Polyimide film and method for producing same

Abstract

A polyimide film and a method for producing the same, said polyimide film containing a polyimide resin having: a structure derived from an acid component, said structure containing a structure derived from a pyromellitic acid derivative and a structure derived from a 3,3',4,4'-biphenyltetracarboxylic acid derivative; and a structure derived from an amine component, said structure containing a structure derived from a 2,2'-bis(trifluoromethyl) benzidine derivative, wherein the yellowness index (15 μｍ film thickness equivalent), the haze, the 1% weight loss temperature, the average coefficient of linear expansion between 50°C and 200°C, and the tensile elongation, are within specific ranges.

Description

Polyimide film and its manufacturing method

[0001] The present invention relates to a polyimide film and a method for producing the same.

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

[0003] To form functional elements such as display elements on polyimide film, a roll-to-roll process is ideal, taking advantage of the flexibility of polyimide film. However, in the display industry and other industries, process 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 to 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 200°C to 300°C, and further heating and dehydrogenation of amorphous silicon to produce low-temperature polysilicon may require heating at temperatures ranging from 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 and hinder device fabrication. Therefore, the difference in CTE between the polyimide film and the inorganic material must be minimized. Since inorganic materials generally have a low CTE, the polyimide film must also have a correspondingly low CTE.

[0005] 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, including 3,3',4,4'-biphenyltetracarboxylic dianhydride (hereinafter sometimes abbreviated as s-BPDA) and pyromellitic dianhydride (hereinafter sometimes abbreviated as PMDA) as tetracarboxylic dianhydrides, and a solvent containing 2,2'-bis(trifluoromethyl)benzidine (hereinafter sometimes abbreviated as TFMB) and a certain amount of 3,3'-diaminosulfone (hereinafter sometimes abbreviated as 3,3'-DAS) or 4,4'-diaminosulfone (hereinafter sometimes abbreviated as 4,4'-DAS) as diamines. It also describes that the resin composition has excellent slit coating properties, and that polyimide films obtained by curing the resin composition have excellent mechanical and optical properties.

[0006] Patent Document 2 describes a resin composition containing a polyamic acid containing s-BPDA and PMDA as tetracarboxylic dianhydrides and TFMB as a diamine, and a solvent, and having 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, such as 190°C, the final polyimide film is transparent and has a CTE of 32 to 47 ppm / K.

[0007] Patent Document 3 describes a resin composition having a solids concentration of 15% by mass, which contains a polyamic acid containing derivatives of s-BPDA and PMDA as tetracarboxylic dianhydrides and a certain amount of a derivative of 2,2'-dimethyl-4,4'-diaminobiphenyl (hereinafter, sometimes abbreviated as m-TB) as a diamine, and a solvent, and describes that a polyimide film obtained by curing the resin composition has a CTE of 10 ppm / K or less and exhibits little warpage.

[0008] JP 2022-167930 A JP 2010-235789 A JP 2019-065266 A

[0009] The CTE of the polyimide film in Patent Document 1 is unclear because it is not described, but it is thought that the inclusion of a flexible structure within the polyimide structure prevents it from achieving a low CTE characteristic that matches the CTE of inorganic materials. The transparent polyimide film described in Patent Document 2 has a high CTE and does not yet achieve a low CTE characteristic that matches the CTE of inorganic materials. There is no description regarding transparency of the polyimide film in Patent Document 3, so it is 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, and mechanical properties at a level that allows it to be used as a substrate film for flexible devices such as flexible displays.

[0010] The present invention is directed to applications where lighter, smaller, thinner, more flexible, and more transparent electronic devices having functional elements, such as display elements, are required. It has been studied to form desired functional elements on the surface of a resin layer of a laminate formed by bonding an inorganic support and a resin layer. In such a configuration, it is an object of the present invention to provide a polyimide film that can be used as the resin layer and simultaneously has transparency, heat resistance, low CTE, and mechanical properties, and a method for producing the same.

[0011] As a result of extensive research, the present inventors have discovered a polyimide film that has a specific chemical structure and is excellent in transparency, heat resistance, low CTE properties, and mechanical properties, and have completed the present invention.

[0012] That is, the present invention has the following configuration: Item 1. A polyimide film comprising a polyimide resin having an acid-based component-derived structure and an amine-based component-derived structure, 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, characterized in that the polyimide film has a yellowness index (YI) equivalent to a film thickness of 15 μm of 20.0 or less, a haze of 2.0% or less, a 1% weight loss temperature of 450°C or higher, an average coefficient of linear expansion (CTE) between 50°C and 200°C of -5 to +20 ppm / °C, and a tensile elongation of 10% or more. Item 1. The polyimide film according to Item 1, 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 resin is 90:10 to 10:90. Item 3. The polyimide film according to Item 1 or 2, characterized in that the pyromellitic acid-derived structure constituting the polyimide resin is a pyromellitic acid dianhydride-derived structure, and the 3,3',4,4'-biphenyltetracarboxylic acid derivative-derived structure is a 3,3',4,4'-biphenyltetracarboxylic acid dianhydride-derived structure. Item 4. The yellowness index (YI) of the polyimide film after heating from room temperature to 360°C at a heating rate of 30°C / min in a nitrogen atmosphere and then immediately maintaining the film at 360°C for 60 minutes (hereinafter sometimes abbreviated as 360°C heat treatment under a nitrogen atmosphere) is calculated as the yellowness index (YI) of the polyimide film in terms of a film thickness of 15 μm. ３６０ Item 5. The polyimide film according to any one of Items 1 to 5, wherein the haze of the polyimide film after heat treatment at 360° C. in a nitrogen atmosphere is 20.0 or less. ３６０Item 6. The polyimide film according to any one of Items 1 to 4, characterized in that its moisture absorption rate is 1.0% by mass or less. Item 7. The polyimide film according to any one of Items 1 to 6, characterized in that its moisture absorption rate is 1.0% by mass or less. Item 8. The polyimide film according to any one of Items 1 to 7, characterized in that its moisture absorption coefficient is 5.0 ppm / % RH or less. Item 9. Item 1 is a method for producing a polyimide film, the method comprising: Step α: coating a support with a resin composition containing a polyimide precursor obtained by reacting an acid component containing a pyromellitic acid derivative and a 3,3',4,4'-biphenyltetracarboxylic acid derivative with an amine component containing a 2,2'-bis(trifluoromethyl)benzidine derivative, and a solvent; and Step β: heat-treating the polyimide precursor film on the support, or peeling it from the support and heat-treating it with its edges fixed, thereby causing a dehydration ring-closing reaction while removing the solvent. Item 10. A method for producing a polyimide film according to Item 9, wherein the maximum temperature reached in the heat treatment in Step β is 300 to 450°C. Item 11. A method for producing a polyimide film according to Item 9 or 10, wherein the temperature profile of the heat treatment in Step β is to increase the temperature from room temperature to the maximum temperature in a single step, with the temperature increase rate being 30°C / min or less. Item 12. Item 12. The method for producing a polyimide film according to any one of Items 9 to 11, wherein the temperature profile of the heat treatment in step β is to increase the temperature from room temperature to a maximum temperature in two stages, with the temperature increase in each stage being carried out at an average temperature increase rate of 50°C / min or less, the maximum temperature in the first stage being in the range of 100 to 250°C, and the holding time after reaching the maximum temperature in the first stage being in the range of 1 to 30 minutes.Item 13. The method for producing a polyimide film according to any one of claims 9 to 11, wherein the temperature profile of the heat treatment in step β is: the temperature is increased from room temperature to a maximum temperature in three stages, and the temperature is increased in each stage at an average rate of 100°C / min or less; the maximum temperature in the first stage is in the range of 100 to 250°C; the maximum temperature in the second stage is in the range of ±50°C of the value obtained by dividing the sum of the maximum temperature in the first stage and the maximum temperature in the third stage by 2; and the holding time after reaching the maximum temperature in each stage is in the range of 1 to 30 minutes. 12. The method for producing a polyimide film according to any one of Items 9 to 11, wherein the temperature profile of the heat treatment in step β is: the temperature is increased from room temperature to the maximum temperature in N stages (N is an integer of 4 or more), the temperature is increased in each stage at an average heating rate of 300°C / min or less, the maximum temperature (T1) in the first stage is in the range of 100 to 250°C, the maximum temperature in each stage from the second stage onwards is in the range of ±50°C of the value obtained by subtracting the maximum temperature (T1) in the first stage from the maximum temperature (Tmax) in step β (Tmax) and dividing the result (Tmax-T1) by N-1 ((Tmax-T1) / (N-1)) (if the value is not divisible, the value is rounded to the nearest integer), and adding this value to the maximum temperature in the previous stage, and the holding time after reaching the maximum temperature in each stage is in the range of 1 to 30 minutes.

