OPTICAL DATA STORAGE MEDIUM AND USE OF SUCH MEDIUM

摘要

A multi-stack optical data storage medium (20) for rewritable recording usin g a focused radiation beam (30), entering through an entrance face (25) is described. The medium (20) has a substrate (1a, 1b) and an L0 recording stac k (2) and an L1 recording stack(3) both comprising a phase-change type L0 and L1 recording layer and the recording stacks are separated by a transparent spac er layer (4). The L0 recording stack (2) is present at a position closest to th e entrance face (25) and has an optical transmission of TL0a and TL0c when the phase-change layer respectively is in the amorphous phase and in the crystalline phase. The medium (20) contains pre-recorded information modulat ed in at least one of: an embossed pregroove (21) in the substrate (1a, 1b), embossed pits in the substrate and recorded phase-change marks in at least o ne of the recording layers L0 and L1 (6, 11). The pre-recorded information contains a flag whether formatting of the L0 recording layer of the L0 recording stack (2) is needed depending on the transmission values TL0a and TL0c of the L0 recording stack (2). In this way it is achieved that the medi um (20) has a good playability, recordability and random access behavior even when the L0 recording layer (2) has been partially recorded with information .