| 摘要 |
PROBLEM TO BE SOLVED: To provide an optical disc, which has a favorable recording reproducing characteristics by recording reproducing device, by which a laser beam having a wavelength of about 780nm is employed and which has a linear speed of 2.4-2.8m/s. SOLUTION: This optical disc is equipped with a first dielectric layer 3 having the film thickness of 100-120nm, a recording layer 4 made of GeSbTe- based material, which reversibly changes between a crystalline state and a amorphous state, and having the film thickness of 18-25nm, a second dielectric layer 5 having the film thickness of 15-45nm and a reflecting layer 6 having the film thickness of 30-200nm laminated to one another in the order named on a transparent base 2. The recording layer 4 of this optical disc 1 has a compositional rate, while is represented by a point within a region surrounded by predetermined first, second, third and fourth points in a GeSbTe ternary phase diagram. Further, signals are written by a laster beam having the wavelength of 780nm at the linear speed of 2.4-2.8m/s in this recording layer 4. |
