Coating processes – Particles – flakes – or granules coated or encapsulated – Inorganic base
Patent
1989-10-27
1990-09-11
Cooper, Jack
Coating processes
Particles, flakes, or granules coated or encapsulated
Inorganic base
2523015, 2523016F, 4273722, C09K 1159
Patent
active
049562029
ABSTRACT:
A method for producing manganese activated zinc silicate phosphor wherein the individual phosphor particles are surrounded with a non-particulate, conformal aluminum oxide coating is disclosed. The method comprises dry blending a mixture of components consisting essentially of zinc oxide, silicic acid, a source of manganese, ammonium chloride, ammonium fluoride, tungstic oxide, and silica, wherein the Zn+Mn/Si mole ratio is from about 1.95 to about 2.02, wherein the silica is colloidal and has a surface area of from about 50 to about 410 m.sup.2 per gram, and wherein the colloidal silica makes up from about 0.01% to about 1.0% by weight of the mixture; firing the resulting dry blend of components in a nitrogen atmosphere at a temperature of from about 1200.degree. C. to about 1300.degree. C. for a sufficient time to produce the phosphor; milling the resulting phosphor for a period of time of from about 60 minutes to about 120 minutes; firing the resulting milled phosphor in air at a temperature of from about 1175.degree. C. to about 1275.degree. C. for a sufficient time to diffuse the tungsten and manganese to the surfaces of the phosphor particles; applying a non-particulate, conformal aluminum oxide coating to the outer surface of individual particles of the phosphor while the phosphor particles are suspended in a fluid bed having a midpoint temperature between 400.degree. and 480.degree. C., the aluminum oxide coating being formed by a chemical vapor deposition reaction involving oxidation of trimethyl aluminum; and annealing the aluminum oxide coated phosphor for a period of time from 4-16 hours at a temperature between 750.degree. and 800.degree. C.
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Hunt Roger B.
Kasenga Anthony F.
Peters Thomas E.
Sigai A. Gary
Cooper Jack
Finnegan Martha Ann
GTE Laboratories Incorporated
GTE Products Corporation
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