With the increased demand for environmentally sustainable consumables, the all important flexo plate continues to evolve.
By Steve Katz
Flexographic printing is fast, efficient and economical. And flexo technology that is used to convert pressure sensitive labels has evolved to the point where the quality can stand toe-to-toe with other printing methods. (See Flexo Trends, L&NW, April 2009). Flexo has advanced to the point where it is now, far and away, the predominant label printing technology in North America and elsewhere, and it continues to pick up steam globally.
Aristotle said, “The whole is more than the sum of its parts.” Of course, he wasn’t referring to flexo printing, but he was drawing upon the idea that various components, of anything, work together and complement each other to form a grander something. And a pressure sensitive label is the coming together of inks, coatings, substrates, adhesive and liner. Like the relationship between a chef, the ingredients and tools he has at his disposal, the label printer also relies on the supplies and tools at hand. In the case of flexo converting, the role of the printing plate is as important as any. After all, it can be said that when plate meets substrate, the graphic portion of the label is ultimately made, and it’s the graphics that consumers pay attention to.
Printing plates are an extension of rubber stamps. They are relief plates with image elements raised above open areas.Flexo plates, in contrast with hard letterpress plates, are elastomeric, as they must conform to a cylinder. And just like any other aspect of label converting consumables, printers want plates that are durable and affordable while maintaining the highest quality. Throw in the ever-increasing drive for environmental sustainability, and the ante is upped when it comes to the importance of choosing the right plate for the job at hand.
Plates have come a long way. In 2002, DuPont introduced Cyrel FAST technology to eliminate the use of solvents in plate processing. Here, the plates, after exposure, are developed by removing the unexposed photopolymer by thermally melting it away. Digital plates are now available from plate suppliers for use in computer-to-plate digital imagers.
“Historically, the desire for improved print quality and the elimination of solvent-based plate processing chemistries have been constant objectives in the flexo tag and label segment – and that’s still the case,” notes Ray Bodwell, marketing manager for DuPont Packaging Graphics, Wilmington, DE, USA. “The launch of digital Cyrel and the small format Esko CDI allowed narrow web printers to significantly close the quality gap with offset, and the introduction of thermal process Cyrel FAST plates, along with the move to UV inks, assisted these printers in removing virtually all solvents from their plants,” he says.
Bodwell also emphasizes that quality and sustainability are key industry issues going forward. “Products such as next generation digital plates, the Cyrel XD system for hybrid dots and DuPont TR3 – our program for the complete recover, reuse or recycling of all DuPont plates and plate packaging – are clearly focused on satisfying the needs of this important packaging segment.”
Plates have also become a vehicle for printers to stand out among the competition. “Label printers are looking for ways to grow their businesses and further differentiate themselves in the marketplace,” says John Anderson, director, packaging segment marketing for Kodak, Rochester, NY, USA. “To do this, label printers are discovering ways to increase their resolution capabilities as well as improve image consistency in order to match, or surpass, labels and other products produced by offset and digital printing. Label printers also seek to increase their plate life,” he says.
Like most any label printing consumable, flexo plates continue to evolve, as it becomes increasingly more pertinent to be environmentally sustainable – and it’s always been important for products to be cost-effective.
Connecting the dots
Some label converters make their own plates, while others outsource. Christopher Green is business development manager for PRP Flexo, Indianapolis, IN, USA. He says there are basically two schools of thought regarding whether to buy or make one’s plates. He says, “With shorter lead times, many printers believe that they must have platemaking internalized, in case they damage a plate on press, for instance. These folks are typically using thermally processed digital plates, to avoid bringing solvents into their building. Although there is a level of convenience and security provided with this, there are some inherent compromises to the approach. The line-screens available for thermally processed plates are limited to about 150-line screen, and the halftone dots created by these systems have rounded tops. Like conventional solvent-processed digital plates, these plates require a bump curve to ensure minimum dots are held in the plate, as well as compression compensation for dot gain.”
Dot gain. Printers and plate people talk about this. Dot gain is a common attribute of flexo print that label converters contend with daily. It occurs because flexo plate dots are compressible and can spread out under pressure, resulting in the application of more ink than is desired.
