Laminated body

A laminated body comprises a thermally conductive sheet, a protective sheet, an auxiliary sheet, a carrier sheet and a coating sheet. The thermally conductive sheet comprises a main sheet body and an adhesive layer. The coefficient of static friction of the main sheet body is 1.0 or lower. The adhesive layer has high adhesiveness in comparison with the main sheet body, and has an outer shape smaller than that of the main sheet body. The protective sheet is formed having an outer shape larger than that of the adhesive layer, and provided with a cutting line extending toward the adhesive layer from the peripheral portion of the protective sheet so that the protective sheet can be cut along the cutting line.

BACKGROUND OF THE INVENTION

The present invention relates to a laminated body which includes a thermally conductive sheet for accelerating thermal conduction from a heat emitting body to a heat discharging body inserted between the heat emitting body and the heat discharging body.

In recent years, power consumption and heat emission have been increased with the performance upgrade of electronic devices, such as CPU's (central processing units) for computers. The processing performance of electronic devices deteriorates due to heat. Accordingly, it is necessary to avoid heat accumulation in electronic devices, in order to maintain the performance of the electronic device, and thus, cooling of electronic devices has become an important issue. Therefore, excellent thermal conductivity has been required for use of thermally conductive sheets inserted between an electronic device, which is a heat emitting body and a heat discharging body, such as a heat sink.

Japanese Laid-Open Patent Publication No. 10-183110 and Japanese Laid-Open Patent Publication No. 11-335472 disclose a thermally conductive sheet made of a silicone gel which contains a thermally conductive filler. This thermally conductive sheet is viscous due to the flexibility of the silicone gel. Therefore, the thermally conductive sheet can make close contact with the heat emitting body and the heat discharging body, and thus, can provide excellent thermal conductivity.

Japanese Laid-Open Patent Publication No. 2006-335957 and Japanese Laid-Open Patent Publication No. 2006-335958 disclose thermally conductive sheets made of a composition which contains a thermally conductive filler in fiber form and a polymer matrix. These thermally conductive sheets can provide excellent thermal conductivity due to the thermally conductive filler being oriented in one direction. Furthermore, an end portion of the thermally conductive filler is exposed from the thermally conductive sheet, and thus, the viscosity of the thermally conductive sheet can be reduced.

Japanese Laid-Open Patent Publication No. 7-149365 discloses a thermally conductive sheet wrapping body provided with a top cover tape and a thermally conductive sheet which is sealed in the top cover tape. Japanese Laid-Open Patent Publication No. 2002-222904 discloses a laminated body comprising a thermally conductive sheet provided with a support tape and a thermally conductive sheet which adheres to the support tape. The top cover tape and the support tape contribute to automation of the work for attaching the thermally conductive sheet to, for example, a heat emitting body using a machine, and at the same time, advantageously of making maintenance and carrying of thermally conductive sheets easy.

However, there is a problem with the thermally conductive sheets described in Japanese Laid-Open Patent Publication No. 10-183110 and Japanese Laid-Open Patent Publication No. 11-335472, such that the viscosity is high, and thus, ease of handling is low, for example, when attached to a heat emitting body and when carried. The thermally conductive sheets described in Japanese Laid-Open Patent Publication No. 2006-335957 and Japanese Laid-Open Patent Publication No. 2006-335958 have a low viscosity and a thermally conductive filler oriented in one direction, and furthermore, the thermally conductive sheets are thin, in order to lower the value of the thermal contact resistance, and therefore, it is easy for the sheets to shift in position or break when the thermally conductive sheet is attached to, for example, a heat emitting body. Therefore, a problem arises, such that it is difficult to attach the thermally conductive sheet. In addition, when a thermally conductive sheet wrapping body as that described in Japanese Laid-Open Patent Publication No. 7-149365 or a laminated body as that described in Japanese Laid-Open Patent Publication No. 2002-222904 is formed using the thermally conductive sheet described in Japanese Laid-Open Patent Publication No. 2006-335957 or Japanese Laid-Open Patent Publication No. 2006-335958, there is a problem with the thermally conductive sheet, of which the viscosity is low and which easily breaks, such that attachment of the thermally conductive sheet is difficult.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a laminated body more appropriate for use in applications where thermal conduction is required from a heat emitting body to a heat discharging body.

To achieve the foregoing and in accordance with an aspect of the present invention, a laminated body is provided. The laminated body includes a thermally conductive sheet and a protective sheet. The thermally conductive sheet has a main sheet body insertable between a heat emitting body and a heat discharging body and an adhesive layer provided on the main sheet body. The protective sheet is provided on the adhesive layer for protecting the adhesive layer. The coefficient of static friction of the main sheet body is 1.0 or lower. The adhesive layer has high adhesiveness in comparison with the main sheet body and has an outer shape smaller than that of the main sheet body. The protective sheet is formed so as to have an outer shape larger than that of the adhesive layer, and is provided with a cutting line extending toward the adhesive layer from a peripheral portion of the protective sheet so that the protective sheet can be cut along the cutting line.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, a preferable embodiment of a laminated body according to the present invention is described in detail with reference to the drawings. As shown inFIGS. 1A to 1C, the laminated body11according to the present embodiment comprises a thermally conductive sheet12, a protective sheet13, an auxiliary sheet14, a carrier sheet15and a coating sheet16. These sheets are layered in the order: carrier sheet15, auxiliary sheet14, thermally conductive sheet12, protective sheet13, coating sheet16, from the bottom. The thermally conductive sheet12comprises a main sheet body21, which is formed of a thermally conductive polymer composition and an adhesive layer22layered on the main body21. The thermally conductive sheet12, that is to say, the main sheet body21, is provided in such a manner as to be inserted between a heat emitting body and a heat discharging body, so that thermal conduction from the heat emitting body to the heat discharging body accelerates. In the following description, the thermally conductive polymer composition is simply referred to as a composition.

The laminated body11is handled when carried, and the thermally conductive sheet12is used for thermal conduction from a heat emitting body to a heat discharging body after sheets other than the thermally conductive sheet12have been peeled off. Therefore, the laminated body11is easy to handle, and the thermally conductive sheet12has thermal conductivity and is easy to attach.

The ease of handling is an indicator for the ease of handling of the laminated body11when carried, for example, based on the rigidity of the sheets that form the laminated body11. The laminated body11is easy to handle due to the appropriate rigidity of the sheets that form the laminated body11, and is very easy to handle. The thermal conductivity is an indicator for the ease of thermal conduction from the heat emitting body to the heat discharging body, mainly based on the thermal conductivity and the thermal resistance value of the main sheet body21and the adhesiveness between the main sheet body21and the heat emitting body, as well as between the main sheet body21and the heat discharging body. The higher the thermal conductivity of the main sheet body21, the lower the thermal resistance value of the main sheet body21, and the higher the adhesiveness between the main sheet body21and the heat emitting body, as well as between the main sheet body21and the heat discharging body is, the more the thermally conductive sheet12accelerates heat conduction from the heat emitting body to the heat discharging body, thus exhibiting excellent thermal conductivity. The ease of attachment is an indicator for the ease with which the thermally conductive sheet12is attached to the heat emitting body or the heat discharging body. The thermally conductive sheet12is very easy to attach because the adhesiveness of the main sheet body21is low and the adhesive layer22has appropriate adhesiveness, so that the thermally conductive sheet12can be attached to the heat emitting body or the heat discharging body without displacement shift being caused.

The composition contains a polymer matrix and a thermally conductive filler. The polymer matrix holds the thermally conductive filler within the main sheet body21. The polymer matrix is selected in accordance with the performance required for the main sheet body21, for example mechanical strength, hardness, durability, resistance to heat, and electrical properties. Specific example of the polymer matrix includes silicone resin.

