Thermally conductive silicone resin sheet and manufacturing method thereof

Abstract

To provide a thermally conductive silicone resin sheet having excellent thermal conductivity in a thickness direction and having a low specific gravity and a method for producing the same.SOLUTION: A thermally conductive silicone resin sheet comprises a thermally conductive thermosetting silicone resin composition comprising (A) a thermosetting silicone resin and (B) a thermally conductive inorganic filler as a diamagnetic material with an aspect ratio between major and minor axes of 5 or more, a specific gravity of 2.0 or more and less than 3.5, and the major axis of 30 μm or more and 300 μm or less, wherein the thermally conductive silicone resin sheet has a coefficient of thermal conductivity in the thickness direction of 10 W / m K or more and a specific gravity of 2.0 or less. The component (A) comprises (A1) an organopolysiloxane having two or more alkenyl groups, each binding to a silicon atom, in one molecule, (A2) an organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule, (A3) a viscosity modifier composed of a hydrolyzable organopolysiloxane represented by the formula (1), and (A4) a platinum group metal-based hydrosilylation reaction catalyst.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a thermally conductive silicone resin sheet and a method for producing the same. [Background technology]

[0002] In electronic devices such as computers and automobile parts, a heat sink or other heat sink is used to dissipate heat generated from a heat generating body such as a semiconductor element or a machine part. In order to increase the efficiency of heat transfer to the heat dissipation body, a heat conductive sheet may be placed between the heat generating body and the heat dissipation body. As such a heat conductive sheet, for example, a heat conductive sheet filled with and oriented with carbon fibers as a heat conductive material is disclosed in Patent Document 1. A heat conductive sheet in which carbon powder is oriented in the thickness direction of the sheet is disclosed in Patent Document 2. Patent Document 3 discloses a heat conductive sheet in which a heat conductive filler is oriented in the thickness direction and has flexibility. Patent Document 4 discloses a heat conductive sheet that is multi-layered with a flexible layer and a heat conductive layer to reduce contact thermal resistance. In addition, a low hardness and high heat conductive sheet is disclosed, although it is pressure oriented. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-146057 A [Patent Document 2] JP 2014-001388 A [Patent Document 3] Patent No. 6671735 [Patent Document 4] Patent No. 6884456 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, electronic devices have become smaller and more sophisticated, and the amount of heat generated has been steadily increasing. This has led to a demand for a thermally conductive silicone resin sheet with a higher thermal conductivity than conventional thermally conductive silicone resin sheets. In addition, in order to meet the demand for smaller size and lighter weight, a thermally conductive silicone resin sheet with a lower specific gravity than conventional ones and a lower hardness to reduce the contact thermal resistance with the adherend is required. In addition, a demand has been made for an integrated thermally conductive silicone resin sheet with a smaller film thickness and no gaps between layers.

[0005] The present invention has been made to solve the above-mentioned problems, and has an object to provide a thermally conductive silicone resin sheet that has excellent thermal conductivity in the thickness direction and a low specific gravity, and a method for producing the same. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention provides (A) Thermosetting silicone resin: 100 parts by mass (B) a thermally conductive inorganic filler that is a diamagnetic material having an aspect ratio of the major axis and minor axis of 5 or more, a specific gravity of 2.0 or more and less than 3.5, and a major axis of 30 μm or more and 300 μm or less: 30 to 150 parts by mass A thermally conductive silicone resin sheet which is a cured product of a thermally conductive thermosetting silicone resin composition containing The component (A) is (A1) Organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in each molecule: 100 parts by mass (A2) Organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the molar ratio of hydrosilyl groups in the component (A2) to alkenyl groups bonded to silicon atoms in the component (A1) is 0.5 to 2. (A3) A viscosity modifier comprising a hydrolyzable organopolysiloxane represented by the following formula (1): 50 to 300 parts by mass [ka] (In the formula, R 4are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. 4 or a group represented by the following formula (2), at least one of which is a group represented by the following formula (2), a is 1≦a≦100, and b is 0≦b≦100. [ka] (In the formula, Q is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, and R 5 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 6 are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, and g is an integer of 0 to 2, and (A4) Platinum group metal hydrosilylation catalyst: 0.1 to 2,000 ppm by mass of platinum group metal element relative to the component (A) and The thermally conductive silicone resin sheet has a thermal conductivity in the thickness direction of 10 W / m K or more and a specific gravity of 2.0 or less. to provide.

[0007] Such a thermally conductive silicone resin sheet can provide a thermally conductive silicone resin sheet that has excellent thermal conductivity in the thickness direction, a low specific gravity, and low hardness.

[0008] The present invention also provides a method for producing a semiconductor device comprising the steps of: The component (A1) is preferably represented by the following average composition formula (3). R 1 m R 2 n SiO (4-m-n) / 2 (3) (In the formula, R 1 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 2are independently an alkenyl group having 2 to 6 carbon atoms. m is a positive number of 0.5 to 2.5, and n is a positive number of 0.0001 to 0.7, with the proviso that m+n is a positive number of 0.8 to 2.7.

[0009] In the present invention, such a component (A1) can be used.

[0010] The present invention also provides a method for producing a semiconductor device comprising the steps of: The component (A2) is preferably represented by the following average composition formula (4). R 3 p1 H q1 SiO (4-p1-q1) / 2 (4) (In the formula, R 3 are independently a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. p1 is a positive number of 0.7 to 2.9, and q1 is a positive number of 0.01 to 2.0, with the proviso that p1+q1 is a positive number of 0.71 to 3.0.

[0011] In the present invention, such a component (A2) can be used.

[0012] The present invention also provides a method for producing a semiconductor device comprising the steps of: The component (A3) is preferably represented by the following formula (5). [ka] (In the formula, R 4 , R 5 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 6 are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, g is an integer of 0 to 2, and c is an integer of 5 to 100.

[0013] In the present invention, such a component (A3) can be used.

[0014] The present invention also provides a method for producing a semiconductor device comprising the steps of: The component (B) is preferably one or more diamagnetic materials selected from carbon fiber, graphite, graphene, carbon nanotubes, silicon carbide, and boron nitride.

[0015] In the present invention, such a component (B) can be used.

