Experience gained by Gallus with EskoArtwork's HD screen and Kodak's Flexcel NX technology

The previous edition of our Gallus In Touch newsletter included detailed information about EskoArtwork's HD screen and Kodak's Flexcel technology. This time round, we focus on our experiences with these two technologies to date.

Screening technologies in flexographic printing

It is a common misconception that the HD screen is a frequency-modulated or hybrid screen. The probable reason for this is that, if an inadequate screen ruling is used, the HD screen takes on a slightly grainy appearance in the highlights. The following overview covers the most commonly encountered screening technologies in flexographic printing and should help prevent this misconception.

Overview of screening technologies in flexographic printing

Kodak's Flexcel technology

Kodak's Flexcel NX printing plate represents a new kind of imaging. The film is first imaged using a laser and then laminated onto the unexposed printing plate prior to exposure with UV light. Having served its purpose, the film can then be removed from the plate. The big advantage of this technology is that it eliminates the disruptive effect of oxygen from the plate exposure process. This ensures consistent screen dots with relatively shallow edges, which results in high plate stability during printing.

Gallus has often used Kodak's Flexcel NX printing plate in the past. Under optimum printing conditions, it produces excellent print results. One particularly positive feature of this type of plate is its low mottling tendency. Mottling is the name given to the cloudy halftone printing that occurs in particular on semi-gloss self-adhesive paper and white self-adhesive polyethylene. This phenomenon is not visible on plastic monofoils. Factors such as the type of printing plate, mounting tape and substrate selected can have an impact on mottling.

Mottling associated with the plate hardness (1.14 mm)

Kodak's Flexcel NX printing plate also benefits from superior ink transfer to many of its competitors, which results in a high optical colour density. In terms of dot size, however, the Flexcel NX plate is subject to far greater dot gain than printing plates imaged using the HD screen. This is not a major problem because it can be corrected as necessary at the prepress stage.

HD screen from EskoArtwork

EskoArtwork's HD technology has the significant benefit that it can be used to image all flexographic printing plates with a LAMS layer. Flexcel technology, on the other hand, can only be used on Kodak's flexographic printing plates, which ties users to a single system.

Being able to use the HD screen on many different types of printing plates does, however, have its downside. HD imaging cannot produce anything like a top-quality product from a problematic flexographic printing plate. The results of tests performed at Gallus with the HD screen revealed huge differences in quality between the various plate types. In other words, the HD screen is only as good as the plate type selected!

Under ideal production conditions, however, unbelievably high qualities can be achieved with a flexographic plate imaged using an HD screen. Particularly impressive features of this screen include its high contrast and screen vignettes down to zero percent ink coverage, with no tonal value jump being visible to the human eye.

Before using the HD screen, it is essential to evaluate the ideal HD imaging. The type of HD screen must be determined for each separate type of plate. Otherwise, there is a risk that print results will fail to meet the high expectations.

HD screen test forme

A specific test forme needs to be used to evaluate the ideal HD imaging for each separate type of printing plate.

Conclusion

Under ideal conditions, top results can be achieved with both EskoArtwork's HD screen and Kodak's Flexcel NX technology. In other words, the reprographic department must know what it is doing, the materials used (mounting tape, anilox roller, ink, etc.) must be coordinated, the press operator must work carefully and the press must operate perfectly. If all these requirements are met, both technologies can achieve outstanding print results of a quality comparable with that achieved using offset printing.

Please feel free to get in touch. We will be happy to send you further details.