Heat conductive resin composition

Abstract

To provide a heat conductive resin composition which suppresses bleeding to a surface of a phase change material and has high reliability, while improving compressibility at high temperature and handleability at normal temperature.SOLUTION: A heat conductive resin composition contains a silicone resin (A), a heat conductive filler (B), and a graft copolymer (C) represented by the following structural formula, wherein the melting point of the graft copolymer (C) is 35°C or higher.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a thermally conductive resin composition. [Background technology]

[0002] In recent years, as electrical equipment has become smaller and more powerful, there has been a demand for material technologies that can efficiently dissipate the heat generated during operation.Heat from heat sources such as IC chips is dissipated through heat sinks, and to ensure efficient thermal conduction between the heat source and the heat sink, a resin composition called TIM (Thermal Interface Material) is often sandwiched between the heat source and the heat sink.

[0003] TIM is a resin composition that combines resin and thermally conductive filler, and is often used in sheet form with a thickness corresponding to the gap between the heat source and the heat sink. In recent years, there has been a demand for highly compressible sheets to broaden the TIM's tolerance range for gap assembly tolerances. Furthermore, high compressibility can cause chip damage when high loads are applied, so the sheets must be flexible. However, imparting flexibility to the sheet tends to make it difficult to handle. Resin compositions containing a matrix such as a silicone resin, a phase change material (PCM), and a thermally conductive filler have been proposed as a means of resolving this trade-off between compressibility and handleability.

[0004] For example, Patent Document 1 discloses a thermal interface material comprising a polymer matrix containing a long-chain alkyl silicone oil, a long-chain vinyl-terminated alkyl silicone oil, and a single-terminated hydroxyl-terminated silicone oil, at least one of which has at least one branched chain of 2 to 32 alkyl carbon atoms, and a thermally conductive filler. It also describes that the thermal interface material is useful for transferring heat from a heat-generating electronic device to a heat dissipation structure such as a heat spreader or heat sink. Patent Document 2 discloses an invention relating to a heat dissipation sheet that softens when heated, has good adhesion between a heat generating element and a heat sink, and has good thermal performance. The heat dissipation sheet contains a polymer gel such as silicone gel, a compound that is solid or paste-like at room temperature but becomes liquid when heated, and a thermally conductive filler.

[0005] Patent Document 3 discloses an invention relating to a heat-softening, heat-conductive silicone grease composition used at the thermal interface between a heat-generating electronic component and a heat-dissipating component such as a heat sink or metal housing, which contains a silicone wax having a melting point of 30 to 80°C, a specific organopolysiloxane, and a heat-conductive filler in specified amounts. Patent Document 4 discloses an invention relating to a thermally conductive film that is easy to handle in film form at room temperature and softens when heated, and that contains a specific silicone resin with a non-fluidity, a wax with a melting point of 20 to 60°C, and a thermally conductive filler in a specified amount.

[0006] Patent Document 5 describes a thermal interface material that undergoes a phase change at the operating temperature of a microprocessor and transfers heat generated by a heat source to a heat sink, and includes a phase change substance that softens near the operating temperature of the heat source, a polymer component, a substance that changes the temperature at which the phase change substance softens, and a material that contains a thermally conductive filler. Patent Document 6 discloses an invention relating to a thermally conductive sheet that contains a binder component that is a mixture of a silicone matrix and a hydrocarbon compound, and a thermally conductive filler, and that has a compressibility of 15% or more at 80°C and 0.276 MPa and shape retention. It also describes that the thermally conductive sheet has good shape retention and reliability while maintaining a certain degree of flexibility and good thermal conductivity during use. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2022-530372 [Patent Document 2] Patent No. 3712943 [Patent Document 3] Patent No. 6436035 [Patent Document 4] Japanese Patent Application Publication No. 2023-47991 [Patent Document 5] Japanese Patent Application Laid-Open No. 2001-89756 [Patent Document 6] International Publication No. 2022 / 070568 Summary of the Invention [Problem to be solved by the invention]

[0008] Although the phase change materials (PCMs) disclosed as prior art can improve the compressibility at high temperatures and the handleability at room temperature of resin compositions containing them, the PCMs can sometimes bleed onto the surface at high temperatures, leaving room for improvement in terms of reliability. Therefore, an object of the present invention is to provide a highly reliable thermally conductive resin composition that has good compressibility at high temperatures (e.g., about 60°C) and good handleability at room temperature (25°C), while suppressing bleeding of the phase-change material onto the surface. [Means for solving the problem]

[0009] The present inventors have discovered that the above-mentioned problems can be solved by a thermally conductive resin composition comprising a silicone resin (A), a thermally conductive filler (B), and a compound (C) having a specific structure, wherein the compound (C) has a melting point of 35°C or higher and is a graft copolymer, and have completed the present invention.

[0010] That is, the present invention relates to the following [1] to [7]. [1] A thermally conductive resin composition comprising a silicone resin (A), a thermally conductive filler (B), and a compound (C) having a structure represented by the following formula (1), wherein the melting point of the compound (C) is 35°C or higher, and the compound (C) is a graft copolymer: [ka] (In formula (1), X1 and X2 are each independently a trivalent organic group, Y1 and Y2 are each independently a divalent organic group, Z is a monovalent organic group, R is each independently a monovalent organic group, k is a number of 16 or more and 33 or less, n, r, and s are each a number of 1 or more, m is a number of 0.5 or more, and p and q are each a number of 0 or more.) [2] The thermally conductive resin composition according to [1] above, wherein X1 and X2 are each independently a trivalent saturated hydrocarbon group having from 2 to 6 carbon atoms, and Y1 and Y2 are each independently a divalent organic group containing an ester group or an amide group. [3] The thermally conductive resin composition according to [1] or [2] above, wherein the content of the compound (C) is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the silicone resin (A). [4] The thermally conductive resin composition according to any one of the above [1] to [3], wherein m, r, and n satisfy the relationship of the following formula (α): m×r / (m+n)≧0.3 Formula (α) [5] The thermally conductive resin composition according to any one of the above [1] to [4], wherein the thermally conductive filler (B) is at least one selected from the group consisting of metals, inorganic hydroxides, inorganic oxides, inorganic nitrides, inorganic carbides, carbon fibers, graphite, and diamonds. [6] A cured product of the thermally conductive resin composition obtained by curing the thermally conductive resin composition according to any one of [1] to [5] above. [7] A thermally conductive sheet comprising a cured product of the thermally conductive resin composition described in [6] above. [Effects of the Invention]

[0011] According to the present invention, it is possible to provide a highly reliable thermally conductive resin composition that has good compressibility at high temperatures and good handleability at room temperature, while suppressing bleeding of the phase change material onto the surface. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram illustrating a measuring device for measuring thermal resistance. DETAILED DESCRIPTION OF THE INVENTION

[0013] [Thermal conductive resin composition] The thermally conductive resin composition of the present invention comprises a silicone resin (A), a thermally conductive filler (B), and a compound (C) having a structure represented by the following formula (1), wherein the melting point of the compound (C) is 35°C or higher, and the compound (C) is a graft copolymer: [ka] (In formula (1), X1 and X2 are each independently a trivalent organic group, Y1 and Y2 are each independently a divalent organic group, Z is a monovalent organic group, R is each independently a monovalent organic group, k is a number of 16 or more and 33 or less, n, r, and s are each a number of 1 or more, m is a number of 0.5 or more, and p and q are each a number of 0 or more.)

