Patent AT-E399642-T1: [Translated] FLAT PLATE PRECURSOR

The invention provides a planographic printing plate precursor including a photosensitive layer containing an infrared absorbent, a polymerization initiator, a polymerizable compound, and a binder polymer, and a protective layer containing an inorganic layered compound, formed in this order on a surface of a hydrophilic aluminum support, wherein at least one of the photosensitive layer and the protective layer contains a phosphonium compound.