Heat dissipation composition, heat dissipation member, and filler aggregate for heat dissipation member

Abstract

The heat-dissipating composition of the present invention contains a polymer matrix and diamond particles, and provides a heat-dissipating composition that has both insulating properties and heat-dissipating properties.

Description

Technical Field

[0001] The present invention relates to a heat dissipation member used in electronic devices and the like, a heat dissipation composition for forming the heat dissipation member, and a filler aggregate for a heat dissipation member to be blended in the heat dissipation member.

Background Art

[0002] In electronic devices, since integrated electronic components generate heat and cause failures, a heat dissipation member for dissipating the heat generated from the electronic components to the outside of the device may be provided. The heat dissipation member is disposed, for example, between an electronic component and a housing or a heat sink. Further, the heat dissipation member is generally a resin or an elastomer blended with a heat conductive filler. For example, Patent Document 1 discloses a thermally conductive silicone rubber composition in which a silicone resin is blended with a thermally conductive filler such as alumina, magnesium oxide, and boron nitride.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, with the miniaturization and high performance of electric devices, a technology for efficiently dissipating heat generated during driving has been demanded. In addition, the shapes of electronic components have become more complex, and accordingly, it has become difficult to accurately apply a paste-like material. Therefore, if a conductive material is applied to an unintended place, it may cause abnormal operation or ignition. Therefore, the heat dissipation member is required to have both insulation and heat dissipation properties.

[0005] However, with conventional general insulating thermal conductive fillers such as alumina, magnesium oxide, and boron nitride, and general non-insulating thermal conductive fillers such as zinc oxide and aluminum, it has not been possible to achieve both heat dissipation and insulation. Therefore, an object of the present invention is to provide a heat dissipation composition, a heat dissipation member, and a filler aggregate for a heat dissipation member that have both insulation and heat dissipation properties.

Means for Solving the Problems

[0006] As a result of intensive studies, the present inventors have found that the above problems can be solved by using diamond as the thermal conductive filler of the heat dissipation composition, the heat dissipation member, and the filler aggregate for the heat dissipation member, and have completed the following present invention. That is, the present invention provides the following (1) to (18). (1) A heat dissipation composition containing a polymer matrix and diamond particles. (2) The heat dissipation composition according to (1) above, wherein the slope of the change in the thermal resistance value with respect to the change in thickness is 1.8 or less. (3) The heat dissipation composition according to (1) or (2) above, wherein the diamond particles contain two or more types of diamonds having different average particle diameters. (4) The heat dissipation composition according to any one of (1) to (3) above, wherein the diamond particles have an average particle diameter of 0.1 μm or more and 200 μm or less. (5) The heat dissipation composition according to any one of (1) to (4) above, wherein the diamond particles contain large-diameter diamonds having an average particle diameter of 10 μm or more and 200 μm or less and small-diameter diamonds having an average particle diameter of 0.1 μm or more and less than 10 μm. (6) The heat dissipation composition according to any one of (1) to (5) above, wherein the diamond particles are surface-treated with a silane compound. (7) The heat dissipation composition according to any one of (1) to (6) above, wherein the sphericity of the diamond particles is 0.5 or more. (8) The heat dissipation composition according to (1) to (7) above, wherein the filling rate of the diamond particles is 15% by volume or more. (9) The heat dissipation composition according to any one of (1) to (8) above, which contains other heat conductive fillers other than diamond particles. (10) The heat dissipation composition according to (9) above, wherein the average particle diameter of the other heat conductive fillers is 0.1 μm or more and 200 μm or less. (11) The diamond particles are contained in the heat dissipation composition, or both diamond particles and other heat conductive fillers other than diamond particles are contained, The heat dissipation composition according to any one of (1) to (10) above, wherein the total filling ratio of the diamond particles and the other heat conductive fillers is 40% by volume or more and 92% by volume or less. (12) The heat dissipation composition contains diamond particles as heat conductive fillers, or both diamond particles and other heat conductive fillers other than diamond particles are contained, The heat dissipation composition according to any one of (1) to (11) above, wherein the volume ratio of the large particle size fillers having an average particle diameter of 10 μm or more and 200 μm or less to the small particle size fillers having an average particle diameter of 0.1 μm or more and less than 10 μm in the heat conductive fillers is 0.2 or more and 5 or less. (13) The heat dissipation composition according to any one of (1) to (12) above, wherein the void ratio is 3% or less. (14) The heat dissipation composition according to any one of (1) to (13) above, wherein the contact angle of the polymer matrix with respect to the heat conductive fillers containing the diamond particles is 70° or less. (15) The heat dissipation composition according to any one of (1) to (14) above, wherein the surface oxygen amount of the diamond particles is 5% or more. (16) A heat dissipation member formed of the heat dissipation composition according to any one of (1) to (15) above. (17) A filler aggregate for a heat dissipation member containing diamond particles. (18) The filler aggregate for a heat dissipation member according to (17) above, which contains two or more types of diamond particles having different average particle diameters from each other.

Advantages of the Invention

[0007] According to the present invention, it is possible to provide a heat dissipation composition, a heat dissipation member, and a filler aggregate for a heat dissipation member that achieve both insulation and heat dissipation properties.

Embodiments for Carrying Out the Invention

[0008] Hereinafter, the present invention will be described using embodiments. [Heat Dissipation Composition] The heat dissipation composition of the present invention contains a polymer matrix and diamond particles. By containing diamond particles with high thermal conductivity as a thermal conductive filler, the heat dissipation composition maintains a high volume resistivity while having a low thermal resistance value, and has both insulation and heat dissipation properties.

[0009] The heat dissipation composition of the present invention preferably has a slope (ΔW / ΔD) of the change in thermal resistance value with respect to the change in thickness of 1.8 or less. Here, ΔW / ΔD (unit: K·cm 2 / W·mm), as described in the examples below, measures the thermal resistance values (W1, W2) in the thickness direction when the heat dissipation composition has different thicknesses (D1, D2), and ΔW (unit: K·cm 2 / W) / ΔD (unit: mm) = (W2 - W1) / (D2 - D1). In the present invention, by setting the slope (ΔW / ΔD) to 1.8 or less, the heat dissipation property becomes good, and for example, heat spots generated by thickness unevenness can be sufficiently suppressed.

[0010] Also, from the viewpoint of making the heat dissipation property better, the slope (ΔW / ΔD) is more preferably 1.6 or less, still more preferably 1.4 or less, and even more preferably 1.1 or less. Also, the slope (ΔW / ΔD) is preferably as low as possible from the viewpoint of heat dissipation property, but in practical terms, for example, it is 0.1 or more, preferably 0.3 or more. The slope (ΔW / ΔD) can be adjusted within the above-described desired range by appropriately changing, for example, the shape, size, blending amount, surface treatment method, etc. of the diamond, and by blending a thermal conductive filler other than diamond as described below and appropriately changing the shape, size, blending amount, surface treatment method, etc. of the thermal conductive filler.

[0011] In addition, the heat dissipation composition of the present invention preferably has a volume resistivity of 1.0×10 13 (Ω·m) or more and a dielectric breakdown voltage strength of 10 kV / mm or more, and more preferably 20 kV / mm or more. Since both the volume resistivity and the dielectric breakdown voltage strength of the heat dissipation composition of the present invention are at least a predetermined value in this way, the insulation property becomes good, and it is possible to prevent the cause of abnormal operation or the like.

[0012] Furthermore, the heat dissipation composition of the present invention preferably has a void ratio of 3% or less. When the void ratio is 3% or less, in the case of containing diamond particles, the thermal conductivity of the heat dissipation composition can be increased to obtain excellent heat dissipation properties. As shown in Reference Examples 1 and 2, for thermal conductive fillers other than diamond particles, the influence of the void ratio on heat dissipation reduction is not significant. It is presumed that this is because, in the case of fillers other than diamond particles, the thermal conductivity of the filler is low and the thermal conductivity of the heat dissipation composition is also low, so the influence of voids is not significant. On the other hand, diamond particles have a high thermal conductivity and can also improve the thermal conductivity of the heat dissipation composition. Therefore, the influence of the void ratio on heat dissipation is large. In particular, when diamond particles are used, if the void ratio is higher than 3%, the thermal conductivity becomes lower compared to the case where the void ratio is 3% or less. That is, the inventors have found that when diamond particles are used, the heat dissipation can be further enhanced by setting the void ratio to 3% or less. It is presumed that such an effect can be achieved because, in the case of diamond particles, the influence of voids on thermal conductivity is large due to the high thermal conductivity.

[0013] In addition, when the void ratio is 3% or less to reduce the voids in the composition, even when a voltage is applied, the progress of the breakdown of the heat dissipation composition starting from the voids can be suppressed. Therefore, the heat dissipation composition is less likely to undergo dielectric breakdown, and it is easier to increase the dielectric breakdown voltage strength. Furthermore, from the viewpoint of obtaining high heat dissipation and high dielectric breakdown voltage strength, the void ratio of the heat dissipation composition is more preferably 2% or less, even more preferably 1% or less, still more preferably 0.9% or less, and most preferably 0.7% or less. The lower the void ratio of the heat dissipation composition, the better, and it may be 0% or more.

[0014] The void ratio can be adjusted, for example, by the wettability between a heat conductive filler such as diamond particles and a polymer matrix. The adjustment of the wettability between the heat conductive filler and the polymer matrix can be achieved, for example, as described below, by the amount of surface oxygen of diamond particles and the presence or absence of surface treatment of the heat conductive filler. Specifically, the preferred wettability between the heat conductive filler and the polymer matrix is, for example, a contact angle between the heat conductive filler and the polymer matrix in the range of 65° or less. Also, the void ratio can be lowered by adopting a method of reducing voids in the manufacturing process of the heat dissipation composition. For example, it is advisable to adopt heat vacuum kneading under reduced pressure when heat kneading the heat dissipation composition. Also, when filling the heat dissipation composition into a syringe, the void ratio may be lowered by filling the syringe while performing vacuum suction. Furthermore, it is also possible to reduce the void ratio by applying pressure after syringe filling and dissolving gas in the resin.

