Highly thermally conductive silicone composition and cured product thereof

Abstract

The invention relates to a high-thermal-conductivity organic silicon composition. The high-thermal-conductivity organic silicon composition is prepared from the following components according to a specific proportion and specific quantity: (A) organopolysiloxane; (B) a spherical magnesium oxide powder having an average sphericity of 0.8 or more, an average particle diameter of 80-150 [mu] m, and a purity of 98 mass% or more; (C) a thermally conductive filler containing (C-I) and (C-II), the volume ratio of the component (C-I) to the component (C-II) being 2: 8-8: 2, (C-I) a spherical alumina powder having an average sphericity of 0.8 or more and the proportion of coarse particles having an average particle diameter of 7-60 [mu] m and 96-150 [mu] m being 0.1-30 mass% of the total component (C-I), and (C-II) a spherical or irregularly shaped alumina powder having an average particle diameter of 0.1-4 [mu] m; and (D) an ion scavenger which is a cation-exchange-type ion scavenger and / or a double-ion-exchange-type ion scavenger that supports at least one element selected from the group consisting of Zr, Bi, Sb, Mg, and Al. The high thermal conductivity silicone composition has a thermal conductivity of 7.0 W / m.K or more and a viscosity of 30 to 800 Pa.s. As a result, it is possible to provide a highly thermally conductive silicone composition having excellent insulating properties, thermal conductivity, moisture resistance, and storage stability.

Description

Technical Field

[0001] The present invention relates to a silicone composition having excellent insulating and thermal conductivity properties, and more particularly to a highly thermally conductive silicone composition having excellent insulating properties and a cured product thereof. When used as a heat dissipation component for electronic components, the highly thermally conductive silicone composition can be incorporated into electronic equipment without damaging heat-generating electronic components such as power elements, transistors, thyristors, and CPUs (central processing units). Background Art

[0002] For heat-generating electronic components such as power devices, transistors, thyristors, and CPUs, removing the heat generated during use is a critical issue. Conventionally, this heat removal method involves mounting the components on a cooling fan or metal plate via an electrically insulating heat sink. This heat sink typically consists of a silicone resin containing a thermally conductive filler dispersed therein.

[0003] In recent years, as electronic components have become increasingly integrated, their heat generation has also increased, leading to a demand for materials with higher thermal conductivity than ever before. To improve the thermal conductivity of thermally conductive materials, a common method currently employed is to incorporate highly thermally conductive fillers such as alumina powder and aluminum nitride powder into a matrix resin (Patent Documents 1-4).

[0004] Therefore, in order to improve thermal conductivity, a method for preparing a high thermal conductivity resin composition has been disclosed. The high thermal conductivity resin composition is prepared by combining spherical alumina powder having a specified average sphericity and hydroxyl content and an average particle size of 10 to 50 μm with alumina powder having an average particle size of 0.3 to 1 μm, with a specified blending ratio and volume ratio. However, when the average particle size of the spherical alumina powder is a maximum of 50 μm, there is a problem that the thermal conductivity is still insufficient (Patent Document 5).

[0005] In addition, while a thermally conductive silicone composition using alumina powder with an average particle size of 0.1 to 100 μm has been proposed, specific thermal conductivity and viscosity are not specified. Furthermore, a thermally conductive silicone composition comprising spherical alumina powder with an average particle size of 5 to 50 μm (but not including 5 μm) and spherical or irregularly shaped alumina powder with an average particle size of 0.1 to 5 μm, with the respective alumina blending ratios and weight ratios, is disclosed. However, similar to Patent Document 5, this composition does not specify the average sphericity and hydroxyl content of the spherical alumina with a larger average particle size, and thus remains insufficient for achieving high thermal conductivity (Patent Document 6).

[0006] Examples of thermally conductive fillers other than alumina include aluminum, copper, silver, boron nitride, and aluminum nitride. While these materials offer high thermal performance, they are still disadvantageous from a cost perspective. Furthermore, the use of metal powders such as aluminum, copper, and silver can reduce the insulation properties of the thermally conductive silicone composition and its cured product.

[0007] On the other hand, the thermal conductivity of magnesium oxide is 42 to 60 W / m·K, which is higher than the 26 to 36 W / m·K of aluminum oxide, which is noteworthy. In addition, magnesium oxide has a Mohs hardness of 6 and a specific gravity of 3.65, which is lighter than aluminum oxide, so it can make the thermally conductive silicone composition and the cured product lighter. However, magnesium oxide still has the disadvantage of high hygroscopicity. Although there is a thermally conductive silicone adhesive composition prepared by calcining a specific magnesium hydroxide at 1100 to 1600°C, it has a high hygroscopicity. As a result, there is a problem of easy cracking of the silicone adhesive due to reasons such as strong alkalinity (Patent Document 7).

[0008] Therefore, a thermally conductive silicone resin composition with excellent moisture resistance is disclosed, which is obtained by treating the surface of magnesium oxide with silazane. However, because the particle size of magnesium oxide is very small, at 1 μm, even increasing the loading is not expected to improve thermal conductivity. Furthermore, it has not been verified whether this method is sufficiently effective when using powders with larger particle sizes (Patent Document 8).

[0009] In addition, a thermally conductive heat sink is disclosed that combines spherical magnesium oxide and granular aluminum oxide to improve formability. However, the magnesium oxide is used in an amount of only about 20% by mass relative to the total weight of the thermally conductive filler, and technical problems such as an increase in specific gravity caused by the large amount of aluminum oxide and wear of the reaction container during mixing have not yet been solved (Patent Document 9).

[0010] Here, a system that uses surface-treated magnesium oxide together with aluminum oxide is effective in resolving the aforementioned issues. Furthermore, by hydrophobizing the surface of the magnesium oxide to improve moisture resistance, a thermally conductive silicone resin composition suitable for use in high-humidity conditions can be obtained. Furthermore, using magnesium oxide at a volume ratio of 50% or more of the combined mass of magnesium oxide and aluminum oxide can suppress wear of the reaction vessel. Furthermore, compared to using aluminum oxide alone as a thermally conductive filler at the same loading, the combined use of aluminum oxide and magnesium oxide has a lower specific gravity, thereby suppressing sedimentation of the thermally conductive filler in the thermally conductive silicone composition.

[0011] Therefore, although a thermally conductive silicone composition has been proposed that solves the above-mentioned technical problems and uses magnesium oxide and aluminum oxide in combination, the shape and purity of the magnesium oxide are not specified, and the thermal conductivity is still insufficient if the average particle size of the magnesium oxide used is less than 80 μm (Patent Document 10).

[0012] Furthermore, a thermally conductive silicone composition has been proposed that uses spherical magnesium oxide and aluminum oxide together to address the thermal conductivity issue. However, this composition is particularly susceptible to the effects of ionic impurities contained in the magnesium oxide, causing the thermally conductive silicone composition to increase in viscosity over time, or causing a delay in curing as a curable composition, resulting in a lack of storage stability (Patent Document 11). [Prior art literature] (Patent Document)

[0013] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-162555 Patent Document 2: Japanese Patent Application Laid-Open No. 2003-342021 Patent Document 3: Japanese Patent Publication No. 2002-280498 Patent Document 4: Japanese Patent Publication No. 2005-209765 Patent Document 5: Japanese Patent No. 5755977 Patent Document 6: International Publication No. 2002 / 092693 Patent Document 7: Japanese Patent Application Laid-Open No. 5-239358 Patent Document 8: Japanese Patent Application Laid-Open No. 7-292251 Patent Document 9: Japanese Patent Application Laid-Open No. 8-88488 Patent Document 10: Japanese Patent No. 6075261 Patent Document 11: International Publication No. 2020 / 261958 Summary of the Invention Technical problem to be solved by the invention

[0014] The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a highly thermally conductive silicone composition having excellent insulation, thermal conductivity, moisture resistance, and storage stability, and in particular to provide a highly thermally conductive silicone composition suitable for forming heat dissipating components for electronic parts, and a cured product thereof. Technical means to solve the problem

[0015] In order to solve the above technical problems, the present invention provides a high thermal conductivity silicone composition, which comprises: (A) organopolysiloxane; (B) spherical magnesium oxide powder having an average sphericity of 0.8 or greater, an average particle size of 80 to 150 μm, and a purity of 98% by mass or greater; (C) A thermally conductive filler comprising (CI) and (C-II), wherein the volume ratio of the following components (CI) and (C-II) ((CI):(C-II)) is 2:8 to 8:2, (CI) spherical alumina powder having an average sphericity of 0.8 or more, an average particle size of 7 to 60 μm, and a ratio of coarse particles of 96 to 150 μm in the laser diffraction particle size distribution of 0.1 to 30% by mass of the total (CI) component. (C-II) spherical or irregularly shaped alumina powder having an average particle size of 0.1 to 4 μm; and (D) an ion scavenger, which is a cation exchange and / or double ion exchange type ion scavenger and supports at least one element selected from Zr, Bi, Sb, Mg, and Al; In the high thermal conductivity silicone composition, The amount of the component (B) is 3300 to 6500 parts by mass relative to 100 parts by mass of the component (A). The amount of the component (D) is 0.01 to 10 parts by mass relative to 100 parts by mass of the component (A). The volume ratio of the components (B) and (C), i.e., (B): (C), is 5:5 to 9.5:0.5, and the total amount of the components (B) and (C) accounts for 80 to 90% of the volume of the composition. The composition has a thermal conductivity of 7.0 W / m·K or higher in the hot disk method according to ISO 22007-2, and a viscosity of 30 to 800 Pa·s at 25° C. when measured using a spiral viscometer at a rotation speed of 10 rpm.

