JP2002167433A - Polyimide and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a polyimide with low dielectric constant, low linear thermal expansion coefficient, high solder heat resistance and enough toughness and a precursor thereof. SOLUTION: The polyimide precursor is obtained by comprising a recurring unit represented by formula (1) of (x) molar fraction [x is 0<x<1] and a unit represented by formula (2) of (y) molar fraction [y is 0<y<1] and having 0<x+y<=1. The polyimide is obtained by the dehydration of the precursor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

2. Description of the Related Art In general, polyimide is easily reacted by equimolar reaction between an aromatic tetracarboxylic dianhydride such as pyromellitic anhydride and an aromatic diamine such as diaminodiphenyl ether in an aprotic polar solvent such as dimethylacetamide. The obtained polyimide precursor having a high degree of polymerization is formed into a film or the like and cured by heating. Such a wholly aromatic polyimide has excellent properties such as excellent heat resistance, chemical resistance, radiation resistance, electrical insulation, and mechanical properties. Currently, it is widely used for various electronic devices such as a protective film of a semiconductor element and an interlayer insulating film of an integrated circuit.

In recent years, in particular, increasing the operation speed of a microprocessor and shortening the rise time of a clock signal have become important issues in the field of information processing and communication. For this purpose, polyimide used as an interlayer insulating film has been used. It is necessary to lower the dielectric constant of the film.

In order to lower the dielectric constant of polyimide, a fluorine group is introduced into the polyimide structure (Macromolecule).
es, 24, 5001 (1991)), or by replacing aromatic units with alicyclic units to reduce π electrons, thereby preventing intramolecular conjugation and charge transfer complex formation (Macromolecule).
s, 32, 4933 (1999)).

On the other hand, when a polyimide film is laminated on a metal substrate such as copper as an interlayer insulating film, residual stress is generated due to a mismatch between respective linear thermal expansion coefficients, and curling,
It is known to cause serious problems such as peeling and cracking of the film. In order to avoid this problem, it is necessary to make the linear thermal expansion coefficient of the polyimide film close to that of the metal substrate, that is, to reduce the thermal expansion of the polyimide film. Most currently known polyimides have a linear thermal expansion coefficient of 40 to 80 ppm / K,
It is much higher than 18ppm / K of copper plate. Recently, with the increase in the density of electronic circuits, the necessity of multi-layer wiring boards has been increasing. However, the residual stress in the multi-layer boards significantly reduces the reliability of devices.

[0005] It is known that in order to develop low thermal expansion of polyimide, it is generally necessary that the main chain structure is linear and internal rotation is restricted (Polymer, 28, 2282 (1)
987)). Currently practical low thermal expansion polyimide materials
Polyimides formed from 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and paraphenylenediamine are known.

[0006] However, it is not easy to obtain a polyimide having a low dielectric constant and a low coefficient of thermal expansion at the same time and maintaining solder heat resistance. Although low-permittivity aromatic polymer materials other than polyimide are also being studied, at present the required properties are not sufficiently satisfied in terms of thermal expansion coefficient and heat resistance. The introduction of a fluorine group into the polyimide structure weakens the intermolecular interaction, and tends to hinder the molecular orientation during imidization, which is a cause of low thermal expansion.

The introduction of alicyclic structural units also has the problem that the linearity of the polyimide main chain is reduced and the coefficient of thermal expansion is increased. For example, when a highly flexible alicyclic diamine such as 4,4'-methylenebis (cyclohexylamine) is used, polymerization easily proceeds with various acid dianhydrides, and a polyamic acid having a high degree of polymerization is produced. The polyimide film obtained by heating has a very high coefficient of linear thermal expansion.

As a tetracarboxylic acid component, 21,51 g of 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and as a diamine component, 5.93 g of p-phenylenediamine and 4,
A polymer obtained from 17.56 g of 4'-diamino-2,2'-bis (trifluoromethyl) biphenyl was disclosed in JP-A-8-361.
No. 83 is disclosed.

