• Bulletin of the Korean Chemical Society
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• v.30 no.8
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• pp.1821-1826
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• 2009

Liquid crystal display (LCD) devices contain a colour filter which can visualise colour images by transmitting or absorbing light. Colour properties of LCD mainly depend on colour materials such as pigments and polymeric binders. In this paper, colour properties were studied to improve colour quality of LCD. Generally, the colour properties can be classified into three categories which are colour purity, brightness and contrast ratio. For this study, photo resists were prepared by treatment of pigments and synthesis of polymeric binder. The treated pigments were dispersed and formulated with additives for preparing a photo resist that could be used for manufacturing colour filters. As a result of what we studied, type, mixture ratio and concentration of pigments were very important to improve colour purity of LCD device.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.421-421
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• 2006

The light and energy-efficiency of classical liquid crystal displays is notoriously poor due to the use of absorption-based linear polarisers and colour filters. For instance, the light efficiency of PVAL polarisers is typically between 40 and 45 % and the colour filters have a typical efficiency below 35 % which results in a total light and energy-efficiency of the display below 10 %. In the past, a variety of polarizers were developed with an enhanced efficiency in generating linearly polarized light. Typically, these polarizers are based on the polarisationselective reflection, scattering or refraction of light i.e. one polarisation direction of light is directly transmitted to the LCD/viewer and the other polarization direction of light is depolarised and recycled which results in a typical efficiency for generating linearly polarized light of 70-85 %. Also, special colour filters have been proposed based on chiral-nematic reactive mesogens which increase the efficiency of generating colour. Despite the enormous progress in this field, a need persists for improved methods for generating polarized light and colour based on low cost optical components with a high efficiency. Here, the use of holographic phase gratings is reported for the generation of polarized light and colour. The phase grating are recorded in a photopolymer which is coated onto a backor frontlight for LCDs. Typically the recording is performed in the transmisson mode or in the waveguiding mode and slanted phase gratings are generated with their refractive index modulation at an angle between 20o and 45o with the normal of the substrate. It is shown that phase gratings with a high refractive index modulation and a high efficiency can be generated by a proper selection of the photopolymer and illumination conditions. These phase gratings coupleout linearly polarized light with a high contrast (> 100) and the light is directed directly to the LCD/viewer without the need for redirection foils. Dependent on the type of phase grating, the different colours are coupled-out at a slightly different angle which potentially increases the efficiency of classical colour filters. Moreover, the phase gratings are completely transparent in direct view which opens the possibility to use them in frontlights for LCDs. Holographic polarization gratings posses a periodic pattern in the polarization state of light (and not in the intensity of light). A periodic pattern in the polarization direction of linearly polarized light is obtained upon interference of two circularly polarized laser beams. In the second part of the lecture, it is shown that these periodic polarization patterns can be recorded in a linear photo-polymerizable polymer (LPP) and that such an alignment layer induces a period rotation in the director of (reactive and non-reactive) liquid crystals. By a proper design, optical components can be produced with only first order diffraction and with a very high efficiency (>0.98). It is shown that these diffraction gratings are potentially useful in projection displays with a high brightness and energy efficiency

• Journal of the Korean Society of Visualization
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• v.7 no.1
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• pp.21-28
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• 2009

The study of swirling flow is of technical and scientific interest because it has an internal recirculation field, and its tangential velocity is related to the curvature of streamline. The fluid flow for tubes and elbow of heat exchangers has been studied largely through experiments and numerical methods, but studies about swirling flow have been insufficient. Using the particle image velocimetry(PTV) method, this study found the time averaged velocity distribution with swirl and without swirl along longitude sections and the results appear to be physically reasonable. In addition, streamwise mean velocity distribution was compares with that of other. Furthermore, other experimental investigation was performed to study the characteristics of turbulent water flow in a horizontal circular tube by using liquid crystal. 2D PIV technique is employed for velocity measurement and liquid crystal is used for heat transfer experiments in water. Temperature visualization was made quantitatively by calibrating the colour of the liquid crystal versus temperature using various approaches.

• Proceedings of the KSME Conference
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• 2001.06d
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• pp.509-515
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• 2001

In a square cavity, the flow phenomena in the surrounding of the bubble attached at the upper cooled solid wall were studied by using a thermo-sensitive liquid-crystal tracer and image processing techniques. This method offers the advantage of measuring the entire flow field in a selected plane within the fluid at a given instant of time in contrast to point by point method like T/C. Quantitative data of the temperature were obtained by applying a colour-image-processing to the. visualized image. As the growing of a bubble, In a bubble size appears the flow phenomena which the direction of flow is reversed in the entire temperature and flow field. The observed phenomena are described with regard to thermocapillary convection.

