JP2009149769A - Elastomer composition, elastomer molded body and heat radiation sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an elastomer composition allowing production of an elastomer molded body and a heat radiation sheet, having low hardness and high thermal conductivity. <P>SOLUTION: The elastomer composition contains an elastomer component and a pitch-based carbon fiber and/or graphite chip, wherein the total content of the pitch-based carbon fiber and the graphite chip is 30 vol.% or more in the elastomer composition; the pitch-based carbon fiber is a short fiber of 150 μm to 2 mm in length; and the graphite chip has a shape of 10-150 μm in thickness, 100 μm to 1 mm in width and 150 μm to 2 mm in length. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

The present invention relates to an elastomer composition, an elastomer molded body, and a heat dissipation sheet.

In recent years, various elastomer molded bodies have been used for the purpose of imparting performances such as desired hardness, high thermal conductivity, and electromagnetic wave shielding properties, and are applied to, for example, uses of heat dissipation sheets. This heat-dissipating sheet is installed between a heat-generating body such as an electronic component and a heat-dissipating body such as a heat sink or heat pipe, and diffuses heat. It is used for electrical equipment and electronic parts such as plasma displays, transistors, capacitors, and personal computers When applied to an IC, a CPU, etc., the generated heat can be dissipated and problems caused by heat (such as unstable operation of components) can be prevented.

As such a heat-dissipating sheet, a heat-dissipating sheet in which a heat-conductive filler is added to a matrix resin has been proposed in the past, and a heat-dissipating sheet composed of a composition in which heat-conductive spherical magnesia is appropriately combined with granular alumina and boron nitride , Heat dissipation sheets using thermally conductive fillers such as aluminum nitride and aluminum oxide, oxide particles such as aluminum oxide and titanium oxide, nitride particles such as boron nitride, carbide particles such as silicon carbide, metals such as copper and aluminum A thermally conductive sheet using particles is disclosed. However, since the thermal conductivity is low, a high heat dissipation effect cannot be expected.

Patent Document 1 discloses a heat-dissipating sheet in which graphitic carbon fibers (raw material: petroleum pitch, etc.) are dispersed in a matrix resin. The carbon fibers used have an average aspect ratio of less than 3 and an average fiber length. 10 to 25 μm and an average aspect ratio of 10 and an average fiber length of 100 μm are shown. Patent Document 2 discloses a heat-softening heat dissipation sheet in which carbon fiber (pitch system) is blended with a polymer gel, but the shape of the carbon fiber has not been studied in detail. Patent Document 3 discloses a heat-dissipating sheet in which graphite is mixed with silicone rubber, and the shape of this graphite is spherical.
JP-A-9-283955 Japanese Patent No. 3712943 JP-A-10-298433

An object of this invention is to provide the elastomer composition which can manufacture the elastomer molded object and heat dissipation sheet which are low hardness and high heat conductivity in view of the said present condition.

The present invention is an elastomer composition containing an elastomer component and pitch-based carbon fibers and / or graphite chips, and the total content of the pitch-based carbon fibers and graphite chips is 30 volumes in the elastomer composition. The pitch-based carbon fiber is a short fiber having a length of 150 μm to 2 mm, and the shape of the graphite chip is a thickness of 10 to 150 μm, a width of 100 μm to 1 mm, and a length of 150 μm to 2 mm. It is an elastomer composition.
The elastomer component is preferably a rubber or polymer gel having a hardness of 25 (JIS K6253 type A durometer) or less.

The present invention is also an elastomer molded product obtained from the above-mentioned elastomer composition, wherein the pitch-based carbon fiber and / or graphite chip is oriented in the elastomer molded product. It is.
It is preferable that the orientation ratio of the pitch-based carbon fiber and the graphite chip is 80% or more.

The present invention is also a heat-dissipating sheet obtained from the above-described elastomer composition, wherein the pitch-based carbon fiber and the graphite chip are oriented in a direction substantially perpendicular to the sheet surface of the heat-dissipating sheet. It is a heat dissipation sheet.
Hereinafter, the present invention will be described in detail.

