In lithographic printing, ink receptive regions, known as image areas, are generated on a hydrophilic surface. When the surface is moistened with water and ink is applied, the hydrophilic regions retain the water and repel the ink the ink receptive regions accept the ink and repel the water. The ink is then transferred to the surface of suitable materials upon which the image is to be reproduced. In some instances, the ink can be first transferred to an intermediate blanket that in turn is used to transfer the ink to the surface of the materials upon which the image is to be reproduced.
Imageable elements useful to prepare lithographic (or offset) printing plates typically comprise one or more imageable layers applied over a hydrophilic surface of a substrate (or intermediate layers). The imageable layer(s) can comprise one or more radiation-sensitive components dispersed within a suitable binder. Following imaging, either the exposed regions or the non-exposed regions of the imageable layer(s) are removed by a suitable developer, revealing the underlying hydrophilic surface of the substrate. If the exposed regions are removed, the element is considered as positive-working. Conversely, if the non-exposed regions are removed, the element is considered as negative-working. In each instance, the regions of the imageable layer(s) that remain are ink-receptive, and the regions of the hydrophilic surface revealed by the developing process accept water or aqueous solutions (typically a fountain solution), and repel ink.
Similarly, positive-working compositions can be used to form resist patterns in printed circuit board (PCB) production, thick-and-thin film circuits, resistors, capacitors, and inductors, multichip devices, integrated circuits, and active semiconductive devices.
“Laser direct imaging” methods (LDI) have been known that directly form an offset printing plate or printing circuit board using digital data from a computer, and provide numerous advantages over the previous processes using masking photographic films. There has been considerable development in this field from more efficient lasers, improved imageable compositions and components thereof.
Positive-working imageable compositions containing novolak or other phenolic polymeric binders and diazoquinone imaging components have been prevalent in the lithographic printing plate and photoresist industries for many years. Imageable compositions based on various phenolic resins and infrared radiation absorbing compounds are also well known.
A wide range of thermally-sensitive compositions that are useful in thermal recording materials are described in patent GB 1,245,924 (Brinckman), whereby the solubility of any given area of the imageable layer in a given solvent can be increased by the heating of the layer by indirect exposure to a short duration high intensity visible light and/or infrared radiation transmitted or reflected from the background areas of a graphic original located in contact with the recording material.
Thermally imageable, single- or multi-layer elements are also described in WO 97/39894 (Hoare et al.), WO 98/42507 (West et al.), WO 99/11458 (Ngueng et al.), U.S. Pat. No. 5,840,467 (Kitatani), U.S. Pat. No. 6,060,217 (Ngueng et al.), U.S. Pat. No. 6,060,218 (Van Damme et al.), U.S. Pat. No. 6,110,646 (Urano et al.), U.S. Pat. No. 6,117,623 (Kawauchi), U.S. Pat. No. 6,143,464 (Kawauchi), U.S. Pat. No. 6,294,311 (Shimazu et al.), U.S. Pat. No. 6,352,812 (Shimazu et al.), U.S. Pat. No. 6,593,055 (Shimazu et al.), U.S. Pat. No. 6,352,811 (Patel et al.), U.S. Pat. No. 6,358,669 (Savariar-Hauck et al.), and U.S. Pat. No. 6,528,228 (Savariar-Hauck et al.), and U.S. Patent Application Publications 2002/0081522 (Miyake et al.) and 2004/0067432 A1 (Kitson et al.).
Positive-working thermally imageable elements containing thermally-sensitive polyvinyl acetals are described in U.S. Pat. Nos. 6,255,033, 6,541,181 (both Levanon et al.), U.S. Pat. No. 7,399,576 (Levanon et al.), and U.S. Pat. No. 7,544,462 (Levanon et al.), WO 04/081662 (Memetea et al.), and U.S. Patent Application Publication 2009/0004599 (Levanon et al.).
Other positive-working imageable elements are described in copending and commonly assigned U.S. Patent Publication No. 2009/0162783 and U.S. Ser. No. 12/025,089 (filed Feb. 4, 2008 by Levanon et al.), U.S. Ser. No. 12/125,084 (filed May 22, 2008 by Levanon et al.), U.S. Ser. No. 12/195,468 (filed Aug. 21, 2008 by Levanon et al.), and Ser. No. 12/339,469 (filed Dec. 19, 2008 by Levanon et al.).
Offset printing plates recently have been the subject of increasing performance demands with respect to imaging sensitivity (imaging speed) and image resolution as well as resistance to common printing room chemicals (chemical resistance). Often, the compositional features used to provide one desired property do not always improve other properties. While the imageable elements described in the patents, publications, and copending applications in the previous two paragraphs have provided useful advances in the art, additional improvements are still desired.