The Year of the Flexo Plate

Today's flexo platemaking systems offer printers a variety of options to match their costs, quality, and speed needs.

FOR MORE THAN a few flips of the calendar, flexography has held top billing as the fastest growing printing method for labels and packaging. Boosted by an impressive succession of technological advances, this once red-headed stepchild of the pressroom has become our industry's new darling.

Despite a developing threat from digital printing just over the horizon, flexo appears capable of maintaining its favored position, too. Its attractive economics and suitability for a wide range of packaging applications—especially for flexible packaging—are certain to keep flexo's popularity on the rise.

In fact, 2005 might just be a banner year for flexo printers and converters. End users are now familiar with flexo's advantages, and more and more packaging buyers are specifying flexo as the preferred printing process for their products. On the other end of the supply chain, equipment and consumables manufacturers are investing significantly in research and development to enhance the process even further. From wild new screening techniques to 7-color ink systems, flexo is in the center of a technology renaissance.

Nowhere is this transformation more apparent than in the area of flexo photopolymer platemaking. Today's packaging printer can choose from a myriad of material, imaging, and processing options. Mixed and matched properly, these options can help him achieve just about any combination of cost, quality, and speed for his flexo product output.

Plentiful options

While there are several distinctly different types of photopolymer flexo plates, they all share common physical characteristics. Whether in liquid or sheet form, they are composed of light-reactive polymers and they undergo similar processing steps to become compressible, flexible image carriers with raised (relief) image areas.

The three basic types of plate systems are 1) solvent washable plates, 2) water washable plates, and 3) dry thermal plates. While each system has unique performance, environmental, and cost attributes, they share a common preparation cycle:

• Back exposure to UV light to harden the plate base and establish the image relief depth;

• Exposing the face of the plate (through a film negative or with a laser imagesetter) to harden the image areas;

• Washout of non-image areas;

• Drying to remove washout fluids;

• Post exposure to UV to "cure" the image; and

• Finishing to remove residual tackiness.

Solvent wash systems are the most mature, but they are typified by long drying times and are considered less environmentally friendly than the newer water wash and dry thermal systems. Within the past five or six years drying times for solvent wash systems have improved as manufacturers switched to percholorethylene alternative solvents (PAS), but these solvents can still be respiratory and eye irritants, so proper plateroom protection should be worn. While not usually considered hazardous waste materials, solvent wash byproducts must still be tested for toxicity and compliance with local disposal regulations.

The first water wash plate systems became commercially available in the early '90s. These plates are processed without harsh solvent chemistry and can be dried in a fraction of the time it takes to dry solvent wash plates (minutes compared to hours depending on plate size and relief). Originally suitable for line and low line screen printing applications, water wash systems, such as MacDermid's Flexceed, are now advanced enough for 150 and 175 line process work.

Requiring less rigorous safety and environmental considerations than solvent wash systems, water wash plate systems can be ideal for printers bringing the platemaking function in-house for the first time. Prepress trade houses have adopted water wash systems as well. James Kadlec, owner of Advanced Prepress Graphics in Wood Dale, Ill., began using Agfa's AquaFLASH plates in late 2004. Kadlec, an outspoken proponent of film-based flexo platemaking, claims that when these water wash plates are exposed with a single point light source, they offer quality and efficiencies "equal to that of more expensive digital systems."

Dry thermal flexo platemaking is the newest technology on the market. The process was first commercialized by Cyrel manufacturer DuPont under the FAST brand name at the turn of this century. DuPont was awarded the prestigious FTA Technical Innovation Award for the technology in 2003.

After digital or film-based exposure, dry thermal plates are processed without the use of wet chemistry. Instead, the non-image areas of the plate are heated, softened, and pulled away by contact with a non-woven synthetic web material in successive passes until the desired relief depth is achieved. By November 2004, DuPont had installed some 300 FAST systems worldwide and the company announced its next generation system—available in a wider 42 x 60 format—was in alpha testing at Flexicon AG, Europe's largest flexo platemaker. In 2004, competitor MacDermid also entered the dry thermal market with its new Lava platemaking line.

Today, these three plate systems have been adapted for digital laser imaging as well as in-the-round imaging, giving printers an unprecedented number of platemaking choices. Also, equipment manufacturers are offering a host of new processing and finishing technologies to optimize productivity for each system.

All-in-one systems

All-in-one processing units are now available in stack, rotary, and in-line configurations. These various configurations provide a wide range of size, speed, and ease-of-use options. Simplification is key as suppliers like Anderson & Vreeland package software, hardware, and consumables into one all-inclusive platemaking system, such as A&V's inline Freedom system for water wash plates.

These all-in-one systems fill a critical void, according to Mekrom Inc.'s Michael Pierce. Mekrom—based in Spain, Switzerland, and France—is one of the world's most prolific platemaking equipment manufacturers, active in virtually every segment of the packaging industry. Pierce heads up the company's new North American operation, opened in early 2004.

Pierce predicts that eventually all mainstream printers will bring platemaking in-house in order to optimize their time-to-press and quality control. He says all-in-one systems like Mekrom's 200C are helping printers save space, are easier to use, and are more affordable than platemaking systems of the past.

The 26 x 32 200C combines exposure, inline washout, a four-drawer dryer, and light finisher with post exposure into one totally enclosed system that requires only about 7.5 ft. of floor space. The operator loads and unloads material from the same side of the unit, and can control the entire process from a single touch panel.

Mekrom also unveiled a revolutionary new dryer technology for solvent wash plates at drupa 2004. According to Pierce, the standalone HTD employs proprietary electronic drying technology that can dry plates much faster than conventional hot air dryers—in as little as 20 minutes regardless of plate size or relief depth. Pierce says the first HTD's will be delivered in this country by the first of this year. "At a cost comparable to hot air drying, the HTD offers double the productivity and increased single-plate speed," he says.

The sheer volume and variety of flexo platemaking equipment on today's market, and new technologies still on the drawing board, will continue to fuel flexo's penetration of the packaging industry. With more choices than ever before, 2005 may prove to be "the year of the flexo plate."