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Exploring UV Inks

(November 2001) posted on Mon Nov 05, 2001

For Industrial Applications


By Alan Carey

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In the early 1970s, increasing environmental awareness inspired the development of the first VOC-free inks that cured with ultraviolet (UV) energy. These safe inks promised the performance characteristics of traditional solvent-based formulations and beneficial side effects, such as quick processing speed. Throughout the years since their introduction, UV inks have made great inroads to dominate a variety of screen-printed graphic-display applications. But their progress in penetrating industrial markets has been less dramatic.

One of the first groups of industrial printers to explore UV screen inks were nameplate, overlay, and membrane-switch printers, who typically work with polycarbonate and polyester substrates. Just as with any untried new product, the early UV inks proved to be unpredictable, and these screen printers found them unreliable for their demanding applications and preferred substrates. Some of the other early drawbacks included limited opacity, poor flexibility for embossing and die cutting, and questionable compatibility with various adhesives.

As ink manufacturers continued to refine their products, they also realized that many of the problems industrial screen printers were experiencing resulted from a lack of information and training about UV inks and their usage. Converting from solvent-based to UV inks was more than just a matter of switching the inks--printers needed education to understand how UV inks work and what changes they bring to the production process.

With the assistance of ink suppliers, many nameplate, overlay, and membrane-switch printers overcame these early obstacles and successfully incorporated UV inks into their operations. But for the past decade, the increased use of UV inks has only paralleled the normal sales growth in these markets. In other words, the move among industrial printers to adopt UV in place of solvent-system inks seems to have run out of steam. The question is, "Why?" But before we answer that question, it might be helpful to review the current state of UV technology for industrial applications.

Industrial UV inks today

If we assess the present situation with UV screen-printing inks, we see that many changes have taken place since their introduction, changes that make UV inks ideal candidates for industrial jobs. UV ink manufacturers have improved opacity levels until they nearly rival those of solvent-based inks. Extremely flexible formulations have been developed that allow embossing, diecutting, and even thermoforming without cracking on polycarbonate and other performance substrates. And their printability and curing characteristics make them excellent for process-color work.

Today's UV inks are compatible with a variety of adhesives, including printable UV-curing adhesives. And experimentation has shown that newer formulations support successful printing and curing of up to 15 layers of ink without delamination.

The latest UV inks for overlays and similar jobs can be processed at high speed and offer large curing windows, so they are difficult to overcure. Special curing instructions and tight-tolerance curing parameters are virtually things of the past. Finally, UV inks are available to support a wider selection of substrates than ever before.

Curing equipment has evolved as well. Today's UV dryers provide reflectors that can direct curing energy in a number of ways while reducing heat, bulbs tuned to the most effective curing wavelengths, and easy-to-use test equipment to monitor and maintain optimum curing-system performance

Reluctance to adopt UV

Despite improvements in UV inks, the early limitations and experiences industrial printers had with UV seems to have created somewhat of an aversion to the technology. While UV inks could satisfy nearly 100% of nameplate, overlay, and membrane-switch applications, their use falls far short of this level.

Two main factors have prevented greater adoption of UV technology. The first is the fear of ink failure (delamination, cracking, etc.). The second is a lack of awareness about the significant progress that has been made in UV-ink chemistry.

While it's true that substrates like polyester still pose challenges for UV ink adhesion, polycarbonate and other common industrial materials are well suited for UV printing. Even more important, the fast-curing characteristics of UV inks make them ideal for the high-volume production frequently associated with industrial printing jobs. Faster processing leads to lower costs and bolsters a company's position in a competitive market. This is why adoption of UV technology frequently leads screen-printing companies to purchase high-speed, multicolor inline-printing systems.

Color matching is another area that has received significant attention from ink manufacturers. Yet many industrial printers only recall the early days of UV, when the ability to achieve accurate color matches was limited.

