Thermally conductive silicone composition

Abstract

To provide a thermally conductive silicone composition that suppresses bubble formation in the composition during heat curing of the composition, and offers excellent heat dissipation properties.SOLUTION: A thermally conductive silicone composition contains (A) a composition containing (A-1), (A-2), and (A-3): (A-1) a silicone gel crosslinked product, (A-2) a silicone oil free of aliphatic unsaturated bonds and SiH groups, and (A-3) a thermally conductive filler, (B) an organopolysiloxane having two or more alkenyl groups bonded to silicon atoms per molecule, (C) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to silicon atoms per molecule, (D) a platinum catalyst, and (E) an addition reaction controller. The thermally conductive silicone composition is curable and has a viscosity at 25°C of 50 to 1,500 Pa s.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive silicone composition that generates minimal bubbles during curing. [Background technology]

[0002] Because electronic components such as CPUs mounted on printed circuit boards can experience performance degradation or damage due to temperature rises caused by heat generation during use, thermal sheets or thermal grease with good thermal conductivity have traditionally been used between electronic components and heat dissipation fins, etc. Thermal sheets have the advantage of being easy to attach, but because the surfaces of CPUs, heat dissipation fins, etc. may appear smooth at first glance but are uneven when viewed microscopically, it is actually difficult to securely attach the sheet to these surfaces, leaving air pockets that prevent the expected heat dissipation effect.

[0003] To solve this problem, proposals have been made to improve adhesion by providing an adhesive layer on the surface of the heat-dissipating sheet, but satisfactory results have not been obtained. Thermal grease conforms well to the surface to which it is attached without being affected by the unevenness of the surface of the CPU, heat-dissipating fins, etc., and provides adhesion. However, problems such as soiling other components and oil leakage after long-term use tend to occur. For this reason, a method has been proposed in which a liquid silicone rubber composition is used as a potting agent or adhesive (see Patent Document 1).

[0004] Generally, electronic components such as CPUs are sealed between the silicon chip and the organic substrate using an epoxy resin-based underfill agent. However, the silicon chip, organic substrate, and underfill agent all have different thermal expansion coefficients. Therefore, temperature changes can cause the silicon chip and substrate to warp due to differences in the thermal expansion coefficients of each component. Sometimes, the silicon chip's periphery warps by several tens of microns compared to its center. However, heat spreaders or heat sinks placed on the silicon chip are large and strong structures, so they do not warp. Therefore, if the heat dissipation material sandwiched between the silicon chip and the heat spreader or heat sink cannot conform to the warpage of the silicon chip, it will peel off, resulting in increased thermal resistance and an inability to achieve the desired heat dissipation performance. Therefore, the heat dissipation material used must be flexible enough to conform to the warpage of the silicon chip. However, the composition described in Patent Document 1 is very hard after curing, and therefore cannot conform to the warpage of the silicon chip that occurs during CPU operation, resulting in peeling from the substrate. As a result, the desired heat dissipation performance cannot be obtained, and problems such as an increase in thermal resistance over time occur.

[0005] To solve these problems, a composition that reduces the modulus of elasticity after curing has been proposed (see Patent Document 2). However, reducing the modulus of elasticity makes it more likely for bubbles to form in the composition during heat curing, which becomes particularly evident when the area of ​​the CPU is large. The formation of bubbles causes problems such as the inability to achieve the desired heat dissipation performance. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-208993 [Patent Document 2] Patent No. 5047505 Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention has been made in light of the above circumstances, and has as its object to provide a highly reliable thermally conductive silicone composition that suppresses the generation of bubbles in the composition during heat curing, and that has excellent heat dissipation properties. [Means for solving the problem]

[0008] As a result of extensive research into achieving the above-mentioned object, the present inventors discovered that the above-mentioned problems could be solved by incorporating a composition containing a pre-prepared cross-linked silicone gel into a thermally conductive silicone composition, and thus completed the present invention.

