An apparatus for aligning an edge, such as a leading edge of a plate, in particular a printing plate or a printing plate precursor. The apparatus includes a support configured for supporting the plate on a support surface, and to be located upstream of a treatment station. At least two movable elements are arranged to be moved by an edge, such as a leading edge, of the plate. The at least two movable elements include a first and a second movable element; a detection means configured to detect a first and second measure representative for a first and second position of the first and second movable element, respectively, at least one controllable component configured to perform an action on the plate, and a control means configured to control the at least one controllable component based on the first and second measure.

Flexographic printing members are prepared from a flexographic printing plate precursor consisting essentially of: backing film, water- or water-dispersible photosensitive layer, and cover sheet in contact with the photosensitive layer. The cover sheet is removed and a mask element is laminated directly in contact with the photosensitive layer. Exposure through the mask element provides exposed regions and non-exposed regions. The non-exposed regions are removed with an aqueous developer having: a) a C.sub.12-20 saturated or unsaturated fatty acid (or alkali metal salt) at 0.25-2.0 weight %, and at least 85 weight % of a C.sub.18 mono- or poly-unsaturated fatty acid (or alkali metal salt); b) an aminopolycarboxylic acid (or alkali metal salt) at 0.05-0.30 weight %; c) a buffer at 05-0.60 weight %; and d) water. The photosensitive layer has a controlled release of 5-500 g/cm using ASTM D-3330 Method D, between its front imaging surface and the mask element.

Provided is a method for production of an aluminium strip for lithographic printing plate supports from an aluminium alloy including (in wt %): 0.05%Si0.25%, 0.2%Fe1%, Cu max. 400 ppm, Mn0.30%, 0.10%Mg0.50%, Cr100 ppm, Zn500 ppm, Ti<0.030%, the remainder aluminium and unavoidable impurities individually at most 0.03%, in total at most 0.15%. In the method, a rolling ingot is cast from an aluminium alloy, and the rolling ingot is homogenised. Further, the rolling ingot is hot rolled to a hot strip final thickness, and the hot strip is cold rolled to final thickness of between 0.1 mm and 0.5 mm. The product of the relative final thicknesses of the aluminium strip after the first and after the second cold rolling pass of the aluminium strip is 15% to 24%.

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.

Flexographic printing members are prepared from a flexographic printing plate precursor consisting essentially of: backing film, water- or water-dispersible photosensitive layer, and cover sheet in contact with the photosensitive layer. The cover sheet is removed and a mask element is laminated directly in contact with the photosensitive layer. Exposure through the mask element provides exposed regions and non-exposed regions. The non-exposed regions are removed with an aqueous developer having: a) a C.sub.12-20 saturated or unsaturated fatty acid (or alkali metal salt) at 0.25-2.0 weight %, and at least 85 weight % of a C.sub.18 mono- or poly-unsaturated fatty acid (or alkali metal salt); b) an aminopolycarboxylic acid (or alkali metal salt) at 0.05-0.30 weight %; c) a buffer at 05-0.60 weight %; and d) water. The photosensitive layer has a controlled release of 5-500 g/cm using ASTM D-3330 Method D, between its front imaging surface and the mask element.

Following cutting of a develop-on-press printing member, a treatment fluid having a pH greater than 6 is applied to one or both edges prior to its development and use in order to avoid ink lines during printing.

Provided are an on-press development type lithographic printing plate precursor having a support and an image-recording layer on the support in which the image-recording layer contains a coloring compound capable of having a coloring reaction with a decomposition product generated by exposure of the image-recording layer, and an on-press development type lithographic printing plate precursor having a support and an image-recording layer on the support in which the image-recording layer contains a compound represented by Formula 1C or Formula 2C and an electron-donating polymerization initiator. In Formula 1C and Formula 2C, R.sup.1C to R.sup.4C each independently represent a monovalent organic group, L.sup.1C and L.sup.2C each independently represent a divalent organic group, A.sup.C represents OH or NR.sup.5CR.sup.6C, and R.sup.5C and R.sup.6C each independently represent a monovalent organic group

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