GB1296283A - - Google Patents

Abstract

1296283 Electroluminescence MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 19 Oct 1970 [20 Oct 1969] 49533/70 Heading C4S A resistive EL member 23 comprises a Zn compound type EL phosphor having a minor portion converted to ZnO and suspended in a binding dielectric material, the phosphor being in amount 25 to 70 vol. per cent. The phosphor may be ZnS, ZnSe, ZnS-ZnSe or ZnS-CdS activated with one of Group Ib e.g. Cu and coactivated with Cl and/or Al, or Mn, or other Group VIb, IIIb, and VIIa elements, and the dielectric may be plastics material comprising urea resin. The member may be prepared by baking the Zn type compound in an oxygen containing atmosphere to convert a minor portion to ZnO and mixing with a plastics material, the specific resistance being adjusted in the range 10<SP>11</SP> to 10<SP>5</SP> # cm. by changing baking time and temperature e.g. in the range 600 to 750‹ C. for 30 minutes at most, Figs 2-4 (not shown). In EL-pc Ac-DC devices, the EL element specific resistance needs be equal to or lower than the pc resistivity (e.g. 10<SP>9</SP> # cm.), so that the pc sensitively and hence EL output may be controlled by varying the D.C. Fig. 1 (not shown) includes glassplate (1), tin oxide electrode (12), EL layer (13), a portion of each particle converted to the oxide and evaporated Al or Ag electrode (14). 50 to 70 Á layer (13) is hardened in position by heating to 160‹ C. The coefficient of non-linearity in the I α V<SP>n</SP> is given in Fig. 2 (not shown), Fig. 4 (not shown) illustrating intensity at 1 KHz against baking conditions, Fig. 5 (not shown) indicating X-ray diffractions. The oxidation of the preferably powdered phosphor may be controlled by varying the oxygen in the hermetically sealed quartz envelope. Resistive light reflecting 20 Á layer 24 comprises ferroelectric BaTiO 3 particles and SnO 2 semiconductive powders in urea resin, resistive light-opaque 10 Á layer 25 comprises carbon in epoxy resin for instance, pc 250 to 300 Á layer 26 may be CdS, CdSe, CdS-CdSe: Cu or Cl with epoxy resin for instance. Electrode 27 may be evaporated Ag or Al or a plurality of 10 to, 50 Á W wires at 300 to 500 Á pitch or a 200 to 500 Á mesh. Desirably the resistance in the thickness direction of layer 23 is greater than that of layers 24, 25 and the dark resistance of p.c. layer 26 > the thickness total resistance of layers 23, 24, 25. L 1 may be light or X-rays. D.C. voltage 31 incresaes the p.c. sensitivity and if layer 23 non- linearity coefficient is one, the sensitivity increases with input decrease, while a coefficient of three effects a varistor action.