Polyimide, polyimide resin composition, and polyimide film

Abstract

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

Description

Technical Field

[0001] This invention relates to polyimide, polyimide resin compositions, and polyimide films. Background Technology

[0002] Polyimides, known for their excellent heat resistance, typically lack solvent solubility. Therefore, a polyamic acid solution, prepared by dissolving polyamic acid (a precursor to polyimide) in a solvent, is used. This solution is then heated at high temperatures for an extended period to achieve dehydration and ring closure. However, this high-temperature heating can sometimes lead to thermal degradation of other components. For example, when a polyimide film is laminated as an insulating layer onto a wiring substrate, the heating of the polyamic acid solution can sometimes cause thermal degradation of the wiring substrate material. Furthermore, if the heat treatment of the polyamic acid solution is insufficient, carboxylic acids contained in the polyamic acid structure may remain, thus reducing electrical insulation properties when used in electronic materials. This problem can be solved by using a polyimide solution containing a solvent-soluble polyimide instead of a polyamic acid solution.

[0003] For example, as a polyimide soluble in organic solvents containing carbonyl groups such as methyl ethyl ketone, Patent Document 1 proposes a polyimide obtained by using alicyclic acid dianhydride, fluorinated aromatic acid dianhydride, and fluoroalkyl-substituted benzidine as essential components. Similarly, as a polyimide soluble in methyl ethyl ketone and ethyl acetate, Patent Document 2 proposes an organosilicon-modified polyimide resin. Hereinafter, organic solvents containing carbonyl groups will sometimes be referred to as "carbonyl-based solvents." Examples of carbonyl-based solvents include ketone solvents such as methyl ethyl ketone; ester solvents such as ethyl acetate; and amide solvents such as N-methyl-2-pyrrolidone.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: International Publication No. 2019 / 073628

[0007] Patent Document 2: Japanese Patent Application Publication No. 2005-126569 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, it is difficult to obtain polyimides with excellent solubility and heat resistance in carbonyl solvents using only the techniques described in Patent Documents 1 and 2.

[0010] The present invention was made in view of the above-mentioned actual situation, and its object is to provide a polyimide with excellent solubility and heat resistance in carbonyl solvents, as well as a polyimide resin composition and a polyimide film containing the polyimide.

[0011] Solution for solving the problem

[0012] <Method of the present invention>

[0013] The present invention includes the following methods.

[0014] [1] A polyimide having a tetracarboxylic dianhydride residue and a diamine residue.

[0015] The tetracarboxylic dianhydride residues include residues with a bisphenol A-type structure.

[0016] The diamine residues include: residues having a fluorene structure, and residues derived from siloxane diamines with a number average molecular weight of 500 or more and 1500 or less.

[0017] The content of residues having the bisphenol A type structure is 50 mol% or more relative to the total amount of the tetracarboxylic dianhydride residues.

[0018] The content of residues derived from siloxane diamine is 30 mol% or more and 50 mol% or less relative to the total amount of diamine residues.

[0019] [2] According to the polyimide described above [1], wherein the residue having the bisphenol A type structure is a 4,4'-(4,4'-isopropylidenediphenoxy) phthalic anhydride residue.

[0020] [3] The polyimide according to [1] or [2] above, wherein the residue having the fluorene structure is selected from one or more of the group consisting of 9,9-bis(4-aminophenyl)fluorene residue and 9,9-bis(4-amino-3-methylphenyl)fluorene residue.

[0021] [4] The polyimide according to any one of [1] to [3] above, wherein the total amount of the tetracarboxylic dianhydride residues divided by the total amount of the diamine residues is less than 1.

[0022] [5] The polyimide according to any one of [1] to [4] above has a glass transition temperature of 150°C or higher.

[0023] [6] The polyimide according to any one of [1] to [5] above is soluble in ethyl acetate.

[0024] [7] A polyimide resin composition comprising: the polyimide described in any one of [1] to [6] above and an organic solvent having a carbonyl group.

[0025] [8] A polyimide film comprising any one of the polyimides described in any one of [1] to [6].

[0026] The effects of the invention

[0027] According to the present invention, it is possible to provide a polyimide with excellent solubility and heat resistance in carbonyl solvents, as well as a polyimide resin composition and a polyimide film containing the polyimide. Detailed Implementation

[0028] The following describes in detail suitable embodiments of the present invention, but the present invention is not limited to these embodiments. Furthermore, all academic and patent documents described in this specification are incorporated herein by reference.

[0029] First, the terms used in this specification will be explained. “Structural unit” refers to a repeating unit that constitutes a polymer. “Polyimide” is a polymer that contains the structural unit shown in the following general formula (1) (hereinafter sometimes referred to as “structural unit (1)”).

[0030]

[0031] In general formula (1), X 1 X represents a tetracarboxylic dianhydride residue (a tetravalent organic group derived from tetracarboxylic dianhydride). 2 It represents a diamine residue (a divalent organic group derived from a diamine).

[0032] The content of structural unit (1) relative to all structural units constituting 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, further preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, and may also be 100 mol%.

