JP2021066759A - Thermosetting resin composition and cured product thereof - Google Patents

Abstract

To provide a new thermosetting resin composition containing a cyanate ester compound and an epoxy resin, wherein it is possible to maintain the heat resistance of a cured product of the thermosetting resin composition while achieving increased toughness.SOLUTION: A thermosetting resin composition contains (A) a cyanate ester compound, (B) an epoxy resin, (C) a curing accelerator, (D) radical-polymerizable monomers and (E) a radical initiator. As (D) the radical-polymerizable monomers, in the total mass of (A) (B) (C) (D) and (E), 0.5-40 mass% of a monofunctional radical-polymerizable monomer and 10 mass% or less of a polyfunctional radical-polymerizable monomer are contained.SELECTED DRAWING: None

Description

The present invention relates to a thermosetting resin composition containing a cyanate ester compound and an epoxy resin, and a cured product thereof.

In recent years, with regard to electrical and electronic equipment materials such as multi-layer circuit boards and highly integrated circuit boards, equipment has become smaller, lighter, and more sophisticated, and further multi-layer, high-density, thin, lightweight, and reliable. Improvements in properties and moldability are required. Various applications of curable resin compositions that can be cured by heat or active energy rays have been studied, and curable resin compositions having excellent properties required for each application have been developed.

Epoxy resin can be mentioned as a typical thermosetting resin. Epoxy resins have been applied to various applications, and are still being improved from the viewpoint of improving heat resistance, moldability, processability, storage stability, and the like.
Further, a cyanate resin can be mentioned as a typical resin for electric / electronic device materials. Cyanate resin has been developed as an insulating layer in a high frequency region, which has been increasing in demand in recent years because it has excellent dielectric properties such as dielectric constant and dielectric loss tangent in addition to good heat resistance as a heat-curable resin.

In recent years, studies have been made to improve the characteristics of cured products by using these cyanate resins and epoxy resins in combination.
For example, Patent Document 1 describes a cyanate ester compound having two or more cyanate ester groups in one molecule, an epoxy resin having two or more epoxy groups in one molecule, and two or more unsaturateds in one molecule. A radical by combining a radically polymerizable compound having a double bond and having a ring structure formed only of carbon and hydrogen in the molecule and having no hydroxyl group in the molecule, and a radical polymerization initiator. The ring structure of the polymerizable compound contributes to the rigidity of the cured product, and not only contributes to the improvement of the mechanical properties of the cured product, particularly the bending elasticity and bending strength, but also the radically polymerizable compound has a hydroxyl group. Therefore, the polymerization can be efficiently promoted without acting as a radical polymerization prohibiting agent.

Further, in Patent Document 2, a curable resin composition having a specific skeleton and containing an epoxy resin, a cyanate ester compound and a curing accelerator is excellent in moldability, processability and storage safety, and is cured at a low temperature. It is disclosed that the cured product has excellent heat resistance.

Japanese Unexamined Patent Publication No. 2011-46815 JP-A-2017-149878

A cured product of a thermosetting resin composition such as a cyanate ester compound or an epoxy resin has a problem that it is inherently brittle and inferior in toughness because it is used as an insoluble and infusible curing having a three-dimensional crosslinked structure. .. Particularly in recent years, the use of thermosetting resins such as epoxy resins has expanded to advanced technology fields such as high-performance composite materials such as carbon fiber used as structural materials for aircraft and encapsulants for semiconductor integrated circuits. Therefore, it is required to further enhance the toughness of the cured product of the thermosetting resin composition.
In Patent Document 1, no study has been made on toughness and heat resistance. Further, in Patent Document 2, although the heat resistance is improved, the brittleness peculiar to the thermosetting resin is not improved.

An object of the present invention is to further develop the invention described in Patent Document 2 with respect to a thermosetting resin composition containing a cyanate ester compound and an epoxy resin to improve the heat resistance of the cured product of the thermosetting resin composition. Specifically, it is an object of the present invention to provide a new thermosetting resin composition capable of increasing toughness while maintaining at least the glass transition temperature (Tg) of the cured product at 220 ° C. or higher.

The present invention contains (A) a cyanate ester compound, (B) an epoxy resin, (C) a curing accelerator, (D) a radically polymerizable monomer and (E) a radical initiator.
(D) As the radically polymerizable monomer, 0.5 to 40% by mass of the monofunctional radically polymerizable monomer is contained in the total mass of (A), (B), (C), (D) and (E), and the amount is large. We propose a thermosetting resin composition containing 10% by mass or less of a functional radically polymerizable monomer.

According to the thermosetting resin composition proposed by the present invention, toughness can be effectively increased while maintaining at least a glass transition temperature (Tg) of 220 ° C. or higher of the cured product. In particular, (A) can be obtained by a method of simultaneously curing (A) a cyanate ester compound and (B) an epoxy resin and (D) radical polymerization of a radically polymerizable monomer (also referred to as "in situ reaction / polymerization method"). A cured product having a phase-separated structure having a phase derived from a cyanate ester compound and (B) epoxy resin and a phase derived from (D) a radically polymerizable monomer can be produced, and the cured product can be toughened. Can be planned.

Next, the present invention will be described based on examples of embodiments of the invention. However, the present invention is not limited to the embodiments described below.

<< This thermosetting resin composition >>
The thermosetting resin composition (referred to as “the thermosetting resin composition”) according to an example of the embodiment of the present invention includes (A) a cyanate ester compound, (B) an epoxy resin, and (C) a curing accelerator. A thermosetting resin composition containing (D) a radically polymerizable monomer, (E) a radical initiator, and, if necessary, (F) other components.

<(A) Cyanate ester compound>
The cyanate ester compound (A) is a resin containing a compound having two or more cyanate ester groups (-OCN) in one molecule, and among them, those having an aromatic ring are preferable. The aromatic ring has the effect of improving the heat resistance of the cured product due to its high rigidity.

Examples of the aromatic ring include monocyclic aromatic hydrocarbons such as benzene; and polycyclic aromatic hydrocarbons such as naphthalene, azulene, anthracene, phenanthrene, pyrene, chrysene, triphenylene, tetracene, and tetraphen.

Further, the cyanate ester compound preferably has biphenyl, triphenylmethane, various biphenols, fluorene, xanthene and the like as a partial structure in addition to the above-mentioned monocyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons.

The cyanate equivalent of the cyanate ester compound contained in the thermosetting resin composition (mass (g) per mol of cyanate group contained in the cyanate ester compound) is not particularly limited. From the viewpoint of various balances such as workability, heat resistance, and electrical characteristics, 50 to 500 g / eq. Of particular, 80 g / eq. Above or 300 g / eq. The following is more preferable, and among them, 100 g / eq. Above or 200 g / eq. The following is particularly preferable.

The molecular weight of the (A) cyanate ester compound is preferably 1000 or less, more preferably 600 or less, and more preferably 400 or less, from the viewpoint of lowering the viscosity of the composition and improving processability. Is particularly preferable.

From this point of view, for example, preferable cyanate ester compounds have the following structures.

The cyanate ester compound contained in the present thermosetting resin composition has at least two or more cyanate groups in one molecule. However, a part of the cyanate group may be added or cyclized to form a multimer (sometimes referred to as a prepolymer) such as a linear adduct or a triazine ring.

Only one type of cyanate ester compound contained in the present thermosetting resin composition may be used, or a combination of two or more types may be used. Further, the cyanate ester compound used in the combination thereof may be a prepolymer.

<(B) Epoxy resin>
The epoxy resin (B) can be appropriately selected depending on the physical characteristics required for the composition and the cured product. Above all, it is more preferable to use a polyfunctional epoxy resin having three or more epoxy groups in one molecule. If the epoxy resin (B) has three or more epoxy groups in one molecule, a high glass transition temperature (Tg) can be maintained. From this point of view, it is more preferable to have four or more epoxy groups in one molecule. On the other hand, if it has 8 or more, unreacted epoxy groups remain, which may lead to deterioration of Tg and mechanical properties. Therefore, it is preferable to have 7 or less, and 6 or less. It is more preferable to have.

The epoxy equivalent of the epoxy compound contained in the thermosetting resin composition (mass (g) per mole of epoxy group contained in the epoxy compound) is not particularly limited. From the viewpoint of various balances such as workability, heat resistance, and electrical characteristics, 50 to 500 g / eq. It is preferably 70 g / eq. Above or 300 g / eq. More preferably, it is 90 g / eq. Above or 250 g / eq. The following is particularly preferable.