[0015] Note that the void ratio can be calculated by (1 - Dr / Di) × 100, where Dr is the actual density of the heat dissipation composition and Di is the ideal density of the heat dissipation composition assuming no voids, calculated from the density and mixing ratio of each component. The density Di can be measured from the heat dissipation composition as shown in the examples described below. At that time, the polymer matrix and various heat conductive fillers contained in the heat dissipation composition are separated, and the weight and density of each component are measured to calculate it. However, the method for separating the polymer matrix and the heat conductive filler is not limited to the method described in the examples below and can be appropriately changed depending on the type of the polymer matrix and the type of the heat conductive filler.

[0016] (Polymer matrix) The polymer matrix in the present invention includes resins, liquid polymer components, and the like. Examples of the resin include curable resins such as silicone resin, epoxy resin, urethane resin, phenol resin, unsaturated polyester resin, and polyimide resin. The curable resin may be any of moisture-curable type, thermosetting type, and photocurable type, but the thermosetting type is preferred. In addition, polyolefin resins such as polypropylene resin, polyethylene resin, poly(1-)butene resin, and polypentene resin, polyester resins such as polyethylene terephthalate, polystyrene resin, acrylonitrile-butadiene-styrene (ABS) resin, ethylene-vinyl acetate copolymer (EVA), (meth)acrylic resins, polyamide resins, and thermoplastic resins such as polyvinyl chloride resin (PVC) may also be used.

[0017] Examples of the elastomer resin include acrylonitrile-butadiene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, natural rubber, polybutadiene rubber, and polyisoprene rubber. These elastomer resins may be liquid elastomers that are liquid at room temperature (23°C) and normal pressure (1 atm), solid ones, or mixtures thereof. In addition, as the elastomer resin, thermoplastic elastomers such as polyester-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and styrene-based thermoplastic elastomers can also be used.

[0018] The polymer matrix may use silicone oil or the like as the liquid polymer component. These liquid polymer components may be used alone or in combination with a resin. The liquid polymer component is liquid at room temperature and normal pressure during compounding and is also liquid or gel-like during use. That is, the liquid polymer component is not cured by a curing agent or the like, and even if it is cured, it remains liquid or gel-like after curing. Therefore, when the liquid polymer component is used alone or at a relatively high compounding ratio, the heat dissipation member formed from the heat dissipation composition can be made into a paste form.

[0019] Among the above-mentioned materials, as the polymer matrix, silicone such as silicone resin and silicone oil, and epoxy resin are preferable, and silicone resin is more preferable. The silicone resin may be either a condensation-curing type silicone resin or an addition-reaction-curing type silicone resin, but the addition-reaction-curing type silicone resin is preferable.

[0020] The addition-reaction-curing type silicone resin preferably consists of a silicone compound as the main agent and a curing agent for curing the main agent. The silicone compound used as the main agent is preferably an organopolysiloxane having an alkenyl group. Specifically, vinyl-terminated organopolysiloxanes such as vinyl-terminated polydimethylsiloxane, vinyl-terminated polyphenylmethylsiloxane, vinyl-terminated dimethylsiloxane-diphenylsiloxane copolymer, vinyl-terminated dimethylsiloxane-phenylmethylsiloxane copolymer, and vinyl-terminated dimethylsiloxane-diethylsiloxane copolymer can be mentioned. The viscosity of the silicone compound used as the main agent 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 150 mPa·s or more and 600 mPa·s or less. In this specification, the viscosity may be measured at a rotational speed of 5 rpm and a measurement temperature of 25°C using a rotor of spindle No. 14 with a viscometer (BROOKFIELD rotational viscometer DV-E).

[0021] As the curing agent used for the addition reaction-curable silicone resin, there is no particular limitation as long as it can cure the above-described silicone compound serving as the main agent. However, organohydrogenpolysiloxane, which is an organopolysiloxane having two or more hydrosilyl groups (SiH), is preferable. The ratio (molar ratio) of the hydrosilyl group to the vinyl group of the silicone compound is preferably 0.3 or more and 5 or less, more preferably 0.4 or more and 4 or less, and still more preferably 0.6 or more and 4 or less. In the heat dissipation composition using diamond particles, the reaction between the main agent and the curing agent may not proceed due to the diamond particles. However, when the molar ratio is 0.6 or more, the reaction proceeds sufficiently, and it becomes possible to obtain a sufficiently cured heat dissipation member.

[0022] Examples of the organohydrogenpolysiloxane include methylhydrogensiloxane-dimethylsiloxane copolymer, polymethylhydrogensiloxane, polyethylhydrogensiloxane, methylhydrogensiloxane-phenylmethylsiloxane copolymer, etc. These may or may not contain a hydrosilyl group at the terminal. The viscosity of the curing agent 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 still more preferably 150 mPa·s or more and 600 mPa·s or less. When the viscosity ranges of the above-described main agent and curing agent are within the above ranges, the heat dissipation composition can be maintained in a paste-like shape and a certain shape, for example, so that it can be easily arranged on electronic components, etc. Also, it becomes easier to blend a large amount of insulating and thermally conductive fillers such as diamond after appropriately dispersing them.

[0023] When a silicone resin is used as the polymer matrix, a curing catalyst is usually blended in the heat dissipation composition. Examples of the curing catalyst include platinum-based catalysts, palladium-based catalysts, rhodium-based catalysts, etc. The curing catalyst is a catalyst for curing the silicone compound serving as the raw material of 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 compound and the curing agent.

[0024] As the epoxy resin, it is preferable to use an epoxy compound having at least one epoxy group, preferably two or more epoxy groups. Examples of the epoxy compound include bisphenol type, novolak type, naphthalene type, triphenolalkane type, biphenyl type, cycloaliphatic type, halides thereof, hydrogenated products thereof, and the like. In addition, as the epoxy resin, the epoxy compound may be used alone, but generally, a composition obtained by using the above epoxy compound as the main component and further adding a curing agent is used. As the curing agent, an addition type or a catalyst type is used. Examples of the addition type curing agent include polyamine-based curing agents, acid anhydride-based curing agents, polyphenol-based curing agents, polymercaptans, dicyandiamide, and the like. Examples of the catalyst type curing agent include tertiary amines, imidazoles, Lewis acid complexes, and the like. These may be used alone or in combination of two or more.

[0025] The thermosetting resin may be either a one-component curing type or a two-component curing type, but preferably a two-component curing type. In the two-component curing type, it is preferable to prepare a heat-radiating composition by mixing one component containing the above-mentioned main component and two components containing a curing agent. In the case of the two-component curing type, the diamond particles may be blended in either one of the one-component and two-component components, or in both components. The same applies to other heat-conductive fillers described later.

[0026] Examples of the silicone oil used for the polymer matrix include methylphenyl silicone oil, dimethyl silicone oil, and modified silicone oil. The silicone oil preferably has a viscosity at 25°C of 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 150 mPa·s or more and 600 mPa·s or less.

[0027] The volume ratio of the polymer matrix is preferably 10% by volume or more and 50% by volume or less, more preferably 11% by volume or more and 40% by volume or less, and still more preferably 12% by volume or more and 35% by volume or less, based on the total amount of the heat dissipation composition. When the volume ratio of the polymer matrix is equal to or higher than these lower limits, heat conductive fillers such as diamond particles dispersed in the polymer matrix can be retained by the polymer matrix, and the heat dissipation composition can maintain a certain shape. Also, by setting it to be equal to or lower than these upper limits, a certain amount or more of heat conductive fillers such as diamond particles can be blended into the heat dissipation composition.

[0028] (Diamond particles) The heat dissipation composition of the present invention contains diamond particles as a heat conductive filler. The sphericity of the diamond particles is, for example, 0.5 or more, preferably 0.55 or more, and still more preferably 0.6 or more. The sphericity is an index indicating that the closer it is to 1, the closer the shape is to a sphere. By increasing the sphericity, it becomes easier to disperse the diamond particles in the polymer matrix, and it also becomes easier to increase the packing ratio. The upper limit of the sphericity is not particularly limited and is 1. In addition, the sphericity of each filler can be determined by checking an electron micrograph of each filler and calculating (the diameter of a circle equal to the projected area of the particle / the diameter of the smallest circle circumscribing the projected image of the particle) for 300 particles in the obtained image, and obtaining the average value.

[0029] The specific shape of the diamond particles is not particularly limited. For example, it may be spherical, may be a crushed shape, or may be other shapes. Spherical means a spherical shape or a shape approximating a sphere. In this specification, those with a sphericity of 0.8 or more are regarded as spherical. Also, the crushed shape means a shape refined by crushing and generally has an angular shape. The crushed shape has a sphericity of, for example, 0.5 or more and less than 0.8, preferably 0.55 or more and less than 0.8, and more preferably 0.6 or more and less than 0.8. By making the diamond particles spherical or in a crushed shape, it becomes easier to increase the packing ratio of the diamond particles, and among them, making them spherical makes it easier to further increase the packing ratio.

