Mechanical Stability of Different Black Inks Printed on Packaging Paper With a Metallised Surface

Today in the graphic industry we are witnessing the rapid growth of the packaging sector, with the consumption of paper and printing inks increasing every year. Therefore, it is important to study the interaction between the printing substrates (paper and cardboard) and the applied inks in order to ensure the quality of the packaging prints and the adequate protection of the wrapped products. The goal of this study is to evaluate the mechanical stability (i.e., rubbing resistance) of printed paper-based packaging materials, which is crucial for the quality of the printed packaging. In the study, metallised paper was used as a printing substrate, while printing was carried out using four different black inks (three conventional and one UV ink) by offset printing technique. All metallized printing papers are coated with a white base ink in one or two layers before being printed with black ink. The mechanical stability of all samples was measured as a colour difference (ΔE2000) before and after the performed rubbing test. The test was done in three iterations of the rubbing cycle under two different weights, simulating the conditions of the packaging during transport and general handling. The colorimetric values of CIE L*a*b* components were further analysed to determine if the colour difference was greater in lightness or in tone components of colour. These findings can help determine which combination of printing substrate and ink should be used, ensuring the optimal quality of product packaging.