Chemical resistant underlayer for positive-working printing plates

A photoimageable 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 top layer comprises a material that comprises a o-diazonaphthoquinone moiety;
• the underlayer is essentially free of the material that comprises a o-diazonaphthoquinone moiety;
• and
• the underlayer comprises a first polymeric material that is a copolymer comprising an N-substituted maleimide, methacrylamide, and methacrylic acid.

A process for preparing a lithographic printing member, the process comprising the steps of:

• imagewise exposing a photoimageable element and forming an exposed element comprising exposed and unexposed regions;
• and
• developing the exposed element with a developer and removing the exposed regions without substantially affecting the complementary unexposed regions;
• in which the photoimageable element comprises:
• 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 top layer comprises a material that comprises a o-diazonaphthoquinone moiety;
• the underlayer is essentially free of material that comprises the o-diazonaphthoquinone moiety;
• and
• the underlayer has a one-minute soak loss in 80 wt % diacetone alcohol/20 wt % water of less than about 20 wt %.