Thermally conductive compositions and thermally conductive materials

Abstract

The present disclosure provides a thermally conductive composition that can produce a thermally conductive material having high thermal conductivity, and that has favorable moldability. The thermally conductive composition according to the present disclosure contains a resin (A) and a carbon-based material (B) the surface of which is covered by an inorganic substance.

Description

Technical Field

[0001] The present disclosure generally relates to thermally conductive compositions and thermally conductive materials, and more particularly to thermally conductive compositions containing a thermally conductive filler, and thermally conductive materials produced from the thermally conductive composition.

Background Art

[0002] A thermally conductive material is disposed between an electrical component such as a transistor, a CPU (central processing unit) of a computer, and a heat sink, so that heat generated from electronic and electrical components is conducted to the heat sink.

[0003] Patent Document 1 describes a heat-dissipating resin composition combining an epoxy resin, metal oxide particles, and a cationic curing agent.

Prior Art Literature

Patent Literature

[0004]

Patent Document 1

Summary of the Invention

[0005] An object of the present disclosure is to provide a thermally conductive composition which can produce a thermally conductive material with high thermal conductivity and has good moldability, and a thermally conductive material produced from the thermally conductive composition.

[0006] The thermally conductive composition according to one aspect of the present disclosure contains a resin (A), and a carbon-based material (B) whose surface is coated with an inorganic substance.

[0007] The thermally conductive material according to one aspect of the present disclosure is obtained by molding the thermally conductive composition into a film shape or a sheet shape.

Brief Description of Drawings

[0008] [Figure 1]Figure 1 is a schematic cross-sectional view of an electronic device comprising a thermally conductive material according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0009] According to the inventor's research, the heat-dissipating resin composition using epoxy resin described in Patent Document 1 (Japanese Patent Publication No. 2019-131668) contains a large amount of metal oxide particles as a thermally conductive filler, which tends to make the cured epoxy resin product hard and brittle. Furthermore, the inclusion of a large amount of metal oxide particles inhibits the curing of the epoxy resin, which tends to lead to a decrease in adhesive strength.

[0010] Therefore, the inventor considered using carbon-based materials as thermally conductive fillers. Although carbon-based materials have high thermal conductivity, practical thermally conductive materials containing carbon-based materials have not yet been sufficiently investigated.

[0011] According to the inventor's findings, using carbon-based materials as thermally conductive fillers resulted in problems such as difficulty in dispersing the carbon-based materials in the resin and deterioration of the resin's curing properties.

[0012] Therefore, the inventors conducted research and development to obtain a thermally conductive composition that can produce a thermally conductive material (TIM) with high thermal conductivity and good moldability, which led to the completion of this disclosure.

[0013] Although this disclosure was completed under the circumstances described above, the content of this disclosure is not limited by those circumstances.

[0014] 1. Overview One embodiment relating to this disclosure will be described below.

[0015] The thermally conductive composition according to this embodiment (hereinafter also referred to as thermally conductive composition (X)) contains a resin (A) and a carbon-based material (B) whose surface is coated with an inorganic material.

[0016] In this embodiment, the thermal conductivity of the thermal conductive material made from the thermal conductive composition (X) is enhanced by the carbon-based material (B). Therefore, even if the filler content in the thermal conductive composition is kept low to prevent the thermal conductive material from becoming hard and brittle, the thermal conductive material can still have high thermal conductivity. Furthermore, since the carbon-based material (B) is coated with an inorganic substance, the carbon-based material (B) disperses easily in the resin (A), and the carbon-based material (B) does not easily inhibit the curing of the resin (A). Therefore, the moldability of the thermal conductive composition (X) is not easily deteriorated by the carbon-based material (B).

[0017] Therefore, in this embodiment, a highly thermally conductive material can be produced from a thermally conductive composition, and the moldability of the thermally conductive composition can be improved.

[0018] 2.Details The thermally conductive composition (X) of this embodiment will be described in detail below.

[0019] As described above, the thermally conductive composition (X) of this embodiment contains a resin (A) and a carbon-based material (B) whose surface is coated with an inorganic substance.

