WO2018025587A1 - Heat transfer sheet - Google Patents

Abstract

This heat transfer sheet is obtained by laminating a plurality of heat transfer pre-sheets, each of which contains a particulate carbon material and one resin or a composite of a plurality of resins, in a direction transecting the thickness direction of the heat transfer sheet; and the Mooney viscosity of the whole resin component is 90 (ML₁₊₄, 100°C) or less.

Description

Heat conduction sheet

The present invention relates to a heat conductive sheet.

In recent years, electronic parts such as a plasma display panel (PDP) and an integrated circuit (IC) chip have increased in calorific value as performance is improved. As a result, in electronic devices using electronic components, it is necessary to take measures against functional failures due to temperature rise of the electronic components.

As countermeasures against functional failures due to temperature rise of electronic components, generally, a method of promoting heat dissipation by attaching a heat sink such as a metal heat sink, heat sink, heat sink or the like to a heat generator such as an electronic component is adopted. ing. In addition, when using a radiator, in order to efficiently transfer heat from the heating element to the radiator, the heating element and the heating element are connected via a sheet-like member (thermal conduction sheet) that exhibits good thermal conductivity. The radiator is in close contact. And the heat conductive sheet arrange | positioned between a heat generating body and a heat radiator is calculated | required that the heat conductivity of the thickness direction is high.

Here, as the heat conductive sheet, a sheet molded using a composite mixture in which a resin and a component exhibiting heat conductivity are usually used. Therefore, in recent years, many studies have been made on the components of the heat conductive sheet in order to improve the heat conductivity of the heat conductive sheet.

Specifically, conventionally, a heat radiating sheet containing a specific rubber component and anisotropic graphite oriented in a certain direction (that is, “thermal conductive sheet”) has been proposed (for example, see Patent Document 1). Patent Document 1 is obtained by blending anisotropic graphite with a resin component containing a thermoplastic rubber component, a thermosetting rubber component, and a thermosetting rubber curing agent that can be cross-linked to the thermosetting rubber component. A heat-dissipating sheet manufactured using the above composition is disclosed. In manufacturing a heat conductive sheet, first, the prepared composition is sandwiched between two films and rolled to produce a primary sheet by orienting anisotropic graphite in a direction substantially parallel to the main surface of the rolled sheet. Was. Then, the primary sheet is rolled in a predetermined direction to obtain a molded body, and the molded body is sliced in a predetermined direction to manufacture a heat conductive sheet.

Japanese Patent No. 4743344

However, the thermal conductive sheet of Patent Document 1 has room for improvement in terms of improving thermal conductivity.
Then, an object of this invention is to provide the heat conductive sheet which is excellent in the heat conductivity of the thickness direction.

The present inventors have intensively studied to achieve the above object. Then, the inventors newly found that the Mooney viscosity of the resin component contained in the heat conductive sheet greatly affects the heat conductivity of the heat conductive sheet, and completed the present invention.

That is, the present invention aims to advantageously solve the above-described problems, and the heat conductive sheet of the present invention includes a particulate carbon material and a pre-compound containing one kind of resin or a composite of plural kinds of resins. A plurality of heat conductive sheets are laminated in a direction transverse to the thickness direction of the heat conductive sheet, and the Mooney viscosity of all resin components made of the one kind of resin or a composite of plural kinds of resins is 90 (ML _{1 +4} , 100 ° C.) or less. A heat conductive sheet having a predetermined structure in which the Mooney viscosity of all resin components is 90 (ML _{1 + 4} , 100 ° C.) or less is excellent in heat conductivity in the thickness direction.
In the present specification, the “Mooney viscosity (ML _{1 + 4} , 100 ° C.)” can be measured at a temperature of 100 ° C. in accordance with JIS K6300.

Here, in the heat conductive sheet of the present invention, when the Mooney viscosity of all the resin components is X and the heat conductivity in the thickness direction of the heat conductive sheet is Y, the relational expression: Y> (− 0.2X + 25) It is preferable to satisfy. A heat conductive sheet that satisfies the above specific relational expression is excellent in production efficiency because it is easy to select a resin to be used during production.
In the present specification, the “thermal conductivity in the thickness direction” of the heat conductive sheet can be measured by the method described in Examples.

The heat conductive sheet of the present invention preferably has an Asker C hardness of 45 or more. A heat conductive sheet having an Asker C hardness of 45 or more is excellent in handleability.
Here, the “Asker C hardness” can be measured at a temperature of 23 ° C. using a hardness meter in accordance with the Asker C method of the Japan Rubber Association Standard (SRIS).

And it is preferable that the content rate of the said particulate carbon material is 35 volume% or more in the heat conductive sheet of this invention. The heat conductive sheet containing 35% by volume or more of the particulate carbon material is further excellent in heat conductivity.

According to the present invention, it is possible to provide a heat conductive sheet having excellent heat conductivity in the thickness direction.

Hereinafter, the present invention will be described in detail based on the embodiments.
The heat conductive sheet of the present invention can be used by directly adhering to the heating element, or can be used by being sandwiched between the heating element and the radiator when the radiator is attached to the heating element. At this time, a heat conductive sheet may be used individually by 1 sheet, and may use multiple sheets together. In addition, the heat conductive sheet of this invention can also comprise a heat radiating device with heat generating bodies and heat sinks, such as a heat sink, a heat sink, and a heat radiating fin.

(Heat conduction sheet)
The heat conductive sheet of the present invention is formed by laminating a plurality of pre-heat conductive sheets in a direction transverse to the thickness direction of the heat conductive sheet. A heat conductive sheet obtained by laminating a plurality of pre-heat conductive sheets in a direction transverse to the thickness direction of the heat conductive sheet is excellent in heat conductivity in the thickness direction. Furthermore, the pre heat conductive sheet which comprises the heat conductive sheet of this invention contains a particulate carbon material and 1 type of resin as a total resin component, or the composite of multiple types of resin. When the pre heat conductive sheet does not contain the particulate carbon material, the heat conductivity of the heat conductive sheet becomes insufficient. Moreover, when a pre heat conductive sheet does not contain a resin component, a softness | flexibility becomes inadequate. And in the heat conductive sheet of this invention, the Mooney viscosity of all the resin components is 90 (ML1 _{+ 4} , 100 degreeC) or less. Total resin component is a base material of the heat conductive sheet (hereinafter, also referred to as "matrix resin") if not Mooney viscosity _{90 (ML 1 + 4, 100} ℃) following resins, the thermal conductivity of the heat conducting sheet It cannot be raised sufficiently.
In addition, since the heat conductive sheet of this invention comprises the laminated structure of a pre heat conductive sheet, naturally the content component of a pre heat conductive sheet can be contained in a heat conductive sheet. Further, the plurality of pre-heat conductive sheets are bonded directly or through a very thin adhesive layer preferably formed of a resin having the same composition as the base resin of the pre-heat conductive sheet or a double-sided tape. For this reason, all the components and ratios thereof contained in the “pre-heat conductive sheet constituting the heat conductive sheet of the present invention” also apply to the “heat conductive sheet of the present invention”.

