Thermally conductive silicone composition

Abstract

A thermally conductive silicone composition including: (A) an organopolysiloxane that has a kinetic viscosity of 10-100,000 mm2 / s at 25°C and is 0.1-20 vol% of the entire composition; (B) a hydrolysable organosiloxane that includes an alkoxysilyl group and is 0.1-30 vol% of the composition; (C) aluminum nitride particles that have an average particle diameter of 5 μm to less than 30 μm, are of one or more types selected from irregularly-shaped, round, and polyhedral, and are 10-50 vol% of the composition; (D) aluminum oxide particles that have an average particle diameter of 2 μm to less than 5 μm, have an average sphericity of 0.8 or greater, and are 15-50 vol% of the composition; and (E) zinc oxide particles that have an average particle diameter of 0.1 μm to less than 2.0 μm and are 10-25 vol% of the composition, wherein the total quantity of (C), (D), and (E) is 70-85.0 vol% of the composition, and the composition has high thermal conductivity, good compressibility, and superior displacement resistance.

Description

Thermally conductive silicone composition

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

[0002] It is widely known that semiconductor devices generate heat during use and experience a resulting decrease in performance. Various heat dissipation technologies are used to address this issue. Generally, heat is dissipated by placing a cooling component (such as a heat sink) near the heat-generating component, placing them in close contact, and efficiently removing heat from the cooling component. In this case, if there is a gap between the heat-generating component and the cooling component, air with low thermal conductivity is trapped, reducing thermal conductivity and preventing the temperature of the heat-generating component from dropping sufficiently. To prevent this phenomenon, heat-dissipating materials with good thermal conductivity and conformability to the surface of the component, such as thermal grease and thermal dissipation sheets, are used.

[0003] In recent years, the amount of heat generated during operation in high-end semiconductors, such as server CPUs and vehicle drive IGBTs, has been increasing. This increase in heat generation has also led to improved heat dissipation performance requirements for thermal greases and thermal sheets. While thermal greases are useful as heat dissipation materials for semiconductor devices due to their low contact thermal resistance, lowering the viscosity of thermal greases to achieve good application performance can cause the grease to slip off due to thermal shock or external vibrations on the device, resulting in insufficient heat dissipation and potentially damaging the device.

[0004] Patent Document 1 proposes a high-thermal-conductivity grease that uses metal oxides to achieve both slippage resistance and application performance, but the examples show that it cannot be sufficiently compressed because it contains a high proportion of large aluminum oxide particles of 10 μm or more.On the other hand, Patent Documents 2 and 3 blend a specific proportion of insulating inorganic filler to improve the discharge performance of the thermal grease, achieving low viscosity and high thermal conductivity of 7.5 W / m·K or more, but the examples show that it blends large aluminum nitride particles of 50 μm or more, which makes it difficult to compress and results in insufficient heat dissipation.

[0005] JP 2020-063365 A International Publication No. 2018 / 016566 International Publication No. 2020 / 262449

[0006] 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 high thermal conductivity, good compressibility, and excellent resistance to displacement due to thermal shock.

[0007] As a result of extensive research into achieving the above-mentioned object, the present inventors discovered that a silicone composition containing an organopolysiloxane, a hydrolyzable organosiloxane, aluminum nitride particles having an average particle size of 5 μm or more and less than 30 μm, spherical aluminum oxide particles having an average particle size of 2 μm or more and less than 5 μm, and zinc oxide having an average particle size of 0.1 μm or more and less than 2.0 μm can provide a thermally conductive silicone composition that combines high thermal conductivity with good compressibility, leading to the completion of the present invention.

