The working principle of a thermal printer is that a semiconductor heating element is installed on the print head. After the print head is heated and contacted with the thermal printing paper, it can print out the required pattern and text. Its principle is similar to that of a thermal fax machine. The image is generated by heating and chemical reaction in the film. The chemical reaction takes place at a certain temperature. The high temperature will accelerate the chemical reaction. When the temperature is lower than 60 ℃, it takes quite a long time, even several years, for the paper to turn dark; when the temperature is 200 ℃, the reaction will be completed in a few microseconds.

The thermal printer selectively heats the thermal paper at a certain position, thus producing the corresponding graphics and text. The heating is provided by a small electric heater on the print head which is in contact with the thermosensitive material. When the heater is driven, a pattern corresponding to the heating element is generated on the thermal paper. The same logic circuit that controls the heating element also controls the paper feed, so that a graphic can be printed on the whole label or paper.

The key to thermal printing technology is heating elements. There is a row of tiny semiconductor elements on the core of the thermal printer. These elements are closely arranged, ranging from 200dpi to 600dpi. These elements will produce high temperatures quickly when passing a certain current. When the coating of thermal paper meets these elements, the temperature will rise in a very short time, and the coating of thermal paper will have a chemical reaction It should be, showing the color.

After receiving the print data, the thermal printer converts the print data into bitmap data, and then controls the heating element on the printer core to pass the current according to the point of bitmap data, so that the print data becomes the print content on the print paper.