[0009] Accordingly, the present invention provides the following thermally conductive silicone composition. 1.(A) (A-1), (A-2) and (A-3) below (A-1) a silicone gel crosslinked product, (A-2) a silicone oil containing neither an aliphatic unsaturated bond nor an SiH group; (A-3) Thermally conductive filler 100 parts by mass of a composition having a viscosity of 100 to 2,000 Pa s at 25°C, (B) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule: 0.01 to 50 parts by mass; (C) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule: an amount such that there are 0.1 to 10 silicon-bonded hydrogen atoms in component (C) per alkenyl group in component (B); (D) a platinum-based catalyst: an effective amount, and (E) Addition reaction inhibitor: effective amount A curable thermally conductive silicone composition having a viscosity of 50 to 1,500 Pa·s at 25°C. 2. (A) component is (A-1) silicone gel crosslinked product: 0.01 to 10% by mass, (A-2) The following general formula (1) [ka] (In the formula, R 1 are each independently an alkyl group having 1 to 6 carbon atoms, R 2 represents one or more groups selected from the group consisting of unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms and no aliphatic unsaturated bonds, and a represents an integer of 5 to 120. 1.0 to 20 mass% of a one-terminal hydrolyzable organopolysiloxane represented by the formula: 2. The thermally conductive silicone composition according to 1, comprising: (A-3) 70 to 98.99 mass% of a thermally conductive filler having an average particle size of 0.1 to 150 μm. 3. (A-1) component is (A-1-1) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule; (A-1-2) Organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule: an amount such that there are 0.1 to 20 silicon-bonded hydrogen atoms in component (A-1-2) per alkenyl group in component (A-1-1) 3. The thermally conductive silicone composition according to 1 or 2, which is an addition reaction product of 4. The component (A-1-1) is represented by 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, and R 4 represents an unsubstituted or substituted monovalent hydrocarbon group that does not have an aliphatic unsaturated bond, b is a number from 0.0001 to 0.2, c is a number from 1.7 to 2.2, and b+c is a number that satisfies the relationship 1.9 to 2.4. 4. The thermally conductive silicone composition according to 3, which is an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule, represented by the formula: 5. Component (A-2) with a kinematic viscosity at 25°C of 10 to 500,000 mm 2 5. The thermally conductive silicone composition according to any one of 1 to 4, which contains 5 to 70 mass % of a non-functional liquid silicone oil having a molecular weight of 1.0 to 1.25 wt %. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a highly reliable thermally conductive silicone composition that suppresses the generation of bubbles in the composition during heat curing, and has excellent heat dissipation properties. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below. The conductive silicone composition of the present invention comprises: (A) (A-1), (A-2) and (A-3) below (A-1) a silicone gel crosslinked product, (A-2) a silicone oil containing neither an aliphatic unsaturated bond nor an SiH group; (A-3) Thermally conductive filler 100 parts by mass of a composition having a viscosity of 100 to 2,000 Pa s at 25°C, (B) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule: 0.01 to 50 parts by mass; (C) an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule: an amount such that there are 0.1 to 10.0 silicon-bonded hydrogen atoms in component (C) per alkenyl group in component (B); (D) a platinum-based catalyst: an effective amount, and (E) Addition reaction inhibitor: effective amount This is a curable, grease-like conductive silicone composition with a viscosity of 50 to 1,500 Pa·s at 25°C.

[0012] [Component (A)] The component (A) of the present invention is the following (A) (A-1), (A-2), and (A-3): (A-1) a silicone gel crosslinked product, (A-2) a silicone oil containing neither an aliphatic unsaturated bond nor an SiH group; (A-3) Thermally conductive filler The composition has a viscosity of 100 to 2,000 Pa·s at 25°C, and various combinations of components (A-1) to (A-3) can be used.

[0013] (A-1) The crosslinked silicone gel is used as the matrix of the thermally conductive silicone composition of the present invention. Component (A-1) can be used alone or in combination of two or more. Component (A-1) can be, for example, (A-1-1) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule, (A-1-2) Organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule: an amount such that the number of silicon-bonded hydrogen atoms in component (A-1-2) is 0.1 to 20 per alkenyl group in component (A-1-1) and addition reaction products with

[0014] (A-1-1) The organopolysiloxane (A-1-1) having two or more silicon-bonded alkenyl groups per molecule can be used alone or in combination of two or more. The component (A-1-1) is represented by 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, and R 4 represents an unsubstituted or substituted monovalent hydrocarbon group that does not have an aliphatic unsaturated bond, b is a number from 0.0001 to 0.2, c is a number from 1.7 to 2.2, and b+c is a number that satisfies the relationship 1.9 to 2.4. and having two or more alkenyl groups bonded to silicon atoms in one molecule.

[0015] R 3R is an alkenyl group, preferably an alkenyl group having 2 to 6 carbon atoms, more preferably an alkenyl group having 2 to 4 carbon atoms. Specific examples thereof include lower alkenyl groups such as vinyl, allyl, propenyl, isopropenyl, butenyl, and isobutenyl, with vinyl being preferred. 4 is an unsubstituted or substituted monovalent hydrocarbon group free from aliphatic unsaturated bonds, preferably having 1 to 10 carbon atoms, and more preferably having 1 to 6 carbon atoms. Specific examples thereof include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclohexyl, octyl, decyl, and dodecyl; aryl groups such as phenyl and tolyl; aralkyl groups such as benzyl and phenylethyl; and chloromethyl and 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine or chlorine. From the viewpoint of ease of synthesis, etc., a methyl group, a phenyl group, or a 3,3,3-trifluoropropyl group is preferred.

[0016] b is a number from 0.0001 to 0.2, and preferably from 0.0005 to 0.1. c is a number from 1.7 to 2.2, and preferably from 1.9 to 2.0, and b+c is a number that satisfies the range of 1.9 to 2.4, and preferably a number that satisfies the range of 1.95 to 2.05.

[0017] The molecular structure of the organopolysiloxane of component (A-1-1) is not particularly limited, and may be linear; 3 SiO 3 / 2 Units, R 4 SiO 3 / 2 units, SiO2 units (wherein R 3 and R 4 The group represented by is as defined above.) may be any of branched, cyclic, three-dimensional network (resinous), etc., but preferred is a linear diorganopolysiloxane whose main chain is basically composed of repeating diorganosiloxane units and whose molecular chain is terminally blocked with triorganosiloxy groups.

