Byung Chul Ahn

Viewing-angle controllable liquid crystal display using a fringe- and vertical-field driven hybrid aligned nematic liquid crystal

Viewing-angle controllable liquid crystal display (LCD) without using an additional panel or pixel division is proposed. In the device, hybrid aligned nematic liquid crystal using a liquid crystal with negative dielectric anisotropy is used. The device shows narrow viewing angle when it is driven only by fringe-electric field, however, it exhibits wide viewing angle if driven by vertical- as well as fringe-electric field. With the approach, the viewing angle of the LCD can be controlled from 120° to 20° in horizontal direction.

Performance improvement of amorphous silicon thin‐film transistors with SiO2 gate insulator by N2 plasma treatment

We studied the performance improvement of hydrogenated amorphous silicon (a‐Si:H) thin‐film transistor (TFT) using atmospheric pressure chemical vapor deposition (APCVD) SiO2 as a gate insulator. The threshold voltage and the subthreshold swing decrease remarkably by N2 plasma treatment on the APCVD SiO2 surface even though the field effect mobility changes little, indicating that the interface state density around the Fermi level is reduced significantly by N2 plasma treatment. We obtained the high performance a‐Si:H TFT with the field effect mobility of 1.25 cm2/V s, the threshold voltage of 3.5 V and the subthreshold swing of 0.45 V/dec.

18.2: 20.7inch QSXGA White and Black Medical Display Employing White OLED

We report 1stacked and 2stacked white OLED WOLED device with higher color temperature and 20.7inch white and black medical display. Fabricating WOLED with two emitting layers of fluorescent blue dopant and phosphorescent dopants, we achieved luminous efficiency of 15.4 cd/A and CIE coordinates of 0.275, 0.303 for 1stacked WOLED, and luminous efficiency of 54.1 cd/A and CLE coordinates of 0.327 0.321 for 2stacked WOLED at 10 mA/cm 2. The 20.7inch WOLED proto type shows higher ambient contrast ratio, lower power consumption compared to conventional LCD, which is critical feature for supporting accurate medical diagnosis.