High-transmittance Multi-domain Vertical Alignment Liquid Crystal Device with Protrusion Structure

Song

Symp Digest of Tech Papers

et al. 2013

Self Cite

In this work we propose a liquid crystal mode in which vertically-aligned negative nematic liquid crystals are switched on by applying a fringe electric field. In the proposed mode, vertically-aligned negative liquid crystals can be switched on by the vertical as well as in-plane components of an applied fringe field so that high transmittance can be achieved. By fabricating a test cell, we experimentally obtained a transmittance of 33.7 %, which is 8.7 % higher than a homogeneously-aligned fringe field switching cell using positive liquid crystals. Author KeywordsLiquid crystals; high transmittance; fringe field switching; vertical alignment Objective and BackgroundThe performance of liquid crystal displays (LCDs) has been greatly improved and this has led to the wide usage of LCDs for applications such as smart phones, monitors, tablet PCs, TVs, etc. LCDs for these applications require high display performances, such as a high contrast ratio, wide viewing angle, fast response, and high transmittance. In particular, high transmittance is required because the aperture ratio can be reduced as the pixel size decreases for ultrahigh resolution [1,2].Several LC modes including in-plane switching (IPS) [3][4][5], fringe-field switching (FFS) [6][7][8], and vertical alignment (VA) [9,10] modes have been in competition with each other in the LCD market [11,12]. Among these modes, the IPS and FFS modes provide wide viewing angle. The rubbing process is used in these modes to align the LC molecules homogeneously. However, the LC molecules may not be perfectly aligned along the rubbing direction. Moreover, use of cotton in the rubbing process can cause defects in the alignment layer [13]. These may result in light leakage in the dark state.On the other hand, the rubbing process is not required in the VA mode. The VA mode has the merit of a superior dark state because the LCs are vertically-aligned thereby giving it a much higher contrast ratio than homogeneously aligned LCs. Various type of VA modes have been proposed to reduce the response time [14,15]. Although in-plane switching of vertically-aligned positive LCs can provide fast response, it suffers from low transmittance because only a small portion of LCs can be switched on by applying an in-plane electric field.In this paper we propose a liquid crystal mode in which vertically-aligned negative nematic liquid crystals are switched on by applying a fringe electric field. Vertically-aligned negative liquid crystals can be switched on by the vertical as well as in-plane components of the applied fringe field so that a high transmittance can be obtained. Mode configuration and operation principleThe equipotential lines in the cell structures for the IPS and FFS modes are shown in Fig.1. In an IPS cell, the pixel and common electrodes are placed alternately on the bottom substrate. The inplane component of the electric field is dominant between adjacent pixel electrodes, whereas the vertical component is dominant above the pixel \electrodes. In a FFS cell, in whic...

Section: Objective and Backgroundmentioning

confidence: 99%

mentioning

confidence: 99%

P.103: High Transmittance LC Mode Based on Fringe Field Switching of Vertically‐Aligned Negative LCs

Song

Symp Digest of Tech Papers

et al. 2013

Self Cite

“…To improve the viewing angles in LCDs, in-plane switching (IPS) and fringe-field switching (FFS) have been used to control the liquid-crystal (LC) molecular behavior in the plane [1,2]. Furthermore, multiple domains have been used to symmetrically arrange LC molecules to reduce the difference in phase retardation according to the direction [3,4].…”

Section: Introductionmentioning

confidence: 99%

Liquid Crystal Displays with Variable Viewing Angles Using Electric-Field-Driven Liquid Crystal Lenses as Diffusers

2020

We propose a novel method for appropriately controlling the luminance distribution of liquid crystal displays (LCDs) for different usage environments by using electric-field-driven liquid crystal (ELC) lenses. The LCD systems are composed of quasi-collimated backlights (QCBLs), LC panels, and ELC lenses that are used as diffusers. To achieve a wide viewing angle, light is diffused with the ELC lenses by controlling its retardation with the voltage applied to the electrodes. For private use, a narrow viewing angle is achieved by turning the ELC lenses off so that the collimated light from the QCBLs passes directly through the liquid-crystal layer of the ELC lens and travels without diffusion. To validate the proposed method, we simulated the luminance distributions of the wide-view and narrow-view modes by using a finite difference method (FDM) and Taguchi’s design of experiments method. The simulation results show that the light distribution of the wide-view mode was 84.3% similar to the ideal Lambertian distribution and was wider than that of IPS-LCDs with wide viewing angle characteristics. In addition, the light distribution of the narrow-view mode had a full width at half maximum of 7°. The luminance of the exiting light at viewing angles of 20° and above was calculated to be close to 0.

Journal of the Optical Society of Korea

“…Over decades, many efforts have been devoted to obtain wide viewing angle (WVA) LCDs and significant improvement has been achieved, especially for large-area panels, with the development of several WVA LC modes such as multi-domain vertical alignment (MVA) [1][2][3], patterned vertical alignment (PVA) [4,5], optically compensated bend (OCB) [6][7][8], and in-plane switching (IPS) LC modes [9][10][11][12]. Improvement on optical compensation films also helped in realizing WVA LCDs [13,14].…”

Section: Introductionmentioning

confidence: 99%

Continuous Viewing Angle Distribution Control of Liquid Crystal Displays Using Polarization-Dependent Prism Array Film Stacked on Directional Backlight Unit

Park

Joo

et al. 2016

We present a polarization-dependent prism array film for controlling the viewing angle distribution of liquid crystal (LC) display panels without loss of light efficiency. On a directional backlight unit, our polarization-dependent prism array film, made into a stacked bilayer with a well-aligned liquid crystalline reactive mesogen (RM) layer on the UV-imprinted prism structure, can continuously control the light refraction function of the prism array by electrically switching incident polarization states of a polarization-controlling layer prepared by a twisted nematic LC mode. The viewing angle control properties of the polarization-dependent prism array film are analyzed under different prism angle and refractive index conditions of the RM layer. A simple analytic model is also presented to describe the intermediate viewing angle distributions with continuously varying applied voltages and incident polarization states.