Patent GB-829588-A (GB)
Title: Improvements in and relating to illuminated panels
IPC: H05B33/22
Filed: 1957-04-30
Abstract: 829,588. Electroluminescence. NEUGASS, E. A. April 30, 1957, No. 13756 /57. Class 39(1). [Also in Groups XI, XV, XIX and XXXVII] A panel 10, such as an aircraft instrument panel, comprises a sheet 13 of transparent material with a layer 12 of translucent material on the front face thereof, an outer layer 11 of opaque material having openings 15 therein through which the layer 12 is exposed to define indicia, a backing sheet 20 disposed against the transparent sheet 13 and having at least one recess 21 in its front face at a position corresponding to the indicia, and, an electroluminescent lighting cell 17 disposed in the or each recess. The sheet 13 can be of methyl methacrylate and may be dyed red, and can have a coating 14 of transparent red fluorescent dye on its back surface. The layer 12 can be of white translucent material such as a vinyl resin having a dispersion of large particles suspended therein as an emulsion. The opaque layer 11 can be black and of polyvinyl or vinyl resins or of their polymers or copolymers and having a matte finish. The contrasting colours of the layers 11 and 12 allow the indicia to be visible under ambient illumination. The backing sheet 20 can be transparent and of an acrylic resin such as methyl methacrylate. The recesses 21 are larger than the lighting cells 17 to allow for temperature changes. The various layers and sheets are preferably made of materials having substantially equal coefficients of expansion. In manufacturing the panel, the layers 11 and 12 and the sheet 13 are joined together by adhesive or by heat and pressure and then the backing sheet 20 is joined to the coated back of the lamination by heat and pressure or by mechanical means such as screws. The thickness D1 is substantially equal to the thickness D2 to prevent warping under temperature changes. The exposed surface 16 of the layer 12 may be flush with the back face of the layer 11 as shown in Fig. 2, or may project forwardly into the opening 15 to be flush with the front face of the layer 11 or to project forwardly thereof. Some areas of the panel 10 may have both layers 11 and 12 cut away as shown in Figs. 1 and 5 so that a dial or pointer can be illuminated by cells 19. Electrical conducting means for the electroluminescent cells can comprise a printed circuit on the front surface of the backing sheet 20 or conductors disposed in grooves therein. The panel 10 can have holes 24, 25, 26 to receive shafts extending from control knobs, &c., to related instruments, &c., mounted at the back of the panel. A black epoxy coating is applied to the surfaces of the holes and the edges of the panel to prevent escape of light. A construction of electroluminescent cell is referred to in which two intermeshed metallic grids are applied to a face of a supporting plate and insulated from each other and a phosphor is then applied over and between the intermeshed grids. Alternatively the phosphor is sandwiched between a metal sheet and a semi-transparent coating on a glass plate. The phosphor, which can be suspended in a solid dielectric, can comprise 75% zinc sulphide and 25% zinc oxide activated by halogens, copper and/or lead. Specifications 692,195, 711,167 and 742,756 are referred to.