Optical data storage medium and use of such medium

Abstract

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