The elastomer composition of the present invention contains an elastomer component and a specific amount of pitch-based carbon fibers and / or graphite chips. For this reason, by using this elastomer composition, an elastomer molded body having low hardness (high flexibility) and high thermal conductivity can be produced.

In order to achieve low hardness (high flexibility) and high thermal conductivity in elastomer elastic bodies, pitch-based carbon short fibers (length: 150 μm to 2 mm) and / or graphite chips (thickness: 10 to 150 μm, width: 100 μm to 1 mm) , 150 μm to 2 mm in length) is oriented in a certain direction in the elastomer molded body, whereby high thermal conductivity can be expressed in the orientation direction of the fibers and graphite chips. Therefore, by using this elastomer molded body, it is possible to manufacture a heat dissipation sheet having a good heat dissipation property in which the pitch-based carbon short fibers and / or graphite chips are oriented in a direction substantially perpendicular to the sheet surface. .
In addition, since pitch-based carbon short fibers and / or graphite chips are blended, it can be expected that good conductivity and electromagnetic wave shielding properties are exhibited.

(Elastomer composition)
The elastomer composition of the present invention contains an elastomer component and pitch-based carbon fibers and / or graphite chips.
It does not specifically limit as said elastomer component, For example, the hardness 25 (JIS K6253 type A durometer) or less can be used. Specifically, silicon rubber, chloroprene rubber, natural rubber, isoprene rubber, nitrile rubber, styrene / butadiene rubber, butadiene rubber, ethylene-α-olefin elastomer, ethylene / propylene rubber, chlorosulfonated polyethylene rubber, acrylic rubber, urethane Examples thereof include polymer gels such as rubber, hydrogenated acrylonitrile rubber, silicone gel, acrylic gel, and urethane gel. Of these, silicone rubber, ethylene / propylene rubber and polymer gel are preferable. These may be used alone or in combination of two or more.

Examples of the ethylene-α-olefin elastomer include a rubber made of a copolymer of an α-olefin excluding ethylene and ethylene and a diene (non-conjugated diene), and a copolymer of an α-olefin excluding ethylene and ethylene. Rubber, partially halogenated products thereof, and the like. The α-olefin excluding ethylene is preferably propylene, butene, hexene or octene. As the diene, a non-conjugated diene such as 1,4-hexadiene, dicyclopentadiene or ethylidene norbornene is usually used as appropriate.

Specific examples of the ethylene-α-olefin elastomer include ethylene-propylene-diene rubber (EPDM), ethylene-propylene copolymer (EPM), ethylene-butene copolymer (EBM), ethylene-octene copolymer (EOM), and the like. And the like.

The pitch-based carbon fiber used in the present invention is a petroleum pitch-based or coal pitch-based carbon fiber having a length of 150 μm to 2 mm. Of these, pitch-based carbon fibers having developed graphitizability, which are fired at a high temperature of 2000 to 3200 ° C. using mesophase pitch as a raw material, are preferable from the viewpoint of improving the thermal conductivity. By using pitch-based carbon fibers, high thermal conductivity can be exhibited in the elastomer molded body, and good heat dissipation can be exhibited in the heat dissipation sheet in which the carbon fibers are oriented in a substantially vertical direction.

When the pitch-based carbon fibers have a length of 150 μm to 2 mm, the fibers can be well dispersed and oriented in substantially the same direction during the production of the elastomer molded body, and the fiber oriented in the molded body can be used as a counterpart material. Can be satisfactorily contacted. As a result, it is possible to exhibit excellent heat dissipation in the manufactured heat dissipation sheet. When the length of the carbon fiber is less than 150 μm, it is difficult to orient in the elastomer. In addition, when creating a sheet by cutting, it is difficult to slice to less than 150 μm. If it exceeds 2 mm, it cannot be oriented as a heat dissipation sheet. On the other hand, if it is longer than 2 mm, the thickness of the sheet exceeds 2 mm, and the performance is not inferior, but it cannot be used as a heat dissipation sheet practically.

