UV printing onto glass

UV Printing onto Glass

Advances in UV digital printing technology have opened up a world of new opportunities for shops willing to experiment with the various types of media options available to them. One of these areas includes the process of printing onto glass. In the past, imaging onto glass was mainly achieved through painting, etching and screen printing—now the same results are being attained faster and more economically using UV-cure inkjet flatbed printer technology.

UV glass printing has really caught on in Europe and is beginning to make inroads in the U.S. With new developments in this area, it is now possible to have graphics and many other items vibrantly rendered with glass printing such as mirrors, windows, signage, glassware and awards.

Sean Roberts, manager of the Global Customer Experience Center, Inkjet Solutions at EFI, says one of the biggest trends with glass printing is being able to get a high-end, high-quality color look.

“Glass printing is now standing out as a way to give a premium look to graphics in retail merchandising,” Sean Roberts says. “There are practical benefits that it eliminates the time and extra materials needed to mount printed film to a glass surface. And, you can also get a superior image compared to a mounted film.”

Roberts adds that while retail merchandising is one of the big uses for printed glass, there is also a growing usage in architectural/construction/interior design applications. “In many instances, it presents the opportunity to offer privacy screening or a different, personalized touch to a room design.”

Getting Personal

Ken VanHorn, director of marketing and business development at Mimaki USA, says the most prominent trend in UV-LED inkjet printing onto glass is toward personalization and customization. “Technology has made it more cost effective to create short-run items with personalized imagery.”

He says that where this differs from ceramic-based glass design is that digital inkjet accommodates photographic quality imaging and smooth gradients, with a larger color gamut.

“UV-LED inkjet is also less process-intensive because it does not require any post-print process such as high-heat curing,” VanHorn says. “It’s a less expensive way to create unique pieces in a considerably shorter amount of time.”

VanHorn says the most popular applications he is seeing is with using glass in the awards and recognition industry, as well as personalized items.

“Print service providers that produce awards, trophy and recognition pieces have been looking into inkjet UV-LED curing technology to create unique and colorful awards. They are no longer limited by laser-etched names and logos with photographic inclusions. Now, the award can be fully made of glass and include smooth color gradient images and logos. The versatility of UV-LED systems can also open the door to many more products that go beyond glass that the award maker wasn’t previously able to create with etching,” he points out.

VanHorn says more products are being personalized with photography. Glass Christmas ornaments are being printed with family pictures, company logos and personalized messages. He adds that images are being printed directly onto glass to create modern, low-profile picture frames.

More Decorating Options for Glass

Glass is one of the most contemporary and desirable building materials used in modern architecture. “Although this traditional material is already found everywhere in the form of windows, glass roofs and glass doors, architects and designers are eager to use this medium more generally for decorative purposes,” says Christopher Howard, vice president of new business development for Durst U.S. He states that the glass decoration performed with the new Rho Vetrocer 250 printer and the ceramic inks offers extremely interesting commercial opportunities.

“The Rho Vetrocer 250 combines all the advantages from our Rho series – our latest Variodrop-CF print head technology, continuous print, maximum print speed and optimal image quality – with a special transport mechanism that gently guides glass plates up to 2.5 meters wide through the print process,” Howard says. “Between one color and another, the time needed for screen production, machine preparation and dry time has been effectively zeroed. Besides the operational and economic advantages, the shorter response and supply times offer customers a real added value.”

Creativity in a New Medium

Artists also making a statement by adding glass printing to their repertoire. Jay Roberts, product manager, UV Printers at Roland DGA, Irvine, California, says that one of the biggest trends he is seeing right now is printing art onto glass.

“This goes hand-in-hand with an increase in interest/demand for interior design and decor that incorporates digital printing,” Jay Roberts says. “Artists have found a new medium printing onto glass. They are printing on dining room tables, coffee tables, shower doors, glass counter tops, glass plates and other items to display and sell their art, combining function with artistic expression. Artists, architects and interior designers have contacted the traditional sign and display companies in order to expand their creativity and, with the developments in UV printing, have found a new ‘canvas’.”

Jay Roberts says that currently, another one of the most popular applications is printing onto glass to create unique architectural signage for use in the interiors of office buildings and reception areas.

“End-users reverse print the signage and mount the glass with stand-offs, which allows the ambient light to show through the sign,” Jay Roberts says. “We have seen prints like this up to 8’ long mounted in entryways. The optical quality of glass enhances the reverse print, brightening and adding contrast to the print onto the glass. Another popular application is printing onto etched glass. The etched glass acts as a natural bonding agent for the UV print, providing both stronger durability (adhesion) and adding a subtle ‘white point’ to the normally clear glass.”

The Printing Process

Roland’s Jay Roberts says printing onto glass using a UV curing printer, such as those offered within their VersaUV series, is truly amazing.

“Our customers have discovered that, with certain end-user applications, it’s possible to print directly onto glass without the aid of adhesion promoters,” he says. “This depends upon the specific application, however. The level of durability when printing to glass without an adhesion promoter depends heavily upon how the end product will hold up to scratching or handling. If durability is a crucial factor, an adhesion promoter should be used. Artists and interior designers have found that reverse printing onto glass is a highly effective method, without the use of promoters. Printing onto the backside, or ‘second surface printing,’ allows the end product to be protected by the glass itself.”

No Coating Required

Jay Roberts explains that it is possible to print UV successfully onto glass without coating the glass first.