[0020] The resin (A) preferably has reaction-curing properties. The resin (A) includes, for example, a thermosetting resin. The resin (A) preferably contains at least one selected from the group consisting of epoxy resins, acrylic compounds, and silicone resins. In this case, the thermally conductive composition (X) can be used as a heat-dissipating adhesive with high adhesive strength. Furthermore, the thermally conductive material made from the thermally conductive composition (X) in this case can have good heat resistance and flexibility. In this specification, the resin (A) may include any of the monomers and prepolymers that are polymer materials, as well as the polymer itself.

[0021] Generally, when the resin (A) contains a polar compound such as an acrylic compound, carbon-based materials such as graphite, graphene, or carbon nanotubes are difficult to disperse in the resin (A). This is considered to be because the acrylic compound has polarity, whereas the aforementioned carbon-based materials do not have polarity. Additionally, when the resin (A) contains a silicone resin, curing of the silicone resin tends to be inhibited.

[0022] However, since the surface of the carbon-based material (B) in the present embodiment is coated with an inorganic substance, the carbon-based material (B) is easily dispersed in the resin (A) even when the resin (A) contains a polar compound such as an acrylic compound. Furthermore, even when the resin (A) contains a silicone resin, the carbon-based material (B) is less likely to inhibit curing of the silicone resin.

[0023] When the resin (A) contains an epoxy resin, the epoxy resin contains at least one selected from the group consisting of, for example, bisphenol A type epoxy resins, bisphenol F type epoxy resins, glycidylamine type epoxy resins, cresol novolac type epoxy resins, and naphthalene type epoxy resins.

[0024] When the resin (A) contains an epoxy resin, the thermally conductive composition (X) may further contain a curing agent. Examples of the curing agent include phenolic curing agents, dicyandiamide curing agents, and the like. The thermally conductive composition (X) may further contain a curing accelerator as necessary. Examples of the curing accelerator include imidazoles, phenolic compounds, amines, organic phosphines, and the like.

[0025] When the resin (A) contains a silicone resin, the silicone resin is, for example, a reaction-curable liquid silicone rubber or silicone gel. The silicone resin may be of two-component type or one-component type. The silicone resin contains, for example, a reactive organosilicon compound such as organopolysiloxane and a curing agent, and further contains a catalyst if necessary. The curing agent contains, for example, at least one selected from organohydrogenpolysiloxane and organic peroxide. The catalyst is, for example, a platinum-based catalyst. It should be noted that the components contained in the silicone resin are not limited to those described above.

[0026] When the resin (A) contains an acrylic compound, the acrylic compound has at least one of an acryloyl group and a methacryloyl group in the molecule. The acrylic compound contains at least one selected from the group consisting of alkyl acrylates such as lauryl acrylate, phenoxydiethylene glycol acrylate, methoxypolyethylene glycol acrylate, and acrylic acid multimer esters, for example.

[0027] The carbon-based material (B) has excellent thermal conductivity. Therefore, the carbon-based material (B) can effectively reduce the thermal resistance of the thermally conductive composition (X). It is preferable that the carbon-based material (B) contains at least one selected from the group consisting of spherical graphite, platy graphite, single-layer graphene, multi-layer graphene, multi-walled carbon nanotubes, and single-walled carbon nanotubes.

[0028] When the carbon-based material (B) contains, for example, spherical graphite, the average particle size of the spherical graphite is preferably 10 μm or more and 200 μm or less. An average particle size of 10 μm or more of spherical graphite allows the thermally conductive composition (X) to have good thermal conductivity. An average particle size of 200 μm or less of spherical graphite allows the thermally conductive composition to have good fluidity. In particular, within this range, it is preferable that the spherical graphite contains two or more particle groups with different average particle sizes. In this case, good thermal conductivity and good fluidity of the thermally conductive composition (X) can be achieved simultaneously. An average particle size of 40 μm or more and 100 μm or less is more preferable. The average particle size of the spherical graphite is the median diameter (D50) calculated from the particle size distribution obtained by the laser diffraction / scattering particle size distribution measurement method.

