JP2011241329A - Heat-conductive self-adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-conductive self-adhesive sheet which can easily adhere a heat-generating member to a heat-releasing member and is excellent in heat conductivity.SOLUTION: The heat-conductive self-adhesive sheet having an adhesive layer prepared by forming a heat-conductive adhesive composition containing a heat-conductive substance and an acrylic polymer component into a sheet-like shape is characterized in that the complex modulus of elasticity of the self-adhesive layer at 100°C is 1.0×10to 1.0×10Pa.

Description

  The present invention relates to a pressure-sensitive adhesive sheet having improved thermal conductivity.

  Conventionally, heat generators such as machines and electronic parts that generate heat have a risk of performance degradation or damage when heat accumulates inside. By doing so, performance is maintained and damage is prevented.

  As a method for adhering the heat generating body and the heat radiating body, a double-sided pressure-sensitive adhesive sheet having thermal conductivity is widely used. The heat-conductive double-sided pressure-sensitive adhesive sheet is a resin composition that has a heat-sensitive adhesive layer composed of a resin composition or contains a heat-conductive substance in the pressure-sensitive adhesive layer. What improved thermal conductivity rather than the case where an agent layer is comprised is known. Thereby, it is possible to effectively move the heat of the heating element attached to one surface of the heat conductive double-sided pressure-sensitive adhesive sheet to the heat radiator attached to the other surface.

  Moreover, the metal which formed the heat radiator and the heat conductive adhesive sheet integrally by using the metal foil of predetermined thickness as a heat radiator, and forming the adhesive layer which has heat conductivity in the single side | surface of this metal foil. A heat conductive adhesive sheet with a foil has also been proposed (see Patent Document 1).

  Furthermore, as another method of bonding the heat generating body and the heat radiating body, there is a method using heat radiating grease having thermal conductivity. The heat dissipating grease is a paste-like material containing silicone, a heat conductive material, etc., and is applied between the heat generating body and the heat dissipating body so as to adhere the heat generating body and the heat dissipating body. It is configured.

JP-A-11-186473

  The heat conductive (double-sided) pressure-sensitive adhesive sheet (hereinafter referred to as a pressure-sensitive adhesive sheet) is formed in a sheet shape and is easier to handle than heat-dissipating grease. In the case where air is interposed between the adherend and the adhesive surface due to the influence of the surface roughness of the adhesive surface (that is, the adherend and the adhesive sheet are not spaced). There is a case where it cannot be adhered).

  In such a case, in a region where air is interposed, heat is transferred between the adherend and the adhesive sheet through the air layer, so that the thermal resistance (contact between the adhesive sheet and the adherend is Thermal resistance) will occur. For this reason, heat transfer between the pressure-sensitive adhesive sheet and the adherend is not efficiently performed, and it becomes difficult to cool the heat generating body by effectively moving the heat of the heat generating body to the heat radiating body side. There is.

  On the other hand, the heat-dissipating grease is easy to become familiar with the surface of the adherend and is used by being applied to the adherend, so that air is less likely to intervene with the adherend. In addition, it requires work to be applied to the adherend and requires a considerable time until it is cured.

  Then, this invention makes it a subject to provide the heat conductive adhesive sheet excellent in heat conductivity while being able to adhere | attach a heat generating body and a heat radiator easily.

  In view of the above problems, the present inventors have found that the contact thermal resistance can be reduced by setting the complex elastic modulus of the pressure-sensitive adhesive layer constituting the heat-conductive pressure-sensitive adhesive sheet within a predetermined range. It came to be completed.

The thermally conductive adhesive sheet according to the present invention includes a thermally conductive adhesive sheet comprising an adhesive layer formed by forming a thermally conductive adhesive composition containing a thermally conductive substance and an acrylic polymer component into a sheet shape. The complex elastic modulus of the pressure-sensitive adhesive layer at 100 ° C. is 1.0 × 10 ^{4 to} 1.0 × 10 ⁶ Pa.

According to such a configuration, the pressure-sensitive adhesive layer becomes flexible by setting the complex elastic modulus of the pressure-sensitive adhesive layer at 100 ° C. to 1.0 × 10 ^{4 to} 1.0 × 10 ⁶ Pa. When pressure-bonded to the body, the pressure-sensitive adhesive surface of the pressure-sensitive adhesive layer is easily adapted to the surface of the adherend. Thereby, it can suppress that air interposes between an adhesive layer and a to-be-adhered body, and can increase the contact area of a heat conductive adhesive sheet and an to-be-adhered body. That is, since the contact thermal resistance is reduced, the heat transfer between the adherend and the thermally conductive adhesive sheet is effectively performed, that is, the thermal conductivity is excellent. It becomes possible to cool the heat generating element by effectively moving the heat of the heat generating element attached to the surface to the side of the heat dissipating member attached to the other surface.

  Moreover, it is preferable that the heat conductive adhesive sheet which concerns on this invention is 0.5 W / m * K or more in heat conductivity.

  As described above, according to the present invention, the heat generating body and the heat radiating body can be easily bonded, and the heat conductivity is excellent.

(A) is the front schematic diagram which showed the apparatus used when measuring a contact thermal resistance in an Example, (b) is the side schematic diagram of the apparatus of (a).

  Hereinafter, preferred embodiments of the present invention will be described.

  The heat conductive adhesive sheet which concerns on this invention is arrange | positioned between a heat generating body and a heat radiator, and while it adheres them, it is comprised so that the heat | fever of a heat generating body may be transmitted to the heat radiator side. Specifically, the heat conductive pressure-sensitive adhesive sheet includes a pressure-sensitive adhesive layer in which a heat conductive pressure-sensitive adhesive composition containing a heat conductive material and an acrylic polymer component is formed into a sheet shape. The thermal conductivity is improved as compared with the case where no substance is contained.

  Further, the heat conductive pressure-sensitive adhesive sheet includes the heat conductive pressure-sensitive adhesive composition itself which is formed into a sheet shape to form a pressure-sensitive adhesive layer, or a resin film or other support. And the like in which an adhesive composition is laminated in a sheet form to form an adhesive layer.

