Photoconductive photography

Claim 1

AN ELECTROSTATIC PRINTING PROCESS COMPRISING THE STEPS OF PRODUCTING A CONDUCTIVITY PATTERN IN A PHOTOCONDUCTING INSULATING LAYER CONSISTING OF A FINELY-DIVIDED PHOTOCONDUCTOR DISPERSED IN AN ELECTRICALLY-INSULATING VEHICLE BY EXPOSING SAID LAYER TO A LIGHT IMAGE BEFORE ANY ELECTRICAL FIELD IS ESTABLISHED THROUGH SAID LAYER, THEN MAGNETICALLY TRANSPORTING ACROSS SAID CONDUCTIVITY PATTERN A DRY PHYSICAL MIXTURE OF LOOSE, MOVABLE PARTICLES OF ELECTROSTATICALLY-ATTRACTABLE POWDER AND SEPARATE ELECTRICALLY CONDUCTIVE MAGNETICALLY-ATTRACTABLE CARRIER PARTICLES BY SUBJECTING SAID MAGNETICALLY ATTRACTABLE PARTICLES TO A MAGNETIC FIELD BROUGHT ACROSS SAID CONDUCTIVITY PATTERN, SAID CARRIER PARTICLES AND POWDER PARTICLES HAVING A TRIBOELECTRIC RELATIONSHIP OF OPPOSITE POLARITY, THE POWDER PARTICLES THEREBY BEING ELECTROSTATICALLY-CHARGED THROUGH TRIBOELECTRIC ACTION BY CONTACT WITH THE CARRIER PARTICLES TO ADHERE ELECTROSTATICALLY TO THE SURFACE OF THE CARRIER PARTICLES, AND DURING SAID TRANSPORTING STEP APPLYING A BIASING VOLTAGE TO SAID ELECTRICALLY CONDUCTING PARTICLES WITH RESPECT TO THE OPPOSITE SURFACE OF SAID LAYER TO ESTABLISH THROUGH SAID LAYER A UNIDIRECTIONAL ELECTRIC FIELD AND TO CAUSE POWDER PARTICLES TO BECOME ATTRACTED TO SAID INSULATING LAYER AND TO ADHERE THEREON IN SUBSTANTIAL CONFIGURATION WITH SAID CONDUCTIVITY PATTERN.