[0016] The present invention also provides a method for producing a semiconductor device comprising the steps of: A method for producing a thermally conductive silicone resin sheet, comprising: (I) (A) thermosetting silicone resin: 100 parts by mass, (B) a thermally conductive inorganic filler that is a diamagnetic material having an aspect ratio of the major axis and minor axis of 5 or more, a specific gravity of 2.0 or more and less than 3.5, and a major axis of 30 μm or more and 300 μm or less: 30 to 150 parts by mass to obtain a thermally conductive thermosetting silicone resin composition, In the step (I), the component (A) is (A1) 100 parts by mass of an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms per molecule; (A2) an organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the molar ratio of hydrosilyl groups in the component (A2) to alkenyl groups bonded to silicon atoms in the component (A1) is 0.5 to 2; (A3) 50 to 300 parts by mass of a viscosity modifier composed of a hydrolyzable organopolysiloxane represented by the following formula (1): [ka] (In the formula, R 4 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. 4 or a group represented by the following formula (2), at least one of which is a group represented by the following formula (2), a is 1≦a≦100, and b is 0≦b≦100. [ka] (In the formula, Q is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, and R 5 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 6 are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, and g is an integer of 0 to 2, and (A4) a platinum group metal-based hydrosilylation catalyst in an amount of 0.1 to 2,000 ppm, calculated as the platinum group metal element mass, relative to the component (A); Using (II) forming the thermally conductive thermosetting silicone resin composition into a sheet, and applying a magnetic field to the composition formed into the sheet to magnetically orient component (B) in the thickness direction of the sheet; (III) thermally curing the magnetically oriented thermally conductive thermosetting silicone resin composition to obtain a thermally conductive silicone resin sheet having a thermal conductivity in the thickness direction of 10 W / m K or more and a specific gravity of 2.0 or less; A method for producing a thermally conductive silicone resin sheet comprising: to provide.

[0017] According to such a method for producing a thermally conductive silicone resin sheet, it is possible to obtain a thermally conductive silicone resin sheet that has excellent thermal conductivity in the thickness direction, a low specific gravity, and a low hardness.

[0018] The present invention also provides a method for producing a semiconductor device comprising the steps of: The component (A1) is represented by the following average composition formula (3): R 1 m R 2 n SiO (4-m-n) / 2 (3) (In the formula, R 1 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 2are independently an alkenyl group having 2 to 6 carbon atoms. m is a positive number of 0.5 to 2.5, and n is a positive number of 0.0001 to 0.7, with the proviso that m+n is a positive number of 0.8 to 2.7. It is preferable that the value be expressed by the following formula:

[0019] In the present invention, such a component (A1) can be used.

[0020] The present invention also provides a method for producing a semiconductor device comprising the steps of: The component (A2) is represented by the following average composition formula (4): R 3 p1 H q1 SiO (4-p1-q1) / 2 (4) (In the formula, R 3 are independently a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. p1 is a positive number of 0.7 to 2.9, and q1 is a positive number of 0.01 to 2.0, with the proviso that p1+q1 is a positive number of 0.71 to 3.0. It is preferable that the value be expressed by the following formula:

[0021] In the present invention, such a component (A2) can be used.

[0022] The present invention also provides a method for producing a semiconductor device comprising the steps of: The component (A3) is represented by the following formula (5): [ka] (In the formula, R 4 , R 5 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 6 are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, g is an integer of 0 to 2, and c is an integer of 5 to 100. It is preferable that the value be expressed by the following formula:

[0023] In the present invention, such a component (A3) can be used.

[0024] The present invention also provides a method for producing a semiconductor device comprising the steps of: The component (B) is preferably one or more diamagnetic materials selected from carbon fiber, graphite, graphene, carbon nanotubes, silicon carbide, and boron nitride.

[0025] In the present invention, such a component (B) can be used. Effect of the Invention

[0026] As described above, the present invention provides a thermally conductive silicone resin sheet that has excellent thermal conductivity in the thickness direction, a low specific gravity, and low hardness. This thermally conductive silicone resin sheet is suitable for removing heat from electric and electronic components that generate heat during use. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] As described above, there has been a demand for the development of a thermally conductive silicone resin sheet that has superior thermal conductivity and a low specific gravity compared to existing thermally conductive silicone resin sheets.

[0028] As a result of extensive investigations into the above problems, the inventors have discovered that the present invention makes it possible to obtain a thermally conductive silicone resin sheet having even higher thermal conductivity and a lower specific gravity, and have thus completed the present invention.

[0029] That is, the present invention provides: (A) Thermosetting silicone resin: 100 parts by mass (B) a thermally conductive inorganic filler that is a diamagnetic material having an aspect ratio of the major axis and minor axis of 5 or more, a specific gravity of 2.0 or more and less than 3.5, and a major axis of 30 μm or more and 300 μm or less: 30 to 150 parts by mass A thermally conductive silicone resin sheet which is a cured product of a thermally conductive thermosetting silicone resin composition containing The component (A) is (A1) Organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in each molecule: 100 parts by mass (A2) Organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the molar ratio of hydrosilyl groups in the component (A2) to alkenyl groups bonded to silicon atoms in the component (A1) is 0.5 to 2. (A3) A viscosity modifier comprising a hydrolyzable organopolysiloxane represented by the following formula (1): 50 to 300 parts by mass [ka] (In the formula, R 4 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. 4 or a group represented by the following formula (2), at least one of which is a group represented by the following formula (2), a is 1≦a≦100, and b is 0≦b≦100. [ka] (In the formula, Q is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, and R 5 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 6 are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, and g is an integer of 0 to 2, and (A4) Platinum group metal hydrosilylation catalyst: 0.1 to 2,000 ppm by mass of platinum group metal element relative to the component (A) and The thermally conductive silicone resin sheet has a thermal conductivity in the thickness direction of 10 W / m K or more and a specific gravity of 2.0 or less. It is.

[0030] The present invention also provides a method for producing a semiconductor device comprising the steps of: A method for producing a thermally conductive silicone resin sheet, comprising: (I) (A) thermosetting silicone resin: 100 parts by mass, (B) a thermally conductive inorganic filler that is a diamagnetic material having an aspect ratio of the major axis and minor axis of 5 or more, a specific gravity of 2.0 or more and less than 3.5, and a major axis of 30 μm or more and 300 μm or less: 30 to 150 parts by mass to obtain a thermally conductive thermosetting silicone resin composition, In the step (I), the component (A) is (A1) 100 parts by mass of an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms per molecule; (A2) an organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the molar ratio of hydrosilyl groups in the component (A2) to alkenyl groups bonded to silicon atoms in the component (A1) is 0.5 to 2; (A3) 50 to 300 parts by mass of a viscosity modifier composed of a hydrolyzable organopolysiloxane represented by the following formula (1): [ka] (In the formula, R 4 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. 4 or a group represented by the following formula (2), at least one of which is a group represented by the following formula (2), a is 1≦a≦100, and b is 0≦b≦100. [ka] (In the formula, Q is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, and R 5 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 6 are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, and g is an integer of 0 to 2, and (A4) a platinum group metal-based hydrosilylation catalyst in an amount of 0.1 to 2,000 ppm, calculated as the platinum group metal element mass, relative to the component (A); Using (II) forming the thermally conductive thermosetting silicone resin composition into a sheet, and applying a magnetic field to the composition formed into the sheet to magnetically orient component (B) in the thickness direction of the sheet; (III) thermally curing the magnetically oriented thermally conductive thermosetting silicone resin composition to obtain a thermally conductive silicone resin sheet having a thermal conductivity in the thickness direction of 10 W / m K or more and a specific gravity of 2.0 or less; A method for producing a thermally conductive silicone resin sheet comprising: It is.

