Process of producing a master plate for offset printing and the master plate so produced

Claim 1

A PROCESS OF MAKING A MASTER PLATE FOR AN OFFSET PRINTING PRESS FROM AN ORIGINAL COMPRISING A POSITIVE IMAGE ON A TRANSLUCENT OR TRANSPARENT SUPPORT WHICH COMPRISES PLACING THE ORIGINAL IN CONTACT WITH THE SENSITIZED SURFACE OF A FIRST BASE, WHICH SURFACE CONSISTS ESSENTIALLY OF A DIAZO-CONTAINING POLYMER WHICH IS SUFFICIENTLY WATER SOLUBLE TO BE CAPABLE OF BEING TRANSFERRED TO A MOIST RECEIVING SURFACE AND WHICH IS CAPABLE OF BEING RENDERED SUBSTANTIALLY COMPLETELY WATER INSOLUBLE AND OF TANNING HYDROPHILIC COLLOIDS UPON EXPOSURE TO ACTINIC LIGHT, EXPOSING THE ASSEMBLY TO ACTINIC LIGHT, WHEREBY THE PORTIONS OF THE POLYMER EXPOSED TO THE LIGHT ARE RENDERED INSOLUBLE, REMOVING THE ORIGINAL, WETTING THE SURFACE OF A HYDROPHILIC COLLOID PREVIOUSLY COATED ON A SECOND BASE WITH A LIQUID COMPRISING WATER, SAID HYDROPHILIC COLLOID BEING CAPABLE OF BEING TANNED BY THE DECOMPOSITION PRODUCTS OF SAID POLYMER AND SELECTED FROM THE GROUP CONSISTING OF GELATIN, GLUE, WATER SOLUBLE CELLULOSE ETHER AND MOIST AMMONIA TREATED VINYL ALKYL ETHER MALEIC ANHYDRIDE COPOLYMERS, CONTACTING THE EXPOSED SENSITIZED SURFACE OF THE FIRST BASE WITH THE WETTED SURFACE OF THE HYDROPHILIC COLLOID ON THE SECOND BASE, SEPARATING THE TWO COATED BASES WHEREBY THE REMAINING SOLUBLE PORTIONS OF THE POLYMER ON THE FIRST BASE ARE TRANSFERRED TO THE SECOND BASE AND DECOMPOSING THE TRANSFERRED PORTIONS OF THE POLYMER TO TAN THOSE PORTIONS OF THE HYDROPHILIC COLLOID ON SAID SECOND BASE IN CONTACT WITH THE TRANSFERRED POLYMER.