Method of manufacturing photoconductive layers

972,944. Photo-conductive layers. PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd. Feb. 11, 1963 [Feb. 14, 1962], No. 5482/63. Heading H1K. A photo-conductive layer is made by applying to a support a powder of cadmium sulphide or selenide or of mixed crystals of these compounds in a solution containing phosphorus in oxidized form and one or more of cadmium chloride, bromide or iodide and then evaporating off the solvent and heating. The phosphorus in an amount of 0.05-0.5 atomic per cent based on the cadmium may be in the form of phosphorus pentoxide, phosphoric acid or ammonium phosphate, and the amount of cadmium halide is preferably 0.7-7 molecules per 100 molecules of cadmium chalkogenide. Heating may be carried out at 450-700‹ C. in air for a sufficient time to evaporate the halide. Preferably, the powder has a grain size of less than 100Á and has been activated by sintering in the presence of activators, for example gallium and copper, to give a content of between 5 x 10-5 and 5 x 10-4 atoms of each per atom of copper. In a typical embodiment powdered cadmium sulphide so activated mixed with a solution in alcohol of cadmium chloride and dilute orthophosphoric acid is sprayed on a glass support, dried at 70‹ C., and then heated in air for half an hour at 550‹ C. Aluminium electrodes 3, 4 or interdigitated electrodes are applied by evaporation through a mask and nickel wires 7, 8 bonded to them a hardenable ethoxylin resin containing silver powder. Finally, after etching the layer off the edges the photo-conductive layer is coated with a protective layer of ethoxylin resin.