Resin composition, method for producing resin composition, and polyimide film

Abstract

A resin composition contains a polyimide precursor and a solvent. The polyimide precursor is a copolymer of a tetracarboxylic dianhydride component and a diamine component containing pyromellitic dianhydride and 3,3',4,4'-biphenyltetracarboxylic dianhydride as tetracarboxylic dianhydride components and 2,2'-bis(trifluoromethyl)benzidine as a diamine component. The weight average molecular weight of the polyimide precursor is 260,000-1,000,000, and the concentration of the polyimide precursor in the resin composition is 5-20 mass%.

Description

Resin composition, method for producing resin composition, and polyimide film

[0001] The present invention relates to a resin composition, a method for producing a resin composition, and a polyimide film.

[0002] In recent years, with the aim of making functional elements such as display elements lighter, smaller, thinner, more flexible, and more transparent, active development has been made into technologies for forming these elements on transparent polyimide films.

[0003] The ideal method for forming functional elements, such as display elements, on polyimide film surfaces is a roll-to-roll process, taking advantage of the flexibility of polyimide film. However, in the display industry and other industries, processing technologies have been developed for rigid, planar substrates, such as wafers or glass substrates. Therefore, to form functional elements on polyimide film using existing infrastructure, a process is used in which the polyimide film is bonded to a rigid inorganic substrate (hereinafter sometimes referred to as an inorganic substrate), such as a glass plate, ceramic plate, silicon wafer, or metal plate, and then the desired elements are formed on the substrate and then peeled off.

[0004] In the process of forming desired functional devices on a laminate formed by bonding a polyimide film and an inorganic support, the laminate is often exposed to high temperatures. For example, the formation of functional devices such as polysilicon or oxide semiconductors requires processes at temperatures ranging from approximately 200°C to 600°C. Furthermore, the fabrication of hydrogenated amorphous silicon thin films may require temperatures ranging from approximately 200°C to 300°C, and further heating and dehydrogenation of amorphous silicon to produce low-temperature polysilicon may require heating at approximately 450°C to 600°C. Therefore, the polyimide film constituting the laminate must be heat-resistant enough to withstand these conditions. Furthermore, a large difference in the coefficient of linear thermal expansion (CTE) between the polyimide film and the inorganic material constituting the laminate can cause warping of the laminate, hindering device fabrication. To prevent warping of the laminate, the difference in CTE between the polyimide film and the inorganic material must be minimized. However, because inorganic materials generally have a low CTE, the polyimide film must also have a correspondingly low CTE.

[0005] Generally, most polyimide resins with high heat resistance and low CTE are insoluble and infusible. Therefore, when producing molded products such as polyimide films, a production method that uses a soluble polyimide precursor resin is often used. In this method, a polyimide precursor resin solution is first prepared, then uniformly coated on a support, and a polyimide precursor film is produced by partially evaporating the solvent. The polyimide precursor film is then peeled from the support, and both ends of the film are fixed with pins, clips, etc., and heat-treated while being transported through a heat treatment furnace. This allows the imidization reaction to proceed while removing residual solvent, producing a polyimide film. Here, when the polyimide precursor film is heat-treated while being fixed with pins, clips, etc., and transported through a heat treatment furnace, a tensile load is applied between both ends of the polyimide precursor film due to shrinkage accompanying the removal of residual solvent and the progress of the imidization reaction. Therefore, the polyimide precursor film must have sufficient strength to prevent tearing, etc.

[0006] Patent Document 1 describes a resin composition having a solids content of 10 to 25% by mass, which contains a polyamic acid, a polyimide precursor having a weight average molecular weight of 110,000 to 250,000, and a solvent. The polyamic acid contains 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes abbreviated as s-BPDA) and pyromellitic dianhydride (hereinafter sometimes abbreviated as PMDA) as acid components, and 2,2'-bis(trifluoromethyl)benzidine (hereinafter sometimes abbreviated as TFMB) and 3,3'-diaminodiphenyl sulfone (hereinafter sometimes abbreviated as 3,3'-DAS) or 4,4'-diaminodiphenyl sulfone (hereinafter sometimes abbreviated as 4,4'-DAS) as amine components. The resin composition has excellent slit coating properties, and the polyimide film obtained by curing the resin composition is also described as having excellent mechanical and optical properties.

[0007] Patent Document 2 describes a resin composition containing a polyamic acid containing s-BPDA and PMDA as tetracarboxylic dianhydride components and TFMB as a diamine component, and a solvent, with a solids concentration of 15% by mass and a solution viscosity of approximately 5,800 to 100,000 cP, and aims to produce a white polyimide film. It also describes a transparent polyimide film as a comparative example. It also describes that when the resin composition is imidized, if the temperature at which the imidization rate reaches 80% or more is relatively high (220°C or higher), the final polyimide film becomes white, but if the temperature at which the imidization rate reaches 80% or more is relatively low (190°C), the final polyimide film is transparent and has a CTE of 32 to 47 ppm / K.

[0008] Patent Document 3 describes a resin composition having a solids concentration of 15% by mass, which contains a polyamic acid containing s-BPDA and PMDA as tetracarboxylic dianhydride components and 2,2'-dimethyl-4,4'-diaminobiphenyl (hereinafter sometimes abbreviated as m-TB) and 4,4'-diaminobiphenyl as diamine components, and a solvent, and describes that a polyimide film obtained by curing the resin composition has a linear expansion coefficient of 10 ppm / K or less and exhibits little warping.

[0009] JP 2022-167930 A JP 2010-235789 A JP 2019-065266 A

[0010] In the resin composition of Patent Document 1, the weight-average molecular weight of the polyimide precursor is low, at 110,000 to 250,000, so when the polyimide precursor film is peeled off from the support, and then conveyed through a heat treatment furnace while fixed at both ends with pins, clips, etc., the film does not have sufficient strength to withstand shrinkage that accompanies the removal of residual solvent and the progress of the imidization reaction, resulting in tearing, etc. Furthermore, the CTE of the polyimide film in Patent Document 1 is unknown because no description is given of it, but it is thought that the inclusion of a flexible structure within the polyimide structure prevents the realization of low CTE characteristics that are commensurate with the CTE of inorganic materials. The weight-average molecular weight of the resin composition in Patent Document 2 is unknown because it is not disclosed. However, the solution viscosity at a solids concentration of 15% by mass is approximately 5,800 to 100,000 cP, suggesting a low weight-average molecular weight. Therefore, when the polyimide precursor film is peeled from the support, fixed at both ends with pins or clips, and transported through a heat treatment furnace for heat treatment, it is likely to lack sufficient strength to withstand the shrinkage associated with the removal of residual solvent and the progress of the imidization reaction, resulting in tearing. Furthermore, the transparent polyimide film described in Patent Document 2 has a high CTE, and is unable to achieve a low CTE characteristic commensurate with the CTE of inorganic materials. Patent Document 3 does not disclose any description of transparency for the polyimide film, making it unclear whether this invention can also achieve transparency. Patent Documents 1 to 3 do not disclose a polyimide film that simultaneously combines transparency, heat resistance, low CTE properties, and mechanical properties at a level that allows it to be used as a base film for flexible devices such as flexible displays. Furthermore, Patent Documents 1 to 3 do not disclose a resin composition containing a polyimide precursor having a molecular weight sufficient to produce a polyimide film without breaking when the polyimide precursor film is peeled off from the support, and then subjected to heat treatment while being transported in a heat treatment furnace with both ends fixed with pins, clips, or the like, or a method for producing the resin composition.

[0011] The present invention aims to provide a resin composition for producing a polyimide film without tearing that is excellent in all of transparency, heat resistance, low CTE, and mechanical properties, a method for producing the resin composition, and a polyimide film that is excellent in all of transparency, heat resistance, low CTE, and mechanical properties.The present invention also aims to provide a polyimide-coated semiconductor wafer, at least a portion of whose surface is covered with a polyimide layer that is excellent in all of transparency, heat resistance, low CTE, and mechanical properties, and a method for producing the same.

[0012] As a result of extensive research, the present inventors have discovered a polyimide precursor resin composition having a specific solid content, which contains at least a polyimide precursor resin having a specific chemical structure and weight-average molecular weight and a solvent, and have thereby completed the present invention.

[0013] That is, the present invention has the following features. Item 1. A resin composition comprising a polyimide precursor having an acid-based component-derived structure and an amine-based component-derived structure, and a first solvent, wherein the acid-based component-derived structure includes a pyromellitic acid derivative-derived structure and a 3,3',4,4'-biphenyltetracarboxylic acid derivative-derived structure, and the amine-based component-derived structure includes a 2,2'-bis(trifluoromethyl)benzidine derivative-derived structure, the polyimide precursor has a weight-average molecular weight of 260,000 to 1,000,000, and the concentration of the polyimide precursor in the resin composition is 5 to 20 mass%. Item 2. The resin composition according to Item 1, wherein the polyimide precursor has a reduced viscosity of 3.0 to 9.0 dl / g in an N,N-dimethylacetamide solution having a concentration of 0.2 g / dl and a temperature of 25.0°C. Item 3. Item 4. A resin composition according to any one of Items 1 to 3, characterized in that the molar ratio of the pyromellitic acid derivative-derived structure and the 3,3',4,4'-biphenyltetracarboxylic acid derivative-derived structure constituting the polyimide precursor is 90:10 to 10:90. Item 5. A method for producing a resin composition according to any one of Items 1 to 3, comprising a step of polymerizing a polyimide precursor by carrying out the following steps I to IV in this order: Step I: Purging the atmosphere inside a polymerization reaction vessel with an inert gas; Step II: Introducing a second solvent into the polymerization reaction vessel; Step III: Introducing an amine component and an acid component into the polymerization reaction vessel in amounts such that the concentration of the second solvent is greater than 20 mass % assuming that the two components completely react to form a polyimide precursor; and Step IV: Adding a third solvent four hours or more after the end of Step III. Item 5-1. A polyimide film obtained from the resin composition according to any one of Items 1 to 3. Item 5-2. A polyimide film having an acid-based component-derived structure and an amine-based component-derived structure, wherein the acid-based component-derived structures include a pyromellitic acid derivative-derived structure and a 3,3',4,4'-biphenyltetracarboxylic acid derivative-derived structure, and the amine-based component-derived structure includes a 2,2'-bis(trifluoromethyl)benzidine derivative-derived structure, and the polyimide film has a weight-average molecular weight of 260,000 to 1,000,000.Item 6. The polyimide film according to Item 5, characterized in that the yellowness index (YI) converted to a 15 μm film thickness is 20 or less, the haze is 2.0% or less, the 1% weight loss temperature is 450°C or higher, the average linear expansion coefficient between 50°C and 200°C is -5 to +20 ppm / °C, and the tensile elongation is 10% or more. Item 7-1. A polyimide-coated semiconductor wafer, at least a portion of whose surface is covered with a polyimide layer obtained from the resin composition according to any one of Items 1 to 3. Item 7-2. A polyimide-coated semiconductor wafer, at least a portion of whose surface is covered with the polyimide film according to Item 5-2. Item 8. A method for producing a polyimide-coated semiconductor wafer according to Item 7, comprising: Step A of applying the resin composition according to Items 1 to 3 to at least a portion of the surface of a semiconductor wafer; Step B of heating the semiconductor wafer that has been subjected to Step A to dry off a portion of the solvent contained in the resin composition; and Step C of further heat-treating the semiconductor wafer that has been subjected to Step B to form a polyimide layer.

