Abstract: A process for producing an information recording medium comprising a substrate and provided thereon a recording layer and protective layer comprises the steps of forming on one substrate sheet a plurality of grooved preformats used for information recording mediums, forming a recording layer on the substrate sheet having thereon said plurality of grooved preformats, forming a protective layer on the substrate sheet on which said recording layer has been formed, and cutting the resulting substrate sheet into individual information recording mediums.

Abstract: A roll stamper which molds a substrate resin sheet into an information recording media by continuously transferring preformat patterns on the substrate resin sheet, and a production process therefor. The preformat pattern on the roll stamper has a value of b/a of greater than 1 when the length of the preformat pattern in a direction parallel to the direction in which the resin sheet is transported is defined as a and the length in a direction perpendicular thereto as b.

Abstract: A roll stamper has a roll substrate and a stamper fixed thereto and having a convexity and concavity preformat pattern. The stamper has an auxiliary layer, including a material different from that of the stamper and a back surface on which the convexity and concavity preformat pattern is formed. The roll substrate has a low-melting layer on its surface and the auxiliary layer is in contact with the low-melting layer so that the stamper is fixed to the roll substrate.

Abstract: A method for producing a substrate sheet for optical recording media, including the steps of continuously forming an ultraviolet-curable resin layer on at least one of i) a roll stamper having thereon a preformat pattern corresponding with preformatting information and ii) a substrate sheet; bringing the substrate sheet into close contact with the roll stamper having the ultraviolet-curable resin layer; curing the ultraviolet-curable resin layer to fix it on the substrate sheet; peeling from the roll stamper the substrate sheet having the cured ultraviolet-curable resin layer; and removing any ultraviolet-curable resin remaining on the surface of the roll stamper, after peeling the substrate sheet.

Abstract: A process for producing a roll stamper which molds a substrate sheet for information recording mediums by continuously transferring preformat patterns on a resin sheet. The roll stamper has the feature that the preformat pattern on the roll stamper has a value b/a of greater than 1, where the length of the preformat pattern in the direction parallel to the direction in which the resin sheet is transported is defined as a and the length in the direction perpendicular thereto as b.

Abstract: A substrate for an optical card having tracking grooves in a stripe form formed on the surface of an extrusion-molded thermoplastic resin sheet is characterized in that the direction of the tracking grooves is in parallel to the extrusion direction of the thermoplastic resin sheet, and the recording or reproduction using the optical card is characterized by that the optical card is bent and reciprocally moved along the direction of tracking grooves.

Abstract: An optical cutting method includes a step of detecting a center position on a sheet film with a position-detecting light flux; and a step of cutting out a disk film from the sheet film by projecting a cutting laser beam along circumference of a substantially circular form around the detected center position.

Abstract: A cast mold and process for casting a substrate for an information recording medium has an uneven preformat pattern formed on the mold surface. The uneven preformat features a pattern corresponding to tracking grooves and information pits, each information pit portion has a size with a length b in the direction parallel to the pattern of the tracking groove of 2 to 15 .mu.m and a width a in the direction perpendicular thereto of 1 to 6 .mu.m and a height c of 300 to 3500 .ANG.. The pit pattern has a pitch which is 1.8-fold or more of pit length b.

Abstract: An apparatus for producing a substrate sheet for optical recording media includes a device for continuously forming an ultraviolet-curable resin layer on at least one of i) a roll stamper having thereon a preformat pattern corresponding with preformatting information and ii) a substrate sheet; a means for bringing the substrate sheet into close contact with the roll stamper having the ultraviolet-curable resin layer; a device for curing said ultraviolet-curable resin layer to fix it on the substrate sheet; a device for peeling from the roll stamper the substrate sheet having the cured ultraviolet-curable resin layer; and a device for removing an ultraviolet-curable resin remaining on the surface of said roll stamper, provided after the means for peeling the substrate sheet.

Abstract: A roll stamper for continuously preparing a substrate used for optical recording mediums, having a convexity and concavity preformat pattern, is prepared by a process comprising the steps of forming a low-melting metal layer on a roll substrate, and forming an auxiliary layer comprising a material different from that of a stamper, on the back of the stamper having on its surface a pattern corresponding with a convexity and concavity preformat pattern. The stamper is overlaid on the roll substrate in such a manner that the low-melting metal layer comes into contact with the auxiliary layer, and thereafter the low-melting metal layer is melted so that the stamper is fixed to the roll substrate.

Abstract: A cast mold and process for casting a substrate for an information recording medium has an uneven preformat pattern formed on the mold surface. The uneven preformat features a pattern corresponding to tracking grooves and information pits, each information pit portion has a size with a length b in the direction parallel to the pattern of the tracking groove of 2 to 15 .mu.m and a width a in the direction perpendicular thereto of 1 to 6 .mu.m and a height c of 300 to 3500 .ANG.. The pit pattern has a pitch which is 1.8-fold or more of pit length b.