JP2022156146A - Thermally conductive composition and thermally conductive sheet - Google Patents

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

The present invention relates to a thermally conductive composition and a thermally conductive sheet.

It is important to dissipate heat generated from various electronic and electrical devices. In recent years, with the advancement of high performance and diversification, in applications such as in-vehicle electrical components and communication equipment, heat dissipation countermeasure materials are used sandwiched between heating elements such as IC devices and radiators such as heat sinks, and have high thermal conductivity. , a thick-film heat-dissipating member is required. Heat-dissipating materials include heat-dissipating sheets, heat-dissipating gap fillers, heat-dissipating adhesives, heat-dissipating greases, etc. However, there is no particular need to control the amount of application and there is no fluidity, so it is sandwiched between the desired heat-generating body and heat-radiating body A thermally conductive sheet with excellent workability that can be used by itself is attracting attention.

As a method for increasing the thermal conductivity of a thermally conductive sheet, increasing the content of a thermally conductive filler can be mentioned. In Patent Document 1, a thermally conductive sheet with high thermal conductivity and a thick film is produced by thermosetting. ing. In addition, in order to improve productivity, in Patent Documents 2 and 3, a photopolymerizable composition containing a photopolymerization initiator is used, and a thermally conductive sheet is produced by photocuring with ultraviolet irradiation.

Moreover, in Patent Document 4, a triazine peroxide derivative having both photopolymerizability and thermal polymerizability is known as a photopolymerization initiator.

JP 2006-111644 A JP 2019-85441 A JP 2020-45386 A JP 2020-094196 A

With the above background, while the 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 has a higher curing efficiency than curing by ultraviolet irradiation. Since it is low, polymerization takes a long time at high temperatures, and there is a limit to shortening the polymerization time even if the polymerization conditions are optimized.

On the other hand, as in Patent Documents 2 and 3, in the method of producing a thermally conductive sheet by photocuring, if the content of the thermally conductive filler is increased, even if the light such as ultraviolet rays is irradiated, the light transmittance decreases and the deep part Since it is difficult to reach the target, the film thickness is limited, resulting in a thin sheet. Therefore, in order to produce a thick thermally conductive sheet, there is a problem that the filler content is limited, resulting in a sheet with low thermal conductivity.

Further, Patent Document 4 suggests that a thick cured product can be produced by using a triazine peroxide derivative having both photopolymerization and thermal polymerization properties as a photopolymerization initiator. It has been unclear whether a cured product having good curability can be obtained from a composition highly filled with a filler having high thermal diffusivity such as a thermally conductive filler.

Accordingly, an object of the present invention is to provide a thermally conductive composition from which a thermally conductive sheet having a high thermal conductivity and a thick film can be obtained with good productivity by light irradiation.

Another object of the present invention is to provide a thermally conductive sheet that is a cured product of the thermally conductive composition.

（式（１）中、Ｒ^１およびＲ^２は独立してメチル基またはエチル基を表す。Ｒ^３は炭素数１～５の脂肪族炭化水素基、またはアルキル基を有してもよい炭素数６～９の芳香族炭化水素基を表す。Ｘは下記一般式（２）：Ａｒ^１、Ａｒ^２、Ａｒ^３またはＡｒ^４で表されるアリール基である。ｎは０から２の整数を表す。）

（式（２）中、ｍは０から３の整数を表す。Ｒ^４は、独立した置換基であって、炭素数１から１８のアルキル基、一般式（３）：Ｒ^５－Ｙ－で表される置換基、ニトロ基、またはシアノ基を表す。前記Ｙは、酸素原子または硫黄原子を表す。前記Ｒ^５は、炭素骨格中に、エーテル結合、チオエーテル結合、および、末端に水酸基のいずれか１つ以上を有していてもよい炭素数１から１８の炭化水素基、アルキル基を有してもよい炭素数６～９の芳香族炭化水素基、または炭素数１～８のアシル基を表す。あるいは、Ｒ^４は隣接する２つの前記一般式（３）：Ｒ^５－Ｙ－により５～６員環を形成してもよい。） The present invention is a thermally conductive composition comprising 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, wherein 100 parts by volume of the binder component , the thermally conductive filler is 100 volume parts or more and 900 volume parts or less, and the photopolymerization initiator is a triazine peroxide derivative represented by the following general formula (1).

