JP7613063B2 - Curable composition, cured product, and laminate - Google Patents

Description

The present invention relates to a curable composition, a cured product, and a laminate that have excellent adhesive strength and flexibility.

In recent years, adhesive bonding has been attracting attention from the perspective of efficiency, miniaturization, and weight reduction in the fields of automotive body structures and semiconductors such as power devices. In these fields, there is a demand for further improvements in heat resistance due to the large thermal load in the usage environment. In addition, this field also requires cooling systems with high heat dissipation properties to dissipate heat generated by electronic components.

In response to these issues, for example, Patent Documents 1 and 2 describe thermally conductive adhesives with heat dissipation properties, and disclose compositions that contain thermally conductive fillers such as aluminum oxide and boron nitride in a high ratio of about 80 mass % of the solid content of the adhesive to achieve high thermal conductivity.

Patent document 3 describes that a thermally conductive sheet containing a flexible silicone resin and a thermally conductive filler combines flexibility with high thermal conductivity.

Patent Document 4 discloses a resin composition that uses an organic solvent-soluble polyimide having a flexible polysiloxane skeleton in combination with an epoxy compound, and shows that by using these in combination, a certain level of adhesive strength and flexibility can be achieved.

JP 2014-177581 A JP 2015-006980 A JP 2010-120980 A International Publication No. 2018/030079

However, the adhesives described in Patent Documents 1 and 2 use epoxy resins, and therefore the adhesive layer deteriorates and becomes brittle when exposed to a high-temperature environment for a long period of time, which poses a problem that cracks occur in the adhesive layer and the adhesive strength decreases when used in applications where the temperature environment changes significantly.
The thermally conductive sheet described in Patent Document 3 uses a silicone-based resin, which has insufficient adhesive strength compared to epoxy resins, and has the problem that the applications in which it can be used are limited.
The resin composition described in Patent Document 4 uses an organic solvent-soluble polyimide having a crosslinking point in the side chain in order to obtain heat resistance by increasing crosslinking with the epoxy compound, but the movement of the main chain of the flexible polyimide is suppressed by crosslinking, so that the obtained flexibility is limited. Therefore, when a substrate with a different linear expansion coefficient is used, there is a problem that the adhesive strength is deteriorated by a thermal cycle test.
Therefore, an object of the present invention is to provide a curable composition, a cured product thereof, and a laminate including a layer made of the cured product, which have high adhesive strength even when a filler is contained at a high blend ratio, excellent thermal cycle resistance, and excellent heat resistance that enables the adhesive strength to be maintained even in a high temperature environment.

As a result of extensive research into solving the above problems, we discovered that the above problems could be solved by the embodiment shown below, and thus completed the present invention.

The curable composition according to one embodiment of the present invention is a curable composition containing a block polymer (C) in which a polyimide unit (A) and a polymer unit (B) of an ethylenically unsaturated monomer are linked by a chain transfer agent residue, a compound (D) having two or more epoxy groups in the molecule, and a filler (E), characterized in that the polymer unit (B) of the ethylenically unsaturated monomer has a structural unit derived from an ethylenically unsaturated monomer (b1) having a carboxy group.

The curable composition according to another embodiment of the present invention is characterized in that the block polymer (C) contains polymer units (B) of an ethylenically unsaturated monomer in an amount ranging from 10 to 50% by mass based on the mass of the block polymer (C).

The curable composition according to another embodiment of the present invention is characterized in that the ethylenically unsaturated monomer constituting the ethylenically unsaturated monomer polymer unit (B) contains an ethylenically unsaturated monomer (b1) having a carboxy group in an amount ranging from 2.5 to 45% by mass based on the total mass of the ethylenically unsaturated monomers.

The curable composition according to another embodiment of the present invention is characterized in that it contains a compound (D) having two or more epoxy groups in the molecule in an amount ranging from 50 to 200% by mass based on the mass of the block polymer (C).

The curable composition according to another aspect of the present invention is characterized in that the filler (E) is a thermally conductive filler.

The curable composition according to another aspect of the present invention is characterized in that the polyimide unit (A) contains a structural unit having a siloxane skeleton in a range of 20 to 60 mass % based on the mass of the polyimide unit (A).

A cured product according to another aspect of the present invention is characterized by being obtained by curing the above-mentioned curable composition.

A laminate according to another aspect of the present invention is characterized in that it has a layer made of the above-mentioned cured product on a substrate.

The present invention can provide a curable composition, a cured product thereof, and a laminate comprising a layer made of the cured product, which have high adhesive strength even when the composition contains a high ratio of filler, excellent thermal cycle resistance, and excellent heat resistance that allows the adhesive strength to be maintained even in high temperature environments.

The curable composition of the present invention is characterized in that it contains a block polymer (C) in which a polyimide unit (A) and a polymer unit (B) of an ethylenically unsaturated monomer are linked by a chain transfer agent residue, a compound (D) having two or more epoxy groups in the molecule, and a filler (E), and the polymer unit (B) of the ethylenically unsaturated monomer has a structural unit derived from an ethylenically unsaturated monomer (b1) having a carboxy group.
When the block polymer (C) comprises the flexible polyimide unit (A) and the polymer unit (B) of an ethylenically unsaturated monomer having a carboxy group in the molecule, the obtained curable composition exhibits not only high adhesive strength and flexibility but also excellent heat resistance even when it contains a filler at a high blending ratio.
In addition, since the polyimide unit (A) and the polymer unit (B) of the ethylenically unsaturated monomer are linked together, the compatibility between the units is excellent compared to when each is mixed alone, and a resin film with high transparency can be obtained. Furthermore, the cured product obtained by curing such a resin film exhibits excellent adhesive strength, flexibility, and heat resistance even when it contains a high compounding ratio of filler.
In addition, by combining the block polymer (C) with the compound (D) having two or more epoxy groups in the molecule, a cured film is obtained in which the polymer unit (B) of the ethylenically unsaturated monomer in the block polymer (C) is firmly incorporated into the tough crosslinked structure formed by the compound (D) having two or more epoxy groups in the molecule. The cured film thus obtained forms a phase-separated structure, and achieves both the flexibility derived from the polyimide unit (A) and the high film strength derived from the compound (D) having two or more epoxy groups in the molecule.
In addition, in a high-temperature environment, the crosslinked structure derived from the compound (D) having two or more epoxy groups in the molecule becomes hard due to heat, but the polyimide unit (A) which has high heat resistance exhibits little change in hardness and can maintain its flexibility.
Furthermore, the crosslinked structure between the compound (D) having two or more epoxy groups in the molecule and the polymer unit (B) of an ethylenically unsaturated monomer is strong due to the presence of multiple crosslinking points, and separation due to heat between the block polymer (C) and the compound (D) having two or more epoxy groups in the molecule is suppressed, making it possible to maintain flexibility.
As a result, the curable composition of the present invention has high adhesive strength even when it contains a filler at a high blend ratio, and exhibits excellent heat resistance that enables it to maintain the adhesive strength even in a high-temperature environment.
The present invention will be described in detail below.

