Thermally conductive silicone composition and cured product of same

Abstract

The present invention pertains to a thermally conductive silicone composition characterized by comprising a silicone component and a silicon nitride filler (E) that exhibits an integrated intensity ratio of [2θ=26.6 to 28.8°] / [2θ=19.6 to 21.6°]=10 or more for peaks detected by an X-ray diffraction method. Accordingly, a thermally conductive silicone composition having excellent thermal conductivity and low viscosity is provided.

Description

Thermally conductive silicone composition and cured product thereof

[0001] The present invention relates to a thermally conductive silicone composition and a cured product thereof.

[0002] In recent years, as electronic devices have become increasingly sophisticated, the density and packaging of semiconductor elements have increased. In particular, the electronics industry has become increasingly electronic, increasing the number of electronic components mounted, and the demand for heat dissipation components has grown. Heat dissipation components come in sheet and grease types, with the sheet type being preferred due to ease of mounting. Furthermore, with the advent of autonomous driving, further improvements in thermal conductivity are required for such heat dissipation components. Thermally conductive resin compositions used for heat dissipation applications can be obtained by dispersing a thermally conductive filler in a polymer resin, and thermally conductive silicone compositions have been devised in which oxides or metals are added to silicone rubber, as in Patent Documents 1 and 2.

[0003] A commonly known method for improving the thermal conductivity of thermally conductive silicone compositions is to highly fill a silicone resin polymer with a thermally conductive filler having a higher thermal conductivity. Patent Document 3 proposes a thermally conductive silicone composition with a thermal conductivity exceeding 8.5 W / m·K by highly filling aluminum nitride and alumina, both of which have high thermal conductivity. Patent Document 4 also discloses a cost-effective thermally conductive silicone composition with a thermal conductivity exceeding 6.5 W / m·K by highly filling only alumina. However, a problem with highly filling a thermally conductive filler is that the absolute viscosity of the composition increases significantly. An increase in the absolute viscosity of the composition not only contributes to poor moldability, such as poor discharge, coating, and extrusion of the composition, but also accelerates wear on the manufacturing equipment itself, such as pumps and piping.

[0004] Japanese Patent Application Laid-Open No. 47-32400 Japanese Patent Application Laid-Open No. 56-100849 Japanese Patent Application Laid-Open No. 2022-181451 Japanese Patent Application Laid-Open No. 2022-184636

[0005] An object of the present invention is to provide a thermally conductive silicone composition that has excellent thermal conductivity and low viscosity.

[0006] The present invention has been made to solve the above-mentioned problems, and provides a thermally conductive silicone composition characterized by containing a silicone component and a silicon nitride filler (E) having a peak integrated intensity ratio, as detected by X-ray diffraction, of [2θ=26.6 to 28.6°] / [2θ=19.6 to 21.6°]=10 or greater.

[0007] Such a thermally conductive silicone composition can provide a thermally conductive silicone composition that has excellent thermal conductivity and low viscosity.

[0008] Furthermore, the average particle size of the component (E) measured by laser diffraction is preferably 20 to 100 μm.

[0009] Such a thermally conductive silicone composition has an appropriate absolute viscosity that is not too high, and can be dispersed in the composition without settling.

[0010] The amount of component (E) blended is preferably 200 to 1,000 parts by mass per 100 parts by mass of the silicone component.

[0011] Such a thermally conductive silicone composition provides sufficient thermal conductivity, has an appropriate absolute viscosity, and does not impair coating or discharge properties.

[0012] It is also preferable that the silicone component contains: (A) an organopolysiloxane having two or more alkenyl groups in each molecule; and (B) an organohydrogenpolysiloxane having two or more hydrogen atoms directly bonded to silicon atoms.

[0013] Such a thermally conductive silicone composition can be an addition-curable composition, and the objective of the present invention of achieving both thermal conductivity and absolute viscosity of the composition can be more favorably achieved.

[0014] Furthermore, the thermally conductive silicone composition preferably contains, in addition to the silicone component, (C) a hydrosilylation catalyst.

[0015] Such a thermally conductive silicone composition accelerates the hydrosilylation reaction between the Si—H groups in component (B) and the alkenyl groups in component (A), imparting a crosslinked three-dimensional network structure to the cured product of the present invention, thereby more effectively achieving the objects of the present invention.

