Electric lamp and discharge devices: systems – Plural power supplies – Plural cathode and/or anode load device
Reexamination Certificate
2001-12-19
2003-05-27
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Plural power supplies
Plural cathode and/or anode load device
C315S169400, C313S485000, C313S506000, C313S582000
Reexamination Certificate
active
06570339
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention pertains to the field of plasma display panels. More particularly, the invention pertains to using glass structures, such as fiber, to construct a color plasma display panel.
2. Description of Related Art
Plasma display panels (PDP) have been around for about 30 years, however they have not seen widespread commercial use. The main reasons are the short lifetime, low efficiency, and cost of the color plasma displays. Most of the performance issues were solved with the invention of the three electrode surface discharge AC plasma display (G. W. Dick, “Three-Electrode per PEL AC Plasma Display Panel”, 1985 International Display Research Conf., pp. 45-50; U.S. Pat. Nos. 4,554,537, 4,728,864, 4,833,463, 5,086,297, 5,661,500, and 5,674,553). The new three electrode surface discharge structure, shown in
FIG. 1
, advances many technical attributes of the display, but its complex manufacturing process and detailed structure makes manufacturing complicated and costly.
Currently, plasma display structures are built up layer by layer on specialty glass substrates using many complex processing steps.
FIG. 1
illustrates the basic structure of a surface discharge AC plasma display made using standard technology. The PDP can be broken down into two parts: top plate
10
and bottom plate
20
. The top plate
10
has rows of paired electrodes referred to as the sustain electrodes
11
a
,
11
b
. The sustain electrodes are composed of wide transparent indium tin oxide (ITO) electrodes
12
and narrow Cr/Cu/Cr bus electrodes
13
. These electrodes are formed using sputtering and multi-layer photolithography. The sustain electrodes
11
are covered with a thick (25 &mgr;m) dielectric layer
14
so that they are not exposed to the plasma. Silk-screening a high dielectric paste over the surface of the top plate and consolidating it in a high temperature process step forms this dielectric layer
14
. A magnesium oxide layer (MgO)
15
is deposited by electron-beam evaporation or sputtering over the dielectric layer to enhance secondary emission of electrons and improve display efficiency. The bottom plate
20
has columns of address electrodes
21
formed by silk-screening silver paste and firing the paste in a high temperature process step. Barrier ribs
22
are then formed between the address electrodes
21
. These ribs
22
, typically 50 &mgr;m wide and 120 &mgr;m high, are formed using either a greater than ten layer multiple silk-screening process, embossing a frit paste, or a sandblasting process. In the sandblasting method, barrier rib paste is blade coated on the glass substrate. A photoresist film laminated on the paste is patterned by photolithography. The rib structure is formed by sandblasting the rib paste between the exposed pattern, followed by removal of the photoresist layer and a high temperature consolidation of the barrier rib
22
. Alternating red
23
R, green
23
G, and blue
23
B phosphors are silk-screened into the channels between the barrier ribs to provide color for the display. After silk-screening the phosphors
23
, the bottom plate is sandblasted to remove excess phosphor in the channels. The top and bottom plates are frit sealed together and the panel is evacuated and backfilled with a gas mixture containing xenon.
The basic operation of the display requires a plasma discharge where the ionized xenon generates ultraviolet (UV) radiation. This UV light is absorbed by the phosphor and emitted as visible light. To address a pixel in the display, an AC voltage is applied across the sustain electrodes
11
, which is large enough to sustain a plasma, but not large enough to ignite one. A plasma is a lot like a transistor, as the voltage is increased nothing happens until a specific voltage is reached where it turns on. Then an additional short voltage pulse is applied to the address electrode
21
, which adds to the sustain voltage and ignites the plasma by adding to the total local electric field, thereby breaking down the gas into a plasma. Once the plasma is formed, electrons are pulled out of the plasma and deposited on the MgO layer
15
. These electrons are used to ignite the plasma in the next phase of the AC sustain electrodes. To turn the pixel off, an opposite voltage must be applied to the address electrode
21
to drain the electrons from the MgO layer
15
, thereby leaving no priming charge to ignite the plasma in the next AC voltage cycle on the sustain electrodes. Using these priming electrons, each pixel can be systematically turned on or off. To achieve gray levels in a plasma display, each video frame is divided into 8 bits (256 levels) and, depending on the specific gray level, the pixels are turned on during these times.
A number of methods have been proposed to create the structure in a plasma display, such as thin and thick film processing, photolithography, silk screening, sand blasting, and embossing. However, none of the structure forming techniques provides as many advantages as using fibers. Small hollow tubes were first used to create structure in a panel by W. Mayer, “Tubular AC Plasma Panels,” 1972 IEEE Conf. Display Devices, Conf. Rec., New York, pp. 15-18, and R. Storm, “32-Inch Graphic Plasma Display Module,” 1974 SID Int. Symposium, San Diego, pp. 122-123, and included in U.S. Pat. Nos. 3,964,050 and 4,027,188. These early applications were focused on using an array of gas filled hollow tubes to produce the rib structure in a plasma display panel. In addition, this work focused on adding the electrode structure to the glass plates that sandwiched the gas filled hollow tubes.
Since this early investigation, no further work was published on further developing a fiber or tube technology until C. Moore and R. Schaeffler, “Fiber Plasma Display”, SID '97 Digest, pp. 1055-1058. This work integrated the wire electrode(s) into glass fibers to produce the structure in a display, as shown in FIG.
2
. U.S. Pat. No. 5,984,747, issued Nov. 16, 1999, entitled “GLASS STRUCTURES FOR INFORMATION DISPLAYS”, was granted covering this technology. Another fiber-based plasma display patent application, Ser. No. 09/299,370, filed on Apr. 26, 1999, entitled “FIBER-BASED PLASMA DISPLAYS”, covers many different additions to the structure in the fiber-based plasma display and is incorporated herein by reference. The manufacturing of the plasma display covered under U.S. Pat. No. 6,247,987, issued Jun. 19, 2001, entitled “PROCESS FOR MAKING ARRAY OF FIBERS USED IN FIBER-BASED
DISPLAYS”, and patent application, Ser. No. 09/299,371, filed Apr. 26, 1999, entitled “FRIT-SEALING PROCESS USED IN MAKING DISPLAYS”, allow for the manufacturing of any multiple strand arrayed plasma display and are incorporated herein by reference.
There are several advantages to creating plasma displays using arrays of fibers. The largest advantage is a reduction in the manufacturing costs of the panel of over a factor of two with a five times less capital cost requirement. These economical advantages result from manufacturing process with no multi-level alignment process steps, no need for large area vacuum deposition equipment, about ½ the process steps (potentially leading to higher yields), simpler process steps (hot glass extrusion, fiber draw, and phosphor spraying compared to photolithography, precision silk screening, and vacuum deposition processes) and the ability to create many different size displays using the same manufacturing equipment. Although using fibers to create the structure in a display has drastically simplified the manufacturing of the panel leading to a large reduction in manufacturing cost, there have been no advancements to the performance of the display. Plasma displays still suffer from low luminous efficiencies and poor color purity, mainly due to a lack of blue phosphor. NEC Corporation has been fabricating plasma displays using a color filter contained within the top plate and aligning the color filter with the corresponding phosphor colors in the bottom plate, as described in U.S.
Brown & Michaels PC
Tran Thuy Vinh
Wong Don
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