Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
1998-03-09
2003-03-04
Rodee, Christopher (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S111320, C430S111340, C430S111350, C430S111410, C430S111100
Reexamination Certificate
active
06528225
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is generally directed to developer compositions, and more specifically, the present invention relates to developer compositions with certain carriers. In embodiments of the present invention the carrier particles can be prepared by insitu processes and which carriers are comprised of a metallic core, or a metal oxide core, and preferably a porous metallic core or porous metal oxide core with a polymer contained in a number of the pores, that is for example from about 70 to about 90 percent of the pores, or all the pores that is about 100 percent of the pores, and wherein each of the pores is filled with polymer, for example from about 50 to about 100 percent, and preferably from about 90 to about 100 percent, and processes thereof. The carriers of the present invention may be mixed with a toner of resin, colorant, and optional toner additives to provide developers that can be selected for the development of images in electrostatographic, especially xerographic imaging systems, and digital systems.
Insitu refers for example, to polymerization of monomer being accomplished simultaneously inside the carrier pores and at the surfaces of the carrier core particles, and porous refers for example, to a foam-like structure, or a core that contains a plurality of pores.
PRIOR ART
The electrostatographic process, and particularly the xerographic process, is well known. This process involves the formation of an electrostatic latent image on a photoreceptor, followed by development and subsequent transfer of the image to a suitable substrate. Numerous different types of xerographic imaging processes are known wherein, for example, insulative developer particles or conductive toner compositions are selected depending on the development systems used. Of importance with respect to the aforementioned developer compositions is the appropriate triboelectric charging values associated therewith, as it is these values that enable for example, continued constant developed images of high quality and excellent resolution.
Carrier particles for use in the development of electrostatic latent images are described in many patents including, for example U.S. Pat. No. 3,590,000. These carrier particles may contain various cores, including steel, with a coating thereover of fluoropolymers, or terpolymers of styrene, methacrylate, and silane compounds. Recent efforts have focused on the attainment of coatings for carrier particles, for the purpose of improving development quality; and also to permit particles that can be recycled, and that do not adversely effect the imaging member in any substantial manner. Some of the present commercial coatings can deteriorate, especially when selected for a continuous xerographic process where the entire coating may separate from the carrier core in the form of chips or flakes, and fail upon impact, or abrasive contact with machine parts and other carrier particles. These flakes or chips, which are not generally reclaimed from the developer mixture, have an adverse effect on the triboelectric charging characteristics of the carrier particles thereby providing images with lower resolution in comparison to those compositions wherein entire carrier coatings are retained on the surface of the core substrate. Further, another problem encountered with some prior art carrier coatings resides in fluctuating triboelectric charging characteristics, particularly with changes in relative humidity. The aforementioned modification in triboelectric charging characteristics provides developed images of lower quality, and with background deposits.
There is illustrated in U.S. Pat. No. 4,233,387, the disclosure of which is totally incorporated herein by reference, coated carrier components for electrostatographic developer mixtures comprised of finely divided toner particles clinging to the surface of the carrier particles. Specifically, there is disclosed in this patent coated carrier particles obtained by mixing carrier core particles of an average diameter of from between about 30 microns to about 1,000 microns, with from about 0.05 percent to about 3.0 percent by weight, based on the weight of the coated carrier particles, of thermoplastic resin particles. The resulting mixture is then dry blended until the thermoplastic resin particles adhere to the carrier core by mechanical impaction, and/or electrostatic attraction. Thereafter, the mixture is heated to a temperature of from about 320° F. to about 650° F. for a period of 20 minutes to about 120 minutes, enabling the thermoplastic resin particles to melt and fuse on the carrier core. While the developer and carrier particles prepared in accordance with the process of this patent, the disclosure of which has been totally incorporated herein by reference, are suitable for their intended purposes, the conductivity values of the resulting particles are not believed to be constant in all instances, for example, when a change in carrier coating weight is accomplished to achieve a modification of the triboelectric charging characteristics; and further with regard to the '387 patent, in many situations carrier and developer mixtures with only specific triboelectric charging values can be generated when certain conductivity values or characteristics are contemplated. With the invention of the present application, the conductivity of the resulting carrier particles are in embodiments substantially constant, and moreover the triboelectric values can be selected to vary significantly, for example, from less than about 80 microcoulombs per gram to greater than about −80 microcoulombs per gram, depending on the polymer mixture selected for affecting the coating processes. Also, with the present invention monomer is initially selected and polymerized insitu and not polymer as is the situation with the above prior art, thus for example with the present invention the carrier pores can be completely filled with monomer and after polymerization with polymer. Penetration of the carrier pores of the present invention are enabled, for example, by the substantially lower viscosity and higher diffusivity of the monomer as compared to the corresponding polymer melt.
With further reference to the prior art, carriers obtained by applying insulating resinous coatings to porous metallic carrier cores using solution coating techniques are undesirable from many viewpoints. For example, insufficient coating material may be present; and therefore is not as readily available for triboelectric charging when the coated carrier particles are mixed with finely divided toner particles. Attempts to resolve this problem by increasing the carrier coating weights, for example, to 3 percent or greater to provide a more effective triboelectric coating to the carrier particles necessarily involves handling excessive quantities of solvents, and further usually these processes result in low product yields. Also, solution coated carrier particles when combined and mixed with finely divided toner particles provide in some instances triboelectric charging values which are too low for many uses. Powder coating processes have been utilized to overcome these disadvantages, and further to enable developer mixtures that are capable of generating high and useful triboelectric charging values with finely divided toner particles; and also wherein the carrier particles are of substantially constant conductivity. Further, when resin coated carrier particles are prepared by the powder coating process, the majority of the coating materials are fused to the carrier surface thereby reducing the number of toner impaction sites on the carrier material.
Powder coating processes typically require polymers in the form of fine powders which can be mixed and properly coat the carrier core. The triboelectric charging value of the aforementioned carriers can be controlled by the polymer or mixture of polymers selected for the coating. The disadvantage of this approach is that only a limited number of polymers are available in the form of fine powders
Agur Enno E.
Creatura John A.
Enright Thomas E.
Gerroir Paul J.
Henderson K. Derek
Palazzo E. O.
Rodee Christopher
Xerox Corporation
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