JP6750617B2 - Insulating heat conductive sheet and method for manufacturing the same - Google Patents

Description

The present invention relates to an insulating heat conductive sheet and a method for manufacturing the insulating heat conductive sheet.

2. Description of the Related Art In recent years, electronic components such as plasma display panels (PDP) and integrated circuit (IC) chips have increased the amount of heat generation as their performance has increased. As a result, in an electronic device using an electronic component, it is necessary to take measures for a functional failure due to a temperature rise of the electronic component.

Here, in general, as a measure against functional failure due to temperature rise, a method of promoting heat dissipation by attaching a heat sink such as a metal heat sink, heat sink, or heat dissipation fin to a heat generator such as an electronic component is adopted. ing. Then, when the heat radiator is used, in order to efficiently transfer heat from the heat generator to the heat radiator, the heat generator and the heat radiator are connected via a sheet-shaped member (heat conductive sheet) having high heat conductivity. Are closely attached. Therefore, the heat conductive sheet used by being sandwiched between the heat generating element and the heat radiating element is required to have high flexibility in addition to high heat conductivity. Further, most of the heat conductive sheets are used for the electronic parts as described above, and therefore it is required to have the insulating property as well.

Therefore, for example, in Patent Document 1, an adhesive layer containing an organic polymer compound having a glass transition temperature of 50° C. or less as a main component is arranged on both surfaces of a heat conductive layer, which has high flexibility and excellent adhesion to a heat sink or the like. Thermally conductive sheets have been proposed. However, in the heat conductive sheet described in Patent Document 1, the adhesive layers located on both sides of the heat conductive layer become heat insulating parts. Therefore, the heat conductive sheet of Patent Document 1 has room for improvement in heat conductivity.

Further, for example, Patent Document 2 proposes a heat dissipation insulating sheet (insulating heat conductive sheet) in which heat dissipation layers made of a conductive material such as carbon, copper, and aluminum are arranged on both sides of an insulating layer. In the heat dissipation insulating sheet according to Patent Document 2, since the heat dissipation layer physically protects the insulation layer, a part of the heat dissipation layer is crushed due to a relatively large surface roughness of the attachment (eg, heat sink). Even if it is done, the insulating layer itself is not damaged and the insulating property can be secured. However, the heat dissipation insulating sheet described in Patent Document 2 having insulation properties and excellent thermal conductivity does not have the flexibility of the heat conduction sheet described in Patent Document 1, and is sufficiently compatible with the heating element and the radiator. I couldn't come into close contact.

JP 2012-109312 A JP, 2014-241340, A

That is, hitherto, an insulating heat conductive sheet having both insulating properties, thermal conductivity, and flexibility has not been realized.

Therefore, an object of the present invention is to provide an insulating heat conductive sheet in which insulation properties, heat conductivity, and flexibility are juxtaposed at a sufficiently high level.
Further, the present invention provides a method for manufacturing an insulating heat conductive sheet capable of efficiently manufacturing an insulating heat conductive sheet in which insulation properties, thermal conductivity, and flexibility are juxtaposed at a sufficiently high level. To aim.

The present inventors have earnestly studied to achieve the above object. Then, the present inventors have formed an insulating heat conductive sheet having a structure in which an insulating layer is sandwiched between heat conductive sheets having a predetermined hardness, which is formed using a composition containing a resin and a particulate carbon material, The present invention has been completed by finding that they are excellent in insulation, thermal conductivity, and flexibility.

That is, the present invention has an object to advantageously solve the above-mentioned problems, and an insulating heat conductive sheet of the present invention contains a resin and a particulate carbon material, and has an Asker C hardness of 70 or less. It is characterized in that the conductive sheets are arranged above and below in the thickness direction of the insulating layer. In such an insulating heat conductive sheet, the insulating property, the heat conductivity, and the flexibility are juxtaposed at a sufficiently high level. In particular, if the heat conducting sheet constituting the surface of the insulating heat conducting sheet is excellent in flexibility, the adhesion of the insulating heat conducting sheet to the attachment can be improved.

Further, the insulating heat conductive sheet of the present invention preferably has a thermal conductivity in the thickness direction of 7 W/m·K or more. Further, the insulating heat conductive sheet of the present invention preferably has a withstand voltage test value of 10 kV/mm or more. In such an insulating heat-conducting sheet, the insulating property and the thermal conductivity are juxtaposed at a higher level.

Further, the insulating heat conductive sheet of the present invention preferably has a density of 1.8 g/m ³ or less. This is because such an insulating heat conductive sheet has high versatility and can contribute to weight reduction of the electronic component when mounted on products such as electronic components.

Here, in the insulating heat conductive sheet of the present invention, it is preferable that the insulating layer contains a cyclic olefin resin and surface-treated aluminum hydroxide. In such an insulating heat conductive sheet, the insulating property and the thermal conductivity are juxtaposed at a higher level. Further, by containing aluminum hydroxide, the flame retardancy of the insulating heat conductive sheet can be improved.

Here, in the insulating heat conductive sheet of the present invention, it is preferable that the amount of the surface-treated aluminum hydroxide is 1/2 to 6 times the amount of the cyclic olefin resin. With such an insulating heat conductive sheet, it is possible to further improve the insulating property and the thermal conductivity while increasing the flame retardancy.

Here, in the insulating heat conductive sheet of the present invention, the heat conductive sheet is formed into a sheet by pressing a composition containing the resin and the particulate carbon material to form a pre-heat conductive sheet. Then, a laminated body obtained by laminating a plurality of the pre-heat conductive sheets in the thickness direction or a laminated body obtained by folding or winding the pre-heat conductive sheet is formed at 45° or less with respect to the laminating direction. It is preferably a sheet obtained by slicing at an angle. In such an insulating heat conductive sheet, the insulating property and the thermal conductivity are juxtaposed at a higher level.

Moreover, this invention aims at solving the said subject advantageously, The manufacturing method of the insulating heat conductive sheet of this invention WHEREIN: Asker C hardness is a process of preparing a heat conductive sheet of 70 or less, And a step of laminating the heat conductive sheet above and below in the thickness direction of the insulating layer, wherein the step of preparing the heat conductive sheet is performed by pressurizing a composition containing a resin and a particulate carbon material into a sheet shape. Obtaining a pre-heat conductive sheet, stacking a plurality of the pre-heat conductive sheets in the thickness direction, or folding or winding the pre-heat conductive sheet to obtain a laminate, and the laminate Is sliced at an angle of 45° or less with respect to the stacking direction to obtain a heat conductive sheet. In the insulating heat conductive sheet manufactured in this manner, the insulating property, the heat conductivity, and the flexibility are juxtaposed at a sufficiently high level.

In the present invention described above, the “Asker C hardness” can be measured at a temperature of 23° C. using a hardness meter according to the Asker C method of the Japan Rubber Association Standard (SRIS).
As the “heat conductivity”, the thermal diffusivity α (m ² /s), constant pressure specific heat Cp (J/g·K) and density (specific gravity) ρ (g/m ³ ) of the insulating heat conductive sheet are used. Then, the following formula (I):
Thermal conductivity λ (W/m·K)=α×Cp×ρ (I)
You can ask more. Here, "thermal diffusivity" can be measured using a thermophysical property measuring device, "constant pressure specific heat" can be measured using a differential scanning calorimeter, and "density (specific gravity)" is an automatic hydrometer. Can be used for measurement.
Further, the "withstanding voltage test value" can be measured by performing a pressure rise test in silicone oil using an in-oil tester.

According to the present invention, it is possible to provide an insulating heat-conducting sheet in which insulation properties, heat conductivity, and flexibility are juxtaposed at a sufficiently high level, and a method for manufacturing the same.

1 is a cross-sectional view showing a schematic structure of an insulating heat conductive sheet according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail.
The insulating heat conductive sheet of the present invention can be used, for example, by sandwiching it between a heating element and a radiator when attaching the radiator to the heating element. That is, the insulating heat conductive sheet of the present invention can form a heat dissipation device together with a heat dissipation member such as a heat sink, a heat dissipation plate, or a heat dissipation fin. And the insulating heat conductive sheet of this invention can be manufactured using the manufacturing method of the insulating heat conductive sheet of this invention, for example.

