JP7776995B2 - Curable composition, thermally conductive material, thermally conductive sheet, and device with thermally conductive layer - Google Patents

Description

The present invention relates to a curable composition, a thermally conductive material, a thermally conductive sheet, and a device with a thermally conductive layer.

Power semiconductor devices used in various electrical equipment such as personal computers, general home appliances, and automobiles have been rapidly becoming smaller in size in recent years. As the size of these devices has increased, it has become more difficult to control the heat generated by these devices.
To address this issue, thermally conductive materials are used to promote heat dissipation from power semiconductor devices.
For example, Patent Document 1 discloses a resin composition that can achieve high thermal conductivity after curing, which is "a resin composition containing an epoxy resin including a multifunctional epoxy resin, a curing agent including a novolac resin having a predetermined structural unit, and an inorganic filler including nitride particles" (Claim 1).

JP 2016-104862 A

The inventors have studied the curable composition described in Patent Document 1 and found that there is room for improvement in the thermal conductivity of the resulting thermally conductive material.

Therefore, an object of the present invention is to provide a curable composition that can form a thermally conductive material having excellent thermal conductivity.
Another object of the present invention is to provide a thermally conductive material, a thermally conductive sheet, and a device with a thermally conductive layer, which are related to the curable composition.

As a result of extensive research into resolving the above-mentioned issues, the inventors have discovered that the following configuration can resolve the above-mentioned issues.

[1] One or more types of inorganic particles selected from the group consisting of inorganic nitride particles and inorganic oxide particles;
A curable composition comprising: a compound having a partial structure represented by formula (1) described below or a partial structure represented by formula (2) described below.
[2] The curable composition according to [1], wherein the compound comprises at least one selected from the group consisting of a compound represented by formula (1A) described later, a compound represented by formula (1B) described later, a compound represented by formula (2A) described later, and a compound represented by formula (2B) described later.
[3] The compound is
A compound represented by the formula (1A) above, wherein X ^E1 represents an m ^E1 +1-valent aromatic ring group, or
The curable composition according to [2], which is a compound represented by the formula (1B) and wherein X ^E2 represents a divalent aromatic ring group.
[4] The curable composition according to any one of [1] to [3], further comprising a phenol compound.
[5] The curable composition according to [4], wherein the phenol compound has 3 to 7 hydroxyl groups in the molecule.
[6] The curable composition according to [4] or [5], wherein the phenol compound has a triazine skeleton.
[7] The curable composition according to any one of [1] to [6], further comprising a maleimide compound.
[8] The curable composition according to any one of [1] to [7], wherein the inorganic particles include boron nitride particles.
[9] The curable composition according to [8], wherein the boron nitride particles include aggregated boron nitride particles having an average particle size of 20 μm or more.
[10] Further comprising a surface modifier,
The curable composition according to [8] or [9], wherein the boron nitride particles, together with the surface modifier that modifies the surfaces of the boron nitride particles, constitute surface-modified boron nitride particles.
[11] The curable composition according to any one of [1] to [10], further comprising a curing accelerator.
[12] The curable composition according to [11], wherein the curing accelerator comprises a compound containing a phosphorus atom.
[13] A thermally conductive material obtained by curing the curable composition according to any one of [1] to [12].
[14] A thermally conductive sheet made of the thermally conductive material according to [13].
[15] A device with a thermally conductive layer, comprising: a device; and a thermally conductive layer including the thermally conductive sheet according to [14] placed on the device.

According to the present invention, it is possible to provide a curable composition that can form a thermally conductive material having excellent thermal conductivity.
Furthermore, the present invention can provide a thermally conductive material, a thermally conductive sheet, and a device with a thermally conductive layer.

The present invention will be described in detail below.
The following description of the components may be based on typical embodiments of the present invention, but the present invention is not limited to such embodiments.

In this specification, a numerical range expressed using "~" means a range that includes the numerical values written before and after "~" as the lower and upper limits.

In this specification, the number average molecular weight and weight average molecular weight are weight average molecular weights determined by gel permeation chromatography (GPC) in terms of polystyrene.

In this specification, "solids" refers to the components that form the thermally conductive material and does not include solvents. The components that form the thermally conductive material may be components that undergo a reaction (polymerization) and change their chemical structure when forming the thermally conductive material. Furthermore, any component that forms the thermally conductive material is considered to be a solid, even if it is in liquid form.

In this specification, "(meth)acrylamide" means "either one or both of acrylamide and methacrylamide." "(meth)acrylic" means "either one or both of acrylic and methacrylic."

In this specification, the acid anhydride group may be either a monovalent group or a divalent group.
When the acid anhydride group is a monovalent group, examples thereof include substituents formed by removing any hydrogen atom from acid anhydrides such as maleic anhydride, phthalic anhydride, pyromellitic anhydride, and trimellitic anhydride. When the acid anhydride group is a divalent group, it means a group represented by *-CO-O-CO-* (* represents the bonding position).

In this specification, the bonding direction of a divalent group (e.g., -COO-) is not limited unless otherwise specified. For example, if Y in a compound represented by the formula "X-Y-Z" is -COO-, the compound may be either "X-O-CO-Z" or "X-CO-O-Z."

In this specification, a substituent or the like that is not specified as substituted or unsubstituted may, if possible, further have a substituent (for example, the substituent group Y described below) in the range that does not impair the intended effect. For example, the expression "alkyl group" means a substituted or unsubstituted alkyl group (an alkyl group that may have a substituent) in the range that does not impair the intended effect.
In addition, in the present specification, when it is stated that "may have a substituent", the type, position, and number of the substituent are not particularly limited. The number of the substituents may be, for example, one or two or more. The substituent may be, for example, a monovalent non-metallic atomic group excluding a hydrogen atom, and is preferably a group selected from the following substituent group Y.
In this specification, examples of halogen atoms include chlorine atoms, fluorine atoms, bromine atoms, and iodine atoms.

Substituent group Y:
Halogen atoms (such as -F, -Br, -Cl, and -I), hydroxy groups, amino groups, carboxylic acid groups and their conjugate base groups, carboxylic anhydride groups, cyanate ester groups, unsaturated polymerizable groups, epoxy groups, oxetanyl groups, aziridinyl groups, thiol groups, isocyanate groups, thioisocyanate groups, aldehyde groups, alkoxy groups, aryloxy groups, alkylthio groups, arylthio groups, alkyldithio groups, aryldithio groups, N-alkylamino groups, N,N-dialkylamino groups, N-arylamino groups, N,N-diarylamino groups, N-alkyl-N-arylamino groups, acyloxy groups, carbamoyloxy groups, N -Alkylcarbamoyloxy group, N-arylcarbamoyloxy group, N,N-dialkylcarbamoyloxy group, N,N-diarylcarbamoyloxy group, N-alkyl-N-arylcarbamoyloxy group, alkylsulfoxy group, arylsulfoxy group, acylthio group, acylamino group, N-alkylacylamino group, N-arylacylamino group, ureido group, N'-alkylureido group, N',N'-dialkylureido group, N'-arylureido group, N',N'-diarylureido group, N'-alkyl-N'-arylureido group, N-alkylureido group, N-arylureido group , N'-alkyl-N-alkylureido group, N'-alkyl-N-arylureido group, N',N'-dialkyl-N-alkylureido group, N',N'-dialkyl-N-arylureido group, N'-aryl-N-alkylureido group, N'-aryl-N-arylureido group, N',N'-diaryl-N-alkylureido group, N',N'-diaryl-N-arylureido group, N'-alkyl-N'-aryl-N-alkylureido group, N'-alkyl-N'-aryl-N-arylureido group, alkoxycarbonylamino group, aryloxycarbonylamino group, N-alkyl- N-alkoxycarbonylamino group, N-alkyl-N-aryloxycarbonylamino group, N-aryl-N-alkoxycarbonylamino group, N-aryl-N-aryloxycarbonylamino group, formyl group, acyl group, alkoxycarbonyl group, aryloxycarbonyl group, carbamoyl group, N-alkylcarbamoyl group, N,N-dialkylcarbamoyl group, N-arylcarbamoyl group, N,N-diarylcarbamoyl group, N-alkyl-N-arylcarbamoyl group, alkylsulfinyl group, arylsulfinyl group, alkylsulfonyl group, arylsulfonyl group, sulfo group (-SO _3H ) and their conjugate base groups, alkoxysulfonyl groups, aryloxysulfonyl groups, sulfinamoyl groups, N-alkylsulfinamoyl groups, N,N-dialkylsulfinamoyl groups, N-arylsulfinamoyl groups, N,N-diarylsulfinamoyl groups, N-alkyl-N-arylsulfinamoyl groups, sulfamoyl groups, N-alkylsulfamoyl groups, N,N-dialkylsulfamoyl groups, N-arylsulfamoyl groups, N,N-diarylsulfamoyl groups, N-alkyl-N-arylsulfamoyl groups, N-acylsulfamoyl groups and their conjugate base groups, N-alkylsulfonylsulfamoyl groups (-SO ₂ NHSO ₂ (alkyl)) and their conjugate base groups, N-arylsulfonylsulfamoyl groups (-SO ₂ NHSO ₂ (aryl)) and its conjugate base group, N-alkylsulfonylcarbamoyl group (-CONHSO ₂ (alkyl)) and its conjugate base group, N-arylsulfonylcarbamoyl group (-CONHSO ₂ (aryl)) and its conjugate base group, alkoxysilyl group (-Si(Oalkyl) ₃ ), aryloxysilyl group (-Si(Oaryl) ₃ ), hydroxysilyl group (-Si(OH) ₃ ) and its conjugate base group, phosphono group (-PO ₃ H ₂ ) and its conjugate base group, dialkylphosphono group (-PO ₃ (alkyl) ₂ ), diarylphosphono group (-PO ₃ (aryl) ₂ ), alkylarylphosphono group (-PO ₃ (alkyl)(aryl)), monoalkylphosphono group (-PO ₃ and its conjugate base group, monoarylphosphono group (-PO ₃ H(aryl)) and its conjugate base group, phosphonooxy group (-OPO ₃ H ₂ ) and its conjugate base group, dialkylphosphonooxy group (-OPO ₃ (alkyl) ₂ ), diarylphosphonooxy group (-OPO ₃ (aryl) ₂ ), alkylarylphosphonooxy group (-OPO ₃ (alkyl)(aryl)), monoalkylphosphonooxy group (-OPO ₃ H(alkyl)) and its conjugate base group, monoarylphosphonooxy group (-OPO ₃ H(aryl)) and its conjugate base group, cyano group, nitro group, aryl group, alkenyl group, alkynyl group, and alkyl group. Furthermore, each of the above groups may further have a substituent (for example, one or more of the above groups) if possible. For example, optionally substituted aryl groups are also included as groups that can be selected from the substituent group Y.
When the group selected from the substituent group Y has a carbon atom, the group has, for example, 1 to 20 carbon atoms.
The number of atoms other than hydrogen atoms contained in the group selected from the substituent group Y is, for example, 1 to 30.
Furthermore, these substituents may or may not bond to each other or to the group they substitute, if possible, to form a ring. For example, an alkyl group (or an alkyl group portion in a group containing an alkyl group as a partial structure, such as an alkoxy group) may be a cyclic alkyl group (cycloalkyl group) or an alkyl group having one or more cyclic structures as a partial structure.

[Curable composition]
The curable composition of the present invention comprises:
one or more types of inorganic particles selected from the group consisting of inorganic nitride particles and inorganic oxide particles;
and a compound having a partial structure represented by formula (1) described below or a partial structure represented by formula (2) described below (hereinafter also referred to as a "specific epoxy compound").

The mechanism by which the above-described configuration solves the problems of the present invention is not clear, but the inventors speculate as follows.
The specific epoxy compound has a structure in which an epoxy group is directly bonded to a ring atom constituting a cyclic moiety (specifically, the aromatic ring and aliphatic ring represented by X in formula (1) and the aliphatic ring represented by Cy in formula (2)). A thermally conductive material (cured product) formed from a curable composition containing the specific epoxy compound has a network structure with a shorter distance between crosslinking points due to the structure of the specific epoxy compound, and it is presumed that as a result, phonon scattering is suppressed and excellent thermal conductivity is exhibited.
Hereinafter, superior thermal conductivity of a thermal conductive material formed using the curable composition and/or superior heat resistance of a thermal conductive material formed using the curable composition is also referred to as superior effects of the present invention.

The components contained in the curable composition are described in detail below.

[Specific epoxy compound]
The curable composition contains a compound (specific epoxy compound) having a partial structure represented by formula (1) or a partial structure represented by formula (2).
Hereinafter, a compound (hereinafter also referred to as "specific epoxy compound (1)") containing a partial structure represented by formula (1) (hereinafter also referred to as "partial structure (1)") and a compound (hereinafter also referred to as "specific epoxy compound (2)") containing a partial structure represented by formula (2) (hereinafter also referred to as "partial structure (2)") will be described.

<Specific Epoxy Compound (1)>
The specific epoxy compound (1) is a compound containing the partial structure (1) described below.
The specific epoxy compound (1) may contain one or more partial structures (1). The upper limit of the number of partial structures (1) in the specific epoxy compound (1) is not particularly limited, and is, for example, preferably 6 or less, more preferably 4 or less.
In the specific epoxy compound (1), the partial structure (1) may be a part or the whole of the specific epoxy compound (1) (in other words, the specific epoxy compound (1) may be the same as the partial structure (1)), but it is preferably a part of the specific epoxy compound (1). Note that when the specific epoxy compound (1) contains only one partial structure (1) and the ring member atoms of the aromatic ring and the aliphatic ring represented by X in the partial structure (1) have a substituent, this substituent is not included in the partial structure (1). Note that the substituent is not limited, and examples thereof include an epoxy group.
When the specific epoxy compound (1) contains two or more partial structures (1) described below, the structures of the two or more partial structures (1) may be the same or different from each other.

The lower limit of the number of epoxy groups in the specific epoxy compound (1) is preferably 2 or more, since this provides better effects of the present invention. The number of epoxy groups here refers to both the epoxy groups contained in the partial structure (1) (i.e., the epoxy groups explicitly shown in formula (1)) and epoxy groups that the specific epoxy compound (1) may have in structural portions other than the partial structure (1). The upper limit of the number of epoxy groups in the specific epoxy compound (1) is not particularly limited, but is, for example, 8 or less, preferably 6 or less, and more preferably 4 or less.
The epoxy group content of the specific epoxy compound (1) is preferably 2.0 to 20.0 mmol/g, more preferably 5.0 to 15.0 mmol/g. The epoxy group content means the number of epoxy groups per 1 g of the epoxy compound.
The molecular weight of the specific epoxy compound (1) is preferably 120 or more, more preferably 150 or more, and the upper limit is preferably 1,000 or less, more preferably 500 or less.
When the molecular weight has a molecular weight distribution, the molecular weight is a weight average molecular weight.

The partial structure (1) will be described below.
(Partial structure (1))

In formula (1), X represents an aromatic ring or an aliphatic ring. That is, in formula (1), X corresponds to a monovalent aromatic ring or a monovalent aliphatic ring. However, as described below, X may be substituted with other substituents.

In the above formula (1), the aromatic ring represented by X may be a monocyclic or polycyclic ring, and preferably has 5 to 30 ring atoms, more preferably 6 to 20 ring atoms, and even more preferably 6 to 14 ring atoms.
The aromatic ring represented by X may be either an aromatic hydrocarbon ring or an aromatic heterocycle. When the aromatic ring represented by X is an aromatic heterocycle, examples of heteroatoms contained in the ring include an oxygen atom, a nitrogen atom, and a sulfur atom. The number of heteroatoms is preferably 1 to 3, for example.
Among these, an aromatic hydrocarbon ring is preferable as the aromatic ring represented by X. Examples of the aromatic hydrocarbon ring include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, and a pyrene ring, and a benzene ring, a naphthalene ring, or an anthracene ring is preferable.

In the above formula (1), the aliphatic ring represented by X may be a monocyclic ring or a polycyclic ring, and the number of ring atoms is preferably 6 to 20, more preferably 6 to 14, still more preferably 6 to 10, and most preferably 6.
The aliphatic ring represented by X may be either an aliphatic hydrocarbon ring or an aliphatic heterocycle. When the aliphatic ring represented by X is an aliphatic heterocycle, examples of heteroatoms contained in the ring include an oxygen atom, a nitrogen atom, and a sulfur atom. The number of heteroatoms is preferably 1 to 3, for example.
Of these, an aliphatic hydrocarbon ring is preferable as the aliphatic ring represented by X. Examples of the aliphatic hydrocarbon ring include a cyclohexane ring, a cycloheptane ring, a decalin ring, a norbornane ring, and an adamantane ring, and of these, a cyclohexane ring is preferable.

The specific epoxy compound (1) is preferably a compound represented by formula (1A) or a compound represented by formula (1B).
The compound represented by formula (1A) and the compound represented by formula (1B) will be described below.