[0013] According to one aspect of the present invention, a film substrate material having excellent transparency and mechanical properties can be obtained, and therefore the film substrate material can be suitably used in applications requiring lightweight, small, thin, flexible, and transparent electronic devices having functional elements such as display elements. Furthermore, the film substrate material obtained by the present invention has heat resistance and a low CTE characteristic that matches the CTE of inorganic materials, and therefore can withstand processes in which the film substrate material is exposed to high temperatures, such as in processes for forming desired functional elements on a laminate laminated with an inorganic support, and further, desired electronic devices can be obtained without significant warping.

[0014] 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.

[0015] <Polyimide Film> The polyimide film of the present invention is a polyimide film containing a polyimide resin having an acid-based component-derived structure and an amine-based component-derived structure, wherein the acid-based component-derived structure includes a pyromellitic acid derivative-derived structure (hereinafter, also referred to as a pyromellitic acid-derived structure) and a 3,3',4,4'-biphenyltetracarboxylic acid derivative-derived structure (hereinafter, also referred to as a 3,3',4,4'-biphenyltetracarboxylic acid-derived structure), and the amine-based component-derived structure includes and a 2,2'-bis(trifluoromethyl)benzidine derivative-derived structure (hereinafter, also referred to as a 2,2'-bis(trifluoromethyl)benzidine-derived structure), characterized in that the polyimide film has a yellowness index (YI) equivalent to a film thickness of 15 μm of 20.0 or less, a haze of 2.0% or less, a 1% weight loss temperature of 450°C or higher, an average coefficient of linear expansion (CTE) between 50°C and 200°C of -5 to +20 ppm / °C, and a tensile elongation of 10% or more.

[0016] 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.

[0017] 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 transparency, heat resistance, low CTE characteristics, and mechanical properties of the final polyimide film are better balanced.

[0018] The ratio of the 2,2'-bis(trifluoromethyl)benzidine-derived structure to the amine component-derived structure 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 100 mol%. Specific examples of structures contained in the amine component-derived structure that are not 2,2'-bis(trifluoromethyl)benzidine-derived structures are structures derived from compounds described below in the description of the production method for the resin composition.

[0019] 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.

[0020] 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.

[0021] The average coefficient of linear expansion (CTE) of the polyimide film in the present invention between 50°C and 200°C is -5 to +20 ppm / °C, preferably -4 to +15 ppm / °C, and 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 bonded to 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.

[0022] 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.

[0023] 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 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.

[0024] The breaking elongation of the polyimide film in the present invention is 10% or more, preferably 15% or more, and more preferably 20% or more. By making the breaking elongation 10% or more, it is possible to ensure appropriate flexibility in the processing of functional elements, etc., and excellent handleability is achieved. The upper limit of the breaking elongation is not particularly limited, 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.

[0025] The yellowness index (YI) of the polyimide film of the present invention, converted into a film thickness of 15 μm, is 20.0 or less, preferably 15.0 or less, and more preferably 10.0 or less. A YI of 20.0 or less makes it 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.

[0026] The yellowness index (YI) of the polyimide film of the present invention is calculated as a value of the film thickness of 15 μm after heating from room temperature to 360° C. at a heating rate of 30° C. / min in a nitrogen atmosphere and then immediately holding at 360° C. for 60 minutes (hereinafter sometimes abbreviated as "heat treatment at 360° C. in a nitrogen atmosphere"). ３６０ ) is preferably 20.0 or less, more preferably 15.0 or less, and even more preferably 10.0 or less. ３６０ If YI is 20.0 or less, it can be more suitably used in flexible devices and flexible displays that require transparency. ３６０ Although there is no particular limitation on the lower limit of YI, in order to use it 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. ３６０ The measurement method is the method described in the Examples.

[0027] The haze of the polyimide film of the present invention is 2.0% or less, preferably 1.7% or less, and more preferably 1.5% or less. When the haze is 2.0% or less, the film can be suitably used in flexible devices and flexible displays that require transparency. 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 by the method described in the examples.

[0028] The haze of the polyimide film of the present invention after heat treatment at 360° C. in a nitrogen atmosphere (Haze ３６０ ) is preferably 2.0% or less, more preferably 1.7% or less, and even more preferably 1.5% or less. ３６０ When the haze is 2.0% or less, the film can be more suitably used in flexible devices and flexible displays that require transparency. ３６０ The lower limit of 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. ３６０ The measurement method is the method described in the Examples.

[0029] 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 more 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.

[0030] The 1% weight loss temperature of the polyimide film of the present invention is 450°C or higher, preferably 500°C or higher, 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.

[0031] 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 more suitable for use in 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.

[0032] The moisture absorption rate of the polyimide film in the present invention is preferably 1.0% by mass or less, more preferably 0.9% by mass or less, even more preferably 0.8% by mass or less, even more preferably 0.7% by mass or less, and particularly preferably 0.6% by mass or less. A moisture absorption rate of 1.0% by mass or less makes the film more suitable for use in processes requiring high-temperature processing, such as the formation of functional elements. The moisture absorption rate is measured by the method described in the Examples.