(Insulating heat conductive sheet)
As shown in FIG. 1, the insulating heat conductive sheet (10) of the present invention includes an insulating layer (2) and heat conductive sheets (1) arranged above and below the insulating layer (2) in the thickness direction. ing. The heat conductive sheet (1) of the insulating heat conductive sheet (10) of the present invention contains a resin and a particulate carbon material and has an Asker C hardness of 70 or less. Since the insulating heat conductive sheet of the present invention includes the heat conductive sheet containing the particulate carbon material and the insulating layer, it has excellent insulating properties and thermal conductivity. Further, the insulating heat conductive sheet of the present invention has an Asker C hardness of 70 or less on the heat conductive sheet located on the front surface side, and therefore has excellent flexibility and is suitable for a mounting object such as a radiator or a heating element. Can be in close contact. Therefore, the insulating heat conductive sheet of the present invention can have the insulating property, the heat conductivity, and the flexibility juxtaposed at a sufficiently high level.
Although FIG. 1 shows an insulating heat conductive sheet (10) in which the insulating layer (2) is directly sandwiched between two layers of the heat conductive sheet (1), the insulating heat conductive sheet of the present invention is Other layers (for example, an adhesive layer) may be provided between the insulating layer and the heat conductive sheet as long as the effects of the present invention are not significantly impaired. Further, although FIG. 1 shows the case where the heat conductive sheet (1) and the insulating layer (2) are composed of a single layer, in the insulating heat conductive sheet of the present invention, the heat conductive sheet and the insulating layer have a multilayer structure. May have. Further, the heat conductive sheet located above the insulating layer and the heat conductive sheet located below the insulating layer may be the same as or different from each other.

<Heat conduction sheet>
The heat conductive sheets provided on both sides of the insulating layer in the thickness direction need to include a resin and a particulate carbon material and have an Asker C hardness of 70 or less. When the heat conductive sheet does not contain the particulate carbon material, sufficient heat conductivity cannot be obtained. Further, if the heat conductive sheet does not contain a resin or the Asker C hardness of the heat conductive sheet exceeds 70, sufficient flexibility cannot be obtained.

[resin]
Here, the resin is not particularly limited, and a known resin that can be used for forming the heat conductive sheet can be used. Specifically, as the resin, a thermoplastic resin or a thermosetting resin can be used. In the present invention, rubber and elastomer are included in “resin”. Moreover, you may use together a thermoplastic resin and a thermosetting resin.

[[Thermoplastic resin]]
Examples of the thermoplastic resin include poly(2-ethylhexyl acrylate), copolymers of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its ester, polyacrylic acid or its acrylic resin such as ester. Silicone resin; Fluorine resin such as polyvinylidene fluoride and polytetrafluoroethylene; Polyethylene; Polypropylene; Ethylene-propylene copolymer; Polymethylpentene; Polyvinyl chloride; Polyvinylidene chloride; Polyvinyl acetate; Ethylene-vinyl acetate copolymer Polyvinyl alcohol; Polyacetal; Polyethylene terephthalate; Polybutylene terephthalate; Polyethylene naphthalate; Polystyrene; Polyacrylonitrile; Styrene-acrylonitrile copolymer; Acrylonitrile-butadiene-styrene copolymer (ABS resin); Styrene-butadiene block copolymer Or a hydrogenated product thereof; a styrene-isoprene block copolymer or a hydrogenated product thereof; polyphenylene ether; modified polyphenylene ether; aliphatic polyamides; aromatic polyamides; polyamideimide; polycarbonate; polyphenylene sulfide; polysulfone; polyether sulfone Polyether nitrile; polyether ketone; polyketone; polyurethane; liquid crystal polymer; ionomer; and the like. These may be used alone or in combination of two or more.

[[Thermosetting resin]]
Examples of the thermosetting resin include natural rubber; butadiene rubber; isoprene rubber; nitrile rubber; hydrogenated nitrile rubber; chloroprene rubber; ethylene propylene rubber; chlorinated polyethylene; chlorosulfonated polyethylene; butyl rubber; halogenated butyl rubber; Polyisobutylene rubber; Epoxy resin; Polyimide resin; Bismaleimide resin; Benzocyclobutene resin; Phenol resin; Unsaturated polyester; Diallyl phthalate resin; Polyimide silicone resin; Polyurethane; Thermosetting polyphenylene ether; Thermosetting modified polyphenylene ether; Is mentioned. These may be used alone or in combination of two or more.

Among the above, it is preferable to use a thermoplastic resin as the resin of the heat conductive sheet constituting the insulating heat conductive sheet. This is because if the thermoplastic resin is used, the flexibility of the heat conductive sheets located above and below the insulating layer can be further improved, and the heat generating element and the heat radiating element can be brought into good contact with each other via the insulating heat conductive sheet. ..

[Particulate carbon material]
The particulate carbon material is not particularly limited, and examples thereof include artificial graphite, flake graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, expanded graphite, and other graphite; carbon black; Can be used. These may be used alone or in combination of two or more.
Above all, expanded graphite is preferably used as the particulate carbon material. When expanded graphite is used, the thermal conductivity of the thermal conductive sheet can be improved, and therefore the thermal conductivity of the insulating thermal conductive sheet can be further improved.

[[Expanded graphite]]
Here, 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-treated and expanded, and then finely divided. Can be obtained. Examples of the expanded graphite include EC1500, EC1000, EC500, EC300, EC100, and EC50 (all are trade names) manufactured by Ito Graphite Industry Co., Ltd.

[[Properties of particulate carbon material]]
Here, the average particle diameter of the particulate carbon material contained in the heat conductive sheet constituting the insulating heat conductive sheet of the present invention is preferably 0.1 μm or more, more preferably 1 μm or more. , 250 μm or less is preferable. When the average particle diameter of the particulate carbon material is within the above range, the thermal conductivity of the thermal conductive sheet can be improved, and therefore the thermal conductivity of the insulating thermal conductive sheet can be further improved. ..
Moreover, the aspect ratio (major axis/minor axis) of the particulate carbon material contained in the heat conductive sheet constituting the insulating heat conductive sheet of the present invention is preferably 1 or more and 10 or less, and 1 or more and 5 or less. Is more preferable.

In the present invention, the "average particle diameter" is obtained by observing a cross section in the thickness direction of the heat conductive sheet with a SEM (scanning electron microscope) and measuring the maximum diameter (major axis) of any 50 particulate carbon materials. Can be obtained by calculating the number average value of the measured long diameters. Further, in the present invention, the “aspect ratio” is the maximum diameter (major axis) of any 50 particulate carbon materials obtained by observing a cross section in the thickness direction of the heat conductive sheet with a SEM (scanning electron microscope). It can be determined by measuring the particle diameter (short diameter) in the direction orthogonal to the maximum diameter 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]]
And the content ratio of the particulate carbon material in the heat conductive sheet constituting the insulating heat conductive sheet of the present invention is preferably 30% by mass or more, more preferably 40% by mass or more, and 50% by mass. % Or more, more preferably 90% by mass or less, further preferably 80% by mass or less, and further preferably 75% by mass or less. This is because when the content ratio of the particulate carbon material in the heat conductive sheet is 30% by mass or more and 90% by mass or less, the thermal conductivity, flexibility and strength of the thermal conductive sheet can be sufficiently increased in a well-balanced manner. Further, if the content ratio of the particulate carbon material is 90 mass% or less, it is possible to sufficiently prevent the particulate carbon material from falling off.

[Fibrous carbon material]
The fibrous carbon material optionally blended with the heat conductive sheet constituting the insulating heat conductive sheet of the present invention is not particularly limited, and examples thereof include carbon nanotubes, vapor grown carbon fibers, and organic fibers carbonized. It is possible to use the carbon fibers obtained by the above, and cut products thereof. These may be used alone or in combination of two or more.
When the fibrous carbon material is contained in the heat conductive sheet constituting the insulating heat conductive sheet of the present invention, the thermal conductivity can be further improved, and the powdered carbon material can be prevented from falling off. Can also The reason why the powdery carbon material can be prevented from falling off by blending the fibrous carbon material is not clear, but the fibrous carbon material forms a three-dimensional network structure, thereby improving thermal conductivity. It is presumed that this is because the desorption of the particulate carbon material is prevented while increasing the strength and strength.

Among the above, as the fibrous carbon material, fibrous carbon nanostructures such as carbon nanotubes are preferably used, and fibrous carbon nanostructures containing carbon nanotubes are more preferably used. This is because the use of a fibrous carbon nanostructure such as a carbon nanotube can further improve the thermal conductivity and strength of the heat conductive sheet constituting the insulating heat conductive sheet of the present invention.

