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Perfection with Protection

Properly Implemented Films and Coatings

Part 1 of 2

By Cassandra Carnes

Depending on the application and its final destination, liquid coatings and overlaminate films provide many levels of protection. Popular uses include guards against UV fading, scratching, and abrasion. Some laminates are specifically designed with anti-slip or anti-graffiti functionality. Additionally, post-print protective layers can change the finish of an application by adding rigidity and even aid in graphic install or removal.

The main function of a protective laminate depends on the application. For floor graphics, anti-slip properties are important, while vehicle wrap applications benefit from dual functions of scratch resistance and thickness for installation ease.

Laminate Type
As with any process, lamination requires trial and error, a thorough understanding of the desired result. Separate procedures exist for thermal, pressure-sensitive films, and liquid laminating. Thermal films are bound to substrates with heat. Laminating thermal films may also be referred to as dry lamination. Pressure-sensitive—or cold—lamination does not require heat and is used for heat-sensitive applications. Liquid laminates are cured with liquid laminating systems. Aqueous, solvent, and UV liquid laminates are available.

"There is no one-size-fits-all type of overlaminate or liquid coating," says Tony Caruso, Eastern sales district manager, Advanced Greig Laminators, Inc. He explains that understanding customer goals and expectations is key. "Selecting the proper laminate for the media minimizes waste and reprinting, controls costs, and adds value," he says.

Once the lamination process is determined, there are still a variety of differences in film and liquid coatings. In terms of vinyl, cast and calendered films are two options. The rule of thumb is that cast overlaminates should be paired with cast vinyl and calendered overlaminates paired with calendered vinyl.

"The vinyl and overlaminates should meet the application need," stresses Paul Roba, technical services manager, Avery Graphics. Cast is required for compound curves and offer conformability. Calendered is generally more affordable and ideal for flat and short-term applications.

The raw materials used to create both cast and calendered vinyl films are similar. "The main difference lies in the additives used, especially in the type and grade of plasticizer, and in the manufacturing process," explains Judy Bellah, public relations manager, Clear Focus Imaging, Inc.

Cast films are made from a liquid polyvinyl chloride (PVC), where calendered films are made by extruding a dough-like PVC-mass, shares Martin Kugler, corporate communications manager, Hexis S.A.

Calendered laminate is manufactured by running the mass of vinyl laminate through a series of flattening rollers until the desired thickness is achieved. However, "like a dough, the laminate is prone to shrinking as it attempts to return to its original form," notes Caruso.

Matching the Media
It is important to consider an application’s destined environment. Once location is determined, the elements the graphic will endure is the next determining factor.

"Match similar materials as close as possible," advises Jeff Leto, team leader product management, LexJet Corporation. Vinyl should be paired with vinyl and polyester to polyester. However, it is the matching of the media and its environment that is important to success.

"The chemical components of the laminate must work with those of the ink and media, as well as the application tape used," explains Tim Boxeth, marketing manger, and Jennifer Greenquist, business development manager, 3M Graphics Market Center.

Ovelaminate Films
Mismatching print media and protective laminates results in a variety of issues. Ritchie Daize, international digital account manager, Arlon, Inc., stresses the importance of matching brands of print media with their overlaminate counterparts. He explains that all vinyl brands feature slightly different shrink rates. If print media from brand A has a higher shrink rate than brand B’s overlaminate and they are matched, the finished product is in danger of lifting around the edges.

Roland Castonguay, new business development manager, product branding business team, FLEXcon offers an explanation of what would happen if a non-vinyl laminate were applied over vinyl. He uses an example of a graphic printed on calendered vinyl that is mispaired with a low-cost thin polyester laminate.

"The materials possess very different tensile and elongation," he explains. Polyester tunneling or pulling from the graphic can occur with this combination. Even worse, he has witnessed a disastrous malfunction where the graphic is pulled off of the application surface. "This is typically due to the amount the overlaminate or media stretched during the lamination process."

In some cases, it is acceptable to laminate calendered vinyl with a cast overlaminate. Window perforations are such an exception, where cast vinyl clarity is superior to calendered vinyl clarity, says Castonguay. However, "in many applications this would be overkill," he adds.

An application’s ink type is also a key factor. "Laminate, ink, and media must all be carefully matched to produce a successful job," says Mary Ann L. Kucera, marketing manager, MACtac Graphic Products. If ink fading or cracking occurs, the job is not a success, even if the media and laminate hold.

Kucera explains that the ability of the laminate to wet-out on the printed surface is particularly important when UV inks are used. "Since UV is close to 100 percent solids and cured immediately after printing, its surface tends to be bumpy," she shares.

Adhesives formulated for use on UV prints flow into and wet-out the surface of UV ink, eliminating the silvering caused by air trapped between the laminate and ink.

Liquid Coatings
Liquid laminates also differ in type, and also perform better when matched properly to the media and ink of the application.

LexJet’s Leto says the intended environment is more important than media choice when it comes to liquid lamination. "The general rule is solvent for outdoor and aqueous for indoor."

"Whether one chooses solvent-, water-based, or UV-cured liquid laminate, the protection is effectively the same," says Stephen H. Berman, CEO, Clearstar LP. The principle distinction is compatibility with the substrate and the inkjet receptive layers. Some inkjet receptive layers are water sensitive so solvent-based liquid laminates should be used.

The inkjet receptive layer typically drives water sensitivity. "Many gel-coated substrates require a solvent-based liquid laminate. Most microporous, water-resistant inkjet substrates allow the use of a water-based liquid laminate. For almost all solvent-based inks in combination with banner or pressure-sensitive adhesive, water-based liquid laminate is the most desirable," he adds. Low odor, little health or environmental exposure, and easy clean-up drives this selection.

The most common methods for applying liquid laminates involve screenprinting and roller coating. These processes meter a specific amount onto the media. "The amount of clear—or liquid laminate—put down by screenprinting is mostly determined by the type of screen mesh and the clear concentration used, but there are many other processing variables that influence the exact amount," say Boxeth and Greenquist.

Roller coating is dependent on the equipment, processing conditions, and variables such as viscosity.

A Quality Product
Graphics treated with a protective layer of film or liquid laminate offer an extra level of appeal. Often, these additional layers are necessary for a printed piece to properly function in its desired environment. A floor graphic without an anti-slip protection can be dangerous. A point of purchase graphic without a laminate is vulnerable to the elements.

Lamination serves a variety of functions. It preserves, protects, and enhances to add value and longevity to a printed graphic of any variety. However, it is important to understand what combinations work best together. "Using materials that don’t match results in premature failure of the application, a dissatisfied customer, and added cost to reproduce the product," says Steve Milazzo, channel marketing manger, GBC.

The benefits of protective coatings are obvious, but if improperly implemented the benefits disappear. Learn more about overlaminate films and liquid coatings in part two of this series on graphics protection.

Click on the link above to get more information on the vendors mentioned in this article.

May2010, Digital OutputDOPWP610
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