Process for preparing printing elements

Claim 1

A PROCESS FOR PREPARING PRINTING RELIEFS BY EXPOSING TO ACTINIC RADIATION A PHOTOPOLYMERIZABLE ELEMENT HAVING A SOLID PHOTOPOLYMERIZABLE LAYER FROM 3 TO 250 MILS IN THICKNESS COMPRISING (1) A PREFORMED COMPATIBLE MACROMOLECULAR POLYMER BINDING AGENT, (2) A NON-GASEOUS, ADDITION-POLYMERIZABLE ETHYLENICALLY UNSATURATED COMPOUND CONTAINING AT LEAST ONE TERMINAL ETHYLENIC GROUP CAPABLE OF FORMING A HIGH POLYMER BY PHOTOINITIAL ADDITION POLYMERIZATION IN THE PRESENCE OF AN ADDITION POLYMERIZATION INITIATOR THEREFOR ACTIVATABLE BY ACTINIC LIGHT, AND (3) FROM 0.0001 TO 10%, BY WEIGHT, OF THE LAYER OF SUCH AN INITIATOR, THROUGH AN IMAGE-BEARING TRANSPARENCY, CHARACTERIZED BY (A) EXPOSING SAID ELEMENT TO SAID RADIATION FOR 1/8 TO 1/2 THE TIME REQUIRED FOR ESSENTIALLY COMPLETE ADDITION POLYMERIZATION IN THE RELIEF HEIGHT-FORMING STRATUM OF SAID LAYER, (B) WASHING THE UNEXPOSED AREAS OF SAID STRATUM WITH A SOLVENT FOR SAID BINDER FOR 1/30 TO 1/2 THE TIME REQUIRED FOR ESSENTIALLY COMPLETE REMOVAL OF THE UNEXPOSED PORTION OF SAID STRATUM, (C) PLACING THE TRANSPARENCY IN REGISTER WITH THE RELIEF IMAGE, (D) EXPOSING THE RESULTING ELEMENT TO ACTINIC LIGHT UNTIL POLYMERIZATION IS ESSENTIALLY COMPLETE IN THE EXPOSED AREAS WITHOUT POLYMERIZATION IN UNEXPOSED AREAS, AND (E) WASHING THE EXPOSED ELEMENT WITH AN AFORESAID SOLVENT TO REMOVE THE UNEXPOSED PORTION OF SAID STRATUM.