ZINC SULFIDE FLUORESCENT SUBSTANCE COACTIVATED WITH COPPER, GOLD AND ALUMINUM, AND PREPARATION THEREOF

摘要

PURPOSE:To obtain a fluorescent substance little varied in luminescent color and little deteriorated in luminance in a baking process, by dissolving and removing the surface layer of a fluorescent crystal prepd. by calcining a mixt. contg. zinc sulfide, a gold compd. and a copper compd. in a reducing atmosphere. CONSTITUTION:A raw material mixt. contg. zinc sulfide, a gold compd. as a raw material for a gold activator and a copper compd. as a raw material for a copper activator is calcined in a reducing atmosphere to obtain a fluorescent crystal. Then a fluorescent crystal having a fresh surface is obtd. by dissolving and removing the surface layer of the fluorescent crystal. For example, the surface layer is dissoved by use of hydrogen peroxide and then washed with an alkali metal cyanate. Thus a zinc sulfide fluorescent substance coactivated with copper, gold and aluminum, in which average concn. of gold present in a fluorescent crystal particle ranging from the surface to a depth, toward the center, of 0.2mum is not more than 1.2 times that of gold present in the crystal particle at least 0.5mum deeper from the surface, is obtd.