Compositions – Inorganic luminescent compositions – Zinc or cadmium containing
Reexamination Certificate
1999-06-07
2001-04-10
Koslow, C. Melissa (Department: 1755)
Compositions
Inorganic luminescent compositions
Zinc or cadmium containing
Reexamination Certificate
active
06214257
ABSTRACT:
TECHNICAL FIELD
This invention relates to electroluminescent phosphors and more particularly to methods of increasing the brightness of such phosphors.
BACKGROUND ART
Electroluminescent phosphors are materials that emit light when energized by an electric field. Such phosphors find use as night lights, watch faces, backlighting for LCD computer screens, copy machines, automotive dashboards, control switch illumination, etc. U.S. Pat. Nos. 3,076,767; 4,859,361; 5,110,499 and 5,009,808 relate to methods of producing ZnS:Cu,Cl electroluminescent phosphors; but do not address the problem of improving the brightness of the base electroluminescent phosphor. Higher brightness is an important requirement for electroluminescent phosphors, specifically where one needs higher light output with lower power consumption (i.e., low voltage applications).
DISCLOSURE OF INVENTION
It is, therefore, an object of this invention to obviate the disadvantages of the prior art.
It is yet another object of the invention to enhance electroluminescent phosphors.
Yet another object of the invention is the provision of a method for producing electroluminescent phosphors having a high brightness.
These objects are accomplished, in one aspect of the invention, by the provision of a method of increasing the brightness of an electroluminescent phosphor comprising the steps of: forming said phosphor as a base phosphor to have a given brightness; and annealing said base phosphor at a temperature and for a time sufficient to increase said given brightness of said base phosphor and form an annealed phosphor.
Brightness increases from about 8% to about 33% are available from this method.
REFERENCES:
patent: 4859361 (1989-08-01), Reilly et al.
patent: 4888129 (1989-12-01), Yale
patent: 5110499 (1992-05-01), Reilly et al.
Koslow C. Melissa
McNeill William H.
Osram Sylvania Inc.
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