[0009]

SUMMARY OF THE INVENTION The present invention provides a polyimide having a low dielectric constant, a low coefficient of linear thermal expansion, a sufficiently high soldering heat resistance and a sufficient toughness, a precursor thereof, and a method for producing the same.

[0010]

Means for Solving the Problems In view of the above problems, intensive studies have been conducted to find that relatively linear trans-1,4-diaminocyclohexane having an alicyclic structural unit can be converted to a highly linear tetracarboxylic acid. It was expected that a polyimide having a low dielectric constant and a low coefficient of linear thermal expansion could be obtained by reacting with a derivative, but 1,2,3,
When 4-cyclobutanetetracarboxylic dianhydride was used, formation of a strong complex salt occurred at the beginning of the polymerization reaction, and it was found that the polymerization reaction did not proceed at all. When polymerized with a composition containing 2,3,4-cyclobutanetetracarboxylic dianhydride, 1,4-diaminocyclohexane as a diamine and 2,2′-bis (trifluoromethyl) benzidine as a copolymerization component, the above-mentioned purpose is obtained. It was found that a polyimide capable of achieving the above was obtained, and the present invention was completed.

That is, the present invention provides a polyimide precursor having a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2):

[0012]

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[0013]

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And a polyimide having a repeating unit represented by the following formula (3) and a repeating unit represented by the following formula (4).

[0015]

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[0016]

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The present invention also relates to a process for producing a polyimide precursor, comprising reacting a substantially equimolar diamine component and a tetracarboxylic acid component in a polymerization solvent, wherein at least 1,2,3,4 1 mol of a tetracarboxylic acid component containing -cyclobutanetetracarboxylic dianhydride and x mol of 2,2'-bis (trifluoromethyl) benzidine [x represents 0 <x <1. Is dissolved and reacted, and then the 1,4-
Diaminocyclohexane y mol [y represents 0 <y <1, and 0 <x + y ≦ 1. And a method for producing a polyimide comprising dehydrating the polyimide precursor.

In order to reduce the thermal expansion of the polyimide of the present invention, it is particularly desirable that the diamine component 1,4-diaminocyclohexane has a steric structure of trans type shown in Chemical formula 9 and both amino groups have an equatorial configuration. . The use of cis 1,4-diaminocyclohexane may not contribute to a decrease in linear thermal expansion coefficient due to its bent structure.

[0019]

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The 1,2,3,4-cyclobutanetetracarboxylic dianhydride, which is an acid dianhydride monomer of the tetracarboxylic acid component, is particularly preferably of the anti-configuration shown in Chemical formula 10. The use of syn-type 1,2,3,4-cyclobutanetetracarboxylic dianhydride may not contribute to a decrease in linear thermal expansion coefficient due to its bent structure.

[0021]

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[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

In the polyimide precursor of the present invention, the repeating unit represented by the formula (1) contains a molar fraction x [x, where 0 <x <1. And the repeating unit represented by the formula (2)
[Y represents 0 <y <1. ]. Where x
And y are 0 <x + y ≦ 1. Further, it is preferable that x ≦ y and / or x + y = 1.

The polyimide precursor of the present invention may contain a repeating unit composed of an amic acid unit different from the repeating units represented by the formulas (1) and (2).

