Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1996-01-16
2001-06-26
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S309000, C313S310000, C313S336000, C313S351000
Reexamination Certificate
active
06252347
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to field emission displays and manufacturing methods, and more particularly to field emission displays having focusing grids.
As is known in the art, field emission displays (FEDS) include an array of field emitting cathodes, a cathodoluminescent anode, and an array of control electrodes. Each one of the control electrodes is associated with a corresponding display pixel and controls the flow of electrons between the cathodes and the corresponding anode pixel. In a monochromatic array, each pixel corresponds to either a so-called “black” or “white” display luminescence; in a color display each pixel corresponds to a luminous blend of a plurality of, typically three colors.
In order to achieve a relatively bright display, (i.e., up to the order of 10,000 foot lamberts) with typical cathodoluminescent efficiencies, a voltage in the order of 10,000 volts is required between the cathode and anode. In order to reduce the effect of electron beam spreading and its concomitant reduction in picture resolution, cathode to anode separations of less than 3-4 millimeters are required. However, in order to prevent arcing between the anode and cathode with 10,000 volts therebetween, an anode to cathode separation in the order of 3-4 millimeters, or greater, is required. Thus, a compromise must be made between resolution and brightness.
SUMMARY OF THE INVENTION
In accordance with the present invention, a field emission display is provided having a plurality of cathodes; a cathodoluminescent anode; a plurality of control electrodes for controlling the flow of electrons between the cathodes and the anode; and a focusing grid, comprising an apertured, conductive sheet, supported in tension over the cathodes.
With such an arrangement, the focusing grid is supported substantially equidistant over the cathodes.
In accordance with another feature of the invention, the emission display including a frame and an apertured, conductive sheet having an array of apertures formed in an interior region thereof and affixed thereto to provide the focusing grid. The conductive sheet is supported at the periphery thereof by the frame with the interior portion of the conductive sheet being suspended in tension by the frame. The apertured, conductive sheet and the affixed frame provide a focusing grid assembly.
In a preferred embodiment, the field emission display includes a plurality of cathodes, an anode, a plurality of control electrodes for controlling the flow of electrons between the cathodes and the anode, and a focusing grid, comprising an apertured, conductive sheet, disposed between the anode and the plurality of cathodes. Each one of the cathodes comprises a set of field emitters. Each aperture is associated with a corresponding set of field emitters. Each aperture is disposed over the corresponding set of field emitters. The apertured, conductive sheet is supported at the periphery thereof by a frame with the interior portion of the apertured, conductive sheet suspended in tension by the frame. The apertured, conductive sheet and attached frame provide a focusing grid assembly.
In accordance with another feature of the invention, a method is provided for providing a focusing grid, comprising an apertured, conductive sheet for disposition over an array of field emitters. The method includes the steps of: providing a frame; affixing the apertured, conductive sheet to the frame while such apertured, conductive sheet is in tension; and, mounting the frame, with the tensioned, apertured, conductive sheet affixed thereto, over the array of field emitters.
In a preferred embodiment, the focusing grid is formed as a conductive sheet with the apertures formed in an interior region of the conductive sheet. A force is provided to the apertured, conductive sheet in a direction from the interior region of the sheet to an outer region to stretch the sheet into tension. With such force applied to the sheet, the sheet is affixed to the frame.
In accordance with an another feature of the invention, a method is provided for providing a focusing grid, comprising an apertured, conductive sheet, over an array of field emitters. The method includes the steps of: providing a frame; affixing the apertured, conductive sheet in tension to the frame; providing an inwardly directed force to a wall of the frame; affixing the tensioned apertured, conductive sheet to the frame when the frame has the force provided to the wall; and, mounting the frame, with the sheet affixed thereto, over the array of field emitters.
In a preferred embodiment of the invention, the method includes the steps of providing a pair of members, such pair of members providing a clamp, a first one of such members having a groove formed therein. A ring member is provided. A conductive sheet, having an array of apertures formed in an inner region thereof, has the peripheral portion thereof disposed between the groove formed in the first one of the pair of clamp members and the ring. The second one of the clamp members is placed over the ring. A force is exerted to the clamp members and, through the ring, to the sheet, the ring urging the sheet into the groove while the periphery of the sheet is fixed to the clamp to stretch the inner region of the sheet to a predetermined tensional force. The tensioned, apertured conductive sheet providing the focusing grid is then affixed to a frame.
In accordance with another feature of the invention, a method for affixing a focusing grid, comprising an apertured, conductive sheet, to a frame is provided. The method includes providing the tensioned, conductive sheet. Forcing a resilient wall of the frame to deflect the wall inwardly, placing a peripheral portion of the tensioned, apertured conductive sheet onto the deflected wall, affixing the placed sheet onto the deflected wall, and after such affixation, removing the applied force. With such arrangement, the resilient wall maintains its tension across the inner region of the sheet.
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Field Emission Displays-A 10,000 fL High-Efficiency Field Emission Display by Alan Palevsky, Gordon Gammie and P. Koufopoulos Society for Information Displays, San Jose, CA, pp. 12-17 Jun. 1994.
Berman Seth A.
Breen R. Dennis
Roach Thomas A.
Daly, Crowley & Mofford LLP
Patel Vip
Raytheon Company
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