(In formula (1), R ¹ and R ² independently represent a methyl group or an ethyl group. R ³ represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or a carbon number which may have an alkyl group. represents an aromatic hydrocarbon group of 6 to 9. X is an aryl group represented by the following general formula (2): Ar ¹ , Ar ² , Ar ³ or Ar ^4. n represents an integer of 0 to 2 .)

(in formula (2), m represents an integer of 0 to 3; R ⁴ is an independent substituent, an alkyl group having 1 to 18 carbon atoms; general formula (3): R ⁵ -Y- represents a substituent, a nitro group, or a cyano group, Y represents an oxygen atom or a sulfur atom, and R ⁵ has an ether bond, a thioether bond, or a hydroxyl group at the end in the carbon skeleton. or a hydrocarbon group having 1 to 18 carbon atoms which may have one or more, 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 Alternatively, R ⁴ may form a 5- to 6-membered ring with two adjacent general formulas (3): R ⁵ -Y-.)

The present invention also relates to a thermally conductive sheet that is a cured product of the thermally conductive composition.

The thermally conductive composition of the present invention, even when highly filled with a filler having high thermal diffusivity such as a thermally conductive filler, has high thermal conductivity with good productivity when it is photocured by irradiating with ultraviolet rays. and a thermally conductive sheet having a thick film can be produced.

The thermally conductive composition of the present invention contains at least one of a radically polymerizable monomer and a partial polymer thereof, a binder component containing a photopolymerization initiator, and a thermally conductive filler. When the thermally conductive composition is irradiated with ultraviolet rays and photocured, the triazine peroxide derivative is quickly activated, and the thermal diffusion of the highly filled thermally conductive filler is not easily affected. A thermally conductive sheet having a high thermal conductivity and a thick film can be produced.

<Radical polymerizable monomer>
A compound having an ethylenically unsaturated group can be preferably used as the radically polymerizable monomer. Examples of radically polymerizable monomers include (meth)acrylic acid esters, styrenes, maleic acid esters, fumaric acid esters, itaconic acid esters, cinnamic acid esters, crotonic acid esters, vinyl ethers, and vinyl esters. , vinyl ketones, allyl ethers, allyl esters, N-substituted maleimides, N-vinyl compounds, unsaturated nitriles, olefins and the like. Among these, it is preferable to contain highly reactive (meth)acrylic acid esters. The radically polymerizable monomers may be used alone or in combination of two or more.

Monofunctional compounds and polyfunctional compounds can be used as the (meth)acrylic acid esters. Monofunctional compounds include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) Alkyl (meth)acrylates such as acrylates; cyclohexyl (meth)acrylate, isobornyl (meth)acrylate, dicyclopentanyl (meth)acrylate, dicyclopentenyl (meth)acrylate, dicyclopentenyloxyethyl (meth) Ester compounds of (meth)acrylic acid and alicyclic alcohol such as acrylate and 2-ethyl-2-adamantyl (meth)acrylate; 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 group-terminated polyethylene glycol mono ( Monomers having a hydroxyl group such as meth)acrylate, hydroxyl-terminated polypropylene glycol mono(meth)acrylate, etc.; methoxyethyl (meth)acrylate, methoxypolyethyleneglycol (meth)acrylate, phenoxypolyethyleneglycol (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 ( Monomers having a chain or cyclic ether bond such as meth)acrylate, cyclic trimethylolpropane formal (meth)acrylate, etc.; 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, N-(meth)acryloyloxyethylhexahydrophthalimide monomers having a nitrogen atom such as; 2-(meth) acryloyloxyethyl isocyanate monomers having an isocyanate group; glycidyl ( Epoxy group-containing monomers such as meth)acrylate and 4-hydroxybutyl (meth)acrylate glycidyl ether; Phosphorus atom-containing monomers such as 2-((meth)acryloyloxy)ethyl phosphate; 3-(meth)acryloxypropyl Silicon atom-containing monomers such as trimethoxysilane; 2,2,2-trifluoroethyl (meth)acrylate, 2,2,3,3,3-pentafluoropropyl (meth)acrylate, 2-(perfluorohexyl) Monomers having a fluorine atom such as ethyl (meth)acrylate; (meth)acrylic acid, monosuccinate (2-(meth)acryloyloxyethyl), monophthalate (2-(meth)acryloyloxyethyl), monomaleate monomers having a carboxyl group such as (2-(meth)acryloyloxyethyl), ω-carboxy-polycaprolactone mono(meth)acrylate, and the like;

