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US-20260125557-A1 - THERMALLY CONDUCTIVE SILICONE COMPOSITION AND CURED PRODUCT THEREOF

US20260125557A1US 20260125557 A1US20260125557 A1US 20260125557A1US-20260125557-A1

Abstract

A thermally conductive silicone composition, which is a liquid silicone and which is curable, contains: (A-1) an organopolysiloxane having an alkenyl group at each end of the molecular chain; (A-2) an organopolysiloxane having an alkenyl group at one end of the molecular chain and no reactive functional group at the other end of the molecular chain; (A-3) an organopolysiloxane having three or more alkenyl groups in the molecule; (A-4) an organohydrogenpolysiloxane having a silicon atom-bonded hydrogen atom at one or both ends of the molecular chain and no silicon atom-bonded hydrogen atoms in side chains of the molecular chain; (B) a hydrosilylation catalyst; and (C) a thermally conductive filler.

Inventors

  • Takahiro Asami

Assignees

  • FUKOKU CO., LTD.

Dates

Publication Date
20260507
Application Date
20230207
Priority Date
20221004

Claims (10)

  1. 1 . A thermally conductive silicone composition, which is a liquid silicone and which is curable, the thermally conductive silicone composition comprising: (A-1) an organopolysiloxane having an alkenyl group at each end of the molecular chain; (A-2) an organopolysiloxane having an alkenyl group at one end of the molecular chain and no reactive functional group at the other end of the molecular chain; (A-3) an organopolysiloxane having three or more alkenyl groups in the molecule; (A-4) an organohydrogenpolysiloxane having a silicon atom-bonded hydrogen atom at one or both ends of the molecular chain and no silicon atom-bonded hydrogen atoms in side chains of the molecular chain; (B) a hydrosilylation catalyst; and (C) a thermally conductive filler.
  2. 2 . The thermally conductive silicone composition according to claim 1 , wherein the liquid silicone comprises an organopolysiloxane represented by the following general Formula (1):
  3. 3 . The thermally conductive silicone composition according to claim 1 , wherein the thermally conductive filler consists of at least one of aluminum hydroxide and zinc oxide.
  4. 4 . The thermally conductive silicone composition according to claim 3 , wherein a minimum value E min of an average square error E expressed by the following Formula (a3) and a coefficient a 0 corresponding to the minimum value E min satisfy 0≤E min ≤45 and 5.7≤a 0 ≤13.0: [ Math . 1 ]  E = 1 R ⁢ ∑ n = 1 R ( c n - y n ) 2 ( a ⁢ 3 ) wherein, y n = { ax n 1 / 2 ( ax n 1 / 2 < 100 ) 100 ( ax n 1 / 2 ≧ 100 ) ( a4 ) and : x n = k n - 1 ⁢ P ⁢ and ( a1 ) x R = Q ( a2 ) where R is the number of particle sizes, which are calculation points for the cumulative frequency in the cumulative particle size distribution on a volume basis of the thermally conductive filler; P (μm) and Q (μm) are minimum and maximum particle sizes, respectively, of the thermally conductive filler among the particle sizes that are calculation points for the cumulative frequency; x n (μm) (where n is an integer satisfying 1≤n≤R) is a particle size of the thermally conductive filler at the nth calculation point defined to satisfy Formulae (a1) and (a2); and c n (%) is a cumulative frequency, on a volume basis, of the particle size of the thermally conductive filler corresponding to the particle size x n in the cumulative particle size distribution.
  5. 5 . The thermally conductive silicone composition according to claim 3 , wherein a percentage of the thermally conductive filler contained in the thermally conductive silicone composition is between 68.0% by volume and 75.0% by volume.
  6. 6 . A cured product cured by a hydrosilylation reaction of the thermally conductive silicone composition according to claim 1 .
  7. 7 . The thermally conductive silicone composition according to claim 2 , wherein the thermally conductive filler consists of at least one of aluminum hydroxide and zinc oxide.
  8. 8 . The thermally conductive silicone composition according to claim 7 , wherein a minimum value E min of an average square error E expressed by the following Formula (a3) and a coefficient a 0 corresponding to the minimum value E min satisfy 0≤E min ≤45 and 5.7≤a 0 ≤13.0: [ Math . 2 ]  E = 1 R ⁢ ∑ n = 1 R ( c n - y n ) 2 ( a ⁢ 3 ) wherein, y n = { ax n 1 / 2 ( ax n 1 / 2 < 100 ) 100 ( ax n 1 / 2 ≧ 100 ) ( a4 ) and : x n = k n - 1 ⁢ P ⁢ and ( a1 ) x R = Q ( a2 ) where R is the number of particle sizes, which are calculation points for the cumulative frequency in the cumulative particle size distribution on a volume basis of the thermally conductive filler; P (μm) and Q (μm) are minimum and maximum particle sizes, respectively, of the thermally conductive filler among the particle sizes that are calculation points for the cumulative frequency; x n (μm) (where n is an integer satisfying 1≤n≤R) is a particle size of the thermally conductive filler at the nth calculation point defined to satisfy Formulae (a1) and (a2); and c n (%) is a cumulative frequency, on a volume basis, of the particle size of the thermally conductive filler corresponding to the particle size x n in the cumulative particle size distribution.
  9. 9 . The thermally conductive silicone composition according to claim 7 , wherein a percentage of the thermally conductive filler contained in the thermally conductive silicone composition is between 68.0% by volume and 75.0% by volume.
  10. 10 . A cured product cured by a hydrosilylation reaction of the thermally conductive silicone composition according to claim 2 .