[0031] The present invention will be described in detail below, but the present invention is not limited thereto.

[0032] [Thermal conductive thermosetting silicone resin composition] The thermally conductive thermosetting silicone resin composition used in the present invention contains (A) 100 parts by mass of a thermosetting silicone resin and (B) 30 to 150 parts by mass of a thermally conductive inorganic filler which is a diamagnetic material having an aspect ratio of major axis to minor axis of 5 or more, a specific gravity of 2.0 or more and less than 3.5, and a major axis of 30 μm or more and 300 μm or less.

[0033] [Component (A)] The component (A) is a thermosetting silicone resin and is composed of the components (A1) to (A4) in the above composition.

[0034] [Component (A1)] The alkenyl-containing organopolysiloxane, which is the component (A1), has two or more alkenyl groups bonded to silicon atoms in one molecule, preferably 2 to 20, and more preferably 2 to 10. These may be used alone or in appropriate combination of two or more. The component (A1) may be a polymer composed of a single siloxane unit, or a copolymer composed of two or more kinds of siloxane units. Furthermore, the position of the alkenyl group bonded to the silicon atom in the component (A1) is not particularly limited, and the alkenyl group may be bonded to either the silicon atom at the molecular chain terminal or the silicon atom at a non-terminal of the molecular chain (in the middle of the molecular chain), or may be bonded to both.

[0035] There are no particular limitations on the molecular structure of component (A1), and examples include a linear structure, a partially branched linear structure, a branched structure, a cyclic structure, and a branched cyclic structure. However, it is usually preferred that the organopolysiloxane is substantially linear, and more specifically, it is preferred that the molecular chain is a linear diorganopolysiloxane whose molecular chain is mainly composed of repeating diorganosiloxane units and whose both molecular chain terminals are blocked with triorganosiloxy groups.

[0036] The viscosity of the (A1) component at 25°C is preferably 0.1 to 20,000 mPa·s, more preferably 10 to 1,000 mPa·s. The alkenyl-containing organopolysiloxane of the (A1) component has a number of silicon atoms (or degree of polymerization) per molecule of 3 to 700, preferably about 4 to 300. When the viscosity is 0.1 mPa·s or more, the (B) thermally conductive inorganic filler in the obtained thermally conductive thermosetting silicone resin composition does not settle, and the long-term storage stability is excellent. When the viscosity is 20,000 mPa·s or less, the (B) thermally conductive inorganic filler of diamagnetic material can be reliably oriented in the magnetic field in the obtained thermally conductive thermosetting silicone resin composition, and the obtained thermally conductive silicone resin sheet has high thermal conductivity in the thickness direction. The viscosity values ​​in the present invention are values ​​measured using a rotational viscometer described in JIS K 7117-1:1999.

[0037] As the component (A1), in particular, a compound represented by the following average composition formula (3) R 1 m R 2 n SiO (4-m-n) / 2 (3) (In the formula, R 1 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 2 are each independently an alkenyl group having 2 to 6 carbon atoms. m is a positive number of 0.5 to 2.5, preferably 1.8 to 2.2, and n is a positive number of 0.0001 to 0.7, preferably 0.002 to 0.5, with the proviso that m+n is a positive number of 0.8 to 2.7. In particular, organopolysiloxanes having two or more alkenyl groups bonded to silicon atoms, represented by the following formula, are preferred.

[0038] Above R 1 Specific examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, hexyl, octyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; cycloalkyl groups such as cyclopentyl and cyclohexyl; aralkyl groups such as benzyl, 2-phenylethyl, and 3-phenylpropyl; and groups in which some of the hydrogen atoms bonded to carbon atoms in these hydrocarbon groups have been substituted with halogen atoms such as chlorine atoms and bromine atoms, for example, chloromethyl, 2-bromoethyl, and 3,3,3-trifluoropropyl. Of these, a methyl group, a phenyl group, or a combination of both is preferred.

[0039] R 1 In the case of component (A1) in which R is a methyl group, a phenyl group, or a combination of these two, synthesis is easy and the chemical stability is good. Furthermore, when an organopolysiloxane with particularly good solvent resistance is used as component (A1), R 1 More preferably, is a combination of a 3,3,3-trifluoropropyl group with a methyl group, a phenyl group, or a combination of both.

[0040] Above R 2 Specific examples of R include vinyl, allyl, 1-propenyl, isopropenyl, 1-butenyl, isobutenyl, and hexenyl groups. Among these, vinyl is preferred. 2 The component (A1) in which is a vinyl group is easy to synthesize and has good chemical stability.

[0041] Specific examples of component (A1) include dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, methylvinylpolysiloxanes capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups, and dimethylvinylsiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups. Examples of the organopolysiloxane include methylvinylpolysiloxane capped with dimethylvinylsiloxy groups at both molecular chain terminals, dimethylsiloxane-methylvinylsiloxane copolymer capped with dimethylvinylsiloxy groups at both molecular chain terminals, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer capped with dimethylvinylsiloxy groups at both molecular chain terminals, dimethylsiloxane-methylvinylsiloxane-diphenylsiloxane copolymer capped with dimethylvinylsiloxy groups at both molecular chain terminals, dimethylpolysiloxane capped with divinylmethylsiloxy groups at both molecular chain terminals, and dimethylpolysiloxane capped with trivinylsiloxy groups at both molecular chain terminals. These organopolysiloxanes may be used alone or in combination of two or more, or one or more types with different degrees of polymerization may be used in combination.

[0042] [(A2) component] The component (A2) is an organohydrogenpolysiloxane having two or more hydrosilyl groups in one molecule, and may be used alone or in appropriate combination of two or more. The organohydrogenpolysiloxane of the component (A2) is a curing agent in the thermally conductive thermosetting silicone resin composition, and preferably has three or more hydrosilyl groups in one molecule, more preferably 4 to 300, and even more preferably 5 to 200 hydrosilyl groups.

