GB660096A - Improvements in or relating to the manufacture of fluorescent lamps - Google Patents

Abstract

660,096. Luminescent materials; discharge lamps. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Dec. 12, 1946 [Aug. 28, 1945], No. 36725/46. Drawings to Specication. Class 39 (i). A method of preparing a zinc beryllium silicate manganese activated phosphor for fluorescent lamps comprises adding to the raw materials forming the phosphor a small amount of an element having a small ionic radius and a valency of not less than two, such as beryllium, magnesium, boron, aluminium, zirconium, tungsten or phosphorus, mixing the ingredients so completely, e.g. by ball milling, and heating them for such a time to a temperature, between 1220‹ and 1270‹ C., preferably between 1240‹ and 1270‹ C., that the reacted phosphor weighs at least eight, and preferably ten to twelve grams per cubic inch, and grinding and heating to about 900‹ C. in a reducing atmosphere, e.g. of carbon monoxide or hydrogen. In examples described the proportions of zinc oxide, beryllium oxide, silica, magnesia and manganous carbonate which are heated to about 1220‹ C. are given. The phosphor is applied to the internal surface of a lamp envelope either electrostatically after being made into a smoke or by the flush method after being mixed with a lacquer binder, the envelope being thereafter baked in air at about 500‹ C. to remove the binder. In the latter case the re-oxidation produced is removed by reduction in carbon monoxide or hydrogen. In order to avoid loss of light from the lamp by reflection the outside of the envelope may be thinly coated with calcium fluoride by dipping the envelope for a short time in dilute hydrofluoric acid.