JP2503814B2 - Thermosetting resin composition - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thermosetting resin composition which gives a cured product having excellent processability and heat resistance.

[0002]

2. Description of the Related Art Thermosetting resin compositions are used as various electrical insulating materials, structural materials, adhesives, etc. as casting, impregnating, laminating and molding materials. In recent years, the usage conditions of materials have tended to be severe in each of these applications, and the heat resistance of materials has become an important requirement.

However, the thermosetting polyimide resin generally used as the thermosetting resin composition has good heat resistance, but it requires heating at a high temperature for a long time at the time of processing and is inferior in processability. It was a thing. Further, although the epoxy resin having improved heat resistance has excellent processability, it has insufficient mechanical properties at high temperature, electrical properties, long-term heat deterioration resistance, and high heat resistance.

Therefore, as an alternative material, for example, a thermosetting resin mixture containing polyimide and alkenylphenol or alkenylphenol ether (JP-A-52-994), maleimide compounds, polyallylated phenol compounds and epoxies. A heat-resistant resin composition containing a resin (Japanese Patent Laid-Open No. 58-1184099) has been proposed.

However, since the polyallylated phenolic compound used here has a structure in which a polyallyl ether compound is subjected to Claisen transfer or has a structure in which a phenolic hydroxyl group is generated by Claisen transfer during heat curing, The nucleus-substituted allyl group and the hydroxyl group or ether group are located at the ortho position of the same aromatic ring, and particularly in the case of a novolac type resin composition, it tends to remain unreacted even after curing, curing characteristics at high temperature, heat resistance There was a problem with degradability.

The present invention has been made in view of the above circumstances.
It is an object of the present invention to provide a thermosetting resin composition which has a good processability and which gives a cured product excellent in heat resistance, low thermal expansion property and low water absorption.

[0007]

Means for Solving the Problems and Actions The inventors of the present invention have conducted extensive studies in order to achieve the above object, and as a result, (A) an imide compound having a maleimide group represented by the following general formula [I], (B) ) A resin having at least two epoxy groups in one molecule and (C) a resin having a phenolic hydroxyl group in one molecule, and an allyl group in at least one of the components (B) and (C). The thermosetting resin composition containing a compound having a naphthalene ring has good processability, and also has high adhesiveness, good mechanical strength and hot water resistance at high temperature, low expansion and low water absorption. It has been found to give excellent cured products.

[0008]

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That is, although a compound having a maleimide group generally has a large effect of imparting heat resistance, a thermosetting resin composition containing this compound has problems in long-term heat resistance, adhesiveness, water absorption, and processability. However, when a compound containing a naphthalene ring having an allyl group is used together with an imide group-containing compound having a maleimide group of the above formula [I], a compound containing a vinyl group and a naphthalene ring having an allyl group in the maleimide group-containing compound It has been found that a vinyl group reacts with each other to form a copolymer, and thus a thermosetting resin composition having the above-mentioned excellent properties can be obtained.

Furthermore, when a copolymer obtained by reacting an aromatic polymer with an organopolysiloxane represented by the following composition formula [II] is added to the above components, the thermosetting resin composition It was also found that the stress property can be reduced, and the present invention was completed.

[0011]

Embedded image (However, in the formula, R ¹ represents a hydrogen atom or an organic group or an alkoxy group containing any functional group selected from an amino group, an epoxy group, a hydroxy group, and a carboxyl group, and R ² represents a substituted or unsubstituted group. A monovalent hydrocarbon group, where a and b are 0.001 ≦ a ≦ 1, 1 ≦ b ≦ 3, 1 ≦ a
It is a positive number that satisfies + b ≦ 3. Further, the number of silicon atoms in one molecule is an integer of 2 to 1000, and the number of R ¹ directly linked to the silicon atoms in one molecule is an integer of 1 or more. )

Therefore, the present invention is a heat-curing method containing the above-mentioned components (A) to (C) and containing at least one of the above-mentioned components (B) and (C) a compound having a naphthalene ring having an allyl group. The present invention provides a thermosetting resin composition, and a thermosetting resin composition to which a copolymer obtained by reacting an aromatic polymer with an organopolysiloxane of the above formula [II] is added in addition to these components.

