This paper reports on the Liquid Crystalline Polymer Stabilized (LCPS) method that can control the alignment of LC molecules in the bulk region due to polymer network structure formed in the LC layer. By using the LCPS method, we can obtain a arbitrary tilted alignment on non-rubbed cell. Adopting the LCPS method in the amorphous TN-LCD, the reverse tilt disclinations in the a-TN are frozen perfectly. Owing to this effect, fluctuation of luminance that is caused when the indication is switched was restrained, and the legibility of the display was improved. We found that these effects were achieved without losing a homogeneous viewing angle characteristic which is feature of a-TN-LCD.

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In the multi-domain TN mode for a wide-viewing-angle LCD, the LC directors are arranged in the splayed TN. The stability of the splayed TN configuration was studied with experiments and simulations. It is shown by the transmittance measurement on conoscopic figure that the reversely-twisted TN is more stable in the high voltage range. The splayed TN stability proved to be evaluated by the balanced voltage, defined as voltage at which the two configurations coexist in an experiment or voltage at which LC bulk energy becomes equal for two configurations in a simulation. Narrow twist angle, short chiral pitch and low pretilt angles raise the balanced voltage, i.e., stabilize the splayed TN configuration.

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Recently, reflective type liquid crystal displays (LCDs) have been paid much attention, due to these nature of low-power consumption ard portability. We fabricate polarizer-free chiral nematic Guest Host displays without using a rubbing process (a-N^*-GHDs) to improve the display performances of conventional reflective type LCDs. We find that a-N^*-GHDs can be operated at low voltage with high contrast ratio without losing brightness and also have homogeneous and wide viewing angle characteristics. Furthermore, a-N^*-GHDs do not show any stripe domain texture and a hysteresis, which also promise usefulness of the a-N^*-GHDs in the grayscale operation.

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[in Japanese]

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A novel a-Si TFT structure having less photo-leakage-current has been developed without changing conventional fabricating process. In order to realize this TFT, the authors had investigated the photo-leakage-current paths in conventional TFTs, and also had estimated non-uniform irradiance distributions on the TFT in LCD by analytical calculations. It was concluded that reduction of irradiance at side-channel in the TFT can reduce the photo-leakage-current, so that it could be realized by elongation of gate electrode at the side-channel. This effect could be confirmed by a measurement of TFT characteristics in LCD.

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A time-domain methcd to evaluate Cgs-Vgs characteristics of an actual size a-Si TFT (W/L-30/11 μm) is suggested. Cgs consists of an overlapping capacitance between the gate and the source and two types of intrinsic MOS-capacitance. The contribution of Cgs in off-region of TFT has the considerable contribution to the feedthrough voltage. The Cgs-Vgs characteristics obtained by this method gives us the most rigid capacitance medel to apply to the circuit analysis of the pixel voltage, because of containing all parasitic effects, e. g., time and frequency dependence in the factual driving conditions.

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A low sheet-resistance of 80Ω/□ (ρ=4×10^<-4>Ω・cm) has been achieved for poly-Si thin film (50nm thick) using an ion doping method with excimer laser activation at room temperature. It was found that more than 0.2 at.% hydrogen remained in this film even after laser activation. And it seems that hydrogen atoms contribute to the formation of a low sheet-resistance poly-Si thin film. It was also found that uniformity of the sheet-resistance in the laser irradiation overlap region can be improved by substrate heating (〜300℃) during excimer laser activation. As an application of this method, a poly-Si TFT with a low resistive source-drain region and a laser recrystallized poly-Si film was fablicated by a low-temperature proess below 600℃, resulting in a high field effect mobility of 440cm^2/V・s.

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Using only one doping process, the LDD structures with good TFT characteristics have been successfully fabricated. In this process, non-mass-separated ion doping method which is a very effective technology for the large area doping is used. Because it has a broad depth profile of phosphorus concentration within the offset SiO_2 region and poly-Si region, the feature is very useful for controlling the TFT characteristics. The LDD TFTs show high ON/OFF ratio of more than 10^8 and no degradation of ON current.

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We propose a new structure of electrodes for flat panel displays embedded in the surface layer of a glass substrate. In order to realize this new structure, we used a selective deposition of SiO_2 by the S-LPD method. We have applied Liquid Phase deposition to embed the electrodes in a surface layer of the glass substrate, and we have developed a new glass substrate with a microscopically flat surface and the pattern of electrodes.

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A high aperture ratio a-Si TFT-LCD has been developed utilizing Aluminum alloys for the gate and source bus-lines. Al-Zr is employed for the gate bus-line and an Al-W/Mo stacked structure is used for the source bus-line. As a result, a 57% aperture ratio has been achieved on a 87 μm×261 μm pixel.

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A high aperture-ratio pixel structure and compensative driving method were investigated for low-power-consumption TFT-LCDs. To improve the aperture ratio of a TFT-LCD, we adopted a "shield-electrode structure" and "storage-capacitor on gate bus-line structure". This structure, however, presented display degradation problems related to level-shift in pixel voltage. The compensative driving method was adopted to solve these problems. By combining the structure with the compensative driving method, a high aperture ratio of 70% was achieved for a 9.5-inch TFT-LCD with good display characteristics.

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A 33-cm-Diagonal High-Resolution TFT-LCD with Fully Self-Aligned a-Si : H TFTs has been developed. With OFF current reduction technology of TFTs under illumination by reducing a-Si : H thickness, a high contrast ratio or 100 : 1 has been achieved. The Fully Self-Aligned a-Si : H TFTs show low and uniform gate-source electrode capacitive coupling by self-alignment technology. The TFT-LCD shows no seems between block shot exposures, even when gray images are displayed.

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Development competition of a-Si TFT technologies is becoming severe. Low-resistance Ta buslines for large and high-resolutional panel, n+type micro-crystal Si contact layer to downsize TFT and ion-doping technology to suppress increase of off current under illumination are described in this paper. Based on the technologies for high-performance, 21" diagonal large size TFT-LCD has been developed. This TFT-LCD is the largest in the world at the present time.

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