Magneto-Optical Memory Disk Using Plastic Substrate

Studies on the changes with time and temperature in the properties of magneto-optical disks employing polycarbonate (PC) substrates are reported. GdTbFe film and a protective film were deposited on injection-molded PC substrates by RF magnetron sputtering, and signals were recorded near the 140, 150, and 160 mm diameters. Disks were fabricated in two configurations, with protective film only on top of the GdTbFe (A), and with protective film both on top and underneath (B); the latter showed only small change in properties with time compared with disks of structure A. Tests of temperature characteristics also indicated that PC disks of structure B are highly stable.