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:
Jan. 09, 1990
Filed:
Jan. 26, 1988
Applicant:
Inventors:
Kunio Takada, Kawasaki, JP;
Teruaki Okuda, Tokyo, JP;
Assignee:
Canon Kabushiki Kaisha, Tokyo, JP;
Attorney:
Primary Examiner:
Int. Cl.
CPC ...
B29D / ;
U.S. Cl.
CPC ...
264106 ; 264-13 ;
Abstract
In a process for producing a substrate for optical disks, first a disk-shaped substrate is formed with polycarbonate with such gradient distribution of double refraction that the value of double refraction is in a range from -10 to -30 nm in the vicinity of the external periphery of the substrate and is in a range from +10 to +30 nm in the vicinity of the center thereof, and then thus formed substrate is annealed.