[0014] <Compound (C)> The compound (C) of the present invention has a structure represented by formula (1) and is a graft copolymer. The compound (C) functions as a phase change material, improving the handleability of a cured product of the thermally conductive resin composition (e.g., a sheet-like cured product) at room temperature (25°C) while increasing its compressibility at high temperatures (e.g., 60°C). Furthermore, because the compound (C) has the specific structure represented by formula (1), it can reduce the amount of surface bleeding in the cured product of the thermally conductive resin composition, thereby improving the reliability of the product.

[0015] The melting point of compound C is at least 35° C. If the melting point of compound C is less than 35° C., the handleability of the cured product of the thermally conductive resin composition at room temperature and the compressibility at high temperatures will be poor. The melting point of compound C is preferably 40° C. or higher, more preferably 42° C. or higher. From the viewpoint of further increasing compressibility at high temperatures, the melting point of compound C is preferably 60° C. or lower, more preferably 58° C. or lower. The melting point of Compound C was measured by differential scanning calorimetry, as described in detail in the Examples.

[0016] Compound (C) has a structure represented by the following formula (1): [ka] (In formula (1), X1 and X2 are each independently a trivalent organic group, Y1 and Y2 are each independently a divalent organic group, Z is a monovalent organic group, R is each independently a monovalent organic group, k is an integer of 16 or more and 33 or less, n, r, and s are each a number of 1 or more, m is a number of 0.5 or more, and p and q are each a number of 0 or more.)

[0017] Compound (C) is a graft copolymer in which the main chain is constituted by X1 and X2, and which has a moiety having a long-chain alkyl group as a branched chain and a moiety having a silicone chain. Compound (C) is a compound having a unit represented by the following formula (2) and a unit represented by formula (3) in a molar ratio of n:m. In this specification, the unit represented by formula (2) is also referred to as a long-chain alkyl group-containing unit, and the unit represented by formula (3) is also referred to as a silicone chain-containing unit. [ka] (In formula (2) and formula (3), X1, X2, Y1, Y2, Z, R, k, p, q, r, and s have the same meanings as in formula (1)).

[0018] Compound (C) has a long-chain alkyl group-containing unit, which is crystalline, and therefore has a melting point above a certain level. Therefore, it is unmelted at room temperature but melts at high temperatures. As a result, a thermally conductive resin composition containing compound (C) (and a sheet made of the thermally conductive resin composition) is thought to have good handleability at room temperature and high compressibility at high temperatures. Furthermore, compound (C) has a silicone chain-containing unit, which makes it compatible with silicone resins and their cured products, improving dispersibility. Furthermore, the presence of silicone chains in the side chains is thought to reduce bleeding and further increase compressibility at high temperatures.

[0019] In compound (C), X1 and X2 are each independently a trivalent organic group. X1 and X2 may contain heteroatoms such as oxygen, nitrogen, or sulfur atoms, but preferably do not contain heteroatoms. That is, X1 and X2 are each independently preferably a hydrocarbon group. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, but is more preferably an aliphatic hydrocarbon group. X1 and X2 are preferably each independently a trivalent hydrocarbon group having from 2 to 6 carbon atoms, more preferably a hydrocarbon group having from 2 to 3 carbon atoms. The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, but is preferably a saturated hydrocarbon group. It is more preferable that X1 and X2 are each independently a group represented by the following formula (4) or (5): It is particularly preferable that X1 is a group represented by formula (4) and X2 is a group represented by formula (5). [ka] (In formulas (4) and (5), *1 is a bond bonded to an atom constituting the main chain of compound (C), and *2 and *3 are bonds bonded to Y1 or Y2.)

[0020] Y1 and Y2 are each independently a divalent organic group. Y1 and Y2 are each independently an organic group having 1 to 10 carbon atoms, preferably an organic group having 1 to 6 carbon atoms. Y1 and Y2 may have a heteroatom such as an oxygen atom, a nitrogen atom, or a sulfur atom, preferably an oxygen atom or a nitrogen atom, more preferably an oxygen atom. More specifically, Y1 and Y2 are preferably each independently a divalent organic group containing an ester group or an amide group, and more preferably an organic group containing an ester group. Among these, it is more preferable that Y1 and Y2 are each independently a group represented by the following formula (6) or (7). It is particularly preferable that Y1 is a group represented by formula (6) and Y2 is a group represented by formula (7). [ka] (In formula (6) and formula (7), *4 is a bond bonding to an atom constituting the main chain of compound (C), and *5 is a bond bonding to an atom constituting the side chain of compound (C). Ra in formula (7) is an alkylene group having 1 to 10 carbon atoms, preferably an alkylene group having 1 to 4 carbon atoms.)

[0021] Z is a monovalent organic group. The organic group preferably has 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms. Z may have a heteroatom such as an oxygen atom, a nitrogen atom, or a sulfur atom, but preferably does not have a heteroatom. That is, Z is preferably a hydrocarbon group. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, but is preferably an aliphatic hydrocarbon group. Z is preferably a hydrocarbon group having from 1 to 10 carbon atoms, more preferably from 1 to 4 carbon atoms. The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, but is preferably a saturated hydrocarbon group.

[0022] In formula (1), k is the number of methylene groups (-CH2-) and is a number between 16 and 33. By setting k within this range, compound (C) has a melting point above a certain level, and the cured product of the thermally conductive resin composition can be made easy to handle at room temperature while improving its compressibility at high temperatures. k is preferably between 16 and 30, and more preferably between 17 and 25. In formula (1), the moiety forming the long-chain alkyl group bonded to Y, i.e., the "-(CH2)k-" moiety, exists in plurality according to the value of n. k is the average value of the plurality of "-(CH2)k-".

[0023] -(SiO 4 / 2 ) p -(SiRO 3 / 2 ) q -(SiR2O 2 / 2 ) r -(SiR3O 1 / 2 ) s The - part is a silicone chain. Generally, it is SiR3O as shown below. 1 / 2 The part is M unit, SiR2O 2 / 2 The part is D unit, SiRO 3 / 2 The part is T unit, SiO 4 / 2 This part is called the Q unit. [ka] The silicone chain in formula (1) is SiR3O 1 / 2 (M units), SiR2O 2 / 2 (D unit) and SiRO 3 / 2 (T units) and SiO 4 / 2 (Q units) in the silicone chain. 1 / 2 (M units), SiR2O 2 / 2 (D units), SiRO 3 / 2 (T units), SiO 4 / 2 The arrangement of the Q units is not particularly limited. In formula (1), p, q, r, and s each represent SiO 4 / 2 (Q units), SiRO 3 / 2 (T units), SiR2O2 / 2 (D units), SiR3O 1 / 2 Represents the number of (M units). In addition, SiR3O 1 / 2 (M unit) is monovalent and is the terminal part of the silicone chain. SiRO 2 / 2 (D unit) is divalent and is the linear part of the silicone chain. 3 / 2 (T unit) is trivalent, and the three oxygen atoms are each bonded to one of the units to form a branched structure. SiO 4 / 2 (Q unit) is tetravalent, and the four oxygen atoms are each bonded to one of the units to form a branched structure.