The present invention will be described in more detail below. The imide compound incorporated into the thermosetting resin composition of the present invention is a compound having at least one maleimide group represented by the following general formula [I].

[0014]

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In the present invention, among the imide compounds of the above formula [I], compounds having an N-substituted maleimide group represented by the following formula [III] are particularly preferably used.

[0016]

[Chemical 6]

Here, the substituent R is 2 having 1 to 20 carbon atoms.
It is a valent aliphatic hydrocarbon group or a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms, and examples thereof include the following groups.

[0018]

[Chemical 7]

Specific examples of the compound having such an N-substituted maleimide group include N, N'-diphenylmethane bismaleimide, N, N'-phenylene bismaleimide, N, N'-diphenyl ether bismaleimide,
N, N′-diphenylsulfone bismaleimide, N,
N'-dicyclohexylmethane bismaleimide, N,
N'-xylene bismaleimide, N, N'-tolylene bismaleimide, N, N'-xylylene bismaleimide,
N, N'-diphenylcyclohexane bismaleimide,
N, N'-dichloro-diphenylbismaleimide, N,
N'-diphenylmethanebismethylmaleimide, N,
N'-diphenyl ether bismethyl maleimide, N,
N′-diphenylsulfone bismethylmaleimide (including isomers), N, N′-ethylene bismaleimide, N, N′-hexamethylene bismaleimide, N,
N, such as N′-hexamethylenebismethylmaleimide,
N'-bismaleimide compound, prepolymer having an N, N'-bismaleimide skeleton at the terminal obtained by adding these N, N'-bismaleimide compound and diamine, maleimide compound of aniline and formalin condensate, methyl Examples include maleimide compounds.

Further, as the imide compound, a compound represented by the following formula, a mono-substituted maleimide, a tri-substituted maleimide, or a mixture of a tetra-substituted maleimide and a substituted bismaleimide can be used.

[0021]

Embedded image (However, R ³ is a hydrogen atom, a halogen atom or a carbon number of 1 to
4 is an alkyl group, and n is an integer of 1 ≦ n ≦ 20. )

Further, it is also possible to use a compound obtained by modifying the above maleimide compound with silicone.

In the present invention, one kind of these imide compounds may be used alone or two or more kinds may be used as a mixture. Among them, N-substituted trimaleimide, N-substituted bismaleimide, especially N, N '-Diphenylmethane bismaleimide is preferably used.

On the other hand, the component (B) of the present invention is an epoxy resin having at least two epoxy groups in one molecule,
Glycidyl ether type epoxy resin such as bisphenol A type epoxy resin, phenol novolac type epoxy resin, allylphenol novolac type epoxy resin, triphenol alkane type epoxy resin and its polymer, naphthalene type epoxy resin, biphenyl type epoxy resin,
Dicyclopentadiene type epoxy resin, phenol aralkyl type epoxy resin, glycidyl ester type epoxy resin, alicyclic epoxy resin, heterocyclic epoxy resin, halogenated epoxy resin, and epoxy resin in part or all in one molecule Examples thereof include epoxy resins having at least one naphthalene ring having a substituted or unsubstituted allyl group. In addition, among these, it is preferable to use the above-mentioned epoxy resin having a naphthalene ring having an allyl group, which makes it possible to obtain a thermosetting resin composition which gives a cured product having a small expansion coefficient and low hygroscopicity.

Specific examples of the naphthalene ring-containing epoxy resin include the following compounds.

[0026]

[Chemical 9]

[0027]

[Chemical 10]

The above epoxy resins may be used alone or in combination of two or more.

Next, the resin having a phenolic hydroxyl group in one molecule of the component (C) of the present invention acts as a curing agent. For example, novolac type phenol resin, resol type phenol resin, triphenol alkane type resin. , Phenol resins such as naphthol type resins and biphenyl type phenol resins, phenol aralkyl resins, and phenol resins having at least one naphthalene ring having a double bond conjugated to a substituted or unsubstituted aromatic group in one molecule. And the like. These can be used alone or in combination of two or more.

Among the above phenolic resins, it is preferable to use a phenolic resin having a naphthalene ring having an allyl group as the curing agent, which has a small expansion coefficient, a high glass transition temperature, and a glass transition temperature or higher. It is possible to obtain a thermosetting resin composition which has a low elastic modulus in the temperature range of 1 and provides a cured product with low hygroscopicity. Specific examples of the naphthalene ring-containing phenol resin include the following compounds.

