JP2002009213A - Heat-conducting sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an easy-to-handle and good heat conductive sheet, which does not make gaps or the like between layers of a plurality of the sheets and makes a close contact with a mounted object to keep heat conductance high when the layers are laminated. SOLUTION: This heat-conductive sheet is formed by laminating under pressing, on at least one side of a graphite sheet layer 1, an elastomer sheet layer 2 in which at least one kind selected from a heat conductive filling agent, carbon nano-tubes and carbon micro-coils is combined.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a heat conductive sheet. In particular, the present invention relates to a heat conductive sheet preferably used as a heat radiating material for efficiently radiating heat generated from heat generating components of various electric and electronic devices.

[0002]

2. Description of the Related Art In various electric and electronic devices,
It is important to efficiently dissipate the heat generated from the heat-producing components in order to prevent malfunctions and extend the life of the product. Therefore, a heat radiating material for radiating generated heat has been used in electric and electronic devices having components that generate heat. As one of such heat dissipating materials, a heat conductive sheet in which a silicone rubber is applied to at least one surface of a graphite sheet is disclosed in Japanese Patent Publication No. 3-51302. Such a heat conductive sheet is easy to handle due to its shape, has silicone rubber on at least one side, has good adhesion to a mounting target portion, and is convenient as a heat radiating material for electric and electronic devices. It is assumed. But,
Since such a heat conductive sheet is obtained by merely applying silicone rubber to a graphite sheet, the adhesion between the graphite sheet and the silicone rubber becomes insufficient, or the flat sheet to be mounted, such as a full-pack transistor, cannot be used. Even if adhesion can be secured, as a general-purpose heat conductive sheet for other electric and electronic devices, there is a drawback such as easy formation of a gap between the part to be attached and the mounting target part, and sufficient heat conductivity It could not be improved. In addition, as a result of deforming the heat conductive sheet along the mounting target portion, the graphite sheet is cleaved, and in some cases, the graphite is lost as a cleaved piece, which also has a problem in reliability during use. Further, even during the production, when attempting to produce a continuous sheet, it is difficult to apply sufficient winding tension because the graphite sheet may be torn.
Problems still remain in mass production.

On the other hand, the present inventor has disclosed in Japanese Patent Laid-Open No. 11-1168.
No. 20 proposed a thermally conductive elastomer molded article in which ferrite was blended with an elastomer such as silicone rubber and cured. Such a molded body exhibits good thermal conductivity due to the compounded ferrite, but it has been desired to further improve the thermal conductivity.

[0004]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to handle easily, have sufficient thermal conductivity, and form a gap between layers when a plurality of layers are laminated. To provide a novel heat conductive sheet that does not generate, can maintain high thermal conductivity by being sufficiently adhered to the mounting target part, hardly causes defects such as cleavage due to deformation, and is excellent in mass productivity. is there.

[0005]

Means for Solving the Problems As a result of intensive studies to achieve the object of the present invention, the present inventor has selected a heat conductive filler, a carbon nanotube and a carbon microcoil for a sheet-like graphite layer. A heat conductive sheet is formed by laminating at least one sheet-like elastomer layer, and upon laminating the above-mentioned sheet-like elastomer layer, the composition is pressed against a sheet-like graphite layer. It has been found that the object of the present invention can be achieved.

Further, the present inventor has found that it is preferable that the thickness of the sheet-like elastomer layer is at least 150 μm or more in order to secure the adhesion between the heat conductive sheet and the mounting target portion. I have.

Further, the present inventor has found that soft magnetic ferrite is preferably used as a thermally conductive filler to be blended in the above-mentioned sheet-like elastomer layer. That is, among various heat conductive fillers, soft magnetic ferrite is inexpensive, has a correspondingly high heat conductivity, and a silicone rubber composition in which a silicone rubber is blended therein causes a significant increase in cost. Without having good thermal conductivity, it was found that it was suitable for forming a sheet-like elastomer layer constituting the thermal conductive sheet.

