KR20150079559A - Thermally conductive adhesive sheet and method for producing same - Google Patents

Abstract

The thermally conductive pressure sensitive adhesive sheet has an acrylic pressure sensitive adhesive layer. The acrylic pressure sensitive adhesive layer contains three or more thermally conductive particles having different average particle diameters and has a void fraction of not less than 72% when three or more thermally conductive particles are mixed, and three or more thermally conductive The content ratio of the particles is 55 vol% or more and 75 vol% or less.

Description

TECHNICAL FIELD [0001] The present invention relates to a thermally conductive pressure-sensitive adhesive sheet,

The present invention relates to a thermally conductive pressure-sensitive adhesive sheet and a method for producing the same.

It is conventionally known that the thermally conductive sheet contains thermally conductive particles in the acrylic pressure-sensitive adhesive to improve thermal conductivity as compared with a pressure-sensitive adhesive which becomes a base.

For example, there has been proposed a thermally conductive pressure-sensitive adhesive sheet containing an acrylic copolymer, particles of a metal oxide having an average particle diameter of 20 to 200 占 퐉, and particles of a hydrated metal compound having an average particle diameter of 10 占 퐉 or less (see Patent Document 1 ).

Japanese Patent Application Laid-Open No. 2004-27039

In the thermally conductive pressure-sensitive adhesive sheet described in Patent Document 1, two kinds of thermally conductive particles having an average particle diameter (metal oxide particles and hydrated metal compound particles) are mixed to densely fill the thermally conductive particles in the pressure- It is raising the city.

However, merely mixing thermally conductive particles of two kinds of average particle diameters can not sufficiently densely fill them, and further improvement of heat conductivity is desired.

In addition, the thermally conductive particles are densely packed so that the thermally conductive particles contact or interfere with each other in the pressure-sensitive adhesive sheet, resulting in an excessively high hardness of the pressure-sensitive adhesive sheet. If so, problems arise as the pressure-sensitive adhesive sheet which requires appropriate softness.

Accordingly, an object of the present invention is to provide a thermally conductive pressure-sensitive adhesive sheet having excellent heat conductivity and good hardness (moderate softness) and a method for producing the same.

The thermally conductive pressure-sensitive adhesive sheet of the present invention comprises an acrylic pressure-sensitive adhesive layer, wherein the acrylic pressure-sensitive adhesive layer contains three or more thermally-conductive particles having different average particle diameters, Is 72% or less, and the content ratio of the three or more thermally conductive particles to the acrylic pressure-sensitive adhesive layer is 55% by volume or more and 75% by volume or less.

The thermally conductive pressure-sensitive adhesive sheet of the present invention is characterized in that at least one of the three or more thermally conductive particles includes a metal oxide or a metal nitride, and the other thermally conductive particles include metal hydroxide Is suitable.

In the thermally conductive pressure-sensitive adhesive sheet of the present invention, the content ratio of the thermally conductive particles containing the metal oxide or the metal nitride is preferably 5% by volume or more and 25% by volume or less based on the acrylic pressure-sensitive adhesive layer.

The thermally conductive pressure-sensitive adhesive sheet of the present invention is characterized in that the above-mentioned three or more thermally conductive particles are composed of the first thermally-conductive particles having an average particle diameter of less than 3 mu m, the second thermally-conductive particles having an average particle diameter of not less than 3 mu m and less than 70 mu m, It is preferable to contain third thermally conductive particles having a diameter of 70 mu m or more.

The thermally conductive pressure-sensitive adhesive sheet of the present invention is characterized in that the above-mentioned three or more thermally conductive particles are composed of the first thermally-conductive particles having an average particle diameter of less than 3 mu m, the second thermally-conductive particles having an average particle diameter of not less than 3 mu m and less than 70 mu m, It is preferable to contain the fourth thermally-conductive particles having a diameter of not less than 3 mu m and not more than 70 mu m and in the form of scales.

In the thermally conductive pressure-sensitive adhesive sheet of the present invention, it is preferable that the acrylic pressure-sensitive adhesive layer contains an acrylic polymer obtained by polymerizing a monomer component containing a (meth) acrylic acid alkyl ester as a main component and containing 5 mass% or more of a polar group- .

In the thermally conductive pressure-sensitive adhesive sheet of the present invention, it is preferable that the above-mentioned monomer component does not substantially contain a monomer having a carboxyl group.

In the thermally conductive pressure-sensitive adhesive sheet of the present invention, the polar group-containing monomer preferably contains a nitrogen-containing monomer and / or a hydroxyl group-containing monomer.

It is preferable that the thermally conductive pressure-sensitive adhesive sheet of the present invention has a hardness of 80 or less when the hardness of the thermally conductive pressure-sensitive adhesive sheet is measured 30 seconds after the pressure surface of the Type C durometer is closely contacted in the Type C hardness test.

In the thermally conductive pressure-sensitive adhesive sheet of the present invention, it is preferable that the thermal conductivity of the thermally conductive pressure-sensitive adhesive sheet in the thickness direction is 1.7 W / m · K or more.

In the thermally conductive pressure-sensitive adhesive sheet of the present invention, the thermally conductive pressure-sensitive adhesive sheet preferably satisfies the V-0 standard in the UL94 flammability test.

A process for producing a thermally conductive pressure-sensitive adhesive sheet of the present invention is a process for producing a thermally conductive pressure-sensitive adhesive sheet comprising an acrylic pressure-sensitive adhesive layer, comprising the steps of: adding to a monomer component containing a (meth) A step of mixing the thermally conductive particles to obtain a pressure-sensitive adhesive raw material, and a step of reacting the pressure-sensitive adhesive raw material to obtain the acrylic pressure-sensitive adhesive layer, wherein the space ratio when mixing the three or more thermally conductive particles is 72% , And the content ratio of the three or more thermally conductive particles to the acrylic pressure-sensitive adhesive layer is 55 vol% or more and 75 vol% or less.

According to the thermally conductive pressure-sensitive adhesive sheet of the present invention, the acrylic pressure-sensitive adhesive layer is provided, and the acrylic pressure-sensitive adhesive layer contains three or more thermally-conductive particles having different average particle diameters, Is 72% or less, and the content ratio of the three or more thermally conductive particles to the acrylic pressure-sensitive adhesive is 55% by volume or more and 75% by volume or less.

Therefore, the thermally conductive pressure-sensitive adhesive sheet of the present invention has excellent thermal conductivity in the thickness direction and has good hardness.

Further, according to the method for producing a thermally conductive pressure-sensitive adhesive sheet of the present invention, it is possible to easily produce a thermally conductive pressure-sensitive adhesive sheet having excellent heat conductivity and good hardness.

1 (a) shows a step of applying a pressure-sensitive adhesive material onto a base film, and FIG. 1 (b) shows a step of applying a pressure- And FIG. 1 (c) shows a step of reacting the pressure-sensitive adhesive raw material.

The thermally conductive pressure-sensitive adhesive sheet of the present invention is formed into a sheet form from a pressure-sensitive adhesive raw material containing a monomer component and / or a polymer component and thermally conductive particles.

Examples of the monomer component include, for example, (meth) acrylic acid alkyl ester monomers as an essential component, and as optional components, a polar group-containing monomer and a copolymerizable monomer copolymerizable with the monomer.

Examples of the (meth) acrylic acid alkyl ester monomer include a methacrylic acid alkyl ester monomer and / or an acrylic acid alkyl ester monomer, and examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, Butyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, isopropyl (meth) acrylate, isobutyl (Meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (Meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, dodecyl (meth) acrylate, isodecyl ) Heptadecyl acrylate, ( Agent) and the like can be mentioned acrylic acid octadecyl, (meth) acrylate, nonadecyl (meth) acrylate, eicosyl.