[0031]

[Chemical 11]

[0032]

[Chemical 12]

The epoxy resin or phenol resin having a naphthalene ring having an allyl group can be synthesized by a conventional method. For example, the allyl etherification of a phenol resin is followed by a Claisen rearrangement reaction to obtain the above-mentioned compound. Phenolic resin can be easily obtained. Further, the above epoxy resin can be obtained by reacting this phenol resin with an epihalogenated hydrin according to a conventional method.

In the composition of the present invention, the total amount of the above-mentioned components (B) and (C) is 20 to 400 relative to 100 parts (parts by weight, the same applies hereinafter) of the imide compound of the component (A).
Parts, especially 50 to 300 parts. (B)
If the total amount of the component and the component (C) is less than 20 parts, it may be difficult to obtain a cured product having excellent processability and heat resistance. If the total amount is more than 400 parts, the glass transition temperature decreases and long-term heat resistance May get worse.

The ratio of the amount of epoxy groups contained in the component (B) (amol) to the amount of phenolic hydroxyl groups contained in the component (C) (bmol) is a / b = 0.5 to 1. It is desirable to be in the range of 0.5, and if a / b is out of the above range, it may be disadvantageous in terms of curability and low stress.

Thus, the composition of the present invention comprises the above-mentioned (A),
(B) and (C) are blended, and at least one of (B) and (C) contains a compound having a naphthalene ring having an allyl group.

In this case, the compound having a naphthalene ring having an allyl group contains a substituted or unsubstituted naphthalene ring in an amount of at least 10% by weight based on 100 parts by weight of the total of the components (B) and (C). When the content of the naphthalene ring is less than 10% by weight, the effect of lowering the moisture absorption of the cured product and the lowering of the elastic modulus in the temperature range above the glass transition temperature are not remarkable, so crack resistance May not be sufficiently improved. Further, if the content of the naphthalene ring exceeds 80% by weight, it may be disadvantageous in dispersibility during production, moldability and the like.

Further, in the present invention, the vinyl group (A ') in the imide compound of the component (A) and the total vinyl group in the compound having an allyl group contained in the component (B) and the component (C) ( B ') functional group ratio B' / A 'is 0.1 to
2, particularly preferably 0.3 to 1. When the functional group ratio is greater than 2 and the vinyl group ratio of the allyl group is high, unreacted matter may increase, causing a problem in curability, which may deteriorate long-term heat resistance and reliability of the cured product. B '/
When A'is smaller than 0.1 and the proportion of vinyl group in the allyl group is small, problems may occur in moldability and mechanical strength.

The composition of the present invention may contain a copolymer obtained by reacting an aromatic polymer with a specific organopolysiloxane as the component (D), if necessary, in order to impart a low stress property. Preferably.

Various compounds can be used as the aromatic copolymer, and examples thereof include compounds having the following structures.

[0041]

[Chemical 13]

[0042]

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Further, an alkenyl group-containing naphthalene resin represented by the following formula can be used as the aromatic polymer.

[0044]

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These alkenyl group-containing naphthalene resins can be obtained by a usual synthetic method. For example, a naphthalene skeleton-containing phenol resin is reacted with allyl glycidyl ether to introduce an alkenyl group into the molecule.
It can be obtained by a method of partially reacting various naphthalene skeleton-containing epoxy resins with 2-allylphenol or the like.

On the other hand, the organopolysiloxane is represented by the following composition formula [II].

[0047]

Embedded image (However, in the formula, R ¹ represents a hydrogen atom or an organic group or an alkoxy group containing any functional group selected from an amino group, an epoxy group, a hydroxy group, and a carboxyl group, and R ² represents a substituted or unsubstituted group. A monovalent hydrocarbon group, where a and b are 0.001 ≦ a ≦ 1, 1 ≦ b ≦ 3, 1 ≦ a
It is a positive number that satisfies + b ≦ 3. Further, the number of silicon atoms in one molecule is an integer of 2 to 1000, and the number of R ¹ directly linked to the silicon atoms in one molecule is an integer of 1 or more. )

