JP4853698B2 - Heat conduction sheet - Google Patents

Description

  The present invention relates to a heat conductive sheet having excellent heat conductivity used for electronic devices, various displays, other devices, devices and the like.

  2. Description of the Related Art In recent years, attention has been focused on sheet-like members that are excellent in heat dissipation or heat transfer, including electronic devices and various display fields. For example, in an electronic device such as a personal computer, the amount of heat generated has been increasing due to an increase in the operating frequency of a CPU (central processing unit) in recent years, and the power consumption of components other than the CPU is also increasing. .

On the other hand, the device itself is required to be further reduced in size and weight, and in addition to this, there is a demand for noise reduction and power consumption reduction. Therefore, a heat dissipation system that does not depend on air cooling by a fan is required.
Also in the field of displays, for example, in plasma displays, it is a big problem to suppress the temperature rise due to heat generation, and in other displays such as organic EL, measures for heat dissipation are required.

In such a field, a member called a heat conductive sheet in which an inorganic filler such as alumina or silica and silicon rubber or acrylic rubber are combined has been used as a conventional heat transfer sheet.
This material is arranged between the heat generating member and the heat sink and functions to transmit heat. However, this material is characterized by being soft and having good adhesion, and the contact thermal resistance between the members can be kept low.

However, the thermal conductivity is general and is about 2 to 5 W / mk, and in order to further increase the heat dissipation efficiency, high thermal conductivity is required.
Moreover, although the heat dissipation material molded object by the composite | combination of an expanded graphite sheet pulverized powder and a binder is also proposed as shown in patent documents 1 and 2, the binder used is a thermosetting resin having a rigid molecular structure. Therefore, the flexibility required for the sheet cannot be satisfied.

JP 2001-031880 A Japanese Patent Laid-Open No. 2001-122663

  Under such circumstances, the point of designing and manufacturing the heat conductive sheet is that the material used (such as graphite) generates very little dust, does not cause a short circuit inside the electronic device, and has a certain flexibility. The heat transfer between the members can be sufficiently achieved without pressure, but there is no heat conductive sheet that can satisfy all of these conditions.

  The present invention provides a heat conductive sheet that does not generate dust from materials such as graphite, does not cause a short circuit inside an electronic device, has excellent sheet physical properties such as thermal conductivity and flexibility, and is stable in quality. To do.

The present invention relates to the following.
(1) an aqueous emulsion rubber binder having elasticity, and expanded graphite powder or expanded graphite sheet pulverized powder is anisotropic graphite that functions as a thermally conductive material were mixed, to remove the used solvent from the mixed material A heat conductive sheet obtained by forming a sheet of a heat conductive sheet material obtained in this way .
(2) The heat conductive sheet according to item (1), wherein the elastic binder is a mixture of an aqueous emulsion rubber and a polymer material other than rubber.
(3) The heat conductive sheet according to item (1) or (2), wherein the anisotropic graphite has a number average particle diameter in the range of 50 μm to 500 μm.
(4) thermal conductive sheet according to any one of claim to expanded graphite sheet pulverized powder, a bulk density in the range of ^{0.15g / cm 3 ~0.3g / cm 3} (1) to (3).
(5) Terms (1) to (4) in which the blending ratio of the elastic binder and the anisotropic graphite is 10 to 1000 parts by weight of the anisotropic graphite with respect to 100 parts by weight of the binder (as a solid content). ).

 The heat conductive sheet of the present invention does not generate dust from materials such as graphite, does not cause a short circuit inside the electronic device, is excellent in sheet physical properties such as heat conductivity and flexibility, is lightweight and has a volatile component. Since there is very little and no inorganic material is used, there is no occurrence of material settling in the production process, and a stable product can be supplied, which is industrially very suitable.

In the present invention, because of the special shape of anisotropic graphite, which is a heat conducting material, the blended graphite and graphite are optimally networked. It is possible to provide a general-purpose sheet that exhibits conductivity and is thin and lightweight.
Also, since the density of the anisotropic graphite used is low, the graphite sedimentation is extremely low when mixed with the liquid binder or after mixing, the mixture (composite) is stable, the thermal conductivity of the final sheet and the sheet The physical properties are stable.