Among the (meth) acrylic acid alkyl ester monomers, a (meth) acrylic acid C2-12 alkyl ester, more preferably a (meth) acrylic acid C4-9 alkyl ester, .

The (meth) acrylic acid alkyl ester monomer is compounded in the monomer component in a proportion of, for example, 60 mass% or more, preferably 80 mass% or more, for example, 99 mass% or less.

Examples of the polar group-containing monomer include a nitrogen-containing monomer, a hydroxyl group-containing monomer, a sulfo group-containing monomer, a nitrogen-hydroxyl group-containing monomer, a nitrogen-sulfo group-containing monomer, a hydroxyl group-phosphate group-containing monomer and a carboxyl group-containing monomer.

Examples of the nitrogen-containing monomer include cyclic (meth) acrylamides such as N- (meth) acryloylmorpholine and N-acryloylpyrrolidine, such as (meth) acrylamide, N-substituted (Meth) acrylamides such as N-ethyl (meth) acrylamide, N-butyl (meth) acrylamide and the like, (Meth) acrylamide, N, N-di (meth) acrylamide, N, N-dipropyl Non-cyclic (meth) acrylamides such as N, N-dialkyl (meth) acrylamide and N, N-di (t-butyl) (meth) acrylamide, Vinylpyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl cyclic amides such as N-vinyl-3,5-morpholinedione, and the like, for example, aminoethyl Amino group-containing monomers such as N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate and N, N-dimethylaminopropyl (meth) acrylate such as N-cyclohexylmaleimide, Maleimide skeleton-containing monomers such as maleimide, such as N-methyl itaconimide, N-ethyl itaconimide, N-butyl itaconimide, N-2-ethylhexyl itaconimide, N And itaconimide-based monomers such as lauryl itaconimide and N-cyclohexyl itaconimide.

Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (Meth) acrylic acid such as 8-hydroxyoctyl acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate and (4-hydroxymethylcyclohexyl) methyl methacrylate.

Examples of the sulfo group-containing monomer include styrene sulfonic acid, allylsulfonic acid, sulfopropyl (meth) acrylate, and (meth) acryloyloxynaphthalenesulfonic acid.

Examples of nitrogen / hydroxyl group-containing monomers include N- (2-hydroxyethyl) (meth) acrylamide (HEAA), N- (2- hydroxypropyl) (meth) (Meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) Acrylamide, N-hydroxyalkyl (meth) acrylamide such as N- (4-hydroxybutyl) (meth) acrylamide.

Examples of the nitrogen-sulfo conjugated monomers include 2- (meth) acrylamide-2-methylpropanesulfonic acid and (meth) acrylamidopropanesulfonic acid.

Examples of the hydroxyl group-phosphate group-containing monomer include 2-hydroxyethyl acryloyl phosphate and the like.

Examples of the carboxyl group-containing monomer include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, maleic anhydride and itaconic anhydride.

Among these polar group-containing monomers, a nitrogen-containing monomer, a hydroxyl group-containing monomer and a nitrogen-hydroxyl group-containing monomer are preferably used in view of giving a high adhesive property and a holding power to the pressure-sensitive adhesive layer (described later) (Meth) acryloylmorpholine, N, N-diethyl (meth) acrylamide, hydroxyethyl (meth) acrylate, hydroxybutyl (meth) acrylate, N - (2-hydroxyethyl) (meth) acrylamide.

The polar group-containing monomer is contained in the monomer component in a proportion of 1 mass% or more, preferably 5 mass% or more, for example, 30 mass% or less, and preferably 25 mass% do. When the proportion of the polar group-containing monomer is within the above range, a good holding force can be imparted to the pressure-sensitive adhesive layer.

In addition, the monomer component preferably does not substantially contain the carboxyl group-containing monomer. Specifically, the mixing ratio of the carboxyl group-containing monomer is, for example, 5 mass% or less, preferably 1 mass% or less, and more preferably 0.5 mass% or less, in the monomer component. When the mixing ratio of the carboxyl group-containing monomer is within the above range, the thermally conductive particles can be dispersed without gelation.

Examples of the copolymerizable monomer include epoxy group-containing monomers such as glycidyl (meth) acrylate and allyl glycidyl ether, such as 2-methoxyethyl (meth) acrylate, 3-meth Alkoxy group-containing monomers such as methoxypropyl, (meth) acrylic acid methoxyethylene glycol and (meth) acrylic acid methoxypolypropylene glycol, for example, cyano group-containing monomers such as acrylonitrile and methacrylonitrile, , Styrene and? -Methylstyrene,? -Olefins such as ethylene, propylene, isoprene, butadiene and isobutylene, for example, 2-isocyanatoethyl acrylate, 2- Isocyanatoethyl methacrylate and the like, vinyl ester monomers such as vinyl acetate and vinyl propionate, vinyl ethers such as alkyl vinyl ethers and the like, (Meth) acrylic esters containing heterocyclic rings, such as, for example, tetrahydrofurfuryl (meth) acrylate, halogen atom-containing monomers such as fluoroalkyl (meth) acrylate, 3-methacryloxypropyltrimethoxysilane, and vinyltrimethoxysilane, such as siloxane skeleton-containing monomers such as (meth) acrylic group-containing silicon, for example, cyclopentyl (Meth) acrylate containing an alicyclic hydrocarbon group such as methyl (meth) acrylate, cyclohexyl (meth) acrylate, bornyl (meth) acrylate and isobornyl (Meth) acrylates containing an aromatic hydrocarbon group such as benzyl (meth) acrylate, phenoxyethyl (meth) acrylate, and phenoxydiethylene glycol (meth) acrylate.

Among these copolymerizable monomers, an alkoxy group-containing monomer is preferable, and 2-methoxyethyl acrylate is more preferable. By adding the alkoxy group-containing monomer, the adhesion of the pressure-sensitive adhesive layer to the adherend can be improved, and the heat from the adherend can be efficiently conducted.

The copolymerizable monomer is compounded in the monomer component in a proportion of, for example, 30 mass% or less, preferably 20 mass% or less, for example, 1 mass% or more, and preferably 5 mass% or more .

These monomers may be used alone (one kind) or two or more kinds may be used in combination.

The monomer component is contained in the pressure-sensitive adhesive material in an amount of 1 mass% or more, preferably 5 mass% or more, more preferably 10 mass% or more, for example, 90 mass% or less By mass, preferably 60% by mass or less, more preferably 50% by mass or less.

As the polymer component, for example, a polymer (polymer) obtained by reacting the above-mentioned monomer component can be mentioned. Specifically, the polymer is not particularly limited, and for example, an acrylic polymer, more specifically, a (meth) acrylic acid alkyl ester monomer is used as an essential component, and as the optional component, a polar group-containing monomer, Acrylic polymers in which possible copolymerizable monomers are used, and the like. In addition, the polymer includes some polymers of the above-mentioned monomers.

These polymers may be used singly (one kind), or two or more kinds may be used in combination.

The polymer component is contained in the pressure-sensitive adhesive material in an amount of 1 mass% or more, preferably 5 mass% or more, more preferably 10 mass% or more, for example, 50 mass% or less, , Not more than 40 mass%, more preferably not more than 30 mass%.

When both the monomer component and the polymer component are blended in the pressure-sensitive adhesive raw material, the total amount of the monomer component and the polymer component in the pressure-sensitive adhesive raw material is, for example, 1% by mass or more, preferably 5% More preferably not less than 10% by mass, and further preferably not more than 50% by mass, preferably not more than 40% by mass, more preferably not more than 30% by mass.

The thermally conductive particles include, for example, hydrated metal compounds.