Further, the following has been found regarding the above soft magnetic ferrite. That is, so-called Cu—Zn based, Ni—Zn based or M
There are various types such as n-Mg type, but these various types have various advantages and disadvantages in characteristics, differences in behavior, and do not necessarily have a uniform effect as a heat conductive filler, Among these various types, it has been found that Ni-Zn soft magnetic ferrite is most preferably used as a thermally conductive filler to be blended with silicone rubber as a base material.
That is, (a) when comparing the above various materials in terms of thermal conductivity, the thermal conductivity is higher than that of Mn-Mg based> Ni-Zn.
System> Cu-Zn system, and Mn-Mg system is the highest. (B) When these various compounds are blended with silicone rubber, the silicone rubber is an addition type silicone rubber whose curing mechanism is addition type. Sometimes, uncured or insufficiently cured portions may occur, so-called curing inhibition may occur, and Mn-Mg-based materials may cause such curing inhibition, and may be Ni-Zn-based and Cu-Zn-based. Means that hardening inhibition is unlikely to occur, and (c)
When these various materials are compared in terms of uniform dispersibility in silicone rubber, many of the Mn-Mg-based materials remain as agglomerated, and some of the Cu-Zn-based materials remain as agglomerated.
It has been found that the -Zn system is uniformly dispersed without aggregation.
That is, among the above various soft magnetic ferrites, Ni-Zn
The system has the properties that it has high thermal conductivity, hardly inhibits the curing of silicone rubber, and has excellent dispersibility in silicone rubber. It was found to be used.

Furthermore, it has been found that even if a sheet-like elastomer layer is laminated on a sheet-like graphite layer, the desired thermal conductivity may not be sufficiently obtained. It was found that bubbles were unavoidable in the process of forming the sheet-like elastomer layer, but the presence of these bubbles could not be completely eliminated. Another factor is that voids between sheets between the sheet graphite layer and the sheet elastomer layer cannot be completely avoided. In Japanese Patent Publication No. 54-33959, only the method of pressurizing and fixing the heat-generating electric circuit element to the heat-dissipating sheet is described, and the sheet lamination technique is not disclosed.

[0010] Furthermore, the present inventor also studied the orientation state of the thermally conductive filler compounded in the silicone rubber. When trying to obtain high thermal conductivity, it is conceivable to increase the amount of the thermal conductive filler, but in this case, the flexibility of the sheet-like elastomer layer is lost, and the workability may be impaired. is there. From the application of the heat dissipating material, it is desirable to have flexibility and excellent workability. Therefore, the present inventor has found that by controlling the orientation of the thermally conductive filler, high thermal conductivity can be obtained even with an appropriate filling amount.

Further, the inventor of the present invention has conceived that a sheet-like graphite layer is reinforced by embedding a woven fabric or a non-woven fabric with respect to a sheet-like elastomer layer to be laminated under pressure on the sheet-like graphite layer. It has been found that in the above method, it is possible to suppress the occurrence of cleavage or the like of graphite, and to make it possible to apply a sufficient winding tension at the time of production, thereby improving mass productivity.

That is, the present invention has been completed based on the above-mentioned various findings, and provides the following heat conductive sheet in order to achieve the object of the present invention.

(1) A sheet-like elastomer layer containing at least one selected from the group consisting of a thermally conductive filler, carbon nanotubes and carbon microcoils is pressed and laminated on at least one surface of the sheet-like graphite layer. A heat conductive sheet characterized by the above-mentioned.

(2) The heat conductive sheet according to the above (1), wherein a sheet-like elastomer layer having a thickness of at least 150 μm is laminated under pressure.

(3) The above-mentioned (1), wherein the sheet-like elastomer layer is cured and laminated by heating and pressing.
Or the heat conductive sheet according to (2).

(4) The pressure to be applied is 10 to 200 kPa
The heat conductive sheet according to any one of the above (1) to (3), wherein

(5) The heat conductive sheet according to the above (1), wherein the heat conductive filler is a soft magnetic ferrite.

(6) The heat conductive sheet according to the above (5), wherein the soft magnetic ferrite is a Ni—Zn soft magnetic ferrite.

(7) The above (1) to (1), wherein the elastomer is based on silicone rubber.
The heat conductive sheet according to any one of (3).

(8) At least one surface of the sheet-like graphite layer is provided with a sheet-like elastomer layer in which at least one selected from the group consisting of a thermally conductive filler, carbon nanotubes and carbon microcoils is blended in a thermally conductive orientation. A heat conductive sheet characterized by being laminated.

