PURPOSE: To improve the tone reproducibility by removing a photosensitive layer by developing, then dipping it in water, and setting the water retention amount and the hydrogen bond component of surface energy at the time of lifting from the water to specific ranges in a photosensitive lithographic printing plate having a photosensitive composition layer on a surface treated aluminum plate.
CONSTITUTION: In a photosensitive lithographic printing plate in which a photosensitive composition layer is provided on an aluminum plate surface treated such as roughed or anodized, the layer is removed by developing, then dipped in water, the water retention amount at the time of vertically lifting at the speed of 2cm/min is in a range of 2.0 to 6.0ml/m2, and the hydrogen bond component γ (H) of surface energy represented by a formula is in a range of 16 to 25dyn/cm, where the contact angle is measured by after 30sec by dropping H2O: 1.7μl and CH2I2: 1.3μl. In the pit formed by roughing the aluminum support, the upper projecting area ratio occupied in the pit having a diameter of 1μm or less is 0.5 or more.
SUGI YASUHISA
TAKAGI KOJI
MITSUBISHI CHEM CORP