[0030] The average particle diameter of the diamond particles is, for example, 0.1 μm or more and 200 μm or less. By setting it to 0.1 μm or more, the thermal resistance of the heat dissipation composition tends to be low, and the above-mentioned slope (ΔW / ΔD) also tends to be low. Further, by setting it to 0.1 μm or more, the specific surface area becomes small, voids are less likely to form in the vicinity of the diamond particles, and the void ratio tends to be low. Further, it becomes possible to improve the thermal conductivity while reducing the void ratio. On the other hand, by setting it to 200 μm or less, it becomes possible to contain diamond particles at a high filling rate while being appropriately dispersed in the polymer matrix. From these viewpoints, the average particle diameter of the diamond particles is preferably 0.5 μm or more and 150 μm or less. Note that the average particle diameter is the average particle diameter obtained by averaging the particle diameters on a volume basis, and can be measured, for example, using a "laser diffraction particle size distribution measuring device" manufactured by Horiba, Ltd. Regarding the method for calculating the average particle diameter, the particle diameter (d50) when the cumulative volume is 50% may be used as the average particle diameter.

[0031] In the present invention, the diamond particles contained in the heat dissipation composition preferably include two or more types of diamonds having different average particle diameters from each other. When using two or more types of diamonds having different average particle diameters, the diamond particles having a smaller average particle diameter enter between the diamonds having a larger average particle diameter, and while appropriately dispersing the diamond particles in the polymer matrix, it becomes easier to increase the filling rate of the diamonds. Note that it can be determined that the heat dissipation composition has two or more types of diamonds having different average particle diameters by two or more peaks appearing in the particle size distribution of the diamond particles.

[0032] When including two or more types of diamonds having different average particle diameters, the diamond particles are preferably a mixture of diamonds having an average particle diameter of 10 μm or more and 200 μm or less (hereinafter also referred to as "large particle diameter diamonds") and diamonds having an average particle diameter of 0.1 μm or more and less than 10 μm (hereinafter also referred to as "small particle diameter diamonds"). In this way, by using both large-sized diamond particles and small-sized diamond particles, it becomes easier to appropriately disperse the diamond particles in the polymer matrix while increasing the filling rate of the diamond, thereby reducing the thermal resistance value and the slope (ΔW / ΔD).

[0033] When the diamond particles contain both small-sized diamond particles and large-sized diamond particles, the volume ratio of the large-sized diamond particles to the small-sized diamond particles (large-sized / small-sized) is, for example, 0.1 or more and 10 or less, preferably 0.2 or more and 8 or less, and more preferably greater than 0.3 and 6 or less. The large-sized diamond particles preferably have an average particle diameter of 15 μm or more and 200 μm or less, and more preferably 18 μm or more and 150 μm or less. The shape of the large-sized diamond particles may be any shape, but the crushed shape or spherical shape described above is preferred, and the spherical shape is more preferred. By making them spherical, the filling rate can be increased while appropriately dispersing the diamond particles.

[0034] Two types of large-sized diamond particles having different average particle diameters from each other may be used in combination. For example, diamond particles having an average particle diameter of 10 μm or more and less than 40 μm (hereinafter also referred to as "first large-sized diamond particles") and diamond particles having an average particle diameter of 40 μm or more and 200 μm or less (hereinafter also referred to as "second large-sized diamond particles") may be used in combination. When the first and second large-sized diamond particles are used in combination, it becomes easier to further increase the filling rate of the diamond particles. Here, the first large-sized diamond particles preferably have an average particle diameter of 12 μm or more and 35 μm or less, and more preferably 14 μm or more and 30 μm or less. On the other hand, the second large-sized diamond particles more preferably have an average particle diameter of 40 μm or more and 150 μm or less, and more preferably 40 μm or more and 125 μm or less. Of course, only one of the first and second large-sized diamond particles may be used as the large-sized diamond particles.

[0035] As for the large-diameter diamond, it is preferable that the filling rate of the second large-diameter diamond is higher than that of the first large-diameter diamond. Specifically, the filling rate of the second large-diameter diamond is preferably 1.5 times or more and 5 times or less, more preferably 2 times or more and 4 times or less, the filling rate of the first large-diameter diamond. By containing a large amount of the second large-diameter diamond with a large particle size, it becomes easier to make the slope (ΔW / ΔD) smaller.

[0036] The small-diameter diamond preferably has an average particle size of 0.2 μm or more and 8 μm or less, and more preferably 0.5 μm or more and 7 μm or less. The shape of the small-diameter diamond may be any, but a crushed shape is preferable. The crushed small-diameter diamond can be easily manufactured by crushing synthetic diamond.

[0037] Two types of diamonds having different average particle sizes may also be used in combination as the small-diameter diamond. For example, a diamond having an average particle size of 0.1 μm or more and less than 2.5 μm (hereinafter, also referred to as "the first small-diameter diamond") and a diamond having an average particle size of 2.5 μm or more and less than 10 μm (hereinafter, also referred to as "the second small-diameter diamond") may be used in combination. In this case, the first small-diameter diamond preferably has an average particle size of 0.5 μm or more and 2 μm or less. On the other hand, the second small-diameter diamond preferably has an average particle size of 3 μm or more and 7 μm or less. When the first and second small-diameter diamonds are used in combination as the small-diameter diamond, it becomes easier to increase the filling rate of the diamond particles. Of course, only one of the first and second small-diameter diamonds may be used as the small-diameter diamond.

[0038] Further, when two or more types of diamonds having different average particles are included, the diamond particles do not necessarily need to include both small-diameter diamonds and large-diameter diamonds. For example, only small-diameter diamonds may be used. In this case, the small-diameter diamond particles may contain the first and second small-diameter diamond particles as described above. Similarly, the diamond particles may be only large-sized diamonds. In that case, the large-sized diamond particles may contain the first and second large-sized diamond particles as described above.

[0039] In the present invention, the filling rate of the diamond particles is preferably 15% by volume or more. By setting the filling rate to 15% by volume or more, the thermal resistance value can be lowered, and the slope (ΔW / ΔD) can be easily adjusted to a desired range. From such a viewpoint, the filling rate of the diamond particles is more preferably 20% by volume or more, and even more preferably 30% by volume or more. Also, the filling rate of the diamond particles is preferably 90% by volume or less. By setting it to 90% by volume or less, the diamond particles can be appropriately dispersed in the polymer matrix. From such a viewpoint, the filling rate of the diamond particles is more preferably 85% by volume or less, and even more preferably 80% by volume or less.

[0040] Further, the present invention can reduce the void ratio while increasing the filling rate of the diamond particles. Specifically, in the present invention, it is preferable to set the filling rate of the diamond particles to 15% by volume or more and the void ratio to 3% or less. When the filling rate of the diamond particles is set to 15% by volume or more to enhance the heat dissipation property, the void ratio tends to increase and the insulation property tends to decrease. However, in the present invention, even when the filling rate is 15% by volume or more, by setting the void ratio to 3% or less as described above, both the insulation property and the heat dissipation property can be made excellent. From the viewpoint of further enhancing the insulation property and the heat dissipation property, it is preferable to set the filling rate to 20% by volume or more and the void ratio to 2% or less, and more preferably to set the filling rate to 30% by volume or more and the void ratio to 1% or less.

[0041] When diamond particles are used alone as the thermal conductive filler (i.e., when no thermal conductive filler other than diamond particles is used), in order to adjust the slope (ΔW / ΔD) to a desired range, it is necessary to increase the filling rate of the diamond particles. Therefore, when diamond particles are used alone as the thermal conductive filler, the filling rate of the diamond particles is preferably 50% by volume or more and 90% by volume or less, more preferably 60% by volume or more and 85% by volume or less, and even more preferably 65% by volume or more and 80% by volume or less. On the other hand, when diamond particles are used in combination with a thermal conductive filler other than the diamond particles described later, it is not necessary to increase the filling rate of the diamond particles so much. Therefore, in such a case, the filling rate of the diamond particles is preferably 15% by volume or more and 80% by volume or less, and more preferably 20% by volume or more and 75% by volume or less.

[0042] In this specification, the "filling rate" means the volume percentage with respect to the total volume of the heat dissipation composition. For example, the filling rate of diamond particles means the volume percentage occupied by diamond particles with respect to the total volume of the heat dissipation composition. The volume of each component can be calculated from the weight of each component and the specific gravity (density). In addition, when measuring the filling rate from the heat dissipation composition, the filling rate can be measured, for example, as follows, by separating each component and calculating the volume of each component.

[0043] Specifically, first, an appropriate solvent is added to the heat dissipation composition to dissolve the polymer matrix, and the polymer matrix is separated from the thermal conductive filler by a centrifuge or the like. Then, the density and weight of the separated polymer matrix are measured, and the volume of the polymer matrix is determined from the measured values. Similarly, for the separated thermal conductive filler, the density and weight are also measured, and the total volume of the thermal conductive filler containing diamond particles is determined from the measured values. Subsequently, taking advantage of the property that diamond particles decompose at a lower temperature than other thermal conductivity fillers, the entire thermal conductivity filler is fired to decompose only the diamond particles. Then, for the thermal conductivity fillers other than the remaining diamond particles, the density and weight are measured, and the volume of the thermal conductivity fillers other than the diamond particles is determined from the measured values. The volume of the diamond particles is determined from the volume of the thermal conductivity fillers other than the diamond particles and the volume of the entire thermal conductivity filler. The filling rate of the diamond particles can be calculated from the volumes of the polymer matrix, the entire thermal conductivity filler, and the diamond particles calculated as described above. Also, the filling rates of the thermal conductivity fillers other than the diamond particles, which will be described later, and the entire thermal conductivity filler can be calculated in the same manner. Also, the density of the separated polymer matrix and the density of the thermal conductivity filler may be measured using a densitometer (for example, the measuring device "Accupic II 1340", manufactured by Shimadzu Corporation) at 23°C.

