JP7163700B2 - thermal conductive sheet - Google Patents

Description

TECHNICAL FIELD The present invention relates to a heat conductive sheet.

In recent years, electronic components such as power semiconductors (such as IGBT modules) and integrated circuit (IC) chips have been increasing in heat generation as their performance has improved. As a result, in electronic equipment using electronic components, it is necessary to take measures against functional failure due to temperature rise of the electronic components.

As a countermeasure against functional failure due to temperature rise of electronic components, generally, a method of accelerating heat dissipation is adopted by attaching a radiator such as a metal heat sink, radiator plate, or radiator fin to the heat generating body of the electronic component. ing. When using a radiator, in order to efficiently transfer heat from the heating element to the radiator, a sheet-shaped member with high thermal conductivity (thermally conductive sheet) is placed between the thermally conductive sheet. A predetermined pressure is applied to the heat generating member and the heat dissipating member.

Patent Literature 1 discloses a heat-conducting sheet having an adhesive layer on its surface to improve adhesion to a building frame.
Further, Patent Document 2 discloses a thermally conductive sheet in which thermal conductivity is ensured by setting the area ratio (exposure) of graphite exposed on the surface to 25% to 80%.
Furthermore, Patent Literature 3 discloses a thermally conductive sheet in which a metal layer is interposed between graphite layers.

Japanese Patent No. 5699556 Japanese Patent No. 6341303 Japanese Unexamined Patent Application Publication No. 2011-178008

However, the above-described conventional heat conductive sheet has room for improvement in terms of improving surface adhesion while maintaining heat conductivity.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thermally conductive sheet having improved surface adhesion while maintaining thermal conductivity.

The inventor of the present invention has made intensive studies in order to achieve the above object. Then, the present inventors found that the surface of a heat conductive sheet containing a thermoplastic resin, a particulate carbon material, and a particulate metal material, and in which the particulate carbon material and the particulate metal material are oriented in the thickness direction, found that by keeping the degree of exposure of the particulate metal material within a predetermined range, it is possible to obtain a thermally conductive sheet with improved surface adhesion while maintaining thermal conductivity. , completed the present invention.

That is, an object of the present invention is to advantageously solve the above problems, and a heat conductive sheet of the present invention is a heat conductive sheet containing a thermoplastic resin, a particulate carbon material, and a particulate metal material. The particulate carbon material and the particulate metal material are oriented in the thickness direction of the heat conductive sheet, and the degree of exposure (area ratio) of the particulate metal material on the surface of the heat conductive sheet is 15. % or more and 30% or less. It contains a thermoplastic resin, a particulate carbon material, and a particulate metal material, wherein the particulate carbon material and the particulate metal material are oriented in the thickness direction, and the exposure of the particulate metal material on the surface is 15% or more and 30%. The following thermally conductive sheet can improve surface adhesion while maintaining thermal conductivity.
Here, the "particulate carbon material" means a carbon material having an aspect ratio of 10 or less, and the "surface of the thermally conductive sheet" means at least one surface of the thermally conductive sheet.
The degree of exposure of the particulate metal material on the surface of the heat conductive sheet can be measured by the method described in Examples.

Further, in the thermally conductive sheet of the present invention, the particulate metal material preferably has a Vickers hardness of 3 or more and 150 or less. If the Vickers hardness of the particulate metal material is 3 or more and 150 or less, it is possible to improve the adhesion to the precursor while maintaining the thermal conductivity.
The Vickers hardness of the particulate metal material is, for example, "List of Metal Hardness and Comparison of Hardness", [online], updated on January 2, 2013, [searched on August 22, 2018], Internet <URL:
1538090429072_0.html
>It is described in.

Moreover, in the heat conductive sheet of the present invention, the metal of the particulate metal material is preferably at least one of silver and copper. If the metal of the particulate metal material is at least one of silver and copper, good adhesion can be obtained while maintaining the thermal conductivity of the thermally conductive sheet.

Moreover, in the heat conductive sheet of the present invention, the average particle size of the particulate carbon material is preferably 10 times or less the average particle size of the particulate metal material. If the average particle diameter of the particulate carbon material is 10 times or less than the average particle diameter of the particulate metal material, the degree of exposure of the particulate metal material on the surface of the heat conductive sheet is adjusted to improve the heat conduction of the heat conductive sheet. It is possible to reliably improve the adhesion of the surface of the heat conductive sheet while reliably maintaining the properties.
The "average particle size" of the particulate carbon material and the particulate metal material can be obtained by wet particle size distribution measurement. In the state of the sheet after kneading, the particulate carbon material and the particulate metal material cannot be separated by wet particle size distribution. The average particle size of each is measured.
Here, the wet particle size distribution measurement is performed as follows.
－Wet particle size distribution measurement－
Prepare a suspension by separating and dispersing each filler (particulate carbon material and particulate metal material) in an arbitrary solution, then use the obtained suspension as a sample, laser diffraction / scattering type particle size distribution A particle size of each filler (particulate carbon material and particulate metal material) contained in the suspension is measured using a measuring device (manufactured by Horiba Ltd., model "LA960"). Then, the particle diameter at the maximum value of the particle diameter distribution curve with the obtained particle diameter on the horizontal axis and the volume of each filler (particulate carbon material and particulate metal material) on the vertical axis is the volume-based mode diameter (μm). Ask as

Further, in the heat conductive sheet of the present invention, it is preferable that the degree of exposure of the thermoplastic resin on the surface of the heat conductive sheet is 30% or more and 70% or less. Good adhesion can be obtained if the degree of exposure of the thermoplastic resin on the surface of the heat conductive sheet is 30% or more and 70% or less.
The degree of exposure of the thermoplastic resin on the surface of the heat conductive sheet can be measured by the method described in Examples.

Further, the heat conductive sheet of the present invention preferably has a heat resistance value of 0.50 (° C./W) or less under pressure of 0.1 MPa. If the thermal resistance value under pressure of 0.1 MPa is 0.50 (° C./W) or less, the thermal conductivity of the thermally conductive sheet can be more reliably improved.
The heat resistance value of the heat conductive sheet can be measured by the method described in Examples.

Furthermore, the thermally conductive sheet of the present invention has a ratio of exposure of the particulate carbon material on the surface of the thermally conductive sheet to exposure of the particulate metal material on the surface of the thermally conductive sheet (exposure of the particulate carbon material /The degree of exposure of the particulate metal material) is preferably 0.5 or more and 3.0 or less. The ratio of the degree of exposure of the particulate carbon material on the surface of the heat conductive sheet to the degree of exposure of the particulate metal material on the surface of the heat conductive sheet (the degree of exposure of the particulate carbon material/the degree of exposure of the particulate metal material) is 0.5 If it is 3.0 or less, it is possible to more reliably maintain the thermal conductivity of the thermally conductive sheet and more reliably improve the adhesion of the surface of the thermally conductive sheet.
The degree of exposure of the particulate carbon material on the surface of the heat conductive sheet can be measured by the method described in Examples.

