Patent ID: 7108956

Claim:
A thermosensitive lithographic printing plate comprising: a hydrophilic support; a lower layer comprising a water-insoluble and alkali-soluble resin; and an upper thermosensitive layer comprising a water-insoluble and alkali-soluble resin and an infrared absorbing dye, whose dissolution in an alkaline aqueous solution increases upon exposure, wherein a surface of the upper thermosensitive layer has protrusions caused by ununiformity of thickness of the upper thermosensitive layer in a proportion of 0.1 or more and not more than 7 per μm 2 , wherein said protrusions caused by ununiformity of thickness of the upper thermosensitive layer on the surface of the upper thermosensitive layer are formed as a result of a method of using a blend of a high-molecular compound to be used in the upper thermosensitive layer with two or more kinds of phase-separating high-molecular compounds, where said phase-separating high-molecular compounds are uniformly dissolved in a solution but cause separation during coating and drying, whereby one of said two or more kinds of phase-separation high-molecular compounds in a lower amount by weight causes phase separation spherically.