Laura Cirstea, Anna Kolesova, Hammad Khan, Mohamed Abouelmagd, Swapnil Patel, Thomas Sprinzing, Matthias Galus, Armin Weichmann

Hochschule der Medien Stuttgart, Institut für Angewandte Forschung (IAF), Nobelstr. 10, 70569 Stuttgart, Germany E-Mail: lc035@hdm-stuttgart.de; ak280@hdm-stuttgart.de; hk060@hdm-stuttgart.de; ma120@hdm-stuttgart.de; sp099@hdm-stuttgart.de; sprinzing@hdm-stuttgart.de; galus@hdm- stuttgart.de; weichmann@hdm-stuttgart.de

Short Abstract

For many decades in rotogravure electro plating a chromium layer on top of the copper surface which holds the cells was used as wear protection for the print form cylinder. Recently, coating the copper with a layer of diamond like carbon (DLC) presents an alternative with even higher wear protection. The price of a DLC coating is significantly higher, so further advantages would be beneficial to justify its application. There were indications that the ink accepting and releasing properties of the DLC are superior to chromium. This would be especially useful for micro structures and fine lines. Therefore, we designed a print form including many different small structures and manufactured two identical cylinders by laser mask etching, one electro plated with chromium, one coated with DLC. A print trial was conducted on our industrial-scale gravure printing machine. We compared the two surfaces with black ink on a white BOPP film under varying ink viscosities, doctor blade materials and doctor blade angles. Analysis of print gradation, missing dots and mottle was done, a visual assessment of a fine line star pattern was conducted and 15, 20 and 50 μm lines in and across the print direction were measured according to their average width and homogeneity. Almost every evaluation shows the micro structures printed were significantly better with the DLC surface. The influence of the surface surpassed by far the other parameters.

Statements by Professor Armin Weichmann:

“DLC outperformed chrome in every test.”

“The improvements were very significant.”

“far superior’ in all print orientations on the substrate.”

“With DLC line continuation in our trial down to 15µm.”

“Superior continuous Tone to the smallest dots.”