Tetsuya AKIYAMA, Kazumi YOSHIOKA, Kazuo INOUE, Hidemi ISOMURA and Takeo OHTA

Materials and Devices Laboratory, Matsushita Electric Industrial Co., Ltd., 3-1-1 Yagumo-Nakamachi, Moriguchi, Osaka, 570 Japan

(Accepted January 10, 1995)

The overwrite cycle characteristics and environmental stability of a phase change optical disk with a new disk structure were demonstrated. The C/N ratio was around 55dB, the erase ratio was around 25dB and the phase jitter was under 50% throughout the one million cycle overwrite test. The accelerated aging test conditions were 90°C, 80%RH, for 600 hours and 70°C, 80%RH for 5,200 hours. The archival and shelf one million overwrite cycle characteristics of phase jitter were stable throughout the aging test. The life expectancy of the disk is anticipated to be more than 60 years in a 32°C, 80%RH environment.

Key words : phase change, optical disk, overwrite, overwrite cycle, thermal deformation, environmental stability, GeTe-Sb₂Te₃-Sb, SiO₂, ZnS-SiO₂