Photomechanical method of producing printing forms

Claim 1

A PHOTOMECHANICAL METHOD FOR PREPARING PRINTING PLATES HAVING CONICAL PRINTING ELEMENTS FREE OF UNDERCUTTING IN THE BASE PORTIONS THEREOF WHICH COMPRISES LIGHT-SENSITIZING A BODY OF POLYAMIDE CONDENSATION POLYMER BY CONTACTING SAID BODY WITH A SOLUTION OF A LIGHT SENSITIVE HARDENING AGENT FOR SAID POLYMER, EXPOSING THE SENSITIVE BODY TO A LIGHT IMAGE, WHEREBY THOSE PORTIONS OF THE POLYAMIDE BODY EXPOSED TO LIGHT ARE HARDENED, AND SUBSEQUENTLY DEVELOPING SAID POLYAMIDE BODY BY PARTIALLY REMOVING UNHARDENED PORTIONS THEREOF TO LEAVEE CONICAL PRINTING ELEMENTS COMPRISING SAID EXPOSED AND HARDENED PORTIONS AND UNREMOVED UNHARDENED PORTIONS SAID PARTIAL REMOVAL BEING EFFECTED BY REPEATEDLY SOFTENING AND ABRADING UNHARDENED SURFACE PORTIONS OF THE POLYAMIDE BODY WITH A PLURALITY OF FINE, FLEXIBLE BRISTLES MOISTENED WITH A SOFTENING AGENT FOR SAID POLYAMIDE, SAID SOFTENING AGENT COMPRISING WATER AND A WATER-MISCIBLE ORGANIC LIQUID, SAID ABRANDING BEING MORE PRONOUNCED IN THOSE PORTIONS OF THE UNHARDENED POLYAMIDE REMOTE FROM THE EXPOSED AND HARDENED PORTIONS THEREOF THAN IN THOSE PORTIONS OF THE UNHARDENED POLYAMIDE ADJOINING SAID HARDENED PORTIONS.