Imide bond-containing polymer and method for producing the same

Abstract

To provide an imide bond-containing polymer such as polyimide and a polyamide-imide resin which is excellent in thermal decomposition resistance and low dielectric characteristics, and a method for producing the same.SOLUTION: An imide bond-containing polymer has one or more polyols (A) selected from the group consisting of polyolefin polyol and dimer diol, polyisocyanate (B) and a trimellitic anhydride as structural units, and substantially no urethane bonds.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a polymer containing an imide bond having excellent dielectric properties and thermal decomposition resistance, and a method for producing the polymer containing an imide bond.

Background Art

[0002] Flexible printed wiring boards (FPCs) have excellent flexibility, so they can cope with the multifunctionalization and miniaturization of personal computers (PCs), smartphones, etc. Therefore, they are widely used for incorporating electronic circuit boards into narrow and complex interiors. In recent years, with the progress of miniaturization, weight reduction, high density, and high output of electronic devices, the requirements for the performance of wiring boards (electronic circuit boards) have become increasingly sophisticated due to these trends. In particular, with the increase in the speed of transmission signals in FPCs, the frequency of signals is increasing. Along with this, the requirements for low dielectric properties (low dielectric constant, low dielectric tangent) in the high-frequency region for FPCs are increasing. In addition, FPCs are also used in applications that require high heat resistance, such as being applied to wiring board materials and mounting substrate materials for electronic devices that require flexibility and space savings. Against this background, a modified polyimide resin using an olefin-based compound effective for reducing the dielectric constant as a raw material has been proposed. (Patent Document 1)

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Disclosure of the Invention

Problems to be Solved by the Invention

[0004] However, as the requirements for low dielectric properties and heat resistance increase, the modified polyimide resin of Patent Document 1 is not fully satisfactory in both low dielectric properties and thermal decomposition resistance. An object of the present invention is to provide a polymer containing an imide bond having excellent thermal decomposition resistance and low dielectric properties.

Means for Solving the Problems

[0005] As a result of investigations by the present inventors, it has been clarified that urethane bonds formed during the production process of polyimide resins have an adverse effect on low dielectric properties and thermal decomposition resistance, leading to the completion of the present invention. That is, the present invention has the following constitution.

[0006] [1] One or more polyols (A) selected from the group consisting of polyolefin polyols and dimer diols, and an imide bond-containing polymer having a polyisocyanate (B) and trimellitic anhydride as structural units and substantially no urethane bonds.

[0007] [2] The imide bond-containing polymer according to [1] above, having a dissipation factor (Df) measured at 10 GHz of 0.0025 or less and a 5% weight loss temperature of 350 °C or higher.

[0008] [3] A method for producing the imide bond-containing polymer according to [1] or [2] above, comprising a step A of reacting an acid anhydride compound (C) having the polyol (A) and trimellitic anhydride as structural units and having two or more acid anhydride ring structures with the polyisocyanate (B).

[0009] [4] The method for producing the imide bond-containing polymer according to [3] above, wherein the step A is carried out in a solvent containing one or more selected from the group consisting of cyclohexanone, 2-methylcyclohexanone, and dimethyl sulfoxide. [Advantages of the Invention]

[0010] According to the present invention, it is possible to provide an imide bond-containing polymer such as polyimide or polyamide-imide resin, which is excellent in thermal decomposition resistance and low dielectric properties, and a method for producing the same. [Embodiments for Carrying Out the Invention]

[0011] Hereinafter, an embodiment of the present invention will be described in detail as follows. However, the present invention is not limited thereto and can be implemented in various modified forms within the scope described above.

[0012] <Polyol (A)> The imide bond-containing polymer of the present invention has, as a structural unit, one or more polyols (A) selected from the group consisting of polyolefin polyols and dimer diols. By having a polyolefin polyol or a dimer diol as the polyol (A), the low dielectric characteristics of the imide bond-containing polymer can be improved. The polyolefin polyol or the dimer diol can be used alone or in combination. The polyolefin polyol is a polyolefin having two or more hydroxy groups, and examples of the polyolefin include polybutadiene and polyisoprene. The hydroxy groups are preferably located at both ends of the polyolefin chain. Specific examples of such polyolefin polyols include, for example, G-1000, G-3000, GI-1000, GI-3000 (manufactured by Nippon Soda Co., Ltd.), Poly ip, Epole (manufactured by Idemitsu Kosan Co., Ltd.), and the like.