(9) The heat conductive sheet according to the above (8), wherein the heat conductive filler is a soft magnetic ferrite.

(10) The heat conductive sheet according to the above (9), wherein the soft magnetic ferrite is a Ni—Zn soft magnetic ferrite.

(11) The heat conductive sheet according to the above (8), wherein the elastomer is based on silicone rubber.

(12) The above (1) to (1), wherein a woven or nonwoven fabric is embedded in the sheet-like elastomer layer.
(3) The heat conductive sheet according to any of (8).

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION As the sheet-like graphite layer constituting the heat conductive sheet in the present invention, various kinds of conventionally known graphite sheets can be appropriately selected and used. For example,
Graphite sheets include various types of graphite sheets, such as those derived from natural graphite and those derived by graphitizing a polymerizable compound, but their production origin does not matter.
The thickness of the graphite sheet can be appropriately set as needed, but generally, 0.2 to 1.6 mm is appropriate.
This graphite sheet preferably has flexibility. In addition, a primer can be applied to the graphite sheet in advance, if necessary, in order to improve the adhesion to the sheet-like elastomer layer. Examples of the primer include Primer C (trade name: manufactured by Shin-Etsu Silicone Co., Ltd.), Primer X (trade name: manufactured by Toray Dow Corning Silicone Co., Ltd.), Primer Y (trade name: manufactured by Toray Dow Corning Silicone Co., Ltd.), ME151 (trade name: manufactured by Toshiba Silicone Co., Ltd.) and the like.

Various elastomers such as urethane rubber and acrylic rubber can be used as the sheet-like elastomer layer constituting the heat conductive sheet in the present invention. Among them, those having a silicone rubber as a base material are preferable. Used for Various conventionally known silicone rubbers can be appropriately selected and used as the silicone rubber.
For example, any of a heat curing type or a room temperature curing type, and a condensation type or addition type curing mechanism can be used. Also, the group bonded to the silicon atom is not particularly limited, and examples thereof include a methyl group, an ethyl group, an alkyl group such as a propyl group, a cyclopentyl group,
In addition to cycloalkyl groups such as cyclohexyl groups, alkenyl groups such as vinyl groups and allyl groups, and aryl groups such as phenyl and tolyl groups, hydrogen atoms of these groups have been partially substituted with other atoms or bonding groups. Things can be mentioned. Among the various silicone rubbers, those having an additional curing mechanism do not produce by-products upon curing, and are preferably used in this regard.

The silicone rubber used for the sheet-like elastomer layer may be in a gel state. For example, a silicone rubber having a penetration of 5-200 according to JIS K2207-1980 (50 g load) after curing can be used. When a silicone rubber having such a softness is used, the adhesiveness of a sheet-like elastomer layer formed from the composition is increased, which is convenient for attaching a heat conductive sheet.

Generally, some commercially available elastomers such as silicone rubber are shipped to the market in the form of fillers, plasticizers, and other additives. An elastomer containing a colorant, a flame retardant, and other additives can be appropriately selected and used within a range that does not impair the object of the present invention.

In constructing the heat conductive sheet of the present invention, various kinds of conventionally known heat conductive fillers and the like are appropriately selected as the heat conductive filler to be blended in the sheet-like elastomer layer. Can be used. Examples thereof include soft magnetic or hard soft magnetic ferrite, aluminum nitride, silicon nitride, boron nitride, titanium nitride, nitrides such as zirconium nitride, aluminum oxide, silicon oxide, boron oxide, titanium oxide, oxides such as zirconium oxide, Pure iron, metallic silicon and the like can be mentioned. These thermal conductive fillers can be used in combination of two or more as necessary. In addition, the shape of the heat conductive filler can be any shape such as a spherical shape, a fibrous shape, and an irregular shape, if necessary,
The size can be appropriately set as required, but in general, a spherical shape having a particle size of about 3 to 50 μm is preferable from the viewpoint of improving dispersibility. The blending amount of the heat conductive filler can be appropriately set as necessary, but generally, it imparts sufficient heat conductivity to the sheet-like elastomer layer and ensures good moldability of the elastomer layer. For this reason, 20 to 80% by weight based on the total weight of the elastomer layer is appropriate.

