Thermal conductive sheet

Abstract

To provide a thermally conductive sheet that is excellent in thermal conductivity, has a small difference between the maximum stress and a residual stress, and has a satisfactory balance between compressibility and restorability, as a heat dissipation member which can be widely applied to various on-vehicle electrical components.SOLUTION: The thermally conductive sheet is formed from a silicone composition that includes an organopolysiloxane having 2 to 10 alkenyl groups only on side chains of the molecular chain, an organohydrogenpolysiloxane having hydrosilyl groups at both terminals, a thermally conductive filler, a platinum-based curing catalyst, and a dimethylpolysiloxane of which one terminal is blocked with a trialkoxysilyl group, wherein a hardness of the above thermally conductive sheet is 7 or lower, which has been measured with an Asker C hardness tester; and when the thermally conductive sheet having an initial thickness of 1.5 mm has been compressed by 50% at a compression rate of 3 mm / min, the maximum stress is 0.7 MPa or smaller and the residual stress is 0.1 MPa or larger, and a ratio of the above maximum stress to the above residual stress is 7 / 1 or smaller.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a thermally conductive sheet. [Background technology]

[0002] With the miniaturization and high integration of electronic components, there is a demand for thermally conductive sheets that not only have excellent thermal conductivity but also have low maximum stress during assembly and are soft enough to minimize the load on heat-generating components. Patent Document 1 proposes a sheet that can conform to electronic components with low load by specifying the average particle size of the thermally conductive filler. Patent Document 2 reports an example of improving flexibility and reducing compressive load by creating irregularities on the surface of a thermally conductive sheet. Patent Document 3 proposes a sheet with excellent flexibility, exhibiting a compressive residual stress of 0.1 MPa or less, by specifying the viscosity of the polymer component.

[0003] However, for various electronic components intended for automotive use, while a low maximum stress during assembly is preferable, they are also required to possess resilience (a certain level of residual stress) that can accommodate fluctuations in the clearance between the thermal conductive sheet and the electronic component caused by vehicle vibrations after mounting. In other words, for thermal conductive sheets used in automotive environments, it is necessary to have a small difference between maximum stress and residual stress, and to achieve both ease of compression and appropriate rebound due to rubber elasticity. Further improvements were needed in this respect. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-253136 [Patent Document 2] Japanese Patent Publication No. 2001-217360 [Patent Document 3] Patent No. 6705067 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a heat-conducting sheet that can be widely applied to various automotive electronic components, exhibiting excellent thermal conductivity, a small difference between maximum stress and residual stress, and a good balance between compressibility and resilience. [Means for solving the problem]

[0006] This invention was made to solve the above problems and provides the following thermally conductive sheet.

[0007] In other words, the present invention is (a) Organopolysiloxane having 2 to 10 alkenyl groups only on the side chains of the molecular chain: 100 parts by mass (b) Organohydrogenpolysiloxane having hydrosilyl groups at both ends: an amount such that the number of moles of hydrosilyl groups is in the range of 0.75 to 1.3 of the number of moles of alkenyl groups derived from component (a). (c) Thermally conductive filler: 1,000 to 4,200 parts by mass (d) Platinum-based curing catalyst: 0.1 to 1,000 ppm of platinum group elements by weight relative to component (a) (e) Dimethylpolysiloxane with one end sealed with a trialkoxysilyl group: 15-200 parts by mass A thermally conductive sheet made of a cured product of a silicone composition containing, wherein the hardness of the thermally conductive sheet measured with an Asker C hardness tester is 7 or less. The present invention provides a thermally conductive sheet characterized in that, when the thermally conductive sheet with an initial thickness of 1.5 mm is compressed by 50% at a compression rate of 3 mm / min, the maximum stress is 0.7 MPa or less, the residual stress is 0.1 MPa or more, and the ratio of the maximum stress to the residual stress is 7 / 1 or less.

[0008] Such a thermally conductive sheet would have excellent thermal conductivity, a small difference between maximum stress and residual stress, and a good balance between compressibility and resilience.

[0009] It is preferable that the above-mentioned (c) heat-conductive filler be at least one selected from aluminum oxide, aluminum hydroxide, magnesium oxide, and aluminum nitride.

[0010] A heat-conductive sheet using such a heat-conductive filler has good heat conductivity and filling properties.