The heat conductive adhesive sheet of this invention is comprised so that the complex elastic modulus of an adhesive layer in 100 degreeC may be 1.0 * 10 < ⁴ > -1.0 * 10 < ⁶ > Pa, Preferably it is 5.0 *. 10 ^{4 to} 8.0 × 10 ⁵ Pa, more preferably 7.0 × 10 ^{4 to} 6.0 × 10 ⁵ Pa. By setting the lower limit of the complex elastic modulus as described above, the pressure-sensitive adhesive performance (particularly the cohesive force) of the pressure-sensitive adhesive layer can be improved.

  Moreover, by setting the upper limit value of the complex elastic modulus as described above, the pressure-sensitive adhesive layer becomes flexible, and the pressure-sensitive adhesive layer is easily adapted to the surface of the adherend. Thereby, when a heat conductive adhesive sheet is crimped | bonded to an adherend, it can suppress that air interposes between a heat conductive adhesive sheet and an adherend, and reduces contact thermal resistance. Can do.

The contact thermal resistance when the thermally conductive adhesive sheet is pressure-bonded to the adherend at a pressure of 200 kPa is preferably 0.6 cm ² · K / W or less, and 0.5 cm ² · K / W or less. It is more preferable. Contact thermal resistance is the effect of the surface roughness of the adhesive surface of the thermally conductive adhesive sheet, and the presence of air between the thermally conductive adhesive sheet and the adherend, and the thermal conductive adhesive sheet and the adherend. It is the thermal resistance that occurs between the body. In addition, about the measuring method of a complex elastic modulus and contact thermal resistance, it is as showing in the following Example.

  Moreover, it is preferable that the heat conductive adhesive sheet of this invention becomes 0.5 W / m * K or more in heat conductivity. As a result, for example, sufficient thermal conductivity can be exhibited even when used by being adhered to a heat sink or the like of a semiconductor module.

  The acrylic polymer component is not particularly limited, and a commonly used acrylic polymer can be used. The acrylic polymer may be composed of a (meth) acrylic monomer represented by the following general formula (1) as a monomer unit.

In the general formula (1), R ¹ is hydrogen or a methyl group. In the above general formula (1), R ² is an alkyl group having 2 to 14 carbon atoms, preferably having 3 to 12 carbon atoms, if the tackiness is ensured, preferably 4 to 9 carbon atoms. Is more preferable. The alkyl group for R ² can be either linear or branched, and preferably has a branched chain because of its low glass transition point.

  Examples of the (meth) acrylic monomer represented by the general formula (1) include ethyl (meth) acrylate, n-butyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, Isobutyl (meth) acrylate, n-pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate, isoamyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (Meth) acrylate, isooctyl (meth) acrylate, n-nonyl (meth) acrylate, isononyl (meth) acrylate, n-decyl (meth) acrylate, isodecyl (meth) acrylate, n-dodecyl (meth) acrylate, isomyristyl Meth) acrylate, n- tridecyl (meth) acrylate, n- tetradecyl (meth) acrylate, stearyl (meth) acrylate, isostearyl (meth) acrylate, etc. phenoxyethyl (meth) acrylate.

  In the present invention, the (meth) acrylic monomer represented by the general formula (1) may be used alone or in combination of two or more. The content of the whole (meth) acrylic monomer is 50 to 100% by weight, preferably 60 to 98% by weight, and preferably 70 to 90% by weight with respect to the whole monomer constituting the acrylic polymer. % Is more preferable. By setting the content of the (meth) acrylic monomer to 50% by weight or more, it has good adhesiveness.

  The acrylic polymer may contain a polar group-containing monomer such as a hydroxyl group-containing monomer or a carboxyl group-containing monomer as a monomer unit. As content of a polar group containing monomer, it is preferable that it is 0-20 weight% with respect to the whole monomer which comprises an acrylic polymer, It is more preferable that it is 0.2-10 weight%, 0.2- More preferably, it is 7% by weight. When the content of the polar group-containing monomer is within the above range, the cohesive force is more fully exhibited. Moreover, it will have favorable adhesiveness by content of the said polar group containing monomer being 20 weight% or less.

  The hydroxyl group-containing monomer means a polymerizable monomer having one or more hydroxyl groups in the monomer structure. For example, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 8-hydroxy Octyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl acrylate, N-methylol (meth) acrylamide, N-hydroxy (meth) Examples include acrylamide, vinyl alcohol, allyl alcohol, 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether, and diethylene glycol monovinyl ether. Of these, 4-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, and the like are preferably used.

  The carboxyl group-containing monomer is a polymerizable monomer having one or more carboxyl groups in the monomer structure. Examples include acrylic acid, methacrylic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, itaconic acid, maleic acid, fumaric acid, and crotonic acid. Of these, acrylic acid and methacrylic acid are preferably used.

  In the acrylic polymer of the present invention, a polymerizable monomer for adjusting the glass transition point and peelability of the acrylic polymer can be used as a monomer other than the above-mentioned monomers within a range not impairing the effects of the present invention. .

Examples of other polymerizable monomers used in the acrylic polymer of the present invention include cohesion and heat resistance such as sulfonic acid group-containing monomers, phosphoric acid group-containing monomers, cyano group-containing monomers, vinyl ester monomers, aromatic vinyl monomers, and the like. Adequate use of components that have functional groups that function as adhesion-improving and crosslinking bases such as improving components, amide group-containing monomers, amino group-containing monomers, imide group-containing monomers, epoxy group-containing monomers, and vinyl ether monomers it can. Furthermore, in the general formula (1), a monomer or the like in which R ² is an alkyl group having 1 or 15 carbon atoms can be used as appropriate. These monomer compounds may be used alone or in admixture of two or more.

  Examples of the sulfonic acid group-containing monomer include styrene sulfonic acid, allyl sulfonic acid, 2- (meth) acrylamide-2-methylpropane sulfonic acid, (meth) acrylamide propane sulfonic acid, sulfopropyl (meth) acrylate, and (meth). Examples include acryloyloxynaphthalene sulfonic acid.

  Examples of the phosphoric acid group-containing monomer include 2-hydroxyethyl acryloyl phosphate.

  Examples of the cyano group-containing monomer include acrylonitrile and methacrylonitrile.

  Examples of the vinyl ester monomer include vinyl acetate, vinyl propionate, vinyl laurate, vinyl pyrrolidone and the like.