[0033] The water absorption of the polyimide film of the present invention is preferably 1.0% by mass or less, more preferably 0.9% by mass or less, even more preferably 0.8% by mass or less, even more preferably 0.7% by mass or less, and particularly preferably 0.6% by mass or less. A water absorption of 1.0% by mass or less makes the film more suitable for use in processes requiring high-temperature processing, such as the formation of functional elements. The water absorption is measured by the method described in the Examples.

[0034] The hygroscopic expansion coefficient of the polyimide film in the present invention is preferably 5.0 ppm / % RH or less, more preferably 4.5 ppm / % RH or less, even more preferably 4.0 ppm / % RH or less, still more preferably 3.9 ppm / % RH or less, particularly preferably 3.8 ppm / % RH or less, and particularly preferably 3.7 ppm / % RH or less. A hygroscopic expansion coefficient of 5.0 ppm / % RH or less makes the film more suitable for use in processes requiring high-temperature processing, such as the formation of functional elements. The hygroscopic expansion coefficient is measured by the method described in the Examples.

[0035] In the polyimide film of the present invention, in order to ensure handleability and productivity, it is preferable to incorporate a particulate lubricant into the polyimide film by some means, thereby imparting fine irregularities to the surface of the polyimide film and ensuring slipperiness. Examples of lubricants include silica, carbon, and ceramic, with silica being preferred. The particle size of the lubricant is preferably 10 to 1,000 nm, more preferably 20 to 500 nm, and even more preferably 30 to 100 nm. The amount of lubricant added / content is preferably 0.03 to 3.00 mass%, more preferably 0.05 to 2.00 mass%, and even more preferably 0.1 to 1.00 mass%. These lubricants may be used alone or in combination of two or more types.

[0036] <Method for Producing Polyimide Film> The method for producing a polyimide film in the present invention is not particularly limited, but preferably includes: Step α of producing a polyimide precursor film by coating a support with a resin composition containing a polyimide precursor obtained by reacting an acid-based component containing a pyromellitic acid derivative and a 3,3′,4,4′-biphenyltetracarboxylic acid derivative with an amine-based component containing a 2,2′-bis(trifluoromethyl)benzidine derivative and a first solvent, and then drying off part of the solvent; and Step β of performing a heat treatment on the support, or while peeled from the support and with the edges fixed, to cause a dehydration ring-closing reaction while removing the solvent.

[0037] The pyromellitic acid derivative is not particularly limited, but is preferably pyromellitic acid or its acid chloride, ester, or acid anhydride, more preferably the acid anhydride, and even more preferably pyromellitic acid dianhydride (PMDA).

[0038] The 3,3',4,4'-biphenyltetracarboxylic acid derivative is not particularly limited, but is preferably 3,3',4,4'-biphenyltetracarboxylic acid or its acid chloride, ester, or acid anhydride, more preferably an acid anhydride, and even more preferably 3,3',4,4'-biphenyltetracarboxylic dianhydride (s-BPDA).

[0039] The 2,2'-bis(trifluoromethyl)benzidine derivative is not particularly limited, but is preferably 2,2'-bis(trifluoromethyl)benzidine or its silylated and amidated derivatives, more preferably 2,2'-bis(trifluoromethyl)benzidine (TFMB).

[0040] 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.

[0041] 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 anhydrides thereof. Further examples include double-decker silsesquioxane derivatives containing an acid anhydride group, which are represented by the following chemical formula (1):

[0042]

[0043] 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 anhydrides thereof.

[0044] 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%.

[0045] In the present invention, the acid component may contain dicarboxylic acids. Examples of dicarboxylic acids 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.

[0046] 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%.

[0047] In the present invention, the amine-based component may contain an amine-based component other than a 2,2'-bis(trifluoromethyl)benzidine derivative. Examples of such amine-based components 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. The amine-based component other than a 2,2'-bis(trifluoromethyl)benzidine derivative may be used alone or in combination of two or more types.

[0048] 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, bis[4-(3- 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 benzoxazoles 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 may be used alone or in combination of two or more.

[0049]

[0050] 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.

[0051] 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 amine components 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 0 mol%.

[0052] The weight-average molecular weight of the polyimide precursor is not particularly limited and may vary depending on the desired application, the type of polyimide precursor, the solids content of the resin composition, and the type of solvent the resin composition may contain. However, it is preferably 260,000 to 1,000,000, more preferably 280,000 to 900,000, even more preferably 300,000 to 800,000, and even more preferably 320,000 to 700,000. By achieving a weight-average molecular weight of 260,000 or more, it becomes easier to obtain a polyimide precursor film with sufficient strength to withstand the tensile load caused by the drying and volatilization of residual solvent during film formation (heat treatment) and the shrinkage that accompanies the imidization reaction. This makes the film less likely to tear during the production process, facilitating the production of a high-quality polyimide film. Furthermore, by achieving a weight-average molecular weight of 1,000,000 or less, it is possible to prevent the solution viscosity of the resin composition from becoming excessively high, thereby improving the coatability of the resin composition.

[0053] 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, 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 final polyimide film can be further improved.

[0054] The type of first solvent contained in the resin composition is not particularly limited, but examples include N,N-dimethylformamide, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), N-methyl-ε-caprolactam, dimethyl sulfoxide, dimethyl sulfone, 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, poor solvents such as toluene and xylene may be used in combination with these solvents to the extent that the resin solids do not precipitate.

[0055] The concentration of the polyimide precursor in the resin composition is not particularly limited and may vary depending on the desired application, the type or weight-average molecular weight of the polyimide precursor, and the type of solvent the resin composition may contain. However, it is preferably 5 to 20% by mass, more preferably 7 to 19% by mass, even more preferably 9 to 18% by mass, and even more preferably 11 to 17% by mass. By setting the concentration of the polyimide precursor within an appropriate range, it becomes easier to achieve an appropriate film thickness for the polyimide precursor film or the final polyimide film, and it becomes easier to obtain a polyimide film that is less likely to tear during film formation and has sufficient mechanical strength. Furthermore, the solution viscosity of the resin composition is within an appropriate range, facilitating uniform coating.

[0056] The resin composition 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 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.

[0057] The content of the imidization accelerator is not particularly limited, but is preferably 0.2 to 4.0 mol, more preferably 0.5 to 3.5 mol, even more preferably 0.8 to 3.0 mol, still more preferably 1.0 to 2.5 mol, and particularly preferably 1.1 to 2.0 mol, per 1 mol of the repeating unit of the polyimide precursor. 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 (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.

[0058] The resin composition may contain functional agents such as inorganic fillers and surfactants, as long as the properties of the polyimide film are not impaired. The amount of the functional 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.

[0059] The solution viscosity of the resin composition 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 keeping 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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 subjected to a heat treatment during transport, a tenter-type transport device is generally used. When a pin 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 film.

[0065] The heating method in the step β is not particularly limited, but examples thereof include air blowing, hot air blowing, infrared radiation, and heat transfer from the support, and two or more of these methods may be combined.