[0011] The shape of the above-mentioned (c) heat-conductive filler can be crushed, rounded, or spherical.

[0012] It is preferable that the average particle size of the above-mentioned (c) heat-conductive filler be 0.5 to 100 μm.

[0013] Those having an average particle size of 0.5 to 10 μm, or those in a crushed or rounded shape can enhance the heat conductivity by forming an efficient heat conduction path.

[0014] In this case, it is preferable that the thermal conductivity be 2.0 W / m-K or more.

[0015] If the thermal conductivity of the heat-conductive sheet is 2.0 W / m-K or more, the heat-conductive sheet can be applied to a heating element with a large calorific value.

Advantages of the Invention

[0016] According to the present invention, by appropriately crosslinking an organopolysiloxane having an alkenyl group only in the side chain of the molecular chain and an organohydrogenpolysiloxane having hydrosilyl groups at both ends, the crosslinking density can be within an appropriate range, and a silicone polymer maintaining good compressibility and residual stress can be obtained. Furthermore, by blending a heat-conductive filler for imparting thermal conductivity with a surface treatment agent having a trialkoxy group at one end, the interaction between the filler surface and the polymer is strengthened, and the residual stress can be improved. Such a sheet is excellent in the balance between the maximum stress and the residual stress, and thus can be used for various in-vehicle electronic components.

Embodiments for Carrying Out the Invention

[0017] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto. The inventor searched for a silicone composition that has a small difference between the maximum stress and the residual stress required for a thermally conductive sheet and can have both crushability and a repulsive property due to appropriate rubber elasticity. As a result, an organopolysiloxane having 2 to 10 alkenyl groups only in the side chains of the molecular chain, an organohydropolysiloxane having hydrosilyl groups at both ends, a thermally conductive filler, a platinum-based curing catalyst, and a dimethylpolysiloxane having one end blocked with a trialkoxysilyl group. A silicone composition, wherein the hardness of the thermally conductive sheet measured by an Asker C hardness meter is 7 or less, the maximum stress when the thermally conductive sheet having an initial thickness of 1.5 mm is compressed by 50% at a compression rate of 3 mm / min is 0.7 MPa or less, the residual stress is 0.1 MPa or more, and the ratio of the maximum stress to the residual stress is 7 / 1 or less. It was found that the above object can be achieved with a thermally conductive sheet characterized by the above, and the present invention was completed. Hereinafter, each component will be described.

[0018] (a) Organopolysiloxane having 2 to 10 alkenyl groups only in the side chains of the molecular chain The alkenyl group-containing organopolysiloxane as the component (a) contains 2 to 10 alkenyl groups only in the side chain portion in one molecule. Usually, the main chain portion is basically composed of a repetition of diorganosiloxane units, and both ends of the molecular chain are generally blocked with triorganosiloxy groups and are linear. It may include a branched structure in a part of the molecular structure, or may be a cyclic body, but a linear diorganopolysiloxane is preferred from the viewpoint of physical properties such as the mechanical strength of the cured product. As an example of the component (a), a structure represented by the following general formula (1) can be mentioned.

Chemical formula

[0019] In general formula (1), R 1 Examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, and hexyl groups; cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl groups; aryl groups such as phenyl, tolyl, and xylyl groups; and aralkyl groups such as benzyl and 2-phenylethyl groups. Typical examples have 1 to 7 carbon atoms, with particularly typical examples having 1 to 5 carbon atoms, and preferably alkyl groups such as methyl, ethyl, and propyl groups, and phenyl groups. Note that these R 1 You may also use a compound in which some of the hydrogen atoms are replaced with halogen atoms such as fluorine.

[0020] In general formula (1), the alkenyl group of X can be any group having 2 to 6 carbon atoms, such as a vinyl group, allyl group, propenyl group, isopropenyl group, butenyl group, or hexenyl group. Among these, the vinyl group and allyl group are preferred, and the vinyl group is particularly preferred. In general formula (1), n ​​is an integer of 0 or greater than or equal to 1, and m is an integer between 2 and 10. Preferably, n and m are integers satisfying 10 ≤ n + m ≤ 5,000, more preferably 50 ≤ n + m ≤ 1,000, and even more preferably integers satisfying 100 ≤ n + m ≤ 500 and 0.001 ≤ m / (n + m) ≤ 0.05. The combination of siloxane units enclosed in parentheses with m and n above may be in blocks or random.

