GB969004A - Improvements in or relating to electroluminescent crossedparallel-conductor systems - Google Patents

Abstract

An electroluminescent crossed-parallel-electrode system is combined with a circuit arrangement which includes a super-linear photoconductive layer to minimize the cross-illumination effect. In the arrangement shown in Fig. 2 the electroluminescent system 1 comprises a layer 2 of zinc selenide activated with 2 x 10-4 copper atoms per mol. between crossed-parallel electrodes Yj and Xi connected to rotary switches. <PICT:0969004/C4-C5/1> <PICT:0969004/C4-C5/2> <PICT:0969004/C4-C5/3> <PICT:0969004/C4-C5/4> The system 1 is positioned opposite the photo conductive system 6 comprising a super-linear photoconductive layer 7 and a photoconductive layer 8 separated by opaque auxiliary electrodes 9 in the form of metal islands and sandwiched between transparent crossed-parallel electrodes 10j and 11i arranged opposite the crossed-parallel electrodes Yj and Xi. The electrodes 10i are connected together through a conductor 101 to a voltage source 12 and the electrodes 11i are connected together through a conductor 111 to the source 12 through a load resistor 13. Output voltage is taken from terminals 131 and 1311. The photoconductive system 6 serves for storing images 14 projected through the lens system 15. The light emitted by the layer 2 can be visible or infra-red light which lies within the spectral range to which the super-linear photoconductive layer 7 is sensitive. The layer 7 can consist of cadmiumindium sulphide activated with 2 x 10-3 copper or 2 x 10-3 gold atoms per mol. Alternatively the super-linear photoconductive layer 7 can consist of cadmium selenide. In the arrangement shown in Fig. 4 the system 16 is used for displaying images and comprises a super-linear photoconductive layer 7 and an electroluminescent layer 19 separated by opaque auxiliary electrodes 20 in the form of islands and sandwiched between transparent electrodes 17 and 18 connected to a video-signal source 21. The electrodes 17 and 18 can be in the form of crossed-parallel electrodes as in Fig. 2. The arrangement shown in Fig. 4 can be used for colour television, the electroluminescent layer 19 being divided into a large number of triplets each comprising three strips capable of luminescing with red, green and blue light respectively, and the electrode 18 being divided into a large number of groups each comprising three electrodes. In the arrangement shown in Fig. 5 the crossed-parallel electrode electroluminescent system 1 irradiates a reading-out device 23 through a punched card 22. The reading-out device 23 comprises a super-linear photoconductive layer 7 between crossed-parallel transparent electrodes 24j and opaque electrodes 25j. The electrodes are connected through conductors 241 and 251 to a voltage source 26 and resistor 27, the output voltage from which is applied to a machine 28 in which the coded information stored in the punched card 22 is processed. Instead of being stored in a punched card the information can be stored in a crossed-parallel-electrode electroluminescent system as shown in Fig. 7 in which the three systems 1, 34 and 35 are mounted in an optically transparent and insulating support such as glass. The system 1 is similar to that shown in Fig. 2 except that the rotary switches are subdivided into a number of two-way switches. The system 34 comprises a layer 31 of electroluminescent material and a layer 32 of super-linear photoconductive material separated by transparent auxiliary electrodes 36 in the form of metal islands and sandwiched between crossed-parallel-electrodes X11 and Yj1, the electrodes X11 being connecte to earth and the electrodes Yj1 being connected separately through two-way switches to an A.C. source. The system 35 coomprises a layer 3 of photoconductive material, which can be the same as that of the layer 32, sandwiched between crossed-parallel electrodes X111 and Yj11. The material of the electroluminescent layer 31 can be the same as that of the layer 2. The mechanical switches used above can be replaced by electronic switches, e.g. discharge tubes or transistors or photoconductive resistors comprising electroluminescent elements as described in Specification 928,137. Specifications 855,425 and 942,470 also are referred to.