[0016] Such a composition can provide a highly thermally conductive silicone composition that is excellent in insulation, thermal conductivity, moisture resistance, and storage stability.

[0017] The highly thermally conductive silicone composition may contain 1 to 6% by mass of the component (A).

[0018] When the content of component (A) is 1% by mass or more, the viscosity of the obtained composition is appropriate and handling becomes easy. When the content is 6% by mass or less, high thermal conductivity of the high thermal conductive silicone composition can be well achieved.

[0019] The above-mentioned high thermal conductivity silicone composition can be any of the following: an addition reaction-curing type using (A-I) an organopolysiloxane having an average of 0.1 or more silicon-bonded alkenyl groups per molecule as component (A); a condensation reaction-curing type using (A-II) an organopolysiloxane having at least two silanol groups or silicon-bonded hydrolyzable groups per molecule as component (A); or an organic peroxide-curing type using (A-III) an organopolysiloxane having at least one silicon-bonded alkenyl group per molecule as component (A).

[0020] Thus, an addition reaction-curable high thermal conductivity silicone composition, a condensation reaction-curable high thermal conductivity silicone composition, and an organic peroxide-curable high thermal conductivity silicone composition can be preferably provided.

[0021] The highly thermally conductive silicone composition may further include (E) a surface treatment agent.

[0022] Thereby, the (B) component and the (C) component can be preferably surface-treated with the (E) surface treatment agent.

[0023] In this case, as the component (A), an organopolysiloxane (AI) having an average of 0.1 or more silicon-bonded alkenyl groups in one molecule or an organopolysiloxane (A-III) having at least one silicon-bonded alkenyl group in one molecule can be used. The following organopolysiloxane is contained as the component (E) in an amount of 5 to 900 parts by mass per 100 parts by mass of the component (AI) or (A-III), wherein the organopolysiloxane is represented by the following general formula (1), contains at least one silyl group in one molecule, and has a viscosity of 0.01 to 30 Pa·s at 25° C. -SiR 1 a (OR 2 ) 3-a (1) In the general formula (1), R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 are independently alkyl, alkoxyalkyl, alkenyl or acyl, and a is 0, 1 or 2.

[0024] Therefore, the component (E) can be more preferably used in the component (AI) or (A-III).

[0025] The present invention may further comprise 0.01 to 10% by mass of (F) spherical glass beads or amorphous glass having a maximum center particle diameter of 160 μm or more and an SiO 2 content of 50% by mass or more, accounting for 0.01 to 10% by mass of the total amount of the composition.

[0026] Thus, by blending the component (F), the high thermal conductive silicone composition can be formed into a more appropriate thickness even in a very small amount.

[0027] Furthermore, the present invention can form a cured product of a highly thermally conductive silicone composition.

[0028] The cured product of the composition of the present invention is excellent in insulation, thermal conductivity, moisture resistance, and storage stability. Effects of the Invention

[0029] As described above, according to the present invention, a highly thermally conductive silicone composition and a cured product thereof that are excellent in insulation, thermal conductivity, moisture resistance, and storage stability can be provided. DETAILED DESCRIPTION

[0030] As described above, there has been a need to develop a highly thermally conductive silicone composition that is excellent in insulation, thermal conductivity, moisture resistance, and storage stability.

[0031] The inventors have conducted extensive research to address the aforementioned technical issues and have discovered that a high thermal conductivity silicone composition having the following structure can address these issues and provide a high thermal conductivity silicone composition with excellent handleability and workability. Furthermore, they have discovered that even when a curing agent is added to this composition to form a curable composition, the composition exhibits excellent storage stability, leading to the completion of the present invention.

[0032] That is, the high thermal conductivity silicone composition of the present invention comprises: (A) organopolysiloxane; (B) spherical magnesium oxide powder having an average sphericity of 0.8 or greater, an average particle size of 80 to 150 μm, and a purity of 98% by mass or greater; (C) A thermally conductive filler comprising (CI) and (C-II), wherein the volume ratio of the following components (CI) and (C-II) ((CI):(C-II)) is 2:8 to 8:2, (CI) spherical alumina powder having an average sphericity of 0.8 or more, an average particle size of 7 to 60 μm, and a ratio of coarse particles of 96 to 150 μm in a laser diffraction particle size distribution of 0.1 to 30% by mass of the entire (CI) component. (C-II) spherical or irregularly shaped alumina powder having an average particle size of 0.1 to 4 μm; and (D) an ion scavenger, which is a cation exchange and / or dual ion exchange type ion scavenger and carries at least one element selected from Zr, Bi, Sb, Mg, and Al; in the high thermal conductivity silicone composition, The amount of the component (B) is 3300 to 6500 parts by mass relative to 100 parts by mass of the component (A). The amount of the component (D) is 0.01 to 10 parts by mass relative to 100 parts by mass of the component (A). The mixing ratio of the above-mentioned components (B) and (C), i.e., the volume ratio ((B): (C)) is 5:5 to 9.5:0.5, and the total amount of the components (B) and (C) is 80 to 90% by volume of the composition. The thermal conductivity of the composition is 7.0 W / m·K or higher by the hot disk method according to ISO 22007-2, and the viscosity of the composition at 25° C. is 30 to 800 Pa·s when measured with a spiral viscometer at a rotation speed of 10 rpm.

[0033] The present invention will be described in detail below, but the present invention is not limited to these descriptions. It should be noted that the "high thermal conductivity silicone composition" may be simply referred to as the "silicone composition."

[0034] [(A) ingredient] The organopolysiloxane of component (A) is the main component of the organosilicon composition of the present invention. The group bonded to the silicon atom in the organopolysiloxane may be an unsubstituted or substituted monovalent hydrocarbon group preferably having 1 to 20 carbon atoms, more preferably 1 to 6 carbon atoms, and examples thereof include linear alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, and eicosyl; isopropyl, tertiary butyl, isobutyl, 2-methylundecyl, 1-hexyl branched alkyl groups such as cycloheptyl, cyclopentyl, cyclohexyl, cyclododecyl, etc.; alkenyl groups such as vinyl, allyl, butenyl, pentenyl, hexenyl, etc.; aryl groups such as phenyl, tolyl, xylyl, etc.; aralkyl groups such as benzyl, phenethyl, 2-(2,4,6-trimethylphenyl)propyl, etc.; halogenated alkyl groups such as 3,3,3-trifluoropropyl, 3-chloropropyl, etc.; silanol groups, silicon atom-bonded hydrolyzable groups; preferably alkyl groups, alkenyl groups, aryl groups, silanol groups, and particularly preferably methyl groups, vinyl groups, and phenyl groups.

[0035] The viscosity of the organopolysiloxane of component (A) at 25°C is not limited, but is preferably in the range of 20 to 100,000 mPa·s, more preferably 50 to 80,000 mPa·s, further preferably 70 to 50,000 mPa·s, and particularly preferably 100 to 30,000 mPa·s. If it is 20 mPa·s or more, the physical properties of the silicone composition will not be reduced and will be good. If it is 100,000 mPa·s or less, the handling workability of the silicone composition will also be good. It should be noted that the viscosity is a value measured at 25°C using a BM viscometer or a BH viscometer (for example, manufactured by Tokyo Keiki Co., Ltd.) (the same below). It should be noted that the rotor, rotation speed, and rotation time can be appropriately selected based on the viscosity according to the usual method.

[0036] The molecular structure of the organopolysiloxane of component (A) is not limited, and examples thereof include linear, branched, partially branched linear, and dendritic (dendritic polymers), with linear and partially branched linear structures being preferred. Examples of such organopolysiloxanes include homopolymers having these molecular structures, copolymers having these molecular structures, and mixtures of these polymers.

