Information recording medium, method for manufacturing the medium, and apparatus for manufacturing the medium

A multi-substrate disk comprising:

• a first disk-shaped substrate having a first information recording layer formed thereon, said first substrate having a predetermined outer diameter, a predetermined inner diameter, and a thickness of about 0.6 mm;
• a second disk-shaped substrate, said second substrate having the predetermined outer diameter, the predetermined inner diameter, and a thickness of about 0.6 mm;
• and
• an intermediate layer provided on said first information recording layer, and having a prescribed thickness;
• a second recording layer formed on said intermediate layer so that said intermediate layer is between said first and second recording layers;
• wherein a refractive index of said first substrate with respect to a sum of the thickness of said first substrate and intermediate layer is selected from the following sets of parameters:
• refractive index=1.45 with the sum of the thickness of 0.653 mm;
• refractive index=1.56 with the sum of the thickness of 0.640 mm;
• refractive index=1.65 with the sum of the thickness of 0.640 mm;
• refractive index=1.65 with the sum of the thickness of 0.550 mm;
• refractive index=1.56 with the sum of the thickness of 0.550 mm;
• and
• refractive index=1.45 with the sum of the thickness of 0.563 mm.