Hydrated metal compound, the decomposition start a temperature in the range of 150 to 500 ℃, formula MxOy · nH ₂ O (M is a metal atom, x, y is determined n contains an integer of 1 or more, as determined by the valency of the metal Or a salt thereof.

As the hydrated metal compound, for example, aluminum hydroxide [Al ₂ O ₃ .3H ₂ O; Or Al (OH) ₃ ], boehmite [Al ₂ O ₃ .H ₂ O; Or AlOOH], magnesium hydroxide [MgO · H ₂ O; Or Mg (OH) ₂ ], calcium hydroxide [CaO.H ₂ O; Or Ca (OH) ₂ ], zinc hydroxide [Zn (OH) ₂ ], silicic acid [H ₄ SiO ₄ ; Or H ₂ SiO ₃ ; Or H ₂ Si ₂ O ₅ ], iron hydroxide [Fe ₂ O ₃ .H ₂ O or 2FeO (OH)], copper hydroxide [Cu (OH) ₂ ], barium hydroxide [BaO · H ₂ O; Or BaO · 9H ₂ O], zirconium oxide hydrate [ZrO · nH ₂ O], tin oxide hydrate [SnO · H ₂ O], basic magnesium carbonate _{[3MgCO 3 · Mg (OH)} 2 · 3H 2 O], hydrotalcite site _{[6MgO · Al 2 O 3 ·} H 2 O], Tosoh nitro _{[Na 2 CO 3 · Al 2} O 3 · nH 2 O], borax _{[Na 2 O · B 2 O} 5 · 5H 2 O], zinc borate [2ZnO · 3B ₂ O ₅ · 3.5H ₂ O].

The hydrated metal compound is commercially available. For example, aluminum hydrate is commercially available under the trade name of "HYDILITE H-100-ME" (average particle diameter 75 μm) (manufactured by Showa Denko KK) Trade name " HYDILITE H-31 " (average particle diameter 18 mu m) (trade name, manufactured by Showa Denko K.K.) Trade name " B103ST " (average particle diameter 8 mu m) (trade name, manufactured by Nihon Keizai Kogyo Co., Ltd.), trade name " BE033T (trade name, manufactured by Showa Denko K.K.), Trade name " HYDILITE H- KISUMA 5A " (average particle diameter 1 占 퐉) (manufactured by KYOWA CHEMICAL INDUSTRIES, LTD.) As the magnesium hydroxide, and the like can be given as examples of the magnesium hydroxide (average particle diameter: 3 탆) .

Examples of the thermally conductive particles include metal nitrides such as boron nitride, aluminum nitride, silicon nitride, and gallium nitride, such as silicon dioxide, aluminum oxide, magnesium oxide, titanium oxide, Metal oxides such as zinc oxide, tin oxide, copper oxide and nickel oxide; metal oxides such as silicon carbide, antimony acid doped tin oxide, calcium carbonate, barium titanate, potassium titanate, copper, silver, gold, , Carbon black, carbon tubes (carbon nanotubes), carbon fibers, and diamonds.

These thermoconductive particles are commercially available. For example, as the boron nitride, there are commercially available products such as trade name " HP-40 " (made by Mizushima Alloy Wire Co.), trade name " PT110 " AL-13KT "(average particle diameter: 97 탆) (trade name, manufactured by Showa Denko K.K.), trade name" AS-50 "(trade name, manufactured by Showa Denko K.K.) SN-100P " (product of Ishihara Sangyo Co., Ltd.), trade name " SN-100S " (product of Ishihara Sangyo Co., Ltd.) SnO-310 "(manufactured by Sumitomo Chemical Co., Ltd.) as zinc oxide, such as" TTO series "(product of Ishihara Sangyo Co., Ltd.) Quot; SnO-410 " (available from Osaka Cement Co., Ltd.), trade name " SnO-350 " (manufactured by Sumitomo Osaka Cement Co., Saka Cement Co., Ltd.) and the like.

Among these thermally conductive particles, a hydrated metal compound is preferable, and aluminum hydroxide is more preferable because it imparts high thermal conductivity and flame retardancy to the pressure-sensitive adhesive layer. Further, metal nitrides and metal oxides are also preferable, and boron nitride, aluminum oxide and magnesium oxide are more preferable.

The shape of the thermally conductive particles is not particularly limited and may be a bulk shape, a needle shape, a plate shape, or a scaly shape (including a layer shape). The bulk shape includes, for example, a spherical shape, a rectangular parallelepiped shape, a crushed shape, a rounded shape, an aggregate, or a deformed shape thereof.

The thermally conductive particles contain three or more thermally conductive particles having different average particle diameters. Concretely, the space ratio when three or more thermally conductive particles having different average particle diameters are mixed is 72% or less, preferably 70% or less, more preferably 65% or less, For example, 30% or more, preferably 50% or more, and more preferably 55% or more.

If the void ratio is within the above range, a high thermal conductivity can be imparted to the pressure-sensitive adhesive layer.

The void ratio is calculated by " space rate (%) = 100 - (tap density) / (true density of thermally conductive particles) x 100 ". Further, the tap density was measured using a device for characterizing a crushed body (powder tester " PT-R ", manufactured by Hosokawa Micron Corporation).

The true density of the thermally conductive particles is, for example, not less than 0.8 g / cm3, preferably not less than 1.5 g / cm3, and is, for example, not more than 20 g / cm3, preferably not more than 10 g / .

The true density of the thermally conductive particles is determined by a dry density meter (gas replacement method).

Preferably, the thermally conductive particles include a first thermally conductive particle having an average particle diameter of less than 3 占 퐉, a second thermally conductive particle having an average particle diameter of at least 3 占 퐉 and less than 70 占 퐉, And further contains conductive particles.

More preferably, the thermally conductive particles contain the first thermally conductive particles, the second thermally conductive particles, and the third thermally conductive particles having an average particle diameter of 70 m or more. Alternatively, the thermally conductive particles contain the first thermally conductive particles, the second thermally conductive particles, and the fourth thermally-conductive particles having an average particle diameter of not less than 3 mu m and less than 70 mu m and scales. When such three or more kinds of thermally conductive particles are contained, a higher thermal conductivity can be imparted to the pressure-sensitive adhesive layer.

The average particle diameter of the first thermally conductive particles is less than 3 mu m, preferably not more than 2 mu m, and is, for example, not less than 0.5 mu m. The shape of the first thermally conductive particle may be a shape as described above, and preferably a bulk shape.

The average particle diameter of the second thermally conductive particles is not less than 3 占 퐉, preferably not less than 20 占 퐉, and is, for example, less than 70 占 퐉, preferably less than 60 占 퐉. The shape of the second thermally conductive particle may be the above-described shape, and preferably, it is a bulk shape.

The average particle diameter of the third thermally conductive particles is not less than 70 mu m, preferably not less than 90 mu m, and is, for example, less than 300 mu m, preferably less than 150 mu m. The shape of the third thermally conductive particle may be a shape as described above, and preferably a bulk shape.

The fourth thermally conductive particle is formed into a scaly shape and has an average particle diameter of not less than 3 mu m, preferably not less than 20 mu m, and, for example, less than 70 mu m, preferably less than 50 mu m to be.

The average particle diameter of the thermally conductive particles is determined by the D50 value (cumulative 50%) based on the particle size distribution obtained by the particle size distribution measurement method in the laser scattering method (specifically, measured by the laser scattering type particle size distribution meter) Median diameter).

In the three or more thermally conductive particles, at least one thermally conductive particle among them is preferably formed of a metal oxide or a metal nitride, and the other thermally conductive particles are formed of a metal hydroxide.