<Block polymer (C)>
The block polymer (C) in the present invention may have a structure in which the polyimide unit (A) and the polymer unit (B) of an ethylenically unsaturated monomer are linked via a chain transfer agent residue, and the method for producing the block polymer (C) is not limited, but it can be preferably produced by the following method.
First, a diamine and an excess of an acid dianhydride are reacted in a solvent to form a polyamic acid, which is then heated at a high temperature to cause dehydration, cyclization, and imidization, forming a polyimide unit (A) having an acid anhydride at both ends (hereinafter, step 1).
Next, a chain transfer agent is added to synthesize a prepolymer having chain transfer agent residues at both ends of the polyimide unit (A) (hereinafter, step 2).
Thereafter, an ethylenically unsaturated monomer including an ethylenically unsaturated monomer (b1) having a carboxy group is chain-transfer polymerized in the presence of a polymerization initiator using the chain transfer agent residue contained in the obtained prepolymer to form an ethylenically unsaturated monomer polymer unit (B) (hereinafter, step 3).
In this manner, a block polymer (C) can be obtained in which the polyimide unit (A) and the polymer unit (B) of an ethylenically unsaturated monomer having a structural unit derived from the ethylenically unsaturated monomer (b1) having a carboxy group are linked via a chain transfer agent residue.

<Polyimide Unit (A)>
The block polymer (C) in the present invention has a structure in which a polyimide unit (A) and a polymer unit (B) of an ethylenically unsaturated monomer are linked by a chain transfer agent residue, and the polyimide unit (A) can be formed by reacting a diamine with an excess of an acid dianhydride in a solvent to form a polyamic acid, which is then heated at a high temperature to dehydrate, cyclize, and imidize.

<Diamine>
Examples of diamines constituting the polyimide unit include:
Alicyclic diamines such as diaminocyclohexane, diaminodicyclohexylmethane, dimethyl-diaminodicyclohexylmethane, tetramethyl-diaminodicyclohexylmethane, diaminodicyclohexylpropane, diaminobicyclo[2.2.1]heptane, bis(aminomethyl)-bicyclo[2.2.1]heptane, 3(4),8(9)-bis(aminomethyl)tricyclo[5.2.1.02,6]decane, 1,3-bisaminomethylcyclohexane, and isophoronediamine;
Bisaminophenoxyphenylpropanes such as 2,2-bis[4-(3-aminophenoxy)phenyl]propane and 2,2-bis[4-(4-aminophenoxy)phenyl]propane;
Diaminodiphenyl ethers such as 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, and 4,4'-diaminodiphenyl ether;
Phenylenediamines such as p-phenylenediamine and m-phenylenediamine;
Diaminodiphenyl sulfides such as 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, and 4,4'-diaminodiphenyl sulfide;
Diaminodiphenyl sulfones such as 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, and 4,4'-diaminodiphenyl sulfone;
Diaminobenzophenones such as 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, and 3,4'-diaminobenzophenone;
Diaminodiphenylmethanes such as 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, and 3,4'-diaminodiphenylmethane;
Diaminophenylpropanes such as 2,2-di(3-aminophenyl)propane, 2,2-di(4-aminophenyl)propane, and 2-(3-aminophenyl)-2-(4-aminophenyl)propane;
Diaminophenylhexafluoropropanes such as 2,2-di(3-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, 2,2-di(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane, and 2-(3-aminophenyl)-2-(4-aminophenyl)-1,1,1,3,3,3-hexafluoropropane;
Diaminophenylphenylethanes such as 1,1-di(3-aminophenyl)-1-phenylethane, 1,1-di(4-aminophenyl)-1-phenylethane, and 1-(3-aminophenyl)-1-(4-aminophenyl)-1-phenylethane;
Bisaminophenoxybenzenes such as 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, and 1,4-bis(4-aminophenoxy)benzene;
Bisaminobenzoylbenzenes such as 1,3-bis(3-aminobenzoyl)benzene, 1,3-bis(4-aminobenzoyl)benzene, 1,4-bis(3-aminobenzoyl)benzene, and 1,4-bis(4-aminobenzoyl)benzene;
Bisaminodimethylbenzenes such as 1,3-bis(3-amino-α,α-dimethylbenzyl)benzene, 1,3-bis(4-amino-α,α-dimethylbenzyl)benzene, 1,4-bis(3-amino-α,α-dimethylbenzyl)benzene, and 1,4-bis(4-amino-α,α-dimethylbenzyl)benzene;
Bisaminoditrifluoromethylbenzylbenzenes such as 1,3-bis(3-amino-α,α-ditrifluoromethylbenzyl)benzene, 1,3-bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene, 1,4-bis(3-amino-α,α-ditrifluoromethylbenzyl)benzene, and 1,4-bis(4-amino-α,α-ditrifluoromethylbenzyl)benzene;
Aminophenoxybiphenyls such as 2,6-bis(3-aminophenoxy)benzonitrile, 2,6-bis(3-aminophenoxy)pyridine, 4,4'-bis(3-aminophenoxy)biphenyl, and 4,4'-bis(4-aminophenoxy)biphenyl;
Aminophenoxyphenyl ketones such as bis[4-(3-aminophenoxy)phenyl]ketone and bis[4-(4-aminophenoxy)phenyl]ketone;
Aminophenoxyphenyl sulfides such as bis[4-(3-aminophenoxy)phenyl]sulfide and bis[4-(4-aminophenoxy)phenyl]sulfide;
Aminophenoxyphenyl sulfones such as bis[4-(3-aminophenoxy)phenyl]sulfone and bis[4-(4-aminophenoxy)phenyl]sulfone;
Aminophenoxyphenyl ethers such as bis[4-(3-aminophenoxy)phenyl]ether and bis[4-(4-aminophenoxy)phenyl]ether;
Aminophenoxyphenylpropanes such as 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, and 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane;
Other diamines include 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(3-aminophenoxy)-α,α-dimethylbenzyl]benzene, 1,4-bis[4-(4-aminophenoxy)-α,α-dimethylbenzyl]benzene, benzene, 4,4'-bis[4-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, 4,4'-bis[4-(4-aminophenoxy)phenoxy]diphenyl sulfone, 3,3'-diamino-4,4'-diphenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 6,6'-bis(3-aminophenoxy 3,3,3,'3,'-tetramethyl-1,1'-spirobiindane, 6,6'-bis(4-aminophenoxy)3,3,3,'3,'-tetramethyl-1,1'-spirobiindane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 1,3-bis(4-aminobutyl)tetramethyldisiloxane, bis(aminomethyl)ether, bis(2-aminoethyl)ether, bis(3-aminopropyl)ether, bis(2-aminomethoxy)ethyl]ether, bis[2-(2-aminoethoxy)ethyl]ether, bis[2-(3-aminopropoxy)ethyl]ether, 1,2-bis(aminomethoxy)ethane, 1,2-bis(2-a Examples of the bis(2-(aminoethoxy)ethane include 1,2-bis[2-(aminomethoxy)ethoxy]ethane, 1,2-bis[2-(2-aminoethoxy)ethoxy]ethane, ethylene glycol bis(3-aminopropyl)ether, diethylene glycol bis(3-aminopropyl)ether, triethylene glycol bis(3-aminopropyl)ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, and 1,12-diaminododecane.

As the diamine, a dimer diamine derived from a dimer acid, which is a dimer of an unsaturated fatty acid such as oleic acid, can be used. Commercially available dimer diamines include, for example, Versamine 551 (manufactured by BASF Japan), Versamine 552 (manufactured by Cognix Japan; hydrogenated Versamine 551), PRIAMINE 1075, and PRIAMINE 1074 (manufactured by Croda Japan).