[0013] <Polyisocyanate (B)> The polyisocyanate (B) (hereinafter also referred to as component (B)) constituting the imide bond-containing polymer of the present invention is not particularly limited as long as it is a polyisocyanate compound, and examples thereof include aromatic polyisocyanates, aliphatic polyisocyanates, or alicyclic polyisocyanates. The aromatic polyisocyanate is not particularly limited, and examples thereof include diphenylmethane-2,4'-diisocyanate, or 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-diethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenyl ether-4,4'-diisocyanate, benzophenone-4,4'-diisocyanate, diphenyl sulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-[2,2-bis(4-phenoxyphenyl)propane]diisocyanate, 3,3' or 2,2'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'- or 2,2'-diethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, 3,3'-diethoxybiphenyl-4,4'-diisocyanate, and the like. Considering heat resistance, adhesion, solubility, cost, etc., aromatic polyisocyanates are preferred, and diphenylmethane-4,4'-diisocyanate, tolylene-2,4-diisocyanate, m-xylylene diisocyanate, 3,3'- or 2,2'-dimethylbiphenyl-4,4'-diisocyanate are more preferred. These can be used alone or in combination of two or more. Note that it is also possible to produce the imide bond-containing polymer of the present invention by using the corresponding polyamine compound instead of the polyisocyanate compound. From the viewpoints of production cost and water generation due to side reactions, etc., a preferred production method is the isocyanate method in which a polymer is obtained by a decarboxylation reaction.

[0014] The imide bond-containing polymer of the present invention has a structural unit derived from trimellitic anhydride. Trimellitic anhydride can react with the polyol (A) on the monocarboxylic acid side to form an ester bond, and react with the polyisocyanate (B) on the acid anhydride ring side to form an imide bond, thereby creating the imide bond-containing polymer of the present invention. As will be described later, as a unit of trimellitic anhydride, trimellitic anhydride halide in which the monocarboxylic acid side is halogenated may be used for reaction with the polyol (A).

[0015] <Imide bond-containing polymer> It is necessary that the imide bond-containing polymer of the present invention substantially does not have a urethane bond in its structure. It is considered that excellent thermal decomposition resistance and low dielectric characteristics are achieved by not having a urethane bond.

[0016] The dielectric tangent of the imide bond-containing polymer of the present invention measured at 10 GHz is preferably 0.0025 or less. More preferably, it is 0.0020 or less, and even more preferably 0.0015 or less. The dielectric tangent is measured by the method described in the examples.

[0017] The 5% weight loss temperature of the imide bond-containing polymer of the present invention is preferably 350 ° C or higher. More preferably, it is 370 ° C or higher. The 5% weight loss temperature is measured by the method described in the examples.

[0018] The imide bond-containing polymer of the present invention substantially does not have a urethane bond as described above. Therefore, a production method in which a urethane bond is substantially not generated in the polymerization step is preferable. Examples of such a production method include, as a first step, synthesizing an acid anhydride compound (C) having a polyol (A) and trimellitic anhydride as structural units and having two or more acid anhydride groups, and as a second step, reacting the acid anhydride groups of the obtained acid anhydride compound (C) with a polyisocyanate (B) to generate an imide bond. By separating the reaction steps in this way, generation of a urethane bond due to the reaction between the hydroxy group of the polyol (A) and the isocyanate group of the polyisocyanate (B) can be avoided.

