Thermally conductive silicone composition

Abstract

To provide a thermally conductive silicone composition containing a filler in a high content, having a low viscosity before curing, and achieving a high adhesive strength after curing.SOLUTION: The heat-conductive silicone composition comprises (A) an organopolysiloxane having at least two silicon-bonded alkenyl groups, (B) an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms, (C) a heat-conductive filler in an amount of 85 to 95 wt% based on the total weight of the composition, and (D) a platinum group metal-based catalyst in an amount sufficient to provide, per 1,000,000 parts by weight of the combined amount of components (A) and (B), (E) 0.3 to 1 part by weight, per 100 parts by weight of components (A) and (B) combined, of a cure retarder having a specific structure, and (F) 5 to 20 parts by weight, per 100 parts by weight of components (A) and (B) combined, of a polysiloxane having the structural unit (MeViSiO2 / 2), a silicon-bonded alkoxy group and an epoxy-containing organic group.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present disclosure relates to thermally conductive silicone compositions. [Background technology]

[0002] In recent years, there has been a demand for thermal interface materials with high thermal conductivity to efficiently dissipate heat generated by electronic devices that handle large volumes of information at high speeds. Thermal interface materials come in a variety of forms. Adhesive-type thermal interface materials generally require not only high thermal conductivity, but also low viscosity before curing to ensure sufficient conformability to opposing surfaces, and high adhesive strength between opposing surfaces after curing. One of the basic guidelines for achieving high thermal conductivity is to incorporate a high content of highly thermally conductive fillers into the resin component. To achieve uniform dispersion of fine fillers in the resin component at a high content, high shear forces may be required to mix the resin component and filler. This mixing process can lead to spontaneous heating of the mixture.

[0003] Patent Document 1 (JP 2015-4043 A) describes a thermally conductive silicone composition in which an organopolysiloxane having at least two aliphatic unsaturated hydrocarbon groups per molecule and an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule undergo a hydrosilylation reaction in the presence of a platinum group metal catalyst. Patent Document 1 also describes that the thermally conductive silicone composition may contain an inhibitor selected from acetylene compounds such as acetylene alcohols, nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. An example of Patent Document 1 describes the use of a platinum group metal catalyst with a platinum content of 9 ppm or less based on the mass of the organopolysiloxane having at least two aliphatic unsaturated hydrocarbon groups per molecule. However, when preparing a thermally conductive silicone composition containing a high filler content, even if a cure inhibitor is present in the thermally conductive silicone composition, spontaneous heating upon mixing can cause the hydrosilylation reaction to proceed partially, making it difficult to obtain a low-viscosity composition.

[0004] Therefore, we attempted to solve this problem caused by spontaneous heating during mixing by adding a cure inhibitor containing ethynyl or vinyl groups in the molecule in a larger than usual amount to the thermally conductive silicone composition. Cure inhibitors containing ethynyl or vinyl groups in the molecule are known. For example, Patent Document 2 (JP-B-64-2627) describes a silane compound containing three ethynyl groups. Patent Document 3 (US Pat. No. 3,445,420) describes compounds such as 3-methyl-1-butyn-3-ol and C6H5Si(OCH2C≡CH)3. Patent Document 4 (JP-B-1-12786) describes an organosilicon compound containing one or two ethynyl groups. Patent Document 5 (JP-B-53-35983) describes an acetylenic silane as a platinum catalyst inhibitor. Patent Document 6 (JP-A-9-143371) describes methylvinylbis(3-methyl-1-butyne-3-oxy)silane as an addition reaction inhibitor. Patent Document 7 (JP-A-2009-523856) describes the general formula of a silylated acetylene inhibitor having 1 to 4 carbon-carbon triple bonds.

[0005] However, depending on the type of cure inhibitor, it may be necessary to add a large amount of the cure inhibitor to the thermally conductive silicone composition. In this case, the thermal conductivity of the cured product may decrease. Furthermore, even if the amount of platinum group metal catalyst is increased to match the increased amount of cure inhibitor, the cured product may not achieve sufficient die shear strength. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-4043 [Patent Document 2] Special Publication No. 64-2627 [Patent Document 3] U.S. Patent No. 3,445,420 [Patent Document 4] Special Publication No. 1-12786 [Patent Document 5] Special Publication No. 53-35983 [Patent Document 6] Japanese Patent Application Publication No. 9-143371 [Patent Document 7] Special Publication No. 2009-523856 [Patent Document 8] European Patent Application Publication No. 0764703A2 [Patent Document 9] Japanese Patent Application Laid-Open No. 2001-139815 [Patent Document 10] Patent No. 6590445 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a thermally conductive silicone composition that contains a high content of thermally conductive filler, has a low viscosity before curing, and produces high adhesive strength after curing. [Means for solving the problem]

[0008] In order to solve the above problems, one embodiment of the present invention comprises the following components (A) to (F): (A) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule and having no silicon-bonded epoxy-containing organic groups; (B) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule: an amount such that the number of silicon-bonded hydrogen atoms in component (B) is 0.1 to 2.5 moles per mole of silicon-bonded alkenyl groups in component (A); (C) thermally conductive filler: an amount of 85 to 95% by mass based on the total mass of the thermally conductive silicone composition; (D) platinum group metal catalyst: an amount such that the platinum group metal element in the component (D) is at least 50 parts by mass per 1,000,000 parts by mass of the total amount of the component (A) and the component (B); (E) one or more curing inhibitors selected from the group consisting of compounds represented by the following general formula (I) and compounds represented by the following general formula (II): an amount of 0.3 to 1 part by mass per 100 parts by mass of the total amount of the component (A) and the component (B); [ka] [ka] In the general formula (I), n is 0 or 1, and when n is 0, R 1 does not exist;R 1 is a hydrocarbon group having 1 to 10 carbon atoms, and R 2 and R 3 are each independently selected from the group consisting of hydrogen and hydrocarbon groups having 1 to 10 carbon atoms, with the proviso that R 2 and R 3 may be linked to each other to form an alicyclic ring; In the general formula (II), R 4 is a hydrocarbon group having 1 to 10 carbon atoms, and R 5 and R 6 are each independently selected from the group consisting of hydrogen and hydrocarbon groups having 1 to 10 carbon atoms, with the proviso that R 5 and R 6 may be linked to each other to form an alicyclic ring, and (F) A compound having at least one alkoxy group bonded to a silicon atom in one molecule and at least one epoxy group-containing organic group bonded to a silicon atom in one molecule, (MeViSiO 2 / 2 ) (wherein Me represents a methyl group and Vi represents a vinyl group) structural unit, and the mass fraction of the vinyl group per molecule is 1 to 20 mass %, in an amount of 5 to 20 parts by mass per 100 parts by mass of the total amount of the component (A) and the component (B); The present invention provides a thermally conductive silicone composition comprising:

[0009] In one embodiment of the present invention, the platinum group metal element in component (D) is present in an amount of 60 to 420 parts by mass per 1 million parts by mass of the combined amount of components (A) and (B).

