HP 5100 Service Manual - Page 86

Photosensitive drum The special properties of the photosensitive drum allow an image to be formed on the drum surface and then transferred to paper. The drum is an aluminum cylinder. The outside of the cylinder is coated with a layer of organic-photoconductive material (OPC) which is non-toxic. The OPC material has properties similar to a photo-resistor. It becomes electrically conductive when exposed to light, and he negative charges deposited on the drum are conducted to the ground potential of the drum base. Areas not exposed to light remain non-conductive and maintain their negative charge. The aluminum base of the photosensitive drum is electrically connected to ground potential. Photosensitive Layer Figure 16. Aluminum Base Photosensitive Drum Cleaning the drum In the transfer stage, not all the toner is transferred to the paper, but some remains on the photosensitive drum. In this stage, the residual toner is cleaned so that the next print image will be clear and distinct. Figure 17. Cleaning the drum The residual toner on the drum surface is scraped away with the cleaning blade to clean the drum surface in preparation for the next print. The removed toner is collected into the cleaner container. 84 Functional information Q1860-90918