Electrophotographic

In other areas, POD has been used to improve the wear resistance of a mbber latex binder by incorporation of 25% of Oksalon fibers. Heat-resistant laminate films, made by coating a polyester film with POD, have been used as electrical insulators and show good resistance to abrasion and are capable of 126% elongation. In some instances, thin sheets of PODs have been used as mold release agents. For this appHcation a resin is placed between the two sheets of POD, which is then pressed in a mold, and the sheets simply peel off from the object and mold after the resin has cured. POD-based membranes exhibit salt rejection properties and hence find potential as reverse osmosis membranes in the purification of seawater. PODs have also been used in the manufacturing of electrophotographic plates as binders between the toner and plate. These improved binders produce sharper images than were possible before. 

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. 

Despite the many advantages of electrophotographic printing processes, a principal economic disadvantage remains each print costs the same. 

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. 

PVF resins have also been used in a variety of other appHcations, including conductive films (152), electrophotographic binders (153), as a component for inks (154), and in membranes (155,156), photoimaging (157), solder masks (158), and reprographic toners (159). 

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. 

Fig. 8. Organic photoreceptors for electrophotographic use. (10), 4-[4-DimethylamiQo]phenyl]-2,6-diphenylthiapyryhumperchlorate [14039-00-0] ...

The XeroX Copier Machine Model A was announced in 1949, and involved compHcated manual operation. Copies of acceptable quaUty were operator dependent. The Copyflo printer, introduced in 1955, was the first automated xerographic machine and enabled the production of copies on a continuous web of ordinary paper. Early electrophotographic products used paper coated with dye-sensitized zinc oxide Electrofax which had met market resistance in terms of aesthetics and cost, so that in 1958 the total market was only about 100 million (1—3,5). 

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. 

Heterocycles as photoconductive materials used for electrophotographic organic photoreceptors 99YGK541. 

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. 

The corona discharges produces oxygen ions and ozone, which may react with the photoconductor [634], As a means to circumvent possible degradation of the surface layer, an extra, protective thin layer was proposed, with high carbon content [101, 635, 636]. This would reduce silicon-oxygen reactions at the surface. Excellent electrophotographic characteristics have been obtained with a thin device comprising a 0.1-/rm-thick n-type a-Si H layer, a 1.0-/rm intrinsic a-Si H layer, a 0.1-/irm undoped a-SiCo i H layer, and a 0.014-/xm undoped a-SiCoj H layer [101]. 

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). 

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