The pitch-based carbon fiber preferably has an aspect ratio (average) of 10 to 500. Thereby, an elastomer molded body having low hardness and high thermal conductivity can be obtained. If it is less than 10, the fiber may be difficult to be uniaxially oriented in the elastomer, and if it exceeds 500, the dispersion of the fiber in the elastomer may be deteriorated. The aspect ratio is more preferably 15 to 300.

The graphite chip used in the present invention is obtained from a graphite sheet such as a natural graphite sheet made from natural graphite or an artificial graphite sheet made from artificial graphite, and has a thickness of 10 to 150 μm, a width of 100 μm to 1 mm, and a long length. It has a shape of 150 μm to 2 mm. Among these, by using graphite chips baked at a high temperature of 1600 to 3000 ° C. using carbon called mesophase microspheres as a raw material, high thermal conductivity can be exhibited in the elastomer molded body, and in a substantially vertical direction. Good heat dissipation can be expressed in the heat dissipation sheet in which the graphite chip is oriented.

When the graphite chip has the specific thickness, width and length, it becomes possible to satisfactorily orient the graphite chip in substantially the same direction during the production of the elastomer molded body, and to disperse and orient in the molded body. The graphite chip thus made can be brought into good contact with the counterpart material. As a result, it is possible to exhibit excellent heat dissipation in the manufactured heat dissipation sheet.

When the thickness is less than 10 μm, orientation in the elastomer is difficult, and when it exceeds 150 μm, it is difficult to maintain the shape in the elastomer. When the width is less than 100 μm, it is difficult to maintain the shape in the elastomer, and when it exceeds 1 mm, dispersion in the elastomer becomes non-uniform. When the length is less than 150 μm, orientation in the elastomer is difficult, and when it exceeds 2 mm, the heat dissipation sheet cannot be maintained and oriented.

The length and aspect ratio of the pitch-based carbon fiber and the thickness, width and length of the graphite chip can be measured by observation with a scanning electron microscope (SEM). Specifically, SEM photography was performed, and the carbon fiber length and aspect ratio [major axis (length) / fiber diameter], graphite chip thickness, width and length for any number (five). Can be obtained by this arithmetic average value. From the viewpoint of obtaining the effects of the present invention, the shapes of the pitch-based carbon fiber and the graphite chip are extremely important.

In the elastomer composition of the present invention, the total content of the pitch-based carbon fiber and the graphite chip is 30% by volume or more in the elastomer composition (100% by volume). When an elastomer molded body containing 30% by volume or more is manufactured and pitch-based carbon fibers and graphite chips are oriented in a certain direction in the molded body, high thermal conductivity can be exhibited in the orientation direction. For this reason, in the heat-radiation sheet manufactured using this elastomer molded object, high heat conductivity is acquired and favorable heat dissipation can be provided. The total content of the pitch-based carbon fiber and the graphite chip is preferably 30 to 70% by volume, more preferably 40 to 60% by volume. If the amount of the pitch-based carbon fiber and the graphite chip is increased, there is a possibility that the processing cannot be performed due to a formability problem. In addition, the sheet is inferior in smoothness and the hardness of the heat dissipation sheet cannot be lowered. As a result, the contact of the sheet becomes a problem, and the thermal conductivity may be deteriorated.

As described above, in the present invention, since a certain amount of the pitch-based carbon fiber and / or the graphite chip is blended, an elastomer molded body having low hardness and high thermal conductivity can be obtained. It is possible to impart good heat dissipation to the heat dissipation sheet.

You may add well-known additives, such as a vulcanizing agent for demonstrating elasticity, a vulcanization adjuvant, and a vulcanization accelerator, to the elastomer composition of this invention.
As the vulcanizing agent, sulfur; organic peroxides such as dialkyl peroxides, peroxyesters, and ketone peroxides can be used. Examples of the vulcanization aid include triallyl isocyanurate and triallyl cyanurate. Examples of the vulcanization accelerator include tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), zinc dimethyldithiocarbamate (ZnMDC), and zinc dibutyldithiocarbamate (ZnBDC).
Further, a filler for reinforcement, a processing aid for processing, and the like may be included.

The method for producing the elastomer composition of the present invention is not particularly limited, and can be produced by a conventionally known method. For example, the above-described components are mixed and kneaded at a predetermined volume ratio using a known method. Can be manufactured.

