Method of producing stamper for optical recording medium, method of producing substrate, and method of producing optical recording medium

Abstract

A method of producing a stamper for roughening a substrate of an optical recording medium contains the steps of placing a conductive ring having a hole at the center thereof on a major surface of an original metal plate, electroforming a metal layer over a portion of the metal plate exposed in the hole of the conductive ring, an inner end-face of the conductive ring, and a portion of a major surface of the conductive ring, and entirely or partly roughening a major surface of the metal layer by a blasting treatment to obtain an original stamper.

1 . A method of producing a stamper for roughening a substrate of an optical recording medium, the method comprising the steps of:
 placing a conductive ring having a hole at a center thereof on a major surface of an original metal plate;   electroforming a metal layer over a portion of said metal plate exposed in said hole of said conductive ring, an inner end-face of said conductive ring, and a portion of a major surface of said conductive ring; and   entirely or partly roughening a major surface of said metal layer by a blasting treatment to obtain an original stamper.   
   
   
       2 . A method of producing a stamper according to  claim 1 , wherein said inner end-face of said conductive ring contains a stepped surface. 
   
   
       3 . A method of producing a stamper according to  claim 1 , wherein said inner end-face of said conductive ring contains a tapered surface. 
   
   
       4 . A method of producing a stamper according to  claim 1 , wherein a pressing jig having a hole at a center thereof is used for pressing said conductive ring against said metal plate in said electroforming step, and an inner diameter of said conductive ring is smaller than that of said pressing jig. 
   
   
       5 . A method of producing a stamper according to  claim 1 , wherein in said blasting treatment step, said major surface of said metal layer exposed in said hole of said conductive ring is entirely or partly roughened by said blasting treatment after removing said metal plate. 
   
   
       6 . A method of producing a stamper according to  claim 1 , further comprising the step of electroforming another metal layer on said roughened metal layer of said original stamper to obtain a second-generation stamper comprising said other metal layer. 
   
   
       7 . A method of producing a stamper according to  claim 1 , wherein a pit forming site for forming a pre-pit on said optical recording medium is formed on a portion of said major surface of said metal plate. 
   
   
       8 . A method of producing a stamper according to  claim 7 , wherein a transfer pattern of said pit forming site is formed on said major surface of said metal layer and the transferred pattern is protected before said blasting treatment for roughening said major surface of said metal layer. 
   
   
       9 . A method of producing a substrate for an optical recording medium having an image recording layer on which a visible image is recorded, the method comprising the steps of producing a stamper having an entirely or partly roughened major surface, and producing said substrate having an entirely or partly roughened major surface by using said stamper, wherein said stamper producing step comprises the steps of:
 placing a conductive ring having a hole at a center thereof on a major surface of an original metal plate;   electroforming a metal layer over a portion of said metal plate exposed in said hole of said conductive ring, an inner end-face of said conductive ring, and a portion of a major surface of said conductive ring; and   entirely or partly roughening a major surface of said metal layer by a blasting treatment to obtain an original stamper.   
   
   
       10 . A method of producing an optical recording medium having a substrate and an image recording layer on said substrate, a visible image being recorded on said image recording layer, the method comprising the steps of producing a stamper having an entirely or partly roughened major surface, and producing said substrate having an entirely or partly roughened major surface by using said stamper, and forming said image recording layer on said substrate, wherein said stamper producing step comprises the steps of:
 placing a conductive ring having a hole at a center thereof on a major surface of an original metal plate;   electroforming a metal layer over a portion of said metal plate exposed in said hole of said conductive ring an inner end-face of said conductive ring, and a portion of a major surface of said conductive ring; and   entirely or partly roughening a major surface of said metal layer by a blasting treatment to obtain an original stamper.