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TONER REMOVAL USING ELECTROSTATIC FIELD GRADIENTS

IP.com Disclosure Number: IPCOM000024151D
Original Publication Date: 1979-Oct-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 4 page(s) / 566K

Publishing Venue

Xerox Disclosure Journal

Abstract

In present day xerography, the absence of 100 percent transfer efficiency requires post-transfer cleaning of the Se cylinder (plate). This disclosure describes an electrostatic method using field and field gradients for the removal of post-transfer toner particles on the Se plate.

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XEROX DISCLOSURE JOURNAL

TONER REMOVAL USING ELECTRO~ STATIC FIELD GRADIENTS
Narendra S. Goel

Proposed Classification
U.S. CI, 355/15 Int, CL G03g 21/00

NON~UNIFORM ELECTRIC

FIELD

In present day xerography, the absence of 100 percent transfer efficiency requires post-transfer cleaning of the Se cylinder (plate). This disclosure describes an electrostatic method using field and field gradients for the removal of post-transfer toner particles on the Se plate.

The method consists of two steps. The first step is to give positive charge to the toner particles (assuming them initially to be negatively charged) using a corotron or some equivalent device. Since the toner particles have high electrical

resistivity, the positive charging presumably will partially neutralize the charge on the toner surface (especially on the surface exposed to the corotron) and in

addition, will create a dipole on the toner particle. This dipole will be oriented away from the Se plate. The second step is to apply an electrostatic, non~uniform

field with the direction of the field away from the Se plate and the maximum gradient near the top of the toner particle, The permanent dipole and the dipole

induced by the electric field will interact with the non~uniformfield, and the toner particle will feel a force which will be in the direction tending to dislodge the toner

particle. If the field and field gradient are large enough, effective removal of the toner particles from the Se substrate is possible.

The differences between the conventional, electrostatic, uniform field method and

the method suggested here is schematically illustrated in the diagram. For simplicity, only one toner particle is shown,

UNIFORM ELECTRIC FIELD

CONVENTIONAL IMPROVEMENT

Volume 4 Number 5 September/October 1979 667

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TONER REMOVAL USING ELECTROSTATIC FIELD GRADIENTS (Cont'd)

To estimate The magnitudes of The field and field gradient, the strength of the adhesion between toner and The e substrate is first estimated. For 20 p toner particles charged to about 2 x 10 e"/particle for a contact time of 10 minutes, the force required for 50 percent removal is about 75 m dynes. This force increases approximately exponentially both with the time of contact, between the toner particle and Se substrate and The percentage removed. For the purpose of illustration, a value of 75 m dynes* is taken for the effective force of removal of the toner particles. It may be noted that this value is without corona charging. Corona charging will probably reduce The force of adhesion which, while it may be significant, is not included in the calculations for the sake of slmpliclty.

Knowing the force of adhesion, the field and field gradients required for effective removal can be estimated. Let q andp be the average net charge and the average dipole moment, respectively, of a toner particle alter corona charging. If a non- uniform electric field i...