Single-layer photoreceptor

Fig. 2. Schematics of (a) single-layer photoreceptor, where the + signs represent the corona-deposited charge, D the photoconductor, and 1 the conductive substrate and (b), the CdS Sej (Katsuragawa) photoreceptor, where D represents the insulating layer, the CdS Sej, and I the...

Conceptually similar are single-layer photoreceptors such as PVK filled with a photoconductive pigment, such as IV,IV-di(3,5-dimethylphenyl)perylene-3,4,9,10-tetracarboxylic acid diimi.de (32), or a photoconductor containing a bisazo photoconductive pigment, a hole transporting molecule such as an indolinyl hydrazone derivative of carbazole shown in Fig. 5i, in a polyester binder (33). In practice, this photoconductor is charged positively even though both holes and electrons are mobile. 

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. 

Figure 4 A cross-section schematic of the single-layer photoreceptor configuration. Thicknesses of single-layer photoreceptors are typically 10 to 15 pm.

Depletion charging was first described by Amick (1959). For single-layer photoreceptors. Amick s model gives the following relationships. For Qs < N L... 

Figure 13 The field dependence of the photogeneration efficiency of a dual-layer photoreceptor, a single-layer photoreceptor, and the photoluminescence quenching of the dual-layer photoreceptor. The generation layer contained AZO-FO. The transport layer contained a stilbene derivative (MAPS).

Umeda and Yokoyama (1997) measured photogeneration efficiencies of single- and dual-layer photoreceptors prepared with 4,4 -[(9,10-dihydro-9,10-dioxo-2,6-anthracenediyl)bis(azo)]bis[N-(3-bromophenyl)-3-hydroxy-2-naphth-alenecaiboxamide] (ABHN) (Hashimoto, 1985) and 4,4 -[l,4-phenylene-bis (2,l-ethenediyl-4,l-phenyleneazo)]bis[N-(2,4-dimethylphenyl)-3-hydroxy-2-na-phthalenecarboxamide] (PDHN) (Sasaki et al., 1980). For the dual-layer configuration, the transport layer contained MAPS. Single-layer photoreceptors... 

Due to its relevance o single-layer photoreceptors, photogeneration in polymers is of considerable importance to xerography. The most widely studied are the polysilanes, poly(N-vinylcarbazole), and various doped polymers. 

Bipolar transport requires both donor and acceptor functionalities. This may be accomplished by doping a polymer with separate donor and acceptor molecules, or by the use of a dopant molecule that contains both donor and acceptor functionalities. The functionalities can be either associated with a dopant molecule or incorporated within the polymer chain. Most literature references are to doped polymers where the donor and acceptor functionalities are associated with separate donor and acceptor molecules. There are few references of bipolar transport in the literature. Because of its importance to single-layer photoreceptors, however, the subject is of considerable technological relevance. 

Mizuta et al. (1993) have reported that a single-layer photoreceptor containing 9-isopropylcarbazole-3-carbaldehyde-N,N-diphenylhydrazone is fatigued on exposure to ultraviolet radiation. The results were interpreted by a mechanism where radiation induces isomerization of the anti- to the -isomer. The latter has a lower ionization potential and is a hole trap. In the single-layer configuration, hole trapping near the free surface results in the creation of volume space charges, which cause decreased sensitivity. 

Figure 6. Surface potential vs. exposure characteristics for a single-layer photoreceptor with a dye-polymer aggregate CGM. The exposure (680 nm) is strongly absorbed and the initial surface potential is -500 V. (Reprinted with permission from Ref. [26d].)...

Figure 17. The electric field dependence of the photogeneration quantum efficiency (580 nm excitation) for photoreceptors with bisazo-based CGMs. Dual-layer photoreceptors (open symbols) with CGL (0.09-0.49 pm) and CTL (22 pm) had a negative surface charge. Single-layer photoreceptors (filled symbols) (0.15 and 0.27 pm) were given negative, and for the thicker sample positive, surface charging. The photolumincscence quenching efficiency (filled diamonds—broken line) was determined on a dual-layer sample CGL (0.15 pm) and CTL (1.9 pm). (Reprinted with permission from Ref [34c].)...

Fig. 6.1 Schematic depiction of the xerographic process for a positively corona-charged single-layer photoreceptor.

Figure 17-6 Transient decay curve of single-layer photoreceptors with X-form metal-free phthalocyanine and Y-form titanyl phthalocyanine.

Dainippon Ink and Chemicals markets its photoconductive X-form metal-free phthalocyanines as the Fastogen Blue 8120 series. Products include materials for printers and material for plate making. X-form metal-free phthalocyanine is less sensitive than titanyl phthalocyanine, but is considerably lower in price. The prices are only 2000 to 5000 a kilogram. Figure 17.6 shows a comparison of the transient decay curve of surface potential of single layer photoreceptors with the X-form metal-free phthalocyanine and the Y-form titanyl phthalocyanine. The... 

Figure 10.2. Schematics of the configuration and the photodischarge process of a single-layer photoreceptor.

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