OPTICAL DATA STORAGE MEDIUM AND USE OF SUCH MEDIUM

摘要

A multi-stack optical data storage medium ( 20 ) for rewritable recording using a focused radiation beam ( 30 ), entering through an entrance face ( 25 ) is described. The medium ( 20 ) has a substrate ( 1 a , 1 b) and an L 0 recording stack ( 2 ) and an L 1 recording stack ( 3 ) both comprising a phase-change type L 0 and L 1 recording layer and the recording stacks are separated by a transparent spacer layer ( 4 ). The L 0 recording stack ( 2 ) is present at a position closest to the entrance face ( 25 ) and has an optical transmission of TL 0 a and TL 0 c when the phase-change layer respectively is in the amorphous phase and in the crystalline phase. The medium ( 20 ) contains pre-recorded information modulated in at least one of: an embossed pregroove ( 21 ) in the substrate ( 1 a , 1 b), embossed pits in the substrate and recorded phase-change marks in at least one of the recording layers L 0 and L 1 ( 6, 11 ). The pre-recorded information contains a flag whether formatting of the L 0 recording layer of the L 0 recording stack ( 2 ) is needed depending on the transmission values TL 0 a and TL 0 c of the L 0 recording stack ( 2 ). In this way it is achieved that the medium ( 20 ) has a good playability, recordability and random access behavior even when the L 0 recording layer ( 2 ) has been partially recorded with information.