Thermally conductive silicone composition, cured product thereof, and method for producing same

Abstract

This thermally conductive silicone composition contains (A) an organopolysiloxane, (B) an aluminum oxide powder, (C) an amorphous aluminum nitride powder having a BET specific surface area of 1.0-4.0 m2 / g and an average particle diameter of 0.5-5 μm, and (D) an organopolysiloxane having, in one molecule, at least one silyl group represented by general formula (1) -SiR1 a(OR2)3-a, and having a viscosity of 0.01-30 Pa·s at 25 °C. The thermally conductive silicone composition is particularly suitable as a heat dissipation member for an electronic component and has excellent insulation properties and thermal conductivity.

Description

Thermally conductive silicone composition, cured product thereof, and manufacturing method

[0001] The present invention relates to a silicone composition with excellent thermal conductivity, and in particular to a thermally conductive silicone composition with excellent insulating properties that, when used as a heat dissipation member for electronic components, can be incorporated into electronic devices without damaging heat-generating electronic components such as power devices, transistors, thyristors, and CPUs (central processing units), and to a cured product thereof, as well as a method for producing the composition.

[0002] In heat-generating electronic components such as power devices, transistors, thyristors, and CPUs, how to remove the heat generated during use is an important issue. Conventionally, a common method for removing heat has been to attach the heat-generating electronic components to a heat-dissipating fin or metal plate via an electrically insulating heat-dissipating sheet, and the heat-dissipating sheet used is made of silicone resin with a thermally conductive filler dispersed therein.

[0003] In recent years, the amount of heat generated by circuits in electronic components has increased with the increasing integration density. Therefore, thermal conductivity at high temperatures, such as temperatures above 100°C, particularly 150°C, has become important. This has led to a demand for materials with even higher thermal conductivity. To improve the thermal conductivity of thermally conductive materials, a common approach has been to incorporate a highly thermally conductive filler, such as aluminum oxide powder or aluminum nitride powder, into a matrix resin (see Patent Documents 1 to 4: JP 2005-162555 A, JP 2003-342021 A, JP 2002-280498 A, and JP 2005-209765 A).

[0004] Therefore, in order to improve thermal conductivity, a method has been disclosed for producing a spherical aluminum oxide powder having a specified average sphericity, hydroxyl group content, and average particle size of 10 to 50 μm, and a highly thermally conductive resin composition having a specified average particle size of 0.3 to 1 μm and a specified blending ratio and volume ratio of each aluminum oxide. However, there is a problem that a spherical aluminum oxide powder having an average particle size of up to 50 μm has insufficient thermal conductivity (Patent Document 5: Japanese Patent No. 5755977).

[0005] Furthermore, while a thermally conductive silicone composition using an alumina powder with an average particle size of 0.1 to 100 μm has been proposed, no specific thermal conductivity or viscosity is specified. Furthermore, a thermally conductive silicone composition has been disclosed that is specified as containing spherical alumina powder with an average particle size of 5 to 50 μm (but excluding 5 μm) and spherical or irregularly shaped alumina powder with an average particle size of 0.1 to 5 μm, and in which the blending ratio and weight ratio of aluminum oxide for each is specified. However, like Patent Document 5, this composition also has the problem that the average sphericity or hydroxyl group content of the spherical alumina with a large average particle size is not specified, and is therefore insufficient to achieve high thermal conductivity (Patent Document 6: Republished Japanese Patent Publication No. 2002-092693).

[0006] Therefore, the average sphericity is 0.8 or more, and the number of hydroxyl groups is 30 / nm 2 Although a thermally conductive silicone composition using spherical aluminum oxide powder with an average particle size of 50 to 150 μm has been proposed, there are limitations to achieving even higher thermal conductivity while maintaining flowability.

[0007] Japanese Patent Application Laid-Open No. 2005-162555 Japanese Patent Application Laid-Open No. 2003-342021 Japanese Patent Application Laid-Open No. 2002-280498 Japanese Patent Application Laid-Open No. 2005-209765 Japanese Patent No. 5755977 Republished Japanese Patent No. 2002-092693 Japanese Patent No. 6648837

[0008] The present invention has been made in view of the above circumstances, and its object is to provide a thermally conductive silicone composition that has excellent insulating properties and thermal conductivity, making it particularly suitable as a heat dissipation material for electronic components.

[0009] As a result of extensive research into achieving the above object, the present inventors have discovered that an organopolysiloxane having the following constitution is used: (A) an organopolysiloxane; (B) an organopolysiloxane having an average sphericity of 0.8 or more and a hydroxyl group density of 30 / nm 2 (C) a spherical aluminum oxide powder having an average particle size of 50 to 150 μm or less, and a BET specific surface area of ​​1.0 to 4.0 m 2 / g and having an average particle size of 0.5 to 5 μm, and (D) an aluminum nitride powder having an irregular shape, the powder being represented by the following general formula (1): -SiR 1 a (OR 2 )3-a (1) (wherein, R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, and a is 0, 1, or 2.) The present inventors discovered that the above-mentioned problems can be solved by blending an organopolysiloxane having a viscosity of 0.01 to 30 Pa s at 25°C and at least one silyl group represented by the formula (I) in each molecule, such that the volume ratio of the blending proportions of components (B) and (C) and the total amount of components (B) and (C) fall within specific ranges, thereby completing the present invention. Furthermore, the silicone composition can also be blended with a curing agent to form a curable composition.