(Compound represented by formula (1A))

In formula (1A), X ^E1 represents an m ^E1 +1 valent aromatic ring group or an aliphatic ring group.

The aromatic ring constituting the aromatic ring group may be a monocyclic or polycyclic ring, and preferably has 5 to 30, more preferably 6 to 20, and even more preferably 6 to 14 ring atoms.
The aromatic ring may be either an aromatic hydrocarbon ring or an aromatic heterocyclic ring. When the aromatic ring is an aromatic heterocyclic ring, examples of heteroatoms contained in the ring include an oxygen atom, a nitrogen atom, and a sulfur atom. The number of heteroatoms is preferably 1 to 3, for example.
Among these, the aromatic ring is preferably an aromatic hydrocarbon ring, such as a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, or a pyrene ring, with a benzene ring, a naphthalene ring, or an anthracene ring being preferred.
The m ^E1 +1 valent aromatic ring group is a group formed by removing m ^E1 +1 hydrogen atoms from the above aromatic ring.
The aromatic ring group may further have a substituent, for example, the groups exemplified in the above-mentioned group Y of substituents.

The aliphatic ring constituting the aliphatic cyclic group may be a monocyclic ring or a polycyclic ring, and the number of ring atoms is preferably 6 to 20, more preferably 6 to 14, still more preferably 6 to 10, and most preferably 6.
The aliphatic ring may be either an aliphatic hydrocarbon ring or an aliphatic heterocyclic ring. When the aliphatic ring is an aliphatic heterocyclic ring, examples of heteroatoms contained in the ring include oxygen atoms, nitrogen atoms, and sulfur atoms. The number of heteroatoms is preferably 1 to 3, for example.
Of the above-mentioned aliphatic rings, aliphatic hydrocarbon rings are preferred. Examples of the aliphatic hydrocarbon ring include a cyclohexane ring, a cycloheptane ring, a decalin ring, a norbornane ring, and an adamantane ring, and of these, a cyclohexane ring is preferred.
The m ^E1 +1 valent aliphatic ring group is a group formed by removing m ^E1 +1 hydrogen atoms from the above aliphatic ring.
The aliphatic cyclic group may further have a substituent, for example, the groups exemplified in the above-mentioned group Y of substituents.

In formula (1B), X ^E1 preferably represents an m ^E1 +1 valent aromatic ring group, in that the effects of the present invention are more excellent.

In formula (1A), m ^E1 represents an integer of 1 or more. m ^E1 is preferably an integer of 1 to 4, and more preferably 1 or 2.

(Compound represented by formula (1B))

In formula (1B), X ^E2 represents a divalent aromatic ring group or an aliphatic ring group, and a plurality of X ^E2 may be the same or different.

The aromatic ring constituting the aromatic ring group may be a monocyclic or polycyclic ring, and preferably has 5 to 30, more preferably 6 to 20, and even more preferably 6 to 14 ring atoms.
The aromatic ring may be either an aromatic hydrocarbon ring or an aromatic heterocyclic ring. When the aromatic ring is an aromatic heterocyclic ring, examples of heteroatoms contained in the ring include an oxygen atom, a nitrogen atom, and a sulfur atom. The number of heteroatoms is preferably 1 to 3, for example.
Among these, the aromatic ring is preferably an aromatic hydrocarbon ring, such as a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, or a pyrene ring, with a benzene ring, a naphthalene ring, or an anthracene ring being preferred.
The divalent aromatic ring group is a group formed by removing two hydrogen atoms from the above aromatic ring.
The aromatic ring group may further have a substituent, for example, the groups exemplified in the above-mentioned group Y of substituents.

The aliphatic ring constituting the aliphatic cyclic group may be a monocyclic ring or a polycyclic ring, and the number of ring atoms is preferably 6 to 20, more preferably 6 to 14, still more preferably 6 to 12, and most preferably 6.
The aliphatic ring may be either an aliphatic hydrocarbon ring or an aliphatic heterocyclic ring. When the aliphatic ring is an aliphatic heterocyclic ring, examples of heteroatoms contained in the ring include oxygen atoms, nitrogen atoms, and sulfur atoms. The number of heteroatoms is preferably 1 to 3, for example.
Of the above-mentioned aliphatic rings, aliphatic hydrocarbon rings are preferred. Examples of the aliphatic hydrocarbon ring include a cyclohexane ring, a cycloheptane ring, a decalin ring, a norbornane ring, and an adamantane ring, and of these, a cyclohexane ring is preferred.
The divalent aliphatic ring group is a group formed by removing two hydrogen atoms from the above aliphatic ring.
The aliphatic cyclic group may further have a substituent, for example, the groups exemplified in the above-mentioned group Y of substituents.

In formula (1B), X ^E2 preferably represents a divalent aromatic ring group, as this provides better effects of the present invention.

In formula (1B), L ^X represents a single bond or m ^E divalent linking group.
m ^E2 represents an integer of 2 or more. m ^E2 is preferably an integer of 2 to 4, and more preferably 2 or 3.
When L ^X in formula (1B) is a single bond, m ^E2 represents 2.
The divalent linking group ^mE represented by ^LX is not particularly limited, but is preferably, for example, a linking group represented by the following formulae (L1) to (L3): The linking groups represented by formulae (L1) to (L3) respectively represent divalent, trivalent, and tetravalent linking groups.

In the above formula (L1), examples of ^M1 include ^{CR1L R2L} , an oxygen atom, a sulfur atom, and a divalent benzene ring group. In the above formula (L2), examples of ^M2 include ^CR3L , a nitrogen atom, and a trivalent benzene ring group. In the above formula (L3), examples of ^M3 include a carbon atom and a tetravalent benzene ring group.
R ^1L to R ^3L each independently represent a hydrogen atom or a substituent. Examples of the substituents represented by ^{R 1L} to R ^3L include the groups exemplified in the above-mentioned substituent group Y.
The divalent to tetravalent benzene ring groups may further have a substituent, for example, the groups exemplified in the above-mentioned group Y of substituents.

In formula (1B), L 1 ^X preferably represents a single bond or a divalent linking group, and m ^{1 E2} preferably represents 2.

<Specific Epoxy Compound (2)>
The specific epoxy compound (2) is a compound containing the partial structure (2) described below.
The specific epoxy compound (2) may contain one or more partial structures (2). The upper limit of the number of partial structures (2) in the specific epoxy compound (2) is not particularly limited and is, for example, 6 or less, more preferably 4 or less.
In the specific epoxy compound (2), the partial structure (2) may be a part or the whole of the specific epoxy compound (2) (in other words, the specific epoxy compound (2) may be the same as the partial structure (2)), but it is preferably a part of the specific epoxy compound (2). If the specific epoxy compound (2) contains only one partial structure (2) and the ring atom of the alicyclic ring represented by Cy in the partial structure (2) has a substituent, this substituent is not included in the partial structure (2). The substituent is not limited, and examples thereof include an epoxy group. The epoxy group may be a monovalent substituent, or may have a structure in which a carbon atom in the epoxy group acts as a spiro atom and is shared with a carbon atom that is a ring atom of the alicyclic ring represented by Cy.
When the specific epoxy compound (2) contains two or more partial structures (2) described below, the structures of the two or more partial structures (2) may be the same or different from each other.

The lower limit of the number of epoxy groups in the specific epoxy compound (2) is preferably 2 or more, since this provides better effects of the present invention. The number of epoxy groups here refers to the epoxy groups contained in the partial structure (2) (i.e., the epoxy groups explicitly shown in formula (2)) and the epoxy groups that the specific epoxy compound (2) may have in structural portions other than the partial structure (2). The upper limit of the number of epoxy groups in the specific epoxy compound (2) is not particularly limited, but is, for example, 8 or less, preferably 6 or less, and more preferably 4 or less.
The epoxy group content of the specific epoxy compound (2) is preferably 2.0 to 20.0 mmol/g, more preferably 5.0 to 15.0 mmol/g. The epoxy group content means the number of epoxy groups per 1 g of the epoxy compound.
The molecular weight of the specific epoxy compound (2) is preferably 120 or more, more preferably 150 or more, and the upper limit is preferably 1,000 or less, more preferably 500 or less.
When the molecular weight has a molecular weight distribution, the molecular weight is a weight average molecular weight.

The partial structure (2) will be described below.
(Partial structure (2))

In formula (2), Cy represents an aliphatic ring.
In formula (2), the epoxy ring and the aliphatic ring represented by Cy share a carbon atom (in other words, the epoxy ring and the aliphatic ring represented by Cy form a spiro ring structure). In other words, in formula (2), Cy corresponds to a divalent aliphatic ring. However, as described below, Cy may be substituted with another substituent.

In the above formula (2), the aliphatic ring represented by Cy may be a monocycle or a polycycle, and the number of ring atoms is preferably 6 to 20, more preferably 6 to 14, still more preferably 6 to 10, and most preferably 6.
The aliphatic ring may be either an aliphatic hydrocarbon ring or an aliphatic heterocyclic ring. When the aliphatic ring is an aliphatic heterocyclic ring, examples of heteroatoms contained in the ring include oxygen atoms, nitrogen atoms, and sulfur atoms. The number of heteroatoms is preferably 1 to 3, for example.
Of the above-mentioned aliphatic rings, aliphatic hydrocarbon rings are preferred. Examples of the aliphatic hydrocarbon ring include a cyclohexane ring, a cycloheptane ring, a decalin ring, a norbornane ring, and an adamantane ring, and of these, a cyclohexane ring is preferred.

The specific epoxy compound (2) is preferably a compound represented by formula (2A) or a compound represented by formula (2B).
The compound represented by formula (2A) and the compound represented by formula (2B) will be described below.

(Compound represented by formula (2A))

In formula (2A), Cy ^E1 represents a 2n ^E1 +divalent aliphatic ring group.
In formula (2A), the epoxy ring located to the left of Cy ^E1 among the epoxy rings shown in the formula and the aliphatic ring represented by Cy ^E1 share a carbon atom (in other words, the epoxy ring and the aliphatic ring represented by Cy ^E1 form a spiro ring structure). Also, the n ^E1 epoxy rings located to the right of Cy ^E1 among the epoxy rings shown in the formula and the aliphatic ring represented by Cy ^E1 each share a carbon atom (in other words, the n ^E1 epoxy rings and the aliphatic ring represented by Cy ^E1 each form a spiro ring structure).

The aliphatic ring constituting the above-mentioned aliphatic cyclic group may be a monocyclic ring or a polycyclic ring, and the number of ring atoms is preferably 6 to 20, more preferably 6 to 12, still more preferably 6 to 10, and most preferably 6.
The aliphatic ring may be either an aliphatic hydrocarbon ring or an aliphatic heterocyclic ring. When the aliphatic ring is an aliphatic heterocyclic ring, examples of heteroatoms contained in the ring include oxygen atoms, nitrogen atoms, and sulfur atoms. The number of heteroatoms is preferably 1 to 3, for example.
Of the above-mentioned aliphatic rings, aliphatic hydrocarbon rings are preferred. Examples of the aliphatic hydrocarbon ring include a cyclohexane ring, a cycloheptane ring, a decalin ring, a norbornane ring, and an adamantane ring, and of these, a cyclohexane ring is preferred.
The 2n ^E1 + divalent aliphatic ring group is a group formed by removing 2n ^E1 + 2 hydrogen atoms from the above aliphatic ring.
The aliphatic cyclic group may further have a substituent, for example, the groups exemplified in the above-mentioned group Y of substituents.

In formula (2A), n ^E1 represents an integer of 1 or more. n ^E1 is preferably 1 or 2, and more preferably 1.

(Compound represented by formula (2B))

In formula (2B), Cy ^E2 represents a trivalent aliphatic cyclic group, and a plurality of Cy ^E2s may be the same or different.
In formula (2B), the epoxy ring shown in the formula and the aliphatic ring represented by Cy ^E2 share a carbon atom (in other words, the epoxy ring and the aliphatic ring represented by Cy ^E2 form a spiro ring structure).

The aliphatic ring constituting the above-mentioned aliphatic cyclic group may be a monocyclic ring or a polycyclic ring, and the number of ring atoms is preferably 6 to 20, more preferably 6 to 14, even more preferably 6 to 10, and most preferably 6.
The aliphatic ring may be either an aliphatic hydrocarbon ring or an aliphatic heterocyclic ring. When the aliphatic ring is an aliphatic heterocyclic ring, examples of heteroatoms contained in the ring include oxygen atoms, nitrogen atoms, and sulfur atoms. The number of heteroatoms is preferably 1 to 3, for example.
Of the above-mentioned aliphatic rings, aliphatic hydrocarbon rings are preferred. Examples of the aliphatic hydrocarbon ring include a cyclohexane ring, a cycloheptane ring, a decalin ring, a norbornane ring, and an adamantane ring, and of these, a cyclohexane ring is preferred.
The trivalent aliphatic ring group is a group formed by removing three hydrogen atoms from the above aliphatic ring.
The aliphatic cyclic group may further have a substituent, for example, the groups exemplified in the above-mentioned group Y of substituents.

In formula (2B), L 1 ^Y represents a single bond or an n ^E divalent linking group.
n ^E2 represents an integer of 2 or more. n ^E2 is preferably an integer of 2 to 4, and more preferably 2 or 3.
When L ^Y in formula (2B) is a single bond, n ^E2 represents 2.
The n ^E2 -valent linking group represented by L ^Y is not particularly limited, and examples thereof include the same as the m ^E2- valent linking group represented by L ^X in formula (1B).

In formula (2B), L 1 ^Y represents a single bond or a divalent linking group, and n 1 ^E2 preferably represents 2.

The specific epoxy compound is preferably a compound represented by formula (1A) in which X represents an m ⁺ monovalent aromatic ring group, or a compound represented by formula (1B) in which ^X represents a divalent aromatic ^ring group, in terms of more excellent effects of the present invention.

Specific examples of specific epoxy compounds are listed below, but the present invention is not limited to these.

Specific epoxy compounds can be synthesized using known methods (e.g., Corey-Tchaikovsky reaction, oxidation reaction, etc.).

The content of the specific epoxy compound in the curable composition is preferably 3 to 90 mass%, more preferably 5 to 50 mass%, still more preferably 5 to 40 mass%, and particularly preferably 7 to 40 mass%, relative to the total solid content of the curable composition.
The specific epoxy compounds may be used alone or in combination of two or more.

The curable composition may also contain epoxy compounds other than the specific epoxy compound (hereinafter also referred to as "other epoxy compounds"). The content of the specific epoxy compound is preferably 30 to 100% by mass, and more preferably 50 to 100% by mass, based on the total mass of the epoxy compounds.

[Other epoxy compounds]
The curable composition may contain an epoxy compound other than the specific epoxy compound (another epoxy compound).
The other epoxy compound is a compound having at least one epoxy group (oxiranyl group) in one molecule.
The epoxy group is a group obtained by removing one or more hydrogen atoms (preferably one hydrogen atom) from an oxirane ring. If possible, the epoxy group may further have a substituent (for example, a linear or branched alkyl group having 1 to 5 carbon atoms).

The number of epoxy groups contained in the other epoxy compounds is preferably 2 or more, more preferably 2 to 1,000, and even more preferably 2 to 40, per molecule.

The molecular weight of the other epoxy compound is preferably 150 or more, more preferably 300 or more, and the upper limit is preferably 100,000 or less, more preferably 10,000 or less.
When the molecular weight has a molecular weight distribution, the molecular weight is a weight average molecular weight.

The epoxy group content of the other epoxy compound is preferably from 2.0 to 20.0 mmol/g, more preferably from 5.0 to 15.0 mmol/g.
The epoxy group content means the number of epoxy groups contained in 1 g of the other epoxy compound.
The other epoxy compound preferably has an aromatic ring group (preferably an aromatic hydrocarbon ring group).
In terms of achieving better effects of the present invention, the content of the epoxy compound having an aromatic ring group in the curable composition is preferably 5 to 100 mass%, more preferably 50 to 100 mass%, and even more preferably 70 to 100 mass%, based on the total amount of epoxy compounds.

The other epoxy compounds may or may not exhibit liquid crystallinity.
That is, the other epoxy compound may be a liquid crystal compound, in other words, a liquid crystal compound having an epoxy group.
Examples of the other epoxy compounds (which may be other liquid crystalline epoxy compounds) include compounds having at least a partial rod-like structure (rod-like compounds) and compounds having at least a partial discotic structure (discotic compounds).
The rod-shaped compounds and discotic compounds will be described in detail below.

- Rod-shaped compound -
Examples of epoxy compounds that are rod-shaped compounds include azomethines, azoxys, cyanobiphenyls, cyanophenyl esters, benzoates, cyclohexanecarboxylic acid phenyl esters, cyanophenylcyclohexanes, cyano-substituted phenylpyrimidines, alkoxy-substituted phenylpyrimidines, phenyldioxanes, tolanes, and alkenylcyclohexylbenzonitriles. In addition to the low molecular weight compounds described above, high molecular weight compounds can also be used. The high molecular weight compounds are polymerized low molecular weight rod-shaped compounds having reactive groups.

