One-sided Plasma Display Panel

Abstract

A thin glass sheet carries seats of spaced, parallel electrodes on opposite surfaces thereof and a gaseous atmosphere overlies one surface. Applying an alternating current voltage exceeding a critical value across selected electrodes of each set causes a gas discharge to take place on the surface carrying the gas at the area of selected electrode crossing with localized visible light output.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to planar display panels and more particularly to a simplified, low-cost display panel which eliminates the need for uniformity in spacing or accurate registration between panel components.

2. Description of the Prior Art

Relatively thin, planar display panels employing a localized plasma effect have been manufactured in the past, in two forms. In one form, glass plates approximately 1/4 inch in thickness are separated by a gas filled gap about 10 mils in width and the gap is maintained by thin glass spacers. The inner faces of the plates carry horizontal and vertical sets of transparent electrodes covered by a thin glass insulating layer. The intersections of these electrodes establish the spots that form the displayed pattern. Alternatively, instead of using two spaced glass plates, a three layer glass sandwich may be employed with holes in the middle layer through which the discharge occurs, although, in all other respects, this arrangement is similar to the first described plasma readout panels. The three layer panel involves inherently a registration problem since the perforated center plate or middle layer must have the perforations accurately aligned with the points of intersection between the transparent electrodes carried by the outer plates. With the two layer panel, there is inherently a uniformity problem since it is hard to maintain a uniform gas chamber of the order of several mils over the complete surface of a large panel.

SUMMARY OF THE INVENTION

The present invention provides a practical solution involving a single layer approach which solves both the registration and uniformity problems. The present invention is directed to a flat panel constructed from a single thin sheet of insulated material with sets of spaced parallel electrodes positioned on opposite sides of the insulator sheet with one set orthogonal to the other. The invention makes use of a gaseous atmosphere applied to one of the surfaces and by raising an alternating current voltage above a predetermined value, a localized gas discharge takes place on the surface subjected to the gas, with localized visible light output.

Preferably a neon atmosphere at 200 torr. is maintained on one side of the glass sheet, confined by a clear glass cover with the matrix electrodes constituting three lines per inch. A 500 volt, peak-to-peak firing voltage is selectively applied to given row and column electrodes to effect bistable action. A thin insulation layer may overlie the electrodes exposed to the gases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a prior art three layer plasma display panel;

FIG. 2 is a perspective view, partially broken away, of the preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Prior to referring to FIG. 2 illustrating one embodiment of the present invention, reference to FIG. 1 illustrates a prior art plasma display panel 1, constituting a matrix display formed as a sandwich of three thin plates 2, 3, and 4. The center plate 3 is honeycombed with either etched or ultrasonically drilled holes 5. Transparent, thin film electrodes 6 and 7 are deposited on the outer surfaces of the two outer plates 2 and 4. The panel is evacuated and the array is filled with a mixture of neon-nitrogen gas or the like. The application of coincident voltages of appropriate magnitude to selected crossed grids, that is, electrodes 6 and 7, allow selected display elements to be ignited. Voltages applied to the crossed electrodes are coupled capacitively into the cell so that only AC excitation voltages are required. Display is seen through one set of highly transparent electrodes either 6 or 7, and the gas discharge is confined totally to the cylindrical cavity formed by the three glass sheets 2, 3, and 4. However, since the display panels can be manufactured such that approximately 18,000 tiny spots may be provided within a 4 inch square area, registration of the three plates is extremely critical. In addition, the manufacture of such display panels has been relatively expensive.

Referring to FIG. 2, the gas discharge display panel 10 of the present invention comprises in the form shown, a rectangular support or base 12 of some thickness which may constitute a block of electrical insulator material. Block 12 constitutes the physical support means or substrate for the panel including, an outer clear glass envelope 14 which acts in this case as a cover for base 12 and is hermetically sealed thereto, preferably about edge 16. While the envelope 14 may comprise clear glass, it is obvious that it may be formed of some other insulator, being at least translucent, so as to allow observation of a localized area of visible light output from the display panel 10.

