JP2015007210A - Heat-conductive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thin adhesive sheet having excellent fire retardancy, as well as excellent heat conductivity and adhesiveness.SOLUTION: A heat-conductive adhesive sheet includes an adhesive layer containing, as heat-conductive particles, a particle group A whose D50 average particle diameter is 10 μm or more and a particle group B whose D50 average particle diameter is less than 10 μm, at a ratio (weight ratio) of 2:8-8:2 with regard to the particle group A and the particle group B. A thickness of the adhesive layer is 50 μm or less. A content of the heat-conductive particles in the adhesive layer is preferably 25-75 vol.%. The heat-conductive adhesive sheet preferably has fire retardancy of VTM-0 or V-0 according to a fire retardancy test of UL 94 standard.

Description

  The present invention relates to a heat conductive adhesive sheet. In more detail, it is related with the heat conductive adhesive sheet with the small thickness of an adhesive layer.

  In recent years, mobile devices, home appliances, and the like have been miniaturized, and pressure-sensitive adhesive sheets used for fixing components inside the mobile devices and the like have been required to be thinner. Since there is a risk of ignition due to heat trapped inside the equipment, these pressure-sensitive adhesive sheets are required to have excellent flame retardancy (a property that is difficult to burn) and thermal conductivity.

  Conventionally, as an adhesive sheet having flame retardancy, an adhesive sheet containing a halogen-based flame retardant (Patent Document 1) and an adhesive sheet containing a phosphoric acid-based flame retardant are known (Patent Documents 2 to 4). However, halogen-based flame retardants have problems in environmental safety, and phosphoric acid-based flame retardants have problems such as causing contact failure in electrical and electronic equipment. For this reason, the use of flame retardants other than halogen-based and phosphoric acid-based materials has been studied.

JP 2002-173657 A JP-A-11-1669 JP-A-11-323268 Japanese Patent Application Laid-Open No. 11-189753

  In order to obtain sufficient flame retardancy using a flame retardant other than halogen or phosphoric acid, it is necessary to increase the blending amount of the flame retardant in the pressure-sensitive adhesive layer. However, when the blending amount of the flame retardant is increased, problems such as non-uniform thickness, roughened pressure-sensitive adhesive layer surface, and reduced adhesive strength may occur. These problems were particularly likely to occur when the pressure-sensitive adhesive layer was thin. That is, the present condition is that the thin adhesive sheet which is excellent in heat conductivity and adhesiveness is known while using the flame retardants other than a halogen type and phosphoric acid type, and having the outstanding flame retardance.

  Therefore, the objective of this invention is providing the adhesive sheet with small thickness of the adhesive layer which is excellent in heat conductivity and adhesiveness while having the outstanding flame retardance.

  As a result of intensive studies to achieve the above object, the present inventors have made the pressure-sensitive adhesive layer contain particles having two specific average particle diameters as heat conductive particles, even if the pressure-sensitive adhesive layer is thin, The present invention was completed by finding that an adhesive sheet excellent in flame retardancy, thermal conductivity, and flame retardancy can be obtained.

  That is, in the present invention, as the thermally conductive particles, the particle group A having a D50 average particle diameter of 10 μm or more and the particle group B having a D50 average particle diameter of less than 10 μm are a ratio (weight ratio) 2 of the particle group A to the particle group B. : It has the adhesive layer mix | blended by 8-8: 2, and provides the heat conductive adhesive sheet whose thickness of this adhesive layer is 50 micrometers or less.

  The content of the heat conductive particles in the pressure-sensitive adhesive layer is preferably 25% by volume or more and 75% by volume or less.

  It is preferable that the heat conductive pressure-sensitive adhesive sheet has VTM-0 or V-0 flame retardance in the flame retardancy test of UL94 standard.

  The thermal conductive pressure-sensitive adhesive sheet preferably has a thermal conductivity of 0.3 W / m · K or more. .

  The holding power (80 ° C., 300 gf) of the heat conductive adhesive sheet is preferably 2 mm or less.

  The pressure-sensitive adhesive layer is preferably an active energy ray-curable pressure-sensitive adhesive layer.

  Since the heat conductive adhesive sheet of this invention has the said structure, even if an adhesive layer is thin, it is excellent in heat conductivity and a flame retardance, and is excellent also in adhesiveness.

FIG. 1 is a schematic diagram showing a thermal characteristic evaluation apparatus.

  In the heat conductive pressure-sensitive adhesive sheet of the present invention, the particle group A having a D50 average particle diameter of 10 μm or more and the particle group B having a D50 average particle diameter of less than 10 μm are used as the heat conductive particles. (Weight ratio) It has a pressure-sensitive adhesive layer (this pressure-sensitive adhesive layer may be referred to as “pressure-sensitive adhesive layer X”) blended at 2: 8 to 8: 2, and the thickness of the pressure-sensitive adhesive layer is 50 μm or less. .

  The heat conductive pressure-sensitive adhesive sheet of the present invention is a single-sided pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer on one side of the base material, a double-sided pressure-sensitive adhesive sheet with a base material having a pressure-sensitive adhesive layer on both sides of the base material, and does not have a base material Any of base material-less pressure-sensitive adhesive sheets (base material-less double-sided pressure-sensitive adhesive sheets) may be used. Among these, a double-sided pressure-sensitive adhesive sheet is preferable from the viewpoint that various materials to be fixed can be selected, and a base-less double-sided pressure-sensitive adhesive sheet is particularly preferable because the thickness of the pressure-sensitive adhesive sheet can be reduced. The pressure-sensitive adhesive layer may be a single layer or multiple layers. The “base material” does not include a release liner (separator) that is peeled off when the heat conductive adhesive sheet is used. Moreover, in the case of a double-sided pressure-sensitive adhesive sheet with a substrate, at least one pressure-sensitive adhesive layer may be the specific pressure-sensitive adhesive layer X.

  In this specification, “adhesive sheet” includes “adhesive tape”. Moreover, in this specification, the composition (coating liquid etc.) used when forming an adhesive layer may be called "adhesive composition."

[Adhesive layer]
The pressure-sensitive adhesive layer of the heat conductive pressure-sensitive adhesive sheet exhibits adhesiveness. Such an adhesive layer is formed of an adhesive composition. For example, the acrylic pressure-sensitive adhesive layer described later is formed from an acrylic pressure-sensitive adhesive composition.

  Although it does not specifically limit as an adhesive which comprises the said adhesive layer, For example, a urethane adhesive, an acrylic adhesive, a rubber adhesive, a silicone adhesive, a polyester adhesive, a polyamide adhesive, epoxy Based pressure-sensitive adhesives, vinyl alkyl ether pressure-sensitive adhesives, fluorine-based pressure-sensitive adhesives, and the like. Among these, an acrylic pressure-sensitive adhesive is preferable from the viewpoint of weather resistance, heat resistance, function, cost, and ease of designing a pressure-sensitive adhesive according to the purpose of use. That is, it is preferable that the heat conductive adhesive sheet of this invention has an acrylic adhesive layer.

  The acrylic pressure-sensitive adhesive layer contains an acrylic polymer as a base polymer. The acrylic polymer is a polymer containing an acrylic monomer (a monomer having a (meth) acryloyl group in the molecule) as a constituent monomer component. The acrylic polymer is preferably a polymer containing (meth) acrylic acid alkyl ester as a constituent monomer component. In addition, an acrylic polymer can be used individually or in combination of 2 or more types.

  Although it does not specifically limit as said (meth) acrylic-acid alkylester, For example, (meth) acrylic-acid methyl, (meth) acrylic-acid ethyl, (meth) acrylic-acid propyl, (meth) acrylic-acid isopropyl, (meth) acrylic Butyl acrylate, isobutyl (meth) acrylate, s-butyl (meth) acrylate, t-butyl (meth) acrylate, pentyl (meth) acrylate, isopentyl (meth) acrylate, hexyl (meth) acrylate, ( Heptyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, nonyl (meth) acrylate, isononyl (meth) acrylate, decyl (meth) acrylate, Isodecyl (meth) acrylate, undecyl (meth) acrylate, (meta Dodecyl acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate, octadecyl (meth) acrylate, (meth) acrylic (Meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms, such as acid nonadecyl and eicosyl (meth) acrylate. Among these, from the viewpoint of easily balancing the adhesive properties, (meth) acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms (particularly 2 to 12 carbon atoms) is preferable, and more preferably 4 to 9 carbon atoms. (Meth) acrylic acid alkyl ester having an alkyl group of The said (meth) acrylic-acid alkylester can be used individually or in combination of 2 or more types.

  The ratio of the (meth) acrylic acid alkyl ester to the total monomer components (100% by weight) constituting the acrylic polymer is not particularly limited, but is preferably 60% by weight or more (for example, 60 to 99% by weight). More preferably, it is 70% by weight or more (for example, 70 to 98% by weight), and further preferably 80% or more (for example, 80 to 98% by weight).

  The acrylic polymer may be a polymer containing only the (meth) acrylic acid alkyl ester as a constituent monomer component, but it is possible to impart functions according to necessity, various properties of the adhesive, From the point of controlling the structure of the acrylic polymer and the like more appropriately, the monomer component may be a polymer containing a copolymerizable monomer together with the (meth) acrylic acid alkyl ester. In addition, a copolymerizable monomer can be used individually or in combination of 2 or more types.

  Examples of the copolymerizable monomer include polar group-containing monomers. Although it does not specifically limit as said polar group containing monomer, For example, a carboxyl group containing monomer, a hydroxyl group containing monomer, a nitrogen containing monomer, a sulfonic acid group containing monomer, a phosphoric acid group containing monomer etc. are mentioned. In addition, a polar group containing monomer can be used individually or in combination of 2 or more types.

  The carboxyl group-containing monomer is a monomer having one or more carboxyl groups in one molecule, but may be in the form of an anhydride. Although it does not specifically limit as said carboxyl group containing monomer, For example, (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, isocrotonic acid, maleic anhydride, itaconic anhydride etc. are mentioned. In addition, a carboxyl group-containing monomer can be used individually or in combination of 2 or more types.

  In particular, the acrylic polymer preferably contains substantially no carboxyl group-containing monomer as a constituent monomer component. Further, “substantially free of” a carboxyl group-containing monomer means that the monomer component constituting the acrylic polymer contains no carboxyl group-containing monomer or all the monomer components (100 wt. %) Of the carboxyl group-containing monomer is 0.1% by weight or less.

