Dynamic Wetting of Water-Based Inks in Flexographic and Gravure Printing
The theory of wetting is reviewed with respect to ink transfer which is based upon measured dynamic surface tension and calculated dynamic spreading coefficient. Laboratory gravure ink transfer results are presented for model water based inks with and without isopropanol as the cosolvent on untreated and corona treated polyethylene film. A mechanism of surface tension driven convection is proposed which is consistent with experimental results. The conclusion, which is based upon the proposed mechanism, is that uniform coverage of a water based ink on a nonpermeable substrate is facilitated by the presence of a high vapor pressure low surface tension cosolvent such as isopropanol. When no cosolvent is present, de-wetting and degree of ink mottling appears to be controlled by dynamics longer than one second.
KeywordsSurface Tension Dynamic Surface Tension Spreading Coefficient Equilibrium Surface Tension Gravure Printing
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