This invention relates to a gas discharge plasma device wherein an ionizable gas is confined within an enclosure and is subjected to sufficient voltage(s) to cause the gas to discharge. This invention particularly relates to the use of hollow microspheres containing ionizable gas in a plasma display panel (PDP).
In a gas discharge plasma display, a single addressable picture element is a cell, sometimes referred to as a pixel. The cell or pixel element is defined by two or more electrodes positioned in such a way, so as to provide a voltage potential across a gap containing an ionizable gas. When sufficient voltage is applied across the gap, the gas discharges and produces light. In an AC gas discharge plasma display, the electrodes at a cell site are coated with a dielectric and insulated from the gas. In a DC gas discharge display, one or more electrodes is in direct contact with the gas. The electrodes are generally grouped in a matrix configuration to allow for selective addressing of each cell or pixel.
To form a display image, several types of voltage pulses may be applied across a plasma display cell gap. These pulses include a write pulse, which is the voltage potential sufficient to ionize the gas at the pixel site. A write pulse is selectively applied across selected cell sites. Sustain pulses are a series of pulses that produce a voltage potential across pixels to maintain ionization of cells previously ionized. An erase pulse is used to selectively extinguish ionized pixels.
The voltage at which a pixel will ionize, sustain, and erase depends on a number of factors including the distance between the electrodes, the composition of the ionizing gas, and the pressure of the ionizing gas. Also of importance is the dielectric composition and thickness. To maintain uniform electrical characteristics throughout the display it is desired that the various physical parameters adhere to required tolerances. Maintaining the required tolerance depends on cell geometry, fabrication methods, and the materials used. The prior art discloses a variety of plasma display structures, a variety of methods of construction, and a variety of materials.
Examples of AC gas discharge (plasma) devices contemplated in the practice of this invention include both monochrome (single color) AC plasma displays and multicolor (two or more colors) AC plasma displays.
Examples of monochrome AC gas discharge (plasma) displays contemplated in the practice of this invention are well known in the prior art and include those disclosed in U.S. Pat. Nos. 3,559,190 (Bitzer et al.), 3,499,167 (Baker et al.), 3,860,846 (Mayer), 3,964,050 (Mayer), 4,080,597 (Mayer), 3,646,384 (Lay), and 4,126,807 (Wedding), all incorporated herein by reference.
Examples of multicolor AC plasma displays contemplated in the practice of this invention are well known in the prior art and include those disclosed in U.S. Pat. Nos. 4,233,623 (Pavliscak), 4,320,418 (Pavliscak), 4,827,186 (Knauer et al.), 5,661,500 (Shinoda et al.), 5,674,553 (Shinoda et al.), 5,107,182 (Sano et al.), 5,182,489 (Sano), 5,075,597 (Salavin et al.), 5,742,122 (Amemiya et al.), 5,640,068 (Amemiya et al.), 5,736,815 (Amemiya), 5,541,479 (Nagakubi), 5,745,086 (Weber), and 5,793,158 (Wedding), all incorporated herein by reference.
In addition, this invention may be practiced in a DC gas discharge (plasma) display, for example as disclosed in U.S. Pat. Nos. 3,886,390 (Maloney et al.), 3,886,404 (Kurahashi et al.), 4,035,689 (Ogle et al.), and 4,532,505 (Holz et al.), all incorporated herein by reference.
In the practice of this invention, the microspheres may be used with any plasma display panel (PDP) structure. The PDP industry has used two different AC plasma display panel (PDP) structures, the two-electrode columnar discharge structure and the three-electrode surface discharge structure.
The two-electrode columnar discharge display structure is disclosed in U.S. Pat. Nos. 3,499,167 (Baker et al.) and 3,559,190 (Bitzer et al.) The two-electrode columnar discharge is also referred to as opposing electrode discharge, twin substrate discharge, or co-planar discharge. In the two-electrode columnar discharge AC plasma display structure, the sustaining voltage is continuously applied between an electrode on a rear or bottom substrate and an opposite electrode on the front or top viewing substrate. The gas discharge takes place between the two opposing electrodes in between the top viewing substrate and the bottom substrate.
