Photoreceptor drum

Selenium recovery from electronic, xerographic, or other scrap for sale on the open market remains small. This was less than 100 t/yr in 1995. The xerographic industry recovers essentially all of the selenium it uses in photoreceptor drums by extremely efficient recycling programs (see... 

Figure 7 A schematic of a process in which the various steps are arranged around the circumference of a photoreceptor drum. Here, (1) is the corona charging apparatus, (2) the exposure system, (3) the development system, (4) the transfer corona, (5) the fusing apparatus, (6) the cleaning system, and (7) the erase exposure system. Processes of this kind are widely used for printer and low-volume copier applications.

Figure 2 A schematic of the ring-coating method for preparing photoreceptor drums.

The electrophotographic method requires a process of forming an electrostatic latent image on a photoreceptor drum by charging and light exposure. Therefore, the system becomes complicated, resulting in increased costs of production (21). 

Several years have passed since the use of a -Si H as a photoreceptor for electrophotography was first proposed. Following the dramatic success in the large-scale fabrication of a-Si H solar cells, from the industrial point of view, remarkable progress has been made in a-Si H drums for copying machines or for laser line printers. 

Now we discuss the PID performances of photoreceptors made of high-resistivity films. In Fig. 6, typical PID curves are illustrated for the a-Si H drum made of a film 44 fim thick containing oxygen. A sufficient amount of chaige with either polarity can be maintained on the surface of the film freshly deposited onto an A1 substrate. Nakayama et al. (1982) had put their a-Si H drum to a practical test inside a copying machine and presented their conclusions from laboratory-level measurements of copying life and image quality. Further critical evaluation should be undertaken for the a-Si H photoreceptor from an industrial viewpoint. The performances are summed up in Table II for the two types of photoreceptor. 

Fig. 6. Typical PID curves for a-Si H drum (44 /zrr thick) "containing oxygen. Light (0.3 cm-2) of various wavelengths impinges on the photoreceptor after sensitizing with (a)...

Organic photoreceptors can be prepared in either a flexible web or drum format. Webs are usually prepared on polymer substrates, polyethylene tere-phthalate being the most common. The substrates are between 100 to 200 pm in thickness and coated with a conducting surface layer. The substrates often contain layers on the reverse side for reduced curl, static discharge prevention, and control of frictional characteristics. The web configuration is also widely used for laboratory studies. For drums, the substrate is a metal cylinder, usually Al. Recently, however, drums of a poly(phenylene sulfide) resin doped with conductive C black have been developed (Kawata and Hikima, 1996). Drums are widely used in low- and mid-volume applications. Drums, however, are not well suited for research purposes. Thus, the preparation and characterization of drum photoreceptors is usually related to a specific application. 

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. 

Photoreceptors are prepared by the sequential application of the various layers onto a web or drum substrate. Vapor-deposition methods can be used for some pigments. Most layers, however, are coated from solution or dispersions in organic solvents. Wicks (1986) has reviewed film formation from polymer solutions. The choice of solvent is determined by such factors as solubility, evaporation rates, surface tension, toxicity, as well as environmental... 

Organic photoreceptors are prepared by solvent coating techniques and can be fabricated in a drum or web configuration. These can be prepared in the single- or dual-layer arrangement. In the dual-layer arrangement, the generation... 

The CTL must be mechanically rugged, to withstand abrasion by the developer. In machines using a photoreceptor belt (rather than a drum), the entire photoreceptor must also be flexible enough to withstand frequent bending without developing cracks. 

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