Label substrates: New challenges for already familiar materials
The marketplace for paper and film products used for labels and packaging continues to expand across the globe, despite occasional economic turn-arounds. Papers remain the top choice for labels, though films, with their abilities to achieve that which papers cannot in a variety of environments, maintain their high level of demand and exhibit steady annual growth in labelling and packaging.
by Jack Kenny
Material costs have spurred on many converters and end users to seek lower caliper label stocks, in films and papers. Reducing the thickness of the substrate comes with its own set of challenges, particularly with respect to press tension, but talented converters are satisfying the growing desire for lighter and less costly label materials.
The growth of digital colour label printing over the past two decades, and particularly in the past few years, has resulted in a subset of printable materials for use on digital presses. UV inkjet presses have required exhaustive testing of materials to determine the best possible treatments in order to achieve satisfactory results.
Paper substrates are entrenched as a label media in many sectors, including wine and beer, foods and canned goods, various types of beverage labels, extended content labels (which continue to grow), pharmaceuticals and nutraceuticals, thermal transfer and direct thermal applications, and many more. Unless it is heavily laminated, paper is not a durable product, which is one area in which films excel.
Film labels are to be found on chemical drums, outdoor equipment, tools of all kinds, automotive parts and assemblies, and many medical products because they can endure exposure to heat and cold, moisture and abrasion, in ways no other label can.
In the realm of beauty products, both papers and films have their special niches. A clear label with distinctive colour graphics will attract the eye of a discerning shopper, as will a textured paper label with embossing and fine metallic treatment. In the area of high quality consumer goods, papers and films are strong competitors. However, both kinds of substrates are also recyclable, and a growing number of end users are enquiring about making use of post-consumer recycled materials in their packaging.
Polypropylene, polyethylene, polyester and polyvinyl chloride still dominate the packaging production process for films. Yet not every film can accept print with ease from all of the various types of presses .
“The differences are in the print technologies – whether it’s UV inkjet or thermal transfer – and the printer has to consider the print receptivity of those films,” said Brian Ayers, product manager with Flexcon’s Product Identification Business Team. “They have to be printable by all processes, including the newer digital technologies.”
His colleague Ron Ducharme, also a product manager with the same team, said the specific challenge is to get the ink to adhere. “Whether it’s inkjet or thermal, they can’t use just a generic topcoat. We are finding that the film materials present more challenges with some of those processes; they are more limited than flexo. A lot more testing is involved; as there are a lot more factors involved than just putting up a good polyester with a topcoat.”
Flexcon, based in Massachusetts, USA, produces a wide range of film products, and one of its specialties is durable materials for hazardous or outdoor use, including shipping containers, whose labels must be manufactured to endure submersion in sea water. “Agency recognitions apply,” said Akers. “The focus is not just on the film any more, but will it pass the recommendations with the print technology chosen. Everyone involved has to make sure those products are going to print, and be durable.”
“We have a team working directly with digital printing OEMs, and we are directly involved with Underwriters Laboratories and CUL (the Canadian counterpart),” noted Ducharme. “We have a big push forward going on in that market area to make it possible for the converter to produce the best printed product. We examine all aspects – the printability, the diecutting capability, the press type, the substrate characteristics, how they run, and how to get the ink to stick.”
Akers makes reference to the Global Harmonized System, a worldwide program governing the labelling of chemical and petroleum products. “We’ve always had to label drums, but in the past every country and region had its own system, its own wording and languages. Over the past two years the industry has been working on new international standards, which are supposed to be fully implemented this year. The idea is to identify hazards based on pictograms, specified through standards that everyone agrees upon, uses and understands. It involves variable information on drum labels in red and black ink, mostly using thermal transfer printers. A lot of folks are using UV inkjet printing for these labels. As you can imagine, there’s a lot of testing being done on these processes with durable substrates – testing for salt water immersion, and many others.
“What we’re trying to do is identify the films that will work with various print technologies, and to identify the films so that we can use one topcoat for all. Right now durable print has very many options with different films and different topcoats. Some companies are using consumer-type printers in industrial applications. There’s quite a lot of investigation going on in the market right now. So we are scrambling to get coatings for these that will pass agency specifications.”
PVC cannot be cut with a laser diecutter because chlorine gas will be released, but polyethylene and polypropylene are diecut every day on paper and glassine liners. One challenge reported by Ducharme is diecutting clear film on a clear release liner. “A lot of people in the industry are wrestling with it right now.” Film liners, he added, are big in the beverage sector, because paper liners leave fibre patterns in the adhesive, which trap air and lead to label application problems.
The market development manager for the wine and spirits sector Jean Willson of UPM Raflatac in the USA sees many packaging and label designers who want to make use of substrates without knowing how or whether they will perform in the various stages of production., Willson works with end users to make sure that their ideas are capable of making it to market.
“Designers often see the types of beautiful papers that are coming out now, with fibres embedded in them, and films and metallics, but many times they have not been tested for the pressure sensitive market,” she said. “What we often find is that designers recommendations can’t be diecut, and then it becomes a development project with a paper company to create a stronger stock that can be diecut. We try to educate them early on about papers and adhesives, about colour and inks, what works and what won’t work.
“Another challenge is that a customer will complain that a wine label has printed poorly on paper, and it turns out that they were printed with water based flexo, which usually will never work. Printers primarily use UV flexo or UV offset for the highly textured sheet in order to get the ink coat weight down. There’s some misunderstanding about how to print some of those graphics. With many wine papers you’re dealing with peaks and valleys, and a lot of pits. It’s important to back off the fine lines on the plate, and to put more ink coverage down. Also, these papers are absorbent, which is a double whammy. Water based flexo will hardly ever work on that type of substrate. Varnish is usually not going to work either because the sheet is uncoated and you will get smearing.”
With film labels, Willson added, one of the biggest issues is press tension. “When the thickness of the film is going down to 1.6 mil or 0.92 mil, then the operator might not be making the connection to readjust the tension on the press. Some education is needed here.”
In discussing substrate trends, Willson mentioned a consumer group that is being closely watched as highly influential these days when it comes to packaging trends: the Millennials, those people now in their late teens to early 30s (see Kenny’s Column, page 17).
“Wineries are taking advantage of wine papers that are textured, embossed, with just a little colour and pattern,” Willson said. “Craft spirits and other beverages are driving this, pushing more toward textured papers, to have either an old style look or something new and different. We are finding in the craft beverages market that there are two things at work: a continuation of the traditional strain that the Millenials want, so that they can go to the shelf and be able to identify their dad’s whiskey. They want that tradition in the standard products, but in other labels they want fresh, clean new packaging, to identify it as new. And third, they want some type of coloured image showing through the bottle.”
Beyond that, she said, the Millennials want to see what they are eating and drinking when it comes to craft beverages and foods. “There’s also a trend in how the Millennials are handling bottles,” she observed. “They’ll take a bottle of vodka or tequila and put it into the freezer, transport it in a cooler to a party where it gets warm, then put it back into the cooler and then once more to the freezer. That exposes the label to a freeze-thaw cycle, which we have had to address.
“We’ve also had to change some of the adhesives on our film products from general all-purpose to cold-stick adhesives. Also with papers: Now we’re being asked to come up with wet strength papers for those bottles going into refrigerators or coolers.”
Substrates and inks are the two most visible aspects of a label, and therefore make producing a high quality identification product an exciting and rewarding challenge. The teamwork among converters, materials suppliers and the end user is certain to meet the label and packaging needs of ever more demanding generations to come.