[0029] As described above, the surface of the carbon-based material (B) is coated with an inorganic substance. The inorganic substance contains at least one selected from the group consisting of, for example, metals and metal compounds, and specifically contains at least one selected from the group consisting of, for example, silver, nickel, magnesium, magnesium carbonate, anhydrous magnesium carbonate, and magnesium hydroxide. It is more preferable that the inorganic substance contains a metal.

[0030] The statement that the surface of carbon-based material (B) is covered with inorganic material includes not only the state in which the entire surface of the particles of carbon-based material (B) is covered with inorganic material, but also the state in which inorganic material adheres to major areas of the surface of the particles of carbon-based material (B), leaving the carbon-based material (B) partially exposed.

[0031] The proportion of carbon-based material (B) is preferably 40% to 80% by volume relative to the total solid content of the thermally conductive composition (X). A proportion of 40% or more of carbon-based material (B) allows the thermally conductive composition (X) to have good thermal conductivity. A proportion of 80% or less of carbon-based material (B) allows the thermally conductive composition (X) to have good fluidity. More preferably, the proportion of carbon-based material (B) is 50% to 70% by volume, and even more preferably 55% to 65% by volume, relative to the total solid content of the thermally conductive composition (X).

[0032] The carbon-based material (B) contains a first carbon-based material (B1) and a second carbon-based material (B2), and it is preferable that the aspect ratio of the second carbon-based material (B2) is greater than that of the first carbon-based material (B1). The combination of the first carbon-based material (B1) and the second carbon-based material (B2) can particularly enhance the thermal conductivity of the thermal conductive composition (X). This is thought to be because the second carbon-based material (B2), with its larger aspect ratio, forms pathways for heat conduction within the thermal conductive composition (X). Furthermore, while the second carbon-based material (B2), with its larger aspect ratio, normally thickens the thermal conductive composition (X), the combination of the first carbon-based material (B1) and the second carbon-based material (B2) can suppress excessive thickening of the thermal conductive composition (X). The aspect ratio can be measured, for example, as follows. Images of 100 particles each of the first carbon-based material (B1) and the second carbon-based material (B2) are extracted and photographed using an electron microscope. The dimensions of the long axis and short axis of each particle are measured from the particle images. At this time, the longest width dimension in the particle image is defined as the long axis dimension, and the shortest width dimension is defined as the short axis dimension. In this way, the long axis and short axis dimensions are measured for 100 particles and the average value is taken. From this result, the aspect ratio is calculated as the average value of the long axis dimensions / the average value of the short axis dimensions.

[0033] The aspect ratio of the first carbon-based material (B1) is preferably 1 or more and 2 or less. When the aspect ratio of the first carbon-based material (B1) is 2 or less, the thermally conductive composition (X) tends to have good fluidity. The aspect ratio of the first carbon-based material (B1) is more preferably 1.5 or less, and even more preferably 1.2 or less.

[0034] The first carbon-based material (B1) preferably contains spherical graphite. Because spherical graphite has a small aspect ratio, when the first carbon-based material (B1) contains spherical graphite, the carbon-based material (B) disperses more easily in the thermally conductive composition (X). In addition, the thermally conductive composition (X) does not become excessively thickened and can have good fluidity.

[0035] The average particle size of the spherical graphite contained in the first carbon-based material (B1) is preferably 10 μm or more and 200 μm or less. An average particle size of 10 μm or more for the spherical graphite enhances the thermal conductivity of the thermal conductive composition (X), while an average particle size of 200 μm or less suppresses excessive viscosity increase of the thermal conductive composition (X). The spherical graphite, having an average particle size of 10 μm or more and 200 μm or less, may contain two or more particle groups with different average particle sizes. An average particle size of 40 μm or more for the spherical graphite is more preferable, and 80 μm or more is even preferable. Furthermore, an average particle size of 100 μm or less is even more preferable. The average particle size of the spherical graphite is the median diameter (D50) calculated from the particle size distribution obtained by the laser diffraction / scattering particle size distribution measurement method.

