JPH0562893B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a novel solvent-soluble polyimide and a method for producing the same. [Prior Art] Conventional aromatic polyimides, which have high heat resistance and good mechanical properties, are difficult to mold because they generally do not melt and are not soluble in common organic solvents. Therefore, in general, soluble polyamic acid is first synthesized by reacting aromatic tetracarboxylic dianhydride and aromatic diamine in a specific polar organic solvent, and after giving it a shape at this stage, it is heated under high temperature. A method of obtaining polyimide by dehydration and ring closure has been implemented. However, this method has drawbacks such as poor stability of polyamic acid as an intermediate, resulting in a decrease in viscosity and formation of cloudiness when left at room temperature. Furthermore, since a dehydration reaction is involved when polyamic acid is imidized after being given a shape, defects such as voids and pinholes occur in the film, for example. Therefore, if the polyimide itself is soluble in an organic solvent, it is expected that a homogeneous polyimide film can be easily obtained by simply casting the solution onto a smooth surface and removing the solvent. For this reason, the development of solvent-soluble polyimides has been desired, and various proposals have been made so far. For example, there is a polyimide that uses a specific tetranuclear m,m'-diamino compound as a diamine component to disrupt the symmetry of the polymer structure and the regulation of repeating units, thereby imparting solvent solubility.
No. 30319). However, in general, m,m'-diamino compounds are extremely difficult to synthesize and have inferior reactivity compared to p,p'-diamino compounds. Further, it has the disadvantage that the thermal decomposition temperature and glass transition temperature of the obtained polyimide are also lowered. A method for producing soluble polyimide using p,p'-diamino compounds is also known (Japanese Patent Application Laid-open No.
No. 61-19634, JP-A-61-28536, JP-A-61-
51033, JP-A No. 61-123634), it is difficult to obtain a product of stable quality because two or more diamines and/or tetracarboxylic acids are used together, and the polymer structure is non-uniform, so polyimide It has the disadvantage that it cannot exhibit the toughness, electrical properties, etc. As described above, all of the methods proposed so far have the disadvantage of impairing the original excellent properties of polyimide due to imparting solvent solubility, and also was also problematic. [Problems to be Solved by the Present Invention] The present inventors have developed a material that has high heat resistance and excellent mechanical and electrical properties equivalent to those of conventional insoluble polyimides, using diamines and tetracarboxylic acids that are easy to produce. As a result of intensive research to develop a new polyimide that is soluble in general-purpose organic solvents and easy to mold, a new polyimide obtained from specific carboxylic acids and p,p'-diamino compounds satisfied the intended purpose. The present invention was completed based on this finding. That is, an object of the present invention is to provide a novel solvent-soluble polyimide and a method for producing the same. [Means for solving the problems] The polyimide according to the present invention is a polyimide obtained by heating an aromatic tetracarboxylic acid and an aromatic diamine, and is a polyimide obtained by heating an aromatic tetracarboxylic acid and an aromatic diamine, in which the repeating unit represented by the general formula () is 50 % or more, and has an intrinsic viscosity (concentration 0.5
g/100ml, solvent N-methyl-2-pyrrolidone,
temperature (30°C) is 0.5 to 5.0 d1/g. [In the formula, Z is

[Formula] or

Represents [formula]. X ¹ and X ² represent -O- or -S-, and Y represents a single bond or a divalent group selected from -O-, -S-, -SO ₂ - or -CO-, and are the same and may also be different. ] The soluble polyimide according to the present invention is obtained by reacting diphenylsulfone-3,3',4,4'-tetracarboxylic acids with an aromatic diamine represented by the general formula (). [In the formula, Z is

