Thermally conductive two-component addition curing type silicone composition, cured product, and sheet

Abstract

The present invention is a thermally conductive two-component addition curing type silicone composition comprising a first liquid and a second liquid, the composition comprising (A) an organopolysiloxane having an alkenyl group, (B) an organohydrogenpolysiloxane, (C) a thermally conductive filler including spherical aluminum oxide powder (C-1)-(C-4) having a specific average particle diameter and spherical or irregular-shaped aluminum oxide powder (C-5) having a specific average particle diameter, (D) a silane coupling agent and / or an organopolysiloxane represented by general formula (1), and (E) a platinum catalyst, wherein the first liquid does not contain the component (B), the second liquid does not contain the component (E), and the components (A) to (E) are included at a specific ratio in the entire composition. As a result, the present invention provides: a high thermal conductive two-component addition curing type silicone composition having high thermal conductivity and high moisture resistance; and a cured product thereof.

Description

Thermally conductive two-component addition-curable silicone composition, cured product, and sheet

[0001] The present invention relates to a thermally conductive two-component addition-curable silicone composition, a cured product, and a sheet.

[0002] It is widely known that heat-generating electronic components generate heat during use, resulting in a decrease in performance. Various heat dissipation technologies are used to address this issue. Generally, heat is dissipated by placing a cooling component (such as a heat sink) near the heat-generating component, placing them in close contact, and efficiently removing heat from the cooling component. In this case, if there is a gap between the heat-generating component and the cooling component, air with poor thermal conductivity is trapped, reducing thermal conductivity and preventing the temperature of the heat-generating component from dropping sufficiently. To prevent this phenomenon, heat-dissipating materials with good thermal conductivity and conformability to the surface of the component, such as thermal grease and thermal dissipation sheets, are used.

[0003] In recent years, the amount of heat generated by mounted components has been increasing due to the miniaturization and increased density of electronic devices. For example, the amount of heat generated by CPUs (central processing units) and GPUs (graphics processing units) has increased as their performance has improved. In order to keep operating temperatures low and maintain high performance, heat dissipation materials used as heat countermeasures must have high heat dissipation performance.

[0004] Furthermore, because the GPUs used in ADAS (Advanced Autonomous Driving Assistance Systems) are used in vehicles, the heat dissipation materials used to control the heat of the GPUs must be insulating and highly reliable. Examples of thermally conductive fillers used in heat dissipation materials include aluminum oxide, aluminum nitride, and magnesium oxide, which are insulating and highly thermally conductive. However, while aluminum nitride and magnesium oxide have higher thermal conductivity than aluminum oxide, they are highly hygroscopic and have the problem of becoming strongly alkaline after absorbing moisture.

[0005] Examples of thermally conductive resin compositions using aluminum oxide as a thermally conductive filler include a highly thermally conductive resin composition using spherical aluminum oxide powder with an average particle size of 10 to 50 μm and specified average sphericity and hydroxyl group content, and aluminum oxide powder with an average particle size of 0.3 to 1 μm, with the respective volumetric blending ratios and fill amounts specified; however, sufficient thermal conductivity could not be obtained with a filler with a maximum average particle size of 50 μm (Patent Document 1: Japanese Patent No. 5755977).

[0006] Further, examples include compound particles for high thermal conductive resin compounds containing 60 to 80 volume % of spherical alumina particles having an average particle size of 80 to 100 μm and 20 to 40 volume % of non-spherical alumina particles having an average particle size of 0.5 to 7 μm, and high thermal conductive resin compounds containing 60 to 85 volume % of the same by volume. However, when a large amount of alumina particles having a large average particle size is contained, there are problems in that oil separation occurs over time and viscosity increases (Patent Document 2: Japanese Patent No. 5085050).

[0007] Also exemplified is a highly thermally conductive silicone composition that contains a total of 80 to 90 volume % of spherical aluminum oxide particles having an average particle size of 50 to 150 μm and spherical or irregularly shaped aluminum oxide particles having an average particle size of 0.5 to 7 μm, with a volume ratio of the spherical aluminum oxide particles having an average particle size of 50 to 150 μm to the spherical or irregularly shaped aluminum oxide particles having an average particle size of 0.5 to 7 μm of 5:5 to 9.5:0.5. However, this composition contains a large amount of a silane coupling agent for organopolysiloxane, and has the problem of a significant increase in hardness and a significant decrease in elongation under high temperature and high humidity conditions (Patent Document 3: Japanese Patent No. 6648837).

[0008] Patent No. 5755977 Patent No. 5085050 Patent No. 6648837

[0009] Increasing the proportion of thermally conductive filler in a thermally conductive composition is considered to achieve high thermal conductivity, but increasing the proportion of thermally conductive filler increases viscosity and makes the composition less easy to handle. Furthermore, increasing the proportion of thermally conductive filler requires increasing the proportion of a silane coupling agent or an organopolysiloxane having an alkoxy group at one end, which treats the surface of the thermally conductive filler. These silane coupling agents and organopolysiloxanes are thought to condense under moisture-resistant conditions, and containing large amounts of them in a thermally conductive composition increases the hardness of the cured product of the thermally conductive composition under moisture-resistant conditions. The cured product of a thermally conductive composition with increased hardness has reduced elongation and is unable to conform to warping of the substrate, reducing its reliability as a heat-dissipating material.

[0010] Furthermore, unlike one-component addition-curing heat-dissipating materials, two-component addition-curing materials are characterized by their room-temperature storage properties. Therefore, because dehydrogenation of the organohydrogenpolysiloxane due to the thermally conductive filler can occur during storage at room temperature, it is necessary to suppress dehydrogenation by surface-treating the thermally conductive filler. Therefore, it is necessary to use an appropriate amount of silane coupling agent or organopolysiloxane having an alkoxy group at one end in order to improve the room-temperature storage stability of two-component addition-curing heat-dissipating materials.

[0011] The present invention has been made in view of the above circumstances, and has as its object to provide a highly thermally conductive two-component addition-curable silicone composition that has high thermal conductivity and high moisture resistance.

[0012] As a result of intensive research by the present inventors to solve the above problems, it has been found that a first liquid containing an alkenyl group-containing organopolysiloxane, spherical aluminum oxide powder having an average particle size of 80 to 120 μm, spherical aluminum oxide powder having an average particle size of 60 to 80 μm, spherical aluminum oxide powder having an average particle size of 25 to 60 μm, spherical aluminum oxide powder having an average particle size of 5 to 25 μm, and spherical or irregularly shaped aluminum oxide powder having an average particle size of 0.1 to 5 μm is blended in specific amounts and specific ratios, and the first liquid contains a silane coupling agent and / or an organopolysiloxane having a hydrolyzable group and a platinum catalyst for hydrosilylation reaction, and the alkenyl group-containing organopolysiloxane and the silane The present inventors have found that the above-mentioned problems can be solved by a thermally conductive two-part addition-curable silicone composition comprising an organohydrogenpolysiloxane having hydrogen atoms bonded to element atoms, a spherical aluminum oxide powder having an average particle size of 80 to 120 μm, a spherical aluminum oxide powder having an average particle size of 60 to 80 μm, a spherical aluminum oxide powder having an average particle size of 25 to 60 μm, a spherical aluminum oxide powder having an average particle size of 5 to 25 μm, and a spherical or irregularly shaped aluminum oxide powder having an average particle size of 0.1 to 5 μm, blended in specific amounts and specific ratios, and comprising a second part which contains a silane coupling agent and / or an organopolysiloxane having a hydrolyzable group.

