Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
2001-12-12
2004-05-11
Patel, Nimeshkumar D. (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S310000, C445S024000
Reexamination Certificate
active
06734620
ABSTRACT:
FIELD OF USE
This invention relates to electron-emitting devices. More particularly, this invention relates to the structure and fabrication, including repair, of an electron-emitting device suitable for use in a flat-panel display of the cathode-ray tube (“CRT”) type.
BACKGROUND
A flat-panel CRT display basically consists of an electron-emitting device and a light-emitting device that operate at low internal pressure. The electron-emitting device, commonly referred to as a cathode, contains electron-emissive regions that selectively emit electrons over a relatively wide area. The emitted electrons are directed towards light-emissive regions distributed over a corresponding area in the light-emitting device. Upon being struck by the electrons, the light-emissive regions emit light that produces an image on the viewing surface of the display.
The electron-emissive regions are often situated over generally parallel emitter electrodes. In an electron-emitting device of the field-emission type, generally parallel control electrodes cross over, and are electrically insulated from, the emitter electrodes. The electron-emissive regions typically consist of electron-emissive elements exposed through openings in the control electrodes. When a suitable voltage is applied between a control electrode and an emitter electrode, the control electrode extracts electrons from the associated electron-emissive region. An anode in the light-emitting device attracts the electrons to the light-emitting device.
Short circuits sometime occur between the control electrodes, on one hand, and the emitter electrodes, on the other hand. The presence of a short circuit can have a highly detrimental effect on display performance. For example, a short circuit at the crossing between a control electrode and an emitter electrode can prevent the associated electron-emissive region from operating properly.
International Patent Publications WO 98/54741 (Spindt et al) and WO 99/56299 (also Spindt et al) describe field-emission flat-panel CRT displays in which the emitter and control electrodes of the electron-emitting devices are configured in various ways to facilitate repairing control-electrode-to-emitter-electrode short-circuit defects. While the electron-emitting devices of International Patent Publications WO 98/54741 and WO 99/56299 present various advantages, the capacitance at each location where one of the control electrodes crosses over one of the emitter electrodes can cause the devices to have unsuitably low switching speeds. It is desirable to configure the emitter or/and control electrodes in such a way that the control-electrode-to-emitter-electrode cross-over capacitance can be reduced so as to increase the switching speed while still facilitating control-electrode-to-emitter-electrode short-circuit repair.
GENERAL DISCLOSURE OF THE INVENTION
The present invention furnishes an electron-emitting device, especially one suitable for use in a flat-panel CRT display, in which a specified portion of an electrode, either a control electrode or an emitter electrode, is situated off to the side of the bulk of the electrode. In the case of the control electrode, the specified portion is an exposure portion having openings that expose electron-emissive elements situated over an emitter electrode. In the case of an emitter electrode, the specified portion is an emitter-coupling portion situated below an electron-emissive element exposed through an opening in the control electrode. By having the specified portion of the electrode situated away from the bulk of the electrode, the control-electrode-to-emitter-electrode cross-over capacitance can be made quite small. Should the specified portion of the electrode be electrically short circuited to the other electrode, the specified portion can be readily severed from the remainder of its electrode to remove the short-circuit defect.
More particularly, an electron-emitting device configured in accordance with one aspect of the invention contains an emitter electrode, an electron-emissive region, and a control electrode. The emitter electrode extends longitudinally in a first lateral direction. The electron-emissive region has an electron-emissive zone in which a multiplicity of electron-emissive elements are situated over part of the emitter electrode.
The control electrode consists at least of a rail, an intersection portion, an exposure portion, and a linkage portion. The rail crosses over the emitter electrode and extends longitudinally in a second lateral direction different from the first lateral direction. The intersection portion is continuous with the rail and extends laterally away from it. The exposure portion largely overlies the electron-emissive region and has a multiplicity of openings through which the electron-emissive elements are exposed. The linkage portion extends between, and thereby electrically connects, the intersection and exposure portions.
At least part of the linkage portion of the control electrode is normally situated lateral, i.e., to the side as viewed vertically, of the emitter electrode. The intersection portion of the control electrode is also normally situated lateral to the emitter electrode. As a result, largely only the rail and the exposure portion of the control electrode are situated above the emitter electrode. In as much as the cross-over capacitance between a control electrode and an emitter electrode depends (in part) on the amount of area where the control electrode overlies the emitter electrode, configuring the control electrode in the foregoing way enables the present electron-emitting device to have a very low control-electrode-to-emitter-electrode cross-over capacitance. Accordingly, the switching speed of the electron-emitting device is enhanced, and its power consumption is reduced.
In the course of manufacturing an electron-emitting device configured according to the invention's teaching, the device can be examined to determine whether the control electrode appears to be short circuited to the emitter electrode at the exposure portion. If so, a cut is made through the linkage portion to electrically separate the exposure portion from the remainder of the control electrode, specifically from the rail and intersection portion. Although the cut causes the exposure portion to become inoperative (disabled), an electron-emitting device having many such exposure portions can often perform adequately when a small number of the exposure portions are inoperative. In such a case, removal of the short-circuited exposure portion repairs the device.
The short-circuit repair operation at the exposure portion of the control electrode is normally done by directing light on the linkage portion of the control electrode. With at least part of the linkage portion being situated lateral to the emitter electrode, the light is typically directed on a part of the exposure portion not vertically in line with the emitter electrode. This enables the short-circuit defect to be removed without significantly affecting the emitter electrode. The configuration of the control electrode thereby facilitates repairing a short-circuit defect between the emitter electrode and the control electrode's exposure portion.
In one variation of the present electron-emitting device, the control electrode includes a further rail extending longitudinally in the second lateral direction and thus generally parallel to the first-mentioned rail. The intersection portion of the control electrode is continuous with, and extends laterally away from, the further rail so as to be at least partially located between the two rails. The exposure portion is normally situated between the rails.
Use of two rails provides redundancy that enables certain defects involving the rails to be overcome. For instance, if a segment of one of the rails becomes short circuited to the emitter electrode, the short-circuited segment of that rail can be severed from the remainder of the rail and thus from the remainder of the control electrode. Current that would otherwise flow th
Bonn Matthew A.
Fahlen Theodore S.
Kemmotsu Hidenori
Radigan Steven J.
Candescent Technologies Corporation
Guharay Karabi
Meetin Ronald J.
Patel Nimeshkumar D.
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