• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.265-267
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• 2007

The liquid crystal(LC) aligning capabilities of a nematic liquid crystal(NLC) on a homeotropic polyimide(PI) surface using a new ion-beam method were studied. Exposure ion-beam of $45^{\circ}$ incidence angle shows a good LC alignment of the NLC on the homeotropic PI surface. Also, on the homeotropic PI surface, the tilt angle of the NLC by exposure ion-beam of $45^{\circ}$ incidence angle had a tendency to decrease as increased ion-beam energy density. And, on the homeotropic PI surface, the alignment character of the NLC with respect to ion-beam energy was good at 1500 eV. And we achieved satisfactory result for EO character.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.398-398
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• 2007

The Liquid Crystal (LC) alignment uniformity is very important in LC devices. The alignment mechanism of LC molecules on a rubbed polyimide (PI) surface is very important for both LC fundamental research and application. So, Generally a rubbing method to align LC has been widely used to mass-produce LCD panels. But because rubbing method is contact method between rubbing fabric and indium-tin-oxide glass or flexible substrate, rubbing method has some defects, such as the electrode charges and the creation of contaminating particles. Thus we strongly recommend a non-contact alignment technique for getting rid of some defects of rubbing method. Most recently, the LC aligning capabilities achieved by ion-beam exposure on the organic and nonorganic thin film surface have been reported successfully. In this research, we studied the tilt angle generation and electro-optical performances for a NLC on homeotropic polyimide surfaces with ion-beam exposure. The LC aligning capabilities of a nematic liquid crystal (NLC) on a homeotropic PI surface using a new ion-beam method were studied. On the homeotropic PI surface, the tilt angle of the NLC by exposure ion-beam had a tendency to decrease as increased ion-beam energy density. And, on the homeotropic PI surface, the alignment character of the NLC with respect to ion-beam energy was good. And we achieved satisfactory result for EO character.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.41-41
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• 2008

In general, polyimides (PIs) are used in alignment layers in liquid crystal displays (LCDs). The rubbing alignment technique has been widely used to align the LC molecules on the PI layer. Although this method is suitable for mass production of LCDs because of its simple process and high productivity, it has certain limitations. A rubbed PI surface includes debris left by the cloth, and the generation of electrostatic charges during the rubbing induces local defects, streaks, and a grating-like wavy surface due to nonuniform microgrooves that degrade the display resolution of computer displays and digital television. Additional washing and drying to remove the debris, and overwriting for multi-domain formation to improve the electro-optical characteristics such as the wide viewing angle, reduce the cost-effectiveness of the process. Therefore, an alternative to non-rubbing techniques without changing the LC alignment layer (i.e, PI) is proposed. The surface of LC alignment layers as a function of the ion beam (IE) energy was modified. Various pretilt angles were created on the IB-irradiated PI surfaces. After IB irradiation, the Ar ions did not change the morphology of the PI surface, indicating that the pretilt angle was not due to microgrooves. To verify the compositional behavior for the LC alignment, the chemical bonding states of the ill-irradiated PI surfaces were analyzed in detail by XPS. The chemical structure analysis showed that ability of LCs to align was due to the preferential orientation of the carbon network, which was caused by the breaking of C=O double bonds in the imide ring, parallel to the incident 18 direction. The potential of non-rubbing technology for fabricating display devices was further conformed by achieving the superior electro-optical characteristics, compared to rubbed PI.

• Journal of Satellite, Information and Communications
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• v.10 no.3
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• pp.89-93
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• 2015

Ion-beam irradiation(IB) on $HfO_2$ surface induced high-performance liquidcrystal(LC) driving at a 1-V threshold with vertical alignment of liquid crystals(LC). The high-k materials Atomic layer deposition was used to obtain LC orientation on ultrathin and high-quality films of $HfO_2$ layers. To analyze surface morphological transition of $HfO_2$ which can act as physical alignment effect of LC, atomic force microscopy images are employed with various IB intensities. The contact angle was measured to elucidate the mechanism of vertical alignment of LC on $HfO_2$ with IB irradiation. Contact angle measurement show the surface energy changes via IB intensity increasing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.11a
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• pp.502-505
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• 2004

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of a SiC (Silicon Carbide) thin film. SiC thin film exhibits good chemical and thermal stability. The good thermal and chemical stability make SiC an attractive candidate for electronic applications. A homeotropic alignment of nematic liquid crystal by ion beam (IB) exposure on the SiC thin film surface was achieved. The about $87^{\circ}$ of stable pretilt angle was achieved at the range from $30^{\circ}$ to $45^{\circ}$ of incident angle. The good LC alignment is maintained by the ion beam alignment method on the SiC thin film surface until annealing temperature of $300^{\circ}C$. Consequently, homeotropic alignment effect of liquid crystal and the good thermal stability by the ion beam alignment method on the SiC thin film layer can be achieved.