As the diamine, diamines having a siloxane skeleton (hereinafter also referred to as diaminopolysiloxanes) such as α,ω-bis(2-aminoethyl)polydimethylsiloxane, α,ω-bis(3-aminopropyl)polydimethylsiloxane, α,ω-bis(4-aminobutyl)polydimethylsiloxane, α,ω-bis(5-aminopentyl)polydimethylsiloxane, α,ω-bis[3-(2-aminophenyl)propyl]polydimethylsiloxane, α,ω-bis[3-(4-aminophenyl)propyl]polydimethylsiloxane, 1,3-bis(3-aminopropyl)tetramethyldisiloxane, and 1,3-bis(4-aminobutyl)tetramethyldisiloxane can be used. Commercially available diamines having a siloxane skeleton include, for example, KF-8010, X-22-161A, and X-22-161B (manufactured by Shin-Etsu Chemical Co., Ltd.).

As the diamine, polyoxypropylene diamine can be used. Commercially available polyoxypropylene diamine products include, for example, Jeffamine D-230, Jeffamine D-400, Jeffamine D-2000, and Jeffamine D-4000 (all manufactured by HUNTSMAN).

These diamines may be used alone or in combination of two or more.
The polyimide unit (A) preferably has at least one constituent unit selected from the group consisting of a constituent unit derived from a diamine having an aromatic ring and a constituent unit derived from a diamine having a siloxane skeleton, more preferably has a constituent unit derived from a diamine having a siloxane skeleton, and even more preferably has a constituent unit derived from a diamine having an aromatic ring and a constituent unit derived from a diamine having a siloxane skeleton.

<Acid dianhydride>
The acid dianhydride is not particularly limited, and examples thereof include aromatic tetracarboxylic dianhydrides such as pyromellitic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-diphenylethertetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride, and 9,9'-bis(3,4-dicarboxyphenyl)fluorene dianhydride; 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, and the like. Water, alicyclic tetracarboxylic dianhydrides such as 1,2,3,4-tetramethyl-1,2,3,4-cyclobutane tetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, 1,2,4,5-cyclohexane tetracarboxylic dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride, 2,3,5-tricarboxy-2-cyclopentane acetic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, 2,3,4,5-tetrahydrofuran tetracarboxylic dianhydride, and 3,5,6-tricarboxy-2-norbornane acetic dianhydride; and aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butane tetracarboxylic dianhydride.

As the acid dianhydride, an acid dianhydride having a siloxane skeleton, such as a polysiloxane modified with a carboxylic acid anhydride at both ends, can be used. Examples of commercially available products of the polysiloxane modified with a carboxylic acid anhydride at both ends include X-22-168AS, X-22-168A, X-22-168B, and X-22-168-P5-B (all manufactured by Shin-Etsu Chemical Co., Ltd.).

These acid dianhydrides may be used alone or in combination of two or more.
The polyimide unit (A) preferably has at least one constituent unit selected from the group consisting of aromatic tetracarboxylic dianhydrides and acid dianhydrides having a siloxane skeleton, more preferably has a constituent unit derived from an aromatic tetracarboxylic dianhydride, and even more preferably has a constituent unit derived from 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride.

The polyimide unit (A) preferably contains 20 to 60% by mass of structural units having a siloxane skeleton, based on the mass of the polyimide unit (A), and more preferably contains 35 to 45% by mass of structural units having a siloxane skeleton. If the structural units having a siloxane skeleton are in the range of 30 to 70% by mass, this is preferred because it provides excellent heat resistance and flexibility.

By mixing the above diamine and acid dianhydride at a temperature of -20 to 150°C, preferably -5 to 100°C, a polyamic acid can be easily formed.
The polyamic acid can be imidized by dehydrating and cyclizing it using known thermal imidization methods and chemical imidization methods. In the thermal imidization method, the polyamic acid can be easily imidized by, for example, heat treatment while dehydrating at a high temperature of 150 to 250° C. In the chemical imidization method, the polyamic acid can be imidized by adding, for example, 2 to 10 molar equivalents of a base such as pyridine or triethylamine and acetic anhydride to the diamine raw material, and carrying out a cyclization reaction at 0 to 50° C.

<Number Average Molecular Weight of Polyimide Unit (A)>
The number average molecular weight of the polyimide unit (A) is preferably in the range of 20,000 to 200,000. When it is 20,000 or more, the resulting cured product has excellent breaking strength, and when it is 200,000 or less, the viscosity can be easily adjusted, which is preferable.

<Chain Transfer Agent>
By reacting the acid anhydride groups at both ends of the polyimide unit (A) obtained above with a chain transfer agent, a prepolymer having chain transfer agent residues at both ends can be obtained.
The chain transfer agent is not particularly limited, but is preferably one having a functional group capable of reacting with an acid anhydride group and a sulfanyl group. When the chain transfer agent is used, the terminal acid anhydride group in the polyimide unit (A) reacts with the functional group capable of reacting with an acid anhydride group in the chain transfer agent to form a prepolymer having sulfanyl groups at both ends. The reaction between the polyimide unit and the chain transfer agent proceeds easily by mixing at any temperature between 20 and 120°C, and the chain transfer agent can be used alone or in combination of two or more of known chain transfer agents.

Examples of the functional group capable of reacting with the acid anhydride group include an amino group and a hydroxyl group, and the hydrogen atom of the amino group may be substituted with an organic residue such as an alkyl group or an aryl group. Examples of such a substituted amino group include mono-substituted amino groups such as an N-alkylamino group and an N-arylamino group. Examples of the hydroxyl group include a primary hydroxyl group, a secondary hydroxyl group, and a tertiary hydroxyl group.
The functional group capable of reacting with an acid anhydride group is preferably an amino group because of its good reactivity with the acid anhydride group. It is preferable to use a chain transfer agent having an amino group and a sulfanyl group because the sulfanyl group can be efficiently introduced to the terminal of the prepolymer.

Examples of such chain transfer agents containing one amino group and one sulfanyl group in the molecule include aminoalkanethiols such as 2-aminoethanethiol, 3-aminopropyl-1-thiol, 1-aminopropyl-2-thiol, and 4-amino-1-butanethiol; and aminobenzenethiols such as 2-aminothiophenol, 3-aminothiophenol, and 4-aminothiophenol. Among these, aminoalkanethiols are preferred, and 2-aminoethanethiol is more preferred.

<Polymer Unit (B) of Ethylenically Unsaturated Monomer>
The ethylenically unsaturated monomer polymer unit (B) has a structural unit derived from an ethylenically unsaturated monomer (b1) having a carboxy group, and is a structure obtained by polymerizing an ethylenically unsaturated monomer including an ethylenically unsaturated monomer (b1) having one or more carboxy groups in the molecule in the presence of a polymerization initiator.
Use of an ethylenically unsaturated monomer (b1) having a carboxy group is preferred because, when reacted with a compound (D) having two or more epoxy groups in the molecule described below, a cured product having better heat resistance and flexibility can be obtained.
Specifically, the prepolymer having chain transfer agent residues at both ends obtained in step 2 and an ethylenically unsaturated monomer including an ethylenically unsaturated monomer (b1) having a carboxy group are polymerized in the presence of a polymerization initiator to obtain a block polymer (C) in which a polyimide unit (A) and a polymer unit (B) of the ethylenically unsaturated monomer are linked by a chain transfer agent residue.

