Jeoung-Yeon Hwang

Liquid Crystal Alignment Effects using a Sio Thin Film

ABSTRACT We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a SiO thin film. The homogenous alignment was obtained by using ion beam (IB) exposure on the SiO thin film, when positive type NLC (Δϵ > 0) was injected into the LC cell. However, the homeotropic alignment was obtained using ion beam exposure on the SiO thin film, when negative type NLC (Δϵ > 0) was injected into the LC cell. The LC aligning capability on the SiO thin film depends on the dielectric anisotropy type of LC.

Investigation of the alignment phenomena using a-C:H thin films for liquid crystal alignment materials

A high pretilt angle is generated by hydrogenated amorphous carbon (a-C:H) thin films treated with an ion beam method. a-C:H thin films are deposited by remote plasma enhanced chemical vapor deposition and are modified by an Ar ion beam at an incidence angle of 45° using an Kaufman ion gun. Ion beam irradiation results in the decrease of the thickness of a-C:H thin films and the increase of the sp2 fraction. The optical transmittance of the ion beam irradiated a-C:H is more affected by thickness than sp2 fraction. An excessive ion beam irradiation, 5 min Ar ion beam, results in the increase of the surface roughness of the a-C:H thin films and the pretilt angle has very low value. The pretilt angle is controlled by the thickness, sp2 fraction and the surface roughness.

Postgrowth irradiation of hydrogenated amorphous carbon thin films by low-energy ion beam

Liquid crystal (LC) alignment property was investigated on hydrogenated amorphous carbon (a-C:H) thin films. a-C:H thin films were deposited by a remote plasma-enhanced chemical vapor deposition (RPECVD) method with C2H2 and He gases. The surface property of a-C:H thin films was controlled by low-energy Ar ion beams. Ion beam irradiation results in the decrease in optical band gap and transmittance, and the increase in the ID/IG ratio of a-C:H thin films. LC alignment was generated by ion beam irradiation on the surface of a-C:H thin films. LC alignment property was affected by ion-beam-induced anisotropic sp2 structures on the surface of a-C:H thin films.

Investigation of electro-optical characteristics of photo-aligned TN-LCDs on PCEMA surfaces

In this work, a novel photo-alignment material, poly(cinnamolyethyl methacrylate) (PCEMA), was synthesized by photo-dimerization. We investigated the electro-optical characteristics of twisted nematic (TN)-liquid crystal displays (LCDs) photo-aligned with linearly polarized UV light irradiation at normal direction on the PCEMA surfaces. Excellent voltagetransmittance characteristics were observed. The threshold voltage of the photo-aligned TN-LCD decreases with increasing UV irradiation time. Additionally, response times are almost the same as for a rubbing-aligned TN-LCD.

Film Compensation of the Optically Compensated Splay Liquid Crystal Device

ABSTRACT Optically compensated splay (OCS) mode, where the LCs are almost homeotropically aligned with a rubbed parallel at both surfaces, and where a mid-director orients itself parallel to the substrate, is known to show a wide-viewing-angle, due to self-compensation effect. Since a cell retardation value exists in the presence of an electric field, film compensation is necessary to realize a wide-viewing-angle and high contrast ratio. In this paper, we show various electro-optic characteristics, depending on cell configurations with optical compensation films.

Liquid Crystal Aligning Capabilities and EO Characteristics of the TN-LCD with Ion-Beam Exposure on a New Diamond-like Carbon Thin Film Layer

Liquid crystal (LC) alignment capabilities with ion beam (IB) exposure on a diamond like carbon (DLC) layer were studied. A high pretilt angle of 3.5° with IB exposure on the DLC layer can be obtained. Superior LC alignment with the IB alignment method on the DLC layer was observed until an annealing temperature of 200°C. Also, excellent voltage-transmittance (V-T) curve of the ion beam aligned twisted nematic (TN) cell with oblique ion beam exposure on the DLC surface for 1 min was observed. The fast response time of the ion beam aligned TN cell with oblique ion beam exposure on the DLC surface for 1 min can be achieved. The residual DC property of the ion beam aligned TN cell with ion beam exposure on the DLC layer for 1 min is almost same as that of the rubbing aligned TN cell on a rubbed polyimide (PI) surface.

Washing effects on the anchoring energy and surface order parameter on rubbed polymer surfaces containing the trifluoromethyl moiety

The washing effects on liquid crystal (LC) alignment capability in a NLC, 4-n-pentyl-4′-cyanobiphenyl (5CB), on a rubbed polyimide (PI) surface containing the trifluoromethyl moiety were studied. The extrapolation length d e of 5CB on the rubbed PI surface decreases with the rubbing strength RS. Also, the large extrapolation length d e of 5CB for washing with IPA was measured at RS=114u2009mm. The polar anchoring energy of 5CB on the rubbed PI surface was decreased by the washing process; it increased with the rubbing strength RS on the PI surface. The surface order parameter S S of 5CB for all the washing processes is smaller than for the non-washing process. Consequently, the polar anchoring energy and surface order parameter S s in 5CB are largely attributed to washing effects.

Residual DC characteristics in the IPS-LCD by capacitance–voltage hysteresis method on a polymer layer ☆

Abstract In this research, the image-sticking property in the in-plane switching (IPS)-liquid crystal display (LCD) with residual DC voltage on a rubbed polyimide (PI) layer was studied. Voltage holding ratio (VHR) and residual DC voltage by capacitance–voltage hysteresis method in the IPS-LCDs was measured. It was found that the VHR increased with increasing specific resistivity of fluorine LCs. The residual DC voltage decreased with increasing concentration of cyano LCs and decreasing with increasing specific resistivity of fluorine LCs. Consequently, the residual DC voltage can be decreased by high polarity of cyano LC.

Electro-Optical Characteristics of Vertical Alignment Cell by Ion-Beam Exposure on the SiC Thin Film Layer

We studied the electro-optical (EO) characteristics and nematic liquid crystal (NLC) aligning capabilities with the new alignment material of the Silicon Carbide (SiC) thin film using two kinds of ion beam (IB) gun. The SiC thin film exhibits good chemical and thermal stability. A vertical alignment of nematic liquid crystal by atomic beam exposure on the SiC thin film surface was achieved via all IB exposure system. The generated NLC tilt angle is about 87° using Kaufman type ion gun. The about 88° of stable tilt angle was achieved with incident angle of 10° using duoPIGatron type ion gun. An excellent voltage-transmittance (V-T) and response time curve of the IB-aligned VA-LCD using duoPIGatron type ion gun was observed. The V-T hysteresis characteristics of IB-aligned VA-LCD are almost the same as that of the rubbing-aligned VA-LCD. Consequently, the vertical alignment effect of liquid crystal and the good EO characteristics by the atomic beam alignment method on the SiC thin film layer can be achieved.

The Alignment Effect of Nematic Liquid Crystal on NDLC Thin Films Surface

ABSTRACT We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of Nitrogen doped diamond-like carbon (NDLC) thin film. The NDLC thin film exhibits high electrical resistivity and thermal conductivity that are similar to the properties shown by diamond-like carbon (DLC) thin films. The diamond-like properties and nondiamond-like bonding make NDLC an attractive candidate for applications. A high pretilt angle of about 9.9° by ion beam (IB) exposure on the NDLC thin film surface was measured. A good LC alignment is achieved by the IB alignment method on the NDLC thin film surface at annealing temperature of 200°C. The alignment defect of the NLC was observed above annealing temperature of 250°C. Consequently, the high pretilt angle and the good LC alignment by the IB alignment method on the NDLC thin film surface can be achieved.