Photosensitive composition, lithographic printing plate precursor, lithographic printing method, and novel cyanine dyes

A photosensitive composition comprising:

• a cyanine dye that has, on a methine chain thereof, a substituent which is a cation moiety of an onium salt structure, wherein
• the cyanine dye is represented by a general formula (3):
• wherein
• R1 and R8 each independently represents a hydrocarbon group which may have a substituent;
• R2, R3, R4, R5, R6, and R7 each independently represents a hydrogen atom or a hydrocarbon group;
• R4 and R5 may be connected to each other to form a ring which may have a substituent;
• X represents a single bond or a linking group;
• Q1 and Q2 each independently represents —NR9—, S, O, —CH═CH—, or a dialkylmethylene group;
• R9 represents a hydrogen atom or a hydrocarbon group which may have a substituent;
• Y+ represents a substituent having a cation moiety of an onium salt structure represented by any one of general formulae (5), (6) and (8):
• wherein R20 to R44 and R50 to R55 each independently represents a hydrogen atom, a halogen atom, or a monovalent organic group;
• and
• one of R20 to R29 in the general formula (5), one of R30 to R44 in the general formula (6), and one of R50 to R54 in the general formula (8) are a single bond connected to X in the general formula (3);
• T1 and T2 each independently represents an aromatic ring or a heteroaromatic ring;
• and
• A− and B− each independently represents a counter ion which exists when charge neutralization is necessary, the counter ion being selected from the group consisting of a halogen ion, a perchlorate ion, a tetrafluoroborate ion, a hexafluorophosphate ion, and a sulfonate ion.