[0033] "Polyamic acid" is a polymer containing the structural unit shown in the following general formula (2) (hereinafter sometimes referred to as "structural unit (2)").

[0034]

[0035] In general formula (2), A 1 Indicates a tetracarboxylic dianhydride residue (derived from a tetravalent organic group of tetracarboxylic dianhydride), A 2 It represents a diamine residue (a divalent organic group derived from a diamine).

[0036] The content of structural unit (2) relative to all structural units constituting 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, further preferably 80 mol% or more and 100 mol% or less, even more preferably 90 mol% or more and 100 mol% or less, and may also be 100 mol%.

[0037] Polyimide is an imide derivative of polyamic acid. Therefore, when the content of structural unit (2) relative to all structural units constituting polyamic acid is 100 mol%, the polyimide, as an imide derivative of said polyamic acid, has A in general formula (2). 1 The residues shown are X in general formula (1) 1 And has A in general formula (2) 2 The residues shown are X in general formula (1) 2 .

[0038] "Residues with a fluorene structure" refers to residues with a fluorene ring. "Residues with a bisphenol A-type structure" refers to residues with a divalent organic group as shown in the following chemical formula (3). The benzene ring in the following chemical formula (3) may further have substituents.

[0039]

[0040] The number-average molecular weight of siloxane diamines is a value calculated based on the amine value. The amine value of siloxane diamines can be determined, for example, using an automatic potentiometric titration apparatus (Kyoto Electronics Industry Co., Ltd. "AT-710M").

[0041] "Solid components" refers to non-volatile components in a composition, such as components other than solvents.

[0042] Hereinafter, the term "system" is sometimes added after the compound name to refer to compounds and their derivatives in an inclusive manner. When "system" is added after the compound name to indicate the polymer name, it means that the repeating unit of the polymer is derived from the compound or its derivative. In addition, tetracarboxylic dianhydride is sometimes referred to as "acid dianhydride". Furthermore, unless otherwise specified, the components, functional groups, etc., illustrated in this specification may be used alone or in combination of two or more.

[0043] <First Embodiment: Polyimide>

[0044] The polyimide of the first embodiment of the present invention comprises tetracarboxylic dianhydride residues and diamine residues. The tetracarboxylic dianhydride residues include residues having a bisphenol A type structure. The diamine residues include: residues having a fluorene structure, and residues derived from siloxane diamines with a number average molecular weight of 500 or more and 1500 or less. The content of residues having a bisphenol A type structure is 50 mol% or more relative to the total amount of tetracarboxylic dianhydride residues (100 mol%). The content of residues derived from siloxane diamines with a number average molecular weight of 500 or more and 1500 or less is 30 mol% or more and 50 mol% or less relative to the total amount of diamine residues (100 mol%).

[0045] Hereinafter, tetracarboxylic acid dianhydride residues having a bisphenol A-type structure are sometimes referred to as "residues containing a bisphenol A-type structure". In addition, diamine residues having a fluorene structure are sometimes referred to as "residues containing a fluorene structure". In addition, residues derived from siloxane diamines with a number average molecular weight of 500 or more and 1500 or less are sometimes referred to as "specific siloxane diamine residues".

[0046] The polyimide of the first embodiment exhibits excellent solubility and heat resistance in carbonyl solvents. The reason for this is speculated as follows.

[0047] The tetracarboxylic dianhydride residues are surrounded by four carbonyl groups, thus their structure significantly affects their solubility in carbonyl solvents. The polyimide of the first embodiment contains bisphenol A-type residues as tetracarboxylic dianhydride residues, which serve as a flexible structure, at a content of 50 mol% or more, thereby improving its solubility in carbonyl solvents. Furthermore, the polyimide of the first embodiment contains specific siloxane diamine residues with high affinity for carbonyl solvents at a content of 30 mol% or more, thereby further improving its solubility in carbonyl solvents. Additionally, the polyimide of the first embodiment has bulky structures, i.e., residues containing fluorene structures as diamine residues, thus suppressing the aggregation of polyimide chains in carbonyl solvents. Therefore, the polyimide of the first embodiment exhibits excellent solubility in carbonyl solvents.

[0048] Furthermore, the polyimide of the first embodiment has fluorene-containing residues as diamine residues, which constitute a rigid structure, thus improving heat resistance. Moreover, in the polyimide of the first embodiment, the content of specific siloxane diamine residues is set to 50 mol% or less, thereby suppressing the decrease in heat resistance caused by these specific siloxane diamine residues. Therefore, the polyimide of the first embodiment exhibits improved solubility in carbonyl solvents and excellent heat resistance.

[0049] [Acid dianhydride]

[0050] The polyimide of the first embodiment contains residues with a bisphenol A-type structure as tetracarboxylic acid dianhydride residues. In order to obtain a polyimide with better solubility in carbonyl solvents, residues with a bisphenol A-type structure are preferably derived from 4,4'-(4,4'-isopropylidenediphenoxy)phthalic anhydride (hereinafter sometimes referred to as "BPADA").

