Applications, photoconductors electrophotography

Coloured materials find application in both toners and organic photoconductors fused in electrophotography. Photoconductors will be covered in detail in Chapter 4 (section 4.4) and only toner resins will be considered in this section. 

As already shown, the sensitized spectra follow the dye absorption. Most of the dyes have sufficiently narrow absorption bands. This does not permit us to obtain the panchromatic sensitivity in the sufficiently broad spectral range. It was proposed to use the polymers with conjugated bonds as sensitizers [21]. The broad diffuse absorption spectra are inherent to such compounds. One can expect higher thermal stability from such sensitizers. In addition the application of binder may be omitted from the preparation of the photosensitive layers, for example, in electrophotography. Polymers with triple bonds, polyphenylenes and polyoxiphenylenes were used as sensitizers [10, 14, 278-280]. The typical results are shown in Fig. 47. The main rules for photoconductivity sensitized by polymers were the same as for the dyes. Optimum sensitization was obtained at the concentration of the sensitizer of 10 1-10-2 g/cm3 relative to the polymeric photoconductor weight. 

Nowadays, polymeric photoconductors may be used in electrophotography, microfilms, photothermoplastic recording, spatial light modulators, and nonlinear elements. The combination of photosensitivity with high quality electrical and mechanical properties permits the use of such materials in optoelectronics, holography, laser recording and information processes. The applications of the various types of polymers were reported in the final parts of the relevant items in the earlier sections. Here, we will briefly analyze the common features of photoconductive polymer applications. The separate questions of each type have been dealt with in some books and papers [3, 11, 14, 329]. 

In addition, some quinacridones have found unusual applications. For example, both quinacridone and its 2,9-dimethyl derivative have been found to exhibit desirable photovoltaic characteristics , and show relatively high power conversion efficiencies in solar cell fabrication. Some quinacridones have also been found to be reasonably good photoconductors, and 2,9-dichloroquinacridone has been shown to be a photoreceptor in electrophotography. A variety of other atypical applications have also been claimed in the patent literature. 

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