Composite photosensitive material for use in electrophotography

Claim 1

A dichromatic electrophotography process, which comprises: providing a composite photosensitive material comprising an electrically conductive substrate layer made of a metal selected from the group consisting of Au, Pt and Pd, a first photoconductive layer made of As 2 Se 3 laminated on said electrically conductive substrate layer, said first photoconductive layer being capable of absorbing and being rendered photoconductive by visible radiation having a first wavelength range, said first photoconductive layer possessing the properties that it can be charged only in one polarity in relation to said substrate and permits light decay, a second photoconductive layer laminated on said first photoconductive layer, said second photoconductive layer being capable of transmitting visible radiation of said first wavelength range and being capable of absorbing and being rendered photoconductive by visible radiation of a second wavelength range which is different from said first wavelength range, the sensitivity ratio of said second photoconductive layer to said first photoconductive layer being in the range of from 1 to 20 when said second photoconductive layer is irradiated with white light so that the sensitivity of said second photoconductive layer is its sensitivity to white light and the sensitivity of said first photoconductive layer is its sensitivity to white light minus the second wavelength range, said first and second photoconductive layers being capable of holding electric charges of opposite polarities with respect to each other and each being capable of accepting and also retaining surface potentials sufficient to develop an electrostatic latent image with toner; applying a first electrostatic charge of a polarity opposite to said one polarity to the second layer in the dark to form a charge of the opposite polarity on said second layer and to cause a second charge of said one polarity to be injected from said electrically conductive substrate layer into said first layer; then applying a second electrostatic charge of said one polarity to the second layer wherein the second electrostatic charge is of lower magnitude than said first electrostatic charge; and then radiating a light image onto said second layer capable of rendering photoconductive a partial region of a single one of said first photoconductive layer and said second photoconductive layer while leaving another partial region of said single photoconductive layer nonconductive whereby to form an electrostatic latent image in which the nonconductive region has a different polarity than the conductive region of said single photoconductive layer; and then developing said electrostatic latent image with two differently colored toners of opposite polarities.