US05400316High density small-diameter magnetic optical disk
AssigneeSony Corporation
Assign./FiledMarch 21, 1995/ Aug. 15, 1991
InventorsIgarashi; Shuichi
SummaryCoverage of the MD substrate, and methods for molding it. By reducing double refraction the inner circumfrences of the disc are made available for recording.
AbstractA magnetic optical disc comprising a magnetic optical recording layer on a transparent substrate. The disc measures less than 80 millimeters in outer diameter and is capable of recording at least 130 megabytes of compressed digital signals. The extreme storage density of the disk is achieved by the suppression of double refraction characteristics near the center area of the disk, whereby the minimum diameter of the recording area can be made smaller. This allows a small-diameter magnetic optical disc to provide a recording area of sufficient storage capacity. In combination with a novel magnetic optical recording system, the disc may illustrative accommodate at least 60 minutes of the user's audio signals while measuring smaller than any other conventional discs of comparable storage capacity.