PURPOSE: To shorten the thermal pressure welding time of an enlarged liquid crystal panel, enhance charge preventing effect, and improve durability by containing boron nitride and a conductive material in silicone rubber.

CONSTITUTION: The composition ratios of an auxiliary sheet for thermal pressure welding have the ranges of 20-40wt.% of silicone rubber, 77-30wt.% of boron nitride, and 3-30% of a conductive material. As the boron nitride, hexagonal system boron nitride powder is used, and as the conductive material, carbon black, a metal powder, or a metal oxide subjected to conductive treatment is used. After a heat resistance improving agent and a vulcanizing agent are mixed thereto in addition to them, sheet molding is conducted followed by heating and pressurizing press. By using the resulting auxiliary sheet for thermal pressure welding, the temperature of a bonding part can be raised to a determined temperature within a short time. The generation of static electricity is suppressed, and the yield of thermal pressure welding of a liquid crystal module having a narrow pitch between electrodes corresponding to higher fineness can be further improved.