INJECTION-MOLDED SUBSTRATE FOR INFORMATION RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To provide a thin injection-molded substrate for information recording medium which hardly give rise to a warpage deformation and has a high strength and a small retardation. SOLUTION: A region T1 where the thickness of the substrate is smallest and a region T2 provided with a stack ring 4 are made overlap each other in the radial direction by formation of the annular groove.