Thermally 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] The present invention relates to a thermally conductive sheet. [Background technology]

[0002] Due to the miniaturization and high integration of electronic components, there is a demand for thermally conductive sheets that have excellent thermal conductivity, as well as a low maximum stress during assembly processing and are soft enough to minimize load on heat-generating components. Patent Document 1 proposes a sheet that can follow electronic components with a 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 providing unevenness on the surface of a thermally conductive sheet. Patent Document 3 proposes a sheet with excellent flexibility that exhibits a compressive residual stress of 0.1 MPa or less by specifying the viscosity of the polymer component.

[0003] However, for various electronic components to be mounted in vehicles, while it is preferable for the maximum stress during assembly to be low, they are also required to have the resilience (a certain level of residual stress) to accommodate fluctuations in the clearance between the thermal conductive sheet and the electronic components caused by vibrations of the vehicle after mounting. In other words, thermally conductive sheets used in automotive environments need to have a small difference between maximum stress and residual stress, and need to be both easy to crush and have appropriate resilience due to rubber elasticity, and further improvement was needed in this regard. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2003-253136 A [Patent Document 2] JP 2001-217360 A [Patent Document 3] Patent No. 6705067 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0005] The present invention aims to provide a thermally conductive sheet that has excellent thermal conductivity, a small difference between maximum stress and residual stress, and a good balance of compressibility and recovery properties, so that it can be used as a heat dissipation member for a wide range of applications to various types of in-vehicle electrical equipment. [Means for solving the problem]

[0006] The present invention has been made to solve the above problems, and provides the following thermally conductive sheet.

[0007] That is, the present invention provides: (a) Organopolysiloxane having 2 to 10 alkenyl groups only on the molecular side chains: 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 by weight of platinum group element relative to component (a) (e) Dimethylpolysiloxane having one end blocked with a trialkoxysilyl group: 15 to 200 parts by mass wherein the thermally conductive sheet has a hardness of 7 or less as measured by an Asker C hardness scale; The thermally conductive sheet is characterized in that when the thermally conductive sheet having an initial thickness of 1.5 mm is compressed 50% at a compression speed 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 has excellent thermal conductivity, a small difference between the maximum stress and the residual stress, and a good balance between compressibility and restorability.

[0009] The above-mentioned (c) thermally conductive filler is preferably at least one selected from aluminum oxide, aluminum hydroxide, magnesium oxide, and aluminum nitride.

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

[0011] The shape of the thermally conductive filler (c) may be crushed, rounded, or spherical.

[0012] The above (c) thermally conductive filler preferably has an average particle size of 0.5 to 100 μm.

[0013] Those having an average particle size of 0.5 to 10 μm and those in a crushed or rounded shape can form an efficient heat conduction path, thereby increasing the thermal conductivity.

[0014] In this case, the thermal conductivity is preferably 2.0 W / mK or more.

[0015] If the thermal conductivity of the thermally conductive sheet is 2.0 W / mK or more, the thermally conductive sheet can be applied to a heat generating body that generates a large amount of heat. Effect of the Invention

[0016] According to the present invention, by appropriately crosslinking an organopolysiloxane having alkenyl groups only on the molecular side chains with an organohydrogenpolysiloxane having hydrosilyl groups at both ends, it is possible to obtain a silicone polymer with an appropriate crosslink density and which maintains good compressibility and residual stress. Furthermore, by blending a thermally conductive filler that imparts 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, thereby improving the residual stress. Such sheets have an excellent balance between maximum stress and residual stress, making them suitable for use in a variety of electronic components for use in automobiles. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The present invention will be described in detail below, but the present invention is not limited thereto. The present inventors have 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 that can combine ease of crushing with a rebound characteristic due to moderate rubber elasticity, and have found that the above-mentioned object can be achieved by a thermally conductive sheet characterized in that the silicone composition contains an organopolysiloxane having 2 to 10 alkenyl groups only on the molecular chain side chain, an organohydrogenpolysiloxane 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, the hardness of the thermally conductive sheet measured with an Asker C hardness tester is 7 or less, the maximum stress is 0.7 MPa or less when the thermally conductive sheet having an initial thickness of 1.5 mm is compressed 50% at a compression speed of 3 mm / min, 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. The present invention has been completed. Each component will be described below.

