Dielectric Characterization of Pigment Inks for Electrohydrodynamic Jet Printing

This article presents a characterization method that could be useful for evaluating the performance of ink in electrohydrodynamic jet printing. The ink contains pigment particles and polymer (stabilizer for pigments) and has a low viscosity and a low elasticity. Depending on the medium (hydrocarbon for oil-based inks and glycol ether for polar solvent-based inks) and the type of pigment (exhibiting different colors), vast differences were found in the dielectric properties even when the viscosities of the inks were almost identical. These differences between the two series of inks were related to differences in the ion concentration n and ion mobility μ estimated from an analysis of the complex dielectric constant ε* (= ε′ – iε″) on the basis of Macdonald theory. These differences between the polar solvent- and oil-based inks are discussed in relation to the performances of the inks in electrohydrodynamic inkjet printing.