PURPOSE: To provide a developer showing no change in performance even used for a long term so that picture images of high quality with high picture density and no fog can be obtd.
CONSTITUTION: This developer is used for such a developing method that a magnetic brush having 5-20 volume % toner particles is formed in a developing zone formed by a latent image holder and a developer carrier and an AC electric field at ≥2.5kHz frequency is applied on the brush. In the distribution of particle size of the developer the toner, the proportion of particles having 2.0-4.0μm particle size is 15-40% in number, and the proportion of particles having 4.0-8.0μm particle size is ≥60% in number. The charge amt. of the toner when mixed with an iron powder carrier is ≥-30μC/g.
TANAKA KATSUHIKO
DOI MICHIYOSHI