<Ethylenically unsaturated monomer having a carboxy group (b1)>
The ethylenically unsaturated monomer (b1) having a carboxy group may be any ethylenically unsaturated monomer having one or more carboxy groups in the molecule, and any known monomer may be used.
Examples of such monomers (b1) include (meth)acrylic acid, acrylic acid dimer, itaconic acid, maleic acid, fumaric acid, crotonic acid, α-(hydroxymethyl)(meth)acrylic acid, 2-(meth)acryloyloxyethyl phthalate, 2-(meth)acryloyloxypropyl phthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate, 2-(meth)acryloyloxypropyl hexahydrophthalate, β-carboxyethyl (meth)acrylate, ethylene oxide-modified succinic acid (meth)acrylate, ω-carboxypolycaprolactone (meth)acrylate, and p-vinylbenzoic acid. One type may be used alone, or two or more types may be used in combination.
The ethylenically unsaturated monomer (b1) having a carboxy group is preferably (meth)acrylic acid.

The content of the ethylenically unsaturated monomer (b1) having a carboxy group is preferably in the range of 2.5 to 45% by mass, more preferably in the range of 5 to 30% by mass, based on the total mass of the ethylenically unsaturated monomers constituting the ethylenically unsaturated monomer polymer unit (B). A range of 2.5 to 45% by mass is preferred because it provides excellent heat resistance and flexibility.

<Other ethylenically unsaturated monomers>
The ethylenically unsaturated monomer constituting the ethylenically unsaturated monomer polymer unit (B) may contain an ethylenically unsaturated monomer other than the ethylenically unsaturated monomer (b1) having a carboxy group.
Other ethylenically unsaturated monomers are not particularly limited, and examples thereof include linear or branched alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tertiary butyl (meth)acrylate, isoamyl (meth)acrylate, octyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cetyl (meth)acrylate, decyl (meth)acrylate, isodecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, isomyristyl (meth)acrylate, stearyl (meth)acrylate, and isostearyl (meth)acrylate;
cyclic alkyl (meth)acrylates such as cyclohexyl (meth)acrylate, tertiary butyl cyclohexyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentanyloxyethyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth)acrylate, and isobornyl (meth)acrylate;
Fluoroalkyl (meth)acrylates such as trifluoroethyl (meth)acrylate, octafluoropentyl (meth)acrylate, perfluorooctylethyl (meth)acrylate, and tetrafluoropropyl (meth)acrylate;
(meth)acrylates having a heterocycle, such as tetrahydrofurfuryl (meth)acrylate and 3-methyl-3-oxetanyl (meth)acrylate;
(meth)acrylates having an aromatic ring, such as benzyl (meth)acrylate, phenoxyethyl (meth)acrylate, phenoxypolyethylene glycol (meth)acrylate, paracumylphenoxyethyl (meth)acrylate, paracumylphenoxypolyethylene glycol (meth)acrylate, and nonylphenoxypolyethylene glycol (meth)acrylate;
(Meth)acrylates having an alkyl ether group such as methoxypolyethylene glycol mono(meth)acrylate, octoxypolyethylene glycol polypropylene glycol mono(meth)acrylate, lauroxypolyethylene glycol mono(meth)acrylate, stearoxypolyethylene glycol mono(meth)acrylate, phenoxypolyethylene glycol mono(meth)acrylate, phenoxypolyethylene glycol polypropylene glycol mono(meth)acrylate, polyethylene glycol monomethyl ether (meth)acrylate, lauroxypolyethylene glycol mono(meth)acrylate, nonylphenoxypolyethylene glycol mono(meth)acrylate, nonylphenoxypolyethylene glycol mono(meth)acrylate, nonylphenoxypolyethylene glycol polypropylene glycol mono(meth)acrylate, phenoxypolyethylene glycol mono(meth)acrylate, methoxypolyethylene glycol (meth)acrylate, n-butoxyethyl (meth)acrylate, n-butoxydiethylene glycol (meth)acrylate, 2-methoxyethyl (meth)acrylate, and 2-ethoxyethyl (meth)acrylate;
ethylenically unsaturated monomers having a hydroxyl group, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 2-hydroxy-3-allyloxypropyl (meth)acrylate, 2-(meth)acryloyloxyethyl-2-hydroxypropyl phthalate, or caprolactone adducts of these monomers (the number of moles added is 1 to 5), polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, and glycerin mono(meth)acrylate;
Glycidyl (meth)acrylate, methyl glycidyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate glycyl diether, 3,4-epoxybutyl (meth)acrylate, 3-methyl-3,4-epoxybutyl (meth)acrylate, 3-ethyl-3,4-epoxybutyl (meth)acrylate, 4-methyl-4,5-epoxypentyl (meth)acrylate, 5-methyl-5,6-epoxyhexyl (meth)acrylate, α-ethyl glycidyl acrylate, allyl glycidyl ether, crotonyl glycidyl ether, (iso)crotonic acid glycidyl ether, (3,4-epoxycyclohexyl)methyl (meth)acrylate, N-(3,5-dimethyl-4-glycidyl)benzyl acrylamide, o-vinylbenzyl glycidyl ether ethylenically unsaturated monomers having an epoxy group, such as styrene, m-vinylbenzyl glycidyl ether, p-vinylbenzyl glycidyl ether, α-methyl-o-vinylbenzyl glycidyl ether, α-methyl-m-vinylbenzyl glycidyl ether, α-methyl-p-vinylbenzyl glycidyl ether, 2,3-diglycidyloxymethylstyrene, 2,4-diglycidyloxymethylstyrene, 2,5-diglycidyloxymethylstyrene, 2,6-diglycidyloxymethylstyrene, 2,3,4-triglycidyloxymethylstyrene, 2,3,5-triglycidyloxymethylstyrene, 2,3,6-triglycidyloxymethylstyrene, 3,4,5-triglycidyloxymethylstyrene, and 2,4,6-triglycidyloxymethylstyrene;
Ethylenically unsaturated monomers having an isocyanate group, such as (meth)acryloyl isocyanate, 2-isocyanatoethyl (meth)acrylate, 2-(meth)acryloyloxyethoxyethyl isocyanate, 1,1-(bis(meth)acryloyloxymethyl)ethyl isocyanate, m-(meth)acryloylphenyl isocyanate, and α,α-dimethyl-4-isopropenylbenzyl isocyanate;
(Meth)acrylamide, N-methyl(meth)acrylamide, N-butylacrylamide, diacetone acrylamide, N-methoxymethyl-(meth)acrylamide, N-ethoxymethyl-(meth)acrylamide, N-propoxymethyl-(meth)acrylamide, N-butoxymethyl-(meth)acrylamide, N-pentoxymethyl-(meth)acrylamide, N,N-dimethylacrylamide, N,N-dibenzyl acrylamide, methacrylformamide, N-methyl N-vinylacetamide, N-vinylpyrrolidone, N,N-di(methoxymethyl)acrylamide, N-ethoxymethyl amide group-containing ethylenically unsaturated monomers such as N-methoxymethyl-N-methacrylamide, N,N-di(ethoxymethyl)acrylamide, N-ethoxymethyl-N-propoxymethylmethacrylamide, N,N-di(propoxymethyl)acrylamide, N-butoxymethyl-N-(propoxymethyl)methacrylamide, N,N-di(butoxymethyl)acrylamide, N-butoxymethyl-N-(methoxymethyl)methacrylamide, N,N-di(pentoxymethyl)acrylamide, N-methoxymethyl-N-(pentoxymethyl)methacrylamide, and cinnamic acid amide;
Vinyls such as styrene, α-methylstyrene, and vinyl acetate;
vinyl ethers having an ether group such as ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, and isobutyl vinyl ether;
These may be used alone or in combination of two or more.

