An Inductive–Inductive–Capacitive Hybrid In-Cell Touch Sensor for Bottom-Emission OLED Displays

초록

In-cell touch sensing has become a key enabler for large-area video and display systems, such as digital whiteboards, industrial panels, and automotive interfaces, where seamless integration of visual output and user interaction is critical. However, in bottom-emission OLED displays, conventional capacitive sensing faces severe limitations due to electric-field shielding by the continuous cathode, which leads to degraded accuracy and scalability. This paper presents a novel inductive–inductive–capacitive (LLC) hybrid in-cell touch sensor architecture that exploits magnetic-field coupling to overcome these limitations. Unlike traditional capacitive approaches, the proposed method leverages the parasitic inductance and capacitance inherently present in the TFT backplane, thereby eliminating the need for additional sensing layers or cathode segmentation. A 5×5 prototype array was implemented and validated through simulation and measurement. The results confirm reliable detection of single-touch, multi-touch, and active stylus interactions. Furthermore, by employing frequency-domain separation, the system supports concurrent recognition of finger and stylus inputs within a single acquisition path, avoiding extra sensing cycles. The proposed LLC architecture preserves display luminance and aperture ratio while reducing cost and complexity, making it highly suitable for next-generation large-area OLED displays in educational, industrial, and automotive applications. © 1991-2012 IEEE.

키워드