Thermally conductive composition and thermally conductive sheet

Abstract

To provide a thermally conductive composition that can be irradiated with light to give a thermally conductive sheet having high thermal conductivity and thickness with high productivity.SOLUTION: A thermally conductive composition contains: a binder component containing a photopolymerization initiator and at least one of a radical polymerizable monomer and a partial polymer thereof; and a thermally conductive filler. Relative to the binder component 100 pts.vol., the thermally conductive filler is 100 pts.vol. or more and 900 pts.vol. or less. The photopolymerization initiator is a triazine peroxide derivative represented by the general formula (1).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a thermally conductive composition and a thermally conductive sheet. [Background technology]

[0002] It is important to dissipate heat generated by various electronic and electrical devices. In recent years, with the advancement of high performance and diversification, heat dissipation materials are used in automotive electrical components and communication devices by sandwiching them between heat generating bodies such as IC devices and heat dissipating bodies such as heat sinks, and there is a demand for heat dissipation materials with high thermal conductivity and thick film. Examples of heat dissipation materials include heat dissipation sheets, heat dissipation gap fillers, heat dissipation adhesives, and heat dissipation greases. However, there is a growing interest in heat conductive sheets that are easy to work with because they do not require any particular control over the amount of material applied and have no fluidity, and can be simply sandwiched between the desired heat generating body and heat dissipating body.

[0003] One method for increasing the thermal conductivity of a thermally conductive sheet is to increase the content of thermally conductive filler, and in Patent Document 1, a thermally conductive sheet with high thermal conductivity and a thick film is produced by thermal curing. In addition, in Patent Documents 2 and 3, in order to increase productivity, a photopolymerizable composition containing a photopolymerization initiator is used to produce a thermally conductive sheet by photocuring with ultraviolet light irradiation.

[0004] Moreover, Patent Document 4 discloses a triazine peroxide derivative having both photopolymerizability and thermal polymerizability as a photopolymerization initiator. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2006-111644 A [Patent Document 2] JP 2019-85441 A [Patent Document 3] JP 2020-45386 A [Patent Document 4] JP 2020-094196 A Summary of the Invention [Problem to be solved by the invention]

[0006] In light of the above, while demand for thermally conductive sheets is expected to increase, the method of producing a thick thermally conductive sheet by heat curing, as in Patent Document 1, requires a long time for polymerization at high temperatures because the curing efficiency is lower than that of curing by ultraviolet irradiation, and there is a limit to how much the polymerization time can be shortened even if the polymerization conditions are optimized.

[0007] On the other hand, in the method of producing a thermally conductive sheet by photocuring as in Patent Documents 2 and 3, when the content of the thermally conductive filler is increased, the light transmittance decreases even when irradiated with light such as ultraviolet light, making it difficult for the light to reach deep inside, limiting the film thickness and resulting in a thin sheet. Therefore, in order to produce a thick thermally conductive sheet, the content of the filler is limited, resulting in a sheet with low thermal conductivity.

[0008] Furthermore, Patent Document 4 suggests that a thick cured material can be produced by using a triazine peroxide derivative having both photopolymerizability and thermal polymerizability as a photopolymerization initiator. However, it was unclear whether the triazine peroxide derivative could provide a cured material having good curability even in a composition highly filled with a filler having high thermal diffusivity, such as a thermally conductive filler.

[0009] Therefore, an object of the present invention is to provide a thermally conductive composition which, when irradiated with light, can provide a thermally conductive sheet having high thermal conductivity and a thick film with good productivity.

[0010] Another object of the present invention is to provide a thermally conductive sheet which is a cured product of the thermally conductive composition. [Means for solving the problem]

[0011] The present invention relates to a thermally conductive composition comprising a binder component containing at least one of a radical polymerizable monomer and a partial polymer thereof, as well as a photopolymerization initiator, and a thermally conductive filler, wherein the thermally conductive filler is present in an amount of 100 to 900 parts by volume per 100 parts by volume of the binder component, and the photopolymerization initiator is a triazine peroxide derivative represented by the following general formula (1). [ka] (In formula (1), R 1 and R 2 R independently represents a methyl group or an ethyl group. 3 X represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group. 1 , Ar 2 , Ar 3 or Ar 4 where n is an integer of 0 to 2. [ka] (In formula (2), m represents an integer of 0 to 3. 4 are independent substituents, and each is an alkyl group having 1 to 18 carbon atoms; 5 The R represents a substituent represented by -Y-, a nitro group, or a cyano group. The Y represents an oxygen atom or a sulfur atom. 5 represents a hydrocarbon group having 1 to 18 carbon atoms which may have at least one of an ether bond, a thioether bond, and a hydroxyl group at a terminal in the carbon skeleton, an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group, or an acyl group having 1 to 8 carbon atoms. 4 R is two adjacent 5 -Y- may form a 5- or 6-membered ring.

