Theory of toner charging

The physics of toner electrostatic charging is studied by measuring the toner charge-to-mass ratio dependence on the toner concentration and charge control agent concentration in a toner-carrier mixture. It is shown that the data are inconsistent with the low-density limit of the surface state theory, but are consistent with the high-density limit, which assumes that charge is exchanged to create an electric field in the interface during the contact event, which shifts the Fermi levels into coincidence. Such a theory is consistent with other published toner-carrier charging experiments.