Lightfastness and Weatherfastness of Overprint Pattern Obtained on Polymer Substrates

The flexographic printing is the fastest growing printing technique nowadays [1]. The principal advantages of flexography are reflected in the markets where it is most often used. The advantages of flexographic printing are low cost and short circle time, precise ink transfer with minimum on-press adjustments, and ability to print one layer and laminate another layer over it in a continuous process [2]. In flexographic printing it is impossible to use one ink for different printing substrate, therefore we have several types of ink: solvent based ink, water based ink and UV and EB curable inks [3]. Both solvent based and water based inks solidify by loss of solvent and water (evaporation). Advantages of solvent based inks are good gloss, excellent adhesion, flexibility on polymer's substrates and they provide good resistance to water, acid and alkali. Main disadvantages of solvent based ink are creation of volatile organic compounds and therewith the risk for environment is increasing. UV curing printing inks have a completely different structure than solvent based inks [4]. UV curable inks are more brilliant without content of inflammable solvent and they have strong mechanical resistance [5, 6]. These are high viscosity inks that require no drying but are photocurable. In the formulations, the solvent is replaced by monomers and photoinitiators that are crosslinked by exposure to UV radiation [2]. One of the fast growing segments in the packaging industry is flexible packaging and its flexible plastic component in particular. New plastic products and new applications for existing products are constantly coming to market. Plastic material is the second most important