[0051] In order to obtain polyimide with better solubility in carbonyl solvents, the content of residues containing bisphenol A type structure is preferably 60 mol% or more, more preferably 70 mol% or more, and even more preferably 80 mol% or more, and may be 85 mol% or more, 90 mol% or more, or 95 mol% or more, or may be 100 mol% or more, relative to the total amount of tetracarboxylic dianhydride residues (100 mol%).

[0052] When synthesizing the polyimide of the first embodiment, acid dianhydrides other than those having a bisphenol A type structure (other acid dianhydrides) may be used as monomers without impairing its performance. Examples of other acid dianhydrides include: 2,3,3',4'-biphenyltetracarboxylic acid dianhydride (hereinafter, sometimes referred to as "a-BPDA"), 3,3',4,4'-biphenyltetracarboxylic acid dianhydride, 4,4'-oxobisphthalic anhydride, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (hereinafter, sometimes referred to as "BPAF"), pyromellitic dianhydride, 1,2,5,6-naphthalenetetracarboxylic acid dianhydride, 2 3,6,7-Naphthalenetetracarboxylic dianhydride, p-phenylene bis(triphenylene anhydride) ester, 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 their derivatives, which may be used alone or in combination.

[0053] When using other acid dianhydrides as monomers, α-BPDA is preferred in order to obtain polyimides with better solubility in carbonyl solvents.

[0054] [Diamine]

[0055] The polyimide of the first embodiment contains residues with a fluorene structure and specific siloxane diamine residues as diamine residues.

[0056] Examples of residues containing a fluorene structure 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. To obtain polyimides with superior solubility and heat resistance in carbonyl solvents, the residues containing a fluorene structure are preferably selected from one or more of the group consisting of BAFL residues and BAMeFL residues.

[0057] In order to obtain polyimide with better solubility and heat resistance in carbonyl solvents, the content of residues containing fluorene structure is preferably 50 mol% or more and 70 mol% or less relative to the total amount of diamine residues (100 mol%), more preferably 60 mol% or more and 70 mol% or less.

[0058] As specific siloxane diamine residues, divalent organic groups represented by the following general formula (4) can be cited.

[0059]

[0060] In general formula (4), R 1 R indicates an alkylene group or a p-phenylene group having 1 or more but less than 8 carbon atoms. 2 and R 3 Each of the following can be independently represented as an alkyl group having 1 or more but less than 5 carbon atoms, an alkoxy group having 1 or more but less than 5 carbon atoms, a phenyl group, or a phenoxy group, where n represents an integer of 1 or more. To obtain polyimides with superior solubility and heat resistance in carbonyl solvents, R in general formula (4) is preferred. 1 It is an alkylene group having 1 or more carbon atoms and 8 or fewer carbon atoms, and R in general formula (4) 2 and R 3 Each is independently an alkyl or phenyl group having 1 or more but less than 3 carbon atoms.

[0061] Commercially available products can be used as monomers for forming specific siloxane diamine residues as shown in general formula (4). Examples of such commercially available products include "KF-8010" manufactured by Shin-Etsu Chemical Industry Co., Ltd. and "X-22-9409" manufactured by Shin-Etsu Chemical Industry Co., Ltd.

[0062] In order to obtain polyimides with better solubility in carbonyl solvents, the number average molecular weight of the siloxane diamine (hereinafter, sometimes referred to as "specific siloxane diamine monomer") used to form specific siloxane diamine residues 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.

[0063] To obtain polyimides with superior solubility in carbonyl solvents, the content of specific siloxane diamine residues is preferably 35 mol% or more relative to the total amount of diamine residues (100 mol%). Furthermore, to obtain polyimides with superior heat resistance, the content of specific siloxane diamine residues is preferably 45 mol% or less, more preferably 40 mol% or less, relative to the total amount of diamine residues (100 mol%).

[0064] When synthesizing the polyimide of the first embodiment, diamines having a fluorene structure and diamines other than specific siloxane diamine monomers (other diamines) may be used as monomers without impairing their performance. Examples of other diamines include 4,4'-diaminodiphenyl sulfone, 4,4'-diaminobenzoylaniline, 1,3-bis(3-aminopropyl)tetramethyldisiloxane (hereinafter, sometimes referred to as "PAM-E"), p-phenylenediamine, m-phenylenediamine, 4,4'-oxodiphenylamine (hereinafter, sometimes referred to as "ODA"), 3,4'-oxodiphenylamine, N,N'-bis(4-aminophenyl)terephthalamide, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-methylenebis(cyclohexaneamine), 2,2-bis[4-(4-aminophenoxy)phenyl]propane (hereinafter, sometimes referred to as "BAPP"), and their derivatives. These diamines may be used alone or in combination with two or more. Alternatively, other diamines such as ethylenediamine can also be used as chain diamines.

[0065] In order to obtain polyimides with better solubility and heat resistance in carbonyl solvents, the total content of residues containing fluorene structure and specific siloxane diamine residues relative to the total amount of diamine residues (100 mol%) is preferably 50 mol% or more and 100 mol% or less, more preferably 60 mol% or more and 100 mol% or less, more preferably 70 mol% or more and 100 mol% or less, more preferably 80 mol% or more and 100 mol% or less, and particularly preferably 90 mol% or more and 100 mol% or less.

