by Melissa Donovan
Digital printing is well-suited to small to medium, variable runs of labels. However, digital printing is an all-encompassing word and many types of ink sets and technologies fall under the heading. No one substrate is truly a fit for every type of technology. Here we discuss the various options for label printing and how they play nicely with each type.
A Well-Suited Match
Labels are printed using liquid electrophotographic (LEP), dry/liquid toner, and inkjet technologies. Each technology favors certain media options. The two many media options for label applications are paper-based and synthetic, which includes polycarbonate, polyester, PVC, and biaxially-oriented polypropylene (BOPP).
“The technologies are different so there are some various requirements that the equipment itself puts on the options,” explains MaryAnn Geers, SVP of corporate strategy and marketing, GPA, part of Fedrigoni Group.
HP Indigo’s LEP technology is essentially its own enclosed system due to the inline primer, Paul Lender, business development manager – digital, Avery Dennison Label and Packaging Materials, notes that this allows for most substrates to be primed inline and printed—offering a range of products to press owners.
Toner-based presses need to be able to work with media that can withstand high heat. Dry toner “can take advantage of most standard substrates without the need for additional priming or treatment, again offering a wide portfolio of products to equipment owners,” shares Lender.
Inkjet technologies offer a nice range of compatible options, however there is still criteria that must be met.
“Looking at inkjet technologies, the application and printing method are critical factors. If you have a more commodity-based application that needs to be wrapped around irregular surfaces, you may choose PVC film. In addition to PVC, common printable coated films for inkjet technologies include polyester and BOPP,” says Neil Gillespie, VP of technologies, Dunmore.
When it comes to UV inkjet technologies, Lender believes most paper substrates can run through these presses without experiencing challenges. “Although some glossier materials may require a primer or treatment. UV inkjet films also typically require a primer for optimal adhesion and print performance.”
Water-based inkjet is a bit more restricted. “This requires all substrates to be printed or coated for optimal performance. This can limit the size of product portfolios offered, but smaller portfolios of the most common papers and films are available,” explains Lender.
Most to Least Challenging
Comparing LEP, dry/liquid toner, and inkjet media support varies as discussed above. Each technology can be ranked from most challenging in terms of media support to easiest.
In terms of most challenging, Lender believes water-based inkjet substrates fall under that category. He says they are the most highly engineered of the digital products. “All require a coating for optimal performance. This comes with increased costs and manufacturing requirements, which can limit the number of products that can be offered for papers and films.”
“Due to print receptive challenges and the limitations with current printable coating technologies, media options are limited,” agrees Gillespie. He provides an example of how clear, glossy water-based inkjet media is not yet available.
Next would be UV inkjet—even though there are some materials that require special primers or treatments, many products exist and just need performance on press verified. UV inkjet OEMs and substrate suppliers work together to determine the best product and equipment combination.
“This allows for a fairly large portfolio of products that include typical core papers and films as well as some specialty products,” explains Lender.
Most vendors agree that dry toner is the easiest in terms of media support. This is because “it typically uses the standard products without any additional need for treatment,” says Lender.
When choosing the correct label stock—outside of pairing to the best ink technology—there are additional factors to consider. These include what it will adhere to, surface conditions, exposure/temperature, permanent or removable, and regulations or testing.
Geers says the folks at GPA ask the following questions to determine the best media for the job. “How is it going to be printed? What type of finishing—kiss cut or die cut? What is the exact surface it is being applied to and how long is the expectation for use? What conditions will it be exposed to? How will the label be applied and what size will it be? Are there compliance regulations it needs to be adhered to? FDA for direct/indirect? RoHS?”
Gillespie believes the most important factors when choosing label stock are the application and the print process. “For example, if you have an outdoor, durable application you want to make sure that you choose a robust substrate such as polyester, which has excellent strength and durability characteristics.”
“First consideration is the substrate itself, paper or film. That should be followed by adhesive requirements—what will the label be adhered to, what are the application and service temperature requirements, permanence/removability. You will also need to consider if there are special needs of UL, pharmaceutical, or other compliance needs. It can be a complicated process,” admits Lender.
Beyond performance requirements, Gillespie also says aesthetics should be addressed. “For instance, you could be looking for a clear, no label look or you may need a bright and shiny label to attract the attention of the consumer.”
Here are some of the latest advancements in terms of label stocks designed for digital print.
LEP technologies are commonly used for shrink and flexpack applications, but Lender says other digital technologies are beginning to be adopted. “EP has been used for a couple of years to a lesser extent. In 2020, the UV inkjet OEMs started to show that they too could print shrink and flexpack materials.”
Avery Dennison continues to work with OEMs to expand its portfolio of qualified and recommended products for all digital print technologies.
Sustainability continues to influence label media. “Label media that utilizes post-consumer recyclable film or biodegradable film are becoming more present in the label market. We predict this trend will continue to be adopted for traditional and digital print technologies. These films bring along new challenges that will need to be addressed with new printable coating technologies,” shares Gillespie.
Coinciding with this, Dunmore recently debuted a new line of UV inkjet compatible films. Dun-Jet UV inkjet films provide excellent print adhesion and print quality across various UV inkjet printers.
Geers says the latest advancements are film facestocks that are PVC free, label materials for customized shelf marking applications, one-step floor graphic label materials vs. standard two step, and label materials with tamper or security features.
GPA now offers materials for customized shelf marking for both liquid ink and dry toner technology; PVC-free film facestocks for liquid ink, UV inkjet, and dry toner; one-step floor graphics for dry toner and UV inkjet; and tamper evident or security features with liquid ink.
In an ideal world, there would be one label media that would work well across all print technologies. “The label market still has challenges with label media working across different printing platforms. Printable, coated films often only excel with a few printing methods. As a result multiple SKUs are needed. Having a more universal, print receptive media would be very beneficial for the whole supply chain,” notes Gillespie.
For now, the important rules of thumb remain—match the application to the media. Where and how the label is used is a large factor in determining the best substrate—and print technology—for the job at hand.
Feb2021, DPS Magazine