[0013] That is, the present invention provides a thermally conductive two-component addition-curable silicone composition comprising a first liquid and a second liquid, comprising: (A) an organopolysiloxane having, per molecule, at least two alkenyl groups bonded to silicon atoms; (B) an organohydrogenpolysiloxane having, per molecule, at least two hydrogen atoms bonded to silicon atoms; (C) a thermally conductive filler comprising: a spherical aluminum oxide powder (C-1) having an average particle size of 80 μm or more and 120 μm or less; a spherical aluminum oxide powder (C-2) having an average particle size of 60 μm or more and less than 80 μm; a spherical aluminum oxide powder (C-3) having an average particle size of 25 μm or more and less than 60 μm; a spherical aluminum oxide powder (C-4) having an average particle size of 5 μm or more and less than 25 μm; and a spherical or irregularly shaped aluminum oxide powder (C-5) having an average particle size of 0.1 μm or more and less than 5 μm; (D) a silane coupling agent and / or a compound represented by the following general formula (1): (In the formula, R １ are independently monovalent hydrocarbon groups, and R ２ are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, a is a positive number of 5 to 100, and b is an integer of 1 to 3; and (E) a platinum catalyst for a hydrosilylation reaction, wherein among the components (A) to (E), the first liquid contains the components (A), (C), (D), and (E) but does not contain the component (B), the second liquid contains the components (A), (B), (C), and (D) but does not contain the component (E), and the entire composition, which is the combination of the first liquid and the second liquid, contains 100 to 200 parts by mass of the component (D) per 100 parts by mass of the total of the components (A) and (B), the composition contains 200 to 600 parts by mass of the component (C-1), 200 to 500 parts by mass of the component (C-2), 200 to 500 parts by mass of the component (C-3), 200 to 500 parts by mass of the component (C-4), and 300 to 700 parts by mass of the component (C-5), relative to 100 parts by mass of the total of the components (A), (B), and (D), and the total of the components (C-1) to (C-5) is 1700 to 2000 parts by mass.

[0014] In the case of such a thermally conductive two-component addition-curable silicone composition, the blending ratio of the thermally conductive filler and the blending amount of the silane coupling agent or organopolysiloxane having an alkoxy group at one end are within appropriate ranges, and when this composition is cured, a sheet-like cured product with high thermal conductivity and high moisture resistance can be obtained.

[0015] In this case, it is preferable that the viscosity of each of the first liquid and the second liquid at 25° C. is 30 to 800 Pa·s when measured at a rotation speed of 10 rpm using a spiral viscometer.

[0016] If the viscosity is within the above range, the thermally conductive two-component addition-curable silicone composition will have a stable shape and will have excellent workability.

[0017] Furthermore, the component (C-5) is preferably an irregularly shaped aluminum oxide powder.

[0018] If the aluminum oxide powder of component (C-5) has an irregular shape, the contact area between filler particles will be larger than when the filler is spherical, and this will increase the thermal conductivity of the thermally conductive two-part addition-curable silicone composition.

[0019] The present invention also provides a cured product of the above-mentioned thermally conductive two-part addition-curable silicone composition, wherein the hardness of the sheet-like cured product obtained by curing the thermally conductive two-part addition-curable silicone composition is in the range of 20 to 80, as measured using a Shore OO hardness tester specified in ASTM D 2240-05.

[0020] If the hardness of the sheet-shaped cured product is within the range of 20 to 80, the cured product will be a low-hardness rubber-like product, reducing the possibility of the cured product coming off from its mounted position due to shock such as vibration. Furthermore, the cured product will not apply large stress to the electronic components it comes into contact with, resulting in a favorable solder life for the electronic components.

[0021] The present invention also provides a cured product of the above-mentioned thermally conductive two-component addition-curable silicone composition, characterized in that the hardness of the sheet-like cured product obtained by curing the thermally conductive two-component addition-curable silicone composition is such that, after being subjected to 85°C / 85% RH for 1000 hours, the elongation at break of the sheet-like cured product is 10% or greater, as measured in the tensile test specified in JIS K 7161 using a No. 2 dumbbell tensile test piece conforming to JIS K 6251.

[0022] If the elongation at break of the sheet-shaped cured material in the above tensile test is 10% or more, when the cured material is used as a heat dissipation material, the heat dissipation material can follow the warping of electronic components that occurs under high temperature and high humidity conditions, and can efficiently remove heat from the electronic components.

[0023] The present invention also provides a thermally conductive sheet obtained by curing the above-described thermally conductive two-part addition-cure silicone composition.

[0024] Such a thermally conductive sheet has high thermal conductivity and is suppressed from increasing in hardness or decreasing in elongation of the cured product under moisture-resistant conditions, making it useful as an excellent heat-dissipating material for heat-generating electronic components.

[0025] According to the present invention, by using an appropriate blend ratio of thermally conductive filler and appropriate amounts of silane coupling agent or organopolysiloxane having an alkoxy group at one end, it is possible to provide a highly thermally conductive two-part addition-curable silicone composition and cured product that have high thermal conductivity and high moisture resistance. The cured product can be used as a heat-dissipating material for heat-generating electronic components even under high temperature and high humidity conditions.

[0026] As a result of extensive research into solving the above problems, the present inventors discovered that a thermally conductive two-part addition-curable silicone composition in which the components of the composition are blended in specific amounts and ratios can solve the above problems, leading to the creation of the present invention.

[0027] That is, the present invention provides a thermally conductive two-component addition-curable silicone composition comprising a first liquid and a second liquid, comprising: (A) an organopolysiloxane having, per molecule, at least two alkenyl groups bonded to silicon atoms; (B) an organohydrogenpolysiloxane having, per molecule, at least two hydrogen atoms bonded to silicon atoms; (C) a thermally conductive filler comprising: a spherical aluminum oxide powder (C-1) having an average particle size of 80 μm or more and 120 μm or less; a spherical aluminum oxide powder (C-2) having an average particle size of 60 μm or more and less than 80 μm; a spherical aluminum oxide powder (C-3) having an average particle size of 25 μm or more and less than 60 μm; a spherical aluminum oxide powder (C-4) having an average particle size of 5 μm or more and less than 25 μm; and a spherical or irregularly shaped aluminum oxide powder (C-5) having an average particle size of 0.1 μm or more and less than 5 μm; (D) a silane coupling agent and / or a compound represented by the following general formula (1): (In the formula, R １ are independently monovalent hydrocarbon groups, and R ２are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, a is a positive number of 5 to 100, and b is an integer of 1 to 3; and (E) a platinum catalyst for a hydrosilylation reaction, wherein among the components (A) to (E), the first liquid contains the components (A), (C), (D), and (E) but does not contain the component (B), the second liquid contains the components (A), (B), (C), and (D) but does not contain the component (E), and the entire composition, which is the combination of the first liquid and the second liquid, contains 100 to 200 parts by mass of the component (D) per 100 parts by mass of the total of the components (A) and (B), and the total amount of components (C-1) to (C-5) is 1,700 to 2,000 parts by mass.

[0028] The present invention will be described in detail below, but the present invention is not limited thereto.