[Formula] or

Represents [formula]. X ¹ and X ² represent -O- or -S-, and Y represents a single bond or a divalent group selected from -O-, -S-, -SO ₂ - or -CO-, and are the same and may also be different. ] Diphenylsulfone-3,3',4,4'-tetracarboxylic acids refer to the carboxylic acids, their acid anhydrides, their halides, and those having 1 to 4 carbon atoms.
Refers to carboxylic acid derivatives such as esters with alcohols. Among these, diphenylsulfone-3,3',4,4'-tetracarboxylic dianhydride (hereinafter abbreviated as "DSTA") is particularly important from the viewpoint of reaction activity.
is preferred. The above diphenyl sulfone-3 as the acid component,
Although it is preferable to use 3',4,4'-tetracarboxylic acids alone, other aromatic tetracarboxylic acids may be used in combination depending on the case. Examples of other aromatic carboxylic acids include aromatic tetracarboxylic acids in which four carboxyl groups are directly bonded to an aromatic ring, specifically, diphenylsulfone-2,3,3',4' -tetracarboxylic acid, diphenylsulfone-2,2',3,3'-tetracarboxylic acid, pyromellitic acid, benzofurantetracarboxylic acid, biphenyltetracarboxylic acid, diphenyl ethertetracarboxylic acid, naphthalenetetracarboxylic acid, and each and various carboxylic acid derivatives such as acid anhydrides thereof, halides thereof, and esters with alcohols having 1 to 4 carbon atoms. The blending amount of these aromatic tetracarboxylic acids is limited to a range that does not impair the properties of diphenylsulfone-3,3',4,4'-tetracarboxylic acids,
Generally, it is preferably 50 mol% or less of the tetracarboxylic acids used. Examples of aromatic diamines represented by the general formula () include 4,4'-bis(p-aminophenoxy)diphenylsulfone, 3,3'-bis(p-aminophenoxy)diphenylsulfone, and 3,4'-bis(p-aminophenoxy)diphenylsulfone. p-aminophenoxy) diphenyl sulfone,
4,4'-bis(p-aminophenylthioether) diphenyl sulfone, 3,3'-bis(p-aminophenyl thioether) diphenyl sulfone, 3,4'-bis(p-aminophenyl thioether) Diphenylsulfone, 4,4'-bis(p-
aminophenoxy) diphenyl ether, 3,
3'-bis(p-aminophenoxy) diphenyl ether, 3,4'-bis(p-aminophenoxy)
Diphenyl ether, 4,4'-bis(p-aminophenoxy) diphenyl sulfide, 3,3'-bis(p-aminophenoxy) diphenyl sulfide, 3,4'-bis(p-aminophenoxy) diphenyl sulfide phenyl sulfide, 4,4'-bis(p-aminophenylthioether) diphenyl sulfide,
3,3'-bis(p-aminophenylthioether) diphenyl sulfide, 3,4'-bis(p-
Aminophenyl thioether) diphenyl sulfide, 4,4'-bis(p-aminophenyl thioether) diphenyl ether, 3,3'-bis(p
-aminophenyl thioether) diphenyl ether, 3,4'-bis(p-aminophenyl thioether) diphenyl ether, 4,4'-bis(p
-aminophenoxy)diphenyl, 3,3'-bis(p-aminophenoxy)diphenyl, 4,4'-
bis(p-aminophenoxy)benzophenone,
3,3'-bis(p-aminophenoxy)benzophenone, 3,4'-bis(p-aminophenoxy)
benzophenone, 4,4'-bis(p-aminophenylthioether) diphenyl, 3,3'-bis(p-aminophenylthioether) diphenyl,
3-(p-aminophenoxy)-4'-(p-aminophenylthioether) diphenyl sulfone, 3
-(p-aminophenoxy)-4'-(p-aminophenylthioether) diphenyl sulfide, 3
-(p-aminophenoxy)-4'-(p-aminophenylthioether) diphenyl ether, 3-
(p-aminophenoxy)-4'-(p-aminophenylthioether)benzophenone, 3-(p-
Aminophenylthioether)-4'-(p-aminophenoxy)diphenyl sulfone, 3-(p-aminophenylthioether)-4'-(p-aminophenoxy)diphenyl sulfide, 3-(p-aminophenyl thioether)-4'-(p-aminophenoxy)diphenyl sulfide, enylthioether)-4'-(p-aminophenoxy)diphenyl ether, 3-(p-aminophenylthioether)-4'-(p-aminophenoxy)benzophenone, 1,4-bis(p-aminophenylthioether) Benzene, 1,3-
(p-aminophenylthioether)benzene,
4-(p-aminophenoxy)-4'-(p-aminophenylthioether) diphenyl sulfone, 4
-(p-aminophenoxy)-4'-(p-aminophenylthioether) diphenyl sulfide, 4
-(p-aminophenoxy)-4'-(p-aminophenylthioether) diphenyl ether, 4-
Examples include (p-aminophenoxy)-4'-(p-aminophenylthioether)benzophenone. As a diamine component, these general formulas ()
Although it is preferable to use the aromatic diamine represented by the following alone, two or more of the diamines can be used in combination. Other diamines include, for example, 4,4'-diaminodiphenyl sulfide, m
-phenylenediamine, o-phenylenediamine, 2,4-toluenediamine, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3, 3′-diaminodiphenyl sulfone,
4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenylmethane, 3,3'-diaminodiphenylmethane,
1,3'-bis(p-aminophenoxy)benzene, 1,4'-bis(p-aminophenoxy)benzene, 4,4'-bis(m-aminophenoxy)diphenyl sulfone, 1,5-diaminonaphthalene, 2, Examples include 6-diaminonaphthalene and 2,6-diaminopyridine, but the amount of these diamines is limited to a range that does not impair the properties of the diamine represented by the general formula (), and generally It is desirable that the amount is 50 mol% or less based on the total amount used. When tetracarboxylic acids other than diphenylsulfone-3,3',4,4'-tetracarboxylic acids and diamines other than the aromatic diamine represented by the general formula () are added in an amount exceeding the above range, the obtained Solvent solubility of polyimide is insufficient,
