Eun Jeong

Viewing angle switching of vertical alignment liquid crystal displays by controlling birefringence of homogenously aligned liquid crystal layer

Viewing angle switching from a wide viewing angle to a narrow viewing angle has been studied. Conventional multidomain vertical alignment (VA) mode offers the advantages of a high contrast ratio (CR) not only in the front view but also in the wide viewing directions only if compensation films such as a negative C plate and a positive A plate are used. The positive A plate can be replaced by a homogeneous aligned (HA) liquid crystal layer, and the retardation of the HA layer at the off axis can be controlled by applying an electric field while keeping the retardation value at zero in the normal direction. Consequently, the viewing angle range of a VA device can be controlled from a wide viewing mode (over 170° in terms of CR=10) to a narrow viewing angle mode (approximately 60° in terms of CR=2) in the horizontal direction while keeping a high image quality at the normal direction.

Viewing angle switching of patterned vertical alignment liquid crystal display

Viewing angle control of a patterned vertical alignment (PVA) liquid crystal display using only one panel is investigated. In conventional PVA modes, a vertically aligned liquid crystal (LC) director tilts down in four directions making 45° with respect to crossed polarizers to exhibit a wide viewing angle. In the viewing angle control device, one pixel was divided into two sub-pixels such that the LC director in the main pixel is controlled to be tilted down in multiple directions making an angle with the polarizer, playing the role of main display with the wide viewing angle, while the LC director in the sub-pixel is controlled to be tilted down to the polarizer axis, playing the role of sub-pixel to the viewing angle control for the narrow viewing angle. Using sub-pixel control, light leakage or any type of information such as characters and image can be generated in oblique viewing directions without distorting the image quality in the normal direction, which will prevent others from peeping at the displayed image by overlapping the displayed image with the made image.

CONIFEROUS FOSSIL WOODS FROM THE JOGYERI FORMATION (UPPER TRIASSIC) OF THE NAMPO GROUP, KOREA

Ninety–four fossil woods were collected from the Upper Triassic Jogyeri Formation of the Nampo Group in the County of Cheongyang-gun, Chungcheongnam- do Province, Korea. Eight of the specimens were preserved well enough to identify them down to species or genus. All were coniferous woods. On the basis of their detailed anatomical features, four specimens were identified as Xenoxylon phyllocladoides Gothan and the other four as Agathoxylon sp. Therefore six taxa of fossil woods, Cedroxylon regulare Goppert, Xenoxylon phyllocladoides Gothan, X. latiporosum (Cramer) Gothan, X. japonicum Vogellehner, Phyllocladoxylon heizyoense Shimakura and Agathoxylon sp., have now been reported from the Early Mesozoic Daedong Supergroup in the Korean Peninsula.

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.

Comparison of Korean and Japanese Tertiary fossil wood floras with special references to the genusWataria

Among 64 fossil woods collected from the Upper Coal-bearing Formation of Janggi Group, Pohang, Korea, four specimens have been characterized by their distinct ring porosity and the presence of tile cells in rays. After detailed anatomical studies, we could identify them as two species ofWataria-W. miocenica andW. parvipora. GenusWataria, known as an extinct taxon of Sterculiaceae, has been found only in the Tertiary formations in Japan. Most of these sterculiaceous plants are thermophilic and reportedly never inhabited in the Korean Peninsula. The existence of fossil woods ofWataria in Korea supports the idea of a common flora established in both countries during the Tertiary. In Japan, fossil woods ofWataria have been found only during the early Miocene formations. Therefore, the age of the Upper Coal-bearing Formation can be said of as the early Miocene.

Some confierous fossil woods from the Cretaceous of Korea

Thirteen silicified fossil woods were collected from the Cretaceous deposits of Haenam Basin and islands of Gwanmae and Byeongpung, Jeollanam-do as well as from the Cretaceous Dadaepo Formation, Busan, Korea. Anatomical features of all of these specimens showed that they were coniferous woods. On the basis of the detailed anatomical features they were identified asDadoxylon byeongpungense sp. nov.,Cupressinoxylon uhangriense sp. nov.,Taxodioxylon cf.nihongii Nishida et H. Nishida,Taxodioxylon albertense (Penhallow) Shimakura, andMesembrioxylon sp. All of them, exceptMesembrioxylon, are described for the first time from the Korean Peninsula. It should be noted that no dicotyledonous wood has been found from this study. Generally the sampled horizons are considered as Upper Cretaceous with dinosaur footprint fossils. In Japan, the Upper Cretaceous sediments bear abundant dicotyledonous fossils. Therefore further studies should be needed to clarify the age of these horizons and the vegetation in the ancient world with dinosaur.

Viewing Angle Switching in Fringe-Field Switching Liquid Crystal Display

We propose a pixel structure of viewing angle switchable liquid crystal display (LCD) associated with fringe-field switching (FFS) mode using one panel. In the device, one pixel is composed of main- and sub-pixel, in which the former has a role of image expression using the FFS mode and the latter has a role of viewing angle switching using the electrically controllable birefringence (ECB) mode. Consequently, before applying voltage to the sub-pixel, the device shows wide viewing angle, however, when the proper voltage is applied to the sub pixel, the displayed image is blocked in an oblique viewing angle.

Switching of off-axis viewing quality in twisted nematic liquid crystal display by controlling phase retardation of additional liquid crystal layers

This study examined the viewing angle control of twisted nematic liquid crystal displays (TN-LCDs). Conventional TN mode has intrinsic characteristics, such as a narrow viewing angle along the vertical direction and a relatively wide viewing angle along the horizontal and diagonal directions. Our study shows that the viewing angle of the TN-LCD can be made wider and smaller than that of a normal TN cell by adding one or two homogeneously aligned liquid crystal layers between the TN cell and polarizers, and controlling their retardation with an applied voltage.

Optimal pixel design for low driving, single gamma curve and single cell‐gap transflective fringe‐field switching liquid crystal display

When a dielectric layer, in‐cell retarder (ICR) is formed between the electrode and LC layer to obtain a single‐gap transflective fringe‐field switching (FFS) display, the driving voltage is highly increased due to the thickness of the dielectric material. In particular, the driving voltage of the transmissive part becomes very high, and goes beyond the driver integrated circuit (IC) range for mobile application because the homogenously aligned liquid crystal director should rotate twice as far as that in the reflective part. The correlation between the driving voltage and electrode structures was investigated. It was found that the problem could be solved by optimisation of the common electrode structure such that the electrode structure changed from a plane to slit shape (in‐plane field is mainly used instead of fringe field), realising a high performance FFS transflective display.

P‐148: Viewing Angle Switching in Vertical Alignment Liquid Crystal Display by Optimizing Pixel Structure and Controlling LC Orientation

Viewing angle control of a vertical alignment (VA) liquid crystal display using only one panel has been investigated. In conventional VA modes, LC director tilts down in four directions making 45° with respect to crossed polarizers to give rise to wide viewing angle. By dividing pixel into two regions or RGBW structure and controlling the LC director to tilt down to the polarizer axes, the image quality in oblique directions can be controlled without distorting the image quality at normal direction. Also using light leakage in oblique directions, any type of information such as characters and image can be generated. This generates extra image over a main image in oblique viewing directions, that is, the original image is overlapped with made image when the voltage is controlled to the extra pixel for viewing angle control.