| 摘要 |
1,042,498. Electrophotographic processes. CHARLES BRUNING CO. Inc. July 23, 1963 [Sept. 6, 1962], No. 29198/63. Heading G2H. A reversal developer powder for use in developing latent electrostatic images by applying the powder by means of a magnetic brush, comprises magnetic carrier particles and toner particles of a smaller particle size than the particle size of the magnetic particles, the toner particles consisting of a mixture of pigmented resin particles and particles of one or more metal salts of an aliphatic carboxylic acid having from 12 to 18 carbon atoms per molecule, the metal of the metal salt being one of the metals calcium, barium, lead, magnesium, or zinc. The aliphatic acid may be stearic, palmitic or oleic acids. The magnetic particles maybe iron, ferrites, nickel or cobalt. The magnetic particles and resin particles are chosen to have a triboelectric relation such as to produce a negative charge on the resin particles. Suitable resins are polystyrene, acrylic resins, rosin, asphalt, gilsonite, polyvinyl resins. In one example (Example 1) the following parts by weight of toner constituents are mixed to form a homogeneous mixture:- 5. 7 parts polystyrene, melting point 100‹C. Œ 3‹C., 3. 8 parts polystyrene, melting point 125‹C.Œ 3‹C., 0. 3 parts carbon black, 0.2 parts green pigment. The mixture was cooled and then ground to a particle size from 10 to 20 microns. The pigmented resin then added to the 0.2 parts calcium stearate and 500 parts of powdered iron and the mixture agitated. In other examples, the calcium stearate is replaced by barium stearate, lead stearate, magnesium stearate or zinc palmitate.
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