Study of correlation between ink trapping and color difference in overprint

Abstract

The ink trapping value is one of the important parameters affecting the appearance of secondary colors in overprint. Usually, the ink trapping parameter is traditionally calculated based on the solid density values of the primary colors and the overprint color. These density values are measured by the complementary color filter of the color final ink layer, and these ink trapping values can be calculated using the Preucil, Ritz, or Brunner formulas. Furthermore, the density measurement is more suitable for testing the color printing and not for overlapping assessment because these density values are measured by the complementary color filter of the second color ink. The ink has a specific transmittance, and light is not only absorbed but also scattered inside the ink layer, so the total density of the overlapping colors will be less accurate. As a result, the color measurement method is used to describe the effect of ink trapping of the second ink layer on the first layer of ink. The main idea is to use the color difference value to evaluate the ink trapping ability. In this paper, the author has quantitatively analyzed the correlation between the percentage value of ink trapping and the color difference parameter ΔEab*. The studied results show that the ΔEab* value has a linear correlation with the ink trapping value calculated according to the traditional methods based on density values. This result is also aimed at the fluctuant tolerance of ink trapping ratio during four-color printing to achieve the standard color value quickly.