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US 12,112,781 B2Granted
Optical recording medium substrate, optical recording medium, and method of manufacturing optical recording medium substrate
AssigneeSony Corporation
InventorsHiroshi Nakayama, Hiroyuki Takemoto, Minoru Kikuchi, Minoru Matsuura
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Abstract
There is provided an optical recording medium substrate including a polycarbonate in which an average molecular weight is in a range from 15000 to 16000, and mass per unit volume at 25° C. is in a range from 1.1930 g/cm3 to 1.2000 g/cm3.
Claims5
A method of manufacturing an optical recording medium substrate, comprising:
- forming the optical recording medium substrate by a polycarbonate in which an average molecular weight is in a range from 15000 to 16000 in a mold;
- setting a cooling time of the polycarbonate in the mold to 6 seconds or more to control a density of the polycarbonate in a range of 1.1930 g/cm3 (gram/cubic centimeter) to 1.2000 g/cm3 at 25° C. (Celsius);
- and
- performing cooling in the mold for the set cooling time, wherein a warpage of the optical recording medium substrate is 0.28 degrees or less in a region where the density of the polycarbonate is above 1.1930 g/cm3 at 25° C.
1 more element
Dependencies are inferred from the claim text.