Further, the epoxy resin preferably has one or more aromatic rings. The aromatic ring has the effect of improving the heat resistance of the cured product due to its high rigidity.
Examples of the aromatic ring include monocyclic aromatic hydrocarbons such as benzene; and polycyclic aromatic hydrocarbons such as naphthalene, azulene, anthracene, phenanthrene, pyrene, chrysene, triphenylene, tetracene, and tetraphen.

The epoxy resin preferably has a partial structure such as biphenyl, triphenylmethane, various biphenols, fluorene, xanthene, etc., in addition to the above-mentioned monocyclic aromatic hydrocarbons and polycyclic aromatic hydrocarbons.

From this point of view, preferred examples of the epoxy resin include epoxy resins represented by the following general formulas (1) to (11).

The structure of the epoxy resin represented by the general formula (1) is as follows.

In the general formula (1), A represents a single bond, -O-, -S-, -SO-, -SO _2- , or a substituted or unsubstituted divalent organic group. Examples of the substituted or unsubstituted divalent organic group include a methylene group, a 1,1-ethylene group, a 2,2-propylene group, and a 1,1,1,1,3,3,3, -hexafluoro-2-. Divalent aliphatic chain hydrocarbon group such as 2-propylene group; for example, cyclopropylidene group, cyclobutylidene group, cyclopentylidene group, cyclohexylidene group, 3,3,5-trimethylcyclohexylidene group. , Cyclooctylidene group, cyclododecylidene group, adamantanylene group, 1,3-cyclopentylene group, 1,3-cyclohexylene group, 1,4-cyclohexylene group, 5-methyl-1,3- Divalent aliphatic cyclic hydrocarbon group such as cyclohexylene group, 5,5-dimethyl-1,3-cyclohexylene group, dicyclopentadienylene group; divalent such as benzylmethylene group, furylmethylene group and fluorenylidene group. Aromatic ring-containing hydrocarbon groups can be mentioned.

R ¹⁰ and R ¹¹ are independently hydrogen atom, hydroxyl group, halogen atom, substituted or unsubstituted alkyl group having 1 to 12 carbon atoms, substituted or unsubstituted alkoxy group having 1 to 12 carbon atoms, and carbon number. It represents a substituted or unsubstituted aryl group of 6 to 12, or a substituted or unsubstituted aryloxy group having 6 to 12 carbon atoms. Among them, R ¹⁰ and R ¹¹ are preferably substituted or unsubstituted alkyl groups, and particularly preferably substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms. Further, R ¹⁰ and R ¹¹ may be connected to each other. Specifically, the following structure can be mentioned.
Further, n and p each independently represent an integer of 0 to 3.

Specific examples of the epoxy resin represented by the general formula (1) are not particularly limited, but the following can be mentioned.

Among them, the following compounds are particularly preferable from the viewpoint of heat resistance and ease of synthesis.

The following can be given as an example in which ^{R 10} and R ^{11 are connected to each other.}

The structures of the epoxy resins represented by the general formulas (2) to (11) are as follows.

In the general formula (2) to (11), the formula ^{R 5} is a hydroxyl group or an organic group having 1 to 10 carbon atoms. Specific examples thereof include an alkyl group such as a methyl group and an ethyl group, an alkoxy group such as a methoxy group and an ethoxy group, and the like. u is 0 to 4. U number of R ⁵ contained in each aromatic ring may be the same or different. Further, t is 2 or more and 99 or less, preferably 2 or more and 19 or less.

The epoxy resin contained in the present thermosetting resin composition preferably has three or more epoxy groups in one molecule as described above. Further, depending on the physical properties of the cured product, a combination of two or more types of epoxy resins having three or more epoxy groups in one molecule may be used, and two epoxy groups are contained in one or more types of one molecule. It may be a combination with an epoxy resin having only.

The properties of the above-mentioned epoxy compound may be solid at room temperature (25 ° C.) such as powder, flakes, pellets, and sheets; or liquid. From the viewpoint of compatibility with other components and handleability, it is preferably solid at room temperature (25 ° C.).

It is also possible to use the above-mentioned epoxy resin after inducing it into a phenoxy resin in advance. The phenoxy resin is a linear epoxy oligomer derived from the epoxy resin by a production method as described in, for example, Japanese Patent Application Laid-Open No. 5348740.
When the epoxy resin is converted into a phenoxy resin before use, the molecular weight of the epoxy resin is not particularly limited. In order to maintain good processability when the composition is prepared, the mass average molecular weight of the epoxy resin is preferably 200 to 5000, and more preferably 300 or more or 2000 or less. Here, the mass average molecular weight can be determined by, for example, general GPC (gel permeation chromatography) measurement using polystyrene as a standard substance.

<(C) Curing accelerator>
The (C) curing accelerator may be any substance that contributes to the curing reaction of the (A) cyanate ester compound and (B) epoxy resin, and is generally known as a curing accelerator for the cyanate ester compound and the epoxy resin. Things can be mentioned.

In this thermosetting resin composition, these curing accelerators can be used alone or in any combination. Further, by containing these curing accelerators alone or in any combination, the present thermosetting resin composition can obtain excellent strength and heat resistance.

Examples of the curing accelerator are not particularly limited, but include imidazoles, tertiary amines, organic phosphines, phosphonium salts, tetraphenylboron salts, metal-based curing accelerators, organic acid dihydrazides, boron halide amine complexes and the like. Can be mentioned.

Among them, as the preferred (C) curing accelerator, quaternary phosphonium borate represented by the following general formula (12) can be mentioned.
In the quaternary phosphonium borate represented by the general formula (12), the catalytic activity is suppressed at room temperature because the active species phosphonium cation and borate anion are protected by forming an ion pair with each other. At the curing temperature, the ion pair dissociates into anions and cations and rapidly develops catalytic activity, making it possible to achieve both room temperature storage and curability of cyanate ester compounds and epoxy resins. Compared with the conventional metal catalyst, it can be cured at a low temperature and in a short time.
For the above reasons, the quaternary phosphonium borate represented by the general formula (12) is preferable as the (C) curing accelerator of the present thermosetting resin composition.

In the general formula (12), P represents a phosphorus atom. R ^{13 to} R ¹⁶ independently represent a substituted or unsubstituted aromatic group or a substituted or unsubstituted alkyl group, and R ^{13 to} R ¹⁶ have a phosphorus atom and each substituent having a PC bond. It is what forms. Further, R ^{13 to} R ¹⁶ may be the same or different. Examples of such a group include a methyl group, an ethyl group, a butyl group, a t-butyl group, an allyl group, a phenyl group, a tolyl group, a benzyl group, an ethylphenyl group, a naphthyl group and the like. It is preferably a phenyl group.

Examples of the phosphonium group constituting the general formula (12) include a tetraphenylphosphonium group, a tetratolylphosphonium group, a tetraethylphosphonium group, a tetramethylphosphonium group, a tetranaphthylphosphonium group, a tetrabenzylphosphonium group and an ethyltriphenylphosphonium. Examples thereof include a group, an n-butyltriphenylphosphonium group, a 2-hydroxyethyltriphenylphosphonium group, a trimethylphenylphosphonium group, a methyldiethylphenylphosphonium group, a methyldiallylphenylphosphonium group, a tetra-n-butylphosphonium group and the like. It is preferably a tetraphenylphosphonium group.

In the general formula (12), B represents a boron atom. ^{R 17 to} R ²⁰ on the volate side independently represent a substituted or unsubstituted aromatic group or a substituted or unsubstituted alkyl group, and R ^{17 to} R ²⁰ have a boron atom and each substituent is B-. It forms a C bond. R ^{17 to} R ²⁰ may be the same or different. Examples of such a group include a methyl group, an ethyl group, a butyl group, a t-butyl group, an allyl group, a phenyl group, a tolyl group, a benzyl group, an ethylphenyl group, a naphthyl group and the like. It is preferably a tolyl group.

Examples of the borate group constituting the general formula (12) include a tetraphenyl borate group, a tetratolyl borate group, a tetraethyl borate group, a tetranaphthyl borate group, and a tetrabenzyl borate group. Preferably, it is a tetratolyl borate group.

Further, as a suitable curing accelerator for efficiently curing the cyanate ester compound and the epoxy resin or the like, a metal-based curing accelerator can be mentioned. These may be used alone or in combination of two or more.

