Enhanced color density from high-viscosity inkjet inks

Abstract

Inkjet printing inks are typically limited to low viscosities, employing highly dilute inks with low pigment loading compared with inks for other printing processes. This reduces color intensity, limits productivity, and requires higher drying energy. This study compares standard-viscosity graphic inkjet inks (~13 mPa.s shear viscosity) with higher-viscosity inkjet inks (~60 mPa.s), traditionally considered outside the normal jetting range, for print outcomes on corrugated cardboard with both white coated and brown uncoated liners. Higher-viscosity inks imparted greater color density to the print; this was assessed as being due to both the inherently higher viscosity of the ink reducing penetration into the substrate and the higher pigment loading capable of being contained within these inks. While standard-viscosity inks tended to plateau in color intensity as ink coverage was increased, higher-viscosity inks could increase in intensity throughout the entire coverage range on coated white liner. This effect was dependent on the substrate, with the coated white liner exhibiting up to a 67% increase in maximum color density but the uncoated brown liner showing up to a 13% increase. It is envisaged that wider adoption of higher-viscosity inks can increase both color intensity and printing speed, thus making inkjet more competitive with conventional printing processes.