How does thermal paper develop color

The production principle of thermal paper is to coat the particulate powder on the ordinary paper base. The active ingredients are phenols or other acidic substances without color dyes, which are separated by the film. Under the precondition of heating, the film melts, the powder mixes to cause a color reaction, and the color writing on the thermal paper is unstable. Easily fade, making the content of the file illegible. When the thermal paper is placed in an environment above 70°C, the thermal coating gradually begins to change color. The root cause of the discoloration needs to start from its active ingredients.

There are two key types of heat-sensitive active ingredients in thermal paper coatings: one is no color dye or leuco dye; the other is a color developer. This type of thermal paper is called two-component chemical thermal recording paper. After the thermal paper is heated, there is no chemical change between the color dye and the developer to form a color. Therefore, when the thermal paper is used to receive a signal on a fax machine or can be directly printed with a thermal printer, the text will be displayed. Considering that there are many types of dyes without color, Therefore, the color of the handwriting presented will be different, such as blue, fuchsia, black and so on. Supermarket receipts and hospital registered receipts are basically thermal paper.

Substandard thermal paper has no clear image, and the storage period of finished products is also very short. It may even lose the printing function and become a normal piece of paper.

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