Photoreceptor development

The Ricoh photoreceptors shown in Fig. 6 have been described by Nishijima (1985) and Ohta (1986). The trisazo pigment AZO-TP A has been used in the preparation of a photoreceptor developed for a laser printer... 

Ehinger B, Juliusson B, Bergstrom A, Sharma RK. 1996. Photoreceptor development in retinal cell transplants. Kato S, Osborne NN, Tamai M, editors. Retinal degenerations and regeneration. Kugler Publications Amsterdam/New York pp. 155-164. 

Zhang J, Gray J, Wu L, Leone G, Rowan S, et al. 2004. Rb regulates proliferation and rod photoreceptor development in the mouse retina. Nat Genet 36 351-360. 

Srinivas, M., Ng, L., Liu, H., Jia, L., and Forrest, D. (2006) Activation of the blue opsin gene in cone photoreceptor development by retinoid-related orphan receptor beta. Mol. Endocrinol. 20, 1728-1741. 

Watanabe, T. and Raff, M.C. (1990) Rod photoreceptor development in vitro intrinsic properties of proliferating neuroepithelial cells change as development proceeds in the rat ttXm. Neuron 4 461-467. 

Satoh, A., O Tousa, J., Ozaki, K. Ready, D. (2005). Rabll mediates post-Golgi trafficking of rhodopsin to the photosensitive apical membrane of Drosophila photoreceptors. Development 132,1487-97. 

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. 

Liquid toners are suspensions of toner particles in a fluid carrier. The carrier is typically a hydrocarbon. Dielectric, chemical, and mechanical properties of the Hquid must be compatible with the photoreceptor, the suspended toner particles, and the materials of the development equipment. Liquid toners are capable of producing higher resolution than dry toners because of the smaller (3—5 -lm) particle size achievable. Development of the latent image occurs as it passes through a bath of toner and the charged particles are attracted to the oppositely charged surface. 

The abihty to accept and hold the electrostatic charge in the darkness. The photoconductive layer should support a surface charge density of approximately 0.5-2 x 10 C/cm. The charge also has to be uniformly distributed along the surface, otherwise nonuniformities can print out as spot defects. The appHed surface potential should be retained on the photoreceptor until the time when the latent electrostatic image is developed and transferred to paper or, if needed, to an intermediate belt or dmm. In other words, the "dark decay" or conductivity in the dark must be very low. The photoconductor materials must be insulators in the dark. 

Fig. 9. (a) Schematic of charged area development (CAD), using toner charged oppositely to that of the photoreceptor and resulting in a positive document (b) discharged area development (DAD), where the toner and photoreceptor polarity are the same, resulting in a negative document. 

Triboelectricity. For development to occur, the toner particles must be reproducibly charged to the correct level and polarity for the specific photoreceptor. The phenomena of triboelectricity, which involves the transfer of charge from one soHd to another, are exceedingly complex, involving the surfaces of soHds and interaction of the surfaces with each other and with the ambient (52). Consequentiy, the specific experimental observations are highly sensitive to the nature and purity of the materials, the physical and chemical state of both surfaces, and the precise details of the experiments performed. 

Development Process Parameters. If a photoreceptor 50 im thick is charged uniformly to a surface potential of 1000 V, assuming a typical dielectric constant of 5, the amount of charge per square centimeter of the photoreceptor is 100 nC. One electronic charge amounts to 1.6 X 10 C thus 6 x 10 singly charged ions would reside on each square centimeter of surface. To achieve complete photodischarge, therefore,... 

Once the latent electrostatic image has been developed on the photoreceptor surface, it must be transferred to plain paper with no loss in clarity. 

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