Magnetic brush developing process for electrostatic images

Claim 1

In a magnetic toner brush developing process for electrostatic images of the type in which a developer containing a magnetic powder is attracted onto a sheeve of a non-magnetic material by means of a magnet disposed within the sleeve to thereby form a magnetic brush, which brush is brought into contact with an electrostatic latent image formed on a record member to provide a developing thereof, the improvement comprising the steps of: providing as a developer a powder mixture of a low resistance toner having a volume resistance of not more than 10 5 Ω cm and a high resistance toner having a volume resistance of not less than 10 13 Ω cm, at least one of which comprises a magnetic toner for forming the magnetic brush; triboelectrically charging both toners; selecting the toner materials in accordance with their orders in the triboelectricity series, the high resistance toner being of a higher order and inducing an electrostatic charge on the low resistance toner, so that the force of electrostatic attraction acting between the toners and the force of electrostatic attraction acting between both toners and the latent image are greater than the force of magnetic attraction exerted by the magnet on the magnetic toner; and causing a deposition of both toners onto the latent image to provide a developing thereof.