GB798506A - Improvements in and relating to electro-luminescent devices - Google Patents

Abstract

798,506. Electroluminescent-photoconductive combinations. THORN ELECTRICAL INDUSTRIES, Ltd. June 8, 1956 [June 15, 1955], No. 17311/55. Class 39(1). [Also in Group XL(c)] A signal responsive device such as a relay switch or amplifier comprises an input circuit supplying voltage changes which excite an electroluminescent device the light from which falls on a photo-conductive device included in the output circuit. Thin layers 10, 11 of electroluminescent and photo-conductive materials respectively are separated by a transparent conductive layer 12 and enclosed between outer electrodes 13, 14 which may be opaque. The edges may be covered with opaque material 17. The photo-conductive material may include resins, plastics or glass beads to modify its resistance or light-absorption. The input and output circuits 15, 16 are connected to the electrode layers. The input may be an A.C. source and the output includes a D.C. source in series with a load, Fig. 2 (not shown). The layer 12 may be replaced by two separate transparent layers, if necessary separated by a transparent insulating layer, Fig. 3 (not shown). The device 11 may comprise a number of electrodes with photo-conductive material sandwiched between them, and alternate electrodes connected together. The two devices may be separate units with an interposed lens or mirror, Fig. 5 (not shown). The two electrodes 13, 14 may each be divided into a number of interlaced elements, Fig. 6 (not shown) and the common layer 12 may also be sub-divided, Fig. 7 (not shown). One or more input circuits may control a plurality of output circuits. In Fig. 8, an input pulse effects a closure of the output circuit until the latter itself is broken. Two electroluminescent cells 26, 27 illuminate a single photo-conductive cell 28. If switch 29 is closed momentarily, cell 26 is activated and the cell 28 rendered conducting so that electroluminescent cell 27 lights up. The circuit through cells 27, 28 persists when switch 29 is again opened. Switch 29 may be replaced by a source of pulses. In Fig. 9, the input activates electroluminescent cell 30 in combination with a photo-conductive cell 31 which is in parallel with a second input circuit 36, 37 and the electroluminescent cell 33 of a further combination 33, 32 with the photoconductive cell 32 connected to the output. Closure of switch 37 energizes cells 32, 33 to close the output circuit, but operation of switch 35 causes a short circuit of the cell 33 and opens the output circuit. The device may be as small as a pin's head, and a large number may be mounted on an insulating base, with some of the electrodes joined together, Fig. 10 (not shown). Specification 798,503 is referred to.