| Popis: |
Obravnavala sem temperaturno občutljive materiale, ki nepovratno spremenijo svojo barvo pri značilni temperaturi. Preiskovala sem štiri vzorce: termični papir, komercialno dostopno tiskarsko barvo in tiskarsko barvo, ki je še v razvoju (dve različni izvedbi). Preučevala sem vpliv dveh različnih vrst segrevanj na nastalo barvo vzorca. Statičen način je bil opravljen v laboratorijski pečici z nastavljivo temperaturo, dinamičen pa na posebni napravi z možnostjo nastavitve hitrosti segrevanja in temperature. Izmerila sem refleksijske spektre v vidni svetlobi in jih pretvorila v barvne vrednosti. S pomočjo posebnega programa sem te vrednosti preračunala v barvne razlike nastale na vzorcu v odvisnosti od temperature. Obravnavani vzorci se med seboj razlikujejo po naslednjih podrobnostih: a) temperaturnem območju, kjer poteka sprememba barve, b) velikosti barvne razlike med neobarvanim in popolnoma obarvanim stanjem, c) odvisnosti barvne spremembe pri dani temperaturi od termične zgodovine, d) razliki v obarvanju pri statičnem in dinamičnem segrevanju vzorca. Rezultati kažejo, da je barva analiziranih vzorcev praviloma neodvisna od termične zgodovine, da imajo vsi obravnavani vzorci podobno odvisnost obarvanja od temperature segrevanja in da imajo vsi segreti vzorci stabilno barvo. Zanimivo pa je, da se pri termičnem papirju celotno obarvanje pokaže šele po ohladitvi vzorca, kar pri ostalih vzorcih nisem opazila. Temperature sensitive materials that permanently change its color at a characteristic temperature were analysed. Four different samples were tested: thermal paper, a commercially available printing ink and printing ink, which is under development (two different versions). The influence of static and dynamic heating on the color of the sample were analysed. The static heating was obtained in a laboratory oven with adjustable temperature, while for the dynamic one a special device with the adjustable heating rate and temperature range was used. Visible reflection spectra were measured and used to determine the corresponding color values. These color values were applied to calculate the differences of color appearing in the sample in dependence on the heating temperature. The analysed samples are different in the following details: a) the temperature range where the color changes, b) the size of the color difference between the initial and completely colored state, c) depending of the color change at given temperature on the thermal history, d) different coloration in the case of static and dynamic heating of the sample. In general, the color of the analysed samples is independent on their thermal history. All of the analysed samples have similar dependence of the color on the heating temperature and have a stable color in the fully coloured states. Interestingly, the analysed thermal paper shows the entire coloration only after the corresponding sample has cooled down, which was not observed on any other sample. |