Specifically, the first thermally conductive particle is preferably formed of a metal hydroxide, more preferably aluminum hydroxide. The second thermally conductive particle is preferably formed of a metal hydroxide, a metal oxide or a metal nitride, more preferably aluminum hydroxide or magnesium oxide. Further, the third thermally conductive particle is preferably formed of a metal oxide or a metal nitride, more preferably a metal oxide, and more preferably, aluminum oxide. Further, the fourth thermally conductive particle is formed of a metal oxide or a metal nitride, more preferably a metal nitride, more preferably boron nitride.

In this case, the thermally conductive particle formed of the metal hydroxide is, for example, at least 30% by volume, preferably at least 40% by volume, more preferably at most 70% by volume, By volume, and 60% by volume or less. The content ratio of the thermally conductive particles formed of a metal oxide or a metal nitride (more preferably, aluminum oxide, magnesium oxide or boron nitride) is, for example, 5% by volume or more, For example, not less than 8 vol% and not more than 25 vol%, preferably not more than 20 vol%.

The thermally conductive particles may contain thermally conductive particles having three or more kinds of average particle diameters and may contain thermally conductive particles having four kinds of average particle diameters, for example.

In the case where the thermally conductive particles contain thermally conductive particles having four kinds of average particle diameters, for example, the first thermally conductive particles may be composed of the second thermally conductive particles, the third thermally conductive particles, and the fourth thermally conductive particles In either case, two or more kinds of particles having an average particle diameter can be provided. Specifically, the second thermally-conductive particles having an average particle diameter of not less than 3 μm and less than 70 μm may also be used as the second thermally-conductive particles having an average particle diameter of not less than 3 μm and less than 40 μm and an average particle diameter of not less than 40 μm and not more than 70 Lt; RTI ID = 0.0 > um. ≪ / RTI >

In addition, the first thermally conductive particles, the second thermally-conductive particles, the third thermally-conductive particles, and the fourth thermally-conductive particles may have thermally conductive particles containing two or more different materials. Specifically, for example, the second thermally conductive particle has thermally conductive particles containing two kinds of different materials. That is, the thermally conductive particles preferably include the first thermally conductive particles and two kinds of second thermally conductive particles formed of different materials. As such two kinds of different materials, a combination of a metal hydroxide and a metal oxide is preferable, and a combination of magnesium hydroxide and magnesium oxide is more preferable.

The mixing ratio of the first thermally conductive particles in the total amount of the thermally conductive particles is, for example, 10 mass% or more, preferably 20 mass% or more, more preferably 30 mass% or more, For example, it is 70 mass% or less, preferably 55 mass% or less, and more preferably 45 mass% or less.

The mixing ratio of the second thermally conductive particles in the total amount of the thermally conductive particles is, for example, 15 mass% or more, preferably 25 mass% or more, more preferably 35 mass% or more, For example, it is 70 mass% or less, preferably 60 mass% or less, and more preferably 50 mass% or less. When the second thermally conductive particles comprise two different materials or have two different average particle diameters, the total blend ratio is preferably 30% by mass or less, for example, For example, 80 mass% or less, preferably 75 mass% or less, and more preferably 70 mass% or more, and preferably 40 mass% or more, and more preferably 50 mass% Or less.

When the thermally conductive particles include the third thermally conductive particles, the mixing ratio of the third thermally conductive particles in the total amount of the thermally conductive particles is, for example, not less than 5% by mass, preferably not less than 10% Preferably not less than 15% by mass, and is not more than 50% by mass, preferably not more than 40% by mass, more preferably not more than 30% by mass, for example.

When the thermally conductive particles include the fourth thermally conductive particles, the blending ratio of the fourth thermally conductive particles in the total amount of the thermally conductive particles is, for example, 1% by mass or more, preferably 5% by mass or more, Preferably 10 mass% or more, for example, 40 mass% or less, preferably 30 mass% or less, and more preferably 20 mass% or less.

The total amount of the thermally conductive particles is, for example, not less than 75 mass%, preferably not less than 80 mass%, such as not more than 90 mass%, preferably not more than 87 mass% . The total amount of thermally conductive particles is contained in the pressure-sensitive adhesive raw material in a proportion of 55% by volume or more, preferably 60% by volume or more, and 75% by volume or less, preferably 70% by volume or less.

When the mixing ratio of the thermally conductive particles is within the above range, a high thermal conductivity, good hardness and flame retardancy can be imparted to the pressure-sensitive adhesive layer.

Next, the production method of the pressure-sensitive adhesive raw material will be described.

To prepare a pressure-sensitive adhesive raw material, first, a monomer composition containing the above-mentioned monomer component and a polymerization initiator is prepared.

To prepare the monomer composition, a polymerization initiator is added to the above-mentioned monomer component.

Examples of the polymerization initiator include a photopolymerization initiator and a thermal polymerization initiator.

Examples of the photopolymerization initiator include benzoin ether photopolymerization initiators, acetophenone photopolymerization initiators,? -Ketol photopolymerization initiators, aromatic sulfonyl chloride photopolymerization initiators, photoactive oxime photopolymerization initiators, benzoin photopolymerization initiators, A photopolymerization initiator, a benzophenone photopolymerization initiator, a thioxanthene photopolymerization initiator, and the like.

Examples of the benzoin ether photopolymerization initiator include benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, benzoin isopropyl ether, benzoin isobutyl ether, 2,2-dimethoxy-1,2- Diphenylethan-1-one, anisole methyl ether, and the like.

Examples of the acetophenone-based photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 4-phenoxydichloroacetophenone, 4- (t-butyl) Phenone, and the like.

Examples of the? -ketol-based photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) Hydroxycyclohexyl phenyl ketone, and the like.

The aromatic sulfonyl chloride-based photopolymerization initiator includes, for example, 2-naphthalenesulfonyl chloride.

Examples of the photoactive oxime-based photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime and the like.

Examples of the benzoin-based photopolymerization initiator include benzoin and the like.

The benzyl-based photopolymerization initiator includes, for example, benzyl.

Examples of the benzophenone-based photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3'-dimethyl-4-methoxybenzophenone, and polyvinylbenzophenone.

Examples of the thioxanthene photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-di Isopropylthioxanthone, decylthioxanthone, and the like.

Examples of the thermal polymerization initiator include 2,2'-azobisisobutyronitrile, 2,2'-azobis-2-methylbutyronitrile, 2,2'-azobis (2-methylpropionic acid) dimethyl Azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2 Azo bis (2-methylpropionamidine) disulphate, 2,2'-azobis (N, N'- Azo type polymerization initiator such as 2,2'-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate such as di Based peroxide polymerization initiators such as benzoyl peroxide, t-butyl fumarate, t-butyl hydroperoxide and hydrogen peroxide, persulfates such as potassium persulfate and ammonium persulfate such as persulfates and sulfoxides With sodium hydrogen A redox polymerization initiator such as a combination of peroxides and sodium ascorbate, and the like.

These polymerization initiators may be used singly (only one type), or two or more types may be used in combination.

Among these polymerization initiators, a photopolymerization initiator is preferably used from the viewpoint of shortening the polymerization time.

When a photopolymerization initiator is blended as a polymerization initiator, the photopolymerization initiator is not particularly limited, but is, for example, 0.01 parts by mass or more, preferably 0.05 parts by mass or more, relative to 100 parts by mass of the monomer component, Further, it is blended at a ratio of, for example, 5 parts by mass or less, preferably 3 parts by mass or less.

When a thermal polymerization initiator is blended as a polymerization initiator, the thermal polymerization initiator is not particularly limited and is blended at a usable ratio.

In the monomer composition, if necessary, a part of the monomer components may be polymerized.

