Resin composition, cured product, and electronic component

Abstract

The present invention provides: a resin composition which is suitable for coating in a varnish state while having excellent dielectric characteristics; and a cured product and an electronic component which are obtained from the resin composition. A resin composition according to one embodiment of the present invention contains: a polyimide sulfide which has a structure represented by formula (1); and a solvent. The number average molecular weight of the polyimide sulfide is 5,000 or more. (In formula (1), R11 and R2 are each independently a divalent organic group and may be the same group or different groups, and R3 to R6 are each independently a hydrogen atom or an alkyl group.)

Description

Resin composition, cured product, and electronic component

[0001] The present invention relates to a resin composition, a cured product, and an electronic component.

[0002] As communication signals become higher in frequency, there is a demand for low-dielectric materials that are easy to process. For example, Patent Document 1 discloses that a resin composition containing a bismaleimide and a thiol exhibits excellent dielectric properties.

[0003] Patent No. 7272284

[0004] In the technology described in Patent Document 1, a film is formed by pouring a solvent-free resin composition into a frame. On the other hand, when large-area coating or thin-film coating is required, it is necessary to coat the resin composition by adjusting the viscosity in a solvent-diluted state (varnish). In addition, such a resin composition is also required to have a long pot life, i.e., the viscosity adjusted does not change between the time the varnish is prepared and the time it is applied.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a resin composition suitable for application in the form of a varnish, as well as a cured product and an electronic component obtained from the resin composition.

[0006] One aspect of the present invention is a resin composition comprising a polyimide sulfide having a structure represented by the following formula (1) and a solvent, wherein the polyimide sulfide has a number average molecular weight of 3,000 or more: {In formula (1), R １ , R ２ are each an independent divalent organic group, and may be the same or different groups; R ３ ~R ６ are each independently a hydrogen atom or an alkyl group.} The resin composition of the above embodiment may further contain a crosslinking agent and / or a radical generator.

[0007] Another aspect of the present invention is a cured product obtained by curing the resin composition of the above-described aspect.

[0008] Yet another aspect of the present invention is an electronic component, which includes a resin layer obtained from the resin composition of the above-described aspect or a cured product of the above-described aspect.

[0009] According to the present invention, it is possible to provide a resin composition suitable for application in the form of a varnish, as well as a technique relating to a cured product obtained from the resin composition and an electronic component including the cured product.

[0010] Polyimide sulfide 1 of Example 1 １ 1 H NMR chart.

[0011] Hereinafter, embodiments of the present invention will be described in detail. In this specification, the expression "a to b" in the description of a range of values ​​means that the range is from a to b, unless otherwise specified.

[0012] In this specification, the term "(iso)cyanurate" is meant to encompass both "isocyanurate" and "cyanurate."

[0013] (Resin Composition) The resin composition according to the embodiment contains a polyimide sulfide having a structure represented by the following formula (1) and a solvent, and the polyimide sulfide has a number average molecular weight of 3,000 or more. {In formula (1), R １ , R ２ are each an independent divalent organic group, and may be the same or different groups; R ３ ~R ６ are each independently a hydrogen atom or an alkyl group. １ , R ２ are a residue of a bismaleimide compound or a derivative thereof (hereinafter also referred to simply as "bismaleimide" or "bismaleimide compound"), and a residue of a polyfunctional thiol compound, respectively. Examples include residues of bismaleimide compounds and polyfunctional thiols that can be used in the synthesis of polyimide sulfides, which will be described later. ３ ~R ６ is a hydrogen atom or an alkyl group, and is preferably a hydrogen atom or a methyl group.

[0014] The number average molecular weight of the polyimide sulfide of the present embodiment is 3,000 or more, preferably 3,000 to 100,000, more preferably 6,000 to 50,000, and even more preferably 7,000 to 20,000.

[0015] Unlike conventional techniques in which a bismaleimide and a polyfunctional thiol are individually blended into a resin composition, or a bismaleimide and a polyfunctional thiol are blended into a resin composition in the form of a partially added oligomer, the resin composition of this embodiment incorporates a polyimide sulfide with a sufficient molecular weight, which is presumably enabling the preparation of a varnish with an appropriate viscosity. Furthermore, by blending the prepolymerized polyimide sulfide into the resin composition, further polymerization in the varnish state can be suppressed, and therefore the resin composition of this embodiment is presumably excellent in pot life. These synergistic effects facilitate adjustment of the viscosity of the varnish, making it possible to obtain a resin composition suitable for application in the varnish state.

