JP2018067695A - Thermal conductive sheet and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat conductive sheet containing a resin and a particulate carbon material and exhibit excellent heat conductivity when used at a relatively low holding pressure, and a method for producing the heat conductive sheet. SOLUTION: The surface roughness Sz of at least one main surface is 3.5 μm or less, and the thermal resistance value under 0.05 MPa pressurization is 0.25 ° C./W or less, which contains a resin and a particulate carbon material. There is a heat conductive sheet. In addition, a step A of laminating a plurality of primary heat conductive sheets containing a resin and a particulate carbon material in the thickness direction, or folding or winding the primary heat conductive sheets to obtain a laminated body, and the laminated body. Is sliced at an angle of 45 ° or less with respect to the stacking direction to obtain a secondary heat conductive sheet, and a step C of pressurizing the secondary heat conductive sheet to obtain a heat conductive sheet. Sheet manufacturing method. [Selection diagram] None

Description

  The present invention relates to a heat conductive sheet and a method for producing the heat conductive sheet.

  In recent years, electronic components such as plasma display panels (PDP) and integrated circuit (IC) chips have increased in heat generation 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. And when using a radiator, in order to efficiently transfer heat from the heater to the radiator, heat is usually generated with a sheet-like member (heat conductive sheet) having high thermal conductivity interposed. The body and the radiator are in close contact.
Accordingly, it has been demanded that a heat conductive sheet used by being sandwiched between a heat generating body and a heat radiating body exhibit excellent thermal conductivity under pressure due to being sandwiched.

  Here, in general, in order to increase the thermal conductivity of the heat conductive sheet when used by being sandwiched between the heat generator and the heat radiator, the thermal resistance value of the heat conductive sheet under pressure by being sandwiched is reduced. It is possible to make it.

For example, in Patent Document 1, a silicone resin composition obtained by mixing a silicone resin, pitch-based carbon fibers, alumina particles, and aluminum nitride is molded and sliced while heat-curing the silicone resin. The silicone resin composition is formed into a sheet shape. Furthermore, in patent document 1, the sheet | seat of the obtained silicone resin composition is manufactured by pressing for 30 minutes with the load of ² kgf / cm < ² > -8kgf / cm <2> at normal temperature. And in patent document 1, while pressing the sheet | seat of a silicone resin composition, the smoothness of the surface of the heat conductive sheet obtained is improved, adhesiveness is improved, and pitch system carbon fiber inside a heat conductive sheet is favorable. The thermal resistance value is lowered by contacting the surface.
In Patent Document 2, a polyacrylate polymer compound derived from butyl acrylate, scaly graphite, and a phosphate ester flame retardant are kneaded and applied to a hydraulic press and a metal roll to obtain a primary product. A sheet is formed. Further, in Patent Document 2, a heat conductive sheet is manufactured by compressing a slice sheet obtained by laminating and slicing the obtained primary sheet at 30% under a temperature of 80 ° C. using a metal roll. . And in the heat conductive sheet of patent document 2, intensity | strength etc. are raised, maintaining the thermal resistance value similar to the slice sheet | seat which was not compressed in the measurement under 1.0 Mpa.

Japanese Patent No. 5541400 Japanese Patent Laying-Open No. 2015-084431

  Here, from the viewpoint of workability, for example, the heat conductive sheet has a pressure applied to the heat conductive sheet when it is sandwiched between the heat generator and the heat radiator (hereinafter, may be referred to as “clamping pressure”). It may be used in a relatively low pressure state of 0.08 MPa or less. However, as for the conventional heat conductive sheets described in Patent Documents 1 and 2, when the present inventors have intensively studied, when the sheet is pressed as in the prior art, the thermal resistance at a low clamping pressure is increased. It became clear that there was a problem.

Accordingly, an object of the present invention is to provide a heat conductive sheet that includes a resin and a particulate carbon material and exhibits excellent thermal conductivity when used at a relatively low clamping pressure, and a method for producing the heat conductive sheet. And
Here, in the present invention, the “relatively low clamping pressure” means that the clamping pressure is 0.08 MPa or less (absolute pressure).

  The present inventors have intensively studied to achieve the above object. Then, the present inventors, in the heat conductive sheet containing the resin and the particulate carbon material, if the surface roughness of at least one main surface is set to a predetermined value or less and the heat resistance value is set to a predetermined value or less, the obtained heat conduction It was found that the sheet can exhibit excellent thermal conductivity when used at a relatively low clamping pressure, and the present invention has been completed.

That is, this invention aims at solving the said subject advantageously, The heat conductive sheet of this invention contains resin and a particulate carbon material, The surface roughness Sz of at least one main surface is It is 3.5 μm or less, and the thermal resistance value under a pressure of 0.05 MPa is 0.25 ° C./W or less. Thus, if the heat conductive sheet containing the resin and the particulate carbon material has a smooth main surface having a surface roughness less than or equal to the predetermined value, and a low heat resistance value not greater than or equal to the predetermined value, a relatively low clamping pressure is obtained. Excellent thermal conductivity can be exhibited during use. Therefore, when the heat conductive sheet of the present invention is attached to the heating element, heat can be efficiently dissipated from the heating element.
In the present invention, the “surface roughness Sz” is the maximum height (distance in the height direction connecting the highest point and the lowest point on a certain surface) defined in the international standard ISO 25178, It is an index for evaluating the roughness state of the certain surface. In the present invention, the “surface roughness Sz” can be measured by a method described in the examples of the present specification using a three-dimensional shape measuring machine.
Further, in the present invention, the “thermal resistance value” can be measured by a steady-state method using a thermal resistance measuring device by the method described in the examples of the present specification.

The heat conductive sheet of the present invention preferably has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 50.0 or less. This is because if the Mooney viscosity is set to the above upper limit or less, the heat conductive sheet can exhibit more excellent heat conductivity at a relatively low clamping pressure.
In the present invention, the “Mooney viscosity (ML _{1 + 4} , 100 ° C.)” is a method described in the examples of the present specification using a Mooney viscometer at a temperature of 100 ° C. according to JIS K6300. Can be measured.

  In the heat conductive sheet of the present invention, it is preferable that the resin is not cured. When a resin cured by crosslinking or the like is used, the composition and the molded body are not easily deformed when the composition or the molded body containing the resin is heated. Therefore, for example, when a heat conductive sheet is formed by applying pressure (heat press) while heating a composition or a molded body containing a cured resin, the surface of the resulting heat conductive sheet is inferior in smoothness. is there.

  And as for the heat conductive sheet of this invention, it is preferable that the said resin is a fluororesin. This is because when the heat conductive sheet contains a fluororesin, excellent heat resistance, oil resistance, and chemical resistance can be provided in addition to good flexibility.

  Moreover, this invention aims at solving the said subject advantageously, and the manufacturing method of the heat conductive sheet of this invention has multiple primary heat conductive sheets containing resin and a particulate carbon material in the thickness direction. Laminating the sheets or folding or winding the primary heat conductive sheet to obtain a laminate, and slicing the laminate at an angle of 45 ° or less with respect to the lamination direction, The method includes a step B of obtaining a conductive sheet and a step C of pressing the secondary heat conductive sheet to obtain any of the predetermined heat conductive sheets described above. Here, one of the predetermined heat conductive sheets described above is a heat conductive sheet that satisfies at least the following conditions. That is, heat containing a resin and a particulate carbon material, having a surface roughness Sz of at least one main surface of 3.5 μm or less, and a thermal resistance value under a pressure of 0.05 MPa of 0.25 ° C./W or less. It is a conductive sheet. Thus, the predetermined heat conductive sheet manufactured by pressurizing the secondary heat conductive sheet obtained by slicing the laminate including the primary heat conductive sheet has excellent heat conductivity at a relatively low clamping pressure. Can be demonstrated. Therefore, if the heat conductive sheet obtained according to the production method of the present invention is attached to the heating element, heat can be efficiently dissipated from the heating element.

  Moreover, the manufacturing method of the heat conductive sheet of this invention is the process D which prepares the composition containing resin and a particulate carbon material before the said process A, and pressurizes the said composition, and shape | molds it in a sheet form, It is preferable to further include the step E of obtaining a primary heat conductive sheet, and to use the primary heat conductive sheet obtained in the step E in the step A. That is, in the manufacturing method of the heat conductive sheet of the present invention, in the step A of obtaining the above-described laminate, the primary heat conductive sheet obtained through the step D of preparing the composition and the step E of obtaining the primary heat conductive sheet. It is preferable to obtain a laminate by laminating a plurality of sheets in the thickness direction or by folding or winding the primary heat conductive sheet. As described above, if the obtained laminate is sliced under predetermined conditions and further pressurized, a heat conductive sheet excellent in thermal conductivity particularly in the thickness direction can be produced satisfactorily at a relatively low clamping pressure. Because it can.

  In the method for producing a heat conductive sheet of the present invention, it is preferable that the resin is a thermoplastic resin and no curing agent is used for the resin. When a resin cured by crosslinking or the like is used, for example, when a heat conductive sheet is formed by hot pressing a secondary heat conductive sheet containing the resin, the surface of the obtained heat conductive sheet is inferior in smoothness. is there.