[0044] Diamond particles are usually synthetic diamonds, which can be synthesized by crystallizing a carbon raw material such as graphite under high temperature and high pressure in the presence of a metal catalyst such as iron. The diamonds synthesized in this way generally have a spherical shape. Also, the diamonds synthesized by crystallization under high temperature and high pressure may be appropriately crushed or the like as necessary to obtain diamond particles with a crushed shape. The synthesized diamond particles are subjected to pickling or reduction treatment using hydrogen gas, etc., as necessary. If the diamond particles are pickled and then left untreated, a small amount of functional groups such as hydroxyl groups will be present on the surface of the diamond particles. When the diamond particles with functional groups such as hydroxyl groups on the surface are surface-treated with a surface treatment agent such as a silane compound, which will be described later, the surface treatment agent is likely to bind or adhere to the diamond particles. Thereby, the diamond particles are more likely to conform to the polymer matrix. Also, even when no surface treatment agent is used, the diamond particles are likely to conform to the polymer matrix depending on the type of the polymer matrix because functional groups such as hydroxyl groups are present on the surface.

[0045] Also, when crushed diamond particles are used, it becomes relatively difficult for functional groups such as hydroxyl groups to exist on the surface. Therefore, even if untreated diamond particles are used after acid washing as described above, the amount of surface oxygen described later may be relatively small. This is because the interior of the diamond particles where substantially no oxygen atoms such as hydroxyl groups exist is exposed due to crushing.

[0046] As described above, it is preferable that the diamond particles have hydroxyl groups on their surface so that the amount of surface oxygen is equal to or more than a certain value. Specifically, the amount of surface oxygen of the diamond particles contained in the heat dissipation composition is preferably 5% or more. Generally, it is difficult for a surface treatment agent to bind or adhere to diamond particles, and it is also difficult for the diamond particles to conform to the polymer matrix. Therefore, voids are likely to form around the diamond particles. Thus, by making hydroxyl groups exist on the surface of the diamond particles and making the amount of surface oxygen equal to or more than the above-mentioned certain value, the surface treatment agent can be bound or adhered to the diamond particles, and the diamond particles can be made to conform to the polymer matrix, and the void ratio can be lowered as described above. From these viewpoints, the amount of surface oxygen of the diamond particles is more preferably 10% or more. The amount of surface oxygen can be measured by XPS analysis as shown in the examples described later, and the amount of surface oxygen with respect to the entire diamond particles contained in the heat dissipation composition may be determined. For example, when using two or more types of diamond particles having different amounts of surface oxygen, the amount of surface oxygen of each type of diamond particle may be measured and the amount of surface oxygen with respect to the entire diamond particles may be determined by weighted average or the like.

[0047] In order to reduce voids at the interface between the polymer matrix and the thermally conductive filler, it is preferable to improve the wettability of the thermally conductive filler with respect to the polymer matrix. In addition, in order to improve the wettability, it is useful to perform surface treatment as described later. The wettability of the polymer matrix and the thermally conductive filler can be evaluated by the contact angle of the thermally conductive filler with respect to the polymer matrix. The contact angle of the thermally conductive filler with respect to the polymer matrix is preferably 70° or less, more preferably 65° or less, and still more preferably 60° or less. As shown in the examples described below, the wettability can be evaluated by creating a substrate (pellet) with an aggregate of thermally conductive fillers contained in the heat dissipation composition and measuring the wettability of the polymer matrix used in the heat dissipation composition with respect to the substrate. The specific measurement of the contact angle is performed by the liquid application method. When measuring the contact angle from the heat dissipation composition, as shown in the examples described below, it is necessary to separate the polymer matrix and various thermally conductive fillers contained in the heat dissipation composition. However, the method for separating the polymer matrix and the thermally conductive filler is not limited to the method described in the examples and can be appropriately changed depending on the type of the polymer matrix and the type of the thermally conductive filler. Note that, as shown in the examples described below, when the thermally conductive filler is surface-treated, the wettability of the surface-treated thermally conductive filler with respect to the polymer matrix is evaluated.

[0048] In order to easily improve the wettability of the thermally conductive filler with respect to the polymer matrix or to easily adhere or bond a surface treatment agent to the surface of the thermally conductive filler, it is preferable to increase the surface oxygen amount as described above. Also, the filler surface may be activated. Examples of methods for activating the filler surface include performing plasma treatment, acid treatment, heat treatment, alumina coating treatment, and the like.

[0049] (Surface Treatment of Diamond Particles) The diamond particles used in the present invention are preferably surface-treated. By surface-treating the diamond particles, they become more compatible with the polymer matrix, and it becomes easier to uniformly disperse a large amount of diamond particles in the polymer matrix. Also, since it is not necessary to blend a compound for dispersing diamond particles such as a silane compound in the heat dissipation composition, it becomes possible to disperse the diamond particles while suppressing a decrease in the viscosity, thixotropy, wettability, thermal conductivity, etc. of the heat dissipation composition. The diamond particles are surface-treated with a surface treatment agent such as a silane compound, an organic titanium compound, an organic aluminum compound, a phosphoric acid compound, etc., and are preferably surface-treated with a silane compound.

[0050] The amount of the surface treatment agent adhered to the diamond particles is, for example, 0.01% by mass or more and 3% by mass or less, preferably 0.02% by mass or more and 2.5% by mass or less, based on the diamond particles.

[0051] There is no particular limitation on the silane compound used for the surface treatment. For example, alkoxysilanes and chlorosilanes can be mentioned, and alkoxysilanes are preferred. Further, when the above-mentioned silicone resin and silicone oil are used for the polymer matrix of the diamond particles surface-treated with the silane compound, the diamond particles are particularly compatible with the polymer matrix, and it becomes easy to increase the blending amount of the diamond particles in the heat dissipation composition. In addition, by using a silane compound, particularly a polymer silane compound as described later, problems such as a decrease in the thixotropic index due to hydrogen bonding between the filler and the resin are less likely to occur.

[0052] Examples of the alkoxysilanes include alkoxysilanes having a reactive group and alkoxysilanes having no reactive group. The reactive group in the alkoxysilane having a reactive group is selected from, for example, an epoxy group, a (meth)acryloyl group, an amino group, a vinyl group, a ureido group, a mercapto group, and an isocyanate group. Examples of the alkoxysilane having an epoxy group include 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, and the like. Examples of the alkoxysilane having a (meth)acryloyl group include 3-(meth)acryloxypropylmethyldimethoxysilane, 3-(meth)acryloxypropyltrimethoxysilane, 3-(meth)acryloxypropylmethyldiethoxysilane, 3-(meth)acryloxypropyltriethoxysilane, and the like. Examples of the silane compound having an amino group include alkoxysilanes such as N-2(aminoethyl)3-aminopropylmethyldimethoxysilane, N-2(aminoethyl)3-aminopropyltrimethoxysilane, N-2(aminoethyl)3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. Examples of the silane compound having a vinyl group include vinyltrimethoxysilane and vinyltriethoxysilane. Examples of the alkoxysilane having a mercapto group include 3-mercaptopropyltrimethoxysilane and 3-mercaptopropylmethyldimethoxysilane. Examples of the alkoxysilane having a ureido group include 3-ureidopropyltrimethoxysilane. Examples of the alkoxysilane having an isocyanate group include 3-isocyanatopropyltriethoxysilane.

[0053] Examples of the alkoxysilane having no reactive group include trialkoxysilanes such as aryltrialkoxysilane and alkyltrialkoxysilane, and dialkoxysilanes such as dialkyldialkoxysilane and diaryldialkoxysilane. Among these, trialkoxysilanes such as alkyltrialkoxysilane are preferred. Examples of alkyltrialkoxysilanes include those with an alkyl group having about 1 to 10 carbon atoms, such as methyltrimethoxysilane, methyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, n-octyltriethoxysilane, n-decyltrimethoxysilane, etc. Examples of aryltrimethoxysilanes include those with an aryl group having about 6 to 10 carbon atoms, such as phenyltrimethoxysilane, benzyltrimethoxysilane, tolyltrimethoxysilane, etc. Examples of dialkoxysilanes include dimethyldimethoxysilane, dimethyldiethoxysilane, etc.

[0054] Also, as a preferred embodiment of the silane compound, a polymer silane compound which is a reaction product of an alkoxysilane having a reactive group and a polyorganosiloxane having a functional group capable of reacting with the reactive group is used. When using the polymer silane compound, diamond particles become even more compatible with the polymer matrix, especially silicone resin and silicone oil, and it becomes easier to increase the filling rate. The polymer silane compound can be obtained, for example, by mixing an alkoxysilane having a reactive group and a polyorganosiloxane, and reacting them by heating in the presence of a catalyst such as a platinum-based catalyst, a palladium-based catalyst, a rhodium-based catalyst, etc. As the alkoxysilane having a reactive group, those listed above can be used, but among them, it is preferable to use trialkoxysilane. As the alkoxysilane having a reactive group, a silane compound having a (meth)acryloyl group or a vinyl group is preferable, and a trialkoxysilane having a (meth)acryloyl group is more preferable. When using a silane compound having a (meth)acryloyl group or a vinyl group, it easily reacts with an organopolysiloxane having a hydrosilyl group (SiH) described later, so a polymer silane compound can be obtained by a simple method.

[0055] The polyorganosiloxane having a functional group used in the high molecular weight silane compound may have one functional group, or may have two or more functional groups. When having two or more functional groups, two or more molecules of alkoxysilane having a reactive group may be bonded to one molecule of this polyorganosiloxane. The polyorganosiloxane having a functional group is preferably an organopolysiloxane having a hydrosilyl group (SiH). Examples of the organopolysiloxane having a hydrosilyl group (SiH) include methylhydrosiloxane-dimethylsiloxane copolymer, methylhydrosiloxane-phenylmethylsiloxane copolymer, etc. These may or may not contain a hydrosilyl group at the terminal. The weight average molecular weight of the polyorganosiloxane having a functional group is preferably 800 to 5000, more preferably 1500 to 4000. The weight average molecular weight is a value in terms of polystyrene measured by GPC.