[0029] [Thermal conductive two-component addition-curable silicone composition] The present invention relates to a thermally conductive two-component addition-curable silicone composition. In particular, the present invention relates to a thermally conductive two-component addition-curable silicone composition that exhibits excellent thermal conductivity, ease of handling, durability under high temperature and high humidity conditions, and reliability. The silicone composition of the present invention is characterized by containing the above-mentioned components (A) to (E), but can also contain other components as necessary. Each component will be described below.

[0030] [(A) Organopolysiloxane Having at Least Two Silicon-Bonded Alkenyl Groups Per Molecule] Component (A) of the composition of the present invention is the main component (base polymer) of the composition. Component (A) is an organopolysiloxane having at least two silicon-bonded alkenyl groups per molecule (hereinafter referred to as "silicon-bonded alkenyl groups"), and is, for example, represented by the following average compositional formula (2): Component (A) preferably has 2 to 50, and more preferably 2 to 20, silicon-bonded alkenyl groups per molecule. These silicon-bonded alkenyl groups may be bonded to silicon atoms at the molecular chain terminals, non-terminal (i.e., other than the molecular chain terminals) silicon atoms, or a combination thereof. (In the formula, R ３ are independently an alkenyl group, and R ４ are independently unsubstituted or substituted monovalent hydrocarbon groups having no aliphatic unsaturated bonds, c is 0.0001 to 0.2, d is 1.7 to 2.2, and c+d is a number that satisfies the range of 1.90 to 2.40.

[0031] In formula (2), R ３ are independently an alkenyl group, and examples of the alkenyl group include those having 2 to 6 carbon atoms, such as a vinyl group, an allyl group, an isopropenyl group, a 1-butenyl group, a 1-pentenyl group, and a 1-hexenyl group. Of these, an alkenyl group having 2 to 4 carbon atoms is preferred, and a vinyl group is particularly preferred.

[0032] In formula (2), the remaining organic group bonded to the silicon atom is an unsubstituted or substituted monovalent hydrocarbon group R ４Examples of the alkyl group include those having 1 to 12 carbon atoms, and preferably monovalent hydrocarbon groups having 1 to 6 carbon atoms. Specific examples thereof include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclohexyl, octyl, and dodecyl; aryl groups such as phenyl, 1-naphthyl, 2-naphthyl, and tolyl; aralkyl groups such as benzyl and 2-phenylethyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, chlorine, and bromine, such as chloromethyl and 3,3,3-trifluoropropyl. From the viewpoint of ease of synthesis, etc., a methyl group, a phenyl group, and a 3,3,3-trifluoropropyl group are preferred.

[0033] Furthermore, c is a number between 0.0001 and 0.2, and preferably between 0.0005 and 0.1. d is a number between 1.7 and 2.2, and preferably between 1.9 and 2.0. c+d is a number that satisfies the range of 1.90 to 2.40, and preferably between 1.95 and 2.05.

[0034] The kinematic viscosity of component (A) at 25°C measured with an Ostwald meter is preferably 10 to 100,000 mm ２ / s, more preferably in the range of 100 to 50,000 mm ２ / s. This kinematic viscosity is 10 to 100,000 mm ２ When the ratio is 1 / s, the resulting cured product has better strength, fluidity and workability.

[0035] Examples of organopolysiloxanes of component (A) that satisfy the above requirements include those represented by the following general formula (3): (In the formula, R ５ are independently unsubstituted or substituted monovalent hydrocarbon groups, provided that R ５ At least two of the groups are alkenyl groups, and e is a number from 10 to 2,000.

[0036] In this formula (3), R ５ The unsubstituted or substituted monovalent hydrocarbon group represented by the R ３ (alkenyl group), and R ４(an unsubstituted or substituted monovalent hydrocarbon group having no aliphatic unsaturated bonds), and the number of carbon atoms, specific examples, etc. are also the same. ５ At least two, preferably 2 to 50, and more preferably 2 to 20, of the alkenyl groups are alkenyl groups. If the number of alkenyl groups is 2 or more, the crosslink density of the resulting thermally conductive silicone cured product will be sufficient. If the number of alkenyl groups is 50 or less, the crosslink density of the resulting thermally conductive silicone cured product will be sufficiently high and the curing properties will be good. Furthermore, e is preferably a number from 40 to 1,200, and more preferably 50 to 600. If the number e is 40 or more, the viscosity of the resulting thermally conductive silicone composition will be sufficient, the handling properties will be good, and the resulting cured product will not be brittle. If the number e is 1,200 or less, the viscosity of the resulting thermally conductive silicone composition will be appropriate and the handling properties will be good.

[0037] Specific examples of organopolysiloxanes represented by the above formula (3) include dimethylpolysiloxanes capped at both molecular chain terminals with dimethylvinylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with trimethylsiloxy groups, dimethylsiloxane-methylvinylsiloxane copolymers capped at one molecular chain terminal with a trimethylsiloxy group and at the other with a dimethylvinylsiloxy group, dimethylsiloxane-methylvinylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups, and dimethylsiloxane-diphenylsiloxane copolymers capped at both molecular chain terminals with dimethylvinylsiloxy groups.

[0038] The organopolysiloxane of component (A) may be used alone or in combination of two or more different compounds. The blending amount of component (A) in the entire composition including the first and second liquids is preferably 0.5 to 10.0 mass%, and more preferably 0.8 to 5.0 mass%.

[0039] The above-mentioned organopolysiloxanes having alkenyl groups are known per se and can be produced by conventional methods.

[0040] [(B) Organohydrogenpolysiloxane Having at Least Two Silicon-Bonded Hydrogen Atoms Per Molecule] Component (B) is an organohydrogenpolysiloxane having at least two silicon-bonded hydrogen atoms per molecule (hereinafter also referred to as "silicon-bonded hydrogen atoms"). The number of silicon-bonded hydrogen atoms per molecule of this organohydrogenpolysiloxane is preferably 2 to 100, more preferably 2 to 50, and particularly preferably 2 to 20. If the number of silicon-bonded hydrogen atoms is too low, the crosslink density of the resulting thermally conductive silicone cured product will be too low, resulting in failure to cure. If the number of silicon-bonded hydrogen atoms is 100 or less, the resulting thermally conductive silicone cured product will have an appropriate crosslink density and flexibility, and will be less susceptible to void formation in the cured product due to dehydrogenation during storage or curing. These silicon-bonded hydrogen atoms may be located at the molecular chain terminals, along the molecular chain, or both.

[0041] Examples of the component (B) include those represented by the following average composition formula (4). (In the formula, R ６ is a hydrogen atom or independently a monovalent hydrocarbon group having no aliphatic unsaturated bonds, and f is a number from 8 to 1,000.

[0042] In the above formula (4), R ６ are independently monovalent hydrocarbon groups free of aliphatic unsaturated bonds, and preferably have 1 to 12 carbon atoms, more preferably 1 to 6 carbon atoms. Specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, cyclohexyl, octyl, and dodecyl; aryl groups such as phenyl, 1-naphthyl, 2-naphthyl, and tolyl; aralkyl groups such as benzyl and 2-phenylethyl; and groups in which some or all of the hydrogen atoms in these groups have been substituted with halogen atoms such as fluorine, chlorine, and bromine, such as a chloromethyl group or a 3,3,3-trifluoropropyl group. Of these, from the viewpoint of ease of synthesis, a methyl group, a phenyl group, and a 3,3,3-trifluoropropyl group are preferred.

