TW202328308A - Coating composition, preparation methods of the coating composition and polyimide resin wherein the coating composition includes polyamic acid, an imidazole compound and a solvent - Google Patents

Abstract

The object of the present invention is to provide a coating composition capable of forming a polyimide resin having less coloration and excellent mechanical properties, a method for producing the coating composition, and a method for producing a polyimide resin using the coating composition. The solution of the present invention includes a coating composition of polyamic acid (A) and a solvent (S). The weight average molecular weight of the polyamic acid (A) is 20,000 or more. The coating composition further includes an imidazole compound (B) with a specific structure. The solvent (S) includes a urea-based solvent (S1) not less than 0% by mass and not more than 10% by mass.

Description

Coating composition, manufacturing method of coating composition, and manufacturing method of polyimide resin

The present invention relates to a coating composition, a method for producing the coating composition, and a method for producing a polyimide resin using the coating composition.

Polyimide resin is widely used in electrical and electronic components such as electronic substrates such as various components or multilayer wiring boards due to its excellent heat resistance, mechanical strength, insulation, and low dielectric constant. Used as insulating or protective material.

Generally, the polyimide resin is formed by heat-treating polyamic acid obtained by polymerizing tetracarboxylic dianhydride components and diamine components in a polar organic solvent. There is also such a background. Most polyimide products used in electronic materials are supplied as solutions of polyimide precursors such as polyamic acid. Specifically, in the manufacture of electrical and electronic parts, the solution of the polyimide precursor is supplied by coating or injection at the point where the insulating material or protective material is formed, and then the solution of the polyimide precursor is heat-treated , and form an insulating material or a protective material.

Technological development of such polyimide resins has been earnestly studied, and various resin compositions including polyamic acid and the like have been disclosed (for example, refer to Patent Document 1 and the like). [Prior Art Literature] [Patent Document]

[Patent Document 1] Japanese Patent Laid-Open No. 2018-58918

[Problem to be solved by the invention]

In polyimide resins, especially polyimide films, depending on the application, less coloring or excellent mechanical properties such as tensile modulus may be desired. However, when a polyimide resin is produced using the resin composition described in Patent Document 1 and the like as a paint composition, it is difficult to form a polyimide resin having both less coloring and excellent mechanical properties.

The present invention was made in view of the above-mentioned problems to provide a coating composition capable of forming a polyimide resin having less coloration and excellent mechanical properties, a method for producing the coating composition, and a coating composition using the coating composition The production method of the polyimide resin is the purpose. [Means to solve the problem]

The inventors of the present invention found that in the coating composition comprising polyamic acid (A) and solvent (S), by using polyamic acid (A) with a weight average molecular weight of 20,000 or more and an imidazole compound with a specific structure (B), and the solvent (S) whose content with the urea-based solvent (S1) is not less than 0% by mass and not more than 10% by mass can solve the above-mentioned problems, and finally complete the present invention. More specifically, the present invention provides the following.

The first aspect of the present invention is a coating composition characterized by comprising polyamic acid (A), imidazole compound (B), and solvent (S), and the weight average molecular weight of polyamic acid (A) is 20,000 or more, the imidazole compound (B) is a compound represented by the following formula (1), (In formula (1), R ¹ is a hydrogen atom or an alkyl group, R ² is an aromatic group that may have a substituent, R ³ is an alkylene group that may have a substituent, and R ⁴ is independently a halogen atom, a hydroxyl group, Mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfonate group, phosphine group, phosphinyl group, phosphonate group or organic group, n is an integer between 0 and 3) including >N The ratio of the mass of the urea-based solvent (S1) in the urea skeleton represented by -CO-N< to the mass of the solvent (S) is 0% by mass or more and 10% by mass or less.

The second aspect of the present invention is a method for producing a coating composition, which is a method for producing a coating composition comprising: polyamic acid (A), imidazole compound (B), and solvent (S), and is characterized in In order to include tetracarboxylic dianhydride and diamine compound in the solvent (S), it is polymerized in the presence of the imidazole compound (B) to generate polyamic acid (A). The imidazole compound (B) is as follows The compound represented by formula (1), (In formula (1), R ¹ is a hydrogen atom or an alkyl group, R ² is an aromatic group that may have a substituent, R ³ is an alkylene group that may have a substituent, and R ⁴ is independently a halogen atom, a hydroxyl group, Mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfonate group, phosphine group, phosphinyl group, phosphonate group or organic group, n is an integer between 0 and 3) including >N The ratio of the mass of the urea-based solvent (S1) to the mass of the solvent (S) of the urea skeleton represented by -CO-N< is 0% by mass or more and 10% by mass or less, and the diamine component and tetracarboxylic dianhydride Polymerization of components is performed until the weight average molecular weight of polyamic acid (A) becomes 20,000 or more.

The 3rd aspect of the present invention is a kind of manufacturing method of polyimide resin, and it is to comprise: The forming step of forming the coating composition of the first aspect, and The imidization step of heating the formed coating composition to imidize it. [Invention effect]

According to the present invention, it is possible to provide a coating composition capable of forming a polyimide resin having less coloration and excellent mechanical properties, a method for producing the coating composition, and a polyimide resin using the coating composition. Manufacturing method.

≪Paint composition≫

The coating composition includes polyamic acid (A), and a solvent (S). This coating composition further contains the imidazole compound (B) mentioned later. The mass ratio of the urea-based solvent (S1) containing the urea skeleton represented by >N-CO-N< to the mass of the solvent (S) is 0% by mass or more and 10% by mass or less. This coating composition is used in the formation of polyimide resin. By using a coating composition that satisfies the above specified requirements, it is possible to form a polyimide resin that has both less coloration and excellent mechanical properties.

Hereinafter, the essential or optional components of the paint composition will be described.

＜Polyamide (A)＞ The coating composition contains polyamic acid (A). Polyamic acid (A) is a precursor polymer of polyimide resin produced when the coating composition is cured. The polyamic acid (A) is not particularly limited as long as it is a resin used as a precursor polymer in the production of a polyimide resin conventionally. The weight average molecular weight of polyamide acid (A) is 20,000 or more. By blending polyamic acid of such a molecular weight with the imidazole compound (B) described later in a coating composition and using the coating composition, a polyimide resin having less coloring and excellent mechanical properties can be formed . The weight average molecular weight of the polyamide acid (A) is preferably from 5,000 to 100,000, more preferably from 10,000 to 75,000.

Polyamic acid (A) can usually be obtained by condensing a monomer component composed of tetracarboxylic dianhydride and diamine. Polyamide acid may have a structural unit represented by the following formula (a1). (In the formula (a1), ^A1 is a tetravalent organic group having 6 to 50 carbon atoms, and ^A2 is a divalent organic group).

Hereinafter, the tetracarboxylic dianhydride used in the manufacture of polyamic acid (A), the diamine compound, and the manufacturing method of polyamic acid (A) are demonstrated below.

[Tetracarboxylic dianhydride] The tetracarboxylic dianhydride that generates the structural unit represented by the formula (a1) is represented by the following formula (a1-1). Tetracarboxylic dianhydride represented by formula (a1-1) reacts with a diamine compound described later to give polyamic acid (A) having a structural unit represented by formula (a1). This tetracarboxylic dianhydride may be used individually by 1 type, and may use it in combination of 2 or more types. (In the formula (a1-1), ^A1 is a tetravalent organic group having 6 to 50 carbon atoms).

In the formula (a1-1), ^A1 is a tetravalent organic group with 6 to 50 carbon atoms, except for the acid anhydride groups represented by the two -CO-O-CO- in the formula (a1-1), It may have 1 or plural substituents. Suitable examples of substituents are preferably fluorine atoms, alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, fluorinated alkyl groups having 1 to 6 carbon atoms, A fluorinated alkoxy group having 1 to 6 carbon atoms. Moreover, the compound represented by formula (a1-1) may contain a carboxyl group and a carboxylate group other than an acid anhydride group. When the substituent is a fluorinated alkyl group or a fluorinated alkoxy group, it is preferably a perfluoroalkyl group or a perfluoroalkoxy group. The same can be said about the above substituents that the aromatic group described later may have one or a plurality of substituents on the aromatic ring.

In the formula (a1-1), A ¹ is a tetravalent organic group, the lower limit of the number of carbon atoms is 6, and the upper limit is 50. The number of carbon atoms constituting ^A1 is more preferably 8 or more, and still more preferably 12 or more. Also, the number of carbon atoms constituting ^A1 is more preferably 40 or less, and still more preferably 30 or less. A ¹ may be an aliphatic group, an aromatic group, or a combination of these structures. ^A1 may contain a halogen atom, an oxygen atom, a nitrogen atom, and a sulfur atom in addition to a carbon atom and a hydrogen atom. When ^A1 is an oxygen atom, nitrogen atom or sulfur atom, the oxygen atom, nitrogen atom or sulfur atom is selected from nitrogen-containing heterocyclic group, -CONH-, -NH-, -N=N-, -CH=N- , -COO-, -O-, -CO-, -SO-, -SO ₂ -, -S- and -SS-, may be contained in A ¹ as a group selected from -O-, -CO-, The groups among -SO-, -SO ₂ -, -S- and -SS- are preferably included in A ¹ .

Tetracarboxylic dianhydrides can be appropriately selected from tetracarboxylic dianhydrides conventionally used as synthesis raw materials of polyamic acid. The tetracarboxylic dianhydride may be an aliphatic tetracarboxylic dianhydride or an aromatic tetracarboxylic dianhydride. The tetracarboxylic dianhydride is preferably an aliphatic tetracarboxylic dianhydride, more preferably an alicyclic tetracarboxylic dianhydride ( A1). Hereinafter, alicyclic tetracarboxylic dianhydride (A1) is demonstrated.

