JP2007311628A - Heat transferable elastic sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new heat transferable elastic sheet in which, by employing a new heat transferable electric insulating agent, an operability enough to mold to an objective sheet shape is ensured, while a heat transfer performance can be considerably enhanced with a smaller mixing amount than a conventional metal oxide. <P>SOLUTION: The heat transferable elastic sheet is obtained by molding a mixture composition composed of a polymer elastic material such as a silicone rubber or the like in the form of a sheet, and crosslinking it. In the heat transferable elastic sheet, a metal silicon powder is employed as the heat transferable electric insulating agent. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a novel heat conductive elastic sheet capable of realizing excellent thermal conductivity while ensuring electrical insulation and rubbery elastic characteristics.

  In heat-generating electrical components such as power transistors, thyristors, rectifiers, and transformers, it is important to efficiently release the heat generated by energization to the outside. Therefore, conventionally, when a heat dissipating component is mounted on a heat generating electrical component, a structure in which a heat conductive elastic sheet is mounted between the heat generating electrical component and the heat dissipating component has been adopted.

  That is, by interposing a heat conductive elastic sheet, it is possible to fill a gap caused by unevenness on the overlapping surface of the heat generating electrical component and the heat radiating component and reduce the contact thermal resistance. Thereby, it is possible to efficiently conduct heat from the heat-generating electrical component to the heat-dissipating component, and to effectively exhibit the heat-dissipating effect of the heat-dissipating component.

  In recent years, in liquid crystal displays, when the electrode terminal row on the liquid crystal panel side and the wiring terminal row on the drive circuit side are lined up in a row, a cushion interposed between the two terminal rows and the electric lamp. A similar heat conductive elastic sheet is also used as the sheet. Even in such a cushion sheet, it is required to realize efficient heat transfer by following the shapes of both terminal rows and electric irons.

  By the way, as such a heat transfer elastic sheet, generally, a heat-resistant silicone rubber is mainly used, and in order to improve its heat transfer performance, a mixture of powders of metal oxides such as aluminum oxide and magnesium oxide is mixed. What used the composition and shape | molded it in the sheet form is employ | adopted (refer patent document 1).

  However, the conventional heat-transfer elastic sheet has a problem that the physical properties of the elastic sheet are lowered when the amount of the metal oxide is increased in order to improve the heat transfer performance. Specifically, due to an increase in the amount of metal oxide blended, it may hinder molding such as calender roll processing, or the shape followability to both members that are superposed via an elastic sheet may be reduced. As a result, a problem arises in that it becomes difficult to stably obtain sufficient heat transfer performance due to the occurrence of gaps.

  Therefore, it has been very difficult to achieve high heat transfer performance while securing the required elastic characteristics with the conventional heat transfer elastic sheet.

JP 47-32400 A

  Here, the present invention has been made in the background as described above, and the problem to be solved is to form a desired sheet shape by adopting a novel heat conductive electrical insulating agent. It is an object of the present invention to provide a novel heat transfer sheet capable of significantly improving the heat transfer performance with a smaller blending amount as compared with conventional metal oxides while ensuring operability sufficient to enable the above.

  In order to solve such a problem, the present inventor has conducted many experiments and examinations, and as a result, the specific powder is blended with the polymer elastic material, so that it is less than when the conventional metal oxide is blended. Heat transfer performance can be improved by blending amount, and therefore, a new rubber-like elastic material that can exhibit excellent heat transfer performance while sufficiently ensuring flexibility, electrical insulation, operability, etc. is realized. Based on this finding, the present invention could be completed.

  That is, a feature of the present invention is that in the heat conductive elastic sheet obtained by forming a mixture composition obtained by blending a polymer elastic material and a heat conductive electric insulating agent into a sheet shape and crosslinking, the heat conductive electric insulation is obtained. It is a heat conductive elastic sheet that employs metal silicon powder as an agent.

  In accordance with the present invention, by incorporating metal silicon as a heat conductive electrical insulation, as is apparent from the description of the embodiments and examples described later, it is compared with the case where a conventional metal oxide is employed as the heat conductive electrical insulation. Thus, a silicone rubber having improved heat transfer performance can be obtained with a small amount.

