Polymeric acetal resins containing free radical inhibitors and their use in lithographic printing

An imageable element comprising:

• (I) a substrate having a hydrophilic surface;
• and,
• (II) a photosensitive layer over the hydrophilic surface;
• in which the photosensitive layer comprises a photosensitive composition comprising a polymeric diazo resin and a polymeric acetal resin comprising the units (A), (B), (C), (D), and (E),
• in which:
• unit (A) has the structure:
• unit (B) has the structure:
• unit (C) has the structure:
• unit (D) is selected from the group consisting of (D1), (D2), and combinations thereof,
• in which unit (D1) has the structure:
• and unit (D2) has the structure
• unit (E) is selected from the group consisting of (E1), (E2), and combinations thereof in which
• unit (E1) has the structure:
• and unit (E2) has the structure
• in which the polymeric acetal resin comprises about 10 to about 60 mol % of unit (A), about 5 to about 60 mol % of unit (B), about 0.3 to about 30 mol % of unit (C), about 1 to about 40 mol % of unit CD), and about 0.01 to about 2 mol % of unit (E);
• in which:
• R and R2 are each independently hydrogen, an aliphatic group, an aromatic group, or an arylaliphatic group;
• Ac1 and Ac2 are each independently a group comprising a carboxylic acid group, a sulfonic acid group, a sulfonamido group, a phosphonic acid group, a proton-bearing phosphoric ester group, a phenolic group, or an alkali metal salt or an ammonium salt thereof;
• R1 is H, C1-C10 alkyl, or carboxyl-substituted C1-C10 alkyl;
• and
• In1 and In2 are each independently a group that inhibits free radical polymerization.

A method for preparing a lithographic printing plate comprising:

• (1) providing an imageable element comprising:
• (I) a lithographic substrate having a hydrophilic surface;
• and,
• (II) a photosensitive layer superposed over the hydrophilic surface, in which the photosensitive layer comprises a photosensitive composition comprising a polymeric diazo resin and a polymeric acetal resin comprising the units (A), (B), (C), (D), and (E),
• in which:
• unit (A) has the structure:
• unit (B) has the structure:
• unit (C) has the structure:
• unit (D) is selected from the group consisting of (D1), (D2), and combinations thereof,
• in which unit (D1) has the structure:
• and unit (D2) has the structure
• unit (E) is selected from the group consisting of (E1), (E2), and combinations thereof in which
• unit (E1) has the structure:
• and unit (E2) has the structure
• in which the polymeric acetal resin comprises about 10 to about 60 mol % of unit (A), about 5 to about 60 mol % of unit (B), about 0.3 to about 30 mol % of unit (C), about 1 to about 40 mol % of unit (D), and about 0.01 to about 2 mol % of unit (E);
• in which:
• R and R2 are each independently hydrogen, an aliphatic group, an aromatic group, or an arylaliphatic group;
• Ac1 and Ac2 are each independently a group comprising a carboxylic acid group, a sulfonic acid group, a sulfonamido group, a phosphonic acid group, a proton-bearing phosphoric ester group, a phenolic group, or an alkali metal salt or an ammonium salt thereof;
• R1 is H, C1-C10 alkyl, or carboxyl-substituted C1-C10 alkyl;
• and
• In1 and In2 are each independently a group that inhibits free radical polymerization;
• in which the photosensitive layer is soluble or dispersible in an aqueous developer;
• (2) Imagewise exposing the photosensitive layer to actinic radiation to produce a photoimaged layer having exposed image areas which are insoluble in the aqueous developer;
• and
• (3) applying the aqueous developer to the surface of the photoimaged layer to remove unexposed portions of the photoimaged layer and uncover underlying portions of the hydrophilic surface.

A polymeric acetal resin comprising the units (A), (B), (C), (D) and (E), in which

• unit (A) has the structure:
• unit (B) has the structure:
• unit (C) has the structure:
• unit (D) is selected from the group consisting of (D1), (D2), and combinations thereof,
• in which unit (D1) has the structure:
• and unit (D2) has the structure
• unit (E) is selected from the group consisting of (E1), (E2), and combinations thereof in which
• unit (E1) has the structure:
• and unit (E2) has the structure
• in which the polymeric acetal resin comprises about 10 to about 60 mol % of unit (A), about 5 to about 60 mol % of unit (B), about 0.3 to about 30 mol % of unit (C), about 1 to about 40 mol % of unit CD), and about 0.01 to about 2 mol % of unit (E);
• in which:
• R and R2 are each independently hydrogen, an aliphatic group, an aromatic group, or an arylaliphatic group;
• Ac1 and Ac2 are each independently a group comprising a carboxylic acid group, a sulfonic acid group, a sulfonamido group, a phosphonic acid group, a proton-bearing phosphoric ester group, a phenolic group, or an alkali metal salt or an ammonium salt thereof;
• R1 is H, C1-C10 alkyl, or carboxyl-substituted C1-C10 alkyl;
• and
• In1 and In2 are each independently a group that inhibits free radical polymerization.