[0066] The maximum heating temperature in step β is 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 setting the maximum heating temperature within this range, it is possible to achieve high mechanical strength and a low CTE without deteriorating the YI of the resulting polyimide film. The temperature profile up to the maximum temperature is 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 stepwise heating.

[0067] In the heating method in step β, when the maximum temperature is reached in one step from room temperature, the temperature rise rate is preferably 30° C. / min or less, more preferably 20° C. / min or less, and even more preferably 10° C. / min or less. By setting the temperature rise rate to 30° C. / min or less when the maximum temperature is reached in one step, whitening of the polyimide film can be suppressed, and a polyimide film having a haze of 2.0% or less can be easily obtained.

[0068] In the heating method in step β, when the maximum temperature is reached in two stages from room temperature, the temperature reached in the first stage is preferably 100 to 250°C, more preferably 110 to 240°C, even more preferably 120 to 230°C, and particularly preferably 130 to 220°C. The holding time after reaching the temperature reached in the first stage is preferably 1 to 30 minutes, more preferably 2 to 15 minutes, and even more preferably 3 to 10 minutes. The temperature rise rate is preferably 50°C / min or less, more preferably 30°C / min or less, even more preferably 20°C / min or less, and particularly preferably 10°C / min or less. The temperature rise rate until the temperature reached in the first stage and the temperature rise rate after reaching the temperature reached in the first stage until the temperature reached in the second stage may be the same or different. Heating within the above range can suppress whitening of the polyimide film, making it easier to obtain a polyimide film with a haze of 2.0% or less.

[0069] In the heating method in step β, when the maximum temperature is reached in three stages from room temperature, the temperature reached in the first stage is preferably 100 to 250°C, more preferably 110 to 240°C, even more preferably 120 to 230°C, and particularly preferably 130 to 220°C. The temperature reached in the second stage is preferably within a range of ±50°C, calculated by dividing the value obtained by adding the temperature reached in the first stage to the maximum temperature by 2. The holding time after reaching each stage is preferably 1 to 30 minutes, more preferably 2 to 15 minutes, and even more preferably 3 to 10 minutes. The holding time after reaching each stage may be different. The heating rate is preferably 100°C / min or less, more preferably 50°C / min or less, even more preferably 30°C / min or less, even more preferably 20°C / min or less, and particularly preferably 10°C / min or less. The heating rate until the temperature reached in the first stage and the heating rate after reaching the temperature reached in the first stage until reaching the temperature in the second stage may be the same or different. By heating within the above range, whitening of the polyimide film can be suppressed, and a polyimide film having a haze of 2.0% or less can be easily obtained.

[0070] In the heating method in step β, when the maximum temperature is reached in N stages (N is an integer of 4 or more) from room temperature, the temperature reached in the first stage is preferably 100 to 250°C, more preferably 110 to 240°C, even more preferably 120 to 230°C, and particularly preferably 130 to 220°C. Furthermore, the temperatures reached in the second stage and thereafter are preferably ±50°C, calculated by subtracting the temperature reached in the first stage (T1) from the maximum temperature reached (Tmax), dividing the result (Tmax-T1) by N-1 ((Tmax-T1) / (N-1)) (if not divisible, round to the nearest integer), and adding this to the temperature reached in the previous stage. For example, when the maximum temperature is reached in four stages, if the temperature reached in the first stage is 150°C and the maximum temperature is 350°C, the temperature in the second stage is preferably 217±50°C. If the second stage is 230°C, the temperature in the third stage is preferably 297±50°C. The holding time after reaching each stage is preferably 1 to 30 minutes, more preferably 2 to 15 minutes, and even more preferably 3 to 10 minutes. The holding time after reaching each stage may be different. The temperature rise 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, particularly preferably 20°C / min or less, and particularly preferably 10°C / min or less. The temperature rise rate until the first temperature is reached, the temperature rise rate from the first temperature to the second temperature, the temperature rise rate from the second temperature to the third temperature, ..., the temperature rise rate from the N-1th temperature to the Nth temperature, may be the same or different. Heating within the above ranges can suppress whitening of the polyimide film, making it easier to obtain a polyimide film with a haze of 2.0% or less.

[0071] <Method for Producing Resin Composition> The method for producing a resin composition is not particularly limited, but preferably includes a step of polymerizing a polyimide precursor in a resin composition, in which the following steps I to IV are carried out 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.

[0072] <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, and as a result, the degree of polymerization of the polyimide precursor is likely to increase, making it easier to obtain a polyimide precursor having a weight-average molecular weight of 260,000 to 1,000,000.

[0073] <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.

[0074] 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.

[0075] <Step III> The amounts of the acid-based component and the amine-based component introduced in Step III are preferably such that, assuming complete reaction to form a polyimide precursor, their concentrations exceed 20% by mass, more preferably exceed 23% by mass, and even more preferably exceed 26% by mass. In a typical example of the present invention, s-BPDA is used as the acid-based component and TFMB as the amine-based 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 system during the polymerization process, which tends to make it difficult to increase the degree of polymerization. Therefore, by focusing on the initial concentrations of the acid-based component and the amine-based component and setting the amounts of the acid-based component and the amine-based component introduced in Step III within 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. This facilitates the production of a polyimide precursor having a weight-average molecular weight in the preferred range of 260,000 to 1,000,000. Although there are no particular upper limits on the amounts of the acidic component and amine 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 amine component becomes, and further, the viscosity of the polymerization solution increases, making it difficult to stir the solution for uniform polymerization. Therefore, the amount is preferably 40% by mass or less.

[0076] 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, but these are all solids, and all or part of them may be powdery. With regard to powdery components, the particles that form the powder may adhere to each other during or after their introduction into the reaction system, forming clumps. If clumps form, they are difficult to dissolve, and polymerization takes a long time. This increases the total amount of polymerization inhibitors (such as water and oxygen) that enter from outside the system during the polymerization process, making it difficult to increase the degree of polymerization. Therefore, when the acid component and amine component are powdery, it is preferable to introduce them without forming lumps, and examples of such methods include a method of introducing them under high-speed stirring, a method of first introducing the amine component and completely dissolving it before introducing the acid component, a method of first introducing the acid component and completely dissolving it before introducing the amine component, etc. The time required to completely dissolve the component introduced first varies depending on the acid component and amine component used, their ratio, the solvent, the stirring state, 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.

[0077] 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 amine components used, their ratios, the 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.

[0078] 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, and 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 the introduction of the 3,3',4,4'-biphenyltetracarboxylic acid derivative to the introduction of the pyromellitic acid derivative, or the time from the introduction of the pyromellitic acid derivative to the introduction of the 3,3',4,4'-biphenyltetracarboxylic acid derivative to the introduction of the 3,3',4,4'-biphenyltetracarboxylic acid derivative, varies depending on the acid components used, their ratios, the 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.

[0079] 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.

[0080] <Step IV> Step IV is preferably carried out at least 4 hours after Step III, 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 system during the polymerization process, 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 aforementioned 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. By carrying out the step IV after a lapse of at least 4 hours from the step III, it becomes easier to obtain a polyimide precursor having a weight average molecular weight in the preferred range of 260,000 to 1,000,000.

