What is Thermal paper ?

Thermal paper is a special type of paper coated with a chemical that changes colour when exposed to heat. Hence its name!

 It is mainly used in thermal printers, cash registers, PDQ and credit card terminals.

The surface of the paper is coated with a special heat reactive dye. When the dye is heated above its melting point, it reacts with the acid in the paper, and transforms to its colored form.Its like magic !

Usually, the coating will turn black when heated, but difefernt dyes that turn blue or red can also be used. While an open heat source, such as a flame, can discolor the paper, a fingernail swiped quickly across the paper will also generate enough heat from friction to activate the dye.

Multicolor thermal paper first became available in the early 1990's with the introduction of the Fuji Thermo-Autochrome (TA) system.This was followed in the early 2000's by the development of the Polaroid "zero-ink" (ZINK) system. Both of these methods rely on multi-layer coatings with three separate colorising layers, but different methods are used for independent activation of each layer.

Most direct thermal papers require a protective top-coating to:

  • reduce fading of the thermal image caused by exposure to UV light, water, oils, grease, lard, fats, plasticizers, and similar causes
  • provide improved print head wear
  • reduce or eliminate residue from the thermal coating on the thermal print heads
  • provide better anchorage of flexographic printing inks applied to the thermal paper
  • focus the heat from the thermal print head on the active coating.