Alexandra Pekarovicova, Veronika Chovancova-Lovell, Sangmeshwar. L. Sangmule, Paul D. Fleming, Yu Ju Wu, Bill Guillot

Abstract
Spot colors are widely used in commercial, product or packaging printing to obtain a colorful appearance. In this work, we focused on spot color matching and gravure printing of decorative paper laminates. For proofing of spot colors, SmartColourTM iVue software was used. The iVue software enabled us to predict how the press job that was run on a low basis weight substrate will look like on a different substrate, in this case solid bleached sulfate board, based on the previously measured and proofed ink systems that are saved in Sun Chemical’s Global Shade Library. The library is accessed via the iVue software and gives the way of choosing and implementing various ink systems on diverse substrates printed at different press conditions.

Two different ink jet printers were evaluated for their ability to cover the color space of the proposed library. The extra inks that are being incorporated into the newer versions of the digital printers allow for better color control and larger coverage of a color space. One of the printers was then used to produce a proof of the design that would be printed on a specific substrate and will be able to match the original press print. The proof was also previewed in the iVue application and compared to the preview of the commercially available prepress design software. The overprint model and the ability to work with the real data and ink settings in iVue produce incomparable better results when previewing the final job just on a calibrated monitor display.

Keywords: Rotogravure, Spot color matching, SmartColour iVue, Digital proofing
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Soile Passoja, Jorma Koskinen, Robert Roozeman

Abstract
The influence of electric field on gravure ink lifting from engraved structures was studied. Ink transfer without electric field occurs only if the physical contact between ink and paper in the nip is achieved. The use of electric field in ink transfer promotes the ink lifting and enables the contact between ink and paper before the actual nip contact. In a nip a non-uniform electric field lifts the ink near the engraved edges over the cylinder surface. This phenomenon is explained by dielectrophoresis and supported by simulation. The electric field lifts the liquid on a microsecond timescale and it defines the ink transfer in gravure as the nip contact in the real press occurs on a millisecond timescale.

Keywords: Gravure printing, Electric field assistance, Ink transfer
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Gert Schlegel, Arved Hübler, Robert Thieme, Alexander Böddicker, Thomas Hädrich, Günter Wozniak

Abstract
This paper has two objectives: First, it aims at defining theoretically and determining by means of experiments ink film formation of sprayed offset printing ink. This refers to the analytic description of the surface covering process in the inking system of an offset printing press. Influencing factors are the temperature-dependent, rheological properties of the printing ink and the resulting drop size spectrum of an offset printing ink sprayed with a two-component jet (external mixture). The main problem is to transfer standard, highly viscous, sticky offset inks into a sufficiently fine spray that guarantees a fine, homogeneous ink film on an ink carrying roller in the inking system of an offset printing press.

The second aim is to design a prototype of a functioning spray inking system and to determine optimum working parameters for the employment of this new inking system in an offset printing press. The analysis is focused on standard offset printing ink (heatset ink, black). Practical tests are done on a rotary offset press.

Keywords: Offset printing, Inking unit, Atomization, Spray, Nozzle
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