The content of the ethylenically unsaturated monomer polymer unit (B) is preferably in the range of 10 to 50% by mass, more preferably in the range of 20 to 40% by mass, based on the mass of the block polymer (C). A range of 10 to 50% by mass is preferred because it provides excellent heat resistance.

<Polymerization initiator>
As the polymerization initiator, known azo compounds and organic peroxides can be used. These may be used alone or in combination of two or more.
The azo compound is not particularly limited, and examples thereof include 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylbutyronitrile), 1,1'-azobis(cyclohexane-1-carbonitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-methoxyvaleronitrile), 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), dimethyl 1,1'-azobis(1-cyclohexanecarboxylate), dimethyl 2,2'-azobis(2-methylpropionate), 4,4'-azobis(4-cyanovaleric acid), 2,2'-azobis(2-hydroxymethylpropionitrile), and 2,2'-azobis[2-(2-imidazolin-2-yl)propane].
The organic peroxide is not particularly limited, and examples thereof include benzoyl peroxide, t-butyl peroxy 2-ethylhexaate, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxydicarbonate, di-n-propyl peroxydicarbonate, di(2-ethoxyethyl)peroxydicarbonate, t-butyl peroxyneodecanoate, t-butyl peroxypivalate, (3,5,5-trimethylhexanoyl)peroxide, dipropionyl peroxide, and diacetyl peroxide.

The amount of polymerization initiator is preferably 0.001 to 15% by mass based on the total amount of ethylenically unsaturated monomers. A range of 0.001 to 15% by mass is preferable because chain transfer polymerization proceeds effectively.

<Number Average Molecular Weight of Polymer Unit (B) of Ethylenically Unsaturated Monomer>
The number average molecular weight of the ethylenically unsaturated monomer polymer unit (B) is preferably in the range of 2,000 to 200,000. When it is 2,000 or more, the resulting cured product has excellent breaking strength, and when it is 200,000 or less, it is preferable because the viscosity can be easily adjusted.

<Number average molecular weight of block polymer (C)>
The number average molecular weight of the block polymer (C) is preferably in the range of 5,000 to 300,000. When it is 5,000 or more, the resulting cured product has excellent breaking strength, and when it is 300,000 or less, it is easy to adjust the viscosity, which is preferable.

<Solvent>
Examples of solvents that can be used when producing the block polymer (C) include acetone, methyl ethyl ketone, cyclohexanone, methyl acetate, ethyl acetate, propyl acetate, toluene, xylene, anisole, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, N-methylcaprolactam, dimethylsulfoxide, tetramethylurea, pyridine, dimethylsulfone, hexamethylsulfoxide, m-cresol, γ-butyrolactone, and γ-valerolactone. These solvents may be used alone or in combination of two or more.

Solvents that can be used in the synthesis of the polyimide unit (A) are preferably high-boiling point solvents that do not react with a chain transfer agent having an amino group and a sulfanyl group. Examples of such solvents include xylene, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethylsulfoxide, m-cresol, γ-butyrolactone, and γ-valerolactone.

<Compound (D) Having Two or More Epoxy Groups in the Molecule>
The curable composition of the present invention further contains a compound (D) having two or more epoxy groups in the molecule. The carboxy group derived from the ethylenically unsaturated monomer (b1) having a carboxy group in the block polymer (C) reacts with the epoxy group of the compound (D) having two or more epoxy groups in the molecule to cure, thereby obtaining a cured product having excellent heat resistance and adhesiveness. Such compounds (D) having two or more epoxy groups in the molecule are broadly classified into compounds having an aromatic ring and compounds not having an aromatic ring.

Examples of the epoxy compounds having an aromatic ring include epoxy compounds having a bisphenol skeleton such as bisphenol A type, bisphenol F type, or bisphenol S type; epoxy compounds having a dicyclopentadiene skeleton such as dicyclopentadiene dioxide or a phenol novolac epoxy compound having a dicyclopentadiene skeleton; epoxy compounds having a naphthalene skeleton such as 1-glycidylnaphthalene, 2-glycidylnaphthalene, 1,2-diglycidylnaphthalene, 1,5-diglycidylnaphthalene, 1,6-diglycidylnaphthalene, 1,7-diglycidylnaphthalene, 2,7-diglycidylnaphthalene, triglycidylnaphthalene, or 1,2,5,6-tetraglycidylnaphthalene; 9,9-bis(4-glycidyloxyphenyl)fluorene, 9,9-bis(4-glycidyloxy-3 -methylphenyl)fluorene, 9,9-bis(4-glycidyloxy-3-chlorophenyl)fluorene, 9,9-bis(4-glycidyloxy-3-bromophenyl)fluorene, 9,9-bis(4-glycidyloxy-3-fluorophenyl)fluorene, 9,9-bis(4-glycidyloxy-3-methoxyphenyl)fluorene, 9,9-bis(4-glycidyloxy-3,5-dimethylphenyl)fluorene, 9,9-bis(4-glycidyloxy-3,5-dichlorophenyl)fluorene, or 9,9-bis(4-glycidyloxy-3,5-dibromophenyl)fluorene, or other epoxy compounds having a fluorene skeleton; 4,4'-diglycidylbiphenyl, or 4,4'-diglycidyl-3,3',5,5'-tetramethylbiphenyl, or other epoxy compounds having a biphenyl skeleton;

Examples of the epoxy compound not having an aromatic ring include alicyclic epoxy compounds, aliphatic glycidyl ether type epoxy compounds, aliphatic glycidyl ester type epoxy compounds, alicyclic glycidyl ether type epoxy compounds, alicyclic glycidyl ester compounds, nitrogen-containing epoxy compounds such as glycidyl amine-based and heterocyclic-based epoxy compounds, and siloxane-based epoxy compounds.
These compounds (D) having two or more epoxy groups in the molecule may be used alone or in combination of two or more.

The curable composition of the present invention contains the compound (D) having two or more epoxy groups in the molecule in a range of preferably 50 to 200% by mass, more preferably 75 to 150% by mass, based on the mass of the block polymer (C). A range of 50 to 200% by mass is preferred because it provides excellent heat resistance and adhesion.

<Curing accelerator>
The curable composition of the present invention preferably contains a curing accelerator in order to adjust the curing rate and the physical properties of the cured product. The curing accelerator is not particularly limited and can be selected appropriately. Specific examples of the curing accelerator include phosphorus-based curing accelerators, amine-based curing accelerators, imidazole-based curing accelerators, guanidine-based curing accelerators, and metal-based curing accelerators. These may be used alone or in combination of two or more.
From the viewpoint of the insulating property and adhesive property of the cured product obtained by curing the curable composition, the curing accelerator preferably contains an imidazole-based curing accelerator. Examples of the imidazole-based curing accelerator include imidazole, 2-methylimidazole, 2-undecylimidazole, 2-ethyl-4-methylimidazole, 2-phenylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-phenylimidazole, 1-cyanoethyl-2-undecylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 2-phenyl-4-methylimid ... Examples of the compound include ethyl-2-phenylimidazolium trimellitate, 2,4-diamino-6-[2'-methylimidazolyl-(1')]-ethyl-s-triazine, 2,4-diamino-6-[2'-undecylimidazolyl-(1')]-ethyl-s-triazine, 2-phenylimidazole isocyanuric acid adduct, 2-phenyl-4,5-dihydroxymethylimidazole, and 2-phenyl-4-methyl-5-hydroxymethylimidazole.
The amount of the curing accelerator blended is preferably in the range of 0.1 to 10 mass %, more preferably 0.1 to 5 mass %, based on the mass of solids contained in the curable composition excluding the filler (E).

