Coating processes – Electrical product produced – Fluorescent or phosphorescent base coating
Patent
1989-11-07
1991-03-12
Morgenstern, Norman
Coating processes
Electrical product produced
Fluorescent or phosphorescent base coating
427 64, 427 67, 427 68, 4271264, 427213, 4272553, 313489, 313487, 313486, B05D 512, H01J 170
Patent
active
049992198
ABSTRACT:
Disclosed is a method for applying a continuous protective coating to the surface of individual phosphor particles. The method involves chemical vapor deposition of an aluminum oxide coating on individual particles of a phosphor powder while the particles are suspended in a fluidized bed. The particles in the fluidized bed are exposed to vaporized coating precursor material, preferably aluminum isopropoxide at a temperature above 300.degree. C. The bed is kept at as nearly an isothermal condition as possible. Prior to entering the fluidized bed the aluminum isopropoxide is vaporized and kept at a temperature less than the decomposition temperature of aluminum isopropoxide. Mechanical means are used to help increase the fluidization efficiency of the fluidized bed. After coating the phosphor particles for approximately 30 minutes the vaporized precursor material is shut off from the bed entrance and the oxygen flow rate to the fluidized bed is increased. This carbon reduction step last for approximately 15 minutes. The coating step and carbon reduction step can be repeated to increase the thickness of the aluminum oxide coating on the phosphor particles.
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Gary Richard A.
Klinedinst Keith A.
GTE Laboratories Incorporated
King Roy V.
Morgenstern Norman
Ruoff Carl F.
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