The thermally conductive filler increases the thermal conductivity of the main sheet body21so that the cooling function of the thermally conductive sheet12increases. Specific examples for the form of the thermally conductive filler include fiber, particle and plate forms. Preferably, at least part of the thermally conductive filler is in fiber form. In the following, a thermally conductive filler in fiber form, that is to say, a thermally conductive sheet12containing a filler in fiber form, is described. Specific examples of the filler in fiber form include carbon fibers and poly(p-phenylenebenzobisoxazole) precursor carbon fibers (PBO carbon fibers). Specific examples of materials for thermally conductive fillers having a form other than fiber form, that is to say, fillers in non-fiber form include aluminum oxide and aluminum hydroxide.

It is preferable for the thermally conductive filler content in the composition be 90 mass % or less. In the case where the thermally conductive filler content exceeds 90 mass %, the main sheet body21becomes fragile, because the flexibility of the main sheet body21is low, and at the same time, there is a risk that the main sheet body21may not stick to the shape of the contour of the heat emitting body and the heat discharging body as much. The composition may contain a plasticizer for adjusting the hardness of, for example, the main sheet body21, and a stabilizer for enhancing durability, in addition to the above described components.

As shown inFIGS. 2A to 2C, the main sheet body21is in quadrilateral plate form and provided with a polymer matrix31and a thermally conductive filler32. The thermally conductive filler32according to the present embodiment has a thermally conductive filler32in fiber form, that is to say, filler in fiber form32aand a thermally conductive filler32in particle form, that is to say, a filler in particle form32b.The filler in fiber form32ais oriented in one direction. In the main sheet body21shown inFIGS. 2A to 2C, for example, the filler in fiber form32ais oriented in the direction of the thickness of the main sheet body21. Therefore, the value of the thermal conductivity of the main sheet body21in the direction of the thickness is equal to the value gained by multiplying the value of the thermal conductivity in the direction of the width by two to several hundred. The end portions of the filler in fiber form32aextend in the direction of the width of the main sheet body21and are exposed on pairs of facing outer surfaces21a.

The adhesiveness of the main sheet body21is very small, and therefore, the adhesiveness of the main sheet body21can be indicated using the coefficient of static friction of the main sheet body21. That is to say, in the case where the coefficient of static friction of the main sheet body21is low, the adhesiveness of the main sheet body21is low, while in the case where the coefficient of static friction of the main sheet body21is high, the adhesiveness of the main sheet body21is high. The coefficient of static friction of the main sheet body21is 1.0 or lower, preferably 0.3 or lower. In the case where the coefficient of static friction of the main sheet body21exceeds 1.0, it becomes difficult to attach the thermally conductive sheet12to the heat emitting body, for example, due to the excessively high adhesiveness of the main sheet body21. The lower limit for the coefficient of static friction of the main sheet body21is not particularly limited, and the smaller the coefficient of static friction of the main sheet body21is, the easier it is to attach the thermally conductive sheet12to the heat emitting body, for example. In the case where the coefficient of static friction of the main sheet body21is 1.0 or lower, the main sheet body21is not sticky when the outer surfaces of the main sheet body21are touched with the fingers, and thus, the main sheet body21does not adhere to the heat emitting body through its own adhesiveness.

The thickness of the main sheet body21is preferably 0.03 mm to 0.5 mm. In the case where the thickness of the main sheet body21is less than 0.03 mm, the manufacture of the main sheet body21becomes difficult. In the case where the thickness of the main sheet body21exceeds 0.5 mm, it takes time for the heat to conduct from the heat emitting body to the heat discharging body, and there is a risk that the cooling function of the thermally conductive sheet12may deteriorate. The main sheet body21having a thickness of 0.5 mm or less easily becomes flexible, due to the material.

The hardness of the main sheet body21as measured in accordance with the type E of JIS K 6253, which is a Japanese Industrial Standard (ISO 7619-1, which is an international standard), is 5 to 80, for example. In the case where the hardness of the main sheet body21is less than 5, the main sheet body21is too flexible, and therefore, the ease of handling of the thermally conductive sheet12deteriorates. Thus, it becomes difficult to handle the thermally conductive sheet12. In the case where the hardness of the main sheet body21exceeds80, the adhesion between the main sheet body21and the heat emitting body or heat discharging body lowers, and there is a risk that the cooling function of the thermally conductive sheet12may deteriorate.

The adhesive layer22is smaller than the main sheet body21in the outer shape, and formed in band form throughout the entirety of one end portion of the outer surface21aof the main sheet body21. The adhesive layer22has a higher adhesiveness than the main sheet body21, and is pasted to the heat emitting body and prevents the thermally conductive sheet12from displacement when the thermally conductive sheet12is attached to a heat emitting body, for example.

As shown inFIG. 2D, the adhesive layer22according to the present embodiment is formed of an adhesive sheet22cprovided with a base sheet22aand an adhesive22b,which is applied on both sides of the base sheet22a.Specific examples of the material for the base sheet22ainclude polyethylene terephthalate resin (PET). The adhesive layer22adheres to the main sheet body21and adheres to the heat emitting body or the heat discharging body, when the thermally conductive sheet12is attached to a heat emitting body or a heat discharging body. The material for the adhesive22bis selected on the basis of the material for the object to which the adhesive layer22adheres, so that the adhesive layer22has an appropriate adhesiveness for the object to which the adhesive layer22adheres. In the case where the polymer matrix of the main sheet body21is a silicone based rubber, for example, the material for the adhesive22bof the base sheet22a,which is located on the outer surface that faces the main sheet body21, is a silicone based adhesive, for example. In the case where the heat emitting body to which the adhesive layer22adheres is formed of a resin or aluminum, for example, the material for the adhesive22bof the base sheet22a,which is located on the outer surface that faces the heat emitting body, is an acryl based adhesive, for example. The thickness of the base sheet22ais, for example, 10 μm, and the thickness of the adhesive22b,which is applied on both sides of the base sheet22a,is, for example, 5 μm on either side.

The ratio of area occupied by the adhesive layer22to area of the entirety of the outer surface21aof the main sheet body21on which the adhesive layer22is provided is preferably 30% or less. When the ratio of the area occupied by the adhesive layer22exceeds 30%, here is a risk that handling of the thermally conductive sheet12may become difficult, due to the adhesiveness of the adhesive layer22. Furthermore, the adhesive layer22does not contain a thermally conductive filler, and therefore, the thermal conductivity of the adhesive layer22is low in comparison with the thermal conductivity of the main sheet body21. As a result, when the ratio of the area occupied by the adhesive layer22exceeds 30%, there is a risk that the thermal conductivity of the thermally conductive sheet12may lower excessively.

In the case where the adhesive layer22is formed in a portion of the main sheet body21, it may be formed in the center portion of the main sheet body21, but it is preferable for it to be formed in the peripheral portion of the main sheet body21. The amount of heat emitted in the center portion of the heat emitting body is usually high in comparison with the amount of heat emitted from the peripheral portion of the heat emitting body, and therefore, the center portion of the heat emitting body has a high temperature in comparison with the peripheral portion. In the case where the adhesive layer22is formed in the peripheral portion of the main sheet body21, the value of the thermal contact resistance in the peripheral portion of the main sheet body21, which is attached to the heat emitting body, is high in comparison with the value of the thermal contact resistance in the center portion of the main sheet body21. Therefore, the center portion of the main sheet body21, of which the value of the thermal contact resistance is low in comparison with the peripheral portion, corresponds to the center portion of the heat emitting body, where the temperature is high in comparison with the peripheral portion, and therefore, the thermal conductivity of the thermally conductive sheet12can be increased in comparison with the case where the adhesive layer is formed in the center portion of the main sheet body21.

