GB870235A - Improvements in or relating to the manufacture of mosaic electrodes such as are utilised in television pick-up tubes - Google Patents

Abstract

870,235. Cathode-ray tubes. ELECTRIC & MUSICAL INDUSTRIES Ltd. Oct. 28, 1957 [Nov. 14, 1956], No. 34765/56. Class 39(1). In a method of making a mosaic electrode in which material, subsequently converted b y oxidation to a caesium resistant metallic oxide, is first deposited on a surface 4 through a mesh 6 spaced from the surface a n d conducting material is then deposited with the mesh in contact with the surface, the first material is evaporated from a source 12 not only in the direction of the surface but towards the envelope and re-directed from there on to the surface so that areas of the surface opposite the bars of the mesh are also effectively covered. The envelope is heated at 15, or by eddy current heating of the wall anode 9 to reflect or re-evaporate the material. The first material deposited may be magnesium. The quantity of magnesium deposited may be measured by observing the quantity deposited on a relatively cool part of the glass wall, leaving a small gap in the heating element for this purpose, or a known weight of magnesium may be evaporated at a known distance from the surface. The envelope wall is heated to between 300‹C and 500‹C. The mesh is then electrostatically attracted to the surface and the conducting elementsformed, e.g. from an alloy of bismuth and silver. The mesh is then moved to a position in which during operation of the tube it acts as a stabilizing electrode. The conducting elements are finally caesiated. Specifications 686,465 and 740,751 are referred to.