Image formation apparatus, developing device incorporated therein and

Abstract

An electrostatic latent image formed on a photosensitive drum is electrostatically developed with a non-magnetic type developer, and is electrostatically transferred from the drum to a paper. The developer is composed of a toner component and a resin powder component, one component of which has a polarity opposite to that of an electric charge of the other component generated by triboelectrification therebetween. In the developing process, a conductive foam rubber developing roller is used, which includes a conductive tubular foam rubber roller element, and a metal shaft inserted into a central bore thereof. The roller element has an outer thicker portion including a conductive filler dispersed therein, and an inner solid skin layer defining the central bore thereof and exhibiting an electrical resistivity considerably higher than that of the thicker portion for lack of conductive filler. Nevertheless, a sufficient electrical contact is established between the roller element and the shaft. A thin metal blade is pressed against the roller for regulating the thickness of the developer entrained thereby, and is arranged to compensate for a resilient deformation of the shaft caused when pressing the blade against the roller.