Thermally conductive silicone composition and method for producing the same

Abstract

A thermally conductive silicone composition comprising (A) a crosslinked silicone gel, (B) a silicone oil containing neither an aliphatic unsaturated bond nor an SiH group, (C) a thermally conductive filler having an average particle diameter of 0.01-100 μm, the amount of which is 10-2,000 parts by mass per 100 parts by mass of the sum of the (A) and (B) components, and (D) gallium or a gallium alloy having a melting point of -20 to 100°C, the amount of which is 1,000-10,000 parts by mass per 100 parts by mass of the sum of the (A) and (B) components. The thermally conductive silicone composition has a high thermal conductivity and is excellent in terms of applicability and dislocation resistance.

Description

Technical Field

[0001] The present invention relates to a thermally conductive silicone composition having high thermal conductivity and excellent displacement resistance, and a method for producing the same.

Background Art

[0002] Generally, since heat is generated during the use of electrical and electronic components, heat removal is necessary to properly operate the electrical components, and various thermally conductive materials for heat removal have been proposed. This thermally conductive material is roughly classified into two types: 1) sheet-like materials that are easy to handle, and 2) paste-like materials.

[0003] The sheet-like materials have the advantages of being easy to handle and having excellent stability. However, due to the nature of the contact thermal resistance being large, the heat dissipation performance is inferior to that of the paste-like materials. In addition, a certain degree of strength / hardness is required to maintain the sheet shape, and the tolerance generated between the electrical and electronic component elements and the heat dissipation member cannot be absorbed, and the element may be destroyed by those stresses.

[0004] On the other hand, the paste-like materials can be adapted to mass production by using a coating device or the like, and have excellent heat dissipation performance because of their low contact thermal resistance. However, when mass-producing by screen printing or the like, the lower the viscosity of the paste is better. However, when the viscosity is low, the paste may shift due to the thermal shock of the element or the like (pump-out phenomenon), and sufficient heat removal cannot be achieved. As a result, the element may malfunction. In addition, the following silicone compositions and the like have been proposed as past technologies, but there has been a demand for a thermally conductive silicone composition that provides further sufficient performance and has excellent displacement resistance.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] This invention has been made in view of the above circumstances, and aims to provide a thermally conductive silicone composition and a method for producing the same that have high thermal conductivity and excellent workability and shear resistance. [Means for solving the problem]

[0007] The inventors have conducted diligent studies to achieve the above objectives and have found that a thermally conductive silicone composition containing a silicone gel crosslinked product, a specific silicone oil, particularly a single-ended hydrolyzable organopolysiloxane, a thermally conductive filler, and gallium or a gallium alloy having a melting point of -20 to 100°C, has high thermal conductivity while also being easy to work with. Shear resistance We discovered that it is possible to achieve both of these conditions simultaneously, and thus we have come up with this invention.

[0008] Accordingly, the present invention provides the following invention. 1. (A) Silicone gel crosslinked material, (B) A silicone oil that does not contain aliphatic unsaturated bonds and SiH groups respectively, (C) A thermal conductivity filler with an average particle size of 0.01 to 100 μm: 10 to 2,000 parts by mass based on 100 parts by mass of the total of components (A) and (B), and (D) Gallium or a gallium alloy having a melting point of -20 to 100 °C: 1,000 to 10,000 parts by mass based on 100 parts by mass of the total of components (A) and (B), A thermally conductive silicone composition containing 2. Further, the thermally conductive silicone composition according to claim 1, which contains (E) a volatile solvent in an amount of 1 to 500 parts by mass based on 100 parts by mass of the total of components (A) and (B). 3. The thermally conductive silicone composition according to claim 1 or 2, wherein the component (B) contains a silicone oil (B-1) composed of a mono-terminal hydrolyzable organopolysiloxane represented by the following general formula (1), and the content of the component (B) is 10 to 90% by mass of the total amount of components (A) and (B). [Chemical formula] (In the formula, R c each independently represents an alkyl group having 1 to 6 carbon atoms, and R 2 represents one or more groups selected from the group of unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bond and having 1 to 18 carbon atoms, and a is an integer of 5 to 120.) 4. The thermally conductive silicone composition according to any one of claims 1 to 3, wherein the component (A) is an addition reaction product of a component (F) and a component (G) in the presence of the following component (H). (F) The following average composition formula (2) R 3 b R 4 c SiO (4-b-c) / 2 (2) (In the formula, R 3 represents an alkenyl group, R 4 represents an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bond, b is a number of 0.0001 to 0.2, c is a number of 1.7 to 2.2, provided that b + c is a number satisfying 1.9 to 2.4.) An organopolysiloxane having at least one alkenyl group bonded to a silicon atom represented by , (G) Each molecule has at least four hydrogen atoms bonded to silicon atoms at the non-terminus of the molecular chain, and the following formula (3) 0.1 < α / β (3) (In the formula, α represents the number of hydrogen atoms bonded to silicon atoms at the non-terminal ends of the molecular chain, and β represents the total number of silicon atoms in component (G).) Organohydrogenpolysiloxanes that satisfy the requirements (H) Platinum-based catalyst. 5. Component (B) is further (B-2) a kinematic viscosity at 25°C of 10 to 500,000 mm². 2 A thermally conductive silicone composition according to any one of 1 to 4, comprising 10 to 70% by mass of a non-functional liquid silicone oil with a viscosity of / s in component (B). 6. A thermally conductive silicone composition according to any one of claims 1 to 5, wherein component (E) is an isoparaffinic solvent with a boiling point of 80 to 360°C. 7. A method for producing the thermally conductive silicone composition according to 1, comprising the step of mixing components (B), (C), and (D). 8. A method for producing the thermally conductive silicone composition according to 4, comprising the steps of mixing components (F), (G), and (H) with components (B), (C), and (D), and heating the resulting mixture to cause an addition reaction between component (F) and component (G). [Effects of the Invention]