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, neopentyl glycol hydroxypivalate di(meth)acrylate, glycerol propoxy tri(meth)acrylate tricyclodecane dimethanol di(meth)acrylate (Meth)acrylate, 2,2-bis(4-(meth)acryloxypolyethoxyphenyl)propane, 2,2-bis(4-(meth)acryloxyethoxyphenyl)propane, 9,9-bis(4- Polyhydric alcohols such as (2-(meth)acryloyloxyethoxy)phenyl)fluorene, 9,9-bis(4-(2-(2-(meth)acryloyloxyethoxy)ethoxy)phenyl)fluorene and (meth)acryl Ester compounds with acids; 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, polyester acrylate, and the like.

<Partial polymer of radically polymerizable monomer>
Since the radically polymerizable monomer generally has a low viscosity, the filler may settle when mixed with the thermally conductive filler. In this case, the radically polymerizable monomer is preferably partially polymerized and thickened in advance to form a partial polymer of the radically polymerizable monomer. Although the viscosity of the partial polymer of the radically polymerizable monomer is not particularly limited, it is preferably about 10 to 10,000 mPa·s.

Partial polymerization can be carried out by various methods, and known polymerization methods such as solution polymerization, emulsion polymerization, bulk polymerization and suspension polymerization can be employed. 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.

Thermal polymerization initiators used for partial polymerization include, for example, diacyl peroxides, peroxyketals, ketone peroxides, hydroperoxides, dialkyl peroxides, peroxyesters, peroxydicarbonates and the like. Organic peroxides; azo polymerization initiators and the like can be used. Specifically, lauroyl peroxide, benzoyl peroxide, cyclohexanone peroxide, 1,1-bis(t-butylperoxy) 3,3,5-trimethylcyclohexane, t-butyl hydroperoxide, 2,2'-azo bisbutyronitrile and the like.

Photopolymerization initiators used for partial polymerization include aromatic ketones, benzoin ethers, halomethyloxadiazole compounds, α-aminoketones, α-aminoacetophenone compounds, acylphosphine compounds, biimidazoles, N,N-dimethylamino Examples include benzophenone, triazine-based compounds, thioxanthone-based 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; ethylbenzoin. benzoin such as; 2-(o-chlorophenyl)-4,5-phenylimidazole dimer and other biimidazoles; 2-trichloromethyl-5-(p-methoxystyryl)-1,3,4-oxadiazole halomethyloxadiazole compounds such as; 2-(4-butoxy-naphth-1-yl)-4,6-bis-trichloromethyl-S-triazine, triazine peroxide derivatives represented by the following general formula (1), etc. 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-phenylketone, benzyl, benzoylbenzoic acid, methyl benzoylbenzoate, 4-benzoyl-4'-methyldiphenylsulfide, benzyl methyl ketal, dimethylaminobenzoate, isoamyl p-dimethylaminobenzoate, 2-n-butoxyethyl-4-dimethylaminobenzoate, 2-chlorothioxanthone, 2,4-diethylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 4-benzoyl-methyldiphenylsulfide, 1-hydroxy-cyclohexyl-phenylketone, 2-benzyl-2-(dimethylamino)-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-trimethyl benzoyl)phosphine oxide, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, 3-benzoyloxyiminobutane-2-one, 3-acetoxyiminobutane- 2-one and the like. Among these, it is preferable to use a triazine peroxide derivative represented by the following general formula (1) from the viewpoint of curability during sheet production. Alternatively, any combination of the thermal initiators or photoinitiators mentioned above can be used.