The metal-based curing accelerator is not particularly limited. Examples thereof include organometallic complexes or organometallic salts of metals such as cobalt, copper, zinc, iron, nickel, manganese and tin.
Specific examples of the organic metal complex are not particularly limited, but are organic cobalt complexes such as cobalt (II) acetylacetonate and cobalt (III) acetylacetonate, organic copper complexes such as copper (II) acetylacetonate, and zinc ( II) Organic zinc complexes such as acetylacetonate, organic iron complexes such as iron (III) acetylacetonate, organic nickel complexes such as nickel (II) acetylacetonate, organic manganese complexes such as manganese (II) acetylacetonate, etc. Can be mentioned.
The organometallic salt is not particularly limited. For example, zinc octylate, tin octylate, zinc naphthenate, cobalt naphthenate, tin stearate, zinc stearate and the like can be mentioned.
Metallic curing accelerators include cobalt (II) acetylacetonate, cobalt (III) acetylacetonate, zinc (II) acetylacetonate, zinc naphthenate, and iron (III) from the viewpoint of curability and solvent solubility. Acetylacetonate is preferable, and cobalt (III) acetylacetonate and zinc naphthenate are particularly preferable. The metal-based curing accelerator may be used alone or in combination of two or more.

The upper limit of the amount of the metal-based curing accelerator added is the metal-based curing promotion with respect to 100% by mass of the total amount of the cyanate ester compound and the epoxy resin from the viewpoint of preventing deterioration of storage stability and insulating property of the resin composition. The metal element-equivalent content contained in the agent is preferably 500 ppm or less, more preferably 200 ppm or less. On the other hand, the lower limit of the amount of the metal-based curing accelerator added to the resin composition is a resin from the viewpoint of preventing difficulty in forming a conductor layer having excellent peel strength on the surface of a low-roughness insulating layer. The metal element-equivalent content contained in the metal-based curing accelerator is preferably 20 ppm or more, more preferably 30 ppm or more, based on 100% by mass of the non-volatile content in the composition.

The type of curing accelerator may be selected according to the balance between the curing conditions, the shape of the cured product, and the physical properties such as the adhesiveness and bending strength of the cured product. Further, these curing accelerators may be used alone or in combination of two or more.

The amount of the above-mentioned curing accelerator other than the metal-based curing accelerator, including the quaternary phosphonium borate represented by the general formula (12), is not particularly limited. It is preferable to use it in the range of 0.001 mass or more and 20 parts by mass or less with respect to 100 parts by mass of the total amount of the cyanate ester compound and the epoxy resin. It is more preferably 0.005 parts by mass or more, further preferably 0.01 parts by mass or more, and more preferably 10 parts by mass or less, still more preferably 5 parts by mass or less.

<(D) Radical Polymerizable Monomer>
The radically polymerizable monomer (D) may be a monomer capable of radical polymerization under radical polymerization conditions, and usually has a radically polymerizable functional group, for example, a carbon-carbon double bond in the molecule. Is preferable.
Examples of such radically polymerizable monomers include styrene-based monomers, maleimide-based monomers, (meth) acrylates, vinyl ethers and vinylamides, and depending on the structure, monofunctional radical-polymerizable monomers and polyfunctional radical-polymerizable monomers. are categorized.

The (D) radical-polymerizable monomer has the (D) radical in the total mass of (A), (B), (C), (D) and (E) from the viewpoint of exhibiting the effect as a modifier in the entire cured product. The polymerizable monomer is preferably contained in an amount of 0.5% by mass or more, more preferably 3% by mass or more, and more preferably 10% by mass or more. On the other hand, in the total mass of (A), (B), (C), (D) and (E) from the viewpoint of maintaining the heat resistance and high mechanical properties of the cured product derived from (A) and (B). , (D) The radically polymerizable monomer is preferably contained in a proportion of 40% by mass or less, more preferably 35% by mass or less, and more preferably 30% by mass or less.

(D) Of the radically polymerizable monomers, the monofunctional radically polymerizable monomer has only one functional group (here, the functional group also includes an atomic group) that performs radical chain polymerization under radical polymerization conditions. Anything that has it is sufficient. More specifically, it is preferable that the monomer does not form or hardly forms a crosslinked structure under radical polymerization conditions.

On the other hand, the polyfunctional radically polymerizable monomer has two or more, preferably only two functional groups (here, the functional group also includes an atomic group) that performs radical chain polymerization under radical polymerization conditions. Anything is fine. More specifically, those that form a crosslinked structure under radical polymerization conditions are preferable.

(D) The radically polymerizable monomer undergoes radical polymerization during the preparation of the cured product. The polymer thus produced acts as a modifier for imparting toughness to a cured product composed of (A) cyanate ester compound and (B) epoxy resin. At this time, a phase-separated structure having a phase derived from (A) cyanate ester compound and (B) epoxy resin and a phase composed of a modifier (D) derived from a radically polymerizable monomer is formed in the cured product. By doing so, it becomes possible to impart toughness without deteriorating the mechanical properties.

In order to further effectively improve the toughness, a modifier derived from (D) a radically polymerizable monomer is used with respect to the composition consisting of (A) cyanate ester compound, (B) epoxy resin and (C) curing accelerator. Is added in the form of a monomer together with the (E) radical initiator, not in the state of a pre-polymerized polymer, and the modifier is polymerized at the same time in the process of curing the thermosetting resin composition. It is preferable to use the "polymerization method". As a result, the modifier component is uniformly dispersed in the cured product rather than adding the modifier in the polymer state, and the phase derived from the (D) radically polymerizable monomer is more suitable for increasing the toughness of the cured product. Since it is possible to adjust the size to a different size, the toughness of the cured product can be increased more effectively.
However, when the "in situ reaction / polymerization method" is used, (D) depending on the type of radically polymerizable monomer, a uniform cured product having no phase-separated structure is obtained, and not only the toughness cannot be expected to be improved, but also Tg and mechanical It may lead to deterioration of characteristics. From this point of view, it is preferable to use the "in situ reaction / polymerization method" as the (D) radically polymerizable monomer containing a monofunctional radically polymerizable monomer as a main component. The main component means a monomer having the largest mass ratio among the monomers constituting the radically polymerizable monomer.

Among them, the (D) radical-polymerizable monomer consists of only a monofunctional radical-polymerizable monomer, or is composed of a combination of a monofunctional radical-polymerizable monomer and a lesser polyfunctional radical-polymerizable monomer. Is preferable.
Among them, those composed of a combination of a monofunctional radically polymerizable monomer and a trace amount of a polyfunctional radically polymerizable monomer are more preferable.
By adding a trace amount of polyfunctional radical-polymerizable monomer to the monofunctional radical-polymerizable monomer, (D) before the phase derived from the radical-polymerizable monomer grows larger than an appropriate size in the curing process, Since the radically polymerizable monomers can undergo a cross-linking reaction to suppress further changes in the phase-separated structure, an appropriate amount derived from the radically polymerizable monomers is included in the phases derived from the cyanate ester compound and the epoxy resin. A sized phase can be formed and the toughness of the cured product can be further increased.

From this point of view, the monofunctional radically polymerizable monomer is contained in a proportion of 0.5 to 40% by mass in the total mass of (A), (B), (C), (D) and (E), and is polyfunctional. The radically polymerizable monomer of No. 1 is preferably contained in a proportion of 10% by mass or less.
Among them, the monofunctional radical polymerizable monomer is 1% by mass in the total mass of (A), (B), (C), (D) and (E) in order to exert the effect as a modifier on the entire cured product. It is more preferably contained in the above ratio, and particularly preferably 2% by mass or more, and particularly preferably 5% by mass or more. On the other hand, in order to maintain the high heat resistance and mechanical properties of the cured product derived from (A) and (B), it is more preferably contained in a proportion of 35% by mass or less, particularly 30% by mass or less. Among them, it is particularly preferable that it is contained in a proportion of 25% by mass or less. Further, as described above, by adding a trace amount of a radically polymerizable monomer, a phase having an appropriate size derived from the radically polymerizable monomer is formed in the cured product, and the toughness of the cured product can be further enhanced. Therefore, the polyfunctional radically polymerizable monomer is preferably contained in a proportion of 0.01% by mass or more in the total mass of (A), (B), (C), (D) and (E), preferably 0.05 mass. It is more preferably contained in a proportion of% or more, and particularly preferably contained in a proportion of 0.1% by mass or more. On the other hand, in order to prevent the curing from progressing before forming the phase-separated structure, it is more preferably contained in a proportion of 5% by mass or less, particularly 3% by mass or less, and particularly 2% by mass or less. It is particularly preferred to be included.