[0016] The weight average molecular weight of the polyimide sulfide of this embodiment is preferably 5,000 to 1,000,000, more preferably 8,000 to 100,000, and particularly preferably 10,000 to 50,000.

[0017] In this embodiment, the number average molecular weight and the weight average molecular weight can be measured by the method described in the examples.

[0018] <Method for Synthesizing Polyimide Sulfide> The polyimide sulfide according to the embodiment can be synthesized using bismaleimide and a polyfunctional thiol as raw materials, for example, according to the following reaction formula.

[0019] The bismaleimide is not particularly limited, but examples thereof include 4,4'-diphenylmethane bismaleimide, m-phenylene bismaleimide, bisphenol A diphenyl ether bismaleimide, 3,3'-dimethyl-5,5'-diethyl-4,4'-diphenylmethane bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)hexane, triethylene glycol bis(maleimidoethyl carbonate), bis(3-ethyl-5-methyl-4-maleimidophenyl)methane, 4,4-bismaleimide diphenyl ether, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 4,4'-bismaleimide diphenylamine, N,N'-dodecamethylene bismaleimide, 1-maleimido-3-maleimidomethyl-3,5,5-trimethyl N,N'-p-phenylenebismaleimide, 1,1'-(cyclohexane-1,3-diylbis(methylene))bis(1H-pyrrole-2,5-dione), 1,1'-(4,4'-methylenebis(cyclohexane-4,1-diyl))bis(1H-pyrrole-2,5-dione), 1,1'-(3,3'-(piperazine-1,4-diyl)bis(propane-3,1-diyl))bis(1H- pyrrole-2,5-dione), 1,2-bis(maleimido)ethane, N-succinimidyl-3-maleimidopropionate, succinimidyl-4-(N-maleimidomethyl)cyclohexane-1-carboxylate, 1,2-bis(maleimido)butane, 1,2-bis(maleimido)hexane, N,N'-1,4-phenylenedimaleimide, bis(2-maleimidoethyl)disulfide, and the like.

[0020] The bismaleimide derivative is not particularly limited, but examples thereof include biscitraconimide compounds described in JP-A-2023-18240.

[0021] The polyfunctional thiol is not particularly limited, but examples thereof include ethylene glycol bisthioglycolate, trimethylolpropane tris(3-mercaptopropionate), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, pentaerythritol tetrakis(3-mercaptopropionate), tetraethylene glycol bis(3-mercaptopropionate), dipentaerythritol hexakis(3-mercaptopropionate), p-xylenedithiol, m-xylenedithiol, 4,4-thiobisbenzenethiol, 1,6-hexanedithiol, 2,2'-thiobisethanethiol, 1,3,5-trimercaptobenzene, 1,4-benzenedithiol, 4,4'-biphenyldithiol, 1,5-naphthalenedithiol, and 4,5-dimethyl-o-xylenedithiol. Among these, bifunctional dithiols are preferred.

[0022] Two or more of these bismaleimides and polyfunctional thiols may be used in combination.

[0023] The reaction between bismaleimide and polyfunctional thiol can be carried out in an organic solvent. The organic solvent is not particularly limited, and known organic solvents can be used. Examples include amide-based organic solvents such as pyridine, N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), and N,N-dimethylformamide (DMF); alcohol-based organic solvents such as methanol, ethanol, isopropanol, butanol, and octanol; ketone-based organic solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; ester-based organic solvents such as ethyl acetate, butyl acetate, and ethyl lactate; ether-based organic solvents such as ethylene glycol monomethyl ether, diethylene glycol monobutyl ether, and tetrahydrofuran (THF); and aromatic hydrocarbon compound-based organic solvents such as benzene, toluene, and xylene.

[0024] The reaction between bismaleimide and polyfunctional thiol can be carried out, for example, in the presence of a base or a nucleophile at 0 to 50°C for 1 minute to 10 hours. Examples of the base include amines (e.g., triethylamine, n-hexylamine), 1,8-diazabicyclo[5.4.0]-7-undecene (DBU), 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), and alkoxide salts (e.g., sodium methoxide). Examples of the nucleophile include phosphines (e.g., triphenylphosphine, dimethylphenylphosphine, tributylphosphine).

[0025] The resin composition of the present embodiment may further contain a crosslinking agent and / or a radical generator.