[0056] The method of surface treatment using a silane compound is not particularly limited and may be carried out by a known method. For example, a wet treatment method, a dry treatment method, or a pretreatment method can be used. In the present invention, among these, the wet treatment method is preferred. In the wet treatment method, for example, diamond particles are added and mixed in a solution in which a silane compound is dispersed or dissolved, and then heat-treated to bond or adhere the silane compound to the surface of the diamond particles. The dry treatment method is a method of surface treatment without using a solution. Specifically, a silane compound is mixed with diamond particles and stirred with a mixer or the like, and then heat-treated to bond or adhere the silane compound to the surface of the diamond particles. Also, the pretreatment method is a method in which diamond particles are added to a solution in which a silane compound is dispersed or dissolved, water is also added and mixed, the silane compound is reacted by the added water, the silane compound is bonded or adhered to the surface of the diamond particles, and then washing, drying, etc. are carried out.

[0057] Note that all diamond particles may be surface-treated, or only some of the diamond particles may be surface-treated, but it is preferable that all diamond particles are surface-treated. Further, for example, when two or more types of diamond particles are surface-treated, the two or more types of diamond particles may be mixed and surface-treated simultaneously, or may be surface-treated separately.

[0058] (Other heat conductive fillers) The heat dissipation composition of the present invention preferably further contains a heat conductive filler other than diamond particles (hereinafter also referred to as "other heat conductive fillers") as the heat conductive filler. By containing other heat conductive fillers, the filling rate of the entire heat conductive filler can be improved, the slope (ΔW / ΔD) can be easily lowered, and the heat dissipation performance can be improved. As the other heat conductive fillers, materials with low electrical conductivity are used from the viewpoint of insulation, and examples include carbides, nitrides, oxides, hydroxides, carbon-based materials other than diamond, and the like. Examples of carbides include silicon carbide, boron carbide, aluminum carbide, titanium carbide, tungsten carbide, and the like. Examples of nitrides include silicon nitride, boron nitride, aluminum nitride, gallium nitride, chromium nitride, tungsten nitride, magnesium nitride, molybdenum nitride, lithium nitride, and the like. Examples of oxides include iron oxide, silicon oxide (silica), alumina, aluminum oxide such as boehmite, magnesium oxide, titanium oxide, cerium oxide, zirconium oxide, and the like. Examples of hydroxides include aluminum hydroxide, calcium hydroxide, magnesium hydroxide, and the like. Examples of carbon-based materials include carbon black, graphite, graphene, fullerene, carbon nanotube, carbon nanofiber, and the like. Further, talc, which is a silicate mineral, can also be used. These other heat conductive fillers may be used alone or in combination of two or more. The thermal conductivity of other thermal conductive fillers is preferably 8 W / m·K or more, more preferably 20 W / m·K or more, from the viewpoint of improving thermal conductivity.

[0059] Other thermal conductive fillers are preferably one or more selected from aluminum oxide, magnesium oxide, boron nitride, talc, aluminum nitride, and graphene, from the viewpoints of thermal conductivity and insulation. More preferably, one or more selected from aluminum oxide, magnesium oxide, and aluminum nitride are used. Even more preferably, one or more selected from aluminum oxide and magnesium oxide are used. Aluminum oxide and magnesium oxide have high water resistance and can prevent the surface from being damaged and decomposed even when, for example, the integral blend method described below is used.

[0060] Other thermal conductive fillers may be surface-treated. By being surface-treated, other thermal conductive fillers become more compatible with the polymer matrix and are more likely to be uniformly dispersed together with a large amount of diamond particles in the polymer matrix. Other thermal conductive fillers are surface-treated with a surface treatment agent such as a silane compound, an organic titanium compound, an organic aluminum compound, or a phosphoric acid compound, and are preferably surface-treated with a silane compound. Note that the details and treatment method of the surface treatment are the same as those for the surface treatment performed on diamond particles, so the description thereof is omitted. Note that for other thermal conductive fillers, all the fillers may be surface-treated, or only some of them may be surface-treated. When other thermal conductive fillers are surface-treated, they are preferably mixed with diamond particles and surface-treated simultaneously with the diamond particles, but they may be surface-treated separately from the diamond particles.

[0061] Other heat conductive fillers have a sphericity of, for example, 0.5 or more, preferably 0.55 or more, and more preferably 0.6 or more. The closer the sphericity is to 1, the closer it is to a spherical shape. By increasing the sphericity, it becomes easier to increase the filling rate of other heat conductive fillers. Also, the upper limit of the sphericity is not particularly limited and is 1. In the present invention, in addition to other heat conductive fillers, by increasing the sphericity of diamond particles as described above, it becomes easier to increase the total filling amount of diamond particles and other heat conductive fillers.

[0062] The shape of other heat conductive fillers is not particularly limited and may be any of plate-like, scaly, needle-like, fibrous, tubular, spherical, crushed shapes, etc., but either spherical or crushed shape is preferred. Note that spherical means a spherical or approximately spherical shape as described above, and the sphericity is 0.8 or more. Also, the crushed shape has a sphericity of, for example, 0.5 or more and less than 0.8, preferably 0.55 or more and less than 0.8, and more preferably 0.6 or more and less than 0.8.

[0063] The average particle diameter of other heat conductive fillers is, for example, 0.1 μm or more and 200 μm or less. When it is 0.1 μm or more, by using it in combination with diamond particles, it becomes easier to lower the thermal resistance in the thickness direction, and also easier to lower the inclination (ΔW / ΔD), and it becomes easier to adjust within the desired range described above. Also, when it is 200 μm or less, in addition to diamond particles, even if other heat conductive fillers are highly filled, problems such as non-uniform dispersion of the fillers are less likely to occur. From these viewpoints, the average particle diameter of other heat conductive fillers is preferably 0.2 μm or more and 150 μm or less, and more preferably 0.4 μm or more and 125 μm or less.

[0064] The filling ratio of other heat conductive fillers may be appropriately adjusted so that the total filling ratio of the fillers falls within the range described below. Preferably, it is 75% by volume or less, more preferably 70% by volume or less. By setting it below these upper limits, a certain amount or more of diamond particles can be blended into the heat dissipation composition, making it easier to adjust the slope (ΔW / ΔD) within the desired range. Also, the filling ratio of other heat conductive fillers is preferably 10% by volume or more, more preferably 20% by volume or more. When it is at or above these lower limits, it becomes easier to exhibit the effects of blending other heat conductive fillers. Also, from the viewpoints of insulation and heat dissipation, the filling ratio of other heat conductive fillers is preferably 0.1 or more and 5 or less, more preferably 0.2 or more and 4 or less, and even more preferably 0.3 or more and 2 or less with respect to the filling ratio of diamond particles, from the viewpoint of further enhancing insulation.

[0065] Other heat conductive fillers may be, for example, heat conductive fillers with an average particle diameter of 10 μm or more and 200 μm or less (hereinafter also referred to as "large particle diameter heat conductive fillers"), or heat conductive fillers with an average particle diameter of 0.1 μm or more and less than 10 μm (hereinafter also referred to as "small particle diameter heat conductive fillers"). Also, both large particle diameter heat conductive fillers and small particle diameter heat conductive fillers may be used as other heat conductive fillers.

[0066] The large particle diameter heat conductive filler preferably has an average particle diameter of 15 μm or more and 150 μm or less, more preferably 18 μm or more and 135 μm or less, and even more preferably 20 μm or more and 125 μm or less. The large particle diameter heat conductive filler may be used alone as one type, or two or more types with different average particle diameters may be used in combination.

[0067] The small particle diameter heat conductive filler more preferably has an average particle diameter of 0.2 μm or more and 8 μm or less, and even more preferably 0.3 μm or more and 7 μm or less. The small particle size thermal conductive filler may be used alone, or two or more kinds having different average particle sizes may be used in combination. For example, a small particle size thermal conductive filler having an average particle size of 0.1 μm or more and less than 2 μm (hereinafter, also referred to as "first small particle size thermal conductive filler") and a small particle size thermal conductive filler having an average particle size of 2 μm or more and less than 10 μm (hereinafter, also referred to as "second small particle size thermal conductive filler") may be used in combination. In this case, the first small particle size thermal conductive filler preferably has an average particle size of 0.3 μm or more and less than 2 μm. On the other hand, the second small particle size thermal conductive filler preferably has an average particle size of 3 μm or more and 7 μm or less. When the first and second small particle size thermal conductive fillers are used in combination as the small particle size thermal conductive filler, it becomes easier to increase the filling rate of the small particle size thermal conductive filler. Of course, only one of the first and second small particle size thermal conductive fillers may be used as the small particle size thermal conductive filler.

[0068] In the present invention, other thermal conductive fillers are preferably contained in a complementary combination with diamond particles. Specifically, in order to lower the slope (ΔW / ΔD), the thermal conductive filler (diamond particles and other thermal conductive fillers) preferably combines a large particle size filler and a small particle size filler and blends both the large particle size and small particle size fillers in a predetermined amount or more. Therefore, when the diamond particles do not contain large particle size diamonds or contain only a small amount, at least a large particle size thermal conductive filler may be blended as other thermal conductive fillers. Similarly, when the diamond particles do not contain small particle size diamonds or contain only a small amount, at least a small particle size other thermal conductive filler may be blended as the thermal conductive filler. In addition, when the diamond particles contain appropriate amounts of both large particle size diamonds and small particle size diamonds, the thermal conductive filler may also be appropriately blended with both the small particle size thermal conductive filler and the large particle size thermal conductive filler.

