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:
Dec. 05, 1995
Filed:
Sep. 14, 1994
Cheryl M Forster, Van Etten, NY (US);
Anthony F Kasenga, Towanda, PA (US);
Osram Sylvania Inc., Danvers, MA (US);
Abstract
A process for producing a manganese and lead activated calcium metasilicate phosphor having the nominal formula CaSiO.sub.3 :MN:Pb. The process involves preparing a uniform aqueous dispersion of fumed silica having an ultrafine average particle size of less than 50 nm, a calcium precursor, a manganese precursor, and a lead precursor. Preferably, the calcium, manganese, and lead precursors are added as powders to an aqueous dispersion of said ultrafine fumed silica. The ultrafine fumed silica aqueous dispersion is heated to a temperature of about 50.degree.-90.degree. C. and the powders are mechanically dispersed in the fumed silica aqueous dispersion to form the uniform aqueous dispersion. The molar ratio of calcium:silicon in the mixture is approximately stoichiometric to 1.3:1; and the molar ratios of manganese and lead in the dispersion are sufficient to activate the phosphor. The precipitate from the dispersion is calcined at a temperature of about 1050.degree.-1135.degree. C. for a time sufficient to form a manganese and lead activated calcium silicate phosphor having a peak emission in the red region of the visible spectrum when stimulated by external radiation at approximately 254 nm. The phosphor product has an average primary particle size of less than 5 .mu.m and a brightness at least equivalent to that of commercially available manganese and lead activated calcium silicate phosphors.