| 摘要 |
PURPOSE:To obtain a superior electrostatic image even in a high-temperature, high-humidity atmosphere by setting a static specific resistance value larger than a specific value so that the impressed voltage dependency of a developer meets specific requirements when an electrostatic image is developed by using a single- component insulating magnetic developer. CONSTITUTION:A saw-tooth wave generating circuit 16 and a high-voltage amplifying circuit 17 flows a +500 and a -500V current through the magnetic toner layer between a cylindrical electrode 11 made of Al and a sleeve 12 made of stainless steel, and the currents are measured by an ammeter A and recorded on a recorder 19. In this case, such a single-component magnetic developer that the impressed voltage dependency of a dynamic current IV satisfied an expression I or II is used to develop the electrostatic image. Said developer has perferably a high static specific resistance value of <=10<16>OMEGAcm, thermoplastic resin suitable for heat fixation is used as a binder, and a magnetic material of 20-70 wt% based upon the developer is incorporated to obtain particles having 20- 40% compressibility. Thus, the high-density developer which attains development at a relatively low potential and makes fogging hard to occur is botained. |
