Abstract: A d.c. or a.c. electroluminescent panel comprises a transparent substrate, a transparent first electrode film, a thin film phosphor layer, a black or dark powder back layer of electrically conductive material, and a second electrode film. Application of a voltage across the phosphor layer causes it to emit light. In this invention, the black powder back-layer significantly enhances the contrast of the panel.

Abstract: The present invention concerns an electroluminescent panel suitable for unidirectional and/alternating voltage order, a transparent glass substrate (10), a thin transparent front electrode film (12) made of indium-tin-oxide, a first thin (preferably 1-2 microns thick) layer (14) of a phosphor in the form of powder particles, the surface of the particles being free of any metallic coating, e.g. Cu coating, an electrically conducting, dark powder layer (16) which is a control layer consisting e.g. of MnO.sub.2 uncoated or undoped with Cu and a (preferably aluminium) back electrode layer )18).

Abstract: A d.c. or a.c. electroluminescent panel comprises a transparent substrate, a transparent first electrode film, a thin film phosphor layer, a control layer and a second electrode film. A black or dark colored material, less than 1 micron thick, is interposed between the thin film phosphor layer and the control layer to enhance the contrast of the panel whenever a voltage is applied across the thin film phosphor layer causing it to emit light.