Thermally conductive silicone composite sheet

Abstract

To provide a thermally conductive silicone composite sheet in which a high-hardness thermally conductive silicone layer and a low-hardness thermally conductive silicone layer are laminated so as to be in a favorable state of adhesion.SOLUTION: A thermally conductive silicone composite sheet comprises a support layer (X), a high-hardness thermally conductive silicone rubber layer (Y), and a low-hardness thermally conductive silicone rubber layer (Z) laminated in this order. The support layer (X) is obtained by filling a mesh-like reinforcing material with a cured product of a thermally conductive composition. The high-hardness thermally conductive silicone rubber layer (Y) and the low-hardness thermally conductive silicone rubber layer (Z) are each a cured product of an addition-curable silicone rubber composition.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a thermally conductive silicone composite sheet.

Background Art

[0002] As a material for radiating heat from electronic components and the like, there is a thermally conductive silicone composite sheet having a high-hardness thermally conductive silicone rubber layer (high-hardness layer) and a low-hardness thermally conductive silicone rubber layer (low-hardness layer). The high-hardness layer is excellent in handling, but when fixed between a heat-generating member and a cooling member, a problem is that a high stress is generated. On the other hand, the low-hardness layer does not apply a high stress to the heat-generating body and has good adhesion, so the contact thermal resistance is low. However, because of its low hardness, it is difficult to handle and easily deforms. By laminating these, a composite sheet that is excellent in handling and difficult to apply stress to the heat-generating member is obtained. Furthermore, it is also known that by reinforcing the high-hardness layer with a glass cloth or the like, the handleability and strength are further improved (Patent Document 1). However, since the high-hardness layer is formed by peroxide vulcanization and the low-hardness layer is formed by addition vulcanization, the affinity between the two is poor. Therefore, a large amount of primer treatment is required to improve the adhesion between the two. Even if the adhesion between the two is improved, there are problems with its reliability, such as oil bleeding from the low-hardness layer. As a countermeasure, there is a method in which an uncured low-hardness layer is applied onto an uncured high-hardness layer and the two are cured simultaneously. By doing so, a method of obtaining sufficient adhesion between the two without treatment with a primer is also known (Patent Document 2). However, when forming the high-hardness layer, a resin film subjected to a release treatment is required as a base material. After molding, a step of peeling off this base material is required, and the use of a fluorine-based release treatment agent having excellent releasability is being restricted from the viewpoint of recent environmental regulations. Furthermore, since the surface of the base material is in a mirror state, tack remains after the high-hardness layer is cured. Then, since it becomes a thermally conductive silicone composite sheet having tack on both the high-hardness layer and the low-hardness layer, there is a risk that workability such as alignment during use may be reduced.

[0003] On the other hand, there is a method of obtaining a thermally conductive silicone composite sheet in which a mesh-like reinforcing material plugged with a thermally conductive material is interposed between a high-hardness layer and a low-hardness layer, and the adhesion is improved by this anchor effect (Patent Document 3). However, when the blending amount of the thermally conductive filler in the low-hardness layer is increased, the flexibility of the low-hardness layer is impaired, so it is difficult to obtain good adhesion between the low-hardness layer and the high-hardness layer. Furthermore, since the thickness of the low-hardness layer is as thin as 0.015 to 0.2 mm, the compression stress becomes high, and it is difficult to use it under high compression.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] The present invention has been made to solve the above problems, and an object thereof is to provide a thermally conductive silicone composite sheet in which a high-hardness thermally conductive silicone layer and a low-hardness thermally conductive silicone layer are laminated in a good adhesion state. Another object of this composite sheet is to suppress oil bleed from the sheet. Furthermore, it is also an object that a resin film required when molding a sheet-like silicone becomes unnecessary.

Means for Solving the Problems

[0006] As a result of intensive studies to solve the above problems, the present inventors have found that the following thermally conductive silicone composite sheet can achieve the above object, and have completed the present invention. That is, the present invention provides the following thermally conductive silicone composite sheet.

[0007] [1] A thermally conductive silicone composite sheet in which a support layer (X), a high-hardness thermally conductive silicone rubber layer (Y), and a low-hardness thermally conductive silicone rubber layer (Z) are laminated in this order, wherein the support layer (X) is formed by plugging a mesh reinforcing material with a cured product of a thermally conductive composition, and the high-hardness thermally conductive silicone rubber layer (Y) and the low-hardness thermally conductive silicone rubber layer (Z) are each a cured product of an addition-curing type silicone rubber composition, and the hardness of the high-hardness thermally conductive silicone rubber layer (Y) measured by a Shore A durometer according to the method described in JIS K6253-1:2012 is 50 to 97, and the hardness of the low-hardness thermally conductive silicone rubber layer (Z) measured by an Asker C durometer according to the method described in JIS K7312:1996 is 2 to 30. A thermally conductive silicone composite sheet. [2] The thermally conductive silicone composite sheet according to [1], wherein the mesh reinforcing material is a glass cloth. [3] The thermally conductive silicone composite sheet according to [1] or [2], wherein the high-hardness thermally conductive silicone rubber layer (Y) is a cured product of an addition-curing type silicone rubber composition containing the following (A1) to (D1). (A1) Organopolysiloxane having two or more alkenyl groups in one molecule and an average degree of polymerization of 100 to 20,000: 100 parts by mass (B1) Organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule: an amount such that the ratio of the number of moles of hydrosilyl groups in component (B1) to the number of moles of alkenyl groups in component (A1) is 1.0 to 3.5 (C1) Platinum group metal-based catalyst: 0.1 to 1,000 ppm in terms of the mass of platinum group metal (D1) Thermally conductive filler: 300 to 4,000 parts by mass [4] To the addition-curing type silicone rubber composition, (E1) as a surface treatment agent, the following formula (2) [Chemical formula] (In the formula, R 5 is independently an alkyl group having 1 to 6 carbon atoms, and c is a number from 4 to 100.) The thermally conductive silicone composite sheet according to [3], which contains dimethylpolysiloxane having a trialkoxy group-blocked molecular chain fragment terminal. [5] The thermally conductive silicone composite sheet according to any one of [1] to [4], wherein the thermally conductive material constituting the (X) layer is the same as the thermally conductive silicone rubber composition constituting the high-hardness thermally conductive silicone rubber layer (Y). [6] The thermally conductive silicone composite sheet according to any one of [1] to [5], wherein the low-hardness thermally conductive silicone rubber layer (Z) is a cured product of an addition-curing type silicone rubber composition containing the following (A2) to (E2). (A2) Organopolysiloxane having two or more alkenyl groups in one molecule and an average degree of polymerization of 100 to 2,000: 100 parts by mass (B2) Organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule: an amount such that the ratio of the number of moles of hydrosilyl groups in the (B2) component to the number of moles of alkenyl groups in the (A2) component is 0.5 to 1.5 (C2) Platinum group metal-based catalyst: 0.1 to 1,000 ppm in terms of the mass of the platinum group metal (D2) Thermally conductive filler: 500 to 4,000 parts by mass (E2) Dimethylpolysiloxane having a trialkoxy group-blocked molecular chain fragment terminal represented by the following formula (2) as a surface treatment agent: 10 to 300 parts by mass [Chemical formula] (In the formula, R 5 is independently an alkyl group having 1 to 6 carbon atoms, and c is a number from 4 to 100.) [7] The thickness of the high-hardness thermally conductive silicone rubber layer (Y) is 0.15 to 0.5 mm, and the thickness of the entire thermally conductive silicone composite sheet is 0.3 to 10 mm. The thermally conductive silicone composite sheet according to any one of [1] to [6]. [8] The thickness of the support layer (X) is 0.03 to 0.10 mm. The thermally conductive silicone composite sheet according to any one of [1] to [6].