（式（１）中、Ｒ^１およびＲ^２は独立してメチル基またはエチル基を表す。Ｒ^３は炭素数１～５の脂肪族炭化水素基、またはアルキル基を有してもよい炭素数６～９の芳香族炭化水素基を表す。Ｘは下記一般式（２）：Ａｒ^１、Ａｒ^２、Ａｒ^３またはＡｒ^４で表されるアリール基である。ｎは０から２の整数を表す。）

（式（２）中、ｍは０から３の整数を表す。Ｒ^４は、独立した置換基であって、炭素数１から１８のアルキル基、一般式（３）：Ｒ^５－Ｙ－で表される置換基、ニトロ基、またはシアノ基を表す。前記Ｙは、酸素原子または硫黄原子を表す。前記Ｒ^５は、炭素骨格中に、エーテル結合、チオエーテル結合、および、末端に水酸基のいずれか１つ以上を有していてもよい炭素数１から１８の炭化水素基、アルキル基を有してもよい炭素数６～９の芳香族炭化水素基、または炭素数１～８のアシル基を表す。あるいは、Ｒ^４は隣接する２つの前記一般式（３）：Ｒ^５－Ｙ－により５～６員環を形成してもよい。） <Photoinitiator>
The photopolymerization initiator of the present invention contains a triazine peroxide derivative represented by the following general formula (1).

(In formula (1), R ¹ and R ² independently represent a methyl group or an ethyl group. R ³ represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or a carbon number which may have an alkyl group. represents an aromatic hydrocarbon group of 6 to 9. X is an aryl group represented by the following general formula (2): Ar ¹ , Ar ² , Ar ³ or Ar ^4. n represents an integer of 0 to 2 .)

(in formula (2), m represents an integer of 0 to 3; R ⁴ is an independent substituent, an alkyl group having 1 to 18 carbon atoms; general formula (3): R ⁵ -Y- represents a substituent, a nitro group, or a cyano group, Y represents an oxygen atom or a sulfur atom, and R ⁵ has an ether bond, a thioether bond, or a hydroxyl group at the end in the carbon skeleton. or a hydrocarbon group having 1 to 18 carbon atoms which may have one or more, 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 Alternatively, R ⁴ may form a 5- to 6-membered ring with two adjacent general formulas (3): R ⁵ -Y-.)

In general formula (1), R ¹ and R ² independently represent a methyl group or an ethyl group. R ¹ and R ² are preferably methyl groups from the viewpoint of increasing the decomposition temperature of the triazine peroxide derivative and increasing the storage stability of the polymerizable composition.

In the general formula (1), R ³ 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 linear or branched. Specific examples of R ³ include methyl group, ethyl group, propyl group, 2,2-dimethylpropyl group, phenyl group and isopropylphenyl group. Among these, a methyl group, an ethyl group, a propyl group, a 2,2-dimethylpropyl group, and a phenyl group are preferable from the viewpoint of easy synthesis of triazine peroxide derivatives. A methyl group and an ethyl group are more preferable because of their high sensitivity to irradiation light.

n in the general formula (1) is an integer of 0 to 2; n is preferably 0 or 1 from the viewpoint of easy synthesis of the triazine peroxide derivative. X is Ar ² , Ar ³ or Ar ⁴ when n is 0, and X is Ar ¹ when n is 1. It is more preferable from the viewpoint that the yellowness can be reduced.

m in the general formula (2) is an integer of 0 to 3; From the viewpoint of facilitating synthesis of the triazine peroxide derivative, m is preferably 0 to 2, and from the viewpoint of efficient absorption of irradiation light, m is more preferably 1.

In general formula (2), R ⁴ is an independent substituent and is an alkyl group having 1 to 18 carbon atoms, general formula (3): a substituent represented by R ⁵ -Y-, a nitro group , or represents a cyano group. Y represents an oxygen atom or a sulfur atom. R ⁵ has, in its carbon skeleton, an ether bond, a thioether bond, and a hydrocarbon group having 1 to 18 carbon atoms which may have one or more hydroxyl groups at its ends, and an alkyl group; represents an aromatic hydrocarbon group having 6 to 9 carbon atoms or an acyl group having 1 to 8 carbon atoms. Alternatively, R ⁴ may form a 5- to 6-membered ring with two adjacent groups of general formula (3): R ⁵ -Y-.

