Patent ID: RE41640

Claim:
An information recording medium usable for either a first recording density D 1 or a second recording density D 2 among a plurality of recording densities including the first recording density D 1 and the second recording density D 2 , the information recording medium comprising: a user data area in which user data is to be recorded; a first defect management information area in which first defect management information is to be recorded, the first defect management information being for managing a defect area existing in the user data area; and a second defect management information area in which second defect management information is to be recorded, the second defect management information having an identical content to that of the first defect management information, wherein: the first defect management information area and the second defect management information area are located so as to fulfill the relationships of 150°≦θ 1 ≦210° and 150°≦θ 2 ≦ 210°, where: θ 1 =(D 1 ×N)/(2π×r)×360(Mod360) (1), θ 2 =(D 2 ×N)/(2π×r)×360(Mod360) (2), θ 1 is an angle made by a start block of the first defect management information area and a start block of the second defect management information area when the user data is recorded in the user data area at the first recording density D 1 , θ 2 is an angle made by the start block of the first defect management information area and the start block of the second defect management information area when the user data is recorded in the user data area at the second recording density D 2 , N is a number of blocks existing between the start block of the first defect management information area and the start block of the second defect management information area, N being a natural number, and r is a radial distance of the first defect management information area from the center of the information recording medium.