[0081] 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.

[0082] 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, dimethyl sulfone, 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 solvent used in Step II and the third solvent used in Step IV may be the same or different.

[0083] 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, deactivation of the acidic components can be suppressed, which in turn facilitates an increase in the degree of polymerization of the polyimide precursor, making it easier to obtain a polyimide precursor with a weight-average molecular weight in the preferred range of 260,000 to 1,000,000. For the same reasons, the water content of the raw materials is also preferably 3,000 ppm by mass or less, more preferably 1,000 ppm by mass or less.

[0084] 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.

[0085] The molar ratio of the acid component to the amine component (acid / amine ratio) when polymerizing the polyimide precursor 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 dianhydride / diamine 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 in the preferred range of 260,000 to 1,000,000.

[0086] The temperature at which the polyimide precursor is polymerized is not particularly limited, but heating may be performed as necessary when dissolving the acid component or amine component in the 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.

[0087] The polymerization time for polymerizing the polyimide precursor 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.

[0088] The polymerization of the polyimide precursor is preferably carried out in an inert gas atmosphere, which is not particularly limited, but includes, for example, nitrogen gas and rare gases such as helium gas, neon gas, and argon gas.

[0089] <Uses of Polyimide Film> The polyimide film of the present invention can be used, for example, as a semiconductor insulating film, a TFT-LCD insulating film, an electrode protective 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. Examples of flexible devices to which the polyimide film according to this 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.

[0090] 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.

[0091] <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

[0092] <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.

[0093] <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 rotation speeds that allow measurement of the viscosity. Note that measurable rotation speeds include, for example, 0.5, 1, 2.5, 5, 10, 20, 50, and 100 rpm. Specific examples of measurable cone rotors include, for example, 1°34′ (angle of cone rotor) × R24 (diameter of cone rotor), 1°34′ × R12, 0.8° × R24, 0.8° × R12, 3° × R24, 3° × R12, 3° × R17.65, 3° × R14, 3° × R12, and 3° × R9.7.

[0094] <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.

[0095] <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.

[0096] <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.

[0097] <Haze of polyimide film ３６０ A 50 mm square piece of film was cut from the center of the film width direction, and the film was heated from room temperature to 360°C at a heating rate of 30°C / min in an inert oven in a nitrogen atmosphere with an oxygen concentration of 0.2% by volume or less, and then immediately held at 360°C for 60 minutes to prepare a sample. A haze test was performed using a hazemeter (NDH5000, manufactured by Nippon Denshoku Co., Ltd.). ３６０ The measurement was performed using a D65 lamp as the light source. The collection of the measurement samples, the measurement, and the handling of the measured values ​​were the same as those for the total light transmittance measurement sample.

[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 (YI) equivalent to 15 μm thick film was calculated using the following formula (where t is the thickness of the polyimide film, unit: μm). 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] <Polyimide film YI ３６０ A 50 mm square piece of film was cut from the center in the width direction of the film, and the film was heated from room temperature to 360°C at a heating rate of 30°C / min in an inert oven in a nitrogen atmosphere with an oxygen concentration of 0.2% or less, and then immediately held at 360°C for 60 minutes to prepare a sample. Using a color meter (ZE6000, manufactured by Nippon Denshoku Co., Ltd.) and a C2 light source, the tristimulus values ​​X, Y, and Z of the sample were measured in accordance with ASTM D1925, and the YI value was calculated using the following formula (where t is the thickness of the polyimide film, in μm): ３６０ was calculated. ３６０={100×(1.28X-1.06Z) / Y}×15 / t

[0100] <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 name AG-5000A), the tensile modulus (unit: GPa), tensile break strength (unit: MPa), and tensile break elongation (unit: %) were measured at a temperature of 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

[0101] <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.

[0102] <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

[0103] <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. 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, during cooling. 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.

[0104] <Water Absorption of Polyimide Film> Measurement was performed using a TGA apparatus (TGA-50, Shimadzu Corporation). A strip-shaped test piece was cut from the center of the width direction of the film to a length of 4 mm in the width direction and a length in the machine direction such that the film weight was 10 mg. The test piece was immersed in deionized water at 23°C for 24 hours, and then water droplets on the surface were thoroughly wiped off. The test piece was placed on an aluminum pan and heated to 150°C at a heating rate of 20°C / min in a nitrogen atmosphere. The weight loss rate after holding at 150°C for 30 minutes was taken as the water absorption (unit: mass%).

[0105] <Moisture absorption rate of polyimide film> Measurement was performed using a TGA apparatus (TGA-50, Shimadzu Corporation). A strip-shaped test piece was cut from the center of the width direction of the film to a length of 4 mm in the width direction and a length in the machine direction such that the film weight was 10 mg. The test piece was left to stand in a constant temperature and humidity chamber at 23°C and 50% RH for 24 hours, then placed on an aluminum pan and heated to 150°C at a heating rate of 20°C / min in a nitrogen atmosphere. The weight loss rate after holding at 150°C for 30 minutes was taken as the moisture absorption rate (unit: mass%).

[0106] <Coefficient of Hygroscopic Expansion (CHE) of Polyimide Film> Polyimide film was cut into strips of 15 mm x 2 mm with the machine direction (MD) or width direction (TD) as the longitudinal direction, respectively, to form test specimens. Measurements were performed using a humidity-controlled TMA (TMA4000SA, Netsch Japan Co., Ltd.). The test specimen was set in the apparatus with a chuck distance of 10 mm and a load of 5 gf, and then stabilized at 25 ° C. and 0% RH under a nitrogen atmosphere. The temperature was then increased to 15% RH, and the expansion coefficient at 15% RH for 4.5 hours was taken as X1 (unit: %). The expansion coefficient at 75% RH for 4.5 hours was taken as X2 (unit: %). The coefficient of hygroscopic expansion (CHE) (unit: ppm / % RH) was calculated using X1 and X2 according to the following formula: The hygroscopic expansion coefficient (CHE) of each polyimide film was calculated by measuring twice, once in the machine direction and once in the transverse direction, and the average value was used as the coefficient of hygroscopic expansion (CHE) of the polyimide film. CHE = {(X2 - X1) x 0.01} / (75-15)

[0107] <Evaluation Criteria for Polyimide Film Transparency> A polyimide film having a yellowness index (YI) of 20.0 or less at a film thickness of 15 μm and a haze of 2.0% or less was evaluated as "good", and any other cases were evaluated as "poor".

[0108] <Evaluation Criteria for Mechanical Properties of Polyimide Film> A polyimide film having a tensile elongation of 10% or more was evaluated as "good", and any other cases were evaluated as "poor".

[0109] <Evaluation Criteria for Thermal Properties of Polyimide Film> When the 1% weight loss temperature of the polyimide film was 450° C. or higher, it was evaluated as "good", and otherwise it was evaluated as "poor".

