There is often confusion regarding these techniques because of their similar names. However, they are very different despite the fact that they both involve the use of heat. Below are the main differences.
Thermal transfer printing
With this type of printing, rather than applying the ink onto the paper (like with traditional printers), the printer heats a thermal transfer ribbon at very specific areas. The regions heated by the thermal printhead make the ink (composed of wax or resin) from the ribbon melt onto the paper, thus forming the desired printed image. This method is preferred for labels that undergo very high temperatures.
Direct thermal printing
Ink ribbons are not required for direct thermal printing. The paper, or “thermal paper,” reacts to heat generated by the printhead. The printhead heats specific areas of the paper where the image or the characters will be printed, and the chemically treated paper blackens when it comes in contact with the heat.
Moreover, the square or rectangular printhead is perfect for printing barcodes because of how well it captures the clearly cut lines.
Mainly because of its short lifecycle, this technique is used in the food industry, especially in grocery stores where printers are used to print barcode labels for products with varying weights or rolls of paper for cash receipts. Not having ribbon to replace is another advantage, especially for the press or scale operator.
In addition, thermal paper is easy to recognize. For example, if you place meat (in its packaging) in the microwave to defrost it, it is highly probable that the heat will cause the barcode label on the plastic film to blacken. The same phenomenon occurs when the cashier hands you your receipt. Scratch the paper with your fingernail. If you see a black line appear, then it’s thermal paper and, thus, the printer used was a direct thermal printer.
Two choice techniques for barcode labels
Several manufacturers, like Zebra Technologies, offer both options (thermal transfer or direct thermal) on a variety of models of compact label printers. This is the case for the ZT230 de Zebra that was recently added to IMS’s catalog. This is also true for the Datamax-O’Neil printers, where certain models can save you up to 100$ if you don’t require direct thermal printing. As for industrial printers, Toshiba offers standard direct thermal and thermal transfer.
In my next blog post, I will discuss the financial and logistical aspects of both techniques in more detail. I’ll also talk about the consumables required and the lifecycle of the equipment and consumables.