Magnetic brush development process

A process for developing an electrostatic latent image on the surface of a photosensitive material drum, which comprises forming a magnetic brush of a two-component magnetic developer comprising a toner and a carrier on a developing sleeve having magnets disposed in the interior thereof, and bringing the magnetic brush of the developer into sliding contact with the surface of the photosensitive material drum in a development zone in an amount such that the developer occupancy ratio R in the developing zone, represented by the following formula, satisfies the requirement of 30<R<75:

• R=M.times.(T/D.times.1/.sigma.t+C/D.times.1/.sigma.c)/H
• wherein M represents the amount (g/cm.sup.2) of the developer delivered per unit area of the developing sleeve, H represents the distance (cm) between the photosensitive material drum and the developing sleeve at the position (S) where both approach each other most closely, T/D represents the toner concentration (% by weight) in the developer, C/D represents the carrier concentration (% by weight) in the developer, .sigma.t represents the true density (g/cm.sup.3) of the toner, and .sigma.c represents the true density (g/cm.sup.3) of the carrier, to develop the surface of the photosensitive material drum, wherein the development is carried out under such conditions that
• (1) at the position where the sliding contact of the magnetic brush with the surface of the photosensitive material drum terminates, the following requirement is satisfied:
• Px.gtoreq.430, or
• Px<430 and P.sub.y .gtoreq.-Px+800,
• wherein P.sub.x represents the magnetic force (Gauss) acting in the tangential direction on the surface of the developing sleeve, and Py represents the magnetic force (Gauss) acting in the normal line direction on the surface of the developing sleeve;
• and
• (2) the magnetic force in the normal line direction on the surface of the developing sleeve in the developing zone becomes maximum at the position located on the upstream side by 0.035 to 0.5 radian in the direction of the flow of the developer from the position(s) where the developing sleeve comes closest to the photosensitive material drum.