[0018] The organopolysiloxane of component (A-1-1) has a kinematic viscosity of 10 to 100,000 mm at 25°C. 2 / s is preferred, and 100 to 50,000 mm 2 / s is more preferable. By setting the kinematic viscosity within the above range, the resulting cured product will have better fluidity and workability. The kinematic viscosity is the value measured at 25°C using an Ostwald viscometer (the same applies hereinafter).

[0019] Examples of organopolysiloxanes that satisfy the above requirements include those represented by the following general formula (3): [ka] (In the formula, R 5 each independently represents an unsubstituted or substituted monovalent hydrocarbon group, provided that R 5 At least one of is an alkenyl group, and d is an integer of 20 to 2,000. Examples include those represented by the following formula:

[0020] R 5 is the above R 3 (alkenyl group) and R 4 (unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bonds), and the number of carbon atoms, specific examples, etc. are also the same. Preferably, R 5 Preferably, two or more of the above groups are alkenyl groups. d is an integer of 20 to 2,000, preferably an integer of 40 to 1,200, and more preferably an integer of 50 to 600.

[0021] Specific examples of organopolysiloxanes represented by the above formula (3) include dimethylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylpolysiloxanes capped at one molecular chain terminal with trimethylsiloxy groups and one terminal with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups and one terminal with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups, and dimethylsiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups.

[0022] (A-1-2) (A-1-2) Organohydrogenpolysiloxanes having two or more silicon-bonded hydrogen atoms per molecule can be used alone or in combination of two or more. Component (A-1-2) reacts with component (A-1-1) above to act as a crosslinking agent. Component (A-1-2) must have two or more silicon-bonded hydrogen atoms (SiH groups) per molecule at non-terminal locations on the molecular chain.

[0023] The molecular structure of component (A-1-2) 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, three-dimensional network (resinous), etc. Among these, from the viewpoints of ease of handling and suppression of bubble formation in the cured product obtained by crosslinking component (A-1-1), the number of silicon atoms (or degree of polymerization) per molecule is preferably 3 to 1,000, more preferably 5 to 400, even more preferably 10 to 300, particularly preferably 10 to 100, and most preferably 10 to 60.

[0024] (A-1-2) The kinematic viscosity of the organohydrogenpolysiloxane is 1 to 10,000 mm 2 / s is preferable, and 3 to 5,000 mm 2 / s is more preferable, 5 to 3,000 mm 2It is more preferable that the viscosity is 1 / s. It is preferable that the viscosity is liquid at room temperature (25°C).

[0025] As an organohydrogenpolysiloxane satisfying the above requirements, for example, one represented by the following average composition formula (4) is preferred. R 6 e H f SiO (4-e-f) / 2 (4) (In the formula, R 6 represents an unsubstituted or substituted monovalent hydrocarbon group that does not have an aliphatic unsaturated bond, e is a number from 0.7 to 2.2, and f is a number from 0.001 to 0.5, with the proviso that e+f is a number that satisfies the condition 0.8 to 2.5.

[0026] In the above formula (4), R 6 is preferably one having 1 to 10 carbon atoms, more preferably an unsubstituted or substituted monovalent hydrocarbon group having no 1 to 6 aliphatic unsaturated bonds. Specific examples thereof include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine or chlorine. Among these, alkyl groups, aryl groups, and 3,3,3-trifluoropropyl groups are preferred, and methyl, phenyl, and 3,3,3-trifluoropropyl groups are more preferred.

[0027] In the above formula (5), e, f, and e+f are as described above, but e is preferably a number from 0.9 to 2.1, f is preferably a number from 0.002 to 0.2, particularly preferably a number from 0.005 to 0.1, and e+f is preferably a number satisfying the range of 1.0 to 2.3, particularly preferably 1.5 to 2.2.

[0028] The molecular structure of the organohydrogenpolysiloxane represented by the above formula (4) is not particularly limited and may be any of linear, cyclic, branched, three-dimensional network (resinous), etc. Among these, linear structures are preferred, in which the number of silicon atoms per molecule and the kinematic viscosity satisfy the above-mentioned ranges.

[0029] Specific examples of organohydrogenpolysiloxanes represented by the above formula (4) include dimethylsiloxane-methylhydrogensiloxane copolymers capped at both molecular chain ends with dimethylhydrogensiloxy groups, methylhydrogensiloxane-dimethylsiloxane-diphenylsiloxane copolymers capped at both molecular chain ends with dimethylhydrogensiloxy groups, dimethylsiloxane-methylhydrogensiloxane copolymers capped at one molecular chain end with a dimethylhydrogensiloxy group and one molecular chain end with a trimethylsiloxy group, methylhydrogensiloxane-dimethylsiloxane-diphenylsiloxane copolymers capped at one molecular chain end with a dimethylhydrogensiloxy group and one molecular chain end with a trimethylsiloxy group, and (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 (CH3)2HSiO units 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 (CH3)2HSiO units 1 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and SiO 4 / 2 A copolymer consisting of (CH3)2HSiO units 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 (CH3)2HSiO units 1 / 2 Units and (CH3)3SiO 1 / 2 Units and (C6H5)2SiO2 / 2 Units and (CH3)HSiO 2 / 2 Units and (CH3)2SiO 2 / 2 Units and SiO 4 / 2 and copolymers consisting of units.