ADVANTAGE OF THE INVENTION According to this invention, the thermally-conductive sheet which improved the adhesiveness of the surface can be provided, maintaining thermal conductivity.

1 is a photograph showing a cross section of a thermally conductive sheet according to an example of the present invention; 1 is a photograph showing the surface of a thermally conductive sheet in Example 1. FIG. 4 is a photograph showing the surface of a thermally conductive sheet in Comparative Example 1. FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.
Since the thermally conductive sheet of the present invention has thermal conductivity, it can be used by sandwiching it between a heating element and a radiator. That is, the heat conductive sheet of the present invention can be used as a heat radiating member to constitute a heat radiating device together with a heat radiating body such as a heat sink, a heat radiating plate, or a heat radiating fin.

(Thermal conductive sheet)
The thermally conductive sheet of the present invention contains a thermoplastic resin, a particulate carbon material, and a particulate metal material, and further optionally contains other components. Further, the heat conductive sheet of the present invention has a structure in which the particulate carbon material and the particulate metal material are oriented in the thickness direction of the heat conductive sheet, and the particulate metal material is exposed on the surface of the heat conductive sheet. is 15% or more and 30% or less. In the thermally conductive sheet of the present invention, a thermally conductive path is formed by the particulate carbon material and the particulate metal material oriented in the thickness direction of the thermally conductive sheet, and the thermal conductivity can be exhibited. Since the degree of exposure of the metal material is 15% or more and 30% or less, the adhesion of the surface of the heat conductive sheet can be improved, and both the thermal conductivity and the adhesion of the heat conductive sheet can be achieved.

<Thermoplastic resin>
By containing a thermoplastic resin in the thermally conductive sheet of the present invention, the flexibility of the thermally conductive sheet is improved in a high-temperature environment during use (during heat dissipation), and the heat generating element and the radiator are connected via the thermally conductive sheet. can be adhered well. A thermosetting resin can be used in combination with the heat conductive sheet provided that the properties and effects of the heat conductive sheet of the present invention are not lost. In this specification, rubber and elastomer shall be included in "resin".
The thermoplastic resin that can be included in the heat conductive sheet of the present invention constitutes the matrix resin and also functions as a binder that binds the particulate carbon material and the particulate metal material.
Examples of such thermoplastic resins include "thermoplastic resins that are liquid at normal temperature and normal pressure" and "thermoplastic resins that are solid at normal temperature and normal pressure". These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.
Among these, even under relatively low pressure, the interfacial adhesion can be improved to reduce the interfacial thermal resistance, and the thermal conductivity (that is, heat dissipation characteristics) of the thermal conductive sheet can be improved. A thermoplastic resin that is liquid at normal temperature and normal pressure” is preferred.
In this specification, "normal temperature" refers to 23°C, and "normal pressure" refers to 1 atm (absolute pressure).

<<Thermoplastic resin that is liquid at normal temperature and pressure>>
When the heat conductive sheet contains a thermoplastic resin that is liquid at normal temperature and normal pressure, the flexibility of the heat conductive sheet can be improved. It is possible to increase the adhesion between the heat generating body and the heat dissipating body, and to exhibit higher thermal conductivity by the heat conductive sheet.

Examples of thermoplastic resins that are liquid at normal temperature and pressure include acrylic resins, epoxy resins, silicone resins, and fluorine resins. These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.
Among these, in addition to improving the flame retardancy, heat resistance, oil resistance, and chemical resistance of the heat conductive sheet, even under relatively low pressure, the interfacial adhesion is increased and the interfacial thermal resistance is reduced. A thermoplastic fluororesin that is liquid at normal temperature and normal pressure is preferable because it can improve the thermal conductivity (that is, the heat dissipation property) of the heat conductive sheet.

[Thermoplastic fluororesin that is liquid at normal temperature and pressure]
The thermoplastic fluororesin that is liquid at normal temperature and pressure is not particularly limited as long as it is a thermoplastic fluororesin that is liquid at normal temperature and pressure. Examples of thermoplastic fluororesins that are liquid at normal temperature and pressure include vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropentene-tetrafluoroethylene terpolymer, perfluoropropene oxide polymer, tetrafluoroethylene-propylene-vinylidene fluoride copolymer, and the like. These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.
Examples of commercially available thermoplastic fluororesins that are liquid at normal temperature and pressure include Viton (registered trademark) LM manufactured by DuPont Co., Ltd., Daiel (registered trademark) G-101 manufactured by Daikin Industries, Ltd., and 3M. Dynion FC2210 manufactured by Co., Ltd., SIFEL series manufactured by Shin-Etsu Chemical Co., Ltd., and the like can be mentioned.

The viscosity of the thermoplastic fluororesin, which is liquid at normal temperature and pressure, is not particularly limited. coefficient) is preferably 500 cP or more and 30,000 cP or less, more preferably 550 cP or more and 25,000 cP or less.

[Content ratio of liquid thermoplastic resin at normal temperature and pressure]
The content of the thermoplastic resin that is liquid at room temperature and pressure is 40% by mass or more of the total content of the thermoplastic resin that is liquid at room temperature and pressure and the thermoplastic resin that is solid at room temperature and pressure, which will be described in detail later. It is preferably 60% by mass or more, more preferably 90% by mass or less, and more preferably 75% by mass or less. If the content of the thermoplastic resin, which is liquid at normal temperature and pressure, is within the above range, the flexibility of the thermally conductive sheet can be further increased, for example, the thermally conductive sheet and the adherend (heating element) sandwiching the thermally conductive sheet. , heat radiator), so that the heat conductive sheet can exhibit high thermal conductivity under a relatively low sandwiching pressure (for example, 0.5 MPa or less). .

<<Thermoplastic resin that is solid at normal temperature and pressure>>
Since the heat conductive sheet contains a thermoplastic resin that is solid under normal temperature and normal pressure, the strength in the heat conductive sheet can be increased, and the handling of the heat conductive sheet can be improved.

