GB1473849A - Glow-discharge display device - Google Patents

Abstract

1473849 Glow discharge lamp; gas discharge display panel MULLARD Ltd 3 July 1974 [28 Sept 1973] 45522/73 Heading H1D In a gas (e.g. Ne) filled D.C. glow discharge display panel with transparent window 9 sealed to insulating base 1, anode wires 10 forming columns of an array oppose discrete unshielded areas under cavities 3 of cathode metal strips 2 forming rows, enabling a discharge to be struck in a cavity 3 at any address: each element of the array must then have sufficiently high differential resistance in the discharge part of its V-I characteristic (Fig. 1, not shown) to limit the current to a safe value; rather than add individual resistors the characteristic is modified by coating the exposed cathode strips with a thick layer of carbon, preferably finely divided C such as carbon black or colloidal graphite, possibly with Na or K silicate bond; the carbon may be admixed with SiC, B 3 C 4 or with alumina or glass powder: alternatively baked carbon of "Papyex" (Registered Trade Mark) carbon paper may be used. Carbon is chosen for its resistance to sputtering: grooves 5 across the ribs 4 of block 1 also prevent crossconnection due to sputtered material. Auxiliary coated cathodes 6 at each end exposed along their whole length to the ends of successive anode wires 10 provide a continuous discharge as a source of ionization to assist starting of the cavity discharges. In an alternative embodiment (Fig. 5, not shown) the cathodes are formed from metallized (Ag) strips on a glass plate, with offset areas coated with carbon. An anodized Al apertured plate is held in contact with the cathode plate, exposing the carbon areas to metallized anode strips on a window spaced above the Al plate. In a third embodiment (Fig. 6, not shown) the carbon coating completely covers the metallized cathode strips. In all embodiments it is essential that no base cathodic metal is exposed to the discharge, the characteristic being immediately impaired. The method of application of carbon disclosed in Specification 1,473,850 is referred to.