Dissecting The Laser Printer’s OPC Drum
The OPC or Organic Photo Conductor Drum is the heart and soul of a laser printer. This is one component that makes laser printing really possible. The process of electro-photographic (EP) printing requires the OPC Drum to play host to the negatively charged raster graphic image routed by the laser scanning assembly. How the OPC Drum accepts and retains the electro-static charge can be determined by inspecting the materials and substances applied to the Drum’s surface.
The term Organic simply indicates that the OPC Drum is coated with biodegradable materials that will not in any way cause harm to the environment. The drum’s coating is made up of petroleum substances such as carbon based chemicals. These are photoconductive polymers extracted from by products of fossil fuel refining activities. Manufactured from organic compounds, OPC Drum coatings are classified as non- hazardous and can therefore be used extensively in various printing applications, particularly that of the laser printing equipment. Earlier released photoreceptors such as the Arsenic Triselinide (As2Se3) and Selenium Tellurium (SeTe) Drums were considered hazardous.
What is the physical make-up of an OPC Drum ?Basically an OPC Drum has an aluminum substrate that helps provide electrical conduction as well as structural and mechanical support; though it does not play an active role in the EP printing process. The Drum coatings comprise of 3 layers, as follows:
Undercoat Layer (UCL) provides adhesion between the substrate and the innermost photoconductive layer that prevents unwanted charge leakage. Just like the aluminum substrate, the UCL does not support the EP process.
Charge Generation Layer (CGL) serves a critical function to Drum performance as catalyst to print speed. The CGL is ultra thin by as much as one micron (human hair is 50 microns in comparison) and actually determines the color of the OPC Drum.
The Charge Transport Layer (CTL) is the transparent, outermost coating that is around 20 to 30 microns thick. The CTL allows the laser beam to pass through the CGL that gauges the Drum’s light-sensitivity aspect and primarily determines charge acceptance and transport. This layer also dictates Drum Life since it comes in contact with toner powder particles, paper, developer roller, the wiper blade, ozone and other totally abrasive agents that consequently affect wear characteristics, durability and resistance.
Learning the physical composition of the OPC Drum will favorably orient users over its sensitive nature. Consequently this will discourage printing practices that will shorten the effective life of OPC Drum components.