An ablation layer for a photosensitive resin for a relief printing plate, the ablation layer containing at least an acid-modified polymer and an infrared-absorbing agent and having a layer acid value as defined below of 2 mg KOH/g or more and 400 mg KOH/g or less, and a neutralized salt ratio as defined below of 0.9 or less, wherein the Layer acid value=(Acid value of the acid-modified polymer)×(Mass ratio of the acid-modified polymer to an entire ablation layer); and wherein the Neutralized salt ratio=(Number of moles of polymer wherein acid in the acid-modified polymer exists in neutralized salt state)/(Total number of moles of the acid-modified polymer).

An ablation layer for a photosensitive resin for a relief printing plate, the ablation layer containing at least an acid-modified polymer and an infrared-absorbing agent and having a layer acid value as defined below of 2 mg KOH/g or more and 400 mg KOH/g or less, and a neutralized salt ratio as defined below of 0.9 or less, wherein the Layer acid value=(Acid value of the acid-modified polymer)×(Mass ratio of the acid-modified polymer to an entire ablation layer); and wherein the Neutralized salt ratio=(Number of moles of polymer wherein acid in the acid-modified polymer exists in neutralized salt state)/(Total number of moles of the acid-modified polymer).

A lithographic printing plate precursor including a hydrophilized aluminum support, and a water-soluble or water-dispersible negative type image recording layer provided on the aluminum support, in which an arithmetic average height Sa of a surface of an outermost layer on a side where the image recording layer is provided is in a range of 0.3 μm to 20 μm; a method of producing a lithographic printing plate precursor; a lithographic printing plate precursor laminate formed of the lithographic printing plate precursor; a plate-making method for a lithographic printing plate; and a lithographic printing method.

A lithographic printing plate precursor including a hydrophilized aluminum support, and a water-soluble or water-dispersible negative type image recording layer provided on the aluminum support, in which an arithmetic average height Sa of a surface of an outermost layer on a side where the image recording layer is provided is in a range of 0.3 μm to 20 μm; a method of producing a lithographic printing plate precursor; a lithographic printing plate precursor laminate formed of the lithographic printing plate precursor; a plate-making method for a lithographic printing plate; and a lithographic printing method.

An ablation layer for a photosensitive resin for a relief printing plate, the ablation layer containing at least an acid-modified polymer and an infrared-absorbing agent and having a layer acid value as defined below of 2 mg KOH/g or more and 400 mg KOH/g or less, and a neutralized salt ratio as defined below of 0.9 or less, wherein the Layer acid value=(Acid value of the acid-modified polymer)×(Mass ratio of the acid-modified polymer to an entire ablation layer); and wherein the Neutralized salt ratio=(Number of moles of polymer wherein acid in the acid-modified polymer exists in neutralized salt state)/(Total number of moles of the acid-modified polymer).

An ablation layer for a photosensitive resin for a relief printing plate, the ablation layer containing at least an acid-modified polymer and an infrared-absorbing agent and having a layer acid value as defined below of 2 mg KOH/g or more and 400 mg KOH/g or less, and a neutralized salt ratio as defined below of 0.9 or less, wherein the Layer acid value=(Acid value of the acid-modified polymer)×(Mass ratio of the acid-modified polymer to an entire ablation layer); and wherein the Neutralized salt ratio=(Number of moles of polymer wherein acid in the acid-modified polymer exists in neutralized salt state)/(Total number of moles of the acid-modified polymer).

[Problem] To provide a negative type photosensitive composition which can be developed with a low-concentration developer. [Means for Solution] A negative type photosensitive composition comprising (I) an alkali-soluble resin having a carboxyl group, (II) a polymerization initiator, (III) a compound containing two or more (meth)acryloyloxy groups, and (IV) a solvent, wherein the content of the compound containing two or more (meth)acryloyloxy groups is 40 to 300 mass % based on the total mass of the alkali-soluble resin.

[Problem] To provide a negative type photosensitive composition which can be developed with a low-concentration developer. [Means for Solution] A negative type photosensitive composition comprising (I) an alkali-soluble resin having a carboxyl group, (II) a polymerization initiator, (III) a compound containing two or more (meth)acryloyloxy groups, and (IV) a solvent, wherein the content of the compound containing two or more (meth)acryloyloxy groups is 40 to 300 mass % based on the total mass of the alkali-soluble resin.

The present invention provides a photosensitive resin composition for a flexographic printing plate, the photosensitive resin composition including at least a hydrophilic copolymer (A), a thermoplastic elastomer (B), a photo-polymerizable monomer (C), a photo-polymerization initiator (D), a plasticizer (E), and an acidic group-containing polymer (F), wherein the photosensitive resin composition for the flexographic printing plate has an acid value of 1 to 100 mgKOH/g, as measured by neutralization titration.

The present invention provides a photosensitive resin composition for a flexographic printing plate, the photosensitive resin composition including at least a hydrophilic copolymer (A), a thermoplastic elastomer (B), a photo-polymerizable monomer (C), a photo-polymerization initiator (D), a plasticizer (E), and an acidic group-containing polymer (F), wherein the photosensitive resin composition for the flexographic printing plate has an acid value of 1 to 100 mgKOH/g, as measured by neutralization titration.