[0008] Therefore, the present invention provides the following inventions: 1. (A) A viscoelastic composition having a kinematic viscosity at 25°C of 10 to 100,000 mm2, represented by the following general formula (1): 2 / s organopolysiloxane: 0.1 to 20% by volume of the total composition, (However, R 1 are independently saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, and m is a value that indicates that the kinematic viscosity of the organopolysiloxane at 25°C is 10 to 100,000 mm 2 / s.) A thermally conductive silicone composition comprising: (B) a hydrolyzable organosiloxane containing an alkoxysilyl group: 0.1 to 30% by volume of the entire composition; (C) one or more types of aluminum nitride particles having an average particle size of 5 μm or more and less than 30 μm and selected from irregular, rounded, and polyhedral shapes: 10 to 50% by volume of the entire composition; (D) aluminum oxide particles having an average particle size of 2 μm or more and less than 5 μm and an average sphericity of 0.8 or more: 15 to 50% by volume of the entire composition; and (E) zinc oxide particles having an average particle size of 0.1 μm or more and less than 2.0 μm: 10 to 25% by volume of the entire composition, wherein the total amount of components (C), (D), and (E) is 70 to 85.0% by volume of the entire composition. 2. A thermally conductive silicone composition comprising: (B) a hydrolyzable organosiloxane containing an alkoxysilyl group: 0.1 to 30% by volume of the entire composition; (C) one or more types of aluminum nitride particles having an average particle size of 5 μm or more and less than 30 μm and an average sphericity of 0.8 or more: 15 to 50% by volume of the entire composition; and (E) zinc oxide particles having an average particle size of 0.1 μm or more and less than 2.0 μm: 10 to 25% by volume of the entire composition. １2. The silicone composition according to claim 1, wherein at least one of the above is an organopolysiloxane having an alkenyl group, and further comprising: (F) a polyorganohydrogensiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, (G) a platinum metal catalyst, and (H) a reaction inhibitor. 3. The thermally conductive silicone composition according to claim 2, which comprises a hydrosilylation reaction product of component (A) and component (F). 4. The thermally conductive silicone composition according to claim 3, wherein, for each silicon-bonded alkenyl group per molecule of component (A), there are 0.5 to 20 silicon-bonded hydrogen atoms per molecule of component (F). 5. 5. The thermally conductive silicone composition according to any one of 1 to 4, wherein the thermally conductive silicone composition has a thickness of 10 to 60 μm when pressed from a thickness of 100 μm at 25°C and 0.1 MPa for 60 minutes, and has a thermal conductivity of 4.0 W / m·K or greater at 25°C, as measured by the hot disc method. 6. A method for producing the thermally conductive silicone composition according to any one of 1 to 5, comprising the step of heating and mixing components (A), (B), (C), (D), and (E) at 100°C or greater for 30 minutes or longer.

[0009] According to the present invention, it is possible to provide a thermally conductive silicone composition that has high thermal conductivity, good compressibility, and excellent resistance to displacement due to thermal shock.

[0010] The present invention will be described in detail below. [Component (A)] The component (A) of the present invention is a polymer having a kinematic viscosity at 25°C of 10 to 100,000 mm, represented by the following general formula (1): 2 and / or s, and these may be used alone or in combination of two or more. (However, in the above formula, R 1 are independently saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, and m is a value that indicates that the kinematic viscosity of the organopolysiloxane at 25°C is 10 to 100,000 mm 2 / s is a positive number.)

[0011] The kinematic viscosity of component (A) is 10 to 100,000 mm 2 / s, 30 to 10,000 mm 2 / s is preferred, and 100 to 8,000 mm2 By setting the viscosity within this range, the kinematic viscosity of component (A) is preferably 10 mm / s. 2 If the kinematic viscosity of component (A) is less than 100,000 mm / s, a slippage occurs in the slippage test. 2 If the kinematic viscosity exceeds 1 / s, the silicone composition will not become homogeneous. In the present invention, the kinematic viscosity is a value measured at 25°C using an Ostwald viscometer.

[0012] The molecular structure of the organopolysiloxane of component (A) is a linear main chain consisting of repeating diorganosiloxane units, with both molecular chain terminals capped with triorganosiloxy groups.

[0013] R 1 are independently saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, preferably 1 to 14 carbon atoms, and may be the same or different. Examples of monovalent hydrocarbon groups include alkyl groups such as methyl, ethyl, propyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl groups, cycloalkyl groups such as cyclopentyl and cyclohexyl groups, alkenyl groups such as vinyl and allyl groups, aryl groups such as phenyl and tolyl groups, aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl groups, and groups in which some or all of the hydrogen atoms have been substituted with halogen atoms such as fluorine, bromine, or chlorine, or with cyano groups, such as 3,3,3-trifluoropropyl, 2-(perfluorobutyl)ethyl, 2-(perfluorooctyl)ethyl, and p-chlorophenyl groups. Among these, a methyl group, a phenyl group, and a vinyl group are preferred, and R 1 In this case, the average number of alkenyl groups in component (A) as a whole is preferably 1 to 2, and more preferably less than 1.8.

[0014] In terms of the effects of the present invention, the amount of component (A) is 0.1 to 20% by volume of the entire composition, preferably 2.0 to 15.0% by volume, and more preferably 2.5 to 10.0% by volume.

[0015] In the thermally conductive silicone composition of the present invention, the component (A) is R １ When at least one of the above is an alkenyl group-containing organopolysiloxane, the following components (F) to (H) can be further added to produce an addition reaction-type thermally conductive silicone composition.

