Negative-working, IR-sensitive printing plates utilize a radiation-sensitive composition having a component polymerizable by a free-radical mechanism, at least part of which comprises or consists essentially of a non-particulate, aliphatic urethane acrylic oligomer that is infinitely water-dilutable but not water-soluble.

By a lithographic printing plate precursor including a support having provided thereon an image-recording layer capable of forming an image by supplying at least any of printing ink and dampening water on a printing machine after image exposure to remove an unexposed area thereof, wherein the image-recording layer contains an infrared absorbing agent, a polymerization initiator, a polymerizable compound and a polysaccharide having a sulfonic acid group or a group made by a salt thereof and a plate making method of a lithographic printing plate using the same, a lithographic printing plate precursor which exhibits good development property while maintaining printing durability of a lithographic printing plate after development and a plate making method of a lithographic printing plate using the same can be provided.

There is provided a photosensitive resin composition which enables production of a lithographic printing plate precursor having a non-image portion which has good solubility in an alkali aqueous solution and which enables production of a lithographic printing plate having excellent printing durability, excellent chemical resistance, and, in particular, excellent printing durability at the time of using a low quality print material, a lithographic printing plate precursor obtained by using the photosensitive resin composition, and a method for producing a lithographic printing plate.

The photosensitive resin composition contains a polymer compound having a linking group represented by Formula A-1 in the main chain; and an infrared absorbing material. In Formula A-1, R.sup.1 and R.sup.2 each independently represent a hydrogen atom or a monovalent organic group, and X.sup.1 is a specific linking group.

##STR00001##

There is provided a photosensitive resin composition which enables production of a lithographic printing plate precursor having a non-image portion which has good solubility in an alkali aqueous solution and which enables production of a lithographic printing plate having excellent printing durability and excellent chemical resistance, a lithographic printing plate precursor obtained by using the photosensitive resin composition, and a method for producing a lithographic printing plate.

The photosensitive resin composition contains a polymer compound having a constitutional unit represented by the following Formula A-1 as a constitutional unit A and at least one constitutional unit among constitutional units represented by the following Formulas B-1 to B-6 as a constitutional unit B in the main chain, and an infrared absorbing material.

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By a lithographic printing plate precursor including a support having provided thereon an image-recording layer capable of forming an image by supplying at least any of printing ink and dampening water on a printing machine after image exposure to remove an unexposed area thereof, wherein the image-recording layer contains an infrared absorbing agent, a polymerization initiator, a polymerizable compound and a polysaccharide having a sulfonic acid group or a group made by a salt thereof and a plate making method of a lithographic printing plate using the same, a lithographic printing plate precursor which exhibits good development property while maintaining printing durability of a lithographic printing plate after development and a plate making method of a lithographic printing plate using the same can be provided.

A system for preparing a photopolymer printing plate includes exposure unit with a plurality of UV sources, a holder comprising a UV translucent material configured to receive the printing plate, and a controller configured to activate the plurality of UV sources. The UV sources include at least one back array of stationary back UV sources configured to emit UV radiation toward the non-printing back side of the printing plate through the holder and at least one front array of front UV sources configured to emit UV radiation toward the printing front side of the printing plate with the printing plate disposed in a stationary position on the holder. The back array defines a collective irradiation field covering an area at least coextensive with the lateral length and width of the plate. At least one of the front array, back array, or both, include light emitting diodes (UV LEDs).

A method and apparatus for processing a lithographic printing plate precursor, comprising development with a first gum solution and subsequently with a second gum solution, wherein both gum solutions are provided in a cascade configuration whereby the second gum solution overflows into the first gum solution and the development is combined with mechanical rubbing and/or brushing by one or more flat brushes.

An on-press development type lithographic printing plate precursor includes: a support; and an image-recording layer on the support, in which the image-recording layer contains a compound represented by Formula (1), a method of preparing a lithographic printing plate using the on-press development type lithographic printing plate precursor, a lithographic printing method, and a novel compound. In the formula, R.sup.1 represents a group represented by Formula (2) or Formula (3), R.sup.10 represents a monovalent organic group having an aryl group, R.sup.11 to R.sup.14 and R.sup.17 to R.sup.20 each independently represent a hydrogen atom, an alkyl group, or an aryl group, R.sup.15 and R.sup.16 each independently represent a hydrogen atom, an alkyl group, or an aryl group, and at least two of R.sup.11 to R.sup.20 may be bonded to each other to form a ring structure.

##STR00001##

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.

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.