Issues and Approaches Imposed on Ink Jet Technologies for the Progress of Printed Electronics

The simplicity of the ink jet process has led to major changes in electronics packaging in what is known as printed electronics. Major changes here means drastic cost reduction relative to the long-term trend, and also creating a new performance axis (flexibility, customization, large area, little environmental load … namely added value). However, simplicity has two sides: `Possibility' and `Limitation.' For the past several years, `Possibility' has been attracting a lot of attention, but in the coming years, if ink jet technology does not overcome `Limitation', the real change will never occur.In this paper, the related issues and status of approaches resolved by ink jet printheads or the printing process are described for the further progress and practical application of printed electronics using ink jet technologies.These issues can be categorized into 1) ejecting processes of functional liquid, 2) drop landing and dot (film) formation on the substrate, and 3) maintaining printhead reliability. In particular, expanding the range of applicable liquids, further miniaturization of the ejected liquid drop, and improved accuracy of dot positioning are strongly required for printheads. In printed electronics, unlike with desktop ink jet printers, impermeable media are often used, so analysis and control of the behavior of the liquid on the substrate are also important. Furthermore, technologies for maintaining stability in the ejected drops make a difference.These novel activities for improving ink jet issues will face tough problems and need revolutionary approaches, but a great innovation in printed electronics using ink jet technologies can be expected when success is achieved.