  When the acrylic pressure-sensitive adhesive layer contains thermally conductive particles described later, if a carboxyl group-containing monomer is included as a monomer component that the acrylic polymer constitutes, depending on the thermally conductive particles, a polar group-containing monomer may be used. It may be difficult to obtain the effect of improving the adhesiveness due to the inclusion, and the fluidity of the acrylic pressure-sensitive adhesive composition, which is a composition forming the acrylic pressure-sensitive adhesive layer, is reduced. Formation of the agent layer may be difficult. The cause of these problems has not been sufficiently clarified, but the carboxyl group of the carboxyl group-containing monomer reacts with the functional group (for example, hydroxyl group) of the thermally conductive particles, so that the acrylic pressure-sensitive adhesive composition is more than necessary. This is presumably because it becomes harder or the pressure-sensitive adhesive layer becomes harder than necessary, and the wettability of the pressure-sensitive adhesive layer decreases.

  When a hydroxyl group-containing monomer is contained as a copolymerizable monomer, the dispersibility of the heat conductive particles is improved, and good wettability to the adherend is easily obtained with the acrylic pressure-sensitive adhesive layer. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, ( 6-hydroxyhexyl (meth) acrylate, 8-hydroxyoctyl (meth) acrylate, 10-hydroxydecyl (meth) acrylate, 12-hydroxylauryl (meth) acrylate, (4-hydroxymethylcyclohexyl) methyl methacrylate Etc. Of these, 2-hydroxyethyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are preferable. In addition, a hydroxyl-containing monomer can be used individually or in combination of 2 or more types.

  When a nitrogen-containing monomer is included as a copolymerizable monomer, appropriate polarity is imparted, and good adhesive properties such as adhesiveness at the initial stage of application and adhesive reliability can be easily obtained with an acrylic pressure-sensitive adhesive layer. Examples of the nitrogen-containing monomer include N- (2-hydroxyethyl) (meth) acrylamide, N- (2-hydroxypropyl) (meth) acrylamide, N- (1-hydroxypropyl) (meth) acrylamide, N- (3-hydroxypropyl) (meth) acrylamide, N- (2-hydroxybutyl) (meth) acrylamide, N- (3-hydroxybutyl) (meth) acrylamide, N- (4-hydroxybutyl) (meth) acrylamide, etc. N-hydroxyalkyl (meth) acrylamides; cyclic (meth) acrylamides such as N- (meth) acryloylmorpholine and N-acryloylpyrrolidine; acyclic (meth) acrylamides such as (meth) acrylamide and N-substituted (meth) acrylamides Is mentioned. Examples of the N-substituted (meth) acrylamide include N-alkyl (meth) acrylamides such as N-ethyl (meth) acrylamide and Nn-butyl (meth) acrylamide; N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N, N-dipropyl (meth) acrylamide, N, N-diisopropyl (meth) acrylamide, N, N-di (n-butyl) (meth) acrylamide, N, N-di (t And N, N-dialkyl (meth) acrylamide such as (butyl) (meth) acrylamide.

  Further, examples of the nitrogen-containing monomer include N-vinyl-2-pyrrolidone (NVP), N-vinyl-2-piperidone, N-vinyl-3-morpholinone, N-vinyl-2-caprolactam, N-vinyl- N-vinyl cyclic amides such as 1,3-oxazin-2-one and N-vinyl-3,5-morpholinedione; aminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N Monomers having amino groups such as dimethylaminopropyl (meth) acrylate; monomers having a maleimide skeleton such as N-cyclohexylmaleimide and N-phenylmaleimide; N-methylitaconimide, N-ethylitaconimide, N-butylitaconimide N-2-ethylhexylitaconimide, N-lauryl Kon'imido and itaconimide monomers such as N- cyclohexyl itaconic imide. In addition, a nitrogen-containing monomer can be used individually or in combination of 2 or more types.

  Among these, as the nitrogen-containing monomer, N-hydroxyalkyl (meth) acrylamide, N-vinyl cyclic amide, cyclic (meth) acrylamide, and N-substituted (meth) acrylamide are preferable, and N- (2-hydroxyethyl) is more preferable. ) (Meth) acrylamide, N-vinyl-2-pyrrolidone, N- (meth) acryloylmorpholine, N, N-diethyl (meth) acrylamide.

  The ratio of the nitrogen-containing monomer to the total monomer component (100% by weight) constituting the acrylic polymer is not particularly limited, but the lower limit is preferably 1% by weight or more, more preferably 2% by weight or more. It is. Further, the upper limit is preferably 10% by weight or less, more preferably 7% by weight or less.

  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, (meth And acryloyloxynaphthalene sulfonic acid. In addition, a sulfonic acid group containing monomer can be used individually or in combination of 2 or more types.

  As said phosphate group containing monomer, 2-hydroxyethyl acryloyl phosphate etc. are mentioned, for example. In addition, a phosphate group containing monomer can be used individually or in combination of 2 or more types.

  The blending ratio of the polar group-containing monomer in the monomer component constituting the acrylic polymer is not particularly limited. For example, 0.1% with respect to the total amount (100% by weight) of the monomer component constituting the acrylic polymer. It is preferably at least 0.5% by weight, more preferably at least 0.5% by weight, even more preferably at least 1% by weight, even more preferably at least 2% by weight, even more preferably at least 3% by weight, particularly preferably at least 5% by weight. Further, the blending ratio of the polar group-containing monomer is not particularly limited. For example, it is preferably 40% by weight or less, more preferably 30% by weight with respect to the total amount of monomer components (100% by weight) constituting the acrylic polymer. % Or less, more preferably 25% by weight or less, and particularly preferably 20% by weight or less. The blending ratio of the polar group-containing monomer in the monomer component is not particularly limited. For example, it is preferably 0.1 to 40% by weight with respect to the total amount of monomer components (100% by weight) constituting the acrylic polymer. . When the blending ratio is within the above range, the cohesive force of the pressure-sensitive adhesive layer becomes appropriate, and high holding power and pressure-sensitive adhesive force can be obtained.

  Moreover, as said copolymerizable monomer, the monomer which has an alkoxy group is mentioned. When a monomer having an alkoxy group is included as a copolymerizable monomer, the wettability of the acrylic pressure-sensitive adhesive layer can be improved, and heat from the adherend (heat generation source) can be efficiently conducted. it can. Examples of the monomer having an alkoxy group include 2-methoxyethyl (meth) acrylate, 3-methoxypropyl (meth) acrylate, methoxyethylene glycol (meth) acrylate, and methoxypolypropylene glycol (meth) acrylate. Can be mentioned. In addition, the monomer which has an alkoxy group can be used individually or in combination of 2 or more types.

  The ratio of the monomer having the alkoxy group to the total monomer component (100% by weight) constituting the acrylic polymer is not particularly limited, but the lower limit is preferably 3% by weight, more preferably 5% by weight. Moreover, it is preferable that the upper limit is 20 weight%, More preferably, it is 15 weight%.

  Furthermore, a polyfunctional monomer is mentioned as said copolymerizable monomer. According to such a polyfunctional monomer, a crosslinked structure can be introduced into the acrylic polymer, and the cohesive force of the pressure-sensitive adhesive layer can be adjusted. Examples of the polyfunctional monomer include hexanediol di (meth) acrylate, butanediol di (meth) acrylate, (poly) ethylene glycol di (meth) acrylate, (poly) propylene glycol di (meth) acrylate, and neopentyl glycol. Di (meth) acrylate, pentaerythritol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, trimethylolpropane tri (meth) acrylate, tetramethylolmethane tri (meth) acrylate, allyl Examples include (meth) acrylate, vinyl (meth) acrylate, divinylbenzene, epoxy acrylate, polyester acrylate, and urethane acrylate. In addition, the said polyfunctional monomer can be used individually or in combination of 2 or more types.

  The ratio of the polyfunctional monomer to the total monomer component (100% by weight) constituting the acrylic polymer is not particularly limited, but the lower limit thereof is preferably 0.01% by weight, more preferably 0.02%. The upper limit is preferably 2% by weight, and more preferably 1% by weight. When the ratio of the polyfunctional monomer is 0.01% by weight or more, it is preferable because a high cohesive force can be obtained and a high holding power can be easily obtained. On the other hand, when the ratio of the polyfunctional monomer is 2% by weight or less, the cohesive force becomes too high, and the occurrence of a problem that the adhesiveness is lowered can be suppressed.

  In addition, examples of the copolymerizable monomer include monomers having an epoxy group such as glycidyl (meth) acrylate and allyl glycidyl ether; monomers having a cyano group such as acrylonitrile and methacrylonitrile; styrene, α-methylstyrene, and the like. Styrene monomers; α-olefins such as ethylene, propylene, isoprene, butadiene, and isobutylene; monomers having isocyanate groups such as 2-isocyanatoethyl acrylate and 2-isocyanatoethyl methacrylate; vinyl esters such as vinyl acetate and vinyl propionate Monomers; vinyl ether monomers such as vinyl ether; (meth) acrylic acid esters having a heterocycle such as tetrahydrofurfuryl (meth) acrylate; fluorine (meth) acrylate A monomer having a halogen atom such as 3-methacryloxypropyltrimethoxysilane, a monomer having an alkoxysilyl group such as vinyltrimethoxysilane; a monomer having a siloxane bond such as silicone (meth) acrylate; a cyclopentyl (meth) acrylate, (Meth) acrylates having alicyclic hydrocarbon groups such as cyclohexyl (meth) acrylate, bornyl (meth) acrylate and isobornyl (meth) acrylate; phenyl (meth) acrylate, benzyl (meth) acrylate, phenoxyethyl (meth) acrylate And (meth) acrylate having an aromatic hydrocarbon group such as phenoxydiethylene glycol (meth) acrylate.

  The glass transition temperature (Tg) of the acrylic polymer is not particularly limited, but it is easy to obtain a low-elasticity acrylic pressure-sensitive adhesive layer, and it is easy to obtain an acrylic pressure-sensitive adhesive layer having good step absorbability. The upper limit is preferably −10 ° C., more preferably −20 ° C., and the lower limit is preferably −70 ° C., more preferably −65 ° C. The Tg of the acrylic polymer can be prepared by selecting the composition and blending amount of the constituent monomer components. Here, the Tg of the acrylic polymer refers to a value obtained from the Fox equation based on the Tg of the homopolymer of each monomer constituting the monomer component and the weight fraction (copolymerization composition) of the monomer. The value of Tg of the homopolymer can be obtained from various known materials (such as “Adhesion Technology Handbook” of Nikkan Kogyo Shimbun).

  The acrylic polymer can be obtained by polymerizing the monomer component. Although it does not specifically limit as a polymerization method, For example, solution polymerization, emulsion polymerization, block polymerization, photopolymerization (active energy ray polymerization) etc. are mentioned. Among them, a polymerization method using heat or active energy rays (for example, ionizing radiation such as α rays, β rays, γ rays, neutral beam, electron beams, ultraviolet rays, etc.) is preferable, more preferably a thermal polymerization initiator. A polymerization method using a heat or active energy ray using a polymerization initiator such as a photopolymerization initiator is preferred. In addition, a polymerization initiator can be used individually or in combination of 2 or more types.

