JPH10120783A - Polyamic acid and polyimide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyamic acid, capable of giving a polyimide low in dielectricity and excellent in heat resistance and solubility in various kinds of solvents by adding specific repeating units and adjusting the logarithmic viscosity within a specific range. SOLUTION: This polyamic acid contains repeating units of formula I A is bis(trifluoromethyl)methylene, a group of formula II [(b) is 1-3], a group of formula III [R<3> , R<4> are each a halogen, a 1-6C (halogenated) alkyl, a 5-12C (halogenated) cyclloalkyl, a 1-6C (halogenated) alkoxy; X is a single bond, O; (c) is 0-4]; R<1> , R<2> are each R<3> ; (a) is 0-3}, and has a logarithmic viscosity of 0.1-4dl/g (solvent: N, N-dimethylformamide, at 30 deg.C, a concentraction of 0.5g/dl). The compound is obtained by polycondensing 9,9-bis[4-(4-aminophenoxy) phenyl]fluorene with a compound of formula IV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyimide having a low dielectric constant and particularly useful as an interlayer insulating film of an LSI.
And a polyamic acid capable of forming the polyimide.

[0002]

2. Description of the Related Art LSIs (Large Scale Integrated Circuits) are continually becoming more highly integrated, multifunctional, and more sophisticated with the progress of fine processing technology. As a result, the circuit resistance and the capacitance between the wirings (hereinafter referred to as “parasitic resistance” and “parasitic capacitance”, respectively) increase, and not only the power consumption increases, but also the delay time for the input signal increases. However, this is a major factor in reducing the signal speed of the device, and the solution is a major issue. As a measure to suppress such a decrease in signal speed, it is conceivable to reduce the parasitic resistance and the parasitic capacitance. One of the measures is to reduce the parasitic capacitance by covering the periphery of the wiring with an interlayer insulating film having a low dielectric constant. Trying to respond to faster devices. As a specific example, attempts have been made to replace a silicon oxide film, which is a conventional typical interlayer insulating film, with an organic film. It is necessary to have heat resistance that can withstand post-processes such as chip connection and pinning in addition to the thinning process. As a typical low dielectric organic material, a fluororesin represented by polytetrafluoroethylene is known, but the fluororesin has insufficient heat resistance. Also, polyimide is known as an organic material having high heat resistance,
In particular, J. Polymer Sci., Part A: Polymer Chemistry, V
ol. 31, 2153-2163 (1993) includes 9,9-bis [4- (4
-Aminophenoxy) phenyl] fluorene, pyromellitic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 3,3', 4,4'-diphenylsulfonetetracarboxylic dianhydride Anhydride, 3,3 ',
Polyimides obtained from 4,4'-benzophenonetetracarboxylic dianhydride or 3,3 ', 4,4'-diphenylethertetracarboxylic dianhydride are disclosed, but the relative dielectric constant of these conventional polyimides is disclosed. Is 2.9
About 3.5, which is L
It is not satisfactory as an interlayer insulating film of SI.

[0003]

SUMMARY OF THE INVENTION The present invention has been made on the background of the above-mentioned prior art, and its object is to provide a low dielectric constant, high heat resistance, and low solubility in various solvents. Another object of the present invention is to provide an excellent polyimide and a polyamic acid capable of forming the polyimide.

[0004]

The gist of the present invention is as follows.
Contains at least one type of repeating unit represented by the following general formula (1), and has a logarithmic viscosity [ηinh] (N, N-
Dimethylformamide solvent, 30 ° C, concentration 0.5g / dl
) Is 0.1 to 4 dl / g.

[0005]

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[In the general formula (1), A is

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[0007]

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[0008] or

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Wherein R ¹ , R ² , R ³ and R ⁴ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms,
X represents a cycloalkyl group having 12 carbon atoms, a halogenated cycloalkyl group having 5 to 12 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms or a halogenated alkoxyl group having 1 to 6 carbon atoms;
Represents a single bond or -O-, and each a is independently 0
B is an integer of 1 to 3, each c is an integer of 0 to 4 independently of each other. ]

The gist of the present invention is, secondly, that it contains at least one kind of repeating unit represented by the following general formula (2), and has a logarithmic viscosity [ηinh] (m-cresol solvent,
(0 ° C., concentration 0.5 g / dl) of 0.1 to 4 dl / g.