[0037] Examples of the organopolysiloxane of the component (A) include: dimethylpolysiloxane terminated with dimethylvinylsiloxy groups at both ends of the molecular chain; dimethylpolysiloxane terminated with methylphenylvinylsiloxy groups at both ends of the molecular chain; dimethylsiloxane-methylphenylsiloxane copolymer terminated with dimethylvinylsiloxy groups at both ends of the molecular chain; dimethylsiloxane-methylvinylsiloxane copolymer terminated with dimethylvinylsiloxy groups at both ends of the molecular chain; dimethylsiloxane-methylvinylsiloxane copolymer terminated with trimethylsiloxane-methylvinylsiloxane; methyl(3,3,3-trifluoropropyl)polysiloxane terminated with dimethylvinylsiloxy groups at both ends of the molecular chain; dimethylsiloxane-methylvinylsiloxane copolymer terminated with silanol groups at both ends of the molecular chain; dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer terminated with silanol groups at both ends of the molecular chain; 1 / 2 Siloxane units represented by the formula (CH3)2(CH2=CH)SiO 1 / 2 The siloxane unit represented by the formula CH3SiO 3 / 2 The siloxane unit represented by the formula (CH3)2SiO 2 / 2An organosiloxane copolymer composed of siloxane units represented by . It should be noted that, when a condensation reaction curing composition is used, the following may also be used: dimethylpolysiloxane with silanol groups blocking the molecular chain at both ends; dimethylsiloxane-methylphenylsiloxane copolymer with silanol groups blocking the molecular chain at both ends; dimethylpolysiloxane with trimethoxysiloxy groups blocking the molecular chain at both ends; dimethylsiloxane-methylphenylsiloxane copolymer with trimethoxysiloxy groups blocking the molecular chain at both ends; dimethylpolysiloxane with methyldimethoxysiloxy groups blocking the molecular chain at both ends; dimethylpolysiloxane with triethoxysiloxy groups blocking the molecular chain at both ends; and dimethylpolysiloxane with trimethoxysilylethyl groups blocking the molecular chain at both ends. These may be used alone or in appropriate combinations of two or more.

[0038] When the silicone composition is cured by a hydrosilylation reaction (addition reaction curing), in component (A), (AI) is preferably an organopolysiloxane having an average of 0.1 or more silicon-bonded alkenyl groups per molecule, more preferably an organopolysiloxane having an average of 0.1 or more and 20 or less silicon-bonded alkenyl groups per molecule, further preferably an organopolysiloxane having an average of 0.5 or more and 15 or less silicon-bonded alkenyl groups per molecule, and even more preferably an organopolysiloxane having an average of 0.8 or more and 10 or less silicon-bonded alkenyl groups per molecule. This is because if the average number of silicon-bonded alkenyl groups per molecule is above the lower limit of the above range, the resulting silicone composition can be sufficiently cured. Examples of the silicon-bonded alkenyl groups in the organopolysiloxane include the same alkenyl groups as described above, with vinyl groups being preferred. Examples of the groups bonded to silicon atoms other than alkenyl groups in the organopolysiloxane include the same linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as described above. Alkyl groups and aryl groups are preferred, and methyl groups and phenyl groups are particularly preferred. It should be noted that the average number of silicon-bonded alkenyl groups in one molecule of the organopolysiloxane can generally be calculated based on the iodine value determined by the Hanus method (a method in which a compound is allowed to react with a Hanus reagent, followed by reaction with an aqueous potassium iodide solution, and the generated iodine is titrated with sodium thiosulfate, in accordance with Japanese Industrial Standard JIS K0070).

[0039] The method for calculating the average number of silicon atom-bonded alkenyl groups in one molecule of organopolysiloxane will be described. The average number of alkenyl groups per molecule is obtained by averaging the number of alkenyl groups per molecule based on the total number of molecules. For example, when the vinyl equivalent of a designed structure is determined by treating vinyl groups as alkenyl groups, it can be calculated using the following formula. The number of alkenyl groups (vinyl groups) per molecule = number average molecular weight (actual measured value) / vinyl equivalent of the designed structure When the designed average unit formula of the organopolysiloxane is clear, the weight can be calculated based on the theoretical value of the vinyl equivalent calculated from the average unit formula and the actual measured value of the number average molecular weight (Mn) obtained by gel permeation chromatography (GPC). Alternatively, when the designed average unit formula of the organopolysiloxane is unclear, the weight can be calculated based on the amount of alkenyl groups contained in a predetermined amount as determined by the Hannus method and the actual measured value of the number average molecular weight obtained by GPC. The number average molecular weight can be measured using GPC as a standard polystyrene equivalent.

[0040] When the silicone composition is cured by a condensation reaction, it is preferred to use an organopolysiloxane (A-II) having at least two silanol groups or silicon-bonded hydrolyzable groups per molecule in component (A). It is even more preferred to use an organopolysiloxane having two or more and ten or fewer silanol groups or silicon-bonded hydrolyzable groups per molecule. Examples of silicon-bonded hydrolyzable groups in the organopolysiloxane include alkoxy groups such as methoxy, ethoxy, and propoxy; alkenyloxy groups such as vinyloxy, propenyloxy, isopropenyloxy, and 1-ethyl-2-methylvinyloxy; dialkoxy groups such as methoxyethoxy, ethoxyethoxy, and methoxypropoxy; acyloxy groups such as acetoxy and octanoyloxy; ketoximo groups such as dimethylketoxime and methylethylketoxime; amino groups such as dimethylamino, diethylamino, and butylamino; aminooxy groups such as dimethylaminooxy and diethylaminooxy; and amide groups such as N-methylacetamide and N-ethylacetamide. Examples of silicon-bonded groups other than silanol groups and silicon-bonded hydrolyzable groups in the organopolysiloxane include the same linear alkyl groups, branched alkyl groups, cyclic alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as described above.

[0041] When the silicone composition is cured by a free radical reaction using an organic peroxide, the organopolysiloxane of component (A) is not limited. In particular, an organopolysiloxane (A-III) having at least one silicon-bonded alkenyl group in one molecule is preferred. In addition, an organopolysiloxane having an average of 0.1 to 20 silicon-bonded alkenyl groups in one molecule is more preferred. Examples of the silicon-bonded alkenyl group in the organopolysiloxane include the same alkenyl groups as described above, preferably vinyl groups. In addition, examples of groups bonded to silicon atoms other than alkenyl groups in the organopolysiloxane include the same linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as described above. Alkyl groups and aryl groups are preferred, and methyl groups and phenyl groups are particularly preferred.

[0042] The amount of component (A) in the silicone composition is preferably 1 to 6% by mass, more preferably 1.1 to 5.8% by mass. When the amount of component (A) is 1% by mass or greater, the viscosity of the resulting composition becomes suitable, making handling easier. When the amount is 6% by mass or less, the thermal conductivity of the composition can be increased without difficulty.

[0043] [(B) ingredient] Component (B) is a spherical magnesium oxide powder having an average sphericity of 0.8 or greater, an average particle size of 80 to 150 μm, and a purity of 98% by mass or greater. Two or more types having different average particle sizes may be used in combination as long as they meet the above ranges.

[0044] The average sphericity of the magnesium oxide powder is 0.8 or more, preferably 0.9 or more. In addition, the upper limit of the average sphericity is as high as possible, for example, it can be set to 1. If the average sphericity is less than 0.8, sometimes the fluidity will decrease, and there will be a tendency that the contact positions between the particles will significantly increase, the concavo-convexity of the sheet surface will increase the interface thermal resistance, and the thermal conductivity will deteriorate.

[0045] The average sphericity in the present invention can be measured by reading the particle image photographed using a scanning electron microscope in an image analysis device, such as the product name "JSM-7500F" manufactured by JEOL Ltd., and performing the following operation. That is, the projected area (X) and the circumference (Z) of the particle are measured from the photograph. If the area of ​​the true circle corresponding to the circumference (Z) is set to (Y), the sphericity of the particle can be expressed as X / Y. Therefore, if a true circle is imagined, which has the same circumference as the circumference (Z) of the sample particle, based on Z = 2πr, Y = πr 2 , we can get Y = π × (Z / 2π) 2 , can be based on sphericity = X / Y = X × 4π / Z 2 The sphericity of each particle is calculated. The sphericity of 100 random particles obtained in this way is calculated, and the average value is defined as the average sphericity (the same applies hereinafter).

[0046] The average particle size of the magnesium oxide powder is 80 to 150 μm, preferably 90 to 130 μm. If the average particle size is too small, achieving the high thermal conductivity of the present invention tends to be difficult. If it is too large, the surface irregularities may become larger, the interfacial thermal resistance may increase, and the thermal conductivity may deteriorate. It should be noted that the magnesium oxide powder preferably has a particle size distribution of D90 (90% of the median particle size when D50 is set) / D10 (10% of the median particle size when D50 is set) = 4 or less.

[0047] The average particle size in the present invention is a volume-based average particle size that can be measured using, for example, the "Laser Diffraction Particle Size Distribution Analyzer SALD-2300" manufactured by Shimadzu Corporation. The evaluation sample is prepared by adding 50cc of pure water and 5g of the thermal conductive powder to be measured to a glass beaker, stirring with a spatula, and then dispersing the mixture in an ultrasonic cleaner for 10 minutes. Using a dropper, the dispersed thermal conductive material powder solution is added drop by drop to the sampling portion of the device, and then wait until it stabilizes and the absorbance can be measured. This operation is performed and the measurement is performed at the time point when the absorbance stabilizes. In the laser diffraction particle size distribution analyzer, the particle size distribution is calculated based on the data of the light intensity distribution of diffracted / scattered light obtained from the particles detected by the sensor. The average particle size is obtained by multiplying the measured particle size value by the relative particle amount (difference %) and then dividing it by the total relative particle amount (100%). It should be noted that the average particle size is the average diameter of the particles (the same below).

[0048] The magnesium oxide powder preferably has a cubic crystal structure (sodium chloride-type structure) and a specific gravity of 3.4 or higher. A specific gravity of 3.4 or higher reduces the proportion of pores and low-crystalline phases within the particles, significantly improving thermal conductivity. Particle size adjustment of the magnesium oxide powder can be achieved through classification and mixing.

