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:
May. 11, 2004
Filed:
Mar. 28, 2001
Nikon Corporation, Tokyo, JP;
Abstract
A production method of synthetic silica glass according to the present invention comprises a first step of ejecting a silicon compound and a combustion gas containing oxygen and hydrogen from a burner to effect hydrolysis of the silicon compound in oxyhydrogen flame to produce fine particles of silica glass, and thereafter depositing and vitrifying the fine particles of silica glass on a target opposed to the burner to obtain a synthetic silica glass ingot; a second step of heating the synthetic silica glass ingot or the like obtained in the first step up to a first retention temperature of not less than 900° C., retaining the ingot or the like at the first retention temperature, and cooling the ingot or the like at a temperature decrease rate of not more than 10° C./h down to a temperature of not more than 500° C.; and a third step of heating the synthetic silica glass ingot or the like obtained in the second step up to a second retention temperature of not less than 500° C. nor more than 1100° C., retaining the ingot or the like thereat, and thereafter cooling the ingot or the like at a temperature decrease rate of not less than 50° C./h down to a temperature 100° C. lower than the second retention temperature.