Presstek, Inc.

Eugene L Langlais

Thomas E Lewis

Albert S Deutsch

Frederick R Kearney

Gerald P Harwood, Jr

Kenneth R Cassidy

Steven J Frank

Affinity transitions from hydrophobic to hydrophilic states, rather than ablation mechanisms, facilitate the creation of an imagewise lithographic pattern on a printing plate. In various embodiments, a lithographic printing member comprises a topmost 'imaging' layer that undergoes, in response to heat, a transition from a hydrophobic and oleophilic state to a hydrophilic state (which may or may not also be oleophilic); and a substrate disposed below the imaging layer. The affinity change in the imaging layer may be due essentially to a foaming agent therein. The foaming agent decomposes upon heating, creating a gas that foams the surface of the imaging layer. The resulting spongelike texture enables the surface to retain water, i.e., renders it hydrophilic.

Printing members having permeability-transition layers and related methods

Permeability transitions rather than ablation mechanisms facilitate selective removal of the imaging layer of a lithographic plate, which allows for imaging with low-power lasers that need not impart ablation-inducing energy levels.

Lithographic printing plates are imaged using an inkjet printer to imagewise apply a chemical or masking agent onto the plate surface. In some embodiments, the chemical inhibits a photoreaction in the top layer.

Inkjet-imageable lithographic printing members and methods of preparing and imaging them

Solubility transitions rather than ablation mechanisms facilitate selective removal of the imaging layer of a lithographic plate, which allows for imaging with low-power lasers that need not impart ablation-inducing energy levels.

Printing members having solubility-transition layers and related methods

Lithographic imaging using non-ablative printing members combines the benefits of simple construction, the ability to utilize traditional metal base supports, and amenability to imaging with low-power lasers that need not impart ablation-inducing energy levels. A representative printing member has a topmost layer that is ink-receptive and does not significantly absorb imaging radiation, a second layer thereunder that is hydrophilic and does absorb imaging radiation, and a metal substrate under the second layer. The printing member is selectively exposed to laser radiation in an imagewise pattern, and laser energy passes substantially unabsorbed through the first layer and is absorbed by the second layer. Heat builds up in the second layer sufficiently to detach the first layer, which is formulated to resist reattachment. But the first layer and, more significantly, the third layer act to dissipate heat from the second layer to prevent its ablation. Where the printing member has received laser exposure&mdash;that is, where the first and second layers have been detached&mdash;remnants of the first layer are readily removed to produce a finished printing plate.

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Amherst, NH, United States of America

Eugene L Langlais