In the method for producing a heat conductive sheet of the present invention, the secondary heat conductive sheet preferably has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 50.0 or less. When the Mooney viscosity is set to the above upper limit or less, the secondary heat conductive sheet and the heat conductive sheet are more easily deformed, so that the surface smoothness and the thermal resistance value at a relatively low clamping pressure are improved. Therefore, the heat conductive sheet can exhibit further excellent heat conductivity at a relatively low clamping pressure.

  Moreover, it is preferable that the pressure of the pressurization in the said process C is 0.8 MPa or more and 5.0 MPa or less as for the manufacturing method of the heat conductive sheet of this invention. If the secondary heat conductive sheet is pressurized at the above lower limit or more, the sheet surface becomes smoother and the heat conductive sheet can exhibit more excellent thermal conductivity even when used at a relatively low clamping pressure. It is. Further, if the secondary heat conductive sheet is pressurized below the above upper limit, for example, the good orientation of the particulate carbon material in the secondary heat conductive sheet is prevented from breaking, and the heat conductive sheet at a relatively low clamping pressure. This is because the excellent thermal conductivity can be maintained better.

And in the said process C, the manufacturing method of the heat conductive sheet of this invention compresses the said secondary heat conductive sheet to make a heat conductive sheet, The reduction rate of the sheet thickness by the said compression is 15% or more and 40% or less It is preferable. This is because if the sheet thickness reduction rate is equal to or greater than the above lower limit, a heat conductive sheet having a smoother surface and further improved thermal conductivity can be obtained even when used at a relatively low clamping pressure. Further, if the sheet thickness reduction rate is less than or equal to the above upper limit, for example, it ensures good orientation of the particulate carbon material in the heat conductive sheet, and excellent heat conductivity of the heat conductive sheet at a relatively low clamping pressure. This is because it is possible to maintain better.
In the present invention, the “sheet thickness reduction rate” is expressed by the following formula (1):
Reduction rate of sheet thickness (%) =
(Secondary heat conductive sheet thickness (mm)-Heat conductive sheet thickness (mm))
/ Thickness of secondary heat conductive sheet (mm) × 100 (1)
Can be calculated according to Here, the thickness of each sheet | seat can be measured by the method as described in the Example of this specification.

ADVANTAGE OF THE INVENTION According to this invention, the heat conductive sheet which contains resin and a particulate carbon material and exhibits the outstanding heat conductivity in the case of use with a comparatively low clamping pressure can be provided.
In addition, according to the present invention, there is provided a method for producing a heat conductive sheet, which can produce a heat conductive sheet that includes a resin and a particulate carbon material and exhibits excellent heat conductivity when used at a relatively low clamping pressure. can do.

Hereinafter, embodiments of the present invention will be described in detail.
The heat conductive sheet of the present invention can be used, for example, by being sandwiched between a heat generator and a heat radiator when the heat radiator is attached to the heat generator. That is, the heat conductive sheet of this invention can comprise a heat radiating device with heat sinks, such as a heat sink, a heat sink, and a heat radiating fin.
And the heat conductive sheet of this invention can be manufactured according to the manufacturing method of the heat conductive sheet of this invention, for example.

(Heat conduction sheet)
The heat conductive sheet of the present invention includes a resin and a particulate carbon material, and may optionally further include a fibrous carbon material and an additive. In the heat conductive sheet of the present invention, the surface roughness Sz of at least one main surface (a surface orthogonal to the thickness direction of the heat conductive sheet) is 3.5 μm or less. Furthermore, the heat conductive sheet of the present invention has a thermal resistance value of 0.25 ° C./W or less under a pressure of 0.05 MPa. The heat conductive sheet of the present invention includes a resin and a particulate carbon material, the surface roughness Sz of at least one main surface is smooth with a predetermined value or less, and the thermal resistance value under a low pressure of 0.05 MPa. Is as low as a predetermined value or less, so that the thermal conductivity in use at a relatively low clamping pressure is excellent. Accordingly, when the heat conductive sheet of the present invention is used in combination with a heat sink such as a heat sink, a heat sink, or a heat sink, the heat conductive sheet is sandwiched between the heat generator and the heat sink with a relatively low clamping pressure. Even if it is a case, heat can be effectively dissipated from the heating element through the heat conductive sheet.

Here, the heat resistance value of the heat conductive sheet is the sum of the value of the bulk heat resistance, which is the heat resistance of the heat conductive sheet itself, and the value of the interfacial heat resistance at the interface between the heat conductive sheet and the heating element / heat radiator. it is conceivable that.
For example, the value of the bulk thermal resistance of the heat conductive sheet is derived from the composition and properties of the heat conductive sheet, and the following formula (2):
Value of bulk thermal resistance (K · m ² / W)
= Thickness (m) / Thermal conductivity (W / m · K) (2)
It can be shown by the relationship.
In addition, the value of the interfacial thermal resistance of the heat conductive sheet includes the adhesion at the interface between the heat generating element and the heat radiating body and the heat conductive sheet (interfacial adhesion), the difference in the bulk heat resistance between the heat generating element and the heat conductive sheet, and the heat dissipation. This is due to the difference in bulk thermal resistance between the body and the heat conductive sheet.

<Resin>
As resin which the heat conductive sheet of this invention contains, it is not specifically limited, Well-known resin which can be used for a heat conductive sheet, for example, a thermoplastic resin and a thermosetting resin, can be used.

  Here, the resin is preferably not cured. That is, the resin is preferably a thermoplastic resin, and more preferably not used in combination with a curing agent such as a crosslinking agent and a vulcanizing agent. When a cured resin is used, the composition and the molded body are not easily deformed when the composition or the molded body containing the resin is heated. Therefore, for example, when a heat conductive sheet is formed by hot pressing a composition or a molded body (for example, a secondary heat conductive sheet described later) containing a cured resin, the surface of the obtained heat conductive sheet is deformed. This is because it is difficult to be performed and is inferior in smoothness. In other words, if the resin is used without curing, for example, when a heat conductive sheet is formed by hot pressing a composition or a molded body (for example, a secondary heat conductive sheet described later) containing the resin, It is because the surface smoothness of the heat conductive sheet obtained can be made better.

The type of the resin is not particularly limited, and examples thereof include a fluororesin, a silicone resin, an acrylic resin, and a urethane resin as described in detail below. Among these, as the resin, a fluororesin and a silicone resin are preferable, a thermoplastic fluororesin and a thermoplastic silicone resin are more preferable, and a thermoplastic fluororesin is still more preferable. This is because if a fluororesin and a silicone resin are used, in particular, if a fluororesin is used, the heat resistance, oil resistance, and chemical resistance of the heat conductive sheet can be further improved in addition to flexibility.
In the present invention, rubber and elastomer are included in “resin”.

<< Thermoplastic resin >>
Here, examples of the thermoplastic resin include a thermoplastic resin that is solid at normal temperature and pressure, and a thermoplastic resin that is liquid at normal temperature and pressure. Among them, in the heat conductive sheet of the present invention, it is preferable to use a thermoplastic resin that is solid at room temperature and normal pressure as the thermoplastic resin, and is a solid thermoplastic fluororesin and / or solid at room temperature and normal pressure. It is more preferable to use a thermoplastic silicone resin, and it is more preferable to use a thermoplastic thermoplastic resin that is solid at least at normal temperature and pressure. If a solid thermoplastic resin is used under normal temperature and normal pressure, in a high temperature environment during use (during heat dissipation), the flexibility of the heat conductive sheet obtained using the composite particles is further improved, This is because the handling property of the heat conductive sheet can be improved in a normal temperature environment such as when the heat generating body and the heat radiating body are in close contact with each other. In addition to the above effects, using a thermoplastic fluororesin that is solid at normal temperature and pressure and a thermoplastic silicone resin that is solid at normal temperature and pressure will further improve the heat resistance, oil resistance, and chemical resistance of the heat conductive sheet. Because it can.
In this specification, “normal temperature” refers to 23 ° C., and “normal pressure” refers to 1 atm (absolute pressure).

[Thermoplastic resin solid at normal temperature and pressure]
Here, as the thermoplastic resin solid at normal temperature and normal pressure, for example, poly (2-ethylhexyl acrylate), a copolymer of acrylic acid and 2-ethylhexyl acrylate, polymethacrylic acid or its ester, polyacrylic acid Or acrylic resins such as esters thereof; silicone resins; fluororesins; polyethylenes; polypropylenes; ethylene-propylene copolymers; polymethylpentenes; polyvinyl chlorides; polyvinylidene chlorides; polyvinyl acetates; Polyethylene terephthalate; Polybutylene terephthalate; Polyethylene naphthalate; Polystyrene; Polyacrylonitrile; Styrene-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 or hydrogenated product thereof; polyphenylene ether; modified polyphenylene ether; aliphatic Polyamides; Aromatic polyamides; Polyamideimide; Polycarbonate; Polyphenylene sulfide; Polysulfone; Polyethersulfone; Polyethernitrile; Polyetherketone; Polyketone; Polyurethane; Liquid crystal polymer; These may be used individually by 1 type and may use 2 or more types together.

