Dye Sublimation printing is a process using heat to vaporize dye on an ink roll. The vapourised ink permeates the glossy surface of the paper roll before returning to solid form. Colours are not laid down as individual dots (as in ink jet printing), which gives a more true photographic look to prints. Besides producing more realistic prints, dye sublimation prints are less vulnerable to fading and distortion over time. Printing is much faster than ink jet technology, there is no drying time, and print cost can be accurately calculated.
Thermal-printing technology can be used to produce color images by adhering a wax-based ink onto paper. As the paper and ribbon travel in unison beneath the thermal print head, the wax-based ink from the transfer ribbon melts onto the paper. When cooled, the wax is permanently adhered to the paper. Unlike dye sublimation printers thermal transfer 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 the quality produced by dye sublimation printers.
Direct thermal printing differs from thermal printing technology in that it uses no ribbon to print images. A thermal head heats and cools to varying temperatures at lightning fast speed to produce “grayscale” images on special receiver paper, for example ultrasound images. Main application is medical imaging and scientific genetic research.