JP2013072031A - Heat radiation sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat radiation sheet which has excellent heat conductivity, can be recycled, does not contain a low molecular weight compound causing contact failure and the like of an electric circuit and suitably adheres to an exothermic member, a cooling member and the like.SOLUTION: The heat radiation sheet includes: a heat radiation layer made of a heat conductive elastomer composition formed by mixing 100 pts.mass hydrogenated thermoplastic styrenic elastomer (E) to be a hydrogenated product of a block copolymer with a weight-average molecular weight of 150,000 to 500,000 and having 20 to 50 mass% content of a styrenic monomer; 100 to 600 pts.mass rubber softening agent having 50 to 500 cSt kinematic viscosity (40°C); 1 to 100 pts.mass olefinic resin; and surface coating aluminum hydroxide and/or surface coating magnesium oxide of 40 to 400 pts.vol. to 100 pts.vol. sum total of the hydrogenated thermoplastic styrenic elastomer (E), the rubber softening agent and the olefinic resin; and an adhesive layer layered on one surface or both surfaces of the heat radiation layer.

Description

  The present invention relates to a heat radiating sheet as a heat radiating member mainly used for cooling a heat-generating member mounted on an electric or electronic device.

For example, power transistors and driver integrated circuits (ICs) used in computer central processing units (CPUs) and the like are electrical and electronic equipment members that are heat-generating members. Therefore, heat radiation measures for the exothermic member are regarded as important. As a heat dissipation measure for the exothermic member, at present, in order to improve the thermal conductivity from the exothermic member to a cooling member such as a heat dissipating housing, a heat dissipation member is used as a spacer between the exothermic member and the cooling member. Members are used.
Examples of the heat radiating member used as the spacer include a heat radiating sheet. In order to increase the heat transfer efficiency from the exothermic member to the cooling member, the heat radiating sheet needs to be in close contact with both the exothermic member and the cooling member. That is, if air enters between the heat generating member or the cooling member and the heat radiating sheet to form an air layer, the heat conductivity of the heat radiating sheet is greatly reduced because the heat conductivity of the air layer is low. It is because it will fall. Therefore, a material having flexibility such as silicone rubber is often used as the material of the heat radiating sheet in order to improve the followability to the heat generating member and the cooling member to improve the adhesion.
On the other hand, the heat dissipation sheet, for example, such as silicone rubber, has low adhesiveness or has no adhesiveness, so in order to adhere to the exothermic member and the cooling member, Adhesives and adhesives are used, primer treatment is applied, and adhesive tapes are used.
For example, in patent document 1, the double-sided adhesive tape which apply | coats an adhesive to both surfaces of a base material is used, and the heat-radiation sheet | seat which consists of a graphite sheet is stuck to the exothermic member and the cooling member.
Further, in Patent Document 2, the surface of the pressure-sensitive adhesive layer is subjected to primer treatment, and the heat-dissipating silicone is heated and crosslinked on the surface, thereby integrating the pressure-sensitive adhesive layer and the silicone.
Patent Document 3 describes a pressure-sensitive adhesive sheet composed of a support, a pressure-sensitive adhesive layer, and a release liner, and a label attached to the release liner.

JP 2010-254979 A Japanese Patent No. 3468420 Japanese Utility Model Publication No. 3-115638

However, in the conventional heat-dissipating sheet, when a double-sided pressure-sensitive adhesive tape is used, if the double-sided pressure-sensitive adhesive tape does not follow the heat-dissipating sheet, the double-sided pressure-sensitive adhesive tape dissipates heat when the heat-dissipating sheet is bent or pulled. There are problems such as peeling from the sheet and air entering when the double-sided pressure-sensitive adhesive tape is applied to the heat radiating sheet to form an air layer.
Further, when using silicone rubber, there is a problem that the primer treatment is required and the operation becomes complicated. In addition, silicone rubber generates low molecular weight siloxane, which may cause poor contact in electrical circuits, etc., so care must be taken when mounting it in electrical and electronic equipment. In addition, since it is a crosslinked rubber, there is no thermoplasticity. There is a problem that recycling is impossible.
In addition, it is difficult to remove the release liner from the pressure-sensitive adhesive layer where there is no label, and when the other party is weak or does not have adhesive properties such as the above-mentioned silicone rubber, not only the release liner but also the adhesive sheet There is a problem that it itself peels off with high probability.
In recent years, in order to avoid the problems associated with the use of the silicone rubber, a heat radiating member having a synthetic resin as a main material and a heat conductive filler added has been proposed. Therefore, it is desired to solve the problem related to the adhesion with the heat generating member and the cooling member.
The present invention has been made by paying attention to the problems existing in the above-mentioned prior art, and the object of the present invention is that it has excellent thermal conductivity, is recyclable, and causes a contact failure of an electric circuit. An object of the present invention is to provide a heat-dissipating sheet that can be suitably adhered to a heat-generating member, a cooling member, or the like without a low molecular compound.

