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Non-yellowing UV curable clear varnish for drop on demand piezo inkjet printing heads

The use of a clear varnish is widespread in digital printing workflows as OVP (Over Print Varnish) or as dedicated Spot Varnish. However a lot of commercial UV curable varnishes have a persistent yellowish appearance due to a mismatch of photoinitiators and UV-monomers that are used in the formulation.
ChemStream developed a non-yellowing UV curable varnish for high speed drop on demand industrial inkjet applications. The varnish has:

➢ An excellent jetting performance on DOD printing heads
➢ An optimized surface tension for uniform spreading.
➢ An optimized photoinitiation / monomer system to achieve a very neutral color

In the following graphs a comparison has been made between a commercial UV-curable varnish and the optimized ChemStream UV-curable varnish, by plotting the a* and b* values of a cured layer (thickness of 12 μm) on a standard Black & White Leneta chart.