the polyamic acid. Polyimides can be obtained by the dehydration ring closure of the polyamic acid 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.

[0053] 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.

[0054] The amount of 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 of the polyamic acid. The amount of 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 of the polyamic acid. In this specification, "amide groups of polyamic acid" refers to amide groups formed by the polymerization reaction of diamines and tetracarboxylic dianhydrides. The imidizing agent and / or dehydration catalyst may be added directly to the polyamic acid composition without dissolving them in an organic solvent, or they may be added dissolved 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.

[0055] An electronic device (e.g., a flexible device) according to this embodiment includes the polyimide film according to this embodiment and electronic elements disposed directly or indirectly on the polyimide film. When manufacturing an electronic device according to this embodiment for use in a flexible display, a polyimide film is first formed on an inorganic substrate such as glass as a support. Electronic elements such as TFTs are then disposed (formed) on the polyimide film to form an electronic device on the support. The process of forming TFTs is generally carried out over a wide temperature range of 150°C to 650°C, but to actually achieve the desired performance, an oxide semiconductor layer or a-Si layer is formed at 300°C or higher, and in some cases, the a-Si or other layer may be further crystallized using a laser or the like.

[0056] In this case, if the thermal decomposition temperature of the polyimide film is low, outgassing occurs during the formation of electronic elements, and the outgassing adheres to the oven interior as sublimate, causing contamination inside the oven and possibly peeling off inorganic films (such as the barrier film described below) formed on the polyimide film or electronic elements. Therefore, the 1% weight loss temperature of the polyimide is preferably 450°C or higher, and more preferably 500°C or higher. The upper limit of the 1% weight loss temperature of the polyimide is the higher the better, but it is, for example, 580°C. The 1% weight loss temperature can be adjusted, for example, by changing the content of residues having a rigid structure (more specifically, BPDA residues, PDA residues, etc.). More specifically, before forming the TFT, a silicon oxide film (SiO ) is formed on the polyimide film as a barrier film. x film), silicon oxynitride film (SiO x N y film) and silicon nitride film (SiN y In this case, if the polyimide has low heat resistance, if imidization is not complete, or if there is a large amount of residual solvent, the polyimide and the inorganic film may peel off due to volatile components such as polyimide decomposition gases during the high-temperature process after lamination of the inorganic film. For this reason, it is desirable that the 1% weight loss temperature of the polyimide is 450°C or higher, and that the weight loss rate when the polyimide is isothermally held at a temperature between 400°C and 450°C is less than 1%.

[0057] Furthermore, if the glass transition temperature (Tg) of the polyimide is significantly lower than the process temperature, misalignment or the like may occur during the formation of electronic elements. Therefore, the Tg of the polyimide is preferably 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 linear 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.

[0058] 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 (more 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. Alkali-free glass is suitably used as the support material. Alternatively, an inorganic oxide film such as an SiOx film may be formed on the support, and then a polyimide film may be formed on the inorganic oxide film. An example of a method for producing a laminate of a polyimide film and a support will be described in detail below.

[0059] First, the polyamic acid composition according to the present embodiment is applied to a support to form a coating film-containing laminate consisting of a coating film containing polyamic acid and the support. The support is preferably a glass substrate, and examples thereof include soda glass, alkali-free glass, quartz glass, aluminosilicate glass, and chemically strengthened glass made from these glasses. Examples of coating methods include slit coating using a slit die, spin coating using a spinner, spray coating, inkjet coating, and roll coating. The coating film thickness is appropriately selected depending on the coating method. Among these, slit coating is particularly preferred from the viewpoint of improving the uniformity of the film thickness within the substrate surface during coating. 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 higher and 120 minutes or lower. A multi-stage heating process may be performed, such as heating the coating film-containing laminate at 50°C for 30 minutes and then at 100°C for 30 minutes. Next, to promote imidization of the polyamic acid in the coating film, the coating film-containing laminate is heated, for example, at a maximum temperature of 200°C to 500°C. The heating time (heating time at the maximum temperature) is, for example, 1 minute to 300 minutes. It is preferable to gradually increase the temperature from a low temperature to the maximum temperature. The temperature increase 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 suppress thermal degradation and discoloration of the polyimide. The coating film may be maintained at any temperature for any time before reaching the maximum temperature. The imidization reaction can be carried out in air, under reduced pressure, or in an inert gas such as nitrogen. However, to achieve higher transparency, it is preferable to carry out the reaction under reduced pressure or in an inert gas such as nitrogen. The heating device may be a known device such as a hot air oven, an infrared oven, a vacuum oven, an inert oven, a hot plate, etc. Through these steps, the polyamic acid in the coating film is imidized, and a laminate (i.e., the laminate according to the present embodiment) of the support and the polyimide film (a film containing an imidized product of polyamic acid) can be obtained.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.

