• Journal of Information Display
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• v.12 no.3
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• pp.115-119
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• 2011

Optically isotropic liquid crystal (LC) mixture such as blue-phase LC and nanostructured LC composites exhibit the advantages of fast response time, high contrast ratio and wide-viewing angle due to the induced birefringence along the horizontal electric field. Utilizing this mixture, a novel single cell gap in-plane switching-type polymer-stabilized blue-phase transflective liquid crystal display by embedding the nanowire grid polarizer as a polarization-dependent reflective polarizer in the R region is proposed. This device can be used as a normal black mode without any quarter-wave plate or patterned in-cell phase retarder. Moreover, the transmittance is identical to the reflectance so that it will be suitable for single gamma driving. Detailed electro-optic performances, such as voltage-dependent light efficiency and viewing angle of the proposed device configuration, are investigated.

• Transactions on Electrical and Electronic Materials
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• v.13 no.5
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• pp.221-224
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• 2012

The present paper reports the comparative optical behavior of a pure nematic mixture E-24 and its anthraquinone dye doped sample. The variation in the ordinary and extraordinary refractive index ($n_o$, $n_e$) of the pure and dye doped samples with temperature has been discussed and it has been found that doped sample have a less refractive index compared to the pure sample. The variation in the order parameter for pure and doped samples with temperature has been discussed and it has been seen that the doped sample has a higher order parameter; the possible reasons have been discussed. The variations in birefringence and optical transmittance have also been presented here.

• Transactions on Electrical and Electronic Materials
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• v.14 no.3
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• pp.111-115
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• 2013

The dielectric anisotropy and dispersion of the real and imaginary part of the permittivity of commercially important nematic mixture E-24 and its polymer composite were investigated in the frequency range from 1 kHz to 10 MHz, and temperature range $14^{\circ}C$ to $55^{\circ}C$. The percentage optical transmittance and density have also been measured for both the systems. The results have been explained by assuming molecular rotation about the long molecular axis, under a hindering nematic potential. The dielectric anisotropy ${\Delta}{\varepsilon}$ is positive, and the mean dielectric permittivity falls with rising temperature. ${\Delta}{\varepsilon}$ is also used to determine the order parameter with varying temperature.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.337-339
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• 2008

Recently, Note PCs have being widely used due to their features such as good mobility and low power consumption. In order to ensure the current market position, further improvement is required. Especially, the lower operating voltage is essential for the long operating time of Note PCs. For the achievement of lower operating voltage, possible contributions from LC materials side are to lower the viscosity and to increase the dielectric constant without sacrificing the reliability. In order to achieve lower driving voltage, new LC mixtures have been developed, optimizing theirs physical properties.

• Journal of the Korean Chemical Society
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• v.26 no.3
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• pp.188-193
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• 1982

Four new thermotropic copolyesters were prepared and their liquid crystal properties were investigated by differential scanning calorimetry and on a hot-stage of a polarizing microscope. Three copolyesters had same mesogenic unit, triad aromatic ester structure, interconnected through a random combination of either odd-even, or odd-odd, or even-even number of methylene groups in the polymethylene flexible spacers. Another random copolyester consisted of mesogenic units of 1 : 1 mixture of central methyl-and bromohydroquinone moieties with two flanking p-oxybenzoate units connected by decamethylene spacer. All of the polyesters formed nematic liquid crystal phase upon melting. The transitions for melting and nematic ${\to}$ isotropic transformations could be reversibly observed by DSC as well as by microscopic study. The thermodynamic properties for their liquid crystal ${\to}$ isotropic phase transitions were discussed in relation to their chemical structures.

• Applied Chemistry for Engineering
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• v.19 no.6
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• pp.661-667
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• 2008

In this study, cholesteric liquid crystal (CLC) was synthesized and applied as a polarizing component on the optical film of back light units (BLU) for LCDs. After mixing CLC with nematic liquid crystal, this mixture was fulfilled in the module consisting of two films and then its amplifying efficiency and polarizing ability for a planarly emitted light were examined to apply as a BLU polarizer film for increasing the brightness of light. The properties of CLC compound were tested by UV/Visible spectroscopy and polarizing optical microscopy (POM). Flexible spacer was made by linear carboxylic acid group of cholesteric derivatives between cholesterol mesogen units for one-axis orientation in each layer. The CLC containing film could be used as a module to increase the ability of polarization and to enhance brightness of BLU and to widen wavelength range by stacking the films.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.186-186
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• 2009