(Alicyclic tetracarboxylic dianhydride (A1)) A suitable example of the alicyclic tetracarboxylic dianhydride (A1) is represented by the aforementioned formula (a1-1), and the aforementioned ^A1 does not contain aromatic A group, a compound containing a tetravalent organic group with an alicyclic ring having 4 to 50 carbon atoms. In this compound, two carboxylic acid anhydride groups are bonded to the alicyclic ring. The alicyclic tetracarboxylic dianhydride (A1) may be used alone or in combination of two or more.

Alicyclic tetracarboxylic dianhydride (A1) is a compound which has two carboxylic anhydride groups bonded to an alicyclic ring and does not contain an aromatic group. The alicyclic tetracarboxylic dianhydride may have a linear or branched chain aliphatic group. The alicyclic and chain aliphatic groups which the alicyclic tetracarboxylic dianhydride (A1) has may contain a halogen atom, an oxygen atom, a nitrogen atom, and a sulfur atom other than a carbon atom and a hydrogen atom. For example, an oxygen atom, a nitrogen atom or a sulfur atom is selected from a nitrogen-containing heterocyclic group, -CONH-, -NH-, -N=N-, -CH=N-, -COO-, -O-, -CO- The groups in , -SO-, -SO ₂ -, -S- and -SS- may be included in alicyclic and chain aliphatic groups.

The alicyclic ring contained in the alicyclic tetracarboxylic dianhydride (A1) may be monocyclic or polycyclic. Examples of the polycyclic alicyclic structure include bridged alicyclic structures such as bicyclo[2.2.1]heptane, and the like. For example, bridged alicyclic structures can be condensed with other bridged alicyclic structures and/or non-bridged alicyclic structures, and bridged alicyclic structures can also be condensed with other bridged alicyclic structures and/or non-bridged alicyclic structures. Screw key to connect. By using the alicyclic tetracarboxylic dianhydride (A1) and using the coating composition, a polyimide resin excellent in transparency can be obtained.

Specific examples of alicyclic tetracarboxylic dianhydride (A1) include 1,2,4,5-cyclohexanetetracarboxylic dianhydride, bicyclo[2.2.2]octane-2,3 ,5,6-tetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 5-(2,5-dioxo-tetrahydrofuran -3-yl)-3-methyl-3-cyclohexene-1,2-dicarboxylic acid anhydride, 4-(2,5-dioxotetrahydrofuran-3-yl)-tetrahydronaphthalene-1,2 -Dicarboxylic anhydride, tetrahydrofuran-2,3,4,5-tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 1,2,3,4-cyclobutane tetra Carboxylic dianhydride, 1,3-dimethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride, and 1,4-dimethyl-1,2,3,4-cyclobutane Tetracarboxylic dianhydride, etc.

Moreover, as alicyclic tetracarboxylic dianhydride (A1), the compound represented by following formula (a2) is preferable. When a compound represented by the following formula (a2) is used, it tends to be easy to obtain a polyimide resin excellent in transparency. Furthermore, a in the formula (a2) is preferably 5 or less, more preferably 3 or less, from the viewpoint of ease of purification of the raw material compound. Moreover, since the chemical stability of the raw material compound is excellent, a is preferably 1 or more, more preferably 2 or more. a in the formula (a2) is particularly preferably 2 or 3.

(In formula (a2), R ^a11 , R ^a12 and R ^a13 are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, and a fluorine atom, and a is 0 or more an integer below 12).

The alkyl group that can be selected as R ^a11 in formula (a2) is an alkyl group having 1 to 5 carbon atoms. The number of carbon atoms in the alkyl group is still more preferably from 1 to 4, particularly preferably from 1 to 3. When R ^a11 is an alkyl group, the alkyl group may be linear or branched.

As R ^a11 in the formula (a2), it is more preferable to be a hydrogen atom, a methyl group, an ethyl group, an n-propyl group or an iso The propyl group is particularly preferably a hydrogen atom or a methyl group. The plurality of R ^a11 in the formula (a2) are preferably the same group because the purification of the tetracarboxylic dianhydride represented by the formula (a2) is easy.

a in the formula (a2) represents an integer of 0 to 12. When the value of a exceeds 12, purification of tetracarboxylic dianhydride which gives a tetravalent organic group represented by formula (a2) becomes difficult. The upper limit of a is preferably 5, more preferably 3, from the viewpoint of easy purification of tetracarboxylic dianhydride represented by formula (a2). The lower limit of a is preferably 1, more preferably 2 from the viewpoint of the chemical stability of tetracarboxylic dianhydride represented by formula (a2). a in the formula (a2) is particularly preferably 2 or 3.

The alkyl group having 1 to 5 carbon atoms that can be selected as R ^a12 and R ^a13 in formula (a2) is the same as the alkyl group having 1 to 5 carbon atoms that can be selected as R ^a11 . R ^a12 and R ^a13 are preferably a hydrogen atom or an alkyl group having 1 to 5 carbon atoms, particularly preferably a hydrogen atom or a methyl group, from the viewpoint of ease of purification of the tetracarboxylic dianhydride represented by the formula (a2). .

As the tetracarboxylic dianhydride represented by formula (a2), for example, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-norbornane-5,5",6 ,6"-tetracarboxylic dianhydride (alias "norbornane-2-spirocycle-2'-cyclopentanone-5'-spirocycle-2"-norbornane-5,5",6,6" -tetracarboxylic dianhydride"), methylnorbornane-2-spiro-α-cyclopentanone-α'-spiro-2"-(methylnorbornane)-5,5",6, 6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclohexanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid Dianhydride (alias "norbornane-2-spiro-2'-cyclohexanone-6'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride" ), Methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2”-(methylnorbornane)-5,5”,6,6”-tetracarboxylic dicarboxylic acid Anhydride, norbornane-2-spiro-α-cyclopropanone-α'-spiro-2”-norbornane-5,5”,6,6”-tetracarboxylic dianhydride, norbornane-2 -spiro-α-cyclobutanone-α'-spiro-2”-norbornane-5,5”,6,6”-tetracarboxylic dianhydride, norbornane-2-spiro-α- Cycloheptanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclooctanone-α' -Spiro-2"-Norbornane-5,5",6,6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclononanone-α'-spiro-2" -Norbornane-5,5",6,6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclodecanone-α'-spiro-2"-norbornane-5 ,5",6,6"-Tetracarboxylic dianhydride, norbornane-2-spiro-α-cycloundecone-α'-spiro-2"-norbornane-5,5", 6,6"-tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclododecanone-α'-spiro-2"-norbornane-5,5",6,6" -Tetracarboxylic dianhydride, norbornane-2-spiro-α-cyclotridecanone-α'-spiro-2”-norbornane-5,5”,6,6”-tetracarboxylic acid Dianhydride, norbornane-2-spiro-α-cyclotetradecanone-α'-spiro-2”-norbornane-5,5”,6,6”-tetracarboxylic dianhydride, norbornane Bornane-2-spiro-α-cyclopentadecanone-α'-spiro-2”-norbornane-5,5”,6,6”-tetracarboxylic dianhydride, norbornane-2 -Spiro-α-(methylcyclopentanone)-α'-spiro-2”-norbornane-5,5”,6,6”-tetracarboxylic dianhydride, norbornane-2-spiro Cyclo-α-(methylcyclohexanone)-α'-spiro-2”-norbornane-5,5”,6,6”-tetracarboxylic dianhydride, etc.

Also, as the tetracarboxylic dianhydride represented by the formula (a2), it is preferable to contain At least one of compound (A2-1) represented by the following formula (a2-1) and compound (A2-2) represented by the following formula (a2-2), and compound (A2-1) and compound ( A2-2) The total amount is more than 30 mol% of tetracarboxylic dianhydride, (In formula (a2-1), R ^a11 , R ^a12 , R ^a13 , and a are synonymous with R ^a11 , R ^a12 , R ^a13 , and a in formula (a2). (In formula (a2-2), R ^a11 , R ^a12 , R ^a13 , and a are synonymous with R ^a11 , R ^a12 , R ^a13 , and a in formula (a2).

The compound (A2-1) represented by the formula (a2-1) has two norbornyl groups trans-configured, and relative to each of the two norbornyl groups, the carbonyl group of the cycloalkanone is end-stereo-configured An isomer of tetracarboxylic dianhydride represented by formula (a2). The compound (A2-2) represented by the formula (a2-2) has two norbornyl groups arranged in cis, and relative to each of the two norbornyl groups, the carbonyl group of the cycloalkanone is end-stereo-configured An isomer of tetracarboxylic dianhydride represented by formula (a2). Also, the method for producing tetracarboxylic dianhydride containing such isomers at the above ratio is not particularly limited, and known methods can be appropriately used, for example, the method described in International Publication No. 2014/034760 can be appropriately used wait.

(aromatic tetracarboxylic dianhydride) As mentioned above, an aromatic tetracarboxylic dianhydride can also be used as a tetracarboxylic dianhydride. The aromatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride containing an aromatic ring in its structure. As the aromatic tetracarboxylic dianhydride, conventionally, aromatic tetracarboxylic dianhydrides used in the production of polyimide resins can be used without any particular limitation.

Specific examples of suitable aromatic tetracarboxylic dianhydrides include pyromellitic dianhydride, 1,4-bis(3,4-dicarboxyphenoxy)phthalic anhydride, 3,3′,4 ,4'-Oxydiphthalic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3,3',4'-biphenyltetracarboxylic dicarboxylic acid anhydride, 3,3',4,4'-diphenyl ketone tetracarboxylic dianhydride, 3,3',4,4'-diphenylphenone tetracarboxylic dianhydride and naphthalene-1,4,5 , 8-tetracarboxylic dianhydride, etc.

