Thermal transfer printing is a process that melts a coating of ribbon onto a receptive label material. A thermal transfer printing head uses small resistors that are selectively heated or cooled. The heated elements come into contact with the ribbon (see diagram above) and the ink is melted onto the label material, where it dries instantly.
Thermal transfer printing is a digital process in that no printing plates are used and that it can print some types of variable data, depending on the software used. Print quality, however, is not as high as that of other digital printing technologies.
While we would never suggest using it as a replacement for versioning, there are situations in which it is useful to overprint professionally printed labels with a thermal transfer printer. Anyone considering using this printing process will need to invest substantial time researching and testing. For instance, some of our nutraceutical customers use thermal printers to overprint lot numbers or batch dates on their product labels, i.e., adding extra data unavailable at the time of original printing. This may not be achievable using any other method. For example, a laser printer could potentially melt the labels.
Anyone considering using thermal printing to overprint professionally printed labels must ensure that the thermal printer they purchase is compatible with the processes and materials used by their commercial print shop; including label core size, roll width, and laminate. It is also critical to test the label materials you wish to use with a thermal printer prior to placing an order. We here at Lightning Labels would be happy to provide you with label samples for this purpose.
(Peter Renton)
