• Journal of the Korean Chemical Society
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• v.45 no.1
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• pp.67-75
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• 2001

A new homologous series with the general formula in which n is the longitudinal alkyloxy group, n=1-10, was synthesized. The thermotropic and liquid crystalline properties were studied by differential scanning calorimetry and on the hot-stage of a polarizing microscope. All of the new compounds were monotropic and texture observations proved that all investigated homologues with n=1-10 exhibited nematic phases. Also, the compounds showed pronounced alternation effects in the homologous series with constant lateral bridging group, oxydecamethyleneoxy, but increasing longitudinal chains, n.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.05a
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• pp.181-184
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• 2005

In this paper, we have improved a novel fast response time liquid crystal operating mode using tilt angle in the unique condition by hot-plate equipment. The new control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by Hot-plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. Especially, the low LC tilt angle of positive type NLC (${\Delta}n$>0) on the rubbed homeotropic PI surface by increasing temperature and time was measured. The EO characteristics of the high tilted OCB(HTOCB) mode using control of tilt angle on the homeotropic surface than that of conventional OCB cell can be improved. We suggest that the developed the HTOCB cell using control of tilt angle on the homeotropic surface is a promising technique for the achievement of a fast response time and a high contrast ratio.

• Applied Chemistry for Engineering
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• v.5 no.6
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• pp.998-1008
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• 1994

Copolyeters consisted of p-oxybenzoly, naphthalene isomer and dimethyldisiloxyl group in different comonomer sequences were synthesized by solution polycondensation and characterized. The naphthalene isomers used in this study were of the 1,4 1,5, 2,6 and 2,7 naphthylene units. The inherent viscosities of the polymers were between 0.27~0.42dl/g and all of the polymers, with the exception of the 2,7-ordered copolyester, showed enantiotropic nematic behavior. Annealing the copolyesters resulted in increasing molecular weights and degree of crystallinity of crystallizable compositions. Ordered copolyesters exhibit significant differences in thermal transitions, thermal stability, crystalline properties and liquid crystallinity when compared with the properties of the corresponding radom copolyesters.

• Applied Chemistry for Engineering
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• v.25 no.1
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• pp.47-52
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• 2014

A series of liquid crystalline polyesters containing X-shaped mesogenic groups in main chain were synthesized through the solution polymerization of 2,5-di(4-substituted benzoate)hydroquinones and 4,4'-dicarboxy-1,8-diphenoxyoctane. The structures and properties of synthesized polymers were investigated by $^1H$-NMR, FT-IR, differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), polarized optical microscopy (POM) and wide angel X-ray diffraction (WXRD). Inherent viscosities (${\eta}_{inh}$) of polymers were measured between 0.35 and 0.66 dL/g in 1,1,2,2-tetrachloroethane, and they were easily soluble in most of organic solvents used for this experiment. All polymers revealed relatively low melting transition temperature ($T_m$) and crystallinity, and also showed thermotropic nematic liquid crystallinity when they were heated to their melting temperatures. These properties of polymers were presumably due to the presence of the bulky substituting groups on the hydroquinone unit in mesogenic group.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.6
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• pp.524-528
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• 2002

Conventional hybrid aligned nematic liquid crystal display (HAN-LCD) has several advantages on low operating voltage, fast response time and rubbing free on one substrate. We have fabricated a new hybrid aligned nematic display driven by fringe field. The new device exhibits much wider viewing: angle than that of the conventional HAN mode, owing to almost in-plane rotation of the LC director. Furthermore, we have developed the device that reveals more efficient electro-optic characteristics by placing common electrode on top and bottom substrates. In this paper, the electro-optic characteristics of the novel cell are investigated.

• 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.17 no.1
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• pp.75-82
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• 2004

We have studied the influence of rubbing directions on electro-optic characteristics of the fringe field driven hybrid aligned nematic liquid crystal (LC) cell by computer simulation. When a LC with positive dielectric anisotropy is used, the results show that the driving voltage and transmittance decreases as the rubbing direction with respect to horizontal electric field direction increases. The reason for decrease in light transmission is the increase of tilt angle on the center of common electrode. In this paper, we have studied how the rubbing angle effects on the transmittance of the cell by investigating a distribution of electric field and LC director.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.265-268
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• 1995

We have studied the effect of the mesogenic core of nematic liquid crystals (NLCs) for polar (out-of-plane tilt) anchoring strength and surface order parameter on rubbed polyimide (PI) films. The order of polar anchoring strength for NLCs on rubbed PI films is 5CB > PCH5 > CCH5. This order is the same for all rubbing strengths investigated. The surface order parameter for NLCs is 5CB > PCH-5 > CCH5 on rubbed PI films. From these results, we suggest that the polar anchoring strength is strongly related to the surface order parameter.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.949-952
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• 2002

The mechanisms of pretilt angle generation for a nematic liquid crystal (NLC) with negative dielectric anisotropy on the blended polyimide (PI) surface containing trifluoromethyl moiety was studied. High LC pretilt angle on the blended polymer surface with F3 was measured and the pretilt angle increased with rubbing strength. However, the low LC pretilt angle on the blended polymer surface with F1 and F2 was measured. The high LC pretilt angle generated is attributable to trifluoromethyl moiety in backbone structure on the blended PI surface. Therefore, the high pretilt angle of NLC can be achieved by using the blended polymer surface.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.11
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• pp.981-984
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• 2002

The mechanisms of pretilt angle generation for a nematic liquid crystal (NLC) with negative dielectric anisotropy on the blended polyimide (PI) surface containing trifluoromethyl moiety were studied. High LC pretilt angle on the blended polymer surface with F3 was measured and the pretilt angle increased with rubbing strength. However, the low LC pretilt angle on the blended polymer surface with F1 and F2 was measured. The high LC pretilt angle generated is attributable to trifluoromethyl moiety in backbone structure on the blended PI surface. Therefore, the high pretilt angle of NLC can be achieved by using the blended polymer surface.