  Furthermore, the heat conductive sheet of the present invention preferably uses at least one of a thermoplastic fluororesin that is solid at normal temperature and normal pressure and a thermoplastic silicone resin that is solid at normal temperature and normal pressure, and is at least a thermoplastic fluorocarbon that is solid at normal temperature and normal pressure. It is more preferable to use a resin, and it is more preferable to use a thermoplastic fluororesin that is solid at normal temperature and pressure and a thermoplastic fluororesin that is liquid at normal temperature and pressure. If at least one of a thermoplastic fluororesin that is solid at normal temperature and pressure and a thermoplastic silicone resin that is solid at normal temperature and pressure are used, the heat conduction sheet can be more flexible in a high temperature environment during use (heat dissipation). This is because the heat conduction sheet, the heating element, and the heat radiating body are more closely adhered to each other and the interfacial thermal resistance during use at a relatively low clamping pressure can be further reduced. In addition, if at least one of a thermoplastic fluororesin that is solid at normal temperature and normal pressure and a thermoplastic silicone resin that is solid at normal temperature and normal pressure are used, the handling of the heat conductive sheet can be improved in a normal temperature environment such as mounting. Because it can.

<< Solid thermoplastic fluororesin at normal temperature and pressure >>
Examples of thermoplastic fluororesins that are solid at room temperature and normal pressure include polymerizing fluorine-containing monomers such as vinylidene fluoride fluororesins, tetrafluoroethylene-propylene fluororesins, tetrafluoroethylene-purple olovinyl ether fluororesins, and the like. Examples include elastomers obtained. More specifically, polytetrafluoroethylene, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-ethylene copolymer, polyvinylidene fluoride, vinylidene fluoride. Ride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, polychlorotrifluoroethylene, ethylene-chlorofluoroethylene copolymer, tetrafluoroethylene-perfluorodioxole copolymer Polymer, polyvinyl fluoride, tetrafluoroethylene-propylene copolymer, acrylic modified product of polytetrafluoroethylene, ester modified product of polytetrafluoroethylene Epoxy-modified product of polytetrafluoroethylene and polytetrafluoroethylene silane modified product, and the like. These may be used individually by 1 type and may use 2 or more types together.
Among these, vinylidene fluoride-hexafluoropropylene copolymer is preferable from the viewpoint of processability.
In the present invention, rubber and elastomer are included in “resin”.

  Examples of commercially available thermoplastic fluororesins that are solid at room temperature and normal pressure include, for example, Daiel (registered trademark) G-300 series / G-700 series / G-7000 series (polyol added) manufactured by Daikin Industries, Ltd. Sulfur / vinylidene fluoride-hexafluoropropylene binary copolymer), Daiel G-550 series / G-600 series (polyol vulcanization / vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer) Daiel G-800 series (peroxide vulcanized vinylidene fluoride-hexafluoropropylene binary copolymer), Daiel G-900 series (peroxide vulcanized vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene 3) Binary copolymer KYNAR (registered trademark) series (vinylidene fluoride fluoropolymer), KYNAR FLEX (registered trademark) series (vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer) manufactured by ALKEMA; manufactured by Chemers A-100 (vinylidene fluoride-hexafluoropropylene binary copolymer); and the like.

<< Thermoplastic fluororesin that is liquid at normal temperature and pressure >>
Examples of the thermoplastic fluororesin that is liquid at normal temperature and pressure include, for example, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-hexafluoropentene-tetrafluoroethylene ternary. Examples thereof include a copolymer, a perfluoropropene oxide polymer, and a tetrafluoroethylene-propylene-vinylidene fluoride copolymer.

  Moreover, as a commercially available thermoplastic fluororesin that is liquid at normal temperature and normal pressure, for example, Viton (registered trademark) LM manufactured by DuPont, Daiel (registered trademark) G-101 manufactured by Daikin Industries, Ltd., 3M Examples include DINION (registered trademark) FC2210 manufactured by Corporation, SIFEL series manufactured by Shin-Etsu Chemical Co., Ltd., and the like.

  Here, the viscosity of the thermoplastic fluororesin that is liquid under normal temperature and normal pressure is not particularly limited, but from the viewpoint of fluidity, kneadability, and moldability, it is preferably 500 cP or more and 30000 cP or less at a temperature of 105 ° C. More preferably, it is 550 cP or more and 25000 cP or less.

<< Solid thermoplastic silicone resin at room temperature and normal pressure >>
Furthermore, as thermoplastic silicone resin solid at normal temperature and normal pressure, for example, commercially available KE-931-U, KE-941-U, KE-951-U, KE-961-U manufactured by Shin-Etsu Chemical Co., Ltd. KE-971-U, KE-981-U, KE-961T-U, KE-971T-U, and the like can be used.

<< Blending ratio >>
The compounding ratio in terms of mass when using a thermoplastic fluororesin that is solid at normal temperature and pressure and a thermoplastic fluororesin that is liquid at normal temperature and pressure as the resin is not particularly limited, and is solid at normal temperature and normal pressure. Thermoplastic fluororesin: The liquid thermoplastic fluororesin can be 40:60 to 70:30 at room temperature and normal pressure.

<Particulate carbon material>
The particulate carbon material included in the heat conductive sheet of the present invention is not particularly limited, and examples thereof include natural graphite, artificial graphite, flake graphite, exfoliated graphite, acid-treated graphite, expandable graphite, and expanded graphite. Graphite; carbon black; etc. can be used. These may be used individually by 1 type and may use 2 or more types together. If the heat conductive sheet does not contain a particulate carbon material, the heat conductive sheet cannot exhibit excellent heat conductivity at a relatively low clamping pressure.
Among them, it is preferable to use expanded graphite as the particulate carbon material. This is because if expanded graphite is used, the thermal conductivity of the thermal conductive sheet can be further improved.

<< Expanded graphite >>
Here, the expanded graphite that can be suitably used as the particulate carbon material is, for example, 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.

<< Particle diameter of particulate carbon material >>
The particle diameter of the particulate carbon material is preferably 100 μm or more in terms of volume average particle diameter, more preferably 150 μm or more, and preferably 300 μm or less. If the particle diameter of the particulate carbon material is greater than or equal to the above lower limit, the particulate carbon material is easily oriented in a desired direction in the heat conductive sheet, and a good heat transfer path is easily formed. Therefore, even if the holding pressure is relatively low, the bulk thermal resistance of the heat conductive sheet can be further lowered and higher heat conductivity can be exhibited. Further, if the particle diameter of the particulate carbon material is not more than the above upper limit, the surface of the heat conductive sheet is made smoother, and heat transfer from the heat generator to the heat conductive sheet is better when contacting the heat generator. Because you can.
In the present invention, the “volume average particle diameter” can be measured according to JIS Z8825, and in the particle size distribution (volume basis) measured by the laser diffraction method, the cumulative volume calculated from the small diameter side is 50%. Represents the particle diameter.

<< Aspect ratio of particulate carbon material >>
The aspect ratio (major axis / minor axis) of the particulate carbon material is preferably 1 or more and 10 or less, and more preferably 1 or more and 5 or less.
In the present invention, the “aspect ratio of the particulate carbon material” means that the particulate carbon material is observed with a scanning electron microscope (SEM). It can be determined by measuring the particle diameter (minor axis) in the direction orthogonal to the maximum diameter and calculating the average value of the ratio of the major axis to the minor axis (major axis / minor axis).

<< Blending amount of particulate carbon material >>
The compounding amount of the particulate carbon material is preferably 50 parts by mass or more, more preferably 80 parts by mass or more, and preferably 300 parts by mass or less with respect to 100 parts by mass of the resin. 200 parts by mass or less, more preferably 150 parts by mass or less, and still more preferably 120 parts by mass or less. If the compounding amount of the particulate carbon material in the heat conductive sheet is not less than the above lower limit, the bulk heat resistance of the heat conductive sheet at a relatively low clamping pressure can be further reduced. Moreover, if the compounding amount of the particulate carbon material in the heat conductive sheet is less than the above upper limit, the sheet is prevented from becoming harder than necessary, and for example, the surface of the secondary heat conductive sheet is further smoothed by pressurization. In addition, the surface of the heat conductive sheet can be more easily deformed even with a low clamping pressure, and the followability to the heating element and the heat dissipation element can be further improved. As a result, high heat conductivity can be exhibited by the heat conductive sheet at a relatively low clamping pressure.

<Fibrous carbon material>
The heat conductive sheet of the present invention may optionally further contain a fibrous carbon material. The fibrous carbon material optionally 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.
If the fibrous carbon material is further included in the thermal conductive sheet of the present invention, the thermal conductivity of the thermal conductive sheet when used at a relatively low clamping pressure can be further improved, and the particulate carbon material It is also possible to prevent powder from falling off. Although it is not clear why the particulate carbon material can be prevented from falling off by blending the fibrous carbon material, the fibrous carbon material forms a three-dimensional network structure, thereby improving thermal conductivity and This is presumably because the detachment of the particulate carbon material is prevented 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 the use of fibrous carbon nanostructures such as carbon nanotubes can further improve the thermal conductivity and strength of the thermal conductive sheet.