[0030] The amount of component (A-1-2) is preferably such that, per alkenyl group in component (A-1-1), there are 0.1 to 20 hydrogen atoms bonded to silicon atoms in component (A-1-2), more preferably 0.5 to 15, and even more preferably 1.0 to 15. By ensuring that the above value is 0.1 or more, the crosslink density does not become too low, and the generation of bubbles in the resulting conductive silicone composition can be further suppressed. On the other hand, if the number is more than 20, the viscosity of the resulting thermally conductive silicone composition may become too high, potentially making it difficult to handle.

[0031] (A-1-3) The (A-1-3) addition reaction catalyst used in component (A-1) includes platinum catalysts for promoting the addition reaction between the silicon-bonded alkenyl groups in component (A-1-1) and the silicon-bonded hydrogen atoms in component (A-1-2), and these can be used alone or in combination of two or more.Specific examples include platinum or platinum-based compounds, and conventionally known compounds can be used, such as platinum black, chloroplatinic acid, alcohol-modified chloroplatinic acid, and complexes of chloroplatinic acid with olefin aldehydes, vinylsiloxanes, acetylene alcohols, etc.

[0032] The amount of component (A-1-3) is sufficient as long as it is an effective amount, and can be increased or decreased as needed depending on the desired curing rate. It is usually 0.1 to 1,000 ppm (by mass) of platinum atoms relative to component (A-1-1), preferably 1 to 300 ppm. If this amount is too small, the addition reaction may be significantly slowed or crosslinking may not occur. If this amount is too large, not only will the heat resistance of the cured product decrease, but also, due to the high cost of platinum, it will be cost-inefficient.

[0033] (A-1-4) An addition reaction inhibitor may be used in component (A-1). These addition reaction inhibitors can be used alone or in combination of two or more. The addition reaction inhibitor may be any known inhibitor used in addition-curable silicone compositions. Examples of such inhibitors include acetylene compounds such as acetylene alcohols (e.g., 1-ethynyl-1-cyclohexanol, 3,5-dimethyl-1-hexyn-3-ol), various nitrogen compounds such as tributylamine, tetramethylethylenediamine, and benzotriazole, organic phosphorus compounds such as triphenylphosphine, oxime compounds, and organic chloro compounds.

[0034] The amount of component (A-1-4) is not particularly limited, as long as it is an amount effective in inhibiting the progress of the hydrosilylation reaction. For example, it is usually about 0.001 to 5 parts by mass, preferably 0.1 to 3 parts by mass, per 100 parts by mass of component (A-1-1). If the amount of component (A-1-4) is too small, a sufficient pot life cannot be ensured, while if it is too large, the curability of the composition of the present invention decreases. If necessary, component (A-1-4) can be diluted with an organic solvent such as toluene, xylene, or isopropyl alcohol to improve its dispersibility in the composition.

[0035] The (A-1) silicone gel crosslinked product can be obtained, for example, by heating and mixing the (A-1-1) and (A-1-2) components in the presence of the (A-1-3) addition reaction catalyst, and crosslinking the components, i.e., by promoting an addition reaction (hydrosilylation reaction). The reaction temperature is typically around 50 to 180°C, but is not limited thereto. The reaction time is affected by the heating temperature, but the reaction will generally proceed sufficiently within 0.5 to 12 hours. A product that has undergone this treatment is defined as a "crosslinked product."

[0036] The content of component (A-1) in component (A) is preferably 0.01 to 10 mass%, more preferably 0.05 to 5 mass%, and even more preferably 0.1 to 3 mass%. If the content is too low, the composition is more likely to develop voids when cured at high temperatures, while if it is more than 10 mass%, the viscosity may become too high, making it difficult to handle.

[0037] (A-2) Component (A-2) is a silicone oil that does not participate in the crosslinking of component (A-1) and does not contain aliphatic unsaturated bonds or SiH groups. It can be used alone or in combination of two or more. Component (A-2) has a kinematic viscosity at 25°C of 5 to 500 mm 2 / s is preferable, 10 to 300 mm 2 / s is more preferred. The component (A-2) is preferably a hydrolyzable organopolysiloxane (A-2-1) having one terminal trifunctionality and represented by the following general formula (1). [ka] (In the formula, R 1 are each independently an alkyl group having 1 to 6 carbon atoms, R 2 represents one or more groups selected from the group consisting of unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms and no aliphatic unsaturated bonds, and a represents an integer of 5 to 120.

[0038] The hydrolyzable organopolysiloxane having trifunctional groups at one end, represented by general formula (1), can treat the surface of the thermally conductive filler (A-3). This not only aids in achieving high powder loading, but also, by covering the powder surface, makes it difficult for the powder particles to aggregate, and this effect persists even at high temperatures, thereby improving the heat resistance of the thermally conductive silicone composition.

