Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1999-11-09
2003-05-27
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S495000, C313S473000
Reexamination Certificate
active
06570322
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a display faceplate. More particularly, the present invention relates to a phosphor screen of a field emission display, wherein a layer of phosphor of the faceplate includes a plurality of openings.
A known display faceplate or phosphor screen, or, hereinafter, anode screen, of a field emission display comprises light permeable conductive material and phosphor layered respectively over a transparent substrate. The anode screen is disposed opposite a cathode emitter plate. Electrons emitted from emitters of the cathode emitter plate impact phosphor of the anode screen and excite the phosphor into illumination by phosphorescence or fluorescence.
Through continued use, electrons accumulate on the surface of the phosphor so as to reduce a voltage potential between a cathode emitter and the phosphor in proportion to the accumulated charge. This lower voltage reduces the acceleration of electrons emitted by the opposite emitters, in turn, limiting the ability of these electrons to obtain velocity and kinetic energy sufficient to excite the phosphor on impact. As a result, image illumination “turn-off” results. This phenomenon becomes more problematic as phosphor developments lead to phosphors of improved flatness, uniformity and resistance, and this phenomenon is especially problematic for monochrome phosphor screens.
In addition to possible image illumination turn-off, some charge of the accumulation is thought to migrate through the phosphor toward an underlying electrode of the anode screen. As the charge migrates through the phosphor, it may react electrochemically with compounds of the phosphor to produce gas contaminates. These gas contaminates are believed at least partially responsible for corrosion of emitters of cathode emitter plates of field emission displays. Furthermore, the electrochemical reactions are also thought to affect the color or intensity of the phosphor's phosphorescence.
SUMMARY OF THE INVENTION
The present invention provides a new anode screen and a field emission display. Such anode screen may be known alternatively as a faceplate assembly, an anode phosphor screen, a display faceplate and the like, or simply a faceplate. The present invention recognizes and addresses some disadvantages of exemplary anode screens of the prior art, including aspects thereof, e.g., wherein a phosphor layer experiences image illumination turn-off, or wherein electrochemical reactions occur within the phosphor.
In accordance with one embodiment of the present invention, a faceplate assembly comprises phosphor layered over a substrate. Walls of the phosphor define a plurality of openings therethrough. Preferably, a light permeable conductive material is layered between the substrate and phosphor.
In accordance with one aspect of this exemplary embodiment, a group of openings of said plurality define, at least in part, a pixel region of the phosphor. Preferably, the openings of the group delimit the pixel region with a shape of a hexagon.
In accordance with another exemplary embodiment of the present invention, a monochrome field emission display comprises a cathode emitter plate with a plurality of electron emitters disposed in spaced and opposing relationship to an anode screen. The anode screen comprises a layer of phosphor that faces the plurality of emitters of the cathode emitter plate. Walls of the phosphor define a plurality of holes through the phosphor. Preferably, a group of holes of the plurality surround a pixel region of the phosphor opposite an associated emitter of the cathode emitter plate.
These and other features of the present invention will become more fully apparent in the following description and independent claims, or may be learned by the practice of the invention as set forth hereinafter.
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Howrey Simon Arnold & White , LLP
Patel Ashok
Zimmerman Glenn
LandOfFree
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