<< Fibrous carbon nanostructure 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 if single-walled carbon nanotubes are used, the thermal conductivity and strength of the thermal conductive sheet can be further improved as compared with the case where multi-walled carbon nanotubes are used.

  In the above points, the fibrous carbon nanostructure containing CNT preferably 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.

[Average diameter (Av) of fibrous carbon nanostructure containing CNT]
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. Is more preferable. If the average diameter (Av) of the fibrous carbon nanostructure containing CNT is not less than the above lower limit, the fibrous carbon nanostructure containing CNT is suppressed by suppressing aggregation of the fibrous carbon nanostructure containing CNT. It is because the dispersibility of a body can be improved. Moreover, if the average diameter (Av) of the fibrous carbon nanostructure containing CNT is not more than the above upper limit, the thermal conductivity and strength of the thermal conductive sheet can be sufficiently increased.
The “average diameter (Av) of fibrous carbon nanostructures containing CNTs” is the diameter (outside of 100 fibrous carbon nanostructures containing CNTs randomly selected using a transmission electron microscope). (Diameter) can be measured. And the average diameter (Av) of the fibrous carbon nanostructure containing CNT may be adjusted by changing the manufacturing method and manufacturing conditions of the fibrous carbon nanostructure containing CNT, or different manufacturing methods. You may adjust by combining multiple types of fibrous carbon nanostructures containing CNT obtained by above.

[3σ / Av]
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 fibrous carbon nanostructure of less than 0.60, more preferably to use a fibrous carbon nanostructure with 3σ / Av exceeding 0.25, and with 3σ / Av exceeding 0.50. It is more preferable to use a fibrous carbon nanostructure. If a fibrous carbon nanostructure having 3σ / Av of more than 0.20 and less than 0.60 is used, the heat of the heat conducting sheet can be obtained even if the amount of the fibrous carbon nanostructure containing CNT is small. This is because the conductivity and strength can be sufficiently increased. Therefore, the thermal conductivity and flexibility of the thermal conductive sheet are suppressed by suppressing the increase in the hardness of the thermal conductive sheet (ie, the decrease in flexibility) due to the incorporation of the fibrous carbon nanostructure containing CNTs. This is because both can be achieved at a sufficiently high level.
The “standard deviation of the diameter of the fibrous carbon nanostructure containing CNT (σ: sample standard deviation)” is the above-mentioned “average diameter (Av) of the fibrous carbon nanostructure containing CNT”. It can be determined in a similar manner. And the said standard deviation ((sigma)) may be adjusted by changing the manufacturing method and manufacturing conditions of the fibrous carbon nanostructure containing CNT, or the fibrous form containing CNT obtained by a different manufacturing method You may adjust by combining multiple types of carbon nanostructure.

  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.

[Average length of fibrous carbon nanostructure containing CNT]
The average length of the fibrous carbon nanostructure containing CNT is preferably 100 μm or more. Moreover, from the viewpoint of suppressing the occurrence of damage such as breakage or cutting in the CNTs during dispersion, the average length of the fibrous carbon nanostructure containing CNTs is preferably 5000 μm or less.

[Specific surface area of fibrous carbon nanostructure containing CNT]
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. This is because if the BET specific surface area of the fibrous carbon nanostructure containing CNTs is not less than the above lower limit, the thermal conductivity and strength of the thermal conductive sheet can be sufficiently increased. Further, if the BET specific surface area of the fibrous carbon nanostructure containing CNT is less than or equal to the above upper limit, the dispersibility of CNT or the like in the heat conductive sheet by suppressing aggregation of the fibrous carbon nanostructure containing CNT It is because it can raise.
In the present invention, the “BET specific surface area” refers to a nitrogen adsorption specific surface area measured using the BET method.

[Mass density of fibrous carbon nanostructure containing CNT]
Further, a fibrous carbon nanostructure containing CNTs is an aggregate oriented in a direction substantially perpendicular to the base material on a base material having a catalyst layer for CNT growth on the surface according to the super growth method described later. Although obtained as (aligned aggregate), the mass density of fibrous carbon nanostructures containing CNTs as the aggregate is preferably 0.002 g / cm ³ or more and 0.2 g / cm ³ or less. . If the mass density is less than or equal to the above upper limit, the bonding between the fibrous carbon nanostructures containing CNTs is weakened, so that the fibrous carbon nanostructures containing CNTs are uniformly dispersed in the heat conductive sheet. Because you can. Moreover, if the mass density is equal to or higher than the above lower limit, the integrity of the fibrous carbon nanostructure containing CNTs can be improved, and the handling can be facilitated because it can be prevented from being broken.

[G / D ratio of fibrous carbon nanostructure containing CNT]
Furthermore, the fibrous carbon nanostructure containing CNTs preferably has a G band peak intensity ratio (G / D ratio) of 1 to 20 in the Raman spectrum. If the G / D ratio is within the above range, the thermal conductivity and strength of the thermal conductive sheet can be sufficiently increased even if the amount of fibrous carbon nanostructures containing CNTs is small. is there. Therefore, it is possible to suppress the increase in the hardness of the heat conductive sheet by blending fibrous carbon nanostructures containing CNTs, and to make the heat conductivity and flexibility of the heat conductive sheet compatible at a sufficiently high level. Because it can.

[Preparation of fibrous carbon nanostructure containing CNT]
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 substrate having a catalyst layer for producing CNTs on the surface, When synthesizing CNTs by the growth method (CVD method), a method (supergrowth method; which dramatically improves the catalytic activity of the catalyst layer by allowing a small amount of an oxidizing agent (catalyst activation material) to be present in the system. According to WO 2006/011655), it can be produced efficiently. 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.

<< Aspect ratio of fibrous carbon material >>
The aspect ratio of the fibrous carbon material is preferably more than 10.
In the present invention, the “aspect ratio of the fibrous carbon material” is the SEM (scanning electron microscope) or TEM (transmission type) of the fibrous carbon material obtained by dissolving and removing the resin in the heat conductive sheet in a solvent. The maximum diameter (major axis) and the fiber diameter (minor axis) in the direction orthogonal to the maximum diameter are measured for any fifty fibrous carbon materials, and the ratio of the major axis to the minor axis ( It can be obtained by calculating an average value of (major axis / minor axis). In particular, when the fiber diameter is small, it is preferable to observe with a TEM (transmission electron microscope).

<< Blending amount of fibrous carbon material >>
And when a heat conductive sheet further contains fibrous carbon material, it is preferable that the compounding quantity of fibrous carbon material is 0.05 mass part or more with respect to 100 mass parts of resin mentioned above, 0.1 mass The amount is more preferably at least 5 parts by weight, more preferably at most 5 parts by weight, and even more preferably at most 2 parts by weight. If the blending amount of the fibrous carbon material in the heat conductive sheet is not less than the above lower limit, the heat conductivity and strength of the heat conductive sheet at a relatively low clamping pressure can be sufficiently improved, and the particulate carbon material This is because powder fall can be sufficiently prevented. Moreover, if the content rate of the fibrous carbon material in a heat conductive sheet is below the said upper limit, it suppresses that the hardness of a heat conductive sheet raises by the mixing | blending of a fibrous carbon material, The heat conductive sheet of this invention This is because thermal conductivity and flexibility can be achieved at a sufficiently high level.

<Additives>
If necessary, the heat conductive sheet of the present invention may further contain known additives that can be used for forming the heat conductive sheet. The additive that can be blended in the heat conductive sheet is not particularly limited. For example, a plasticizer such as a fatty acid ester such as sebacic acid ester; a flame retardant such as a red phosphorus flame retardant or a phosphate ester flame retardant ; Toughness improvers such as urethane acrylate; Hygroscopic agents such as calcium oxide and magnesium oxide; Adhesive strength improvers such as silane coupling agents, titanium coupling agents and acid anhydrides; Nonionic surfactants, fluorinated surfactants Wettability improvers such as; ion trapping agents such as inorganic ion exchangers; and the like.

  And when a heat conductive sheet further contains an additive, the compounding quantity of an additive can be 0.1 to 20 mass parts with respect to 100 mass parts of resin mentioned above, for example, 10 masses Part or less.