[0012] The present invention also relates to a thermally conductive sheet which is a cured product of the thermally conductive composition. Effect of the Invention

[0013] Even when the thermally conductive composition of the present invention is highly loaded with a filler having high thermal diffusivity, such as a thermally conductive filler, when photocured by irradiation with ultraviolet light, a thermally conductive sheet having high thermal conductivity and a thick film can be produced with good productivity. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The thermally conductive composition of the present invention contains a binder component containing at least one of a radically polymerizable monomer and a partial polymer thereof, and a photopolymerization initiator, and a thermally conductive filler. When the thermally conductive composition is photocured by irradiation with ultraviolet light, the triazine peroxide derivative is quickly activated and the composition is not easily affected by the thermal diffusivity of the highly filled thermally conductive filler, so that a thermally conductive sheet having high thermal conductivity and a thick film can be produced with good productivity.

[0015] <Radical polymerizable monomer> As the radical polymerizable monomer, a compound having an ethylenically unsaturated group can be preferably used. As the radical polymerizable monomer, for example, (meth)acrylic acid esters, styrenes, maleic acid esters, fumaric acid esters, itaconic acid esters, cinnamic acid esters, crotonic acid esters, vinyl ethers, vinyl esters, vinyl ketones, allyl ethers, allyl esters, N-substituted maleimides, N-vinyl compounds, unsaturated nitriles, olefins, etc. are listed. Among these, it is preferable to include (meth)acrylic acid esters having high reactivity. The radical polymerizable monomer may be used alone or in combination of two or more kinds.

[0016] The (meth)acrylic acid esters may be monofunctional or polyfunctional compounds. Examples of the monofunctional compounds include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, and stearyl (meth)acrylate; cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, and dicyclopentenyloxyethyl (meth)acrylate. -, 2-ethyl-2-adamantyl (meth)acrylate and other ester compounds of (meth)acrylic acid and alicyclic alcohol; aryl (meth)acrylates such as phenyl (meth)acrylate and benzyl (meth)acrylate; 2-hydroxyethyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, 3-hydroxy-1-adamantyl (meth)acrylate, hydroxyl-terminated polyethylene glycol mono(meth)acrylate, hydroxyl-terminated poly Monomers having a hydroxy group such as propylene glycol mono(meth)acrylate; methoxyethyl(meth)acrylate, methoxypolyethylene glycol(meth)acrylate, phenoxypolyethylene glycol(meth)acrylate, 2-phenylphenoxyethyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, (2-methyl-2-ethyl-1,3-dioxolan-4-yl)methyl(meth)acrylate, (3-ethyloxetan-3-yl)methyl(meth)acrylate, cyclic trimer Monomers having a chain or cyclic ether bond, such as thyrolpropane formal (meth)acrylate; and monomers having a nitrogen atom, such as N,N-dimethylaminoethyl (meth)acrylate, N,N-dimethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-isopropyl (meth)acrylamide, N,N-dimethylaminopropyl (meth)acrylamide, diacetone (meth)acrylamide, (meth)acryloylmorpholine, and N-(meth)acryloyloxyethylhexahydrophthalimide.Monomers having an isocyanate group such as 2-(meth)acryloyloxyethyl isocyanate; monomers having an epoxy group such as glycidyl (meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether; monomers having a phosphorus atom such as 2-((meth)acryloyloxy)ethyl phosphate; monomers having a silicon atom such as 3-(meth)acryloxypropyltrimethoxysilane; monomers having a fluorine atom such as 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3,3-pentafluoropropyl (meth)acrylate, and 2-(perfluorohexyl)ethyl (meth)acrylate; monomers having a carboxyl group such as (meth)acrylic acid, succinic acid mono(2-(meth)acryloyloxyethyl), phthalic acid mono(2-(meth)acryloyloxyethyl), maleic acid mono(2-(meth)acryloyloxyethyl), and ω-carboxy-polycaprolactone mono(meth)acrylate;

[0017] Examples of the polyfunctional compound include ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, polypropylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, pentaerythritol di(meth)acrylate monostearate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, hydroxypivalic acid neopentyl glycol di(meth)acrylate, glycerin propoxy tri(meth)acrylate tricyclodecane dimethanoate, and the like. Examples of the polyhydric alcohols include ester compounds of polyhydric alcohols such as aryl di(meth)acrylate, 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxyethoxyphenyl)propane, 9,9-bis(4-(2-(meth)acryloyloxyethoxy)phenyl)fluorene, and 9,9-bis(4-(2-(2-(meth)acryloyloxyethoxy)ethoxy)phenyl)fluorene with (meth)acrylic acid; bis(4-(meth)acryloxyphenyl)sulfide, bis(4-(meth)acryloylthiophenyl)sulfide, tris(2-(meth)acryloyloxyethyl)isocyanurate, ethylene bis(meth)acrylamide, zinc (meth)acrylate, zirconium (meth)acrylate, aliphatic urethane acrylate, aromatic urethane acrylate, epoxy acrylate, and polyester acrylate.

