Transfer Vs Direct

The printers use a fixed width thermal print head, pressing onto a paper or plastic label, over a driven rubber roller called a platen. Between the print head and the label is sandwiched a very thin thermal transfer ribbon (sometimes called foil), which is a polyester film which has been coated on the label side with a wax, wax-resin or pure resin "ink". The ribbon is spooled onto reels up to 625 meters (1965 feet) long and is driven through the printing mechanism in sync with the labels, at speeds of up to 12 inches per second (although 6 inches per second is adequate for most applications).

As the label and ribbon are driven beneath the printhead together, tiny pixels across the width of the printhead are heated and cooled so as to melt the "ink" off the polyester film and onto the label. This process happens very quickly and accounts for the fast speed of the printers and is dry instantly. Thermal printheads are often 203 dots per inch (8 dots per mm) or 300 dpi (12 dots per mm). Though some manufacturers now make 600 dpi printers to produce very small barcodes for electronics industries (look inside the battery compartment of your mobile phone.)

Because of the high print speeds, the label printers have become very sophisticated, with powerful processors and large memory capacities, to allow them to produce the label images to be printed at the same speed as the print mechanism. To achieve this speed, almost all thermal label printers use special internal description languages to allow the label to be laid out inside the printers' memory prior to printing.

Direct thermal labels, and thermal tags are available in a wide range of sizes and quantities and can be printed with a permanent, removable, or freezer adhesive..