| 摘要 |
PURPOSE:To sufficiently fix a toner image even in parts low in image density by setting a developing bias voltage at the time of forming a printing master to a value lower than that in a test printing step. CONSTITUTION:Test printing and formation of a printing master are carried out in a developing bias voltage of 200V, and prints are formed from the obtained printing master. The relation between the copy density of the test printing and the print and the original density are as shown in the graph, and the copy density of the print in the low density region is excessively lowered to deteriorate gradation. This is due to the poor fixing in the low density region of the master image and peeling of the toner image. Then, the developing bias voltage is lowered from 200V at the test printing to 120V to from a master image, and it is found that the relation of the master image and the original image is improved as shown in the right hand graph, and a print sufficient in density is obtained. It is due to the fact that fixing in the low density region is executed sufficiently by lowering the bias voltage. |