[0018] (a) Organopolysiloxane having 2 to 10 alkenyl groups only on the side chains of the molecular chain The alkenyl-containing organopolysiloxane, which is component (a), contains 2 to 10 alkenyl groups only in the side chain portion of each molecule, and is generally a straight-chain structure in which the main chain portion is basically composed of repeated diorganosiloxane units and both ends of the molecular chain are blocked with triorganosiloxy groups. The molecular structure may include a branched structure or may be cyclic, but linear diorganopolysiloxanes are preferred in terms of physical properties such as the mechanical strength of the cured product. An example of component (a) is a structure represented by the following general formula (1). [ka] (In general formula (1), R 1are independently selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms, X is an alkenyl group having 2 to 6 carbon atoms, n is an integer of 0 or 1 or more, and m is an integer of 2 or more. The siloxane units enclosed in parentheses with m and n may be bonded in a block or random manner.

[0019] In general formula (1), R 1 Examples of the alkyl group 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. Representative groups have 1 to 7 carbon atoms, and particularly representative groups have 1 to 5 carbon atoms, and preferably alkyl groups such as methyl, ethyl, and propyl groups, and phenyl groups. In addition, these R 1 In addition, a part of the hydrogen atoms may be substituted with halogen atoms such as fluorine.

[0020] In the general formula (1), examples of the alkenyl group for X include those having 2 to 6 carbon atoms, such as a vinyl group, an allyl group, a propenyl group, an isopropenyl group, a butenyl group, and a hexenyl group. Of these, a vinyl group and an allyl group are preferred, and a vinyl group is particularly preferred. In the general formula (1), n ​​is an integer of 0 or 1 or more, and m is an integer of 2 to 10. Moreover, n and m are preferably integers satisfying 10≦n+m≦5,000, more preferably 50≦n+m≦1,000, and even more preferably 100≦n+m≦500 and 0.001≦m / (n+m)≦0.05. The bonds of the siloxane units enclosed in parentheses with the above m and n may be block or random.

[0021] (b) Organohydrogenpolysiloxane The organohydrogenpolysiloxane of component (b) must have at least two, preferably 2 to 4, hydrogen atoms (hydrosilyl groups) directly bonded to silicon atoms in each molecule, with hydrosilyl groups at both ends. If the number of hydrosilyl groups is less than two, there is a risk that the resin will not cure. An example of the organohydrogenpolysiloxane is represented by the following general formula (2). [ka] (In general formula (2), R 1 is the same as above. o is an integer of 0 or more and less than 200, and p is an integer of 0 or more and less than 200. The bonds of the siloxane units enclosed in parentheses with o and p above may be block or random.

[0022] In the above general formula (2), R 1 As in the above general formula (1), each is independently a group selected from an alkyl group having 1 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, and an aralkyl group having 7 to 10 carbon atoms. Specific examples and preferred aspects thereof are the same as those in the above general formula (1). In the above general formula (2), o represents an integer of 0 or more and less than 200, and p represents an integer of 0 or more and less than 200. These numerical values ​​indicate the numerical values ​​in the average structural formula of component (b), and are not limited at the molecular level. The bonds of the siloxane units enclosed in parentheses with o and p may be block or random.

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

[0024] (c) Thermally conductive filler The thermally conductive filler, component (c), can be any of the following materials generally considered to be thermally conductive fillers: non-magnetic metals such as copper and aluminum; metal oxides such as aluminum oxide, silicon dioxide, magnesium oxide, beryllium oxide, titanium oxide and zirconium oxide; metal nitrides such as aluminum nitride, silicon nitride and boron nitride; metal hydroxides such as aluminum hydroxide and magnesium hydroxide; artificial diamond or silicon carbide.

[0025] In particular, from the viewpoints of thermal conductivity and filling ability with silicone, it is preferable to use aluminum oxide, aluminum hydroxide, magnesium oxide, and aluminum nitride. The thermally conductive filler preferably has an average particle size of 0.5 to 100 μm, more preferably 1 to 80 μm. These fillers may be used alone or in combination. 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 measuring device, for example, Microtrac MT3300EX (Nikkiso), and the average particle size is a volume-based value (when measuring the volume distribution of particles, this refers to the diameter at which the larger and smaller sides are equal in amount when divided into two at the average particle size).

[0026] The shape of the thermally conductive filler is preferably crushed, rounded, or spherical, and a combination of different shapes can be used. In particular, those with an average particle size of 10 to 100 μm are preferably spherical from the viewpoint of packing properties, and those with an average particle size of 0.5 to 10 μm are preferably crushed or rounded because they can get into the gaps between larger particle size fillers and efficiently form a heat conduction path. In the present invention, the term "spherical" refers to a thermally conductive filler with an aspect ratio of 1.5 or less, and the term "crushed or rounded" refers to a thermally conductive filler with an aspect ratio of more than 1.5. Furthermore, the term "fractured" includes angular portions, and the term "rounded" refers to a rounded shape.

