US3551721A - Gas-filled display device having capacitive envelope - Google Patents

Description

United States Patent 169TV,171, 248; 313/108,204, 210, 325, 329, 153(Cursory), 161(Cursory), 201; 178/7.3 (D & Advisory); 340/324, 324.1, 343, 344

56 References Cited UNITED STATES PATENTS 2,925,530 2/1960 Engelbart 3 l 5/84.6

[72] Inventor George E. Holz 2,933,648 4/1960 Bentley 315/169 North Plainfield, NJ. 2,967,965 l/1961 Schwartz 315/169X [2]] Appl. No. 668,290 3,042,823 7/1962 Willard 315/169X [22] Filed Sept. 11,1967 3,157,824 11/1964 Jones 315/169 [45] Patented Dec. 29, 1970 3,206,638 9/1965 Moore 315/169X 73] Assignee Burroughs Corporation 1,676,790 7/1928 Mailey 3 13/201 Detroit, Mich. 2,624,858 1/1953 Greenlee 313/201 a corporation of Michigan 2,629,839 2/1953 Greenlee 313/201 2,943,223 6/1960 Fay 313/201 3,258,644 6/1966 Rajchman 315/169X 1. 1 GAS-FILLED DISPLAY DEVICE HAVING 3,050,654 8/1962 Toulon 315/169X I CAPACITWE ENVELOPE Primary Examiner James W Lawrence 3 7 Drawing Assistant ExaminerDavid OReilly [52] us. Cl. 313/204, A"0meys |(enneth L. Miller and Robert A Green 313/210, 315/169 [51 1 Int. Cl; ..H0lj 17/04, H01j 61/04 [50] Field of Search 315/169,

ABSTRACT: The disclosure is of a gas plasma cell having electrode carrying end walls of a material having a high dielectric constant, greater than that of glass, so that the cell has high capacitance. The disclosure is also of a matrix of such cells and combinations of such cells and other cells having lower capacitance.

SUSTAIN SUSTAIN I I I l c 2/0 229' FIRE FIRE I r 1' I I I (229 224 22s 22? 1 PATENIEDnEmm SHEET 1- OF v Ma/5m ATTORNEY FBG4 . 1v GAS-FILLED DISPLAY nEvrCE-nAvmo CAPACIT I ENVELOPE BACKGROUND OF INVENTION The present invention relatesto a gas plasma cell made of glass andcontaining a gas which is adapted to glow when a operatingpoten tial is applied between electrodes on the end walls of the cell. The'cellhas the characteristic that,..when glow is produced, electrical charges are generated and stored on the end walls of the cell, and the glow can be sustained by the application of sustaining potential which may be smaller than thefiringpotential. Known gas plasma cells normally have small capacitance, and this characteristic imposes certain limitations on the operation and utility of the cells.

' functions.

' BRIEF oas calrriouorraa DRAWING In the drawing: I FIG. I is a sectional elevationaluview of a light-producing cell embodying the inventionand a circuit in which it may be operated; f FIG. 2 is a sectionalelevationaljview of a portion of a modification of the invention;

FIG. 3 is a sectional elevational view of a modification of the invention;- 1

FIG. 4 is a sectional 'elevational view of amo'dificati'on of the device of FIG. 3; I

FIG 5 is a perspectiveview of a device embodying the invention and schematic representationof a circuit in which it maybedperated; I

FIG. 6 is a sectional elevational view of a modification of the invention and a schematic representation of a circuit in which it may be operated; and

FIG. '7 isja sectional elevational view of a modification of the invention and schematic representation of a circuit in which it may be operated. g

DESCRIPTION'OF THE PREFERRED EMBODIMENTS Apparatus l0 embodying the invention comprises a cell formed'of insulating material such as glass andincluding a hollow cylindrical envelope having end walls and which form a gastight seal therewith. According to the invention, discs or plates and of a material having a relatively high dielectric constant, called K, are secured to the end walls 30 and 40, respectively, and electrodes and 80, respectively, are secured in turn to the discs 50 and 60. The discs 50 and 60 increase the capacitance of the cell to a favorably high level, and they may be of any suitable material, for example, a ceramic such as barium titanate. The discs may also be of any convenient thickness. It is clear, of course, that glass walls 30 and 40 may be omitted and discs 50 and 60 can themselves comprise end walls to cell 10, as shown in part FIG. 2. Glass typically has a dielectric constant of 7s, and .plates 50 and 60 preferably are in the range of about 400m about 29006,.

The cell 10 includes an ionizable gas which can be fired and caused to flow and maintain the glow when a suitable sustaining voltage is applied to it. Suitable gases are argon, neon, krypton, nitrogen," helium, etc., or mixtures'of these gases.

Mixtures of neon and nitrogen are effective, and a mixture of A typical circuit for operating cell 10 includes, in series, a source of sustaining potential, a source of firing pulses, and an impedance, for example, a resistor connected between contacts 70 and 80. Output terminals are provided on resistor 120. Operating parameters are determined generally by the size of the cell, the gas content, and the like, and for a cell having a thickness of a few mils and with a neonnitrogen gas mixture, the sustainingpotential produced by source 100 is an alternating signal of about 700 volts and a frequency of about 500 kc., and the firing signal produced by source 110 is a pulse of about t I00 volts.