[[Fibrous carbon nanostructure containing carbon nanotubes]]
Here, the fibrous carbon nanostructure containing carbon nanotubes, which can be preferably used as the fibrous carbon material, may be composed of only carbon nanotubes (hereinafter, also referred to as “CNT”). Alternatively, it may be a mixture of CNT and a fibrous carbon nanostructure other than CNT.
The CNTs in the fibrous carbon nanostructure are not particularly limited, and single-walled carbon nanotubes and/or multi-walled carbon nanotubes can be used. Nanotubes are preferable, and single-walled carbon nanotubes are more preferable. This is because the use of single-walled carbon nanotubes can further improve the thermal conductivity and strength of the heat-conducting sheet constituting the insulating heat-conducting sheet of the present invention, as compared with the case of using multi-walled carbon nanotubes. ..

Further, as a fibrous carbon nanostructure containing CNTs, the ratio (3σ/Av) of the value (3σ) obtained by multiplying the standard deviation (σ) of the diameter by 3 with respect to the average diameter (Av) is more than 0.20. It is preferable to use a carbon nanostructure of less than 0.60, more preferably to use a carbon nanostructure having a 3σ/Av of more than 0.25, and to use a carbon nanostructure of 3σ/Av of more than 0.50. More preferably. By using a fibrous carbon nanostructure containing CNTs with 3σ/Av of more than 0.20 and less than 0.60, the insulating heat conductive sheet of the present invention can be obtained even if the amount of the carbon nanostructure is small. It is possible to sufficiently enhance the thermal conductivity and the strength of the thermal conductive sheet that constitutes it. Therefore, the hardness of the heat conductive sheet constituting the insulating heat conductive sheet of the present invention is prevented from increasing (that is, the flexibility is lowered) by blending the fibrous carbon nanostructure containing CNTs, and The heat conductivity and flexibility of the insulating heat conductive sheet of the invention can be juxtaposed at a sufficiently high level.
The “average diameter of the fibrous carbon nanostructure (Av)” and the “standard deviation of the diameter of the fibrous carbon nanostructure (σ: sample standard deviation)” were measured by using a transmission electron microscope. The diameter (outer diameter) of 100 randomly selected fibrous carbon nanostructures can be measured and obtained. Then, the average diameter (Av) and standard deviation (σ) of the fibrous carbon nanostructures containing CNTs are adjusted by changing the manufacturing method and manufacturing conditions of the fibrous carbon nanostructures containing CNTs. Alternatively, it may be adjusted by combining a plurality of fibrous carbon nanostructures containing CNT obtained by different production methods.

As the fibrous carbon nanostructure containing CNT, the diameter measured as described above is plotted on the abscissa and the frequency thereof is plotted on the ordinate, and a normal distribution is obtained when approximated by Gaussian. Things are usually used.

Furthermore, the fibrous carbon nanostructure containing CNT preferably has a peak of Radial Breathing Mode (RBM) when evaluated using Raman spectroscopy. It should be noted that RBM does not exist in the Raman spectrum of the fibrous carbon nanostructure composed only of multi-walled carbon nanotubes having three or more layers.

The fibrous carbon nanostructure containing CNTs preferably has a ratio of the G band peak intensity to the D band peak intensity in the Raman spectrum (G/D ratio) of 1 or more and 20 or less. When the G/D ratio is 1 or more and 20 or less, the thermal conductivity and strength of the heat conductive sheet constituting the insulating heat conductive sheet of the present invention can be improved even if the amount of the fibrous carbon nanostructure is small. It can be increased sufficiently. Therefore, it is possible to suppress an increase in hardness (that is, decrease in flexibility) of the heat conductive sheet due to the incorporation of the fibrous carbon nanostructure, and to improve the heat conductivity and flexibility of the insulating heat conductive sheet of the present invention. Can be juxtaposed at a sufficiently high level.

Furthermore, the average diameter (Av) of the fibrous carbon nanostructure containing CNT is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, and 10 nm or less. More preferably, When the average diameter (Av) of the fibrous carbon nanostructures is 0.5 nm or more, aggregation of the fibrous carbon nanostructures can be suppressed and the dispersibility of the carbon nanostructures can be increased. When the average diameter (Av) of the fibrous carbon nanostructure is 15 nm or less, the heat conductivity and strength of the heat conductive sheet constituting the insulating heat conductive sheet of the present invention can be sufficiently increased.

Further, the fibrous carbon nanostructure containing CNTs preferably has an average length of the structure at the time of synthesis of 100 μm or more and 5000 μm or less. The longer the length of the structure during synthesis is, the more easily the CNTs are damaged or broken during dispersion. Therefore, the average length of the structure during synthesis is preferably 5000 μm or less.

Furthermore, the BET specific surface area of the fibrous carbon nanostructure containing CNTs is preferably 600 m ² /g or more, more preferably 800 m ² /g or more, and 2500 m ² /g or less. It is more preferably 1200 m ² /g or less. Furthermore, when the CNTs in the fibrous carbon nanostructure are mainly open, the BET specific surface area is preferably 1300 m ² /g or more. If the BET specific surface area of the fibrous carbon nanostructure containing CNTs is 600 m ² /g or more, the thermal conductivity and strength of the thermal conductive sheet constituting the insulating thermal conductive sheet of the present invention can be sufficiently enhanced. it can. Further, when the BET specific surface area of the fibrous carbon nanostructure containing CNT is 2500 m ² /g or less, aggregation of the fibrous carbon nanostructure is suppressed to form the insulating heat conductive sheet of the present invention. The dispersibility of CNT in the heat conductive sheet can be enhanced.
In addition, in this invention, "BET specific surface area" refers to the nitrogen adsorption specific surface area measured using the BET method.

Further, the fibrous carbon nanostructure containing CNTs is, according to the supergrowth method described later, collected on a base material having a catalyst layer for growing carbon nanotubes on its surface, and oriented in a direction substantially perpendicular to the base material. Although it is obtained as a body (oriented aggregate), the mass density of the fibrous carbon nanostructure as the aggregate is preferably 0.002 g/cm ³ or more and 0.2 g/cm ³ or less. When the mass density is 0.2 g/cm ³ or less, the fibrous carbon nanostructures are weakly bound to each other, so that the fibrous carbon nanostructures can be uniformly dispersed in the heat conductive sheet. Further, if the mass density is 0.002 g/cm ³ or more, the integrity of the fibrous carbon nanostructures can be improved, and the fibrous carbon nanostructures can be prevented from coming loose, which facilitates the handling.

Then, the fibrous carbon nanostructure containing CNTs having the above-described properties is obtained by, for example, supplying a raw material compound and a carrier gas onto a base material having a catalyst layer for producing carbon nanotubes on the surface thereof and chemically vaporizing it. When CNTs are synthesized by the phase growth method (CVD method), a small amount of an oxidizing agent (catalyst activating substance) is present in the system to dramatically improve the catalytic activity of the catalyst layer (super growth method). ; International Publication No. 2006/011655), and can be efficiently produced. Note that, hereinafter, the carbon nanotube obtained by the super growth method may be referred to as “SGCNT”.

Here, the fibrous carbon nanostructure containing CNTs produced by the super growth method may be composed only of SGCNT, or in addition to SGCNT, for example, other non-cylindrical carbon nanostructures or the like. Carbon nanostructures may be included.

[[Properties of fibrous carbon material]]
The average fiber diameter of the fibrous carbon material that can be contained in the heat conductive sheet is preferably 1 nm or more, more preferably 3 nm or more, preferably 2 μm or less, and 1 μm or less. More preferable. This is because when the average fiber diameter of the fibrous carbon material is within the above range, the thermal conductivity, flexibility and strength of the heat conductive sheet can be juxtaposed at a sufficiently high level. Here, the aspect ratio of the fibrous carbon material is preferably more than 10.

In the present invention, the “average fiber diameter” means that the cross section in the thickness direction of the heat conductive sheet is observed with an SEM (scanning electron microscope) or a TEM (transmission electron microscope), and any 50 fibrous carbon materials are used. Can be determined by measuring the fiber diameter and measuring the number average value of the measured fiber diameters. In particular, when the fiber diameter is small, it is preferable to observe the same cross section with a TEM (transmission electron microscope).