[0019] Examples of the method for synthesizing the acid anhydride compound (C) in the above first step include a method of synthesizing by an esterification reaction between a polyol (A) and trimellitic anhydride, and a method of reacting a polyol (A) with trimellitic anhydride halide. The method using trimellitic anhydride halide is preferable from the viewpoint of reactivity. Specifically, the following methods are exemplified. That is, as a first step, under a nitrogen atmosphere in a reaction vessel, trimellitic anhydride halide, polyol (A), a solvent, and an amine for capturing the generated hydrogen halide are added, and the non-volatile component is 10 to 50% by mass, preferably 20 to 30% by mass, at less than 5°C, and the mixture is stirred and reacted. As a procedure, for example, under a nitrogen atmosphere, trimellitic anhydride halide is first dissolved in a solvent at less than 5°C, and a mixture in which a polyol (A) and a basic compound are separately dissolved is added dropwise while maintaining the liquid temperature at less than 5°C. At this time, a catalyst such as antimony, titanium, tin, zinc, cobalt, germanium, aluminum, etc. may be used. Also, since hydrogen halide is generated as a reaction by-product, a basic compound is used for capture. Examples of the basic compound include organic tertiary amines such as pyridine, triethylamine, N,N-dimethylaniline, epoxies such as propylene oxide, and inorganic bases such as potassium carbonate and sodium hydroxide. Usually, after the reaction is completed, the salt formed by the reaction of hydrogen halide and the base compound is filtered off and purified.

[0020] Examples of the solvent used in the first step of the method for producing the imide bond-containing polymer of the present invention include tetrahydrofuran, diethyl ether, acetone, cyclopentanone, 2-methylcyclohexanone, cyclohexanone, dimethyl sulfoxide, ethyl acetate, gamma-butyrolactone, and the like. Considering the reaction between the obtained acid anhydride compound (C) and the polyisocyanate (B), from the viewpoint of solubility in both the structure of the low-polarity polyol (A) residue and the high-polarity amide-imide structure, 2-methylcyclohexanone, cyclohexanone, and dimethyl sulfoxide are desirable.

[0021] The reaction charge amount of trimellitic anhydride halide and polyol (A) is preferably 0.475 to 0.500, more preferably 0.498 to 0.500, in terms of the molar ratio of trimellitic anhydride halide / polyol (A). If it exceeds 0.500, polyol (A) remains as an unreacted substance, and when the polyisocyanate (B) in the next step is added, a urethane bond is formed, which becomes a factor in deteriorating the thermal decomposition resistance and dielectric properties. On the other hand, if it is less than 0.475, unreacted trimellitic anhydride halide reacts with moisture in the air during operations such as filtration and deactivates, and salts precipitate, which is not preferable. As the trimellitic anhydride halide, trimellitic anhydride chloride is preferably used because it is inexpensive and readily available.

[0022] As the second step described above, for example, using the acid anhydride compound (C), polyisocyanate (B), solvent, and polymerization catalyst obtained in the first step, in a nitrogen atmosphere, at 80 to 190 °C, preferably 100 to 160 °C, with a non-volatile component of 10 to 50% by mass, preferably 30 to 40% by mass, and reacting for 5 hours or more, then diluting with the solvent to an appropriate viscosity and cooling, the target imide bond-containing polymer can be obtained.

[0023] The reaction charge amount of the above-mentioned acid anhydride compound (C) and the polyisocyanate (B) is preferably 1.01 to 5, more preferably 1.01 to 2, in terms of the molar ratio of polyisocyanate (B) / acid anhydride compound (C). When the charge amount is less than 1.01, a resin with a low molecular weight and poor strength is obtained. On the other hand, when it exceeds 5, the viscosity during the reaction becomes high and gelation easily occurs, so neither is preferable.

[0024] In addition, a polycarboxylic acid anhydride such as trimellitic anhydride, pyromellitic anhydride, or ethylene glycol bisanhydrotrimellitate may be further added to the above-mentioned acid anhydride compound (C) to form a copolymer with the polyisocyanate (B). When the above-mentioned acid anhydride compound (C) and trimellitic anhydride are used in combination, the reaction charge amount with the polyisocyanate (B) is the same as above, that is, it is preferably 1.01 to 5, more preferably 1.01 to 2, in terms of the molar ratio of polyisocyanate (B) / (the total of acid anhydride compound (C) and polycarboxylic acid anhydride). When the charge amount is less than 1.01, a resin with a low molecular weight and poor strength is obtained. On the other hand, when it exceeds 5, the viscosity during the reaction becomes high and gelation easily occurs, so neither is preferable. When the above-mentioned acid anhydride compound (C) and polycarboxylic acid anhydride are used in combination, the ratio between the two can be arbitrarily set in consideration of required heat resistance, low dielectric properties, cost, etc. Preferably, the acid anhydride compound (C) is 40 mol parts or more, more preferably 60 mol parts or more, and still more preferably 80 mol parts or more, based on 100 mol parts in total of the acid anhydride compound (C) and the polycarboxylic acid anhydride.