[0036] The second carbon-based material (B2) preferably contains at least one selected from the group consisting of plate-like graphite, single-layer graphene, multilayer graphene, multilayer carbon nanotubes, and single-layer carbon nanotubes. In this case, the second carbon-based material (B2) has particularly high thermal conductivity, and therefore the thermal conductivity of the thermal conductive composition (X) can be effectively enhanced. Multilayer graphene is composed of multiple layers of single-layer graphene. It is preferable that the number of layers of single-layer graphene in the multilayer graphene is 30 or less, or that the thickness of the multilayer graphene is 30 nm or less.

[0037] The aspect ratio of the second carbon-based material (B2) is preferably 3 or more and 1200 or less. If the aspect ratio of the second carbon-based material (B2) is 3 or more, the carbon-based material (B2) can form paths for heat conduction in the thermally conductive composition (X), thereby improving the thermal conductivity of the thermally conductive composition (X). If the aspect ratio of the second carbon-based material (B2) is 1200 or less, the thermally conductive composition (X) can have good fluidity.

[0038] If the second carbon-based material (B2) contains at least one selected from the group consisting of plate-like graphite, single-walled graphene, multi-walled graphene, multi-walled carbon nanotubes, and single-walled carbon nanotubes, it is preferable that its average particle size is 1 μm or more and 60 μm or less. The average particle size of the second carbon-based material (B2) is the median diameter (D50) calculated from the particle size distribution obtained by the particle image analysis system method.

[0039] The proportion of the first carbon-based material (B1) is preferably 1% to 90% by volume relative to the total thermal conductive composition (X). A proportion of 1% or more of the first carbon-based material (B1) relative to the total thermal conductive composition (X) suppresses excessive thickening of the thermal conductive composition (X) by the second carbon-based material (B2). A proportion of 90% or less of the first carbon-based material (B1) relative to the total thermal conductive composition (X) allows the thermal conductive composition (X) to contain the second carbon-based material (B2), potentially increasing the thermal conductivity of the thermal conductive composition (X). A proportion of 60% to 80% by volume, and even more preferably 65% ​​to 75% by volume, relative to the total thermal conductive composition (X).

[0040] The proportion of the second carbon-based material (B2) is preferably 0.1% to 30% by volume relative to the total thermal conductive composition (X). A proportion of 0.1% or more of the second carbon-based material (B2) relative to the total thermal conductive composition (X) can further enhance the thermal conductivity of the thermal conductive composition (X). A proportion of 30% or less of the second carbon-based material (B2) relative to the total thermal conductive composition (X) further suppresses excessive thickening of the thermal conductive composition (X). The proportion of the second carbon-based material (B1) is more preferably 1% to 10% by volume, and even more preferably 2% to 5% by volume, relative to the total thermal conductive composition (X).

[0041] The proportion of the first carbon-based material (B1) to the total thermal conductive composition (X) is preferably greater than the proportion of the second carbon-based material to the total thermal conductive composition (X). A larger proportion of the first carbon-based material (B1), which has a smaller aspect ratio, allows for both suppression of excessive thickening of the thermal conductive composition (X) and improvement of thermal conductivity. The volume ratio of the first carbon-based material (B1) to the second carbon-based material (B2) is preferably between 29:1 and 9:1, more preferably between 19:1 and 10:1, and even more preferably between 15:1 and 12:1.

[0042] Preferably, the thermally conductive composition (X) further contains an inorganic filler (C) other than the carbon-based material (B). The carbon-based material (B) tends to increase the viscosity of the thermally conductive composition (X), but the inorganic filler (C) does not increase the viscosity of the thermally conductive composition (X) as much as the carbon-based material (B). In other words, by using a combination of the carbon-based material (B) and the inorganic filler (C), excessive thickening of the thermally conductive composition (X) can be particularly suppressed. Specific examples of the inorganic filler (C) include, but are not limited to, spherical alumina.