This brings about unfavorable results such as decreased heat resistance and unstable quality. The aromatic polyimide according to the present invention is generally produced by the following method. That is, first diphenylsulfone-3,3',4,
Polyamic acid is synthesized by reacting 4'-tetracarboxylic acids and aromatic diamines in an organic solvent. The molar ratio of diphenylsulfone-3,3',4,4'-tetracarboxylic acids and aromatic diamine is preferably from 0.7 to 1.3, particularly from 0.95 to 1.05, in order to obtain a high molecular weight polyimide. preferable. The reaction temperature is generally 0 to 120°C, preferably 5 to 80°C, and the reaction time varies depending on the diamines used, the solvent, and various conditions, but is usually
0.5-50 hours. In addition, as the organic solvent used in this reaction,
Aprotic polar or phenolic solvents are generally preferred, for example N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-
dimethylacetamide, dimethyl sulfoxide,
Tetramethylurea, 1,3-dimethyl-2-imidazolidinone, hexamethylphosphate triamide,
Phenol, cresol, dimethylphenol,
Examples include chlorphenol and bromophenol. In addition to these solvents, common organic solvents such as ketones, esters, lactones, ethers, cellosolves, halogenated hydrocarbons, and hydrocarbons, such as acetone, methyl ethyl ketone, and methyl Isobutyl ketone, cyclohexanone, acetophenol, methyl acetate,
Ethyl acetate, butyl acetate, diethyl oxalate, diethyl malonate, γ-butyrolactone, diethyl ether, ethylene glycol dimethyl ether, diethyl glycol dimethyl ether, tetrahydrofuran, diglyme, methyl cellosolve, ethylene glycol monomethyl ether, dichloromethane, 1,2-dichloroethane, 1 ,4
-Dichlorobutane, trichloroethane, chlorobenzene, dichlorobenzene, hexane, heptane, octane, benzene, toluene, xylene, etc. can also be used. The obtained organic solvent solution of polyamic acid is used as it is, or the polyamic acid is recovered from the organic solvent solution by a conventional method, purified if necessary, and then dissolved again in the above-mentioned aprotic polar solvent or phenolic solvent. After that, it can be subjected to an imidization reaction. If an organic solvent other than an aprotic polar solvent or a phenolic solvent is used during the production of polyamic acid, collect the polyamic acid using a conventional method, purify it if necessary, and then use the aprotic polar solvent again. Alternatively, it is desirable to perform the imidization reaction by dissolving it in a phenolic solvent. In the imidization reaction, a solution of the polyamic acid in an organic solvent is heated at usually 60 to 250°C, particularly preferably at 100 to 250°C.
It is carried out by heating to 200°C. Below 60°C, an economical reaction rate cannot be obtained, and above 250°C, coloring of the reaction system, side reactions, etc. occur, which is disadvantageous. In addition, if water is produced as a by-product during the reaction, a solvent that is azeotropic with water, such as benzene, toluene, xylene, ethylbenzene, hexane, heptane, octane, nonane, decane, cyclohexane, etc., or phosphorus pentoxide, anhydrous The reaction can also be accelerated by adding a dehydrating agent such as acetic acid. The reaction time varies depending on the type of substrate, solvent, various conditions, etc., but is usually 0.5 to 50 hours. The concentration of polyamic acid and polyimide in the reaction solution is preferably 1 to 50% by weight, particularly 3 to 40% by weight. If it is less than 1% by weight, it is economically disadvantageous, and if it is more than 50% by weight, it is difficult to adjust the molecular weight or viscosity, and the resulting polyimide solution may become gel-like. The polyimide resin solution obtained as described above is casted or spin coated onto the smooth surface of a base material such as a glass plate or metal plate, and then the organic solvent, etc. is removed by heating or other methods. A yellow-brown transparent polyimide film can be easily obtained by this method. Alternatively, after the polyimide is once separated from the polyimide resin solution after the reaction, it can be redissolved in an organic solvent and then formed into a film by the above method. The organic solvent used for this redissolution is
Similar to the above, aprotic polar solvents, phenolic solvents, etc. are suitable. This film has high mechanical strength and flexibility, and a film with a thickness of 30 μm can withstand repeated bending tests. Furthermore, it exhibits good heat resistance at a thermal decomposition temperature of 500°C or higher, and also has good chemical resistance. Furthermore, at temperatures above the melting temperature, it exhibits thermoplasticity and can be heat-pressed and compression-molded into films. Intrinsic viscosity ηinh (concentration) of the polyimide according to the present invention
