Thermal printers are widely used, but not everyone knows how they work. The combination of thermal printer and thermal paper can solve our daily printing needs. So how does a thermal printer work?
Generally, a semiconductor heating element is installed on the print head of a thermal printer. The print head will heat up when it is working. After contacting with thermal paper, a pattern can be printed. The thermal paper is covered with a layer of transparent film. Thermal printers have options. The thermal paper is heated at a certain position, and through heating, a chemical reaction is generated in the film to generate an image, the principle is similar to a fax machine. The heaters are logically controlled by the printer in the form of square dots or strips. When driven, a graphic corresponding to the heating element is generated on the thermal paper.
Thermal paper is a special kind of coated processed paper whose appearance is similar to ordinary white paper. The surface of thermal paper is smooth and is made of ordinary paper as the paper base, and a layer of heat-sensitive chromophoric layer is coated on the surface of the ordinary paper. It is called leuco dye), which is not separated by microcapsules, and the chemical reaction is in a “latent” state. When the thermal paper encounters the hot print head, the color developer and the leuco dye at the place where the print head prints chemically reacts and changes color to form images and texts.
When the thermal paper is placed in an environment above 70°C, the thermal coating begins to change color. The reason for its discoloration also starts from its composition. There are two main thermal components in thermal paper coating: one is leuco dye or leuco dye; the other is color developer. This type of thermal paper is also called two-component chemical type thermal recording paper.
Commonly used as leuco dyes are: crystal violet lactone (CVL) of trityl phthalide system, fluoran system, colorless benzoylmethylene blue (BLMB) or spiropyran system. Commonly used as color-developing agents are: para-hydroxybenzoic acid and its esters (PHBB, PHB), salicylic acid, 2,4-dihydroxybenzoic acid or aromatic sulfones and other substances.
When the thermal paper is heated, the leuco dye and the developer react chemically to produce color, so when the thermal paper is used to receive signals on a fax machine or print directly with a thermal printer, the graphics and text are displayed. Since there are many varieties of leuco dyes, the color of the handwriting displayed is different, including blue, purple, black and so on.
Post time: Mar-18-2022