[0043] The average particle size of the inorganic filler (C) is preferably 0.1 μm or more and 10 μm or less. When the thermal conductive composition (X) contains the above average particle size of inorganic filler (C) in addition to the carbon-based material (B), the thermal conductivity of the thermal conductive composition (X) tends to be further improved. The reason for this is not clear, but it is presumed that the size distribution of the carbon-based material (B) and the inorganic filler (C) is appropriate, making it easier for heat conduction paths to be formed in the thermal conductive composition (X). Within the above range, the inorganic filler (C) may contain two or more groups of particles with different average particle sizes. The average particle size of the inorganic filler (C) is more preferably 0.2 μm or more and 5 μm or less, and even more preferably 0.4 μm or more and 1 μm or less. The average particle size of the inorganic filler (C) is the median diameter (D50) calculated from the particle size distribution obtained by the laser diffraction particle size distribution measurement method.

[0044] The thermally conductive composition (X) may further contain a dispersant (D). When the thermally conductive composition (X) contains a dispersant (D), the dispersibility of the carbon-based material (B) and the inorganic filler (C) in the resin (A) is improved.

[0045] The thermal conductive composition (X) is preferably liquid at 25°C. The viscosity of the thermal conductive composition (X) at 25°C is preferably 3000 Pa·s or less. In this case, the thermal conductive composition (X) can have good moldability and can be easily molded into a film, for example, using a dispenser. Furthermore, the thermal conductive composition (X) is easily degassed, and therefore voids are less likely to form in the thermal conductive composition (X). The viscosity is the value measured using an E-type rotational viscometer at a rate of 0.3 rpm.

[0046] The thermally conductive composition (X) is prepared, for example, by kneading the above components. If the thermally conductive composition (X) contains a silicone resin and the silicone resin is a two-component type, the thermally conductive composition (X) may be prepared consisting of a first component containing a reactive organosilicon compound in the silicone resin and a second component containing a curing agent, and the first and second components may be mixed at the time of use. In this case, the carbon-based material (B) only needs to be contained in at least one of the first and second components.

[0047] A thermally conductive material is, for example, a thermally conductive composition molded into a film or sheet. When producing a thermally conductive material from a thermally conductive composition (X), the thermally conductive composition (X) is molded into a film or sheet by an appropriate method such as press molding, extrusion molding, or calendering. It is also preferable to mold the thermally conductive composition (X) into a film or sheet using a dispenser. If the thermally conductive composition (X) contains a thermosetting resin, the film-like thermally conductive material is obtained by subsequently heating and curing the film-like thermally conductive composition (X) under conditions corresponding to its composition.

[0048] The thermally conductive composition (X) and the thermally conductive material are not limited to film or sheet forms, but may be in any suitable shape. Furthermore, if the resin (A) is room-temperature curing, the thermally conductive composition (X) can be cured without heating to obtain the thermally conductive material. The thermally conductive material comprises a resin matrix made from resin (A) and a carbon-based material (B) dispersed within this resin matrix.

[0049] Thermally conductive materials tend to have low thermal resistance when they contain a carbon-based material (B). This is thought to be because, as mentioned above, the carbon-based material (B) has high thermal conductivity. When a thermally conductive material contains both a first carbon-based material (B1) and a second carbon-based material (B2), the thermally conductive material tends to have even lower thermal resistance. This is thought to be because, as mentioned above, the second carbon-based material (B2), which has a large aspect ratio, forms paths for heat conduction within the thermally conductive material.

[0050] The thermal resistance in the thickness direction of a thermally conductive material under no pressure is preferably 1.5 K / W or less. In this case, the thermally conductive material can exhibit excellent thermal conductivity and efficiently transfer heat. This thermal resistance is more preferably 1.0 K / W or less, and even more preferably 0.8 K / W or less.

[0051] The Asker C hardness of the thermally conductive material is preferably 40 or less. The Asker C hardness is measured using, for example, an Asker rubber hardness tester Type C manufactured by Polymer Instruments Co., Ltd. When the Asker C hardness is 40 or less, the thermally conductive material can have good flexibility and can be easily adhered to surfaces with various shapes, such as warped or undulating surfaces. An Asker C hardness of 30 or less is even more preferable. Also, an Asker C hardness of 10 or more is preferable. This low Asker C hardness can be achieved by selecting the resin (A), selecting the aspect ratios of the first carbon-based material (B1) and the second carbon-based material (B2), and selecting the proportions of the first carbon-based material (B1) and the second carbon-based material (B2).