  In the present invention, as the anisotropic graphite, a material that functions as a heat conducting material is used, and for example, expanded graphite powder is preferably used. Although there is no restriction | limiting in particular about expanded graphite powder, If importance is attached to cost, it is preferable to use natural graphite and artificial graphite as raw material graphite. There is no restriction | limiting in the particle size and shape of raw material graphite to be used, What is used industrially can be used.

There are no restrictions on the usage properties of the expanded graphite powder produced from the raw material graphite, and the obtained expanded graphite may be used as it is, but in order to simplify the blending, the expanded graphite is made into a sheet, pulverized, and expanded. Expanded graphite sheet pulverized powder having a higher density than graphite powder can also be used.
In addition, as a method of uniformly dispersing anisotropic graphite functioning as a heat conduction material in an elastic binder, it is common to mix with a device such as a reiki machine or a kneader, but the mixing time, shear force It is necessary to pay attention so that anisotropic graphite is not destroyed during mixing.

  There is no particular limitation on the production method of the expanded graphite powder or expanded graphite sheet pulverized powder used as a preferable one. For example, a step of immersing raw graphite in a solution containing an acidic substance and an oxidizing agent to form a graphite intercalation compound and The graphite intercalation compound can be heated to expand the C-axis direction of the graphite crystal to produce expanded graphite. As a result, the expanded graphite has a worm-like shape and is intricately intertwined.

  The magnification of the expanded graphite is not particularly limited, but is preferably 100 times or more and more preferably 100 times to 500 times in consideration of thermal conductivity, flexibility, strength, and the like. Use of expanded graphite having an expansion ratio of less than 100 times or more than 500 times tends to hinder thermal conductivity, flexibility, strength, and the like.

If it is necessary to further reduce the volatile components, the expanded graphite is heat-treated at a higher temperature to remove impurities contained in the expanded graphite. If also desire more graphite uniform one of, it may be classified, using adjusted to the desired average particle size by fractionation.

  Although there is no restriction | limiting in particular as said raw material, The graphite with which the crystal | crystallization developed highly, such as natural graphite, a bush graphite, and a pyrolytic graphite, is mentioned as a preferable thing. Natural graphite is preferable in consideration of the balance between obtained characteristics and economic efficiency.

  There is no restriction | limiting in particular as natural graphite to be used, Commercial products, such as F48C (brand name made by Nippon Graphite Industry Co., Ltd.) and H-15 (brand name made by Chuetsu Graphite Industry Co., Ltd.), can be used. . These are preferably used in the form of scales.

  As the acidic substance used for the processing of the raw material graphite, one that can enter an interlayer of graphite such as sulfuric acid and generate an acidic root (anion) having sufficient expansion ability is generally used. There is no restriction | limiting in particular about the usage-amount of an acidic substance, It determines with the target expansion ratio, For example, it is preferable to use 100 weight part-1000 weight part with respect to 100 weight part of graphite.

  As the oxidizing agent used with the acidic substance, peroxides such as hydrogen peroxide, potassium perchlorate, potassium permanganate and potassium dichromate, and acids having an oxidizing action such as nitric acid can be used. Hydrogen peroxide is particularly preferable from the viewpoint of easily obtaining good expanded graphite.

  When hydrogen peroxide is used as the oxidizing agent, it is preferably used as an aqueous solution. At this time, the concentration of hydrogen peroxide is not particularly limited, but is preferably in the range of 20 wt% to 40 wt%. Although there is no restriction | limiting in particular also about the usage-amount, It is preferable to mix | blend in 5 to 60 weight part as hydrogen peroxide with respect to 100 weight part of graphite.

The acidic substance and the oxidizing agent are preferably used in the form of an aqueous solution.
Sulfuric acid as an acidic substance is used at an appropriate concentration, but is preferably 95% by weight or more, and particularly preferably concentrated sulfuric acid.

  The acid-treated graphite obtained by the above method is further washed with a large amount of water to remove excess acidic substances, and dried to remove moisture, thereby obtaining acid-treated graphite as a raw material for expanded graphite. Next, expanded graphite is obtained by heating the acid-treated graphite at a temperature of 1000 ° C. or higher.

  The average particle size of the expanded graphite used as the heat conductive material is not particularly limited, but if it is desired to improve the thermal conductivity, it is preferable to use a number average particle size in the range of 50 μm to 500 μm. If the number average particle size is less than 50 μm, the complex entanglement (network) of carbon fibers, which is a feature of expanded graphite, is destroyed, and it tends to be difficult to obtain a sheet having desired thermal conductivity. On the other hand, when the number average particle diameter exceeds 500 μm, the mixing property with the elastic binder used is remarkably lowered, the uniform mixing is difficult, and the physical property values including the heat conductivity of the obtained heat conductive sheet are likely to vary. .