In this case, the substituent R ¹ is, for example, a hydrogen atom, an amino group, an epoxy group, a hydroxy group or —C _x H.
Organic group containing any functional group selected from carboxyl groups such as _2X COOH (x is an integer of 0 to 10), methoxy group, ethoxy group, n-propoxy group, butoxy group, methoxyethoxy group, ethoxyethoxy And an alkoxy group such as a group. R ² is, for example, an alkyl group such as a methyl group, an ethyl group, an n-propyl group or an n-butyl group, an alkenyl group such as a vinyl group or an allyl group, an aryl group such as a phenyl group or a tolyl group, a benzyl group or a phenyl group. Aralkyl groups such as ethyl groups, or chloromethyl groups, 3,3,3-trifluoropropyl groups, trimethoxysilylethyl groups in which some or all of the hydrogen atoms of these groups have been replaced with halogen atoms, alkoxysilyl groups, etc. Group, an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms such as a methyldimethoxysilylethyl group.

Specific examples of the organopolysiloxane of the above formula [II] include the following compounds.

[0050]

[Chemical 17]

The molecular weight of the organopolysiloxane of the above formula [II] is not limited, but is 100
-70000 is preferable. This is because when the obtained copolymer is blended with a thermosetting resin composition, the copolymer of the aromatic polymer and the organopolysiloxane is not compatible with each other in the matrix, and a fine sea-island structure is formed. This is because the organopolysiloxane preferably has a molecular weight of 100 to 70,000. When the molecular weight is less than 100, flexibility may not be imparted when the obtained copolymer is blended in a thermosetting resin composition, or a high glass transition temperature may not be obtained, and the molecular weight may be 70,000. If it exceeds, the molecular weight of the organopolysiloxane copolymer becomes large, the compatibility with the thermosetting resin is lost, the copolymer is separated, and the flexural strength as a physical property may be particularly reduced.

A copolymer of the aromatic polymer and the organopolysiloxane of the formula [II] can be obtained by subjecting both compounds to an addition reaction by a usual method. In particular, the addition reaction of the aromatic polymer and the organopolysiloxane of the formula [II] by hydrosilylation is the most excellent method for obtaining the copolymer as set. For the addition reaction, it is preferable to use a conventionally known addition catalyst, for example, a platinum-based catalyst such as chloroplatinic acid in a catalytic amount and an inert solvent such as benzene, toluene or methyl isobutyl ketone. The reaction temperature is not particularly limited, but is preferably 60 to 120 ° C., and the reaction time is usually 30 minutes to 24 hours. Also,
A copolymer of an aromatic polymer and aminopolysiloxane or epoxypolysiloxane can be obtained by reacting the respective components at room temperature or high temperature, but since both are mixed in a uniform or nearly uniform state. For example, methyl isobutyl ketone, toluene, dioxane,
It is desirable to use a solvent such as methyl cellosolve, water or butanol, isopropyl alcohol, alcohols such as ethanol or phenols to promote the reaction, or tributylamine as a reaction catalyst,
Amines such as 1,8-diazabicycloundecene-7, organic phosphines such as triphenylphosphine, 2
It is desirable to use imidazoles such as -phenylimidazole.

A curing catalyst is preferably added to the composition of the present invention in order to complete the cross-linking between the imide compound having the maleimide group of the formula [I] and the resin having the allyl group.

In this case, as the curing catalyst, for example, benzoyl peroxide, parachlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide,
Capryl peroxide, lauroyl peroxide,
Acetyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, bis (1-
Hydroxycyclohexyl peroxide), hydroxyheptyl peroxide, tertiary butyl hydroperoxide, p-methane hydroperoxide, cumene hydroperoxide, di-tertiary butyl peroxide, dicumyl peroxide, 2,5-dimethyl −
2,5-di (tertiary butyl peroxide) hexane,
2,5-dimethylhexyl-2,5-di (peroxybenzoate), tertiary butyl perbenzoate, tertiary butyl peracetate, tertiary butyl peroctoate, tertiary butyl peroxyisobutyrate, Examples thereof include organic peroxides such as di-tertiary butyl-di-perphthalate, and these can be used alone or in combination of two or more.

