An electronic printing process in which a special heat-sensitive surface coated material is turned selectively black by the direct application of heat through the contact apertures of an electronically controlled thermal print head. the paper reacts to a heat of 90 to ll0C ribbon. For short term label applications and where there is little chance of label image degradation or contamination, appropriate direct thermal labels are mostly used.
A simple test to determine whether a substrate is a direct thermal image material or not is to hold it close to a match or open flame or other hot surface where the materials will rapidly darken and turn black. Accelerating a finger nail across the label surface will produce a black friction line.
For applications that require a shelf life longer that six months – unless it is well controlled or in a dark environment – thermal transfer labelling is used.