<Composition>
[Particulate carbon material]
Here, the particulate carbon material is not particularly limited. For example, graphite such as artificial graphite, flaky graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable 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.
Among them, it is preferable to use expanded graphite as the particulate carbon material. This is because if the expanded graphite is used, the thermal conductivity of the thermal conductive sheet can be improved.

-Expanded graphite-
Here, the expanded graphite that can be suitably used as the particulate carbon material is, for example, finely expanded after heat-treating expandable graphite obtained by chemically treating graphite such as scaly graphite with sulfuric acid or the like. Can be obtained. Examples of expanded graphite include EC1500, EC1000, EC500, EC300, EC100, and EC50 (all trade names) manufactured by Ito Graphite Industries Co., Ltd.

-Properties of particulate carbon materials-
Here, the particle diameter of the particulate carbon material is preferably 100 μm or more, more preferably 150 μm or more, more preferably 300 μm or less, and more preferably 250 μm or less in terms of volume-based mode diameter. . If the particle diameter of the particulate carbon material is equal to or greater than the above lower limit, the particulate carbon materials are brought into contact with each other in the heat conductive sheet to form a good heat transfer path, so that the heat conductive sheet exhibits high thermal conductivity. Because it can. Also, if the particle size of the particulate carbon material is less than or equal to the above upper limit, the heat conduction sheet is given higher flexibility and heat transfer from the heating element to the heat conduction sheet when in contact with the heating element is improved. Because you can.
The aspect ratio (major axis / minor axis) of the particulate carbon material contained in the heat conductive sheet of the present invention is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less.

In the present invention, the “volume reference mode diameter” can be determined according to the method described in the examples of the present specification using a laser diffraction / scattering particle size distribution measuring apparatus.
In the present invention, the “aspect ratio of the particulate carbon material” is determined by observing the particulate carbon material obtained by dissolving and removing the resin in the heat conductive sheet in a solvent with an SEM (scanning electron microscope). Measure the maximum diameter (major axis) and the particle diameter (minor axis) in the direction perpendicular to the maximum diameter and measure the average value of the ratio of major axis to minor axis (major axis / minor axis). Can be obtained by calculating.

-Content ratio of particulate carbon material-
And the content rate of the particulate carbon material in the heat conductive sheet of the present invention is preferably 35% by volume or more, more preferably 45% by volume or more, and further preferably 50% by volume or more. Usually, it is 70 volume% or less. If the content rate of the particulate carbon material in a heat conductive sheet is more than the said minimum, it will become easy to contact particulate carbon materials in a heat conductive sheet, and it will become easy to form a favorable heat-transfer path | pass. As a result, the heat conductive sheet can exhibit higher heat conductivity in the thickness direction. Furthermore, if the content ratio of the particulate carbon material in the heat conductive sheet is within the above range, the composite particles are likely to be subjected to a force due to pressurization such as roll rolling. This is because the carbon material can be oriented better in the desired direction.
In the present invention, the “content ratio (volume%)” can be obtained as a theoretical value according to the method described in the examples of the present specification.

[Fibrous carbon material]
The heat conductive sheet of the present invention may optionally further contain a fibrous carbon material. The fibrous carbon material arbitrarily contained is not particularly limited, and for example, carbon nanotubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cut products thereof are used. Can do. These may be used individually by 1 type and may use 2 or more types together.
And if fibrous carbon material is contained in the heat conductive sheet of this invention, while being able to further improve the heat conductivity of a heat conductive sheet, the powder-off of particulate carbon material can also be prevented. The reason why powder 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, so that the thermal conductivity This is presumably because the particulate carbon material is prevented from being detached while increasing the strength.

Among the above, as the fibrous carbon material, it is preferable to use a fibrous carbon nanostructure such as a carbon nanotube, and it is more preferable to use a fibrous carbon nanostructure including a carbon nanotube. This is because if a fibrous carbon nanostructure such as a carbon nanotube is used, the thermal conductivity and strength of the thermal conductive sheet obtained using the thermal conductive sheet can be further improved.

-Fibrous carbon nanostructures containing carbon nanotubes-
Here, the fibrous carbon nanostructure containing carbon nanotubes that can be suitably used as the fibrous carbon material may be composed only of carbon nanotubes (hereinafter sometimes referred to as “CNT”). Alternatively, a mixture of CNT and a fibrous carbon nanostructure other than CNT may be used.
The CNT in the fibrous carbon nanostructure is 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 obtained using the heat-conducting sheet as compared with the case of using multi-walled carbon nanotubes.

In addition, the fibrous carbon nanostructure containing CNT has a ratio (3σ / Av) of a 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 a carbon nanostructure with 3σ / Av exceeding 0.25, and a carbon nanostructure with 3σ / Av exceeding 0.50. More preferably. If a fibrous carbon nanostructure containing CNTs with 3σ / Av of more than 0.20 and less than 0.60 is used, the heat conduction of the obtained heat conducting sheet can be obtained even if the amount of carbon nanostructure is small. This is because the properties and strength can be sufficiently increased. Therefore, the thermal conductivity and flexibility of the thermal conductive sheet are suppressed by suppressing the hardness of the thermal conductive sheet from being excessively high (that is, the flexibility is lowered) by blending the fibrous carbon nanostructure containing CNT. This is because the two can be juxtaposed at a sufficiently high level.
The “average diameter (Av) of the fibrous carbon nanostructure” and the “standard deviation of the diameter of the fibrous carbon nanostructure (σ: sample standard deviation)” are respectively measured using a transmission electron microscope. It can be determined by measuring the diameter (outer diameter) of 100 randomly selected fibrous carbon nanostructures. And the average diameter (Av) and standard deviation ((sigma)) of the fibrous carbon nanostructure containing CNT are adjusted by changing the manufacturing method and manufacturing conditions of the fibrous carbon nanostructure containing CNT. Alternatively, it may be adjusted by combining a plurality of types of fibrous carbon nanostructures containing CNTs obtained by different production methods.

And as a fibrous carbon nanostructure containing CNT, the diameter measured as described above is plotted on the horizontal axis, the frequency is plotted on the vertical axis, and a normal distribution is obtained when approximated by Gaussian. Things are usually used.

Furthermore, it is preferable that the fibrous carbon nanostructure containing CNT has a peak of Radial Breathing Mode (RBM) when evaluated using Raman spectroscopy. Note that there is no RBM in the Raman spectrum of a fibrous carbon nanostructure composed of only three or more multi-walled carbon nanotubes.

The average diameter (Av) of the fibrous carbon nanostructure containing CNTs is preferably 0.5 nm or more, more preferably 1 nm or more, preferably 15 nm or less, and preferably 10 nm or less. More preferably it is. If the average diameter (Av) of the fibrous carbon nanostructure is 0.5 nm or more, the aggregation of the fibrous carbon nanostructure can be suppressed and the dispersibility of the carbon nanostructure can be increased. . Moreover, if the average diameter (Av) of the fibrous carbon nanostructure is 15 nm or less, the thermal conductivity and strength of the thermal conductive sheet obtained using the thermal conductive sheet can be sufficiently increased.

