| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the stress applied to a ceramic layer and suppress the reduction in flatness by forming, on a metal board, the ceramic layer forming an attracting surface through an electric insulating elastic layer. SOLUTION: A disc-like metal board 12, an electric insulating elastic layer 14, an insulating film 16 an adhesive layer 20 and a ceramic layer 22 are layered successively from under, and electrodes 18, 18... are formed in prescribed positions on the insulating film layer 16. The electric insulating elastic layer 14 is formed by adding a rubber component and a phenolic antioxidant to an adhesive. Proper elasticity is imparted to the adhesive layer, whereby the stress can be moderated to prevent the distortion of the ceramic layer 22 even if a stress is generated by the difference in thermal expansion ratio between the ceramic plate and the metal board, or a volume change is caused in the adhesive itself. The phenolic antioxidant absorbs the radical generated by the rubber component, for example, when exposed to a high temperature, to prevent the deterioration of the rubber component.</p> |
