Method for recording and erasing information

Claim 1

A method for recording and erasing information, which comprises irradiating a recording medium comprising a substrate, having superimposed thereon a recording layer composed of Sb, Te, Ge and at least one element selected from the group consisting of Pb, Bi, In, Sn and Tl, with a single laser beam, while migrating said recording layer relative to said single laser beam, Sb, Te, Ge and said element selected from the group consisting of Pb, Bi, In, Sn and Tl, being present in said recording layer in atomic ratios represented by the formula: (Te.sub.x Ge.sub.y Sb.sub.l-x-y).sub.l-z M.sub.z wherein M is at least one element selected from the group consisting of Pb, Bi, In, Sn and Tl, and 0.3≦x≦0.7, 0.1≦y, 0.01≦z≦0.3 and x+y<1, said recording layer being capable of reversibly converting between an amorphous phase and a crystalline phase in accordance with a laser beam intensity applied to the recording layer, the reversible conversion being effective for recording and erasing information, said single laser beam being applied with two different intensities, respectively, for crystallizing said recording layer and for amorphizing said recording layer, while changing the laser beam intensity between said two different intensities in accordance with a laser beam intensity pattern corresponding to predetermined information, to thereby form amorphous areas and crystalline areas in the recording layer, which correspond to said predetermined information.

Claim 2

A method for recording and erasing information, which comprises irradiating a recording medium comprising a substrate, having superimposed thereon a recording layer composed of Sb, Te, Ge and at least one element selected from the group consisting of Pb, Bi, In, Sn and Tl, with a single laser beam, while migrating said recording layer relative to said single laser beam, Sb, Te, Ge and said element selected from the group consisting of Pb, Bi, In, Sn and Tl, being present in said recording layer in atomic ratios represented by the formula: (Te.sub.x Ge.sub.y Sb.sub.l-x-y).sub.l-z M.sub.z wherein M is at least one element selected from the group consisting of Pb, Bi, In, Sn and Tl, and 0.3≦x≦0.7, 0.1≦y, 0.01≦z≦0.3 and x+y<1, said recording layer being capable of reversibly converting between an amorphous phase and a crystalline phase in accordance with a laser beam intensity applied to the recording layer, the reversible conversion being effective for recording and erasing information, said single laser beam being applied with two different intensities, respectively, for crystallizing said recording layer and for amorphizing said recording layer, while changing the laser beam intensity between said two different intensities in accordance with a laser beam intensity pattern corresponding to predetermined information, to thereby form amorphous areas and crystalline areas in the recording layer, which correspond to said predetermined information.