Advantages of the Invention

[0008] The thermally conductive silicone composite sheet of the present invention can be simply and stably laminated and manufactured with the high-hardness thermally conductive silicone rubber layer and the low-hardness thermally conductive silicone rubber layer of the thermally conductive silicone composite sheet in a good adhesion state. Further, since the high-hardness thermally conductive silicone rubber layer is applied onto the support layer plugged with a thermally conductive material, a release-treated resin film as a base material is not required, and the process of peeling the base material by the user can be reduced. Furthermore, the high-hardness thermally conductive silicone rubber layer can reduce the tack force by curing through addition curing, and it is also possible to store the coated surface without covering it with a release-treated resin film before laminating the low-hardness thermally conductive silicone layer. In addition, after the low-hardness thermally conductive silicone layer is adhered, when oil bleed occurs from the low-hardness thermally conductive silicone rubber layer, the support layer having a mesh structure can accommodate it. Therefore, compared with the conventional thermally conductive silicone composite sheet, it has excellent oil bleed resistance. Therefore, the thermally conductive silicone composition of the present invention is useful as a heat dissipation material for electric vehicles, mobile devices, and wearable devices that require weight reduction.

Embodiments for Carrying out the Invention

[0009] Hereinafter, the present invention will be described in more detail.

[0010] <Thermally Conductive Silicone Composite Sheet> The present invention relates to a thermally conductive silicone composite sheet having a high-hardness thermally conductive silicone rubber layer (Y) laminated on a support layer (X) in which a mesh-like reinforcing material is sealed with a cured product of a thermally conductive material, and a low-hardness thermally conductive silicone rubber layer (Z) laminated on the high-hardness thermally conductive silicone rubber layer (Y), wherein the hardness of the high-hardness silicone rubber layer (Y) is harder than the hardness of the low-hardness silicone rubber layer (Z).

[0011] The thermally conductive silicone composite sheet has a support layer (X), a high-hardness thermally conductive silicone rubber layer (Y), and a low-hardness thermally conductive silicone rubber layer (Z). The support layer (X) is formed by sealing a mesh-like reinforcing material with a cured product of a thermally conductive composition. The high-hardness thermally conductive silicone rubber layer (Y) and the low-hardness thermally conductive silicone rubber layer (Z) are each a cured product of an addition-curing type silicone rubber composition. By using the addition-curing type silicone rubber composition for both the silicone rubber layer (Y) and the silicone rubber layer (Z), adhesion between these two layers is possible without applying a primer layer. Optionally, a primer treatment may be performed. Hereinafter, these will be described in more detail.

[0012] <Support layer (X)> The support layer (X) is formed by sealing a mesh-like reinforcing material with a cured product of a thermally conductive material. In the thermally conductive silicone composite sheet of the present invention, it imparts good workability due to tack-free and serves as an oil bleed suppression mechanism.

[0013] <Mesh-like reinforcing material> Examples of the mesh-like reinforcing material used here include inorganic fiber cloth such as glass cloth, ceramic cloth, and quartz cloth, or organic fiber cloth such as nylon and polyester. Considering heat resistance and the like, inorganic fiber cloth is preferred, and glass cloth is more preferred. There is no particular specification for the mesh opening or weaving method of the cloth, but it is preferable to use yarns of a count of 5 Tex or more and a density of 25 threads / 25 mm or more. By using such a mesh-like reinforcing material, a sufficient reinforcing effect can be obtained. The thickness of the mesh reinforcing material is preferably 0.02 to 0.09 mm, more preferably 0.04 to 0.08 mm. If the thickness of the mesh reinforcing material is less than 0.02 mm, the strength of the laminated sheet may be significantly reduced. On the other hand, if it exceeds 0.09 mm, it may be difficult to obtain the required thermal conductivity.

[0014] <Material for caulking> The caulking material is not particularly limited as long as it is a heat-conductive material, but is preferably a heat-conductive silicone rubber material. Further, in consideration of cost and adhesion, it is more preferable that it is the same as the material used in the high-hardness heat-conductive silicone layer (Y) described later.

[0015] Also, when the surface roughness Rz measured by the surface property measuring instrument SV-C3200 (manufactured by Daiichi Kagaku Co., Ltd.) of the support layer (X) is preferably 20 μm or more, more preferably 25 μm or more, and further preferably 30 μm or more, the above-described workability improvement due to tack-free and the effect of suppressing oil bleed become good.

[0016] <High-hardness heat-conductive silicone rubber layer (Y)> The high-hardness heat-conductive silicone rubber layer (Y) serves as a reinforcing layer carrying a low-hardness layer in the heat-conductive silicone composite sheet of the present invention. This silicone rubber layer (Y) is preferably composed of a cured product of an addition-curing type heat-conductive silicone composition containing the following components (A1) to (D1). Each component will be described below.

[0017] [(A1) Organopolysiloxane] The organopolysiloxane of the component (A1) is an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in one molecule and having an average degree of polymerization of 100 to 20,000. The organopolysiloxane is preferably a linear organopolysiloxane having a repeating unit of a diorganosiloxane unit in the main chain portion, but may include a branched structure in a part of the molecular structure or may be a cyclic body. From the viewpoint of physical properties such as the mechanical strength of the cured product, linear diorganopolysiloxane is preferable.

[0018] Examples of the functional group other than the alkenyl group bonded to the silicon atom include monovalent hydrocarbon groups, preferably monovalent hydrocarbon groups having 1 to 10 carbon atoms, particularly preferably 1 to 6 carbon atoms. Examples of the monovalent hydrocarbon group include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, dodecyl group, etc., cycloalkyl groups such as cyclopentyl group, cyclohexyl group, cycloheptyl group, etc., aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, biphenylyl group, etc., aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, methylbenzyl group, etc. Among these, preferably, alkyl groups having 1 to 3 carbon atoms such as methyl group, ethyl group, propyl group and phenyl group. In addition, those in which a part of the hydrogen atoms bonded to these groups are substituted with halogen atoms may be used. Further, not all of the functional groups other than the alkenyl group bonded to the silicon atom are limited to be the same.

[0019] In addition, examples of the alkenyl group include those having 2 to 8 carbon atoms such as vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, hexenyl group, and cyclohexenyl group. Among them, vinyl group, allyl group, etc. are preferable, and vinyl group is particularly preferable. The component (A1) may have two or more alkenyl groups bonded to the silicon atom in one molecule, preferably 2 to 20 alkenyl groups, more preferably 2 to 10 alkenyl groups.

[0020] The organopolysiloxane of the component (A1) may be used alone or in combination of two or more kinds. The organopolysiloxane of the component (A1) is preferably linear, but may have some branches as long as it does not impair the rubber strength as a high thermal conductivity and high hardness layer, and may also be a mixture of two or more kinds of organopolysiloxanes having different molecular structures and degrees of polymerization. Furthermore, the organopolysiloxane preferably has an average degree of polymerization of 100 to 20,000, particularly preferably 1,000 to 10,000. The average degree of polymerization is a value determined as the number average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC). [Measurement conditions] Developing solvent: Tetrahydrofuran (THF) Flow rate: 0.6 mL / min Detector: Differential refractive index detector (RI) Column: TSK Guardcolumn SuperH-L TSKgel SuperH4000 (6.0 mm I.D. × 15 cm × 1) TSKgel SuperH3000 (6.0 mm I.D. × 15 cm × 1) TSKgel SuperH2000 (6.0 mm I.D. × 15 cm × 2) (All are manufactured by Tosoh Corporation) Column temperature: 40 °C Sample injection volume: 20 μL (THF solution with a concentration of 0.5 mass%)

[0021] In the addition-curing type thermally conductive silicone composition containing the above components (A1) to (D1), the proportion of the component (A1) with respect to the whole composition is preferably 5 to 50 mass%, more preferably 7 to 45 mass%, and still more preferably 10 to 40 mass%.