[0043] The molecular structure of component (A2) is not particularly limited and may be, for example, any resinous material having a linear, branched, cyclic, or three-dimensional network structure. It is preferable to use one represented by the following average composition formula (4). R 3 p1 H q1 SiO (4-p1-q1) / 2 (4) (In the formula, R 3 are independently a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. p1 is a positive number of 0.7 to 2.9, preferably 0.8 to 1.2, and q1 is a positive number of 0.01 to 2.0, preferably 0.01 to 1.01, provided that p1+q1 is a positive number of 0.71 to 3.0.

[0044] R in Equation (4) 3 Examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, isopropyl, isobutyl, tert-butyl, and cyclohexyl; aryl groups such as phenyl, tolyl, and xylyl; aralkyl groups such as benzyl and phenethyl; and halogenated alkyl groups such as 3-chloropropyl and 3,3,3-trifluoropropyl, which exclude aliphatic unsaturated bonds and which are generally unsubstituted or halogen-substituted and have 1 to 10 carbon atoms, and preferably about 1 to 8 carbon atoms. Among these, methyl, ethyl, propyl, phenyl, and 3,3,3-trifluoropropyl are preferred, and methyl is more preferred.

[0045] Specific examples of the organohydrogenpolysiloxane of component (A2) include 1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethylcyclotetrasiloxane, methylhydrogencyclopolysiloxane, methylhydrogensiloxane-dimethylsiloxane cyclic copolymer, tris(dimethylhydrogensiloxy)methylsilane, tris(dimethylhydrogensiloxy)phenylsilane, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain ends with dimethylhydrogensiloxy groups, methylhydrogenpolysiloxane capped at both molecular chain ends with dimethylhydrogensiloxy groups, and copolymers thereof. Methylhydrogenpolysiloxane capped at both molecular chain ends with trimethylsiloxy groups, dimethylpolysiloxane capped at both molecular chain ends with dimethylhydrogensiloxy groups, dimethylsiloxane-diphenylsiloxane copolymer capped at both molecular chain ends with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-diphenylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymer capped at both molecular chain ends with dimethylhydrogensiloxy groups, H(CH3)2SiO 1 / 2 Copolymer of SiO2 units and H(CH3)2SiO 1 / 2 Units and (CH3)3SiO 1 / 2 Examples of the organohydrogenpolysiloxane include copolymers of SiO2 units and SiO2 units, and mixtures of two or more of these organohydrogenpolysiloxanes.

[0046] There are no particular limitations on the viscosity of component (A2) at 25°C, but it is preferably 0.5 to 1,000,000 mPa s, and more preferably 1 to 100,000 mPa s. Furthermore, the number of silicon atoms (or degree of polymerization) in one molecule of the organohydrogenpolysiloxane of component (A2) is preferably 3 to 500, and more preferably 4 to 300.

[0047] The amount of the (A2) component is such that the molar ratio of hydrosilyl groups in the (A2) component to alkenyl groups bonded to silicon atoms in the (A1) component is 0.5 to 2. If the amount of the (A2) component is less than the lower limit, the product may not cure, or the strength of the cured product may be insufficient and the product may not be able to maintain its shape as a molded product and may not be able to be handled. If the amount of the (A2) component is more than the upper limit, the cured product may lose flexibility and have a significantly increased heat resistance, which is undesirable. The molar ratio is more preferably 0.7 to 1.8, and even more preferably 0.8 to 1.7.

[0048] [(A3) component] The thermally conductive thermosetting silicone resin composition of the present invention further contains a viscosity modifier consisting of a hydrolyzable organopolysiloxane as component (A3) in order to reduce the viscosity before heat curing, and can use one type alone or two or more types in appropriate combination. Component (A3) maintains the fluidity of the composition even when the thermally conductive thermosetting silicone resin composition is highly filled with the thermally conductive inorganic filler (B) described below, and imparts good handleability to the composition. Component (A3) is a hydrolyzable organopolysiloxane represented by the following general formula (1), and it is particularly preferable to contain a trifunctional (g=0 in formula (2) below) hydrolyzable organopolysiloxane.

[0049] [ka] (In the formula, R 4 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. 4 or a group represented by the following formula (2), at least one of which is a group represented by the following formula (2), a is 1≦a≦100, and b is 0≦b≦100. [ka] (In the formula, Q is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, and R 5are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 6 are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, and g is an integer of 0 to 2.

[0050] The component (A3) is preferably an organopolysiloxane represented by the following general formula (5), and in particular, an organopolysiloxane having a viscosity at 25° C. of 0.005 to 100 mPa·s is preferred. [ka] (In the formula, R 4 , R 5 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 6 are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, g is an integer of 0 to 2, and c is an integer of 5 to 100.

[0051] In the above formulas (1) and (5), R 4 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms, and examples thereof include a linear alkyl group, a branched alkyl group, a cyclic alkyl group, an aryl group, an aralkyl group, and a halogenated alkyl group.

[0052] Examples of linear alkyl groups include methyl, ethyl, propyl, hexyl, and octyl groups. Examples of branched alkyl groups include isopropyl, isobutyl, tert-butyl, and 2-ethylhexyl groups. Examples of cyclic alkyl groups include cyclopentyl and cyclohexyl groups. Examples of aryl groups include phenyl and tolyl groups. Examples of aralkyl groups include 2-phenylethyl and 2-methyl-2-phenylethyl groups. Examples of halogenated alkyl groups include 3,3,3-trifluoropropyl, 2-(nonafluorobutyl)ethyl, and 2-(heptadecafluorooctyl)ethyl groups. R 4 As the alkyl group, a methyl group and a phenyl group are preferable.

[0053] R 5 is a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 5 As a specific example of R 1 Examples of the above are given below.

[0054] Above R 6 are independently selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms. Examples of the alkyl group include a methyl group, an ethyl group, a propyl group, and a butyl group. Examples of the alkoxyalkyl group include a methoxyethyl group and a methoxypropyl group. Examples of the acyl group include an acetyl group. R 6 is preferably an alkyl group, and particularly preferably a methyl group or an ethyl group.

[0055] a is 1≦a≦100, b is 0≦b≦100, and preferably a+b is 10 to 50. c is an integer of 5 to 100, and preferably an integer of 10 to 50. g is an integer of 0 to 2, and preferably 0. In addition, in the molecule, OR 6 The number of groups is preferably 1 to 6, and more preferably 3 or 6.

