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.

The present invention provides a printing plate precursor including a layer which includes a polymer and is provided on a printing surface side of an aluminum support, and a layer which includes particles and is provided on a side opposite to the printing surface side, in which a modulus of elasticity of the particles is 0.1 GPa or more, and in a case where a Bekk smoothness of an outermost layer surface on the side opposite to the printing surface side is denoted by b second, a specific expression (1) is satisfied; a printing plate precursor laminate; a method for making a printing plate; and a printing method.

Lithographic printing plate precursors are prepared with a unique substrate and one or more radiation-sensitive imageable 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 a multiplicity of inner micropores having an average inner micropore diameter (D.sub.i) of 15 nm. A formed outer aluminum oxide layer comprises a multiplicity of 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) according to the following equation:

0.3P.sub.o0.8

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

Described herein are aluminum alloys, and methods of making the aluminum alloys, that are advantageous for use as lithographic printing plates. The aluminum alloys, and methods of making the aluminum alloys described herein provide lithographic printing plates without surface defects, but with the mechanical and physical properties currently demanded by the printing industry.

The invention relates to a litho sheet for electrochemical roughening, consisting of a rolled aluminium alloy, wherein the sheet surface has a topography with a maximum peak height Rp or Sp of not more than 1.4 m, preferably not more than 1.2 m, in particular not more than 1.0 m. The invention also relates to a method which is intended for producing a litho sheet and in the case of which a litho sheet consisting of an aluminium alloy is cold-rolled and in the case of which the litho sheet, following the final cold-rolling pass, is subjected to a degreasing treatment with a pickling step using an aqueous pickling medium.

A manufacturing method of a support for a planographic printing plate including at least an alkaline etching step of dissolving an aluminum surface layer of an aluminum web with an alkaline solution during a surface roughening treatment on a surface of the aluminum web continuously traveling, the manufacturing method comprising: a circulating step of cyclically using the alkaline solution between a treatment tank for the etching and an alkaline solution reservoir during adjusting composition concentration of the alkaline solution; and a filtering step of filtering the alkaline solution cyclically used so as to remove solid matter in the alkaline solution.

IR-sensitive lithographic printing plate precursors provide a stable print-out image using a unique IR radiation-sensitive composition in an infrared radiation-sensitive image-recording layer. This IR radiation-sensitive composition includes: (1) a free radical initiator composition that comprises an electron-donating agent; (2) a free radically polymerizable composition; and (3) a color-changing compound that is represented by the Structure (I) having a conjugated carbon chain between the aromatic terminal groups. The compound also has a SO.sub.2R.sup.3 group wherein R.sup.3 represents alkyl, aryl or heteroaryl groups. After IR imaging, these precursors exhibit desirable printout images both fresh and after dark storage. The precursors can be developed off-press or on-press.