• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.118-122
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• 2005

Liquid crystal (LC) alignment using a photoalignment method by irradiation of polarized ultraviolet (UV) on an alignment layer has been investigated. Photoalignment method exhibits weaker anchoring energy than rubbing method so that we have studied electro-optic characteristics of fringe-field switching (FFS) mode with alignment layers using the photo and rubbing alignment methods. The cell using photo alignment layer shows lower threshold and operation voltage than those using rubbed alignment layer. Also. the former method shows higher transmittance than that of the latter.

• Macromolecular Research
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• v.9 no.6
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• pp.339-344
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• 2001

In order to investigate the photoalignment mechanism of nematic liquid crystals on a polymer film, a new photoreactive polymer having chalcone groups as side chains was synthesized. Linearly polarized UV light causes preferential photoreactions of the chalcone unit along the polarization direction and thus induces the anisotrpy in the polymer alignment layer resulting in homogeneous LC alignment perpendicular to the polarization direction. The sequential investigations of photoalignment generated by the preferential E/Z isomerization and (2+2) cycloaddition reactions show that either photoreaction can solely induce the LC alignment in the direction perpendicular to UV polarization.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.834-838
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• 2004

We report on a simple method of fabricating multimode transflective liquid crystal displays (LCDs) using the photoalignment technique. Using a self-masking process of ultraviolet light by the reflector as a photomask as well as a reflective mirror, the periodic multimode is obtained with no additional fabrication processes. Moreover, variations of the cell gap are not required for such trasflective LCDs

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1351-1354
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• 2005

We report on the photoalignment process of pentacene thin film with optical anisotropy on treated buffer layers. The photopolymer, showing an anchoring transition, was used as a buffer layer to control the structural order of the pentacene molecules. Using the photoelastic modulator, it was found that the grain size and the optical anisotropy of the pentacene thin film were strongly correlated with each other.

• Bulletin of the Korean Chemical Society
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• v.22 no.2
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• pp.179-182
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• 2001

Photocyclizable poly(cinnam-4'-yl methyl methacrylate) derivatives bearing methoxy benzene (PMCMMA), anthracene (PACMMA), and coumarin (PCCMMA) have been synthesized via Heck type reaction. Three different types of polymers are photoreactable usin g linearly polarized UV light and applicable as liquid crystal alignment layer. Anthracence and coumarin containing polymers (PACMMA, PCCMMA) have better thermal stability than PMCMMA. This observation may be attributed to the glass transition temperature elevation due to the bulky size and another photocrosslinking site provided by anthracene or coumarin group.

• Journal of Information Display
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• v.5 no.3
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• pp.8-13
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• 2004

We demonstrate a transflective liquid crystal display (LCD), doped with a chiral agent to produce a low helical twisting power, in a multimode configuration consisting of the homogeneous alignment and the hybrid alignment. The multimode transflective LCD with a single cell gap was fabricated using a single-step photoalignment technique with a self-masking process of an array of metal reflectors in the reflective region. In our configuration, the electro-optical disparity between the transmissive region and the reflective region was found to be significantly reduced by the low helical twisting power of the chiral dopant.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.3
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• pp.264-268
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• 2002

Three types of polymer, a photoalignment material based N- (phenol)maleimide were synthesized and the liquid crystal (LC) aligning capabilities on the photopolymer layer were studied. A good LC alignment with UV exposure on the PMI5CA(N-(phenol)maleimide with 5-carbon chain cinnamoyl group) can be obtained. However, the LC alignment defects were observed on the PM13CA (N-(phenol)maleimide with 3-carbon chain cinnamoyl group) and PMIF (N-(phenyl)maleimide 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 aligning ability on the photopolymer layer based N-(phenol)maleimide depends on the side chain length of photopolymer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.07b
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• pp.1007-1009
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• 2004

We investigated the electro-optical(EO) performances of the super twisted nematic liquid crystal display(STN-LCD) on the polyimide(PI) surface with polymer film using rubbing and photoalignment method. Monodomain alignment of the plastic STN-LCD can be observed. A faster response time for the photoaligned plastic STN-LCD on the polyimide(PI) surfaces can be achieved than rubbingaligned plastic STN-LCD.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.210-213
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• 2004

We synthesized photoalignment material of high thermal resistance with hydroxyl aromatic polyimide, and studied the liquid crystal (LC) aligning capabilities on the photopolymer layers. Also, electro-optical (EO) performances for the twisted-nematic (TN)-liquid crystal display (LCD) photoaligned with linearly polarized UV exposure were investigated. A good LC alignment with UV exposure on the photopolymer surface can be obtained. However, the low pretilt angles were obtained below $1^{\circ}$. The Voltage-transmittance (V-T) curve without backflow bounce in the photoaligned TN cell with UV exposure was observed. The response time of photoaligned TN cell was measured about 24 ms. Finally, The photoaligned TN cell has few hysteresis, and shows the residual DC voltage that is less.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11b
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• pp.117-120
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• 2001

A new photoalignment material PFCPMI, poly[4-(fluorocinnamate)phenylmaleimide], was synthesized and the nematic liquid crystal (NLC) aligning capabilities on the photopolymer surface. The NLC pretilt angle generated by non-UV filter method on the PFCPMI surface was higher than that of the UV filter method. A good LC alignment by non-UV filter method was observed at $150^{\circ}C$ of annealing temperature. However, the alignment defect of the NLC by UV filter method was measured above $150^{\circ}C$ of annealing temperature. Consequently, the high pretilt angle and the good LC alignment in NLC using non-UV filter method can be acheived.