Examples of thermoplastic resins that are solid under normal temperature and pressure include poly(2-ethylhexyl acrylate), copolymers of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its esters, polyacrylic acid or its esters. Acrylic resin such as acrylic resin; silicone resin; fluorine resin; polyethylene; polypropylene; ethylene-propylene copolymer; polymethylpentene; polyethylene terephthalate; polybutylene terephthalate; polyethylene naphthalate; polystyrene; polyacrylonitrile; styrene-acrylonitrile copolymer; acrylonitrile-butadiene-styrene copolymer (ABS resin); Styrene-isoprene block copolymer or hydrogenated product thereof; Polyphenylene ether; Modified polyphenylene ether; Aliphatic polyamides; Aromatic polyamides; Polyamideimide; Polycarbonate; ether ketone; polyketone; polyurethane; liquid crystal polymer; These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.
Among these, from the viewpoint of improving the flame retardancy, heat resistance, oil resistance, chemical resistance, etc. of the heat conductive sheet, thermoplastic resins that are solid at room temperature and pressure A fluororesin is preferred.

[Thermoplastic fluororesin that is solid at normal temperature and pressure]
The thermoplastic fluororesin that is solid at normal temperature and normal pressure is not particularly limited as long as it is a thermoplastic fluororesin that is solid at normal temperature and normal pressure. Thermoplastic fluororesins that are solid at normal temperature and pressure include, for example, vinylidene fluoride fluororesins, tetrafluoroethylene-propylene fluororesins, tetrafluoroethylene-purple vinyl ether fluororesins, and the like, which are obtained by polymerizing fluorine-containing monomers. The resulting elastomer and the like can be mentioned. More specifically, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, polychloro trifluoroethylene, ethylene-chlorofluoroethylene copolymer, tetrafluoroethylene-perfluorodioxole copolymer, polyvinyl fluoride, tetrafluoroethylene-propylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, Vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, acrylic-modified polytetrafluoroethylene, ester-modified polytetrafluoroethylene, epoxy-modified polytetrafluoroethylene and silane-modified polytetrafluoroethylene , and so on. These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.
Among them, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkylvinyl ether copolymer, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymer, acrylic-modified polytetrafluoroethylene, from the viewpoint of workability , is preferred.

In addition, commercially available thermoplastic fluororesins that are solid under normal temperature and pressure include, for example, DAIEL (registered trademark) G-912 and G-700 series manufactured by Daikin Industries, Ltd., DAIEL G-550 series/G- 600 series, Daiel G-310; KYNAR (registered trademark) series and KYNAR FLEX (registered trademark) series manufactured by ALKEMA; Dyneon FC2211 and FPO3600ULV manufactured by 3M;

[[Content ratio of thermoplastic fluororesin]]
When the thermoplastic resin is a thermoplastic fluororesin, the content of the thermoplastic fluororesin in the heat conductive sheet is preferably 30% by mass or more and 60% by mass or less. If the content of the thermoplastic fluororesin is within the above range, the flame retardancy, heat resistance, oil resistance, chemical resistance, etc. of the thermally conductive sheet can be further improved. When the thermoplastic resin contains both a thermoplastic fluororesin that is liquid under normal temperature and pressure and a thermoplastic fluororesin that is solid under normal temperature and pressure, the total content of each of them may be within the above range. preferable.

<Thermosetting resin>
Provided that the properties and effects of the heat conductive sheet of the present invention are not lost, thermosetting resins that can optionally be used in the heat conductive sheet include, for example, natural rubber; butadiene rubber; isoprene rubber; nitrile rubber; Nitrile rubber; Chloroprene rubber; Ethylene propylene rubber; Chlorinated polyethylene; Chlorosulfonated polyethylene; Butyl rubber; Halogenated butyl rubber; Polyisobutylene rubber; Epoxy resin; diallyl phthalate resin; polyimide silicone resin; polyurethane; thermosetting polyphenylene ether; thermosetting modified polyphenylene ether; These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.

<Particulate carbon material>
When the thermally conductive sheet of the present invention contains a particulate carbon material, the thermal conductivity of the thermally conductive sheet can be further enhanced.
The particulate carbon material is not particularly limited, and examples thereof include graphite such as artificial graphite, flake graphite, exfoliated graphite, natural graphite, acid-treated graphite, expansive graphite, and expanded graphite; carbon black; can be used. These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.
Among these, expanded graphite is preferred. If expanded graphite is used for the thermally conductive sheet, the thermal conductivity of the thermally conductive sheet can be further improved.

<<expanded graphite>>
Here, the expanded graphite that can be suitably used as the particulate carbon material is, for example, expandable graphite obtained by chemically treating graphite such as flake graphite with sulfuric acid or the like, heat-treating it to expand it, and then making it fine. can be obtained by Examples of commercially available expanded graphite include EC-1500, EC-1000, EC-500, EC-300, EC-100, EC-50, and EC-10 manufactured by Ito Graphite Industry Co., Ltd. first name), etc.

<<Average particle size>>
The average particle size of the particulate carbon material is preferably 5 µm or more, more preferably 25 µm or more, preferably 200 µm or less, and more preferably 150 µm or less.
If the average particle diameter of the particulate carbon material is at least the above lower limit, the thermal conductivity and the like of the thermally conductive sheet can be further improved. Further, if the average particle size of the particulate carbon material is equal to or less than the above upper limit, the strength and shape retention ability of the heat conductive sheet can be further enhanced.
The average particle size of the particulate carbon material is preferably 10 times or less, more preferably 8 times or less, and preferably 6 times or less the average particle size of the particulate metal material described later. It is particularly preferably 0.5 times or more, more preferably 2 times or more, and particularly preferably 4 times or more.
If the average particle diameter of the particulate carbon material is equal to or less than the above upper limit of the average particle diameter of the particulate metal material, the degree of exposure of the particulate metal material on the surface of the heat conductive sheet is adjusted so that the surface of the heat conductive sheet is Adhesion can be reliably improved. Moreover, if the average particle size of the particulate carbon material is equal to or greater than the lower limit of the average particle size of the particulate metal material, the thermal conductivity of the heat conductive sheet can be reliably maintained.

<<aspect ratio>>
The aspect ratio (major axis/minor axis) of the particulate carbon material is preferably 1 or more and 10 or less, more preferably 1 or more and 5 or less.
In this specification, the "aspect ratio" refers to the maximum diameter (major diameter) and the maximum diameter of any 50 particulate carbon materials observed with a SEM (scanning electron microscope). It can be obtained by measuring the particle diameter (short diameter) in the orthogonal direction and calculating the average value of the ratio of the long diameter to the short diameter (long diameter/short diameter).

<<Content ratio of particulate carbon material>>
The content of the particulate carbon material in the heat conductive sheet is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and 40 parts by mass with respect to 100 parts by mass of the thermoplastic resin. It is particularly preferably 70 parts by mass or less, more preferably 60 parts by mass or less, and particularly preferably 50 parts by mass or less. If the content of the particulate carbon material is at least the above lower limit, thermal conductivity can be improved. Further, when the content of the particulate carbon material is equal to or less than the above upper limit, the adhesion can be improved.