[0027] The amount of component (c) must be 1,000 to 4,200 parts by mass, and preferably 1,500 to 3,800 parts by mass, per 100 parts by mass of component (a). If the amount is less than 1,000 parts by mass, the resulting composition will have poor thermal conductivity, and the thermal conductive sheet will have poor storage stability. On the other hand, if the amount 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 curing 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 examples of such catalysts include platinum-based catalysts well known as catalysts used in hydrosilylation reactions. Specific examples thereof include platinum group metals such as platinum (including platinum black), rhodium, and palladium, platinum chlorides such as HPtCl4·nH2O, HPtCl6·nH2O, NaHPtCl6·nH2O, KHPtCl6·nH2O, Na2PtCl6·nH2O, K2PtCl4·nH2O, PtCl4·nH2O, PtCl2, and Na2HPtCl4·nH2O (wherein n is an integer of 0 to 6, preferably 0 or 6), chloroplatinic acid and chloroplatinic acid salts, and alcohol-modified chloroplatinic acid (see U.S. Pat. No. 3,220,972, specification), and the like. Examples of such catalysts include platinum complexes, complexes of chloroplatinic acid and olefins (see U.S. Pat. Nos. 3,159,601, 3,159,662, and 3,775,452), platinum black, platinum group metals such as palladium supported on carriers such as alumina, silica, and carbon, rhodium-olefin complexes, chlorotris(triphenylphosphine)rhodium (Wilkinson's catalyst), complexes of platinum chloride, chloroplatinic acid, or chloroplatinate salts with vinyl group-containing siloxanes, particularly vinyl group-containing cyclic siloxanes. The amount of component (d) used is 0.1 to 1,000 ppm, preferably 1 to 500 ppm, calculated as the volume of the platinum group metal element relative to component (a).

[0029] (e) Dimethylpolysiloxane with one end capped with a trialkoxysilyl group Component (e), dimethylpolysiloxane with one end capped 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, R2 is independently an alkyl group having 1 to 6 carbon atoms, preferably a methyl group or an ethyl group. q is an integer of 5 to 100, preferably an integer of 10 to 60. The amount of the component (e) added is 15 to 200 parts by mass, preferably 30 to 150 parts by mass, per 100 parts by mass of the component (a). If the amount of the component (e) is less than 15 parts by mass, the wettability of the heat conductive filler (c) and the polymer is poor, and there are problems with the moldability of the sheet and the maximum stress during compression. On the other hand, if the amount exceeds 200 parts by mass, oil separation is easily induced, the storage stability of the material is poor, and the residual stress during compression is reduced.

[0031] [Other optional ingredients] In addition, it is possible to add effective amounts of various additives to improve functionality, such as reaction control agents for adjusting the curing speed, pigments and dyes for coloring, flame retardants, internal release agents for improving release from metal molds or separator films, and plasticizers for adjusting the viscosity of the composition and the hardness of molded products.

[0032] Examples of the reaction inhibitor and the plasticizer are given below, but the present invention is not limited to these.

[0033] [(f) Plasticizers] The composition of the present invention further comprises (f) a plasticizer represented by the following general formula (4): [ka] (R 6 are each independently a monovalent hydrocarbon group having 1 to 8 carbon atoms and containing no aliphatic unsaturated bonds, and d is an integer of 5 to 2,000. The kinematic viscosity at 25°C measured using a Cannon-Fenske viscometer is 10 to 100,000 mm 2 The organopolysiloxane may include an organopolysiloxane having the formula: The component is not particularly limited as long as it is appropriately used to impart properties such as viscosity adjusting agent to the thermal conductive composition. One type may be used alone, or two or more types may be used in combination.

[0034] Above R 6 are each independently a monovalent hydrocarbon group having 1 to 8 carbon atoms and containing no aliphatic unsaturated bonds, 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. Examples include alkyl groups such as methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, neopentyl, hexyl, heptyl, and octyl, cycloalkyl groups such as cyclopentyl, cyclohexyl, and cycloheptyl, aryl groups such as phenyl, tolyl, and xylyl, and aralkyl groups such as benzyl, phenylethyl, phenylpropyl, and methylbenzyl. Preferred are methyl, ethyl, propyl, and phenyl, and particularly preferred are methyl and phenyl.

[0035] The kinematic viscosity of the organopolysiloxane at 25° C. as measured with a Canon-Fenske viscometer is preferably 10 to 100,000 mm 2 / s, and particularly preferably 100 to 10,000 mm 2 / s. The kinetic viscosity is 10mm 2 If the kinematic viscosity is 100,000 mm / s or more, the resulting cured product of the composition will not exhibit oil bleeding. 2 If the viscosity is less than or equal to 1 / s, the resulting thermally conductive composition has good flexibility. In the above general formula (4), d may be any value that allows the kinematic viscosity of the organopolysiloxane to fall within the above-mentioned range, and is preferably an integer from 5 to 2,000, and more preferably an integer from 10 to 1,000.