[0110] <Preparation of Polyimide Film / Glass Laminate> A polyimide film was cut into a size of 360 mm x 480 mm. Next, the film surface was treated with UV / O ３ Using an irradiator (SKR1102N-03 manufactured by LAN Technical), UV / O ３ The UV / O irradiation was carried out for 3 minutes. ３ The distance between the lamp and the film was 30 mm. 3-aminopropyltrimethoxysilane (KBM-903, manufactured by Shin-Etsu Chemical Co., Ltd.) was applied as a silane coupling agent to a G2 size (370 x 470 mm) glass substrate with a thickness of 0.4 mm using a spray coater. The glass substrate was washed with pure water, dried, and then irradiated with UV / O. ３ UV / O irradiation with an irradiator (SKR1102N-03 manufactured by LAN Technical) ３The glass substrate coated with the silane coupling agent in this manner was set in a roll laminator equipped with a silicone rubber roller, and 500 ml of pure water was first dripped onto the silane coupling agent-coated surface using a dropper so that it spread over the entire substrate, wetting the substrate. Next, the surface-treated surface of the polyimide film was placed facing the silane coupling agent-coated surface of the glass substrate, i.e., the surface wetted with pure water, and the glass substrate and polyimide film were laminated by sequentially pressing the rotating roll from one side of the glass substrate while pushing out the pure water between the polyimide film and the glass substrate to obtain a temporary laminate. The laminator used was a laminator with an effective roll width of 1350 mm manufactured by MCK Corporation, and the lamination conditions were: air source pressure: 0.5 MPa, lamination speed: 50 mm / sec, roll temperature: 22 ° C, ambient temperature 22 ° C, humidity 55% RH.

[0111] <Low Warpage of Polyimide Film / Glass Laminate> After heating the temporary laminate at 280°C for 1 hour, it was placed on a surface plate with the glass substrate facing downward, and 500 µm thick shim plates were inserted into the four corners of the laminate. If the shim plate was caught on the inorganic substrate at 2 to 4 corners, it was evaluated as "Good", and if the shim plate was caught on the inorganic substrate at 0 to 1 corner, it was evaluated as "Poor".

[0112] <Production 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 (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.

[0113] Example 1 A dispersion ("Snowtex (registered trademark) DMAC-ST-ZL" manufactured by Nissan Chemical Industries, Ltd.) 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 (manufactured by Toyobo Co., Ltd.) using a comma coater to a thickness such that the final polyimide film thickness would be 15 μm. This was then subjected to a heat treatment for 18 minutes in a dry atmosphere at 100°C, yielding a self-supporting film (polyimide precursor film) composed 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 pin sheet spacing was adjusted to prevent unnecessary slack in the film. The film was then heated in a dry atmosphere at an average heating rate of 10°C / min between each set temperature. Four stages of heating were performed to promote imidization: 150°C for 3 minutes, 230°C for 3 minutes, 300°C for 3 minutes, and 350°C for 3 minutes. 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-long polyimide film roll A2 with a width of 450 mm. The film properties of the polyimide film roll A2 were as shown in Table 3.

[0114] <Production Example 2> Resin composition B1 was obtained in the same manner as in Production 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 properties of resin composition B1 were as shown in Table 1.

[0115] <Production Example 2> Resin composition C1 was obtained in the same manner as in Production 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 properties of resin composition C1 are as shown in Table 1.

[0116] Production Example 4 Resin composition D1 was obtained in the same manner as in Production 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 properties of resin composition D1 are as shown in Table 1.

[0117] <Production Example 5> Resin composition E1 was obtained in the same manner as in Production 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 properties of resin composition E1 are as shown in Table 1.

[0118] Production Example 6 Resin composition F1 was obtained in the same manner as in Production 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 properties of resin composition F1 were as shown in Table 1.

[0119] Production Example 7 Resin composition G1 was obtained in the same manner as in Production 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 properties of resin composition G1 were as shown in Table 1.

[0120] Examples 2 to 7 Polyimide film rolls B2 to G2 were obtained in the same manner as in Example 1, except that resin compositions B1 to G1 obtained in Production Examples 2 to 7 were used. The film properties of polyimide film rolls B2 to G2 were as shown in Table 3.

[0121] <Production 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 DMAc (3940 g) with a moisture content of 80 ppm and stirring for 40 hours to obtain a resin composition H1. The physical properties of resin composition H1 were as shown in Table 1.

[0122] Example 8 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 film properties of the polyimide film roll H2 are shown in Table 3.

[0123] Production 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.

[0124]

[0125] 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.

[0126] Example 9 Except for using resin composition I1, coating, drying, and heat treatment were performed in the same manner as in Example 1 to obtain a 50 m long polyimide film roll I2 having a width of 450 mm. The film properties of polyimide film roll I2 are shown in Table 3.

[0127] <Production Example 10> 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 (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 2.

[0128] Comparative Example 1 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 transportation, and a polyimide film roll could not be obtained.

[0129] <Production Example 11> 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 (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 2.

[0130] Comparative Example 2: 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 film properties of polyimide film roll K2 are shown in Table 4.

[0131] <Production Example 12> 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 a resin composition L1. The physical properties of resin composition L1 were as shown in Table 2.

[0132] Comparative Example 3: 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 heat treatment was carried out in four stages: 150°C x 3 minutes, 200°C x 3 minutes, 250°C x 3 minutes, and 280°C x 3 minutes, to obtain a 50 m polyimide film roll L2 having a width of 450 mm. The film properties of polyimide film roll L2 are shown in Table 4.

[0133] <Production Example 13> 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 2.

[0134] Comparative Example 4: 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 film properties of the polyimide film roll M2 are shown in Table 4.

[0135] Example 10 A polyimide film was produced in the same manner as in Example 1, except that the heat treatment of the polyimide precursor film was a one-stage heat treatment in which the temperature was raised to 350°C at a rate of 7°C / min and then maintained at 350°C for 3 minutes, and a 50 m long polyimide film roll A3 with a width of 450 mm was obtained. The film properties of the polyimide film roll A3 are shown in Table 4.

[0136] Example 11 A polyimide film was produced in the same manner as in Example 1, except that the heat treatment of the polyimide precursor film was performed in two stages: at 150°C for 6 minutes and at 350°C for 6 minutes, and a 50 m polyimide film roll A4 with a width of 450 mm was obtained. The film properties of the polyimide film roll A4 are shown in Table 4.

[0137] Example 12 A polyimide film was produced in the same manner as in Example 1, except that the heat treatment of the polyimide precursor film was performed in three stages: 150°C for 4 minutes, 250°C for 4 minutes, and 350°C for 4 minutes, to obtain a 50 m polyimide film roll A5 having a width of 450 mm. The film properties of the polyimide film roll A5 are shown in Table 4.