[0018] <Partial polymer of radical polymerizable monomer> The radical polymerizable monomer generally has a low viscosity, and therefore when mixed with a thermally conductive filler, the filler may settle. In this case, it is preferable to partially polymerize the radical polymerizable monomer in advance to increase the viscosity, and to obtain a partial polymer of the radical polymerizable monomer. The viscosity of the partial polymer of the radical polymerizable monomer is not particularly limited, but is preferably about 10 to 10,000 mPa·s.

[0019] The partial polymerization can be carried out by various methods, and known polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization, suspension polymerization, etc. During the polymerization, a partial polymer can be obtained by using a polymerization initiator such as a thermal polymerization initiator or a photopolymerization initiator depending on the polymerization method.

[0020] Examples of the thermal polymerization initiator used in partial polymerization include organic peroxides such as diacyl peroxides, peroxyketals, ketone peroxides, hydroperoxides, dialkyl peroxides, peroxy esters, and peroxydicarbonates; azo-based polymerization initiators, etc. Specific examples include lauroyl peroxide, benzoyl peroxide, cyclohexanone peroxide, 1,1-bis(t-butylperoxy)3,3,5-trimethylcyclohexane, t-butyl hydroperoxide, and 2,2'-azobisbutyronitrile.

[0021] Examples of photopolymerization initiators used for partial polymerization include aromatic ketones, benzoin ethers, halomethyloxadiazole compounds, α-aminoketones, α-aminoacetophenone compounds, acylphosphine compounds, biimidazoles, N,N-dimethylaminobenzophenone, triazine compounds, thioxanthone compounds, and oxime compounds.Specific examples of the photopolymerization initiator include aromatic ketones such as benzophenone, 4,4'-bisdiethylaminobenzophenone, and 4-methoxy-4'-dimethylaminobenzophenone; benzoin ethers such as benzoin methyl ether; benzoins such as ethylbenzoin; biimidazoles such as 2-(o-chlorophenyl)-4,5-phenylimidazole dimer; halomethyloxadiazole compounds such as 2-trichloromethyl-5-(p-methoxystyryl)-1,3,4-oxadiazole; naphth-1-yl)-4,6-bis-trichloromethyl-S-triazine, triazine-based compounds such as triazine peroxide derivatives represented by the following general formula (1); 2,2-dimethoxy-1,2-diphenylethan-1-one, 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropanone, 1,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1,1-hydroxy-cyclohexyl-phenyl ketone, benzyl, benzoylbenzoic acid, methyl benzoylbenzoate , 4-benzoyl-4'-methyldiphenyl sulfide, benzyl methyl ketal, dimethylaminobenzoate, p-dimethylaminobenzoic acid isoamyl, 2-n-butoxyethyl-4-dimethylaminobenzoate, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 4-benzoyl-methyldiphenyl sulfide, 1-hydroxy-cyclohexyl-phenyl ketone, 2-benzyl-2-(dimethylamino)-1-[4-(4- Examples of such compounds include 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, α-dimethoxy-α-phenylacetophenone, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 3-benzoyloxyiminobutan-2-one, and 3-acetoxyiminobutan-2-one. Among these, from the viewpoint of curing property during sheet production, it is preferable to use a triazine peroxide derivative represented by the following general formula (1).Alternatively, any combination of the thermal or photoinitiators mentioned above may be used.

[0022] <Photopolymerization initiator> The photopolymerization initiator of the present invention contains a triazine peroxide derivative represented by the following general formula (1). [ka] (In formula (1), R 1 and R 2 R independently represents a methyl group or an ethyl group. 3 X represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group. 1 , Ar 2 , Ar 3 or Ar 4 where n is an integer of 0 to 2. [ka] (In formula (2), m represents an integer of 0 to 3. 4 are independent substituents, and each is an alkyl group having 1 to 18 carbon atoms; 5 The R represents a substituent represented by -Y-, a nitro group, or a cyano group. The Y represents an oxygen atom or a sulfur atom. 5 represents a hydrocarbon group having 1 to 18 carbon atoms which may have at least one of an ether bond, a thioether bond, and a hydroxyl group at a terminal in the carbon skeleton, an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group, or an acyl group having 1 to 8 carbon atoms. 4 R is two adjacent 5 -Y- may form a 5- or 6-membered ring.