[0021] (b) Organohydrogenpolysiloxane (b) The organohydrogenpolysiloxane component must have two or more, preferably two to four, hydrogen atoms (hydrosilyl groups) directly bonded to silicon atoms in one molecule, with hydrosilyl groups at both ends. If the number of hydrosilyl groups is less than two, curing may not occur. An example of an organohydrogenpolysiloxane is represented by the general formula (2) below. [ka] (In general formula (2), R 1 The above is the same. o is an integer between 0 and 200 (exclusive), and p is an integer between 0 and 200 (exclusive). Note that the combination of siloxane units enclosed in parentheses with o and p above may be in a block or random.

[0022] In the above general formula (2), R 1 These are groups independently selected from C1-C10 alkyl groups, C6-C10 aryl groups, and C7-C10 aralkyl groups, as shown in general formula (1) above. Specific examples and preferred embodiments are the same as those listed in general formula (1) above. In general formula (2) above, o represents an integer between 0 and 200, and p represents an integer between 0 and 200. These values ​​represent the values ​​in the average structural formula of component (b), and are not limited to the individual molecular level. The bonding of the siloxane units enclosed in parentheses with o and p above may be in blocks or random.

[0023] The amount of these components (b) added is such that the amount of hydrosilyl groups derived from component (b) is 0.75 to 1.3 moles, preferably 0.78 to 1.25 moles, and more preferably 0.9 to 1.2 moles, relative to 1 mole of alkenyl groups derived from component (a). When a sheet is formed with component (b) in this range, the difference between the maximum stress and residual stress is reduced, resulting in a sheet with well-balanced compression properties.

[0024] (c) Thermally conductive filler (c) The thermally conductive filler component can be a substance commonly used as a thermally conductive filler, such as a nonmagnetic metal like copper or aluminum, a metal oxide like aluminum oxide, silicon dioxide, magnesium oxide, beryllium oxide, titanium oxide, or zirconium oxide, a metal nitride like aluminum nitride, silicon nitride, or boron nitride, a metal hydroxide like aluminum hydroxide or magnesium hydroxide, artificial diamond, or silicon carbide.

[0025] In particular, from the viewpoint of thermal conductivity and filling properties for silicone, it is preferable to use aluminum oxide, aluminum hydroxide, magnesium oxide, and aluminum nitride. These thermally conductive fillers preferably have an average particle size of 0.5 to 100 μm, and more preferably 1 to 80 μm. These fillers may be used individually or in mixtures of multiple types. It is also possible to use two or more types of particles with different average particle sizes. The particle size of the thermally conductive filler is measured using a laser diffraction / scattering particle size distribution analyzer, such as the Microtrac MT3300EX (Nikkiso), and the average particle size is a volume-based value (when the volume distribution of the particles is measured and divided into two parts at this average particle size, it refers to the diameter at which the larger and smaller sides are equal in volume).

[0026] The shape of the thermally conductive filler is preferably crushed, rounded, or spherical, and a combination of several different shapes can be used. In particular, for those with an average particle size of 10 to 100 μm, a spherical shape is preferred from the viewpoint of filling ability, and for those with an average particle size of 0.5 to 10 μm, a crushed or rounded shape is preferred because it can penetrate between larger particle size fillers and efficiently form thermal conduction paths. In the present invention, "spherical" refers to a thermally conductive filler with an aspect ratio of 1.5 or less, and "crushed" or "rounded" refers to a thermally conductive filler with an aspect ratio greater than 1.5. Furthermore, "crushed" refers to a material that contains angular parts, while "rounded" refers to a material with a rounded shape.

[0027] The amount of component (c) must be 1,000 to 4,200 parts by mass per 100 parts by mass of component (a), preferably 1,500 to 3,800 parts by mass. If the amount is less than 1,000 parts by mass, the resulting composition will have poor thermal conductivity, and the thermally conductive sheet will have poor storage stability. On the other hand, if it exceeds 4,200 parts by mass, the sheet will become hard and brittle, the maximum stress will increase, and high compression will be difficult.

