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 printing because they produce accurate, high-quality images with excellent edge definition. Thermal 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 printing produces sharp print quality with good scannability.
Direct thermal is ideal for applications requiring only a short shelf life — meaning the label image does not need to last very long. Shipping labels and receipts are ideal applications, for instance, while product labels are not.
Direct thermal printers are simple to operate compared to most other print technologies because there is no ink, toner or ribbon to monitor or replenish.
With no supplies to replace other than the material to be printed, long-term maintenance costs remain low.
Direct thermal enables batch or single label printing with virtually no waste.
With recyclable materials available, direct thermal printers offer environmental economy.
Direct thermal printers are typically built more durably than dot matrix or laser printers, allowing reliable operation in industrial as well as office applications.
Direct thermal limitations
Direct thermal printing is extremely sensitive to environmental conditions such as heat and light (fluorescent and / or direct sunlight).
Direct thermal paper remains chemically active after printing. Because of this, thermal labels, tags or ticket stock are often top coated to resist UV light exposure, chemicals and abrasion.