Moreover, as an aromatic tetracarboxylic dianhydride, the compound represented by following formula (a1-2)-(a1-4) can also be used, for example.

In the above formula (a1-2) and formula (a1-3), R ^a1 , R ^a2 and R ^a3 respectively represent an aliphatic group which may be substituted by a halogen, an oxygen atom, a sulfur atom, or a divalent element through which one or more Any of the aromatic groups, or a divalent group constituted by a combination thereof. R ^a2 and R ^a3 may be the same or different. That is, R ^a1 , R ^a2 and R ^a3 may contain a carbon-carbon single bond, a carbon-oxygen-carbon ether bond, or a halogen element (fluorine, chlorine, bromine, iodine). Examples of compounds represented by formula (a1-2) include 2,2-bis(3,4-dicarboxyphenoxy)propane dianhydride and 1,4-bis(3,4-dicarboxyphenoxy)benzene Dianhydride, etc.

In addition, in the above-mentioned formula (a1-4), R ^a4 and R ^a5 represent any one of an aliphatic group which may be substituted by halogen, an aromatic group through which one or more divalent elements, halogen, or A combination of monovalent substituents. R ^a4 and R ^a5 may be the same or different. As a compound represented by formula (a1-4), difluoropyromellitic dianhydride, dichloropyromellitic dianhydride, and the like can also be used.

Examples of tetracarboxylic dianhydrides used to obtain fluorine-containing polyimides containing fluorine in their molecular structure include (trifluoromethyl)pyromellitic dianhydride, bis(trifluoromethyl)pyromellitic Formic dianhydride, bis(heptafluoropropyl)pyromellitic dianhydride, pentafluoroethylpyromellitic dianhydride, bis{3,5-bis(trifluoromethyl)phenoxy}pyromellitic acid Dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxybis Phenyl dianhydride, 2,2',5,5'-tetra(trifluoromethyl)-3,3',4,4'-tetracarboxybiphenyl dianhydride, 5,5'-bis(trifluoromethyl) Methyl)-3,3',4,4'-tetracarboxydiphenyl ether dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxydiphenyl Methyl ketone dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}phthalic anhydride, bis{(trifluoromethyl)dicarboxyphenoxy}(trifluoromethyl)phthalic anhydride, bis( Dicarboxyphenoxy)(trifluoromethyl)phthalic anhydride, bis(dicarboxyphenoxy)bis(trifluoromethyl)phthalic anhydride, bis(dicarboxyphenoxy)tetra(trifluoromethyl) Phthalic anhydride, 2,2-bis{4-(3,4-dicarboxyphenoxy)phenyl}hexafluoropropane dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}biphenyl anhydride, bis{(trifluoromethyl)dicarboxyphenoxy}bis(trifluoromethyl)biphenyl dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}diphenylether dianhydride, Bis(dicarboxyphenoxy)bis(trifluoromethyl)biphenyl dianhydride, difluoropyromellitic dianhydride, 1,4-bis(3,4-dicarboxytrifluorophenoxy)tetrafluoro Phthalic anhydride, 1,4-bis(3,4-dicarboxytrifluorophenoxy)octafluorobiphenyldianhydride, etc.

Tetracarboxylic dianhydride and dicarboxylic anhydride can be used together. When these carboxylic anhydrides are used in combination, the properties of the obtained imide ring-containing polymer such as polyimide resin may be further improved. Examples of dicarboxylic anhydrides include maleic anhydride, succinic anhydride, itaconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methylendomethylene tetrahydrophthalic anhydride, Phthalic anhydride, chlorendic anhydride, methyltetrahydrophthalic anhydride, glutaric anhydride, cis-4-cyclohexene-1,2-dicarboxylic anhydride, etc.

[Diamine Compound] As a diamine compound, generally, a compound represented by the following formula (a3-1) can be used. A diamine compound may be used individually by 1 type, and may use it in combination of 2 or more types. (In the formula (a3-1), A ² represents a divalent organic group).

In formula (a3-1), A ² is a divalent organic group, which may have one or more substituents in addition to the two amino groups in formula (a3-1). Suitable examples of substituents are preferably fluorine atoms, alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, fluorinated alkyl groups having 1 to 6 carbon atoms, A fluorinated alkoxy group or hydroxyl group having 1 to 6 carbon atoms. When the substituent is a fluorinated alkyl group or a fluorinated alkoxy group, it is preferably a perfluoroalkyl group or a perfluoroalkoxy group.

In formula (a3-1), the lower limit of the number of carbon atoms in the organic group of ^A2 is preferably 2, more preferably 6, and the upper limit is preferably 50, more preferably 30. A ² may be an aliphatic group, but is preferably an organic group including one or more aromatic rings. When ^A2 is an organic group containing one or more aromatic rings, the organic group may be one aromatic group itself, or two or more aromatic groups through an aliphatic hydrocarbon group or a halogenated aliphatic hydrocarbon group, Or a bonded group including a bond of a heteroatom such as an oxygen atom, a sulfur atom, or a nitrogen atom. Bonds including heteroatoms such as oxygen atoms, sulfur atoms, and nitrogen atoms included in ^A2 include -CONH-, -NH-, -N=N-, -CH=N-, -COO-, - O-, -CO-, -SO-, -SO ₂ -, -S- and -SS-, etc., preferably -O-, -CO-, -SO-, -SO ₂ -, -S- and - SS-. The aromatic ring bonded to the amine group in ^A2 is preferably a benzene ring. When the ring bonded to the amino group in ^A2 is a condensed ring containing two or more rings, it is preferable that the ring bonded to the amino group in the condensed ring is a benzene ring. In addition, the aromatic ring included in ^A2 may be an aromatic heterocyclic ring. Since it is easy to obtain a polyamide resin excellent in mechanical properties, the diamine compound is preferably an aromatic diamine compound (A2) described later.

(Aromatic diamine compound (A2)) As the aromatic diamine compound (A2), a diamine compound having an aromatic group that has been conventionally used in the production of polyimide resins can be used without particular limitation. Here, the diamine compound whose two amine groups are all bonded to an aromatic group is defined as an aromatic diamine compound (A2).

Examples of the aromatic diamine compound (A2) include compounds represented by the aforementioned formula (a3-1), wherein ^A2 is a divalent organic group containing an aromatic group. In this case, the organic group of ^A2 may have one or more substituents in addition to the two amino groups in the formula (a3-1). Also, in this case, the lower limit of the number of carbon atoms in the organic group of ^A2 is preferably 6, and the upper limit of the number of carbon atoms is preferably 50, more preferably 30.

As suitable examples of the substituent that the organic group including the aromatic group as ^A2 may have, a fluorine atom, an alkyl group having 1 to 6 carbon atoms, and an alkoxy group having 1 to 6 carbon atoms are preferable. , A fluorinated alkyl group having 1 to 6 carbon atoms, a fluorinated alkoxy group or a hydroxyl group having 1 to 6 carbon atoms. When the substituent is a fluorinated alkyl group or a fluorinated alkoxy group, it is preferably a perfluoroalkyl group or a perfluoroalkoxy group.

An organic group containing an aromatic group as ^A2 may be an aromatic group itself, or two or more aromatic groups through an aliphatic hydrocarbon group or a halogenated aliphatic hydrocarbon group, or may contain an oxygen atom, a sulfur atom, and a nitrogen atom The bonded base of the bonded heteroatoms. Examples of bonds of heteroatoms including oxygen atoms, sulfur atoms, and nitrogen atoms included in ^A2 include -CONH-, -NH-, -N=N-, -CH=N-, -COO-, - O-, -CO-, -SO-, -SO ₂ -, -S- and -SS-, etc., preferably -O-, -CO-, -SO-, -SO ₂ -, -S- and - SS-.

The aromatic ring bonded to the amine group in ^A2 is preferably a benzene ring. When the ring bonded to the amino group in ^A2 is a condensed ring containing two or more rings, it is preferable that the ring bonded to the amino group in the condensed ring is a benzene ring. In addition, the aromatic ring included in ^A2 may be an aromatic heterocyclic ring.

When ^A2 is an organic group containing an aromatic ring, it is preferable that the aromatic diamine compound (A2) has the following formulas (21) to ( 24) At least one of the compounds represented. (In the formulas (21) to (24), R ¹¹¹ represents a group consisting of a hydrogen atom, a fluorine atom, a hydroxyl group, an alkyl group with 1 to 4 carbon atoms, and a halogenated alkyl group with 1 to 4 carbon atoms. One of the group. In formula (24), Q represents 9,9'-fenylene, or is selected from the formula: -C ₆ H ₄ -, -CONH-C ₆ H ₄ -NHCO-, -NHCO- C ₆ H ₄ -CONH-, -OC ₆ H ₄ -CO-C ₆ H ₄ -O-, -OCO-C ₆ H ₄ -COO-, -OCO-C ₆ H ₄ -C ₆ H ₄ -COO- , -OCO-, -O-, -S-, -CO-, -CONH-, -SO ₂ -, -C(CF ₃ ) ₂ -, -C(CH ₃ ) ₂ -, -CH ₂ -, - OC ₆ H ₄ -C(CH ₃ ) ₂ -C ₆ H ₄ -O-, -OC ₆ H ₄ -C(CF ₃ ) ₂ -C ₆ H ₄ -O-, -OC ₆ H ₄ -SO ₂ - C ₆ H ₄ -O-, -C(CH ₃ ) ₂ -C ₆ H ₄ -C(CH ₃ ) ₂ -, -OC ₁₀ H ₆ -O-, -OC ₆ H ₄ -C ₆ H ₄ -O One of the groups represented by - and -OC ₆ H ₄ -O-. In the example of Q, -C ₆ H ₄ - is a phenylene group, preferably m-phenylene group and p - Phenylylene, more preferably p-phenylene. Also, -C ₁₀ H ₆ - is naphthalene diyl, preferably naphthalene-1,2-diyl, naphthalene-1,4-diyl, naphthalene- 2,3-diyl, naphthalene-2,6-diyl and naphthalene-2,7-diyl, more preferably naphthalene-1,4-diyl and naphthalene-2,6-diyl).