[0014] According to one aspect of the present invention, when a polyimide precursor film is subjected to heat treatment while being transported through a heat treatment furnace with both ends fixed with pins, clips, or the like, a polyimide precursor film having sufficient strength to withstand the tensile load between both ends of the polyimide precursor film caused by the drying and volatilization of residual solvent and the shrinkage associated with the progress of the imidization reaction can be obtained, thereby preventing the film from breaking during the production process and enabling the production of a high-quality polyimide film. Furthermore, the resulting polyimide film has excellent transparency, heat resistance, low CTE, and mechanical properties, making it particularly suitable for use in the field of transparent flexible display substrates. According to another aspect of the present invention, a polyimide-coated semiconductor wafer can be produced, at least a portion of whose surface is covered with a polyimide layer that is excellent in all of transparency, heat resistance, low CTE, and mechanical properties.

[0015] The present invention will be described in detail below, but these are only embodiments of the present invention and the present invention is not limited to these details.

[0016] <Resin Composition> The resin composition of the present invention is a resin composition comprising a polyimide precursor having an acid-based component-derived structure and an amine-based component-derived structure, and a solvent, wherein the acid-based component-derived structure includes a pyromellitic acid derivative-derived structure (hereinafter may be abbreviated as a pyromellitic acid-derived structure) and a 3,3',4,4'-biphenyltetracarboxylic acid derivative-derived structure (hereinafter may be abbreviated as a 3,3',4,4'-biphenyltetracarboxylic acid-derived structure), and the amine-based component-derived structure includes a 2,2'-bis(trifluoromethyl)benzidine derivative-derived structure (hereinafter may be abbreviated as a 2,2'-bis(trifluoromethyl)benzidine-derived structure), wherein the weight-average molecular weight of the polyimide precursor is 260,000 to 1,000,000, and the concentration of the polyimide precursor in the resin composition is 5 to 20% by mass.

[0017] The total ratio of pyromellitic acid-derived structures and 3,3',4,4'-biphenyltetracarboxylic acid-derived structures to the acid component-derived structures is not particularly limited, but is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 98 mol% or more, particularly preferably 99 mol% or more, and may be 99.5 mol% or more or even 100 mol%. Examples of structures contained in the acid component-derived structures that are not pyromellitic acid-derived structures and not 3,3',4,4'-biphenyltetracarboxylic acid-derived structures include structures derived from tetracarboxylic acids and dicarboxylic acids other than the two tetracarboxylic acids listed above, and derivatives thereof. Specific examples are structures derived from compounds described below in the description of the production method for the resin composition.

[0018] The pyromellitic acid-derived structure has a rigid backbone and a linear structure, contributing to the high heat resistance and low CTE of the final polyimide film. However, the pyromellitic acid-derived structure alone results in a polyimide film with insufficient strength and poor film formability. In contrast, the 3,3',4,4'-biphenyltetracarboxylic acid-derived structure has a moderately rigid backbone and a linear structure while ensuring a certain degree of polyimide molecular chain mobility, contributing to the development of high strength and high toughness without significantly impairing the high heat resistance and low CTE of the polyimide film. Furthermore, the 3,3',4,4'-biphenyltetracarboxylic acid-derived structure has a twisted structure, contributing to the suppression of intramolecular charge-transfer complex formation in the polyimide and contributing to the development of high transparency in the final polyimide film.

[0019] The ratio (molar ratio) of the pyromellitic acid-derived structure to the 3,3',4,4'-biphenyltetracarboxylic acid-derived structure is not particularly limited, but the pyromellitic acid-derived structure:3,3',4,4'-biphenyltetracarboxylic acid-derived structure is preferably 90:10 to 10:90, more preferably 80:20 to 20:80, even more preferably 70:30 to 30:70, still more preferably 65:35 to 35:75, and particularly preferably 60:40 to 40:60. By setting the molar ratio of the pyromellitic acid-derived structure to the 3,3',4,4'-biphenyltetracarboxylic acid-derived structure within the above range, the strength of the polyimide precursor film, as well as the transparency, heat resistance, low CTE characteristics, and mechanical properties of the final polyimide film are better balanced.

[0020] The ratio of 2,2'-bis(trifluoromethyl)benzidine-derived structures to amine-based component-derived structures is not particularly limited, but is preferably 70 mol% or more, more preferably 80 mol% or more, even more preferably 90 mol% or more, even more preferably 98 mol% or more, particularly preferably 99 mol% or more, and may be 99.5 mol% or more or even 100 mol%. Examples of structures contained in the amine-based component-derived structures that are not 2,2'-bis(trifluoromethyl)benzidine-derived structures include structures derived from diamines other than the diamines listed above. Specific examples are structures derived from compounds described below in the description of the production method for the resin composition.

[0021] The 2,2'-bis(trifluoromethyl)benzidine-derived structure has a rigid backbone and a linear structure, which contributes to the high heat resistance and low CTE of the final polyimide film. Furthermore, the 2,2'-bis(trifluoromethyl)benzidine-derived structure has a highly electron-withdrawing, bulky substituent in the side chain, and a twisted structure, which contributes to the suppression of intramolecular and intermolecular charge-transfer complex formation in the polyimide, and also contributes to the high transparency of the final polyimide film.

[0022] The weight-average molecular weight of the polyimide precursor in the present invention is 260,000 to 1,000,000. If the weight-average molecular weight is less than 260,000, the polyimide precursor film obtained will not have sufficient strength to withstand the tensile load caused by the evaporation of residual solvent during film formation, particularly during heat treatment, and the shrinkage that accompanies the imidization reaction. This can lead to film tearing during the production process, making it impossible to produce a high-quality polyimide film. On the other hand, if the weight-average molecular weight is greater than 1,000,000, the solution viscosity of the resin composition will be excessively high, resulting in poor coatability of the resin composition. The preferred weight-average molecular weight may vary depending on the desired application, the type of polyimide precursor, the solids content of the resin composition, the type of solvent the resin composition may contain, and other factors; however, it is preferably 280,000 to 900,000, more preferably 300,000 to 800,000, and even more preferably 320,000 to 700,000.

[0023] The molecular weight distribution Mw / Mn, which is the ratio of the weight average molecular weight Mw to the number average molecular weight Mn of the polyimide precursor in the present invention, is not particularly limited, but is preferably 1.0 to 5.0, more preferably 1.5 to 4.5, and even more preferably 2.0 to 4.0. By ensuring that the molecular weight distribution is within the above range, the heat resistance of the polyimide film finally obtained can be further improved.

[0024] The type of first solvent contained in the resin composition of the present invention is not particularly limited, and examples thereof include N,N-dimethylformamide, N,N-dimethylacetamide (hereinafter sometimes abbreviated as DMAc), N-methyl-2-pyrrolidone (hereinafter sometimes abbreviated as NMP), N-methyl-ε-caprolactam, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, 3-methyl-2-oxazolidone, hexamethylphosphoramide, and γ-butyrolactone (hereinafter sometimes abbreviated as GBL), which may be used alone or in combination of two or more. In addition to these solvents, poor solvents such as toluene and xylene may also be used to the extent that the resin solids do not precipitate.

[0025] The concentration of the polyimide precursor in the resin composition of the present invention is 5 to 20% by mass. By setting the polyimide precursor concentration within an appropriate range, it becomes easier to achieve an appropriate film thickness for the polyimide precursor film or the final polyimide film, making it easier to obtain a polyimide film that is less likely to tear during film formation and has sufficient mechanical strength. Furthermore, suppressing tearing during the film formation process improves production efficiency and reduces production costs. Furthermore, the solution viscosity of the resin composition falls within an appropriate range, facilitating uniform coating. The preferred polyimide precursor concentration may vary depending on the desired application, the type of polyimide precursor, the weight-average molecular weight, the type of solvent contained in the resin composition, and the like; however, it is preferably 7 to 19% by mass, more preferably 9 to 18% by mass, and even more preferably 11 to 17% by mass or less.

[0026] The resin composition of the present invention may contain an imidization accelerator. The type of imidization accelerator is not particularly limited, and two or more compounds may be used in combination. Suitable examples of imidization accelerators include basic catalysts such as pyridine compounds, azole compounds, and tertiary amine compounds, and acidic catalysts such as benzoic acid. Examples of the pyridine compounds include isoquinoline, 1-methylisoquinoline, 4-dimethylaminopyridine, 2,2'-bipyridyl, nicotinic acid, pyridine, 4-phenylpyridine, 4-hydroxypyridine, and 2-methylpyridine. Examples of the azole compounds include 1-methylimidazole, N-tert-butoxycarbonylimidazole (N-Boc-imidazole), 2-methylimidazole, 2-phenylimidazole, benzimidazole, 2-ethyl-4-methylimidazole, 4-ethyl-2-methylimidazole, 4-methyl-2-phenylimidazole, 2-undecylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1H-imidazole, 1,2-dimethylimidazole, triazole, and benzotriazole. Examples of tertiary amine compounds include 1,8-diazabicyclo[5.4.0]-7-undecene, 1,5-diazabicyclo[4.3.0]nonene-5, 1,4-diazabicyclo[2.2.2]octane, etc. Examples of acidic catalysts include tetrazole, p-hydroxybenzoic acid, o-hydroxybenzoic acid, p-hydroxyphenylacetic acid, 2,4-dihydroxybenzoic acid, 4-hydroxyphenylpropionic acid, p-phenolsulfonic acid, p-aminophenol, m-aminobenzoic acid, p-aminobenzoic acid, etc.

[0027] The content of the imidization accelerator is not particularly limited, but is preferably 0.2 to 4.0 mol per mole of the repeating unit of the polyimide precursor, more preferably 0.5 to 3.5 mol, even more preferably 0.8 to 3.0 mol, even more preferably 1.0 to 2.5 mol, and particularly preferably 1.1 to 2.0 mol. By setting the content of the imidization accelerator within the above range, the storage stability of the resin composition can be appropriately maintained, while the mechanical strength of the film can be maintained at a higher level during film formation, particularly during heat treatment, and the flatness of the film can be maintained at a higher level. Furthermore, the mechanical strength of the polyimide film obtained can be further improved, and the flatness can be maintained at a higher level.