[0010] In one embodiment of the present invention, the cure inhibitor is selected from the group consisting of compounds represented by general formula (I) and compounds represented by general formula (II), wherein in general formula (I), R 1 , R 2 , and R 3 are each independently selected from the group consisting of a methyl group, an ethyl group, a propyl group, a phenyl group, and a vinyl group, and in general formula (II), R 4 , R 5 , and R 6 are each independently selected from the group consisting of a methyl group, an ethyl group, a propyl group, a phenyl group, and a vinyl group.

[0011] In one embodiment of the present invention, the curing inhibitor has a melting point of −20° C. or lower. In this embodiment, the curing inhibitor does not crystallize and precipitate even during low-temperature storage, and the curing inhibitor remains uniformly dispersed in the system.

[0012] In one embodiment of the present invention, the cure inhibitor has a boiling point of at least 200°C. In this embodiment, the low volatility of the cure inhibitor allows it to exhibit a stable cure-inhibiting effect, and also achieves the goal of stabilizing the viscosity of the thermally conductive silicone composition after mixing with the thermally conductive filler.

[0013] In one embodiment of the present invention, the cure inhibitor is one or more compounds selected from the group consisting of methyltris(3-methyl-1-butyn-3-oxy)silane and methylvinylbis(3-methyl-1-butyn-3-oxy)silane.

[0014] In one embodiment of the present invention, the thermally conductive filler has a color other than colorless or white. Generally, a combination of the platinum group metal catalyst at the above concentrations and the cure inhibitor at the above concentrations discolors the silicone component to brown or black. Therefore, in this embodiment, by having the thermally conductive filler have a color other than colorless or white, the objective of stabilizing the color of the thermally conductive silicone composition can also be achieved. [Effects of the Invention]

[0015] The thermally conductive silicone composition of the present invention has the advantages of having low viscosity before curing and exhibiting high adhesive strength and high thermal conductivity after curing. DETAILED DESCRIPTION OF THE INVENTION

[0016] Component (A) of the thermally conductive silicone composition of the present invention is an organopolysiloxane that contains two or more silicon-bonded alkenyl groups per molecule, but does not contain any silicon-bonded epoxy-containing organic groups. Examples of the alkenyl groups include alkenyl groups having 2 to 12 carbon atoms, such as vinyl, allyl, butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, and dodecenyl, with vinyl being preferred. In addition, examples of groups bonded to silicon atoms in component (A) other than alkenyl groups include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 12 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 12 carbon atoms, such as benzyl, phenethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine.

[0017] As long as the organopolysiloxane of component (A) has two or more silicon-bonded alkenyl groups per molecule and an epoxy-containing organic group per molecule, the molecular structure of component (A) is not limited. It may be, for example, linear, partially branched, cyclic, branched, or a three-dimensional network structure. In one embodiment, the molecular structure of component (A) is linear or partially branched, preferably linear. Component (A) may be a single polymer having these molecular structures, a copolymer containing these molecular structures, or a mixture of two or more of these polymers. Furthermore, in one embodiment, a small amount of hydroxyl or alkoxy groups may be bonded to silicon atoms in the component (A) molecule, provided that the objectives of the present invention are not impaired. In another embodiment, component (A) does not contain silicon-bonded hydroxyl or alkoxy groups. In one embodiment, component (A) does not contain two or more silicon-bonded hydrogen atoms per molecule. In another embodiment, component (A) does not contain any hydrogen atoms bonded to silicon atoms.

[0018] Examples of linear organopolysiloxanes include dimethylpolysiloxanes end-blocked with dimethylvinylsiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers end-blocked with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers end-blocked with dimethylvinylsiloxy groups, methylphenylpolysiloxanes end-blocked with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers end-blocked with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymers end-blocked with trimethylsiloxy groups, and mixtures of two or more of these. In one embodiment, component (A) is a dimethylpolysiloxane end-blocked with dimethylvinylsiloxy groups. Furthermore, such organopolysiloxanes may contain small amounts of hydroxyl or alkoxy groups bonded to silicon atoms within the molecule, provided that the objectives of the present invention are not impaired.

[0019] In one embodiment, the branched or three-dimensional network structure organopolysiloxane may be, for example, an organopolysiloxane represented by the formula: R 7 3SiO 1 / 2 Siloxane units represented by the formula: R 7 2nd Round 8 SiO 1 / 2 and siloxane units represented by the formula: SiO 4 / 2 Organopolysiloxane resins containing siloxane units represented by the formula:

[0020] In the formula, R 7 are the same or different and are monovalent hydrocarbon groups having 1 to 12 carbon atoms and no aliphatic unsaturated bonds. Examples of such monovalent hydrocarbon groups include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 12 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 12 carbon atoms, such as benzyl, phenethyl, and phenylpropyl; and groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine. In one embodiment, R 7 is a methyl group.

[0021] In the formula, R 8 is an alkenyl group having 2 to 12 carbon atoms, and examples of this alkenyl group include a vinyl group, an allyl group, a butenyl group, a pentenyl group, a hexenyl group, a heptenyl group, an octenyl group, a nonenyl group, a decenyl group, an undecenyl group, and a dodecenyl group. 8 is a vinyl group.

[0022] The organopolysiloxane resin has the formula: R 7 3SiO 1 / 2 Siloxane units represented by the formula: R 7 2nd Round 8 SiO 1 / 2 and siloxane units represented by the formula: SiO4 / 2 However, the present invention is not limited to the above-mentioned siloxane units represented by the formula: R 7 SiO 3 / 2 Furthermore, such organopolysiloxane resins may contain small amounts of hydroxyl groups or alkoxy groups bonded to silicon atoms in the molecule, provided that the object of the present invention is not impaired.

[0023] There are no particular restrictions on the viscosity of component (A). However, from the perspective of ensuring good handling and workability of the composition, the viscosity of component (A) at 25°C is preferably within the range of 20 to 2000 mPa·s, and more preferably within the range of 500 to 1500 mPa·s.

[0024] The component (B) of the thermally conductive silicone composition of the present invention is an organohydrogenpolysiloxane containing two or more silicon-bonded hydrogen atoms per molecule. Component (B) can function as a crosslinker and / or chain extender. The bonding positions of the silicon-bonded hydrogen atoms in component (B) are not limited, and they may be at the molecular chain terminals, side chains, or both terminals and side chains of the organohydrogenpolysiloxane. The molecular structure of component (B) is not particularly limited, and may be, for example, a linear, partially branched linear, branched, cyclic, or three-dimensional network structure. In one embodiment, the molecular structure of component (B) may be a linear or partially branched linear structure. Component (B) may be a single polymer having these molecular structures, a copolymer containing these molecular structures, or a mixture of two or more of these polymers. In addition to the silicon-bonded hydrogen atoms, component (B) contains organic groups bonded to the silicon atoms. In one embodiment, a small amount of hydroxyl groups or alkoxyl groups may be bonded to silicon atoms in the molecules of component (B) as long as the object of the present invention is not impaired. In one embodiment, component (B) does not contain any hydroxyl groups or alkoxyl groups bonded to silicon atoms. In one embodiment, component (B) does not contain any epoxy-containing organic groups bonded to silicon atoms.