Green says that PRP Flexo’s label customers request plates that are manufactured with the company’s patent-pending Digital ExSpect process. Here, the material choice is solely up to the customer, and it’s the process that they’re after that results in the right dot levels and no curves. He explains: “We manufacture plates from the customer’s preferred digital material, in any standard caliper, and at sizes up to 52 x 80. The dot profile generated by this process is a truly flat-topped dot. Digital ExSpect plates tend to last longer than conventional digital plates – including thermally processed plates – particularly in vignette areas, and may reduce the need for emergency replacement plates significantly. Halftone dots are exactly the same size as the ablated lam layer, with no bump curves required. Additionally, the dot bevel is engineered to provide about 1/3 more relief depth between the halftone dots, where it matters. Thus, the individual dots respond individually to variations in impression. Dot gain is dramatically reduced, often eliminating the need for any cutback curves,” Green says.
Kodak’s John Anderson says a popular plate among the company’s label customers is the Kodak Flexcel NX Plate, which he describes as “a high-quality flexographic plate providing excellent ink transfer, smooth solids, uniform lay down and robust on-press performance.” Anderson points to the plate’s versatility as key attribute. He says, “Flexcel NX plates are designed to print on a wide variety of substrates, including flexible packaging, foil, film, paper, plastic bags, labels and envelopes. The plates are part of the complete solution that Kodak offers to packaging printers. There are a number of wine label printers in California using and finding success with these plates,” Anderson adds.
Tyler Harrell, technologies manager, Anderson & Vreeland Inc., Bryan, OH, USA, emphasizes that it’s difficult to determine one type of plate being better than others. “It’s a difficult question as there are so many plates for so many different applications,” he says. “The three most popular plates today are nyloflex ACE, ACT and FAB from Flint Group. The nyloflex ACE plate is an excellent plate that is very widely used in the label arena. Printers like the dot gain control of this plate and it’s durability. The nyloflex FAB plate is making a push as some narrow web printers need the qualities of the ACE plate but require better ‘drape’ and the FAB plate delivers on both accounts, while also delivering excellent results with UV inks. A softer durometer plate that’s performed very well in labeling is the nyloflex ACT plate. It offers minimal dot gain in halftone areas while ensuring consistent ink lay down and good solid ink densities,” Harrell says.
Dot structure is most important as it relates to dot gain, Harrell points out. “Typically, the flatter the dot top the more difficult gain is to control, particularly as it pertains to run length. Traditional digital dots (rounded tops, steep shoulders) still provide the optimum results as they print with a low dot gain aspect, and reverses and shadows will not fill in. While this can be achieved with analog or flat top technologies, it is much more difficult to control,” he says.
Mark Barnard, president of Sarasota, FL, based Trinity Graphic USA, says dot structure and integrity has become paramount, and its today’s computer-driven technology that’s become a real prepress asset. “Software to allow various dot structures have come along way in recent years. At Trinity Graphic, we use several of these depending on the subject to be printed. I think that is the most exciting thing in the flexo arena. New technology is still coming at a fast pace. Software companies are constantly improving the ability to put smaller dots on plate along with smoother gradients and faster trapping. The list goes on,” Barnard says.
Harrell also emphasizes the importance of the newer – and better – prepress software. He says, “Plate manufacturers are looking for ways to get lower dot gain and better ink transfer all the time. Software vendors are looking at various new screening technologies that help solid densities and improve the flexo ‘transition to zero.’ From the screening/imaging side you have Esko’s new HD flexo which is a combination of specialized flexo screens and a higher than normal output resolution, and from the plate side the new FAB plate is a dot gain-friendly plate that wraps small cylinders without the possibility of plate lift that some harder plates have.”
Kodak’s John Anderson says the Kodak Flexcel NX plate achieves 1:1:1 imaging from the digital file all the way through to the plate, “allowing for excellent repeatability and consistency for the printing. To do this, the Flexcel NX plate is able to handle a flat top dot structure for impression latitude and plate life. Flexcel NX plates have unique imaging technology with Kodak Squarespot Imaging Technology in combination with a lamination process to achieve outstanding performance,” notes Anderson.