Today, ink suppliers have invested in sophisticated electronic tools to measure and assist in tuning the color-matching capabilities of their inks. As a result, most now offer complete color-mixing guides for the majority of their UV-ink lines, many of which may even be licensed to simulate a broad range of Pantone colors. Additionally, with low-cost spectrophotometers available for color measurement, printers themselves have the ability to test and correct any color errors they may discover.

Finally, because UV inks typically cost more than solvent-based formulations, some printers assume that converting to UV will increase their net expenses. However, studies published by groups such as the Screenprinting and Graphic Imaging Association International demonstrate that the use of UV inks improves productivity and efficiency while reducing ink waste. The resulting savings more than offset higher ink costs and justify the expense of new curing equipment.

Making the switch

A direct correlation exists between maximizing the use of UV inks and boosting productivity. But the process of increasing UV-ink usage creates anxiety in many industrial printers, who fear the risk of ink failure.

Increasing the use of UV and realizing the benefits of this technology requires a company-wide commitment. For the change to be successful, it must have the support of top management, regardless of whether the change is being pursued to reduce VOC emissions, increase productivity, reduce costs, increase efficiency, or all of the above.

When embarking upon this change, it is advisable to appoint an agent to coordinate the effort. This person could be an employee of the printing company or an outside agent, such as an ink company representative. The ink rep would likely have the advantage of familiarity and experience with solvent-to-UV conversions.

The actual conversion process will vary from print shop to print shop depending on the type of applications being printed and the shop's familiarity with UV technology. An assortment of variables will influence the conversion time and the necessary steps in the process. These variables include the skill level of press operators, typical substrates used, the nature of the printing and finishing equipment employed, and similar concerns.

Once the agent of change has been appointed, this person's first step should be to blueprint the conversion process, establish its time frame, and then present this information to the printing company management. This important step assures that everyone will work together to make the conversion smooth and successful.

A useful approach for blueprinting the change is to apply the Action Research model for system analysis. This procedure ensures that all relevant factors are taken into account as specific conversion plans are formed. The analysis comprises four primary stages: data collection data feedback intervention follow-up

The Action Research approach views the existing situation and the end goal. In the case of a conversion from solvent-based inks to UV, the existing situation covers all the procedures, equipment, and employee skills currently in place, as well as various external factors. The desired outcome is the maximized use of UV inks.

Data Collection The first step in performing the analysis is to consider the current technical and procedural framework of the organization, including the following elements: types of presses used and their capabilities the status of UV-curing units (do they need to be added?) types of screens used (mesh characteristics) types of frames used screenmaking capabilities, procedures, and standards types of emulsions used inkroom procedures and tools types of substrates printed (material, sizes, etc.) finishing procedures and equipment (embossing, diecutting, etc.) the types of printing conducted (low or high detail, fine lines, windows, process or spot colors, special color-matching requirements) type, durometer, and edge characteristics of squeegees used repeat order history commonality between applications that might allow ganging of jobs for shops that already have some level of UV capability, assessment of jobs that were not printed with UV ink and reasons for why they weren't (lack of equipment, size limitations, substrate compatibility issues, etc.)

The next facet of data collection considers the human/social side of the operation. In this step, the goal is to evaluate the skills of employees throughout the operation, including sales reps, estimators, customer-service staff, and others who will be affected by the change. The most important area to assess, however, is the skill of production employees, namely press operators and inkroom staff.

Data feedback After the internal and external assessments have been completed, a feedback meeting takes place so that the implementers of the change can establish a realistic timeline for the conversion. The timeline will address equipment upgrades, staff training, production-floor organization, procedural alterations, job-scheduling issues, and any other issues influenced by the conversion process.

Intervention With the plan in place, it's time to begin taking the steps laid out in the timeline and implement changes. The first step is to make sure that the UV inks will work for the applications that the printer produces. This is verified by sending substrate samples to the ink manufacturer, who will create test prints on the materials to ensure that the inks perform as needed, delivering the opacity, durability, adhesion, color, and additional characteristics that the printer desires. Next come the physical changes, which involve equipment purchases and perhaps some reorganization of existing equipment in the plant.