<Filler (E)>
The curable composition of the present invention further contains a filler (E). The filler (E) is not particularly limited and can be appropriately selected according to the desired function, and for example, a particulate or fibrous filler can be used. The filler (E) may be used alone or in combination of two or more kinds.

The constituent materials of the filler (E) include, for example, metals such as silver, gold, copper, platinum, nickel, aluminum, chromium, iron, and stainless steel; metal oxides such as aluminum oxide, calcium oxide, magnesium oxide, silicon oxide (typically silicon dioxide), titanium oxide, zirconium oxide, zinc oxide, tin oxide, antimony acid-doped tin oxide, copper oxide, and nickel oxide; hydrated metal compounds such as aluminum hydroxide, boehmite, magnesium hydroxide, calcium hydroxide, zinc hydroxide, silicic acid, iron hydroxide, copper hydroxide, barium hydroxide, zirconium oxide hydrate, tin oxide hydrate, basic magnesium carbonate, hydrotalcite, dawsonite, borax, and zinc borate; silicon carbide, boron carbide, nitrogen carbonitride, and the like. Examples of the inorganic materials include carbides such as calcium carbide and calcium carbide; nitrides such as aluminum nitride, silicon nitride, boron nitride, and gallium nitride; carbonates such as calcium carbonate and magnesium carbonate; titanates such as barium titanate and potassium titanate; silicates such as calcium silicate and magnesium silicate; carbon-based materials such as carbon black, carbon tubes (typically carbon nanotubes), carbon fibers, and diamond; inorganic materials such as glass; polymers such as polystyrene, acrylic resins, phenolic resins, benzoguanamine resins, urea resins, silicone resins, polyesters, polyurethanes, polyethylene, polypropylene, polyamides, polyimides, polyvinylidene chloride, and rubber; and natural raw material particles such as volcanic sirasu, clay, and sand.

As the fibrous filler, various synthetic fiber materials and natural fiber materials can be used. Normally, even if the content in the curable composition is relatively high, the smoothness of the cured film is not easily impaired, so particulate fillers are preferred as the filler (E). The shape of the particles is not particularly limited, and may be bulk, needle, plate, or layered. Bulk shapes include, for example, spherical, rectangular, crushed, or irregular shapes thereof. The structure of the particles is not particularly limited, and may be, for example, a dense structure, a porous structure, a hollow structure, etc.

When the curable composition of the present invention is a curable composition having thermal conductivity, a thermally conductive filler is used as the filler (E).
As the thermally conductive filler, a known thermally conductive filler can be used, and preferred constituent materials of such thermally conductive fillers include silver, gold, copper, nickel, alumina, aluminum hydroxide, magnesium hydroxide, calcium carbonate, magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum oxide, aluminum nitride, crystalline silica, amorphous silica, silicon nitride, silicon carbide, boron nitride, and the like.
From the viewpoint of excellent dispersibility in resin components such as the block polymer (C) constituting the curable composition, the filler (E) is preferably at least one selected from the group consisting of boron nitride and alumina, and more preferably boron nitride.

The average particle size of the filler is not particularly limited, but typically, the filler has an average particle size (D50) of 100 μm or less calculated by the laser diffraction scattering method. The average particle size of the filler is preferably 0.1 μm or more and 50 μm or less, and more preferably 1 μm or more and 50 μm or less.

The content of the filler (E) in the curable composition is not particularly limited and can be determined according to the desired function and required performance. The content of the filler (E) may be 5 mass% or more, 10 mass% or more, or 33 mass% or more based on the solid content mass contained in the curable composition.
When the filler is a thermally conductive filler, the content of the thermally conductive filler is preferably 70% by mass or more, more preferably 75% by mass or more, based on the mass of the solid content contained in the curable composition. From the viewpoint of suppressing a decrease in adhesiveness, the content of the thermally conductive filler is usually suitably 90% by mass or less, preferably 85% by mass or less, based on the mass of the solid content contained in the curable composition.

<Other ingredients>
The curable composition may further include known additives such as silane coupling agents, fillers, propellants, plasticizers, superplasticizers, wetting agents, flame retardants, viscosity modifiers, preservatives, stabilizers, and colorants, etc. Such additives may be used alone or in combination of two or more.

Examples of the silane coupling agent include trialkoxysilanes having a vinyl group, such as vinyltrimethoxysilane and vinyltriethoxysilane; trialkoxysilanes having an amino group, such as 3-aminopropyltriethoxysilane and N-(2-aminoethyl)3-aminopropyltrimethoxysilane; trialkoxysilanes having a glycidyl group, such as 3-glycidoxypropyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane and 3-glycidoxypropyltriethoxysilane; trialkoxysilanes having an isocyanate group, such as 3-isocyanatepropyltriethoxysilane; and trialkoxysilanes having a mercapto group, such as 3-mercaptopropylmethyldimethoxysilane and 3-mercaptopropyltrimethoxysilane.
The amount of the silane coupling agent added is preferably 0.05 to 10% by mass based on the mass of the block polymer (C) in the curable composition.

<Cured product, laminate>
The cured product of the present invention is obtained by curing the above-mentioned curable composition, and is useful in the fields of pressure-sensitive adhesives, pressure-sensitive adhesive sheets, coating agents, film substrates, elastomers, medical materials, optical materials, etc. Among them, it is preferably used as an adhesive sheet from the viewpoints of having high adhesive strength, flexibility, and excellent heat resistance.
The method for forming the cured product is not particularly limited. For example, the curable composition may be applied to a substrate after adjusting the viscosity of the composition to a suitable coating method using a solvent or the like, and then the composition is heated to a temperature of, for example, 50° C. to 200° C. to remove the solvent, and then cured at a temperature of 20° C. to 200° C. to obtain the cured product.

The laminate of the present invention comprises a layer of the above-mentioned cured product on a substrate. The method for producing the laminate is not particularly limited, and for example, the laminate can be produced by applying a curable composition onto a first substrate, drying volatiles such as the solvent in an oven to form an uncured resin layer, overlaying a second substrate on the resin layer, and curing the resin layer while softening and adhering the resin layer by thermocompression or the like as necessary. The laminate of the present invention can also be produced by sandwiching an uncured resin layer formed by drying a curable composition that has been molded into a sheet shape in advance between two substrates, and curing the uncured resin layer while softening and adhering the resin layer by thermocompression or the like. The thickness of the layer after curing is preferably 0.1 μm to 300 mm.

The substrate is not particularly limited, and examples thereof include metals such as aluminum and copper; thermoplastic polymers such as polyethylene, polypropylene, polyurethane, polyacrylate, polycarbonate, and copolymers thereof; thermosetting polymers such as vulcanized rubber; urea-formaldehyde foam, melamine resin, wood, super engineering plastics such as polyphenylene sulfide, polyarylate, liquid crystal polymer (LCP), polysulfone, and polyethersulfone; carbon fiber reinforced plastic, glass fiber reinforced plastic, and other fiber reinforced plastics.
When the laminate of the present invention comprises two or more substrates, the substrates may be the same or different.

The laminate of the present invention has excellent adhesive strength and heat resistance, and is useful as a structural member in the fields of power devices and automobiles.

