Toner adhesion mechanical

The dry-processed, peel-apart system (Fig. 8b) used for negative surprint apphcations (39,44) is analogous to the peel-apart system described for the oveday proofing apphcation (see Fig. 7) except that the photopolymer layer does not contain added colorant. The same steps ate requited to produce the image. The peel-apart system rehes on the adhesion balance that results after each exposure and coversheet removal of the sequentially laminated layer. Each peel step is followed by the apphcation of the appropriate process-colored toners on a tacky adhesive to produce the image from the negative separations. The mechanism of the peel-apart process has been described in a viscoelastic model (45—51) and is shown in Figure 8c. 

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. 

The adhesion of particles by such mechanisms is vitally important in Pharmaceuticals, xerography, semiconductors, printing, and agriculture. Many articles are written on these topics each year. A particular contribution has been made by Rimai, Demejo and Bowen in understanding the adhesion of toner particles which must transfer from a photoconductor to a receiva-. JKR behavior was observed for glass spheres on polyurethane, as shown in Fig. 9.22. Curious effects of large deformation, engulfment and hysteresis were seen. This hysteresis is to be considered next. 

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