<Particulate metal material>
By including the particulate metal material in the thermally conductive sheet of the present invention, the adhesion of the thermally conductive sheet can be further enhanced.

The particulate metal material is not particularly limited, and examples thereof include silver, copper, gold, platinum, and aluminum. These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.
Among these, silver and copper are preferable because of their high thermal conductivity.

<<Vickers Hardness>>
The Vickers hardness of the particulate metal material is not particularly limited, but is preferably 3 or more, more preferably 10 or more, particularly preferably 20 or more, and 150 or less. is preferred, 120 or less is more preferred, and 100 or less is particularly preferred. There is no metal with a Vickers hardness of 3 or less in the particulate metal material. Further, when the Vickers hardness of the particulate metal material is equal to or less than the above upper limit, it is possible to improve the adhesion to the precursor while maintaining good workability.
Silver has a Vickers hardness of about 25, bronze has a Vickers hardness of 50 to 100, brass has a Vickers hardness of 80 to 150, and pure copper has a Vickers hardness of about 120.

<<Average particle size>>
The average particle size of the particulate metal material is preferably 1 µm or more, more preferably 3 µm or more, particularly preferably 5 µm or more, and preferably 100 µm or less, and 50 µm or less. is more preferable, and 30 μm or less is particularly preferable. If the particle size of the particulate metal material is equal to or greater than the above lower limit, thermal conductivity and adhesion can be maintained. Moreover, if the particle diameter of the particulate metal material is equal to or less than the above upper limit, good workability can be maintained.

<<Content ratio of particulate metal material>>
The content of the particulate metal material in the heat conductive sheet is preferably 80 parts by mass or more, more preferably 100 parts by mass or more, and 150 parts by mass with respect to 100 parts by mass of the thermoplastic resin. It is particularly preferably 400 parts by mass or less, more preferably 300 parts by mass or less, and particularly preferably 250 parts by mass or less. Adhesion can be improved if the content of the particulate metal material is at least the above lower limit. Moreover, if the content rate of a particulate metal material is below the said upper limit, thermal conductivity can be improved.

<Other ingredients>
If necessary, the thermally conductive sheet can further contain other components that can be used for molding the thermally conductive sheet. Other components that can be blended into the heat conductive sheet are not particularly limited, and include, for example, fibrous carbon materials; inorganic nitride materials; flame retardants such as red phosphorus flame retardants and phosphate ester flame retardants. Plasticizers such as fatty acid ester plasticizers; Toughness improvers such as urethane acrylate; Moisture absorbers such as calcium oxide and magnesium oxide; Adhesion improvers such as silane coupling agents, titanium coupling agents and acid anhydrides; wettability improvers such as surfactants and fluorine-based surfactants; ion trapping agents such as inorganic ion exchangers; and the like.

<<Fibrous carbon material>>
The fibrous carbon material that the thermally conductive sheet may optionally contain is not particularly limited, and includes, for example, fibrous carbon nanostructures such as carbon nanotubes (hereinafter sometimes referred to as "CNT"), Vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, cut products thereof, and the like can be used. These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.
For example, if the thermally conductive sheet contains a fibrous carbon material, the thermal conductivity of the thermally conductive sheet can be improved, and powder falling of the particulate carbon material can be prevented. Although the reason why powder falling off of the particulate carbon material can be prevented by blending the fibrous carbon material is not clear, the formation of a three-dimensional network structure by the fibrous carbon material contributes to heat conduction. It is presumed that this is because detachment of the particulate carbon material is prevented while improving the properties and strength.

Among the materials described above, fibrous carbon nanostructures such as CNTs are preferably used as the fibrous carbon material, and fibrous carbon nanostructures containing CNTs are more preferably used. This is because the use of fibrous carbon nanostructures containing CNTs can further improve the thermal conductivity and strength of the thermally conductive sheet at a relatively low clamping pressure.

<<Inorganic nitride material>>
Examples of inorganic nitride materials include boron nitride, silicon nitride, and aluminum nitride. These may be used individually by 1 type, and may use 2 or more types together by arbitrary ratios.
Among these, boron nitride is preferable from the viewpoint of imparting insulating properties and thermal conductivity.
Here, specific examples of commercially available boron nitride particles include, for example, Momentive Performance Materials Japan's "PT" series (eg, "PT-110"); Showa Denko's "Showby N UHP" series (eg, "ShowBN UHP-1"); Dangdong Chemical Engineering Institute Co., Ltd.; , Ltd. "HSL", "HS";

Moreover, the shape of the inorganic nitride material includes, for example, a plate shape and a scale shape, preferably a scale shape.

<Structure and Properties of Heat Conductive Sheet>
The heat conductive sheet of the present invention has the following structure and properties without being particularly limited.

<<Structure of Thermally Conductive Sheet>>
The thermally conductive sheet of the present invention has a structure in which the particulate carbon material and the particulate metal material as described above are oriented in the thickness direction of the thermally conductive sheet. Here, "orientation in the thickness direction of the heat conductive sheet" means that the cross section of the heat conductive sheet (secondary sheet) is first observed using a SEM (scanning electron microscope), and the particulate carbon material and particles in the sheet It refers to the state in which the metallic material is oriented in the thickness direction of the sheet.

<<Thermal resistance value of the thermally conductive sheet>>
The heat conductive sheet preferably has a thermal resistance value of 0.50 (° C./W) or less under pressure of 0.1 MPa (10 N/cm ² ), and preferably 0.35 (° C./W) or less. is more preferable, and 0.25 (° C./W) or less is particularly preferable. When the thermal resistance value under pressure of 0.1 MPa (10 N/cm ² ) is equal to or less than the above upper limit value, excellent thermal conductivity can be obtained under a usage environment in which relatively low pressure is applied.
Here, the thermal resistance value can be measured using a known measuring method that is usually used to measure the thermal resistance of the heat conductive sheet, and a resin material thermal resistance tester (for example, manufactured by Hitachi Technology and Service Co., Ltd. , trade name “C47108”).

<<Thickness of thermally conductive sheet>>
The thickness of the heat conductive sheet is preferably 50 μm or more, more preferably 100 μm or more, particularly preferably 150 μm or more, and preferably 500 μm or less, more preferably 300 μm or less. It is preferably 250 μm or less, and particularly preferably 250 μm or less. If the thickness of the thermally conductive sheet is equal to or less than the above upper limit, when it becomes necessary to interpose the thermally conductive sheet between the heating element and the radiator, the heat between the heating element and the radiator through the thermally conductive sheet Easy to move. Moreover, if the thickness of the thermally conductive sheet is equal to or more than the above lower limit, the strength of the thermally conductive sheet can be increased and the handleability can be improved.

