Optical recording medium and cover sheet for optical recording media
Provided are a cover sheet for optical recording media comprising a transparent disk-shaped sheet having a central hole and a hardcoat layer formed thereon wherein the hardcoat layer has a linear crack groove in the circumferential direction in the area close to the outer circumferential edge thereof; and an optical recording medium comprising a disk-shaped substrate having a central hole and at least a recording layer, a transparent sheet, and a hardcoat layer formed in that order thereon wherein the hardcoat layer has a linear crack groove in the circumferential direction in the area close to the outer circumferential edge thereof.
1 . A cover sheet for optical recording media, comprising a transparent disk-shaped sheet having a central hole and a hardcoat layer formed thereon, wherein the hardcoat layer has a linear crack groove in a circumferential direction in an area close to an outer circumferential edge thereof.
2 . The cover sheet for optical recording media according to claim 1 , wherein the linear crack groove is present around the entire circumference in the area of the hardcoat layer close to the outer circumferential edge.
3 . The cover sheet for optical recording media according to claim 1 , wherein the cover sheet is a lamninated film having a release sheet adhered via a pressure sensitive adhesive layer onto the face of the transparent sheet opposite to the hardcoat layer.
4 . The cover sheet for optical recording media according to claim 3 , wherein the pressure sensitive adhesive layer contains an acrylic pressure sensitive adhesive.
5 . The cover sheet for optical recording media according to claim 1 , wherein the hardcoat layer has a surface elastic modulus of 4 GPa or more.
6 . The cover sheet for optical recording media according to claim 1 , wherein the transparent sheet contains polycarbonate or cellulose triacetate.
7 . The cover sheet for optical recording media according to claim 1 , wherein the transparent sheet has a thickness of 0.03 to 0.15 mm.
8 . The cover sheet for optical recording media according to claim 1 , wherein the hardcoat layer contains a bi- or higher-functional acrylate or methacrylate compound.
9 . An optical recording medium, comprising a disk-shaped substrate having a central hole and at least a recording layer, a transparent sheet, and a hardcoat layer formed in that order thereon, wherein the hardcoat layer has a linear crack groove in a circumferential direction in an area close to an outer circumferential edge thereof.
10 . The cover sheet for optical recording media according to claim 9 , wherein the linear crack groove is present around the entire circumference in the area of the hardcoat layer close to the outer circumferential edge.
11 . The cover sheet for optical recording media according to claim 9 , wherein the hardcoat layer has a surface elastic modulus of 4 GPa or more.
12 . The cover sheet for optical recording media according to claim 9 , wherein the transparent sheet contains polycarbonate or cellulose triacetate.
13 . The cover sheet for optical recording media according to claim 9 , wherein the transparent sheet has a thickness of 0.03 to 0.15 mm.
14 . The cover sheet for optical recording media according to claim 9 , wherein the hardcoat layer contains a bi- or higher-functional acrylate or methacrylate compound.