  Examples of the aromatic vinyl monomer include styrene, chlorostyrene, chloromethyl styrene, α-methyl styrene, and the like.

  Examples of the amide group-containing monomer include (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-diethylmethacrylamide, N-isopropyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, dimethylaminoethyl (meth) acrylate, t-butylaminoethyl (meth) acrylate, diacetone (meth) ) Acrylamide, N-vinylacetamide, N, N′-methylenebis (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-vinylcaprolactam, N-vinyl-2-pyrrolidone and the like.

  Examples of amino group-containing monomers include aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N- (meth) acryloylmorpholine, and the like. It is done.

  Examples of the imide group-containing monomer include N-cyclohexylmaleimide, N-phenylmaleimide, N-methylmaleimide, N-ethylmaleimide, N-propylmaleimide, N-isopropylmaleimide, N-butylmaleimide, and itaconimide.

  Examples of the epoxy group-containing monomer include glycidyl (meth) acrylate and allyl glycidyl ether.

  Examples of the vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, isobutyl vinyl ether, and the like.

  Examples of the (meth) acrylic monomer having an alkyl group having 1 or 15 carbon atoms include methyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, and octadecyl (meth) acrylate. It is done.

  Moreover, in order to improve characteristics, such as a cohesion force, the monomer which comprises an acrylic polymer may contain the other copolymerizable monomer as needed. Examples of such copolymerizable monomers include vinyl compounds such as vinyl acetate, styrene, and vinyl toluene; (meth) acrylic acid esters of cyclic alcohols such as cyclopentyl di (meth) acrylate and isobornyl (meth) acrylate; Neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, propylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylol methanetri (meth) acrylate, dipentaerythritol hexa (meth) Examples include (meth) acrylic acid esters of polyhydric alcohols such as acrylates.

  The other copolymerizable monomers may be used singly or in combination of two or more, but the total content is 0 with respect to the whole monomer constituting the acrylic polymer. It is preferably ˜50% by weight, more preferably 0 to 35% by weight, and further preferably 0 to 25% by weight.

  The acrylic polymer preferably has a weight average molecular weight of 600,000 or more, more preferably 700,000 to 3,000,000, and even more preferably 800,000 to 2,500,000. When the weight average molecular weight is 600,000 or more, it has good durability. On the other hand, from the viewpoint of workability, the weight average molecular weight is preferably 3 million or less. The weight average molecular weight is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene.

  In addition, the glass transition temperature (Tg) of the acrylic polymer is −5 ° C. or lower, preferably −10 ° C. or lower, because the pressure-sensitive adhesive layer easily balances the adhesiveness. When the glass transition temperature is −5 ° C. or lower, the flowability of the acrylic polymer is good, the wettability is sufficient with respect to the adherend, and the adhesive strength is good. The glass transition temperature (Tg) of the acrylic polymer can be adjusted within the above range by appropriately changing the monomer component and composition ratio to be used.

  Such an acrylic polymer can be produced by a known production method such as solution polymerization, bulk polymerization, emulsion polymerization, photopolymerization, and various radical polymerizations. Further, the obtained acrylic polymer may be a homopolymer or a copolymer, and when it is a copolymer, it may be any of a random copolymer, a block copolymer, a graft copolymer, and the like. .

  In solution polymerization, for example, ethyl acetate, toluene or the like is used as a polymerization solvent. As a specific solution polymerization example, the reaction is carried out under an inert gas stream such as nitrogen, and as a polymerization initiator, for example, azobisisobutyronitrile 0.01 to 0.2 parts per 100 parts by weight of the total amount of monomers. Addition of parts by weight is usually performed at about 50 to 70 ° C for about 8 to 30 hours.

  The polymerization initiator, chain transfer agent, emulsifier and the like used for radical polymerization are not particularly limited, and can be appropriately selected and used.

  Examples of the polymerization initiator used in the present invention include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-amidinopropane) dihydrochloride, 2,2′-azobis [2- ( 5-methyl-2-imidazolin-2-yl) propane] dihydrochloride, 2,2′-azobis (2-methylpropionamidine) disulfate, 2,2′-azobis (N, N′-dimethyleneisobutylamidine) ), 2,2′-azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate (manufactured by Wako Pure Chemical Industries, Ltd., VA-057); potassium persulfate, ammonium persulfate Persulfates such as: di (2-ethylhexyl) peroxydicarbonate, di (4-t-butylcyclohexyl) peroxydicarbonate Di-sec-butylperoxydicarbonate, t-butylperoxyneodecanoate, t-hexylperoxypivalate, t-butylperoxypivalate, dilauroyl peroxide, di-n-octanoyl peroxide, 1,1,3,3-tetramethylbutylperoxy-2-ethylhexanoate, di (4-methylbenzoyl) peroxide, dibenzoyl peroxide, t-butylperoxyisobutyrate, 1,1-di ( t-hexylperoxy) peroxide initiators such as cyclohexane, t-butyl hydroperoxide, hydrogen peroxide; peroxidation such as a combination of persulfate and sodium bisulfite, a combination of peroxide and sodium ascorbate Redox initiators that combine products and reducing agents. But it is not limited thereto.

  The said polymerization initiator may be used independently, and may mix and use 2 or more types. The content of the polymerization initiator as a whole is preferably about 0.005 to 1 part by weight and more preferably about 0.02 to 0.5 part by weight with respect to 100 parts by weight of the monomer.

  In the present invention, a chain transfer agent may be used in the polymerization. By using a chain transfer agent, the molecular weight of the acrylic polymer can be appropriately adjusted.

  As the chain transfer agent, for example, lauryl mercaptan, glycidyl mercaptan, mercaptoacetic acid, 2-mercaptoethanol, thioglycolic acid, 2-ethylhexyl thioglycolate, 2,3-dimercapto-1-propanol and the like can be used.

  These chain transfer agents may be used alone or in combination of two or more. The content of the chain transfer agent as a whole is usually about 0.01 to 0.1 parts by weight with respect to 100 parts by weight of the monomer.

  Examples of the emulsifier used for emulsion polymerization include anionic emulsifiers such as sodium lauryl sulfate, ammonium lauryl sulfate, sodium dodecylbenzene sulfonate, ammonium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate; polyoxy Nonionic emulsifiers such as ethylene alkyl ether, polyoxyethylene alkyl phenyl ether, polyoxyethylene fatty acid ester, and polyoxyethylene-polyoxypropylene block polymer can be used. These emulsifiers may be used alone or in combination of two or more.