[0016] The silicone component is (D) a dimethylpolysiloxane having one molecular chain end blocked with a trialkoxy group, represented by the following formula (1): (In the formula, R 1 are independently an alkyl group having 1 to 6 carbon atoms, and m is an integer of 5 to 100. Preferably, the component (A) further contains 10 to 200 parts by mass of the following compound (A) per 100 parts by mass of the component (A).

[0017] Such a thermally conductive silicone composition is preferable because it allows for appropriate dispersibility of the thermally conductive filler, has an appropriate absolute viscosity, and is free from the risk of a decrease in thermal conductivity.

[0018] The kinematic viscosity of the component (A) is 10 to 100,000 mm ２ / s is preferred.

[0019] If the thermally conductive silicone composition falls within this range, the resulting silicone composition will have good storage stability and will be easy to knead.

[0020] Furthermore, the thermally conductive silicone composition preferably contains (F) aluminum oxide having an average particle size of 1 to 20 μm as measured by laser diffraction.

[0021] In such a thermally conductive silicone composition, the aluminum oxide is co-filled with the silicon nitride filler, thereby increasing the thermal conductivity of the composition. Furthermore, the interaction between the hydroxyl groups on the aluminum oxide surface and component (D) improves dispersibility and reduces the absolute viscosity of the entire composition.

[0022] The thermally conductive silicone composition preferably has an absolute viscosity of 10 to 300 Pa·s.

[0023] A thermally conductive silicone composition within this range allows for an appropriate pumping time, does not reduce productivity, does not cause wear on piping, and can maintain the required thickness when applied by coating or dispenser.

[0024] The thermal conductivity of the thermally conductive silicone composition is preferably 4.0 W / mK or greater.

[0025] Such a thermally conductive silicone composition is more suitable for use in parts that generate a large amount of heat.

[0026] Also provided is a cured thermally conductive silicone product, which is a cured product of the above-mentioned thermally conductive silicone composition.

[0027] Such a thermally conductive silicone cured product can provide a heat dissipation component that meets the thermal conductivity required for heat dissipation applications.

[0028] The present invention can provide a thermally conductive silicone composition that has excellent thermal conductivity and low viscosity. The thermally conductive silicone composition of the present invention is a heat-dissipating material that, by containing β-type silicon nitride, has a thermal conductivity of more than 4.0 W / mK and a low viscosity of 300 Pa s or less, which provides excellent processability and coatability.

[0029] As described above, there has been a need for the development of a thermally conductive silicone composition that has excellent thermal conductivity and low viscosity.

[0030] As a result of extensive research conducted by the present inventors in order to solve the above problems, they discovered that a thermally conductive silicone composition with excellent thermal conductivity and low viscosity can be obtained by incorporating a silicone component and a silicon nitride filler having a peak integrated intensity ratio, as detected by X-ray diffraction, of [2θ=26.6-28.6°] / [2θ=19.6-21.6°]=10 or greater, and this discovery led to the completion of the present invention.

[0031] That is, the present invention is a low-viscosity thermally conductive silicone composition with excellent thermal conductivity, in which a β-type silicon nitride filler is filled into the silicone component.

[0032] The present invention will be described in detail below, but the present invention is not limited thereto.

[0033] [Thermal Conductive Silicone Composition] The composition of the present invention is a thermally conductive silicone composition characterized by containing a silicon nitride filler (E) having an integrated peak intensity ratio, as detected by X-ray diffraction, of [2θ=26.6 to 28.6°] / [2θ=19.6 to 21.6°]=10 or greater, and a silicone component.

[0034] The silicone component contained in the thermally conductive silicone composition of the present invention, as well as additional components that may be contained therein, are described in detail below.

[0035] [Silicone Component of the Present Invention] The silicone component of the present invention is preferably an addition-curable organopolysiloxane component. The silicone component of the present invention preferably contains the following components (A) and (B): (A) an organopolysiloxane having two or more alkenyl groups per molecule; and (B) an organohydrogenpolysiloxane having two or more hydrogen atoms directly bonded to silicon atoms.

[0036] [(A) Organopolysiloxane Having Two or More Alkenyl Groups Per Molecule] Component (A) is an organopolysiloxane having two or more alkenyl groups per molecule, and serves as the main component of the thermally conductive silicone composition of the present invention. Typically, the main chain portion is essentially composed of repeating diorganosiloxane units. The molecular structure may contain a branched structure or may be cyclic. Among these, linear diorganopolysiloxanes are preferred from the standpoint of physical properties such as the mechanical strength of the cured product.

