Research on the Color Development and Waterproofing Properties of Thermal Paper

Due to the reversible nature of the thermal color development reaction, thermally recorded images are prone to fading when exposed to water and organic solvents such as oil. Compared with other printing methods, thermally recorded documents have poor preservation properties. To improve the durability and weather resistance of thermally recorded images, papermakers have conducted extensive research on the production process and color layer formulation of thermal paper. This work focuses on two aspects: first, the protective coating method, which involves coating a protective layer onto the surface of ordinary thermal paper to prevent the color layer from directly contacting water or other damaging solvents in the environment; second, improving the thermal coating method, which involves improving the formulation or coating process of the thermal paper's color layer, such as using special chemicals or microencapsulation coating methods to improve the stability of thermal images.

The color development properties of thermal paper reflect the sensitivity and image clarity of thermal recording, while preservation reflects the stability of thermally recorded images; these are two important indicators for evaluating the performance of thermal paper.

Conclusions:

1. In the fluorane-based colorless dye/bisphenol A/stearamide system, polyvinyl alcohol adhesives exhibit the best static color development performance of thermal paper when used as the chromophore adhesive, followed by carboxylated styrene-butadiene latex. Acrylic latex results in the worst static color development performance.

2. In the fluorane-based colorless dye/bisphenol A/stearamide system, when using a single chromophore adhesive, carboxylated styrene-butadiene latex provides the best water resistance, with an 80% image retention rate in the chromophore area during water resistance testing.

3. Using a combination of polyvinyl alcohol and carboxylated styrene-butadiene latex as the chromophore adhesive enables thermal paper to achieve both good static color development and water resistance.