[0010] Therefore, the present invention provides the following inventions: 1. (A) an organopolysiloxane, (B) an organopolysiloxane having an average sphericity of 0.8 or more and 30 hydroxyl groups / nm 2 (C) a spherical aluminum oxide powder having an average particle size of 50 to 150 μm or less, and a BET specific surface area of ​​1.0 to 4.0 m 2 / g and having an average particle size of 0.5 to 5 μm, and (D) an aluminum nitride powder having an irregular shape, the powder being represented by the following general formula (1): -SiR 1 a (OR 2 ) 3-a (1) (wherein, R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2is independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, and a is 0, 1, or 2. A thermally conductive silicone composition comprising an organopolysiloxane containing per molecule at least one silyl group represented by the formula (I) and having a viscosity of 0.01 to 30 Pa·s at 25°C, wherein the volume ratio of components (B) to (C) ((B):(C)) is 5:5 to 8:2, the total amount of components (B) and (C) is 52 to 79 volume% of the thermally conductive silicone composition, the viscosity of the thermally conductive silicone composition at 25°C is 30 to 800 Pa·s when measured at 10 rpm with a spiral viscometer, and the thermal conductivity is 8.0 W / m·K or higher as measured by the hot disc method in accordance with ISO 22007-2. 2. Furthermore, the thermally conductive silicone composition comprises an organopolysiloxane having an oxygen content of 0.5% by mass or less and a BET specific surface area of ​​1.0 m 2 The thermally conductive silicone composition according to 1, comprising an aluminum nitride powder having a viscosity of less than 1000 kJ / g, an average particle size of 10 to 40 μm, and a proportion of coarse particles having a diameter of 44 to 105 μm in a volume-based laser diffraction particle size distribution of 10.0 mass% or less of the total mass of component (E). 3. The thermally conductive silicone composition according to 2, wherein the total amount of components (B), (C), and (E) in the thermally conductive silicone composition is 80 to 85 volume%, the amount of component (E) in the thermally conductive silicone composition is 30 to 35 volume%, and the thermal conductivity is 8.5 W / m·K or higher as measured by the hot disc method in accordance with ISO 22007-2. 4. The thermally conductive silicone composition according to any one of 1 to 3, further comprising a curing agent. 5. The thermally conductive silicone composition according to 4, which is an addition reaction curing type, a condensation reaction curing type, or an organic peroxide curing type. 6. The thermally conductive silicone composition according to 5, which is an addition reaction curing type. 7. A cured product of the thermally conductive silicone composition according to any one of 4 to 6. 8. (A) Organopolysiloxane, (B) Average sphericity of 0.8 or more, 30 hydroxyl groups / nm 2 (C) a spherical aluminum oxide powder having an average particle size of 50 to 150 μm or less, and a BET specific surface area of ​​1.0 to 4.0 m 2 / g and having an average particle size of 0.5 to 5 μm, and (D) an aluminum nitride powder having an irregular shape, the powder being represented by the following general formula (1): -SiR 1 a (OR2 ) 3-a (1) (wherein, R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 wherein each of the formula (I) and (II) is independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, and a is 0, 1, or 2.

[0011] According to the present invention, it is possible to provide a thermally conductive silicone composition that has excellent insulating properties and thermal conductivity.

[0012] The present invention will be described in detail below. The term "thermally conductive silicone composition" may sometimes be abbreviated simply as "silicone composition." [Component (A)] The organopolysiloxane of component (A) is the main component of the silicone composition of the present invention, and may be used alone or in combination of two or more. Examples of groups bonded to silicon atoms in this organopolysiloxane include linear alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and eicosyl; branched alkyl groups such as isopropyl, tertiary butyl, isobutyl, 2-methylundecyl, and 1-hexylheptyl; cyclohexane, ... alkenyl groups such as vinyl group, allyl group, butenyl group, pentenyl group, hexenyl group, etc.; aryl groups such as phenyl group, tolyl group, xylyl group, etc.; aralkyl groups such as benzyl group, phenethyl group, 2-(2,4,6-trimethylphenyl)propyl group, etc.; and halogenated alkyl groups such as 3,3,3-trifluoropropyl group, 3-chloropropyl group, etc., of which alkyl groups, alkenyl groups, and aryl groups are preferred, and methyl groups, vinyl groups, and phenyl groups are particularly preferred.

[0013] There are no limitations on the viscosity of the organopolysiloxane at 25°C, but it is preferably 20 to 100,000 mPa·s, more preferably 50 to 100,000 mPa·s, even more preferably 50 to 50,000 mPa·s, and particularly preferably 100 to 50,000 mPa·s. If the viscosity is too low, the physical properties of the silicone composition may be significantly reduced, while if the viscosity is too high, the handling and workability of the silicone composition may be significantly reduced. Note that this absolute viscosity is a value measured using a rotational viscometer (the same applies hereinafter unless otherwise specified).

[0014] The molecular structure of the organopolysiloxane is not limited, and examples thereof include linear, branched, partially branched linear, and dendritic (dendrimer) structures, with linear and partially branched linear structures being preferred. Examples of such organopolysiloxanes include single polymers having these molecular structures, copolymers comprising these molecular structures, and mixtures of these polymers.

[0015] Specific examples include dimethylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylpolysiloxanes capped at both molecular chain terminals with methylphenylvinylsiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, methyl(3,3,3-trifluoropropyl)polysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with silanol groups, and dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with silanol groups, and the formula: (CH3)3SiO 1 / 2 and a siloxane unit represented by the formula: (CH3)2(CH2=CH)SiO 1 / 2 and a siloxane unit represented by the formula: CHSiO 3 / 2 and a siloxane unit represented by the formula: (CH3)2SiO 2 / 2and organosiloxane copolymers composed of siloxane units represented by the formula (I), dimethylpolysiloxanes capped at both molecular chain terminals with silanol groups, dimethylsiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with silanol groups, dimethylpolysiloxanes capped at both molecular chain terminals with trimethoxysiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers capped at both molecular chain terminals with trimethoxysilyl groups, dimethylpolysiloxanes capped at both molecular chain terminals with methyldimethoxysiloxy groups, dimethylpolysiloxanes capped at both molecular chain terminals with triethoxysiloxy groups, and dimethylpolysiloxanes capped at both molecular chain terminals with trimethoxysilylethyl groups. These can be used alone or in appropriate combination of two or more types.

[0016] When the silicone composition cures via a hydrosilylation reaction, component (A) is preferably (A-I) an organopolysiloxane having an average of 0.1 or more silicon-bonded alkenyl groups per molecule, more preferably an organopolysiloxane having an average of 0.5 or more silicon-bonded alkenyl groups per molecule, and even more preferably an organopolysiloxane having an average of 0.8 or more silicon-bonded alkenyl groups per molecule. This is because if the average number of silicon-bonded alkenyl groups per molecule is below the lower limit of the above range, the resulting silicone composition tends not to cure sufficiently. Examples of the silicon-bonded alkenyl groups in this organopolysiloxane include the same alkenyl groups as described above, with vinyl groups being preferred. Furthermore, groups bonded to silicon atoms in this organopolysiloxane other than alkenyl groups include the same linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as described above, with alkyl groups and aryl groups being preferred, and methyl groups and phenyl groups being particularly preferred.

