JPS5498248A - Development apparatus for static latent image - Google Patents

Abstract

PURPOSE:To prevent occurrence of overcurrent and to eliminate consumption of bias effect due to characteristics change of toner, by forming a thin dielectric layer on a sleeve surface in forming static latent images by using magnetic toner and applying a bias voltage to a sleeve. CONSTITUTION:Conductive sleeve is rotatably provided in the upper interior of developing vessel 31 near the surface of photosensitive drum 35. In the inside of sleeve 36 a plurality of bar magnets 38 having are provided having magnetic poles in the end faces and circular sections. Dielectric layer 37 of resistivity 10<3> oh.cm or more and thickness below 200 um is coated on the surface of sleeve 36. The surface voltage of layer 37 is equalized to that of the part highest in charge density of the static latent image, that is, the nonimage part by bias voltage source V connected to sleeve 36. Large current does not flow directly through toner on layer 37 by layer 37, permitting change of bias characteristics due to overcurrent, toner fusion adhesion, breakdown of a bias circuit, or the like to be prevented and stabilized good images to be obtained.