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FLEXO Magazine : August 2014
The final effect of the process, achieved in a much simpler and more effective way, is very similar to the more conventional “de metalliza- tion” process, produced by a downstream metal layer removal from selected areas. Pattern metallization is, instead, an inline process that occurs in the vacuum chamber during the metallization step, without any subsequent removal process. Examples, as seen in Figure 1, show existing and potential applications are numerous and diversified. The packaging industry can use patterned metallization for different applications and functions such as: • Showing the content of a metallized package (window metalli- zation) • Decoration purposes • Labels • Product identification and security in combination with multiple features that include » Holograms » Covert images » Optically variable surfaces as anti counterfeiting on selected products In the non packaging field, a selectively metallized surface can also have multiple uses, taking advantage of the electrically and thermally conductive properties of the metal pattern. Examples of possible ap- plications currently being studied are heat concentrating or shielding surfaces for microwave cooking, RFID (Radio Frequency Identifica- tion) and smart labels, electromagnetic filters, and, in general, contri- bution to the further development of flexible electronics. In compar- ison with existing and established production technology, such as de metallization of foil laminated structures, the advantage of selective metallization consists of being made with extremely thin metal and in a single vacuum step with no use of solvent or acids. IN VACUUM PRINTING In vacuum printing of a repulsive substance to metal deposition is achieved by means of a specially designed printing unit, installed within the vacuum chamber, immediately before the metallization zone. The target is to protect the areas to keep clear from aluminum condensation during the metallization process. On the protected ar- eas, the evaporating aluminum will not condense and deposit so that the final product will show the combination of metallized and non metallized areas as required. The drawing in Figure 2 shows a typical metallizer web diagram in its essential parts: the vacuum chamber, the winding mechanism and the aluminum evaporation system. This last system consists of a distri- bution of multiple heated ceramic bars on which the aluminum wire will melt and evaporate continuously fed from two rows of spools. The metal vapors generated from the evaporation will condense on to the film supported by a chilled drum. The figure also shows the printing module for pattern metalliza- tion (the yellow and red rollers to the left of the chilled drum). That AUGUST 2014 | FLEXO 43 Figure 1 Figure 2 Figure 3 “The packaging industry can use patterned metallization for different applications and functions, such as showing the content of a metallized package, decoration purposes, labels, and product identification and security in combination with multiple features. ”