| 摘要 |
1495554 Coated magnetic particles SUBLISTATIC HOLDING SA 28 Nov 1974 [30 Nov 1973] 51641/74 Heading C1A [Also in Divisions B2 and G2] An electrophotographic developer comprises magnetic cores each covered with an organic substance which contains a dyestuff which vaporizes at a temperature between 100‹ and 220‹ C. at atmospheric pressure. The cores may be particles of iron or magnetic alloys, or oxides of cobalt, nickel or iron, with an average particle size of 0À5 to 10 microns. In the examples: core materials used are iron powder, magnetite and a mixture thereof; core coating materials used are polyvinyl acetate, polyamides and ethyl cellulose; and a number of known dyes, including mixtures of dyes, are used. Surfactants, and especially anti-static agents, may be mixed with the developer. The developer may be prepared by spray drying a dispersion of the magnetic cores and the dyestuff in a solution of the coating material, or by coating the cores and subsequently dyeing the coating. |