[0052] An example of an electronic device equipped with thermally conductive materials will be described. The electronic device 1 shown in Figure 1 comprises a substrate 2, chip components 3, a heat spreader 4, a heat sink 5, and two types of thermally conductive materials 6 (hereinafter referred to as the first thermally conductive material 61 and the second thermally conductive material 62). The chip components 3 are mounted on the substrate 2. The substrate 2 is, for example, a printed circuit board. The chip components 3 are, for example, transistors, CPUs, MPUs, driver ICs, memory, etc., but are not limited to these. Multiple chip components 3 may be mounted on the substrate 2. In this case, the thicknesses of the chip components 3 may differ from each other. The heat spreader 4 is mounted on the substrate 2 so as to cover the chip components 3. There is a gap between the chip components 3 and the heat spreader 4, and the first thermally conductive material 61 is placed in this gap. A heat sink 5 is placed on top of the heat spreader 4, and the second thermally conductive material 62 is placed between the heat spreader 4 and the heat sink 5.

[0053] The thermal conductive material in this embodiment can be either the first thermal conductive material 61 or the second thermal conductive material 62 described above. Because the thermal conductive material in this embodiment has low thermal resistance, it can efficiently transfer the heat generated in the chip component 3 to the heat spreader 4 and heat sink 5, making it easier to realize an electronic device 1 with good heat dissipation. [Examples]

[0054] More specific examples of this embodiment will be described below. However, this embodiment is not limited to the examples described below.

[0055] 1. Preparation of the thermally conductive composition (X) The following materials were used as raw materials for the thermal conductive composition (X) of each example and comparative example, and were prepared by mixing them in the proportions shown in Tables 1 and 2. -Epoxy resin 1: Epoxy resin manufactured by DIC Corporation, product number Epiclon 830S. -Epoxy resin 2: Epoxy resin manufactured by Mitsubishi Chemical Corporation, product number YX7400. -Hardening agent 1: Phenolic hardening agent manufactured by Meiwa Kasei Co., Ltd., product number MEH-8000H. -Hardening agent 2: Phenolic hardening agent manufactured by Gun-ei Chemical Industry Co., Ltd., product number ELPC75. - Curing accelerator: Imidazole-based curing accelerator "Curezol" manufactured by Shikoku Chemicals Co., Ltd., product number 2E4MZ. -Acrylic compound A: Acrylic compound manufactured by Kao Corporation, product code: Excepal L-MA. - Acrylic compound B: Acrylic compound manufactured by Shin-Nakamura Chemical Industry Co., Ltd., product number AMP-20GY. -Crosslinking agent: A polyfunctional thiol manufactured by Showa Denko Corporation. Part number: Karenz PE1. - Radical initiator: Manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., catalog number VAm-110 (2,2'-azobis(N-butyl-2-methylpropionamide)). -Silicone resin: Two-component silicone resin manufactured by Toray Dow, product number SE1885. -Coupling agent A: Silane coupling agent manufactured by Shin-Etsu Chemical Co., Ltd., product name KBM-503. -Coupling agent B: Silane coupling agent manufactured by Toray Dow, product name Z-6583. - Dispersant: Wetting dispersant for ceramics and metal materials manufactured by NOF Corporation, product name Marialim SC0505K. -Surface-coated spherical graphite 1: Graphite manufactured by Ito Graphite Industries Co., Ltd., with a surface coating of silver and nickel, average particle size 40 μm, aspect ratio 1.5. -Surface-coated spherical graphite 2: Graphite manufactured by Ito Graphite Industries Co., Ltd., with a surface coating of magnesium carbonate, average particle size 40 μm, aspect ratio 1.5. -Surface-coated spherical graphite 3: Graphite manufactured by Ito Graphite Industries Co., Ltd., with a surface coating of magnesium carbonate, average particle size 8 μm, aspect ratio 1.5. - Surface-coated multilayer graphene: Multilayer graphene surface-coated with magnesium carbonate manufactured by Ishihara Chemical Co., Ltd., with a width of 5-15 μm, a thickness of 10-20 nm, and an aspect ratio of 750. - Spherical graphite 1: Manufactured by Ito Graphite Industry Co., Ltd., spherical graphite without surface coating, average particle size 40 μm, aspect ratio 1.0. - Spherical graphite 2: Manufactured by Ito Graphite Industry Co., Ltd., spherical graphite without surface coating, average particle size 8 μm, aspect ratio 1.0. - Multilayer graphene: Manufactured by Ishihara Chemical Co., Ltd., multilayer graphene without surface coating, width 5-15 μm, thickness 10-20 nm, aspect ratio 750. - Spherical alumina 1: Polyhedral spherical alumina manufactured by Sumitomo Chemical Co., Ltd., average particle size 0.45 μm, product number AA04. - Spherical Alumina 2: Polyhedral spherical alumina manufactured by Sumitomo Chemical Co., Ltd., average particle size 5 μm, product code AA5. - Spherical alumina 3: Spherical alumina manufactured by Denka Co., Ltd., average particle size 45 μm, product number DAW45. -Large particle size zinc oxide: Zinc oxide manufactured by Sakai Chemical Industry Co., Ltd., average particle size 5 μm, product number LPZINC5. - Fine zinc oxide: Zinc oxide manufactured by Sakai Chemical Industry Co., Ltd., with an average particle size of 0.28 μm.