[0037] Examples of the alkenyl group include those having 2 to 8 carbon atoms, such as vinyl, allyl, propenyl, isopropenyl, butenyl, hexenyl, and cyclohexenyl groups. Of these, lower alkenyl groups having 2 to 4 carbon atoms, such as vinyl and allyl, are preferred. Vinyl groups are particularly preferred. It is necessary that two or more alkenyl groups be present in the molecule, and in order to ensure good flexibility of the resulting cured product, it is more preferred that they be present bonded only to silicon atoms at the molecular chain terminals.

[0038] The functional group other than the alkenyl group is a monovalent hydrocarbon group, preferably one having 1 to 10 carbon atoms, and particularly preferably one having 1 to 6 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, and decyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; aryl groups such as phenyl, tolyl, xylyl, and naphthyl; and aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl. The monovalent hydrocarbon group other than the alkenyl group is preferably an alkyl group having 1 to 3 carbon atoms, such as methyl, ethyl, or propyl, or a phenyl group. Furthermore, the functional groups other than the alkenyl group bonded to the silicon atom may all be the same or different.

[0039] The kinematic viscosity of this organopolysiloxane at 25°C is 10 to 100,000 mm ２ / s range is preferred. ２ The kinematic viscosity is particularly preferably in the range of 10 mm / s. ２ / s or more, the resulting silicone composition will have good storage stability, and ２ / s, kneading is easy. In this specification, kinematic viscosity is the value measured at 25°C using a Cannon-Fenske viscometer as described in JIS Z 8803:2011. The organopolysiloxane of component (A) may be used alone, or two or more different organopolysiloxanes with different structures or kinematic viscosities may be used in combination.

[0040] [(B) Organohydrogenpolysiloxane Having Two or More Hydrogen Atoms Directly Bonded to Silicon Atoms] The organohydrogenpolysiloxane of component (B) has two or more, preferably 2 to 100, hydrogen atoms (Si—H groups) directly bonded to silicon atoms per molecule. It functions as a crosslinker in component (A). That is, the Si—H groups in component (B) and the alkenyl groups in component (A) undergo addition via a hydrosilylation reaction promoted by the hydrosilylation catalyst of component (C), described below, to impart a three-dimensional network structure with a crosslinked structure to the resulting cured product. Note that organohydrogenpolysiloxanes of component (B) with two or more Si—H groups are preferred for curing. A number of Si—H groups of 100 or less is preferred because it allows for a flexible cured product and prevents an increase in thermal resistance. Examples of organohydrogenpolysiloxanes include those represented by the following formula (2):

[0041] (In formula (2), R ２ are independently an unsubstituted or substituted monovalent hydrocarbon group containing no aliphatic unsaturated bonds or a hydrogen atom. ２ At least two of the groups are hydrogen atoms. n is an integer of 1 or more.

[0042] In formula (2), R ２ Specific examples of unsubstituted or substituted monovalent hydrocarbon groups that do not contain aliphatic unsaturated bonds other than hydrogen include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, octyl, nonyl, decyl, and dodecyl; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl; aryl groups such as phenyl, tolyl, xylyl, naphthyl, and biphenylyl; and aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl.

[0043] R ２may be a group in which some or all of the hydrogen atoms bonded to carbon atoms of the above group have been substituted with halogen atoms such as fluorine, chlorine or bromine, or with a cyano group, etc. Specific examples of these groups include a chloromethyl group, a 2-bromoethyl group, a 3-chloropropyl group, a 3,3,3-trifluoropropyl group, a chlorophenyl group, a fluorophenyl group, a cyanoethyl group, and a 3,3,4,4,5,5,6,6,6-nonafluorohexyl group.

[0044] Among these, R ２ The unsubstituted or substituted monovalent hydrocarbon group not containing an aliphatic unsaturated bond preferably has 1 to 10 carbon atoms, and more preferably has 1 to 6 carbon atoms. More preferred are unsubstituted or substituted alkyl groups having 1 to 3 carbon atoms, such as methyl, ethyl, propyl, chloromethyl, bromoethyl, 3,3,3-trifluoropropyl, and cyanoethyl, and unsubstituted or substituted phenyl groups, such as phenyl, chlorophenyl, and fluorophenyl. ２ may all be the same or different. In formula (2), n is an integer of 1 or more, preferably 1 to 200.

