JP6555009B2 - Thermal conductive sheet and manufacturing method thereof - Google Patents

Description

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

  Electronic parts such as a plasma display panel (PDP) and an integrated circuit (IC) chip are becoming smaller and thinner, and the amount of heat generated is increasing as the performance becomes higher. As a result of higher performance of electronic components, it is necessary to take countermeasures against functional failures due to temperature rise of electronic components in electronic devices using electronic components.

  Here, in general, as a countermeasure against functional failure due to a temperature rise, a method of promoting heat dissipation by attaching a heat sink such as a metal heat sink, a heat sink, or a heat sink to a heat generator such as an electronic component is adopted. ing. And when using a heat radiator, in order to transfer heat efficiently from a heat generating body to a heat sink, a heat generating body, a heat sink, and a heat conductive sheet through a sheet-like member (heat conductive sheet) with high heat conductivity. Are in close contact. Therefore, the heat conductive sheet used by being sandwiched between the heat generator and the heat radiator is required to have high adhesion and high heat conductivity.

  Therefore, in recent years, a heat conductive sheet including a resin and a heat conductive filler as a heat conductive sheet excellent in adhesion and heat conductivity, and having the heat conductive filler oriented in the thickness direction of the heat conductive sheet. Has been proposed (see, for example, Patent Documents 1 to 3).

  Specifically, for example, in Patent Documents 1 and 2, a thermally conductive filler such as expanded graphite powder and boron nitride particles is oriented in a sheet main surface direction (direction orthogonal to the thickness direction) in a resin. After forming a laminate by laminating a plurality of primary sheets in the thickness direction of the primary sheet, the thermally conductive filler is oriented in the thickness direction of the heat conduction sheet by slicing the obtained laminate in the lamination direction. A technique for obtaining a heat conductive sheet is disclosed. Since the heat conductive sheets of Patent Documents 1 and 2 contain a resin, they can exhibit high adhesion. Moreover, since the heat conductive filler of the patent documents 1 and 2 is orientating in the thickness direction of a heat conductive sheet, it is excellent in the heat conductivity of the thickness direction.

  Further, for example, in Patent Document 3, a molding material containing a polymer matrix such as silicone rubber, carbon fibers, and spherical carbon is solidified in a state where the carbon fibers are oriented in one direction using a magnetic field or an electric field. After the molded body is obtained, the molded body is sliced in a direction intersecting with the carbon fiber, and the end face of the carbon fiber exposed from the surface of the obtained slice piece is polished to crush the end face of the carbon fiber, thereby A technique for obtaining a heat conductive sheet in which fibers are oriented in the thickness direction of the heat conductive sheet is disclosed. The heat conductive sheet of Patent Document 3 includes a polymer matrix such as silicone rubber, and the end face of the carbon fiber exposed on the surface is crushed by polishing, so that high adhesion can be exhibited. . Moreover, since the carbon fiber orientates in the thickness direction of a heat conductive sheet, the heat conductive sheet of patent document 3 is excellent in the heat conductivity of the thickness direction.

JP 2002-026202 A Table 2008-053843 JP 2010-254766 A

  Here, the conventional heat conductive sheets described in Patent Documents 1 to 3 are based on the premise that the heat is transmitted from the heat generating body to the heat radiating body and is dissipated through the heat radiating body. Then, it focused only on improving the adhesiveness and heat conductivity of a heat conductive sheet.

  However, in recent years, from the viewpoint of responding to the demand for increased heat generation and further downsizing of electronic devices due to further enhancement of performance of electronic devices, Therefore, there has been a demand for more efficiently dissipating the heat generated in the heating element.

  Then, an object of this invention is to provide the heat conductive sheet which enables efficient dissipation of heat.

  The present inventors have intensively studied to achieve the above object. The inventors have found that a heat conductive sheet excellent in heat radiation can be obtained by smoothing the surface of the heat conductive sheet, and completed the present invention.

That is, the present invention aims to advantageously solve the above problems, and the heat conductive sheet of the present invention includes a resin and a carbon material, and has a ten-point average surface roughness of at least one main surface. Is 40 μm or less.
As described above, when the ten-point average surface roughness of at least one main surface is set to 40 μm or less, a heat conductive sheet excellent in thermal radiation can be obtained. Therefore, when the heat conductive sheet is attached to the heating element, heat can be efficiently dissipated from the heat conductive sheet itself.
In the present invention described above, the “ten-point average surface roughness” can be measured using a surface roughness measuring machine (manufactured by Mitutoyo Corporation, model number “SJ-201”).

Here, the heat conductive sheet of the present invention preferably has a heat conductivity in the thickness direction of 20 W / m · K or more. If the thermal conductivity in the thickness direction is 20 W / m · K or more, heat can be efficiently transferred from the heating element to the radiator when sandwiched between the heating element and the radiator.
In the present invention described above, “thermal conductivity” is defined as the thermal diffusivity α (m ² / s), the constant pressure specific heat Cp (J / g · K), and the specific gravity ρ (g / m ³ ) of the thermal conductive sheet. Using the following formula (I):
Thermal conductivity λ (W / m · K) = α × Cp × ρ (I)
It can be obtained more. Here, "thermal diffusivity" can be measured using a thermophysical property measuring device, "constant pressure specific heat" can be measured using a differential scanning calorimeter, and "specific gravity" can be measured using an automatic hydrometer. Can be measured.

  In the heat conductive sheet of the present invention, the carbon material preferably contains expanded graphite. If expanded graphite is contained, the thermal conductivity and thermal radiation of the thermal conductive sheet can be further improved.

  Furthermore, in the heat conductive sheet of the present invention, it is preferable that the carbon material includes a fibrous carbon nanostructure. If the fibrous carbon nanostructure is contained, the thermal conductivity and thermal radiation of the thermal conductive sheet can be further improved.

  And the heat conductive sheet of this invention shall be formed by parallel-joining the strip containing the said resin and the said carbon material. If it is set as the structure which joined in parallel the strip containing resin and a carbon material, a heat conductive sheet can be manufactured easily.

  Moreover, this invention aims at solving the said subject advantageously, and the manufacturing method of the heat conductive sheet of this invention includes the process (A) which prepares the sheet | seat containing resin and a carbon material. And the step (B) of setting the ten-point average surface roughness of at least one main surface of the sheet to 40 μm or less. When the step (B) is performed and the ten-point average surface roughness of at least one main surface is set to 40 μm or less, a heat conductive sheet excellent in thermal radiation can be obtained. Therefore, when attached to the heating element, a heat conductive sheet capable of efficiently dissipating heat from the heat conductive sheet itself can be obtained.

