Service Guide OKIFAX 5750/5950Chapter B Print Operation DescriptionPage: 2903) ExposureLight emitted from the LED head irradiates the EP (image) drum surface with negative charges. The surface potential of the irradiated part of the EP drum drops,thereby forming an electrostatic latent image associated with the image signal.The EP (image) drum is coated with an underlayer (UL), a carrier generation layer (CGL), and carrier transfer layer (CTL) on the aluminum base. The organicphoto conductor layer (OPC), comprising a CTL and a CGL, is about 20 mm thick.