Process of producing printing plates

Claim 1

THE PROCESS OF PRODUCING A PRINTING PLATE COMPRIS ING THE STEPS OF APPLYING ON A METAL PLATE, A FIRST LAYER OF A LIGHT SENSITIVE MATERIAL WHICH IS SEMI-PERMEABLE TO ETCHING FLUID AND WATER, AS IT CAN BE IMPREGNATED THERE WITH EVEN WHEN HARDENED BY LIGHT, AND A SECOND LAYER OVERLYING SAID FIRST LAYR AND OF A SMALLER THICKNESS THAT SAID FIRST LAYER AND MADE OF A LIGHT SENSITIVE MATERIAL WHICH HAS A SMALLER LIGHT SENSITIVITY THAN THAT OF THE FIRST LAYER, SAID SECOND LAYER BEING IMPERMEABLE TO ETCHING FLUID AND WATER AND CANNOT BE REMOVED THEREBY WHEN LIGHT HARDENED EXPOSING THE PRE-SENSITIZED PLATE TO LIGHT PASSING THROUGH A HALF-TONE PHOTOGRAPH OF THE IMAGE TO BE REPRODUCED, DEVELOPING SAID PLATE IN A DEVELOPER FOR THE IMPERMEABLE LAYER TO THEREBY REMOVE THE NONHARDENED AREAS OF SAID SECOND LAYER, SUBSEQUENTLY RINSING SAID PLATE IN WATER TO THEREBY REMOVE THE NON-HARDENED AREAS OF SAID FIRST LAYER, WHEREBY THE PLATE OBTAINED HAS UNCOVERED METAL AREAS SURROUNDED BY AN UNCOVERED FRINGE OF LIGHT HARDENED FIRST LAYER IN TURN SURROUNDED BY A ZONE OF LIGHT HARDENED SECOND LAYER, AND THEN ETCHING THE PRINTING PLATE WITH AN ETHCHING FLUID TO OBTAIN A PLATE WITH ETCHED DEPRESSIONS OF VARYING DEPTH AND SIZE.