[0022] [(B1) Organohydrogenpolysiloxane] The component (B1) is an organohydrogenpolysiloxane having two or more, preferably 2 to 100 hydrogen atoms (hydrosilyl groups) directly bonded to silicon atoms in one molecule, and acts as a crosslinking agent for the component (A1). That is, the hydrosilyl group in the component (B1) and the alkenyl group in the component (A) undergo a hydrosilylation reaction in the presence of a platinum group catalyst (C1) described below to give a three-dimensional network structure having a crosslinked structure. Also, if the number of hydrosilyl groups is 1 or less, there is a risk of non-curing. The above organohydrogenpolysiloxane is represented by, for example, the following formula (1). [Chemical formula]

[0023] In formula (1), each R is independently a hydrogen atom or a monovalent hydrocarbon group having no aliphatic unsaturated bond, provided that two or more of the Rs are hydrogen atoms, x is a number of 1 or more, preferably a number of 2 to 100, more preferably a number of 3 to 50. In formula (1), the hydrogen atom directly bonded to the silicon atom may be present either in the side chain or at the terminal, but preferably two or more of the Rs in the side chain are hydrogen atoms.

[0024] In formula (1), the monovalent hydrocarbon group having no aliphatic unsaturated bond represented by R is preferably a monovalent hydrocarbon group having 1 to 10 carbon atoms, particularly preferably 1 to 6 carbon atoms. Examples of the monovalent hydrocarbon group having no aliphatic unsaturated bond include alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, octyl group, nonyl group, decyl group, and dodecyl group; cycloalkyl groups such as cyclopentyl group, cyclohexyl group, and cycloheptyl group; aryl groups such as phenyl group, tolyl group, xylyl group, naphthyl group, and biphenylyl group; and aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, and methylbenzyl group. Among them, alkyl groups having 1 to 3 carbon atoms such as methyl group, ethyl group, and propyl group, and phenyl group are preferred. In addition, those in which a part of the hydrogen atoms bonded to the carbon atoms of these groups are substituted with halogen atoms may be used. Also, not all of the Rs are limited to be the same.

[0025] The amount of component (B1) is such that the ratio of the number of hydrosilyl groups in component (B1) to the number of alkenyl groups in component (A1) is 1.0 or more, preferably 1.1 or more, more preferably 1.2 or more. The upper limit is not particularly specified, but it is 3.5 or less, preferably 2.5 or less. When the amount of the (B1) component is within this range, good adhesion with the low-hardness thermally conductive silicone rubber layer (Z) described later can be obtained. The organohydrogenpolysiloxane of the (B1) component may be used alone or in combination of two or more.

[0026] [(C1) Platinum group metal-based catalyst] The (C1) component is an addition reaction catalyst that promotes the addition reaction between the alkenyl group of the (A1) component and the hydrosilyl group of the (B1) component. As this catalyst, a well-known platinum group metal-based catalyst used in the hydrosilylation reaction may be used. For example, platinum group metal simple substances such as platinum (including platinum black), rhodium, and palladium, H2PtCl4·nH2O, H2PtCl6·nH2O, NaHPtCl6·nH2O, KaHPtCl6·nH2O, Na2PtCl6·nH2O, K2PtCl4·nH2O, PtCl4·nH2O, PtCl2, Na2HPtCl4·nH2O (wherein n is a number from 0 to 6, preferably 0 or 6), etc., platinum chloride, chloroplatinic acid and chloroplatinic acid salts, alcohol-modified chloroplatinic acid (see U.S. Patent No. 3,220,972), complexes of chloroplatinic acid and olefins (see U.S. Patent Nos. 3,159,601, 3,159,662, 3,775,452), platinum black, platinum group metals such as palladium supported on carriers such as alumina, silica, and carbon, rhodium-olefin complexes, chlorotris(triphenylphosphine)rhodium (Wilkinson catalyst), complexes of platinum chloride, chloroplatinic acid or chloroplatinic acid salts and vinyl group-containing siloxanes, particularly vinyl group-containing cyclic siloxanes, etc. The platinum group metal-based catalyst may be used alone or in combination of two or more.

[0027] The amount of the (C1) component may be a so-called catalyst amount (that is, an effective amount for promoting the above addition reaction). It is 0.1 to 1,000 ppm in terms of the mass conversion of the platinum group metal element with respect to the (A1) component, preferably 1 to 500 ppm.

[0028] [(D1) Thermally conductive filler] (D1) The thermally conductive filler may be a known filler contained in the thermally conductive composition, but is preferably at least one selected from the group consisting of metals, metal oxides, and metal nitrides. Known thermally conductive fillers such as non-magnetic metals such as copper and aluminum, metal oxides such as alumina, silica, magnesia, red iron oxide, beryllia, titania, and zirconia, metal nitrides such as aluminum nitride, silicon nitride, and boron nitride, artificial diamond or silicon carbide, etc. may be used. The thermally conductive filler preferably has an average particle size of 0.1 to 70 μm, more preferably 0.5 to 60 μm, and even more preferably 1 to 50 μm. The thermally conductive filler may be used alone or in combination of two or more kinds. Also, two or more kinds of particles having different average particle sizes may be used. In the present invention, the average particle size is the volume average particle size and is the measured value by a microtrack particle size distribution measuring device MT3300EX (Nikkiso Co., Ltd.).

[0029] The compounding amount of the thermally conductive filler is 300 to 4,000 parts by mass, preferably 500 to 3,500 parts by mass, based on 100 parts by mass of the (A1) component. If the compounding amount of the thermally conductive filler exceeds 4,000 parts by mass based on 100 parts by mass of the (A1) component, the adhesion to the low-hardness thermally conductive silicone rubber layer (Z) described later may decrease. If the compounding amount of the thermally conductive filler is less than 300 parts by mass based on 100 parts by mass of the (A1) component, it may not be possible to obtain the desired thermal conductivity.

[0030] For the high-hardness thermally conductive silicone rubber composition of the present invention, a surface treatment agent such as a silane coupling agent that improves the compatibility between the (D1) component and the (A1) component may be added.

[0031] [(E1) Surface treatment agent] Also, in the high-hardness thermally conductive silicone rubber layer (Y), as a surface treatment agent that improves the compatibility between the (D1) component and the (A1) component, it is preferable to add dimethylpolysiloxane represented by the following formula (2) in which the molecular chain fragment terminal is blocked with a trialkoxy group to the addition-curable thermally conductive silicone composition. [Chemical formula] (In the formula, R 5 is independently an alkyl group having 1 to 6 carbon atoms, and c is a number from 4 to 100.)

