| 摘要 |
PROBLEM TO BE SOLVED: To suppress image density fall and fogging aggravation due to sensitivity fall at low temperature and low humidity when a photoreceptor having a small diameter and a highly durable surface layer is used in a quick image formation process. SOLUTION: An electrophotographic receptor having carrier mobility of≤3.0×10<SP>-6</SP>cm<SP>2</SP>/V×s at 2.3×10<SP>5</SP>V/cm electric field strength, and toner containing at least a binding resin, a colorant and a charge controlling agent, are used. The charge controlling agent contains at least a resin containing a vinyl monomer unit having sulfonic acid or sulfonate. Further the charge controlling agent has (i) a first acid number A and a second acid number B measured by a potentiometric titration method, (ii) the second acid number B is 2 to 10 mgKOH/g and (iii) the first acid number A and the second acid number B satisfy a relation: 1.20≤A/B≤2.00. COPYRIGHT: (C)2006,JPO&NCIPI |