[0026] Examples of suitable crosslinking agents include polyfunctional vinyl compounds such as divinylbenzene, divinylnaphthalene, and divinylbiphenyl; vinylbenzyl ether compounds synthesized by the reaction of phenol with vinylbenzyl chloride; allyl ether compounds synthesized by the reaction of styrene monomer, phenol with allyl chloride; and trialkenyl isocyanurate. Trikenyl (iso)cyanurate is preferred as the crosslinking agent, and specifically, triallyl isocyanurate (hereinafter referred to as TAIC (registered trademark)) and triallyl cyanurate are particularly preferred. These compounds exhibit low dielectric properties and can enhance heat resistance.

[0027] The content of the crosslinking agent is preferably 1 to 100 parts by mass, more preferably 20 to 80 parts by mass, per 100 parts by mass of the solid content of polyimide sulfide in the resin composition.

[0028] The radical generator is a compound that has the effect of generating radicals by heat or irradiation with light such as ultraviolet light. As such a radical generator, either a thermal radical generator that generates radicals by heat or a photoradical generator that generates radicals by irradiation with light may be used depending on the application of the resin composition. The resin composition of this embodiment becomes a thermosetting resin composition when a thermal radical generator is used, and becomes a photocurable resin composition when a photoradical generator is used.

[0029] Examples of the thermal radical generator include peroxides, such as methyl ethyl ketone peroxide, methyl acetoacetate peroxide, acetylacetonperoxide, 1,1-bis(t-butylperoxy)cyclohexane, 2,2-bis(t-butylperoxy)butane, t-butyl hydroperoxide, cumene hydroperoxide, diisopropylbenzene hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, di-t-butyl hydroperoxide, t-butyl hydroperoxide, dicumyl peroxide, and 2,5-diisopropyl benzene hydroperoxide. Examples of the peroxide include methyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne, 2,5-dimethyl-2,5-di(t-butylperoxy)-3-butene, acetyl peroxide, octanoyl peroxide, lauroyl peroxide, benzoyl peroxide, m-toluyl peroxide, diisopropyl peroxydicarbonate, t-butylene peroxybenzoate, di-t-butyl peroxide, t-butylperoxyisopropyl monocarbonate, α,α'-bis(t-butylperoxy-m-isopropyl)benzene, etc. One type of peroxide may be used alone, or two or more types may be used.

[0030] Examples of photoradical generators include benzoin ketals such as 2,2-dimethoxy-1,2-diphenylethan-1-one; α-hydroxyketones such as 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, and 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one; α-aminoketones such as 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butan-1-one and 1,2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one; oxime esters such as 1-[4-(phenylthio)phenyl]-1,2-octadione-2-(benzoyl)oxime; Phosphine oxides such as bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide, and 2,4,6-trimethylbenzoyldiphenylphosphine oxide; 2,4,5-triarylimidazole dimers such as 2-(o-chlorophenyl)-4,5-diphenylimidazole dimer, 2-(o-chlorophenyl)-4,5-di(methoxyphenyl)imidazole dimer, 2-(o-fluorophenyl)-4,5-diphenylimidazole dimer, 2-(o-methoxyphenyl)-4,5-diphenylimidazole dimer, and 2-(p-methoxyphenyl)-4,5-diphenylimidazole dimer; Benzophenone compounds such as benzophenone, N,N,N',N'-tetramethyl-4,4'-diaminobenzophenone, N,N,N',N'-tetraethyl-4,4'-diaminobenzophenone, and 4-methoxy-4'-dimethylaminobenzophenone; quinone compounds such as 2-ethylanthraquinone, phenanthrenequinone, 2-tert-butylanthraquinone, octamethylanthraquinone, 1,2-benzanthraquinone, 2,3-benzanthraquinone, 2-phenylanthraquinone, 2,3-diphenylanthraquinone, 1-chloroanthraquinone, 2-methylanthraquinone, 1,4-naphthoquinone, 9,10-phenanthraquinone, 2-methyl-1,4-naphthoquinone, and 2,3-dimethylanthraquinone;Examples of the benzoin ethers include benzoin methyl ether, benzoin ethyl ether, and benzoin phenyl ether; benzoin compounds such as benzoin, methylbenzoin, and ethylbenzoin; benzyl compounds such as benzyl dimethyl ketal; acridine compounds such as 9-phenylacridine and 1,7-bis(9,9'-acridinylheptane); N-phenylglycine; and coumarin.

