Patent ID: 8703264
Filing Date: 2014-04-22
Classification: G11B

Abstract:
1. An optical disc in which at least a light reflecting layer and a light transmitting layer that includes a cured film of an ultraviolet curable composition are stacked on a substrate, and information is reproduced by making a blue laser beam be incident on the optical disc from a side of the light transmitting layer, wherein the elastic modulus at 25° C. as measured by indenting a Vickers indenter having a vertex angle of 136° under a load of 100 mN into a surface of the cured film of the ultraviolet curable composition is 1500 MPa or less; the loss modulus (E″) at 60° C. in a dynamic viscoelastic spectrum of the cured film measured at a frequency of 3.5 Hz is 10 MPa or less; the loss tangent (tan δ) at 60° C. in the dynamic viscoelastic spectrum of the cured film measured at a frequency of 3.5 Hz is 0.25 or less; and the cured film has a glass transition temperature of 50° C. or less, and wherein the ultraviolet curable composition contains, as a (meth)acrylate oligomer, an epoxy (meth)acrylate represented by the formula (1) wherein in the formula (1), R 1 s each independently represent a hydrogen atom or a methyl group; A 1 is a group represented by the formula (2) wherein in the formula (2), E B wherein in the formulae (3) to (5), J wherein the ultraviolet curable composition contains at least one of ethylene-oxide-modified bisphenol A di(meth)acrylate or propylene-oxide-modified bisphenol A di(meth)acrylate.