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Lamination: Beyond the Surface
By Regan Dickinson
New advances in laminate materials and adhesives are designed to keep up with ever-changing printer and ink technologies. Following are some important criteria to consider when choosing a laminate, plus finishing tips to ensure a successful project.
Keeping up with the wide format printing Joneses has always been a challenge. With the advent of solvent and UV-curable printing technologies—as well as pigmented ink sets and waterproof media for aqueous printers—one of the more challenging aspects of building better graphics has been on the laminate side.
While it appeared that lamination might be on its way out, rumors of its death were greatly exaggerated. The true value of lamination is found in its ability to add texture and rigidity to the print, to create special applications (like floor graphics), and to provide extra protection from prying hands, keys, rocks, and anything else determined to damage the print. The UV and weather protection is simply an added bonus.
Signs Now Bradenton showcased its printing capabilities at an open house last year, making sure to include carpet graphics as part of the presentation. Carpet, sidewalk, countertop, and floor advertising all require lamination in order to create a non-slip surface, and to protect the graphic from foot and finger traffic. This carpet graphic was printed on FLEXmark® Vinyl for Carpet Surfaces and laminated with FLEXmark® OV 650 R 6.5 Mil Velvet PSA overlaminate.
Translating the Technicalities
When choosing a laminate, it’s a good idea to go beyond the simple, marketing-driven product descriptions and look into the technical data to help you find the right laminate for the application. It sounds boring (and technical), but it’s actually quite simple. Always ask questions about the makeup and characteristics of the laminates you’re comparing.
Here are the characteristics to look for and ask about when selecting a laminate:
Adhesive: The preference will usually be for a solvent-based acrylic adhesive. Peel adhesion and sheer strength are affected by the content of the adhesive, and solvent-based acrylic adhesives will have much better peel adhesion and sheer strength (which basically means a stronger bond). This stronger bond greatly mitigates tunneling, de-lamination, curling, and shrinkage.
This characteristic is especially crucial for tradeshow graphics that will be rolled, shipped, unrolled, installed, re-rolled, shipped, and so on and so forth for as long as the customer would like to use the graphics.
Even solvent prints need the extra value provided by lamination, depending on the application. Wellington Signs typically prints its pop-up tradeshow displays on LexJet 12 Mil Solvent Display Film SR and laminates them with 10 Mil PreLume DisplayFlex.
Solvent acrylic adhesives also bode well for users of UV-curable printers, since UV-curable ink creates a slightly textured surface that’s more difficult for laminates to stick to than solvent and water-based ink. Most solvent acrylic adhesives bond well and true to a UV-curable print. Even with a solvent-acrylic adhesive, there must be sufficient heat and pressure to ensure a good bond between the UV-curable ink and the laminate. Recommended settings are at least 100 degrees and 60 psi.
Moreover solvent-based adhesives are stiffer and firmer than water-based adhesives (making them more weather-resistant and less penetrable). All of this translates to a worry-free application, so make sure to ask about the shear and peel strengths of the adhesive, because not all solvent adhesives are created equal. However, water-based adhesives will work fine for high production runs of shorter-term graphics that won’t be handled very often.
Monomeric vs. polymeric: A vinyl laminate that is polymeric expands and contracts in many directions, whereas a monomeric vinyl moves in only one direction. What this means in practice is that a polymeric vinyl laminate will move with the substrate it’s protecting. A monomeric material, on the other hand, will not, thus causing premature de-lamination, edge creep, curling, and tunneling. Always ask your supplier whether the vinyl laminate is polymeric or monomeric. If it’s a three-day special event project, this won’t be as crucial as it will be for something that’s expected to last for months or years.
Gloss Level: This element is obviously not as important as the chemical makeup and subsequent strength and flexibility of the laminate, but it’s something that can be measured and may provide some additional insight into the relative sheen of the product. The Gloss Level is usually defined as a percentage of reflected light taken from a light meter at a 60-degree angle.
