What is the color rendering principle of color thermal label paper?

The color development principle of color thermal label paper is mainly based on physical and chemical reactions, the specific process is as follows:

First, foundation structure

Color thermal label paper usually has a multi-layer structure, mainly including a paper base, thermal coating and a protective layer (sometimes the protective layer can be omitted). Among them, the thermal coating is the key to color development, which contains two main chemical components: leach dye (also known as colorless dye) and color development agent (in some cases may be acidic substances or other chemicals that can react with leach dye).

Second, the color development process

1.Dark dye properties: Dark dyes are colorless at room temperature, which makes thermal paper look indistinguishable from ordinary paper when not heated.

2.Temperature change triggers reaction: When the thermal paper passes through the thermal printer, the heat of the print head acts on the thermal coating. As the temperature rises, the leach dye and the developing agent (or acid) successively melt into a liquid state, making the originally bound molecules become active.

3.Chemical reaction color development: In the liquid state, the leach dye molecule meets the color development agent molecule and immediately reacts. This reaction results in the conversion of the leucous dye into a colored product, resulting in the appearance of a predetermined color on the thermal paper. The type of color depends on the type of leach dye and color developer used, common blue, purple, black and so on.

Third, the complement of physical reaction color rendering

It is worth noting that in addition to the above principle of color development based on chemical reactions, there are also some types of thermal paper with physical reaction color development. For example, the physical thermal paper may achieve color rendering through the physical state transformation of the thermal material after heating (such as melt transparent type, melt transfer printing, thermal sublimation type, etc.). However, the application of these physical reaction color sensitive paper in color thermal label paper is relatively small, and its color development mechanism is different from that of chemical reaction color development.

Fourth, summary

In summary, the color rendering principle of color thermal label paper mainly depends on the chemical reaction of the dark dye and the color developer (or acidic substance) in the thermal coating under temperature changes. This reaction allows the originally colorless thermal paper to show a predetermined color when heated, thus achieving the printing effect. This principle not only simplifies the printing process (without ink and other consumables), but also makes color thermal label paper widely used in supermarkets, shopping malls, fruit stores, bakeries and other places.