[0032] (E1) When the component is blended in the addition-curable thermally conductive silicone composition, the amount is 10 to 300 parts by mass, preferably 20 to 150 parts by mass, based on 100 parts by mass of the (A1) component. When the ratio of this component exceeds 300 parts by mass with respect to 100 parts by mass of the (A1) component, oil separation is likely to be induced, and the adhesion between the (Y) layer and the (Z) layer may decrease. Also, when the ratio is less than 10 parts by mass with respect to 100 parts by mass of the (A1) component, the wettability between the (A1) organopolysiloxane and the (D1) thermally conductive filler decreases, and the moldability of the composition may decrease.) Note that the surface treatment agent of the (E1) component may be used alone or in combination of a plurality of kinds.)

[0033] Furthermore, if necessary, a pigment, an internal release agent, and a plasticizer may be added as optional components to the addition-curable thermally conductive silicone composition.)

[0034] <Low-hardness thermally conductive silicone rubber layer (Z)> The low-hardness thermally conductive silicone rubber layer (Z) provides stress relaxation, tolerance absorption, and reduction of contact thermal resistance in the thermally conductive silicone composite sheet of the present invention. This silicone rubber layer (Z) is composed of a cured product of an addition-curable thermally conductive silicone composition containing the following components (A2) to (D2). Hereinafter, each component will be described.)

[0035] [(A2) Organopolysiloxane] (A2) component of the organopolysiloxane has two or more alkenyl groups bonded to silicon atoms in one molecule, and is an organopolysiloxane with an average degree of polymerization of 100 to 2,000. The organopolysiloxane is preferably linear, but may have some branches within a range that does not impair the rubber strength as a low thermal conductivity and low hardness layer, and may also be a mixture of two or more types of organopolysiloxanes with different molecular structures and degrees of polymerization. From the viewpoint of physical properties such as the mechanical strength of the cured product, linear diorganopolysiloxane is preferred.

[0036] Examples of the functional groups other than the alkenyl group bonded to the silicon atom include the same functional groups as those exemplified in the (A1) component. The (A2) component in the low hardness thermal conductive silicone rubber layer (Z) only needs to have two or more alkenyl groups bonded to silicon atoms in one molecule, preferably 2 to 20, more preferably 2 to 10 alkenyl groups.

[0037] (A2) component of the organopolysiloxane may be used alone or in combination of multiple types. Also, the (A2) component in the low hardness thermal conductive silicone rubber layer (Z) has an average degree of polymerization of 100 to 2,000, particularly preferably 200 to 1,000. The average degree of polymerization is the value determined as the number average degree of polymerization in terms of polystyrene by gel permeation chromatography (GPC). [Measurement conditions] Developing solvent: Tetrahydrofuran (THF) Flow rate: 0.6 mL / min Detector: Differential refractive index detector (RI) Column: TSK Guardcolumn SuperH-L TSKgel SuperH4000 (6.0 mm I.D.×15 cm×1) TSKgel SuperH3000 (6.0 mm I.D.×15 cm×1) TSKgel SuperH2000 (6.0 mm I.D.×15 cm×2) (All are manufactured by Tosoh Corporation) Column temperature: 40 °C Sample injection volume: 20 μL (THF solution with a concentration of 0.5% by mass)

[0038] In the addition-curing type thermally conductive silicone composition containing the above components (A2) to (D2), the ratio of the component (A2) to the whole composition is preferably 5 to 45% by mass, more preferably 7 to 40% by mass, and even more preferably 10 to 40% by mass.

[0039] [(B2) Organohydrogenpolysiloxane] The component (B2) is an organohydrogenpolysiloxane having two or more, preferably 2 to 100 hydrogen atoms (hydrosilyl groups) directly bonded to silicon atoms, and acts as a crosslinking agent for the component (A2). Specifically, the same ones as the component (B1) can be exemplified. The amount of the component (B2) is such that the ratio of the number of hydrosilyl groups in the component (B2) to the number of alkenyl groups in the component (A2) is 1.5 or less, preferably 1.3 or less, and even more preferably 1.1 or less. The lower limit is not particularly specified, but it is 0.5 or more, preferably 0.6 or more. When the amount of the component (B2) is within this range, it is easy to lower the hardness of the (Z) layer, and it is also possible to adhere to the (Y) layer. In addition, the organohydrogenpolysiloxane of the component (B2) may be used alone or in combination of two or more.

[0040] [(C2) Platinum group metal-based catalyst] The component (C2) is an addition reaction catalyst that promotes the addition reaction between the alkenyl group of the component (A2) and the hydrosilyl group of the component (B2). As the catalyst, a well-known platinum group metal-based catalyst used in the hydrosilylation reaction may be used. Specifically, the same ones as the component (C1) can be exemplified. The platinum group metal-based catalyst may be used alone or in combination of two or more. (C2) The amount of the component may be a so-called catalytic amount (i.e., an effective amount for promoting the addition reaction). It is 0.1 to 1,000 ppm, preferably 1 to 500 ppm in terms of the mass of the platinum group metal element relative to the (A2) component.

[0041] [(D2) Thermal conductivity filler] (D2) The thermal conductivity filler may be a known filler contained in the thermal conductivity composition, but is preferably at least one selected from the group consisting of metals, metal oxides, and metal nitrides. Specifically, the same ones as the (D1) component can be exemplified. (D2) The compounding amount of the component is 500 to 4,000 parts by mass, preferably 700 to 3,000 parts by mass with respect to 100 parts by mass of the (A2) component. If the compounding amount of the thermal conductivity filler exceeds 4,000 parts by mass with respect to 100 parts by mass of the (A2) component, not only a silicone rubber layer with a desired hardness cannot be obtained, but also the adhesion to the high-hardness thermal conductivity silicone rubber layer (Y) may decrease. If it is less than 500 parts by mass with respect to 100 parts by mass of the (A2) component, there is a possibility that the desired thermal conductivity cannot be obtained.

[0042] [(E2) Surface treatment agent] As a surface treatment agent for improving the compatibility between the (D2) component and the (A2) component, a dimethylpolysiloxane represented by the following formula (2) in which the molecular chain terminal is blocked with a trialkoxy group is added to the addition-curable thermal conductivity silicone composition. Further, this surface treatment agent also contributes to the reduction of the hardness of the low-hardness thermal conductivity silicone rubber layer (Z). [Chemical formula] (In the formula, R 5 is independently an alkyl group having 1 to 6 carbon atoms, and c is a number from 4 to 100.)

[0043] When the (E2) component is blended into the addition-curing type thermally conductive silicone composition, the amount is 10 to 300 parts by mass, preferably 20 to 150 parts by mass, based on 100 parts by mass of the (A2) component. If the proportion of this component exceeds 300 parts by mass with respect to 100 parts by mass of the (A2) component, oil separation is likely to be induced, and the adhesion between the (Y) layer and the (Z) layer may decrease. Also, if the proportion is less than 10 parts by mass with respect to 100 parts by mass of the (A1) component, the wettability of the (A2) polyorganosiloxane and the (D2) thermally conductive filler decreases, the moldability of the composition decreases, and there is a possibility that it becomes difficult to lower the hardness. Note that the surface treatment agent for the (E2) component may be used alone or in combination of a plurality of types.

[0044] Furthermore, if necessary, a pigment, an internal release agent, and a plasticizer may be further added as optional components to the addition-curing type thermally conductive silicone composition.