<Surface roughness Sz>
The heat conductive sheet of the present invention requires that the surface roughness Sz of at least one main surface is 3.5 μm or less. If the surface roughness Sz of at least one main surface of the heat conductive sheet is not less than the predetermined value, the heat conductive sheet cannot exhibit excellent heat conductivity at a relatively low clamping pressure. In addition, the surface roughness Sz of the heat conductive sheet is not particularly limited, and can be appropriately adjusted, for example, by adjusting a pressurizing condition such as a method of pressing the secondary heat conductive sheet, pressure, time, and temperature.
Further, from the viewpoint of further improving the thermal conductivity of the heat conductive sheet at a relatively low clamping pressure, the heat conductive sheet preferably has a surface roughness Sz of at least one main surface of 3.0 μm or less. More preferably, it is 0.5 μm or less, preferably 1.0 μm or more, more preferably more than 1.1 μm, and still more preferably 1.2 μm or more. If the surface roughness Sz of at least one main surface of the heat conductive sheet is less than or equal to the above upper limit, the main surface is sufficiently smooth, so that the heat conductive sheet is relatively sandwiched between the heat generator and the heat radiator. This is because even when sandwiched between, the adhesion between the heat conductive sheet and the heating element and / or the radiator is further increased, and the interfacial thermal resistance is further reduced. Further, when the surface roughness Sz of at least one main surface of the heat conductive sheet is equal to or higher than the above lower limit, for example, when the heat conductive sheet is manufactured by pressurizing the secondary heat conductive sheet described later, the secondary heat conductive sheet This is because the desired orientation of the particulate carbon material and any fibrous carbon material in the heat conductive sheet can be ensured without excessively pressing, and low bulk thermal resistance can be ensured.
Furthermore, from the viewpoint of further increasing the thermal conductivity of the heat conductive sheet at a relatively low clamping pressure, the surface roughness Sz of both main surfaces (front surface and back surface) of the heat conductive sheet is within the preferred range. Further preferred.

<Thermal resistance value>
Moreover, the heat conductive sheet of this invention requires that the thermal resistance value under 0.05 MPa pressurization is 0.25 degrees C / W or less. If the thermal resistance value of the thermal conductive sheet is not less than the predetermined value, the thermal conductive sheet cannot exhibit excellent thermal conductivity when used at a relatively low clamping pressure such as 0.05 MPa.
Furthermore, from the viewpoint of further increasing the thermal conductivity of the heat conductive sheet at a relatively low clamping pressure, the heat resistance value of the heat conductive sheet is preferably 0.24 ° C./W or less under 0.05 MPa pressure. More preferably, it is 0.23 ° C./W or less. This is because if the thermal resistance value is less than or equal to the above upper limit, the thermal conductive sheet can exhibit more excellent thermal conductivity at a low clamping pressure such as 0.05 MPa.

  From the viewpoint of exhibiting excellent thermal conductivity in the heat conductive sheet even when used at a relatively high clamping pressure, the heat conductive sheet of the present invention has a thermal resistance value of 0.1 at a pressure of 0.9 MPa. It is preferable that it is below ℃ / W.

<Mooney viscosity>
The heat conductive sheet of the present invention preferably has a Mooney viscosity (ML _{1 + 4} , 100 ° C.) of 10.0 or more, preferably 50.0 or less, and preferably 40.0 or less. More preferably, it is 20.0 or less. If the Mooney viscosity is less than or equal to the above upper limit, the components in the heat conductive sheet have good fluidity when pressed and can be easily deformed even at a relatively low clamping pressure, generating heat. The followability to the body and the heat radiating body is increased. Therefore, the heat conductivity of the heat conductive sheet when used at a relatively low clamping pressure can be improved. Moreover, if Mooney viscosity is more than the said minimum, it will receive moderate force, when the component in a heat conductive sheet is pressurized, having moderate intensity | strength as a heat conductive sheet. Therefore, even when the heat conductive sheet is used while being pressed with a relatively low holding pressure, the effect of the holding pressure is sufficiently obtained, the interfacial thermal resistance of the heat conductive sheet is further reduced, and the heat conductive sheet This is because the thermal conductivity of can be improved.
Normally, the Mooney viscosity of the heat conductive sheet has the same value and effect as the Mooney viscosity of the secondary heat conductive sheet described later.

<Asker C hardness>
Moreover, the heat conductive sheet of this invention can make Asker C hardness in the temperature of 25 degreeC 50 or more and 90 or less. This is because if the Asker C hardness is within the above range, the flexibility and handling of the heat conductive sheet in a room temperature environment can be improved.
In general, the Asker C hardness of the heat conductive sheet has the same value and effect as the Asker C hardness of the secondary heat conductive sheet described later.
In the present invention, the “Asker C hardness” can be measured at a predetermined temperature using a hardness meter in accordance with the Asker C method of the Japan Rubber Association standard (SRIS 0101).

<Thickness>
The heat conductive sheet of the present invention preferably has a thickness of 0.105 mm or more, more preferably 0.120 mm or more, preferably 0.145 mm or less, and 0.129 mm or less. Is more preferable. This is because if the thickness of the heat conductive sheet is less than or equal to the above upper limit, the value of the bulk thermal resistance can be further reduced according to the above-described formula (2). In addition, if the thickness of the heat conductive sheet is equal to or less than the above upper limit, even if the heat conductive sheet is used at a relatively low clamping pressure, the thin heat conductive sheet is more than the heat generator and / or the heat radiator. This is because the value of the interfacial thermal resistance can be further lowered because of good adhesion. Moreover, it is because it will be excellent by the intensity | strength of a heat conductive sheet, durability, and handling property if the thickness of a heat conductive sheet is more than the said minimum.

(Method for producing heat conductive sheet)
The manufacturing method of the heat conductive sheet of the present invention is a method of manufacturing the above-described heat conductive sheet, in which a plurality of primary heat conductive sheets including a resin and a particulate carbon material are laminated in the thickness direction, or the primary heat Step A for obtaining a laminate by folding or winding the conductive sheet; Step B for obtaining a secondary heat conduction sheet by slicing the laminate at an angle of 45 ° or less with respect to the lamination direction; And a step C of pressing the next heat conductive sheet to obtain the above-described heat conductive sheet. That is, the heat conductive sheet obtained by the production method of the present invention includes a resin and a particulate carbon material, and the surface roughness Sz of at least one main surface is 3.5 μm or less, and under a pressure of 0.05 MPa. The thermal resistance value of 0.25 ° C./W or less. Moreover, in addition to the said process AC, the manufacturing method of the heat conductive sheet of this invention may further include the process DE mentioned later, for example.
Here, the resin, the particulate carbon material used in the production method of the present invention, and the suitable composition, properties, and blending amount of any fibrous carbon material and additive are the same as those described above for the heat conductive sheet. The amount can be similar.

<Process A>
The manufacturing method of the heat conductive sheet of this invention includes the process A. In step A, for example, a plurality of primary heat conductive sheets obtained in step E described later are laminated in the thickness direction, or the primary heat conductive sheet obtained in step E described later is folded or wound, A laminate is obtained. Moreover, you may purchase a commercial item as a primary heat conductive sheet containing resin and a particulate carbon material.

<< Formation of Laminate >>
Formation of the laminated body by folding the primary heat conductive sheet is not particularly limited, and can be performed by folding the primary heat conductive sheet with a constant width using a folder. Further, the formation of the laminate by winding the primary heat conductive sheet is not particularly limited, and by rolling the primary heat conductive sheet around an axis parallel to the short direction or the long direction of the primary heat conductive sheet. It can be carried out.

  Here, usually, in the laminate, the adhesive force between the surfaces of the primary heat conductive sheets is sufficiently obtained by the pressure when the primary heat conductive sheets are laminated and the pressure when folding or winding. However, when the adhesive force is insufficient or when it is necessary to sufficiently suppress delamination of the laminate, the laminate may be formed with the surface of the primary heat conductive sheet slightly dissolved with a solvent. And a laminated body may be formed in the state which applied the adhesive agent to the surface of the primary heat conductive sheet, or the state which provided the contact bonding layer in the surface of the primary heat conductive sheet.

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

Moreover, it does not specifically limit as an adhesive agent apply | coated to the surface of a primary 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 primary heat conductive sheet. And the thickness of the adhesive agent apply | coated to the surface of a primary 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 primary 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 is pressed at a pressure of 0.05 MPa or more and 1.0 MPa or less in the lamination direction at a temperature of 20 ° C. or more and 100 ° C. or less for 1 minute or more and 30 minutes. It is preferable to press below.

  In the laminate obtained by laminating, folding or winding the primary heat conductive sheet, it is assumed that the particulate carbon material and any fibrous carbon material are arranged in a direction substantially perpendicular to the laminating direction. .

<Process B>
Moreover, the manufacturing method of the heat conductive sheet of this invention further includes the process B. In step B, the laminate obtained in step A is sliced at an angle of 45 ° or less with respect to the stacking direction to obtain a secondary heat conductive sheet.

<< Slice of laminate >>
Here, the method for slicing the laminate is not particularly limited, and examples thereof include a multi-blade method, a laser processing method, a water jet method, 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 shape of the knife used in the knife processing method may be single-edged, double-edged, or asymmetrical, but single-edged is preferred from the viewpoint of achieving thickness accuracy. 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.

  From the viewpoint of further increasing the thermal conductivity of the heat conductive sheet when used at a relatively low clamping pressure, the angle at which the laminate is sliced is preferably 30 ° or less with respect to the stacking direction, and the stacking direction The angle is more preferably 15 ° or less with respect to the stacking direction, and approximately 0 ° with respect to the stacking direction (that is, the direction along the stacking direction).