  In particular, the amount of blending can be reduced compared to the case where conventional metal oxides are used as heat-conducting electrical insulating agents, so that the formability and flexibility of the sheet shape must be maintained at a practical level. Is possible.

  It should be noted that the reason why such a special effect can be exhibited by adopting metallic silicon as the heat conductive electrical insulating agent has not yet been fully elucidated, and scientific elucidation is not the object of the present invention. However, for example, it is estimated that one of the reasons is related not only to the high thermal conductivity of metal silicon but also to physical properties such as tap density.

  That is, metal silicon has a tap density of about 660, which is smaller than that of metal oxides 800 to 1320 such as aluminum oxide and magnesium oxide. Therefore, when mixed with a polymer elastic material such as a silicone rubber material, the metal silicon powder has better dispersibility in the mixed state in the polymer elastic material than the metal oxide, and is well mixed. It is presumed that the state is stably expressed.

  Moreover, metallic silicon has a thermal conductivity of about 168 W / mK, which is very large compared to 10 to 60 W / mK of metal oxides such as aluminum oxide and magnesium oxide.

As described above, the physical properties inherent to metallic silicon are suitably matched to the polymeric elastic material, and as a result, metallic silicon is dispersed and mixed almost uniformly throughout the polymeric elastic material with a relatively small amount. Thus, it is considered that the desired heat transfer performance can be expressed well and stably by the whole elastic material while advantageously securing elastic properties such as flexibility and strength and moldability. In addition, when silicone rubber is particularly used as the polymer elastic material, the tackiness which is the rubber characteristic of the silicone rubber itself can be sufficiently maintained. This eliminates the need for it and provides excellent operability.

  Hereinafter, in order to clarify the present invention more specifically, embodiments of the present invention will be described.

  First, as the polymer elastic material used in the present invention, both a rubber material and an elastomer material can be mentioned. Specific examples include rubber materials such as silicone rubber, ethylene propylene rubber, natural rubber, isoprene rubber, and styrene butadiene rubber, as well as elastomer materials such as ethylene vinyl acetate, ethylene methacrylate copolymer, and chlorinated polyethylene. Various known rubber materials and elastomer materials are employed as the polymer elastic material in the present invention.

  In particular, silicone rubber can be suitably employed as the polymer elastic material, but such silicone rubber is obtained by crosslinking a known polyorganosiloxane, and as such is known, after crosslinking, It has excellent physical properties such as electrical insulation and heat resistance, and has low hardness and excellent flexibility, shape followability and workability. That is, in the present invention, various types of conventionally known silicone rubbers can be particularly suitably employed as the matrix material of the intended heat-transfer elastic sheet.

  Specifically, as the crosslinking form, in addition to radical reaction type by organic peroxide, addition reaction type by polyorganosiloxane containing vinyl group, organohydrogen having hydrogen atom bonded to silicon atom, and platinum catalyst. The condensation reaction type and the like are not limited. In addition to the methyl vinyl silane, the composition includes methyl phenyl silane, dimethyl silane, methyl fluoroalkyl silane, and the like without limitation. This is because all of these silicone rubbers have the above-mentioned physical properties in common.

  Here, in the present invention, it is particularly desirable to use methylvinylsilane-based silicone rubber. As a result, even when the amount of metal silicon is set relatively large, the flexibility and formability of the rubber sheet can be secured more advantageously, and the use range of the sheet can be set broadly. It becomes possible.

  In the present invention, in particular, a liquid silicone rubber material can be suitably used in order to improve the operability of the compounding of the metal silicon and further uniformize the dispersion of the metal silicon in the matrix.

  In addition, such silicone rubber materials and various elastic materials such as the above-mentioned ethylene propylene rubber materials and elastomeric materials such as elastomer materials include cross-linking agents, conventionally known plasticizers and adhesives, Molding aids such as oil and crosslinking retarder, colorants, heat resistance improvers and the like can be appropriately blended as necessary. In addition, aluminum oxide, magnesium oxide, etc., which have been conventionally employed as a heat conductive electrical insulating agent, may be added as necessary. Furthermore, silicon carbide, graphite, reinforcing silicon dioxide, antistatic carbon and the like can be blended.