  In particular, as the polymerization method, the point that the polymerization time can be shortened, and even when a thin pressure-sensitive adhesive layer containing thermally conductive particles is produced, the thermally conductive particles are uniformly dispersed, A polymerization method using active energy rays (particularly ultraviolet rays) using a photopolymerization initiator is preferred in that an adhesive layer having a uniform thickness and a smooth surface can be easily produced. That is, the adhesive layer X is preferably an active energy ray-curable adhesive layer. When using a solution polymerization method or the like, when producing a thin pressure-sensitive adhesive layer containing heat conductive particles, the heat conductive particles may be difficult to uniformly disperse and the surface of the pressure-sensitive adhesive layer may become rough.

  The photopolymerization initiator is not particularly limited. For example, benzoin ether photopolymerization initiator, acetophenone photopolymerization initiator, α-ketol photopolymerization initiator, aromatic sulfonyl chloride photopolymerization initiator, photo Examples thereof include active oxime photopolymerization initiators, benzoin photopolymerization initiators, benzyl photopolymerization initiators, benzophenone photopolymerization initiators, ketal photopolymerization initiators, and thioxanthone photopolymerization initiators. In addition, a photoinitiator can be used individually or in combination of 2 or more types.

  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-1-one, Anisole methyl ether etc. are mentioned. Examples of the acetophenone photopolymerization initiator include 2,2-diethoxyacetophenone, 2,2-dimethoxy-2-phenylacetophenone, 1-hydroxycyclohexyl phenyl ketone, 4-phenoxydichloroacetophenone, and 4- (t-butyl). ) Dichloroacetophenone and the like. Examples of the α-ketol photopolymerization initiator include 2-methyl-2-hydroxypropiophenone and 1- [4- (2-hydroxyethyl) phenyl] -2-methylpropan-1-one. It is done. 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, polyvinylbenzophenone, α-hydroxycyclohexyl phenyl ketone, and the like. Examples of the ketal photopolymerization initiator include benzyl methyl ketal. Examples of the thioxanthone photopolymerization initiator include thioxanthone, 2-chlorothioxanthone, 2-methylthioxanthone, 2,4-dimethylthioxanthone, isopropylthioxanthone, 2,4-diisopropylthioxanthone, decylthioxanthone, and the like.

  Although the usage-amount of the said photoinitiator is not specifically limited, It is preferable that the minimum is 0.01 weight part with respect to 100 weight part of monomer components which comprise the said acrylic polymer, More preferably, it is 0. The upper limit is preferably 5 parts by weight, and more preferably 3 parts by weight.

  In the photopolymerization, the irradiation energy, irradiation time, etc. of active energy rays (particularly ultraviolet rays) are not particularly limited. It is only necessary that the photopolymerization initiator is activated to cause the monomer component to react.

  Examples of the thermal polymerization initiator include 2,2′-azobisisobutyronitrile, 2,2′-azobis-2-methylbutyronitrile, 2,2′-azobis (2-methylpropionic acid) dimethyl, , 4'-azobis-4-cyanovaleric acid, azobisisovaleronitrile, 2,2'-azobis (2-amidinopropane) dihydrochloride, 2,2'-azobis [2- (5-methyl-2-imidazoline) -2-yl) propane] dihydrochloride, 2,2'-azobis (2-methylpropionamidine) disulfate, 2,2'-azobis (N, N'-dimethyleneisobutylamidine) hydrochloride, 2,2 Azo polymerization initiators such as' -azobis [N- (2-carboxyethyl) -2-methylpropionamidine] hydrate; Peroxide-based polymerization initiators such as sid, t-butylpermaleate, t-butyl hydroperoxide, hydrogen peroxide; persulfates such as potassium persulfate and ammonium persulfate; persulfates and sodium bisulfite Examples thereof include redox polymerization initiators such as a combination and a combination of peroxide and sodium ascorbate. In addition, a thermal polymerization initiator can be used individually or in combination of 2 or more types.

  Although the usage-amount of a thermal-polymerization initiator is not specifically limited, For example, conventionally, it can select in the range which can be utilized as a polymerization initiator. In the case of polymerization using heat, for example, the monomer component and the thermal polymerization initiator are dissolved in an appropriate solvent (for example, an organic solvent such as toluene or ethyl acetate), for example, 20 to 100 ° C. (preferably 40 to 80 ° C.). ) To obtain an acrylic polymer.

[Thermal conductive particles]
The heat conductive pressure-sensitive adhesive sheet of the present invention contains heat conductive particles in the pressure-sensitive adhesive layer, so that good heat conductivity can be obtained, the pressure-sensitive adhesive sheet can hardly be burned, and the flame can be hardly spread by the pressure-sensitive adhesive sheet. . That is, excellent thermal conductivity and flame retardancy are obtained. Thermally conductive particles can be used alone or in combination of two or more.

Examples of the thermally conductive particles include metal hydroxides and hydrated metal compounds. The hydrated metal compound has a decomposition start temperature in the range of 150 to 500 ° C., and has a general formula M _m1 O _n1 .XH ₂ O (where M is a metal and m1, n1 is 1 or more determined by the valence of the metal) Or a double salt containing the compound.

As the metal hydroxide and the hydrated metal compound is not particularly limited, 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 ( _{H) 2 · 3H 2 O]} , hydrotalcite _{[6MgO · Al 2 O 3 ·} H 2 O], dawsonite _{[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] and the like. Of these, aluminum hydroxide and magnesium hydroxide are preferred because excellent flame retardancy can be obtained. The hydrated metal compound and the metal hydroxide may be used alone or in combination of two or more.

  A commercial item can be used for the said hydrated metal compound and metal hydroxide. As a commercial product of aluminum hydroxide, for example, trade name “Hijilite H-31” (average particle size 18 μm) (manufactured by Showa Denko KK), trade name “Hijilite H-32” (average particle size 8 μm) (Showa) Manufactured by Denko Co., Ltd.), trade name “Hijilite H-42” (average particle size 1 μm) (Showa Denko), product name “Hijilite H-43M” (average particle size 0.8 μm) (produced by Showa Denko) And trade name “B103ST” (average particle size 8 μm) (manufactured by Nippon Light Metal Co., Ltd.). Moreover, as a commercial item of magnesium hydroxide, for example, trade name “KISUMA 5A” (average particle diameter 1 μm) (manufactured by Kyowa Chemical Industry Co., Ltd.), trade name “ECOMAG Z-10” (average particle diameter 1.4 μm, vertical) Chemical Industry Co., Ltd.).

  Furthermore, examples of the heat conductive particles include metal nitrides such as boron nitride, aluminum nitride, silicon nitride, and gallium nitride; aluminum oxide (alumina), magnesium oxide, titanium oxide, zinc oxide, tin oxide, copper oxide, Examples thereof include metal oxides such as nickel oxide and antimonic acid doped tin oxide. In addition, silicon carbide, silicon dioxide, calcium carbonate, barium titanate, potassium titanate, copper, silver, gold, nickel, aluminum, platinum, carbon black, carbon tube (carbon nanotube), carbon fiber, diamond, etc. .

  A general commercial item can be used for such a heat conductive particle. As a commercial item of boron nitride, a brand name "HP-40" (made by Mizushima alloy iron company), a brand name "PT620" (made by Momentive company), etc. are mentioned, for example. As a commercial item of aluminum oxide, a brand name "AS-50" (made by Showa Denko KK), a brand name "AL-13KT" (average particle diameter 96 micrometers) (made by Showa Denko KK), etc. are mentioned, for example. As a commercial item of antimonic acid dope tin, for example, a brand name "SN-100S" (made by Ishihara Sangyo Co., Ltd.), a brand name "SN-100P" (made by Ishihara Sangyo Co., Ltd.), and a brand name "SN-100D (water dispersion product). (Ishihara Sangyo Co., Ltd.). As a commercial item of titanium oxide, a brand name "TTO series" (made by Ishihara Sangyo Co., Ltd.) etc. are mentioned, for example. As commercial products of zinc oxide, trade name “SnO-310” (manufactured by Sumitomo Osaka Cement Co., Ltd.), trade name “SnO-350” (manufactured by Sumitomo Osaka Cement Co., Ltd.), trade name “SnO-410” (Sumitomo Osaka Cement Co., Ltd.) Manufactured).

  Among these, as the heat conductive particles, metal hydroxides, hydrated metal compounds, and metal oxides are preferable from the viewpoint of thermal conductivity, flame retardancy, and cost, and more preferably aluminum hydroxide, alumina, and magnesium hydroxide. , Magnesium oxide. That is, the thermally conductive particles are preferably at least one particle selected from the group consisting of metal hydroxides, hydrated metal compounds, and metal oxides, and more preferably aluminum hydroxide, alumina, magnesium hydroxide. And at least one particle selected from the group consisting of magnesium oxide. As the heat conductive particles, aluminum hydroxide is particularly preferable.

  The shape of the heat conductive particles 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.

  The heat conductive pressure-sensitive adhesive sheet of the present invention includes a particle group A having a D50 average particle diameter of 10 μm or more and a particle group B having a D50 average particle diameter of less than 10 μm as the heat conductive particles in the pressure-sensitive adhesive layer X. The ratio of A to the particle group B (weight ratio) is from 2: 8 to 8: 2. Since the particle group A having a D50 average particle diameter of 10 μm or more and the particle group B having a D50 average particle diameter of less than 10 μm are blended at a specific ratio, the thickness of the pressure-sensitive adhesive layer is thin (even if it is 50 μm or less), It is possible to obtain a pressure-sensitive adhesive layer having excellent adhesiveness and a uniform thickness and a smooth surface (excellent coatability). On the other hand, when only the particle group A having a D50 average particle size of 10 μm or more is used, if the thickness of the pressure-sensitive adhesive layer is thin, it becomes difficult to obtain a pressure-sensitive adhesive layer having a uniform thickness and a smooth surface ( Inferior in coatability). In addition, when only the particle group B having a D50 average particle size of less than 10 μm is used, it is difficult to obtain high adhesive strength if the pressure-sensitive adhesive layer is thin.

  The average particle size is a volume-based value obtained by a 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.

  The D50 average particle diameter of the particle group A having a D50 average particle diameter of 10 μm or more is, for example, 10 to 100 μm, and the lower limit thereof is preferably 12 μm, more preferably 15 μm. Moreover, the upper limit becomes like this. Preferably it is 50 micrometers, More preferably, it is 30 micrometers, More preferably, it is 25 micrometers.