[0069] The volume ratio (large particle size / small particle size) of the large particle size filler to the small particle size filler in the entire heat conductive filler (i.e., the total of diamond particles and other heat conductive fillers) is, for example, 0.2 or more and 5 or less. This volume ratio is preferably 0.5 or more and 2 or less, more preferably 1.0 or more and 1.8 or less. The large particle size filler means a heat conductive filler having an average particle size of 10 μm or more and 200 μm or less, and its volume is the total volume of the large particle size diamond particles and the large particle size heat conductive filler. The small particle size filler means a heat conductive filler having an average particle size of 0.1 μm or more and less than 10 μm, and its volume is the total volume of the small particle size diamond particles and the small particle size heat conductive filler. When the volume ratio (large particle size / small particle size) in the entire heat conductive filler is within the above range, even if a large amount of the heat conductive filler is contained, it is possible to uniformly disperse the heat conductive filler in the polymer matrix. Further, the thermal resistance value of the heat dissipation composition can be lowered, and furthermore, the slope (ΔW / ΔD) can also be lowered.

[0070] Also, the total filling rate of the heat conductive filler (i.e., the total of the filling rate of diamond particles and the filling rate of other heat conductive fillers) is preferably 40% by volume or more and 92% by volume or less, more preferably 50% by volume or more and 90% by volume or less, still more preferably 65% by volume or more and 85% by volume or less. By setting these lower limit values or more, the thermal resistance value can be lowered, and furthermore, the slope (ΔW / ΔD) can be lowered. Also, by setting it below the upper limit value, it becomes possible to appropriately disperse the heat conductive filler in the polymer matrix.

[0071] (Dispersant) The heat dissipation composition of the present invention preferably contains a dispersant. By containing a dispersant, it becomes easier to disperse heat conductive fillers such as diamond particles in the heat dissipation composition, and a large amount of diamond particles and the like can be blended in the heat dissipation composition. As the dispersant, for example, a polymer dispersant can be used. Examples of the polymer dispersant used include polymer compounds having functional groups. Examples of the polymer compound include acrylic, vinyl, polyester, polyurethane, polyether, epoxy, polystyrene, amino, etc. Examples of the functional group include carboxyl group, phosphate group, sulfonic acid group, carboxylic acid ester group, phosphate ester group, sulfonic acid ester group, hydroxyl group, amino group, quaternary ammonium base, amide group, etc., and a phosphate ester group is preferred. The dispersant is preferably used when the polymer matrix contains, for example, an epoxy resin. The content of the dispersant is preferably 0.1% by mass or more and 5% by mass or less, more preferably 0.4% by mass or more and 2.5% by mass or more, based on the total amount of the heat dissipation composition. When the content is at or above these lower limits, it becomes easier to appropriately disperse heat conductive fillers such as diamond particles in the heat dissipation composition. Also, by setting it below the upper limit, dispersibility commensurate with the content can be imparted.

[0072] (Other Additives) The heat dissipation composition of the present invention may contain additives generally used for heat dissipation members such as antioxidants, heat stabilizers, colorants, flame retardants, antistatic agents, etc., as necessary. Also, when a thermosetting resin is used in the heat dissipation composition, a reaction retardant may be contained.

[0073] (Preparation of Heat Dissipation Composition) The heat dissipation composition of the present invention may be prepared by mixing a polymer matrix, diamond particles, and further other heat conductive fillers, additives such as a dispersant, etc., as required. The method of mixing these components is not particularly limited. For example, diamond particles, and further other heat conductive fillers, additives, etc. may be added to the polymer matrix, and then adjusted by stirring or kneading, etc. Also, in the case of a two-component curing type thermosetting resin, as described above, it may be prepared by mixing the previously prepared one-component and the two-component. When preparing each of the one-component and the two-component, various components may be mixed and prepared in the same manner. Here, the temperature when mixing each component is not particularly limited. However, when diamond particles or a heat conductive filler are dispersed by a dispersant and the polymer matrix is an epoxy resin, for example, it may be 20°C or higher and 140°C or lower. When the kneading temperature is 140°C or lower, the dispersibility of various fillers dispersed by the dispersant is maintained. Also, for the same reason, when diamond particles or a heat conductive filler are dispersed by a dispersant and the polymer matrix is an epoxy resin, as will be described later, the temperature when shaping the heat dissipation composition into a predetermined shape and then curing it should also be 140°C or lower.

[0074] Also, the heat conductive filler and diamond are preferably surface-treated with a silane compound as described above and then blended into the polymer matrix, but an integral blend method may also be used. That is, the heat conductive filler and diamond may be mixed with the polymer matrix by adding the above-described silane compound or the like without performing the above-described surface treatment.

[0075] [Heat dissipation member] The heat dissipation member of the present invention is formed by the above-described heat dissipation composition. When the polymer matrix contains a curable resin, the heat dissipation member is a cured product of the heat dissipation composition. For example, when the polymer matrix contains a curable resin, the heat dissipation member can be obtained by shaping the above-described heat dissipation composition into a predetermined shape and then curing it by appropriately heating or the like to form a heat dissipation member having a predetermined shape. Also, even when the polymer matrix does not contain a curable resin, the heat dissipation composition may be shaped into a predetermined shape to form a heat dissipation member. The method for shaping the heat dissipation composition into a predetermined shape is not particularly limited, and it may be shaped into a thin film shape, sheet shape, block shape, irregular shape, etc. by coating, casting, potting, extrusion molding, or the like.

[0076] The heat dissipation member of the present invention is used, for example, inside an electric device. Since the heat dissipation member of the present invention is excellent in insulation and heat dissipation, high heat dissipation can be ensured without causing abnormal operation or the like even when used inside an electric device. More specifically, the heat dissipation member is disposed on the electronic component and used to dissipate the heat generated by the electronic component. Preferably, it is disposed and used on the uneven surface of the electronic component having unevenness on the surface. By being disposed on the uneven surface, the heat dissipation member may have uneven thickness where a part of the thickness is different from other parts. However, since the heat dissipation member of the present invention uses diamond particles and has a small inclination (ΔW / ΔD) and excellent heat dissipation performance, it can suppress the heat spots caused by the uneven thickness.

[0077] Also, the heat dissipation member of the present invention is preferably disposed and used to fill the gap between two opposing members. The two opposing members may be, for example, one being an electronic component and the other being any of a heat sink for releasing heat from the electronic component, a housing of an electronic device, a substrate, etc. It is preferable that either one of the opposing surfaces of the two opposing members has unevenness. When either one of the opposing surfaces has unevenness, uneven thickness may occur in the heat dissipation member according to the unevenness. However, since the heat dissipation member of the present invention uses diamond particles and has a small inclination (ΔW / ΔD) and excellent heat dissipation performance, it can suppress the heat spots caused by the uneven thickness.

[0078] [Filler Aggregate for Heat Dissipation Member] Another aspect of the present invention provides a filler aggregate for a heat dissipation member containing diamond particles as a thermally conductive filler. The diamond particles used in the filler aggregate for the heat dissipation member contain, for example, at least two or more types of diamond particles, and specifically, include two or more types of diamonds having different average particle diameters. Note that the filler aggregate for the heat dissipation member can be determined to have two or more types of diamonds having different average particle diameters when two or more peaks appear in the particle size distribution of the diamond particles. In addition, the filler aggregate for the heat dissipation member may further contain a heat conductive filler other than diamond particles (other heat conductive fillers). The diamond particles contained in the filler aggregate for the heat dissipation member may be surface-treated with a silane compound or the like as described above. Similarly, the heat conductive filler may also be surface-treated with a silane compound or the like. The characteristics of the diamond particles and other heat conductive fillers are as described above, and the description thereof is omitted. By blending the filler aggregate for heat dissipation of the present invention with the above-described polymer matrix, a heat dissipation composition can be obtained. Therefore, the filler aggregate for heat dissipation of the present invention may be mixed with the polymer matrix, for example, before use and used as a heat dissipation composition.

Examples

[0079] Examples of the present invention will be described below. However, the present invention is not limited to the following examples.

[0080] The evaluation methods and measurement methods carried out in the examples and comparative examples are as follows. [Slope (ΔW / ΔD)] The heat dissipation compositions obtained in each example, comparative example, and reference example were immediately applied onto the measurement part of the measuring device so as to have a thickness of 500 μm (D2), and the thermal resistance value (W2) of the heat dissipation composition at that time was measured in accordance with ASTM D5470 using a device “DynTIM” manufactured by Mentor Graphics Corporation. Thereafter, the thickness of the heat dissipation composition was adjusted, and the thermal resistance value (W2) at a thickness of 300 μm (D1) was similarly measured. Using the obtained thermal resistance values, the formula: ΔW (unit: K·cm 2 / W) / ΔD (unit: mm) = (W2 - W1) / (D2 - D1) was used to calculate the slope (ΔW / ΔD, unit: K·cm 2 / W·mm).