<<Surface Roughness of Heat Conductive Sheet>>
The surface roughness Sz of the heat conductive sheet is preferably 10 μm or more, more preferably 15 μm or more, particularly preferably 20 μm or more, and preferably 100 μm or less, and 70 μm or less. is more preferable, and 50 μm or less is particularly preferable. If the surface roughness Sz of the heat conductive sheet of the present invention is equal to or less than the above upper limit, good smoothness can be obtained.
Here, the surface roughness Sz of the heat conductive sheet is measured using a laser microscope (manufactured by Keyence Corporation, shape analysis laser microscope, VK-X250 series) at a magnification of 20 times, and optionally 4 lines and a length of 200 μm. can be selected to obtain the surface roughness Sz with respect to the line roughness.

<<Adhesion of thermal conductive sheet (tacking)>>
Adhesion (tacking) of the heat conductive sheet is preferably 1.7 N or more, more preferably 2.0 N or more. Further, when the adhesion (tacking) of the heat conductive sheet is equal to or higher than the above lower limit, the adhesion of the heat conductive sheet can be improved.
Here, the adhesion (tacking) of the heat conductive sheet can be measured using a probe tack tester (manufactured by Lesca Co., Ltd., trade name "TAC1000"). Specifically, the tip of a flat-shaped probe with a diameter of 10 mm is pressed against the heat conductive sheet with a load of 0.5 N (50 gf) for 10 seconds, and the force required to separate the probe from the heat conductive sheet is measured at a measurement temperature of 25 ° C. . The larger the measured value of the adhesion (tacking) of the thermally conductive sheet, the higher the adhesion and the better the adhesion to the frame.
In addition, when the degree of exposure of the thermoplastic resin on the surface of the thermally conductive sheet increases, the adhesion (tacking) increases, and when the degree of exposure of the particulate metal material on the surface of the thermally conductive sheet increases, the adhesion (tacking) increases. increases and the degree of exposure of the particulate carbon material on the surface of the heat conductive sheet increases, the adhesion (tacking) decreases.

<<Exposure of each component (thermoplastic resin, particulate carbon material, particulate metal material) on the surface of the heat conductive sheet>>
The degree of exposure of the thermoplastic resin on the surface of the heat conductive sheet is preferably 30% or more, more preferably 40% or more, particularly preferably 50% or more, and 70% or less. is preferred, and 60% or less is more preferred. If the degree of exposure of the thermoplastic resin on the surface of the heat conductive sheet of the present invention is equal to or less than the above upper limit, the heat conductivity can be improved. Moreover, if the degree of exposure of the thermoplastic resin on the surface of the thermally conductive sheet is equal to or higher than the above lower limit, the adhesion can be improved.
The degree of exposure of the particulate carbon material on the surface of the heat conductive sheet is preferably 18% or more, more preferably 21% or more, particularly preferably 30% or more, and 42% or less. It is preferably 35% or less, more preferably 35% or less. If the degree of exposure of the particulate carbon material on the surface of the heat conductive sheet of the present invention is equal to or less than the above upper limit value, the adhesion can be improved. Moreover, if the degree of exposure of the particulate carbon material on the surface of the thermally conductive sheet is equal to or higher than the above lower limit, the thermal conductivity can be improved.
The degree of exposure of the particulate metal material on the surface of the heat conductive sheet should be 15% or more, preferably 20% or more, and should be 30% or less, and should be 25% or less. is preferred. If the degree of exposure of the particulate metal material on the surface of the heat conductive sheet of the present invention is equal to or less than the above upper limit, the heat conductivity can be improved. Further, when the degree of exposure of the particulate metal material on the surface of the heat conductive sheet is equal to or higher than the above lower limit, the adhesion can be improved.
The degree of exposure of each component (thermoplastic resin, particulate carbon material, particulate metal material) on the surface of the heat conductive sheet was measured using a scanning microscope (SU3500 manufactured by Hitachi High-Technologies Corporation) at a magnification of 400. , an acceleration voltage of 5 kV, a spot intensity of 60, an image of the surface of the thermal conductive sheet (for example, FIGS. 2 and 3) is obtained, and image processing is performed using Winroof (manufactured by Mitani Shoji Co., Ltd.). can be calculated.

In addition, the ratio of the degree of exposure of the particulate carbon material on the surface of the heat conductive sheet to the degree of exposure of the particulate metal material on the surface of the heat conductive sheet (the degree of exposure of the particulate carbon material/the degree of exposure of the particulate metal material) is It is preferably 0.5 or more, more preferably 1.0 or more, particularly preferably 1.5 or more, and preferably 3.0 or less, and 2.5 or less. is more preferable, and 2.0 or less is particularly preferable. The ratio of the degree of exposure of the particulate carbon material on the surface of the heat conductive sheet to the degree of exposure of the particulate metal material on the surface of the heat conductive sheet of the present invention (the degree of exposure of the particulate carbon material/the degree of exposure of the particulate metal material) is If the content is equal to or less than the above upper limit value, adhesion can be improved, and if the content is equal to or more than the above lower limit value, thermal conductivity can be improved.

<Asker C hardness of heat conductive sheet>
The Asker C hardness of the heat conductive sheet is preferably 60 or more, more preferably 65 or more, and preferably 80 or less, more preferably 75 or less. If the Asker C hardness of the thermally conductive sheet of the present invention is equal to or less than the above upper limit, the flexibility of the thermally conductive sheet is increased, and for example, the thermally conductive sheet and the adherend (heating element, It is possible to improve the adhesion between the thermal conductive sheet and the radiator), and if it is at least the above lower limit value, the strength of the thermally conductive sheet can be improved.
Here, the Asker C hardness of the heat conductive sheet is measured according to the Asker C method of the Rubber Society of Japan (SRIS) using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., trade name "ASKER CL-150LJ"). It can be carried out at a temperature of 25°C.
Although the Asker C hardness of the thermally conductive sheet does not increase significantly when the amount of the particulate metal material added increases, the Asker C hardness of the thermally conductive sheet increases when the amount of the particulate carbon material added increases. Further, when the average particle size of the particulate carbon material is reduced, the Asker C hardness of the heat conductive sheet increases.

<Preparation of heat conductive sheet>
The thermally conductive sheet of the present invention is prepared by, for example, a thermally conductive sheet preparation method including (i) a pre-thermally conductive sheet forming step, (ii) a laminate forming step, (iii) a slicing step, etc., which will be described in detail below. be done.