Further, 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. Preferably, it is 1200 m ² / g or less. Furthermore, when the CNT in the fibrous carbon nanostructure is mainly opened, 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 obtained using the thermal conductive sheet can be sufficiently increased. is there. Moreover, if the BET specific surface area of the fibrous carbon nanostructure containing CNT is 2500 m ² / g or less, the aggregation of the fibrous carbon nanostructure is suppressed and the dispersibility of the CNT in the heat conductive sheet is increased. Because it can.
In the present invention, the “BET specific surface area” refers to a nitrogen adsorption specific surface area measured using the BET method.

The fibrous carbon nanostructure containing CNTs having the above-described properties can be obtained, for example, by 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. When synthesizing CNTs by the phase growth method (CVD method), a method of dramatically improving the catalytic activity of the catalyst layer by making a small amount of oxidizing agent (catalyst activation material) present in the system (super growth method) According to International Publication No. 2006/011655). Hereinafter, the carbon nanotube obtained by the super growth method may be referred to as “SGCNT”.

Here, the fibrous carbon nanostructure containing CNT produced by the super-growth method may be composed only of SGCNT, and in addition to SGCNT, other carbon nanostructures such as non-cylindrical carbon nanostructures may be used. Carbon nanostructures may be included.

-Properties of fibrous carbon materials-
And the average fiber diameter of the fibrous carbon material which can be contained in a heat conductive sheet is preferably 1 nm or more, more preferably 3 nm or more, preferably 2 μm or less, and preferably 1 μm or less. More preferred. If the average fiber diameter of the fibrous carbon material is within the above range, the thermal conductivity, flexibility and strength of the thermal conductive sheet obtained using the thermal conductive sheet can be juxtaposed at a sufficiently high level. .
Here, the aspect ratio of the fibrous carbon material preferably exceeds 10.

In the present invention, the “average fiber diameter” refers to a fibrous carbon material obtained by dissolving and removing the resin in the heat conductive sheet in a solvent by SEM (scanning electron microscope) or TEM (transmission electron microscope). It can be obtained by observing, measuring the fiber diameter of any 50 fibrous carbon materials, and calculating 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).
Further, in the present invention, the “aspect ratio of the fibrous carbon material” refers to the observation of the fibrous carbon material obtained by dissolving and removing the resin in the heat conductive sheet with a TEM (transmission electron microscope), and an arbitrary 50 pieces. For the fibrous carbon material, measure the maximum diameter (major axis) and the particle diameter (minor axis) in the direction orthogonal to the maximum diameter, and calculate the average value of the ratio of the major axis to the minor axis (major axis / minor axis). It can ask for.

[resin]
Here, the base material resin constituting the heat conductive sheet of the present invention needs to be a resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less. Such a matrix resin is not particularly limited as long as it has a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less, and is a known type of resin or a plurality of types of resins that can be used for the production of heat conductive sheets. Resin composites can be used. In addition, the base material resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less can be an unvulcanized resin without particular limitation. In this specification, rubber and elastomer are included in “resin”. Further, in the present specification, “unvulcanized” means such a resin or resin composition regardless of whether or not a vulcanizing agent (crosslinking agent) is contained in the resin composition as a resin or resin material. It means a state where no cross-linking reaction is caused by heating or the like.

Furthermore, the base material resin is preferably a resin having thermoplasticity. Here, in the present specification, “thermoplastic” means a property of being softened by heating, becoming moldable, and solidifying by cooling. Further, when the resin is “thermoplastic”, the polymer structure of the solidified resin usually does not contain a crosslinked structure. Here, in general, resins may be broadly classified into “thermoplastic resins” and “thermosetting resins”. However, even a resin that can be generally classified as a “thermosetting resin” may not form a crosslinked structure in the polymer structure if it is solidified in the absence of a crosslinking agent. Therefore, in this specification, regardless of whether it is generally classified as a thermoplastic resin or a thermosetting resin, the resins having “thermoplasticity” as defined above are collectively referred to as “thermoplasticity”. It is referred to as “resin having”.
And if "resin which has thermoplasticity" is mix | blended with a heat conductive sheet, the adhesiveness between heat conductive sheets and members, such as a heat generating body and a heat radiator, can be improved. This is because the “resin having thermoplasticity” can enhance the flexibility of the heat conductive sheet in a high temperature environment when the heat conductive sheet is used (at the time of heat dissipation).

The “resin having thermoplasticity” used as the base resin is solid at normal temperature and pressure. If the resin used as the base resin is solid at room temperature and normal pressure, the flexibility of the thermal conductive sheet is further improved in a high-temperature environment during use (during heat dissipation), and the thermal conductive sheet and the heating element are more The handling property of the heat conductive sheet can be improved in a normal temperature environment such as attachment while being in good contact. In this specification, “normal temperature” refers to 23 ° C., and “normal pressure” refers to 1 atm (absolute pressure).
Further, as described above, the base resin may be composed of one type of resin or a composite obtained by mixing two or more types of resins. When using a composite as a base material resin, each resin constituting the composite may be a solid resin or a liquid resin under normal temperature and normal pressure, but when a composite is formed, It is necessary for such a composite to become a solid at normal temperature and pressure.

-Thermoplastic resin-
(1) Resin having thermoplasticity that is solid under normal temperature and normal pressure A thermoplastic resin that can be used as a base material resin and is solid under normal temperature and normal pressure includes poly (2-ethylhexyl acrylate), Copolymer of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its ester, acrylic resin such as polyacrylic acid or its ester; silicone resin; fluororesin; polyethylene; polypropylene; ethylene-propylene copolymer; Polyvinyl chloride; Polyvinylidene chloride; Polyvinyl acetate; Ethylene-vinyl acetate copolymer; Polyvinyl alcohol; Polyacetal; Polyethylene terephthalate; Polybutylene terephthalate; Polyethylene naphthalate; Polystyrene; Polyacrylonitrile; Acryl-acrylonitrile copolymer; acrylonitrile-butadiene copolymer (nitrile rubber); acrylonitrile-butadiene-styrene copolymer (ABS resin); styrene-butadiene block copolymer or hydrogenated product thereof; styrene-isoprene block copolymer Polyphenylene ether; Modified polyphenylene ether; Aliphatic polyamides; Aromatic polyamides; Polyamideimide; Polycarbonate; Polyphenylene sulfide; Polysulfone; Polyethersulfone; Polyethernitrile; Polyetherketone; Polyketone; Liquid crystal polymer; ionomer and the like. These may be used individually by 1 type and may use 2 or more types together.

Furthermore, it is preferable that the “resin having thermoplasticity” used as a base material resin, which is solid at normal temperature and pressure, is a fluororesin. This is because if the base resin is a fluororesin, the heat resistance, oil resistance, and chemical resistance of the heat conductive sheet can be improved. Specific examples include elastomers obtained by polymerizing fluorine-containing monomers, such as vinylidene fluoride fluororesins, tetrafluoroethylene-propylene fluororesins, tetrafluoroethylene-purple olovinyl ether fluororesins, and the like. 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-hexafluoropropylene-tetrafluoroethylene copolymer, acrylic modification of polytetrafluoroethylene, ester modification of polytetrafluoroethylene Epoxy-modified product of polytetrafluoroethylene and polytetrafluoroethylene silane modified product, and the like. Among these, from the viewpoint of processability, polytetrafluoroethylene, polytetrafluoroethylene modified acrylic, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride -A hexafluoropropylene-tetrafluoroethylene copolymer is preferred.

