The paper is impregnated with a solid-state mixture of a dye and a suitable matrix; a combination of a fluoran leuco dye and an octadecylphosphonic acid is an example. When the matrix is heated above its melting point, the dye reacts with the acid, shifts to its colored form, and the changed form is then conserved in metastable state when the matrix solidifies back quickly enough.
Most direct thermal papers require a protective topcoating to:
Reduce fading of the thermal image caused by exposure to UV light, water, oils, grease, lard, fats, plasticizers, and similar causes
Provide improved printhead wear
Reduce or eliminate residue from the thermal coating on the thermal printheads
Provide better anchorage of flexographic printing inks applied to the thermal paper
Focus the heat from the thermal printhead on the active coating.
Thermal paper is cleaner than your standard ink, produces a crisper resolution, and is ultimately cheaper. Though thermal paper used to be considerably more expensive, the price has come down in recent years, thanks in part to better technology that allows its manufacturers to produce it at a more reasonable cost. Moreover, a thermal paper roll is quieter than bond paper, which is an added bonus for any shopper at the end of a long day.
You can buy thermal paper from your local office store and pay more, or you can order it in bulk along with your POS paper and other cash register supplies. Purchasing over the Internet also gives you added convenience -- you can modify your order with just a few mouse clicks, buy additional products, or speak with customer service about any questions you might have. So don't spend precious hours sitting in your car trying to cram in a quick stop at the office store between work and home. Go online and save your money--both on thermal paper and other office necessities.