The adhesive layer22according to the present embodiment is located in the peripheral portion of the main sheet body21. The peripheral portion of the main sheet body21is a region between the periphery of the main sheet body21and ⅗ of the distance from the periphery of the main sheet body21to the center. In a main sheet body21in quadrilateral plate form having sides of 40 mm, for example, the peripheral portion of the main sheet body21is in quadrilateral annular form with a width of 24 mm. In addition, in a main sheet body in disc form having a radius of 20 mm, the peripheral portion of the main sheet body21is in annular form with a width of 12 mm.

The thickness of the adhesive layer22is preferably 30 μm or less. In the case where the thickness of the adhesive layer22exceeds 30 μm, the base sheet22abecomes thick. Therefore, the base sheet22ahas high rigidity due to the material for the base sheet22a,and laminating of the adhesive layer22on the main sheet body21may become difficult. As described above, the thermal conductivity of the adhesive layer22is low in comparison with the thermal conductivity of the main sheet body21. Therefore, the lower limit for the thickness of the adhesive layer22is not particularly limited, and the thinner the adhesive layer22is, the higher the adhesiveness between the main sheet body21and the heat emitting body or heat discharging body becomes, and the lower the ratio of the adhesive layer22becomes in the direction of thermal conduction in the thermally conductive sheet12, and thus, the smaller the value of the thermal contact resistance of the thermally conductive sheet12becomes.

As shown inFIGS. 1B and 3, the protective sheet13is in quadrilateral plate form and faces the main sheet body21with the adhesive layer22in between. The protective sheet13adheres to the adhesive layer22before the thermally conductive sheet12is used for thermal conduction from the heat emitting body to the heat discharging body, and is peeled off from the adhesive layer22when the thermally conductive sheet12is attached to, for example, a heat emitting body.

The protective sheet13is larger than the adhesive layer22in the outer shape, in order to protect the entirety of the adhesive layer22. The protective sheet13according to the present embodiment is formed throughout the entirety of the adhesive layer22, and in addition, throughout the entirety of the main sheet body21. As a result, the protective sheet13in the present embodiment protects the entirety of the outer surface21aof the main sheet body21, in addition to the adhesive layer22. Specific examples of the material for the protective sheet13include polyethylene (PE). The thickness of the protective sheet is, for example, 25 μm.

A peripheral portion of the protective sheet13, that is to say, one end portion of the protective sheet13, is located on the adhesive layer22. The protective sheet13has a number of perforated lines for cutting23which extend linearly from the end portion (left end portion inFIG. 3) which faces the end portion (right end portion inFIG. 3) corresponding to the adhesive layer22toward the adhesive layer22, and is formed so that it can be cut along these cutting lines23. The respective cutting lines23are drawn in such a manner as to cross the adhesive layer22and the cutting lines23. In the present embodiment respective cutting lines23are drawn in such a manner as to cross the adhesive layer22perpendicularly.

The intervals of the cutting lines23are preferably set to ¼ or less of the length of the adhesive layer22in the direction in which the adhesive layer22crosses the cutting lines23(in the perpendicular direction in the present embodiment). Preferably at least one of the number of cutting lines23is drawn in a portion corresponding to the vicinity of the center portion of the adhesive layer22. In this case, only the protective sheet13is peeled off from the main sheet body21, and the adhesive layer22is not peeled off together with it when the protective sheet13is peeled off from the thermally conductive sheet12. In the case where only one cutting lines23is drawn on the protective sheet13, it is difficult to make the line for cutting23correspond to the vicinity of the center portion of the adhesive layer22. In contrast, in the case where a number of cutting lines23where the intervals are set as described above are drawn on the protective sheet13, it is easy to make one of the cutting lines23correspond to the vicinity of the center portion of the adhesive layer22.

The adhesiveness between the main sheet body21and the adhesive layer22is preferably set high in comparison with the adhesiveness between the protective sheet13and the adhesive layer22. In the case where the adhesiveness between the main sheet body21and the adhesive layer22is low in comparison with the adhesiveness between the protective sheet13and the adhesive layer22, the adhesive layer22may be peeled off from the main sheet body21together with the protective sheet13when the protective sheet13is peeled off.

As shown inFIGS. 1A to 1C, the auxiliary sheet14is in quadrilateral plate form and faces the outer surface21aof the main sheet body21where the adhesive layer22is not formed. The auxiliary sheet14adheres to the main sheet body21before the thermally conductive sheet12is used for thermal conduction from the heat emitting body to the heat discharging body, and is peeled off from the main sheet body21after the thermally conductive sheet12is attached to, for example, a heat emitting body. The auxiliary sheet14makes it easy to handle the laminated body11by reinforcing the thin and flexible main sheet body21when it adheres to the main sheet body21, and makes it much easier to attach the thermally conductive sheet12to a heat emitting body by serving as an auxiliary means for attaching the thermally conductive sheet12to a heat emitting body when the thermally conductive sheet12is attached to, for example, a heat emitting body.

The auxiliary sheet14is formed of a resin film where an adhesive is applied on the outer surfaces, for example. The auxiliary sheet14has an appropriate rigidity, in order to make it easier to handle the laminated body11, and in order to prevent attachment of the thermally conductive sheet12to a heat emitting body from becoming difficult due to bending of the auxiliary sheet14when the thermally conductive sheet12is attached to, for example, a heat emitting body. Preferably the above described resin film is formed of a hard resin. The term “hard resin” is defined in ASTM-D883, which is an American Society for Testing Materials standard. The elastic modulus in bending of the hard resin as defined in JIS K 7171 (ISO 178) is 7000 kg/cm2or higher in a stationary state. Specific examples of the hard resin include polyester based resins, polyacrylate based resins, polyamide resins and polyimide resins. Specific examples of polyester based resins include polypropylene resins, PET and polybutylene terephthalate resins. Specific examples of polyacrylate based resins include polycarbonate resins and polymethyl methacrylate resins. The position of the thermally conductive sheet12on the heat emitting body is easily perceivable with the eye through the auxiliary sheet14from the outside when the thermally conductive sheet12is attached to a heat emitting body, for example, and therefore, the auxiliary sheet14is preferably transparent. For these reasons, polyester based resins are preferable, from among the specific examples of the above described hard resin, and PET is more preferable.

The thickness of the auxiliary sheet14is, for example, 50 μm to 300 μm. The auxiliary sheet14according to the present embodiment is formed throughout the entirety of the main sheet body21, in order to protect the entirety of the outer surface21aof the main sheet body21.

The peripheral portion of the auxiliary sheet14is provided with a protruding portion14awhich is exposed to the outside from the main sheet body21. This protruding portion14acan be pinched by the user of the thermally conductive sheet12so that attachment of the thermally conductive sheet12to, for example, a heat emitting body is made possible without the thin and flexible thermally conductive sheet12being pinched, and thus, makes attachment of the thermally conductive sheet12easier. Furthermore, the protruding portion14amakes it easy to peel off the auxiliary sheet14. The protruding portion14ais formed of a portion of a resin film which forms the auxiliary sheet14and extends outward. The above described adhesive is not applied on the outer surface in the portion of the resin film which extends outward and forms the protruding portion14ain order to make it easy to pinch and release the protruding portion14a.The protruding portion14ais formed in a portion that corresponds to the adhesive layer22in the peripheral portion of the auxiliary sheet14.

The adhesiveness between the main sheet body21and the adhesive layer22is preferably set high in comparison with the adhesiveness between the auxiliary sheet14and the main sheet body21. In the case where the adhesiveness between the main sheet body21and the adhesive layer22is low in comparison with the adhesiveness between the auxiliary sheet14and the main sheet body21, the main sheet body21and the adhesive layer22may separate from each other when the main sheet body21is peeled off together with the auxiliary sheet14, when the auxiliary sheet14is peeled off after the thermally conductive sheet12is attached to, for example, a heat emitting body. In addition, it is preferable for the adhesiveness between the auxiliary sheet14and the main sheet body21to be high to such an extent that the thermally conductive sheet12does not peel from the auxiliary sheet14due to its own weight when the thermally conductive sheet is handled holding the protruding portion14ain order to attach the thermally conductive sheet12to, for example, a heat emitting body.