“We have seen multiple techniques used,” he says. “One artist told us that he prints to glass with a low-curing lamp level, and then cures the print with another non-printed pass. Another user told us that he likes to ‘double hit’ his glass prints, and then set the prints outside after printing, allowing the natural light to cure the glass print. Double hitting or ‘multiple strikes’ onto the glass builds up the density of the print, creating a richer, deeper image when the light shines through the image of the print.”

“Glass etching is also a method being used as an alternative to adding adhesion promoters or liquid laminate protection to the glass. The etched glass adds a ‘tooth’ to the printing surface. This tooth allows the UV ink to bond to the glass better and is highly durable. There are several ways to etch the glass,” Jay Roberts explains.

He adds that they have found that users report that they either protect their prints before printing with a glass adhesion promoter, or they protect the prints after printing with a liquid laminate, such as ClearStar ClearShield.

Using Glass as Your Canvas

One of their end users, photographer, artist, print-maker and author Bonny Lhotka, has developed a SuperSauce Solution, which contains about 91 percent isopropyl alcohol, that she uses to transfer images to glass using pigment inkjet prints. “These transfers bond extremely well to the glass,” Lhotka says.

Lhotka tested her solution by printing on Roland VersaUV LEF-12, using a process she says is suitable for art and photography imaged onto glass with a UV printer.

“I coated the SuperSauce Solution Gloss on low iron tempered glass and let that dry overnight before printing on the LEF-12,” she says. “The UV ink prints and bonds nicely to the glass, and you can’t see the coating after printing. I am continuously impressed by the way my Roland LEF-12 prints onto glass. In this case, I printed the matte varnish over the image and placed it on a mirror to create a truly stunning finished product.”

Techniques with UV-LED Technology

VanHorn agrees that successful printing on glass requires excellent adhesion and bonding capability. In printing with UV-LED technology, he says there are three primary techniques used to improve adhesion.

The first way he points out is called wipe-on primer.

“This technique requires a primer that is wiped on to coat the entire surface of the glass, preferably with a lint-free rag,” Van Horn says. “After about 30 seconds of drying time, this technique may leave a cloudy, dull look to the primed surface. Prior to printing, a clean rag can be used to buff out the cloudiness. If the full surface of the glass is going to be printed, buffing the glass completely after drying is not required.”

The second utilizes Mimaki’s PR-100 primer jetted from the printer. “The PR-100 is a ‘printed’ primer that is used as part of the ink configuration for the UJF series UV-LED tabletop flatbed printers, as well as the JFX Series UV-LED (larger) flatbed printers. The advantage to this application method is that it can be precisely placed where it is needed. There is no need to take the extra steps of wiping on or buffing off; however, starting with a clean surface is highly recommended.”

VanHorn calls the third technique plasma treatment.

“This technique is not unique to digital printing, but it is widely used in digital printing applications,” he says. “Plasma treatment works in two ways. First, it removes any surface impurities such as dust or residue that solvent cleaners may leave behind. At the same time, it creates a surface more conducive to bonding with the ink. The advantage to this compared to a process such as flame treating is that plasma is not as likely to damage or melt the surface of the substrate or coating.” However, plasma treatment equipment is not cheap, with units starting at about $6,000.

Award-Winning Results

VanHorn says one of their innovative end users is Elk Grove Village, Illinois-based Cristaux International, a shop that designs and manufactures a range of awards, trophies and recognition items. Tim Walsh of Cristaux says they use the Mimaki UJF-6042 LED tabletop flatbed printer to personalize a range of items.

“We often print on 5” x 7” glass blocks that are 12mm thick,” Walsh says. “We’ll produce breakout awards, and are gearing up to create bamboo frames with custom photos. The printer works great.”

Other Tips and Techniques

For the most longevity, EFI’s Sean Roberts says there are a few key steps to follow.

“For starters, we recommend cotton gloves when you print: bare hands or latex gloves will leave oils that contaminate the glass surface,” Seah Roberts says. “Also, due to its manufacturing process, glass has a clear and a ‘foggy’ side (one is exposed to air during cooling), and you first have to make sure you are printing on the clear side of the glass.”

He adds that perhaps the biggest difference between other UV printing techniques and specialty glass printing is a post print baking process. “For our UV inkjet printers, EFI recommends baking a printed glass in a conveyor oven at 650 degrees Fahrenheit for 10 minutes. This baking process permanently bonds the glass, primer, and ink for a lasting product.”

Austrian Glass Vendor Breaking New Ground

Sean Roberts reports one of EFI’s customers in Austria has installed EFI’s H652 UV-curing hybrid printer. The shop, Schrei GmbH, based in the Austrian town of Gars am Kamp, is setting new standards for architecture and interior design by printing directly onto glass. Partners Christian Hable, Manfred Reinisch and Jochen Schinkel were glass vendors who decided to extend their market reach by offering pre-printed glass for a variety of applications.

According to Schinkel, he struck gold with the addition of the EFI H652 printer. “With this UV printing system, we are able to render quality standards that have not yet been attainable on the Austrian market,” he says.

Dazzling Effects on Glass

Schinkel reports that the EFI H652 guarantees a resolution of 900 x 900 dpi, and using eight grayscale levels it delivers realistic photo quality directly onto the glass.

“The feedback that we have received from our partners, for example kitchen studios, is simply outstanding,” Schinkel says. “Our clients are impressed with the rich colors and smooth, harmonious color gradients.”

Apart from kitchen studios, Schrei is currently working for architects, and retailers in particular, who are keen to break into the printed glass market where there is no limit to the number of possible applications. The spectrum of products ranges from kitchen splashbacks, doors, partition walls for offices and restaurants to shower walls, staircase banisters and much more.