The diamine derived from the structure constituting such a repeating unit is not particularly limited, but includes 3,5-diaminobenzotrifluoride, 2,5-diaminobenzotrifluoride, 3,3'-bistrifluoromethyl −
4,4'-diaminobiphenyl, 3,3'-bistrifluoromethyl-5,5'-diaminobiphenyl, bis (trifluoromethyl) -4,4'-diaminodiphenyl, bis (fluorinated alkyl) -4,4 '-Diaminodiphenyl, dichloro-4,4'-diaminodiphenyl,
Dibromo-4,4'-diaminodiphenyl, bis (fluorinated alkoxy) -4,4'-diaminodiphenyl, diphenyl-4,4'-diaminodiphenyl, 4,4'-
Bis (4-aminotetrafluorophenoxy) tetrafluorobenzene, 4,4′-bis (4-aminotetrafluorophenoxy) octafluorobiphenyl, 4,
4'-binaphthylamine, o-, m-, p-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene, 2,4-diaminoxylene, 2,4-diaminodulene, dimethyl-4, 4'-diaminodiphenyl, dialkyl-4,4'-diaminodiphenyl, dimethoxy-4,4'-diaminodiphenyl, diethoxy-
4,4'-diaminodiphenyl, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylether, 3,4'-diaminodiphenylether, 4,4 '
-Diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4 -Aminophenoxy) benzene, 1,4-bis (4
-Aminophenoxy) benzene, 4,4'-bis (4-
Aminophenoxy) biphenyl, bis (4- (3-aminophenoxy) phenyl) sulfone, bis (4- (4
-Aminophenoxy) phenyl) sulfone, 2,2-
Bis (4- (4-aminophenoxy) phenyl) propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4-
(3-aminophenoxy) phenyl) propane, 2,2
-Bis (4- (3-aminophenoxy) phenyl) hexafluoropropane, 2,2-bis (4- (4-amino-2-trifluoromethylphenoxy) phenyl) hexafluoropropane, 2,2-bis (4 -(3-amino-5-trifluoromethylphenoxy) phenyl) hexafluoropropane, 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-bis (3-aminophenyl) hexafluoropropane, , 2-bis (3-amino-4-hydroxyphenyl) hexafluoropropane, 2,2-bis (3-amino-4-methylphenyl) hexafluoropropane, 4,4′-bis (4
-Aminophenoxy) octafluorobiphenyl, 4,
Examples thereof include 4'-diaminobenzanilide and the like, and two or more of these can be used in combination.

The tetracarboxylic acid derived from the structure constituting such a repeating unit is not particularly limited. Examples thereof include pyromellitic acid, trifluoromethylbenzenetetracarboxylic acid, bistrifluoromethylbenzenetetracarboxylic acid, Difluorobenzenetetracarboxylic acid, biphenyltetracarboxylic acid, terphenyltetracarboxylic acid, hexafluoroisopropylidene diphthalic acid, oxydiphthalic acid, bicyclo (2,2,2) oct-7-ene-2,3,5,6- And tetracarboxylic acid. The preparation of these repeating units having a tetracarboxylic acid structure is as follows:
It can be performed by mixing with tetraamine dianhydride, tetracarboxylic acid ester, and diamine as tetracarboxylic acid chloride.

The method for producing the polyimide precursor of the present invention is not particularly limited, and a known method can be applied. Usually, a polyimide precursor can be produced by reacting substantially equimolar diamine components and tetracarboxylic acid components in a polymerization solvent. For example, as a route for synthesizing a polyimide precursor using an aliphatic diamine, synthesis of an alkyl ester of a polyamic acid from an acid chloride of a dialkyl ester of a tetracarboxylic acid and an aliphatic diamine is generally known (High Performance Polymer, 1
0, 11 (1998)). In this method, a strong complex salt occurring in the early stage of the polymerization can be avoided, but a trace amount of a chlorine component remains in the finally obtained polyimide resin, which may erode a metal substrate or the like.

As another method of synthesizing a polyimide precursor using an aliphatic diamine, there is known a method of synthesizing a silyl ester of a polyamic acid by reacting a disilylated aliphatic diamine with an acid dianhydride. (Preprints of the Symposium on Polymer Science, 49, 1917 (2000)). This method requires the steps of synthesizing and isolating the disilylated aliphatic diamine,
The process becomes complicated.

It is also known to add a polymer dissolution accelerator often added during the polymerization of polyamide or the like, that is, a metal salt such as lithium bromide or lithium chloride.

A particularly preferred method for producing the polyimide precursor of the present invention will be described below.