[0028] The resin composition of the present invention may contain a function-imparting agent such as an inorganic filler or a surfactant, as long as the properties of the polyimide film are not impaired. The amount of the function-imparting agent is not particularly limited, but is preferably 10% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the polyimide precursor in the resin composition.

[0029] The solution viscosity of the resin composition of the present invention is not particularly limited, but is preferably 200 to 6000 P, more preferably 500 to 4500 P, even more preferably 800 to 3500 P, still more preferably 1000 to 3000 P, and particularly preferably 1200 to 2500 P at a temperature of 20° C. By setting the solution viscosity within the above range, it is possible to suppress the occurrence of uneven thickness of the coating film and coating streaks in the coating step when forming a polyimide precursor film from the resin composition, and a more uniform coating film can be obtained.

[0030] <Method for Producing Resin Composition> The method for producing a resin composition in the present invention is not particularly limited, but preferably comprises a step of polymerizing a polyimide precursor in a resin composition by carrying out the following steps I to IV in this order: Step I: Purging the inside of a polymerization reaction vessel with an inert gas; Step II: Introducing a second solvent into the polymerization reactor; Step III: Introducing an amine-based component and an acid-based component into the polymerization reactor in amounts such that the concentration of the component becomes greater than 20% by mass, assuming that the two components react completely to form a polyimide precursor; Step IV: Adding a third solvent at least 4 hours after the end of step III.

[0031] <Step I> The inert gas in Step I is not particularly limited, and examples thereof include rare gases such as nitrogen gas, helium gas, neon gas, and argon gas. By replacing the atmosphere inside the polymerization reaction vessel with an inert gas, the amount of moisture and oxygen inside the polymerization reaction vessel is reduced, which leads to suppressing deactivation of acid components and amine components in the subsequent polymerization step, making it easier to increase the degree of polymerization and to obtain a polyimide precursor having a weight-average molecular weight of 260,000 to 1,000,000.

[0032] <Step II> The type of second solvent in Step II is not particularly limited, and examples thereof include N,N-dimethylformamide, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N-methyl-ε-caprolactam, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, 3-methyl-2-oxazolidone, hexamethylphosphoramide, and γ-butyrolactone (GBL), which may be used alone or in combination of two or more. Furthermore, a poor solvent such as toluene or xylene may be used in combination with these solvents to the extent that resin solids do not precipitate in the subsequent polymerization step.

[0033] The water content of the second solvent in Step II is not particularly limited, but is preferably low from the viewpoint of increasing the molecular weight of the polyimide precursor. For example, it is preferably 200 ppm by mass or less, more preferably 150 ppm by mass or less, and even more preferably 100 ppm by mass or less, and may even be 50 ppm by mass or less. By setting the water content of the solvent within the above range, deactivation of the acidic component in the subsequent polymerization step is suppressed, which results in an increase in the degree of polymerization of the polyimide precursor and makes it easier to obtain a polyimide precursor having a weight-average molecular weight of 260,000 to 1,000,000.

[0034] <Step III> The pyromellitic acid derivative as the acid component is not particularly limited, but is preferably pyromellitic acid, or its acid chloride, ester, or anhydride, more preferably anhydride, and even more preferably pyromellitic acid dianhydride (PMDA).

[0035] The 3,3',4,4'-biphenyltetracarboxylic acid derivative as the acid component is not particularly limited, but is preferably 3,3',4,4'-biphenyltetracarboxylic acid or its acid chloride, ester, or acid anhydride, more preferably the acid anhydride, and even more preferably 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA).

[0036] The 2,2'-bis(trifluoromethyl)benzidine derivative as the amine component is not particularly limited, but is preferably 2,2'-bis(trifluoromethyl)benzidine or its silylated or amidated derivative, and more preferably 2,2'-bis(trifluoromethyl)benzidine (TFMB).

[0037] In the present invention, the acid component may contain an acid component other than a pyromellitic acid derivative and a 3,3',4,4'-biphenyltetracarboxylic acid derivative. Examples of such acid components include aromatic tetracarboxylic acid derivatives, aliphatic tetracarboxylic acid derivatives, and alicyclic tetracarboxylic acid derivatives. Among these, aromatic tetracarboxylic acid derivatives and alicyclic tetracarboxylic acid derivatives are preferred, with aromatic tetracarboxylic acid derivatives being more preferred from the viewpoint of heat resistance, and alicyclic tetracarboxylic acid derivatives being more preferred from the viewpoint of transparency. These may be used alone or in combination of two or more.

[0038] Examples of aromatic tetracarboxylic acid derivatives include 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid, 4,4'-oxydiphthalic acid, 3,4'-oxydiphthalic acid, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylic acid)1,4-phenylene, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-yl)benzene-1,4-dicarboxylate, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(benzene-1,4-diyloxy)]dibenzene, and the like. 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(4-isopropyl 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(benzene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol- 1,1-dioxide-3,3-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(4-isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-diphenylsulfonetetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, 2,2',3,3'-biphenyltetracarboxylic acid, 2,2'-diphenoxy-4,4',5,5'-biphenyltetracarboxylic acid, pyromellitic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]diphthalic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]diphthalic acid, and other tetracarboxylic acids, as well as acid chlorides, esters, and acid anhydrides thereof. Further examples include double-decker silsesquioxane derivatives containing an acid anhydride group, which are represented by the following chemical formula (1):

[0039]

[0040] Examples of alicyclic tetracarboxylic acid derivatives include 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 1,2,3,4-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,3',4,4'-bicyclohexyltetracarboxylic acid, bicyclo[2,2,1]heptane-2,3,5,6-tetracarboxylic acid, bicyclo[2,2,2]octane-2,3,5,6-tetracarboxylic acid, and bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic acid. carboxylic acid, tetrahydroanthracene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic acid, decahydronaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4:5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6,7-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane norbornane-5,5'',6,6''-tetracarboxylic acid (also known as "norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid (also known as "norbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid) pyro-2'-cyclohexanone-6'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid), methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclopropanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclobutanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cycloheptanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclooctanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclononanone-α'-spiro-2''-norbornane-5,5'',6 ,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclodecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cycloundecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclododecanone-α'-spiro-2''-norbornane-5,5'', ,6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotridecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotetradecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentadecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-(methylcyclopentanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-(methylcyclohexanone)-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, and acid chlorides, esters, and acid anhydrides thereof.

[0041] The content of acidic components other than pyromellitic acid derivatives and 3,3',4,4'-biphenyltetracarboxylic acid derivatives is not particularly limited, but when the amount of all acidic components is taken as 100 mol%, the content of acidic components other than pyromellitic acid derivatives and 3,3',4,4'-biphenyltetracarboxylic acid derivatives is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, even more preferably 2 mol% or less, particularly preferably 1 mol% or less, and may be 0.5 mol% or less or even 0 mol%.

[0042] In the present invention, the acid component may further include a dicarboxylic acid. Examples of the dicarboxylic acid include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, and 4,4'-oxydibenzenecarboxylic acid, and aliphatic dicarboxylic acids such as oxalic acid, succinic acid, glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecadioic acid, dodecanedioic acid, 2-methylsuccinic acid, and maleic acid, as well as acid chlorides, esters, and anhydrides thereof.

[0043] The content of dicarboxylic acids is not particularly limited, but when the amount of all acid components is taken as 100 mol%, the content of dicarboxylic acids is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, still more preferably 5 mol% or less, particularly preferably 1 mol% or less, and may be 0.5 mol% or less or even 0 mol%.

[0044] In the present invention, the amine-based component may contain a diamine other than a 2,2'-bis(trifluoromethyl)benzidine derivative. Examples of such amine-based components that can be used include aromatic diamine derivatives, aliphatic diamine derivatives, and alicyclic diamine derivatives. Among these, aromatic diamine derivatives are preferred from the viewpoint of heat resistance, and alicyclic diamine derivatives are preferred from the viewpoint of transparency. Diamines other than 2,2'-bis(trifluoromethyl)benzidine derivatives may be used alone or in combination of two or more.

[0045] Examples of aromatic diamine derivatives include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide ... N-(4-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 4-amino-N-(4-aminophenyl)benzamide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2 '-trifluoromethyl-4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4 '-Diaminobenzophenone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(4-aminophenoxy)phenyl]ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 1,1-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,1-bis[4-(4-aminophenoxy)phenyl]butane, 1,3-bis[4-(4-aminophenoxy)phenyl]butane, 1,4-bis[4-(4-aminophenoxy)phenyl]butane, 2,2-bis[4-(4-aminophenoxy)phenyl]butane, 2,3-bis[4-(4-aminophenoxy)phenyl]butane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3-methylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl] 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4'-bis( 4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4- Bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[(3-aminophenoxy)benzoyl]benzene, 1,1-bis[4-(3-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl sulfide, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, bis[4-(3-aminophenoxy)phenyl]sulfoxide, 4,4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, bis[4-{4-(4-aminophenoxy)pheno hydroxy}phenyl] sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α,α-dimethylbenzyl]benzene , 1,3-bis[4-(4-amino-6-cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4'-diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone, 3,3'-diamino-4, 4'-diviphenoxybenzophenone, 4,4'-diamino-5,5'-diviphenoxybenzophenone, 3,4'-diamino-4,5'-diviphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis(3-amino-4-phenoxybenzoyl)benzene, 1,4-bis(3-amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(4-amino-5-biphenoxybenzoyl)benzene, 1,4-bis(4-amino-5-biphenoxybenzoyl)benzene, 2,6-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzonitrile, 4,4'-[9H-fluorene-9,9-diyl]bisaniline (also known as "9,9-bis(4-aminophenyl)fluorene"), spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]bisaniline, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]bisaniline,

[0033] Examples of the aromatic diamines include aromatic diamines having a benzoxazole structure, 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]bisaniline, 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]bisaniline, 9,10-bis(4-aminophenyl)adenine, 2,4-bis(4-aminophenyl)cyclobutane-1,3-dimethyldicarboxylate, aromatic diamines having a benzoxazole structure, amino group-containing double-decker silsesquioxane derivatives represented by the structure of the following chemical formula (2), and aromatic diamines in which some or all of the hydrogen atoms on the aromatic ring of the above aromatic diamines have been substituted with halogen atoms, alkyl or alkoxy groups having 1 to 3 carbon atoms, cyano groups, or halogenated alkyl or alkoxy groups having 1 to 3 carbon atoms in which some or all of the hydrogen atoms of the alkyl or alkoxy groups have been substituted with halogen atoms, and silylated and amidated products thereof. The aromatic diamines having a benzoxazole structure are not particularly limited, and examples thereof include 5-amino-2-(p-aminophenyl)benzoxazole, 6-amino-2-(p-aminophenyl)benzoxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2′-p-phenylenebis(5-aminobenzoxazole), 2,2'-p-phenylenebis(6-aminobenzoxazole), 1-(5-aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(4,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, Examples of such oxazoles include 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:5,4-d']bisoxazole, and 2,6-(3,3'-diaminodiphenyl)benzo[1,2-d:4,5-d']bisoxazole. These oxazoles may be used alone or in combination of two or more.