Matte surfaces are typically below 15, luster surfaces will range from a low of 15 to around 70, and a mirror-like gloss above 70. You’ll find that luster, satin, and semi-matte are generally interchangeable terms, though the alternate terms satin and semi-matte will often be used to address the subtleties of the surface sheen found in the luster range.
You don’t want to hit the streets without lamination, regardless of the printing technology used. This bus project by USA Image Technologies was printed on BUSart™ Vinyl for Bus & Train Wraps and laminated with BUSart™ OV5040C 3.5 Mil Gloss PSA overlaminate.
Rules for Thumbs
However there are rules of thumb one can follow to experience a better lamination process.
Rule of Thumb #1. Don’t rush the print/laminate/trim process. Ideally you should allow the print to dry for twenty-four hours before lamination. Allow the laminate to cure for seventy-two hours before trimming it.
Unfortunately we all have to live in the so-called Real World, where deadlines are yesterday and customers are rather unyielding. Therefore a good rushed rule of thumb is to print in the morning, laminate in the afternoon, and trim the next morning. (Note: Keep in mind that this “rushed rule of thumb” applies only to prints from aqueous inkjet printers, like the HP Designjet series or Canon’s iPF series.)
The problem with printing, laminating, and trimming in one fell swoop is that the adhesive won’t have time to cure and the ink will still be outgassing, increasing the chance that your customer will experience the thrill (not!) of delamination. When laminating solvent prints, it’s especially important to keep dry times in mind. A full twenty-four hours of drying before laminating is mandatory. Leftover solvents will cause the color to shift. Though most print shops have some type of ventilation system built into or attached to their solvent printers, it’s a great idea to install a portable air scrubber/HEPA filter.
Even after a solvent print comes off the printer, volatile organic compounds (VOCs) are still outgassing. An air scrubber accelerates the outgassing process, causing the prints to dry more quickly. Print shops who have installed an additional air scrubber/filter in their finishing area report faster drying times and thus faster overall production.
Rule of Thumb #2. When trimming a laminated graphic, remember the three Ss—surface, slice, and score. The cutting surface should be hard (preferably tempered glass). Those handy cutting mats aren’t so handy when it comes to trimming laminated graphics, because the softer surface causes the material to belly in and thereby place undue stress on the adhesive. On a related note, the cutting table should be level and true.
When cutting into the graphic, your knife slice should be at a ninety-degree angle. A different angle cutting down on the graphic creates a lip between the print and the laminate, thus exposing the adhesive.
Rather than trying to cut through the graphic in one pass, score it two or three times to ease the tension on the layers—print material, laminate, and backer—as you cut through them. The ideal is an automatic or manual cutter that quickly and cleanly trims the graphics.
In this case, lamination provides the nice texture and finish required by the museum customer, plus it ensures durability in a high-touch environment. This display was printed by Northern Arizona Signs on 4-Mil Universal White DuPont Melinex Polyester and laminated with LexJet 15 Mil PreLume DisplayFlex.
Rule of Thumb #3. Roll the graphics for shipping no tighter than a twelve-inch diameter. Though you can roll certain laminates tighter than others, you should try your best to stick with this rule. When you’re rolling up the graphics for shipment, the thinnest, lightest material should face out, and the graphics should always be rolled in the same direction every time.
So if you’re using a 4-mil base material, a 5-mil laminate, and a 10-mil backer, roll the image side out. Place a sticker with short, bullet-point instructions for your customer and your logo on the outside of the roll. The primary information you want to get across to whoever unpacks and unrolls the graphics is: (1.) After unpacking and unrolling the graphics, lay them out flat to uncurl, making sure not to roll them in the opposite direction, (2.) when packing, don’t roll tighter than a twelve-inch diameter, and (3.) the side always faces out when you roll it up.
Regan Dickinson is LexJet’s marketing communications specialist.
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