In order to polymerize a part of the monomer component, when a photopolymerization initiator is added, a mixture of the monomer component and the photopolymerization initiator is irradiated with ultraviolet rays. In order to irradiate ultraviolet rays, it is preferable that the viscosity of the monomer composition (BH viscometer, No. 5 rotor, 10 rpm, measurement temperature 30 ° C) is 5 Pa · s or more, preferably 10 Pa S or more, for example, 30 Pa · s or less (preferably 20 Pa · s or less).

When a thermal polymerization initiator is blended, the mixture of the monomer component and the thermal polymerization initiator may be mixed with a photopolymerization initiator, for example, at a decomposition temperature of the thermal polymerization initiator, specifically at a polymerization temperature of about 20 to 100 ° C, The viscosity of the monomer composition (BH viscometer, No. 5 rotor, 10 rpm, measurement temperature 30 占 폚) is set to, for example, 5 Pa · s or more (preferably 10 Pa · s or more) In this case, it is heated until it becomes 30 Pa · s or less (preferably 20 Pa · s or less).

When a monomer composition is produced by polymerizing a part of the monomer component, a polymerization initiator may be blended with a (meth) acrylic acid alkyl ester monomer, a monomer selected from a polar group-containing monomer and a copolymerizable monomer, and a polymerization initiator, A part of the monomer may be polymerized, and then a cross-linking agent may be added.

The crosslinking agent is a polyfunctional compound having a plurality of ethylenically unsaturated hydrocarbon groups, and examples thereof include hexane diol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (Meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, (Meth) acrylate, polyester (meth) acrylate, urethane (meth) acrylate, and the like can be used. Of a bifunctional or higher polyfunctional oligomer.

The crosslinking agent may be used alone or in combination of two or more.

As the crosslinking agent, dipentaerythritol hexa (meth) acrylate is preferably used.

The content of the crosslinking agent is, for example, not less than 0.001 part by mass, preferably not less than 0.01 parts by mass, and, for example, not more than 10 parts by mass, preferably not less than 1 part by mass, based on 100 parts by mass of the monomer component Or less.

Subsequently, in order to produce a pressure-sensitive adhesive raw material, the above-mentioned thermoconductive particles are mixed and mixed with the obtained monomer composition.

The thermally conductive particles and the like can be incorporated into the monomer composition in a state of being dispersed or dissolved in a solvent such as an organic solvent.

Thereby, a pressure-sensitive adhesive raw material is produced.

The pressure-sensitive adhesive material can be obtained by polymerizing all monomer components in a monomer composition containing thermally conductive particles to form a polymer component containing thermally conductive particles and then dissolving the polymer component in a solvent such as an organic solvent , Or as a polymer composition.

Additives such as a dispersing agent, a tackifier, an acrylic oligomer, a silane coupling agent, a fluorine surfactant, a plasticizer, a filler, an anti-aging agent, and a colorant may be added to the monomer composition or the polymer composition.

From the standpoint of stably dispersing the thermally conductive particles without aggregation, a dispersant is preferably incorporated into the monomer composition or the polymer composition. As the dispersant, for example, a phosphoric acid ester-based dispersant can be enumerated, and specifically, a phosphoric acid monoester of polyoxyethylene alkyl (or alkylallyl) ether or polyoxyethylene alkylaryl ether, a polyoxyethylene alkylether or polyoxy Phosphoric acid diester of ethylene alkyl aryl ether, phosphoric acid triester, derivatives thereof and the like.

Specifically, "Flysurf series" A212E, A208F, A210G, A212C, A215C manufactured by Daiichi Kogyo Seiyaku Co., Ltd., "Fosphenol" RE610, RS710, RS610 and the like manufactured by Toho Chemical Industry Co., Ltd. are listed.

These phosphate ester dispersants may be used alone or in combination of two or more.

The blending ratio of the dispersant in the pressure-sensitive adhesive material is, for example, not less than 0.01% by mass, preferably not less than 0.1% by mass, and more preferably not more than 10% by mass, and preferably not more than 5% Do.

The obtained viscosity of the pressure-sensitive adhesive material (BM viscometer, No. 4 rotor, 12 rpm, measurement temperature 23 캜) is, for example, 50 Pa · s or less, preferably 40 Pa · s or less, more preferably 35 Pa · s or less , For example, 5 Pa · s or more, and more preferably 10 Pa · s or more.

The pressure-sensitive adhesive raw material may contain bubbles. The thermally conductive pressure-sensitive adhesive sheet can be made into a foam by producing a thermally conductive pressure-sensitive adhesive sheet using a pressure-sensitive adhesive material containing bubbles.

In order to contain bubbles in the pressure-sensitive adhesive raw material, for example, a stator (stationary toothed) having a plurality of teeth on a disk having a through hole at the center thereof, and a rotor And a gas for forming bubbles through the through holes of the stator is introduced into the pressure-sensitive adhesive raw material by introducing the pressure-sensitive adhesive material between the teeth of the stator and the teeth of the rotor by using a stirring device equipped with a stirring device do.

The gas to be introduced into the pressure-sensitive adhesive raw material is not particularly limited, and examples thereof include an inert gas such as nitrogen, carbon dioxide, and argon, for example, air.

As the gas to be introduced into the pressure-sensitive adhesive raw material, an inert gas, more preferably nitrogen, is preferable because it is difficult to inhibit the reaction of the pressure-sensitive adhesive raw material.

The bubble is, for example, at least 5% by volume, preferably at least 10% by volume, more preferably at least 12% by volume, based on the total volume of the pressure-sensitive adhesive raw material, By volume or less, preferably 40% by volume or less, and more preferably 35% by volume or less.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is an explanatory view for explaining a manufacturing method of a thermally conductive pressure-sensitive adhesive sheet. FIG.

Next, a method of manufacturing the thermally conductive pressure-sensitive adhesive sheet will be described.

In order to produce a thermally conductive pressure-sensitive adhesive sheet, first, as shown in Fig. 1 (a), the pressure-sensitive adhesive material 2 is applied to the surface of the base film 1 as a base material subjected to the release treatment.

As the base film 1, for example, a polyester film (such as a polyethylene terephthalate film), for example, a fluoropolymer (for example, polytetrafluoroethylene, polychlorotrifluoroethylene, polyvinyl fluoride, For example, an olefin resin (polyethylene, polypropylene, or the like) containing a fluorine-containing vinylidene fluoride, a fluorine-containing vinylidene fluoride, a polytetrafluoroethylene-hexafluoropropylene copolymer, a chlorofluoroethylene- (Synthetic resin film) such as an olefin resin film including a polyvinyl chloride film, a polyimide film, a polyamide film (nylon film), and a rayon film, Papers such as paper, kraft paper, gloss paper, synthetic paper, and top coated paper, for example, composites obtained by layering them.

When the pressure-sensitive adhesive material (2) is prepared as a monomer composition and contains a photopolymerization initiator, a base film (1) which transmits ultraviolet rays is used so as not to interfere with the irradiation of ultraviolet rays to the pressure- .

Examples of the method of applying the pressure-sensitive adhesive raw material 2 to the base film 1 include a roll coating, a kiss roll coating, a gravure coating, a reverse coating, a roll brush, a spray coating, a dip roll coating, Air knife coating, curtain coating, lip coating, die coater, and the like.

The applied thickness of the pressure-sensitive adhesive raw material 2 is, for example, 10 mu m or more, preferably 50 mu m or more, more preferably 100 mu m or more and, for example, , Not more than 5000 mu m, and more preferably not more than 3000 mu m.