[0016] [Component (B)] Component (B) is a hydrolyzable organopolysiloxane containing alkoxysilyl groups, and can be used alone or in combination of two or more. Component (B) functions as a surface treatment agent for components (C) to (E). Therefore, by adding component (B), the thermally conductive silicone composition can maintain its fluidity even when components (C) to (E) are loaded in large amounts into the composition. At the same time, deterioration of heat dissipation performance due to oil separation and pump-out over time can be suppressed.

[0017] Examples of component (B) include organopolysiloxanes represented by the following general formula (2). Among these, it is preferable to contain a trifunctional hydrolyzable organopolysiloxane. (In the formula, R 2 are independently unsubstituted or substituted monovalent hydrocarbon groups. 1 , X 2 are independently, R 2 or -(R 3 ) n -SiR 4 b (OR 5 ) 3-b and each may be different, but at least one is -(R 3 ) n -SiR 4 b (OR 5 ) 3-b It is. 3 is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, R 4 are independently unsubstituted or substituted monovalent hydrocarbon groups containing no aliphatic unsaturated bonds, and R 5 are independently an alkyl group, alkoxyalkyl group, alkenyl group or acyl group having 1 to 4 carbon atoms, a is a positive number of 1 to 1,000, n is 0 or 1, and b is an integer of 0 to 2.

[0018] R 2 are independently an unsubstituted or substituted monovalent hydrocarbon group. The number of carbon atoms is preferably 1 to 10, more preferably 1 to 6, and even more preferably 1 to 3. Examples 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, and octyl 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. 2 As the alkyl group, a methyl group, a phenyl group, and a vinyl group are preferred.

[0019] X 1 , X 2 are independently, R 2 or -(R 3 ) n -SiR 4 b (OR 5 ) 3-b and each may be different, but at least one is -(R 3 ) n -SiR 4 b (OR 5 ) 3-b is.

[0020] R 3 is an oxygen atom or an alkylene group having 1 to 4 carbon atoms, and examples of the alkylene group having 1 to 4 carbon atoms include a methylene group, an ethylene group, a propylene group, and a butylene group.

[0021] R4 are independently unsubstituted or substituted monovalent hydrocarbon groups containing no aliphatic unsaturated bonds, and preferably have 1 to 10 carbon atoms, more preferably 1 to 6, and even more preferably 1 to 3. Examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl groups, cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups, aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl groups, aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl groups, and groups in which some or all of the hydrogen atoms bonded to carbon atoms of these groups have been substituted with halogen atoms such as fluorine, chlorine, and bromine, or with cyano groups.

[0022] R 5 are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group having 1 to 4 carbon atoms; R 5 Examples of the alkyl group include R 2 Examples of the alkoxyalkyl group include a methoxyethyl group and a methoxypropyl group. Examples of the alkenyl group include a vinyl group and an allyl group. Examples of the acyl group include those having 2 to 8 carbon atoms, such as an acetyl group and an octanoyl group. R 5 is preferably an alkyl group, more preferably a methyl group or an ethyl group.

[0023] a is a positive number from 1 to 1,000, n is 0 or 1, preferably 0, and b is an integer from 0 to 2, preferably 0. 5 The number of groups is preferably 1 to 6, and more preferably 3 or 6. The bonding order of the siloxane units shown in parentheses is not limited to the following.

[0024] Specific examples of suitable components (B) include the following: (B-2) Si-Si is -CH ２- is.

[0025] The amount of component (B) is 0.1 to 30% by volume, preferably 8 to 25% by volume, and more preferably 10 to 25% by volume, of the total composition.

[0026] [Component (C)] Component (C) is one or more types of aluminum nitride particles selected from irregular, rounded, and polyhedral shapes, having an average particle diameter of 5 μm or more and less than 30 μm, and can be used alone or in combination of two or more types.

[0027] The average particle size of component (C) is 5 μm or more and less than 30 μm, preferably 10 μm or more and less than 25 μm, and more preferably 15 μm or more and less than 20 μm. If the average particle size of component (C) is less than 5 μm, the thermal conductivity of the thermally conductive silicone will decrease, and if it exceeds 30 μm, the resulting silicone composition may not be sufficiently thinned when compressed. In the present invention, the average particle size is the cumulative average diameter D50 (median diameter) in the volume-based particle size distribution measured by laser diffraction scattering method, and can be measured, for example, using a Microtrac MT330OEX manufactured by Nikkiso Co., Ltd.

