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The Latest Advances in UV Inks, Part I

Screen Printing asked industry experts to comment on the latest advancements in UV inks.

The advantages of using UV inks are clear, and innovative advancements continue. This article asks suppliers involved in basic R&D and industry experts about improvements, comparisons, and problems with UV inks.

When did UV inks find acceptance?

Larry Hettinger The first patent for a UV-curable printing ink was granted in 1946. The printing industry witnessed a rapid growth in interest in this new technology 20 years later, brought on by the introduction of the first solvent-restrictive legislation (the Los Angeles Pollution Act, 1966). Aimed at reducing the emission of volatile organic compounds (VOCs) into the atmosphere, the Act heralded an age of heightened environmental awareness amongst governments, businesses, and consumers. The printing industry recognized the need for a long-term alternative to its traditional solvent-based ink chemistry. UV curable inks, which contain little or no organic solvents, offered a potential solution.

Bruce Ridge Sales of the first UV inks for screen printing began in the late 1970s. At that time very few printers had the equipment to cure the inks. It was not until the mid-1980s that UV inks were being used and accepted by a large number of screen printers. This is a unique example of something where screen printing has led the way, ahead of all the other printing processes. UV inks for wide-format inkjet printing were introduced in the early 1990s and have quickly advanced in parallel with the development of the printers and their UV curing capabilities. Since it is not practical for inkjet printers to change out inks when they change to printing on different media, there is a far greater need for UV inkjet inks to be more multipurpose in function.

Johnny Shell, Ray Greenwood, Jeff Burton UV inks appeared in the printing industry in the 1970s. They really started gaining momentum in the late 1980s and now are extensively used in the screen-printing industry. Wide-format digital saw popularity of UV begin to grow in the early 2000s. Sales of UV printers have been given considerable momentum with extensive environmental regulations worldwide.

Scott Schinlever In terms of digital printing, back in 2002 was when UV inks entered the scene. VUTEk, Durst, and Inca all came out with digital printers using UV inks at the same time then. We develop and produce our own inks for use with our digital printers. The advantage to producing your own UV inks is that you can optimize the process, do more testing and develop ink sets for a particular printer. By having the control, it gets you to market faster. Unlike screen printing, with digital, the inks are developed for a particular printer performance. Inks are tightly coupled to the printer. Because of this, it’s an advantage to produce UV inksets matched to a particular printer.

Robin McMillan Since the 1980s, there has been a gradual migration toward UV ink usage. The plastic-container market has evolved to about 70% use today. The graphics market has evolved to 90% acceptance. Other markets, like optical disc and narrow web for labels, have been 100% UV usage since the mid-1990s when CD-ROMs and CDs went mainstream. The automotive market, on the other hand, has the smallest acceptance at this point, at maybe 10-15%. This is an area where we foresee significant growth.

Michael Plier UV inks started being accepted almost immediately. The logistics and theory behind this technology was logical. However, while this technology was welcomed, or at least considered feasible, it did come with drawbacks. There was a learning curve to say the least.

Why?

Johnny Shell, Ray Greenwood, Jeff Burton UV inks provide color density and image quality, while also providing greater production efficiencies. Unlike solvent or water-based ink systems where a large percentage evaporates, UV is 100% solids, so there is less waste. Curing occurs instantly with UV, whereas solvent-based systems require inline heaters (digital). Screen requires ovens or drying racks. UV inks for screen printing also have the added benefit of faster print cycles and less viscosity changes due to evaporation on press. This makes the print speed and color more consistent throughout the run. One of the added benefits is the need for excessive floor space to accommodate curing equipment. The length of UV is about one quarter that of forced-air systems for solvent-based inks. As air-quality requirements have become more stringent due to the evaporative nature of solvent-based screen-printing inks, UV inks have become even more attractive.

Scott Schinlever The advantage of UV ink is that it adheres to a wide variety of rigid substrates. There are minimal VOCs released in the printing process, making printing with UV inks a greener process than using solvent-based ink. And the solvent-based inks only adhere to flexible substrates. It takes more time and labor if the printing is done on a flexible laminate, and the laminate needs to adhere to a rigid substrate. UV inks are expandable and print well on either flexible or rigid substrates.

Larry Hettinger The advances in UV chemistry were accompanied by corresponding advances in the design and manufacture of UV curing equipment. The case for UV was further strengthened by the availability of specialized inks geared toward particular applications. There are now few limitations on what can be printed using UV ink.

Bruce Ridge It was critical for screen printing to increase production speeds, which UV ink facilitated by allowing the development of inline and circular-format multicolor printing machines for graphics applications. The development of UV inks for inkjet printing has facilitated faster production speeds in all formats, as well as the development of flatbed machines that print large-format rigid media.

What are customers looking for in UV inks?

Mike Plier Is this a trick question? They’re looking for speed, efficiency and performance. UV systems are fast, eco-friendly, and performance is king.

Larry Hettinger They’re looking for the ability to produce superior quality prints faster and at lower cost using more environmentally friendly chemistry. Today’s product improvements have evolved to improve performance for numerous unique applications, reduce ink consumption, and minimize waste. It is all about productivity. Getting from proof to press faster and maintaining color through a press run is critical to ensure process control in today’s wide-format-print environment. It is about printing repeatable and consistent color.

Steve Mitchell Energy curable inks and coatings continue to be one of the fastest growing segments within the printing industry. One of the big reasons for this is continued interest in green technology. Energy curable (EC) inks are considered to be 100% solids. A goal of EC printers is to continually improve cure speeds. Faster and faster press speeds are now being offered by most ink companies. It is not uncommon to cure a fairly heavy ink film with one or two UV lamps where in the past several were required. Because there is instantaneous cure of the ink, it is not uncommon to apply a heavy coverage of screen white, overprint with UV flexo, and then apply a coating, diecut inline, and ship labels right out the door.