[0017] When the silicone composition cures via a condensation reaction, component (A) is (A-II) an organopolysiloxane containing at least two silanol groups or silicon-bonded hydrolyzable groups per molecule. Examples of the silicon-bonded hydrolyzable groups in this organopolysiloxane include alkoxy groups such as methoxy, ethoxy, and propoxy; alkenoxy groups such as vinyloxy, propenoxy, isopropenoxy, and 1-ethyl-2-methylvinyloxy; alkoxyalkoxy groups such as methoxyethoxy, ethoxyethoxy, and methoxypropoxy; acyloxy groups such as acetoxy and octanoyloxy; ketoxime groups such as dimethylketoxime and methylethylketoxime; amino groups such as dimethylamino, diethylamino, and butylamino; aminoxy groups such as dimethylaminooxy and diethylaminooxy; and amide groups such as N-methylacetamido and N-ethylacetamido. Furthermore, examples of groups bonded to silicon atoms in this organopolysiloxane other than silanol groups and silicon-bonded hydrolyzable groups include the same linear alkyl groups, branched alkyl groups, cyclic alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as described above.

[0018] When the silicone composition is cured by a free radical reaction caused by an organic peroxide, the organopolysiloxane of component (A) is not limited, but preferred is (A-III) an organopolysiloxane having at least one silicon-bonded alkenyl group per molecule. Examples of the group bonded to the silicon atom in this organopolysiloxane include the same linear alkyl groups, branched alkyl groups, cyclic alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as described above, with alkyl groups, alkenyl groups, and aryl groups being preferred, and methyl groups, vinyl groups, and phenyl groups being more preferred.

[0019] The blend amount of component (A) in the silicone composition is preferably 1.0 to 4.0 mass %, and more preferably 1.0 to 3.0 mass %.

[0020] [Component (B)] Component (B) has an average sphericity of 0.8 or more and a hydroxyl group density of 30 / nm2 The aluminum oxide powder is spherical and has an average particle size of 50 to 150 μm or less. Two or more types of aluminum oxide powder with different average particle sizes may be used in combination, provided that the above range is satisfied.

[0021] The crystalline structure of the aluminum oxide powder may be either a single crystal or a polycrystal, but the crystalline phase is preferably the α phase from the viewpoint of high thermal conductivity, and the specific gravity is 3.7 (g / cm 3 ) or more is preferable. By making the specific gravity 3.7 or more, the proportion of voids and low crystalline phases present inside the particles can be reduced, and thermal conductivity can be further increased. The particle size of the aluminum oxide powder can be adjusted by classification and mixing operations.

[0022] The average sphericity is 0.8 or more, and more preferably 0.9 or more. If the average sphericity is less than 0.8, the fluidity may decrease, the particles may come into contact with each other more, the unevenness of the sheet surface increases, the interfacial thermal resistance increases, and the thermal conductivity tends to decrease. There is no particular upper limit, but the closer to a sphere (average sphericity 1), the better.

[0023] The average sphericity in the present invention can be measured by importing particle images taken with a scanning electron microscope into an image analyzer, for example, a JEOL product called "JSM-7500F," and then measuring the particle's projected area (X) and perimeter (Z) from the photograph. If the area of ​​a perfect circle corresponding to the perimeter (Z) is (Y), the particle's sphericity can be expressed as X / Y. Therefore, assuming a perfect circle with the same perimeter as the perimeter (Z) of the sample particle, Z = 2πr and Y = πr 2 Therefore, Y = π × (Z / 2π) 2 The sphericity of each particle is given by: Sphericity = X / Y = X × 4π / Z 2 The sphericity of 100 randomly selected particles thus obtained is determined, and the average value is taken as the average sphericity.

[0024] 30 hydroxyl groups / nm 2 or less, and 2 The lower limit is not particularly limited, but is preferably 5 particles / nm 2 The number of surface hydroxyl groups is 30 / nm2 If the content exceeds this range, the silicone composition tends to be poorly filled and the thermal conductivity tends to be poor.

[0025] The number of hydroxyl groups, i.e., the surface hydroxyl group concentration, in the present invention can be measured by Karl Fischer coulometric titration, for example, using a trace moisture analyzer CA-100 manufactured by Mitsubishi Chemical Corporation. Specifically, 0.3 to 1.0 g of a sample is placed in a moisture vaporizer, and the temperature is raised by heating with an electric heater while supplying dehydrated argon gas as a carrier gas. In the Karl Fischer coulometric titration, the amount of moisture generated at temperatures exceeding 200°C up to 900°C is defined as the amount of surface hydroxyl groups. The concentration of surface hydroxyl groups is calculated from the measured amount of moisture and specific surface area.

[0026] The average particle size is 50 to 150 μm, preferably 60 to 140 μm. If the average particle size is less than 50 μm, the particles tend to have less contact with each other, increasing the interparticle contact thermal resistance and resulting in poor thermal conductivity. If the average particle size is more than 150 μm, the sheet surface may become uneven, increasing the interfacial thermal resistance and tending to deteriorate the packing ability.

[0027] The average particle size in the present invention can be measured using a laser diffraction particle size analyzer, such as the "Laser Diffraction Particle Size Analyzer SALD-2300" manufactured by Shimadzu Corporation. To prepare an evaluation sample, 50 cc of pure water and 5 g of the thermally conductive powder to be measured are added to a glass beaker, stirred with a spatula, and then dispersed in an ultrasonic cleaner for 10 minutes. The dispersed solution of the thermally conductive material powder is added dropwise to the sampler section of the analyzer using a dropper, and the absorbance is allowed to stabilize until it can be measured. Measurement is performed once the absorbance has stabilized. In a laser diffraction particle size analyzer, the particle size distribution is calculated from the light intensity distribution data of the diffracted / scattered light by the particles detected by the sensor. The average particle size is calculated by multiplying the measured particle size value by the relative particle amount (difference %) and dividing by the total relative particle amount (100%). The average particle size is the average diameter of the particles.