[0025] As the catalyst for producing the imide bond-containing polymer, ordinary reaction catalysts are used. Examples include tin-based catalysts such as dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate, and stannous octoate; iron-based catalysts such as iron acetylacetonate and ferric chloride; and amines such as triethylamine, lutidine, picoline, undecene, triethylenediamine (1,4-diazabicyclo[2,2,2]octane), and DBU (1,8-diazabicyclo[5,4,0]-7-undecene).

Examples

[0026] Hereinafter, the present invention will be specifically described with reference to examples.

[0027] <5% weight loss temperature (5% Td)> Using a differential thermal - thermogravimetric simultaneous measurement device "DTG - 60" (manufactured by Shimadzu Corporation), 10 mg of the measurement sample was placed in an aluminum pan, covered with a lid and sealed, and measured at a heating rate of 5 °C / min from room temperature under a nitrogen atmosphere. As the measurement sample, a sample solution was formed into a coating film, dried at 170 °C for 15 minutes to remove the solvent.

[0028] <Dielectric tangent> Using a cavity resonator (manufactured by A&T Corporation) compliant with JIS C2565, the dielectric tangent (tanδ) at a frequency of 10 GHz was calculated from the measurement by the cavity resonator perturbation method. As the measurement sample, a resin obtained by applying a sample solution to a release substrate so that the dried thickness becomes 25 μm, drying at 170 °C for 15 minutes, and then peeling it off from the release film was used.

[0029] (Production Example 1) In a reaction vessel equipped with a stirring device, a thermometer, a condenser, and a nitrogen inlet tube, 15.00 g (0.071 mol) of trimellitic anhydride chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) as an anhydrous trimellitic acid halide was dissolved in 150 g of cyclohexanone (manufactured by Fujifilm Wako Pure Chemical Corporation) with the inside of the glove box filled with nitrogen. Then, the container was immersed in an ice bath to keep the liquid temperature below 5°C. Separately, 56.70 g (0.035 mol) of GI-1000 (a polyolefin polyol, manufactured by Nippon Soda Co., Ltd., polybutadiene polyol) and 7.89 g (0.078 mol) of triethylamine (manufactured by Tokyo Chemical Industry Co., Ltd.) were dissolved in 133 g of cyclohexanone (manufactured by Fujifilm Wako Pure Chemical Corporation). Then, while maintaining a temperature below 5°C using a dropping funnel, the solution of the polyolefin polyol was added dropwise into the solution of the anhydrous trimellitic acid chloride. After completion of the dropwise addition, the ice bath was removed and the temperature was returned to room temperature. Then, the generated hydrochloride was filtered off and purified to obtain a solution of the acid anhydride compound (C1). As a result of analyzing the reaction solution at this time by gel chromatography (GPC), peaks were confirmed at retention times different from those of GI-1000 and anhydrous trimellitic acid chloride. Also, 10 mg of a dried sample of the reaction solution was dissolved in 0.6 ml of CDCl3, and then the solution was filled into an NMR tube and measured by nuclear magnetic resonance method ( 1 1H-NMR). CDCl3 was used as the lock solvent, and the number of integrations was 64 times. The measurement was carried out using an NMR apparatus AVANCE-NEO 600 (resonance frequency 600 MHz) manufactured by BRUKER. When the peak of CDCl3 was set at 7.3 ppm, since the peak (3.6 ppm) derived from the proton bonded to the carbon closest to the terminal hydroxy group of GI-1000 had almost disappeared, the completion of the reaction was confirmed.

