| 摘要 |
PURPOSE:To prevent the deterioration and loss of magnetic carrier particles and to extend the period for automatic concn. control by an immobile layer by forming the immobile layer and satisfying the average grain size of the insulating magnetic carrier particles and the distribution thereof to stabilize the state thereof. CONSTITUTION:The insulating magnetic carrier particles 27 are formed of >=45mum and <=75mum average grain sizes and of the grain size distribution consisting of <=20wt.% >=45mum and >=30wt.% <=75mum. The substantially immobile layer 30 mainly contg. such particles 27 is formed on the upper stream side with respect to the rotating direction of a developer carrier from the member which faces the surface of the developer carrier in a developing container 21 and controls the developer layer carried on the surface of the developer carrier. The size of the toner particle taking region formed on the upper stream side of the immobile layer 30 is automatically increased or decreased to control the mixing ratio of the carrier particles and toner particles in the developer layer. The loss of the magnetic particles is thereby prevented and the power to impart the electric charge to the toner particles is stabilized, by which the formation of the good-quality developed image is permitted. |
