Junzo Nakajima

Conductive fur brush charging of a dielectric surface

A dielectric surface is charged without a corona discharge using a conductive fur brush to which an electrical potential of several hundred volts is applied. The fur brush, which consists of 10- mu m-thick conductive fiber, lightly touches the surface of the (Mylar film or photoreceptor) dielectric. It is clear that brush charging is accomplished by direct charge transfer, gas discharge, and triboelectric charging. The direct charge transfer, which is the primary charging process, is analyzed using an ohmic contact model. The charge potential is nearly proportional to that of the brush. When the charging time is longer than 0.3 s, the charged potential on the surface photoreceptor saturates at almost that of the brush, the difference being less than 50 V. This is about the same as in corona charging. Brush charging is, therefore, useful as a low-voltage charging technique. >

An Analysis of Air Breakdown in Electrostatic Recording

Air breakdown between a very small stylus and a dielectric layer, as is often used in electrostatic recording, has been studied both theoretically and experimentally. In the experiments, styli of 60-pm diameter were placed aginst the dielectric layer of various thicknesses with an air gap of 1-60 pm. Breakdown time lag and breakdown voltage was thereby clarified as follows. 1) The logarithm of the mean statistical time lag is proportional to the logarithm of the repetition rate of breakdown and is inversely proportional to field strength in the air gap. 2) Breakdown voltage in electrostatic recording as a function of the air gap agrees well with the modified Paschen curve obtained in previous experiments using large plane parallel electrodes. These results clarify the limitation of the recording speed, the minimum recording voltage, and optimum air-gap length in electrostatic recording.