Browse Prior Art Database

Electrical Addressing of Plasma Cathode Display Tubes

IP.com Disclosure Number: IPCOM000074651D
Original Publication Date: 1971-May-01
Included in the Prior Art Database: 2005-Feb-23
Document File: 3 page(s) / 40K

Publishing Venue

IBM

Related People

Kazan, B: AUTHOR [+2]

Abstract

Described is a low-voltage multielement display device which can be addressed by a set of X and Y electrodes or by shift registers external to or incorporated in the display structure. The mechanism for generating light involves the use of a gas plasma as a source of low-voltage electrons for exciting a phosphor by electron bombardment.

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Electrical Addressing of Plasma Cathode Display Tubes

Described is a low-voltage multielement display device which can be addressed by a set of X and Y electrodes or by shift registers external to or incorporated in the display structure. The mechanism for generating light involves the use of a gas plasma as a source of low-voltage electrons for exciting a phosphor by electron bombardment.

The device comprises a glass envelope 2 which contains a noble gas such as argon at a pressure of about 1 Torr. Extending along one edge or more inside the envelope are an elongated pair of electrodes in the form of a cathode strip 4 and an anode strip 6. Cathode 4 can be shaped to increase the current density. As indicated, a voltage source 8, in series with a resistance 10, is connected across these two electrodes 4 and 6, maintaining a gas discharge 12 between the electrodes 4 and 6. A plasma 14 of positive ions and free electrons produced by the discharge then diffuses around the anode 6 into the remaining space of the envelope. A set of parallel electrode strips 16, is provided inside one surface of the envelope running in a direction perpendicular to the plane of the paper, the strips 16 being connected to the leads X1, X2, etc., which extend through the glass envelope 2. The surface of the electrode strips 16 is covered with a layer of ZnO phosphor 18 and above the phosphor surface 18 a set of parallel control wires 20 is provided each of which has an external connection 22. In the Figure, only one of the control wires 20 is shown with its external line Y1. Each of the external Y lines is connected to an individual load resistor, RL 24 and to a common bias supply voltage 26, for example, -10 volts.

In operation, an individual picture element can be made to light up by applying a suitable voltage to selected X and Y lines. It is assumed initially that a -10 volt bias voltage on the Y lines prevents electrons in the plasma 14 from reaching the phosphor surface 18. When a particular Y line is shifted by an applied signal to zero volts, electrons from the plasma 14 diffuses past this control wire 20 and reach the phosphor layer 18 in the neighborhood below th...