Digital Dilemma, Part Two

Editor’s Note: Jim continues his discussion about digital-printing technologies, inkjet media and how to determine whether a digital-printing unit is right for your sign business. In the large-format, screenprinting market, and among large signshops, flatbed printers have generated a great deal of interest over the past three years. These systems, which use either UV-curable or solvent-based inks, can print onto a wide range of rigid or flexible substrates. Because flatbed printers print directly onto rigid sign substrates, material costs for vinyl, mounting adhesives and overlaminates are reduced. By eliminating some production steps, labor costs are also reduced. Although UV flatbed presses print directly onto uncoated vinyl, special films with permanent and removable adhesives have been developed by such companies as Avery Dennison Corp. (Hamilton, OH). These films comprise a coating that promotes ink adhesion so the printed image doesn’t scratch off. When exposed to intense UV light, ink-system components undergo a chemical reaction that instantly hardens the ink. These systems can print at resolutions of 360 dpi at high-production speeds ranging from 500 to 1,000 sq. ft. per hour. Unlike solvent-based inks, UV-curable inks don’t penetrate vinyl films and attack the adhesive system. Because UV curing systems can produce ozone and airborne particles, and solvent-based inkjet systems can produce hazardous fumes, both equipment types require a ventilation system. Some printers incorporate a ventilation system. Systems that incorporate UV-curable inks provide shops with numerous features and benefits. The inks are lightfast, making them ideal for outdoor signage projects. Because UV inks only cure when they’re exposed to intense UV light, the printheads don’t clog as readily as inkjet printheads using conventional inks. The systems incorporate piezo-inkjet printheads, which require daily cleaning, and offer a print resolution between 360 and 720 dpi. The Durst U.S. Rho 160, Zund UVjet, Nur America Inc. Tempo, EFI-VUTEk PressVu UV 180 EC, Inca Eagle and 3M Graphics Market Center Scotchprint ® 2500UV are among the UV flatbed printers available. Durst, NUR, Vutek, Mutoh, 3M, Oce

Not all flatbed printers use UV-curable inks. Solvent-based inkjet systems include the |2248| Arizona T220, and |1478| Toucan Hybrid. Although the resolution of earlier grand-format printers was rather limited, and suitable only for graphics viewed at a distance, today’s printers have been greatly improved.

Because some flatbed systems are rather large and hefty, consider the amount of floor space required and whether your existing floor can support the machine’s weight. $image1

Eco-solvent printers

Today, eco-solvent printers that can print onto uncoated vinyl films, thus reducing direct-material costs, are making big waves. With pricing starting at approximately $14,000, eco-solvent printers are affordable. Unlike solvent-based inks, eco-solvent systems don’t produce fumes. Therefore, no ventilation hood is required. To accelerate drying and promote ink adhesion, the printers use dryers that fuse the pigmented inks to the vinyl media’s surface.

The printers’ resolutions range from 180 to 1,440 dpi, and they print at speeds up to 200 to 300 sq. ft. per hour.

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Although eco-solvent inks are lightfast and adhere well to vinyl, Laura Wilson, |2323|’s (Irvine, CA) product manager, recommends using overlaminates, especially for demanding applications. An ink may adhere well to vinyl and withstand UV light, but may not be scratch and chemical resistant. Using overlaminates for such applications as vehicle graphics provides added protection. Some available eco-solvent systems include Roland’s VersaCAMM printer/cutter and SOLJET PRO II, and Mutoh’s Falcon Outdoor.

Gerber’s ELAN™ printers are solvent (not eco-solvent) systems that can print onto uncoated media. The printers’ solvent inks are non-toxic and don’t contain harmful VOCs. Plus, they’re extremely vibrant, and chemical and abrasion resistant.

Thermal-transfer printers

Signmakers interested in adding digital-printing services to their arsenal should seriously consider purchasing a thermal-transfer system. Some examples include the Gerber EDGE®, Gerber MAXX® 2 and Roland’s ColorCAMM® PC-600 series printers. These affordable systems are ideal for producing sign applications that require outdoor durability.

Often, thermal-transfer-printer operation is compared to how a typewriter works — both use colored ribbons and transfer color onto a substrate. However, thermal-transfer technology is more sophisticated.