The rod-shaped compound is preferably a compound represented by formula (E1).

In formula (E1), L ^E1 each independently represents a divalent linking group.
The divalent linking group is preferably -O-, -S-, -CO-, -NH-, -CH=CH-, -C≡C-, -CH=N-, -N=CH-, -N=N-, an alkylene group which may have a substituent, or a group formed from a combination of two or more thereof, and more preferably -O-alkylene group- or -alkylene group-O-.
The alkylene group may be straight-chain, branched-chain, or cyclic, but is preferably a straight-chain alkylene group having 1 to 2 carbon atoms.
A plurality of L ^E1's may be the same or different.

In formula (E1), L ^E2 each independently represent a single bond, -CH=CH-, -CO-O-, -O-CO-, -C(-CH ₃ )=CH-, -CH=C(-CH ₃ )-, -CH=N-, -N=CH-, -N=N-, -C≡C-, -N=N ⁺ (-O ^- )-, -N + (-O ^- )=N-, -CH=N ⁺ (-O ^- )-, -N ⁺ (-O ^- )=CH-, ^-CH =CH-CO-, -CO-CH=CH-, -CH=C(-CN)-, or -C(-CN)=CH-.
Each L ^E2 is preferably independently a single bond, —CO—O—, or —O—CO—.
When a plurality of L ^E2s are present, the plurality of L ^E2s may be the same or different.

In formula (E1), L ^{and E3} each independently represent a single bond, or an optionally substituted 5- or 6-membered aromatic ring group, an optionally substituted 5- or 6-membered non-aromatic ring group, or a polycyclic group composed of these rings.
Examples of aromatic and non-aromatic ring groups represented by L ^E3 include optionally substituted 1,4-cyclohexanediyl, 1,4-cyclohexenediyl, 1,4-phenylene, pyrimidine-2,5-diyl, pyridine-2,5-diyl, 1,3,4-thiadiazole-2,5-diyl, 1,3,4-oxadiazole-2,5-diyl, naphthalene-2,6-diyl, naphthalene-1,5-diyl, thiophene-2,5-diyl, and pyridazine-3,6-diyl groups. In the case of the 1,4-cyclohexanediyl group, it may be either a trans or cis structural isomer, or a mixture in any proportion. The trans isomer is preferred.
L ^E3 is preferably a single bond, a 1,4-phenylene group or a 1,4-cyclohexenediyl group.
The substituents possessed by the group represented by L ^E3 are each independently preferably an alkyl group, an alkoxy group, a halogen atom, a cyano group, a nitro group or an acetyl group, more preferably an alkyl group (preferably having 1 carbon atom).
When a plurality of substituents are present, the substituents may be the same or different.
When a plurality of L ^E3s are present, the plurality of L ^E3s may be the same or different.

In formula (E1), pe represents an integer of 0 or more.
When pe is an integer of 2 or more, a plurality of (-L ^E3 -L ^E2 -) may be the same or different.
pe is preferably 0 to 2, more preferably 0 or 1, and even more preferably 0.

In formula (E1), L ^{and E4} each independently represent a substituent.
The substituents are each independently preferably an alkyl group, an alkoxy group, a halogen atom, a cyano group, a nitro group or an acetyl group, more preferably an alkyl group (preferably having one carbon atom).
A plurality of L ^E4 's may be the same or different from each other. When l e described below is an integer of 2 or more, a plurality of L ^E4's present in the same (L ^E4 ) _l e may be the same or different from each other.

In formula (E1), each le independently represents an integer of 0 to 4.
Each le is preferably 0 to 2.
A plurality of le's may be the same or different.

Also preferred are compounds represented by formula (E1) in which one or both of the two "epoxy groups -L ^E1 -" are replaced with a diglycidylaminoalkylene group (preferably a diglycidylaminomethylene group).

The rod-like compound preferably has a biphenyl skeleton, since the resulting thermally conductive material has better thermal conductivity.
In other words, the other epoxy compound preferably has a biphenyl skeleton, and in this case, the other epoxy compound is preferably a rod-like compound.

-Disc-shaped compounds-
The discotic epoxy compound has at least a partial discotic structure.
The discotic structure has at least an alicyclic ring or an aromatic ring. In particular, when the discotic structure has an aromatic ring, the discotic compound can form a columnar structure by forming a stacking structure due to intermolecular π-π interactions.
Specific examples of the discotic structure include the triphenylene structure described in Angew. Chem. Int. Ed. 2012, 51, 7990-7993 or JP-A-7-306317, and the tri-substituted benzene structures described in JP-A-2007-002220 and JP-A-2010-244038.

When a discotic compound is used as another epoxy compound, a thermally conductive material with high thermal conductivity can be obtained. The reason for this is thought to be that while rod-shaped compounds can only conduct heat linearly (one-dimensionally), discotic compounds can conduct heat planarly (two-dimensionally) in the normal direction, which increases the number of heat conduction paths and improves thermal conductivity.

The discotic compound preferably has three or more epoxy groups. A cured product of a curable composition containing a discotic compound having three or more epoxy groups tends to have a high glass transition temperature and high heat resistance.
The number of epoxy groups contained in the discotic compound is preferably 8 or less, more preferably 6 or less.

Examples of discotic compounds include those described in C. Destrade et al., Mol. Crysr. Liq. Cryst., vol. 71, page 111 (1981); Quarterly Review of Chemistry, No. 22, Chemistry of Liquid Crystals, edited by the Chemical Society of Japan, Chapter 5, Chapter 10, Section 2 (1994); B. Kohne et al., Angew. Chem. Soc. Chem. Comm., page 1794 (1985); and J. Zhang et al., J. Am. Chem. Soc., vol. 116, page 2655 (1994) and Japanese Patent No. 4592225, in which at least one (preferably three or more) terminal groups are epoxy groups.
Examples of the discotic compound include the triphenylene structure described in Angew. Chem. Int. Ed. 2012, 51, 7990-7993 and JP-A-7-306317, and the trisubstituted benzene structure described in JP-A-2007-002220 and JP-A-2010-244038 in which at least one (preferably three or more) of the terminals is an epoxy group.

- Epoxy compounds other than rod-shaped compounds and discotic compounds -
As other epoxy compounds, in addition to the rod-like compounds and discotic compounds described above, compounds represented by the formula (Z), formula (Z1), or formula (Z2) described later in the description of phenolic compounds in which the phenolic hydroxy group is replaced with an epoxy-containing group can also be used.
The epoxy-containing group is a group which is an epoxy group itself or a monovalent group which partially contains an epoxy group.
The monovalent group partially containing an epoxy group is a group having one or more (preferably 1 to 8) epoxy groups within the entire group.
The monovalent group partially containing an epoxy group is preferably a group represented by "-(divalent hydrocarbon group) _M1 -(-O-divalent hydrocarbon group-) _M2 -epoxy group". In the above group, M1 represents 0 or 1. M2 represents an integer of 1 or more (preferably 1 to 10). Examples of the divalent hydrocarbon group in the above group include alkylene groups (preferably having 1 to 6 carbon atoms), alkenylene groups (-CH=CH-, etc., preferably having 2 to 6 carbon atoms), alkynylene groups (-C≡C-, etc., preferably having 2 to 6 carbon atoms), arylene groups (phenylene group, etc., preferably having 6 to 15 carbon atoms), and combinations thereof. The divalent hydrocarbon group may or may not have a substituent, and the divalent hydrocarbon group may further have an epoxy-containing group as a substituent. A plurality of the divalent hydrocarbon groups may be present and may be the same or different.

Other epoxy compounds include, for example, bisphenol A type epoxy compounds, bisphenol F type epoxy compounds, bisphenol S type epoxy compounds, bisphenol AD type epoxy compounds, etc., which are glycidyl ethers of bisphenol A, F, S, AD, etc.; hydrogenated bisphenol A type epoxy compounds, hydrogenated bisphenol AD type epoxy compounds, etc.; phenol novolac type glycidyl ethers (phenol novolac type epoxy compounds), cresol novolac type glycidyl ethers (cresol novolac type epoxy compounds), bisphenol A novolac type glycidyl ethers, etc.; dicyclopentadiene type glycidyl ethers (dicyclopentadiene type epoxy compounds); dihydrido Examples of the epoxy compound include glycidyl ethers of hydroxypentadiene type (dihydroxypentadiene type epoxy compounds); polyhydroxybenzene type glycidyl ethers (polyhydroxybenzene type epoxy compounds) such as glycidyl ethers of dihydroxybenzenes such as resorcinol; benzenepolycarboxylic acid type glycidyl esters (benzenepolycarboxylic acid type epoxy compounds); trisphenolmethane type epoxy compounds; phenoxy resins; acrylic resins having epoxy groups in their side chains; and polyol type epoxy compounds such as glycidyl ethers of polyols such as trimethylolpropane, triethanolamine, erythritol, pentaerythritol, xylitol, mannitol, and dipentaerythritol. Compounds in which one or more of the glycidyl ether groups and/or glycidyl ester groups in the above-mentioned compounds are replaced with diglycidylamino groups or diglycidylaminoalkylene groups (diglycidylaminomethylene groups, etc.) may also be used as the epoxy compound.
Each of the above-mentioned compounds may have a substituent. For example, the aromatic ring group, cycloalkane ring group, and/or alkylene group contained in each of the above-mentioned compounds may have a substituent other than a glycidyl ether group, a glycidyl ester group, a diglycidylamino group, and/or a diglycidylaminoalkylene group.

In the following, when simply referring to an "epoxy compound," this is intended to refer to both the specific epoxy compound and other epoxy compounds (i.e., all epoxy compounds in the composition).

[Phenol compounds]
The curable composition preferably comprises a phenolic compound.
The phenol compound is a compound having one or more (preferably two or more, more preferably 2 to 10) phenolic hydroxyl groups.
The phenol compound preferably has a triazine skeleton.
The phenol compound "having a triazine skeleton" means that the phenol compound has one or more (preferably 1 to 5) triazine ring groups.

The phenol compound is preferably a compound represented by formula (Z).

In the above formula (Z), when there are multiple groups represented by the same symbol, unless otherwise specified, the multiple groups represented by the same symbol may be the same or different.

In formula (Z), E ¹ to E ⁶ each independently represent a single bond, —NH— or —NR—.
R represents a substituent, such as a linear or branched alkyl group having 1 to 5 carbon atoms.
E ¹ to E ⁶ each independently represent preferably —NH— or —NR—, more preferably —NH—.

In formula (Z), ^B1 represents a single bond or a (k+1)-valent organic group.
^B2 represents a single bond or a l+1-valent organic group.
^B3 represents a single bond or an (m+1)-valent organic group.
^B4 represents a single bond or an (n+1)-valent organic group.
The values of k, l, m, and n in the k+1-valent organic group, the l+1-valent organic group, the m+1-valent organic group, and the n+1-valent organic group are the same as the values of k, l, m, and n specified in formula (Z).
In addition, when r is 2 or more and the values of m present in a plurality of groups are different, the value of m in the (m+1)-valent organic group represented by ^B3 is the same as the value of m indicating the number of ^X3 to which ^B3 is bonded.

Examples of the organic group represented by B ¹ to B ⁴ include groups in which j hydrogen atoms have been removed from a hydrocarbon having 1 to 20 carbon atoms and which may have a heteroatom, where j refers to k+1, l+1, m+1, or n+1.
Here, examples of the hydrocarbon before removing the j hydrogen atoms include one or more hydrocarbons selected from the group consisting of an aliphatic hydrocarbon having 1 to 20 carbon atoms which may have a substituent, an aliphatic ring having 3 to 20 carbon atoms which may have a substituent, and an aromatic ring having 3 to 20 carbon atoms which may have a substituent. Furthermore, the one or more hydrocarbons may be further combined with one or more divalent linking groups selected from the group consisting of -O-, -S-, -CO-, -NR ^N - (R ^N represents a hydrogen atom or a substituent), and -SO ₂ -.
Examples of aliphatic hydrocarbons having 1 to 20 carbon atoms include methane, ethane, propane, butane, pentane, hexane, and heptane.
Examples of the aliphatic ring having 3 to 20 carbon atoms include a cyclohexane ring, a cycloheptane ring, a norbornane ring, and an adamantane ring.
Examples of aromatic rings having 3 to 20 carbon atoms include aromatic hydrocarbons having 6 to 20 carbon atoms and aromatic heterocycles having 3 to 20 carbon atoms.
Examples of aromatic hydrocarbons having 6 to 20 carbon atoms include a benzene ring, a naphthalene ring, and an anthracene ring, and examples of aromatic heterocycles having 3 to 20 carbon atoms include a furan ring, a pyrrole ring, a thiophene ring, a pyridine ring, a thiazole ring, a carbazole ring, an indole ring, and a benzothiazole ring.

In formula (Z), k, l, m, and n each independently represent an integer of 0 or greater, provided that the sum of k, l, r×m, and n is an integer of 2 or greater, preferably an integer of 2 to 12, and more preferably an integer of 4 to 8.
The value of m in "r x m" is the average value of multiple possible m's.
k, l, m, and n each independently represent preferably an integer of 0 to 5, more preferably an integer of 1 or 2.
For example, k is preferably an integer of 1 or more (for example, an integer of 1 or 2, etc.), l is preferably an integer of 1 or more (for example, an integer of 1 or 2, etc.), m is preferably an integer of 1 or more (for example, an integer of 1 or 2, etc.), and n is preferably an integer of 1 or more (for example, an integer of 1 or 2, etc.).
When k is 0, ^B1 does not have ^X1 . When l is 0, ^B2 does not have ^X2 . When m is 0, ^B3 does not have ^X3 . When n is 0, ^B4 does not have ^X4 .
Furthermore, when ^B1 is a single bond, k is 1. When ^B2 is a single bond, l is 1. When ^B3 is a single bond, m is 1. When ^B4 is a single bond, n is 1.

L represents a divalent organic group.
Examples of the divalent organic group include a divalent aromatic ring group which may have a substituent, a divalent aliphatic hydrocarbon group which may have a substituent, a divalent aliphatic ring group which may have a substituent, -N(R ^NA )-, -CO-, and groups combining these. R ^NA represents an organic group. The groups exemplified as the above divalent organic group may further have -O-, -S-, -N(R ^N )-, and groups combining these.
R 1 ^N represents a substituent. Examples of the substituent represented by R ^{1 N} include a linear or branched alkyl group having 1 to 5 carbon atoms.
Furthermore, examples of the substituent that the aromatic ring group, the aliphatic hydrocarbon group, and the aliphatic ring group may have include linear or branched alkyl groups having 1 to 5 carbon atoms.

Examples of the divalent aromatic ring group include a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms and a divalent aromatic heterocyclic group having 3 to 20 carbon atoms.
Examples of aromatic rings constituting a divalent aromatic hydrocarbon group having 6 to 20 carbon atoms include monocyclic aromatic rings such as a benzene ring; and polycyclic aromatic ring groups such as a naphthalene ring and an anthracene ring. Examples of aromatic heterocycles constituting a divalent aromatic heterocyclic group having 3 to 20 carbon atoms include monocyclic aromatic rings such as a furan ring, a pyrrole ring, a thiophene ring, a pyridine ring, and a thiazole ring; and polycyclic aromatic rings such as a benzothiazole ring, a carbazole ring, and an indole ring.
The divalent aromatic ring group represented by L may be any of the above-exemplified groups in which two hydrogen atoms have been removed.

Examples of divalent aliphatic hydrocarbon groups include alkylene groups having 1 to 12 carbon atoms, such as methylene, ethylene, propylene, butylene, pentylene, hexylene, methylhexylene, and heptylene groups.

Examples of the aliphatic ring constituting the divalent aliphatic ring group include a cyclohexane ring, a cycloheptane ring, a norbornane ring, and an adamantane ring.
The aliphatic cyclic group represented by L may be any of the above-listed groups in which two hydrogen atoms have been removed.

The divalent aromatic ring group which may have a substituent, the divalent aliphatic hydrocarbon group which may have a substituent, the divalent aliphatic ring group which may have a substituent, or the group combining -O-, -S-, -NR ^N - or -CO- may be not only a divalent linking group consisting of a combination of two or more of these, but also a divalent linking group in which two or more of the same types of groups (for example, aromatic ring groups, etc.) are combined via a single bond.

In the present invention, it is preferable that both ends of L are carbon atoms, in that the effects of the present invention are more excellent. The terminal carbon atoms may be part of a cyclic structure.
Furthermore, in the present invention, in terms of achieving better effects of the present invention, L in the above formula (P2) is preferably a divalent organic group having at least one selected from the group consisting of a divalent aromatic ring group which may have a substituent, a divalent aliphatic ring group which may have a substituent, and an alkylene group having two or more carbon atoms which may have a branch, and is more preferably a divalent organic group having a divalent aromatic ring group which may have a substituent.

In formula (Z), r is an integer of 0 or more.
r is preferably an integer of 0 to 20, and more preferably an integer of 0 to 10.

