Polyimide, polyimide resin composition, and polyimide film

Abstract

This polyimide has a tetracarboxylic acid dianhydride residue and a diamine residue. The tetracarboxylic acid dianhydride residue contains a residue having a bisphenol A type structure. The diamine residue contains a residue having a fluorene structure and a residue derived from a siloxane diamine having a number-average molecular weight of 500-1500. The content of the residue having the bisphenol A type structure is 50 mol% or more with respect to the total amount of the tetracarboxylic acid dianhydride residue. The content of the residue derived from a siloxane diamine having a number-average molecular weight of 500-1500 is 30-50 mol% with respect to the total amount of the diamine residue.

Description

Polyimide, polyimide resin composition, and polyimide film

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

[0002] Polyimides with excellent heat resistance are usually not solvent-soluble. Therefore, they are obtained by using a polyamic acid solution in which polyamic acid, a polyimide precursor, is dissolved in a solvent and heating the solution at high temperatures for a long period of time to dehydrate and cyclize the solution. However, heating at high temperatures can cause thermal degradation of other components. For example, when a polyimide film is laminated on a wiring board as an insulating layer, heating the polyamic acid solution can cause thermal degradation of the wiring board material. Furthermore, if the polyamic acid solution is not sufficiently heated, carboxylic acids contained in the polyamic acid structure remain, which can cause a decrease in electrical insulation when used in electronic materials. These problems can be solved by using a polyimide solution containing a solvent-soluble polyimide instead of a polyamic acid solution.

[0003] For example, Patent Document 1 proposes a polyimide obtained from an alicyclic acid dianhydride, a fluorine-containing aromatic acid dianhydride, and a fluoroalkyl-substituted benzidine as essential components as a polyimide soluble in an organic solvent having a carbonyl group, such as methyl ethyl ketone. Similarly, Patent Document 2 proposes a silicone-modified polyimide resin as a polyimide soluble in methyl ethyl ketone or ethyl acetate. Hereinafter, organic solvents having a carbonyl group may be referred to as "carbonyl-based solvents." Examples of carbonyl-based solvents include ketone-based solvents such as methyl ethyl ketone; ester-based solvents such as ethyl acetate; and amide-based solvents such as N-methyl-2-pyrrolidone.

[0004] International Publication No. 2019 / 073628 Japanese Patent Application Laid-Open No. 2005-126569

[0005] However, it is difficult to obtain polyimides that are excellent in solubility in carbonyl-based solvents and heat resistance only by the techniques described in Patent Documents 1 and 2.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyimide having excellent solubility in carbonyl-based solvents and heat resistance, as well as a polyimide resin composition and a polyimide film containing the polyimide.

[0007] <Aspects of the Present Invention> The present invention includes the following aspects.

[0008] [1] A polyimide having a tetracarboxylic dianhydride residue and a diamine residue, wherein the tetracarboxylic dianhydride residue contains a residue having a bisphenol A type structure, and the diamine residue contains a residue having a fluorene structure and a residue derived from a siloxane diamine having a number average molecular weight of 500 to 1500, wherein the content of the residue having the bisphenol A type structure is 50 mol % or more based on the total amount of the tetracarboxylic dianhydride residues, and the content of the residue derived from the siloxane diamine is 30 mol % or more and 50 mol % or less based on the total amount of the diamine residues.

[0009] [2] The polyimide according to [1] above, wherein the residue having a bisphenol A structure is a 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride residue.

[0010] [3] The polyimide according to [1] or [2] above, wherein the residue having a fluorene structure is at least one selected from the group consisting of a 9,9-bis(4-aminophenyl)fluorene residue and a 9,9-bis(4-amino-3-methylphenyl)fluorene residue.

[0011] [4] The polyimide according to any one of [1] to [3] above, wherein a value obtained by dividing the total amount of substance of the tetracarboxylic dianhydride residues by the total amount of substance of the diamine residues is less than 1.

[0012] [5] The polyimide according to any one of [1] to [4] above, which has a glass transition temperature of 150°C or higher.

[0013] [6] The polyimide according to any one of [1] to [5] above, which is soluble in ethyl acetate.

[0014] [7] A polyimide resin composition containing the polyimide according to any one of [1] to [6] above and an organic solvent having a carbonyl group.

[0015] [8] A polyimide film comprising the polyimide according to any one of [1] to [6] above.

[0016] According to the present invention, it is possible to provide a polyimide having excellent solubility in carbonyl-based solvents and heat resistance, as well as a polyimide resin composition and a polyimide film containing the polyimide.

[0017] Preferred embodiments of the present invention will be described in detail below, but the present invention is not limited thereto. In addition, all academic and patent documents described in this specification are incorporated herein by reference.

[0018] First, the terms used in this specification will be explained. A "structural unit" refers to a repeating unit that constitutes a polymer. A "polyimide" is a polymer containing a structural unit represented by the following general formula (1) (hereinafter, sometimes referred to as "structural unit (1)").

[0019]

[0020] In general formula (1), X １ represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from a tetracarboxylic dianhydride), and X ２ represents a diamine residue (a divalent organic group derived from a diamine).

[0021] The content of the structural unit (1) relative to all structural units constituting the polyimide is, for example, 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, even more preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%.

[0022] The "polyamic acid" is a polymer containing a structural unit represented by the following general formula (2) (hereinafter, sometimes referred to as "structural unit (2)").

