Damage Control

The key to a high-performance, flawless flexo printing plate is time—imaging time, processing time, and drying time.

by Kate Sharon, Associate Editor

EMERIL LAGASSE IS a thorough chef who doesn't take shortcuts when preparing his mouth-watering cuisine. He never skips over the most tedious of cooking chores, and he never forgets to "take it up a notch" or add a "bam!".

As flexo platemakers take it up a notch to meet today's demands for faster turnarounds, shortcuts can quickly spoil the key ingredients consumer product companies need most to build their brands: accurate and consistent color.

The platemaker's role is more important than ever in today's fast-paced production environment and good platemakers have learned that taking shortcuts in the platemaking process often produces plates that fail, said Charlotte Cushing, senior technical service analyst for DuPont Imaging Technologies.

"It comes down to process control," Cushing said. "You have to follow all the steps for quality control—for consistency, to construct a quality plate every time."

Step by step

Making flexo plates is a fairly simple process. According to the Cyrel Process-of-Use Manual, there are six basic steps to platemaking: back exposure, main exposure, processing, drying, finishing, and post exposure.

On the imager, a plate undergoes both back and main exposure. During back exposure, "a photopolymer (UV light-sensitive, extruded plastic) plate is exposed to UV light through the dimensionally stable polyester backing to build/polymerize a predetermined floor on which the image will secure to," explained Jim Vertullo, president of JV Imaging Systems, Inc.

Main, or front, exposure is a bit more complicated. In this step, "a film negative with a matte emulsion containing the desired image is placed in contact with the surface of the plate after the protective sheet is removed," Vertullo said. "… An exposure cover sheet is then placed over the negative and plate, and the air is removed by introducing vacuum to the underside of the sheet, thus removing any air trapped between the plate, negative, and exposure cover sheet. … At this point, UV light is introduced to the plate and negative 'sandwich' and the polymerization/curing process begins." When front exposure is complete, the image will have transferred from the negative to the plate.