Magnetic brush developing method for use in electrography employing dual-component developing material

Claim 1

A magnetic brush developing method for use in electrography which comprises the steps of providing a dual-component developing material which includes electrically insulative magnetizable particles as carrier mainly composed of magnetizable powder and bonding material, and electrically insulative non-magnetizable particles as toner mainly composed of coloring material, dye and thermoplastic resin for bonding material; attracting said developing material onto a developing sleeve made of non-magnetizable material, by the action of a magnet member provided in said developing sleeve, to form a magnetic brush of said developing material on said developing sleeve; and bringing said magnetic brush into contact with an electrostatic latent image formed on a recording medium under the impression of a toner fogging prevention bias voltage so as to develop said electrostatic latent image into a visible image; said magnetic brush developing method further including the step of causing silica to adhere onto the surfaces of said electrically insulative non-magnetizable particles to reduce the triboelectric charge on said magnetizable particles to make the magnetic attractive force exerted by said magnet member on said electrically insulative magnetizable particles contacting said recording medium larger than the electric repelling force acting on said magnetizable particles in the direction toward said recording medium, thereby to prevent adhesion of said electrically insulative magnetizable particles to said recording medium.