Method for preparing flexographic printing plates

A method for forming a flexographic printing plate, comprising:

• A) providing a flexographic printing plate precursor consisting essentially of:
• a backing film,
• a water-soluble or water-dispersible photosensitive layer comprising a photosensitive resin composition and having a front imaging surface and a backside imaging surface that is in contact with the backing film, and
• a cover sheet directly in contact with the front imaging surface;
• B) removing the cover sheet from the front imaging surface of the photosensitive layer;
• C) laminating a mask element directly in contact with the front imaging surface of the water-soluble or water-dispersible photosensitive layer;
• D) frontside imagewise exposing the photosensitive layer through the mask element and front imaging surface to provide an exposed photosensitive layer having exposed regions and non-exposed regions;
• and
• E) processing the exposed photosensitive layer to remove non-exposed regions in the exposed photosensitive layer at a temperature of at least 40° C. and up to and including 60° C., using an aqueous flexographic developer having a pH of at least 9 and up to and including 12 and comprising:
• a) a fatty acid composition consisting of one or more saturated or unsaturated fatty acids or alkali metal salts thereof, each saturated or unsaturated fatty acid or alkali metal salt thereof independently having 12 to 20 carbon atoms, the fatty acid composition being present in an amount of at least 0.25 weight % and up to and including 2.0 weight %;
• wherein at least 85 weight % of the fatty acid composition is composed of one or more C18 mono- or poly-unsaturated fatty acids or alkali metal salts thereof;
• b) one or more aminopolycarboxylic acids or alkali metal salts thereof in an amount of at least 0.05 weight % and up to and including 0.30 weight %;
• c) a buffer compound in an amount of at least 0.05 weight % and up to and including 0.60 weight %;
• and
• d) water in an amount of at least 97 weight % and up to and including 99.5 weight %;
• all amounts being based on the total weight of the aqueous flexographic developer,
• to provide a flexographic printing plate with a relief image,
• wherein the water-soluble or water-dispersible photosensitive layer has a peel force of at least 5 g/cm and up to and including 700 g/cm as determined using the procedure of ASTM D-3330 Method D, between the front imaging surface and the mask element.