Radiation imagery chemistry: process – composition – or product th – Electric or magnetic imagery – e.g. – xerography,... – Post imaging process – finishing – or perfecting composition...
Reexamination Certificate
2002-01-16
2003-05-20
Goodrow, John (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Electric or magnetic imagery, e.g., xerography,...
Post imaging process, finishing, or perfecting composition...
C430S110200, C430S137110
Reexamination Certificate
active
06566025
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to toner additive compositions and more specifically, to toners with surface additives, such as polymers, like polymethylmethacrylates, halogenated, such as fluorinated, polymethylmethacrylates, and the like and which toners, prepared for example, by conventional grind processes or emulsion/aggregation processes, use these additives as a transfer and/or blade cleaning aid and these additives improve the transfer efficiency and/or blade cleanability of the developed toners. Yet more specifically the toner surface additives permit the lessening of photoreceptor scratching initiated in the cleaning blade nip present in an imaging or printing apparatus. With further regard to the surface additives, the size thereof and average molecular weight thereof can be selected to minimize the prior art disadvantages of, for example, abrasive toner and additive crush on the blade, which causes photoreceptor scratching, while maintaining the prior art advantage of improved transfer efficiency.
2. Description of Related Art
In electrophotography, a photoreceptor containing a photoconductive insulating layer on a conductive layer is imaged by first uniformly electrostatically charging its surface. The photoreceptor is then exposed to a pattern of activating electromagnetic radiation, such as light or a laser source. In charged area development (CAD) processes, the radiation selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer while leaving behind an electrostatic latent image in the non-illuminated areas. This electrostatic latent image may then be developed to form a visible image by depositing finely divided toner particles on the surface of the photoconductive insulating layer. In discharged area development (DAD) processes, the radiation selectively dissipates the charge in the illuminated areas of the photoconductive insulating layer to form an electrostatic latent image. This discharged electrostatic latent image may then be developed to form a visible image by depositing finely divided toner particles on the surface of the photoconductive insulating layer. In either process, the resulting visible image may then be transferred from the photoconductor to a support, such as transparency or paper. Alternatively, in the case of tandem development systems, the resulting visible image may then be transferred from the photoconductor to an intermediate transfer belt where the image is built up and then transferred to a support, such as transparency or paper. This imaging process may be repeated many times.
Various toner compositions for such a printing system are well known in the art, and have been produced having a wide range of internal and external additives and constituent materials. Generally, however, the toner particles include a binding material such as a resin, a colorant such as a dye and/or a pigment, and any of various internal and external additives to provide particular properties to the toner particles.
One type of external additive that is commonly used in toner compositions is a surface additive. The surface additive can be incorporated for any of various reasons, including for providing improved charging characteristics, improved flow properties, and the like.
For example, toner compositions with certain surface additives, including certain silicas, are known. Examples of these additives include fumed silicas, such as certain AEROSILS like R972™ available from Degussa, metal salts and metal salts of fatty acids inclusive of zinc stearate, calcium stearate, aluminum oxides, cerium oxides, other metal oxides, and mixtures thereof. Generally, such additives are each present in an amount of from about 0.1 percent by weight to about 5 percent by weight, and preferably in an amount of from about 1 percent by weight to about 3 percent by weight, of the toner composition. Several of the aforementioned additives are illustrated, for example, in U.S. Pat. Nos. 3,590,000 and 3,900,588, the entire disclosures of which are incorporated herein by reference.
For example, U.S. Pat. No. 6,214,510 discloses external toner additives, which function as transfer aids. The external additives are inorganic oxides, such as silica or titania, having a volume average particle diameter of from 0.05 to 0.5 micron.
In a like manner, U.S. Pat. Nos. 6,294,302 and 6,153,346 disclose the use of various organic and inorganic fine powders in toner production. The inorganic fine powders can include silica, titania, calcium carbonate, magnesium carbonate, tricalcium phosphate and cerium oxide, and the organic fine powders can include vinyl series resin, a polyester resin and a silicone resin. The powders are useful as external additives, such as for cleaning aids.
Also known are toners containing a mixture of hexamethyldisilazane (HMDZ) and aminopropyltriethoxysilane (APTES) treated silicas. Disadvantages associated with these toners may include, in certain instances, a low, relatively unstable triboelectric charge, and high relative humidity sensitivity. Further, disadvantages of toners containing surface additives treated with HMDZ include, for example, unstable triboelectric charge, relative humidity sensitivity, and low charge/wrong sign toner as measured by a charge spectrograph.
Developer compositions with charge enhancing additives, which impart a positive or negative charge to the toner resin, are also known. For example, U.S. Pat. No. 3,893,935 describes the use of quaternary ammonium salts as internal charge control agents for electrostatic toner compositions. U.S. Pat. No. 4,221,856 discloses electrophotographic toners containing resin compatible quaternary ammonium compounds in which at least two R radicals are hydrocarbons having from 8 to about 22 carbon atoms, and each other R is a hydrogen or hydrocarbon radical with from 1 to about 8 carbon atoms, and A is an anion, for example sulfate, sulfonate, nitrate, borate, chlorate, and the halogens, such as iodide, chloride and bromide. Similar teachings are presented in U.S. Pat. Nos. 4,312,933 and 4,291,111. There is also described in U.S. Pat. No. 2,986,521 developer compositions comprised of toner resin particles coated with certain finely divided colloidal silica. According to the disclosure of this patent, the development of electrostatic latent images on negatively charged surfaces is accomplished by applying a developer composition having a positively charged triboelectric relationship with respect to the colloidal silica.
Also there is disclosed in U.S. Pat. No. 4,338,390, the entire disclosure of which is incorporated herein by reference, developer compositions containing as charge enhancing additives organic sulfate and sulfonates, which additives can impart a positive charge to the toner composition. Further, there is disclosed in U.S. Pat. No. 4,298,672, the entire disclosure of which is incorporated herein by reference, positively charged toner compositions with resin particles and pigment particles, and as charge enhancing additives alkyl pyridinium compounds. Additionally, other patents disclosing positively charged toner compositions with charge control additives include, for example, U.S. Pat. Nos. 3,944,493; 4,007,293; 4,079,014; 4,394,430 and 4,560,635, which illustrate a toner with a distearyl dimethyl ammonium methyl sulfate charge additive. Surface additives, such as silicas like AEROSILS, may be incorporated into the toners of these patents.
Moreover, toner compositions with negative charge enhancing additives are known, as described, for example, in U.S. Pat. Nos. 4,411,974 and 4,206,064, the entire disclosures of which are incorporated herein by reference. The '974 patent discloses negatively charged toner compositions comprised of resin particles, pigment particles, and as a charge enhancing additive ortho-halo phenyl carboxylic acids. Similarly, there are disclosed in the '064 patent toner compositions with chromium, cobalt, and nickel complexes of salicylic acid as negative charge enhancing additive
Hirsch Mark James
Koch Ronald J.
McStravick Mary L.
Pike Thomas W.
Goodrow John
Oliff & Berridg,e PLC
Palazzo Eugene O.
Xerox Corporation
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