First, in the first step, 2,2′-bis is added to 1 mol of a tetracarboxylic acid component containing at least 1,2,3,4-cyclobutanetetracarboxylic dianhydride in a polymerization solvent.
X mole of (trifluoromethyl) benzidine [x is 0 <x
<1. Is dissolved and reacted. Where x is 1,2,
It is preferably at least the number of moles of 3,4-cyclobutanetetracarboxylic dianhydride. As a tetracarboxylic acid derivative
When a compound other than 1,2,3,4-cyclobutanetetracarboxylic dianhydride is used in combination, the above-mentioned tetracarboxylic acid derivative can be used. The aforementioned tetracarboxylic acid derivative is used in less than 0.5 mol. In the first step, only a part of the diamine component is added and reacted. The reaction time can be shortened by stirring. Reaction time is 1-4
It is about 8 hours. The reaction temperature is about 0 to 60 ° C., and the reaction can be usually performed at an ambient temperature (room temperature) where heating and cooling are not performed.

The polymerization solvent is preferably an aprotic solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, dimethylsulfoxide, etc. The structure is not particularly limited as long as the anhydride is dissolved. Specific examples include N-methylpyrrolidone, sulfolane, m
-Cresol, p-cresol, 3-chlorophenol, 4-chlorophenol, γ-butyrolactone, γ-
Valerolactone, δ-valerolactone, γ-caprolactone, ε-caprolactone, α-methyl-γ-butyrolactone, ethylene carbonate, propylene carbonate, triethylene glycol, acetophenone, 1,3
-Dimethyl-2-imidazolidinone, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide and the like are preferably employed. Further, other common organic solvents, i.e., phenol, o-cresol, butyl acetate, ethyl acetate, ethyl cellosolve, butyl cellosolve, 2-methyl cellosolve acetate, ethyl cellosolve acetate, butyl cellosolve acetate, ethyl acetate, butyl acetate, isobutyl acetate, Dibutyl ether, diethylene glycol dimethyl ether,
Propylene glycol methyl acetate, tetrahydrofuran, dimethoxyethane, diethoxyethane, methyl isobutyl ketone, diisobutyl ketone, cyclohexanone, methyl ethyl ketone, acetone, butanol, ethanol, xylene, toluene, chlorobenzene, terpen, mineral spirit, petroleum naphtha-based solvent, etc. Can be used.

In the second step, following the first step,
4-mol of diaminocyclohexane [y represents 0 <y <1, and 0 <x + y ≦ 1. Is dissolved and reacted.
1,4-Diaminocyclohexane can be added in the form of a powder, and the powder gradually dissolves. After stirring for a predetermined time, a polyimide precursor solution is obtained as a viscous uniform solution.

In the above production method, when other than 1,4-diaminocyclohexane and 2,2′-bis (trifluoromethyl) benzidine are used in combination as the diamine component,
It can be added together with diaminocyclohexane or 2,2′-bis (trifluoromethyl) benzidine or separately. The amount used is preferably less than 0.5 mol. The reaction time is about 1 to 48 hours. The reaction temperature is about 0 to 60 ° C., and the reaction can be usually performed at an ambient temperature (room temperature) where heating and cooling are not performed.

The polyimide precursor of the present invention has an intrinsic viscosity in N, N-dimethylacetamide at 30 ° C. of 0.01 to 3.
It is about 0 dL / g.

The polyimide precursor of the present invention is used at a temperature of 200 ° C to 400 ° C.
C., preferably 300 to 350.degree. C. to give a polyimide. Alternatively, the reaction can be performed chemically by reacting with a dehydrating reagent such as acetic anhydride instead of heat treatment.

The polyimide precursor of the present invention can form a film on the surface of an article as a solution using the polymerization solvent as a solvent, and then form a polyimide film by the above-mentioned heat treatment or chemical dehydration. After the polyimide precursor solution is applied, it is dried in advance at a temperature of 50 ° C to 150 ° C, and then heat-treated at a temperature of 200 ° C to 400 ° C, preferably 300 ° C to 350 ° C to form a polyimide film.

