Optical data recording disc with protrusion between clamping area and center hole

Abstract

A disc-shaped optical data recording medium has a signal recording layer for reading and/or writing data using light, and a 10 μm to 200 μm thick transparent protective layer disposed over the signal recording layer. The optical data recording medium includes a protrusion projecting from a surface of the transparent protective layer on a light-incidence surface side to which light is emitted to the signal recording layer. The protrusion is disposed in an area between a center hole and a clamping area where the optical data recording medium is held when reading and/or writing data in the signal recording layer.

1 . An optical data recording medium having a signal recording layer for reading and/or writing data, and a transparent protective layer disposed over the signal recording layer, the optical data recording medium comprising:
 a protrusion projecting from a surface of the transparent protective layer on a light-incidence surface side to which light is emitted to the signal recording layer,   the protrusion disposed in an area that is located between a center hole of the optical data recording medium and a clamping area where the optical data recording medium is held when reading and/or writing data in the signal recording layer,   a diameter of the center hole being 15.0 mm,   the protrusion being located between 17.5 mm diameter and 22.0 mm diameter,   a height of the protrusion measured from a surface of the transparent protective layer being 0.3 mm or less.   
     
     
         2 . A playback device for playing-back of information from the optical data recording medium according to  claim 1 , comprising:
 an optical head which condenses light beam of 405 nm wavelength onto the signal recording layer through the transparent protective layer so as to playback information from the optical data recording medium.   
     
     
         3 . A recording device for recording information onto the optical data recording medium according to  claim 1 , comprising:
 an optical head which condenses light beam of 405 nm wavelength onto the signal recording layer through the transparent protective layer so as to record information onto the optical data recording medium.   
     
     
         4 . A playback method for playing-back of information from the optical data recording medium according to  claim 1 , comprising:
 playing-back information from the optical data recording medium by an optical head which condenses light beam of 405 nm wavelength onto the signal recording layer through the transparent protective layer.   
     
     
         5 . A recording method for recording information onto the optical data recording medium according to  claim 1 , comprising:
 recording information onto the optical data recording medium by an optical head which condenses light beam of 405 nm wavelength onto the signal recording layer through the transparent protective layer.   
     
     
         6 . A manufacturing method for manufacturing an optical data recording medium, comprising:
 forming a signal recording layer for reading and/or writing data,   forming a transparent protective layer disposed over the signal recording layer, and   forming a protrusion projecting from a surface of the transparent protective layer on a light-incidence surface side to which light is emitted to the signal recording layer,   wherein the protrusion is formed in an area that is located between a center hole of the optical data recording medium and a clamping area where the optical data recording medium is held when reading and/or writing data from/onto the signal recording layer,   a diameter of the center hole being 15.0 mm,   the protrusion being located between 17.5 mm diameter and 22.0 mm diameter,   a height of the protrusion measured from a surface of the transparent protective layer being 0.3 mm or less.