[0024] R in the silicone chain bonded to Y2 in formula (1) is a monovalent organic group. The organic group preferably has 1 to 10 carbon atoms, more preferably 1 to 4 carbon atoms. R may have a heteroatom such as an oxygen atom, a nitrogen atom, or a sulfur atom, but preferably does not have a heteroatom. In other words, R is preferably a hydrocarbon group. The hydrocarbon group may be an aliphatic hydrocarbon group or an aromatic hydrocarbon group, but is preferably an aliphatic hydrocarbon group. R is preferably a monovalent hydrocarbon group having from 1 to 10 carbon atoms, and more preferably a hydrocarbon group having from 1 to 4 carbon atoms. The hydrocarbon group may be a saturated hydrocarbon group or an unsaturated hydrocarbon group, but is preferably a saturated hydrocarbon group.

[0025] In the compound of formula (1), r is a number equal to or greater than 1. From the viewpoint of improving the compressibility of the cured product of the thermally conductive resin composition and reducing bleeding, r is preferably equal to or greater than 5 and equal to or less than 200, more preferably equal to or greater than 10 and equal to or less than 150, and even more preferably equal to or greater than 30 and equal to or less than 100.

[0026] It is also preferable that m, r, and n in formula (1) satisfy the relationship of the following formula (α). m*r / (m+n)≧0.3 Formula (α) As described above, when m*r / (m+n) is 0.3 or more, the compressibility of the cured product of the thermally conductive resin composition is increased, and further, the reduction in bleeding is likely to be reduced. Note that m*r / (m+n) is an index of the content of the linear silicone chain portion (D unit) in the compound of formula (1), and a certain value or more of this index is effective for the compressibility and bleeding reduction effects of the present invention. From this viewpoint, m*r / (m+n) is preferably 0.5 or more, more preferably 0.8 or more, even more preferably 1.2 or more, and is preferably 3.0 or less, more preferably 2.5 or less.

[0027] In the compound of formula (1), s is a number of 1 or more. s is preferably 1 or more and 10 or less, more preferably 1 or more and 5 or less, and even more preferably 1. In the compound of formula (1), p is a number of 0 or more, preferably 0 or more and 5 or less, more preferably 0 or more and 1 or less, and even more preferably 0. In the compound of formula (1), q is a number of 0 or more, preferably 0 or more and 5 or less, more preferably 0 or more and 1 or less, and even more preferably 0. In formula (1), there are multiple silicone chains bonded to Y2 depending on the number m. The values ​​of p, q, r, and s in formula (1) are calculated as the average values ​​of the multiple silicone chains.

[0028] In formula (1), n ​​and m correspond to the number of long-chain alkyl group-containing units and the number of silicone chain-containing units, respectively. These numbers are preferably set as follows, from the viewpoint of improving the compressibility of the cured product of the thermally conductive resin composition at high temperatures while reducing bleeding. n is a number of 1 or more, preferably 10 or more and 500 or less, more preferably 50 or more and 300 or less, and even more preferably 100 or more and 250 or less. m is a number of 0.5 or more, preferably 0.5 or more and 50 or less, more preferably 1 or more and 50 or less, even more preferably 1 or more and 30 or less, and even more preferably 2 or more and 10 or less.

[0029] n, m, k, p, q, r, and s in formula (1) are 1 H-NMR, 29 It can be determined by Si-NMR, size exclusion chromatography, etc., and details are as described in the Examples.

[0030] The method for producing compound (C) is not particularly limited, but examples include a method in which a monomer (crystalline monomer) for forming the long-chain alkyl group-containing unit represented by the above formula (2) and a monomer (silicone monomer) for forming the silicone chain-containing unit represented by formula (3) are prepared and polymerized. Examples of the crystalline monomer include (meth)acrylic acid alkyl esters. Examples of the silicone monomer include single-end (meth)acrylic acid-modified silicones in which one end of the silicone chain is modified with (meth)acrylic acid. Note that (meth)acrylic is a concept that includes both acrylic and methacrylic.

[0031] The content of the compound (C) in the thermally conductive resin composition is not particularly limited, but is preferably 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the silicone resin (A). When the content of compound (C) is 10 parts by mass or more, the handleability and compressibility of the cured product of the thermally conductive resin composition are likely to be improved, and when the content of compound (C) is 50 parts by mass or less, the amount of bleeding in the cured product of the thermally conductive resin composition is likely to be reduced. The content of the compound (C) in the thermally conductive resin composition is preferably 15 to 40 parts by mass, more preferably 20 to 30 parts by mass, per 100 parts by mass of the silicone resin (A).

[0032] <Silicone resin (A)> The thermally conductive resin composition of the present invention contains a silicone resin (A), which is a component that forms the matrix of the thermally conductive resin composition, and a thermally conductive filler (B), which will be described later, is dispersed in the silicone resin (A). The silicone resin (A) may be a non-curable silicone resin or a curable silicone resin, but is preferably a curable silicone resin. The curable silicone resin may be either a condensation curable silicone resin or an addition reaction curable silicone resin, but is preferably an addition reaction curable silicone resin. In addition, the silicone resin is preferably a silicone rubber. The addition reaction curable silicone resin preferably comprises a silicone compound (silicone base) as the base component and a curing agent (silicone curing agent) that cures the base component. The silicone compound used as the base component is preferably an organopolysiloxane having an alkenyl group, more preferably an organopolysiloxane having a vinyl group. The number of alkenyl groups in one molecule of the organopolysiloxane is preferably two or more, and more preferably contains alkenyl groups at both ends. Specific examples of organopolysiloxanes having vinyl groups include organopolysiloxanes having vinyl groups at both ends, such as polydimethylsiloxane having vinyl groups at both ends, polyphenylmethylsiloxane having vinyl groups at both ends, a copolymer of dimethylsiloxane and diphenylsiloxane having vinyl groups at both ends, a copolymer of dimethylsiloxane and phenylmethylsiloxane having vinyl groups at both ends, and a copolymer of dimethylsiloxane and diethylsiloxane having vinyl groups at both ends.

[0033] The curing agent used in the addition reaction curing silicone resin is not particularly limited as long as it can cure the silicone compound that is the main component described above. However, organohydrogenpolysiloxane, which is an organopolysiloxane having two or more hydrosilyl groups (SiH) in one molecule, is preferred.

[0034] Examples of organohydrogenpolysiloxanes include methylhydrosiloxane-dimethylsiloxane copolymers, polymethylhydrosiloxanes, polyethylhydrosiloxanes, methylhydrosiloxane-phenylmethylsiloxane copolymers, etc. These may or may not contain hydrosilyl groups at the terminals.

[0035] The viscosity of the silicone resin at 25°C is preferably 5 mPa·s or more and 1000 mPa·s or less, more preferably 30 mPa·s or more and 700 mPa·s or less, and even more preferably 50 mPa·s or more and 600 mPa·s or less. The viscosity of the silicone resin is preferably measured using a viscometer (BROOKFIELD rotational viscometer DV-E) with a rotor of spindle No. 14 at a rotation speed of 5 rpm and a measurement temperature of 25°C. When the silicone resin contains a base agent and a curing agent, as described above, the viscosity of the mixture of the base agent and curing agent at 25°C should preferably be within the above range, but the viscosity of the base agent and curing agent at 25°C may also each be within the above range.

[0036] When an addition reaction curing type silicone resin is used as the silicone resin, a curing catalyst is usually blended into the thermally conductive resin composition. Examples of the curing catalyst include platinum-based catalysts, palladium-based catalysts, and rhodium-based catalysts, with platinum-based catalysts being preferred. The curing catalyst is used to cure the silicone compound, which is the raw material for the silicone resin, and the curing agent. The blending amount of the curing catalyst is usually 0.1 to 200 ppm, preferably 0.5 to 100 ppm, based on the total mass of the silicone resin.

