Toner deposit

Experimental data relating the spatial frequency dependence of image quality parameters obtained from electrophotographic toner deposits with the toner particle size distributions are presented. 

Figure 6. Schematic of toner deposits and optical density traces, obtained using a slit aperture, of large particles (left), and small particles (right).

A theoretical model to relate the Wiener spectrum to the toner deposit parameters is difficult to construct because the mathematical difficulties of dealing with projections of transforms of probability distributions quickly "hide" any simple relationships. Models have been constructed however for a crowded monolayer photographic emulsion (11), and for multilayers of emulsion (12). Although the analysis was done for one-dimensional geometry, extension to two dimensions was outlined. A different approach will be used here, which relies on the linearity property of the Fourier transform, and assumes that the location of the toner particles is independent of neighbors. 

The correlation analyses of toner particle size and size distribution parameters and image quality characteristics of toner deposits as measured by the spectral dependence of contrast transfer function and noise show high coefficients of correlation Specifically the Wiener spectrum data appear to yield the weight geometric mean and standard deviation of the toner population in this study. Therefore the Wiener spectrum may be another analytical tool in characterizing particle populations. It must be pointed out that the analysis reported here is mainly empirical. Further work is needed to refine the models and to examine the limits of applicability of these tests. Factors such as particle clumping, non-uniform depositions and optical limitations are specific areas for examination. 

Sulfide/hypo-alum toners are reusable and often improve with age. They usually contain a milky-white deposit, the result of sulfurization, which should not be filtered but stirred well before use. 

In the development step, charged toner particles are deposited on the photoreceptor surface. There are several techniques by which this can be accomplished, most of which involve the use of a second component called a carrier. 

In early copiers, deposition of the toner particles onto the photoreceptor surface was accomplished simply bv cascading the particles over the photoreceptor surface. Cascade development was first described by Walkup (1952) and used in all earl) Xerox copiers. Figure 15 shows a cascade development process. Carriers for cascade development were usually glass or metal beads with diameters of several hundred pm. The limitations of cascade development... 

The solution is to clean the corona wires. LaserJet Series II printers contain a small corona wire brush to help in this procedure. It s usually a small, green-handled brush located near the transfer corona wire. To use it, remove the toner cartridge and run the brush in the charge corona groove on top of the toner cartridge. Replace the cartridge and use the brush to brush away any foreign deposits on the transfer corona. Be sure to put it back in its holder when you re finished. 

Mechanical force and surface chemical finesse must be used to overcome van der Waals forces, which may account for as much as 75% of the total adhesion ( 3, 4) (Figure 16). A rapidly rotating fiber brush is often used to produce a local cloud of toner, which is then drawn away through a vacuum filter. The bristle tips may be "flicked" against a bar or edge to free them of dust. Teflon fiber brushes ( 5), stearate wax dispensers ( 6), and fluorocarbon powder ( 7.) have been effectively used to deposit thin low-energy films on the photoconductor surface to facilitate release. 

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