  On the other hand, the metal silicon blended in such a polymer elastic material is a well-known material excellent in thermal conductivity and electrical insulation, and this is powdered and dispersed in the polymer elastic material as a matrix. . Metallic silicon is generally obtained by reducing silica with raw materials such as an electric furnace, and is easily obtained in the market because it is provided as a material such as silicon nitride, new ceramics, and refractory bricks. It can be done. In particular, in the present invention, generally available metal silicon powder is sufficient, and it is possible to adopt a product before high purification treatment, that is, a purity of about 95 to 99%.

  The metal silicon powder desirably has an average particle size of 20 μm or less. The powdered metal silicon can be easily obtained in the market in a powder state having an average particle size.

  If the average particle size of the metal silicon is larger than 20 μm, the heat transfer performance can be improved. However, depending on the properties of the intended polymer elastic sheet, the strength, tear strength, durability, rubber elasticity (elongation), etc. It becomes difficult to satisfy the required value. Further, depending on the thickness dimension of the intended polymer elastic sheet and the required adhesion, unevenness on the sheet surface may become a problem.

  In particular, in order to obtain better sheet strength, durability, elasticity, and the like, a metal silicon powder having an average particle size of preferably 20 μm or less, more preferably 10 μm or less is employed.

  On the other hand, if the particle size of the metal silicon powder is too small, there are problems in powder processing and handling, resulting in a decrease in yield and an increase in cost. Therefore, the average particle diameter of the metal silicon powder is preferably 2 μm or more, and more preferably, the metal silicon powder having an average particle diameter of 5 μm or more is employed.

  Furthermore, the compounding quantity with respect to the polymeric elastic material of such a metal silicon powder is suitably set according to the use of an elastic sheet, a required characteristic, etc., and is not specifically limited. However, in consideration of a mounting application between a general electric component and a heat dissipation component, the compounding amount of metal silicon is desirably 15 to 300 parts by weight per 100 parts by weight of the polymer elastic material. More preferably, the metal silicon powder is blended in an amount of 50 parts by weight or more, more preferably 100 parts by weight or more per 100 parts by weight of the polymer elastic material. More preferably, the metal silicon powder is blended in an amount of 200 parts by weight or less, more preferably 150 parts by weight or less, per 100 parts by weight of the polymer elastic material.

  This is because it is difficult to obtain the desired effect of improving the thermal conductivity in the obtained polymer elastic sheet when the amount of the metal silicon powder is too small, and conversely, the amount of the metal silicon is too large. The elastic properties of the resulting polymer elastic sheet will be reduced, and it will be difficult to obtain the required flexibility and elongation depending on the application, etc. This is because it may be difficult to obtain sufficient adhesion.

  The polymer elastic material that is the calculation standard for the blending amount is not a material for elastic material alone but a molding material for a polymer elastic body in which an appropriate additive and a crosslinking material are blended. Specifically, for example, in the case of a silicone rubber material, it is not a raw material of polyorganosiloxane, but a rubber material blended with an appropriate additive and a crosslinking agent. Such a polymer elastic material is provided by a plurality of companies in the market as each material or as a material in which an appropriate additive is pre-blended with a silicone rubber raw material, and can be easily obtained. In addition, the calculation standard for the amount of metallic silicon is not simply a raw material for a polymer elastic material such as polyorganosiloxane, but an elastic material containing an appropriate additive or the like is simply obtained and implemented. In addition to the fact that the effect of improving the thermal conductivity and the change in elastic properties expressed by the amount of metallic silicon are based on the dispersed state of metallic silicon, This is because it can be understood more significantly based on a polymer elastic material such as a silicone rubber material than on the basis of a single raw material of the polymer elastic body.

  Moreover, the metal silicon employ | adopted in this invention does not specifically limit the particle shape. For example, a spherical shape, a flat shape, a granular shape, a lump shape, a fibrous shape, a needle shape, a scale shape, a pellet shape, a whisker shape, or the like may be provided on the market or an indefinite shape. Especially, what is provided to the market as a general crushed form is effective because it is relatively inexpensive and easily available.