Of course, the right plate is dependent on the situation. “The various qualities are desirable depending on the print conditions, and the job specifications,” Harrell points out. “Harder plates tend to be better for high line screens and fine detail, softer plates for applications where solid coverage is paramount. Converters are looking for a single plate that will handle a wide tonal range for the reproduction of the finest image elements and provide good solid ink densities.”
Thin is in
Flint Group Flexographic Products, Charlotte, NC, USA, acknowledges that environmental awareness and sustainability are on the minds of printers these days. The company has recently launched a line of thin flexo plates that it says offers a host of advantages, including eco-friendliness.
Flint Group’s thinner flexo plate offers
environmental advantages as well cost savings.
The benefits of using a .030" plate as opposed to the most prevalent .067" or even .045" gauge plates are numerous, Stewart says. “These plates offer lower dot gain, faster processing speeds and increased consistency, less distortion and cupping of plates. And the lower weight also leads to reduced shipping costs as well as waste and energy consumption.”
Dan Rosen, sales director, national accounts, says that dot gain is by no means sacrificed with the thinner plates. “Dot gain is equal, or even better with .030" plates as opposed to .067" plates. The same rule holds true in most flexo plate comparisons – thin plates print higher quality. As far as cushion tapes are concerned, recent print studies continue to show the best combination of dot gain and solid ink density is displayed when using firm or medium-firm cushion tapes. The good news is while .030" plates print well; their quality is not so drastically different as to require new separations. In most cases, print jobs can be transitioned from .067" plates to .030" without the need to re-fingerprint and produce new separations.
“Less polymer material results in less absorption of solvents during plate processing, which significantly reduces the drying time,” says Rosen. “Complete solvent processing from exposure through detack takes a little less than an hour, depending on the equipment. In addition to faster processing, thin plates exhibit a more consistent relief layer, because the polymer is washed away to the PET backing.The usual floor variations of ± several thousandths on a .067" plate is reduced to only a few microns. The increase in the consistency of the relief, together with a more consistent floor, result in significantly fewer rejects during platemaking,” he says.
Rosen makes a compelling case for thin plates when it comes to cost savings, and the saving are in the shipping, he says. “Approximately half of the finished plate weight is reduced when changing from .067" to .030" plates.Moreover, thinner plates require less packaging per plate, since more plates can be packaged into one box. Less weight and packaging affords significant savings to companies that ship their plates. For example, using the on-line quotation of UPS next-day air service, a cost was calculated for shipping a box with 7 plates, 42" x 60" in size, from Chicago to Dallas. By simply reducing the weight in changing from .067" to .030" plates, the quoted cost went from $191.85 to $138.70, a savings of $53.15 per shipment. In a year, one would save $13,288 in shipping cost, based on just one shipment per business day, 50 weeks per year. Of course many companies ship much more than one job per day, so the savings would be even higher.”
Reducing the amount of polymer plate material consumed by the use of thinner plates reduces the impact on the environment, adds Stewart. “Less plate material requires fewer raw materials and less energy to produce; less energy is required to process, and less waste is produced at the end of the plate life cycle, as demonstrated in the Eco-Efficiency Analysis (EEA) from BASF, published in November 2008.
“The benefits associated with the use of thinner plates make them a viable choice when considering a more efficient workflow,” says Stewart. “As we learn more about true eco-efficiency, we find that sometimes less equals more, that we can do more with less in a faster period of time, and we can make improvements to our processes and finished print work at the same time. Moving to more sustainable and eco-friendly solutions does not mean we have to give up quality or step backwards in terms of efficiency or cost, but as in the case with using thinner plates, we can even possibly achieve it all.”
Plate manufacture has been an area where avoiding the use of chemicals isn’t always easy. While making the switch from solvent to water-based inks has been quite doable for label converters, removing chemicals from the platemaking process hasn’t been as seamless – perhaps until now.