From the same viewpoint, the content mass ratio of the monofunctional radical polymerizable monomer and the polyfunctional radical polymerizable monomer among the (D) radical polymerizable monomers is the monofunctional radical polymerizable monomer: polyfunctional. The content-mass ratio of the radically polymerizable monomer is preferably 200: 1 to 1: 1, among which 180: 1 to 2: 1, among which 150: 1-3: 1, and among which 100: 1 to 5: 1. Among them, 50: 1 to 8: 1 is particularly preferable.

Preferred examples of the (D) radically polymerizable monomer include one or a combination of one or more of a styrene-based monomer, a maleimide-based monomer, (meth) acrylate, vinyl ether and vinyl amide, and these monofunctional ones. A radically polymerizable monomer or a polyfunctional radically polymerizable monomer can be preferably used.

(Styrene-based monomer)
Examples of the monofunctional styrene-based monomer which is a monofunctional radically polymerizable monomer include a styrene derivative substituted with a group not involved in the radical reaction. For example, styrene; α-alkylstyrene such as α-methylstyrene (the number of carbon atoms of alkyl is preferably 1 to 4); halogen-substituted styrene such as p-chlorostyrene and p-bromostyrene; 4-methylstyrene, 4 Alkyl-substituted styrenes such as-ethylstyrene; alkoxy-substituted styrenes such as p-methoxystyrene (alkyls and alkoxys preferably have 1-12 carbon atoms, more preferably 1-4); vinylbenzyl-ω-methylpoly Styrene-polyoxyalkylene adducts such as oxyethylene oxide; hydroxyl group substituted styrenes such as hydroxystyrene can be mentioned.

Examples of the polyfunctional styrene-based monomer which is a polyfunctional radically polymerizable monomer include vinyl group-substituted styrenes such as 1,3-divinylbenzene and 1,4-divinylbenzene.

(Maleimide-based monomer)
Examples of the monofunctional maleimide-based monomer which is a monofunctional radically polymerizable monomer include maleimides having one maleimide group. For example, maleimide; methylmaleimide, ethylmaleimide, propylmaleimide, butylmaleimide, hexylmaleimide, octyl. Examples thereof include aliphatic hydrocarbon group-containing maleimides such as maleimide, dodecyl maleimide, stearyl maleimide, and cyclohexyl maleimide, and aromatic ring-containing maleimides such as phenyl maleimide.

Examples of the polyfunctional maleimide-based monomer which is a polyfunctional radically polymerizable monomer include bismaleimides having two maleimide groups, 1,2-bis (maleimide) ethane and 1,4-bis (maleimide). Butane, maleimide containing aliphatic hydrocarbon groups such as 2,2'-(ethylenedioxy) bis (ethylmaleimide), N, N'-m-phenylene bismaleimide, N, N'-p-phenylene bismaleimide, 1 , 1'-(methylenedi-4,4'-phenylene) bismaleimide and other aromatic ring-containing maleimides can be mentioned.

((Meta) acrylic monomer)
Examples of the monofunctional (meth) acrylic monomer which is a monofunctional radically polymerizable monomer include (meth) acrylic acid and a (meth) acrylic monomer having one (meth) acrylic group. Examples of the (meth) acrylic monomer having one (meth) acrylic group include (meth) acrylate, for example, (meth) acrylic acid; methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, and the like. Unsubstituted chain alkyl (meth) acrylates such as isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate; 2-methoxyethyl (meth) acrylate, 3 -Methoxybutyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, stearyl (meth) acrylate, glycidyl (meth) acrylate, 2-aminoethyl (meth) acrylate, γ-( Chains with substituents such as metaacryloyloxypropyl) trimethoxysilane, perfluoroisopropyl (meth) acrylate, 2-perfluorohexylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate, trifluoromethylmethyl (meth) acrylate, etc. Alkyl (meth) acrylate; Substituent or unsubstituted aliphatic cyclic alkyl (meth) acrylate such as cyclohexyl (meth) acrylate and adamantyl (meth) acrylate; benzyl (meth) acrylate, phenyl (meth) acrylate, 2,4 Substituted or unsubstituted aromatic ring-containing (meth) acrylates such as 5-tribromophenyl (meth) acrylate, 2,3,4,5,6-pentafluorophenyl (meth) acrylate and trill (meth) acrylate; (meth). ) Acrylate-ethylene oxide adducts and the like can be mentioned.

Examples of the polyfunctional (meth) acrylic monomer which is a polyfunctional radically polymerizable monomer include (meth) acrylic acid anhydride and (meth) acrylic monomer having two or more (meth) acrylic groups, and include (meth) acrylic monomer. ) Examples of the (meth) acrylic monomer having two or more acrylic groups include ethylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, 2,2,3,3,4,5 , 5-Octafluoro-1,6-hexanediol di (meth) acrylate, diacrylate such as 2,2-dimethyl-1,3-propanediol diacrylate, 2-ethyl-2 (hydroxymethyl) -1,3 -Triacrylates such as propanediol tri (meth) acrylate can be mentioned.

(Vinyl ether)
Examples of the monofunctional vinyl ether which is a monofunctional radically polymerizable monomer include methyl vinyl ether, ethyl vinyl ether, trifluoroethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, t-butyl vinyl ether, and 2 -Chain vinyl ethers such as methoxyethyl vinyl ether and diethylene glycol ethyl vinyl ether; aliphatic ring-containing vinyl ethers such as cyclohexyl vinyl ether and 2- (vinyloxy) tetrahydropyran; aromatic ring-containing vinyl ethers such as phenyl vinyl ether, benzyl vinyl ether and 4-methoxybenzyl vinyl ether. Can be mentioned.

Examples of the polyfunctional vinyl ether which is a polyfunctional radically polymerizable monomer include diethylene glycol divinyl ether, divinyl ether, 1,4-butanediol divinyl ether, 1,6-hexanediol divinyl ether, triethylene glycol divinyl ether, and bis (). Chain vinyl ethers such as vinyloxybutyl) succinate; aliphatic ring-containing vinyl ethers such as 1,4-cyclohexanedimethanol divinyl ether; aromatic ring-containing vinyl ethers such as bis [4- (vinyloxy) butyl] terephthalate can be mentioned. ..

(Vinylamide)
Examples of the monofunctional vinylamide which is a monofunctional radically polymerizable monomer include chain vinylamides such as N-vinylformamide, N-vinylacetamide, N-methyl-N-vinylacetamide, and N-methyl-N-vinylacetamide; Examples thereof include aliphatic ring-containing vinylamides such as N-vinylpyrrolidone, N-vinyl-ε-caprolactam, and 5-methyl-3-vinyloxazolidine-2-one.

(Other)
Other radically polymerizable monomers include fluorine-containing vinyl monomers such as perfluoroethylene, perfluoropropylene, and vinylidene fluoride;
For example, silicon-containing vinyl monomers such as vinyltrimethoxysilane and vinyltriethoxysilane;
Monoalkyl and dialkyl esters such as maleic anhydride, maleic acid, monoalkyl and dialkyl esters of maleic acid;
Fumaric acid, and monoalkyl and dialkyl esters of fumaric acid;
Nitrile-containing vinyl monomers such as acrylonitrile, meta-acrylonitrile, etc .;
Amide-containing vinyl monomers such as acrylamide, metaacrylamide, etc .;
Vinyl esters such as vinyl acetate, vinyl propionate, vinyl pivalate, vinyl benzoate, vinyl cinnamic acid, etc .;
Alkenes such as ethylene and propylene;
Examples thereof include vinyl chloride, vinylidene chloride, allyl chloride and allyl alcohol.

As described above, these monomers may be used alone or in combination of two, as long as they form a phase-separated structure. Whether or not a phase-separated structure is formed is affected by the compatibility between the (A) cyanate ester compound and the (B) epoxy resin. Therefore, the combination of the (A) cyanate ester compound and the (B) epoxy resin to be used is affected. It is preferable to select an appropriate (D) radically polymerizable monomer according to the ratio.

In this thermosetting resin composition, if the radically polymerized component is obtained by radical polymerization of a radically polymerizable monomer in a mixture with a cocurable resin component, any form of polymer is produced. Also well, homopolymers, non-block copolymer copolymers, or block polymers can be included. It is preferably a homopolymer or a copolymer that is not a block copolymer. Here, the "non-block copolymer" includes a random copolymer, an alternating copolymer, and all other copolymers obtained by simultaneously polymerizing a plurality of types of monomers.

