| 摘要 |
PURPOSE:To stably obtain an image excellent in fine line reproducibility and in gradation through the use of fine toner grains by coating a sleeve surface layer with material obtained by adding carbon black and/or graphite to synthetic resin in a developing device employing magnetic toner with a specific grain size distribution and selecting surface layer roughness in a prescribed manner. CONSTITUTION:With respect to the grain size distribution of one-component magnetic toner, grains with a grain size of 5 mum or below are 17 to 60 number %, grains with a grain size of 35 to 10.08 mum are 5 to 50 number %., and grains with a grain size of 17.70 mum or above are 2 vol.% or below. Their volumetric average grain size is 6 to 9 mum. Grains with a grain size of 5 mum or below satisfy N/V= - 0.05 + k, where N(17 to 60) is number % of these grains, V is vol.% of the same, and k = 4.6 to 6.7. A thin layer made of composite material comprising adhesive resin and/or carbon graphite is provided on the surface of a developer carrier, and its surface roughness Ra = 0.3 to 5 mum, and Rz = 1.0 to 30 mum. Then, a uniform coating is obtained, and accordingly a decrease in density, which results from electrification, and sleeve ghost can be prevented. |