  Here, as for the manufacturing method of the heat conductive sheet of this invention, it is preferable that the said process (B) includes the process which makes an organic solvent contact the said main surface. If an organic solvent is used, the ten-point average surface roughness of the main surface can be easily adjusted.

  In addition, it is preferable that the said process (B) further includes the process of applying a pressure to the said main surface of the said sheet | seat which contacted the said organic solvent. If the main surface of the sheet is smoothed by applying pressure to the main surface of the sheet in contact with the organic solvent, the ten-point average surface roughness of the main surface can be easily reduced.

  Moreover, the manufacturing method of the heat conductive sheet of this invention WHEREIN: It is preferable that the said process (B) includes the process of grind | polishing the said main surface. If polishing is used, the ten-point average surface roughness of the main surface can be easily adjusted.

  And the manufacturing method of the heat conductive sheet of this invention WHEREIN: The said process (A) pressurizes the composition containing the said resin and the said carbon material, and shape | molds it in a sheet form, and the process of obtaining a pre heat conductive sheet, A step of laminating a plurality of the pre-heat conductive sheets in the thickness direction, or folding or winding the pre-heat conductive sheets to obtain a laminate, and the laminate is 45 ° with respect to the lamination direction. And slicing at the following angle to obtain the sheet. In this way, if a laminate composed of a pre-heat conductive sheet formed by pressurizing a resin and a composition containing a carbon material is sliced at an angle of 45 ° or less with respect to the stacking direction, the heat conductivity and heat radiation can be improved. An excellent heat conductive sheet can be easily produced.

  In addition, in the manufacturing method of the heat conductive sheet of this invention, it is preferable that the said carbon material contains expanded graphite. If expanded graphite is contained, the thermal conductivity and thermal radiation of the thermal conductive sheet can be further improved.

  Furthermore, in the manufacturing method of the heat conductive sheet of this invention, it is preferable that the said carbon material contains a fibrous carbon nanostructure. If the fibrous carbon nanostructure is contained, the thermal conductivity and thermal radiation of the thermal conductive sheet can be further improved.

  ADVANTAGE OF THE INVENTION According to this invention, the heat conductive sheet excellent in thermal radiation property can be provided.

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. Moreover, the heat conductive sheet of this invention can also be attached to a heat generating body independently, and can also be used as a heat radiating sheet, for example. That is, the heat conductive sheet of this invention can comprise a thermal radiation device individually or in combination with a heat radiator.
And the heat conductive sheet of this invention can be manufactured, for example using the manufacturing method of the heat conductive sheet of this invention.

(Heat conduction sheet)
The heat conductive sheet of the present invention contains a resin and a carbon material. In the heat conductive sheet of the present invention, the ten-point average surface roughness of at least one main surface (at least one of the surfaces orthogonal to the thickness direction of the heat conductive sheet) is 40 μm or less. And since the 10-point average surface roughness of at least one main surface is 40 micrometers or less, the heat conductive sheet of this invention is excellent in thermal radiation property. Therefore, when the heat conductive sheet of this invention is attached to a heat generating body independently, heat conductive sheet itself can be effectively utilized as a heat radiating sheet, without using a heat radiator. In addition, 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 main surface of the heat conductive sheet sandwiched between the heat generator and the heat sink Of these, heat can be effectively dissipated from a portion not in contact with the heat radiating body or the heat generating body. As a result, the heat generated by the heating element can be efficiently dissipated in a small space. Moreover, since the heat conductive sheet of the present invention contains both a resin and a carbon material, the heat conductivity can be maintained at a sufficiently high level.

  In addition, in the heat conductive sheet of this invention, thermal radiation improves from the said at least one main surface (main surface whose ten-point average surface roughness is 40 micrometers or less) being accelerated | stimulated. Therefore, in the heat conductive sheet of the present invention, at least a part of the main surface having a 10-point average surface roughness of 40 μm or less is usually in contact with the space for radiating heat (in other words, the 10-point average surface roughness is 40 μm). The following main surface has a non-attachment portion that does not come into contact with a heating element or a heat radiating body). Therefore, from the viewpoint of being able to promote heat radiation from both main surfaces regardless of the mounting direction, the heat conduction sheet of the present invention has a ten-point average surface roughness of both main surfaces (front surface and back surface). It is preferable that it is 40 micrometers or less.

<Resin>
Here, as resin, it is not specifically limited, Known resin which can be used for formation of a heat conductive sheet can be used. Specifically, a thermoplastic resin or a thermosetting resin can be used as the resin. Moreover, you may use together a thermoplastic resin and a thermosetting resin.

[Thermoplastic resin]
Examples of the thermoplastic resin include acrylic resins such as a copolymer of acrylic acid and 2-ethylhexyl acrylate, poly (2-ethylhexyl acrylate), polymethacrylic acid or an ester thereof, polyacrylic acid or an ester thereof. ; Silicone resin; Fluorine resin such as polyvinylidene fluoride and polytetrafluoroethylene; polyethylene; polypropylene; ethylene-propylene copolymer; polymethylpentene; polyvinyl chloride; polyvinylidene chloride; Polyvinyl alcohol; Polyacetal; Polyethylene terephthalate; Polybutylene terephthalate; Polyethylene naphthalate; Polystyrene; Polyacrylonitrile; Styrene-acrylonitrile copolymer; Acrylonitrile Butadiene-styrene copolymer (ABS resin); styrene-butadiene block copolymer or hydrogenated product thereof; styrene-isoprene block copolymer or hydrogenated product thereof; polyphenylene ether; modified polyphenylene ether; aliphatic polyamides; Polyamideimide; Polycarbonate; Polyphenylene sulfide; Polysulfone; Polyethersulfone; Polyethernitrile; Polyetherketone; Polyketone; Polyurethane; Liquid crystal polymer; Ionomer; These may be used individually by 1 type and may use 2 or more types together.

[Thermosetting resin]
Examples of the thermosetting resin include natural rubber, butadiene rubber, isoprene rubber, nitrile rubber, hydrogenated nitrile rubber, chloroprene rubber, ethylene propylene rubber, chlorinated polyethylene, chlorosulfonated polyethylene, butyl rubber, and halogenated butyl rubber. Polyisobutylene rubber; Epoxy resin; Polyimide resin; Bismaleimide resin; Benzocyclobutene resin; Phenolic resin; Unsaturated polyester; Diallyl phthalate resin; Polyimide silicone resin; Polyurethane; Is mentioned. These may be used individually by 1 type and may use 2 or more types together.

