Electrophotographic Photoreceptor

Electrophotography is today s leading process for duplication and print, and is one of the most successful applications of phthalocyanine compounds in noncolorant fields. 

Amorphous selenium metal was originally used as the photoconductor (photo charge carrier generator) of the Carlson process in electrophotographic reprography. However, because of its toxicity and difficulty of fabrication, selenium has been progressively replaced by organic photoconductor materials (OPC). 

In the ten years following the expiration of the basic application patent of Xerox [11], extremely photosensitive phthalocyanine compounds have been developed and phthalocyanine OPCs have become the leading materials. 

In 1998, about 70 million OPC photoreceptors were produced, compared to 800 000 and 500 000 of selenium photoreceptors and amorphous silicon photoreceptors, respectively. Of these, 70 milUon OPC photoreceptors, 45 million are by Canon, 10 million by Mitsubishi Chemicals, 4 million by Fuji Electric, 3 million each by Yamanashi Electronics and Dainippon Ink and Chemicals, and 5 million by others. The largest portion of these OPC photoreceptors is based upon titanyl phthalocyanines. 

Although titanyl phthalocyanine was known to have two crystal forms, and p, in the course of OPC investigations in the past 15 years, many new crystal modifications have come to hght, exhibiting different patterns of X-ray diffraction spectra. 

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Halogenated indanthrones provide improved resistance to hypochlorite treatments and many derivatives have been examined. Direct halogenation of indanthrone leads to substitution at the 7-, 8-, 16- and 17-positions. The commercially important 7,16-dichloroindanthrone (6.72 Cl Vat Blue 6) can be synthesised by a rather lengthy route from phthalic anhydride and chlorobenzene (Scheme 6.13). Polycyclic vat dyes of this type also find use as electrophotographic photoreceptors. 

A few applications of isobenzofurans have been reported in the patent literature, e.g., for the preparation of polymers [90JAP(K)02/75625 90JAP(K)02/263824], for electrophotographic photoreceptors [88JAP(K)-63/60453 93JAP(K)04/212166, 93USP5250395 94JAP(K)05/158620,... 

Charge generating and transporting behavior of irradiated m.etallotetrapyr-role layers is exploited in the function of colour copiers [281-284]. Suited and practically used electrophotographic photoreceptors in the copiers comprise TiPc, TiOPc, VOPc, MnPc as parts of the layers. 

In numerous patents the synthesis of suitable furo-, thieno-, and pyrrolo-tropylium salts is described, for example, that of squarylium dyes like 623 and 624 (Scheme 169 85JAP60/262163 86JAP61/185487 88JAP63/41858, 88JAP63/102990). These substances serve as components of photoconduc-tive thin layers for electrophotographic photoreceptors. The materials are claimed to exhibit increased sensitivity, stability on storage, and durability to laser-beam reading. 

JP 05197182 (Japanese) 1993 Electrophotographic Photoreceptor with Amorphous Silicon Pho-toconductive Layer Fuji Xerox Co. Ltd., Japan S Yagi et al. Copolymer useful for surface protective coating photoreceptor shows stability and gives sharp images Maleimide-terminated siloxane-imides crosslinked coatings were used to protect photoreceptors. 

Most practical polymer-based electrophotographic photoreceptor systems now in use are in fact solid solutions of an active species in a binder host polymer 11). This system concept embodies the notion of full chemical control of the transport process. Thus, the concentration of dopant molecules directly controls the drift mobility, which is in turn controlled by the overlap of wave functions between active sites. The host polymer binder is then specialized for its mechanical and adhesive properties. Understanding the key features of small-molecule transport provides guidelines for the optimization of injected-carrier range. The key point is to understand how chemically induced traps arise in such systems and how molecularly doped materials containing various contaminants in substantial quantities can still efficiently transport charge. (Even part-per-million concentrations of con-... 

Well over 100 patents have been issued for a variety of practical applications of calixarene-based molecules. Many of these, not surprisingly, involve the chemistry that is discussed in this book, especially the use of calixarenes in systems in which selective ion complexation plays the central role. A number, however, deal with quite different sorts of applications including, inter alia, the use of calixarenes as adhesion promoters, electrophotographic photoreceptors, ... 

The use of these polymers in electrophotographic photoreceptors has been patented [9,10]. In another patent, a material consisting of poly(vinyl chloride), a plasticizer, an ion-conductive additive, and poly(vinylcarbazole), among other components, was suggested as a thermosensor in thermistor materials [11]. 

Electrophotographic photoreceptors containing stilbene derivatives having triphe-nylamine structures have been designed. In the work [33], stilbeneamine derivatives having general structure I (Ari = aryl, sUyl-, or silyl ether-substituted aryl). 

Ariga, T. Adachi, H. High-sensitivity electrophotographic photoreceptor. Jpn. Kokai Tokkyo Kobo JP 07191477, 1995 Chem. Abstr. 1995, 123, 270749. 

Akeyoshi, H. Tamura, H. Suzuki, R. Positive-charging electrophotographic photoreceptor. Jpn. Kokai Tokkyo Koho JP 01267555, 1989 Chem. Abstr. 1990,113, 31905. 

Shoji, M. Komai, Y. Azo compounds useful for electrophotographic photoreceptors, coupling compounds therefor, and manufacture. Jpn. Kokai Tokkyo Koho JP 2003206411,2003 Chem. Abstr. 2003, 139, 118730. 

CVD of boron nitride films on silicon or germanium or on printed circuit boards is now a common practice in the electronic industry [154 to 162]. The high thermal conductivity combined with the excellent electrical insulation properties are most valuable for these applications [163] see additional references in Section 4.1.1.10.8, p. 129. The use of a-BN layers is of particular importance in the manufacture of electrophotographic photoreceptors (such as solar cells) and of X-ray lithographic masks (see Section 4.1.1.10.8, p. 129). In the last mentioned application, structural aspects of the deposited films are of importance. In films still containing hydrogen, (N)H moieties are depleted by annealing at about 600°C, while (B)H moieties are depleted above 1000°C [164]. Also, elastic stiffness and thermal expansion of boron nitride films have to be viewed in connection with the temperature-dependent stress of CVD-deposited boron nitride films [165]. Reviews of properties and electronic applications of boron nitride layers have appeared in Polish [166] and Japanese [167]. 

Another field of application for boron nitride is its use as blocking layer and/or surface layer in electrophotographic photoreceptors [69 to 96,380]. Again, these layers are produced by the CVD methods described in Section 4.1.1.10.2, p. 62. Depending on the deposition method or specific conditions, the boron nitride layers in the electrophotographic receptors may also consist of or contain p-BN [97 to 100]. 

Electrophotographic photoreceptors based on polycarbonate resins have been prepared by treating aromatic dioxy compounds with phosgene [274]. Electrophotographic photoconductors containing fluorine-bearing polycarbonate binders have also been prepared from bisphenol A, phosgene, and 1,1,1,3,3,3-hexafluoro-2,2-bis(4-hydroxyphenyl)propane [275]. 

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