[0028] (d) Platinum-based curing catalyst The platinum-based hardening catalyst of component (d) is a catalyst for promoting the addition reaction between the alkenyl group derived from component (a) and the Si-H group derived from component (b), and is a well-known platinum-based catalyst used in hydrosilylation reactions. Specific examples include, for example, elemental platinum group metals such as platinum (including platinum black), rhodium, and palladium, as well as platinum chloride, chloroplatinic acid and chloroplatinate salts, and alcohol-modified chloroplatinic acid (US Patent No. 3,220,972). Examples include (see reference), a complex of chloroplatinic acid and olefins (see U.S. Patent Nos. 3,159,601, 3,159,662, and 3,775,452), platinum black, platinum group metals such as palladium supported on a carrier such as alumina, silica, or carbon, rhodium-olefin complex, chlorotris(triphenylphosphine)rhodium (Wilkinson catalyst), platinum chloride, chloroplatinic acid or chloroplatinate salts with vinyl group-containing siloxanes, particularly vinyl group-containing cyclic siloxanes. (d) The amount of component used is the amount of platinum group metal elements relative to component (a) weight This translates to 0.1 to 1,000 ppm, with 1 to 500 ppm being preferable.

[0029] (e) Dimethylpolysiloxane with one end sealed with a trialkoxysilyl group (e) Dimethylpolysiloxane in which one end of component is sealed with a trialkoxysilyl group is used as a surface treatment agent. Specifically, it can be represented by the following general formula (3). [ka]

[0030] In the above general formula, R 2 is independently an alkyl group having 1 to 6 carbon atoms, preferably a methyl group or an ethyl group. q is an integer from 5 to 100, preferably an integer from 10 to 60. The amount of component (e) added is 15 to 200 parts by mass per 100 parts by mass of component (a), preferably in the range of 30 to 150 parts by mass. If the amount of component (e) is less than 15 parts by mass, the wettability between the polymer and the thermally conductive filler component (c) is poor, resulting in difficulties with sheet moldability and maximum stress during compression. On the other hand, if it exceeds 200 parts by mass, oil separation is easily induced, leading to poor storage stability of the material and a decrease in residual stress during compression.

[0031] [Other optional components] In addition, various additives can be added in effective amounts to improve functionality, such as reaction control agents to adjust the curing speed, pigments and dyes for coloring, flame retardants, mold release agents to improve release from molds and separator films, and plasticizers to adjust the viscosity of the composition and the hardness of the molded product.

[0032] Examples of reaction regulators and plasticizers are given below, but the present invention is not limited thereto.

[0033] [(f) Plasticizers] The composition of the present invention further comprises (f) the following general formula (4) as a plasticizer [ka] (R 6 (Each is a monovalent hydrocarbon group with 1 to 8 carbon atoms, without aliphatic unsaturated bonds, and d is an integer between 5 and 2,000.) The organopolysiloxane represented by the following formula and having a kinematic viscosity at 25°C measured by a Cannon-Fenske viscometer of 10 to 100,000 mm 2 / s can be included. This component may be appropriately used to impart properties such as a viscosity regulator of the heat conductive composition, and is not particularly limited. It may be used alone or in combination of two or more.

[0034] The above R 6 are each independently a monovalent hydrocarbon group having 1 to 8 carbon atoms and not containing an aliphatic unsaturated bond, specifically a group selected from an alkyl group having 1 to 8 carbon atoms, an aryl group having 6 to 8 carbon atoms, and an aralkyl group having 7 to 8 carbon atoms. For example, alkyl groups such as methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, tert-butyl group, pentyl group, neopentyl group, hexyl group, heptyl group, and octyl group, cycloalkyl groups such as cyclopentyl group, cyclohexyl group, and cycloheptyl group, aryl groups such as phenyl group, tolyl group, and xylyl group, aralkyl groups such as benzyl group, phenylethyl group, phenylpropyl group, and methylbenzyl group, etc. are mentioned. Preferably, they are a methyl group, an ethyl group, a propyl group, and a phenyl group, and particularly preferably, a methyl group or a phenyl group.