[0023] In the general formula (1), R 1 and R 2 R independently represents a methyl group or an ethyl group. 1 and R 2is preferably a methyl group, from the viewpoints of increasing the decomposition temperature of the triazine peroxide derivative and increasing the storage stability of the polymerizable composition.

[0024] In the general formula (1), R 3 R is an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group. The alkyl group may be either a straight chain or a branched chain. 3 Specific examples of the group include a methyl group, an ethyl group, a propyl group, a 2,2-dimethylpropyl group, a phenyl group, and an isopropylphenyl group. Among these, from the viewpoint of easiness in synthesis of the triazine peroxide derivative, a methyl group, an ethyl group, a propyl group, a 2,2-dimethylpropyl group, and a phenyl group are preferable. From the viewpoint of high sensitivity to irradiation light, a methyl group and an ethyl group are more preferable.

[0025] In the general formula (1), n ​​is an integer of 0 to 2. From the viewpoint of easiness in synthesis of the triazine peroxide derivative, n is preferably 0 or 1. When n is 0, X is Ar 2 , Ar 3 , or Ar 4 When n is 1, X is Ar 1 It is more preferable from the viewpoint of efficiently absorbing the irradiated light and reducing the yellowness of the cured product.

[0026] In the general formula (2), m is an integer of 0 to 3. From the viewpoint of easiness in synthesis of the triazine peroxide derivative, m is preferably 0 to 2, and from the viewpoint of efficient absorption of irradiated light, m ​​is more preferably 1.

[0027] In the general formula (2), R 4 are independent substituents, and each is an alkyl group having 1 to 18 carbon atoms; 5 The R represents a substituent represented by -Y-, a nitro group, or a cyano group. Y represents an oxygen atom or a sulfur atom. 5represents a hydrocarbon group having 1 to 18 carbon atoms which may have at least one of an ether bond, a thioether bond, and a hydroxyl group at a terminal in the carbon skeleton, an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group, or an acyl group having 1 to 8 carbon atoms. 4 R is two adjacent 5 -Y- may form a 5- or 6-membered ring.

[0028] R 4 is an independent substituent from the viewpoint of efficiently absorbing irradiated light, and is an alkyl group having 1 to 6 carbon atoms, or a group represented by the general formula (3): R 5 represents a substituent represented by -Y-, Y represents an oxygen atom, R 5 is preferably a hydrocarbon group having 1 to 6 carbon atoms which may have at least one of an ether bond and a hydroxyl group at a terminal in the carbon skeleton, or an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group. 4 R is two adjacent 5 It is preferable that —Y— forms a 5- or 6-membered ring.

[0029] R 4Specific examples of the aryloxy group include alkyl groups such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and an n-hexyl group; a methoxy group, an ethoxy group, an n-propyloxy group, an isopropyloxy group, an n-butyloxy group, a sec-butyloxy group, a tert-butyloxy group, an n-pentyloxy group, a cyclopentyloxy group, an n-hexyloxy group, a cyclohexyloxy group, a 2-hydroxyethoxy group, a 2-methoxyethoxy group, a 2-ethoxyethoxy group, a 2-butoxyethoxy group, a 2-(2-hydroxyethoxy)ethoxy group, a 2-(2-ethoxyethoxy)ethoxy group, a 1,2-dihydroxypropoxy group, and a methylenedioxy group. Examples of the functional groups include alkoxy groups such as oxy, dimethylmethylenedioxy, and ethylenedioxy; aryloxy groups such as phenyloxy and 4-isopropylphenyloxy; alkylsulfanyl groups such as methylsulfanyl, ethylsulfanyl, hexylsulfanyl, 2-methoxyethylsulfanyl, and 2-(2-methoxyethoxy)ethylsulfanyl; arylsulfanyl groups such as phenylsulfanyl, 2-methylphenylsulfanyl, and 4-methylphenylsulfanyl; and acyl groups such as acetyl, n-butanoyl, 2-ethylhexanoyl, benzoyl, and 2-methylbenzoyl. Compounds having these functional groups and represented by the general formula (1) are preferred because they have a high absorbance at 365 nm and efficiently absorb irradiated light.

[0030] Among these, the triazine peroxide derivatives R are particularly preferred because they have high solubility in the thermally conductive composition, are easy to synthesize, and are highly sensitive to irradiated light. 4 is more preferably a methoxy group, an ethoxy group, or a 2-hydroxyethoxy group.

