Electrostatic latent image development

Kaneko, G. Electrostatic latent image development magenta toner. Jpn. Kokai Tokkyo Koho JP 08137135, 1996 Chem. Abstr. 1996, 125, 181193. 

The final step in the development process involves the transfer of the toner particles from the carrier beads to the photoreceptor surface. The forces that bind the toner to the beads are electrostatic and van der Waals dispersion forces. Development thus requires that the forces due to the fields associated with the latent image exceed the forces that holds the toner to the carrier. For a discussion of processes by which toner particles are transferred from carrier beads to photoreceptor surfaces, see Schein (1975), Hays (1977, 1978), and Schein and Fowler (1985). For a discussion of the roles of van der Waals and electrostatic forces, see Gady et al. (1996). 

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. 

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. 

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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