[0043] The number of silicon atoms per molecule of the organohydrogenpolysiloxane of component (B) (i.e., degree of polymerization) is typically 8 to 1,000, but from the viewpoints of improving the handling of the composition and the properties of the resulting cured product, it is preferably 20 to 500, and more preferably 20 to 100. If the degree of polymerization is 8 or higher, the resulting thermally conductive silicone composition will have an appropriate viscosity, will be easy to handle, and will not be brittle. If the degree of polymerization is 1,000 or lower, the resulting thermally conductive silicone composition will have an appropriate viscosity and will be easy to handle.

[0044] Furthermore, the molecular structure of the organohydrogenpolysiloxane of component (B) is not particularly limited as long as it satisfies the above requirements.

[0045] The viscosity of the organohydrogenpolysiloxane of component (B) is typically 1 to 10,000 mPa s, preferably 3 to 2,000 mPa s, and more preferably 10 to 1,000 mPa s, and it is desirable that it be liquid at room temperature (25°C). In the present invention, unless otherwise specified, the viscosity is a value measured with a BM-type viscometer (for example, manufactured by Tokyo Keiki Co., Ltd.). The rotor, rotation speed, and rotation time are selected appropriately in accordance with the viscosity using conventional methods.

[0046] The organohydrogenpolysiloxane of component (B) may use either a single compound, or a combination of two or more different compounds.

[0047] This organohydrogenpolysiloxane is synthesized by a conventionally known method.

[0048] The amount of organohydrogenpolysiloxane in component (B) is such that, per alkenyl group in component (A) in the entire composition consisting of parts 1 and 2 combined, there are 0.1 to 5.0 silicon-bonded hydrogen atoms (SiH groups), preferably 0.2 to 2.0, and more preferably 0.5 to 1.5. An amount of 0.1 or more provides a sufficient effect of improving storage stability, while an amount of 5.0 or less ensures stable physical properties for the resulting thermally conductive silicone cured product.

[0049] Component (B) is used in Liquid 2, but is not contained in Liquid 1. When component (B) is used in Liquid 1, Liquid 1 thickens and hardens over time at room temperature, and therefore cannot maintain its viscosity at the time of production.

[0050] [(C) Thermally Conductive Filler] Component (C) is a thermally conductive filler and comprises spherical aluminum oxide powder (C-1) having an average particle size of 80 to 120 μm, spherical aluminum oxide powder (C-2) having an average particle size of 60 to 80 μm, spherical aluminum oxide powder (C-3) having an average particle size of 25 to 60 μm, spherical aluminum oxide powder (C-4) having an average particle size of 5 to 25 μm, and spherical or irregularly shaped aluminum oxide powder (C-5) having an average particle size of 0.1 to 5 μm. When the ranges of the average particle sizes of components (C-1) to (C-5) are expressed as above, the range of the average particle size of component (C-1) is inclusive, but the range of the average particle size of components (C-2) to (C-5) is inclusive of the lower limit of the numerical range but exclusive of the upper limit. That is, the average particle size of component (C-1) is 80 μm or more and 120 μm or less, and for example, the average particle size of component (C-2) is 60 μm or more and less than 80 μm.

[0051] The average particle size in the present invention can be measured using a laser diffraction / scattering particle size distribution analyzer, for example, the "Microtrac MT3300EX" manufactured by Nikkiso Co., Ltd. The average particle size is determined by multiplying the measured particle size value by the relative particle amount (difference %) and dividing the result by the total relative particle amount (100%). The average particle size is the average diameter of the particles.

[0052] The average particle size of component (C-1) is 80 to 120 μm, preferably 90 to 110 μm. If the average particle size of component (C-1) is greater than 120 μm, it may cause wear on the kneader and stirring blades, increase the material thickness during packaging, and increase the unevenness of the sheet surface, resulting in an increased thermal resistivity. The spherical aluminum oxide powder of component (C-1) may be of one type, or two or more types with different average particle sizes may be used in combination.

[0053] When the powder size is measured using a laser diffraction / scattering particle size distribution measuring device, such as a "Microtrac MT3300EX" manufactured by Nikkiso Co., Ltd., and expressed as a particle size distribution, and the distribution is divided into two, the particle size at which the larger side has an abundance ratio of 10% and the smaller side has an abundance ratio of 90% is taken as d90, the d90 of component (C-1) is from 90 μm to 170 μm, and preferably from 110 μm to 150 μm.

[0054] The average particle size of component (C-2) is 60 to 80 μm, preferably 65 to 75 μm. The spherical aluminum oxide powder of component (C-2) may be a single type or a combination of two or more types with different average particle sizes.

[0055] The average particle size of component (C-3) is 25 to 60 μm, preferably 30 to 55 μm. The spherical aluminum oxide powder of component (C-3) may be a single type or a combination of two or more types with different average particle sizes.

[0056] The average particle size of component (C-4) is 5 to 25 μm, preferably 8 to 20 μm. The spherical aluminum oxide powder of component (C-4) may be a single type or a combination of two or more types with different average particle sizes.

[0057] The average particle size of component (C-5) is 0.1 to 5 μm, preferably 0.5 to 3 μm. If the average particle size is less than 0.1 μm, the surface area of ​​the particles increases, and the interface area between the particles and the resin also increases, which tends to increase interfacial thermal resistance, resulting in poor thermal conductivity and a significant increase in the viscosity of the composition. The aluminum oxide powder of component (C-5) may be a single type, or a combination of two or more types with different average particle sizes.

[0058] The shape of component (C-5) is spherical or irregularly shaped aluminum oxide powder. While either spherical or irregularly shaped particles can be used, irregularly shaped particles are more preferable because spherical particles result in point contact between filler particles, reducing the contact area between the filler particles. In other words, in the present invention, it is preferable that component (C-5) is irregularly shaped aluminum oxide powder. Shapes other than spherical are considered irregular. Here, "spherical" refers to fillers with an average circularity of 0.85 or more. The average circularity is calculated as follows. In a particle image taken with a scanning electron microscope, if the projected area (S) and perimeter (L) of a particle are taken, and the area of ​​a perfect circle corresponding to the perimeter (L) is taken as (X), the circularity of the particle can be calculated as S / X. Therefore, assuming a perfect circle (radius r) with the same perimeter as the perimeter (L) of the sample particle, L = 2πr and X = πr. ２ Therefore, X = π × (L / 2π) ２ The sphericity of each particle is given by Sphericity = S / X = S × 4π / L ２ A circularity of 1 is a perfect circle, and the further away from a perfect circle the circularity is, the closer to 0. The sphericities of 100 random particles thus obtained are determined, and the average value is taken as the average sphericity.

[0059] The blending amount of component (C-1) is 200 to 600 parts by mass, preferably 230 to 550 parts by mass, per 100 parts by mass of the total of components (A), (B), and (D). If the blending amount of component (C-1) is too small, the filling property deteriorates and the thermal conductivity decreases. If the blending amount of component (C-1) is too large, the filling property deteriorates, the viscosity increases, and wear on the kneader and stirring blades increases.

[0060] The amount of component (C-2) blended is 200 to 500 parts by mass, preferably 230 to 450 parts by mass, and more preferably 250 to 400 parts by mass, per 100 parts by mass of the total of components (A), (B), and (D). If the amount of component (C-2) blended is too small or too large, it becomes difficult to densely pack component (C), resulting in a decrease in thermal conductivity and an increase in viscosity.