[0035] The kinematic viscosity at 25°C of the above organopolysiloxane measured by a Cannon-Fenske viscometer is preferably 10 to 100,000 mm 2 / s, and particularly preferably 100 to 10,000 mm 2 / s. If the kinematic viscosity is 10 mm 2 / s or more, the cured product of the resulting composition does not generate oil bleed. If the kinematic viscosity is 100,000 mm 2 / s or less, the resulting heat conductive composition has good flexibility. In the above general formula (4), d may be a value such that the kinematic viscosity of the organopolysiloxane falls within the above-mentioned range. Preferably, it is an integer of 5 to 2,000, and more preferably an integer of 10 to 1,000.

[0036] The amount of component (f) in the composition of the present invention is not particularly limited and should be any amount that provides the desired effect as a plasticizer. Typically, it is preferably 1 to 20 parts by mass, and more preferably 2 to 10 parts by mass, per 100 parts by mass of component (a). When the amount of component (f) is within the above range, the thermally conductive composition before curing is more likely to maintain good fluidity and workability, and it is easier to fill the composition with the thermally conductive filler component (c).

[0037] [(g) Reaction control agent] (g) Any known addition reaction control agent used in typical addition-curing silicone compositions can be used as the reaction control agent. Examples include acetylene compounds such as 1-ethynyl-1-hexanol and 3-butyne-1-ol, various nitrogen compounds, organophosphorus compounds, oxime compounds, and organochloro compounds. The amount used is preferably about 0.01 to 1 part by mass.

[0038] [Viscosity of the composition] The viscosity of the thermally conductive silicone composition of the present invention at 25°C is preferably 500 Pa·s or less, more preferably 350 Pa·s or less. Within this range, the thermally conductive silicone composition can be dispensed by a pump, allowing for high-yield molding of thermally conductive sheets. A viscosity of 300 Pa·s or less is particularly preferable because it results in better moldability. The lower limit of viscosity is not particularly limited, but is usually around 10 Pa·s. Viscosity is measured using a modular rheometer, the MARS40, manufactured by HAAKE.

[0039] [Method for manufacturing a thermally conductive sheet] A thermally conductive sheet can be obtained by coating the thermally conductive silicone composition of the present invention onto a substrate such as a resin film and curing it. As the resin film, one that can withstand heat treatment after lamination and has a heat distortion temperature of 100°C or higher can be appropriately selected from films made of PET, PBT, or polycarbonate. As a coating device for applying organohydrogen polysiloxane oil to the resin film in a uniform thickness, post-metering type blade coaters, gravure coaters, kissroll coaters, spray coaters, etc., can be used.

[0040] The curing conditions may be the same as those for known addition-curing type silicone rubber compositions. Curing may occur at room temperature, but heating may be used as needed. Preferably, curing is performed at 100°C to 150°C for 1 to 40 minutes, and more preferably at 110°C to 130°C for about 10 to 20 minutes.

[0041] [Hardness of thermal conductive sheet] In the present invention, the hardness of the thermally conductive sheet is preferably 7 or less, more preferably 5 or less, as measured at 25°C using an Asker C hardness tester. If the hardness exceeds 7, it is difficult to obtain the desired good maximum stress.

[0042] [Thermal conductivity of thermal conductive sheets] In the present invention, the thermal conductivity of the molded article is preferably 2.0 W / mK or higher, more preferably 2.5 W / mK or higher, as measured at 25°C by the hot disk method. - If the value is above K, it can be applied to heat-generating elements with high heat output. Regarding the upper limit of thermal conductivity, a higher value is generally better, but it can be set at 5.0 W / mK.

[0043] [Compressive stress of thermally conductive sheets] The compressive stress of the thermally conductive sheet in this invention was measured using an Autograph measuring instrument manufactured by Shimadzu Corporation. This apparatus consists of a sample stage and a compression load cell. A thermally conductive sheet is placed between aluminum plates of a predetermined size, and this is placed on the stage. The load cell compresses the sheet to a specified thickness. For an initial thickness of 1.5 mm, the maximum stress at 50% compression and the residual stress after stress relaxation by holding the compressed material for one minute were measured. The detailed measurement conditions are described below.

