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JP-2026075600-A - Thermally conductive silicone composition and its cured product

JP2026075600AJP 2026075600 AJP2026075600 AJP 2026075600AJP-2026075600-A

Abstract

[Problem] The present invention provides a thermally conductive silicone composition and a cured product thereof that are excellent in insulating properties, thermal conductivity, and processability. In particular, it provides a highly thermally conductive silicone composition and a cured product thereof in which the hardness of the cured product does not decrease easily even if a long time elapses between mixing the curing agent and heat curing. [Solution] A thermally conductive silicone composition comprising: (A) 100 parts by mass of an alkenyl group-containing organopolysiloxane consisting of components (A-1) and (A-2); (B) 5,300 to 7,500 parts by mass of a thermally conductive filler consisting of components (C-1) to (C-3) of an organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to a silicon atom; (D) 0.1 to 2,000 ppm in terms of the mass of platinum group metal elements; and (E) 1.0 to 1.4 parts by mass of an addition reaction control agent. [Selection Diagram] None

Inventors

  • 森村 俊晴

Assignees

  • 信越化学工業株式会社

Dates

Publication Date
20260508
Application Date
20250930
Priority Date
20241022

Claims (9)

  1. A thermally conductive silicone composition, (A) Organopolysiloxane having at least two alkenyl groups in one molecule, comprising the following components (A-1) and (A-2), with a mass ratio of (A-1)/(A-2) of 70/30 to 30/70: 100 parts by mass, (A-1) Alkenyl group-containing organopolysiloxane having a main chain consisting of repeating diorganosiloxane units, an average degree of polymerization of 145 to 220, and a kinematic viscosity of 400 to 1,000 mm² /s at 25°C. (A-2) Alkenyl group-containing organopolysiloxane having a main chain consisting of repeating diorganosiloxane units, an average degree of polymerization of 450 to 1,100, and a kinematic viscosity of 5,000 to 100,000 mm² /s at 25°C. (B) Organohydrogenpolysiloxane having at least two hydrogen atoms directly bonded to a silicon atom: an amount such that the number of moles of hydrogen atoms directly bonded to the silicon atom is 0.1 to 5.0 times the number of moles of alkenyl groups derived from component (A), (C) Thermally conductive filler consisting of the following components (C-1) to (C-3): 5,300 to 7,500 parts by mass, (C-1) Spherical alumina filler with an average particle size greater than 70 μm and less than or equal to 135 μm: 2,300 to 3,800 parts by mass, (C-2) Spherical alumina filler having an average particle size greater than 8 μm and less than or equal to 40 μm: 1,000 to 2,300 parts by mass, (C-3) Irregularly shaped alumina filler having an average particle size greater than 0.4 μm and less than or equal to 4 μm: 1,200 to 2,300 parts by mass, (D) Platinum group metal-based hardening catalyst: 0.1 to 2,000 ppm in terms of the mass of platinum group metal elements relative to component (A), (E) Addition reaction control agent: A thermally conductive silicone composition characterized by containing 1.0 to 1.4 parts by mass.
  2. Furthermore, as component (F), (F-1) Alkoxysilane compounds represented by the following general formula (1), and R 1 aR 2 bSi (OR 3 ) 4-a-b (1) (In the formula, R1 is independently an alkyl group having 6 to 15 carbon atoms, R2 is independently an unsubstituted or substituted monovalent hydrocarbon group having 1 to 12 carbon atoms, R3 is independently an alkyl group having 1 to 6 carbon atoms, a is an integer from 1 to 3, b is an integer from 0 to 2, where a + b is an integer from 1 to 3.) (F-2) Dimethylpolysiloxane in which the molecular chain ends represented by the following general formula (2) are sealed with trialkoxysilyl groups, (In the formula, R4 is independently an alkyl group having 1 to 6 carbon atoms, and c is an integer from 5 to 100.) The thermally conductive silicone composition according to claim 1, characterized in that it contains at least one selected from the group consisting of the above in 0.01 to 300 parts by mass per 100 parts by mass of component (A).
  3. The thermally conductive silicone composition according to claim 1, characterized in that the ratio of the number of moles of hydrogen atoms directly bonded to the silicon atoms of component (B) to the number of moles of alkenyl groups derived from component (A) is 1.7 to 2.1.
  4. The thermally conductive silicone composition according to claim 1, characterized in that its viscosity at 23°C is 700 Pa·s or less.
  5. A cured thermally conductive silicone product characterized by being a cured product of the thermally conductive silicone composition described in claims 1 to 4.
  6. The thermally conductive silicone cured product according to claim 5, characterized in that the decrease in Asker C hardness of a cured product heated and cured 15 hours after the addition of components (B) and (E) is 5 points or less compared to the Asker C hardness of a cured product heated and cured 1 hour after the addition of components (B) and (E).
  7. The thermally conductive silicone cured product according to claim 5, characterized in that its thermal conductivity at 23°C is 7.5 W/m·K or higher.
  8. The thermally conductive silicone cured product according to claim 5, characterized in that the dielectric breakdown voltage at a thickness of 1 mm is 10 kV/mm or more.
  9. The heat-conductive silicone cured product according to claim 5, characterized in that its shape is sheet-like.

