| 摘要 |
1,034,158. Electrophotographic developers. KALLE A.G. Feb. 5,1965 [Feb. 7,1964],No. 5133/65. Addition to 944, 393. Heading G2H. An electrophotographic developer consists of a finely divided positively charging inorganic or organic powder and a negatively self-charging toner comprising wholly or partially a copolymer of an unsaturated organic compound containing one or more carboxyl groups and a vinyl ester. The toner is dyed and may be a copolymer from 95 mole-% vinyl acetate and 5 mole-% crotonic acid. Suitable inorganic positively charging powdered salts are:- potassium sulphate, ammonium chloride, potassium bromide, sodium meta-borate etc.; metal oxides as of aluminium, iron, lead, titanium, zinc and copper; also kieselguler, silica gel, iron, glass &c. powders. Suitable organic positivelycharging powders may be starch, cellulose, lignin, and brass. Low melting point vinyl esters of fatty acids such as propionic acid, butyric acid or acetic acid are used and permit heat fixing of the developed electrostatic image. The compound with carboxyl groups may be crotonic or cinnamic acid as examples of unsaturated mono-carboxylic acids, or maleic, fumanic, or itaconic acid as examples of unsaturated dicarboxylic acids. The developed powder image may, before fixing be transferred to another material such as paper, aluminium, or plastics foil using a corona discharge. The fixed image may be used for off-set printing if the non-printing areas are rendered hydrophilic. Photo-conductive surfaces of zinc oxide on paper are sensitized by corona discharge to a polarity giving a positive or negative copy, and exposure to a light image is made by contact or projection. With a magnetic carrier, the developer is applied by bar magnet or magnetic roller. The developer may be applied simultaneously with a direct-current voltage to the photo-conductive surface. |
