The word “organic” in Organic PhotoConductor (OPC) means that a photoconductor is manufactured from carbon-based chemical compounds. These photoconductive compounds are actually petrochemical derivatives originating from the fossil fuels petroleum, natural gas, and coal.
In contrast obsolete cadmium sulfide, older selenium-based, and newer amorphous silicon photoconductor materials are manufactured from inorganic alloys or compounds. These photoconductive materials originate from purified, naturally occurring elements such as cadmium, sulfur, selenium, tellurium, arsenic, and silicon. All are actually inorganic photoconductors (IPCs), but the industry has historically classified and referred to them based on the photoconductive material used in their manufacture.
Kalle, A.G., a German firm, patented the first OPC formula in the late 1950s. Under license from Kalle, International Business Machines Corporation (IBM) introduced the first production OPC in their IBM Copier 1 in 1970.
In 1983, Canon, Inc. revolutionized OPC usage by introducing the OPC cartridge-based “personal copier” (PC) and subsequent laser printer (LP) engines.
OPC surface receives uniform negative charge from corona or charge roller.
Light energy from exposure passes through the CTL and into the CGL.
Reaction from light energy creates free electrons in the CGL. These electrons migrate to the positively charged substrate.
The resulting electron hole, a positive charge, moves through the CTL to neutralize (discharge) the surface in the exposed area.
All OPCs can be damaged when overexposed to light. The type and extent of the damage depends on the chemical composition of the specific OPC, the amount of time the OPC was exposed, and the type of light which it was subjected.
Temporary Damage from Visible Light:
In sufficient quantities, visible light causes OPC fatigue. After the OPC has been exposed, light prints (decreased charge acceptance) or heavy background may indicate visible-fatigue. Sometimes the OPC will gradually recover, depending on the time and intensity of exposure.
When OPC visible-light fatigue occurs, print quality is degraded. The technician/engineer has two options: wait until the OPC recovers, or replace the OPC. Each option costs money, so preventing light fatigue is worth the effort. Make sure to use light-protective sleeves (provided with most OPCs) during installation and service.
Permanent Damage from Ultraviolet (UV) Light:
The CTL allows visible and infrared light to pass through to the CGL. However, the CTL absorbs UV light, reducing charge transport performance. CTL damage causes higher voltages in discharged areas of the latent (undeveloped) image, resulting in reduced density and/or background on prints. Ultraviolet exposure from sunlight causes permanent, cumulative damage to OPC coatings.
Factors Affecting OPC Life
An OPC is much softer than a selenium-based photoreceptor, and will flex and rebound before chipping. Still, OPC is highly susceptible to damage from impact or mishandling. Excluding impact, mishandling, mechanical, or electrical damage, the two primary failure modes for page printer OPCs are mechanical wear and electrical deterioration. How long an OPC can last inside a given page printer model primarily depends on design-created environmental factors within the specific machine. The following sections present page printer design considerations as they relate to OPCs.
All OPCs eventually wear out. When the CTL coating wears thin, electrical charge acceptance diminishes and the OPC fails to produce prints with good resolution and contrast. Given that coating wear causes most OPC failures, it might seem that reducing OPC abrasion would be a top priority for page printer designers. However, printer engine designers often must design abrasion into the system to keep the OPC surface free of a film called “oxidation”.
Paper is also an important factor in OPC abrasion. Most OEMs recommend using high-quality. xerographic or bond paper stocks in page printers which utilize OPCs. These papers have smoother surfaces and contain fewer chemical contaminants, making them less abrasive to OPCs. The use of poor quality paper (recycled), paper stock, or label stock accelerates abrasion of an OPC surface and can cause premature failure. Adhesive chemical materials from label stock can also contaminate to OPC surface and create print quality problems.
Charge acceptance and photosensitivity characteristics gradually change as an OPC wears. These changes are the results of mechanical wear, oxidation, and light fatigue or damage. As wear reduces the thickness of the CTL, the capability of the OPC to charge electrically is diminished. A controlled rate of OPC surface wear is required to reduce oxidation-related problems; OPCs could last longer if highly abrasive oxidation-removing components were not necessary. OEMs attempt to compensate for the expected electrophotographic change caused by OPC surface wear.
OPC wear rate depends on the wear coefficient of the CTL material, and on CTL interaction with toner, developer, and toner additives. Paper dust and other contaminants contribute to OPC wear, but not to the extent that the toner/OPC relationship does. Other than switching toner or OPC type, the technician/engineer cannot reduce OPC wear, beyond the reduction achieved by maintaining the page printer to OEM specifications.
OPC Maintenance and Handling
Routine OPC maintenance will not significantly increase the life or reliability of an OPC. OPC surface are sensitive to contamination and to physical contact. Use extreme care, and follow the methods below. Any time an OPC coating is handled, the chance of damage is significant.
Lint Free Cloth like Lens Wipe
These are not expensive and readily available. Lightly wipe the affected surface area with even pressure. Be sensitive to any surface scratches caused by wiping.
Soft Bristle Paint Brushes and yellow toner as a lubricant
Soft Bristle paint brushes are available at most art stores and stationery supplier. Applying a light layer of yellow colour toner using these brushes over the surface of the OPC drum before installing it, helps with the initial process of the rotating drum in the cartridge. Remember that the drum (coated metal) rotates against the wiper blade (soft plastic). Not coating the OPC may result in abrasions or a flipped blade. It is also best to coat both. Using yellow toner to coat drums and blades are the cheapest and safest option. It will not affect the print and is generally removed the moment the printer initializes and starts the drum rotation, thereafter the drum will be lubricated by the cartridge specific toner. Fourways Imaging recommends using any yellow toner except for some copier toner that contain carrier. You may however use any colour however the yellow appears to be more presentable. You may also prefer to coat the OPC and blade with the cartridge specific toner, however you need to take into account that some Monochrome toner contain abrasive particles like metals and even though they are wax coated and used in that specific cartridge, it still may be a bit abrasive for the initial run of that OPC.
Lint Free or Microfibre Cloth and Isopropyl Alcohol
Isopropyl Alcohol remains one of the best cleaners for OPC Drums, both in the fact that it is readily available at most pharmacies and they are not costly. Isopropyl Alcohol is also use to clean electrical components, so they are fast drying and they do not water damage components. Be sure that after the OPC is cleaned using Isopropyl Alcohol that you remove not only stubborn Caked toner, dust and other dirt, you also remove the lubricated coating that was placed over the drum by the toner of that cartridge, so lubricating (with yellow toner) will be a good idea. Most people recommend 99% Isopropyl alcohol but we have received good results from as low as 70%, try not to get Isopropyl Alcohol below this percentage, as what ever other chemicals are added may damage your OPC Drum.