In order to solve the above problems, the present invention provides a block copolymer comprising a block unit (S) of a polymer comprising a styrene monomer and a block unit (B) of a polymer comprising a conjugated diene compound. 100 parts by mass of a hydrogenated thermoplastic styrene elastomer (E) which is a hydrogenated polymer (Z) and has a weight average molecular weight of 150,000 to 500,000 and a styrene monomer content of 20 to 50% by mass 100 to 600 parts by weight of a rubber softener having a kinematic viscosity of 40 to 50 ° C. at 50 to 500 centistokes (cSt), 1 to 100 parts by weight of an olefin resin, and the hydrogenated thermoplastic styrene elastomer (E) Surface-coated aluminum hydroxide formed by surface-coating aluminum hydroxide with an organic coupling agent for 100 parts by volume of the rubber softener and the olefin resin. A heat-dissipating layer which is a sheet made of a thermally conductive elastomer composition obtained by mixing 40 to 400 parts by volume of a surface-coated magnesium oxide obtained by coating a surface of magnesium and / or magnesia clinker with an inorganic material and / or an organic material; And a heat-dissipating sheet having an adhesive layer laminated on one or both surfaces of the heat-dissipating layer.
Desirably, the thickness of the said adhesion layer is 1/100 or more and less than 1/6 of the thickness of the said thermal radiation layer.

[Action]
The hydrogenated thermoplastic styrene-based elastomer (E) in the thermally conductive elastomer composition (hereinafter referred to as the composition) contained in the heat dissipation layer of the heat dissipation sheet is thermoplastic, and thus can be recycled. Also, thermoforming such as injection molding is easy. When the above-mentioned hydrogenated thermoplastic styrene elastomer (E) having a weight average molecular weight (Mw) of less than 150,000 is used, the heat resistance of the resulting molded product is deteriorated and the molded product has long-term heat resistance. When the test is performed, deformation occurs. Further, the softener retention is deteriorated, and the softener becomes easy to bleed in the molded product, resulting in stickiness on the surface of the molded product. On the other hand, when the one having Mw exceeding 500,000 is used, the fluidity of the hot melt of the composition is lowered and the moldability is deteriorated.
The method for measuring the weight average molecular weight will be described later.
When the content of the styrene monomer is less than 20% by mass, the heat resistance of the obtained molded product is deteriorated, and when the molded product is subjected to a long-term heat test, deformation occurs. become. On the other hand, when the styrene monomer content exceeds 50% by mass, the resulting molded product has poor flexibility and loses rubber elasticity.

The rubber softener in the composition is a component that imparts flexibility to the composition and improves adhesion to the heat-generating member and the cooling member, but has a kinematic viscosity of 50 centistokes (cSt at 40 ° C.). When a material less than () is used, gas is remarkably generated when the resulting composition is molded, and bleeding tends to occur in the molded product. In addition, when a material having a kinematic viscosity exceeding 40 cSt at 40 ° C. is used, the surface of the resulting molded product becomes noticeable, causing trouble in handling and reducing workability.
When the addition amount of the rubber softening agent exceeds 600 parts by mass with respect to 100 parts by mass of the hydrogenated thermoplastic styrene elastomer (E), the rubber softening agent is added to the surface of the obtained molded product. When the surface of the molded product becomes noticeably sticky and the addition amount of the rubber softener is less than 100 parts by mass with respect to 100 parts by mass of the hydrogenated thermoplastic styrene elastomer (E), The composition is difficult to be agglomerated and cannot be molded.

The olefin resin in the composition is a component that gives the molded product appropriate hardness, rigidity, and heat resistance.
When the addition amount of the olefin resin exceeds 100 parts by mass with respect to 100 parts by mass of the hydrogenated thermoplastic styrene elastomer (E), the resulting molded product becomes hard and the flexibility becomes poor. On the other hand, when the addition amount is less than 1 part by mass with respect to 100 parts by mass of the hydrogenated thermoplastic styrene elastomer (E), it becomes impossible to impart appropriate hardness, rigidity and heat resistance to the molded product. .

In the present invention, surface-coated aluminum hydroxide and / or surface-coated oxidation is used as a heat-conductive filler in order to make the thermal conductivity of the above composition suitable and not to damage the screw or the mold during molding. Use magnesium.
The surface-coated aluminum hydroxide is obtained by surface-coating aluminum hydroxide with an organic coupling agent from the viewpoint of imparting moisture resistance and dispersibility in the composition.
The surface-coated magnesium oxide is obtained by applying a surface coating to magnesia clinker with an inorganic substance and / or an organic substance from the viewpoint of imparting moisture resistance and dispersibility in the composition. The magnesia clinker is a burned ingot (clinker) in which the main component magnesium oxide (magnesia) is inactivated by firing a magnesia raw material (raw material containing magnesium oxide as a main component) at a high temperature (1600 ° C. or higher). ).
40 to 400 parts by volume of the thermally conductive filler is added to 100 parts by volume of the mixture of the hydrogenated thermoplastic styrene elastomer (E), the rubber softener, and the olefin resin. When the addition amount is less than 40 parts by volume, the thermal conductivity of the composition is low, and when the addition amount exceeds 400 parts by volume, the heat dissipation layer including the sheet material of the composition is hardened. The rubber elasticity is lowered, and the adhesion to the heat generating member and the cooling member is deteriorated.

Since the heat dissipation sheet is configured by laminating an adhesive layer on one or both surfaces of the heat dissipation layer which is a sheet material made of the composition, the exothermic member or the cooling member and the heat dissipation layer are interposed through the adhesive layer. Can be adhered without gaps.
The adhesive layer has a thickness of 1/100 or more and less than 1/6 of the thickness of the heat-dissipating layer, so that the adhesiveness to the exothermic member or the cooling member is favorable, and the thermal conductivity Can be suppressed.

〔effect〕
In the present invention, heat dissipation that is excellent in thermal conductivity, is recyclable, does not include low molecular compounds that cause poor contact of an electric circuit, and can be suitably adhered to a heat generating member, a cooling member, or the like. A sheet is provided.

