GB1401229A - Multibeam cathode ray tube - Google Patents

Abstract

1401229 Cathode ray tubes A W STANDAART 10 Aug 1972 [18 Aug 1971] 37265/72 Heading H1D A multi-beam cathode ray tube, for high writing speeds in computer displays for example, comprises pohsphor screen 13A, single gun 16 including beam control perforated electrode 18 and beam shaping perforated electrode (19) (Fig. 3, not shown) each electrode having aligned rows and columns of holes lined with conductive material, the holes of the control electrode being connected by individual conductor strips to terminals for applying selected potentials, and an accelerating anode 28, the cathode comprising joined metallic sheet members (23, 24) having outwardly projecting truncated V-shaped formations (Fig. 2, not shown), the sided channels so formed housing coiled filament wire along their length and flat faces (23C) coated with thermally activated electron emissive material. The gun members are mounted on frame 21. Helical electrode 28 provides a potential gradient from a maximum negative potential near the cathode and eliminates beam divergences due to mutual repulsion. The helix may be 2 mms. wide, 70 M# resistance, and potentials are given. The helix terminates with a metal distortion correction anode (30) (Fig. 3, not shown) to eliminate pin-cushion or barrel distortion of a 70 degree deflection system. Members (23, 24) of the cathode may be machined stamped or die rolled and spot-welded, and W filament (25) insulated by a layer of high temperature alumina or fused aluminium oxide. The honeycomb design resists heat warpage. The emissive material, referred to by Trade Name, may be sprayed, painted or electrophoretically deposited and protected from atmospheric poisoning by an organic lacquer until activation. Control grid 18 has stepped apertures (18A) (Fig. 7, not shown) in ceramic substrate (18B), the sputtered Au layer (18C) being increased in thickness by electroplating and providing a non-oxidizing or tarnishing metal conductor, or may alternatively be a Cu-Ni composite layer. Dimensions of the grid components are specified. A photographic method of production by etching is detailed. First anode 19 has a continuous Au layer on the surface away from the grid 18, and 0À001 inch wide Au around the aperture rims on the near side. Fig. 5 (not shown) indicates a cathode-control grid assembly.