Evonik – Innovations in Linerless Thermal Label Systems

For linerless labels, the silicone release coating is applied invisibly to the upper surface of the printed label and the adhesive is coated on the backside, allowing the labels to be rolled-up without sticking to each other (Source: Evonik)

Linerless technology is gaining importance in the label market – Evonik is driving this development with an innovative release coating. For producing linerless thermal labels with more economical paper, Evonik has designed TEGO RC 1717 which provides the required barrier properties.

This enables a special Eco-grade paper to be used that has no top coat resulting in significant cost savings. Using Tego RC 1717 with Tego RC 902, and Tego photo initiator A18 provides a superior coating layer. This blend offers good silicone hold out and improved anchorage, providing stable premium release properties over time and shows outstanding printing performance with no silicone build-up on printing heads. Additionally, substrates coated with the above blend are safe to use in food applications (ISEGA).

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For linerless labels, the silicone release coating is applied invisibly to the upper surface of the printed label and the adhesive is coated on the backside, allowing the labels to be rolled-up without sticking to each other.

With 23.2 billion square metres, the pressure-sensitive label market represents the majority of the global release liner market. According to the latest research from AWA (Alexander Watson Associates), the linerless label market accounts for just 4% of the total label market. However, with cost savings of up to 14.5%, a 30 % reduction in waste and energy savings gained from leaner logistics, the eco-friendly benefits are strong drivers for linerless technology.

Linerless thermal labels

Variable information print (VIP) is another driver in the label market pushing thermal print solutions forward. Direct thermal print labels have a thermal sensitive face stock material like paper or film. Linerless thermal labels are printable by thermal printers after siliconizing allowing VIP on demand for labels with differing lengths. Daily life examples include packages from delivery services and at the supermarket’s cheese counter. The required variable information about the goods is printed on a thermal label. In both examples linerless labels provide a cost effective alternative to standard thermal labels.

Linerless thermal labels mean fewer roll changes due to 50 % more labels per roll, a variable label length, handling and consumer safety advantages by replacing  the  stapling of the sales slip, stain protection and premium haptics due to the smooth silicone coating.

The linerless thermal label market has the potential to grow from the current size of several hundred million square metres to more than 2 billion square metres. Upgrades for the thermal printing equipment (non-stick coated carrier rollers and knifes, dispensers) to implement linerless label production and use are already available, but until now siliconizing has required top coated thermal paper.

Standard Eco-grade papers without a top coat have a poor silicone hold out and require a high silicone coat weight, and do not work for linerless thermal labels because printing performance is poor: silicone penetrates into the thermal sensitive layer and constrains the colour response. The lack of a barrier layer can also lead to migration of adhesive components or dye to the thermal sensitive layer.

Samples of linerless labels displayed at Labelexpo Europe 2017 (Source: Evonik) (Image: Carsten Behler, cb@carstenbehler.de)

Siliconisation for linerless thermal technology

UV curable silicones are the only release technology that works without activating the heat sensitive dye of thermal paper. Conventional thermal silicones cure through heat, so are not suitable for thermal sensitive layers. According to the company, radiation curable silicones from Evonik cure when subjected to ultraviolet light and adhere to the surface in a fraction of a second.

According to the company, its Tego RC 1717 provides the required barrier properties for using linerless thermal labels with more economical papers. By enabling the use of cost-effective thermal papers for linerless applications, Evonik’s RC technology provides an economic advantage and ecological benefits from reducing wastage and using less energy.

This article was first published in NarrowWebTech, print issue 2-2018.

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