• Korean Journal of Optics and Photonics
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• v.26 no.2
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• pp.110-114
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• 2015

We propose a reflective cholesteric liquid crystal cell with reduced color shift, using dichroic dyes. Color-shifted light is absorbed by dye molecules in the proposed dye-doped cholesteric liquid crystal (DDCLC) cell. We have shown that the color shift can be reduced by increasing the concentration of dye molecules in the proposed DDCLC cell.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.40 no.2
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• pp.141-153
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• 2014

This study is about the development of cholesteric liquid crystals (CLCs), which are highly applicable to cosmetics formulation. The CLCs made from non-animal origin were chosen not only because they are free of animal viruses but also because they give a sense of security to the cosmetic consumers. Three kinds of new cholesteric derivatives (CI, CC, CN) were synthesized using non-animal cholesterol [NAB cholesterol (ARCH LONZA)], which was originally made by fermentation process. To develop high applicability to cosmetics formulation, we attempted to find out the optimum compositions in which CLCs can maintain their color over a wide range of temperature. The CLCs in 41 different compositions were prepared by the combinations of three cholesteric derivatives and a visual evaluation method was employed to determine the range of temperature at which the CLCs display their color. The 205 UV-VIS spectral data obtained from 41 CLCs at various temperatures were simultaneously analyzed to investigate the critical factors affecting the characteristics of the CLCs. Results showed that A4, A5, A6 and A7 were the best compositions to cosmetics formulation. A6 composition had a great moisturizing effect by the artificial skin test ($AmoReSkin^{TM}$).

• Applied Chemistry for Engineering
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• v.28 no.2
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• pp.230-236
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• 2017

We synthesized liquid crystalline polymers containing isosorbide group as a cholesteric derivative and methylene group for controlling the transition temperature to the liquid crystal phase. Effects of the concentration of the isosorbide group and the position of the methylene group on the properties of the liquid crystalline polymer were investigated. Among all the synthesized polymers, polymers (MnHI-x) with a methylene group in the main chain showed higher melting transition temperature and thermal stability than those (SnBI-x) with a methylene group in the side chain. All the synthesized polymers showed an enantiotropic liquid crystal phase. The polymers having 10 mol% isosorbide as a cholesteric liquid crystal phase derivative showed nematic phase, and those having 20 mol% or more isosorbide showed a cholesteric or chiral smectic phase. Thus, we can conclude that the isosorbide group plays a role as a cholesteric liquid crystal phase derivative.

• Korean Journal of Optics and Photonics
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• v.11 no.2
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• pp.91-96
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• 2000

We propose a novel in-line fiber optic circular polarizing mirror utilizing cholesteric lIquid crystal (CLC) polymer [11m for the fiber laser applications. Ions matrix representation of this device has been derived and venfied experimentally. In a Fabry-Perot cavity configuration, a CLC fiber optic rmrror has been used to achieve longitudinal mode suppression as well as to obtain passively mode~locked laser operations with 630 fs laser pulses via nonlinear polarization evoluhon.oluhon.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.294-301
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• 2008

We have performed modeling and simulations of optical characteristics for a cholesteric liquid crystal (CLC) color filter. Berreman's $4{\times}4$ matrix method was used for the calculation of reflectance spectra of the CLC color filter with respect to the incident angle. The results were employed as input parameters for a user-defined coating property of an illumination design software based on the ray-tracing method, LightTools. Color shift characteristics of a planar transmission-type CLC color filter were simulated using LightTools. The results were compared with the results obtained with Berreman's $4{\times}4$ matrix method. It was found that color shift characteristics of the CLC color filter could be simulated to a reasonable accuracy when the reflectance spectra with less than 5 degrees of incremental incidence-angle were used as the input data for the user-defined coating property of LightTools. We have simulated color shift characteristics of a reflection-type CLC color filter having hemi-spherical patterns. The simulation method reported in this paper has been found to be also used for a non-planar CLC color filter structure.

• Polymer(Korea)
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• v.32 no.2
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• pp.169-177
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• 2008

The thermal and optical properties of cellulose tri(cholesteryloxy) carbonate(CCE0) and cellulose tri(cholesteryloxycarbonyl)alkanoates (CCEn, n=$2{\sim}8$, 10, the number of methylene units in the spacer) were investigated. CCE0 formed an enantiotropic cholesteric phase, whereas all the CCEn exhibited monotropic cholesteric phases. CCEn with n=$3{\sim}8$ formed cholesteric phases with left-handed helical structures whose optical pitches (${\lambda}_m's$) decrease with increasing temperature. On the other hand, CCE0 and CCEn with n=2 or 10 did not display reflection colors over the full cholesteric range, suggesting that the helical twisting power of the cholesteryl group highly depends on the length of the spacer connecting the cholesteryl group to the main chain. The thermal stability and degree of order in the mesophase and the temperature dependence of the ${\lambda}_m$ observed for CCEn highly depended on n. The results were discussed in terms of the differences in the internal plasticization, the arrangement of the side groups, and the conformation of the molecules.

• 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.

• Polymer(Korea)
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• v.31 no.4
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• pp.356-367
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• 2007

Three kinds of amylose derivatives such as: cholesteryloxycarbonated amyloses(CAMs) with degree of esterification(DE) ranging from 1.8 to 3, (6-cholesteryloxycarbonyl)pentanoated amyloses(PAMs) with DE ranging from 0.3 to 3, and fully cholesteryloxycarbonated PAMs(CPAMs) were synthesized, and their thermotropic liquid crystalline properties were investigated. CAMs with $DE{\geq}2.6$, PAM with DE=1.6 and all the CPAMs formed enantiotropic cholesteric phases, whereas PAM with $DE{\geq}2.2$ exhibited monotropic cholesteric phases. PAM with $DE{\geq}2.2$ and CPAMs with (6-cholesteryloxycarbonyl)pentanoyl DE (DS) more than 1.0 formed cholesteric phases with left-handed helical structures whose optical pitches (${\lambda}_{m'}s$) decrease with increasing temperature. However, the ${\lambda}_{m'}s$ of these samples decreased with increasing DS at the same temperature. On the other hand, CAMs, PAM with DE=1.6, and CPAM with DS=0.3 did not display reflection colors over the full cholesteric range, suggesting that the helicoidal twisting power of the cholesteryl group highly depends on the length of the spacer joining the cholesteryl group to the main chain and DS. The thermal stability and degree of order in the mesophase observed for the amylose derivatives highly depended on DE or DS. The results were discussed in terms of the difference ul the hydrogen bond, the internal plasticization, and the decoupling of the motion of side group with the main chain.

• Korean Journal of Materials Research
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• v.3 no.3
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• pp.223-229
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• 1993

A homologous series of cholesteryl biphenyl ester derivatives was prepared. The thermal behaviors of compounds were studied by differential scanning calorimetry and by polarizing microscope equipped with a hot-stage. The cholesteric phase is present in all the compounds, whereas the smectic one is absent in the compounds with R = 1 and 2. The compounds possessed higher phase transitiof' temperature and wider temperature range of meso phase in comparison with known cholesteric liquid crystal phases.

• Proceedings of the Materials Research Society of Korea Conference
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• 2000.11a
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• pp.84-84
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• 2000