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FLEXO Magazine : September 2011
Technologies & Techniques Choosing UV/EB Flexo for Food Packaging The Promise: Bold graphics & outstanding Print quality By Don P. Duncan Ultraviolet and electron beam inks have been used as the premier choice for food packaging for many years, but until recently, mostly in lithographic print- ing. UV/EB technologies have been proven to give high quality printing, sharp dots and excellent color reproduction. The immediate cure off the press allows same-day shipping and filling. For the most part, the substrates have been paper- board (frozen prepared food) and polyboard (juice and ice cream cartons). For food packaging, flexo is better known on flexible substrates, rather than boards, and its inks are made from solvent-based or water-based chemistry, rather than UV/EB. In recent years, though: 1. UV flexo has made significant penetration into food and pharmaceutical labels. 2. EB flexo white has proven to be a viable commercial product. 3. Full-color EB flexo has seen much development work done. The technology does not yet have a significant installed base. We’ll address these three types of energy-curable flexo printing in turn and see where they fit and why. SIMILARITIES & DIFFERENCES Let’s first make sure the differences between UV and EB are clear. Even though both are chemically reactive, fully dry immediately off the press and have very low, usually called “es s entially zero,” VOC (volatile organic compound) content, there are some differences. UV inks are cured by passing under a UV-emitting bulb after each printing unit. This allows them to dry trap, as is the ENERGY-CURABLE FLEXO • UV/EB technologies have been proven to give high quality printing, sharp dots and excellent color re- production. The immediate cure off the press allows same-day shipping and filling. • UV flexo is most commonly used on food and phar- maceutical labels. These can be paper or plastic, shrink or static. • EB -cured products are photoinitiator-free and can easily be formulated with fast-curing, low-migration, raw materials that makes them suitable for food packaging. Last-down EB flexo whites are used mostly in flexible packaging. • The low-residual, photoinitiator-free EB process, coupled with the strength of flexo printing on wide- web presses running film, is a perfect fit. 62 FLeXO sePTemBer 2011 www.flexography.org