[0028] The (C) particles are selected from amorphous, rounded, and polyhedral shapes, and are preferably rounded. Here, "irregular" refers to any shape that has not been intentionally spheroidized by melting, granulation, or other processes. Meanwhile, "rounded," "polyhedral," and "spherical" refer to commercially available particles that have been melted, granulated, or other processes. Here, "rounded" refers to particles with few corners, which are rounded and smooth, and does not include spherical shapes. Rounded shapes are clearly different from spherical shapes in that they have corners. Spherical aluminum nitride is not preferred because of its poor thermal conductivity.

[0029] The aluminum nitride particles of component (C) can be synthesized by known methods such as direct nitridation and reduction nitridation, and can be adjusted to any particle size range by pulverization, etc. For example, rounded aluminum nitride particles can be obtained by heat treating amorphous or polyhedral aluminum nitride in a non-oxidizing atmosphere at 1,600°C to 2,000°C.

[0030] Furthermore, the residue of component (C) after sieving through a 200-mesh wire gauze is preferably less than 1.0% by mass, more preferably less than 0.5% by mass, and even more preferably less than 0.1% by mass. Furthermore, the residue after sieving through a 325-mesh wire gauze is particularly preferably less than 1.0% by mass, and most preferably less than 0.5% by mass and less than 0.1% by mass. The 200-mesh wire gauze and 325-mesh wire gauze used here are wire gauze specified in JIS Z 8801. When the residue of component (C) after sieving through a 200-mesh wire gauze is less than 1.0% by mass, the thickness of the coating film of the composition interposed between the heat-generating component and the cooling component in a semiconductor device can be sufficiently thin.

[0031] The amount of component (C) is 10 to 50% by volume of the total composition, preferably 25 to 40% by volume. If the amount of component (C) is less than 10% by volume, the thermal conductivity will be low, and if it exceeds 50% by volume, the proportion of large particles in the composition will be high, making it difficult to compress sufficiently.

[0032] [Component (D)] Component (D) is aluminum oxide particles having an average particle size of at least 2 μm but less than 5 μm and an average sphericity of at least 0.8, and can be used alone or in combination of two or more. The average particle size of component (D) is at least 2 μm but less than 5 μm, preferably at least 2.5 μm but less than 4.5 μm, and more preferably at least 3.0 μm but less than 4.5 μm. If the average particle size of component (D) is less than 2 μm, the thermal conductivity of the resulting thermally conductive silicone composition will decrease, while if it exceeds 5 μm, the resulting thermally conductive silicone composition will tend to be non-uniform.

[0033] The average sphericity of component (D) is 0.8 or more, preferably 0.85 or more. If the average sphericity of component (D) is less than 0.80, the particles will come into close contact with each other, which will prevent them from being crushed sufficiently when compressed after application, resulting in poor heat resistance. There is no upper limit to the average sphericity of component (D), but it can be set to, for example, 0.95.

[0034] 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 designated as (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 (r is the radius.) 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 was determined, and the average value was taken as the average sphericity.

[0035] The residue of component (D) after sieving through a 325 mesh wire netting is preferably less than 1.0 mass%, more preferably less than 0.5 mass%, and even more preferably less than 0.1 mass%.

[0036] The amount of component (D) is 15 to 50% by volume of the total composition, preferably 20 to 40% by volume. If the amount of component (D) is less than 15% by volume, the viscosity of the resulting thermally conductive silicone composition increases, making it difficult to form a thin film when compressed. If the amount of component (D) exceeds 50% by volume, the thermal conductivity of the thermally conductive silicone decreases. The total amount of components (C) and (D) is preferably 50% to less than 80% by volume of the total composition, more preferably 60% to 70% by volume. By making the total amount of components (C) and (D) 50% by volume or more, the thermal conductivity becomes higher, and by making it 80% by volume or less, the proportion of large particles in the composition decreases, resulting in a more uniform composition.

[0037] [Component (E)] Component (E) is zinc oxide particles with an average particle size of 0.1 μm or more and less than 2.0 μm, and can be used alone or in combination of two or more. The average particle size of component (E) is 0.1 μm or more and less than 2.0 μm, and preferably 0.4 μm or more and less than 1.5 μm. If the average particle size is less than 0.1 μm, the viscosity of the thermally conductive silicone composition increases, making it difficult to handle. If the average particle size exceeds 2.0 μm, the thermally conductive silicone composition will not be uniform. The shape of component (E) may be irregular, rounded, polyhedral, or spherical, but irregular shapes are preferred.