[0011]

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[In the general formula (2), A is

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[0013]

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Or

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Wherein R ¹ , R ² , R ³ and R ⁴ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms, a halogenated alkyl group having 1 to 6 carbon atoms,
X represents a cycloalkyl group having 12 carbon atoms, a halogenated cycloalkyl group having 5 to 12 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms or a halogenated alkoxyl group having 1 to 6 carbon atoms;
Represents a single bond or -O-, and each a is independently 0
B is an integer of 1 to 3, each c is an integer of 0 to 4 independently of each other. ]

Hereinafter, the present invention will be described in detail. Polyamic acid The polyamic acid of the present invention contains a repeating unit represented by the general formula (1). In the polyamic acid of the present invention, A, R ¹ , R ^{2 of the} general formula (1)
Alternatively, each a may contain two or more types of repeating units different from each other, and in this case, the two or more types of repeating units can be bonded to the polyamic acid molecular chain in a random or block manner. .

In the general formula (1), R ¹ , R ² , R ³
Examples of the halogen atom for R ⁴ include a fluorine atom, a chlorine atom, and a bromine atom. Examples of the alkyl group or the halogenated alkyl group include:
Methyl group, ethyl group, n-propyl group, i-propyl group, n-butyl group, i-butyl group, sec-butyl group,
Examples thereof include a t-butyl group and the like, and halogenated derivatives thereof. Examples of the cycloalkyl group or the halogenated cycloalkyl group include, for example, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, and the like. Halogenated derivatives,
Examples of the alkoxyl group or halogenated alkoxyl group include, for example, methoxy group, ethoxy group, n-propoxy group, i-propoxy group, n-butoxy group, i-butoxy group, sec-butoxy group, t-butoxy group, These halogenated derivatives can be mentioned. As the polyamic acid in the present invention, particularly, A of the general formula (1)

[0018]

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[0019]

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Or

[0021]

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Wherein a is 0.

The polyamic acid of the present invention comprises, for example, 9,9-bis [4- (4-aminophenoxy) phenyl] fluorene represented by the following formula (3) and the following general formula (4)
Can be usually produced by polycondensation with at least one kind of tetracarboxylic dianhydride represented by the following formula in an appropriate organic solvent.

[0024]

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[0025]

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[0026] [A in the general formula (4), R ^1, R ² and a are each A, same as R ^1, R ² and a formula (1). However, in the present invention, at least one other diamine and / or at least one other tetracarboxylic dianhydride can be used in combination as long as the desired effect is not impaired. In this case, the amount of other diamine or other tetracarboxylic dianhydride used is 9,9-
With respect to bis [4- (4-aminophenoxy) phenyl] fluorene or the tetracarboxylic dianhydride represented by the general formula (4), each is usually 50 mol% or less, preferably 30 mol% or less, The content of the repeating unit represented by the general formula (1) in the polyamic acid is preferably at least 50 mol%. As the organic solvent used when producing the polyamic acid of the present invention, those that are inert to the diamine component and the tetracarboxylic dianhydride component used and dissolve these are used, Specifically, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 1,2-dimethoxyethane, bis (2- Methoxyethyl) ether, 1,2-bis (2-
Methoxyethoxy) ethane, tetrahydrofuran, 1,
3-dioxane, 1,4-dioxane, pyridine, picoline, dityl sulfoxide, dimethyl sulfone, tetramethylurea, o-cresol, m-cresol, p-cresol, o-chlorophenol, m-chlorophenol, p-chlorophenol And the like. These organic solvents can be used alone or in combination of two or more. The reaction temperature at the time of producing the polyamic acid of the present invention is usually 60 ° C. or lower, preferably room temperature to 50 ° C., and the reaction pressure is not particularly limited, and the reaction can be usually performed at normal pressure. The reaction time is usually 0.5
~ 24 hours. In addition, the concentrations of the diamine component and the tetracarboxylic dianhydride component during the reaction can be appropriately adjusted, but the total weight of both components is usually 2 to 50% by weight, preferably 2 to 50% by weight, and preferably the total solution weight. 5-30% by weight
It is. Logarithmic viscosity of the polyamic acid of the present invention [ηinh]
(N, N-dimethylformamide solvent, 30 ° C., concentration 0.5 g / dl) is 0.1 to 4 dl / g, preferably 0.3 to 2 dl / g.