[0046]

[0047] Examples of the alicyclic diamine derivative include alicyclic diamines such as 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, and 4,4'-methylenebis(2,6-dimethylcyclohexylamine), as well as silylated and amidated products thereof. These may be used alone or in combination of two or more.

[0048] The content of amine components other than 2,2'-bis(trifluoromethyl)benzidine derivatives is not particularly limited, but when the amount of all amine components is taken as 100 mol%, the content of diamines other than 2,2'-bis(trifluoromethyl)benzidine derivatives is preferably 30 mol% or less, more preferably 20 mol% or less, even more preferably 10 mol% or less, still more preferably 2 mol% or less, particularly preferably 1 mol% or less, and may be 0.5 mol% or less or even 0 mol%.

[0049] The amounts of the acid component and amine component introduced in Step III are preferably introduced in amounts that result in a concentration greater than 20% by mass, assuming complete reaction to form a polyimide precursor, more preferably greater than 23% by mass, and even more preferably greater than 26% by mass. In a typical example of the present invention, s-BPDA is used as the acid component and TFMB is used as the amine component. However, s-BPDA and TFMB, especially TFMB, have low reactivity and therefore require a long polymerization time. This increases the total amount of polymerization inhibitors (e.g., water and oxygen) entering the polymerization process from outside the system, which tends to make it difficult to increase the degree of polymerization. Therefore, by focusing on the initial concentrations of the acid component and amine component and adjusting the amounts of the acid component and amine component introduced in Step III to achieve the above-mentioned concentration ranges, it was found that the polymerization reaction rate increased and the polymerization time could be shortened. Shortening the polymerization time also reduces the total amount of polymerization inhibitors entering from outside the system, thereby increasing the achievable degree of polymerization. This facilitates the production of a polyimide precursor having a weight-average molecular weight of 260,000 to 1,000,000. Although there are no particular limitations on the upper limit of the amount of the acidic component and the amineic component introduced in Step III, the higher the concentration of the polyimide precursor in Step III, the worse the solubility of the acidic component and the amineic component becomes, and further, the viscosity of the polymerization solution increases, making it difficult to stir for uniform polymerization. Therefore, the amount is preferably 40% by mass or less.

[0050] The method for introducing the acid component and the amine component in Step III is not particularly limited, but examples include a method in which the acid component and the amine component are introduced simultaneously, a method in which the amine component is introduced first and then the acid component, and a method in which the acid component is introduced first and then the amine component. In a typical example of the present invention, PMDA and s-BPDA are used as the acid component and TFMB as the amine component. Because these components are all solids (powder), the solids may adhere to each other and form lumps during or after introduction. If lumps form, they are difficult to dissolve, prolonging polymerization, increasing the total amount of polymerization inhibitors (such as water and oxygen) entering from outside the system during the polymerization process, and as a result, making it difficult to increase the degree of polymerization. Therefore, when the acid component and the amine component are solids (powder), it is preferable to introduce them without forming lumps. Examples of such methods include a method in which they are introduced under high-speed stirring, a method in which the amine component is introduced first and then completely dissolved before introducing the acid component, and a method in which the acid component is introduced first and then completely dissolved before introducing the amine component. The time required to completely dissolve the components introduced earlier varies depending on the acid component and amine component used, their ratio, the solvent, etc., but is typically preferably 10 minutes or more, more preferably 15 minutes or more, even more preferably 30 minutes or more, still more preferably 1 hour or more, and particularly preferably 2 hours or more.

[0051] When there are two or more amine components including a 2,2'-bis(trifluoromethyl)benzidine derivative in Step III, the method for introducing the amine components is not particularly limited, and examples include a method in which all amine components including the 2,2'-bis(trifluoromethyl)benzidine derivative are introduced at once, and a method in which the 2,2'-bis(trifluoromethyl)benzidine derivative is first introduced and then the amine components other than the 2,2'-bis(trifluoromethyl)benzidine derivative are introduced at once. The time from first introducing the 2,2'-bis(trifluoromethyl)benzidine derivative until the amine components other than the 2,2'-bis(trifluoromethyl)benzidine derivative are introduced at once varies depending on the acid component and amine component used, their ratio, solvent, etc., but is typically preferably 10 minutes or more, more preferably 15 minutes or more, even more preferably 30 minutes or more, still more preferably 1 hour or more, and particularly preferably 2 hours or more.

[0052] The method for introducing the acid components, pyromellitic acid derivative and 3,3',4,4'-biphenyltetracarboxylic acid derivative, in Step III is not particularly limited, but examples include a method in which the pyromellitic acid derivative and 3,3',4,4'-biphenyltetracarboxylic acid derivative are introduced all at once, a method in which the 3,3',4,4'-biphenyltetracarboxylic acid derivative is introduced first and then the pyromellitic acid derivative is introduced, and a method in which the pyromellitic acid derivative is introduced first and then the 3,3',4,4'-biphenyltetracarboxylic acid derivative is introduced. The time from introducing the 3,3',4,4'-biphenyltetracarboxylic acid derivative first to introducing the pyromellitic acid derivative, or the time from introducing the pyromellitic acid derivative first to introducing the 3,3',4,4'-biphenyltetracarboxylic acid derivative first, varies depending on the acid components used, their ratios, solvent, etc., but is typically preferably 10 minutes or more, more preferably 15 minutes or more, even more preferably 30 minutes or more, even more preferably 1 hour or more, and particularly preferably 2 hours or more.

[0053] In the step III, when the acid component is three or more components including a pyromellitic acid derivative and a 3,3',4,4'-biphenyltetracarboxylic acid derivative, the method of introducing the acid component is not particularly limited, but includes a method of introducing all of the acid components including the pyromellitic acid derivative and the 3,3',4,4'-biphenyltetracarboxylic acid derivative all at once, a method of first introducing the pyromellitic acid derivative and the 3,3',4,4'-biphenyltetracarboxylic acid derivative and then introducing the other acid components all at once, a method of first introducing the 3,3',4,4'-biphenyltetracarboxylic acid derivative and then introducing the acid components other than the 3,3',4,4'-biphenyltetracarboxylic acid derivative all at once, a method of first introducing the pyromellitic acid derivative and then introducing the acid components other than the pyromellitic acid derivative all at once, and the like. The time from first introducing the pyromellitic acid derivative and 3,3',4,4'-biphenyltetracarboxylic acid derivative until all other acid components are introduced at once, the time from first introducing the 3,3',4,4'-biphenyltetracarboxylic acid derivative until all other acid components are introduced at once, and the time from first introducing the pyromellitic acid derivative until all other acid components are introduced at once will vary depending on the acid components used, their ratios, solvent, etc., but is typically preferably 10 minutes or more, more preferably 15 minutes or more, even more preferably 30 minutes or more, still more preferably 1 hour or more, and particularly preferably 2 hours or more.

[0054] <Step IV> Step IV is preferably performed at least 4 hours after Step III (after the introduction of the entire amine and acid components has been completed), more preferably at least 5 hours, and even more preferably at least 6 hours. In a typical example of the present invention, s-BPDA is used as the acid component and TFMB as the amine component. However, s-BPDA and TFMB, especially TFMB, have low reactivity and therefore require a long polymerization time. This increases the total amount of polymerization inhibitors (e.g., water and oxygen) entering the polymerization process from outside the system, which tends to make it difficult to increase the degree of polymerization. Therefore, by focusing on the initial concentrations of the acid and amine components and adjusting the amounts of the acid and amine components introduced in Step III to achieve the above-mentioned concentration ranges, it was found that the polymerization reaction rate increased and the polymerization time could be shortened. Shortening the polymerization time also reduces the total amount of polymerization inhibitors entering the system from outside, thereby increasing the achievable degree of polymerization. Furthermore, by carrying out the step IV after a lapse of at least 4 hours from the step III, it has become even easier to obtain a polyimide precursor having a weight-average molecular weight of 260,000 to 1,000,000.

[0055] The amount of the third solvent added in step IV is not particularly limited, but it is preferable to add an amount such that the concentration of the polyimide precursor in the resin composition becomes 5 to 20 mass %. The solvent can be added in multiple batches.

[0056] The type of third solvent used in Step IV is not particularly limited, and examples include N,N-dimethylformamide, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N-methyl-ε-caprolactam, dimethyl sulfoxide, sulfolane, 1,3-dimethyl-2-imidazolidinone, 1,3-dimethyl-3,4,5,6-tetrahydro-2(1H)-pyrimidinone, 3-methyl-2-oxazolidone, hexamethylphosphoramide, and γ-butyrolactone (GBL). These solvents may be used alone or in combination of two or more. Furthermore, a poor solvent such as toluene or xylene may be used in combination with these solvents to the extent that resin solids are not precipitated. Furthermore, the second and third solvents used in Steps II and IV may be the same or different.

[0057] The water content of the third solvent in Step IV is not particularly limited, but a low water content is preferable from the viewpoint of increasing the molecular weight of the polyimide precursor. For example, it is preferably 200 ppm by mass or less, more preferably 150 ppm by mass or less, even more preferably 100 ppm by mass or less, and even more preferably 50 ppm by mass or less. The presence of water deactivates the acidic components through hydrolysis, making it difficult to increase the degree of polymerization. However, by keeping the water content of the solvent within the above range, the amount of deactivation of the tetracarboxylic dianhydride can be suppressed, which in turn facilitates increasing the degree of polymerization of the polyimide precursor and makes it easier to obtain a polyimide precursor with a weight-average molecular weight of 260,000 to 1,000,000. For the same reason, the water content of raw materials other than the solvent is also preferably 3,000 ppm by mass or less, more preferably 1,000 ppm by mass or less.

[0058] The moisture content of a solvent is thought to be affected by factors such as the grade of the solvent used, the solvent container, storage conditions, and the time between opening and use. It is also thought to be affected by factors such as whether the reactor is purged with inert gas before polymerization and whether an inert gas is circulated during polymerization. Therefore, when polymerizing a polyimide precursor, it is recommended to use high-purity raw materials and a solvent with a low moisture content, as well as to take measures to prevent moisture from the external environment from entering the system before and during the reaction.

[0059] The molar ratio of the acid component to the amine component (acid / amine ratio) when polymerizing the polyimide precursor in the resin composition of the present invention is not particularly limited, but is preferably 0.990 to 1.010, more preferably 0.992 to 1.008, even more preferably 0.994 to 1.006, and even more preferably 0.996 to 1.004. By setting the acid / amine ratio within the above range, the degree of polymerization of the polyimide precursor tends to increase, making it easier to obtain a polyimide precursor having a weight-average molecular weight of 260,000 to 1,000,000.

