Electrophotographic Films

The process of photoconductivity can be broken down into several steps  

Formation of excitons. An exciton is an excited state where an electron is still bound to the matrix, but the matrix is going to form a gap of charge. In other words, an exciton is a pair of electron and a hole of charge, 

Formation of movable charges. The excitons dissociate by the help of donor acceptor sites present in the material into movable 

The carbazole group absorbs light in the UV range. Therefore, polymers of this type can become photoconductive as such only in the UV range. However, colored sensitizers can be added to shift the photoconductivity into the visible region. 

After the formation of excitons, the charges become more separated. Important for the final yield of charges is the efficiency by which the excitons are converted into free charges. The yield can be improved by doping with an electron acceptor or by tailoring the molecule as electron acceptors are introduced as substituents or side chains. Both an intermolecular and 

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Resins for high-speed electrophotography Metal primer Electrophotographic films Glossy, aqueous paints Metal... 

Electrophotographic films Britain 1,004,461 1965 Gevaert Photo Producten N.V. 

Radiation-sensitive resins Photoresist coatings Electrophotographic film barrier layer... 

Electrophotographic film barrier Methyl vinyl France 2,231,991 1974 Eastman Kodak... 

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. 

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 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). 

Dual-Spectrum Also called Workman. A thermographic copying process. A transparent film base, coated with 4-methoxy-l-naphthol and a photo-reducible dye such as erythrosine, receives the image, which is then transferred to a paper sensitized with sodium behenate. Invented in 1961 by W. R. Workman at the Minnesota Mining and Manufacturing Company, MN, and commercialized for office copying, but later superseded by various electrophotographic processes. 

Many other applications have been described for these compounds and the hst is so extensive that it is impossible to cover each example here. Nevertheless, it is noteworthy that appropriately substituted 4-arylidene-5(4r/)-oxazolones, for example, 359 and 360 have been reported as organic Iruninophores" " and electrophotographic light-sensitive materials," respectively. The use of apoca-rotenoid derivatives such as 362 as monomolecular films has also been described." For new materials, a number of water-insoluble oxazolones have been used for dyeing or printing synthetic fibers" and, in this context, 4-(pyren-1-ylmethylene)-2-substituted-5(4/i/)-oxazolones 357, prepared from pyrene-1-carboxaldehyde, have... 

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],... 

Compared to Kapton, more sensitive soluble polyimide films were investigated [235-236]. A photosensitivity of up to 30 m2 J 1 was achieved in electrophotographic regimes. The photogeneration of the charge carriers occured via exiplex formation and the holes are the predominant carriers. The spectral... 

Plasma-polymerized phenylacetylene, styrene, PVC, merocyanine dyes and other materials [323-328] were also photoconductive in various spectral ranges. Most of them made Schottky type barriers with electrodes. As a rule, electrophotographic properties attracts attention to polymeric films possessing them. 

H. Gleskova, S. Wagner, and D. Shen, Electrophotographic patterning of thin-film silicon on glass foil, IEEE Electron Dev. Lett., 1995, 36, 418. 

Patents have been issued for the use of polydiacetylene derivatives as coloured photoresist films and electrophotographic print-out materials " . ... 

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