  Subsequently, a target elastic sheet using as a molding material a mixed composition in which a polymer elastic material such as silicone rubber as described above is used as a matrix and a metal silicon powder as a heat-conducting electrical insulating agent is mixed in a dispersed state. A description will be given of the process of manufacturing the.

  First, when the metal silicon powder is blended in a polymer elastic material such as a silicone rubber material, it is desirable to disperse the metal silicon powder as uniformly as possible. For this purpose, for example, a kneading process using a mixer or the like is employed. As such a mixer, a known mixer such as a rotary mixer or a planetary mixer can be employed.

  In addition, in order to further improve the uniform dispersibility of the metal silicon powder in the polymer elastic material, for example, a suitable surface treatment can be applied to the metal silicon powder. As this surface treatment, for example, a silane coupling agent, an aluminum coupling agent, a silicon compound, or the like can be employed.

  In order to obtain the desired elastic sheet using the molding material thus obtained, an appropriate molding method is adopted in consideration of the target sheet shape, sheet size, and the characteristics of the molding material. Is done. Although not particularly limited, for example, extrusion molding, blow molding, compression molding, injection molding, press rolling molding, and the like can be employed in addition to calendar molding. When a liquid polymer elastic material such as a liquid silicone rubber material is employed, a molding method such as a coating method, a printing method, bonding, or dipping can be suitably employed. In addition to crosslinking by heating and pressurization at the same time as molding or after molding, those by electromagnetic waves or radiation can be employed. In addition, in any case of the molding method and the cross-linking method, the addition or additional blending of raw materials and various additives is not limited as long as there is no problem in the properties of the target elastic sheet. Can be changed and set. Needless to say, in the case of an elastomer material or the like, a crosslinking treatment is not necessarily required.

  And, in the heat conductive elastic sheet according to the present invention obtained in this way, the metal silicon powder as the heat conductive electrical insulating agent has a structure that is uniformly dispersed in the polymer elastic body. In addition, by realizing such a specific structure of the specific substance, the heat transfer performance can be advantageously improved with a small amount compared to the case where a conventional metal oxide is used as the heat transfer electrical insulating agent. It is.

  In particular, it is possible to obtain excellent heat transfer performance while suppressing the blending amount of metal silicon powder as the heat conductive electrical insulating agent, compared to the case where a conventional metal oxide is adopted as the heat conductive electrical insulating agent. Therefore, along with the realization of a high degree of heat transfer performance, the elongation and shape followability of the heat transfer elastic sheet can be obtained well, and good practicality is exhibited.

In particular, high heat transfer characteristics can be achieved even with less than 200 parts by weight of metal silicon powder, 100 parts by weight or less, 50 parts by weight or less, or 15 parts by weight based on 100 parts by weight of the polymer elastic material. Is possible. Since excellent heat transfer characteristics are realized with such a small amount of heat conductive electrical insulation, an elastic sheet having sufficient elongation characteristics, tensile strength and hardness while ensuring high thermal conductivity Can be advantageously obtained.

  Hereinafter, the present invention will be more specifically clarified by giving examples and comparative examples of the present invention. It should be noted that the present invention is not construed as being limited to the specific descriptions in the following examples and the exemplary descriptions in the above-described embodiments.

  Moreover, the measurement of the thermal conductivity in the following Examples and Comparative Examples was performed by directly obtaining the same thermal conductivity value as in the hot wire method by adopting a probe method based on the principle of the unsteady hot wire method. Specifically, the thermal conductivity of the sample was measured using a “Kemtherm QTM-D3 rapid thermal conductivity meter” (trade name) manufactured by Kyoto Electronics Industry Co., Ltd.