[0025] Examples of organic groups bonded to silicon atoms contained in component (B) include alkyl groups having 1 to 12 carbon atoms, such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, and dodecyl; aryl groups having 6 to 12 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups having 7 to 12 carbon atoms, such as benzyl and phenethyl; and groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms, such as fluorine, chlorine, or bromine, for example, halogen-substituted alkyl groups such as 3-chloropropyl and 3,3,3-trifluoropropyl, with methyl being preferred.

[0026] Examples of component (B) include methylhydrogenpolysiloxanes terminated at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups, dimethylsiloxane-methylhydrogensiloxane-methylphenylsiloxane copolymers terminated at both molecular chain ends with trimethylsiloxy groups, dimethylpolysiloxanes terminated at both molecular chain ends with dimethylhydrogensiloxy groups, dimethylsiloxane-methylphenylsiloxane copolymers terminated at both molecular chain ends with dimethylhydrogensiloxy groups, methylphenylpolysiloxanes terminated at both molecular chain ends with dimethylhydrogensiloxy groups, cyclic methylhydrogenpolysiloxanes, and compounds of the formula: R 9 3SiO 1 / 2 Siloxane units represented by the formula: R 9 2HSiO 1 / 2 Siloxane units represented by the formula: SiO 4 / 2 Organopolysiloxane copolymers consisting of siloxane units represented by the formula: R 9 2HSiO 1 / 2 Siloxane units represented by the formula: SiO 4 / 2 Organopolysiloxane copolymers consisting of siloxane units represented by the formula: R 9 HSiO 2 / 2 Siloxane units represented by the formula: R 9 SiO 3 / 2 Siloxane units or compounds represented by the formula: HSiO3 / 2 Examples of the organopolysiloxane include organopolysiloxane copolymers consisting of siloxane units represented by the formula: 9 is an alkyl group having 1 to 6 carbon atoms or a phenyl group, and is preferably a methyl group.

[0027] In one embodiment, the amount of component (B) in the thermally conductive silicone composition of the present invention is such that the number of silicon-bonded hydrogen atoms in component (B) is preferably 0.1 to 2.5 moles, and more preferably 0.7 to 2.5 moles, per mole of silicon-bonded alkenyl groups in component (A).

[0028] Component (C) of the thermally conductive silicone composition of the present invention is a thermally conductive filler. In one embodiment of the present invention, the thermally conductive filler (component (C)) is preferably contained in the thermally conductive silicone composition in an amount of 85 to 95 mass%, more preferably 87 to 93 mass%, and even more preferably 89 to 91 mass%, based on the total mass of the thermally conductive silicone composition. As used herein, the phrase "based on the total mass of the thermally conductive silicone composition" means that when specifying the amount of thermally conductive filler contained in the thermally conductive silicone composition, the mass % of the thermally conductive filler is calculated based on the combined mass of all components contained in the thermally conductive silicone composition.

[0029] In one embodiment of the present invention, the thermally conductive filler (component (C)) is preferably contained in the thermally conductive silicone composition in an amount of 68 to 90 volume %, more preferably 73 to 85 volume %, and even more preferably 76 to 80 volume %, based on the total volume of the thermally conductive silicone composition. Here, volume % is measured at 25°C. In this specification, the phrase "based on the total volume of the thermally conductive silicone composition" means that when specifying the amount of thermally conductive filler contained in the thermally conductive silicone composition, the volume % of the thermally conductive filler is calculated based on the volume of the entire thermally conductive silicone composition.

[0030] In one embodiment of the present invention, the amount of the thermally conductive filler as component (C) is preferably 850 to 2000 parts by mass, more preferably 1000 to 1600 parts by mass, and even more preferably 1100 to 1500 parts by mass, per 100 parts by mass of the combined amount of components (A) and (B).

[0031] Component (C) may be a single type of thermally conductive filler or a combination of two or more thermally conductive fillers that differ in at least one property, such as particle shape, average particle size, particle size distribution, and filler type. In one embodiment, a mixture of thermally conductive fillers may be used. In this case, multiple thermally conductive fillers with different average particle sizes, which may be composed of the same or different chemical substances, may be used. For example, in one embodiment, a first thermally conductive filler having a larger average particle size may be used, and a second thermally conductive filler having a smaller average particle size than the first filler. In another embodiment, a first thermally conductive filler having a larger average particle size may be used, and a second thermally conductive filler having a smaller average particle size than the first filler may be used, and a third thermally conductive filler having a smaller average particle size than the second filler. Using multiple thermally conductive fillers with different average particle sizes can improve the loading efficiency of the thermally conductive filler in the thermally conductive silicone composition, reduce viscosity, and improve thermal conductivity. For example, in one embodiment, a combination of a first aluminum filler having a larger average particle size and a second aluminum filler having a smaller average particle size may be used, or in one embodiment, a combination of a first aluminum filler having a larger average particle size, a second aluminum filler having a smaller average particle size, and a third zinc oxide and / or aluminum oxide filler having an average particle size smaller than the average particle size of the second aluminum filler may be used.

[0032] The shape of the thermally conductive filler particles is not particularly limited, but if the thermally conductive filler is circular or spherical, undesirable increases in viscosity due to high thermally conductive filler content can be suppressed. The average particle size of the thermally conductive filler depends on various factors, including the type and amount of thermally conductive filler and the thickness of the bond in the device in which the cured product of the thermally conductive silicone composition is used. In one embodiment, the thermally conductive filler may have an average particle size preferably in the range of 0.1 to 80 micrometers, more preferably 0.1 to 50 micrometers, or even more preferably 0.1 to 10 micrometers.

[0033] Any known thermally conductive filler can be used as component (C) as long as it does not contradict the objectives of the present invention. Materials constituting the thermally conductive filler include, for example, the following materials: metals such as bismuth, lead, tin, antimony, indium, cadmium, zinc, silver, copper, nickel, aluminum, iron, and metallic silicon; alloys such as alloys of two or more metals selected from the group consisting of bismuth, lead, tin, antimony, indium, cadmium, zinc, silver, aluminum, iron, and metallic silicon; metal oxides such as aluminum oxide, silica (SiO2), silica gel, zinc oxide, silicon oxide, magnesium oxide, beryllium oxide, chromium oxide, and titanium oxide; metal hydroxides such as magnesium hydroxide, aluminum hydroxide, barium hydroxide, and calcium hydroxide; metal nitrides such as boron nitride, aluminum nitride, and silicon nitride; metal carbides such as silicon carbide, boron carbide, and and titanium carbide; metal silicides such as magnesium silicide, titanium silicide, zirconium silicide, tantalum silicide, niobium silicide, chromium silicide, tungsten silicide, and molybdenum silicide; carbon such as diamond, graphite, fullerenes, carbon nanotubes, graphene, activated carbon, and amorphous carbon black; soft magnetic alloys such as Fe—Si alloys, Fe—Al alloys, Fe—Si—Al alloys, Fe—Si—Cr alloys, Fe—Ni alloys, Fe—Ni—Co alloys, Fe—Ni—Mo alloys, Fe—Co alloys, Fe—Si—Al—Cr alloys, Fe—Si—B alloys, and Fe—Si—Co—B alloys; and ferrites such as Mn—Zn ferrite, Mn—Mg—Zn ferrite, Mg—Cu—Zn ferrite, Ni—Zn ferrite, Ni—Cu—Zn ferrite, and Cu—Zn ferrite. Preferably, component (C) can be a thermally conductive filler made of a material selected from the group consisting of aluminum oxide, aluminum nitride, boron nitride, zinc oxide, magnesium oxide, aluminum, silver, and copper.

