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Acta graphica : journal for printing science and graphic communications, Vol. 23 No. 1-2, 2012.

Original scientific paper

Dynamic Colour Possibilities and Functional Properties of Thermochromic Printing Inks

Rahela Kulčar orcid id orcid.org/0000-0003-3599-9806 ; Faculty of Graphic Arts, University of Zagreb, Croatia
Marta Klanjšeg Gunde ; National Institute of Chemistry, Ljubljana, Slovenia
Nina Knešaurek ; Faculty of Graphic Arts, University of Zagreb, Croatia

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Abstract

Thermochromic printing inks change their colour regarding the change in temperature
and they are one of the major groups of colour-changing inks. One of the
most frequently used thermochromic material in printing inks are leuco dyes. The
colour of thermochromic prints is dynamic, it is not just temperature-dependent,
but it also depends on thermal history. The effect is described by colour hysteresis.
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. Thermochromic material
is protected in round-shaped capsules. They are much larger than pigments in conventional
inks. The polymer envelopes of pigment capsules are more stable against
oxidation than the binder. If these envelopes are damaged, the dynamic colour is
irreversibly lost. Our aim is to analyse the colorimetric properties of several reversible
screen-printed UV-curing leuco dye thermochromic inks with different activation
temperatures printed on paper. A small analysis of irreversible thermochromic
inks will be presented for comparison with reversible thermochromic inks.
Moreover, so as to show interesting possibilities, a combination of different inks
was made, an irreversible thermochromic ink was printed on top of the red and
blue reversible thermochromic inks. Special attention was given to the characterization
of colour hysteresis and the meaning of activation temperature.

Keywords

Thermochromic inks; colour hysteresis; pigment capsules; variable-temperature colour measurement

Hrčak ID:

86090

URI

https://hrcak.srce.hr/86090

Publication date:

11.7.2012.

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