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Browse Prior Art Database

IMPROVING BLACK TEXT ON COLOR COPIES

IP.com Disclosure Number: IPCOM000025622D
Original Publication Date: 1986-Oct-31
Included in the Prior Art Database: 2004-Apr-04

Publishing Venue

Xerox Disclosure Journal

Abstract

In color copiers, three colors are used, cyan, magenta, and yellow, to make process color. Generally the combination of the three colors does not make a true black but rather black text comes out as brown or grey and in many cases, the image registration is such that the three colors show, giving a blurry unacceptable appearance. This may be corrected by additional process steps wherein a fourth exposure of the document to be reproduced is made using highlight illumination intensity such that the image is overexposed so that only the very dark black on the document, especrally the black text, will remain of the fourth image Accordingly the photoreceptor will be exposed with a low level charge remaining in the black areas Not only is the black image overexposed, but the overexposure broadens or magnifies the black image by an amount equal to the expected misreestration of the image in the system The fourth electrostatic latent image is now deveIoped with a black developer which will highlight the image and at the same time overlay a black image on the text such that it will make it black and it will cover over the color misregistration thus eliminating the blur caused by the image misregistration The polar liquid development technique IS particularly suitable to this application since it is a high gamma system and therefore development of the low voltage black image can be controlled