In one mode of operation of the cell 10, a sustaining signal is applied between electrodes 70 and 80 from source 100, and at a selected time a firing pulse from source 110 is also applied. This combination of voltages causes the gas within the cell to ionize and glow, and the glow can be sustained by the sustaining potential. Due to the relatively high capacitance of the cell, when the cell fires, a'usable current pulse can be detected in resistor 120. The cell may also be operated by first applying a firing pulse of sufiicient amplitude and then sustaining the glow by the application of the sustaining potential.

Due to the relatively high capacitanceof the cell, the cell exhibits a more intense or brighter glow at a selected operating frequency than would have been exhibited by cells of the prior art at the same frequency.

In a modification of the invention shown in FIG. 3, a display panel is provided which includes a plurality of cells 10 of the type described above. In this case, it may be desirable to have the regions or bodies 50 and 60'of high dielectric material of one cell mechanically isolated from those of adjacent cells, as shown, to maintain electrical isolation between cells. It may be desirable for bodies 50 and 60 to have a larger diameter than the gas-filled volume of the cell as shown in FIG. 1, for example. The panel 150 may be made in relatively simple fashion fashion by assembling a sandwich of glass plates including an apertured central plate and top and bottom glass plates and 180. The individual bodies of high dielectric material 50 and 60 are secured to the top and bottom glass plates in vertical alignment with apertures in the central plate, and the individual contacts 70 and 80 aresecured to the bodies 50 and 60. Separate electrical connec- 'tions including output resistors 120 may be made to each cell through contacts 70 and 80 each cell, and each cell may be operated individually to record intelligence and to display a light pattern.

In an alternative construction, shown in FIG. 4, the end walls of the cells themselves comprise the bodies 50 and 60 of high K material without an intervening plain glasslayer being provided. This type of cell may also be made in the manner described above, with plates 170 and being apertured and bodies 50 and 60 comprising inserts, or it may be made by embedding individual glass cells having bodies 50 and 60 as end walls in a suitable support medium of a synthetic resinous material.

Electrical connections may also be made as shown in FIG. 5. Assuming that the cells in panel 150 are arrayed in rows and columns, a single row lead 200 may be connected to each row of contacts 70 on the top surface, and a single column I ead 206 may be connected to each column'of contacts 80 on the bottom surface. An output impedance 120 is also provided for each cell in either its row or column conductor. As is' well known with matrix-type devices such as this, an input signal applied to one row lead 200 and one column lead 206 will cause one cell-to glow where the leads cross. Thus, the panel 150 as shown in FIG. 5 can be used to record intelligence in many different ways. For example, if a cell is on and is being sustained and has a firing signal applied to it, it will not change state and no current pulse will be detected in the associated resistor 120. Or, if a cell has sustaining signal applied to it but is not on, a firing pulse is applied and it turns on, then a detectable signal canfbe derived from the associated resistor I20. Operations of this type can be used in electronic logic systems to process information. Systems and methods for using the panel 150 in logic operations will occur readily to those skilled in the art.

Another unique embodiment of the invention is shown in FIG. 6 and comprises a cell pair including a first cell 210 having an envelope and end walls of low K glass, known as a low K cell, which is coupled to a second cell 220 of the type described above and known as a high K cell which has end walls 221 and 222 of material having high dielectric constant. In the simplest arrangement, one cell of each type is provided and both cells are formed in a single glass panel in operative relation with each other. Operative relation means that the cells are close enough to each other so that, when one generates ultraviolet light, the light can penetrate to and affect the operation of the other. Cell 210 has end electrodes 223 and 224, and cell 220 has end electrodes 225 and 226.

In one mode of operation of the cell pair, both cells 210 and 220 have sustaining potential applied to them from sources 227 and 228, respectively, and the low K cell 210 is fired by the application of a firing pulse from source 229. The firing of cell 210 generates ultraviolet light which is coupled to cell 220 through the glass between them. This radiation generates photoelectrons in cell 220 which, acting in the applied electric field, causes cell 220 to fire and generate a visual output and an electrical output in resistor 120. The cell pair in this case may be considered to be an amplifier.

The reverse operating sequence may be employed with cell 220 turning on cell 210 by means of ultraviolet light. Or in still another mode of operation (FIG. 7), the high K cell 220 may be coupled through its output impedance by leads 230 to one or more low K cells 210, and the relatively large electrical output of the cell 220, when it is fired, can be used to fire the low K cells 210.

Of course, it is clear that the required synchronization between the various signals and the ultraviolet light is"'r' 'rovided. in addition, different numbers of the two types of cells may be provided as required by a particular application.

1. A display panel including a gas filled cell having low capacitance and a gas-filled cell having high capacitance, circuit means coupled to each cell for firing the cell, said cells being coupled in close relationship so that the firing of one facilitates the firing of the other 2. The panel defined in claim 1 wherein said cells are positioned close together so that ultraviolet light generated by one when it fires can be transmitted to the other to facilitate its fir- 3. The cell defined in claim 1 and including an output impedance in the circuit of said high capacitance cell and leads coupling said output impedance across said low capacitance cell.

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