Thermal Transfer Printing
Thermal Transfer Vs Direct Thermal
Direct thermal labels are sometimes known as chemi-thermal labels
Thermal transfer printed labels require a thermal transfer ribbon – the image on the label is a result of the pixels in the print head heating up and melting the ribbon onto the surface of the label in precise areas to form the barcode, text or whatever image is required.
In simples terms the direct thermal label does without a ribbon – the top surface of the label is chemically treated to react and darken when in contact with the heated pixels on the print head. The image is “burnt” onto the surface of the label.
There is little difference in the visible image print quality – a barcode will scan and text will be easily readable using either thermal transfer or direct thermal.
It’s all about the life of the label!
We going to answer the four main questions to help you decide if direct thermal labels are right for you
- Label life
- Media choice
- Thermal print head life
- Environmental waste considerations
1) Label life
The key to choosing direct thermal or thermal transfer labels is to understand the life of the label throughout the supply chain. Direct thermal labels are unable to offer the lifetime service length of a traditionally thermal transfer ribbon printed label.
The direct (or chemi) thermal label reacts to heat so if the product to be labelled is in the supply chain for an extended period or the label is exposed to direct sunlight, heat or chemicals it could darken and make the image unreadable. Thermal transfer labels would be the best choice.
However if the supply chain is short and the product is handled in a clean, relatively protected environment free from chemicals, abrasion and heat the direct thermal label would be preferred.
Chemical or warnings labels should use thermal transfer labels and ribbons due to the statutory regulations requiring the label to remain readable throughout the life of the product.
Parcel shipping, fresh produce and dairy are all examples of short supply chin products ideal for direct thermal.
2) Media choice
With direct thermal labels there is no need for a ribbon so the initial expectation may be to see a reduced cost of direct thermal labels are used. In reality, this is rarely the case. The higher initial cost of the chemically treated direct thermal label and the mentioned limitations to use often outweigh real cost savings Why not test this theory by asking us for a quote both ways?
The media selection will also have an impact on print speeds, image print quality and label life. Poorly printed barcodes which do not scan first time throughout the supply chain can lead to product rejects, fines and unnecessary delays. Ask us for help in choosing the right label type for your application.
3) Thermal print head life
Thermal transfer printing utilises a thermal transfer ribbon to produce the printed image. No major benefit of thermal transfer printing is that the ribbon acts as a protective barrier between the print head and the label surface. Readability’s thermal transfer ribbons have a silicon back coat specifically designed to protect the print head. This leads to longer print head life.
Direct thermal labels come directly into contact with the print head and whether coated or not the abrasive effect of labels running directly over the head will always produce more wear leading to more frequent print head changes.
Opinion differs as to how many more print heads would be required if direct thermal labels were used with some OEMs stating that the head life is reduced by as much as 50%. With Readability’s high quality direct thermal papers and good manufacturing practices at the print site, we would not expect to see such high figures but it is an inescapable truth that without the protective ribbon headwear will increase.
4) Environmental waste considerations
Recycling and waste disposal are key issues which are not going to go away. When a paper label is applied to a cardboard box or pack the whole can usually be recycled together. If paper labels are applied to shrink wrap they should be removed prior to recycling or a synthetic label should be used.
Dispensing with ribbons entirely can have a significant positive impact on a company’s waste figures. The waste backing paper can be collected and recycled.
Linerless labels also offer waste reduction benefits and process improvements
Direct thermal labels are the right choice if the print environment and label life are suitable.
Direct thermal labels will cause premature printhead wear.
Thermal transfer labels and ribbons are always the correct choice when high speeds, extended delivery time, longer supply chains and harsh conditions exist.
Please feel free to make contact to discuss your label and ribbon needs.
MD – Readability Ltd