Also, commercially available fluororesins having a thermoplastic property at room temperature and normal pressure include, for example, Daiel (registered trademark) G-300 series / G-700 series / G-7000 series (manufactured by Daikin Industries, Ltd.) Vinylidene fluoride-hexafluoropropylene binary copolymer), Daiel G-550 series / G-600 series (vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer), Daiel G-800 series (Vinylidene fluoride-hexafluoropropylene binary copolymer), Daiel G-900 series (vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer); KYNAR (registered trademark) manufactured by ALKEMA Series (bifluoride (Ridene-based fluororesin), KYNAR FLEX® series (vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer); A-100 (vinylidene fluoride-hexafluoropropylene binary) manufactured by Chemers Copolymer); Dyneon E made by 3M Japan? 20575 (registered trademark) (vinylidene fluoride-hexafluoropropylene binary copolymer).

(2) Resin having liquid thermoplasticity under normal temperature and normal pressure As described above, the composite becomes solid under normal temperature and normal pressure, and is not solid under normal temperature and normal pressure as long as the effect of the present invention is not significantly impaired. A resin having thermoplasticity that is liquid at room temperature and normal pressure may be used in combination with a resin having thermoplasticity. Examples of the resin having liquid thermoplasticity under normal temperature and normal pressure include acrylic resins, epoxy resins, silicone resins, and fluororesins other than the resin corresponding to the resin of (1) above. These may be used individually by 1 type and may use 2 or more types together.

The viscosity of the resin having liquid thermoplasticity under normal temperature and normal pressure is not particularly limited, but the viscosity at 105 ° C. from the viewpoint of good kneadability, fluidity, crosslinking reactivity, and excellent moldability, 500 mPa · s to 30,000 mPa · s is preferable, and 550 mPa · s to 25,000 mPa · s is more preferable.

-Other resins-
As long as the effects of the present invention are not significantly impaired, the heat conductive sheet may contain other resins than the above-described resins.
Other resins that can be generally classified as thermosetting resins, such as natural rubber; butadiene rubber; isoprene rubber; hydrogenated nitrile rubber; chloroprene rubber; ethylene propylene rubber; chlorinated polyethylene; 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; And thermosetting modified polyphenylene ether. These may be used individually by 1 type and may use 2 or more types together.

-Mooney viscosity-
The base resin must have a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 90 (ML _{1 + 4} , 100 ° C.) or less, and 65 (ML _{1 + 4} , 100 ° C.) or less. More preferably, it is 36 (ML _{1 + 4} , 100 ° C.) or less. Usually, it is 3 (ML _{1 + 4} , 100 ° C.) or more. If the Mooney viscosity of the base resin contained in the heat conductive sheet is not more than the above upper limit, the heat conductivity of the heat conductive sheet can be increased.
The Mooney viscosity of the base resin contained in the heat conductive sheet is prepared by dissolving the heat conductive sheet in a solvent capable of dissolving the base resin and then isolating the base resin to prepare a Mooney viscosity measurement sample. The obtained sample can be obtained by measuring (ML _{1 + 4} , 100 ° C.) according to JIS-K6300. In addition, the Mooney viscosity value obtained in this way is, in principle, substantially the same as the Mooney viscosity value of the base resin at the material stage.

-Resin content-
And the content rate of all the resin components in the heat conductive sheet of this invention is preferable that it is 65 volume% or less with the whole volume of a heat conductive sheet being 100 volume%, and it is more preferable that it is 55 volume% or less. , 50% by volume or less is more preferable, and usually 30% by volume or more. If the content rate of all the resin components in a heat conductive sheet is below the said upper limit, high heat conductivity can be exhibited with a heat conductive sheet. Moreover, if the content ratio of all resin components in the heat conductive sheet is equal to or higher than the above lower limit value, the heat conductive sheet is given high flexibility, and heat transfer from the heat generator to the heat conductive sheet when in contact with the heat generator is achieved. Can be better.

[Additive]
If necessary, the heat conductive sheet of the present invention can be blended with known additives that can be used for producing the heat conductive sheet. Additives that can be blended in the heat conductive sheet are not particularly limited, for example, plasticizers such as fatty acid esters; flame retardants such as red phosphorus flame retardants and phosphate ester flame retardants; fluorine oil ( Additives that serve as both plasticizers and flame retardants, such as Daikin Industries Ltd.'s demnam series; toughness improvers such as urethane acrylate; moisture absorbents such as calcium oxide and magnesium oxide; silane coupling agents, titanium couplings Agents, adhesive improvers such as acid anhydrides; wettability improvers such as nonionic surfactants and fluorosurfactants; ion trapping agents such as inorganic ion exchangers, and the like.

<Properties>
[Asker C hardness]
The heat conductive sheet of the present invention preferably has an Asker C hardness of 45 or more, more preferably 55 or more, and preferably over 60. This is because if the Asker C hardness is equal to or higher than the lower limit, the handling properties of the heat conductive sheet can be improved. The value of Asker C hardness of a heat conductive sheet can be adjusted by selecting the content rate of the particulate carbon material mix | blended with a heat conductive sheet, and the resin component to be used.
Conventionally, as a general method for increasing the thermal conductivity of the thermal conductive sheet itself, means for increasing the content ratio of the thermal conductive material such as the particulate carbon material has been selected. If the content ratio of the heat conductive material is high, the heat conductive sheet tends to be hard. Here, conventionally, the hardness of the heat conductive sheet is the interfacial resistance between the heat conductive sheet and another member (heat generating body or heat radiating body) to which the heat conductive sheet is attached (hereinafter referred to as “interfacial resistance between members”). Asker C hardness has been used as an indicator of hardness. And while increasing the thermal conductivity of the thermal conductive sheet itself, various ways to improve the thermal conductivity of the thermal conductive sheet have been studied by balancing so that the Asker C hardness is not excessively increased. I came. However, when the present inventors examined again, it became clear that there is no correlation between the Asker C hardness of the heat conductive sheet and the interfacial resistance between members. As a result of further studies, the present inventors have newly found that the interfacial resistance between members can be advantageously suppressed by blending a base material resin having a Mooney viscosity of a predetermined value or less. Furthermore, the heat conductive sheet containing the base material resin having a Mooney viscosity of a predetermined value or less has a moderate value of Asker C hardness, and has a higher heat than previously assumed in relation to Asker C hardness. It became clear that it had conductivity.

[Thermal conductivity]
In the heat conductive sheet of the present invention, when the Mooney viscosity of the base resin is X (ML _{1 + 4} , 100 ° C.) and the heat conductivity in the thickness direction of the heat conductive sheet is Y, the relational expression: Y> (− 2.6X + 25) is preferable, relational expression: Y> (− 2.6X + 42) is more preferable, and relational expression: Y> (− 2.6X + 120) is more preferable. Using such a relational expression as an index, it is possible to easily select a resin material to be used as a base resin by calculating back from the target thermal conductivity of the thermal conductive sheet, and to improve the manufacturing efficiency of the thermal conductive sheet. it can. On the contrary, since the thermal conductivity of the obtained heat conductive sheet can be estimated from the base material resin to be used, the design efficiency of the heat conductive sheet can be improved.

