Charge generation materials

To prepare the charge generation material of photoreceptor used in xerography, the crude VOPc synthesized at 150 °C for 4 h in the microwave synthesis was acid-treated, and then recrystallized. As shown in Fig. 4, the amorphous VOPc can be obtainol from crude VOPc by acid-treatment and the fine crystal VOPc can he obtained fixim amorphous VOPc by recrystallization. From XRD results, it can be calculated that the crystallite size of fine crystal VOPc is about 18 nm. As shown in Fig. 5, the fine crystal VOPc is well dispersed with uniform size. It indicates that this fine crystal VOPC can be probably used as the chaige generation material of photoreceptor. Thus, further research will be required to measure the electrophotographic properties of fine crystal VOPc. 

Several classes of organic compounds have been developed as carrier generation materials. The most important characteristics of a charge generation material are the spectral response, which is determined by the absorption spectrum, and the sensitivity, which depends on the charge generation efficiency. 

Figure 4 Examples of organic compounds used as charge-generation materials for practical image reproduction systems in the (a) visible and (b) near-IR ranges.

Scheme 1. Chemical structures of some typical charge generation materials. See Schemes 4 and 5 for examples of azo pigments.

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... 

Recently, Fuji Xerox armounced a new series of printers, with hydroxygallium phthalocyanine as the charge generating material. Hydroxygallium phthalocyanine is reported to have several crystal forms, with the V form as the most photosensitive. The photosensitivity of the V form hydroxygallium phthalocyanine is comparable to that of Y form titanyl phthalocyanine, but is independent of the humidity l... 

Recently, Fuji Xerox announced a new series of printers, using hydroxygaUium phthalocyanine as the charge-generating material. HydroxygaUium phthalocya-... 

In spite of its low photochemical stability, PMPS in combination with an effective charge generating material, such as amorphous selenium or phthalocya-nine pigments, can be applied in high-sensitivity photoreceptors [493,494]. On the other hand, the inclination of PMPS to photodegradation in air with... 

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