[0045] <Manufacturing method> <Step 1> Step (1) is a step of applying a thermally conductive material to a mesh-shaped reinforcing material and forming a blocked support layer (X). By applying and curing this blocking material to the mesh-shaped reinforcing material, a resin film for sheet production becomes unnecessary when laminating the high-hardness thermally conductive silicone layer (Y) in the next step. Regarding the blocking method, it is a known method. Dilute the thermally conductive material with a solvent to prepare a blocking liquid and apply it to the mesh-shaped reinforcing material. Subsequently, using a coating device such as a knife coater or a kiss coater equipped with a drying furnace, a heating furnace, and a winding device, continuously apply it to the mesh-shaped reinforcing material, then dry the solvent, etc., and preferably heat-cure it to about 80 to 120 °C, more preferably 100 to 150 °C, to obtain a blocked mesh-shaped reinforcing material.

[0046] <Step 2> Step (2) is a step of obtaining a high-hardness thermally conductive silicone layer (Y) by laminating a high-hardness thermally conductive silicone composition on the support layer (X) produced in step (1) and performing a curing treatment. The method of coating the high-hardness thermally conductive silicone composition on the support layer (X) is not particularly limited. For example, by using a comma coater, the high-hardness thermally conductive silicone rubber layer (Y) can be continuously laminated on the support layer (X) in one step. Further, if necessary, the high-hardness thermally conductive silicone composition may be diluted with a solvent (e.g., xylene, toluene, etc.), coated, and then the solvent may be volatilized. In the present invention, it is preferable that the high-hardness thermally conductive silicone rubber layer (Y) completes the curing reaction before laminating the low-hardness thermally conductive silicone rubber layer (Z) described later. By curing, the tack force on the surface of the (Y) layer is reduced, so there is no need to protect it with a resin film subjected to a release treatment. The curing conditions are 100°C to 170°C for 5 minutes to 30 minutes, preferably 120°C to 150°C for 10 minutes to 20 minutes. Further, the tack force on the surface of the (Y) layer after curing is preferably 30 gf or less, more preferably 20 gf or less, and even more preferably 10 gf or less. If the tack force is within this range, even if the high-hardness thermally conductive silicone rubber layer formed into a sheet shape is directly wound into a roll shape, sticking (blocking) of the sheets can be suppressed. The hardness of the obtained sheet can be measured with a Shore A hardness meter by the method described in JIS K6253-1:2012.

[0047] <Step 3> In step (3), a low-hardness thermally conductive silicone composition is laminated on the high-hardness thermally conductive silicone rubber layer (Y) and cured to adhere the (Y) and the low-hardness thermally conductive silicone rubber layer (Z) to obtain a thermally conductive silicone composite sheet. The hardness of the obtained sheet can be measured with an Asker C hardness meter by the method described in JIS K7312:1996. The method of laminating and curing the low-hardness thermally conductive silicone composition on the (Y) layer to form the (Z) layer is not particularly limited, but examples include coating and press molding. The curing conditions are 100°C to 150°C for 5 minutes to 30 minutes, preferably 110°C to 130°C for 10 minutes to 20 minutes. After curing, the hardness of the low-hardness thermally conductive silicone layer is preferably 2 to 30 in Asker C, more preferably 20 or less in Asker C. If the hardness of the low-hardness thermally conductive silicone layer is within this range, the stress applied to the heat-generating member can be reduced due to good compression characteristics.

[0048] <Thermally Conductive Silicone Composite Sheet> In the present invention, the thickness of the high-hardness thermally conductive silicone rubber layer (Y) can be 0.15 mm or more and 0.5 mm or less, the hardness of the low-hardness thermally conductive silicone rubber layer (Z) after curing can be 30 or less in Asker C, and the thickness of the thermally conductive silicone composite sheet can be 0.3 mm or more and 10 mm or less. Also, in the present invention, the hardness of the high-hardness thermally conductive silicone rubber layer (Y) in the thermally conductive silicone composite sheet can be 50 or more and 97 or less in Shore A, and the thickness can be 0.15 mm or more and 0.5 mm or less. When manufacturing the thermally conductive silicone composite sheet of the present invention, a resin film required for manufacturing ordinary sheet-like silicone is unnecessary, and blocking can be suppressed even when storing the high-hardness thermally conductive silicone rubber layer (Y). Furthermore, the low-hardness thermally conductive silicone rubber layer (Z) can be laminated in a good adhesion state, and the obtained thermally conductive silicone composite sheet exhibits excellent workability and compression characteristics.

Examples

[0049] Hereinafter, examples and comparative examples will be shown to specifically explain the present invention, but the present invention is not limited to the following examples.

[0050] <Preparation of Compositions 1-A to 1-D and Compositions 2-A to 2-C> Each component was mixed according to the formulations shown in Tables 1 and 2 to prepare Compositions 1-A to 1-D and Compositions 2-A to 2-C. Compositions 1-A, 1-B, 1-C, and 1-D were kneaded using a kneader. Compositions 2-A, 2-B, and 2-C were kneaded using a planetary mixer.

[0051] [Component (a)] Component (a-1): Dimethylpolysiloxane capped at both ends with dimethylvinyl groups and having an average degree of polymerization of 8,000, represented by the following formula (3) Component (a-2): Dimethylpolysiloxane capped at both ends with dimethylvinyl groups and having an average degree of polymerization of 400, represented by the following formula (3) [Chemical formula] (p is a number satisfying the above average degree of polymerization)

[0052] [Component (b)] Component (b-1): Organohydrogenpolysiloxane where q = 20 and r = 9 in the following formula (4) Component (b-2): Organohydrogenpolysiloxane where q = 27 and r = 3 in the following formula (4) [Chemical formula]

[0053] [Component (c)] 5% Platinum chloride 2-ethylhexanol solution

[0054] [Component (d)] Component (d-1): Aluminum hydroxide with an average particle size of 2 μm Component (d-2): Aluminum hydroxide with an average particle size of 8 μm Component (d-3): Aluminum hydroxide with an average particle size of 50 μm Component (d-4): Aluminum oxide with an average particle size of 1 μm Component (d-5): Aluminum oxide with an average particle size of 10 μm Component (d-6): Aluminum oxide with an average particle size of 45 μm Component (d-7): Aluminum oxide with an average particle size of 70 μm

[0055] [Component (e)] Dimethylpolysiloxane with one end capped with a trimethoxysilyl group, represented by formula (5) [Chemical formula]

[0056] [Component (f)] Addition reaction control agent: 2-ethynyl-2-undecanol

[0057] [Component (g)] Internal release agent: Dimethyldiphenyl silicone oil ("KF-54" manufactured by Shin-Etsu Chemical Co., Ltd.)

[0058] [Component (h)] Plasticizer: Dimethyl silicone oil ("KF-96-100cs" manufactured by Shin-Etsu Chemical Co., Ltd.)

[0059] [Evaluation of high-hardness thermally conductive silicone rubber layer (Y)] [Manufacturing method] The obtained compositions 1-A to 1-D were molded into a sheet with a thickness of 6 mm and cured to obtain a sheet-like cured product (hereinafter referred to as a sheet). [Thermal conductivity] Using two of the obtained sheets, the thermal conductivity (W / m·K) of the sheet was measured with a thermal conductivity meter (TPA-501, manufactured by Kyoto Electronics Industry Co., Ltd.). [Tack force] The tack force of the obtained sheet was measured with a solder paste type tackiness tester. [Hardness] The hardness of the obtained sheet was measured with a Shore A hardness meter by the method described in JIS K6253-1:2012.