More specifically, the thermal conductivity of the heat conductive sheet is preferably 19 W / m · K or more, more preferably 25 W / m · K or more, and further preferably 35 W / m · K or more. preferable. This is because if the thermal conductivity of the heat conductive sheet is equal to or higher than the lower limit, for example, when the heat conductive sheet and the heating element are used in close contact, heat can be efficiently dissipated from the heating element.

[Mooney viscosity]
The heat conductive sheet of the present invention preferably has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 50 (ML _{1 + 4} , 100 ° C.) or less, and 30 (ML _{1 + 4} , 100 ° C.) or less. More preferably, it is usually 2 (ML _{1 + 4} , 100 ° C.) or more. If the Mooney viscosity of the heat conductive sheet is less than or equal to the above upper limit, when the heat conductive sheet is used under high temperature conditions, the heat conductive sheet and a member to which the heat conductive sheet such as a heating element or a heat radiator is attached It is considered that the heat radiation efficiency can be improved by improving the adhesion of the material.

[Construction]
The heat conductive sheet of the present invention is formed by laminating a plurality of pre-heat conductive sheets containing the above-mentioned particulate carbon material, resin component, and optional additives in a direction transverse to the thickness direction. It has a structure. Furthermore, in the pre-heat conductive sheet, the particulate carbon material is preferably oriented along the surface direction of the pre-heat conductive sheet (in a direction transverse to the thickness direction of the pre-heat conductive sheet). This is because if the particulate carbon material is oriented along the surface direction of the pre-heat conductive sheet, the thermal conductivity in the thickness direction of the heat conductive sheet can be increased. And the evidence that “the heat conductive sheet was obtained by laminating and slicing a plurality of pre-heat conductive sheets in the plane direction” is, for example, a method of microscopically observing a cross section in the thickness direction of the heat conductive sheet, A comprehensive determination can be made by using a method for determining whether or not there is anisotropy in thermal conductivity.

[Thickness]
The thickness of a heat conductive sheet is not specifically limited, For example, it may be 0.05 mm or more and 10 mm or less. In general, if the thickness of the heat conductive sheet is too thick, the heat resistance of the heat conductive sheet increases and the thermal conductivity decreases, and if the thickness of the heat conductive sheet is too small, the thermal conductivity of the heat conductive sheet is sufficient. This is because it cannot be used.

Furthermore, a plurality of heat conductive sheets having a certain thickness stacked in the thickness direction and integrated by standing for a predetermined time can be used as the heat conductive sheet. In the heat conductive sheet thus obtained, it is presumed that the particulate carbon material and any fibrous carbon material remain oriented in the thickness direction of the heat conductive sheet. Therefore, the thermal conductivity of a thick (thickness x) thermal conductive sheet obtained by laminating a plurality of thin thermal conductive sheets in the thickness direction is substantially the same as that of a single thermal conductive sheet having the same thickness (thickness x). It is thought to have an equivalent thermal conductivity. For this reason, by preparing a plurality of (thin) heat conductive sheets of a predetermined thickness without preparing heat conductive sheets of various thicknesses, heat having a thickness corresponding to the thickness of the location where the heat conductive sheet is to be applied is prepared. A conductive sheet can be obtained.

(Method for producing heat conductive sheet)
The manufacturing method for manufacturing the heat conductive sheet of the present invention is not particularly limited, and a manufacturing method that can be used at the time of manufacturing a heat conductive sheet in which a plurality of pre-heat conductive sheets are laminated in the plane direction is adopted. be able to. As such a production method, for example, a step of preparing a composite mixture containing a particulate carbon material and a base resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less; The manufacturing method including the process of obtaining a sheet | seat, the process of obtaining the laminated body of a pre heat conductive sheet, and a slicing process is mentioned.

<Step of preparing a composite mixture>
In the step of preparing the composite mixture, a composite mixture containing the particulate carbon material and the resin is prepared. Specifically, in the step of preparing the composite mixture, the particulate carbon material, the base resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less, and any fibrous carbon material are not particularly limited. And / or a composite mixture may be prepared by combining with additives in a known manner. Moreover, in the step of preparing the composite mixture, the composite mixture may be prepared by purchasing a commercially available composite mixture containing a particulate carbon material and a base resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less. . In the case of preparing a composite mixture by combining the above, more specifically, for example, the following methods (I) to (III) can be used.
(I) A composite mixture is obtained by mixing and kneading a particulate carbon material, a base resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less, and any fibrous carbon material and / or additive. .
(II) Dry granulating a dispersion containing a particulate carbon material, a base resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less, and any fibrous carbon material and / or additive. A composite mixture is obtained.
(III) A base material resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less is sprayed on the particulate carbon material and any fibrous carbon material to obtain a composite mixture.
Among these, it is desirable to use the method (I) from the viewpoint of ease of work.
The particulate carbon material used in the step of preparing the composite mixture, the base resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or lower, the optional fibrous carbon material and / or the additive include the above-mentioned heat The same components as the particulate carbon material that the conductive sheet can contain, the base resin with Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less, and any fibrous carbon material and / or additive can be used. The content ratio can be the same.

[Mixing and kneading method]
The mixing and kneading method is not particularly limited, and can be performed using a known mixing apparatus such as a kneader, roll, Henschel mixer, Hobart mixer or the like. And mixing and kneading | mixing time can be made into 5 hours or more and 6 hours or less, for example. Moreover, mixing and kneading | mixing temperature can be made into 5 to 150 degreeC, for example.
Here, mixing and kneading may be performed in the presence of a solvent such as ethyl acetate. However, when a solvent is used during mixing and kneading, the solvent is removed prior to crushing / pulverizing the composite mixture described later. It is preferable. The removal of the solvent may be performed by a known drying method, or may be performed while arbitrarily defoaming the composite mixture. For example, if defoaming is performed using vacuum defoaming, the solvent can be removed simultaneously with defoaming.

[Composite mixture]
The resulting composite mixture includes a particulate carbon material and a base resin having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less, and optionally further includes a fibrous carbon material and an additive. The composite mixture is usually a lump having a diameter of about 1 mm to 200 mm.

Optionally, a pulverization step of pulverizing the composite mixing cylinder into particles may be performed. In this case, in the pulverization step, the obtained composite mixture is pulverized by an arbitrary method to obtain composite particles. In the step of obtaining composite particles, the obtained composite mixture may be pulverized and then classified by any method to obtain composite particles.

