Polymeric binders for aqueous processable photopolymer compositions

Claim 1

A process for forming a photoresist on a surface comprising: (1) applying to a surface the surface of a photopolymerizable layer on a film support, said photopolymerizable layer formed from a photopolymerizable composition containing 0.1 to 10% by weight of an organic radiation-sensitive free radical-generating photoinitiator system, 7.5 to 35% by weight of a nongaseous ethylenically unsaturated compound capable of forming a high polymer by free radical-initiated chain addition polymerization, and 30 to 92.4% by weight of polymeric binder wherein the binder is comprised of a mixture of from 15 or 60% by weight each of two free acid containing polymers which are insoluble in water at 85° F., the first polymer (A) (a) being film forming when cast from solution in volatile solvent onto copper after evaporation of the solvent, the film having (1) the thickness of 0.0003 to 0.0023 inch; (2) good adhesion to copper as measured by zero delamination in the scribe cross hatch test; and (3) complete solubility within five minutes to a spray of dilute aqueous alkali at 0.04 normal NaOH, 20 p.s.i., and 80°-85° F.; (b) having a molecular weight of at least 30,000; and (c) having an acid number of at least 20; and the second polymer (B) (1) having an acid number of at least 5; and (2) when in film form of 0.0003 to 0.0023 inch thickness, being insoluble for at least 5 minutes to a spray of dilute aqueous alkali at 0.04 normal NaOH, 20 p.s.i., and 80°-85° F.; then, in either order, (2) exposing the layer, imagewise, to actinic radiation to form a polymeric image; and (3) stripping the film support; (4) washing away the unexposed areas of the photopolymerizable layer to form a resist image of polymeric material with an alkaline, aqueous solution; and (5) permanently modifying the adjacent areas on said surface which are unprotected by the resist image by using a reagent capable of etching said areas or depositing a material on said areas.