[0049] The purity of the magnesium oxide powder is 98% by mass or more, more preferably 99% by mass or more. The upper limit of the purity of the magnesium oxide powder can be set to 100% by mass or less. If the purity of the magnesium oxide powder is lower than 98% by mass, the thermal conductivity obtained will tend to deteriorate. It should be noted that, as impurities of magnesium oxide, calcium oxide, silicon dioxide, aluminum oxide, iron oxide, etc. can be listed. The purity in the present invention can be measured by ICP emission spectrometry (the same below). Furthermore, as ionic impurities present in the magnesium oxide powder, Ca, 2+ ions and Mg 2+ ions. Especially Ca 2+ The amount of ions is preferably 1000 ppm or less. These ionic components may cause the thermally conductive silicone composition to increase in viscosity over time or cause curing delay in the curable composition, so it is necessary to add the component (D) described below.

[0050] Furthermore, it is preferred that the surface of the spherical magnesium oxide powder of the component (B) be treated with a surface treatment agent of the component (E) described later. This further improves the moisture resistance of the highly thermally conductive silicone composition of the present invention.

[0051] The amount of component (B) is 3300 to 6500 parts by mass, preferably 3400 to 6200 parts by mass, per 100 parts by mass of component (A). If the amount of component (B) exceeds 6500 parts by mass, it may be difficult to properly knead the composition of the present invention. If the amount is less than 3300 parts by mass, it may be difficult to achieve the high thermal conductivity of the present invention.

[0052] [(C) ingredient] The component (C) is an alumina powder and contains the following components (CI) and (C-II).

[0053] (CI) ingredients The (CI) component is a spherical alumina powder having an average sphericity of 0.8 or greater, an average particle size of 7 to 60 μm, and a ratio of coarse particles of 96 to 150 μm in a laser diffraction particle size distribution of 0.1 to 30% by mass of the total (CI) component. Within this range, the powder may be used singly or in combination of two or more types having different average particle sizes.

[0054] The average sphericity of the (CI) component is 0.8 or greater, preferably 0.9 or greater. If the average sphericity is less than 0.8, the fluidity may be reduced, and in some cases, the number of contact points between particles may be significantly increased, resulting in greater irregularities on the sheet surface, increased interfacial thermal resistance, and poorer thermal conductivity.

[0055] The average particle size of the (CI) component is 7 to 60 μm, preferably 9 to 50 μm. When the average particle size is less than 7 μm, it will overlap with the average particle size of the (C-II) component described later, so there will be a tendency for the contact positions between the particles to decrease, the interparticle contact thermal resistance to increase, and the thermal conductivity to deteriorate, and the effect of adding the (CI) component will not be observed. In addition, if the average particle size exceeds 60 μm, there will be a tendency for the contact positions between the particles to increase significantly, the interface thermal resistance to increase, and the thermal conductivity to deteriorate.

[0056] The proportion of coarse particles of 96 to 150 μm in the laser diffraction particle size distribution of the (CI) component is 0.1 to 30% by mass, preferably 0.1 to 20% by mass, of the total (CI) component. If the proportion of coarse particles is too high, the number of contact points between particles may increase significantly, increasing interfacial thermal resistance and deteriorating thermal conductivity. If the proportion is too low, achieving the high thermal conductivity of the present invention may become difficult.

[0057] The amount of component (CI) is preferably 380 to 2700 parts by mass, more preferably 400 to 2500 parts by mass, per 100 parts by mass of component (A). If the amount of component (CI) is 2700 parts by mass or less, the fluidity of the composition is not reduced. If the amount is 380 parts by mass or more, the high thermal conductivity of the present invention is enhanced.

[0058] (C-II) ingredient Component (C-II) is aluminum oxide powder having an average particle size of 0.1 to 4 μm, which may be spherical or irregular in shape. It should be noted that shapes other than spherical are irregular in shape. Within the above range, a single type may be used, or two or more types with different average particle sizes may be used in combination.

[0059] The average particle size of the (C-II) component is 0.1 to 4 μm, preferably 0.5 to 2 μm. If the average particle size is less than 0.1 μm, there is a tendency for the contact positions between the particles to decrease, the contact thermal resistance between the particles to increase, and the thermal conductivity to deteriorate. In addition, if the average particle size exceeds 4 μm, it will overlap with the average particle size of the (CI) component mentioned above, so the effect of adding the (C-II) component cannot be observed. It should be noted that when the (C-II) component is spherical, it is preferably the same as the (B) component with an average sphericity of 0.8 or more.

[0060] The amount of component (C-II) is preferably 380 to 2700 parts by mass, more preferably 400 to 2500 parts by mass, relative to 100 parts by mass of component (A). If the amount of component (C-II) is 2700 parts by mass or less, the fluidity of the composition is not reduced, while if it is 380 parts by mass or more, the fluidity of the present invention is improved.

[0061] The crystalline structure of the alumina powder as component (C) may be either a single crystal or a polycrystalline one, but from the perspective of high thermal conductivity, the crystal phase is preferably an α phase, and the specific gravity is preferably 3.7 or more. If the specific gravity is 3.7 or more, the ratio of pores and low crystalline phases present inside the particles will decrease, so it will be easier to improve the thermal conductivity. The particle size of the alumina powder can be adjusted by classification and mixing operations. Furthermore, as ionic impurities present in component (C), Na + Ions. Especially preferred is Na + The ion content is 100 ppm or less. These ion components may cause the thermally conductive silicone composition to increase in viscosity over time or cause curing delay in the curable composition, so it is necessary to add the component (D) described below.

[0062] Furthermore, it is preferred that the surface of the alumina powder of the component (C) be treated with a surface treatment agent of the component (E) described later. This tends to reduce the viscosity of the highly thermally conductive silicone composition of the present invention.

[0063] The volume ratio of component (CI) to component (C-II), i.e., (CI): (C-II) is 2:8 to 8:2, preferably 4:6 to 6:4. If the volume ratio of component (C-1) is less than 2 / 10, the packing properties of the thermally conductive filler (components (B) and (C), hereinafter the same) tend to be poor. On the other hand, if the volume ratio of component (C-1) is greater than 8 / 10, dense packing of the thermally conductive filler becomes difficult, and the thermal conductivity tends to decrease.

[0064] The volume ratio of component (B) to component (C), i.e., (B): (C), is 5:5 to 9.5:0.5, preferably 5:5 to 9:1. If the volume ratio of component (B) is less than 5 / 10, the thermal conductivity of the silicone composition may be insufficient. On the other hand, if the volume ratio of component (B) exceeds 9.5 / 10, filling with the thermally conductive filler may become difficult.

[0065] The combined amount of components (B) and (C) is 80-90% by volume, preferably 80-85% by volume, of the silicone composition. If the combined amount is less than 80% by volume, the thermal conductivity of the silicone composition may be insufficient. If the combined amount exceeds 90% by volume, the thermally conductive filler may be difficult to incorporate.

[0066] [(D) ingredient] The component (D) is a cation exchange and / or double ion exchange type ion scavenger, and is capable of suppressing the Ca2+ contained in the component (B) in the composition of the present invention. 2+ ions and Mg 2+ ions, Na contained in component (C) + Ions cause the deterioration of components (H), (K), and (L) described below over time. Therefore, anion exchange scavengers are not suitable for the present invention. Here, "cation exchange and / or dual ion exchange ion scavengers" refer to either cation exchange ion scavengers or dual ion exchange ion scavengers, or an ion scavenger composed of both. Component (D) may be either a cation exchange ion scavenger or a dual ion exchange ion scavenger, or a combination of both (including a mixture).

[0067] The component (D) is characterized by supporting at least one element selected from the group consisting of Zr, Bi, Sb, Mg, and Al, preferably an element selected from the group consisting of Zr, Bi, Mg, and Al, and more preferably an element selected from the group consisting of Zr, Mg, and Al.

[0068] The remainder of component (D) is not particularly limited. Preferred carriers include one or more inorganic ion exchangers selected from hydrotalcites and polyvalent metal salts. Among these, hydrotalcites are particularly preferred for improved storage properties of the composition of the present invention.

[0069] The supported amount of the element as component (D), as the total exchange capacity of each ion, is preferably 0.1 to 10 meq / g, and particularly preferably 1 to 8 meq / g. Within this range, the storage characteristics of the composition of the present invention can be further effectively improved. It should be noted that the total exchange capacity of ions refers to the ion exchange capacity in 0.1N hydrochloric acid or 0.1N aqueous sodium hydroxide solution.

[0070] As the component (D), commercially available products such as IXE-100, IXE-600, IXEPLAS-A1, and IXEPLAS-A2 (manufactured by Toagosei Co., Ltd.) can be used.

[0071] The amount of component (D) added is 0.01 to 10 parts by mass, preferably 0.05 to 8 parts by mass, and more preferably 0.1 to 5 parts by mass, relative to 100 parts by mass of component (A). If the amount of component (D) is less than 0.01 parts by mass, the aging degradation of component (H) may not be suppressed. If the amount of component (D) exceeds 10 parts by mass, appropriate curing properties may not be achieved.