  The D50 average particle diameter of the particle group B having a D50 average particle diameter of less than 10 μm is, for example, 0.1 μm or more and less than 10 μm, and the lower limit thereof is preferably 0.3 μm, more preferably 0.5 μm. Moreover, the upper limit becomes like this. Preferably it is 8 micrometers, More preferably, it is 5 micrometers, More preferably, it is 3 micrometers.

  The ratio (weight ratio) between the particle group A and the particle group B is preferably 3: 7 to 7: 3.

  The total content of the particle group A and the particle group B in the pressure-sensitive adhesive layer X is not particularly limited, but is 25 volume% or more and 75 volume% or less with respect to the total volume (100 volume%) of the pressure-sensitive adhesive layer X. Preferably there is. The lower limit is more preferably 30% by volume. Moreover, the upper limit is 70 volume% more preferably, More preferably, it is 60 volume%. When the content ratio of the heat conductive particles (the total content of the particle group A and the particle group B) is 25% by volume or more, good thermal conductivity and good flame retardancy are easily obtained, which is preferable. Further, when the content ratio of the heat conductive particles (the total content of the particle group A and the particle group B) is 75% by volume or less, a decrease in flexibility can be suppressed, and a decrease in adhesive force and holding power can be suppressed. Can be suppressed, which is preferable. The unit “volume%” used in the total content (content ratio) can be converted to the unit “weight%” using the density of the heat conductive particles.

[Dispersant]
In the pressure-sensitive adhesive layer X, a dispersant may be further contained in order to stably disperse the heat conductive particles without agglomeration within a range not impairing the effects of the present invention.

  Although it does not specifically limit as said dispersing agent, For example, phosphate ester is used suitably. Phosphoric acid esters include polyoxyethylene alkyl (or alkylallyl) ether or polyoxyethylene alkyl aryl ether phosphoric acid monoester, polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether phosphoric acid diester, phosphoric acid triester Or a derivative thereof. Among these, it is preferable to use a phosphoric acid monoester or a phosphoric acid diester of polyoxyethylene alkyl ether or polyoxyethylene alkyl aryl ether. The said dispersing agent can be used individually or in combination of 2 or more types.

  The content of the dispersant is not particularly limited. For example, the content of the dispersant is 0.1 with respect to 100 parts by weight of the base polymer in the pressure-sensitive adhesive layer X (for example, the acrylic polymer in the case of the acrylic pressure-sensitive adhesive layer). It is preferable that it is 01-10 weight part. The lower limit is more preferably 0.05 parts by weight, still more preferably 0.1 parts by weight. Further, the upper limit is more preferably 5 parts by weight, still more preferably 3 parts by weight.

  As the dispersant, a general commercial product can be used. For example, a trade name “Plisurf A212E” (Daiichi Kogyo Seiyaku Co., Ltd.), a trade name “Plisurf A210G” (Daiichi Kogyo Seiyaku Co., Ltd.), Name “Plisurf A212C” (Daiichi Kogyo Seiyaku Co., Ltd.), Trade Name “Plisurf A210F” (Daiichi Kogyo Seiyaku Co., Ltd.), Trade Name “Phosphanol RE610” (Toho Chemical Co., Ltd.) Examples include “Fanol RS710” (manufactured by Toho Chemical Co., Ltd.), trade name “Phosphanol RS610” (manufactured by Toho Chemical Co., Ltd.), and the like.

[Fluorosurfactant]
The pressure-sensitive adhesive layer X may further contain a fluorinated surfactant. By using the fluorosurfactant, the degree of adhesion and frictional resistance between the base polymer and the thermally conductive particles may be reduced, and the stress dispersibility may be improved. Therefore, in the heat conductive adhesive sheet of this invention, higher adhesiveness may be obtained.

The fluorine-based surfactant is not particularly limited, but for example, a fluorine-based surfactant having an oxy C _2-3 alkylene group and a fluorinated hydrocarbon group in the molecule is preferable. Among these, from the viewpoint of dispersibility with respect to a base polymer such as an acrylic polymer, the above-mentioned fluorine-containing surfactant is a fluorine-based nonionic surfactant having a C _2-3 alkylene group and a fluorinated hydrocarbon group in the molecule. It is preferable that In addition, the said fluorosurfactant can be used individually or in combination of 2 or more types.

  Although it does not restrict | limit especially as said fluorinated hydrocarbon group, For example, a perfluoro group is preferable. The perfluoro group may be monovalent or divalent or higher. The fluorinated hydrocarbon group may have a double bond or a triple bond, and may be a straight chain or a branched structure or a cyclic structure. Although carbon number of the said fluorinated hydrocarbon group is not specifically limited, For example, 1 or 2 or more are preferable, More preferably, it is 3-30, More preferably, it is 4-20. When it has a fluorinated hydrocarbon group, when the said adhesive layer X contains a bubble, the effect which improves bubble mixing property and bubble stability is also acquired. 1 type of the said fluorinated hydrocarbon group may be introduce | transduced in the said fluorine-type surfactant molecule | numerator, and 2 or more types may be introduce | transduced.

The oxy C _2-3 alkylene group is represented by the formula: —R—O— (R is a linear or branched alkylene group having 2 or 3 carbon atoms). The oxy C _2-3 alkylene group is not particularly limited, and examples thereof include an oxyethylene group (—CH ₂ CH ₂ O—) and an oxypropylene group [—CH ₂ CH (CH ₃ ) O—]. The oxy C _2-3 alkylene group may be any form such as an alcohol having a hydrogen atom bonded to a terminal oxygen atom, an ether bonded to another hydrocarbon group, or an ester bonded to another hydrocarbon group via a carbonyl group. But you can. Moreover, the form which has this structure in a part of cyclic structure, such as cyclic ethers and lactones, may be sufficient. One kind of the oxy C _2-3 alkylene group may be introduced into the fluorine-based surfactant molecule, or two or more kinds thereof may be introduced.

The fluorosurfactant is not particularly limited, and is obtained, for example, by polymerizing a monomer component containing a monomer having an oxy C _2-3 alkylene group and a monomer having a fluorinated hydrocarbon group. A copolymer is mentioned. When the fluorosurfactant is a copolymer, it may be, for example, a block copolymer or a graft copolymer.

The block copolymer (copolymer having an oxy C _2-3 alkylene group and a fluorinated hydrocarbon group in the main chain) is not particularly limited, but examples thereof include polyoxyethylene perfluoroalkyl ether, polyoxyethylene peroxy ether, and the like. Fluoroalkylate, polyoxypropylene perfluoroalkyl ether, polyoxyisopropylene perfluoroalkyl ether, polyoxyethylene sorbitan perfluoroalkylate, polyoxyethylene polyoxypropylene block copolymer perfluoroalkylate, polyoxyethylene glycol perfluoroalkyl Chelate etc. are mentioned.

The graft copolymer (a copolymer having an oxy C _2-3 alkylene group and a fluorinated hydrocarbon group in the side chain) is not particularly limited, but for example, a vinyl compound having at least a polyoxyalkylene group and fluorine And a copolymer obtained by polymerizing a monomer component containing a vinyl compound having a functionalized hydrocarbon group, and an acrylic copolymer is particularly preferable. Examples of the vinyl compound having a polyoxyalkylene group include polyoxyalkylene (meth) acrylates such as polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate, and polyoxyethylene polyoxypropylene (meth) acrylate. Is mentioned. Examples of the vinyl compound having a fluorinated hydrocarbon group include perfluoroalkyl (meth) acrylates such as perfluorobutyl (meth) acrylate, perfluoroisobutyl (meth) acrylate, and perfluoropentyl (meth) acrylate. (Meth) acrylic acid ester containing a fluorinated hydrocarbon is mentioned.

In addition to the oxy C _2-3 alkylene group and the fluorinated hydrocarbon group, the above-mentioned fluorosurfactant contains an alicyclic hydrocarbon group, an aromatic group in the molecule within a range that does not impair dispersibility in the acrylic polymer. It may have various functional groups such as an aromatic hydrocarbon group, a carboxyl group, a sulfonic acid group, a cyano group, an amide group, and an amino group. For example, when the fluorosurfactant is a vinyl copolymer, the monomer component can be copolymerized with a vinyl compound having a polyoxyalkylene group and a vinyl compound having a fluorinated hydrocarbon group as a monomer component. May be used. Such copolymerizable monomers can be used alone or in combination of two or more.

Examples of the copolymerizable monomer component include (meth) acrylic acid C _1-20 alkyl esters such as undecyl (meth) acrylate and dodecyl (meth) acrylate; alicyclic carbonization such as cyclopentyl (meth) acrylate. A (meth) acrylic acid ester having a hydrogen group; a (meth) acrylic acid ester having an aromatic hydrocarbon group such as phenyl (meth) acrylate is preferably used. In addition, carboxyl group-containing monomers such as maleic acid and crotonic acid; sulfonic acid group-containing monomers such as sodium vinyl sulfonate; aromatic vinyl compounds such as styrene and vinyl toluene; olefins and dienes such as ethylene and butadiene Vinyl ethers such as vinyl alkyl ethers; amide group-containing monomers such as acrylamide; amino group-containing monomers such as (meth) acryloylmorpholine; glycidyl group-containing monomers such as methyl glycidyl (meth) acrylate; 2 -Isocyanate group-containing monomers such as methacryloyloxyethyl isocyanate; polyfunctional copolymerizable monomers (polyfunctional monomers) such as dipentaerythritol hexa (meth) acrylate and divinylbenzene.

  The weight average molecular weight of the fluorosurfactant is not particularly limited. For example, when it is less than 20000 (for example, 500 or more and less than 20000), the base polymer such as the acrylic polymer and the thermally conductive particles The effect of reducing the adhesion and frictional resistance between them is high. Further, when a fluorosurfactant having a weight average molecular weight of 20000 or more (for example, 20000 to 100000, preferably 22000 to 80000, more preferably 24000 to 60000) is used in combination, And stability of mixed bubbles is increased.

  The amount of use (solid content) of the fluorosurfactant is not particularly limited. For example, with respect to 100 parts by weight of all monomer components (100 parts by weight of the base polymer) for forming the base polymer such as the acrylic polymer. 0.01 to 5 parts by weight is preferable. The lower limit is preferably 0.02 parts by weight, and more preferably 0.03 parts by weight. Moreover, the upper limit is preferably 3 parts by weight, and more preferably 2 parts by weight. When the use amount is 0.01 parts by weight or more, when the pressure-sensitive adhesive layer X contains bubbles, the stability of the bubbles is obtained, and when it is 5 parts by weight or less, good adhesive performance is obtained. .

