Sustainable Diamond-Like Carbon Fabricated Gravure Cylinders for Printing Fine Lines of Electrodes and Graphic Structures
Date of Award
Doctor of Philosophy
Chemical and Paper Engineering
James R. Springstead, Ph.D.
Priyanka Sharma, Ph.D.
Harvey R. Levenson, Ph.D.
Chrome (Cr), diamond-like carbon (DLC), fine line electrode, gravure printing, printed electronics, surface-free-energy (SFE)
The main objective of this work is to evaluate the potential of Diamond-Like Carbon (DLC) as an alternative to chrome for use on gravure cylinders. DLC coatings consist of carbon atoms, arranged into a diamond-like structure that closely resembles that of natural diamond. In contrast to chrome, DLC is environmentally friendly. The focus of the study is to determine the viability of DLC as a substitute material for chrome to be used on gravure cylinders by determining key material properties and evaluating printing performance.
In the first research paper, four DLC variants (Standard DLC, A-DLC, S-DLC, and Organic Silica) and chrome were analyzed and tested for surface properties and durability. Data suggests that both Standard DLC and S-DLC had higher surface free energy, allowing for good ink wetting on surface when compared to chrome. In addition, the Standard DLC and S-DLC surfaces are generally smoother than the chrome, resulting in lower relative hydrophilicity and allowing for easier removal of ink in the non-image regions with the doctor blade. The Elcometer adhesion test demonstrated that the bond strength of the Diamond-like Carbon (DLC) variants to their base layer was comparable to bond strength of chrome, indicating that the adhesion strength of the two materials was similar. Furthermore, in the abrasion test, the Standard DLC surface wear was significantly less than that of chrome after 2,000,000 wiping actions of a metal doctor blade in the presence of abrasive TiO2 ink pigments. Statistical analysis on Standard DLC vs chrome suggests that DLC fabrication is effective and durable on plain and patterned surfaces. Therefore, from a sustainable and ecofriendly perspective, Standard DLC and S-DLC would be a good alternative durable surface for print cylinders and other components used in various industries due to superior wear resistance properties.
In the second research paper eight experimental trials were conducted to assess the quality of print reproduction. Various combinations of ink, substrate, doctor blade, and gravure surface were used as printing conditions. The ink, substrate, and gravure surfaces underwent a qualification process to ensure they were suitable for the experiment. The quantitative data generated during the qualification process provided insight into the properties related to different print conditions and how they affect the reproduction of fine lines. The higher total surface free energy (SFE) and its polar component of the PET (Polyethylene terephthalate) substrate, viscosity, and contact angle of the ink all influenced the spreading of ink on the substrate. The ink used in the experiment demonstrated excellent adhesion to the substrate and flexibility without cracking when bent. The marginally higher hydrophilic properties of DLC and lower surface roughness of the Standard DLC surfaces helped to repel the ink from non-image areas while still providing good ink wetting and transfer to the substrate in the image areas. It is observed from the experimental data that under various printing conditions, the prints of electrode grids reproduced from Standard DLC had increased line widths for 20 and 30 μm lines compared to chrome. Additionally, the statistical analysis in the t-test and Tukey comparison for surface indicated that Standard DLC was statistically different from chrome, providing a higher mean line width due to its good ink release and transfer characteristics.
In the third and final study we evaluated the use of DLC-fabricated gravure cylinders for rollto- roll printing of fine line electrodes and microtext patterns for flexible electronics and graphics authentication. Results suggest that DLC is an exceptional coating candidate for reproducing grids and lines of 15, 20, and 30 μm, as well as solid electrodes with low electrical resistance and high density. In addition, DLC printed lines showed that its fine line engravings exhibit easy ink transfer behavior onto PET substrate, resulting in more ink deposition, electrode line width density gain, and lower electrical resistance when compared to results using chrome. Statistical analysis confirmed the reliability and repeatability of the findings. Visual analysis of microtext also demonstrated the superior reproduction capabilities of DLC-coated surfaces. Overall, these results suggest that DLC fabrication is a promising alternative for producing high-quality, high-volume electronic components in a more sustainable process.
Restricted to Campus until
Seetharamiah Srinivasaraju, Chandramohan, "Sustainable Diamond-Like Carbon Fabricated Gravure Cylinders for Printing Fine Lines of Electrodes and Graphic Structures" (2023). Dissertations. 4045.