GB820763A - Improvements in or relating to electrostatic printing - Google Patents

Abstract

820,763. Electrophotographic processes. KODAK Ltd. July 15, 1957 [July 16, 1956], No. 22282/57. Class 98(2) [Also in Group XVI] Prints are made by focusing an image of radiation on to the front of a paperbacked photoconductive layer supported with the paper backing on a conductive support, while subjecting the front of the photoconductive layer to a corona discharge and to a mist of electrostatically charged ink particles, so that they deposit to form an image on the exposed areas. As shown (Fig. 2), a lamp 10 and lens 17 project an image of a transparency 12 on to a photoconductive layer 30 on a paper backing 31. The conductive support 32 is earthed or otherwise held at a potential difference with respect to the corona discharge needle 34, and ink is sprayed from a gun 41 and is charged by the corona discharge from needle 34. A fan 47 draws air into the enclosure 49 at 48 so as to prevent the ink mist from drifting on to the lens. Another embodiment is described using two needles 34 and with the paperbacked photoconductive layer in the form of a roll. An apparatus is also shown for producing colour prints by repeating the process with colour separation images and different coloured inks, an infra-red lamp being used to discharge the photoconductive layer between each successive exposure. The spray gun has three nozzles for different inks which are sprayed along the corona discharge needle. A prior art arrangement is described wherein the image is projected on to the photoconductive layer through its transparent, conductive backing, and a mist of ink or smoke is sprayed through a grid on to paper placed over the front of the photoconductive layer, the grid being held at a potential difference with respect to the conductive backing.