The present invention relates to a water-based or solvent-based washing unit for washing a flexographic plate. The washing unit comprises a containment structure which defines a lower basin and at least two side basins which are supplied with the washing liquid and are arranged so that the water overflowing from the side basins is collected in the lower basin. A brush partially immersed in the liquid bath defined by the basin itself is installed at each basin.

Provided are a planographic printing plate precursor including: a support; and an image recording layer provided on the support, in which the image recording layer contains an infrared absorbing agent, a polymerization initiator, a polymerizable compound containing a hydrogen bonding group, and a hard polymer particle containing at least one group selected from the group consisting of a urethane group, a urea group, an imide group, an amide group, and a sulfonamide group on the surface of the hard polymer particle, and a number average primary particle diameter of the hard polymer particle is in a range of 0.01 to 1 m; and a plate-making method for a planographic printing plate obtained by using the planographic printing plate precursor.

An on-press development type lithographic printing plate precursor including a support and an image-recording layer on the support, in which the image-recording layer contains a polymerizable compound, a polymerization initiator, and an infrared absorber, and a color forming substance precursor, and a color forming substance generated from the color forming substance precursor has a maximal absorption wavelength in a wavelength range of 380 nm or more and less than 580 nm, at which an absorbance difference with respect to the color forming substance precursor is 0.1 or more, and a maximal absorption wavelength in a wavelength range of 580 nm or more and 750 nm or less, at which an absorbance difference with respect to the color forming substance precursor is 0.07 or more, and a method of preparing lithographic printing plate or a lithographic printing method, using the on-press development type lithographic printing plate precursor.

A lithographic printing plate precursor including a support and a coating comprising a photopolymerizable layer including a polymerisable compound, optionally a sensitizer, a photoinitiator and discrete particles which comprise a plurality of silane groups, and/or silanol groups and/or siloxane reaction products of said silane and/or silanol groups.

A planographic printing plate precursor includes: a support; and an image recording layer on the support, and the image recording layer contains a polymer having any group selected from a sulfonamide group, an amide group, an imide group and a carbonate group in a main chain and having a group represented by the following Formula (1):

XRa.sub.n(1)

wherein X represents a single bond or an oxygen atom, Ra represents an alkylene group having 6 to 40 carbon atoms in a case where X represents a single bond and Ra represents an alkylene group having 2 to 20 carbon atoms in a case where X represents an oxygen atom, and n represents an integer of 1 to 90

A lithographic printing plate precursor has a substrate comprising a hydrophilic surface and two opposing edges; a radiation-sensitive imagable layer, and optionally, a protective layer disposed over that layer. The precursor has a shear droop at each opposing edge, each shear droop having a shear droop depth Y of 20-200 m and a shear droop width X of 500-2000 m. The precursor also has a hydrophilic coating band extending from each of the two opposing edges inwardly along the hydrophilic surface independently to provide a hydrophilic coating band width A of at least 1.5 times the shear droop width X. This hydrophilic coating band comprises amphoteric surfactant(s) in an amount greater than all other surfactants. Such individual precursors are obtained by cutting a continuous radiation-sensitive web into strips and such cutting creates the shear droop that can result in edge staining if the hydrophilic coating band is not present.

Flexographic printing members are prepared by developing an exposed flexographic printing member precursor with an aqueous flexographic developer. The aqueous flexographic developer comprises: a) a fatty acid composition consisting of one or more saturated or unsaturated fatty acids or alkali metal salts thereof, each saturated or unsaturated fatty acid or alkali metal salt thereof independently having 12 to 20 carbon atoms, the fatty acid composition being present in an amount of 0.25-2.0 weight %, and at least 85 weight % of the fatty acid composition is composed of one or more C.sub.18 mono- or poly-unsaturated fatty acids or alkali metal salts thereof; b) an aminopolycarboxylic acid or alkali metal salt thereof in an amount of 0.05-0.30 weight %; c) a buffer compound in an amount of 05-0.60 weight %; and d) water. Such aqueous flexographic developers can also be provided in concentrated form and appropriately diluted before or during use.

A negative-working lithographic printing plate precursor has a negative-working infrared radiation-sensitive image-recording layer that has a) two or more free radically polymerizable components; b) an initiator composition capable of generating free radicals; and c) one or more infrared radiation absorbing cyanine dyes. The a) two or more free radically polymerizable components comprise a combination of a urethane (meth)acrylate and a polyester (meth)acrylate, which together, comprise 75-100 weight % of all free radically polymerizable components. The weight ratio of the urethane (meth)acrylates to the polyester (meth)acrylates is from 90:10 to and including 35:65. The urethane (meth)acrylates comprise one or more urethane linkages and at least 4 acrylate or methacrylate ester groups. Each of the one or more polyester (meth)acrylates is free of a urethane linkage and is represented following structure (I). These precursors are less sensitive to ambient ozone and can be infrared radiation imaged and developed on-press during lithographic printing.

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.

Provided are an on-press development type lithographic printing plate precursor including: a support; and an image-recording layer on the support, in which the image-recording layer contains an electron-accepting polymerization initiator, an electron-donating polymerization initiator, an infrared absorber, and a salt compound A, and an HOMO value of an anion constituting a salt in the salt compound A is 6.2 eV or more and 4.4 eV or less, and a method of preparing a lithographic printing plate or a lithographic printing method using the on-press development type lithographic printing plate precursor.