[0038] The amount of component (E) is 10 to 25% by volume of the total composition, preferably 10 to 20% by volume, and more preferably 15 to 20% by volume. If the amount of component (E) is less than 10% by volume, the thermally conductive silicone composition will not be uniform. If the amount is more than 25% by volume, the viscosity of the thermally conductive silicone composition will increase, making it difficult to handle. Furthermore, the total amount of components (C) and (E) is preferably 30% to less than 70% by volume of the total composition, more preferably 30 to 65% by volume, and even more preferably 30 to 60% by volume. By making the total amount of components (C) and (E) 30% by volume or more, thermal conductivity will be increased, and by making it 70% by volume or less, compressibility will be further improved.

[0039] The total amount of components (C), (D), and (E) is 70 to 85.0% by volume of the entire composition, preferably 72 to 83% by volume, and more preferably 78 to 81% by volume. If the total amount of components (C), (D), and (E) is less than 70% by volume, the thermal conductivity of the resulting composition will decrease, and if it exceeds 85% by volume, the composition will not become grease-like.

[0040] [Component (F)] Component (F) is an organohydrogenpolysiloxane having two or more, preferably three to fewer than 40, hydrogen atoms (SiH groups) bonded to silicon atoms per molecule, and can be used alone or in combination of two or more. The hydrogen atoms bonded to silicon atoms in the molecule undergo an addition reaction with aliphatic unsaturated hydrocarbon groups in the composition in the presence of a platinum group metal catalyst described below, forming a crosslinked structure.

[0041] The molecular structure of component (F) is not particularly limited and may be, for example, linear, branched, or cyclic, and may be represented by the following average composition formula (3): 7 e H f SiO (4-e-f) / 2 (3) (wherein, R 7 are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, excluding unsaturated group-containing aliphatic hydrocarbon groups; e is 1.0 to 3.0, f is 0.005 to 2.0, and e+f is a positive number that satisfies the range of 0.5 to 3.0.

[0042] R 7 are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, excluding aliphatic hydrocarbon groups containing unsaturated groups, and may be saturated or unsaturated. The number of carbon atoms is preferably 1 to 14. 7 Examples of R include alkyl groups such as methyl, ethyl, propyl, hexyl, octyl, decyl, dodecyl, tetradecyl, hexadecyl, and octadecyl groups, cycloalkyl groups such as cyclopentyl and cyclohexyl groups, alkenyl groups such as vinyl and allyl groups, aryl groups such as phenyl and tolyl groups, aralkyl groups such as 2-phenylethyl and 2-methyl-2-phenylethyl groups, and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, bromine, and chlorine, or with cyano groups, such as 3,3,3-trifluoropropyl, 2-(perfluorobutyl)ethyl, 2-(perfluorooctyl)ethyl, and p-chlorophenyl groups. 7 As the alkyl group, a methyl group and a phenyl group are particularly preferred.

[0043] e is a positive number that is 1.0 to 3.0, preferably 0.5 to 2.5, f is 0.005 to 2.0, preferably 0.01 to 1.0, and e+f is 0.5 to 3.0, preferably 0.8 to 2.5.

[0044] The amount of component (F) is preferably 0.5 to 20, more preferably 0.5 to 13, and even more preferably 0.5 to 1.0 silicon-bonded hydrogen atoms per molecule of component (F) per silicon-bonded aliphatic unsaturated hydrocarbon group per molecule of component (A).Within these ranges, better slippage resistance is achieved.

[0045] In the present invention, it is preferable that the composition contains a hydrosilylation reaction product of the components (A) and (F). By containing such a component, it is possible to further improve the slippage resistance.

[0046] [Component (G)] Component (G) is a platinum group metal catalyst that promotes the hydrosilylation reaction between the silicon-bonded aliphatic unsaturated hydrocarbon groups in component (A) and the SiH groups in component (F). Component (G) can be used alone or in combination of two or more. Conventional platinum group metal catalysts used in addition reactions can be used. Examples include platinum-based, palladium-based, and rhodium-based catalysts. Of these, platinum or platinum compounds are preferred, as they are relatively readily available. Examples include platinum itself, platinum black, chloroplatinic acid, platinum-olefin complexes, platinum-alcohol complexes, and platinum coordination compounds.

[0047] The amount of component (G) is preferably 1 to 2,000 ppm, and more preferably 2 to 1,000 ppm, calculated as platinum group metal atoms by mass relative to the organopolysiloxane of component (A).Within this range, the reaction rate of the addition reaction is appropriate.

[0048] [Component (H)] Component (H) is a reaction inhibitor that suppresses the progress of the hydrosilylation reaction at room temperature and functions to extend shelf life and pot life. Component (H) can be used alone or in combination of two or more types. The reaction inhibitor can be any conventional reaction inhibitor used in addition-curable silicone compositions. Examples of such reaction inhibitors include acetylene compounds such as acetylene alcohols (e.g., ethynylmethyldecylcarbinol, ethynylcyclohexanol, 3,5-dimethyl-1-hexyn-3-ol), various nitrogen compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole, organophosphorus compounds such as triphenylphosphine, oxime compounds, and organochloro compounds.