  Among the above, as the resin of the heat conductive sheet, it is preferable to use a thermoplastic resin, more preferably an acrylic resin, and still more preferably a copolymer of acrylic acid and 2-ethylhexyl acrylate. If a thermoplastic resin such as an acrylic resin is used, the flexibility of the heat conductive sheet is further improved, the adhesion between the heat generating body and the heat radiating body via the heat conductive sheet, or between the heat generating body and the heat conductive sheet itself. This is because the adhesion can be improved.

<Carbon material>
The carbon material is not particularly limited, and a known carbon material can be used. Specifically, as the carbon material, a particulate carbon material, a fibrous carbon material, or the like can be used. One of the particulate carbon material and the fibrous carbon material may be used alone, or both may be used in combination.

[Particulate carbon material]
The particulate carbon material is not particularly limited, and examples thereof include artificial graphite, flaky graphite, exfoliated graphite, natural graphite, acid-treated graphite, expandable graphite, expanded graphite, and the like; carbon black; Can be used. These may be used individually by 1 type and may use 2 or more types together.
Among them, it is preferable to use expanded graphite as the particulate carbon material. This is because if expanded graphite is used, the thermal conductivity and thermal radiation 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 are product names) manufactured by Ito Graphite Industries.

[[Properties of particulate carbon material]]
Here, the particle diameter of the particulate carbon material used for forming the heat conductive sheet is preferably a number-based mode diameter of 1 μm or more, more preferably 5 μm or more, and 200 μm or less. Is preferable, and it is more preferable that it is 150 micrometers or less. This is because, if the number-based mode diameter of the particulate carbon material is within the above range, the thermal conductivity and thermal radiation of the thermal conductive sheet can be further improved.
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 “number-based mode diameter” can be measured using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Horiba, Ltd., model “LA960”). Specifically, the particle diameter of the particulate carbon material contained in the suspension is measured using a suspension in which the particulate carbon material used for forming the heat conductive sheet is dispersed in methyl ethyl ketone. The particle diameter at the maximum value of the particle diameter distribution curve with the obtained particle diameter as the horizontal axis and the number of the particulate carbon materials as the vertical axis can be obtained as the mode diameter based on the number of the particulate carbon materials.
In the present invention, the “aspect ratio” can be determined using a scanning electron microscope (SEM). Specifically, the particulate carbon material used for forming the heat conductive sheet is observed, and for any 50 particulate carbon materials, the maximum diameter (major axis) and the particle diameter in the direction orthogonal to the maximum diameter (short) Diameter) and measuring the average value of the ratio of the major axis to the minor axis (major axis / minor axis).

[[Particulate carbon material content]]
The content ratio of the particulate carbon material in the heat conductive sheet is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably 50% by mass or more, and 90% by mass. % Or less, more preferably 80% by mass or less, still more preferably 75% by mass or less, and even more preferably 70% by mass or less. This is because if the content ratio of the particulate carbon material in the heat conductive sheet is 30% by mass or more and 90% by mass or less, the heat conductivity, flexibility, and strength of the heat conductive sheet can be improved in a balanced manner.

[Fibrous carbon material]
The fibrous carbon material is not particularly limited, and for example, carbon nanotubes, vapor-grown carbon fibers, carbon fibers obtained by carbonizing organic fibers, and cut products thereof can be used. These may be used individually by 1 type and may use 2 or more types together.
Among these, as the fibrous carbon material, it is preferable to use a fibrous carbon nanostructure such as a carbon nanotube, and a fibrous carbon nanostructure including a carbon nanotube (hereinafter sometimes referred to as “CNT”) is used. It is more preferable. This is because if the fibrous carbon nanostructure is used, the thermal conductivity and thermal radiation of the thermal conductive sheet can be further improved.

[[Fibrous carbon nanostructure containing CNT]]
The fibrous carbon nanostructure containing CNT that can be suitably used as the fibrous carbon material may be composed of CNT alone or a mixture of CNT and a fibrous carbon nanostructure other than CNT. May be.

  For example, the non-cylindrical carbon nanostructure may be contained in the fibrous carbon nanostructure containing CNT. Specifically, the fibrous carbon nanostructure containing CNT includes, for example, a single-layer or multi-layer flat cylindrical carbon nanostructure (hereinafter referred to as a tape-shaped portion in which inner walls are close to or bonded to each other). , Which may be referred to as “graphene nanotape (GNT)”).

  Here, GNT is presumed to be a substance in which a tape-like portion in which inner walls are close to each other or bonded is formed over the entire length from the synthesis, and a carbon six-membered ring network is formed in a flat cylindrical shape. The And the shape of GNT is a flat cylindrical shape, and the presence of a tape-like part in which the inner walls are close to each other or bonded is present in GNT. For example, GNT and fullerene (C60) are sealed in a quartz tube. When the fullerene insertion GNT obtained by heat treatment (fullerene insertion treatment) under reduced pressure is observed with a transmission electron microscope (TEM), there is a portion (tape-like portion) in which fullerene is not inserted in GNT. Can be confirmed.

  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. Preferably, it is a single-walled carbon nanotube. This is because if single-walled carbon nanotubes are used, the thermal conductivity, thermal radiation and strength of the thermal conductive sheet can be further improved as compared with the case where multi-walled carbon nanotubes are used.

-Properties of fibrous carbon nanostructures containing CNT-
As the fibrous carbon nanostructure containing CNT, the ratio (3σ / Av) of the value (3σ) obtained by multiplying the standard deviation (σ) of the diameter by 3 with respect to the average diameter (Av) is more than 0.20 and 0.60. It is preferable to use a carbon nanostructure of less than 3, preferably 3σ / Av is more than 0.25, more preferably 3σ / Av is more than 0.50. preferable. If a fibrous carbon nanostructure containing CNTs with 3σ / Av of more than 0.20 and less than 0.60 is used, the thermal conductivity and thermal radiation of the thermal conductive sheet can be achieved even if the amount of carbon nanostructure is small. In addition, since the strength can be sufficiently increased, it is possible to suppress the increase in the hardness of the heat conductive sheet (that is, the flexibility is reduced) by blending the fibrous carbon nanostructure containing CNTs, and the heat conductivity. It is possible to obtain a heat conductive sheet in which heat radiation, flexibility and strength are juxtaposed at a sufficiently high level.
“Average diameter (Av) of fibrous carbon nanostructure” and “standard deviation of diameter of fibrous carbon nanostructure (σ: sample standard deviation)” are randomized using a transmission electron microscope, respectively. It can be determined by measuring the diameter (outer diameter) of 100 fibrous carbon nanostructures selected. And the average diameter (Av) and standard deviation ((sigma)) 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. And you may adjust by combining multiple types of fibrous carbon nanostructures containing CNT obtained by a different manufacturing method.