[0056] 2. Evaluation (1) Viscosity The viscosity of the thermally conductive composition was measured using an E-type viscometer (model number RC-215) manufactured by Toki Sangyo Co., Ltd., under the conditions of a rotation speed of 0.3 rpm and a measurement time of 200 seconds.

[0057] (2) Thermal conductivity and thermal resistance A sample was prepared by sandwiching a thermally conductive composition (X) between two 1 mm thick copper plates. This sample was then subjected to direct pressure pressing at a press pressure of 1060 kPa, and the thickness of the thermally conductive composition (X) in the sample was adjusted to the thickness shown in Tables 1 and 2. Under these conditions, the temperature of the upper surface of the sample was maintained at 50°C and the temperature of the lower surface at room temperature. The thermal diffusivity in the direction of the press pressure of the sample was measured using a DynTIM Tester manufactured by Mentor Graphic, and the thermal conductivity and thermal resistance in the direction of the press pressure were determined from the results.

[0058] (3) Asker C hardness The Asker C hardness of the sample was measured using an Asker rubber hardness tester Type C manufactured by Polymer Instruments Co., Ltd.

[0059] [Table 1]

[0060] [Table 2]

[0061] As shown in the results above, when epoxy resin was used, the viscosity in Comparative Example 1 was higher compared to Examples 1 and 2. Also, the thermal conductivity in Comparative Examples 2 and 3 was lower compared to Examples 3 and 4.

[0062] Furthermore, when using acrylic compounds, Comparative Example 4 showed lower thermal conductivity compared to Examples 5-7, while Comparative Example 5 showed higher viscosity.

[0063] Furthermore, when using silicone resin, the curing properties were worse in Comparative Examples 6 and 7 compared to Examples 8 and 9, making it impossible to measure the Asker C hardness.

Claims

1. A resin (A) which is at least one selected from the group consisting of epoxy resins, acrylic compounds, and silicone resins, A carbon-based material (B) whose surface is coated with at least one inorganic substance selected from the group consisting of silver and magnesium carbonate, The carbon-based material (B) contains spherical graphite, The average particle size of the spherical graphite is 10 μm or more and 100 μm or less. The spherical graphite comprises two or more groups of particles with different average particle sizes. Thermally conductive composition.

2. The proportion of the carbon-based material (B) is 40% by volume or more and 80% by volume or less with respect to the total solid content of the thermally conductive composition. The thermally conductive composition according to claim 1.

3. The thermal conductive composition according to claim 1 or 2 is formed into a film or sheet, Thermally conductive material.

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