Polyimide The polyimide of the present invention contains a repeating unit represented by the general formula (2). The polyimide of the present invention can be produced by dehydrating and ring-closing the polyamic acid containing the repeating unit represented by the general formula (1) to imidize the polyamic acid. At the time of the imidization, a heat imidation method or a chemical imidization method can be employed. As the heat imidization method, for example, a method in which a polyamic acid solution is cast on a substrate having a smooth surface such as glass or metal and heated, or a method in which the polyamic acid solution is directly heated is applied. As the solvent for the polyamic acid solution in these methods, for example, the same organic solvents as those used for producing polyamic acid can be mentioned. In the above-mentioned heat imidization method, a film-like polyimide can be obtained by heating a thin film formed by casting a polyamic acid solution on a substrate under normal pressure or reduced pressure. The heating temperature in this case is usually 100 to 450
℃, preferably 150 to 400 ℃, it is preferable to gradually increase the temperature during the reaction. In the above-mentioned heat imidization method, the polyimide is obtained as a powder or a solution by heating the polyamic acid solution. The heating temperature in this case is usually 80 to 300 ° C, preferably 100 to 250 ° C. In the heat imidization method, a component which azeotropes with water and which can be easily separated from water especially outside the reaction system, for example, benzene, toluene, xylene, etc. May be present as a dehydrating agent. In addition, in the heat imidization method, tertiary amines, for example, aliphatic tertiary amines such as trimethylamine, triethylamine, tripropylamine, and tributylamine; N, N-dimethylaniline, to promote dehydration ring closure Tertiary amines such as pyridine, quinoline and isoquinoline, and a catalyst such as aromatic tertiary amines such as pyridine, quinoline and isoquinoline, for example, 10 to 400 parts by weight per 100 parts by weight of polyamic acid. It can also be used.

Next, as the chemical imidization method, for example, a method in which a ring closing agent for dehydrating and cyclizing a polyamic acid is used to form a polyimide in a solution state is employed, and the polyimide is obtained as a powder or a solution. Examples of the solvent used in this method include, for example, the same organic solvents as those used in the production of polyamic acid.
Examples of the ring closing agent used in the chemical imidation method include acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride. These ring-closing agents can be used alone or as a mixture of two or more kinds. The amount of the ring-closing agent is usually 2 to 100 mol per mol of the repeating unit represented by the general formula (1), Preferably it is 2 to 50 mol. The reaction temperature in the chemical imidation method is usually 0 to 200 ° C. In the chemical imidization method, a tertiary amine can be used as a catalyst as in the case of the thermal imidization method. When the polyimide is obtained as a powder by the heat imidization method or the chemical imidization method, the polyimide powder can be separated and recovered from the medium by an appropriate method such as filtration, spray drying, or steam distillation.

