Lithographic printing plate precursors and processes for preparing lithographic printing plates

A lithographic printing plate precursor comprising:

• a substrate;
• a photosensitive layer provided on the substrate;
• and an extra layer optionally provided between the substrate and the photosensitive layer;
• wherein the photosensitive layer or the extra layer adjacent to the substrate contains (A) a copolymer;
• and wherein the copolymer (A) comprises:
• (a1) a repeating unit having a structure represented by formula (a1-1) below in a side chain, and
• (a2) a repeating unit having at least one of the structure represented by formulae (a2-1) and (a2-2) below in a side chain;
• in formula (a1-1), L1 represents a single bond, a divalent aromatic group containing 6 to 14 carbon atoms, —C(═O)—O—, or —C(═O)—NR2— wherein R2 represents a hydrogen atom, alkyl or aryl;
• Z1 represents methylene, ethylene, propylene, butylene, pentylene, hexylene, heptylene, octylene, cyclohexane-1,4-diyl, 1,2-phenylene, 1,3-phenylene, 1,4-phenylene, 1,2-naphthalene, 1,5-naphthalene and a linking group composed of two or more of these divalent linking groups linked through —O— or —S—, wherein a hydrogen atom in these divalent linking groups may be replaced by substituents;
• R1 represents a hydrogen atom, alkyl, aryl, heterocyclyl, sulfo, alkylsulfonyl and arylsulfonyl;
• R21, R22 and R23 each independently represent a hydrogen atom, halogen atom or C1-8 alkyl;
• and the asterisk (*) indicates the point of attachment to the main chain of the copolymer;
• in formula (a2-1) or (a2-2), M1 to M4 each independently represents a hydrogen atom, a metal atom contained in an alkali metal or an alkaline earth metal or ammonium;
• Y21 or Y22 represent a single bond, or a divalent linking group selected from the Y group consisting of —CO—, —O—, —NH—, a divalent aliphatic group, a divalent aromatic group and a combination thereof;
• and the asterisk (*) indicates the point of attachment to the main chain of the polymer compound,
• and wherein the copolymer (A) further comprises (a3) a repeating unit having a hydrophilic group in a side chain, the hydrophilic group being a group having a zwitterionic structure represented by formula (a3-1) or formula (a3-2) below:
• in formula (a3-1), R31 and R32 each independently represents a hydrogen atom, alkyl, alkenyl, alkynyl, aryl, or heterocyclyl, or R31 and R32 may be joined together to form a ring structure, L31 represents a linking group, and A− represents an anion-containing structure;
• Y3 represents a single bond, or a divalent linking group selected from the group consisting of —CO—, —O—, —NH—, a divalent aliphatic group, a divalent aromatic group and a combination thereof;
• the asterisk (*) indicates the point of attachment to the main chain of the copolymer;
• in formula (a3-2) above, L32 represents a linking group, and E+ represents a cation-containing structure;
• Y4 represents a single bond, or a divalent linking group selected from the group consisting of —CO—, —O—, —NH—, a divalent aliphatic group, a divalent aromatic group and a combination thereof;
• and the asterisk (*) indicates the point of attachment to the main chain of the copolymer.