From the viewpoint of efficiently absorbing irradiation light, R ⁴ is an independent substituent which is an alkyl group having 1 to 6 carbon atoms, or a substituent represented by general formula (3): R ⁵ -Y- , Y represents an oxygen atom, and R ⁵ is a hydrocarbon group having 1 to 6 carbon atoms which may have one or more of an ether bond and a hydroxyl group at the end in the carbon skeleton. , or an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group. Alternatively, R ⁴ preferably forms a 5- to 6-membered ring with two adjacent general formulas (3): R ⁵ -Y-.

Specific examples of R ⁴ include alkyl groups such as methyl group, ethyl group, n-propyl group, isopropyl group and n-hexyl group; methoxy group, ethoxy group, n-propyloxy group, isopropyloxy group; n-butyloxy group, sec-butyloxy group, tert-butyloxy group, n-pentyloxy group, cyclopentyloxy group, n-hexyloxy group, cyclohexyloxy group, 2-hydroxyethoxy group, 2-methoxyethoxy group, 2-ethoxy ethoxy group, 2-butoxyethoxy group, 2-(2-hydroxyethoxy)ethoxy group, 2-(2-ethoxyethoxy)ethoxy group, 1,2-dihydroxypropoxy group, methylenedioxy group, dimethylmethylenedioxy group, alkoxy groups such as ethylenedioxy group; aryloxy groups such as phenyloxy group and 4-isopropylphenyloxy group; methylsulfanyl group, ethylsulfanyl group, hexylsulfanyl group, 2-methoxyethylsulfanyl group, 2-(2-methoxy Alkylsulfanyl groups such as ethoxy)ethylsulfanyl group; Arylsulfanyl groups such as phenylsulfanyl group, 2-methylphenylsulfanyl group and 4-methylphenylsulfanyl group; and acyl groups such as 2-methylbenzoyl group. Compounds represented by general formula (1) having these functional groups are preferable because they have high absorbance at 365 nm and efficiently absorb irradiation light.

Furthermore, among these, ^triazine peroxide derivatives have high solubility in thermally conductive compositions, are easy to synthesize, and have high sensitivity to irradiation light. A hydroxyethoxy group is more preferred.

The substitution position of R ⁴ is not particularly limited, but when X is Ar ¹ , at least one R ⁴ is preferably substituted at the 4-position of the benzene ring substituted with a triazine group. Moreover, when X is Ar ² , at least one of R ⁴ is preferably substituted at the 4-position of a benzene ring other than the benzene ring substituted with the triazine group. Also, when X is Ar ³ , at least one R ⁴ is preferably substituted at the 4-position of the triazine group substituted at the 1-position. Moreover, when X is Ar ⁴ , at least one of R ⁴ is preferably substituted at the 4-position of a benzene ring other than the benzene ring substituted with a triazine group, in order to efficiently absorb irradiation light.

Specific examples of the triazine peroxide derivative are shown below, but are not limited thereto.

As the triazine peroxide derivative, preferably 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 compound 25, compound 26, compound 31, compound 32, compound 35, compound 37, compound 38, compound 41 and compound 44.

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, with respect to 100 parts by mass of at least one of the radically polymerizable monomer and the partial polymer thereof. more preferably 0.1 to 10 parts by mass. If the content of the triazine peroxide derivative is less than 0.01 parts by mass with respect to 100 parts by mass of at least one of the radically polymerizable monomer and the partial polymer thereof, the curing reaction does not proceed, which is not preferable. When the content of the triazine peroxide derivative is more than 40 parts by mass with respect to 100 parts by mass of at least one of the radically polymerizable monomer and the partial polymer thereof, at least one of the radically polymerizable monomer and the partial polymer thereof When the solubility of the photopolymerization initiator reaches saturation, crystals of the photopolymerization initiator precipitate during the film formation of the thermally conductive composition, and roughening of the film surface becomes a problem. It is not preferable because the light does not reach the deep part of the In addition, when the triazine peroxide derivative contains the following other polymerization initiator, the ratio of the other polymerization initiator is preferably 80% by mass or less in the total of the triazine peroxide derivative and the other polymerization initiator. It is more preferably 50% by mass or less.

