Linerless Labels: Technology and its history, how to print and convert and apply linerless labels
This article is part of a new series about the basics of label printing, in cooperation with Label Academy.
Linerless pressure-sensitive label technology is not new, it has been around for over 35 years. Today the improved techniques being used and developed have coincided with a greater awareness of the importance of sustainability and the need for retail chains and brand owners to prioritize the environmental issues facing the packaging industry. Millions of tons of used silicone-coated paper and filmic release liners are land filled each year and this is not good environmental practice.
Conventional pressure-sensitive labels, also called self-adhesive labels consist of a face material, an adhesive and a siliconized release liner backing that functions as a carrier for the label and protects the adhesive layer during handling, printing, finishing and right up to the point that the label is ready to be applied.
Applicators and labelers for conventional pressure-sensitive labels need to peel away the backing release liner for each label to be dispensed and successfully apply it to a container, product or pack. The liner then needs to be disposed of as waste.
Conventional pressure-sensitive laminated labels like this produce the highest waste levels of any packaging component, with over 50 percent lost during conversion and final end-use application.
No release liner necessary
Linerless pressure-sensitive labels however enable the release liner to be eliminated. Indeed, the development of the linerless process was driven by the need to remove the backing liner used in pressure-sensitive labeling, in order to minimise wastage.
Today, linerless labels are most commonly found in the form of pressure-sensitive labels for the blank label industry and as thermal labels used in print and apply weigh-price label dispensers. They are also popular in market sectors such as food and logistics, but the impact and growth in the other label markets has been slow.
That situation is now beginning to change as more countries start to tax liner waste as packaging material rather than industrial process waste and it is becoming more difficult and complicated to dispose of the liner. Some of the major packaging users have the ambitious objective of ensuring 100 percent of its packaging designs are reusable, recyclable or suitable for good environmental waste management.
Linerless technology ticks many of the sustainability packaging requirements and with improved coating technology and advanced applicator equipment, there is the potential to impact on several prime label sectors, particularly in food packaging and the labeling of glass bottles and jars.
Manufacturers of packaging converting equipment are now realising the full potential of the linerless decoration system.
HISTORICAL CONTEXT – MONOWEB
Monoweb introduced in the mid 1980’s by Waddington PLC was the first truly linerless pressure-sensitive label.
A silicone coating applied over the surface of the printed substrate allowed a non-contaminated release from the reel. The reel of printed substrate was positioned into the applicator and the profile shape of the label being applied was die-cut at the point of application and then removed from the web by direct application to the container.
There were some drawbacks with the Monoweb system. Any problems with the die-cutting operation immediately stopped the line and the quality and durability of the die tooling was critical. The system also introduced a new set of skills for the line operators, which required
additional knowledge and operating skills, particularly with the die-cutting process, in order to extract the best performance out of the cutting tool.
The system of print to die-cut registration was achieved using a sprocket punched hole system using pins which located into the punched holes to ensure the correct registration between the printed image and the die-cutter. The punched holes located at the edges of the web required removal using slitting and waste extraction.
THE EVOLUTION OF THE LINERLESS LABEL
The development of the linerless labeling has evolved considerably in recent years.
Linerless labels use the same adhesive method as a pressure sensitive label, in that the label has an adhesive layer on the back of the label substrate. There are however some fundamental differences.
A conventional pressure-sensitive label has a face substrate positioned onto a siliconized liner ensuring that the adhesive and face stock do not stick to each other in the roll. The liner also acts as the carrier for the printed and profile cut labels which are dispensed onto the product direct from the liner.
In the linerless process the face stock is printed as a single layer and the label surface is coated with a silicone layer and the adhesive coating applied to the back of the label stock.
Alternatively a separate liner is coated with the adhesive and laminated onto the printed label stock allowing the adhesive to transfer from the liner to the back of the label stock.
The liner and face stock are then de-laminated, the liner is re-wound for reuse leaving a single layer of printed face stock, which is then rewound into a reel. Figure 4.21 compares the structure of a linerless label with that of conventional pressure-sensitive laminate.