[0037] When an addition reaction curing silicone resin is used as the silicone resin, a curing retarder may be blended into the thermally conductive resin composition. Known curing retarders can be used, including acetylene compounds such as 1-ethynyl-1-cyclohexanol and 3,5-dimethyl-1-hexyn-3-ol, various nitrogen compounds such as tributylamine and tetramethylethylenediamine, organic phosphorus compounds such as triphenylphosphine, oxime compounds, and organic chloro compounds. The addition of a curing retarder to suppress the catalytic activity of the curing catalyst can extend the shelf life and pot life of the thermally conductive resin composition. The content of the curing retarder in the thermally conductive resin composition is preferably 0.01 to 2 parts by mass, more preferably 0.1 to 1 part by mass, relative to 100 parts by mass of the silicone resin.

[0038] <Thermal conductive filler (B)> The thermally conductive resin composition of the present invention contains a thermally conductive filler (B). By containing the thermally conductive filler (B), the thermal conductivity of the thermally conductive resin composition and the cured product formed from the thermally conductive resin composition is improved, thereby enhancing heat dissipation. The type of thermally conductive filler (B) is not particularly limited, but is preferably at least one selected from the group consisting of metals, inorganic hydroxides, inorganic oxides, inorganic nitrides, inorganic carbides, carbon fibers, graphite, and diamonds.

[0039] Examples of the metal include aluminum, copper, nickel, and silver. Examples of the inorganic hydroxide include aluminum hydroxide, calcium hydroxide, and magnesium hydroxide. Examples of the inorganic oxide include iron oxide, zinc oxide, silicon oxide (silica), alumina, magnesium oxide, titanium oxide, cerium oxide, and zirconium oxide. Examples of the inorganic nitride include silicon nitride, aluminum nitride, gallium nitride, chromium nitride, tungsten nitride, magnesium nitride, molybdenum nitride, lithium nitride, and boron nitride. Examples of the inorganic carbide include silicon carbide, boron carbide, aluminum carbide, iron carbide, titanium carbide, vanadium carbide, chromium carbide, zirconium carbide, niobium carbide, and molybdenum carbide. Examples of the carbon fiber include pitch-based carbon fiber, PAN-based carbon fiber, fiber obtained by carbonizing resin fiber, fiber obtained by graphitizing resin fiber, and the like. The graphite may be, for example, natural graphite or artificial graphite. As the above-mentioned diamond, for example, it can be as-grown particle, or it can be the crushed diamond particle obtained by crushing as-grown particle, or it can be other diamond particle, and two or more of these can be used together.In addition, generally, as-grown particle is the crystalline diamond particle that maintains the shape at the time of synthesis without crushing, and has polyhedral shape.Crushed diamond particle is obtained by crushing crystalline diamond particle, and generally has angular shape due to crushing. These thermally conductive fillers may be used alone or in combination of two or more kinds.

[0040] As the thermally conductive filler (B), among the above, inorganic oxides are preferred, and alumina is particularly preferred, from the viewpoint of facilitating an improvement in thermal conductivity.

[0041] The average particle size of the thermally conductive filler (B) is not particularly limited, but is preferably 0.1 μm or more and 250 μm or less, and more preferably 0.2 μm or more and 100 μm or less. The average particle size can be measured using, for example, a laser diffraction particle size distribution analyzer manufactured by Horiba, Ltd., and the particle size at which the cumulative volume is 50% (d50) can be taken as the average particle size.

[0042] The thermally conductive filler (B) preferably contains two or more types of particles with different average particle sizes. When two or more types of particles with different average particle sizes are used, the particles with the smaller average particle size are inserted between the particles with the larger average particle size, which makes it easier to increase the loading rate of the thermally conductive filler while properly dispersing the thermally conductive filler in the silicone resin. The thermally conductive resin composition can be determined to contain two or more types of particles with different average particle sizes when two or more peaks appear in the particle size distribution of the thermally conductive filler.

[0043] The amount of the thermally conductive filler (B) is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and even more preferably 70% by mass or more, based on the total amount of the thermally conductive resin composition. When the amount of the thermally conductive filler is equal to or greater than these lower limits, the thermal conductivity of the thermally conductive resin composition is easily improved. The upper limit of the amount of the thermally conductive filler (B) is not particularly limited, but is, for example, 95% by mass or less, based on the total amount of the thermally conductive resin composition.

[0044] (Other additives) The thermally conductive resin composition of the present invention may contain, as necessary, additives generally used in thermally conductive resin compositions, such as a dispersant, an antioxidant, a heat stabilizer, a colorant, a flame retardant, and an antistatic agent.

[0045] <Cured product> The present invention can also provide a cured product of the thermally conductive resin composition obtained by curing the thermally conductive resin composition described above. The cured product can be formed by forming the thermally conductive resin composition into a predetermined shape, etc., and then appropriately heating it. Furthermore, the present invention can provide a thermally conductive sheet comprising a cured product of the thermally conductive resin composition.

[0046] [Thermal Conduction Sheet] The thermally conductive sheet of the present invention is a cured product of the thermally conductive resin composition, and has a thermally conductive filler dispersed in a matrix made of silicone resin.

[0047] (Thickness) The thickness of the thermally conductive sheet is not particularly limited and may be set appropriately depending on the shape and use of the electronic device in which the thermally conductive sheet is mounted, but may be in the range of 0.1 mm to 5 mm, for example. From the viewpoint of ease of use in small electronic devices, the thickness of the thermally conductive sheet is preferably 0.1 mm or more and 3 mm or less, and more preferably 0.1 mm or more and 1 mm or less.

[0048] (E hardness) The thermally conductive sheet of the present invention preferably has a type E hardness (hereinafter also referred to as "E hardness") as defined by JIS K6253 of 60 or less, more preferably 55 or less, and even more preferably 50 or less. When the E hardness is a certain level or less, the thermally conductive sheet has excellent flexibility. The E hardness is, for example, 20 or more, preferably 30 or more, and more preferably 35 or more, from the viewpoint of ease of handling of the thermally conductive sheet. The E hardness referred to here is the initial hardness, and specifically, is obtained by measurement in an environment of 25°C.

[0049] The thermally conductive sheet of the present invention preferably has an E hardness (hereinafter also referred to as "post-heating E hardness") of 70 or less, more preferably 65 or less, and even more preferably 60 or less, after being heated at 150°C for 250 hours. When the E hardness is a certain level or less, the thermally conductive sheet maintains good flexibility even when exposed to a high-temperature environment. The E hardness is, for example, 30 or more, preferably 40 or more, and more preferably 45 or more, from the viewpoint of ensuring a certain degree of shape retention during actual use of the thermal conductive sheet.

[0050] [Method of manufacturing thermal conductive sheets] The thermally conductive sheet of the present invention can be produced, for example, by a production method including the following steps X and Y. Step X: A step of mixing at least the curable silicone composition, the thermally conductive filler (B), and the compound (C) to obtain a thermally conductive resin composition. Step Y: A step of curing the thermally conductive resin composition obtained in Step X by heating. Each step will be described in detail below.