In addition, in the above and the following, the description of "(meth) acrylic" and "(meth) acrylate" and the like means "methacrylic or acrylic" and "methacrylate or acrylate" as is commonly used.

Among these, as the monofunctional radically polymerizable monomer, a monomer that gives a polymer having excellent heat resistance is particularly preferable. For example, styrene-based monomers, maleimide-based monomers, (meth) acrylic monomers, nitrile-containing vinyl monomers, amide-containing vinyl monomers and the like and mixtures thereof are preferable, and in particular, styrene-based monomers, aromatic ring-containing maleimides, substituted or unsubstituted aromatic rings. Monomers having an aromatic ring in the molecule, such as a containing (meth) acrylate and an aromatic ring-containing vinyl ether, and a mixture containing the same are preferable. Preferred specific compounds are styrene, 4-methylstyrene, 4-ethylstyrene, α-methylstyrene, phenylmaleimide, benzylmethacrylate, benzylacrylate, phenylmethacrylate, phenylacrylate and mixtures thereof.

Among these, as the polyfunctional radically polymerizable monomer, a monomer having a vinyl group having particularly excellent reactivity is preferable. For example, styrene-based monomers, maleimide-based monomers, and (meth) acrylic monomers are preferable.

From the viewpoint of lowering the viscosity of the composition and improving the moldability, the polyfunctional radically polymerizable monomer preferably has a mass average molecular weight of 1000 or less, more preferably 500 or less, and 350 of these. The following is more preferable. The lower limit of the mass average molecular weight is usually 100 or more.

<(E) Radical initiator>
As the radical initiator (E), various radical initiators such as a thermal radical initiator, a photoinitiator, and a redox-type initiator can be used. Of these, a thermal radical generator is preferable from the viewpoint of convenience. For example, organic peroxides such as benzoyl peroxide, lauroyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, and 2,2'-azobisisobutyronitrile, 2,2'-azobis. Azo compounds such as methylbutyronitrile and 2,2'-azobisdimethylvaleronitrile can be mentioned.

In this thermosetting resin composition, it is preferable to mix (A) to (E) and other components and heat them as necessary to make them uniform, and further, the radically polymerizable monomer (D) by heating. It is necessary to suppress polymerization and prevent deterioration of moldability due to an increase in viscosity. From this viewpoint, the one-hour half-life temperature of the (E) radical initiator is preferably 80 ° C. or higher, more preferably 100 ° C. or higher, and particularly preferably 130 ° C. or higher. Specifically, dicumyl peroxide and di-tert-butyl peroxide are preferable.

<(F) Other ingredients>
The thermosetting resin composition can contain, if necessary, a curing agent usually used for curing an epoxy resin or a cyanate ester compound, as other components, as long as the effect is not impaired.

Examples of the curing agent that may be used are not particularly limited, but are phenol-based curing agent, ester-based curing agent, benzoxazine-based curing agent, acid anhydride-based curing agent, amine-based curing agent, mercaptan-based curing agent, and organic. A phosphine-based curing agent and the like can be mentioned. It is also possible to use a phenoxy resin as a curing agent.
These curing agents may be used alone, or one or more other curing agents may be mixed and used in any combination and ratio.

The content of the curing agent that can be used in the thermosetting resin composition is preferably large in that the epoxy groups contained in the composition do not remain unreacted, but the curing of the thermosetting resin composition It is preferable that there are few sites that react with the epoxy group of the curing agent so as not to remain unreacted. When a curing agent is used, it is desirable to make appropriate adjustments from these viewpoints. For example, the epoxy group contained in this thermosetting resin composition and the reaction site in the curing agent (hydroxyl of phenol-based curing agent, ester group of ester-based curing agent, NO group of benzoxazine-based curing agent, acid anhydride-based The equivalent ratio with the acid anhydride group of the curing agent, the amino group of the amine-based curing agent, etc.) is preferably 0.05 or more, and more preferably 0.1 or more. On the other hand, it is preferable to use it so that it is 1.5 or less, and it is more preferable to use it so that it is 1.2 or less.

Only one type of curing agent may be used, or two or more types may be used in any combination and ratio. When two or more kinds of curing agents are used, the total amount thereof is preferably in the above-mentioned preferable range.

Other components that may be contained in this thermosetting resin composition include inorganic fillers such as silica, alumina, calcium carbonate, boron nitride, aluminum nitride, talc, and clay, colorants, antioxidants, and difficulties. Known additives such as flame retardants and surface treatment agents can be mentioned, and may be appropriately selected depending on the intended use. For example, for semiconductor encapsulant applications, it preferably contains silica.

Further, the present thermosetting resin composition may contain a diluent and a solvent for adjusting the viscosity during processing and handling during curing.
As the diluent, a reactive diluent or solvent having only one epoxy group can be used. Examples of the reactive diluent include alkyl monoglycidyl ethers such as butyl glycidyl ether; and alkyl phenyl glycidyl ethers such as phenyl glycidyl ether.
The solvent is not particularly limited, but for example, ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; ethers such as ethylene glycol monomethyl ether; N, N. -Amids such as dimethylformamide, N, N-dimethylacetamide; alcohols such as methanol, ethanol and isopropanol; alkanes such as hexane and cyclohexane; aromatics such as toluene and xylene can be mentioned.
These diluents and solvents may be used alone or in any combination and ratio of two or more.
When a solvent is used, the content of the solvent is preferably not used or small because voids are unlikely to be formed in the cured product due to residual solvent. On the other hand, it is preferable that there are many cracks that are unlikely to occur due to the high viscosity of the composition. When a solvent is used, it is desirable to appropriately adjust the amount used from these viewpoints.

<This thermosetting resin composition>
The present thermosetting resin composition may be any thermosetting resin composition having a property of being thermosetting, that is, having a property of curing reaction when heated, and its form may be liquid or solid. , It may be in the form of a gel or in other forms.

In the present thermosetting resin composition, the content of the (A) cyanate ester compound is excellent in heat resistance and dielectric properties, and from the viewpoint of utilizing the advantages of the cyanate resin, the present thermosetting resin composition. It is preferably 30 to 99% by mass, and more preferably 40% by mass or more or 95% by mass or less, and more preferably 50% by mass or more or 80% by mass or less.
In the present invention, the content of the contained components with respect to the total amount of the present thermosetting resin composition is defined as 100% by mass of the total amount of the above-mentioned five components (A) to (E).

In this thermosetting resin composition, the content ratio of the (A) cyanate ester compound and the (B) epoxy resin is better than that of the cyanate resin alone while maintaining the high glass transition temperature of the cyanate resin. From the viewpoint of excellent workability and enabling curing at a low temperature, the epoxy group is preferably 0.01 mol or more and 1.0 mol or less with respect to 1 mol of cyanate group, and more than 0.03 mol or more of the epoxy group. Alternatively, it is more preferably 0.7 mol or less.

In this thermosetting resin composition, the total content of (A) cyanate ester compound and (B) epoxy resin is 100 parts by mass for the purpose of lowering the curing start temperature and further lowering the energy cost of (C) curing accelerator. It is preferably contained in a proportion of 0.01 parts by mass or more, and more preferably 0.1 parts by mass or more, and more preferably 0.5 parts by mass or more. On the other hand, in order to suppress the runaway of each reaction related to curing and safely obtain a cured product having an appropriate degree of curing, it is preferably contained in a proportion of 10 parts by mass or less, particularly 5 parts by mass or less, among them. It is more preferably contained in a ratio of 2 parts by mass or less.

This thermosetting resin composition has (A), (B), (C), (D), and (E) from the viewpoint of causing the (D) radically polymerizable monomer to exert an effect as a modifier on the entire cured product. It is preferable that the radical polymerizable monomer (D) is contained in an amount of 0.5% by mass or more, particularly preferably 3% by mass or more, and more preferably 10% by mass or more. On the other hand, in the total mass of (A), (B), (C), (D) and (E) from the viewpoint of maintaining the heat resistance and high mechanical properties of the cured product derived from (A) and (B). , (D) The radically polymerizable monomer is preferably contained in a proportion of 40% by mass or less, more preferably 35% by mass or less, and more preferably 30% by mass or less.

In this thermosetting resin composition, 0.001 with respect to 100 parts by mass of (D) radical-polymerizable monomer (D) from the viewpoint of sufficiently advancing the polymerization of (D) radical-polymerizable monomer with (E) radical initiator. It is preferably contained in a proportion of parts by mass or more, and more preferably 0.01 parts by mass or more, and more preferably 0.05 parts by mass or more. On the other hand, from the viewpoint of improving the storage stability of the thermosetting resin composition and preventing thermal runaway due to a rapid reaction during curing, it is preferably contained in a proportion of 10 parts by mass or less, particularly 5 parts by mass or less. Among them, it is more preferably contained in a ratio of 1 part by mass or less.

