Photoreceptor surfaces

Once the latent electrostatic image has been developed on the photoreceptor surface, it must be transferred to plain paper with no loss in clarity. 

Fig. 15. Transfer of the toned image from the photoreceptor surface to paper is accompHshed by charging the paper with a corotron of appropriate...

In the development step, charged toner particles are deposited on the photoreceptor surface. There are several techniques by which this can be accomplished, most of which involve the use of a second component called a carrier. 

In early copiers, deposition of the toner particles onto the photoreceptor surface was accomplished simply bv cascading the particles over the photoreceptor surface. Cascade development was first described by Walkup (1952) and used in all earl) Xerox copiers. Figure 15 shows a cascade development process. Carriers for cascade development were usually glass or metal beads with diameters of several hundred pm. The limitations of cascade development... 

Figure 15 A cascade development system. Cascade development operates by cascading developer particles across the photoreceptor surface under the force of gravity.

The final step in the development process involves the transfer of the toner particles from the carrier beads to the photoreceptor surface. The forces that bind the toner to the beads are electrostatic and van der Waals dispersion forces. Development thus requires that the forces due to the fields associated with the latent image exceed the forces that holds the toner to the carrier. For a discussion of processes by which toner particles are transferred from carrier beads to photoreceptor surfaces, see Schein (1975), Hays (1977, 1978), and Schein and Fowler (1985). For a discussion of the roles of van der Waals and electrostatic forces, see Gady et al. (1996). 

After the toner is separated from the photoreceptor surface, it is usually removed by air flow. 

When ions produced by a corona discharge are deposited on a photoreceptor surface, charges of the opposite polarity are created in the substrate electrode. When equal charge distributions reside at the surfaces, the potential V is related to the surface charge density Os as... 

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