  The expanded graphite obtained above can also be used as the heat conductive material of the present invention, but considering the blending operation with the binder having elasticity, the mixing property, the destruction of the graphite at the time of mixing, etc., as described above It is preferable to use expanded graphite once in a sheet (high density) and pulverized (expanded graphite sheet pulverized powder). The method for forming expanded graphite into a sheet is not particularly limited, but in general, the expanded graphite obtained above is preferably formed into a sheet by applying pressure with a press, a roll or the like.

There are no particular restrictions on the thickness and bulk density of the expanded graphite sheet, but the thickness is in the range of 0.5 mm to 1.5 mm and the bulk density is 0.2 g / cm ^{3 to} 1.7 g /. Those in the range of cm ³ are preferred. If the thickness is less than 0.5 mm, there is a tendency to cause a reduction in work in the pulverization process (the sheet breaks brittlely during handling), and if it exceeds 1.5 mm, pulverization tends to be difficult.

Moreover, when the bulk density is less than 0.2 g / cm ³ , the conductivity of the obtained heat conductive powder tends to decrease, and when it exceeds 1.7 g / cm ³ , the flexibility of the heat conductive sheet tends to decrease. is there. The bulk density can be adjusted by adjusting the amount of pressurization, the roll gap, and the like. The pulverization of the expanded graphite sheet is preferably performed by coarse pulverization and fine pulverization. After that, the expanded graphite sheet pulverized powder having the desired average particle diameter and anisotropy by classification and classification as necessary. Can be obtained.

No particular limitation is imposed on the bulk density of the expanded graphite sheet pulverized powder but if desired a more thermally ^conductive, ground powder in the range of 0.15g / cm ³ ~0.3g / cm 3 are preferred. If the bulk density of the expanded graphite sheet pulverized powder is less than 0.15 g / cm ³ , there will be a lot of powder in which the complex entanglement (network) of the carbon fiber is broken, and there is concern about the thermal conductivity of the manufactured sheet. If it exceeds 0.3 g / cm ³ , it becomes a rigid structure and tends to lose the flexibility of graphite powder alone.

There is no particular limitation on the type of elastic binder used in combination with anisotropic graphite, and it can be used in an atmosphere of 120 ° C. in consideration of the temperature inside the equipment in which the heat conductive sheet is used. It is preferable to use a binder having elasticity that does not significantly lower the physical property value at room temperature. In addition, said room temperature refers to a thing of 10 to 40 degreeC.
Liquid binders (including those in which solid rubber is dissolved in an organic solvent), modified polymer materials, and the like are used as binders suitable for the above, but synthetic rubber may be used in consideration of sheet physical properties and cost. In consideration of the environment and safety, the use dilution solvent is preferably an aqueous solvent.

  The usable synthetic rubber is not limited to the number average molecular weight and the acrylonitrile group content. As the acrylonitrile butadiene rubber (NBR), for example, Nipol-1041, Nipol-1042, Nipol-1043, Nipol-1042AL, Nipol-1052J, Nipol-1032, DN201, DN202, DN202H, DN204, DN206, DN207, DN211, DN215, DN219, DN221, DN223, DN103, DN115 (above, product names of Nippon Zeon Co., Ltd.), Clinac 801 ( For example, a product name manufactured by Policer) and N220SH (a product name of Nippon Synthetic Rubber Co., Ltd.).

  Moreover, as styrene butadiene rubber (SBR), for example, Nipol-1006, Nipol-1009, Nipol-1500, Nipol-1502, Nipol-1507, Nipol-1712, Nipol-1778J, Ameripol 1013, Ameripol 1503, Ameriol 1506, Ameriol 1506 Solid rubber such as 1509, Ameripol 1511, Ameripol 1513 (trade name, manufactured by Nippon Zeon Co., Ltd.) can be used, and the above rubbers can be mixed and used depending on the application.

  Further, the rubber property is solid, and when mixed with anisotropic graphite as a heat conducting material, the rubber is diluted and dissolved in an organic solvent. The dilution factor is arbitrarily determined by the amount of anisotropic graphite, the particle size, and the like.