  Furthermore, as a reactive emulsifier, an emulsifier having a radical polymerizable functional group such as propenyl group or allyl ether group introduced therein, for example, Aqualon HS-10, HS-20, KH-10, BC-05, BC-10, BC -20 (all are manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adekaria soap SE10N (manufactured by ADEKA), and the like can be used. Reactive emulsifiers are preferred because they are incorporated into the polymer chain after polymerization and thus improve water resistance. The amount of the emulsifier used is more preferably 0.3 to 5 parts by weight and 0.5 to 1 part by weight with respect to 100 parts by weight of the monomer in view of polymerization stability and mechanical stability.

  The polymerization initiator (photopolymerization initiator), chain transfer agent, emulsifier and the like used when using photopolymerization are not particularly limited, and can be appropriately selected and used.

  The photopolymerization initiator is not particularly limited, and for example, benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photoactivity An oxime photopolymerization initiator, a benzoin photopolymerization initiator, a benzyl photopolymerization initiator, a benzophenone photopolymerization initiator, a ketal photopolymerization initiator, a thioxanthone photopolymerization initiator, and the like can be used. Two or more may be used together.

Specifically, 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-diphenylethane- Examples include 1-one and anisole methyl ether.
Examples of the acetophenone photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, 4-t-butyl-dichloro. Examples include acetophenone.
Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone, 1- [4- (2-hydroxyethyl) -phenyl] -2-hydroxy-2-methylpropane-1- ON etc. are mentioned.
Examples of the aromatic sulfonyl chloride photopolymerization initiator include 2-naphthalenesulfonyl chloride.
Examples of the photoactive oxime photopolymerization initiator include 1-phenyl-1,1-propanedione-2- (o-ethoxycarbonyl) -oxime.
Examples of the benzoin photopolymerization initiator include benzoin.
Examples of the benzyl photopolymerization initiator include benzyl.
Examples of the benzophenone photopolymerization initiator include benzophenone, benzoylbenzoic acid, 3,3′-dimethyl-4-methoxybenzophenone, polyvinyl benzophenone, α-hydroxycyclohexyl phenyl ketone, and the like.
Examples of the ketal photopolymerization initiator include benzyl dimethyl ketal.
Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-dichlorothioxanthone, 2,4-diethylthioxanthone, 2,4. -Diisopropyl thioxanthone, dodecyl thioxanthone, etc. are mentioned.

  As content of a photoinitiator, for example, 0.001-5 weight part with respect to 100 weight part of all the monomer components contained in a heat conductive adhesive composition, Preferably it is the range of 0.01-3 weight part. You can choose from.

  When activating the photopolymerization initiator, it is important to irradiate the heat conductive pressure-sensitive adhesive composition containing the photopolymerization initiator with an active energy beam. Examples of such active energy rays include ionizing radiation such as α rays, β rays, γ rays, neutron rays, electron rays, and ultraviolet rays, and ultraviolet rays are particularly preferable. The irradiation energy, irradiation time, irradiation method and the like of the active energy beam are not particularly limited as long as the photopolymerization initiator can be activated to cause the monomer component to react.

  The heat conductive pressure-sensitive adhesive composition containing the photopolymerization initiator may contain additives within an appropriate range as necessary (for example, a range that does not inhibit the photopolymerization reaction). . Examples of such additives include thickeners such as acrylic rubber, epichlorohydrin rubber, and butyl rubber; thixotropic agents such as colloidal silica and polyvinylpyrrolidone; extenders such as calcium carbonate, titanium oxide, and clay; inorganic hollow bodies (for example, Glass balloons, alumina balloons, ceramic balloons, etc., organic hollow bodies (eg, vinylidene chloride balloons, acrylic balloons, etc.), organic spheres (eg, nylon beads, acrylic beads, silicone beads, etc.), single fibers (eg, polyester) , Rayon, nylon, etc.), fine powders (for example, fine powders such as polyethylene and polypropylene); plasticizers; anti-aging agents; antioxidants; colorants such as pigments and dyes; Acrylate (HDDA), trim Crosslinking agents, such as trimethylolpropane triacrylate (TMPTA); and the like tackifiers.

  Moreover, it is preferable to contain a crosslinking agent as a component which comprises the acrylic polymer in a heat conductive adhesive composition in order to improve the adhesive force and durability of an adhesive layer more. As the crosslinking agent, a known crosslinking agent such as an isocyanate crosslinking agent, an epoxy crosslinking agent, a melamine crosslinking agent, an oxazoline crosslinking agent, a carbodiimide crosslinking agent, an aziridine crosslinking agent, or a metal chelate crosslinking agent may be used. Although it is possible, it is particularly preferable to contain an isocyanate-based crosslinking agent.

  As the isocyanate-based crosslinking agent, aromatic isocyanates such as tolylene diisocyanate and xylene diisocyanate; alicyclic isocyanates such as isophorone diisocyanate; aliphatic isocyanates such as hexamethylene diisocyanate can be used.

  More specifically, lower aliphatic polyisocyanates such as butylene diisocyanate and hexamethylene diisocyanate; alicyclic isocyanates such as cyclopentylene diisocyanate, cyclohexylene diisocyanate and isophorone diisocyanate; 2,4-tolylene diisocyanate, 4, Aromatic diisocyanates such as 4′-diphenylmethane diisocyanate, xylylene diisocyanate, polymethylene polyphenyl isocyanate; trimethylolpropane / tolylene diisocyanate trimer adduct (trade name Coronate L, manufactured by Nippon Polyurethane Industry Co., Ltd.), trimethylolpropane / Hexamethylene diisocyanate trimer adduct (made by Nippon Polyurethane Industry Co., Ltd., trade name Coronate HL), hexamethylene diisocyanate Isocyanurate bodies (made by Nippon Polyurethane Industry Co., Ltd., trade name Coronate HX) and other isocyanate adducts; polyether polyisocyanates, polyester polyisocyanates, and adducts of these with various polyols, isocyanurate bonds, burette bonds, A polyisocyanate polyfunctionalized with an allophanate bond or the like can be used.

