Process for transferring a magnetizable developing powder in

Abstract

An improved process for transferring a magnetizable developing powder from an insulating substitute, such as an electrostatic duplication master or photoconductive element to a receiving material, such as paper, in electrostatic image development enables the transfer of powder having a specific resistance greater than 10.sup.13 Ohm.cm. without the need for specially treated paper. The powder is applied imagewise, corresponding to a charge image, on an insulating substrate, the substrate with the powder image brought in contact with the receiving material to which the powder is to be transferred, two separate charges are applied to the free side of the receiving material during the period of contact with the substrate, the first of such charges, a pre-transfer charge, having a polarity opposite to that of the charge image and the second of such charges, a transfer charge, being greater than the first and having the same polarity as that of the charge image, and the powder transferred. Advantageously, the first charge is between 0.08 to 0.17 .mu.C per cm.sup.2., the second charge is at least 0.5 .mu.C per cm.sup.2. and the charges are applied within 0.5 second after each other. Transfer yields of 85 percent may be obtained and the receiving material may be ordinary paper with a surface resistance between 5.times.10.sup.9 to 10.sup.11 Ohm per square.