Surface preparation and embellishments are proving crucial for converters looking to maximise quality, efficiency, and differentiation in today’s competitive label and packaging markets.
Two experts explain how crucial coating and varnishing technologies are for the digital printing industry.
Kevin McKell, CSO at Vetaphone:
“Surface treatment, whether by coating or other method, in this case corona treatment, is fundamental to the performance of a substrate and therefore the quality of the finished product. This could be a label, various types of flexible packaging, or even a folding carton. The principle is to ensure that the surface of the substrate is in premium condition to accept a liquid, which could be ink, lacquer, or adhesive. This is obviously easier with an absorbent substrate like paper or carton board – but with film and foil types, where the liquid ‘balls-up’ on the surface there is a need to modify the surface of the substrate to guarantee adhesion.
“This is where corona treatment brings benefits to production efficiency and quality of end-product. By giving the ink/lacquer the ability to adhere to the substrate, the resulting print quality is consistently higher, and the printing press can operate at its optimum speed. There will also be no need for expensive re-runs, which with the more complex substrates in use these days, can make a serious dent in the profitability of any job – and finally, good ink/lacquer adherence makes for smoother and faster downstream finishing and converting.
“Essentially, it’s the substrate not the method of printing that is the key. For example, in terms of surface treatment there is no difference between toner and inkjet printing. But where digital can vary from other printing techniques such as offset and flexo is the tendency to use stocks that have been primed. In certain cases, surface treatment can offer a more cost-effective alternative to using primed material.
“To appreciate what corona treatment offers it’s necessary to delve into the science behind the process. Non-absorbent substrates like film and foil have property known as a ‘dyne level’. This is a measure of surface tension (or energy) and needs to match the dyne level of the liquid ink/lacquer being applied. Usually, the dyne level of the substrate is lower than the liquid, so needs boosting to allow the ink to wet-out and not bead-up on the surface. Corona treatment raises the dyne level of the substrate with an electrical discharge at close range and in doing so changes the molecular structure of the substrate surface. This allows the liquid ink/lacquer to adhere securely.
“The better the ink adhesion the sharper the dot and the better the image resolution. With on-shelf appeal so critical to a brand’s performance, every stage of print production is vital. The adage that ‘you are only as strong as your weakest link’ applies here. The quality and therefore saleability of the end-product is determined by what happens upstream in the production process. Often seen as a minor ancillary, corona technology that prepares the substrate for printing and converting plays a vital role in determining the final quality of the job.
“Except for the inline primers that certain manufacturers recommend, there are no other special surface treatment requirements for substrates printed digitally. In practice, most substrates can be printed by any process, offset, flexo, gravure, and digital – it’s the substrate that’s the key. Incidentally, although invented and developed for plastic substrates, corona is effective on paper board too because it removes the surface fibres to create a smoother surface for printing.
Paul Edwards, Vice president of the Digital division at INX International Ink Co:
“INX has clear ink (varnish) formulations which can be applied digitally to achieve several effects. Spot varnishing can create areas of the package or label that are glossy. Hence, it can contrast with areas with less gloss and be used to highlight specific areas of interest on the printed product.
“Digital printing systems can use this varnish coat to create embossing effects which are created by different heights and structures; these effects can be both seen and felt by the consumer. INX also has a foil adhesive, which allows the digital creation of metallic effects and can provide a luxuriant look to a product.
“INX does provide analogue varnishes which can be used to change the look and feel of a product. By changing the gloss levels and providing a finish such as ‘Soft Touch’, it can really differentiate a product.
“In Europe, JEDV is a digital varnish solution we supply to premium equipment manufacturers. It delivers excellent performance for high thickness spot varnish applications, and serves as an effective adhesive for high build, coil foil processes. These manufacturers often offer customised lines dedicated to spot varnish and cold foil, ensuring that the formulation is optimised for each specific application.”
“Embellishments have garnered great interest in the digital printing of labels and packaging. These effects, created by both digital and analogue stations on a hybrid digital press, really do enhance the differentiation of the product and are of great interest to brand owners. The trends related to digital printing systems – which can add multiple different embellishments – are currently very strong. I would expect them to grow as the competition in the marketplace increases.
“The challenges start with defining what is the range of embellishments the final customers of brands wish to see. High end label producers likely would implement as many options for differentiation as possible, whereas if the business is more industrial, then a more limited set would be required. It then impacts the choice of printing system and looking for systems that can provide the level of differentiation required, so as not to purchase effects that won’t be utilised by the customer base.
“Some hybrid systems are very customisable and would allow for additions or upgrades later if required. Some systems may only be designed for limited effects. Another consideration is providing potential customers with sample products which can highlight the different embellishment capabilities. It’s likely that many may not know what is possible and thus, the marketing of its capabilities is important.
“We are at a time when interest from brand owners and other customers are looking at the technology, not only to do short run work but also to add digital content and differentiate themselves from other brands and products. The better the differentiation that can be produced, the more you can charge for the final product.
“Adding these differentiators is a relatively low-cost way to increase margins. If you have chosen the most suitable equipment, then the product can be printed in one run and the increase in cost of production is minimal.”
“New technologies can provide even more opportunities. The introduction of high viscosity and high laydown printhead technology can enhance what can be done with digital embellishments, therefore providing even greater differentiation possibilities. Other technologies are available today which allow for a varnish to be patterned in many ways. Some examples would be a different feel, different visual effects, and even holographic effects. This can extend the capabilities of the converter significantly.”
