By Cassandra Balentine
Liquid coatings are popular for flexible applications, like fabric or wallcoverings, but their use extends to non-flexible substrates as well. Point of purchase (POP) applications created on rigid substrates benefit from UV and water-based coatings.
Benefits of Coating
Liquid coatings are advantageous to non-flexible substrates such as corrugated board, coroplast, foamboard, gator board, styrene, and other POP substrates for a variety of reasons.
“UV liquid coatings enhance images while providing a hard, durable, washable coating for low-cost protection of digitally printed materials,” says Bob Leidlein, VP of sales and marketing, Alliance Technology Corporation (ATC).
Chuck McGettrick, sales manager, Marabu North America, adds that liquid coatings provide high resistance to abrasion, chemicals and harmful UV rays, and graffiti while providing an eye-catching professional look.
Kara Work, product manager, S-One Holdings Corporation, agrees, adding that the benefits of a liquid coating can include abrasion resistance, achieving a desired finish, minimizing glare, extending the life of the graphic, and improving cleanability.
Brad Riley, global business development manager, performance coatings, The Lubrizol Corporation, says depending on the application, liquid coatings may be a requirement for an application. “Liquid coatings deliver benefits of improved image quality, higher resolution, and more robust durability. They also enable gloss modifications.”
In Terms of Advancements
While inks have come a long way in regard to the life of a graphic, coatings provide added—and sometimes necessary—protection or enhancement.
Work says finishing a graphic with a coating will always improve the life of the print in some capacity. “In some POP applications where UV light is shining through a window and coming in direct contact with the graphic, it is important to coat in order to achieve some customers’ graphic life expectations,” she comments.
“Today’s inks are very good, but like analog inks, they are not designed to address every need for every application,” shares Riley. “Liquid coatings help bridge the performance gap for aesthetics and durability.”
Leidlein says printed images on non-flexible materials still benefit from adding low-cost UV liquid protection from abrasion, graffiti, and the elements. “Plus, UV liquid coating enhances the images with a variety of finishes and protected images are washable.”
Mike Plier, ink business development director, inkjet, EFI, comments that UV- and LED-cured inks provide a durability advantage, but they do not necessarily provide the extra levels of sun, weather, and hard impact resistance that might be needed in some applications. With display graphics, he says the need for coating is determined by the question of whether or not the graphics have a lot of outdoor exposure and resilience needed in high-traffic areas.
Ink and coating combinations are directly influenced by the chemical makeup of each component. “Ink chemistry can vary significantly from brand to brand and from technology to technology, it is always best to test for compatibility before producing an entire job,” says Work.
Many variables are considered when using liquid coatings. “The coatings perform differently depending on the type of materials and inks. One liquid coating does not necessarily work well with all of the different inks and materials in the market. Different inks and materials have different adhesion characteristics. It is best to sample coat printed images that have been printed on a specific printer, using a specific type of ink, and a specific type of material in production,” recommends Leidlein.
McGettrick agrees that ink compatibility is a concern when selecting a liquid coating for a non-flexible substrate. “Each ink and substrate combination contains different properties that require specific formu-lations to obtain maximum results.”
Riley shares that the highest performing coating is designed with both the ink and end application in mind. “There are coatings with broad ink compatibility, but often at the sacrifice of another performance parameter,” he warns.
Liquid coatings are either machine or hand applied. Depending on the type of coating, an automated or semi-automated method is desired.
Riley suggests that coatings can be applied in many ways, depending on deposition requirements. “Primers can be applied inline, whereas coatings require a higher laydown and are typically applied prepress through analog processes such as gravure and Meyer rod.”
For POP materials, McGettrick suggests automated or semi-automated machinery be used. “This allows for an even, consistent coating to be applied across each piece, leaving little—if any—room for error.”
Work says that UV-curable coatings need to be cured by UV light, and therefore are typically machine applied.
Leidlein also believes the preferred method for UV coating is an automated application where the rigid substrate is fed into a machine that coats and dries, using UV curing in seconds in a high-speed production process.
Water-based coatings can be machine or hand applied and do not require UV light to cure, they simply dry with heat or time.