[0034] In one embodiment of the present invention, the thermally conductive filler may have a color other than colorless and white. The thermally conductive filler having a color other than colorless and white may be selected from, for example, any of the materials specifically listed above. For example, thermally conductive fillers having a color other than colorless and white include, but are not limited to, graphite, silver, aluminum, boron nitride, and aluminum nitride.

[0035] Component (D) is a platinum group metal catalyst. The platinum group metal catalyst functions as a hydrosilylation catalyst to accelerate the curing of the thermally conductive silicone composition of the present invention. Component (D) may contain one or more platinum group elements selected from the group consisting of platinum, rhodium, ruthenium, palladium, osmium, and iridium. In one embodiment, examples of component (D) include platinum-based catalysts, rhodium-based catalysts, and palladium-based catalysts. From the perspective of accelerating the curing of the thermally conductive silicone composition of the present invention, platinum-based catalysts are preferred as component (D). Examples of platinum-based catalysts include platinum fine powder, chloroplatinic acid, an alcohol solution of chloroplatinic acid, a platinum-alkenylsiloxane complex, a platinum-olefin complex, and a platinum-carbonyl complex. Examples of the alkenylsiloxane of the platinum-alkenylsiloxane complex include 1,3-divinyl-1,1,3,3-tetramethyldisiloxane, 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, alkenylsiloxanes in which some of the methyl groups of these alkenylsiloxanes have been substituted with ethyl groups, phenyl groups, or the like, and alkenylsiloxanes in which the vinyl groups of these alkenylsiloxanes have been substituted with allyl groups, hexenyl groups, or the like.

[0036] The content of component (D) in the thermally conductive silicone composition of the present invention is an amount such that the platinum group metal element in component (D) is at least 50 parts by weight, preferably 50 to 220 parts by weight, per 1 million parts by weight of the combined total of components (A) and (B). The content of component (D) in the present invention is significantly greater than the amount of platinum group metal catalyst typically used in prior art thermally conductive silicone compositions, such as those disclosed in Patent Document 1 (JP 2015-4043 A). This amount allows for adequate hydrosilylation reaction when the amount of component (E), described below, is 0.3 to 1 part by weight per 100 parts by weight of the combined total of components (A) and (B). If the content of component (D) in the composition of the present invention is less than the lower limit of the above range, the cured product may not exhibit sufficient die shear strength.

[0037] Component (E) in the thermally conductive silicone composition of the present invention is one or more cure inhibitors selected from the group consisting of compounds represented by the following general formula (I) and compounds represented by the following general formula (II):

[0038] [ka] [ka]

[0039] In the general formula (I), n is 0 or 1, and when n is 0, R 1 does not exist;R 1 is a hydrocarbon group having 1 to 10 carbon atoms, and R 2 and R 3 are each independently selected from the group consisting of hydrogen and hydrocarbon groups having 1 to 10 carbon atoms, with the proviso that R 2 and R 3 may be linked to each other to form an alicyclic ring;

[0040] In general formula (II), R 4 is a hydrocarbon group having 1 to 10 carbon atoms, and R 5 and R6 are each independently selected from the group consisting of hydrogen and hydrocarbon groups having 1 to 10 carbon atoms, with the proviso that R 5 and R 6 may be linked to each other to form an alicyclic ring.

[0041] R in general formula (I) and general formula (II) 1 , R 2 , R 3 , R 4 , R 5 , and R 6 The hydrocarbon groups having 1 to 10 carbon atoms each independently include, for example, an alkyl group, an alkenyl group, an alkynyl group, and an aromatic hydrocarbon group. In general formula (I) and general formula (II), unless otherwise specified, R 1 ~R 6 The alkyl group, alkenyl group, and alkynyl group as the hydrocarbon group may have a straight chain, branched chain, or cyclic structure, and may have an aromatic hydrocarbon group as a substituent. 1 ~R 6 In the case where the alkyl group, alkenyl group, and alkynyl group as the hydrocarbon group have a substituent, the number of carbon atoms of the alkyl group, alkenyl group, and alkynyl group including the substituent is 10 or less. In general formula (I) and general formula (II), unless otherwise specified, R 1 ~R 6 The aromatic hydrocarbon group as the hydrocarbon group may have an alkyl group, an alkenyl group, or an alkynyl group as a substituent. 1 ~R 6 When the aromatic hydrocarbon group as the hydrocarbon group has a substituent, the aromatic hydrocarbon group including the substituent has 10 or less carbon atoms.

[0042] In one embodiment, R in general formula (I) 1 and R in general formula (II) 4is selected from the group consisting of a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a phenyl group, a vinyl group, an allyl group, a 1-propenyl group, an ethynyl group, and a 2-propynyl group, and R 2 and R 3 and R in general formula (II) 5 and R 6 are each independently selected from the group consisting of hydrogen, methyl, ethyl, n-propyl, isopropyl, phenyl, vinyl, allyl, 1-propenyl, ethynyl, and 2-propynyl. 1 is selected from the group consisting of an alkenyl or alkynyl group, e.g., a vinyl group, an allyl group, a 1-propenyl group, an ethynyl group, and a 2-propynyl group; R 2 and R 3 are each independently selected from hydrogen, an alkyl group, and an aromatic hydrocarbon group, preferably hydrogen, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a phenyl group. 4 is selected from the group consisting of an alkenyl or alkynyl group, e.g., a vinyl group, an allyl group, a 1-propenyl group, an ethynyl group, and a 2-propynyl group; R 5 and R 6 are each independently selected from hydrogen, an alkyl group, and an aromatic hydrocarbon group, preferably hydrogen, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, and a phenyl group. 1 , R 2 and R 3 are each independently selected from alkyl groups and aromatic hydrocarbon groups, preferably from methyl, ethyl, n-propyl, isopropyl, and phenyl groups. 4 , R 5 and R 6are each independently selected from alkyl groups and aromatic hydrocarbon groups, preferably from methyl, ethyl, n-propyl, isopropyl, and phenyl groups. 1 , R 2 , and R 3 In another embodiment, in general formula (II), R 4 , R 5 , and R 6 In another embodiment, in general formula (I), R 2 and R 3 may be linked to each other to form an alicyclic ring, and R 2 and R 3 The alicyclic ring formed by the mutual connection of R is preferably a 5- to 7-membered ring, more preferably a 6-membered ring. 5 and R 6 may be linked to each other to form an alicyclic ring, and R 5 and R 6 The alicyclic ring formed by the mutual connection of R is preferably a 5- to 7-membered ring, more preferably a 6-membered ring. 2 and R 3 and an alicyclic ring formed by interconnecting them, and 5 and R 6 The alicyclic ring formed by the mutual bonding of these groups may have a substituent, and this substituent is preferably an alkyl group.