The carrier sheet15is in quadrilateral plate form and adheres to the auxiliary sheet14. The carrier sheet15is larger than the thermally conductive sheet12, the protective sheet13and the auxiliary sheet14in the outer shape. The carrier sheet15works as a support for the auxiliary sheet14and the thermally conductive sheet12when the laminated body11is manufactured, for example. The carrier sheet15makes it easier to handle the laminated body11by reinforcing the thin and flexible main sheet body21together with the auxiliary sheet14when the laminated body11is handled. The state of the thermally conductive sheet12and the auxiliary sheet14is easy to perceive by the eye through the carrier sheet15from the outside, and therefore, the carrier sheet15is preferably transparent. For these reasons, polyester based resins are preferable, from among the specific examples of the above described hard resin, and PET is more preferable.

The carrier sheet15is formed of a resin film on the surface of which an adhesive is applied, for example, in the same manner as the auxiliary sheet14. The carrier sheet15has an appropriate rigidity, in order to make it easy to handle the laminated body11, and the above described resin sheet is preferably formed of a hard resin, as described above. The thickness of the carrier sheet15is, for example, 50 μm to 300 μm.

The coating sheet16is in quadrilateral plate form, and larger than the thermally conductive sheet12, the protective sheet13and the auxiliary sheet14in the outer shape, and at the same time, approximately the same as the carrier sheet15in the outer shape. The coating sheet16reinforces the thin and flexible main sheet body21together with the auxiliary sheet14and the carrier sheet15so as to make it easier to handle the laminated body11. Furthermore, the coating sheet16protects the thermally conductive sheet12, the protective sheet13and the auxiliary sheet14together with the carrier sheet15, so as to prevent foreign substances, for example, from adhering to these, and prevent the sheets from being scratched.

The coating sheet16and the carrier sheet15make contact with each other throughout the entirety of the peripheral portion. At this time, the carrier sheet15adheres to the coating sheet16due to the adhesiveness of the carrier sheet15. When the thermally conductive sheet12is used, the coating sheet16is peeled off from the carrier sheet15. In the case where the coating sheet16is adhesive, it becomes difficult to peel the coating sheet16off from the carrier sheet15, due to the adhesiveness of the carrier sheet15, for example. Therefore, the coating sheet16is formed of a resin film on the outer surface of which a mold releasing agent is applied, for example.

The resin film which forms the coating sheet16is preferably made of a flexible resin material so that the coating sheet16is easy to peel off from the carrier sheet15. Specific examples of the flexible resin material include polyethylene resins (PE), and PE is referred to as semi-hard resin. This semi-hard resin is defined in ASTM-D883, and the elastic modulus in bending of the semi-hard resin as defined in JIS K 7171 (ISO 178) is 7000 kg/cm2or lower in a stationary state. The coating sheet16is easy to peel off from the carrier sheet15, and therefore, preferably thinner than the carrier sheet15. The state of the protective sheet13and the like are easy to perceive from the outside, and therefore, the coating sheet16is preferably transparent.

The laminated body11is manufactured when an auxiliary sheet14, a thermally conductive sheet12, a protective sheet13and a coating sheet16are laminated on a carrier sheet15in this order after the thermally conductive sheet12is formed. Specifically, the respective members which form the auxiliary sheet14, the thermally conductive sheet12and the protective sheet13are laminated on one carrier sheet15, for example, and after that, the respective members are cut to a predetermined size and unnecessary portions are removed, and thus, a number of auxiliary sheets14, thermally conductive sheets12and protective sheets13, are simultaneously formed on one carrier sheet15. Next, the carrier sheet15is cut into pieces for each thermally conductive sheet12, and after that, a coating sheet16is laminated on top of the cut carrier sheet15.

The thermally conductive sheet12is manufactured through a preparation step of preparing a composition, an orientation step of orienting a filler in fiber form32a,a formation step of forming a main sheet body21, an exposure step of exposing the filler in fiber form32a,and a laminating step of laminating an adhesive layer22on top of the main sheet body21.

In the preparation step, the above described respective components are mixed in appropriate amounts so that a composition is prepared. In the orientation step, a mold, for example, is filled with the composition, and after that, the filler in fiber form32ais oriented in one direction. As the method for orienting the filler in fiber form32ain one direction, a method for applying a magnetic field to the composition using a magnetic field generating apparatus and a method for applying vibration to the composition using a vibration apparatus can be used, and a method for applying both a magnetic field and vibration to the composition is preferable, because the filler in fiber form32ais easy to orient. At this time, the magnetic field and vibration are applied to the filler in fiber form32athrough the composition.

In the formation step, a polymer matrix31is hardened or solidified within a mold in such a state that the orientation of the filler in fiber form32ais maintained, and thus, a main sheet body21in a predetermined form is prepared. As shown inFIG. 4, the filler in fiber form32ain the main sheet body21is not exposed from the outer surface21aof the main sheet body21after the formation step. In the exposure step, a blade in mesh form, for example, is pressed against the outer surface21aof the main sheet body21, and after that, slid over the outer surface21a,and thus, the polymer matrix31is removed from the outer surface21a,so that the filler in fiber form32ais exposed from the outer surface21a.In the laminating step, the adhesive sheet22cwhich forms the adhesive layer22is pasted on the outer surface21aof the main sheet body21in accordance with a well known method, and thus, the adhesive layer22is laminated on top of the outer surface21aof the main sheet body21.

When the thermally conductive sheet12is attached to a heat emitting body and a heat discharging body, as shown inFIG. 5, the carrier sheet and the coating sheet are peeled off, so that the protective sheet13and the auxiliary sheet14are exposed. Specifically, the coating sheet is peeled off from the carrier sheet, and after that, the protruding portion14aof the auxiliary sheet14, for example, is pinched and the auxiliary sheet14peeled off from the carrier sheet. Next, both side of the cutting line23, which corresponds to the vicinity of the center portion of the adhesive layer22, for example, is pinched on the protective sheet13, and after that, as shown inFIG. 6, the protective sheet13is cut toward the adhesive layer22along the cutting line23. Then, the protective sheet13is cut into two pieces along the cutting line23, and after that, each piece is peeled off toward the end of the adhesive layer22so that the adhesive layer22is exposed.

Next, as shown inFIG. 7A, a thermally conductive sheet12is mounted on a heat emitting body42(for example an electronic device) provided on a substrate41, for example. The lower portion of the heat emitting body42is coated with an electrically insulating layer43, and terminals44for connecting the heat emitting body42to an electrical circuit, not shown, on the substrate41are provided between the substrate41and the electrically insulating layer43. When the thermally conductive sheet12is mounted on the heat emitting body42, the above described adhesive layer22is made to face the heat emitting body42while the thermally conductive sheet12is positioned. Next, the portion of the auxiliary sheet14which corresponds to the adhesive layer22is pressed toward the heat emitting body42with the fingertips, for example. At this time, the adhesive layer22is exposed, and therefore pasted to the heat emitting body42due to the adhesiveness, so that the thermally conductive sheet12can be prevented from displacement. Furthermore, the main sheet body21, of which the thickness is, for example, 0.5 mm or less, makes contact with the heat emitting body42, due to its flexibility.