[0039] In the above formula (1), R 1 R is, for example, an alkyl group having 1 to 6 carbon atoms such as a methyl group, an ethyl group, or a propyl group, with a methyl group or an ethyl group being particularly preferred. 2are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 14 carbon atoms, and having no 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; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as fluorine or chlorine. Preferred 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 from 5 to 120, and preferably an integer from 10 to 90.

[0040] When (A-2-1) a hydrolyzable organopolysiloxane having trifunctional groups at one end is blended, its content in component (A) is preferably 1.0 to 20 mass%, more preferably 1.5 to 15 mass%, and even more preferably 2.0 to 10 mass%. It may be 100 mass% in component (A-2), and when (A-2-2) described below is blended, its content in component (A-2) is preferably 30 to 95 mass%.

[0041] In addition to the above-mentioned one-terminal trifunctional hydrolyzable organopolysiloxane, a non-functional liquid silicone oil (A-2-2) having no reactive groups may also be added as component (A-2).The non-functional liquid silicone oil may be used alone or in combination of two or more.

[0042] Non-functional liquid silicone oil has a dynamic viscosity of 10 to 500,000 mm at 25°C. 2 / s, preferably 30 to 10,000 mm 2The organopolysiloxane has a kinematic viscosity of 1 / s. If the organopolysiloxane has a kinematic viscosity below the lower limit, the resulting thermally conductive silicone composition is prone to oil bleeding. If the kinematic viscosity is above the upper limit, the resulting thermally conductive silicone composition will have a high viscosity, which may make it difficult to handle.

[0043] The non-functional liquid silicone oil may be any known organopolysiloxane as long as it has the above-mentioned kinematic viscosity. The molecular structure of the organopolysiloxane (silicone oil) is not particularly limited and may be linear, branched, cyclic, or the like. In particular, it is preferable for the main chain to be composed of repeating diorganosiloxane units, with a linear structure in which both ends of the molecular chain are blocked with triorganosiloxy groups.

[0044] The organopolysiloxane as the non-functional liquid silicone oil can be represented by the following average composition formula (5). R 7 g SiO (4-g) / 2 (5) (In the formula, R 7 is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms and no aliphatic unsaturated bonds, and g is 1.8 to 2.2.

[0045] R 7is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 14, and having no aliphatic unsaturated bonds. Specific examples thereof include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, nonyl, and decyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; aralkyl groups such as benzyl, phenylethyl, and phenylpropyl; and 3,3,3-trifluoropropyl groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as fluorine or chlorine, among which alkyl groups, aryl groups, and 3,3,3-trifluoropropyl groups are preferred, and methyl, phenyl, and 3,3,3-trifluoropropyl groups are more preferred.

[0046] The value of g is 1.8 to 2.2, and preferably 1.9 to 2.1. When g is within this range, the resulting thermally conductive silicone composition will have the required good kinematic viscosity.

[0047] The organopolysiloxane represented by the above average composition formula (5) is preferably a linear organopolysiloxane represented by the following formula (6). [ka] (In the formula, R 8 are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms and containing no aliphatic unsaturated bonds; h is a value indicating that the kinematic viscosity of the organopolysiloxane at 25°C is 10 to 500,000 mm 2 / s.)

[0048] R 8 are each independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 18 carbon atoms, preferably 1 to 14 carbon atoms, and having no aliphatic unsaturated bonds. Examples of the monovalent hydrocarbon group include the groups mentioned above. Among these, R 8 Preferably, all of are methyl groups. h is the kinematic viscosity of the organopolysiloxane at 25°C of 10 to 500,000 mm2 / s, preferably 30 to 10,000 mm 2 / s, more preferably 100 to 8,000 mm 2 / s.

[0049] When non-functional liquid silicone oil (A-2-2) is added, its content in the component (A-2) is preferably 5 to 70% by mass.

[0050] The content of component (A-2) in component (A) is preferably 1.0 to 20 mass%, more preferably 1.5 to 15 mass%, and even more preferably 2.0 to 10 mass%. If it is less than 1.0 mass%, the viscosity of the resulting conductive silicone composition may become too high, making it difficult to handle, while if it is more than 20 mass%, the conductive silicone composition may be prone to voids when cured at high temperatures.

[0051] (A-3) The thermally conductive filler is used to impart thermal conductivity to the thermally conductive silicone composition of the present invention. Examples of thermally conductive fillers include aluminum, silver, copper, nickel, zinc oxide, alumina, magnesium oxide, aluminum nitride, boron nitride, silicon nitride, diamond, and graphite, and these can be used alone or in combination of two or more. When two or more types are used in combination, the method for producing component (A) preferably includes a step of mixing them.

[0052] The thermally conductive filler has an average particle size of 0.1 to 150 μm, preferably 0.5 to 140 μm. If the average particle size is too small, the viscosity of the composition becomes too high, making it difficult to handle, while if the average particle size is too large, the resulting composition tends to be non-uniform. The shape of the thermally conductive filler may be either spherical or irregular.

