JP2020047650A - Heat dissipation sheet and method for manufacturing the same, and heat dissipation device - Google Patents

Abstract

To provide a heat dissipation sheet which exhibits a satisfactory adhesive force and has a superior heat dissipation property, a method for manufacturing the same, and a heat dissipation device which is high in adhesion between members and superior in heat dissipation property.SOLUTION: A heat dissipation sheet 1 comprises a resin and a thermally conductive filler. The resin has a glass transition temperature (Tg) of -90°C or higher and 0°C or lower. In the heat dissipation sheet 1, the content of the thermally conductive filler is 50 mass% or more and 96 mass% or less. A value determined by dividing an arithmetic mean roughness Ra(μm) of at least one face of the heat dissipation sheet 1 by a thickness (μm) of the heat dissipation sheet 1 is 4% or less.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a heat dissipation sheet, a method for manufacturing the same, and a heat dissipation device.

  2. Description of the Related Art Conventionally, in an electronic device such as a semiconductor device such as a thermoelectric conversion device, a photoelectric conversion device, and a large-scale integrated circuit, a heat dissipation sheet having thermal conductivity has been used in order to release generated heat. For example, as a method for efficiently radiating heat generated from a semiconductor device to the outside, a heat radiating sheet having excellent thermal conductivity is provided between a semiconductor device and a heat sink.

  As exemplified in Patent Document 1, the heat dissipation sheet as described above is formed by applying a coating solution of a heat dissipation material containing an adhesive resin, an inorganic filler, a curing agent, and a solvent to a release sheet or a base material, and drying. It is manufactured by doing. Here, in order to increase the thermal conductivity of the heat radiation sheet, it is desirable to increase the amount of the heat radiation filler.

JP-A-2015-67713

  However, when the heat radiating sheet is manufactured by the above method, the surface of the heat radiating sheet obtained after the drying of the coating liquid is roughened and uneven. In this case, there is a problem that the contact area between the heat radiating sheet and the adherend decreases, whereby sufficient adhesive strength cannot be obtained, and the heat conductivity is reduced, and the heat radiating property is deteriorated.

  The present invention has been made in view of such a situation, and has a sufficient heat-radiating property, a heat-dissipating sheet having excellent heat-dissipating properties, a method for manufacturing the same, and high adhesion between members, and heat-dissipating properties. It is another object of the present invention to provide an excellent heat dissipation device.

  In order to achieve the above object, first, the present invention is a heat dissipation sheet containing a resin and a thermally conductive filler, wherein the resin has a glass transition temperature (Tg) of not less than -90 ° C and not more than 0 ° C. The content of the heat conductive filler is 50% by mass or more and 96% by mass or less, and the arithmetic average roughness Ra (μm) of at least one surface of the heat dissipation sheet is represented by the thickness (μm) of the heat dissipation sheet. The heat dissipation sheet is characterized in that the value obtained by dividing the heat dissipation sheet is 4% or less (Invention 1).

  Secondly, the present invention is a heat dissipation sheet containing a resin and a heat conductive filler, wherein the resin has a glass transition temperature (Tg) of not less than -90 ° C and not more than 0 ° C, The amount is 50% by mass or more and 96% by mass or less, and the value obtained by dividing the ten-point average roughness Rz (μm) of at least one surface of the heat dissipation sheet by the thickness (μm) of the heat dissipation sheet is 29% or less. The present invention provides a heat dissipation sheet (Invention 2).

  The heat dissipation sheet according to the above inventions (Inventions 1 and 2) has a sufficient surface smoothness even if the content of the thermally conductive filler is large, and the resin has a predetermined glass transition temperature (Tg), so that the heat dissipation sheet has sufficient adhesion. Demonstrate power. Further, since the content of the heat conductive filler is large, the contact area with the adherend is large, and the adhesion is high, so that the heat dissipation is excellent.

  In the above inventions (Inventions 1 and 2), it is preferable that the adhesive force of at least one surface to stainless steel is 100 mN / 25 mm or more (Invention 3).

  The heat dissipation sheet according to the above inventions (Inventions 1 to 3) may be sandwiched between two release sheets (Invention 4).

  Thirdly, the present invention relates to a method for producing the heat radiating sheet (Inventions 1 to 4), wherein an active energy ray-curable composition for forming a heat radiating sheet is applied to a first release sheet; A step of laminating a second release sheet on the coating layer of the heat-dissipating sheet-forming composition, and a step of irradiating the coating layer with active energy rays to cure the heat-dissipating sheet-forming composition. A method of manufacturing a heat dissipation sheet is provided (Invention 5).

  Fourthly, the present invention is characterized by comprising a heat generating member, a heat transfer member, and the heat radiating sheet (Inventions 1 to 3) provided between the heat generating member and the heat transfer member. An apparatus is provided (Invention 6).

  The heat dissipation sheet according to the present invention exhibits a sufficient adhesive force and is excellent in heat dissipation. Further, according to the method for producing a heat radiation sheet according to the present invention, a pressure-sensitive adhesive sheet exhibiting sufficient adhesive strength and having excellent heat radiation properties can be produced. Furthermore, the heat dissipation device according to the present invention has high adhesion between members and excellent heat dissipation.

It is sectional drawing of the heat dissipation sheet (with release sheet) which concerns on one Embodiment of this invention. It is an outline sectional view of the heat dissipation device concerning one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described.
[Heat dissipation sheet]
The heat dissipation sheet according to one embodiment of the present invention contains a resin and a heat conductive filler, the glass transition temperature (Tg) of the resin is −90 ° C. or more and 0 ° C. or less, and the content of the heat conductive filler is 50% by mass or more and 96% by mass or less, a value obtained by dividing the arithmetic average roughness Ra (μm) of at least one surface (preferably both surfaces) of the heat radiation sheet by the thickness (μm) of the heat radiation sheet. Is 4% or less.

  Further, the heat dissipation sheet according to another embodiment of the present invention contains a resin and a heat conductive filler, the glass transition temperature (Tg) of the resin is −90 ° C. or more and 0 ° C. or less, and the heat conductive filler The content is 50% by mass or more and 96% by mass or less, and the ten-point average roughness Rz (μm) of at least one surface (preferably both surfaces) of the heat radiation sheet is determined by the thickness (μm) of the heat radiation sheet. Is less than or equal to 29%.

  The heat radiating sheet having the above-mentioned physical properties and constitution has high surface smoothness even when the content of the heat conductive filler is large, and exhibits sufficient adhesive strength because the resin has a predetermined glass transition temperature (Tg). I do. Further, since the content of the heat conductive filler is large, the contact area with the adherend is large, and the adhesion is high, so that the heat dissipation is excellent.

  In particular, from the viewpoint of adhesive strength, the glass transition temperature (Tg) of the resin needs to be 0 ° C. or lower, is preferably -5 ° C. or lower, and particularly preferably -10 ° C. or lower. In addition, the glass transition temperature (Tg) needs to be −90 ° C. or higher, and is preferably −60 ° C. or higher, and particularly −35 ° C. or higher, from the viewpoint of increasing the cohesive strength. Is preferred. The method for measuring the glass transition temperature (Tg) of the resin is as shown in the test examples described later. In addition, the resin referred to here mainly corresponds to a resin obtained by curing or crosslinking a resin component described later.

  From the viewpoint of heat dissipation, the content of the thermally conductive filler needs to be 50% by mass or more, and is preferably 70% by mass or more, and particularly preferably 85% by mass or more. Further, from the viewpoint of surface smoothness and adhesive strength, the content of the thermally conductive filler needs to be 96% by mass or less, preferably 92% by mass or less, particularly 88% by mass or less. Is preferred.

  From the viewpoint of adhesive strength, the value obtained by dividing the arithmetic average roughness Ra (μm) by the thickness (μm) needs to be 4% or less, preferably 3% or less, and particularly preferably 2% or less. % Is preferable. The lower limit of the value is most preferably 0%, but is usually preferably 0.1% or more, and particularly preferably 0.3% or more.

  Similarly, particularly from the viewpoint of adhesive strength, the value obtained by dividing the ten-point average roughness Rz (μm) by the thickness (μm) needs to be 29% or less, and is preferably 25% or less, and particularly preferably 25% or less. It is preferably at most 20%. The lower limit of the value is most preferably 0%, but is usually preferably 1% or more, and particularly preferably 4% or more.

  From the viewpoint of increasing the reproducibility of the thermal conductivity, the arithmetic average roughness Ra of at least one surface (preferably, both surfaces) of the heat dissipation sheet according to the present embodiment is preferably 3.0 μm or less. In particular, it is preferably 2.0 μm or less, and more preferably 1.1 μm or less. The lower limit of the arithmetic average roughness Ra is most preferably 0 μm, but is usually preferably 0.1 μm or more, and particularly preferably 0.5 μm or more.