[0036] The amount of component (f) in the composition of the present invention is not particularly limited, and may be an amount that provides the desired effect as a plasticizer. Usually, the amount is preferably 1 to 20 parts by mass, 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 tends to maintain good fluidity and workability, and it becomes easy to fill the thermally conductive filler of component (c) into the composition.

[0037] [(g) Reaction control agent] (g) The reaction inhibitor may be any known addition reaction inhibitor used in ordinary addition reaction curing silicone compositions. Examples include acetylene compounds such as 1-ethynyl-1-hexanol and 3-butyn-1-ol, various nitrogen compounds, organic phosphorus compounds, oxime compounds, and organic chloro compounds. The amount used is preferably about 0.01 to 1 part by mass.

[0038] [Viscosity of 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. If the viscosity is within this range, the thermally conductive silicone composition can be discharged using a pump, and the thermally conductive sheet can be molded with good yield. In particular, a viscosity of 300 Pa·s or less is preferable because it provides better moldability. There is no particular lower limit to the viscosity, but it is usually about 10 Pa·s. The viscosity is measured using a modular rheometer, MARS40, manufactured by HAAKE.

[0039] [Method of manufacturing thermally conductive sheets] The thermally conductive silicone composition of the present invention can be applied to a substrate such as a resin film and cured to obtain a thermally conductive sheet. The resin film can be selected from those that can withstand heat treatment after lamination and have a heat distortion temperature of 100°C or higher, such as PET, PBT, and polycarbonate films. A post-metering type blade coater, gravure coater, kiss roll coater, spray coater, etc. can be used as a coating device for applying organohydrogenpolysiloxane oil to the resin film in a uniform thickness.

[0040] The curing conditions may be the same as those for known addition reaction curing silicone rubber compositions, and the composition may be cured at room temperature, or may be heated as necessary. The curing is preferably carried out at 100°C to 150°C for 1 to 40 minutes, and more preferably at 110 to 130°C for about 10 to 20 minutes.

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

[0042] [Thermal conductivity of thermally conductive sheets] The thermal conductivity of the molded article of the present invention is desirably 2.0 W / mK or more, more desirably 2.5 W / mK or more, as measured by the hot disk method at 25° C. If the thermal conductivity is 2.0 W / mK or more, the molded article can be applied to a heating body that generates a large amount of heat.

[0043] [Compressive stress of thermal conductive sheet] The compressive stress of the thermally conductive sheet in the present invention was measured using an autograph manufactured by Shimadzu Corporation. This device is equipped with a sample stage and a compression load cell, and a thermally conductive sheet is sandwiched between aluminum plates of a specified size, which is placed on the stage and compressed to a specified thickness by the load cell. For an initial thickness of 1.5 mm, the maximum stress at 50% compression and the residual stress after stress relaxation by holding the sheet in compression for one minute were measured. The detailed measurement conditions are described below.

[0044] [Measurement conditions] Sample: circular (diameter: 32 mm, thickness: 1.5 mm) Aluminum plate size: circular (diameter: 32 mm, thickness: 2.0 mm) Compression amount: 50% Compression speed: 3mm / min Compression method: Trigger method (counts the amount of compression after detecting 2N load)

[0045] The present invention is a thermally conductive sheet in which, when the thermally conductive sheet having an initial thickness of 1.5 mm is compressed 50% at a compression speed 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. Such a thermal conductive sheet has a small difference between the maximum stress and the residual stress, and has a good balance between compressibility and recovery, and can therefore be used in various electronic parts for vehicles and the like. 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. Component (a): Alkenyl group-containing organopolysiloxane [ka]

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

[0049] (c) Ingredients: A thermally conductive filler having an average particle size as follows: (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 above average particle size was measured using a Microtrac MT3300EX (Nikkiso).

[0050] (d) Ingredients: 5% chloroplatinic acid solution in 2-ethylhexanol

[0051] (e) Ingredients: [ka]

[0052] (f) Ingredients: Dimethylpolysiloxane as a plasticizer. [ka]

[0053] (g) Ingredients: 3-Butyn-2-ol as an addition reaction regulator

[0054] [Examples 1 to 6 and Comparative Examples 1 to 6] The components (a), (c), (e) and (f) were added in the amounts shown in Tables 1 and 2, and kneaded for 60 minutes in a planetary mixer. To this were added the components (d) and (g) in the prescribed amounts shown in Tables 1 and 2, and further an effective amount of an internal release agent for promoting release from the separator was added, followed by kneading for a further 30 minutes. The component (b) was further added in a prescribed amount shown in Tables 1 and 2, and the mixture was kneaded for 30 minutes to obtain a composition.