In addition to the triazine peroxide derivative described above, the thermally conductive composition can be improved in surface curability, depth curability, etc. of the polymerizable composition by using other polymerization initiators. Other polymerization initiators are optional thermal polymerization initiators or photopolymerization initiators, and when selected, at least one of radically polymerizable monomers and partial polymers thereof, thermally conductive fillers, types of other additives, thermal conductivity The filling amount of the filler, the film thickness of the cured product, and the like are taken into consideration. Examples of the other polymerization initiator include the thermal polymerization initiator used for the partial polymerization and the photopolymerization initiator used for the partial polymerization (excluding the triazine peroxide derivative represented by the general formula (1)). mentioned.

<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, silver and the like. In order to improve the strength of the sheet, a filler surface-treated with silane, titanate, or the like may be used. In addition, a filler having a surface coated with ceramics, polymer, etc., such as a waterproof coating, an insulating coating, or the like, may also be used. Among these, those having high thermal conductivity at room temperature are preferred, and the thermal conductivity (W/m·k) at 20°C is 1 or more, preferably 5 or more, more preferably 10 or more. The thermally conductive fillers may be used alone or in combination of two or more.

The shape of the thermally conductive filler is regular or irregular, and examples thereof include polygonal, cubic, elliptical, spherical, needle-like, plate-like, flake-like, or combinations thereof. . Alternatively, particles in which a plurality of crystal particles are aggregated may be used. The shape of the filler is selected according to the viscosity of the radically polymerizable monomer or its partial polymer and the processability of the final thermally conductive composition after polymerization.

In addition, the average particle size of the thermally conductive filler is preferably 0.5 μm or more and 100 μm or less. It is preferable to use a large-diameter filler having a particle size of 25 μm or more and 100 μm or less.

The thermally conductive filler is 100 volume parts or more and 900 volume parts or less with respect to 100 volume parts of the binder component containing at least one of the radically polymerizable monomer and its partial polymer and the photopolymerization initiator. In conventional compositions that are photocured by ultraviolet light or the like, the content of the thermally conductive filler is limited in order to ensure the light transmittance necessary for curing, but the thermally conductive composition of the present invention is a triazine peroxide derivative , the thermally conductive filler can be contained in an amount of 100 parts by volume or more with respect 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 with respect to 100 parts by volume of the binder component, It is more preferably 600 parts by volume or less. If the amount of the thermally conductive filler is less than 100 parts by volume with respect to 100 parts by volume of the binder component, sufficient thermal conductivity cannot be imparted.

<Other additives, etc.>
The thermally conductive composition may optionally contain a sensitizer (isopropylthioxanthone, diethylthioxanthone, 4,4′-bis(diethylamino)benzophenone, 9,10-dibutoxyanthracene, 9-phenylacridine, coumarin, ketocoumarin, acridine orange, camphorquinone, etc.), cross-linking agents, cross-linking accelerators, silane coupling agents, tackifying resins (rosin derivatives, polyterpene resins, petroleum resins, oil-soluble phenols, etc.), anti-aging agents, fillers, coloring agents (pigments and dyes, etc.), UV absorbers, antioxidants, chain transfer agents, plasticizers, softeners, surfactants, antistatic agents, thickeners, flame retardants, inorganic compounds, inorganic fillers, electromagnetic wave absorbing fillers, etc. Known additives can be used singly or in combination as long as the properties of the present embodiment are not impaired. Moreover, when forming the said heat conductive sheet, various general solvents can also be used.

The method of mixing each of the above constituent materials is not particularly limited, but manual mixing is possible for small amounts, but universal mixers, planetary mixers, hybrid mixers, Henschel mixers, kneaders, ball mills, and mixing. Common mixers such as rolls are used.

<Heat conductive sheet>
The thermally conductive sheet of the present invention is a cured product of the thermally conductive composition.

Examples of the method for processing the heat conductive sheet include conventionally known methods such as roll coating, spin coating, dip coating, brush coating, bar coating, knife coating, die coating, doctor blade, Various molding methods such as extrusion molding, injection molding, and press molding can be used.

The method for curing the thermally conductive composition is not particularly limited, and irradiation with active energy rays such as electron beams, ultraviolet rays, visible rays, and radiation is preferable.

