(Ethylene, vinyl acetal) copolymers and their use in lithographic printing plate precursors

1. A copolymer comprising:

(i) a plurality of ethylenic moieties A having a structure according to the formula:

wherein

R 2 and R 3 independently represent hydrogen;

(ii) a plurality of acetal moieties B having a structure according to the formula:

wherein

L 1 is a divalent linking group;

X=0 or 1; and

R 1 represents an optionally substituted aromatic or heteroaromatic group including at least one hydroxyl group; and

(iii) a plurality of acetal moieties C and/or a plurality of acetal moieties D which are different from the plurality of acetal moieties B, and which include at least one nitrogen atom.

2. The copolymer according to claim 1 , wherein the plurality of acetal moieties C and/or the plurality of acetal moieties D have a structure according to the formulae:

wherein

L 2 and L 3 independently represent a linking group;

y and z independently represent 0 or 1;

R 4 and R 5 independently represent an optionally substituted alkyl group, or an optionally substituted aromatic or heteroaromatic group;

in the plurality of acetal moieties C, at least one of R 4 or L 2 includes a nitrogen atom; and

in the plurality of acetal moieties D, at least one of R 5 or L 3 includes a nitrogen atom.

3. The copolymer according to claim 2 , wherein the plurality of acetal moieties C and/or the plurality of acetal moieties D includes the plurality of acetal moieties C.

4. The copolymer according to claim 3 , wherein the plurality of acetal moieties C are present in an amount of 3 to 40 mol %.

5. The copolymer according to claim 1 , further comprising one or more optionally substituted vinyl alcohol moieties E and/or one or more optionally substituted vinyl moieties F represented by the formula:

wherein

R 6 represents hydrogen, an optionally substituted alkyl group, or an optionally substituted aromatic group or heteroaromatic group.

6. The copolymer according to claim 5 , which is represented by the following formula:

wherein

L 2 represents a linking group;

R 1 represents an optionally substituted aromatic or heteroaromatic group including at least one hydroxyl group;

R 4 represents an optionally substituted alkyl group, or an optionally substituted aromatic or heteroaromatic group;

R 6 is an optionally substituted alkyl group;

m is in a range of 10 to 55 mol %;

n is in a range of 15 to 60 mol %;

o is in a range of 10 to 60 mol %;

p is in a range of 0 to 10 mol %;

q is in a range of 3 to 40 mol %; and

y represents 0 or 1.

7. A positive-working lithographic printing plate precursor comprising:

a support including a hydrophilic surface or which is provided with a hydrophilic layer; and

a heat- and/or light-sensitive coating provided thereon; wherein

the coating includes the copolymer according to claim 1 .

8. The precursor according to claim 7 , wherein the coating includes:

a first layer including a binder including a sulfonamide group, an imide group, a nitrile group, a urea group, a carboxyl group, a sulfonic acid group, and/or a phosphoric acid group; and

a second layer, located above the first layer, including the copolymer.

9. The precursor according to claim 7 , wherein the coating includes:

a first layer including a binder including a sulfonamide group, an imide group, a nitrile group, a urea group, a carboxyl group, a sulfonic acid group, and/or a phosphoric acid group, and the copolymer; and

a second layer, located above the first layer, including a phenolic resin selected from a novolac resin, a resol resin, or a polyvinylphenolic resin.