| 摘要 |
PURPOSE:To make an image sharper without developing carrier attachment by applying a developing bias of a relatively low potential after a scorotron charger causes the surface potential of a non-image part to drop, and performing reversal-developing. CONSTITUTION:After a negative latent image is formed on the surface of a photosensitive drum 1, charges of the opposite polarity to that of an electrifying charger 2 are given by the scorotron charger 4. As it does so, the potential of the non-image part is caused to drop by applying a voltage to a grid 43, the voltage having the same polarity as that of the charger 2 and having a potential lower than the surface potential of the non-image part. Then, the latent image is reversal-developed with toner of the same polarity as that of the charger 22. As it does so, a developing bias voltage is applied after being set to the same polarity as that of the grid voltage and to a potential equivalent to light quantity equal to or greater than about two-seventh exposure quantity obtained by a print head 3 with respect to the optical attenuation characteristic of the drum 1. Thus, toner sticks to an image part of the potential lower than that of the developing bias voltage, and a positive toner image can be obtained. |
