A special rank among the printing inks has been obtained by those printing inks applying metal pigments, iridescent pearl effect pigments, or interference pigments.
This type of printing inks are additionally known as gold and silver, or inks that display a metal-like nature. Gold bronze pigments are purchased from ground brass alloys with a varying quantity of copper and zinc. The bigger the copper content material in the alloy, the redder the gold bronze. The technique employed in the manufacture of bronzes enables the particle measures of the metal pigments to be adopted for the particular printing technology. For offset printing this is 3.5 micro meter; for rotogravure and flexographic printing 8-9 micro meter (the ink film thickness is for that reason greatly 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 assumed. After melting in induction furnaces, the liquid molten mass is lacerated by a compressed air stream. The end product is a metal grind with a metallic-ally polished surface. This kind of inks dry like a usual offset printing ink by absorption and oxidation.
The latest developments are gold and silver inks which are made up on water-dilatation dispersion varnishes and are connected 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 larger brilliance than the usual gold and silver printing inks which are based on varnish.
Inks with pearlescent effect pigments enable a characteristic gloss of the printed image similar to the iridescent gloss of pearls. This kind of pigments have a mica core which is covered by one or more metal oxide components.
Printing inks with metal pigments can be applied in rotogravure and flexographic printing. The construction of these inks is identical to that of organic or inorganic color pigments.
Silver-metallic inks which are combined with colored inks in different measure are labeled as satin inks.
UV Inks – UV curing inks have a totally different structure than standard printing inks. They are largely used in the printing of non-absorbent materials such as plastics and metal sheets, but also for high-grade card goods and labels. There are UV inks for all conventional printing technologies also for the ink jet technique.
UV curing printing inks are made up of:
Some great benefits of these inks are
• “abrupt”(1-100 ms) drying or curing so that aluminum melting induction furnace finishing of the print is possible,
• free of solvents,
• no drying in the inking unit or on the rollers (thus-less necessity of cleaning of the inking units),
• zero or only minimum warming of the substrate,
• extremely high mechanical strength and chemical resistance.