GB907116A - Improvements in or relating to face plates for use with cathode ray tubes - Google Patents

Abstract

907,116. Cathode-ray tubes. AMERICAN OPTICAL CO. Jan. 17, 1961, No. 1940/61. Class 39 (1). A face-plate for a cathode-ray tube 10 comprises a plurality of slender, light - conducting fibres 12 bundled and secured together in sideby - side, air - tight relationship by a transparent material 11 having a lower index of refraction than the fibres, and secured thereto a cellular structure 13 having opaque walls and containing luminescent material 14. As shown in Fig. 2, flint glass fibres 12 of hexagonal, octagonal or other crosssection are coated with crown glass 11 by inserting the fibres into tubes of crown glass and heating and drawing to a desired size. After fusing the coated fibres together, the end surfaces thereof are ground and polished. The cellular structure 13 may be formed by fusing together glass tubes and drawing the assembly to reduce the crosssectional size of the tubes, which are then provided with opaque and reflective coatings by gas-plating evaporation or chemical-silvering. Alternatively, copper wires may be goldplated, secured together, rolled to a reduced size and the copper removed by etching. The cellular structure 13 is fused or cemented to the fibre assembly either before or after filling the cells with a mixture of phosphor powder and water glass in liquid or paste form or by vapour deposition of the phosphor. The cells 14 may be of larger or smaller cross-section than the fibres 12, or may be of equal size and aligned therewith. Since the face-plate prevents light from being scattered from one cell to another, the thickness of the phosphor layer, and hence the electron beam voltage, may be increased over conventional tubes to obtain increased brightness. In Fig. 5, flint glass fibres 19 are coated with aluminium metaphosphate glass 22 and fused together, after which portions of the fibres are removed by etching to provide cells for the phosphor 23. The inner walls of these cells are provided with opaque and reflective coatings 24 or alternatively the coated fibres 19 may be provided with an opaque, metal coating before they are sealed together.