The present invention is described in detail below.
[Hydrogenated thermoplastic styrene elastomer]
The hydrogenated thermoplastic styrene elastomer (E) contained in the composition of the present invention (thermally conductive elastomer composition) is a block unit (S) of a polymer comprising a styrene monomer (hereinafter simply referred to as polymer block). A block copolymer (Z) composed of a block unit (B) of a polymer composed of a conjugated diene compound (hereinafter also simply referred to as a polymer block unit (B)), The block unit (B) of the polymer mainly composed of the conjugated diene compound in the block copolymer (Z) is partially or entirely hydrogenated.
Examples of the polymer block unit (S) composed of the styrene monomer include styrene, o-methylstyrene, p-methylstyrene, pt (tertiary) -butylstyrene, 1,3-dimethylstyrene, It is a polymer block made of a styrene monomer such as α-methylstyrene, vinylnaphthalene, vinylanthracene and the like.
The polymer block unit (B) composed of the conjugated diene compound is a polymer block mainly composed of a conjugated diene compound such as butadiene, isoprene or 1,3-pentadiene.
Examples of the hydrogenated thermoplastic styrene elastomer (E) used in the present invention include, in addition to the thermoplastic styrene elastomer (TPS), for example, styrene-ethylene-butylene-styrene block copolymer (SEBS), styrene-ethylene. -Propylene-styrene block copolymer (SEPS), styrene-ethylene-ethylene-propylene-styrene block copolymer (SEEPS), etc. are illustrated.
The hydrogenated thermoplastic styrene elastomer (E) of the present invention is useful as a block copolymer having two or more polymer block units (S) and one or more polymer block units (B). It is a hydrogenated product of a polymer (Z), and among them, a block copolymer in which one (total of two) polymer block units (S) are bonded to both ends of one polymer block unit (B) ( ZBS is a hydrogenated thermoplastic styrenic elastomer (E) which is desirable from the viewpoint of heat resistance, and SEBS in which butadiene which is a constituent unit of the polymer block unit (B) is converted into ethylene and butylene by hydrogenation to Z). is there.
The hydrogenated thermoplastic styrene-based elastomer (E) includes styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), pyridine-butadiene rubber, styrene-isoprene rubber (SIR) unless departing from the object of the present invention. ), Styrene-ethylene copolymer, polystyrene-polybutadiene-polystyrene (SBS), polystyrene-polyisoprene-polystyrene (SIS), poly (α-methylstyrene) -polybutadiene-poly (α-methylstyrene) (α-MeSBα- MeS), poly (α-methylstyrene) -polyisoprene-poly (α-methylstyrene), ethylene-propylene copolymer (EP), styrene-chloroprene rubber (SCR), styrene-butadiene-styrene (SBS) copolymer Coalescence, styrene-isopropyl Emission - some amount of other elastomers or synthetic rubbers styrene (SIS) copolymer and the like may be added.

(Weight average molecular weight)
In the present invention, as the hydrogenated thermoplastic styrene elastomer (E), those having a weight average molecular weight (Mw) in the range of 150,000 to 500,000 are used.
When the weight average molecular weight (Mw) is less than 150,000, the heat resistance is poor. Therefore, when a long-term heat test is performed, deformation is likely to occur, and the softener is poorly retained and the softener tends to bleed. There is a risk of stickiness. When the weight average molecular weight (Mw) exceeds 500,000, the fluidity of the melt at the time of molding is lowered, the moldability is deteriorated, and the rubber elasticity of the composition is lowered.
As the weight average molecular weight (Mw) of the hydrogenated thermoplastic styrene-based elastomer (E), a measured value by a gel permeation chromatograph (GPC) method described below is used.
[Measurement of polystyrene equivalent molecular weight by GPC (gel permeation chromatography) method]
The measurement conditions of molecular weight by GPC are as follows.
-Pump: JASCO (JASCO Corporation) PU-980
-Column oven: Showa Denko Co., Ltd. AO-50
Detector: Hitachi RI (differential refractometer) detector L-3300
Column type: Showa Denko Co., Ltd. “K-805L (8.0 × 300 mm)” and “K-804L (8.0 × 300 mm)” used in series. Column temperature: 40 ° C.
Guard column: KG (4.6 × 10 mm)
・ Eluent: Chloroform ・ Eluent flow rate: 1.0 ml / min ・ Sample concentration: about 1 mg / ml
Sample solution filtration: 0.45 μm pore size disposable filter made of polytetrafluoroethylene Standard sample for calibration curve: Polystyrene made by Showa Denko KK The above hydrogenated thermoplastic styrene elastomer (E) may be used alone. Two or more different weight average molecular weights (Mw), 1,2-vinyl bond amounts, etc. can be used in combination.

(Styrene monomer content)
In the present invention, the hydrogenated thermoplastic styrene elastomer (E) is one having a styrene monomer content of 20 to 50% by mass.
When the content ratio of the styrene monomer is less than 20% by mass, the heat resistance is deteriorated, and deformation occurs when a long-term heat test is performed. When the content rate of a styrene-type monomer exceeds 50 mass%, the rubber elasticity of the said hydrogenated thermoplastic styrene-type elastomer (E) obtained falls, and adhesiveness to a heat generating body, a cooling component, etc. worsens.

(1,2-vinyl bond amount)
In the block copolymer (Z) composed of a conjugated diene compound constituting the hydrogenated thermoplastic styrene-based elastomer (E), the proportion of the 1,2-vinyl bond amount is desirably less than 50% by mass. When the 1,2-vinyl bond ratio is less than 50% by mass, the composition is less likely to be sticky.

