What Is the Difference Between Direct Thermal and Thermal Transfer Printing?
There are two thermal printing methods: direct thermal and thermal transfer. Each method uses a thermal printhead that applies heat to the surface being marked. Direct thermal printing uses chemically treated, heat-sensitive media that blackens when it passes under the thermal printhead, while thermal transfer printing uses a heated ribbon to produce durable, long-lasting images on a wide variety of materials.
Overall thermal label printers are ideal for barcode labels because they produce accurate, high-quality images with excellent edge definition. Thermal transfer printers are engineered to print within tight tolerances and to produce the exact bar widths that successful barcode printing and scanning require. Each technology can produce one- and two-dimensional barcode symbologies, graphics and text at the same print resolutions and speeds.
Direct Thermal Printing
Because they print without a ribbon, direct thermal printers are noted for their simplicity. Direct thermal printed labels typically have a considerable shelf life but are not well suited for environments that expose them to heat, long periods of direct sunlight, or abrasion. Direct thermal printers have no ink, toner, or ribbon.
If the label is overexposed to heat, light, or other catalysts, the material will darken and make the text or barcode unreadable. For these reasons, direct thermal printing is not used for lifetime identification applications. The readability of direct thermal labels, wristbands, and receipt papers varies greatly, depending on the usage conditions, but the technology provides ample lifespan for many common barcode printing applications including shipping labels, patient and visitor identification, receipts, and ticket printing.
Direct Thermal Printing Advantages
Direct thermal limitations
Thermal Transfer Printing
Thermal transfer printed labels are easily identified by the crisp, often glossy, printed surface. The clarity is achieved by using a thin ribbon roll that when heated by the printhead melts onto the label to form the image. The ink is absorbed so that the image becomes part of the media. When matched with suitable media, thermal transfer technology is not only impervious to heat and moisture, but the image cannot be rubbed off, making the printed labels the most durable available. An additional benefit of this technology is the continuity of the printed image. Because the color and density of the printed image is determined by the ribbon and the resolution of the printer, thermal transfer printing produces consistent, reliable printing on every label. This technique provides image quality and durability that is unmatched by other on-demand printing technologies.
The specific label material and ribbon must be carefully matched to ensure print performance and durability. By selecting the right media-ribbon combination, as well as specialty adhesives, users can create archival-quality labels to withstand temperature extremes, ultraviolet exposure, chemicals, sterilization, and more. Typical thermal transfer applications include: product identification; circuit board tracking; permanent identification; sample and file tracking; asset tagging; inventory identification; certification labels such as UL/CSA; laboratory specimens; cold storage and freezers; and outdoor applications.