[0028] [Component (C)] Component (C) is a sintered body having a BET specific surface area of ​​1.0 to 4.0 m 2The BET specific surface area of ​​component (C) is 1.0 to 4.0 m / g, and the average particle size is 0.5 to 5 μm. These powders can be used alone or in combination of two or more. 2 / g, preferably 1.5 to 3.5. The average particle size is 0.5 to 5 μm, preferably 0.6 to 3 μm. Shapes other than spherical are considered irregular. Within the scope of the present invention, one type may be used alone, or two or more types with different average particle sizes may be used in combination. The BET specific surface area (nitrogen gas adsorption method) of component (C) is 1.0 m 2 If the specific surface area of ​​component (C) is less than 4.0 m / g, the unevenness of the sheet surface will increase, which will increase the interfacial heat resistance and tend to deteriorate the thermal conductivity. 2 If the average particle size exceeds 1 / g, the contact between particles will be reduced, and the thermal conductivity will tend to deteriorate due to an increase in interparticle contact thermal resistance. The BET specific surface area of ​​component (C) can be analyzed using, for example, Mountech's "Macsorb (registered trademark) HM Model-1201" (the same applies hereinafter). If the average particle size of component (C) is less than 0.5 μm, the contact between particles will be reduced, and the thermal conductivity will tend to deteriorate due to an increase in interparticle contact thermal resistance. Furthermore, if it exceeds 5 μm, the unevenness of the sheet surface will increase, increasing the interfacial thermal resistance and decreasing the thermal conductivity. Note that when component (C) is spherical, it must have an average sphericity of 0.8 or more and a density of 30 hydroxyl groups / nm, similar to component (B). 2 The average particle size, average sphericity, and hydroxyl group content are measured in the same manner as for component (B).

[0029] The volume ratio ((B):(C)) of the above-mentioned components (B) and (C) is 5:5 to 8:2, preferably 5.0:5.0 to 8.0:2.0, and more preferably 6:4 to 7:3. When the volume ratio of component (B) is less than 5 (component (B) and component (C) combined = 10, the same applies below), the packing properties of components (B) and (C) tend to deteriorate. On the other hand, when the volume ratio of component (B) is greater than 8, it becomes difficult to pack components (B) and (C) densely, and thermal conductivity tends to decrease. Furthermore, the total amount of components (B) and (C) in the silicone composition is 52 to 79% by volume, and 75 to 79% by volume is preferred to achieve a thermal conductivity of 8.0 W / m / K or higher. If the total amount of the (B) component and the (C) component is less than 52% by volume, it is difficult to obtain the desired thermal conductivity, and if the total amount of the (B) component and the (C) component is more than 79% by volume, the filling property tends to be poor.

[0030] [Component (D)] The component (D) is a compound represented by the following general formula (1): —SiR 1 a (OR 2 ) 3-a (1) (wherein, R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, and a is 0, 1, or 2.) The organopolysiloxane contains at least one silyl group represented by the formula (I) in each molecule and has a viscosity of 0.01 to 30 Pa s at 25°C. These organopolysiloxanes may be used alone or in combination of two or more. This component enables the surface treatment of components (B), (C), and (E), described below, with silane coupling agent (D).

[0031] Examples of component (D) include organopolysiloxanes represented by the following general formula (2). (In the formula, R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, b is an integer of 2 to 100, and a is 0, 1, or 2.

[0032] In formulas (1) and (2), R1 are independently unsubstituted or substituted monovalent hydrocarbon groups, preferably having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and even more preferably 1 to 3 carbon atoms. Examples of such groups include linear alkyl groups, branched alkyl groups, cyclic alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups. Examples of linear alkyl groups include methyl groups, ethyl groups, propyl groups, hexyl groups, octyl groups, and decyl groups. Examples of branched alkyl groups include isopropyl groups, isobutyl groups, tert-butyl groups, and 2-ethylhexyl groups. Examples of cyclic alkyl groups include cyclopentyl groups and cyclohexyl groups. Examples of alkenyl groups include vinyl groups and allyl groups. Examples of aryl groups include phenyl groups and tolyl groups. Examples of aralkyl groups include 2-phenylethyl groups and 2-methyl-2-phenylethyl groups. Examples of halogenated alkyl groups include a 3,3,3-trifluoropropyl group, a 2-(nonafluorobutyl)ethyl group, and a 2-(heptadecafluorooctyl)ethyl group. 1 As the alkyl group, a methyl group and a phenyl group are preferred.

[0033] In formulas (1) and (2), R 2 are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group. Examples of alkyl groups include R 1 Examples of the alkoxyalkyl group include a methoxyethyl group and a methoxypropyl group. Examples of the alkenyl group include R 1 Examples of the acyl group include the same groups as those exemplified in R. The number of carbon atoms is preferably 1 to 8. Examples of the acyl group include an acetyl group and an octanoyl group. 2 is preferably an alkyl group, and particularly preferably a methyl group or an ethyl group. b is an integer of 2 to 100, preferably 5 to 50. a is 0, 1 or 2, preferably 0.

[0034] Specific examples of suitable organopolysiloxanes of component (D) include the following: (In the formula, Me is a methyl group.)

[0035] The viscosity of the organopolysiloxane of component (D) at 25°C, measured at 10 rpm using a spiral viscometer, is 0.01 to 30 Pa·s, preferably 0.01 to 10 Pa·s. If the viscosity is lower than 0.01 Pa·s, oil bleeding from the silicone composition may occur easily, and the composition may be prone to dripping. If the viscosity is higher than 30 mPa·s, the fluidity of the resulting silicone composition may be significantly reduced, potentially worsening application workability.

[0036] The blend amount of component (D) is preferably 5 to 900 parts by mass, more preferably 10 to 900 parts by mass, and even more preferably 20 to 700 parts by mass, per 100 parts by mass of component (A).

[0037] Examples of silane coupling agents other than component (D) include vinyl silane coupling agents, epoxy silane coupling agents, acrylic silane coupling agents, and long-chain alkyl silane coupling agents, and these can be used alone or in appropriate combinations of two or more in combination with component (D). Among these, long-chain alkyl silane coupling agents are preferred, and decyltrimethoxysilane is preferred.

[0038] The surface treatment method for components (B), (C), and (E) described below with the silane coupling agent other than component (D) can be a spraying method using a fluid nozzle, a stirring method with shear force, a dry method using a ball mill or mixer, or a wet method using an aqueous or organic solvent system. Stirring is performed at a temperature that does not cause destruction of the spherical aluminum oxide powder. In the dry method, the temperature in the system or the drying temperature after treatment is appropriately determined depending on the type of surface treatment agent within a range that does not cause volatilization or decomposition of the surface treatment agent, but is generally 80 to 180°C.

[0039] When the silane coupling agent other than the component (D) is used, it is preferably used in an amount of 0.1 to 5 parts by mass per 100 parts by mass of the total of the components (B), (C), and (E), which will be described later. If the amount is less than 0.1 part by mass, the effect of the addition may be small, and if the amount is more than 5 parts by mass, the effect corresponding to the amount used may not be realized.