[[Content ratio of fibrous carbon material]]
The content ratio of the fibrous carbon material in the heat conductive sheet constituting the insulating heat conductive sheet of the present invention is preferably 0.05% by mass or more, and more preferably 0.2% by mass or more. It is preferably 5% by mass or less, and more preferably 3% by mass or less. When the content ratio of the fibrous carbon material in the heat conductive sheet is 0.05% by mass or more, the thermal conductivity and strength of the heat conductive sheet can be sufficiently improved, and the powder of the particulate carbon material can be prevented from falling off. This is because it can be sufficiently prevented. Furthermore, when the content ratio of the fibrous carbon material in the heat conductive sheet is 5% by mass or less, it is possible to prevent the hardness of the heat conductive sheet from increasing (that is, the flexibility decreases) due to the blending of the fibrous carbon material. Then, the heat conductivity and flexibility of the insulating heat conductive sheet of the present invention can be juxtaposed at a sufficiently high level.

[Additive]
The heat conductive sheet constituting the insulating heat conductive sheet of the present invention can be blended with known additives which can be used for forming the heat conductive sheet, if necessary. The additives that can be added to the heat conductive sheet are not particularly limited, and examples thereof include plasticizers; flame retardants such as red phosphorus flame retardants and phosphoric acid ester flame retardants; toughness improvers such as urethane acrylates. Moisture absorbents such as calcium oxide and magnesium oxide; Adhesive strength improving agents such as silane coupling agents, titanium coupling agents, acid anhydrides; Wetting improvers such as nonionic surfactants and fluorochemical surfactants; inorganic Ion trap agents such as ion exchangers; and the like.

[Properties of heat conductive sheet]
The heat conductive sheet constituting the insulating heat conductive sheet of the present invention is not particularly limited and preferably has the following properties.

[[Thermal Conductivity of Thermal Conductive Sheet]]
The thermal conductivity of the heat conductive sheet in the thickness direction at 25° C. is preferably 20 W/m·K or more, more preferably 30 W/m·K or more, and 40 W/m·K or more. More preferably. When the thermal conductivity is 20 W/m·K or more, the thermal conductivity of the insulating thermal conductive sheet provided with the thermal conductive sheet is sufficiently enhanced, and for example, the insulating thermal conductive sheet is sandwiched between the heating element and the radiator. When used in, heat can be efficiently transferred from the heating element to the radiator.

[[Hardness of heat conduction sheet]]
Further, the Asker C hardness of the heat conductive sheet needs to be 70 or less, preferably 65 or less. When the Asker C hardness of the heat conductive sheet constituting the insulating heat conductive sheet of the present invention is 70 or less, the insulating heat conductive sheet of the present invention is used, for example, sandwiched between a heating element and a radiator. In addition, excellent flexibility can be exhibited, and the heat generating element and the heat radiating element can be brought into good contact with each other.

[[Thickness of heat conduction sheet]]
The thickness of the heat conductive sheet is preferably 0.1 mm to 10 mm.

<Insulation layer>
The insulating layer is a layer for ensuring the insulating property of the insulating heat conductive sheet. Since the above-mentioned thermal conductive sheet contains the particulate carbon material, it usually has not only thermal conductivity but also electrical conductivity. However, if an insulating layer is arranged between the thermal conductive sheets, the insulating thermal Good insulating properties can be imparted to the conductive sheet. Then, the insulating layer can be formed using a thermoplastic resin or a thermosetting resin. As the thermoplastic resin or the thermosetting resin, a known resin that can be used for forming the above-mentioned heat conductive sheet or a cyclic olefin resin can be adopted. Above all, it is preferable to form the insulating layer using a cyclic olefin resin. Further, the insulating layer may contain a known additive other than the resin as long as the insulating property can be secured. Above all, in order to enhance the flame retardancy of the insulating layer, it is preferable that the insulating layer contains a flame retardant filler.

[Cyclic olefin resin]
The cyclic olefin resin that can be used for the insulating layer of the insulating heat conductive sheet of the present invention is obtained by polymerizing a monomer composition containing a cyclic olefin monomer using a known polymerization method such as ring-opening metathesis polymerization. You can Here, the cyclic olefin monomer which is a raw material of the cyclic olefin resin is a compound having a ring structure formed of carbon atoms and having a carbon-carbon double bond in the ring. Specific examples thereof include norbornene-based monomers and monocyclic olefins. The preferred cyclic olefin monomer is a norbornene-based monomer. The norbornene-based monomer is a monomer containing a norbornene ring. Specific examples of the norbornene-based monomer include norbornenes, dicyclopentadiene and tetracyclododecene. These may contain a hydrocarbon group such as an alkyl group, an alkenyl group, an alkylidene group and an aryl group; a polar group such as a carboxyl group and an acid anhydride group as a substituent.
The norbornene-based monomer may further have a double bond in addition to the double bond of the norbornene ring. Further, a preferable norbornene-based monomer is a non-polar norbornene-based monomer composed of only carbon atoms and hydrogen atoms.

Specific examples of the non-polar norbornene-based monomer include non-containing compounds such as dicyclopentadiene, methyldicyclopentadiene, and dihydrodicyclopentadiene (also referred to as tricyclo[5.2.1.0 ^2,6 ]dec-8-ene). Polar dicyclopentadiene; tetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-methyltetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-ethyltetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-cyclohexyltetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-cyclopentyltetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-methylenetetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]Dodeca-4-ene, 9-ethylidene tetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-vinyltetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-propenyltetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-cyclohexenyl tetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-cyclopentenyltetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodec-4-ene, 9-phenyltetracyclo[6.2.1.1 ^3,6 . Nonpolar tetracyclododecenes such as 0 ^2,7 ]dodec-4-ene; 2-norbornene, 5-methyl-2-norbornene, 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5 -Hexyl-2-norbornene, 5-decyl-2-norbornene, 5-cyclohexyl-2-norbornene, 5-cyclopentyl-2-norbornene, 5-ethylidene-2-norbornene, 5-vinyl-2-norbornene, 5-propenyl 2-norbornene, 5-cyclohexenyl-2-norbornene, 5-cyclopentenyl-2-norbornene, 5-phenyl-2-norbornene, tetracyclo ^{[9.2.1.0 2,10.} 0 ^3,8 ]Tetradeca-3,5,7,12-tetraene (also referred to as 1,4-methano-1,4,4a,9a-tetrahydro-9H-fluorene), tetracyclo[10.2.1.0]. ^2,11 . Non-polar norbornenes such as 0 ^4,9 ]pentadeca-4,6,8,13-tetraene (also referred to as 1,4-methano-1,4,4a,9,9a,10-hexahydroanthracene); Pentacyclo[6.5.1.1 ^3,6 . 0 ^2,7 . 0 ^9,13] pentadeca-4,10-diene, pentacyclo [9.2.1.1 ^4,7. 0 ^2,10 . 0 ^3,8 ]Pentadeca-5,12-diene, hexacyclo[6.6.1.1 ^3,6 . 1 ^{10, 13} . 0 ^2,7 . 0 ^9,14] heptadec-4-non-polar cyclic olefins or pentacyclic body such as ene; and the like.

From the viewpoint of easy availability and improvement of the insulating property of the insulating layer, preferred nonpolar norbornene-based monomers are nonpolar dicyclopentadiene and nonpolar tetracyclododecene, and more preferred nonpolar norbornene-based monomer is nonpolar. It is a dicyclopentadiene. That is, the cyclic olefin resin that can be used for the insulating layer of the insulating heat conductive sheet of the present invention preferably contains a dicyclopentadiene monomer unit.

Specific examples of the norbornene-based monomer containing a polar group include tetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]Methyl dodeca-9-ene-4-carboxylate, tetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodeca-9-ene-4-methanol, tetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodeca-9-ene-4-carboxylic acid, tetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]Dodeca-9-ene-4,5-dicarboxylic acid, tetracyclo[6.2.1.1 ^3,6 . 0 ^2,7 ]dodeca-9-ene-4,5-dicarboxylic acid anhydride, methyl 5-norbornene-2-carboxylate, methyl 2-methyl-5-norbornene-2-carboxylate, 5-norbornene-2 acetate -Yl, 5-norbornene-2-methanol, 5-norbornen-2-ol, 5-norbornene-2-carbonitrile, 2-acetyl-5-norbornene, 7-oxa-2-norbornene and the like.

Specific examples of the monocyclic olefin include cyclobutene, cyclopentene, cyclohexene, cyclooctene, cyclododecene, 1,5-cyclooctadiene, and derivatives thereof having a substituent.

These cyclic olefin monomers may be used alone or in combination of two or more.