  In addition, from the viewpoint of setting a value obtained by dividing the ten-point average roughness Rz (μm) by the thickness (μm) of the heat radiation sheet within the above-described upper limit, at least one surface (preferably, the heat radiation sheet according to the present embodiment). The ten-point average roughness Rz of both surfaces) is preferably 40 μm or less, and more preferably 30 μm or less, particularly 25 μm or less in view of enhancing the reproducibility of thermal conductivity. Is more preferable, and more preferably 15 μm or less. The lower limit of the ten-point average roughness Rz is most preferably 0 μm, but is usually preferably 1 μm or more, and particularly preferably 5 μm or more.

  The arithmetic average roughnesses Ra and Rz are values measured according to JIS B0601-1994.

  The thickness (the value measured according to JIS K7130) of the heat radiation sheet according to the present embodiment is preferably 1 μm or more, more preferably 10 μm or more, and particularly preferably 20 μm or more as a lower limit value. Preferably, the thickness is 110 μm or more. When the lower limit of the thickness of the heat radiating sheet is as described above, good adhesive strength is easily exerted. Further, it is possible to make it difficult for the heat conductive filler having a particle size excellent in heat dissipation property to protrude from the surface of the heat dissipation sheet, and to easily maintain the surface smoothness of the heat dissipation sheet at a high level.

  In addition, the thickness of the heat dissipation sheet according to the present embodiment is preferably 1000 μm or less as an upper limit, more preferably 500 μm or less, particularly preferably 200 μm or less, and further preferably 40 μm or less. Is preferred. When the upper limit of the thickness of the heat radiating sheet is as described above, the heat radiating property can be further improved. Note that the heat dissipation sheet may be formed with a single layer, or may be formed by laminating a plurality of layers.

  The adhesive strength of the heat dissipation sheet according to this embodiment to stainless steel (SUS304, # 360 polished) is preferably 100 mN / 25 mm or more. Thereby, it can adhere | attach well to a heat generating member and a heat transfer member, and can exhibit the outstanding heat dissipation. Such adhesive strength can be achieved by the heat dissipation sheet according to the present embodiment having the above-described physical properties and configuration.

  Further, the adhesive strength is preferably 50 N / 25 mm or less, particularly preferably 20 N / 25 mm or less, and further preferably 1 N / 25 mm or less. Thereby, good reworkability can be obtained, and re-attachment becomes possible even when an attachment error occurs. The adhesive force in the present specification basically refers to the adhesive force measured by a 180-degree peeling method according to JIS Z0237: 2009, and a specific measuring method is as shown in a test example described later.

  The type of the resin contained in the heat radiation sheet according to the present embodiment may be any of an acrylic type, a polyester type, a polyurethane type, a rubber type, a silicone type, and the like, and among them, an acrylic type that easily satisfies the above-mentioned properties is preferable. Further, the resin may be any of an emulsion type, a solvent type and a non-solvent type. Furthermore, the resin may be obtained by curing a curable resin component, may be a cross-linked resin component, or may be a non-cured or non-cross-linked resin. Good. In addition, the curable resin component may be active energy ray-curable or thermosetting.

  The heat radiating sheet according to the present embodiment includes a resin component (A) and a heat conductive filler (B) and a heat radiating sheet forming composition (hereinafter, may be referred to as a “radiating sheet forming composition C”). Is preferably obtained from In particular, the heat dissipation sheet according to the present embodiment is a heat dissipation sheet containing an active energy ray-curable resin component (A1), a heat conductive filler (B), and preferably further a photopolymerization initiator (C). Energy-cured product of the composition for heat dissipation (hereinafter sometimes referred to as "composition C1 for heat-dissipation sheet formation") (the composition C1 for heat-dissipation sheet formation cured with active energy rays) or crosslinkable (Hereinafter sometimes referred to as “heat-dissipating sheet-forming composition C2”) containing a resin component (A2), a heat-conductive filler (B), and preferably a crosslinking agent (D). ) (A composition obtained by crosslinking the heat-dissipating sheet-forming composition C2 by heat or the like).

1. Each component (1) Resin component (A1)
The active energy ray-curable resin component (A1) contained in the heat-radiating sheet-forming composition C1 preferably contains a polar monomer, and particularly preferably contains the polar monomer in an amount of 20% by mass or more. Thereby, even if a solvent is not used, the viscosity is low, the dispersibility of the heat conductive filler (B) is good, and the coating property is excellent. Therefore, even if a large amount of the thermally conductive filler (B) is blended, the above-mentioned parameters are easily satisfied, and a heat radiation sheet exhibiting a sufficient adhesive force can be obtained.

  Here, when the heat conductive filler (B) is a filler made of a metal oxide or a metal hydroxide, the heat conductive filler (B) is combined with the heat conductive filler (B) and a polar monomer. ), The coating properties are excellent without a solvent, the above-mentioned parameters are easily satisfied, and the heat radiation effect is particularly excellent. Moreover, even when the heat radiation sheet is made thin (for example, 100 μm or less, particularly 40 μm or less), sufficient adhesive strength is exhibited.

  Further, the composition C1 for forming a heat radiation sheet which does not use a solvent is preferable from the viewpoint of environmental problems and work environment measures. However, the present invention does not exclude the use of the composition C1 for forming a heat radiation sheet with a solvent added thereto.

  The polar monomer is preferably a monomer containing at least one selected from a hydroxyl group, a carboxyl group, an amino group and an amide group as a polar group, and in particular, a (meth) acryloyl containing a (meth) acryloyl group together with the polar group It is preferably a group-containing monomer. In addition, in this specification, (meth) acryloyl means both acryloyl and methacryloyl. The same applies to other similar terms.

  Examples of such polar monomers include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and (meth) acrylate. ) Hydroxyalkyl (meth) acrylates such as 3-hydroxybutyl acrylate and 4-hydroxybutyl (meth) acrylate; ethylenically unsaturated esters such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, itaconic acid and citraconic acid; Saturated carboxylic acid; monoalkyl (meth) acrylate such as monomethylaminoethyl (meth) acrylate, monoethylaminoethyl (meth) acrylate, monomethylaminopropyl (meth) acrylate, monoethylaminopropyl (meth) acrylate Aminoalkyl; N-methylo Acrylamide such as methacrylamide. These polar monomers may be used alone or in combination of two or more.

  Among the above, a monomer having a hydroxyl group (hydroxyl group-containing monomer) is preferable. According to the hydroxyl group-containing monomer, the dispersibility of the thermally conductive filler (B) is good in combination with the thermally conductive filler (B), particularly, the thermally conductive filler (B) made of metal oxide or metal hydroxide. In addition, the viscosity of the obtained heat radiation sheet forming composition C1 can be effectively reduced.

  The hydroxyl group-containing monomer is preferably a (meth) acryloyl group-containing monomer having a hydroxyl group, from the viewpoint of further reducing the arithmetic average roughness Ra and the ten-point average roughness Rz of the obtained heat dissipation sheet. ) Hydroxyalkyl acrylates are more preferred. Specifically, 2-hydroxyethyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate is preferable, and 2-hydroxyethyl acrylate or 4-hydroxybutyl acrylate is particularly preferable.

  The viscosity of the hydroxyl group-containing (meth) acryloyl group-containing monomer (particularly, 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate) is generally 500 mPa · s or less, which is considerably low. Indicates a value.

  The proportion of the polar monomer in the resin component (A1) is preferably 20% by mass or more, and more preferably 40% by mass, from the viewpoint of further reducing the arithmetic average roughness Ra and the ten-point average roughness Rz of the obtained heat dissipation sheet. More preferably, it is more preferably 60% by mass or more, and further preferably 80% by mass or more. The upper limit of the proportion of the polar monomer in the resin component (A1) is 100% by mass.

  The resin component (A1) may contain at least one of monomers (other monomers) and oligomers other than the above polar monomers in order to develop other properties such as adhesiveness and flexibility of the obtained heat dissipation member. Good.

  The other monomer is preferably the above-mentioned (meth) acryloyl group-containing monomer having no polar group (hereinafter sometimes referred to as “(meth) acryloyl group-containing monomer M”). As the (meth) acryloyl group-containing monomer M, one type may be used alone, or two or more types may be used in combination.

  As the (meth) acryloyl group-containing monomer M, for example, a (meth) acrylic acid alkyl ester having an alkyl group having 1 to 20 carbon atoms is preferably exemplified. The alkyl group may be linear or branched. Examples of the alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and pentyl (meth). Acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) Acrylate, lauryl (meth) acrylate and the like can be mentioned. Among these, from the viewpoint of imparting flexibility to the heat-dissipating sheet to be formed, alkyl (meth) acrylates having 1 to 10 carbon atoms in the alkyl group are preferable, and in particular, high adhesion to various adherends From the viewpoint of expression, an alkyl acrylate having 4 to 8 carbon atoms in the alkyl group is preferable. Specifically, for example, butyl acrylate, isooctyl acrylate, or 2-ethylhexyl acrylate is preferably exemplified.

  Further, as the (meth) acryloyl group-containing monomer M, a (meth) acrylate having an alicyclic structure in the molecule ((meth) acrylate containing an alicyclic structure) is also preferably exemplified. The alicyclic structure-containing (meth) acrylate has a bulky alicyclic structure, provides an appropriate distance between the formed polymers, and can impart flexibility to the obtained heat dissipation member.