[0009] The present invention provides a thermally conductive silicone composition that has high thermal conductivity and excellent workability and shear resistance, as well as a method for producing the same. [Modes for carrying out the invention]

[0010] The present invention will be described in detail below. The thermally conductive silicone composition of the present invention is (A) Silicone gel crosslinked material, (B) Silicone oil that does not contain aliphatic unsaturated bonds or SiH groups, (C) Thermally conductive filler with an average particle size of 0.01 to 100 μm: 10 to 2,000 parts by mass per 100 parts by mass of the total of components (A) and (B), and (D) Gallium or gallium alloy having a melting point of -20 to 100°C: 1,000 to 10,000 parts by mass per 100 parts by mass of the total of components (A) and (B), It contains.

[0011] The silicone gel crosslinked component (A) is used as the matrix of the thermally conductive silicone composition of the present invention. Component (A) is preferably obtained by adding components (F) and (G) in the presence of component (H) (hydrosilylation). (F) The following average composition formula (2) R 3 b R 4 c SiO (4-b-c) / 2 (2) (In the formula, R 3 represents an alkenyl group, R 4 (where b represents an unsubstituted or substituted monovalent hydrocarbon group without an aliphatic unsaturated bond, b is a number between 0.0001 and 0.2, c is a number between 1.7 and 2.2, and b+c is a number satisfying 1.9 to 2.4.) An organopolysiloxane having at least one alkenyl group bonded to a silicon atom represented by , (G) Each molecule has at least four hydrogen atoms bonded to silicon atoms at the non-terminus of the molecular chain, and the following formula (3) 0.1 < α / β (3) (In the formula, α represents the number of hydrogen atoms bonded to silicon atoms at the non-terminal ends of the molecular chain, and β represents the total number of silicon atoms in component (G).) Organohydrogenpolysiloxanes that satisfy the requirements (H) Platinum-based catalyst.

[0012] Component (F) is the main component of component (A), and may be used alone or in combination of two or more. Component (F) is an organopolysiloxane having at least one alkenyl group bonded to a silicon atom in one molecule, represented by the average composition formula (2) above (hereinafter referred to as "silicon atom-bonded alkenyl group"). Preferably, there are at least two of these alkenyl groups in one molecule, more preferably 2 to 50, and particularly preferably 2 to 20. These alkenyl groups may be bonded to silicon atoms at the ends of the molecular chain, to silicon atoms at the non-terminants of the molecular chain (i.e., other than both ends of the molecular chain), or a combination thereof.

[0013] In equation (2) above, R 3 This represents an alkenyl group having 2 to 6 carbon atoms, more preferably 2 to 4 carbon atoms. Specific examples include lower alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, and isobutenyl groups, with vinyl being even more preferred. R 4 This represents an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bonds, preferably with 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclohexyl, octyl, and decyl groups; aryl groups such as phenyl and tolyl groups; aralkyl groups such as benzyl and phenylethyl groups; and chloromethyl and 3,3,3-trifluoropropyl groups, in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine and chlorine. However, from the viewpoint of ease of synthesis, methyl, phenyl, and 3,3,3-trifluoropropyl groups are preferred.

[0014] In formula (2) above, the values ​​of b, c, and b+c are as described above, but it is preferable that b is a number between 0.0005 and 0.1, c is a number between 1.9 and 2.0, and b+c is a number that satisfies 1.95 and 2.05.

[0015] The molecular structure of the organopolysiloxane of component (F) is not particularly limited, and is linear; part of the molecular chain contains R 3 SiO 3 / 2 Unit, R 4 SiO 3 / 2 Units, SiO2 units (in the formula, R 3 and R 4 The group represented by is as defined above. It may be branched, cyclic, or three-dimensional network (resinous), including ), but is usually a linear diorganopolysiloxane in which the main chain basically consists of repeating diorganosiloxane units and both ends of the molecular chain are sealed with triorganosiloxy groups.

[0016] The kinematic viscosity of the organopolysiloxane component (F) is preferably 50 to 100,000 mm² at 25°C. 2 / s, more preferably 100~10,000mm 2 This kinematic viscosity is 50-100,000 mm². 2 When the value is / s, the resulting cured product exhibits superior fluidity and workability. In this invention, the kinematic viscosity is the value obtained at 25°C using an Ostwald viscometer (the same applies hereinafter).