[Polymerization catalyst]
The ring-opening metathesis polymerization catalyst that can be used during the above-mentioned cyclic olefin resin polymerization is not particularly limited, and known ring-opening metathesis polymerization catalysts can be used. Specifically, a complex formed by binding a plurality of ions, atoms, polyatomic ions and/or compounds around a transition metal atom can be used as a ring-opening metathesis polymerization catalyst. Atoms of groups 5, 6, and 8 (long-periodic periodic table, the same applies hereinafter) can be used as transition metal atoms. Although the atoms of each group are not particularly limited, the atoms of the preferred Group 5 are tantalum, the atoms of the preferred Group 6 are molybdenum and tungsten, and the preferred atoms of the Group 8 are ruthenium and osmium.
A preferable ring-opening metathesis polymerization catalyst is a complex of Group 8 ruthenium and osmium, and a particularly preferable ring-opening metathesis polymerization catalyst is a ruthenium carbene complex. Since the ruthenium carbene complex has excellent catalytic activity during bulk polymerization, a crosslinked cyclic olefin resin containing a small amount of residual unreacted monomer can be obtained with good productivity.

[Flame-retardant filler]
The flame-retardant filler that can be contained in the insulating layer constituting the insulating heat conductive sheet of the present invention is not particularly limited, but usually, a hydroxide of a metal of Group 2 or Group 13 of the periodic table is preferably used. .. Examples of metals in Group 2 of the periodic table include magnesium, calcium, strontium, barium, and the like, and examples of metals in Group 13 of the periodic table include aluminum, gallium, indium, and the like. Among them, magnesium hydroxide or aluminum hydroxide is preferable as the flame-retardant filler, and aluminum hydroxide is more preferable. A flame-retardant filler that does not contain halogen is generally suitable.

The flame-retardant filler can be subjected to a surface treatment for the purpose of imparting water resistance and dispersibility to the extent that the flame-retardant properties and the physical properties given to the resin are not impaired. Examples of the surface treatment agent used include aliphatic treatment agents such as stearic acid and calcium stearate; ester-based surfactants such as polyglycerin fatty acid ester and polyoxyethylene fatty acid ester; silane coupling agents, titanate coupling agents. And the like; and titanate coupling agents are particularly preferable.

Examples of titanate coupling agents include known titanate coupling agents, for example, isopropyl triisostearoyl titanate, isopropyl tridodecylbenzenesulfonyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, Tetraoctyl bis(ditridecyl phosphite) titanate, bis(dioctyl pyrophosphate) oxyacetate titanate, bis(dioctyl pyrophosphate) ethylene titanate, isopropyl trioctanoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl isostearoyl diacrylic titanate, Examples thereof include isopropyl tris(dioctyl phosphate)titanate, isopropyl tricumylphenyl titanate, isopropyl tri(N-amidoethyl aminoethyl)titanate, dicumylphenyloxyacetate titanate, and diisostearoyl ethylene titanate.

In particular, by blending titanate-treated aluminum hydroxide in the insulating layer, the thermal conductivity and the withstand voltage characteristic of the insulating layer can be further improved. The flame-retardant fillers described above may be used alone or in combination of two or more.

The surface treatment method is not particularly limited, and examples thereof include a dry method using a Henschel mixer or the like, a wet method of treating in a solvent slurry, and an integral blending method of adding a treatment agent during compounding. The amount of the surface treatment agent added is preferably 0.1 to 5% by mass, and particularly preferably 0.5 to 3% by mass, based on the object to be treated. Mechanical properties etc. are deteriorated.

The amount of the flame-retardant filler compounded in the insulating layer constituting the insulating heat conductive sheet of the present invention is usually 50 parts by mass or more, preferably 100 parts by mass or more, and more preferably 100 parts by mass of the resin. It is 150 parts by mass or more, more preferably 200 parts by mass or more, particularly preferably 300 parts by mass or more, usually 600 parts by mass or less, preferably 500 parts by mass or less, and more preferably 400 parts by mass or less. When the content of the flame-retardant filler exceeds 600 parts by mass, the hardness of the insulating layer increases, and when the content is too large, it may be difficult to form the insulating layer itself. On the other hand, if the content of the flame-retardant filler is less than 100 parts by mass, the flame retardancy of the insulating layer may be insufficient, and the thermal conductivity and withstand voltage characteristics of the insulating heat conductive sheet may be further deteriorated. ..

[Other]
A commercially available film can be used as the insulating layer. Specifically, a film containing a material such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and polyimide can be used as the insulating layer.

[Insulation layer thickness]
The thickness of the insulating layer constituting the insulating heat conductive sheet of the present invention is preferably 50 μm or more, more preferably 200 μm or more, preferably 500 μm or less, and more preferably 300 μm or less. preferable. By setting the thickness of the insulating layer within the above range, sufficient thermal conductivity, insulating property and flexibility can be secured.

(Properties of insulating heat conductive sheet)
[Thermal conductivity of the insulating heat conductive sheet]
The insulating thermal conductive sheet of the present invention has a thermal conductivity in the thickness direction at 25° C. of 7 W/m·K or more, preferably 10 W/m·K or more, and 15 W/m·K. It is more preferably K or more. When the thermal conductivity is 10 W/m·K or more, when the insulating heat conductive sheet of the present invention is used by being sandwiched between a heating element and a radiator, heat is efficiently transferred from the heating element to the radiator. Can be communicated.

[Withstand voltage test value of heat conductive sheet]
The withstand voltage test value of the insulating heat conductive sheet of the present invention is preferably 10 kV/mm or more, and more preferably 12 kV/mm or more. When the withstand voltage test value is 10 kV/mm or more, when the insulating heat conductive sheet of the present invention is used for an electronic component, for example, it can sufficiently function as an insulating sheet.

[Density of heat conduction sheet]
Furthermore, insulating thermally conductive sheet of the present invention preferably has a density of less 1.8 g / ^{m 3,} more preferably 1.6 g / ^{m 3} or less. This is because such an insulating heat-conducting sheet has high versatility and can contribute to weight reduction of such electronic parts when mounted on products such as electronic parts.

(Method for manufacturing insulating heat conductive sheet)
The insulating heat conductive sheet described above is not particularly limited, and a step of preparing a heat conductive sheet having an Asker C hardness of 70 or less (heat conductive sheet preparing step) and heat conduction in the thickness direction of the insulating layer up and down. It is preferably manufactured through a step of laminating sheets (insulating layer-heat conductive sheet laminating step). Further, in the step of preparing the heat conductive sheet, the composition containing the resin and the particulate carbon material is pressed into a sheet shape to obtain a pre heat conductive sheet (pre heat conductive sheet molding) and pre heat conductive sheet. A plurality of sheets are laminated in the thickness direction, or a pre-heat conduction sheet is folded or wound to obtain a laminate (formation of a heat conduction sheet laminate), and the obtained laminate is laminated in the lamination direction. Slicing at an angle of 45° or less to obtain a heat conductive sheet (slicing) is preferably included.

<Heat conduction sheet preparation process>
[Pre-heat conductive sheet molding]
In the pre-heat conduction sheet molding, a composition containing a resin and a particulate carbon material and optionally further containing an additive is pressed into a sheet shape to obtain a pre-heat conduction sheet.

[[Composition]]
Here, the composition can be prepared by mixing the resin and the particulate carbon material with any additive. Then, as the resin, the particulate carbon material, and the additive, those described above as the resin, the particulate carbon material, and the additive that can be included in the heat conductive sheet constituting the insulating heat conductive sheet of the present invention may be used. it can. Incidentally, when the resin of the heat conductive sheet is a crosslinkable resin, a preheat conductive sheet may be formed using a composition containing the crosslinkable resin, or a crosslinkable resin and a curing agent may be used. A cross-linkable resin may be contained in the heat conductive sheet by forming a pre-heat conductive sheet using the contained composition and crosslinking the cross-linkable resin after molding the pre-heat conductive sheet.

The mixing is not particularly limited, and can be performed using a known mixing device such as a kneader, a roll, a Henschel mixer, or a Hobart mixer. Further, the mixing may be performed in the presence of a solvent such as ethyl acetate. The mixing time can be, for example, 5 minutes or more and 6 hours or less. Further, the mixing temperature can be set to, for example, 5°C or higher and 150°C or lower.

[[Molding of composition]]
Then, the composition prepared as described above can be defoamed and crushed, and then pressed to form a sheet. In addition, when a solvent is used during mixing, it is preferable to remove the solvent and then form into a sheet shape. For example, if defoaming is performed using vacuum defoaming, the solvent is simultaneously removed during defoaming. be able to.

Here, the composition is not particularly limited as long as it is a molding method in which a pressure is applied, and can be molded into a sheet by 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 the rolls while being sandwiched between the protective films. The protective film is not particularly limited, and a sandblasted polyethylene terephthalate film or the like can be used. The roll temperature can be set to 5°C or higher and 150°C or lower.