[0061] The amount of component (C-3) blended is 200 to 500 parts by mass, preferably 230 to 450 parts by mass, and more preferably 250 to 400 parts by mass, per 100 parts by mass of the total of components (A), (B), and (D). If the amount of component (C-3) blended is too small or too large, it becomes difficult to densely pack component (C), resulting in a decrease in thermal conductivity and an increase in viscosity.

[0062] The amount of component (C-4) blended is 200 to 500 parts by mass, preferably 230 to 450 parts by mass, and more preferably 250 to 400 parts by mass, per 100 parts by mass of the total of components (A), (B), and (D). If the amount of component (C-4) blended is too small or too large, it becomes difficult to densely pack component (C), resulting in a decrease in thermal conductivity and an increase in viscosity.

[0063] The amount of component (C-5) blended is 300 to 700 parts by mass, preferably 330 to 660 parts by mass, and more preferably 350 to 630 parts by mass, per 100 parts by mass of the total of components (A), (B), and (D). If the amount of component (C-5) blended is too small, it becomes difficult to densely pack component (C), and oil separation over time increases. If the amount of component (C-5) blended is too large, the viscosity of the composition increases significantly, and thermal conductivity decreases.

[0064] The total amount of components (C-1) to (C-5) is 1,700 to 2,000 parts by mass, preferably 1,800 to 1,900 parts by mass, per 100 parts by mass of the total of components (A), (B), and (D). If the blending amount is less than 1,700 parts by mass, the thermal conductivity of the composition may be insufficient, while if it exceeds 2,000 parts by mass, it becomes difficult to fill the thermally conductive filler.

[0065] The crystalline structure of the aluminum oxide powder may be either single crystal or polycrystalline, but the crystalline phase is preferably the α phase from the viewpoint of high thermal conductivity, and the specific gravity is preferably 3.7 or higher. If the specific gravity is 3.7 or higher, the ratio of voids and low crystalline phase present inside the particles is appropriate, making it easy to increase thermal conductivity. In addition, the particle size of the aluminum oxide powder can be adjusted by classification.

[0066] As the thermally conductive filler of component (C), only aluminum oxide powder is suitable from the viewpoints of thermal conductivity, moisture resistance, and packing properties, and other thermally conductive fillers are not included.

[0067] The component (C) is used in both the first liquid and the second liquid, and the ratio of the component (C) used in the first liquid and the second liquid is not particularly limited, as long as the mixing ratio of the first liquid to the second liquid is approximately the same mass ratio.

[0068] [(D) Surface Treatment Agent] The component (D) is a surface treatment agent, and is a silane coupling agent and / or a compound represented by the following general formula (1): (In the formula, R １ are independently monovalent hydrocarbon groups, and R ２ are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, a is a positive number of 5 to 100, and b is an integer of 1 to 3.

[0069] By incorporating component (D), the viscosity of the resulting silicone composition can be reduced.

[0070] Examples of silane coupling agents include vinyl silane coupling agents, epoxy silane coupling agents, acrylic silane coupling agents, and long-chain alkyl silane coupling agents, and these can be used alone or in appropriate combinations of two or more. Examples include hexyltrimethoxysilane, decyltrimethoxysilane, hexadecyltrimethoxysilane, decylmethyldimethoxysilane, decyldimethylmethoxysilane, decyltriethoxysilane, 7-octenyltrimethoxysilane, and phenyltrimethoxysilane, with decyltrimethoxysilane being particularly preferred.

[0071] In the above formula (1), R １are independently unsubstituted or substituted monovalent hydrocarbon groups preferably having 1 to 10 carbon atoms, more preferably 1 to 6, and even more preferably 1 to 3 carbon atoms, and specific examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, cyclohexyl, octyl, and dodecyl; aryl groups such as phenyl; and groups in which some or all of the hydrogen atoms of these groups have been substituted with halogen atoms such as fluorine, chlorine, and bromine, or with cyano groups, such as chloromethyl, 3,3,3-trifluoropropyl, and cyanoethyl. １ As the alkyl group, a methyl group, a phenyl group, and a 3,3,3-trifluoropropyl group are preferred.

[0072] In the above general formula (1), R ２ are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group. Examples of the alkyl group include the above-mentioned R ３ Examples of the alkoxyalkyl group include the same straight-chain alkyl group, branched-chain alkyl group, and cyclic alkyl group as those exemplified in . Examples of the alkoxyalkyl group include a methoxyethyl group, a methoxypropyl group, and the like, and those having 2 to 10 carbon atoms are preferred. Examples of the alkenyl group include a vinyl group, an allyl group, an isopropenyl group, a 1-butenyl group, a 1-pentenyl group, a 1-hexenyl group, and the like, and those having 1 to 8 carbon atoms are preferred. Examples of the acyl group include an acetyl group, an octanoyl group, and the like, and those having 2 to 10 carbon atoms are preferred. R ２ is preferably an alkyl group, and particularly preferably a methyl group or an ethyl group.

[0073] Furthermore, a is a number from 5 to 100, preferably a number from 8 to 50, and b is a number from 1 to 3, preferably 3.

[0074] Specific examples of suitable organopolysiloxanes of component (D) include the following: (In the formula, Me is a methyl group. The same applies hereinafter.)

[0075] The viscosity of the organopolysiloxane of component (D) at 25°C is typically 0.01 to 30 Pa·s, and preferably 0.1 to 10 Pa·s. If the viscosity is 0.01 Pa·s or higher, oil bleeding of component (D) from the silicone composition is unlikely to occur. If the viscosity is 30 Pa·s or lower, the resulting silicone composition has good fluidity and is easy to apply.

[0076] In the present invention, when component (D) is used, it is preferably prepared as a heat-treated mixture together with the above-mentioned component (C) or components (A) to (C) at a temperature of 70°C or higher, more preferably 80 to 180°C.

[0077] When component (D) is used in the present invention, the aforementioned component (C) can also be pretreated with component (D). Treating component (C) with component (D) has the effect of lowering the viscosity of the resulting silicone composition. In this case, the surface treatment of component (C) with component (D) can be performed using a spraying method using a fluid nozzle, a stirring method that applies shear force, a dry method using a ball mill or mixer, or a wet method using an aqueous or organic solvent system. Stirring is performed to a temperature that does not destroy the thermally conductive filler. In the dry method, the system temperature or the drying temperature after treatment is determined appropriately depending on the type of surface treatment agent, within a range that does not cause the surface treatment agent to volatilize or decompose, but is, for example, 80 to 180°C.

[0078] When component (D) is used, its blending amount is 100 to 200 parts by weight, preferably 110 to 190 parts by weight, and more preferably 120 to 180 parts by weight, per 100 parts by weight of the combined total of components (A) and (B). Less than 100 parts by weight results in little viscosity reduction. Furthermore, in two-component addition-curable materials, dehydrogenation of the organohydrogenpolysiloxane by the thermally conductive filler occurs during storage at room temperature. Therefore, if the amount of silane coupling agent or organopolysiloxane having an alkoxy group at one end is too small, the deterioration over time in hardness during storage at room temperature cannot be suppressed. More than 200 parts by weight results in increased hardness of the cured sheet under humidity-resistant conditions, reducing elongation and resulting in a material with poor reliability. The blending amount of component (D) in the entire composition (combining the first and second components) is preferably 1.5 to 4.7% by weight, more preferably 2.0 to 3.5% by weight.