If it is desired to further improve the heat resistance of the synthetic rubber, there is a method in which the rubber is vulcanized.
As a general vulcanizing agent, sulfur and a vulcanization accelerator are used in combination. There is no restriction | limiting in sulfur to be used, for example, colloidal sulfur, precipitated sulfur, etc. are used. The amount of sulfur used is preferably in the range of 10 to 30 parts by weight with respect to 100 parts by weight of the rubber used (solid content).

The vulcanization accelerator to be used is not limited. For example, thiazole-based Noxeller M, Noxeller DM (the trade name of Ouchi Shinsei Chemical Co., Ltd.), thiuram-based Xcerer TT, Noxeller TET, Xeller TS, Noxeller TRA ( As mentioned above, the product name of Ouchi Shinsei Chemical Co., Ltd.), dithiocarbamate-based Xerar PPD, Noxeller P, Noxeller PZ, Noxeller EZ, Noxeller BZ, Noxeller PX, Noxeller ZP, Xeller S, Noxeller SDC, Noxeller TP ( As described above, the product name of Ouchi Shinsei Chemical Co., Ltd.) can be used. Usually, the above components are mixed and used for adjusting the vulcanization time. In addition, zinc white is used if necessary.
The amount of the vulcanization accelerator used is preferably 1 part by weight or less with respect to 100 parts by weight of the rubber used (as a solid content).

  In addition, it is preferable to use an emulsion type synthetic rubber in which rubber particles in nm units are dispersed in an aqueous solvent as a synthetic rubber used when importance is attached to the environment, safety, and the inclusion of volatile components. Examples of the emulsion rubber that can be used include styrene butadiene rubber (SBR) such as Nipol 2518FS, Nipol 2518G, Nipol LX603, Nipol LX110, Nipol LX112, Nipol LX430, Nipol LX433C, Nipol LX435, Nipol C48, Nipol C48, Nipol C48 As mentioned above, the product name of Nippon Zeon Co., Ltd.) can be used.

Further, if the heat resistance of the above property rubber is desired, as acrylonitrile butadiene rubber (NBR), Nipol 1561, Nipol 1562, Nipol 1571H, Nipol 1571C, Nipol 1571CL, lNipol LX517A, Nipol 1577, Nipol LX511A, Nipol LX511A, 5 Nippon Zeon Co., Ltd. product name) can be used.
In consideration of durability, it is preferable that the rubber used contains an anti-aging agent.

  Furthermore, in the present invention, by blending different polymer materials (for example, thermosetting resin or thermoplastic resin) into the rubber component, physical property values (for example, heat resistance) that cannot be expressed by rubber alone. Improvement in mechanical strength, increase in softening point, suppression of volatile components, etc.).

  Different polymer materials used include thermoplastic resins such as thermosetting resins such as epoxy resins, melamine resins, polyester resins, and phenol resins, polyamideimide resins, polyimides, polyetherimides, phenoxy resins, polyethylene resins, and polycarbonate resins. Is mentioned.

In the case of rubber having a carbonyl group, the molecular bond between the rubber and the dissimilar polymer material can be ring-opening polymerized with a resin having an epoxy group to achieve the bond at the molecular level, thereby further improving the physical properties. I can expect.
Even when molecular bonding is not possible, if the rubber and the different polymer material are uniformly distributed for each molecular unit by uniform dispersion and the sea (rubber) and island (heterogeneous polymer material) structures are formed, With this structure, the functions can be shared and correspondence can be achieved.

  The expanded graphite powder or expanded graphite sheet pulverized powder that functions as the above-described heat conductive material, an elastic binder, and a material to be used as necessary are uniformly mixed to obtain a heat conductive sheet material by removing the solvent component. be able to.

  The mixing ratio of the expanded graphite powder or the expanded graphite sheet pulverized powder and the elastic binder is not particularly limited, but considering the thermal conductivity and flexibility of the obtained thermal conductive sheet, flying dust, an elastic binder ( The expanded graphite or expanded graphite sheet pulverized powder is preferably in the range of 10 to 1000 parts by weight and more preferably in the range of 20 to 900 parts by weight with respect to 100 parts by weight (as solid content). When the blending amount of the expanded graphite or the expanded graphite sheet pulverized powder is less than 10 parts by weight, the thermal conductivity of the obtained heat conductive sheet tends to decrease significantly. There is a tendency that the binder effect is weakened, the flexibility of the heat conductive sheet is lowered, and the amount of dust is increased.

