Time-dependent rheology effects on print quality using water-based ink compositions

An investigation into the dependence of water-based gravure ink rheology oil image quality was conducted. We prepared a dilution series of a water-based process red gravure ink system ranging from 20 (fast ink) to 60 (slow ink) seconds (#2 Zahn Cup). Upon gravure printing using a range of screen resolutions from I 10 to 200 LPI, we found that print defects exhibited as long streaks devoid of ink within the image area increased as the gravure Cell volume decreased. We initially attributed these results to pigment agglomeration. The process red ink, more so than the other two process colors, bodied significantly over a short period of time. Sedimentation experiments suggest that this increase in viscosity may be do more to pigment: resin associations rather than simple pigment agglomeration. A rheology and thermodynamic investigation continues to explore the reasons for this bodying reaction oil the molecular level.