[0017] (F) The organopolysiloxane is, for example, the following general formula (4) [ka] (In the formula, R 5 Each of these independently represents an unsubstituted or substituted monovalent hydrocarbon group, except R 5 At least one, preferably two or more, of these is an alkenyl group, and d is an integer between 20 and 2,000. Examples include those represented by the following:

[0018] In equation (4), R 5 The unsubstituted or substituted monovalent hydrocarbon group represented by R 3 (Alkenyl group) and R 4This is the same as the definition of (unsubstituted or substituted monovalent hydrocarbon group without aliphatic unsaturated bonds), and the number of carbon atoms, specific examples, etc. are also the same. Furthermore, d is preferably an integer between 40 and 1,200, more preferably an integer between 50 and 600.

[0019] Specific examples of organopolysiloxanes represented by formula (4) above include dimethylpolysiloxane with dimethylvinylsiloxy groups sealed at both ends of the molecular chain, dimethylpolysiloxane with a trimethylsiloxy group at one end of the molecular chain and a dimethylvinylsiloxy group sealed at the other end, dimethylsiloxane-methylvinylsiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-methylvinylsiloxane copolymer with a trimethylsiloxy group at one end of the molecular chain and a dimethylvinylsiloxy group sealed at the other end, dimethylsiloxane-methylvinylsiloxane copolymer with dimethylvinylsiloxy groups sealed at both ends of the molecular chain, and dimethylsiloxane-diphenylsiloxane copolymer with dimethylvinylsiloxy groups sealed at both ends of the molecular chain.

[0020] [(G) component] Component (G) reacts with component (F) above to act as a crosslinking agent. Component (G) must have at least four hydrogen atoms (i.e., SiH groups, hereinafter referred to as "silicon-bonded hydrogen atoms") bonded to silicon atoms at the non-terminus of the molecular chain, as fewer than three of these would not provide sufficient shear resistance. Furthermore, it must be in accordance with the following formula (3) 0.1 < α / β (3) (In the formula, α represents the number of hydrogen atoms bonded to silicon atoms at the non-terminal ends of the molecular chain, and β represents the total number of silicon atoms in component (G).) It is an organohydrogenpolysiloxane that satisfies the following conditions. If the above α / β range is small, such as 0.1 or less, the shear resistance of this composition will be poor, so it is also necessary that 0.1 < α / β. In this case, α / β is preferably 0.11 or more, particularly 0.12 or more, and there is no particular upper limit, but it is preferably 0.95 or less, particularly 0.90 or less.

[0021] The molecular structure of component (G) is not particularly limited as long as it satisfies the above requirements, and may be any of the conventionally known structures, such as linear, cyclic, branched, or three-dimensional network (resinous). In particular, from the viewpoint of ease of handling and the shear resistance of the cured product obtained by crosslinking component (F), it is desirable that the number of silicon atoms (or degree of polymerization) in one molecule is usually 3 to 1,000, preferably 5 to 400, more preferably 10 to 300, even more preferably 10 to 100, and especially preferably 10 to 60.

[0022] The kinematic viscosity of the organohydrogenpolysiloxane component (G) is typically 1 to 10,000 mm². 2 / s, preferably 3-5,000 mm 2 / s, more preferably 5-3,000mm 2 It is preferable that the solution has a temperature of / s and is liquid at room temperature (25°C).

[0023] As for component (G), an organohydrogenpolysiloxane represented by the following average composition formula (5) is preferred. R 6 e H f SiO (4-e-f) / 2 (5) (In the formula, R 6 (where e represents an unsubstituted or substituted monovalent hydrocarbon group without an aliphatic unsaturated bond, e is a number between 0.7 and 2.2, and f is a number between 0.001 and 0.5, where e + f satisfies the condition 0.8 to 2.5.)

[0024] In the above equation (5), R 6The group is preferably an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and lacking an aliphatic unsaturated bond. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl groups; and 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine and chlorine. More preferably, the group is alkyl, aryl, or 3,3,3-trifluoropropyl, and particularly preferably, methyl, phenyl, or 3,3,3-trifluoropropyl.

[0025] In formula (5) above, e, f, and e+f are as described above, but e is preferably a number between 0.9 and 2.1, f is preferably a number between 0.002 and 0.2, particularly between 0.005 and 0.1, and e+f is preferably a number that satisfies 1.0 and 2.3, particularly between 1.5 and 2.2.

[0026] The molecular structure of the organohydrogenpolysiloxane represented by formula (5) above is not particularly limited and may be linear, cyclic, branched, or three-dimensional network (resinous). Among these, those that satisfy the above-mentioned range for the number of silicon atoms in one molecule and kinematic viscosity are preferred, and linear structures are particularly preferred.

[0027] Specific examples of organohydrogenpolysiloxanes represented by formula (5) above include: dimethylsiloxane-methylhydrogensiloxane copolymer with trimethylsiloxy groups sealed at both ends of the molecular chain, methylhydrogenpolysiloxane with trimethylsiloxy groups sealed at both ends of the molecular chain, dimethylsiloxane-methylhydrogensiloxane copolymer with dimethylhydrogensiloxy groups sealed at both ends of the molecular chain, methylhydrogensiloxane-dimethylsiloxane-diphenylsiloxane copolymer with dimethylhydrogensiloxy group sealed at both ends of the molecular chain, dimethylsiloxane-methylhydrogensiloxane copolymer with dimethylhydrogensiloxy group at one end of the molecular chain and trimethylsiloxy group sealed at one end of the molecular chain, methylhydrogensiloxane-dimethylsiloxane-diphenylsiloxane copolymer with dimethylhydrogensiloxy group at one end of the molecular chain and trimethylsiloxy group sealed at the other end of the molecular chain, (CH3)2HSiO 1 / 2 Units and (CH3)3SiO 1 / 2 Units and (CH3)HSiO 2 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and (CH3)3SiO 1 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and SiO 4 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and SiO 4 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and (C6H5)3SiO 1 / 2 A copolymer consisting of units, (CH3)2HSiO 1 / 2 Units and (CH3)3SiO 1 / 2 Units and (C6H5)2SiO 2 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and SiO 4 / 2Examples include copolymers consisting of units.

