Analysis of ink penetration depth inside substrates for secondary packaging

Abstract

Today, the packaging industry is experiencing growth, which in turn leads to an increased amount of packaging waste. To reduce packaging waste, it is necessary to reduce the use of packaging and combine primary and secondary packaging into one. For secondary packaging, which is usually made of paper or cardboard, to replace primary packaging, the penetration depth of the ink into the substrate must be checked, as this is the most important indicator that the product it protects is not affected. The low penetration depth of the printing ink into the interior of the paper printing substrate is crucial for the safety of using this packaging. The penetration depth of the ink into the printing substrate is a very important factor in primary and secondary packaging, as it affects the overall efficiency of the packaging, health, safety, and print quality. The most important factors influencing the ink penetration depth are the porosity of the substrate, the composition of the substrate, the surface energy of the substrate, and the viscosity of the ink. This research is based on analysing and comparing the ink penetration depth in different printing materials most commonly used for secondary packaging. Based on the microscopic analysis of cross-sections of offset prints produced with cyan ink, the maximum ink penetration depth was estimated and observed in parallel with the ink coverage of the substrate. Microscopic images of the printed parts, calculated using image analysis software, were used to determine the coverage of the printing substrate. This research aims to determine which secondary packaging material achieves the lowest penetration depth of the printing ink into the substrate, which opens up the possibility of using these substrates as primary packaging substrates. In this way, the use of polymeric, ecologically unacceptable materials, which are most commonly used as primary packaging substrates, is reduced, and the use of paper or cardboard materials for primary packaging is increased. The results obtained show that the GT2 and GC2 substrates printed with higher cyan ink halftone values contain the lowest ink penetration values into the printing substrate. When printing with a 40% halftone value of cyan ink, the lowest values were achieved when printing on the substrates KD silk and GC2. The ink penetration from the unprinted side of the print was also observed and measured. Ink penetration from the unprinted side of the print occurs when the prints are output after printing, with the unprinted side of the print placed in a stack on top of the printed side.