Electrophotographic developers

The detection of spectral sensitizing action often depends on amplification methods such as photographic or electrophotographic development or, alternatively, on chemical or biochemical detection of reaction products. Separation of the photosensitization reaction from the detection step or the chemical reaction allows selection of the most effective spectral sensitizers. Prime considerations for spectral sensitizing dyes include the range of wavelengths needed for sensitization and the absolute efficiency of the spectrally sensitized process. Because both sensitization wavelength and efficiency are important, optimum sensitizers vary considerably in their stmctures and properties. 

The first application of pyrazino[2,3-6]pyrazines as vulcanization accelerators for rubber copolymerization has been reported in CHEC-I. Some new pyrazino[2,3-A]pyrazine derivatives are in use as electrophotographic developers <90JAP(K)2135365) and light-resistant fluorescent polymers <89JAP(K)0l 153750). Some alkylsubstituted decahydropyrazino[2,3-6]pyrazines are suitable as delayed-action catalysts for the preparation of urethanes <83USP452839l>. Other pyrazinopyrazine derivatives are reported to have inhibitory effects on tomato spotted wilt virus <83MI 719-01). 

Imai, T. Agata, T. Electrophotographic developer encapsulated toner and its manufacture. JP 06317924, 1994. 

Hakata, T. (2002). A novel composite carrier for electrophotographic developers. /. Imaging... 

The electrophotographic system (102,103) involves two key physicochemical elements a photoreceptor and a toner. The minimum requirements of the process are (/) to charge a photoconductive photoreceptor uniformly (2) to illuminate selectively the photoreceptor to form a latent electrostatic image and (J) to develop the image by applying charged toner. These steps are illustrated in Figure 17. 

Humectants and low vapor pressure cosolvents are added to inhibit drying of ink in the no22les. Surfactants or cosolvents that lower surface tension are added to promote absorption of ink vehicle by the paper and to prevent bleed. For improvements in durabiUty, additional materials such as film-forming polymers have been added. Ink developments are providing ink-jet prints with improved lightfastness, waterfastness, and durabiUty. As a result, such prints are beginning to rival the quaUty of electrophotographic prints. 

The Development Process. In the original electrophotographic demonstration, development was accompHshed by dusting lycopodium powder over an exposed sulfur film. This yielded low density images of poor resolution. Considerable powder settied in the exposed background areas (the white areas of a document), and image transfer to paper could only be achieved by prior coating of the paper with wax or another sticky material. 

Electrical Conductivity. Changes in the electrical conductivity within or on the surface of a photopolymer film can be used to visualize the results of a photochemical reaction. A limited number of electrophotographic/electrostatic processes have been developed employing this readout method (22). 

Mobility measurements by the TOP methods considered in Chapters 3 and 4 are particularly important, but they cannot give information about the whole spectrum of states in the mobility gap of amorphous chalcogenides. Therefore, in addition to TOP, XTOP, IPTOP, TSC, and TSDC, other complimentary techniques that probe the gap states are needed. Xerographic techniques that were initially developed to characterize properties of electrophotographic (xerographic) receptors [1] seemed to be informative, suitable, and widely applicable for the study of amorphous thin films and photoconductive insulator thin films [2],... 

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... 

Because of the very considerable process complexity of xerography, there have been many attempts to develop alternative electrophotographic processes. A review of early work has been given by Caillson (1965), Claus and Corrsin (1965), Schaffert (1965. 1975), and Weigl (1977). More recent work has been reviewed by Schein (1988. 1992, 1995). The more prominent of these processes are briefly discussed below. 

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