PURPOSE: To improve the thermal conductivity of a heat roll and to promote energy saving by coating the heat roll of a copying machine with a liquefied silicone rubber composition containing boron nitride and liquid crystal.

CONSTITUTION: A liquefied silicone rubber composition is obtained by mixing uniformly boron nitride of 50pts.wt. and nematic liquid crystal (aniliden-para- aminophenylacetate) of 5pts.wt. in a normal-temperature-setting type silicone rubber composition of 100pts.wt. The composition thus obtained is applied on the core metal of a heat roll having an outside diameter of 28mm and then is set and ground, and thereby a heat roll having an outside diameter of 29mm, a wall thickness of 0.5mm and a length of 270mm is prepared. The thermal conductivity of this heat roll is 8.5×10-13cal/cm.sec.°C.