  The pressure-sensitive adhesive layer X is stably contained without aggregation of the metal hydroxide and / or the hydrated metal compound in a smaller content than when the dispersant or the fluorosurfactant is used alone. From the viewpoint of being present and improving the stress dispersibility of the pressure-sensitive adhesive layer and expecting higher pressure-sensitive adhesiveness, the dispersant and the fluorosurfactant may be used in combination. When the dispersant and the fluorosurfactant are used in combination, the blending ratio is not particularly limited, but the ratio of the dispersant to the fluorosurfactant (weight ratio) is 1:20 to 20: 0.01 is preferable, More preferably, it is 1: 10-10: 0.01, More preferably, it is 1: 5-5: 0.01.

Specific examples of the fluorosurfactant having an oxy C _2-3 alkylene group and a fluorinated hydrocarbon group and having a weight average molecular weight of less than 20,000 include a trade name “Futgent 251” (manufactured by Neos Co., Ltd.), Name “FTX-218” (manufactured by Neos Co., Ltd.), product name “Megafuck F-477” (manufactured by DIC), product name “Megafuck F-470” (manufactured by DIC), product name “Surflon S-381” (AGC Seimi Chemical Co., Ltd.), trade name “Surflon S-383” (AGC Seimi Chemical Co., Ltd.), trade name “Surflon S-393” (AGC Seimi Chemical Co., Ltd.), trade name “Surflon KH-20” ( AGC Seimi Chemical Co., Ltd.) and trade name “Surflon KH-40” (manufactured by AGC Seimi Chemical Co., Ltd.). As a specific example of a fluorosurfactant having an oxy C2-3 alkylene group and a fluorinated hydrocarbon group and having a weight average molecular weight of 20000 or more, a trade name “F-top EF-352” (Mitsubishi Materials Electronics Chemical Co., Ltd.) Product name, “F-top EF-801” (manufactured by Mitsubishi Materials Electronics Chemical Co., Ltd.), product name “Unidyne TG-656” (manufactured by Daikin Industries, Ltd.), and the like.

[Crosslinking agent]
From the viewpoint that the cohesive force of the pressure-sensitive adhesive layer can be adjusted, the pressure-sensitive adhesive layer X may further contain a crosslinking agent. As the crosslinking agent, a known and commonly used crosslinking agent can be used. For example, epoxy crosslinking agent, isocyanate crosslinking agent, silicone crosslinking agent, oxazoline crosslinking agent, aziridine crosslinking agent, silane crosslinking agent, alkyl Examples include etherified melamine-based crosslinking agents and metal chelate-based crosslinking agents. Of these, isocyanate crosslinking agents and epoxy crosslinking agents are preferred.

  Examples of the isocyanate crosslinking agent include tolylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, xylylene diisocyanate, hydrogenated xylylene diisocyanate, diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, tetramethylxylylene diisocyanate, naphthalene diisocyanate, triphenyl. Examples include methane triisocyanate, polymethylene polyphenyl isocyanate, and adducts of these with polyols such as trimethylolpropane. A compound having at least one isocyanate group and one or more unsaturated bonds in one molecule, specifically, 2-isocyanatoethyl (meth) acrylate or the like can also be used.

  Examples of the epoxy crosslinking agent include bisphenol A, epichlorohydrin type epoxy resin, ethylene glycidyl ether, polyethylene glycol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, 1,6-hexanediol glycidyl ether, Methylolpropane triglycidyl ether, diglycidyl aniline, diamine glycidyl amine, N, N, N ′, N′-tetraglycidyl-m-xylylenediamine and 1,3-bis (N, N′-diamine glycidylaminomethyl) cyclohexane Etc.

  Although content of the said crosslinking agent is not specifically limited, For example, 0.01-5 weight part is preferable with respect to 100 weight part of base polymers, such as the said acrylic polymer in the said adhesive layer X. The upper limit is more preferably 3 parts by weight, still more preferably 2 parts by weight. When the content is 5 parts by weight or less, good flexibility is obtained, and when the content is 0.01 parts by weight or more, high cohesiveness is obtained.

[Tackifying resin]
The pressure-sensitive adhesive layer X may further contain a tackifier resin from the viewpoint that the adhesiveness is further improved. In particular, when the monomer component that constitutes the base polymer such as the acrylic polymer does not contain a carboxyl group-containing monomer, it is difficult to obtain a high adhesive force when the pressure-sensitive adhesive layer is thin, so a tackifier resin is included. It is preferred that The tackifying resin is not particularly limited. However, when an acrylic polymer is obtained by copolymerizing monomer components by irradiating ultraviolet rays, a hydrogenated type adhesive is used because it is difficult to inhibit polymerization even when used together. It is preferable to use an imparting resin. Examples of hydrogenated tackifying resins include derivatives obtained by hydrogenating tackifying resins such as rosin resins, petroleum resins, terpene resins, coumarone-indene resins, styrene resins, alkylphenol resins, xylene resins ( And hydrogenated rosin resins, hydrogenated petroleum resins, hydrogenated terpene resins, and the like. Among these, a hydrogenated rosin resin is preferable. Examples of the hydrogenated rosin-based tackifying resin include modified rosin obtained by modifying unmodified rosin (raw rosin) such as gum rosin, wood rosin and tall oil rosin by hydrogenation.

  Although the softening point of the said tackifying resin is not specifically limited, For example, 80-200 degreeC is preferable, More preferably, it is 90-200 degreeC. When the softening point of the tackifying resin is within the range, the cohesive force is further improved.

  Although content of the said tackifying resin is not specifically limited, 1-50 weight part is preferable with respect to 100 weight part of base polymers, such as the said acrylic polymer in the said adhesive layer. The lower limit is more preferably 2 parts by weight, still more preferably 3 parts by weight. The upper limit is more preferably 40 parts by weight, still more preferably 30 parts by weight. When the content is 50 parts by weight or less, high cohesive force is obtained, and when the content is 1 part by weight or more, high adhesive force is obtained.

  As the tackifying resin, a general commercial product can be used. For example, a trade name “Super Ester A-100” (softening point 95 to 105 ° C., manufactured by Arakawa Chemical Industries), a trade name “Super Ester A-125”. Hydrogenated rosin resins such as “(softening point 120 to 130 ° C., manufactured by Arakawa Chemical Industries, Ltd.)” can be used.

[Acrylic oligomer]
The pressure-sensitive adhesive layer X may further contain an acrylic oligomer from the viewpoint that the adhesiveness is further improved. The acrylic oligomer is a polymer having a glass transition temperature (Tg) higher than that of the acrylic polymer and a small weight average molecular weight, functions as a tackifier resin, and inhibits polymerization during polymerization using ultraviolet rays. It has the advantage of being difficult to wake up.

[Silane coupling agent]
The pressure-sensitive adhesive layer X is further improved in terms of adhesive strength and durability, and from the viewpoint of further improving the affinity between the thermally conductive particles and the base polymer such as the acrylic polymer. A ring agent may be included.

  As said silane coupling agent, a well-known thing can be used suitably, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-glycidoxypropylmethyldiethoxysilane Epoxy group-containing silane coupling agents such as 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane; 3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane, Amino group-containing silane coupling agents such as 3-triethoxysilyl-N- (1,3-dimethylbutylidene) propylamine; (methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, etc. ) Acrylic group-containing silane coupling Agents; such Inshianeto group-containing silane coupling agents such as 3-isocyanate propyl triethoxysilane and the like. The silane coupling agent may be used alone or in combination of two or more.

  Although content of the said silane coupling agent is not specifically limited, For example, 0.01-10 weight part is preferable with respect to 100 weight part of base polymers, such as the said acrylic polymer in the said adhesive layer X. The lower limit is more preferably 0.02 parts by weight, still more preferably 0.05 parts by weight. Further, the upper limit is more preferably 5 parts by weight, still more preferably 2 parts by weight. By using the silane coupling agent in the above range, the cohesive strength and durability are further improved.

[Bubble]
The pressure-sensitive adhesive layer X may be a pressure-sensitive adhesive layer containing bubbles. The pressure-sensitive adhesive layer containing bubbles can impart thickness and cushioning properties to the pressure-sensitive adhesive layer, and the performance of filling the unevenness of the adherend surface, that is, the unevenness absorbability (unevenness followability) is improved.

[Other additives]
The pressure-sensitive adhesive layer X includes a base polymer such as the acrylic polymer, the thermally conductive particles, the dispersant, the fluorosurfactant, the crosslinking agent, the tackifier resin, the acrylic oligomer, and the silane. In addition to the coupling agent, other additives may be included depending on the application. As said other additive, a plasticizer, a filler, anti-aging agent, a coloring agent (a pigment, dye, etc.) etc. are mentioned, for example.

  The thickness of the pressure-sensitive adhesive layer X is 50 μm or less (for example, 1 to 50 μm), and the lower limit is preferably 5 μm, more preferably 10 μm, and particularly preferably 20 μm. By setting the thickness to 50 μm or less, the pressure-sensitive adhesive layer becomes flexible and excellent rebound resistance is obtained. Further, when the pressure-sensitive adhesive sheet is processed into various shapes, it is difficult for re-bonding (blocking) of the punched portion after punching out the pressure-sensitive adhesive layer, and the processability is excellent. Furthermore, since there is little fall of adhesive force by making thickness thin, it is excellent in adhesiveness. When the thickness is 1 μm or more, the coating property is excellent. In the pressure-sensitive adhesive sheet of the present invention, since the thickness of the pressure-sensitive adhesive layer is in the above range, problems such as blurring after coating are unlikely to occur.

  The pressure-sensitive adhesive layer X can be formed from a pressure-sensitive adhesive composition in which a base polymer such as the acrylic polymer, the heat conductive particles, and the dispersant added as necessary are mixed. Specifically, for example, a monomer component for forming a base polymer such as the acrylic polymer, the polymerization initiator (for example, photopolymerization initiator, thermal polymerization initiator, etc.), an appropriate solvent (toluene or ethyl acetate). Etc.) are mixed to prepare a monomer solution, and a polymer solution containing a base polymer such as an acrylic polymer in which monomer components are copolymerized by performing a polymerization reaction according to the type of the polymerization initiator on the monomer solution. After preparing the above, the heat conductive particles and, if necessary, the dispersing agent are blended into the polymer solution to prepare a pressure-sensitive adhesive composition having a viscosity suitable for coating. In addition, when curing with an active energy ray such as ultraviolet irradiation, a monomer mixture for forming a base polymer such as an acrylic polymer, a photopolymerization initiator, etc. is mixed to prepare a monomer mixture, and the monomer mixture is mixed with the monomer mixture. After irradiating active energy rays such as ultraviolet rays to the composition to prepare a composition (syrup) containing a partial polymer in which only a part of the monomer components is polymerized, the thermally conductive particles are added to the syrup as needed. The above-mentioned dispersant and the like may be blended to prepare a composition having a viscosity suitable for coating, and the pressure-sensitive adhesive layer X may be formed using the composition.

