Systems and methods for reducing electrostatic memory

Details Systems and methods for reducing electrostatic memory Systems and methods for reducing electrostatic memory

2003-08-14

2004-11-09

Ngo, Hoang (Department: 2852)

Electrophotography

Supplemental electrophotographic process

Exposure or charging

C399S043000

Reexamination Certificate

active

06816689

ABSTRACT:

BACKGROUND
Electrophotographic printing and copying (i.e. imaging) devices include photoconductor members on which latent images are formed for the purpose of developing toner images that can be transferred to appropriate recording media, such as pieces of paper. During printing of a received print job or a scanned document, the photoconductor member is first uniformly electrically charged by an appropriate charging apparatus, such as a charge roller. Next, portions of the photoconductor member are then discharged, for instance by laser pulses, such that toner particles provided by a developing apparatus, such as a developing roller, will be attracted to the portions of the photoconductor member that were not discharged, which correlate to print content (text and/or graphics) that is to be printed.
When print content is repeated on several consecutive pages, the photoconductor member can develop an electrostatic “memory” of the repeated content. Specifically, electrostatic charges representative of the repeated print content may remain on the photoconductor member after toner transfer, resulting in relatively light, yet noticeable, images of the print content being transferred to pages that are subsequently printed but that are not supposed to include that content. For example, when a large document that includes a logo that is provided at the top of each page is printed, a ghost image of the logo may appear on pages of another document that is subsequently printed. In similar manner, if a large number of copies of a given single-page document are generated using a photocopier, a ghost image of the document content may appear on other hardcopy documents that are subsequently output by the photocopier.
The above-described phenomenon occurs because, when given content is repeatedly printed, a charge that represents that content builds on surface of the photoconductor member without being completely erased during the print cycle. The charge build up occurs, in part, due to the fact that the print engines of most imaging devices are operated such that the leading edge of each page of the printed document coincides with the same point on the surface of the photoconductor member. This manner of engine operation may facilitate correct alignment of the print content on the pages and/or account for the physical characteristics of the photoconductor member.
From the above, it can be appreciated that it would be desirable to have a system and a method for reducing electrostatic memory to avoid unintended printing of ghost images.
SUMMARY
Disclosed are systems and methods for reducing of electrostatic memory. In one embodiment, a system and a method pertain to determining whether print content is to be repeated across consecutive pages, and if the print content is to be repeated, controlling a print engine of the imaging device to reduce electrostatic memory on a photoconductor member of the print engine.


REFERENCES:
patent: 4264186 (1981-04-01), Fujiwara et al.

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