Image forming apparatus with a two-component type developer

摘要

A developing method of the present invention is practicable with a developing unit (1) of the type including a rotatable, nonmagnetic sleeve (7) and a rigid metering member (9). A two ingredient type developer made up of magnetic carrier grains and toner grains is magnetically deposited on the sleeve (7). The metering member (9) meters the amount of the developer deposited on the sleeve (7). The sleeve (7) has surface roughness Rz ranging from 5 mu m to 20 mu m. The carrier grains each are covered with a coating layer containing at least binder resin and grains. The ratio of the diameter D of the individual grain contained in the coating layer to the thickness h of the binder resin layer lies in the range of 1 < D/h < 10. The carrier grains have a weight-mean grain size ranging from 20 mu m to 60 mu m.