Among the above various heat conductive fillers, soft magnetic ferrite is preferably used. As the soft magnetic ferrite, conventionally known various soft magnetic ferrites can be appropriately selected and used.
Soft magnetic ferrites such as n-Mg, Ni-Zn, and Cu-Zn are exemplified. Among these soft magnetic ferrites, the Ni-Zn type has a suitably high thermal conductivity, hardly inhibits the hardening of the silicone rubber, and has excellent dispersibility in the silicone rubber. Can be Soft magnetic ferrites can be obtained at a much lower price compared to high thermal conductive fillers such as boron nitride and are economical.

The above-mentioned various heat-conductive fillers may, if necessary, have their surfaces subjected to silane coupling in order to further enhance the mixing with the silicone rubber and to more easily obtain a uniform silicone rubber composition. Agent.
Examples of the silane coupling agent include γ-chloropropyltrimethoxysilane, vinyltrichlorosilane, vinyltriethoxysila, vinyltrimethoxysilane, vinyl tris (β-methoxyethoxy) silane, γ-methacryloxypropyltrimethoxysilane, β- (3,4
-Epoxycyclohexyl) ethyltrimethoxysilane, γ-crysidoxypropyltrimethoxysilane, γ
-Mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropyltrimethoxysilane, γ-ureidopropyltriethoxysilane and the like. The amount of the silane coupling agent to be used can be appropriately set as needed, but is generally preferably about 0.2 to 10% by weight based on the weight of the thermally conductive filler.

In forming the heat conductive sheet of the present invention, various known carbon nanotubes and carbon microcoils are appropriately selected as carbon nanotubes or carbon microcoils to be incorporated in the sheet-like elastomer layer. Can be used. Carbon nanotubes are generally made of carbon and have an outer diameter of 2
～70Nm, be of cylindrical hollow fiber is not less than 10 ² times the diameter length, vapor phase decomposition reaction or a carbon-containing gas, carbon rod, by an arc discharge method using carbon fibers It is obtained. Further, the terminal shape does not necessarily have to be cylindrical, and may be deformed, for example, into a conical shape. Further, the ends may be closed or open. Examples of carbon nanotubes preferably used include Graphite Fiber manufactured by Hyperion Catalysis International.
ls-Grades BN (trade name) and the like.
A carbon microcoil is generally made of carbon and has a fiber diameter of 0.05 to 5 μm and an outer coil diameter of 2 mm of the fiber diameter.
A coiled fiber having a length of 10 to 10 times and a number of turns of 5 / coil outer diameter (μm) to 50 / coil outer diameter (μm) per 10 μm, which is obtained by a gas phase decomposition reaction of a carbon-containing gas. It is. These carbon nanotubes and carbon microcoils can be used together if necessary. The compounding amount of carbon nanotubes and carbon microcoils is extremely expensive due to the fact that the total production amount thereof is still small. 0.05 to 10% by weight with respect to the total weight is suitable. These carbon nanotubes and carbon microcoils have thermal conductivity and are excellent in electromagnetic wave absorption, so that when they are blended, the electromagnetic wave absorption of the sheet-like elastomer layer and thus the entire heat conductive sheet is improved. If necessary, the carbon nanotubes or carbon microcoils may be used in combination with the heat conductive filler. In this case, the total weight of these fillers is 20 to 80 weight based on the total weight of the sheet-like elastomer layer. % Is appropriate.

Further, in forming the heat conductive sheet of the present invention, the sheet-like elastomer layer may be added, if necessary, to the heat conductive filler, carbon nanotubes, carbon microcoils and the like. As long as the object of the present invention is not impaired, a general additive such as a curing agent, a curing accelerator, a coloring agent, a flame retardant and the like generally used in elastomers can be blended in an appropriate amount.

