Duy Linh Nguyen

Quality control of embossed hologramsby measuring gloss and color values

Embossed holograms are increasingly often used for the decorative refinement of printed products. So far, there has not been much scientific research about quality control of embossed holograms as well as research about the influence of the background color on the quality of embossed holograms. For this purpose, hologram samples with different background colors were produced in a laboratory setup, using the principle of UV embossing. At first, the quality of the samples was evaluated through a visual experiment. The conceptual design of that experiment was part of this research. Second, gloss and color values were measured with conventional hand-held measuring instruments used by the graphics industry. Color measurements were conducted with an X-Rite MA98 multi-angle spectrophotometer and measurements of gloss values with a BYK micro-TRI-gloss gloss meter. The comparison of the results of the visual experiment and the color measurement led to the conclusion that conventional color measuring instruments can evaluate the influence of the background color on the quality of embossed holograms. It was found out that calculating the color difference ΔE*ab between background color and sample can be used to recreate the results of the visual experiment, whereas the samples’ chroma C*ab is not suitable for evaluating the influence of the background color. The number of provided measuring geometries is a limitation of this approach. Moreover, the comparison of the results of the visual experiment and the gloss measurements showed that conventional gloss meters cannot evaluate the influence of the background color. However, conclusions concerning the UV embossing process can be drawn from a sample’s gloss. This suggests the usage of gloss measurement for process control.