MULTI-STACK OPTICAL DATA STORAGE MEDIUM AND USE OF SUCH MEDIUM.

摘要

A multi-stack optical data storage medium (30) for recording using a focused radiation beam (40) having a wavelength ? and entering through an entrance face (41) of the medium (30) is described. It has a first substrate (31a) with present on a side thereof a first recording stack (33) named L0, comprising a recordable type L0 recording layer (35), and formed in a first L0 guide groove (38). The L0 recording layer (35) has a thickness dL0G in the groove (38) and a thickness dL0L adjacent the groove (38). A second substrate (31b) has present on a side thereof a second recording stack (32) named L1 comprising a recordable type L1 recording layer (34). The L1 recording layer has a thickness dL1G in the groove and a thickness dL1L adjacent the groove. The second recording stack (32) is present at a position closer to the entrance face (41) than the L0 recording stack (33) and is formed in a second L1 guide groove (37). The depth of the first L0 guide groove (38) is smaller than 0.15? and dL0L is substantially equal to or larger than dL1G by which it is achieved that the L0 stack (33) has a reflection level and a modulation level of recorded marks compatible with the dual layer DVD-ROM specification.