Thermal labels - production, advantages and areas of application
Thanks to their special coating, thermal labels can be used flexibly and do not need a laser or inkjet printer. Thermal labels contain pigments that change colour when exposed to heat and become visible as legible print - recognisable by a grey-black colouring of the corresponding areas.
Thermal labels are sensitive to heat sources. In the long run, the print of the labels fades, so they are not suitable for long-term storage. For longer lasting print durability, we recommend our Therma transfer labels.
Thermal labels can be found at Labelprint24 as roll labels in many sizes, as a simple and cost-effective label variant for printing variable data. We offer thermal labels in different materials for different applications. All papers and films are described in detail in our product configurator regarding their possible applications. If you still have questions, please feel free to contact our customer support.
What is a Thermal label?
Thermal labels are special labels that are not printed conventionally but with a direct thermal printer. The print head generates heat at different points, which creates the print image on the label. With this printing method, no ribbon or ink is needed.
Depending on the degree of heating, thermal labels can nowadays display several colours. However, the labels are susceptible to heat and turn dark when exposed to heat. Therefore, thermal label printing is primarily suitable for labels that do not need to last long or are located inside buildings.
Adhesive-coated shipping labels are now often thermal labels as well. When used with a barcode, the parcel labels can be printed out directly in the shop and affixed to the shipping packaging. Due to the now short shipping times, the discolouration of the labels does not play a significant role in the mail order business.
How is a thermal label printed?
Thermal labels receive their information by means of thermal printing. They consist of thermal paper that has a heat-sensitive layer. During printing, the thermal paper is heated selectively: a reaction occurs, and the heated areas change colour. This makes the printed image visible on the paper.
What are the properties of thermal paper?
The thermal paper is coated with a thermosensitive layer on the print side. Pigments, binders, developers, auxiliary materials and colour images are integrated into this layer. Thermal paper is available in different colours regarding the typeface used later.
Black is used most often, blue second. Nowadays, the realisation of different colour levels is no longer a problem. The solution lies in the use of different printing temperatures.
However, colour thermal printing requires more technical effort, which is why colour rolls are rarely used in industrial and commercial applications. Usually, the thermal paper is wound onto a roll core made of plastic or paper.
How does thermal paper work?
The thermal printer works with heat. The heat heats a specific spot on the paper. The heating of the thermo-sensitive paper is continued in rows across the width. There are colour formers and developers in the paper that react to the heat and thus produce the printed image.
A simple thermal printer operates at a temperature of 90 degrees. The printing mechanism itself consists of a rotating roller that moves the paper past a heating bar with hundreds of heating elements, the printing pixels. The selective heating turns the thermo-sensitive paper black and writing, numbers and logos become visible.
The simple design keeps the acquisition costs low - the low susceptibility to faults also has a positive effect. Modern direct thermal printers can print up to 100 km of paper in their operating time. That is up to 30 times more than a conventional dot matrix printer can achieve.
The printers are available in different versions. There are some useful features that make every day work easier:
- Dispenser - the label is peeled directly from the liner
- Rewinder - in case the label is to be rewound onto a roll after printing
- Cutter function - cutting device that eliminates the need to tear off the label
Thermal paper consists of five different chemical layers, four of which are on the front and one on the back. These layers define the properties of the thermal paper.
The front layer gives the printed image protection against water, grease, oil, plasticisers and alcohol. The thermal layer determines image sharpness, sensitivity, protection of the image and background density.
The undercoat concentrates the heat of the print head onto the thermal layer. This optimises the thermal reaction, enhancing image sharpness, sensitivity and gloss.
The basis of the thermal paper consists of paper or a film. This can be of different thicknesses. The mechanical properties such as stiffness, breaking strength or tear resistance also result from the base.
The back protective layer protects the thermal paper from plasticisers, alcohol, grease, oil or water. It ensures that the paper does not curl, and that solvents, adhesives and inks can be used.
What advantages do thermal labels have?
The direct thermal printing process is characterised by low noise. The process is also energy-saving. Printing is fast: The printing speed in the POS area reaches up to 300 mm/s, in label printing even up to 500 mm/s. Since no additional inks are needed, the printing costs are relatively low.
It requires little maintenance as the compact printer has few components. Handling is easy because no ribbon is required. Set-up times are also low because the handling of the label rolls is simple.
