| 摘要 |
PURPOSE:To obtain a sharp color image by incorporating in a toner, fine silica- treated gamma-iron oxide particles obtained by treating fine alpha-iron oxide particles with a silicon compd., and executing oxidation and reduction heat treatments of them. CONSTITUTION:The fine alpha-iron oxide particles are treated with a silicon compd., for example, they are dispersed into an aq. soln. of sodium silicate and silicon hydroxide is precipitated on the surfaces of them by adding dilute sulfuric acid, and they are subjected to reduction heat treatment at about 400-500 deg.C to give magnetite, and further subjected to oxidation heat treatment at about 200-300 deg.C to convert them into the fine gamma-iron oxide particles. These are mixed with the binder resin of the toner without agglomeration of these iron oxide particles, and uniformly dispersed, thus permitting the silicon compd. treated gamma-iron oxide fine particles to be uniformly dispersed into the toner binder resin, and a sharp color image to be obtained. |
