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Technology Focus

What Sets UV, Aqueous and Laminates Apart?

by Staff

May-June, 1996
Graphic finishers and commercial printers alike have constantly dealt with the challenges of matching the right coating or laminate with the printed sheet. Many factors are involved in this decision that can affect the outcome of the project. And while no set rules exist on choosing one over the other, there are specific advantages and disadvantages of each process that can help determine the best overall choice.

Ultra-Violet Coatings
UV is a very popular coating choice due mostly to the high gloss finish one can achieve, adding a brilliance to the finished sheet unlike any other coating method. UV coatings also provide good resistance to solvents and abrasion - much better than most water-based coatings. Because of its high sheen, UV coatings are popular on a wide variety of consumer products, including paperback books, trading cards, and cosmetic packaging.

However, UV coatings are not the best choice for all applications. Special precautions are necessary, especially when hot stamping foil, scoring, folding, or gluing is involved. "Everyone loves the look of UV, but it can be extremely demanding when other finishing processes are being used," state Mike Weber, Production Manager for Midwest Laminating & Coatings, Inc., of Chicago, IL. Weber suggests utilizing spot UV on cartons or other applications to keep the UV coating off the glue flap area. Certain types of UV coatings can also cause cracking problems if the sheet or carton is to be scored and folded. UV coatings are a challenge when foil stamping is involved as well. If the coating has a high level of silicone, hot stamping foils will simply not adhere. Even special UV coatings without a heavy silicone addition are difficult in many situations. It is suggested to foil stamp first and then apply the UV coating to avoid potential problems. Even in this scenario, the foil stamper should check with its foil supplier to choose a foil that is overcoatable.

In addition, UV coatings have been known to yellow over long periods of time and are highly susceptible to fingerprinting. Environmental concerns also surround the use of UV coatings. Although very little waste is left to dispose of when applying UV, what is left is very toxic. Special arrangements are necessary to dispose of this waste.

Aqueous Coatings
Probably the number one advantage of aqueous coating is the cost savings you can achieve - especially in sheet-fed applications. Elmer Griese, Marketing Manager for Cork Industries, Inc., told InsideFinishing, "The vast majority of aqueous coating use is in-line being applied in conjunction with a printing process, offering an enormous cost advantage over other off-line applications such as UV coating and film lamination." Cork Industries is a manufacturer of aqueous and UV coatings for the graphic arts industry. Aqueous coatings are very user-friendly when additional finishing is necessary as well. They work efficiently over most printing process inks, wet over wet or in some cases, wet over dry. They also accept many glues and are very receptive to hot stamping foil.

Aqueous coating is promoted as environmentally friendly. There is a small percentage of solid waste (about 10%) left from an aqueous run and should still be handled with some precautions. It is certainly the environmental choice when compared to UV or film lamination.

On the other hand, aqueous-base coatings do not provide the exceptional high gloss of UV or film laminates. If this is a major factor in the final outcome of the finished product, aqueous may not be the best choice. Also, aqueous does not offer the protection against abrasion or the solvent resistance you find with thermal lamination or UV coatings. Again, the final use of the product will determine the importance of this issue. For example, chemicals found in perfumes or other cosmetic products may inhibit the use of an aqueous coating on the inside or outside packaging.

One specialized process for aqueous coating is a method called calendering. Many calender systems utilize specially formulated aqueous-based coatings to achieve gloss levels comparable to UV coatings. The process creates a smooth surface which is highly resistant to scuffing, cracking, fingerprinting, and yellowing.

Thermal Film Lamination
When protecting the printed sheet or carton from abrasion, chemicals, or even when fingerprinting is of utmost importance, film lamination is the best choice without exception. The solid coverage and thickness that thermal lamination offers cannot be matched by UV or water-based coatings. Another advantage film lamination offers is its flexibility. You can achieve a high-gloss finish on a variety of stocks, including coated, uncoated, non-wovens, and even vinyl and styrene plastics. "Film laminating was once used mostly for protection purposes only, while today, you see it being used on all types of presentation materials for its high-gloss and premium look," stated Lynndah Easterwood, Marketing Manager for D&K Laminating Films and Equipment. "In many applications, customers are willing to pay a little extra to receive a higher quality product that they know will last." Film lamination is available in several matte and gloss finishes and can even be applied with a special embossed roller that leaves a textured pattern over the laminated sheet.

As the number one advantage of aqueous coatings is the cost savings, a major deterrent to the use of film lamination is the price. High volume production of many packaging applications prohibits the use of thermal lamination because of the expense of the film itself and the slower off-line application used to apply the film compared to UV or water-based coatings. In addition, certain types of film laminates have a very low dyne count, meaning the surface tension of the sheet restricts the adhesion of other finishing processes, including hot stamping foils and glues. In the past, the film was corona treated, providing an acceptable surface. The challenge was that the corona treatment would wear off over a period of time. Special films have now been developed with a permanent chemical additive that will readily accept hot stamping foils and glues. If you have questions on the overstampability of the film, it may be wise to consider foil stamping before laminating the sheet.

From an application standpoint, film lamination is the most environmentally acceptable. It is a completely dry process. However, there are questions on the biodegradability and breakdown capabilities of thermal films.

As you can see, a great deal of analysis must go into the decision when choosing between UV coating, aqueous coating, and film lamination. From a graphic finisher's point of view, you might think steering your customer towards UV or lamination (because you offer the service and know aqueous will be applied in-line) is the best choice. This certainly is not the right approach for long-term growth with the customer. Helping printers or other customers you work with analyze the advantages and disadvantages of the different coatings and laminates available and helping them match the right choice with the right application will solidify your position with the customer. Suggesting aqueous over UV when the application warrants it, even when it might mean money out of your pocket, will translate to a happier customer and a longer lasting relationship for the future.