Logarithmic viscosity [ηinh] of the polyimide of the present invention
(M-cresol solvent, 30 ° C., concentration 0.5 g / dl)
Is 0.1 to 4 dl / g, preferably 0.3 to 2 dl
/ G. The polyimide of the present invention has a low dielectric constant and high heat resistance, and its relative dielectric constant (1 MHz) is usually 3.0.
Or less, preferably 2.9 or less, and the 5% by weight weight reduction temperature (in a nitrogen atmosphere) is usually 400 ° C. or more, preferably 500 ° C. or more. Moreover, the polyimide of the present invention has excellent solubility in various solvents. Therefore, the polyimide of the present invention can be very suitably used especially as an interlayer insulating film in an LSI,
It is also useful as a general insulating material, a heat-resistant material, and the like. When an interlayer insulating film is formed from the polyimide of the present invention, a varnish or paste of the polyamic acid, which is a precursor thereof, a film of the polyimide, and the like are used. An example of a method of forming the interlayer insulating film is as follows. (A) A varnish of a polyamic acid is cast between layers of the device, and an excess solvent in the varnish is removed under heating and / or reduced pressure to form a thin film of the polyamic acid. A method in which the polyamic acid is dehydrated and ring-closed under a normal pressure or under pressure to imidize the polyamic acid; (b) a film-like polyimide is arranged between layers of the device; for example, at 100 to 450 ° C. under normal pressure or under pressure. How to crimp. As a method for obtaining polyimide in the form of a film, for example, (c) a varnish of polyamic acid is cast on a substrate which has been subjected to a release treatment in advance, for example, a substrate of glass, Teflon, polyester, or the like, and is gradually heated. And dehydration ring closure and imidization while removing the solvent, and (d) a method of molding the polyimide powder into a film by an appropriate method such as press molding or injection molding. It is not limited to these.

[0030]

Embodiments of the present invention will be described below more specifically with reference to examples. However, the present invention is not limited to these embodiments.

【Example】

Example 1 Production of Polyamic Acid Nitrogen gas was passed through a container equipped with a stirrer, a reflux condenser and a nitrogen gas inlet tube, and the inside of the container was sufficiently replaced with nitrogen gas.
After 276.8 g of N, N-dimethylformamide was added, 26.633 g (50 mmol) of 9,9-bis [4- (4-aminophenoxy) phenyl] fluorene was added and dissolved sufficiently at room temperature. Then, 22,213 g (50 mmol) of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride was added,
The mixture was stirred at room temperature for 5 hours to obtain a polyamic acid solution.
The logarithmic viscosity [ηinh] (N, N-dimethylformamide solvent, 30 ° C., 0.5 g / dl) of this polyamic acid was 1.31 dl / g as measured as follows. Infrared absorption spectrum (IR) of this polyamic acid
Is shown in FIG. <Measurement of logarithmic viscosity [ηinh]> Using an Ubbelohde viscometer, it was calculated by the formula ln (t / t ₀ ) / c. However, t is the transit time between the marked lines of the polyamic acid solution, t ₀ is N, N- dimethylformamide transit time between the marked lines of the solvent, c is the concentration of the polyamic acid solution (0.5g / dl). Production of Polyimide (i) The solution of the polyamic acid was applied on a SUS304 substrate by spin coating,
While sequentially heating to 0 ° C, 200 ° C, 250 ° C, and 300 ° C, each temperature was heated for 20 minutes to form a polyimide film. Thereafter, a gold electrode was formed on the polyimide film by mask evaporation, and the relative dielectric constant (ε) was measured as a sample for relative dielectric constant measurement as follows. As a result, ε = 2.82, which was a sufficiently low value. <Measurement of relative dielectric constant (ε)> 1 MH of polyimide film
The capacitance at z was measured with an LCR meter 4284A manufactured by Yokogawa Hewlett-Packard Co., Ltd., and the relative dielectric constant (ε) was determined by the following equation. Here, C is the capacitance, d is the film thickness, ε ₀ is the dielectric constant in vacuum, and S is the area of the upper electrode. (Ii) After the solution of the polyamic acid is cast on a glass substrate, the solution is heated to 80 ° C, 140 ° C, 200 ° C,
While sequentially heating to 50 ° C. and 300 ° C., each was heated at each temperature for 20 minutes to form a polyimide film, and the glass transition temperature (Tg) and 5% weight loss temperature (Td5) were measured as described below. . As a result, Tg = 293 ° C., Td5 = 53
It was 4 ° C, and it was confirmed that the composition had high heat resistance. FIG. 2 shows the infrared absorption spectrum (IR) of this polyimide. <Measurement of glass transition temperature (Tg)> Differential scanning calorimeter (DS
According to C), the measurement was performed at a heating temperature of 20 ° C./min in a nitrogen atmosphere. <Measurement of 5% Weight Loss Temperature (Td5)> Using a thermobalance, heating was performed in nitrogen at a heating rate of 10 ° C./min, and the temperature at which 5% weight loss was observed was measured.

