Photoreceptors blocking layers

Fig. 2. Structure of a-Si H photoreceptor and its energy diagram indicating the blocking behaviors. (1) Photoconductive layer, (2) blocking layer, (3) conducting substrate.

Fig. 10.26. Typical structure of a xerographic photoreceptor showing the blocking layer at the substrate, the surface layer and the photoconductor (Pai 1988).

For webs, the substrate electrode is usually a vapor-deposited, semitransparent metal layer (Ritchie and Fenn, 1987 Chen, 1993). Al, Ni, and Cr are commonly used. The use of semi-transparent electrodes permits the use of rear exposures for erase purposes. In the case of drums, the metal cylinder serves as the electrode. Usually, a thin, less than 1 pm, blocking layer is interposed between the electrode and the photoreceptor to prevent charge injection. This layer must not be so thick that a residual potential builds up during cycling. Many insulating polymers have been used acrylic polymers, epoxy resins, polyamides, polyesters, polyphosphazenes, polysiloxanes, polyurethanes, vinyl polymers, etc. 

Another field of application for boron nitride is its use as blocking layer and/or surface layer in electrophotographic photoreceptors [69 to 96,380]. Again, these layers are produced by the CVD methods described in Section 4.1.1.10.2, p. 62. Depending on the deposition method or specific conditions, the boron nitride layers in the electrophotographic receptors may also consist of or contain p-BN [97 to 100]. 

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