[0060] The temperature at which the polyimide precursor contained in the resin composition of the present invention is polymerized is not particularly limited, but heating may be performed as necessary when dissolving the acid component or amine component in a solvent. However, excessively high temperatures can accelerate depolymerization of the polyimide precursor, making it difficult to increase the molecular weight to the specified level. The temperature at which the acid component or amine component is dissolved is preferably 0 to 60°C, more preferably 5 to 50°C, and even more preferably 10 to 40°C.

[0061] The polymerization time for polymerizing the polyimide precursor contained in the resin composition of the present invention is preferably 6 to 72 hours, more preferably 8 to 48 hours. If the polymerization time is shorter than 6 hours, a polyimide precursor with a narrow polymerization degree distribution cannot be obtained. On the other hand, if the polymerization time is longer, moisture, oxygen, etc. will flow into the system, deactivating the reaction sites and making it difficult to increase the molecular weight of the polyimide precursor composition. Furthermore, from the viewpoint of productivity, the polymerization time is preferably 72 hours or less.

[0062] The polymerization of the polyimide precursor contained in the resin composition of the present invention is preferably carried out under an inert gas atmosphere, which is not particularly limited and includes, for example, nitrogen gas and rare gases such as helium gas, neon gas, and argon gas.

[0063] <Polyimide Film> A polyimide film can be obtained from the resin composition of the present invention. The method for producing the polyimide film is not particularly limited, but preferred embodiments are as described below. The physical properties of the polyimide film are not particularly limited, but preferred embodiments are as described below.

[0064] The thickness of the polyimide film in the present invention is not particularly limited, but is preferably in the range of 1 to 50 μm, more preferably in the range of 5 to 20 μm.

[0065] The average coefficient of linear expansion (CTE) of the polyimide film in the present invention between 50°C and 200°C is preferably -5 to +20 ppm / °C, more preferably -4 to +15 ppm / °C, and even more preferably -3 to +10 ppm / °C. When the CTE is within the above range, no significant warpage occurs in the process of forming a desired functional element into a laminate laminated with an inorganic support, which does not interfere with element formation and provides excellent processability. The CTE was measured according to the method described in the Examples.

[0066] The tensile strength of the polyimide film of the present invention is preferably 150 MPa or more, more preferably 200 MPa or more, even more preferably 250 MPa or more, and even more preferably 300 MPa or more. If the tensile strength is 150 MPa or more, the film is less likely to break during the processing of functional elements, etc., and is easier to handle. There is no particular upper limit to the tensile strength, but it is preferably 1000 MPa or less, more preferably 900 MPa or less, and even more preferably 800 MPa or less. The tensile strength is measured according to the method described in the Examples.

[0067] The tensile modulus of the polyimide film of the present invention is preferably 2 GPa or more, more preferably 4 GPa or more, and even more preferably 6 GPa or more. If the tensile modulus is 2 GPa or more, the film is less likely to be tensilely deformed during the processing of functional elements, etc., and is therefore easier to handle. The upper limit of the tensile modulus is not particularly limited, but is preferably 20 GPa or less, more preferably 18 GPa or less, and even more preferably 16 GPa or less. The tensile modulus is measured according to the method described in the Examples.

[0068] The breaking elongation of the polyimide film in the present invention is preferably 10% or more, more preferably 15% or more, and even more preferably 20% or more. If the breaking elongation is 10% or more, it is possible to ensure appropriate flexibility in the processing of functional elements, etc., and the handling properties will be better. There is no particular upper limit to the breaking elongation, but it is preferably 200% or less, more preferably 180% or less, and even more preferably 160% or less. The breaking elongation is measured by the method described in the examples.

[0069] The yellowness index (YI) of the polyimide film of the present invention, calculated as a film thickness of 15 μm, is preferably 20.0 or less, more preferably 15.0 or less, and even more preferably 10.0 or less. A YI of 20.0 or less makes the film suitable for use in flexible devices and flexible displays that require transparency. The lower limit of YI is not particularly limited, but for use in flexible devices, it is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. The YI is measured according to the method described in the Examples.

[0070] The haze of the polyimide film of the present invention is preferably 2.0% or less, more preferably 1.7% or less, and even more preferably 1.5% or less. If the haze is 2.0% or less, the film can be suitably used as a component of a flexible device that requires transparency, particularly as a component of a flexible display. The lower limit of the haze is not particularly limited, but for use as a flexible device, it is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more. The haze is measured according to the method described in the examples.

[0071] The total light transmittance of the polyimide film of the present invention is preferably 85% or more, more preferably 86% or more, even more preferably 87% or more, and even more preferably 88% or more. A total light transmittance of 85% or more makes it suitable for use as a component of a flexible device that requires transparency, particularly as a component of a flexible display. There is no particular upper limit for the total light transmittance, but for use as a flexible device, it is preferably 99% or less, more preferably 98% or less, and even more preferably 97% or less. The total light transmittance is measured according to the method described in the Examples.

[0072] The 1% weight loss temperature of the polyimide film in the present invention is preferably 450°C or higher, more preferably 500°C or higher, even more preferably 520°C or higher, and even more preferably 530°C or higher. A 1% weight loss temperature of 450°C or higher makes it applicable to processes requiring high-temperature processing, such as the formation of functional elements. In particular, when forming low-temperature polysilicon, the film is exposed to high temperatures of 450°C or higher, and a 1% weight loss temperature of 450°C or higher can withstand this. The upper limit of the 1% weight loss temperature is not particularly limited, but is preferably 800°C or lower, more preferably 780°C or lower, and even more preferably 760°C or lower. The 1% weight loss temperature is measured according to the method described in the Examples.

[0073] The glass transition temperature of the polyimide film in the present invention is preferably 350°C or higher, more preferably 360°C or higher, even more preferably 370°C or higher, still more preferably 380°C or higher, and particularly preferably 390°C or higher. A glass transition temperature of 350°C or higher makes it applicable to processes requiring high-temperature processing, such as the formation of functional elements. The glass transition temperature is measured by the method described in the Examples.

[0074] <Method for Producing Polyimide Film> The method for producing a polyimide film, which is a cured product of the resin composition of the present invention, is not particularly limited, but preferably includes step α of coating a support with a resin composition containing a polyimide precursor and then drying off part of the solvent to produce a polyimide precursor film, and step β of peeling the polyimide precursor film from the support and, with its edges fixed, heat treating it to cause a dehydration ring-closure reaction while removing the solvent.

[0075] The support used in step α is not particularly limited, and examples thereof include a resin film substrate, a stainless steel belt substrate, a glass substrate, etc. As the resin film substrate, it is preferable to use a resin film substrate that does not swell or dissolve in the solvent contained in the resin solution, and examples thereof include a polyethylene terephthalate (PET) film, a polyethylene naphthalate (PEN) film, a polyolefin (PO) film, a cycloolefin (COP) film, etc. Furthermore, it is preferable to use a support that has easy peelability so that the solvent-containing resin film can be peeled off from the support.

[0076] In the step α, the method for coating the support with the resin composition is not particularly limited, but examples thereof include die coating, comma coating, blade coating, roll coating, knife coating, and bar coating, and two of these methods may be combined. The comma coating, die coating, or a combination of these is preferred from the viewpoint of productivity.

[0077] In step α, the method for drying a portion of the solvent in the resin composition on the support is not particularly limited, and examples include air drying, hot air drying, infrared heat drying, and heat drying by heat transfer from the support, and two or more of these methods may be combined. The solvent content of the polyimide precursor film obtained by drying a portion of the solvent is preferably 3 to 50 mass %, more preferably 5 to 40 mass %, and even more preferably 7 to 30 mass %. If the solvent content is above the above upper limit, the elasticity of the polyimide precursor film will be too weak, making it difficult to peel from the support. If the solvent content is below the above lower limit, the adhesion between the polyimide precursor film and the support will be too strong, making peeling from the support more likely to result in poor peeling. However, by keeping the solvent content within the above range, peeling from the support will be easier.

[0078] In the step β, the method for peeling the polyimide precursor film from the support is not particularly limited, and examples thereof include a method of peeling the polyimide precursor film from the edge using tweezers or the like, a method of making an incision in the laminate, attaching adhesive tape to one side of the incision and then peeling the film from the tape, and a method of vacuum-adsorbing one side of the incision in the resin film and then peeling the film from the tape.

[0079] In step β, the method for fixing the ends of the polyimide precursor film is not particularly limited. However, when the polyimide precursor film is heated during transport, a tenter-type transport device is generally used. When a tenter-type transport device is used, it is preferable to hold both ends of the polyimide precursor film by piercing them with multiple pins of the pin tenter-type transport device. When a clip tenter-type transport device is used, it is preferable to hold both ends of the polyimide precursor film by clamping them with multiple clips of the clip tenter-type transport device. It is preferable to fix the polyimide precursor film only at the both ends. It is also preferable to transport the polyimide precursor film while adjusting the pin spacing or clip spacing in the film width direction so as to prevent unnecessary slack in the polyimide precursor film.

[0080] The heating method in step β is not particularly limited, but examples include air blowing, hot air blowing, infrared radiation, and heat transfer from a support, and two of these methods may be combined. The maximum heating temperature is also not particularly limited, but is preferably 300 to 450°C, more preferably 310 to 400°C, and even more preferably 320 to 380°C. By maintaining the maximum heating temperature within this range, high mechanical strength and a low CTE can be achieved without deteriorating the YI of the resulting polyimide film. The method for increasing the temperature to the maximum temperature is also not particularly limited, but the maximum temperature may be reached in one step at a predetermined heating rate, or the maximum temperature may be reached by increasing the temperature stepwise. The heating rate is preferably 300°C / min or less, more preferably 100°C / min or less, even more preferably 40°C / min or less, even more preferably 30°C / min or less, even more preferably 20°C / min or less, and especially preferably 10°C / min or less.

[0081] The resin composition can be used to form a polyimide layer (polyimide film) that covers a part or the entirety of a semiconductor wafer. The thickness of the polyimide layer to be formed is not particularly limited and may be a thickness appropriate for the desired function, but may be, for example, 0.1 μm to 1000 μm, 1 μm to 500 μm, 3 μm to 300 μm, 5 μm to 150 μm, or 10 μm to 100 μm.

[0082] The material of the semiconductor wafer is not particularly limited, and examples thereof include silicon wafers, silicon carbide wafers, and compound semiconductor wafers. Silicon wafers are thin sheets of single-crystal or polycrystalline silicon, and include n-type or p-type doped silicon wafers, intrinsic silicon wafers, and silicon wafers with a silicon oxide layer or various thin films deposited on the surface of the silicon wafer. Also usable are semiconductor wafers and compound semiconductor wafers of germanium, silicon-germanium, gallium-arsenic, aluminum-gallium-indium, nitrogen-phosphorus-arsenic-antimony, SiC, InP (indium phosphide), InGaAs, GaInNAs, LT, LN, ZnO (zinc oxide), CdTe (cadmium tellurium), and ZnSe (zinc selenide).