[0045] The amount of component (B) added is preferably an amount that results in 0.2 to 2.0 Si-H groups derived from component (B) per alkenyl group derived from component (A). An amount that results in 0.3 to 1.5 groups is more preferred. An amount that results in 0.5 to 1.0 groups is particularly preferred. When the number of Si-H groups in component (B) is 0.2 or more per alkenyl group derived from component (A), the composition is sufficiently cured, and the cured product can retain its shape as a molded product with sufficient strength. Furthermore, when the number of Si-H groups in component (B) is within 2.0 per alkenyl group derived from component (A), the flexibility of the cured product is maintained and there is no increase in thermal resistance.

[0046] [(C) Hydrosilylation Catalyst] When the silicone component of the present invention is an addition curing type, it preferably contains a hydrosilylation catalyst (C). The hydrosilylation catalyst of component (C) is a catalyst for promoting the addition reaction between the alkenyl group derived from component (A) and the hydrosilyl group derived from component (B), and any catalyst well known for use in hydrosilylation reactions can be used. Specific examples thereof include platinum group metals such as platinum (including platinum black), rhodium, and palladium; ２ PtCl ４ ・nH ２ O, H ２ PtCl ６ ・nH ２ O, NaHPtCl ６ ・nH ２ O, KHPtCl ６ ・nH ２ O, Na ２ PtCl ６ ・nH ２ O.K. ２ PtCl ４ ・nH ２ O, PtCl ４ ・nH ２ O, PtCl ２ , Na ２ HPtCl ４ ・nH ２ O (wherein n is an integer of 0 to 6, preferably 0 or 6), chloroplatinic acid and chloroplatinate salts, alcohol-modified chloroplatinic acid (see U.S. Pat. No. 3,220,972), complexes of chloroplatinic acid with olefins (see U.S. Pat. Nos. 3,159,601, 3,159,662 and 3,775,452), platinum black, platinum group metals such as palladium supported on a support such as alumina, silica or carbon, rhodium-olefin complexes, chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst), complexes of platinum chloride, chloroplatinic acid or chloroplatinate salts with vinyl group-containing siloxanes, particularly vinyl group-containing cyclic siloxanes.

[0047] The content of component (C), calculated as the mass of platinum group metal element relative to component (A), is preferably in the range of 100 to 3,000 ppm, and more preferably 100 to 2,000 ppm. A content of 100 ppm or more provides sufficient catalytic activity, while a content of 3,000 ppm or less provides a sufficient effect of promoting the addition reaction without being excessive and thus not uneconomical.

[0048] [(D) Dimethylpolysiloxane with one molecular chain end capped with a trialkoxy group, represented by the following formula (1)] The silicone component of the present invention preferably contains (D) a dimethylpolysiloxane with one molecular chain end capped with a trialkoxy group, represented by the following formula (1). Component (D) is a surface treatment agent, and is incorporated for the purpose of uniformly dispersing a thermally conductive filler in a matrix primarily composed of component (A). Component (D) is a dimethylpolysiloxane with one molecular chain end capped with a trialkoxy group, represented by the following formula (1). (In formula (1), R 1 are independently alkyl groups having 1 to 6 carbon atoms, and m is an integer of 5 to 100.

[0049] R in formula (1) 1 Specific examples of the alkyl group having 1 to 6 carbon atoms represented by the formula (I) include a methyl group, an ethyl group, a propyl group, an isopropyl group, a butyl group, an isobutyl group, a tert-butyl group, a pentyl group, a neopentyl group, and a hexyl group. 1 is preferably a methyl group.

[0050] The amount of component (D) in the silicone component is preferably in the range of 10 to 200 parts by mass per 100 parts by mass of component (A). A range of 20 to 150 parts by mass is particularly preferred. When the amount of component (D) is 10 parts by mass or more, the dispersibility of the thermally conductive filler containing the silicon nitride filler is improved, and the absolute viscosity of the composition falls within a preferred range. When the amount of component (D) is 200 parts by mass or less, the proportion of the thermally conductive filler containing the silicon nitride filler is not reduced, and thermal conductivity is good.

