AC corona to remove background from the imaging member of a magnetic copier
AssigneeE. I. Du Pont de Nemours and Company
InventorsDonald W. Edwards, Emery J. Gorondy, Arend Van Roggen
Life of this patent
Estimating the term…
Abstract
A process for reproducing graphic information wherein a magnetic image is formed in a premagnetized layer of acicular chromium dioxide by heating the chromium dioxide selectively to above its Curie point. Ferromagnetic toner particles are then applied uniformly to the chromium dioxide layer, so as to adhere only in the magnetized areas. The toner particles are electrostatically transferred to a substrate and fused into position. Alternating current coronas or other static neutralizing devices are used to neutralize unwanted charges on toner particles which would otherwise cause fuzzy images and unwanted background markings on the final copies.
Claims16
A process for repetitive reproduction of graphic information comprising:
- (a) transferring toner particles by bringing a substrate capable of maintaining an electrostatic charge into superposed position with an image of uncharged toner particles having an electrical conductivity of less than about 1.times.10.sup.-13 mho/cm magnetically adhered to a grounded electrically conductive imaging member having a resistivity of less than about 1.times.10.sup.+9 ohm-cm and applying an electric field at this position which electric field is generated by applying an electrostatic charge to the side of the substrate away from the toner particles, separating said substrate from said imaging member, whereby said toner particles adhere to said substrate upon separation of the substrate from the imaging member;
- (b) reapplying toner particles to the imaging member;
- (c) repeating step (a);
- (d) applying static neutralizing means selected from the class consisting of alternating current coronas and nuclear bars to said imaging member and any toner particles thereon, either between the steps of transferring toner particles to said substrate and reapplying toner particles to the imaging member, or between the steps of reapplying toner to the imaging member and bringing said substrate into superposed position with said imaging member;
- and (e) removing residual toner from non-magnetized areas of said imaging member between the steps of reapplying toner to said imaging member and transferring toner to said substrate.
A process comprising the following ordered steps (a) spatially periodic magnetizing a layer of acicular chromium dioxide particles in a binder which particles comprise from 40 to 85 weight percent of a layer of from 0.001 to 0.15 mm thick adhered to a grounded electrically conductive layer, bringing said layer of acicular chromium dioxide into superposed position with a document containing thereon indicia which are to be copied, uniformly illuminating said document whereby radiant energy is transmitted through said document in the areas of said document not covered by indicia whereby the acicular chromium dioxide in the areas where it is illuminated and heated to above its Curie point and demagnetized while the areas of acicular chromium dioxide adjacent the indicia contained on said document are not heated above its Curie point, (b) applying uncharged toner particles having a conductivity of less than about 1.times.10.sup.-13 mho/cm comprising ferromagnetic material and a fixable material uniformly to the chromium dioxide layer whereby said toner particles adhere only to the magnetized areas of the chromium dioxide, maintaining said toner particles in the uncharged condition, (c) removing toner particles from non-magnetized areas of the chromium dioxide layer, (d) superposing a dielectric substrate capable of maintaining an electrostatic charge adjacent said acicular chromium dioxide layer, (e) applying an electric field while said substrate is in superposed position with the acicular chromium dioxide layer which electric field is generated by applying an electrostatic charge to the side of the substrate which is away from the toner particles whereby said toner particles are adhered to said substrate upon separation of said substrate from said layer, (f) separating said substrate from said imaging member, (g) repeating steps (b) through (f), and (h) either between the steps of transferring toner particles to said substrate and reapplying toner particles to the acicular chromium dioxide layer or between the steps of reapplying toner to the imaging member and bringing said substrate into superposed position with the acicular chromium dioxide layer, applying static neutralizing means selected from the class consisting of alternating current coronas and nuclear bars whereby any toner particles on the imaging member bearing an electrostatic charge are neutralized.
Dependencies are inferred from the claim text.