| 摘要 |
PURPOSE:To stabilize a triboelectrostatic charge quantity and to sharpen and uniformize the distribution of the electrostatic charge quantity by adequately selecting the content of FeO in magnetic iron oxide and the acid value of a binder resin. CONSTITUTION:The magnetic iron oxide is formed by neutralizing FeSO4 with NaOH to obtain Fe(OH)2, adjusting the its pH to 12 to 13 by alkaline adjustment, then oxidizing the same by steam and air to obtain the slurry of magnetite. The content of the FeO in the magnetic iron oxide is confined to 25 to 30wt.% by controlling the drying temp. and drying time. The specific acid value is imparted to the binder resin used for the toner. First, the acid anhydride group is hydrolyzed and the measured total acid value (A) is specified to 2 to 100mgKOH/g or the total acid value (B) derived from the acid anhydride group to <6mgKOH/g. The electrostatic charge quantity of the magnetic toner is judged by A and B and B/AX100 is selected at <=60%. The excess rise of the temp. of the electrostatic charge quantity of the toner is prevented under a low humidity by this constitution and the magnetic toner which maintains the adequate electrostatic charge quantity over a long period of time is obtd. |