Robin McMillan More and more of our customers are increasingly turning to UV solutions. The main reason is because UV inks help cost savings even further. UV inks may typically cost more than solvent-based inks, but they can ultimately save users by as much as 30%, depending on the printers they use. The inks are easy to use, dry instantly when cured, and provide significant throughput savings, which are derived from a higher coverage per pound, thus reducing ink usage, requiring fewer stops and wash-ups, and increasing productivity. In the screen-printing industry, unlike other ink-printing processes that might require cleaning during a print job, screens don’t have to be cleaned when using UV inks, thus increasing screen stability and productivity.

Grant Shouldice The main value proposition for UV inks is in the generation of efficiency in the printing process. Other reasons include superior aesthetic properties including gloss (acrylic polymers formed in situ are inherently glossy), superior mechanical properties with great adhesion to a variety of substrates, and there are zero VOCs.

Bruce Ridge Printers are looking for inks that cure fast, work well on a multitude of substrates/media, have a low residual odor, low VOCs, and are competitively priced.

What are some of the specific advances in UV inks for screen and digital printing?

Scott Schinlever I can only talk about printing with UV ink on a digital printer. As substrates, UV ink can adhere to a wider range of substrates. The color gamut is wider using UV ink. It’s more flexible (can be stretched), such as in fleet graphics, where vehicles are wrapped in print. In the future users will want more stretch and adherence in their prints.

Bruce Ridge For the most part, UV-ink technology for screen printing has not seen a lot of big advances in the last five years. Most of the advancements in UV screen inks have been in modifying products to meet the specific needs of the market. There have been a lot of advancements in the inkjet UV products as the demand increases, which leads to more competition and more innovation.

Steve Mitchell Many advances in UV screen and digital are currently proprietary, but I can hint that there’s a big interest in LED curing and UV shrink.

Michael J. Plier We are seeing an age where the potential digital print or decorating is literally limited only by our imagination. With the artesian supply of new UV components, it appears that digital printing is well on its way to being one of the most versatile printing methods we have ever seen. In in-mold-decorating inks, UV inks can be specifically designed to withstand extreme heat and pressure created by the backfilling process. In architectural glass inks, UV digital systems can achieve 100% adhesion along with excellent moisture, steam, frost, and thermocycling resistance. New UV digital adhesives have a broad range of applications from laminating to mounting. You can print chemical- and solvent-resistant inks for fleet graphics or decals.

Larry Hettinger In recent years, the availability of new raw materials has allowed us to develop UV inks that print and cure faster, use less energy, and provide more vibrant colors. Four-color-process work has benefited the most from these advancements—specifically with low-dot-gain UV formulations that allow for increased press speeds.

Johnny Shell, Ray Greenwood, Jeff Burton The gamut for digital UV inks has improved dramatically, as have the improvements in flexibility. Adhesion is more of an issue with the media than the ink itself. In screen printing, there is a specific ink for every type of substrate, while in digital, you’re trying to shoehorn every substrate on the planet to work with one type of ink.

Curt Baskin Our firm invests significantly in the development and research needed to provide the highest quality UV inks in each of the various industries we serve. The automotive market is one area where we are working on advancements in UV inks. Auto manufacturers are increasingly using 3-D plastic parts that require robust and durable ink systems that pass the OEM’s specifications but still maintain elongation properties.

Are there problems with UV inks?

Steve Mitchell In some instances it is important as you increase cure speed of the ink or coating that you maintain flexibility as well.

Scott Schinlever Cracking can occur on some substrates when the lamps are not properly set for curing the ink. We have seen this on acrylics; however, there is now at least one company that makes an acrylic for digital printing that has eliminated this issue.

Curt Baskin There are limitations, but our ink formulations have been tested and designed to meet and often exceed customer and end-user expectations, when following our processing guidelines in terms of high productivity, consistent printing of solid and vibrant colors, and the reproduction of sharp lines to obtain readability of bar codes and small text. The ink must also perform as good as, if not better than, conventional inks in managing scuff and abrasion resistance, flaking, and fade.

Johnny Shell, Ray Greenwood, and Jeff Burton UV ink formulations are typically focused on a specific range of applications: usually rigid or flexible. Formulators are constantly working to bridge this gap; unfortunately, the monomers and oligomers commonly used have limited characteristics. For digital inkjet printing, bi-directional printing can still leave a visual path or swath (often called banding or bi-directional banding). Different manufacturers have ways of mitigating these stripes by either using a software solution or by using a varnish to create an equal gloss level over the entire print.

Grant Shouldice There are system challenges in UV printing and, as such, inks and presses and other inputs to the system need to work in concert to achieve the desired output for any application.

Michael J. Plier You bet. Please keep in mind that UV inks are 100% solids. Solvents are 30% solids, or in the case of digital inks, considerably less. Right form the start, UV systems have an initial disadvantage, as the cured ink film is considerably greater; with solvent, considerably less. With any coating or ink there are a variety of resins to choose from for a given application. Often to obtain the best overall performance, the blending of a variety of these components can offer an extremely broad range of adhesion and physical properties. The difficulty in such formulations is to find the correct ratios for the wide range of applications.

Larry Hettinger The primary problems are encountered when inks are not used for the intended application they were designed for. Current inks can be designed for greater application latitude than they were in the past, though inks must always be matched up with their intended use and application requirements. For instance, when you mention cracking—you might be asking about misuse of UV ink for applications such as printing double-sided on styrene and then diecutting or too much UV that can result in brittle ink and media that will cause cracking.  

Click here to read Part II of this panel discussion.

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