Abstract A fluorescent lamp having a phosphor coating on the inside surface of the tubular glass envelope, the phosphor coating comprising finely divided phosphor particles coated with a glassy phosphate material. The lamp is prepared by providing an aqueous slurry of the phosphor particles in a solution containing a material yielding a phosphate glass upon firing, coating the interior envelope walls with the aqueous suspension, and firing the phosphor coating at a temperature which promotes the formation of the phosphate glass coating about the particulate phosphor material. A suitable phosphate glass-yielding material is ammonium dihydrogen phosphate, and phosphor coatings produced therewith have been found to have improved adherence to the envelope walls.
An aqueous suspension comprising water; finely-divided phosphor particles; a temporary organic binder which can be essentially completely removed from a lamp envelope, on which the suspension has been coated, upon firing under appropriate conditions; and a minor amount of an additive which will yield a phosphate glass coating on said phosphor particles when a lamp envelope, on which the suspension has been coated, is fired under appropriate conditions, said additive comprising a mixture of orthophosphoric acid and zinc nitrate.
Claim 2
Dependent Claim
79 words
An aqueous suspension comprising water; finely-divided phosphor particles; a temporary organic binder which can be essentially completely removed from a lamp envelope, on which the suspension has been coated, upon firing under appropriate conditions; and a minor amount of an additive which will yield a phosphate glass coating on said phosphor particles when a lamp envelope, on which the suspension has been coated, is fired under appropriate conditions, said additive comprising a mixture of orthophosphoric acid and zinc nitrate.
Claim 3
Dependent Claim
32 words
The suspension of claim 1 wherein said orthophosphoric acid and said zinc nitrate are each present in amounts such that the atomicratio of zinc to phosphorus is about 0.1 to about 0.5.
Claim 4
Dependent Claim
33 words
The suspension of claim 1 wherein about 0.002 - 0.0002 moles of said orthophosphoric acid, and 0.00004 - 0.0004 moles of said zinc nitrate are added per 100 grams of said phosphor particles.
Claim 5
Dependent Claim
33 words
The suspension of claim 1 wherein said phosphate glass-yielding additive is present in an amount from about 0.01 gram to about 0.5 gram per 100 grams of said phosphor particles in said suspension.
Claim 6
Dependent Claim
13 words
The suspension of claim 1 wherein the viscosity thereof is about 90 centipoise.