Provided is a lithographic printing plate precursor having a support, an image-recording layer, and an overcoat layer in this order, in which the image-recording layer contains a polymerization initiator, a polymerizable compound, and particles, and the overcoat layer contains a discoloring compound. Also provided is a method of preparing a lithographic printing plate or a lithographic printing method that uses the lithographic printing plate precursor.

There are free radical scavengers of formula (P.sub.m-L).sub.n-T.sub.q. Also provided are negative-working lithographic printing plate precursors comprising a hydrophilic substrate and a NIR photopolymerizable or UV-violet photopolymerizable imageable layer coated on the hydrophilic layer, the imageable layer also being photopolymerizable by visible light, the imageable layer having an outer surface and a thickness, the outer surface of the imageable layer being uniformly, and partially or completely crosslinked down to a depth corresponding to at most about 70% of the thickness of the imageable layer.

The purpose of the present invention is to provide a planographic printing plate precursor which suppresses bleeding or transferring of a substance over time while maintaining edge stain preventing performance, a plate-making method of a planographic printing plate, and a printing method using the planographic printing plate. The planographic printing plate precursor includes a support; and an image recording layer formed on the support, in which layer arrangement described in any one of the following i to iv is provided, a hydrophilizatioin agent layer containing a hydrophilization agent is provided in a region in a specific position of the layer arrangement from the end portion of the planographic printing plate precursor to a portion inside the end portion by 1 cm, and the image recording layer includes an infrared absorbing agent and a specific radical polymerizable compound. i: a mode in which the support layer and the image recording layer are provided in this order. ii: a mode in which the support layer, an undercoat, and the image recording layer are provided in this order. iii: a mode in which the support layer, the image recording layer, and a protective layer are provided in this order. iv: a mode in which the support layer, the undercoat, the image recording layer, and the protective layer are provided in this order.

Provided is an on-press development type lithographic printing plate precursor having a support, an image-recording layer, and an outermost layer in this order, in which the outermost layer has a sea-island structure consisting of a discontinuous phase that contains a hydrophobic polymer and a continuous phase that contains a water-soluble polymer. Also provided are a method of preparing a lithographic printing plate and a lithographic printing method in which the on-press development type lithographic printing plate precursor is used.

Provided is an on-press development type lithographic printing plate precursor having a support, an image-recording layer, and an outermost layer in this order, in which the image-recording layer contains an infrared absorber, an electron-donating polymerization initiator, and a polymerizable compound, HOMO of the infrared absorber - HOMO of the electron-donating polymerization initiator is 0.60 eV or less, and the outermost layer contains a discoloring compound. Also provided are a method of preparing a lithographic printing plate and a lithographic printing method in which the on-press development type lithographic printing plate precursor is used.

A lithographic printing plate precursor is disclosed which comprises a support, a photopolymerizable image recording layer and an overcoat which comprises a low-molecular radical inhibitor. After image-wise exposure, the plate is heated whereby the radical inhibitor diffuses from the overcoat to the image recording layer, resulting in an increase of the daylight stability of the exposed and heated precursor. Such plate is especially suitable for on-press processing.

A lithographic printing plate precursor is disclosed including a support and a coating comprising (i) a photopolymerisable layer including a polymerisable compound, a photoinitiator and an asymmetrically substituted infrared absorbing compound.

A mask element for flexographic printing can include: a substrate; a polymeric layer on the substrate and having a first infrared absorbing material; a non-silver halide thermally-ablatable imaging layer on the polymeric layer and having a second infrared absorbing material and an ultraviolet absorbing material in an thermally-ablatable polymeric binder; and a particulate-treated protective topcoat on the non-silver halide thermally-ablatable imaging layer and having a thermally-ablatable polymer containing inorganic particles of from about 0.25% to about 20% by dry weight of the particulate-treated protective topcoat. The inorganic particles include silicon dioxide or metal dioxide or combinations thereof. The inorganic particles can be thermally-ablatable particles, such as iron oxide, or be not thermally ablatable particles, such as silica, titanium dioxide, zinc oxide, or combinations thereof. the inorganic particles are present from about 0.5% to 10%. The inorganic particles have a size range from 0.05 microns to 1 micron.

A lithographic printing plate precursor has an image-recording layer on a hydrophilic support, wherein the image-recording layer includes a polymer particle including an addition polymerization resin having a hydrophilic structure and a crosslinking structure. A method for producing a lithographic printing plate uses the lithographic printing plate precursor. A polymer particle includes an addition polymerization resin having a hydrophilic structure and a crosslinking structure. A composition includes the polymer particle.

Provided are a planographic printing plate precursor including an aluminum support, and an image recording layer and a protective layer which are provided on the aluminum support in this order, in which a thickness of the protective layer is 0.2 μm or greater, and Expression (1) is satisfied in a case where a Bekk smoothness of a surface of an outermost layer on a side opposite to a side where the image recording layer is provided is denoted by b seconds; a planographic printing plate precursor laminate; a plate-making method for a planographic printing plate; and a planographic printing method.