R ¹¹¹ in the formulas (21) to (24) is more preferably a hydrogen atom, a hydroxyl group, a fluorine atom, a methyl group, an ethyl group or a trifluoro group from the viewpoint of heat resistance of the formed polyimide resin A methyl group is particularly preferably a hydrogen atom, a hydroxyl group or a trifluoromethyl group.

As Q in the formula (24), from the viewpoint of the heat resistance of the polyimide resin to be formed, 9,9'-berylene, -OC ₆ H ₄ -O-, -C( CF ₃ ) ₂ -, -O-, -C(CH ₃ ) ₂ -, -CH ₂ - or -OC ₆ H ₄ -C(CH ₃ ) ₂ -C ₆ H ₄ -O-, -CONH-, more Preferably it is -CONH-, -OC ₆ H ₄ -O-, -C(CF ₃ ) ₂ - or -O-, particularly preferably -CONH-.

As the aromatic diamine compound represented by formula (a3-1), the compounds shown below can be suitably used. That is, examples of the aromatic diamine compound (A2) include p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 4,4'-diaminobiphenyl, 4, 4'-Diamino-2,2'-bis(trifluoromethyl)biphenyl, 3,3'-diaminodiphenyl, 4,4'-diaminodiphenyl, 4 ,4'-Diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminobenzanilide, 3,3'-diaminobenzaniline, 1,4-bis(4-amine phenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 4,4'-bis(4-aminophenoxy)benzene Phenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]pyridine, bis[4-(3-aminophenoxy)phenyl]pyridine, 2,2-bis[ 4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 9,9-bis(4-amino Phenyl) fluorene, 9,9-bis(4-amino-3-methylphenyl) fluorene and 4,4'-[1,4-phenylene bis(1-methylethane-1,1 -diyl)] diphenylamine and the like. Among these, p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, and 4,4'-diaminodiphenyl ether are preferable in terms of price and availability. and 4,4'-diaminobenzamide aniline.

The aromatic diamine compound (A2) is preferably a compound represented by the following formula (25). (In formula (25), Ar ¹ and Ar ² are each independently an aromatic hydrocarbon group having 6 to 18 carbon atoms, and R ¹¹² is a hydrogen atom or a monovalent organic group).

Specific examples of the aromatic diamine compound (A2) represented by the formula (25) include 2,4-bis(4-aminoanilino)-1,3,5-trisalpine, 2,4-bis( 4-aminoanilino)-6-methyl-1,3,5-trimethanone, 2,4-bis(4-aminoanilino)-6-ethyl-1,3,5-trimethanone, 2,4-bis(4-aminoanilino)-6-phenyl-1,3,5-trimethanone, 2,4-bis(4-aminoanilino)-6-amino-1,3 ,5-Trisalpine, 2,4-bis(4-aminoanilino)-6-methylamino-1,3,5-trithiol, 2,4-bis(4-aminoanilino)- 6-Dimethylamino-1,3,5-trimethanol, 2,4-bis(4-aminoanilino)-6-ethylamino-1,3,5-trimethanol, 2,4 -Bis(4-aminoanilino)-6-diethylamino-1,3,5-trimethanone, 2,4-bis(4-aminoanilino)-6-anilino-1,3 , 5-three 𠯤 and 2,4-bis(4-aminoanilino)-6-diphenylamino-1,3,5-tris 𠯤 and so on. Among these, 2,4-bis(4-aminoanilino)-6-amino-1,3,5-trimethanone, 2,4-bis(4-aminoanilino)-6 -Methylamino-1,3,5-tri-methanol, 2,4-bis(4-aminoanilino)-6-ethylamino-1,3,5-tri-methanol and 2,4-bis (4-Aminoanilino)-6-anilino-1,3,5-trisulfone, more preferably 2,4-bis(4-aminoanilino)-6-anilino-1,3,5 -Three 𠯤.

[Manufacturing method of polyamide acid (A)] The polyamic acid (A) can be obtained by, for example, polymerizing tetracarboxylic dianhydride and a diamine compound in an organic solvent. The method for synthesizing polyamic acid (A) is not particularly limited as long as polyamic acid (A) having a weight average molecular weight of 20,000 or more can be produced.

As a preferred synthesis method of polyamic acid (A), it can be mentioned that tetracarboxylic dianhydride and diamine compound are polymerized in an organic solvent in the presence of the imidazole compound (B) described later to form a polyamic acid dianhydride. Method for Amino Acid (A). An organic solvent can be used individually or in mixture of 2 or more types.

In the presence of the imidazole compound (B), by polymerizing the tetracarboxylic dianhydride and the diamine compound, it is easy to obtain the polyamic acid (A) with high molecular weight. When polymerizing a tetracarboxylic dianhydride and a diamine compound in the presence of an imidazole compound (B), as an organic solvent, the solvent (S) mentioned later is preferable. In the solvent (S) described later, by polymerizing tetracarboxylic dianhydride and diamine compound in the presence of imidazole compound (B), polyamic acid (A) with especially high molecular weight can be easily obtained. When tetracarboxylic dianhydride and diamine compound are polymerized in the presence of imidazole compound (B), the usage amount of imidazole compound (B) is preferably 0.01 mol or more and 0.30 mol to 1 mol of tetracarboxylic dianhydride. Mole or less, more preferably 0.02 mole or more and 0.15 mole or less.

Among the organic solvents that can be used as the solvent (S) described later, N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-diethylacetamide, N, Nitrogen-containing polar solvents such as N-dimethylformamide, N,N-diethylformamide and N-methylcaprolactam; dimethylsulfoxide; acetonitrile; diethylene glycol dimethyl Ether, diethylene glycol diethyl ether, ethers such as dioxane and tetrahydrofuran are used as the solvent used in the above polymerization reaction.

The usage-amount of tetracarboxylic dianhydride and a diamine compound at the time of synthesizing a polyamic acid (A) is not specifically limited. With respect to 1 mol of tetracarboxylic dianhydride, it is preferable to use 0.50 mol to 1.50 mol of diamine compound, more preferably to use 0.60 mol to 1.30 mol, and particularly preferably to use 0.70 mol to 1.20 mol below the ears. As mentioned above, the weight average molecular weight of the polyamic acid (A) is not less than 20,000, preferably not less than 5,000 and not more than 100,000, more preferably not less than 10,000 and not more than 75,000. The weight average molecular weight may be set to the above value by adjusting the compounding quantity of tetracarboxylic dianhydride and diamine compound, the reaction conditions, such as a solvent, and reaction temperature.

The temperature at the time of making tetracarboxylic dianhydride and a diamine compound react will not be specifically limited as long as reaction progresses favorably. Generally speaking, the reaction temperature between tetracarboxylic dianhydride and diamine compound is preferably from -5°C to 150°C, more preferably from 0°C to 120°C, particularly preferably from 0°C to 70°C. The time for reacting the tetracarboxylic dianhydride and the diamine compound varies depending on the reaction temperature, but generally, it is preferably from 1 hour to 50 hours, more preferably from 2 hours to 40 hours, especially Preferably, it is not less than 5 hours and not more than 30 hours.

By the method explained above, the solution containing polyamide acid (A) was obtained. By carrying out the polymerization reaction in the solvent (S) described later, the solution containing polyamic acid (A) obtained as above can be directly used as a coating composition, or can also be used in the preparation of a coating composition. The solution containing polyamic acid (A) obtained as described above is under reduced pressure, and at a low temperature that does not produce the degree of transformation of the polyimide resin of polyamic acid (A), it is also possible to obtain the solution from polyamic acid (A). The paste or solid of the polyamic acid (A) obtained by removing at least a part of the solvent from the solution of the amide acid (A) is used in the preparation of a paint composition.

The content of the polyamic acid (A) in the paint composition can be appropriately determined in consideration of the coatability of the paint composition or the solubility to the solvent (S) of the polyamic acid (A). Generally speaking, the content of the polyamic acid (A) in the coating composition is preferably not less than 5 mass % and not more than 45 mass %, more preferably not less than 7 mass % and not more than 40 mass %, relative to the mass of the coating composition, More preferably, it is 10 mass % or more and 30 mass % or less.

＜Imidazole compound (B)＞ The paint composition contains a compound represented by the following formula (1) as the imidazole compound (B). The paint composition is made by combining polyamic acid (A) with a weight average molecular weight of 20,000 or more, imidazole compound (B), and urea-based solvent (S1) with a content of 0% by mass to 10% by mass (S1). ) includes, the use of the paint composition can form a polyimide resin with less coloring and excellent mechanical properties.

(In formula (1), R ¹ is a hydrogen atom or an alkyl group, R ² is an aromatic group that may have a substituent, R ³ is an alkylene group that may have a substituent, and R ⁴ is independently a halogen atom, a hydroxyl group, Mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfonate group, phosphine group, phosphinyl group, phosphonate group or organic group, n is an integer ranging from 0 to 3).