[0023]

[0024] In general formula (2), A １ represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from a tetracarboxylic dianhydride), A ２ represents a diamine residue (a divalent organic group derived from a diamine).

[0025] The content of the structural unit (2) relative to all structural units constituting the polyamic acid is, for example, 50 mol% or more and 100 mol% or less, preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, even more preferably 80 mol% or more and 100 mol% or less, still more preferably 90 mol% or more and 100 mol% or less, and may be 100 mol%.

[0026] Polyimide is an imide of polyamic acid. Therefore, when the content of the structural unit (2) relative to all structural units constituting the polyamic acid is 100 mol %, the polyimide, which is an imide of the polyamic acid, is represented by X in the general formula (1). １ As A in general formula (2), １ and X in general formula (1) ２ As A in general formula (2), ２ The residue is represented by:

[0027] The term "residue having a fluorene structure" refers to a residue having a fluorene ring. The term "residue having a bisphenol A structure" refers to a residue having a divalent organic group represented by the following chemical formula (3). However, the benzene ring in the following chemical formula (3) may further have a substituent.

[0028]

[0029] The "number average molecular weight" of a siloxane diamine is a value calculated based on the amine value. The amine value of a siloxane diamine can be measured, for example, using an automatic potentiometric titrator ("AT-710M" manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0030] "Solid content" refers to non-volatile components in the composition, such as components other than the solvent.

[0031] Hereinafter, the compound name may be followed by "system" to collectively refer to the compound and its derivatives. When the compound name is followed by "system" to represent the name of a polymer, it means that the repeating unit of the polymer is derived from the compound or its derivative. Furthermore, tetracarboxylic acid dianhydride may be referred to as "acid dianhydride." Furthermore, unless otherwise specified, the components and functional groups exemplified in this specification may be used alone or in combination of two or more types.

[0032] <First Embodiment: Polyimide> A polyimide according to a first embodiment of the present invention has a tetracarboxylic dianhydride residue and a diamine residue. The tetracarboxylic dianhydride residue includes a residue having a bisphenol A structure. The diamine residue includes a residue having a fluorene structure and a residue derived from a siloxane diamine having a number average molecular weight of 500 to 1500. The content of the residue having the bisphenol A structure is 50 mol % or more relative to the total amount (100 mol %) of the tetracarboxylic dianhydride residues. The content of the residue derived from a siloxane diamine having a number average molecular weight of 500 to 1500 is 30 mol % or more and 50 mol % or less relative to the total amount (100 mol %) of the diamine residues.

[0033] Hereinafter, a tetracarboxylic dianhydride residue having a bisphenol A structure may be referred to as a "bisphenol A structure-containing residue." A diamine residue having a fluorene structure may be referred to as a "fluorene structure-containing residue." A residue derived from a siloxane diamine having a number average molecular weight of 500 to 1500 may be referred to as a "specific siloxane diamine residue."

[0034] The polyimide according to the first embodiment has excellent solubility in carbonyl-based solvents and heat resistance, and the reason for this is presumed to be as follows.

[0035] Because the tetracarboxylic dianhydride residue is surrounded by four carbonyl groups, its structure significantly affects the solubility in carbonyl-based solvents. The polyimide according to the first embodiment contains, as the tetracarboxylic dianhydride residue, a bisphenol A-type structure-containing residue, which has a flexible structure, at a content of 50 mol % or more, thereby enhancing the solubility in carbonyl-based solvents. Furthermore, the polyimide according to the first embodiment contains, as the diamine residue, a specific siloxane diamine residue, which has a high affinity for carbonyl-based solvents, at a content of 30 mol % or more, thereby enhancing the solubility in carbonyl-based solvents. Furthermore, the polyimide according to the first embodiment contains, as the diamine residue, a fluorene structure-containing residue, which has a bulky structure, thereby suppressing aggregation of polyimide chains in carbonyl-based solvents. Therefore, the polyimide according to the first embodiment has excellent solubility in carbonyl-based solvents.

[0036] Furthermore, the polyimide according to the first embodiment has a fluorene structure-containing residue, which has a rigid structure, as the diamine residue, and therefore can improve heat resistance. Furthermore, in the polyimide according to the first embodiment, the content of the specific siloxane diamine residue is 50 mol% or less, so that a decrease in heat resistance caused by the specific siloxane diamine residue is suppressed. Therefore, the polyimide according to the first embodiment has excellent heat resistance while improving solubility in carbonyl-based solvents.

[0037] [Acid Dianhydride] The polyimide according to the first embodiment contains a bisphenol A type structure-containing residue as a tetracarboxylic acid dianhydride residue. In order to obtain a polyimide having excellent solubility in carbonyl solvents, the bisphenol A type structure-containing residue is preferably a residue derived from 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride (hereinafter, sometimes referred to as "BPADA").

[0038] In order to obtain a polyimide having excellent solubility in carbonyl-based solvents, the content of the bisphenol A type structure-containing residue is preferably 60 mol % or more, more preferably 70 mol % or more, and even more preferably 80 mol % or more, relative to the total amount (100 mol %) of tetracarboxylic dianhydride residues. It may be 85 mol % or more, 90 mol % or more, or 95 mol % or more, or even 100 mol %.