  Examples of the alicyclic structure-containing (meth) acrylate include cyclohexyl (meth) acrylate, dicyclopentanyl (meth) acrylate, adamantyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentenyl (meth) acrylate, and dicyclopentyl (meth) acrylate. And cyclopentenyloxyethyl (meth) acrylate. Among these, dicyclopentanyl acrylate, adamantyl acrylate, or isobornyl acrylate is preferred from the viewpoint of imparting flexibility.

  When the (meth) acryloyl group-containing monomer M is used in combination with the alkyl (meth) acrylate having 1 to 20 carbon atoms and the (meth) acrylate having an alicyclic structure, their mass ratio is 90. : 1 to 50:50, preferably 90:10 to 60:40, and more preferably 80:20 to 70:30.

  The oligomer may have the above-described polar group or may not have the above-described polar group.

  Examples of the oligomer include polyester-based, epoxy-based, urethane-based, polyether-based, polybutadiene-based, and silicone-based oligomers having a radical polymerizable group. Among these, a urethane oligomer having a radical polymerizable group (polymerizable urethane oligomer) is preferable from the viewpoint of imparting flexibility and improving cohesive strength.

  In order to obtain the above viscosity, the upper limit of the polymerization average molecular weight of the polymerizable urethane oligomer is preferably 100,000 or less, particularly preferably 50,000 or less, and more preferably 20,000 or less. Preferably, there is. On the other hand, the lower limit of the polymerization average molecular weight of the polymerizable urethane oligomer is preferably 1,000 or more, more preferably 3,000 or more, particularly preferably 5,000 or more, and further preferably 8 or more. It is preferably at least 2,000. The weight average molecular weight in the present specification is a value in terms of standard polystyrene measured by a gel permeation chromatography (GPC) method.

  The polymerizable urethane oligomer is preferably polyfunctional, and the polymerizable group of the polymerizable urethane oligomer is preferably present at terminals, particularly at both terminals. As the type of the polymerizable group, for example, a (meth) acryloyl group, a vinyl group and the like are preferable, and a (meth) acryloyl group is particularly preferable. That is, the polymerizable urethane oligomer is preferably a urethane acrylate oligomer.

  Urethane acrylate oligomers are, for example, polyurethane oligomers obtained by reacting a compound such as polyalkylene polyol, polyether polyol, polyester polyol, hydrogenated isoprene having a hydroxyl group end, hydrogenated butadiene having a hydroxyl group end with polyisocyanate Can be obtained by esterification with (meth) acrylic acid or a (meth) acrylic acid derivative.

  Among urethane acrylate oligomers, polyether urethane acrylate is particularly preferable from the viewpoint of dispersibility of the thermally conductive filler (B).

  One of the above oligomers may be used alone, or two or more may be used in combination. It is also preferable that the oligomer is used in combination with the (meth) acryloyl group-containing monomer M described above.

  When the resin component (A1) contains a polar monomer and a (meth) acryloyl group-containing monomer M, the ratio of the polar monomer in the resin component (A1) is preferably 20% by mass or more, and particularly preferably 40% by mass or more. It is preferable that the amount is at least mass%. On the other hand, the proportion is preferably 80% by mass or less, particularly preferably 60% by mass or less. Further, the content of the (meth) acryloyl group-containing monomer M in the resin component (A1) is preferably 20% by mass or more, and particularly preferably 40% by mass or more. On the other hand, the proportion is preferably 80% by mass or less, particularly preferably 60% by mass or less. When each component has the above ratio, the viscosity and the flexibility can be effectively improved while the viscosity is kept low.

  When the resin component (A1) contains a polar monomer, a (meth) acryloyl group-containing monomer M, and an oligomer, the ratio of the polar monomer in the resin component (A1) is preferably 20% by mass or more. In particular, it is preferably at least 30% by mass, more preferably at least 35% by mass. On the other hand, the proportion is preferably 80% by mass or less, particularly preferably 60% by mass or less, and further preferably 50% by mass or less. Further, the proportion of the (meth) acryloyl group-containing monomer M in the resin component (A1) is preferably 10% by mass or more, particularly preferably 20% by mass or more, and further preferably 40% by mass or more. Is preferred. On the other hand, the proportion is preferably 70% by mass or less, particularly preferably 60% by mass or less, and further preferably 50% by mass or less. Further, the proportion of the oligomer in the resin component (A1) is preferably 1% by mass or more, particularly preferably 5% by mass or more, and further preferably 10% by mass or more. On the other hand, the proportion is preferably 50% by mass or less, particularly preferably 40% by mass or less, and further preferably 20% by mass or less. When each component has the above ratio, the viscosity and the flexibility can be effectively improved while the viscosity is kept low.

  The content of the resin component (A1) in the heat radiation sheet forming composition C1 is preferably 4% by mass or more, particularly preferably 8% by mass or more, and further preferably 12% by mass or more. preferable. This makes it possible to maintain the viscosity of the heat-dissipating sheet forming composition C at a low level, improve the coating properties, and further improve the surface smoothness of the obtained heat-dissipating sheet. On the other hand, the content of the resin component (A1) is preferably 50% by mass or less, more preferably 40% by mass or less, particularly preferably 30% by mass or less, and further preferably 15% by mass or less. It is preferred that Thereby, the content of the heat conductive filler (B) can be secured, and the heat radiation sheet obtained can have excellent heat radiation properties.

(2) Photopolymerization initiator (C)
When the resin component (A1) is an active energy ray-curable resin and the ultraviolet ray is used as the active energy ray for the curing, the heat radiation sheet forming composition C1 further comprises a photopolymerization initiator (C). It is preferred to contain. By containing the photopolymerization initiator (C) in this manner, the resin component (A1) can be efficiently polymerized, and the polymerization curing time and the irradiation amount of the active energy ray can be reduced.

  Examples of such a photopolymerization initiator (C) include benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin-n-butyl ether, benzoin isobutyl ether, acetophenone, dimethylaminoacetophenone, and 2,2-dimethoxy. -2-phenylacetophenone, 2,2-diethoxy-2-phenylacetophenone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-hydroxycyclohexylphenylketone, 2-methyl-1- [4- (Methylthio) phenyl] -2-morpholino-propan-1-one, 4- (2-hydroxyethoxy) phenyl-2- (hydroxy-2-propyl) ketone, benzophenone, p-phenylbenzophenone, 4,4 -Diethylaminobenzophenone, dichlorobenzophenone, 2-methylanthraquinone, 2-ethylanthraquinone, 2-tert-butylanthraquinone, 2-aminoanthraquinone, 2-methylthioxanthone, 2-ethylthioxanthone, 2-chlorothioxanthone, 2,4-dimethylthioxanthone , 2,4-diethylthioxanthone, benzyldimethyl ketal, acetophenone dimethyl ketal, p-dimethylaminobenzoic acid ester, oligo [2-hydroxy-2-methyl-1 [4- (1-methylvinyl) phenyl] propanone], 2 , 4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis (2,4,6-trimethylbenzoyl) -phenylphosphine oxide and the like. These may be used alone or in combination of two or more.

  The content of the photopolymerization initiator (C) in the heat radiation sheet forming composition C1 is preferably at least 0.1 part by mass, particularly preferably 0.5 part by mass, based on 100 parts by mass of the resin component (A1). Parts or more. Further, the content of the photopolymerization initiator (C) is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less.

(3) Resin component (A2)
The crosslinkable resin component (A2) contained in the heat radiation sheet forming composition C2 preferably contains a (meth) acrylate polymer. In the present specification, the term “polymer” includes the concept of “copolymer”.

  The (meth) acrylate polymer in the present embodiment contains, as a monomer unit constituting the polymer, a reactive group-containing monomer having a reactive group that reacts with a crosslinking agent (D) described later in the molecule. Is preferred. The reactive group derived from the reactive group-containing monomer reacts with the crosslinking agent (D) to form a crosslinked structure (three-dimensional network structure), and a heat dissipation sheet having a desired cohesive force is obtained.

  As the reactive group-containing monomer, those listed as the polar monomer described above can be used. Among them, a monomer having a carboxy group in the molecule (carboxy group-containing monomer) is preferable, and acrylic acid is particularly preferable, from the viewpoints of adhesive strength and reactivity with the crosslinking agent (D).

  The (meth) acrylate polymer preferably contains, as a monomer unit constituting the polymer, a reactive group-containing monomer at a lower limit of 1% by mass or more, particularly preferably 5% by mass or more. And more preferably 15% by mass or more. Further, the (meth) acrylic acid ester polymer preferably contains, as a monomer unit constituting the polymer, a reactive group-containing monomer as an upper limit of 40% by mass or less, particularly preferably 30% by mass or less. And more preferably 20% by mass or less. When the (meth) acrylate polymer contains the reactive group-containing monomer in the above amount as a monomer unit, a favorable crosslinked structure is formed in the obtained heat dissipation sheet, and a desired cohesive force is obtained.

  The (meth) acrylic acid ester polymer preferably contains a (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer. Thereby, good adhesiveness can be exhibited. The alkyl group may be linear, branched or cyclic.

