Labelling on flexible plastic packaging

Thermal transfer (TTO) is the most common labelling method for flexible plastic films and is primarily used in conjunction with vertical and horizontal flowpack machines.

The technology transfers ink from an ink ribbon directly to the plastic film using heat, resulting in very high print quality and sharp details.

The big advantage of TTO is that the marking is both clear and flexible. By choosing different ribbons, the print can be adapted to the design of the packaging. For example, a white ribbon can be used on dark packaging or a black ribbon on light materials to create maximum contrast.

This makes it easy to produce multiple product variants with different colors without having to change the other production equipment.

TTO is particularly suitable for marking:

• best before date
• batch number
• production date
• barcodes
• QR codes and Datamatrix codes
• product information with multiple lines of text

To achieve the best possible results, we recommend that the packaging design is adapted from the start. For example, if a barcode or 2D code is to be scanned quickly in store, it is a great advantage to create a light or white marking surface on the plastic film where the print is placed.

Inkjet marking is a flexible option when applying simpler variable information to plastic packaging.

Both CIJ and TIJ printers are used depending on production speed, material, and print quality requirements.

The method is mainly suitable for:

• best before date
• batch number
• production date
• simpler barcodes
• internal traceability information

In many production lines, labelling is done directly on the plastic film before the package is formed. This provides a more controlled process than trying to label finished bags that often come out of the packaging machine in varying positions and orientations.

When very high print quality or advanced 2D codes are required, TTO is often a better option. However, for simpler date and batch marking, inkjet technology can be both cost-effective and fully adequate.

Laser marking is less common on flexible food packaging and requires careful evaluation of the packaging material.

Many flexible packaging materials consist of multiple thin layers of plastic and barrier materials that protect the product from oxygen and moisture. When a laser is used, there is a risk that these protective layers will be affected or damaged.

If the laser burns through or degrades the barrier layer, the durability of the packaging can be affected. In the worst case, the marking can even go so deep that the product itself is damaged.

Therefore, laser marking is mainly used when:

• the packaging material is specially adapted for laser
• the barrier material is not affected
• a permanent marking is required
• the material supplier has verified that the marking does not impair the function of the packaging

Labels are often used when marking on flexible plastic packaging needs to be supplemented with product information, branding or customized variants.

Depending on the size of the production, labels can be applied both manually and automatically.

Smaller producers often use semi-automatic labelling solutions where the operator places the package and the label is applied with high precision. For larger production lines, labelling machines are integrated directly after the packaging machine where the finished bags are labeled automatically on the conveyor.

Labelling is particularly useful when:

• the same basic packaging is used for several products
• different retailers require their own labels
• information needs to be varied between different markets
• the design changes more often than the packaging film itself

Labels are therefore often used as a flexible complement to printed packaging, especially for smaller series or many product variants.