Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Metal or metal alloy
Reexamination Certificate
2001-07-31
2003-03-11
Phasge, Arun S. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Metal or metal alloy
C205S717000, C205S741000, C205S640000
Reexamination Certificate
active
06531048
ABSTRACT:
BACKGROUND OF THE INVENTION
Substrates for industrial applications frequently are required to have exacting dimensional tolerances, and in some situations also are required to have non-reflective surfaces. The exacting dimensional tolerances can be obtained via lathing or grinding. Of the two methods, grinding provides the more exacting dimensional tolerances. The lathed surface may be roughened via, for example, honing, when a non-reflective surface is required or, in some cases, rough lathed. Lathing and grinding, however, may produce metal fibers connected to the surface of the substrates (with grinding producing more metal fibers than lathing). If not removed, these metal fibers may cause problems since they can affect the performance of devices incorporating the substrates. For photoreceptors, metal fibers attached to the substrate surface may not allow the formation of sufficient charge in the areas located above the metal fibers. Xerographic prints made using such a photoreceptor substrate (containing the attached fit metal fibers) may have a deletion or a dark spot in the areas associated with the metal fibers. Applicants tolerated the presence of the metal fibers and adjusted the lathing parameters to keep the number of metal fibers produced low. However, it is desirable to remove the metal fibers for a number of reasons. Thus, there is a need which the present invention addresses for a process that can quickly remove metal fibers from substrates.
Conventional electrochemical surface treatments are illustrated in Herbert et al., U.S. Pat. No. 6,048,657; and Vidal et al., U.S. Pat. No. 5,997,722.
SUMMARY OF THE INVENTION
The present invention is accomplished in embodiments by providing a process comprising:
(a) creating an electrolytic cell comprised of a metal surface as a first electrode, a second electrode, and an electrolytic solution, wherein the metal surface has a plurality of metal fibers connected to the metal surface; and
(b) treating electrochemically the metal surface with externally supplied power to the electrolytic cell to sever a number of the metal fibers from the metal surface to result in severed metal fiber fragments unconnected with the metal surface.
DETAILED DESCRIPTION
The present invention involves creating an electrolytic cell composed of the metal surface having attached metal fibers as a first electrode, a second electrode, and an electrolytic solution. In the electrolytic cell, the working electrode is the metal surface having the metal fibers. The counterelectrode (i.e., second electrode) may be for example concentric, surrounding the metal surface. The counterelectrode or electrodes may be: a noble metal such as gold, silver, platinum, palladium; an inert material such as graphite; or a strongly passive material such as titanium, lead, tantalum, or alloys thereof.
The metal surface is part of a substrate. The substrate can be formulated entirely of an electrically conductive material, or it can be an insulating material having an electrically conductive surface. The entire substrate can comprise the same material as that in the electrically conductive surface or the electrically conductive surface can merely be a coating on the substrate. Any suitable electrically conductive material can be employed. Typical electrically conductive materials include copper, brass, nickel, zinc, chromium, stainless steel, aluminum, semitransparent aluminum, steel, cadmium, titanium, silver, gold, indium, tin, metal oxides including tin oxide and indium tin oxide, and the like. In embodiments, the metal fibers and metal surface are a metal selected from stainless steel, aluminum, and an aluminum alloy. The substrate can be flexible or rigid, and can have any number of configurations such as a cylindrical drum, an endless flexible belt, and the like. The substrate may be used for a number of industrial purposes including for example in photoreceptors, donor rolls, fuser rolls, contact charge rolls, or in any roll (or part, for that matter) that has to interface with a photoreceptor or other device that is charged or partly charged. This is especially the case if the device is coated with a thin layer of a material that has to have uniform electrical properties. One can see how the presence of metal fibers on the substrate would cause the same or similar problem in all of above situations.
The metal fibers typically have the same composition as the metal surface. Following is a description of the metal fibers prior to the present process. The metal fibers may have a length ranging for example from about 20 to about 500 micrometers and a thickness ranging from about 2 to about 15 micrometers. The number of metal fibers may vary depending upon the metal surface and the process causing the formation of the metal fibers. For example, the metal fibers may be present in a concentration ranging from about 0.03 to about 10 metal fibers per square centimeter of metal surface produced via a grinding process, and from 0 to about 1 metal fiber per square centimeter produced via a lathing process. The metal fibers may be straight, slightly curved, or severely bent with the tip pointing in the direction of the metal surface.
The electrolytic solution includes water, an electrolyte, and optionally one or more diffusion layer thickening agents. The electrolyte can be any of many salts or weak acids (or well-buffered strong acids). The function of the electrolyte is to make the solution (electrolyte) sufficiently conductive to allow the passage of small currents on the order of for example a few mill-amps. NaCl in concentrations of from about 1 g/L to about 10 g/L can be used, as well as the same concentrations of KCl. Sulfamic acid at concentrations of from about 0.01 to about 0.1 g/L that was buffered with about 35 g/L Boric Acid can be also used. Boric Acid and Phosphoric Acid can be used without any buffer at concentrations of from about 0.1 to about 1.0 g/L.
Suitable diffusion layer thickening agents include for example Glycerin (CH
2
OHCH(OH)COOH) from about 500 ml/L to about 900 ml/L, Polyethylene Glycol 200 (H(OCH
2
CH
2
)
4
OH) (PEG-200) from about 350 ml/L to about 800 ml/L, and Polyethylene Glycol 400 (H(OCH
2
CH
2
)
8.2-9.1
OH) (PEG-400) from about 200 ml/L to about 675 ml/L. Other diffusion layer thickening agents include for example sugar (cane or beet) and honey (clover or orange blossom). The diffusion layer thickening agent may be partially or fully soluble in water, especially being miscible with water. In embodiments, the diffusion layer thickening agent may have a density at least greater than one, may cause the viscosity of the electrolytic solution to increase when added, and/or may be, for the most part, non-conductive.
The function of the diffusion layer thickening agent is now discussed. As is known, the diffusion layer is the region near an electrode where the concentration of an ionic or molecular species differs from its bulk concentration. As the boundary between the diffusion layer and the unaltered bulk solution is not sharp, it has been defined arbitrarily as that region where the concentration of a particular species differs from its bulk concentration by more than 1%. The diffusion layer thickening agent retards the mobility of ions in the diffusion layer, thereby slowing down the rate of reaction. In the prior art, a diffusion layer thickening agent has been added to electropolishing solutions in a concentration that retards the action of the electrolytic polishing processes near the low areas of the surface of the material being polished (the low areas are low in respect to the overall surface of the substrate and may be about 0.01 to about 0.50 micrometer from the high areas). This helps insure that little or no reactions are occuring in the low areas. By restricting the rate of reaction in the low areas one is protected from pitting and from the uniform removal of material, and this facilitates the reactions at the high areas. Thus, material is removed from the high areas (in this case greater than 0.01 micrometer from the low areas of t
Byers Catherine N.
Glanzel Garry O.
Herbert William G.
Hwang Jennifer
Maier Gary J.
Phasge Arun S,.
Soong Zosan S.
Xerox Corporation
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