<Method for producing this thermosetting resin composition>
The thermosetting resin composition comprises (A) a cyanate ester compound, (B) an epoxy resin, (C) a curing accelerator, (D) a radically polymerizable monomer, (E) a radical initiator, and (F) other components. Can be obtained by mixing and stirring, dispersing, heating and the like as necessary.
At this time, the mixing may be produced by mixing all at the same time, or may be mixed sequentially. For example, after mixing (A) a cyanate ester compound and (B) an epoxy resin, (C) a curing accelerator is added, and then (D) a radically polymerizable monomer and (E) a radical initiator are added. May be good. At this time, the (A) cyanate ester compound and (B) epoxy resin may be mixed and heated to 50 to 200 ° C. to prepolymerize a part of the cyanate ester compound and the epoxy resin to react with each other. On the other hand, if the prepolymerization progresses too much, it becomes difficult to uniformly disperse the (D) radical-polymerizable monomer and (E) radical initiator to be added next, so it is preferable to heat at 150 ° C. or lower (D). After adding the radically polymerizable monomer and the (E) radical initiator, the composition may be heated to 50 to 200 ° C. so that the composition becomes uniform. On the other hand, when heated above the decomposition temperature of the radical initiator, the viscosity of the composition increases due to the start of radical polymerization, which may lead to a decrease in moldability. Therefore, heating is performed below the decomposition temperature of the radical initiator used. It is preferable to carry out the above, and specifically, it is preferable to carry out heating at 150 ° C. or lower. In addition, (F) other components may be added at an appropriate timing.

<< This cured product >>
The cured product (referred to as "the present cured product") according to an example of the embodiment of the present invention can be obtained by heating and curing the thermosetting resin composition.

The cured product is preferably a cured product having a phase-separated structure having a phase derived from (A) cyanate resin and (B) epoxy resin and a phase derived from (D) radically polymerizable monomer. ..
If the cured product has such a phase-separated structure, the toughness can be enhanced while maintaining the excellent properties of the matrix resin, that is, the (A) cyanate resin and the (B) epoxy resin, for example, high Tg and high strength. Can be done.
In order for this cured product to have such a phase-separated structure, an in situ reaction / polymerization method as described later is adopted, and (A) a reaction between a cyanate resin and (B) an epoxy resin, and further curing of these. At the same time as the reaction, the radical polymerization of the (D) radically polymerizable monomer may be carried out. However, the method is not limited to this method.

In the phase-separated structure, if the size of the phase derived from the (D) radically polymerizable monomer is small, the dispersibility of the polymer polymerized by the (D) radically polymerizable monomer as a modifier is improved, and the modifying effect is enhanced. Can be enhanced. However, if the size of the phase becomes too small and approaches a uniform state, the reforming effect may not be obtained. Therefore, the size of the phase derived from the radically polymerizable monomer (D) is preferably 0.01 μm or more, and more preferably 0.05 μm or more. Further, it is preferably 5 μm or less, more preferably 3 μm or less, and further preferably 1 μm or less.
In order to adjust the size of the phase derived from (D) radically polymerizable monomer in the phase separation structure within the above range, an in situ reaction / polymerization method in which (D) radically polymerizable monomer is added in a monomer state is adopted. Furthermore, by selecting an appropriate (D) radically polymerizable monomer for the type and ratio of (A) cyanate resin and (B) epoxy resin, the curing rate can be adjusted to an appropriate rate, and (D) ) The size of the phase derived from the radically polymerizable monomer can be adjusted within the above range.

From the viewpoint of heat resistance, the cured product preferably has a glass transition temperature (Tg) of 220 ° C. or higher, more preferably 230 ° C. or higher, and more preferably 240 ° C. or higher.
In order to adjust the glass transition temperature (Tg) of the cured product concentration within the above range, for example, (A) a cyanate ester compound having an aromatic ring can be used, or (B) a polyfunctional epoxy resin as an epoxy resin. , The ratio of the (A) cyanate ester compound in the composition may be increased, or the crosslink density may be adjusted by selecting an appropriate cyanate equivalent or epoxy equivalent resin.

Fracture toughness value of the cured product _{(K IC)} is, (A) the cyanate resin and (B) depending on the epoxy resin of the kind and mixing ratio is preferably at 0.5 mN ^{/ m 3/2} or more and preferably 0.6MN ^{/ m 3/2} or more, more preferably at 0.7MN ^{/ m 3/2} or more. among them, 0.8Mn ^{/ m 3/2} or more are particularly preferred.

Fracture toughness value of the cured product _{(K IC),} compared with the cured product K1C when no added as modifier (D), it is preferable to increase 0.1 mN ^{/ m 3/2} or more and preferably 0 .2MN ^{/ m 3/2} or more, more preferably to improved 0.3 mN ^{/ m 3/2} or more therein.

<Method of producing this cured product>
The cured product can be obtained by heat-molding the thermosetting resin composition according to the intended use.
At this time, the curing temperature may be appropriately selected according to the reactivity of each component in the composition, but is 150 ° C. or higher in order to suppress the deterioration of heat resistance and mechanical properties due to the decrease in the degree of curing. Is preferable, 160 ° C. or higher is more preferable, and 190 ° C. or higher is particularly preferable. On the other hand, from the viewpoint of process rationality, 300 ° C. or lower is preferable, 250 ° C. or lower is further preferable, and 220 ° C. or lower is particularly preferable.
Further, heating for curing may be carried out in multiple stages.

As a preferable method for producing the cured product, for example, (A) a cyanate ester compound and (B) an epoxy resin are reacted, (C) a curing accelerator is added and dissolved, and a modifier capable of radical polymerization is further added. (D) Radical polymerizable monomer and (E) Radical initiator are added and dissolved, and further heat-cured to react the (A) cyanate ester compound with (B) epoxy resin, and further, these Examples thereof include a method (also referred to as “in situ reaction / polymerization method”) in which (D) radical polymerization of a radically polymerizable monomer is carried out at the same time as the curing reaction.
When this cured product is prepared by the in situ reaction / polymerization method in this way, it has a phase derived from (A) a cyanate ester compound and (B) an epoxy resin, and a phase derived from (D) a radically polymerizable monomer. A cured product having a phase-separated structure can be obtained, and the cured product can be toughened. Compared with the conventional method, that is, a method in which a modifier in a polymer state is added to an uncured resin and cured, a phase-separated structure can be formed with a smaller domain size of the modifier phase, which is more excellent. A reforming effect can be obtained. Further, since it is added and dissolved in a monomer state, the resin viscosity at the time of injection into the mold and at the time of molding is low, and the handleability is easy.
Further, by selecting and using an appropriate (D) radically polymerizable monomer, that is, a modifier containing a monofunctional radically polymerizable monomer or a slightly polyfunctional radically polymerizable monomer as a main component is selected. As a result, the curing rate can be adjusted to an appropriate speed, and the size of the phase derived from the (D) radically polymerizable monomer can be adjusted to an appropriate size, so that the toughness can be further improved.

<Characteristics and applications of the thermosetting resin composition and the cured product>
Cyanate ester compounds are known to exhibit high strength, thermal stability, and good dielectric properties by self-triquantizing the cyanate groups contained in the cyanate group by an addition reaction and forming a network while forming a triazine ring. .. On the other hand, epoxy resins are known to have a high crosslink density.
By reacting such a cyanate ester compound and an epoxy resin in combination with each other, mutual reaction products such as (1) oxazoline and oxazolidinone derivatives, and (2) isocyanurate derivatives can be formed. Therefore, by mixing and curing the cyanate ester compound and the epoxy resin, the formation of the crosslinked network containing the plurality of interaction products and the like proceeds more densely, so that the present curable molding material has high thermal stability. Is given, and it is considered that it exhibits excellent heat resistance.

Further, in the present thermosetting resin composition and the present cured product, a cured product having a phase-separated structure can be formed, and the toughness can be made particularly excellent while maintaining heat resistance. Therefore, the thermosetting resin composition or the cured product can be suitably used as a sealing material for electrical / electronic materials, for example, semiconductor devices.
Further, since the cured product is particularly excellent in toughness, the thermosetting resin composition or the cured product can be preferably used as a matrix resin in a composite material such as carbon fiber or as an adhesive. ..

