What is the principle of printing color thermal label paper?

The principle of printing colored thermal sensitive label paper is mainly based on the chemical reactions in the thermal sensitive coating. Here is a detailed explanation:

1、 Thermal sensitive coating composition

The manufacturing principle of colored thermosensitive label paper is to apply a special layer of "thermosensitive coating" or thermosensitive color changing layer on the base paper. This thermal sensitive coating is mainly composed of two key components:

Colorless dye (hidden dye): This is a special dye that is colorless at room temperature. When subjected to heat, this dye undergoes a chemical reaction, resulting in the appearance of color.

Color developer: In addition to colorless dyes, thermal sensitive coatings also contain color developers. Under heating conditions, colorless dyes undergo chemical reactions with colorants to produce color.

2、 Working principle

When colored thermal label paper passes through a thermal printer, the print head generates heat. This heat is transferred to the thermosensitive coating on the label paper, causing a chemical reaction between the colorless dye and the color developer. Specifically:

Temperature change: As the temperature of the print head increases, the colorless dye and color developer in the thermal sensitive coating begin to melt and mix.

Chemical reaction: The melted colorless dye meets with the developer molecule and undergoes a chemical reaction, resulting in the color appearing. This chemical reaction is rapid, so the moment it moves on the print head, the required image, text, barcode or QR code information will appear on the label paper.

3、 Thermal label paper structure

Color thermal label paper is usually divided into three layers:

Paper based: The bottom layer that provides basic support and strength for label paper.

Thermal sensitive coating: The intermediate layer contains colorless dyes and colorants, and is the key layer for producing color.

Protective layer (optional): The topmost layer used to protect the thermosensitive coating from external environmental damage, such as chemical corrosion, pollution, etc. Meanwhile, the protective layer can also slow down the deterioration of printing paper and extend its storage time.

4、 Application and Limitations

Color thermal label paper is widely used in various fields such as retail, logistics, medical, etc. due to its advantages of fast printing speed, easy operation, and no need for ink cartridges. However, it also has some limitations, such as the durability of printed content may not be as good as some other printing methods (such as laser printing), and prolonged exposure to high temperatures or strong light may cause color fading or deterioration.

In summary, the principle of printing colored thermal sensitive label paper is based on the chemical reaction between colorless dyes and color developing agents in the thermal sensitive coating under heating conditions, resulting in color development. This principle makes colored thermal label paper a fast, simple, and economical printing solution.