[0083] The method for forming a polyimide layer that covers a part or the whole of a semiconductor wafer is not particularly limited, and the following manufacturing method can be given as an example: A method for manufacturing a polyimide-coated semiconductor wafer, comprising: Step A of applying a resin composition to at least a part of the surface of a semiconductor wafer; Step B of heating the semiconductor wafer that has undergone Step A to dry off a part of the solvent contained in the resin composition; and Step C of further heat-treating the semiconductor wafer that has undergone Step B to form a polyimide layer.

[0084] The method for applying the resin composition to the semiconductor wafer in step A is not particularly limited, and application can be performed by, for example, a spin coating method, a bar coater method, a dispenser method, an inkjet method, a screen printing method, a spray coating method, etc. When applying the resin composition to the semiconductor wafer, a part of the semiconductor wafer may be masked.

[0085] The method for drying a portion of the solvent in the resin composition in step B is not particularly limited, but is preferably the same as the method described in the description of step α. In step B, at least a portion of the volatile components contained in the resin composition are volatilized, and the imidization reaction of the polyimide precursor may proceed in parallel with this.

[0086] The method and temperature of the heat treatment in step C are not particularly limited, but are preferably the same as the heating method, maximum heating temperature, and method of increasing the temperature to reach the maximum temperature described in the description of step β. In step C, the imidization reaction of the polyimide precursor contained in the resin composition proceeds, and volatilization of volatile components may occur in parallel with this.

[0087] By employing such a method for producing a polyimide-coated semiconductor wafer, a polyimide layer having physical properties equivalent to those of a polyimide film can be obtained.

[0088] <Uses of Polyimide Film> The polyimide film obtained from the polyimide precursor according to the present embodiment can be widely used, for example, as an insulating coating for semiconductor wafers such as silicon wafers, an insulating film in a semiconductor element structure, an underfill, fixing of chip components, an insulator in wafer-level packaging, a TFT-LCD insulating film, an electrode protection film, etc. Furthermore, in the production of flexible devices, the polyimide film can be suitably used, particularly as a TFT substrate, a color filter substrate, or a touch panel substrate. Here, examples of flexible devices to which the polyimide film according to the present embodiment can be used include TFT devices for flexible displays, flexible solar cells, flexible touch panels, flexible lighting, flexible batteries, flexible printed circuit boards, flexible color filters, and surface cover lenses for smartphones.

[0089] The present invention will be described in detail below using examples, but is not limited to the following examples. Measurement values ​​in the examples and comparative examples were measured by the following methods unless otherwise specified.

[0090] <Weight-average molecular weight of polyimide precursor> A predetermined amount of resin composition was mixed with 4 mL of solvent so that the concentration of polyimide precursor was 0.1% by mass. After 7 to 9 hours, the mixture was filtered through a 0.20 μm membrane filter to obtain a sample solution. Using the obtained sample solution, gel permeation chromatography (GPC) measurement was performed under the following conditions, and the weight-average molecular weight was calculated in terms of standard polystyrene. Instrument name: TOSOH HLC-8420GPC Column: TSKgel SuperAWM-H x 2 (TOSOH) Solvent: DMAc / 30 mM LiBr / 60 mM H3PO4 Flow rate: 0.3 mL / min Injection volume: 10 μL Temperature: 40°C Detector: RI

[0091] <Reduced Viscosity of Polyimide Precursor> A sample solution was prepared by mixing predetermined amounts of the resin composition and N,N-dimethylacetamide so that the concentration of the polyimide precursor was 0.2 g / dl, and then the reduced viscosity was measured in a thermostatic water bath at 25±1°C using an Ubbelohde-type viscometer.

[0092] <Solution Viscosity (η) of Resin Composition> Using a temperature-controlled viscometer (RE85U manufactured by Toki Sangyo Co., Ltd.), the viscosity of the resin composition to be measured was measured at 20° C. using a cone rotor and a rotation speed that allows measurement of the viscosity. Note that measurable rotation speeds are, for example, 0.5, 1, 2.5, 5, 10, 20, 50, and 100 rpm, and specific examples of measurable cone rotors are, for example, 1°34′ (cone rotor angle)×R24 (cone rotor diameter), 1°34′×R12, 0.8°×R24, 0.8°×R12, 3°×R24, 3°×R12, 3°×R17.65, 3°×R14, 3°×R12, and 3°×R9.7.

[0093] <Coatability Evaluation> Coating was performed and evaluated by the methods described in Examples 1 to 9 and Comparative Examples 1 to 8. The support was visually observed, and if the coating was uniform, the coatability was rated as "good," and if unevenness or streaks occurred and the coating was not uniform, the coatability was rated as "poor."

[0094] <Evaluation of Film Formability of Polyimide Precursor Films> Coating, drying, and heat treatment were carried out by the methods described in Examples 1 to 9 and Comparative Examples 1 to 7. If the film broke during the process, the film formability was rated as "×", and otherwise the film formability was rated as "○".

[0095] <Polyimide Film Thickness> The thickness of the polyimide film was measured using a film thickness measuring instrument HKT-1216 (manufactured by Mahl Corporation). A 50 mm square piece of film was cut out from the center of the film in the width direction, and the film thickness at the center was measured. Measurement samples were taken from three different positions along the length of the film roll, and each sample was measured once, and the average value of the three measured values ​​was taken as the film thickness.

[0096] <Total Light Transmittance (TT) of Polyimide Film> The total light transmittance (TT) of the film was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.). A D65 lamp was used as the light source. A 50 mm square piece of film was cut out from the center of the film in the width direction, and the total light transmittance was measured. Measurement samples were taken from three different positions in the length direction of the film roll, and one measurement was performed on each sample, and the average value of the three measured values ​​was used as the total light transmittance (TT) of the film.

[0097] <Haze of Polyimide Film> The haze of the film was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). A D65 lamp was used as the light source. The collection of the measurement sample, measurement, and handling of the measurement value were the same as for the sample for measuring total light transmittance.

[0098] <Yellowness Index of Polyimide Film, Equivalent to 15 μm Thickness, YI> Using a color meter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) and a C2 light source, the tristimulus values ​​X, Y, and Z of the film were measured in accordance with ASTM D1925, and the yellowness index, Equivalent to 15 μm thick, YI was calculated using the following formula (where t is the thickness of the polyimide film). The collection and measurement of the measurement sample and the handling of the measured values ​​were the same as for the total light transmittance measurement sample. YI = {100 × (1.28X - 1.06Z) / Y} × 15 / t

[0099] <Tensile Modulus, Tensile Break Strength, and Tensile Break Elongation of Polyimide Film> Polyimide film was cut into 100 mm x 10 mm strips with the machine direction (MD) or width direction (TD) as the longitudinal direction. Six test pieces were cut from the center of the width direction of the roll film, three in each direction, with the machine direction or the width direction as the longitudinal direction. Using a tensile tester (Shimadzu Corporation, Autograph (registered trademark), model AG-5000A), the tensile modulus (unit: GPa), tensile break strength (unit: MPa), and tensile break elongation (unit: %) were measured at 25°C, a pulling rate of 50 mm / min, and a chuck distance of 40 mm. The average values ​​of the six measurements were used to determine the tensile modulus, tensile break strength, and tensile break elongation of the film. The tensile modulus was calculated using the tensile strengths Y1 and Y2 (unit: MPa) and tensile elongations X1 and X2 (unit: %) at tensile loads of 5N and 10N, respectively, according to the following formula: Tensile modulus = [(Y2 - Y1) / {(X2 - X1) / 100}] / 1000

[0100] <1% Weight Loss Temperature of Polyimide Film> Measurement was performed using a TGA device (TGA-50, Shimadzu Corporation). A sample of approximately 10 mg was cut from the center portion in the width direction, placed on an aluminum pan, and measured under a nitrogen atmosphere at a heating rate of 10°C / min. The weight at which the film reached 150°C was used as the base point, and the temperature at which the film lost 1% weight was defined as the 1% weight loss temperature.

[0101] <Glass Transition Temperature of Polyimide Film> Polyimide films were cut into strips measuring 30 mm x 5 mm in either the machine direction (MD) or the width direction (TD), with the machine direction being the longitudinal direction, to prepare test specimens. The storage modulus (E') and loss modulus (E") were measured under the following conditions, and the glass transition temperature was determined as the peak temperature at which the peak height was greatest in the temperature dependence curve of tan δ (= E" / E'), which is the value obtained by dividing the loss modulus by the storage modulus. Two measurements were performed on each polyimide film test specimen in the MD and TD directions, one each, and the average value was used as the glass transition temperature of the polyimide film. Device name: Discovery DMA 850 manufactured by TA Instruments Distance between chucks: 20 mm Sample width: 5 mm Preload force: 0.1 N Strain: 0.1% Force track: 125% Heating start temperature: 25°C Heating end temperature: 500°C Heating rate: 5°C / min Measurement frequency: 10 Hz

[0102] <Coefficient of Linear Expansion (CTE) of Polyimide Film> Polyimide film was cut into 15 mm x 4 mm strips with the machine direction (MD) or width direction (TD) as the longitudinal direction. Measurements were performed using a TMA (TMA4000S, BRUKER AXIS). The sample was placed in the apparatus with a chuck distance of 10 mm and a load of 5 gf. The sample was heated to 250°C at a heating rate of 20°C / min under an argon atmosphere, and then cooled to 30°C at a rate of 5°C / min. During the cooling process, the difference in chuck length / temperature difference was measured at 15°C intervals, such as from 200°C to 185°C and from 185°C to 170°C. This measurement was repeated up to 50°C, and the average of 10 measurements from 200°C to 50°C was calculated and used as the CTE for that measurement. The measurement was carried out twice for each polyimide film sample, once in the MD direction and once in the TD direction, and the average value was taken as the CTE of the polyimide film.

[0103] <Production Examples of Polyimide Precursor Resin Compositions> <Example 1> After the atmosphere inside a reaction vessel equipped with a nitrogen inlet tube, thermometer, stirring blade, and temperature control function was replaced with nitrogen, the temperature control function was set to 20°C under a nitrogen stream, and DMAc (3068 g) with a moisture content of 80 ppm was introduced into the reaction vessel. Subsequently, TFMB (640.00 g) was introduced and stirred and mixed for 30 minutes to dissolve. Subsequently, s-BPDA (234.26 g) was introduced and stirred and mixed for 2 hours. Subsequently, PMDA (260.50 g) was introduced and stirred and mixed for 4 hours. Subsequently, DMAc (3903 g) with a moisture content of 80 ppm was introduced and stirred for 40 hours to obtain Resin Composition A1. The physical properties of Resin Composition A1 are as shown in Table 1.