[0072] [(E) ingredient] In the present invention, it is preferred that (E) a surface treatment agent is further contained, and that the components (B) and (C) are surface-treated with the surface treatment agent (E). As the surface treatment agent (E), the following (EI) is preferably used.

[0073] (EI) component The component (EI) is an organopolysiloxane represented by the following general formula (1), containing at least one silyl group in one molecule and having a viscosity of 0.01 to 30 Pa·s at 25° C. -SiR 1 a (OR 2 ) 3-a (1) (In general formula (1), R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 are independently alkyl, alkoxyalkyl, alkenyl or acyl, and a is 0, 1 or 2). It should be noted that component (EI) is preferably used in a composition using an organopolysiloxane having a silicon atom-bonded alkenyl group as component (A), and is particularly preferably used in an addition reaction-curable composition using component (AI) as component (A), or an organic peroxide-curable composition using (A-III) an organopolysiloxane having at least one silicon atom-bonded alkenyl group in one molecule as component (A).

[0074] As the component (EI), an organopolysiloxane represented by the following general formula (2) can be mentioned. [Chemical Formula 1] (In general formula (2), R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 are independently alkyl, alkoxyalkyl, alkenyl or acyl, b is an integer from 2 to 100 and a is 0, 1 or 2.

[0075] In the general formulas (1) and (2), R 1 It is independently unsubstituted or substituted and preferably has a monovalent hydrocarbon group with 1 to 10 carbon atoms, more preferably 1 to 6 carbon atoms, and further preferably 1 to 3 carbon atoms. Examples thereof include linear alkyl groups, branched alkyl groups, cyclic alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups. Examples of linear alkyl groups include methyl groups, ethyl groups, propyl groups, hexyl groups, octyl groups, and decyl groups. Examples of branched alkyl groups include isopropyl groups, isobutyl groups, tertiary butyl groups, and 2-ethylhexyl groups. Examples of cyclic alkyl groups include cyclopentyl groups and cyclohexyl groups. Examples of alkenyl groups include vinyl groups and allyl groups. Examples of aryl groups include phenyl groups and tolyl groups. Examples of aralkyl groups include 2-phenylethyl groups and 2-methyl-2-phenylethyl groups. Examples of halogenated alkyl groups include 3,3,3-trifluoropropyl groups, 2-(nonafluorobutyl)ethyl groups, and 2-(heptadecafluorooctyl)ethyl groups. As R 1 , preferably a group without aliphatic unsaturated bonds, more preferably a methyl group or a phenyl group.

[0076] In the general formulas (1) and (2), R 2 are independently alkyl, alkoxyalkyl, alkenyl or acyl. As alkyl, for example, R 1 Examples of the alkyl groups include the straight-chain alkyl groups, branched-chain alkyl groups, and cyclic alkyl groups shown in the examples. Examples of the alkoxyalkyl groups include methoxyethyl groups and methoxypropyl groups. Examples of the alkenyl groups include 1 The same groups as those exemplified in . Examples of the acyl group include acetyl and octanoyl. 2 A group having 1 to 8 carbon atoms is preferred, an alkyl group is more preferred, and a methyl group or an ethyl group is particularly preferred. b is an integer of 2 to 100, preferably 5 to 50. a is 0, 1 or 2, preferably 0.

[0077] Specific examples of suitable organopolysiloxane as the component (EI) include the following. [Chemical Formula 2] (Wherein, Me is a methyl group.)

[0078] The viscosity of the organopolysiloxane (EI) component at 25°C is generally 0.01 to 30 Pa·s, preferably 0.02 to 10 Pa·s. A viscosity of 0.01 Pa·s or greater reduces oil leakage and dripping from the silicone composition. A viscosity of 30 Pa·s or less prevents the resulting silicone composition from exhibiting poor fluidity, thereby minimizing the risk of deteriorating coating workability.

[0079] Surface treatment methods for components (B) and (C) using component (EI) include: spraying using a fluid nozzle; stirring with shear force; dry methods using a ball mill, a blender, or the like; and wet methods using aqueous or organic solvents. Stirring should be performed to a degree that does not damage the spherical magnesium oxide and aluminum oxide powders. The system temperature during the dry method and the post-treatment drying temperature should be appropriately determined based on the type of surface treatment agent, within a range where the surface treatment agent does not volatilize or decompose, and are preferably between 80 and 180°C.

[0080] When the (EI) component is added, the amount thereof is preferably 5 to 900 parts by mass, more preferably 50 to 700 parts by mass, and even more preferably 100 to 500 parts by mass, relative to 100 parts by mass of the (A) component. When the (EI) component is 5 parts by mass or more, the viscosity is reduced, allowing for good kneading. When the (EI) component is 900 parts by mass or less, the amount of (EI) that leaks out of the composition is also reduced.

[0081] (E-II)Ingredient As component (E), component (E-II) may further be used. Component (E-II) is a silane coupling agent. Examples of the silane coupling agent include vinyl silane coupling agents, epoxy silane coupling agents, acrylic silane coupling agents, and long-chain alkyl silane coupling agents having 6 or more carbon chains. These silane coupling agents may be used alone or in combination of two or more. In particular, long-chain alkyl silane coupling agents are preferred, and decyltrimethoxysilane is even more preferred.

[0082] Surface treatment methods for components (B) and (C) using component (E-II) include: spraying using a fluid nozzle; stirring with shear force; dry methods using a ball mill, a blender, or the like; and wet methods using aqueous or organic solvents. Stirring should be performed to a degree that does not damage the spherical magnesium oxide powder and aluminum oxide powder. The system temperature during the dry method and the post-treatment drying temperature can be appropriately determined based on the type of surface treatment agent, within a range where the surface treatment agent does not volatilize or decompose, and are preferably between 80 and 180°C.

[0083] When the component (E-II) is formulated, the amount used is preferably 0.1 to 5 parts by mass relative to 100 parts by mass of the total of the components (B) and (C). A sufficient effect is achieved when the amount is 0.1 parts by mass or more, while an effect corresponding to the amount used is achieved when the amount is 5 parts by mass or less.

[0084] [(F)INGREDIENT] The high thermal conductivity silicone composition of the present invention may further be formulated with (F) a center particle size (median particle size D 50 ) has a maximum value of 160 μm or more and spherical glass beads or amorphous glass having a SiO2 content of 50% by mass or more. By adding component (F), a high thermal conductive silicone composition can be formed into an appropriate thickness even in a very small amount.

[0085] The maximum value of the center particle diameter of the component (F) is 160 μm or greater, preferably 160 to 300 μm, and is characterized by being larger than the average particle diameter of the component (B). When the maximum value of the center particle diameter is 160 μm or greater, the desired thickness can be well ensured. It should be noted that the center particle diameter can be measured by laser diffraction using a "Laser Diffraction Particle Size Distribution Analyzer SALD-2300" manufactured by Shimadzu Corporation.

[0086] The SiO2 content of component (F) is preferably 50% by mass or more, more preferably 50 to 99.99% by mass. If the SiO2 content is 50% by mass or more, the desired thickness cannot be ensured due to brittleness. It should be noted that the SiO2 content can be measured by ICP emission spectrometry.

[0087] Examples of the material of component (F) include soda-lime glass, soda-lime silica glass, and borosilicate glass. From the perspective of uniformity of cured thickness, component (F) is preferably spherical rather than irregular. When component (F) is spherical glass beads, it is preferred that the average sphericity be 0.8 or greater, similar to that of components (B) and (C).

[0088] When the component (F) is formulated, it is preferably added in a small amount within the above-mentioned range. Specifically, in order not to significantly reduce the thermal conductivity of the highly thermally conductive silicone composition, it is preferably added in an amount of 0.01 to 10% by mass, more preferably 0.01 to 5% by mass, based on the total amount of the silicone composition.

[0089] The high thermal conductive silicone composition of the present invention may maintain its composition or further be formulated with a curing agent to form a curable composition. When forming a curable high thermal conductivity silicone composition, the following three forms can be listed. They can be prepared by using the organopolysiloxanes of the above-mentioned components (AI) to (A-III) as the base polymer, i.e., the organopolysiloxane component (A), and mixing them with the above-mentioned spherical magnesium oxide powder (B) and aluminum oxide powder (C).

[0090] [i] Addition reaction curing type high thermal conductivity silicone composition [ii] Condensation reaction curing type high thermal conductivity silicone composition [iii] Organic peroxide-curable high thermal conductivity silicone composition In particular, [i] addition reaction curing type high thermal conductivity silicone composition is preferred because it cures quickly without generating by-products. Each composition is specifically described below.

[0091] [i] Addition reaction curing type high thermal conductivity silicone composition When the silicone composition is an addition reaction curable high thermal conductivity silicone composition that cures by hydrosilylation, the above-described component (AI) is used as the above-described component (A), and the following components are further included, and the curing agent is the following components (G) and (H). (G) an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms; (H) a platinum group metal curing catalyst; As needed, (I) Addition reaction control agent.

[0092] [(G) ingredient] (G) The organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to silicon atoms is a component that functions as a crosslinking agent.