The silicone coating on the face on the printed label, prevents the adhesive from adhering to the face of the label (Figure 4.22).
The removal of the need for the backing liner offers significant environmental and cost benefits
Release liners used in conventional self-adhesive systems generally are not recycled and the bulk of them find their way into landfill. By removing the need for a release liner the amount of waste material is significantly reduced and therefore the costs related to waste disposal, storage, transportation and substrate usage are drastically cut.
The removal of the release liner also increases the number of labels per roll resulting in fewer roll changes for press operators and also a reduction in downtime on the filling and label application lines. The increased number labels per reel also reduces the amount of inventory storage space required for the printed label stock.
PRINTING AND CONVERTING LINERLESS LABELS
A common misconception with the linerless system is that special printing equipment is needed to print them. This is not the case and labels are printed using conventional printing machinery.
A typical linerless press configuration will comprise of a single unwind unit, flexographic printing units and a rewind unit. As there is no liner, printing on a single side or both sides of the label substrate can be carried out.
When printing is completed the reels are ready for the second stage which is the application of the adhesive and the silicone coating which also helps to protect against UV and moisture exposure.
Next is the die-cutting process, waste removal and finally the checking/slitting operations.
Individual coating units are used for the hot-melt adhesive and the silicone coating process.
A base liner substrate is coated with the adhesive, at the same time the UV silicone coating is applied to the printed side of the face-stock.
The adhesive coated liner is then laminated to the reverse side of the printed face stock allowing the adhesive coating to be transferred to it. The laminated web then proceeds into the die-cutting unit, the waste matrix is removed and the liner and face stock are separated.
The liner is rewound ready for re-use and the finished linerless printed reels are slit and wound into smaller reels ready for application on the filling or labeling lines.
This method of linerless label manufacturing makes the labels suitable for the following end-use applications.
- Print and apply labeling which require variable data etc. as used in product distribution and logistics tracking
- Primary product decoration of a product or container which does not require a profile shape i.e. best suited for applications requiring square or rectangular cut labels.
It is at the application stage where additional equipment is required. A special cutting unit is required which separates the label ready for application
To apply the label a mechanical or laser cutting system cuts/slits a single label from the adhesive coated linerless reel.
After the cutting process has been completed the label is applied by adhering the leading edge of the label to the container and then wiping the remainder of the label onto the container.
For difficult and uneven surface applications, the single label can be blown onto the container surface using suction to hold the label and air jet to apply the label.
One of the big differences between linerless and pressure-sensitive labels is that linerless labels cannot be profile die-cut during the printing operations.
As explained previously the printing and embellishing processes are carried out using only the single layer of face paper and not the sandwich of substrates used in the conventional pressure sensitive label system.
Because the labels are printed in a continuous reel with no liner to support the individual profile cut label, this means that there are limits on the profile shape of the linerless label.
This limits the label shape to a rectangular or square cut profile. Developments however are taking place to overcome this issue of profile shapes produced in a linerless format.
Because of the limits on the shapes which can be used, linerless systems often use clear film to create the effect of a profile shaped label. The design of the printed image is used to create the effect of a profile shaped label albeit that the label may be square or rectangular in shape.
ADVANTAGES AND DISADVANTAGES OF LINERLESS SYSTEMS
A summary of the advantages and disadvantages of linerless systems is summarized below:
- No release liner required
- Printing, adhesive application, die-cutting and rewinding of finished reels takes place in one pass
- Eliminates the problem of waste removal and re-cycling of the liner material
- Minimal waste matrix required making a material cost saving on face substrate
- More labels per roll and less roll changes during application
- Lower reel weights and transportation costs
- Investment is required for the linerless application equipment
- Some materials are unsuitable for linerless application
- The printer has to apply silicones and adhesives (hotmelt)
- The printer will require suitable coating units
- Filler/labeler will require suitable applicator to apply the linerless labels.