Process for depositing magnetic toner material on electrostatic latent images

Claim 1

A process for depositing single component magnetic toner material on electrostatic latent images formed on an image bearing member and characterized by a dark voltage, comprising the steps of: Providing a magnet roll adjacent the image bearing member, the magnet roll including a cylindrical rotatable shell of non-magnetic material and a rotatable permanent magnet member positioned coaxially within the shell, the rotatable permanent magnet member having on its outer periphery a plurality of magnetic poles of alternating polarity; supplying magnetic toner material onto the surface of the shell of the magnet roll; rotationally advancing the image bearing member in relation to the magnet roll; rotating both the shell and the permanent magnet in the same direction to form an A.C. magnetic field for advancing the magnetic toner material to a contacting area with the image bearing member, the A.C. magnetic field having a frequency of greater than one per millimeter of the advancing of the image bearing member in relation to the magnet roll; subjecting the magnetic toner material in the contacting area to the A.C. magnetic field; and subjecting the magnetic toner material in the contacting area to an A.C. electrical field to render the toner substantially conductive, said A.C. electrical field having a peak voltage which is greater than the dark voltage of the latent images but less than 3,200 volts and having a frequency which is greater than v/0.3 where v is the advancing speed in millimeter/second of the image bearing member in relation to the magnet roll.