Thermal Transfer Printing – 4
Colour Thermal Printers
Thermal-printing technology can be used to produce color images by adhering a wax or resin-based ink onto paper. As the paper and ribbon travel in unison beneath the thermal print head, the wax or resin-based ink from the transfer ribbon melts onto the paper. When cooled, the wax permanently adheres to the paper.
This type of thermal printer uses a like-sized panel of ribbon for each page to be printed, regardless of the contents of the page. Monochrome printers have a black panel for each page to be printed, while color printers have either three (CMY) or four (CMYK) colored panels for each page. Unlike dye-sublimation printers, these printers cannot vary the dot intensity, which means that images must be dithered.
Although acceptable in quality, the printouts from these printers cannot compare with modern inkjet printers and color laser printers. Currently, this type of printer is rarely used for full-page printing but is now employed for industrial label printing due to its water fastness and speed. These printers are considered highly reliable due to their small number of moving parts.
Printouts from color thermal printers using wax are sensitive to abrasion, as the wax ink can be scraped, rubbed off, or smeared. However, wax-resin compounds and full resins can be used on materials such as polypropylene or polyester in order to increase durability.
For more: https://en.wikipedia.org/wiki/Thermal-transfer_printing