Abstract
We developed a phase-change recording medium which has a high transmittance and a large reflectivity contrast (that is defined as the equation of (R_<cry>-R_<amo>)/(R_<cry>+R_<amo>). This medium is very suitable for the front-side recording layer of a dual-layer optical disk. The layer structure is characterized by a TiO_2 top film with a large refractive index of 2.7 in addition to a conventional structure which has very thin films of GeTe-Sb_2Te_3 phase-change film (6nm) and Ag-alloy reflective film (10nm). A high transmittance (>50%) is realized by a new optical interference arising from a TiO_2 top film. Moreover, we adopted so-called "high to low" optical designing (R_<cry>>R_<amo>) to achieve a large reflectivity contrast (>0.7). In the case of50GB/side (25GB/laver) condition, the jitter value usine a limit eaualizer is 7.4%.