In formula (Z), X ¹ to X ⁴ each independently represent an aromatic ring group having a phenolic hydroxyl group.
The "aromatic ring group having a phenolic hydroxyl group" may be an aromatic ring group having one or more (e.g., 1 to 4) hydroxyl groups (phenolic hydroxyl groups) directly bonded to the aromatic ring. The aromatic ring group may or may not have a substituent other than the hydroxyl group. The aromatic ring group may be monocyclic or polycyclic, and may have a heteroatom as a ring member atom. The number of ring member atoms in the aromatic ring group is preferably 5 to 15, more preferably 6 to 10, and even more preferably 6.
The aromatic ring group is preferably a benzene ring group.
The substituent that the aromatic ring group may have other than the hydroxyl group is preferably a substituent having 1 to 6 carbon atoms, more preferably a hydrocarbon group having 1 to 6 carbon atoms, and still more preferably a linear or branched alkyl group having 1 to 6 carbon atoms.

In formula (Z), at least one of the k X ¹ s, 1 X ² s, r×m X ³ s, and n X ^{4 s} is preferably an aromatic ring group having a phenolic hydroxyl group and a substituent located at the ortho-position of the phenolic hydroxyl group. The substituent may be located at only one or both of the ortho-positions of the phenolic hydroxyl group.
The value of m in "r x m" is the average value of multiple possible m's.
Furthermore, the "substituent located at the ortho position" is preferably a substituent having 1 to 6 carbon atoms, more preferably a hydrocarbon group having 1 to 6 carbon atoms, and even more preferably a linear or branched alkyl group having 1 to 6 carbon atoms.
In other words, of the (k+l+r×m+n) "aromatic ring groups having a phenolic hydroxyl group" represented by any one of X ¹ to X ⁴ , at least one (preferably 30% or more, more preferably 50% or more, even more preferably 65% or more; preferably 100% or less, more preferably 90% or less, even more preferably 80% or less) may represent an "aromatic ring group having a phenolic hydroxyl group and a substituent arranged at the ortho-position of the phenolic hydroxyl group".

In the aromatic ring groups having a phenolic hydroxyl group represented by X ¹ to X ⁴ , the aromatic ring groups other than "aromatic ring groups having a phenolic hydroxyl group and a substituent arranged at the ortho-position of the phenolic hydroxyl group" may or may not have a substituent other than a hydroxyl group (phenolic hydroxyl group).
Examples of aromatic ring groups other than "aromatic ring groups having a phenolic hydroxyl group and a substituent positioned at the ortho-position of the phenolic hydroxyl group" include hydroxyphenyl groups.
It is also preferred that at least one (e.g., one or two) of the (k+l+r×m+n) "aromatic ring groups having a phenolic hydroxyl group" represented by any one of X ¹ to X ⁴ is an aromatic ring group other than an "aromatic ring group having a phenolic hydroxyl group and a substituent positioned at the ortho-position of the phenolic hydroxyl group".
In the aromatic ring groups having a phenolic hydroxyl group represented by X ¹ to X ⁴ , the presence of aromatic ring groups other than "an aromatic ring group having a phenolic hydroxyl group and a substituent arranged at the ortho-position of the phenolic hydroxyl group" is thought to disrupt the symmetry of the compound as a whole, lower the melting point of the compound, and improve the handleability of the semi-cured film formed from the curable composition.

The phenol compound is also preferably a compound represented by formula (Z1).
The phenol compound preferably contains a compound represented by formula (Z1), or may be the compound represented by formula (Z1) itself. The content of the compound represented by formula (Z1) is preferably 10 to 100 mass%, more preferably 25 to 100 mass%, and even more preferably 50 to 100 mass%, based on the total mass of the phenol compound.

In formula (Z1), r represents an integer of 0 or greater. r is preferably an integer of 0 to 20, and more preferably an integer of 0 to 10.
L represents a divalent organic group. The divalent organic group represented by L in formula (Z1) is, for example, the same as the divalent organic group represented by L in formula (Z1).
R 1 and ^Z represent a hydrogen atom or a substituent.
The substituent represented by R 1 ^Z is preferably a substituent having 1 to 6 carbon atoms, more preferably a hydrocarbon group having 1 to 6 carbon atoms, and even more preferably a linear or branched alkyl group having 1 to 6 carbon atoms.
At least one of the (3+r) R ^Z's (preferably 30% or more, more preferably 50% or more, even more preferably 65% or more; preferably 90% or less, more preferably 80% or less) present in formula (Z1) may represent a substituent.
At least one (for example, one or two) of the (3+r) R 1 ^Z's in formula (Z1) may represent a hydrogen atom.
In the benzene ring group to which R ^z (preferably R ^z as a substituent) and OH are bonded in formula (Z1), it is also preferable that the R ^z (preferably R ^z as a substituent) is located at the para position relative to the NH to which the benzene ring group is bonded.

The phenol compound is also preferably a compound represented by formula (Z2).
The phenol compound preferably contains a compound represented by formula (Z2), or may be the compound represented by formula (Z2) itself. The content of the compound represented by formula (Z2) is preferably 10 to 100 mass%, more preferably 25 to 100 mass%, and even more preferably 50 to 100 mass%, based on the total mass of the phenol compound.

In formula (Z2), R 1 ^Z represents a hydrogen atom or a substituent.
At least one of the two R 1 ^Z's preferably represents a substituent, and both of them preferably represent a substituent.
The substituent represented by R 1 ^Z is preferably a substituent having 1 to 6 carbon atoms, more preferably a hydrocarbon group having 1 to 6 carbon atoms, and even more preferably an alkyl group having 1 to 6 carbon atoms.
The alkyl group may be linear or branched, and is preferably unsubstituted.
In formula (Z2), two ^Rz 's may be the same or different.

The phenol compound is also preferably a phenol compound having 3 to 7 hydroxyl groups in the molecule.
Examples of the phenol compound having 3 to 7 hydroxyl groups in the molecule include compounds represented by formula (Z3) or formula (Z4). Of the compounds represented by formula (Z3) and formula (Z4), the compound represented by formula (Z3) is more preferred in terms of achieving better effects of the present invention.

In formula (Z3), m represents an integer of 1 to 6.
m is more preferably 1 to 3, and further preferably 1.

In formula (Z3), n1 and n2 each independently represent an integer of 1 or more.
n1 and n2 each independently represent preferably 2 to 4, and more preferably 2 or 3.
The sum of n1, n2 and m is 3 to 7.

In formula (Z3), R ¹ to R ⁶ each independently represent a hydrogen atom, a halogen atom, a carboxylic acid group, an alkyl group, an alkoxy group, or an alkoxycarbonyl group.
The halogen atom is preferably a chlorine atom, a fluorine atom, a bromine atom, or an iodine atom, and more preferably a chlorine atom.
The alkyl group may be linear or branched, preferably has 1 to 10 carbon atoms, and may or may not have a substituent.
The alkyl group moiety in the alkoxy group and the alkyl group moiety in the alkoxycarbonyl group are the same as the alkyl group described above.
Among these, R ¹ and R ⁶ are each independently preferably a hydrogen atom or a halogen atom, more preferably a hydrogen atom or a chlorine atom, and even more preferably a hydrogen atom.
It is preferable that R ² to R ⁵ each independently represent a hydrogen atom.
In addition, when there are a plurality of ^R4s in formula (Z3), the plurality of ^R4s may be the same or different. When there are a plurality of ^R5s , the plurality of ^R5s may be the same or different.

In formula (Z3), Q represents an alkyl group, a phenyl group, a halogen atom, a carboxylic acid group, an alkoxy group, or an alkoxycarbonyl group.
The alkyl group may be linear or branched, preferably has 1 to 10 carbon atoms, and may or may not have a substituent.
The alkyl group moiety in the alkoxy group and alkoxycarbonyl group, and the alkyl group moiety in the alkoxycarbonyl group are the same as the alkyl group.
The phenyl group may or may not have a substituent.
The halogen atom is preferably a chlorine atom, a fluorine atom, a bromine atom, or an iodine atom.
Among these, Q is preferably an alkyl group, more preferably a methyl group.
When a plurality of Q's are present in formula (Z3), the plurality of Q's may be the same or different.

In formula (Z4), m, n1, n2, R ¹ , R ² , R ⁴ , and R ⁶ have the same meanings and preferred embodiments as m, n1, n2, R ¹ , R ² , R ⁴ , and R ⁶ in formula (Z3), respectively.
The sum of n1, n2 and m is 3 to 7.

In formula (Z4), ^R3 and ^R5 each independently represent an aromatic ring group having a phenolic hydroxyl group. The "aromatic ring group having a phenolic hydroxyl group" may be an aromatic ring group having one or more (e.g., 1 to 4) hydroxyl groups (phenolic hydroxyl groups) directly bonded to the aromatic ring. The aromatic ring group may or may not have a substituent other than the hydroxyl group. The aromatic ring group may be monocyclic or polycyclic, and may have a heteroatom as a ring member atom. The number of ring member atoms in the aromatic ring group is preferably 5 to 15, more preferably 6 to 10, and even more preferably 6.
The aromatic ring group is preferably a benzene ring group.
The substituent that the aromatic ring group may have other than the hydroxyl group is preferably a substituent having 1 to 6 carbon atoms, more preferably a hydrocarbon group having 1 to 6 carbon atoms, and still more preferably a linear or branched alkyl group having 1 to 6 carbon atoms.
When a plurality of R ^5s are present in formula (Z4), the plurality of R ^5s may be the same or different.

Examples of phenolic compounds include benzene polyols such as bisphenol A, F, S, AD, benzenediol, and benzenetriol, biphenyl aralkyl phenolic resins, phenol novolac resins, cresol novolac resins, aromatic hydrocarbon formaldehyde resin-modified phenolic resins, dicyclopentadiene phenol adduct resins, phenol aralkyl resins, polyhydric phenol novolac resins synthesized from polyhydric hydroxy compounds and formaldehyde, naphthol aralkyl resins, trimethylolmethane resins, tetraphenylolethane resins, naphthol novolac resins, naphtholphenol co-condensed novolac resins, naphthol-cresol co-condensed novolac resins, biphenyl-modified phenolic resins, biphenyl-modified naphthol resins, aminotriazine-modified phenolic resins, and alkoxy group-containing aromatic ring-modified novolac resins.

The molecular weight of the phenol compound is preferably 225 to 2,000, more preferably 225 to 1,000.
When the molecular weight has a molecular weight distribution, the molecular weight is a weight average molecular weight.

The hydroxyl group content of the phenol compound is preferably 2.0 mmol/g or more, more preferably 4.0 mmol/g or more, and the upper limit is preferably 25.0 mmol/g or less, more preferably 20.0 mmol/g or less, and even more preferably 10.0 mmol/g or less.
The hydroxyl group content means the number of hydroxyl groups (preferably phenolic hydroxyl groups) contained in 1 g of the phenol compound.
In addition to hydroxyl groups, the phenolic compound may or may not have an active hydrogen-containing group (e.g., carboxyl group) capable of polymerizing with an epoxy compound. The lower limit of the active hydrogen content of the phenolic compound (total content of hydrogen atoms in hydroxyl groups, carboxylic acid groups, etc.) is preferably 2.0 mmol/g or more, more preferably 4.0 mmol/g or more. The upper limit is preferably 25.0 mmol/g or less, more preferably 10.0 mmol/g or less.

The curable composition may contain, in addition to the phenol compound, a compound having a group capable of reacting with an epoxy compound (also referred to as "other active hydrogen-containing compounds").
However, in the curable composition, the mass ratio of the content of the other active hydrogen-containing compound to the content of the phenol compound is preferably 0 to 1, more preferably 0 to 0.1, and even more preferably 0 to 0.05.

The content of the phenol compound in the curable composition is preferably 3 to 90 mass% relative to the total solids content of the curable composition, more preferably 5 to 50 mass%, even more preferably 5 to 40 mass%, and particularly preferably 7 to 40 mass%.

[Maleimide Compound]
The curable composition also preferably comprises a maleimide compound.
A maleimide compound is a compound having one or more maleimide groups.
The number of maleimide groups contained in the maleimide compound is preferably 1 to 100, more preferably 2 to 10, and even more preferably 2.
The maleimide compound may be either a high molecular weight compound or a low molecular weight compound. For example, the molecular weight of the maleimide compound is preferably 100 to 3,000, more preferably 200 to 2,000, and even more preferably 300 to 1,000.

The maleimide group possessed by the maleimide compound is preferably a group represented by the following formula (M):

In formula (M), * represents a bonding position.
X and Y each independently represent a hydrogen atom or a substituent.
X and Y are each preferably a hydrogen atom.

The maleimide compound is also preferably a compound having one or more (preferably 1 to 10) aromatic ring groups (such as benzene ring groups) and a compound having a mesogen group.
The maleimide compound is preferably a compound represented by the following formula (1):

In formula (1), m represents 0 or 1. Preferably, m is 1.
n represents 0 or 1. n is preferably 1.

In formula (1), R ¹ and R ² each independently represent a hydrogen atom or a substituent.
The substituent is preferably an alkyl group, which may be linear or branched and preferably has 1 to 10 carbon atoms.
When R ¹ and/or R ² are substituents, they are preferably located adjacent to the maleimide group on the benzene ring group, for example.
When R ¹ and R ² are both substituents, it is also preferable that R ¹ and R ² are different substituents. For example, it is also preferable that R ¹ is a methyl group and R ² is an ethyl group.

In formula (1), L ¹ represents a divalent linking group.
Examples of the divalent linking group include an ether group (-O-), a carbonyl group (-CO-), an ester group (-COO-), a thioether group (-S-), -SO ₂ -, -NR- (R is a hydrogen atom or an alkyl group), a divalent aliphatic hydrocarbon group (for example, an alkylene group, a cycloalkylene group, an alkenylene group (-CH=CH-, etc.), an alkynylene group (-C≡C-, etc.)), a divalent aromatic ring group (an arylene group and a heteroarylene group), and a group formed by combining these.
In formula (1), L ¹ preferably has 1 or more carbon atoms, more preferably 1 to 100 carbon atoms, and even more preferably 3 to 15 carbon atoms.

L ¹ is preferably a mesogenic group, and more preferably a group represented by "* ^p- (L ² -Ar) _k- * ^q ".
* ^q represents the bonding position on the side directly bonded to the maleimide group, and * ^p represents the bonding position on the opposite side.
k represents an integer of 1 or more, preferably 1 to 10, more preferably 1 to 5, still more preferably 1 to 3, and particularly preferably 1.
L ² represents a single bond, —C(R ³ )(R ⁴ )—, —O—, or —CO—, and is preferably a single bond or —C(R ³ )(R ⁴ )—.
^R3 and ^R4 each independently represent a hydrogen atom or a substituent, and are preferably an alkyl group (which may be linear or branched and has, for example, 1 to 10 carbon atoms).
Ar represents an arylene group. The number of ring atoms in the arylene group is preferably 6 to 15, and more preferably 6. When the arylene group has a substituent, the number of atoms is preferably 1 to 4, and more preferably 1 or 2. The substituent that the arylene group may have is preferably an alkyl group (which may be linear or branched, and has, for example, 1 to 10 carbon atoms). Examples of structures that Ar can have include structures similar to the benzene ring group bonded to ^R1 and ^R2 as specified in formula (1).
When a plurality ^{of L2s} and a plurality of Ars are present, the plurality of ^L2s and the plurality of Ars may be the same or different.

In formula (1) when n is 1, on the benzene ring group bonding to ^R1 and ^R2 , the two groups, the maleimide group and the group represented by "-( ^L1 ) _m -maleimide group", may be located at the ortho position, meta position, or para position relative to each other. The two groups are preferably located at the meta position or para position.

In the compound represented by formula (1), m is 1, n is 1, and the divalent linking group represented by ^L1 preferably has 3 to 20 (preferably 3 to 15) carbon atoms.

The maleimide compounds may be used alone or in combination of two or more.
The content of the maleimide compound is preferably 0.1 to 40 mass%, more preferably 1 to 15 mass%, and even more preferably 3.5 to 8 mass%, relative to the total solid content of the curable composition, and from the viewpoint of better handleability of the semi-cured film formed from the curable composition, is further preferably 3.5 to 8 mass%.
In the curable composition, the content of the maleimide compound is, for example, 1 to 200 mass%, preferably 5 to 100 mass%, more preferably 10 to 70 mass%, and still more preferably 20 to 60 mass%, relative to the total content of the epoxy compound and the phenol compound.
The content of the maleimide compound is, for example, 1 to 500% by mass, preferably 20 to 300% by mass, more preferably 50 to 200% by mass, and even more preferably 70 to 130% by mass, relative to the content of the phenol compound.

[Relationship between phenolic compounds and epoxy compounds]
In the curable composition, the total content of the epoxy compound and the phenol compound is preferably 3 to 90 mass %, more preferably 5 to 50 mass %, and still more preferably 7 to 40 mass %, based on the total solid content of the curable composition.

