GB1389737A - Luminescent screens - Google Patents

Abstract

1389737 Luminescent screens GENERAL ELECTRIC CO Ltd 17 May 1973 [17 May 1972] 23237/72 Heading C4S [Also in Division H1] A luminescent screen (e.g. electroluminescent (Figs. 1 to 5), c.r.t., X-ray or image intensifier screen), comprises one or more plates 2 of rigid transparent material, phosphor layer 6, broad band anti-reflection layer 1, circular polarizer 3 and band pass interference filter 4 permitting passage of light corresponding to the whole or part (e.g. 20 nm.), of the phosphor emission, incident light 8 falling, in use, directly on layer 1. The figures include electrodes 5 and 7 for an EL panel. Refractive index matching and otherwise is discussed, as are the functions of the individual layers in producing overall contrast enhancement. The narrower the filter 4 pass-band, the more restricted the viewing angle. Support plates and optical layers may be glass or plastic and different combinations of each are disclosed, e.g. plates or films of glass may support each optical layer and the polarizer may be a plate or film of plastic incorporating polarizer material. For ZnS EL phosphor, the filter is a combination allowing near monochromatic transmission, e.g. alternating high and low Á such as ZnS and magnesium fluoride, ZnS and cryolite, titanium dioxide and silica, and ZnS and thorium fluoride, and similarly layer 1. The screen may be flat or slightly curved and layers 1, 3 and 4 on the front of layer 2 (Fig. 2, not shown). Fig. 3 (not shown), includes additional plate (2<SP>1</SP>) and the plates are bonded by optical cement. Figs. 4 and 5 (not shown), are further alternatives with additional plate (211) and the polarizer is incorporated in celluloid film. Layer (2<SP>1</SP>) may be omitted and the tin oxide coating (5) deposited directly on filter 4. Back electrode 7 may be of Al and a plurality of electrodes may be on that phosphor surface. The EL panels are encapsulated in a controlled atmosphere.