Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Patent
1993-06-01
1997-07-01
Le, H. Thi
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
313364, 313463, 313467, 428404, 428702, 428917, B32B 900, H01J 2900
Patent
active
056436742
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 precursors 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, 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 cause the oxalate to form a phosphor coating over the surface of the core particles.
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Bruno Salvatore Anthony
Swanson Donald Keith
E. I. Du Pont de Nemours and Company
Le H. Thi
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