"SE1647U" (trade name) manufactured by Toray Dow Corning Co., Ltd. is used as the methyl vinyl silane-based silicone rubber material. 340 cm ³ of powder (tap density: 659 kg / m ³ ) was blended. To this was added “RC-4” (trade name) containing 2.5 dimethyl, 2.5 di (tertiary butyl peroxy) hexane produced by Toray Dow Corning Co., Ltd. as an active ingredient, This was kneaded to obtain a molding material as a mixed composition. In addition, silicon dioxide and antistatic carbon are previously blended in predetermined amounts into the above-mentioned commercially available silicone rubber material (SE1647U). That is, in this example, a polymer elastic material is constituted by these commercially available silicone rubber materials (SE1647U) and a crosslinking agent (RC-4).

  The obtained molding material was formed into a sheet having a thickness of 0.3 mm by calendar molding, and then crosslinked at a temperature of 164 ° C. for 10 minutes.

  The results obtained by actually measuring the thermal conductivity of the silicone rubber sheet as the heat conductive elastic sheet thus obtained are shown in Table 1 below as Example 1.

  Further, in place of the above metal silicon powder, five types of aluminum oxide, magnesium oxide, silicon carbide, and graphite were respectively employed as the heat conductive electrical insulator, and silicone rubber was used under the same conditions. A sheet was obtained. About these 8 types of obtained silicone rubber sheets, the result of having measured the thermal conductivity, respectively is shown together in [Table 1] as Comparative Examples 1-8.

  In Comparative Example 8 in which graphite was used as the heat conductive electrical insulating agent, although high thermal conductivity was obtained, the obtained rubber sheet had almost no elasticity and showed almost no rubber properties. Since cracks and cracks occurred, it was impossible to put to practical use.

  From the results shown in [Table 1], it can be seen that by adding metal silicon powder in the silicone rubber, the thermal conductivity can be significantly improved as compared with the conventionally used heat conductive electrical insulation. I know I can do it.

  Next, the same silicone rubber material (SE1647U) and cross-linking agent (RC-4) as those in the above examples were adopted, and various types of metal silicon powders as heat-conducting electrical insulating agents to be blended were used. A molding material was obtained. Using these molding materials, a sheet-like molded product having a thickness of 0.3 mm is obtained by calender molding in the same manner as in the above examples, and the silicone rubber according to the present invention is crosslinked at a temperature of 164 ° C. for 10 minutes. Examples 2 to 7 were obtained as sheets.

  About these Examples 2-7, while measuring thermal conductivity, respectively, tensile strength (JIS K6251) was measured. The results are shown in [Table 2] below. In addition, the compounding quantity of the metal silicon powder in [Table 2] is represented by the compounding weight with respect to 100 parts by weight of the polymer elastic material.

  Moreover, the silicone rubber sheet was obtained on the same conditions about the case where a metal silicon powder is not mix | blended on the same conditions as the said Examples 2-7. Furthermore, under the same conditions as in Examples 2 to 7, in the case where aluminum oxide or magnesium oxide that has been conventionally used as a heat conductive electrical insulating agent is blended instead of the metal silicon powder, both are the same conditions. A silicone rubber sheet was obtained. For these three types of silicone rubber sheets obtained, the results of measuring the thermal conductivity and the like in the same manner are shown in Table 2 as Comparative Examples 9-11.

  Also from the results shown in [Table 2], it was confirmed that the metal silicon powder can effectively act as a heat conductive electrical insulating agent by blending the metal silicon powder with the silicone rubber material. In particular, from these examples employing a methylvinylsilane-based silicone rubber material, by mixing 50 parts by weight or more of metal silicon powder with respect to 100 parts by weight of the silicone rubber material, an excellent of 1.0 W / mK or more was obtained. It was also confirmed that a rubber sheet with thermal conductivity could be obtained. In addition, by adding metal silicon powder according to the present invention, the thermal conductivity in the resulting rubber sheet is advantageously improved as compared with the case where conventional aluminum oxide or magnesium oxide is added as a heat conductive electrical insulating agent. Of course, it is recognized that rubber properties such as tensile strength and molding operability (handling) can be greatly improved.

