Finnegan, Henderson, Farabow and Garrett
Developer for latent electrostatic image and process for preparation thereof
 The present invention is for the improvements of a developer for a one-component latent electrostatic image and the process for the preparation thereof. The present invention is the one which has improved points at issue in the case of using a developer for the conventional conductive one-component latent electrostatic image for a copying machine using a corona discharger and in which particles are prepared by uniformly mixing a magnetic substance in resin and the magnetic substance is substantially exposed on the particle surface by heat treatment and hydrophobic silica fine powders are supported on, or interposed in, said particles; the particles are, as a whole, electrically insulating and given electric charge necessary to form an image by friction of mutual particles; thus even in a copying machine using a corona discharger, good development can be obtained with this developer; and further the present invention is the one which provides a process for the preparation of said particles. 
Konishiroku Photo Industry Co. Ltd.
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Fumio Katsutoshi Shotaro Shigeru
Koizumi Tozawa Watanabe Uetake