Thermal printing (or direct thermal printing) is a digital printing process which produces a printed image by selectively heating coated thermo-chromic paper, or thermal paper as it is commonly known, when the paper passes over the thermal print head. The coating turns black in the areas where it is heated, producing an image. Two-colour direct thermal printers can print both black and an additional colour (often red) by applying heat at two different temperatures.
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, thermo-sensitive paper is inserted between the thermal head and the platen. The printer sends an electrical current to the heating elements of the thermal head, which generate heat. The heat activates the thermo-sensitive coloring layer of the thermo-sensitive paper, which changes color where heated. Such a printing mechanism is known as a thermal system or direct system. The heating elements are usually arranged as a matrix of small closely spaced dots—thermal printers are actually dot-matrix printers, though they are not so called.
Controller boards are embedded with firmware to manage the thermal printer mechanisms. The firmware can manage multiple bar code types, graphics and logos. They enable the user to choose between different resident fonts (also including Asian fonts) and character sizes. Controller boards can drive various sensors such as paper low, paper out, door open and so on, and they are available with a variety of interfaces, such as RS-232, parallel, USB and wireless. For point of sale application some boards can also control the cash drawer.
Benefits: ? Fast printing – Ideal for high volume retailers ? Quiet printing – when noise is unacceptable ? No ribbons to replace ? Two color printing on specific models
Drawbacks: ? Special thermal paper media ? More expensive than impact