[0079] The component (D) is used in both the first and second liquids. The ratio of the component (D) used in the first and second liquids is not particularly limited, but for example, the same amount can be used in the first and second liquids. The ratio can be set depending on the amount of the component (C) in each liquid.

[0080] [(E) Platinum Group Metal Catalyst] The component (E) of the composition of the present invention is a platinum group metal catalyst, which is a catalyst that promotes the addition reaction between the alkenyl group in component (A) and the hydrogen atom bonded to the silicon atom in component (B).For example, chloroplatinic acid, alcohol-modified chloroplatinic acid, coordination compounds of chloroplatinic acid with olefins, aldehydes, vinylsiloxanes, or acetylene compounds, tetrakis(triphenylphosphine)palladium, chlorotris(triphenylphosphine)rhodium, etc. can be used, but platinum catalysts are preferred, and coordination compounds of chloroplatinic acid with vinylsiloxane are most preferred.

[0081] The amount of component (E) may be a catalytic amount, but is usually an amount that corresponds to 0.1 to 500 ppm, and preferably 1 to 100 ppm, calculated as platinum group metal mass relative to the total composition consisting of components 1 and 2. Keeping the amount of component (E) within this range is preferred because it allows for appropriate curing properties to be obtained.

[0082] The component (E) is used in the first liquid and is not contained in the second liquid.

[0083] [Others] In addition to the above-described components (A) to (E), the composition of the present invention may contain various known additives as needed. Examples of other additives are listed below.

[0084] For example, it is possible to blend reaction inhibitors for adjusting the curing rate and storage stability, specifically acetylene alcohols such as triallyl isocyanate alkyl maleate, ethynyldecylmethylcarbinol, and ethynylcyclohexanol, and silanes thereof, siloxane-modified products, hydroperoxides, tetramethylethylenediamine, colorants such as ferrous oxide and ferric oxide, either alone or in combination, and thixotropic agents such as fumed silica.The amount of each of these blended is preferably 0.01 to 100,000 ppm by mass per composition.

[0085] The mixing device used to prepare the composition may be a known mixer such as a static mixer, a planetary mixer, or a paddle mixer.

[0086] [Production Method] The composition of the present invention is a thermally conductive two-component addition-curable silicone composition comprising a first component that contains the components (A), (C), (D), and (E) above but does not contain the component (B), and a second component that contains the components (A), (B), (C), and (D) above but does not contain the component (E).

[0087] The method for producing the composition of the present invention simply involves mixing the components of the first and second liquids, and examples of production methods for the first liquid include a production method comprising the following steps: mixing components (A), (C), and (D) and heat-treating them at a temperature of 70°C or higher to obtain a heated mixture, cooling the heated mixture obtained above to room temperature (25°C) or lower, and then adding component (E), a reaction inhibitor, a colorant, and a thixotropic agent. The second liquid includes a production method comprising a step of mixing components (A), (C), and (D) and heat-treating them at a temperature of 70°C or higher to obtain a heated mixture, and cooling the heated mixture obtained above to room temperature (25°C) or lower, and then adding component (B), a reaction inhibitor, a colorant, and a thixotropic agent.

[0088] The heating temperature in the heat treatment step is preferably 70°C or higher, more preferably 70 to 180°C. The heating time is not particularly limited, and is preferably 1 hour or longer, more preferably 1 to 3 hours. When an additive is added, it may be added in any step, but it is preferably added after the heated mixture has been cooled. As a mixing device for preparing the above composition, known mixers such as a static mixer, a planetary mixer, or a paddle mixer can be used.

[0089] In the present invention, it is preferable that each of the first liquid and the second liquid has a viscosity at 25° C. of 30 to 800 Pa·s when measured at a rotation speed of 10 rpm using a spiral viscometer.

[0090] The viscosity of the composition of the present invention at 25°C, measured using a spiral viscometer: Malcom viscometer (Type PC-10AA, rotation speed: 10 rpm), is 30 to 800 Pa·s for each of the first and second liquids, and preferably 70 to 400 Pa·s. If the viscosity is 30 Pa·s or higher, the shape retention of the composition is sufficient, and if it is 800 Pa·s or lower, workability is not impaired. In the present invention, the viscosity can be adjusted to the above range by adjusting the blending amount and blending ratio of component (C) within the range specified above.

[0091] The thermal conductivity of the composition of the present invention is preferably 5.5 W / m K or more, and more preferably 5.7 W / m K or more, as measured by the hot disk method in accordance with ISO 22007-2. A thermal conductivity of 5.5 W / m K or more ensures sufficient heat dissipation performance for heat-generating electronic components. There is no particular upper limit to the thermal conductivity, but it is preferably 6.9 W / m K or less, and more preferably 6.7 W / m K or less. In the present invention, achieving the thermal conductivity within the above range can be achieved by adjusting the blending amount and blending ratio of component (C) within the ranges specified above.

[0092] The present invention provides a thermally conductive sheet obtained by curing the above-described thermally conductive two-component addition-curable silicone composition. For example, the first and second components of the composition of the present invention are mixed in any desired ratio, molded, and then left at room temperature or heated at 40 to 200°C to obtain a thermally conductive sheet. However, the preferred mixture ratio by weight is first component:second component = 130:100 to 100:130, and more preferably first component:second component = 110:100 to 100:110.

[0093] The thermal conductive sheet may be in any form, including, for example, a gel, a low-hardness rubber, or a high-hardness rubber, with a low-hardness rubber being preferred. In this case, low hardness refers to a value measured using a Shore OO hardness tester as specified in ASTM D 2240-05 of 20 to 80, preferably 30 to 70. A hardness of 20 or more makes the heat dissipation material less likely to shift or fall off from its mounted position due to shocks such as vibration after mounting. Furthermore, a hardness of 80 or less prevents the stress on electronic components from increasing, thereby not adversely affecting solder life.

[0094] Thus, the present invention provides a cured product of the above-mentioned thermally conductive two-component addition-curable silicone composition, characterized in that the hardness of the sheet-like cured product obtained by curing the above-mentioned thermally conductive two-component addition-curable silicone composition is in the range of 20 to 80, as measured using a Shore OO hardness tester specified in ASTM D 2240-05.

[0095] Regarding the elongation of the sheet-like cured product (thermal conductive sheet) obtained by curing the composition of the present invention, the elongation at break measured by a tensile test specified in JIS K 7161 using a No. 2 dumbbell-shaped tensile test piece conforming to JIS K 6251 is preferably 20% or more. If the elongation is 20% or more, the heat dissipation material can accommodate warpage of electronic components when heat is applied to the electronic components after mounting. There is no particular upper limit to the elongation, but it is preferably 70% or less.

[0096] The thickness of the sheet is not particularly limited, but is preferably 150 μm or more, and in consideration of the size of the electronic components to be mounted, is preferably 5 mm or less.

[0097] The present invention also provides a cured product of the above-mentioned thermally conductive two-part addition-curable silicone composition, characterized in that the hardness of the sheet-shaped cured product obtained by curing the above-mentioned thermally conductive two-part addition-curable silicone composition is such that, after 1000 hours at 85°C / 85% RH, the elongation at break measured using a No. 2 dumbbell tensile test piece conforming to JIS K 6251 in accordance with the tensile test specified in JIS K 7161 is 10% or more. The elongation at break is preferably 20% or more. The elongation after a humidity resistance test within the above range can be achieved, particularly by adjusting the amount of component (D) to fall within the above-specified range.

