Recording medium of flat surface with resin filled ring grove

A manufacturing method of a disc including the steps of attaching a stamper having a center hole and an information signal surface to a metal mold by causing an inner peripheral portion of the center hole and the outer peripheral portion of the stamper to engage with a first collar of a first retainer and with a second collar of a second retainer provided in the metal mold respectively, molding a disc substrate having a generally flat surface including a replica corresponding to the information signal surface by the stamper and a groove formed as an inverted replica by a shape of the first collar by injecting transparent resin into the metal mold, and forming a center through hole at a center of the disc substrate by hole forming means provided in the metal mold, said groove dividing concentrically with said center through hole the generally flat surface of said disk substrate into inner and outer surfaces comprising the steps of:

• forming a protecting layer on the reflecting layer;
• filling resin into the groove in such a manner that a top flat surface of the resin becomes approximately the same level as that of the inner and outer surfaces for causing said inner and outer surfaces to be bridged and flush with one another;
• and
• printing each label on the inner and outer surfaces without being interrupted by the groove.