[0081] [Void ratio] The heat-dissipating composition was used to dissolve the polymer in a solvent (a mixed solution of 50% by mass of toluene and 50% by mass of xylene) (dilution ratio: 10 times (mass ratio)), and the heat-conductive filler and the polymer (polymer matrix) were separated using a centrifuge. The solvent was removed from the polymer-containing solution by vacuum drying, and the density was measured using a densitometer (measurement device: "Accupic II 1340", manufactured by Shimadzu Corporation, measurement conditions: temperature 23°C), and the weight was also measured. The measured weight was designated as Wp, and the density was designated as Dp. The density of the separated heat-conductive filler was similarly measured using a densitometer, and the weight was measured simultaneously. The measured weight was designated as Wf, and the density was designated as Df. The separated heat-conductive filler was fired in a tabletop small electric furnace ("NHK-170", manufactured by Nitto Kagaku Co., Ltd.) at 900°C for 48 hours to decompose the diamond particles. The density and weight of the filler after firing were measured. The measured weight was designated as Wa, and the measured density was designated as Da. The measured weight Wa and density Da are the weight and density of the heat-conductive filler other than the diamond particles. Using Wf, Df, Wa, and Da, the weight (Wd) and density (Dd) of the diamond particles were determined by the following equations. Wd = Wf - Wa Dd = Wd / ((Wf / Df) - (Wa / Da)) Using these values, the ideal density Di of the heat-dissipating composition in the case of no voids was determined by the following equation. Di = (Wp + Wa + Wd) / ((Wa × Da) + (Wp × Dp) + (Wd + Dd)) Furthermore, the density Dr of the actual heat-dissipating composition was measured using a densitometer (measurement device: "Accupic II 1340", manufactured by Shimadzu Corporation, measurement conditions: temperature 23°C), and the void ratio was calculated by (1 - Dr / Di) × 100. The void ratio was evaluated according to the following evaluation criteria. A: Void ratio is 1.0% or less B: Void ratio is more than 1.0% and 2.0% or less C: Void ratio is more than 2.0% and 3.0% or less D: Void ratio is more than 3.0%

[0082] [Surface oxygen content] The diamond particles used were measured by XPS analysis (measurement apparatus: "VersaprobeII" manufactured by ULVAC-PHI, Inc.) to determine the surface element ratio, and the intensity ratio of oxygen at that time was defined as the surface oxygen amount. Evaluation was performed according to the following evaluation criteria based on the surface oxygen amount. In addition, for two or more types of diamond particles used in each example, the surface oxygen amounts of various diamond particles were measured, and the mass of each type of diamond particle was used as a weight to calculate the weighted average. A: The surface oxygen amount is 10% or more B: The surface oxygen amount is 5% or more and less than 10% C: The surface oxygen amount is less than 5%

[0083] [Contact angle] From the heat dissipation composition used, the polymer matrix and the heat conductive filler were separated. Specifically, the prepared heat dissipation composition was dissolved in a solvent (50% by mass of toluene, 50% by mass of xylene) to dissolve the polymer (dilution ratio: 10 times (mass ratio)), and the heat conductive filler and the polymer were separated using a centrifuge. The solvent was removed from the obtained polymer solution by vacuum heating to obtain substantially only the polymer matrix. The separated heat conductive filler was put into a mold (5 cm × 5 cm, thickness 0.8 mm), and pellets were produced under the condition of 10 MPa using a tabletop press. However, in the case of a two-component type, separation was performed for each of the one-component and two-component in the same manner as above, and the heat conductive filler separated in one component and the heat conductive filler separated in two components were mixed to prepare the above pellets. Similarly, the polymer matrix separated in one component and the polymer matrix separated in two components were mixed, and the contact angle described later was measured using the polymer matrix immediately after the mixing. Using a wettability tester (product name "Dropmaster DMo-701", manufactured by Kyowa Interface Science Co., Ltd.), the contact angle was measured by the liquid application method under the conditions of 23 °C and 50% RH. The measurement was carried out using an aggregate of pelletized heat conductive filler as the substrate in the liquid application method and the separated polymer matrix as the liquid. The contact angle obtained from the liquid droplet after 500 ms using the θ / 2 method was evaluated according to the following criteria. A: 55° or less B: More than 55° and 60° or less C: Over 60° and below 65° D: Over 65° and below 70° E: Over 70°

[0084] [Insulation Evaluation] (Volume Resistivity) The volume resistivity of the heat dissipation compositions of each example and comparative example was measured using a flat sample electrode SME - 8310 (manufactured by Hioki Electric Co., Ltd.) and evaluated according to the following criteria. A: 1.0×10 13 (Ω·cm) or more D: Less than 1.0×10 13 (Ω·cm) (Dielectric Breakdown Voltage Strength) For the heat dissipation compositions of each example and comparative example, an AC voltage was applied at a temperature of 25°C using a withstand voltage tester (ETECH Electronics "MODEL7473") such that the voltage increased at a rate of 0.33 kV / second between the test samples. The voltage at which a current of 10 mA flowed through the test sample was defined as the dielectric breakdown voltage. The dielectric breakdown strength was calculated by dividing the dielectric breakdown voltage by the thickness of the test sample. The dielectric breakdown strength was evaluated according to the following criteria. A: 20 kV / mm or more B: 10 kV / mm or more and less than 20 kV / mm C: 5 kV / mm or more and less than 10 kV / mm D: Less than 5 kV / mm (Comprehensive Evaluation) When the volume resistivity is A and the dielectric breakdown voltage strength is either A or B, the insulation is considered excellent and evaluated as A. Also, when the volume resistivity is A but the dielectric breakdown voltage strength is C, the insulation is considered practically usable and evaluated as B. Further, when either or both of the volume resistivity and the dielectric breakdown voltage strength are D, the insulation is considered insufficient and evaluated as D.

[0085] The diamond particles and other thermal conductive fillers used in the examples, comparative examples, and reference examples are as follows. <Diamond Particles> Diamond 1: Second large-sized diamond, untreated, manufactured by Tomei Diamond Co., Ltd., product name TMS 325-400, average particle size 50 μm, sphericity 0.9, spherical product Diamond 2: First large-sized diamond, untreated, manufactured by Tomei Diamond Co., Ltd., product name AGD400 / 500, average particle size 25 μm, sphericity 0.9, spherical product Diamond 3: Second small-sized diamond, untreated, manufactured by Tomei Diamond Co., Ltd., product name CMM4-8, average particle size 4 μm, sphericity 0.6, crushed product Diamond 4: First small-sized diamond, untreated, manufactured by Tomei Diamond Co., Ltd., product name MD-1000, average particle size 1 μm, sphericity 0.6, crushed product Diamond 5: Second large-sized diamond, untreated, average particle size 50 μm, manufactured by Sangoban Co., Ltd., MB grade, sphericity 0.6, crushed product Diamond 6: First large-sized diamond, untreated, manufactured by Tomei Diamond Co., Ltd., product name CMM20-40, average particle size 20 μm, sphericity 0.6, crushed product Diamond 7: Second large-sized diamond, end-hydrogenated treatment, manufactured by Tomei Diamond Co., Ltd., product name TMS―OB 325-400, average particle size 50 μm, sphericity 0.9, spherical product Diamond 8: First large-sized diamond, end-hydrogenated treatment, manufactured by Tomei Diamond Co., Ltd., product name AGD―OB400 / 500, average particle size 25 μm, sphericity 0.9, spherical product Diamond 9:: Second small-sized diamond, end-hydrogenated treatment, manufactured by Tomei Diamond Co., Ltd., product name CMM4-8, average particle size 4 μm, sphericity 0.6, crushed product Diamond 10: First small-sized diamond, end-hydrogenated treatment, manufactured by Tomei Diamond Co., Ltd., product name MD-1000, average particle size 1 μm, sphericity 0.6, crushed product ※In the above description, "untreated" means that no additional treatment such as acid washing and end-hydrogenated treatment is performed after acid washing.

[0086] <Other thermal conductivity fillers> (Alumina) Alumina 1: Second small-sized thermal conductivity filler, manufactured by Micron Co., Ltd., product name "AL3", average particle size 4 μm, sphericity 1, spherical filler Alumina 2: The first small particle size thermal conductivity filler, manufactured by Admatechs Co., Ltd., product name "AO502", average particle size 0.5 μm, sphericity 1, spherical filler Alumina 3: Large particle size thermal conductivity filler, manufactured by Micron Co., product name "AL35", average particle size 35 μm, sphericity 1, spherical filler (Aluminum nitride) AlN(1): The second small particle size thermal conductivity filler, manufactured by Toyo Aluminum Co., product name "TFZ-N05P", average particle size 5 μm, sphericity 0.6, crushed product AlN(2): The first small particle size thermal conductivity filler, manufactured by Toyo Aluminum Co., product name "TFZ-N01P", average particle size 1 μm, sphericity 0.6, crushed product AlN(3): Large particle size thermal conductivity filler, manufactured by Thrutek Co., product name "ALN300AF", average particle size 30 μm, sphericity 1, spherical filler (Magnesium oxide) MgO(1): The second small particle size thermal conductivity filler, manufactured by Kyowa Chemical Industry Co., Ltd., product name "Piroxma 5301", average particle size 2 μm, sphericity 0.6, crushed product MgO(2): The first small particle size thermal conductivity filler, manufactured by Tateho Chemical Industry Co., product name "PUREMAG (R) FNM-G", average particle size 0.5 μm, sphericity 0.6, crushed product MgO(3): Large particle size thermal conductivity filler, manufactured by Ube Materials Co., product name RF-98, average particle size 50 μm, sphericity: 0.6, crushed product (Zinc oxide) ZnO: Zinc oxide particles, product name "WZ-0501", manufactured by Panasonic Co., average particle size 10 μm, sphericity 0.1 (Aluminum) Aluminum: Aluminum particles, product name "TFS-A05P", manufactured by Toyo Aluminum Co., Ltd., average particle size 5 μm, sphericity 0.9

[0087] <Surface treatment agent> (Surface treatment agent 1) 1 g of 3-acryloxypropyltrimethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd., trade name "KBM5103"), 8 g of a methylhydrogensiloxane-dimethylsiloxane copolymer with trimethylsilyl groups blocked at both ends (trade name "HMS031", manufactured by Gelest, weight average molecular weight: 1900 - 2000), and 0.01 g of a platinum catalyst were mixed. The mixture was heated in an oven at 150 °C for 2 hours to obtain Surface Treatment Agent 1. (Surface Treatment Agent 2) n-Hexyltrimethoxysilane (Dispersant) Phosphate group-containing polymer dispersant (trade name "DISPERBYK-145", manufactured by BYK Chemie GmbH)

[0088] [Example 1] (Surface Treatment) First, a surface treatment solution was prepared by diluting Surface Treatment Agent 1 with ethanol as a solvent to a concentration of 1% by mass. Next, a filler mixture in which 7.5 parts by mass of Diamond 1, 2.5 parts by mass of Diamond 2, 4.2 parts by mass of Diamond 3, and 3.5 parts by mass of Diamond 4 were mixed was added to the surface treatment solution. Then, the surface treatment solution containing the filler was stirred at 30 °C for 30 minutes and then heated at 70 °C for 12 hours to remove the solvent, obtaining a mixture of Diamond 1 - 4 surface-treated with Surface Treatment Agent 1. The amount of the surface treatment agent adhered to the mixture of Diamond 1 - 4 was as shown in Table 1.

