Dual charge generation layer

Fig. 6.2 Schematic depiction of the light-induced discharge process for a negatively corona-charged dual-layer photoreceptor. CGL and CTL denote the charge generation layer and the charge transport layer, respectively.

Figure 1 V versus 0 relationships for (a) capacitive charging, (b) charging of a single layer with depletion of one sign carrier, and (c) charging of a dual layer with one sign carrier depletion from the generation layer.

The effects of the generation-layer fabrication variables on the sensitometry of a dual-layer photoreceptor prepared with bis(4-dimethylaminophenyl) squaraine (X = H in Appendix 2) have been extensively investigated by Law (1987). The charge acceptance, dark discharge, sensitivity, and the residual... 

A squaraine prepared from N-chlorobenzyl-N-methylaniline and squaric acid has found utility as a generation layer in a dual-layer photoreceptor with an inverted structure for positive charging applications (Yamamoto et al 1986). The photoreceptor showed full-process stability. 

Within the framework of current transport theories, the task of the chemist is to prepare donor molecules in which the molecule has the appropriate oxidation potential, orbital delocalization, and solubility. Further, the effects of dipolar disorder and intermolecular dimer sites must be minimized. Finally, the physical and chemical interactions of the transport and generation materials (whether in a single or dual-layer configuration) must promote efficient charge generation and injection. The systematic integration of all of these characteristics is indeed formidable. 

Environment effects have been described by Law (1987) in studies of a dual-layer photoreceptor with a squaraine-pigment-based generation layer. Seasonal fluctuations in dark decay and charge acceptance were observed and related to humidity. Water adsorption on the pigment particles was suggested as the underlying cause. 

Vanadyl phthalocyanine (VOPc) has three crystal forms. Phase I has the major absorption at 725 nm and Phase II at 840 nm [39a]. Figure 27 shows the absorption spectra of Phases II, V, and XI. A dual-layer xerographic photoreceptor with VOPc as the charge generation material had a high-field photogeneration efficiency of 0.2 from 400 to 900 nm [39b]. The effects of molecular structure on aggregation have been studied with t-butyl-substituted VOPcs [39c]. Such substitution increases... 

Fig. 6.3 Charge generation in a dual-layer photoreceptor system. The quantum yield of charge generation as a function of the wavelength of the incident light at...

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