A direct thermal printer is commonly used for printing barcodes on labels, but to get the best quality printing, you need to be sure you start with the right labels. Here’s a buyer’s guide to understanding direct thermal printer labels to get you started.
Direct thermal printing technology requires a specific type of specially coated direct thermal label. Unlike thermal transfer, which uses a ribbon to transfer the image to paper, the direct thermal printing process applies heat directly to the heat-sensitive paper. The heat activates a chemical reaction that causes the image to appear. There is no ink, ribbon, or toner involved, which makes direct thermal printing slightly more affordable than thermal transfer.
Direct thermal printing was originally designed for use in photocopiers and fax machines about 50 years ago. Since those early days, both the technology and paper—remember those curly faxes?—have been vastly improved.
How direct thermal printing works
A direct thermal printer contains a thermal printhead with hundreds of heating elements. Each element is electronically controlled to emit the right amount of heat (thermal energy) in a specific location during the printing process. The more saturated the image, the longer the image will last under various conditions.
The problem is that you can’t easily see the difference between a fully saturated direct thermal printout and a less saturated one. The saturation depends on a combination of the particular direct thermal label and the print setting you choose. Setting “Default” on your printer isn’t necessarily the solution. And adjusting the printer’s heat energy settings without knowing the correct one can damage the print head.
Remember that the temperature in the area where you are printing your direct thermal labels is not necessarily equal to where those labels might end up. If you’ve ever left a receipt produced by a direct thermal printer in a hot car, you know that some thermal papers are highly sensitive to heat and light because that piece of paper turned black. The paper reacts to the heat in your vehicle in the same way it responds to the heat from the print head; it activates a chemical reaction. In this case, the entire paper turned black.
Choosing the right direct thermal labels
But not all direct thermal labels are created equal. The sensitivity level—to heat, light, chemicals, moisture, and abrasion—varies from one paper to the next, depending on the chemistry used. You will have many choices of combinations of facestock and coatings for direct thermal labels, including fade resistance when exposed to higher temperatures, UV light, water, and environmental conditions (which is key if your barcode labels will be used outdoors).
The coating on good quality direct thermal labels will also protect the printer itself. Not only will it provide the necessary resistance, but a good protective coating will also reduce the wear on the print head and won’t leave debris or residue from the coating on the print head.
The best option to ensure a fully saturated output from your direct thermal printer is to stick with the direct thermal labels specified by your vendor for use with your particular equipment. The printer manufacturer will probably recommend which heat setting is best for direct thermal labels. Choosing a lesser quality label material could mean that your label image doesn’t last, which could cause a problem if you’re using your direct thermal labels for anything that needs to withstand exposure to some of the elements mentioned here. Be sure to communicate that to your label supplier.
If you need more information about or help with choosing the best direct thermal labels for your printer and applications, please download our free ebook, Label Language and Ribbon Talk. Or contact us.