PURPOSE: To maintain flatness and to prevent curling by laminating a specified flexible dielectric image forming layer and a flexible supporting substrate.

CONSTITUTION: The flexible dielectric image forming layer has uniform thickness of about 10 to 50μm and contains a thermoplastic film forming polymer. The flexible supporting substrate consists of a single substrate layer having a conductive surface and uniform thickness of 25 to 200μm and containing a thermoplastic film forming polymer, or the substrate has a two-layer structure of an inner substrate layer and an outer substrate layer. The inner substrate layer has about 25 to 200μm uniform thickness and contains a thermoplastic polymer. The outer substrate layer has about 10 to 50μm uniform thickness and contains a thermoplastic film forming polymer. Linear tensions measured in any directions along the plane of the dielectric image forming layer are substantially same as linear tensions measured along the plane of the outer substrate layer in the same directions as those selected for the measurement of linear tensions in the dielectric image forming layer.