Advantage ... Digital
The future for flexo may be digital, but the present still belongs to analog platemaking.
April 2006 by Jean-Marie Hershey
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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.”
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.”
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