engleski

Ultraviolet protection of thermochromic printings

Light with larger photon energy has a detrimental effect on colour and appearance over longer periods of time. Conventional printing inks usually have an acceptable lightfastness, mainly because of the high stability of applied pigments. On the contrary, novel smart printing inks have more sophisticated pigments which, in most cases, are not crystalline and therefore have a low resistance to light and also to high temperatures and some chemicals, thus needing additional protection. Our work is based on protection of thermochromic printing inks against UV light. Such inks have microencapsulated thermochromic composite (leuco dye, developer, solvent). A theromochromic ink applied in different thickness was tested. A lacquer was applied over printed samples as a protective layer. The dynamic colour of protected theromochromic layers was compared with the properties of the corresponding unprotected samples.

thermochromics; lightfastness; spectral distribution of light; ultraviolet light; colour hysteresis

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