[0031] The content of the radical generator is preferably 0.01 to 20 parts by mass, more preferably 0.05 to 10 parts by mass, and particularly preferably 0.10 to 5 parts by mass, in total relative to 100 parts by mass of the solid content of polyimide sulfide in the resin composition.

[0032] A varnish can be prepared by adding an appropriate amount of solvent to the resin composition of this embodiment. Examples of the solvent include the organic solvents that can be used in the reaction between bismaleimide and polyfunctional thiol described above, as well as conventionally known solvents such as chloroform, methylene chloride, propylene glycol monomethyl ether acetate (PMA), and diethylene glycol monoethyl ether acetate (CA). Only one solvent may be used, or two or more solvents may be used.

[0033] The resin composition of the present embodiment may contain other components as long as the effects of the present embodiment are not impaired. Examples of other components that can be used include known components that can be contained in resin compositions, such as fillers, adhesion agents, surfactants, plasticizers, thermal acid generators, photoacid generators, sensitizers, leveling agents, colorants, and fibers.

[0034] The filler may include organic fillers and inorganic fillers. Examples of organic fillers include imide-based fillers having an imide structure, such as polyimide, polyamideimide, and polyetherimide; and organic fillers made of engineering plastics, such as polyarylate, polysulfone, polyethersulfone, polyphenylene sulfide, polyetheretherketone, polyetherketone, and polyoxybenzoate. Examples of inorganic fillers include clay minerals, such as talc, mica, sericite, and montmorillonite; metal oxides, such as silica, alumina, and titanium oxide; metal hydroxides, such as aluminum hydroxide and magnesium hydroxide; fillers having a ferovskite crystal structure, such as barium titanate and strontium titanate; boron nitride, aluminum borate, barium sulfate, and calcium carbonate. Among these, silica is particularly preferred.

[0035] When a filler is contained, the content of the filler can be, for example, 1 to 99 mass% relative to the total solid content of the resin composition of the present embodiment, and from the viewpoint of an excellent balance between thermal properties and mechanical properties, it is preferably 10 to 90 mass%, and more preferably 20 to 80 mass%.

[0036] (Dry Film) The resin composition of the present embodiment is suitable for application in the form of a varnish, and a dry film can be produced by applying the varnish to a substrate and drying it to form a resin layer.

[0037] The substrate may be, for example, a polyester film such as polyethylene terephthalate, etc. The thickness of the resin layer of the dry film may be, for example, 1 to 100 μm.

[0038] (Cured Film) The cured film according to the embodiment can be formed by applying and drying the resin composition of the above-described aspect, or by laminating the dry film on a substrate, followed by heat curing or photocuring.

[0039] (Electronic component) The electronic component according to the embodiment has a resin layer obtained from the cured product or resin composition described above. The resin layer obtained from the cured product or resin composition according to the embodiment exhibits low dielectric properties and can be used for various purposes as a material for constituting the electronic component.

[0040] The use of the electronic component according to the embodiment is not particularly limited, but preferred examples include insulating materials in electronic components such as those used in large-capacity, high-speed communications typified by fifth-generation communication systems (5G) and millimeter-wave radars for automotive ADAS (Advanced Driver Assistance Systems).

[0041] Although the embodiments of the present invention have been described above, these are merely examples of the present invention, and various other configurations can also be adopted.

[0042] EXAMPLES The present invention will be described below with reference to examples and comparative examples, but the present invention is not limited to these.

[0043] (Synthesis of Polyimide Sulfide 1) 1.76 g (7.03 mmol) of bis(4-mercaptophenyl) sulfide as a polyfunctional thiol, 3.11 g (7.02 mmol) of BMI-70 (manufactured by K.I. Chemical Co., Ltd.) as a bismaleimide, 14 mL of THF as a solvent, and Et ３ 0.03 mL of N was prepared and mixed in a 50 mL vial, and the reaction shown below was carried out. After stirring at room temperature for 6.5 hours, the mixture was diluted with 60 mL of THF and reprecipitated with 360 mL of MeOH. After filtration using a Kiriyama funnel, the mixture was vacuum dried (80°C, 16 hours) to obtain 4.76 g (yield 98%) of pale yellow polyimide sulfide 1 (solid).