[0028] The content of component (G) is preferably such that there are 0.3 to 2.0 silicon atom-bonded hydrogen atoms in component (G) per silicon atom-bonded alkenyl group in component (F), more preferably 0.4 to 1.5, and even more preferably 0.5 to 1.0. If there are fewer than 0.3 silicon atom-bonded hydrogen atoms, the crosslinking density becomes too low, resulting in poor shear resistance of the resulting thermally conductive silicone composition. If there are more than 2.0, the viscosity of the resulting thermally conductive silicone composition becomes too high, potentially leading to poor handling. The organohydrogenpolysiloxane component (G) may be used alone or in combination of two or more types.

[0029] [(H) Component: Platinum-based catalyst] Component (H) is a component that promotes the addition reaction between the silicon atom-bonded alkenyl group in component (F) and the silicon atom-bonded hydrogen atom in component (G). Component (H) is a platinum-based catalyst, specifically platinum and / or a platinum-based compound. Conventionally known platinum and platinum-based compounds can be used, specifically, for example, platinum black; chloroplatinic acid; alcohol-modified chloroplatinic acid; and complexes of chloroplatinic acid with olefin aldehydes, vinylsiloxanes, acetylene alcohols, etc.

[0030] The content of component (H) should be an effective amount and may be increased or decreased as appropriate depending on the desired curing rate, but it is preferably 0.1 to 1,000 ppm, and more preferably 1 to 300 ppm, in terms of the mass of platinum atoms relative to component (F). If the content is too low, the addition reaction may be significantly slowed down or crosslinking may not occur. If the content is too high, not only will the heat resistance of the cured product decrease, but platinum is also expensive, which is disadvantageous from a cost perspective. The platinum-based catalyst of component (H) may be used alone or in combination of two or more types.

[0031] [Other optional components] In order to obtain component (A) of the present invention, a reaction control agent may be used in addition to the above-mentioned components (F), (G), and (H). The reaction control agent may be a conventionally known reaction control agent used in addition-curing silicone compositions. Examples include acetylene compounds such as acetylene alcohols (e.g., 1-ethynyl-1-cyclohexanol, 3,5-dimethyl-1-hexyne-3-ol), various nitrogen compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole, organophosphorus compounds such as triphenylphosphine, oxime compounds, and organochloro compounds.

[0032] The silicone gel crosslinked product of component (A) is obtained by heating and mixing components (F) and (G) in the presence of a platinum-based catalyst of component (H), thereby allowing crosslinking, or addition reaction (hydrosilylation reaction), to proceed. The reaction temperature is usually around 50 to 180°C, but is not limited to this range. The reaction time is also affected by the heating temperature, but usually the reaction proceeds sufficiently in 0.5 to 12 hours. The product that has undergone this treatment is defined as a "crosslinked product".

[0033] Details of components (B) to (E) will be described later, but in the present invention, components (F) and (G) may be subjected to an addition reaction (hydrosilylation reaction) in the presence of component (H) to obtain component (A), and then components (B) to (E) may be mixed. Alternatively, in order to obtain component (A), component (B) may be added to components (F), (G), and (H) before heating, and then components (F) and (G) may be heated and mixed in the presence of component (H), and then components (C), (D), and (E) may be mixed. To obtain component (A), it is possible to pre-add all of components (B) to (E) to components (F), (G), and (H) before heating, and then heat and mix components (F) and (G) in the presence of component (H). However, from the viewpoint of efficiency and safety, to obtain component (A), it is preferable to mix components (F), (G), and (H) with components (B), (C), and (D) before heating, heat the resulting mixture to cause an addition reaction between components (F) and (G), and then, if necessary, add component (E) after cooling.

[0034] [(B) Component] Component (B) is a component that does not participate in the crosslinking of components (F) and (G) above, and is therefore a silicone oil that does not contain aliphatic unsaturated bonds and SiH groups, and is used as a surface treatment agent for components (C) and (D) described later. Component (B) can be used alone or in combination of two or more. Component (B) is preferably a hydrolyzable organopolysiloxane (B-1) with one end trifunctionality represented by the following general formula (1). [ka] (In the formula, R 1 Each of these independently represents an alkyl group having 1 to 6 carbon atoms, and R 2 (where a represents one or more groups selected from the group of unsubstituted or substituted monovalent hydrocarbon groups with 1 to 18 carbon atoms that do not have an aliphatic unsaturated bond, and a is an integer from 5 to 120.)

[0035] [(B-1) component] The organopolysiloxane of general formula (1), which is component (B-1), is used to treat the surface of the thermally conductive filler components (C) and (D). Not only does it help to increase the density of the powder, but by covering the powder surface, it makes it less likely for the powders to aggregate, and this effect persists even at high temperatures, thus improving the heat resistance of the thermally conductive silicone composition of the present invention.