[0098] The thermally conductive sheet described above has high thermal conductivity and is suppressed from increasing in hardness or decreasing in elongation of the cured product due to humidity-resistant conditions, making it useful as an excellent heat dissipation material for heat-generating electronic components.

[0099] EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0100] Component (A) A-1: ​​Dimethylpolysiloxane terminated at both molecular chain ends with dimethylvinylsiloxy groups (kinematic viscosity 400 mm ２ / s, amount of Vi group per 100 g is 0.0185 mol, e in general formula (3) is 146)

[0101] Component (B) B-1: Trimethylsiloxy-blocked methylhydrogen-dimethylpolysiloxane represented by formula (5) (Si—H content: 0.00128 mol / g)

[0102] B-2: Dimethylhydrogensiloxy-blocked dimethylpolysiloxane represented by formula (6) (Si—H content: 0.00130 mol / g)

[0103] Component (C) C-1-1: spherical aluminum oxide (average particle diameter 100 μm, density 3.98 g / cm ３ ) C-2-1: Spherical aluminum oxide (average particle diameter 70 μm, density 3.98 g / cm ３ ) C-3-1: Spherical aluminum oxide (average particle size 45 μm, density 3.98 g / cm ３ ) C-4-1: Spherical aluminum oxide (average particle diameter 10 μm, density 3.98 g / cm ３ ) C-5-1: Spherical aluminum oxide (average particle diameter 3 μm, density 3.98 g / cm ３ ) C-5-2: irregularly shaped aluminum oxide (average particle diameter 1.2 μm, density 3.98 g / cm ３ ) (For comparison) c-6-1: Spherical aluminum oxide (average particle size 150 μm, density 3.98 g / cm ３ )

[0104] Component (D) D-1: organopolysiloxane represented by formula (7)

[0105] Component (E) E-1: vinylsiloxane complex of chloroplatinic acid (Pt content 1% by mass)

[0106] First Liquid: Components (A), (C), and (D) were added to a 5 L planetary mixer manufactured by Inoue Seisakusho Co., Ltd. in the mass mixing ratios shown in Tables 1 to 3, and mixed, followed by heat treatment and mixing at 150°C for 1 hour to obtain Mixture 1. Next, after this Mixture 1 was sufficiently cooled to room temperature (25°C), component (E) was added in the mass mixing ratios shown in Tables 1 to 3 below, and the mixture was mixed uniformly at room temperature (25°C) for 20 minutes to obtain a first liquid.

[0107] Liquid 2: Components (A), (C), and (D) were added to a 5L planetary mixer manufactured by Inoue Seisakusho Co., Ltd. in the mass mixing ratios shown in Tables 1 to 3, and then heated and mixed at 150°C for 1 hour to obtain Mixture 2. Mixture 2 was then sufficiently cooled to room temperature (25°C), after which component (B) was added in the mass mixing ratios shown in Tables 1 to 3 below, and the mixture was mixed uniformly at room temperature (25°C) for 20 minutes to obtain Liquid 2.

[0108] Viscosity The viscosity of each of the first and second liquids in each example was measured at 25° C. using a spiral viscometer: Malcom viscometer (type PC-10AA, rotation speed: 10 rpm).

[0109] Thermal Conductivity The first and second parts of each example were mixed uniformly at a mass ratio of 1:1 using a static mixer MXA6.3-21 (manufactured by Noritake Co., Ltd.) at room temperature (25°C), discharged, thoroughly degassed under vacuum, and then poured into a mold that would result in a thickness of 6 mm after curing. The mixture was cured at 25°C for 24 hours to obtain a sheet-like cured product. The thermal conductivity of the resulting cured product at 25°C was measured using a hot disc method thermal property measuring device TPS 2500 S (manufactured by Kyoto Electronics Manufacturing Co., Ltd.) (hot disc method in accordance with ISO 22007-2).

[0110] Hardness: The first and second parts of each example were mixed uniformly at a 1:1 mass ratio using a static mixer MXA6.3-21 (manufactured by Noritake Co., Ltd.) at room temperature (25°C), discharged, thoroughly degassed under vacuum, and then poured into a mold that would result in a thickness of 6 mm after curing. The mixture was then cured at 25°C for 24 hours to obtain a sheet-like cured product. The hardness (hardness) of the resulting cured product was measured using a Shore OO hardness tester as specified in ASTM D 2240-05, and the value 30 seconds after the start of the measurement was used.

[0111] Moisture Resistance Test The first and second parts of Example 1 and Comparative Example 1 were mixed and discharged at room temperature (25°C) using a static mixer MXA6.3-21 (manufactured by Noritake Co., Ltd.) to a uniform 1:1 mass ratio. The mixture was then thoroughly vacuum degassed and poured into a mold to a thickness of 2 mm after curing. The mixture was then cured at 25°C for 24 hours to obtain a sheet-like cured product. The thermally conductive silicone cured product was then stored in a constant temperature and humidity chamber at 85°C / 85% RH and aged for 1000 hours. After 1000 hours, the silicone cured product was removed. Type 2 dumbbell-shaped tensile test specimens conforming to JIS K 6251 were punched out of the cured product before and after aging, and the elongation at break of the test specimens was measured using a tensile test specified in JIS K 7161.

[0112] The results of the viscosity, thermal conductivity, and hardness are shown in Tables 1 to 3, and the results of the moisture resistance test are shown in Table 4. In the tables, "H / Vi" represents the molar ratio of silicon-bonded hydrogen atoms (SiH groups) in component (B) to one alkenyl group in component (A) in the entire composition consisting of the first and second parts combined.

[0113]

[0114]

[0115]

[0116]

[0117] The above results show that the thermally conductive two-part addition-curable silicone compositions of Examples 1 to 7 of the present invention yielded sheet-shaped cured products with thermal conductivities in the preferred range of 5.5 to 6.9 W / m·K as measured by the hot disk method according to ISO 22007-2, demonstrating excellent thermal conductivity. Furthermore, the viscosities of the first and second parts of the thermally conductive silicone composition and the hardness of the sheet-shaped cured products were also suitable for use as heat-dissipating materials for heat-generating electronic components (Tables 1 and 2). Furthermore, as shown in Table 4, Example 1, which contains an appropriate amount of component (D), exhibits minimal loss of elongation after 1,000 hours of storage at 85°C / 85% RH. Comparative Example 1, which contains an excessive amount of component (D), exhibits a significant loss of elongation under humidity-resistant conditions, demonstrating poor reliability. Furthermore, Comparative Example 2 demonstrates that sufficient thermal conductivity cannot be achieved when component (C-1) is not included (Table 2). It can be seen that in Comparative Example 3, when the particle size of component (C-1) is large (and component (c-6-1), which has a larger particle size, is included instead), and in Comparative Example 4, when the amount of component (D) is too small, the viscosity increases significantly to the point where it is unmeasurable (Tables 2 and 3). Furthermore, it can be seen that in Comparative Example 5, the viscosity also increases when there is a large amount of component (C-1) and a small amount of component (C-5). It can be seen that in Comparative Example 6, when there is a small amount of component (C-1) and an excessive amount of component (C-5), sufficient thermal conductivity cannot be obtained. Thus, according to the present invention, a thermally conductive silicone composition and a cured product thereof can be obtained that have high thermal conductivity and high reliability under moisture-resistant conditions.