  The said crosslinking agent may be used independently and may mix and use 2 or more types. The content of the entire crosslinking agent is preferably 0.02 to 5 parts by weight, more preferably 0.04 to 3 parts by weight, and 0.05 to 2 parts by weight with respect to 100 parts by weight of the acrylic polymer. More preferably. By using the cross-linking agent in the above range, the cohesive force and durability can be more reliably improved. Moreover, it becomes moderate bridge | crosslinking formation by setting it as 2 weight part or less, and it has favorable adhesiveness.

  In this invention, it is preferable to adjust the addition amount of a crosslinking agent so that the gel fraction of the bridge | crosslinked thermally conductive adhesive composition may be 40 to 90 weight%, and it may be 50 to 85 weight% It is more preferable to adjust to 50 to 80% by weight. By setting the gel fraction to 40% by weight or more, the cohesive force is improved and the durability is good. Moreover, it will have favorable adhesiveness by setting it as 90 weight% or less.

  The gel fraction (% by weight) was obtained by taking a dry weight W1 (g) sample from the crosslinked thermally conductive adhesive composition, immersing it in ethyl acetate, and then removing the insoluble content of the sample from ethyl acetate. The weight W2 (g) after taking out from the inside and drying can be measured, and (W2 / W1) × 100 can be calculated and obtained.

  The said heat conductive substance can improve the heat conductivity of a heat conductive adhesive sheet by being contained in an adhesive layer. The thermal conductive material that can be used in the present invention is not particularly limited, but boron nitride, aluminum nitride, silicon nitride, gallium nitride, aluminum hydroxide, magnesium hydroxide, silicon carbide, silicon dioxide, oxidation Aluminum, titanium oxide, zinc oxide, tin oxide, copper oxide, nickel oxide, antimonic acid doped tin oxide, calcium carbonate, barium titanate, potassium titanate, copper, silver, gold, nickel, aluminum, platinum, carbon black, carbon Examples include tubes (carbon nanotubes), carbon fibers, and diamonds. Among these thermally conductive substances, boron nitride, aluminum hydroxide, and aluminum oxide are preferably used because they have high thermal conductivity and electrical insulation. These heat conductive substances may be used alone or in combination of two or more.

  The shape of the heat conductive substance used in the present invention is not particularly limited, and may be a bulk shape, a needle shape, a plate shape, or a layer shape. The bulk shape includes, for example, a spherical shape, a rectangular parallelepiped shape, a crushed shape, or a deformed shape thereof.

In the present invention, when the heat conductive material is in a bulk shape (spherical), the primary average particle diameter is 0.1 to 1000 μm, preferably 1 to 100 μm, more preferably 2 to 20 μm. By setting the primary average particle size to 1000 μm or less, even when the pressure-sensitive adhesive layer is formed with a thickness of less than 1000 μm, the bulk-shaped thermally conductive material exceeds the thickness of the pressure-sensitive adhesive layer, and the thickness of the pressure-sensitive adhesive layer It is possible to prevent the variation from occurring.
The primary average particle diameter is a volume-based value obtained by the particle size distribution measurement method in the laser scattering method. Specifically, it is calculated | required by measuring D50 value with a laser scattering type particle size distribution meter.

  When the heat conductive material is needle-shaped or plate-shaped, the maximum length is 0.1 to 1000 μm, preferably 1 to 100 μm, and more preferably 2 to 20 μm. By setting the maximum length to 1000 μm or less, agglomeration between needle-shaped or plate-shaped thermally conductive substances is suppressed, and handling becomes easy. Furthermore, these aspect ratios (in the case of acicular crystals, they are expressed as major axis length / minor axis length, or major axis length / thickness. In the case of plate crystals, the diagonal length is also expressed. / Expressed in thickness / long side length / thickness) is 1 to 10000, preferably 10 to 1000.

  As the above-described heat conductive material, those commonly used can be used. For example, as boron nitride, “HP-40” manufactured by Mizushima Alloy Iron Co., “PT620” manufactured by Momentive, etc. As aluminum oxide, "Hijilite H-32" and "Hijilite H-42" manufactured by Showa Denko KK, as aluminum oxide, "AS-50" manufactured by Showa Denko KK, and as magnesium hydroxide, Kyowa. “KISUMA 5A” manufactured by Kagaku Corporation and antimony-doped tin oxide include “SN-100S” “SN-100P” “SN-100D (water dispersion)” manufactured by Ishihara Sangyo Co., Ltd. as titanium oxide Uses “TTO series” manufactured by Ishihara Sangyo Co., Ltd., and “ZnO-310”, “ZnO-350”, “ZnO-410” manufactured by Sumitomo Osaka Cement Co., Ltd., etc. are used as zinc oxide. Door can be.

  The amount of the heat conductive material used is preferably 10 to 1000 parts by weight, more preferably 50 to 500 parts by weight, and more preferably 100 to 400 parts by weight with respect to 100 parts by weight of the acrylic polymer component. Is more preferable. By making the usage-amount of a heat conductive substance into 1000 weight part or less, while having favorable flexibility, it has favorable adhesive force. Moreover, sufficient thermal conductivity can be provided by setting it as 10 weight part or more.

  In addition, when producing a heat conductive adhesive composition, a silane coupling agent is used for the purpose of improving the affinity between the heat conductive substance and the acrylic polymer, or for improving the adhesive strength and durability of the adhesive layer. Can be used. The silane coupling agent is not particularly limited, and a known silane coupling agent can be appropriately selected and used.

  For example, epoxy such as 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane Group-containing silane coupling agent; 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propyl Amino group-containing silane coupling agents such as amines; (Meth) acrylic group-containing silane coupling agents such as 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropyltriethoxysilane; 3-isocyanatopropyltriethoxysilane and the like Insane Such as group-containing silane coupling agent. Use of such a silane coupling agent is preferable for improving durability.

  The silane coupling agents may be used alone or in combination of two or more. The total content of the silane coupling agent is preferably 0.01 to 10 parts by weight and more preferably 0.02 to 5 parts by weight with respect to 100 parts by weight of the acrylic polymer. 0.05 to 2 parts by weight is more preferable. By using the silane coupling agent in the above range, the cohesive force and durability can be improved more reliably. Moreover, by setting it as 0.01 weight part or more, the surface of a particulate-form heat conductive substance can fully be coat | covered, and affinity with an acrylic polymer can be improved. Moreover, it will have favorable thermal conductivity by setting it as 10 weight part or less.

