Browse Prior Art Database

CORONA POWERED BIASED TRANSFER ROLLER

IP.com Disclosure Number: IPCOM000026863D
Original Publication Date: 1994-Feb-28
Included in the Prior Art Database: 2004-Apr-06
Document File: 4 page(s) / 175K

Publishing Venue

Xerox Disclosure Journal

Abstract

Electrostatic transfer of powder images from a photoreceptor 12 to a copy sheet 14 requires that the two be in close proximity to one another to avoid blurred images, caused by gap transfer and image deletions within the transfer nip, 16. To insure contact during the transfer process within nip 16, the 9000 Series of Xerox* copiers uses a bias transfer roller, 18 that forces the copy sheet to conform to the photoreceptor within the nip or transfer zone. However, the roll must meet complex requirements relative to its electrical properties, wherein the resistivity (p) and the unit area capacitance of the roll coating must:

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

CORONA POWERED BIASED Proposed Classification TRANSFER ROLLER U.S. C1.3551273 Lloyd F. Bean Int. C1. G03g 15/14

FIG. I

f 30

32

FIG. 2

f 40

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CORONA POWERED BIASED TRANSFER ROLLER(Cont'd)

FIG.

FIG. 5

44 XEROX DISCLOSURE JOURNAL - Vol. 19, No. 1 JanuaryFebruary 1994

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CORONA POWERED BIASED TRANSFER ROLLER(Cont'd)

Electrostatic transfer of powder images from a photoreceptor 12 to a copy sheet 14 requires that the two be in close proximity to one another to avoid blurred images, caused by gap transfer and image deletions within the transfer nip, 16. To insure contact during the transfer process within nip 16, the 9000 Series of Xerox* copiers uses a bias transfer roller, 18 that forces the copy sheet to conform to the photoreceptor within the nip or transfer zone. However, the roll must meet complex requirements relative to its electrical properties, wherein the resistivity (p) and the unit area capacitance of the roll coating must:

1) not allow the electrostatic field in the pre-nip region to cause image transfer or air breakdown which would result respectively in either blurred images or deletions produced because of the reduction or change in sign of the image charge;

2) allow the electrostatic field in the nip to exceed a threshold value which is required for image transfer; or

3) allow the electrostatic field in the post-nip region to exceed the air breakdown voltage such that charge is deposited on the copy sheet.

This disclosure describes a continuous surface member, for example, a roll or belt, having less stringent electrical requirements than those commonly used in the 9000 Series copiers for bias transfer rollers. The members described herein are not limited to given surface speed ranges as are the 9000 Series bias transfer rollers. The electrostatic field conditions required for good or excellent electrostatic transfer are generally met by spraying corona charge on the interior surface of the member as further displayed in Figure 1 where corona element 20 sprays corona ions 22 along the interior surface of bias transfer roll 18. Improvement of such a system includes the use of an improved member which consists of embedded conductive elements within an insulating matrix, as illustrated in Figure 2. Insulating matrix 30 has conductive elements 32 embedded therein in a regular or irregular fashion to improve the conductivity of the matrix in general and thereby that of the member. In an alternative embodimen...