Most liquid crystal display modes, including the twisted nematic (TN) $mode^1$, the in-plane switching (IPS) $mode^2$, the fringe field switching (FFS) $mode^3$, and the vertically aligned (VA) $mode^4$ are based on either a horizontal or a vertical alignment. However, for some applications, such as no-bias-bend (NBB) pi cell or bistable bend-splay display, an intermediate pretilt angle is essential$^5$. NBB pi cells have been a focus of interest because of their fast response time; however, the reliable control of the intermediate pretilt angle of liquid crystals that is required for the fabrication of NBB pi cells is challenging. The controllable pre-tilt angle of liquid crystals was investigated using a blend of horizontal and vertical polyimide prepared by a rubbing method. Various pretilt angles in the range from 0^{\circ}$ to 90^{\circ}$ were achieved as a function of the vertical polyimide content. We observed uniform liquid crystal alignment on the rubbing-treated blended polyimide layer. A NBB pi cell with an intermediate pretilt angle of 47.8^{\circ}$ was manufactured. This cell had no initial bias voltage and a low threshold voltage, which indicates that it has low power consumption. In addition, the response time of the NBB pi cell was rapid.

• Journal of the Korean Applied Science and Technology
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• v.21 no.1
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• pp.31-36
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• 2004

Liquid crystalline phases were formed from acylglutamate; polyglyceryl-10 myristate and glycerine mixture and they were used as a base material for preparing an O/W emulsion. When an oil phase is added into the liquid crystalline phases, it was inserted into the dispersed liquid crystal droplets rather than stayed outside the liquid crystals, which can be known by the fact that the size of liquid crystal droplets increases with the increasing oil phase content. Along with the increase in the droplet size, the complex modulus increases from 100 to 350 pascals and the loss angle decreases from 60 to 24 degrees, from which it can be known that the increase in the internal phase volume results in the increase in the elastic property of oil in liquid crystalline-phases (O/LC). When the water phase was lastly added into the O/LC phase, the emulsification occurred to form a O/W emulsion and the averaged particle size of the O/W emulsion changes from 22.5nm to 538nm with the addition of water phase. The results from the droplet size measurements and stability tests under accelerated conditions such as high temperature show that the obtained O/W emulsion is very consistent with time.

• Korean Chemical Engineering Research
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• v.52 no.3
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• pp.321-327
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• 2014

Polymer dispersed liquid crystal lenses of the cell gap of $11{\mu}m$ and $30{\mu}m$ were made from a uniformly dispersed mixture of 40 wt% NOA65 prepolymer - 60 wt% E7 liquid crystal with the variations of the additional photoinitiator. The photoinitiator, benzophenone of 5.0 wt% was originally in the commercial prepolymer NOA65. In this works, the influence of the benzophenone amount intentionally added in the commercial NOA65 on the electrical properties of polymer dispersed liquid crystal lens for smart electronic glasses. The additional quantities of the photoinitiator were 1, 2, 4, 8 and 16 wt% of the weight of NOA65 - E7 mixture. All the electro-optical properties of the sample with added benzophenone such as the driving voltage, the slope of the linear region, the response time and contrast ratio were more improved than that of commercial NOA65 only. These improvements were due to the increase of the average size of E7 liquid crystal droplets in the samples with the increase of the added benzophenon amount. The liquid crystal droplet size was increased from $5.3{\mu}m$ to $12.2{\mu}m$ when the photoinitiator was added from 0 wt% to 8 wt%. At the same concentration range of the photoinitiator, the driving voltage was ranged from 11.1 V to 17.3 V. The slopes of the linear region were in the range of 10.35~13.96 %T/V, which were more enhanced than that of NOA65 without the additional benzophenone. In particular, though the deteriorations by cell gap of $11{\mu}m$ were so effective to offset the influence of the added benzophenone for both rising and falling response time, it is confirmed that there were still somewhat improvement by the additional benzophenone. Response time and contrast ratios of all the samples with excess benzophenone were slightly enhanced.

• Korean Journal of Optics and Photonics
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• v.4 no.2
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• pp.168-172
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• 1993

We measured the spectral transmittance of the cholesteric mixtures of ZLI-1167 and CB15 for various weight fractions of CB15 in the mixture to find out the relationship between the center wavelength of the selective reflection band and the weight fraction of CB15 in the mixture. Left handed circular polarizer for 632.8 nm was designed and fabricated with this mixture whose weight fraction of CB15 was 33.19%. The ellipticity of the elliptical polarization of the transmitted light was measured to be 0.98 showing excellent property of the CLC circular polarizer.