The relationship between white ink coating weight and color fidelity when blocking chromatic contents in compostable flexible packaging

Abstract

As leaders in the consumer goods industry embrace compostable flexible packaging, the challenge lies in maintaining the fidelity of the design colors printed on it. When printing transparent flexible substrates, a white ink underlayer is necessary to reproduce saturated colors. Nevertheless, to comply with American and European compostability standards, white ink coating weight (Ctg Wt) cannot exceed 1 % of the total weight of the package, a limitation that restricts the amount of white ink used in reverse printed compostable packaging to as little as 25 % of the Ctg Wt used today. The objective of this study is to investigate the influence of background color, design color, and Ctg Wt on resulting design color deviations (ΔE00). A supermarket survey was conducted to identify problematic design and background colors used in retail packages. The supermarket survey confirmed that maintaining the fidelity of design colors on reverse printed flexible packages is a problem, even for packages using today’s standard Ctg Wt. The survey identified 91 collation packages where design color fidelity was compromised by the background color. For these packages, blue (in 40 % of the packages), black (in 34 %), and red/brown (in 14 %) were the most commonly encountered background colors. The most commonly compromised design colors were white (41 %), yellow (15 %), green (11 %), orange (11 %), and red (9 %). To analyze the influence of background color, design color, and Ctg Wt on design color deviations (ΔE00), a designed experiment (DOE) was conducted. The DOE explored the relationship between design color deviations and six levels of background color, six levels of design color, and two levels of Ctg Wt. The DOE showed that all three main effects (background color, design color, Ctg Wt) are significant at the .001 level. The DOE also showed that all of the interactions (three two-way interactions and one three-way interaction) are significant at the 0.05 level. After adjusting for the number of degrees of freedom, Ctg Wt had the most pronounced influence on design color deviations (ΔE00), followed by design color, and, more distantly, by the background. The strongest interaction was shown to be design color cross background color. Finally, the psychophysical causes of this interaction were identified for several design color cross background color pairs (e.g. yellow design color cross bright red background color).