[0051] (Process X) In step X, the thermally conductive resin composition is preferably obtained by mixing at least the curable silicone composition, the thermally conductive filler (B), and the compound (C), but it is preferable to further mix a volatile substance into the thermally conductive resin composition. Furthermore, other components such as additives may be appropriately added to the thermally conductive resin composition as needed.

[0052] In step X, the mixing method and order of mixing are not particularly limited, as long as the above components can be mixed to obtain a thermally conductive resin composition. The curable silicone composition, thermally conductive filler (B), compound (C), a volatile substance that is added as needed, and other components that are optionally added as needed may be mixed appropriately in any order to obtain a thermally conductive resin composition. As described above, the curable silicone composition is composed of, for example, a base agent and a curing agent. In such cases, the base agent, curing agent, thermally conductive filler (B), compound (C), and optionally added volatile substances and other components as required may be mixed in any order to obtain the thermally conductive resin composition. The thermally conductive resin composition may be in the form of either a one-component type or a two-component type consisting of a first component and a second component. In the two-component type, the first component and the second component are mixed together at the time of use to obtain the thermally conductive resin composition.

[0053] (volatile substances) The volatile substance used in the present invention may be any component that volatilizes in step Y, which will be described later. The volatile substance volatilizes when heated during curing, thereby increasing the content of the thermally conductive filler in the thermally conductive sheet. Furthermore, the inclusion of a volatile substance in the thermally conductive resin composition reduces the viscosity. This makes it easier to increase the amount of thermally conductive filler (B) incorporated, and further makes it easier to orient the anisotropic filler in a predetermined direction, for example, by magnetic field orientation, which will be described later.

[0054] Furthermore, the volatile substance is preferably a compatible substance that is compatible or soluble in the curable silicone composition. If the volatile substance is a compatible substance, the curable silicone composition and the volatile substance can be mixed uniformly, making it easier to reduce viscosity and increase the amount of thermally conductive filler (B) incorporated. Furthermore, the bubbles formed by the evaporation of the volatile substance can be made fine and uniform.

[0055] The volatile substance is preferably a substance that is liquid at room temperature (25° C.) and 1 atmosphere. Examples of volatile substances include alkoxysilane compounds, hydrocarbon solvents, and alkoxysiloxane compounds. These compounds can increase the solubility or compatibility with the curable silicone composition, making it easier to reduce the viscosity of the thermally conductive resin composition and increase the amount of thermally conductive filler added. Furthermore, the evaporation of the volatile substance makes it easier to form fine, uniform bubbles. The volatile substances may be used alone or in combination of two or more.

[0056] As the volatile substance, it is preferable to use an alkoxysilane compound, which can prevent roughness from appearing on the surface of the thermally conductive sheet obtained by curing and provide a good appearance. The alkoxysilane compound used as the volatile substance is a compound having a structure in which one to three of the four bonds possessed by the silicon atom (Si) are bonded to alkoxy groups, and the remaining bonds are bonded to organic substituents. By having an alkoxy group and an organic substituent, the alkoxysilane compound can increase the compatibility of compound (C) with the curable silicone composition. Examples of alkoxy groups contained in the alkoxysilane compound include methoxy, ethoxy, protoxy, butoxy, pentoxy, and hexatoxy groups. The alkoxysilane compound may be contained in the curable silicone composition as a dimer.

[0057] Among alkoxysilane compounds, from the viewpoint of easy availability, alkoxysilane compounds having at least one of a methoxy group and an ethoxy group are preferred. From the viewpoints of compatibility with the curable silicone composition and compound (C), solubility, etc., the number of alkoxy groups in the alkoxysilane compound is preferably 2 or 3, and more preferably 3. Specifically, the alkoxysilane compound is preferably at least one selected from a trimethoxysilane compound, a triethoxysilane compound, a dimethoxysilane compound, and a diethoxysilane compound.

[0058] Examples of functional groups contained in the organic substituents of alkoxysilane compounds include acryloyl groups, alkyl groups, carboxyl groups, vinyl groups, methacrylic groups, aromatic groups, amino groups, isocyanate groups, isocyanurate groups, epoxy groups, hydroxyl groups, and mercapto groups. When a platinum catalyst is used as the curing catalyst for the curable silicone composition, it is preferable to select and use an alkoxysilane compound that is less likely to affect the curing reaction of the organopolysiloxane. Specifically, when an addition reaction-type organopolysiloxane using a platinum catalyst is used, it is preferable that the organic substituents of the alkoxysilane compound do not contain amino groups, isocyanate groups, isocyanurate groups, hydroxyl groups, or mercapto groups.

[0059] From the viewpoint of dispersibility of compound (C) in the curable silicone composition, the alkoxysilane compound preferably includes an alkylalkoxysilane compound having an alkyl group bonded to a silicon atom, i.e., an alkoxysilane compound having an alkyl group as an organic substituent. Therefore, dialkyldialkoxysilane compounds and alkyltrialkoxysilane compounds are preferred, and alkyltrialkoxysilane compounds are particularly preferred. The number of carbon atoms in the alkyl group bonded to the silicon atom may be, for example, from 1 to 16. In trialkoxysilane compounds such as trimethoxysilane compounds and triethoxysilane compounds, the number of carbon atoms in the alkyl group is preferably 6 or more, more preferably 8 or more, and is preferably 12 or less, more preferably 10 or less. On the other hand, in dialkoxysilane compounds such as dimethoxysilane compounds and triethoxysilane compounds, the alkyl group may have one or more carbon atoms, and preferably has 10 or less carbon atoms, more preferably 6 or less carbon atoms, and even more preferably 4 or less carbon atoms.

[0060] Examples of alkyl group-containing alkoxysilane compounds include methyltrimethoxysilane, dimethyldimethoxysilane, diethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, di-n-propyldimethoxysilane, di-n-propyldiethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, methylcyclohexyldimethoxysilane, methylcyclohexyldiethoxysilane, n-octyltrimethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, and n-decyltriethoxysilane. Among alkyl group-containing alkoxysilane compounds, n-decyltrimethoxysilane and n-octyltriethoxysilane are even more preferred from the standpoint of compatibility with the curable silicone composition.

[0061] The alkoxysiloxane compound used as the volatile substance has two or more siloxane bonds and a structure in which an alkoxy group is bonded to at least one silicon atom. The alkoxysiloxane compound has a structure in which an organic substituent is bonded to at least one of the silicon atoms constituting the siloxane bond. The alkoxysiloxane compound has an alkoxy group and an organic substituent, which can improve the dispersibility of compound (C) in the curable silicone composition. Examples of the alkoxy group and organic substituent that the alkoxysiloxane compound has include those exemplified in the description of the alkoxysilane compound above, and from the viewpoint of improving the dispersibility of compound (C), it is preferable that the compound has at least an alkyl group.

[0062] Examples of the alkoxysiloxane compound include methyl methoxy siloxane oligomer, methyl phenyl methoxy siloxane oligomer, methyl epoxy methoxy siloxane oligomer, methyl mercapto methoxy siloxane oligomer, and methyl acryloyl methoxy siloxane oligomer. The alkoxysiloxane compound may be used alone or in combination of two or more.

[0063] Examples of hydrocarbon solvents used as volatile substances include aromatic hydrocarbon solvents. Among these, aromatic hydrocarbon solvents are preferred from the viewpoint of compatibility with the curable silicone composition. Examples of aromatic hydrocarbon solvents include aromatic hydrocarbon solvents having from 6 to 10 carbon atoms, such as toluene, xylene, mesitylene, ethylbenzene, propylbenzene, butylbenzene, and t-butylbenzene, with toluene and xylene being preferred.