The present invention will be explained in more detail below with reference to examples, but the following examples do not limit the scope of the invention in any way. In addition, unless otherwise specified, "parts" and "%" in the examples represent "parts by mass" and "% by mass", respectively.

<Solid content>
The solid content concentration of the resin was measured in accordance with JIS K5601-1-2 at a heating temperature of 150° C. for a heating time of 20 minutes, and the heating residue was used.

<Number average molecular weight (Mn), weight average molecular weight (Mw)>
The number average molecular weight (Mn) and weight average molecular weight (Mw) of the resin were measured by gel permeation chromatography (GPC) using polystyrene equivalents with known molecular weights. The solvent was tetrahydrofuran as the eluent, and three TSKgel Super HM-M columns (Tosoh Corporation) were connected in series. The conditions were a flow rate of 0.6 ml/min, an injection volume of 10 μl, and a column temperature of 40° C.

<Acid value>
The acid value was measured by the following procedure. First, 1 g of the resin solution was dissolved in 40 mL of toluene, and then 20 mL of methanol and 1 mL of ion-exchanged water were added to prepare a sample for acid value measurement. Next, potentiometric titration was performed using an automatic titration device "AT-510" manufactured by Kyoto Electronics Manufacturing Co., Ltd., connected with the company's "APB-510-20B" as a burette, and a 0.02 mol/L ethanolic potassium hydroxide solution was used as the titration reagent, and the number of mg of KOH per 1 g of solid resin was calculated from the solid content concentration of the resin.

The abbreviations used in this specification are as follows.
BPADA: 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic anhydride X-22-168AS: tetracarboxylic dianhydride modified polysiloxane, product name "X-22-168AS", manufactured by Shin-Etsu Chemical Co., Ltd. BAPP: 2,2-bis[4-(4-aminophenoxy)phenyl]propane KF-8010: diaminopolysiloxane, product name "KF-8010", manufactured by Shin-Etsu Chemical Co., Ltd. DMF: N,N-dimethylformamide AIBN: 2,2'-azobisisobutyronitrile MMA: methyl methacrylate St: styrene MAA: methacrylic acid AA: acrylic acid

jER828US: Bisphenol A type liquid epoxy resin, product name "jER828US", manufactured by Mitsubishi Chemical Corporation jER157S70: Bisphenol A novolac type solid epoxy resin, product name "jER157S70", manufactured by Mitsubishi Chemical Corporation jER630: p-aminophenol type liquid epoxy resin, product name "jER630", manufactured by Mitsubishi Chemical Corporation C11Z-CN: 1-cyanoethyl-2-undecylimidazole, product name "Curesol C11Z-CN", manufactured by Shikoku Kasei Corporation AGG50: Granulated boron nitride with an average particle size of 15 to 30 μm, product name "Agglomerates 50", manufactured by 3M Japan Ltd. AO-509: Spherical alumina with an average particle size of 10 μm, product name "Admafine"AO-509", manufactured by Admatechs Co., Ltd. C20: Boehmite particles having an average particle size of 2.3 μm, product name "Boehmite C20", manufactured by Taimei Chemical Industry Co., Ltd.

<Production of Block Polymer>
(Production Example 1) Block polymer (C-1) solution A reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer was charged with 100.0 parts of BPADA, 38.3 parts of BAPP, 80.1 parts of KF-8010, and 510 parts of DMF, and the atmosphere was replaced with nitrogen gas. The reaction vessel was heated to 150° C. with stirring, and the reaction was allowed to proceed until the acid value became less than 5 mgKOH/g, thereby obtaining a polyimide unit.
Then, the mixture was cooled to 80° C., 0.89 parts of 2-aminoethanethiol was added, and the mixture was reacted at 80° C. for 5 hours to obtain a polyimide prepolymer.
Next, 84.6 parts of MMA, 9.4 parts of MAA, and 221 parts of DMF were added to the polyimide prepolymer that had been returned to room temperature, and the mixture was stirred uniformly, and then heated to 75° C. under a nitrogen atmosphere. 0.1 parts of AIBN was added thereto as a polymerization initiator in 13 divided portions every 30 minutes, and the mixture was allowed to react for another 2 hours after the addition of the polymerization initiator to form a polymer unit of an ethylenically unsaturated monomer, and DMF was added so that the solid concentration was 30%, to obtain a block polymer (C-1) solution. The number average molecular weight (Mn) of the block polymer (C-1) was 50,000, and the weight average molecular weight (Mw) was 98,000.

(Production Examples 2 to 38) Solutions of Block Polymers (C-2) to (C-38) Solutions of block polymers (C-2) to (C-38) were obtained by the same operation as in Production Example 1, except that the blending compositions were changed to those shown in Table 1 or Table 2.

(Comparative Production Example 1) Comparative resin (H-1) solution 100.0 parts of BPADA, 38.3 parts of BAPP, 80.1 parts of KF-8010, and 510 parts of DMF were charged into a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, and the atmosphere was replaced with nitrogen gas. The reaction vessel was heated to 150° C. with stirring, and the mixture was reacted until the acid value became less than 5 mg KOH/g. Then, DMF was added so that the solid content concentration became 30%, and a comparative resin (H-1) solution, which is a polyimide unit, was obtained.

(Comparative Production Example 2) Comparative resin (H-2) solution 135.0 parts of MMA, 15.0 parts of MAA, and 350 parts of DMF were added to a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, and the mixture was stirred uniformly, and then heated to 75°C under a nitrogen atmosphere. 0.1 parts of AIBN was added as a polymerization initiator in 13 portions every 30 minutes, and the mixture was allowed to react for another 2 hours after the addition of the polymerization initiator. DMF was added so that the solid concentration was 30%, and a comparative resin (H-2) solution, which is a polymer unit of an ethylenically unsaturated monomer, was obtained.

Comparative Production Example 3 Comparative Resin (H-3) Solution 100.0 parts of BPADA, 38.3 parts of BAPP, 80.1 parts of KF-8010, and 510 parts of DMF were charged into a reaction vessel equipped with a gas inlet tube, a thermometer, a condenser, and a stirrer, and the atmosphere was replaced with nitrogen gas. The reaction vessel was heated to 150° C. with stirring, and the reaction was allowed to proceed until the acid value became less than 5 mgKOH/g, thereby obtaining a polyimide unit.
Then, the mixture was cooled to 80° C., 0.89 parts of 2-aminoethanethiol was added, and the mixture was reacted at 80° C. for 5 hours to obtain a polyimide prepolymer.
Next, 94.0 parts of MMA and 221 parts of DMF were added to the polyimide prepolymer returned to room temperature, and the mixture was stirred uniformly, and then heated to 75° C. under a nitrogen atmosphere. 0.1 parts of AIBN was added thereto as a polymerization initiator in 13 divided portions every 30 minutes, and the mixture was further reacted for 2 hours after the addition of the polymerization initiator to form a polymer unit of an ethylenically unsaturated monomer, and DMF was added so that the solid content concentration became 30%, to obtain a comparative resin (H-3) solution, which is a block polymer in which a polyimide unit and a polymer unit of an ethylenically unsaturated monomer not having a structural unit derived from an ethylenically unsaturated monomer (b1) having a carboxy group are linked by a chain transfer agent residue.