[0060] [Table 1]

[0061] [Evaluation of low-hardness thermally conductive silicone rubber layer (Z)] [Manufacturing method] The obtained compositions 2-A to 2-C were molded into a sheet with a thickness of 6 mm and cured to obtain a sheet-like cured product (hereinafter referred to as a sheet). [Thermal conductivity] Using two of the obtained sheets, the thermal conductivity (W / m·K) of the sheets was measured with a thermal conductivity meter (TPA-501, manufactured by Kyoto Electronics Industry Co., Ltd.). [Hardness] The hardness of the obtained sheet was measured with an Asker C hardness meter by the method described in JIS K7312:1996.

[0062]

Table 2

[0063] <Fabrication of Composite Sheet> [Mesh Reinforcement] As the mesh reinforcement for producing the support layer (X), a glass cloth (thickness 30 μm) with 50 warp and weft threads per 25 mm using 5 Tex glass fibers was used.

[0064] (Example 1) 80% by mass of xylene was added to Composition 1-A to obtain a glass cloth sizing solution. The sizing solution was put into a container having a volume capable of placing the glass cloth, and then the glass cloth was placed in the container and immersed in the sizing solution to impregnate the glass cloth with the sizing solution. When the sizing solution was impregnated into the glass cloth at room temperature for 5 minutes, the glass cloth was continuously pulled up, and after removing the excess sizing solution adhering to the glass cloth, it was put into an oven and dried at 80°C for 10 minutes and cured at 120°C for 10 minutes to obtain a support layer (X) with a thickness of 0.05 mm. Next, a coating solution was prepared by adding 20% by mass of xylene to Composition 1-A. The coating solution was coated on one side of the support layer (X) with a comma coater at a coating speed of 0.5 m / min. The oven temperature was set at 80°C / 80°C / 150°C / 150°C, and heating was performed for a total of 15 minutes to obtain a laminate having a silicone rubber layer (Y) which is a cured product of Composition 1-A on the support layer (X). Subsequently, Composition 2-A was applied to the surface of the silicone rubber layer (Y), press-molded under the conditions of 120 °C / 10 min to cure Composition 2-A, and a thermally conductive silicone composite sheet in which the support layer (X), the silicone rubber layer (Y), and the silicone rubber layer (Z) which is the cured product of Composition 2-A were laminated in this order was obtained. X: 0.05 mm, Y: 0.15 mm, Z: 0.8 mm, total thickness: 1.0 mm

[0065] (Example 2) 60% by mass of xylene was added to Composition 1-B to obtain a glass cloth sealer solution. The sealer solution was put into a container having a volume capable of placing a glass cloth, and then the glass cloth was placed in the container and immersed in the sealer solution to impregnate the glass cloth with the sealer solution. When the glass cloth was sufficiently impregnated with the sealer solution, the glass cloth was continuously pulled up, and after removing the excess sealer solution adhering to the glass cloth, it was put into an oven and dried at 80 °C / 10 minutes and cured at 120 °C / 10 minutes to obtain a support layer (X) with a thickness of 0.05 mm. Next, a coating solution was prepared by adding 20% by mass of xylene to Composition 1-B. The coating solution was applied to one side of the support layer (X) at a coating speed of 0.5 m / min using a comma coater. The oven temperature was set to 80 °C / 80 °C / 150 °C / 150 °C, and a laminate having a silicone rubber layer (Y) which is the cured product of Composition 1-B on the support layer (X) was obtained. Subsequently, Composition 2-B was applied to the surface of the silicone rubber layer (Y), press-molded under the conditions of 120 °C / 10 min to cure Composition 2-B, and a thermally conductive silicone composite sheet in which the support layer (X), the silicone rubber layer (Y), and the silicone rubber layer (Z) which is the cured product of Composition 2-B were laminated in this order was obtained. X: 0.05 mm, Y: 0.10 mm, Z: 0.35 mm, total thickness: 0.5 mm

[0066] (Example 3) 80% by mass of xylene was added to Composition 1-A to obtain a glass cloth sealing liquid. The sealing liquid was placed in a container having a volume capable of placing a glass cloth, and then the glass cloth was placed in the container, immersed in the sealing liquid, and the glass cloth was impregnated with the sealing liquid. When the glass cloth was impregnated with the sealing liquid at room temperature for 5 minutes, the glass cloth was continuously pulled up, and after removing the excess sealing liquid adhering to the glass cloth, it was put into an oven, dried at 80°C for 10 minutes, and cured at 120°C for 10 minutes to obtain a support layer (X) with a thickness of 0.05 mm. Next, a coating liquid was prepared by adding 20% by mass of xylene to Composition 1-A. The coating liquid was coated on one side of the support layer (X) at a coating speed of 0.5 m / min using a comma coater. The oven temperature was set at 80°C / 80°C / 150°C / 150°C, and heating was performed for a total of 15 minutes to obtain a laminate having a silicone rubber layer (Y) which is a cured product of Composition 1-A on the support layer (X). Subsequently, Composition 2-A was coated on the surface of the silicone rubber layer (Y), press-molded under the conditions of 120°C / 10 min, and Composition 2-A was cured to obtain a thermally conductive silicone composite sheet in which a support layer (X), a silicone rubber layer (Y), and a silicone rubber layer (Z) which is a cured product of Composition 2-A are laminated in this order. X: 0.05 mm, Y: 0.15 mm, Z: 1.8 mm, total thickness: 2.0 mm

[0067] (Example 4) 60% by mass of xylene was added to Composition 1-C to obtain a glass cloth sealing liquid. The sealing liquid was placed in a container having a volume capable of placing a glass cloth, and then the glass cloth was placed in the container, immersed in the sealing liquid, and the glass cloth was impregnated with the sealing liquid. When the glass cloth was impregnated with the sealing liquid at room temperature for 5 minutes, the glass cloth was continuously pulled up, and after removing the excess sealing liquid adhering to the glass cloth, it was put into an oven, dried at 80°C for 10 minutes, and cured at 120°C for 10 minutes to obtain a support layer (X) with a thickness of 0.05 mm. Next, a coating solution was prepared by adding 30% by mass of xylene to Composition 1-C. The coating solution was coated on one side of the support layer (X) at a coating speed of 0.5 m / min using a comma coater. The oven temperature was set at 80°C / 80°C / 150°C / 150°C, and heating was performed for a total of 15 minutes to obtain a laminate having a silicone rubber layer (Y), which is a cured product of Composition 1-C, on the support layer (X). Subsequently, Composition 2-A was coated on the surface of the silicone rubber layer (Y) and press-molded under the conditions of 120°C / 10 min to cure Composition 2-A, thereby obtaining a thermally conductive silicone composite sheet in which the support layer (X), the silicone rubber layer (Y), and a silicone rubber layer (Z), which is a cured product of Composition 2-A, were laminated in this order. X: 0.05 mm, Y: 0.15 mm, Z: 0.8 mm, total thickness: 1.0 mm

[0068] (Example 5) 60% by mass of xylene was added to Composition 1-C to obtain a glass cloth sealing solution. The sealing solution was placed in a container having a volume capable of placing a glass cloth, and then the glass cloth was placed in the container and immersed in the sealing solution to impregnate the glass cloth with the sealing solution. When the glass cloth was impregnated with the sealing solution at room temperature for 5 minutes, the glass cloth was continuously pulled up, and after removing the excess sealing solution adhering to the glass cloth, it was put into an oven and dried at 80°C for 10 minutes and cured at 120°C for 10 minutes to obtain a support layer (X) having a thickness of 0.05 mm. Next, a coating solution was prepared by adding 30% by mass of xylene to Composition 1-C. The coating solution was coated on one side of the support layer (X) at a coating speed of 0.5 m / min using a comma coater. The oven temperature was set at 80°C / 80°C / 150°C / 150°C, and heating was performed for a total of 15 minutes to obtain a laminate having a silicone rubber layer (Y), which is a cured product of Composition 1-C, on the support layer (X). Subsequently, Composition 2-B was coated on the surface of the silicone rubber layer (Y) and press-molded under the conditions of 120°C / 10 min to cure Composition 2-B, thereby obtaining a thermally conductive silicone composite sheet in which the support layer (X), the silicone rubber layer (Y), and a silicone rubber layer (Z), which is a cured product of Composition 2-B, were laminated in this order. X: 0.05 mm, Y: 0.15 mm, Z: 1.3 mm, Total thickness: 1.5 mm