  From the viewpoint of easily slicing the laminate, the temperature of the laminate when slicing is preferably -20 ° C or higher and 40 ° C or lower, and more preferably 10 ° C or higher and 30 ° C or lower. Furthermore, for the same reason, it is preferable that the laminated body to be sliced is sliced while applying a pressure in a direction perpendicular to the lamination direction (stacking cross-sectional direction of the laminated body), and 0. 0 in the direction perpendicular to the lamination direction. It is more preferable to slice while applying a pressure of 1 MPa or more and 0.5 MPa or less. In the secondary heat conductive sheet obtained in this way, it is presumed that the particulate carbon material and any fibrous carbon material are arranged in the thickness direction.

<Process C>
Moreover, the manufacturing method of the heat conductive sheet of this invention further includes the process C. In step C, the above-mentioned predetermined heat conductive sheet is obtained by pressurizing the secondary heat conductive sheet obtained in step B. In step C, since the secondary heat conductive sheet obtained through the above predetermined step is pressurized, the resulting heat conductive sheet has a smooth surface and is used at a relatively low clamping pressure. Exhibits excellent thermal conductivity.
In Step C, by pressing the secondary heat conductive sheet in the thickness direction, the surface roughness of the heat conductive sheet obtained after pressurization is usually higher than the surface roughness Sz of the secondary heat conductive sheet before pressurization. Sz is reduced. Thus, in the process C, the surface roughness Sz of the secondary heat conductive sheet is usually changed.

<< Secondary heat conduction sheet >>
As described above, the secondary heat conductive sheet is formed by slicing a laminate having a primary heat conductive sheet containing a resin and a particulate carbon material, and may optionally further include a fibrous carbon material and an additive. It is a molded article.
In addition, it is preferable that a secondary heat conductive sheet has the same Mooney viscosity and hardness as the suitable Mooney viscosity and hardness about the heat conductive sheet mentioned above.

<< Pressurization method >>
The method for pressurizing the secondary heat conductive sheet is not particularly limited as long as the pressure is applied in the thickness direction of the secondary heat conductive sheet, and a known pressurizing device such as a press machine or a roll machine is used. The method to use is mentioned. Especially, it is preferable to pressurize a secondary heat conductive sheet with a press from a viewpoint of workability | operativity.
In addition, from the viewpoint of further increasing the thermal conductivity of the heat conductive sheet, the pressure is applied so that both main surfaces (front surface and back surface) of the secondary heat conductive sheet have the surface roughness Sz described above. Is preferred.

[pressure]
The pressure for pressurizing the secondary heat conductive sheet is an absolute pressure, preferably 0.8 MPa or more, more preferably 1.0 MPa or more, still more preferably 2.0 MPa or more, and 5.0 MPa. Or less, more preferably 3.5 MPa or less, and even more preferably 2.8 MPa or less. If the secondary heat conductive sheet is pressurized at a pressure equal to or higher than the above lower limit, the surface of the resulting heat conductive sheet becomes smoother, and even when the heat conductive sheet is sandwiched at a relatively low clamping pressure, the interface is used. Thermal resistance can be further reduced. As a result, the thermal conductivity of the thermal conductive sheet can be further improved even when sandwiched and used at a relatively low clamping pressure. Further, if the secondary heat conductive sheet is pressurized at a pressure below the upper limit, the particulate carbon material and any fibrous carbon material in the obtained heat conductive sheet are secured, and the particulate carbon material In addition, it is possible to suppress the collapse of a good heat transfer path due to contact between arbitrary fibrous carbon materials, and it is possible to keep the bulk thermal resistance low when the heat conductive sheet is sandwiched at a relatively low clamping pressure. As a result, the high thermal conductivity of the thermal conductive sheet can be realized in the case where the thermal conductive sheet is sandwiched and used at a relatively low clamping pressure. That is, if the secondary heat conductive sheet is pressurized at a pressure within the above range, a heat conductive sheet that exhibits better thermal conductivity can be produced when used at a relatively low clamping pressure. .

Moreover, although the press temperature which pressurizes a secondary heat conductive sheet can be suitably adjusted according to the characteristic of resin to be used, it can be 25 degreeC-200 degreeC, for example, shall be 50 degreeC-80 degreeC. Is preferred.
Furthermore, the press time for pressurizing the secondary heat conductive sheet is not particularly limited, and can be, for example, 5 seconds to 1 minute, and can be about 5 seconds to 30 seconds (30 seconds ± 5 seconds). Is preferred. It has been confirmed that even if the pressing time is longer than about 30 seconds, there is not much difference in the effect of pressurization.

[Reduction rate of sheet thickness]
Further, when the heat conductive sheet is obtained by pressurizing the secondary heat conductive sheet, the reduction rate of the sheet thickness from the secondary heat conductive sheet to the heat conductive sheet is preferably 15% or more, and more preferably 20% or more. More preferably, it is preferably 40% or less, and more preferably 30% or less. If the secondary heat conductive sheet is pressed at a reduction rate of the sheet thickness that is equal to or greater than the above lower limit, the surface thermal resistance is even when the surface is smoother and the heat conductive sheet is sandwiched at a relatively low clamping pressure. Further reduction. As a result, it is possible to obtain a heat conductive sheet with further improved thermal conductivity even when sandwiched and used at a relatively low clamping pressure. Moreover, if the secondary heat conductive sheet is pressurized at a reduction rate of the sheet thickness below the upper limit, for example, the particulate carbon material and any fibrous carbon material oriented in a desired direction in the heat conductive sheet In securing the orientation, suppressing the collapse of a good heat transfer path due to contact between the particulate carbon material and any fibrous carbon material, and using the heat conductive sheet sandwiched at a relatively low clamping pressure, Bulk thermal resistance can be kept even lower. As a result, it is possible to obtain a heat conductive sheet that realizes higher heat conductivity when used by being sandwiched at a relatively low clamping pressure. That is, if the reduction rate of the sheet thickness is within the above range, a heat conductive sheet exhibiting further excellent heat conductivity can be produced when used at a relatively low clamping pressure.
Note that the reduction rate of the sheet thickness can be appropriately adjusted by adjusting the pressurization conditions such as the pressurization method, pressure, time, and temperature in step C, for example.

<Process D>
The manufacturing method of the heat conductive sheet of this invention can further include the process D in addition to the said process AC. Step D is usually performed before Step A above. In Step D, a composition containing a resin and a particulate carbon material is prepared. Here, in preparing the composition, it is preferable that the resin is a thermoplastic resin and no curing agent is used.
The effect of using the resin without curing is the same as the effect described above for the heat conductive sheet.

<< Preparation of composition >>
The composition can be prepared by stirring and mixing the resin and the particulate carbon material, and any fibrous carbon material and / or additive by any method. And as resin, particulate carbon material, arbitrary fibrous carbon material, and additive, it was mentioned above as resin, particulate carbon material, arbitrary fibrous carbon material, and additive which can be contained in the heat conductive sheet of this invention. Ingredients can be used. Moreover, as a composition containing resin and particulate carbon material, you may purchase a commercial item.

  The stirring and mixing can be performed using a known mixing apparatus such as a kneader, a roll, a Henschel mixer, a Hobart mixer, a high speed mixer, or a twin-screw kneader without any particular limitation. The stirring and mixing may be performed in the presence of a solvent such as ethyl acetate or methyl ethyl ketone. As stirring mixing conditions, it can set suitably, for example with reference to the below-mentioned Example. Moreover, stirring and mixing temperature can be made into 5 to 150 degreeC, for example.

<Process E>
The manufacturing method of the heat conductive sheet of this invention may further include the process E in addition to said AC and arbitrary said processes D. Step E is usually performed before Step A and after Step D. In step E, the composition obtained in step D is pressed to form a sheet, thereby obtaining a primary heat conductive sheet. And the primary heat conductive sheet obtained at the process E is normally used in the said process A. FIG. Here, when forming a primary heat conductive sheet by pressurizing the composition, the composition can be defoamed and crushed arbitrarily, and then pressed to form a sheet. In addition, when a solvent is used at the time of mixing, it is preferable to form the sheet after removing the solvent. For example, if defoaming is performed using vacuum defoaming, the solvent is simultaneously removed at the time of defoaming. be able to.

<< Pressurization of primary heat conductive sheet >>
Here, the pressure forming method of the primary heat conductive sheet is not particularly limited as long as it is a method in which a pressure is applied to the composition and can be formed into a sheet shape, and known methods such as press forming, rolling forming, and extrusion forming are known. The pressure molding method can be as follows. Especially, it is preferable to shape | mold a composition in a sheet form by rolling shaping | molding, and it is more preferable to pass between rolls in the state which sandwiched the composition in the protective film, and to shape | mold into a sheet form. In addition, as a protective film, it is not specifically limited, The mold release polyethylene terephthalate (PET) film excellent in mold release property, the PET film which performed the sandblast process, etc. can be used. The roll temperature can be 5 ° C. or more and 150 ° C.