Subsequently, as shown inFIG. 7B, the protruding portion14aof the auxiliary sheet14is pinched, and after that, the auxiliary sheet14is peeled off from the main sheet body21toward the side opposite to the portion of the heat emitting body42in which the adhesive layer22is pasted. At this time, the outer surface21aof the main sheet body21is exposed. Thus, as shown inFIG. 8A, the heat discharging body45is mounted on the thermally conductive sheet12, and after that, a load is applied from the heat discharging body45to the heat emitting body42so that the thermally conductive sheet12makes close contact with the heat emitting body42and the heat discharging body45, and thus, the thermally conductive sheet12is sandwiched between the heat emitting body42and the heat discharging body45. At this time, as shown inFIG. 8B, an end portion of the filler in fiber form32athat is exposed from the outer surface21aof the main sheet body21is pressed into the main sheet body21as a result of the above described load. Furthermore, the polymer matrix31soaks out from between the exposed filler in fiber form32aas a result of the above described load. Therefore, the above described exposed filler in fiber form32ais relatively submerged in the polymer matrix31inside the main sheet body21. As a result, the adhesiveness of the main sheet body21increases, and the main sheet body21makes close contact with the heat emitting body42and the heat discharging body45without any spaces being created between the main sheet body21and the heat emitting body42, or between the main sheet body21and the heat discharging body45. The value of the load applied to the heat discharging body45is, for example, 4.9 N.

The above described embodiment has the following advantages.

The laminated body11according to the present embodiment comprises a protective sheet13to which an adhesive layer22adheres, in addition to a thermally conductive sheet12. The outer shape of the protective sheet13is larger than the outer shape of the adhesive layer22. Therefore, the protective sheet13can prevent foreign substances from adhering to the adhesive layer22and prevent the adhesive layer22from being scratched, and thus, can easily protect the entirety of the adhesive layer22.

The protective sheet13has the cutting line23, and when the protective sheet13is peeled off, the protective sheet13is cut into two pieces along the cutting line23, and after that, each cut piece is peeled off toward the end of the adhesive layer22. As a result, only the protective sheet13can be easily peeled off without the adhesive layer22being peeled off together with the protective sheet13when the protective sheet13is peeled off. Furthermore, the protective sheet13is easy to peel off, and thus, the thin and flexible main sheet body21can be prevented from breaking and being scratched when the protective sheet13is peeled off.

In the case where no cutting line23is drawn on the protective sheet13, the protective sheet13is usually peeled off from one end of the adhesive layer22toward the other end when the protective sheet13is peeled off. The ends of the adhesive layer22are easy to peel off from the main sheet body21in comparison with the center portion. Therefore, when a protective sheet13having no cutting line23is peeled off, the adhesive layer22is easy to peel off together with the protective sheet13. In contrast, in the present embodiment, the protective sheet13can be peeled off from the center portion of the adhesive layer22to the ends, and thus, the adhesive layer22can easily be prevented from peeling off.

The coefficient of static friction of the main sheet body21and the adhesiveness of the adhesive layer22are set as described above, and at the same time, the adhesive layer22is formed only in a portion of the main sheet body21. Therefore, the thermally conductive sheet12according to the present embodiment can have excellent thermal conductivity without being affected by the adhesive layer22, of which the thermal conductivity is low in comparison with the main sheet body21, and at the same time, is easy to handle, due to the low adhesiveness of the main sheet body21. Therefore, the thermally conductive sheet12can have excellent thermal conductivity and be easy to handle.

The coefficient of static friction of the main sheet body21is set to 0.3 or lower, and thus, the auxiliary sheet14is easy to peel off.

The adhesiveness between the main sheet body21and the adhesive layer22is set high in comparison with the adhesiveness between the protective sheet13and the adhesive layer22, and thus, the adhesive layer22can easily be prevented from peeling off from the main sheet body21when the protective sheet13is peeled off.

Each cutting line23extends toward the adhesive layer22from the end portion which faces the end portion of the peripheral portion of the protective sheet13that corresponds to the adhesive layer22. Therefore, the protective sheet13can easily be cut along the cutting line23.

The laminated body11comprises an auxiliary sheet14, and the auxiliary sheet14is provided with a protruding portion14a.Thus, when the auxiliary sheet14is peeled off, the protruding portion14ais pinched. Therefore, when the auxiliary sheet14is peeled off from the carrier sheet15, the auxiliary sheet14can easily be peeled off, by pinching the protruding portion14a.In addition, it is not necessary to pinch the portion that corresponds to the main sheet body21when the auxiliary sheet14is peeled off from the adhesive layer22, and the thin and flexible main sheet body21can be prevented from being scratched when the protruding portion is held in this manner. Furthermore, the auxiliary sheet14can easily be peeled off by pinching the protruding portion14a.In addition, the auxiliary sheet14can easily prevent the thin and flexible main sheet body21from bending due to the rigidity and the adhesiveness of the auxiliary sheet14when the thermally conductive sheet12is attached to, for example, a heat emitting body42.

The adhesiveness between the main sheet body21and the adhesive layer22is set high in comparison with the adhesiveness between the auxiliary sheet14and the main sheet body21, and thus, the main sheet body21and the adhesive layer22can easily be prevented from separating from each other when the auxiliary sheet14is peeled off.

The protruding portion14ais formed in a portion corresponding to the adhesive layer22. Therefore, the auxiliary sheet14can be peeled off in the portion where the thermally conductive sheet12is pasted to the heat emitting body42, and thus, the thin and flexible main sheet body21can be prevented from bending and breaking when the auxiliary sheet14is peeled off, so that the auxiliary sheet14can easily be peeled off.

The laminated body11comprises a carrier sheet15and a coating sheet16, and the carrier sheet15adheres to the coating sheet16throughout the entirety of the peripheral portion. Therefore, the carrier sheet15and the coating sheet16seal the thermally conductive sheet12, the protective sheet13and the auxiliary sheet14, which are located inside the carrier sheet15and the coating sheet16, so as to prevent foreign substances from becoming attached. Furthermore, the carrier sheet15adheres to the coating sheet16, and thus, the outer surface having adhesiveness in the peripheral portion of the carrier sheet15is coated with the coating sheet16. Therefore, foreign substances can be prevented from becoming attached in the peripheral portion of the carrier sheet15. Furthermore, the laminated body11can be rolled up, and thus, the laminated body11can be made easier to handle.

As shown inFIG. 9A, a perforated or half cut cutting line14bis drawn on the auxiliary sheet14along the adhesive layer22so that the auxiliary sheet14is formed so that it can be cut along the cutting line14b.The portion of the auxiliary sheet14where the cutting line14bis drawn is not particularly limited, and the line may be drawn in the center portion of the auxiliary sheet14, for example. In this case, as shown inFIG. 9B, when the thermally conductive sheet12is attached to the heat emitting body42, for example, first the protruding portion14ais held and peeled off from the carrier sheet15, and thus, the auxiliary sheet14is cut into two pieces along the cutting line14b,and after that, only the cut piece having a protruding portion14ais peeled off from the carrier sheet15. Next, as shown inFIG. 9C, the piece of auxiliary sheet14is peeled off, after the thermally conductive sheet12is attached to the heat emitting body42, for example.

In this configuration, when the auxiliary sheet14is peeled off from the thermally conductive sheet12that is attached to the heat emitting body42, the outer shape of the auxiliary sheet14to be peeled off is smaller than the outer shape of the auxiliary sheet14according to the present embodiment, and therefore, the auxiliary sheet14can be easily peeled off. In the case of this configuration, the protruding portion14ais preferably formed in a portion corresponding to the adhesive layer22. In the case where the protruding portion14ais formed in a portion which does not correspond to the adhesive layer22, when a piece of the auxiliary sheet14is peeled off from the carrier sheet15, the piece of auxiliary sheet14is not located in a portion corresponding to the adhesive layer22. Therefore, when the thermally conductive sheet12is attached to the heat emitting body42, for example, the portion of the main sheet body21having the adhesive layer22easily bends, and there is a risk that attachment of the thermally conductive sheet12may be less easy.