<<(i) Pre-thermal conductive sheet forming step>>
In the pre-thermal conductive sheet forming step, a composition containing a thermoplastic resin, a particulate carbon material, a particulate metal material, and optionally other components is pressurized into a sheet to form a pre-thermal conductive sheet. get a sheet.

〔Composition〕
Here, the composition can be prepared by mixing the thermoplastic resin, the particulate carbon material, the particulate metal material, and any other ingredients. As the thermoplastic resin, the particulate carbon material, the particulate metal material, and any other components, the above-described thermoplastic resin, the above-described particulate carbon material, the above-described Particulate metal materials such as those described above may be used, as well as other components described above.
Incidentally, when the resin of the heat conductive sheet is a crosslinkable resin, the pre-heat conductive sheet may be molded using a composition containing a crosslinkable resin, or a crosslinkable resin and a curing agent may be mixed. A pre-thermally conductive sheet may be formed using the containing composition, and the crosslinkable resin may be crosslinked after the pre-thermally conductive sheet forming step, so that the thermally conductive sheet contains a crosslinkable resin.

The mixing of the above-described components is not particularly limited, and can be performed using known mixing devices such as kneaders; mixers such as Henschel mixers, Hobart mixers, and high-speed mixers; twin-screw kneaders; can. Mixing may also be performed in the presence of a solvent such as ethyl acetate. A thermoplastic resin may be previously dissolved or dispersed in a solvent to form a resin solution, which may be mixed with the particulate carbon material, the particulate metal material, and any other components. And mixing time can be 5 minutes or more and 60 minutes or less, for example. Moreover, the mixing temperature can be, for example, 5° C. or higher and 150° C. or lower.

[Molding of composition]
The composition prepared as described above can be optionally defoamed and pulverized, and then pressurized to form a sheet. A sheet-like product obtained by pressure-molding the composition in this way can be used as a pre-heat conductive sheet. In addition, when a solvent is used during mixing, it is preferable to form the sheet after removing the solvent. For example, if defoaming is performed using vacuum defoaming, the solvent is removed at the same time as defoaming. It can be carried out.

Here, the composition is not particularly limited as long as it is a molding method in which pressure is applied, and it can be molded into a sheet using a known molding method such as press molding, rolling molding, or extrusion molding. . Above all, the composition is preferably formed into a sheet by roll forming, and more preferably formed into a sheet by passing between rolls while sandwiched between protective films. The protective film is not particularly limited, and a sandblasted polyethylene terephthalate (PET) film or the like can be used. In addition, the roll temperature is 5° C. or higher and 150° C. or lower, the roll gap is 50 μm or higher and 2500 μm or lower, the roll linear pressure is 1 kg/cm or higher and 3000 kg/cm or lower, and the roll speed is 0.1 m/min or higher and 20 m/min or lower. can.

[Pre-thermal conductive sheet]
In the pre-heat conductive sheet formed by pressurizing the composition and forming it into a sheet, the particulate carbon material and the particulate metal material are oriented mainly in the in-plane direction, and in particular, heat is generated in the in-plane direction of the pre-heat conductive sheet. It is presumed that the conductivity is improved.

<<(ii) Laminate forming step>>
In the laminate forming step, a plurality of pre-thermally conductive sheets obtained in the pre-thermally conductive sheet forming step are laminated in the thickness direction, or the pre-thermally conductive sheets are folded or wound, and the thermoplastic resin and the particulate A laminate is obtained in which a plurality of thermally conductive sheets containing a carbon material and a particulate metal material are formed in the thickness direction. Here, the formation of the laminate by folding the pre-heat conductive sheet is not particularly limited, and can be performed by folding the pre-heat conductive sheet to a certain width using a folding machine. Moreover, the formation of the laminate by winding the pre-heat conductive sheet is not particularly limited. It can be carried out. Moreover, the formation of the laminate by laminating the pre-thermally conductive sheets is not particularly limited, and can be performed using a laminating apparatus. For example, if a sheet lamination apparatus (manufactured by Nikkiso Co., Ltd., product name: "High Stacker") is used, it is possible to prevent air from entering between layers, so that a good laminate can be obtained efficiently.

Here, in the laminate obtained in the laminate formation step, the adhesive force between the surfaces of the pre-heat conductive sheets is usually sufficient due to the pressure applied when laminating the pre-heat conductive sheets and the pressure applied when folding or winding. obtained in

From the viewpoint of suppressing delamination, the obtained laminate is heated at 120° C. or more and 170° C. or less for 1 minute or more and 8 hours or less while being pressed in the lamination direction with a pressure of 0.1 MPa or more and 0.5 MPa or less. is preferred. Here, delamination may be prevented by applying an adhesive or a solvent to the pre-heat conductive sheets and bonding the pre-heat conductive sheets together when forming the laminate. From the standpoint of practical preparation, it is preferred not to use adhesives or solvents.

In the laminate obtained by laminating, folding, or winding the pre-heat conductive sheets, it is presumed that the particulate carbon material and the particulate metal material are oriented in a direction substantially perpendicular to the stacking direction.

<<(iii) Slicing step>>
In the slicing step, the laminate obtained in the laminate forming step is sliced at an angle of 45° or less with respect to the lamination direction to obtain a heat conductive sheet made of sliced pieces of the laminate. Here, the method for slicing the laminate is not particularly limited, and examples thereof include a multi-blade method, a laser processing method, a water jet method, a knife processing method, and the like. Among them, the knife processing method is preferable because the thickness of the heat conductive sheet can be easily made uniform. Also, the cutting tool for slicing the laminate is not particularly limited, and a slicing member having a smooth board surface with a slit and a blade protruding from the slit (for example, a sharp blade) A planer or slicer) can be used.

Embodiments of blades that can be used as the blade portion will now be described.
A single blade having a blade portion may be a "double-edged" blade having cutting edges on both front and back sides, or may be a "single-edged" blade having a cutting edge only on the front side.

Also, the cross-sectional shape of the cutting edge is not particularly limited, and may be asymmetrical or symmetrical with respect to the central axis passing through the tip of the cutting edge.

The number of blades constituting the blade portion is not particularly limited, and for example, it may be composed of one blade consisting of one blade, or may be composed of two blades consisting of two blades. good.

Here, each of the two blades may be single-edged or double-edged.
Further, when one or both of the two blades are double-edged, the double-edged blades may be symmetrical or asymmetrical.
In addition, the two blades may be single-stepped blades or double-stepped blades.

The material of the blade is not particularly specified, and may be any of metal, ceramic, and plastic, but cemented carbide is particularly desirable from the standpoint of resistance to impact. The surface of the blade may be coated with silicone, fluorine, or the like for the purpose of improving slipperiness and cutting performance.