[0040] [Component (E)] Furthermore, the use of component (E) in the present invention is suitable for further increasing the thermal conductivity while maintaining the fluidity of the silicone composition of the present invention. Component (E) of the present invention is a silicone compound having an oxygen content of 0.5% by mass or less and a BET specific surface area of ​​1.0 m 2 / g or less, an average particle size of 10 to 40 μm, and the proportion of coarse particles having a size of 44 to 105 μm in a volume-based laser diffraction particle size distribution is 10.0 mass % or less of the total amount of component (E). These aluminum nitride powders may be used singly or in combination of two or more.

[0041] The oxygen content of component (E) is 0.5% by mass, preferably 0.2% by mass or less. The lower limit is not particularly limited and may be 0.01% by mass or even 0% by mass. By setting the oxygen content, which serves as a guide for the nitriding rate of component (E), within the above range, the thermal conductivity of the silicone composition is further improved. However, if the oxygen content exceeds 0.5% by mass, the crystallite size becomes small and the chemical purity of component (E) deteriorates, which may result in poor thermal properties after moisture resistance. The oxygen content of component (E) can be measured using an oxygen / nitrogen analyzer and analyzed by comparison with a standard silicon nitride. An oxygen / nitrogen analyzer such as the "EMGA-920" manufactured by Shimadzu Corporation can be used.

[0042] The BET specific surface area (as determined by nitrogen gas adsorption) of component (E) is preferably as low as possible, and is preferably 1.0 m or less, in order to increase the thermal conductivity of the silicone composition. 2 The lower limit of the BET specific surface area is not particularly limited, but from the upper limit of the average particle size specified for component (C) and the proportion of coarse particles specified, it is preferable that the lower limit be 0.05 m 2The BET specific surface area of ​​component (E) can be analyzed using, for example, a Macsorb (registered trademark) HM Model-1201 manufactured by Mountech.

[0043] The average particle size of component (E) measured by laser diffraction particle size distribution (volume basis) is 10 to 40 μm, preferably 20 to 40 μm. An average particle size of less than 10 μm may result in poor fillability into the resin and significantly increased viscosity. On the other hand, an average particle size of more than 40 μm is preferable from the viewpoint of increasing the thermal conductivity of the silicone composition, but may facilitate oil separation over time. Furthermore, the proportion of coarse particles of 44 to 105 μm measured by volume-based laser diffraction particle size distribution is 10.0% by mass or less of the total component (E), preferably 8.0% by mass or less. A proportion of coarse particles of 44 to 105 μm of 10.0% by mass or less of the total component (E) improves both thermal resistance and high thermal conductivity. While there is no particular lower limit for the proportion of coarse particles of 44 to 105 μm measured by laser diffraction particle size distribution, it can be approximately 0.01% by mass. On the other hand, by making the proportion of coarse particles of 44 to 105 μm 10.0 mass% or less of the entire component (E), the desired thermal resistance can be more easily achieved, but if the proportion of coarse particles of 44 to 105 μm exceeds 10.0 mass% of the entire component (E), the thickness of 44 to 105 μm may not be achieved.

[0044] The component (E) can be obtained by any method that satisfies the requirements of the present invention, including reduction nitridation and direct nitridation. Of these, direct nitridation is preferred because it is easier to obtain a material with an oxygen content of 0.5% by mass or less. The direct nitridation method improves chemical purity, further improving thermal properties after moisture resistance.

[0045] The method for producing component (E) is not particularly limited and may be carried out according to a known direct nitriding method (including combustion synthesis). One example is a method in which metallic aluminum powder is nitrided alone in a nitrogen atmosphere at 0.2 to 3 MPa. If necessary, it can be pulverized, and pulverization can be carried out according to known methods such as a ball mill, jet mill, or crusher.

[0046] Another example is a method that involves heat-treating component (E) obtained by direct nitriding in a non-oxidizing atmosphere at 1,600 to 2,000°C. This method removes the corners from particles with angular, irregular shapes and turns them into rounded particles, which is suitable for lowering the viscosity of the silicone composition. Note that temperatures below 1,600°C make it difficult to achieve a rounded shape, while temperatures above 2,000°C can cause component (E) particles to sinter together, resulting in an undesired average particle size.

[0047] The shape of component (E) is not particularly limited, and may be spherical, polyhedral, or irregular, as long as it does not impair the present invention. Among these, a rounded shape is preferred, as it reduces the initial viscosity of the silicone composition, minimizes viscosity change even when treated at 200°C, and further improves heat resistance. In the present invention, the term "rounded" refers to a shape with an aspect ratio of 2.0 or less.

[0048] Component (E) is preferably added within a range that does not impair the present invention. When component (E) is added, specifically, in order to avoid a significant decrease in the thermal conductivity of the thermally conductive silicone composition, the amount of component (E) relative to the total amount of the silicone composition is preferably 30 to 35% by volume. By adding component (E) in an amount of 30% by volume or more, the thermal conductivity of the silicone composition can be further improved. On the other hand, if the amount exceeds 35% by volume, the viscosity of the silicone composition may become too high. The median particle size can be measured by laser diffraction using, for example, a laser diffraction particle size analyzer SALD-2300 manufactured by Shimadzu Corporation.

[0049] When component (E) is added, the total amount of components (B), (C), and (E) in the thermally conductive silicone composition is preferably 80 to 85% by volume, more preferably 80 to 84% by volume. By adding 80% or more by volume, the thermal conductivity of the silicone composition can be further improved. If the amount exceeds 85% by volume, it may become difficult to fill the thermally conductive filler.

[0050] The thermally conductive silicone composition of the present invention may be used as is, or may be further blended with a curing agent to form a curable composition.

[0051] Curable thermally conductive silicone compositions can be prepared in the following three forms. The organopolysiloxane (A), which is the base polymer, is made from the organopolysiloxanes of the components (A-I) to (A-III) described above, and can be blended with the thermally conductive fillers (B) and (C), and, as needed, (B), (C), and (E). [I] Addition reaction-curable thermally conductive silicone composition [II] Condensation reaction-curable thermally conductive silicone composition [III] Organic peroxide-curable thermally conductive silicone composition Among these, the addition reaction-curable thermally conductive silicone composition [I] is preferred because it cures quickly and does not produce by-products. Specific examples of each composition are shown below.

