Hyeok Jin Lee

Single-mode transflective liquid crystal display tailored for wide-band single gamma curve

This paper proposes a single cell gap transflective patterned vertically aligned liquid crystal mode with the same gamma curve for both reflective and transmissive operation. The gamma curve of the proposed transflective mode is obtained by tuning the chevron-type electrode structure in the reflective part to diminish the difference of the optical polarization path on the Poincare sphere, between the transmissive and reflective parts. Wide-band characteristics can be obtained by using in-cell lambda/4 retardation films with different optic axes in the transmissive and reflective parts.

Study on the light leakage mechanism of a blue phase liquid crystal cell with oblique interfaces

The mechanism of light leakage in the dark state of a blue phase liquid crystal display cell which has protruded electrodes was investigated. We have performed a hybrid numerical simulation by combining the geometrical optics with the extended Jones matrix method. The light leakage in the cell was caused by changes in the polarization state which has been explained by the asymmetric amplitude change of transverse electric and transverse magnetic fields at the oblique interface and the change in an effective angle between crossed polarizers by the light path refraction. Based on our analysis, light leakage can be suppressed by the matching of the refractive indices of adjacent materials to the interface of the protruded electrodes whose surfaces are not parallel to the substrate.

Temperature-Dependent Behaviours of Blue Phase I Observed for a Bent-Core Molecular System

Temperature-dependent behaviours, such as the Bragg reflection band and the EO performance, of the liquid-crystalline BP I observed for a nematogenic achiral bent-core molecule doped with a small amount of chiral additive was investigated. Our experimental results indicate that the physical behaviours of our sample were highly sensitive to temperature changes.

P-190: Wide-Band Transflective Liquid Crystal Display in a Patterned Vertically Aligned Mode with a Single Cell Gap

We propose optical configuration for wide-band characteristics in transflective liquid crystal display with a single cell gap at patterned vertically aligned mode. Difference of the optical path between transmissive and reflective parts is compensated by designing the electrode structure and adopting two retardation films which show wide band characteristics calculated from mirror imaging method.

Four-domain twisted nematic structure with enhanced liquid crystal alignment stability and fast response time

In this paper, we propose a stable four-domain twisted nematic structure with wide viewing angle characteristics and a fast response time. A stable structure was realized by introducing a high pre-tilt angle approach incorporating stacked planar and vertical alignment layers. The response time and thermal stability of the proposed device were dramatically improved by the addition of UV-curable reactive mesogen (RM) mixed with a vertical alignment material. Polymerized RMs along the liquid crystal (LC) director increased the polar anchoring energy and reduced back-flow phenomena. A wide viewing angle and fast response time characteristics were achieved over all gray levels.

Uniformity measurement of electron emission from carbon using electron beam resist

In this report, the direct measurement of the emission sites from practically working CNT emitters is presented using an electron resist (ER) coated anode substrate. It allows checking a detailed emission site distribution from randomly oriented CNT emitters without light spreading effect when using a phosphor screen. The estimation of emission uniformity is best performed by general image comparison containing many dots of the developed ER surface images.

Reduction of light leakage in protruded electrode by refractive index matching between protrusion and blue phase liquid crystal

We have studied the light leakage mechanism of the protruded electrode used for blue phase LCD. According to our study, the light leakage can be reduced by identical refractive indices of the protrusion and BPLC.

Structural deformation of single-wall carbon nanotubes during field emission process

Stable electron emission from CNT emitters at required current densities is necessary to apply to the commercial devices. Generally, the current degradation during field emission has been understood as evaporation of emitter or breaking apart of tip end under intensive electrical field. In this report, we suggest one more possible mechanism that the emission current degradation may occur by increased resistance of emitters through structural deformation under field emission. The effect of current density and time on the structure of SWNT emitters was studied with TEM, low current density (100 /spl mu/A/cm/sup 2/ for 1 h) application gave no detectable structural deformation with comparison to pristine SWNTs. However, the bundles of SWNTs were deformed to amorphous structure starting at tip ends or defect sites when a high current density (500 /spl mu/m/cm/sup 2/ for more than 1h) was applied. It supports that the deformation of SWNT results from heat during emission at emitters. It is understood that the heat during emission could give a rise to destruct the crystalline structure and reconstruct the carbon bonding in SWNTs bundles. We also understood that the increase of the turn-on voltage is attributed to the increase of electrical resistance of emitters raising from structural deformation during emission process.