Understanding the difference between Thermal Transfer and Direct Thermal Transfer Printing
Which is a Thermal Transfer label and which is a Direct Thermal Label?
The heated elements in a printer's printhead is what directs heat directly to a direct thermal label coated with a chemical that produces the printed text, graphs or black/ white logo.
If you’re printing barcode labels on a regular basis, you are most likely using a thermal printer (as opposed to laser, inkjet, or dot matrix, which are not optimized to produce high or lasting label printing quality). Thermal printers, engineered to produce crisp, clear, high quality barcodes, use one of two printing technologies: direct thermal or thermal transfer.
Although the two printing methods are both used to produce barcodes, there’s a big difference between them and the labels that should be used with them.
Direct thermal printers require a paper that is formulated for use with this technology. The paper is coated with a chemical to react with the heat process. When the heated elements of the print head heat the direct thermal paper, the paper responds to the heat and produces an image where those elements contact it. It’s basically a chemical reaction of the dye coating on the paper that creates the, as opposed to depositing printing ink on top of the label. There is no ink or toner involved with direct thermal printing, which reduces the total cost of ownership of using this process. Direct thermal printers most often produce only black images but there are specialty direct thermal labels with a secondary dye color (usually red) that are available.
Thermal transfer prints with the use of a ribbon. Heat from the print head melts ink from the ribbon onto special thermal transfer paper or synthetic label media that is specially treated for thermal transfer use. The label media does not directly contact the print head, as the ribbon is between the print head and the thermal transfer media.
The thermal transfer ribbon has a coating of wax, resin, or a combination of the two. When the heat from the print head is applied to the ribbon, the surface coating melts and adheres to the label, which cools quickly and produces an image that is more durable than those generated from direct thermal printers. The durability of the thermal transfer labels will depend partly on the selection of the ribbon and label media combination. Wax, which has a lower melting point than resin, is more subject to smudging, scratches, and damage. If you want the most lasting barcode labels, invest in a resin ribbon, or, at the very least, a wax/resin ribbon.
Unlike direct thermal printers, thermal transfer is not limited to one or two colors. For applications where you want to include more graphics (e.g., logo), the broader color options is a definite advantage to thermal transfer printing.
There are advantages and disadvantages to both thermal transfer and direct thermal printers. The type you choose will depend on your priorities, including functionality, print quality, image durability, and cost of ownership.
Direct thermal printers are slightly more economical to own because they don’t require a ribbon and the label media is generally less expensive than thermal transfer ribbons and media. However, the cost savings is not a benefit if you require printing that is less sensitive to conditions like UV light, moisture, heat, smudging, scratches, and chemicals. The direct thermal media lower cost advantage is offset by shorter print head life, as the print head is not protected by a ribbon and the label media directly contacts the print head. The direct contact causes abrasion of the protective coating over the print head elements, which causes earlier print head failure compared to thermal transfer printing. The imaging dye coating on direct thermal labels and paper is often insufficient to deliver lasting quality. The images will fade in the presence of sunlight or in the presence of high heat will turn completely black. You can, however, purchase direct thermal media that offers better protection, such as polypropylene, which is waterproof. Otherwise, special coatings only provide a limited degree of additional protection.
Thermal transfer printing has a somewhat higher total cost of ownership than direct thermal printers. You need to replace the thermal transfer printer ribbons, which aren’t required for direct thermal printing. The ribbons will vary in price, depending on whether you choose wax, wax/resin, or the high-end resin ribbons. Thermal transfer printing delivers high quality, lasting images that withstand heat, light, and extreme environmental conditions. You can also print with a wider array of colors, and on more types of media, such as synthetic films.
Before you make your decision on a barcode printer, consider your options, and the pros and cons of each thermal printing technology. If you need help, please contact us.