• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.11
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• pp.1014-1018
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• 2003

A photoalignment material of a PGMAcr, poly[3-(acryloyloxy)-2-hydroxypropyl methacrylate] using a photopolymerized the acrylate unit by photo-initiator and a PGMA4Ch, poly[3(4-chalconyloxy)-2-hydroxypropyl methacrylate] using a photodimerization by chalcone group were synthesized. Also, the liquid crystal (LC) aligning capabilities on the photopolymer layers were studied. A good LC alignment with UV exposure on the PGMAcr surface can be obtained. However, the LC alignment defects were observed on the PGMA4Ch surface. The LC aligning capabilities of the PGMAcr surface by photo-initiator were better than that of the PGMA4Ch surface by chalcone group as photosensitive moiety.

• Transactions on Electrical and Electronic Materials
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• v.5 no.1
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• pp.15-18
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• 2004

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a-C:H thin film by plasma enhanced chemical vapor deposition (PECVD) system for 30 sec under 30W rf power at a gas pressure of 1.4＊10$\^$-1/ torr. A high pretilt angle of about 5 by ion beam exposure on the a-C:H thin film surface was measured. A good LC alignment by the ion beam alignment method on the a-C:H thin film surface was observed at annealing temperature of 250$^{\circ}C$, and the alignment defect of NLC was observed above annealing temperature of 300$^{\circ}C$. Consequently, the high LC pretilt angle and the good thermal stability of LC alignment by the ion beam alignment method on the a-C:H thin film by PECVD method as working gas at 30W rf bias condition can be achieved.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.611-614
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• 2003

We have investigated electric field effect on the formation of phase separated composite organic film structure which is utilized by anisotropic phase separation from LC and prepolymer mixtures. Application of bias field resulted in a significant change in liquid crystal alignment between glass substrate and polymer layer. The liquid crystal molecules segregated into the inter-electrodes and formed twisted structure which is the result of imprinting of LC alignment by the bias field on polymer layers during polymerization process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.336-339
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• 2000

Effects of liquid crystal (LC) alignment using an in-situ photo-alignment method by linearly polarized UV exposure during imidization of polyirnide (PI) on the two kinds of PI surfaces with side chain were investigated. The generated pretilt angle in nematic (N) LC using an in-situ photo-alignment method was smaller than that of a conventional photo-alignment method for short UV exposure time. Also, the pretilt angle of the NLC using an in-situ photo-alignment method increases with increasing UV exposure time on the two kinds of the PI surfaces. Finally, the pretilt angle of NLC can be improved by annealing treatment.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1762-1764
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• 1999

We investigated the annealing effect on generating pretilt angle and aligning liquid crystal (LC) using the photo-depolymerization reaction in this study. In case of rubbing polyimide (PI) surface with the side chain, pretilt angle tends to increase with increasing the annealing time. It is considered because the steric interaction is increased by annealing which cause the side chain to come back to original position. For obliquely irradiating ultraviolet (UV) light on PI surface, pretilt angle shows to $0^{\circ}$ and is increased by annealing. The pretilt angle in rubbed PI surface is much higher than in photo-aligned PI surface. It is attributed to the steric interaction and the number of LC molecular arrangement on azimuthal direction. In addition. in case of obliquely irradiating UV light on PI surface. it showed LC alignment to increase by annealing. It can be regarded due to the fact that the re-alignment of LC molecule is improved to residual polymer direction by annealing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.33 no.1
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• pp.21-24
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• 2020

We investigated a solution-driven Yttrium Tin Oxide (YSnO) film that was imprinted using a parallel nanostructure as a liquid crystal (LC) alignment layer. The imprinting process was conducted at the annealing temperature of 100℃. To evaluate the effect of this process, we conducted surface analyses including atomic force microscopy (AFM). During imprinting, the surface roughness was reduced, and anisotropic characteristics were observed. Planar LC alignment was observed at a pretilt angle of 0.22° on YSnO film. Surface anisotropy induced by imprinting method forces LC to align along the direction of the parallel nanostructure, which is an alternative to conventional polyimide treated using a rubbing process.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.695-699
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• 2006

Injection time of liquid crystal (LC) by capillary action in a vertically aligned (VA) nematic LC cell takes longer than that in a homogeneously aligned (HA) LC cell because Miesowicz viscosity in the former is bigger than that in the latter. To reduce liquid crystal injection time in the VA cell, we applied vertical electric field while injecting so that the orientation of LC molecules is changed from vertical alignment to homogeneous alignment. Consequently, the injection speed is improved by 25 % when compared with the cell without an applied field.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.4
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• pp.302-306
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• 2019

We investigated a solution-derived $Y_2O_3$ film treated by ion beam (IB) irradiation as a liquid crystal (LC) alignment layer. With IB irradiation, homogeneous LC alignment was achieved irrespective of the annealing temperature. To verify the effect of IB irradiation, we conducted surface analyses such as X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). As $Y_2O_3$ is a high-k material, the electro-optical properties of the twisted nematic (TN) cells were superior to those of conventional TN cells based on a rubbed polymer, with an LC rising time of 4.1ms and falling time of 2.9ms. The IB-irradiated $Y_2O_3$ is a good alternative as an alignment layer for fast-switching TN LC displays.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.11
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• pp.821-825
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• 2013

Effect of multi-stacked layer (MSL), 0.1 mol (M) and 0.3 mol (M) hafnium oxide ($HfO_2$) alignment layers were fabricated via a solution-process for LCs orientation. The solutions were spin-coated and annealed in a furnace. MSL consists of three sub-layers using 0.1 M solution, mono-layer (ML) is composed of 0.3 M $HfO_2$ solution. Then ion-beam irradiation was treated with 1.8 keV for 2 min. $HfO_2$-based LC cells were investigated through photographs, pre-tilt angle using crystal rotation method, X-ray photoelectron spectroscopy (XPS) measurement, and surface roughness using atomic force microscopy(AFM) for their characteristic research. Good LC orientation characteristics were observed on MSL $HfO_2$ surface. The LC alignment mechanism on MSL $HfO_2$ and ML $HfO_2$ surfaces was attributed to van der Waals (VDW) interaction between the LC molecular and substrate surface.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1812-1814
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• 1999

The effects of polarity of the polymer on transcription-aligned twisted nematic (TN)-liquid crystal display (LCD) on various the polyimide (PI) surfaces were investigated. The monodomain alignment of nematic (N)LC is obtained in cells fabricated by transcription alignment method on PI surface with medium polarity. The LC alignment using transcription alignment method is attributed to polarity of the polymer. The threshold voltage of transcription-aligned TN-LCD decreases with increasing the polarity of the polymer on three kinds of the PI surfaces. The threshold voltage of transcription-aligned TN-LCD on PI surface with high polarity is almost the same compared to rubbing-aligned TN-LCD. The response time of transcription-aligned TN-LCD decreases with the increasing the polarity of the polymer on all PI surfaces. The decay time of transcription-aligned TN-LCD is slow compared with the rubbing-aligned TN-LCD.