The active energy ray preferably has a wavelength of 250 to 450 nm, and more preferably 350 to 410 nm from the viewpoint of rapid curing. The amount of exposure to the active energy ray should be appropriately set according to the wavelength and intensity of the active energy ray and the composition of the thermally conductive composition. In addition, the intensity of the active energy ray is arbitrary, and when the intensity is high, curing can be performed in a short time, and when the intensity is low, curing can be performed by extending the time.

Light sources for the light irradiation include low-pressure mercury lamps, high-pressure mercury lamps, ultra-high-pressure mercury lamps, metal halide lamps, ultraviolet electrodeless lamps, light emitting diodes (LEDs), xenon arc lamps, carbon arc lamps, sunlight, YAG lasers, and the like. A solid laser, a semiconductor laser, a gas laser such as an argon laser, or the like can be used. When visible light to infrared light, which is less absorbed by the triazine peroxide derivative, is used, effective curing can be achieved by using a sensitizer that absorbs the light as the additive. .

In addition, as the method for producing the cured product, a dual curing step may be applied, and a step of heating may be performed before and after the step of irradiating with active energy rays. In the step of heating the thermally conductive composition, the method of heating includes, for example, heating, ventilation heating, and the like. The heating method is not particularly limited, and examples thereof include an oven, a hot plate, infrared irradiation, electromagnetic wave irradiation and the like. Moreover, as a ventilation heating method, for example, a ventilation drying oven or the like can be used.

The film thickness of the thermally conductive sheet is preferably 0.3 mm or more and 5 mm or less. Conventional compositions that are photo-cured with ultraviolet light or the like have limitations on the film thickness in order to ensure the light transmittance necessary for curing. A film thickness of 3 mm or more and 5 mm or less can be cured. The thermally conductive sheet can be produced in a wide range of film thicknesses (for example, film thicknesses of 0.5 mm or more and 0.8 mm or more can be exemplified), so that it can be applied to various uses. The thermally conductive sheet is usually used as a single layer, but may be used as a multilayer of two or more layers, if necessary. In addition, the thermally conductive sheet preferably has a thermal conductivity of 1.5 (W/mK) or more at room temperature (23°C) under a general environment, and preferably 2.0 (W/mK). ) or more is more preferable.

The present invention will be described in more detail with reference to examples below. The invention is not limited to these examples.

<Example 1>
<Preparation of partial polymer>
0.5 parts by mass of compound 25 as a photopolymerization initiator is mixed with 100 parts by mass of 2-ethylhexyl acrylate (2-EHA) and irradiated with ultraviolet rays to polymerize 10 to 20% of the total amount of monomers. to obtain a thickened partial polymer.

<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), and 0.1 part of 1,6-hexanediol diacrylate (HDDA) were added. Thermally conductive filler 1 (alumina: average particle diameter 50 μm, thermal conductivity at 20° C.) 25 W / m · k) and 80 volume parts of thermally conductive filler 2 (alumina: average particle size 2 μm, thermal conductivity at 20 ° C. 25 W / m · k) were mixed, and a rotation and revolution mixer (THINKY A thermally conductive composition was obtained by stirring for 2 minutes with Awatori Mixer ARV-310).

<Production of thermally conductive sheet>
The heat conductive composition obtained above was sandwiched between the release-treated surfaces of two polyethylene terephthalate films, each of which had been subjected to a release treatment on one side, using a spacer. After that, ultraviolet irradiation (illuminance of 2000 mW/cm ² ) was performed for 10 seconds from one side of the two release films using a 365 nm LED light source to cure the thermally conductive composition, thereby producing a thermally conductive sheet.

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

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

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

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

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

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

<Example 8>
Heating was carried out in the same manner as in Example 7 except that the mixed amount of the thermally conductive filler 1 was changed to 400 parts by volume and the mixed amount of the thermally conductive filler 2 was changed to 150 parts by volume with respect to 100 parts by volume of the binder component. A conductive sheet was produced.

<Comparative Example 1>
Using compound R1 (2,4,6-trimethylbenzoyldiphenylphosphine oxide: manufactured by IGM) as a photopolymerization initiator in place of compound 25 in the preparation of the partial polymer and the preparation of the thermally conductive composition, and A thermally conductive sheet was produced in the same manner as in Example 1, except that 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.