[0066] [Method for manufacturing polyimide according to the first embodiment]

[0067] The polyimide of the first embodiment is obtained, for example, by imidizing a polyamic acid with a specific structure (hereinafter, sometimes referred to as "specific polyamic acid"). Specific polyamic acid can be synthesized using known general methods, for example, by reacting a diamine with a tetracarboxylic dianhydride in an organic solvent. An example of a specific synthesis method for the specific polyamic acid will be described. First, a diamine solution is prepared by dissolving or dispersing a diamine in an organic solvent into a slurry under an inert gas atmosphere such as argon or nitrogen. Then, the tetracarboxylic dianhydride, either dissolved or dispersed in an organic solvent into a slurry or in a solid state, is added to the diamine solution.

[0068] When synthesizing a specific polyamic acid using diamines and tetracarboxylic dianhydrides, the desired specific polyamic acid (a polymer of diamines and tetracarboxylic dianhydrides) can be obtained by adjusting the amount of diamine (or the amount of each diamine when using multiple diamines) and the amount of tetracarboxylic dianhydrides (or the amount of each tetracarboxylic dianhydride when using multiple tetracarboxylic dianhydrides). The molar fraction of each residue in the specific polyamic acid is, for example, consistent with the molar fraction of each monomer used in the synthesis of the specific polyamic acid (the monomer corresponding to each residue). Alternatively, a specific polyamic acid containing multiple tetracarboxylic dianhydride residues and multiple diamine residues can also be obtained by blending two polyamic acids. The temperature conditions for the reaction of the diamine with 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 or higher and 150°C or lower. The reaction time for the synthesis reaction of the specific polyamic acid is, for example, in the range of 10 minutes or more and 30 hours or less.

[0069] The organic solvent used in the synthesis of a 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 produced. Examples of organic solvents used in the synthesis of a specific polyamic acid include urea solvents such as tetramethylurea and N,N-dimethylethylurea; sulfoxide solvents such as dimethyl sulfoxide; sulfone 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-dimethylpropionamide (MPA), 3-butoxy-N, Amide solvents such as N-dimethylpropionamide, N,N-dimethylpropionamide, N,N-diethylformamide, 1,3-dimethyl-2-imidazolinone, and hexamethylphosphotriamide; ester solvents such as γ-butyrolactone; haloalkane solvents such as chloroform and dichloromethane; aromatic hydrocarbon solvents such as benzene and toluene; phenol 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 can be used in combination as needed. To improve the solubility and reactivity of a 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. Amide solvents are more preferred, and solvents selected from the group consisting of NMP, MPA, 1-butyl-2-pyrrolidone, 3-butoxy-N,N-dimethylpropionamide, N,N-dimethylpropionamide, N,N-diethylformamide, and 1,3-dimethyl-2-imidazolinone are even more preferred. Furthermore, the synthesis reaction of the specific polyamic acid is preferably carried out under an inert gas atmosphere such as argon or nitrogen.

[0070] Furthermore, methods for controlling the molecular weight of a specific polyamic acid include using an excess of either the dianhydride or the diamine, and quenching the reaction by reacting with monofunctional anhydrides or amines such as phthalic anhydride or aniline. When polymerization is carried out in excess of either the dianhydride or the diamine, a polyimide film with sufficient strength can be obtained if their molar ratio is between 0.95 and 1.05. To obtain a polyimide with better solubility in carbonyl solvents, it is preferable to polymerize in excess of the diamine. It should be noted that the above molar ratio is the ratio of the total amount of diamine used in the synthesis of the specific polyamic acid to the total amount of dianhydride used in the synthesis of the specific polyamic acid (total amount of diamine / total amount of dianhydride).

[0071] As a method for imidizing a specific polyamic acid, one example is the method of imidizing the specific polyamic acid in a solution containing the specific polyamic acid (polyamic acid solution). When obtaining the specific polyamic acid using the above method, the reaction solution (the solution after the reaction) can also be used as the polyamic acid solution. Alternatively, a polyamic acid solution can be prepared by dissolving the solid obtained by removing the solvent from the reaction solution in an organic solvent. The concentration of the solid component in 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.

[0072] There are no particular limitations on the method for imidizing a specific polyamic acid in a polyamic acid solution, and known methods can be used. Specific imidization methods include thermal methods and chemical methods. From a productivity point of view, the method of imidization using a chemical method (chemical imidization) is preferred.

[0073] As a chemical imidization method, examples include adding one or more selected from the group consisting of an imidization catalyst and a dehydrating agent to a polyamic acid solution containing a specific polyamic acid, thereby imidizing the specific polyamic acid. The temperature conditions for imidization of the specific polyamic acid are, for example, in the range of 20°C or higher and 150°C or lower. The reaction time for imidization of the specific polyamic acid is, for example, in the range of 10 minutes or higher and 30 hours or lower.

