Young-Chol Yang

9.2: Implementation of RGBW Color System in TFT‐LCDs

Last year, we introduced a TFT-LCD with RGBW color system. The primary advantage of the RGBW system is that its optical efficiency is at least 50% higher than the RGB system. However, it is not a simple task to incorporate the new color system into the existing infrastructure of the RGB system: the driving circuitry, fabrication of color filter, and color conversion. In this report, the practical hurdles are discussed and the solutions are presented.

31.1: Development of Six Primary-Color LCD

We developed the multiple primary color LCDs where the pixels were composed of red(R), green(G), blue(B), cyan(C), magenta(M) and yellow(Y) subpixels. The color gamut was extended 99% of NTSC standard, while the brightness was also increased by 15%, compared to the conventional RGB three primary color LCDs. To get a natural color image we designed the color coordinates and luminance levels of each six subpixles, and developed color algorithm to convert the RGB signal to RGBCMY signal.

Transflective Liquid Crystal Display with Single Cell Gap in Patterned Vertically Aligned Mode

We propose a novel transflective liquid crystal display (LCD) configuration with a single cell gap in a patterned vertically aligned (PVA) mode. In this work, the optical path difference in a single cell gap is simply compensated by introducing pixel electrode structures between transmissive and reflective parts in a PVA mode. In addition, our transflective LCD was constructed with the same optical configuration such as that of polarizers and retardation films over the whole panel area. The simulated and measured electro-optic characteristics in the transmissive and reflective parts of our novel transflective LCD have shown good agreement with each other over the whole gray scale range.

P‐164: Single Cell Gap Transflective Mode for Vertically Aligned Negative Nematic Liquid Crystals

Single cell gap transflective liquid crystal display mode with vertically aligned negative liquid crystal was developed. Reflectance curve as a function of voltage matched exactly with transmittance curve. Threshold voltage in reflectance curve was around 2.0V, as in transmittance curve, and the voltage for maximum reflectance was around 4.5V∼5.0V, which gave also the maximum transmittance. Reflective region was divided into two parts. First reflective part was driven by the voltage supplied by switching transistor directly, while the second reflective part was driven by the voltage lower than that of first part using the voltage-dividing capacitor connected to switching transistor in series. Normal 8 mask-count process was applied to fabrication of real panels. No special optical film or extra driving circuit was required.

60.3: Spatio-Temporal Edge Enhancement for Reducing Motion Blur

LCDs suffer from a loss of resolution when displaying moving images (motion blur). Solutions to this problem have included overdriving and reduction of temporal aperture by introducing blanks or by increasing the frame rate. These methods usually require additional hardware, thereby increasing cost. We propose a purely mathematical operation to reduce motion blur. In the proposed method, the degree of overdriving is not constant over the whole image. Rather, it depends on the spatial complexity surrounding a given area, wherein more overdriving is applied to areas of high spatial frequency. In this way, motion blur can be reduced without inducing artifacts which may otherwise result from excessive overdriving. The new method shows easily distinguishable improvement and the MPRT (Motion Picture Response Time) values are reduced by 5 ∼ 10%.

38.4L: Late‐News Paper: A New Vertical Alignment Mode for TFT‐LCDs

A simple and cost-effective vertical alignment mode, named Smart Viewing Angle(SVA) mode, for active-matrix (AM) LCDs was developed where all the domain dividers are fabricated only on the TFT substrate side. The crucial component is the director control electrode (DCE) under the openings of the pixel electrode. The DCE maintains higher voltage than that of the pixel electrode via additional TFTs, which distorts the electric field in such a way that stable domain division is accomplished. Compared to the conventional VA modes where the additional process is required, SVA mode can achieve the wide viewing angle without any additional processes.