The pulverization of the composite mixture can be performed by a known method without particular limitation as long as the obtained composite particles are a powder fluid rather than a lump of the composite mixture. Prior to pulverization, pulverization or the like for loosening the lump may be performed. The complex mixture can be pulverized / pulverized using, for example, a known pulverization / pulverization machine utilizing a shearing action or an attrition action or an agitated known pulverization / pulverization machine. Examples of the known crushing / pulverizing machine include a hammer crusher, a cutter mill, a hammer mill, a bead mill, a vibration mill, a meteor ball mill, a sand mill, a ball mill, a roll mill, a three-roll mill, a jet mill, and a high-speed rotary pulverizer. , A fine pulverizer, a pulverizing and sizing machine, and a nano jet mizer.
The conditions such as the type of the crushing / pulverizing machine, energy during crushing / crushing, and time are appropriately selected according to the state of the aggregate of the composite mixture, the desired powder fluid state such as the particle size of the composite particles, Adjust it.

Here, the composite mixture is not particularly limited and is preferably pulverized to a particle size of less than 1000 μm by sieve classification.

<Step of obtaining a pre-heat conductive sheet>
In the step of obtaining the pre-heat conductive sheet, the composite mixture or composite particles obtained in the previous step are pressed by an arbitrary method and formed into a sheet shape.

[Pressurization method]
The method for pressurizing the pre-heat conductive sheet is not particularly limited as long as it is a molding method in which pressure is applied. The pre-heat conductive sheet can be formed into a sheet shape by using a known forming method such as press forming, rolling forming or extrusion forming. Especially, it is preferable to shape | mold a heat conductive sheet in a sheet form by rolling, and it is more preferable to pass between rolls in the state pinched | interposed into the protective film, and to shape | mold into a sheet form. In addition, as a protective film, it does not specifically limit, The polyethylene terephthalate (PET) film etc. which performed the sandblast process can be used. The roll temperature can be 5 ° C. or more and 150 ° C.

In addition, the thickness of a pre heat conductive sheet is not specifically limited, For example, it can be 0.05 mm or more and 2 mm or less. Further, from the viewpoint of improving the thermal conductivity of the heat conductive sheet by increasing the heat conductivity of the pre heat conductive sheet, the thickness of the pre heat conductive sheet is not more than 5000 times the average particle diameter of the particulate carbon material. Is preferred.

<Step of obtaining a laminate>
In the step of obtaining a laminate, a plurality of the pre-heat conductive sheets obtained in the previous step are laminated in the thickness direction of the pre-heat conductive sheet, or the pre-heat conductive sheet obtained in the previous step is folded or wound. Thereby, a laminated body is formed.

[Lamination method]
Formation of the laminated body by lamination | stacking of a pre heat conductive sheet is not specifically limited, You may carry out using a lamination apparatus, and may carry out manually. Moreover, formation of the laminated body by folding of a pre heat conductive sheet is not specifically limited, It can carry out by folding a heat conductive primary sheet by fixed width using a folder. Further, the formation of the laminate by winding the pre-heat conductive sheet is not particularly limited, and by rolling the pre-heat conductive sheet around an axis parallel to the short direction or the long direction of the pre-heat conductive sheet. It can be carried out.

Here, usually, in the step of obtaining the laminate, the adhesive force between the surfaces of the pre-heat conductive sheets is sufficiently obtained by the pressure when the pre-heat conductive sheets are laminated and the pressure when folding or winding. However, when the adhesive strength is insufficient or when it is necessary to sufficiently suppress delamination of the laminate, the laminate may be formed in a state where the surface of the pre-heat conductive sheet is slightly dissolved with a solvent. Then, the laminate may be formed in a state where an adhesive is applied to the surface of the pre-heat conductive sheet or in a state where an adhesive layer is provided on the surface of the pre-heat conductive sheet.

In addition, as a solvent used when melt | dissolving the surface of a pre heat conductive sheet, it is not specifically limited, The known solvent which can melt | dissolve the resin component contained in the pre heat conductive sheet can be used.

Moreover, it does not specifically limit as an adhesive agent apply | coated to the surface of a pre heat conductive sheet, A commercially available adhesive agent and adhesive resin can be used. Among these, 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. And the thickness of the adhesive agent apply | coated to the surface of a pre heat conductive sheet can be 10 micrometers or more and 1000 micrometers or less, for example.
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.

In addition, from the viewpoint of suppressing delamination, the obtained laminate is pressed at a pressure of 0.05 MPa or more and 1.0 MPa or less in the stacking direction at 20 ° C. or more and 150 ° C. or less for 1 minute or more and 30 minutes or less It is preferable to press.

In addition, in the laminated body obtained by laminating, folding, or winding the pre-heat conductive sheet, it is assumed that the particulate carbon material and any fibrous carbon material are oriented in a direction substantially orthogonal to the laminating direction.

<Slicing process>
In the slicing step, the laminated body obtained in the above-described step 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.

[Slicing method]
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. Especially, the knife processing method is preferable at the point which makes the thickness of a heat conductive sheet uniform. The cutting tool for slicing the laminate is not particularly limited, and includes a slice member (for example, a sharp blade) having a smooth board surface having a slit and a blade portion protruding from the slit portion. Canna and slicer) can be used.

In addition, from the viewpoint of increasing 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, it is approximately 0 ° with respect to the stacking direction (that is, the direction 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 more and 40 ° C. or less, and more preferably 10 ° C. or more and 30 ° C. or less. Furthermore, for the same reason, the laminated body to be sliced is preferably sliced while applying a pressure in a direction perpendicular to the lamination direction, and a pressure of 0.1 MPa to 0.5 MPa in the direction perpendicular to the lamination direction. It is more preferable to slice while loading.

And since the heat conductive sheet obtained according to the manufacturing method as described above is formed through a step of obtaining a laminate and a slicing step, the particulate carbon material and any fibrous carbon material are in the thickness direction of the heat conductive sheet. It is presumed that they are oriented. Therefore, for example, the heat generated from the heat generating element can be efficiently dissipated in the thickness direction of the heat conductive sheet by satisfactorily adhering the heat generating element and the heat conductive sheet.

(Use of heat conduction sheet)
And the heat conductive sheet obtained according to the manufacturing method of this invention is excellent in heat conductivity, and is generally excellent also in intensity | strength and electroconductivity. Therefore, for example, the heat conductive sheet is applied when heat-pressing heat-dissipating materials, heat-dissipating parts, cooling parts, temperature-adjusting parts, electromagnetic wave shielding members, electromagnetic wave absorbing members, and objects to be bonded used in various devices and devices. It is suitable as a thermocompression-bonding rubber sheet interposed between the press-bonded product and the thermocompression bonding apparatus.
Here, various devices and devices are not particularly limited, and are electronic devices such as servers, server personal computers, desktop personal computers, etc .; portable electronic devices such as notebook personal computers, electronic dictionaries, PDAs, mobile phones, and portable music players. Liquid crystal display (including backlight), plasma display, LED, organic EL, inorganic EL, liquid crystal projector, display device such as clock; ink jet printer (ink head), electrophotographic device (developing device, fixing device, heat roller, Image forming apparatuses such as heat belts; semiconductor-related components such as semiconductor elements, semiconductor packages, semiconductor encapsulating cases, semiconductor die bonding, CPUs, memories, power transistors, power transistor cases; rigid wiring boards, flexible wiring boards, ceramic wirings Board, bi Wiring boards such as doup-up wiring boards and multilayer boards (wiring boards include printed wiring boards); manufacturing equipment such as vacuum processing equipment, semiconductor manufacturing equipment, display equipment manufacturing equipment; heat insulating materials, vacuum heat insulating materials, radiation heat insulating materials Thermal insulation equipment for materials, etc .; DVD (optical pickup, laser generator, laser receiver), data recording equipment such as hard disk drive, etc .; Camera, video camera, digital camera, digital video camera, microscope, CCD, etc. image recording equipment; Examples thereof include battery devices such as devices, lithium ion batteries, and fuel cells.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the following description, “parts” representing amounts are based on mass unless otherwise specified.
In Examples and Comparative Examples, the Mooney viscosity of the base resin and the Mooney viscosity of the heat conductive sheet; the content of the particulate carbon material in the heat conductive sheet and the volume standard mode diameter; the Asker C hardness of the heat conductive sheet; The thermal conductivity of the conductive sheet was measured and calculated using the following methods.