  Moreover, when manufacturing the said heat conductive adhesive composition, tackifying resin can be used in order to improve the adhesive force and durability of an adhesive layer more. The tackifier resin is not particularly limited, and a known one can be appropriately selected and used. Examples of tackifying resins include rosin resins, terpene resins, aliphatic petroleum resins, aromatic petroleum resins, copolymer petroleum resins, alicyclic petroleum resins, xylene resins, and elastomers. Can do.

  As content of the said tackifying resin, it is preferable that it is either 10-100 weight part with respect to 100 weight part of acrylic polymers, It is more preferable that it is either 20-80 weight part, 30-50 More preferably, it is any part by weight.

  Further, although not described in detail here, in addition to the acrylic polymer component and the heat conductive material as described above, the heat conductive pressure-sensitive adhesive composition includes a dispersant, an antioxidant, an antioxidant, and a processing aid. In addition, rubbers such as stabilizers, antifoaming agents, flame retardants, thickeners, pigments, and the like that are generally used as plastic compounding chemicals can be appropriately added within a range not impairing the effects of the present invention.

  Next, a method for producing a heat conductive double-sided pressure-sensitive adhesive sheet using the heat conductive pressure-sensitive adhesive composition comprising the above-described components will be described. In the following description, a case where boron nitride particles are used as the thermally conductive material will be described.

First, a method for producing a liquid thermal conductive pressure-sensitive adhesive composition (coating solution) containing an acrylic polymer component composed of the above-described components and aggregated boron nitride particles having an average particle size of 60 to 200 μm. Will be described.
The average particle diameter is a volume-based value obtained by the particle size distribution measurement method in the laser scattering method. Specifically, it is calculated | required by measuring D50 value with a laser scattering type particle size distribution meter.

When preparing the coating liquid, a mixer capable of stirring boron nitride particles with an acrylic polymer under reduced pressure is used.
If necessary, the coating liquid may contain a dispersant that improves the dispersibility of the boron nitride particles in the acrylic polymer. As the dispersant, it is preferable to use a dispersant containing a compound having an amine value of more than 0 mgKOH / g and not more than 35 mgKOH / g from the viewpoint of excellent dispersibility improvement effect of boron nitride particles with respect to the acrylic polymer.

  First, boron nitride particles are charged into the mixer, and then a part of a resin solution in which an acrylic polymer and other components are dispersed in a solvent is charged into the mixer. And the particle size adjustment process which refines | miniaturizes the boron nitride particle of an aggregated state is implemented by stirring at normal temperature under reduced pressure of 1-20 kPa, for example.

At this time, the mixture of the boron nitride particles and the resin solution can be brought into a high-viscosity state by carrying out stirring without adding the entire amount of the resin solution necessary for producing the heat conductive adhesive composition. It can be stirred while applying high share stress.
Therefore, the aggregated boron nitride particles subjected to high shear stress are released from the aggregated state and refined to a state close to primary particles, for example, to an average particle size of 3 μm to 20 μm. It becomes.

  More specifically, for example, the rotation speed of the mixer is 30 rpm or less, preferably 10 to 20 rpm, and all boron nitride particles are dispersed in the resin solution, and adhesion to the stirring blades of the mixer is observed. A method of continuing the agitation operation until the viscosity becomes such that it is no longer possible can be employed.

Next, the remaining amount of the resin solution is added to the mixer, and, for example, the mixture is stirred at room temperature under a reduced pressure of 1 to 20 kPa. The particle size readjustment process is carried out.
In addition, if necessary, the remaining amount of the resin solution can be divided into several degrees, and the particle size readjustment step can be performed in a plurality of steps in a stepwise manner.

  More specifically, for example, the rotational speed of the mixer is 20 to 50 rpm, preferably 20 to 30 rpm, which is equal to or higher than the particle size adjustment step, and this stirring operation is continued until large aggregates are not visually observed. It is possible to adopt a method of making it.

  In this particle size readjustment step, since the shear stress is lower than that in the particle size adjustment step, the agglomerated boron nitride particles are not refined to a very fine particle size, for example, medium to more than 20 μm and less than 60 μm More boron nitride particles having an average particle size of are formed than in the particle size adjusting step.

  Thus, by carrying out the particle size adjustment step and one or more particle size readjustment steps, the average particle size of the boron nitride particles in the coating liquid can be brought into a state of 3 μm or more and 300 μm or less, and the particle size distribution thereof 3 to 20 μm is 5 to 45% by volume, 20 to 60 μm is 30 to 70% by volume, and 60 to 300 μm is 10 to 40% by volume.

  Next, a method for producing a heat conductive pressure-sensitive adhesive sheet using the coating liquid produced as described above will be described. For example, after coating the coating liquid on both sides of the support with a predetermined thickness, it is dried to form an adhesive layer on the support, and a thermally conductive double-sided pressure-sensitive adhesive sheet with a support can be produced.

  Alternatively, after one surface is coated with a coating liquid with a predetermined thickness on the treated surface side of a release film treated with a release agent (silicone or the like), the release film is peeled off and only the pressure-sensitive adhesive layer is removed from the support. You may laminate on both surfaces and produce a heat conductive adhesive sheet with a support body.

  Alternatively, the treatment surface side of the release film may be coated with a coating liquid with a predetermined thickness and dried to produce a thermally conductive double-sided pressure-sensitive adhesive sheet consisting only of the pressure-sensitive adhesive layer.

  As a method of coating the coating liquid on the support or release film with a predetermined thickness, a conventionally widely used method can be employed. For example, roll coat, kiss roll coat, gravure coat, reverse coat, roll brush, spray coat, dip roll coat, bar coat, knife coat, air knife coat, curtain coat, lip coat, extrusion coat method by die coater, etc. The method can be used.

  Examples of the support include plastic base materials such as polyethylene terephthalate (PET) and polyester film, porous materials such as paper and nonwoven fabric, and metal foil.

