Users of this system can compete directly with gravure production, offering their customers top quality flexo printing at a price that’s more affordable than gravure printing. But there are further benefits – NX plate users experience faster setup times, they find that plates last longer and they gain several savings on the press, where less ink is needed to print a clean dot without corresponding loss of density.
Printers get the full benefit of the NX-imaging and plate-making technology when they use the combined capabilities that the plates deliver, which has been proven to reduce the number of colours required to print a flexo press job, often eliminating the need for spot colours and saving on the number of print unit setups and the number of plates needed to produce a high-quality flexo print job.
For example, flexo jobs are often printed using two black plates, with a process black for the halftones and a high density black for line work and barcodes. Using the Kodak Flexcel NX system, the same densities and black sharpness can be achieved with a single black plate, saving one plate right away.
How does it work?
The system doesn’t use the LAMS technology employed by other digital flexo plates. Instead it relies on imaging a high-resolution mask material – the Kodak Flexcel NX TIL (thermal imaging layer) – that’s imaged and then laminated on to a photopolymer plate before receiving required UV exposure.
The TIL holds a 10µm micron dot and accurately reproduces exactly what’s in the digital file – every time.
Nick Fisher, manager at Kodak’s flexo demo centre in the UK, has this to say: ‘You can reproduce a 0.4% dot on the flexo plate, which is the lowest grey scale level, and it can be held on the file, the TIL and the plate. There’s no need for a bump-up curve, so the tonal range is 100% down to 0.4%, which gives more contrast to the images.’
At the heart of the system is Kodak’s Squarespot imaging technology, first developed for imaging litho plates and currently in use in over 16 000 offset CtP devices around the world. This best-in-class imaging technology has become the centrepiece of the Flexcel NX System.
The Squarespot technology is a way of channelling the edges of a laser beam for a precise, more defined dot. The laser is capable of producing 10 000dpi resolution, which Kodak has divided by four in order to concentrate on creating sharp edges around the dot.
Nick Fisher explains further: ‘A normal Gaussian laser, like those used on other flexo CtP systems, has a hot spot in the middle, which results in imprecise dot edges. But because we can channel the edges of the laser, you get a very nice, step-sided sharp dot.’ In practice, this means that where a normal exposure at 2 400dpi yields a 15µm dot with a soft edge, Squarespot technology gives 10.6µm dots with hard edges.
Kodak has also developed an option called Kodak Digicap NX screening that significantly improves ink transfer from the surface of the plate, resulting in cleaner, brighter colours. A filter applied in the software to the 1-bit tiff file alters the texture of the surface of the plate in order to lay the ink down in a more efficient way, especially where solids are required. Gravure-like print can be achieved without the need to pile more ink on and printers can enjoy a wider colour gamut than that achievable with traditional digital flexo – another factor than can reduce the need for spot colour inks.
Exposing the plates
There are several steps needed to create a Kodak Flexcel NX plate. Firstly, the TIL, a dark glossy green material with a film base, is imaged directly on a Flexcel NX imager, a device available in narrow, mid or wide formats. The TIL is held on the top of the machine by a vacuum and then clamped to the drum. The imager ablates the dye-based layer on the TIL and then it removes the ablated debris.
A sensor within the thermal head follows the contours of the TIL allowing constant automatic focusing to adjust for any imperfections in the drum or the presence of foreign material.
Once the TIL has been imaged, it’s laminated to the polymer plate in a process that ensures the complete absence of oxygen between the two surfaces during subsequent UV exposure. This results in perfect pixel for pixel reproduction on the plate.
As with all photopolymer plates, the Flexcel NX plate requires a short UVA back-flash exposure – commonly done before lamination.
The laminator is easy to use. A vacuum pump holds the plate on the bed while the operator feeds the TIL between two rollers and then slides them across on to the surface of the plate. After 15 to 20 minutes of UV exposure, the TIL is peeled away leaving a perfect image on the plate. Normal solvent processing, drying and finishing are the final steps.
According to Nick Fisher, it’s a simple but effective system: ‘We have over 100 installations in Europe and I have never had an instance of loss of contact, and, by implication, no loss of dot resolution.’
Flexcel NX certification programme
Kodak has introduced a certification programme to ensure that repro houses are producing Flexcel NX plates to a recognised standard. It gives repro houses a tangible way of demonstrating their skills and means that brand owners are confident that jobs are produced to a consistent standard.
Finally, it’s worth noting that as well as serving the main packaging markets in flexibles, cartons and labels, the Flexcel NX system lends itself to a number of niche applications. The accurate reproduction of plate elements opens up options for security printing as Flexcel NX plates can reproduce important features such as micro text, not easy with other flexo-processing systems. Flexcel NX plates have also been used for lenticular printing that’s not possible with other flexo plate types.
All in all, Kodak claims that the Flexcel NX system is transforming the flexo market with better image quality and lower total cost of production, both adding up to higher margins for printers.