[0074] As the imidization catalyst described above, there are no particular limitations, and tertiary amines can be used. Heterocyclic tertiary amines are preferred. Specific examples of preferred heterocyclic tertiary amines include pyridine, methylpyridine, dimethylpyridine, ethylpyridine, diethylpyridine, isoquinoline, and 1,2-dimethylimidazole. As the dehydrating agent described above, there are no particular limitations, and acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride, and trifluoroacetic anhydride are preferred examples.

[0075] The amount of imidization catalyst added is preferably 0.5 molar equivalents or more and 5.0 molar equivalents or less relative to the amide group of a specific polyamic acid, more preferably 0.5 molar equivalents or more and 2.5 molar equivalents or less, and even more preferably 0.6 molar equivalents or more and 2.0 molar equivalents or less. The amount of dehydrating agent added is preferably 0.5 molar equivalents or more and 10.0 molar equivalents or less relative to the amide group of a specific polyamic acid, more preferably 0.5 molar equivalents or more and 5.0 molar equivalents or less, and even more preferably 0.6 molar equivalents or more and 3.0 molar equivalents or less. It should be noted that, in this specification, "amide group of a specific polyamic acid" refers to an amide group generated by the polymerization reaction of a diamine and a tetracarboxylic dianhydride.

[0076] After imidizing a specific polyamic acid in a polyamic acid solution, the solution is immersed in a poor solvent (e.g., 2-propanol), whereby the polyimide precipitates out as a solid component. The precipitated solid component is then separated and washed with the poor solvent to remove impurities, dehydrating agents, imidization catalysts, etc., generated during polyamic acid synthesis. Next, the washed solid component is dried to obtain the polyimide of the first embodiment.

[0077] [Preferred embodiment of polyimide in the first embodiment]

[0078] In order to avoid usage restrictions caused by legal regulations (PFAS regulations) that restrict the manufacture of organofluorine compounds (PFAS), the polyimide of the first embodiment is preferably free of fluorine in all acid dianhydride residues and free of fluorine in all diamine residues.

[0079] To obtain a polyimide with superior solubility in carbonyl solvents, it is preferable that the total amount of tetracarboxylic dianhydride residues divided by the total amount of diamine residues is less than 1. In this case, the polyimide of the first embodiment has an amino group at its end. Amino groups have a high affinity for carbonyl solvents, therefore, when the total amount of tetracarboxylic dianhydride residues divided by the total amount of diamine residues is less than 1, the solubility in carbonyl solvents becomes even higher.

[0080] To obtain polyimide with superior heat resistance, the glass transition temperature of the polyimide in the first embodiment is preferably 150°C or higher, more preferably 155°C or higher, and even more preferably 160°C or higher, and can be 165°C or higher or 170°C or higher. The upper limit of the glass transition temperature of the polyimide in the first embodiment is not particularly limited, for example, it is 300°C or lower. The method for determining the glass transition temperature of the polyimide is the same as or based on the method used in the embodiments described later.

[0081] The polyimide of the first embodiment is preferably soluble in a carbonyl solvent. "Polyimide soluble in a carbonyl solvent" refers to a polyimide whose solubility in a carbonyl solvent is evaluated as A or B in the following examples. To obtain a polyimide with even better solubility in carbonyl solvents, the polyimide of the first embodiment is preferably soluble in one or more carbonyl 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, thus drying is easier when forming a polyimide film from the polyimide resin composition described later. Therefore, to improve the productivity of polyimide films, the polyimide of the first embodiment is preferably soluble in one or more carbonyl solvents selected from the group consisting of methyl ethyl ketone and ethyl acetate, and more preferably soluble in ethyl acetate.

[0082] To obtain a polyimide with superior solubility and heat resistance in carbonyl solvents, the polyimide of the first embodiment preferably has a weight-average molecular weight (Mw) of 5,000 or more and 200,000 or less, more preferably 10,000 or more and 150,000 or less, further preferably 12,000 or more and 100,000 or less, and even more preferably 13,000 or more and 50,000 or less. Furthermore, to obtain a polyimide with superior solubility and heat resistance in carbonyl solvents, the polyimide of the first embodiment preferably has a number-average molecular weight (Mn) of 2,000 or more and 50,000 or less, more preferably 3,000 or more and 40,000 or less, and even more preferably 4,000 or more and 30,000 or less. The methods for determining the Mw and Mn of the polyimide are the same as or based on the methods used in the embodiments described later.

[0083] In order to obtain a polyimide with better solubility in carbonyl solvents and better heat resistance, the polyimide of 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.

[0084] Condition 1: The residues containing the bisphenol A type structure are BPADA residues, and the residues containing the fluorene structure are selected from one or more of the group consisting of BAFL residues and BAMeFL residues.

[0085] Condition 2: The above condition 1 is satisfied, and the content of residues containing the fluorene structure is more than 50 mol% and less than 70 mol% relative to the total amount of diamine residues (100 mol%).

[0086] Condition 3: Condition 2 above must be met, and Mw must be between 5000 and 200000.

