Abstract
Based on the surface state theory, a definite equation for the time constant of toner charging was derived by formulating the dynamic charging equation. The time constant was expressed by the parameters obtained through regression analysis of the measured data of the specific toner charge as well as the mixing ratio of toner to carrier. The equation showed that the reduction of the time constant was quantitatively predictable.
The relationship among the work functions of toner and carrier and the corresponding time constant was analyzed on the assumption that the distributions of surface state densities are exponential to electron energy level. This analysis successfully explained the experimental result that the logarithm of charging speed (inverse of the time constant) is proportionate to the difference in work functions between toner and carrier.
The surface state theory was shown to be effectually utilized not only for the evaluation of developers but also for the design of materials for developers.