[0039] When synthesizing the polyimide according to the first embodiment, an acid dianhydride other than the acid dianhydride having a bisphenol A structure (another acid dianhydride) may be used as a monomer within a range that does not impair its performance. Examples of other acid dianhydrides include 2,3,3',4'-biphenyltetracarboxylic dianhydride (hereinafter, sometimes referred to as "a-BPDA"), 3,3',4,4'-biphenyltetracarboxylic dianhydride, 4,4'-oxydiphthalic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (hereinafter, sometimes referred to as "BPAF"), pyromellitic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, and the like. Examples of suitable dianhydrides include 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and derivatives thereof, and these may be used alone or in combination.

[0040] When other acid dianhydrides are used as monomers, a-BPDA is preferred as the other acid dianhydride in order to obtain polyimides having superior solubility in carbonyl solvents.

[0041] [Diamine] The polyimide according to the first embodiment contains a fluorene structure-containing residue and a specific siloxane diamine residue as a diamine residue.

[0042] Examples of the fluorene structure-containing residue include residues derived from 9,9-bis(4-aminophenyl)fluorene (hereinafter sometimes referred to as "BAFL"), residues derived from 9,9-bis(4-amino-3-methylphenyl)fluorene (hereinafter sometimes referred to as "BAMeFL"), residues derived from 2,7-diamino-9,9-diphenyl-9H-fluorene, residues derived from 9,9-dimethyl-9H-fluorene-2,7-diamine, and residues derived from 2,7-diaminofluorene. In order to obtain a polyimide that has excellent solubility in carbonyl solvents and excellent heat resistance, the fluorene structure-containing residue is preferably one or more selected from the group consisting of BAFL residues and BAMeFL residues.

[0043] In order to obtain a polyimide having excellent solubility in carbonyl-based solvents and excellent heat resistance, the content of the fluorene structure-containing residue is preferably 50 mol % or more and 70 mol % or less, and more preferably 60 mol % or more and 70 mol % or less, relative to the total amount (100 mol %) of the diamine residues.

[0044] The specific siloxane diamine residue may be a divalent organic group represented by the following general formula (4).

[0045]

[0046] In general formula (4), R １ represents an alkylene group having 1 to 8 carbon atoms or a p-phenylene group, and R ２ and R ３ each independently represents an alkyl group having 1 to 5 carbon atoms, an alkoxy group having 1 to 5 carbon atoms, a phenyl group, or a phenoxy group, and n represents an integer of 1 or more. In order to obtain a polyimide having excellent solubility in carbonyl solvents and excellent heat resistance, R １ is an alkylene group having 1 to 8 carbon atoms, and R ２ and R ３ are each independently an alkyl group having 1 to 3 carbon atoms or a phenyl group.

[0047] Commercially available products may be used as the siloxane diamine monomer for forming the specific siloxane diamine residue represented by general formula (4). Examples of such commercially available products include "KF-8010" and "X-22-9409" manufactured by Shin-Etsu Chemical Co., Ltd.

[0048] In order to obtain a polyimide having superior solubility in a carbonyl-based solvent, the number average molecular weight of the siloxane diamine for forming the specific siloxane diamine residue (hereinafter, may be referred to as a "specific siloxane diamine monomer") is preferably 600 or more and 1500 or less, more preferably 700 or more and 1500 or less, even more preferably 800 or more and 1500 or less, and even more preferably 800 or more and 1400 or less.

[0049] In order to obtain a polyimide having superior solubility in carbonyl solvents, the content of the specific siloxane diamine residue is preferably 35 mol % or more relative to the total amount (100 mol %) of diamine residues. In addition, in order to obtain a polyimide having superior heat resistance, the content of the specific siloxane diamine residue is preferably 45 mol % or less, more preferably 40 mol % or less, relative to the total amount (100 mol %) of diamine residues.

[0050] When synthesizing the polyimide according to the first embodiment, diamines other than the diamine having a fluorene structure and the specific siloxane diamine monomer (other diamines) may be used as monomers within a range that does not impair the performance of the polyimide. Examples of other diamines include 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzanilide, 1,3-bis(3-aminopropyl)tetramethyldisiloxane (hereinafter sometimes referred to as "PAM-E"), p-phenylenediamine, m-phenylenediamine, 4,4'-oxydianiline (hereinafter sometimes referred to as "ODA"), 3,4'-oxydianiline, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-methylenebis(cyclohexanamine), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter sometimes referred to as "BAPP"), and derivatives thereof, and these may be used alone or in combination of two or more. Furthermore, chain diamines such as ethylenediamine may also be used as the other diamine.

[0051] In order to obtain a polyimide having excellent solubility in carbonyl-based solvents and excellent heat resistance, the total content of the fluorene structure-containing residue and the specific siloxane diamine residue is preferably 50 mol% or more and 100 mol% or less, more preferably 60 mol% or more and 100 mol% or less, even more preferably 70 mol% or more and 100 mol% or less, still more preferably 80 mol% or more and 100 mol% or less, and particularly preferably 90 mol% or more and 100 mol% or less, relative to the total amount (100 mol%) of the diamine residues.

