Thermal printers have been in use for many years, but were not used for high-quality barcode printing until the early 1980s. The principle of thermal printers is to coat a light-colored material (usually paper) with a transparent film, and heat the film for a period of time to turn into a dark color (usually black, but also blue). The image is created by heating, which produces a chemical reaction in the film. This chemical reaction is carried out at a certain temperature. High temperatures accelerate this chemical reaction. When the temperature is lower than 60°C, it takes a considerable time, even several years, for the film to become dark; when the temperature is 200°C, this reaction is completed within a few microseconds. The thermal printer selectively heats the thermal paper at certain locations, thereby producing corresponding graphics. Heating is provided by a small electronic heater on the printhead that is in contact with the heat-sensitive material. 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.
The same logic that controls the heating element also controls the paper feed, allowing graphics to be printed on the entire label or sheet. The most common thermal printer uses a fixed print head with a heated dot matrix. The print head shown in the figure has 320 square dots, each of which is 0.25mm×0.25mm. Using this dot matrix, the printer can print on any position of the thermal paper. This technology has been used on paper printers and label printers. Usually, the paper feeding speed of the thermal printer is used as the evaluation index, that is, the speed is 13mm/s. However, some printers can print twice as fast when the label format is optimized. This thermal printer process is relatively simple, so it can be made into a portable battery-operated thermal label printer. Due to the flexible format, high image quality, high speed and low cost printed by thermal printers, the barcode labels printed by it are not easy to be stored in an environment higher than 60°C, or exposed to ultraviolet light (such as direct sunlight) for long periods of time. time storage. Therefore, thermal barcode labels are usually limited to indoor use.
Post time: Feb-25-2022
