Yuka Utsumi

Depolarized light scattering from liquid crystals as a factor for black level light leakage in liquid-crystal displays

Depolarized light scattering due to thermally excited orientational fluctuations of liquid-crystal directors was investigated in the context of the black level light leakage in liquid-crystal displays. Particular attention was given on the comparison between homogeneous and homeotropic liquid-crystal alignments which are both used as black states of liquid-crystal displays. The homeotropic alignment was found to have lower light-scattering intensity and less light leakage than the homogeneous alignment in the small scattering angle regions. The dependency of the scattering intensity on the cell gap and the extrapolation length was also evaluated. The cell gap and the extrapolation length were found to have a large influence.

Analysis of Light Leakage Caused by Color Filter between Crossed Polarizers

The light leakage caused by color filters between crossed polarizers was analyzed in terms of light scattering due to pigments inside color filter layers. Localized pigment particles in the color filter layers used in devices were observed with a scanning transmission electron microscope. The direct observation of the scattering light revealed that the pigment particles cause Rayleigh scattering. We found that the depolarized light leakage by color filters between crossed polarizers is governed by light scattering.

28.1: Optically Compensated IPS‐LCD for TV Applications

A light leakage and a color shift along diagonal viewing angle directions in the black representation were dramatically reduced for IPS-LCDs using a newly developed biaxial film and pixel structure. We have studied the optical compensation method suitable for a newly developed panel with the higher white transmission (IPS-Pro). This new film technology has been successfully applied for the 32-inch IPS-LCD with performances of significantly wide viewing angle performance in all images and contrast ratio over 900:1.

11.2: Improved Contrast Ratio in IPS-Pro LCD TV by Using Quantitative Analysis of Depolarized Light Leakage from Component Materials

The degree of imperfection was defined as the independent intrinsic index of the degree of degraded contrast ratio for each component. The scattering index of liquid crystal layer gives an effective guideline for reducing light leakage intensity. By using this guideline, we have made an IPS-Pro LCD with a uniform contrast ratio of 1500:1 within ±16.5° of polar angle.

Light Leakage Behaviors of Homogenously Aligned Liquid Crystal Layers Placed between Crossed Polarizers

We investigated the light leakage behaviors homogeneously aligned liquid crystal layers placed between crossed polarizers using a backlight unit with diffused light to reduce the transmittance in the black state in in-plane liquid crystal displays. The light leakage intensity was clearly proportional to a specific variable (Scell) consisting of the ordinary refractive index no, the extraordinary refractive index ne, their difference Δn, the elastic constant K, and the thickness of the liquid crystal layers d. A high elastic constant and a low Δn can result in a low light leakage intensity.

Correlation of Light Scattering of Homogenous Alignment Liquid Crystal Layers with Material Properties of Liquid Crystals

We investigated light scattering properties of conventional liquid crystal layers by 651.8 nm laser illumination. The intensity of light scattering strongly depended on the incidence angle of illumination. Although the total light intensity changed with the ordinary refractive index no, the extraordinary refractive index ne, their difference Δn, the elastic constant K, and the thickness of the liquid crystal layers d, it was simply proportional to a specific variable S consisting of those values, as S = Δn2( ne + no )2d/K.

An IPS-LCD with a high contrast ratio of over 80:1 at all viewing angles

Abstract— A 32-in. IPS-LCD with a significantly wide-viewing-angle performance has been developed using a new optical compensation method. It provides a contrast ratio of over 80:1 at all viewing angles, which enhances its color saturation at oblique angles. According to our study, it is important to shorten the path of the optical compensation in the Poincare sphere. We have found an effective method using two retardation films, one with an Nz value larger than 0.5 and one with a value smaller than 0.5.

Wide-viewing angle in-plane switching liquid crystal displays for television applications using optical compensation technology

Viewing angle performance in in-plane switching liquid crystal displays (IPS-LCDs) has been greatly improved, using two technologies. One is optical compensation technology using a biax- ial film. The other is a newly developed IPS-Pro cell structure with higher transmission efficiency. These technologies are successfully introduced into the fabrication of 32-in. IPS-LCDs with a minimum contrast ratio over three times that of conventional IPS-LCDs and with color saturation (area ratio to NTSC at CIE1931 xy chromaticity coordinates) of more than 70% at almost all viewing angles.

Quantitative Analysis Method for Measuring Light Leakage Intensity of Three Primary Color Filters Placed between Crossed Polarizers

We investigated the light leakage properties of three-primary-color filters placed between crossed polarizers. Although light leakage is caused by light scattering due to pigment cohesion in the filter layers of a color filter, the detectability of this intensity is strongly related to the spectral properties of polarizers. We have developed a quantitative analysis method for measuring light leakage intensity using the degree of imperfection, derived from the depolarization index. The degree of imperfection is an intrinsic property of the color of the filters.

21.2: IPS-LCD with High Contrast Ratio Over 80:1 at All Viewing Angles

A 32-inch IPS-LCD with a significantly wide viewing angle performance has been developed using a new optical compensation method. It provides a contrast ratio over 80: 1 at all viewing angles. According to our study, it is important to shorten the path for the optical compensation in the Poincare sphere. We have found an effective method using two retardation films, one with an Nz value larger than 0.5 and one with a value smaller than 0.5.