Advantage ... Digital

When it comes to flexo plates, there’s just one evolving story to tell. It concerns the growth in computer-to-plate (CTP) technology, including its slow-growing acceptance among flexo trade shops, many of which remain skeptical that digital imaging technology has all that much to offer them—yet.

Historically, the biggest disadvantage of flexo plates, especially when compared with the litho variety, has been quality, and this perceived disadvantage is largely responsible for the rapid development in CTP flexo. In fact, these developments have resulted in a quality advantage for image reproduction with digital dots vs. film-plate dots.

There are dissenters, however. The future may be digital, but among some skeptical flexo trade shops, the present still belongs to analog platemaking. During the transition, suppliers continue to develop and refine both their conventional and digital flexo plate lines.

Most flexo plates are made of photopolymer material, and there are currently a wide variety on the market (see sidebar on p. 19). After imaging, the majority of flexo plates are processed using chemical solvents, water, or heat. All processes work by removing the unexposed polymer after imaging to create the relief in the printing plate, and each method has distinct benefits and disadvantages. While photopolymer dissolves in chemical solvent, water processing works by separating the polymer from the nonpolymerized photopolymer and provides an environmental alternative to solvent-processed plates.

New thermal processes eliminate the need for prolonged plate drying and use heat and pressure, with an inert material receiving the heated non-polymerized photopolymer. Because they are totally dry platemaking systems, there is no need to handle, store, recycle, or dispose of chemicals.

The flexo advantage

The economics and flexibility associated with flexo plates make them the standard for package printing, especially when compared with litho plates. Asserts James Kadlec, president, Advanced Prepress Graphics, “Flexo plates retain a cost per square inch vs. a full sheet like litho plates. Litho printing relies on ink transferring from the plate to a blanket, but flexo prints on the final substrate directly. This means that flexo can print on a wider variety of substrates. Flexo offers production and converting benefits not available as economically with litho.” However, Ian Hole, director for market development, Esko-Graphics, adds, “Due to the nature of flexo, the surface of an offset plate is much flatter and easier to image. The undulation in a polymer (flexo) plate makes imaging a bit more complicated.”

Flexo plates are created by conventional plate and film technology or through a direct-to-plate “digital” solution that integrates the film into the plate construction. “As the industry evaluates ways to improve workflow and integrate the use of digital file management, the next logical step is to include digital platemaking into the mix,” says Geoffrey Barba, director, product strategy, MacDermid Printing Solutions. “The benefits arise from using the same digital file to create any number of plates at any number of platemaking facilities, thereby providing consistency from location to location. The digital imaging of photopolymer plates also produces a much finer dot, and is capable of expanding the overall tonal range in the plate and on press.”

Advantage—Digital? Not so fast ...

For prepress shops, says Hole, “Traditional work with film cannot achieve the quality of digital plates. There is a dramatic increase of the sharpness of ‘perfect’ dots, with a much wider tonal range. The shape of a digital dot has a better, stronger conical top. [As a result], it gets a more precise transfer of ink relative to the size of the dot it prints. Press impression is less critical to the size or sharpness of the dot print result, as the exact size required on the printed substrate has already been produced on the plate.” Moreover, says Hole, digital plates run color shades reliably between 1-99 percent of full color, while the range for film plates is about 5-93 percent for flexible packaging and 12- 93 percent for corrugated.

On the other hand, says Kadlec, lithography lends itself more readily to computer-to-plate than does flexo, and the associated costs of the transition are factors to be considered in making the switch from analog to digital. “Compared with a 30˝ x 40˝ litho plate costing $10 ($.22/square inch), a photopolymer plate of the same size costs $264. This makes making flexo errors cost-prohibitive,” says Kadlec. “As with litho plates, digital errors find their way to the press. Litho is a much less time consuming makeready compared to flexo. In my opinion, until the digital environment can be cost justified, digital flexo platemaking will be aspiring to come to life.”

Suppliers acknowledge the reluctance of many trade shops to follow the digital path. Says MacDermid’s Barba, “There is still a huge group of analog plate advocates, who don’t need the benefits of the digital workflow, yet can still achieve superior print quality. For those, there are new flexo plate exposure technologies entering the market that allow printers to achieve near digital plate quality, without (the) large capital investment” in equipment required by digital platemaking.

Kadlec agrees. “Cost, awkward processing, and imaging restrictions handcuff digital flexo platemaking. Only a few organizations with deep pockets can afford digital flexo platemaking’s substantial expenses of material, sheet layout of usable work, (not to mention) press proofing of the incorrectly imaged plates.”

The customer is always right

As in the offset world, however, customer demand ultimately drives the adoption of digital flexo plate technology, counters Hole. “The quality of digital flexo plate technology is making people reconsider how to print their packaging,” he says. “Consumer goods companies are requesting digital plates.” If the industry does not move to digital flexo imaging technologies, he cautions, “gravure and offset will take back the market shares that flexography has recently gained and currently enjoys.” Concerning the cost of digital plates and platemaking equipment, recent thermal processing advances could translate into a price drop in flexo plates, he says.

At the present time, only around 20 percent of flexographic facilities worldwide are digital. Nevertheless, says MacDermid’s Barba, “Computer-to-plate flexo continues to grow as a technology. Around the world, consumer product companies demand consistency. In order to achieve this consistency and still use a variety of printers to produce their packaging, a digital file ensures that each location is getting the identical information with which to produce a plate. As plate makers and printers see the benefits derived from the use of a digital workflow, the natural integration of computer-to-plate makes a lot of sense.” n