As the name implies, thermal-transfer printers use heat in the printing process. The printheads contain multiple heating elements — each of which rapidly turns on and off to control the printing process. In some systems, the printheads extend the entire width of the print substrate; in other systems, they move back and forth across the web.

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Thermal-transfer systems use a cartridge with a printing ribbon. One side of the ribbon is lightly coated with colored wax or resin. During the printing process, the ribbon’s coated side makes contact with the print media, and the printhead presses on the ribbon’s uncoated side. As the resistors heat up, the coating melts and transfers to the print substrate.

The primary advantages of thermal-transfer systems are brilliant colors and extended outdoor durability (UV stability and water resistance). Many spot colors are available, which makes matching corporate colors easy and accurate.

Thermal printers are also easy to operate and maintain. According to Chris Christensen, product manager for Advantage Sign Supply (Grand Rapids, MI), "Thermal-transfer printers are low maintenance — they require daily cleaning, which involves wiping down the printheads with isopropyl alcohol and cleaning the sprockets."

Although the cost of printing cartridges may seem high, thermal- transfer printing systems don’t require expensive topcoated print media. Also, spot colors allow for the use of a single color, reducing print costs.

Overlaminates may not be required for many jobs, but they’re recommended for demanding applications. The finished product’s competitive cost and good outdoor durability make thermal-transfer systems viable digital-printing options for signmakers.

Thermal-transfer printers also produce relatively photorealistic output. For example, the |1137| MAXX™ 2 can print at resolutions up to 300 dpi. Production speeds for this printer are reportedly as high as 110 sq. ft. per hour, when printing one color. When printing four-color process work, production speeds are approximately 24 sq. ft. per hour. Gerber Scientific Products

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The EDGE 2 prints nearly 300 sq. ft. per hour for a single spot color and nearly 60 sq. ft. per hour for CMYK. Coupled with minimal drying times and other post-print processes, thermal-transfer throughput is tough to match.

Electrostatic printers

Contrary to many industry predictions, electrostatic printing still exists — and for good reason. "When solvent-based inkjet systems came on the market, I thought their introduction marked the beginning of the end for electrostatic printers," said Rich Thompson, president of |2279|(Pompano Beach, FL). Ad Graphics

He continued, "I fell in love with inkjet technology and immediately purchased a printer for my shop. However, after working with the solvent-based inks, I realized the technology’s drawbacks. Today, to print fleet graphics, vehicle wraps or outdoor signage, we use our Scotchprint® 2000 electrostatic printer."

According to Thompson, the advantages of electrostatic printing include high-production speeds, excellent outdoor durability and reliability. He also discovered that the heavy solvents used in his shop’s inkjet printer attacked the vinyl’s adhesive. The solvent inks also required the installation of a ventilation hood. After subjecting prints to outdoor weathering tests, Thompson believed 3M Scotchprint graphics outperformed inkjet prints.

Electrostatic printers operate similarly to a Xerox® office copier. Printing is usually a two-step process. The image is first printed, in reverse, on a special paper. Then the image is transferred from the paper, onto a substrate, using a lamination process. The new generation of electrostatic printers streamlined the process by directly printing onto pressure-sensitive vinyl.

Electrostatic technology works on the idea that opposite, electrical charges attract. The system’s printhead comprises thousands of electrical wires, which deliver, or deposit, electrical charges to the paper. As the paper passes over pigmented particles with an opposite electrical charge, the particles are transferred to the paper. The paper is then laminated to the substrate, and, during a heating process, the particles are deposited and fused to the substrate.

It doesn’t matter that the electrostatic prints’ resolution (200 to 400 dpi) isn’t as high as inkjet prints, because large-format electrostatic prints for fleet graphics, banners, outdoor advertising and construction-site signage are generally viewed from a distance.

Electrostatic printing’s major disadvantage is system cost, which can range from $100,000 to $250,000. Electrostatic systems also require constant air conditioning and humidity control, because electrostatic toner is sensitive to changes in humidity. Because electrostatic graphics are unappealingly dull when printed, they require lamination or clearcoating.

