Development of electrostatic images

1,035,953. Electrophotographic processes. COMMONWEALTH OF AUSTRALIA; DEPARTMENT OF SUPPLY. April 17, 1963,No. 15183/63. Heading G2H. A method of developing electrostatic images which comprises producing an electrostatic latent image on a base containing a photoconductor, developing the image with a suspension in a carrier, liquid of a photo-chemical substance capable of being catalysed by or reacting with a substance in the base and subsequently rendering the image visible and fixed by subjecting the deposited developer to electromagnetic waves. The photo-chemical substance may be chloro-auric acid, silver nitrate, copper sulphate,ferric chloride, lead oxide or bromo-platinec acid. In one example, a sheet of paper, wood, plastic or metal is coated with photoconductive material e.g. zinc oxide in resin according to the following composition:- Alkyd Resin 100 grms, Durham special zinc oxide, cobalt naphenate 6% 0. 5 grms, manganese napthenate 4%, tolnene 100 grms. The ingredients are milled together to produce a finely dispersed paint which is applied e.g. by roller or brush spray after the required amount of dilution with toluene. The coated sheet is cured to produce uniform electrical properties and then charged to produce a uniform surface charge and exposed to an image to produce an electrostatic image. The latent image is developed by liquid developer made as follows:- Solution A comprising chloro-auric acid 5 grms, iso-propyl alcohol 100 grms: Solution B is made by dispersing 10 grms of solution A in 100 grms of cyclohexane to form a colloidal dispersion. The liquid developer is then applied by roller or immersion and the resultant solid image is exposed to light to darken the deposit. In another example, the developer is made from Solution A containing 5 grms cupric sulphate and 100 grms idioxane and then dispersing solution A to form a 10% dispersion in Shell solvent X55 (Registered Trade Mark). In another example, for use with a photo conductive layer of bismuth trioxide, the developer may be bromoplatinic acid, 3 grms and ethyl alcohol 100 grms as a 5% dispersion in Freon 113 (Registered Trade Mark) or perchlorethylene. Another developer may be a solution of silver nitrate, 5 grms and dioxane 100 grms dispersed to form a 5% dispersion in a solution of carbon tetrachloride in a solvent. The developer may be subjected to X-rays or heat instead of visible light.