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FLEXO Magazine : June2010
Technologies & Techniques 58 FLeXO june 2010 www.flexography.org Troubleshooting Guide: Poor Ink Adhesion By john signet Poor ink adhesion is found many times with film sub- strates, vinyls, polyesters, and polypropylenes. You may also see that the ink is not wetting out on the substrate during printing; or, you will see that the ink does not adhere to the film substrate during post-print testing. The first thing to check is to ensure that you are using the correct ink system for the substrate. While today ’s ink formu- lations are designed to print on a wide variety of substrates, many times you need an ink system specifically formulated to work on film substrates. After this, you need to consider if the substrate that you are using has the proper surface tension, or dyne level, to accept ink. The generally accepted dyne level for printing inks is 38 to 42. There are dyne level testing kits available to help you test for surface tension and they are very easy to use. If you find that the dyne level is too low, you need to raise the dyne level. This is usually done through corona treating. A surface treatment can be done in-line or off-line. Your substrate sup- plier can also supply stock that is pretreated. Note that the effects of corona treating are not permanent; it will diminish over time. An alternative to treating your substrate is to apply a primer to the film or purchase a film that is already topcoated with a print receptive overprint varnish. Finally, there are times when poor ink adhesion is caused by contamination of the substrate surface by particulate matter or chemicals. There are different systems available to clean the surface prior to printing. n ABOUT THE AUTHOR: John Signet is director of marketing at ACTEGA WIT Inc. He has more than 20 years of experi- ence in flexo inks and coatings. He serves on the board of the Phoenix Challenge Foundation and the Graphic Arts and Im- aging Technology Advisory Committee for Central Piedmont Community College in Charlotte, NC. He can be reached at firstname.lastname@example.org. effects of poor ink adhesion in film wetting (top) and tape adhesion (bottom) can be seen on the right side of both images. Art courtesy ACTegA WiT inc. FLX_June2010_mech.indd 58 6/10/10 9:39 AM