[0052] [I] Addition-Reaction-Curable Thermally Conductive Silicone Composition When the silicone composition is an addition-reaction-curable thermally conductive silicone composition that cures via a hydrosilylation reaction, the silicone composition uses the component (AI) shown above as (A) and further contains the following components, where the curing agents are the following components (F) and (G): (F) an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms, (G) a platinum group metal-based curing catalyst, and (H) if necessary, an addition reaction inhibitor.

[0053] [Component (F)] An organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms is a component that functions as a crosslinking agent. Examples of groups bonded to silicon atoms in the organohydrogenpolysiloxane include the same linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as described above. Preferred are alkyl groups and aryl groups, with methyl and phenyl groups being particularly preferred. The viscosity of component (F) at 25°C is not limited, but should preferably be in the range of 1 to 100,000 mm. 2 / s is preferably in the range of 1 to 5,000 mm 2 / s is more preferable. The molecular structure of component (F) is not limited, and examples include linear, branched, partially branched linear, cyclic, and dendritic (dendrimer) structures. Examples of such organopolysiloxanes include homopolymers having these molecular structures, copolymers comprising these molecular structures, and mixtures thereof. The above is the kinematic viscosity, measured at 25°C using an Ostwald viscometer (the same applies hereinafter).

[0054] Examples of component (F) include dimethylpolysiloxanes terminated at both molecular chain terminals with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers terminated at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers terminated at both molecular chain terminals with dimethylhydrogensiloxy groups, and copolymers of the formula: (CH3)3SiO 1 / 2 and a siloxane unit represented by the formula: (CH3)2HSiO 1 / 2 and a siloxane unit represented by the formula: SiO 4 / 2 Examples of the organosiloxane copolymer include organosiloxane copolymers comprising siloxane units represented by the following formula: and these can be used alone or in appropriate combination of two or more.

[0055] The amount of component (F) blended is the amount necessary for curing the silicone composition, and specifically, it is preferably an amount such that, per mole of silicon-bonded alkenyl groups in component (A-I), there are 0.1 to 10 moles of silicon-bonded hydrogen atoms in component (F), more preferably an amount in the range of 0.1 to 5 moles, and particularly preferably an amount in the range of 0.1 to 3.0 moles. This is because if the amount of this component blended is below the lower limit of the above range, the resulting silicone composition tends not to cure sufficiently, whereas if it exceeds the upper limit of the above range, the resulting silicone cured product will be very hard and may develop numerous cracks on the surface.

[0056] (G) The platinum group metal curing catalyst is a catalyst for accelerating the curing of the silicone composition, and examples thereof include chloroplatinic acid, an alcohol solution of chloroplatinic acid, an olefin complex of platinum, an alkenylsiloxane complex of platinum, and a carbonyl complex of platinum.

[0057] The amount of component (G) blended is the amount necessary for curing the thermally conductive silicone composition, and specifically, it is preferably an amount such that the platinum metal in component (G) is in the range of 0.01 to 1,000 ppm by mass relative to component (AI), and particularly preferably an amount in the range of 0.1 to 500 ppm. This is because if the amount of component (G) blended is below the lower limit of this range, the resulting silicone composition tends not to cure sufficiently, while if an amount exceeding the upper limit of this range is blended, the cure rate of the resulting silicone composition does not improve significantly.

[0058] (H) Curing Reaction Inhibitor In order to adjust the curing rate of the silicone composition and improve handling and workability, a curing reaction inhibitor can be blended in. Examples of curing reaction inhibitors include acetylene-based compounds such as 2-methyl-3-butyn-2-ol, 2-phenyl-3-butyn-2-ol, and 1-ethynyl-1-cyclohexanol; ene-yne ​​compounds such as 3-methyl-3-penten-1-yne and 3,5-dimethyl-3-hexen-1-yne; and other hydrazine-based compounds, phosphine-based compounds, and mercaptan-based compounds. These can be used alone or in appropriate combinations of two or more.

[0059] Although there are no particular restrictions on the amount of component (H) blended, it is preferable that the blending amount be 0.0001 to 1.0 mass% of the silicone composition, which will result in more favorable workability and curing speed for the silicone composition.

[0060] [II] Condensation-Curable Thermally Conductive Silicone Composition When the silicone composition is a condensation-curable thermally conductive silicone composition, the component (A-II) shown above is used as the component (A) and the following components are further included, with the curing agent being the component (I) shown below: (I) a silane having at least three silicon-bonded hydrolyzable groups per molecule or a partial hydrolyzate thereof, and (J) a condensation reaction catalyst, if necessary.

[0061] Examples of the silicon-bonded hydrolyzable groups in component (I) include the same alkoxy groups, alkoxyalkoxy groups, acyloxy groups, ketoxime groups, alkenoxy groups, amino groups, aminoxy groups, and amide groups as described above.In addition to the hydrolyzable groups described above, the silicon atoms of this silane may be bonded with, for example, the same linear alkyl groups, branched alkyl groups, cyclic alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as described above.Examples of such silanes or their partial hydrolyzates include methyltriethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, and ethylorthosilicate.

[0062] The amount of component (I) blended is the amount necessary for curing the silicone composition, and specifically, it is preferably in the range of 0.01 to 20 parts by mass, and especially preferably in the range of 0.1 to 10 parts by mass, per 100 parts by mass of component (A-II). If the amount of this silane or its partial hydrolyzate blended is less than the lower limit of this range, the storage stability of the resulting silicone composition may be reduced, while if the amount exceeds the upper limit of this range, the curing of the resulting silicone composition may be significantly slowed.

[0063] Component (J) is an optional component and is not essential when, for example, a silane having a hydrolyzable group such as an aminoxy group, an amino group, or a ketoxime group is used as the curing agent. Examples of such condensation reaction catalysts include organic titanate esters such as tetrabutyl titanate and tetraisopropyl titanate; organic titanium chelate compounds such as diisopropoxybis(acetylacetate)titanium and diisopropoxybis(ethylacetoacetate)titanium; organic aluminum compounds such as aluminum tris(acetylacetonate) and aluminum tris(ethylacetoacetate); organic aluminum compounds such as zirconium tetra(acetylacetonate) and zirconium tetrabutylate; dibutyltin dioctoate and dibutyltin dioctoate; metal salts of organic carboxylic acids such as tin naphthenate, tin oleate, tin butyrate, cobalt naphthenate, and zinc stearate; amine compounds and salts thereof such as hexylamine and dodecylamine phosphate; quaternary ammonium salts such as benzyltriethylammonium acetate; lower fatty acid salts of alkali metals such as potassium acetate and lithium nitrate; dialkylhydroxylamines such as dimethylhydroxylamine and diethylhydroxylamine; and guanidyl group-containing organosilicon compounds.

