Lithographic printing plate precusor

1. A method of preparing a negative-working lithographic printing plate precursor comprising the steps of:

providing a support having a hydrophilic surface or which is provided with a hydrophilic layer;

providing a coating on the support, the coating including a photopolymerizable layer and optionally an intermediate layer between the photopolymerizable layer and the support, the coating further including a polysiloxane present in the photopolymerizable layer and/or in the optional intermediate layer; wherein

the polysiloxane is obtained by reacting a first organosilicon compound represented by the general Formula (I) and a second organosilicon compound represented by the general Formula (II):

R 1 represents a group including at least one free radical polymerizable group;

R 2 , R 3 , R 6 , and R 7 independently represent an alkoxy, aryloxy, or an acyloxy group, or an optionally substituted alkyl, cycloalkyl, alkenyl, alkynyl, aryl, or heteroaryl group;

R 4 and R 8 independently represent an optionally substituted alkyl, cycloalkyl, alkenyl, alkynyl, aryl, heteroaryl group, or acyl group;

R 5 represents a hydrophilic group selected from a carboxylic acid or a salt thereof, a sulphonic acid or a salt thereof, a sulphuric acid or a monoester or a salt thereof, a hydrocarbon group substituted with at least one hydroxyl group, an oligoalkylene oxide group, a quaternary ammonium group, a phosphonium group, or combinations thereof; and

L 1 represents a di- or trivalent linking group; and

R 1 and L 1 are bonded to the silicon atom via a carbon atom.

2. The method according to claim 1 , wherein the polysiloxane is present in the photopolymerizable layer.

3. The method according to claim 1 , wherein R 1 includes two, three, four, or five free radical polymerizable groups.

4. The method according to claim 1 , wherein L 1 represents an alkylene, cycloalkylene, arylene, heteroarylene, —O—(CH 2 ) k —, —S—(CH 2 ) k —, —(CH 2 ) k —O—CO—(CH 2 ) l —, —CS—(CH 2 ) k —, —CO—(CH 2 ) k —, —O—CO—NH—, —(CH 2 ) k —CO—NH—, —(CH 2 ) k —NH—CO—, —NR*—CO—NH—, >N—CO—NH—, —NR*—CS—NH—, or combinations thereof;

k and l independently represent 0, 1, or an integer greater than 1; and

R* represents hydrogen or a methyl group.

5. The method according to claim 1 , wherein the polysiloxane is obtained by reacting the first organosilicon compound in an amount ranging between 10 to 50 mol % with the second organosilicon compound in an amount ranging between 20 to 90 mol %.

6. The method according to claim 1 , wherein the polysiloxane further includes a third organosilicon compound according to Formula (III):

wherein

R 9 and R 10 independently represent an alkoxy, aryloxy, or an acyloxy group, or an optionally substituted alkyl, alkenyl, alkynyl, aryl, or heteroaryl group;

L 2 represents a divalent linking group selected from an alkylene, cycloalkylene, arylene, heteroarylene, (poly)alkylene oxide group, —O—(CH 2 ) k , —S—(CH 2 ) k , —CO—(CH 2 ) k , —(CH 2 ) k —O—CO—(CH 2 ) l —, —CS—(CH 2 ) k , —CO—(CH 2 ) k —, —O—CO—NH—, —(CH 2 ) k —CO—NH—, —NR′—CO—NH—, —NH—CS—NH—, or combinations thereof;

k and l independently represent 0, 1, or an integer greater than 1;

R′ represents hydrogen or a methyl group; and

R 11 represents an optionally substituted alkyl, alkenyl, alkynyl, aryl, heteroaryl group, or acyl group.

7. The method according to claim 6 , wherein the polysiloxane is obtained by reacting the first organosilicon compound in an amount ranging between 10 to 50 mol % with the second organosilicon compound in an amount ranging between 20 to 90 mol % and the third organosilicon compound in an amount ranging between 20 to 90 mol %.

8. The method according claim 1 , wherein the photopolymerizable layer includes a polymerizable compound, a binder, and a polymerization initiator.

9. A method of preparing a lithographic printing plate comprising the steps of:

image-wise exposing the precursor obtained according to the method of claim 1 ; and

developing the precursor off-press by treating the coating of the precursor with a developing solution thus removing non-exposed areas of the coating from the support.

10. The method according to claim 9 , wherein the developing solution is a gum solution and the precursor is developed and gummed in one single step.