Thermochromic inks – dynamic colour possibilities

Thermochromic inks are one of the major groups of colour-changing inks. This paper aims at discussing general aspects of thermochromic inks, dynamic colorimetric properties of leuco dye-based thermochromic inks, their stability and principle of variable-temperature colour measurement. We will analyse here a colorimetric properties of the screen-printed UV-curing leucodye thermochromic inks in red and blue shades with activation temperature of 31°C, and in green shade with activation temperature of 33°C. A small analysis of irreversible thermochromic inks will be also presented for comparison with reversible thermochromic inks. Also, a combination of different inks was made, an irreversible thermochromic ink was printed on top of the blue reversible thermochromic ink. Special attention was devoted to characterization of the colour hysteresis and the meaning of the activation temperature.