Lithographic printing plate having high chemical resistance

An imageable element comprising:

• a) a substrate, the substrate comprising a hydrophilic surface;
• b) an underlayer over the hydrophilic surface;
• and
• c) a top layer over the underlayer;
• wherein:
• the top layer is ink receptive;
• exposed regions of the top layer are more readily removable by aqueous alkaline developer than unexposed regions;
• the underlayer is soluble or dispersible in aqueous alkaline developer;
• the underlayer comprises a combination of at least a first polymeric material and a second polymeric material;
• the underlayer comprises about 10% to about 900 by weight of a first polymeric material and about 10% to about 90% by weight of a second polymeric material, based on the total weight of the first polymeric material and the second polymeric material in the underlayer;
• the first polymeric material has a one-minute soak loss of less than 20% in 80 wt % diacetone alcohol/20 wti water, and
• the second polymeric material has a one-minute soak loss of less than 20% in 80 wt % 2-butoxyethanol/20 wt % water.

An imageable element comprising:

• a) a substrate, the substrate comprising a hydrophilic surface;
• b) an underlayer over the hydrophilic surface;
• and
• c) a top layer over the underlayer;
• wherein:
• the top layer is ink receptive;
• exposed regions of the top layer are more readily removable by aqueous alkaline developer than unexposed regions;
• the underlayer is soluble or dispersible in aqueous alkaline developer;
• the underlayer comprises a combination of at least a first polymeric material and a second polymeric material;
• the underlayer comprises about 10% to about 90% by weight of a first polymeric material and about 10% to about 90% by weight of a second polymeric material, based on the total weight of the first polymeric material and the second polymeric material in the underlayer;
• the first polymeric material comprises about 25 to about 75 mol % of N-phenylmaleimide;
• about 10 to about 50 mol % of methacrylamide;
• and about 5 to about 30 mol % of methacrylic acid.

A method for forming an image, the method comprising:

• (1) imaging an imageable element to form an imaged element, the imageable element comprising:
• a) a substrate, the substrate comprising a hydrophilic surface;
• b) an underlayer over the hydrophilic surface;
• and
• c) a top layer over the underlayer:
• wherein:
• the top layer is ink receptive;
• the underlayer is soluble in aqueous alkaline developer;
• the underlayer comprises a combination of at least a first polymeric material and a second polymeric material;
• the top layer comprises a third polymeric material;
• and
• the chemical resistance parameter for the underlayer is greater than about 0.4:
• and
• (2) developing the imaged element with an aqueous alkaline developer to form an imaged and developed element, the imaged and developed element comprising an image.

A composition comprising at least 50 wt % of a combination comprising about 10% to about 90% by weight of a first polymeric material and about 10% to about 90% by weight of a second polymeric material, based on the total weight the first polymeric material and the second polymeric material in the composition:

• in which:
• the first polymeric material comprises about 25 to about 75 mol % of N-phenylmaleimide;
• about 10 to about 50 mol % of methacrylamide;
• and about 5 to about 30 mol % of methacrylic acid;
• and
• the second polymeric material comprises either:
• (1) about 20 to 80 wt % of one of more monomers represented by the general formula:
• [CH2═C(R)—CO2—X—NH—CO—NH—Y—Z],
• in which R is —H or —CH3;
• X is a bivalent linking group;
• Y is a substituted or unsubstituted bivalent aromatic group;
• and Z is —OH, —COOH, or —SO2NH2;
• or (2) about 10 to 90 mol % of a sulfonamide monomer unit;
• acrylonitrile or methacrylonitrile;
• and methyl methacrylate or methyl acrylate.

An imaged and developed element useful as a lithographic printing member, the element prepared by a method comprising:

• (1) imaging an imageable element to form an imaged element comprising imaged and unimaged regions, the imageable element comprising:
• a) a substrate, the substrate comprising a hydrophilic surface;
• b) an underlayer over the hydrophilic surface;
• and
• c) a top layer over the underlayer;
• wherein:
• the top layer is ink receptive;
• exposed regions of the top layer are more readily removable bv aqueous alkaline developer than unexposed regions;
• the underlayer is soluble or dispersible in aqueous alkaline developer;
• the underlayer comprises a combination of at least a first polymeric material and a second polymeric material;
• the top layer comprises a third polymeric material;
• and
• the chemical resistance parameter for the underlayer is greater than about 0.4;
• and
• (2) developing the imaged element with an aqueous alkaline developer and removing the exposed regions to form the imaged and developed element, the imaged and developed element comprising an image.