  As described above, in particular, when a method of forming a pressure-sensitive adhesive layer by active energy ray irradiation is employed, even when a thin pressure-sensitive adhesive layer containing thermally conductive particles is produced, the thermal conductivity An adhesive layer in which the particles are uniformly dispersed, the thickness is uniform, and the surface is smooth can be easily produced.

  The pressure-sensitive adhesive composition preferably has an appropriate viscosity from the viewpoint of excellent coatability. As a viscosity of the said adhesive composition, 0.5-50 Pa.s is preferable, for example, and a minimum is more preferably 1 Pa.s, More preferably, it is 5 Pa.s. The upper limit is more preferably 40 Pa · s. When the viscosity is 50 Pa · s or less, application of the pressure-sensitive adhesive composition is facilitated when forming the pressure-sensitive adhesive layer X. In the present specification, the viscosity means a rotor: No. using a BH viscometer as a viscometer. The viscosity measured under the conditions of 5 rotors, rotation speed: 10 rpm, measurement temperature: 30 ° C.

  The viscosity of the pressure-sensitive adhesive composition is, for example, a method of blending various polymer components such as acrylic rubber and a thickening additive, a monomer component for forming an acrylic polymer (for example, forming an acrylic polymer ( It can be adjusted by a method of partially polymerizing a monomer component such as (meth) acrylic acid ester, etc.) to obtain a partial polymer.

[Base material]
The base material is not particularly limited. For example, polyester resins such as polyethylene terephthalate (PET), acrylic resins such as polymethyl methacrylate, polycarbonate, triacetyl cellulose, polysulfone, polyarylate, polyimide, polyvinyl chloride, Examples thereof include plastic films made of materials such as polyvinyl acetate, polyethylene, polypropylene, and ethylene-propylene copolymer. Among these, a polyimide film is preferable from the viewpoint of excellent flame retardancy.
The plastic film material may be one kind or a combination of two or more kinds.

  The thickness of the base material can be appropriately selected depending on the application, and is, for example, 2 to 250 μm. The lower limit is preferably 8 μm, more preferably 10 μm. The upper limit is preferably 150 μm, more preferably 50 μm, and still more preferably 30 μm. When the thickness is 2 μm or more, sufficient adhesive strength, holding power, and flame retardancy can be obtained. By setting the thickness to 250 μm or less, the pressure-sensitive adhesive layer becomes flexible, and a pressure-sensitive adhesive sheet having excellent resilience resistance is easily obtained. In addition, the said base material may have any form of a single layer and a multilayer. The surface of the base material may be appropriately subjected to known and conventional surface treatments such as physical treatment such as corona discharge treatment and plasma treatment, and chemical treatment such as undercoating treatment.

  In this invention, the base material-less double-sided adhesive sheet which does not have a base material is preferable at the point which can make the total thickness of an adhesive sheet very thin.

[Adhesive layer other than adhesive layer X]
When the heat conductive pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet with a substrate, at least one surface may be the pressure-sensitive adhesive layer X, and the other surface may be the pressure-sensitive adhesive layer X or another pressure-sensitive adhesive layer. Good. The other pressure-sensitive adhesive layer is not particularly limited as long as the effects of the present invention are not impaired. For example, a urethane-based pressure-sensitive adhesive, an acrylic pressure-sensitive adhesive, a rubber-based pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, a polyester-based pressure-sensitive adhesive, and a polyamide-based pressure-sensitive adhesive layer. Examples include known and commonly used pressure-sensitive adhesive layers formed from known pressure-sensitive adhesives such as pressure-sensitive adhesives, epoxy-based pressure-sensitive adhesives, vinyl alkyl ether-based pressure-sensitive adhesives, and fluorine-based pressure-sensitive adhesives.

[Release liner]
The pressure-sensitive adhesive layer surface (adhesive surface) of the heat conductive pressure-sensitive adhesive sheet of the present invention may be protected by a release liner until use. In addition, when the heat conductive adhesive sheet of this invention is a double-sided adhesive sheet, each adhesive surface may be protected by two separators, respectively, or by one separator whose both surfaces are release surfaces, You may protect in the form wound by roll shape. The release liner is used as a protective material for the pressure-sensitive adhesive layer, and is peeled off when the pressure-sensitive adhesive sheet is attached to an adherend. The release liner also serves as a support for the pressure-sensitive adhesive layer. Note that the release liner is not necessarily provided.

  As the release liner, a conventional release paper or the like can be used. Specifically, for example, in addition to a substrate having a release treatment layer with a release treatment agent on at least one surface, a fluoropolymer (for example, polytetrafluoro Low adhesion substrates made of ethylene, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, tetrafluoroethylene-hexafluoropropylene copolymer, chlorofluoroethylene-vinylidene fluoride copolymer, etc. A low adhesive substrate made of a polymer (for example, an olefin resin such as polyethylene or polypropylene) can be used.

  As the release liner, for example, a release liner in which a release treatment layer is formed on at least one surface of a release liner base material can be suitably used. Such release liner substrates include polyester films (polyethylene terephthalate film, etc.), olefin resin films (polyethylene film, polypropylene film, etc.), polyvinyl chloride films, polyimide films, polyamide films (nylon films), rayon films. In addition to plastic base film (synthetic resin film) and papers (quality paper, Japanese paper, kraft paper, glassine paper, synthetic paper, topcoat paper, etc.), etc., these are laminated by laminating or coextrusion. (2-3 layer composite) etc. are mentioned.

  The release treatment agent constituting the release treatment layer is not particularly limited. For example, a silicone release treatment agent, a fluorine release treatment agent, a long-chain alkyl release treatment agent, or the like can be used. The release treatment agents can be used alone or in combination of two or more. The thickness of the release liner, the formation method, etc. are not particularly limited.

The method for producing the pressure-sensitive adhesive sheet of the present invention varies depending on the composition of the pressure-sensitive adhesive composition and is not particularly limited, and a known forming method can be used. For example, the following (1) to (3) The method is mentioned.
(1) Monomer component forming a base polymer such as the acrylic polymer, a partial polymer of the monomer component, a particle group A having a D50 average particle diameter of 10 μm or more, a particle group B having a D50 average particle diameter of less than 10 μm, and as necessary Then, the pressure-sensitive adhesive composition containing the above-described dispersant or the like is applied (coated) on a base material or a separator to form a composition layer, and the composition layer is cured (for example, heat curing, activity such as ultraviolet rays) (2) Method of producing a pressure-sensitive adhesive sheet by forming a pressure-sensitive adhesive layer by curing with energy rays (2) Base polymer (including polymer solution) such as the above acrylic polymer, D50 Particle group A having an average particle diameter of 10 μm or more D50 particle group B having an average particle size of less than 10 μm, and if necessary, a pressure-sensitive adhesive composition in which the above-mentioned dispersant or the like is uniformly dissolved and dispersed is applied (coated) onto a substrate or a separator and dried. The method further drying the pressure-sensitive adhesive sheets prepared by the method (3) above (1) to produce a pressure-sensitive adhesive sheet to form an adhesive layer by

  As a curing method in the above (1) to (3), a pressure-sensitive adhesive layer having a uniform thickness and a smooth surface is formed even when a thin pressure-sensitive adhesive layer containing heat conductive particles is formed, and the productivity is excellent. In terms of formation, a method of curing with active energy rays (particularly a method of curing with ultraviolet rays) is preferable. In addition, since hardening with active energy rays may be inhibited by oxygen in the air, for example, when hardening, oxygen is obtained by bonding a separator on the pressure-sensitive adhesive layer or hardening in a nitrogen atmosphere. Is preferably blocked.

  When obtaining a pressure-sensitive adhesive layer containing bubbles, a bubble-containing pressure-sensitive adhesive composition obtained by introducing and mixing bubbles (bubble-forming gas) into the pressure-sensitive adhesive composition containing the thermally conductive particles, It can apply | coat on a predetermined | prescribed surface and can form the adhesive layer containing a bubble.

  As a method of applying (coating) the pressure-sensitive adhesive composition onto a predetermined surface, a known coating method can be adopted, and is not particularly limited. For example, roll coating, kiss roll coating, gravure coating, reverse coating , Roll brushing, spray coating, dip roll coating, bar coating, knife coating, air knife coating, curtain coating, lip coating, extrusion coating using a die coater, and the like.

  The thickness (total thickness) of the heat conductive pressure-sensitive adhesive sheet of the present invention is preferably 5 to 270 μm, for example, in order to cope with the recent miniaturization of mobile devices and home appliances. The lower limit is more preferably 15 μm, still more preferably 20 μm. The upper limit is more preferably 200 μm, still more preferably 100 μm, and particularly preferably 50 μm. When the thickness is 5 μm or more, it becomes easier to follow the stepped portion and the step absorbability is improved. By the said thickness being 270 micrometers or less, it is further excellent in resilience resistance. In addition, the thickness (total thickness) of a heat conductive adhesive sheet is the thickness from one adhesive surface to the other adhesive surface, and does not include the thickness of a release liner.

  180 ° peel adhesive strength (180 ° peeling adhesive strength) (23 ° C., 50% RH, tensile speed 300 mm / min, peeling angle 180 ° of the adhesive layer X surface of the heat conductive adhesive sheet of the present invention. The condition, SUS304 steel plate) is preferably 2N / 20 mm or more (for example, 2 to 20 N / 20 mm), more preferably 2.5 N / 20 mm or more (for example, 2.5 to 20 N / 20 mm). When the heat conductive pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, it is preferable that the 180 ° peel adhesive strength of at least one pressure-sensitive adhesive surface satisfy the above range. The 180 ° peel adhesive strength can be measured, for example, by the method described in “(2) 180 ° peel adhesive strength” in (Evaluation) described later.

  The heat conductive adhesive sheet of the present invention preferably has a heat conductivity of 0.3 W / m · K or more. The thermal conductivity can be evaluated by, for example, the method described in “(3) Thermal conductivity” in (Evaluation) described later.

  It is preferable that the heat conductive adhesive sheet of this invention has the flame retardance of VTM-0 or V-0 by the flame retardance test of UL94 specification. The flame retardancy can be evaluated by, for example, the method described in “(4) Flame retardance” in (Evaluation) described later.

  The holding power (80 ° C., 300 gf) measured on the surface of the pressure-sensitive adhesive layer X of the heat conductive pressure-sensitive adhesive sheet of the present invention is preferably 2 mm or less, more preferably 1 mm or less, still more preferably 0.6 mm or less, particularly preferably. Is 0.3 mm or less. In addition, the holding power (80 ° C., 100 gf) measured on the surface of the pressure-sensitive adhesive layer X of the heat conductive pressure-sensitive adhesive sheet of the present invention is preferably 2 mm or less, more preferably 1 mm or less, still more preferably 0.3 mm or less, Especially preferably, it is 0.2 mm or less. When the heat conductive pressure-sensitive adhesive sheet is a double-sided pressure-sensitive adhesive sheet, it is preferable that the holding force of at least one pressure-sensitive adhesive surface satisfies the above range. The holding force can be measured, for example, by the method described in “(5) Holding force” in (Evaluation) described later.

