# The Impact of Underlying Opaque White Coating Parameters on Flexographic Print Quality
## 4 Results and Discussion
### Analysis of Colorimetric Values in Color Samples  
The influence of anilox roller volume on the colorimetric values of the process colors and the spot red P 485 C color is shown using the color differences. The color difference was determined based on the CIELAB value of color samples measured on the white background, and calculated using Equation (2) for CIEDE2000 (\(K_{L}=K_{C}=K_{H}=1\)). The values of the DE2000 color differences and difference in lightness (\(\Delta\)L) for the last two stages of the experiment, compared to the initial state from the first stage of the experiment for all tested samples, can be found in Table 4.  
Generally speaking, the values of color differences in the second stage of the experiment compared to the initial state were in the range of \(\Delta\)E2000 = 0.5-1.0. According to the classification of color differences (Table 2), this means that despite the higher white ink film thickness on printouts, the observer could hardly or very slightly visually distinguish the same color samples [(39)]. The values of the color differences in the third stage of the experiment were significantly higher (\(\Delta\)E2000 = 2.0-2.7), which was consistent with the increase in color samples ink opacity. According to the classification mentioned, the color differences were noticeable to an ordinary observer. This means that a significant increase ink layer (6 cm\({}^{3}\)/m\({}^{2}\)/4 BCM) was necessary for an ordinary observer to notice the final color difference. Yellow and cyan showed more sensitivity to an increase in anilox volume for white ink than other chromatic colors. This effect can be attributed to their greater brightness than magenta and the red spot color. By increasing the white ink layer, all tested color samples generally became lighter (\(\Delta\)L > 0), except for black, which became darker (\(\Delta\)L < 0). This can be connected with the greater transparency of chromatic inks compared to black ink, which still had higher opaque with equal ink film thickness.  
Figure 9 graphically shows CIEDE2000 color differences for all color samples in the two last stages of the experiment compared to the initial state where an anilox roller volume of 10 cm\({}^{3}\)/m\({}^{2}\) was applied.  
According to the results of the research, a significantly thicker film of white ink is needed, which would result in a significant increase in opacity in order to visually notice the color difference on printouts. However, the question of the efficiency and economy of applying thicker white ink film arises. A better insight into the cost-effectiveness of increasing the ink film thickness can be shown through the total costs of white ink, especially for larger print runs.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Color Samples**} & \multicolumn{4}{c}{**Anilox Roller Volume (cm\({}^{3}\)/m\({}^{2}\))**} \\ \cline{2-5}  & \multicolumn{2}{c}{**Stage II: 13**} & \multicolumn{2}{c}{**Stage III: 16**} \\ \cline{2-5}  & \(\Delta\)L & \(\Delta\)E2000 & \(\Delta\)L & \(\Delta\)E2000 \\ \hline C & 0.36 & 0.489 & 2.35 & 2.448 \\ M & 0.18 & 0.838 & 1.92 & 2.043 \\ Y & 0.51 & 0.712 & 2.82 & 2.694 \\ K & –0.73 & 0.931 & –2.23 & 2.306 \\ R & 0.36 & 0.841 & 1.76 & 2.246 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Color differences \(\Delta\)E2000 and differences in lightness \(\Delta\)L for all tested color samples.