[0052] [Method for Producing Polyimide According to the First Embodiment] The polyimide according to the first embodiment can be obtained, for example, by imidizing a polyamic acid having a specific structure (hereinafter, sometimes referred to as "specific polyamic acid"). The specific polyamic acid can be synthesized by a known general method, for example, by reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. An example of a specific method for synthesizing the specific polyamic acid will be described. First, in an inert gas atmosphere such as argon or nitrogen, a diamine is dissolved or dispersed in a slurry state in an organic solvent to prepare a diamine solution. Then, the tetracarboxylic dianhydride is added to the diamine solution after being dissolved or dispersed in a slurry state in the organic solvent, or in a solid state.

[0053] When synthesizing a specific polyamic acid using a diamine and a tetracarboxylic dianhydride, the desired specific polyamic acid (a polymer of a diamine and a tetracarboxylic dianhydride) can be obtained by adjusting the molar amount of the diamine (or, if multiple diamines are used, the molar amount of each diamine) and the molar amount of the tetracarboxylic dianhydride (or, if multiple tetracarboxylic dianhydrides are used, the molar amount of each tetracarboxylic dianhydride). The molar fraction of each residue in the specific polyamic acid corresponds, for example, to the molar fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the specific polyamic acid. Furthermore, a specific polyamic acid containing multiple tetracarboxylic dianhydride residues and multiple diamine residues can also be obtained by blending two types of polyamic acid. The temperature conditions for the reaction between the diamine and the tetracarboxylic dianhydride, i.e., the synthesis reaction of the specific polyamic acid, are not particularly limited, but are, for example, in the range of 20°C to 150°C. The reaction time for the synthesis reaction of the specific polyamic acid is, for example, in the range of 10 minutes to 30 hours.

[0054] The organic solvent used in the synthesis of the specific polyamic acid is preferably a solvent capable of dissolving the tetracarboxylic dianhydride and diamine used, and more preferably a solvent capable of dissolving the specific polyamic acid to be produced. Examples of organic solvents used in the synthesis of the specific polyamic acid include urea-based solvents such as tetramethylurea and N,N-dimethylethylurea, sulfoxide-based solvents such as dimethyl sulfoxide, sulfone-based solvents such as diphenyl sulfone and tetramethyl sulfone, N,N-dimethylacetamide (DMAC), N,N-dimethylformamide (DMF), N,N-diethylacetamide, N-methyl-2-pyrrolidone (NMP), 1-butyl-2-pyrrolidone, 3-methoxy-N,N-dimethylpropanamide (MPA), 3-butoxy-N,N-dimethylpropanamide, N,N-dimethylpropionamide, and N,N-dimethylpropionamide. Examples of suitable solvents include amide solvents such as diethylformamide, 1,3-dimethyl-2-imidazolidinone, and hexamethylphosphoric triamide; ester solvents such as γ-butyrolactone; halogenated alkyl solvents such as chloroform and methylene chloride; aromatic hydrocarbon solvents such as benzene and toluene; phenolic solvents such as phenol and cresol; ketone solvents such as cyclopentanone; and ether solvents such as tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, dimethyl ether, diethyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, and p-cresol methyl ether. These solvents are usually used alone, but two or more of them may be used in appropriate combination as needed. In order to enhance the solubility and reactivity of the specific polyamic acid, the organic solvent used in the synthesis reaction of the specific polyamic acid is preferably one or more solvents selected from the group consisting of amide solvents, ketone solvents, ester solvents, and ether solvents, more preferably amide solvents, and even more preferably one or more solvents selected from the group consisting of NMP, MPA, 1-butyl-2-pyrrolidone, 3-butoxy-N,N-dimethylpropanamide, N,N-dimethylpropionamide, N,N-diethylformamide, and 1,3-dimethyl-2-imidazolidinone. Furthermore, the synthesis reaction of the specific polyamic acid is preferably carried out under an inert gas atmosphere such as argon or nitrogen.

[0055] Methods for controlling the molecular weight of the specific polyamic acid include using an excess of either the acid dianhydride or the diamine, or quenching the reaction by reacting with a monofunctional acid anhydride or amine, such as phthalic anhydride or aniline. When polymerizing with an excess of either the acid dianhydride or the diamine, a polyimide film with sufficient strength can be obtained as long as the molar ratio of the diamines is between 0.95 and 1.05. To obtain polyimides with superior solubility in carbonyl solvents, it is preferable to polymerize with an excess of diamines. The molar ratio is the ratio of the total amount of diamines used in the synthesis of the specific polyamic acid to the total amount of dianhydrides used in the synthesis of the specific polyamic acid (total amount of diamines / total amount of dianhydrides).

[0056] An example of a method for imidizing a specific polyamic acid is a method of imidizing the specific polyamic acid in a solution containing the specific polyamic acid (polyamic acid solution). When the specific polyamic acid is obtained by the above-mentioned method, the reaction solution (the solution after the reaction) may be used as the polyamic acid solution. Alternatively, the solid specific polyamic acid obtained by removing the solvent from the reaction solution may be dissolved in an organic solvent to prepare a polyamic acid solution. The solid content concentration of the polyamic acid solution is, for example, 3% by weight or more and 35% by weight or less, preferably 5% by weight or more and 25% by weight or less.

[0057] The method for imidizing the specific polyamic acid in the polyamic acid solution is not particularly limited and can be carried out using a known method. Specific imidization methods include thermal methods and chemical methods. From the viewpoint of productivity, a method for imidizing by a chemical method (chemical imidization method) is preferred.