Description

CROSS-REFERENCE TO RELATED APPLICATIONS The present application claims priority under 35 U.S.C. § 371 to International Patent Application No. PCT/JP2023/003987, filed Feb. 7, 2023, which claims priority to and the benefit of International Patent Application No. PCT/JP2022/037078, filed on Oct. 4, 2022. The contents of these applications are hereby incorporated by reference in their entireties. TECHNICAL FIELD The present invention relates to thermally conductive silicone compositions and cured products of these thermally conductive compositions. BACKGROUND ART In recent years, electric and electronic components have become smaller and more integrated, and the amount of heat generated has increased accordingly. Similarly, the capacity and output of secondary batteries have been increasing, and the amount of heat generated has also been increasing. Since excessive heat rise of heat-generating elements such as electric and electronic components and secondary batteries must be prevented, a structure is adopted in which the heat generated by the heat-generating elements is dissipated to heat-dissipating elements or an exterior case. Thermally conductive compositions or their cured products are interposed between heat-generating elements and heat-dissipating elements to strengthen thermal bonding between the heat-generating elements and the heat-dissipating elements and to efficiently transfer heat from the heat-generating elements to the heat-dissipating elements. Thermally conductive compositions or their cured products are commercially available in various forms, such as heat dissipation grease and heat dissipation sheets. Among these thermally conductive compositions and their cured products, referred to as gap fillers are widely used because they are liquid when applied to heat-generating elements or heat-dissipating elements, have excellent tracking properties for uneven surfaces (i.e., gap-filling properties), enable precision coating, and harden over time to prevent dripping or a pump-out phenomenon. In order to improve the heat dissipation performance by interposing a thermally conductive composition or its cured product between a heat-generating element and a heat-dissipating element, the thermally conductive composition or its cured product must first have high thermal conductivity. In order to increase thermal conductivity, the thermally conductive composition is mixed with a thermally conductive filler having high thermal conductivity. Reducing the thermal resistance at the interface between the heat-generating element and the thermally conductive composition or its cured product and at the interface between the heat-dissipating element and the thermally conductive composition or its cured product is also of crucial importance for improving the heat dissipation properties. However, increasing the mixing ratio of the thermally conductive filler to obtain high thermal conductivity also increases the compound viscosity of the thermally conductive composition, resulting in a decrease in adhesion when the thermally conductive composition or its cured product comes into contact with a heat-generating element or a heat-dissipating element as well as an increase in thermal resistance at the interface. Increasing the mixing ratio of the thermally conductive filler also increases the hardness of the cured product of the thermally conductive composition. High hardness of a cured product decreases impact absorption ability, decreases the effect of mitigating stress generated by expansion and contraction due to temperature changes, and increases the mechanical impact on the electric and electronic components and secondary batteries that are the heat-generating elements. When a thermally conductive composition and its cured product contain a volatile component or generate gases due to a chemical reaction that progresses over time, tiny gaps are generated at the interface with the heat-generating element or heat-dissipating element or bubbles are generated inside the thermally conductive composition and its cured product. Gaps and bubbles interfere with heat conduction of the thermally conductive composition or its cured product. A representative example of a thermally conductive composition called gap filler is a composition in which a liquid (i.e., uncured silicone) matrix is mixed with a thermally conductive filler and other materials. For example, Patent Literature 1 discloses a thermally conductive silicone gel composition containing: (A) an alkenyl group-containing organopolysiloxane; (B) a straight-chain organohydrogenpolysiloxane; (C) a catalyst for a hydrosilylation reaction; and (D) a thermally conductive filler. The thermally conductive filler is surface-treated with an alkoxysilane having an alkyl group with six or more carbon atoms in the molecule. This allows reduction of the viscosity of the thermally conductive silicone gel composition even when a large amount of the thermally conductive filler is a