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FLEXO Magazine : July 2008
TECHNOLOGIES & TECHNIQUES Protection layer EmUISi Sublaye L PET Antistatic sublayer Antihalation layer --------- Protection layer FIGURE 1. STRUCTURE OF A NEGATIVE FILM. 1 0 /0 Dots Reproduction Difficulties in Flexo By Maxim Siniak, Ph.D. and Pierre Paul Moyson A chieving the smallest dot size possible has been the cen- ter point of much debate within the flexographic printing industry within the past few years. Through this work, we will demonstrate the advantages and disadvantages of holding the dot-size variance to 1 percent on conventional flexographic plates (I-percent dots). Furthermore, we will provide a few sug- gestions for improving quality in this process. Holding this degree of detail is often viewed as a means of competing or matching the appearance of offset. In the vast ma- jority of cases, the drawbacks far outweigh the benefits of holding a I-percent dot at both the plate development stage and again at the final print process. We also contend that it is very important to have proper process control on each plate at each of the pro- duction stages. The first dynamic we must consider is the number of I-percent dots present in the original image. In the vast majority of cases (except for special designs for particular needs), the I-percent dot population is quite small. Next, we will consider the limited im- - provement that controlling dot size to 1 percent imparts on the final printed image. Finally we will consider the impact of maintaining the I-per- cent dot on the workflow in general. 1% ON FILMS First to be considered is the accuracy of negative films that have been reproduced. Usually, low percentages (below 2 percent) are difficult to reproduce and control due to the instability (dis- tribution of density inside) of small dots themselves and/or high- quality demands for the reproduction process and equipment. There are indeed many factors that can influence dot reproduc- tion during film processing. This means that achieving a true I-percent variance on film is extremely difficult and needs to be accurately and extensively controlled. Two types of repro graphic films that must be considered are found on the global market: clear and matt. These films are of no key importance to guaranteeing a good and stable platemaking J U L Y 2008 www.flexography.org FLEXO
Flexo Sustainable Fall 2008