[0064] In the thermally conductive resin composition, the content of the volatile substance per 100 parts by mass of the curable silicone composition is preferably 6 parts by mass or more and 60 parts by mass or less. When the content is 6 parts by mass or more, the effect of the volatile substance is easily exerted, for example, an appropriate amount of fine bubbles can be formed in the silicone resin. Furthermore, when the content is 60 parts by mass or less, an effect commensurate with the amount of volatile substance used can be obtained. From these viewpoints, the content of the volatile substance is more preferably 8 parts by mass or more and 50 parts by mass or less, and even more preferably 10 parts by mass or more and 35 parts by mass or less. It is preferable that the volatile substance is partially or completely volatilized by the heating in step Y. Therefore, the volatile substance does not need to be contained in the thermally conductive sheet, but may be contained in the thermally conductive sheet in an amount less than the content in the thermally conductive resin composition.

[0065] In the thermally conductive resin composition, the content of each component other than the volatile substance (thermally conductive filler (B) and compound (C)) per 100 parts by mass of the curable silicone composition is the same as the content of each component (thermally conductive filler (B) and compound (C)) per 100 parts by mass of the silicone resin (A).

[0066] (Process Y) Step Y is a step of curing the thermally conductive resin composition by heating. The temperature at which the thermally conductive resin composition is heated is not particularly limited as long as the curable silicone composition can be cured by heating. It is sufficient to heat the composition to a temperature higher than room temperature (23°C), preferably 50°C or higher. The heating temperature is also not particularly limited, but it is sufficient to heat the thermally conductive sheet and the thermally conductive resin composition at a temperature that does not cause thermal degradation. For example, it is 180°C or lower, preferably 150°C or lower. The thermally conductive resin composition may be heated in one stage or in two or more stages. When heating in two or more stages, the heating temperature in at least one stage may be within the above range, but it is preferable that the heating temperature in all stages be within the above range. Furthermore, it is preferable that at least the first heating stage be heated at a temperature lower than the boiling point of the volatile compound. The total heating time is, for example, about 10 minutes to 24 hours. When the curing is carried out in two or more stages, for example, the thermally conductive resin composition may be partially cured in the first stage (primary curing) and fully cured by heating in the second or subsequent stage (secondary curing). Alternatively, the thermally conductive resin composition may be fully cured by the primary curing, but not cured by heating in the second or subsequent stages.

[0067] In step Y, the thermally conductive resin composition may be molded into a predetermined shape such as a block or sheet, and then heated to harden. In step Y, if the thermally conductive resin composition contains an anisotropic filler as the thermally conductive filler, the anisotropic filler may be oriented in one direction and then hardened by heating. The anisotropic filler can be oriented by a magnetic field orientation method or a flow orientation method, but magnetic field orientation is preferred. An anisotropic filler is a thermally conductive filler with an aspect ratio of more than 2, preferably 5 or more. By increasing the aspect ratio to more than 2, the anisotropic filler can be more easily oriented in one direction, such as the thickness direction of the sheet, which makes it easier to increase the thermal conductivity of the thermally conductive sheet in one direction, such as the thickness direction. The upper limit of the aspect ratio is not particularly limited, but is practically 100. The aspect ratio is the ratio of the length in the long axis direction to the length in the short axis direction of an anisotropic filler, and in the case of fibrous materials, it means the fiber length / fiber diameter, and in the case of scaly materials, it means the length in the long axis direction of the scaly materials / thickness.

[0068] In the magnetic field orientation method, the thermally conductive resin composition is injected into a mold or the like and then placed in a magnetic field to orient the anisotropic filler along the magnetic field. The curable silicone composition is then cured to obtain an oriented molded article. The thermally conductive resin composition is cured under the heating conditions described above. The oriented molded body is preferably in the form of a block, but may also be in the form of a sheet. By making it in the form of a sheet, the oriented molded body can be used as a heat conductive sheet as is without slicing. On the other hand, by making it in the form of a block, the orientation of the anisotropic filler can be enhanced.

[0069] In the magnetic field orientation method, a release film may be placed inside the mold in the portion that comes into contact with the thermally conductive resin composition. The release film may be, for example, a resin film with good releasability or a resin film whose one side has been treated with a release agent or the like. The use of a release film makes it easier to release the oriented molded body from the mold.

[0070] The viscosity of the thermally conductive resin composition used in the magnetic field orientation method is preferably 10 Pa·s or more and 300 Pa·s or less to allow for magnetic field orientation. A viscosity of 10 Pa·s or more makes the anisotropic filler less likely to settle. A viscosity of 300 Pa·s or less improves fluidity, allowing the anisotropic filler to be properly oriented in the magnetic field without causing problems such as excessive orientation time. The viscosity is measured at 25°C using a rotational viscometer (Brookfield viscometer DV-E, spindle SC4-14) at a rotational speed of 10 rpm. However, when a thermally conductive filler that does not easily settle is used or when an additive such as an anti-settling agent is combined, the viscosity of the thermally conductive resin composition may be less than 10 Pa·s.

[0071] In the magnetic field orientation method, magnetic field line generating sources for applying magnetic field lines include superconducting magnets, permanent magnets, electromagnets, etc., but superconducting magnets are preferred because they can generate a magnetic field with a high magnetic flux density. The magnetic flux density of the magnetic field generated by these magnetic field line generating sources is preferably 1 Tesla or more and 30 Tesla or less. If the magnetic flux density is 1 Tesla or more, it becomes possible to easily orient the above-mentioned anisotropic filler made of a carbon material, etc. Furthermore, if the magnetic flux density is 30 Tesla or less, practical production becomes possible.

[0072] In the flow orientation method, a shear force is applied to the thermally conductive resin composition to produce a primary sheet in which the anisotropic filler is oriented in the plane direction. More specifically, in the flow orientation method, the thermally conductive resin composition prepared in step X is first flattened and stretched while applying a shear force to form a sheet (primary sheet). By applying a shear force, the anisotropic filler can be oriented in the shear direction. Examples of sheet-forming methods include applying the thermally conductive resin composition to a substrate film using a coating applicator such as a bar coater or doctor blade, or by extrusion molding or nozzle discharge. The thermally conductive resin composition may then be dried, semi-cured, or fully cured as necessary. The thickness of the primary sheet is preferably approximately 50 μm to 5,000 μm. In the primary sheet, the anisotropic filler is oriented in one direction along the plane direction of the sheet. The thermally conductive resin composition used in the flow orientation method has a relatively high viscosity so that a shear force is applied when the composition is stretched into a sheet. Specifically, the viscosity of the thermally conductive resin composition is preferably 3 Pa s or more and 500 Pa s or less.

[0073] The primary sheet may be used as a thermally conductive sheet without being formed into a block, as described below. Alternatively, a laminated block (a block-shaped oriented molded product) may be formed by laminating a plurality of primary sheets so that they are oriented in the same direction, and then bonding the primary sheets together by a heat press or the like while curing them by heating as necessary. Furthermore, when forming a laminated block, at least one of the surfaces of the primary sheets to be laminated may be irradiated with vacuum ultraviolet light, and then the primary sheets may be laminated. When the primary sheets are laminated via the surfaces irradiated with vacuum ultraviolet light, the primary sheets can be firmly bonded to each other. Furthermore, when irradiating with vacuum ultraviolet light, the thermally conductive resin composition may be fully cured when the primary sheets are produced, and there is no need to cure the primary sheets by heating or the like when they are laminated to form a laminated block. In the flow orientation method, the thermally conductive resin composition may also be cured under the heating conditions described above.