[0036] In the above equation (1), R 1 Examples of alkyl groups include C1-C6 groups such as methyl, ethyl, and propyl groups, but methyl and ethyl groups are particularly preferred. R 2These are unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, preferably 1 to 14 carbon atoms, and lacking aliphatic unsaturated bonds. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl groups; and 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine and chlorine. Preferably, these are alkyl groups, aryl groups, and 3,3,3-trifluoropropyl groups, and more preferably methyl, phenyl, and 3,3,3-trifluoropropyl groups. a is an integer between 5 and 120, preferably between 10 and 90.

[0037] The kinematic viscosity of component (B-1) at 25°C is 5-500 mmHg. 2 / s is preferred, and 10-300mm 2 / s is preferable.

[0038] (B-1) Specific examples of components include the following: [ka]

[0039] The (B) component of the present invention may also contain a non-functional liquid silicone oil (B-2) that does not participate in the crosslinking process, which is free of reactive groups. The non-functional liquid silicone oil of component (B-2) can be used alone or in combination of two or more types.

[0040] [(B-2) component] The non-functional liquid silicone oil of component (B-2) has a kinematic viscosity of 10 to 500,000 mm at 25°C. 2 / s, preferably 30-10,000 mm 2This is an organopolysiloxane with a viscosity of / s. If the kinematic viscosity of the organopolysiloxane is lower than the lower limit, the resulting thermally conductive silicone composition will be prone to oil bleeding. Conversely, if it is higher than the upper limit, the resulting composition will have too high a viscosity, making it difficult to handle.

[0041] The non-functional liquid silicone oil of component (B-2) above may have any kinematic viscosity as described above, and conventionally known organopolysiloxanes can be used. The molecular structure of the organopolysiloxane (silicone oil) is not particularly limited and may be linear, branched, cyclic, etc. In particular, it is preferable to have a linear structure in which the main chain consists of repeating diorganosiloxane units and both ends of the molecular chain are sealed with triorganosiloxy groups.

[0042] This non-functional liquid silicone oil can be represented by the following average composition formula (6). R 7 g SiO (4-g) / 2 (6) In the above equation (6), R 7 These are independently unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, preferably 1 to 14 carbon atoms, and lacking aliphatic unsaturated bonds. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl groups; aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl groups; and 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms of these groups are substituted with halogen atoms such as fluorine and chlorine. Preferably, these are alkyl groups, aryl groups, and 3,3,3-trifluoropropyl groups, and more preferably methyl, phenyl, and 3,3,3-trifluoropropyl groups. In formula (6) above, g is a number in the range of 1.8 to 2.2, particularly in the range of 1.9 to 2.1. As long as g is within this range, the resulting thermally conductive silicone composition can have the required good kinematic viscosity.

[0043] As the organopolysiloxane represented by formula (6) above, a linear organopolysiloxane represented by formula (7) below is preferred. [ka]

[0044] In the above equation (7), R 8 These are, independently of each other, unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms, preferably 1 to 14 carbon atoms, and lacking aliphatic unsaturated bonds. The monovalent hydrocarbon group is R in formula (6) described above. 7 Similar to those exemplified above, the following are examples. Among them, R 8 It is preferable that all of them are methyl groups. h is the kinematic viscosity of the organopolysiloxane at 25°C, which is 10 to 500,000 mmHg. 2 / s, preferably 30-10,000 mm 2 / s, more preferably 100-8,000 mm 2 This is the number that equals / s.

[0045] (B- 2 Specific examples of these ingredients include the following: [ka]

[0046] When component (B-2) is included, its content is preferably 10 to 70% by mass, more preferably 10 to 60% by mass, and even more preferably 10 to 50% by mass, of component (B). If the amount of component (B-2) is too high, component (B-1) will be relatively reduced, which may result in insufficient surface treatment of the thermal conductive filler of component (C) and (D). If the amount is too low, it may be uneconomical in terms of cost. When the amount of component (B-2) is as described above, component (B-1) is preferably 30 to 90% by mass, more preferably 40 to 90% by mass, and even more preferably 50 to 90% by mass, of component (B).

[0047] (B) The content of silicone oil is preferably 10 to 90% by mass of the total of components (A) and (B), and 30 to 80% by mass. % More preferably, 50 to 80% by mass is even more preferred. If the amount is less than 10% by mass, the viscosity of the resulting composition may be high and difficult to handle, and if it is more than 90% by mass, the shear resistance of the composition may be poor. When the amount of component (B) is as described above, the amount of component (A) is preferably 10 to 90% by mass, more preferably 20 to 70% by mass, and even more preferably 20 to 50% by mass.

[0048] [(C) component] Component (C) is a thermally conductive filler and can be used alone or in combination of two or more types. The type of thermally conductive filler is not particularly limited, and powders conventionally used in heat dissipation (thermally conductive) greases can be used. In particular, those with high thermal conductivity are preferred, and examples include inorganic compound powders such as zinc oxide powder, alumina powder, boron nitride powder, aluminum nitride powder, aluminum hydroxide powder, and magnesium oxide powder. These inorganic compound powders may be used after their surface has been hydrophobized with organosilane, organosilazane, organopolysiloxane, or organofluorine compounds as needed. Hydrophobization can also be performed with organopolysiloxane represented by formula (1) above.

