Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2000-05-01
2003-02-04
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S309000, C313S310000, C313S336000, C313S34600R, C313S351000
Reexamination Certificate
active
06515414
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to field emission displays, and more particularly to the formation of low work function emitters.
The required turn-on voltage for an emitter at a constant current is a function of the work function of the material at the surface of the emitter. For example, see U.S. Pat. No. 4,325,000, issued Apr. 13, 1982, incorporated herein by reference, and Michaelson, H. B. “Relation Between An Atomic Electronegativity Scale and the Work Function,” 22 IBM Res. Develop., No. 1, January 1978. Reduction of the work function of a material can be achieved by coating the surface with an electropositive element. For example, see U.S. Pat. No. 5,089,292, incorporated herein by reference. However, such knowledge has never been translated into a useful field emission display. Electropositive materials are very reactive, and, therefore, upon coating on an emitter, they quickly begin to react with most atmospheres, resulting in a high work function material coating the emitter. Accordingly emitters coated with low work function materials on the surface have traditionally not been useful. Also, the compositions in which electropositive elements normally exist (for example, as a salt with Cl) include elements that have a very large work function (e.g. Cl).
The present invention provides solutions to the above problems.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a field emission display is provided comprising: an anode; a phosphor located on the anode; a cathode; an evacuated space between the anode and the cathode; an emitter located on the cathode opposite the phosphor; wherein the emitter comprises an electropositive element both in a body of the emitter and on a surface of the emitter.
According to another aspect of the invention a process for manufacturing an FED is provided comprising the steps of: forming an emitter comprising an electropositive element in the body of the tip; positioning the emitter in opposing relation to a phosphor display screen; creating an evacuated space between the emitter tip and the phosphor display screen; and causing the electropositive element to migrate to the an emission surface of the emitter.
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Cathey David A.
Chadha Surjit S.
Moradi Behnam
Hale and Dorr LLP
Patel Vip
Quarterman Kevin
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