Coating processes – Particles – flakes – or granules coated or encapsulated – Fluidized bed utilized
Reexamination Certificate
2000-06-01
2001-10-30
Kiliman, Leszek (Department: 1773)
Coating processes
Particles, flakes, or granules coated or encapsulated
Fluidized bed utilized
C427S064000, C427S068000, C427S070000, C427S215000, C427S255290, C428S403000, C428S404000
Reexamination Certificate
active
06309700
ABSTRACT:
TECHNICAL FIELD
This invention relates to coated particles and more particularly to particles having a conformal coating thereon. More particularly, this invention relates to phosphors and still more particularly to electroluminescent phosphors having thereon a coating that protects the phosphor from moisture absorption and greatly increases the life and efficacy.
BACKGROUND ART
Coated phosphors are known from U.S. Pat. Nos. 4,585,673; 4,825,124; 5,080,928; 5,118,529; 5,156,885; 5,220,243; 5,244, 750; and 5,418,062. It is known from some of the just-mentioned patents that a coating precursor and oxygen can be used to apply a protective coating. See, for example, U.S. Pat. Nos. 5,244,750 and 4,585,673. The coating processes in several of the others of these patents employ chemical vapor deposition to apply a protective coating by hydrolysis. It would be an advance in the art if a coating process could be developed that operated in the absence of water or water vapor. It would be a further advance to increase the efficacy and the life of such coated phosphors.
DISCLOSURE OF INVENTION
It is, therefore, an object of the invention to obviate the disadvantages of the prior art.
It is another object of the invention to enhance the operation of coated phosphors.
Yet another object of the invention is the provision of a phosphor coating method that does not employ water or water vapor,
These objects are accomplished, in one aspect of the invention, by a method of coating phosphor particles that comprises the steps of introducing an inert gas into a reaction vessel; charging phosphor particles into said reaction vessel while preferably agitating same; heating said reaction vessel to a reaction temperature; introducing a coating precursor into said reaction vessel; introducing an oxygen/ozone mixture into said reaction vessel; and maintaining said inert gas flow, oxygen/ozone mixture flow and precursor supply for a time sufficient to coat said phosphor particles. This process yields phosphors with a conformal coating thereon that substantially eliminates moisture absorption and provides a phosphor having a half-life of upwards of 3100 hours with efficacy's of greater than 6 lumens per watt (lm/w). Additionally, the process is accomplished in the absence of water or water vapor.
BEST MODE FOR CARRYING OUT THE INVENTION
REFERENCES:
patent: 4585673 (1986-04-01), Sigai
patent: 4825124 (1989-04-01), Sigai
Benjamin Dale E.
Dang Tuan Anh
Fan Chen-Wen
Gingerich Richard G. W.
Kiliman Leszek
McNeill William H.
Osram Sylvania Inc.
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