Certain liquid coatings are also used as primers to improve adhesion to hard-to-print to surfaces. “Some materials are not compatible for printing. There may be adhesion issues,” cautions Leidlein. “In this case, a white or clear primer is applied first to the material. Then printing takes place on the white primer and printed images are subsequently coated with a clear coat for protection,” he explains.
McGettrick says some UV inkjet inks could fail to adhere properly to challenging substrates such as glass. “Certain coatings create an evenly applied primer as a bonding layer for inks. This allows for a far greater range of substrates and applications to be used than ever before.”
Coating is an added step, and comes with an additional cost when it comes to print production. However, it is a step that provides value to the printed piece.
While substrate pricing is always variable, here we provide estimates for UV and water-based liquid coatings for non-flexible wide format applications.
“There are many variables to consider, such as media type, application, and the amount of coating being deposited. While there are exceptions, as a rule of thumb the average cost is $0.02 to $0.08 per square foot,” says Plier.
Leidlein estimates UV liquid coating costs to be in the $0.03 to $0.06 per square foot range, adding that these costs are generally added to the overall price of the printed substrate.
“Primers for UV are typically less expensive than coatings required for water-based dye or pigment inkjet printing,” shares Riley.
McGettrick says for POP projects, liquid coating costs depend on several factors including the liquid used, application method, and the quantity of liquid purchased with costs between $0.05 and $0.08 per square foot.
Work estimates UV-curable coating to cost from $0.04 to $0.10 per square foot depending on the product.
She says water-based coating is priced between $0.08 to $0.18 per square foot depending on the product, container size, and application method.
On the Market
Several vendors offer liquid coatings, in either UV-curable or water-based formulations suitable for use on non-flexible substrates for applications like POP displays. Here we outline a few.
ATC offers a variety of UV liquid coatings for many different applications, including gloss, matte, satin, soft touch, non-skid, anti-graffiti, and dry erase finishes. Leidlein says ATC UV liquids have excellent adhesion to most direct printing substrates, such as styrene, coroplast, and di-bond. They provide a hard cured surface, making them ideal for rigid applications, which are in need of additional scuff/scratch resistance. Several of the coatings may be used as a primer coat and top printed, according to Leidlein.
The EFI Armor line of coatings feature excellent chemical, solvent, and abrasion resistance, along with proprietary UV absorbers formulated to protect and prolong the life of any ink it covers. One of EFI’s UV-curable coatings is EFI Armor Erase, a protective anti-graffiti coating that provides a protective barrier against markers, spray paints, and added abrasion resistance.
The company also offers a set of thermoformable inks and coatings that are often used on rigid substrates to produce everything from vending machine enclosures to marine parts, automotive trim, ATVs, and riding lawnmowers bodies and fenders. In many of those types of applications, protective coatings are a must, adheres Plier.
Lubrizol finds it valuable to help educate the industry when it comes to liquid coatings for non-flexible substrates for applications like POP. “We offer performance ink-receptive technologies and prefer to work with customers to identify the right technology for their specific needs,” says Riley.
Marabu’s MaraShield UV-curable liquid coatings are applied by a UV roller coating machine. Applications include primer, finishing, and protection. The coatings are specifically designed for each application, as opposed to a catch all of all-purpose coating, says McGettrick. These include products like UV-PGL primer glass, UV-RG rigid gloss, UV-RM rigid matte, UV-FXG flexible gloss, UV-FXM flexi-ble matte, and UB-CBG corrugated board gloss.
For priming, MaraShield coatings create an evenly coated primer as a bonding layer for inks. This means UV flatbed printers can be used for a greater range of substrates and applications. For finishing, MaraShield offers a professional look. For protection, MaraShield provides resistance to abrasion, chemicals, harmful UV rays, and graffiti.
S-One distributes a comprehensive portfolio of liquid coatings in both wide format and commercial print, offering brands like Marabu and LexJet EnduraCoat.
Digitally printed applications benefit from liquid coating solutions. Used to prime, finish, and protect, UV and water-based liquid coating technologies are available for non-flexible substrates like corrugate, styrene, foamboard, and gator board.
Jan2018, Digital Output