0.5g/100ml, solvent N-methyl-2-pyrrolidone, temperature 30°C) is 0.5-50d1/g, preferably
It is 0.5-2.0d1/g. When the intrinsic viscosity is less than 0.5,
Formability is insufficient. The polyimide obtained by the present invention can be applied preferably in the form of a solution to heat-resistant varnishes, heat-resistant laminates, heat-resistant films, heat-resistant adhesives, electrical equipment, electronic materials, and devices, and specifically, for printing. It is used for wiring boards, flexible wiring boards, tape carriers, surface protection films or interlayer insulation films for semiconductor integrated circuit elements, covering materials for enameled electric wires, various laminated plate gaskets, etc. [Examples] Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 43.2 g (0.1 mol) of 4,4'-bis(p-aminophenoxy) diphenyl sulfone and N-methyl-2 were placed in a reactor equipped with a stirring device, a cooling tube, a thermometer, and a nitrogen gas inlet tube. -pyrrolidone (hereinafter referred to as
It will be abbreviated as “NMP”. ), and after purging with nitrogen, stirred at room temperature until dissolved. next,
Gradually add 35.8 g (0.1 mol) of DSTA,
The reaction was carried out at 30°C for 1 hour to obtain a transparent and viscous polyamic acid solution. This solution was heated to 160°C and reacted for 5 hours to obtain the desired transparent and viscous polyimide acid solution. The viscosity of this solution was 35 poise (25°C). The polyimide solution thus obtained was poured into methanol, the resulting polymer was reprecipitated, dried under reduced pressure, and the infrared absorption spectrum was measured.
A characteristic absorption based on imide groups was observed at cm ^-1 (Figure 1). Table 1 shows the intrinsic viscosity, thermal decomposition temperature, softening point, and other physical properties of the polyimide. In addition, this polyimide contains N,N-dimethylformamide (hereinafter abbreviated as "DMF") and m
- Easily dissolved in cresol. Example 2 38.4 g (0.1 mol) of 4,4'-bis(p-aminophenoxy) diphenyl ether was dissolved in 300 g of DMF, 35.8 g (0.1 mol) of DSTA was gradually added thereto, and the reaction was carried out in the same manner as in Example 1. did. The reaction was carried out at 150°C for 5 hours to obtain the desired transparent and viscous polyimide solution. The viscosity of this solution is 41 poise (25
℃). A polyimide was obtained by processing in the same manner as in Example 1, and its intrinsic viscosity, thermal decomposition temperature, softening point, and other physical properties are shown in Table 1. Also, this polyimide
It also easily dissolved in NMP and m-cresol. Example 3 32.4 g (0.1 mol) of 1,4-bis(p-aminophenylthioether)benzene was dissolved in 250 g of m-cresol, and 35.8 g (0.1 mol) of DSTA was gradually added thereto. Reacted similarly.
The reaction was carried out at 170°C for 3 hours to obtain the desired transparent and viscous polyimide solution. The viscosity of this solution is 32
It was poise (25℃). Intrinsic viscosity, thermal decomposition temperature,
The softening point and other physical properties are shown in Table 1. This polyimide also easily dissolved in NMP and DMF. Example 4 4,4′-bis(p-aminophenylthioether) diphenyl ether and DSTA were prepared in Example 1.
The corresponding polyimide was synthesized by the same reaction. The resulting m-cresol solution of polyimide (polyimide concentration: 20% by weight) had a viscosity of 37 poise (25°C). Various properties of the obtained polyimide are shown in Table 1. Example 5 4,4'-bis(p-aminophenoxy)diphenyl sulfide and DSTA were reacted in the same manner as in Example 1 to synthesize a corresponding polyimide. NMP solution of the obtained polyimide (polyimide concentration 20
The viscosity (% by weight) was 36 poise (25°C). Various properties of the obtained polyimide are shown in Table 1. Example 6 4,4'-bis(p-aminophenoxy)benzophenone and DSTA were reacted in the same manner as in Example 1 to synthesize a corresponding polyimide. The resulting NMP solution of polyimide (polyimide concentration: 20% by weight) had a viscosity of 38 poise (25°C). Various properties of the obtained polyimide are shown in Table 1. Example 7 4,4′-bis(p-aminophenylthioether) diphenyl sulfone and DSTA were prepared in Example 1.
The corresponding polyimide was synthesized by the same reaction. The resulting m-cresol solution of polyimide (polyimide concentration: 20% by weight) had a viscosity of 32 poise (25°C). Various properties of this polyimide are shown in Table 1. Examples 8 to 41 Various diamines shown in Table 2 and DSTA were reacted in the same manner as in Example 1 to synthesize corresponding polyimides. Intrinsic viscosity ηinh of the obtained polyimide,
