by Melissa Donovan
We often talk about devices designed to output decorative laminates used in flooring, countertops, and walls, but the process of digital printing involves more than just the print. Sometimes certain surfaces require a pretreatment prior to printing to directly.
There are many surface types able to be printed to, from concrete and wood to plastic. Depending on their chemical makeup, a surface pretreatment is necessary prior to print. If manufacturing decorative surfaces, it’s important to look at a few considerations before implementing a digital printing workflow.
Positivity Start
In general, digital printing presents a host of benefits to the decorative surface space, whether it be a flooring manufacturer or a decorative laminate used for walls or countertops.
“Digital printing is set to play a crucial role in the future of new material flooring, countertops, and walls as it enables unlimited design as well as embossing-in-register flexibility and can be applied to a wide range of materials. This facilitates faster response times to market demands and trends while reducing material waste,” notes Dr. René Pankoke, president/CEO, Hymmen GmbH.
Bas Buser, global market segment manager printing applications, Plasmatreat, says it’s because digital printing is “faster, cheaper, and easier than other printing processes; individual printing is possible; personification; and low quantities. However, for existing manufacturers digital is new. To transfer to digital print, investments are needed in regard to the operators and other disciplines compared to conventional printing processes.”
This market has been slow in adapting new technology, admits Pankoke. For example, it took more than ten years after presenting Hymmen Digital Printing technology for the woodworking and surface decoration industry at the Ligna fair in Hannover in 2009 before the technology was also accepted outside of Europe.
“Reasons for that might be the investment volume and the fact that digital printing disrupts the well-known process chain in the industry. Suddenly the producer can decide on the design of the surface décor himself. Design knowledge needs to be built up internally. And then there was the insecurity about how reliable the new technology is,” continues Pankoke.
And in 2022, the facts speak for themselves. Hymmen sold three digital printing lines in the U.S. this year, and two to China and Europe.
Limitations Overcome
Not to start us off on the wrong foot, but digital printing does have limitations—specifically for our purposes in regards to ink adhesion. Surface pretreatment technologies like corona, plasma, and flame can aid in overcoming the challenges.
Mark Plantier, VP marketing and communications, Enercon Industries Corporation, points out that all ink printing processes—not just digital but even gravure and flexographic—require strong bonds behind ink and the surface being printed to. “This means surfaces must be free from contaminants that inhibit the bonding and have a high surface energy to be receptive for wettability and bonding with inks.”
“Depending on the type of ink—solvent, water based, UV—in general all have the same limitations. But with the use of pretreatment there are only a small number of limitations.
With inks like UV and water based, the surface to be printed on needs a pretreatment to bring the surface to a condition that the ink adheres to,” explains Buser.
Surface pretreatment solidifies that high-quality appearance expected in these situations. “To make sure that the digitally printed décors have constantly and sustainably the same colors, and at the same time ink adhesion is good, also the underground on which the ink is printed plays a crucial rule. When putting the digital printing lines into operation, Hymmen always has—among others—a special focus on the primer that is put on the material. The right pretreatment of the material is the basis for the highest color stability and adhesion,” shares Pankoke.
Latest Advancements
Digital printers and surface pretreaters used in the decorative surface space constantly undergo advancements, responding to demand.
According to Plantier, Enercon is in a unique position to help manufacturers of decorative products because it offers a complete range of surface treatment technologies including variations of corona, plasma, and flame. These technologies are available for processes involving rolls of film, sheets, and dimensional objects. “With such a range of technologies, the best way to determine which is best for optimizing a surface for a specific application is through lab testing. Recent innovations include the development of a wider blown-ion plasma surface treater, which increases the width the technology can treat in a single pass.”
The latest innovation from Hymmen is Digital Embossing (DLE plus) technology, which allows digital structuring inline with digital décor printing. Even emboss in register if desired. Additionally, DLE plus opens up new design opportunities for surfaces by only structuring the surface without underlying décor by using three-dimensional structure as well as matte/gloss effects.
With Openair-Plasma from Plasmatreat, the properties of the surface are changed to enable better adhesion from the inks to the surface. Buser explains plasma, the fourth state of matter, in a bit more detail. “The addition of energy causes the states of matter to change. Solids become liquids, and liquids become gases. If additional energy is added to a gas, it ionizes and becomes energized plasma. If the plasma, with its high energy level, subsequently comes into contact with materials, the surface properties of those materials may change—for example, a hydrophobic surface may become hydrophilic.”
This can be used for different surfaces like plastic, metal, glass, ceramic, textiles, and wood.
Other benefits according to Buser include “cleaning of organic residues, physico-chemical nano-modification of the surface, electrostatic neutralization of the component, removal of any remaining dust particles, and no volatile organic compounds.”
Surface Variety
With so many surfaces to print to, do they all require pretreatment? It depends on many factors.
It’s all about the material being treated, ink formulation, and the process, according to Plantier. On the topic of materials, he notes that the polymer materials engineered for decorative purposes are usually nonporous and as such have an inherently low surface energy. “It’s important to note that different materials such as polypropylene, polyethylene, and vinyl respond differently to the same type and levels of treatment. Additives such as fluorine can also have a major impact on bonding success.”
“If a product or surface is manufactured and will follow by other processes like bonding, printing, or lacquering, often a pretreatment of this surface to prepare it for the next process step is a must,” says Buser.
“The need for a pretreatment depends on the surface features and the expected quality and reliability of the printing result,” concurs Pankoke.
With ink formulation, Plantier notes this in combination with the application process plays an important role in determining the need for pretreatment. “Ink manufacturers will have a recommended target surface energy for optimal adhesion and in some cases one type of plasma or flame will do a better job of achieving the desired polar-free surface energy. Lab or field testing is generally used to determine the best recipe for success.”
Another important consideration is that surface treating sometimes occurs prior to print but also prior to coating or laminating a decorative surface. “When printing is the final step in the manufacturing process prior steps may have relied on corona, plasma, or flame for coating or laminating success. Likewise, after printing many printed materials are subsequently coated or laminated with adhesives, coatings, and other materials for increased performance and usability,” adds Plantier.
Invest and Grow
Manufacturers should consider implementing a digital workflow for printing/pretreatment when it comes to decorative surface design. It is worth the investment and is growing.
Oct2022, Industrial Print Magazine