[0069] (Example 6) 60% by mass of xylene was added to Composition 1-B to obtain a glass cloth sealing liquid. The sealing liquid was put into a container having a volume capable of placing a glass cloth, and then the glass cloth was placed in the container and immersed in the sealing liquid to impregnate the glass cloth with the sealing liquid. When the glass cloth was impregnated with the sealing liquid at room temperature for 5 minutes, the glass cloth was continuously pulled up, and after removing the excess sealing liquid adhering to the glass cloth, it was put into an oven and dried at 80°C for 10 minutes and cured at 120°C for 10 minutes to obtain a support layer (X) with a thickness of 0.05 mm. Next, a coating liquid was prepared by adding 20% by mass of xylene to Composition 1-B. The coating liquid was coated on one side of the support layer (X) at a coating speed of 0.5 m / min using a comma coater. The oven temperature was set at 80°C / 80°C / 150°C / 150°C, and heating was performed for a total of 15 minutes to obtain a laminate having a silicone rubber layer (Y) which is a cured product of Composition 1-B on the support layer (X). On the other hand, a toluene solution containing 1% by mass of both-end trimethylsiloxy-blocked dimethylpolysiloxane (number of dimethylsiloxane units: 38) was prepared as a primer. Using a gravure coater, the primer was applied to the surface of the silicone rubber layer (Y) of the laminate and dried at 80°C to obtain a dimethylpolysiloxane-treated silicone rubber layer (Y'). Subsequently, Composition 2-B was coated on the surface of the silicone rubber layer (Y'), and press-molded under the conditions of 120°C / 10 min to cure Composition 2-B, obtaining a thermally conductive silicone composite sheet in which a support layer (X), a silicone rubber layer (Y'), and a silicone rubber layer (Z) which is a cured product of Composition 2-B are laminated in this order. X: 0.05 mm, Y: 0.15 mm, Z: 0.8 mm, Total thickness: 1.0 mm

[0070] (Comparative Example 1) A coating solution was prepared by adding a 20% by mass xylene solution to Composition 1-A. On one side of a 50-μm thick fluorine-treated PET film (FL-1-01 (Takara Incorporation)), using a comma coater, the coating solution was applied at a coating speed of 0.5 m / min. The oven temperature was set at 60°C / 60°C / 60°C / 60°C, and heating was carried out for a total of 15 minutes to obtain a laminate having an uncured silicone rubber layer of Composition 1-A on the substrate. With respect to this uncured silicone rubber layer, a glass cloth was laminated at a pressure of 0.1 MPa, immersed in the coating solution, and the coating solution was impregnated into the glass cloth. Thereafter, a fluorine-treated PET film (FL-1-01 (Takara Incorporation)) was further laminated on the coated surface. Subsequently, Composition 2-A was applied to the surface of the laminated fluorine-treated PET film and press-molded under the conditions of 120°C / 10 min to cure Composition 2-A, obtaining a thermally conductive silicone composite sheet. X: 0.05 mm, Y: 0.15 mm, Z: 0.8 mm, total thickness: 1.0 mm

[0071] (Comparative Example 2) In Composition 1-B, without adding Components (B), (C), and (F), instead, 1.5 parts of Perhexa 25B (manufactured by NOF Corporation) was added as a vulcanizing agent to prepare Composition 1-B'. 60% by mass of xylene was added to this Composition 1-B' to obtain a glass cloth sealing solution. The sealing solution was put into a container having a volume capable of placing a glass cloth, and then the glass cloth was placed in the container, immersed in the sealing solution, and the sealing solution was impregnated into the glass cloth. When the sealing solution was impregnated into the glass cloth at room temperature for 5 minutes, the glass cloth was continuously pulled up, and after removing the excess sealing solution adhering to the glass cloth, it was put into an oven and dried at 80°C / 10 minutes and cured at 150°C / 10 minutes to obtain a support layer (X) having a thickness of 0.05 mm. Next, a coating solution was prepared by adding 20% by mass of xylene to Composition 1-B'. The coating solution was coated on one side of the support layer (X) at a coating speed of 0.5 m / min using a comma coater. The oven temperature was set at 80°C / 80°C / 150°C / 150°C, and heating was performed for a total of 15 minutes to obtain a laminate having a silicone rubber layer (Y), which is a cured product of Composition 1-B', on the support layer (X). Subsequently, Composition 2-B was coated on the surface of the silicone rubber layer (Y) and press-molded under the conditions of 120°C / 10 min to cure Composition 2-B, thereby obtaining a thermally conductive silicone composite sheet in which the support layer (X), the silicone rubber layer (Y), and a silicone rubber layer (Z), which is a cured product of Composition 2-B, were laminated in this order. X: 0.05 mm, Y: 0.15 mm, Z: 0.8 mm, total thickness: 1.0 mm

[0072] (Comparative Example 3) An 80% by mass of xylene was added to Composition 1-A to obtain a glass cloth sealer solution. The sealer solution was placed in a container having a volume capable of placing a glass cloth, and then the glass cloth was placed in the container and immersed in the sealer solution to impregnate the glass cloth with the sealer solution. When the glass cloth was impregnated with the sealer solution at room temperature for 5 minutes, the glass cloth was continuously pulled up, and after removing the excess sealer solution adhering to the glass cloth, it was put into an oven and dried at 80°C for 10 minutes and cured at 120°C for 10 minutes to obtain a support layer (X) having a thickness of 0.05 mm. Next, a coating solution was prepared by adding 20% by mass of xylene to Composition 1-A. The coating solution was coated on one side of the support layer (X) at a coating speed of 0.5 m / min using a comma coater. The oven temperature was set at 80°C / 80°C / 150°C / 150°C, and heating was performed for a total of 15 minutes to obtain a laminate having a silicone rubber layer (Y), which is a cured product of Composition 1-A, on the support layer (X). Subsequently, Composition 2-A was applied to the other surface of the support layer (X) of the laminate that does not have the silicone rubber layer (Y), and press-molded under the conditions of 120°C / 10 min to cure Composition 2-A, obtaining a thermally conductive silicone composite sheet in which the silicone rubber layer (Y), the support layer (X), and the silicone rubber layer (Z) which is the cured product of Composition 2-A are laminated in this order. X: 0.05 mm, Y: 0.15 mm, Z: 0.15 mm, total thickness: 0.35 mm

