Optical recording medium, and method of manufacturing same

Abstract

There are provided an optical recording medium and a method of manufacturing the optical recording medium. The optical recording medium has a pattern of microscopic depressions and projections molded thereon with a high fidelity of replication. The method of manufacturing the optical recording medium comprises the steps of forming a photoresist layer on a substrate; exposing a predetermined area of the photoresist layer formed on the substrate to form a plurality of trains of depressions in the photoresist layer; removing the photoresist layer between the adjoining depression trains to form a master; plating the master with a metal; separating the metal coating to form a master stamper; replicating the master stamper repeatedly an odd number of times to form a mother stamper; replicating the mother stamper to form a resin substrate; and forming at least a light-transparent layer on a surface of the resin substrate on which the mother stamper is replicated. The method can mold a pattern of microscopic depressions and projections with a high accuracy.

What is claimed is:  
     
         1 . An optical recording medium comprising a substrate and at least a light-transparent layer provided on the substrate, and with respect to which a signal is written and/or read by a light of a predetermined wavelength irradiated from above and through the light-transparent layer; 
 the substrate having formed thereon projections being convex as viewed from the light-transparent layer and depressions positioned in line with the projections and deep from a same height as the main surfaces of the projections.    
     
     
         2 . The optical recording medium according to  claim 1 , further comprising: 
 a reflective layer formed on the substrate; and    a recording layer formed on the reflective layer;    the recording layer on the projections being used as a recordable area.    
     
     
         3 . The optical recording medium according to  claim 2 , wherein the recording layer is any one of a phase-change recording layer, magneto-optical recording layer and organic-dye type recording layer.  
     
     
         4 . A method of manufacturing an optical recording medium, comprising the steps of: 
 forming a photoresist layer on a substrate;    exposing a predetermined area of the photoresist layer formed on the substrate to form a plurality of trains of depressions in the photoresist layer;    removing the photoresist layer between the adjoining depression trains to form a master;    plating the master with a metal;    separating the metal coating to form a master stamper;    replicating the master stamper repeatedly an odd number of times to form a mother stamper;    replicating the mother stamper to form a resin substrate; and    forming at least a light-transparent layer on a surface of the resin substrate on which the mother stamper has been replicated.    
     
     
         5 . The method according to  claim 4 , further comprising the step of: 
 forming grooves in line with the train of depressions.    
     
     
         6 . The method according to  claim 5 , wherein the substrate is exposed at the bottoms of the grooves and depressions, respectively.  
     
     
         7 . The method according to  claim 4 , wherein the photoresist layer is a positive-type one.  
     
     
         8 . The method according to  claim 7 , further comprising the steps of: 
 forming the depressions by exposing the photoresist layer to a first light; and    removing the photoresist layer between the trains of depressions by exposing the photoresist layer to a second light.    
     
     
         9 . The method according to  claim 8 , wherein the first light and second light are obtained by splitting a light from a single source and irradiated to the photoresist layer through a same objective lens.