[0056] Specific examples of suitable components (A3) include the following:

[0057] [ka]

[0058] The amount of the (A3) component blended is 50 to 300 parts by mass, and more preferably 60 to 250 parts by mass, per 100 parts by mass of the (A1) component. If the amount is less than 50 parts by mass, the thermally conductive thermosetting silicone resin composition may thicken and become impossible to discharge, whereas if the amount is more than 300 parts by mass, the viscosity may be too low, causing the (A3) component to bleed, or, if a thermally conductive filler other than the (B) component is blended, causing sedimentation.

[0059] [(A4) component] The thermally conductive thermosetting silicone resin composition of the present invention contains (A4) a platinum group metal-based hydrosilylation catalyst, which is an addition reaction catalyst for promoting the above reaction. Component (A4) includes well-known catalysts used in hydrosilylation reactions. These can be used alone or in appropriate combination of two or more. Among them, a hydrosilylation catalyst in which a platinum complex such as chloroplatinic acid or chloroplatinate is diluted with an organopolysiloxane having a vinyl group such as an alkenyl group is preferred. This can be obtained by mixing a platinum complex with an organopolysiloxane having a vinyl group. If the platinum complex contains a solvent such as toluene, it is recommended to remove the solvent after mixing.

[0060] The amount of the platinum group metal hydrosilylation catalyst is 0.1 to 2,000 ppm, preferably 0.5 to 1,000 ppm, calculated as the mass of the platinum group metal element relative to component (A). If the amount of the platinum group metal hydrosilylation catalyst added is less than 0.5 ppm, curability will decrease, whereas if it exceeds 1,000 ppm, the cost will increase and it will be uneconomical.

[0061] [(B) Component] The thermally conductive inorganic filler of component (B) is a component for improving the thermal conductivity of the thermally conductive silicone resin sheet. Component (B) is a diamagnetic thermally conductive inorganic filler selected from diamagnetic materials, with a major axis / minor axis aspect ratio of 5 or more, a major axis of 30 μm or more and 300 μm or less, and a specific gravity of 2.0 or more and less than 3.5. By using such a thermally conductive inorganic filler, component (B) in the thermally conductive thermosetting silicone resin composition is easily oriented by application of a magnetic field, and the thermal conductivity in the thickness direction of the produced thermally conductive silicone resin sheet can be improved.

[0062] Among them, it is preferable to use one or more diamagnetic materials selected from carbon fiber, graphite, graphene, carbon nanotube, silicon carbide, and boron nitride.

[0063] The amount of component (B) is 30 to 150 parts by mass, and preferably 35 to 145 parts by mass, per 100 parts by mass of the thermosetting silicone resin (A). If the amount of component (B) is less than 30 parts by mass, the thermal conductivity will be poor, and if it is more than 150 parts by mass, the viscosity of the thermally conductive thermosetting silicone resin composition will be significantly increased, which may make magnetic field orientation difficult.

[0064] [Other ingredients] The thermally conductive thermosetting silicone resin composition may contain any components other than those mentioned above.

[0065] In the present invention, a thermally conductive inorganic filler other than the above component (B) may be blended. Examples include aluminum oxide powder, zinc oxide powder, magnesium oxide, aluminum nitride, boron nitride powder, aluminum, silver, nickel, silicon oxide, magnesium oxide, aluminum nitride, silicon nitride, silicon carbide, metallic silicon, etc. These may be used alone or in appropriate combination of two or more. When these thermally conductive inorganic fillers are blended, the content of the fillers in the thermally conductive thermosetting silicone resin composition is preferably 40 parts by mass or less per 100 parts by mass of the component (A1).

[0066] Other fillers include clays such as wollastonite, talc, aluminum oxide, calcium sulfate, magnesium carbonate, and kaolin; copper carbonates such as aluminum hydroxide, magnesium hydroxide, barite, and malachite; nickel carbonates such as zarakite; barium carbonates such as witherite; strontium carbonates such as strontianite; silicates such as forsterite, sillimanite, mullite, pyrophyllite, kaolinite, and vermiculite; non-reinforcing fillers such as diatomaceous earth; and fillers whose surfaces are treated with organic silicon compounds. These fillers may be used alone or in combination of two or more. When these fillers are blended, the content of the fillers in the heat-conductive thermosetting silicone resin composition is preferably 5 parts by mass or less per 100 parts by mass of the (A1) component.

[0067] In order to improve the adhesiveness of the thermally conductive thermosetting silicone resin composition, an adhesion promoter may be added. Specific examples of adhesion promoters include alkyl alkenyl dialkoxy silanes such as methyl vinyl dimethoxy silane, ethyl vinyl dimethoxy silane, methyl vinyl diethoxy silane, and ethyl vinyl diethoxy silane; alkyl alkenyl dioxime silanes such as methyl vinyl dioxime silane and ethyl vinyl dioxime silane; alkyl alkenyl diacetoxy silanes such as methyl vinyl diacetoxy silane and ethyl vinyl diacetoxy silane; alkenyl alkyl dihydroxy silanes such as methyl vinyl dihydroxy silane and ethyl vinyl dihydroxy silane; organo trialkoxy silanes such as methyl trimethoxy silane, vinyl trimethoxy silane, allyl trimethoxy silane, 3-methacryloxypropyl trimethoxy silane, 3-glycidoxypropyl trimethoxy silane, 3-aminopropyl trimethoxy silane, N-(2-aminoethyl)-3-aminopropyl trimethoxy silane, bis(trimethoxysilyl)propane, and bis(trimethoxysilyl)hexane; triallyl isocyanurate, diaryl isocyanurate compounds such as tris(3-trimethoxysilyl)isocyanurate, tris(3-trimethoxysilylpropyl)isocyanurate, tris(3-triethoxysilylpropyl)isocyanurate, and tris(3-tripoxysilylpropyl)isocyanurate; titanium compounds such as tetraethyl titanate, tetrapropyl titanate, tetrabutyl titanate, tetra(2-ethylhexyl)titanate, titanium ethylacetonate, and titanium acetylacetonate; aluminum compounds such as ethylacetoacetate aluminum diisopropylate, aluminum tris(ethylacetoacetate), alkylacetoacetate aluminum diisopropylate, aluminum tris(acetylacetonate), and aluminum monoacetylacetonate bis(ethylacetoacetate); and zirconium compounds such as zirconium acetylacetonate, zirconium butoxyacetylacetonate, zirconium bisacetylacetonate, and zirconium ethylacetoacetate. The adhesion promoter may be used alone or in appropriate combination of two or more kinds.