[0073] (Comparative Example 4) 80% by mass of xylene was added to Composition 1-A to obtain a glass cloth sizing solution. The sizing solution was put into a container having a volume capable of placing a glass cloth, and then the glass cloth was placed in the container and immersed in the sizing solution to impregnate the glass cloth with the sizing solution. When the glass cloth was impregnated with the sizing solution at room temperature for 5 minutes, the glass cloth was continuously pulled up, and after removing the excess sizing solution adhering to the glass cloth, it was put into an oven and dried at 80°C / 10 minutes and cured at 120°C / 10 minutes to obtain a sized glass cloth with a thickness of 0.05 mm. Next, a coating solution was prepared by adding 20% by mass of xylene to Composition 1-A. The coating solution was applied to one side of the sized glass cloth by a comma coater at a coating speed of 0.5 m / min. The oven temperature was set to 80°C / 80°C / 150°C / 150°C, and heating was performed for a total of 15 minutes to obtain a laminate having a silicone rubber layer (Y) which is the cured product of Composition 1-A on the sized glass cloth. Subsequently, Composition 2-A was applied to the other surface of the sized glass cloth layer of the laminate that does not have the silicone rubber layer (Y), and press-molded under the conditions of 120°C / 10 min to cure Composition 2-C, obtaining a thermally conductive silicone composite sheet in which the silicone rubber layer (Y), the sized glass cloth layer, and the silicone rubber layer (Z) which is the cured product of Composition 2-C are laminated in this order. X: 0.05 mm, Y: 0.15 mm, Z: 1.8 mm, total thickness: 2.0 mm

[0074] <Evaluation of Composite Sheet> [Adhesion between the high-hardness thermally conductive silicone rubber layer (Y) and the low-hardness thermally conductive silicone rubber layer (Z)] In the obtained thermally conductive silicone composite sheet, when the low-hardness thermally conductive silicone rubber layer was peeled off from the high-hardness thermally conductive silicone rubber layer, the case with adhesive residue was defined as "cohesive failure", and the case without adhesive residue and with separation was defined as "interface peeling".

[0075] [Compressive stress] The maximum stress when the obtained thermally conductive silicone composite sheet was compressed by 50% at a compression rate of 0.5 mm / min using an autograph (manufactured by Shimadzu Corporation) was measured.

[0076] [Oil bleed] The obtained thermally conductive silicone composite sheet was cut into a disk shape with a diameter of 13 mm, placed on a ground glass, compressed by 50% using a compression jig, and then aged at 100 °C for 100 hours in the compressed state. After aging, the compression was released, and the width (mm) of the oil oozing out onto the ground glass from the thermally conductive silicone composite sheet was measured.

[0077] [Number of uses of the release PET film] The number of uses of the release PET film used until the formation of the thermally conductive silicone composite sheet was described.

[0078] The results of Examples 1 to 6 are shown in Table 3, and the results of Comparative Examples 1 to 4 are shown in Table 4.

[0079]

Table 3

[0080]

Table 4

[0081] As can be seen from Tables 3 and 4, in Examples 1 to 5, it is possible to supply a thermally conductive silicone composite sheet that shows good adhesion and compression characteristics without using a release PET film and also has excellent reliability in terms of oil bleed. On the other hand, in Comparative Example 1, when forming the high-hardness thermally conductive silicone layer, the release PET film was used twice, which was a problem in terms of increased cost and the addition of a peeling process by the user. In Comparative Example 2, since the high-hardness thermally conductive silicone rubber layer was prepared by a peroxide vulcanization system, good adhesion with the low-hardness thermally conductive silicone rubber layer could not be obtained, and furthermore, oil bleed increased significantly. In Comparative Examples 3 and 4, a composite sheet was formed with a mesh-shaped reinforcing material plugged with a thermally conductive material as an intermediate layer. In Comparative Example 3, even if good adhesion was obtained between the high-hardness thermally conductive silicone rubber layer and the low-hardness thermally conductive silicone rubber layer, the thickness of the low-hardness thermally conductive silicone rubber layer was thin, and the compression stress when highly compressed became high, which was a problem. Also, in Comparative Example 4, when the low-hardness silicone rubber layer was made highly thermally conductive, interfacial peeling occurred, which was a problem.

Claims

1. A thermally conductive silicone composite sheet in which a support layer (X), a high-hardness thermally conductive silicone rubber layer (Y), and a low-hardness thermally conductive silicone rubber layer (Z) are laminated in this order, The support layer (X) is formed by plugging a mesh reinforcing material with a cured product of a thermally conductive composition, The high-hardness thermally conductive silicone rubber layer (Y) and the low-hardness thermally conductive silicone rubber layer (Z) are each a cured product of an addition-curing type silicone rubber composition. The shore A hardness measured by the method described in JIS K6253-1:2012 of the high-hardness thermally conductive silicone rubber layer (Y) is 50 to 97, and the Asker C hardness measured by the method described in JIS K7312:1996 of the low-hardness thermally conductive silicone rubber layer (Z) is 2 to 30. A thermally conductive silicone composite sheet.

2. The thermally conductive silicone composite sheet according to claim 1, wherein the mesh reinforcing material is a glass cloth.

3. The thermally conductive silicone composite sheet according to claim 1, wherein the high-hardness thermally conductive silicone rubber layer (Y) is a cured product of an addition-curing type silicone rubber composition containing the following (A1) to (D1). (A1) Organopolysiloxane having two or more alkenyl groups in one molecule and an average degree of polymerization of 100 to 20,000: 100 parts by mass (B1) Organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule: an amount such that the ratio of the number of moles of hydrosilyl groups in component (B1) to the number of moles of alkenyl groups in component (A1) is 1.0 to 3.5 (C1) Platinum group metal-based catalyst: 0.1 to 1,000 ppm in terms of the mass of the platinum group metal (D1) Thermally conductive filler: 300 to 4,000 parts by mass

4. To the addition-curing type silicone rubber composition, (E1) as a surface treatment agent, the following formula (2) 【Chemical formula 1】 (In the formula, R 5is independently an alkyl group having 1 to 6 carbon atoms, and c is a number from 4 to 100. The thermally conductive silicone composite sheet according to claim 3, comprising a dimethylpolysiloxane having a molecular chain segment end blocked with a trialkoxy group.

5. The thermally conductive silicone composite sheet according to claim 1, wherein the thermally conductive material constituting the (X) layer is the same as the thermally conductive silicone rubber composition constituting the high-hardness thermally conductive silicone rubber layer (Y).

6. The thermally conductive silicone composite sheet according to claim 1, wherein the low-hardness thermally conductive silicone rubber layer (Z) is a cured product of an addition-curing type silicone rubber composition containing the following (A2) to (E2). (A2) An organopolysiloxane having two or more alkenyl groups in one molecule and an average degree of polymerization of 100 to 2,000: 100 parts by mass (B2) An organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule: an amount such that the ratio of the number of moles of hydrosilyl groups in the (B2) component to the number of moles of alkenyl groups in the (A2) component is 0.5 to 1.5 (C2) A platinum group metal-based catalyst: 0.1 to 1,000 ppm in terms of the mass of the platinum group metal (D2) A thermally conductive filler: 500 to 4,000 parts by mass (E2) A dimethylpolysiloxane having a molecular chain segment end blocked with a trialkoxy group represented by the following formula (2) as a surface treatment agent: 10 to 300 parts by mass 【Chemical Formula 2】 (In the formula, R 5 is independently an alkyl group having 1 to 6 carbon atoms, and c is a number from 4 to 100.)

7. The thermally conductive silicone composite sheet according to claim 1, wherein the thickness of the high-hardness thermally conductive silicone rubber layer (Y) is 0.15 to 0.5 mm, and the thickness of the entire thermally conductive silicone composite sheet is 0.3 to 10 mm.

8. The thermally conductive silicone composite sheet according to claim 1, wherein the thickness of the support layer (X) is 0.03 to 0.10 mm.

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