The principal component of the panel comprises a thin electrical insulator sheet 18 which may also be of glass, ceramic, etc. A first set of metal electrodes 20 are preferably first applied to the top of the substrate 12 by electrodeposition or any other conventional process, the electrodes 20 being spaced from each other and parallel. In the illustrated embodiment there are approximately three lines per inch. The thin insulator 18 (soft glass, hard glass, ceramic) is applied on top of the substrate 12 overlying conductors 20 of a thickness typically in the range of a micron to several mils. On the upper surface 22 of the thin insulator sheet 18 there is formed a second set of electrodes 24 which are similarly formed, consisting of thin strips of metal which lie preferably orthogonal or approximately so to the underlying conductors 20. As such, the upper and lower conductors or electrodes 24 and 20 extend in crossed paths, spaced from each other by the thickness of the insulator sheet 18. The hermetically sealed cover or envelope 14 confines an inert gaseous atmosphere such as neon, indicated at 26, in contact with one surface 22 of the insulator sheet 18 carrying conductive electrodes 24.

The invention involves the phenomena of localized gas discharge which takes place on the surface of the insulator 18 creating localized areas of visible light output as identified at 28, in this case, on either side of the upper electrode 24. Alternating current voltage is selectively applied to the electrode by conventional switch means. However, to illustrate in the most simple manner the application of the same, a source of alternating voltage (not shown) is connected to terminals 30 with lead 32 connecting one of the terminals 30 to a selected upper electrode 24 while lead 34 connects the other terminal 30 to a selected underlying or bottom electrode 20. In the area of the intersection of these spaced electrodes, corona discharge occurs on the upper surface 22 of the insulator, that is, that surface which faces the inert gas atmosphere 26.

The crossed but spaced electrodes define individual gaseous display cells and, in the illustrated embodiment, a matrix constituting three lines per inch has been successfully fired in a neon atmosphere of 200 torr. With the application of an alternating current firing voltage of about 500 volts (peak-to-peak), the device shown is bistable in a neon atmosphere of .+-. 10 percent nitrogen (at 150 torr.). The upper set of electrodes 24 which are normally exposed to the inert gaseous atmosphere, may be protected by a thin layer 36 of electrical insulation material which has the effect of slowing down the sputtering process and increases the memory margin.

Claims

What is claimed is:

1. A gas discharge display panel comprising: an insulator substrate, a first set of spaced parallel electrodes on one surface of said substrate, a glass sheet overlying said first set of electrodes, a second set of spaced electrodes carried on the outer surface of said glass sheet orthogonally to said first set, a clear glass envelope overlying one surface of said sheet carrying said second electrode set and spaced therefrom, a confined neon atmosphere within the space between the one surface and said clear glass envelope, and means for supplying an alternating current voltage of sufficient magnitude across selected electrodes of each set to cause a discharge on the surface of said glass sheet facing the gaseous atmosphere with localized visible light output in the crossing area of selected electrodes.

2. A display panel comprising:

an electrical insulator in the form of a thin sheet, means for maintaining an inert ionizable gas atmosphere on one side of said sheet, at least one conductor formed on said one side of said sheet, at least one conductor formed on the side of said sheet opposite to said one side, said two conductors partially overlapping to form a crossover point, and means connected to said two conductors for applying a potential difference across said crossover point to cause a gas discharge in said inert ionizable gas atmosphere in the vicinity of the crossover point.

3. The display panel of claim 2 further including a first plurality of parallel conductors on said one side of said sheet and a second plurality of parallel conductors on said opposite side, said second plurality of conductors being orthogonal to said first plurality of conductors, and means coupled to pairs of electrical conductors comprising one conductor of said first plurality and one conductor of said second plurality for selectively applying an alternating potential difference at the crosspoint of said conductor pairs.

4. The display panel as claimed in claim 3 wherein said thin insulator sheet is supported by an electrical insulator block which underlies the same and said inert gaseous atmosphere is confined to the display surface thereof by an overlying glass envelope hermetically sealed to said block.

5. The display panel of claim 3 further including an insulation layer overlying and in contact with said first plurality of conductors.

6. In a gas discharge display device wherein a potential difference applied at selective locations across an ionizable gas atmosphere retained in a display panel causes selective discharges along with the generation of positive and negative charges tending to counteract the potential difference and extinguish the discharge, subsequent reversals of the potential difference causing successive pulsating discharges at the selected locations, the improvement comprising:

a display panel including a dielectric sheet, one surface of which is in contact with said ionizable gas atmosphere;

a first plurality of conductors spaced along said one surface;

a second plurality of conductors spaced along a second surface of said dielectric sheet parallel to said first surface, and remote from said gas atmosphere, said second plurality of conductors at least partially overlapping said first plurality of conductors to form a plurality of crossover points; and

means coupled to said first and second pluralities of conductors for selectively applying the potential difference across selected crosspoints to generate a discharge in the gas atmosphere in the vicinity of the selected crosspoints.