Special Inks in Printing: Metallic/pearlescent And UV Inks

A specific status among the printing inks is earned by those printing inks working with metal pigments, iridescent pearl effect pigments, or interference pigments. This kind of printing inks are additionally named gold and silver printing inks, or inks that reveal a metal-like nature. Gold bronze pigments are extracted from ground brass alloys with a various amount of copper and zinc. The bigger the copper content material in the alloy, the redder the gold bronze. The technique utilized in the manufacture of bronzes enables the particle measures of the metal pigments to be modified to fit the various printing technology. For offset printing this is 3.5 μm; for rotogravure and flexographic printing 8–9 μm (the ink film thickness is for that reason substantially higher than is usual with conventional inks/pigments (0.1–3 μm). For the production of silver pigments, aluminum with a purity of 99.5% is regarded. After melting in induction furnaces, the liquid molten mass is lacerated by a compressed air stream. The end product is a metal powder with a metallic refined surface. This type of inks dry like a usual offset printing ink by absorption and oxidation. Current progressions are gold and silver printing inks which are built up on water-dilatation dispersion varnishes and are transferred via coating units with a chambered blade system . These inks dry by assimilation straight into the substrate and evaporation of the water contained in the ink. They have a clearly superior brilliance than the regular gold and silver printing inks which are based on varnish. Inks with pearlescent effect pigments allow a characteristic gloss of the printed image similar to the iridescent gloss of pearls. This type of pigments possess a mica core which is covered by one or more metal oxide components. Printing inks with metal pigments can also be utilized in rotogravure and flexographic printing. The constitution of these inks is identical to that of organic or inorganic color pigments. Silver-metallic printing inks which are combined with colored inks in various amount are categorized as satin inks. UV Inks. UV curing printing inks have a quite different structure than conventional printing inks. They are predominantly used in the printing of non-absorbent substances such as plastics and metal sheets, but also for high-grade card goods and labels. There are UV inks for all conventional printing technologies and also for the ink jet technologies. UV curing printing inks are made up of: • monomers, • polymers/oligomers, • pigments, • additives, • photo-initiators/synergistic. The good sides of these inks arern• “abrupt”(1–100 ms) drying or curing so that immediate finishing of the print is possible, • free of solvents, • no drying in the inking unit or on the rollers (thus-less requirement for cleaning of the inking units), • zero or only minimum heating of the substrate, • high mechanical strength and chemical resistance. The weaknesses arern• all of these inks are more expensive than standard printing inks, • dryer construction is at a high technical stage, • raised ink handling request for reasons of health and safety.