[0093] Examples of groups other than hydrogen atoms bonded to silicon atoms of the organohydrogenpolysiloxane include the same linear alkyl groups, branched alkyl groups, cyclic alkyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as those for the component (A). Alkyl groups and aryl groups are preferred, and methyl groups and phenyl groups are particularly preferred.

[0094] The viscosity of the component (G) at 25° C. is not particularly limited, but is preferably in the range of 1 to 100,000 mPa·s, more preferably in the range of 5 to 5,000 mPa·s.

[0095] The molecular structure of component (G) is not limited, and examples thereof include linear, branched, partially branched linear, cyclic, and dendritic (dendritic polymers). Furthermore, component (G) contains at least two, and preferably 2 to 50, hydrogen atoms directly bonded to silicon atoms in the molecule. These hydrogen atoms may be located at the ends of the molecular chain, within the molecular chain, or both. Examples of such organopolysiloxanes include homopolymers having these molecular structures, copolymers having these molecular structures, and mixtures thereof.

[0096] As the component (G), for example, dimethylpolysiloxane having dimethylhydrogensiloxy groups blocking the molecular chain ends; dimethylsiloxane-methylhydrogensiloxane copolymer having trimethylsiloxy groups blocking the molecular chain ends; dimethylsiloxane-methylhydrogensiloxane copolymer having dimethylhydrogensiloxy groups blocking the molecular chain ends; 1 / 2 Siloxane units represented by the formula (CH3)2HSiO 1 / 2 The siloxane unit represented by the formula SiO 4 / 2 The organosiloxane copolymer composed of the siloxane units represented by can be used alone or in combination of two or more. The organohydrogenpolysiloxane of the component (G) is different from the organopolysiloxane component (AI) having a silicon atom-bonded alkenyl group, and is also different from the component (A-II) in that it does not contain a hydrolyzable group.

[0097] The amount of component (G) is the amount required for curing of the silicone composition. Specifically, the amount of silicon-bonded hydrogen atoms in component (G) is preferably in the range of 0.1 to 10 moles per 1 mole of silicon-bonded alkenyl groups in component (AI), more preferably in the range of 0.1 to 5 moles, and particularly preferably in the range of 0.1 to 3 moles. This is because if the content of this component is at least the lower limit of the above range, the resulting silicone composition will cure sufficiently. On the other hand, if it is at or below the upper limit of the above range, the resulting cured silicone product will not become extremely hard, thereby preventing the formation of numerous cracks on the surface.

[0098] [(H) ingredient] (H) Platinum group metal curing catalysts are catalysts for accelerating the curing of the silicone composition, and examples thereof include chloroplatinic acid, alcohol solutions of chloroplatinic acid, platinum olefin complexes, platinum alkenylsiloxane complexes, and platinum carbonyl complexes.

[0099] The amount of component (H) to be added is the amount required for curing the silicone composition. Specifically, the amount of platinum group metal in component (H) is preferably within the range of 0.01 to 1000 ppm by mass relative to component (AI), and particularly preferably within the range of 0.1 to 500 ppm. This is because when the amount of component (H) is at least the lower limit of the above range, the resulting silicone composition can be sufficiently cured. On the other hand, when the amount is below the upper limit of the above range, waste is avoided and the curing speed of the resulting silicone composition is significantly improved.

[0100] [(I)INGREDIENTS] (I) Addition reaction control agents (curing reaction control agents) can be formulated to adjust the curing rate of the silicone composition and improve workability. Examples of curing reaction inhibitors include acetylene compounds such as 2-methyl-3-butyn-2-ol, 2-phenyl-3-butyn-2-ol, and 1-ethynyl-1-cyclohexanol; enyne compounds such as 3-methyl-3-pentene-1-yne and 3,5-dimethyl-3-hexene-1-yne; and other hydrazine compounds, phosphine compounds, and thiol compounds. These can be used alone or in combination of two or more.

[0101] The amount of component (I) added is not particularly limited, but is preferably 0.0001 to 1% by mass in the silicone composition. Within this range, the workability and curing speed of the silicone composition become more appropriate.

[0102] [ii] Condensation reaction curing type high thermal conductivity silicone composition When the silicone composition is a condensation reaction curable high thermal conductivity silicone composition, the above-described component (A-II) is used as the component (A) and further contains the following components, and the curing agent is the following component (J). (J) Silane having at least three silicon-bonded hydrolyzable groups in one molecule or a partial hydrolyzate thereof As needed, (K) Catalyst for condensation reaction

[0103] [(J) ingredient] (J) A silane having at least three silicon-bonded hydrolyzable groups per molecule, or a partial hydrolyzate thereof, serves as a curing agent. Examples of the silicon-bonded hydrolyzable groups in this silane include the same alkoxy, dialkoxy, acyloxy, ketoxime, alkenyloxy, amine, aminooxy, and amide groups as described above. Furthermore, in addition to the aforementioned hydrolyzable groups, the silicon atoms of this silane may also be bonded with, for example, linear alkyl groups, branched alkyl groups, cyclic alkyl groups, alkenyl groups, aryl groups, aralkyl groups, and halogenated alkyl groups as described in component (A). Examples of such silanes or partial hydrolyzates thereof include methyltriethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, and ethyl orthosilicate.

[0104] The amount of component (J) is the amount required to cure the silicone composition. Specifically, it is preferably in the range of 0.01 to 20 parts by mass, and particularly preferably 0.1 to 10 parts by mass, relative to 100 parts by mass of component (A-II). If the content of the silane or its partial hydrolyzate is at least the lower limit of the above range, the resulting silicone composition will not have a risk of reduced storage stability. On the other hand, if the content is at most the upper limit of the above range, the curing of the resulting silicone composition will not be slowed.

[0105] [(K) ingredient] (K) The condensation reaction catalyst is an optional component. For example, it is not essential to use a silane having a hydrolyzable group such as an amino group, an amine group, or a ketoxime group as a curing agent. Examples of such condensation reaction catalysts include organic titanates such as tetrabutyl titanate and tetraisopropyl titanate; organic titanium chelates such as diisopropoxybis(acetoacetate)titanium and diisopropoxybis(ethyl acetoacetate)titanium; organic aluminum compounds such as tri(acetylacetonate)aluminum and tri(ethyl acetoacetate)aluminum; organic zirconium compounds such as tetra(acetylacetonate)zirconium and zirconium tetrabutyrate; organic tin compounds such as dibutyltin dioctoate, dibutyltin dilaurate, and butyltin 2-ethylhexanoate; metal salts of organic carboxylic acids such as tin naphthenate, tin oleate, tin butyrate, cobalt naphthenate, and zinc stearate; amine compounds such as hexylamine and dodecylamine phosphate, and their salts; quaternary ammonium salts such as benzyltriethylammonium acetate; lower fatty acid salts of alkali metals such as potassium acetate and lithium nitrate; dialkylhydroxylamines such as dimethylhydroxylamine and diethylhydroxylamine; and guanidine-containing organic silicon compounds.

[0106] When component (K) is added, the amount required to cure the silicone composition may be sufficient. Specifically, it is preferably in the range of 0.01 to 20 parts by mass, and particularly preferably in the range of 0.1 to 10 parts by mass, relative to 100 parts by mass of component (A). This is because, when component (K) is used, if the catalyst content is at least the lower limit of the above range, the resulting silicone composition will readily and sufficiently cure. On the other hand, if the catalyst content is at or below the upper limit of the above range, the storage stability of the resulting silicone composition will be less likely to deteriorate.

[0107] [iii] Organic peroxide-curable high thermal conductivity silicone composition When the silicone composition is an organic peroxide-curable high thermal conductivity silicone composition, the above-described component (A-III) is used as the component (A) and the following components are further included, and the curing agent is the following component (L). (L) Organic peroxide

[0108] [(L) ingredient] (L) As an organic peroxide, benzoyl peroxide, dicumyl peroxide, 2,5-dimethylbis(2,5-tert-butylperoxy)hexane, di(tert-butyl peroxide), and tert-butyl perbenzoate are mentioned, for example.

[0109] The amount of component (L) is the amount required to cure the silicone composition. Specifically, it is preferably in the range of 0.1 to 5 parts by mass per 100 parts by mass of the organopolysiloxane in component (A-III). If the amount of component (L) is at least the lower limit of this range, the resulting silicone composition will cure sufficiently. On the other hand, even if the amount exceeds the upper limit of this range, the curing speed of the resulting silicone composition will not be significantly improved, and there is a risk of voids forming.

[0110] Furthermore, the organosilicon composition of the present invention may contain other optional ingredients such as fillers such as fumed silica, precipitated silica, and fumed titanium oxide; fillers whose surfaces have been hydrophobized using an organosilicon compound; tackifiers such as 3-glycidoxypropyltrimethoxysilane and 3-methacryloxypropyltrimethoxysilane; and pigments, dyes, fluorescent dyes, heat-resistant additives, flame retardants such as triazole compounds, and plasticizers. It should be noted that thermally conductive fillers other than components (B) and (C) may be incorporated into the composition. Examples include aluminum powder, copper powder, silver powder, nickel powder, gold powder, zinc oxide powder, boron nitride powder, aluminum nitride powder, diamond powder, and carbon powder.

