Void defect formed in wiping step of gravure printing

In order to print various functional components for printed electronics, inks with different viscosities may be used in gravure printing. In this study, influence of ink viscosity on gravure printing quality at individual cell level is reported. In gravure printing experiments using dielectric Barium Titanate (BaTiO3) nanoparticles inks of different viscosities, a void defect can be observed at the front edge of the printed pattern of an individual engraved cell. And the void became larger both for ink with higher viscosity and at higher printing speed. In our experiments, it was noticed that the voids can lead to open defects in the whole printed pattern of high viscosity ink, undermining the printing quality. In order to study the forming mechanism of the voids, experimental results were analyzed based on computational fluid dynamic (CFD) simulation studies of wiping step in the gravure printing process. Simulation confirmed that the observed void is caused by the unfilled space at the leading edge of the engraved cell during wiping. Effects of wiping speed and ink viscosity have been investigated, and the simulation results are consistent with experiments. Based on the experimental and theoretical results, it can be concluded that, for gravure printing using high viscosity ink, printing speed needs to be slowed down in order to reduce defects. The present study enhanced understanding of ink transfer in gravure printing and provided a guide line for high quality gravure printing.