Bornemann, Nils (2014)
Characterization and Investigation of Large-Area, Ultra-Thin Gravure Printed Layers.
Technische Universität Darmstadt
Ph.D. Thesis, Primary publication
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Item Type: | Ph.D. Thesis | ||||
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Type of entry: | Primary publication | ||||
Title: | Characterization and Investigation of Large-Area, Ultra-Thin Gravure Printed Layers | ||||
Language: | English | ||||
Referees: | Dörsam, Prof. Edgar | ||||
Date: | 2014 | ||||
Place of Publication: | Darmstadt | ||||
Date of oral examination: | 26 November 2013 | ||||
Abstract: | Graphical gravure printing is a very reliable process to transfer smallest amounts of fluid droplets to a substrate. Nevertheless, enabling this printing technique to produce large-area, ultra-thin layers for applications such as organic light emitting diodes (OLEDs) is a challenging task. This application not only imposes strong requirements on the printing technology but also on large-area measurement methods. Characterizing the homogeneity of sub-100 nm thin layers across the total printing area is one of the two central topics of the present investigation. Utilizing optical interference from the thin film samples I developed and evaluated a method which successfully determined the thickness of thin, organic semiconductor layers with an accuracy better than 5 nm. Sample sizes of up to 150 × 150 mm² could be characterized within seconds using two hardware setups. I enabled a microscope and a modified flatbed scanner to acquire conventional RGB-images of the thin film samples. These images were then compared to a corresponding physical model using MATLAB resulting in a laterally resolved thickness map. The method is predestinated for being part of an inline process control. In the second part of the thesis, I deduced a physical understanding of gravure printing to produce ultra-thin, homogeneous layers from low viscous ink solutions which are based on small molecules dissolved in toluene. To this purpose, I processed on two consecutively mounted 150 × 150 mm² ITO-coated glass substrates with varying process parameters, resulting in a total number of 128 different gravure printed fields, each 30 × 30 mm² in size. Applying the large-area characterization method developed in the first part, I measured the thicknesses of all sub-100 nm printed layers (with a total area of ~1800 cm²). This thickness data was analyzed regarding several surface parameters, such as roughness, dominant lateral wavelength, skewness and kurtosis. These surface parameters were referred to the physical models of fluid and thin film dynamics with respect to the underlying process parameters. As a consequence, two distinct process windows for the gravure printing process to produce homogeneous, ultra-thin layers were identified. The process windows were defined by two types of ink transfer mechanisms, namely single cell transfer and film splitting transfer, as well as appropriate film leveling and drying times. The two process windows for producing homogeneous, ultra-thin layers using gravure printing have been reported in the literature and were demonstrated through the present experiments. By combining the two different topics, for the first time, these experimentally observed process windows were theoretically verified. |
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URN: | urn:nbn:de:tuda-tuprints-38479 | ||||
Classification DDC: | 500 Science and mathematics > 500 Science 500 Science and mathematics > 530 Physics 600 Technology, medicine, applied sciences > 600 Technology 600 Technology, medicine, applied sciences > 620 Engineering and machine engineering 600 Technology, medicine, applied sciences > 670 Manufacturing |
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Divisions: | 16 Department of Mechanical Engineering 16 Department of Mechanical Engineering > Institute of Printing Science and Technology (IDD) |
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Date Deposited: | 07 May 2014 12:49 | ||||
Last Modified: | 07 May 2014 12:49 | ||||
URI: | https://tuprints.ulb.tu-darmstadt.de/id/eprint/3847 | ||||
PPN: | 339756403 | ||||
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