[0051] [(E) Silicon nitride filler in which the ratio of the integrated intensity of the β-phase-derived X-ray diffraction peak in the range [2θ = 26.6 to 28.6°] to the integrated intensity of the α-phase-derived peak in the range [2θ = 19.6 to 21.6°] is 10 or greater] Thermal conductivity can be adjusted by adjusting the type and particle size of the thermally conductive filler, but adding a large amount of thermally conductive filler significantly increases the absolute viscosity of the composition. Therefore, in order to achieve both high thermal conductivity and absolute viscosity of the composition, it is important to select a thermally conductive filler that can increase thermal conductivity with a small amount of incorporation. The thermally conductive silicone composition of the present invention is characterized by containing (E) a silicon nitride filler in which the ratio of the integrated intensity of the β-phase-derived X-ray diffraction peak in the range [2θ = 26.6 to 28.6°] to the integrated intensity of the α-phase-derived peak in the range [2θ = 19.6 to 21.6°] is 10 or greater. Silicon nitride has a crystalline polymorphism consisting of α-phase, β-phase, and γ-phase, and the atmospheric pressure phases include the α-phase with a trigonal crystal structure and the β-phase with a hexagonal crystal structure. Silicon nitride produced by direct nitriding or other methods is known to undergo a phase transition from part of the α-phase to the β-phase at temperatures between 1400 and 1500°C, and generally takes a form in which the two phases coexist.

[0052] The X-ray diffraction peak positions (2θ) of each phase are as specified in JIS R 1640:2002: [α phase] (101) 20.6°, (110) 22.9°, (200) 26.5°, (201) 31.0°, (002) 31.8°, (102) 34.6°, (210) 35.3°, (310) 43.5°; [β phase] (110) 23.4°, (200) 27.1°, (101) 33.7°, (210) 36.1°.

[0053] In the silicon nitride filler of the present invention, the ratio of the integrated intensity in the range [2θ = 26.6 to 28.6°], which is the peak derived from the β phase, to the integrated intensity in the range [2θ = 19.6 to 21.6°], which is the peak derived from the α phase, is [2θ = 26.6 to 28.6°] / [2θ = 19.6 to 21.6°] = 10 or more. Such silicon nitride is suitable as a thermally conductive filler because its β phase ratio exceeds 90%. If the integrated intensity ratio is less than 10, the proportion of the α phase increases, resulting in a decrease in thermal conductivity. The ratio of the integrated intensity of the peak derived from the β phase to the integrated intensity of the peak derived from the α phase is preferably 15 or more. The intensity ratio is more preferably 20 or more. The intensity ratio is particularly preferably 100 or more. %

[0054] The silicon nitride filler preferably has an average particle size in the range of 20 to 100 μm, more preferably 30 to 80 μm. If the average particle size of the silicon nitride filler is 20 μm or more, the thermal conductivity increases sufficiently, eliminating the need for a large amount of filling, and as a result, the absolute viscosity of the composition becomes appropriate. Furthermore, if the average particle size is 100 μm or less, the filler can be uniformly dispersed in the composition without settling. The silicon nitride filler may have a single average particle size, or multiple types with different average particle sizes may be mixed.

[0055] The average particle size is measured by the median diameter (the particle size at which, when a powder is divided into two at a certain particle size, the particles larger than that particle size and the particles smaller than that particle size are equal in amount, generally referred to as D50) measured by laser diffraction using a laser diffraction / scattering particle size distribution analyzer. The shape of the silicon nitride filler is not particularly limited, and an appropriate shape can be selected taking into account the thermal conductivity, absolute viscosity, etc. of the composition.

[0056] The content of the silicon nitride filler is preferably in the range of 200 to 1,000 parts by mass per 100 parts by mass of the silicone component. A range of 200 to 900 parts by mass is more preferred. A range of 250 to 800 parts by mass is particularly preferred. If the content of the silicon nitride filler is 200 parts by mass or more, sufficient thermal conductivity can be obtained. Furthermore, if the content is 1,000 parts by mass or less, the absolute viscosity of the composition will be an appropriate value, and there will be no deterioration in coatability or dischargeability.

[0057] [(F) Aluminum Oxide Having an Average Particle Size of 1 to 20 μm as Measured by Laser Diffraction] The thermally conductive silicone composition of the present invention containing the silicon nitride filler and a silicone component described above may additionally contain (F) an aluminum oxide component having an average particle size of 1 to 20 μm as measured by laser diffraction.

