UV-curing printing inks currently represents the fastest growing market segment in the printing industry. The rapidly growing demand for low-emission products and the high processing capabilities of UV inks are contributing to the steady growth of UV-curing printing inks in the market.
In this segment, the formulation of black UV-curing printing inks, above all, poses a great challenge. On the one hand, the Carbon Black pigments absorb a portion of the UV radiation which is needed to crosslink the binders and thereby affects the curing of the ink but on the other hand the customer expects a deep-colored black, which, as a rule can be accomplished by adding fine Carbon Black Pigments.
Besides the primary particle size, the surface chemistry and structure of the applied Carbon Black also have a strong effect on the rheology of the printing ink. As a rule, the finer the pigment, the higher the viscosity of the printing ink. Carbon Black pigments that have been surface treated and those, with low structures, give lower viscosity.
For these reasons, the choice of pigments, the amount of photo-initiators, wetting agents, the composition of the binder, and the intensity of the UV-radiation must be adjusted to give the optimum properties.