US Patent 7803443 Optical disk including a sulfuration suppressing dielectric film

A phase change optical disk includes a first dielectric film, a recording film, a second dielectric film and a reflecting film which are consecutively formed on a substrate. The second dielectric film includes therein a zinc sulfide at a rate of 10 to 40 mol % and a tantalum oxide at a rate of 20 to 50 mol %, for preventing sulfuration of Ag in the reflecting film.