<Explanation of words>
When expressed as "X to Y" (X and Y are arbitrary numbers) in the present specification, unless otherwise specified, they mean "X or more and Y or less" and "preferably larger than X" or "preferably Y". It also includes the meaning of "smaller".
Further, when expressed as "X or more" (X is an arbitrary number) or "Y or less" (Y is an arbitrary number), it means "preferably larger than X" or "preferably less than Y". Including intention.

Next, the present invention will be further described with reference to the following examples. However, the following examples do not limit the present invention.

Various analysis methods in Examples and Comparative Examples are as follows.

(Epoxy equivalent)
Measured according to JIS K7236: 2001.

(Glass transition temperature (Tg))
From the cured product (sample) obtained in Examples and Comparative Examples, strips having a length of 41.5 mm, a width of 10 mm, and a thickness of 2 mm were cut out to prepare a sample for measurement.
The glass transition temperature was defined as the temperature at the maximum point of the Tanδ peak in the dynamic viscoelasticity measurement. However, when there are a plurality of Tanδ peaks, the temperature at which the largest maximum value among those maximum points is taken is defined as the glass transition temperature.
Equipment: DMS-6100 manufactured by SII Nanotechnology Inc.
Heating rate: 5 ° C / min
Frequency: 1Hz

(Presence or absence of phase separation structure)
The fracture surface of the cured product (sample) obtained in Examples and Comparative Examples was observed with a scanning electron microscope (JSM-6390LV, manufactured by JEOL Ltd.) to determine the presence or absence of a phase-separated structure. Further, even when the phase-separated structure is fine and cannot be observed with a scanning electron microscope, the phase-separated structure is formed when a Tanδ peak corresponding to the phase derived from the radically polymerizable monomer is observed in the dynamic viscoelasticity measurement. It was judged to be present.

(Fracture toughness value)
_{The fracture toughness value K IC} [MN / m ^3/2 ] was determined by a three-point bending test based on ASTM D5045 for the cured product (sample) obtained in Examples and Comparative Examples.
The size of the test piece is length: 61.6 [mm] (= 4.4W), width (W): 14.0 [mm], thickness (B): 7.0 [mm] (= W / 2). The test piece was notched at 5.3 to 5.6 [mm] using a diamond cutter, and then dried in an oven at 60 ° C. for 3 hours. Then, the blade of the cutter was applied to the tip of the notch and tapped with a mallet several times to insert a crack of about 1.5 [mm]. At this time, the "notch + crack length" (a) was set to 0.45 <a / W <0.55. The span length (S) in the three-point bending test was S = 4W, and the crosshead speed was 10 mm / min. The 3-point bending test was performed using a precision universal testing machine AGX-10kN manufactured by Shimadzu Corporation.

The manufacturing raw materials used in Examples and Comparative Examples are as follows.

(Cyanate Ester Compound (BAD))
BAD is a bisphenol A type cyanate ester, which is 2,2-bis (4-cyanatephenyl) propane (manufactured by Mitsubishi Gas Chemical Company, Inc.) represented by the following formula (1), and is calculated from the theoretical molecular weight and the theoretical number of functional groups. The cyanate equivalent to be produced is 139 g / eq. Is.

(Epoxy resin EP-1)
EP-1 is jER1032H60 (manufactured by Mitsubishi Chemical Corporation) represented by the following formula (2), and has an epoxy equivalent of 167 g / eq. Is.

(Epoxy resin EP-2)
EP-2 is a 3,3'-diglycidyl biphenyl-4,4'-diglycidyl ether represented by the following formula (3), and has an epoxy equivalent of 104 g / eq. Is.

EP-2 can be produced as follows.
To a 10 L autoclave, 840 mL of N, N-dimethylformamide, 575 g (7.51 mol) of allyl chloride, 1245 g (9.01 mol) of potassium carbonate, and 280 g (1.50 mol) of biphenol were added, sealed, and heated to 40 ° C. The temperature was raised to 65 ° C. over 1 hour. After aging at 65 ° C. for 5 hours, the mixture was cooled to room temperature and the autoclave was opened. To this, 1678 g of water and 1600 g of methyl isobutyl ketone were added to dissolve the inorganic salt and crystals, and the aqueous phase was removed by a liquid separation operation. After repeating the operation of adding 1678 g of water to the remaining methyl isobutyl ketone phase and washing with water at 60 ° C. three times, methyl isobutyl ketone was distilled off to obtain 4,4-dialyloxybiphenyl.
Next, 165 g (620 mmol) of 4,4-dialyloxybiphenyl and 825 mL of N, N-diethylaniline obtained by the above method were placed in a 2 L four-necked flask, heated at 200 ° C. for 6 hours, and then brought to room temperature. Cooled. Subsequently, 495 ml of water and 149 mL (1.86 mol) of a 50 mass% sodium hydroxide aqueous solution were placed in a 2 L separable flask and cooled to 10 ° C., and the above N, N-diethylaniline solution was added dropwise over 15 minutes. After stirring for 30 minutes, the mixture was allowed to stand, and the upper phase and the lower phase were extracted, respectively. Next, 495 mL of water and 93.1 g (1.86 mol) of concentrated sulfuric acid were placed in a 2 L separable flask and cooled to 10 ° C., and then the lower phase extracted in the previous operation was added dropwise and stirred for 1 hour. The precipitated solid was collected by filtration, washed with water, and dried under reduced pressure to obtain 148 g (1.19 mol, 2-step yield 80.4%) of 3,3-diallyl-4,4-biphenol as a gray solid.

Next, 105 g (394 mmol) of 3,3-diallyl-4,4-biphenol, 1028 g (11.1 mol) of epichlorohydrin, 400 g of isopropanol and 143 g of water synthesized as described above were placed in a 3 L four-necked flask and heated to 40 ° C. After the temperature was raised to uniformly dissolve the mixture, 76 g (912 mmol) of an aqueous sodium hydroxide solution having a concentration of 48% by mass was added dropwise over 90 minutes to raise the temperature to 65 ° C. After completion of the dropping, the mixture was aged at 65 ° C. for 30 minutes, and then 66 g of water was added and washed with water to remove inorganic salts. Then, epichlorohydrin and isopropanol were distilled off under reduced pressure to obtain a brown oily substance. After adding 191 g of methyl isobutyl ketone to homogenize it, 5.8 g (69.6 mmol) of an aqueous sodium hydroxide solution having a concentration of 48% by mass was added, and the mixture was reacted at 75 ° C. for 2 hours. After adding 223 g of methyl isobutyl ketone to the obtained reaction solution, the mixture was washed with 525 g of water at 70 ° C. four times. Subsequently, methyl isobutyl ketone was distilled off to obtain 142 g of 3,3-diallyl-4,4-diglycidyloxybiphenyl as a yellow oil. 56.1 g of the obtained 3,3-diallyl-4,4-diglycidyloxybiphenyl was placed in a 1 L eggplant flask, 224 mL of methanol and 101 mL of 2-methoxyethanol were added, and the mixture was heated to 50 ° C. The solution was gradually cooled, and after stirring at 4 ° C. for 1 hour, the precipitated white crystals were collected by filtration. The white crystals were washed with methanol and dried under reduced pressure at 50 ° C. to obtain 29.8 g (yield 57%) of a purified product of 3,3-diallyl-4,4-diglycidyloxybiphenyl.

Subsequently, 40.0 g (106 mmol) of a refined product of 3,3-diallyl-4,4-diglycidyloxybiphenyl synthesized by the same method as described above, and 1.74 g (5.30 mmol) of sodium tungstate dihydrate. , 20% (mass / volume) aqueous phosphoric acid solution 3.63 mL (7.42 mmol), N-butyl-N, N-di [2- (4-t-butylbenzoyloxy) ethyl] -N-methylammonium monomethylsulfate A mixed solution of 1.69 g (2.65 mmol) of salt, 80 mL of toluene, and 1.10 mL of water was prepared. This mixed solution was heated to 60 ° C. under a nitrogen stream, and then 26.8 mL (318 mmol) of 35% by mass hydrogen peroxide solution was added dropwise over 5 hours, followed by aging for 2 hours. After completion of the reaction, 34 mL of toluene was added and the separated aqueous phase was extracted. The remaining organic phase was washed with water and 40 L each of a 5 mass% sodium thiosulfate aqueous solution, 40 mL of methanol and 7.30 g (530 mmol) of potassium carbonate were added to the organic phase, and the mixture was stirred at 40 ° C. for 1 hour. After adding 40 mL of water to dissolve the inorganic salt and discharging the aqueous phase, the organic phase was washed once with 40 mL of a 1 mol / L sodium hydroxide aqueous solution and three times with 200 mL of warm water at 55 ° C. When the obtained organic phase was concentrated, 3,3-diglycidyl-4,4-diglycidyloxybiphenyl containing 10% by mass of toluene was obtained.