Description

This invention relates to a thermally conductive silicone composition and its cured product. In recent years, the increasing performance, miniaturization, and high integration of electronic components such as CPUs, driver ICs, and memory used in electronic devices like smartphones, personal computers, and car navigation systems have led to the generation of large amounts of heat at high density. Conventional technologies have resulted in problems such as overheating of electronic devices and components, causing malfunctions and failures. Therefore, many heat dissipation methods and various heat dissipation materials have been proposed to suppress the temperature rise of electronic devices and components. Recently, there has been a growing demand for high thermal conductivity materials with excellent thermal conductivity. Conventionally, in electronic devices, heat sinks made of metal plates with high thermal conductivity, such as aluminum or copper, have been used to suppress the temperature rise of the operating chip. These heat sinks conduct the heat generated from the chip and release that heat through the temperature difference with the surrounding air. Furthermore, in order to efficiently transfer the heat generated from the heat-generating components to the heat sink, it is necessary to ensure that the heat sink is in close contact with the components. However, due to differences in the height of each component and tolerances caused by assembly processes, a flexible sheet or grease is interposed between the component and the heat sink, and heat conduction to the heat sink is achieved through these materials. There are various types of heat dissipation materials, and numerous materials have been proposed, including heat dissipation greases and flexible heat dissipation sheets. Sheet-type heat dissipation materials are in the form of a product sandwiched between release films, requiring no heating during use and offering excellent handling. For example, an insulating composition is disclosed (Patent Document 1) containing at least one metal oxide selected from beryllium oxide, aluminum oxide, hydrated aluminum oxide, magnesium oxide, and zinc oxide in 100 parts by mass of synthetic rubber such as silicone rubber. Flexible thermal conductive sheets offer superior handling compared to grease and are used in a variety of fields. Silicone is known as a material with particularly excellent heat resistance, weather resistance, and flame retardancy, and a silicone-based, thermally conductive silicone rubber sheet with a thermal conductivity of 7.5 W/m·K or higher has been proposed (Patent Document 2). These high-thermal-conductivity silicone rubber sheets are formed by curing a composition consisting of thermally conductive filler and silicone, and then molding it into a sheet. However, when the filling ratio of thermally conductive filler increases, impurities contained in the thermally conductive filler cause a problem where the hardness at the time of curing decreases as the time elapsed from mixing the curing agent with the thermally conductive filler-containing silicone composition until heat curing increases. To solve this problem, one method is to reduce the filling rate of the thermally conductive filler. However, if the filling rate is reduced too much, the thermal conductivity will decrease significantly. Another method is to suppress the decrease in hardness by increasing the proportion of high-viscosity oil in the silicone composition. However, if the proportion of high-viscosity oil is increased too much, the viscosity of the composition becomes high, resulting in poor moldability of the sheet. Japanese Unexamined Patent Publication No. 47-032400Japanese Patent Publication No. 2023-153695 As described above, there was a need for the development of a thermally conductive silicone composition and its cured product that excels in insulation, thermal conductivity, processability, and suppression of hardness reduction when cured after a period of time has elapsed since the addition of the curing agent. The inventors of this invention conducted diligent research to solve the above problems and, as a result, discovered that by controlling the amount of addition reaction control agent and the ratio of the following components (A-1)/(A-2), it is possible to suppress the decrease in hardness that occurs when time elapses between the addition of the curing agent and heat curing, thereby enabling sheet molding with stable hardness. This led to the completion of the present invention. In other words, the present invention relates to a thermally conductive silicone composition, (A) Organopolysiloxane having at least two alkenyl groups in one molecule, comprising the following components (A-1) and (A-2), with a mass ratio of (A-1)/(A-2) of 70/30 to 30/70: 100 parts by mass, (A-1) Alkenyl group-containing organopolysiloxane having a main chain consisting of repeating diorganosiloxane units, an average degree of p