A number of adhesive layers22may be formed on the main sheet body21as shown inFIG. 10A, a number of adhesive layers22in circular form may be formed in the four corners of the main sheet body21as shown inFIG. 10B, or an adhesive layer22in elliptical form may be formed in the main sheet body21as shown inFIG. 10C. Furthermore, the adhesive layer22may be formed in multi-dot form throughout the entirety of the main sheet body21. In the case where the adhesive layer22is in multi-dot form, a number of pieces of adhesive layer22in circular form with a diameter of, for example, 1.5 mm or less, are formed with intervals of 5 mm to 10 mm. In the case where the intervals between the respective pieces of adhesive layer22are 5 mm or less, too much adhesive layer22is formed throughout the main sheet body21, and therefore, the thermal conductivity of the thermally conductive sheet12may lower, due to the adhesive layer22. When the intervals between the respective pieces of adhesive layer22exceed10mm, there is too little adhesive layer22, and therefore, attachment of the thermally conductive sheet12may be less easy.

The main sheet body21may be formed of a thermally conductive member, for example a graphite sheet. In this case, the coefficient of static friction of the main sheet body21is 1.0 or lower, due to the graphite. Furthermore, the adhesive layer22has a high viscosity in comparison with the main sheet body21. In addition, an end portion of the filler in fiber form32amay not be exposed from the outer surface21aof the main sheet body21, or the filler in fiber form32amay not be oriented.

The adhesive layer22may be formed by applying an acryl based, silicone based, urethane based, vinyl based or synthetic rubber based adhesive or bonding agent to the main sheet body21. Though bonding agents have adhesiveness immediately after being applied to the main sheet body21, the adhesiveness is lost as time elapses. In contrast, the adhesive layer22maintains its adhesiveness, so that the thermally conductive sheet12can be used repeatedly, and therefore, it is preferable for the material of the adhesive layer22to be an adhesive.

The cutting line23may extend toward the adhesive layer22from the peripheral portion of the protective sheet13, and may be drawn so as to extend in curved form, so as to extend from a portion which does not face the portion corresponding to the adhesive layer22, or so as to diagonally cross the adhesive layer22. Furthermore, only one cutting line23may be drawn. In addition, the cutting line23may have a form other than perforated, for example half cut form.

The coating sheet16may be formed of a resin film the surface on which an emboss process has been carried out so that unevenness is created. In this configuration also, the adhesiveness of the coating sheet16can be lowered.

At least one of the auxiliary sheet14, the carrier sheet15and the coating sheet16may be omitted. In the case where the carrier sheet15and the coating sheet16are omitted, for example, the protruding portion14aof the auxiliary sheet14is held, and thus, the laminated body11is easy to handle.

The protruding portion14amay be formed in a portion of the auxiliary sheet14other than a portion corresponding to the adhesive layer22.

Though the protective sheet13and the auxiliary sheet14according to the present embodiment are of the same size as the main sheet body21in the outer shape, they may be smaller than the main sheet body21in the outer shape, or larger than the main sheet body21in the outer shape.

The thermally conductive sheet12may be sandwiched between the heat emitting body42and the heat discharging body45after being attached to the heat discharging body45instead of the heat emitting body42.

The above embodiment is described more specifically by way of Examples and Comparative Examples below.

In Example 1-a, carbon fibers, which are a filler in fiber form32a,and alumina (aluminum oxide) in spherical form, which is a filler in particle form32b,were mixed into addition type liquid silicone (hereinafter referred to as liquid silicone gel), which is a polymer matrix31, so that a composition was prepared in the preparation step. The liquid silicone gel becomes a gel after hardening. The amount of the respective components in the mixture is shown in Table 1. The unit for the amount of the respective components in the mixture is mass ratio. The viscosity of the liquid silicone gel at 25° C. was 400 mPa·s, and the specific gravity of the liquid silicone gel was 1.0. The average fiber diameter of the carbon fibers was 10 μm, and the average fiber length of the carbon fibers was 160 μm. The average particle diameter of the alumina in spherical form was 3.2 μm. Next, the composition was stirred until the carbon fibers and the alumina in spherical form were homogeneously dispersed, and after that, the composition was degassed.

Subsequently, the viscosity of the composition at 25° C. was measured using a rotational viscometer, and after that, a mold was filled with the composition in the orientation step. The results of measurement for the viscosity are shown in Table 1. Next, a magnetic field having a magnetic flux density of 100,000 Gauss was applied to the composition using a superconducting magnet, and at the same time, vibration having a frequency of 3.0 Hz and an amplitude of 10 mm was applied to the composition through the mold using compressed air, so that the carbon fibers were oriented in the direction of the thickness of the main sheet body21.

Next, the composition was heated for 90 minutes at 120° C., and thus, the liquid silicone gel was hardened, so that a main sheet body21was obtained in the formation step. Then, the hardened silicone having a thickness of 5 μm was removed from a pair of outer surfaces21aof the main sheet body21using a rotational cutter, and thus, the carbon fiber was exposed. The thickness of the main sheet body21was 0.3 mm after the exposure step. When the outer surface21aof the main sheet body21was observed using through an electron microscope after the exposure step, it could be confirmed that the carbon fibers were exposed. The thus obtained main sheet body21was cut into pieces in square plate form (sides: 40 mm).

Subsequently, as shown inFIG. 11A, a silicone based adhesive is applied on the outer surface21ain the peripheral portion of the main sheet body21in the laminating step, and thus, an adhesive layer22in square form (thickness: 30 μm, sides: 5 mm) was prepared, so that a thermally conductive sheet12was obtained.

Next, an auxiliary sheet14, a thermally conductive sheet12, a protective sheet13and a coating sheet16were laminated on a carrier sheet15in this order, and thus, a laminated body11was obtained. The protective sheet13was formed of a PET film, the thickness of the protective sheet13was 25 μm, and the length of the sides was 40 mm. The auxiliary sheet14was formed of a PET film on the surface of which an acryl based adhesive was applied, and the thickness of the auxiliary sheet14was 90 μm, the length of the longitudinal side was 40 mm and the length of the lateral side was 50 mm. The carrier sheet15was formed of a PET film on the surface of which an acryl based adhesive was applied, the thickness of the carrier sheet15was 85 μm, and the length of the sides was 60 mm. The coating sheet16was formed of a PET film, the thickness of the coating sheet16was 40 μm, and the length of the sides was 60 mm.

As shown inFIG. 11Band Table 2, a laminated body11was obtained in the same manner as in Example 1-a, except that the length of the lateral sides of the adhesive layer22was changed to 30 mm so that the adhesive layer22became of a rectangular form.

As shown inFIG. 1C, a laminated body11was obtained in the same manner as in Example 1-a, except that adhesive layers22(thickness: 50 μm, sides: 10 mm) was formed in the four corners of the main sheet body21.

As shown inFIG. 1D, a laminated body11was obtained in the same manner as in Example 1-a, except that an adhesive layer22was formed by pasting an adhesive tape (thickness: 20 mm, width: 2 mm, length: 20 mm) where an acryl silicone based adhesive was applied to a PET film on the outer surface21ain the peripheral portion of the main sheet body21.

As shown inFIG. 11Eand Table 2, a laminated body11was obtained in the same manner as in Example 1-c, except that the length of the sides of the adhesive layer22was changed to 12 mm.

As shown inFIG. 11Fand Table 2, a laminated body11was obtained in the same manner as in Example 1-a, except that a number of adhesive layers22in circular form having a diameter of 1.0 mm were formed in multi-dot form with intervals of 5 mm throughout the entirety of the main sheet body21. “Φ” in Table 2 indicates the diameter of the adhesive layer22.

As shown in Table 2, a laminated body11was obtained in the same manner as in Example 1-d, except that the thickness of the adhesive layer22was changed to 70 μm.

EXAMPLES 2-A TO 2-G

In Examples 2-a to 2-g, PBO carbon fibers were used as the filler in fiber form32a,and the amount of the respective components in the mixture was changed as shown in Table 1, and furthermore, the silicone was removed through polishing using a metal mesh in the exposure step. Except for this, the main sheet body21was obtained in the same manner as in Examples 1-a to 1-g. When the outer surface21aof the main sheet body21was observed through an electron microscope after the exposure step, it was confirmed that the PBO carbon fibers were exposed. The thus obtained main sheet body21was cut into pieces in square plate form (length of sides: 40 mm). Then, as shown in Table 3, an adhesive layer22was formed and the respective sheets were laminated in the same manner as in Examples 1-a to 1-g, and thus, a laminated body11was obtained.

