GB1245595A - Energy-responsive luminescent device - Google Patents

Abstract

1,245,595. Electroluminescence. MATSUSHITA ELECTRIC INDUSTRIAL CO. Ltd. 4 Sept., 1968 [11 Sept., 1967], No. 42126/68. Heading C4S. An energy responsive luminescent device comprises light pervious electrode 110, electroluminescent layer 100 (e.g. 20 to 50 micron thick ZnS), a second electrode 210, energy-responsive layer 200 (e.g. photoconductive, stress sensitive resistive or magneto-resistive) the resistivity of which varies in response to incident radiation (e.g. light, X-rays, or gamma rays) and a grid or net-shaped electrode 301 coated with dielectric 302 in any one or more of the layers between the two electrodes, an A.C. field producing luminescence the waveform of which, by application of a D.C. field, varies as the resistance of layer 200. The EL material may be dispersed in a resistive or accumulatively polarizable dielectric medium (e.g. glass enamel with 5n0 2 and Li or Li and Ti mixed with ZnS powder and fused to electrode 110). Slightly conductive layer 600 may be a mixture of epoxy resin and pulverized carbon or 5n0 2 or of powdered frit, inorganic black pigment, 5n0 2 and ferroelectric BaTiO 3 . The inclusion of CdS : Cl or Si instead of metal oxide renders layer 600 non-linearly resistive. An additional layer of powdered frit or epoxy resin, ferroelectric powder, and light reflective material (e.g. BaTiO 3 orSnO 2 ) may be fused and bonded as a reflecting layer between layers 600 and 100. The single or composite layer 600 should be 5 to 10 microns and 10 to 20 microns thick for non- pervious and reflective layers respectively to ensure the resistivity across the thickness of layer 600 is low relative to EL layer 100. Electrode 110 may be heat resistive, light pervious tin oxide and electrode 310 of W or Cu wire (10 to 30 Á diam. and spaced less than 400 microns) with a 2 to 10 micron thick polyester resin or glass coating 302. Electrode 310 may be on layers 600 or 100 or partly or entirely embedded therein. In the latter case, layer 700 is formed over layers 100 or 600. Alternatively, all the layers may be in the gap between wires 301. Auxiliary resistive layer 700 is preferably of resistivity 10<SP>6</SP> to 10<SP>9</SP> ohm cm. and, if layers 600 and 302 are of vitreous material, is epoxy resin or frit powder with SnO 2 , or if layers 600 and 302 comprise a low m.p. binder, e.g. epoxy resin, layer 700 comprises a similar metal binder with resistive metal oxides (e.g. 5n0 2 ) and a high dielectric material (e.g. ferroelectric BaTiO 3 ) which may be made non-linearly resistive by CdS : Cl or SiC additions in lieu of metaloxide. Photoconductive layer 200, of epoxy resin binder with CdS, CdSe or CdS.Se for instance, should preferably be 50 to 500 microns thick so that its dark resistivity (> 10<SP>9</SP> ohm cm.) is greater than the resistivity of layer 100. Layer 200 may, on omission of layer 700, fill the gaps between wires 301. Electrode 210 may be Au or Al foil, vapour deposited film, silver paint, or a grid embedded in layer 200 for example. Electrode 110 is negatively biased for conversion, amplification and erasure of stored images and positively for writing a stored image. The device may be used as a preamplifier for a T.V. system including a Vidicon image pick-up tube.