Optical information medium having separate recording layers

Abstract

The optical information medium for rewritable recording by means of a laser-light beam (14, 15) has a first recording stack (8) having a phase change type recording layer (10), sandwiched between two dielectric layers (9, 11), and has a second recording stack having a phase change type recording layer (5), sandwiched between two dielectric layers (3, 5). A transparent spacer layer (7) is interposed between the first recording stack (8) and the second recording stack (2). A metal mirror layer (3) is present proximate the second recording stack (2) at a side remote from the transparent spacer layer (7). The first recording stack (8) has a phase change type recording layer (10) with substantially growth dominated or substantially nucleation dominated crystallization. The second recording stack (2) has a phase change type recording layer (5) of a kind different from the kind selected for the first recording stack (8). An optimal recording and erasing behavior is achieved with a laser-light write pulse strategy and a recording velocity which are substantially equal for the recording layers (5, 10).

Description

technical field [0001] The invention relates to an optical information medium capable of being rewritably recorded with a laser beam, said medium comprising a substrate having on one side a [0002] - a first recording stack comprising a phase-changing type recording layer sandwiched between two insulating layers, [0003] - a second recording stack comprising a recording layer of phase changing type sandwiched between two insulating layers, [0004] - a transparent spacer layer positioned between the first and second recording stacks and having a thickness greater than the depth of focus of the laser beam, [0005] - a metal mirror layer close to the second recording stack on the side of the second recording stack remote from said transparent spacer layer. Background technique [0006] US patent US 6,190,750 discloses one such optical information medium. This patent describes an optical information medium for single-sided double-layer recording. [0007] Optical data st...

AI Technical Summary

Problems solved by technology

Further, the relatively thin metal layer M1 necessarily blocks a substantial portion of the laser light resulting in reduced recording power at the P-layer

[0011] A disadvantage of the known media is that the recording and erasing of the first and second recording layers are substantially different

Different laser pulse writing methods and recording speeds are required for each recording layer, resulting in more complex recording devices

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