[Rubber softener]
In the present invention, a rubber softener is used as a material for increasing the flexibility of the composition and improving the adhesion to the heat-generating member.
As the rubber softening agent used in the present invention, non-aromatic oils are used, for example, paraffinic oils and naphthenic oils are used, and the hydrogenated thermoplastic styrene elastomers of the present invention are good. Paraffinic oils that exhibit compatibility are desirable rubber softeners.
As the rubber softener, one having a kinematic viscosity in the range of 50 to 500 centistokes (cSt) at 40 ° C. is used. When the kinematic viscosity is less than 50 cSt at 40 ° C., gas generation becomes significant when the composition is molded, and bleeding tends to occur. On the other hand, if the kinematic viscosity exceeds 500 cSt at 40 ° C., the sticking of the molded product becomes intense and workability is lowered.

[Olefin resin]
In the present invention, an olefin-based resin is used as a material that plays a bridging role when the composition is kneaded and prepared, and further imparts heat resistance, appropriate rigidity, and fluidity of the melt during molding to the composition. To do.
A typical example of the olefin resin used in the present invention is polypropylene. Examples of the polypropylene include propylene homopolymer, propylene-ethylene copolymer, and modified polypropylene obtained by adding polyethylene or ethylene-propylene copolymer to polypropylene.
As the olefin resin used in the present invention, it is more preferable in terms of heat resistance to use a resin having a deflection temperature under load measured in accordance with JIS K 6921-2 of 80 ° C to 140 ° C. If the deflection temperature under load is less than 80 ° C., the molded product may be deformed.

(Thermal conductive filler)
The composition of the present invention is blended with a heat conductive filler from the viewpoint of improving the heat conductivity.
The heat conductive filler includes a surface-coated aluminum hydroxide obtained by surface-coating aluminum hydroxide with an organic coupling agent, and / or a surface coating obtained by surface-treating magnesia clinker with an inorganic substance and / or an organic substance. Magnesium oxide is used.

(Surface coated aluminum hydroxide)
As the aluminum hydroxide used for the surface-coated aluminum hydroxide, a soda component (Na ₂ O) content as low as possible (for example, containing less than 0.4% by mass) is desirable. Aluminum hydroxide with a low soda content is a desirable material because of its high decomposition temperature, low hygroscopicity, and high insulating properties.
Examples of the organic coupling agent used to coat the aluminum hydroxide include titanate esters such as tetraisopropyl titanate, tetrabutyl titanate, tetra (2-ethylhexyl) titanate, tetrastearyl titanate, and γ- Examples thereof include a silicon compound (silane coupling agent) having two groups of a Si (OR) ₃ portion such as methacryloxypropyltrimethoxysilane and an organic functional group such as a vinyl group, amino group, and epoxy group.
The coupling agent may contain two or more of the organic functional groups in one molecule, and two or more of the coupling agents may be used in combination.

(Surface coating magnesium oxide)
The magnesia clinker used for the surface-coated magnesium oxide is produced, for example, by the following method.
(1) An alkali substance such as caustic soda is added to a magnesium-containing raw material such as seawater and bitter juice to prepare a magnesium hydroxide slurry.
(2) The magnesium slurry is filtered and dried, for example, under conditions of 120 ° C. × 10 hours.
(3) The dried product (magnesium hydroxide) is calcined at 600 to 1000 ° C. to obtain light-burned magnesia (magnesium oxide).
(4) The light burned magnesia is inactivated by dead burning at 1600 ° C. or higher, preferably 1800-2100 ° C. with a rotary kiln or the like to obtain a magnesia clinker.
Burning the magnesium oxide at 1600 ° C. or higher to obtain a surface-inactive magnesia clinker is called death firing. Here, the magnesia clinker means that the magnesia (magnesium oxide) component is melted into a lump (burned lump: clinker) by the dead burning.
In the said calcination, when a calcination temperature exceeds 1200 degreeC, the activity of the magnesium oxide obtained will fall significantly. Furthermore, in the above-mentioned dead firing, when the firing temperature is 1600 ° C. or higher, magnesium oxide is inactivated, that is, no reactivity with acid or water vapor is caused, and large crystallization occurs.
As described above, the magnesia clinker is inactivated and large crystallized by dead burning, and thus has excellent moisture resistance and thermal conductivity.
Examples of the inorganic substance used for the surface coating of the magnesia clinker include an aluminum compound, a silicon compound, and a titanium compound, and two or more kinds of the inorganic substances may be used in combination. Examples of the inorganic materials include ceramic compounds such as oxides, nitrides, borides, salts such as nitrates, sulfates, and chlorides, hydroxides, and the like.
Examples of the organic substance used for the surface coating of the magnesia clinker include the organic coupling agent, silane coupling material, and organic synthetic resin used for the aluminum hydroxide coating. Two or more of the above organic substances may be used in combination.
The magnesia clinker is surface-treated with the inorganic material and / or organic material to form a surface-coated magnesium oxide, thereby improving moisture resistance and dispersibility.

(Water absorption rate)
The thermally conductive filler used in the present invention desirably has a water absorption rate (after the moisture resistance test) of less than 1.5% by mass (after the moisture resistance test). When a thermally conductive filler having a water absorption rate of 1.5% by mass or more is added to the composition, the elastomer in the composition is deteriorated and the insulating property is lowered.
The water absorption rate by the moisture resistance test is measured as follows.
10 g of the heat conductive filler is put in a petri dish, left in a thermostat at 90 ° C. × 90 RH%, and the mass change after 48 hours is measured with an electronic balance. ).
Mass change rate (mass%) = mass of thermally conductive filler after test / mass of thermally conductive filler before test × 100

(hardness)
The heat conductive filler used in the present invention desirably has a new Mohs hardness of less than 10. If the new Mohs hardness of the heat conductive filler is less than 10, the wear of the kneader and the molding apparatus during molding using the composition can be suppressed.
Here, the new Mohs hardness is a hardness expressed by a numerical value of 1 to 15 depending on the presence or absence of scratches at the time when the solid surface is sequentially scratched with 15 kinds of standard minerals having different hardnesses. A New Mohs hardness of less than 10 indicates that the garnet will be scratched.

