A lithographic printing plate precursor is disclosed including a support and a coating comprising (i) a photopolymerisable layer including a polymerisable compound and a photoinitiator, and a toplayer provided above the photopolymerisable layer: characterized in that the toplayer includes a halogenated polymer and a nitrite and/or nitrate salt.

The present invention provides a lithographic printing plate precursor that enables a lithographic printing plate formed therefrom to have excellent image visibility and a long press life, as well as a lithographic printing plate manufacturing method and a printing method. The lithographic printing plate precursor of the invention is a lithographic printing plate precursor including an aluminum support and an image recording layer, the aluminum support includes an aluminum plate and an anodized film of aluminum formed on the aluminum plate, the anodized film is positioned closer to the image recording layer than the aluminum plate is, the anodized film has micropores extending in a depth direction of the anodized film from a surface of the anodized film on the image recording layer, the micropores have an average diameter of more than 10 nm but not more than 100 nm at the surface of the anodized film, and the surface of the anodized film on the image recording layer side has a lightness L* of 70 to 100 in a L*a*b* color system.

A method for producing flexographic printing plates, using a photopolymerizable flexographic printing element having, arranged one atop another, a dimensionally stable support, a photopolymerizable, relief-forming layer, an elastomeric binder, an ethylenically unsaturated compound, and a photoinitiator, and optionally a rough, UV-transparent layer, a particulate substance, and digitally imagable layer. The method includes: (a) producing a mask by imaging the digitally imagable layer, (b) exposing the photopolymerizable, relief-forming layer through the mask with actinic light, and photopolymerizing the image regions of the layer, and (c) developing the photpolymerized layer by washing out the unphotopolymerized regions of the relief-forming layer with an organic solvent, or by thermal development. Step (b) includes (1) exposure with actinic light with an intensity of 100 mW/cm2 from a plurality of UV-LEDs and (2) exposure with actinic light with an intensity of <100 mW/cm2 from a UV radiation source other than UV-LEDs.

The imaging sensitivity of negative-working lithographic printing plate precursors is improved by removing ozone from the ambient air surrounding the precursors that can be stored near an imaging means such as a platesetter prior to use. Ozone can be removed using a suitable filter containing activated charcoal or other ozone decomposing means, through which ambient air is filtered before and during the imaging process.

On-press developable, negative-working lithographic printing plate precursors are used to provide lithographic printing plates. Such precursors are prepared with a substrate and one or more negative-working, infrared radiation-sensitive imagable layers. The substrate is prepared by two separate anodizing processes to provide an inner aluminum oxide layer having an average dry thickness (T.sub.i) of 650-3,000 nm and inner micropores having an average inner micropore diameter (D.sub.i) of <15 nm. A formed outer aluminum oxide layer comprises outer micropores having an average outer micropore diameter (D.sub.o) of 15-30 nm; an average dry thickness (T.sub.o) of 130-650 nm; and a micropore density (C.sub.o) of 500-3,000 micropores/m.sup.2. The ratio of D.sub.o to D.sub.i is greater than 1.1:1, and D.sub.o in nanometers and the outer aluminum oxide layer micropore density (C.sub.o) in micropores/m.sup.2, are further defined by the outer aluminum oxide layer porosity (P.sub.o) as:

0.3P.sub.o0.8

wherein P.sub.o is 3.14(C.sub.o)(D.sub.o.sup.2)/4,000,000.

Provided are a planographic printing plate precursor for furnishing a planographic printing plate in which edge stain does not occur, adhesion to interleaving paper is prevented, and the water width with respect to edge stain at the time of printing is wide; a method of producing the same, and a printing method using the same. The planographic printing plate precursor including: a support; an image recording layer formed on the support; and a water-soluble compound having a molecular weight in a range of 60 to 300 and a solubility of 10 g/L or greater in water at 20 C., in which a content of the compound per unit area in a region on the image recording layer side from an end portion of the planographic printing plate precursor to a portion inside the end portion by 5 mm is greater than a content of the compound per unit area in a second region other than the first region by an amount of 50 mg/m.sup.2 or greater.

Provided are a seamless cylindrical offset printing plate which enables seamless continuous printing to be performed, a manufacturing method therefor, and a reproduction processing method. The seamless cylindrical offset printing plate comprises: a cylindrical plate base material; a hydrophilic satin-like rough surface which is formed on a surface of the cylindrical plate base material; and a hydrophobic resist pattern part which is formed on the satin-like rough surface, wherein an exposed part of the satin-like rough surface serves as a non-printing area and the resist pattern part serves as a printing area.

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.

Provided are a planographic printing plate precursor for on-press development, including: an aluminum support; an interlayer which contains a compound containing a support absorptive group and a hydrophilic group; and an image recording layer which contains an infrared absorbing agent, a polymerization initiator, a polymerizable compound, and polymer particles formed of a styrene copolymer, on the aluminum support, in which the aluminum support is an aluminum plate having an anodized film on a surface in contact with the interlayer and the anodized film has micropores extending in a depth direction from a surface in contact with the interlayer, and an average pore diameter of the micropores in the surface of the anodized film is in a range of 20 to 40 nm; a method of preparing a planographic printing plate and a planographic printing method obtained by using the planographic printing plate precursor for on-press development.

A stack including: a lithographic printing plate precursor including an image-recording layer which contains an infrared absorber, a polymerizable compound, and a polymerization initiator; and an interleaving paper stacked on the lithographic printing plate precursor, in which air permeation resistance of the interleaving paper is 55 seconds or more, or a stack including: a lithographic printing plate precursor including an image-recording layer which contains an infrared absorber, a polymerizable compound, and a polymerization initiator; and an interleaving paper stacked on the lithographic printing plate precursor, in which the interleaving paper is overlapped with the lithographic printing plate precursor to be in contact with a surface of the lithographic printing plate precursor on an image-recording layer side, and a color difference ?E of the image-recording layer before and after storage in a dark room in an environment of 25? C. and 55% RH for 3 days is less than 3.0.