The effect of Rheological Property of Ink on the Generation of Inkjet Droplet

H. Yoo, C. Kim
Korea University, KR

Keywords: suspension, rheology, shear thinning

Summary:

In inkjet printing the ink is usually a suspension of particles in liquid. Suspensions usually have shear-thinning viscosities. Also they have large zero shear viscosities. To understand the jetting and drop generation mechanism we investigated a similar system for which the rheological properties are well characterized. We prepared different kinds of ink by dissolving xanthan gum in the mixtures of water and glycerin. The solutions show different levels of zero shear viscosity, power law exponent and infinite shear viscosity. Using a drop-on-demand (DOD) inkjet printing system, the diameter and velocity of droplet were measured and the effects of the rheological properties were examined. The result shows that drop velocity is strongly affected also by zero shear viscosity. Also depending on zero shear viscosity the operating window has to be changed to generate droplets. At a fixed zero shear viscosity, the fluid with smaller infinite shear viscosity gives a smaller drop velocity with a larger drop diameter. This can be ascribed to the blunted velocity profile of the strongly shear-thinning fluid. It is concluded that the zero shear viscosity is also strongly affecting the drop generation characteristics in addition to the infinite shear viscosity.