[0058] Aluminum oxide is added to the composition together with silicon nitride filler to increase the thermal conductivity of the composition. Furthermore, the interaction between the hydroxyl groups on the surface of the aluminum oxide and component (D) improves dispersibility and reduces the absolute viscosity of the entire composition.

[0059] The average particle size of aluminum oxide particles filled with silicon nitride is preferably in the range of 1 to 20 μm, more preferably in the range of 1 to 15 μm. If the particle size is 1 μm or more, the specific surface area will not become too large, and there will be no shortage of component (D), allowing the absolute viscosity to be set to an appropriate value. If the particle size is 20 μm or less, the proportion of the heat conduction path will not be too large, allowing the thermal conductivity of the composition to be set high.

[0060] [Co-filled thermally conductive filler] The thermally conductive silicone composition of the present invention may contain other co-filled thermally conductive fillers. If necessary, inorganic particles such as magnesium oxide, aluminum hydroxide, aluminum nitride, and silica can be used in combination as the thermally conductive filler co-filled with the silicon nitride filler. This is a preferred embodiment, as it allows the thermal conductivity and absolute viscosity of the composition to be adjusted by using other insulating inorganic particles in combination.

[0061] [Other Components] Various additives can be further blended into the thermally conductive silicone composition as needed. Specific examples include thixotropy-imparting agents, dispersants, curing agents, cure accelerators, retarders, slight tackifiers, plasticizers, flame retardants, antioxidants, stabilizers, colorants, etc. For example, modified silicones in which some of the methyl groups in organopolysiloxane have been replaced with other functional groups can be added as internal release agents that promote release from films or molds.

[0062] [Method for producing thermally conductive silicone composition] The thermally conductive silicone composition is preferably produced by kneading the β-type silicon nitride filler, the silicone component, and any other components that may be added as needed, using a kneading method that exerts a shear force, such as a mixer such as Trimix, Twinmix, or Planetary Mixer (all of which are registered trademarks of mixers manufactured by Inoue Seisakusho Co., Ltd.), a kneader, or a twin-roll mill, but is not particularly limited thereto.

[0063] [Absolute Viscosity of Thermally Conductive Silicone Composition] The absolute viscosity of the thermally conductive silicone composition of the present invention is preferably in the range of 10 to 300 Pa·s at 25°C. Of these, a range of 50 to 200 Pa·s is more preferable. If the absolute viscosity of the composition is 300 Pa·s or less, there is no decrease in productivity due to prolonged pumping time, and significant wear of piping can be avoided. Furthermore, if the absolute viscosity is 10 Pa·s or more, the required thickness can be maintained when applying by coating or dispenser. The absolute viscosity of the thermally conductive silicone composition of the present invention is measured using a viscosity / viscoelasticity measuring device (HAAKE MARS 40 / 60) at a composition temperature of 25°C and a shear rate of 10 s －１ is the value.

[0064] [Thermal Conductivity of Thermally Conductive Silicone Composition] The thermal conductivity of the thermally conductive silicone composition of the present invention is measured at 25°C using the hot disc method and is preferably at least 4.0 W / m K, and more preferably at least 4.5 W / m K. A thermal conductivity of 4.0 W / m K or higher makes it suitable for use in components that generate a large amount of heat.

[0065] [Preparation of Thermally Conductive Silicone Composition] Components (A) to (G) used in the following examples and comparative examples are shown below.

[0066] Component (A): an organopolysiloxane represented by the following formula: In the above formula, X is a vinyl group, and n is the kinematic viscosity of 600 mm ２ / s.

[0067] Component (B): an organohydrogenpolysiloxane represented by the following formula: (The order of the siloxane units in parentheses is unspecified.)

[0068] Component (C): 5% chloroplatinic acid 2-ethylhexanol solution

[0069] Component (D): A dimethylpolysiloxane represented by the following formula, in which one molecular chain end is blocked with a trimethoxy group:

[0070] Component (E): Silicon nitride filler The average particle size of the silicon nitride filler that constitutes component E, the integrated intensity (β) in the range [2θ = 19.6 to 21.6°] derived from the α phase obtained by X-ray diffraction, the integrated intensity (β) in the range [2θ = 26.6 to 28.6°] derived from the β phase, and the (β) / (α) ratio are shown in Table 1 below.