[0138] Example 13 A dispersion (Nissan Chemical Industries, Ltd., "Snowtex (registered trademark) DMAC-ST-ZL") prepared by dispersing colloidal silica (average particle size 80 nm) in DMAc was added as a lubricant to Resin Composition A1 so that the silica (lubricant) accounted for 0.3 mass% of the total polymer solids in the resin composition, and the mixture was thoroughly stirred. Subsequently, 1-methylimidazole was added as an imidization accelerator in an amount (180.78 g) of 1.1 moles per mole of the repeating unit of the polyimide precursor, and completely dissolved. A polyimide film was produced in the same manner as in Example 1, yielding a 50 m long, 450 mm wide polyimide film roll A6. The film properties of Polyimide Film Roll A6 were as shown in Table 4.

[0139] Example 14 A polyimide film was produced in the same manner as in Example 1, except that the polyimide precursor film was heated in four stages: 150°C for 3 minutes, 200°C for 3 minutes, 250°C for 3 minutes, and 300°C for 3 minutes. A 50 m polyimide film roll A7 with a width of 450 mm was obtained. The film properties of the polyimide film roll A7 are shown in Table 5.

[0140] Example 15 A polyimide film was produced in the same manner as in Example 1, except that the heat treatment of the polyimide precursor film was performed at an average temperature increase rate of 300°C / min between each set temperature, and in eight stages: 100°C x 2 min, 135°C x 2 min, 170°C x 2 min, 205°C x 2 min, 240°C x 2 min, 275°C x 2 min, 310°C x 2 min, and 350°C x 2 min. A polyimide film was produced in the same manner as in Example 1, and a 450 mm wide polyimide film roll A8 (50 m long) was obtained. The film properties of the polyimide film roll A8 are shown in Table 5.

[0141] Example 16 A polyimide film was produced in the same manner as in Example 1, except that the heat treatment of the polyimide precursor film was performed at an average temperature increase rate of 100°C / min between each set temperature, and in eight stages: 100°C x 3 minutes, 150°C x 3 minutes, 200°C x 3 minutes, 250°C x 3 minutes, 300°C x 3 minutes, 350°C x 3 minutes, 400°C x 3 minutes, and 450°C x 3 minutes. A polyimide film was produced in the same manner as in Example 1, and a 450 mm wide polyimide film roll A9 (50 m long) was obtained. The film properties of the polyimide film roll A9 are shown in Table 5.

[0142] Comparative Example 5 A polyimide film was produced in the same manner as in Example 1, except that the heat treatment of the polyimide precursor film was a one-stage heat treatment in which the temperature was increased to 350°C at an average heating rate of 100°C / min and then maintained at 330°C for 40 minutes, thereby obtaining 50 m of a polyimide film roll A10 having a width of 450 mm. The film properties of the polyimide film roll A10 are shown in Table 5.

[0143] Comparative Example 6 A polyimide film was produced in the same manner as in Example 1, except that the polyimide precursor film was heat-treated at an average temperature-rise rate of 500°C / min between each set temperature in four stages: 150°C x 3 minutes, 230°C x 3 minutes, 300°C x 3 minutes, and 350°C x 30 minutes. A polyimide film was produced in the same manner as in Example 1, and a 50 m long polyimide film roll A11 with a width of 450 mm was obtained. The film properties of the polyimide film roll A11 were as shown in Table 5.

[0144] Comparative Example 7 A polyimide film was produced in the same manner as in Example 1, except that the polyimide precursor film was heat-treated in four stages: 125°C for 3 minutes, 170°C for 3 minutes, 215°C for 3 minutes, and 250°C for 3 minutes, to obtain 50 m of a 450 mm wide polyimide film roll A12. The film properties of the polyimide film roll A12 are shown in Table 5.

[0145] Comparative Example 8 A polyimide film was produced in the same manner as in Example 1, except that the polyimide precursor film was heat-treated in eight stages: 100°C x 3 minutes, 160°C x 3 minutes, 220°C x 3 minutes, 280°C x 3 minutes, 340°C x 3 minutes, 400°C x 3 minutes, 450°C x 3 minutes, and 500°C x 3 minutes, with an average temperature rise rate of 100°C / min between each set temperature. A polyimide film was produced in the same manner as in Example 1, and a 50 m long polyimide film roll A13 with a width of 450 mm was obtained. The film properties of the polyimide film roll A13 were as shown in Table 5.

[0146]

[0147]

[0148]

[0149]

[0150]

[0151] The polyimide films of Examples 1 to 16 contained a PMDA-derived structure and an s-BPDA-derived structure as the acid-based component-derived structure, and a TFMB-derived structure as the amine-based component-derived structure; each had a yellowness index (YI) equivalent to a 15 μm film thickness of 20.0 or less, a haze of 2.0% or less, a 1% weight loss temperature of 450° C. or more, an average coefficient of linear expansion (CTE) between 50° C. and 200° C. of −5 to +20 ppm / ° C., and a tensile elongation of 10% or more. Therefore, the polyimide films can be suitably used in applications requiring lighter weight, smaller size / thinner thickness, flexibility, and transparency in electronic devices having functional elements such as display elements, and can withstand high temperature exposure in processes such as forming a desired functional element on a laminate bonded to an inorganic support, and further have transparency, mechanical properties, heat resistance, and low CTE properties sufficient to contribute to obtaining a desired electronic device without significant warpage. Comparison of Examples 1, 4, and 5 revealed that increasing the proportion of the PMDA-derived structure improved the CTE, and increasing the proportion of the s-BPDA-derived structure tended to result in a polyimide film with a lower YI.

[0152] Comparison of Examples 1, 2, 3, and 7 and comparison of Examples 4 and 6 revealed that when the acid / amine ratio was brought closer to 1, a polyimide precursor with a higher weight average molecular weight and a polyimide film with a higher tensile elongation tended to be obtained.

[0153] Comparison of Examples 1, 14, 15, and 16 revealed that when the maximum temperature reached in the heat treatment was increased, the resulting polyimide film tended to have low total light transmittance, high haze, high YI, high mechanical properties (tensile strength, tensile modulus, and tensile elongation), high 1% weight loss temperature, low CTE, and high glass transition temperature.

[0154] Example 8 is a case where the acid-based component-derived structure includes a structure that is neither a PMDA-derived structure nor an s-PMDA-derived structure, and Example 9 is a case where the amine-based component-derived structure includes a structure that is not a TFMB-derived structure.

[0155] In Example 10, the temperature profile of the heat treatment is one in which the temperature is increased from room temperature to the maximum temperature in one stage, and the rate of increase is 30°C / min or less. In Example 11, the temperature profile of the heat treatment is one in which the temperature is increased from room temperature to the maximum temperature in two stages, the temperature in the first stage is in the range of 100 to 250°C, the holding time after reaching the temperature in the first stage is in the range of 1 to 30 minutes, and the rate of increase is 50°C / min or less. In Example 12, the temperature is increased from room temperature to the maximum temperature in three stages, the temperature in the first stage is in the range of 100 to 250°C, the temperature in the second stage is in the range of ±50°C of the value obtained by adding the temperature in the first stage to the maximum temperature divided by 2, the holding time after reaching each stage is in the range of 1 to 30 minutes, and the rate of increase is 100°C / min or less.