  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 when it is approximated by Gaussian, it takes a normal distribution Is usually used.

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. Further preferred. When the average diameter (Av) of the fibrous carbon nanostructure is 0.5 nm or more, aggregation of the fibrous carbon nanostructure can be suppressed and the dispersibility of the fibrous carbon nanostructure can be enhanced. Moreover, if the average diameter (Av) of fibrous carbon nanostructure is 15 nm or less, the thermal conductivity, thermal radiation property, and intensity | strength of a heat conductive sheet can fully be improved.
Here, the average diameter (Av) can be determined using a transmission electron microscope by the method described above.

Further, the BET specific surface area of the fibrous carbon nanostructure containing CNTs is preferably 600 m ² / g or more, more preferably 800 m ² / g or more, and preferably 2500 m ² / g or less. More preferably, it is 1200 m ² / g or less. Furthermore, when the CNTs in the fibrous carbon nanostructure are mainly opened, it is preferable that the BET specific surface area is 1300 m ² / g or more. If the BET specific surface area of the fibrous carbon nanostructure containing CNT is 600 m ² / g or more, the thermal conductivity, thermal radiation, and strength of the thermal conductive sheet can be sufficiently increased. Moreover, if the BET specific surface area of the fibrous carbon nanostructure containing CNT is 2500 m ² / g or less, the aggregation of the fibrous carbon nanostructure can be suppressed and the dispersibility of the CNT in the heat conductive sheet can be improved. it can.
In the present invention, the “BET specific surface area” refers to a nitrogen adsorption specific surface area measured using the BET method.

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

  The fibrous carbon nanostructure containing CNT produced by the super-growth method may be composed only of SGCNT, or may be composed of SGCNT and a non-cylindrical carbon nanostructure. . Specifically, the above-described graphene nanotape (GNT) may be included in the fibrous carbon nanostructure containing CNTs manufactured by the super growth method.

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

  In the present invention, the “average fiber diameter” refers to a fiber carbon material used for forming the heat conductive sheet observed with a TEM (transmission electron microscope), and the fiber diameter of any 50 fibrous carbon materials. It can be determined by measuring and calculating the number average value of the measured fiber diameters.

[Content ratio of fibrous carbon material]
The content of the fibrous carbon material in the heat conductive sheet is preferably 0.05% by mass or more, more preferably 0.2% by mass or more, and preferably 5% by mass or less. It is more preferable that the amount is not more than mass%. This is because if the content ratio of the fibrous carbon material in the heat conductive sheet is 0.05% by mass or more, the heat conductivity, heat radiation and strength of the heat conductive sheet can be sufficiently improved. Furthermore, if the content ratio of the fibrous carbon material in the heat conductive sheet is 5% by mass or less, the hardness of the heat conductive sheet is prevented from being increased (that is, the flexibility is lowered) by blending the fibrous carbon material. This is because it is possible to obtain a heat conductive sheet in which heat conductivity, heat radiation, flexibility and strength are juxtaposed at a sufficiently high level.

<Additives>
If necessary, known additives that can be used for forming the heat conductive sheet can be blended in the heat conductive sheet. Additives that can be blended in the heat conductive sheet are not particularly limited, for example, plasticizers such as sebacic acid; flame retardants such as red phosphorus flame retardants and phosphate ester flame retardants; urethane acrylates and the like Toughness improvers; hygroscopic agents such as calcium oxide and magnesium oxide; adhesive strength improvers such as silane coupling agents, titanium coupling agents, and acid anhydrides; wettability such as nonionic surfactants and fluorosurfactants Improvers; ion trapping agents such as inorganic ion exchangers; and the like.

<Properties of thermal conductive sheet>
And the heat conductive sheet of this invention is not specifically limited, It is preferable to have the following properties.

[Surface roughness]
The heat conductive sheet needs to have a 10-point average surface roughness Rz of at least one main surface of 40 μm or less. If the ten-point average surface roughness of at least one main surface of the heat conductive sheet is 40 μm or less, the heat radiation of the heat conductive sheet can be increased. Therefore, for example, when a heat conductive sheet is used on a heating element, or when sandwiched between a heat generating element and a heat radiator, heat is efficiently dissipated from the heat generating element via the heat conductive sheet. can do. In addition, from the viewpoint of further increasing the heat radiation property of the heat conductive sheet, the ten-point average surface roughness of at least one main surface is preferably 35 μm or less, and more preferably 30 μm or less. Furthermore, from the viewpoint of further increasing the thermal radiation of the heat conductive sheet, and when the heat conductive sheet is sandwiched between the heat generator and the heat radiator, it can be attached without considering the direction of the sheet. From the viewpoint of advantages, it is more preferable that the ten-point average surface roughness of both main surfaces is within the above range. Moreover, the ten-point average surface roughness of the main surface of the heat conductive sheet is usually 20 μm or more.

[Thermal conductivity]
The thermal conductivity sheet has a thermal conductivity in the thickness direction of preferably 20 W / m · K or more at 25 ° C., more preferably 30 W / m · K or more, and 40 W / m · K or more. More preferably. When the thermal conductivity is 20 W / m · K or more, for example, when the heat conductivity is sandwiched between the heat generator and the heat radiator, heat can be efficiently transferred from the heat generator to the heat radiator.

[Thickness]
In addition, the thickness of a heat conductive sheet becomes like this. Preferably it is 0.1 mm or more and 10 mm or less.

(Method for producing heat conductive sheet)
The method for producing a heat conductive sheet of the present invention includes a step (A) of preparing a sheet containing a resin and a carbon material, and a step of setting the ten-point average surface roughness of at least one main surface of the sheet to 40 μm or less. (B). Thus, if the ten-point average surface roughness of at least one main surface of the sheet is adjusted to 40 μm or less, a heat conductive sheet excellent in heat radiation can be obtained. Moreover, if the sheet | seat containing resin and a carbon material is used, the heat conductive sheet excellent in heat conductivity will be obtained.

<Process (A)>
In the step (A), a sheet containing a resin and a carbon material is prepared. Here, the sheet containing the resin and the carbon material is not particularly limited, and can be formed using a known method using, for example, a composition containing the resin and the carbon material. Among them, the sheet is preferably manufactured through a step of orienting the carbon material in the thickness direction of the sheet using a known method at the time of forming the sheet, and the sheet containing the resin and the carbon material is pressed into a sheet shape. And a step of obtaining a pre-heat conductive sheet (pre-heat conductive sheet forming step), a step of forming a laminate using the obtained pre-heat conductive sheet (laminate formation step), and a step of slicing the laminate ( It is more preferable to manufacture through a slicing step. In addition, the sheet prepared in the step (A) usually has a ten-point average surface roughness of the main surface of more than 40 μm.
Hereinafter, as an example of the step (A), a case where a sheet is obtained by sequentially performing the pre-heat conductive sheet forming step, the laminate forming step, and the slicing step will be described.

