Direct thermal paper forms an image when heat from a printhead activates a coated layer. It does not need an ink ribbon, which keeps compact receipt and label printers mechanically simple. Thermal transfer is different: a heated head melts colour from a ribbon onto the receiving stock.
A layered construction
The face paper provides strength and smoothness. A thermal coating contains components that react under controlled heat to form colour, while topcoats and backcoats can improve resistance, printhead contact and converting. Adhesive and release liner are added when the construction is a pressure-sensitive label.
Image life varies with heat, ultraviolet light, oils, plasticisers, moisture and abrasion. A grade suitable for a short-lived till receipt may not meet the needs of a logistics or laboratory label.
Match durability to use
Specify the expected service temperature, scanning period, chemical exposure and required image life. Test barcodes after handling, not only immediately after printing. Store unused rolls away from heat and direct light, in their protective packaging. When records must remain readable for years, evaluate durable direct thermal grades or a thermal-transfer construction instead of assuming every thermal sheet has the same stability.