[0060] 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.

[0061] 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 an electronic device, or the yield may decrease when the polyimide film is peeled off after the formation of the electronic device. 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, an inorganic oxide film, etc.) due to outgassing or residual solvent generated during imidization. Specific examples of "floating" include a state in which the polyimide film is lifted from the glass substrate, a state in which a portion of the polyimide film is broken and interlayer delamination occurs between the polyimide film and other material layers, and a state in which a barrier film is lifted from the polyimide film. The polyamic acid composition according to this embodiment can form a polyimide film with excellent gas release properties as described above, thereby suppressing the occurrence of floating.

[0062] 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, in order to use a polyimide film in an application 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 SFDA 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 the back surface of which sensors or camera modules are provided.

[0063] Furthermore, there are two types of light extraction methods for flexible displays: a top-emission method in which light is extracted from the front side of the TFT, 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.

[0064] In a batch-type device production process in which a polyamic acid composition is applied to a support, heated to imidize it, and then an electronic element or the like is formed, and the polyimide film is peeled off, if the adhesion between the support and the polyimide film is low, the polyimide film may peel off from the support in the electronic element formation step, which may adversely affect the formation of the electronic element. In particular, when an inorganic oxide film (e.g., SiO x In the case of a laminate in which a polyimide film is provided via an inorganic oxide film or the like, it is preferable that the adhesion between the inorganic oxide film and the polyimide film is excellent. Here, adhesion means adhesion strength. When an electronic device is manufactured using a laminate in which a polyimide film is provided on a support via an inorganic oxide film, from the viewpoint of improving productivity, the peel strength between the polyimide film and the inorganic oxide film is preferably 0.05 N / cm or more, more preferably 0.10 N / cm or more, and even more preferably 0.10 N / cm or more and 0.80 N / cm or less. The peel strength is measured by the same method as in the examples described below or a method equivalent thereto.

[0065] 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.

[0066] 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 film-shaped molded articles. 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 or polyimide.

[0067] 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.

[0068] 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 3 μm to 100 μm. The thickness of the polyimide film can be measured using a laser hologram.

[0069] Furthermore, the polyamic acid composition according to this embodiment can be suitably used in a batch-type device production process in which the polyamic acid composition is applied to a support, heated to imidize, electronic elements, etc., are formed, and then the polyimide film is peeled off. Therefore, this embodiment also includes a method for producing a polyimide film in which a laminate is obtained by the above-described method for producing a laminate according to this embodiment, and then the polyimide film is peeled off from the support to obtain a polyimide film. This embodiment also includes a method for producing an electronic device in which a laminate is obtained by the above-described method for producing a laminate according to this embodiment, and then electronic elements are formed on the formed polyimide film. [Example]

[0070] Examples of the present invention will be described below, but the scope of the present invention is not limited to the following examples.

[0071] <Measurement and evaluation methods> First, the measurement and evaluation methods will be described. [surface tension] The surfactant was diluted with the amide solvent (B) to prepare a surfactant solution with a solid content of 1% by weight at 23°C. The surface tension of the 1% surfactant solution was then measured by the hanging drop method using a DMo-501 manufactured by Kyowa Interface Science Co., Ltd., using equation (4).

[0072] γL=g·ρ·(de)2H-1 (4) (γL: surface tension of 1% surfactant solution g:Gravity acceleration ρ: liquid density de: Maximum droplet diameter H-1: Correction term calculated from ds / de ds: diameter at the point where the liquid bottom edge rises

[0073] [Defoaming] Each amic acid solution obtained in the examples and comparative examples described below was stirred at 200 rpm for 10 minutes using a shaker, and the time from when the stirring was stopped until the bubbles in the amic acid solution disappeared was measured, and the defoaming ability was evaluated according to the following criteria. A score of B or higher was considered to be acceptable. A: The time from stopping stirring until the bubbles in the amic acid solution disappear is less than 5 minutes. B: The time from stopping stirring to the disappearance of bubbles in the amic acid solution is 5 minutes or more but less than 10 minutes. C: The time from stopping stirring until the bubbles in the amic acid solution disappears is 10 minutes or more.