[Pre-heat conductive sheet forming process]
In the pre-heat conductive sheet forming step, a composition containing a resin and a carbon material and optionally further containing an additive is pressed to form a sheet to obtain a pre-heat conductive sheet.

[[Composition]]
Here, the composition can be prepared by mixing a resin and a carbon material and an arbitrary additive. And as resin, carbon material, and an additive, what was mentioned above as resin, carbon material, and additive which can be contained in the heat conductive sheet of this invention can be used. Incidentally, when the heat conductive sheet resin is a cross-linked resin, a pre-heat conductive sheet may be formed using a composition containing the cross-linkable resin, or a cross-linkable resin and a curing agent may be used. A pre-heat conductive sheet may be formed using the composition contained, and a cross-linkable resin may be contained in the heat conductive sheet by crosslinking a cross-linkable resin after the pre-heat conductive sheet forming step.

  In addition, mixing is not specifically limited, It can perform using known mixers, such as mixers, such as a kneader, a Hobart mixer, and a high speed mixer, a biaxial kneader, and a roll. Mixing may be performed in the presence of a solvent such as ethyl acetate. And mixing time can be made into 5 minutes or more and 60 minutes or less, for example. Also, the mixing temperature can be, for example, 5 ° C. or more and 150 ° C. or less.

  When a carbon material containing a fibrous carbon nanostructure is used as the carbon material, the fibrous carbon nanostructure easily aggregates and has low dispersibility, so it is mixed with other components such as a resin as it is. Then, it is hard to disperse | distribute favorably in a composition. On the other hand, the fibrous carbon nanostructure can suppress the occurrence of aggregation by mixing with other components such as resin in the state of dispersion dispersed in a solvent (dispersion medium), but in the state of dispersion. In the case of mixing, since a large amount of solvent is used when solidifying the solid content after mixing to obtain a composition, the amount of the solvent used for preparing the composition may increase. Therefore, when a fibrous carbon nanostructure is blended in the composition used to form the pre-heat conductive sheet, the fibrous carbon nanostructure is obtained by dispersing the fibrous carbon nanostructure in a solvent (dispersion medium). It is preferable to mix with other components in the state of an aggregate (easy-dispersible aggregate) of fibrous carbon nanostructures obtained by removing the solvent from the obtained dispersion. The aggregate of fibrous carbon nanostructures obtained by removing the solvent from the dispersion of fibrous carbon nanostructures is composed of fibrous carbon nanostructures once dispersed in a solvent, and is dispersed in the solvent. Since the dispersibility is superior to the previous aggregate of fibrous carbon nanostructures, it becomes an easily dispersible aggregate with high dispersibility. Therefore, if the easily dispersible aggregate and other components such as a resin are mixed, the fibrous carbon nanostructure can be efficiently dispersed in the composition efficiently without using a large amount of solvent. it can.

  Here, the dispersion liquid of the fibrous carbon nanostructure can be obtained by, for example, a coarse dispersion liquid obtained by adding the fibrous carbon nanostructure to the solvent to obtain a dispersion treatment or a disintegration effect capable of obtaining a cavitation effect. It can be obtained by subjecting it to a dispersion treatment. In addition, the dispersion process which can obtain a cavitation effect is a dispersion method using a shock wave generated when a vacuum bubble generated in water bursts when high energy is applied to a liquid. Specific examples of the dispersion treatment that can provide a cavitation effect include dispersion treatment using an ultrasonic homogenizer, dispersion treatment using a jet mill, and dispersion treatment using a high shear stirrer. In addition, the dispersion treatment that can obtain the crushing effect is to apply shear force to the coarse dispersion to crush and disperse the aggregates of the fibrous carbon nanostructures, and further to apply a back pressure to the coarse dispersion. This is a dispersion method in which fibrous carbon nanostructures are uniformly dispersed in a solvent while suppressing the generation of bubbles. And the dispersion | distribution process from which a crushing effect is acquired can be performed using a commercially available dispersion | distribution system (For example, product name "BERYU SYSTEM PRO" (product made from a beautiful grain) etc.).

  The solvent can be removed from the dispersion using a known solvent removal method such as drying or filtration. From the viewpoint of removing the solvent quickly and efficiently, filtration such as vacuum filtration is used. It is preferable to carry out.

[[Formation of composition]]
The composition prepared as described above can be defoamed and crushed arbitrarily, and then pressed to form a sheet. Thus, the sheet | seat formed by pressure-molding a composition can be used as a pre heat conductive 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.

  Here, the composition is not particularly limited as long as it is a molding method to which pressure is applied, and can be molded into a sheet using a known molding method such as press molding, rolling molding or extrusion molding. Among these, the composition is preferably formed into a sheet by rolling, and more preferably formed into a sheet by passing between rolls in a state of being sandwiched between protective films. In addition, as a protective film, it does not specifically limit, The polyethylene terephthalate (PET) film etc. which performed the sandblast process can be used. The roll temperature is 5 ° C. or more and 150 ° C. or less, the roll gap is 50 μm or more and 2500 μm or less, the roll linear pressure is 1 kg / cm or more and 3000 kg / cm or less, and the roll speed is 0.1 m / min or more and 20 m / min or less. it can.

And in the pre heat conductive sheet formed as mentioned above, it is speculated that the carbon material is arranged mainly in the in-plane direction, and in particular, the heat conductivity in the in-plane direction is improved.
In addition, the thickness of a pre heat conductive sheet is not specifically limited, For example, it can be 0.05 mm or more and 2 mm or less. In addition, when the carbon material includes a particulate carbon material, from the viewpoint of further improving the thermal conductivity and thermal radiation of the thermal conductive sheet, the thickness of the pre-thermal conductive sheet is the particulate carbon used for the formation of the thermal conductive sheet. It is preferably more than 4 times and not more than 5000 times the mode diameter based on the number of materials.