[0104] A dispersion (Nissan Chemical Industries, Ltd.'s "Snowtex (registered trademark) DMAC-ST-ZL") prepared by dispersing colloidal silica (average particle size 80 nm) in DMAc at a concentration of 20% by mass as a lubricant was added to resin composition A1 in an amount such that the silica content was 0.3% by mass relative to the total polymer solids content in the resin composition, and the mixture was thoroughly stirred. The resin composition was then degassed and coated onto the non-lubricated side of polyethylene terephthalate film A4100 (Toyobo Co., Ltd.) using a comma coater to a thickness such that the final polyimide film thickness was 15 μm. This was then subjected to a heat treatment for 18 minutes in a dry atmosphere at 100°C to obtain a self-supporting film (polyimide precursor film) made of a polyimide precursor. The polyimide precursor film was peeled from the support and passed through a pin tenter with a pin sheet. The film edges were inserted into the pins to hold them. The film was conveyed while adjusting the pin sheet spacing to prevent unnecessary slack. The film was then heated in a dry atmosphere at a heating rate of 10°C / min between each set temperature for 3 minutes at 150°C, 3 minutes at 230°C, 3 minutes at 300°C, and 3 minutes at 350°C to allow the imidization reaction to proceed. The film was then cooled to room temperature over 2 minutes, and the poorly flat portions at both ends of the film were cut off with a slitter to obtain a 50-meter polyimide film roll A2 with a width of 450 mm. The processability of resin composition A1 and the physical properties of polyimide film roll A2 were as shown in Table 1.

[0105] Example 2 Resin composition B1 and polyimide film roll B2 were obtained in the same manner as in Example 1, except that the amount of DMAc initially introduced was 3070 g, the amount of s-BPDA introduced was 234.61 g, the amount of PMDA introduced was 260.89 g, and the amount of DMAc additionally introduced was 4878 g. The physical properties and processability of resin composition B1 and the film physical properties of polyimide film roll B2 were as shown in Table 1.

[0106] Example 3 Resin composition C1 and polyimide film roll C2 were obtained in the same manner as in Example 1, except that the amount of DMAc initially introduced was 3067 g, the amount of s-BPDA introduced was 234.02 g, the amount of PMDA introduced was 260.24 g, and the amount of DMAc additionally introduced was 3361 g. The physical properties and processability of resin composition C1 and the film properties of polyimide film roll C2 were as shown in Table 1.

[0107] Example 4 Resin composition D1 and polyimide film roll D2 were obtained in the same manner as in Example 1, except that the amount of DMAc initially introduced was 3027 g, the amount of s-BPDA introduced was 175.69 g, the amount of PMDA introduced was 303.92 g, and the amount of DMAc additionally introduced was 3851 g. The physical properties and processability of resin composition D1 and the film physical properties of polyimide film roll D2 were as shown in Table 1.

[0108] Example 5 Resin composition E1 and polyimide film roll E2 were obtained in the same manner as in Example 1, except that the amount of DMAc initially introduced was 3109 g, the amount of s-BPDA introduced was 292.82 g, the amount of PMDA introduced was 217.08 g, and the amount of DMAc additionally introduced was 3109 g. The physical properties and processability of resin composition E1 and the film physical properties of polyimide film roll E2 were as shown in Table 1.

[0109] Example 6 Resin composition F1 and polyimide film roll F2 were obtained in the same manner as in Example 1, except that the amount of DMAc initially introduced was 3031 g, the amount of s-BPDA introduced was 176.22 g, the amount of PMDA introduced was 304.83 g, and the amount of DMAc additionally introduced was 8304 g. The physical properties and processability of resin composition F1 and the film properties of polyimide film roll F2 were as shown in Table 1.

[0110] Example 7 Resin composition G1 and polyimide film roll G2 were obtained in the same manner as in Example 1, except that the amount of DMAc initially introduced was 3079 g, the amount of s-BPDA introduced was 236.14 g, the amount of PMDA introduced was 262.59 g, and the amount of DMAc additionally introduced was 3916 g. The physical properties and processability of resin composition G1 and the film physical properties of polyimide film roll G2 were as shown in Table 1.

[0111] Example 8 After replacing the inside of a reaction vessel equipped with a nitrogen inlet tube, thermometer, stirring blade, and temperature control function with nitrogen, under a nitrogen stream, the temperature control function was set to 20 ° C., and DMAc (3098 g) with a moisture content of 80 ppm was introduced into the reactor, followed by TFMB (640.00 g) and stirring and mixing for 30 minutes to dissolve, followed by s-BPDA (234.61 g) and stirring and mixing for 2 hours, followed by PMDA (239.15 g) and 4,4'-oxydiphthalic dianhydride (ODPA, 31.92 g) and stirring and mixing for 4 hours, followed by N,N-dimethylacetamide (DMAc, 3940 g) with a moisture content of 80 ppm was introduced and stirred for 40 hours to obtain a resin composition H1. The physical properties of the resin composition H1 were as shown in Table 1.

[0112] A 50 m polyimide film roll H2 having a width of 450 mm was obtained in the same manner as in Example 1, except that resin composition H1 was used. The processability of resin composition H1 and the film properties of polyimide film roll H2 were as shown in Table 1.

[0113] Example 9 An amino group-containing double-decker silsesquioxane derivative (AMSQ1) represented by the structure of the following chemical formula (2) was produced by the method described in JP-A-2006-265243.

[0114]

[0115] Next, a nitrogen inlet tube, a thermometer, a stirring blade, and a reaction vessel equipped with a temperature control function were substituted with nitrogen, and then the temperature control function was set to 20 ° C. under a nitrogen stream, and DMAc (3245 g) with a moisture content of 80 ppm was introduced into the reactor, followed by TFMB (640.00 g) and AMSQ1 (54.49 g) and stirring and mixing for 30 minutes to dissolve, followed by s-BPDA (239.40 g) and stirring and mixing for 2 hours, followed by PMDA (266.22 g) and stirring and mixing for 4 hours, followed by DMAc (4445 g) with a moisture content of 80 ppm and stirring for 40 hours to obtain a resin composition I1. The physical properties of the resin composition I1 were as shown in Table 1.

[0116] Except for using resin composition I1, coating, drying, and heat treatment were carried out in the same manner as in Example 1 to obtain a 50 m polyimide film roll I2 having a width of 450 mm. The processability of resin composition I1 and the film properties of polyimide film roll I2 were as shown in Table 1.

[0117] Comparative Example 1: After the air inside a reaction vessel equipped with a nitrogen inlet tube, thermometer, stirring blade, and temperature control function was replaced with nitrogen, the temperature control function was set to 20°C under a nitrogen stream, and DMAc (2904 g) with a moisture content of 80 ppm was introduced into the reaction vessel, followed by TFMB (640.00 g) which was dissolved by stirring and mixing for 30 minutes, followed by PMDA (434.17 g) which was stirred and mixed for 6 hours, followed by DMAc (3694 g) with a moisture content of 80 ppm which was introduced and stirred for 40 hours, to obtain resin composition J1. The physical properties of resin composition J1 are as shown in Table 1.

[0118] Except for using resin composition J1, coating, drying, and heat treatment were carried out in the same manner as in Example 1. However, the film broke during transport, and a polyimide film roll could not be obtained.

[0119] Comparative Example 2: After the air inside a reaction vessel equipped with a nitrogen inlet tube, thermometer, stirring blade, and temperature control function was replaced with nitrogen, the temperature control function was set to 20°C under a nitrogen stream, and DMAc (3314 g) with a moisture content of 80 ppm was introduced into the reaction vessel, followed by TFMB (640.00 g) which was dissolved by stirring and mixing for 30 minutes, followed by s-BPDA (585.65 g) which was stirred and mixed for 6 hours, followed by DMAc (4215 g) with a moisture content of 80 ppm which was introduced and stirred for 40 hours to obtain resin composition K1. The physical properties of resin composition K1 were as shown in Table 1.

[0120] Resin composition K1 was used, and coating, drying, and heat treatment were carried out in the same manner as in Example 1, except that the heat treatment temperatures were set to 150°C for 3 minutes, 200°C for 3 minutes, 250°C for 3 minutes, and 300°C for 3 minutes, to obtain 50 m of polyimide film roll K2 having a width of 450 mm. The processability of resin composition K1 and the film properties of polyimide film roll K2 were as shown in Table 1.

[0121] <Comparative Example 3> After replacing the inside of a reaction vessel equipped with a nitrogen inlet tube, thermometer, stirring blade, and temperature control function with nitrogen, under a nitrogen stream, the temperature control function was set to 20 ° C., and DMAc (3456 g) with a moisture content of 80 ppm was introduced into the reactor, followed by 3,3'-DAS (640.00 g) and stirring and mixing for 30 minutes to dissolve, followed by s-BPDA (302.13 g) and stirring and mixing for 2 hours, followed by PMDA (335.98 g) and stirring and mixing for 4 hours, followed by DMAc (2785 g) with a moisture content of 80 ppm and stirring for 40 hours to obtain resin composition L1. The physical properties of resin composition L1 were as shown in Table 1.

[0122] Resin composition L1 was used, and coating, drying, and heat treatment were carried out in the same manner as in Example 1, except that the temperatures during the heat treatment were set to 150°C for 3 minutes, 200°C for 3 minutes, 250°C for 3 minutes, and 280°C for 3 minutes, to obtain 50 m of polyimide film roll L2 having a width of 450 mm. The processability of resin composition L1 and the film properties of polyimide film roll L2 were as shown in Table 1.

[0123] Comparative Example 4 After replacing the inside of a reaction vessel equipped with a nitrogen inlet tube, thermometer, stirring blade, and temperature control function with nitrogen, the temperature control function was set to 20°C under a nitrogen stream, and DMAc (3656 g) with a moisture content of 80 ppm was introduced into the reaction vessel. Subsequently, 2,2'-dimethyl-4,4'-diaminobiphenyl (m-TB, 640.00 g) was introduced and stirred and mixed for 30 minutes to dissolve, followed by the introduction of s-BPDA (220.85 g) and stirring and mixing for 2 hours, followed by the introduction of PMDA (491.19 g) and stirring and mixing for 4 hours, followed by the introduction of DMAc (4650 g) with a moisture content of 80 ppm and stirring for 40 hours to obtain a resin composition M1. The physical properties of the resin composition M1 were as shown in Table 1.

[0124] Except for using the resin composition M1, coating, drying, and heat treatment were performed in the same manner as in Example 1 to obtain a 50 m polyimide film roll M2 having a width of 450 mm. The processability of the resin composition M1 and the film properties of the polyimide film roll M2 were as shown in Table 1.

[0125] Comparative Example 5 Coating, drying, and heat treatment were carried out in the same manner as in Example 1, except that the amount of DMAc initially introduced was 3091 g, the amount of s-BPDA introduced was 238.35 g, and the amount of PMDA introduced was 265.05 g. However, the film broke during transport, and a polyimide film roll could not be obtained.