In formula (1), R ¹ is a hydrogen atom or an alkyl group. When R ¹ is an alkyl group, the alkyl group can also be a straight-chain alkyl group or a branched-chain alkyl group. The number of carbon atoms in the alkyl group is not particularly limited, but is preferably from 1 to 20, more preferably from 1 to 10, and still more preferably from 1 to 5.

Specific examples of alkyl groups suitable as ^R include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n- Pentyl, isopentyl, tert-pentyl, n-hexyl, n-heptyl, n-octyl, 2-ethyl-n-hexyl, n-nonyl, n-decyl, n-undecyl base, n-dodecyl, n-tridecyl, n-tetradecyl, n-pentadecyl, n-hexadecyl, n-heptadecyl, n-octadecyl , n-nonadecanyl and n-eicosyl.

In formula (1), R ² is an aromatic group which may have a substituent. The aromatic group which may have a substituent may be an aromatic hydrocarbon group which may have a substituent, or may be an aromatic heterocyclic group which may have a substituent.

The type of aromatic hydrocarbon group is not particularly limited within the range that does not hinder the object of the present invention. The aromatic hydrocarbon group may be a monocyclic aromatic group, a group formed by condensing two or more aromatic hydrocarbon groups, or a group formed by bonding two or more aromatic hydrocarbon groups with a single bond. The aromatic hydrocarbon group is preferably phenyl, naphthyl, biphenyl, anthracenyl, or phenanthrenyl.

The type of aromatic heterocyclic group is not particularly limited insofar as it does not hinder the object of the present invention. The aromatic heterocyclic group may be a monocyclic group or a polycyclic group. The aromatic heterocyclic group is preferably pyridyl, furyl, thienyl, imidazolyl, pyrazolyl, oxazolyl, thiazolyl, isoxazolyl, isothiazolyl, benzoxazolyl, benzo Thiazolyl and benzimidazolyl.

Examples of substituents that a phenyl group, a polycyclic aromatic hydrocarbon group, or an aromatic heterocyclic group may have include a halogen atom, a hydroxyl group, a mercapto group, a sulfide group, a silyl group, a silanol group, a nitro group, a nitroso group, and a sulfinic group. Acid group, sulfo group, sulfonate group, phosphino group, phosphinyl group, phosphono group, phosphonate group, amine group, ammonium group and organic group. When a phenyl group, a polycyclic aromatic hydrocarbon group, or an aromatic heterocyclic group has a plurality of substituents, the plurality of substituents may be the same or different.

When the substituent which the aromatic group has is an organic group, an alkyl group, an alkenyl group, a cycloalkyl group, a cycloalkenyl group, an aryl group, an aralkyl group etc. are mentioned as this organic group. This organic group may contain a bond or a substituent other than a hydrocarbon group such as a hetero atom in the organic group. In addition, this organic group may be any of linear, branched and cyclic. This organic group is usually monovalent, but it may be a divalent or higher organic group when forming a ring structure.

When there is a substituent on the carbon atom adjacent to the aromatic group, two substituents bonded to the adjacent carbon atom may bond to form a ring structure. As a cyclic structure, an aliphatic hydrocarbon ring or an aliphatic ring containing a heteroatom is mentioned.

When the substituent of the aromatic group is an organic group, the bond included in the organic group is not particularly limited as long as it does not impair the effect of the present invention, and the organic group may contain oxygen atoms, nitrogen atoms, silicon atoms, etc. Contains linkages of heteroatoms. Specific examples of bonds containing heteroatoms include ether bonds, thioether bonds, carbonyl bonds, thiocarbonyl bonds, ester bonds, amide bonds, urethane bonds, and imide bonds (-N=C (-R)-, -C(=NR)-: R represents hydrogen atom or organic group), carbonate bond, sulfonyl bond, sulfinyl bond, azo bond, etc.

From the standpoint of the heat resistance of the imidazole compound represented by the formula (1), the bond including a heteroatom that the organic group may have is preferably an ether bond, a thioether bond, a carbonyl bond, a thiocarbonyl bond, an ester bond, Amide bond, amine bond (-NR-: R represents a hydrogen atom or a 1-valent organic group) urethane bond, imide bond (-N=C(-R)-, -C(=NR )-: R represents a hydrogen atom or a monovalent organic group), a carbonate bond, a sulfonyl bond, or a sulfinyl bond.

When the organic group is a substituent other than a hydrocarbon group, the type of the substituent other than a hydrocarbon group is not particularly limited insofar as it does not hinder the object of the present invention. Specific examples of substituents other than hydrocarbon groups include halogen atoms, hydroxyl groups, mercapto groups, sulfide groups, cyano groups, isocyano groups, cyanoxy groups, isocyanato groups, thiocyano groups, isothiocyano groups, and silyl groups. , silanol, alkoxy, alkoxycarbonyl, amino, monoalkylamino, dialkylaluminum, monoarylamino, diarylamine, aminoformyl, thioamine Formyl group, nitro group, nitroso group, carboxylate group, acyl group, acyloxy group, sulfinate group, sulfonate group, phosphine group, phosphine oxide group, phosphonate group, alkyl ether group, Alkenyl ether group, alkyl sulfide group, alkenyl sulfide group, aryl ether group, aryl sulfide group, etc. Hydrogen atoms contained in the above-mentioned substituents may also be substituted by hydrocarbon groups. Moreover, the hydrocarbon group contained in the said substituent may be any of linear, branched and cyclic.

As a substituent of a phenyl group, a polycyclic aromatic hydrocarbon group, or an aromatic heterocyclic group, an alkyl group having 1 to 12 carbon atoms, an aryl group having 1 to 12 carbon atoms, and an aryl group having 1 to 12 carbon atoms are preferable. An alkoxy group having 12 or less carbon atoms, an aryloxy group having 1 or more carbon atoms but not more than 12, an arylamino group having 1 or more carbon atoms and not more than 12, and a halogen atom.

As R ² , since the imidazole compound represented by the formula (1) can be synthesized cheaply and easily, and has good solubility in water or organic solvents of the imidazole compound, it is preferably phenyl, furyl, and thiophene, which may have substituents, respectively. base.

In formula (1), R ³ is an alkylene group which may have a substituent. The substitution which an alkylene group may have is not specifically limited in the range which does not hinder the object of this invention. Specific examples of the substituent that the alkylene group may have include a hydroxyl group, an alkoxy group, an amino group, a cyano group, and a halogen atom. The alkylene group may be a straight chain alkylene group or a branched chain alkylene group, preferably a straight chain alkylene group. The number of carbon atoms in the alkylene group is not particularly limited, but is preferably from 1 to 20, more preferably from 1 to 10, and still more preferably from 1 to 5. Also, the number of carbon atoms in the alkylene group does not include the carbon atoms of the substituent bonded to the alkylene group.

The alkoxy group as a substituent bonded to an alkylene group may be a straight-chain alkoxy group or a branched-chain alkoxy group. The number of carbon atoms of the alkoxy group as a substituent is not particularly limited, but is preferably from 1 to 10, more preferably from 1 to 6, and particularly preferably from 1 to 3.

The amine group as a substituent bonded to an alkylene group may be a monoalkylamine group or a dialkylamine group. The alkyl group contained in the monoalkylamine group or the dialkylamine group may be a straight-chain alkyl group or a branched-chain alkyl group. Although the number of carbon atoms of the alkyl group contained in the monoalkylamine group or dialkylamine group is not particularly limited, it is preferably from 1 to 10, more preferably from 1 to 6, and particularly preferably from 1 to 3. .

Specific examples of alkylene groups suitable for ^R include methylene, ethane-1,2-diyl, n-propane-1,3-diyl, n-propane-2,2-diyl , n-butane-1,4-diyl, n-pentane-1,5-diyl, n-hexane-1,6-diyl, n-heptane-1,7-diyl, n -octane-1,8-diyl, n-nonane-1,9-diyl, n-decane-1,10-diyl, n-undecane-1,11-diyl, n- Dodecane-1,12-diyl, n-tridecane-1,13-diyl, n-tetradecane-1,14-diyl, n-pentadecane-1,15-diyl, n-hexadecane-1,16-diyl, n-heptadecane-1,17-diyl, n-octadecane-1,18-diyl, n-nonadecane-1,19-diyl and n-eicosane-1,20-diyl.

^R4 is a halogen atom, hydroxyl group, mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfonate group, phosphine group, phosphinyl group, phosphonate group or organic group, n is 0 or more An integer of 3 or less. When n is an integer of 2 to 3, the plurality of R ⁴ may be the same or different.

When R ⁴ is an organic group, the organic group is the same as the organic group that an aromatic group may have as a substituent for R ² .

When R ⁴ is an organic group, the organic group is preferably an alkyl group, an aromatic hydrocarbon group, and an aromatic heterocyclic group. The alkyl group is preferably a linear or branched chain alkyl group having 1 to 8 carbon atoms, more preferably methyl, ethyl, n-propyl and isopropyl. As the aromatic hydrocarbon group, phenyl, naphthyl, biphenyl, anthracenyl and phenanthrenyl are preferred, phenyl and naphthyl are more preferred, and phenyl is particularly preferred. The aromatic heterocyclic group is preferably pyridyl, furyl, thienyl, imidazolyl, pyrazolyl, oxazolyl, thiazolyl, isoxazolyl, isothiazolyl, benzoxazolyl, benzo Thiazolyl and benzimidazolyl, more preferably furyl and thienyl.

When R ⁴ is an alkyl group, the bonding position on the imidazole ring of the alkyl group is preferably any one of the 2-position, 4-position, and 5-position, more preferably the 2-position. When R ⁴ is an aromatic hydrocarbon group and an aromatic heterocyclic group, the bonding position on the imidazole of these groups is preferably at the 2-position.