The ratio of the total number of epoxy groups contained in the epoxy compound to the total number of hydroxyl groups (preferably phenolic hydroxyl groups) contained in the phenol compound (number of epoxy groups/number of hydroxyl groups) is often 0.03 to 33, preferably 0.4 to 2.5, more preferably 0.6 to 1.5, and even more preferably 0.8 to 1.3.
In other words, the ratio of the contents of the phenol compound and the epoxy compound in the curable composition is preferably such that the "number of epoxy groups/number of phenolic hydroxyl groups" falls within the above range.

The equivalent ratio of epoxy groups to active hydrogens in the epoxy compound (number of epoxy groups/number of active hydrogens) is often 0.03 to 33, preferably 0.4 to 2.5, more preferably 0.6 to 1.5, and even more preferably 0.8 to 1.3.
The active hydrogen may be an active hydrogen derived from a phenolic hydroxyl group, or may be an active hydrogen of another active hydrogen-containing compound.

The ratio of the total number of epoxy groups contained in the epoxy compound to the total number of hydroxyl groups (preferably phenolic hydroxyl groups) contained in the phenol compound (number of epoxy groups/number of hydroxyl groups) is preferably 1.1 to 3.0, more preferably 1.2 to 2.0, and even more preferably 1.3 to 1.8.
In particular, when the curable composition contains the maleimide compound, the ratio preferably falls within the above range.
When the ratio is equal to or greater than a predetermined value, flexibility is introduced into the semi-cured film formed from the curable composition, improving storage stability, and the semi-cured film has good handleability even after a certain period of time has passed since its formation. When the ratio is equal to or less than a predetermined value, the heat resistance of the thermal conductive material formed from the curable composition is superior. Such an improvement effect is particularly remarkable when the curable composition contains a maleimide compound described below.

[Inorganic particles]
The curable composition comprises inorganic particles selected from the group consisting of inorganic nitride particles and inorganic oxide particles.

Examples of _inorganic nitrides include _boron nitride (BN), carbon nitride ( _C3N4 ), silicon nitride ( _Si3N4 ), gallium nitride (GaN), indium nitride (InN), aluminum nitride (AlN), chromium nitride ( _Cr2N ), copper nitride ( _Cu3N ), iron nitride ( _Fe4N ), iron nitride ( _Fe3N ), lanthanum nitride (LaN), lithium nitride ( _Li3N ), magnesium nitride ( _Mg3N2 ), molybdenum nitride ( _Mo2N ), niobium nitride (NbN), tantalum nitride (TaN), titanium nitride (TiN), tungsten nitride ( _{W2N )} , tungsten nitride ( _WN2 ), yttrium nitride (YN), and zirconium nitride (ZrN).
Among these, inorganic nitride particles are preferred because of their excellent thermal conductivity. Materials constituting inorganic nitride particles with excellent thermal conductivity include, for example, aluminum nitride (AlN) and boron nitride (BN), with boron nitride being preferred.

Examples of inorganic oxides include zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), aluminum oxide (Al ₂ O ₃ ), iron oxide (Fe ₂ O ₃ , FeO, Fe 3 O ₄ ), copper oxide (CuO, Cu ₂ O), zinc oxide (ZnO), yttrium oxide (Y ₂ O ₃ ), niobium oxide (Nb ₂ O ₅ ), molybdenum oxide (MoO ₃ ), indium oxide (In ₂ O ₃ , _{In 2 O} ), tin oxide (SnO ₂ ), tantalum oxide (Ta ₂ O ₅ ), tungsten oxide (WO ₃ , W ₂ O ₅ ), lead oxide (PbO, PbO ₂ ), bismuth oxide (Bi ₂ O ₃ ), cerium oxide (CeO ₂ , Ce 2 O ₅ ), and the like. Examples _{of inorganic oxides include antimony oxide (Sb2O3 , Sb2O5 )} , germanium oxide ( _GeO2 , GeO), lanthanum oxide ( _La2O3 ), and ruthenium oxide ( _RuO2 ). The inorganic oxide may be an oxide produced _by oxidizing a metal prepared as a non-oxide under environmental conditions.
In particular, inorganic oxide particles having excellent thermal conductivity are preferred. Examples of materials constituting inorganic oxide particles having excellent thermal conductivity include silicon oxide (silica, SiO ₂ ) and aluminum oxide (alumina, Al ₂ O ₃ ), with alumina being preferred.
The inorganic particles preferably contain inorganic nitride particles, and more preferably contain boron nitride particles, in that the effects of the present invention are more excellent.

The particle size _D50 of the inorganic particles is often 10 μm or more, preferably 20 μm or more, and more preferably 30 μm or more. The upper limit is preferably 500 μm or less, more preferably 300 μm or less, even more preferably 200 μm or less, and particularly preferably 100 μm or less.
_D50 means the median diameter and can be measured, for example, using a Mastersizer 2000 (manufactured by Malvern Panalytical). When commercially available inorganic particles are used, the median diameter listed in the catalog value can be used. Furthermore, the median diameter can be determined by measuring the particle size of 100 particles selected arbitrarily using an electron microscope (e.g., a scanning electron microscope or a transmission electron microscope), and then determining the frequency distribution. When the inorganic particles are not spherical, the median diameter is determined by using the longest diameter of the inorganic particles as the particle size.

The inorganic particles may be shaped like rice grains, spheres, cubes, spindles, scales, aggregates (aggregates), or irregular shapes, with aggregates being preferred. It is also preferred that the inorganic particles be aggregates of inorganic nitride particles (more preferably boron nitride particles).

The inorganic particles are preferably surface-treated.
Examples of surface treatments include plasma treatments (e.g., vacuum plasma treatment, atmospheric pressure plasma treatment, aqua plasma treatment, etc.), ultraviolet irradiation treatment, corona treatment, electron beam irradiation treatment, ozone treatment, baking treatment, flame treatment, and oxidizing agent treatment. The oxidizing agent treatment may be carried out under either acidic or basic conditions (e.g., pH 12 to 14, etc.).
Among these, the surface treatment is preferably an oxidizing agent treatment carried out under basic conditions.
The surface treatment introduces functional groups onto the surfaces of the inorganic particles, which is thought to facilitate interaction of the inorganic particles with other components that may be incorporated into the curable composition (e.g., epoxy compounds, phenolic compounds, maleimide compounds, and alkoxysilyl group-containing compounds that are surface modifiers for inorganic particles), resulting in better thermal conductivity.

The inorganic particles may be used alone or in combination of two or more kinds.
The content of the inorganic particles is preferably 20% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and particularly preferably 70% by mass or more, based on the total solid content of the curable composition. The upper limit is preferably less than 100% by mass, more preferably 95% by mass or less, and even more preferably 85% by mass or less.

[Curing accelerator]
The curable composition also preferably contains a curing accelerator.
As the curing accelerator, a known compound known as a curing accelerator for epoxy compounds can be used. Among them, the curing accelerator preferably contains at least one selected from the group consisting of the compound represented by formula (P1) and the compound represented by formula (P2), and more preferably contains the compound represented by formula (P3), in terms of more excellent effects of the present invention.
When optical isomers exist in the compound contained in the curing accelerator, any of the optical isomers may be used. Furthermore, one type of optical isomer may be used alone, or multiple optical isomers may be used in combination. When one type of optical isomer is primarily used, its optical purity (ee) is preferably 90 or more, more preferably 95 or more. Similarly, when optical isomers exist in the formulae (P1) to (P3) shown below, any of the optical isomers may be included.

In formula (P1), ^Lp represents a single bond or a divalent linking group.
Examples of the divalent linking group include an ether group (-O-), a carbonyl group (-CO-), an ester group (-COO-), a thioether group (-S-), -SO ₂ -, -NR- (wherein R represents a hydrogen atom or an alkyl group), a divalent aliphatic hydrocarbon group (for example, an alkylene group, a cycloalkylene group, an alkenylene group (-CH=CH-, etc.), an alkynylene group (-C≡C-, etc.)), a divalent aromatic ring group (for example, an arylene group and a heteroarylene group), and a group formed by combining these. The divalent linking group may further have a substituent. Examples of the substituent include the substituents exemplified in the substituent group Y above.
The arylene group may be monocyclic or polycyclic, and preferably has 6 to 25 carbon atoms.
The arylene group is preferably a phenylene group, a naphthylene group, an anthracenylene group or a binaphthylene group, and more preferably a binaphthylene group.
^Lp is preferably a divalent aliphatic hydrocarbon group or a divalent aromatic ring group, more preferably an alkylene group or an arylene group.

R ^p11 to R ^p14 each independently represent a phenyl group which may have a substituent.
Examples of the substituent include the substituents exemplified in the above-mentioned group Y of substituents, and an alkyl group is preferable, and a linear or branched alkyl group having 1 to 3 carbon atoms is more preferable.

_np represents 0 or 1. _np is preferably 1.

In formula (P2), R ^p21 to R ^p24 each independently represent a phenyl group which may have a substituent.
Examples of the substituent include the substituents exemplified in the above-mentioned group Y of substituents, and an alkyl group is preferable, and a linear or branched alkyl group having 1 to 3 carbon atoms is more preferable.

X ⁻ represents an anion.
Examples of the anion include hydroxide ion, fluoride ion, chloride ion, bromide ion, iodide ion, hexafluorophosphate ion, tetrafluoroborate ion, tetraphenylborate ion, dicyanamide ion, alkylphosphate ion (e.g., diethylphosphate ion, etc.), hydrogen sulfate ion, dihydrogen phosphate ion, hydrogen phosphate ion, sulfamate ion, perchlorate ion, benzotriazolide anion, and tetratolylborate anion (e.g., tetra-p-tolylborate anion, etc.).
The anion is preferably a tetratolylborate anion.

In formula (P3), R ^p31 to R ^p34 each independently represent a phenyl group which may have a substituent.
Examples of the substituent include the substituents exemplified in the above-mentioned group Y of substituents, and an alkyl group is preferable, and a linear or branched alkyl group having 1 to 3 carbon atoms is more preferable.

The molecular weight of the curing accelerator is often 200 or more, preferably 250 or more, more preferably 400 or more, even more preferably 430 or more, and particularly preferably 600 or more. The upper limit is preferably 10,000 or less, more preferably 1,000 or less, and even more preferably 800 or less.
When the molecular weight of the curing accelerator is 250 or more, the vaporization of the curing accelerator itself and/or its thermal decomposition products can be more effectively suppressed when subjected to heat treatment at high temperatures, resulting in better solder heat resistance. Also, when the molecular weight of the curing accelerator is 10,000 or less, it is easy to function as a curing accelerator.

In order to obtain better effects of the present invention, the curing accelerator preferably contains a compound containing a phosphorus atom, and also preferably contains a phosphonium salt. The curing accelerator may be a compound containing a phosphorus atom or a phosphonium salt itself. When a phosphonium salt is used as the curing accelerator, the storage stability of the semi-cured film formed from the curable composition is also improved.
The content of the phosphorus atom-containing compound or phosphonium salt is preferably from 10 to 100 mass %, more preferably from 50 to 100 mass %, and even more preferably from 80 to 100 mass %, based on the total mass of the curing accelerator.

The curing accelerators may be used alone or in combination of two or more.
The content of the curing accelerator is preferably 0.002% by mass or more, more preferably 0.02% by mass or more, and even more preferably 0.07% by mass or more, based on the total solid content of the curable composition, and the upper limit is preferably 5% by mass or less, more preferably 2% by mass or less, and even more preferably 1% by mass or less, based on the total solid content of the curable composition.
The content of the curing accelerator is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.10% by mass or more, based on the total amount of epoxy compounds. The upper limit is preferably 40% by mass or less, more preferably 12% by mass or less, even more preferably 10% by mass or less, and particularly preferably 5% by mass or less, based on the total amount of epoxy compounds.

[Surface modifier]
The curable composition may contain a surface modifier for the inorganic particles.
Examples of the surface modifier include silane coupling agents, and among these, at least one selected from the group consisting of an alkoxysilyl group-containing compound (hereinafter also referred to as "compound A"), a hydrolyzate of compound A, and a hydrolysis condensate of compound A (hereinafter also referred to as "compound A, etc.") is preferred.

The form in which the surface modifier is introduced into the curable composition is not particularly limited, and may be a form in which inorganic particles surface-modified with a surface modifier are introduced, or a form in which both the inorganic particles and the above-mentioned surface modifier are introduced.
When the curable composition contains inorganic particles surface-modified with a surface modifier, the ratio of the content of the surface modifier to the content of the inorganic particles in the curable composition is preferably 0.01 to 10 mass%, more preferably 0.02 to 5 mass%, and even more preferably 0.05 to 3 mass%. When the curable composition contains both inorganic particles and the above-mentioned surface modifier, the ratio of the content of the surface modifier to the content of the inorganic particles in the curable composition is preferably 0.01 to 10 mass%, more preferably 0.02 to 5 mass%, and even more preferably 0.05 to 3 mass%.

The term "inorganic particles surface-modified with a surface modifier" refers to inorganic particles whose surfaces are at least partially covered with the surface modifier. At least a portion of the inorganic particle surface is preferably covered with the surface modifier via a chemical bond or a physical bond (non-chemical bond), more preferably via a chemical bond, and even more preferably via a "-Si-O-" bond.
Among inorganic particles surface-modified with a surface modifier, surface-modified boron nitride particles are preferred. The surface-modified boron nitride particles are particles composed of boron nitride particles and a surface modifier that modifies the surfaces of the boron nitride particles.
Furthermore, in the case where inorganic particles and the above-mentioned surface modifier are each introduced into the curable composition, when a thermally conductive material is formed using the curable composition, the surface modifier covers the surfaces of the inorganic particles, thereby increasing the dispersibility of the inorganic particles in the thermally conductive material.

Compound A will be described below.
Compound A contains an alkoxysilyl group. The alkoxysilyl group is preferably a group represented by the following formula (x):

In formula (x), * represents a bonding position.
In formula (x), R ^x1 , R ^x2 , and R ^x3 each independently represent an alkoxy group, a hydroxy group, or an alkyl group, provided that at least one of R ^x1 , R ^x2 , and R ^x3 represents an alkoxy group.
The alkyl group contained in the alkoxy group represented by R ^x1 , R ^x2 , and R ^x3 may be linear or branched, but is preferably linear. The alkyl group contained in the alkoxy group may have a substituent, but is preferably an unsubstituted alkyl group. The number of carbon atoms contained in the alkyl group contained in the alkoxy group is preferably 1 to 6, more preferably 1 to 3, and even more preferably 1 or 2. That is, the alkoxy group represented by R ^x1 , R ^x2 , and R ^x3 is preferably a methoxy group or an ethoxy group.
The alkyl groups represented by R ^x1 , R ^x2 , and R ^x3 may be linear or branched, but are preferably linear. The alkyl groups represented by R ^x1 , R ^x2 , and R ^x3 may have a substituent, but are preferably unsubstituted. The number of carbon atoms in the alkyl groups represented by R ^x1 , R ^x2 , and R ^x3 is preferably 1 to 6, more preferably 1 to 3, and even more preferably 1 or 2.

A preferred embodiment of the alkoxysilyl group represented by ^Xa is an embodiment in which all of R ^x1 , R ^x2 , and R ^x3 are alkoxy groups, and a preferred embodiment is an embodiment in which all of R ^x1 , R ^x2 , and R ^x3 are methoxy groups or ethoxy groups.

The number of alkoxysilyl groups in Compound A is not particularly limited, as long as it is one or more.
Known compounds can be used as compound A. Suitable examples of compound A having one alkoxysilyl group include "X-12-967C" manufactured by Shin-Etsu Silicone Co., Ltd. and "VD-5" manufactured by Shikoku Chemicals Co., Ltd. Furthermore, suitable examples of compound A having two or more alkoxysilyl groups include compound AX, which will be described later.
Compound AX, as well as a hydrolysate of compound AX and a hydrolyzed condensate of compound AX will be described below. Note that, hereinafter, one or more selected from compound AX, a hydrolyzate of compound AX and a hydrolyzed condensate of compound AX may be referred to as compound AX, etc.

<Compound AX, hydrolysate of compound AX, hydrolysis condensate of compound AX>
(Compound AX)
The compound AX is a compound having a polymer chain and two or more alkoxysilyl groups.
The compound AX is not particularly limited as long as it has a polymer chain and two or more alkoxysilyl groups, but a compound represented by the following formula (a) is preferred in terms of achieving better effects of the present invention.

In formula (a), ^Ya represents a polymer chain.
The polymer chain represented by ^Ya is not particularly limited, but examples thereof include vinyl polymers, ester polymers, ether polymers, urethane polymers, amide polymers, epoxy polymers, and silicone polymers.
The polymer chain preferably contains carbon atoms in the main chain of the polymer chain. The number of carbon atoms in the main chain of the polymer chain is preferably 30% or more, more preferably 50% or more, and even more preferably 70% or more, based on the total atoms constituting the main chain of the polymer chain. The upper limit can be 100%, and may be 100%. The main chain refers to the relatively longest bond chain in the polymer chain.