[0053] In the present invention, the term "average particle size" refers to the particle size at 50% of the cumulative value in the volume-based particle size distribution determined by a laser diffraction / scattering method. Measurement by the laser diffraction / scattering method can be performed, for example, using a Microtrac particle size analyzer MT3300EX (manufactured by Nikkiso Co., Ltd.).

[0054] The amount of component (A-3) in component (A) is preferably 70 to 98.99 mass%, more preferably 80 to 98 mass%, and even more preferably 90 to 97 mass%. A content of 70 mass% or more makes it easier to achieve the desired thermal conductivity, but if it is more than 98.99 mass%, the thermally conductive silicone composition may be more susceptible to voids when cured at high temperatures.

[0055] (A) Method for producing the composition The method for producing composition (A) may involve crosslinking components (A-1-1) and (A-1-2) to obtain component (A-1), and then mixing (A-2) and component (A-3), or, to obtain component (A-1), (A-2) may be added in advance before heating and then heated and mixed, and then component (A-3) may be mixed, or, to obtain component (A-1), all of components (A-2) and (A-3) may be added in advance before heating and then heated and mixed. Considering efficiency, the method of adding all of components (A-2) and (A-3) in advance before heating and then heating and mixing is preferred.

[0056] The viscosity of the (A) composition at 25°C is 100 to 2,000 Pa·s, preferably 200 to 1,500 Pa·s, and more preferably 300 to 1,000 Pa·s. If the viscosity is less than 100 Pa·s, the thermally conductive silicone composition will generate more bubbles during curing, while if it is more than 2,000 Pa·s, it will be difficult to handle. Viscosity can be measured at 25°C using a spiral viscometer. An example of a spiral viscometer is the Malcom Viscometer (Type PC-10AA) manufactured by Malcom.

[0057] The method for producing the (A) composition is not particularly limited, and the (A) composition can be obtained by stirring and mixing the components contained in the above-mentioned (A) composition using a mixer such as Trimix, Twinmix, or Planetary Mixer (all of which are registered trademarks of mixers manufactured by Inoue Seisakusho Co., Ltd.), Ultra Mixer (a registered trademark of mixers manufactured by Mizuho Kogyo Co., Ltd.), or Hivis Dispermix (a registered trademark of mixers manufactured by Tokushu Kika Kogyo Co., Ltd.).

[0058] [(B) Component] Component (B) is an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule, and can be used alone or in combination of two or more. Component (B) is the same as component (A-1-1) used to prepare component (A-1), and the preferred components and the like are also the same.

[0059] The content of component (B) is 0.01 to 50 parts by mass, preferably 0.05 to 20 parts by mass, and more preferably 0.1 to 10 parts by mass, per 100 parts by mass of (A). If the content of (B) is less than 0.01 part by mass, sufficient curing will not occur, and if it is more than 50 parts by mass, the thermal conductivity will be low.

[0060] [(C) component] Component (C) is an organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule, and can be used alone or in combination of two or more. Component (C) is the same as component (A-1-2) used in preparing component (A-1), and the preferred components and the like are also the same.

[0061] The content of component (C) is such that, per alkenyl group in component (B), there are 0.1 to 10 hydrogen atoms bonded to silicon atoms in component (C), preferably 0.3 to 7, and more preferably 0.5 to 5. If the value is less than 0.1, sufficient curing will not occur, but if it is more than 10, the resulting conductive silicone composition will be too hard and will have poor reliability.

[0062] [(D) component] Component (D) is a platinum catalyst, and can be used alone or in combination of two or more. Component (D) is the same as component (A-1-3) used in preparing component (A-1), and the preferred components and the like are also the same.

[0063] The content of component (D) is sufficient as long as it is an effective amount, and can be increased or decreased as appropriate depending on the desired curing rate. However, it is usually 0.1 to 1,000 ppm (by mass) of platinum atoms relative to component (A), preferably 1 to 300 ppm. If this amount is too small, the addition reaction may be significantly slowed or crosslinking may not occur. If this amount is too large, not only will the heat resistance of the cured product decrease, but it will also be disadvantageous in terms of cost due to the high price of platinum.

[0064] [(E) component] Component (E) is an addition reaction inhibitor and can be used alone or in combination of two or more. Component (E) is the same as component (A-1-4) used in preparing component (A-1), and the preferred components and the like are also the same.

[0065] The amount of component (E) used varies depending on the amount of component (A) used, making it difficult to generalize. However, there are no particular limitations as long as it is an amount effective in inhibiting the progress of the hydrosilylation reaction. For example, the amount is typically about 0.001 to 5 parts by mass, preferably 0.1 to 3 parts by mass, per 100 parts by mass of component (A). If the amount of component (E) is too small, a sufficient pot life cannot be ensured, while if it is too large, the curability of the composition of the present invention decreases. If necessary, component (E) can be diluted with an organic solvent such as toluene, xylene, or isopropyl alcohol to improve its dispersibility in the composition.