• Journal of Information Display
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• v.4 no.1
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• pp.9-13
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• 2003

An overview of author activity in the area diffractive LCDs are given. The formation of colour spectrum DL CDs is made by switchable phase diffraction gratings created in a LC layer due to using of comb-like electrodes. The offered DLCDs functionate without polarizes, have high contrast and spectral of pure colours, broad viewing ngles. The existing production equipment can be adapted to manufacturing of DLCD without considerable alterations.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.12
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• pp.1879-1886
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• 2001

n a enclosed square cavity occurred B nard convection, the flow phenomena in the surrounding of the bubble attached at the upper cooled solid wall were studied by using a thermo-sensitive liquid-crystal tracer and image processing techniques. This method offers the advantage of measuring the entire flow field in a selected plane within the fluid at a given instant of time in contrast to point by point method like T/C. Quantitative data of the temperature were obtained by applying a colour-image-processing to the visualized image. As the flowing in a bubble, In a bubble size appears the flow phenomena which the direction of flow is reversed in the entire temperature and flow field. The observed phenomena are described with regard to the thermocapillary convection.

• Journal of Technologic Dentistry
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• v.35 no.3
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• pp.185-192
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• 2013

Purpose: The aim of this study was to compare with color reproducibility of the coating method and dipping method using a colour liquid. Methods: Two groups of square-shaped specimens ($10mm{\times}10mm$ in diameter, 1.5mm thickness) were prepared for analysis(n=15/group). The CM(Coating Method) group was fabricated as full zirconia specimens with the coating coloring method and Group DM(Dipping Method) was prepared as specimens of 0.7 mm-thick zirconia plate using the dipping coloring method and veneered with 0.8mm-thick porcelain. Color parameters were measured with ShadeEye $NCC^{(R)}$ spectrophotometer and color differences were calculated using the equation ${\Delta}E^*= \{({\Delta}L^*)^2+({\Delta}a^*)^2+({\Delta}b^*)^2\}^{1/2}$. Non-parametric statistical methods, the Mann-Whitney test, and the Kruskal-Wallis test were used to analyze the data. Type one error rate was set at 0.05. Results: Color difference values larger than 7 were observed between specimens with the coating method and the dipping method, which were detectable difference in a clinical setting. Conclusion: Cautious application of the coating coloring method in a clinical setting and further researches to standardize the coating method are needed.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.509-512
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• 2008

In this study, colorimetric characteristics of a 2.2-inch iriver MP4 based upon OLED was evaluated and compared with another MP4 based upon Liquid Crystal Display (LCD). According to IEC61966-4, the two displays were tested in terms of spectral power distribution, tone reproduction curve (TRC), luminance, contrast, correlated color temperature, 2D color gamut and spatial uniformity. Consequently, the OLED showed better performance for the first four aspects but a similar quality was observed for the rest.

• Fashion & Textile Research Journal
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• v.11 no.5
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• pp.818-826
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• 2009

Dyeability of microbial violacein produced from Chromobacterum violaceum CV107 on to multifiber fabrics has been studied. The bluish-purple colourants were produced by cultivation of Chromobacterum violaceum using LB liquid medium for 2 days. The colourant was extracted with 80% acetone and identified as violacein by LC/MS analysis. The violacein could be dyed on not only natural fibers such as Cotton, Silk and Wool but also synthetic fibers such as Diacetate, Triacetate, Creslan 61 and Nylon 66. Maximum K/S values were shown at 540-580 nm according to different fiber with color appearance of purple or blue. An optimum pH and temperature under dyeing condition were 10 and $70^{\circ}C$, respectively. Any mordants were not improved colour density and quality on various fabrics. From this studies, pigments produced microbe have a high potentials for natural dyeing on fabrics. Finally, development of new colourants from microbe has made a possible change for new dyeing field in respects of eco-friend and repeatability of natural dyeing for apparels.

• Journal of Plant Biotechnology
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• v.35 no.1
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• pp.81-86
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• 2008

This study describes conditions for plant regeneration from protoplasts-derived from embryogenic callus of satsuma mandarin. Plants were generated via somatic embryogenesis. Protoplasts isolated directly from nucellar callus induced from immature ovule of satsuma mandarin cv. Okitsu (Citrus unshiu Marc.) were cultured in 0.6M $BH_3$ medium. Cell division and plating efficiency were affected by protoplast culture method. The liquid over solid method was the most effective for formation of microcalli. Most of microcalli grew rapidly and transferred onto embryoid formation medium. Optimum embryoid formation medium was MT medium containing 1.5 g/L malt extract, 0.146 M sucrose and the medium for plantlet regeneration was MS medium containing 0.09M sucrose, 1.0 mg/L $GA_3$. No differences were noticed in growth habits and leaf characters such as shape, thickness, and colour between protoplast-derived plants and nucellar seedlings. This plant regeneration system from protoplasts-derived from embryogenic callus provides an alternative way for producing new scion and rootstock cultivar from citrus species which can not be crossed.