|
Waterless printing is an offset lithographic printing process that eliminates the water or dampening system used in conventional printing. It uses silicone rubber coated printing plates and specially formulated inks, and typically a temperature-control system is integrated into waterless presses. File:Waterless vs. Conventional Printing Plates.jpg|Waterless vs. Conventional Printing Plates Waterless offset presses do not use dampening solution to keep the plate's nonimage areas free of ink. These presses function because the plate's nonimage areas consist of a layer of silicon that repels ink. A waterless press resembles a conventional offset press, except the dampening system might be missing. A more common design, however, includes a dampening system to allow the press to function conventionally when needed. Direct imaging (digital) offset presses are waterless, with no dampening system. Waterless offset inks have a higher tack and viscosity (thickness) and are generally stiffer than conventional offset inks. The temperature of the inks must be strictly controlled to maintain the correct viscosity because the plate surface is designed to repel inks of a specific viscosity. This temperature distinction is achieved by running chilled water through tubing in the hollow cores of two or more vibrating rollers in the ink train on the printing press. The image surface of a waterless plate is intaglio (recessed), allowing the plate to carry a greater volume of ink than a conventional plate does and allowing extremely high screen rulings, ranging from 300 to well over 800 lpi. (lines per inch). Waterless printing yields higher ink densities and a broader color spectrum than conventional offset printing does. Waterless plates used on sheetfed presses are commonly rated for runs of 100,000 to 200,000 impressions. The plates designed for use on web-offset presses can yield 300,000 to 500,000 impressions. When a job is to be run again, the plate can be rehung on the press, and although the register must be achieved manually, a portion of the makeready is simplified, since the ink-key profiles could have been saved and reloaded. A more likely option is that the original prepress files or the plate-format that the original prepress files or the plate-format bitmaps are saved or RIPped again. The bitmap data can be reloaded via the direct imaging server, reimaged on press, and run normally on press. Direct imaging plates are nonphotographic, contain no hazardous waste, and can be recycled through normal aluminum-recycling channels. A compact list of the advantages of waterless printing includes the following: * Higher screen rulings, resulting in better image definition, increased print contrast, and the elimination of rosette patterns. * Greater color range than conventional offset plates. * Higher ink densities with excellent ink holdout on any paper. * More consistence of color during the run. * Sharper dots and more highlight and shadow detail. * Makeready time is cut in half. * Elimination of ink-and-water balance variables yields reduced running time and waste. * Better register control (elimination of paper stretch caused by fountain solution). * Elimination of dampening solution result in no emission of hazardous VOCs if using alcohol. * No waste water or fountain concentrates to worry about. ==History== Waterless printing was originally developed and brought to market by the 3M company under the trade name Driography in the late 1960s. Results with the product however, were mixed. Several problems were encountered both in the development of suitable inks for this process and more importantly, in the durability of the driography plate. After several years of R&D and many millions of dollars invested, 3M chose not to pursue further development of the product. In 1972 Toray Industries, a large Japanese company specializing in synthetic materials development and manufacturing, purchased the patents for the driography product from 3M. Related patents were also purchased from the Scott Paper Co., who were working on a similar project. Toray's experience in working with synthetic materials and advanced polymer compounds allowed them to improve on the original product design. After some five years in research and development, the Toray Waterless Plate was introduced at DRUPA in 1977. Marketing of the product began in 1978 with the TAP-type positive plate. Because the first plate was based on a positive working format, the product was first marketed in Japan. (The Japanese commercial printing market is about 95% positive working vs. the U. S., which is approximately 5% positive). Cooperative efforts from press, ink, and paper manufacturers helped to support the product, and the overall market acceptance was very good. The first North American demonstration of the waterless process was at Print '80, but it wasn't until the introduction of the negative (TAN) type plate in 1982 that this market could be seriously pursued. Initial acceptance of the waterless printing system in the U.S. was quite slow. There are several reasons for this: # memories of the problems encountered with the original 3M system just ten years earlier had left many U. S. printers unreceptive to a new waterless system, # a suitable source for waterless inks did not exist in the U.S. and # Toray's marketing effort was fairly conservative. Until just recently, the U. S. printing industry had taken a cautious stance towards the waterless process, but in the last two years that situation has changed dramatically. Market conditions, greater cooperative efforts from related manufacturers (press, paper and ink), and a more aggressive approach by Toray and its distributors have helped to establish waterless printing as a viable production process. Currently there are over 1000 waterless printers world-wide. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Waterless printing」の詳細全文を読む スポンサード リンク
|