  The plastic substrate is not particularly limited as long as it can be formed into a sheet shape or a film shape. For example, polyethylene, polypropylene, poly-1-butene, poly-4-methyl-1-pentene, ethylene Polyolefin films such as propylene copolymer, ethylene / 1-butene copolymer, ethylene / vinyl acetate copolymer, ethylene / ethyl acrylate copolymer, ethylene / vinyl alcohol copolymer; polyethylene terephthalate, polyethylene naphthalate, poly Polyester film such as butylene terephthalate; Polyacrylate film, Polystyrene film, Polyamide film such as nylon 6, Nylon 6,6, Partially aromatic polyamide; Polyvinyl chloride film, Polyvinylidene chloride film, Polycar Such as titanate film, and the like. The thickness of the film is usually about 4 to 100 μm, preferably about 4 to 25 μm.

  For plastic substrates, if necessary, silicone-based, fluorine-based, long-chain alkyl-based or fatty acid amide-based mold release agents, mold release with silica powder, etc., acid treatment, acid treatment, alkali treatment, primer treatment, Anti-adhesive treatment such as corona treatment, plasma treatment and ultraviolet treatment, coating type, kneading type, vapor deposition type and the like can also be carried out.

  Examples of the constituent material of the release film include plastic films such as polyethylene, polypropylene, and polyethylene terephthalate, porous materials such as paper, cloth, and nonwoven fabric, nets, foam sheets, metal foils, and thin leaves such as laminates thereof. In view of excellent surface smoothness, a plastic film is preferably used.

  The plastic film is not particularly limited as long as it can protect the pressure-sensitive adhesive layer. For example, a polyethylene film, a polypropylene film, a polybutene film, a polybutadiene film, a polymethylpentene film, a polyvinyl chloride film, A vinyl chloride copolymer film, a polyethylene terephthalate film, a polybutylene terephthalate film, a polyurethane film, an ethylene-vinyl acetate copolymer film, or the like can be used.

  For the release film, if necessary, mold release and antifouling treatment with silicone, fluorine, long chain alkyl or fatty acid amide release agent, silica powder, etc., coating type, kneading type, vapor deposition An antistatic treatment such as a mold may be performed. In particular, the release property from the pressure-sensitive adhesive layer can be further improved by appropriately performing a release treatment such as silicone treatment, long-chain alkyl treatment, or fluorine treatment on the surface of the release film.

  The thickness of the release film is usually about 5 to 200 μm, preferably about 5 to 100 μm.

  The thickness of the pressure-sensitive adhesive layer in the heat conductive pressure-sensitive adhesive sheet of the present invention is preferably 20 μm to 5 mm, more preferably 50 μm to 2 mm, and further preferably 100 μm to 1 mm.

  The above heat conductive pressure-sensitive adhesive sheet has a high adhesive force because acrylic polymer is used as a polymer component. For example, a peel test is performed on a SUS304 steel sheet at a peel angle of 180 ° and a peel speed of 300 mm / min. When carried out, it has an adhesive strength of 1.0 N / 20 mm or more, preferably 3.0 N / 20 mm or more, more preferably 5.0 N / 20 mm or more. If the adhesive strength with respect to a SUS304 steel plate is 1.0 N / 20 mm or more, sufficient adhesive performance can be exhibited even if it is used by being attached to a heat sink or the like of a semiconductor module, for example.

  EXAMPLES Next, although an Example is given and this invention is demonstrated in more detail, this invention is not limited to these.

<Example 1>
1. Preparation of acrylic resin solution In a reaction vessel equipped with a cooling tube, a nitrogen introduction tube, a thermometer and a stirrer, 100 parts by weight of 2-ethylhexyl acrylate (2EHA), a photopolymerization initiator (trade names “Irgacure 651” and “Irgakiure” 184 "manufactured by Ciba Japan Co., Ltd.) was added and mixed. Thereafter, nitrogen gas is introduced to remove dissolved oxygen, and ultraviolet rays (UV) are irradiated until the viscosity (BH viscometer, No. 5 rotor, 10 rpm, measurement temperature: 30 ° C.) reaches 10 Pa · s. An acrylic resin solution in which part was polymerized was obtained.

2. Preparation of coating liquid For 100 parts by weight of acrylic resin solution, 0.2 parts by weight of trimethylolpropane triacrylate, 0.1 part by weight of photopolymerization initiator (trade name “Irgakia 184” manufactured by Ciba Japan), heat conduction Boron nitride powder (trade name “HP-40”, manufactured by Mizushima Alloy Iron Co., Ltd.) 33 parts by weight was added and stirred as a conductive substance to obtain a coating liquid of a heat conductive adhesive composition.

3. Production of Thermally Conductive Adhesive Sheet Next, a roll coater was applied to the release treated surface of a polyester film (trade name “Lumirror S-10 # 38”, thickness: 38 μm, manufactured by Toray Industries, Inc.), one side of which was peeled off with silicone as a release film. The coating liquid was applied so that the thickness after curing was 50 μm, and an uncured pressure-sensitive adhesive layer was formed. And the peeling film comprised similarly to the said peeling film was bonded together to the uncured adhesive layer so that a peeling process surface might contact | connect the said uncured adhesive layer. Then, UV irradiation (illuminance: 5 mW / cm ² ) is performed for 5 minutes using black light from both sides to cure the uncured pressure-sensitive adhesive layer to form a pressure-sensitive adhesive layer. From the pressure-sensitive adhesive layer having a thickness of 50 μm The heat conductive adhesive sheet (henceforth an adhesive sheet) obtained was obtained.

<Example 2>
The same as Example 1 except that 40 parts by weight of boron nitride powder (trade name “HP-40” manufactured by Mizushima Alloy Iron Co., Ltd.) was added as a heat conductive substance to 100 parts by weight of the acrylic resin solution. The adhesive sheet was produced by the method.

<Example 3>
Instead of 2-ethylhexyl acrylate (2EHA) used in the acrylic resin solution of Example 1, butyl acrylate (BA) was used, and boron nitride powder (trade name “HP” manufactured by Mizushima Alloy Iron Co., Ltd.) was used as the heat conductive material. −40 ”) A pressure-sensitive adhesive sheet was produced in the same manner as in Example 1 except that 60 parts by weight were added.