[0043] In one embodiment of the present invention, examples of the curing inhibitor include methyltris(3-methyl-1-butyn-3-oxy)silane, methylvinylbis(3-methyl-1-butyn-3-oxy)silane, tetra(3-methyl-1-butyn-3-oxy)silane, divinylbis(3-methyl-1-butyn-3-oxy)silane, ethyltris(3-methyl-1-butyn-3-oxy)silane, ethylvinylbis(3-methyl-1-butyn-3-oxy)silane, propyltris(3-methyl-1-butyn-3-oxy)silane, propylvinylbis(3-methyl-1-butyn-3-oxy)silane, phenyltris(3-methyl-1-butyn-3-oxy)silane, phenylvinylbis(3-methyl-1-butyn-3- oxy)silane, methyltris(3-methyl-1-pentyn-3-oxy)silane, methylvinylbis(3-methyl-1-pentyn-3-oxy)silane, tetra(3-methyl-1-pentyn-3-oxy)silane, divinylbis(3-methyl-1-pentyn-3-oxy)silane, ethyltris(3-methyl-1-pentyn-3-oxy)silane, ethylvinylbis(3-methyl-1-pentyn-3-oxy)silane, methyltris(cyclohexyl-1-ethyn-1-oxy)silane, methylvinylbis(cyclohexyl-1-ethyn-1-oxy)silane, tetra(cyclohexyl-1-ethyn-1-oxy)silane, divinylbis(cyclohexyl-1-ethyn-1-oxy)silane, and the like may be mentioned.

[0044] In one embodiment of the present invention, the amount of component (E) in the thermally conductive silicone composition is 0.3 to 1 part by mass, preferably 0.5 to 1 part by mass, and more preferably 0.7 to 1 part by mass, per 100 parts by mass of the combined total of components (A) and (B). If the amount of component (E) is less than 0.3 part by mass per 100 parts by mass of the combined total of components (A) and (B), the cure inhibitor effect will be insufficient, the viscosity of the thermally conductive silicone composition will increase when the thermally conductive filler is mixed with other components, and the cured product may not achieve sufficient die shear strength. If the amount of component (E) is more than 1 part by mass per 100 parts by mass of the combined total of components (A) and (B), the platinum group metal catalyst in component (D) may be deactivated, resulting in poor curing of the thermally conductive silicone composition.

[0045] While not wishing to be bound by any theory, it is believed that in the present invention, by having component (E) have three or more ethynyl groups per molecule, as specified by the above general formula (I), or by having two or more ethynyl groups and one or more vinyl groups per molecule, as specified by the above general formula (II), component (E) functions as a cure inhibitor under conditions where curing of the thermally conductive silicone composition is not desired, such as conditions below the curing temperature, while component (E) acts as a crosslinker, reacting with SiH groups under the curing conditions of the thermally conductive silicone composition, improving resin strength and also improving the adhesive strength of the cured product of the thermally conductive silicone composition. Furthermore, while not wishing to be bound by any theory, it is believed that because component (E), which is a cure inhibitor, also functions as a crosslinker, the amount of crosslinker added as an additional component to the thermally conductive silicone composition can be reduced, allowing the proportion of thermally conductive filler contained in the thermally conductive silicone composition to be increased, resulting in an increase in thermal conductivity while maintaining the adhesive strength of the cured product of the thermally conductive silicone composition.

[0046] In one embodiment of the present invention, the total mass fraction of ethynyl groups and vinyl groups contained in one molecule of component (E), expressed as the total mass fraction of vinyl groups when one ethynyl group is equivalent to two vinyl groups, is preferably 45% by mass or more, and more preferably 50% by mass or more, per molecule. Without wishing to be bound by any theory, it is believed that in this embodiment, because component (E) has a high mass fraction of ethynyl groups and, in some cases, vinyl groups, it is possible to increase the number of crosslinks per silicone component in the thermally conductive silicone composition, and as a result, it is possible to achieve the above-mentioned effects of the present invention.

[0047] The compounds represented by general formula (I) or general formula (II) can be synthesized according to known synthesis methods, for example, methods disclosed in Patent Document 7 (JP-A-2009-523856) and Patent Document 8 (EP-A-0764703A2). For example, in the case of the compound of general formula (I), R 1 n SiCl 4-n and HO-CR 2 R 3 For example, in the case of a compound of general formula (II), R 4 (CH2=CH-)SiCl2 and HO-CR 5 R 6 It can be prepared by silylation of an alcohol, such as by reacting R with —C≡CH. 1 , R 2 , R 3 , R 4 , R 5 , R 6 and n is as defined above.

[0048] In one embodiment of the present invention, the cure inhibitor has a melting point of −20° C. or lower. Examples of cure inhibitors having a melting point of −20° C. or lower include methyltris(3-methyl-1-butyn-3-oxy)silane and methylvinylbis(3-methyl-1-butyn-3-oxy)silane. Note that the melting point in the present invention is the melting point at 1 atmosphere.

[0049] In one embodiment of the present invention, the cure inhibitor has a boiling point of 200°C or higher. Examples of cure inhibitors having a boiling point of 200°C or higher include methyltris(3-methyl-1-butyn-3-oxy)silane (boiling point: 250°C). Note that the boiling point in the present invention is the boiling point at 1 atmosphere.

[0050] Component (F) of the thermally conductive silicone composition of the present invention is an adhesion promoter. In one embodiment, the adhesion promoter of the present invention has at least one alkoxy group bonded to a silicon atom per molecule, and at least one epoxy-containing organic group bonded to a silicon atom per molecule, and is (MeViSiO 2 / 2 ) (wherein Me represents a methyl group and Vi represents a vinyl group), and the mass fraction of vinyl groups per molecule is 1 to 20 mass%. The mass fraction of vinyl groups per molecule of the polysiloxane of component (F) is preferably 1 to 20 mass%, more preferably 5 to 10 mass%. The tackifier has the function of improving the adhesion of the thermally conductive silicone composition to a substrate. Without wishing to be bound by any theory, it is believed that in the thermally conductive silicone composition of the present invention, the tackifier has a certain amount of vinyl-containing structural units in the polysiloxane chain, and the amount of tackifier used is greater than the amount typically used (an amount that does not significantly affect the cure rate of the composition, for example, about 2 mass% of the combined amount of components (A) and (B)). This increases the number of vinyl groups in the tackifier that coordinate to Pt, resulting in a delay in the cure of the thermally conductive silicone composition.

