Devices such as semiconductor (power chip, power transistor) manufacturing devices and vacuum devices (PVD, CVD) themselves generate a large quantity of heat with increase in speed or increase in integration, and temperature rise of the devices due to the heat causes malfunction and failure. On that account, how the heat generated in a larger quantity than before is removed without increasing the size and/or the weight of the device is a serious problem.
Such a problem is coped with by the use of a thermally conductive member wherein a rubber•gel or a grease is filled with a thermally conductive filler. The above devices that are objects of heat removal have parts that are used at not lower than 200° C., and therefore, they are required to have not only thermal conduction property but also extremely high heat resistance.
In particular, a gel•rubber shaped product is more easily processed as compared with a grease, so that it has been paid attention, and for such a shaped product, properties of low hardness, high elasticity and high releasability are desired in order to efficiently carry out thermal conduction.
As materials having high heat resistance among the materials of the conventional gel•rubber shaped products, silicone-based materials can be mentioned. The silicone-based shaped products, however, have a problem that siloxane or the like is emitted as a gas (outgas) and also has a problem that they are insufficient in resistance to heat of not lower than 200° C.
Then, in patent literatures 1 and 2, a problem of emission of siloxane as outgas from a thermally conductive shaped product and a problem of heat resistance of a thermally conductive shaped product have been solved by adopting a fluorine-based gel (specifically, “SIFEL (registered trademark)” available from Shin-Etsu Chemical Co., Ltd.) as a base material of a thermally conductive shaped product.
However, the binder “SIFEL” used for the thermally conductive shaped product of the patent literatures 1 and 2 has poor film-formability as compared with the conventional silicone rubber, and hence, with increase in the filling quantity, the formability of the SIFEL tends to be seriously lowered. Therefore, in order to obtain a shaped product, it is necessary to improve the shaped product strength to a certain extent by, for example, increasing the amount of a fibrous material added. By using such a technique, a shaped product is obtained, but the shaped product has high hardness, and it tends to be difficult to satisfy low hardness property that is required for a gel shaped product.
In order to lower hardness of a sheet, a technique of adding a large amount of a silicone oil or a fluorinated oil is generally used. However, when the sheet is used at a high temperature, there is a fear that the plasticizer component bleeds on the surface of the sheet (bleeding phenomenon) to stain the periphery of the sheet.
In a patent literature 3, there is disclosed a thermally conductive sheet which exhibits high heat resistance and has both of low hardness and high surface tack even if it is highly filled with a thermally conductive filler, by blending four kinds of SIFEL that are different in the types of the functional end groups and the number thereof. However, control of crosslinking is difficult, and there is a fear of bleeding of the uncrosslinked polymer component.