Patent ID: 7869328
Filing Date: 2011-01-11
Classification: G11B

Abstract:
1. An optical disk comprising: a substrate preliminarily provided with concave/convex recording marks formed thereon for recording main information; and a reflection film which covers the substrate and of which a reflection coefficient is changed by irradiating laser light at or above a certain intensity; wherein the reflection film is preliminarily provided with additional marks for recording sub information by changing the reflection coefficient of the reflection film on a region where the concave/convex recording marks are formed, wherein the sub information is recorded for every predetermined recording unit for recording the main information, wherein the laser light at or above the certain intensity is irradiated onto the region where the sub information is recorded to thereby reproduce the main information and delete the sub information, wherein the sub information is deleted by minimizing a difference of an average value of the reflection coefficient between a region where the additional marks are formed and a region where the additional marks are not formed before and after the laser light at or above the certain intensity is irradiated, and wherein the certain intensity is a light intensity higher than a reproduction laser light intensity for reproducing the concave/convex recording marks.