Further, it is preferable to use various curing accelerators for the purpose of promoting the crosslinking reaction. Examples of the curing accelerator include triphenylphosphine, tricyclohexylphosphine, tributylphosphine, methyldiphenylphosphine, 1,2-bis (diphenylphosphino).
Organic phosphine compounds such as ethane and bis (diphenylphosphino) methane, 1,8-diazabicyclo [5.
4.0] Tertiary amines such as undecene-7, imidazoles and the like can be mentioned, and these can be used alone or in combination of two or more within a range not impairing the object of the present invention.

The total amount of the curing catalyst and the curing accelerator compounded is 10 (A), (B), (C) and (D).
It is preferably 0.01 to 10 parts, especially 0.1 to 2 parts, relative to 0 parts. When the amount of the catalyst is less than 0.01 part, the curability is insufficient, so that good performance may not be obtained. On the other hand, when the amount exceeds 10 parts, the curability is increased, and the moldability may be deteriorated.

Further, the composition of the present invention may optionally contain an inorganic filler.

As the inorganic filler, those which are usually blended with the thermosetting resin composition can be used, and examples thereof include silicas such as fused silica and crystalline silica, alumina, carbon black, mica, clay, kaolin and glass. Examples thereof include beads, glass fibers, aluminum nitride, silicon carbide, zinc oxide, antimony trioxide, calcium carbonate, aluminum hydroxide, beryllium oxide, boron nitride, titanium oxide, iron oxide and the like.

One of these inorganic fillers may be used alone, or two or more thereof may be used in combination. The compounding amount is not particularly limited, but (A), (B),
The total amount of the components (C) and (D) and the amount of the catalyst is 100 to 1000 parts, and particularly preferably 200 to 700 parts.

The composition of the present invention may further contain various additives, if desired. For example, thermoplastic resin, thermoplastic elastomer, organic synthetic rubber, fine powder of a cured product of silicone gel or silicone rubber, waxes such as carnauba wax, release agents such as fatty acids such as stearic acid and metal salts thereof, carbon black, Pigments such as cobalt blue and red iron oxide, antimony oxide, flame retardants such as halogen compounds, surface treatment agents (aminopropyltrimethoxysilane, methacryloxytrimethoxysilane, γ
-Glycidoxypropyltrimethoxysilane, etc.), epoxysilane, vinylsilane, boron compound, coupling agent such as alkyl titanate, antiaging agent, and one or more kinds of other additives.

In the production of the thermosetting resin composition of the present invention, predetermined amounts of the above-mentioned components are uniformly stirred and mixed, and kneaded by a kneader, roll, extruder or the like which is preheated to 70 to 95 ° C. It can be obtained by methods such as cooling, crushing, and the like. Here, there is no particular limitation on the order of mixing the components.

The thermosetting resin composition of the present invention can be suitably used as a molding material, a powder coating material, an adhesive, etc., and can also seal semiconductor devices such as ICs, LSIs, transistors, thyristors and diodes. It can also be used effectively for the production of printed circuits and printed circuit slopes.

[0063]

EFFECTS OF THE INVENTION The thermosetting resin composition of the present invention has low stress, high adhesiveness, good workability, excellent mechanical strength at high temperature and hot water resistance, heat resistance and low water absorption. It gives a cured product with excellent properties. Therefore, the composition of the present invention sufficiently satisfies the use conditions of recent thermosetting resin compositions, and various electrical insulating materials, structural materials, adhesives, powder coating materials,
It is useful as a material for semiconductor encapsulation.

[0064]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples. In the following examples, all parts are parts by weight.

[Examples 1 to 15, Comparative Examples 1 to 6] N,
N'-4,4'-diphenylmethane bismaleimide 30
For the parts, epoxy resin, phenolic resin of the following structure,
While using the curing catalyst in the compounding amounts shown in Table 1, 260 parts of quartz powder, 1.5 parts of γ-glycidoxypropyltrimethoxysilane, 1.5 parts of wax E, and 1.0 part of carbon black were added thereto, The obtained blend was uniformly melt-mixed with a hot twin roll to produce various thermosetting resin compositions (Examples 1 to 15 and Comparative Examples 1 to 6).