The polyimide of the present invention can contain additives such as an oxidation stabilizer, a filler, a silane coupling agent, a photosensitizer, a photopolymerization initiator, and a sensitizer, if necessary.

[0039]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 16.1 g (0.05 mol) of 2,2'-bis (trifluoromethyl) benzidine was placed in a reaction vessel and dissolved in 234 g of N, N-dimethylacetamide.
19.61 g of 3,4-cyclobutanetetracarboxylic dianhydride powder
(0.1 mol) and stirred at room temperature for about 2 hours. 5.71 g (0.05 mol) of trans-1,4-diaminocyclohexane powder was gradually added to the obtained homogeneous solution while stirring. twenty four
After an hour, a clear, viscous polyimide precursor solution was obtained. N,
Intrinsic viscosity measured at 30 ° C in N-dimethylacetamide is
It was 1.0 dL / g. This solution is applied to a glass substrate and
After drying at 1 hour at 300 ° C., thermal imidization was performed at 330 ° C. for 1 hour to obtain a flexible polyimide film having a thickness of 10 μm. The physical properties of the film are a dielectric constant of 2.6 (1 MHz) and a linear thermal expansion coefficient of 30 ppm / K (100 ° C to 2 ° C).
Average value between 00 ° C), and the glass transition temperature was 370 ° C. FIGS. 1 and 2 show the infrared absorption spectra of the synthesized polyimide precursor and its thermosetting film, respectively.

(Comparative Example 1) 10.8 g (0.1 mol) of paraphenylenediamine was placed in a reaction vessel, dissolved in 362 g of N, N-dimethylacetamide, and then stirred with 3,3 ', 4,4'-biphenyl. 29.4 g (0.1 mol) of tetracarboxylic dianhydride powder was gradually added. After stirring at room temperature for 3 hours, a viscous polyimide precursor solution was obtained. Thus, a polyimide film having a thickness of 10 μm was obtained in the same manner as in Example 1. The physical properties of the film are a dielectric constant of 3.2, a linear thermal expansion coefficient of 6 ppm / K, and a glass transition temperature of 360.
° C. It can be seen that the coefficient of linear thermal expansion is very low, but the dielectric constant is high. This is due to the use of aromatic monomers for both the acid dianhydride component and the diamine component.

Comparative Example 2 21.04 g (0.1 mol) of 4,4'-methylenebis (cyclohexylamine) was placed in a reaction vessel, and dissolved in 230 g of N, N-dimethylacetamide. 19.61 g (0.1 mol) of 3,4-cyclobutanetetracarboxylic dianhydride powder was added and stirred at room temperature for 24 hours to obtain a uniform solution. This solution is applied to a glass substrate and
After drying for 1 hour at 300 ° C., thermal imidization was performed at 300 ° C. for 1 hour to obtain a brittle polyimide film having a thickness of 10 μm. As a film property, a low dielectric constant of 2.6 was obtained, but the coefficient of linear thermal expansion was 6
It was as high as 0 ppm / K. This is because the in-plane orientation was alienated by using the flexible aliphatic diamine.

Comparative Example 3 32.02 g (0.1 mol) of 2,2′-bis (trifluoromethyl) benzidine was placed in a reaction vessel.
After dissolving in 305 g of N, N-dimethylacetamide, 21.81 g (0.1 mol) of pyromellitic dianhydride powder was added with stirring, followed by stirring at room temperature for 24 hours to obtain a uniform and viscous solution. This solution was applied to a glass substrate and dried at 60 ° C for 1 hour.
The polyimide was thermally imidized at 0 ° C. for 1 hour to obtain a flexible polyimide film having a thickness of 10 μm. The film has a linear thermal expansion coefficient of 3 ppm / K.
, But the dielectric constant was as high as 3.2. This is because the use of pyromellitic dianhydride as the acid dianhydride component increased the number of imide carbonyl groups having high polarizability and π electrons.

