Process for the transfer printing of electrostatic charge images using N2 atmosphere

Claim 1

Process for transferring charge images for the production of color-prints of colored continuous tone originals wherein a latent image is formed on a photoconductive layer and the latent image is transferred to a charge image on an electrically insulating sheet material said method comprising (a) placing a primary charge image on the surface of a photoconductive layer including the steps of (i) placing a photoconductive layer in contact with an electrode surface maintained at a given electrical potential and thus charging the photoconductive layer, (ii) directing said charged layer to exposure to apparatus providing electromagnetic radiation and positioning the charged layer in said apparatus, (iii) imagewise exposing the charged photoconductive layer to an image to provide a positive primary charge image on a surface of the photoconductive layer; (b) directing an electrically insulating sheet material in contact with the surface of the photoconductive layer carrying the primary charge image, said contact being along an elongated narrow area of contact between the charged photoconductive layer and a first surface of the sheet material (c) supplying a gas having a high concentration of nitrogen having less than 1% of air with nitrogen in a stream flow directed on a second and opposite side of the sheet material and into the vicinity of the elongated narrow area of contact and producing a current consisting of high-speed electrons for providing a negative charge on said opposite side by means of a voltage source at a needle electrode located in the stream of concentrated nitrogen producing a corona discharge within the stream of concentrated nitrogen, so as to (d) uniformly charge the insulating sheet material by the charge carrying current of high speed electrons on the opposite side at the narrow strip of contact between the first surface and the photoconductive layer, (e) and transfer printing the primary charge image to a secondary charge image in the surface of the insulating sheet material in contact with the photoconductive layer, said secondary charge image produced in a charging area along said area of contact by high-speed electrons from the corona discharge, and including the step of (f) separating the sheet material from the photoconductive layer.