GB1297994A - - Google Patents

Abstract

1297994 Photoconductive materials MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 3 March 1970 [6 March 1969 7 March 1969 (2)] 10098/70 Heading H1K An A<SP>II</SP>B<SP>VI</SP> photoconductor is sintered in the presence of a vitreous enamel and of a solvent flux; the sintered photoconductor includes copper or silver as activator and chlorine, bromine, or iodine as co-activator. The enamel is incorporated into the pores of the sintered material while the flux, which acts as a solvent for and as a promoter of crystallinity in the material, evaporates during the sintering process. The process is applied to the formation of photoconductive bodies from cadmium sulphoselenide or from either or both of cadmium selenide and cadmium sulphide. The bodies may be formed on substrates of soda glass (softening point ca. 690‹ C., volume expansion coefficient ca. 310 x 10<SP>-7</SP>, high resistivity), potash glass, borosilicate glass, quartz, mica, rock crystal, ceramics, or of a metal (molybdenum). The enamel composition may be chosen to have a softening point of 450-515‹ C. and a volume expansion coefficient of 260-340 Î 10<SP>-7</SP>/‹ C. and consist of (in weight percentage) 14À5-44À1% SiO 2 , 23À7-28À7% B 2 O 3 , 2À2-23À5% ZnO, 10À9-15À4% Na 2 O, 0-14À6% BaO, 0-4À2% K 2 O, 0-9À0% TiO 2 , 0-2À7% Al 2 O 3 , and 0-1À2% of CaO, MgO, Fe 3 O 4 and/or lead monoxide. The volume ratio of the enamel in the sintered material is made 5-16%. Fluxes suggested are cadmium chloride, cadmium bromide, or cadmium iodide. The component powders for the sintering process (which may follow one or more various earlier firing steps) may be dispersed in water, or an alcohol higher than amyl alcohol (e.g. octyl alcohol) or a glycol higher than ethylene glycol, and the mixture painted, pressed or moulded on to a substrate, dried and then sintered. Electrodes may be of aluminium, indium, gold or silver and may be applied by conventional methods. In one method the photoconductor is dispersed in a solution of copper chloride and is then dried and fired. The copper chloride provides the copper activator and some of the chlorine coactivator. The crushed doped photoconductor is then mixed with cadmium chloride (flux) and vitreous enamel and sintered. The flux, most of which is evaporated, also acts as the main source of the chlorine coactivator. A subsidiary function of the vitreous enamel is to regulate the concentrations of activator and coactivator in the photoconductor by acting as a sink. In a variant method some cadmium chloride is included before the final firing and the main bulk added (as before) for the sintering step. In another variant all components are mixed initially and are sintered without other firing stages.