EXAMPLES 3-A TO 3-G

In Examples 3-a to 3-g, A main sheet body21was obtained using a graphite sheet (PGS (registered trademark) made by Panasonic Electronic Devices Co., Ltd.) having a thickness of 0.1 mm and a thermal conductivity of 15 W/m·K in the direction of the thickness. Then, as shown in Table 4, an adhesive layer22was formed and the respective sheets were laminated in the same manner as in Examples 1-a to 1-g, and thus, a laminated body11was obtained.

The alphabetic letters in Examples 2-a to 2-g and Examples 3-a to 3-g indicate the correspondence to Examples 1-a to 1-g. In Example 2-a, for example, an adhesive layer22was formed in the same manner as in Examples 1-a, and in Example 2-b, an adhesive layer22was formed in the same manner as in Example 1-b. Likewise, in Example 3-a, an adhesive layer22was formed in the same manner as in Example 1-a, and in Example 3-b, an adhesive layer22was formed in the same manner as in Example 1-b.

COMPARATIVE EXAMPLES 1 TO 3

In Comparative Example 1, a laminated body was obtained in the same manner as in Example 1-a, except that there was no adhesive layer22. In Comparative Example 2, a laminated body was obtained in the same manner as in Example 2-a, except that there was no adhesive layer22. In Comparative Example 3, a laminated body was obtained in the same manner as in Example 3-a, except that there was no adhesive layer22.

Thus, the main sheet body and the thermally conductive sheet in each example were measured and evaluated in terms of the following respective properties. The results are shown in Tables 1 to 4. The numeral values in the column “ratio (%) (relative to outer surface)” in Tables 2 to 4 indicate the ratio of the area occupied by the adhesive layer22to the entire-area of the outer surface21aon which the adhesive layer22is attached in the main sheet body21.

Ease of Handling

The ease of handling of the main sheet body21in each example and comparative example was evaluated on the basis of the adhesiveness. In the column “ease of handling” in Table 1, “o” indicates that the viscosity of the main sheet body21was low and moderate, and it was easy to handle the main sheet body21.

Thermal Conductivity

A test piece in disc form (diameter: 10 mm, thickness: 0.3 mm) was obtained from the main sheet body21in each example and comparative example, and after that, the thermal conductivity of the test piece was measured in accordance with the laser flash method.

Value of Thermal Resistance

The thermally conductive sheet12was taken out from the laminated body11, and after that, as shown inFIG. 12, the thermally conductive sheet12in each example and comparative example and a heat discharging body45made of a metal were mounted on the heat emitting body42formed on a substrate41in this order, and a weight46of 10 kg was mounted on the heat discharging body45, so that a load of 6.1×104Pa was applied to the thermally conductive sheet12. Then, the heat emitting body42was left for 10 minutes in such a state as to be emitting heat, and after that, the temperature T1on the outer surface on the heat emitting body42of the thermally conductive sheet12and the temperature T2on the outer surface on the heat discharging body45were measured using a measuring apparatus47. Then, the value of the thermal resistance of the thermally conductive sheet12was calculated using the following formula (1). Though the heat emitting body42is usually an electronic component, such as a CPU, a heater having an amount of heat emission of 100 W was used as the heat emitting body42in the present test, in order to simplify and increase the speed of performance evaluation for the thermally conductive sheet12. The above described value of the load indicates the magnitude of the load usually applied to the thermally conductive sheet12when the thermally conductive sheet12is applied to an electronic component.
Value of thermal resistance (° C./W)=(T1(° C.)−T2(° C.))/amount of heat emission   (1)
Positioning

In the above described value of thermal resistance, the ease of positioning of the thermally conductive sheet12when the thermally conductive sheet12was attached to the heat emitting body42was evaluated. In the column “positioning” in Tables 2 to 4, “o” indicates that the thermally conductive sheet12did not shift in position even when the heat emitting body42to which the thermally conductive sheet12was attached was inclined diagonally. “x” indicates that the thermally conductive sheet12slipped down or the like and the thermally conductive sheet12shifted in position when the heat emitting body42to which the thermally conductive sheet12was attached was inclined diagonally.

Ease of Transfer

The ease with which the thermally conductive sheet12can be taken out from the laminated body11and transferred (pasted) onto a heat emitting body42, for example, was evaluated. Specifically, the probability of the thermally conductive sheet12being properly transferred onto the heat emitting body42without being broken or transferred in a slack or bent state was examined. At this time, examination was conducted for auxiliary sheets14of various sizes. The numeral values within parentheses in the column “ease of transfer” in Tables 2 to 4 indicate the ratio of the area in the portion of the main sheet body21which faces the auxiliary sheet14relative to the entire area of the outer surface21a.“oo” in the column “ease of transfer” in Tables 2 to 4 indicates that the thermally conductive sheet12could be properly transferred with a probability of 95% or higher. “o” indicates that the thermally conductive sheet12could be properly transferred with a probability of 70% or higher and less than 95%. “Δ” indicate that the thermally conductive sheet12could be properly transferred with a probability of 50% or higher and less than 70%. “x” indicates that the thermally conductive sheet12could be properly transferred with a probability of less than 50%. In the case where the outer shape of the auxiliary sheet14was smaller than the outer shape of the main sheet body21, the protruding portion14awas formed in a portion corresponding to the adhesive layer22.

As shown in Table 1, excellent results of evaluation were obtained for the respective properties of the main sheet body21in each example. Therefore, the main sheet body21in each example had excellent thermal conductivity and was easy to handle. As shown in Tables 2 to 4, excellent results of evaluation were obtained for the respective properties of the thermally conductive sheet12in each example. Therefore, the thermally conductive sheet12in each example could be easily attached to the heat emitting body42without any reduction in the thermal conductivity due to the adhesive layer22, and without any shift in position. As described above, the thermally conductive sheet12in each example had excellent thermal conductivity and was easy to attach. In addition, the laminated body11in each example had excellent handling ability, and the laminated body11was easy to handle. In addition, it can be seen that in the case where the outer shape of the auxiliary sheet14was smaller than the outer shape of the main sheet body21, the thermally conductive sheet12could be easily transferred using the protruding portion14a.

Meanwhile, in Comparative Examples 1 to 3, the results of evaluation for the positioning and ease of transfer were inferior to those for the examples. Therefore, the ease of attachment of the thermally conductive sheet in each comparative example was inferior to in the examples.

In Example 4, a main sheet body21(thickness: 0.3 mm) was obtained in the same manner as in Example 1-a.

In Example 5, a main sheet body21(thickness: 0.3 mm) was obtained in the same manner as in Example 2-a.

In Example 6, a main sheet body21(thickness: 0.13 mm) was obtained in the same manner as in Example 3-a.

In Example 7, a main sheet body21(thickness: 0.3 mm) was obtained in the same manner as in Example 1-a, except that there was no filler in fiber form32a,aluminum hydroxide and alumina in spherical form were used as the filler in particle form32b,no magnetic field or vibration was applied in the orientation step, and the exposure step was omitted. The amount of the respective components in the mixture is shown in Table 5.

In Example 8, a main sheet body21was obtained in the same manner as in Example 1-a, except that the exposure step was omitted.

COMPARATIVE EXAMPLE 4

In Comparative Example 4, a main sheet body (thickness: 0.3 mm) was obtained in the same manner as in Example 1-a, except that no filler in fiber form32awas used, and aluminum hydroxide and alumina in spherical form were used as a filler in particle form32b,no magnetic field or vibration was applied in the orientation step, and the exposure step was omitted. The type and amount of the respective components in the mixture are shown in Table 5. One outer surface of the main sheet body in Comparative Example 4 had adhesiveness, and the other outer surface did not have adhesiveness.

