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There are two types of print technology used for labels:
As their names imply, both use heat to create the printed information, but they do so in different ways.
Thermal transfer printing transfers ink from a ribbon to the paper, using heat. The printer uses a ribbon which contains a layer of ink and paper-based or synthetic labels that can absorb the ink. As the heated print head passes over the ribbon, ink is released and the image created.
Direct thermal printing does not use ink, and therefore has no ribbon. Instead it uses thermal paper - paper that has a leuco dye coating that changes colour when heated. As the paper passes over the thermal print head, the paper changes colour to create the image.
The type of print technology you choose will very much depend on what you are labelling and why. You’ll need to take into account how the labels will be used - their expected life and their treatment during their life, remembering that the primary goal of your label is to remain legible,
Thermal transfer is great for…
Thermal transfer technology produces a very clear printed image that is very stable and long lasting. Because the image is made with ink, which is absorbed, and effectively becomes part of, the label stock, it can’t be rubbed off and won’t fade or smudge. Thermal transfer is therefore ideal for labels that need to last a long time, or labels that will undergo harsh conditions or processes. Examples include asset tagging, laboratory or medical specimens, long distance shipping, outdoor use, chemical or hazardous goods containers, labels that will be heated, frozen, or disinfected. No matter what the application, a thermal transfer print will always outlast a direct thermal print, and globally, 80% of all label printing uses thermal transfer technology.
Direct thermal is great for…
Direct thermal printers also produce a clear image and, because they use no ribbon or ink, are lighter, cheaper and easier to operate (although this should be offset against the cost of replacing print heads more frequently - see point 4). Portable printers, for when label printing is needed in the field, all use direct thermal technology.
But the printed image from direct thermal is less stable than a thermal transfer image. This is because the thermal paper remains sensitive to heat, so the image is prone to fading in bright light or darkening when exposed to heat. Even the friction from a scratch or knock can cause the label to blacken.
So direct thermal printing is a very cost-effective way to print labels that only need a shorter life and which will have relatively stable conditions. It’s used for receipts, parking tickets, price labels on retail goods, and by field service technicians, Government service staff and utilities companies.