[0058] An example of the chemical imidization method is a method in which one or more selected from the group consisting of an imidization catalyst and a dehydrating agent are added to a polyamic acid solution containing the specific polyamic acid to imidize the specific polyamic acid. The temperature condition for imidizing the specific polyamic acid is, for example, in the range of 20° C. to 150° C. The reaction time for imidizing the specific polyamic acid is, for example, in the range of 10 minutes to 30 hours.

[0059] The imidization catalyst is not particularly limited, but a tertiary amine can be used. The tertiary amine is preferably a heterocyclic tertiary amine. Specific preferred examples of heterocyclic tertiary amines include pyridine, picoline, lutidine, ethylpyridine, diethylpyridine, isoquinoline, and 1,2-dimethylimidazole. The dehydrating agent is not particularly limited, but preferred examples include acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride.

[0060] The amount of imidization catalyst added is preferably 0.5 to 5.0 molar equivalents, more preferably 0.5 to 2.5 molar equivalents, and even more preferably 0.6 to 2.0 molar equivalents, relative to the amide groups of the specific polyamic acid. The amount of dehydrating agent added is preferably 0.5 to 10.0 molar equivalents, more preferably 0.5 to 5.0 molar equivalents, and even more preferably 0.6 to 3.0 molar equivalents, relative to the amide groups of the specific polyamic acid. In this specification, the term "amide groups of the specific polyamic acid" refers to amide groups formed by the polymerization reaction of a diamine and a tetracarboxylic dianhydride.

[0061] After imidizing the specific polyamic acid in the polyamic acid solution, the solution is poured into a poor solvent (e.g., 2-propanol, etc.), whereby the polyimide precipitates as a solid. The precipitated solid is isolated and then washed with a poor solvent to remove impurities, dehydrating agents, imidization catalysts, etc., generated during the synthesis of the polyamic acid. The washed solid is then dried to obtain the polyimide according to the first embodiment.

[0062] [Preferred Aspect of Polyimide According to First Embodiment] In order to avoid restrictions on use due to legal regulations (PFAS regulations) that restrict the production, etc. of organic fluorine compounds (PFAS), it is preferable that all acid dianhydride residues of the polyimide according to the first embodiment do not contain fluorine and all diamine residues do not contain fluorine.

[0063] In order to obtain a polyimide having superior solubility in carbonyl-based solvents, it is preferable that the value obtained by dividing the total amount of tetracarboxylic dianhydride residues by the total amount of diamine residues is less than 1. In this case, the polyimide according to the first embodiment has an amino group at the terminal. Since amino groups have a relatively high affinity for carbonyl-based solvents, when the value obtained by dividing the total amount of tetracarboxylic dianhydride residues by the total amount of diamine residues is less than 1, the solubility in carbonyl-based solvents is further enhanced.

[0064] In order to obtain a polyimide having superior heat resistance, the glass transition temperature of the polyimide according to the first embodiment is preferably 150° C. or higher, more preferably 155° C. or higher, even more preferably 160° C. or higher, and may be 165° C. or higher or 170° C. or higher. The upper limit of the glass transition temperature of the polyimide according to the first embodiment is not particularly limited, and is, for example, 300° C. or lower. The method for measuring the glass transition temperature of the polyimide is the same as or a similar method to the measurement method in the examples described below.

[0065] The polyimide according to the first embodiment is preferably soluble in a carbonyl-based solvent. The term "polyimide soluble in a carbonyl-based solvent" refers to a polyimide that receives a result of A or B in the evaluation method for "Solubility in carbonyl-based solvents" in the examples described below. To obtain a polyimide with superior solubility in carbonyl-based solvents, the polyimide according to the first embodiment is preferably soluble in one or more carbonyl-based solvents selected from the group consisting of N-methyl-2-pyrrolidone, methyl ethyl ketone, and ethyl acetate. Methyl ethyl ketone and ethyl acetate have low boiling points, which facilitate drying when forming a polyimide film from the polyimide resin composition described below. Therefore, to increase the productivity of polyimide films, the polyimide according to the first embodiment is preferably soluble in one or more carbonyl-based solvents selected from the group consisting of methyl ethyl ketone and ethyl acetate, and more preferably soluble in ethyl acetate.

[0066] In order to obtain a polyimide having excellent solubility in carbonyl-based solvents and excellent heat resistance, the weight-average molecular weight (Mw) of the polyimide according to the first embodiment is preferably 5,000 to 200,000, more preferably 10,000 to 150,000, even more preferably 12,000 to 100,000, and even more preferably 13,000 to 50,000. Furthermore, in order to obtain a polyimide having excellent solubility in carbonyl-based solvents and excellent heat resistance, the number-average molecular weight (Mn) of the polyimide according to the first embodiment is preferably 2,000 to 50,000, more preferably 3,000 to 40,000, and even more preferably 4,000 to 30,000. The Mw and Mn of the polyimide are measured by the same method as or a method equivalent to the measurement methods in the examples described below.

[0067] In order to obtain a polyimide having even better solubility in carbonyl-based solvents and even better heat resistance, the polyimide according to the first embodiment preferably satisfies the following condition 1, more preferably satisfies the following condition 2, and even more preferably satisfies the following condition 3. Condition 1: The bisphenol A type structure-containing residue is a BPADA residue, and the fluorene structure-containing residue is one or more selected from the group consisting of a BAFL residue and a BAMeFL residue. Condition 2: The above condition 1 is satisfied, and the content of the fluorene structure-containing residue is 50 mol % or more and 70 mol % or less with respect to the total amount (100 mol %) of diamine residues. Condition 3: The above condition 2 is satisfied, and the Mw is 5,000 or more and 200,000 or less.

