Reversible optical recording medium of the phase charge type

Claim 1

In the method of reversible optical laser recording utilizing a phase changing medium wherein the medium is first written upon by laser light and is subsequently erased by laser light, the improvement wherein said medium comprises at least one substrate and at least one storage layer of the phase change type and possessing at least three states of differing optical behavior which are reversibly switchable into one another and which are each associated with different volume fractions of crystalline and amorphous phase in the storage layer, the difference in reflectivity between at least one pair of states being greater than between the amorphous and the crystalline state, in its amorphous state, and wherein prior to writing and erasure, the medium is initialized by one or more laser pulses at least 10 times longer in duration than those used in writing or erasing, whereby a crystalline or a partially crystalline state is formed.

Claim 8

The method of 6 wherein the substrate supports an arrangement comprising a) a first AlN layer from 50 to 200 nm in thickness, b) a storage layer of GeTe or GeSb 2 Te 4 from 10 to 50 nm in thickness, c) a second AlN layer from 15 to 100 nm in thickness, and d) an Al layer greater than 20 nm in thickness in the stated order.

Claim 9

The method of 6 wherein the substrate supports an arrangement comprising a) a first AlN layer from 50 to 200 nm in thickness, b) a storage layer of GeTe or GeSb 2 Te 4 from 10 to 50 nm in thickness, c) a second AlN layer from 15 to 100 nm in thickness, and d) an Al layer greater than 20 nm in thickness in the stated order.