How does thermal paper achieve inkless printing?

In daily life, we all come into contact with thermal sensitive paper, such as cash receipts, instrument records, etc. Unlike ordinary paper, thermosensitive paper generates imprints by heating and does not require the use of ink or ribbons. So, how does it achieve this? This article will provide a detailed introduction to the working principle of thermosensitive paper and the methods for achieving inkless printing.

The principle of realizing inkless printing with thermal paper is to use a property called Thermochromism.
Thermochromism material refers to the material whose visible spectrum changes due to heating within a certain temperature range.

In thermal printers, thermal paper usually consists of two layers, one of which is the Layer of rods and cones, and the other is the protective layer. When the heating element heats the thermosensitive paper, the thermosensitive dye in the Layer of rods and cones will be heated to its reaction temperature, so that a chemical reaction will occur, and the color will change to form an impression. Thermotropic dyes will decompose and react into a certain colored product, which can be selected according to reaction temperature, molecular structure, etc., to make the output display beautiful and high contrast.

Therefore, the reason why thermosensitive paper can achieve inkless printing is that thermal dyes can undergo chemical reactions after being heated within a certain range, and this color change effect can be maintained for a long time, thus achieving long-lasting imprinting.