[0068] When the adhesion promoter is incorporated, the content of the adhesion promoter in the heat conductive thermosetting silicone resin composition is not particularly limited, but is preferably 0.01 to 10 parts by mass per 100 parts by mass of component (A1).

[0069] [Method of manufacturing thermally conductive silicone resin sheet] The above-mentioned method for producing the thermally conductive silicone resin sheet of the present invention can be exemplified by a method including the following steps (I) to (III).

[0070] (I) This is a step of mixing 100 parts by mass of component (A) and 30 to 150 parts by mass of component (B) to obtain a thermally conductive thermosetting silicone resin composition. Component (A) consists of components (A1) to (A4) in the following blending amounts. (A1) Organopolysiloxane having two or more alkenyl groups bonded to silicon atoms in each molecule: 100 parts by mass (A2) Organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the molar ratio of hydrosilyl groups in the component (A2) to alkenyl groups bonded to silicon atoms in the component (A1) is 0.5 to 2. (A3) A viscosity modifier comprising a hydrolyzable organopolysiloxane represented by the following formula (1): 50 to 300 parts by mass [ka] (In the formula, R 4 are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. 4 or a group represented by the following formula (2), at least one of which is a group represented by the following formula (2), a is 1≦a≦100, and b is 0≦b≦100. [ka] (In the formula, Q is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, and R 5are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R 6 are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, and g is an integer of 0 to 2, and (A4) A platinum group metal-based hydrosilylation catalyst in an amount of 0.1 to 2,000 ppm, calculated as the platinum group metal element mass, relative to the component (A).

[0071] (II) forming the thermally conductive thermosetting silicone resin composition into a sheet, and applying a magnetic field to the composition formed into the sheet to magnetically orient component (B) in the thickness direction of the sheet.

[0072] (III) a step of thermally curing the magnetically oriented thermally conductive thermosetting silicone resin composition to obtain a thermally conductive silicone resin sheet having a thermal conductivity in the thickness direction of 10 W / m K or more and a specific gravity of 2.0 or less.

[0073] In the above step (I), for example, the above components (A1), (A3) and (B) are mixed and mixed using a mixer such as Trimix, Twinmix, Planetary Mixer (all registered trademarks of mixers manufactured by Inoue Seisakusho Co., Ltd.), Ultra Mixer (registered trademark of mixers manufactured by Mizuho Kogyo Co., Ltd.), or Hivis Dispermix (registered trademark of mixers manufactured by Tokushu Kika Kogyo Co., Ltd.). The temperature and time for mixing components (A1), (A3) and (B) are not particularly limited, but are preferably mixed at room temperature to 150°C for 30 minutes to 3 hours, and more preferably mixed at 100°C to 150°C for 1 hour to 2 hours from the viewpoint of the stability of the physical properties of the thermally conductive thermosetting silicone resin composition. The mixture obtained by the above mixing may be blended with (A4) a platinum group metal-based hydrosilylation reaction catalyst and component (A2) and mixed at room temperature to 40°C for 10 minutes to 1 hour to produce a thermally conductive thermosetting silicone resin composition.

[0074] In the above step (II), the magnetic field orientation of the (B) component in the thickness direction of the sheet can be performed by applying a magnetic field strength of 8T to 12T, a magnetic field duration of 5 minutes or more but less than 1 hour, and a temperature during magnetic field application of 60°C to 90°C to magnetically orient the (B) component in the thickness direction of the sheet. By setting the magnetic field strength at 8T or more, the (B) component can be more reliably oriented in the thickness direction of the sheet, and setting it at 12T or less is economical. By setting the magnetic field duration at 5 minutes or more, the (B) component can be more reliably oriented in the thickness direction of the sheet, and setting it at less than 1 hour is economical. If the temperature during magnetic field application is 60°C or more, the viscosity of the composition decreases and the fluidity increases, making it easier for the (B) component to be oriented. If the temperature is 90°C or less, there is no risk that the composition will suddenly harden and lose fluidity, making it impossible to orient the (B) component.

[0075] In the above step (III), the magnetically oriented thermally conductive thermosetting silicone resin composition is thermally cured at 90° C. to 150° C. for 1 to 2 hours to obtain the thermally conductive silicone resin sheet of the present invention.

[0076] [Thermal conductive silicone resin sheet] The thermal conductivity of the thermally conductive silicone resin sheet of the present invention in the thickness direction is 10 W / m·K or more, preferably 20 W / m·K or more, and more preferably 30 W / m·K or more. There is no particular upper limit, but it can be 50 W / m·K or less. If the thermal conductivity in the thickness direction is 10 W / m·K or more, it is suitable for heat dissipation. In the present invention, the thermal conductivity is measured by a xenon flash analyzer manufactured by NETZSCH.

[0077] The specific gravity of the thermally conductive silicone resin sheet of the present invention is 2.0 or less, preferably 1.6 or less, more preferably 1.5 or less, and even more preferably 1.4 or less. Since the thermally conductive silicone resin sheet of the present invention has such a low specific gravity, it is useful from the viewpoint of miniaturization and weight reduction of electronic devices. In the present invention, the specific gravity of the sheet can be measured by the A method (underwater displacement method) described in JIS K6268:1998.

[0078] As described above, the thermally conductive silicone resin sheet of the present invention has a high thermal conductivity in the thickness direction of the sheet despite its low specific gravity. This is because the high aspect ratio thermally conductive inorganic filler of component (B) is oriented in the thickness direction of the sheet by a magnetic field, allowing a smaller amount of component (B) to contribute more effectively to thermal conduction in the thickness direction of the sheet than in the case where no magnetic field orientation is performed.

[0079] In the thermally conductive silicone resin sheet of the present invention, the hardness of the surface close to the magnetic field source during magnetic field orientation is referred to as the backside hardness. A low backside hardness provides good contact with the adherend and is excellent in removing heat from electric and electronic components that generate heat during use, so the backside hardness is preferably low. The backside hardness is preferably 50 to 85, more preferably 60 to 80. The hardness of the thermally conductive silicone resin sheet is a value measured using an Asker C hardness tester according to the method described in JIS K7312:1996. EXAMPLES

[0080] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0081] The components used in the examples and comparative examples are described below. The amounts (parts by mass) of each component in the compositions prepared in the examples and comparative examples are as shown in Tables 1 and 2.

