GB1055696A - Electro-photographic reproduction - Google Patents

Abstract

1,055,696. Photo-conductographic processes. EASTMAN KODAK CO. July 9, 1964 [July 15, 1963], No. 28296/64. Heading G2H. A photo-conductive layer 12 such as zinc oxide is exposed to a light image to produce a conductivity image, an electric potential is applied across said image an electrolytic developer 16 solution being in contact with it either simultaneously with or subsequent to the exposure, and the light exposure or the electric potential is terminated when the total electric charge passed through said layer reaches a predetermined value. The electrolyte may deposit an image of metal, metal hydroxide or dye, whose density depends on the total charge passed. The zinc oxide in a resin binder forms layer 12 on aluminium foil 13 on a paper base 14. For contact printing, electrolyte is sandwiched between layer 12 and a second electrode 18 or layer 12 may be covered by a uni-dimensional conductor, 20 to improve image resolution. In this case the image appearing on conductor 20 is transferred to a receiving sheet which may be the electrode 18. This system may also be used for projection printing from transparency 26 using lamp 25. Electrolyte 35 is contained by metal frame 31 insulated from layer 12 by layer 32 of polytetrafluoroethylene the electrolyte being added after exposure if a persistent conductivity layer 12 is used, or if non-persistent, a transparent electrolyte 13 used as development proceeds during exposure. In Fig. 4 electrolysis current from battery 42 passes through integrator 43 which provides a signal to switch off the lamp 25 at 39 when the predetermined charge has passed. Alternatively shutter 28 is used to end the exposure. In a modification in which development is either simultaneous or subsequent to the exposure, integrator 43 is used to switch off the electrolysis current. Two integrators are used in a variation whereby exposure is coded first and then, after a period of electrolysis at a higher potential, development is ended. The electrolysis current is selected by means of variable resistor 65 the voltage across which is applied to the integrating circuit consisting of resistor 64 and capacitor 68 and the output voltage is applied to the grids of double triode 66. Relay 72 is then actuated through a meter relay 71 and switch 62 is opened to end the exposure, and switch 73 is closed to discharge and re-set capacitor 68. A similar circuit may be used for controlling development time.