<Mooney viscosity>
The Mooney viscosity of the base material resin used for the production of the heat conductive sheet is cut out from the base material resin and cut according to JIS-K6300 using a Mooney viscometer (manufactured by Shimadzu Corporation, “MOONEY VISCOMETER SMV-202”) (ML _{1 +4} , 100 ° C.).
A similar section was cut out from the obtained heat conductive sheet and measured in the same manner.

<Content ratio of particulate carbon material>
The theoretical value in the volume fraction was used for the content ratio of the particulate carbon material in the heat conductive sheet. Specifically, for each component of the particulate carbon material, the resin, and any fibrous carbon material and additive contained in the heat conductive sheet, the volume (from the density (g / cm ³ ) and the blending amount (g) ( cm ³ ) was calculated, and the content ratio of the particulate carbon material in the heat conductive sheet was determined as a volume fraction (volume%).

<Volume-based mode diameter of particulate carbon material in heat conductive sheet>
1 g of the heat conductive sheet was placed in a methyl ethyl ketone solvent, and the resin component was dissolved to obtain a suspension in which the particulate carbon material was separated and dispersed. Next, using the obtained suspension as a sample, the particle size of the particulate carbon material contained in the suspension is measured using a laser diffraction / scattering particle size distribution measuring apparatus (Horiba, Model “LA960”). Was measured. Then, the particle diameter at the maximum value of the particle diameter distribution curve with the obtained particle diameter as the horizontal axis and the volume of the particulate carbon material as the vertical axis was determined as the volume standard mode diameter (μm).

<Asker C hardness of heat conductive sheet>
In accordance with the Asker C method of the Japan Rubber Association Standard (SRIS), the hardness was measured at a temperature of 23 ° C. using a hardness meter (trade name “ASKER CL-150LJ” manufactured by Kobunshi Keiki Co., Ltd.).
Specifically, six heat conductive sheet test pieces prepared to have a size of width 30 mm × length 60 mm × thickness 1.0 mm were stacked and left in a temperature-controlled room maintained at 23 ° C. for 48 hours or more. Asker C hardness was measured using a sample. Then, the height of the damper was adjusted so that the pointer was 95 to 98, and the hardness 20 seconds after the sample and the damper collided was measured five times, and the average value was taken as the Asker C hardness of the sample. .

<Thermal conductivity of thermal conductive sheet>
In calculating the thermal conductivity of the thermal conductive sheet, first, the thermal resistance value was measured using a resin material thermal resistance tester (trade name “C47108” manufactured by Hitachi Technology & Service Co., Ltd.). In the measurement, the heat conductive sheet was cut into a 1 cm square and used as a measurement sample. Then, the thermal resistance value R of the measurement sample under the conditions of a test temperature of 50 ° C. and a pressure of 0.50 MPa was measured. It shows that it is excellent in thermal conductivity, and is excellent in the thermal radiation characteristic when it interposes between a heat generating body and a heat radiator as a heat resistance value R, and is set as a heat radiating device.
And thermal conductivity was computed from the obtained thermal resistance value R and thickness d of the heat conductive sheet after pressurization according to the following formula.
Thermal conductivity [W / m · K] = thickness d [m] of thermal conductive sheet / thermal resistance value R [m ² · K / W] (I)

Example 1
<Preparation of fibrous carbon nanostructure containing CNT>
According to the description of WO 2006/011655, fibrous carbon nanostructures containing SGCNTs were obtained by the super-growth method.
The obtained fibrous carbon nanostructure had a BET specific surface area of 800 m ² / g. In addition, as a result of measuring the diameter of 100 randomly selected fibrous carbon nanostructures using a transmission electron microscope, the average diameter (Av) was 3.3 nm, and the sample standard deviation (σ) of the diameter was The value (3σ) multiplied by 3 was 1.9 nm, and the ratio (3σ / Av) was 0.58. Further, the obtained fibrous carbon nanostructure was mainly composed of single-walled CNT (also referred to as “SGCNT”).

<Preparation of an easily dispersible assembly of fibrous carbon nanostructures>
[Preparation of dispersion]
400 mg of the fibrous carbon nanostructure obtained above as a fibrous carbon material was weighed, mixed in 2 L of methyl ethyl ketone as a solvent, and stirred for 2 minutes with a homogenizer to obtain a crude dispersion. Next, using a wet jet mill (product name “JN-20”, manufactured by Joko Co., Ltd.), the obtained coarse dispersion was passed through a 0.5 mm flow path of the wet jet mill at a pressure of 100 MPa for two cycles. Then, the fibrous carbon nanostructure was dispersed in methyl ethyl ketone. And the dispersion liquid of solid content concentration 0.20 mass% was obtained.
[Removal of solvent]
Thereafter, the dispersion obtained above was filtered under reduced pressure using Kiriyama filter paper (No. 5A) to obtain a sheet-like easily dispersible aggregate.