  In the primary heat conductive sheet formed by pressing the composition into a sheet shape, the particulate carbon materials are arranged mainly in the in-plane direction, and in particular, the heat conductivity in the in-plane direction of the primary heat conductive sheet is improved. I guess that. Moreover, when using arbitrary fibrous carbon material together, since the fibrous carbon material also orientates in a primary heat conductive sheet, it is guessed that the heat conductivity of a primary heat conductive sheet improves further.

  In addition, the thickness of a primary 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 further improving the thermal conductivity of the finally produced heat conductive sheet when used at a relatively low clamping pressure, the thickness of the primary heat conductive sheet is 0.10 mm or more. Is preferably 0.80 mm or less.

EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples. In the following description, “%” and “part” representing amounts are based on mass unless otherwise specified.
And in an Example and a comparative example, the thickness of each sheet | seat used for calculation of the reduction | decrease rate of sheet | seat thickness, the Mooney viscosity and Asker C hardness of a secondary heat conductive sheet, and the surface roughness Sz and heat resistance value of a heat conductive sheet Were measured or evaluated according to the following methods.

<Thickness>
The thickness of the secondary heat conductive sheet and the heat conductive sheet used for calculating the reduction rate of the sheet thickness was measured using a film thickness meter (manufactured by Mitutoyo, product name “Digimatic Indicator ID-C112XBS”). And it measured about five arbitrary places on each sheet | seat surface, and made the average value (mm) of the measured value the thickness of each sheet | seat.

<Mooney viscosity>
The Mooney viscosity (ML _{1 + 4} , 100 ° C.) of the secondary heat conductive sheet was measured at a temperature of 100 ° C. according to JIS-K6300 using a Mooney viscometer (manufactured by Shimadzu Corporation, product name “MOONEY VISCOMETER SMV-202”). It was measured. In general, the lower the Mooney viscosity, the higher the fluidity of the components in the sheet.

<Asker C hardness>
The Asker C hardness of the secondary heat conductive sheet is based on the Asker C method of the Japan Rubber Association Standard (SRIS 0101), using a hardness meter (product name “ASKER CL-150LJ” manufactured by Kobunshi Keiki Co., Ltd.) The test was performed in an environment at a temperature of 25 ° C.
Specifically, the obtained secondary heat conductive sheet was cut into a size of 20 mm × 50 mm and laminated so as to have a height (thickness) of 12 mm. Then, the superposed secondary heat conductive sheet was allowed to stand for 48 hours or more in a temperature-controlled room maintained at a temperature of 25 ° C. to obtain a test specimen. Next, the height of the damper was adjusted so that the pointer became 95 to 98, and the specimen and the damper were made to collide. And the Asker C hardness of the test body 60 seconds after the said collision was measured twice using the said hardness meter, and the average value of the measurement result was employ | adopted. Generally, the smaller the Asker C hardness, the higher the flexibility.

<Surface roughness Sz>
The surface roughness Sz of the heat conductive sheet was measured using a three-dimensional shape measuring machine (manufactured by Keyence Corporation, product name “One Shot 3D Measurement Macroscope”). Here, a heat conductive sheet cut into a substantially square of an arbitrary size of 1 cm square or more was used as a sample, the analysis range was 1 cm × 1 cm, and the three-dimensional shape was measured on the front and back surfaces of the sample. Then, the surface roughness Sz (μm) was automatically calculated by further filtering (2.5 mm) with software on the measurement result of the three-dimensional shape and removing the swell component.

<Thermal resistance value>
The thermal resistance value of the heat conductive sheet was measured by a steady method using a thermal resistance measuring device (product name “resin material thermal resistance measuring device” manufactured by Hitachi Technology & Service Co., Ltd.). Here, a heat conductive sheet cut into a substantially square of 1 cm square is used as a sample, and 0.05 MPa which is a relatively low pressure and 0.9 MPa which is a relatively high pressure are added, respectively. W) was measured. In addition, the sample temperature at the time of measurement was 50 degreeC. The smaller the thermal resistance value, the better the thermal conductivity of the heat conductive sheet, and the better the heat dissipation characteristics when it is interposed between the heat generator and the heat radiator.

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 G / D ratio of 3.0, a BET specific surface area of 800 m ² / g, and a mass density of 0.03 g / cm ³ . 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, the ratio (3σ / Av) was 0.58, and the average length was 100 μm. In addition, the obtained fibrous carbon nanostructure was mainly composed of single-walled CNTs (hereinafter sometimes referred to as “SGCNT”).

<Preparation of an easily dispersible assembly of fibrous carbon nanostructures>
<< Preparation of dispersion >>
400 mg of the fibrous carbon nanostructure containing SGCNT 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 coarse dispersion. Next, using a wet jet mill (product name “JN-20”, manufactured by Joko Co., Ltd.), the obtained coarse dispersion is 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 an easily dispersible aggregate of sheet-like fibrous carbon nanostructures as a fibrous carbon material. .

<Preparation of composition>
40 parts of a thermoplastic fluororesin that is solid under normal temperature and normal pressure (made by Daikin Industries, Ltd., trade name “DAIEL G-704BP”) as a resin, and a thermoplastic fluororesin that is liquid under normal temperature and normal pressure (product of Daikin Industries, Ltd.) 45 parts by weight (name “DAIEL G-101”), 85 parts expanded graphite (product name “EC-50”, volume average particle size: 250 μm, manufactured by Ito Graphite Industries Co., Ltd.) as a particulate carbon material, fiber 0.1 part of the easily dispersible aggregate of fibrous carbon nanostructures obtained above as a fibrous carbon material and sebacic acid ester as a plasticizer (trade name “DOS” manufactured by Daihachi Chemical Industry Co., Ltd.) )) 5 parts were stirred and mixed at room temperature for 5 minutes using a Hobart mixer (manufactured by Kodaira Manufacturing Co., Ltd., product name “ACM-5 LVT type”) in the presence of 100 parts of ethyl acetate as a solvent. Next, the obtained stirred mixture was vacuum degassed for 30 minutes, and ethyl acetate was removed at the same time as degassing to obtain a composition containing a resin, a particulate carbon material, and a fibrous carbon material. And the obtained composition was thrown into the crusher and crushed for 10 seconds.

<Formation of primary heat conductive sheet>
Next, 5 g of the crushed composition was 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 / min. And a primary heat conductive sheet having a thickness of 0.5 mm was obtained.

<Formation of laminate>
Subsequently, the obtained primary heat conductive sheet was cut into a length of 60 mm × width of 60 mm × thickness of 0.5 mm and laminated with 120 double-sided tapes in the thickness direction of the primary heat conductive sheet to obtain a laminate having a thickness of about 60 mm. .

<Formation of secondary heat conductive sheet>
Then, while pressing the laminated section of the obtained laminate of the primary heat conductive sheet with a pressure of 0.3 MPa, a woodworking slicer (manufactured by Marunaka Co., Ltd., trade name "Super Finished Planer Super Mecha S") ), And sliced at an angle of 0 degrees with respect to the stacking direction (in other words, sliced in the normal direction of the main surface of the stacked primary heat conductive sheet), 60 mm long × 60 mm wide × 0 thickness A secondary heat conductive sheet of 5 mm was obtained. Here, as a knife for a woodworking slicer, two single blades (front blade and back blade) are in contact with each other on the opposite side of the cutting blade, and the cutting edge of the front blade is the cutting edge of the back blade. A two-blade one having a height 0.5 mm higher than that of the slit portion and a protruding length from the slit portion of 0.11 mm and a blade angle of the front blade being 21 ° was used.
In addition, among the main surfaces of the obtained secondary heat conductive sheet, the surface that directly contacts the blade during slicing was defined as the front surface, and the surface that did not directly contact the blade but contacted the slide surface was defined as the back surface.
And about the obtained secondary heat conductive sheet, according to the above-mentioned method, the Mooney viscosity and Asker C hardness were measured, and the result is shown in Table 1.

<Manufacture of heat conductive sheet>
Subsequently, the obtained secondary heat conductive sheet was heated to 50 ° C. using a precision hot press machine (manufactured by Shinto Kogyo Co., Ltd., product name “CYPT-20”) to 2.6 MPa. A heat conductive sheet was obtained by pressing with pressure for 30 seconds. In addition, the thickness of the obtained heat conductive sheet was 0.125 mm, and the decreasing rate of the sheet thickness from the secondary heat conductive sheet to the heat conductive sheet was 26%.
And about the obtained heat conductive sheet, according to the above-mentioned method, the surface roughness Sz and the thermal resistance value were measured. The results are shown in Table 1.

(Example 2)
In the production of a heat conductive sheet, a fibrous carbon nanostructure containing CNTs, fibrous, in the same manner as in Example 1, except that the pressing pressure was changed to 0.9 MPa and the reduction rate of the sheet thickness was 18%. An easily dispersible assembly of carbon nanostructures, a composition, a primary heat conductive sheet, a laminate, a secondary heat conductive sheet, and a heat conductive sheet were produced. In addition, the thickness of the obtained heat conductive sheet was 0.139 mm.
And it measured like Example 1. The results are shown in Table 1.

