Collisional dynamics of charge exchange in xerographic developers

摘要

A model of the dynamics of charge exchange between metal and polymer spheres is applied to charging of xerographic carriers and toners. The model shows that the magnitude of charge exchange during mixing of carrier and toner particles depends upon a material rate constant (barrier height of carrier‐toner contact), temperature at contact, geometry of carrier and toner surfaces (sizes), velocity of approach between carrier and toner, and the ratio of volume of voids to that occupied by the solid matter in the cavity. Using thermionic emission as the mechanism of charge transfer across the carrier‐toner interfacial layer, an expression showing the dependence of current density on the barrier height of the carrier‐toner contact and the temperature at the contact is investigated in depth. If we assume surface state charges to be much greater than the space charges on the toner surface, the barrier height will depend upon the work‐function difference between carrier and toner, the density of surface states of toner, and the level to which states are filled up on the neutral surface. From the expression of current density, we derive an equation for charge on the carrier sphere resulting from collisions with a single or a group of toner spheres.