[Elastomer molded product]
The elastomer molded body of the present invention is obtained from the elastomer composition of the present invention, and the pitch-based carbon fibers and / or graphite chips are oriented in the elastomer molded body.
Hereinafter, the elastomer molded body of the present invention will be specifically described with reference to FIG.

FIG. 1 is an example of a schematic view of an elastomer molded body 1 of the present invention, in which pitch-based carbon fibers 2 are used.
The elastomer molded body 1 of FIG. 1 has pitch-based carbon fibers 2 oriented substantially uniformly in the orientation direction 3 in the molded body. That is, in the elastomer molded body of the present invention, “the pitch-based carbon fibers and / or graphite chips are oriented” means that the pitch-based carbon fibers and / or graphite chips are aligned in substantially the same direction in the elastomer molded body. It means the state that is arranged.

The angle formed by the orientation direction of each pitch-based carbon fiber and each graphite chip in the elastomer molded body (the direction in which the pitch-based carbon fiber or graphite chip in the elastomer molded body is oriented and the other pitch-based carbon fibers And the angle formed by the direction in which the graphite chip is oriented) is preferably an acute angle, more preferably 30 ° or less, and even more preferably 10 ° or less. In the case of the “substantially uniform orientation”, the angle is 10 ° or less.

In the elastomer molded body 1 of FIG. 1, portions other than the pitch-based carbon fibers 12 are mainly composed of an elastomer component.
In addition, the elastomer molded body of the present invention in which the graphite chip is oriented is obtained by orienting the graphite chip 4 having the shape shown in the enlarged schematic view of FIG. FIG. 2 shows a graphite chip 4 having a thickness of 5, a width of 6, and a length of 7.

In the elastomer molded body 1 of the present invention, the orientation ratio of the pitch-based carbon fiber 2 and the graphite chip 4 is preferably 80% or more. In the present invention, “the orientation ratio is 80% or more” means that all pitch-based carbon fibers 2 and all graphite chips 4 arranged in the elastomer molded body 1 are arranged in substantially the same direction. It means that the total ratio of the pitch-based carbon fibers and graphite chips is 80% or more (number ratio). It is more preferably 90% or more, and further preferably 95% or more. The orientation ratio can be obtained by, for example, cutting the elastomer molded body 1, observing the cut surface with an electron microscope, and image processing.

The method for producing the elastomer molded body of the present invention is not particularly limited as long as it is a method capable of orienting pitch-based carbon fibers and graphite chips in a substantially uniform direction in the obtained elastomer molded body. Can be manufactured.
The elastomer component and, if necessary, additives are appropriately blended and kneaded with an elastomer blending roll. Next, pitch-based carbon fibers and / or graphite chips are added to the obtained kneaded rubber and kneaded to obtain an elastomer composition as a compounded rubber. Further, the obtained compounded rubber is molded into a sheet according to the present invention. An elastomer molded body (elastomer sheet) can be produced. In the present invention, for example, calendar molding, extrusion molding, or the like can be used as a sheet molding method.

[Heat dissipation sheet]
The heat dissipation sheet of the present invention is obtained from the elastomer composition of the present invention, and the pitch-based carbon fibers and / or graphite chips are oriented in a direction substantially perpendicular to the sheet surface of the heat dissipation sheet. .
Hereinafter, the heat dissipation sheet of the present invention will be specifically described with reference to FIG.

FIG. 3 is an example of a schematic view of the heat-dissipating sheet 11 of the present invention, and uses pitch-based carbon fibers 12.
In the heat dissipation sheet 11 of FIG. 3, the pitch-based carbon fibers 12 are substantially uniformly oriented in a substantially vertical direction (orientation direction 13) with respect to the sheet surface 14. That is, in the heat dissipation sheet 11 of the present invention, the pitch-based carbon fibers 12 are oriented substantially uniformly in the thickness direction of the sheet. In the heat dissipation sheet 11 of the present invention, the pitch-based carbon fibers 12 are exposed on the sheet surface 14. In the heat dissipation sheet 11 of FIG. 3, the portion other than the pitch-based carbon fiber 12 is mainly composed of an elastomer component.
In addition, the heat radiation sheet | seat in which the graphite chip | tip is orientated is what the graphite chip | tip 4 of the shape shown in the enlarged schematic of FIG.