[0044] [Measurement conditions] Sample: Circular (Diameter: 32mm, Thickness: 1.5mm) Aluminum plate size: Circular (Diameter: 32mm, Thickness: 2.0mm) Compression amount: 50% Compression speed: 3 mm / min Compression method: Trigger type (After detecting a load of 2N, the amount of compression is counted)

[0045] The present invention relates to a thermal conductive sheet having an initial thickness of 1.5 mm, which, when compressed by 50% at a compression rate of 3 mm / min, exhibits a maximum stress of 0.7 MPa or less, a residual stress of 0.1 MPa or more, and a ratio of 7 / 1 or less between the maximum stress and the residual stress. Such a material results in a thermally conductive sheet with a small difference between maximum stress and residual stress, and a good balance between compressibility and resilience. Therefore, it can be used in various electronic components, such as those for automotive applications. [Examples]

[0046] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0047] [Preparation of composition] The components (a) to (f) used in the following examples and comparative examples are shown below. (a) Components: Alkenyl group-containing organopolysiloxane [ka]

[0048] (b) Ingredients: Organohydrogenpolysiloxane [ka]

[0049] (c) Ingredients: A thermally conductive filler with the following average particle size. (c-1) Average particle size: 1 μm: Aluminum hydroxide (c-2) Average particle size: 8 μm: Aluminum hydroxide (c-3) Average particle size: 50 μm: Aluminum hydroxide (c-4) Average particle size: 1 μm: Alumina (c-5) Average particle size: 10 μm: Alumina (c-6) Average particle size: 45 μm: Alumina (c-7) Average particle size: 75 μm: Alumina The average particle size mentioned above was measured using Microtrac MT3300EX (Nikkiso).

[0050] (d) Ingredients: 5% 2-ethylhexanol chloroplatinate solution

[0051] (e) Ingredients: [ka]

[0052] (f) component: Dimethylpolysiloxane is used as a plasticizer. [ka]

[0053] (g) Ingredients: As an addition reaction control agent, 3-buty-2-ol

[0054] [Examples 1-6, Comparative Examples 1-6] The ingredients (a), (c), (e), and (f) were added in the specified amounts shown in Tables 1 and 2, and mixed in a planetary mixer for 60 minutes. Then, the specified amounts of component (d) and component (g) shown in Tables 1 and 2 were added, and an effective amount of an internal release agent to promote release from the separator was added, and the mixture was kneaded for another 30 minutes. The composition was then obtained by adding the specified amounts of component (b) shown in Tables 1 and 2, kneading for 30 minutes, and then adding the mixture.

[0055] [Method for molding thermally conductive sheets] The obtained composition was poured into a 60mm x 60mm x 6mm mold or a 170mm x 130mm x 1.5mm mold and molded using a press molding machine at 110°C for 10 minutes.

[0056] [Evaluation Method] Hardness: The compositions obtained in Examples 1-6 and Comparative Examples 1-6 were hardened into 6 mm thick sheets, and two of these sheets were stacked together and measured using an Asker C hardness tester. The results are shown in Tables 1 and 2.

[0057] Thermal conductivity: The compositions obtained in Examples 1-6 and Comparative Examples 1-6 were cured into 6 mm thick sheets, and the thermal conductivity of two of these sheets was measured using a thermal conductivity meter (TPA-501, product name manufactured by Kyoto Electronics Manufacturing Co., Ltd.). The results are shown in Tables 1 and 2.

[0058] Compressive stress: The compositions obtained in Examples 1-6 and Comparative Examples 1-6 were cured into 1.5 mm thick sheets, and the maximum stress and residual stress at 50% compression were measured using the Shimadzu Autograph as described above. The results are shown in Tables 1 and 2.

[0059] [Table 1]

[0060] [Table 2]

[0061] In Examples 1 to 6, thermally conductive sheets were molded within the scope described in the present invention, exhibiting good thermal conductivity and a ratio of 7 / 1 or less of maximum stress to residual stress at 50% compression, thus providing a heat dissipation member suitable for automotive electronic components and the like. In Comparative Example 1, the ratio of moles of hydrosilyl groups from component (b) to moles of vinyl groups from component (a) (H / Vi) exceeded 1.3, resulting in an increase in the maximum stress of the sheet and making high compression difficult. In Comparative Example 2, the H / Vi ratio was below 0.75, resulting in a residual stress of less than 0.1 MPa in the sheet and poor sheet resilience. In Comparative Example 3, the amount of thermally conductive filler exceeded 4200 parts by mass, resulting in a maximum stress of over 0.7 MPa on the sheet, making it difficult to compress. In Comparative Example 4, the amount of thermally conductive filler was less than 1000 parts by mass, resulting in poor thermal conductivity of the sheet, making it difficult to apply to high-heat generating elements. In Comparative Example 5, the amount of surface treatment agent was less than 15 parts by mass, resulting in a high maximum stress on the sheet and making high compression difficult. In Comparative Example 6, the amount of surface treatment agent exceeded 200 parts by mass, leading to a decrease in the residual stress on the sheet and resulting in problems with resilience.