Table 2 shows the reaction solvent used and the solution viscosity after the reaction. Comparative Example 1 43.1 g (0.1 mol) of 4,4'-bis(p-aminophenoxy) diphenylsulfone was dissolved in 300 g of NMP, and 32.2 g of benzophenone-3,3',4,4'-tetracarboxylic dianhydride ( When 0.1 mol) was gradually added and the reaction was carried out at 150°C for 5 hours in the same manner as in Example 1, a non-uniform gel-like substance was formed. 300g of NMP was further added to this and stirred while heating.
A homogeneous solution could not be obtained. Comparative Example 2 38.4 g (0.1 mol) of 4,4'-bis(p-aminophenoxy) diphenyl ether was dissolved in 300 g of DMF, and 32.2 g of benzophenone-3,3',4,4'-tetracarboxylic dianhydride ( When 0.1 mol) was gradually added and the reaction was carried out at 170°C for 3 hours in the same manner as in Example 2, a non-uniform gel-like substance was formed. Although 300 g of DMF was further added to this mixture and the mixture was heated and stirred, a homogeneous solution could not be obtained. Comparative Example 3 1,4-bis(p-
Aminophenylthioether)benzene 32.4g
(0.1 mol) was added with 29.4 g (0.1 mol) of diphenyl-3,3',4,4'-tetracarboxylic dianhydride,
In the same manner as in Example 1, at 25 to 30°C for 1 hour, and then
When the reaction was carried out at 160°C for 5 hours, a resin insoluble in NMP was precipitated. This resin was separated and heated in DMF at 80°C for 24 hours, but it did not dissolve at all.
The same was true for m-cresol. Comparative Example 4 43.2 g of 4,4'-bis(p-aminophenoxy) diphenyl sulfone dissolved in 300 g of NMP
(0.1 mol) was added with 21.8 g (0.1 mol) of pyromellitic anhydride, and reacted in the same manner as in Example 1 at 25 to 30°C for 1 hour and then at 160°C for 5 hours.
A resin insoluble in NMP precipitated. This resin was separated and heated in DMF at 80°C for 24 hours, but it did not dissolve at all. The same was true for m-cresol. Comparative Example 5 36.8 g (0.1 mol) of 4,4'-bis(p-aminophenoxy) diphenyl dissolved in 300 g of NMP
Add 31.0 g (0.1 mol) of diphenyl ether-3,3',4,4'-tetracarboxylic dianhydride to
In the same manner as in Example 1, at 25 to 30°C for 1 hour, and then
When the reaction was carried out at 160°C for 5 hours, a resin insoluble in NMP was precipitated. This resin was separated and heated in DMF at 80°C for 24 hours, but it did not dissolve at all.
The same was true for m-cresol. Comparative Example 6 24.4 g (0.1 mol) of naphthalene-1,4,5,8-tetracarboxylic dianhydride was added to 39.6 g (0.1 mol) of 4,4'-bis(p-aminophenoxy)benzophenone dissolved in 300 g of NMP. was added and heated in the same manner as in Example 1 at 25 to 30°C for 1 hour and then at 160°C.
When the reaction was carried out at ℃ for 5 hours, a resin insoluble in NMP was precipitated. Separate this resin and 80% in DMF.
℃ for 24 hours, but it did not dissolve at all. m-
The same was true for cresol. Comparative Example 7 43.2 g of 4,4'-bis(m-aminophenoxy)diphenylsulfone dissolved in 300 g of NMP
(0.1 mol) benzophenone-3,3',4,4'-
32.2 g (0.1 mol) of tetracarboxylic dianhydride was added and reacted in the same manner as in Example 1 at 25 to 30°C for 1 hour and then at 160°C for 5 hours.
A heterogeneous gel-like substance insoluble in NMP was obtained. 300 g of NMP was further added to this mixture, and the mixture was heated and stirred at 80° C. for 1 hour, but a homogeneous solution could not be obtained. Comparative Example 8 29.4 g (0.1 mol) of pyromellitic anhydride was added to 43.2 g (0.1 mol) of 4,4'-(m-aminophenoxy)diphenylsulfone dissolved in 300 g of NMP, and 25 When reacted at ~30℃ for 1 hour and then at 160℃ for 5 hours,
A resin insoluble in NMP precipitated. This resin was separated and heated in DMF at 80°C for 24 hours, but it did not dissolve at all. The same was true for m-cresol. [Effects of the Invention] The novel aromatic polyimide obtained by the present invention is soluble in general-purpose polar organic solvents, has a high thermal decomposition temperature and high softening point, and has excellent heat resistance similar to conventional solvent-insoluble aromatic polyimides. has. Further, since the organic solvent solution of polyimide obtained by dissolving the polyimide in an organic solvent is a relatively low viscosity solution that is fluid at room temperature, it is extremely easy to handle and mold. Moreover, it has high stability in a solution state and can be stored for a long period of time at room temperature without causing deterioration such as a decrease in viscosity or deterioration of insoluble analysis. Furthermore, the polyimide of the present invention can be produced industrially at low cost since the raw materials are diphenylsulfone-3,3',4,4'-tetracarboxylic acids and p,p'-diamine compounds which are easy to synthesize.