(Other)
The thermal conductive filler used in the present invention is more flexible and better in the case of using a mixture of two or more of different particle sizes at a predetermined ratio than when using one kind alone. From the viewpoint of exhibiting excellent thermal conductivity.

[Third component]
In addition to the above components, other compounding components can be blended as required within the range not impairing the characteristics of the present invention. As a desirable third component, there is a processing aid that improves the stretchability by improving the tension of the melt when the composition of the present invention is molded by extrusion molding, injection molding or the like. Further, the processing aid is a desirable third component from the viewpoint of improving the flame retardancy of the composition. Typical examples of the processing aid are modifiers for polyolefins such as acrylic modified polytetrafluoroethylene (PTFE) and high molecular weight special acrylic resins. When the processing aid is added, the extensibility and tension of the melt of the composition of the present invention are improved and the film is easily stretched. Therefore, even if a tensile force is applied to the melt, the melt is hardly cut. As a result, for example, when forming a sheet or film by extrusion molding, the shape is maintained, so that molding defects are less likely to occur.
Examples of other third components include talc, calcium carbonate, magnesium carbonate, barium sulfate, calcium sulfate, calcium sulfite, calcium phosphate, calcium hydroxide, magnesium hydroxide, aluminum hydroxide, magnesium oxide, titanium oxide, iron oxide, Zinc oxide, alumina, silica, diatomaceous earth, dolomite, gypsum, calcined clay, asbestos, mica, calcium silicate, bentonite, white carbon, carbon black, iron powder, aluminum powder, stone powder, blast furnace slag, fly ash, cement, zirconia powder Inorganic fillers such as linter, linen, sisal, wood flour, palm flour, walnut flour, starch, wheat flour, rice flour, natural fibers such as cotton, hemp, wool, polyamide fibers, polyester fibers, Acrylic fiber, viscose fiber, Organic synthetic fibers such as cetate fibers, fiber fillers such as asbestos fibers, glass fibers, carbon fibers, ceramic fibers, metal fibers, whisker fibers, colorants such as pigments, pigments, carbon black, or antistatic agents , Conductivity enhancer, anti-aging agent, flame retardant, flame retardant, water repellent, oil repellent, insect repellent, antiseptic, waxes, surfactant, lubricant, UV absorber, DBP, DOP, heat stabilizer Various additives such as chelating agents and dispersing agents may be added.
In addition, the composition of the present invention can be used by blending with other polymers as long as the characteristics of the present invention are not impaired.

(Metal soap)
Among the various additives mentioned in the third component above, the dispersant improves the compatibility between the resin and the like used in the present invention and the heat conductive filler, etc., so that the molding is excellent in dispersion and flexibility. You can get a body. As the dispersant, a metal soap can be used, and the metal soap is a metal salt of a higher fatty acid, and examples of the higher fatty acid include stearic acid, 1,2-hydroxystearic acid, behenic acid, lauric acid and the like. Examples of the metal include magnesium, calcium, lithium, barium, sodium, and zinc. Among these metal soaps, it is particularly desirable to use magnesium stearate and calcium stearate which have extremely good fluidity and have a melting point of 160 ° C. or less and are easily dispersed during kneading.

[Combination]
The composition of the present invention is a mixture of the following (a) to (d).
(A) 100 parts by mass of the hydrogenated thermoplastic styrene elastomer (E).
(B) The rubber softener is 100 to 600 parts by mass.
(C) The said olefin resin is 1-100 mass parts.
(D) The thermally conductive filler is 40 to 400 parts by volume with respect to 100 parts by volume of the total of the above (a), (b), and (c).
Moreover, the composition of this invention may mix the following (e), if desired.
(E) The metal soap is 1 to 80 parts by mass.

When the amount of the rubber softener added exceeds 600 parts by mass with respect to 100 parts by mass of the hydrogenated thermoplastic styrene-based elastomer (E) (hereinafter referred to as elastomer), molding obtained using the above composition The rubber softener bleeds on the surface of the product, and stickiness is remarkably generated. Further, when the amount of the rubber softener added is less than 100 parts by mass with respect to 100 parts by mass of the elastomer, there is almost no fluidity of the melt at the time of molding using the composition, and molding is impossible. Become.
When the addition amount of the olefin resin is less than 1 part by mass with respect to 100 parts by mass of the elastomer, the linking effect by the olefin resin is insufficient, and the kneaded product is difficult to be gathered during kneading. Since it becomes easy, molding becomes impossible. Moreover, when the addition amount of olefin resin exceeds 100 mass parts, the rubber elasticity of the molded article obtained using the said composition becomes poor (lower), and the adhesiveness with respect to objects, such as a heat-generating member, worsens.
When the blending amount of the thermally conductive filler is less than 40 parts by volume with respect to 100 parts by volume of the total of the elastomer, the rubber softener, and the olefin resin, the thermal conductivity of the composition becomes low. Moreover, when the compounding quantity of the said heat conductive filler exceeds 400 volume part, since the molded article obtained using the said composition becomes hard, rubber elasticity becomes low.
Moreover, when the addition amount of the metal soap is less than 1 part by mass with respect to 100 parts by mass of the elastomer, the metal soap may not be able to exhibit the effect as a dispersant, and when it exceeds 80 parts by mass, There is a risk of appearance defects due to bleed out and molding defects due to gas generation.