[0051] Examples of alkoxy groups contained in the polysiloxane of component (F) include methoxy, ethoxy, propoxy, and methoxyethoxy groups, with methoxy being preferred. In this specification, the term "silicon-bonded epoxy-containing organic group" refers to an epoxy-containing organic group bonded to a silicon atom via a carbon atom of the epoxy-containing organic group. In one embodiment of the present invention, the "epoxy-containing organic group" is an organic group containing an oxirane ring, preferably an alkyl group containing an oxirane ring. Examples of epoxy-containing organic groups include, but are not limited to, glycidoxyalkyl groups such as 2-glycidoxyethyl, 3-glycidoxypropyl, and 4-glycidoxybutyl; epoxycyclohexylalkyl groups such as 2-(3,4-epoxycyclohexyl)ethyl and 3-(3,4-epoxycyclohexyl)propyl; and oxiranylalkyl groups such as 3,4-epoxybutyl (also referred to as 4-oxiranylbutyl) and 7,8-epoxyoctyl (also referred to as 8-oxiranyloctyl). Examples of groups other than the alkoxy groups and epoxy-containing organic groups bonded to the silicon atoms of the polysiloxane as an adhesion promoter include substituted or unsubstituted monovalent hydrocarbon groups such as alkyl, alkenyl, aryl, aralkyl, and halogenated alkyl groups; (meth)acrylic-containing monovalent organic groups such as 3-methacryloxypropyl; and hydrogen atoms. The molecular structure of the polysiloxane used as the adhesion promoter can be linear, partially branched linear, branched, cyclic, or network, with linear, branched, or network structures being particularly preferred. Here, the term "(meth)acrylic" in this specification refers to either or both of acrylic and methacrylic. Furthermore, the term "polysiloxane" in this specification for component (F) encompasses not only siloxane polymers but also siloxane oligomers.

[0052] The polysiloxane of component (F) as an adhesion promoter is (MeViSiO 2 / 2In addition to the structural unit (where Me represents a methyl group and Vi represents a vinyl group), any structural unit may be included as long as it does not contradict the objectives of the present invention. For example, examples of adhesion promoters include reaction mixtures of vinyl- and methyl-containing diorganosiloxane oligomers capped at both molecular chain ends with silanol groups, such as dimethylsiloxane-methylvinylsiloxane copolymer oligomers capped at both molecular chain ends with silanol groups, and methylvinylsiloxane oligomers capped at both molecular chain ends with silanol groups, with epoxy-containing alkoxysilanes such as 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. Preferably, component (F) is a reaction mixture of a vinyl- and methyl-containing diorganosiloxane oligomer capped at both molecular chain ends with silanol groups, such as a dimethylsiloxane-methylvinylsiloxane copolymer oligomer capped at both molecular chain ends with silanol groups, or a methylvinylsiloxane oligomer capped at both molecular chain ends with silanol groups, with an epoxy-containing alkoxysilane. In one embodiment, component (F) is a compound represented by the formula: (MeViSiO 2 / 2 ) a (MeSiO 2 / 2 ) b (GlySiO 3 / 2 ) c (MeO 1 / 2 ) d (wherein Me represents a methyl group, Vi represents a vinyl group, Gly represents a 3-glycidoxypropyl group, and a, c, and d are positive numbers, and b is 0 or a positive number).

[0053] The tackifier is preferably a low-viscosity liquid, and although there are no limitations on its viscosity, it is more preferably in the range of 1 to 500 mPa·s at 25° C. Furthermore, in the above composition, the content of this tackifier is preferably 5 to 20 parts by mass, more preferably 8 to 15 parts by mass, per 100 parts by mass of the combined total of components (A) and (B).

[0054] In one embodiment of the present invention, the thermally conductive silicone composition may further comprise a surface treatment agent as component (G). Treating the surface of the thermally conductive filler with a surface treatment agent can further improve the dispersibility of the thermally conductive filler in the composition and further improve the handleability and moldability of the composition. There are no particular limitations on the surface treatment agent that can be used in the present invention, and known surface treatment agents can be used. Examples of surface treatment agents include the oligosiloxanes described in Patent Document 9 (JP 2001-139815 A) and the organosiloxanes represented by the following general formula (III) described in Patent Document 10 (JP Patent No. 6590445 A). In one embodiment, component (G) does not contain an epoxy group-containing organic group bonded to a silicon atom.

[0055] R 10 R 11 2SiO-(SiR 11 2O) e -(SiR 11 2)-R 12 -SiR 11 (3-f) (OR 13 ) f (III) In formula (III), R 10 is an unsubstituted or halogen-substituted monovalent hydrocarbon group, such as a linear alkyl group, a branched alkyl group, a cyclic alkyl group, an alkenyl group, an aryl group, an aralkyl group, or a halogenated alkyl group; R 11 may be the same or different and are monovalent hydrocarbon groups free of aliphatic unsaturated bonds, such as linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, aralkyl groups, or halogenated alkyl groups; R 12 is an oxygen atom or a divalent hydrocarbon group, for example, an alkylene group such as an ethylene group, a propylene group, a butylene group, a pentylene group, or a hexylene group, or an alkylenearylenealkylene group such as an ethylenephenyleneethylene group or an ethylenephenylenepropylene group, and R 13is an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, e is an integer of 1 or more, preferably an integer of 1 to 200, and f is an integer of 1 to 3. In another embodiment, the component (F) is a group represented by the above formula (III), where -R 12 -SiR 11 (3-f) (OR 13 ) f -O-(divalent hydrocarbon group)-SiR 11 (3-f) (OR 13 ) f The organosiloxane may be an organosiloxane having the following structure:

[0056] The amount of the surface treatment agent is not particularly limited as long as it is an amount that can fully exhibit the properties of the surface treatment agent, but it is preferably 0.01 to 10 parts by mass, and more preferably 0.1 to 2 parts by mass, per 100 parts by mass of component (C).

[0057] In addition to the above components, the thermally conductive silicone composition may contain optional components other than those described above, as long as the object of the present invention is achieved. Examples of optional components include pigments, dyes, fluorescent dyes, heat-resistant additives, flame retardants such as triazole-based compounds, and plasticizers.

[0058] The method for producing the thermally conductive silicone composition of the present invention is not particularly limited. The thermally conductive silicone composition of the present invention can be produced according to conventional methods for producing silicone compositions containing a thermally conductive filler. Conventional mixing / stirring devices, such as kneaders, Ross mixers, Hobart mixers, and dental mixers, can be used when mixing the thermally conductive filler with the silicone component. Because the thermally conductive silicone composition of the present invention contains a high amount of thermally conductive filler, it is preferable to use kneaders, Ross mixers, dental mixers, and other devices capable of providing high shear forces that can efficiently disperse the thermally conductive filler. During the production process, mixing of components (A), (B), and (D) in the presence of a thermally conductive filler that may cause a hydrosilylation reaction is preferably performed while cooling. More preferably, cooling is performed so that the composition reaches room temperature. When the thermally conductive filler is treated with a surface treatment agent, the thermally conductive filler may be previously treated with the surface treatment agent before being mixed with the other components, including component (A), or the thermally conductive filler that has not been treated with the surface treatment agent may be treated with the surface treatment agent at the same time as being mixed with the other components, including component (A). For example, the thermally conductive silicone composition of the present invention can be produced by a series of steps: adding component (A) to a kneader and stirring under nitrogen, adding component (C) to a kneader and stirring, heating (e.g., 100°C to 140°C) under vacuum (e.g., less than 10 mmHg) while stirring for a certain period of time, returning to normal pressure and cooling while adding component (E) and stirring, adding component (B) to a kneader and stirring for a certain period of time while cooling at normal pressure, adding component (D) to a kneader and stirring for a certain period of time while cooling at normal pressure, continuing stirring under reduced pressure and cooling, and then returning to normal pressure after stirring to recover the resulting thermally conductive silicone composition.