[0087] <Second Embodiment: Polyimide Resin Composition>

[0088] Next, the polyimide resin composition of the second embodiment of the present invention will be described. The polyimide resin composition of the second embodiment contains the polyimide of the first embodiment of the present invention and a carbonyl solvent. Because the polyimide resin composition of the second embodiment contains the polyimide of the first embodiment, it is possible to suppress the generation of polyimide dissolution residues and to improve the heat resistance of the polyimide film obtained using the polyimide resin composition of the second embodiment. In the following description, content repeated in the first embodiment will sometimes be omitted.

[0089] To improve the productivity of polyimide films, the carbonyl solvent in the polyimide resin composition is preferably one or more selected from the group consisting of methyl ethyl ketone and ethyl acetate, and more preferably ethyl acetate.

[0090] In order to facilitate the formation of a polyimide film, the polyimide content in the polyimide resin composition is preferably 8% by weight or more and 30% by weight or less, more preferably 10% by weight or more and 25% by weight or less.

[0091] In the polyimide resin composition of the second embodiment, various organic or inorganic low-molecular-weight compounds or high-molecular-weight compounds can be blended as additives. Examples of additives include plasticizers, antioxidants, dyes, surfactants, leveling agents, organosilicones, microparticles, and sensitizers. The microparticles may include organic microparticles formed from polystyrene, polytetrafluoroethylene, etc., and inorganic microparticles formed from colloidal silica, carbon, layered silicates, etc., which can have porous or hollow structures. Furthermore, the function and morphology of the microparticles are not particularly limited; for example, they can be pigments, fillers, or fibrous particles.

[0092] <Third Embodiment: Polyimide Film>

[0093] Next, the polyimide film according to the third embodiment of the present invention will be described. The polyimide film of the third embodiment includes the polyimide of the first embodiment of the present invention described above. Because the polyimide film of the third embodiment includes the polyimide of the first embodiment, it is possible to improve the uniformity of thickness and heat resistance. In the following description, content that is repeated with the first and second embodiments will sometimes be omitted.

[0094] The polyimide content (of the polyimide in the first embodiment) in the polyimide film of the third embodiment is, for example, 70% by weight or more, preferably 80% by weight or more, more preferably 90% by weight or more, and may also be 100% by weight, relative to the total amount of the polyimide film. Other than polyimide, the above-mentioned additives (more specifically, microparticles, etc.) can be listed as components in the polyimide film. Furthermore, the thickness of the polyimide film of the third embodiment is, for example, 1 μm or more and 200 μm or less, preferably 5 μm or more and 100 μm or less. The thickness of the polyimide film can be measured using a laser holographic measuring instrument.

[0095] The molding method for the polyimide film in the third embodiment is not particularly limited, and examples include melt molding and solution molding. However, the solution molding method is preferred in order to form a film with uniform thickness. In the solution molding method, the polyimide resin composition of the second embodiment is coated onto a support, and the solvent is dried and removed, thereby obtaining a polyimide film.

[0096] As a method for coating the polyimide resin composition onto a support, known methods using rod coating machines, comma coating machines (registered trademarks), etc., can be employed. As the support, metal substrates such as stainless steel substrates, glass plates, metal cylinders, metal strips, plastic films, etc., can be used. From the viewpoint of improving productivity, annular supports such as metal cylinders or metal strips, or long strips of plastic film, are preferred as the support, and the polyimide film is manufactured using a roll-to-roll method. When using a plastic film as the support, a material that is insoluble in the solvents of the polyimide resin composition can be appropriately selected.

[0097] When drying the coated film obtained by coating a polyimide resin composition onto a support, it is preferable to heat the coated film. The heating temperature is not particularly limited as long as it is sufficient to remove the solvent and suppress coloration of the resulting polyimide film; it can be appropriately set within the range of room temperature to 300°C, preferably 50°C to 250°C, more preferably 80°C to 220°C, and also 120°C to 180°C. The heating temperature can also be increased in stages. The heating time is not particularly limited, for example, within the range of 10 minutes to 10 hours. To improve solvent removal efficiency, the resin film can be peeled off from the support and dried after a certain degree of drying. To promote solvent removal, heating can be performed under reduced pressure.

[0098] The polyimide film of the third embodiment can also be laminated on a flexible printed circuit board as an insulating material or adhesive.

[0099] Example

[0100] The following describes embodiments of the present invention, but the scope of the present invention is not limited to the following embodiments.

[0101] <Preparation of Polyamic Acid Solution>

[0102] The preparation methods of polyamic acid solutions P1 to P18 used in the examples and comparative examples will be described below. It should be noted that, hereinafter, compounds and reagents will be referred to by the following abbreviations. Furthermore, the preparation of polyamic acid solutions P1 to P18 was carried out under a nitrogen atmosphere.

