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 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.

A planographic printing plate precursor having an image recording layer on a support, and an overcoat layer in this order, in which the overcoat layer includes particles, the overcoat layer is an outermost layer, and an occupation area ratio of the particles in a surface of the overcoat layer is 30% by area or more; and a method of producing 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 negative-working infrared radiation-sensitive lithographic printing plate precursor can be imaged and developed on-press to provide a lithographic printing plate. Such precursor has an initiator composition that contains compound A of Structure (I) and one or more compounds collectively as compound B of Structure (II) or Structure (III):

##STR00001##

wherein R.sub.1, R.sub.2, R.sub.3, R.sub.4, R.sub.5 and R.sub.6 are independently alkyl groups each having 3 to 6 carbon atoms; at least one of R.sub.3 and R.sub.4 is different from R.sub.1 or R.sub.2; the difference of total number of carbon atoms in R.sub.1 and R.sub.2 and the total number of carbon atoms in R.sub.3 and R.sub.4 is 0, 1, or 2; the difference of total number of carbon atoms in R.sub.1 and R.sub.2 and the total number of carbon atoms in R.sub.5 and R.sub.6 is 0, 1, or 2; and X.sub.1, X.sub.2 and X.sub.3 are the same or different anions.

A negative type lithographic printing plate precursor includes a support having a hydrophilic surface; and an image recording layer, on the support, containing a polymerization initiator and a polymer compound having a structure represented by Formula 1 in a main chain and an ethylenically unsaturated bond. Further, a method of preparing a lithographic printing plate includes, in order, an exposure step of image-exposing the negative type lithographic printing plate precursor; and a development step of performing development by removing a non-exposed portion of the exposed negative type lithographic printing plate precursor using a developer. In Formula 1, R.sup.1 represents an (x+2)-valent aromatic hydrocarbon ring group, and x represents an integer of 1 to 4.

##STR00001##

A planographic printing plate precursor includes: a hydrophilic support; and an image recording layer which contains an organic-inorganic hybrid particle (A) and an infrared-ray absorbent (B) on the hydrophilic support, and the organic-inorganic hybrid particle (A) is an organic-inorganic hybrid particle in which an inorganic particle (a) containing a hydroxyl group and an organic component (b) are linked to each other through a linking group (c) having a urethane bond or a urea bond.