Thermal paper protection coat slurry （topcoat）

The main functions of the protection layer can be summarized as follows:

1. Improve chemical resistance and prevent fading or blackening of the ink.

This is the core function of the protective layer. Thermal paper ink (generated by the reaction of dyes and developers) is very fragile and easily reacts with external substances.

• Prevent plasticizer corrosion: This is the most common destructive factor. Many plastic products (such as PVC credit cards, plastic bags, and document bags) contain plasticizers. Without a protective layer, when thermal paper receipts come into contact with these items, the plasticizers will penetrate the paper layer and react with the unreacted developers, causing the ink to blacken over a large area or disappear completely.

• Resist grease, alcohol, and solvents: Kitchen grease, hand sanitizer, alcohol (such as alcohol-based hand sanitizers), and certain organic solvents (such as acetone) can all damage thermal ink. The protective layer effectively blocks the corrosion of these chemicals.

2. Improve scratch and abrasion resistance.

The surface of thermal paper is relatively fragile and easily scratched.

• Prevents physical scratches: During daily handling, friction, and contact with hard objects (such as keys and coins), the protective layer provides a hard surface, protecting the underlying thermal layer from scratches and preventing illegible print or scratches.

• Improves mechanical durability: For documents requiring high-speed operation in printers or frequent processing (such as logistics orders), abrasion resistance is crucial to prevent damage during printing and transportation.

3. Improves printhead protection

The thermal printhead is in direct contact with and heated by the paper surface during operation.

• Reduces friction: A smooth protective layer reduces friction between the printhead and paper, resulting in smoother paper feeding and less wear on the printhead, extending its lifespan.

• Prevents contamination: During printing, tiny particles or coating substances may adhere to the printhead. Long-term accumulation can lead to decreased print quality (white lines) and even printhead damage. A high-quality protective layer effectively reduces this contamination.

4. Improved Water Resistance and Moisture Resistance

• Water and Moisture Resistance: Moisture is one of the enemies of thermal paper. Once exposed to moisture, the thermal coating may react prematurely, causing the paper background to turn gray or the text to become blurry. The protective layer can effectively block moisture and liquid water, ensuring that the paper remains clearly legible in humid environments (such as refrigerators, cold storage, and rainy days).

5. Adjusted Feel and Appearance

• Improved Feel: Adding a protective layer can make the paper feel smoother and more pleasant to the touch.

• Controlled Gloss: The formula of the protective layer can be adjusted to give the paper different visual effects, such as high gloss or matte, to meet different aesthetic needs.