| 摘要 |
A multi stack optical data storage medium ( 15 ) for recording and reading by means of a focused radiation beam ( 10 ) is described. The beam enters the medium ( 15 ) through a first entrance face ( 11 ), and has at least a first substrate ( 1 ) with on at least one side thereof: a first layer stack ( 2 ), comprising a first information layer, a second layer stack ( 4 ), comprising a second information layer. The second layer stack is present at a position closer to the first entrance face ( 11 ) than the first layer stack ( 2 ), and is separated from the first layer stack by a first transparent spacer layer ( 3 ). The first and the second layer stack each have an effective radiation beam reflection R<SUB>e </SUB>if between 0.04 and 0.08 according to the Blu-ray Disc (BD) standard specification. A third layer stack ( 6 ), comprising a third information layer, is present at a position closest to the first entrance face ( 11 ), and is separated from the second layer stack ( 4 ) by a second transparent spacer layer ( 5 ). The third layer stack has a radiation beam transmission T<SUB>3 </SUB>larger than 0.70, and the third information layer is a read only layer or a write once layer. A multi stack optical data storage medium is achieved which has increased data capacity and which has reflection values compatible with the dual stack BD standard specification.
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