Japanese company Asahi Photoproducts, with US operations in Atlanta, GA, has recently launched the Asahi AWP line of water-washable digital plates, that David Chinnis, the company’s senior technical advisor, says have been getting a lot of attention from label converters. “The Asahi AWP water-washable plate is a very sustainable, high-resolution plate that has the best ink release of any digital plate in the market today,” he says. “It lets converters print with equivalent densities at lower ink volumes. Extensive trials and live production jobs prove that AWP plates print conventional circular dots down to 15-20 microns and with special screening technologies can reproduce vignette fades down to zero,” he says, adding, “AWP plates also last longer and are more abrasion-resistant. Because the plates forgive changes to printing conditions – like impression – make-readies are faster and cheaper.”
Improvements in drying time are another advantage that the water-based system provides, Chinnis says. “It doesn’t come with the long drying times associated with solvent plate systems – but offers solvent quality dots. The result is that it’s faster, doesn’t emit harmful volatile organic compounds (VOCs), and has smaller energy bills than thermal and solvent processes,” he says.
Asahi AWP plates are new. “They are the result of more than 10 years of research to create a more sustainable plate,” adds Chinnis. “AWP allows converters to print at quality levels superior to solvent plates, and far better than thermal. And while this is a new introduction, we will continue to refine the plate and process to meet even more demanding environmental and quality requirements.”
Many common flexo plates today have a much higher durometer than those in the recent past – the measure of hardness and durability. “Typically, a high durometer means that a plate is very stiff and will have a hard time conforming to the cylinder. Of course, this is of primary concern to anyone printing on a narrow web flexo press. Asahi AWP plates, while having a high durometer, also have a very good drape – along with a better printing surface – to conform to a narrow cylinder.
“One also cannot underestimate the ink transfer of a plate,” adds Chinnis.“The Asahi AWP plate is able to maintain an excellent print surface on the top of the dot that is minimally affected by oxygen present in the exposure of digital plates, unlike most solvent plates. It can carry off and print good solids and shapes. While ink on some plates may slide to the side of a dot and result as ‘dirt’, AWP plates transfer just about all the ink they accept, resulting in clean dots. This clean printing aspect of AWP has allowed printers to minimize the downtime needed to clean plates and maximize the quality output of their presses. The unique resilience of the plate may also allow the press speed to increase without the typical negative results one sees with other materials.”
Digital, Durable ... and LUX
MacDermid Printing Solutions, Atlanta, GA, USA, offers plates that feature resiliency, as well as a technology unique to the company. What’s more, is that the plates are versatile in that there’s not just one way they can be processed.
MacDermid’s Digital CST photopolymer plate
“In addition, these plates offer very quick processing speeds, especially thermal. The capped digital plate (Digital CST) has a micro rough surface that allows for more uniform ink transfer in troublesome areas. This plate also images over 200 line screen, but for printers that suffer from pinholes and other ink transfer related problems, the capped plate can help. MacDermid is the only supplier that makes a digital capped plate,” she says.
Barrett emphasizes that printers want their plates to last and also crave consistency. “The printing plate is one of the most important tools in the entire print production workflow because it’s the only element that translates the information from prepress to the printed substrate. So, very fine imaging, consistency in production, and high resiliency ensure that when these plates go on press each time, they are consistent,” she adds.
Since digital plates have been on the market, the “classic” digital bullet-shaped dot, Barrett says, has allowed a step change in quality for flexo that has enabled print quality rivaling gravure or offset. MacDermid has recently developed a plate technology that results in more of a planar-shaped dot as opposed to the bullet shape. MacDermid has named the line of plates “LUX,” and it officially launched in early May at a press conference at the FTA Forum in Las Vegas, NV, USA.
“Planar dots have been seen to provide more consistency on press as the plates run,” notes Barrett. “The LUX Process uses the same digital pre-press workflow and plates, so no change to the customer’s prepress or capital equipment is required. There is just a simple addition of a tool that enables them to achieve planar dots with normal, commercially available MacDermid plates. In addition, LUX plates from MacDermid can still be processed thermally or in solvent, so there is no special equipment necessary to image the plate, nor is there a special film/emulsion technology required.”