<Comparative Example 2>
Heat conduction was performed in the same manner as in Example 1 except that the mixed amount of the thermally conductive filler 1 was changed to 30 parts by volume and the mixed amount of the thermally conductive filler 2 was changed to 15 parts by volume with respect to 100 parts by volume of the binder component. A sex sheet was produced.

<Comparative Example 3>
Heat conduction was performed in the same manner as in Example 1 except that the mixed amount of the thermally conductive filler 1 was changed to 800 parts by volume and the mixed amount of the thermally conductive filler 2 was changed to 300 parts by volume with respect to 100 parts by volume of the binder component. A sex sheet was produced.

<Comparative Examples 4 and 5>
In the preparation of the thermally conductive composition, compound R2 (lauroyl peroxide "Perroyl L" manufactured by NOF), which is a thermal polymerization initiator, was used instead of compound R1 as a polymerization initiator, and instead of irradiating ultraviolet rays Second, a thermally conductive sheet was produced in the same manner as in Comparative Example 1, except that heating was performed at 150° C. for 600 seconds or 900 seconds.

<Curability>
When peeling off the release film of the thermally conductive sheet obtained in 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 thermally conductive sheet is not damaged.
x: The release film cannot be peeled off, or the thermally conductive sheet is damaged.

<Film thickness>
The film thickness of the thermally conductive sheets obtained in Examples and Comparative Examples was measured using a digital micrometer.

<Thermal conductivity>
The thermal conductivity of the thermally conductive sheets obtained in Examples and Comparative Examples was measured using a thermal conductivity meter (QTM-710: manufactured by Kyoto Electronics Industry Co., Ltd.).

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

Comparative Example 1 used a photopolymerization initiator that was not a triazine peroxide derivative, resulting in poor curability. Comparative Example 2 had poor thermal conductivity because the content of the thermally conductive filler was small. Comparative Example 3 had poor curability because the content of the thermally conductive filler was too large. In Comparative Examples 4 and 5, since the thermal polymerization initiator (compound R2) was used, curing was not possible even in 600 seconds, and it took 900 seconds to cure.

Claims (4)

a binder component containing at least one of a radically 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 100 volume parts or more and 900 volume parts or less with respect to 100 volume parts of the binder component,
A thermally conductive composition, wherein the photopolymerization initiator is a triazine peroxide derivative represented by the following general formula (1).

(In formula (1), R ¹ and R ² independently represent a methyl group or an ethyl group. R ³ represents an aliphatic hydrocarbon group having 1 to 5 carbon atoms, or a carbon number which may have an alkyl group. represents an aromatic hydrocarbon group of 6 to 9. X is an aryl group represented by the following general formula (2): Ar ¹ , Ar ² , Ar ³ or Ar ^4. n represents an integer of 0 to 2 .)

(in formula (2), m represents an integer of 0 to 3; R ⁴ is an independent substituent, an alkyl group having 1 to 18 carbon atoms; general formula (3): R ⁵ -Y- represents a substituent, a nitro group, or a cyano group, Y represents an oxygen atom or a sulfur atom, and R ⁵ has an ether bond, a thioether bond, or a hydroxyl group at the end in the carbon skeleton. or a hydrocarbon group having 1 to 18 carbon atoms which may have one or more, 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 Alternatively, R ⁴ may form a 5- to 6-membered ring with two adjacent general formulas (3): R ⁵ -Y-.) In general formula (2), m represents an integer of 0 to 3, R ⁴ is an independent substituent and an alkyl group having 1 to 6 carbon atoms, or general formula (3): R ⁵ -Y represents a substituent represented by -, the Y represents an oxygen atom, and the R ⁵ may have one or more of an ether bond in the carbon skeleton and a hydroxyl group at the end. represents a hydrocarbon group having 1 to 6 carbon atoms or an aromatic hydrocarbon group having 6 to 9 carbon atoms which may have an alkyl group, or R ⁴ represents two adjacent general formulas (3): R 2. The thermally conductive composition according to claim 1, wherein ⁵ -Y- may form a 5- to 6-membered ring. A thermally conductive sheet, which is a cured product of the thermally conductive composition according to claim 1 or 2. 4. The thermally conductive sheet according to claim 3, having a thickness of 0.3 mm or more and 5 mm or less.