From the viewpoint of enhancing the thermal conductivity of the heat conductive sheet, the angle at which the laminate is sliced is preferably 30° or less with respect to the stacking direction, and more preferably 15° or less with respect to the stacking direction. Preferably, the angle is approximately 0° with respect to the stacking direction (that is, the direction along the stacking direction).

From the viewpoint of slicing the laminate easily, the temperature of the laminate during slicing is preferably -20° C. or higher and 40° C. or lower, more preferably 10° C. or higher and 30° C. or lower. Furthermore, for the same reason, the laminate to be sliced is preferably sliced while applying pressure in the direction perpendicular to the lamination direction, and the pressure is 0.1 MPa or more and 0.5 MPa or less in the direction perpendicular to the lamination direction. Slicing while loading is more preferable. It is presumed that the particulate carbon material and the particulate metal material are oriented in the thickness direction in the heat conductive sheet thus obtained. Therefore, the thermally conductive sheet prepared through the above steps has not only thermal conductivity in the thickness direction but also electrical conductivity.

EXAMPLES The present invention will be specifically described below based on examples, but the present invention is not limited to these examples. In the following description, "%" and "parts" representing amounts are based on mass unless otherwise specified.

In each example and each comparative example, (i) the volume fraction of each component (thermoplastic resin, particulate carbon material, particulate metal material) in the heat conductive sheet, (ii) the thermal resistance value of the heat conductive sheet, ( iii) the Asker C hardness of the heat conductive sheet, (iv) the degree of exposure of each component (thermoplastic resin, particulate carbon material, particulate metal material) on the surface of the heat conductive sheet, and (v) tacking of the heat conductive sheet. Measurements or evaluations were made using the following methods, respectively. Table 1 shows the results.

<(i) Volume fraction of each component in the heat conductive sheet>
The volume fraction of each component in the heat conductive sheet was calculated using the added amount and specific gravity of each component.

<(ii) Thermal resistance value of thermally conductive sheet>
The thermal resistance value of the thermal conductive sheet was measured using a resin material thermal resistance tester (manufactured by Hitachi Technology and Service Co., Ltd.). Here, a thermal conductive sheet cut into a square of 1.0 cm ² was used as a sample, and the thermal resistance value (° C./W) was measured when a relatively low pressure of 0.10 MPa was applied at a sample temperature of 50° C. . The smaller the thermal resistance value, the better the thermal conductivity of the thermally conductive sheet.

<(iii) Asker C hardness of thermal conductive sheet>
The Asker C hardness of the heat conductive sheet is measured in accordance with the Asker C method of the Japan Rubber Society Standard (SRIS) using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., trade name "ASKER CL-150LJ" at a temperature of 25 ° C. I went with
Specifically, the thermally conductive sheets obtained in Examples and Comparative Examples were cut into a size of 25 mm in width×50 mm in length×0.5 mm in thickness, and 24 sheets were laminated to obtain a test piece. A thermal conductive sheet layer was obtained as a test piece by allowing the obtained test piece to stand in a thermostatic chamber maintained at a temperature of 25° C. for 48 hours or longer. Next, the height of the damper was adjusted so that the pointer was 95 to 98, and the heat conductive sheet layer and the damper were caused to collide. The Asker C hardness of the heat conductive sheet layer 60 seconds after the collision was measured twice using a hardness tester (manufactured by Kobunshi Keiki Co., Ltd., trade name “ASKER CL-150LJ”), and the average value of the measurement results was calculated. did. A lower Asker C hardness indicates superior softness and flexibility, and a higher Asker C hardness indicates higher hardness.

<(iv) Degree of exposure of each component on the surface of the thermally conductive sheet>
The degree of exposure of each component on the surface of the thermally conductive sheet was measured using a scanning microscope (SU3500, manufactured by Hitachi High-Technologies Corporation) at a magnification of 400, an accelerating voltage of 5 kV, and a spot intensity of 60. An image of the surface (for example, Figs. 2 and 3) was obtained and image processing was performed using winroof (manufactured by Mitani Shoji Co., Ltd.) for calculation.
In addition, each component was projected with different shades of colors (white: metal material, gray: thermoplastic resin, black: carbon material (graphite)).

<(v) Adhesion (Tacking) of Thermally Conductive Sheet>
The adhesion (tacking) of the heat conductive sheet was measured using a probe tack tester (manufactured by Lesca Co., Ltd., trade name "TAC1000"). Specifically, the tip of a flat-shaped probe with a diameter of 10 mm was pressed against the heat conductive sheet for 10 seconds with a load of 0.5 N (50 gf), and the force required to separate the probe from the heat conductive sheet was measured at a measurement temperature of 25°C. . The larger the measured value of the adhesiveness (tacking) of the heat conductive sheet, the higher the adhesiveness and the better the adhesion to the frame, and 1.7 N or more is within the allowable range.

(Example 1)
<Preparation of composition>
70 parts of a thermoplastic fluororesin that is liquid under normal temperature and pressure as a flame-retardant resin (manufactured by Daikin Industries, Ltd., trade name "DAIEL G-101") and a thermoplastic fluororesin that is solid under normal temperature and pressure (3M Japan Co., Ltd. Company, trade name "Dynion FC2211") 30 parts, expanded graphite as a particulate carbon material (manufactured by Ito Graphite Industry Co., Ltd., trade name "EC500", volume average particle size: 30 μm) 47 parts, and particulate 200 parts of silver flakes (manufactured by DOWA Electronics, trade name “FA-S-13”, average particle size: 14.7 μm, Vickers hardness: 25) as a metal material are used in a pressure kneader (manufactured by Nihon Spindle). and stirred and mixed at a temperature of 150° C. for 20 minutes. Next, the resulting mixture was put into a crusher (manufactured by Osaka Chemical Co., Ltd., trade name “Wonder Crush Mill D3V-10”) and crushed for 10 seconds to obtain a composition.

<Molding of pre-thermal conductive sheet>
Next, 50 g of the resulting composition was sandwiched between sandblasted PET films (protective films) having a thickness of 50 μm, and the roll gap was 900 μm, the roll temperature was 50° C., the roll linear pressure was 50 kg/cm, and the roll speed was 1 m/min. to obtain a pre-heat conductive sheet having a thickness of 0.8 mm.

<Formation of laminate>
Subsequently, the obtained pre-heat conductive sheet was cut into a size of 150 mm long×150 mm wide×0.8 mm thick, and 75 sheets were laminated in the thickness direction of the pre-heat conductive sheet to obtain a laminate having a height of about 60 mm. Furthermore, a laminate with a height of 50 mm was obtained by pressing (secondary pressure) in the lamination direction at a temperature of 80° C. and a pressure of 0.2 MPa for 2 minutes.

