The most widely used technologies for dedicated bar coding systems are thermal transfer printing and direct thermal printing.  While both methods use a heated printhead to create a barcode or variable image on a label, the two methods are best suited for different applications and both have their pros and cons. 

Q. What is the difference between thermal transfer printing and direct thermal printing?

A. Thermal transfer printing is a process that requires a thermal transfer printer, thermal transfer ribbons, software and a substrate (i.e. label or tag stock).  As the ribbon passes between the heated printhead and label substrate, the wax, wax/resin or resin coating from the ribbon is transferred as an image onto the label. The coating or ink is absorbed into the medial so that the image becomes part of the label.

Direct thermal printing on the other hand does not use a ribbon, but rather uses chemically treated, heat sensitive media designed specifically for direct thermal printers.  The media blackens when it passes under the heated thermal printhead causing a reaction in the coating of the label and forms an image. 

Q. What is the pros and cons between thermal transfer printing and direct thermal printing?

A. Thermal transfer printing produces very dark, dense images, has a longer shelf life, and is more durable than direct thermal print, especially when exposed to heat and solvents. Thermal transfer can accept a wider variety of media than direct thermal printing giving the user printing flexibility.  In addition, thermal printheads typically last longer than direct thermal printheads meaning long-term maintenance costs are lower.

With direct thermal the printing is not as crisp as thermal transfer ribbons and direct thermal printing is more sensitive to environmental conditions such as heat and sunlight, which tends to discolor the media over time.  Since a ribbon is not required, the primary benefit to using direct thermal printing over thermal transfer printing is that it is an inexpensive way to print labels.
Direct thermal paper remains chemically active after printing, so if the label needs more durability it needs to be top coated in order to resist UV light exposure, chemicals and abrasion, adding another step to the process.

Q. What are the typical applications for thermal transfer printing and direct thermal printing?

A. Typical thermal transfer applications include product identification, compliance labeling, electronic processing labeling, shelf/bin labeling that require a longer label life, and outdoor applications to name just a few.

Direct thermal printed labels have a limited shelf life and are best used on labels that are for temporary use.  Shipping labels and receipts for instance are ideal applications, while product labels are not.