<Manufacture of heat conductive sheet>
[Step of preparing a composite mixture]
130 parts of expanded graphite as a particulate carbon material (trade name “EC-50”, average particle diameter: 250 μm, manufactured by Ito Graphite Industries Co., Ltd.) and an easily dispersible assembly of carbon nanostructures as a fibrous carbon material 0.1 parts of the body (indicated in the table as “SGCNT”), a thermoplastic fluororesin that is solid under normal temperature and normal pressure as a base resin that is a resin component (manufactured by 3M Japan, trade name “Dyneon ( (Registered trademark) E-20575 ", Mooney viscosity: 3.5ML _{1 + 4} , 100 ° C) 80 parts, and phosphoric acid ester as a flame retardant (trade name" PX-110 "manufactured by Daihachi Chemical Industry Co., Ltd.) By mixing and kneading 10 parts with a kneader (manufactured by Inoue Seisakusho) for 15 minutes, a composite mixture containing a particulate carbon material, a base resin, a fibrous carbon material, and a flame retardant was obtained. .
[Step of obtaining composite particles]
Next, the composite mixture obtained above is put into a pulverizer (manufactured by Sansho Industry Co., Ltd., product name “hammer crusher HN34S”) and pulverized for 60 seconds, whereby particulate carbon material, base resin, fibrous form Composite particles containing a carbon material and a flame retardant were obtained.
[Step of obtaining pre-heat conductive sheet]
Subsequently, 5 g of the composite particles obtained above were sandwiched between sandblasted PET films (protective film) having a thickness of 50 μm, a roll gap of 550 μm, a roll temperature of 50 ° C., a roll linear pressure of 50 kg / cm, and a roll speed of 1 m / A pre-heat conductive sheet having a thickness of 0.5 mm was obtained by rolling under the condition of minutes.
[Step of obtaining laminated body]
Further, the pre-heat conductive sheet obtained above is cut into a length of 6 cm, a width of 6 cm, and a thickness of 0.5 mm, and 120 sheets are laminated in the thickness direction via a double-sided tape as an adhesive layer, and a laminate having a thickness of about 6 cm. Got.
[Slicing process]
Then, while pressing the laminated section of the laminate at a pressure of 0.3 MPa, using a woodworking slicer (manufactured by Marunaka Steel Works, trade name “Super-finished plane super mechanism S”) with respect to the lamination direction Then, it was sliced at an angle of 0 ° (in other words, sliced in the normal direction of the main surface of the laminated heat conductive primary sheet) to obtain a heat conductive sheet 6 cm long × 6 cm wide × 150 μm thick. Here, the knife of the woodworking slicer has two single blades in contact with each other on the opposite sides of the cutting blade, and the leading edge of the front edge is 0.5 mm higher than the leading edge of the back edge. A two-blade blade having a blade angle of 22 ° with a front blade angle of 0.11 mm was used.
About the obtained heat conductive sheet, Mooney viscosity, volume standard mode diameter of particulate carbon material, Asker C hardness, and heat conductivity were measured by the above-mentioned method. The results are shown in Table 1.

(Example 2)
In the step of preparing the composite mixture, the matrix resin is made of a thermoplastic fluororesin that is solid at room temperature and normal pressure, which is different from that in Example 1 (trade name “A-100”, manufactured by Kemers, Mooney viscosity: 30.2 ML _{1. A} heat conductive sheet was produced in the same manner as in Example 1 except that the temperature was changed to ₊₄ , 100 ° C. Various measurements similar to those in Example 1 were performed. The results are shown in Table 1.

(Example 3)
In the step of preparing the composite mixture, the amount of expanded graphite as the particulate carbon material was changed to 100 parts. Also, the resin was changed to a thermoplastic fluororesin that was solid at room temperature and normal pressure (product name “A-100”, product name “A-100”, Mooney viscosity: 30.2 ML _{1 + 4} , 100 ° C.) different from Example 1. A heat conductive sheet was produced in the same manner as in Example 1 except that. Various measurements similar to those in Example 1 were performed. The results are shown in Table 1.

(Example 4)
In the step of preparing the composite mixture, the base resin is made of a thermoplastic fluororesin that is solid at room temperature and normal pressure, which is different from that in Example 1 (Daikin Industries, trade name “DAI_EL (registered trademark) G-704BP”, (Mooney viscosity: 62.4 ML _{1 + 4} , 100 ° C.) A heat conductive sheet was produced in the same manner as in Example 1 except that the viscosity was changed to 100). Various measurements similar to those in Example 1 were performed. The results are shown in Table 1.

(Example 5)
In the step of preparing the composite mixture, the base resin is made of a thermoplastic fluororesin that is solid at room temperature and atmospheric pressure, which is different from that in Example 1 (Daikin Industries, trade name “DAI_EL® G-912”), A heat conductive sheet was produced in the same manner as in Example 1 except that the Mooney viscosity was changed to 87.6 ML _{1 + 4} , 100 ° C. Various measurements similar to those in Example 1 were performed. The results are shown in Table 1.

(Example 6)
In the step of preparing the composite mixture, the amount of expanded graphite as the particulate carbon material was changed to 160 parts. The base resin was changed to a solid thermoplastic silicone resin (trade name “KE-931-U”, Mooney viscosity: 18.0 ML _{1 + 4} , 100 ° C., manufactured by Shin-Etsu Chemical Co., Ltd.) at room temperature and normal pressure. A heat conductive sheet was produced in the same manner as in Example 1 except that. Various measurements similar to those in Example 1 were performed. The results are shown in Table 1.

(Example 7)
In the step of preparing the composite mixture, the amount of expanded graphite as the particulate carbon material was changed to 220 parts. In addition, the base resin is made into a solid thermoplastic nitrile rubber (manufactured by Zeon Corporation, trade name “Nipol (registered trademark) DN3335”, Mooney viscosity: 35.0 ML _{1 + 4} , 100 ° C.) under normal temperature and normal pressure. A heat conductive sheet was produced in the same manner as in Example 1 except for the change. Various measurements similar to those in Example 1 were performed. The results are shown in Table 1.

(Example 8)
In the step of preparing the composite mixture, the amount of expanded graphite as the particulate carbon material was changed to 210 parts. Other than changing the base resin to a thermoplastic acrylic resin (manufactured by Nippon Zeon Co., Ltd., trade name “AR-12”, Mooney viscosity: 33.0 ML _{1 + 4} , 100 ° C.) under normal temperature and normal pressure. Produced a heat conductive sheet in the same manner as in Example 1. Various measurements similar to those in Example 1 were performed. The results are shown in Table 1.

Example 9
In the step of preparing the composite mixture, the amount of expanded graphite as the particulate carbon material was changed to 70 parts. In addition, the base resin is a thermoplastic fluororesin that is solid at room temperature and atmospheric pressure, which is different from that in Example 1 (manufactured by Chemers, trade name “A-100”, Mooney viscosity: 30.2 ML _{1 + 4} , 100 ° C.). A heat conductive sheet was produced in the same manner as in Example 1 except that the above was changed. Various measurements similar to those in Example 1 were performed. The results are shown in Table 1.

From Table 1, a heat conductive sheet obtained by laminating a plurality of pre-heat conductive sheets containing a particulate carbon material and a resin component having a Mooney viscosity of 90 (ML _{1 + 4} , 100 ° C.) or less in a direction transverse to the thickness direction. Is excellent in the thermal conductivity in the thickness direction.

According to the present invention, it is possible to provide a heat conductive sheet having excellent heat conductivity in the thickness direction.

Claims (4)

A heat conductive sheet,
A pre-heat conductive sheet containing a particulate carbon material and a kind of resin or a composite of a plurality of resins is laminated in a plurality of layers in a transverse direction with respect to the thickness direction of the heat conduction sheet, and the kind of resin or The heat conductive sheet whose Mooney viscosity of all the resin components which consist of a composite of multiple types of resin is 90 (ML1 _{+ 4} , 100 degreeC) or less. 2. The heat conduction according to claim 1, wherein when the Mooney viscosity of all the resin components is X and the heat conductivity in the thickness direction of the heat conduction sheet is Y, the relational expression: Y> (− 0.2X + 25) is satisfied. Sheet. The heat conductive sheet according to claim 1 or 2, wherein the Asker C hardness is 45 or more. The heat conductive sheet according to any one of claims 1 to 3, wherein a content ratio of the particulate carbon material is 35% by volume or more.