Patent ID: 6815029
Filing Date: 2004-11-09
Classification: B29C,Y10T

Abstract:
A stamper for forming at least a data recording region on a recording medium substrate by means of a transfer surface thereof, the transfer surface transferring a predetermined set of data to the recording medium substrate, the stamper fitted on at least one of metal molds arranged opposite one another for forming the recording medium substrate, whereina stepped portion formed as bends in the material of the stamper, and the stepped portion is configured to project from the transfer surface toward the recording medium substrates, the stepped portion is formed to have a circular shape so as to form a circumferential recess radially outside a data recording region on at least one of the surfaces of the recording medium substrate, the circle is sized so that an end surface of the stepped portion engages an edge of an inner peripheral wall of the mold, the inner peripheral wall forming an outer peripheral surface of the recording medium substrate, and a radially innermost edge of the recess is positioned at a distance of 0.965 d from a center of the substrate or further, assuming d is a radius of an outermost circumference of the substrate.