Information recording medium and method of manufacturing resinous substrate for use in the recording medium

Abstract

An information recording medium comprising a substrate having a recording surface provided with emboss pits or guiding grooves, a reflective film formed on the recording surface of the substrate, and a first protective film formed on the reflective film. This information recording medium is featured in that both sides of the information recording medium are constituted by a first surface provided with the protective film and by a second surface formed opposite to the first surface, and that an irradiated light beam is irradiated through the first surface, a recorded information being reproduced based on changes in light intensity of the reflected light beam. The distance between the recording surface of the substrate and the light incident surface is smaller than a thickness of the substrate, and a surface roughness “R” of the light incident surface meets a relationship represented by the following formula (1): R≦λ/(8n)   (1) wherein λ is a wavelength of the light beam, and n is a refractive index of the first protective film to a light having the wavelength λ.

What is claimed is: 
     
       1. An information recording medium, which comprises:
 a supporting substrate;   a first reflective layer formed on said supporting substrate;   a spacer layer formed on said first reflective layer;   a second reflective layer formed on said spacer layer; and   a covering layer formed on said second reflective layer and having a light incident surface;   wherein a light beam can enter through said light incident surface and be reflected to produce a reflected light beam, a recorded information being reproduced based on changes in light intensity of the reflected light beam.   
     
     
       2. The information recording medium according to  claim 1 , wherein the thickness of said covering layer is in the range of 0.0001 to 0.6 mm. 
     
     
       3. The information recording medium according to  claim 2 , wherein the thickness of said spacer layer is 30 μm or less. 
     
     
       4. The information recording medium according to  claim 2 , wherein the thickness of said spacer layer is 20 μm or more. 
     
     
       5. The information recording medium according to  claim 2 , wherein the reflectance of at least one of said first reflective layer and said second reflective layer is 15% or more. 
     
     
       6. The information recording medium according to  claim 2 , wherein the reflectance of at least one of said first reflective layer and said second reflective layer is 45% or less. 
     
     
       7. An information recording medium, which comprises:
 a supporting substrate;   a first recording layer formed on said supporting substrate;   a spacer layer formed on said first recording layer;   a second recording layer formed on said spacer layer; and   a covering layer formed on said second recording layer and having a light incident surface;   wherein a light beam can enter through said light incident surface and be reflected to produce a reflected light beam, a recorded information being reproduced based on changes in light intensity of the reflected light beam.   
     
     
       8. The information recording medium according to  claim 7 , wherein the thickness of said covering layer is in the range of 0.0001 to 0.6 mm. 
     
     
       9. The information recording medium according to  claim 8 , wherein the thickness of said spacer layer is 30 μm or less. 
     
     
       10. The information recording medium according to  claim 8 , wherein the thickness of said spacer layer is 20 μm or more. 
     
     
       11. The information recording medium according to  claim 8 , wherein the reflectance of at least one of said first recording layer and said second recording layer is 15% or more. 
     
     
       12. The information recording medium according to  claim 8 , wherein the reflectance of at least one of said first recording layer and said second recording layer is 45% or less. 
     
     
       13. An information recording medium comprising:
 a supporting substrate;   a first recordable or rewritable layer formed on said supporting substrate;   a spacer layer formed on said first recordable or rewritable layer, wherein the thickness of said spacer layer is within a range of 20 to 30 μm;   a second recordable or rewritable layer formed on said spacer layer;   a cover layer formed on said second recordable or rewritable layer; and   a protective over-coating layer formed on said cover layer and having a light incident surface,   wherein a light beam can enter through said light incident surface and can be reflected to produce a reflected light beam, and a recorded information is reproduced based on changes in light intensity of the reflected light beam,   wherein a recess or a projection is formed inward of a recording area, and   wherein the cover layer is formed radially outward of the recess or the projection and is not formed radially inward of the recess or the projection.