Further, the sheet-like elastomer layer includes:
If necessary, a woven or nonwoven fabric can be embedded. The term "embedding" as used herein refers to a state in which the woven fabric / nonwoven fabric is embedded in the sheet-like elastomer layer and the interface between the woven fabric / nonwoven fabric and the sheet-like graphite layer. Mean any of the states embedded so as to be located at As a result, the woven or nonwoven fabric functions as a reinforcing material for the sheet graphite layer, and it is possible to prevent cleavage or loss of the sheet graphite caused by deformation of the heat conductive sheet. In the case where the woven fabric or the nonwoven fabric is provided with the sheet-like elastomer layer on both sides of the sheet-like graphite layer, it is desirable to embed the sheet-like elastomer layer on both sides of the sheet-like graphite layer. You can also.

As the woven or nonwoven fabric, various synthetic fibers, natural fibers,
It can be appropriately selected and used from woven fabrics and nonwoven fabrics such as glass fibers and metal fibers. However, of the heat conductive sheet,
The woven or non-woven fabric embedded in the sheet-like elastomer layer provided on the side to be attached to the electric / electronic device or the like needs to have electric insulation. A preferred example of such a woven or nonwoven fabric is meta-aramid paper (trade name:
And non-woven fabrics made of aramid fibers such as DuPont Teijin Advanced Paper Co., Ltd.). In addition, the thickness of the woven or nonwoven fabric is too large, the thermal conductivity of the entire heat conductive sheet is reduced, and the flexibility of the sheet is also impaired. Since a sufficient reinforcing effect cannot be obtained, it is set appropriately in consideration of these. More specifically, the thickness is suitably about 30 to 100 μm, but is not limited thereto.

Next, the method for producing the heat conductive sheet of the present invention will be described by taking the case where silicone rubber is used as the base material of the sheet-like elastomer layer as an example. In the case of embedding a woven fabric or a non-woven fabric, each will be described below.

In the case of the above (a), first, at least one kind selected from the above-mentioned heat conductive filler, carbon nanotube and carbon microcoil, and if necessary, a general additive generally used in the past. By blending, a thermally conductive silicone rubber composition is prepared. The silicone rubber composition can be prepared by adding the above-mentioned various components to the silicone rubber and mixing them appropriately using a known mixing means such as a Henschel mixer, a Banbury mixer, or a three-roll kneader. . In the heat conductive sheet according to the above (a), the uncured and fluid silicone rubber composition is poured onto one or both sides of a graphite sheet, and the poured silicone rubber composition is applied to the graphite sheet. It can be produced by curing while pressing. At this time, the thickness of the silicone rubber composition to be poured can be appropriately set as necessary.However, a heat conductive filler is added to improve the heat conductivity, and the heat conductive filler is added. However, in order to ensure the adhesion to the mounting target portion, the thickness after curing is preferably at least 150 μm, and in particular, 0.2 to 1 μm.
mm is particularly preferred. The total thickness of the heat conductive sheet to be produced, that is, the total thickness of the sheet-like graphite layer and the thickness of the sheet-like elastomer layer after curing can also be appropriately set as necessary. , Generally 0.
3 to 3.6 mm (the minimum thickness on one side to the maximum thickness on both sides) is appropriate. The casting of the uncured silicone rubber composition into the graphite sheet can be appropriately performed using a known method such as a spray method, a dipping method, a calendering method, a wire bar coating method, or the like.

The uncured silicone rubber composition poured into the graphite sheet is cured while being pressed against the graphite sheet. For example, the uncured silicone rubber composition is pressed and heated by various presses such as a roll or a flat plate press. The method is appropriately performed by adopting the method described above. As a result, curing proceeds while the silicone rubber composition is strongly adhered to the graphite sheet, so that defects between layers that cause peeling or voids later are removed, and high thermal conductivity is maintained.

The pressure to be applied is appropriately set according to the temperature at which the silicone composition is cured, the concentration of the thermally conductive filler, and the like. If the pressure is too low, however, the effect of adhering the layers to remove defects is insufficient. Yes, conversely, if it is too high, it is not preferable due to uneven distribution of the heat conductive filler, so in consideration of these,
The pressure is preferably set to 10 to 200 kPa.

The graphite sheet itself has anisotropic thermal conductivity, and its thermal conductivity in the thickness direction is lower than that in other directions. Therefore, a high thermal conductivity can be obtained as a whole by making the sheet-like elastomer layer that isotropically conducts heat to make up for the thermal conductivity in the thickness direction. For example, when a squeegee is used to spread the poured silicone rubber composition to a uniform thickness on a graphite sheet, pressure can be applied using the squeegeeing pressure.