[0049] The average particle size of the thermally conductive filler is 0.01 to 100 μm, preferably 0.1 to 80 μm, and more preferably 0.5 to 50 μm. If the average particle size of the thermally conductive filler is smaller than the lower limit or larger than the upper limit, the filling rate in the resulting silicone composition cannot be increased.

[0050] Note that the "average particle size" of component (C) refers to the particle size at 50% of the cumulative value in the volume-based particle size distribution determined by laser diffraction and scattering. ru powder The average particle size and particle size distribution can be measured, for example, using a Microtrac particle size analyzer MT3300EX (manufactured by Nikkiso Co., Ltd.). The shape of the thermally conductive filler can be irregular, spherical, or any other shape.

[0051] (C) The content of the thermally conductive filler is 10 to 2,000 parts by mass per 100 parts by mass of the total of components (A) and (B), preferably 100 to 1,500 parts by mass, and more preferably 100 to 1,000 parts by mass. Below the lower limit, the silicone composition cannot be given sufficient thermal conductivity, and above the upper limit, the viscosity of the silicone composition becomes high and difficult to handle.

[0052] [(D) component] Component (D) is gallium or a gallium alloy with a melting point of -20 to 100°C, and can be used alone or in combination of two or more. The melting point of component (D) is -20 to 100°C, preferably -20 to 50°C. Below -20°C it is difficult to manufacture and therefore uneconomically undesirable, and above 100°C it does not melt quickly during the composition preparation process, resulting in poor workability and precipitation and non-uniformity during manufacturing. Therefore, gallium or a gallium alloy with a melting point in the range of -20 to 100°C is an economically necessary and appropriate condition for handling.

[0053] The melting point of metallic gallium is 29.8°C. Representative gallium alloys with melting points within this range include, for example, gallium-indium alloys (e.g., Ga-In, mass ratio = 75.4:24.6, melting point = 15.7°C), gallium-tin-zinc alloys (e.g., Ga-Sn-Zn, mass ratio = 82:12:6, melting point = 17°C), gallium-indium-tin alloys (e.g., Ga-In-Sn, mass ratio = 21.5:16.0:62.5, melting point = 10.7°C or 68.5:21.5:10, melting point = -19°C), and gallium-indium-bismuth-tin alloys (e.g., Ga-In-Bi-Sn, mass ratio = 9.4:47.3:24.7:18.6, melting point = 48.0°C).

[0054] The liquid or solid fine particles of gallium or its alloy present in the composition of the present invention are usually approximately spherical in shape, but irregularly shaped particles may also be included. The average particle size is preferably 0.1 to 200 μm, and more preferably 10 to 100 μm. If the average particle size is above the lower limit, the viscosity of the composition will not become excessively high, resulting in excellent spreadability and thus excellent coating workability. Conversely, if it is below the upper limit, separation will not occur. Furthermore, the dispersion state of the fine particles, with the aforementioned shape and average particle size, is maintained even when stored at room temperature because the composition possesses an appropriate viscosity.

[0055] The particle size of component (D) is the value of the average particle size automatically measured by automatic area measurement through image binarization of an image of the particle being measured, captured with a microscope. For example, it can be measured with the VHX-8000 microscope from Keyence Corporation. The particle to be measured is sandwiched between two glass slides, photographed with a microscope, and the average particle size can be automatically measured using the accompanying image processing function (automatic area measurement by image binarization).

[0056] The content of component (D) is 1,000 to 10,000 parts by mass, preferably 1,500 to 7,000 parts by mass, relative to 100 parts by mass of the total of components (A) and (B). If the content is less than 1,000 parts by mass, the thermal conductivity will be low, and sufficient heat dissipation performance cannot be obtained when the composition is thick. On the other hand, if it exceeds 10,000 parts by mass, it becomes difficult to obtain a uniform composition, and the viscosity of the composition will be too high, making it impossible to obtain a composition that is spreadable and grease-like.

[0057] [(E) component] As the volatile solvent for component (E), any solvent that can dissolve or disperse components (A) and (B) is acceptable. Examples include toluene, xylene, acetone, methyl ethyl ketone, cyclohexane, n-hexane, n-heptane, butanol, IPA (isopropyl alcohol), and isoparaffin. Isoparaffin-based solvents are preferred from the standpoint of safety, health, and workability in printing.

[0058] The volatile solvent of component (E) has a boiling point of 80 to 360°C, preferably 150 to 350°C. If the boiling point is below 80°C, evaporation is too rapid, which may cause problems as the viscosity increases during the coating process. If the boiling point exceeds 360°C, it is more likely to remain in the thermally conductive silicone composition of the present invention, which may reduce its thermal properties.

[0059] When component (E) is included, its content is preferably 1 to 500 parts by mass, more preferably 5 to 300 parts by mass, and even more preferably 10 to 200 parts by mass, per 100 parts by mass of the total of components (A) and (B). By having a content of 1 part by mass or more, the viscosity of the thermally conductive silicone composition of the present invention at room temperature can be further reduced, and workability can be further improved. On the other hand, by having a content of 300 parts by mass or less, shelf life can be further improved.