Among the imidazole compounds represented by the above-mentioned formula (1), compounds represented by the following formula (1-1) are preferred, more preferably: Formula (1-1) represents a compound in which R ³ is a methylene group.

(In formula (1-1), R ¹ , R ³ , R ⁴ and n are the same as formula (1), R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are independently hydrogen atom, halogen atom, hydroxyl , mercapto, sulfide, silyl, silanol, nitro, nitroso, sulfinate, sulfo, sulfonate, phosphino, phosphinyl, phosphonyl, phosphonate, amine , ammonium group or organic group, provided that at least one of R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ is a group other than a hydrogen atom).

When R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ are organic groups, the organic groups are the same as those that R ² in formula (1) has as a substituent. R ⁵ , R ⁶ , R ⁷ and R ⁸ are preferably hydrogen atoms from the viewpoint of solubility in the solvent (S) of the imidazole compound.

Among them, preferably at least one of R ⁵ , R ⁶ , R ⁷ , R ⁸ and R ⁹ is the following substituent, particularly preferably R ⁹ is the following substituent. When R ⁹ is the following substituent, R ⁵ , R ⁶ , R ⁷ and R ⁸ are preferably hydrogen atoms. (R ¹⁰ is a hydrogen atom or an organic group).

When R ¹⁰ is an organic group, the organic group is the same as the organic group that R ² in formula (1) has as a substituent. R ¹⁰ is preferably an alkyl group, more preferably an alkyl group having 1 to 8 carbon atoms, particularly preferably an alkyl group having 1 to 3 carbon atoms, most preferably a methyl group.

Among the compounds represented by the above formula (1-1), compounds represented by the following formula (1-1-1) are preferred. (In formula (1-1-1), R ¹ , R ⁴ and n are the same as formula (1), R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ are independently hydrogen atom, hydroxyl, mercapto, Sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfinate group, sulfo group, sulfonate group, phosphino group, phosphinyl group, phosphono group, phosphonate group, amine group, ammonium group or an organic group, provided that at least one of R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ is a group other than a hydrogen atom).

Among the compounds represented by formula (1-1-1), at least one of R ¹¹ , R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ is preferably the group represented by the aforementioned -OR ¹⁰ , particularly preferably R ¹⁵ is -OR ¹⁰ represents the base. When R ¹⁵ is a group represented by -OR ¹⁰ , R ¹¹ , R ¹² , R ¹³ and R ¹⁴ are preferably hydrogen atoms.

The synthesis method of the imidazole compound represented by the above formula (1) is not particularly limited. For example, the halogen-containing carboxylic acid derivative represented by the following formula (I) can be reacted with the imidazole compound represented by the following formula (II) according to the usual method to carry out imidazolylation to synthesize the compound represented by the above formula (1). of imidazole compounds.

(In formula (I) and formula (II), R ¹ , R ² , R ³ , R ⁴ and n are the same as in formula (1). In formula (I), Hal is a halogen atom).

Also, when the imidazole compound is represented by formula (1), and R ³ is a compound of methylene, that is, when the imidazole compound is a compound represented by the following formula (1-2), even by the following The method of Michael addition reaction can also synthesize imidazole compounds.

(In formula (1-2), R ¹ , R ² , R ⁴ and n are the same as formula (1)).

Specifically, for example, by mixing the 3-substituted acrylic acid derivative represented by the following formula (III) and the imidazole compound represented by the above formula (II) in a solvent, a Michael addition reaction occurs to obtain the above formula (1 -2) The imidazole compound represented.

(In formula (III), R ¹ and R ² are the same as formula (1)).

Also, an imidazole compound represented by the following formula (1-3) is obtained by adding a 3-substituted acrylic acid derivative containing an imidazole group represented by the following formula (IV) to a solvent containing water.

(In formula (IV) and formula (1-3), R ² , R ⁴ and n are the same as formula (1)).

In this case, the imidazole compound represented by the above formula (II) and the 3-substituted acrylic acid represented by the following formula (V) are produced by hydrolysis of the 3-substituted acrylic acid derivative represented by the above formula (IV). Furthermore, a Michael addition reaction occurs between the 3-substituted acrylic acid represented by the following formula (V) and the imidazole compound represented by the above formula (II) to produce the imidazole compound represented by the above formula (1-3).

(In formula (V), R ² is the same as formula (1)).

Suitable specific examples of the imidazole compound represented by formula (1) include the following compounds.

The content of the imidazole compound (B) in the paint composition is preferably from 1 to 20 parts by mass, more preferably from 2 to 10 parts by mass, based on 100 parts by mass of the total solid content. By using the imidazole compound (B) in the amount within this range, without excessive volatilization or sublimation of the pyrolyzed product of the imidazole compound (B), it is possible to effectively promote the production of polyamide from polyamic acid (A). Resin production. As a result, a polyimide resin with less coloring and excellent mechanical properties can be obtained.

＜Solvent (S)＞ The paint composition contains a solvent (S). The mass ratio of the urea-based solvent (S1) containing the urea skeleton represented by >N-CO-N< to the mass of the solvent (S) is 0% by mass or more and 10% by mass or less. The ratio of the mass of the urea-based solvent (S1) to the mass of the solvent (S) is preferably from 0% by mass to 5% by mass, more preferably from 0% by mass to 3% by mass, still more preferably 0% by mass The above is 1% by mass or less, particularly preferably 0% by mass. The solvent (S) is not particularly limited as long as the content of the urea-based solvent (S1) is within the specified range. As the solvent (S), an organic solvent is usually used. The paint composition may be a paste containing solids or a solution, but is preferably a solution. A solvent (S) can be used individually or in mixture of 2 or more types.

A typical example of the urea-based solvent (S1) is N,N,N',N'-tetraalkylurea. Especially the ratio of the mass of N,N,N',N'-tetramethylurea and the ratio of the mass of N,N,N',N'-tetraethylurea to the mass of the solvent (S) are relatively Preferably, it is 0 mass % or more and 5 mass % or less, More preferably, it is 0 mass % or more and 3 mass % or less, More preferably, it is 0 mass %.

The type of solvent (S) is not particularly limited within the range that does not hinder the purpose of the present invention, and examples thereof include water, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monopropyl ether, Glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Ethylene glycol monopropyl ether, and glycol monoethers such as diethylene glycol monophenyl ether; ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol dipropyl ether, propylene glycol di Glycol diethers such as methyl ether, propylene glycol diethyl ether, propylene glycol dipropyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol dipropyl ether; Ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monopropyl ether acetate, ethylene glycol monobutyl ether acetate, ethylene glycol monophenyl Ether acetate, diethylene glycol monomethyl ether acetate, and glycol monoacetate such as diethylene glycol monoethyl ether acetate; diethylene glycol monopropyl ether acetate, Diethylene glycol monobutyl ether acetate, diethylene glycol monophenyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monopropyl ether acetate , 2-methoxybutyl acetate, 3-methoxybutyl acetate, 4-methoxybutyl acetate, 2-methyl-3-methoxybutyl acetate, 3-Methyl-3-methoxybutyl acetate, 3-ethyl-3-methoxybutyl acetate, 2-ethoxybutyl acetate, 4-ethoxybutyl Acetate, 4-propoxybutyl acetate, 2-methoxypentyl acetate, 3-methoxypentyl acetate, 4-methoxypentyl acetate, 2- Methyl-3-methoxypentyl acetate, 3-methyl-3-methoxypentyl acetate, 3-methyl-4-methoxypentyl acetate, and 4-methoxypentyl acetate Monoether monoacetate of diols such as 4-methoxypentyl acetate; acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, ethyl isobutyl Ketones such as ketone and cyclohexanone; methyl propionate, ethyl propionate, propyl propionate, isopropyl propionate, methyl 2-hydroxypropionate, ethyl 2-hydroxypropionate, 2-hydroxy -2-methyl, methyl-3-methoxypropionate, ethyl-3-methoxypropionate, ethyl-3-ethoxypropionate, ethyl-3-propoxy Propionate, Propyl-3-methoxypropionate, Isopropyl-3-methoxypropionate, Ethoxyacetate, Ethyloxyacetate, 2-Hydroxy-3-methyl Methyl butyrate, methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, isopentyl acetate, methyl carbonate, ethyl carbonate, propyl carbonate, butyl carbonate, methyl pyruvate ester, ethyl pyruvate, propyl pyruvate, butyl pyruvate, methyl acetoacetate, ethyl acetoacetate, benzyl acetate, ethyl benzoate, diethyl oxalate, diethyl maleate and Esters of γ-butyrolactone, etc.; ethers of diethyl ether, dipropyl ether, dibutyl ether, dihexyl ether, benzyl methyl ether, benzyl ethyl ether, dioxane, tetrahydrofuran, etc. ; Aromatics such as benzene, toluene, xylene, ethylbenzene, cresol and chlorobenzene; Methanol, ethanol, n-propanol, isopropanol, n-butanol, n-hexanol and cyclohexanol, etc. Aliphatic alcohols; glycols such as polyethylene glycol, ethylene glycol, diethylene glycol, propylene glycol, and dipropylene glycol; glycerin; N-methyl-2-pyrrolidone, N,N-dimethylacetyl Nitrogen-containing polar solvents such as amine, N,N-diethylacetamide, N,N-dimethylformamide, N,N-diethylformamide and N-methylcaprolactam; Dimethylsulfone; acetonitrile, etc.