[0062] This specification includes the following embodiments: [1]: (a) Organopolysiloxane having 2 to 10 alkenyl groups only on the side chains of the molecular chain: 100 parts by mass (b) Organohydrogenpolysiloxane having hydrosilyl groups at both ends: an amount such that the number of moles of hydrosilyl groups is in the range of 0.75 to 1.3 of the number of moles of alkenyl groups derived from component (a). (c) Thermally conductive filler: 1,000 to 4,200 parts by mass (d) Platinum-based curing catalyst: 0.1 to 1,000 ppm of platinum group elements by weight relative to component (a) (e) Dimethylpolysiloxane with one end sealed with a trialkoxysilyl group: 15-200 parts by mass A thermally conductive sheet made of a cured product of a silicone composition containing, wherein the hardness of the thermally conductive sheet measured with an Asker C hardness tester is 7 or less. A thermal conductive sheet characterized in that, when the thermal conductive sheet with an initial thickness of 1.5 mm is compressed by 50% at a compression rate of 3 mm / min, the maximum stress is 0.7 MPa or less, the residual stress is 0.1 MPa or more, and the ratio of the maximum stress to the residual stress is 7 / 1 or less. [2]: The thermal conductive sheet according to [1], characterized in that the thermal conductive filler in (c) above is one or more selected from aluminum oxide, aluminum hydroxide, magnesium oxide, and aluminum nitride. [3]: The thermal conductive sheet according to [1] or [2], characterized in that the shape of the thermal conductive filler in (c) above is crushed, rounded, or spherical. [4]: A thermal conductive sheet according to any one of [1] to [3], characterized in that the average particle size of the thermal conductive filler in (c) above is 0.5 to 100 μm. [5]: A thermally conductive sheet according to any one of [1] to [4], characterized in that it has a thermal conductivity of 2.0 W / mK or more.

[0063] It should be noted that the present invention is not limited to the embodiments described above. The embodiments described above are illustrative, and any configuration that is substantially identical to the technical idea described in the claims of the present invention and achieves similar effects is included within the technical scope of the present invention.

Claims

1. (a) Organopolysiloxane having 2 to 10 alkenyl groups only on the side chains of the molecular chain: 100 parts by mass (b) Organohydrogenpolysiloxane having hydrosilyl groups at both ends: an amount such that the number of moles of hydrosilyl groups is in the range of 0.75 to 1.3 of the number of moles of alkenyl groups derived from component (a). (c) Thermally conductive filler: 1,000 to 4,200 parts by mass (d) Platinum-based curing catalyst: 0.1 to 1,000 ppm of platinum group elements by weight relative to component (a) (e) Dimethylpolysiloxane with one end sealed with a trialkoxysilyl group: 15 to 200 parts by mass A thermally conductive sheet made of a cured product of a silicone composition containing, wherein the hardness of the thermally conductive sheet measured with an Asker C hardness tester is 7 or less. A thermally conductive sheet characterized in that, when the thermally conductive sheet with an initial thickness of 1.5 mm is compressed by 50% at a compression rate of 3 mm / min, the maximum stress is 0.7 MPa or less, the residual stress is 0.1 MPa or more, and the ratio of the maximum stress to the residual stress is 7 / 1 or less.

2. The thermal conductive sheet according to claim 1, characterized in that the (c) thermal conductive filler is one or more selected from aluminum oxide, aluminum hydroxide, magnesium oxide, and aluminum nitride.

3. The thermal conductive sheet according to claim 1, characterized in that the shape of the thermal conductive filler (c) is crushed, rounded, or spherical.

4. The thermal conductive sheet according to claim 1, characterized in that the average particle size of the thermal conductive filler (c) is 0.5 to 100 μm.

5. The thermal conductive sheet according to claim 1, characterized in that its thermal conductivity is 2.0 W / m-K or higher.

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