Photopolymerizable composition, light sensitive planographic printing plate material and manufacturing method of planographic printing plate

A photopolymerizable composition containing an ethylenically unsaturated monomer, a photopolymerization initiator and a sensitizing dye, wherein the photopolymerization initiator is comprised of an iron-arene compound and a tribromoacetic acid ester having a molecular weight of not less than 500, and the sensitizing dye is at least one selected from the group consisting of compounds represented by the following formulae (A1), (A2) and (A3),

• wherein R1, R2, R3, R4, R5, R11, R12, R13, R14, R15 and R16 independently represent a hydrogen atom or a substituent, provided that at least one of R11, R12, R13, R14, R15 and R16 is a substituent;
• Y1 represents an oxygen atom or a sulfur atom;
• and Y2 represents an oxygen atom or N—R17 in which R17 represents a hydrogen atom or a substituent,
• wherein R1, R2, R3, R5, R6, R21, R22, R23, R24, R25 and R26 independently represent a hydrogen atom or a substituent, provided that at least one of R21, R22, R23, R24, R25 and R26 is a substituent;
• Y1 represents an oxygen atom or a sulfur atom;
• and Y2 represents an oxygen atom or N—R17 in which R17 represents a hydrogen atom or a substituent,
• wherein R1, R2, R3, R11, R12, R13, R14, R15, R16, R21, R22, R23, R24, R25 and R26 independently represent a hydrogen atom or a substituent, provided that at least one of R11, R12, R13, R14, R15, R16, R21, R22, R23, R24, R25 and R26 is a substituent;
• Y1 represents an oxygen atom or a sulfur atom;
• and Y2 represents an oxygen atom or N—R17 in which R17 represents a hydrogen atom or a substituent.