Color Prediction of Two-Ink Layer Overprint Based on Solid Print Color Model

Abstract

Multicolor printing inevitably results in the overprinting of ink layers and wet-on-wet printing. In this case, the ink trapping rate is defined to describe how much less the volume of the second ink printed on the wet ink layer is than it printed on the dried ink layer or on the blank paper. In order to predict accurately the color of overprint solids, a new color prediction model was built on the basis of the simplest two-color overprint solid in this paper. Firstly, the uneven distribution of ink layers in two-color overprint solid was reduced to evenly distributed ink layers. As a result, the ink trapping rate was provided in which the rate of thickness of second ink layer printed on the wet first ink layer or on the blank paper was calculated. Secondly, referring to the color prediction model based on the light scattering characteristics of the paper and ink layer, the necessity of selecting the simulation ink layer to measure the optical parameters of ink layer was explained, a new preparation method of the simulation ink layer was described, an algorithm for calculating the thickness of ink layer with the reverse transmittance of ink layer based on a specific wavelength was built, a new production method of experimental samples to simulate accurately the process of overprinting was provided, the necessity and method of correcting the reflectance of simulation ink layer was emphasized, the color prediction model of the two-color overprint solid based on a solid print was given in this paper. Finally, by comparing the predicted and measured values of the experimental samples, the proposed model can accurately predict the color of two-color overprint solids.