Example 2 Production of Polyimide A nitrogen gas was flowed into a container equipped with a stirrer, a reflux condenser and a nitrogen gas inlet tube, and the inside of the container was sufficiently replaced with nitrogen gas.
After adding 276.8 g of m-cresol, 22.213 g (50 mmol) of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride was added and dissolved sufficiently at 100 ° C. Then, 9,9-bis [
4- (4-aminophenoxy) phenyl] fluorene 2
6.633 g (50 mmol) was added and stirred at 160 ° C. for 5 hours to obtain a polyimide solution. Logarithmic viscosity [ηinh] of this polyimide (m-cresol solvent, 30 ° C.,
0.5 g / dl) was measured in the same manner as in Example 1 except that the solvent was changed, and it was 0.72 dl / g. Further, the polyimide solution was diluted with m-cresol so that the polyimide concentration was 3% by weight, and then poured into a 10-fold volume of methanol to precipitate the polyimide. Thereafter, the deposited precipitate was separated by filtration and dried to obtain a polyimide powder. This polyimide powder contains N, N-dimethylformamide, N, N-dimethylacetamide, N
-Methyl-2-pyrrolidone, dimethyl sulfoxide, m
-Soluble in cresol and o-chlorophenol.

Example 3 Preparation of polyamic acid Instead of 22,213 g (50 mmol) of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 4,4'-bis (3,3 4-dicarboxyphenoxy) octafluorobiphenyl dianhydride 3
A polyamic acid solution was obtained in the same manner as in Example 1 except that 1.117 g (50 mmol) was used. About this polyamic acid, logarithmic viscosity [ηinh] (N, N-dimethylformamide solvent, 3
0 ° C., 0.5 g / dl) was measured to be 0.53 dl /
g. FIG. 3 shows the infrared absorption spectrum (IR) of this polyamic acid. Production of Polyimide A polyimide film was formed using the above polyamic acid in the same manner as in Example 1, and the relative dielectric constant (ε), glass transition temperature (Tg), and 5% weight loss temperature (Td5) were measured. As a result, ε = 2.85, Tg = 284 ° C., Td5
= 541 ° C, it was confirmed that the relative dielectric constant was sufficiently low and the heat resistance was excellent. FIG. 4 shows the infrared absorption spectrum (IR) of this polyimide.

Example 4 Preparation of Polyimide Instead of 22.213 g (50 mmol) of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 4,4'-bis (3,4 -Dicarboxyphenoxy) octafluorobiphenyl dianhydride 3
A polyimide powder was obtained in the same manner as in Example 2 except that 1.117 g (50 mmol) was used. This polyimide powder was soluble in N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, m-cresol, and o-chlorophenol.

Example 5 Preparation of polyamic acid Instead of 22,213 g (50 mmol) of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 9,9-bis [4- ( 3,4-dicarboxyphenoxy) phenyl] fluorene dianhydride 3
A polyamic acid solution was obtained in the same manner as in Example 1 except that 2.131 g (50 mmol) was used. About this polyamic acid, logarithmic viscosity [ηinh] (N, N-dimethylformamide solvent, 3
0 ° C., 0.5 g / dl) was measured to be 0.47 dl /
g. FIG. 5 shows the infrared absorption spectrum (IR) of this polyamic acid. Production of Polyimide A polyimide film was formed using the above polyamic acid in the same manner as in Example 1, and the relative dielectric constant (ε), glass transition temperature (Tg), and 5% weight loss temperature (Td5) were measured. As a result, ε = 2.77, Tg = 284 ° C., Td5 =
It was 543 ° C., and it was confirmed that the relative dielectric constant was sufficiently low and the heat resistance was excellent. FIG. 6 shows the infrared absorption spectrum (IR) of this polyimide.