[0068] Second Embodiment: Polyimide Resin Composition Next, a polyimide resin composition according to a second embodiment of the present invention will be described. The polyimide resin composition according to the second embodiment contains the polyimide according to the first embodiment of the present invention described above and a carbonyl-based solvent. Because the polyimide resin composition according to the second embodiment contains the polyimide according to the first embodiment, it is possible to suppress the occurrence of undissolved polyimide, and also to improve the heat resistance of a polyimide film obtained using the polyimide resin composition according to the second embodiment. In the following description, explanations of content that overlap with the first embodiment may be omitted.

[0069] In order to increase the productivity of polyimide films, the carbonyl solvent in the polyimide resin composition is preferably at least one selected from the group consisting of methyl ethyl ketone and ethyl acetate, and more preferably ethyl acetate.

[0070] In order to easily form a polyimide film, the polyimide content in the polyimide resin composition is preferably 8% by weight or more and 30% by weight or less, and more preferably 10% by weight or more and 25% by weight or less.

[0071] The polyimide resin composition according to the second embodiment may contain various organic or inorganic low-molecular-weight compounds or polymeric compounds as additives. Examples of additives that can be used include plasticizers, antioxidants, dyes, surfactants, leveling agents, silicones, fine particles, and sensitizers. Examples of fine particles include organic fine particles made of polystyrene, polytetrafluoroethylene, and the like, and inorganic fine particles made of colloidal silica, carbon, layered silicates, and the like, which may have a porous or hollow structure. The function and form of the fine particles are not particularly limited, and they may be, for example, pigments, fillers, or fibrous particles.

[0072] <Third Embodiment: Polyimide Film> Next, a polyimide film according to a third embodiment of the present invention will be described. The polyimide film according to the third embodiment contains the polyimide according to the first embodiment of the present invention described above. Because the polyimide film according to the third embodiment contains the polyimide according to the first embodiment, it is possible to improve thickness uniformity and heat resistance. In the following description, descriptions that overlap with the first and second embodiments may be omitted.

[0073] The content of polyimide in the polyimide film according to the third embodiment (the polyimide according to the first embodiment) is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may even be 100% by weight, based on the total weight of the polyimide film. Examples of components other than polyimide in the polyimide film include the additives described above (more specifically, fine particles, etc.). The thickness of the polyimide film according to the third embodiment is, for example, 1 μm or more and 200 μm or less, and preferably 5 μm or more and 100 μm or less. The thickness of the polyimide film can be measured using a laser hologram.

[0074] The method for forming the polyimide film according to the third embodiment is not particularly limited, and examples thereof include a melting method and a solution method. In order to form a film with a uniform thickness, the solution method is preferred. In the solution method, the polyimide resin composition according to the second embodiment is applied to a support, and the solvent is removed by drying to obtain a polyimide film.

[0075] The polyimide resin composition can be applied to a support by a known method using a bar coater, a Comma Coater (registered trademark), or the like. Examples of the support that can be used include a metal substrate such as a stainless steel substrate, a glass plate, a metal drum, a metal belt, and a plastic film. From the viewpoint of improving productivity, it is preferable to use an endless support such as a metal drum or a metal belt, or a long plastic film as the support, and produce a polyimide film by a roll-to-roll method. When a plastic film is used as the support, it is sufficient to appropriately select a material that is insoluble in the solvent in the polyimide resin composition.

[0076] When drying a coating film obtained by applying a polyimide resin composition to a support, it is preferable to heat the coating film. The heating temperature is not particularly limited as long as it can remove the solvent and suppress coloration of the resulting polyimide film, and is appropriately set in the range of room temperature to 300°C, preferably 50°C to 250°C, more preferably 80°C to 220°C, and may be 120°C to 180°C. The heating temperature may be increased stepwise. The heating time is not particularly limited, and is, for example, in the range of 10 minutes to 10 hours. In order to increase the efficiency of solvent removal, the resin film may be peeled off from the support and dried after drying has progressed to a certain extent. In order to promote solvent removal, heating may be performed under reduced pressure.

[0077] The polyimide film according to the third embodiment may be laminated on a flexible printed circuit board as an insulating material or adhesive.

[0078] Examples of the present invention will be described below, but the scope of the present invention is not limited to the following examples.