[0060] The viscosity of the thermally conductive silicone composition of the present invention, before the inclusion of component (E), is preferably 100 Pa·s or more from the point of improving shear resistance, and preferably 2,000 Pa·s or less from the point of suitable hardness for semiconductor devices. 300 to 1,500 Pa·s is more preferred, and 500 to 1,000 Pa·s is even more preferred. On the other hand, the viscosity after the inclusion of component (E) is preferably 10 Pa·s or more from the point of preventing sedimentation of the thermally conductive filler, and preferably 500 Pa·s or less from the point of handling. 30 to 400 Pa·s is more preferred, and 30 to 300 Pa·s is even more preferred. In this invention, viscosity is the value at 25°C measured by a rotational viscometer (the same applies hereinafter).

[0061] The method for producing the thermally conductive silicone composition of the present invention is not particularly limited, but it can be obtained by mixing the above components (A) to (D), and component (E) and other components may be added as needed. The mixing apparatus is not particularly limited, and mixers such as planetary mixers, Trimix, and Twinmix can be used. By having a step of mixing components (B), (C), and (D), components (C) and (D) are surface-treated on component (B). As mentioned above, the mixing of components (A) to (D) and (E) as needed may be done by first preparing component (A) and then mixing components (B) to (E). Alternatively, component (A) may be prepared by mixing the raw materials for component ((F), (G), and (H)) with components (B) to (E) and then heating, and component (E) may be added after heating.

[0062] The thermally conductive silicone composition of the present invention exhibits suitable shear resistance when applied by screen printing or the like and left at room temperature for a certain period of time, as the volatile solvent evaporates and the viscosity of the thermally conductive silicone composition increases.

[0063] When the thermally conductive silicone composition of the present invention is thinly applied to a heat sink or the like using a printing method such as a metal screen, the contained solvent can be easily evaporated at room temperature or by actively heating it. Therefore, a high-performance thermally conductive silicone composition, which was previously difficult to apply uniformly and thinly, can be easily put into practical use.

[0064] The thermally conductive silicone composition of the present invention is particularly preferable for use in heat dissipation of heat-generating devices such as CPUs and GPUs in laptop computers, and in heat-generating devices in automotive ECUs. [Examples]

[0065] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited thereto. In the following examples, the kinematic viscosity is the value obtained at 25°C using an Ostwald viscometer. The tests related to the examples and comparative examples, which were conducted to further clarify the advantages of the present invention, were carried out as follows.

[0066] [Average particle size measurement] (C) The average particle size of component C is the volume-based cumulative average diameter measured using the Microtrac MT3300EX particle size analyzer manufactured by Nikkiso Co., Ltd. The particle size of component (D) was measured using a VHX-8000 microscope manufactured by Keyence Corporation.

[0067] [Thermal conductivity] The thermal conductivity of the thermally conductive silicone composition (before and after the addition of component (E)) was measured at 25°C using the hot disk method in accordance with ISO 22007-2, with a TPS-2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0068] [Viscosity of thermally conductive silicone compositions] The viscosity of the thermally conductive silicone composition (before and after the addition of component (E)) was measured at 25°C using a rotational viscometer with a Malcolm viscometer (Type PC-10AA) manufactured by Malcolm Corporation.

[0069] [Printing workability] A 120 μm thick stainless steel plate for metal screens, cut into 3 cm squares, was prepared, and a thermally conductive silicone composition (grease) manufactured using a squeegee was applied to the heat sink. (Evaluation results) ○; The coating was applied uniformly across the entire surface. △; Slight unevenness occurred on the grease surface. ×; Grease gets stuck to the squeegee and cannot be applied at all.

[0070] A 0.3 mm spacer was placed between two glass slides, and a thermally conductive silicone composition was sandwiched between them in a circular shape with a diameter of 1.5 cm. This test specimen was then placed in an ESPEC Corporation thermal shock tester (model number: TSE-11-A) set to alternate between -40°C and 125°C (30 minutes each), with the specimen tilted 90 degrees to the ground, and a 500-cycle test was performed. After 500 cycles, the amount the thermally conductive silicone composition had shifted from its original position was measured. <Standards> If the difference is 1 mm or less, it can be said that the resistance to shearing is excellent.

[0071] [Appearance after displacement test] The state of the thermally conductive silicone composition after 500 cycles was observed. A composition without voids or cracks was rated as ○, while one with voids or cracks was rated as ×.

[0072] [Examples, Comparative Examples] As shown in Tables 1 and 2, each component was placed in a planetary mixer, and a thermally conductive silicone composition was prepared according to the following procedure. Specifically, components (B), (C), (D), and (F) were placed in a planetary mixer and stirred at room temperature for 10 minutes. Then, components (G) and (H) were added, the temperature was raised to 170°C, and the mixture was heated and mixed for 2 hours to allow the hydrosilylation reaction by components (F) and (G) to occur, thereby preparing a silicone gel crosslinked product of component (A). After cooling to below 40°C, component (E) was added to obtain the composition. The various tests described above were performed using the obtained composition. The results are shown in Tables 1 and 2.

[0073] [(B) Component] (B-1-1) [ka] Kinematic viscosity 35mm 2 / s (B-2-1) A linear 1,000 mm molecule with trimethylsilyl groups at both ends. 2 / s dimethylpolysiloxane.