[0059] The thermally conductive silicone composition of the present invention can be applied, for example, between a heat-generating component such as an integrated circuit (IC) and a heat-dissipating component such as a heat spreader. The cured product obtained by curing the applied composition can efficiently transfer heat from the heat-generating component to the heat-dissipating component. The curing conditions for the thermally conductive silicone composition of the present invention are not particularly limited, but curing is carried out, for example, by heating at 50°C to 200°C, preferably 100°C to 180°C, and more preferably 120°C to 150°C. [Example]

[0060] The thermally conductive silicone composition of the present invention will be described in more detail in the following examples, but the present invention is not limited to the descriptions in the examples.

[0061] The various properties of the thermally conductive silicone compositions and their cured products in the examples and comparative examples were measured as follows. [viscosity] The viscosity of the thermally conductive silicone composition was measured at 25°C using a rotational viscometer (Anton Paar MCR 302, manufactured by Anton Paar GmbH). In Table 1, the viscosity of the thermally conductive silicone composition prepared by mixing the components of the composition is shown as "viscosity after mixing."

[0062] [Die shear strength] The adhesive strength of the cured polysiloxane is 36 mm 2 The thermally conductive silicone composition was cured at 150°C for 2 hours at the square adhesion site, and the adhesive strength of the cured silicone to the aluminum heat dissipation substrate was measured using a Seishin Shoji Bond Tester Model SS-100KP.

[0063] [Thermal conductivity evaluation] The thermal conductivity of a 10 mm × 60 mm × 30 mm cured silicone product obtained by curing the thermally conductive silicone composition at 150°C for 2 hours was measured using a hot disc thermal property measuring device TPS 2500 S manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0064] [Measurement of scorch time (ts1) and 90% vulcanization time (tc(90))] The thermally conductive silicone composition was cured for 600 seconds at a typical die bonding temperature (150°C) using a Curastometer® (PREMIER MDR manufactured by Alpha Technologies) according to the method specified in JIS K 6300-2:2001, "Unvulcanized Rubber - Physical Properties - Part 2: Determination of Vulcanization Properties Using an Oscillating Vulcanization Tester," and ts1 and tc(90) were measured. The measurement was performed by placing 5 ml of the thermally conductive silicone composition in the lower die and starting the measurement when the upper die closed. The measurement was performed using an R-type rubber die with an amplitude angle of 0.5°, a frequency of 100 rpm, and a torque range of 230 kgf cm.

[0065] [Viscosity increase during mixing] If the viscosity of the material inside the kneader obtained when preparing the thermally conductive silicone composition does not exceed 300 Pa s, it is determined that there was no increase in viscosity during mixing, and if the viscosity exceeded 300 Pa s, it was determined that there was an increase in viscosity during mixing. In the tables, cases where there was no increase in viscosity are shown as "none," and cases where there was an increase in viscosity are shown as "increase."

[0066] The components used in the examples and comparative examples are as follows: The following components were used as component (A): Component (a1): Dimethylpolysiloxane terminated at both ends of the molecule with dimethylvinylsiloxy groups (number average molecular weight (Mn) = 18,000, and number of dimethylsiloxane units = 200) (the mass fraction of vinyl groups bonded to silicon atoms in the molecule was 0.4 mass% based on the mass of the molecule).

[0067] The following components were used as component (B): Component (b1): Dimethylpolysiloxane terminated at both ends of the molecule with dimethylhydrogensiloxy groups (the mass fraction of hydrogen atoms bonded to silicon atoms in the molecule was 0.14 mass% based on the mass of the molecule). Component (b1) can function as a chain extender. Component (b2): Dimethylsiloxane-methylhydrogensiloxane copolymer terminated at both ends with trimethylsiloxy groups (the mass fraction of hydrogen atoms bonded to silicon atoms in the molecule was 1.59% by mass based on the molecular mass). Component (b2) can function as a crosslinking agent.

[0068] The following components were used as component (C): (c1) Component: Aluminum filler (D 50 = 17 μm; A19-1331 manufactured by Toyo Aluminum) (In this specification, D 50 is the particle size at which the cumulative frequency of the particle size distribution is 50%.) (c2) Component: Aluminum filler (D 50 = 2 μm; TCP2 manufactured by Toyo Aluminum) (c3) Component: ZnO filler (D 50 = 0.12 μm; ZoChem ZoCo102) In the examples of the present invention, in addition to zinc oxide, aluminum oxide filler (product name: Advanced Alumina AA04 (manufactured by Sumitomo Chemical Co., Ltd.)) can also be used.

[0069] The following components were used as component (D): Component (d1): Pt catalyst (Pt-VTSC-3.0IPA, manufactured by Umicore Japan Co., Ltd.; a solution of platinum complex in isopropyl alcohol with a Pt concentration of 3% by mass)

[0070] The following components were used as component (E): Component (e1): methyltris(3-methyl-1-butyn-3-oxy)silane (JH-AkSi-1) (Component (e1) corresponds to the curing inhibitor of the present invention.) Component (e2): tetramethyltetravinylcyclotetrasiloxane (Component (e2) is a comparative example of a cure inhibitor that does not fall under the category of the cure inhibitor of the present invention.) Component (e3): 1-ethynyl-1-cyclohexanol (Component (e3) is a comparative example of a curing inhibitor that does not fall under the category of the curing inhibitors of the present invention.)

[0071] (F) The following components were used as adhesion promoters: Component (f1): a siloxane compound represented by the following formula: (MeViSiO 2 / 2 )8(Me2SiO 2 / 2 ) 19 (GlySiO 3 / 2 ) 38 (MeO 1 / 2 ) x In the formula, Me represents a methyl group, Vi represents a vinyl group, Gly represents a 3-glycidoxypropyl group, and x represents a positive number equal to or greater than 1. The mass fraction of vinyl groups per molecule was 5.63 mass%.

[0072] (G) The following components were used as surface treatment agents: Component (g1): Polydimethylsiloxane having the following formula: (CH3O)3Si-(C2H4) x -(O-Si(CH3)2) n -C4H9 In the formula, n is 58 to 65, and x is 3.