Example 6 Preparation of Polyimide Instead of 22,213 g (50 mmol) of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, 9,9-bis [4- (3 , 4-Dicarboxyphenoxy) phenyl] fluorene dianhydride 3
A polyimide powder was obtained in the same manner as in Example 2 except that 2.131 g (50 mmol) was used. This polyimide powder was soluble in N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, m-cresol, and o-chlorophenol.

Comparative Example 1 3.3 ', 4,4'-biphenyltetracarboxylic acid was used instead of 22.213 g (50 mmol) of 2,2-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride 14.711 g (50 mmol) of acid dianhydride
A polyamic acid solution was obtained in the same manner as in Example 1 except for using. Using this polyamic acid solution, a polyimide film was formed in the same manner as in Example 1, and the relative dielectric constant (ε), glass transition temperature (Tg), and 5% weight loss temperature (Td5) were measured. As a result, ε = 2.95,
Tg = 302 ° C. and Td5 = 567 ° C., and the heat resistance was good, but the relative dielectric constant was high, and it was not satisfactory as an interlayer insulating film of LSI.

[0037]

The polyimide of the present invention has a low dielectric constant, high heat resistance, and excellent solubility in various solvents. Therefore, the polyimide of the present invention,
It can be used very suitably as an insulating material, a heat-resistant material, and the like for various electronic and electric devices. In particular, a highly reliable device capable of coping with high speed can be provided as an interlayer insulating film of an LSI.

[Brief description of the drawings]

FIG. 1 shows IR of a polyamic acid obtained according to Example 1.
FIG.

FIG. 2 is a view showing an IR of the polyimide obtained in Example 1.

FIG. 3 IR of polyamic acid obtained according to Example 3
FIG.

FIG. 4 is a view showing an IR of the polyimide obtained in Example 3.

FIG. 5: IR of polyamic acid obtained in Example 5
FIG.

FIG. 6 is a view showing an IR of the polyimide obtained in Example 5.

Claims (2)

[Claims] 1. A composition comprising at least one type of repeating unit represented by the following general formula (1) and having a logarithmic viscosity [ηinh]
(N, N-dimethylformamide solvent, 30 ° C., concentration 0.5 g / dl) Polyamic acid having a concentration of 0.1 to 4 dl / g. Embedded image [In the general formula (1), A is , Or Wherein R ¹ , R ² , R ³ and R ⁴ are each independently a halogen atom, an alkyl group having 1 to 6 carbon atoms,
6, a halogenated alkyl group, a cycloalkyl group having 5 to 12 carbon atoms, a cycloalkyl group having 5 to 12 carbon atoms, an alkoxyl group having 1 to 6 carbon atoms or 1 to 6 carbon atoms
X represents a single bond or -O-, each a is independently an integer of 0-3, b
Is an integer of 1 to 3, and each c is an integer of 0 to 4 independently of each other. ] 2. It comprises at least one kind of repeating unit represented by the following general formula (2), and has a logarithmic viscosity [ηinh].
(M-cresol solvent, 30 ° C., concentration 0.5 g / dl) A polyimide having a concentration of 0.1 to 4 dl / g. Embedded image [In the general formula (2), A represents ## STR2 ## or R ¹ , R ¹ , R ² , R ³ and R ⁴ are each independently a halogen atom and a carbon atom of 1; -6 alkyl groups, halogenated alkyl groups having 1-6 carbon atoms, cycloalkyl groups having 5-12 carbon atoms, halogenated cycloalkyl groups having 5-12 carbon atoms, alkoxyl groups having 1-6 carbon atoms or carbon atoms X represents a single bond or -O-, each a is independently an integer of 0-3, b is an integer of 1-3, each c is independently of each other, Then 0-4
Is an integer. ]