[0111] The silicone composition of the present invention can be prepared by uniformly mixing the specific amounts of the above-mentioned components. For example, in the case of a single-liquid composition, it can be produced by the following methods: a method of mixing components (A), (B), (C), and (D) to obtain a mixture (production method 1); a method of mixing components (A), (B), (C), and (D) to obtain a mixture and then mixing component (E) into the mixture (production method 2); or a method of mixing components (A), (B), (C), (D), and (E) simultaneously (production method 3). Mixing can be performed using a known method. In addition, when treating the surfaces of components (B) and (C) with components (A) and (E), a heat treatment at 150°C, for example, can be performed to promote the treatment. The method for adding component (F) is not particularly limited. It is preferred that component (F) be added and mixed after components (A), (B), (C), (D), and (E) are added and mixed. A known method can be used for mixing. Furthermore, the step of mixing any of the components may be included.

[0112] [High thermal conductivity silicone composition] The thermal conductivity of the high thermal conductivity silicone composition is 7.0 W / m·K or higher, more preferably 8.0 W / m·K or higher, as measured by the hot plate method according to ISO 22007-2. The upper limit is not particularly limited; the higher the better, but can be 12.0 W / m·K or lower. A thermal conductivity less than 7.0 W / m·K will not produce the high thermal conductivity silicone composition desired by the present invention. The measurement temperature is 25°C. It should be noted that in order to achieve a thermal conductivity of 7.0 W / m·K or higher in the highly thermally conductive silicone composition of the present invention, the aforementioned components (A) to (C) are used in specific blending ratios, particularly by setting the volume ratio of component (B) to component (C) to 5:5 to 9.5:0.5, and by setting the total amount of components (B) and (C) to 80 to 90% by volume of the composition. This thermal conductivity can be achieved.

[0113] The high thermal conductive silicone composition should have a viscosity of 30 to 800 Pa·s, more preferably 50 to 600 Pa·s, at 25°C, when measured using a spiral viscometer at a rotation speed of 10 rpm. If the viscosity is too low, the composition may not maintain a specific shape, while if the viscosity is too high, the composition may be difficult to apply. It should be noted that in order to set the viscosity of the highly thermally conductive silicone composition of the present invention within the above-mentioned range, the viscosity of the highly thermally conductive silicone composition at 25°C can be set within the above-mentioned range by using the aforementioned components (A) to (C) in a specific blending ratio and further adjusting the blending amount and viscosity of component (A).

[0114] [cured material] When the silicone composition is curable, the method for curing it is not limited. Examples include: leaving the formed silicone composition at room temperature or heating the formed silicone composition to 40-200°C. Furthermore, the properties of the silicone adhesive (silicone elastomer molded product) obtained in this manner are not limited. Examples include: a gel-like, low-hardness rubber-like, or high-hardness rubber-like. It should be noted that, considering the exothermic properties of the silicone composition of the present invention, the cured thickness of the silicone adhesive obtained is preferably 100 μm to 2 mm. [Example]

[0115] The present invention will be described in detail below with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples. In the following formulae, Me represents a methyl group. The components used in Examples and Comparative Examples are as follows.

[0116] (A)Ingredients A-1: dimethyl polysiloxane having a viscosity of 400 mPa·s at 25°C, a specific gravity (25°C) of 0.98, end-capped with dimethylvinylsiloxy groups at both ends, and a vinyl (Vi) group content of 0.018 mol / 100 g (one molecule having an average of 2.0 silicon-bonded alkenyl groups) [component (AI)] A-2: a dimethylsiloxane-diphenylsiloxane copolymer with trimethylsiloxy groups capped at both ends of the molecular chain, KF-54 manufactured by Shin-Etsu Chemical Co., Ltd., with a specific gravity (25°C) of 1.07 and a dynamic viscosity (25°C) of 400 mm 2 / s A-3: dimethylsiloxane-diphenylsiloxane copolymer with trimethylsiloxy groups at both ends of the molecular chain, KF-50-1000cs manufactured by Shin-Etsu Chemical Co., Ltd., with a specific gravity (25°C) of 1.00 and a dynamic viscosity (25°C) of 1000 mm 2 / s The dynamic viscosities are all values ​​measured at 25°C using an Ostwald viscometer.

[0117] (B) Ingredients Spherical magnesium oxide having the properties shown in Table 1 below

Table 1

[0118] (C) Ingredients Spherical or irregular-shaped alumina having the properties shown in Table 2 below [Table 2] Table 2 *1: Ratio of coarse particles in the laser diffraction particle size distribution range of 96 to 150 μm

[0119] (D) Ingredients D-1: Dual ion exchange type ion scavenger IXEPLAS-A1 (manufactured by Toagosei Co., Ltd.), with a bulk density of 0.25 (25°C) and loaded with Zr, Mg, and Al elements D-2 (for comparison): an anion exchange type ion scavenger IXE500 (manufactured by Toagosei Co., Ltd.), having a bulk density of 0.73 (25°C) and loaded with Bi element

[0120] (E) Ingredients E-1: a methyl polysiloxane terminated at one end with trimethoxysilyl group, represented by the following formula, having a specific gravity (25°C) of 0.97 and a viscosity at 25°C of 30 mPa·s [Chemical Formula 3]

[0121] (F)Ingredients F-1: spherical glass beads (material: soda-lime glass), with a specific gravity (25°C) of 2.5, MIL particle size series M-9 manufactured by Potters-Ballotini Co., Ltd. (maximum center particle diameter of 180 μm), and a SiO2 content of 99.4% by mass

[0122] (G) Ingredients G-1: methyl hydrogen polysiloxane represented by the following formula, having a specific gravity (25° C.) of 0.97 and a viscosity at 25° C. of 28 mPa·s [Chemical Formula 4] G-2: methyl hydrogen polysiloxane represented by the following formula, having a specific gravity (25°C) of 0.97 and a viscosity at 25°C of 17 mPa·s [Chemical Formula 5]

[0123] (H) ingredient H-1: chloroplatinic acid-1,3-divinyltetramethyldisiloxane complex, with a specific gravity (25°C) of 1.00 and a platinum concentration of 1% by mass

[0124] (I)Ingredients I-1: 50% by mass toluene solution of 1-ethynyl-1-cyclohexanol, with a specific gravity (25°C) of 0.92

[0125] [Examples 1 to 7, Comparative Examples 1 to 8] The above components were used in the amounts shown in Tables 3 and 4, and silicone compositions were prepared using the method described below. Thermally conductive molded articles were obtained using these silicone compositions. These molded articles were evaluated for initial viscosity, hardness after curing, and thermal conductivity using the methods described below. The results are reported in Tables 3 and 4.

[0126] [Method for preparing silicone composition] The above-mentioned components (A) to (I) were used in the amounts shown in Tables 3 and 4 and mixed as follows to obtain the compositions of Examples 1 to 7 and Comparative Examples 1 to 8. Specifically, components (A), (B), (C), and (E) were added in the amounts shown in Tables 3 and 4 in a 5-liter gate mixer (manufactured by Inoue Seisakusho Co., Ltd., trade name: 5-liter planetary mixer), degassed at 150°C, and heated for 2 hours. The mixture was then cooled to room temperature (25°C), and components (D) and (H) were added. The mixture was mixed at room temperature (25°C) until uniform. Component (I) was then added and mixed at room temperature (25°C) until uniform. Component (G) was then added, and the mixture was degassed and mixed at room temperature (25°C) until uniform. Component (F) was added as needed, and the mixture was degassed and mixed at room temperature (25°C) until uniform. The compositions thus obtained were evaluated for initial viscosity, hardness after curing, and thermal conductivity by the following methods. The results are reported in Tables 3 and 4.

[0127] [Initial viscosity evaluation] The initial viscosity of the silicone composition is a value at 25° C., and this measurement was performed using a rotational viscometer: Malcom viscometer (PC-10AA model, rotation speed 10 rpm).

[0128] [Hardness evaluation after curing] The silicone composition was poured into a mold having a cured thickness of 6 mm and cured at 100° C. for 1 hour. Two cured products having a thickness of 6 mm were then stacked and the hardness was measured using an Asker C durometer.

[0129] [Thermal conductivity evaluation] The thermal conductivity of the silicone composition before curing at 25° C. was measured using a hot plate method thermophysical property measuring apparatus TPS2500S manufactured by Kyoto Electronics Co., Ltd. (hot plate method in accordance with ISO 22007-2).

[0130] [Preservation evaluation] When the viscosity, thermal conductivity, and hardness of each Example and Comparative Example were observed after storage at 5°C for 6 months, although no significant change in thermal conductivity was observed in Comparative Examples 3 and 4 compared to the initial value, the viscosity was significantly higher than the initial viscosity, and the hardness was significantly lower by more than 10 points compared to the initial value, indicating that delayed curing was observed.