  Each of the above materials (a) to (d) or (e) is mixed by, for example, a mixing device such as a Banbury mixer, and the mixture is usually melt-kneaded by an extruder, extruded into a strand, and cooled in cold water. Then, cut into pellets with a cutter. The obtained pellet is usually made into a predetermined molded product by injection molding or extrusion molding. Further, the kneaded composition can be formed into pellets with a ruder or the like and used as a forming raw material.

The thermal conductivity of the composition produced as described above is preferably 1.0 W / m · K or more, more preferably 1.7 W / m · K or more. The volume resistivity after the moisture absorption test is preferably 1.0 × 10 ¹⁰ Ω · cm or more and has no deformation.
The flame retardancy of the composition is preferably UL standard, HB (sample thickness: 1.0 mm) or more, and if it is less than HB, the burning rate is high and the flame retardancy is sufficient. That's not true.

[Heat dissipation sheet]
The heat-dissipating sheet of the present invention is obtained by forming the above composition into a heat-dissipating layer by forming it into a sheet shape by a normal forming method such as extrusion molding or injection molding, and then laminating an adhesive layer on one or both surfaces of the heat-dissipating layer. Obtained by.
If the heat-dissipating sheet is a heat-dissipating member interposed between the heat-generating member and the cooling member, for example, both the heat-generating member and the cooling member are obtained by laminating an adhesive sheet on both surfaces of the heat-dissipating layer. It is desirable to improve the adhesiveness to.
On the other hand, when the heat-dissipating layer of the heat-dissipating sheet is integrated with a cooling member such as a heat sink or a heat pipe via an undercut means or by insert molding, only on one surface of the heat-dissipating layer. It is desirable to improve the adhesion to the exothermic member by laminating the adhesive layer.

(Adhesive layer)
The pressure-sensitive adhesive layer of the present invention is provided in order to closely adhere the heat-dissipating layer of the heat-dissipating sheet to the heat-generating member and the cooling member.
For the formation of the adhesive layer, an adhesive sheet is used. The pressure-sensitive adhesive sheet has adhesiveness on both surfaces thereof, and is laminated by being stuck to the heat dissipation layer. Moreover, it is desirable to protect the other surface and maintain its adhesiveness by attaching a release sheet to the other surface of the pressure-sensitive adhesive sheet that is not attached to the heat dissipation layer. Examples of the release sheet include ordinary sheets in which the surface of a sheet such as paper, film or nonwoven fabric is coated with a release agent such as silicone or paraffin.
As the pressure-sensitive adhesive sheet used for the pressure-sensitive adhesive layer, there are two types, a pressure-sensitive adhesive sheet formed by applying or impregnating a pressure-sensitive adhesive to a base material such as nonwoven fabric and paper, and a pressure-sensitive adhesive sheet consisting of only a pressure-sensitive adhesive. Any pressure-sensitive adhesive sheet may be used for the pressure-sensitive adhesive layer of the present invention.
As the pressure-sensitive adhesive used for the pressure-sensitive adhesive sheet, the composition used for the heat dissipation layer is a hydrogenated thermoplastic styrene-based elastomer containing an olefin-based resin as described above. Is desirable. Moreover, in the case of the adhesive sheet which consists only of adhesives, a thing with high cohesion force is used for an adhesive. Examples of the pressure-sensitive adhesive having good adhesion to the olefin resin include acrylic pressure-sensitive adhesives and acrylic urethane-based pressure-sensitive adhesives, or pressure-sensitive adhesives having high cohesive force are post-crosslinked with polyisocyanate. Examples thereof include polyester polyurethane pressure-sensitive adhesives and (meth) acrylic pressure-sensitive adhesives copolymerized with polar monomers.
From the viewpoint of maintaining the adhesiveness with the exothermic member and the cooling member while suppressing the decrease in thermal conductivity when the thickness of the adhesive layer is laminated on the heat dissipation layer to constitute the heat dissipation sheet, It is desirable that it is 1/100 or more and less than 1/6 of the thickness of the heat dissipation layer. When the thickness of the adhesive layer is less than 1/100 of the thickness of the heat dissipation layer, the heat dissipation layer may not be sufficiently adhered to the heat generating member or the cooling member. In some cases, the thermal conductivity may be excessively reduced.

Examples and comparative examples for describing the present invention more specifically will be described below.
[Examples 1 to 6]
[Material of heat dissipation layer]
The following materials were used.
1. Hydrogenated thermoplastic styrene elastomer (TPS)
G1651H [trade name, manufactured by Kraton Polymer Japan Co., Ltd.], SEBS, styrene monomer content: 33%, Mw: 290,000, 1,2-vinyl bond content: 37% by mass.
2. Softener for rubber PW90 [trade name, manufactured by Idemitsu Petrochemical Co., Ltd.], kinematic viscosity (40 ° C.): 84.0 cSt.
3. Olefin-based resin PX600A [trade name, manufactured by Sun Allomer Co., Ltd.], polypropylene (block type), melting point: 161 ° C. (measured by the applicant in accordance with JIS K7123), flexural modulus: 1600 MPa, MFR (230 ° C.): 5 g / 10 min, deflection temperature under load: 105 ° C.
4). Thermally conductive filler (filler)
(1) RF-50-HR [trade name, manufactured by Ube Materials Co., Ltd.], magnesia clinker (dead burning temperature 1800 ° C. or higher), average particle size 50 μm, surface coating with silane coupling agent, water absorption 0.2 %, New Mohs hardness 7 of the coating layer.
(2) BF083T [trade name, manufactured by Nippon Light Metal Co., Ltd.], aluminum hydroxide, average particle size 10 μm, surface coating with organic titanate compound, water absorption 0.2%, soda component 0.08%.