The solvent (S) may contain a nitrogen-containing compound represented by the following formula (S1). (In the formula (S1), R ^S1 and R ^S2 are independently an alkyl group with 1 to 3 carbon atoms, and R ^S3 is a hydrogen atom or a group represented by the following formula (S1-1), R ^S4 is a hydrogen atom or a hydroxyl group, R ^S5 and R ^S6 are each independently a hydrogen atom, an alkyl group with 1 to 3 carbon atoms, and when R ^S3 is a group represented by formula (S1-1), R ^S2 and R ^S3 can be bonded to each other to form a ring).

Among the nitrogen-containing compounds represented by formula (S1), specific examples of when R ^S3 is a hydrogen atom or a group represented by formula (S1-1) include N, N-dimethylformamide, N, N-di Methylacetamide, N,N,2-trimethylpropionamide, N-ethyl,N,2-dimethylpropionamide, N,N-diethyl-2-methylpropionamide , N,N,2-trimethyl-2-hydroxypropionamide, N-ethyl-N,2-dimethyl-2-hydroxypropionamide and N,N-diethyl-2-hydroxy- 2-methylacrylamide, etc.

Among the nitrogen-containing compounds represented by formula (S1), R ^S3 is a group represented by formula (S1-1), and specific examples of when R ^S2 and R ^S3 are bonded to each other to form a ring include N-methyl-2- Pyrrolidone and N-ethyl-2-pyrrolidone, etc.

Among the above examples of nitrogen-containing compounds represented by formula (S1), particularly preferred compounds include N,N-dimethylformamide, N,N-dimethylacetamide and N,N,2 - Trimethylacrylamide. Among these, N,N,2-trimethylacrylamide is preferred. The boiling point of N,N,2-trimethylacrylamide at atmospheric pressure is 175°C. Thus, N,N,2-trimethylacrylamide has relatively low boiling point. Therefore, when using a coating composition containing a solvent (S) containing N,N,2-trimethylacrylamide, when forming a polyimide resin, it is difficult to remain in the polyimide resin generated by heating The solvent (S) is unlikely to cause a decrease in the mechanical properties of the polyimide resin obtained.

Furthermore, N,N,2-trimethylacrylamide will not be designated as a substance of harmful concern in the REACH regulations of the EU (European Union) like SVHC (Substance of Very High Concern, Substance of Very High Concern) , It is also useful for substances with low harmfulness.

The content of the solvent (S) in the paint composition is not particularly limited within the range that does not hinder the object of the present invention. The content of the solvent (S) in the coating composition is properly adjusted according to the solid content in the coating composition. The solid content in the paint composition is, for example, in the range of 5% by mass to 99.9% by mass, preferably 5% by mass to 70% by mass, more preferably 10% by mass to 60% by mass.

＜Other ingredients＞ The paint composition may contain various additives as necessary. Examples of additives include coloring agents, dispersants, sensitizers, adhesion promoters, antioxidants, ultraviolet absorbers, anti-aggregating agents, antifoaming agents, and surfactants. Also, the paint composition may contain various fillers or reinforcing materials as necessary. The usage-amount of various additives is not specifically limited in the range which does not hinder the object of this invention. The mass of the solid content of the paint composition may be appropriately adjusted within a range of, for example, 0.001% by mass to 60% by mass, preferably 0.05% by mass to 5% by mass. The usage-amount of a filler or a reinforcing material is not specifically limited in the range which does not hinder the object of this invention. The amount of the filler or reinforcing material used is usually preferably from 1% by mass to 300% by mass, more preferably from 5% by mass to 200% by mass, and more preferably with respect to the mass of the polyamic acid (A). Preferably, it is not less than 10% by mass and not more than 100% by mass.

As mentioned above, according to the above-mentioned coating composition, it is possible to form a polyimide resin with less coloring and excellent mechanical properties such as elongation at break, tensile modulus of elasticity, tensile strength, and low thermal expansion.

≪Manufacturing method of paint composition≫ Suitable manufacturing methods of the coating composition include: A method for producing polyamic acid (A) by polymerizing tetracarboxylic dianhydride and diamine compound in the aforementioned solvent (S) in the presence of imidazole compound (B). Polymerization of tetracarboxylic dianhydride and a diamine compound is performed until the weight average molecular weight of polyamic acid (A) becomes 20,000 or more.

The method for polymerizing tetracarboxylic dianhydride and diamine compound is as described above.

Depending on the temperature at the time of reaction, when tetracarboxylic dianhydride and a diamine compound are reacted, the imidazole compound (B) may decompose. In this case, when preparing a paint composition from the obtained polymerization reaction liquid, a desired amount of imidazole compound (B) can be added to the polymerization reaction liquid. Also, after the polymerization reaction, the coating composition can be prepared by concentrating the polymerization reaction liquid or adding a solvent (S) to the polymerization reaction liquid.

≪Manufacturing method of polyimide resin≫ It can be formed by the forming step including forming the above-described coating composition, and A method of imidizing the formed coating composition by heating and imidizing it to produce a polyimide resin.

The shape of the paint composition to be molded when molding the paint composition is not particularly limited. The method for forming the coating composition is not particularly limited. For example, a method of injecting a coating composition into a mold having a desired shape, a method of filling a mold with a coating composition using a squeegee, or a method of coating a coating composition on a substrate may be mentioned. Among these methods, since the polyimide resin film is in great demand, or it is easy to remove the solvent (S) from the coating composition well when the polyimide resin is produced, it is preferable to coat the coating on the substrate. Method of composition. After the coating composition is applied, it is placed in a heating and/or vacuum or reduced pressure environment to dry the coating film and form a dry film.

The temperature for heating the paint composition or the paint composition after the drying step is not particularly limited as long as it is a temperature at which the polyimide resin with desired properties can be obtained. The temperature for heating polyamic acid is preferably from 120°C to 450°C, more preferably from 150°C to 435°C. By heating the paint composition at a temperature in such a range, thermal deterioration or thermal decomposition of the produced polyimide resin can be suppressed, the solvent (S) can be removed, and the polyimide resin can be produced. In addition, since it is easy to form a polyimide resin with a high glass transition temperature, excellent mechanical properties of elongation at break, low thermal expansion rate, and less coloring, the polyimide resin is kept at a temperature above 70°C and below 120°C for 10 minutes to For about 2 hours, further heating at 150° C. to 435° C. for 5 minutes to 2 hours while increasing the temperature step by step is also preferable to produce polyimide resin.

According to the production method of the polyimide resin described above, it is possible to produce a polyimide resin with less coloration and excellent mechanical properties such as elongation at break, tensile modulus of elasticity, tensile strength, and low thermal expansion. [Example]

Hereinafter, although the present invention will be described in detail through examples, the scope of the present invention is not limited to these examples.

In Examples and Comparative Examples, a compound of the following formula of an alicyclic tetracarboxylic dianhydride was used as tetracarboxylic dianhydride. In Examples and Comparative Examples, 4,4'-diaminobenzanilide, which is an aromatic diamine compound, was used as the diamine compound.

In Examples and Comparative Examples, as the imidazole compound (B), a compound of the following formula was used.

[Examples 1 to 4 and Comparative Example 1] Heat a three-neck flask with a capacity of 30mL with a heat gun to fully dry it. Next, the environment in the three-necked flask was replaced with nitrogen, and the inside of the three-necked flask was set as a nitrogen environment. In a three-necked flask, add 0.2045 g (0.90 mmol: DABAN) of 4,4'-diaminobenzylaniline and the imidazole compound (B) in the amount listed in Table 1, Further N-methyl-2-pyrrolidone (NMP) was added. The contents of the three-necked flask were stirred to obtain a slurry liquid in which aromatic diamine (DABAN) was dispersed in NMP. Still, in Comparative Example 1, no imidazole compound was used in the synthesis of polyamic acid (A). The quantity of NMP is the same mass as the total of the mass of tetracarboxylic dianhydride, and the mass of a diamine compound. Next, 0.3459 g (0.90 mmol) of the above-mentioned tetracarboxylic dianhydrides were added in the three-necked flask. Then, the content of the flask was stirred at 40° C. for 6 hours under a nitrogen atmosphere to obtain a reaction liquid. Furthermore, in the reaction liquids of Examples 1-4, the imidazole compound (B) remained as it was. In Examples 1 to 4, for the reaction solution containing the polyamic acid (A) obtained in this way, 10% by mass of polyamide was added to the total mass of the tetracarboxylic dianhydride and the mass of the diamine compound. The amount of imidazole compound (B) was 55.04 mg. Also in Comparative Example 1, after the synthesis of polyamic acid (A) was completed, imidazole was added in an amount equivalent to 10% by mass based on the total mass of the tetracarboxylic dianhydride and the mass of the diamine compound. Compound (B) 55.04 mg. Next, the reaction liquid containing polyamic acid (A) was diluted with NMP so that the density|concentration of polyamic acid (A) might become 22 mass %, and the coating composition of each Example and each comparative example was obtained. Table 1 shows the weight average molecular weight (Mw) and dispersion (Mw/Mn, where Mn is the number average molecular weight) as polystyrene-equivalent values measured by gel permeation chromatography of the obtained polyamic acid (A) .

Using the coating compositions of the various examples and comparative examples obtained as above, according to the following method, film formation of polyimide resin films was carried out, and the yellowness (YI) of the formed polyimide resin films was measured. , Light transmittance, coefficient of thermal expansion (CTE), elongation at break, tensile strength and tensile modulus of elasticity. Record these evaluation results in Table 1.