Concurrent with these changes, employee training begins. It's critical that the ink manufacturer be closely involved in training to assure that employee skill levels are up to speed. This training should incorporate hands-on training with UV inks and can be conducted in the print shop or at the ink manufacturer's site. The second option is most frquently used, either because elements of the new UV technology are not yet in place in the print shop or because offsite training is free from distractions and workplace pressures.

At this point, it is often a good idea to begin "fingerprinting" the presses and curing equipment to determine the optimum settings for processing UV inks with the types of applications that the shop typically produces. This is a long process that involves testing and documenting setup parameters, equipment performance, and resulting print quality. This step is not a necessity, but it can be useful to ensure consistency and maximum productivity.

Once all the pieces are in place, the shop will begin processing actual jobs with UV inks, starting with simple spot-color prints and working up to more complex applications, eventually leading to process color. Throughout this phase, inkroom personnel will be developing their color-matching skills.

Follow-up Once training in process-color printing is complete, and UV inks are being used regularly in production, a new assessment is done to evaluate the success of the conversion by reviewing the goals originally set forth. Customer satisfaction with the finished products should be considered, as should the viewpoints of production employees working with the inks.

This is also the time to look at whether use of UV ink is being optimized. Production managers must determine whether they are fully utilizing their UV equipment and using UV inks on every job that could take advantage of them.

If other goals or objectives have not yet been met, the situation is analyzed to discover the causes. Next, a new program of change is developed and initiated to accomplish the goals, and the four-tier cycle of change repeats.

The continuing evolution of UV

The great strides UV technology has made in satisfying industrial-printing applications continue even now. One of the most exciting developments is occurring in electronics printing, where new UV-curable conductive inks and adhesives are showing much promise.

The previously mentioned limitations of UV on polyester are also being addressed. Substrate manufacturers are developing new forms of polyester and coatings for these films that greatly improve their compatibility with UV inks. This allows printers to enjoy the benefits of UV processing and deliver the flexibility, chemical resistance, and durability of polyester to their customers.

An emerging growth area for overlay printers who use UV inks is in-mold decorating. As "In-Mold Decorating" (left) illustrates, this process involves printing on polycarbonate, polyester, or a similar film. After the film is printed (either first or second surface), it is placed into a mold. Next, molten plastic resin is injected into the mold behind the film, softening the material and allowing it to take on the shape of the mold (occasionally, the film is preformed after printing to precisely fit the mold). The resin and film bond during the molding process, creating a single three-dimensional part with nearly indestructible graphics. The process is used to create a variety of products, including automotive components, consumer electronics, and appliance components.

Today, most in-mold decorating is done with solvent-based inks, but recent developments in formable, temperature-resistant UV inks are changing this. However, the use of UV inks for in-mold applications is still in its infancy, and the process requires skill in both graphic design and printing. Graphics must be designed to achieve the desired appearance when they distort during the molding process, and care must be taken to ensure that the depth of draw doesn't exceed the ink's capabilities.

Since the molding process is also quite complex, screen printers will usually work with experienced injection-molding companies. They can design molds so that when the plastic resin is injected against the film, it doesn't reduce ink adhesion, wash out the print, or cause related damage to the graphics.

People make UV work

Changing to UV is a low-risk change when it is well planned, but the real keys to successfully adopting the technology are the people who make the process work. They include managers, production employees, and customer support staff who are open to change, committed to finding better ways to accomplish tasks, and willing to learn. Equally important is finding a trustworthy ink supplier, one who is experienced in UV technology and willing to be a partner in the conversion process and ensure its success. With support from inside and outside the organization, industrial printers who make the switch can realize a more competitive position and see their sales grow.

Today, the question for industrial screen printers is not, "Should we convert to UV." The question is, "How can we take advantage of UV technology in 100% of our applications?"


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