[0074] [Contact angle increase rate over time] First, SiO was deposited on a Corning glass substrate (product name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm × 100 mm) by plasma CVD. x membrane, or SiO x N y A SiO film (thickness: 600 nm) was laminated on the SiO film. x membrane, or SiO x N yAfter preparing the polyamic acid solutions obtained in the Examples and Comparative Examples described below at 23°C, 2 μL of each solution was dropped onto the surface of the film, and the contact angles were measured after 2 and 4 minutes, and the rate of increase in the contact angle over time was calculated using equation (2). The contact angles were measured using a DMo-501 manufactured by Kyowa Interface Science Co., Ltd. Increase in contact angle over time = (contact angle after 4 minutes / contact angle after 2 minutes - 1) × 100 [%] (2)

[0075] [Membrane contraction] First, a SiOxNy film (thickness: 600 nm) was laminated on a Corning glass substrate (trade name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm × 100 mm) by plasma CVD. Next, each polyamic acid solution prepared in the Examples and Comparative Examples described below was applied to the SiOxNy film using a spin coater. After application, the substrate was left to stand for 10 minutes, and then the film shrinkage of the amic acid solution at the edge of the substrate was evaluated according to the following criteria. A score of B or higher was considered acceptable. A: Film shrinkage is less than 0.5 mm from the edge of the substrate. B: Film shrinkage is 0.5 mm or more but less than 1.0 mm from the edge of the substrate. C: Film shrinkage is 1.0 mm or more but less than 2.0 mm from the edge of the substrate. D: Film shrinkage is 3.0 mm or more and less than 5.0 mm from the edge of the substrate. E: Film shrinkage is 5.0 mm or more from the edge of the substrate.

[0076] [Heat resistance] Polyimide films (specifically, polyimide films sampled to a weight of 10 mg) were used as measurement samples, and the samples were heated from 25°C to 650°C at a rate of 20°C / min in a nitrogen atmosphere using a simultaneous differential thermal and thermogravimetric analyzer (Hitachi High-Tech Science Corporation, "TG / DTA7200"). The sample weight at 150°C was used as the reference weight, and the measurement temperature at which the sample weight decreased by 1% by weight relative to this reference weight was defined as the 1% weight loss temperature (TD1). Heat resistance was evaluated according to the following criteria: C or higher was considered acceptable. A:TD1 is between 530℃ and 540℃. B: TD1 is 520℃ or more and less than 530℃. C: TD1 is 510℃ or more and less than 520℃. D: TD1 is less than 510°C. [Adhesion] First, SiO was deposited on a Corning glass substrate (product name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm × 100 mm) by plasma CVD. x N y A film (thickness: 600 nm) was then laminated on the SiO x N y Each polyamic acid solution prepared in the examples and comparative examples described below was applied onto the film using a spin coater, and heated in air at 80°C for 30 minutes, and then heated in a nitrogen atmosphere at 350°C for 60 minutes to form a SiO x N y A laminate was obtained in which a film and a polyimide film (thickness: 6 μm) were laminated in this order. A 10 mm-wide cut was made in the polyimide film of the resulting laminate with a cutter knife in accordance with ASTM D1876-01. Using a tensile tester ("Strograph VES1D" manufactured by Toyo Seiki Co., Ltd.), the polyimide film was peeled off for 50 mm at a tensile speed of 50 mm / min and a peel angle of 90° under conditions of 23°C and 55% relative humidity. The peel strength was calculated from the average peel strength when the polyimide film was peeled off. The adhesion was evaluated according to the following criteria. A grade of C or higher was considered pass. A: Peel strength is 0.05N / cm or more and less than 0.12N / cm. B: Peel strength is 0.12 N / cm or more and less than 0.19 N / cm. C: Peel strength is 0.19 N / cm or more and less than 0.26 N / cm. D: Peel strength is less than 0.19 N / cm.