[Manufacture of heat dissipation layer]
100 parts by mass of a hydrogenated thermoplastic styrene elastomer and 12 parts by mass of an olefin resin are dry blended and impregnated with 350 parts by mass of a rubber softening agent to prepare a mixture.
Thereafter, the mixture is melt-kneaded with an extruder under the following conditions to produce pellets of the composition.
Extruder: KZW32TW-60MG-NH (trade name, manufactured by Technobel Co., Ltd.)
Cylinder temperature ... 180-220 ° C
Screw rotation speed: 300rpm

Pellets of the composition produced as described above are put into a Brabender plastograph, heated and melted, then the filler is added and kneaded under the following conditions to produce a composition (thermally conductive elastomer composition). did. In addition, with respect to 100 parts by volume of the mixture, 120 parts by volume of surface-coated magnesium oxide (RF-50-HR) and 30 parts by volume of surface-coated aluminum hydroxide (BF083T) were added to the filler.
Brabender Plastograph (Brabender Plastograph, trade name, manufactured by Brabender)
Bath temperature ... 160 ° C
Rotor rotation speed: 100rpm
Kneading time ... 11min

The composition produced as described above was molded into a sheet under the following conditions to obtain a heat dissipation layer.
Injection molding machine: 100MSIII-10E (trade name, manufactured by Mitsubishi Heavy Industries, Ltd.)
Injection molding temperature: 170 ° C
Injection pressure: 30%
Injection time ... 10sec
Mold temperature ... 40 ℃

The heat dissipation layer obtained as described above was punched into a size of 1.0 mm or 0.3 mm in thickness, 200 mm in width, and 200 mm in length under the following conditions to prepare a sample.
Press machine ... 40ton electric hydraulic molding machine Heating temperature ... Upper die: 195 ° C, Lower die: 200 ° C
Heating time: 2 minutes Pressing pressure: 5 MPa
Cooling time: 2 minutes

(Adhesive layer)
The following were used.
(1) 7021 [trade name, manufactured by Teraoka Seisakusho], base material-less, acrylic, thickness 0.05 mm.
(2) 7075 [trade name, manufactured by Teraoka Seisakusho], with substrate (polyester), acrylic, thickness 0.05 mm.
(3) 9671LE [trade name, manufactured by Sumitomo 3M], base material-less, acrylic, thickness 0.05 mm.

[Manufacture of heat dissipation sheet]
It laminated | stacked by sticking the said adhesion layer on the single side | surface of the 1.0-mm-thick heat dissipation layer obtained as mentioned above, and obtained the sample of Examples 1-3.
Moreover, it laminated | stacked by sticking the said adhesion layer on the single side | surface of the 0.3-mm-thick heat dissipation layer obtained as mentioned above, and obtained the sample of Examples 4-6.

〔Evaluation method〕
The following evaluation was performed about Examples 1-6. The evaluation results of each physical property are shown in Table 1.
(1) Thermal conductivity: thermal diffusivity measured by laser flash method (xenon flash method) (temperature 19-30 ° C.) (JIS R 1611)
Measure specific heat by DSC (conforms to JIS K 7123)
Measure specific gravity by underwater displacement method (conforms to JIS K 7112)
Based on the measurement results, the thermal conductivity was calculated as follows.
Thermal conductivity = thermal diffusivity x specific heat x specific gravity
Sample: disk having a diameter of 10 mm and a thickness of 1.0 mm (2) Reduction rate: The thermal conductivity (blank) measured only with the heat dissipation layer was compared with the measured thermal conductivity and evaluated as follows.
○: The reduction rate is less than 35% of the blank, Δ: The reduction rate is 35% or more and less than 50% of the blank, and X: The reduction rate is 50% or more of the blank.
[Required performance]
Thermal conductivity: 1.0 W / m · K or more (If the thermal conductivity is low, the heat transfer efficiency is lowered and a sufficient heat dissipation effect cannot be obtained.)

Examples 1 to 6 all have a thermal conductivity of 1.0 W / m · K or more, indicating that they have excellent thermal conductivity.
For Examples 1 to 3 in which the thickness of the adhesive layer is 1/100 or more and less than 1/6 (1/20) of the thickness of the heat dissipation layer, the rate of decrease in thermal conductivity is less than 35%, It can be seen that the decrease in conductivity is suppressed.
About Examples 4-6 whose thickness of the adhesion layer is 1/6 or more (1/6) of the thickness of a thermal radiation layer, the fall rate of thermal conductivity is high compared with Examples 1-3, and heat conduction. It can be seen that the thickness of the adhesive layer is preferably less than 1/6 of the thickness of the heat dissipation layer from the viewpoint of suppressing the decrease in rate.

[Examples 7 to 12]
[Heat dissipation layer]
The same thing as what was used in the said Examples 1-6 was used. The thickness of the heat dissipation layer was 1.0 mm, and the thermal conductivity was 2.47 W / m · K.