[0064] When component (J) is incorporated, its amount need only be the amount necessary to cure the silicone composition, and specifically, it is preferably in the range of 0.01 to 20 parts by mass, and particularly preferably in the range of 0.1 to 10 parts by mass, per 100 parts by mass of component (A). This is because, when this catalyst is essential, if the amount of this catalyst incorporated is below the lower limit of the above range, the resulting silicone composition tends not to cure sufficiently, and conversely, if the amount exceeds the upper limit of the above range, the storage stability of the resulting silicone composition tends to decrease.

[0065] [III] Organic Peroxide-Curable Thermally Conductive Silicone Composition When the silicone composition is an organic peroxide-curable thermally conductive silicone composition, the silicone composition uses the component (A-III) shown above as the component (A) and further contains the component shown below, and the curing agent is the organic peroxide shown below (K).

[0066] (K) Examples of organic peroxides include benzoyl peroxide, dicumyl peroxide, 2,5-dimethylbis(2,5-t-butylperoxy)hexane, di-t-butyl peroxide, and t-butyl perbenzoate.

[0067] The amount of component (K) blended is the amount necessary for curing the silicone composition, and specifically, it is preferably in the range of 0.1 to 5 parts by mass per 100 parts by mass of the organopolysiloxane of component (A-III) above. If the amount of component (K) blended is below the lower limit of this range, the resulting silicone composition tends not to cure sufficiently, while if the amount blended exceeds the upper limit of this range, the curing rate of the resulting silicone composition does not improve significantly and may even cause voids.

[0068] Furthermore, the silicone composition of the present invention may contain other optional components, as long as the object of the present invention is not impaired, such as fillers such as zinc oxide, fumed silica, precipitated silica, and fumed titanium oxide, fillers whose surfaces have been hydrophobized with an organosilicon compound, adhesion promoters such as 3-glycidoxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane, and other flame retardants and plasticizers such as pigments, dyes, fluorescent dyes, heat-resistant additives, and triazole-based compounds. Furthermore, thermally conductive fillers other than component (B) may also be blended within the scope of the present invention, such as aluminum powder, copper powder, silver powder, nickel powder, gold powder, zinc oxide powder, magnesium oxide powder, boron nitride powder, aluminum nitride powder, diamond powder, and carbon powder.

[0069] [Production Method] The silicone composition of the present invention can be prepared by uniformly mixing the predetermined amounts of the above-mentioned components, for example, (A) an organopolysiloxane, (B) a silicone-based silicone having an average sphericity of 0.8 or more and a hydroxyl group density of 30 / nm 2 (C) a spherical aluminum oxide powder having an average particle size of 50 to 150 μm or less, and a BET specific surface area of ​​1.0 to 4.0 m 2 / g and an average particle size of 0.5 to 5 μm, optionally (E) (E) an irregularly shaped aluminum nitride powder having an oxygen content of 0.5 mass% or less and a BET specific surface area of ​​1.0 m 2 / g or less, an average particle size of 10 to 40 μm, and a proportion of coarse particles of 44 to 105 μm in a volume-based laser diffraction particle size distribution is 10.0 mass % or less of the total of component (E), and (D) an aluminum nitride powder having a composition represented by the following general formula (1): -SiR 1 a (OR 2 ) 3-a (1) (wherein, R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, and a is 0, 1, or 2.) An example of a production method includes a step of mixing an organopolysiloxane containing at least one silyl group represented by the formula (I) and having a viscosity of 0.01 to 30 Pa s at 25°C per molecule, such that the volume ratio of components (B) to (C) ((B):(C)) is 5:5 to 8:2, and the total amount of components (B) and (C) in the thermally conductive silicone composition is 52 to 79 volume %. When component (E) is added, the total amount of components (B), (C), and (E) in the silicone composition is 80 to 85 volume %.

[0070] [Thermal Conductive Silicone Composition] The thermal conductivity of the thermally conductive silicone composition, measured by the hot disk method in accordance with ISO 22007-2, is preferably 8.0 W / m K or more, more preferably 8.5 W / m K or more, and even more preferably 9.0 W / m K or more. There are no particular upper limits and the upper limit may be higher, but it can be set to 11.0 W / m K or less. The measurement temperature is 25°C.

[0071] The viscosity of the thermally conductive silicone composition at 25°C, measured at 10 rpm using a spiral viscometer, is 30 to 800 Pa·s, and preferably 100 to 600 Pa·s.

[0072] [Cured Product] When the silicone composition is curable, the curing method is not limited. Examples include molding the silicone composition and then leaving it at room temperature, or molding the silicone composition and then heating it to 40 to 200°C, resulting in a silicone elastomer molded product. The properties of the silicone rubber thus obtained are not limited, but examples include gel, low-hardness rubber, and high-hardness rubber. The cured thickness is preferably 150 μm or more. There is no particular upper limit, but considering the size of the heat-generating electronic component using this composition, 5 mm or less is preferred. The hardness of the cured product is preferably 3 to 90, more preferably 5 to 80, when the silicone composition is poured into a mold that will give a cured thickness of 6 mm, cured at 100°C for 1 hour, and then measured with a Shore 00 hardness tester 30 seconds after pressing the 6 mm-thick cured product.

[0073] The components used in the examples and comparative examples are shown below. The present invention will be explained in detail below with reference to the examples and comparative examples, but the present invention is not limited to the following examples. In the following formula, Me is a methyl group, and the bonding order of the siloxane units does not matter. The components used are shown below. Component (A) A-1: ​​Dimethylpolysiloxane having an absolute viscosity (25°C) of 400 mPa·s, a specific gravity (25°C) of 0.98, both ends capped with dimethylvinylsilyl groups, and a vinyl group content of 0.018 mol / 100 g A-2: Dimethylpolysiloxane having a specific gravity (25°C) of 1.07, a kinematic viscosity (25°C) of 400 mm 2 A-3: Specific gravity (25°C) of 1.00, kinematic viscosity (25°C) of 1,000 mm 2 / s Dimethylsiloxane-diphenylsiloxane copolymer with both ends of the molecular chain blocked by trimethylsiloxy groups

[0074] Component (B) Spherical aluminum oxide (specific gravity: 3.98) having the properties shown in the table below

[0075]

[0076] Component (C): Irregular shaped aluminum nitride powder (specific gravity: 3.32) having the properties shown in the table below.