[0118] The thermally conductive silicone composition obtainable by the present invention possesses particularly excellent thermal conductivity, is easy to handle, and also exhibits excellent durability and reliability under high-temperature, high-humidity conditions. As a result, it is expected to improve reliability in applications where the composition serves as both a heat dissipation and protection device for electronic components such as power devices, transistors, thyristors, CPUs (central processing units), and GPUs (graphics processing units).

[0119] This specification encompasses the following aspects: [1]: A thermally conductive two-component addition-curable silicone composition consisting of a first liquid and a second liquid, comprising: (A) an organopolysiloxane having, per molecule, at least two alkenyl groups bonded to silicon atoms; (B) an organohydrogenpolysiloxane having, per molecule, at least two hydrogen atoms bonded to silicon atoms; (C) a thermally conductive filler comprising: a spherical aluminum oxide powder (C-1) having an average particle size of 80 μm to 120 μm; a spherical aluminum oxide powder (C-2) having an average particle size of 60 μm to less than 80 μm; a spherical aluminum oxide powder (C-3) having an average particle size of 25 μm to less than 60 μm; a spherical aluminum oxide powder (C-4) having an average particle size of 5 μm to less than 25 μm; and a spherical or irregularly shaped aluminum oxide powder (C-5) having an average particle size of 0.1 μm to less than 5 μm; (D) a silane coupling agent and / or a compound represented by the following general formula (1): (In the formula, R １ are independently monovalent hydrocarbon groups, and R ２are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, a is a positive number of 5 to 100, and b is an integer of 1 to 3; and (E) a platinum catalyst for a hydrosilylation reaction, wherein among the components (A) to (E), the first liquid contains the components (A), (C), (D), and (E) but does not contain the component (B), the second liquid contains the components (A), (B), (C), and (D) but does not contain the component (E), and the entire composition, which is the combination of the first liquid and the second liquid, contains 100 to 200 parts by mass of the component (D) per 100 parts by mass of the total of the components (A) and (B), a thermally conductive two-component addition-curable silicone composition comprising, per 100 parts by mass of the total of the components (A), (B), and (D), 200 to 600 parts by mass of the component (C-1), 200 to 500 parts by mass of the component (C-2), 200 to 500 parts by mass of the component (C-3), 200 to 500 parts by mass of the component (C-4), and 300 to 700 parts by mass of the component (C-5), the total of the components (C-1) to (C-5) being 1700 to 2000 parts by mass. [2]: The thermally conductive two-component addition-curable silicone composition of [1], wherein the viscosity of each of the first and second components at 25°C is 30 to 800 Pa s when measured at 10 rpm using a spiral viscometer. [3]: The thermally conductive two-part addition-curable silicone composition of [1] or [2], wherein component (C-5) is an amorphous aluminum oxide powder. [4]: ​​A cured product of the thermally conductive two-part addition-curable silicone composition of any one of [1] to [3], wherein the hardness of the sheet-like cured product obtained by curing the thermally conductive two-part addition-curable silicone composition is in the range of 20 to 80 as measured using a Shore OO hardness tester specified in ASTM D 2240-05.[5]: A cured product of the thermally conductive two-component addition-curable silicone composition of any one of [1] to [3], characterized in that the hardness of the sheet-shaped cured product obtained by curing the thermally conductive two-component addition-curable silicone composition is such that, after being subjected to 85°C / 85% RH for 1000 hours, the elongation at break measured using a No. 2 dumbbell tensile test piece conforming to JIS K 6251 in accordance with JIS K 7161 is 10% or more. [6]: A thermally conductive sheet characterized in that it is obtained by curing the thermally conductive two-component addition-curable silicone composition of any one of [1] to [3].

[0120] The present invention is not limited to the above-described embodiments, which 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 provides similar effects is included within the technical scope of the present invention.

Claims

1. A thermally conductive two-liquid addition curing silicone composition comprising a first liquid and a second liquid, comprising: (A) an organopolysiloxane having an alkenyl group bonded to two or more silicon atoms in one molecule; (B) an organohydrogenpolysiloxane having two or more hydrogen atoms bonded to two or more silicon atoms in one molecule; (C) a thermally conductive filler comprising a spherical aluminum oxide powder (C-1) having an average particle size of 80 μm or more and 120 μm or less; a spherical aluminum oxide powder (C-2) having an average particle size of 60 μm or more and less than 80 μm; a spherical aluminum oxide powder (C-3) having an average particle size of 25 μm or more and less than 60 μm; a spherical aluminum oxide powder (C-4) having an average particle size of 5 μm or more and less than 25 μm; and a spherical or irregular aluminum oxide powder (C-5) having an average particle size of 0.1 μm or more and less than 5 μm; (D) a silane coupling agent and a compound represented by the following general formula (1): (In the formula, R １ are independently monovalent hydrocarbon groups; R ２ are independently an alkyl group, an alkoxyalkyl group, an alkenyl group, or an acyl group, a is a positive number from 5 to 100, and b is an integer from 1 to 3; and (E) a platinum catalyst for hydrosilylation reaction, wherein among the components (A) to (E), the first liquid contains the components (A), (C), (D), and (E) but does not contain the component (B), the second liquid contains the components (A), (B), (C), and (D) but does not contain the component (E), and the entire composition consisting of the first liquid and the second liquid contains 100 to 200 parts by mass of the component (D) per 100 parts by mass of the total of the components (A) and (B), a thermally conductive two-component addition curable silicone composition comprising, relative to a total of 100 parts by mass of the component (A), the component (B), and the component (D), 200 to 600 parts by mass of the component (C-1), 200 to 500 parts by mass of the component (C-2), 200 to 500 parts by mass of the component (C-3), 200 to 500 parts by mass of the component (C-4), and 300 to 700 parts by mass of the component (C-5), and the total of the components (C-1) to (C-5) is 1700 to 2000 parts by mass.

2. The thermally conductive two-component addition curing silicone composition according to claim 1, characterized in that the viscosity of each of the first and second liquids at 25°C is 30 to 800 Pa·s when measured at a rotation speed of 10 rpm using a spiral viscometer.

3. The thermally conductive two-part addition curing silicone composition according to claim 1, wherein component (C-5) is an amorphous aluminum oxide powder.

4. A cured product of the thermally conductive two-part addition curable silicone composition according to any one of claims 1 to 3, characterized in that the hardness of the sheet-like cured product obtained by curing the thermally conductive two-part addition curable silicone composition is in the range of 20 to 80 as measured using a Shore OO hardness tester as specified in ASTM D 2240-05.

5. A cured product of the thermally conductive two-component addition curing silicone composition according to any one of claims 1 to 3, characterized in that the hardness of the sheet-like cured product obtained by curing the thermally conductive two-component addition curing silicone composition is such that after being subjected to 85°C / 85% RH for 1000 hours, the elongation at break measured by the tensile test specified in JIS K 7161 using a tensile test piece of type 2 dumbbell conforming to JIS K 6251 is 10% or more.

6. A thermally conductive sheet obtained by curing the thermally conductive two-part addition curing type silicone composition according to any one of claims 1 to 3.

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