Furthermore, the heat conductivity can be improved without filling the sheet-like elastomer layer with a large amount of the heat conductive filler. In other words, even when a large amount of the thermally conductive filler is not filled, it is possible to obtain high thermal conductivity by setting the thermally conductive fillers to be thermally connected to each other or to be oriented so as to be thermally close to each other. Can be. In addition, high thermal conductivity can be obtained by regularly orienting the thermal conductive filler. The control of the orientation state is performed by applying ultrasonic vibration, a magnetic field, or the like during heating.

On the other hand, in the case of the above (b), in the case where the woven or nonwoven fabric is embedded so as to be wrapped in the sheet-like elastomer layer, first, the woven or nonwoven fabric is prepared by the silicone prepared in the above (a). The woven or nonwoven fabric is impregnated with the silicone rubber composition by immersing it in the rubber composition or the like. Then, a woven or non-woven fabric impregnated with the silicone rubber composition is laminated on the sheet graphite, and cured while being pressed, whereby the heat conductive sheet according to the above (b) can be obtained. Alternatively, a similar heat conductive sheet can be obtained by pouring the above-mentioned silicone rubber composition into sheet graphite, laminating a woven or nonwoven fabric thereon, and further pouring and curing the silicone rubber composition while applying pressure. be able to. In the case of the above (b), when the woven or nonwoven fabric is embedded so as to be located at the interface between the sheet-like elastomer layer and the sheet-like graphite layer,
For example, it is possible to obtain a desired heat conductive sheet by applying a thin adhesive to sheet graphite, then laminating a woven or nonwoven fabric, further pouring a silicone rubber composition thereon, and curing it while applying pressure. it can. In addition, as an adhesive applied to the sheet graphite, any component can be used as long as it can sufficiently adhere the woven or nonwoven fabric to the sheet graphite. Another example is
When laminating a woven / non-woven fabric and sheet graphite, the woven / non-woven fabric can be laminated by welding without using the above-mentioned adhesive. In addition, it is preferable that the silicone composition poured onto the woven fabric or nonwoven fabric is cured while being impregnated into the woven fabric or nonwoven fabric because the adhesion is enhanced. The means for pouring the silicone rubber composition and the thickness of the cured elastomer layer are the same as those in the case (a). Further, means for pressurizing the poured silicone rubber composition,
The pressure to be applied also conforms to the case of the above (a).

By embedding a woven or non-woven fabric in the sheet-like elastomer layer as in the case of (b) above, the sheet-like graphite layer is reinforced, so that an external force such as winding tension is applied in the manufacturing process. In such a case, it is possible to avoid such a situation that the sheet-like graphite layer is torn off. Therefore, the target heat conductive sheet can be manufactured as a continuous sheet, and mass productivity is improved.

FIGS. 1 to 4 schematically show cross sections of an example of the heat conductive sheet produced by the above method.
In the example of FIG. 1, a sheet-like elastomer layer 2 in which a predetermined compound is blended is laminated on one surface of a sheet-like graphite layer 1. In the example of FIG. 2, sheet-like elastomer layers 2 and 2 ′ containing a predetermined compound are laminated on both surfaces of the sheet-like graphite layer 1. 3 and 4
Are the sheet-like elastomer layers 2 in FIG.
FIG. 3 shows an example in which the nonwoven fabric 3 is embedded so as to be wrapped in the sheet-like elastomer layer 2, and FIG. 4 shows the nonwoven fabric 3 embedded in the sheet-like elastomer layer. FIG. 2 shows a state where the semiconductor device is embedded so as to be located at an interface between the sheet-like graphite layer 2 and the sheet-like graphite layer 1. The heat conductive sheet of the present invention is generally a flexible sheet.