[0131] As shown in Tables 3 and 4, in each embodiment of the present invention, the viscosity, thermal conductivity, hardness, and their storage stability after storage at 5° C. for 6 months all showed good results. On the other hand, in Comparative Example 1, the average particle size of component (B-3) is small, and thus the thermal conductivity is low. In Comparative Example 2, the average sphericity of component (B-4) is low, and thus the thermal conductivity is low. In Comparative Example 3, component (D-2) is anion exchange type, and thus the viscosity after storage at 5°C for 6 months is significantly higher than the initial viscosity, and the hardness after storage at 5°C for 6 months is significantly lower than the initial hardness. In Comparative Example 4, component (D) is not formulated, and thus the viscosity after storage at 5°C for 6 months is significantly higher than the initial viscosity, and the hardness after storage at 5°C for 6 months is significantly lower than the initial hardness. In Comparative Example 5, the average particle sizes of components (C-3) and (C-4) are both small, and mixing is impossible, and thus the viscosity, thermal conductivity, and hardness cannot be measured. In Comparative Example 6, the volume ratio of component (B) to component (C), ((B):(C), was 9.6:0.4. The B ratio was too high, making mixing impossible, and thus, the viscosity, thermal conductivity, and hardness measurements were impossible. In Comparative Example 7, the volume ratio of component (CI) to component (C-II), ((CI):(C-II), was 1.8:8.2. The (CI) ratio was too low, making mixing impossible, and thus, the viscosity, thermal conductivity, and hardness measurements were impossible. In Comparative Example 8, the volume ratio of component (CI) to component (C-II), ((CI):(C-II)), was 8.2:1.8. The (CI) ratio was too high, resulting in low thermal conductivity.

[0132]

Table 3

[0133]

Table 4

[0134] This manual contains the following methods. [1] A high thermal conductivity silicone composition comprising: (A) organopolysiloxane; (B) spherical magnesium oxide powder having an average sphericity of 0.8 or greater, an average particle size of 80 to 150 μm, and a purity of 98% by mass or greater; (C) A thermally conductive filler comprising (CI) and (C-II), wherein the volume ratio of the following components (CI) and (C-II) ((CI):(C-II)) is 2:8 to 8:2, (CI) spherical alumina powder having an average sphericity of 0.8 or more, an average particle size of 7 to 60 μm, and a ratio of coarse particles of 96 to 150 μm in the laser diffraction particle size distribution of 0.1 to 30% by mass of the total (CI) component. (C-II) spherical or irregularly shaped alumina powder having an average particle size of 0.1 to 4 μm; and (D) an ion scavenger, which is a cation exchange and / or dual ion exchange type ion scavenger and carries at least one element selected from Zr, Bi, Sb, Mg, and Al; in the high thermal conductivity silicone composition, The amount of the component (B) is 3300 to 6500 parts by mass relative to 100 parts by mass of the component (A). The amount of the component (D) is 0.01 to 10 parts by mass relative to 100 parts by mass of the component (A). The mixing ratio of the above-mentioned components (B) and (C), i.e., the volume ratio ((B): (C)) is 5:5 to 9.5:0.5, and the total amount of the components (B) and (C) accounts for 80 to 90% by volume of the composition. The thermal conductivity of the composition is 7.0 W / m·K or higher by the hot disk method according to ISO 22007-2, and the viscosity of the composition at 25° C. is 30 to 800 Pa·s when measured with a spiral viscometer at a rotation speed of 10 rpm. [2] The highly thermally conductive silicone composition according to [1] above, wherein the composition contains 1 to 6% by mass of the component (A). [3] The high thermal conductivity silicone composition according to [1] or [2] above, wherein the high thermal conductivity silicone composition is any of the following: an addition reaction curing type using (A-I) an organopolysiloxane having an average of 0.1 or more silicon atom-bonded alkenyl groups in one molecule as component (A); a condensation reaction curing type using (A-II) an organopolysiloxane having at least two silanol groups or silicon atom-bonded hydrolyzable groups in one molecule as component (A); or an organic peroxide curing type using (A-III) an organopolysiloxane having at least one silicon atom-bonded alkenyl group in one molecule as component (A). [4] The highly thermally conductive silicone composition according to any one of [1] to [3] above, further comprising (E) a surface treatment agent. [5] The high thermal conductivity silicone composition according to [4] above, wherein (A) an organopolysiloxane having an average of 0.1 or more silicon-bonded alkenyl groups per molecule (AI) or (A-III) an organopolysiloxane having at least one silicon-bonded alkenyl group per molecule is used as component (A); The following organopolysiloxane is contained as the component (E) in an amount of 5 to 900 parts by mass per 100 parts by mass of the component (AI) or (A-III), wherein the organopolysiloxane is represented by the following general formula (1), contains at least one silyl group in one molecule, and has a viscosity of 0.01 to 30 Pa·s at 25° C. -SiR 1 a (OR 2 ) 3-a (1) (In general formula (1), R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 are independently alkyl, alkoxyalkyl, alkenyl or acyl, and a is 0, 1 or 2). [6] The high thermal conductivity silicone composition according to any one of [1] to [5] above, further comprising (F) spherical glass beads or amorphous glass having a maximum center particle diameter of 160 μm or greater and a SiO2 content of 50% by mass or greater, which accounts for 0.01 to 10% by mass of the total amount of the composition. [7] A cured product of a highly thermally conductive silicone composition, wherein the highly thermally conductive silicone composition is the highly thermally conductive silicone composition according to any one of [1] to [6].

[0135] It should be noted that the present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are exemplary, and any embodiments having substantially the same structure as the technical concept described in the scope of the present invention and having the same effects are included in the technical scope of the present invention.

Claims

1. A high thermal conductivity silicone composition, characterized in that: Include: (A) organopolysiloxane; (B) spherical magnesium oxide powder having an average sphericity of 0.8 or greater, an average particle size of 80 to 150 μm, and a purity of 98% by mass or greater; (C) A thermally conductive filler comprising (CI) and (C-II), wherein the volume ratio of the following components (CI) and (C-II) ((CI):(C-II)) is 2:8 to 8:2, (CI) spherical alumina powder having an average sphericity of 0.8 or more, an average particle size of 7 to 60 μm, and a ratio of coarse particles of 96 to 150 μm in the laser diffraction particle size distribution of 0.1 to 30% by mass of the total (CI) component. (C-II) spherical or irregularly shaped alumina powder having an average particle size of 0.1 to 4 μm; and (D) an ion scavenger, which is either a cation exchange type ion scavenger or a double ion exchange type ion scavenger, or an ion scavenger composed of these two ion scavengers, and which supports one or more elements selected from Zr, Bi, Sb, Mg, and Al; In the high thermal conductivity silicone composition, The amount of the component (B) is 3300 to 6500 parts by mass relative to 100 parts by mass of the component (A). The amount of the component (D) is 0.01 to 10 parts by mass relative to 100 parts by mass of the component (A). The volume ratio of the components (B) and (C), i.e., (B): (C), is 5:5 to 9.5:0.5, and the total amount of the components (B) and (C) accounts for 80 to 90% by volume of the composition. The thermal conductivity of the composition is 7.0 W / m·K or higher according to the hot disk method in accordance with ISO 22007-2, and the viscosity of the composition at 25° C., when measured using a spiral viscometer at a rotation speed of 10 rpm, is 30 to 800 Pa·s.

2. The high thermal conductivity silicone composition according to claim 1, characterized in that The composition contains 1 to 6% by mass of the component (A).

3. The high thermal conductivity silicone composition according to claim 1, characterized in that The high thermal conductivity silicone composition is any one of the following: An addition reaction curing type using (AI) an organopolysiloxane having an average of 0.1 or more silicon atom-bonded alkenyl groups per molecule as the (A) component; A condensation reaction curing type using (A-II) an organopolysiloxane having two or more silanol groups or silicon atom-bonded hydrolyzable groups in one molecule as component (A); or As the organic peroxide-curable component (A), an organopolysiloxane (A-III) having one or more silicon-bonded alkenyl groups in one molecule was used.

4. The high thermal conductivity silicone composition according to claim 1, wherein (E) a surface treatment agent is further included.

5. The high thermal conductivity silicone composition according to claim 4, characterized in that (A) As the component (A), an organopolysiloxane having an average of 0.1 or more silicon-bonded alkenyl groups in one molecule (AI) or an organopolysiloxane having 1 or more silicon-bonded alkenyl groups in one molecule (A-III) is used, and The following organopolysiloxane is contained as the component (E) in an amount of 5 to 900 parts by mass per 100 parts by mass of the component (AI) or (A-III), wherein the organopolysiloxane is represented by the following general formula (1), contains one or more silyl groups in one molecule, and has a viscosity of 0.01 to 30 Pa·s at 25° C. -SiR 1 a (OR 2 ) 3-a (1) In the general formula (1), R 1 are independently unsubstituted or substituted monovalent hydrocarbon groups, R 2 are independently alkyl, alkoxyalkyl, alkenyl or acyl, and a is 0, 1 or 2.

6. The high thermal conductivity silicone composition according to claim 1, characterized in that The composition further comprises (F) spherical glass beads or amorphous glass having a maximum center particle diameter of 160 μm or more and a SiO 2 content of 50% by mass or more, which accounts for 0.01 to 10% by mass of the total amount of the composition.

7. A cured product of a high thermal conductivity silicone composition, characterized in that: The high thermal conductivity silicone composition is the high thermal conductivity silicone composition according to any one of claims 1 to 6.

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