Multilayer photoimageable elements, useful for forming lithographic printing members, are disclosed. The elements comprise a support, a top layer, and a chemical resistant underlayer. The underlayer is resistant to aggressive washes, such as a UV wash. In one embodiment, the underlayer comprises a copolymer of N-substituted maleimide, methacrylamide, and methacrylic acid. A process for preparing a lithographic printing member is also disclosed.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims priority on U.S. Provisional Patent Application Ser. No. 60/171,554, filed on Dec. 22, 1999, incorporated herein by reference.
Processes for imaging and developing imageable elements useful as lithographic printing plate precursors either thermally or with ultraviolet radiation that use the same developer are disclosed. The imageable elements comprise a top layer and an underlayer. The top layer contains a phenolic polymer and a material that has either the o-benzoquinonediazide functionality or the o-diazonaphthoquinone functionality. The developer is a 20:80 to 80:20 mixture of (1) an aqueous alkaline developer that has a pH greater than 11 and contains about 2 wt % to about 8 wt % of an alkali metal silicate, and (2) a solvent based developer that contains about 0.5 wt % to about 15 wt % of an organic solvent or mixture of organic solvents.
Multilayer, positive working, thermally imageable elements are disclosed. The elements produce bakeable lithographic printing plates that are resistant to press chemistries. The elements have a substrate, an underlayer, and a top layer. The underlayer comprises a resin or resins having activated methylol and/or activated alkylated methylol groups, such as a resole resin, and a polymeric material that comprises, in polymerized form, (a) methacrylic acid; (b) N-phenylmaleimide, N-cyclohexylmaleimide, N-benzylmaleimide, or a mixture thereof; and (c) one or more monomers of the structure: ##STR1## in which: R.sub.1 is H or methyl; X is --(CH.sub.2).sub.n --, where n is an integer from 2 to 12; --(CH.sub.2 --CH.sub.2 --O).sub.p --CH.sub.2 --CH.sub.2 --, where p is an integer from 1 to 3; or --Si(R')(R")-- where R' and R" are each independently methyl or ethyl; and m is 1, 2, or 3.
A process for forming a negative image useful as a printing plate is disclosed. A photosensitive assembly that comprises (a) a hydrophilic support, (b) a first layer that comprises a polymer that is soluble or dispersible in an aqueous alkaline solution, (c) a second layer that comprises at least one o-quinonediazide compound, and (d) an infrared absorbing compound is: (1) flood exposed with ultraviolet radiation; (2) imagewise exposed with infrared laser radiation; and (3) developed to produce the negative image.
A method for forming an image by imaging and developing a multi-layer imageable element is disclosed. When thermally imageable, multi-layer imageable elements that have been imaged using stochastic screening are developed, a much smaller variation in dot percentage throughout the developer loading cycle is observed when a smaller initial charge of developer and a higher replenishment rate than are used in a conventional developing process are used. The developer is a solvent based developer with a pH below about 10.5. The developed imageable elements are useful as lithographic printing plates.
Multi-layer thermally imageable elements, useful as a lithographic printing plate precursors, are disclosed. The elements contain a top layer, an absorber layer that contains a photothermal conversion material and a hydrophilic substrate. An optional underlayer may also be present between the absorber layer and the hydrophilic substrate. The elements can be thermally imaged and processed with an aqueous alkaline developer.