  As the alkyl (meth) acrylate, an alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group is preferable from the viewpoint of adhesiveness. Examples of the alkyl (meth) acrylate having 1 to 20 carbon atoms in the alkyl group include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, and n- (meth) acrylate. Butyl, n-pentyl (meth) acrylate, n-hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, isooctyl (meth) acrylate, n-decyl (meth) acrylate, (meth) acrylic acid n-dodecyl, myristyl (meth) acrylate, palmityl (meth) acrylate, stearyl (meth) acrylate and the like. Among them, from the viewpoint of further improving the adhesiveness, (meth) acrylic acid esters having 1 to 8 carbon atoms in the alkyl group are preferable, and methyl (meth) acrylate, n-butyl (meth) acrylate or (meth) acrylic acid is preferable. 2-ethylhexyl acid is particularly preferred, and methyl acrylate or n-butyl acrylate is more preferred. These may be used alone or in combination of two or more.

  The (meth) acrylate polymer preferably contains at least 50% by mass, more preferably at least 60% by mass of alkyl (meth) acrylate as a monomer unit constituting the polymer. It is preferably contained in an amount of 70% by mass or more. When the lower limit of the content of the alkyl (meth) acrylate is as described above, the (meth) acrylate polymer can exhibit suitable adhesiveness. Further, the (meth) acrylic acid ester polymer preferably contains 99% by mass or less, particularly preferably 94% by mass or less, of a (meth) acrylic acid alkyl ester as a monomer unit constituting the polymer. And more preferably 85% by mass or less. When the upper limit of the content of the alkyl (meth) acrylate is the above, other monomer components such as a reactive functional group-containing monomer can be introduced into the (meth) acrylate polymer in a suitable amount. .

  The (meth) acrylate polymer may optionally contain another monomer as a monomer unit constituting the polymer.

  The (meth) acrylate polymer is preferably a linear polymer. When the polymer is a straight-chain polymer, entanglement of molecular chains is likely to occur, improvement in cohesion can be expected, and a heat-dissipating sheet excellent in durability can be easily obtained.

  Further, the (meth) acrylate polymer is preferably a solution polymer obtained by a solution polymerization method. By being a solution polymer, a high molecular weight polymer can be easily obtained, an improvement in cohesion can be expected, and a heat radiation sheet having excellent durability can be easily obtained.

  The polymerization mode of the (meth) acrylic acid ester polymer may be a random copolymer or a block copolymer.

  The weight average molecular weight of the (meth) acrylate polymer is preferably 200,000 or more, more preferably 400,000 or more, and even more preferably 500,000 or more, as the lower limit. When the lower limit of the weight average molecular weight of the (meth) acrylic acid ester polymer is equal to or more than the above, the durability of the obtained heat radiation sheet becomes excellent.

  Further, the weight average molecular weight of the (meth) acrylic acid ester polymer is preferably 2,000,000 or less, more preferably 1.5,000,000 or less, and further preferably 900,000 or less, as the upper limit. When the upper limit of the weight average molecular weight of the (meth) acrylate polymer is not more than the above, the adhesion of the obtained heat dissipation sheet to the adherend will be excellent.

  In the heat radiation sheet forming composition C2, the (meth) acrylate polymer may be used alone or in combination of two or more.

(4) Crosslinking agent (D)
The cross-linking agent (D) cross-links the (meth) acrylate polymer by heating the heat-radiating sheet-forming composition C2, whereby a three-dimensional network structure can be favorably formed. Thereby, the cohesive force of the obtained heat dissipation sheet is improved, and the durability is excellent.

  The crosslinking agent (D) may be any as long as it reacts with the reactive group of the (meth) acrylic acid ester polymer, and is, for example, an isocyanate-based crosslinking agent, an epoxy-based crosslinking agent, an amine-based crosslinking agent, or a melamine-based crosslinking agent. Crosslinking agents, aziridine crosslinking agents, hydrazine crosslinking agents, aldehyde crosslinking agents, oxazoline crosslinking agents, metal alkoxide crosslinking agents, metal chelate crosslinking agents, metal salt crosslinking agents, ammonium salt crosslinking agents, and the like. . Among the above, it is preferable to use an isocyanate-based crosslinking agent having excellent reactivity with the reactive group of the (meth) acrylate polymer. The crosslinking agent (D) may be used alone or in combination of two or more.

  The isocyanate-based crosslinking agent contains at least a polyisocyanate compound. As the polyisocyanate compound, for example, aromatic polyisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, aliphatic polyisocyanates such as hexamethylene diisocyanate, isophorone diisocyanate, alicyclic polyisocyanates such as hydrogenated diphenylmethane diisocyanate, etc. And their biuret forms, isocyanurate forms, and adducts which are reaction products with low-molecular-weight active hydrogen-containing compounds such as ethylene glycol, propylene glycol, neopentyl glycol, trimethylolpropane, and castor oil. Above all, from the viewpoint of reactivity with hydroxyl groups, trimethylolpropane-modified aromatic polyisocyanates, particularly trimethylolpropane-modified tolylene diisocyanate and trimethylolpropane-modified xylylene diisocyanate are preferred.

  The content of the crosslinking agent (D) in the heat radiation sheet forming composition C2 is preferably at least 0.01 part by mass, more preferably at least 0.05 part by mass, based on 100 parts by mass of the (meth) acrylate polymer. It is preferably at least 0.1 part by mass, more preferably at least 0.1 part by mass. Further, the content is preferably 10 parts by mass or less, particularly preferably 5 parts by mass or less, and further preferably 1 part by mass or less. When the content of the cross-linking agent (D) is in the above range, the obtained heat-radiating sheet exhibits good cohesive force and has excellent durability.

(5) Thermal conductive filler (B)
The heat radiation sheet forming composition C contains a heat conductive filler (B). In the present specification, the thermally conductive filler refers to a filler having a high thermal conductivity, for example, a filler having a thermal conductivity at 25 ° C. of 10 W / m · K or more, preferably 20 W / m · K or more. A filler, particularly preferably a filler of 30 W / m · K or more. The upper limit of the thermal conductivity at 25 ° C. of the thermally conductive filler is not limited, but is usually 300 W / m · K or less.

  Examples of the material of the thermally conductive filler (B) include metal oxides such as aluminum oxide, magnesium oxide, zinc oxide, titanium oxide, and iron oxide; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; boron nitride; and aluminum nitride. And the like, silicon carbide, carbide such as calcium carbide, talc and the like.

  Among these, metal oxides, metal hydroxides or nitrides are preferred from the viewpoint of heat dissipation and dispersibility in the resin component (A) (particularly, the resin component (A1) containing 20% by mass or more of a polar monomer), and in particular, , Metal oxides or metal hydroxides are preferred. Among them, aluminum oxide (alumina) which is excellent in heat dissipation and dispersibility is particularly preferable. In addition, since aluminum oxide does not have conductivity, it is preferable from the viewpoint of use where insulation is required. In addition, the said heat conductive filler (B) may be used individually by 1 type, and may be used in combination of 2 or more type.

  The shape of the heat conductive filler (B) includes, for example, a granular shape, a needle shape, a plate shape, a flake shape, an irregular shape, and the like, and the granular shape includes a round shape, a true spherical shape, a polygonal shape, and the like. In this specification, the term “rounded” means a shape that is rounded as a whole, and includes a shape such as a spherical shape, an elliptical spherical shape, and an oval shape, but does not necessarily mean a shape having only a curved surface. Instead, it also includes a shape having a flat surface.

  When the thermally conductive filler (B) is made of a metal oxide or a metal hydroxide, particularly alumina, it is preferable to use at least a round or spherical particulate filler among the above. It is also preferable to use them in combination. When combining a granular filler and an amorphous filler, it is preferable to use a combination of a round or spherical filler and an amorphous filler, and it is particularly preferable to use a combination of a round filler and an amorphous filler. . In these cases, the filling rate of the thermally conductive filler (B) in the obtained heat dissipation sheet is improved, and an efficient heat conduction path is formed in the heat dissipation sheet, and as a result, the heat dissipation sheet has better heat dissipation properties. Becomes

  On the other hand, when the thermally conductive filler (B) is made of a nitride, particularly boron nitride, it is preferable to use a scaly filler among the above.

  The average particle size of the thermally conductive filler (B) is preferably smaller than the thickness of the target heat dissipation sheet. This makes it difficult for the heat conductive filler (B) to protrude from the surface of the heat radiating sheet, and makes the surface of the heat radiating sheet smoother.

  When the heat conductive filler (B) is granular, the average particle size is preferably 8 μm or more, more preferably 15 μm or more, particularly preferably 25 μm or more, and further preferably 30 μm or more. Preferably, there is. Further, the average particle size is preferably 100 μm or less, particularly preferably 70 μm or less, and further preferably 40 μm or less. When the average particle size of the granular filler is in the above range, the filling rate of the thermally conductive filler (B) in the obtained heat dissipation sheet can be increased, and the heat dissipation properties can be further improved. Surface smoothness can be further improved.