The polymer chain represented by ^Ya above preferably has a repeating unit represented by the following formula (y):

In formula (y), R ^y1 , R ^y2 , and R ^y3 each independently represent a hydrogen atom or a monovalent substituent.
Examples of the substituents represented by R ^y1 , R ^y2 , and R ^y3 include groups selected from the above-mentioned substituent group Y, and specific examples include alkyl groups having 1 to 3 carbon atoms which may further have a substituent, halogen atoms, and hydroxy groups.
The alkyl group having 1 to 3 carbon atoms which may further have a substituent is preferably an unsubstituted alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group.
Among these, it is preferable that R ^y1 and R ^y2 represent a hydrogen atom, and R ^y3 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms (preferably a methyl group) which may further have a substituent.

In formula (y), L ^y1 represents a single bond or a divalent linking group.
Examples of the divalent linking group represented by L ^y1 include an ether group (-O-), a carbonyl group (-CO-), an ester group (-COO-), a thioether group (-S-), -SO ₂ -, -NR ^T - (R ^T represents a hydrogen atom, an alkyl group, or an aryl group), -CONR ^T -, an aliphatic hydrocarbon group which may have a divalent substituent (for example, an alkylene group, a cycloalkylene group, an alkenylene group (-CH=CH-, etc.), and an alkynylene group (-C≡C-, etc.)), an aromatic ring group which may have a divalent substituent (for example, an arylene group and a heteroarylene group), and groups combining these. Examples of the aliphatic hydrocarbon group which may have a divalent substituent and the substituent of the aromatic ring group which may have a divalent substituent include groups selected from the above-mentioned substituent group Y.
Of these, —O—, —S—, —COO—, —NR ^T —, —CONR ^T —, an alkylene group, a phenylene group, or a group formed by combining two or more of these is preferred. R ^T is preferably a hydrogen atom, a methyl group, or an ethyl group.
Examples of groups combining two or more of the above include -COO-alkylene group-, -COO-alkylene group-L ^T1 -alkylene group- (L ^T1 represents any of -O-, -COO-, and -OCO-), -COO-alkylene group-L ^T1 -alkylene group-S-, -COO-(CH ₂ -CH ₂ -O-) _k (k is an integer of 1 to 10), -COO-alkylene group-OCO-, -COO-alkylene group-COO-, and -CONR ^T -L ^T2 - (L ^T2 represents an alkylene group or a phenylene group).

In formula (y), ^Zy represents a monovalent substituent. Examples of the monovalent substituent include groups selected from the above-mentioned group Y of substituents.
Preferred examples of the group represented by ^Zy include an alkyl group, an alkoxy group, an aromatic ring group, an epoxy group (oxiranyl group), a hydroxy group, a carboxy group, and an amino group.
The group represented by ^Zy is preferably a polymerizable group capable of undergoing a polymerization reaction, such as an acryloyl group, a methacryloyl group, an oxiranyl group, or a vinyl group. The polymerizable group is preferably an oxiranyl group.
The alkyl group in the alkyl group and alkoxy group may be linear, branched, or cyclic. The number of carbon atoms in the alkyl group and alkoxy group is not particularly limited, but is preferably 1 to 10, and more preferably 1 to 5.
The aromatic ring group includes an aromatic hydrocarbon group and an aromatic heterocyclic group.
Examples of the ring constituting the aromatic hydrocarbon group include a benzene ring and a naphthalene ring.
Examples of rings constituting the aromatic heterocyclic group include a furan ring, a pyrrole ring, an imidazole ring, a pyrazole ring, a triazole ring, a thiophene ring, a pyridine ring, a benzimidazole ring, a benzotriazole ring, and a benzothiazole ring. Of these, a benzimidazole ring, a benzotriazole ring, or a benzothiazole ring is preferred.
The alkyl group, the alkyl group in the alkoxy group, and the aromatic ring group may further have a monovalent substituent. Examples of the monovalent substituent include groups selected from the above-mentioned substituent group Y.
The aromatic ring group is preferably an aromatic hydrocarbon group, and is more preferably a benzimidazole ring, a benzotriazole ring, or a benzothiazole ring in terms of excellent peel strength.

In formula (y), R ^y2 and Z ^y may be bonded to form a ring, in which case L ^y1 , Z ^y , R ^y2 , the carbon atom bonded to R ^y2 in formula (y), and the carbon atom bonded to L ^y1 in formula (y) form the ring.
A preferred embodiment in which R ^y2 and Z ^y are bonded to form a ring is a repeating unit represented by the following formula (yy): That is, it is also preferred that the repeating unit represented by formula (y) is a repeating unit having an acid anhydride group represented by the following formula (yy):

In formula (yy), R ^y1 and R ^y3 each independently represent a hydrogen atom or a monovalent substituent, and preferred embodiments thereof are the same as those in formula (y).
When the polymer chain contains a repeating unit having an acid anhydride group represented by the formula (yy), peel strength is excellent, which is preferable.

The polymer chain represented by ^Ya preferably has a repeating unit having an acid anhydride group or a repeating unit having an aromatic heterocyclic group.
The repeating unit having an acid anhydride group may be any repeating unit as long as it has an acid anhydride group (—CO—O—CO—) in the repeating unit, and examples thereof include repeating units having an acid anhydride group represented by the above formula (yy).
The repeating unit having an aromatic heterocyclic group may be any repeating unit as long as it contains an aromatic heterocyclic group, and examples thereof include repeating units in which ^Zy in formula (y) is an aromatic heterocyclic group.
The repeating unit in the polymer chain represented by ^Ya may be of one type (homopolymer chain) or of two or more types (copolymer chain).

In formula (a), L ^a1 and L ^a2 each independently represent a single bond or a divalent linking group.
Examples of the divalent linking group represented by L ^a1 and L ^a2 include an ether group (-O-), a carbonyl group (-CO-), an ester group (-COO-), a thioether group (-S-), -SO ₂ -, -NR- (R represents a hydrogen atom, an alkyl group, or an aryl group), a divalent aliphatic hydrocarbon group (for example, an alkylene group, a cycloalkylene group, an alkenylene group (-CH=CH-, etc.), and an alkynylene group (-C≡C-, etc.)), a divalent aromatic ring group (for example, an arylene group and a heteroarylene group), and a group formed by combining these.
L ^a1 and L ^a2 are preferably groups formed by combining two or more groups selected from -CO-, -O-, -S-, and alkylene groups. Preferred examples of L ^a1 and L ^a2 include -CO-alkylene group-, -CO-alkylene group-O-alkylene group-, -CO-alkylene group-S-, and -CO-alkylene group-S-alkylene group-.
The alkylene group may be either linear or branched.
The alkylene group preferably has 1 to 10 carbon atoms, and more preferably 1 to 5 carbon atoms.

In formula (a), n ^a represents an integer of 1 or more.
n ^a is preferably 1 to 5, more preferably 2 to 4, and even more preferably 2 or 3.

In formula (a), m ^a represents an integer of 2 or more.
m ^a is preferably 2 to 5, more preferably 2 to 4, and even more preferably 3 or 4 in terms of peel strength.

In formula (a), A ^a represents a linking group having a valence of n ^a +m ^a .
n ^a +m ^a is 3 or more, preferably 3 to 10, more preferably 4 to 8, even more preferably 4 to 6, and particularly preferably 6.
The n ^a +m ^a valent linking group represented by A ^a is not particularly limited.
The n ^a +m ^a -valent linking group represented by A ^a may have a cyclic structure or may not have a cyclic structure. The cyclic structure may be an aromatic ring or an alicyclic ring. In particular, it is preferable that the n ^a +m ^a -valent linking group represented by A ^a does not have a cyclic structure.
The linking group having a valence of n ^a +m ^a and not having a cyclic structure is preferably a linking group obtained by removing a hydrogen atom from a hydroxy group of a polyol. The polyol may contain an ether bond (-O-) or an amine bond (-N<). Some or all of the hydrogen atoms of the hydroxy group of the polyol may be removed. However, the valence of the linking group should be 3 or more.
Examples of linking groups derived from polyols include linking groups obtained by removing a hydrogen atom from a hydroxy group contained in polyols such as glycerin, trimethylolpropane, triethanolamine, erythritol, pentaerythritol, xylitol, mannitol, and dipentaerythritol. Of these, linking groups obtained by removing a hydrogen atom from a hydroxy group contained in trimethylolpropane, pentaerythritol, or dipentaerythritol are preferred.

In formula (a), ^Xa represents an alkoxysilyl group, and the alkoxysilyl group is preferably an alkoxysilyl group represented by formula (X) above.

The weight-average molecular weight of compound AX is not particularly limited, but is preferably 2,000 to 200,000, more preferably 5,000 to 100,000, and even more preferably 10,000 to 50,000.

(Hydrolysate of Compound AX)
The alkoxysilyl group of the compound AX is likely to be hydrolyzed to form a silanol group (Si—OH). The hydrolyzate of the compound AX may be one in which all of the hydrolyzable groups are hydrolyzed (complete hydrolyzate) or one in which only a portion of the hydrolyzable groups are hydrolyzed (partial hydrolyzate). In other words, the hydrolyzate may be a complete hydrolyzate, a partial hydrolyzate, or a mixture thereof.
The silanol group easily condenses with a hydroxy group or the like present on the surface of the inorganic particle to form a bond of --Si--O--on the surface of the inorganic particle.

(Hydrolyzed condensate of compound AX)
The hydrolyzate of compound AX can be a hydrolysis condensation product in which silanol groups undergo dehydration condensation between two molecules to form an —Si—O—Si— bond. Because compound AX has two or more alkoxysilyl groups, silanol groups remain even in the hydrolysis condensation product of compound AX, and these silanol groups are likely to condense with hydroxy groups or the like present on the surfaces of inorganic particles to form —Si—O— bonds on the surfaces of the inorganic particles, as in the case of the hydrolysis product of compound AX.

[Ion scavenger]
The curable composition may also include an ion scavenger.
The ion scavenger adsorbs ionic impurities in the curable composition or in the thermally conductive material formed using the curable composition, thereby enabling the insulating properties of the thermally conductive material to be maintained better even when the curable composition or the thermally conductive material absorbs moisture.
Examples of the ion scavenger include the inorganic ion scavenger and organic ion scavenger as described above.
Examples of organic ion scavengers include triazine thiol compounds, triazine amine compounds, benzimidazole compounds, benzotriazole compounds, aminotriazole compounds, and bisphenol reducing agents.
All or part of the inorganic particles may also function as an ion scavenger.

The ion trapping agent may be used alone or in combination of two or more kinds.
When the curable composition contains an ion scavenger, the content of the ion scavenger (inorganic ion scavenger and/or organic ion scavenger) is preferably 0.01 to 10 mass%, more preferably 0.1 to 20 mass%, and even more preferably 0.2 to 10 mass%, based on the total solid content of the curable composition.
When the ion scavenger contains an inorganic ion scavenger, part or all of the ion scavenger may simultaneously fall under the category of inorganic substances.

[Acid anhydride]
The curable composition may include an acid anhydride.
An acid anhydride is a compound having one or more acid anhydride groups (groups represented by —CO—O—CO—). However, the acid anhydride is a compound different from the above-mentioned compound A and the like.

The number of acid anhydride groups in the acid anhydride is 1 or more, preferably 2 or more, and more preferably 3 or more. The upper limit of the number is, for example, 1,000 or less.
The molecular weight of the acid anhydride (weight average molecular weight when there is a molecular weight distribution) is preferably 100 or more, more preferably 2,000 or more, and even more preferably 6,000 or more. The upper limit of the molecular weight is preferably 100,000 or less, more preferably 30,000 or less, and even more preferably 17,000 or less.
The acid anhydride may be a low molecular weight compound or a high molecular weight compound.
Examples of acid anhydrides that are low molecular weight compounds include maleic anhydride, phthalic anhydride, pyromellitic anhydride, and trimellitic anhydride.
In the acid anhydride polymer compound, the acid anhydride group may be incorporated into the main chain or may be present in a side chain. For example, when the polymer compound has a repeating unit based on maleic acid, the acid anhydride group contained in the repeating unit is considered to be incorporated into the main chain.

The acid anhydrides may be used alone or in combination of two or more.
The content of the acid anhydride is preferably from 0.01 to 40 mass %, more preferably from 0.1 to 10 mass %, and even more preferably from 0.6 to 5 mass %, based on the total solid content of the curable composition.
The content of the acid anhydride is preferably from 0.1 to 100% by mass, more preferably from 1 to 70% by mass, and even more preferably from 5 to 60% by mass, based on the total content of the epoxy compound and the phenol compound.

〔solvent〕
The curable composition may further comprise a solvent.
The solvent is preferably an organic solvent, such as cyclopentanone, cyclohexanone, ethyl acetate, methyl ethyl ketone, dichloromethane, and tetrahydrofuran.
When the curable composition contains a solvent, the content of the solvent is preferably an amount that makes the solid content concentration of the curable composition 20 to 90 mass %, more ...
The content of the solvent is preferably from 10 to 80 mass %, more preferably from 15 to 70 mass %, and even more preferably from 20 to 50 mass %, based on the total mass of the curable composition.

[Other ingredients]
The curable composition may contain other components in addition to the above components.

[Method of producing curable composition]
The curable composition can be produced by a known method, for example, by mixing the components that can be contained in the curable composition described above. When mixing, the components may be mixed all at once or sequentially.
Prior to mixing the components of the curable composition, a step of modifying the surfaces of the inorganic particles with a surface treatment agent (for example, the above-mentioned compound A, etc.) (surface modification step) may be carried out.
Furthermore, prior to mixing the components of the curable composition, a step (modification step) of surface-treating inorganic particles (for example, surface modification with plasma or the like) to obtain modified inorganic particles may be carried out.
When the modification step is included, it is preferable that the modification step is carried out before the surface modification step, that is, it is preferable that the surface modification step is carried out on the surfaces of the modified inorganic particles.
An example of a method for producing the curable composition will now be described.
The method for producing the curable composition of this embodiment corresponds to a production method including the above-mentioned modification step and surface modification step.
Each step will be described below.

[Modification step]
The modification step is a step of surface-treating inorganic particles to obtain modified inorganic particles.
The modification step is not particularly limited, and examples thereof include the above-mentioned surface treatments. Among them, a step of performing a treatment to oxidize the surfaces of inorganic particles is preferred, and a step of contacting inorganic particles with an oxidizing agent in an aqueous solution to obtain modified inorganic particles is more preferred.

Furthermore, the inorganic particles subjected to the above-mentioned modification step are preferably boron nitride particles or agglomerates thereof, more preferably agglomerates of boron nitride particles. Therefore, the resulting modified inorganic particles are preferably modified boron nitride particles or particles obtained by modifying agglomerates of boron nitride particles, more preferably particles obtained by modifying agglomerates of boron nitride particles.

The aqueous solution is preferably an alkaline aqueous solution. The pH of the alkaline aqueous solution is often 8 or higher, preferably 12 or higher, more preferably greater than 12, even more preferably 13 or higher, and particularly preferably greater than 13. The upper limit is preferably 14 or lower. The pH of the aqueous solution refers to the pH of the aqueous solution when it contains inorganic particles and the oxidizing agent. In other words, the aqueous solution contains an alkaline compound, water, inorganic particles, and an oxidizing agent as necessary.

The time for which the inorganic particles are brought into contact with the oxidizing agent in the aqueous solution is preferably from 0.1 to 24 hours, more preferably from 0.5 to 10 hours, and even more preferably from 1.5 to 6 hours.
The temperature of the aqueous solution when the inorganic particles are brought into contact with the oxidizing agent is preferably 1 to 95°C, more preferably 25 to 80°C, and even more preferably 45 to 65°C.

As a method for contacting the inorganic particles with the oxidizing agent in the aqueous solution, for example, a method for contacting them in a mixed liquid can be mentioned.
Specifically, the inorganic particles, the oxidizing agent, and the mixture containing water and/or an organic solvent are brought into contact with each other.

Examples of organic solvents include methanol, ethanol, 2-propanol, acetonitrile, cyclopentanone, cyclohexanone, ethyl acetate, methyl ethyl ketone, dichloromethane, and tetrahydrofuran.
The organic solvent may be used alone or in combination of two or more kinds.

Methods for contacting the inorganic particles with the oxidizing agent include, for example, contacting them while stirring using a mechanical stirrer such as a Three-One Motor or a magnetic stirrer, and contacting them while circulating a solution containing the oxidizing agent through a cartridge filled with inorganic particles using a pump or the like.

It is preferable that after the inorganic particles are brought into contact with the oxidizing agent in the aqueous solution, the resulting modified inorganic particles are taken out from the aqueous solution.
The modified inorganic particles can be extracted from the aqueous solution by, for example, filtering the aqueous solution and separating out the modified inorganic particles as a residue.
It is also preferable to wash the extracted modified inorganic particles with water and/or an organic solvent, etc. It is also preferable to dry the washed inorganic particles in an oven, etc.