[Laminated body forming step]
In the laminated body forming step, a plurality of pre heat conductive sheets obtained in the pre heat conductive sheet forming step are laminated in the thickness direction, or the pre heat conductive sheets are folded or wound to obtain a laminate. Here, formation of the laminated body by folding of a pre heat conductive sheet is not specifically limited, It can carry out by folding a pre heat conductive sheet by fixed width using a folding machine. Further, the formation of the laminate by winding the pre-heat conductive sheet is not particularly limited, and by rolling the pre-heat conductive sheet around an axis parallel to the short direction or the long direction of the pre-heat conductive sheet It can be carried out. Moreover, formation of the laminated body by lamination | stacking of a pre heat conductive sheet can be performed using a lamination apparatus, without being specifically limited. For example, if a sheet laminating apparatus (manufactured by Nikkiso Co., Ltd., product name “Hi-Stacker”) is used, air can be prevented from entering between the layers, so that a good laminate can be obtained efficiently.

  In addition, from the viewpoint of suppressing delamination, the obtained laminate can be heated at 120 ° C. or more and 170 ° C. or less for 2 to 8 hours while being pressed at a pressure of 0.1 MPa or more and 0.5 MPa or less in the lamination direction. preferable. Here, prevention of delamination may be performed by applying an adhesive or a solvent to the pre-heat conductive sheets and bonding the pre-heat conductive sheets to each other when forming the laminate, From the viewpoint of production, it is preferable not to use an adhesive or a solvent.

  And in the laminated body obtained by laminating | stacking, folding, or winding a pre heat conductive sheet, it is guessed that the carbon material has arranged in the direction substantially orthogonal to the lamination direction.

[Slicing process]
In the slicing step, the laminated body obtained in the laminated body forming step is sliced at an angle of 45 ° or less with respect to the laminating direction to obtain a heat conductive sheet composed of sliced pieces of the laminated body. Here, the method for slicing the laminate is not particularly limited, and examples thereof include a wire saw method, a multi-blade method, a laser processing method, a water jet method, and a knife processing method. Especially, the knife processing method is preferable at the point which makes the thickness of a heat conductive sheet uniform. The cutting tool for slicing the laminate is not particularly limited, and includes a slice member (for example, a sharp blade) having a smooth board surface having a slit and a blade portion protruding from the slit portion. Cutter, canna, slicer) can be used.

  In addition, from the viewpoint of increasing the thermal conductivity and thermal radiation of the heat conductive sheet, the angle at which the laminate is sliced is preferably 30 ° or less with respect to the stacking direction, and 15 ° or less with respect to the stacking direction. It is more preferable that the angle is substantially 0 ° with respect to the stacking direction (that is, the direction along the stacking direction).

  And as for the heat conductive sheet formed using the sheet | seat obtained through the slicing process, the strip (slice piece of the pre heat conductive sheet which comprised the laminated body) normally containing resin and a carbon material is joined in parallel. It has the structure formed.

<Process (B)>
In step (B), the ten-point average surface roughness of at least one principal surface of the sheet prepared in step (A) is smoothed to 40 μm or less. Here, the smoothing of the main surface of the sheet is not particularly limited, for example, a method (solvent contact method) in which an organic solvent is brought into contact with the main surface (main surface to be smoothed), or the main surface Can be performed by a method of polishing (polishing method). In addition, the solvent contact method and the polishing method may be used in combination, and the execution order in the case of using them together is not particularly limited.
Hereinafter, each step will be specifically described.

[Solvent contact method]
In the solvent contact method, an organic solvent is brought into contact with at least one main surface of the sheet obtained in the step (A) to smooth the main surface. Here, from the viewpoint of easily adjusting the ten-point average surface roughness of the main surface of the sheet, in the solvent contact method, after performing the solvent contact step of bringing the organic solvent into contact with the main surface, It is preferable to carry out a pressure loading step of applying pressure to the contacted main surface.
In addition, when smoothing by the solvent contact method is performed on the sheet having the configuration in which the strips including the resin and the carbon material are joined in parallel, the main surface is configured by contact with the organic solvent. By dissolving the resin, the bonding between the strips can be further strengthened without using an adhesive during sheet formation.

[[Solvent contact process]]
In the solvent contact step, the organic solvent is not particularly limited, and can be brought into contact with the main surface of the sheet by coating the sheet with the organic solvent or immersing the sheet in the organic solvent.

  The organic solvent to be brought into contact with the main surface is not particularly limited as long as it is an organic solvent capable of dissolving the resin constituting the main surface of the heat conductive sheet. For example, hexane, benzene, toluene, diethyl ether, chloroform which are nonpolar organic solvents , Ethyl acetate, methylene chloride, tetrahydrofuran, polar organic solvents such as acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, isophorone acetonitrile, N, N-dimethylformamide, dimethyl sulfoxide, acetic acid 1-butanol, 2-propanol, 1-propanol, ethanol, methanol, formic acid and the like can be used. Of these, methyl ethyl ketone is preferred.

If applying the organic solvent to the main surface of the sheet, the amount of organic solvent to be coated is preferably 2 g / ^{m 2} or more 40 g / ^{m 2} or less. Moreover, when immersing a sheet | seat in an organic solvent, as for immersion time, 1 second or more and 20 seconds or less are preferable. The application of the organic solvent is not particularly limited, and can be performed using, for example, a brush, a roller, or a finger.

[[Pressure load process]]
In the pressure loading process, the main surface that has undergone the solvent contact step (the main surface that has been contacted with the organic solvent) is pressurized so that the main surface of the sheet in which the resin is dissolved by contact with the organic solvent is leveled, and the main surface is fully The point average surface roughness is further reduced. The pressing operation is not particularly limited, and can be performed, for example, by pressing the main surface of the sheet using a roll. Note that the pressure applied to the main surface is not particularly limited, and can be, for example, 1 kN or more and 100 kN or less. The pressure load is not particularly limited, and can be performed for 10 seconds or more and 5 minutes or less after an organic solvent is brought into contact with the main surface, and is preferably performed for 1 minute or less.

[Polishing method]
In the polishing method, the sheet obtained by the step (A) is polished until the ten-point average surface roughness Rz of at least one main surface is 40 μm or less.
Here, the polishing is not particularly limited, and can be performed using, for example, a tool capable of physically grinding the main surface. Specifically, the polishing can be performed by hand with a sandpaper or using a polishing apparatus (manufactured by Musashino Electronics, model number “MA-150”). The polishing time is not particularly limited and can be 10 seconds to 5 minutes. The count of the sandpaper is not particularly limited, but # 800 to # 2000 is desirable.

  In the case where the solvent contact method and the polishing method are used in combination, from the viewpoint of efficiently reducing the ten-point average surface roughness of at least one main surface of the sheet, polishing is performed by heat conduction through the above-described solvent contact step. It is preferable to perform without performing a pressure load process with respect to the said main surface of a sheet | seat.

