Patent ID: 7948852
Filing Date: 2011-05-24
Classification: G11B

Abstract:
1. An optical storage medium, formed in a disk shape, comprising stacked data storage layers each of which is readable/writeable separately from the other layers by means of a light beam striking one side of the optical storage medium, wherein a recordable area of a first data storage layer including at least one recordable extended area portion is provided above a second data storage layer in a direction in which the first and second data storage layers are stacked, and said at least one recordable extended area portion extends in a radial direction of said optical storage medium past an entire recordable area of the second data storage layer, wherein a length of said at least one recordable extended area portion in the radial direction of said optical storage medium is equal to or longer than a thickness of an intermediate layer, which is provided between the first data storage layer and the second data storage layer, plus an amount equivalent to an eccentricity between the first data storage layer and the second data storage layer, and, further, wherein said second data storage layer is located furthest from said light-striking surface of said optical storage medium, and the first data storage layer is located next to the second data storage layer, closer to said light striking surface, wherein at least one of said at least one extended area portion is assigned as a test write area.