[0031] R 4 The substitution position of X is not particularly limited, but 1 In the case of R 4 At least one of the following is preferably substituted at the 4-position of the benzene ring substituted with the triazine group. 2 In the case of R 4It is preferable that at least one of the following is substituted at the 4-position of a benzene ring other than the benzene ring substituted with the triazine group. 3 In the case of R 4 is preferably substituted at the 4-position of the triazine group substituted at the 1-position. 4 In the case of R 4 In order to efficiently absorb irradiated light, it is preferable that at least one of the above is substituted at the 4-position of a benzene ring other than the benzene ring substituted with the triazine group.

[0032] Specific examples of the triazine peroxide derivative are shown below, but the invention is not limited thereto. [ka] TIFF0007647240000006.tif216136TIFF0007647240000007.tif210136TIFF0007647240000008.tif109134

[0033] The triazine peroxide derivatives preferably include Compound 23, Compound 25, Compound 26, Compound 27, Compound 28, Compound 31, Compound 32, Compound 33, Compound 35, Compound 37, Compound 38, Compound 39, Compound 40, Compound 41, Compound 42, Compound 43, Compound 44, and Compound 46, and more preferably include Compound 25, Compound 26, Compound 31, Compound 32, Compound 35, Compound 37, Compound 38, Compound 41, and Compound 44.

[0034] The content of the triazine peroxide derivative is preferably 0.01 to 40 parts by mass, more preferably 0.05 to 20 parts by mass, and even more preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of at least one of the radical polymerizable monomer and the partial polymer thereof. If the content of the triazine peroxide derivative is less than 0.01 parts by mass relative to 100 parts by mass of at least one of the radical polymerizable monomer and the partial polymer thereof, the curing reaction does not proceed, which is not preferable. In addition, if the content of the triazine peroxide derivative is more than 40 parts by mass relative to 100 parts by mass of at least one of the radical polymerizable monomer and the partial polymer thereof, the solubility in at least one of the radical polymerizable monomer and the partial polymer thereof reaches saturation, crystals of the photopolymerization initiator are precipitated during film formation of the thermal conductive composition, and roughness of the film surface may become a problem, or light may not reach the depth of the cured product due to light absorption by the photopolymerization initiator itself. In addition, when the triazine peroxide derivative contains other polymerization initiators described below, the proportion of the other polymerization initiators in the total of the triazine peroxide derivative and the other polymerization initiators is preferably 80 mass % or less, and more preferably 50 mass % or less.

[0035] In addition, the thermally conductive composition can improve the surface curing property, deep curing property, etc. of the polymerizable composition by using other polymerization initiators other than the above triazine peroxide derivative. The other polymerization initiator is any of a thermal polymerization initiator and a photopolymerization initiator, and the selection is made taking into consideration at least one of a radical polymerizable monomer and its partial polymer, the type of thermally conductive filler, other additives, the amount of thermally conductive filler filled, the film thickness of the cured product, etc. Examples of the other polymerization initiator include the thermal polymerization initiator used for the partial polymerization and the photopolymerization initiator used for partial polymerization (excluding the triazine peroxide derivative represented by general formula (1)).

[0036] <Thermal conductive filler> The thermally conductive filler is not particularly limited, and examples thereof include aluminum oxide, silicon oxide, magnesium oxide, zinc oxide, titanium oxide, zirconium oxide, iron oxide, silicon carbide, boron nitride, aluminum nitride, titanium nitride, silicon nitride, titanium boride, carbon black, carbon fiber, carbon nanotube, diamond, nickel, copper, aluminum, titanium, gold, and silver. In order to improve the strength of the sheet, a filler whose surface has been treated with silane, titanate, or the like may be used. A filler whose surface has been coated with ceramics, polymer, or the like to provide a water-resistant coat, an insulating coat, or the like may also be used. Among these, a filler having high thermal conductivity at room temperature is preferred, and the thermal conductivity (W / m·k) at 20° C. is 1 or more, preferably 5 or more, and more preferably 10 or more. The thermally conductive filler may be used alone or in combination of two or more kinds.

[0037] The shape of the thermally conductive filler may be regular or irregular, for example, polygonal, cubic, elliptical, spherical, needle-like, flat, or flake-like, or a combination thereof. It may also be a particle formed by agglomeration of multiple crystal particles. The shape of the filler is selected based on the viscosity of the radical polymerizable monomer or its partial polymer and the ease of processing of the final thermally conductive composition after polymerization.