When the composition contains a fibrous carbon material, it is preferable to perform the following treatment in order to improve the dispersibility of the fibrous carbon material. First, since the fibrous carbon material easily aggregates and has low dispersibility, it is difficult to disperse well in the composition when it is mixed with other components such as resin as it is. On the other hand, fibrous carbon materials can suppress the occurrence of agglomeration by mixing with other components in the state of a dispersion liquid dispersed in a solvent (dispersion medium), but when mixed in the state of a dispersion liquid, Since a large amount of solvent is used when the solid content is solidified after mixing to obtain the composition, the amount of the solvent used for preparing the composition may increase. Therefore, when the fibrous carbon material is added to the composition used for forming the pre-heat conductive sheet, the fibrous carbon material is a solvent obtained by dispersing the fibrous carbon material in a solvent (dispersion medium). It is preferable to mix with other components in the state of an aggregate (easily dispersible aggregate) of the fibrous carbon material obtained by removing. Here, the dispersion liquid used for the preparation of the easily dispersible aggregate is not particularly limited, and a dispersion liquid obtained by dispersing the aggregate of the fibrous carbon material in a solvent using a known dispersion treatment method is used. be able to. Specifically, as the dispersion liquid, a dispersion liquid containing a fibrous carbon material and a solvent and optionally further containing a dispersion liquid additive such as a dispersant can be used.

The aggregate of the fibrous carbon material obtained by removing the solvent from the dispersion liquid of the fibrous carbon material is composed of the fibrous carbon material once dispersed in the solvent, and the fibrous carbon material before being dispersed in the solvent. Since the dispersibility is higher than that of the aggregate, the dispersible aggregate has high dispersibility. Therefore, if the easily dispersible aggregate is mixed with other components, the fibrous carbon material can be efficiently dispersed in the composition efficiently without using a large amount of solvent. That is, when the insulating heat conductive sheet is manufactured, it is preferable to prepare the composition before forming the pre-heat conductive sheet.

[[Pre-heat conductive sheet]]
Then, in the pre-heat conductive sheet formed by pressing the composition into a sheet shape, the particulate carbon material is mainly arranged in the in-plane direction, and particularly when the heat conductivity in the in-plane direction of the pre-heat conductive sheet is improved. Inferred.
The thickness of the pre-heat conductive sheet is not particularly limited and can be, for example, 0.05 mm or more and 2 mm or less. Further, from the viewpoint of further improving the thermal conductivity of the heat conductive sheet, the thickness of the pre-heat conductive sheet is preferably more than 20 times and 5000 times or less of the average particle diameter of the particulate carbon material.

[Laminate formation]
In forming the laminated body, a plurality of pre-heat conductive sheets obtained by forming the pre-heat conductive sheet are laminated in the thickness direction, or the pre-heat conductive sheet is folded or wound to obtain a laminated body. Here, the formation of the laminated body by folding the pre-heat conductive sheet is not particularly limited, and can be performed by folding the pre-heat conductive sheet with a constant width using a folding machine. Further, the formation of the laminate by winding the pre-heat conductive sheet is not particularly limited, by winding the pre-heat conductive sheet around an axis parallel to the lateral direction or the longitudinal direction of the pre-heat conductive sheet. It can be carried out.

Here, usually, in the laminate obtained by forming the laminate, the adhesive force between the surfaces of the pre-heat conductive sheet is sufficiently determined by the pressure at the time of laminating the pre-heat conductive sheet or the pressure at folding or winding. can get. However, when the adhesive strength is insufficient, or when it is necessary to sufficiently suppress delamination of the laminate, the laminate may be formed with the surface of the pre-heat conductive sheet slightly dissolved with a solvent. Then, the laminated body may be formed in a state in which an adhesive is applied to the surface of the pre-heat conductive sheet or in a state in which an adhesive layer is provided on the surface of the pre-heat conductive sheet.

The solvent used to dissolve the surface of the pre-heat conductive sheet is not particularly limited, and a known solvent capable of dissolving the resin component contained in the pre-heat conductive sheet can be used.

The adhesive applied to the surface of the pre-heat conductive sheet is not particularly limited, and a commercially available adhesive or tacky resin can be used. Above all, as the adhesive, it is preferable to use a resin having the same composition as the resin component contained in the pre-heat conductive sheet. The thickness of the adhesive applied to the surface of the pre-heat conductive sheet can be, for example, 10 μm or more and 1000 μm or less.
Furthermore, the adhesive layer provided on the surface of the pre-heat conductive sheet is not particularly limited, and a double-sided tape or the like can be used.

From the viewpoint of suppressing delamination, the obtained laminate may be pressed at 20° C. or higher and 100° C. or lower for 1 to 30 minutes while being pressed in the stacking direction at a pressure of 0.05 MPa to 1.0 MPa. preferable.

When a fibrous carbon material is added to the composition, or when expanded graphite is used as the particulate carbon material, a laminated body obtained by laminating, folding or winding a pre-heat conductive sheet, It is assumed that the expanded graphite and the fibrous carbon material are arranged in a direction substantially orthogonal to the stacking direction.

[slice]
At the time of slicing, the laminated body obtained by forming the laminated body is sliced at an angle of 45° or less with respect to the laminating direction to obtain a heat conductive sheet composed of sliced pieces of the laminated body. 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, and a knife processing method. Among them, the knife processing method is preferable because it is easy to make the thickness of the heat conductive sheet uniform. Further, the cutting tool when slicing the laminate is not particularly limited, a smooth board surface having a slit, and a slicing member having a blade portion protruding from the slit portion (for example, a sharp blade is provided. Canna or slicer) can be used.
Then, the heat conductive sheet obtained through slicing is usually a strip containing a resin, a particulate carbon material, and an optional additive (a slice piece of the pre-heat conductive sheet that was included in the laminate). It has a configuration in which they are joined in parallel.

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 laminating direction, and more preferably 15° or less with respect to the laminating direction. It is preferable that the angle is approximately 0° with respect to the stacking direction (that is, the direction is along the stacking direction).

Further, from the viewpoint of easily slicing the laminate, the temperature of the laminate during slicing is preferably −20° C. or higher and 40° C. or lower, and more preferably 10° C. or higher and 30° C. or lower. Further, for the same reason, it is preferable that the laminated body to be sliced is sliced while applying pressure in a direction perpendicular to the laminating direction, and a pressure of 0.1 MPa to 0.5 MPa in the direction perpendicular to the laminating direction. It is more preferable to slice while loading. In the heat conductive sheet thus obtained, it is presumed that the particulate carbon material and the fibrous carbon material are arranged in the thickness direction. Therefore, the heat conductive sheet prepared through the above steps has high conductivity as well as heat conductivity in the thickness direction.

<Insulating layer-heat conductive sheet laminating step>
In the insulating layer-heat conduction sheet laminating step, heat conduction sheets are laminated above and below the thickness direction of the insulation layer. As described above, a commercially available film or the like can be used as the insulating layer, but the insulating layer can also be manufactured as follows.

[Insulation layer]
The insulating layer is obtained by heating a coating film of a raw material containing the above-mentioned monomer composition, a metathesis polymerization catalyst, and optionally an additive such as a flame retardant filler to form a film. Examples of the film-forming substrate used for obtaining the coating film include a resin substrate and a glass substrate. Here, as the resin substrate, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polytetrafluoroethylene (PTFE), polyimide, polyphenylene sulfide, aramid, polypropylene, polyethylene, polylactic acid, polyvinyl chloride, polycarbonate, Examples of the base material include polymethyl methacrylate, alicyclic acrylic resin, cycloolefin resin, triacetyl cellulose and the like. Further, as the glass substrate, a substrate made of normal soda glass can be mentioned. As the coating method, for example, casting method, dipping method, roll coating method, gravure coating method, knife coating method, air knife coating method, roll knife coating method, die coating method, screen printing method, spray coating method, gravure offset method, etc. Can be used.
The film thickness of the insulating layer is not particularly limited, and it is desirable that the insulating layer has a film thickness capable of paralleling the insulating property and the thermal conductivity of the insulating heat conductive sheet.