[0049] [Other Components] The thermally conductive silicone composition of the present invention may contain an organo(poly)siloxane such as methylpolysiloxane for the purpose of adjusting the modulus of elasticity and viscosity. Furthermore, to prevent deterioration of the thermally conductive silicone composition, a known antioxidant such as 2,6-di-t-butyl-4-methylphenol may be added as needed. Furthermore, dyes, pigments, flame retardants, anti-settling agents, thixotropy improvers, and the like may be added as needed. When other components are added, their amount is preferably in the range of 0.01 to 1.0% by volume of the thermally conductive silicone composition.

[0050] [Thermal Conductivity] The thermal conductivity of the thermally conductive silicone composition of the present invention, as measured by the hot disk method in accordance with ISO 22007-2, is preferably 4.0 W / m K or higher. There is no upper limit to the thermal conductivity, but it can be set to 13.0 W / m K or lower. The detailed method for measuring thermal conductivity is described in the Examples section below.

[0051] [Viscosity] The viscosity of the thermally conductive silicone composition of the present invention at 25°C is preferably 10 to 1,300 Pa·s, and more preferably 200 to 1,000 Pa·s. The viscosity of the thermally conductive silicone composition at 25°C is measured using a spiral viscometer at a rotation speed of 10 rpm.

[0052] [Thickness] The thickness of the thermally conductive silicone composition of the present invention is preferably 10 to 60 μm, and more preferably 25 to 50 μm. The thickness is measured by the method described in the Examples.

[0053] [Thermal Resistance] The thermal resistance of the thermally conductive silicone composition of the present invention is 2 °C / W or less is preferable, 8 mm 2 ° C. / W or less is more preferable. The thermal resistance is measured by the laser flash method described in the examples.

[0054] [Slippage Resistance] The thermally conductive silicone composition of the present invention has slippage resistance, making it ideal as a thermally conductive silicone composition. The slippage resistance was measured as described in the Examples below.

[0055] [Method for Producing Thermally Conductive Silicone Composition] The following describes a method for producing the thermally conductive silicone composition of the present invention, but the method is not limited thereto. The method for producing the thermally conductive silicone composition of the present invention may be any method for producing a conventional thermally conductive silicone composition and is not particularly limited. For example, the composition can be obtained by mixing the above-mentioned components (A) to (H) and, as necessary, other optional components. The mixing device is not particularly limited, and mixers such as Trimix, Twinmix, and 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.), and Hivis Dispermix (registered trademark of mixers manufactured by Tokushu Kika Kogyo Co., Ltd.) can be used. In addition, a three-roll finishing process or the like may be used to break down agglomerations of the thermally conductive fillers (C), (D), and (E).

[0056] Preferably, the process includes a step of heating and mixing components (A), (B), (C), (D), and (E) at 100° C. or higher for 30 minutes or longer. When component (A) is an organopolysiloxane containing one or more silicon-bonded aliphatic unsaturated hydrocarbon groups per molecule and also contains components (F) and (G), stirring at 100° C. or higher for 30 minutes or longer is preferred, as this allows components (A) and (F) to sufficiently crosslink via a hydrosilylation reaction and gives the thermally conductive silicone composition an appropriate viscosity.

[0057] The components used in the examples and comparative examples are shown below. The present invention will be specifically explained below with reference to the examples and comparative examples, but the present invention is not limited to the following examples.

[0058] The components used are as follows. The kinematic viscosity is a value measured at 25°C using an Ostwald viscometer (manufactured by Shibata Scientific Co., Ltd.). [Component (A)] A-1: ​​A copolymer having a kinematic viscosity of 5,000 mm at 25°C and a terminal end capped with trimethylsilyl groups. 2 A-2: Dimethylpolysiloxane (specific gravity 0.98, vinyl group amount 0.000 mol / 100 g) with both ends blocked with dimethylvinylsilyl groups and a kinematic viscosity at 25°C of 600 mm 2 A-3: Dimethylpolysiloxane (specific gravity 0.98, vinyl group amount 0.015 mol / 100 g) whose ends are blocked with dimethylvinylsilyl groups and trimethylsilyl groups, and whose kinematic viscosity at 25°C is 700 mm 2 a-4: Dimethylpolysiloxane (specific gravity 0.98, vinyl group amount 0.005 mol / 100 g) with a kinematic viscosity of 6 mm at 25 ° C. 2 a-5: Dimethylpolysiloxane (specific gravity 0.93, vinyl group content 0.000 mol / 100 g) with a kinematic viscosity of 300,000 m / s at 25°C. 2 / s dimethylpolysiloxane (specific gravity 0.98, vinyl group content 0.000 mol / 100 g)

