How Does Thermal Transfer Ribbon Work?
Thermal transfer printing is a fast and clean process with no warm-up or cooling time required. It is not a wet or dirty process either and the results are instantly dry, requiring no curing. By using a single-pass ribbon, the print is perfect from the start to the very end of a roll, making it the standard for producing barcodes and variable information labels, on-demand.
A thermal transfer label printer from the likes of Avery, Sato, Novexx, TEC, Zebra etc produces text, barcodes and graphics by using a fixed low-powered print head which spans the entire width of the print area. The print head comprises of a single row of thousands of tiny elements (“dots”) of a size typically 8 or 12 dots per millimetre, yeilding a print resolution of 200dpi or 300dpi – but even 600dpi is available.
The Difference Between “Direct Thermal” and “Thermal Transfer”?
A Direct Thermal printer uses the heat from the dots in the print head to activate a chemical coating in a specially produced thermal label, which darkens the area in contact with each dot, in order to produce the label image. A thermal transfer printer uses a thermal transfer ribbon:
Thermal transfer ribbon is a roll of clear plastic (PE) film coated on one side with a coloured pigment, or “ink”, most commonly black (although many colours are available). Depending on the printing requirements, the coating can be formulated using either wax, resin or a mixture of both. The thermal transfer ribbon passes over the thermal print head, with the coated side pressed against the label surface. The heat energy produced by each dot causes the pigment to transfer off the carrier film and bond to the surface of the label.
The element dots which make up the print head are electronically heated up and cooled rapidly by the printer as both the label and ribbon pass under it at the same time. Speeds of 300mm per second and faster are quite achievable with the right match of ribbon, label and printer.
What is Meant By Flat Head and Near-Edge Print Heads?
There are two types of print head: “Flat” and “Near-Edge” and so there are two types of thermal ribbon. There are benefits of each technology which merits another article in its own right. One is neither “better” than the other without explanation but suffice to say, you must match your thermal transfer printer with the correct thermal transfer ribbon! For example, all Zebra printers use flat print-heads while others such as TEC, use near-edge. Avery Dennison and others produce a range of label printers that take both types, so it is essential to know which head is in your machine before you purchase the wrong ribbon. Using a flat head ribbon in a near edge printer or vice-versa, won’t dammage the printer but you won’t get very acceptable results. Beware though, you could drastically reduce your print head life by increasing print head temperature and increasing the head pressure excessively in attempt to improve print quality using the wrong type of ribbon! A false economy if ever there was one, as print heads aren’t cheap.
Over time, thermal print heads will wear out eventually and you will notice this as each element “dot” stops working, the appearance of lines (actually, non-printed lines, to be correct) will get increasingly worse. The dots are like lightbulbs – one day one will stop working and more will tend to fail afterwards. However, it is quite ok to carry on printing with an odd dot “down” unless so many are missing that either the printed output looks a mess or worse still, they affect the readability of the barcode.
To prolong the life of your print head it is essential to use a good quality ribbon with a low-friction back coating which minimises wear on the head and to also match the correct ribbon to your printer, so that you can lower the head power and reduce the pressure applied. You should of course clean your print head regularly, the frequency of which is dependent on usage and will be advised by your printer/ribbon supplier.
We stock a wide range of ribbons, from general purpose wax grades, high performance wax/resin grades and pure resin ribbons for specialist applications, all in a wide choice of print widths and matched to your specific label printer model, many available for next-day delivery. If you’re not sure which ribbon you need, then don’t worry, we will help identify the correct ribbons that are compatible for your specific printer, suitable for printing on various label materials.
For more specialist requirements or some help and advice, call us on 01844 264835