The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jul. 16, 1996
Filed:
Oct. 21, 1993
Applicant:
Inventors:
Tsuneo Kuwahara, Saku, JP;
Noriyasu Akashio, Saku, JP;
Assignee:
TDK Corporation, Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
B29D / ; B29D / ;
U.S. Cl.
CPC ...
264-133 ; 29406 ; 156 731 ; 264248 ; 2643281 ; 360135 ; 369282 ; 425810 ;
Abstract
Resin, typically polycarbonate is injection molded into a disc substrate under select conditions, for example, at a mold temperature of 100-160.degree. C., an injection velocity of 100-120 g/sec., and a pressure of 10-60 kg/cm.sup.2, such that the birefringence of a radially inner portion of the substrate is higher by about 15-50 nm than the remaining substrate. A center hole is perforated in the substrate and a hub is attached to the substrate around the center hole. At the end of hub attachment, the substrate has a uniform distribution of birefringence over the entire area. Any increase of DC modulation is thus avoided.