| 摘要 |
PURPOSE:To take out an image of an electrostatic latent image of low potential in high contrast by forming an insulating layer on the surface of a sleeve for supply of magnetic toners so that the charges of the toners may be differenct in polartity from those of the electrostatic latent image and so that the quantity of the charges of the toners may be increased. CONSTITUTION:The insulating layer 5 formed on the surface of a sleeve 4 is cleared of toners by means of a scraping plate 9 and then is charged with the opposite polarity to that of an electrostatice latent image which is formed on a drum 1. Then, the magnetic toners 3 thus trapped are conveyed in the rotating direction of the sleeve 4. As a result, the charges on the insulating layer 5 are shifted to the magnetic toners and turned into the positive polarity when they reach the developing unit b having a magnet 73. Since, on the other hand, a negative electrostatic latent image is formed on the drum 1, the magnetic toners are trapped by the latent image. As a result, the quantity of the charges of the toners is independent of the charges of the latent image so that the development can be accomplished even if there is a latent image of low charge exiss on a photosensitive element. Since, moreover, the toners themselves are charged at a high potential, it is possible to produce an image of high contrast. |