The following tests (a) to (f) were conducted on these thermosetting resin compositions. The results are shown in Tables 1 to 3.
Shown in (A) Spiral flow value Using a mold conforming to EMMI standard, 175 ° C, 70
It was measured under the condition of kg / cm ² . (B) Mechanical strength (flexural strength and flexural modulus) 180 ° C, 70 kg / cm according to JIS-K6911
^2. A bending strength bar of 10 × 4 × 100 mm was molded under the condition of a molding time of 2 minutes and post-cured at 180 ° C. for 4 hours, and then measured at 215 ° C. (C) Using a test piece having a coefficient of expansion and a glass transition temperature of 4 mmφ × 15 mm, the value when the temperature was raised at a rate of 5 ° C./min was measured by a deratometer. (D) Crack resistance after moisture absorption soldering A silicon chip with a size of 2 × 6 × 0.3 mm is 4 × 1
It was adhered to a 2 × 1.8 mm SO package, and the thermosetting resin composition was molded thereon at 175 ° C. × 2 minutes, and post-cured at 180 ° C. for 4 hours. 85 ℃ / 85% RH
After leaving it in the atmosphere for 24 hours and 48 hours,
It was immersed in a solder bath at 40 ° C. for 10 seconds, and the number of package cracks / total number was measured. (E) A moisture-resistant 4M DRAM chip is bonded to a 20-pin SOJ frame, and a thermosetting resin composition is formed thereon at a molding condition of 180 ° C. ×
It was molded in 2 minutes and post-cured at 180 ° C. for 4 hours.
Aluminum wiring after being left in a 121 ° C / 100% RH atmosphere for 24 hours to absorb moisture, immersed in a 260 ° C solder bath for 10 seconds, and then left in a 121 ° C / 100% RH atmosphere for 300 hours The number of breaks / total number was measured. (F) Water absorption of 180 ° C., 70 kg / cm ² , molding time of 2 minutes 5
A disk of 0φ x 3 mm was molded and post-cured at 180 ° C for 4 hours, then it was placed in 121 ° C / 100% PCT for 24 hours.
After standing for a time, the water absorption rate was measured.

[0067]

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[0068]

[Chemical 19]

[0069]

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[0070]

[Chemical 21]

[0071]

[Table 1]

[0072]

[Table 2]

[0073]

[Table 3]

From the results of Tables 1 to 3, a thermosetting resin composition containing the maleimide group-containing imide compound according to the present invention and the allyl group-containing naphthalene-containing resin (Examples 1 to 1) was prepared.
15) has a higher glass transition point, higher bending strength at high temperature, and higher crack resistance, moisture resistance, and water absorption than thermosetting resin compositions (Comparative Examples 1 to 6) that do not contain these components. It was confirmed to be excellent.

Front page continuation (72) Inventor Narumi Manabu 1 Hitomi, Oita, Matsuida-cho, Usui-gun, Gunma Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory (56) Reference JP-A-5-112630 (JP, A) ) JP-A-5-43659 (JP, A) JP-A-4-314723 (JP, A) JP-A-3-192114 (JP, A) JP-A-3-174433 (JP, A) JP-A-63- 3033 (JP, A) JP 53-41399 (JP, A) JP 52-154896 (JP, A) JP 4-48760 (JP, A) JP 3-250017 (JP, A)

Claims (2)

(57) [Claims] 1. (A) an imide compound having a maleimide group represented by the following general formula [I]: (B) a resin having at least two epoxy groups in one molecule, (C) a resin having a phenolic hydroxyl group in one molecule, and an allyl group in at least one of the components (B) and (C) A thermosetting resin composition comprising a compound having a naphthalene ring having 2. The thermosetting resin composition according to claim 1, wherein a copolymer obtained by reacting an aromatic polymer with an organopolysiloxane represented by the following composition formula [II] is added. Embedded image (However, in the formula, R ¹ represents a hydrogen atom or an organic group or an alkoxy group containing any functional group selected from an amino group, an epoxy group, a hydroxy group, and a carboxyl group, and R ² represents a substituted or unsubstituted group. A monovalent hydrocarbon group, where a and b are 0.001 ≦ a ≦ 1, 1 ≦ b ≦ 3, 1 ≦ a
It is a positive number that satisfies + b ≦ 3. Further, the number of silicon atoms in one molecule is an integer of 2 to 1000, and the number of R ¹ directly linked to the silicon atoms in one molecule is an integer of 1 or more. )