[0074] [(C) component] (C-1) Zinc oxide powder (average particle size: 1.0 μm) (C-2) Alumina powder (average particle size: 10 μm)

[0075] [(D) component] (D-1) Metallic gallium [Melting point = 29.8°C] (D-2) Ga-In alloy [mass ratio = 75.4:24.6, melting point = 15.7℃] (D-3) Ga-In-Bi-Sn alloy [mass ratio = 9.4:47.3:24.7:18.6, melting point = 48.0℃] (D-4) Ga-In-Sn alloy [mass ratio = 68.5:21.5:10, melting point = -19℃] (D-5) Metallic Indium [Melting point = 156.2°C] <For comparison>

[0076] [(E) component] (E-1) IP Solvent 2028 (Isoparaffinic solvent, Idemitsu Kosan Co., Ltd. product name, boiling point: 210~254℃)

[0077] [Component (F)] (F-1) A linear dimethylpolysiloxane having vinyl groups at both ends and a kinematic viscosity of 600 mm 2 / s (F-2) A linear dimethylpolysiloxane having vinyl groups at both ends and a kinematic viscosity of 30,000 mm 2 / s

[0078] [Component (G)] (G-1) [Chemical formula] α / β = 0.35, kinematic viscosity 113 mm 2 / s (G-2) [Chemical formula] α / β = 0.13, kinematic viscosity 25 mm 2 / s

[0079] [Component (H)] (H-1) A solution obtained by dissolving a platinum-divinyltetramethyldisiloxane complex in the same dimethylpolysiloxane as (F-1) above (platinum atom content: 1% by mass).

[0080] [Table 1]

[0081] [Table 2]

Claims

1. (A) Silicone gel crosslinked material, (B) Silicone oil consisting of (B-1) and (B-2) below, which does not contain aliphatic unsaturated bonds and SiH groups, respectively: 30 to 90% by mass of the total of components (A) and (B), (B-1) Silicone oil comprising a single-ended hydrolyzable organopolysiloxane represented by the following general formula (1) 【Chemistry 1】 (In the formula, R 1 Each of these independently represents an alkyl group having 1 to 6 carbon atoms, and R 2 (where a represents one or more groups selected from the group of unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms and lacking an aliphatic unsaturated bond, and a is an integer from 5 to 120.) (B-2) Represented by the average composition formula (6) below, with a kinematic viscosity of 10 to 500,000 mm at 25°C. 2 / s non-functional liquid silicone oil R 7 g SiO (4-g) / 2 (6) (In the formula, R 7 Each of these is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms and lacking an aliphatic unsaturated bond. (g is a number in the range of 1.8 to 2.2.) (C) Thermally conductive filler with an average particle size of 0.01 to 100 μm: 10 to 2,000 parts by mass per 100 parts by mass of the total of components (A) and (B), and (D) Gallium or gallium alloy having a melting point of -20 to 100°C: 1,000 to 10,000 parts by mass per 100 parts by mass of the total of components (A) and (B), A thermally conductive silicone composition containing [a specific substance].

2. Furthermore, the thermally conductive silicone composition according to claim 1, further comprising (E) a volatile solvent in an amount of 1 to 500 parts by mass per 100 parts by mass of the total of components (A) and (B).

3. The thermally conductive silicone composition according to claim 1 or 2, wherein component (B-2) is a linear organopolysiloxane represented by the following formula (7). 【Chemistry 2】 (wherein, R 8 is a methyl group. h is a number such that the kinematic viscosity of the organopolysiloxane at 25 °C is 10 to 500,000 mm 2 / s.)

4. The thermally conductive silicone composition according to claim 3, wherein the amount of component (B-1) is 30 to 90% by mass of component (B), and the amount of component (B-2) is 10 to 70% by mass of component (B).

5. The thermally conductive silicone composition according to claim 1 or 2, wherein component (A) is an addition product of component (F) and component (G) in the presence of component (H) described below. (F) The following average composition formula (2) R 3 b R 4 c SiO (4-b-c) / 2 (2) (In the formula, R 3 represents an alkenyl group, R 4 (where b represents an unsubstituted or substituted monovalent hydrocarbon group without an aliphatic unsaturated bond, b is a number between 0.0001 and 0.2, c is a number between 1.7 and 2.2, and b + c is a number satisfying 1.9 to 2.4.) An organopolysiloxane having at least one alkenyl group bonded to a silicon atom represented by , (G) A molecule having at least four hydrogen atoms bonded to silicon atoms at the non-terminus of the molecular chain, and the following formula (3) ０．１＜α／β （３） (In the formula, α represents the number of hydrogen atoms bonded to silicon atoms at the non-terminal ends of the molecular chain, and β represents the total number of silicon atoms in component (G).) Organohydrogenpolysiloxanes that satisfy the requirements (H) Platinum-based catalyst.

6. The thermally conductive silicone composition according to claim 2, wherein component (E) is an isoparaffinic solvent having a boiling point of 80 to 360°C.

7. A method for producing the thermally conductive silicone composition according to claim 1, comprising the step of mixing components (B), (C), and (D).

8. A method for producing the thermally conductive silicone composition according to claim 5, comprising the steps of mixing components (F), (G), and (H) with components (B), (C), and (D), and heating the resulting mixture to cause an addition reaction between component (F) and component (G).