engleski

Dynamic colour and appearance of thermochromic offset inks

The application properties of offset-printable air-drying thermochromic inks in red, black and magenta colours were analysed. They have an activation temperature of 31C, according to the producer data. In similar-sized microcapsules the thermochromic composite is protected from the environment. Up to 2, 5 µm large particles make the surface of thin-printed layer very uneven which considerably reduces specular gloss. It increases with layer thickness to steady value where a colour saturation also occur. The surface appearance is influenced additionally by the applied paper. The dynamic colour of samples was evaluated by several parameters suitable to describe the colour hysteresis loops. Very similar results were obtained for the red and magenta samples and somewhat different for the black ones. The decolourization process occurs in the black sample at higher temperatures and is confined to narrower temperature range, comparing to the other two samples. The other properties of colour hysteresis are practically the same.

thermochromic ink; colorimetry; hysteresis; gloss; roughness

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