The sheet surface 14 of the heat radiating sheet means the front surface and the back surface of the heat radiating sheet 11. In the heat radiating sheet 11, in use, one sheet surface functions as a heat receiving surface that contacts the heat generating element and receives heat from the heat generating element, and the other sheet surface functions as a heat radiating surface that contacts the heat radiating element and transfers heat to the heat radiating element. Function. In the heat dissipation sheet 11 of the present invention, high thermal conductivity is exhibited by the pitch-based carbon fibers 12 (and graphite chips) exposed on the sheet surface 14 and oriented in the sheet thickness direction.

Furthermore, since the heat dissipation sheet 11 has an elastomer component with a hardness of 25 or less, the entire sheet is excellent in flexibility. Therefore, when the heat radiating sheet 11 is used, the surface of the sheet surface 14 and the pitch-based carbon fiber 12 (and / or the graphite chip) exposed on the sheet surface 14 can be brought into good contact with the heating element and the heat radiating element. Further, pitch-based carbon fibers and graphite chips are 150 μm to 2 mm, which are considerably long compared to the sheet thickness. Therefore, in this invention, high heat conductivity can be provided to the heat-radiation sheet 11, and favorable heat dissipation can be expressed.

The heat dissipation sheet 11 of the present invention may include a highly heat conductive filler.
As the high thermal conductive filler, various kinds of conventionally used materials can be used. For example, aluminum hydroxide, aluminum oxide, silicon dioxide, titanium dioxide, mica, potassium titanate, iron oxide, talc, etc. Examples thereof include oxide particles, nitride particles such as boron nitride, silicon nitride, and aluminum nitride, carbide particles such as silicon carbide, and metal particles such as copper and aluminum. Moreover, you may mix | blend conventionally used additives, such as a hardening | curing agent, a processing aid, and a characteristic improvement agent, suitably. These components can be mix | blended in a sheet | seat using a conventionally well-known method.

The heat dissipation sheet 11 preferably has a thickness 15 of 0.2 to 1.5 mm. If it is less than 0.2 mm, the orientation and smoothness in the thickness direction of the pitch-based carbon fiber or graphite chip may be inferior, and if it exceeds 1.5 mm, the thermal conductivity may be lowered.
Moreover, in the said heat radiating sheet 11, it is preferable that the orientation rate of the pitch-type carbon fiber 12 (and / or a graphite chip) in a sheet | seat is the same as that of the said elastomer molded object (elastomer sheet).
The heat transfer rate of the heat dissipation sheet of the present invention is preferably 60 to 400 W / mk. Thereby, high heat dissipation is obtained.

Hereinafter, the manufacturing method of the said heat-radiation sheet of this invention is demonstrated.
Although it will not specifically limit if it is a method of obtaining the sheet | seat shown in FIG. 3 as a manufacturing method of a thermal radiation sheet, For example, the following method can be mentioned.
Step (I) of obtaining the elastomer composition containing the elastomer component and the pitch-based carbon fiber and / or graphite chip, and the total content of the pitch-based carbon fiber and the graphite chip is 30% by volume or more; Using the elastomer composition obtained in the step (I), the step (II) for obtaining an elastomer sheet in which the pitch-based carbon fibers and graphite chips are oriented in the sheet surface direction, and the step (II) are obtained. The obtained elastomer sheet is laminated to obtain an elastomer laminate, and the elastomer laminate obtained in the step (III) is cut in a direction substantially perpendicular to the sheet surface of the elastomer sheet in the laminate. The heat-radiation sheet of this invention can be manufactured with the manufacturing method including process (IV).