[0030] (Example 1) From the total amount of the solution of the acid anhydride compound (C1) obtained in Production Example 1, a part of cyclohexanone was volatilized using an evaporator. At this time, the total amount was 186 g and the non-volatile content was 38.6 mass%. The total amount of the solution was transferred to a separable flask, and 36.0 g of cyclohexanone and 9.12 g (0.036 mol) of 4,4'-diphenylmethane diisocyanate (MDI) were added under a nitrogen stream so that the non-volatile content became 35.0 mass%. Then, the reaction was carried out at 130 °C for 1 hour, 0.028 g (0.184 mmol) of 1,8-diazabicyclo[5.4.0]-7-undecene was added as a catalyst, and the reaction was further carried out at 130 °C for 4 hours. After completion of the reaction, it was diluted with cyclohexanone and the solution temperature was cooled to room temperature to obtain a solution of a thick, dark reddish-brown polyimide resin (P1) with a non-volatile content of 30 mass%.

[0031] (Example 2) The procedure was the same as in Example 1 except that trimellitic anhydride was added so that the total of the acid anhydride compound (C1) and trimellitic anhydride (TMA) was 0.035 mol and the molar ratio was C1 / TMA = 70 / 30, to obtain a solution of a thick, dark reddish-brown polyamideimide resin (P2) with a non-volatile content of 30 mass%.

[0032] (Example 3) The procedure was the same as in Example 1 except that trimellitic anhydride was added so that the total of the acid anhydride compound (C1) and trimellitic anhydride (TMA) was 0.035 mol and the molar ratio was C1 / TMA = 50 / 50, to obtain a solution of a thick, dark reddish-brown polyamideimide resin (P3) with a non-volatile content of 30 mass%.

[0033] (Production Example 2) A solution of the acid anhydride compound (C2) was obtained by the same procedure as in Production Example 1 except that 20.20 g (0.035 mol) of Pripol 2033 (manufactured by Croda Japan Co., Ltd.), which is a dimer diol, was used as the polyol. As a result of analyzing the reaction solution at this time by gel chromatography (GPC), peaks were confirmed at retention times different from those of Pripol 2033 and trimellitic anhydride chloride. Also, in the same manner as in Production Example 1 11H-NMR measurement was performed, and since the peaks (3.9 ppm and 4.4 ppm) derived from the protons bonded to the carbon closest to the terminal hydroxyl group of Pripol 2033 had almost disappeared, the completion of the reaction was confirmed.

[0034] (Example 4) The same procedure as in Example 1 was carried out except that the acid anhydride compound (C2) obtained in Production Example 2 was used as the acid anhydride compound, and a solution of a polyamide-imide resin (P4) that was dark red-brown and viscous with a non-volatile content of 30% by mass was obtained.

[0035] (Production Example 3) A solution of the acid anhydride compound (C3) was obtained by the same procedure as in Production Example 1 except that 35.44 g (0.035 mol) of Duranol T5651 (manufactured by Asahi Kasei Corporation), which is a polycarbonate polyol, was used as the polyol. As a result of analyzing the reaction solution at this time by gel chromatography (GPC), peaks were confirmed at retention times different from those of Duranol T5651 and trimellitic anhydride chloride. In addition, 1H-NMR measurement was performed in the same manner as in Production Example 1, and since the peak (4.3 ppm) derived from the proton bonded to the carbon closest to the terminal hydroxyl group of Duranol T5651 had almost disappeared, the completion of the reaction was confirmed.

[0036] The same procedure as in Example 1 was carried out except that the acid anhydride compound (C3) obtained in Production Example 3 was used as the acid anhydride compound, and a solution of a polyamide-imide resin (P5) that was dark red-brown and viscous with a non-volatile content of 30% by mass was obtained.

[0037] (Comparative Example 2) With the reaction vessel equipped with a stirring device, thermometer, condenser, and nitrogen inlet tube filled with nitrogen, 3.47 g (0.018 mol) of trimellitic anhydride, 28.88 g (0.018 mol) of GI-1000, and 9.12 g (0.036 mol) of MDI were mixed and stirred in 71.1 g of cyclohexanone (manufactured by Fujifilm Wako Pure Chemical Corporation) so that the non-volatile content became 35% by mass and the molar ratio of trimellitic anhydride to GI-1000 was 50:50, and then dissolved. Thereafter, the temperature was raised to 130 °C and reacted for 5 hours to obtain a solution of polyurethane amide imide resin (P6).