[0082] Ingredient (A1) (A1-1) Dimethylpolysiloxane terminated at both ends with dimethylvinylsiloxy groups, with a viscosity of 600 mPa s (vinyl group content: 0.015 mol / 100 g, equivalent to m = 2.000 and n = 0.011 in formula (3)) (A1-2) Methylpolysiloxane terminated at both molecular chain ends by dimethylvinylsiloxy groups on average, with a viscosity of 30,000 mPa s (vinyl group content: 0.0036 mol / 100 g, equivalent to m = 2.000 and n = 0.003 in formula (3))

[0083] (A2) Component (A2-1) Organohydrogenpolysiloxane represented by the following formula: [ka] (Hydrosilyl group content: 0.00128 mol / g, corresponding to p1=1.969 and q1=0.098 in formula (4)) (A2-2) Organohydrogenpolysiloxane represented by the following formula: [ka] (Hydrosilyl group content: 0.0107 mol / g, corresponding to p1 = 1.320 and q1 = 0.700 in formula (4)) The bonding order of the siloxane units is not limited to the above.

[0084] (A3) Viscosity modifier [ka]

[0085] (A4) Ingredients A platinum group metal hydrosilylation catalyst was used, prepared as follows.

[0086] [Preparation Example: Preparation of Addition Reaction Catalyst] 8.0 g of chloroplatinic acid, HPtCl6·6H2O (37.6% by mass platinum), was placed in a 100 mL reaction flask equipped with a reflux condenser, thermometer, and stirrer, followed by the addition of 40.0 g of ethanol and 16.0 g of divinyltetramethyldisiloxane. After heating and reacting at 70°C for 50 hours, the reaction mixture was neutralized by gradually adding 16 g of sodium bicarbonate while stirring at room temperature (25°C) for 2 hours. The reaction mixture was filtered under suction, and the filtrate was distilled under reduced pressure to essentially remove the ethanol and excess divinyltetramethyldisiloxane, after which it was diluted with toluene to a total weight of 600 g (containing 0.5% by mass of platinum).

[0087] To the above-mentioned toluene solution of platinum-vinylsiloxane complex, 290 g of a dimethylpolysiloxane terminated at both molecular chain terminals with dimethylvinylsiloxy groups and a viscosity of 600 mPa s was added and stirred, and the toluene was removed under reduced pressure at 60°C / 27 hPa. The product from which the toluene had essentially been removed was used as a hydrosilylation reaction catalyst (containing 1.0 mass% platinum) and was blended as component (A4).

[0088] (B) Thermally conductive inorganic filler (diamagnetic) B-1: XN-100-05M (average diameter 1 μm, average length 50 μm, specific gravity 2.2): Made by Nippon Graphite Fiber Co., Ltd. B-2: XN-100-15M (average diameter 1 μm, average length 150 μm, specific gravity 2.2): Made by Nippon Graphite Fiber Co., Ltd. B-3: XN-100-25M (average diameter 1 μm, average length 250 μm, specific gravity 2.2): Made by Nippon Graphite Fiber Co., Ltd. B-4: Spherical aluminum oxide (average particle size 10 μm): manufactured by Admatechs

[0089] The thermally conductive thermosetting silicone resin compositions used in Examples 1 to 10 and Comparative Examples 1 to 10 shown in Tables 1 and 2 were prepared by the following method.

[0090] [Preparation of Thermally Conductive Thermosetting Silicone Resin Composition] Components (A1), (A3) and (B) were blended at room temperature (25°C) in the amounts shown in Tables 1 and 2, and mixed for 10 to 30 minutes using a planetary mixer. The resulting mixture was heated to 150°C and stirred and mixed under reduced pressure for 120 minutes. Heating was then stopped and the mixture was cooled to 50°C or less at room temperature under air blowing conditions. After cooling, components (A2) and (A4), a platinum metal-based hydrosilylation reaction catalyst, were added in the amounts shown in Tables 1 and 2, and the mixture was stirred and mixed at room temperature (25°C) to obtain a thermally conductive thermosetting silicone resin composition.

[0091] [Preparation of thermally conductive silicone resin sheet] The above composition was formed into a sheet and thermally cured by applying a magnetic field under the conditions shown in Tables 1 and 2 to produce a thermally conductive silicone resin sheet.

[0092] The properties of the thermally conductive silicone resin sheet obtained above were measured by the following methods. The measurement results are shown in Tables 1 and 2.

[0093] [Measurement of thermal conductivity in the thickness direction of a thermally conductive silicone resin sheet] Measurement was carried out at 25° C. using a xenon flash analyzer LFA447 manufactured by NETZSCH.

[0094] [Specific gravity measurement] The specific gravity was measured at 25°C according to Method A (underwater displacement method) described in JIS K6268:1998.

[0095] [Backside hardness measurement] In the process of producing a thermally conductive silicone resin sheet, a thermally conductive thermosetting silicone resin composition was filled into a cylindrical container with a bottom, and the bottom surface was treated as the back surface and the open surface as the front surface. The hardness of the back surface of the obtained thermally conductive silicone resin sheet was measured at 25°C using an Asker C hardness tester according to the method described in JIS K7312:1996.

[0096] [Table 1]

[0097] [Table 2]

[0098] The results in Table 1 demonstrate that the thermally conductive silicone resin sheets of the present invention of Examples 1 to 10 not only have excellent thermal conductivity in the thickness direction of the sheet, but also have low backside hardness, which allows for good contact with the adherend, and are therefore excellent at removing heat from electrical and electronic components that generate heat during use. Furthermore, their low specific gravity makes them useful from the standpoint of miniaturization and weight reduction.

[0099] On the other hand, from the results of Table 2, in Comparative Examples 1, 4, and 5, the magnetic field application step was not performed under appropriate conditions, so the (B) component could not be sufficiently oriented, and the thermal conductivity in the thickness direction of the sheet was low. In Comparative Example 2, the amount of the (B) component blended was too small, so the thermal conductivity in the thickness direction of the sheet was low. In Comparative Example 3, the amount of the (B) component blended in the composition was too large, so the viscosity became too high, and the (B) component could not be sufficiently oriented, so the thermal conductivity in the thickness direction of the sheet was low. Furthermore, in Comparative Examples 6 to 10, a large amount of the B-4 component was blended in addition to the (B) component, so a high thermal conductivity was obtained in the thickness direction of the sheet, but the specific gravity was high.

[0100] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention. [Industrial Applicability]

[0101] The above results demonstrate that the thermally conductive silicone resin sheet of the present invention has excellent thermal conductivity and a low specific gravity, making it suitable for removing heat from electronic devices and components.