  When the shape of the thermally conductive filler (B) is irregular, the average particle size is preferably 0.1 μm or more, particularly preferably 0.5 μm or more, and further preferably 1.0 μm or more. Preferably, there is. Further, the average particle diameter is preferably 7 μm or less, particularly preferably 4 μm or less, and further preferably 2 μm or less. When the average particle size of the amorphous filler is in the above range, the filling rate of the thermally conductive filler (B) in the obtained heat dissipation sheet can be increased, and the heat dissipation properties can be further improved. Can further improve the surface smoothness and thus the adhesive strength.

  When the shape of the thermally conductive filler (B) is scale-like, the average particle size is preferably 1 μm or more, particularly preferably 5 μm or more, and further preferably 8 μm or more. Further, the average particle diameter is preferably 50 μm or less, particularly preferably 30 μm or less, and further preferably 15 μm or less. When the average particle diameter of the flaky filler is in the above range, the filling rate of the thermally conductive filler (B) in the obtained heat dissipation sheet can be increased, and the heat dissipation properties can be further improved. Can further improve the surface smoothness and thus the adhesive strength.

  In addition, the average particle diameter of the filler in this specification refers to a particle diameter calculated by measuring the long axis diameter of 20 randomly selected fillers with an electron microscope and calculating the arithmetic average value thereof.

  The content of the thermally conductive filler (B) in the composition C for forming a heat radiation sheet is the same as the content in the heat radiation sheet, and is as described above.

(6) Various additives Various additives such as a tackifier, a flame retardant, an antioxidant, a light stabilizer, a softener, and a rust inhibitor may be added to the composition C for forming a heat radiation sheet, if desired. Can be.

2. Preparation of Composition for Forming Heat Dissipating Sheet (1) Preparation of Composition C1 for Forming Heat Dissipating Sheet The composition C1 for forming heat radiating sheet is obtained by mixing each component as the resin component (A1) with the thermally conductive filler (B). And, if desired, a photopolymerization initiator (C) and an additive.

  Here, the heat radiation sheet forming composition C1 contains a large amount of the heat conductive filler (B) by a combination of the resin component (A1) containing the polar monomer at 20% by mass or more and the heat conductive filler (B). Even so, the viscosity is low and the coatability is excellent. Therefore, the heat radiation sheet forming composition C1 can be used as it is as a coating liquid without adding a solvent or the like. That is, the composition C1 for forming a heat radiation sheet preferably does not contain a solvent. This eliminates the need for a drying step for volatilizing the solvent after application, prevents surface roughness due to drying, and provides a heat dissipation sheet having high smoothness and high adhesive strength.

(2) Preparation of Composition C2 for Forming Heat Dissipating Sheet The composition C2 for forming a heat radiating sheet produced a (meth) acrylate polymer, and the obtained (meth) acrylate polymer and a crosslinking agent (D ) And, if desired, an additive.

  The (meth) acrylate polymer can be produced by polymerizing a mixture of monomers constituting the polymer by an ordinary radical polymerization method. The polymerization of the (meth) acrylate polymer is preferably carried out by a solution polymerization method using a polymerization initiator, if desired. Examples of the polymerization solvent include ethyl acetate, n-butyl acetate, isobutyl acetate, toluene, acetone, hexane, methyl ethyl ketone, and the like, and two or more kinds may be used in combination.

  Examples of the polymerization initiator include azo compounds and organic peroxides, and two or more of them may be used in combination. Examples of the azo compound include 2,2′-azobisisobutyronitrile, 2,2′-azobis (2-methylbutyronitrile), 1,1′-azobis (cyclohexane 1-carbonitrile), , 2'-Azobis (2,4-dimethylvaleronitrile), 2,2'-azobis (2,4-dimethyl-4-methoxyvaleronitrile), dimethyl 2,2'-azobis (2-methylpropionate) 4,4'-azobis (4-cyanovaleric acid), 2,2'-azobis (2-hydroxymethylpropionitrile), 2,2'-azobis [2- (2-imidazolin-2-yl) Propane] and the like.

  Examples of the organic peroxide include benzoyl peroxide, t-butyl perbenzoate, cumene hydroperoxide, diisopropyl peroxy dicarbonate, di-n-propyl peroxy dicarbonate, and di (2-ethoxyethyl) peroxy. Examples include dicarbonate, t-butyl peroxy neodecanoate, t-butyl peroxy bivalate, (3,5,5-trimethylhexanoyl) peroxide, dipropionyl peroxide, diacetyl peroxide and the like.

  In the above polymerization step, the weight average molecular weight of the obtained polymer can be adjusted by adding a chain transfer agent such as 2-mercaptoethanol.

  Once the (meth) acrylate polymer has been obtained, the crosslinking agent (D), and optionally the diluting solvent and additives, are added to the solution of the (meth) acrylate polymer, and thoroughly mixed, The composition C2 for heat radiation sheet formation diluted with the solvent is obtained. In addition, in any of the above components, when using a solid, or when precipitation occurs when mixed with another component in an undiluted state, the component alone is previously added to a diluting solvent. After dissolving or diluting, it may be mixed with other components.

  As the diluting solvent, for example, hexane, heptane, aliphatic hydrocarbons such as cyclohexane, toluene, aromatic hydrocarbons such as xylene, methylene chloride, halogenated hydrocarbons such as ethylene chloride, methanol, ethanol, propanol, butanol, Alcohols such as 1-methoxy-2-propanol, ketones such as acetone, methyl ethyl ketone, 2-pentanone, isophorone and cyclohexanone, esters such as ethyl acetate and butyl acetate, and cellosolve solvents such as ethyl cellosolve are used.

  The viscosity of the heat-dissipating sheet-forming composition C2 thus prepared is not particularly limited as long as it can be coated, and can be appropriately selected depending on the situation. The addition of a diluting solvent or the like is not a necessary condition, and the diluting solvent may not be added as long as the composition C2 for forming a heat radiation sheet can be coated. In this case, the heat radiation sheet forming composition C2 is a coating solution using the polymerization solvent of the (meth) acrylate polymer as a diluting solvent.

3. Configuration Example of Heat Dissipating Sheet It is also preferable that the heat dissipating sheet according to the present embodiment has, for example, a configuration sandwiched between two release sheets. Hereinafter, description will be made with reference to the drawings.

  As shown in FIG. 1, a first release sheet 11 a is laminated on one surface (the upper surface in FIG. 1) of the heat radiation sheet 1 according to the present embodiment as an example, and the other of the heat radiation sheet 1. (The lower surface in FIG. 1) is laminated with a second release sheet 11b. Each of the release sheets 11a and 11b is laminated on the heat radiating sheet 1 such that their release surfaces are in contact with the heat radiating sheet 1. In addition, the release surface of the release sheet in this specification refers to a surface having releasability in the release sheet, and includes both the surface subjected to the release treatment and the surface exhibiting the releasability even without performing the release treatment. .

(1) Heat-dissipating sheet The heat-dissipating sheet 1 in the present embodiment is the above-described heat-dissipating sheet, and is preferably obtained from the heat-dissipating sheet-forming composition C, and particularly preferably the heat-dissipating sheet-forming composition C1. It is obtained by curing with an active energy ray or by crosslinking the composition C2 for forming a heat radiation sheet.

  Although the thickness of the heat radiation sheet is as described above, especially in the case of the heat radiation sheet 1 obtained from the heat radiation sheet forming composition C2, the lower limit of the thickness is preferably 110 μm or more, and more preferably 140 μm or more. Is more preferable. As a result, the value obtained by dividing the arithmetic average roughness Ra (μm) by the thickness (μm) and the value obtained by dividing the ten-point average roughness Rz (μm) by the thickness (μm) easily fall within the above-described ranges. Sufficient adhesive strength is obtained. The upper limit of the thickness is as described above.

  The thermal conductivity of the heat radiation sheet 1 at 23 ° C. and 50% RH (measured in accordance with ISO 22007-3) is preferably 1.5 W / m · K or more, particularly 1.8 W / m · K. It is preferably at least 2.0 W / m · K or more. Thereby, it can be said that the heat dissipation sheet 1 is excellent in heat dissipation. The heat radiating sheet 1 obtained from the composition C for forming a heat radiating sheet described above can satisfy the above thermal conductivity. The upper limit of the thermal conductivity of the heat dissipation sheet 1 at 23 ° C. and 50% RH is not particularly limited, but is usually preferably 14 W / m · K or less, particularly preferably 7 W / m · K or less. preferable.

  Further, the difference (width) between the maximum value and the minimum value obtained by measuring the thermal conductivity of any 10 samples of the heat radiation sheet 1 is preferably 1.5 W / m · K or less. It is more preferably 6 W / m · K or less, particularly preferably 0.4 W / m · K or less, and further preferably 0.2 W / m · K or less. Thereby, it can be said that the reproducibility of the thermal conductivity is good.

