GB817551A - Improvements in or relating to electric discharge tubes - Google Patents

Abstract

817,551. Discharge tubes. PHILIPS ELECTRICAL INDUSTRIES Ltd. July 15, 1955 [July 20, 1954], No. 20540/55. Class 39(1). A cathode-ray tube screen consists of two sets of intersecting wires 7, 8, Fig. 3, and radiation is produced at each intersection by controlling the potential difference between the wires at that point. The ends of the wires are scanned by beams 9 and 13, the ends of one set of wires being secondary emissive so that the potentials of the wires are increased and the ends of the other set of wires collecting electrons so that the potentials of these wires are decreased. In the second case the wires may collect electrons from auxiliary secondary emissive electrodes which are scanned by the beam. The radiation produced may be visible or invisible and may be obtained (a) by producing a gas filling in the tube so that luminous glow discharges are produced, (b) by providing luminescent material on one set of wires and photo-emissive material on the other set, (c) by providing luminescent material on one set of wires and shaping the wires of the other set with sharp edges at points so that cold emission can be obtained or (d) by providing electro-luminescent material between the two sets of wires. In a flat tube, Fig. 4 the scanning beams impact plates 25 at the far ends of the wires. Bent-over ends of the wires may be used instead of the plates 25. Each set of wires connected to a common terminal by high resistance material. Intensity control may be obtained by applying the signals to a grid at the gun or by controlling the current distribution between the secondaryemissive electrode 54, Fig. 8 at the end of the wire 53 and the secondary electron collector electrode 57 by means of a deflection electrode 59. The deflection electrode 59 may be common to all the wires and may be located near the gun. Electrode 55 collects the secondary electrons. Electrode 57 may be omitted and the plate 54 may have secondary emissive properties which are not the same at all points, or the secondary emission may depend on the angle at which the beam strikes the surface. The potentials of the wires may be stabilized despite changes in the discharge current by providing additional deflection electrodes 69, Fig. 9 connected conductively with the secondary-emissive electrodes 60 and which act to determine what part of the beam 68 will strike the electrodes 60 and what part will strike the collecting electrode 73. The electrodes 69 may be so arranged that the additional deflection is in the direction of scan. Similar control arrangements may be used for the system in which the wires collect electrons, primary or secondary, to decrease their potentials. In a colour television system one set of wires is multiple and is coated with three luminescent materials or three electro-luminescent materials may be provided. Colour switching may be obtained by applying the colour signals to the collecting electrode associated with the secondary emissive set of wires, or three beams may be associated with the multiple set of wires. Biasing signals may be applied to increase the intensity of the light output. Electromagnetic deflection of the electron beams may be used instead of electrostatic deflection.