Thermal Printing

Thermal printing comprises of two different techniques, namely direct thermal printing and thermal transfer printing. Of the two, the most commonly utilized technique is direct thermal technology as it is easy to use and economical. As the name suggests, direct thermal printing technology makes use of heat generated by the thermal print head to get the desired prints. In typical ink based printers, the print head marks the targeted area with ink to get the desired prints, but in thermal printers, thermochromic paper is used, which turns black when it is heated. Colored images can also be printed, but for that color-based thermochromic paper would have to be used. Color-based printing substrate is chemically treated to produce different colors at different temperatures. For example, if the image has red and blue colors, then the thermal print head will apply different temperatures at the required areas on the printing substrate to produce the desired color.

Main components used in thermal printing technology

In thermal printing technology, the main components are the thermal head, which is used for generating heat and printing on paper; rubber rollers technically referred to as Platen, used for feeding paper; the spring, used for applying pressure to the thermal print head; and controller boards for controlling all the various components of the thermal printer.

The printing process

The printing process is quite simple. To get the desired prints, the thermo-sensitive paper is inserted between the thermal print head and the Platen. The spring placed beneath the print head applies the requisite amount of pressure so that the heat generated can be easily transferred from the print head to the thermal printing substrate. When the printing process is activated, the in-built mechanism sends electrical current to the heating resistors inside the thermal print head. The heat in turn causes a chemical reaction to take place, visible in the form of black patches, which make up the final print.

Colored images are created when color-based thermal printing substrate is coated with a mixture of dyes and acids in a predetermined matrix. When heated to a certain level, the dye and the acid together produce a chemical reaction, generating the required colors according to the print requirements. The whole process is managed through controller boards that form a part of the overall firmware. The controller boards are utilized to configure the printer to get different types of thermal prints. They can be used for controlling the printing of bar codes, graphics, and logos. Selecting color combinations, font type and font size is also done by utilizing the controller boards. Various sensors placed inside thermal printers, which check current printer status such as ‘paper low’, ‘no paper’ etc., are also connected to the controller boards. Such connections are usually made through technologies such as RS232, Parallel, USB, and wireless.

Uses and benefits of thermal printing technology

The easy to use features and cost benefits offered by thermal printing technology has made it a popular choice for managing different types of printing requirements such as printing bills at filling station pumps, printing leaflets at information kiosks, printing invoices at point-of-sale systems, and printing vouchers at slot machines. These printers are preferred because they are faster and much quieter compared to typical dot matrix printers. They are economical because the only consumable is the thermal printing substrate. Even though the thermal printing substrate is costlier than a single plain printing paper, the overall printing costs are certainly lower because the other consumables such as ink cartridges or ribbons are not required.

Thermal printing technology has gained prominence only in the last few years with the availability of modern thermal printing substrates, which are coated with special formulations that are resistant to incidental heat, abrasion, friction, light, and water. Although more advanced printers such as laser printers are now available in the market, the importance of thermal printers cannot be underestimated, because they come quite handy, especially when the task is to get high-resolution prints at affordable costs. Low maintenance has also helped in increasing the popularity of thermal printing technology.

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