[0077]

[0078] Component (D) D-1: Represented by the following formula, specific gravity (25°C) is 0.97, kinematic viscosity (25°C) is 30 mm 2 / s Organopolysiloxane

[0079] (In the formula, Me represents a methyl group.)

[0080]

[0081] Component (F) F-1: Represented by the following formula, specific gravity (25°C) is 0.97, kinematic viscosity (25°C) is 28 mm 2 The bonding order of the siloxane units is not limited to the order shown below. (wherein Me represents a methyl group) F-2: Represented by the following formula, specific gravity (25°C) is 0.97, kinematic viscosity (25°C) is 17 mm 2 / s organohydrogenpolysiloxane (In the formula, Me represents a methyl group.)

[0082] Component (G) G-1: chloroplatinic acid-1,3-divinyltetramethyldisiloxane complex having a specific gravity (25°C) of 1.00 and a platinum concentration of 1% by mass

[0083] Component (H) H-1: 50% toluene solution of 1-ethynyl-1-cyclohexanol, with a specific gravity (25°C) of 0.92

[0084] [Examples 1 to 7, Comparative Examples 1 to 6] Using the above components, silicone compositions were prepared by the methods described below, and these silicone compositions were used to obtain thermally conductive molded articles. These were then evaluated by the methods described below. The results are also shown in the tables.

[0085] The above components were mixed in the amounts shown in Tables 1 and 2 below to obtain silicone compositions. Specifically, components (A), (B), (C), (D), and, if specified, (E) were placed in a 5-liter gate mixer (manufactured by Inoue Seisakusho Co., Ltd., product name: 5-liter planetary mixer) in the amounts shown in the tables, and mixed at 150°C for 2 hours under degassing and heating. The mixture was then cooled to room temperature (25°C), and component (G) was added and mixed at room temperature (25°C) until uniform. Subsequently, component (H) was added and mixed at room temperature (25°C) until uniform. Components (E) and (F) were then added, and mixed under degassing and heating at room temperature until uniform. The silicone compositions thus obtained were evaluated for viscosity, post-cure hardness, and post-cure thermal conductivity using the methods described below. The results are also shown in the tables.

[0086] [Viscosity Evaluation] The viscosity (initial) of the silicone composition was measured at 25°C using a spiral viscometer: Malcom viscometer (Type PC-10AA, rotation speed 10 rpm). [Hardness Evaluation after Curing] The silicone composition was poured into a mold to give a cured thickness of 6 mm and cured at 100°C for 1 hour. The resulting 6 mm-thick cured product was then measured using a Shore 00 hardness tester. [Thermal Conductivity Evaluation] The silicone composition was poured into a mold to give a cured thickness of 6 mm and cured at 100°C for 1 hour. The thermal conductivity of the resulting 6 mm-thick cured product was then measured at 25°C using a hot disc method thermal property measuring device TPS2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd. (hot disc method in accordance with ISO 22007-2).

[0087]

[0088]

Claims

1. (A) Organopolysiloxane, (B) Average sphericity of 0.8 or more, 30 hydroxyl groups / nm 2 (C) a spherical aluminum oxide powder having an average particle size of 50 to 150 μm or less, and a BET specific surface area of ​​1.0 to 4.0 m 2 / g and having an average particle size of 0.5 to 5 μm, and (D) an aluminum nitride powder having an irregular shape represented by the following general formula (1): -SiR 1 a (OR 2 ) 3-a (1) (wherein, R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups; R 2 is independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, and a is 0, 1, or 2.) A thermally conductive silicone composition comprising an organopolysiloxane having per molecule at least one silyl group represented by the formula: and having a viscosity at 25°C of 0.01 to 30 Pa·s, wherein the volume ratio of the blending proportions of components (B) and (C) ((B):(C)) of above components (B) and (C) is 5:5 to 8:2, the total amount of components (B) and (C) is 52 to 79 volume% in the thermally conductive silicone composition, the viscosity of the thermally conductive silicone composition at 25°C is 30 to 800 Pa·s when measured with a spiral viscometer at a rotation speed of 10 rpm, and the thermal conductivity measured by the hot disk method in accordance with ISO 22007-2 is 8.0 W / m·K or more.

2. Furthermore, (E) the oxygen content is 0.5 mass% or less, and the BET specific surface area is 1.0 m 2 2. The thermally conductive silicone composition according to claim 1, which comprises an aluminum nitride powder having a molecular weight of less than 1.0 mass % based on the total mass of component (E), an average particle size of 10 to 40 μm, and a proportion of coarse particles having a size of 44 to 105 μm, as determined by volume-based laser diffraction particle size distribution, of 10.0 mass % or less based on the total mass of component (E).

3. The thermally conductive silicone composition according to claim 2, wherein the total amount of components (B), (C), and (E) in the thermally conductive silicone composition is 80 to 85 volume % and the amount of component (E) in the thermally conductive silicone composition is 30 to 35 volume %, and the thermal conductivity is 8.5 W / m K or greater when measured by the hot disk method in accordance with ISO 22007-2.

4. The thermally conductive silicone composition of claim 1, further comprising a curing agent.

5. The thermally conductive silicone composition according to claim 4, which is an addition reaction curing type, a condensation reaction curing type, or an organic peroxide curing type.

6. The thermally conductive silicone composition according to claim 5, which is of the addition reaction curing type.

7. A cured product of the thermally conductive silicone composition according to any one of claims 4 to 6.

8. (A) Organopolysiloxane, (B) Average sphericity of 0.8 or more, 30 hydroxyl groups / nm 2 (C) a spherical aluminum oxide powder having an average particle size of 50 to 150 μm or less, and a BET specific surface area of ​​1.0 to 4.0 m 2 / g and having an average particle size of 0.5 to 5 μm, and (D) an aluminum nitride powder having an irregular shape represented by the following general formula (1): -SiR 1 a (OR 2 ) 3-a (1) (wherein, R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups; R 2 is independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, and a is 0, 1, or 2.) and has a viscosity of 0.01 to 30 Pa·s at 25°C.

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