In laminating the insulating layer and the heat conductive sheet, the layers above and below the insulating layer may be the same or different. The insulating layer and the heat conductive sheet may each be a single layer or have a multilayer structure in which two or more sheets are laminated. The method for adhering the laminated insulating layer and the heat conductive sheet is not particularly limited, and examples thereof include heat pressing, use of an adhesive, attachment with an adhesive tape, and adhesion of an anchor effect by dissolving the sheet surface with an organic solvent. To be Above all, a method of utilizing the self-adhesiveness of each layer to bring them into close contact is preferable from the viewpoint of improving the thermal conductivity and durability of the insulating thermally conductive sheet. Therefore, when the laminated insulating layer and the heat conductive sheet are brought into close contact with each other, heat pressing with a pressing machine is preferably used. The temperature condition during hot pressing is preferably in the range of 20 to 100°C. This is because if the temperature is too high, the resin contained in the heat conductive sheet becomes brittle, and if the temperature is too low, the resin contained in the heat conductive sheet does not soften. Furthermore, the pressure condition during hot pressing is preferably 0.05 MPa to 1.0 MPa.

In addition, when the insulating layer and the heat conductive sheet are laminated using an adhesive, the adhesive is not particularly limited, and examples thereof include polyurethane-based, epoxy resin-based, modified olefin-based, and hydrogenated elastomer-based adhesives. It is desirable that the solvent is used for dissolving the surface of the pre-heat conductive sheet, and further that the resin liquid containing the resin component of the pre-heat conductive sheet of about 10% by mass is used for adhesion.

Hereinafter, the present invention will be specifically described 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 Examples and Comparative Examples, the Asker C hardness of the heat conductive sheet, and the density (specific gravity), thermal conductivity and withstand voltage test value of the insulating heat conductive sheet were measured or evaluated using the following methods, respectively. ..

<Asker C hardness>
It was measured at a temperature of 23° C. according to the Asker C method of Japan Rubber Association Standard (SRIS) using a hardness meter (manufactured by Kobunshi Keiki Co., Ltd., trade name “ASKER (registered trademark) CL-150LJ”).
Specifically, six test pieces of a heat conductive sheet prepared to have a size of width 30 mm×length 60 mm×thickness 1.0 mm were overlapped and left to stand in a thermostatic chamber kept at 23° C. for 48 hours or more. Asker C hardness was measured using the sample as a sample. Then, the damper height was adjusted so that the pointer was 95 to 98, and the hardness 20 seconds after the collision between the sample and the damper was measured 5 times, and the average value was taken as the Asker C hardness of the sample. ..
<Density (specific gravity) and thermal conductivity>
The thermal diffusivity α (m ² /s) in the thickness direction, the constant pressure specific heat Cp (J/g·K) and the density (specific gravity) ρ (g/m ³ ) of the insulating heat conductive sheet were measured by the following methods. ..
[Thermal diffusivity]
It was measured using a thermophysical property measuring device (product name "Thermo Wave Analyzer TA35" manufactured by Bethel Co., Ltd.).
[Constant pressure specific heat]
Using a differential scanning calorimeter (manufactured by Rigaku, product name “DSC8230”), specific heat at a temperature of 25° C. was measured under a temperature rising condition of 10° C./min.
[Density (specific gravity) of insulating heat conductive sheet]
The measurement was performed using an automatic hydrometer (manufactured by Toyo Seiki Co., Ltd., trade name "DENSIMETER-H").
Then, using the obtained measured value, the following formula (I):
λ=α×Cp×ρ (I)
The thermal conductivity λ (W/m·K) in the thickness direction of the insulating heat conductive sheet at 25° C. was determined from the above.
<Withstand voltage test value>
The withstand voltage test value of the insulating heat conductive sheet was measured using an in-oil tester (Tama Densoku Co., Ltd., trade name "TJ-20S"). The pressure was set to 0.6 kV/s, the detection current was set to 10 mA in silicone oil at 23° C., the sample was immersed in the silicone oil for 1 minute, and then the measurement was performed. The results are shown in the table.

(Preparation of acrylic resin)
A reactor was charged with 100 parts of a monomer mixture consisting of 94 parts of 2-ethylhexyl acrylate and 6 parts of acrylic acid, 0.03 part of 2,2′-azobisisobutyronitrile and 700 parts of ethyl acetate and homogenized. Was dissolved in, and the atmosphere was replaced with nitrogen, and then a polymerization reaction was performed at 80° C. for 6 hours. The polymerization conversion rate was 97%. Then, the obtained polymer was dried under reduced pressure and ethyl acetate was evaporated to obtain a viscous solid acrylic resin. The weight average molecular weight (Mw) of the acrylic resin was 270000, and the molecular weight distribution (weight average molecular weight (Mw)/number average molecular weight (Mn)) was 3.1. In addition, the weight average molecular weight (Mw) and the number average molecular weight (Mn) were calculated|required by standard polystyrene conversion by the gel permeation chromatography which uses tetrahydrofuran as an eluent.

(Preparation of easily dispersible aggregate of fibrous carbon material)
About 400 mg of fibrous carbon material SGCNT (average diameter: 3 to 5 nm, specific surface area = 800 m ² /g) was weighed and mixed in 2 L of methyl ethyl ketone and stirred for 2 minutes with a homogenizer to prepare an SGCNT/methyl ethyl ketone dispersion solution. did. Using a wet jet mill (manufactured by Tsuneko Co., Ltd., trade name “JN-20”), this solution was passed through a 0.5 mm channel for 2 cycles at a pressure of 100 MPa to disperse the CNT aggregate in methyl ethyl ketone, and the mass concentration A 0.20 mass% carbon nanotube microdispersion was obtained. The particle diameter of the obtained dispersion was measured with a particle size distribution meter (manufactured by Horiba, Ltd., trade name “LA960”), and the center particle diameter was 24.1 μm. The resulting dispersion was filtered under reduced pressure using Kiriyama filter paper (No. 5A), and a fibrous filler nonwoven fabric which was an easily dispersible aggregate of fibrous carbon material was obtained by filter paper molding.

(Production of heat conductive sheet A)
200 parts of expanded graphite (made by Ito Graphite Industry Co., Ltd., trade name “EC-50”, average particle diameter: 250 μm) as a particulate carbon material, and an acrylic resin prepared as described above as a resin 100 parts and 1 part of a fibrous filler nonwoven fabric, which is a readily dispersible aggregate of the fibrous carbon material (SGCNT) produced as described above, in the presence of 20 parts of ethyl acetate as a solvent, a Hobart mixer ( The mixture was stirred and mixed for 1 hour using a product name "ACM-5LVT type" manufactured by Kodaira Seisakusho Co., Ltd.). Then, the obtained mixture is vacuum defoamed for 1 hour, and ethyl acetate is removed at the same time as defoaming to obtain a composition containing a fibrous carbon material (SGCNT), expanded graphite and an acrylic resin. It was Then, the obtained composition was put into a crusher and crushed for 10 seconds.
Next, 5 g of the crushed composition was sandwiched between sandblasted PET films (protective films) having a thickness of 50 μm, a roll gap of 330 μm, a roll temperature of 50° C., a roll linear pressure of 50 kg/cm, and a roll speed of 1 m/min. Roll forming was performed under the conditions to obtain a pre-heat conductive sheet having a thickness of 0.3 mm.
Then, 200 sheets of the obtained pre-heat conductive sheet were laminated in the thickness direction to obtain a laminate having a thickness of 6 cm.
Then, the laminated body of the pre-heat conductive sheet was cooled to −10° C. with dry ice, and then the sliced section of 6 cm×30 cm was pressed at a pressure of 0.3 MPa while being sliced for woodworking (manufactured by Marunaka Iron Works Co., Ltd.). Slice (in other words, laminated) at an angle of 0 degree with respect to the stacking direction using the product name "Super Finishing Planer Super Mechanical", the protruding length of the sword part from the slit part: 0.11 mm The pre-heat conductive sheet was sliced in the direction normal to the main surface to obtain a heat conductive sheet having a length of 6 cm, a width of 30 cm and a thickness of 0.50 mm. When the Asker C hardness of the obtained heat conductive sheet A was measured, it was 70.

(Production of heat conductive sheet B)
200 parts of expanded graphite (manufactured by Ito Graphite Industry Co., Ltd., trade name "EC-50", average particle size: 250 μm) as a particulate carbon material, and 100 parts of the acrylic resin produced as described above, 1 part of the fibrous filler non-woven fabric, which is an easily dispersible aggregate of the fibrous carbon material produced as described above, and 1000 parts of copper powder were mixed with 20 parts of ethyl acetate as a solvent in a Hobart mixer (K.K. The mixture was stirred and mixed for 1 hour using a product name "ACM-5LVT type" manufactured by Kodaira Seisakusho. A heat conductive sheet B was produced in the same manner as the heat conductive sheet A except for the above. The Asker C hardness of the obtained heat conductive sheet B was measured and found to be 90.

