RFID: Types of Printing – Direct vs. Thermal Transfer
Direct Thermal printing is the standard in many industries that need to consistently print text or images, the best example being printing receipts. The Direct Thermal process involves two steps: heating up the printhead, and the printhead coming into contact with the heat-sensitive paper. The paper type is the key in this process because, if the paper is not chemically-coated to be heat sensitive, the printhead will not be able to produce the color change that occurs when the paper is in contact with heat.
Direct Thermal printers are more expensive when compared to generic ink or LaserJet printers; however, because direct thermal printers do not require a regular ink supply the investment over the long term is typically much lower. The downside to direct thermal printing is that the paper used is very sensitive to light, heat, and abrasion, so if the label is exposed to any of those elements for too long, the printed information may become unreadable.
Direct thermal printing is also not recommended for items that need to be labeled for a long-time period because the text will begin to fade over time.
Barcodes on shipping labels, receipts, parking tickets, and some logistics applications use direct thermal printing because the labels do not need to have a long lifespan. Mobile printers typically use direct thermal as well, because of the transient nature of the barcode printed labels.
Thermal Transfer printing is typically used in RFID label printing because of its general resistance to environmental elements and longer lifespan. Thermal Transfer printing requires purchasing a thermal transfer ribbon which is an added cost associated with this type of printing (in comparison to direct thermal). Thermal transfer involves the process of heating up the printhead and pressing it to the back of the thermal ribbon. The heated printhead melts the ribbon and transfers the color to the front of the label, which creates the printed text or image.
The pros of thermal transfer printing are long ink lifespan and little reactance to heat, light, or abrasions. Another positive aspect of this printing process is that there is a ribbon in between the printhead and label, which acts as a buffer for foreign items like dust and dirt. The ribbon helps keeps these impurities out of the printed text or image as well as expands the lifespan of the printhead. A negative aspect of printing via thermal transfer is the reoccurring ribbon cost.