  The heat dissipation sheet 1 obtained from the heat dissipation sheet forming composition C1 preferably has a residual ratio (residual ratio after solvent immersion) of not less than 80% by mass after immersion in ethyl acetate at 23 ° C. for 24 hours, and is preferably 90% by mass. %, More preferably 94% by mass or more, and even more preferably 96% by mass or more. Accordingly, the heat radiation sheet 1 has a very high cohesive force, and it is possible to effectively prevent a phenomenon in which the filler (B) changes its position due to heat to cause a change in heat radiation. That is, the reproducibility of the thermal conductivity becomes more excellent even under repeated heating. The upper limit of the residual ratio after immersion in the solvent is not particularly limited, but is preferably 100% by mass or less, and particularly preferably 99% by mass or less. Here, the details of the method of measuring the residual ratio of the heat radiation sheet after immersion in the solvent in this specification are as shown in Test Examples described later.

(2) Release Sheets As the release sheets 11a and 11b, for example, polyethylene film, polypropylene film, polybutene film, polybutadiene film, polymethylpentene film, polyvinyl chloride film, vinyl chloride copolymer film, polyethylene terephthalate film, polyethylene na Phthalate film, polybutylene terephthalate film, polyurethane film, ethylene vinyl acetate film, ionomer resin film, ethylene / (meth) acrylic acid copolymer film, ethylene / (meth) acrylic acid ester copolymer film, polystyrene film, polycarbonate film , A polyimide film, a fluororesin film, or the like. These crosslinked films are also used. Further, these laminated films may be used.

  The release surfaces of the release sheets 11a and 11b (particularly, the surfaces in contact with the heat radiation sheet 1) are preferably subjected to a release treatment. Examples of the release agent used in the release treatment include alkyd-based, silicone-based, fluorine-based, unsaturated polyester-based, polyolefin-based, and wax-based release agents.

  The thickness of the release sheets 11a and 11b is not particularly limited, but is usually about 20 to 150 μm.

4. Production of Heat Dissipation Sheet As an example of a method for producing a heat radiation sheet, a method for producing the heat radiation sheet 1 shown in FIG. 1 will be described.

(1) When using the composition C1 for forming a heat radiating sheet When using the composition C1 for forming a heat radiating sheet, as an example of manufacturing the heat radiating sheet 1, the release surface of one release sheet 11a (or 11b) A coating layer is formed by applying the heat radiation sheet forming composition C1. Next, the release surface of the other release sheet 11b (or 11a) is overlapped with the coating layer and pressed. After that, the application layer is irradiated with a predetermined amount of active energy rays to cure the heat radiation sheet forming composition C1, thereby forming the heat radiation sheet 1.

  Irradiation of the active energy ray to the coating layer may be performed through one of the release sheets 11a (or 11b), or may be performed through both of the release sheets 11a and 11b. In order to cure the heat radiation sheet forming composition C1 efficiently and reliably, it is preferable to irradiate the active energy ray through both the release sheets 11a and 11b.

  A desired position between the first release sheet 11a and the second release sheet 11b (for example, when the release sheets 11a and 11b are long, both edges along the longitudinal direction; release sheets 11a and 11b In the case where is a rectangle, a spacer having a predetermined thickness may be interposed at the edge of each side). In this state, the laminate of the first release sheet 11a / the coating layer of the heat radiation sheet forming composition C1 / the second release sheet 11b is pressed, so that the thickness of the coating layer of the heat radiation sheet forming composition C1 is obtained. Can be adjusted to the thickness of the spacer, and the heat radiation sheet 1 having a desired thickness can be easily formed.

  As a method of applying the composition C1 for forming a heat radiation sheet, for example, a bar coating method, a knife coating method, a roll coating method, a blade coating method, a die coating method, a gravure coating method, or the like can be used.

  Here, the active energy beam refers to a beam having an energy quantum among electromagnetic waves or charged particle beams, and specific examples include ultraviolet rays and electron beams. Among the active energy rays, ultraviolet rays which are easy to handle are particularly preferable.

Irradiation with ultraviolet rays can be performed with a high-pressure mercury lamp, a fusion H lamp, a xenon lamp, or the like, and the irradiation amount of the ultraviolet rays is preferably about 50 to 300 mW / cm ² . Further, the light quantity is preferably 50~2000mJ / cm ^2, more preferably 100~1000mJ / cm ^2, and particularly preferably 200 to 600 mJ / cm ^2. On the other hand, the irradiation of the electron beam can be performed by an electron beam accelerator or the like, and the irradiation amount of the electron beam is preferably about 1 to 1000 krad. When the irradiation amount of the active energy ray is within the above range, the composition C1 for heat radiation sheet formation can be efficiently cured.

  In addition, although the hardening of the composition C1 for heat dissipation sheet | seats can also be performed by irradiation of active energy rays and heat processing, it is preferable to perform only irradiation of active energy rays. This can prevent thermal degradation, thermal shrinkage, and the like of the resin film or the like to which the composition C1 for heat radiation sheet formation is applied. In addition, by not heating, it is possible to suppress the disappearance of the volatile component in the heat radiation sheet forming composition C1 by heating.

(2) When using the composition C2 for forming a heat radiating sheet When using the composition C2 for forming a heat radiating sheet, as an example of manufacturing the heat radiating sheet 1, a release surface of one of the release sheets 11a (or 11b) may be used. The composition C2 for forming a heat radiating sheet is applied, and the composition is heat-treated to crosslink (thermally crosslink) the composition C2 for forming a heat radiating sheet. After forming an application layer, the other release sheet 11b (or The peeled surfaces of 11a) are overlapped. When a curing period is required, a curing period is provided. When the curing period is not required, the above-mentioned coating layer becomes the heat radiation sheet 1 as it is. Thereby, the heat dissipation sheet 1 is obtained.

  The method for applying the heat-dissipating sheet forming composition C2 is the same as the method for applying the heat-dissipating sheet forming composition C1.

  As described above, the crosslinking of the heat-dissipating sheet-forming composition C2 can be usually performed by heat treatment. In addition, this heat treatment can also serve as a drying treatment when the diluting solvent or the like is volatilized from the coating layer of the heat radiation sheet forming composition C2 applied to the desired target.

  The heating temperature of the heat treatment is preferably from 50 to 150 ° C, particularly preferably from 70 to 120 ° C. The heating time is preferably from 10 seconds to 10 minutes, particularly preferably from 50 seconds to 2 minutes.

  After the heat treatment, a curing period of about 1 to 2 weeks at room temperature (for example, 23 ° C., 50% RH) may be provided as necessary to complete the crosslinking reaction. When the curing period is required, the heat radiation sheet 1 is formed after the curing period has elapsed, and when the curing period is not required, after the heat treatment is completed.

(Heat dissipation device)
As shown in FIG. 2, the heat radiation device 2 according to one embodiment of the present invention includes a heat generating member 21, a heat transfer member 22, and a heat release sheet 1 provided between the heat generation member 21 and the heat transfer member 22. It has.

  The heat radiation sheet 1 is the heat radiation sheet 1 according to the above-described embodiment. The heat-radiating sheet 1 exhibits a sufficient adhesive strength, so that the heat-generating member 21 and the heat-transfer member 22 are fixed via the heat-radiating sheet 1. Further, the heat dissipation sheet 1 has a large content of the heat conductive filler, and has a large contact area with the adherend (the heat generation member 21 and / or the heat transfer member 22) due to high surface smoothness, and high adhesion. Excellent heat dissipation. Therefore, the heat generated by the heat generating member 21 satisfactorily conducts heat to the heat transfer member 22 through the heat radiating sheet 1 and is efficiently radiated from the heat transfer member 22 to the outside.

  The heat generating member 21 in the present embodiment generates heat in accordance with the performance of a predetermined function, but is required to control the temperature of the member or to control the flow of heat generated by the member in a specific direction. Member. Examples of the heat generating member 21 include electronic devices such as thermoelectric conversion devices, photoelectric conversion devices, semiconductor devices such as large-scale integrated circuits, LED light-emitting elements, optical pickups, and power transistors, and various types of electronic devices such as mobile terminals and wearable terminals. Examples include equipment, batteries, batteries, motors, engines, and the like.

  The heat transfer member 22 in the present embodiment is a member that dissipates the received heat or a member that transfers the received heat to another member. The heat transfer member 22 is preferably made of a material having high heat conductivity, for example, a metal such as aluminum, stainless steel, or copper, graphite, or carbon nanofiber. The form of the heat transfer member 22 may be any of a substrate, a housing, a heat sink, a heat spreader, and the like, and is not particularly limited.

  To manufacture the heat radiation device 2, one of the release sheets 11 a (or 11 b) is peeled from the heat radiation sheet 1, and one surface of the exposed heat radiation sheet 1 is attached to the heat generating member 21. Next, the other release sheet 11 b (or 11 a) is peeled off from the heat radiation sheet 1 provided on the heat generating member 21, and the other surface of the exposed heat radiation sheet 1 is attached to the heat transfer member 22. Further, after one surface of the heat dissipation sheet 1 is attached to the heat transfer member 22, the heat generation member 21 may be attached to the other surface of the heat dissipation sheet 1.

