Electrophotography – Image formation – Development
Reexamination Certificate
2002-04-19
2003-04-08
Tran, Hoan (Department: 2852)
Electrophotography
Image formation
Development
C399S238000, C430S117200
Reexamination Certificate
active
06546221
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to a developer storage and delivery system, and more particularly concerns storing a phase change developer on a continuous web or on an endless belt and delivering the phase change developer to a liquid electrophotographic developing system.
2. Background of the Art
In electrophotography, a photoreceptor in the form of a plate, belt, or drum having an electrically insulating photoconductive element on an electrically conductive substrate is imaged by first uniformly electrostatically charging the surface of the photoconductive element, and then exposing the charged surface to a pattern of light. The light exposure selectively dissipates the charge in the illuminated areas, thereby forming a pattern of charged and uncharged areas (i.e., an electrostatic latent image). A liquid or dry developer is then deposited in either the charged or uncharged areas to create a toned image on the surface of the photoconductive element. The resulting visible image can be fixed to the photoreceptor surface or transferred to a surface of an intermediate transfer material or a suitable receiving medium such as sheets of material, including, for example, paper, polymer, transparency, metal, metal coated substrates, composites and the like. The imaging process can be repeated many times on the reuseable photoconductive element.
In some electrophotographic imaging systems, the latent images are formed and developed on top of one another in a common imaging region of the photoreceptor. The latent images can also be formed and developed in multiple passes of the photoreceptor around a continuous transport path (i.e., a multi-pass system). Alternatively, the latent images can be formed and developed in a single pass of the photoreceptor around the continuous transport path. A single-pass system enables the multi-color images to be assembled at extremely high speeds relative to the multi-pass system. At each color development station, color developers are applied to the photoreceptor belt, for example, by electrically biased rotating developer rolls.
Image developing methods can be classified into liquid type and dry type. The dry type method uses dry (e.g., powder) developers and the wet type method uses liquid developers.
Dry developers are generally prepared by mixing and dispersing colorant particles and a charge director into a thermoplastic binder resin. This mixing and dispersing is followed by milling or micropulverization. The resulted developer often comprises a powder having particle sizes that are generally in the range of about 4 to 10 microns. If the fine powder of a dry developer is scattered, it poses an environmental problem because of its small particle size. Therefore, most dry developers are stored in a cartridge which is easily handled and disposed of Furthermore, the stability of dry developer is usually much better than that of liquid developer.
Liquid developers are usually prepared by dispersing colorant particles, a charge director, and a binder in an insulating liquid (i.e., a carrier or a vehicle). Liquid developer based imaging systems incorporate many features similar to those of dry developer based system. However, liquid developer particles are significantly smaller than dry developer particles. Because of their small particle size, ranging from
3
microns to submicron size, liquid developers are capable of producing very high resolution images. However, liquid developers have some drawbacks.
The major drawbacks of liquid developers are (1) the emission of the liquid carrier from liquid developers to the environment during the drying and transfer process due to inefficient solvent recovery system; (2) the need and difficulty in disposing the waste liquids; (3) the inconvenience of using and handling of liquid developers; (4) and the aggregation and sedimentation instability of (the materials inside the developer are stable, both individually and in their association with other materials in the developer, e.g., non-reactive) liquid developers.
While known liquid developers and processes are suitable for their intended purposes, a need remains for liquid developers and processes that reduce or substantially eliminate the above-mentioned drawbacks. Additionally, there is a need for liquid developers and processes that enable the formation of high quality images on a wide variety of substrates.
There have been many attempts to solve some of the above-mentioned drawbacks of liquid developers and dry developers. For example, U.S. Pat. No. 5,075,735 to Tsuchiya et al. discloses a developer delivery system comprising stripes or bars of solid developer mounted across a belt. The stripes or bars of solid developer are caused to drop onto a heater by a cutter and then the solid developer is melted by the heater into liquid. The resulted liquid developer is then used to develop electrophotographic images.
U.S. Pat. No. 5,815,780 to Boerger et al. discloses an apparatus for storing and delivering toner. The toner is stored on a belt in discretely sealed toner bubbles filled with toner. An extractor unit then causes toner bubbles to rupture, allowing the toner to fall into a developer housing to replenish the toner supply.
U.S. Pat. No. 5,998,081 to Morrison et al. discloses a metallic web coated with a solid developer which is melted by an external conductive heating element. The melted developer is caused to form visible images by contacting with electrostatic latent images.
SUMMARY OF THE INVENTION
This invention provides an improved developer storage and delivery system which eliminates or reduces the above-mentioned drawbacks of liquid developers and processes while providing high quality images on a wide variety of substrates.
In a first aspect, the invention features a developer storage and delivery system for liquid electrophotography that includes:
a conductive substrate with a first surface and a second surface;
a plurality of discrete conductive heating elements mounted on said first surface; and
a phase change developer having a melting point of at least 22° C., wherein said phase change developer is on the top surface of each of said conductive heating elements, except that a minor portion of the top surface of each of said conductive heating elements is free of said phase change developer. The term minor portion is used in its normal sense as less than 50% of the surface area directly over the conductive stripes is free of the phase change developer. It is preferred that this minor area be a small area, defined herein as less than 20% of the surface area over the conductive stripes or of the entire surface of the developer system, for example, 0.05 or 0.1% to 20%, 1 to 15%, 0.2 to 10%, 0.1 to 5% and 0.1 to 2% of the surface area over the conductive stripes or the developer system. The conductive stripes are for conducting electricity, preferably as part of a resistive heating element to heat the phase change developer. The developer is not necessarily conductive, and there must be at least a minor area and preferably a small area (as defined above) that is exposed to enable external electrical contact to connect the resistive heating element with an external power source.
In a second aspect, the invention features a developer storage and delivery system for liquid electrophotography that includes:
a conductive substrate with a first surface and a second surface;
a plurality of discrete conductive heating elements mounted on said first surface; and
a phase change developer having a melting point of at least 22° C., wherein said phase change developer is a continuous layer on the top surface of each of said conductive heating elements and on said first surface free of said conductive heating elements, except that a small of the top surface of each of said conductive heating elements is free of said phase change developer for conducting electricity.
In a third aspect, the invention features a developer storage and delivery system for liquid electrophotography that includes:
an insulatin
Baker James A.
Brenner Robert E.
Herman Gay L.
Law Kam W.
Mark A. Litman and Assoc. P.A.
Samsung Electronics Co,. Ltd.
Tran Hoan
LandOfFree
Developer storage and delivery system for liquid... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Developer storage and delivery system for liquid..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Developer storage and delivery system for liquid... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3051970