[0044] The obtained polyimide sulfide 1 was dissolved in chloroform (CHCl ３) and GPC measurement was carried out under the following conditions. Apparatus name: e2695 (Waters) Mobile phase: chloroform Column: Shodex K-805L Column temperature: 40°C Flow rate: 1.0 mL / min. Detector: 2414 (RI detector, Waters, wavelength 410 nm) Sample concentration: 1.0 mg / mL Sample solvent: same as mobile phase STD reagent: standard polystyrene STD concentration: 1.0 mg / mL STD solvent: same as mobile phase Analysis time: 20 min

[0045] As a result of GPC measurement, the weight average molecular weight was 3.50 × 10 ４ , number average molecular weight 1.46×10 ４ The dispersity index (PDI) was 2.39.

[0046] Further, for the obtained polyimide sulfide 1, １ 1 H NMR was measured. １ 1 is a 1 H NMR chart. From FIG. 1, it was confirmed that the target compound was obtained.

[0047] (Synthesis of Polyimide Sulfide 2) 0.43 g (1.72 mmol) of bis(4-mercaptophenyl) sulfide as a polyfunctional thiol, 0.80 g (1.81 mmol) of BMI-70 (manufactured by K.I. Chemical Co., Ltd.) as a bismaleimide, 5 mL of THF as a solvent, and Et ３ 0.03 mL of N was prepared and mixed in a 50 mL vial. After stirring at room temperature for 4.4 hours, the mixture was diluted with 8.5 mL of THF and reprecipitated with 120 mL of MeOH. After filtration using a Kiriyama funnel, the mixture was vacuum dried (80°C, 17 hours) to obtain 1.13 g (yield 91%) of pale yellow polyimide sulfide 2 (solid). GPC measurement revealed a weight-average molecular weight of 2.24 × 10 ４ , number average molecular weight 9.63×10 ３ The dispersity index (PDI) was 2.33.

[0048] (Synthesis of Polyimide Sulfide 3) 0.68 g (2.72 mmol) of bis(4-mercaptophenyl) sulfide as a polyfunctional thiol, 1.20 g (2.71 mmol) of BMI-70 (manufactured by K.I. Chemical Co., Ltd.) as a bismaleimide, and 15 mL of 1,4-dioxane as a solvent were prepared and mixed in a 50 mL vial. The mixture was stirred at 100°C for 2.2 hours and then reprecipitated using 170 mL of MeOH. After filtration using a Kiriyama funnel and vacuum drying (90°C, 3 hours), 1.33 g (71% yield) of pale yellow polyimide sulfide 3 (solid) was obtained. GPC measurement revealed a weight-average molecular weight of 1.35 × 10 ３ , number average molecular weight 1.09×10 ３ The dispersity index (PDI) was 1.24.

[0049] (Synthesis of Polyimide Sulfide 4) 0.87 g (3.47 mmol) of bis(4-mercaptophenyl) sulfide as a polyfunctional thiol, 1.80 g (4.07 mmol) of BMI-70 (manufactured by K.I. Chemical Co., Ltd.) as a bismaleimide, 22 mL of THF as a solvent, and Et ３ 0.100 mL of N was prepared and mixed in a 50 mL vial. The mixture was stirred at room temperature for 5.1 hours, and then reprecipitated with 150 mL of MeOH and 50 mL of water. The mixture was filtered using a Kiriyama funnel and then vacuum dried (90°C, 17 hours) to obtain 2.45 g (yield 92%) of pale yellow polyimide sulfide 4 (solid). GPC measurement revealed a weight-average molecular weight of 9.79 x 10 ３ , number average molecular weight 4.68×10 ３ The dispersity index (PDI) was 2.09.

[0050] (Synthesis of Polyimide Sulfide 5) Citraconic anhydride, 4,4'-methylenebis(2-ethyl-6-methylaniline), and acetone as a solvent were prepared and stirred in a 100 mL two-neck flask at room temperature for 1.5 hours. Then, 4.9 mL of acetic anhydride and 15.4 mL of triethylamine were added and stirred overnight at 50°C. After distilling off the solvent, 1.45 g (yield 27%) of BMI-70-Me (solid) was obtained by column chromatography. 0.361 g (1.44 mmol) of bis(4-mercaptophenyl) sulfide as a polyfunctional thiol, 0.697 g (1.48 mmol) of BMI-70-Me, 9 mL of THF as a solvent, and 0.09 mL of EtN as a base were prepared and mixed in a 50 mL vial, and the reaction shown below was carried out. After stirring at room temperature for 5.7 hours, the mixture was diluted with 3.5 mL of THF and reprecipitated using 150 mL of MeOH. After filtration using a Kiriyama funnel and vacuum drying (60°C, 3 hours), pale yellow polyimide sulfide 5 (solid. GPC measurement showed a weight average molecular weight of 3.34 × 10 ４ , number average molecular weight 1.34×10 ４ The dispersity index (PDI) was 2.49.