[0066] [Method for producing thermally conductive silicone composition] The thermally conductive silicone composition can be produced by mixing a previously prepared composition (A) with components (B) to (D), optionally component (E), and other optional components. Examples of mixing equipment include Trimix, Twinmix, and Planetary Mixer (all registered trademarks of mixers manufactured by Inoue Seisakusho Co., Ltd.), Ultra Mixer (registered trademarks of mixers manufactured by Mizuho Kogyo Co., Ltd.), and Hivis Dispermix (registered trademarks of mixers manufactured by Tokushu Kika Kogyo Co., Ltd.).

[0067] [Thermal conductive silicone composition] The thermally conductive silicone composition of the present invention has a viscosity at 25°C of 50 to 1,500 Pa·s and is grease-like. The viscosity is preferably 100 to 700 Pa·s, and more preferably 100 to 500 Pa·s. If the viscosity is less than 50 Pa·s, the shear resistance will be poor, and if it is more than 1,500 Pa·s, handling will be poor. Viscosity can be measured at 25°C using a spiral viscometer. An example of a spiral viscometer is the Malcom Viscometer (Type PC-10AA) manufactured by Malcom.

[0068] The thermal conductivity of the thermally conductive silicone composition of the present invention is preferably 2.0 W / mK or higher, and more preferably 3.0 W / mK or higher, to ensure sufficient heat dissipation. There is no particular upper limit, and it can be appropriately selected, for example, from 15.0 W / mK or lower. The thermal conductivity is measured using the hot disc method in accordance with ISO 22007-2.

[0069] The thermally conductive silicone composition of the present invention is curable, and the curing conditions for heat curing the thermally conductive silicone composition of the present invention are not particularly limited, but are typically 80 to 200°C, preferably 100 to 180°C, for 30 minutes to 4 hours, preferably 30 minutes to 3 hours.

[0070] [Cured product] The shear modulus of the cured product of the thermally conductive silicone composition of the present invention is preferably 20,000 to 200,000 Pa. The shear modulus of the cured product is measured according to the method specified in ISO 6721-10, with details given in the Examples. [Example]

[0071] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples. Measurement methods are shown below. [Average particle size] The average particle size is a cumulative average diameter on a volume basis measured using a particle size analyzer, Microtrac MT3300EX, manufactured by Nikkiso Co., Ltd. 〔viscosity〕 The viscosity was measured at 25°C using a Malcom viscometer (type PC-10AA) manufactured by Malcom Co., Ltd. [Kinematic viscosity] The kinematic viscosity was measured at 25°C using an Ostwald viscometer.

[0072] [(AI~V) composition] The components according to the compositions shown in Table 1 were charged into a planetary mixer, and components (AI to V) were prepared according to the following procedure. Components (A-1-1), (A-2), and (A-3) were added to a planetary mixer and stirred for 10 minutes at 25° C. Components (A-1-2) and (A-1-3) were then added, and the temperature was raised to 170° C. The mixture was then heated and mixed for 2 hours to induce an addition reaction (hydrosilylation reaction) between components (A-1-1) and (A-1-2), yielding compositions (AI-V) containing a crosslinked silicone gel.

[0073] [(A-VI) Ingredients: Comparative product] The composition (A-VI) was obtained in the same manner as in the production of (AI), except that the platinum catalyst (A-1-3) was not used. Specifically, components (A-1-1)[1], (A-2-1)[1], (A-3)[3], and (A-3)[4] in Table 1 were added to a planetary mixer and stirred at room temperature for 10 minutes. Then, component (A-1-2)[1] was added, and the temperature was raised to 170°C. The mixture was heated and mixed for 2 hours to obtain composition (A-VI). The viscosity of composition (A-VI) was 150 Pa·s.

[0074] [Table 1]

[0075] The components used are shown below. The bonding order of the siloxane units is not limited to the order shown below (the same applies hereinafter). [(A-1-1)] [1] A linear chain polymer with a kinematic viscosity of 600mm2 having vinyl groups at both ends. 2 / s dimethylpolysiloxane [2] linear chain with vinyl groups at both ends, kinematic viscosity 30,000 mm 2 / s dimethylpolysiloxane

[0076] [(A-1-2)] [1] [ka] Kinematic viscosity 113mm 2 / s [2] [ka] Kinematic viscosity 25mm 2 / s

[0077] [(A-1-3)] A solution (platinum atom content: 1% by mass) of platinum-divinyltetramethyldisiloxane complex dissolved in the same dimethylpolysiloxane as in (A-1-1)[1] above

[0078] [(A-2-1)] [ka] Kinematic viscosity 35mm 2 / s

[0079] [(A-2-2)] A linear 1,000mm long polymer with trimethylsilyl groups at both ends 2 / s dimethylpolysiloxane

[0080] (A-3) [1] Alumina powder (average particle size: 140 μm) [2] Alumina powder (average particle size: 45 μm) [3] Aluminum powder (average particle size: 10 μm) [4] Zinc oxide powder (average particle size: 1.0 μm)

[0081] [Examples and Comparative Examples] The components shown in Tables 2 and 3 were charged into a planetary mixer, and a thermally conductive silicone composition was prepared according to the following procedure. All of the following steps were carried out at room temperature. Specifically, components (A) and (B) were added to a planetary mixer and stirred for 30 minutes. Then, component (E) was added and stirred for 10 minutes, followed by component (D) and stirring for a similar 10 minutes. Then, component (C) was added, and the mixture was stirred for 15 minutes while degassing with a vacuum pump, yielding a thermally conductive silicone composition. The resulting thermally conductive silicone composition was evaluated as follows. The results are shown in Tables 2 and 3.

