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. 17, 1995
Filed:
Feb. 25, 1994
Salvatore A Bruno, Wilmington, DE (US);
Donald K Swanson, Wilmington, DE (US);
E. I. Du Pont de Nemours and Company, Wilmington, DE (US);
Abstract
The present invention relates to a novel cost efficient luminescent composition comprising particles of a core material which have been coated with a luminescent material that is distributed in the form of a chemically homogeneous layer. The average diameter of the core particle is in the range of from about 0.5 to 20 microns, and the coating corresponds to between about 2 and 30 wt % of the total composition. One aspect the invention relates to a process for preparing the composition which comprises decomposing chelated metal luminescent compositions in solution at a relatively high pH while in the presence of dispersed core particles, thereby coating the core particles with hydrous metal oxides, recovering the coated particles, optionally washing the coated particles substantially free from soluble species, drying and calcining. In another aspect, a hydrous oxide coating is converted to a sulfide coating by treating the hydrous coating with a source of active sulfur. In yet another aspect, the invention relates to adding an acidic solution of metal oxides along with a solution of oxalic acid to a slurry of dispersed core particles which become coated with the metal oxalates, recovering the product, washing the coated particles substantially free from soluble species, drying the oxalate composition. In a further aspect of the invention, the core material and metal oxalate powders can be dry mixed and calcined at a temperature high enough to induce at least a portion of the oxalate to form a phosphor coating over the surface of the core particles.