Electrophotography – Image formation – Development
Reexamination Certificate
2001-11-05
2003-06-17
Royer, William J. (Department: 2852)
Electrophotography
Image formation
Development
C399S252000, C399S253000
Reexamination Certificate
active
06580890
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to electrophotographic printers and copiers employing color toners, and, more particularly, to conditioning components of the toner development systems by exposure to toner or a toner-like substance prior to use.
BACKGROUND ART
Color electrophotographic printing processes have a unique challenge in the toner development systems currently in use. The toner developing systems for both roll type and two part type developers require that the components of the system be exposed to toner prior to use; that is, when installing a new cartridge to replace an exhausted cartridge. The initial exposure to the toner is to provide sufficient time and energy for the particles of toner to properly adhere to the surfaces of the development system. This exposure is called “conditioning”.
Conditioning may occur at the factory of manufacture or by extended operation in the printer prior to use. The conditioning is required to properly prepare the surfaces so that new supplies of additional toner can be delivered to the system and quickly incorporated in the charging and development process. The conditioning also acts to lubricate and protect various components and sensitive interfaces in the development system from damage during initial use, shipping, and storage. The toner may also provide a protective cover which mitigates the effect of accidental contact with skin oil from handling.
Currently, conditioning for all toner cartridge colors is done using yellow toner. A single color of toner was selected to improve the speed and efficiency of the manufacturing process. Further, the developer rollers or media can all be conditioned independent of the final assembly. Yellow toner has been selected because it has the least effect on other toner colors. The small amount of toner which is left on the developer roller or carrier beads is more quickly diluted by the stronger color strength of the cyan or magenta colors.
However, there are several problems that exist with this approach.
First, a usability problem has been identified with this approach. Customers, unfamiliar with the phenomena of yellow being used as a conditioning color, have returned cartridges of magenta and cyan to the manufacturer, claiming the cartridge contained the wrong color of toner. They have purchased a cyan cartridge and opened the cartridge to find yellow toner on the developer roller. Thus, customers are receiving a mixed message in the case of cyan and magenta toners—the obvious color of toner on the developer roller does not correspond with the expected color of toner purchased.
An additional usability issue concerns the “toner mess” associated with changing a toner cartridge. In an effort to reduce cost in the products, shutters over the development systems have been eliminated. However, this elimination results in exposing customers' hands, clothing, and office equipment to color toner while handling the toner cartridges.
Finally, a print quality (PQ) problem also exists. While dilution occurs quickly, there still can be discernable amounts of yellow in the printed image of the first couple of pages which are printed. This is especially notable because yellow is a significant component of two important “memory colors”. Red colors or the green of grass are challenging colors in which the hue of the color must be matched very closely for customer satisfaction. As a result, if a toner cartridge for magenta or cyan is changed in the middle of a print job and the job contains these colors, there is a high probability that the hue will be unacceptable as a result of the additional yellow being deposited in the secondary color.
Thus, there is a need to provide a solution that solves most, if not all, of the foregoing problems without creating new problems.
DISCLOSURE OF INVENTION
In accordance with the present invention, a method is provided for conditioning development systems in electrophotographic-based printers employing color toners, comprising:
(a) providing clear toner particles; and
(b) causing the clear toner particles to initially be moved through the development systems and then transferred and fused on a print medium prior to printing other toner particles thereon.
Thus, clear toner is used to condition the development systems. The clear toner is made of similar resins and contains all of the flow and charge agents of the color toners, but does not contain any pigment.
Since the toner is clear, the toner is not visible to customers and therefore will not cause confusion or give conflicting information regarding the color of the toner contained in the cartridge.
Also since the toner is clear, the toner will not stain the hands or clothing of individuals handling the shutter-less cartridges, thereby reducing the “toner mess” problem.
Finally, print quality is improved where a toner cartridge containing magenta or cyan is changed in the middle of a print job, since only clear toner is deposited on the first few pages being printed.
REFERENCES:
patent: 5512988 (1996-04-01), Donaldson
patent: 5758234 (1998-05-01), Binder et al.
patent: 6075548 (2000-06-01), Gillen
patent: 6226463 (2001-05-01), Phillips et al.
Christensen K. Trent
Phillips Quintin T.
Yergenson Robin P.
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