[0059] [Component (B)] B-1: Hydrolyzable organopolysiloxane (specific gravity 0.98) represented by the following formula:

[0060] [Component (C)] C-1: Rounded aluminum nitride powder having an average particle size of 19.6 μm (sieve residue on 200 mesh wire mesh: 0.02% by mass, comb residue on 325 mesh wire mesh: 0.90% by mass, specific gravity: 3.26) C-2: Rounded aluminum nitride powder having an average particle size of 18.6 μm (sieve residue on 200 mesh wire mesh: 0.01% by mass, comb residue on 325 mesh wire mesh: 0.01% by mass, specific gravity: 3.26) C-3: Rounded aluminum nitride powder having an average particle size of 6.6 μm (sieve residue on 200 mesh wire mesh: 0.01% by mass, comb residue on 325 mesh wire mesh: 0.01% by mass, specific gravity: 3.26) c-4: Spherical aluminum oxide particles having an average particle size of 10.0 μm (200 mesh wire mesh sieve residue: 0.15 mass%, 325 mesh wire mesh comb residue: 4.6 mass%, specific gravity: 3.99: comparative component) c-5: Spherical aluminum oxide particles having an average particle size of 45.0 μm (200 mesh wire mesh sieve residue: 1.6 mass%, 325 mesh wire mesh comb residue: 64.6 mass%, specific gravity: 3.99: comparative component)

[0061] [Component (D)] D-1: Spherical aluminum oxide particles having an average particle size of 2.6 μm and an average sphericity of 0.87 (remaining in a comb of 0.00 mass% on a 325 mesh wire net, specific gravity: 3.99) D-2: Spherical aluminum oxide particles having an average particle size of 4.7 μm and an average sphericity of 0.91 (remaining in a comb of 0.00 mass% on a 325 mesh wire net, specific gravity: 3.99) D-3: Spherical aluminum oxide particles having an average particle size of 3.1 μm and an average sphericity of 0.91 (remaining in a comb of 0.00 mass% on a 325 mesh wire net, specific gravity: 3.99) d-3: Crushed aluminum nitride particles having an average particle size of 2.6 μm and an average sphericity of 0.60 (remaining in a comb of 0.00 mass% on a 325 mesh wire net, specific gravity: 3.26)

[0062] [Component (E)] E-1: irregular zinc oxide particles having an average particle size of 1.2 μm (specific gravity: 5.61) E-2: irregular zinc oxide particles having an average particle size of 0.4 μm (specific gravity: 5.61)

[0063] [Component (F)] F-1: a copolymer having a kinematic viscosity of 100 mm at 25°C and a trimethylsilyl group-blocked end 2 / s, organohydrogenpolysiloxane with a SiH content of 0.0055 mol / g and a specific gravity of 0.98

[0064] [Component (G)] G-1: A solution of platinum-divinyltetramethyldisiloxane complex dissolved in the same dimethylpolysiloxane as in A-2 (platinum atom content: 1% by mass, specific gravity: 0.98)

[0065] [Component (H)] H-1: Ethynylcyclohexanol (specific gravity 0.97)

[0066] Examples and Comparative Examples Preparation of Thermally Conductive Silicone Compositions Thermally conductive silicone compositions were prepared by blending the above components (A) to (H) in the amounts shown in the table below using the method described below. Components (A) to (H) were added to a 5-liter planetary mixer (manufactured by Inoue Seisakusho Co., Ltd.) and mixed at 150°C for 4 hours. The mixture was then cooled to 25°C to prepare a thermally conductive silicone composition. The compositions obtained by the above method were evaluated for thermal conductivity, shear resistance, thickness, and thermal resistance using the methods described below. The results are shown in Tables 1 to 3.

[0067] [Viscosity] The viscosity of the thermally conductive silicone composition was measured at 25° C. using a spiral viscometer (Type PC-1T) manufactured by Malcom Co., Ltd. (Rotor A, 10 rpm, shear rate 6 [1 / s]).

