Electrophotography – Control of electrophotography process – Control of developing
Reexamination Certificate
2002-12-17
2004-08-31
Chen, Sophia S. (Department: 2852)
Electrophotography
Control of electrophotography process
Control of developing
C399S024000, C399S237000, C399S248000
Reexamination Certificate
active
06785483
ABSTRACT:
BACKGROUND OF THE INVENTION
The present Invention pertains to the art of printing systems and more particularly to liquid immersion development (LID) image reproduction systems.
Liquid immersion development image reproduction systems are well known, and generally each includes an image bearing member or photoreceptor having an image bearing surface on which latent images are formed and developed as single color or multiple color toner images for eventual transfer to a receiver substrate or copy sheet. Each such image reproduction system thus includes a development system or systems that each utilizes a liquid developer material (hereinafter, also described as “ink”) typically having about 2 percent by weight of charged, solid particulate toner material of a particular color, that is dispersed at a desired concentration in a clear liquid carrier.
The latent images formed on the image bearing surface of the image bearing member or photoreceptor are developed with the charged toner particles, with excess liquid carrier being left behind or removed. The developed image or images on the image bearing member are then further conditioned and subsequently electrostatically transferred from the image bearing surface to an intermediate transfer member. Following that, the conditioned image or images are then hot or heat transferred from the intermediate transfer member, at a heated transfer or transfix nip, to an output image receiver substrate or copy sheet.
LID image reproduction systems conventionally include a print engine including ink applicator for supplying or applying an even layer of the ink for image development. A supply of ink is maintained in an ink sump which must be replenished to compensate for the consumption of toner components associated with printing. The composition of such ink typically includes ink subcomponents such as carrier fluid, toner particles and charge director. During printing, images developed in image areas will consume all three subcomponents at respective rates and development of non-image areas will consume these components at respectively different rates.
Replenishment of these subcomponents is required to maintain compositional stability of the ink, which is a prerequisite for stable printing performance. Due to the multiple component nature of the ink, and due to the different consumption rates for each of the subcomponents, the design and operation of the particular scheme chosen for replenishing such components will affect the performance and lifetime of the ink sump.
There is therefore a need for a method and system for LID image reproduction which operates an ink sump, wherein there is improved ink replenishment so as to extend the performance and lifetime of the ink sump.
SUMMARY OF THE INVENTION
Due to the multiple component nature of the ink in a LID image reproduction system, and due to the different consumption rates for each of the subcomponents, the design and operation of the particular scheme chosen for replenishing such components will affect the performance and lifetime of the ink sump. For example, a scheme of constant composition replenishment is not sufficient, to guarantee constant imaging performance. The attainment of chemical equilibrium (or at least chemical steady state) among the subcomponents is generally required as well. Phenomena, such as add-mix failure, are the undesired consequence of failure to attain the required chemical equilibrium. For a system with slow kinetics, the dynamics of ink replenishing is complicated. Not only the printing sequence, but also the printing rate and the time interval between prints will have significant impact on the ink sump performance. In this invention, an ink replenishment system and methods are described in which the time required for attainment of the chemical equilibrium is much faster than any other time scale that is relevant to the printing and replenishing subsystems.
It is easily seen that if each ink subcomponent is replenished independently, then compositional stability can be obtained. If such a printing system is restricted to replenish from only two sources, as Is the case in many common printers, compositional control may well be lost. Factors that will help to determine the rate of loss of compositional control include the consumption of various components include factors primarily dependent on the fluctuation in the consumption rate.
When printing at a fixed image coverage document, the consumption of each toner component will be fixed and given by the weighted sum of image and background consumption. A simplifying assumption may be made to neglect the effects of certain image features (e.g. lines or dots) on ink consumption.
A fixed replenishing rate of the various components can be sufficient to maintain the compositional balance of the ink in such a fixed image coverage system. That is, it is possible to find a replenishment ratio which will maintain a working ink sump composition indefinitely as long as a fixed image is printed.
It is desirable, however, to derive a replenishment ratio for a three-subcomponent Ink sump replenishment system operable in an Image reproduction system for printing documents of widely varying image content.
In accordance with the present invention, there is provided in an electrostatographic liquid immersion development (LID) image system for printing documents of widely varying image content wherein there is improved replenishment of plural ink subcomponents.
Presented herein is an ink replenishment model in which only two replenishing sumps are needed to maintain compositional stability in a working ink sump operable in such a three subcomponent ink replenishment system. Determinations of failure modes of the toner sump are made and basic principles for replenishment are presented to enhance the ink sump performance and to extend the ink sump lifetime.
In accordance with one aspect of the present invention, an electrostatographic liquid immersion development (LID) imaging system includes an automated scheduling of a plurality of print jobs of various or varying characteristics according to one or more job scheduling criteria determinable so as to extend the ink sump lifetime.
Further advantages will become apparent to one of ordinary skill in the art upon a reading and understanding of the subject specification.
REFERENCES:
patent: 5592298 (1997-01-01), Caruso
patent: 6374065 (2002-04-01), Nishimura et al.
patent: 6510303 (2003-01-01), Bessette
patent: 2003/0099477 (2003-05-01), Shimmura
patent: 02-306275 (1990-12-01), None
Gibson George A.
Larson James R.
Liu Chu-heng
Chen Sophia S.
Xerox Corporation
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