Investigation of toner adhesion in the electrophotographic process

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Adhesion between particles and surfaces is an essential phenomenon for many industrial applications. For example, the key to optimize the electrophotographic process is to understand the adhesion forces between charged toner particles and the photoconductive drum surface. The relevant adhesion forces in this process are the van der Waals, the capillary and the electrostatic forces. In the frame of this work these forces and their dependence on various parameters are investigated by means of AFM, centrifugal detachment and electric field detachment methods. The results are compared with each other and further with model calculations and numerical simulations.
The van der Waals force is identified as the dominating adhesion force in the observed systems. This force is mainly depending on the Hamaker constants and the structure of the contact region. In case of deformable adhesion partners their mechanical properties and the applied load have strong impacts on the van der Waals force as well. The capillary force amounts to the same order of magnitude as the van der Waals force, if the surfaces of the adhesion partners are smooth, while it is negligible between rough adhesion partners. The electrostatic force is usually significantly smaller than the van der Waals force. However, it can result in the relocation of particles and may thus lead to a significant increase of the van der Waals force.