Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Physical dimension specified
Reexamination Certificate
1999-11-01
2002-02-26
Kiliman, Leszek (Department: 1773)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Physical dimension specified
C428S336000, C428S208000, C428S195100, C428S688000, C428S689000, C427S419100, C427S419200
Reexamination Certificate
active
06350516
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to printing machines and printing processes. More specifically, the present invention relates to coated corona charging articles, preparative and coating processes thereof, and to imaging processes that include the coated articles. The coated charging articles of the present invention provide for improved image copy quality, greater service lifetimes of corona charging articles, and relatively inexpensive and simple control of acidic oxides of nitrogen compounds formed in corona charging and imaging processes.
Imaging systems including corona charging articles and corona charging methods are known and are illustrated, for example, in U.S. Pat. No. 5,853,941, issued Dec. 29, 1998, to Rimai, et al., the disclosure of which is incorporated herein by reference in its entirety.
In U. S. Pat. No. 5, 839,024, issue Nov. 17, 1998, to May et al., there is disclosed, for example, corona chargers generally and an electrical regulation approach to solving corona induced image defects. A corona charger is disclosed for depositing an electrostatic charge on a charge retentive surface, without the creation of sheeting defects, the charger includes a coronode, and a power supply operating in cycles and providing in each of the cycles electrical power to the coronode to produce a net positive charging current with voltage to the coronode from the power supply operating in a portion of each cycle with a positive polarity to generate positive corona emissions. The power supply operates so that an AC component of the voltage provided by the power supply has a positive polarity in the range of about 60% to about 85% of each cycle. When operating in a broader range of greater than 50% but less than 100%, DC equivalent current to the coronode is controlled below a value causing sheeting.
A common problem associated with corona charging articles is their known propensity to generate compounds of acidic oxides of nitrogen, such as nitric acid, during charging and discharging processes. The acidic oxide compounds can degrade the charge capability of the corona charging article; the compounds can degrade the environmental quality in and around the corona charging article; and the compounds can ultimately degrade the resulting print quality by, for example, oxidizing the photoreceptor, especially its surface, resulting in image defects or blurring or discoloring portions of printed images.
The present invention provides a simple solution to the aforementioned and other problems by providing a corotron electrode with a protective coating thereover, wherein the protective coating contains at least one additive which, for example, scavenges, removes, sequesters, or neutralizes the aforementioned deleterious acidic oxide compounds. The present invention improves print quality, for example, in xerographic printing processes which employ corona charging of an imaging member, compared to an uncoated corotron charger, or alternatively, a coated corotron charger which does not include the protective coating compositions of the present invention. The operational life of charging subsystems can also be extended using the coating compositions and coated corotron charger articles of the present invention.
The disclosure of the above mentioned patent is incorporated herein by reference its entirety. Appropriate components and processes of the patent may be selected for the articles and processes of the present invention in embodiments thereof.
SUMMARY OF THE INVENTION
Embodiments of the present invention, include:
An article comprising:
a corotron assembly with a protective coating thereover, the coating comprising at least one additive which sequesters acidic oxygenates of nitrogen, such as nitrates or nitrites;
A process comprising:
forming a coating mixture comprising a metal oxide or oxides, such as alumina; a sequesterant compound for oxygenates of nitrogen, including for example organic acid salts, such as ferrous fumarate alone or in admixture with a sulfamate salt such as ferrous sulfamate; a conductive additive, such as graphite or carbon black; and optionally a binder;
applying the coating to a corotron assembly; and thereafter using the corotron assembly for charging in imaging processes; and
a printing machine that includes a protectively coated negative corona charging article in accordance with the present invention.
These and other aspects are achieved, in embodiments, of the present invention as described and illustrated herein.
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides, in embodiments, an article comprising:
a corotron assembly with a protective coating thereover, the coating comprising at least one additive which, for example, sequesters or neutralizes acidic oxygenates of nitrogen, including nitrates or nitrites, such as nitric acid and nitrous acid.
The corotron assembly can include, for example, a wire electrode, also known as a coronode, a housing, and a screen member. In the present invention the wire electrode is preferably and purposefully left uncoated while the other components of the corotron assembly are preferably coated in accordance with the present invention. The wire electrode can be any suitable conducting material which provides the necessary electron discharge and charging of the photoreceptor, for example, tungsten or its alloys, stainless steel, platinum, rhenium, molybdenum, and the like highly conductive materials.
The protective coating can include one or more additive compounds which are selected primarily for their ability to sequester compounds of acidic oxides of nitrogen, such as nitrates. Acidic nitrate compounds are known to be generated during charging events by the interaction of the electron discharge or plasma of the corona charging wire and atmospheric nitrogen.
The term “sequester” and “sequesteration” is to be construed broadly and includes a host of meanings that embody the concept of nullifying or negating the chemical effects of the aforementioned acidic oxygenates of nitrogen, such as nitrate and nitrite compound(s), and can include, for example, withdrawal, separation, isolation, seizure, segregation, removal, obliteration, transformation, and the like concepts which connote that the acidic oxygenates of nitrogen compound(s) are unavailable for, for example, degradative chemical reaction or reversible adsorption or desorption with the corotron assembly components, the coronode, associated printing machine componentry, or printing marking materials. Thus, the sequesteration of acidic oxygenates of nitrogen by the coating compositions of the present invention protects, for example, the corotron wire and wire surfaces, and surrounding surfaces from the negative and deleterious effects of ambient or otherwise acidic nitrate compounds. Importantly, the “sequesteration” of acidic nitrogen compounds protects the surrounding environment and associated structural, mechanical, and imaging componentry and marking materials, particularly the imaging process and resulting copy quality associated with the coated corotron assembly article. The sequesteration capability provides protection to the electrode and environment surrounding the wire from wire generated acidic oxygenates of nitrogen compounds, ambient acidic nitrate compounds, or derivative compounds formed from the interaction of such compounds with the wire, the coating, or nearby surfaces. The sequestration mitigates or eliminates the negative effects of acidic oxygenates of nitrogen compounds, such as for example, corrosion, oxidation, and the like deterioration, by for example, chemical reduction, neutralization, chelation, physical or chemical absorption, and the like chemical and physical processes.
In embodiments, from about to 2 to about 10 additives can be selected for use in the coating compositions of the present invention.
The coating compositions of the present invention can include one or more binder materials which binder acts as a matrix that holds the coating constituents to the corotron assembly surface and to s
Ewing Joan R.
Weber Joseph R.
Haack John L.
Kiliman Leszek
Xerox Corporation
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