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HYBRID SWITCHING MODE LIQUID CRYSTAL DISPLAYS

IP.com Disclosure Number: IPCOM000013409D
Original Publication Date: 2000-Mar-01
Included in the Prior Art Database: 2003-Jun-18
Document File: 1 page(s) / 60K

Publishing Venue

IBM

Abstract

Thin-film transistor (TFT) driving liquid crystal display (LCD) using in-plane switching (IPS) mode was demonstrated by Ohta et al. IPS mode shows wide viewing angle characteristics, but it suffers from a low optical transmission. Therefore IPS mode LCDs are not likely to be suitable for notebook application. Even for the desk top or home TV application, higher optical transmission is still preferred. In this disclosure, hybrid switching mode (HSM) LCDs were proposed. They will have wide viewing angle characteristics as well as high optical trans- mission.

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HYBRID SWITCHING MODE LIQUID CRYSTAL DISPLAYS

    Thin-film transistor (TFT) driving liquid crystal display (LCD) using in-plane switching (IPS) mode was demonstrated by Ohta et al. IPS mode shows wide viewing angle characteristics, but it suffers from a low optical transmission. Therefore IPS mode LCDs are not likely to be suitable for notebook application. Even for the desk top or home TV application, higher optical transmission is still preferred. In this disclosure, hybrid switching mode (HSM) LCDs were proposed. They will have wide viewing angle characteristics as well as high optical trans- mission.

    Hybrid switching mode (HSM) LCD uses both twisted nematic (TN) mode and IPS mode. Two unit cell structures of HSM LCD are shown in Figs. 1 and 2. For simplicity, the array structure (TFT and bus lines) is shown. Both structures have top ITO. In Fig. 1, top ITO is a continuous layer and connected to a voltage Vcom. In Fig. 2, the top ITO is pat- terned to cover the top of each pixel but top ITO of each pixel is separated from the adjacent pixels. Electrically, the top ITO is not connected to any power supply. It is floating and its voltage is determined by the area ratio of two bottom electrodes, A1 and A2. If these two areas are equal, we have voltage of top ITO of each pixel equal to the arithmetic average of the voltages of the two bottom electrodes, e.i. (V1 + V2)/2. Bottom electrode 2 of Fig. 1 and two bottom electrodes of Fig. 2 are transparent electrode, such as ITO. The electrode 1 of Fig. 1 can be any suitable metal material. The LC alignment directions (shown for a left-handed twist structure) and the polarizer directions for each structure are also shown in both figures. The dashed lines represent those on the bottom sur...