[0071] The count numbers for each silicon nitride filler in the X-ray analysis were calculated by measuring using a BRUKER JAPAN D2 PHASER 2nd Generation tabletop powder X-ray diffractometer under the following conditions: scan range: 20-90°, step size: 0.024°, sample rotation: 10 rpm, voltage: 30 kV, current: 10 mA. The average particle size is the cumulative average particle size (median diameter) on a volume basis, measured using a Microtrac MT3300EXII particle size analyzer manufactured by Microtrac Bell. There is no known prior art relating to thermally conductive silicone compositions containing silicon nitride fillers with a (β) / (α) ratio of 10 or greater, such as E-1, E-2, and E-3.

[0072]

[0073] (F) Component: Comparative thermally conductive filler, and aluminum oxide co-filled with silicon nitride filler (F-1) Average particle size: 40 μm: crushed aluminum oxide (for Comparative Example 1) (F-2) Average particle size: 70 μm: crushed aluminum nitride (for Comparative Example 2) (F-3) Average particle size: 1 μm: crushed aluminum oxide (co-filled filler) (F-4) Average particle size: 10 μm: spherical aluminum oxide (co-filled filler) (particle size measured by laser diffraction method)

[0074] Component (G): Phenyl-modified silicone represented by the following formula: (The order of the siloxane units in parentheses is unspecified.)

[0075] [Preparation of Thermally Conductive Silicone Composition] The following components were added in order according to the formulation shown in Table 2 below. First, components (A), (C), (D), (E), and (F) were kneaded for 60 minutes using a planetary mixer. Next, phenyl-modified silicone component (G), which serves as an internal release agent to promote release of the composition, was added to this composition and kneaded for 30 minutes. Component (B) was then added and kneaded for 30 minutes to obtain a thermally conductive silicone composition.

[0076] [Evaluation Method] (Absolute Viscosity) The absolute viscosity of the prepared thermally conductive silicone composition was measured using a viscosity / viscoelasticity measuring device (HAAKE MARS 40 / 60) at a composition temperature of 25°C and a shear rate of 10 s －１ In the present examples and comparative examples, thermally conductive silicone compositions with absolute viscosities in the range of 10 to 300 Pa·s were deemed to pass.

[0077] (Thermal Conductivity) The prepared thermally conductive silicone composition was poured into a 60 mm x 60 mm x 6 mm thick mold, the opening of the mold was sandwiched between two sheets of PET film, and then the composition was heat-pressed using a press molding machine at 120°C for 10 minutes to obtain a thermally conductive silicone cured product (thermally conductive silicone sheet). Two of the obtained 6 mm thick sheets of the cured product were used to measure the thermal conductivity of the cured product using a thermal conductivity meter (TPA-501, product name, manufactured by Kyoto Electronics Manufacturing Co., Ltd.). In these examples and comparative examples, thermally conductive silicone compositions with a thermal conductivity of 4.0 W / mK or higher were considered to have passed the test.

[0078] The absolute viscosities and thermal conductivities of the compositions of Examples 1 to 5 and Comparative Examples 1 to 4 are shown in Table 2 below.

[0079]

[0080] In Examples 1 to 5, silicon nitride (E-1, E-2, E-3) with a high β ratio (β / α ratio of 10 or more) and aluminum oxide (F-3, F-4) as defined in claim 8 were used in combination. Meanwhile, in Comparative Examples 1 and 2, silicon nitride E-4 and E-5 with a β / α ratio of less than 10 were used. Furthermore, in Comparative Examples 3 and 4, silicon nitride was replaced with aluminum oxide F-1 or F-2, and no silicon nitride was used. As a result, the compositions of Examples 1 to 5 had a viscosity of 300 Pa·s or less, suitable for molding and coating, and a thermal conductivity of 4.0 W / mK or more. In other words, the objective of the present invention, which is to achieve both high thermal conductivity and an appropriate absolute viscosity of the silicone composition, was achieved. Meanwhile, Comparative Examples 1 and 2 did not use silicon nitride with a high β ratio (β / α ratio of 10 or more), a feature of the present invention, and therefore had a thermal conductivity of less than 4.0 W / mK and were therefore unsuccessful. Furthermore, in Comparative Examples 3 and 4, in which no silicon nitride was used, the absolute viscosity of the silicone composition was 300 or more, and the composition was unsuccessful.

[0081] This specification includes the following inventions.

