Hak-Rin Kim

Transflective Liquid Crystal Display with Single Cell Gap in Patterned Vertically Aligned Mode

We propose a novel transflective liquid crystal display (LCD) configuration with a single cell gap in a patterned vertically aligned (PVA) mode. In this work, the optical path difference in a single cell gap is simply compensated by introducing pixel electrode structures between transmissive and reflective parts in a PVA mode. In addition, our transflective LCD was constructed with the same optical configuration such as that of polarizers and retardation films over the whole panel area. The simulated and measured electro-optic characteristics in the transmissive and reflective parts of our novel transflective LCD have shown good agreement with each other over the whole gray scale range.

Optical detection of deoxyribonucleic acid hybridization using an anchoring transition of liquid crystal alignment

We demonstrate an optical method for detecting specific binding events in an oligo deoxyribonucleic acid (DNA) chip using an anchoring transition of a nematic liquid crystal (NLC) as a result of DNA hybridization. A homeotropic orientation of the NLC supported by oligoDNA changes to a random planar orientation after hybridization. Such DNA hybridization and subsequent NLC reorientation are easily observable with a simple detection system via long-range orientational order and large optical anisotropy of the NLC.

Liquid crystal alignment with a molecular template of imprinted polymer layer during phase separation

We developed a liquid crystal (LC) alignment method using a molecular template of an imprinted polymer layer during polymerization-induced phase separation. Our results showed that the nematic ordering of LC is transferred to the polymer chain ordering during an anisotropic phase separation, which produces an anisotropic azimuthal surface anchoring. Using in-plane field treatment during phase separation, a twisted nematic cell is demonstrated.

P-120: Tight Bonding of Two Plastic Substrates for Flexible LCDs

a novel technique to maintain a constant cell gap of the flexible LCD under various external distortions. The two flexible substrates were assembled tightly by the UV curable polymer placed on top of rigid pillar spacer array. In this technique, we designed the columnar micro-structure to lead the self-collected construct of adhesive polymer which promotes the good adhesion and high mechanical stability against the external deformations.

Mechanical Stability of Pixel-Isolated Liquid Crystal Mode for Flexible Display Application

We have fabricated the Pixel-Isolated Liquid Crystal (PILC) mode using micro-supporting structures and anisotropic phase separation method. Since the cell gap is sustained by polymer walls and the phase separated polymer layer, this novel structure shows good electro-optic properties having stability against external mechanical distortion. The mechanical stability of this configuration against external forces like pressure and bending is confirmed to be useful for diverse flexible display applications.

Design and Fabrication of High-Performance Liquid Crystal Gratings

We present basic principles of designing and fabricating high-performance liquid crystal (LC) gratings with binary alignment structures which produce a variety of the diffraction properties. The periodic binary structure in the LC layer was fabricated through a selective irradiation of the UV light using the single-masking process. An alternating homeotropic and hybrid alignment configuration produces the input polarization-dependent diffraction suitable for the polarization-separating devices while an oppositely twisted binary alignment configuration gives the input polarization-insensitive diffraction. It is found that a dye-doped bidirectional alignment configuration can be used for obtaining optically controllable polarization properties.

56.2: Invited Paper: Pixel-Isolated Liquid Crystal Mode for Plastic Liquid Crystal Displays

Abstract We proposed a pixel-isolated liquid crystal (PILC) mode for enhancing mechanical stability of flexible display applications. Since the LC molecules in this mode are isolated in pixels by patterned or phase-separated microstructures, the LC alignment is stable against external pressure. Moreover, the cell gap of our structure is uniformly preserved against bending deformation of the plastic substrates since two substrates are tightly attached each other by the solidified polymer layer produced by photo-induced anisotropic phase separation. For flexible display applications, we have tested the mechanical stability of electro-optic properties in PILC structures with plastic substrates. 1. Introduction In recent years, roll-up displays have drawn considerable attention for next-generation information displays because of their excellent portability such as light weight, thin packaging, and flexibility. Among several available technologies, it is expected that a liquid crystal display (LCD) using plastic film substrates is the most promising device because of its superior visibility with low power consumption over other displays such as organic light-emitting device or electrophoretic displays. However, there are still critical problems regarding the fabrication of commercially available plastic LCDs with current technologies based on the glass substrates. One of those problems is the instability of LC structures due to hydrodynamic properties of LCs at bending and another is the separation of two plastic substrates due to the flexibility of film substrates. Such problems do not exist in conventional glass-substrate-based LCDs since glass substrates can sustain a stable LC alignment condition against external bending or pressure. To solve these problems, several types of polymer wall and/or network as supporting structures have been proposed and demonstrated [1]-[7]. These structures were fabricated using an anisotropic phase separation method from polymer and LC composite systems by applying a patterned electric field or spatially modulated UV intensity. However, these methods require high electric field to initiate the anisotropic phase separation or remain residual polymers in unexposed regions that reduce optical properties and increase the operating voltage of the devices.

Wide Viewing Transflective Liquid Crystal Display with a Patterned Electrode

We studied various dynamic characteristics of the transflective liquid crystal display (LCD) having a single cell gap and a single liquid crystal (LC) mode simultaneously. In this configuration, intrinsic optical path difference between transmissive and reflective part was compensated by modifying LCs optic axis with different patterned electrode configurations and voltage application. The angle of electrode was designed to induce appropriate optical retardations in each part and the resultant electro-optic characteristics were matched identically. Also, we minimized the mismatches in grey level by optimizing the angle of reflective part through the simulation. Moreover, the wide viewing characteristics of transflective LCD was verified from the 8-domain LC structure of our sample while only 4-domains can be achieved in the conventional case. By using this technique, we can easily achieve transflective LCD of good performances under same optical setup such as polarizers and retardation films over the whole panel area without complicated fabrication.

P‐162: Transflective LCD in a Patterned Vertically Aligned Mode with a Single Cell Gap

We proposed a transflective liquid crystal display (LCD) with a single cell gap in a patterned vertically aligned mode by adopting different geometry of electrode in the transmissive and reflective parts. Since the difference of the electrode structure induces the difference of the optical retardation in each part, we can easily fabricate transflective LCDs with good electro-optic characteristics even in the same cell gap.

Pixel‐isolated liquid‐crystal mode by using a patterned anisotropic phase separation for flexible LCDs

Abstract— A pixel-isolated liquid-crystal (PILC) mode for enhancing the mechanical stability of flexible-display applications is proposed. Because liquid-crystal (LC) molecules in this mode are isolated in each pixel by patterned or phase-separated microstructures, and the two substrates are tightly attached to each other by a solidified polymer layer, the LC alignment is stable against external pressure, and the cell gap of our structure is uniformly preserved against bending deformation of the plastic substrates. The mechanical stability of the PILC structure having plastic substrates was tested for its electro-optic properties.