[0073] The thermally conductive silicone compositions of the examples and comparative examples were prepared according to the following procedure. (i) (a1) The components were placed in a kneader (a tabletop kneader SNV-1H manufactured by Irie Shokai Co., Ltd.). (ii) While purging with nitrogen and stirring, component (g1) and components (c1) and (c2) were added to the kneader, and stirring was continued (rotation speed: 1 / sec, stirring time: 0.25 hours, temperature: room temperature). (iii) The nitrogen purge was stopped, and component (c3) was added to the kneader. (iv) The contents of the kneader were heated to 120°C and stirred under reduced pressure (less than 10 mmHg) for 2 hours, at which point the temperature reached 140°C. (v) The pressure inside the kneader was returned to normal pressure, and the hardening inhibitor component (e1), (e2), or (e3) was added to the kneader, and the contents were stirred at normal pressure and room temperature for 0.5 hours. In this process, the contents of the kneader were cooled and stirred until they reached room temperature. (vi) Components (b1), (b2), (d1), and (f1) were added to a kneader. If used, component (f2) was also added to the kneader. (vii) The contents were stirred for 0.5 hours at normal pressure and room temperature. In this step, stirring was carried out while cooling the contents of the kneader so that the temperature of the contents was at room temperature. (viii) The contents were stirred for 0.5 hours at room temperature under reduced pressure (less than 10 mmHg). In this step, stirring was carried out while cooling the contents of the kneader so that the temperature reached room temperature. (ix) After stirring was completed, the pressure was returned to normal and the thermally conductive silicone composition was removed from the kneader.

[0074] Table 1 shows the parts by weight of each component used to prepare the thermally conductive silicone compositions of the examples and comparative examples, the various amounts and ratios of each component, and various properties of the resulting thermally conductive silicone compositions and their cured products. In Table 1, H / Vi represents [total number of silicon-bonded hydrogen atoms in component (B)] / [(total number of silicon-bonded vinyl groups in component (A)) + (total number of ethynyl groups in component (E) × 2 + total number of vinyl groups)]. When comparing the curing inhibitor of the present invention (Example 1) with the curing inhibitors of the comparative examples (Comparative Examples 1 and 2), the amounts of each curing inhibitor were determined so that the H / Vi values ​​were the same. In Examples 1 to 3 and Comparative Examples 1 to 4, there were 2.1 moles of silicon-bonded hydrogen atoms in component (B) per mole of silicon-bonded alkenyl groups in component (A). In Table 1, Pt (ppm) / [(A)(B)] represents the parts by mass of platinum element in component (D) relative to 1 million parts by mass of the total amount of components (A) and (B) in the composition. (In this specification, the term "ppm" represents parts per million, and 1 ppm represents one part per million.) In Table 1, Pt (ppm) / [(A)(B)(E)(F)(G)] represents the parts by mass of platinum element in component (D) per 1,000,000 parts by mass of the total amount of components (A), (B), (E), (F), and (G) in the composition. In Table 1, "Filler content (vol %)" represents the percentage by total volume of components (c1), (c2), and (c3) based on the total volume of the thermally conductive silicone composition at 25°C. In Table 1, the "filler content (mass %)" represents the percentage by total mass of components (c1), (c2), and (c3) based on the total mass of the thermally conductive silicone composition.

[0075] [Table 1]

[0076] The results of Examples 1 to 3 demonstrate that the thermally conductive silicone composition of the present invention has high thermal conductivity exceeding 3.0 W / m K, low viscosity of the composition after mixing the components (less than 150 Pa s), and a compressibility of 300 N / cm 2 This has the advantageous effect of enabling a high die shear strength exceeding 1000 MPa to be achieved. On the other hand, when the cure inhibitor was not a compound specified in the present invention (Comparative Examples 1 and 2), the viscosity of the resulting thermally conductive silicone composition was too high and the die shear strength of the cured product was low, making the composition unsuitable for use as a thermal interface material. When the amount of platinum group metal catalyst was below the lower limit of the range specified in the present invention (Comparative Example 3), the die shear strength of the cured product was low, and this composition was not suitable for use as a thermal interface material. When the amount of cure inhibitor was below the lower limit of the range specified in the present invention (Comparative Example 4), the viscosity of the resulting thermally conductive silicone composition was too high and the die shear strength of the cured product was low, making the composition unsuitable for use as a thermal interface material. [Industrial Applicability]

[0077] The thermally conductive silicone composition of the present invention can be used as a thermal interface material, etc.

Claims

1. The following components (A) to (F): (A) an organopolysiloxane having two or more silicon-bonded alkenyl groups in each molecule and having no silicon-bonded epoxy-containing organic groups; (B) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule: an amount such that the number of silicon-bonded hydrogen atoms in component (B) is 0.1 to 2.5 moles per mole of silicon-bonded alkenyl groups in component (A); (C) thermally conductive filler: an amount that is 85 to 95% by mass, based on the total mass of the thermally conductive silicone composition; (D) a platinum group metal catalyst: an amount such that the platinum group metal element in the component (D) is at least 50 parts by mass per 1,000,000 parts by mass of the total amount of the component (A) and the component (B); (E) one or more curing inhibitors selected from the group consisting of compounds represented by the following general formula (I) and compounds represented by the following general formula (II): an amount of 0.3 to 1 part by mass per 100 parts by mass of the total amount of the (A) component and the (B) component; 【Chemistry 1】 【Chemistry 2】 In the general formula (I), n is 0 or 1, and when n is 0, R １ does not exist; R １ is a hydrocarbon group having 1 to 10 carbon atoms, and R ２ and R ３ are each independently selected from the group consisting of hydrogen and hydrocarbon groups having 1 to 10 carbon atoms, with the proviso that R ２ and R ３ may be linked to each other to form an alicyclic ring; In the general formula (II), R ４ is a hydrocarbon group having 1 to 10 carbon atoms, and R ５ and R ６ are each independently selected from the group consisting of hydrogen and hydrocarbon groups having 1 to 10 carbon atoms, with the proviso that R ５ and R ６ may be linked to each other to form an alicyclic ring, and (F) A polymer having at least one alkoxy group bonded to a silicon atom in one molecule and at least one epoxy-containing organic group bonded to a silicon atom in one molecule, (MeViSiO ２／２ ) (wherein Me represents a methyl group and Vi represents a vinyl group) structural unit, and the mass fraction of the vinyl group per molecule is 1 to 20 mass %, in an amount of 5 to 20 parts by mass per 100 parts by mass of the total amount of the component (A) and the component (B); A thermally conductive silicone composition comprising:

2. 2. The thermally conductive silicone composition according to claim 1, wherein the platinum group metal element in component (D) is present in an amount of 60 to 420 parts by mass per 1,000,000 parts by mass of the combined total of components (A) and (B).

3. In the general formula (I), R １ , R ２ , and R ３ are each independently selected from the group consisting of a methyl group, an ethyl group, a propyl group, a phenyl group, and a vinyl group, and in the general formula (II), R ４ , R ５ , and R ６ 2. The thermally conductive silicone composition according to claim 1, wherein each of the groups is independently selected from the group consisting of a methyl group, an ethyl group, a propyl group, a phenyl group, and a vinyl group.

4. 2. The thermally conductive silicone composition according to claim 1, wherein the cure inhibitor has a melting point of −20° C. or lower.

5. 2. The thermally conductive silicone composition according to claim 1, wherein the cure inhibitor has a boiling point of 200°C or higher.

6. 2. The thermally conductive silicone composition according to claim 1, wherein the cure inhibitor is one or more compounds selected from the group consisting of methyltris(3-methyl-1-butyn-3-oxy)silane and methylvinylbis(3-methyl-1-butyn-3-oxy)silane.

7. 10. The thermally conductive silicone composition of claim 1, wherein the thermally conductive filler has a color other than colorless and white.

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