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.
In the examples and comparative examples, the surface roughness, thermal conductivity, thermal radiation, and productivity of the thermal conductive sheet were measured or evaluated using the following methods, respectively.

<Surface roughness>
About the heat conductive sheet, 10-point average surface roughness Rz (micrometer) was measured as follows, and it was set as the surface roughness of each main surface.
Specifically, for the heat conductive sheet, the 10-point average surface roughness Rz (μm) of each main surface (front surface and back surface), surface roughness measuring machine (product name “SJ-201” manufactured by Mitutoyo Corporation) Measured using.
Here, the ten-point average surface roughness Rz is extracted from the roughness curve by the reference length L in the direction of the average line, and measured from the average line of the extracted portion in the direction of the vertical magnification, from the highest peak. It is the sum of the average value of the absolute values of the elevations (Yp1 to Yp5) at the top of the fifth mountain and the average value of the absolute values of the elevations (Yv1 to Yv5) of the bottom from the lowest valley to the fifth. II):
Rz = (| Yp1 + Yp2 + Yp3 + Yp4 + Yp5 |
+ | Yv1 + Yv2 + Yv3 + Yv4 + Yv5 |) / 5 (II)
Is a value calculated by.

<Thermal conductivity>
About the heat conductive sheet, the thermal diffusivity α (m ² / s) in the thickness direction, the constant pressure specific heat Cp (J / g · K), and the specific gravity ρ (g / m ³ ) were measured by the following methods.
[Thermal diffusivity]
The thermal diffusivity at a temperature of 25 ° C. was measured using a thermophysical property measuring apparatus (product name “Thermo Wave Analyzer TA35” manufactured by Bethel Co., Ltd.).
[Specific pressure specific heat]
Using a differential scanning calorimeter (manufactured by Rigaku, product name “DSC8230”), the specific heat at a temperature of 25 ° C. was measured under a temperature rising condition of 10 ° C./min.
[specific gravity]
The specific gravity at a temperature of 25 ° C. was measured using an automatic hydrometer (product name “DENSIMETER-H” manufactured by Toyo Seiki Co., Ltd.).
And the following formula (I):
λ = α × Cp × ρ (I)
Further, the thermal conductivity λ (W / m · K) in the thickness direction of the thermal conductive sheet at 25 ° C. was determined.

<Thermal radiation>
About the heat conductive sheet, the thermal radiation property was measured using the heat propagation test | inspection apparatus (The Betel company make, product name "thermal imaging scope TSI").
Specifically, an aluminum plate on which a heat conductive sheet is placed is placed on a pedestal, and the heat conductive sheet is pushed from above with a finger to such an extent that a space that can be visually confirmed is not formed between the heat conductive sheet and the aluminum plate. . And the back surface temperature of the heat conductive sheet was heated up to 70 degreeC, and was maintained. Five minutes after the back surface temperature reached 70 ° C., the luminance of the main surface (front surface) of the heat conductive sheet was measured with the heat propagation inspection device, and the thermal radiation was evaluated based on the following criteria. It shows that it is excellent in thermal radiation property, so that the magnitude | size of a brightness | luminance is large.
○: Difference in luminance from Comparative Example 1 is 100 or more ×: Difference in luminance from Comparative Example 1 is less than 100

<Productivity>
The time required to complete the smoothing of the slicing process and the subsequent sheet, including the laminate forming process described in the following examples, was measured and evaluated according to the following criteria. It shows that productivity is excellent, so that the time which manufacture requires is short.
○: 15 minutes or less ×: Over 15 minutes

Example 1
<Preparation of heat conduction sheet>
[Preparation of acrylic resin]
A reactor was charged with 100 parts of a monomer mixture composed of 94% 2-ethylhexyl acrylate and 6% acrylic acid, 0.03 parts 2,2′-azobisisobutyronitrile and 700 parts ethyl acetate. After dissolving in nitrogen and purging with nitrogen, a polymerization reaction was carried out at 80 ° C. for 6 hours. The polymerization conversion rate was 97%. The obtained polymer was dried under reduced pressure to evaporate ethyl acetate, and a viscous solid copolymer was obtained as an acrylic resin.
The weight average molecular weight (Mw) of the acrylic resin was 270000, and the molecular weight distribution (weight average molecular weight (Mw) / number average molecular weight (Mn)) was 3.1. The weight average molecular weight (Mw) and the number average molecular weight (Mn) were determined in terms of standard polystyrene by gel permeation chromatography using tetrahydrofuran as an eluent.

[Preparation of fibrous carbon nanostructure]
SGCNT prepared by the super-growth method was prepared as a fibrous carbon nanostructure. The SGCNT had an average diameter of 3.3 nm, (3σ / Av) of 0.58, and a BET specific surface area of 800 m ² / g.

[Preparation of easily dispersible aggregates]
About 400 mg of SGCNT was mixed with 2 L of methyl ethyl ketone and stirred for 2 minutes by a homogenizer to prepare a SGCNT / methyl ethyl ketone dispersion.
This dispersion solution is passed through a wet jet mill having a flow path of 0.5 mm (model “JN20”, manufactured by Jokkou Co., Ltd.) for two cycles under a pressure of 100 MPa to disperse the aggregate of SGCNT in methyl ethyl ketone. As a result, a carbon nanotube micro-dispersion was obtained.
The concentration of the carbon nanotube micro-dispersion was 0.20%, and the center particle size was 24.1 μm. The central particle size was measured using a laser diffraction / scattering particle size distribution measuring apparatus (manufactured by Horiba, Ltd., model “LA960”).
The obtained carbon nanotube micro-dispersion was filtered under reduced pressure using filter paper (manufactured by Kiriyama Co., No. 5A) to obtain an easily dispersible aggregate (nonwoven fabric sheet) of SGCNT.

[Sheet formation]
Expanded graphite as a particulate carbon material (produced by Ito Graphite Industries Co., Ltd., product name “EC50”, number-based mode diameter (measured value): 110 μm) is 200 parts, the acrylic resin is 100 parts, and the SGCNT 1 part of an easily dispersible aggregate (nonwoven fabric sheet) of No. 1 in the presence of 20 parts of ethyl acetate as a solvent using a Hobart mixer (manufactured by Kodaira Manufacturing Co., Ltd., trade name “ACM-5LVT type”) for 1 hour Stir and mix.
And the obtained mixture was degas | defoamed for 1 hour, the ethyl acetate was removed simultaneously with degassing | defoaming, and the composition containing expanded graphite, an acrylic resin, and SGCNT was obtained. And the obtained composition was thrown into the crusher and crushed for 10 seconds.
Subsequently, 5 g of the crushed composition was sandwiched between 50 μm thick PET films (protective film) subjected to sandblast treatment, a roll gap of 330 μm, a roll temperature of 50 ° C., a roll linear pressure of 50 kg / cm, and a roll speed of 1 m / min. Roll forming was performed under the conditions to obtain a pre-heat conductive sheet having a thickness of 0.5 mm (pre-heat conductive sheet forming step).

