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:
Nov. 23, 1999
Filed:
Sep. 15, 1998
Tatsuhiro Sato, Takefu, JP;
Shigeo Mizuno, Takefu, JP;
Mitsuo Matsumura, Takefu, JP;
Hiroyuki Watanabe, Takefu, JP;
Shin-Etsu Quartz Products Co., Ltd., Tokyo, JP;
Heraeus Quarzglas GmbH, Hanau, DE;
Abstract
A large diameter quartz crucible with an inner diameter of 22 inches or more comprises an opaque silica glass outer layer having bubbles of 10 .mu.m to 250 .mu.m in diameter and 5 mm to 20 mm in thickness and a transparent silica glass inner layer having 0.5% or less in a bubble content and 0.3 mm or more in thickness which is molten and integrated with an inner surface of the outer layer. The outer layer has an OH group concentration of 80 ppm or less and the gas pressure in a bubble in the outer layer is lower than atmospheric pressure so that a volume expansion ratio of the bubble is minimized when being heated in condition of pulling a single crystal.