Multilayer phase-change type optical disc capable of recording and reproducing information at high transfer rate
View Patent ↗The present invention is a multilayer optical disc formed of a plurality of information recording sections having a phase change recording layer. A first information recording section provided at a laser-incident side uses, as a recording material, a phase change recording material which uses Sb and Te as major components and satisfies their ratio of 2.3<Sb/Te≦4.0 according to the atomic ratio. Since this phase change recording material provides a fast crystallization speed, it is possible to stably record, reproduce, and rewrite an information signal at a high transfer rate.
1. A multilayer optical disc comprising at least a first information recording section, an intermediate layer having optical permeability, and a second information recording section sequentially formed on a substrate and using laser irradiated from a side of the first information recording section, wherein
the first information recording section includes a phase change recording material layer formed of a phase change recording material which uses at least Sb and Te as major components and satisfies their ratio of 2.3<Sb/Te≦4.0 according to the atomic ratio.
2. The multilayer optical disc according to claim 1 , wherein the laser has a wavelength of 385 nm or more and 450 nm or less.
3. The multilayer optical disc according to claim 1 , wherein the second information recording section includes a phase change recording material layer formed of a phase change recording material which uses at least Sb and Te as major components and satisfies their ratio of 2.3<Sb/Te≦4.0 according to the atomic ratio.
4. The multilayer optical disc according to claim 1 , wherein at least one of Ge, In, Zn, Sn, Ag, and Au is added to the phase change recording material layer.
5. The multilayer optical disc according to claim 1 , wherein the first information recording section includes the phase change recording material layer configured to be sandwiched between a pair of dielectric layers having optical permeability.
6. The multilayer optical disc according to claim 5 , wherein at least one of the pair of dielectric layers is a single layer including at least a dielectric material having a higher thermal conductivity than ZnS—SiO 2 , or a multilayer of the dielectric material having the high thermal conductivity and another transparent dielectric material.
7. The multilayer optical disc according to claim 6 , wherein the dielectric material having the high thermal conductivity contains at least one of Si 3 N 4 , AlN, SiC, BeO, and BN as a major component.
8. The multilayer optical disc according to claim 1 , wherein, when information is recorded on all recording tracks, the first information recording section is provided with an average transmittance (Tavg) satisfying equation 1 below.
70%≧Tavg≧40% Equation 1
9. The multilayer optical disc according to claim 1 , wherein the phase change recording material is provided with a light absorption coefficient (A 1 c ) for the first information recording section in a crystalline state and a light absorption coefficient (A 1 a ) for the first information recording section in an amorphous state satisfying equation 2 below.
1.7≧A 1 c /A 1 a ≧0.8 Equation 2
10. The multilayer optical disc according to claim 1 , wherein the phase change recording material is provided with a higher optical reflectance for the first information recording section in an amorphous state than that for first information recording section in a crystalline state.