[0045]

The present invention will be described more specifically with reference to the following examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 A thermally conductive filler was added to 25 parts by weight of a silicone gel (manufactured by Dow Corning Silicone Toray Co., Ltd .; CF5057 (trade name)) having a penetration of 100 according to JIS K2207-1980 (50 g load). Spherical N with an average particle size of 16 μm
A composition was prepared by mixing 7 parts by weight of i-Zn soft magnetic ferrite powder (manufactured by Powder Tech) at room temperature with a three-roll kneader. After vacuum defoaming the obtained composition, a 0.3 mm thick graphite sheet (manufactured by Nippon Carbon Co., Ltd .; Nikafilm FL) having a surface coated with a primer (manufactured by Shin-Etsu Silicone Co .; primer C (trade name)) in advance. −401
(Trade name)) was poured into one side so that air was not entrapped, covered with glass plates with spacers interposed at the four corners from above, and heated and pressed at 100 ° C. for 30 minutes at a pressure of 100 kPa. . After confirming that the silicone gel composition was cured, the glass plate was removed to obtain a heat conductive sheet. The obtained heat conductive sheet is a state in which a silicone gel as a sheet elastomer layer is laminated on one side of the sheet graphite, and the thickness of the silicone gel layer is 1.0 mm. The entire sheet was 1.3 mm. The thermal conductivity of this thermal conductive sheet was measured with a thermal conductivity meter (manufactured by Kyoto Electronics Industry Co., Ltd .; QTM500). As a result, the thermal conductivity was 3.25 W / m.
K, which was higher than that of Comparative Example 1 described later.

Example 2 In Example 1, Ni—Zn was used as the heat conductive filler.
Average particle size 6.3 μm instead of soft magnetic ferrite powder
A heat conductive sheet was produced in the same manner as in Example 1 except that spherical Cu—Zn-based soft magnetic ferrite powder (manufactured by Powder Tech) was used. The heat conductivity of the obtained heat conductive sheet was measured. As a result, the thermal conductivity was 3.20 W / mK, which was higher than that of Comparative Example 1 described later.

Example 3 In Example 1, Ni—Zn was used as the heat conductive filler.
Soft magnetic ferrite powder 52.5 parts by weight and average particle size 10
A heat conductive sheet was produced in the same manner as in Example 1, except that 22.5 parts by weight of a spherical metal silicon powder having a thickness of μm (manufactured by Atomatec; 10 μm of metal silicon) was used.
The heat conductivity of the obtained heat conductive sheet was measured. As a result, the thermal conductivity was 3.63 W / mK, which was higher than that of Comparative Example 1 described later.

Example 4 In Example 3, in addition to the Ni—Zn soft magnetic ferrite powder and the metal silicon powder, carbon nanotubes (manufactured by Hyperion Catalysis International; Graphite Fibers Grades)
A heat conductive sheet was produced in the same manner as in Example 3, except that 1 part by weight of BN (trade name) was further added.
The heat conductivity of the obtained heat conductive sheet was measured. As a result, the thermal conductivity was 3.64 W / mK, which was higher than that of Comparative Example 1 described later.

Example 5 A heat conductive sheet was produced in the same manner as in Example 1 except that ultrasonic vibration was applied during heating without pressing. The heat conductivity of the obtained heat conductive sheet was measured. As a result, the thermal conductivity was 3.40 W /
mK, which was higher than that of Comparative Example 1 described later.

Example 6 An aramid nonwoven fabric of 120 μm thick meta-aramid paper (trade name: manufactured by DuPont Teijin Advanced Paper) was impregnated with the silicone gel composition prepared in Example 1 beforehand. A 0.3 mm-thick graphite sheet (manufactured by Nippon Carbon Co., Ltd .; Nikafilm FL-401 (trade name)) having a primer (Shin-Etsu Silicone; Primer C (trade name)) applied to the surface is laminated on one side, and the The four corners from above were covered with a glass plate having spacers interposed therebetween, and heated and pressed at 100 ° C. for 30 minutes at a pressure of 100 kPa. After confirming that the silicone gel composition was cured, the glass plate was removed to obtain a heat conductive sheet. The obtained heat conductive sheet is a state in which a silicone gel as a sheet-like elastomer layer in which an aramid nonwoven fabric is embedded is laminated on one side of the sheet-like graphite, and the thickness of the silicone gel layer is 0.35 mm. And
The entire heat conductive sheet was 1.0 mm. The thermal conductivity of this heat conductive sheet was measured. As a result, the thermal conductivity was 2.98 W / mK.
The value was higher than that of. Furthermore, when the obtained heat conductive sheet was cut by punching with a press,
Cleavage from the cut surface of the sheet-like graphite layer and lack of graphite were not observed at all, as was observed when no woven or non-woven fabric was embedded. Furthermore, in order to evaluate the handling property of the heat conductive sheet at the time of manufacturing, a) Hold both ends of one short side of a long heat conductive sheet (1 m × 40 cm) by hand, and hold the heat conductive sheet by its own weight. Hanged. As a result, no cracks were found in the sheet graphite layer, and no cleavage was observed between the layers. Also, b) grasp the midpoint of the two opposing short sides of the long heat conductive sheet by hand, bring the opposing short sides closer to about 30 cm, and loosen the center of the heat conductive sheet. Was. As a result, no crack was found in the sheet graphite layer at the free bending portion, and no cleavage was observed between the layers.