To prepare the thermally conductive pressure-sensitive adhesive sheet, the cover film 3 is then placed on the coating film of the pressure-sensitive adhesive raw material 2, as shown in Fig. 1 (b). In order to arrange the cover film 3 on the coating film, the cover film 3 is disposed so that the surface subjected to the peeling treatment is in contact with the coating film.

As the cover film 3, for example, a film similar to that of the base film 1 can be mentioned. When the pressure-sensitive adhesive raw material (2) is prepared as a monomer composition and contains a photopolymerization initiator, a cover film (3) that transmits ultraviolet rays is used so as not to interfere with the irradiation of ultraviolet light to the pressure- .

In the case where the pressure-sensitive adhesive raw material 2 is produced as a monomer composition, the pressure-sensitive adhesive raw material 2 is caused to react with the acrylic pressure-sensitive adhesive 2 as shown in Fig. 1 (c) To form a layer (4).

When a photopolymerization initiator is blended as described above, the pressure-sensitive adhesive raw material 2 is irradiated with ultraviolet rays and the pressure-sensitive adhesive raw material 2 is irradiated with ultraviolet rays, .

When the pressure-sensitive adhesive material (2) is made of a polymer composition, the acrylic pressure sensitive adhesive layer (4) is formed by applying the pressure-sensitive adhesive raw material (2), drying it and removing the solvent.

Thus, a thermally conductive pressure-sensitive adhesive sheet is obtained.

The thickness of the acrylic pressure-sensitive adhesive layer 4 of the obtained thermally conductive pressure-sensitive adhesive sheet is, for example, 10 占 퐉 or more, preferably 50 占 퐉 or more, more preferably 100 占 퐉 or more, Preferably not more than 5000 mu m, more preferably not more than 3000 mu m.

By setting the thickness of the acrylic pressure-sensitive adhesive layer 4 to 10 m or more, a better adhesive force can be obtained. Further, by setting the thickness of the acrylic pressure sensitive adhesive layer 4 to 10,000 m or less, more excellent thermal conductivity can be obtained.

The obtained thermally conductive pressure-sensitive adhesive sheet is preferably such that the content ratio of the thermally conductive particles to the acrylic pressure-sensitive adhesive layer 4 is 55 vol% or more, preferably 60 vol% or more and 75 vol% or less, , And not more than 70% by volume.

When the content ratio of the thermally conductive particles is less than 55% by volume, sufficient thermal conductivity can not be obtained. On the other hand, when the content ratio of the thermally conductive particles exceeds 75% by volume, the shape as a sheet can not be maintained.

The content ratio of the thermally conductive particles containing the metal oxide or the metal nitride (preferably aluminum oxide, magnesium oxide or boron nitride) is preferably 5% by volume or more, more preferably 5% by volume or more, , Not less than 8% by volume, for example, not more than 25% by volume, preferably not more than 20% by volume. When the content of the metal oxide or the metal nitride is within the above range, the thermal conductivity and the flame retardancy are improved.

The content ratio of the thermally conductive particles containing a metal hydroxide is, for example, not less than 30% by volume, preferably not less than 40% by volume, and more preferably not more than 70% by volume with respect to the acrylic pressure- , Preferably not more than 60 vol%.

The thermally conductive pressure-sensitive adhesive sheet thus obtained preferably has first thermally-conductive particles having an average particle diameter of less than 3 占 퐉, second thermally-conductive particles having an average particle diameter of not less than 3 占 퐉 and less than 70 占 퐉, 3 thermally conductive particles and / or fourth thermally conductive particles having an average particle diameter of not less than 3 mu m and less than 70 mu m in a scale-like shape.

The obtained thermally conductive pressure-sensitive adhesive sheet has a 90 degree peel adhesion strength (an adhesive strength when peeled to a stainless steel plate at a peel angle of 90 degrees and a peel rate of 300 mm / min after being adhered to a stainless steel plate), for example, Preferably 10 N / 20 mm or more, and more preferably 15 N / 20 mm or more, for example, 100 N / 20 mm or less.

The hardness (measured in accordance with the type C hardness test specified in JIS K 7312) of the obtained thermally conductive pressure-sensitive adhesive sheet is, for example, 80% or less as measured after 30 seconds from the pressing surface of the type C durometer, Or less, preferably 70 or less, for example, 20 or more, and preferably 30 or more.

When the hardness is in the above-mentioned range, step following property and workability are good.

The thermal conductivity of the acrylic pressure-sensitive adhesive layer 4 of the obtained thermally conductive pressure-sensitive adhesive sheet (for example, measured by the method described in Examples to be described later) is 1.7 W / m · K or more, preferably 2.0 W / mK or more, more preferably 2.5 W / mK or more, for example, 10 W / mK or less.

The resulting thermally conductive pressure-sensitive adhesive sheet is, for example, V-0 in the flammability UL94 standard. The thermally conductive pressure-sensitive adhesive sheet is excellent in flame retardancy when the flame-retardant UL94 standard is V-0.

This thermally conductive pressure sensitive adhesive sheet is provided with an acrylic pressure sensitive adhesive layer (4). As a result, the acrylic pressure-sensitive adhesive layer 4 has adhesiveness on both surfaces thereof. Therefore, it can be used as a double-sided pressure-sensitive adhesive (pressure-sensitive adhesive) sheet.

Further, in this thermally conductive pressure-sensitive adhesive sheet, the acrylic pressure-sensitive adhesive layer (4) contains three or more thermally conductive particles having different average particle diameters, and the space ratio when mixing three or more thermally conductive particles is 72% , And the content ratio of three or more thermally conductive particles to the acrylic pressure-sensitive adhesive layer (4) is 55% by volume or more and 75% by volume or less.

According to this thermally conductive pressure-sensitive adhesive sheet, since the thermally conductive particles are densely filled in the acrylic pressure-sensitive adhesive layer 4 while maintaining a proper distance, even when the acrylic pressure-sensitive adhesive layer 4 is deformed, Or interference is suppressed. Therefore, it has excellent thermal conductivity and good hardness (moderate softness). Furthermore, it has a good flame retardancy.

Further, the above-mentioned method for producing a thermally conductive pressure-sensitive adhesive sheet is characterized in that three or more thermally conductive particles having different average particle diameters are mixed with a monomer component (monomer composition) comprising a (meth) acrylic acid alkyl ester as a main component, , And a step of reacting the pressure-sensitive adhesive raw material (2) to obtain an acrylic pressure-sensitive adhesive layer (4).

As a result, the acrylic pressure-sensitive adhesive layer 4 can be formed by applying the pressure-sensitive adhesive raw material 2 to the base film 1, so that the thermally conductive particles are densely packed even if no compression step such as hot pressing is performed, It is possible to reduce gaps (sites where monomer components and polymer components are charged) between thermally conductive particles. As a result, a thermally conductive pressure-sensitive adhesive sheet having excellent thermal conductivity can be easily produced.

This thermally conductive pressure-sensitive adhesive sheet is excellent in heat conductivity and flame retardancy, and therefore can be applied to a semiconductor device, a hard disk, an LED device (television, illumination, display), an EL device (organic EL display, , Batteries (lithium ion batteries, etc.), power modules, and the like.

Example

Hereinafter, the present invention will be described based on each example and each comparative example, but the present invention is not limited at all by these examples and comparative examples.

Further, the numerical values of the embodiments shown below can be replaced with the numerical values described in the above embodiments (that is, the upper limit value or the lower limit value).

Details of the measurement methods used in the respective Examples and Comparative Examples are described below.

Average particle diameter of thermally conductive particles: Measured according to the following.

(Specifically, based on the particle size distribution measured by a laser scattering type particle size distribution meter (trade name SALD-2100, manufactured by Shimadzu Corporation), the D50 value ( Cumulative 50% median diameter)).

