A model for space charge evolution and charge deposition in the electrophotographic toner transfer process

A model, based on several simplifying assumptions, for an electrophotographic toner transfer process in which some toner particles are assumed to become airborne when the electric field between photoconductor and paper surfaces becomes large enough to overcome adhesive forces is described. The model for the coupling between the electric field and the space charge associated with toner particles requires a self-consistent description of space charge and electric field structures. One-dimensional and two-dimensional models are described. The one-dimensional model provides a closed-form description of charge density and electric field magnitudes across a gap of fixed height. The two-dimensional model, based on coupling the finite element method with the method of characteristics, brings in significant geometric effects, including spreading of the beam of toner particles as it crosses the gap. A dynamic process is described whereby the toner and its associated charge are removed from the photoconductor surface and deposited on the paper surface while the toner and charge are transported on both moving surfaces