Direct thermal and thermal transfer printing—although these terms sound very similar, they refer to two distinct printing methods.
Direct thermal printing (sometimes simply referred to as “thermal printing”) was first invented by Nobel Prize-winning engineer Jack Kilby in 1965. In contrast with many other forms of printing, direct thermal printing does not use any ink or toner to mark substrates. Instead, the idea behind direct thermal printing is to apply heat to specific areas of specially-coated pieces of paper to create a desired image or text. This heat is applied by a thermal printhead within the printer. When the paper passes over the printhead, the coating upon the heated area becomes blackened, thus producing the intended image.
While thermal transfer printers similarly use thermal printheads to create images and text, the heat isn’t applied to specially coated pieces of paper; instead, it’s applied to an ink-coated carrier film sometimes called a “ribbon.” The same thermal printhead heats the ribbon and the carrier ribbon melts ink onto the substrate, creating the design. To be able to mark a variety of substrates at varying speeds, thermal transfer ribbons are made from different combinations of wax and resin. With the ability to match the proper ribbon to the substrate, thermal transfer printers can place variable information such as codes on everything from pharmaceutical packaging and frozen food bags to event tickets and more.
Below we delve deeper into some of the more significant variances between direct thermal and thermal transfer technology as well as preferred applications for each.
For a closer look at the differences between these two printing methods, we will break down the direct thermal vs. thermal transfer conversation into four key areas:
Here’s how they stack up against one another.
In both direct thermal and thermal transfer printing, the printhead plays an important role by producing the heat that creates the intended image. The difference between these two methods lies in the material the printhead comes into contact with:
When a direct thermal printer is in operation, the constant contact between the printhead and the substrate inevitably results in significant friction and static. Over time, this wears the printhead down, reducing operational effectiveness. Conversely, thermal transfer printers benefit from the buffer the ink ribbons create between the label substrate and the printhead. Most ribbons are made up of layers including a slick backcoating. The backcoating is designed in a way that reduces friction, leading to a longer printhead life.
Generally speaking, thermal transfer printheads last anywhere from 25-50% longer than direct thermal printheads. Depending on a company’s required printer output, this difference can have a dramatic effect on overall expenses.
Simply stated, labels created through direct thermal printing do not last as long as those made through thermal transfer. Direct thermal labels are liable to fade over time and are vulnerable to chemicals, excessive physical contact, heat, and even sunlight. Thermal transfer labels are more resilient to these factors, making them a good fit for applications that require longevity and environmental protection.
For example, thermal transfer printing is commonly used to mark:
Although direct thermal labels don’t offer the same longevity as thermal transfer labels, they are still good choices for applications that don’t require long life or environmental resistance. Retail tags, for instance, are commonly made with direct thermal printers. Many food producers, including poultry, dairy, and egg operations, also frequently use direct thermal printers to make their labels.
While ink ribbons extend the life of both thermal transfer printheads and their produced labels, they complicate printer operation and configuration. Direct thermal printers contain fewer hardware parts than their thermal transfer counterparts, making them:
With thermal transfer printers, operators periodically need to adjust ribbon settings to ensure proper code application. Further, ink ribbons must be replaced regularly—an action that causes profit-draining downtime.
Consequently, one will generally find that maintenance costs associated with thermal transfer machines will be higher than with direct thermal printers.
Along with downtime, printing consumables are another cost consideration when operating a thermal transfer printer. Both direct thermal and thermal transfer machines will require money to be spent on label materials, but only thermal transfer printers will require operators to repeatedly buy ink ribbons. However, this doesn’t necessarily mean that thermal transfer printers will carry higher consumable costs than direct thermal printers.
Remember that direct thermal printers inherently cause friction between the printhead and the label material. As mentioned above, this causes direct thermal printheads to deteriorate at a quicker rate than thermal transfer printheads. To counteract this effect, many operators choose to use label materials that are specifically coated to reduce friction. These coated labels are significantly more expensive than uncoated labels, and when performing a direct price comparison between direct thermal and thermal transfer consumable costs, they often cancel out any potential savings associated with ribbon elimination. In fact, most companies that use coated labels find that they spend more money on consumables than they would if they used a combination of uncoated labels and ink ribbons.
However, this cost difference can be influenced by several different factors, including overall output, environmental factors, and required resolution. Essentially, it is best to choose a label printing solution that is the proper choice for the application and then consult with industry experts for ideas to save money on consumables like labels, printheads, and ribbons.
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