US 12,112,781 B2
Optical recording medium substrate, optical recording medium, and method of manufacturing optical recording medium substrate
Hiroshi Nakayama, Miyagi (JP); Hiroyuki Takemoto, Miyagi (JP); Minoru Kikuchi, Miyagi (JP); and Minoru Matsuura, Miyagi (JP)
Assigned to SONY CORPORATION, Tokyo (JP)
Filed by SONY CORPORATION, Tokyo (JP)
Filed on Jul. 23, 2019, as Appl. No. 16/519,426.
Application 16/519,426 is a division of application No. 14/074,965, filed on Nov. 8, 2013, abandoned.
Claims priority of application No. 2012-251413 (JP), filed on Nov. 15, 2012.
Prior Publication US 2020/0051590 A1, Feb. 13, 2020
Int. Cl. G11B 7/00 (2006.01); B29C 45/00 (2006.01); B29D 17/00 (2006.01); G11B 7/2534 (2013.01)
CPC G11B 7/2534 (2013.01) [B29C 45/00 (2013.01); B29C 45/0001 (2013.01); B29D 17/005 (2013.01); Y10T 428/31507 (2015.04)] 5 Claims
OG exemplary drawing
 
1. 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.