![]() More so when heated or brought near a candle flame or exposed to sunlight. ![]() It is common to see these printouts fade over time, even when stored at normal room temperature. Usually black colour printouts are obtained, but it is also possible to generate red printouts by controlling the temperature of print heads. When the print-head made of regular array of minuscule heating elements receives the signal for printing, it raises the temperature to the melting point of the organic coating to cause print impression on the paper roll through the process of thermochromism. The paper used is a special thermal paper that is impregnated with mixture of a dye and a suitable matrix such as a fluoran leuco dye and an octadecylphosphonic acid. Thermal printing essentially works by creating impressions using print-heads over a special kind of paper roll (found in ATMs, vending machines) coated with organic dyes, waxes. It is based on the principle of thermochromism, a process of change in colour with heating. ATM receipts are made by a simple printing method called thermal printing.
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