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Flexo Magazine : March 2011
treatment, an ink with an aggressive solvent mixture would be required so that it will “bite” through the surface contamination and anchor to the film. The ability of in-line corona treatments to remove excess slip compounds from the surface will vary with the speed and watt density. Some cases will require lower press speeds to allow a high enough treatment level to address this issue. • Check lot-to-lot variations to ensure as much consistency as possible. If there is a large amount of variability, con- tact the substrate supplier and initiate corrective action. • In some cases variability can be overcome by a more robust ink system which can operate on a wider variety of surface conditions. One caveat: These ink systems may increase ink costs even as they drive down total costs. • Printers may not often be in a position to dictate substrate choice, or they may not feel empowered to do so; but choosing a consistent substrate is key. • Match ink selection vs. slip levels in the film to avoid scav- enging or seasonal variations. Modify the slip additives in the ink so that the slip agents in the film are less attracted to the ink surface. Porosity. All uncoated paper surfaces have some level of porosity which allows the ink to partially absorb beyond the surface into the underlying paper mass. But some fiber-based substrates may have a very porous surface character. This generates a sponge-like surface that will absorb the ink rather than allow it to remain on the surface while drying. A highly porous substrate may cause the ink to look weak or penetrate to the non-print side. It will also reduce gloss. Higher porosity may also allow UV inks to deeply penetrate the surface, which could inhibit the complete curing of the UV inks. (See Figures 2a, 2b and 2c.) The Solutions • Speed up the drying rate of the ink so that it will begin to dry before it can be absorbed. • Choose an ink system specially formulated for rough surfaces which is optimized for their ink hold out. • Increase the ink film thickness to flooding the surface and com- pensate for the ink that is absorbed, keeping in mind that this will increase ink use (and cost), while decreasing print fidelity. Caution: This is not a good solu- THE FUTURE IS ROUND Until now, if you wanted the superior print quality and high press speed of continuous-print flexo sleeves, you had to accept the long lead times associated with custom-made products manufactured in Europe. Faced with a fast turnaround project? Your options were limited. Not anymore. DuPont is opening its first Nor th American manufacturing site for Cyrel® round sleeves. Finally, you will be able to enjoy the benefits of Cyrel® round sleeves—gravure-like image quality, near-perfect register, improved tonal range, excellent ink laydown, high press speed and more— all with improved lead times. Whether you’re interested in solvent-process continuous print blanks or our new Cyrel® FAST round system, your choice has never been clearer. And, the results have never been faster. At DuPont Packaging Graphics, we create print technologies—innovations that move the flexographic industry forward. Copyright © 2011 DuPont. All rights reserved. The DuPont Oval, DuPontTM, The miracles of scienceTM and Cyrel® are trademarks or registered trademarks of E.I. DuPont de Nemours and Company or its affiliates. DuPont Packaging Graphics “Advancing Flexography” www.cyrel.com/na DPG-FLEXO-ADS.indd 1 12/7/10 11:00 PM FLX_March11.indd 19 3/18/11 1:28 PM