Because the production principle of thermal paper is to coat granular powder on ordinary paper base, its composition is colorless dye phenol or other acidic substances, with a film in the middle. Under the heating condition, the film melts and the powder is mixed to form a color reaction. The color handwriting on thermal paper is unstable and easy to fade, which makes it difficult to identify the contents of the document.

Commonly used lottery tickets are made of heat-sensitive paper. Ordinary thermal paper is not suitable for long-term storage, and good thermal paper can be stored for 30 years or even longer.

Extended data:

1, appearance:

If the paper is very white, it means that the protective coating and thermal coating of the paper are unreasonable and too much phosphor is added. Better paper should be slightly green. The smoothness of the paper is not high or it looks uneven, indicating that the coating of the paper is uneven. If the paper looks strong under the reflected light, the quality is not very good if the phosphor is added too much.

2, fire roasting:

The method of roasting with fire is also very simple. Heat the back of the paper with a lighter. If the color of the paper after heating is brown, it means that the heat-sensitive formula is unreasonable and the storage time may be short. If the black part of the paper has fine stripes or uneven color patches, the coating is uneven.

Good quality paper should be dark green (with a little green) after heating, with uniform color blocks, and the color gradually fades from the center to the periphery.

3. Comparison and identification of sunlight exposure:

After the printed paper is smeared with a fluorescent pen, it is dried in the sun (this can speed up the reaction of the heat-sensitive coating to light), and which paper turns black the fastest means the shorter the storage time.

Baidu encyclopedia-thermal paper