| abstract |
Even when adapting to high speed, sleeve contamination is prevented in advance, and good development characteristics can be obtained even in long-term use. A line connecting a rotation center of a first developer carrier 3a and a rotation center of a second developer carrier 3b is a reference line L, and a rotation center of a second magnetic pole B and the first developer carrier 3a. Where b is the intersection angle between the line connecting the reference line L and the reference line L, and c is the intersection angle between the line connecting the third magnetic pole C and the center of rotation of the second developer carrier 3b and the reference line L. 0 and c ≧ 0 are satisfied, and the polarity of each magnetic pole is defined. The maximum electric field strength E1 between the photosensitive drum 100 and the first developer carrier 3a is larger than the maximum electric field strength E2 between the photosensitive drum 100 and the second developer carrier 3b. Further, the saturation magnetization of the developer is 20 Am 2 / kg or more and 40 Am 2 / kg or less, and the surface roughness of the resin layers of the first developer carrier 3a and the second developer carrier 3b is within a predetermined range. Set. [Selection] Figure 1 |