| 摘要 |
PURPOSE:To obtain density to which even a black original part such as a character can be reproduced faithfully as to even half-tones of a photograph by putting developers which are in the same hue, but differ in color toner in two developing devices which develop a latent image in order. CONSTITUTION:When a latent image having a specific potential is developed with black toner 7 by applying a developing bias VB1 set properly by the 1st developing sleeve 3 of the 1st developing device 4, some black toner 7 sticks on a part corresponding to an original black part with a high latent image potential and a little black toner 7 sticks on a part of half-tones higher than the potential VB1. Then, development is carried out with a developing bias potential VB2 lowered sufficiently by the 2nd developing sleeve 5 of the 2nd developing device 6. At this time, the amount of black toner 7 sticking on the high-potential part by the device 4 is large, so even if a little gray toner 8 sticks, variation in image density is small. The amount of sticking black toner 7 decreases with density and the amount of sticking gray toner 8 increases, so that the density depends upon the gray toner 8. Consequently, the latent image is visualized according to the potential determined by the kinds of the color tones of various images. |