＜Film Formation Method of Polyimide Resin Film＞ On a glass substrate (100 mm in length, 100 mm in width, and 1.3 mm in thickness), the coating composition obtained as described above was spin-coated so that the thickness of the coating film after heating and hardening became 13 μm to form a coating film. Next, the glass substrate provided with the coating film was vacuum-dried under the conditions of a temperature of 50° C. and a pressure of 13 Pa to remove the solvent in the coating film. After removal of the solvent, the glass substrate provided with the coating film was put into an inert oven flowing nitrogen at a flow rate of 3 L/min. In an inert oven, under a nitrogen atmosphere, at a temperature of 80°C, let stand for 0.5 hours, then stand at a temperature of 300°C for 0.5 hours, and then heat at a temperature of 430°C (final heating temperature) for 5 minutes, so that The coating film was cured to obtain a polyimide-coated glass coated with a thin film (polyimide film) made of polyimide. The obtained polyimide-coated glass was immersed in hot water at 90°C, and the polyimide film was peeled off from the glass substrate to obtain a polyimide film (100 mm in length, 100 mm in width, and 13 μm in thickness) .

＜Yellowness (YI), light transmittance＞ The values (unit: %) and yellowness (YI) of the light transmittance (unit: %) and the yellowness (YI) of the polyimide film of each embodiment and the comparative example are obtained by using the trade name "haze meter NDH" manufactured by Nippon Denshoku Industries Co., Ltd. -5000" was used as a measuring device, and it was determined in accordance with JIS K7361-1 (issued in 1997). The light transmittance is the value at the wavelength of light from 380nm to 780nm. Regarding the degree of yellowness, the evaluation results are judged according to the following criteria. ⊚: YI value is less than 4.0. 〇: YI value is not less than 4.0 and not more than 5.0. ×: YI value exceeds 5.0.

＜Coefficient of Thermal Expansion (CTE)＞ From the polyimide films of the respective examples and comparative examples, a film for measurement having a size of 20 mm in length and 5 mm in width was formed. Next, by using a thermomechanical analyzer (trade name "TMA-60" manufactured by Shimadzu Corporation) as a measurement device, the obtained thin film for measurement was measured under a nitrogen atmosphere at a temperature increase rate of 10°C/ Changes in the length of the sample at 100°C to 400°C when the temperature is raised from 30°C to 200°C, once cooled to 30°C, and then heated from 30°C to 500°C at a heating rate of 10°C/min. , Obtain the average value of the change in length per 1°C between 100°C and 400°C. Still, the tensile mode was set at 49mN.

＜Elongation at break, tensile strength and tensile modulus＞ For the polyimide films of the respective examples and comparative examples, a product named "SUPER" manufactured by DUMBBEL Co., Ltd. was installed on an SD-type lever type sample cutter (a cutter made by DUMBBEL Co., Ltd. (type SDL-200)). DUMBBELL CUTTER (type: SDMK-1000-D, in accordance with A22 standard of JIS K7139 (issued in 2009))", the size of the polyimide film becomes the overall length: 75mm, the distance between the label parts: 57mm, the length of the parallel part: 30mm, radius of shoulder: 30mm, width of end: 10mm, width of central parallel part: 5mm, thickness: 13μm, and the test piece of DUMBBEL shape (except that the thickness is set to 13μm, according to A test piece conforming to the standard of JIS K7139 type A22 (reduced scale test piece)) was prepared as a measurement sample. Next, using a tension-type universal testing machine (model "UCT-10T" manufactured by A&D Co., Ltd.), the measurement sample was made so that the width between the grips became 57mm and the width of the pinched part became 10mm (full width of the end) After the configuration is carried out, under the conditions of full load scale: 0.05kN and test speed: 1-300mm/min, carry out the tensile test of the tensile measurement sample, and obtain the values of tensile strength, elongation at break and tensile elastic modulus . The above test is based on the test of JIS K7162 (published in 1994). In addition, the value (%) of the elongation at break is based on the length of the parallel portion of the test piece (=length of the parallel portion: 30mm) as L0, and the length of the parallel portion of the test piece until it breaks (test piece at the time of breakage) The length of the parallel part: 30mm+α) is defined as L, and the following formula is calculated: [Elongation at break (%)]={(L-L0)/L0}×100 Find out. Regarding the elongation at break, the evaluation results were judged on the basis of the following criteria. ◎: The elongation at break exceeds 15%. 〇: Elongation at break is 10% or more and 15% or less. ×: Elongation at break is less than 10%.

According to Table 1, it is understood that the polyamic acid (A) with a combined weight average molecular weight of 20,000 or more, the imidazole compound (B) with the above-mentioned specific structure, and the content of urea-based solvent (S1) are 0% by mass or more. When the coating composition of the example containing the solvent (S) is 10% by mass or less, a polyimide resin having less coloring and excellent mechanical properties can be formed. On the other hand, according to Comparative Examples, when the weight average molecular weight of the polyamic acid (A) is less than 20,000, the obtained polyimide resin is colored and mechanical properties such as elongation at break are lowered. Also, from the comparison of Examples and Comparative Examples, it is understood that in the solvent (S) whose content of the urea-based solvent (S1) is 0% by mass to 10% by mass, the imidazole compound ( In the presence of B), polymerize tetracarboxylic dianhydride and diamine compound to obtain polyamic acid with high molecular weight.

Claims (8)

A coating composition, characterized by comprising polyamic acid (A), imidazole compound (B), and solvent (S), the weight average molecular weight of the aforementioned polyamic acid (A) is more than 20,000, and the aforementioned imidazole compound ( B) is a compound represented by the following formula (1), (In formula (1), R ¹ is a hydrogen atom or an alkyl group, R ² is an aromatic group that may have a substituent, R ³ is an alkylene group that may have a substituent, and R ⁴ is independently a halogen atom, a hydroxyl group, Mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfonate group, phosphine group, phosphinyl group, phosphonate group or organic group, n is an integer between 0 and 3) including >N The ratio of the mass of the urea-based solvent (S1) in the urea skeleton represented by -CO-N< to the mass of the solvent (S) is 0% by mass or more and 10% by mass or less. The coating composition according to claim 1, wherein the aforementioned polyamic acid (A) is a polymer of alicyclic tetracarboxylic dianhydride (A1) and aromatic diamine compound (A2). The coating composition according to claim 2, wherein the aforementioned alicyclic tetracarboxylic dianhydride (A1) comprises a compound represented by the following formula (a2), (In formula (a2), R ^a11 , R ^a12 and R ^a13 are each independently selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, and a fluorine atom, and a is 0 or more an integer below 12). The coating composition according to any one of claims 1 to 3, wherein the aromatic diamine compound (A2) is one or more compounds selected from the following formulas (21) to (24), (In the formulas (21) to (24), ^R111 represents a group consisting of a hydrogen atom, a fluorine atom, a hydroxyl group, an alkyl group with 1 to 4 carbon atoms, and a halogenated alkyl group with 1 to 4 carbon atoms. One of the group, in formula (24), Q represents 9,9'-fenylene, or is selected from the formula: -C ₆ H ₄ -, -CONH-C ₆ H ₄ -NHCO-, -NHCO- C ₆ H ₄ -CONH-, -OC ₆ H ₄ -CO-C ₆ H ₄ -O-, -OCO-C ₆ H ₄ -COO-, -OCO-C ₆ H ₄ -C ₆ H ₄ -COO- , -OCO-, -O-, -S-, -CO-, -CONH-, -SO ₂ -, -C(CF ₃ ) ₂ -, -C(CH ₃ ) ₂ -, -CH ₂ -, - OC ₆ H ₄ -C(CH ₃ ) ₂ -C ₆ H ₄ -O-, -OC ₆ H ₄ -C(CF ₃ ) ₂ -C ₆ H ₄ -O-, -OC ₆ H ₄ -SO ₂ - C ₆ H ₄ -O-, -C(CH ₃ ) ₂ -C ₆ H ₄ -C(CH ₃ ) ₂ -, -OC ₁₀ H ₆ -O-, -OC ₆ H ₄ -C ₆ H ₄ -O - and -OC ₆ H ₄ -O- is one of the group consisting of groups represented by -C ₆ H ₄ - is phenylene, -C ₁₀ H ₆ - is naphthalenediyl). The coating composition according to claim 4, wherein the aforementioned aromatic diamine compound (A2) includes a compound represented by the aforementioned formula (24). The coating composition according to Claim 5, wherein the above-mentioned aromatic diamine compound (A2) is represented by the above-mentioned formula (24), and the above-mentioned Q is a compound of -CONH-. A method for producing a coating composition, which is a method for producing a coating composition comprising polyamic acid (A), an imidazole compound (B), and a solvent (S), characterized in that it comprises tetracarboxylic dianhydride, Polymerize with diamine compound in the aforementioned solvent (S) in the presence of imidazole compound (B) to generate the aforementioned polyamic acid (A). The aforementioned imidazole compound (B) is represented by the following formula (1): compound, (In formula (1), R ¹ is a hydrogen atom or an alkyl group, R ² is an aromatic group that may have a substituent, R ³ is an alkylene group that may have a substituent, and R ⁴ is independently a halogen atom, a hydroxyl group, Mercapto group, sulfide group, silyl group, silanol group, nitro group, nitroso group, sulfonate group, phosphine group, phosphinyl group, phosphonate group or organic group, n is an integer between 0 and 3) including >N The ratio of the mass of the urea-based solvent (S1) of the urea skeleton represented by -CO-N< to the mass of the solvent (S) is 0% by mass or more and 10% by mass or less, and the aforementioned diamine component and the aforementioned tetracarboxylic acid The superposition|polymerization of a dianhydride component is performed until the weight average molecular weight of the said polyamic acid (A) becomes 20,000 or more. A method for producing a polyimide resin, comprising a step of forming the aforementioned coating composition according to any one of claims 1 to 6, and An imidization step of heating the shaped coating composition to imidize it.