Organic photoconductor

Photoconductors. Only the most recently developed organic photoconductors (OPC) approach optimum behavior (see Photoconductive POLYAffiRS). 

The trend in the xerographic copying and printing industry is to expand the use of organic photoconductors which are typically inexpensive and have a useful life. However, the a-Si H photoreceptors, even though more expensive to manufacture, may ultimately have an advantage in greater durabihty. 

Metal complex dyes and pigments perform key functions in both the image generation step and the toner development step. It is the metal complex pigment that produces the positive hole in the organic photoconductor. 

Koch-Yee Law. Organic photoconductor materials for xerographic photoreceptors (Advanced Tutorial A2). IS and T s Non-Impact Printing Conference 12, San Antonio, Texas, October 27, 1996. 

Poly-N-vinylcarbazole is one of the very important organic photoconductors now in use in electrophotography. For practical use, a little amount of sensitizer is usually added. 

Figure 2.37 The electrophotographic process using organic photoconductors (a) photocopying and (b) laser printing.

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. 

Titanyl phthalocyanines are used as the CGMs in commercial organic photoconductors, e.g. in the engines from Canon, Xerox, Konica and other OEMs. 

Other molecular classes that have been used as CGMs in commercial organic photoconductors include quinones, e.g. dibromanthanthrone (4.24) by Xerox and Konica,... 

Warta W, Stehle R, Karl N (1985) Ultrapure, high mobility organic photoconductors. 

Bassler H (1993) Charge transport in disordered organic photoconductors - a Monte-Carlo simulation study. Phys Status Solidi B 175 15... 

Fig. 9. Dependence of -type or p-type organic photoconductors on trapping, (a) Symmetric trapping (b) Asymmetric trapping -type (c) Asymmetric trapping p-type pt, nr — empty and filled centers, respectively = Fermi energy...

It has recently been shown that organic photoconductor-liquid crystal sandwich cells can in theory act as dynamic scattering devices 164> and the technical possibilities ought to be tested. In this context, it should be noted that dyes can be used in two-layer photocondensers (consisting e.g. of phthalocyanine and a ferroelectric ceramic), which are very sensitive to light and have a response time of lO-4 to 10-3 Sec 165). 

It is certain that organic photoconductors will be used on an industrial scale in the near future in methods of reproduction based on photoelectric and electrostatic processes (reviews are given in 10>166)). 

There seems no doubt that organic photoconductor systems will permit the development of new reproduction processes based on the electrophotographic principle 10>. Dyes play an important role in this development on the one hand they act as spectral sensitizers of the organic photoconductors (e.g. poly-N-vinyl-carbazole 161> and on the other hand, the photoelectric effects of dyes are important for... 

Various types of the photoconductive polymers are available now. The photoconductivity of such materials may be essentially increased by means of the chemical and spectral sensitization [12-14]. Spectral sensitization is connected with the appearance of the photosensitivity in the new spectral bands and the chemical sensitization with the increase of the proper sensitivity. As a rule both types of sensitisation may take place in the photoconductor at the same turn. The first data about chemical and spectral sensitization in organic photoconductors appeared in [19, 20]. The example of the chemical and spectral sensitization of the photoconductivity by dyes in polymeric copper-phenyl-acetylenide is presented in Fig. 2. Later on it was proposed that not only low molecular weight compounds but polyconjugated polymers could also be used as sensitizers [21] having broad absorption tends and high thermostability compared with dyes. Now it is clear that various types of molecules may be used as a photosensitizers. 

Polymers with triple bonds have been applied in electrophotography [176] and were the first among organic photoconductors with sensitized by dyes photoconductivity [19,20]. 

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