(Comparative Example 4) In a reaction vessel, 32.02 g (0.1 mol) of 2,2'-bis (trifluoromethyl) benzidine was added.
After dissolving in 433 g of N, N-dimethylacetamide, 44.42 g (0.1 mol) of 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropanoic acid dianhydride powder is added with stirring and added at room temperature for 24 hours. Stirring yielded a homogeneous, viscous solution. This solution was applied to a glass substrate, dried at 60 ° C for 1 hour,
The polyimide was thermally imidized at 1 ° C. for 1 hour to obtain a flexible polyimide film having a thickness of 10 μm. The physical properties of the film were as low as 2.8, but the coefficient of linear thermal expansion was as high as 60 ppm / K. This is because the in-plane orientation was alienated by using 2,2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride having low linearity as the acid dianhydride component.

[0045]

The polyimide of the present invention has the effect of having high heat resistance and having both a low dielectric constant and a low coefficient of linear thermal expansion.

[Brief description of the drawings]

FIG. 1 is an infrared absorption spectrum of a polyimide precursor obtained in an example.

FIG. 2 is an infrared absorption spectrum of a polyimide obtained in an example.

Continuation of the front page F term (reference) 4J043 PA04 PA19 PC015 PC016 PC135 PC136 PC145 PC146 QB15 QB26 QB31 RA35 SA06 SA42 SA43 SA52 SA53 SA54 SA55 SA56 SA71 SA72 SB02 SB03 TA22 TA47 TA66 TA67 TB01 TB02 UA022 UA041 UA062 UA121 UA122 UA 141 UA261 UA632 UA662 UA672 UB011 UB021 UB061 UB062 UB121 UB122 UB131 UB151 UB221 UB301 UB401 UB402 VA011 VA021 VA031 VA041 VA051 VA061 VA071 VA081 VA091 XA15 XA16 XA17 XA19 ZB06 ZB37 ZA37

Claims (9)

[Claims] (1) A repeating unit represented by the formula (1) is represented by a mole fraction x
[X represents 0 <x <1. ] And the repeating unit represented by the formula (2) in a molar fraction y [y represents 0 <y <1. And a polyimide precursor satisfying 0 <x + y ≦ 1. Embedded image Embedded image 2. The polyimide precursor according to claim 1, wherein x ≦ y. 3. The polyimide precursor according to claim 1, wherein x + y = 1. 4. The repeating unit represented by the formula (3) is represented by a mole fraction x
[X represents 0 <x <1. ] And the molar unit y [y of the repeating unit represented by the formula (4) represents 0 <y <1. ], Wherein 0 <x + y ≦ 1. Embedded image Embedded image 5. The polyimide according to claim 4, wherein x ≦ y. 6. The polyimide according to claim 4, wherein x + y = 1. 7. A process for producing a polyimide precursor, comprising reacting substantially equimolar amounts of a diamine component and a tetracarboxylic acid component in a polymerization solvent, wherein the solvent comprises at least 1,2,3,4-cyclobutanetetracarboxylic acid in the solvent. 1 mol of a tetracarboxylic acid component containing an acid dianhydride and x mol of 2,2′-bis (trifluoromethyl) benzidine [x represents 0 <x <1. ]
Reacting and then ymol 1,4-diaminocyclohexane [y represents 0 <y <1, 0 <x + y ≦
It is one. The method for producing a polyimide precursor according to claim 1, further comprising a step of dissolving and reacting the polyimide precursor. 8. A method for producing a polyimide precursor, comprising reacting a diamine component and a tetracarboxylic acid component in substantially equimolar amounts in a polymerization solvent, wherein 1,2,3,4-cyclobutanetetracarboxylic acid is contained in the solvent. 1 mol of dianhydride and x mol of 2,2'-bis (trifluoromethyl) benzidine [x represents 0 <x <1. Is dissolved and reacted, and then ymol of 1,4-diaminocyclohexane [y represents 0 <y <1, x + y
= 1. The method for producing a polyimide precursor according to claim 1, comprising dissolving and reacting. 9. A method for producing a polyimide, comprising dehydrating the polyimide precursor according to any one of claims 1 to 3. [0002]