• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.394-395
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• 2007

In order to make full color cholesteric displays, color filter-less R, G, B sub-pixel structured cholesteric LC cells have been studied. To make R, G, B colors, UV induced pitch variant chiral dopant was added to cholesteric LC mixtures. The concentration of the photo-sensitive chiral dopant was adjusted so that the initial state showed blue color and the color was changed from blue to green and red with increase of UV irradiation to the cholesteric cells. To prevent the mixing of R, G, B reflective sub-pixel liquid crystals, separation walls were formed using negative photo resister in boundary area between sub-pixels. Through the optimization of the material concentrations and UV irradiation condition, vivid R, G, B colors were achieved.

• Polymer(Korea)
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• v.24 no.3
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• pp.418-430
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• 2000

A new hydroxylpropyl chitosan (HPCTO) capable of forming both thermotropic and lyotropic liquid crystalline phases was synthesized by reaction of alkali chitosan with propylene oxide and its solid films cross-linked with glyoxal were prepared by casting the liquid crystalline solution in methanol. The thermal and swelling properties of the cross-linked films were investigated. The films displayed fingerprint patterns characteristic of cholesteric liquid-crystalline phase, and their pitches increased with increasing temperature and cross-linker concentration. The cross-linked samples exhibited an anisotropic swelling in both water and methanol, suggesting that the two-dimensional cross-linking preferentially performs between HPCTO molecules. The degree of anisotropy highly depended on the solvent, but hardly on the cross-linker concentration investigated.

• Korean Journal of Materials Research
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• v.2 no.6
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• pp.398-407
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• 1992

Cholesteryl S-alkoxybenzene thiocarbonates was synthesized and their liquid crystal transition temperature were determined. Those compounds exhibit enantiotropic cholesteric mesophases. The cholestric-isotropic transition temperatures decrease gradually with increasing alkoxy chain length and mesophase transition were investigated by differential scanning calorimetry.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.803-805
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• 2006

In the paper we have proposed a fabrication method for color reflective cholesteric LCD by an in-plane switching. By applying an in plane electric field, the cholesteric helix could be partially unwound, which lead to shift of selective reflection and exhibition of color change.

• Journal of Information Display
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• v.6 no.1
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• pp.8-11
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• 2005

A flexible reflective cholesteric liquid crystal display (ChLCD) is fabricated on plastic substrates by using the pixel isolation method. The polymer walls between pixels and the polymer layers in the pixels are formed by two-step UV irradiation. Electro-optical response of the ChLCD with polymer wall and layer is studied and compared with conventional bistable ChLCD cells.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.484-487
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• 2005

In order to find out LC cell spacing method suitable for flexible cholesteric LCDs with high mechanical stability, we carried out bending and mechanical shock tests by using various spacing techniques: bead spacer, photo spacer, polymer wall with bead spacer and polymer wall with photo spacer. As a result, it was found that the spacing method using polymer wall incorporated with photo spacer is the best for flexible cholesteric LCDs in terms of mechanical stability. The investigation is discussed in detail.

• Journal of Radiation Protection and Research
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• v.30 no.1
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• pp.27-30
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• 2005

New possibilities are discussed for cholesteric liquid crystals (CLC) as sensor materials for detection of ionizing radiation, biologically active UV radiation, and the presence of hazardous vapors in atmosphere. A distinguishing property of CLC-based detectors is their 'bioequivalence', i.e., mechanisms of their response to external factors essentially imitate the corresponding mechanisms of biological tissues. Such detectors can ensure sufficiently high sensitivity to make feasible their use as alarm indicators or in biophysical studies. Specific examples ate given of sensor compositions and their response characteristics.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1024-1027
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• 2003

The formation of cholesteric liquid crystal (CLC) film reflecting a broadbanded visible spectrum by application of a liquid crystalline coating followed by UV polymerization (photo-curing) is described. Also, the formation of patterned coatings obtained by a sequence of UV exposure steps is discussed. Such coatings play an important role in the improvement of the performance of liquid crystal displays. In order to make these CLC films, we synthesized new cholesteric liquid crystal molecules (Ch-chol) containing the active reaction site to UV light and investigated to broaden the bandwidth of these cholesteric filters based on the various UV treatments.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07a
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• pp.480-483
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• 2005

We report on studies of photoalignment of cholesteric liquid crystals on photosensitive phenylon-based polymer. We found that reflective and electro-optical characteristics of cholesteric cells strongly depend on UV exposure doze. The optimized UV treatment of the polymer allowed us to obtain the same quality of alignment on standard rubbed polyimide orientants. At the same time, the photosensitive orientant possesses evident advantage of the effective control of cholesteric textures

• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.356-359
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• 2007

Writable Cholesteric Liquid Crystal Display and the algorithm used to detect its image were developed. We could use any hard tip, ex: the tip of a forefinger, to directly write an image on the surface of Cholesteric Liquid Crystal Display (CHLCD). By measuring the capacitance of one pixel of test cell (12mm x 15mm/1x1), F-state or P-state could be detected. By measuring the capacitance of one pixel of 4.1" CHLCD (241um x 241um/ 320x320), F-state or Pstate could not be detected, due to the effect of parasitic capacitance. Therefore, high frequency measurement and the algorithm were developed to detect the image on CHLCD.