<Molding of thermal conductive sheet>
After that, leaving a length necessary for slicing, the entire upper surface of the obtained laminate was pressed with a metal plate, and a pressure of 0.1 MPa was applied in the lamination direction (that is, from above) to fix the laminate. . The side and back surfaces of the laminate were not fixed. At this time, the temperature of the laminate was 25°C.
Next, a cutting blade (double-edged, blade angle 2θ: 20°, maximum thickness of blade: 3.5 mm, material: carbide, Rockwell hardness: 91 5, silicon processing of the blade surface: none, total length: 200 mm), and the lamination direction of the laminate (in other words, the main surface of the laminated pre-heat conductive sheet) under the conditions of a slicing speed of 200 mm / sec and a slice width of 100 μm. ) to obtain a heat conductive sheet of length 150 mm x width 60 mm x thickness 0.10 mm.
Then, the obtained heat conductive sheet was subjected to the above-described measurements according to the above-described method. Table 1 shows the results.

(Example 2)
In Example 1, instead of 200 parts of silver flakes, copper flakes (manufactured by DOWA Electronics, trade name “AO-YCD-1”, average particle size: 7.0 μm, Vickers hardness: 120) were used as the particulate metal material. In the same manner as in Example 1, except that 168 parts were used, "preparation of composition", "pre-heat conductive sheet molding", "laminate formation" and "heat conductive sheet molding" were carried out. .

(Example 3)
In Example 1, except that the added amount of expanded graphite was changed from 47 parts to 24 parts, and the added amount of silver flakes was changed from 200 parts to 120 parts, ""Preparation of composition", "Formation of pre-heat conductive sheet", "Formation of laminate" and "Formation of heat conductive sheet" were carried out.

(Example 4)
In Example 3, the addition amount of the liquid thermoplastic fluororesin under normal temperature and pressure was changed from 70 parts to 77 parts, and the addition amount of the solid thermoplastic fluororesin under normal temperature and pressure was changed from 30 parts to 33 parts. And, in the same manner as in Example 3, except that the amount of silver flakes added was changed from 120 parts to 150 parts, "Preparation of composition", "Formation of pre-heat conductive sheet", "Formation of laminate ” and “Molding of heat conductive sheet” were performed.

(Comparative example 1)
In Example 1, instead of using expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., trade name “EC500”, volume average particle size: 30 μm) as the particulate carbon material, expanded graphite (manufactured by Ito Graphite Industry Co., Ltd. , trade name "EC100", volume average particle size: 250 μm), in the same manner as in Example 1, "Preparation of composition", "Formation of pre-heat conductive sheet", "Formation of laminate ” and “Molding of heat conductive sheet” were performed.

(Comparative example 2)
In Example 2, instead of using expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., trade name "EC500", volume average particle size: 30 μm) as the particulate carbon material, expanded graphite (manufactured by Ito Graphite Industry Co., Ltd. , trade name “EC100”, volume average particle size: 250 μm), in the same manner as in Example 2, “Preparation of composition”, “Formation of pre-heat conductive sheet”, “Formation of laminate ” and “Molding of heat conductive sheet” were performed.

(Comparative Example 3)
In Example 3, instead of using expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., trade name "EC500", volume average particle size: 30 μm) as the particulate carbon material, expanded graphite (manufactured by Ito Graphite Industry Co., Ltd. , trade name “EC100”, volume average particle size: 250 μm), in the same manner as in Example 3, “Preparation of composition”, “Formation of pre-heat conductive sheet”, “Formation of laminate ” and “Molding of heat conductive sheet” were performed.

(Comparative Example 4)
In the same manner as in Example 1, except that instead of using 47 parts of expanded graphite and 200 parts of silver flakes, only 90 parts of expanded graphite was used, "preparation of composition", "preparation of Formation of heat conductive sheet”, “Formation of laminate” and “Formation of heat conductive sheet” were performed.

ADVANTAGE OF THE INVENTION According to this invention, the thermally-conductive sheet which improved the adhesiveness of the surface can be provided, maintaining thermal conductivity.

Claims (9)

A thermally conductive sheet containing a thermoplastic resin, a particulate carbon material, and a particulate metal material,
The particulate carbon material and the particulate metal material are oriented in the thickness direction of the heat conductive sheet,
The particulate carbon material has an average particle size of 25 μm or more and 150 μm or less,
The average particle size of the particulate carbon material is determined by using a suspension of the particulate carbon material as a sample and using a laser diffraction/scattering particle size distribution analyzer to determine the particulate carbon material contained in the suspension. is the particle size at the maximum value of a particle size distribution curve in which the obtained particle size is taken as the horizontal axis and the volume of the particulate carbon material is taken as the vertical axis,
The particulate carbon material has an aspect ratio (major axis/minor axis) of 1 or more and 10 or less,
A heat conductive sheet, wherein the degree of exposure of the particulate metal material on the surface of the heat conductive sheet is 15% or more and 30% or less. The heat conductive sheet according to claim 1, wherein the particulate metal material has a Vickers hardness of 3 or more and 150 or less. 3. The thermally conductive sheet according to claim 1, wherein the metal of said particulate metal material is at least one of silver and copper. 4. The heat conductive sheet according to claim 1, wherein the average particle size of the particulate carbon material is 10 times or less the average particle size of the particulate metal material. The thermally conductive sheet according to any one of claims 1 to 4, wherein the degree of exposure of the thermoplastic resin on the surface of the thermally conductive sheet is 30% or more and 70% or less. The heat conductive sheet according to any one of claims 1 to 5, having a heat resistance value of 0.50 (°C/W) or less under pressure of 0.1 MPa. The ratio of the degree of exposure of the particulate carbon material on the surface of the heat conductive sheet to the degree of exposure of the particulate metal material on the surface of the heat conductive sheet (the degree of exposure of the particulate carbon material/the degree of exposure of the particulate metal material degree) is from 0.5 to 3.0, the heat conductive sheet according to any one of claims 1 to 6. The particulate metal material has an average particle size of 5 μm or more and 30 μm or less,
The average particle size of the particulate metal material contained in the suspension is determined by using a suspension of the particulate metal material as a sample and using a laser diffraction/scattering particle size distribution analyzer. 8. The particle size at the maximum value of a particle size distribution curve with the obtained particle size as the horizontal axis and the volume of the particulate metal material as the vertical axis. The thermally conductive sheet described in . The particulate carbon material contains at least one selected from the group consisting of artificial graphite, flake graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, expandable graphite, and carbon black. The heat conductive sheet according to any one of claims 1 to 8.

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