In which industries and for which products are thermal labels used?
Thermal labels are used as standard for:
- Admission tickets
- Parking tickets
- Price labels
- Scale labels
- Food labels
- Shipping labels
High-quality thermal labels, which have a shelf life of up to 25 years, have also been used successfully in document archiving.
When was thermal printing invented?
Pressure less thermal printing is still relatively young compared to other types of printing. It was not until 1966 that the first thermal printer was released by Texas Instruments INC. from Dallas. The components required for printing with precise heat could only be manufactured for the new printing process at this time.
There were some difficulties at the beginning: The thermosensitive paper contained many aggressive substances that damaged the print head. The wear and tear were so great that unusable print heads often had to be replaced with an expensive spare part. It was only in the following years that the formulation of thermal paper improved, but it is still questionable from the point of view of sustainability and health care.
Thermal labels and sustainability
Thermal paper is often used as receipt paper in shops, restaurants or pharmacies. The heat resistance of the paper comes from certain components, which unfortunately also contain harmful substances.
The best-known critical ingredient is bisphenol A, which is considered to influence hormones and to be carcinogenic. The problem is that the harmfulness is not only limited to the paper, but also affects the health of the user. Because of its critical composition, thermal paper must be disposed of in the residual waste.
In the production of thermal paper, colour developers and binders are added to the thermal layer. Bisphenol is usually used as a colour developer. Other additives ensure the strength of the paper.
Manufacturers strive to achieve the best possible durability and colour result with their paper. Bisphenol A is therefore added to the paper to create the colour. In addition, bisphenol S also ensures a good colour result and makes the paper more durable.
In addition, Pergafast 201 is contained in thermal paper. This is a chemical that promotes colour development and is now also used as a substitute for bisphenol S. D-8 is another chemical that aids colour development.
Chemicals used in the production of thermal paper also have an impact on the environment. Most chemicals are disposed of without concern, which has dire consequences. The substitutes D-8 and Pergafast 201 are generally considered less risky - but they are not harmless.
If they get into the water, they trigger fish kills and harm other aquatic animals. Bisphenol A is particularly harmful to humans. Besides cancer, it can trigger or promote several other diseases, such as:
Pregnant women should not have any contact with the substance in order not to harm the unborn child, as it will be exposed to artificial hormones in this case. Young children should also avoid contact with receipts, tickets, etc. made of thermal paper.
The bisphenol is absorbed by the body through the skin. In an adult, this is not dangerous due to its size and severity, as the toxin spreads further, thus containing its danger. With children it is a different story - under no circumstances should they put these slips of paper in their mouths.
Alternatives to conventional thermal labels are organic products. These are produced without phenol.
1.How do I store thermal paper?
The dyes in thermal paper react with solvents and compounds in adhesives. If the printed image encounters these agents, the image will be destroyed over time. Therefore, thermal paper is best stored in dry and cool environments.
High humidity above 60 per cent and temperatures above 40 degrees Celsius should be avoided. These cause the print image to fade. In addition, thermal paper should not be stored together with the following items:
- Adhesives that contain solvents
- Paper containing organic solvents
- Cleaning agents and solvents containing ketone, alcohol or ester
- Carbonless and carbon paper.
Thermal paper is best stored separately from other papers. It can be protected in a plasticiser-free wrapper or in a laminating film. High-quality thermal paper ages much more slowly than low-quality paper.
Inferior thermal paper may tempt you with a low price, but the writing becomes illegible after just a few weeks. There is thermal paper on the market that has a 25-year shelf-life guarantee. But even the best thermal paper only develops its qualities optimally if the storage conditions are ideal.
2.What accessories are available for thermal paper?
Thermal paper is particularly present in industry. Moreover, thermal paper is mainly available in the form of receipt rolls. There are now many accessories that make handling and storage easier.
The receipt roll goes directly into the cash register or into the mobile thermal printer and does not have to be permanently refilled. There is the addition roll and handy holders. These enable the use of several rolls. In this way, the machine can change the roll during use and continue working immediately.
Thermal paper is also used in offices and households, for example in fax machines. Thermal paper is popular with fax machines because it enables high printing speeds. The print quality of thermal paper used in fax machines is also impeccable. Thermal paper is also often used in mobile devices for printing address labels, tags or small receipts.