GB780162A - Electroluminescent lamps - Google Patents

Abstract

780,162. Electroluminescence. SYLVANIA ELECTRIC PRODUCTS, Inc. Jan. 8, 1954 [Jan. 9, 1953], No. 649/54. Drawings to Specification. Class 39(1). An electroluminescent material comprises a host crystal of one or more of the sulphide, selenide or silicate of one or more of the metals cadmium, zinc, calcium or strontium, an activator e.g. copper, manganese or silver, and a donator consisting of one or more of the metals thallium, indium or tin. Zinc oxide may be included in the host crystal e.g. zinc sulphide, up to an amount of 25 per cent thereof, as may zinc chloride. The donator material is between 0À00005 and 0À0000005 gram atom per mole of host crystal. The presence of activator and absence of donator in certain parts of the host crystal are said to produce depletion layers of higher resistivity than the donator-containing material, which are locations of high field density. These layers are produced by chemical treatment of the fired powder with acetic acid or ammonium acetate, the two being successively ground together with increasing dilution of the acetic acid or the acetate, finally rinsing with pure water. Other ammonium salts may be used. Zinc sulphide activated with copper and containing zinc oxide is stated to give greenish yellow luminescence at 60 cycles/sec. and blue luminescence at 2000 cycles. The electroluminescent materials may be mixed with or embedded in dielectric material, e.g. nitrocellulose or castor oil, and enclosed between conductive electrodes, either reflective or transparent, or disposed between two conductor wires wound side by side or between conducting coatings formed on insulating supports, Figs. 1-5 (not shown).