DUAL-STACK OPTICAL DATA STORAGE MEDIUM FOR WRITE ONCE RECORDING

摘要

A dual-stack optical data storage medium ( 10 ) for write-once recording using a focused radiation beam ( 9 ) having a wavelength lambda of approximately 655 nm is described. The radiation beam enters through an entrance face ( 8 ) of the medium ( 10 ) during recording. The medium comprises at least one substrate ( 1, 7 ) with present on a side thereof: a first recording stack ( 6 ), named L 0 , comprising a write-once type L 0 recording layer, said first recording stack L 0 having an optical reflection value R_L0 and an optical transmission value T_L0, a second recording stack ( 3 ), named L 1 , comprising a write-once type L 1 recording layer, said second recording stack L 1 having an effective optical reflection value R_L1eff. The first recording stack ( 6 ) is present at a position closer to the entrance face ( 8 ) than the second recording stack. ( 3 ). A transparent spacer layer ( 4 ) is sandwiched between the recording stacks ( 3, 6 ). The reflection values R_L0 and R_L1eff are within the following ranges: 0.12<=R_L0<=0.18 and 0.12<=R_L1eff<=0.18 by which an improved sensitivity of the dual stack medium is achieved.