Spatial rate of thermally conductive particles (%)

The void fraction of the thermally conductive particles was calculated according to the following equation.

Space rate (%) = 100 - {(tap density) / (true density of thermally conductive particle)} x 100

The tap density was measured by using a powder tester " PT-R " (manufactured by Hosokawa Micron Corporation) and selecting the " hardening bulk density " measurement as a measurement mode. Specifically, the cup was filled with the thermally conductive particles using a sieve having a scale of 1.1 mm, and then the tapping stroke was set to 18 mm, and the cup was tapped 360 times. After completion of the tapping, the top of the cup was flattened with a flat plate, and the tap density was determined from the mass of the thermally conductive particles filled in the cup.

The true density of the thermally conductive particles was calculated by a dry density meter (trade name: Akyppe 1330, manufactured by Shimadzu Corporation) (gas replacement method).

In the case of thermally conductive particles containing different materials, the theoretical true density was calculated from the true density and blending ratio of each thermally conductive particle. These values are shown in Table 1.

1. Examples and Comparative Examples

Example 1

(Preparation of monomer composition)

82 parts by mass of 2-ethylhexyl acrylate (2EHA) and 12 parts by mass of 2-methoxyethyl acrylate (MEA) as the alkyl (meth) acrylate ester, and N-vinyl-2-pyrrolidone NVP) and 1 part by mass of hydroxyethyl acrylamide (HEAA) were mixed and mixed to obtain a monomer component.

To the monomer component thus obtained, 0.10 parts by mass of a trade name "Irgacure 651" (2,2-dimethoxy-1,2-diphenylethane-1-one, manufactured by Shiba Japan Co.) as a photopolymerization initiator and " (1-hydroxycyclohexyl phenyl ketone, manufactured by Shiba Japan Co., Ltd.).

Thereafter, ultraviolet light was irradiated to the mixture until viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 ° C) reached about 20 Pa · s to prepare a partial polymerized (syrupy) polymerized part of the monomer Respectively.

0.05 part by mass of DPHA (dipentaerythritol hexaacrylate, trade name " KAYARAD DPHA-40H ", manufactured by Nippon Kayaku Co., Ltd.) as a cross-linking agent and 0.5 parts by mass of a trade name "Flysurf A212E" Ltd.) were mixed and mixed to obtain a monomer composition.

(Production of pressure-sensitive adhesive raw material)

266 parts by mass of HYDILITE H-42 (trade name, manufactured by Showa Denko K.K., aluminum hydroxide, average particle diameter of 1 mu m, crushing shape) as thermally conductive particles, 6 parts by mass of HYDILITE H-10 (trade name, 74 parts by mass of an aluminum hydroxide, average particle diameter of 55 mu m, crushing shape) and 85 parts by mass of AL-13KT (trade name, trade name; average particle diameter of 97 mu m, agglomerate) were mixed and mixed to obtain a pressure- .

(Production of thermally conductive pressure-sensitive adhesive sheet)

The pressure-sensitive adhesive material thus obtained was applied to the release surface of a base film (polyethylene terephthalate film, trade name "Di Foil® MRF38" manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.) (See Fig. 1 (a)).

Subsequently, a cover film (a film such as a base film) was disposed on the coating film of the pressure-sensitive adhesive raw material so as to sandwich the coating film of the pressure-sensitive adhesive material between the pressure-sensitive adhesive and the base film (see FIG.

Subsequently, ultraviolet rays (roughness of about 5 mW / cm 2) were irradiated from both sides (base film side and cover film side) to the pressure-sensitive adhesive raw material for 3 minutes (corresponding to irradiation energy of 900 mJ / cm 2).

Thereby, the monomer component in the pressure-sensitive adhesive material was polymerized to form an acrylic pressure-sensitive adhesive layer to produce a thermally conductive pressure-sensitive adhesive sheet (see Fig. 1 (c)).

The pressure-sensitive adhesive layer of the thermally conductive pressure-sensitive adhesive sheet of Example 1 had stickiness on its front and back surfaces. From this, it was confirmed that the sheet was a double-sided pressure-sensitive adhesive sheet.

(Volume%, volume%) of the thermoconductive particles in the pressure-sensitive adhesive layer, the mixing ratio (volume%) of the aluminum hydroxide in the pressure-sensitive adhesive layer, the metal oxides and metal nitrides (specifically, (Volume%) of aluminum, magnesium oxide and boron nitride, and the void fraction of the thermally conductive particles are shown in Table 1.

Examples 2 to 6

A thermally conductive pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the kind of the thermally conductive particles and the blending ratio thereof were changed to those shown in Table 1.

All of the pressure-sensitive adhesive layers of the thermally conductive pressure-sensitive adhesive sheets of the respective Examples had stickiness on the front and rear surfaces thereof. From this, it was confirmed that the sheet was a double-sided pressure-sensitive adhesive sheet.

(Volume%, volume%) of the thermally conductive particles in the pressure-sensitive adhesive layer, the mixing ratio (volume%) of the aluminum hydroxide in the pressure-sensitive adhesive layer, the mixing ratio of the metal oxide and the metal nitride in the pressure- ), And the space ratio of the thermally conductive particles are shown in Table 1.

Comparative Examples 1 to 4

A thermally conductive pressure-sensitive adhesive sheet was prepared in the same manner as in Example 1 except that the kind of the thermally conductive particles and the blending ratio thereof were changed to those shown in Table 1. In Comparative Example 4, the pressure-sensitive adhesive raw material in the blend ratio described in Comparative Example 4 could not be formed into a sheet.

All of the pressure-sensitive adhesive layers of the thermally conductive pressure-sensitive adhesive sheets of Comparative Examples had adhesive properties on the front and back surfaces thereof. From this, it was confirmed that the sheet was a double-sided pressure-sensitive adhesive sheet.

(Volume%, volume%) of the thermally conductive particles in the pressure-sensitive adhesive layer, the mixing ratio (volume%) of the aluminum hydroxide in the pressure-sensitive adhesive layer, the mixing ratio of the metal oxide and the metal nitride in the pressure- ), And the space ratio of the thermally conductive particles are shown in Table 1.

2. Evaluation

(Thermal conductivity)

The thermal conductivity of the thermally conductive tape was measured. That is, the thermal conductivity in the thickness direction (TD) was measured by a pulse heating method using a xenon flash analyzer "LFA-447 type" (manufactured by NETZSCH).

The thermally conductive adhesive sheet was cut into squares of 1 cm x 1 cm to obtain slices. A thermally conductive sheet carbon spray (alcohol dispersion solution of carbon) was applied to the surface of the slice (one side in the thickness direction) and dried, , And carbon spray was applied to the back surface (the other surface in the thickness direction), and this was used as a detection portion.

Subsequently, an energy ray was irradiated to the light-receiving portion by a xenon flash, and the temperature of the detection portion was detected to measure the thermal diffusivity D1 in the thickness direction.

From the obtained thermal diffusivity (D1), the thermal conductivity (TC1) in the thickness direction of the thermally conductive pressure-sensitive adhesive sheet was determined by the following formula. The results are shown in Table 1.

TC1 = D1 x px Cp

ρ: Density at 25 ° C (density of the sample was measured from thickness and weight by punching the sample into 2.5 cmφ)

Cp: Specific heat of the thermally conductive tape (specific heat was measured by DSC according to the following specific heat capacity measurement)

(Specific heat capacity measurement)

The specific heat capacity was measured using a differential scanning calorimeter (hereinafter referred to as DSC) "EXSTAR6200" (manufactured by Seiko Instruments Inc.) under the following conditions.

When DSC is used to measure the specific heat capacity, it can be calculated by the following equation.

