| 摘要 |
914,703. Electrophotographic developer powders. RADIO CORPORATION OF AMERICA. March 24, 1959 [March 28, 1958], No. 10220/59. Class 98 (2). An electrophotographic developer powder suitable for producing reversed prints comprises particles of electroscopic material coated with 1.5 to 9 parts by weight per 100 parts of said particles of colloidal silica, the electroscopic material being tribo-electrically positive with respect to the colloidal silica. The electroscopic material may be a thermoplastic film-forming material having a melting-point of 90‹ C. to 250‹ C., or it may comprise zinc oxide coated with such a thermoplastic material, especially a coated photoconductive zinc oxide according to Specification 914,702. Suitable thermoplastic materials are Piccolastic, Carnauba Wax, Polymekon Wax, specified petroleum waxes, Piccolyte (a hydrocarbon terpene resin) or a mixture of Acrawax C (a synthetic wax) with calcium stearate or a solid silicone resin. Dyes and pigments are specified for adding to the developer powders.
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