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

[0056] [Evaluation method] Hardness: The compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were cured into a sheet having a thickness of 6 mm, and two of the sheets were stacked 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 to 6 and Comparative Examples 1 to 6 were cured into sheets having a thickness of 6 mm, and the thermal conductivity of two of the sheets was measured using a thermal conductivity meter (TPA-501, product name of Kyoto Electronics Manufacturing Co., Ltd.). The results are shown in Tables 1 and 2.

[0058] Compressive stress: The compositions obtained in Examples 1 to 6 and Comparative Examples 1 to 6 were cured into sheets having a thickness of 1.5 mm, and the maximum stress and residual stress at 50% compression were measured under the conditions described above using an autograph manufactured by Shimadzu Corporation. 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 ranges described in the present invention, and exhibited good thermal conductivity. The ratio of maximum stress to residual stress at 50% compression was 7 / 1 or less, providing a heat dissipation member suitable for in-vehicle electronic components, etc. In Comparative Example 1, the ratio (H / Vi) of the number of moles of hydrosilyl groups derived from component (b) to the number of moles of vinyl groups derived from component (a) exceeded 1.3, so the maximum stress of the sheet increased, making it difficult to achieve high compression. In Comparative Example 2, the ratio H / Vi was below 0.75, so the residual stress of the sheet was below 0.1 MPa, making it difficult to restore the sheet. In Comparative Example 3, the amount of the thermally conductive filler exceeded 4200 parts by mass, so the maximum stress of the sheet exceeded 0.7 MPa, and there were problems with compressibility. In Comparative Example 4, the amount of the thermally conductive filler was less than 1000 parts by mass, so the thermal conductivity of the sheet was poor and it was difficult to apply it to a high heat generating body. In Comparative Example 5, the amount of the surface treatment agent was less than 15 parts by mass, so the maximum stress of the sheet was high and it was difficult to achieve high compression.In Comparative Example 6, the amount of the surface treatment agent was more than 200 parts by mass, so the residual stress of the sheet was low and there was a problem with the restoring ability.

[0062] The present specification includes the following aspects. [1]: (a) organopolysiloxane having 2 to 10 alkenyl groups only on the molecular side chains: 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 by weight of platinum group element relative to component (a) (e) Dimethylpolysiloxane having one end blocked with a trialkoxysilyl group: 15 to 200 parts by mass wherein the thermally conductive sheet has a hardness of 7 or less as measured by an Asker C hardness scale; A thermally conductive sheet characterized in that, when the thermally conductive sheet having an initial thickness of 1.5 mm is compressed 50% at a compression speed 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 thermally conductive sheet according to [1], wherein the thermally conductive filler (c) is at least one selected from the group consisting of aluminum oxide, aluminum hydroxide, magnesium oxide, and aluminum nitride. [3]: The thermally conductive sheet according to [1] or [2], characterized in that the shape of the thermally conductive filler (c) is crushed, rounded, or spherical. [4]: The thermally conductive sheet according to any one of [1] to [3], wherein the average particle size of the thermally conductive filler (c) is 0.5 to 100 μm. [5]: A thermally conductive sheet according to any one of [1] to [4], characterized in that the thermal conductivity is 2.0 W / mK or more.

[0063] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention.

Claims

1. (a) Organopolysiloxane having 2 to 10 alkenyl groups only on the molecular side chains: 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 by weight of platinum group element relative to component (a) (e) Dimethylpolysiloxane having one end blocked with a trialkoxysilyl group: 15 to 200 parts by mass wherein the thermally conductive sheet has a hardness of 7 or less as measured by an Asker C hardness scale; A thermally conductive sheet characterized in that, when the thermally conductive sheet having an initial thickness of 1.5 mm is compressed 50% at a compression speed 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. 2. The thermally conductive sheet according to claim 1, wherein the thermally conductive filler (c) is at least one selected from the group consisting of aluminum oxide, aluminum hydroxide, magnesium oxide, and aluminum nitride.

3. The thermally conductive sheet according to claim 1 , wherein the shape of the thermally conductive filler (c) is crushed, rounded, or spherical.

4. 2. The thermally conductive sheet according to claim 1, wherein the average particle size of the thermally conductive filler (c) is 0.5 to 100 μm.

5. 2. The thermally conductive sheet according to claim 1, which has a thermal conductivity of 2.0 W / mK or more.

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