Advanced Inkjet Screens

Advanced Inkjet Screens™ have been specifically developed after development on inkjet presses from a large number of OEMs using UV, aqueous and other inks. They are designed to improve print quality “out of the box” on many inkjet presses so they are quick to deploy.

Absorbent substrates

On fairly absorbent and/or wettable substrates drops tend to coalesce along the substrate surface, causing visible streaking, especially at the print speeds associated with high speed inkjet. This is especially the case in mid- and three-quarter tones. Pearl and Opal are advanced dispersed (FM) screens, optimized for natural images on a more or less absorbent substrate at lower and higher resolutions respectively. They are targeted especially at addressing chaining and streaking artefacts.

Non-absorbent, poorly wettable substrates

On non-absorbent, poorly wettable substrates prints are characterized by a mottle effect that looks like orange peel. The problem appears to be triggered by ink shrinkage during the cure and is especially noticeable in areas with reasonably high total area coverage. The Mirror Advanced Inkjet Screen is designed with a microstructure targeted at countering this mottling. It’s also useful when dense inks such as metallics are used, or where the print should not interfere with the smoothness of the reflection from a shiny substrate.

Multi-level Screening

If you’re using grayscale print heads, multiple nozzles printing on the same location on the substrate, or multi-pass heads you probably need a multi-level screen. A multi-level screen can achieve the appearance of a much higher resolution than could be achieved with a binary screen at, say, 600 or 1200dpi. More than that, the right screen can make sure that your press delivers exactly the right amount of ink where it needs to be on the substrate.

Harlequin Core has a very powerful and flexible API to specify how many ink levels (drop sizes) should be used, the tonal ranges that should be assigned to each and the transitions between them. This supports output in two or four bits per pixel, for between two and fifteen ink levels.

ScreenPro

Although Harlequin Core can apply Advanced Inkjet Screens and has a powerful multi-level screening capability, there are also cases where separating the rendering and screening processes can be useful, e.g. when recompositing partial page rasters after the RIP for maximum speed on variable data print jobs, or where other downstream processing of composite rasters is required. In these situations Global Graphics’ ScreenPro Core™ stand-alone screening engine can be used to apply the screens.

And ScreenPro can apply the same Advanced Inkjet Screens as Harlequin can, providing consistency and continuity across your product range, even if you have different presses with different workflow requirements.

Our innovative technology, PrintFlat™, is available as an option with ScreenPro. PrintFlat reduces banding or non-uniformity across the web. It mitigates the artifacts caused by variation within a head, commonly known as inkjet smile, between heads or wear on the head itself. By being able to address every nozzle separately on any combination of head and electronics it can achieve very fine granularity.

Other print technologies

The discussion above focuses on screening for inkjet presses. Global Graphics has spent many years developing advanced screening for offset, flexo, toner and other printing technologies. Ask about Harlequin Dispersed Screens for FM/stochastic for hybrid and about Harlequin Cross-Modulated screening.