[0051] Varnishes were prepared according to the components and formulations shown in Table 1, and the pot life, film-forming properties, and dielectric properties were examined. Note that the blending amounts in Table 1 indicate parts by mass of the slurry containing the solvent for the filler, and parts by mass of the solid content for the other components.

[0052] Details of the components listed in Table 1 are as follows: Polyimide sulfides 1 to 5: Polyimide sulfides obtained by the above-mentioned synthesis examples Bismaleimide: BMI-70 manufactured by K.I. Chemical Co., Ltd. Thiol: bis(4-mercaptophenyl) sulfide Crosslinking agent: TAIC manufactured by Mitsubishi Chemical Corporation Peroxide: Perbutyl P40 manufactured by NOF Corporation Filler: Silica-containing slurry (solid concentration 70 wt %, cyclohexanone solvent), SC2050HNF manufactured by Admatechs Co., Ltd. Solvent: cyclohexanone

[0053] (Pot life) The prepared varnish was allowed to stand at room temperature for 20 minutes. The viscosity immediately after preparation and after standing for 20 minutes were visually confirmed, and the pot life was evaluated according to the following criteria: A: The viscosity did not change immediately after preparation and after standing for 20 minutes. B: The varnish increased in viscosity after standing for 20 minutes.

[0054] (Film-Forming Properties) Cured films were prepared under the following curing conditions, and the film-forming properties were evaluated. For Comparative Example 3, the viscosity of the varnish increased significantly in a short time, making it difficult to maintain a viscosity suitable for coating. Therefore, the following evaluations were not performed. The resin composition was applied to copper foil using an applicator with a gap of 200 μm. Next, the composition was dried at 90°C for 5 minutes in a hot-air circulating drying oven. The temperature was then raised to 200°C in an inert oven under a fully nitrogen-substituted atmosphere, and the composition was cured for 1 hour to obtain a cured film on the copper foil. The copper foil was removed from the obtained cured film on the copper foil by etching, obtaining a free-standing cured film. The film-forming properties of the process of obtaining a free-standing cured film were evaluated according to the following criteria. A: No cracks or unevenness occurred in the obtained free-standing cured film. B: Cracks occurred in part of the obtained free-standing cured film. C: The varnish flowed during coating, causing unevenness in the cured film. In addition, cracks occurred in the cured film on the copper foil, making it impossible to obtain a free-standing film.

[0055] (Dielectric Properties) The relative permittivity Dk and dielectric loss tangent Df were measured according to the following method. The free-standing cured film prepared in the film-forming evaluation was cut into a length of 80 mm and a width of 45 mm, and used as a test piece for measurement by the SPDR (Split Post Dielectric Resonator) resonator method. The measuring device used was a vector network analyzer E5071C manufactured by Keysight Technologies, Inc., an SPDR resonator, and a calculation program manufactured by QWED. The conditions were a frequency of 10 GHz and a measurement temperature of 25°C. Note that for Comparative Examples 1 and 2, free-standing cured films could not be obtained, so the dielectric properties were not evaluated.

[0056] The resin composition of the present disclosure is suitable for application in the form of a varnish, and can therefore be suitably used as a material for forming electronic components. CROSS-REFERENCE TO RELATED APPLICATIONS

[0057] This application claims priority based on Japanese Patent Application No. 2024-137055, filed with the Japan Patent Office on August 16, 2024, the entire disclosure of which is incorporated herein by reference in its entirety.

Claims

1. A resin composition comprising a polyimide sulfide having a structure represented by the following formula (1) and a solvent, wherein the polyimide sulfide has a number average molecular weight of 3,000 or more. {In formula (1), R １ , R ２ are each an independent divalent organic group, and may be the same or different groups; R ３ ~R ６ are each independently a hydrogen atom or an alkyl group.

2. The resin composition according to claim 1, further comprising a crosslinking agent and / or a radical generator.

3. A cured product obtained by curing the resin composition according to claim 2.

4. An electronic part comprising a resin layer obtained from the resin composition according to claim 1 or the cured product according to claim 3.

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