  Next, after 120 sheets of the obtained pre-heat conductive sheets were laminated in the thickness direction to obtain a 6 cm thick laminate, the obtained laminate was compressed by hand and adhered (laminate formation step). ).

  Then, after cooling the laminated body of the pre-heat conductive sheet to −10 ° C. with dry ice, while pressing the laminated section at a pressure of 0.3 MPa, the cutter (manufactured by Olfa, blade width sizes are 9 mm, 18 mm, angle of broken line) Is 59 degrees) and sliced at an angle of 0 degrees with respect to the stacking direction at a speed of 2 mm / min (in other words, sliced in the normal direction of the main surface of the stacked pre-heat conductive sheets), A sheet 6 cm long x 5 cm wide x 0.50 mm thick was obtained (slicing step).

[Smoothing of sheet]
One main surface (surface) of the sheet (sheet containing resin and carbon material) obtained by the above-described method was coated with methyl ethyl ketone (organic solvent) corresponding to 10 g / m ² at a temperature of 25 ° C. Then, 30 seconds after the coating of the organic solvent, the main surface coated with the organic solvent was made uniform using a tape press roll manual mold (model SA-1003-B, manufactured by Tester Sangyo Co., Ltd.). Moreover, the same operation | work was performed regarding the back surface, and the heat conductive sheet was obtained.
And about the obtained heat conductive sheet, surface roughness, heat conductivity, thermal radiation property, and productivity were measured or evaluated. The results are shown in Table 1.

<Example 2>
A heat conductive sheet was prepared in the same manner as in Example 1 except that the sheet was smoothed as follows and evaluated in the same manner as in Example 1. The results are shown in Table 1.
[Smoothing of sheet]
Both main surfaces of the sheet obtained by the above-described method are polished for 3 minutes using a sandpaper (made by Truss Nakayama Co., Ltd., product name “Water Resistant Paper # 2000”) until the surface becomes uniform to obtain a heat conductive sheet. It was.

<Example 3>
A heat conductive sheet was prepared in the same manner as in Example 1 except that the sheet was smoothed as follows and evaluated in the same manner as in Example 1. The results are shown in Table 1.
[Smoothing of sheet]
One main surface (surface) of the sheet obtained by the above-described method was coated with methyl ethyl ketone (organic solvent) corresponding to 10 g / m ² at a temperature of 25 ° C. Then, 30 seconds after the application of the organic solvent, the main surface coated with the organic solvent was used for 3 minutes until the surface became uniform using a sandpaper (product name “Waterproof Paper # 2000” manufactured by Truss Nakayama Co., Ltd.). Polished. Moreover, the same operation | work was performed regarding the back surface, and the heat conductive sheet was obtained.

<Comparative Example 1>
A heat conductive sheet was prepared in the same manner as in Example 1 except that the sheet obtained in the slicing step was directly used as a heat conductive sheet without smoothing the sheet, and evaluated in the same manner as in Example 1. It was. The results are shown in Table 1.

<Comparative Example 2>
At the time of forming the sheet, in the laminate forming step, each time a pre-heat conductive sheet is laminated, methyl ethyl ketone is applied, and the pre-heat conductive sheets are laminated while adhering to each other, and the sheet is not smoothed. A heat conductive sheet was prepared in the same manner as in Example 1 except that the sheet obtained in the slicing step was directly used as a heat conductive sheet, and evaluation was performed in the same manner as in Example 1. The results are shown in Table 1.

From Table 1, in the heat conduction sheets of Examples 1 to 3 in which the ten-point average surface roughness Rz of at least one main surface is 40 μm or less, the ten-point average surface roughness Rz of both main surfaces is larger than 40 μm. Compared with the heat conductive sheet of Comparative Examples 1-2, it turns out that thermal radiation property is improving.
Moreover, in the comparative example 2 which adhered the pre heat conductive sheet for every layer, it turns out that production efficiency is falling.

  ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the heat conductive sheet which enables efficient dissipation of heat, and the heat dissipation sheet which enables efficient dissipation of heat can be provided.

Claims (11)

Including a resin and a carbon material,
Ten-point average surface roughness of at least one principal Ri der less 40 [mu] m, the thermal conductivity in the thickness direction is 20W / m · K or more, heat conductive sheet (however, Asker C hardness at 70 ° C. is 60 or less Note that the Asker C hardness at 70 ° C. means that a heat conductive sheet having a thickness of 5 mm or more is heated on a hot plate so that the temperature measured by a surface thermometer is 70 ° C. It is a value measured with a hardness meter C type.) . The heat conductive sheet according to claim 1 , wherein the carbon material includes expanded graphite. The heat conductive sheet according to claim 1 or 2 , wherein the carbon material includes a fibrous carbon nanostructure. The heat conductive sheet in any one of Claims 1-3 by which the strip containing the said resin and the said carbon material is joined in parallel. It is a manufacturing method of the heat conductive sheet in any one of Claims 1-4,
Preparing a sheet containing a resin and a carbon material (A);
A step (B) of setting the ten-point average surface roughness of at least one main surface of the sheet to 40 μm or less;
The manufacturing method of the heat conductive sheet containing this. The method for producing a heat conductive sheet according to claim 5 , wherein the step (B) includes a step of bringing an organic solvent into contact with the main surface. The manufacturing method of the heat conductive sheet of Claim 6 with which the said process (B) further includes the process of applying a pressure to the said main surface of the said sheet | seat which contacted the said organic solvent. Step (B) comprises a step of polishing the main surface, the heat conducting sheet manufacturing method according to any one of claims 5-7. The step (A)
Pressurizing a composition containing the resin and the carbon material to form a sheet, and obtaining a pre-heat conductive sheet;
Laminating a plurality of the pre-heat conductive sheets in the thickness direction, or folding or winding the pre-heat conductive sheet to obtain a laminate; and
Slicing the laminate at an angle of 45 ° or less with respect to the lamination direction to obtain the sheet;
The containing, heat conducting sheet manufacturing method according to any one of claims 5-8. Wherein the carbon material comprises expanded graphite, a manufacturing method of the heat conducting sheet according to any one of claims 5-9. Wherein the carbon material comprises a fibrous carbon nanostructures, a manufacturing method of the heat conducting sheet according to any one of claims 5-10.