Why don't my labels come off the liner

Written by Oliver Stockton, Managing Director, CILS

Why can’t I easily remove labels from the paper they are supplied on?

You may be wondering why labels are sometimes difficult to remove from their release liner and in this blog, you will see that this is usually down to poor die-cutting.

How labels are cut

Labels and stickers are cut from label material using a rotary or flat-bed die. A good analogy is a cookie-cutter cutting through cookie dough.

A brief explanation of how label material is made

Label material is a two-layer construction comprising of materials such as paper, polyester, vinyl etc and an adhesive. A release liner is then applied to the adhesive. During the label material manufacturing process, the adhesive cures to the label material and becomes a solid. It does not cure to the siliconized release liner and stays tacky ready for you to peel and apply to your product.  This material then needs to be cut out.

The difference between ‘die cut’ and ‘kiss cut’

If we continue the analogy of the cookie cutter, in baking you push the cutter all the way through the dough to create a clean cut all the way through. For labels, this cutting principle is known as ‘die cutting’ and is fine if you want labels cut out in entirety including the liner. This is usually the way that individual decals, branding labels, children’s stickers etc are produced.

Durable Computer imprintable labels need to be manufactured with more precision because you need the label shape to be cut out but still hold on the release liner for feeding through a Laser or Thermal Transfer printer. i.e. the cutter must not cut all the way through the label and the liner.

Rather than using a male and female die set that cuts both the label and liner, dies are used that push the die against a solid flat or cylindrical surface. The die is set up to cut through the label material and adhesive but not cut into the liner. This is known as a ‘kiss cut’.

‘Kiss cut’ precision

If we change analogies, imagine a sandwich where the top layer of bread is the label material, the adhesive is the filling, and the release liner is the bottom layer of bread. Now imagine the pressure, precision and balance that would be required to cut out a shape using a cookie cutter when you only want to cut through the top layer of bread and the filling but must not cut into the bottom layer of bread whatsoever. This is especially difficult if the filling is not fully firm!

Now imagine that this sandwich may only be 25 microns thick!

Consequence of poor die cutting

The biggest problem label users encounter is where the die has cut into the release liner slightly or all the way through in some places. The consequence is that you can’t peel the edge of the label away from the liner and when you do, it tears away with a thin layer of paper stuck to the adhesive rather than removing cleanly.

Anybody who has ever bought a sticker book for a child will have come across this problem. These sticker books are mass-produced to remain cheap and have quality issues that you can live with given their low cost. This level of quality is not acceptable for durable computer imprintable labels.

If you suffer this frustration with your durable labels it is down to one or more of the following:

• They are being cut too quickly
• The cutting heads are not properly balanced
• The die is worn/blunt
• There is an inconsistent coat weight of adhesive
• Inconsistent thickness of label material
• The label die cutting machinery does not have the balance and control to cut through tough durable label materials
• The wrong die cutting machinery is being used
• Poor quality control

Poor die cutting should be one of the main things to look for in a good label production quality control procedure and should never reach the customer.

Removal of waste material from around the label.

During the label material cutting process the waste material is removed from around the labels and it is immediately obvious if the cut is not deep enough because the label will be removed with the waste. Cutting too deep is not so obvious and can only be spotted with frequent manual quality checks during production.

Labels for Thermal Transfer printing always have the waste removed so that the printer can sense the label but some manufacturers prefer to leave the waste material on laser printable labels to give the sheets rigidity rather than use the correct lay-flat liners. Leaving the waste on makes it doubly difficult to see if the cut is precise and these types of labels are usually the worst offenders for problematic label removal.

Conclusion

We believe that during the production process of durable computer imprintable labels there should be as much care and precision in the quality of the die cut as there is in with the print quality and end-use performance.

If you are suffering inconsistent quality make an enquiry and we will provide you with samples and examples of what you should expect.