Direct thermal printing uses chemically treated, heat-sensitive media that blackens when it passes under the thermal printhead. Direct thermal printers have no ink, toner, or ribbon.
Their simple design makes thermal printers durable and easy to use. Because there is no ribbon, direct thermal printers cost less to operate than inkjet, laser, impact, and thermal transfer printers. Most mobile printers use direct thermal technology.
Thermal media images may fade over time. If the label is overexposed to heat, light, or other catalysts, the material will darken and make the text or bar code 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 bar code printing applications including shipping labels, patient and visitor identification, receipts, and ticket printing.