Processes of producing lithographic electrostatic printing plates

Claim 1

A METHOD OF PRODUCING LITHOGRAPHIC PRINTING PLATES, WHICH COMPRISES, CHARGING A SUPPORT HAVING A PHOTO-CONDUCTIVE SURFACE CONSISTING ESSENTIALLY OF PHOTO-CONDUCTIVE ZINC OXIDE IMBEDDED IN AN ELECTRICALLY-INSULATING RESINOUS FILM-FORMING LAYER COVERING THE FACE OF SAID SUPPORT TO PRODUCE AN ELECTROSTAIC CHARGE THEREON, EXPOSING THE CHARGED SUPPORT TO A LIGHT IMAGE OF MATERIAL TO BE COPIED TO PRODUCE A LATENT ELECTROSTATIC IMAGE OF SAID MATERIAL, APPLYING HYDROPHOBIC RESINOUS DEVELOPER POWDER TO THE LATENT ELECTROSTATIC IMAGE THUS PRODUCED SO THAT SAID HYDROPHOBIC RESINOUS POWDER ADHERES ELECTROSATICALLY TO THE CHARGED IMAGE AND NOT TO THE BACKGROUND AREAS OF SAID PHOTO-CONDUCTIVE SURFACE, FIXING THE HYDROPHOBIC RESINOUS POWDER TO PRODUCE AN ELECTROSTATIC COPY IN WHICH THE HYDROPHOBIC RESINOUS LAYER THUS FORMED DEFINES THE IMAGE AREAS AND THE SAID ELECTRICALLY-INSULATING RESINOUS LAYER HAVING THE ZINC OXIDE IMBEDDED THEREIN CONSTITUTES THE BACKGROUND AREAS, AND SWABBING THE THUS PRODUCED ELECTROSTATIC COPY WITH AN AQUEOUS SOLUTION OF A SALT FROM THE GROUP CONSISTNG OF THE HALIDES AND SULFATES TO ALUMINUM AND FERRIC IRON TO REACT THE ZINC OXIDE IN THE SAID BACKGROUND AREAS WITH THE SAID SALT AND THUS PRODUCE A SOLID HYDROPHILIC FILM CONSTITUTED SUBSTANTIALLY ENTIRELY OF THE REACTION PRODUCT OF SAID SALT AND THE ZINE OXIDE IN THE BACKGROUND AREAS, WHICH FILM COVERS THE BACKGROUND AREAS, RESISTS THE PENETRATION OF LITHOGRAPHIC FOUNTAIN SOLUTIONS AND REPELS LITHOGRAPHIC INKS.

Claim 2

A METHOD OF PRODUCING LITHOGRAPHIC PRINTING PLATES, WHICH COMPRISES, CHARGING A SUPPORT HAVING A PHOTO-CONDUCTIVE SURFACE CONSISTING ESSENTIALLY OF PHOTO-CONDUCTIVE ZINC OXIDE IMBEDDED IN AN ELECTRICALLY-INSULATING RESINOUS FILM-FORMING LAYER COVERING THE FACE OF SAID SUPPORT TO PRODUCE AN ELECTROSTAIC CHARGE THEREON, EXPOSING THE CHARGED SUPPORT TO A LIGHT IMAGE OF MATERIAL TO BE COPIED TO PRODUCE A LATENT ELECTROSTATIC IMAGE OF SAID MATERIAL, APPLYING HYDROPHOBIC RESINOUS DEVELOPER POWDER TO THE LATENT ELECTROSTATIC IMAGE THUS PRODUCED SO THAT SAID HYDROPHOBIC RESINOUS POWDER ADHERES ELECTROSATICALLY TO THE CHARGED IMAGE AND NOT TO THE BACKGROUND AREAS OF SAID PHOTO-CONDUCTIVE SURFACE, FIXING THE HYDROPHOBIC RESINOUS POWDER TO PRODUCE AN ELECTROSTATIC COPY IN WHICH THE HYDROPHOBIC RESINOUS LAYER THUS FORMED DEFINES THE IMAGE AREAS AND THE SAID ELECTRICALLY-INSULATING RESINOUS LAYER HAVING THE ZINC OXIDE IMBEDDED THEREIN CONSTITUTES THE BACKGROUND AREAS, AND SWABBING THE THUS PRODUCED ELECTROSTATIC COPY WITH AN AQUEOUS SOLUTION OF A SALT FROM THE GROUP CONSISTNG OF THE HALIDES AND SULFATES TO ALUMINUM AND FERRIC IRON TO REACT THE ZINC OXIDE IN THE SAID BACKGROUND AREAS WITH THE SAID SALT AND THUS PRODUCE A SOLID HYDROPHILIC FILM CONSTITUTED SUBSTANTIALLY ENTIRELY OF THE REACTION PRODUCT OF SAID SALT AND THE ZINE OXIDE IN THE BACKGROUND AREAS, WHICH FILM COVERS THE BACKGROUND AREAS, RESISTS THE PENETRATION OF LITHOGRAPHIC FOUNTAIN SOLUTIONS AND REPELS LITHOGRAPHIC INKS.