Thermal paper still plays many important roles
The uneven coating of thermal paper will result in dark color in some places and light color in some places, which will obviously reduce the printing quality. If the chemical formula of thermal paper coating is unreasonable, the storage time of thermal paper will become very short. Good thermal paper can be stored for 5 years after printing (at room temperature and out of direct sunlight). Now there are even long-term thermal papers that can be stored for 10 years. But if the thermal paper coating formula is not reasonable, it may only be stored for a few months.
Although there are more than a dozen chemical substances used in this color-changing layer, there are at least the following compounds: leuco dyes, a wide variety, commonly used fluorescent compounds; color developers accounting for less than 20%, commonly used bisphenol and p-hydroxybenzene formic acid. Sensitizers account for less than 10%, including benzenesulfonic acid amide compounds; fillers account for less than 50%, commonly used calcium carbonate (particles); adhesives account for about 10% or less, such as polyvinyl acetate; stabilizers , such as diphenyl terephthalate; lubricants, etc. Therefore, the process is difficult and the technical requirements are high.
When the thermal paper is heated, the leuco dye reacts with the developer to produce color, so when the thermal paper is used to receive signals and print on a fax machine or directly on a thermal printer, graphics and text are displayed. Due to the wide variety of leuco dyes, the color of the handwriting is also different, such as blue, purple, black, etc.
Thermal paper has been used for many years. While thermal paper still has many important functions, some of them have disappeared. During its lifetime, the other popular product, thermal paper, has undergone several improvements, eliminating some outdated views. A major reason is that documents remain in the printing process after publication. Although fax machines now use plain paper, many people still believe that thermal paper is printed first and then rolled. However, consider accepting a lengthy grocery store receipt. This is printed on thermal paper, but don't roll it up.