  Subsequently, “SE955U” (trade name) manufactured by Toray Dow Corning Co., Ltd. is used as a methylphenylsilane-based silicone rubber material, and “RC-4” (trade name) manufactured by Toray Dow Corning Co., Ltd. is used as a crosslinking agent. )It was adopted. That is, the silicone rubber as the polymer elastic material of this example is composed of these commercially available methylphenylsilane-based silicone rubber materials (SE955U) and the crosslinking agent (RC-4). Metallic silicon powder as a heat conductive electrical insulating agent was employed for this, and 194 parts by weight of metallic silicon powder was blended with 100 parts by weight of the polymer elastic material to obtain a molding material. Using this molding material, a sheet-like molded body having a thickness of 0.3 mm is obtained by calender molding in the same manner as in Examples 2 to 7 described above, and is crosslinked at a temperature of 164 ° C. for 10 minutes in accordance with the present invention. Example 8 was obtained as a silicone rubber sheet.

  About Example 8, while measuring thermal conductivity, each value of elongation (JIS K6251) and hardness (JIS-A) was measured. The results are shown in [Table 3] below.

  In addition, in the case where aluminum oxide or magnesium oxide, which has been conventionally used as a heat conductive electrical insulating agent, is blended in place of the silicon powder, the molding of the silicone rubber sheet under the same conditions and the obtained rubber An attempt was made to measure the characteristics of the sheet. The results are also shown in Table 3 as Comparative Examples 12 and 13.

  From the results shown in [Table 3], it is clear that the present invention is advantageously applied even when a methylphenylsilane-based silicone rubber material is employed. In particular, compared to the case where conventional aluminum oxide or magnesium oxide is added as a heat conductive electrical insulating agent, by adding metal silicon powder according to the present invention, the thermal conductivity of the resulting rubber sheet is made equal or higher. In realization, it is recognized that very good moldability and rubber properties can be exhibited in the examples according to the present invention.

  Next, “SH747U” (trade name) manufactured by Toray Dow Corning Co., Ltd. is used as a methyl vinylsilane-based silicone rubber material, and “RC-4” (trade name) manufactured by Toray Dow Corning Co., Ltd. is used as a crosslinking agent. It was adopted. That is, in this embodiment, a polymer elastic material is constituted by these commercially available methylvinylsilane-based silicone rubber materials (SH747U) and a crosslinking agent (RC-4). The metal silicon powder as a heat conductive electrical insulating agent was employ | adopted for this, and 10-146 weight part of metal silicon powder was mix | blended with respect to 100 weight part of polymeric elastic materials, respectively, and each molding material was obtained. Using these molding materials, a sheet-like molded body having a thickness of 0.3 mm was obtained by calendar molding in the same manner as in Examples 2 to 7, and the crosslinking was performed at a temperature of 164 ° C. for 10 minutes. Examples 9-12 were obtained as silicone rubber sheets according to the above.

  About these Examples 9-12, while measuring thermal conductivity, the tensile strength (JIS K6251) was measured. The results are shown in [Table 4] below.

  Moreover, the silicone rubber sheet was shape | molded using the material which does not mix | blend a metal silicon powder on the same conditions as the said Examples 9-12. Furthermore, under the same conditions as in Examples 9 to 12, in place of metal silicon powder, aluminum oxide or magnesium oxide conventionally used as a heat conductive electrical insulating agent was blended, and in all cases, the same conditions A silicone rubber sheet was obtained. The results of measuring the thermal conductivity and the like of these three types of silicone rubber sheets obtained in the same manner are shown in Table 4 as Comparative Examples 14 to 16.

  From the results shown in [Table 4], it was confirmed that the metal silicon powder can effectively act as a heat conductive electrical insulating agent by blending the metal silicon powder with the silicone rubber material. In particular, from these examples employing a methyl vinyl silane-based silicone rubber material, by adding 15 parts by weight or more of metal silicon powder to 100 parts by weight of the polymer elastic material, a favorable value of 1.0 W / mK or more is obtained. It was confirmed that a rubber sheet having thermal conductivity could be obtained. Moreover, compared with the case where the conventional aluminum oxide and magnesium oxide are added as a heat conductive electrical insulation agent, by adding metal silicon powder according to the present invention, excellent thermal conductivity can be obtained and obtained. It is recognized that rubber properties such as tensile strength and molding operability in the rubber sheet can be greatly improved.