  The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

  For example, one or both of the release sheets 11a and 11b laminated on the heat radiation sheet 1 may be omitted. Further, the shapes of the heat generating member 21 and the heat transfer member 22 in the heat radiation device 2 are not limited to those shown in FIG. 2 and may be various shapes.

  Hereinafter, the present invention will be described more specifically with reference to Examples and the like, but the scope of the present invention is not limited to these Examples and the like.

[Example 1]
1. Preparation of a composition for forming a heat radiation sheet 100 parts by mass of 2-hydroxyethyl acrylate as a resin component (A1) and an alumina filler as a heat conductive filler (B) (product name "AS-400" manufactured by Showa Denko KK) A mixture of a round filler having an average particle size of 35 μm and an irregular filler having an average particle size of 1.5 μm), 400 parts by mass, and 3 parts by mass of 1-hydroxycyclohexyl phenyl ketone as a photopolymerization initiator (C). Then, the composition for forming a heat radiation sheet was obtained by stirring with a disper for 1 minute.

2. Manufacture of heat radiation sheet The heat radiation sheet forming composition obtained in the above step 1 was subjected to release treatment on one side of a polyethylene terephthalate film with a silicone-based release agent (first release sheet; manufactured by Lintec, product name "SP"). -PET751031 ") was applied to the release-treated surface with an applicator.

  Next, a release sheet (second release sheet; manufactured by Lintec Corporation, product name "SP-PET751130") in which the coating layer on the release sheet obtained above and one surface of the polyethylene terephthalate film were subjected to release treatment with a silicone-based release agent. Were bonded so that the release-treated surface of the release sheet was in contact with the coating layer, and pressed using a hand roller (1.25 kg).

Thereafter, the coating layer is irradiated with active energy rays (ultraviolet rays) once under each of the following conditions under the following conditions through the release sheet on each side, that is, from both sides, to form the coating layer of the composition for forming a heat radiation sheet. The composition was cured to form a heat dissipation sheet having a thickness of 150 μm.
<Active energy ray irradiation conditions>
・ Use of high pressure mercury lamp ・ Illuminance 180mW / cm ² , Light intensity 230mJ / cm ²
・ UV illuminance and light meter use "UVPF-A1" manufactured by Eye Graphics

[Example 2]
A heat dissipation sheet was produced in the same manner as in Example 1, except that 100 parts by mass of 4-hydroxybutyl acrylate was used instead of 100 parts by mass of 2-hydroxyethyl acrylate as the resin component (A1).

[Example 3]
In the same manner as in Example 1 except that 50 parts by mass of 4-hydroxybutyl acrylate and 50 parts by mass of 2-ethylhexyl acrylate were used as the resin component (A1) instead of 100 parts by mass of 2-hydroxyethyl acrylate. A heat dissipation sheet was manufactured.

[Example 4]
1 mol of polypropylene glycol having a weight average molecular weight of 9,200, 2 mol of isophorone diisocyanate, and 2 mol of 2-hydroxyethyl acrylate are polymerized to obtain a polyether urethane acrylate having a weight average molecular weight of 9,900 as a urethane acrylate oligomer. I got

The weight average molecular weights of polypropylene glycol and polyether urethane acrylate are standard polystyrene equivalent values measured by gel permeation chromatography (GPC) under the following conditions.
<Measurement conditions>
・ Measuring device: HLC-8320, manufactured by Tosoh Corporation
GPC column (passed in the following order): TSK gel superH-H manufactured by Tosoh Corporation
TSK gel super HM-H
TSK gel superH2000
-Measurement solvent: tetrahydrofuran-Measurement temperature: 40 ° C

  As the resin component (A1), instead of 100 parts by mass of 2-hydroxyethyl acrylate, 37 parts by mass of 4-hydroxybutyl acrylate, 35 parts by mass of 2-ethylhexyl acrylate, 12 parts by mass of isobornyl acrylate, and the resin obtained above. A heat radiation sheet was produced in the same manner as in Example 1, except that 16 parts by mass of the obtained polyether urethane acrylate was used.

[Example 5]
A heat dissipation sheet was produced in the same manner as in Example 2, except that the amount of the alumina filler was changed to 667 parts by mass.

[Example 6]
As the heat conductive filler (B), an alumina filler (manufactured by Showa Denko KK, product name “AS-40”; a round filler having an average particle diameter of 28 μm and an average particle diameter of 1.5 μm) was used instead of the alumina filler of Example 1. A heat radiation sheet was produced in the same manner as in Example 2, except that a mixture with an irregular shaped filler) was used.

[Example 7]
Example 2 Example 2 was repeated except that an alumina filler (manufactured by Showa Denko KK, product name “A20S”; a spherical filler having an average particle size of 22 μm) was used as the heat conductive filler (B) instead of the alumina filler of Example 1. A heat radiation sheet was manufactured in the same manner as described above.

Example 8
Example 2 Example 2 was repeated except that an alumina filler (manufactured by Showa Denko KK, product name “AS50”; a round filler having an average particle diameter of 10 μm) was used as the heat conductive filler (B) instead of the alumina filler of Example 1. A heat radiation sheet was manufactured in the same manner as described above.

[Example 9]
A heat dissipation sheet was manufactured in the same manner as in Example 8, except that the thickness of the heat dissipation sheet obtained was adjusted to 30 μm by adjusting the applicator to which the composition for heat dissipation sheet formation was applied.

[Example 10]
Boron nitride filler (manufactured by Showa Denko KK, product name “UHP-2”; scale-like filler having an average particle diameter of 10 μm) 57 parts by mass instead of 400 parts by mass of the alumina filler of Example 1 as the thermally conductive filler (B) A heat radiation sheet was manufactured in the same manner as in Example 1 except for using the parts.

[Example 11]
A heat dissipation sheet was produced in the same manner as in Example 10, except that the amount of the boron nitride filler was changed to 80 parts by mass.

[Example 12]
1. Preparation of (meth) acrylic acid ester polymer 60 parts by mass of n-butyl acrylate, 20 parts by mass of methyl acrylate, and 20 parts by mass of acrylic acid are copolymerized by a solution polymerization method to obtain a (meth) acrylic acid ester polymer. (A) was prepared. When the molecular weight of this (meth) acrylate polymer (A) was measured by the GPC method described above, the weight average molecular weight (Mw) was 600,000.

2. Preparation of Composition for Forming Heat Dissipating Sheet 100 parts by mass of a (meth) acrylate polymer (solid equivalent: the same applies hereinafter) as the resin component (A2) obtained in the above step 1, and a crosslinking agent (D )) And 0.7 parts by mass of a trimethylolpropane-modified tolylene diisocyanate (manufactured by Toyochem Co., Ltd., product name "BHS8515") and an alumina filler (manufactured by Showa Denko KK, product name "AS-85") as a thermally conductive filler (B) 400 "; a mixture of a round filler having an average particle size of 35 μm and an irregular filler having an average particle size of 1.5 μm), 400 parts by mass, diluted with methyl ethyl ketone, and sufficiently stirred to obtain a solid content of 50%. A mass% of the composition for forming a heat radiation sheet was obtained.

3. Manufacture of heat radiation sheet The heat radiation sheet forming composition obtained in the above step 2 was subjected to release treatment on one side of a polyethylene terephthalate film with a silicone-based release agent (first release sheet; manufactured by Lintec, product name "SP" -PET751031 ") was applied to the release-treated surface with an applicator, and then heated at 90 ° C for 1 minute and at 120 ° C for 1 minute to form a coating layer. A release sheet (second release sheet; manufactured by Lintec Co., Ltd., product name "SP-PET751130") in which the coating layer side surface of the obtained release sheet with the coating layer and one surface of the polyethylene terephthalate film are subjected to release treatment with a silicone-based release agent. )), And cured under conditions of 23 ° C. and 50% RH for 7 days to crosslink the coating layer to form a heat-dissipating sheet having a thickness of 220 μm.

[Example 13]
As the heat conductive filler (B), instead of 400 parts by mass of the alumina filler of Example 12, a boron nitride filler (manufactured by Showa Denko KK, product name "UHP-2"; flaky filler having an average particle size of 10 μm) 57 parts by mass A heat radiation sheet was manufactured in the same manner as in Example 12, except that the parts were used.

[Comparative Example 1]
A heat radiation sheet was manufactured in the same manner as in Example 12, except that the thickness of the obtained heat radiation sheet was adjusted to 100 μm by adjusting the applicator to which the composition for heat radiation sheet formation was applied.

[Comparative Example 2]
A heat dissipation sheet was manufactured in the same manner as in Example 13, except that the thickness of the heat dissipation sheet obtained was adjusted to 50 μm by adjusting the applicator to which the composition for heat dissipation sheet formation was applied.

[Test Example 1] (Measurement of glass transition temperature)
The glass transition temperature (Tg) of a resin obtained by curing or cross-linking the resin components (A1) and (A2) used or prepared in Examples and Comparative Examples in the same manner as in Examples and Comparative Examples was measured by differential scanning calorimetry. The measurement was carried out with a device (manufactured by TA Instruments Japan Co., Ltd., product name “DSC Q2000”) at a heating / cooling rate of 20 ° C./min. Table 1 shows the results.

