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ELIMINATION OF GHOSTING IN OVER-COATED XEROGRAPHY

IP.com Disclosure Number: IPCOM000025371D
Original Publication Date: 1984-Dec-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 4 page(s) / 149K

Publishing Venue

Xerox Disclosure Journal

Abstract

In conventional copy machines, the photoreceptor in one xerographic cycle goes through the following stations: charging, image exposure, development, transfer, cleaning and erase. Between the exposure and the cleaning station, the photo-receptor is usually exposed to other corotrons which are necessary for various machine functions. An example is the AC preclean corotron. When an insulating overcoating is used on top of the photoreceptor surface, the presence of a corotron before the erase can cause severe ghosting. This ghosting can be eliminated by exposing the photoreceptor, after development, to an erase lamp before it is exposed to corotrons.

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1 XEROX DISCLOSURE JOURNAL

ELIMINATION OF GHOSTING IN OVER- COATED XEROGRAPHY
Heinz W. Pinsler
Edward C. Savage
Merlin E. Scharfe
Carl B. Fisher

Proposed Classification
U.S. Cl. 427/18 Int. C1. G03g 13/06

FIG. /

Hi6 I I0

J++++t+ I

I

1 I I

-I

SURFACE SPEED V

FIG 2

voc

't t

DARK LIGHT

Volume 9 Number 6 November/December 1984 405

[This page contains 1 picture or other non-text object]

Page 2 of 4

ELIMINATION OF GHOSTING IN OVERCOATED XEROGRAPHY (Cont'd)

In conventional copy machines, the photoreceptor in one xerographic cycle goes through the following stations: charging, image exposure, development, transfer, cleaning and erase. Between the exposure and the cleaning station, the photo- receptor is usually exposed to other corotrons which are necessary for various machine functions. An example is the AC preclean corotron. When an insulating overcoating is used on top of the photoreceptor surface, the presence of a corotron before the erase can cause severe ghosting. This ghosting can be eliminated by exposing the photoreceptor, after development, to an erase lamp before it is exposed to corotrons.

Any electrical charge accumulation on the overcoating results in a voltage across the overcoating which is directly superimposed on the photoinduced discharge curve (PIDC). Charge nonuniformities on the overcoating cause variations of the development potential, the background potential and the toner density on the developed drum.

The following is an illustration of how charge variations on the overcoating and subsequent ghosting can be introduced by exposure to an AC corotron. In the attached Figure 1, an overcoated photoreceptor 10 is shown after image exposure. A portion 12 of the photoreceptor is light discharged. For the sake of simplicity, it is assumed that the photoreceptor voltage is zero in the discharge !light) region 12 and some positive value in the dark region 14. There is no voltage across the overcoating. Under the AC corotron 16, the photoreceptor receives a net DC current which can be expressed in the following way:

I = -s (V - VN)

     P I = net DC current

S = characteristic constant of the corotron

V = photoreceptor voltage

VN = "neutralization" voltage.

P

VN is essentially determined by the corotron shield potential.

If the voltage of photoreceptor is VN, no net DC charge is deposited by the AC corotron. Further mathematical treatment yields the following relationship between the initial voltage Vi before the corotron and Vf after the corotron:

'iVN - exp - S = leveling factor

v.-vN I cv

C = photoreceptor capacity

V = surface velocity of the photoreceptor

XEROX 406 DISCLOSURE JOURNAL

Volume 9 Number 6 November/December 1984

[This page contains 1 picture or other non-text object]

Page 3 of 4

ELIMINATION OF GHOSTING IN OVERCOATED XEROGRAPHY (Cont'd)

This means if the photoreceptor remains long enough under the corotron (low V),
the voltage V after the corotron will be close to VN, independent of the initia...