Hereinafter, the manufacturing method of the said heat-radiation sheet is demonstrated concretely using FIGS.
In the manufacturing method, first, the step (I) is performed, and then the step (II) is performed. Step (I) can be performed by the same method as the method for producing the elastomer composition described above. Further, in the step (II), an elastomer sheet in which pitch-based carbon fibers and graphite chips are oriented in the sheet surface direction can be obtained by a method similar to the method for producing an elastomer molded body (elastomer sheet) described above. In the step (II), when both the pitch-based carbon fiber and the graphite chip are used, both are oriented, and when only one of them is used, it is oriented. By performing steps (I) and (II) of the above production method, the elastomer molded body 1 (elastomer sheet) as shown in FIG. 1 can be produced.

In the said manufacturing method, after the said process (II), the process (III) which laminates | stacks the elastomer sheet obtained at the said process (II) and obtains an elastomer laminated body is performed.
FIG. 4 is an example of a schematic view of the elastomer laminate 21 obtained in the step (III), in which an elastomer sheet 22 is laminated. The elastomer sheet 22 is the same as the elastomer molded body 1 (elastomer sheet) shown in FIG.

As a method for producing the elastomer laminate 21 by laminating the elastomer sheet 22, a conventionally known lamination method can be used.
For example, by using an elastomer composition, a large number of unvulcanized elastomer sheets 22 are produced by the above steps (I) and (II), the sheets are laminated, and vulcanized by a known means. 21 (vulcanized) can be obtained.

In the manufacturing method, after the step (III), the step (IV) of cutting the elastomer laminate obtained in the step (III) in a direction substantially perpendicular to the sheet surface of the elastomer sheet in the laminate is performed. Is called. That is, in FIG. 4, the elastomer laminate 21 is cut in a substantially vertical direction 24 (cutting direction) with respect to the sheet surface 23 of the elastomer sheet constituting the laminate. As described above, the heat radiation sheet 11 of the present invention shown in FIG. 3 can be manufactured by performing the steps (I) to (IV).

As said cutting method, the method of using a wire, a laser cutting machine, a water jet cutting machine etc. can be mentioned, for example.

The following method can also be used as a method for manufacturing the heat dissipation sheet.
A step (i) of orienting the pitch-based carbon fibers and / or graphite chips in substantially the same direction in a container; and the elastomer component in the container in which the pitch-based carbon fibers and graphite chips are oriented. The step (ii) of obtaining a molded product by casting so that the total content of the fiber and the graphite chip is 30% by volume or more, and the obtained molded product in the orientation direction of the pitch-based carbon fiber and the graphite chip. On the other hand, the heat radiating sheet of the present invention can also be manufactured by a manufacturing method including the step (iii) of cutting in a substantially vertical direction.

The step (i) is not particularly limited as long as it is a method capable of orienting the pitch-based carbon fiber and the graphite chip in the container. For example, the step (i) is substantially perpendicular to the bottom surface of the container. The above pitch-based carbon fiber, a method of installing a graphite chip, etc. can be used. The container is not particularly limited as long as pitch-based carbon fibers and graphite chips can be installed, and the shape, material and the like are not limited.

For the casting of the elastomer component in the step (ii), a known method can be used without any particular limitation, thereby obtaining a molded body in which pitch-based carbon fibers and graphite chips are oriented in substantially the same direction. Can do. Further, the cutting in the step (iii) is performed using the same method as in the above-described step (IV), and adjusted so as to cut in a direction substantially perpendicular to the orientation direction of the pitch-based carbon fiber and the graphite chip. Thus, the heat dissipation sheet of the present invention can be manufactured.

The elastomer composition of the present invention can produce an elastomer molded body having low hardness and high thermal conductivity. Moreover, the heat dissipation sheet excellent in heat dissipation can also be obtained by using this elastomer composition.

EXAMPLES Hereinafter, although an Example is hung up and demonstrated in more detail, this invention is not limited only to these Examples. In the examples, “parts” and “%” mean “parts by mass” and “% by mass” unless otherwise specified.

