engleski

Spectroscopic evaluation of color play effect of thermochromic liquid crystal printing inks

Color changes of a thermochromic liquid crystal (TLC) ink printed on a black substrate are clearly observed by naked eye, therefore it is reasonable to expect that every approach recommended for color measurements of samples with solid color would be appropriate. In addition, the published spectroscopic analyses of TLC inks do not provide any guidances and limitations for the measuring geometry. On the other hand, our study demonstrates that spectroscopic measurements of such samples are not so straightforward. When using most simple and commonly used measurement equipment with directional illumination and viewing approach, the temperature-dependent spectral features resolve in a narrow spectral region which gives only a small part of the color play effect. Detection of the entire effect requires using integrating spheres, which spatially integrate radiant flux reflected on a sample in any direction ; better results are obtained by spheres with larger diameter. The comparision of spectroscopic and colorimetric results obtained when different measurement geometries are applied on the same sample may demonstrate certain properties of the liquid crystal material inside microcapsules and help in understanding some details of the optical properties of the ink layer.

thermochromics ; liquid crystal ; printing inks ; optical properties ; measuring geometry

Glavna autorica: Jakovljević, Maja.