Phase-change optical disk

Abstract

A phase-change optical disk includes a first dielectric layer, reflecting layer, first interface layer, recording layer, second interface layer, second dielectric layer, and light-transmitting layer sequentially formed on a support substrate. Information is written on, read from, and erased from the phase-change optical disk by changing a crystalline state of the recording layer with a laser beam radiated from a light-transmitting layer side. A disk reflectance Rc obtained when the recording layer is in a crystalline state is not less than 3% and not more than 12%. A difference in absolute value between the disk reflectance Rc and a disk reflectance Ra which is obtained when the recording layer is in an amorphous state is not less than 10%. A refractive index of one of the first and second interface layers for the laser beam with a wavelength λ is higher than 2. The reflecting layer contains, as a main component, either one of one element selected from the group consisting of silver, copper, titanium, and nickel and a mixture of at least two elements selected from the group consisting of silver, cupper, titanium, and nickel.

Dependencies are inferred from the claim text.