DIRECT THERMAL VERSUS THERMAL TRANSFER
How do direct thermal and thermal transfer labels work?
Direct thermal labels are designed to react with heat. They come into direct contact with the print-head (through the thermal label printer) which heats up and reacts with the surface of the thermal label to create the print. The nature of this material means it is ideal for short-term print solutions.
Thermal transfer labels offer a more robust long – term option. They require thermal transfer ribbon to print with. The ribbon runs between the label material and the print-head of the thermal label printer. Heat from the print-head burns the ribbon onto the label, creating the print. Using thermal transfer labels reduces print-head wear.
The printers use a fixed width thermal print head, pressing onto a paper or plastic label, over a driven rubber roller called a platen. Between the print head and the label is sandwiched a very thin thermal transfer ribbon (sometimes called foil), which is a polyester film which has been coated on the label side with a wax, wax-resin or pure resin "ink". The ribbon is spooled onto reels up to 625 meters (1965 feet) long and is driven through the printing mechanism in sync with the labels, at speeds of up to 12 inches per second (although 6 inches per second is adequate for most applications).
As the label and ribbon are driven beneath the printhead together, tiny pixels across the width of the printhead are heated and cooled so as to melt the "ink" off the polyester film and onto the label. This process happens very quickly and accounts for the fast speed of the printers and is dry instantly. Thermal printheads are often 203 dots per inch (8 dots per mm) or 300 dpi (12 dots per mm). Though some manufacturers now make 600 dpi printers to produce very small barcodes for electronics industries (look inside the battery compartment of your mobile phone.)
Because of the high print speeds, the label printers have become very sophisticated, with powerful processors and large memory capacities, to allow them to produce the label images to be printed at the same speed as the print mechanism. To achieve this speed, almost all thermal label printers use special internal description languages to allow the label to be laid out inside the printers' memory prior to printing.
What shapes and sizes of thermal label are available?
All shapes and sizes are available for both direct thermal and thermal transfer labels. The main variables include:
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what the labels will be used for (their application)
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the printer model (if you want to over-print labels that we have pre-printed for you)
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the label roll core size, for example, 25mm, 44mm, and 76mm (the size you will need is determined by the type of your printer. This is important if you want to over-print labels that we have pre-printed for you).
You can specify the number of labels per roll.
What colours of thermal label are available?
Direct thermal labels: Because the print is created by the heat of the print head, black is the only printable colour. However, the labels themselves can be colour washed so a large range of coloured direct thermal labels are available.
Thermal transfer labels: Various ribbon spot colours are available for thermal transfer labels including black, red, blue, orange, magenta, green and brown.
What are thermal labels typically used for?
Examples of direct thermal label applications include:
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batch numbering
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stock taking
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in-house labelling.
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Examples of thermal transfer labels applications include:
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sequential barcoding (code39)
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sequential numbering
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food production
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medical
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electrical manufacturing.
What adhesives are available for thermal labels?
Direct thermal labels and thermal transfer labels can be supplied with peelable, permanent or freezer adhesives.
What materials can thermal label be made from?
Direct thermal labels: are available on paper but can also be supplied in the form of thermal tags. These would be made to measure.
Thermal transfer labels: are available on matt or velum paper, direct polyester, and direct polyurethane. These would be made to measure.
