| 摘要 |
PROBLEM TO BE SOLVED: To obtain a satisfactory image free of an image-density decrease and a density irregularity in a black solid part irrespectively of image formation modes. SOLUTION: The value of a development bias by a development-bias application means 11 is switched by a control means 19 according to the image formation mode, and the value of a transfer bias by a transfer-bias application means 12 is also switched simultaneously according to the switch of the value of the development bias. Thus, because the value of the transfer bias is also correctingly changed to a proper value according to an amount of toner electrification which is so changed by the switch of the development bias so as to match the image formation mode, a good-quality image can be obtained every time irrespective of the image formation mode. For example, in the case of the photograph image formation mode, the development bias in which an AC bias overlaps a DC bias is applied and also the transfer bias is switched to a big bias value. |
