JPS5491329A - Reversal development - Google Patents

Abstract

PURPOSE:To form an excellent picture image having no texture blotted by applying a potential of the same polarity and at least equal to the potential, which is impressed upon a sleeve, to a doctor, which is operative to regulate the thickness of an insulating toner layer immediately before the development of the sleeve, thereby to uniformly charge the toner layer. CONSTITUTION:There is arranged rotatably above a grounded conductive and nonmagnetic developing container 31 a conductive sleeve 36 which is located in the vicinity of the surface of a photosensitive drum 35. The sleeve 36 is connected with a DC bias power source V1 through a resistor R4. There is arranged above the other wall of the developing container through an insulating member 38 a conductive doctor 29 which has its one leading end located in the vicinity of the surface of the sleeve 36. The doctor 39 is connected with a DC bias power source V2 through a resistor R2. The bias power source V1 has the same polarity as that of the electrostatic latent image on the photosensitive element so that the potential close to that at that portion of the latent image, which has the highest charge density, is impressed upon the sleeve 36. On the other hand, the bias power source V2 supplies the dector 39 with the potential of the same polarity and at least equal to the potential applied to the sleeve.