[0082] The ingredients used are listed below. [(B) Component] [I] A linear chain polymer with a kinematic viscosity of 400mm 2 / s dimethylpolysiloxane [II] A linear chain having a kinematic viscosity of 30,000mm2 with vinyl groups at both ends 2 / s dimethylpolysiloxane (same as (A-1-1)[2])

[0083] [(C) component] [I] [ka] Kinematic viscosity 28mm 2 / s [II] (same as (A-1-2)[1]) [ka] Kinematic viscosity 113mm 2 / s

[0084] [(D) component] [I] A solution of platinum-divinyltetramethyldisiloxane complex dissolved in the same dimethylpolysiloxane as in (A-1-1)[1] above (platinum atom content: 1% by mass, same as in (A-1-3)[1])

[0085] [(E) component] [I] 1-ethynyl-1-cyclohexanol

[0086] [Thermal conductivity] The thermal conductivity was measured at 25°C using a TPS-2500S manufactured by Kyoto Electronics Manufacturing Co., Ltd.

[0087] [Shear modulus] In accordance with ISO 6721-10, a viscoelasticity measuring device (Rheometric Scientific, Type RDA III) was used, with two parallel plates of 2.5 cm diameter (the thickness of the thermally conductive silicone composition was set to 2 mm). The measurement was performed by first raising the temperature from room temperature to 125°C at a rate of 5°C / min, and then maintaining that temperature for two hours to completely cure the thermally conductive silicone composition. The composition was then cooled to 25°C, and the shear modulus of the cured thermally conductive silicone composition was measured (frequency: 1.0 Rad / sec, strain (displacement): 10%).

[0088] [Void test] 0.1 g of the thermally conductive silicone composition of the present invention was sandwiched between two glass slides, both ends secured with commercially available clips, and left for 1 hour. The test piece was then placed in an oven at 170°C and heated for 2 hours to cure. After 2 hours, the test piece was removed and cooled, and then visually inspected for the presence of bubbles in the thermally conductive silicone composition. If no bubbles were present, the rating was "Good," and if bubbles were visible to the naked eye, the rating was "Poor."

[0089] [Table 2]

[0090] [Table 3]

Claims

1. (A) The following (A-1), (A-2) and (A-3) (A-1) (A-1-1) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule; (A-1-2) Organohydrogenpolysiloxane having two or more silicon-bonded hydrogen atoms per molecule: an amount such that there are 0.1 to 20 silicon-bonded hydrogen atoms in component (A-1-2) per alkenyl group in component (A-1-1) a silicone gel crosslinked product obtained by an addition reaction with (A-2) a silicone oil containing neither an aliphatic unsaturated bond nor an SiH group; (A-3) Thermally conductive filler 100 parts by mass of a composition having a viscosity of 100 to 2,000 Pa s at 25°C, (B) an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule: 0.01 to 50 parts by mass; (C) 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 (C) is 0.1 to 10 per alkenyl group in component (B); (D) a platinum-based catalyst: an effective amount, and (E) Addition reaction inhibitor: effective amount a curable thermally conductive silicone composition having a viscosity of 50 to 1,500 Pa·s at 25°C.

2. The component (A) is (A-1) Silicone gel crosslinked product: 0.01 to 10 mass %, (A-2) The following general formula (1) 【Chemistry 1】 (In the formula, R 1 are each independently an alkyl group having 1 to 6 carbon atoms, R 2 represents one or more groups selected from the group consisting of unsubstituted or substituted monovalent hydrocarbon groups having 1 to 18 carbon atoms and no aliphatic unsaturated bonds, and a represents an integer of 5 to 120. 1.0 to 20 mass% of a one-terminal hydrolyzable organopolysiloxane represented by the formula:

2. The thermally conductive silicone composition according to claim 1, further comprising: (A-3) 70 to 98.99 mass% of a thermally conductive filler having an average particle size of 0.1 to 150 μm.

3. The component (A-1-1) is represented by 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, and R 4 represents an unsubstituted or substituted monovalent hydrocarbon group that does not have an aliphatic unsaturated bond, b is a number from 0.0001 to 0.2, c is a number from 1.7 to 2.2, and b+c is a number that satisfies the range of 1.9 to 2.

4.

3. The thermally conductive silicone composition according to claim 1, which is an organopolysiloxane having two or more silicon-bonded alkenyl groups per molecule, and represented by the formula:

4. Component (A-2) has a kinematic viscosity at 25°C of 10 to 500,000 mm 2 3. The thermally conductive silicone composition according to claim 1, further comprising 5 to 70 mass % of a non-functional liquid silicone oil.

Images