[0038] The average particle size of the thermally conductive filler is preferably 0.5 μm or more and 100 μm or less. In particular, from the standpoint of dispersibility and thermal conductivity, it is preferable to use a small-diameter filler having an average particle size of 1 μm or more and 20 μm or less in combination with a large-diameter filler having an average particle size of 25 μm or more and 100 μm or less.

[0039] The thermally conductive filler is 100 parts by volume or more and 900 parts by volume or less relative to 100 parts by volume of the binder component containing at least one of a radical polymerizable monomer and a partial polymer thereof, and a photopolymerization initiator. In the conventional composition photocured by ultraviolet light or the like, the content of the thermally conductive filler was limited in order to ensure the light transmittance required for curing, but since the thermally conductive composition of the present invention contains a triazine peroxide derivative, the thermally conductive filler can be contained in an amount of 100 parts by volume or more relative to 100 parts by volume of the binder component. The thermally conductive filler is preferably 200 parts by volume or more, more preferably 300 parts by volume or more, and preferably 700 parts by volume or less, and more preferably 600 parts by volume or less relative to 100 parts by volume of the binder component. If the amount of the thermally conductive filler is less than 100 parts by volume relative to 100 parts by volume of the binder component, sufficient thermal conductivity cannot be imparted, and if it exceeds 900 parts by volume, the strength of the thermally conductive sheet is weakened.

[0040] <Other additives, etc.> The thermally conductive composition may contain, as appropriate, known additives such as sensitizers (isopropylthioxanthone, diethylthioxanthone, 4,4'-bis(diethylamino)benzophenone, 9,10-dibutoxyanthracene, 9-phenylacridine, coumarin, ketocoumarin, acridine orange, camphorquinone, etc.), crosslinking agents, crosslinking accelerators, silane coupling agents, tackifier resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), antioxidants, fillers, colorants (pigments and dyes, etc.), ultraviolet absorbers, antioxidants, chain transfer agents, plasticizers, softeners, surfactants, antistatic agents, thickeners, flame retardants, inorganic compounds, inorganic fillers, and electromagnetic wave absorbing fillers, either alone or in combination, as long as the properties of the present embodiment are not impaired. In addition, various common solvents may be used when forming the thermally conductive sheet.

[0041] The method for mixing the above-mentioned constituent materials is not particularly limited. Although manual mixing is possible for small amounts, a general mixer such as a universal mixer, a planetary mixer, a hybrid mixer, a Henschel mixer, a kneader, a ball mill, or a mixing roll may be used.

[0042] <Thermal conductive sheet> The thermally conductive sheet of the present invention is a cured product of the thermally conductive composition.

[0043] The thermally conductive sheet can be processed by any of the conventional methods, such as roll coating, spin coating, dip coating, brush coating, bar coating, knife coating, die coating, doctor blade, extrusion molding, injection molding, and press molding.

[0044] The method for curing the thermally conductive composition is not particularly limited, and it is preferable to cure the composition by irradiation with active energy rays such as electron beams, ultraviolet rays, visible light, and radiation.

[0045] The active energy ray is preferably light having a wavelength of 250 to 450 nm, and more preferably light having a wavelength of 350 to 410 nm from the viewpoint of rapid curing. The exposure dose of the active energy ray should be appropriately set according to the wavelength and intensity of the active energy ray and the composition of the thermal conductive composition. The intensity of the active energy ray is optional, and curing can be performed in a short time at high intensity, and curing can be performed by extending the time at low intensity.

[0046] Examples of light sources for the light irradiation include low-pressure mercury lamps, high-pressure mercury lamps, extra-high-pressure mercury lamps, metal halide lamps, ultraviolet electrodeless lamps, light-emitting diodes (LEDs), xenon arc lamps, carbon arc lamps, sunlight, solid-state lasers such as YAG lasers, semiconductor lasers, gas lasers such as argon lasers, etc. When using visible light to infrared light, which is poorly absorbed by triazine peroxide derivatives, effective curing can be achieved by using a sensitizer that absorbs the light as the additive.

[0047] In addition, as the method for producing the cured product, a dual cure process may be applied, and a heating process may be performed before and after the process of irradiating with active energy rays. In the process of heating the thermally conductive composition, examples of the heating method include heating and ventilation heating. The heating method is not particularly limited, and examples of the heating method include an oven, a hot plate, infrared irradiation, and electromagnetic wave irradiation. In addition, examples of the ventilation heating method include a ventilation drying oven.