[Test Example 2] (Evaluation of viscosity)
Regarding the composition for forming a heat radiation sheet prepared in Examples and Comparative Examples, whether the viscosity is low enough to allow stirring and mixing in a production line (〇) or high enough to be unsuitable for the mixing and stirring (×) The judgment was made using a stir bar. Table 1 shows the results.

[Test Example 3] (Evaluation of coating properties)
While judging the situation when the composition for heat dissipation sheet formation prepared in Examples and Comparative Examples was applied with an applicator, it was visually judged whether or not the coating layer obtained by applying with the applicator had any streaks. did. Then, the coatability was evaluated based on the following criteria. Table 1 shows the results.
：: A uniform surface was formed without any streaks.
Δ: Streaks occurred.
X: The viscosity of the composition for forming a heat radiation sheet was too high to apply.

[Test Example 4] (Measurement of residual ratio after solvent immersion)
The heat-dissipating sheets obtained in Examples 1 to 11 were cut into a size of 40 mm × 40 mm, the release sheets on both sides were peeled off, wrapped in a polyester mesh (mesh size 200), and the mass was weighed with a precision balance. The mass of the heat dissipation sheet alone was calculated by subtracting the mass of the mesh alone. The mass at this time is defined as M1.

  Next, the heat dissipation sheet wrapped in the polyester mesh was immersed in ethyl acetate at room temperature (23 ° C.) for 24 hours. Thereafter, the heat-dissipating sheet was taken out, air-dried for 24 hours in an environment at a temperature of 23 ° C. and a relative humidity of 50%, and further dried in an oven at 80 ° C. for 12 hours. After drying, the mass was weighed with a precision balance, and the mass of the heat dissipation sheet alone was calculated by subtracting the mass of the mesh alone. The mass at this time is defined as M2. The residual rate (%) after solvent immersion is represented by (M2 / M1) × 100. Thereby, the residual ratio after immersion of the heat dissipation sheet in the solvent was derived. Table 1 shows the results.

[Test Example 5] (Measurement of surface roughness)
The arithmetic average roughness Ra (μm) and the ten-point average roughness Rz (μm) of both surfaces (the surface on the first release sheet side / the surface on the second release sheet side) of the heat dissipation sheets obtained in the examples and comparative examples ) Were measured using a stylus type surface roughness meter (manufactured by Mitutoyo Corporation, product name “SURF TEST SV-3000”) in accordance with JIS B0633: 2001, for 10 samples each. And the average value is shown in Table 1 as Ra and Rz of each example. In the table, the upper value is the surface roughness of the second release sheet side surface, and the lower value is the surface roughness of the first release sheet side surface.

  In addition, the value obtained by dividing the arithmetic average roughness Ra (μm) obtained above by the thickness (μm) of the heat dissipation sheet and the ten-point average roughness Rz (μm) obtained above are the thickness of the heat dissipation sheet. The value divided by (μm) was calculated for each surface. Table 1 shows the results. In the table, the upper value is the value of the surface on the second release sheet side, and the lower value is the value of the surface on the first release sheet side.

[Test Example 6] (Measurement of adhesive strength)
The second release sheet was peeled off from the heat radiation sheets obtained in the examples and comparative examples, and the exposed surface was exposed to a polyethylene terephthalate film (Toyobo Co., Ltd., Toyobo Co., Ltd., product name “PET A4300”, thickness: (25 μm). The laminate was cut into a width of 25 mm and a length of 100 mm, which was used as a sample. Then, the first release sheet was peeled off from the sample, and the exposed surface was attached to a stainless steel plate (SUS304, # 360 polished).

  Within 1 minute after the application, the adhesive force (N / 25 mm) was measured using a tensile tester (manufactured by Orientec, product name "Tensilon") under the conditions of a peeling speed of 300 mm / min and a peeling angle of 180 °. Conditions other than those described here were measured for 10 samples each in accordance with JIS Z0237: 2009. The measurement of the adhesive strength was performed on both surfaces of the heat dissipation sheet.

  As a result of the measurement, when all of the samples had an adhesive strength of 100 mN / 25 mm or more, the adhesive strength was good (○), and when one of the samples had an adhesive strength of less than 100 mN / 25 mm, the adhesive strength was poor ( ×). Table 1 shows the results. In the table, the values in the upper row are results for the surface on the second release sheet side, and the values in the lower row are results for the surface on the first release sheet side.

  When the above adhesive force is 100 mN / 25 mm or more, it is possible to prevent the LED light emitting element from laterally displacing on the aluminum plate, and also to improve the adhesion between the LED light emitting element and the aluminum plate and improve the heat conductivity. Can be enhanced.

[Test Example 7] (Measurement of thermal conductivity)
The heat radiation sheets obtained in the examples and the comparative examples were measured using a thermal diffusivity / thermal conductivity measuring device (manufactured by i-Phase Co., Ltd., product name “ai-phase mobile”) in accordance with ISO 22007-3. The conductivity (W / mK) was measured. The measurement was performed on each of 10 samples, and the maximum value, the minimum value, and the difference (width) between the maximum value and the minimum value were obtained. Table 1 shows the results.

[Test Example 8] (Evaluation of heat dissipation)
A heat radiating member having a size of 10 mm × 25 mm was cut out from a sample of the heat radiating member according to each example in which the thermal conductivity measured in Test Example 7 showed the maximum value, and this was used as a sample. The sample is placed on a 1 mm-thick aluminum plate (manufactured by Paltec, product name “Aluminum alloy plate A1050P”), and an LED light-emitting element (LED headlamp bulb “H4 24V manufactured by IPF”) is placed on the sample. 6500K 34VHLB ").

  Next, the LED light emitting device was caused to emit light by passing electricity of a voltage of 24 V and a current of 3 A through the LED light emitting device. At the same time, the aluminum plate was cooled from a position 5 mm below the aluminum plate with an air cooling fan (manufactured by Nidec, product name “D02X-05TS102”). Then, the temperature of the LED light emitting element 210 seconds after the light emission was measured from a position 35 cm above the LED light emitting element using a thermo camera (manufactured by Testo, product name "testo 870-1 thermography"). If the measurement temperature is 80 ° C. or less, it can be said that the heat radiation property is excellent. Table 1 shows the results.

  As Comparative Example 3, the LED light emitting element was directly mounted on an aluminum plate, and the temperature of the LED light emitting element was measured in the same manner as described above.

  As can be seen from Table 1, the heat dissipation sheet manufactured in the examples had good adhesive strength, high surface smoothness, and excellent heat conductivity and heat dissipation. Further, the heat dissipation sheet manufactured in the examples had a small lot-to-lot error in thermal conductivity and was excellent in reproducibility. Furthermore, the heat radiation sheet manufactured in the example had a high residual ratio after immersion in the solvent, and was excellent in reproducibility of the thermal conductivity under repeated heating.

  The heat dissipation sheet according to the present invention can be suitably used for cooling the electronic device, for example, by being interposed between an electronic device that generates heat and a heat dissipation substrate or a heat sink. Further, the heat dissipation device according to the present invention is useful, for example, as a device including an electronic device that generates heat and a heat dissipation substrate or heat sink.

DESCRIPTION OF SYMBOLS 1 ... Heat radiating sheet 11a ... 1st peeling sheet 11b ... 2nd peeling sheet 2 ... Heat dissipation device 21 ... Heat generation member 22 ... Heat transfer member

Claims (6)

A heat dissipation sheet containing a resin and a thermally conductive filler,
The glass transition temperature (Tg) of the resin is −90 ° C. or more and 0 ° C. or less;
The content of the heat conductive filler is 50% by mass or more and 96% by mass or less,
A heat dissipation sheet, wherein a value obtained by dividing an arithmetic average roughness Ra (μm) of at least one surface of the heat dissipation sheet by a thickness (μm) of the heat dissipation sheet is 4% or less. A heat dissipation sheet containing a resin and a thermally conductive filler,
The glass transition temperature (Tg) of the resin is −90 ° C. or more and 0 ° C. or less;
The content of the heat conductive filler is 50% by mass or more and 96% by mass or less,
A heat dissipation sheet, wherein a value obtained by dividing a ten-point average roughness Rz (μm) of at least one surface of the heat dissipation sheet by a thickness (μm) of the heat dissipation sheet is 29% or less.   The heat-dissipating sheet according to claim 1, wherein at least one surface has an adhesive strength to stainless steel of 100 mN / 25 mm or more.   The heat dissipation sheet according to any one of claims 1 to 3, which is sandwiched between two release sheets. It is a manufacturing method of the heat dissipation sheet according to any one of claims 1 to 4,
Applying a composition for forming an active energy ray-curable heat radiation sheet to the first release sheet;
Laminating a second release sheet on the coating layer of the heat radiation sheet forming composition,
Irradiating the coating layer with active energy rays to cure the heat-dissipating sheet-forming composition. A heating element,
A heat transfer member,
A heat dissipating device comprising: the heat dissipating sheet according to claim 1 provided between the heat generating member and the heat transfer member.

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