US 4,513,025 AGranted

Line emission penetration phosphor for multicolored displays

AssigneeSperry Corporation

InventorsThomas E. Clark, Charles T. Burilla

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Abstract

A single particle penetration phosphor employs La.sub.2 O.sub.2 S:Tb particles as a core particle having a thin layer of La.sub.2 O.sub.2 SO.sub.4 :Tb formed thereon by oxidation to provide a barrier which must be penetrated by excitation electrons to produce narrow bandwidth green spectral emission from the particle. The thin barrier is in turn coated by a layer of YVO.sub.4 :Eu particles which produce narrow bandwidth red spectral emission upon electron excitation. The barrier layer increases the voltage turn on characteristic of the green carrier host thereby causing the electron irradiated phosphor to radiate in the red spectrum for low voltages and in the green spectrum for higher voltages. Additionally, methods are disclosed for synthesizing the above single particle penetration phosphor.

Claims11

Dependent claims

A method for making a coated cathodoluminescent line emission penetration phosphor particle having a central region consisting of La.sub.2 O.sub.2 S:Tb, a non-luminescent barrier region substantially uniformly surrounding said central region consisting substantially of La.sub.2 O.sub.2 SO.sub.4 :Tb and forming a core particle with said central region and a layer of coating particles consisting substantially of YVO.sub.4 -Eu surrounding said barrier region, comprising the steps of:

selecting a host material consisting of particles of La.sub.2 O.sub.2 S:Tb with a diameter greater than the diameter of said coating particles;
oxidizing ones of said host particles to form said barrier region thereover in a thickness of about 0.5 to 1 micron thereby forming a plurality of core particles;
acidifying a first solution of gelatin with glacial acetic acid to pH in the range of 3 to 5;
agitating said core particles in said first acidified gelatin solution in a concentration of 0.1 gm/ml for a period of about 25 min. to apply a first gelatin coating;
removing an excess of said first acidified gelatin solution;
selecting a quantity of YVO.sub.4 :Eu substantially free of absorptive film material and having a ratio by weight to said core particles of about 1:3 and a particle size of about 0.5 to 2 microns and agitating in an aqueous solution having a pH of about 3.9;
agitating said core particles in said aqueous solution and said coating particles for about 25 min. sufficient to cause said coating particles to coat said core particles in at least a single layer thickness;
and
removing an excess of said aqueous solution from said core and said coating particles in said aqueous solution.

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Dependencies are inferred from the claim text.