[0103] NMP: N-methyl-2-pyrrolidone

[0104] BPADA: 4,4'-(4,4'-isopropylidene diphenoxy)phthalic anhydride

[0105] BPAF: 9,9-bis(3,4-dicarboxyphenyl)fluorene dihydride

[0106] a-BPDA: 2,3,3',4'-Biphenyltetracarboxylic acid dianhydride

[0107] PAM-E: 1,3-bis(3-aminopropyl)tetramethyldisiloxane (molecular weight: 260)

[0108] KF-8010: A siloxane diamine with a number average molecular weight of 860 (Shin-Etsu Chemical Industry Co., Ltd.'s "KF-8010" is an organopolysiloxane with amino-terminal modification).

[0109] X-22-9409: A siloxane diamine with a number average molecular weight of 1340 (Shin-Etsu Chemical Co., Ltd. manufactures "X-22-9409", an organopolysiloxane with amino-terminal modification).

[0110] X-22-161A: A siloxane diamine with a number average molecular weight of 1600 (Shin-Etsu Chemical Industry Co., Ltd. manufactures "X-22-161A", an organopolysiloxane with amino-terminal modification).

[0111] BAFL: 9,9-bis(4-aminophenyl)fluorene

[0112] BAMeFL: 9,9-bis(4-amino-3-methylphenyl)fluorene

[0113] BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane

[0114] ODA: 4,4'-Oxydiphenylamine

[0115] [Preparation of polyamic acid solution P1]

[0116] In a 2000 mL glass flask equipped with a stirrer featuring a stainless steel stirring rod and a nitrogen inlet tube, 280 g of NMP was added 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 and dissolved. Then, 34.0 g of BPADA was added to the contents of the flask, and the mixture was stirred for 24 hours at 23°C to obtain a polyamic acid solution P1 (solid content concentration: 20% by weight).

[0117] [Preparation of polyamic acid solutions P2~P18]

[0118] Except for the dianhydride and its feeding ratio used, and the diamine and its feeding ratio used, as shown in Table 1, polyamic acid solutions P2 to P18 were prepared using the same method as polyamic acid solution P1. It should be noted that the total amount of diamine used in preparing polyamic acid solutions P2 to P18 is the same as that used in polyamic acid solution P1.

[0119] For polyamic acid solutions P1-P18, the dianhydrides used and their proportions, as well as the diamines used and their proportions, are shown in Table 1. It should be noted that in Table 1, "-" indicates that this component was not used. Furthermore, the values ​​in the "Dianhydrides" column of Table 1 represent the content of each dianhydride relative to the total amount of diamines used (100 mol%) (in mol%). Similarly, the values ​​in the "Diamines" column of Table 1 represent the content of each diamine relative to the total amount of diamines used (100 mol%) (in mol%). Additionally, for polyamic acid solutions P1-P18, the molar fraction of each polyamic acid residue in the prepared polyamic acid solutions is consistent with the molar fraction of each monomer used in the synthesis of polyamic acid (the monomer corresponding to each residue).

[0120] [Table 1]

[0121]

[0122] <Formation of Polyimide>

[0123] [Example 1]

[0124] 2.3 g of pyridine, acting as an imidization catalyst, was added to 40 g of polyamic acid solution P1, and the solution was stirred to disperse the imidization catalyst in the solution. Next, 2.9 g of acetic anhydride was added to the solution containing the imidization catalyst, and the solution was maintained at 90°C and stirred for 2 hours. Then, the stirred solution was cooled to 23°C and added to 200 g of 2-propanol to precipitate the solid component. The solid component was then washed with 2-propanol and dried in a vacuum oven at 120°C for 12 hours to obtain the polyimide of Example 1.

[0125] [Examples 2-5 and Comparative Examples 1-13]

[0126] Using the polyamic acid solution described in Table 2 below instead of polyamic acid solution P1, the polyimides of Examples 2-5 and Comparative Examples 1-13 were obtained by the same method as in Example 1. It should be noted that in Examples 2-5 and Comparative Examples 1-13, the amount of polyamic acid solution used was 40g.

[0127] <Fabrication of Polyimide Film>

[0128] First, 85 parts by weight of NMP and 15 parts by weight of polyimide (any of the polyimides in Examples 1-5 and Comparative Examples 1-13) were mixed to obtain a polyimide resin composition. Next, the obtained polyimide resin composition was coated onto an alkali-free glass plate, dried in air at 80°C for 60 minutes, and then dried at 180°C for 60 minutes to obtain a polyimide film with a thickness of 10 μm.

[0129] <Determination Methods and Evaluation Methods>

[0130] The following describes the methods for determining and evaluating the physical properties of polyimide and polyimide films.

[0131] [Solubility in carbonyl solvents]

[0132] (Solubility in methyl ethyl ketone)

[0133] Add 1g of the polyimide to be evaluated to 9g of methyl ethyl ketone, stir for 24 hours at 23°C, visually confirm whether there is any dissolved residue of polyimide, and determine the solubility in methyl ethyl ketone according to the following criteria.

[0134] A: There was no dissolved residue, and no turbidity was detected in the solution.

[0135] B: No dissolved residue was found, but the solution was confirmed to be cloudy.

[0136] C: There is residual dissolution, or the solution has become gel-like.

