| 摘要 |
PROBLEM TO BE SOLVED: To stably obtain a uniform and high-density image over a long term without making the device larger by setting the circumferential speed of a developer carrier to a specified value or more, making a 1st stirring and carrying means satisfy a specified condition and using specified toner. SOLUTION: A 1st toner housing chamber 12 is provided with the 1st stirring and carrying means 18 and a 2nd toner housing chamber 13 is provided with a 2nd stirring and carrying means 19 arranged to be opposed to the means 18 and carrying the toner to the chamber 12 while stirring the toner. Then, the circumferential speed (a) of the developer carrier 15 is >=250 mm/sec, the means 18 satisfies the condition shown by an expression; 0.007<=b/a<=0.030, and the toner whose weight average diameter is 4 to 9 μm, whose fluidity index is <=20 and whose condensation is 20 to 60% is used. In the expression, (a) means the circumferential speed of the developer carrier and (b) means the circumferential speed (mm/sec) of the 1st stirring means. |
