OPTICAL DISK SUBSTRATE AND ITS PRODUCTION

摘要

PURPOSE: To increase the information quantity which can be stored in the same area by arranging plural data tracks into the respective regions of the lands and grooves of an optical disk. CONSTITUTION: Rugged patterns 31 are arranged on the extension lines of slopes 51 of guide grooves. An example in which two pieces of data tracks exist in one guide groove or in the inter-groove region is illustrated. The case where one tracking spot 51 and two spots 53 for data are made into a set is illustrated. The number of the spots 52 for data may be >=3. The tracking spot 52 has a function to execute positioning of an optical head while the rugged patterns 31 are reproduced. The recording and reproducing of arbitrary data are executed by the spots 53 for data. A stamper replica is produced by an ordinary process from a master disk completed by exposing and developing patterns of a track pitch of 2.4μm and first guide groove width of 1.2μm. A reflection film of alumina, etc., is deposited on this replica substrate and the two data tracks are formed in the one guide groove by the two light spots.