Manufacture of sub-μm thin, particulate-based ITO layers by roller coating

This paper presents the development of nanoparticulate indium tin oxide (ITO) inks for the continuous manufacture of ultrathin (∼280 nm) ITO layers on PET substrates by roller coating at very high coating speeds. Ethanol- and water-based ITO inks containing polyvinylpyrrolidone as binder were prepared and rheologically characterized. The influence of different ink compositions on coating properties was evaluated by the concept of the dimensionless capillary number Ca. The ITO films were characterized concerning optical and electrical properties in dependence on ink composition and coating parameters. The organic solvent ethanol could be replaced by water, being cheap and environmental friendly. These inks allow the manufacture of sub-μm thin ITO layers with high layer quality and low specific electrical resistance of 3 Ω cm. Flexible and highly transparent ITO films with an inline-transmission of 88% in the regime of visible light which absorbed simultaneously up to 96% in the NIR region were produced.