Example 1 Production of heat-dissipating sheet (A) Composition comprising the following composition, (B) Pitch-based carbon fiber (Japan graphite fiber chopped fiber, length 25 mm, diameter 7 μm), 8 inches 2 By this roll machine, they were mixed at a volume ratio of (A) :( B) = 70: 30.
After mixing, the sheet was put out with the roll gap set to 0.7 mm, and (B) was oriented.
Next, the obtained sheets were laminated, molded into a 5 cm width × 10 cm length × 20 mm thickness, and vulcanized (vulcanizing conditions 160 ° C. × 60 minutes).
The obtained molded product was cut into 1.0 mm in the vertical direction using a water jet machine manufactured by Shibuya Kogyo Co., Ltd. to produce a heat dissipation sheet. The length of the pitch-based carbon fiber at this time is 1 mm.

[(A) Composition]
EP98; (oil-extended ethylene propylene rubber, manufactured by JSR) 175 parts process oil PW-90: 100 parts SRF carbon black: 10 parts zinc white 3; 5 parts stearic acid; 1 part vulcanization accelerator; Zinc di-n -Butyl dithiocarbamate (ZnBDC) 0.5 part vulcanization accelerator; Tetra methyl thiuramidsulfide (TMTD) 0.5 part vulcanization accelerator: Dibenzothiadisulfide (MBTS) 1.5 parts sulfur; 1.5 parts ) Was 11.

Example 2 Production of Heat Dissipation Sheet (B) Pitch-based carbon fiber (Japanese graphite fiber chopped fiber, length 25 mm, diameter 7 μm) arranged vertically in a polyethylene container 5 cm × 5 cm × 25 mm in height (A) Silicone gel (KE-1056 manufactured by Shin-Etsu Chemical Co., Ltd., hardness 1 or less) was cast at a volume ratio of (A) and (B) at 50:50, and the resulting molded product was used with a water jet machine manufactured by Shibuya Kogyo. Then, the heat-dissipating sheet was prepared by cutting the sheet in the vertical direction to 1.0 mm, and the pitch-based carbon fiber at this time had a length of 1 mm.

Example 3 Production of heat dissipation sheet The molded product obtained in Example 1 was cut into 0.2 mm in the vertical direction using a Shibuya industrial universal sliding machine to produce a heat dissipation sheet. The length of the pitch-based carbon fiber at this time is 0.2 mm.

Comparative Example 1 Production of Heat Dissipation Sheet A heat radiation sheet was produced in the same manner as in Example 1 except that the capacity ratio of (A) and (B) was (A) :( B) = 80: 20.

Comparative Example 2 A heat radiating sheet was produced in the same manner as in Example 2 except that pitch-based carbon fibers (milled fiber made of Japanese graphite fiber, length 50 μm, diameter 7 μm) were used for the production (B) of the heat radiating sheet.

Example 4 Production of Heat Dissipation Sheet (B) A heat radiation sheet was obtained in the same manner as in Example 1 except that (C) graphite chips (thickness 50 μm, width 0.5 mm, length 25 mm) were used instead of pitch-based carbon fiber. Manufactured. The length of the graphite chip at this time is 1 mm.

Example 5 Production of Heat Dissipation Sheet (B) A heat radiation sheet was obtained in the same manner as in Example 2 except that (C) graphite chips (thickness 50 μm, width 0.5 mm, length 25 mm) were used instead of pitch-based carbon fiber. Manufactured. The length of the graphite chip at this time is 1 mm.

Example 6 Production of heat dissipation sheet The molded product obtained in Example 4 was cut into 0.2 mm in the vertical direction using a Shibuya industrial universal sliding machine to produce a heat dissipation sheet. The length of the graphite chip at this time is 0.2 mm.

Comparative Example 3 Production of Heat Dissipation Sheet A heat radiation sheet was produced in the same manner as in Example 3 except that the capacity ratio of (A) and (C) was (A) :( C) = 80: 20.

Comparative Example 4 Production of Heat Dissipation Sheet (C) A heat radiation sheet was produced in the same manner as in Example 3 except that spherical graphite (average particle diameter or average length 6 μm) was used instead of graphite chips.