Comparative Example 1 A heat conductive material having a thickness of 1.3 mm was prepared in the same manner as in Example 1, except that the silicone gel was directly poured into a graphite sheet without adding any heat conductive filler. A functional sheet was produced. About the obtained heat conductive sheet,
The thermal conductivity was measured. As a result, the thermal conductivity was 1.57 W
/ MK, which is less than half the value of the first embodiment.

[0053]

According to the present invention, a heat conductive sheet having a sufficient heat conductivity is provided. In particular, the sheet-like graphite layer and the sheet-like elastomer layer strongly adhere to each other to maintain the integrity, and also sufficiently adhere to the attachment target portion to maintain high thermal conductivity. Furthermore, high thermal conductivity can be secured while maintaining the flexibility of the sheet-like elastomer layer,
Mounting workability can be improved. The heat conductive sheet of the present invention can be widely used in various fields, but is particularly preferably used as a heat dissipating material in the field of electric and electronic devices that generate heat. Furthermore, the heat conductive sheet of the present invention has high reliability during use because cleavage and the like hardly occur in the sheet-like graphite layer. Because there will be no tears,
Excellent mass productivity.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing a cross section of one embodiment of a heat conductive sheet of the present invention.

FIG. 2 is a diagram schematically showing a cross section of one embodiment of the heat conductive sheet of the present invention.

FIG. 3 is a diagram schematically showing a cross section of one embodiment of the heat conductive sheet of the present invention.

FIG. 4 is a diagram schematically showing a cross section of one embodiment of the heat conductive sheet of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Sheet graphite layer 2 Sheet elastomer layer 2 'Sheet elastomer layer 3 Nonwoven fabric

Claims (12)

[Claims] 1. A sheet-like elastomer layer containing at least one selected from the group consisting of a thermally conductive filler, carbon nanotubes and carbon microcoils is pressed and laminated on at least one side of a sheet-like graphite layer. A heat conductive sheet characterized by the above-mentioned. 2. The heat conductive sheet according to claim 1, wherein a sheet-like elastomer layer having a thickness of at least 150 μm is laminated under pressure. 3. The heat conductive sheet according to claim 1, wherein the sheet-like elastomer layer is cured and laminated by heating and pressing. 4. The heat conductive sheet according to claim 1, wherein the pressure to be applied is 10 to 200 kPa. 5. The heat conductive sheet according to claim 1, wherein the heat conductive filler is a soft magnetic ferrite. 6. The heat conductive sheet according to claim 5, wherein the soft magnetic ferrite is a Ni—Zn soft magnetic ferrite. 7. The heat conductive sheet according to claim 1, wherein the elastomer is based on silicone rubber. 8. A sheet-like elastomer layer in which at least one selected from the group consisting of a thermally conductive filler, carbon nanotubes and carbon microcoils is blended in at least one surface of the sheet-like graphite layer in a thermally conductive orientation. A heat conductive sheet characterized by being made. 9. The heat conductive sheet according to claim 8, wherein the heat conductive filler is a soft magnetic ferrite. 10. The heat conductive sheet according to claim 9, wherein the soft magnetic ferrite is a Ni—Zn soft magnetic ferrite. 11. The heat conductive sheet according to claim 8, wherein the elastomer is based on silicone rubber. 12. A woven or non-woven fabric is embedded in the sheet-like elastomer layer.
The heat conductive sheet according to any one of the above.