[0137] (Solubility in ethyl acetate)

[0138] Using 9g of ethyl acetate instead of 9g of methyl ethyl ketone, the solubility in ethyl acetate was determined using the same method as described above (solubility in methyl ethyl ketone). If the determination result is A or B, it is evaluated as "excellent solubility in carbonyl solvents". On the other hand, if the determination result is C, it is evaluated as "not excellent solubility in carbonyl solvents".

[0139] [Glass transition temperature (Tg)]

[0140] First, a sample of the polyimide film to be evaluated, measuring 3 mm in width and 10 mm in length, was obtained to prepare a specimen for Tg determination. Next, using a thermal analysis apparatus (Hitachi High-Tech Co., Ltd. "TMA7100"), a load of 29.4 mN was applied to the long side of the specimen, and the temperature was increased from 20 °C to 250 °C at a rate of 10 °C / min. 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). A Tg of 150 °C or higher was evaluated as "excellent heat resistance." Conversely, a Tg less than 150 °C was evaluated as "not excellent heat resistance."

[0141] [Weight-average molecular weight (Mw) and number-average molecular weight (Mn)]

[0142] The Mw and Mn of the polyimide being tested were determined under the following conditions.

[0143] • Device used: Tosoh Corporation "HLC-8220GPC"

[0144] • Pillar: 2 x "TSK gel super AWM-H" manufactured by Tosoh Corporation

[0145] • Protective column: 1 piece of "TSK gel guard column super AW-H" manufactured by Tosoh Corporation

[0146] Column temperature: 40℃

[0147] • Eluent: N,N-dimethylformamide solution containing LiBr (concentration: 30 mmol / L) and phosphoric acid (concentration: 23.5 mmol / L).

[0148] • Sample concentration: 5.0 mg / mL

[0149] Injection volume: 20μL

[0150] • Flow rate: 0.6 mL / min

[0151] • Detector: RI (Differential Refractometer)

[0152] Standard sample: Polyethylene oxide

[0153] • Standard curve iteration: 1

[0154] <Results>

[0155] For Examples 1-5 and Comparative Examples 1-13, the types of polyamic acid solutions used, Mw, Mn, Tg, and the results of determining their solubility in carbonyl solvents are shown in Table 2. It should be noted that in Table 2, "MEK" refers to acetophenone, and "AcOEt" refers to ethyl acetate. Additionally, in Table 2, "-" indicates that the determination was not performed.

[0156] [Table 2]

[0157]

[0158] In the polyimides of Examples 1-5, the tetracarboxylic dianhydride residues contain residues with a bisphenol A-type structure, and the diamine residues contain residues with a fluorene structure and specific siloxane diamine residues. In the polyimides of Examples 1-5, the content of residues containing a bisphenol A-type structure is 50 mol% or more relative to the total amount of tetracarboxylic dianhydride residues. In the polyimides of Examples 1-5, the content of specific siloxane diamine residues is 30 mol% or more and 50 mol% or less relative to the total amount of diamine residues.

[0159] As shown in Table 2, the Tg in Examples 1-5 was above 150°C. Therefore, the polyimides in Examples 1-5 exhibit excellent heat resistance. In Examples 1-5, the solubility in ethyl acetate was determined to be either A or B. Therefore, the polyimides in Examples 1-5 exhibit excellent solubility in carbonyl solvents.

[0160] The tetracarboxylic acid dianhydride residues of the polyimides in Comparative Examples 4, 6, and 13 do not contain residues containing a bisphenol A type structure. The diamine residues of the polyimides in Comparative Examples 1, 5, 7, 11, and 12 do not contain specific siloxane diamine residues. In the polyimides of Comparative Examples 2 and 3, the content of specific siloxane diamine residues exceeds 50 mol% relative to the total amount of diamine residues. The content of specific siloxane diamine residues of the polyimides in Comparative Examples 8 and 9 is less than 30 mol% relative to the total amount of diamine residues. The diamine residues of the polyimides in Comparative Examples 4 and 10-13 do not contain residues containing a fluorene structure.

[0161] As shown in Table 2, in Comparative Examples 3 and 10, the heat resistance (Tg) was less than 150°C. Therefore, the polyimides in Comparative Examples 3 and 10 did not exhibit excellent heat resistance. In Comparative Examples 1, 2, 4-9, and 11-13, the solubility in ethyl acetate was determined to be C. Therefore, the polyimides in Comparative Examples 1, 2, 4-9, and 11-13 did not exhibit excellent solubility in carbonyl solvents.

[0162] The results above show that, according to the present invention, a polyimide with excellent solubility and heat resistance in carbonyl solvents can be obtained.

Claims

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

2. The polyimide according to claim 1, wherein, The residue with the bisphenol A-type structure is a 4,4'-(4,4'-isopropylidene diphenoxy) phthalic anhydride residue.

3. The polyimide according to claim 1, wherein, The residues having the fluorene structure are selected from one or more of the group consisting of 9,9-bis(4-aminophenyl)fluorene residues and 9,9-bis(4-amino-3-methylphenyl)fluorene residues.

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, wherein the glass transition temperature is above 150°C.

6. The polyimide according to 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.

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