[0079] <Preparation of Polyamic Acid Solutions> First, the methods for preparing polyamic acid solutions P1 to P18 used in the Examples and Comparative Examples will be described. In the following, compounds and reagents are referred to by the following abbreviations. Furthermore, the preparation of polyamic acid solutions P1 to P18 was all carried out under a nitrogen atmosphere. NMP: N-methyl-2-pyrrolidone BPADA: 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride a-BPDA: 2,3,3',4'-biphenyltetracarboxylic dianhydride PAM-E: 1,3-bis(3-aminopropyl)tetramethyldisiloxane (molecular weight: 260) KF-8010: siloxane diamine having a number average molecular weight of 860 ("KF-8010" manufactured by Shin-Etsu Chemical Co., Ltd., an organopolysiloxane having amino groups modified at both ends) X-22-9409: siloxane diamine having a number average molecular weight of 1340 ("X-22-9409" manufactured by Shin-Etsu Chemical Co., Ltd., an organopolysiloxane having amino groups modified at both ends) X-22-161A: siloxane diamine having a number average molecular weight of 1600 ("X-22-161A" manufactured by Shin-Etsu Chemical Co., Ltd., organopolysiloxane having amino groups modified at both ends) BAFL: 9,9-bis(4-aminophenyl)fluorene BAMeFL: 9,9-bis(4-amino-3-methylphenyl)fluorene BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane ODA: 4,4'-oxydianiline

[0080] [Preparation of Polyamic Acid Solution P1] 280 g of NMP was placed in a 2000 mL glass separable flask equipped with a stainless steel stirrer and a nitrogen inlet tube as the organic solvent for polymerization. Next, while stirring the contents of the flask, 13.8 g of BAFL and 22.2 g of KF-8010 were added to the flask and dissolved. Next, 34.0 g of BPADA was added to the flask, and the contents of the flask were stirred for 24 hours in an atmosphere at 23°C to obtain Polyamic Acid Solution P1 (solids concentration: 20 wt%).

[0081] [Preparation of Polyamic Acid Solutions P2 to P18] Polyamic acid solutions P2 to P18 were prepared in the same manner as polyamic acid solution P1, except that the acid dianhydrides used and their charging ratios, and the diamines used and their charging ratios were as shown in Table 1. Note that for each of polyamic acid solutions P2 to P18, the total amount of diamines used in preparing the polyamic acid solution was the same as for polyamic acid solution P1.

[0082] Table 1 shows the acid dianhydrides used and their charge ratios, as well as the diamines used and their charge ratios for polyamic acid solutions P1 to P18. In Table 1, a "-" indicates that the corresponding component was not used. The values ​​in the "acid dianhydride" column in Table 1 represent the content (unit: mol%) of each acid dianhydride relative to the total amount (100 mol%) of diamines used. The values ​​in the "diamine" column in Table 1 represent the content (unit: mol%) of each diamine relative to the total amount (100 mol%) of diamines used. For each of polyamic acid solutions P1 to P18, the molar fraction of each polyamic acid residue in the prepared polyamic acid solution matched the molar fraction of each monomer (each monomer corresponding to each residue) used in the synthesis of the polyamic acid.

[0083]

[0084] <Formation of Polyimide> [Example 1] 2.3 g of pyridine was added as an imidization catalyst to 40 g of polyamic acid solution P1, and the solution was then stirred to disperse the imidization catalyst in the solution. Next, 2.9 g of acetic anhydride was added to the solution with the imidization catalyst dispersed therein, and the solution was stirred for 2 hours while maintaining the temperature at 90°C. The stirred solution was then cooled to 23°C and poured into 200 g of 2-propanol to precipitate a solid. The solid was then washed with 2-propanol and dried for 12 hours in a vacuum oven set at 120°C, yielding the polyimide of Example 1.

[0085] [Examples 2 to 5 and Comparative Examples 1 to 13] Polyimides of Examples 2 to 5 and Comparative Examples 1 to 13 were obtained in the same manner as in Example 1, except that the polyamic acid solutions shown in Table 2 below were used instead of polyamic acid solution P1. In Examples 2 to 5 and Comparative Examples 1 to 13, the amount of polyamic acid solution used was 40 g.

[0086] <Preparation of Polyimide Film> First, 85 parts by weight of NMP and 15 parts by weight of polyimide (any of the polyimides of Examples 1 to 5 and Comparative Examples 1 to 13) were mixed to obtain a polyimide resin composition. Next, the obtained polyimide resin composition was applied to an alkali-free glass plate and dried in an air atmosphere at a temperature of 80°C for 60 minutes, and then at a temperature of 180°C for 60 minutes to obtain a polyimide film having a thickness of 10 μm.

[0087] <Measurement and Evaluation Methods> Hereinafter, methods for measuring and evaluating the physical properties of polyimides and polyimide films will be described.

[0088] [Solubility in Carbonyl-Based Solvents] (Solubility in Methyl Ethyl Ketone) 1 g of the polyimide to be evaluated was added to 9 g of methyl ethyl ketone and stirred for 24 hours in an atmosphere at a temperature of 23°C. The presence or absence of undissolved polyimide was then visually confirmed, and the solubility in methyl ethyl ketone was evaluated according to the following criteria: A: No undissolved polyimide was present, and no cloudy solution was observed. B: No undissolved polyimide was present, but cloudy solution was observed. C: Undissolved polyimide was present, or the solution became gelatinous.

[0089] (Solubility in ethyl acetate) The solubility in ethyl acetate was determined in the same manner as described above (Solubility in methyl ethyl ketone), except that 9 g of ethyl acetate was used instead of 9 g of methyl ethyl ketone. When the result of the determination was A or B, the sample was evaluated as having "excellent solubility in carbonyl-based solvents." On the other hand, when the result of the determination was C, the sample was evaluated as having "not excellent solubility in carbonyl-based solvents."

