Jong-In Baek

Fast In-Plane Switching of a Liquid Crystal Cell Triggered by a Vertical Electric Field

We propose a fast two-step switching method of a homogeneous-aligned liquid crystal (LC) cell, where a trigger pulse is applied to align LCs vertically for a moment before they are in-plane switched to show a bright state. Because LCs aligned vertically by a trigger pulse are in a transient state rather than the stable state, the turn-on becomes faster. The turn-off also becomes faster because the pulse forcibly aligns the LC vertically to show the dark state. Experimental results show that significant acceleration of the grey-to-grey response as well as on-off switching can be achieved by the proposed switching method.

Fast Switching of Vertical Alignment Liquid Crystal Cells with Liquid Crystalline Polymer Networks

This paper reports on the electro-optic characteristics of vertical alignment (VA) liquid crystal (LC) cells with liquid crystalline polymer networks. Optical bouncing, that occurs during the turn-on of VA cells, can be eliminated by introducing in-cell polymer networks. Furthermore, the turn-off also becomes much faster because of the anchoring effect caused by the anisotropy in the molecular shape of the liquid crystalline polymers. These response times have been found to vary for different LC/prepolymer mixtures. When the concentration of the liquid crystalline prepolymer in the initial LC/prepolymer mixture was 3, 5, or 10 wt %, the response times were measured to be 34, 56, and 87% faster than those of a VA cell with pure LC. These switching behaviors of VA cells with liquid crystalline polymer networks are demonstrated and compared with those using pure LC and with polymer networks made of isotropic prepolymers.

Dual-mode switching of a liquid crystal panel for viewing angle control

The authors propose a method to control the viewing angle of a liquid crystal (LC) panel using dual-mode switching. To realize both wide viewing angle (WVA) characteristics and narrow viewing angle (NVA) characteristics with a single LC panel, the authors use two different dark states. The LC layer can be aligned homogeneously parallel to the transmission axis of the bottom polarizer for WVA dark state operation, while it can be aligned vertically for NVA dark state operation. The authors demonstrated that viewing angle control can be achieved with a single panel without any loss of contrast at the front.

Initially π-twisted nematic liquid crystal cell stabilized by a fluorinated polymer wall

The authors propose an initially π-twisted nematic liquid crystal (NLC) cell which can be made by phase separation of LC molecules and fluorinated polymer material without using a chiral material. Excellent phase separation is achieved due to strong immiscibility of the fluorinated acrylates with LC molecules. The π-twist state of the LCs surrounded with the fluorinated polymer wall is almost permanently stabilized. The initially π-twisted NLC cell can be operated at a lower driving voltage compared to those of a conventional pi cell and chiral-doped cell. The switching time of the cell is as fast as the conventional pi cell.

Pixel-isolation walls of liquid crystal display formed by fluorinated UV-curable polymers

A pixel isolation wall of liquid crystal display is fabricated by utilizing the excellent phase separation between liquid crystal molecules and fluorinated UV-curable polymers. Due to the strong immiscibility of the fluorinated monomers, the segregation of the material occurs effectively to form a polymer wall during the UV exposure. Twisted nematic liquid crystal cells with fluorinated polymer wall are fabricated for the comparison with other devices made of ordinary polymer wall. The fluorinated polymer wall device exhibits enhancement of contrast due to the suppression of the light leakage through the polymer wall as well as reduced saturation voltage by anchoring enhancement.

Pretilt angle control and multidomain alignment of liquid crystals by using polyimide mixed with liquid crystalline prepolymer

We propose a method to control the pretilt angle of liquid crystals by employing a mixture of the vertical alignment polyimide and the liquid crystalline prepolymer (LCP). The pretilt angle between 10° and 90° can be controlled continuously by changing the mixing ratio of the LCP. Multidomains with different pretilt angles can be formed because the pretilt angle between 50° and 90° can be obtained by varying the UV exposure time region by region under a fixed mixing ratio. We confirmed experimentally that proposed alignment layers are thermally stable.

P-173: Fast Turn-Off Switching of a Liquid Crystal Cell by Optically Hidden Relaxation

A method for fast turn-off switching of a liquid crystal (LC) cell is proposed. LC in the bright state is twist-deformed by the in-plane field, whereas LC starts to relax in the turn-off process from the vertically aligned state, during which the director is in parallel to the rubbing direction so that the relaxation is optically hidden. A three-terminal (3T) structure is employed for both in-plane and vertical switching. The turn-off time of about 0.6 ms was obtained with no decrease in transmittance.

Viewing Angle Control of a Fringe-Field Switching Cell by Electrical Tilting of Liquid Crystal

The authors propose a method to control the viewing angle of a liquid crystal panel by electrically tilting the liquid crystal without incurring either an increase in cost from additional panels, or a decrease in transmittance by pixel division. Instead, an additional electrode is introduced to the top substrate of a fringe-field switching panel for the tilt control of the liquid crystal. We found that, without any loss of on-axis display performances, the viewing angle with a contrast ratio of over 10:1 can be switched between ±70 and ±10° along the azimuthal direction perpendicular to the rubbing angle by applying a small vertical bias voltage.

A new electrode structure for color‐shift reduction in PVA LCD

Abstract We introduce a new electrode structure for the patterned vertical alignment (PVA) mode, which has a lower color‐shift at large viewing angle than the one‐domain VA mode. By manipulating the period of electrode structure, we can make more multi‐domains and use the existing fabrication processes without having to use additional materials.

Viewing Angle Control of a Hybrid-Aligned Liquid Crystal Display

A method for viewing angle control of a hybrid-aligned liquid crystal (LC) cell is reported. The viewing angle of proposed structure can be controlled by using vertical switching, by which the tilt angle of LC is controlled, while the optical transmittance can be controlled by using horizontal switching, by which the optic axis (OA) of LC can be rotated. A 3-terminal electrode structure composed of the top common electrode, the bottom grid electrodes, and the bottom common electrode is employed for both the vertical switching and the horizontal one.