Jinyool Kim

Concept of a liquid-crystal polarization beamsplitter based on binary phase gratings

We propose a concept of fabricating a liquid-crystal (LC) polarization beamsplitter based on binary phase gratings. The binary grating phenomenon in the LC layer physically originates from two different interfacial interactions at periodically alternating domain boundaries. The periodic LC domains are produced by employing a single-step photoalignment technique which precisely controls the surface orientation of the LC molecules in an alternating homeotropic and hybrid aligned geometry. In this binary configuration, the polarization-separating phase modulation of an input beam is achieved in a wide range of the wavelengths under an applied voltage. The experimental data are consistent with our linearly graded binary model.

Polarization-invariant grating based on a photoaligned liquid crystal in an oppositely twisted binary configuration

We demonstrate a polarization-invariant liquid-crystal (LC) grating in an oppositely twisted and mutually orthogonal configuration. The polarization-invariant LC grating with high diffraction efficiency is fabricated using a single-masking process with two-step exposure of a linearly polarized ultraviolet light. It is found that the zeroth- and the first-order diffracted beams are linearly polarized and perpendicular to each other irrespective of the incident polarization for the phase retardation of m pi (m=integer).

Importance of the Functional Group Density of a Polymeric Gate Insulator for Organic Thin-Film-Transistors

We describe the importance of the functional group density of polymeric insulators (PI) for organic thin-film-transistors (OTFTs) in terms of the insulator processing temperature and the exposure of a linearly polarized ultraviolet (LPUV) light. The PI layers processed at lower temperatures than the boiling temperature (Tb) of the solvent have higher densities of functional groups than those processed above Tb. The carrier mobility in the pentacene OTFT processed below Tb increases at least by a factor of three with maintaining other electrical properties such as the threshold voltage and the current on/off ratio. Our results suggest that the preferential alignment of the pentacene molecules is not the main physical mechanism for the mobility enhancement. From the mobility anisotropy resulting from the polarization of the LPUV, the packing density of the pentacene molecules on the PI layer, dictated primarily by the density of functional groups, is found to play a critical role on the magnitude of the mobility.

Design of binary diffraction gratings of liquid crystals in a linearly graded phase model

We report on a linearly graded phase model for the design of binary diffraction gratings of liquid crystals (LCs) associated with the periodic interfacial effect. The binary nature of the LC grating is produced by use of periodic striped domains in an alternating homeotropic and hybrid geometry. In our graded phase model the diffraction patterns and the diffracted intensities of the LC binary grating is primarily governed by three length scales: the cell thickness and two distortion parameters scaled by the grating period at two domain boundaries. The experimental data agree well with theoretical predictions made in our linearly graded phase model as well as the elastic continuum theory.

Brightness-Enhanced Transflective Liquid Crystal Display Having Single-Cell Gap in Vertically Aligned Configuration

A brightness-enhanced transflective liquid crystal display having a single-cell gap was demonstrated in a vertically aligned (VA) configuration with a patterned retardation layer. The photopatterned retarder was made of a UV-polymerizable liquid crystal (LC) through a single patterning process. The homeotropic LC alignment in the transmissive region and the planar LC alignment in the reflective region were directly produced on the patterned retarder. High reflectance and fast response characteristics were achieved in a single VA transflective LCD with a patterned retardation layer.

P-100: A Transflective Liquid Crystal Display in a Multimode Configuration

We report on a transflective liquid crystal display (LCD) in a multimode configuration consisting of an electrically controllable birefringence mode and a hybrid aligned nematic mode. In this configuration, the multimode transflective LCD was obtained by a single-step exposure of ultraviolet light, blocked by a metal reflector in the reflective area as an amplitude photomask, producing an alternating homogeneous and homeotropic geometry with no additional fabrication processes and cell gap variations.

New Configuration of a Transflective Liquid Crystal Display Having a Single Cell Gap and a Single Liquid Crystal Mode

We report on a new tranflective liquid crystal display (LCD) mode having a single cell gap and a single LC mode. For this display mode, a low twisted nematic liquid crystal cell, having the twist angle of 60°, is used for both transmissive and reflective applications. The measured electro-optic characteristics of our transflective cell agree well with numerical simulation results. It is found that the transmittance and the reflectance become identical to each other in the high voltage regime. The new transflective configuration is useful for mobile LCD applications.

P-158: Single Driving Transflective Liquid Crystal Display in a Single Mode Configuration with an Inner-Patterned Retarder

We have developed a single driving transflective liquid crystal display having an inner-patterned retarder in a single LC mode configuration. The inner-patterned retarder was fabricated on a patterned photoalignment layer using a self-masking technique. The measured electro-optic curves in the transmissive and the reflective parts were found to share common features that allow for a single driving scheme.

A New Transflective Geometry of Low Twisted Nematic Liquid Crystal Display having a Single Cell Gap

Abstract We have developed a new type of transflective liquid crystal display (LCD) with a single cell gap and a single LC mode. In our transflective configuration, a single LC mode of a 60° twisted nematic LC was used for both transmissive and reflective applications. The measured electro‐optic characteristics of our transflective LC cell agree well with numerical simulation results. Moreover, the transmittance was found to show similar behavior to the reflectance.

Photorefractivity and Optical Transmittance of Hybrid Liquid Crystal Cell with Homeotropically Photoaligned Layer and Fullerene Initiation.

A hybrid photorefractive liquid crystal cell was prepared with poly(9-vinylcarbazole) as a photoconduction layer and with a photocrosslinkable polymer of the pendant cinnamoyl group as a vertical photoalignment layer. The hybrid structure could increase the diffraction efficiency and transmittance by eliminating light loss by undesirable scattering of the incident beam through the liquid crystal cell. The use of the photoalignment layer in the hybrid liquid crystal structure resulted in a gain coefficient over 900 cm-1, diffraction efficiency over 13%, and transmittance over 85%. These results indicate that the hybrid cell design provides high efficiency for many applications in real-time holography and data storage devices.