[0048] The thickness of the thermally conductive sheet is preferably 0.3 mm or more and 5 mm or less. Conventional compositions that are photocured by ultraviolet rays or the like have a limit on the thickness in order to ensure the light transmittance required for curing, but the thermally conductive composition of the present invention contains a triazine peroxide derivative, so it can be cured at a thickness of 0.3 mm or more and 5 mm or less. The thermally conductive sheet can be applied to various applications because it can be produced in a wide range of thicknesses (for example, a thickness of 0.5 mm or more, 0.8 mm or more can be exemplified). The thermally conductive sheet is usually used in a single layer, but can also be used in a multilayer structure of two or more layers as necessary. In addition, the thermally conductive sheet preferably has a thermal conductivity of 1.5 (W / m·K) or more, more preferably 2.0 (W / m·K) or more at room temperature (23° C.) under normal conditions. EXAMPLES

[0049] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0050] <Example 1> <Preparation of partial polymer> 0.5 parts by mass of compound 25 was mixed with 100 parts by mass of 2-ethylhexyl acrylate (2-EHA) as a photopolymerization initiator, and the mixture was irradiated with ultraviolet light to obtain a partial polymer in which 10 to 20% of the total amount of monomers was polymerized and thickened.

[0051] <Preparation of Thermally Conductive Composition> 85 parts by mass of the partial polymer of 2-ethylhexyl acrylate (2-EHA) obtained above, 15 parts by mass of isobornyl acrylate (IBXA), 0.1 parts by mass of 1,6-hexanediol diacrylate (HDDA), and 0.5 parts by mass of compound 25 as a photopolymerization initiator were mixed to obtain 100 parts by volume of a binder component, and 220 parts by volume of thermally conductive filler 1 (alumina: average particle size 50 μm, thermal conductivity at 20°C 25 W / m·k) and 80 parts by volume of thermally conductive filler 2 (alumina: average particle size 2 μm, thermal conductivity at 20°C 25 W / m·k) were mixed and stirred for 2 minutes with a planetary centrifugal mixer (THINKY, Awatori Rentaro ARV-310) to obtain a thermally conductive composition.

[0052] <Manufacture of thermally conductive sheets> The thermally conductive composition obtained above was sandwiched between the release-treated surfaces of two polyethylene terephthalate films, one of which had been subjected to a release treatment, using a spacer, and molded. Thereafter, ultraviolet light (illuminance 2000 mW / cm 2 ) was irradiated from one side of the two release films using a 365 nm LED light source. 2 ) was carried out for 10 seconds to cure the thermally conductive composition, thereby producing a thermally conductive sheet.

[0053] <Example 2> A thermally conductive sheet was produced in the same manner as in Example 1, except that in the production of the partial polymer and the preparation of the thermally conductive composition, compound 35 was used instead of compound 25 as the photopolymerization initiator.

[0054] <Example 3> A thermally conductive sheet was produced in the same manner as in Example 2, except that a monomer of 2-ethylhexyl acrylate (2-EHA) was used instead of a partial polymer of 2-ethylhexyl acrylate (2-EHA) as the radical polymerizable compound.

[0055] <Example 4> A thermally conductive sheet was produced in the same manner as in Example 1, except that in the production of the partial polymer and the preparation of the thermally conductive composition, compound 41 was used instead of compound 25 as the photopolymerization initiator.

[0056] <Example 5> A thermally conductive sheet was produced in the same manner as in Example 4, except that the amount of thermally conductive filler 1 mixed was changed to 150 parts by volume and the amount of thermally conductive filler 2 mixed was changed to 50 parts by volume relative to 100 parts by volume of the binder component.

[0057] <Example 6> A thermally conductive sheet was produced in the same manner as in Example 4, except that the thickness of the thermally conductive sheet after curing was changed to the thickness shown in Table 1 and the ultraviolet irradiation was carried out for 60 seconds.

[0058] <Example 7> A thermally conductive sheet was produced in the same manner as in Example 1, except that in the production of the partial polymer and the preparation of the thermally conductive composition, compound 44 was used instead of compound 25 as the photopolymerization initiator.

[0059] <Example 8> A thermally conductive sheet was produced in the same manner as in Example 7, except that the amount of thermally conductive filler 1 mixed was changed to 400 parts by volume and the amount of thermally conductive filler 2 mixed was changed to 150 parts by volume relative to 100 parts by volume of the binder component.

[0060] <Comparative Example 1> A thermally conductive sheet was produced in the same manner as in Example 1, except that in the production of the partial polymer and the preparation of the thermally conductive composition, compound R1 (2,4,6-trimethylbenzoyldiphenylphosphine oxide: manufactured by IGM) was used instead of compound 25 as a photopolymerization initiator, and 4 parts by mass of compound R1 was mixed with 100 parts by mass of 2-ethylhexyl acrylate (2-EHA) in the production of the partial polymer.

