| 摘要 |
PURPOSE:To prevent black toner from being mixed with an alpha toner image by using a developer consisting of black toner containing a magnetic material, alpha color toner and two kinds of carriers which give those toner particles the positive and negative polarities, and developing images at the same time. CONSTITUTION:The photosensitive body 10 which has photoconductive layers 10B and 10A provided on a base 10C is charged electrostatically to the positive polarity by being irradiated with red light, and then charged in the dark to charge the layers 10A and 10B in the opposite direction. The photosensitive body 10 is irradiated with a light image of an original O which has a black image N and, for example, a red image R on a white ground part W to make a part corresponding to the image R plus and hold the white ground W at zero V. The image is developed at the same time by using the developer obtained by mixing the black toner TN, a carrier which charges TN to a specific polarity, alpha color (red) toner TR and a carrier which charge TR and TN to the opposite polarities. The image is transferred to transfer paper lastly. In this case, TN contains at least the magnetic material. This method prevents colors from being mixed at a part corresponding to the image R, so that a chromatic color image becomes sharp.
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