| 摘要 |
PURPOSE:To prevent the decrease of an image density by repeated uses by incorporating a magnetic material treated with a compd. having >=2 isocyanate groups into a title toner. CONSTITUTION:The magnetic material treated with the compd. having >=2 isocyanate groups (-NCO) is used and the acid value of a binder resin is made 10-100. The compd. having >=2 isocyanate groups makes the magnetic material hydrophobic by reacting with the OH group on the surface of the magnetic material, thereby improving the dispersibility of the magnetic material in the binder resin. The magnetic material adheres securely with the binder resin by reacting with the COOH group or OH group in the binder resin. The compd. having >=2 isocyanate groups is dissolved in 10-100 times volume of an org. solvent and after the soln. is stirred thoroughly for 1-2hr with the magnetic material, the soln. is filtered and is dried for 24-48hr in a thermostatic chamber kept at 40-80 deg.C. The compd. having >=2 isocyanate groups includes tolylenediisocyanate, etc. The toner which obviates the decrease of the image density even in repeated development is thus obtd. |