(Adhesive layer)
The following were used.
(4) 7053 [trade name, manufactured by Teraoka Seisakusho], with base material, acrylic, thickness 0.02 mm.
(5) 707 [trade name, manufactured by Teraoka Seisakusho], with substrate (polyester), acrylic, thickness 0.03 mm.
(6) 7075 [trade name, manufactured by Teraoka Seisakusho], with substrate (polyester), acrylic, thickness 0.05 mm.
(7) 7021 [trade name, manufactured by Teraoka Seisakusho], base material-less, acrylic, thickness 0.05 mm.

[Manufacture of heat dissipation sheet]
Lamination was performed by adhering only one adhesive layer on one side of a 1.0 mm thick heat dissipation layer to obtain samples of Examples 7-10.
Samples of Examples 11 and 12 were obtained by laminating two adhesive layers on one side of a 1.0 mm thick heat dissipation layer.

〔Evaluation method〕
The following evaluation was performed about Examples 7-12. The evaluation results of each physical property are shown in Table 2.
(1) Thermal conductivity: thermal diffusivity measured by laser flash method (xenon flash method) (temperature 19-30 ° C.) (JIS R 1611)
Measure specific heat by DSC (conforms to JIS K 7123)
Measure specific gravity by underwater displacement method (conforms to JIS K 7112)
Based on the measurement results, the thermal conductivity was calculated as follows.
Thermal conductivity = thermal diffusivity x specific heat x specific gravity
Sample: disk having a diameter of 10 mm and a thickness of 1.0 mm (2) Reduction rate: The thermal conductivity (blank) measured only with the heat dissipation layer was compared with the measured thermal conductivity and evaluated as follows.
○: The reduction rate is less than 35% of the blank, Δ: The reduction rate is 35% or more and less than 50% of the blank, and X: The reduction rate is 50% or more of the blank.
[Required performance]
Thermal conductivity: 1.0 W / m · K or more (If the thermal conductivity is low, the heat transfer efficiency is lowered and a sufficient heat dissipation effect cannot be obtained.)

Examples 7 to 12 all had a thermal conductivity of 1.0 W / m · K or more, and were found to have excellent thermal conductivity. It was also found that the thermal conductivity decreased almost in proportion to the increase in the thickness of the adhesive layer.
The thickness of the adhesive layer is the same (0.05 mm), and Examples 9 and 10 having different base materials have no significant difference in thermal conductivity, and the adhesive layer is thicker than Examples 9 and 10. (0.1 mm) Examples 11 and 12 were found to have the same thermal conductivity.

[Reference Examples 1-3]
Reference Example 1: Two heat radiation layers having a thickness of 1.0 mm obtained in the same manner as in the above example were bonded to each other through an adhesive layer, and the thermal conductivity and the reduction rate were measured.
Reference Example 2: Two heat-dissipating layers having a thickness of 2.0 mm obtained in the same manner as in the above example were bonded to each other through an adhesive layer, and the thermal conductivity and the reduction rate were measured.
Reference Example 3: A heat dissipation layer having a thickness of 2.0 mm and a stainless steel plate having a thickness of 0.7 mm, which were obtained in the same manner as in the above example, were bonded to each other via an adhesive layer, and the thermal conductivity and the decrease were reduced. The rate was measured.
The results of Reference Examples 1 to 3 are shown in Table 2.
In addition to the (1) to (3) used in the above examples, the following were used for the adhesive layer.
(4) 585 [trade name, manufactured by Nitto Denko], with substrate (cellulose), acrylic, thickness 0.05 mm.

It can be seen that all of Reference Examples 1 to 3 have a thermal conductivity of 1.0 W / m · K or more and have excellent thermal conductivity.
About the reference example 1 which adhere | attached two heat dissipation layers with the adhesion layer, it turns out that the fall rate of thermal conductivity is large compared with Examples 1-3.
On the other hand, in Reference Example 2 in which two heat-dissipating layers with increased thickness were bonded with an adhesive layer, the thermal conductivity was improved as compared with only one heat-dissipating layer.
In Reference Example 3 in which one heat-dissipating layer having an increased thickness was bonded to a stainless steel plate with an adhesive layer, the thermal conductivity was remarkably improved.

The heat-dissipating sheet of the present invention has good thermal conductivity and can be suitably adhered to a heat-generating member, a cooling member, etc., so that it can be used industrially because it is useful for heat-dissipating members such as electronic parts. It is.

Claims (2)

A hydrogenated product of a block copolymer (Z) comprising a block unit (S) of a polymer comprising a styrene monomer and a block unit (B) of a polymer comprising a conjugated diene compound, and having a weight average 100 parts by mass of a hydrogenated thermoplastic styrene elastomer (E) having a molecular weight of 150,000 to 500,000 and a styrene monomer content of 20 to 50% by mass;
100 to 600 parts by weight of a rubber softener having a kinematic viscosity of 50 to 500 centistokes (cSt) at 40 ° C;
1 to 100 parts by mass of an olefin resin,
For a total of 100 parts by volume of the hydrogenated thermoplastic styrene elastomer (E), the rubber softener and the olefin resin,
Surface-coated aluminum hydroxide formed by surface-coating aluminum hydroxide with an organic coupling agent,
And / or
Surface-coated magnesium oxide obtained by surface-coating magnesia clinker with an inorganic material and / or an organic material,
40 to 400 parts by volume,
A heat dissipation layer that is a sheet made of a thermally conductive elastomer composition mixed with
An adhesive layer laminated on one or both surfaces of the heat dissipation layer;
A heat dissipating sheet characterized by comprising: The heat dissipation sheet according to claim 1, wherein the thickness of the adhesive layer is 1/100 or more and less than 1/6 of the thickness of the heat dissipation layer.