Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Utility Patent
1998-06-01
2001-01-02
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
C501S032000
Utility Patent
active
06168490
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a plasma display device and method of making the same, and, more particularly, to a plasma display in which the back panel is made of a metal core having layers of a dielectric material thereon and metal electrodes on and between the dielectric layers.
BACKGROUND OF THE INVENTION
A typical plasma display includes a front panel and a back panel both made of sheet glass (e.g. conventional float-glass). Electrical connections and mechanical structures are formed on one or both of the panels. For example, the back panel may have a ribbed structure formed on it such that the space between the ribs defines a single color pixel in a direct current (DC) display or column of single color pixels in an alternating current (AC) display. The color display pixel consists of three color pixels (red, green and blue). The ribs prevent optical cross-talk, that is to say, color from one pixel leaking into an adjacent pixel. Fabrication of these ribbed structures, called barrier ribs, poses a challenge both in the materials and manufacturing techniques that are used.
Plasma displays operate by selectively exciting an array of glow discharges in a confined rarefied noble gas. Full color displays are made by generating a glow discharge in a mixture of gases, such as He—Xe or Ne—Xe gas mixture to produce ultraviolet light. The ultraviolet light excites phosphors in the pixel cell, as defined by the barrier ribs, to produce light of desired color at the pixel position.
A typical plasma display back panel comprises a glass substrate having a plurality of substantially parallel, spaced first electrodes on a surface thereof. In AC displays, a thin layer of a dielectric material, such as a glass, may cover the electrodes. Barrier ribs are formed on the surface of the glass substrate between the first electrodes. The barrier ribs project from the surface of the substrate at a distance greater than the thickness of the first electrodes. Red, green and blue (R-G-B) phosphor layers overlie alternating columns of the first electrodes in the spaces between the barriers and also may overlie the walls of the barriers. A front transparent glass substrate, the front panel, with horizontal transparent electrodes overlies the rear panel and may rest on the barrier ribs so as to be spaced from the rear glass substrate by the barrier ribs.
Typically, the barrier ribs are walls which define troughs or channels on the back panel. Alternating current (AC) plasma displays typically have barriers that form the separators for the column pixels, and hence, have continuous vertical ribs on the back plate. By contrast, direct current (DC) plasma displays typically have ribbed barriers which isolate each single color pixel from all of its neighbors. Thus, for DC displays, the rib structure has a rectangular lattice-like layout. In either case, the desired resolution for the display device and its size determine the size of the ribbed barriers. In a typical display, the ribs are 0.1 to 0.2 mm in height, 0.03 to 0.2 mm wide and on a 0.1 to 1.0 mm pitch.
These barrier ribs may be formed separately from the back plate and attached using an adhesive or, as set forth in U.S. Pat. No. 5,674,634 to Wang et al., the barriers may be formed on the back plate by laminating a ceramic green tape to the back plate, sandblasting the green tape to form the channels between the barriers and then firing the back plate in a kiln to convert the green tape barriers into ceramic barriers.
The front panel includes an array of substantially parallel, spaced second electrodes on its inner surface. These second electrodes extend substantially orthogonally to the first electrodes. A layer of a dielectric material, typically glass, covers the second electrodes. A layer of MgO covers the dielectric layer. Voltages applied to the electrodes in the proper manner excite, maintain and extinguish a plasma in the gas within the region formed by the barriers. Addressing of individual pixels is done using external circuitry at the periphery of the panel. Barrier structures are typically used to confine the discharge to the addressed pixel, eliminating both electrical and optical cross talk between adjacent pixel elements. The columns of pixels are separated by the barriers, and the first electrodes are arranged beneath the gaps between the barriers. In a DC plasma display, the electrodes are not covered with glass or MgO, and the barrier structures are typically crossed, providing a box-like structure at each pixel element.
Although the structure described above provides a plasma display having satisfactory operating conditions, it does not solve certain problems. One problem arises from the fact that the materials used to form the back panel are desirably mutually compatible and compatible with the glass plate used for the front panel. In particular for the case of the metal-ceramic composite used as the back panel, the thermal expansion coefficient of the ceramic formed from the green tape should match the thermal expansion coefficient of the metal backing of the back panel and the thermal expansion coefficient of the composite back panel should match that of the front panel glass. This is to prevent the breaking of the seal which secures the back panel to the front panel during its operation.
SUMMARY OF THE INVENTION
The invention is a method for forming a back panel for a plasma display device comprising the steps of preparing a green ceramic tape which has a temperature coefficient of expansion (TCE) which matches the TCE of a metal core; cutting the prepared green tape to form a plurality of green tape blanks; laminating the green tape blanks; embossing the laminated green tape using an embossing die by applying pulsed pressure to the embossing die to form barrier ribs on the green tape ceramic; and cofiring the bonded formed green ceramic tape and metal core to form the back panel.
The invention is also a back panel for a plasma display device comprising a metallic core having a temperature coefficient of expansion (TCE); a ceramic structure bonded to the metallic core, the ceramic structure having a TCE that matches the TCE of the metallic core, the ceramic structure having a formulation a Glass
1
between about 92 and 95 percent weight and Forsterite between about 5 and 8 percent weight, wherein Glass
1
has a formulation defined by percent weight as ZnO between about 15 and 50 percent weight, MgO between about 10 and 45 percent weight, B
2
O
3
between about 5 and 30 percent weight, and SiO
2
between about 10 and 45 percent weight.
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Hozer Leszek
Palit Kalipada
Prabhu Ashok Narayan
Quinn Robert L.
Sreeram Attiganal Narayanaswamy
Burke William J.
Ramsey Kenneth J.
Sarnoff Corporation
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