  Subsequently, as ethylene propylene rubber as the olefin rubber material, “EP33” (trade name) manufactured by JSR Corporation is adopted, and is transmitted to 100 parts by weight of the polymer elastic material having this as a main component. Metallic silicon powders were blended as thermal electrical insulating agents as shown in the following [Table 5]. That is, 73.5 parts by weight of ethylene propylene rubber material (EP33), 3.7 parts by weight of “Dicup40C” (trade name) manufactured by Mitsui Petrochemical Co., Ltd. as a crosslinking agent, and “Idemitsu Kosan Co., Ltd.” 22.1 parts by weight of Diana PW-50 ”and 0.7 parts by weight of“ Stearic acid 150 ”manufactured by Kao Corporation as a surfactant were added, and each predetermined amount of metal silicon powder was added. A molding material was obtained by kneading.

  The obtained molding material was dispensed at a thickness of approximately 2.3 mm and subjected to a crosslinking treatment to obtain a rubber sheet having a thickness of approximately 2 mm. The crosslinking condition is a temperature of 170 ° C. × 15 minutes.

  The results obtained by actually measuring the thermal conductivity of the seven types of rubber sheets thus obtained are shown in Table 5 below as Examples 13 to 19.

  Moreover, it replaced with the said metal silicon powder, and the case where aluminum oxide was employ | adopted as a heat conductive electrical insulating agent obtained the ethylene propylene rubber sheet on the same conditions in all. The results of measuring the thermal conductivity and tensile strength of the four types of rubber sheets obtained are shown in Table 5 as Comparative Examples 17-20.

  From the results shown in [Table 5], it is possible to improve the thermal conductivity by using metal propylene rubber in the ethylene propylene rubber as compared with the conventionally used heat conductive electrical insulation. You can see that In particular, from these examples employing an ethylene propylene rubber material, by adding 100 parts by weight or more of metal silicon powder to 100 parts by weight of the polymer elastic material, a good thermal conductivity of 0.6 W / mK or more is obtained. It can be confirmed that the prepared rubber sheet can be obtained, and further, by adding 200 parts by weight or more of metal silicon powder, it is possible to obtain a rubber sheet having a further excellent thermal conductivity of 1.1 W / mK or more. It was. In addition, compared with the case where conventional aluminum oxide or magnesium oxide is added as a heat conductive electrical insulating agent, a large thermal conductivity can be efficiently obtained with a small addition amount by adding metal silicon powder according to the present invention. It is recognized that rubber properties such as tensile strength in the resulting rubber sheet can be greatly improved.

Incidentally, the measurement results of the thermal conductivity of Examples 17 to 19 and Comparative Examples 17 to 20 shown in the graph are shown in FIG. From this [Fig. 1], the heat transfer performance of ethylene propylene rubber is improved very efficiently by adopting metallic silicon according to the present invention, compared with aluminum oxide conventionally used as a heat transfer electrical insulating agent. Can be more clearly recognized.

The graph which shows the measurement result of the thermal conductivity in Examples 17-19 of this invention with the measurement result of the thermal conductivity in Comparative Examples 17-20.

Claims (6)

In a heat conductive elastic sheet obtained by forming a mixed composition in which a heat conductive electrical insulating agent is blended with a polymer elastic material into a sheet shape and crosslinking,
A heat conductive elastic sheet characterized in that metallic silicon powder is employed as the heat conductive electrical insulating agent.   The heat conductive elastic sheet according to claim 1, wherein an average particle diameter of the metal silicon powder is 20 µm or less.   The heat conductive elastic sheet according to claim 1 or 2, wherein a compounding amount of the metal silicon powder is 15 to 300 parts by weight per 100 parts by weight of the polymer elastic material.   The heat conductive elastic sheet according to any one of claims 1 to 3, wherein the polymer elastic material is silicone rubber.   The heat conductive elastic sheet according to claim 4, wherein the silicone rubber is methylvinylsilane-based silicone rubber. The heat conductive elastic sheet according to any one of claims 1 to 5, which has a thermal conductivity of 1.0 W / mK or more.

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