Optical disk with plural substrates

Abstract

An optical disk of the present invention includes a first substrate having a signal area on a principal plane and a central hole, and a second substrate that is transparent and attached to the first substrate. The second substrate is thinner than the first substrate, and has a central hole whose diameter is larger than that of the first substrate. The first substrate and the second substrate are attached to each other with radiation curable resin (adhesive member) disposed therebetween so as to extend at least from an inner peripheral edge of the second substrate to an outer peripheral edge thereof.

1 - 40 . (canceled) 
     
     
         41 . An optical disk comprising:
 a substrate having a signal area on a principal plane and a central hole;   a transparent layer provided in a first region of the principal plane, the first region including the signal area and the transparent layer being arranged so as to be exposed to a laser light for recording/reproducing signals; and   a convex portion provided at a second region of the principal plane and formed of a part of the substrate in a circular shape so as to surround the central hole, with an outer diameter of the convex portion being equal to or smaller than an inner diameter of the transparent layer, the second region being located between a peripheral edge of the center hole and an inner peripheral edge of the first region;   wherein the height of the convex portion from the principal plane is larger than the thickness of the transparent layer, so that the top of the convex portion projects above the surface of the transparent layer.