Electrophotographic method of generating electrostatic images on two sides of an insulating foil

Claim 1

An electrophotographic process comprising the steps of: providing a highly electrically insulating foil, said foil having first and second opposite sides; generating identical electrostatic charge images of a radiation image on the first and second opposite sides of the foil, respectively, the charge image on the first side having an opposite sign as compared to the charge image on the second side; and depositing pigment on each side of the foil, said pigment comprising a developer having a charge whose sign is opposite to that of the electrostatic charge image on the side of the foil on which the pigment is being deposited; CHARACTERIZED IN THAT: the electrostatic charge image is generated on the first side of the foil by generating charge pairs, all charges of one sign from each pair being collected on the first side of the foil, said charge pairs being generated by a reaction between radiation-sensitive material and incident radiation; the electrostatic charge image is generated on the second side of the foil by a charge exchange between the second side of the foil and an electrode adjacent thereto, said charge exchange effectively collecting all of the remaining generated charges, of opposite sign from the charges on the first side, on the second side of the foil; and further comprising the step of separating the electrode from the foil prior to depositing the pigment.