The water content in the aqueous solution is preferably 20 to 99% by mass, more preferably 50 to 95% by mass, and even more preferably 65 to 90% by mass, based on the total mass of the aqueous solution.

<Oxidizing agent>
Examples of oxidizing agents used in the modification step include persulfates such as sodium persulfate, potassium persulfate, and ammonium persulfate; nitrates such as cerium ammonium nitrate, sodium nitrate, and ammonium nitrate; peroxides such as hydrogen peroxide and tert-butyl hydroperoxide; transition metal compounds such as divalent copper compounds and manganese compounds; hypervalent iodine compounds such as potassium periodate and sodium periodate; quinone compounds such as benzoquinone, naphthoquinone, anthraquinone, and chloranil; and salts of halogen oxoacids such as sodium hypochlorite and sodium chlorite.
Preferably, the oxidizing agent comprises a persulfate, and more preferably is a persulfate.
In addition, a catalyst may be used separately from the oxidizing agent to assist the action of the oxidizing agent. Examples of the catalyst include divalent iron compounds (e.g., _FeSO4 ) and trivalent iron compounds. The oxidizing agent and/or catalyst may be a hydrate.

The standard redox potential of the oxidizing agent is preferably 0.30 V or higher, more preferably 1.50 V or higher, and even more preferably 1.70 V or higher. The upper limit is preferably 4.00 V or lower, more preferably 2.50 V or lower. The above standard redox potential is a value based on the standard hydrogen electrode.

The oxidizing agents may be used alone or in combination of two or more.
The content of the oxidizing agent in the aqueous solution is preferably 0.05 to 20 parts by mass, more preferably 0.1 to 20 parts by mass, and even more preferably 1 to 20 parts by mass, per 100 parts by mass of water in the aqueous solution.

The catalyst may be used alone or in combination of two or more.
When the aqueous solution contains a catalyst, the content of the catalyst is preferably 0.005 to 2 parts by mass, more preferably 0.01 to 2 parts by mass, and even more preferably 0.1 to 2 parts by mass, per 100 parts by mass of water in the aqueous solution.

<Alkaline compounds>
The aqueous solution preferably contains an alkaline compound in addition to the above components in order to adjust the pH of the aqueous solution.
Examples of the alkaline compound include inorganic bases such as alkali metal hydroxides (for example, sodium hydroxide, etc.) and alkaline earth metal hydroxides; and organic bases.
The content of the alkaline compound in the aqueous solution may be any amount that allows the pH of the aqueous solution to be adjusted to a desired value, and may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of water in the aqueous solution.

[Surface modification process]
The surface modification step is a step of carrying out a surface modification treatment on the surfaces of inorganic particles with a surface modifier (for example, the above-mentioned compound A, preferably the above-mentioned compound AX).
In the surface modification step, it is preferable to bring the inorganic particles into contact with the compound A, etc. Examples of the method for bringing the inorganic particles into contact with the compound A, etc. include the same methods as those in the modification step.
The compound A or the like to be brought into contact with the inorganic particles is preferably a hydrolysate of compound A or a hydrolysis condensate of compound A. That is, compound A is preferably subjected to a hydrolysis treatment before being brought into contact with the inorganic particles.

<Hydrolysis treatment>
The hydrolysis treatment is a treatment in which the compound A is hydrolyzed.
By the hydrolysis treatment, the alkoxysilyl groups of the compound A are hydrolyzed to generate silanol groups, which can form bonds with the surfaces of the inorganic particles.

The hydrolysis method is not particularly limited as long as the conditions are such that the alkoxy group is hydrolyzed.
Specifically, it is preferable to use an acidic solution (for example, an aqueous solution of hydrochloric acid and acetic acid, etc.) The acidic solution may contain an organic solvent.

There are no particular restrictions on the method for mixing the components that can be contained in the curable composition, and any known method can be used. The mixing device used for mixing is preferably a submerged disperser, and examples include agitators such as planetary mixers and high-speed rotary shear mixers, colloid mills, roll mills, high-pressure jet dispersers, ultrasonic dispersers, bead mills, and homogenizers. One type of mixing device may be used alone, or two or more types may be used in combination. Degassing treatment may be performed before, after, or simultaneously with mixing.

As an example of a method for producing a curable composition, a production method including a modification step and a surface modification step has been described in the upper part, but the curable composition may also be produced by mixing inorganic particles with components other than the inorganic particles that may be contained in the curable composition including compound A, etc. In the production method of this embodiment, it is also preferable that the inorganic particles have been subjected to a modification step in advance.
When mixing, the components may be mixed all at once or sequentially.

[Method for curing curable composition]
The curable composition of the present invention is preferably a composition for forming a thermally conductive material.
The curable composition of the present invention is cured to obtain a thermally conductive material.
The curable composition is preferably cured by a thermal curing reaction.
The heating temperature during the thermosetting reaction is not particularly limited and may be appropriately selected, for example, within the range of 50 to 250° C. Furthermore, when carrying out the thermosetting reaction, heat treatments at different temperatures may be carried out multiple times.
The curing treatment is preferably carried out on a curable composition in the form of a film or sheet. Specifically, for example, the curable composition may be applied to form a film, and then the curing reaction may be carried out.
When performing the curing treatment, it is preferable to apply the curable composition to a substrate to form a coating film and then cure it. In this case, the coating film formed on the substrate may be brought into contact with another substrate before the curing treatment. The cured product (thermal conductive material) obtained after curing may or may not be separated from one or both of the substrates.
Alternatively, when performing the curing treatment, the curable composition may be applied to separate substrates to form coating films on each substrate, and the curing treatment may be performed in a state where the resulting coating films are in contact with each other. The cured product (thermal conductive material) obtained after curing may or may not be separated from one or both of the substrates.

The curing treatment may be terminated when the curable composition is in a semi-cured state, or after the curable composition is in a semi-cured state, further curing treatment may be carried out to complete the curing.
The curing treatment for bringing the curable composition into a semi-cured state (also referred to as "semi-curing treatment") and the curing treatment for completing the curing (also referred to as "main curing treatment") may be carried out in separate steps.

For example, in the semi-curing treatment, after applying a curable composition to a substrate to form a coating film, the coating film on the substrate may be heated without pressure to form a semi-cured thermal conductive material (also referred to as a "semi-cured film" or "semi-cured sheet"). Alternatively, the coating film on the substrate may be heated while also being subjected to press working to form a semi-cured film. When press working is performed, the press working may be performed before, after, or during the heating process. Performing press working in the semi-curing treatment may facilitate adjustment of the film thickness of the resulting semi-cured film and/or reduction of the amount of voids in the semi-cured film.
The semi-curing treatment may be carried out in a state where coating films formed on different substrates are laminated together, or may be carried out without laminating the coating films together. The semi-curing treatment may be carried out in a state where the coating film formed from the curable composition is further in contact with a material other than the coating film.

The resulting semi-cured film may be used as a heat conductive material as is, or may be further subjected to a main curing treatment and then used as a completely cured heat conductive material.
In the main curing treatment, the semi-cured film may be heated as is without pressure, or may be heated after or while being pressed. In this case, the main curing treatment may be performed with separate semi-cured films stacked on top of each other, or may be performed without stacking the semi-cured films on top of each other.
The main curing treatment may be carried out in a state where the semi-cured film is placed in contact with a device or the like in which it is used. It is also preferable that the main curing treatment adheres the device to the thermally conductive material of the present invention.

There is no limitation on the press used for the press working that may be carried out during the hardening treatment in the semi-hardening treatment and/or the full hardening treatment, and for example, a flat press or a roll press may be used.
When using a roll press, for example, it is preferable to sandwich a coated substrate obtained by forming a coating film on a substrate between a pair of opposing rolls, and apply pressure in the film thickness direction of the coated substrate while rotating the pair of rolls to pass the coated substrate. The coated substrate may have a substrate on only one side of the coating film, or may have a substrate on both sides of the coating film. The coated substrate may be passed through the roll press once or multiple times.
During the hardening treatment in the semi-hardening treatment and/or the full hardening treatment, either one of the treatment by platen pressing and the treatment by roll pressing may be carried out, or both may be carried out.

For information on the production of thermally conductive materials, including curing reactions, please also refer to "High Thermally Conductive Composite Materials" (CMC Publishing, written by Takezawa Yoshitaka).

The shape of the thermally conductive material is not particularly limited, and it can be molded into various shapes depending on the application. A typical shape of the molded thermally conductive material is, for example, a sheet shape.
That is, the thermally conductive material obtained using the curable composition of the present invention is preferably a thermally conductive sheet.
Furthermore, the thermal conductivity of the thermally conductive material obtained using the curable composition of the present invention is preferably isotropic rather than anisotropic.

The thermally conductive material is preferably insulating (electrically insulating), in other words, the curable composition of the present invention is preferably a thermally conductive insulating composition.
For example, the volume resistivity of the thermal conductive material at 23° C. and a relative humidity of 65% is preferably 10 ¹⁰ Ω·cm or more, more preferably 10 ¹² Ω·cm or more, and even more preferably 10 ¹⁴ Ω·cm or more. The upper limit is preferably 10 ¹⁸ Ω·cm or less.

[Uses of thermal conductive materials]
The thermally conductive material obtained using the curable composition of the present invention can be used as a heat dissipation material such as a heat dissipation sheet, and can be used for heat dissipation purposes in various devices. More specifically, a device with a thermally conductive layer can be produced by disposing a thermally conductive layer containing the thermally conductive material of the present invention on the device, and the heat generated from the device can be efficiently dissipated by the thermally conductive layer. The thermally conductive layer may be a thermally conductive layer containing a thermally conductive multilayer sheet, which will be described later.
The thermally conductive material obtained using the curable composition of the present invention has sufficient thermal conductivity and high heat resistance, and is therefore suitable for heat dissipation applications in power semiconductor devices used in various electrical equipment such as personal computers, general home appliances, and automobiles.
Furthermore, since the thermally conductive material obtained using the curable composition of the present invention has sufficient thermal conductivity even in a semi-cured state, it can be used as a heat dissipation material to be placed in areas where it is difficult for light for photocuring to reach, such as gaps between components of various devices.In addition, since it has excellent adhesive properties, it can also be used as a thermally conductive adhesive.
The present inventors have also demonstrated that the thermally conductive material obtained using the curable composition of the present invention is excellent in copper foil peel strength, electrical properties such as voltage resistance, and solder heat resistance.

The thermally conductive material obtained using the curable composition of the present invention may be used in combination with a component other than a component formed from the curable composition.
For example, a thermally conductive material (such as a thermally conductive sheet) may be combined with a support (adherend) other than the layer formed from the curable composition.
Examples of the support (adherend) include plastic materials, metal materials, and glass. Examples of the plastic materials include polyesters such as polyethylene terephthalate (PET), polycarbonates, acrylic resins, epoxy resins, polyurethanes, polyamides, polyolefins, cellulose derivatives, and silicones. Examples of the metal materials include copper and aluminum.
The support (adherend) is preferably in the form of a sheet.
The thickness of the sheet-like thermally conductive material (thermally conductive sheet) is preferably 100 to 300 μm, and more preferably 150 to 250 μm.

Furthermore, the thermally conductive material (preferably the thermally conductive sheet) may be combined with an adhesive layer and/or a pressure-sensitive adhesive layer.
By joining the thermally conductive material to an object to which heat should be transferred, such as a device, via such an adhesive layer and/or pressure-sensitive adhesive layer, a stronger bond between the thermally conductive material and the object can be achieved. The thermally conductive material formed from the curable composition of the present invention also has good adhesion to the adhesive layer and pressure-sensitive adhesive layer, and peeling at the interface between the thermally conductive material and the adhesive layer or pressure-sensitive adhesive layer can be suppressed.
For example, a thermally conductive multilayer sheet may be produced which has a thermally conductive sheet and an adhesive layer or pressure-sensitive adhesive layer provided on one or both sides of the thermally conductive sheet.
One or both sides of the thermally conductive sheet may be provided with either an adhesive layer or a pressure-sensitive adhesive layer, or both. An adhesive layer may be provided on one side of the thermally conductive sheet, and a pressure-sensitive adhesive layer may be provided on the other side. Furthermore, an adhesive layer and/or a pressure-sensitive adhesive layer may be provided partially or entirely on one or both sides of the thermally conductive sheet.
As described above, in the present invention, the thermally conductive material such as the thermally conductive sheet may be in a semi-cured state (semi-cured film), and the thermally conductive sheet in the thermally conductive multilayer sheet may be in a semi-cured state. The adhesive layer in the thermally conductive multilayer sheet may be in a cured, semi-cured, or uncured state.

The present invention will be explained in more detail below based on the following examples. The materials, amounts used, ratios, processing details, processing procedures, etc. shown in the following examples can be modified as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be interpreted as being limited by the examples shown below.

[Preparation and Evaluation of Curable Compositions]
[Synthesis Example]
The specific epoxy compounds (compounds B-1 to B-7) and surface modifier 1 to be blended in the curable composition were synthesized according to the following procedure.

<Method for synthesizing specific epoxy compound>
The synthesis procedures for the specific epoxy compounds (compounds B-1 to B-7) are shown below, taking the synthesis procedure for compound B-1 as an example. Compounds B-2 to B-7 were synthesized according to the synthesis method for compound B-1.

Potassium hydroxide powder (Tokyo Chemical Industry Co., Ltd., 21.2 g) was added to a solution of trimethylsulfonium iodide (Tokyo Chemical Industry Co., Ltd., 68.4 g) in dimethyl sulfoxide (200 mL) and stirred at room temperature for 30 minutes. Terephthalaldehyde (Tokyo Chemical Industry Co., Ltd., 20 g) was then added and stirred at room temperature for 2 hours. After stirring was completed, ethyl acetate and water were added to the resulting reaction solution, and the organic layer was extracted and concentrated to obtain 18 g of the desired epoxy compound B-1.

<Method for synthesizing surface modifier 1 (multi-terminal type)>
The synthesis procedure for surface modifier 1 (multi-terminal type) is shown below.

V-601 (Fujifilm Wako Pure Chemical Industries, Ltd., 32 mg) was added to a solution of dipentaerythritol hexakis(3-mercaptopropionate) (Fujifilm Wako Pure Chemical Industries, Ltd., 14.5 g) and a silane coupling agent (KBE-1003, Shin-Etsu Chemical Co., Ltd., 10.5 g) in cyclopentanone (CPO, 60 mL). The mixture was stirred for 2 hours at 80°C under a nitrogen atmosphere. Subsequently, V-601 (Fujifilm Wako Pure Chemical Industries, Ltd., 32 mg) was added, and the mixture was stirred for 2 hours at 90°C under a nitrogen atmosphere. After confirming the disappearance of the silane coupling agent by NMR, cyclopentanone was added to adjust the concentration, yielding a 30% by mass cyclopentanone solution of compound YP-3-1.

M-4 was synthesized according to the following procedure.

2-Hydroxyethyl methacrylate (Tokyo Chemical Industry Co., Ltd., 20.9 g), 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (Tokyo Chemical Industry Co., Ltd., 30.8 g), and 4-dimethylaminopyridine (Fujifilm Wako Pure Chemical Industries, Ltd., 1.9 g) were added to a THF/DMF = 9/1 solution (500 mL) of 5-benzotriazolecarboxylic acid (Tokyo Chemical Industry Co., Ltd., 25 g), and the mixture was stirred for 6 hours at 70°C under atmospheric pressure. After the reaction was complete, distilled water (200 mL) and ethyl acetate were added, and the organic layer was extracted and concentrated to obtain M-4 (35 g).

A 30% by weight solution of compound YP-3-1 in cyclopentanone (synthetic product, 1.22 g), M-1 (2-methoxyethyl methacrylate, manufactured by Tokyo Chemical Industry Co., Ltd., 3.82 g), M-4 (synthetic product, 3.82 g), and a dimethylacetamide (11.6 mL) solution of V-601 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 28 mg) were added dropwise to dimethylacetamide (DMAc, 5.4 mL) over a period of 2.5 hours while maintaining the temperature at 80°C under a nitrogen atmosphere. After the addition was complete, the mixture was stirred for 2.5 hours. After adding V-601 (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., 28 mg), the mixture was heated to 90°C and stirred for an additional 2 hours to obtain a 25% by weight solution of compound YP-3 (surface modifier 1) in dimethylacetamide. In compound YP-3 (surface modifier 1), n1 and n2 represent the average number of units added. Also, the number "3" in parentheses represents the average value.

[Various ingredients]
The various components used in the examples and comparative examples are listed below.

<Phenol compounds>
The average value of n in A-3 is 1.

<Epoxy Compound>
The compounds B-1 to B-7 correspond to the specific epoxy compounds.

<Maleimide Compound>
E-1: MIR-3000-70MT, the average value of n for E-1 is 1, manufactured by Nippon Kayaku Co., Ltd. E-2: BMI-70, manufactured by Keiai Kasei Co., Ltd.