[0082] [1]: A thermally conductive silicone composition comprising a silicone component and a silicon nitride filler (E) having an integrated peak intensity ratio of [2θ=26.6-28.8°] / [2θ=19.6-21.6°]=10 or greater as detected by X-ray diffraction. [2]: The thermally conductive silicone composition according to [1], wherein the average particle size of component (E) measured by laser diffraction is 20-100 μm. [3]: The thermally conductive silicone composition according to [1] or [2], wherein the amount of component (E) blended is 200-1000 parts by mass per 100 parts by mass of the silicone component. [4]: ​​The thermally conductive silicone composition according to any one of [1] to [3], wherein the silicone component comprises: (A) an organopolysiloxane having two or more alkenyl groups per molecule; and (B) an organohydrogenpolysiloxane having two or more hydrogen atoms directly bonded to silicon atoms. [5]: The thermally conductive silicone composition according to [4], characterized in that the thermally conductive silicone composition contains, in addition to the silicone component, (C) a hydrosilylation catalyst. [6]: The silicone component contains (D) a dimethylpolysiloxane having one molecular chain end capped with a trialkoxy group, represented by the following formula (1): (In the formula, R 1 are independently alkyl groups having 1 to 6 carbon atoms, and m is an integer from 5 to 100. The thermally conductive silicone composition according to [4] or [5] further comprises 10 to 200 parts by mass of the compound (A) per 100 parts by mass of component (A). [7]: The compound (A) has a kinematic viscosity of 10 to 100,000 mm ２ / s. [8]: The thermally conductive silicone composition according to any one of [1] to [7], characterized in that the thermally conductive silicone composition contains (F) aluminum oxide having an average particle size of 1 to 20 μm as measured by laser diffraction. [9]: The thermally conductive silicone composition according to any one of [1] to [8], characterized in that the thermally conductive silicone composition has an absolute viscosity of 10 to 300 Pa·s or less.

[10] : The thermally conductive silicone composition according to any one of [1] to [9], characterized in that the thermal conductivity of the thermally conductive silicone composition is 4.0 W / mK or more.

[11] : A thermally conductive silicone cured product formed from the thermally conductive silicone composition according to any one of [1] to

[10] .

[0083] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits similar effects is included within the technical scope of the present invention.

Claims

1. A thermally conductive silicone composition comprising a silicone component and a silicon nitride filler (E) having an integrated peak intensity ratio of [2θ=26.6-28.6°] / [2θ=19.6-21.6°]=10 or greater as detected by X-ray diffraction.

2. The thermally conductive silicone composition according to claim 1, wherein component (E) has an average particle size of 20 to 100 μm as measured by laser diffraction.

3. The thermally conductive silicone composition according to claim 1 or 2, wherein the blend amount of component (E) is 200 to 1000 parts by mass per 100 parts by mass of the silicone component.

4. The thermally conductive silicone composition according to claim 1, wherein the silicone component comprises: (A) an organopolysiloxane having two or more alkenyl groups per molecule; and (B) an organohydrogenpolysiloxane having two or more hydrogen atoms directly bonded to silicon atoms.

5. The thermally conductive silicone composition according to claim 4, characterized in that the thermally conductive silicone composition contains, in addition to the silicone component, (C) a hydrosilylation catalyst.

6. The silicone component is (D) a dimethylpolysiloxane represented by the following formula (1) in which one molecular chain end is blocked with a trialkoxy group: (In formula (1), R 1 are independently an alkyl group having 1 to 6 carbon atoms, and m is an integer from 5 to 100. The thermally conductive silicone composition according to claim 4, further comprising 10 to 200 parts by mass of the compound (A) per 100 parts by mass of component (A).

7. The kinematic viscosity of component (A) is 10 to 100,000 mm ２ 5. The thermally conductive silicone composition according to claim 4, wherein the composition is a hydroxyl group-containing silicone compound.

8. The thermally conductive silicone composition according to claim 1, characterized in that the thermally conductive silicone composition contains (F) aluminum oxide having an average particle size of 1 to 20 μm as measured by laser diffraction.

9. The thermally conductive silicone composition according to claim 1, wherein the absolute viscosity of said thermally conductive silicone composition is 10 to 300 Pa·s.

10. The thermally conductive silicone composition according to claim 1, wherein the thermal conductivity of said thermally conductive silicone composition is 4.0 W / mK or more.

11. A cured thermally conductive silicone product, which is a cured product of the thermally conductive silicone composition according to claim 1.

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