[0074] As described above, when forming a block-shaped oriented molded body, the obtained oriented molded body may be cut perpendicular to the orientation direction of the anisotropic filler by slicing or the like to form a sheet-shaped molded body. Slicing may be performed using, for example, a shear blade or a laser. By slicing or cutting the sheet-shaped molded body, a portion of the fibrous filler is exposed from the matrix at each surface, which is the cut surface. The sheet-like molded article obtained by cutting may be used as a thermally conductive sheet as is, or may be further processed. For example, each cut surface may be polished. The surface may be polished, for example, using abrasive paper.

[0075] The cured product of the present invention or a thermally conductive sheet made from the cured product can be used as a heat dissipation member. The heat dissipation member is used, for example, inside an electronic device. A heat dissipation member made from a cured product of the thermally conductive resin composition of the present invention or a heat dissipation member made from a thermally conductive sheet has good thermal conductivity, so when used inside an electronic device, high heat dissipation can be ensured even when a large amount of heat is generated. Furthermore, the heat dissipation member has excellent handleability at room temperature and excellent compressibility at high temperatures. Furthermore, the amount of bleeding is small, making it an excellent product with high reliability. The heat dissipation member is, for example, placed on an electronic component and used to dissipate heat generated by the electronic component. The heat dissipation member of the present invention may also be used by being placed so as to fill the gap between two opposing components. The two opposing components may be, for example, one electronic component and the other a heat sink, a housing for an electronic device, a circuit board, or the like, for dissipating heat from the electronic component. The heat dissipation member may also be used as a so-called TIM (Thermal Interface Material). [Example]

[0076] The present invention will be clarified below by showing specific examples and comparative examples of the present invention, but the present invention is not limited to the following examples.

[0077] [Compound (C)] The following materials were used to synthesize compound (C).

[0078] (Silicone Monomer) · One-end methacrylic modified silicone 1 A compound with a structure that has a viscosity of 60 cSt or less at 25°C. [ka] · One-end methacrylic modified silicone 2 A compound with a structure that has a viscosity of 27 cSt or less at 25°C. [ka]

[0079] (crystalline monomer) Stearyl acrylate Docosyl acrylate

[0080] (initiator) 5wt% azo initiator toluene solution (solvent) toluene

[0081] <Synthesis of Compound (C): PCM(E1) to PCM(E6)> Silicone monomer and crystalline monomer were mixed with toluene and N2 bubbling was performed for over 20 minutes. Heating was started, and after the temperature had risen to 62°C, a 5 wt% toluene solution of azo initiator was added. After heating and stirring at 62°C for 17 hours, the mixture was allowed to cool, the solvent was distilled off, and the mixture was heated under vacuum at 150°C for 2 hours to synthesize PCM (E1) to PCM (E6) as graft copolymer compound (C). The amount of each raw material added is listed in Table 1.

[0082] <Synthesis of a comparative compound of compound (C): PCM (C1)> PCM (C1) was obtained in the same manner as in the synthesis of compound (C) above, except that the silicone monomer was not used.

[0083] PCM(E1) to PCM(E6) are compounds having the structure of the above formula (1), and more specifically, have the following structures: Table 2 shows the details of the structures of the synthesized compounds. [ka]

[0084] PCM(C1) has a structure shown in the following formula (10). [ka]

[0085] [Table 1]

[0086] <PCM other than compound (C)> In addition to PCM (C1), the following compounds were also used as PCMs other than compound (C). PCM(C2) KP-561P, manufactured by Shin-Etsu Chemical Co., Ltd. (Acrylates / Stearyl Acrylate / Dimethicone Methacrylate) Copolymer, melting point 30°C PCM(C3) ALT-292 (Gelest) Compound with the structure shown in formula (11) below Melting point: 40°C [ka] PCM (C4) A compound having the structure shown in the following formula (12) Melting point: 38°C Synthesized with reference to Japanese Patent No. 6436035. [ka] PCM (C5) HS-Crysta 4100P, Toyokuni Oil Co., Ltd., polyalphaolefin, melting point 35°C

[0087] [Table 2]

[0088] [Table 3]

[0089] <Weight average molecular weight> The weight-average molecular weight (Mw) of each synthesized PCM was measured by size exclusion chromatography using THF as a solvent. Note that the weight-average molecular weight (Mw) is a value converted to standard polystyrene.

[0090] <Melting point> The melting points of the synthesized products (each PCM) were determined by measurement using a differential scanning calorimeter (DSC). The temperature was changed at a rate of 10°C / min from -20°C to 100°C to -20°C to 100°C. The peak temperature of the maximum peak in the chart obtained during the temperature drop from 100°C to -20°C (Temperature 1) and the peak temperature of the maximum peak in the chart obtained during the second temperature increase from -20°C to 100°C (Temperature 2) were obtained, and the average value of Temperature 1 and Temperature 2 was taken as the melting point.

[0091] <Calculation of each structural parameter in formula (1)> (Calculation of p, q, r, s) Each synthesized PCM 29Si NMR spectra were measured in a solution of 0.1% tetramethylsilane in deuterated chloroform. The peak of tetramethylsilane is set to 0 ppm, and the peaks around 6.5 to 9.0, 20 to 24, -55 to -65, and -105 to -115 ppm are assigned to (SiO1 / 2), (SiO2 / 2), (SiO3 / 2), and (SiO4 / 2), respectively, and p, q, r, and s are determined using the following formula. However, when R is other than a methyl group and the peak positions are different, the following formula is applied based on the appropriate peak assignment.

[0092] <sio4 2>When ≠ 0, p=1 q= <sio3 2> / <sio4 2> r=s* <sio2 2> / <sio1 2> s=p*3*q*2

[0093] <sio4 2>=0, and <sio3 2>When ≠ 0, p=0 q=1 r=s* <sio2 2> / <sio1 2> s=2*q

[0094] <sio4 2>=0, and <sio3 2>When =0, p=0 q=0 r=s* <sio2 2> / <sio1 2> s=1 however, <siox 2>represents the integral value of the peak attributed to SiOx / 2.

[0095] (Calculation of k) Each synthesized PCM 1 1 H NMR spectra were measured in deuterated chloroform solution and determined based on appropriate peak assignments. The case of PCM(E1) is shown below. k=(<4.0> / <0.9>+<1.6> / <0.9>+<1.3> / <0.9>)*3 / 2 however,<x.x> represents the integral value of the peak having a peak top near x.x ppm.

[0096] (Calculation of m×r / (m+n)) Each synthesized PCM 1 1 H NMR spectra were measured in deuterated chloroform solution and determined based on appropriate peak assignments. The case of PCM(E1) is shown below. m×r / (m+n)=(<0.1> / 6) / (<4.0> / 2) however,<x.x> represents the integral value of the peak having a peak top near x.x ppm.

