Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2001-06-20
2004-09-07
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...
C430S108800, C430S109300
Reexamination Certificate
active
06787279
ABSTRACT:
FIELD OF INVENTION
The present invention relates to developers used to visualize latent images in electrophotographic systems such as electrophotographic copiers, printers, and like devices.
BACKGROUND OF THE INVENTION
Electrophotographic toners, or when blended with a carrier, electrophotographic developers, are used to produce visible images from a latent static electric image formed within an electrophotographic device. The basic steps involved in electrophotography and the equipment by which those steps are carried out is well known in the art. In general the electrophotographic process involves the formation of a latent electrostatic image, usually by depleting the charge on an insulating photoconductive plate or drum (photoconductive element) which has received a uniform static charge. Charge depletion of the photoconductive element is typically accomplished through exposure of the charged photoconductive element to an image (pattern of light and dark areas), the areas of the photoconductive element thereby receiving illumination being discharged in proportion to the light received. The image thus formed is visualized by treating it with colored material (a “toner” or “developer”) which has been triboelectrically charged so that it is attracted to and adheres to the charged areas of the latent image through electrostatic interaction. This “developed” image is thereafter transferred to a support material, such as paper or acetate. This image is then affixed to the support by physical or chemical means, such as by applying heat or pressure (or both) to the developed image sufficient to fuse it to the support.
Representative examples of the current art of electrophotography are to be found disclosed in U.S. Pat. No. 5,437,949 to Kanbayashi et. al., U.S. Pat. No. 4,298,672 to Lu, U.S. Pat. No. 4,338,390 to Lu, U.S. Pat. No. 4,560,635 to Hoffend, et. al., U.S. Pat. No. 4,883,735 to Watanabe et al., U.S. Pat. No. 3,900,588 to Fisher, U.S. Pat. No. 3,720,617 to Arun et. al., and U.S. Pat. No. 3,590,00 to Frank et. al. as representative examples of the art.
In the electrophotographic art, a developer is any composition employed to visualize a latent image. The term toner is applied to a finely divided pigmented powder capable of receiving an electrostatic charge and used to develop the latent image in an electrophotographic process. One skilled in the art will appreciate from the following disclosure that the present invention, while directed to toner compositions, is equally well employed in dry powder compositions directed at developing latent electrostatic images wherein such “developer” compositions would also fit within the definition of a toner composition as it is used in this disclosure.
The fundamental toner composition consists of a thermoplastic primary resin (although primary resin materials other than thermoplastics are known in the art) and a coloring agent. The primary resin serves as a medium into which the other components are suspended or dissolved, as well as serving to facilitate fusing of the developed image to the support. The coloring agent (which includes black) is incorporated to form an easily visualized image.
The requirements of the electrophotographic process usually require that the toner composition also incorporate additional materials (beside the primary resin and the coloring agent) which facilitate its manufacturability and enhance the imaging properties and performance of the finished toner composition.
One of the primary requirements of a toner is that the material must be capable of developing and holding a triboelectric charge. In use, the toner particles acquire a triboelectric charge to enable them to adhere to the latent electrostatic image. The charge control agent is added to impart the charge retention and mass/charge ratio characteristics desired for a particular toner in a particular application. For this reason, in addition to the primary resin and coloring agent, a typical toner material also contains a charge control agent. Numerous charge control agents are known in the art, the disclosures of U.S. Pat. No. 5,318,883 to Yamanaka et. al; U.S. Pat. No. 4,883,735 to Watanabe et. al.; U.S. Pat. No. 4,560,635 to Hoffend et. al.; and U.S. Pat. No. 4,298,672 to Lu disclose examples of such agents. Charge control agents are well known in the prior art. Additional examples of some specific charge control agents incorporated into toner compositions are disclosed in U.S. Pat. No. 4,883,735 to Watanabe et. al., U.S. Pat. No. 4,560,635 to Hoffend, et. al., and U.S. Pat. No. 4,298,672 to Lu, although this is by no means an exhaustive list, many other materials are well known and used by those skilled in the art of toner manufacture.
Examples of toner compositions having these basic components are, by way of example, recited in the all of the patents cited above, such compositions also appearing frequently in the literature of the art of toner compositions. Examples of common primary resins chosen for toner compositions are polymers based on styrenes, epoxides, esters, acrylates, and urethanes, although the use of numerous other thermoplastics, alone and in combinations, are well known and practiced in the art.
Coloring agents may be any colorant such as is well known in the industry, examples of which are disclosed in the above-cited prior art and elsewhere in the literature. The most common colorants being carbon black and magnetite. Colorant may be black, or any color. In particular, colored materials having cyan, magenta, or yellow hue are employed to reproduce “full color” images, and such use is well known to one skilled in the art. Additional materials contemplated as colorants include such materials as polymer grafted carbon blacks, such as those grafted with hydrophobic styrene acrylic copolymers, commercially available from Rit-Chem Co., Inc. of Pleasantville, N.Y., and polymeric dyes disclosed in a paper entitled “In Situ Generation of Polymeric Dyes by Thermal Activation”, presented by Kolb, et. al. in May, 1994 in Rochester, N.Y., at the 1994 annual conference of The Society for Imaging Science and Technology.
The toner composition is typically manufactured as a melt-blended pellet, the pellets being derived from the blend by any method such as is well known in the chemical processing industry. Examples of such processes (and the related processing equipment) are extrusion and spray drying. Pellet formation is not limited to these specific techniques, as it will be apparent to one skilled in the processing industry that there are many other methods and adaptations of these basic process that are equally suitable to pellet formation from this material. Typically, toner compositions may be blended in (but are not limited to) Banbury mixers, rubber mills, conical mixers, band mixers, blenders, and extruder hoppers. Once rendered into pellet form, the pellets are milled in any equipment such as is well know to produce particles of suitable size for use in electrophotographic equipment. The milled material is then typically classified. Any number of mechanical means such as are well known in the industry to produce a narrow particle size range powder may be employed. Typically, most of the fines (particles significantly smaller in diameter than the desired average particle diameter, typically on the order of 5 microns) separated out of the raw milled material are recycled back into the pelletizing process to minimize materials toner raw materials waste.
Conventional dry toner material may be used in a wide variety of eletrophotographic imaging systems such as are well known in the art. In general, dry toner is classified depending upon the equipment in which it is employed. The various systems in which dry toner is used are distinguished by the mechanism(s) by which the toner is applied to the latent image (cascade; powder cloud; magnetic brush, magnetic roller, electrostatic roller), the type of imaging system used (negative or positive image), and whether the toner material acquires a triboelectric charge from contact with a surface
Livengood Bryan Patrick
Marshall George P.
Olson John Melvin
Brady John A.
Lexmark International Inc.
RoDee Christopher
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