International Business Machines Corporation

Gary Scott Beardsley

Michael H Lee

Lawrence B Schein

Francis Chee-Shuen Lee

Gary Scott Keller

A system is provided for obtaining enhanced quality grayscale printing using standard printer architecture. An image to be printed is scanned to produce several bit maps for image pixels having different optical intensities. The different bit maps are handled by a standard print engine separately, in the same manner as multicolor bit maps would be handled. The image is then printed using a print head assembly having separate print heads for grayscale printing using different optical intensities. Thus, a printed image having enhanced resolution and quality, because of the optical intensity discrimination, is produced using a printer architecture which is the same as a standard multicolor printer architecture except for the front end, which scans for optical intensity, and the print head assembly, which has different print heads designed to produce different optical intensities. The print heads use either different ink dot sizes, inks having different pigment concentrations, or other suitable techniques for varying the optical intensity.

Grayscale printing system

It has been determined that the two systems that contribute to edge raggedness in producing electrophotographic images are the development and transfer systems. Conventional development systems cause wrong sign toner to be attracted to the edges of the formed characters. Conventional transfer systems utilize electrostatic transfer whereby large electric fields are applied across a small air gap. In order to reduce edge raggedness, wrong sign toner is eliminated during the development step by using tribolelectrically charged toner and electrostatic transfer is replaced with non-electrostatic transfer techniques, either thermal or pressure, or combinations thereof. In either event, the resistivity of the intermediate surface is preferably 10.sup.10 ohm-cm or lower. Significantly improved electrophotographic images result.

Method for reducing high quality electrophotographic images

An electrophotographic apparatus is provided with an electrically conductive voltage control bar between the photoconductor drum or belt and the developer or developer/cleaner roll. The voltage control bar prevents toner filming on said cleaning roll, and makes it possible for that roll to be made of an insulating material such as molded plastic.

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Morgan Hill, CA, United States of America

Gary Scott Beardsley