[0077] [Transparency] For each polyimide film obtained in the Examples and Comparative Examples described below, the haze was measured using an integrating sphere haze meter ("COH 300A" manufactured by Nippon Denshoku Industries Co., Ltd.) according to the method described in JIS K7136-2000, and the transparency was evaluated according to the following criteria: C or higher was considered acceptable. A: Haze is between 0 and less than 1.0. B: Haze is 1.0 or more and less than 3.0. C: Haze is 3.0 or more and less than 5.0. D: Haze is 5.0 or higher.

[0078] <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 preparation of polyamic acid compositions used for producing polyimide films was carried out in a nitrogen atmosphere. MPA: 3-methoxy-N,N-dimethylpropanamide BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride ODPA: 4,4'-oxydiphthalic anhydride SFDA: spiro[11H-difuro[3,4-b:3',4'-i]xanthene-11,9'-[9H]fluorene]-1,3,7,9-tetrone PDA: p-phenylenediamine 4-BAAB: 4-aminophenyl-4-aminobenzoate

[0079] [Example 1] A 300 mL glass separable flask equipped with a stainless steel stirrer and a nitrogen inlet tube was charged with 85.0 g of MPA as the polymerization organic solvent. Next, while stirring the contents of the flask, 3.467 g of PDA and 0.804 g of 4-BAAB were added and dissolved in the flask. Next, 0.816 g of SFDA, 1.093 g of ODPA, and 8.821 g of BPDA were added to the flask and stirred for 4 hours at 40°C. After stirring the contents of the flask for 24 hours at 23°C, 149.75 g of MPA and 0.25 g of a 1 wt% surfactant solution (BYK-361N) diluted with MPA were added to the flask. The contents of the flask were stirred for 1 hour at 23°C to obtain a polyamic acid solution. The obtained polyamic acid solution was applied to a Corning glass substrate (trade name: Eagle XG, material: alkali-free glass, thickness: 0.7 mm, size: 100 mm × 100 mm) using a spin coater, and heated in air at 80°C for 30 minutes, followed by heating in a nitrogen atmosphere at 350°C for 60 minutes to obtain a laminate (laminate of Example 1) comprising a 6 μm-thick polyimide film on the glass substrate. Note that in Example 1, the ratio of the total amount of diamines used to the total amount of dianhydrides used (total amount of diamines / total amount of dianhydrides) was 101 / 100.

[0080] [Examples 2 to 29 and Comparative Examples 1 to 9] The amide acid solutions and laminates of Examples 2 to 29 and Comparative Examples 1 to 9 were obtained in the same manner as in Example 1, except that the acid dianhydrides used and their charging ratios, the diamines used and their charging ratios, and the solids concentrations of the amide acid solutions were as shown in Table 1, and the types and amounts of surfactants added were as shown in Table 2.

[0081] <Result> The acid dianhydrides used and their charging ratios, as well as the diamines used and their charging ratios for Examples 1 to 29 and Comparative Examples 1 to 9, are shown in Table 1. Furthermore, the evaluation results for Examples 1 to 29 and Comparative Examples 1 to 9 in terms of coatability, heat resistance, adhesion, and transparency are shown in Table 2.

[0082] In Table 1, "-" indicates that the component was not used. In Table 1, the values ​​in the "Acid dianhydride" column indicate the content (unit: mol%) of each acid dianhydride relative to the total amount of acid dianhydrides used. In Table 1, the values ​​in the "Diamine" column indicate the content (unit: mol%) of each diamine relative to the total amount of diamines used. In each of Examples 1 to 29 and Comparative Examples 1 to 9, the molar fraction of each polyamic acid residue in the prepared polyamic acid composition was consistent with the molar fraction of each monomer (diamine and tetracarboxylic dianhydride) used in synthesizing the polyamic acid.

[0083] As shown in Table 2, in Examples 1 to 29, the surface tension of a surfactant solution having a solid content concentration of 1 wt % obtained by diluting the surfactant with the amide solvent (B) at 23°C was 24 mN / m or more and 34 mN / m or less.