<Comparative Example 1>
An acrylic heat conductive sheet (manufactured by Achilles, trade name “HN-020-B”) was used as an adhesive sheet.

<Measurement of complex modulus>
The complex elastic modulus G ^* at 100 ° C. was measured using a rheometer (ARES) manufactured by TA Instruments. Measurement conditions are as follows.
・ Deformation mode: Torsion ・ Measurement frequency: 1 Hz (constant)
・ Temperature increase rate: 5 ° C./min ・ Measurement temperature: 160 ° C. from near the glass transition temperature of the heat conductive adhesive composition
・ Measurement jig: Parallel plate (diameter 8.0mm)

<Measurement of thermal conductivity>
The thermal conductivity of the pressure-sensitive adhesive sheet of each example and comparative example was measured. The thermal conductivity is obtained by obtaining the thermal diffusivity using the product name “ai-phase mobile” manufactured by Eye Phase, and multiplying the thermal diffusivity by the heat capacity per unit volume of the pressure-sensitive adhesive sheet measured with a differential scanning calorimeter (DSC). Calculated by The measurement results are shown in Table 1 below.

<Contact thermal resistance>
The contact thermal resistance was measured using the thermal characteristic evaluation apparatus shown in FIG.
Specifically, each of the implementations in which the release film on both sides was peeled between a pair of rods L made of aluminum (A5052, thermal conductivity: 140 W / m · K) formed so as to be a cube having a side of 20 mm. The pressure-sensitive adhesive sheet S (20 mm × 20 mm × 50 μm) of Examples and Comparative Examples was sandwiched, and a pair of rods L were bonded together with the pressure-sensitive adhesive sheet.
And it arrange | positioned between the heat generating body (heater block) H and the heat radiating body (cooling base board comprised so that a cooling water circulates inside) C so that a pair of rod L might become up-down. Specifically, the heating element H is disposed on the upper rod L, and the radiator C is disposed below the lower rod L. At this time, the pair of rods L bonded together with the adhesive sheet S is positioned between a pair of pressure adjusting screws T penetrating the heating element and the heat radiating body. A load cell R is installed between the pressure adjusting screw T and the heating element H so that the pressure when the pressure adjusting screw T is tightened is measured. Was used as a pressure applied to the pressure-sensitive adhesive sheet S.
In addition, three probes P (diameter 1 mm) of a contact displacement meter were installed so as to penetrate the lower rod L and the adhesive sheet S from the radiator C side. At this time, the upper end portion of the probe P is in contact with the lower surface of the upper rod L, and the distance between the upper and lower rods L (the thickness of the adhesive sheet S) can be measured.
A temperature sensor D was attached to the heating element H and the upper and lower rods L. Specifically, the temperature sensor D was attached at one place on the heating element H and five places at intervals of 5 mm in the vertical direction of each rod L.

  The contact thermal resistance was measured as follows.

(1) Total thermal resistance First, the pressure adjusting screw T is tightened to apply pressure to the adhesive sheet S, the temperature of the heating element H is set to 100 ° C., and cooling water of 20 ° C. is applied to the radiator C. It was circulated.
Then, after the temperatures of the heating element H and the upper and lower rods L are stabilized, the temperature of the upper and lower rods L is measured by each temperature sensor D, and passes through the adhesive sheet S from the thermal conductivity and temperature gradient of the upper and lower rods L. While calculating a heat flux, the temperature of the interface of the upper and lower rods L and the adhesive sheet S was calculated. And the total thermal resistance (cm < ² > * K / W) in the said pressure was computed using these.
The pressure applied to the pressure-sensitive adhesive sheet S was in the range of 150 to 800 kPa, and the total thermal resistance was measured at each pressure selected every 50 kPa in the pressure range.

(2) Thermal resistance of the pressure-sensitive adhesive sheet itself The pressure applied to the pressure-sensitive adhesive sheet S is changed within the above range, the total thermal resistance at each pressure is measured several times, and the relationship between the total thermal resistance at each pressure and the inverse of each pressure is An approximate straight line was created by plotting, and the total thermal resistance when the pressure was infinite in the approximate straight line (that is, when 1 / pressure≈0) was defined as the thermal resistance of the adhesive sheet itself.
That is, when the pressure is infinite, it is approximated that air does not intervene between the adhesive sheet S and the upper and lower rods L, that is, the contact thermal resistance becomes 0. The heat resistance of the adhesive sheet itself was used.

(3) Contact thermal resistance The contact thermal resistance (cm ² · K / W) at such pressure was calculated by subtracting the thermal resistance of the adhesive sheet itself from the total thermal resistance when the pressure was 200 kPa. The calculation results of the contact thermal resistance are as shown in Table 1 below.

<Heat dissipation>
The temperature of the heating element H was measured by the temperature sensor D in a state where the pressure applied to the adhesive sheet was 200 kPa. The measurement results are as shown in Table 1 below.

When Examples 1 to 3 and Comparative Example 1 are compared, it is recognized that the contact thermal resistance is lower in each of the examples configured such that the complex elastic modulus of the pressure-sensitive adhesive layer is lower. Further, it is recognized that in Examples 1 and 2, the heating element temperature is lower than that of Comparative Example 1 although the thermal conductivity is lower than that of Comparative Example 1.
In other words, by configuring the pressure-sensitive adhesive layer so that the complex elastic modulus is low, the pressure-sensitive adhesive layer becomes flexible. Become familiar with the surface. Thereby, it is suppressed that air interposes between an adhesive layer and a to-be-adhered body, and the movement of the heat between an to-be-adhered body and a heat conductive adhesive sheet comes to be performed effectively. For this reason, it is recognized that the heat of a heat generating body can move efficiently to the heat radiating body side, and can reduce the temperature of a heat generating body effectively.

Claims (2)

A heat conductive pressure-sensitive adhesive sheet comprising a pressure-sensitive adhesive layer in which a heat conductive pressure-sensitive adhesive composition containing a heat conductive material and an acrylic polymer component is formed into a sheet shape,
The heat conductive adhesive sheet characterized by the complex elastic modulus of the adhesive layer in 100 degreeC being 1.0 * 10 < ⁴ > -1.0 * 10 < ⁶ > Pa.   The heat conductive adhesive sheet according to claim 1, wherein the heat conductivity is 0.5 W / m · K or more.

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