Evaluation (thermal conductivity)
About the heat conductivity of the thermal radiation sheet obtained by the Example and the comparative example, it measured by the steady-state heat-conductivity measuring method by a heat conductivity measuring machine (Thermolab 2 by Kato Tech Co., Ltd.). The results are shown in Tables 1-2.
(Measurement condition)
Water at room temperature is poured into the water box, a 5 × 5 cm sample is placed on the box, and a hot plate of the BT box on the sample is placed on the sample. After reaching steady state, the heat flow loss (W) of the BT box is read with a panel meter.
Since the heat flow loss (W) in the steady state can be expressed by the following equation, the thermal conductivity is obtained.
W = K × (A · ΔT / D)
W: Heat flow loss in steady state D: Sample thickness ΔT: Sample temperature difference A: BT hot plate area K: Thermal conductivity

〔Hardness〕
The hardness of the heat-dissipating sheets obtained in the examples and comparative examples was measured by JIS K6253 durometer hardness test type A. The results are shown in Tables 1-2.

[Orientation ratio of pitch-based carbon fiber and graphite chip]
The orientation ratios of the pitch-based carbon fibers and the graphite chips in the heat-dissipating sheets obtained in Examples and Comparative Examples were measured by image processing after cutting the heat-dissipating sheet and observing the cut surface with an electron microscope. The results are shown in Tables 1-2.

From Tables 1-2, the heat-radiation sheet obtained in Examples 1, 3, 4 and 6 was low in hardness and excellent in flexibility and exhibited high thermal conductivity. Moreover, the heat conductivity of the thermal radiation sheet obtained in Example 2 and 5 showed still higher heat conductivity. On the other hand, the heat dissipation sheets obtained in Comparative Examples 1 and 3 were inferior in thermal conductivity because there were few heat conductive materials. In the heat dissipation sheets obtained in Comparative Examples 2 and 4, short length fibers are used and spherical graphite is used, so the connection in the thickness direction is poor and the thermal conductivity is significantly inferior. It was.

The heat dissipation sheet of the present invention can be suitably used for heat dissipation of heating elements such as ICs and CPUs used in electrical equipment and electronic components.

It is the schematic of the elastomer molded object of this invention. It is an expansion schematic of the graphite chip in the present invention. It is the schematic of the heat-radiation sheet of this invention. It is the schematic of the elastomer laminated body obtained at process (III) in the manufacturing method of the thermal radiation sheet of this invention.

Explanation of symbols

1 Elastomer molded body (elastomer sheet)
2, 12, 25 Pitch-based carbon fiber 3 Orientation direction of pitch-based carbon fiber (substantially parallel to the sheet surface of the elastomer sheet)
4 Graphite chip 5 Graphite chip thickness 6 Graphite chip width 7 Graphite chip length 11 Heat dissipation sheet 13 Orientation direction of pitch-based carbon fiber (substantially perpendicular to the sheet surface of the heat dissipation sheet)
14 Sheet surface 15 of heat radiating sheet Thickness 21 of heat radiating sheet Elastomer laminate 22 Unvulcanized elastomer sheet 23 Sheet surface of elastomer sheet constituting laminate 24 Cutting direction of elastomer laminate (sheet of elastomer sheet constituting laminate) (Substantially perpendicular to the surface)

Claims (5)

An elastomer composition containing an elastomer component and pitch-based carbon fibers and / or graphite chips,
The total content of the pitch-based carbon fiber and the graphite chip is 30% by volume or more in the elastomer composition,
The pitch-based carbon fiber is a short fiber having a length of 150 μm to 2 mm,
The graphite chip has a thickness of 10 to 150 μm, a width of 100 μm to 1 mm, and a length of 150 μm to 2 mm. The elastomer composition according to claim 1, wherein the elastomer component is a rubber or a polymer gel having a hardness of 25 (JIS K6253 type A durometer) or less. An elastomer molded body obtained from the elastomer composition according to claim 1 or 2,
In the elastomer molded body, pitch-based carbon fibers and / or graphite chips are oriented. The elastomer molded body according to claim 3, wherein the orientation ratio of the pitch-based carbon fiber and the graphite chip is 80% or more. A heat dissipation sheet obtained from the elastomer composition according to claim 1 or 2,
The heat-dissipating sheet, wherein pitch-based carbon fibers and graphite chips are oriented in a direction substantially perpendicular to the sheet surface of the heat-dissipating sheet.

Images