GB813854A - Screen for direct-viewing storage tube - Google Patents

Abstract

813,854. Cathode-ray storage tubes. HUGHES AIRCRAFT CO. June 28, 1956 [July 1, 1955], No. 20112/56. Class 39(1) In a direct-viewing electronic storage tube, the storage screen comprises a layer of secondary electron emissive dielectric material disposed over one side of a conductive screen having meshes, the meshes being free from dielectric material in the region of each interstice, so that each interstice of the screen exerts the same control over the flow of flood electrons. In a process for fabricating such a screen an electroformed nickel screen 14, having about 250 meshes per inch, is first coated over its entire surface with a layer of photo resist. Light is then projected towards one side of the screen so that the photo resist on that side and over the inner periphery of each interstice is hardened. The unhardened portions of the photo resist are removed, e.g. by immersing the screen in water or alcohol, after which the dielectric material, e.g. magnesium fluoride, is evaporated and thereafter condensed onto the uncoated side of the nickel screen to form a layer 12 of thickness from 1 to 10 microns. When the hardened portion of the photo resist has been removed by heating or by dissolving it in an appropriate chemical solution, any dielectric material left unsupported-may be broken away by agitating the screen in a suitable medium. The storage screen is completed by electroplating a metallic coating 24 onto the uncoated surfaces of the nickel screen so that the ultimate transparency of the screen is approximately 40 per cent. and the thickness of the conductive screen is about 1 mil. Specification 780,907 is referred to.