  There is no particular limitation on the method for uniformly mixing the materials shown above, but if the mixing is performed using a motor equipped with a stirring blade, mixing using a raikai machine, a kneader, etc., in terms of material uniformity and manufacturing cost. This is preferable because it is advantageous. However, it is necessary to carry out a detailed examination before mass production to grasp the optimum viscosity (solvent dilution ratio) of the binder having elasticity, and the values of the optimum viscosity and thixotropy of the mixed material. In addition, it is necessary to examine the setting of mixing conditions (mixing time, stress applied to the heat conduction powder during mixing, etc.) in detail, and if these are neglected, the heat conductivity is lower than the design value due to destruction of the heat conduction material. A sheet is produced, or a sheet with large variations in sheet physical properties is produced.

  The solvent to be used is removed from the material uniformly mixed by the above-described method, but the removal method is not particularly limited. For example, by using a vacuum dryer, the solvent can be removed in a short time. Since the treatment can be performed at a temperature equal to or lower than the boiling point, the reaction of the used binder having elasticity and the acceleration of vulcanization can be suppressed, which is suitable for producing a stable sheet.

Finally, a heat conductive sheet is produced using the above mixed material, but the production method is not particularly limited, but a heating roll or heat press having a constant gap width is used, and the material used is uniform. Heat and pressure can be applied to form a sheet. In particular, when latex rubber is used, it is an important point for improving physical property values to uniformly fuse the rubber particles.
Moreover, an adhesive sheet and a metal plate can be affixed on both the one side and both surfaces of the obtained heat conductive sheet as needed, and can be combined and used.

Hereinafter, the present invention will be described by way of examples.
Example 1
(1) Selection of elastic binder (aqueous latex-modified NBR rubber) Nipol 1571C (for gaskets, trade name of Nippon Synthetic Rubber Co., Ltd.), resin solid content 45%, aqueous solvent, viscosity 25 (mPa · s) It was used.

(2) Production of heat conductive material (expanded graphite powder) 800 g of concentrated sulfuric acid was put into a 3 liter glass beaker, and 400 g of natural graphite (fixed carbon number 99% by weight or more, Chinese-made # 599 graphite) was added to this. The mixture was stirred for 10 minutes with a stirring motor (3 rotations / 1 minute) equipped with a glass stirring blade. Thereafter, 32 g of hydrogen peroxide (concentration 35%) was blended and stirred for 15 minutes. After completion of the stirring, the acid-treated graphite and the acid component are separated by filtration under reduced pressure, the obtained acid-treated graphite is transferred to another container, 5 liters of water is added, stirred with a large stirring blade, and washed with acid-treated graphite by vacuum filtration. And wash water separated. This operation was performed twice.

The resulting washed acid-treated graphite was transferred to a hollow enamel container, and uniformly leveled, and dried for 1 hour with a vacuum dryer heated to 110 ° C. to remove moisture. This was further placed in a heating furnace heated to 1000 ° C. for 10 minutes to obtain expanded graphite powder. After cooling, the obtained expanded graphite powder was used as a heat conductive material. The resulting expanded graphite powder had a bulk density of 0.02 g / cm ³ (measured by a graduated cylinder measurement method).

(3) Preparation of heat conductive composite material 222 g (rubber solid content: 100 g) of the elastic binder of (1) was weighed into a 40 cm × 30 cm × 4 cm metal container, and the expanded graphite powder obtained in (2) 10 g was carefully weighed (blending ratio: elastic binder / expanded graphite = 100 parts by weight / 10 parts by weight), and then the expanded graphite powder weighed above in the elastic binder dispersed in water was uniformly 5 It was immersed for 1 minute, and then filtered under reduced pressure to obtain expanded graphite impregnated with an elastic binder.
Furthermore, the elastic binder-impregnated expanded graphite obtained above was treated with a vacuum dryer heated to 80 ° C. for 1 hour to remove water that was a solvent for the elastic binder, thereby obtaining a heat conductive sheet material.

