Bistable storage tube having storage dielectric of phosphor particles coated with secondary emissive material

Abstract

The present invention relates generally to charge image storage tubes having a direct viewing storage target including a storage dielectric of phosphor material capable of bistable storage of a charge image and which emits a light image corresponding to such charge image, and in particular to an improved storage dielectric of phosphor particles coated with smaller particles of a high secondary electron emissive material bonded to such phosphor particles and to a method of manufacture thereof. A small amount of secondary emissive material is employed efficiently to increase the writing speed and useful lifetime of the storage dielectric without greatly decreasing the brightness of the light image emitted by the phosphor. In one embodiment using 3.5 per cent of magnesium oxide secondary emissive material with 96.5 per cent of manganese activated zinc orthosilicate phosphor material, a writing speed of 400,000 centimeters per second and a light image brightness of 3.5 foot-lamberts was obtained. The method of manufacture of the improved storage dielectric includes coating the phosphor particles with a secondary emissive forming substance, and then heating the coated phosphor particles to produce the secondary emissive material and to simultaneously bond such secondary emissive material to the phosphor particles.

Dependencies are inferred from the claim text.