The columnar discharge structure has been widely used in monochrome AC plasma displays that emit orange or red light from a neon gas discharge. Luminescent substances such as phosphors may be used in a monochrome structure to obtain a color other than neon orange.
In a multicolor PDP, two or more different luminescent substances such as phosphors are used. In a multicolor columnar discharge (PDP) structure as disclosed in U.S. Pat. No. 5,793,158 (Wedding), phosphor stripes or layers are deposited along the barrier walls and/or on the bottom substrate adjacent to and extending in the same direction as the bottom electrode. The discharge between the two opposite electrodes generates electrons and ions that bombard and deteriorate the phosphor thereby shortening the life of the phosphor and the PDP. Wedding ('158) teaches the use of phosphor overcoats to protect the phosphor from electron/ion bombardment and extend life.
In a two electrode columnar discharge PDP as disclosed by Wedding ('158), each light-emitting pixel is defined by a gas discharge between a bottom or rear electrode x and a top or front opposite electrode y, each cross-over of the two opposing arrays of bottom electrodes x and top electrodes y defining a pixel or cell.
The three-electrode multicolor surface discharge AC plasma panel structure is widely disclosed in the prior art including U.S. Pat. Nos. 5,661,500 (Shinoda et al.), 5,674,553 (Shinoda et al.), and 5,736,815 (Amemiya), all are incorporated herein by reference.
In a surface discharge PDP, each light-emitting pixel or cell is defined by the gas discharge between two electrodes on the top substrate. In a multicolor RGB display, the pixels may be called sub-pixels or sub-cells. Photons from the discharge of an ionizable gas at each pixel or sub-pixel excite a luminescent substance such as photoluminescent phosphor that emits red, blue, or green light.
In a three-electrode surface discharge AC plasma display, a sustaining voltage is applied between a pair of adjacent parallel electrodes that are on the front or top viewing substrate. These parallel electrodes are called the bulk sustain electrode and the row scan electrode. The row scan electrode is also called a row sustain electrode because of its dual functions of address and sustain. The opposing electrode on the rear or bottom substrate is a column data electrode and is used to periodically address a row scan electrode on the top substrate. The sustaining voltage is applied to the bulk sustain and row scan electrodes on the top substrate. The gas discharge takes place between the row scan and bulk sustain electrodes on the top viewing substrate.
In a three-electrode surface discharge AC plasma display color panel containing phosphor, the sustaining voltage and resulting gas discharge occurs between the electrode pairs on the top or front viewing substrate above and remote from the phosphor on the bottom substrate. This separation of the discharge from the phosphor minimizes electron bombardment and deterioration of the phosphor deposited on the walls of the barriers or in the grooves (or channels) on the bottom substrate adjacent to and/or over the third (data) electrode. Because the phosphor is spaced from the discharge between the two electrodes on the top substrate, the phosphor is subject to less electron bombardment than in a columnar discharge PDP.
This invention may be practiced with an AC and/or DC plasma display panel structure having two opposing substrates. It may also be practiced in an AC and/or DC monolithic plasma display panel structure having one substrate with or without a top or front viewing envelope or dome. Single-substrate or monolithic plasma display panel structures are disclosed by U.S. Pat. Nos. 3,860,846 (Mayer), 3,964,050 (Mayer), and 3,646,384 (Lay), all cited above and incorporated herein by reference.
Each microsphere may be positioned on the surface of the single substrate or within a substrate cavity, well, or hollow. The microsphere may be in electrical contact with 2, 3, or more electrodes.
In one embodiment of this invention, the microspheres are positioned on the surface of or within a single-substrate or monolithic gas discharge structure that has a flexible or bendable substrate.
The practice of this invention is not limited to flat surface displays. The microspheres may be positioned or located on a conformal surface of a substrate so as to conform to a predetermined shape such as a curved surface, round shape, or multiple sides.