[Brief explanation of the drawing]

FIG. 1 shows an infrared absorption spectrum of the polyimide obtained in Example 1.

【table】

【table】

【table】

Claims (1)

[Scope of Claims] 1. A polyimide obtained by heating an aromatic tetracarboxylic acid and an aromatic diamine, which contains 50% or more of repeating units represented by the general formula (), and has an intrinsic viscosity (concentration of 0.5 g/100ml, solvent N-methyl-2-pyrrolidone, temperature 30℃) is 0.5-5.0d1/g
A novel solvent-soluble polyimide characterized by: [In the formula, Z represents [formula] or [formula]. X ¹ and X ² are -O- or -S-, Y is a single bond or -O
It represents a divalent group selected from -, -S-, _-SO2- , or -CO-, and may be the same or different. ] 2. Reacting diphenylsulfone-3,3',4,4'-tetracarboxylic acids with one or more diamines selected from aromatic diamines represented by the general formula (). Contains 50% or more of repeating units represented by the general formula () characterized by
A method for producing a novel solvent-soluble polyimide. [In the formula, Z represents [formula] or [formula]. X ¹ and X ² are -O- or -S-, Y is a single bond or -O
It represents a divalent group selected from -, -S-, _-SO2- , or -CO-, and may be the same or different. ] [In the formula, Z represents [formula] or [formula]. X ¹ and X ² are -O- or -S-, Y is a single bond or -O
It represents a divalent group selected from -, -S-, _-SO2- , or -CO-, and may be the same or different. ]