Jung Yeal Lee

Ultra‐FFS TFT‐LCD with super image quality, fast response time, and strong pressure‐resistant characteristics

Fringe-field-switching (FFS) devices using liquid-crystal (LC) with a negative dielectric anisotropy exhibit high transmittance and wide viewing angle simultaneously. Recently, we have developed an Ultra-FFS thin-film-transistor (TFT) LCD using LC with a positive dielectric anisotropy that exhibits high transmittance, is color-shift free, has a high-contrast ratio in a wide range, experiences no crosstalk and has a fast response time of 25 msec. In this paper, the device concept is discussed, and, in addition, the pressure-resistant characteristics of the devices compared with that of the twisted-nematic (TN) LCD is discussed.

An overview of product issues in wide-viewing TFT-LCDs

Several TFT-LCD devices exhibiting high image quality have been developed and commercialized, overcoming the narrow viewing-angle characteristics of conventional twisted-nematic (TN) devices. Nevertheless, no single device dominates large-sized TFT-LCDs. In this paper, the product issues of existing LC devices related to manufacturing process and performance are discussed.

A novel portable LCD using a new AFFS technology for outdoor readability

— The advanced fringe-field switching (AFFS) mode is suitable for portable display devices. It has high transmittance, wide viewing angle, low power consumption, high contrast ratio, and a ripple-free property resistant to pressure. Recently, a 10.4-in. XGA prototype which demonstrates excellent transmittance and very good outdoor readability has been developed. To obtain these properties, a new pixel structure has been designed which has a large aperture and a metal embossing pattern for inner reflectance without the use of a black matrix on the embossing metal pattern. Precise control of the liquid-crystal electrodynamics and surface reflectance using an AR polarizer was achieved. This new panel shows distinguished characteristics for outdoor readability with the backlight on under a bright outside light source.

3P‐113: Pixel Structure of the Ultra‐FFS TFT‐LCD for Strong Pressure‐Resistant Characteristic

We have developed a pixel structure of the Ultra-fringe-field switching (FFS) TFT-LCD using the LCs with positive dielectric anisotropy for superior pressure-resistant characteristic. We have improved the pressure-resistant characteristic of the “Ultra-FFS” device by changing ‘⁁’ shape of pixel electrode into ‘<’ shape in one pixel. This indicates that its excellent electro-optical characteristics remained unchanged under external pressure and thus the device can be applied to position- and pressure- sensitive touch panel display.

P‐146: Image‐Sticking characteristic at the Fringe‐Field Switching (FFS) mode with Gate‐Shielding Structure

We have investigated image-sticking characteristic at the FFS mode with gate-shielding structure that can eliminate the noise field which is the source of residual DC voltage between pixel electrode and gate bus line. The FFS mode with new Pixel Common Inversion (PCI) structure which has gate-shielding structure shows good image sticking property compared to the conventional structure and this new structure has many advantages for image quality at wide size LCD-TVs and high end monitor display.

28.2: Invited Paper: SLS Technology for High Performance Poly‐Si TFTs and Its Application to Advanced LCD and SOG

SLS crystallization and CMOS LTPS process have been developed for high performance and uniform characteristics. By strictly optimizing SLS optics in conventional 2 shot SLS process, threshold voltage variation of 720 pixel TFTs in 2.2-inch QVGA panel (240×RGB) was remarkably decreased from 1.89 V to 0.56 V of 3sigma value. Mobility of the channel doped NTFT and PTFT for circuits were 146 and 38 cm2/Vs, respectively. Functional unit circuits for SOG were also fabricated and properly operated.

P-94: Valley-Aligned VA Mode LCD

We have developed a new vertical alignment mode that uses a valley or hole as a source of moving liquid crystal when the voltage is applied. As the valley or hole can be made by the same process steps as the TN color filter, this new VA mode can be manufactured by the simplest process steps than any other TFT-LCD modes. We also have found that liquid crystal aligns parallel to the surface of the valley or hole when the voltage is applied. Finally, the electro-optic characteristics of this mode are studied with various parameters such as the birefringence and pitch of liquid crystal.