[0090] [Glass Transition Temperature (Tg)] First, a sample of 3 mm wide and 10 mm long was prepared from the polyimide film to be evaluated to obtain a sample for Tg measurement. Next, using a thermal analyzer (Hitachi High-Tech Science Corporation, "TMA7100"), a load of 29.4 mN was applied to the long side of the sample, and the sample was heated from 20°C to 250°C at a rate of 10°C / min. The temperature and strain (elongation) were plotted to obtain a TMA curve. The temperature at the inflection point of the obtained TMA curve was taken as the glass transition temperature (Tg). When the Tg was 150°C or higher, the sample was evaluated as having "excellent heat resistance." On the other hand, when the Tg was less than 150°C, the sample was evaluated as having "poor heat resistance."

[0091] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)] The Mw and Mn of the polyimide to be measured were measured under the following conditions: Apparatus used: "HLC-8220GPC" manufactured by Tosoh Corporation Column: "TSK gel super AWM-H" x 2 manufactured by Tosoh Corporation Guard column: "TSK gel guard column super AW-H" x 1 manufactured by Tosoh Corporation Column temperature: 40°C Eluent: N,N-dimethylformamide solution containing LiBr (concentration: 30 mmol / L) and phosphoric acid (concentration: 23.5 mmol / L) dissolved therein Sample concentration: 5.0 mg / mL Injection volume: 20 μL Flow rate: 0.6 mL / min Detector: RI (differential refractometer) Standard sample: polyethylene oxide Calibration curve order: 1st order

[0092] <Results> For Examples 1 to 5 and Comparative Examples 1 to 13, the type of polyamic acid solution used, Mw, Mn, Tg, and the results of solubility in carbonyl solvents are shown in Table 2. In Table 2, "MEK" means methyl ethyl ketone, and "AcOEt" means ethyl acetate. In Table 2, "-" means that no measurement was performed.

[0093]

[0094] In the polyimides of Examples 1 to 5, the tetracarboxylic dianhydride residue contained a bisphenol A type structure-containing residue, and the diamine residue contained a fluorene structure-containing residue and a specific siloxane diamine residue. In the polyimides of Examples 1 to 5, the content of the bisphenol A type structure-containing residue was 50 mol % or more relative to the total amount of the tetracarboxylic dianhydride residue. In the polyimides of Examples 1 to 5, the content of the specific siloxane diamine residue was 30 mol % or more and 50 mol % or less relative to the total amount of the diamine residue.

[0095] As shown in Table 2, in Examples 1 to 5, the Tg was 150°C or higher. Therefore, the polyimides of Examples 1 to 5 had excellent heat resistance. In Examples 1 to 5, the solubility in ethyl acetate was evaluated as A or B. Therefore, the polyimides of Examples 1 to 5 had excellent solubility in carbonyl-based solvents.

[0096] In the polyimides of Comparative Examples 4, 6, and 13, the tetracarboxylic dianhydride residue did not contain a residue containing a bisphenol A type structure. In the polyimides of Comparative Examples 1, 5, 7, 11, and 12, the diamine residue did not contain a specific siloxane diamine residue. In the polyimides of Comparative Examples 2 and 3, the content of the specific siloxane diamine residue exceeded 50 mol% relative to the total amount of diamine residues. In the polyimides of Comparative Examples 8 and 9, the content of the specific siloxane diamine residue was less than 30 mol% relative to the total amount of diamine residues. In the polyimides of Comparative Examples 4 and 10 to 13, the diamine residue did not contain a residue containing a fluorene structure.

[0097] As shown in Table 2, in Comparative Examples 3 and 10, the Tg was less than 150°C. Therefore, the polyimides of Comparative Examples 3 and 10 did not have excellent heat resistance. In Comparative Examples 1, 2, 4 to 9, and 11 to 13, the evaluation result for solubility in ethyl acetate was C. Therefore, the polyimides of Comparative Examples 1, 2, 4 to 9, and 11 to 13 did not have excellent solubility in carbonyl-based solvents.

[0098] The above results demonstrate that the present invention makes it possible to obtain polyimides that are excellent in solubility in carbonyl solvents and heat resistance.

Claims

1. A polyimide having a tetracarboxylic dianhydride residue and a diamine residue, wherein the tetracarboxylic dianhydride residue includes a residue having a bisphenol A structure, and the diamine residue includes a residue having a fluorene structure and a residue derived from a siloxane diamine having a number average molecular weight of 500 to 1500, wherein the content of the residue having the bisphenol A structure is 50 mol % or more relative to the total amount of the tetracarboxylic dianhydride residues, and the content of the residue derived from the siloxane diamine is 30 mol % or more and 50 mol % or less relative to the total amount of the diamine residues.

2. The polyimide according to claim 1, wherein the residue having a bisphenol A type structure is a residue of 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride.

3. The polyimide according to claim 1, wherein the residue having a fluorene structure is at least one selected from the group consisting of a 9,9-bis(4-aminophenyl)fluorene residue and a 9,9-bis(4-amino-3-methylphenyl)fluorene residue.

4. The polyimide according to claim 1, wherein the value obtained by dividing the total amount of the tetracarboxylic dianhydride residues by the total amount of the diamine residues is less than 1.

5. The polyimide according to claim 1, having a glass transition temperature of 150°C or higher.

6. The polyimide of claim 1, which is soluble in ethyl acetate.

7. A polyimide resin composition comprising the polyimide according to any one of claims 1 to 6 and an organic solvent having a carbonyl group.

8. A polyimide film comprising the polyimide according to any one of claims 1 to 6.

Images