Patent ID: 8921033

Claim:
A method of preparing a lithographic printing plate comprising: exposing a lithographic printing plate precursor comprising a photosensitive layer containing (A) a polymerization initiator, (B) a polymerizable compound, (C) a sensitizing dye and (D) a binder polymer and a protective layer in this order on a hydrophilic support with laser; and then removing the protective layer and an unexposed area of the photosensitive layer in the presence of a developer, wherein: the developer is a developer which has pH of from 2 to less than 10 and contains an amphoteric surfactant and a nonionic surfactant having an alkylene oxide chain; the amphoteric surfactant is at least one amphoteric surfactant represented by the following formula (1) or (2): wherein, in the formula (1), R 1 represents an alkyl group having from 8 to 20 carbon atoms or an alkyl group having a connecting group which has from 8 to 20 carbon atoms in total, R 2 and R 3 each independently represents an alkyl group or a group containing an ethyleneoxide group, R 4 represents a single bond or an alkylene group, and two groups of R 1 , R 2 , R 3 and R 4 may be combined with each other to form a ring structure; and in the formula (2), R 11 represents an alkyl group having from 8 to 20 carbon atoms or an alkyl group having a connecting group which has from 8 to 20 carbon atoms in total, R 12 and R 13 each independently represents a hydrogen atom, an alkyl group or a group containing an ethyleneoxide group, R 14 represents a single bond or an alkylene group, and two groups of R 11 , R 12 , R 13 and R 14 may be combined with each other to form a ring structure; and the nonionic surfactant having an alkylene oxide chain is at least one nonionic aromatic ether surfactant represented by the following formula (3): X—Y—O-(A) n -(B) m —H (3) wherein, in the formula (3), X represents an aromatic group, Y represents single bond or an alkylene group having from 1 to 10 carbon atoms, A and B, which are different from each other, each represents —CH 2 CH 2 O— or —CH 2 CH(CH 3 )O—, and n and m each represents an integer from 0 to 100, provided that the sum of n and m is 2 or more.