[0038] (Comparative Example 3) The procedure was the same as in Comparative Example 2 except that Duranol T5651 was used instead of GI-1000 as the polyol, and a solution of polyurethane amide imide resin (P7) was obtained.

[0039] (Reference Example 1) With the reaction vessel equipped with a stirring device, thermometer, condenser, and nitrogen inlet tube filled with nitrogen, 3.47 g (0.018 mol) of trimellitic anhydride and 9.50 g (0.038 mol) of MDI were mixed and stirred in 71.1 g of cyclohexanone (manufactured by Fujifilm Wako Pure Chemical Corporation) and dissolved. Thereafter, when reacted at 130 °C, gelation occurred.

[0040] (Reference Example 2) The acid anhydride compound was synthesized in the same manner as in Production Example 1 except that N-methylpyrrolidone (NMP) was used as the solvent, and subsequently, the same operations as in Example 1 were attempted in the NMP solvent, but gelation occurred during the polymerization reaction after the addition of MDI.

[0041] (Reference Example 3) The acid anhydride compound was synthesized in the same manner as in Production Example 1 except that toluene was used as the solvent, and subsequently, the same operations as in Example 1 were attempted in the toluene solvent, but gelation occurred during the polymerization reaction after the addition of MDI.

[0042] (Reference Example 4) An acid anhydride compound was synthesized in the same manner as in Production Example 1 except that methyl ethyl ketone was used as the solvent, and then the same operations as in Example 1 were attempted in a methyl ethyl ketone solvent. However, gelation occurred during the polymerization reaction after the addition of MDI.

[0043]

Table 1

[0044] As is clear from Table 1, the imide bond-containing polymers of Examples 1 to 4 have a low dielectric tangent and a high 5% weight loss temperature. Therefore, they are excellent in low dielectric properties and thermal decomposition resistance. On the other hand, the polymer of Comparative Example 1 used polycarbonate diol instead of polyolefin polyol or dimer diol as the polyol component, so the dielectric tangent was high. In the polymer of Comparative Example 2, a urethane bond was formed in the polymerization step, resulting in an increase in the dielectric tangent and a decrease in the 5% weight loss temperature. The polymer of Comparative Example 3 used polycarbonate diol as the polyol component and also contained a urethane bond, so the dielectric tangent was high and the 5% weight loss temperature decreased. In addition, in Reference Example 1, polymerization was carried out only with trimellitic anhydride and isocyanate without having a polyol component, so the polymer did not dissolve in cyclohexanone and gelated. In Reference Examples 2 to 4, the polymers containing low-polarity units derived from polyol did not dissolve in each solvent or the solubility decreased with the progress of polymerization, resulting in gelation and inability to polymerize.

Industrial Applicability

[0045] The imide bond-containing polymer of the present invention is excellent in dielectric properties and thermal decomposition resistance. Therefore, it can be applied as a material for substrates and adhesives of electronic devices such as flexible printed circuit boards (FPCs) used in the high-frequency region.

Claims

1. A polyimide or polyamideimide (excluding polyimide or polyamideimide having a structural unit derived from caprolactam), obtained by reacting an acid anhydride compound (C) having two or more acid anhydride groups, which is obtained by reacting one or more polyols (A) selected from the group consisting of polyolefin polyol and dimer diol with trimellitic anhydride, with a polyisocyanate (B), and having a 5% weight loss temperature of 350°C or higher.

2. The polyimide or polyamideimide according to Claim 1, having a dielectric tangent (Df) measured at 10 GHz of 0.0025 or less.

3. A method for producing the polyimide or polyamideimide according to Claim 1 or 2, comprising a step A of reacting the polyol (A) and trimellitic anhydride as structural units, and an acid anhydride compound (C) having two or more acid anhydride groups, with the polyisocyanate (B).

4. The method for producing the polyimide or polyamideimide according to Claim 3, wherein the step A is carried out in a solvent containing one or more selected from the group consisting of cyclohexanone, 2-methylcyclohexanone, and dimethyl sulfoxide.

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