[0068] [Thermal Conductivity] Each composition was wrapped in kitchen wrap to form a pouch, and the thermal conductivity was measured at 25°C using a TPA-501 manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0069] [Slippage Resistance] A test piece was prepared by sandwiching 1.0 g of the composition between a 60 mm × 60 mm aluminum plate and a glass plate using a spacer to a thickness of 0.5 mm. The test piece was left standing vertically at 25 ° C for 12 hours, and then those in which the composition had moved were marked with ×, and those in which it had not moved were marked with ◯. The test piece was then placed vertically in a thermal tester in which one cycle consisted of −40 ° C for 30 minutes and 120 ° C for 30 minutes, and those in which the composition had not moved after 1,000 cycles were marked with ⊚.

[0070] [Thickness] A composition (thickness 100 μm) was sandwiched between two circular aluminum plates having a diameter of 12.6 mm and a thickness of 1 mm, and pressure was applied at 25° C. and 0.1 MPa for 60 minutes. The thickness was then measured with a micrometer (manufactured by Mitutoyo Corporation), and the thickness of the aluminum plates was subtracted from the thickness.

[0071] [Thermal Resistance] Using the above test piece, the thermal resistance (mm 2 The thermal resistance (°C / W) was measured at 25°C using a thermal resistance measuring device based on the laser flash method (Xenon Flash Analyzer; LFA447 NanoFlash, manufactured by Netsch).

[0072]

[0073]

[0074]

[0075] The results in Tables 1 to 3 show that the thermally conductive silicone compositions of the examples that satisfied the requirements of the present invention had good compressibility, were small in thickness, and were able to combine high thermal conductivity with resistance to displacement due to thermal shock.

[0076] On the other hand, Comparative Example 1, which had a low viscosity of component (A), had poor shear resistance, and Comparative Example 2, which had a high viscosity of component (A), did not achieve uniformity. Comparative Example 3, which did not contain component (D), had poor thickness. Comparative Example 4, which contained a large amount of component (D), had poor thermal conductivity. Furthermore, Comparative Example 5, which contained a small amount of component (E), had poor shear resistance, and Comparative Example 6, which contained a large amount, had poor thermal conductivity. Comparative Example 7, which contained a large amount of thermally conductive filler, did not achieve uniformity. Comparative Example 8, which used spherical aluminum oxide particles instead of components (C) and (D), had poor thickness. Comparative Example 9, which used crushed aluminum nitride instead of component (D) of the present invention, had poor shear resistance.

[0077] The present invention is not limited to the above-described embodiments, which are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that provides similar effects is included within the technical scope of the present invention.

Claims

1. (A) A kinematic viscosity at 25°C represented by the following general formula (1) of 10 to 100,000 mm 2 / s organopolysiloxane: 0.1 to 20% by volume of the total composition, (However, R 1 are independently saturated or unsaturated, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, and m is a value that indicates that the kinematic viscosity of the organopolysiloxane at 25°C is 10 to 100,000 mm 2 / s.) A thermally conductive silicone composition comprising: (B) a hydrolyzable organosiloxane containing an alkoxysilyl group: 0.1 to 30% by volume of the entire composition; (C) one or more types of aluminum nitride particles having an average particle size of 5 μm or more and less than 30 μm, and selected from irregular, rounded, and polyhedral shapes: 10 to 50% by volume of the entire composition; (D) aluminum oxide particles having an average particle size of 2 μm or more and less than 5 μm, and an average sphericity of 0.8 or more: 15 to 50% by volume of the entire composition; and (E) zinc oxide particles having an average particle size of 0.1 μm or more and less than 2.0 μm: 10 to 25% by volume of the entire composition, wherein the total amount of components (C), (D), and (E) is 70 to 85.0% by volume of the entire composition.

2. R in formula (1) of (A) １ 2. The silicone composition according to claim 1, wherein at least one of the above is an organopolysiloxane having an alkenyl group, and further comprising: (F) a polyorganohydrogensiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule; (G) a platinum metal catalyst; and (H) a reaction inhibitor.

3. The thermally conductive silicone composition according to claim 2, which comprises a hydrosilylation reaction product of said component (A) and said component (F).

4. The thermally conductive silicone composition according to claim 3, wherein for each silicon-bonded alkenyl group in each molecule of component (A), there are 0.5 to 20 silicon-bonded hydrogen atoms in each molecule of component (F).

5. The thermally conductive silicone composition according to any one of claims 1 to 4, wherein when a thickness of 100 µm is applied to the thermally conductive silicone composition at 25°C under a pressure of 0.1 MPa for 60 minutes, the thickness of the composition is 10 to 60 µm, and the thermal conductivity at 25°C, as measured by the hot disk method, is 4.0 W / m K or greater.

6. A method for producing the thermally conductive silicone composition of claim 1, comprising the step of heating and mixing components (A), (B), (C), (D), and (E) at 100°C or higher for 30 minutes or longer.

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