• Proceedings of the KIEE Conference
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• 2001.11a
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• pp.182-185
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• 2001

A photoalignment material based N-(phenyl)maileimide were synthesized and the liquid crystal (LC) aligning capabilities on the photopolymer layer were studied. A goof LC alignment with UV exposure on the PM15CA(N-(phenyl)maileimide with 5-carbon chain cinnamoyl group) can be obtained However, the LC alignment defects were observed on the PM13CA (N-(phenyl)maileimide with 3-carbon cam cinnamoyl group) and PMIF (N-(Phenyl)maileimide including fluoro cinnamoyl group). Also, the good LC alignment with UV exposure on the PM15CA surface was observed at until $150^{\circ}C$ of annealing temperature. The LC aliging ability on the photopolymer layer based N-(phenyl)maleimide depends on the side chin length of photopolymer.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1132-1136
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• 2004

In this paper, we intend to make FFS mode cell with LC alignment used non-rubbing method, ion beam alignment method on the a-C:H thin film, to analyze electro-optical characteristics in this cell. We studied on the suitable inorganic thin film for FFS-LCD and the aligning capabilities of nematic liquid crystal (NLC) using the new alignment material of a-C:H thin film as working gas at rf bias condition. A high pretilt angle of about 5$^{\circ}$ by ion beam(IB) exposure on the a-C:H thin film surface was measured. An excellent voltage-transmittance (V-T) and response time curve of the ion-beam-aligned FFS-LCD was observed with oblique ion beam exposure on the DLC thin films.

• Journal of Satellite, Information and Communications
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• v.10 no.2
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• pp.75-79
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• 2015

In this study, we investigated the electro-optical (EO) characteristic of fringe-field switching (FFS) mode cell by the ion beam alignment method on the a-C:H thin film. The suitable inorganic thin films for FFS cell and the aligning capabilities of nematic liquid crystal (NLC) using the new alignment material of a-C:H thin film were studied. An excellent voltage-transmittance (V-T) and response time curve of the ion beam aligned FFS-LCD was observed with oblique ion beam exposure on the a-C:H thin films. Also, the V-T hysteresis characteristics of the ion beam-aligned FFS-LCD with IB exposure on the a-C:H thin films is almost the same as that of the rubbing-aligned FFS cell on a polyimide surface.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.585-588
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• 2003

We have studied how rubbing direction affects generation of disclination line in transmissive microdisplay for $90^{\circ}$ twisted nematic (TN) mode with pixel size of $22.2{\mu}m$. The rubbing direction of bottom substrate is changed from $0^{\circ}$ to $-135^{\circ}$ with a decrease step of $45^{\circ}$, and the results show that the generation regions of the disclination line are of a smallest size in $-135^{\circ}$ direction. The results were the same although the pixel size decreased. Consequently, the use of proper rubbing direction of liquid crystal can help overcome the problems of low aperture ratio and low contrast ratio in transmissive-type microdisplays. In addition, the pretilt angle of initial liquid crystal is found to make an important contribution to generation of the disclination line.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03b
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• pp.15-16
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• 2010

We used Brewster's Law to examine the mechanism of liquid crystal (LC) alignment on an organic insulation layer when subjected to ion-beam irradiation. Brewster's Law implies that the maximum rate polarized rayon a slanted insulation layers on the substrate and it illustrates the dependence of polarization and themechanical structure on the ion beam irradiation process. The pretilt angle of nematic LCs on the organic insulation surface was about $1.13^{\circ}$ for an ion beam exposure of $45^{\circ}$ for 1 minute at 1800eV. This shows the dependence of LC alignment on the polarization ratio in a slanted organic insulation layer. We also discussed the electro-optical characteristic of twisted nematic (TN) LCD using ion beam irradiation on organic overcoat layer.