  Since the heat conductive pressure-sensitive adhesive sheet of the present invention is excellent in heat conductivity, flame retardancy and pressure-sensitive adhesiveness even when the pressure-sensitive adhesive layer is thin, mobile devices (for example, mobile phones, smartphones, portable information terminals, etc.), home appliances (For example, a digital camera, a video movie, a personal computer, etc.), a hard disk, LED lighting, a lithium ion battery, etc. It is suitably used in applications such as fixing components (electronic device components) used inside electronic devices. Can do. In recent years, as electronic devices have become smaller and more dense, heat generated inside the electronic device has become difficult to cool to the outside of the device, and the interior of the electronic device exposed to high heat ignites. There is a fear. Since the heat conductive pressure-sensitive adhesive sheet of the present invention has excellent heat conductivity and flame retardancy, it is easy to store heat inside the small or thin (for example, 1 to 20 mm thick) electronic equipment inside the electronic device. It is suitable for fixing equipment component members.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by these.

Example 1
As monomer components, 82 parts by weight of 2-ethylhexyl acrylate, 12 parts by weight of 2-methoxyethyl acrylate, 5 parts by weight of N-vinyl-2-pyrrolidone (NVP), and 1 part by weight of hydroxyethyl acrylamide (HEAA) are mixed. To the monomer mixture, 0.05 part by weight of a trade name “Irgacure 651” (2,2-dimethoxy-1,2-diphenylethane-1-one, manufactured by BASF Japan Ltd.) as a photopolymerization initiator and a trade name “Irga After compounding 0.05 part by weight of “Cure 184” (1-hydroxycyclohexyl phenyl ketone, manufactured by BASF Japan), the viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30 ° C.) becomes about 20 Pa · s. To a mixture of some of the monomer components polymerized (partial weight of the monomer mixture) Things, syrup) was prepared.
To 100 parts by weight of the syrup, 0.05 parts by weight of dipentaerythritol hexaacrylate (trade name “KAYARAD DPHA-40H”, manufactured by Nippon Kayaku Co., Ltd.) as a polyfunctional monomer and trade name “Plisurf A212E” (as a dispersant) 1 part by weight of Daiichi Kogyo Seiyaku Co., Ltd.) was added. Furthermore, as heat conductive particles, 100 parts by weight of aluminum hydroxide powder, trade name “Hijilite H-31” (shape: crushed, average particle size: 18 μm, manufactured by Showa Denko KK), aluminum hydroxide powder A trade name “Hijilite H-42” (shape: crushed, average particle size: 1 μm, Showa Denko KK) 100 parts by weight was added to obtain a composition.
A composition layer is formed by applying the above composition to the release treatment surface of a release liner made of polyethylene terephthalate (trade name “Diafoil MRF38” (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.)). On this composition layer, the same release liner as described above was laminated such that the release treatment surface was on the composition layer side.
Next, ultraviolet rays with an illuminance of about 5 mW / cm ² are irradiated from both sides of the laminate for 3 minutes to cure the composition layer to form an adhesive layer having a thickness of 50 μm. Release liner / adhesive layer / release liner A pressure-sensitive adhesive sheet (substrate-less pressure-sensitive adhesive sheet) having the following structure was obtained. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content ratio (particle volume ratio) of the heat conductive particles in the pressure-sensitive adhesive layer was 42.9% by volume.
The glass transition temperature of the acrylic polymer contained in the pressure-sensitive adhesive layer was −62.8 ° C. Further, the weight of the acrylic polymer contained in the pressure-sensitive adhesive layer corresponds to the total amount of the monomer constituting the syrup and the polyfunctional monomer.

(Example 2)
As heat conductive particles, trade name “Hijilite H-31” which is aluminum hydroxide powder (shape: crushed, average particle size: 18 μm, manufactured by Showa Denko KK), and product which is aluminum hydroxide powder The name “Hijilite H-42” (shape: crushed, average particle size: 1 μm, Showa Denko Co., Ltd.) was added in an amount of 50 parts by weight to obtain a composition. A sheet (baseless pressure-sensitive adhesive sheet) was obtained. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content rate of the heat conductive particle in an adhesive layer was 27.3 volume%.

Example 3
As heat conductive particles, trade name “Hijilite H-31” which is aluminum hydroxide powder (shape: crushed, average particle size: 18 μm, manufactured by Showa Denko KK), and product which is aluminum hydroxide powder Name "Hijilite H-42" (shape: crushed, average particle size: 1 μm, Showa Denko Co., Ltd.) 200 parts by weight was added to obtain a composition. A sheet (baseless pressure-sensitive adhesive sheet) was obtained. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content rate of the heat conductive particle in an adhesive layer was 48.5 volume%.

Example 4
As heat conductive particles, trade name “Hijilite H-31” which is aluminum hydroxide powder (shape: crushed, average particle size: 18 μm, manufactured by Showa Denko KK) and product which is aluminum hydroxide powder Name "Hijilite H-42" (shape: crushed, average particle size: 1 μm, Showa Denko KK) 150 parts by weight was added, and the composition was obtained in the same manner as in Example 1 except that the composition was obtained. A sheet (baseless pressure-sensitive adhesive sheet) was obtained. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content rate of the heat conductive particle in an adhesive layer was 48.5 volume%.

(Example 5)
As heat conductive particles, trade name “Hijilite H-31” which is aluminum hydroxide powder (shape: crushed, average particle size: 18 μm, manufactured by Showa Denko KK) 125 parts by weight and product which is aluminum hydroxide powder Name "Hijilite H-42" (shape: crushed, average particle size: 1 μm, Showa Denko Co., Ltd.) 125 parts by weight was added to obtain a composition. A sheet (baseless pressure-sensitive adhesive sheet) was obtained. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content rate of the heat conductive particle in an adhesive layer was 48.5 volume%.

(Example 6)
As heat conductive particles, trade name “Hijilite H-31” which is aluminum hydroxide powder (shape: crushed, average particle size: 18 μm, manufactured by Showa Denko KK) 150 parts by weight and product which is aluminum hydroxide powder Adhesive as in Example 1 except that 100 parts by weight of “Hijilite H-42” (shape: crushed, average particle size: 1 μm, Showa Denko KK) was added to obtain a composition. A sheet (baseless pressure-sensitive adhesive sheet) was obtained. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content rate of the heat conductive particle in an adhesive layer was 48.5 volume%.

(Example 7)
As heat conductive particles, trade name “Hijilite H-31” (shape: crushed, average particle size: 18 μm, manufactured by Showa Denko KK) 200 parts by weight as aluminum hydroxide powder, and product as aluminum hydroxide powder The name “Hijilite H-42” (shape: crushed, average particle size: 1 μm, Showa Denko Co., Ltd.) was added in an amount of 50 parts by weight to obtain a composition. A sheet (baseless pressure-sensitive adhesive sheet) was obtained. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content rate of the heat conductive particle in an adhesive layer was 48.5 volume%.

(Comparative Example 1)
A pressure-sensitive adhesive sheet (baseless pressure-sensitive adhesive sheet) was obtained in the same manner as in Example 1 except that no heat conductive particles were used. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content rate of the heat conductive particle in an adhesive layer was 0 volume%.

(Comparative Example 2)
As heat conductive particles, 250 parts by weight of trade name “Hijilite H-42” (shape: crushed, average particle size: 1 μm, manufactured by Showa Denko KK) which is aluminum hydroxide powder was added to obtain a composition. Except that, an adhesive sheet (baseless adhesive sheet) was obtained in the same manner as in Example 1. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content rate of the heat conductive particle in an adhesive layer was 48.5 volume%.

(Comparative Example 3)
As heat conductive particles, 250 parts by weight of trade name “Hijilite H-31” (shape: crushed, average particle size: 18 μm, Showa Denko KK) which is aluminum hydroxide powder was added to obtain a composition. Except that, an adhesive sheet (baseless adhesive sheet) was obtained in the same manner as in Example 1. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content rate of the heat conductive particle in an adhesive layer was 48.5 volume%.

(Comparative Example 4)
As a monomer component, 100 parts by weight of 2-ethylhexyl acrylate, a trade name “Irgacure 651” (2,2-dimethoxy-1,2-diphenylethane-1-one, manufactured by BASF Japan) as a photopolymerization initiator 0 .05 parts by weight and trade name “Irgacure 184” (1-hydroxycyclohexyl phenyl ketone, manufactured by BASF Japan Ltd.) were mixed with 0.05 parts by weight, followed by viscosity (BH viscometer No. 5 rotor, 10 rpm, measurement temperature 30). (° C.) was irradiated with ultraviolet rays until it reached about 20 Pa · s to prepare a mixture (partially polymerized monomer mixture, syrup) in which a part of the monomer component was polymerized.
To 100 parts by weight of the syrup, 0.05 parts by weight of dipentaerythritol hexaacrylate (trade name “KAYARAD DPHA-40H”, manufactured by Nippon Kayaku Co., Ltd.) as a polyfunctional monomer and trade name “Plisurf A212E” (as a dispersant) 1 part by weight of Daiichi Kogyo Seiyaku Co., Ltd.) was added. Furthermore, as heat conductive particles, trade name “Hijilite H-31” (shape: crushed, average particle size: 18 μm, manufactured by Showa Denko KK) which is aluminum hydroxide powder, 125 parts by weight, and aluminum hydroxide powder A trade name “Hijilite H-42” (shape: crushed, average particle size: 1 μm, Showa Denko) 125 parts by weight was added to obtain a composition.
A composition layer is formed by applying the above composition to the release treatment surface of a release liner made of polyethylene terephthalate (trade name “Diafoil MRF38” (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.)). On this composition layer, the same release liner as described above was laminated such that the release treatment surface was on the composition layer side.
Next, ultraviolet rays with an illuminance of about 5 mW / cm ² are irradiated from both sides of the laminate for 3 minutes to cure the composition layer to form an adhesive layer having a thickness of 50 μm. Release liner / adhesive layer / release liner A pressure-sensitive adhesive sheet (substrate-less pressure-sensitive adhesive sheet) having the following structure was obtained. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content ratio (particle volume ratio) of the heat conductive particles in the pressure-sensitive adhesive layer was 52% by volume.
The glass transition temperature of the acrylic polymer contained in the pressure-sensitive adhesive layer was −30 ° C. Further, the weight of the acrylic polymer contained in the pressure-sensitive adhesive layer corresponds to the total amount of the monomer constituting the syrup and the polyfunctional monomer.