<Curing accelerator>
C-1: Tetraphenylphosphonium tetra-p-tolylborate (TPP-MK, manufactured by Hokko Chemical Industry Co., Ltd.)
C-2: 2-phenyl-4,5-dihydroxymethylimidazole (2PHZ-PW, manufactured by Shikoku Chemical Industry Co., Ltd.)

<Inorganic particles>
As the inorganic particles, particles X1 to X7 and surface-modified particles Y1 to Y14 whose surfaces were modified with a silane coupling agent were used.
Particles X1 to X7 and surface-modified particles Y1 to Y14 are shown below.

(Particles X1 to Particles X7)
Particle X1: PTX-60, boron nitride aggregate, particle size D ₅₀ : 60 μm, manufactured by Momentive Corporation. Particle X2: HP-40, boron nitride aggregate, particle size D ₅₀ : 40 μm, manufactured by Mizushima Ferroalloy Co., Ltd. Particle X3: PCTL5MHF, boron nitride aggregate, particle size D ₅₀ : 80 μm, manufactured by Saint-Gobain. Particle X4: PT-110, flaky boron nitride, particle size D ₅₀ : 45 μm, manufactured by Momentive Corporation. Particle X5: SGPS, boron nitride aggregate, particle size D ₅₀ : 12 μm, manufactured by Denka Company, Limited. Particle X6: AA-3, spherical aluminum oxide, particle size D ₅₀ : 3 μm, manufactured by Sumitomo Chemical Co., Ltd. Particle X7: AA-18, spherical aluminum oxide, particle size D ₅₀ : 18 μm, manufactured by Sumitomo Chemical Co., Ltd.

(Surface modified particles Y1 to Y14)
Surface-modified particles Y1 to Y14 were produced by preparing modified particles X1 to X12 using the above-described particles X1 to X5 through the following modification step, and then subjecting these modified particles X1 to X12 to a surface modification treatment using the following surface modifiers 1 to 3 in accordance with the predetermined procedure described below. The procedure for producing surface-modified particles Y1 to Y14 is described below.

<<Modified Particles X1 to X12>>
Modified particle X1: modified boron nitride produced by production method 1 shown below. Modified particle X2: modified boron nitride produced by production method 2 shown below. Modified particle X3: modified boron nitride produced by production method 3 shown below. Modified particle X4: modified boron nitride produced by production method 4 shown below. Modified particle X5: modified boron nitride produced by production method 5 shown below. Modified particle X6: modified boron nitride produced by production method 6 shown below. Modified particle X7: modified boron nitride produced by production method 7 shown below. Modified particle X8: modified boron nitride produced by production method 8 shown below. Modified particle X9: modified boron nitride produced by production method 9 shown below. Modified particle X10: modified boron nitride produced by production method 10 shown below. Modified particle X11: modified boron nitride produced by production method 11 shown below. Modified particle X12: modified boron nitride produced by production method 12 shown below.

-Manufacturing method 1-
Boron nitride (particles X1, 50 g) was added to aqueous NaOH (40 g NaOH/400 mL water) and stirred. Sodium persulfate solution (9.6 g sodium persulfate/100 mL water) was then added to the aqueous NaOH, and the resulting solution was heated to 50°C and stirred for an additional 3 hours (modification step). Stirring was performed at 150 rpm using a Three-One Motor (manufactured by Shinto Scientific Co., Ltd.).
After the NaOH water was cooled to room temperature, the boron nitride in the NaOH water was filtered off, and the filtered boron nitride was washed with water (500 mL) and acetonitrile (250 mL) to obtain modified particles X1.

-Manufacturing method 2-
Boron nitride (particles X1, 50 g) was added to water (400 mL) and stirred to obtain a mixed solution. 30% by mass hydrogen peroxide solution (30 mL) was further added to the mixed solution, and the mixed solution was then heated to 50°C and stirred for an additional 3 hours. Stirring was performed at 150 rpm using a Three-One Motor (manufactured by Shinto Scientific Co., Ltd.).
After the mixture was cooled to room temperature, the boron nitride in the mixture was filtered off and washed with water (500 mL) and acetonitrile (250 mL) to obtain modified particles X2.

-Manufacturing method 3-
Modified particles X3 were obtained in the same manner as in Production Method 1, except that the NaOH water in Production Method 1 was changed to (NaOH: 0.02 g/water: 400 mL).
In Production Method 3, the pH of the liquid (aqueous solution) obtained by mixing NaOH water (NaOH: 0.02 g/water: 400 mL), boron nitride (50 g), and sodium persulfate water (sodium persulfate: 9.6 g/water: 100 mL) was 11.

-Manufacturing method 4-
Boron nitride (particles X1, 50 g) was heated at 1,000° C. for 1 hour in an oxidizing atmosphere to obtain modified particles X4.

-Manufacturing method 5-
Boron nitride (particles X2, 15 g) was subjected to vacuum plasma treatment (gas type: O ₂ , pressure: 30 Pa, output: 500 W) using a plasma cleaner PDC210 (manufactured by Yamato Scientific Co., Ltd.) The boron nitride to be treated was stirred every 5 minutes of vacuum plasma treatment, and the vacuum plasma treatment was continued until the total treatment time reached 30 minutes, thereby obtaining modified particles X5.

-Manufacturing method 6-
Modified particles X6 were obtained in the same manner as in Production Method 1, except that boron nitride (particles X1, 50 g) was changed to boron nitride (particles X2, 50 g).

-Manufacturing method 7-
Boron nitride (particles X2, 50 g) was added to water (400 mL) and stirred to obtain a mixed solution. Sodium hypochlorite water (sodium hypochlorite pentahydrate: 48 g / water: 100 mL) was further added to the mixed solution, and the mixed solution was heated to 50 ° C. and stirred for an additional 3 hours. Stirring was performed at 150 rpm using a Three-One Motor (manufactured by Shinto Scientific Co., Ltd.).
After the mixture was cooled to room temperature, the boron nitride in the mixture was filtered off and washed with water (500 mL) and acetonitrile (250 mL) to obtain modified particles X7.

-Manufacturing method 8-
Boron nitride (particles X2, 50 g) was heated at 1000° C. for 1 hour to obtain modified particles X8.

-Manufacturing method 9-
Boron nitride (particles X2, 50 g) was heated at 900° C. for 4 hours to obtain modified particles X9.

-Manufacturing method 10-
Modified particles X10 were obtained in the same manner as in Production Method 1, except that boron nitride (particles X1, 50 g) was changed to boron nitride (particles X3, 50 g).

-Manufacturing method 11-
Modified particles X11 were obtained in the same manner as in Production Method 1, except that boron nitride (particles X1, 50 g) was changed to boron nitride (particles X4, 50 g).

-Manufacturing method 12-
Modified particles X12 were obtained in the same manner as in Production Method 1, except that boron nitride (particles X1, 50 g) was changed to boron nitride (particles X5, 50 g).

<Types of surface modifiers 1 to 3>
Surface modifier 1 (a silane coupling agent having the following structure, a synthetic product. n1 and n2 represent the average number of additions, and the number "3" in parentheses represents the average value. In the formula, "AX" is as defined above.)

Surface modifier 2 (compound having the following structure: "X-12-967C" (manufactured by Shin-Etsu Silicones Co., Ltd.))

Surface modifier 3 (compound having the following structure: "VD-5" (manufactured by Shikoku Chemicals Corporation))

<<Preparation of Surface-Modified Particles Y1 to Y14 (Surface Modification Treatment)>>
(Preparation of Surface-Modified Particles Y1)
The synthesis procedure for the surface-modified particles Y1 used in Example 36 is shown below.
Isopropyl alcohol (3.3 g), distilled water (1.2 g), and acetic acid (0.3 g) were added to a 25% by mass solution (6.3 g) of compound YP-3 (surface modifier 1), the synthesis example of which is shown in the upper part of the figure, and the mixture was stirred at room temperature for 1 hour to obtain a hydrolyzed solution of surface modifier 1.
Next, modified particles X1 (200 g) were added to acetonitrile (400 mL), and the hydrolysis solution of surface modifier 1 was further added and stirred for 1 hour. The boron nitride in the acetonitrile was filtered, washed with acetonitrile (40 mL), and dried in an oven at 40° C. to obtain surface-modified particles Y1.

(Preparation of Surface-Modified Particles Y2 to Y14)
Surface-modified particles Y2 to Y14 were prepared in the same manner as for surface-modified particle Y1, except that the type of surface modifier and the type of modified particle were changed as shown in Table 1.

[Preparation of Curable Composition]
Next, the solvent (cyclopentanone), phenol compound, epoxy compound, maleimide compound, and curing accelerator were mixed in this order, and then the inorganic particles were added, as shown in Table 1. The resulting mixture was treated for 5 minutes in a planetary centrifugal mixer (THINKY Corporation, Awatori Rentaro ARE-310) to obtain a curable composition.

The amount of solvent added to each curable composition was set so that the solid content of each curable composition would be 50 to 80% by mass.
The solid content concentration of each curable composition was adjusted within the above range for each curable composition so that the viscosity of each curable composition would be approximately the same.
The amounts of the epoxy compound and the phenol compound added were adjusted so that the total content of the epoxy compound and the phenol compound would be the amount shown in the "Total amount (mass%)" column in the table relative to the total solid content of the curable composition, and so that the epoxy compound and the phenol compound would be equivalent amounts (amounts such that the number of epoxy groups in the epoxy compound is equal to the number of hydroxyl groups in the phenol compound).
In the curable composition, the amounts of the maleimide compound, the curing accelerator, and the inorganic particles were each adjusted to the amount (mass %) shown in parentheses in each column of the table, relative to the total solid content of the curable composition.

[evaluation]
[Preparation of semi-cured sheet (semi-cured film)]
Using an applicator with a micrometer, the prepared curable composition was uniformly applied onto the release surface of a release-treated PET film (PET756501 manufactured by Lintec Corporation, film thickness 75 μm), and then dried at 120°C for 4 minutes to produce a semi-cured sheet (semi-cured film).

[Preparation of thermally conductive sheet (thermally conductive material)]
The resulting semi-cured sheet was covered with a release-treated PET film and heat-pressed in air (heat plate temperature 180°C, pressure 5-20 MPa for 5 minutes). This was then heat-treated at 180°C for 90 minutes under normal pressure to obtain a resin sheet. The PET films on both sides of the resin sheet were peeled off to obtain a thermally conductive sheet (thermally conductive material) with an average film thickness of 120 μm.

[Evaluation of thermal conductivity]
(1) The thermal diffusivity of the thermal conductive sheet in the thickness direction was measured by the laser flash method using "LFA467" manufactured by NETZSCH.
(2) Using a balance "XS204" manufactured by Mettler Toledo, the specific gravity of the thermally conductive sheet was measured by the Archimedes method (using a "solid specific gravity measurement kit").
(3) Using a DSC320/6200 manufactured by Seiko Instruments Inc., the specific heat of the thermally conductive sheet at 25° C. was determined under the condition of a temperature increase of 10° C./min.
(4) The thermal conductivity of the thermally conductive sheet was calculated by multiplying the obtained thermal diffusivity by the specific gravity and specific heat.

The thermal conductivity of the thermally conductive sheet was classified according to the following criteria, and the thermal conductivity of the thermally conductive sheet (thermally conductive material) obtained using the curable composition of each Example or Comparative Example was evaluated.
A 18W/mK or more B 15W/mK or more but less than 18W/mK C 12W/mK or more but less than 15W/mK D Less than 12W/mK

[Evaluation of Tg (heat resistance)]
The Tg of the obtained thermally conductive sheet was measured.
The measurement was performed using a dynamic viscoelasticity measuring device "Rheogel-E4000" manufactured by UBM, and the tan δ peak at a frequency of 1 Hz was taken as Tg. The temperature was increased at a rate of 5°C/min in the range of 25 to 300°C.

The Tg of the thermally conductive sheet was classified according to the following criteria, and the heat resistance of the thermally conductive sheet (thermally conductive material) obtained using the curable composition of each Example or Comparative Example was evaluated.
A: 170°C or higher B: 160°C or higher but lower than 170°C C: 150°C or higher but lower than 160°C D: Lower than 150°C

Table 1 is shown below.
In the columns of "Type of modified particles" and "Type of surface modifier" in the table, inorganic particles that have not undergone the above-mentioned surface treatment are indicated by "-".
The "partial structure" column in the table indicates the type of partial structure possessed by the specific epoxy compound. When the specific epoxy compound has partial structure (1), it is indicated as "(1)," and when the specific epoxy compound has partial structure (2), it is indicated as "(2)."
The "Compound Structure" column in the table shows the structure of the specific epoxy compound. If the specific epoxy compound is a compound represented by formula (1A), it is shown as "(1A)," if the specific epoxy compound is a compound represented by formula (2A), it is shown as "(2A)," if the specific epoxy compound is a compound represented by formula (1B), it is shown as "(1B)," and if the specific epoxy compound is a compound represented by formula (2B), it is shown as "(2B)."

From the results in Table 1, it was confirmed that the thermally conductive materials formed from the curable compositions of the Examples had excellent thermal conductivity and Tg (heat resistance).
Furthermore, by comparing the examples, it was confirmed that when the specific epoxy compound contains the partial structure (1) and X is an aromatic ring (preferably, when the specific epoxy compound is a compound represented by formula (1A) and X ^E1 represents an m ^E1 + monovalent aromatic ring group, or when the specific epoxy compound is a compound represented by formula (1B) and X ^E2 represents a divalent aromatic ring group), the thermal conductivity and Tg (heat resistance) of the formed thermal conductive material are more excellent.
Furthermore, by comparing the examples, it was confirmed that when the inorganic particles contain inorganic nitride particles (preferably when the inorganic particles contain inorganic nitride particles and the content of the inorganic nitride particles is 90 mass% or more of the total mass of the inorganic particles), the thermal conductivity of the formed thermal conductive material is superior.
Furthermore, comparison of the examples confirmed that when the curable composition contains a maleimide compound, the Tg (heat resistance) of the formed thermally conductive material is superior.
Furthermore, a comparison of the examples confirmed that when the curable composition contains the compound represented by formula (P2) as a curing accelerator, the thermal conductivity and Tg (heat resistance) of the resulting thermal conductive material are superior.
On the other hand, the curable compositions of the comparative examples did not provide the expected effects.

Claims (14)

one or more types of inorganic particles selected from the group consisting of inorganic nitride particles and inorganic oxide particles;
A curable composition comprising a compound having a partial structure represented by the following formula (1) or a partial structure represented by the following formula (2) ,
The curable composition further comprises a maleimide compound.
In formula (1), X represents an aromatic ring or an aliphatic ring.
In formula (2), Cy represents an aliphatic ring. The curable composition according to claim 1, wherein the compound comprises at least one compound selected from the group consisting of a compound represented by the following formula (1A), a compound represented by the following formula (1B), a compound represented by the following formula (2A), and a compound represented by the following formula (2B):
In formula (1A), X ^E1 represents an m ^E1 +1 valent aromatic ring group or aliphatic ring group, and m ^E1 represents an integer of 1 or more.
In formula (1B), X 1 ^E2 represents a divalent aromatic ring group or a divalent aliphatic ring group, ^{L 1 X} represents a single bond or m 1 ^E2 represents a divalent linking group, and m ^{1 E2} represents an integer of 2 or greater.
In formula (2A), Cy ^E1 represents a 2n ^E1 +divalent aliphatic ring group, where n ^E1 represents an integer of 1 or more.
In formula (2B), Cy ^<E2> represents a trivalent aliphatic cyclic group, L ^<Y> represents a single bond or an n ^<E2> divalent linking group, and n ^<E2> represents an integer of 2 or greater. The compound is
The compound represented by formula (1A) above, wherein X ^E1 represents an m ^E1 +1-valent aromatic ring group, or
The curable composition according to claim 2, which is a compound represented by formula (1B), and wherein X ^E2 represents a divalent aromatic ring group. The curable composition according to any one of claims 1 to 3, further comprising a phenolic compound. The curable composition according to claim 4, wherein the phenolic compound has 3 to 7 hydroxyl groups in the molecule. The curable composition according to claim 4 or 5, wherein the phenolic compound has a triazine skeleton. The curable composition according to any one of claims 1 to 6 , wherein the inorganic particles include boron nitride particles. 8. The curable composition of claim 7 , wherein the boron nitride particles comprise aggregated boron nitride having an average particle size of 20 μm or greater. Further, a surface modifier is included,
9. The curable composition according to claim 7 , wherein the boron nitride particles, together with the surface modifier that modifies the surfaces of the boron nitride particles, constitute surface-modified boron nitride particles. The curable composition according to any one of claims 1 to 9 , further comprising a curing accelerator. The curable composition of claim 10 , wherein the curing accelerator comprises a compound containing a phosphorus atom. A thermally conductive material obtained by curing the curable composition according to any one of claims 1 to 11 . A thermally conductive sheet comprising the thermally conductive material according to claim 12 . A device with a thermally conductive layer, comprising: a device; and a thermally conductive layer comprising the thermally conductive sheet according to claim 13 disposed on the device.