[0156] In Example 13, the resin composition contained an imidization accelerator.

[0157] In Examples 1 to 9 and 14 to 16, the temperature was raised from room temperature to the maximum temperature in N stages (N is an integer of 4 or more), the temperature reached in the first stage (T1) was in the range of 100 to 250°C, the temperatures reached in the second stage and thereafter were in the range of ±50°C of the value obtained by subtracting the temperature reached in the first stage (T1) from the maximum temperature reached (Tmax), dividing the result (Tmax-T1) by N-1 ((Tmax-T1) / (N-1)) (if the result is not divisible, the value is rounded to the nearest integer), and adding this to the temperature reached in the previous stage, the holding time after reaching each stage was in the range of 1 to 30 minutes, the heating rate was 300°C / min or less, and N was 4 or 8.

[0158] In Comparative Example 1, since the s-BPDA-derived structure was not contained, the strength during heat treatment was insufficient, and a polyimide film roll could not be obtained. In Comparative Example 2, since the PMDA-derived structure was not contained, the CTE of the polyimide film was significantly increased. In Comparative Example 3, the CTE of the polyimide film was significantly increased by using a highly flexible 3,3'-DAS-derived structure instead of a TFMB-derived structure as the amine-based component. In Comparative Example 4, the YI of the polyimide film was significantly increased by using an m-TB-derived structure having an electron-emitting substituent instead of a TFMB-derived structure as the amine-based component.

[0159] In Comparative Examples 5 and 6, the temperature rise rate in the heat treatment of the polyimide precursor film was too fast, resulting in severe whitening of the polyimide film and, consequently, deterioration in mechanical properties, transparency, and low CTE properties. In Comparative Example 7, the maximum temperature reached in the heat treatment of the polyimide precursor film was too low, resulting in deterioration in mechanical properties, heat resistance, and low CTE properties. In Comparative Example 8, the maximum temperature reached in the heat treatment of the polyimide precursor film was too high, resulting in deterioration in transparency of the polyimide film.

[0160] As described above, the present invention can provide a polyimide film that is excellent in transparency, heat resistance, low CTE characteristics, and mechanical properties. The polyimide film can be suitably used in processes for forming desired functional elements in a laminate laminated with an inorganic support, in applications where lighter weight, smaller size, thinner size, greater flexibility, and greater transparency are required for electronic devices having functional elements, such as display elements.

Claims

1. A polyimide film comprising a polyimide resin having an acid-based component-derived structure and an amine-based component-derived structure, 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, characterized in that the polyimide film has a yellowness index (YI) of 20.0 or less (equivalent to a film thickness of 15 μm), a haze of 2.0% or less, a 1% weight loss temperature of 450°C or higher, an average coefficient of linear expansion (CTE) between 50°C and 200°C of -5 to +20 ppm / °C, and a tensile elongation of 10% or more.

2. The polyimide film 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 resin is 90:10 to 10:

90.

3. The polyimide film according to claim 1 or 2, wherein the pyromellitic acid-derived structure constituting the polyimide resin is a pyromellitic acid dianhydride-derived structure, and the 3,3',4,4'-biphenyltetracarboxylic acid derivative-derived structure is a 3,3',4,4'-biphenyltetracarboxylic acid dianhydride-derived structure.

4. In a nitrogen atmosphere, the temperature is raised from room temperature to 360°C at a rate of 30°C / min, and then immediately held at 360°C for 60 minutes. The yellowness index (YI) of the polyimide film is calculated as a film thickness of 15 μm. ３６０ 3. The polyimide film according to claim 1, wherein the modulus of elasticity is 20.0 or less.

5. Haze of polyimide film after heat treatment at 360°C under nitrogen atmosphere ３６０ 3. The polyimide film according to claim 1, wherein the tensile strength is 2.0% or less.

6. The polyimide film according to claim 1 or 2, characterized in that the moisture absorption rate is 1.0% by mass or less.

7. The polyimide film according to claim 1 or 2, characterized in that the water absorption rate is 1.0 mass % or less.

8. The polyimide film according to claim 1 or 2, characterized in that the coefficient of moisture expansion is 5.0 ppm / % RH or less.

9. A method for producing a polyimide film according to claim 1, comprising: step α of coating a support with a resin composition comprising a polyimide precursor obtained by reacting an acid component including a pyromellitic acid derivative and a 3,3',4,4'-biphenyltetracarboxylic acid derivative with an amine component including a 2,2'-bis(trifluoromethyl)benzidine derivative, and a solvent, and then heating the coating to dry off part of the solvent, to produce a polyimide precursor film; and step β of heating the polyimide precursor film on the support, or peeling it off from the support and heating it with its edges fixed, to cause a dehydration ring-closing reaction while removing the solvent.

10. The method for producing a polyimide film according to claim 9, wherein the maximum temperature reached in the heat treatment in step β is 300 to 450°C.

11. The method for producing a polyimide film according to claim 9 or 10, wherein the temperature profile of the heat treatment in step β is a single-stage temperature rise from room temperature to the maximum temperature, with a temperature rise rate of 30°C / min or less.

12. The method for producing a polyimide film according to claim 9 or 10, wherein the temperature profile of the heat treatment in step β is such that the temperature is increased in two stages from room temperature to the maximum temperature, with the temperature increase in each stage being carried out at an average rate of 50°C / min or less, the maximum temperature in the first stage being in the range of 100 to 250°C, and the holding time after reaching the maximum temperature in the first stage being in the range of 1 to 30 minutes.

13. The method for producing a polyimide film according to claim 9 or 10, wherein the temperature profile of the heat treatment in step β is such that the temperature is increased from room temperature to the maximum temperature in three stages, with the temperature increase in each stage being carried out at an average rate of 100°C / min or less, the maximum temperature in the first stage being in the range of 100 to 250°C, the maximum temperature in the second stage being in the range of ±50°C of the value obtained by adding the maximum temperature in the first stage to the maximum temperature in the third stage and dividing the result by 2, and the holding time after reaching the maximum temperature in each stage being in the range of 1 to 30 minutes.

14. The method for producing a polyimide film according to claim 9 or 10, wherein the temperature profile of the heat treatment in step β is: the temperature is raised from room temperature to the maximum temperature in N stages (N is an integer of 4 or greater), the temperature is raised in each stage at an average heating rate of 300°C / min or less, the maximum temperature (T1) in the first stage is in the range of 100 to 250°C, the maximum temperature in each stage from the second stage onwards is within the range of ±50°C of the value obtained by subtracting the maximum temperature (T1) in the first stage from the maximum temperature (Tmax) in step β (Tmax) and dividing the result (Tmax - T1) by N-1 ((Tmax - T1) / (N-1)) (if the result is not divisible, the integer is rounded to the nearest tenth), and adding this value to the maximum temperature in the previous stage, and the holding time after reaching the maximum temperature in each stage is in the range of 1 to 30 minutes.

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