Inkjet media

In an ideal world, every inkjet vinyl would work with every inkjet printer, and purchasing decisions would be based on price comparisons. However, this isn’t the case. Selecting inkjet vinyl is difficult, because photorealistic reproduction, color gamut and outdoor durability rely on the interrelationships of printer, ink, vinyl and (when used) overlaminate.

Media selection becomes even more confusing with the increasing number of media manufacturers entering the sign market. Although several printer manufacturers and media producers have formed business partnerships, and developed consumables warranty packages, whether a particular inkjet print will survive outdoors is often unknown.

Because the technology is constantly changing, many real-time test results are simply not available yet. The only way to find out if a pressure-sensitive vinyl, ink and overlaminate are compatible and durable outdoors is to subject the combination to outdoor exposure in the intended area of use.

Vinyl and inks are usually tested in demanding environments located between the latitudes of 30° N and 30° S. Test sites in coastal areas, at higher elevations or in areas of significant chemical pollution subject a graphics system to the most demanding environmental conditions. Thus, such outdoor exposure is usually the most reliable test.

The secret is the topcoat

Inkjet vinyls differ from standard films due to their topcoating systems. These water-soluble topcoats absorb and bind the ink to the substrate. Topcoats also speed up ink-drying times. Without this special surface treatment, tiny ink droplets bleed together, destroying any print definition. With untreated vinyl, the inks would also wash off with the first sprinkling of rain, or quickly abrade with a light fingernail scratch. Each topcoating is specially formulated to match the substrate and work with an ink’s chemistry.

The most complex topcoating systems comprise two layers. In a dual-layer topcoat, ink is passed through a top layer and absorbed into a base coat. The top layer acts as a barrier, protecting the ink system from UV light, water and abrasion. The coating must also be absorbent enough to accept heavy saturation.

In a perfect marriage between ink and film, ink droplets are drawn directly down into the topcoat, where they’re absorbed and prevented from spreading. Good drop integrity results in crisper images and more intense, vibrant colors.

In contrast, when the chemistry between the ink and coating is wrong, prints can be plagued by dot gain — a spreading or bleeding of the ink on the surface of the topcoating, resulting in washed-out colors and fuzzy images.

In evaluating products, remember that all topcoated vinyls aren’t created equal. The system’s chemistry, the thickness of the coating and the consistency of the finished film all affect print quality, durability and print-production waste.

Also important are overlaminates and clearcoats. Regardless of which printer you select for your shop, the printed image can often be easily damaged by abrasion and chemicals. Some overlaminates even help block UV light, slowing the fading to which inkjet prints are susceptible.

Testing an overlaminate is important to ensure compatibility with the other components and assess a print’s overall durability. Unlikely as it may seem, an overlaminate’s adhesive could react adversely with the ink system.

For your consideration

When evaluating inkjet vinyls, buyers should:

* Compare the color richness from one print to another.

* Look for fuzzy edges or loss of detail.

* Determine the time it takes for the print to become dry to the touch.

* Consider the vinyl’s adhesive system and whether it’s aggressive.

* Consider repositionable and removable adhesives.

* Find out about any effects the liner paper may have on the printing process.

In comparing print quality, such statistics as resolution and dot size only tell part of the story. When testing different inks on the same vinyl, the results can vary greatly. A graphic printed with pigmented inks can look significantly different when printed with dye-based inks.

Pigmented inks have improved UV resistance. However, their color gamut is limited. Dye-based inks are bolder and brighter, and you can achieve more realistic pictures with visual punch.

Some topcoatings merely bind the ink to the substrate, while others enhance the ink’s appearance. Two different coatings on the same vinyl will produce dramatically different results.

Sign-supply distributors, and printer and vinyl manufacturer representatives, can provide guidance in selecting the right product for the job. This is what value-added sales is all about.

Conclusion

To justify your investment in a new printing system, ask yourself if the equipment will help generate enough additional business to provide you with an acceptable return on your investment.

You should purchase a new printer if it will help you increase sales among existing customers and/or pursue new markets. Ensuring that your investment pays off requires proactive marketing and selling. Today’s new digital-printing equipment may be the sign industry’s better mousetrap. However, the world will never beat a path to the signmaker’s door just for the sake of the latest and greatest technology.