Thus, the respective main sheet bodies in Examples 4 to 8 and Comparative Example 4 were measured and evaluated in terms of the following respective properties. The results are shown in Table 6. “Adhesive surface” in the column “Comparative Example 4” in Table 6 shows the results for the outer surface having adhesiveness of the main sheet body in Comparative Example 4, and “non-adhesive surface” shows the results for the outer surface having no adhesiveness of the main sheet body in Comparative Example 4.

Coefficient of Static Friction

As shown inFIG. 13, a test piece49made of the main sheet body in each example and comparative example was placed on a horizontal base48, and after that, a sliding piece50and a weight51of 120 g (columnar form, diameter: 28 mm, height: 25 mm) were placed on the test piece49in this order. Next, one end of the tape52for pulling was pasted to the weight51, and the other end of the tape52was secured to a push-pull gauge53(CPU gauge M-9500, made by Aikoh Engineering Co., Ltd.). Subsequently, as shown by the arrow inFIG. 13, the push-pull gauge53was pulled at a speed of 100 mm/min in the direction parallel to the outer surface of the test piece49. Next, the force of static friction Fs (N) between the test piece49and the sliding piece50was measured when the push-pull gauge53was pulled.

Then, the coefficient of static friction was calculated using the following formula (2). Here, the force of static friction FS was measured and the coefficient of static friction was calculated five times for the main sheet body in each example and comparative example, and the average value of these values of the coefficient of static friction was taken to be the coefficient of static friction of the main sheet body. In addition, two types of material: a PET film (Lumirror S10, made by Toray Industries, Inc., 75 μm) and an aluminum foil tape (Scotch Brand Tape 433HD, made by 3M Corporation) were used for the sliding piece50. The aluminum foil tape was placed on the test piece49in such a manner that the aluminum foil surface of the aluminum foil tape faced the test piece49. In addition, measurement and calculation were carried out on both the outer surface having adhesiveness and the outer surface having no adhesiveness of the main sheet body in Comparative Example 4.
Coefficient of static friction=Fs(N)/Fp(N)   (2)

In the above formula (2), Fp indicates the force of vertical resistance caused by the mass of the sliding piece50, and the value of Fp can be represented by 0.12 kg (mass of weight51)×9.8 m/s2(gravitational acceleration)=0.1176 N.

The adhesiveness of the main sheet body in each example and comparative example was measured in accordance with JIS Z 0237. Specifically, as shown inFIG. 14, a film54was secured on the surface of the horizontal base48, and after that, the test piece49of each example and comparative example was mounted on this. Then, one end of the test piece49was attached to the load cell55of a tension tester. Then, the load was measured when the test piece49was pulled and peeled along a line perpendicular to the horizontal base48at a speed of 300 mm/min. Here, the load was measured five times for the test piece49of each example and comparative example, and the average value of these measured values was taken to be the adhesiveness of the main sheet body. Two types of material: a PET film (Lumirror S10, made by Toray Industries Co., Ltd., 75 μm) and an aluminum foil tape (Scotch Brand Tape 433 HD, made by 3M Co., Ltd.) were used for the film54. The aluminum foil tape was secured to the horizontal base48in such a manner that the aluminum foil surface of the aluminum foil tape faced the test piece49. In addition, the outer surface having adhesiveness and the outer surface having no adhesiveness were both measured for the test piece49in Comparative Example 4. The column “adhesiveness (relative to aluminum) (N/25 mm)” in Table 6 shows the results of measurement for the adhesiveness in the case where an aluminum foil tape was used, and the column “adhesiveness (relative to PET) (N/25 mm)” shows the results of measurement for the adhesiveness in the case where a PET film was used. In these columns, “−” shows that the adhesiveness was too small to measure in accordance with the above described method.

TABLE 6Comparative example 4ExamplesAdhesiveNon-adhesive45678surfacesurfaceCoefficient of static friction0.1340.1290.1720.4980.5562.2621.770(relative to aluminum)Coefficient of static friction0.1700.1660.1960.9470.9732.9172.167(relative to PET)Adhesiveness———0.230.331.130.60(relative to aluminum)(N/25 mm)Adhesiveness———0.410.531.890.97(relative to PET)(N/25 mm)

As shown in Table 6, the coefficient of static friction of the main sheet body21in Examples 4 to 6 was 1.0 or lower, and thus, the adhesiveness was too small to measure in accordance with the above described method. Therefore, the main sheet body21in Examples 4 to 6 was easy to handle. The coefficient of static friction of the main sheet body21in Examples 7 and 8 was also 1.0 or lower. Furthermore, the main sheet body21in Examples 7 and 8 had such adhesiveness as to be measurable in accordance with the above described method, and was sufficiently durable for practical use, though it was slightly difficult to handle in comparison with the main sheet body21in Examples 4 to 6.

Meanwhile, the coefficient of static friction on the respective outer surfaces of the main sheet body in Comparative Example 4 exceeded 1.0, and therefore, had high adhesiveness in comparison with the respective examples. Therefore, it was difficult to handle the main sheet body in Comparative Example 4 in comparison with the respective examples.

In Example 9, a laminated body11was obtained in the same manner as in Example 1-b. Then, the laminated body11in Example 9 was measured in terms of the following properties.

The adhesiveness of each sheet that formed the laminated body11, that is to say, the load required to peel off each sheet, was measured using a tension tester in compliance with JIS K 6854-1 (ISO 8510-1). The results of measurement are shown in Table 7. The column “peeling off of coating sheet from carrier sheet” in Table 7 shows the load required to peel off the coating sheet16from the carrier sheet15. The column “peeling off of protective sheet from adhesive layer” shows the load required to peel off the protective sheet13from the adhesive layer22. The column “peeling off of carrier sheet from auxiliary sheet” shows the load required to peel off the carrier sheet15from the auxiliary sheet14. The column “peeling off of auxiliary sheet from thermally conductive sheet” shows the load required to peel off the auxiliary sheet14from the thermally conductive sheet12. The column “peeling off of adhesive layer from aluminum plate” shows the load required to peel off the adhesive layer22from the aluminum plate used instead of a heat emitting body42.

TABLE 7Load (N)Peeling off of coating sheet from carrier sheet0.89Peeling off of protective sheet from adhesive layer0.005Peeling off of carrier sheet from auxiliary sheet0.64Peeling off of auxiliary sheet from thermally conductive sheet0.1Peeling off of adhesive layer from aluminum plate0.7

As shown in Table 7, the load required to peel off the auxiliary sheet14from the thermally conductive sheet12had a lower value than the load required to peel off the adhesive layer22from the aluminum plate used instead of a heat emitting body42. Therefore, it can be seen that only the auxiliary sheet14could be easily peeled off from the thermally conductive sheet12in Example9without the main sheet body21and the adhesive layer22being separated from each other when the auxiliary sheet14was peeled off after the thermally conductive sheet12was attached to the heat emitting body42. In addition, the load required to peel off the auxiliary sheet14from the thermally conductive sheet12was an appropriate and high value. Therefore, it can be seen that when the thermally conductive sheet12is handled by holding the protruding portion14ain order to attach the thermally conductive sheet12to the heat emitting body42, the thermally conductive sheet12continues to adhere to the auxiliary sheet14without peeling from the auxiliary sheet14due to its own weight. In addition, though the adhesiveness between the main sheet body21and the adhesive layer22could not be measured using the above described tension tester, the load required to peel off the adhesive layer22from the main sheet21is estimated to be 1 N or higher. In the case where the load required to peel off the adhesive layer22from the main sheet body21was 1 N or higher, the thermally conductive sheet12could be reused by attaching the thermally conductive sheet12to another heat emitting body42, for example.