| 摘要 |
PURPOSE:To improve offset resistance and fixability by using a thermoplastic resin specified in mol.wt. melt viscosity, glass transition point, softening point, and the content of a magnetic powder contained therein, and specifying electrostatic blowoff charge amt. and charged potential on a nonmagnetic sleeve. CONSTITUTION:The thermoplastic resin used here has a weight average mol.wt. of 10,000-15,000, a melt viscosity of 5,000-50,000cP at 160 deg.C, a glass transition point of 60-65 deg.C, and a softening point of 100-110 deg.C. As fine ferromagnetic particles, a material strongly magnetizable in the direction of a magnetic field is used, preferably, in an amt. of 65-75wt% of the total weight of toner. The magnetic toner needs to have sufficient charge, preferably, as much as -2- -10muC/g measured by the blowoff method. Fog-free good development can be executed by feeding 3g of the magnetic toner 7 onto a sleeve 2, fixing the sleeve 2, and rotating only permanent magnets 3 in the direction of arrow B as shown in the figure, at a speed of 1,000r.p.m. for 1min, measuring the toner electrode at that time, and selecting and using the magnetic toner having this potential within -5--20V. |