(Production of heat conductive sheet C)
Expanded graphite as a particulate carbon material (manufactured by Ito Graphite Industry Co., Ltd., trade name “EC-50”, average particle diameter: 250 μm) is 200 parts, and 100 parts of the acrylic resin produced as described above. In the presence of 20 parts of ethyl acetate as a solvent, the mixture was stirred and mixed for 1 hour using a Hobart mixer (manufactured by Kodaira Seisakusho Co., Ltd., trade name "ACM-5LVT type"). A heat conductive sheet C was produced in the same manner as the heat conductive sheet A except for the above. The Asker C hardness of the obtained heat conductive sheet C was 68.

・・・（Ｉ）(Production of insulating layer A)
To 95 parts of dicyclopentadiene, 300 parts of titanate-treated aluminum hydroxide (manufactured by Nippon Light Metal Co., Ltd., trade name "B303T", average particle size: 8 μm) was introduced, and Hobart mixer (manufactured by Kodaira Seisakusho, Ltd., Using a trade name "ACM-5LVT type"), a reaction stock solution was obtained by mixing in a vacuum state at a rotation speed of 5 for 30 minutes. Next, 5 parts of a ruthenium catalyst having a structure of the following formula I was added to the above reaction stock solution, and stirred by hand for 1 minute. The obtained reaction solution was dropped on a carrier film made of polyethylene terephthalate having a thickness of 75 μm, and the same carrier film was covered from above. The film thus obtained was passed between rolls having a gap of 250 μm, and then heated at 200° C. for 10 minutes to polymerize dicyclopentadiene, and the titanate-treated aluminum hydroxide was dispersed in the cyclic polyolefin resin. Insulating layer A was obtained. The thickness of the obtained insulating layer A was 200 μm.

...(I)

(Production of insulating layer B)
An insulating layer B was obtained in the same manner as the insulating layer A except that the amount of titanate-treated aluminum hydroxide was changed to 500 parts. The thickness of the obtained insulating layer B was 200 μm.

(Manufacture of insulating layer C)
Titanate treatment was performed on 200 parts of a nitrile rubber solution obtained by dissolving non-crosslinked nitrile rubber (NBR) in toluene so that the solid content was 50% (at this time, the compounding amount of nitrile rubber was 100 parts). 500 parts of the obtained aluminum hydroxide was added. Using a Hobart mixer (trade name "ACM-5LVT type" manufactured by Kodaira Seisakusho Co., Ltd.), the mixture was stirred for 40 minutes at a rotation speed of 5 in a vacuum state. The obtained solution was applied on a polyethylene terephthalate (PET) substrate using comma roll to a thickness of 400 μm. The coated PET base material was dried in an atmosphere of 100° C. for 30 minutes and then in an atmosphere of 150° C. for 30 minutes to obtain an insulating layer C. The thickness of the obtained insulating layer C was 300 μm.

(Manufacture of insulating layer D)
An insulating layer D was obtained in the same manner as the insulating layer A except that the amount of titanate-treated aluminum hydroxide added was changed to 100 parts. The thickness of the obtained insulating layer D was 200 μm.

(Manufacture of insulating layer E)
Two-component silicone resin (manufactured by Momentive Co., trade name "TSE3062", mixing ratio A liquid: B liquid) for a base material on which a metal frame of 50 x 50 x 0.5 mm is placed on a PET film. 1:1) was mixed and poured into a frame so that the thickness after drying was 50 μm. The obtained base material was dried in an atmosphere of 80° C. for 6 hours to prepare an insulating layer E made of only a silicone resin. The thickness of the obtained insulating layer E was 50 μm.

(Example 1)
The heat conductive sheets A were arranged on the upper and lower sides of the insulating layer A in the thickness direction, and pressed at 25° C. for 5 minutes at 0.1 MPa. The thermal conductivity and the withstand voltage test value of the obtained insulating heat conductive sheet were measured. The results are shown in Table 1.

(Examples 2 to 6)
An insulating heat conductive sheet was manufactured in the same manner as in Example 1 except that the combination of the insulating layer and the heat conductive sheet was changed as shown in Table 1. The thermal conductivity and the withstand voltage test value of the obtained insulating heat conductive sheet were measured. The results are shown in Table 1.

(Comparative example 1)
The acrylic resin produced as described above was applied to the upper and lower sides of the insulating layer A in the thickness direction so as to have a dry film thickness of 500 μm, to produce an insulating heat conductive sheet. The thermal conductivity and the withstand voltage test value of the obtained insulating heat conductive sheet were measured. The results are shown in Table 1. Further, the Asker C hardness of the acrylic resin layer was such that six acrylic resin test pieces prepared to have a width of 30 mm, a length of 60 mm and a thickness of 1.0 mm were superposed and placed in a temperature-controlled room kept at 23° C. What was left still for a time or longer was measured as a sample. The Asker C hardness of the acrylic resin layer thus measured was 50.

(Comparative example 2)
An insulating heat conductive sheet was manufactured in the same manner as in Example 1 except that the combination of the insulating layer and the heat conductive sheet was changed as shown in Table 1. The thermal conductivity and the withstand voltage test value of the obtained insulating heat conductive sheet were measured. The results are shown in Table 1.

(Comparative example 3)
The heat conductive sheet A was arranged as an intermediate layer, and the same acrylic resin as in Comparative Example 1 was applied to the upper and lower sides in the thickness direction to a dry film thickness of 500 μm, to manufacture an insulating heat conductive sheet. The thermal conductivity and the withstand voltage test value of the obtained insulating heat conductive sheet were measured. The Asker C hardness of the acrylic resin layer measured in the same manner as in Comparative Example 1 was 50.

From Table 1, in the insulating heat conductive sheets of Examples 1 to 6, in which the heat conductive sheets containing the resin and the particulate carbon material and having an Asker C hardness of 70 or less are arranged above and below in the thickness direction of the insulating layer, In comparison with Comparative Example 1 containing no particulate carbon material, Comparative Example 2 having an Asker C hardness of more than 70, and Comparative Example 3 having a thermal conductive sheet as an intermediate layer, insulating property, thermal conductivity, And it can be seen that the flexibility can be juxtaposed at a sufficiently high level.

According to the present invention, it is possible to provide an insulating heat conductive sheet in which the insulating property, thermal conductivity, and flexibility are juxtaposed at a sufficiently high level, and an efficient manufacturing method thereof.

1 Thermal Conductive Sheet 2 Insulating Layer 10 Insulating Thermal Conductive Sheet

Claims (8)

An insulative heat-conducting sheet, comprising a heat-conducting sheet containing a resin and a particulate carbon material and having an Asker C hardness of 70 or less and arranged directly above and below in the thickness direction of the insulating layer so as to directly contact the insulating layer . The insulating heat conductive sheet according to claim 1, wherein the heat conductivity in the thickness direction is 7 W/m·K or more. The insulating heat conductive sheet according to claim 1, which has a withstand voltage test value of 10 kV/mm or more. The insulating heat conductive sheet according to any one of claims 1 to 3, which has a density of 1.8 g/m ³ or less. The insulating heat conductive sheet according to claim 1, wherein the insulating layer contains a cyclic olefin resin and surface-treated aluminum hydroxide. The insulating heat conductive sheet according to claim 5, wherein the amount of the surface-treated aluminum hydroxide is 1/2 to 6 times the amount of the cyclic olefin resin. The heat conductive sheet, the resin, the composition containing the particulate carbon material is pressed to form a sheet, after forming a pre-heat conductive sheet, a plurality of the pre-heat conductive sheet in the thickness direction. It is a sheet obtained by slicing a laminated body obtained by laminating or a laminated body obtained by folding or winding the pre-heat conductive sheet at an angle of 45° or less with respect to the laminating direction. The insulating heat conductive sheet according to any one of 1 to 6. A step of preparing a heat conductive sheet having an Asker C hardness of 70 or less,
A step of directly laminating the heat conductive sheet above and below in the thickness direction of the insulating layer,
Including,
The step of preparing the heat conductive sheet,
Forming a sheet by pressing a composition containing a resin and a particulate carbon material to obtain a pre-heat conductive sheet,
Stacking a plurality of the pre-heat conductive sheets in the thickness direction, or folding or winding the pre-heat conductive sheet to obtain a laminate,
Slicing the laminate at an angle of 45° or less with respect to the laminating direction to obtain a heat conductive sheet,
A method for manufacturing an insulating heat conductive sheet, comprising:

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