(Example 3)
In the production of the heat conductive sheet, a fibrous carbon nanostructure containing CNTs, fibrous, in the same manner as in Example 1, except that the pressing pressure was changed to 3.0 MPa and the reduction rate of the sheet thickness was 35%. An easily dispersible assembly of carbon nanostructures, a composition, a primary heat conductive sheet, a laminate, a secondary heat conductive sheet, and a heat conductive sheet were produced. In addition, the thickness of the obtained heat conductive sheet was 0.110 mm.
And it measured like Example 1. The results are shown in Table 1.

Example 4
In the preparation of the composition, a thermoplastic fluororesin that is liquid at room temperature and normal pressure as a resin is used without using a liquid thermoplastic fluororesin (trade name “DAIEL G-101”, manufactured by Daikin Industries, Ltd.) and solid at normal temperature and pressure. The amount of resin (trade name “DAIEL G-704BP” manufactured by Daikin Industries, Ltd.) was changed to 80 parts. Also, an easily dispersible aggregate of fibrous carbon nanostructures as a fibrous carbon material is not used, and expanded graphite as a particulate carbon material (trade name “EC-50” manufactured by Ito Graphite Industries Co., Ltd.) ”, The volume average particle diameter: 250 μm) was changed to 130 parts. Furthermore, the amount of sebacic acid ester (made by Daihachi Chemical Industry Co., Ltd., trade name “DOS”) as a plasticizer was changed to 10 parts. The amount of expanded graphite is a value adjusted so as to be the same amount as in Example 1 in terms of volume.
In the production of the heat conductive sheet, the pressing pressure was changed to 3.2 MPa, and the reduction rate of the sheet thickness was 19%. In addition, the thickness of the obtained heat conductive sheet was 0.130 mm. Except for the above, in the same manner as in Example 1, fibrous carbon nanostructures containing CNTs, easily dispersible aggregates of fibrous carbon nanostructures, compositions, primary heat conductive sheets, laminates, secondary heat Conductive sheets and heat conductive sheets were produced.
And it measured like Example 1. The results are shown in Table 1.

(Example 5)
In preparing the composition, 80 parts of a solid thermoplastic silicone resin (manufactured by Shin-Etsu Chemical Co., Ltd., trade name “KE-931-U”) was used in place of the fluororesin under normal temperature and normal pressure. Further, the amount of expanded graphite (product name “EC-50”, volume average particle size: 250 μm, manufactured by Ito Graphite Industries Co., Ltd.) as the particulate carbon material was changed to 160 parts. Furthermore, the amount of sebacic acid ester (made by Daihachi Chemical Industry Co., Ltd., trade name “DOS”) as a plasticizer was changed to 10 parts. The amount of expanded graphite is a value adjusted so as to be the same amount as in Example 1 in terms of volume.
In the production of the heat conductive sheet, the pressing pressure was changed to 2.0 MPa, and the reduction rate of the sheet thickness was set to 28%. In addition, the thickness of the obtained heat conductive sheet was 0.135 mm. Except for the above, in the same manner as in Example 1, fibrous carbon nanostructures containing CNTs, easily dispersible aggregates of fibrous carbon nanostructures, compositions, primary heat conductive sheets, laminates, secondary heat Conductive sheets and heat conductive sheets were produced.
And it measured like Example 1. The results are shown in Table 1.

(Comparative Example 1)
In the production of a heat conductive sheet, a fibrous carbon nanostructure containing CNTs and a fibrous carbon nanostructure are obtained in the same manner as in Example 1 except that the secondary heat conductive sheet is used as it is without being pressed. An easily dispersible assembly, composition, primary heat conductive sheet, laminate, secondary heat conductive sheet and heat conductive sheet were produced. In addition, the thickness of the obtained heat conductive sheet was 0.170 mm.
And it measured like Example 1. The results are shown in Table 1.

(Comparative Example 2)
In the production of a heat conductive sheet, a fibrous carbon nanostructure containing CNTs, fibrous, in the same manner as in Example 1, except that the pressing pressure was changed to 0.2 MPa and the reduction rate of the sheet thickness was 11%. An easily dispersible assembly of carbon nanostructures, a composition, a primary heat conductive sheet, a laminate, a secondary heat conductive sheet, and a heat conductive sheet were produced. In addition, the thickness of the obtained heat conductive sheet was 0.150 mm.
And it measured like Example 1. The results are shown in Table 1.

(Comparative Example 3)
In the production of a heat conductive sheet, a fibrous carbon nanostructure containing CNTs, fibrous, in the same manner as in Example 1, except that the pressing pressure was changed to 3.6 MPa and the reduction rate of the sheet thickness was 41%. An easily dispersible assembly of carbon nanostructures, a composition, a primary heat conductive sheet, a laminate, a secondary heat conductive sheet, and a heat conductive sheet were produced. In addition, the thickness of the obtained heat conductive sheet was 0.100 mm.
And it measured like Example 1. The results are shown in Table 1.

(Comparative Example 4)
In the production of the heat conductive sheet, a fibrous carbon nanostructure containing CNTs and a fibrous carbon nanostructure were obtained in the same manner as in Example 4 except that the secondary heat conductive sheet was used as it was without being pressed. An easily dispersible assembly, composition, primary heat conductive sheet, laminate, secondary heat conductive sheet and heat conductive sheet were produced. In addition, the thickness of the obtained heat conductive sheet was 0.173 mm.
And it measured like Example 1. The results are shown in Table 1.

From Table 1, the surface roughness Sz of at least one main surface containing a resin and a particulate carbon material is 3.5 μm or less, and the thermal resistance value under a pressure of 0.05 MPa is 0.25 ° C./W. It turns out that the heat conductive sheet of Examples 1-5 which are the following can exhibit favorable heat conductivity, when it uses it by comparatively low clamping pressure.
On the other hand, the thermal conductive sheets of Comparative Examples 1-2 and 4 in which the surface roughness Sz on both surfaces (front surface and back surface) is more than 3.5 μm have a thermal resistance value of 0.25 under a low pressure of 0.05 MPa. It can be seen that when it is used at a relatively low clamping pressure, it is inferior in thermal conductivity.
Furthermore, the thermal conductivity sheet of Comparative Example 3 having a thermal resistance value under a low pressure of 0.05 MPa exceeding 0.25 ° C./W is also inferior in thermal conductivity when used at a relatively low clamping pressure. I understand that.

ADVANTAGE OF THE INVENTION According to this invention, the heat conductive sheet which contains resin and a particulate carbon material and exhibits the outstanding heat conductivity in the case of use with a comparatively low clamping pressure can be provided.
In addition, according to the present invention, there is provided a method for producing a heat conductive sheet, which can produce a heat conductive sheet that includes a resin and a particulate carbon material and exhibits excellent heat conductivity when used at a relatively low clamping pressure. can do.

Claims (10)

Including resin and particulate carbon material,
The surface roughness Sz of at least one main surface is 3.5 μm or less,
The heat conductive sheet whose heat resistance value under 0.05MPa pressurization is 0.25 degrees C / W or less. The heat conductive sheet of Claim 1 whose Mooney viscosity (ML1 _{+ 4} , 100 degreeC) is 50.0 or less.   The heat conductive sheet according to claim 1 or 2, wherein the resin is not cured.   The heat conductive sheet according to any one of claims 1 to 3, wherein the resin is a fluororesin. Laminating a plurality of primary heat conductive sheets containing a resin and a particulate carbon material in the thickness direction, or folding or winding the primary heat conductive sheet to obtain a laminate, and
Step B for slicing the laminate at an angle of 45 ° or less with respect to the lamination direction to obtain a secondary heat conductive sheet;
Step C for pressurizing the secondary heat conductive sheet to obtain the heat conductive sheet according to any one of claims 1 to 4,
The manufacturing method of the heat conductive sheet containing this. Before step A,
Preparing a composition comprising a resin and a particulate carbon material, step D;
Pressing the composition into a sheet and obtaining a primary heat conductive sheet E;
Further including
The manufacturing method of the heat conductive sheet of Claim 5 which uses the primary heat conductive sheet obtained at the said process E in the said process A.   The method for producing a thermally conductive sheet according to claim 5 or 6, wherein the resin is a thermoplastic resin, and a curing agent is not used for the resin. The manufacturing method of the heat conductive sheet as described in any one of Claims 5-7 whose Mooney viscosity (ML1 _{+ 4} , 100 degreeC) of the said secondary heat conductive sheet is 50.0 or less.   The manufacturing method of the heat conductive sheet as described in any one of Claims 5-8 whose pressurization pressure in the said process C is 0.8 Mpa or more and 5.0 Mpa or less. In the step C, the secondary heat conductive sheet is compressed into a heat conductive sheet,
The manufacturing method of the heat conductive sheet as described in any one of Claims 5-9 whose reduction rate of the sheet | seat thickness by the said compression is 15% or more and 40% or less.