Organic photoreceptor, development

The poly-TV-vinylcarbarzole trinitrofluorenone (PVK TNF) charge-transfer complex [21-23] was the first commercial organic photoreceptor used in electrophotography by IBM. The photoconductivity of this material is comparable to that of amorphous selenium, but its utilization in practical devices was limited, owing to its toxicity and long transit-time value, comparable, as for most single-layer photoreceptors, to the development process time. 

The requirement on the response time of the photoreceptor is minimal, even at high copy rates. The image is developed entirely in parallel, so that the response time need only be that of the development time for the entire page, which is 0.5 s for a copy speed of 120 pages per minute. Photoreceptors with very low carrier mobility are therefore adequate and, in fact, many organic photoreceptors have mobilities below 10 cm s , much less than both carriers in a-Si H. (This situation can be contrasted with a laser printer, which for the same printing speed requires a data rate of 1 GHz.) The a-Si H photo-... 

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. 

With further improvements in the chemistry of organic materials, the continued development of materials with improved properties may be anticipated. The technology of organic photoreceptors, however, is approaching maturity. 

The first major commercial application of amorphous semiconductors was as the photoreceptor in xerographic copiers and subsequently in laser printers. The early photoreceptors were selenium films, but several other materials were subsequently developed, including ASgSCg and various organic films. Amorphous silicon is a good material for a xerographic photoreceptor (e.g. Shimizu (1985), Pai (1988)) and is used in some commercial copying machines. 

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