[0097] (Calculation of m and n) As described above, the weight average molecular weight Mw of each PCM was calculated by size exclusion chromatography measurement using THF solvent. Using Mw and m×r / (m+n), m and n were calculated from the following formula. m=Mw / (Mcryst*(rm*r / (m+n)) / (m*r / (m+n))+Msil) n=m*((rm*r / (m+n)) / (m*r / (m+n))) however, Mcryst: Formula weight of repeating unit derived from crystalline monomer Msil: Formula weight of repeating units derived from silicone monomers is. These values ​​are shown in the tables in this example, but can be determined by combining appropriate one-dimensional, two-dimensional, and multinuclear NMR spectroscopy methods.

[0098] <Examples 1 to 10 and Comparative Examples 1 to 5> The specified amounts of thermally conductive filler, dispersant, silicone base, and PCM were mixed in a sample vial, lightly mixed by hand, and then kneaded twice with a THINKY MIXER (manufactured by THINKY CORPORATION) at 1400 rpm / 30 seconds. The mixture was then heated at 80°C for 30 minutes and kneaded again with the THINKY MIXER. The mixture was cooled to room temperature, and the silicone curing agent was added. The mixture was further kneaded with the THINKY MIXER and allowed to stand under vacuum for 5 minutes to degas, yielding a thermally conductive resin composition. The thermally conductive resin composition was sandwiched between release films and formed into a sheet with a stretching roll. It was then heated at 150°C for 1 hour to yield a cured thermally conductive resin composition. Table 4 shows the formulations of the thermally conductive resin compositions prepared in each Example and Comparative Example. The dispersant used was decyltrimethoxysilane, a silane coupling agent; the silicone base material was an organopolysiloxane having vinyl groups; and the silicone curing agent was an organohydrogenpolysiloxane. The silicone base material contained a small amount of curing catalyst. The thermally conductive fillers used were alumina with an average particle size of 0.5 μm, alumina with an average particle size of 3 μm, and alumina with an average particle size of 10 μm.

[0099] (Hardness change rate) Three test pieces were stacked on top of each other, each 3.5 mm thick, of a cured thermally conductive resin composition, and the Type E hardness was measured using a durometer. To measure hardness during heating, a hot plate was placed near the durometer to heat the test piece, and once a thermometer was used to confirm that the upper surface of the test piece had exceeded 60°C, the hardness was quickly measured using the durometer. The hardness change rate was calculated using the following formula: Hardness change rate = ((measured value at 25°C) - (measured value at 60°C)) / (measured value at 25°C) (Evaluation criteria) ◎: Hardness change rate is 45% or more ○: Hardness change rate is 25% or more but less than 45% △: Hardness change rate is 20% or more but less than 25% ×: Hardness change rate is less than 20%

[0100] (bleed amount) A cured product of the thermally conductive resin composition was molded into a 3.5 mm thick sheet, and the sheet was cut into a 20 mm x 1 mm square to prepare test pieces T, and their weights were measured (weight 1). Each test piece T was sandwiched between metal plates and compressed to a thickness of 2 mm, and then heated at 150°C for 64 hours. After heating, the test pieces were removed and their weights were measured (weight 2), and the amount of bleeding was calculated using the following formula. Bleed amount = (weight 1 - weight 2) / (weight 1) (Evaluation criteria) ◎: Bleeding amount is 0.3 or less Good: Bleed amount is over 0.3 and 0.4 or less △: Bleed amount is over 0.4 and 0.5 or less ×: Bleeding amount is more than 0.5

[0101] (thermal resistance) The cured product of the thermally conductive resin composition was molded into a 1.1 mm thick sheet as a test piece, and the thermal resistance of the test piece was measured using a thermal resistance measuring device as shown in FIG. 1 by the following method. For each sample, a test piece S measuring 30 mm × 30 mm was prepared for this test. Each test piece S was attached to a copper block 22 with a measurement surface of 25.4 mm × 25.4 mm and sides covered with thermal insulation material 21. The test piece S was then sandwiched between upper copper blocks 23, and a load of 40 psi (0.276 MPa) was applied using a load cell 26. The lower copper block 22 was in contact with a heater 24. The upper copper block 23 was also covered with thermal insulation material 21 and connected to a heat sink 25 equipped with a fan. Next, the heater 24 was operated at a heat output of 25 W. After 10 minutes, when the temperature had reached a substantially steady state, the temperature (θj0) of the upper copper block 23, the temperature (θj1) of the lower copper block 22, and the heat output (Q) of the heater were measured, and the thermal resistance of each sample was calculated using the following formula (a). The temperature was adjusted so that the sheet was 80°C. Thermal resistance = (θj1-θj0) / Q Formula (a) In equation (a), θj1 is the temperature of the lower copper block 22, θj0 is the temperature of the upper copper block 23, and Q is the amount of heat generated. (Evaluation criteria) 〇: Thermal resistance is less than 1.6m2·K / W ×: Thermal resistance is 1.6m2·K / W or more

[0102] [Table 4]

[0103] The results of Examples 1 to 10 show that the cured product of the thermally conductive resin composition of the present invention, which contains a compound (C) having the structure represented by formula (1) and a melting point of 35°C or higher as a phase change material, is easy to handle and compressible, has little bleeding, and is highly reliable. Furthermore, it has low thermal resistance and excellent heat dissipation properties. On the other hand, as shown in Comparative Examples 1 to 5, cured products made of thermally conductive resin compositions using phase-change materials other than compound (C) were poor in handleability and compressibility, or contained a large amount of bleeding and were low in reliability. [Explanation of symbols]

[0104] 21 Insulation 22 Lower Copper Block 23 Upper Copper Block 24 Heater 25 Heatsink 26 load cells S test piece θ j0 Temperature of the upper copper block θ j1 Temperature of the lower copper block< / siox> < / sio2> < / sio2> < / sio2> < / sio4> < / sio3>

Claims

1. The composition comprises a silicone resin (A), a thermally conductive filler (B), and a compound (C) having a structure represented by the following formula (1): The melting point of the compound (C) is 35°C or higher, The thermally conductive resin composition, wherein the compound (C) is a graft copolymer. 【Chemical 1】 (In formula (1), X1 and X2 each independently represent a trivalent organic group, Y1 and Y2 each independently represent a divalent organic group, Z is a monovalent organic group, R is each independently represent a monovalent organic group, k is a number of 16 or more and 33 or less, n, r, and s each are a number of 1 or more, m is a number of 0.5 or more, and p and q each are a number of 0 or more.)

2. 2. The thermally conductive resin composition according to claim 1, wherein X1 and X2 are each independently a trivalent saturated hydrocarbon group having 2 to 6 carbon atoms, and Y1 and Y2 are each independently a divalent organic group containing an ester group or an amide group.

3. 3. The thermally conductive resin composition according to claim 1, wherein the content of the compound (C) is 10 parts by mass or more and 50 parts by mass or less per 100 parts by mass of the silicone resin (A).

4. The thermally conductive resin composition according to claim 1 or 2, wherein m, r, and n satisfy the relationship of the following formula (α): m×r / (m+n)≧0.3 Formula (α)

5. 3. The thermally conductive resin composition according to claim 1, wherein the thermally conductive filler (B) is at least one selected from the group consisting of metals, inorganic hydroxides, inorganic oxides, inorganic nitrides, inorganic carbides, carbon fibers, graphite, and diamonds.

6. A cured product of the thermally conductive resin composition obtained by curing the thermally conductive resin composition according to claim 1 or 2.

7. A thermally conductive sheet comprising a cured product of the thermally conductive resin composition according to claim 6.

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