Next, 24 mL of methyl isobutyl ketone and 12 mL of methanol were added to 3,3-diglycidyl-4,4-diglycidyloxybiphenyl containing 10% by mass of the toluene obtained as described above, and the mixture was heated at 50 ° C. to make it uniform. After making the solution, it was gradually cooled and precipitation started at 17 ° C. 24 mL of methanol was added thereto, and the mixture was ice-cooled, and the precipitated pale yellow crystals were collected by filtration. When the crystals were washed with 20 mL of methanol and dried under reduced pressure at 50 ° C., 41.6 g (78% yield) of epoxy resin containing 3,3-diglycidyl-4,4-diglycidyloxybiphenyl was obtained as pale yellow crystals. Obtained. The pale yellow crystals were purified by silica gel column chromatography to obtain EP-2.

(Curing accelerator (TPP-MK))
TPP-MK is manufactured by Hokuko Chemical Industry Co., Ltd. (chemical name: tetraphenylphosphonium tetra-p-tolylborate) represented by the following formula (4).

(Monofunctional radically polymerizable monomer (PMI))
PMI is N-phenylmaleimide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) represented by the following formula (5).

(Monofunctional radically polymerizable monomer (St))
St is a styrene monomer (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) represented by the following formula (6).

(Monofunctional radically polymerizable monomer (EVB), polyfunctional radically polymerizable monomer (DVB))
EVB is ethylvinylbenzene represented by the following formula (7), and DVB is divinylbenzene represented by the following general formula (8). Divinylbenzene manufactured by Fujifilm Wako Pure Chemical Industries, Ltd. containing 45% ethylvinylbenzene and 55% divinylbenzene was used as a mixture.

(Monofunctional radically polymerizable monomer (BzMA))
BzMA is a benzyl methacrylate (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) represented by the following formula (9).

(Monofunctional radically polymerizable monomer (EGDMA))
EGDMA is ethylene glycol dimethacrylate (manufactured by Sigma-Aldrich Japan Co., Ltd.) represented by the following formula (10).

(Radical Initiator (DCP))
The DCP is a dicumyl peroxide (manufactured by Sigma-Aldrich Japan Co., Ltd.) represented by the following formula (11).

<Example 1>
20.3 parts by mass of epoxy resin (EP-1) (BAD: EP-1 = 1.0: 0.3 in functional group equivalent ratio) was added to 56.3 parts by mass of the cyanate ester compound (BAD), and the temperature was 120 ° C. Further, 0.8 parts by mass of the curing accelerator (TPP-MK) (corresponding to 1.0 part by mass with respect to 100 parts by mass of the total mass of the BAD and EP-1) was added at 120 ° C. After stirring for 20 minutes, 13.9 parts by mass of a monofunctional radically polymerizable monomer (PMI), 8.4 parts by mass of a monofunctional radically polymerizable monomer (St), and 0.4 parts by mass of a radical initiator (DCP). (1 mol% of the total amount of the radically polymerizable monomer) was added, and the mixture was further stirred at 120 ° C. for 20 minutes to obtain a thermosetting resin composition (sample).

The thermosetting resin composition (sample) obtained as described above was poured into a mold, vacuum degassed at 120 ° C. for 20 minutes, and then 120 ° C. for 1 hour, 160 ° C. for 2 hours, 180 ° C. for 2 hours. Heat curing was performed at 200 ° C. for 2 hours to obtain a cured product (sample) having a thickness of about 8 mm.

<Examples 2 to 7>
In Example 1, a thermosetting resin composition (sample) and a cured product (sample) were obtained according to Example 1, except that the type and amount of the radically polymerizable monomer were changed as shown in Table 1. The exact amount of each component is shown in Table 1.

<Comparative example 1>
A thermosetting resin composition (sample) and a cured product (sample) were obtained in accordance with Example 1 except that the radically polymerizable monomer and the radical initiator were not added in Example 1. The exact amount of each component is shown in Table 1.

<Example 8, Comparative Example 2>
A thermosetting resin composition (sample) and a cured product (sample) were obtained in accordance with Example 1 except that the type of epoxy resin was changed to EP-2 in Example 1. The exact amount of each component is shown in Table 2.

(Discussion)
Based on the above examples and the test results obtained by the present invention, (A) cyanate ester compound, (B) epoxy resin, (C) curing accelerator, (D) radically polymerizable monomer and (E) radical initiator. As (D) radically polymerizable monomer, 0.5 to 40% by mass of monofunctional radically polymerizable monomer is contained in the total mass of (A), (B), (C), (D) and (E). Moreover, according to the thermosetting resin composition containing 10% by mass or less of a polyfunctional radically polymerizable monomer, the toughness of the cured product can be effectively increased while maintaining the glass transition temperature (Tg) of 220 ° C. or higher. I found that I could do it.

Further, when producing the thermosetting resin composition or the cured product, the reaction between the (A) cyanate ester compound and the (B) epoxy resin, the curing reaction thereof, and the (D) radically polymerizable monomer By adopting the method of simultaneously performing radical polymerization (“in situ reaction / polymerization method”), (A) a phase derived from a cyanate ester compound and (B) an epoxy resin, and (D) a radically polymerizable monomer. It was also found that a cured product having a phase-separated structure having a phase of an appropriate size can be produced, and the toughness of the cured product can be further enhanced.

Claims (13)

It contains (A) cyanate ester compound, (B) epoxy resin, (C) curing accelerator, (D) radically polymerizable monomer and (E) radical initiator.
(D) As the radically polymerizable monomer, 0.5 to 40% by mass of the monofunctional radically polymerizable monomer is contained in the total mass of (A), (B), (C), (D) and (E), and the amount is large. A thermosetting resin composition containing 10% by mass or less of a functional radically polymerizable monomer. (D) The invention according to claim 1, wherein the content-mass ratio of the monofunctional radical-polymerizable monomer: the polyfunctional radical-polymerizable monomer among the radical-polymerizable monomers is 200: 1 to 1: 1. Thermosetting resin composition. (A) (B) (C) (D) and (E) according to claim 1 or 2, wherein the radically polymerizable monomer (D) is contained in an amount of 0.5 to 40% by mass in the total mass. Thermosetting resin composition. The thermosetting resin composition according to any one of claims 1 to 3, wherein the epoxy resin (B) is a polyfunctional epoxy resin having three or more epoxy groups in one molecule. (A) The thermosetting resin composition according to any one of claims 1 to 4, wherein the cyanate ester compound has one or more aromatic rings. (C) The thermosetting resin composition according to any one of claims 1 to 5, which contains a quaternary phosphonium borate represented by the following general formula (12) as a curing accelerator.

(In the general formula (12), R ^{13 to} R ¹⁶ each independently represent a substituted or unsubstituted aromatic group or a substituted or unsubstituted alkyl group, and these represent a phosphorus atom and a P- in the formula. Forming a C bond. R ^{17 to} R ²⁰ each independently represent a substituted or unsubstituted aromatic group or a substituted or unsubstituted alkyl group, and these represent a boron atom and B- in the formula. Form a C bond.) (D) Claims 1 to 1, wherein the radically polymerizable monomer contains one or a combination of one or more of a styrene-based monomer, a maleimide-based monomer, a (meth) acrylate-based monomer, a vinyl ether-based monomer, and a vinylamide-based monomer. The thermosetting resin composition according to any one of 6. (E) The thermosetting resin composition according to any one of claims 1 to 7, which contains an organic peroxide as a radical initiator. A cured product comprising the thermosetting resin composition according to any one of claims 1 to 8. The cured product is characterized by having a phase-separated structure having a phase derived from (A) a cyanate ester compound and (B) an epoxy resin and a phase derived from (D) a radically polymerizable monomer. The cured product according to claim 9. A semiconductor encapsulant comprising the thermosetting resin composition according to any one of claims 1 to 8 or the cured product according to claim 9 or 10. A matrix resin in a composite material comprising the thermosetting resin composition according to any one of claims 1 to 8 or the cured product according to claim 9 or 10. An adhesive comprising the thermosetting resin composition according to any one of claims 1 to 8 or the cured product according to claim 9 or 10.