To provide an optical recording medium by which stripping is prevented when a light transmissive layer is formed, flatness of a cramp reference surface is improved to restrict face-runout when the optical recording medium is placed on the spindle of a recorder/reproducer or a reproducer and rotated, the cramp reference surface is made to be highly frictional to prevent idling and recording/reproducing is performed with a high reliability.
A disk baseboard 1 provided with an information signal part 1c on one main surface is irradiated with a laser beam from a side where the information signal part 1c exists and, then, an information signal is recorded/reproduced in an optical disk. In the optical disk, the cramp reference surface 3c is set at the side of the information signal part 1c on a replica baseboard 1a which constitutes the optical disk. The cramp reference surface 3a is made to be flat and the thickness of the replica baseboard 1a in a cramp area 3 is made to be larger than that of the replica baseboard 1a in an information recording area 4. A projected baseboard which is thicker at the circumference of a center hole 1b than at the information recording area 4 is used as the replica baseboard 1a.
KOSHIDA AKIO
NAKANO ATSUSHI