Claims

1. (A) Thermosetting silicone resin: 100 parts by mass (B) A thermally conductive inorganic filler that is a diamagnetic material having an aspect ratio of the major axis and minor axis of 5 or more, a specific gravity of 2.0 or more and less than 3.5, and a major axis of 30 μm or more and 300 μm or less: 30 to 150 parts by mass A thermally conductive silicone resin sheet which is a cured product of a thermally conductive thermosetting silicone resin composition containing The component (A) is (A1) Organopolysiloxane having two or more alkenyl groups bonded to silicon atoms per molecule: 100 parts by mass (A2) Organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the molar ratio of hydrosilyl groups in component (A2) to alkenyl groups bonded to silicon atoms in component (A1) is 0.5 to 2. (A3) Viscosity modifier consisting of a hydrolyzable organopolysiloxane represented by the following formula (1): 50 to 300 parts by mass 【Chemistry 1】 (In the formula, R ４ are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. ４ or a group represented by the following formula (2), at least one of which is a group represented by the following formula (2), a is 1≦a≦100, and b is 0≦b≦100. 【Chemistry 2】 (In the formula, Q is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, and R ５ are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R ６ are independently selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, and g is an integer of 0 to 2; and (A4) Platinum group metal hydrosilylation catalyst: 0.1 to 2,000 ppm by mass of platinum group metal element relative to the component (A) and The thermally conductive silicone resin sheet is characterized in that the thermal conductivity in the thickness direction is 25 W / m·K or more and the specific gravity is 2.0 or less.

2. 2. The thermally conductive silicone resin sheet according to claim 1, wherein the component (A1) is represented by the following average composition formula (3): R １ ｍ R ２ ｎ SiO （４－ｍ－ｎ）／２ (3) (In the formula, R １ are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R ２ are independently an alkenyl group having 2 to 6 carbon atoms. m is a positive number of 0.5 to 2.5, and n is a positive number of 0.0001 to 0.7, provided that m+n is a positive number of 0.8 to 2.

7.

3. 3. The thermally conductive silicone resin sheet according to claim 1, wherein the component (A2) is represented by the following average composition formula (4): R ３ ｐ１ H ｑ１ SiO （４－ｐ１－ｑ１）／２ (4) (In the formula, R ３ are independently a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. p1 is a positive number of 0.7 to 2.9, and q1 is a positive number of 0.01 to 2.

0. However, p1+q1 is a positive number of 0.71 to 3.

0.

4. The thermally conductive silicone resin sheet according to any one of claims 1 to 3, characterized in that the component (A3) is represented by the following formula (5): 【Chemistry 3】 (In the formula, R ４ , R ５ are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R ６ are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, g is an integer of 0 to 2, and c is an integer of 5 to 100.

5. The thermally conductive silicone resin sheet according to any one of claims 1 to 4, characterized in that the component (B) is one or more diamagnetic materials selected from the group consisting of carbon fiber, graphite, graphene, carbon nanotubes, silicon carbide, and boron nitride.

6. A method for producing a thermally conductive silicone resin sheet, comprising: (I) (A) thermosetting silicone resin: 100 parts by mass, (B) A thermally conductive inorganic filler that is a diamagnetic material having an aspect ratio of the major axis and minor axis of 5 or more, a specific gravity of 2.0 or more and less than 3.5, and a major axis of 30 μm or more and 300 μm or less: 30 to 150 parts by mass to obtain a thermally conductive thermosetting silicone resin composition, In the step (I), the component (A) is (A1) 100 parts by mass of an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms per molecule; (A2) an organohydrogenpolysiloxane having two or more hydrosilyl groups per molecule: an amount such that the molar ratio of hydrosilyl groups in said component (A2) to alkenyl groups bonded to silicon atoms in said component (A1) is 0.5 to 2; (A3) 50 to 300 parts by mass of a viscosity modifier composed of a hydrolyzable organopolysiloxane represented by the following formula (1), 【Chemistry 4】 (In the formula, R ４ are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. ４ or a group represented by the following formula (2), at least one of which is a group represented by the following formula (2), a is 1≦a≦100, and b is 0≦b≦100. 【Chemistry 5】 (In the formula, Q is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, and R ５ are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R ６ are independently selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, and g is an integer of 0 to 2; and (A4) 0.1 to 2,000 ppm, calculated as the mass of the platinum group metal element, of a platinum group metal-based hydrosilylation reaction catalyst relative to the component (A) Using (II) forming the thermally conductive thermosetting silicone resin composition into a sheet, and applying a magnetic field to the composition formed into the sheet to magnetically orient component (B) in the thickness direction of the sheet; (III) heat-curing the magnetically oriented thermally conductive thermosetting silicone resin composition to obtain a thermally conductive silicone resin sheet having a thermal conductivity in the thickness direction of 25 W / m K or more and a specific gravity of 2.0 or less; A method for producing a thermally conductive silicone resin sheet, comprising:

7. The component (A1) is represented by the following average composition formula (3): R １ ｍ R ２ ｎ SiO （４－ｍ－ｎ）／２ (3) (In the formula, R １ are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R ２ are independently an alkenyl group having 2 to 6 carbon atoms. m is a positive number of 0.5 to 2.5, and n is a positive number of 0.0001 to 0.7, provided that m+n is a positive number of 0.8 to 2.

7. The method for producing a thermally conductive silicone resin sheet according to claim 6, characterized in that the thermally conductive silicone resin sheet is represented by the formula:

8. The component (A2) is represented by the following average composition formula (4): R ３ ｐ１ H ｑ１ SiO （４－ｐ１－ｑ１）／２ (4) (In the formula, R ３ are independently a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. p1 is a positive number of 0.7 to 2.9, and q1 is a positive number of 0.01 to 2.

0. However, p1+q1 is a positive number of 0.71 to 3.

0. The method for producing a thermally conductive silicone resin sheet according to claim 6 or 7, characterized in that the thermally conductive silicone resin sheet is represented by the formula:

9. The component (A3) is represented by the following formula (5): 【Chemistry 6】 (In the formula, R ４ , R ５ are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms; R ６ are independently a group selected from an alkyl group having 1 to 4 carbon atoms, an alkoxyalkyl group having 1 to 4 carbon atoms, and an acyl group having 1 to 4 carbon atoms, g is an integer of 0 to 2, and c is an integer of 5 to 100. The method for producing a thermally conductive silicone resin sheet according to any one of claims 6 to 8, characterized in that the thermally conductive silicone resin sheet is represented by the formula:

10. The method for producing a thermally conductive silicone resin sheet according to any one of claims 6 to 9, characterized in that the component (B) is one or more diamagnetic materials selected from the group consisting of carbon fiber, graphite, graphene, carbon nanotubes, silicon carbide, and boron nitride.

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