Cleaning and liquid contact with solids – Processes – Using solid work treating agents
Reexamination Certificate
1999-11-29
2002-10-08
Gulakowski, Randy (Department: 1746)
Cleaning and liquid contact with solids
Processes
Using solid work treating agents
C134S002000, C134S022100, C134S022140, C134S022190, C134S023000, C134S025300
Reexamination Certificate
active
06461442
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to electrostatography and, more specifically, to a system for removing coating material from an end of a drum.
In electrostatography, and particularly in electrophotography, coated substrates such as cylindrical photoreceptor drums (photoreceptors) are commonly used in copier, duplicator, facsimile and multifunctional machines. Photoreceptor embodiments include at least one coating of photosensitive material comprising film forming polymer material, which can be formed on the photoreceptor by known techniques such as immersion or dip coating.
The peripheral ends of a coated photoreceptor are often used to engage members such as spacers, rollers, seals, developer housings, grounding devices and the like. If these members ride on a coated area of the drum, the coating material is rubbed off and the resulting debris can contaminate various components in the machine such as the cleaning system and any optical exposure systems employed in the machine. Also, the coating can interfere with devices that are designed to electrically ground the drum by contacting the outer surface at one end of the drum. Moreover, if the coating thickness is irregular because of poor removal techniques, spacing devices riding on the outside surface of the drum cannot maintain precise spacing between the drum and critical subsystems such as charging, developing, cleaning or other subsystems. Further, if coating material is present in the interior of the drums adjacent the ends of the drum, insertion of supporting end caps may be prevented or hindered. Also, uneven coating deposits in the interior of the drums can cause misalignment of the end caps which, in turn, can cause the drum to wobble during image cycling. The uncoated region at the end of the drum is also necessary to prevent delaminating or cracking of the organic layers at the base of the photoreceptor when the photoreceptor is cycled in an imaging machine. Thus, specified areas at both the outer and inner peripheral ends of a photoreceptor must be free of coating material.
The top of the drum may be maintained free of deposited coating by not immersing a small portion of the upper end of the drum into the coating solution. More specifically, the upper end of the photoreceptor drum can be kept free of coating material by orienting the drum vertically and dipping the drum into a bath of coating material to a predetermined depth which avoids complete immersion of the drum. However, the coating formed over the lower end of the photoreceptor must still be removed or prevented from depositing during dip coating. There are many methods and techniques for accomplishing this. One technique for preventing coatings from depositing is by masking the lower end of the drum prior to dip coating. This technique is time consuming and requires excessive handling. Systems for removing deposited coatings include, for example, laser ablation, mechanically wiping the lower end with blades or brushes and/or by applying solvents to it.
In the laser ablation coating removal technique, a predetermined portion of a coating on a photoreceptor is treated to remove at least part of the coating by directing high energy radiation such as a laser beam and a number of fluid jets at the coating to remove at least part of the coating. This process is often referred to as “laser ablation.” The laser ablation process functions to effectively remove at least part of a predetermined portion of a coating without the need for chemical or mechanical treatments. During laser ablation, the coated substrate is rotated at high speeds. However, a problem is that a rotating cylindrical substrate which is supported only at one end, i.e., a cantilevered state, may sway when the rotation speed is high and/or when the substrate has a relatively small diameter. Swaying of the substrate during for example laser ablation may affect the precision of the ablation process. The laser ablation process is described in detail in U.S. Pat. No. 5,418,349, U.S. Pat. No. 5,424,508 and U.S. Pat. No. 5,628,918, the entire disclosures thereof being incorporated herein by reference. Supplemental devices to reduce drum sway during laser ablation is described in U.S. Pat. No. 5,628,918, the entire disclosure thereof being incorporated herein by reference. Laser ablation systems are complex, expensive and occupy valuable manufacturing space.
Another coating removal method involves using a wiper blade or brush to wipe off the bottom portion of each drum with solvent, to remove the organic polymer films in the intended uncoated region. One technique involves lowering the drum onto a sponge spindle to steady the end of the drum and thereafter, wipe the bottom outside edge of the drum with a flexible wiper blade. This blade wiping system utilizes tapered elastomeric rollers. Each roller is mounted on one end of an arm which has a center pivot point. The other end of the arm carries a wiping blade. As a drum is lowered, the end of the drum engages the tapered end of each roller causing it to offset and move the arm which, in turn, causes the blade to wipe the coating material from the outer surface of one end of the lowered photoreceptor. This method performs well with photoreceptors which require a large coating-free circumferential strip having, for example, a width of 9 millimeters. However, for photoreceptors requiring a relatively small coating-free circumferential strip having, for example, a width of 4 millimeters, consistent, reliable wiping cannot be achieved. Part of this reduction in quality for narrow coating-free circumferential strips is due to the drum wobbling during coating removal, misalignment of the wiper blades on the surface of the drum, and loss of elastomeric roller material as the drum is lowered into contact with the tapered end of the elastomeric rollers. Loss of the material from the rollers causes the rollers to roll erratically rather than smoothly. Moreover, loss of material from the rollers aggravates precise alignment of the drum and blades for cleaning. Also, during lowering, the drum will occasionally contact the blades and dislodge them from alignment. If the rollers are biased against the drum with too much pressure, the drum is pulled off of the mandrel when the mandrel is retracted to remove the drum from the cleaning station. Moreover, the nicked rollers produce debris that deposit on the wiped surface of the bottom of the drum. Replacement and realignment of the rollers requires downtime during which production must be stopped. Further, solvent used to carry away removed coating material often rides up on the rollers and form unwanted coating deposits on the cleaned bottom surface of the drum. Thus, quality control is difficult to maintain. Further, these cleaning systems require frequent replacement of parts, along with attendant downtime. Even with optimization of the bottom edge wipe with wiper blades the reject rate can be as high as 20 to 25 percent.
Another technique for cleaning drums is to utilize brushes with solvents. Because the bristles of the brush tend to flick coating material and solvent during the cleaning operation, the coating material in the imaging area can receive unwanted solvent and/or coating material from the brushes during the cleaning operation. These cleaning devices become less efficient and reliable when the cleaned strip at the end of the drum has a very small width, for example, about 4 mm wide.
Thus, each coating prevention or removal technique has its advantages and disadvantages. In all cases, there should be little or no residual organic polymer in the bottom uncoated area or it is considered defective for the reasons described above. To prevent defective photoreceptors from getting to the customers, it is necessary to carefully inspect each photoreceptor to detect these defects during the manufacturing process. Therefore, a very large amount of time and expense is required to weed out otherwise acceptable photoreceptors.
INFORMATION DISCLOSURE STATEMENT
U.S. Pat. No. 5,418,349 issu
Bush Steven D.
Duggan Michael J.
Mastalski Henry T.
Wallace Kathryn A.
Kornakov M.
Thompson Robert
Xerox Corporation
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