(4) Production of heat conductive sheet A mold having a length of 10 cm and a width of 20 cm (designed to be 1 mm thick by pressing) was left on a hot plate of a 70-ton hydraulic press heated to 120 ° C. for 2 hours, (3) 20 g of the heat conductive sheet material obtained in the above was quickly and uniformly filled into the heated female mold. After that, a male mold was attached, the mold was put back on the hot plate and allowed to stand for 2 minutes. Then, the molding pressure was slowly applied, and when the gauge pressure reached 9.8 MPa, the pressurization was stopped. This was left for a minute, and the molding was completed to obtain a heat conductive sheet.
The obtained heat conductive sheet was a sufficiently flexible heat conductive sheet having a beautiful appearance in which the elastic binder and the expanded graphite were uniform.

Example 2
(5) Selection of elastic binder (water-based latex-modified NBR rubber) The one used in Example 1 was used.
(6) Production of heat conductive material (expanded graphite sheet pulverized powder) Expanded graphite sheet (Carbofit HGP-105, manufactured by Hitachi Chemical Co., Ltd.) having a plate thickness of 1.0 mm and a bulk density of 1.0 g / cm ³ . The product name) was pulverized with a coarse pulverizer and a fine pulverizer, and the obtained pulverized powder was classified to obtain an expanded graphite sheet pulverized powder having a number average particle size of 100 μm.

(7) Preparation of heat conductive composite material 222 g of elastic binder (rubber solid content: 100 g) of (5) was weighed into a metal container similar to that in Example 1, and further expanded graphite sheet pulverized in (6) 100 g of powder was carefully weighed (blending ratio: elastic binder / expanded graphite = 100 parts by weight / 100 parts by weight), and using the same apparatus as in Example 1 (3), the same process as in Example 1 (3) After that, a heat conductive sheet material was obtained.
(8) Preparation of heat conductive sheet Using the heat conductive sheet raw material obtained in (7), and using the same apparatus as in Example 1 (4), heat is passed through the same steps as in Example 1 (4). A conductive sheet was obtained. The obtained heat conductive sheet was a sufficiently flexible heat conductive sheet having a beautiful appearance in which the elastic binder and the expanded graphite sheet pulverized powder were uniform.

Comparative Example 1
An expanded graphite sheet (Carbofit HGP-105, trade name manufactured by Hitachi Chemical Co., Ltd.) having a plate thickness of 1.0 mm and a bulk density of 1.0 g / cm ³ was directly used as a heat conductive sheet.

  Next, the thermal conductive sheets obtained in Examples 1 and 2 and Comparative Example 1 were subjected to a comparative test of thermal conductivity, thermal diffusivity, specific heat, flexibility, and dust generation (dust). The test results are shown in Table 1. In addition, the evaluation and measurement method in a comparative test are as follows.

(1) Thermal conductivity, thermal diffusivity Using a laser flash method thermal constant measuring device (TC-7000) manufactured by ULVAC, measurement was performed with a sample (30 mm × 30 mm × 1.0 mm).
(2) Flexibility evaluation Evaluation was made at the time of occurrence of cracks in the heat conductive sheet by the minimum bending radius test.
(3) Dust generation (flying dust)
The sheet was carefully cut with a cutter, a soft brush tip was brought into contact with the cut surface and reciprocated several times, and the amount of sheet material dropped was judged.

As shown in Table 1, it is clear that the heat conductive sheets obtained in Examples 1 and 2 are superior in physical properties as a heat conductive sheet as compared to the heat conductive sheet obtained in Comparative Example 1.

Claims (5)

It is obtained by mixing water-based emulsion rubber , which is an elastic binder, and expanded graphite powder or expanded graphite sheet pulverized powder , which is anisotropic graphite that functions as a heat conducting material, and removing the solvent used from the mixed material. A heat conductive sheet obtained by forming a heat conductive sheet material into a sheet.   The heat conductive sheet according to claim 1, wherein the elastic binder is a mixture of a water-based emulsion rubber and a polymer material other than rubber.   The heat conductive sheet according to claim 1 or 2, wherein the anisotropic graphite has a number average particle diameter in a range of 50 µm to 500 µm. The heat conductive sheet according to any one of claims 1 to ³ , wherein the expanded graphite sheet pulverized powder has a bulk density in a range of 0.15 g / cm ^{3 to} 0.3 g / cm ³ .   The blending ratio between the elastic binder and the anisotropic graphite is 10 to 1000 parts by weight of the anisotropic graphite with respect to 100 parts by weight of the binder (as a solid content). Heat conduction sheet.