(Comparative Example 5)
As a monomer component, 90 parts by weight of 2-ethylhexyl acrylate and 10 parts by weight of acrylic acid were mixed into a monomer mixture, and a trade name “Irgacure 651” (2,2-dimethoxy-1,2-diphenyl) was used as a photopolymerization initiator. Ethane-1-one (manufactured by BASF Japan) 0.05 parts by weight and trade name “Irgacure 184” (1-hydroxycyclohexyl phenyl ketone, BASF Japan) 0.05 parts by weight were blended, and the viscosity (BH Viscometer No. 5 rotor, 10 rpm, measurement temperature 30 ° C.) was irradiated with ultraviolet rays until it reached about 20 Pa · s, and a mixture (partially polymerized monomer mixture, syrup) in which a part of the monomer component was polymerized was produced. .
To 100 parts by weight of the syrup, 0.05 parts by weight of dipentaerythritol hexaacrylate (trade name “KAYARAD DPHA-40H”, manufactured by Nippon Kayaku Co., Ltd.) as a polyfunctional monomer and trade name “Plisurf A212E” (as a dispersant) 1 part by weight of Daiichi Kogyo Seiyaku Co., Ltd.) was added. Furthermore, as heat conductive particles, trade name “Hijilite H-31” (shape: crushed, average particle size: 18 μm, manufactured by Showa Denko KK) which is aluminum hydroxide powder, 125 parts by weight, and aluminum hydroxide powder A trade name “Hijilite H-42” (shape: crushed, average particle size: 1 μm, Showa Denko) 125 parts by weight was added to obtain a composition.
A composition layer is formed by applying the above composition to the release treatment surface of a release liner made of polyethylene terephthalate (trade name “Diafoil MRF38” (manufactured by Mitsubishi Chemical Polyester Film Co., Ltd.)). On this composition layer, the same release liner as described above was laminated such that the release treatment surface was on the composition layer side.
Next, ultraviolet rays with an illuminance of about 5 mW / cm ² are irradiated from both sides of the laminate for 3 minutes to cure the composition layer to form an adhesive layer having a thickness of 50 μm. Release liner / adhesive layer / release liner A pressure-sensitive adhesive sheet (substrate-less pressure-sensitive adhesive sheet) having the following structure was obtained. The thickness of the pressure-sensitive adhesive sheet (excluding the release liner) is 50 μm. The content ratio (particle volume ratio) of the heat conductive particles in the pressure-sensitive adhesive layer was 48.5% by volume.
The glass transition temperature of the acrylic polymer contained in the pressure-sensitive adhesive layer was 5 ° C. Further, the weight of the acrylic polymer contained in the pressure-sensitive adhesive layer corresponds to the total amount of the monomer constituting the syrup and the polyfunctional monomer.

(Evaluation)
The following measurement or evaluation was performed about the adhesive sheet obtained by the Example and the comparative example. The results are shown in Table 1.

(1) 50 μm coatability The thickness uniformity of the pressure-sensitive adhesive layer of the pressure-sensitive adhesive sheets obtained in the above Examples and Comparative Examples, and the surface smoothness of the pressure-sensitive adhesive layer were confirmed visually, and the thickness of the pressure-sensitive adhesive layer was When the surface of the pressure-sensitive adhesive layer is uniform and “smooth” (good), the thickness of the pressure-sensitive adhesive layer is uneven, or the surface of the pressure-sensitive adhesive layer is blurred (where the pressure-sensitive adhesive layer exists and where it does not exist) The case where it occurred) was evaluated as “bad (×)”.

(2) 180 ° peel adhesive strength (adhesive strength)
A tape piece having a length of 100 mm and a width of 20 mm was cut out from the pressure-sensitive adhesive sheets obtained in the above Examples and Comparative Examples to produce a strip-shaped tape piece. In addition, the thickness of each tape piece is the thickness described in said Example and the comparative example.
Next, the release liner is peeled off from the strip-shaped tape piece, and the adhesive surface (measurement surface) is pressure-bonded to the SUS304 steel sheet by reciprocating a 2 kg roller once in a 23 ° C., 50% RH atmosphere. A sample was made.
The measurement sample was allowed to stand for 30 minutes in an atmosphere of 23 ° C. and 50% RH, and then subjected to a 180 ° peel test using a tensile tester (trade name “TCM-1kNB”, manufactured by Minebea Co., Ltd.). 180 ° peel adhesive strength (180 ° peel adhesive strength) (N / 20 mm) was measured. The measurement was performed in an atmosphere of 23 ° C. and 50% RH under conditions of a peeling angle of 180 ° and a tensile speed of 300 mm / min.

(3) Thermal conductivity About the adhesive sheet obtained by said Example and comparative example, the thermal conductivity in the thickness direction was implemented using the thermal-characteristic evaluation apparatus shown in FIG. 1A is a schematic front view of the thermal characteristic evaluation apparatus, and FIG. 1B is a schematic side view of the thermal characteristic evaluation apparatus. Note that the release liner was removed during the measurement.
Specifically, between a pair of aluminum blocks (A5052, thermal conductivity: 140 W / m · K) (sometimes referred to as “rods”) L formed so as to form a cube having one side of 20 mm. The pressure-sensitive adhesive sheet 1 (width: 20 mm, length: 20 mm) was sandwiched between them, and a pair of blocks L were bonded together with the pressure-sensitive adhesive sheet 1.
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 block L might become up-down. Specifically, the heating element H is disposed on the upper block L, and the radiator C is disposed below the block L on the lower side.
At this time, the pair of blocks L bonded together with the pressure-sensitive adhesive sheet 1 is positioned between a pair of pressure adjusting screws T that penetrates the heating element H and the radiator C. A load cell R is disposed between the pressure adjusting screw T and the heating element H, and is configured to measure the pressure when the pressure adjusting screw T is tightened. The pressure applied to the pressure-sensitive adhesive sheet 1 was used.
Specifically, in this test, the pressure adjusting screw T was tightened so that the pressure applied to the pressure-sensitive adhesive sheet 1 was 25 N / cm ² (250 kPa).
In addition, three probes P (diameter 1 mm) of a contact-type displacement meter were installed so as to penetrate the lower block L and the adhesive sheet 1 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 block L, and the distance between the upper and lower blocks L (the thickness of the adhesive sheet 1) can be measured.
A temperature sensor D was attached to the heating element H and the upper and lower blocks L. Specifically, the temperature sensor D was attached to one place of the heating element H, and the temperature sensors D were attached to the five places of each block L at intervals of 5 mm in the vertical direction.
In the measurement, first, the pressure adjusting screw T was tightened, pressure was applied to the adhesive sheet 1, the temperature of the heating element H was set to 80 ° C., and cooling water of 20 ° C. was circulated through the radiator C. .
After the temperature of the heating element H and the upper and lower blocks L is stabilized, the temperature of the upper and lower blocks L is measured by each temperature sensor D, and the thermal conductivity (W / m · K) and temperature gradient of the upper and lower blocks L are measured. The heat flux passing through the pressure-sensitive adhesive sheet 1 was calculated, and the temperature at the interface between the upper and lower blocks L and the pressure-sensitive adhesive sheet 1 was calculated. And the thermal conductivity (W / m * K) and thermal resistance (cm < ² > * K / W) in pressure were calculated using the following thermal conductivity equations (Fourier's law) using these.
Q = −λgradT
R = L / λ
Q: Heat flow rate per unit area gradT: Temperature gradient L: Sheet thickness λ: Thermal conductivity R: Thermal resistance

(4) Flame retardancy The following flame retardancy test was conducted in accordance with the flame retardancy test standard UL94.
Five test pieces having a length of 200 mm and a width of 50 mm were obtained from the pressure-sensitive adhesive sheets obtained in the above Examples and Comparative Examples. In addition, the thickness of each tape piece is the thickness described in said Example and the comparative example. One end of the test piece was hung vertically. After that, using a burner, flame was applied to the other end for 3 seconds, once separated from the flame, and then the state of the test piece after further flame was applied for 3 seconds. The flame retardancy was evaluated as “VTM-0” and the case of not satisfying the standard X being “inferior (×)” (VTM test).
Criteria X: All the following (i) to (v) are satisfied.
(I) The flammable combustion time of each test piece (the total of the combustion time after applying the first flame and the combustion time after applying the second flame) is within 10 seconds.
(Ii) The total time of the flammable combustion time of the five test pieces is within 50 seconds.
(Iii) The total time of the flaming combustion time and the flameless combustion time of each test piece after applying the flame for the second time is within 30 seconds.
(Iv) Of the five test pieces, there is no test piece in which the combustion drops dropped from the test piece and the cotton disposed below ignited.
(V) All the test pieces do not burn up to the suspended part (upper end part).

(5) Holding power It carried out according to evaluation of the holding power of JISZ1528 by using the adhesive sheet obtained by said Example and comparative example as an evaluation sample. A sample with a backing material was obtained on one side of the pressure-sensitive adhesive sheet using “Lumirror S-10 # 25” manufactured by Toray Industries, Inc. A sample with a backing material is pasted by reciprocating a 2 kg roller so as to have an area of 10 mm × 20 mm, cured at room temperature of 23 ° C. for 30 minutes, and then loaded with 100 g (or 300 g) under an atmosphere of 80 ° C. It was applied for a period of time, and the amount of displacement from the initial stage of application was confirmed to determine the holding force (mm).

DESCRIPTION OF SYMBOLS 1 Adhesive sheet 2 Thermometer 3 Contact-type displacement meter C Radiator D Temperature sensor H Heat generating body (heat block)
L block (rod)
P probe R load cell T pressure adjusting screw

Claims (6)

  As the thermally conductive particles, a particle group A having a D50 average particle diameter of 10 μm or more and a particle group B having a D50 average particle diameter of less than 10 μm are a ratio (weight ratio) of the particle group A to the particle group B of 2: 8 to 8: 2. The heat conductive adhesive sheet which has an adhesive layer mix | blended by (5) and whose thickness of this adhesive layer is 50 micrometers or less.   The heat conductive adhesive sheet according to claim 1 whose content of heat conductive particles in said adhesive layer is 25 volume% or more and 75 volume% or less.   The heat conductive adhesive sheet of Claim 1 or 2 which has a flame retardance of VTM-0 or V-0 in the flame retardance test of UL94 specification.   The heat conductive adhesive sheet according to any one of claims 1 to 3, wherein the heat conductivity is 0.3 W / m · K or more.   Retention force (80 degreeC, 300gf) is 2 mm or less, The heat conductive adhesive sheet of any one of Claims 1-4.   The heat-sensitive adhesive sheet according to claim 1, wherein the pressure-sensitive adhesive layer is an active energy ray-curable pressure-sensitive adhesive layer.

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