[0089] (Preparation of Heat Dissipation Composition) As a polymer matrix, to 1.5 parts by mass of vinyl-terminated organopolysiloxane (viscosity at 25 °C: 300 mPa·s) constituting the main component of an addition reaction type silicone resin, the surface-treated Diamond 1 - 4 were added in the compounding parts shown in Table 1. Further, 0.015 parts by mass of a reaction retarder and a catalytic amount of a platinum catalyst were added to prepare one liquid of the heat dissipation composition. Also, to 1.5 parts by mass of organohydrogenpolysiloxane (viscosity at 25 °C: 400 mPa·s) constituting the curing agent of the addition reaction type silicone resin, the surface-treated Diamond 1 - 4 were added in the compounding parts shown in Table 1 to prepare two liquids of the heat dissipation composition. Liquid 1 and Liquid 2 were mixed at a mass ratio (Liquid 1 / Liquid 2) of 1:1 to prepare a heat-dissipating composition, which was then evaluated. The results are shown in Table 1.

[0090] [Examples 2 to 8, 15 to 23, Comparative Examples 1 and 2, Reference Example 1] The thermally conductive filler treated with the surface treatment liquid was changed as shown in Tables 1, 3, 7, and 8, and the surface-treated thermally conductive filler was adjusted as shown in Tables 1, 3, and 7. The one-liquid and two-liquid components of the heat-dissipating composition were prepared in the same manner as in Example 1, except for the above changes.

[0091] [Examples 9 to 14] In the preparation of the surface treatment liquid, Surface Treatment Agent 2 was used instead of Surface Treatment Agent 1. Also, the thermally conductive filler treated with the surface treatment liquid was changed as shown in Table 2, and the surface-treated thermally conductive filler was adjusted as shown in Table 2. The one-liquid and two-liquid components of the heat-dissipating composition were prepared in the same manner as in Example 1, except for the above changes.

[0092] [Example 24] (Preparation of Heat-Dissipating Composition) As the polymer matrix, 10 parts by mass of dicyandiamide (manufactured by Tokyo Chemical Industry Co., Ltd.) and 1 part by weight of an imidazole curing agent (trade name "2MZA-PW", manufactured by Shikoku Kasei Kogyo Co., Ltd.) were added to 100 parts by mass of an epoxy resin (trade name "Epicoat 828US", manufactured by Mitsubishi Chemical Corporation) as a thermosetting agent to prepare a resin mixture. To 1.4 parts by mass of this resin mixture, a dispersant and Diamonds 1 to 4 were added in the formulations shown in Table 4, and the mixture was stirred at 25°C and 500 rpm for 25 minutes using a planetary stirrer to obtain a heat-dissipating composition.

[0093] [Examples 25 to 40] The thermally conductive filler was changed as shown in Tables 4 and 5, and the formulation was adjusted as shown in Tables 4 and 5. The heat-dissipating composition was prepared in the same manner as in Example 24, except for the above changes.

[0094] [Examples 41 to 42] As the polymer matrix, 1.4 parts by mass of dimethylpolysiloxane (silicone oil, trade name "SH200CV", manufactured by Mitsubishi Chemical Corporation, viscosity: 100 mPa·s) was added with diamond 1 to 4 treated on the surface in the formulation shown in Table 6, and stirred at 25°C and 500 rpm for 25 minutes using a planetary stirrer to obtain a heat dissipation composition.

[0095] [Example 43] The heat conductive filler treated with the surface treatment liquid was changed as shown in Table 6, and the one-component and two-component liquids of the heat dissipation composition were prepared in the same manner as in Example 1. [Reference Example 2] The heat conductive filler was not surface-treated, and the same procedure as in Reference Example 1 was carried out except that the blending parts were changed as shown in Table 8.

[0096] [Table 1] ※Note that the resin filling ratio in each table includes the surface treatment agent and the dispersant.

[0097] [Table 2]

[0098] [Table 3]

[0099] [Table 4]

[0100] [Table 5]

[0101] [Table 6]

[0102]

Table 7

[0103]

Table 8

[0104] As is clear from the results of Tables 1 to 7, according to each example, by using diamond particles as the thermal conductive filler, it was possible to achieve both insulation and heat dissipation. On the other hand, in Comparative Examples 1 and 2, although a plurality of types of fillers were used, diamond particles were not used, so it was difficult to achieve both insulation and heat dissipation.

Claims

1. A heat dissipation composition containing a polymer matrix and a heat conductive filler, wherein the polymer matrix contains a silicone resin or a silicone oil, and the heat conductive filler contains diamond particles having an average particle diameter of 0.5 μm or more and 200 μm or less, the void ratio is 2% or less, the diamond particles are surface-treated with a silane compound, and the surface oxygen amount of the diamond particles is 5% or more, the heat dissipation composition.

2. The heat dissipation composition according to claim 1, wherein the void ratio is 1.5% or less.

3. The void ratio is calculated by (1 - Dr / Di) × 100, where Dr is the actual density of the heat dissipation composition and Di is the ideal density of the heat dissipation composition assuming no voids, calculated from the density and mixing ratio of each component. The heat dissipation composition according to claim 1 or 2.

4. The heat dissipation composition according to any one of claims 1, 2, and 3, wherein the slope of the change in the heat resistance value with respect to the change in thickness is 1.8 or less.

5. The heat dissipation composition according to any one of claims 1 to 4, wherein the diamond particles contain two or more types of diamonds having different average particle diameters.

6. The heat dissipation composition according to any one of claims 1 to 5, wherein the diamond particles contain large-diameter diamonds having an average particle diameter of 10 μm or more and 200 μm or less, and small-diameter diamonds having an average particle diameter of 0.1 μm or more and less than 10 μm.

7. The sphericity of the diamond particles is 0.5 or more, The sphericity is obtained by confirming an electron micrograph of the filler, calculating (diameter of a circle equal to the projected area of the particle / diameter of the smallest circle circumscribing the projected image of the particle) for 300 particles in the obtained image, and taking the average value. The heat dissipation composition according to any one of claims 1 to 6.

8. The heat dissipation composition according to any one of claims 1 to 7, wherein the filling rate of the diamond particles is 15% by volume or more.

9. The heat dissipation composition according to any one of claims 1 to 8, further containing other heat conductive fillers other than diamond particles.

10. The heat dissipation composition according to claim 9, wherein the average particle diameter of the other heat conductive fillers is 0.1 μm or more and 200 μm or less.

11. The heat dissipation composition according to any one of claims 1 to 10, wherein the total filling rate of the heat conductive fillers is 40% by volume or more and 92% by volume or less.

12. The heat dissipation composition according to claim 11, wherein the total filling ratio of the heat conductive filler is 50% by volume or more.

13. The heat dissipation composition according to claim 12, wherein the total filling ratio of the heat conductive filler is 65% by volume or more.

14. The heat dissipation composition contains diamond particles as the heat conductive filler, or contains both diamond particles and other heat conductive fillers other than diamond particles. The heat dissipation composition according to any one of claims 1 to 13, wherein the volume ratio of the large particle size filler having an average particle size of 10 μm or more and 200 μm or less to the small particle size filler having an average particle size of 0.1 μm or more and less than 10 μm in the heat conductive filler is 0.2 or more and 5 or less.

15. The heat dissipation composition according to any one of claims 1 to 14, wherein the contact angle of the polymer matrix with respect to the heat conductive filler containing diamond particles is 70° or less.

16. The heat dissipation composition according to any one of claims 1 to 15, wherein the diamond particles contain a metal catalyst.

17. The heat dissipation composition according to any one of claims 1 to 16, wherein the diamond particles are crystallized diamond particles.

18. The heat dissipation composition according to any one of claims 1 to 17, wherein the diamond particles are diamond particles synthesized by crystallization under high temperature and high pressure in the presence of a metal catalyst.

19. The heat dissipation composition according to any one of claims 1 to 18, wherein the diamond particles contain diamond particles having an average particle size larger than 1 μm.

20. The heat dissipation composition according to any one of claims 1 to 19, wherein the heat dissipation composition is in a paste form.

21. The heat dissipation composition according to any one of claims 1 to 20, wherein the heat conductive filler includes diamond having an average particle size of 10 μm or more and 200 μm or less and spherical filler having an average particle size of 0.1 μm or more and less than 10 μm.

22. A heat dissipation member formed of the heat dissipation composition according to any one of claims 1 to 21.

23. An electronic component, An electronic device including the heat dissipation member according to claim 22 disposed on the electronic component.

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