thermal printer - Essential mechanisms, Applications

A type of printer which generally uses thermally sensitive paper and produces characters using a set of electrically heated wires. Although thermal printers are relatively inexpensive, the special paper they use is not.

For the type of printer which uses sparks and aluminised paper (and is sometimes referred to as a "thermal printer"), see spark printer. See also: Thermal transfer printer

A thermal printer (or direct thermal printer) produces a printed image by selectively heating coated thermochromic paper, or thermal paper as it is commonly known, when the paper passes over the thermal print head. Two-color direct thermal printers are capable of printing both black and an additional color (often red), by applying heat at two different temperatures.

Thermal transfer printing is a related method that uses a heat-sensitive ribbon instead of heat-sensitive paper.

Essential mechanisms

A thermal printer comprises these key components:

Thermal head — generates heat; prints on paper Platen — a rubber roller that feeds paper Spring — applies pressure to the thermal head, causing it to contact the thermo-sensitive paper Controller boards — for controlling the mechanism

In order to print, one inserts thermo-sensitive paper between the thermal head and the platen. The printer sends an electrical current to the heating resistor of the thermal head, which in turn generates heat in a prescribed pattern.

Controller boards with embedded firmware to manage the thermal printer mechanisms.

Controller boards can drive various sensors like paper low, paper out, door open, top of form etc., and they are available with the most commonly used interfaces (RS232, Parallel, USB, wireless).

Applications

Thermal printers print faster and more quietly than dot matrix printers. Possible commercial applications of thermal printers include filling station pumps, information kiosks, point of sale systems, and voucher printers in slot machines.

Through the 1990s, many fax machines used thermal printing technology. Toward the beginning of the 21st century, however, thermal wax transfer, laser, and inkjet printing technology largely supplanted thermal printing technology in fax machines in order to allow plain-paper printouts.

Early formulations of the thermo-sensitive coating used in thermal paper were sensitive to incidental heat, abrasion, friction (which can cause heat, thus darkening the paper), light (which can fade printed images), and water.