Cp = h / H · m '/ m · C'p

Cp: Specific heat capacity of thermally conductive tape (J / g ° C)

C'p: specific heat capacity of reference substance (J / g ° C)

h: Difference in DSC curve between empty container and heat-conducting tape

H: Difference in DSC curve between empty container and reference material

m: heat conduction tape weight (g)

m ': Reference substance weight (g)

As the reference material, measurement was carried out using sapphire (specific heat capacity at 25 캜: 0.75 J / g 占 폚), each of the empty container, sapphire and heat conductive tape was maintained at -15 占 폚 for 5 minutes, / Min and reached isothermal temperature for 5 minutes. Thus, the DSC curve of each of the empty container, sapphire, and heat-conducting tape was obtained, and the specific heat capacity of the heat-conducting tape at 25 ° C was obtained by the above-mentioned formula. This operation was repeated three times, and the average value thereof was used as the specific heat capacity.

(Hardness)

Using the thermally conductive pressure-sensitive adhesive sheets of the respective Examples and Comparative Examples, tests were conducted under the following conditions in accordance with JIS K 7312 (1996).

Specifically, the pressure-sensitive adhesive layer of the thermally conductive pressure-sensitive adhesive sheet was cut to a width of 20 mm and a length of 20 mm and laminated so as to have a thickness of 4 mm was evaluated with an Asuka C hardness meter (manufactured by Polymer Instruments Co., Ltd.) Under the RH atmosphere, the hardness (Asuka C hardness) after 30 seconds of adhesion of the pressing surface of the Asuka C hardness meter was measured. The results are shown in Table 1.

(Flame retardancy)

The thermally conductive pressure-sensitive adhesive sheets produced in each of the examples and the comparative examples were cut to a size of 12.7 mm x 127 mm, and the base film and the cover film were peeled off to prepare five test pieces each, and the UL94 flammability test was carried out.

Specifically, the test specimens were fixed at the upper end thereof and lowered at the lower end thereof. Then, at the lower end of the test piece, the flame of the burner was first applied for 10 seconds, and after that, the flame was separated from the test piece, and then sparked for 10 seconds to the lower end of the test piece again.

Then, according to the following evaluation criteria, whether or not the V-0 standard passed is evaluated. The results are shown in Table 1.

1: The total flame burning time of each specimen (the sum of the burning time after the first flame and the second burning flame) is within 10 seconds.

2: The sum of the total flue gas burning time of each test piece is within 50 seconds.

3: The flame burning time and the non-salt burning time of each specimen after the second flame is less than 30 seconds.

4: When the combustion load falls from the test specimen, the surface placed below does not ignite.

5: Not all of the specimens are covered by the suspension.

?: The number of evaluation items satisfying the above 1 to 5 is 3 or more, and satisfies the V-0 standard.

X: The number of evaluation items satisfying the above 1 to 5 is less than 3, and the V-0 standard is not satisfied.

The units of the monomer components, the polymerization initiator, the crosslinking agent and the dispersing agent are parts by mass.

Details of each component in the table are described below.

High-dilute H-42: product name, aluminum hydroxide, average particle diameter 1 mu m, shredded shape, true density 2.4 g / cm &

BE033: Product name, manufactured by Nippon Keizi Kogyo Co., Ltd., aluminum hydroxide, average particle diameter 3 mu m, crushed shape, true density 2.4 g / cm &

Aluminum hydroxide, average particle diameter 18 mu m, crushed shape), a true density of 2.4 g / cm < 3 >

HI-10: product name, aluminum hydroxide, average particle diameter 55 mu m, shredded shape, true density 2.4 g / cm < 3 &

MCP 524-50: trade name, manufactured by Ube Materials, magnesium oxide, average particle diameter 50 탆, spherical, true density 3.6 g / cm 3

AL-13KT: trade name, manufactured by Showa Denko KK, aluminum oxide, average particle diameter 97 μm, aggregate, true density 4.0 g / cm 3

PT110: Product name, manufactured by Momentiv, boron nitride, average particle diameter 35 탆, scaly shape, true density 2.3 g / cm 3

The present invention has been described as an exemplary embodiment of the present invention, but this is merely an example and should not be construed as limiting. Variations of the invention which are obvious to those skilled in the art are included in the later patent claims.

The thermally conductive pressure-sensitive adhesive sheet of the present invention can be applied to various industrial products. For example, the thermally conductive pressure-sensitive adhesive sheet of the present invention can be applied to various semiconductor devices, hard disks, LED devices, EL devices, .

Claims (12)

Acrylic pressure sensitive adhesive layer,
Wherein the acrylic pressure sensitive adhesive layer contains three or more thermally conductive particles having different average particle diameters,
The space ratio when mixing the three or more thermally conductive particles is 72% or less,
Wherein the content ratio of the three or more thermally conductive particles to the acrylic pressure-sensitive adhesive layer is 55 vol% or more and 75 vol% or less. The method according to claim 1,
Wherein one of the three or more thermally conductive particles comprises a metal oxide or a metal nitride and the other thermally conductive particles include a metal hydroxide. 3. The method of claim 2,
Wherein the content of the thermally conductive particles containing the metal oxide or the metal nitride is 5% by volume or more and 25% by volume or less with respect to the acrylic pressure-sensitive adhesive layer. The method according to claim 1,
Wherein the three or more thermally conductive particles comprise a first thermally conductive particle having an average particle diameter of less than 3 占 퐉, a second thermally conductive particle having an average particle diameter of 3 占 퐉 or more and less than 70 占 퐉 and a third thermally conductive particle having an average particle diameter of 70 占 퐉 or more And a thermally conductive particle. The method according to claim 1,
Wherein the three or more thermally conductive particles comprise a first thermally conductive particle having an average particle diameter of less than 3 占 퐉, a second thermally conductive particle having an average particle diameter of not less than 3 占 퐉 and less than 70 占 퐉 and an average particle diameter of not less than 3 占 퐉 and less than 70 占 퐉, Wherein the thermally conductive particles contain the fourth thermally conductive particles in a piece form. The method according to claim 1,
Wherein the acrylic pressure sensitive adhesive layer contains an acrylic polymer obtained by polymerizing a monomer component containing a (meth) acrylic acid alkyl ester as a main component and containing 5 mass% or more of a polar group-containing monomer. The method according to claim 6,
Wherein the monomer component is substantially free of a monomer having a carboxyl group. The method according to claim 6,
The thermally conductive pressure-sensitive adhesive sheet is characterized in that the polar group-containing monomer contains a nitrogen-containing monomer and / or a hydroxyl group-containing monomer. The method according to claim 1,
Wherein the hardness of the thermally conductive pressure-sensitive adhesive sheet is 80 or less when measured 30 seconds after the pressure surface of the type C durometer is closely contacted in the type C hardness test. The method according to claim 1,
Wherein the thermal conductive adhesive sheet has a thermal conductivity of 1.7 W / m · K or more in the thickness direction. The method according to claim 1,
The thermally conductive pressure-sensitive adhesive sheet is characterized in that it satisfies the V-0 standard in UL94 flammability test. Sensitive adhesive sheet comprising an acrylic pressure-sensitive adhesive layer,
A step of mixing a thermally conductive particle having three or more kinds of different average particle diameters into a monomer component containing a (meth) acrylic acid alkyl ester as a main component to obtain a pressure-sensitive adhesive raw material; and
A step of reacting the pressure-sensitive adhesive raw material to obtain the acrylic pressure-sensitive adhesive layer
And,
The space ratio when mixing the three or more thermally conductive particles is 72% or less,
Wherein the content ratio of the three or more thermally conductive particles to the acrylic pressure-sensitive adhesive layer is 55 vol% or more and 75 vol% or less.

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