<Preparation of Curable Composition>
[Example 1]
333.3 parts of a block polymer (C-1) solution with a solid content of 30% (100.0 parts as block polymer), 100.0 parts of JER828US as a compound (D) having two or more epoxy groups in the molecule, 3.6 parts of C11Z-CN as a curing catalyst, and 690.0 parts of AGG50 as a filler (E) were added and kneaded using a homodisper type stirrer. When the homodisper type stirrer was difficult to rotate during kneading, the mixture was appropriately diluted with a solvent (DMF).
The obtained kneaded liquid was applied onto a release film (PET-38 GS, manufactured by Lintec Corporation) using a doctor blade so that the thickness after drying would be 200 μm, and the coating was dried at 100° C. under reduced pressure, and the release film was peeled off to obtain a sheet-like curable composition.

[Examples 2 to 46, Comparative Examples 1 to 6]
The same operation as in Example 1 was carried out, except that the blending compositions were changed to those shown in Tables 4 to 7, to obtain sheet-shaped curable compositions of Examples 2 to 46 and Comparative Examples 1 to 6. In Comparative Examples 2 and 5, the filler (E) was not dispersed, so that a curable composition could not be obtained.

<Evaluation of Curable Composition>
The obtained sheet-shaped curable compositions (hereinafter also referred to as sheets) were used to carry out the following evaluations. The results are shown in Tables 4 to 7.

[Adhesion test]
The obtained sheet was cut into a size of 10.0 mm x 25.0 mm, and the cut sheet was sandwiched between two copper substrates (dimensions: 2.0 mm x 25 mm x 100 mm), and pressed and bonded for 1 hour using a press under conditions of 180 ° C. and a press pressure of 5 MPa to obtain a test piece. The test piece was pulled using a tensile tester under conditions of a temperature of 23 ° C. and a relative humidity of 50%, and the shear adhesive strength (MPa) between the two copper substrates was measured and evaluated according to the following criteria. The larger the shear adhesive strength value, the better, and the practical level is B or higher.
(Evaluation Criteria)
S: Shear adhesive strength is 10.0 MPa or more (very good)
A: Shear adhesive strength is 7.0 MPa or more and less than 10.0 MPa (good)
B: Shear adhesive strength is 4.0 MPa or more and less than 7.0 MPa (usable)
C: Shear adhesive strength is less than 4.0 MPa (unusable)

[Cold-heat cycle test]
The obtained sheet was cut into a size of 10.0 mm x 25.0 mm, and the cut sheet was sandwiched between a copper substrate (dimensions: 2.0 mm x 25 mm x 100 mm) and an aluminum substrate (dimensions: 2.0 mm x 25 mm x 100 mm), and pressed and bonded for 1 hour using a press under conditions of 180 ° C. and a press pressure of 5 MPa to obtain a test piece. The test piece was placed in a thermal cycle tester (manufactured by Tabai Espec Co., Ltd.) and subjected to 1000 cycles, with one cycle being at -40 ° C. for 15 minutes and at 150 ° C. for 15 minutes. The test piece after the thermal test was pulled using a tensile tester under conditions of a temperature of 23 ° C. and a relative humidity of 50%, and the shear adhesive strength (MPa) between the copper substrate and the aluminum substrate was measured and judged according to the following criteria. The larger the numerical value of the shear adhesive strength, the better it is, and the practical level is B or higher.
(Evaluation Criteria)
S: Shear adhesive strength of 5.0 MPa or more (very good)
A: Shear adhesive strength is 3.5 MPa or more and less than 5.0 MPa (good)
B: Shear adhesive strength is 2.0 MPa or more and less than 3.5 MPa (usable)
C: Shear adhesive strength is less than 2.0 MPa (unusable)

[Heat resistance test]
The obtained sheet was cut into 5 mm-wide strips to prepare test pieces, which were then left to stand in an oven at 180°C for 1000 hours. The test pieces before and after a 180°C, 1000-hour heat resistance test were subjected to dynamic viscoelasticity measurement using DVA-200/L2 (IT Measurement and Control Co., Ltd.). The measurement conditions for dynamic viscoelasticity are as follows. Using the temperature of the tan δ peak top, the temperature change (°C) of the tan δ peak top before and after the heat resistance test was calculated, and the results were judged according to the following criteria. The less the temperature of tan δ before and after the heat resistance test, the better the product, and the practical level is B or higher.
<Dynamic viscoelasticity measurement conditions>
Measurement mode: Tensile mode Frequency: 10Hz
Temperature range: -80°C to measurement limit Temperature rise condition: 10°C/min
(Evaluation Criteria)
S: Temperature change of tan δ peak top is less than 20° C. (very good)
A: The temperature change of the tan δ peak top is 20° C. or more and less than 35° C. (good)
B: The temperature change of the tan δ peak top is 35°C or more and less than 50°C (usable)
C: The temperature change of the tan δ peak top is 50°C or more (unusable)

[Thermal Conductivity Test]
The obtained sheet was cut into 10 mm squares and blackened with graphite spray, and then the thermal diffusivity was evaluated using the xenon flash method (manufactured by NETZSCH). The thermal conductivity of the cured product was calculated from the product of this value, the density measured by the Archimedes method, and the specific heat measured by DSC (manufactured by PerkinElmer). The higher the thermal conductivity value, the better the product, and the practical level is B or higher.
(Evaluation Criteria for Heat Resistance)
S: Thermal conductivity is 10 W/m·K or more (very good)
A: Thermal conductivity is 6 W/m.K or more and less than 10 W/m.K (good)
B: Thermal conductivity is 2 W/m.K or more and less than 6 W/m.K (usable)
C: Thermal conductivity is less than 2 W/m K (unusable)

According to the evaluation results in Tables 4 to 7, when the curable composition of the present invention contains a high blend ratio of filler, it has high adhesive strength and excellent flexibility, and therefore exhibits good thermal cycle properties. Furthermore, the curable composition of the present invention has excellent heat resistance that allows it to maintain adhesive strength even in high temperature environments. Furthermore, the curable composition of the present invention can contain a high blend ratio of thermally conductive filler, and exhibits excellent thermal conductivity.

Claims (7)

A curable composition comprising: a block polymer (C) in which a polyimide unit (A) and a polymer unit (B) of an ethylenically unsaturated monomer are linked by a chain transfer agent residue; a compound (D) having two or more epoxy groups in the molecule; and a filler (E),
the polyimide unit (A) contains a structural unit having a siloxane skeleton in a range of 20 to 60 mass % based on the mass of the polyimide unit (A);
The curable composition, wherein the polymer unit (B) of an ethylenically unsaturated monomer has a structural unit derived from an ethylenically unsaturated monomer (b1) having a carboxy group. The curable composition according to claim 1, wherein the block polymer (C) contains 10 to 50 mass% of the polymer unit (B) of an ethylenically unsaturated monomer based on the mass of the block polymer (C). The curable composition according to claim 1 or 2, wherein the ethylenically unsaturated monomer constituting the ethylenically unsaturated monomer polymer unit (B) contains an ethylenically unsaturated monomer (b1) having a carboxy group in an amount ranging from 2.5 to 45% by mass based on the total mass of the ethylenically unsaturated monomers. The curable composition according to any one of claims 1 to 3, which contains a compound (D) having two or more epoxy groups in the molecule in an amount ranging from 50 to 200 mass% based on the mass of the block polymer (C). The curable composition according to any one of claims 1 to 4, wherein the filler (E) is a thermally conductive filler. A cured product obtained by curing the curable composition according to any one of claims 1 to 5 . A laminate comprising a substrate and a layer comprising the cured product according to claim 6 .