[0084] As shown in Table 3, in Examples 1 to 29, the coating properties were x N y The film shrinkage was B or more. Therefore, the polyimides obtained in Examples 1 to 29 were SiO x N y The polyimides obtained in Examples 1 to 29 had excellent coating properties. In Examples 1 to 29, the heat resistance was C or higher. Therefore, the polyimides obtained in Examples 1 to 29 had excellent heat resistance. In Examples 1 to 29, the adhesion was C or higher. Therefore, the polyimides obtained in Examples 1 to 29 had excellent adhesion. In Examples 1 to 29, the transparency was C or higher. Therefore, the polyimides obtained in Examples 1 to 29 had excellent transparency.

[0085] As shown in Table 1, the polyamic acid solution prepared in Comparative Example 1 did not contain a surfactant. In Comparative Examples 2 to 9, the surfactant solutions with a solid content of 1% by weight, obtained by diluting the surfactant with the amide solvent (B), had surface tensions at 23°C of 24 mN / m or less or exceeding 34 mN / m.

[0086] As shown in Table 3, in Comparative Examples 1 to 9, the film shrinkage on SiOxNy with respect to the coatability was C or less. Therefore, the polyimides obtained in Comparative Examples 1 to 9 did not have excellent coatability on SiOxNy. In Comparative Example 9, the heat resistance was D. Therefore, the polyimide obtained in Comparative Example 9 did not have excellent heat resistance. In Comparative Example 9, the adhesion was D. Therefore, the polyimide obtained in Comparative Example 9 did not have excellent adhesion. In Comparative Example 9, the transparency was D. Therefore, the polyimide obtained in Comparative Example 9 did not have excellent transparency.

[0087] The above results demonstrate that the present invention can provide a polyamic acid composition that uses a solvent that is safer than NMP, has high defoaming properties, has good coating properties even on passivation layers with high barrier properties, and is also excellent in heat resistance, adhesion, and optical properties.

[0088] [Table 1]

[0089] [Table 2]

[0090] [Table 3]

Claims

1. A polyamic acid solution containing a polyamic acid (A) which is a reaction product of an acid dianhydride and a diamine compound, an amide solvent (B), and a surfactant (C), The amide solvent (B) is 3-methoxy-N,N-dimethylpropanamide represented by chemical formula (1), The polyamic acid (A) contains 3,3',4,4'-biphenyltetracarboxylic dianhydride in an amount of 80% or more of all acid dianhydrides and p-phenylenediamine in an amount of 80% or more of all diamine compounds; the surface tension at 23°C of a surfactant solution having a solid content concentration of 1% by weight obtained by diluting the surfactant (C) with the amide solvent (B) is 24 mN / m or more and 34 mN / m or less; A 600 nm SiO film formed on a 0.7 mm thick glass substrate maintained at 23°C. ｘ N ｙ 2 μL of a polyamic acid solution at 23° C. is dropped onto the surface of the film, and the contact angle is measured after 2 minutes and 4 minutes. The polyamic acid solution has an increase in the contact angle over time of 10% or less (where, the increase in the contact angle over time = (contact angle after 4 minutes / contact angle after 2 minutes - 1) × 100 [%]). 【Chemical 1】

2. 2. The polyamic acid solution according to claim 1, wherein the content of the surfactant (C) is 5 ppm or more and 500 ppm or less based on the total of (A), (B), and (C).

3. 2. The polyamic acid solution according to claim 1, wherein the weight average molecular weight (Mw) of the polyamic acid (A) is 30,000 or more and 200,000 or less.

4. 2. The polyamic acid solution according to claim 1, wherein the surfactant (C) is a polyether-modified siloxane-based surfactant or a poly(meth)acrylate-based surfactant.

5. The polyamic acid solution according to claim 1, which is for slit coating.

6. A polyimide film which is an imidized product of the polyamic acid solution according to any one of claims 1 to 5.

7. 7. The polyimide film according to claim 6, wherein the 1% weight loss temperature is 450° C. or higher.

8. A method for producing a polyimide film, comprising the steps of applying the polyamic acid solution according to any one of claims 1 to 5 to a substrate and heating the applied solution at a temperature of 300°C or higher.

9. A laminate comprising the polyimide film according to claim 6 and a substrate.

10. A method for manufacturing an electronic device, comprising forming an electronic element on or under the polyimide film according to claim 6.

11. An electronic device comprising an electronic element formed on or under the polyimide film according to claim 6.

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