GB798504A - Improvements in electroluminescent devices - Google Patents

Abstract

798,504. Electroluminescence. THORN ELECTRICAL INDUSTRIES, Ltd. May 4, 1955 [May 10, 1954], No. 13633/54. Class 39(1). In a light source of the type comprising two parallel plane electrodes, one of which is transparent, separated by electro-luminescent dielectric material, the remaining electrode is composed of a material, such as lead dioxide and/or manganese dioxide, which is conducting but which is converted locally to a non-conducter upon the break-down of the dielectric material and the resultant heating due to the passage of a spark, whereby the portion of the dielectric which has broken down is isolated. The light source illustrated comprises an electro-luminescent dielectric layer 22 and two electrodes 19, 24, the electrode 19 comprising a transparent metallic coating upon a glass plate 18 the coating being applied by exposing the glass plate while hot to stanic chloride vapour. The electrode 24 which is separated from the electroluminescent layer by a light-reflecting layer 23 as described in Specification 798,503 preferably consists mainly of lead dioxide which is converted upon being locally heated when a break-down of the dielectric material occurs to a non-conducting oxide of lead, thus isolating the broken-down portion of the dielectric. The electrode 24 which forms a coating upon the light reflecting layer 23 is applied as a suspension of lead dioxide in ammonia solution to which may be added a cellulosic binding material to give added strength to the layer and also graphite or metal to increase its conductivity. A further layer of graphite 25 is applied over the electrode layer 24. Terminals 20, 21 are connected respectively to the layers 19 and 25. The back and the edges of the lamps are coated with a layer 26 of a moisture proof insulating material.