[0126] Comparative Example 6 After the atmosphere inside a reaction vessel equipped with a nitrogen inlet tube, a thermometer, a stirring blade, and a temperature control function was replaced with nitrogen, the temperature control function was set to 20°C under an air flow, and DMAc (6971 g) with a moisture content of 80 ppm was introduced into the reaction vessel, followed by the simultaneous introduction of TFMB (640.00 g), s-BPDA (234.26 g), and PMDA (260.50 g) and stirring for 80 hours, thereby obtaining resin composition O1. The physical properties of resin composition O1 are as shown in Table 1.

[0127] Except for using resin composition O1, coating, drying, and heat treatment were carried out in the same manner as in Example 1. However, the film broke during transport, and a polyimide film roll could not be obtained.

[0128] Comparative Example 7: After the interior of a reaction vessel equipped with a nitrogen inlet tube, thermometer, stirring blade, and temperature control function was purged with nitrogen, the temperature control function was set to 20°C under a nitrogen stream, and DMAc (3072 g) with a moisture content of 80 ppm was introduced into the reaction vessel. Subsequently, TFMB (640.00 g) was introduced and stirred and mixed for 30 minutes to dissolve. Subsequently, s-BPDA (234.96 g) was introduced and stirred and mixed for 2 hours. Subsequently, PMDA (261.29 g) was introduced and stirred and mixed for 4 hours. Subsequently, DMAc (33667 g) with a moisture content of 80 ppm was introduced and stirred for 40 hours to obtain resin composition P1. The physical properties of resin composition P1 were as shown in Table 1.

[0129] A self-supporting film (polyimide precursor film) was obtained by coating and drying in the same manner as in Example 1, except that Resin Composition A1 was used. However, the polyimide precursor film broke when peeled from the support, and a polyimide film roll could not be obtained.

[0130] Comparative Example 8: After the air inside a reaction vessel equipped with a nitrogen inlet tube, thermometer, stirring blade, and temperature control function was replaced with nitrogen, the temperature control function was set to 20°C under a nitrogen stream, and DMAc (3067 g) with a moisture content of 80 ppm was introduced into the reaction vessel. Subsequently, TFMB (640.00 g) was introduced and dissolved by stirring and mixing for 30 minutes. Subsequently, s-BPDA (234.02 g) was introduced and stirred and mixed for 2 hours. Subsequently, PMDA (260.24 g) was introduced and stirred for 44 hours, thereby obtaining resin composition Q1. The physical properties of resin composition Q1 are as shown in Table 1.

[0131] Coating was carried out in the same manner as in Example 1 except that resin composition Q1 was used, but the coating properties were poor, with many vertical streaks appearing, and subsequent film formation was not possible.

[0132] <Semiconductor Wafer Treatment> A silicon wafer with a diameter of 300 mm and a thickness of 0.7 mm and a mirror finish on one side was used as the semiconductor wafer. The silicon wafer was washed with pure water and dried, and then subjected to UV / O ３ UV / O irradiation with an irradiator (SKR1102N-03 manufactured by LAN Technical) ３ The substrate was then dry cleaned by irradiating the substrate with 1000 W of fluorine for 1 minute.

[0133] <Preparation of Polyimide-Coated Semiconductor Wafer> The resin composition was applied to one surface of a silicon wafer using an applicator so that the final polyimide layer thickness would be 15 μm. The wafer was then dried in a hot air oven at 100° C. for 30 minutes, and then heated at a rate of 7° C. / min to 350° C., whereupon it was subjected to a heat treatment for an additional 10 minutes.

[0134] <Evaluation of Polyimide-Coated Semiconductor Wafer> The appearance was observed and the 90° peel strength was measured. The appearance was evaluated as "○" when the polyimide layer and the semiconductor wafer were in close contact and no peeling was observed, "△" when slight peeling was observed, and "×" when major peeling occurred.

[0135] <90° Peel Test> The 90° peel strength of the polyimide-coated silicon wafer obtained above was measured under the following conditions. A 1 cm wide notch was made in the polyimide layer on the silicon wafer. Five measurements were taken for each sample, and the average value was used as the measured value. Measuring device: JSV-H1000 manufactured by Japan Measurement Systems Measuring temperature: 25°C Peel speed: 100 mm / min Atmosphere: Air Sample width: 1 cm

[0136]

[0137]

[0138] Examples 1 to 9 comprise a resin composition containing a polyimide precursor containing a PMDA-derived structure and an s-BPDA-derived structure as acid-based component-derived structures and a TFMB-derived structure as amine-based component-derived structure, and a first solvent. The polyimide precursor had a weight-average molecular weight of 260,000 to 1,000,000 and a solids content of 5 to 25% by mass. This enabled the production of polyimide films with excellent transparency, heat resistance, low CTE, and mechanical properties without tearing. Furthermore, when a silicon wafer was coated with a polyimide layer, the CTE difference between the polyimide layer and the silicon wafer was small, preventing peeling of the polyimide layer from the wafer and allowing the production of polyimide-coated wafers with sufficient adhesion. Comparing Examples 1, 4, and 5 revealed that increasing the proportion of the PMDA-derived structure improved the CTE, while increasing the proportion of the s-BPDA-derived structure tended to result in polyimide films with lower YI. Comparison of Examples 1, 2, 3, and 7, as well as comparison of Examples 4 and 6, revealed that when the acid / amine ratio is closer to 1, a polyimide precursor with a higher weight-average molecular weight and a polyimide film with a higher tensile elongation tend to be obtained. Example 8 is a case in which the acid-based component-derived structure includes a structure that is not a PMDA-derived structure and not an s-PMDA-derived structure, and Example 9 is a case in which the amine-based component-derived structure includes a structure that is not a TFMB-derived structure. In Examples 8 and 9, polyimide films with excellent mechanical and optical properties were also obtained.

[0139] In Comparative Example 1, the absence of an s-BPDA-derived structure resulted in insufficient strength during heat treatment, making it impossible to obtain a polyimide film roll. In Comparative Example 2, the absence of a PMDA-derived structure resulted in a significantly higher CTE of the polyimide film. Furthermore, when a polyimide layer was formed on one surface of a silicon wafer, peeling occurred, likely due in part to the large difference in CTE between the polyimide layer and the silicon wafer. In Comparative Example 3, the use of a highly flexible 3,3'-DAS-derived structure instead of a TFMB-derived structure as the amine-based component significantly increased the CTE of the polyimide film. Similarly, when a polyimide layer was formed on one surface of a silicon wafer as in Comparative Example 2, peeling of the polyimide layer from the silicon wafer was observed. In Comparative Example 4, the use of an m-TB-derived structure with an electron-emitting substituent instead of a TFMB-derived structure as the amine-based component significantly increased the YI of the polyimide film. Similarly, when a polyimide layer was formed on one surface of a silicon wafer as in Comparative Example 2, the polyimide layer was able to cover the silicon wafer without peeling. One possible reason for this is the small difference in CTE between the polyimide layer and the silicon wafer. In Comparative Examples 5 and 6, the weight-average molecular weight was less than 260,000, resulting in insufficient mechanical strength during heat treatment, making it impossible to obtain a polyimide film. In Comparative Example 7, the polyimide precursor concentration was less than 5% by mass, making the polyimide precursor too thin and resulting in breakage when peeled from the support, making it impossible to obtain a polyimide film. In Comparative Example 8, the polyimide precursor concentration was greater than 25% by mass, making it impossible to achieve a uniform coating.

[0140] As described above, the present invention can provide a resin composition for producing a polyimide film roll without tearing, which has excellent transparency, heat resistance, low CTE characteristics, and mechanical properties, and can be suitably used in flexible devices, particularly flexible displays.

[0141] According to another aspect of the present invention, a polyimide-coated semiconductor wafer can be produced, in which at least a portion of the surface is covered with a polyimide layer that is excellent in all of transparency, heat resistance, low CTE characteristics, and mechanical properties. In this case, the polyimide layer can be suitably used as an insulating coating for semiconductor wafers such as silicon wafers, an insulating film in a semiconductor element structure, an underfill, fixing of chip components, an insulator in wafer-level packaging, or the like.

Claims

1. A resin composition comprising a polyimide precursor having an acid-based component-derived structure and an amine-based component-derived structure, and a first solvent, wherein the acid-based component-derived structures include a pyromellitic acid derivative-derived structure and a 3,3',4,4'-biphenyltetracarboxylic acid derivative-derived structure, and the amine-based component-derived structure includes a 2,2'-bis(trifluoromethyl)benzidine derivative-derived structure, wherein the polyimide precursor has a weight-average molecular weight of 260,000 to 1,000,000, and wherein the concentration of the polyimide precursor in the resin composition is 5 to 20% by mass.

2. The resin composition according to claim 1, wherein the polyimide precursor has a reduced viscosity of 3.0 to 9.0 dl / g in an N,N-dimethylacetamide solution at a temperature of 25.0°C and a concentration of 0.2 g / dl.

3. The resin composition according to claim 1, characterized in that the molar ratio of the structure derived from a pyromellitic acid derivative to the structure derived from a 3,3',4,4'-biphenyltetracarboxylic acid derivative constituting the polyimide precursor is 90:10 to 10:

90.

4. A method for producing a resin composition according to any one of claims 1 to 3, comprising a step of polymerizing a polyimide precursor by carrying out the following steps I to IV in this order: Step I: Purging the interior of a polymerization reaction vessel with an inert gas; Step II: Introducing a second solvent into the polymerization reaction vessel; Step III: Introducing an amine-based component and an acid-based component into the polymerization reaction vessel in amounts such that the concentration of the component becomes greater than 20 mass % assuming that the two components react completely to form a polyimide precursor; and Step IV: Adding a third solvent four hours or more after the end of step III.

5. A polyimide film obtained from the resin composition according to any one of claims 1 to 3.

6. The polyimide film according to claim 5, characterized in that the yellowness index (YI) converted into a film thickness of 15 μm is 20 or less, the haze is 2.0% or less, the 1% weight loss temperature is 450°C or higher, the average linear expansion coefficient between 50°C and 200°C is -5 to +20 ppm / °C, and the tensile elongation is 10% or higher.

7. A polyimide-coated semiconductor wafer, at least a portion of whose surface is covered with a polyimide layer obtained from the resin composition according to any one of claims 1 to 3.

8. A method for producing a polyimide-coated semiconductor wafer according to claim 7, comprising: step A of applying the resin composition according to any one of claims 1 to 3 to at least a portion of the surface of a semiconductor wafer; step B of heating the semiconductor wafer that has undergone step A to dry off a portion of the solvent contained in the resin composition; and step C of further heat-treating the semiconductor wafer that has undergone step B to form a polyimide layer.

Images