[0061] <Comparative Example 2> A thermally conductive sheet was produced in the same manner as in Example 1, except that the amount of thermally conductive filler 1 mixed was changed to 30 parts by volume and the amount of thermally conductive filler 2 mixed was changed to 15 parts by volume relative to 100 parts by volume of the binder component.

[0062] <Comparative Example 3> A thermally conductive sheet was produced in the same manner as in Example 1, except that the amount of thermally conductive filler 1 mixed was changed to 800 parts by volume and the amount of thermally conductive filler 2 mixed was changed to 300 parts by volume relative to 100 parts by volume of the binder component.

[0063] <Comparative Examples 4 and 5> In preparing the thermally conductive composition, a thermal polymerization initiator, compound R2 (lauroyl peroxide "Perloyl L": manufactured by NOF Corp.), was used instead of compound R1 as the polymerization initiator, and the thermally conductive sheet was produced in the same manner as in Comparative Example 1, except that heating at 150°C for 600 seconds or 900 seconds was performed instead of irradiating with ultraviolet light.

[0064] <Curability> When the release film was peeled off from the thermally conductive sheets obtained in the Examples and Comparative Examples, the interface between the thermally conductive sheet and the release film was visually observed. ◯: The release film can be peeled off smoothly and the thermal conductive sheet is not damaged. ×: The release film cannot be peeled off, or the thermal conductive sheet is damaged.

[0065] <Film thickness> The thickness of each of the thermally conductive sheets obtained in the examples and comparative examples was measured using a digital micrometer.

[0066] <Thermal conductivity> The thermal conductivity of the thermally conductive sheets obtained in the examples and comparative examples was measured using a thermal conductivity measuring device (QTM-710: manufactured by Kyoto Electronics Manufacturing Co., Ltd.).

[0067] [Table 1]

[0068] In Examples 1 to 8, thermally conductive sheets having high thermal conductivity and thick films were obtained.

[0069] Comparative Example 1 had poor curability because a photopolymerization initiator that was not a triazine peroxide derivative was used. Comparative Example 2 had poor thermal conductivity because the content of thermally conductive filler was low. Comparative Example 3 had poor curability because the content of thermally conductive filler was too high. Comparative Examples 4 and 5 used a thermal polymerization initiator (compound R2), so they were unable to cure even in 600 seconds, and took 900 seconds to cure.

Claims

1. a binder component containing at least one of a radical polymerizable monomer and a partial polymer thereof, and a photopolymerization initiator; A thermally conductive composition containing a thermally conductive filler, the thermally conductive filler is at least one selected from the group consisting of magnesium oxide, aluminum oxide, boron nitride, aluminum nitride, and carbon black, and has a thermal conductivity (W / m·k) at 20° C. of 10 or more; The thermally conductive filler is present in an amount of 300 parts by volume or more and 900 parts by volume or less relative to 100 parts by volume of the binder component, A thermally conductive composition, characterized in that the photopolymerization initiator is a triazine peroxide derivative represented by the following general formula (1): 【Chemistry 1】 (In formula (1), R １ and R ２ R independently represents a methyl group or an ethyl group. ３ X represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group. １ , Ar ２ , Ar ３ Or Ar ４ where n is an integer of 0 to 2. 【Chemistry 2】 (In formula (2), m represents an integer of 0 to 3. ４ are independent substituents, an alkyl group having 1 to 18 carbon atoms, a general formula (3): R ５ The R represents a substituent represented by -Y-, a nitro group, or a cyano group. The Y represents an oxygen atom or a sulfur atom. ５ represents a hydrocarbon group having 1 to 18 carbon atoms which may have one or more of an ether bond, a thioether bond, and a hydroxyl group at a terminal in the carbon skeleton, an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group, or an acyl group having 1 to 8 carbon atoms. ４ is two adjacent groups of the general formula (3): R ５ -Y- may form a 5- or 6-membered ring.

2. In the general formula (2), m represents an integer of 0 to 3; ４ are independent substituents, each of which is an alkyl group having 1 to 6 carbon atoms, or a group represented by the general formula (3): R ５ represents a substituent represented by -Y-, wherein Y represents an oxygen atom, and R ５ represents a hydrocarbon group having 1 to 6 carbon atoms which may have at least one of an ether bond and a hydroxyl group at a terminal in the carbon skeleton, or an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group, or R ４ is two adjacent groups of the general formula (3): R ５ 2. The thermally conductive composition according to claim 1, wherein -Y- may form a 5- or 6-membered ring.

3. A thermally conductive sheet comprising a cured product of the thermally conductive composition according to claim 1 or 2.

4. 4. The thermally conductive sheet according to claim 3, having a thickness of 0.3 mm or more and 5 mm or less.

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