• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.839-842
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• 2004

We present a fast-switching electro-optical device based on flexoelectro-optic effect in short pitch cholesterics oriented in uniform lying helix texture. The device has two operating modes: amplitude and phase modulation mode. The amplitude modulation mode is a fast in-plane switching of the device optic axis that enables to achieve a high percent of modulation of the transmitted light intensity whereas the phase mode gives a continuous change of the refractive index and thus of the phase shift of the transmitted light. By using a small concentration of diacrylate monomer and selecting the illumination conditions we have been able to create a inhomogeneous polymeric network mostly localized at both substrate surfaces and stabilize the two switching modes.

• Journal of Korea Multimedia Society
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• v.9 no.8
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• pp.963-970
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• 2006

In this paper, we proposed a motion picture processor for using low-cost color super twisted nematic liquid crystal display(CSTN-LCD). The proposed processor apply a new driving scheme using SFP(Subgroup Frame Pattern), so we extends gray scale and eliminates flicker phenomenon. In addition, we apply the BFI (Black Field Insertion) to the design compensated for response time of a LC (Liquid Crystal). We use an edge enhancement and interpolation method to improve image quality of motion picture. The hardware architecture of proposed processor has been implemented and verified on a prototype FPGA board. The proposed method can be used in the display devices such as PDA(Personal Digital Assistants), mobile phone, and PMP(Portable Multimedia Player).

• Journal of Korean Vacuum Science & Technology
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• v.6 no.3
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• pp.126-132
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• 2002

The origin of image-sticking in metal-insulator-metal type thin-film diode liquid crystal displays(TFD-LCDs) is the asymmetric current-voltage(I-V) characteristic of TFD element. We developed that TFD-LCDs have reduced-image-sticking. Tantalum pentoxide(Ta$_2$O$\sub$5/) is a candidate for use in metal-insulator-metal(MIM) capacitors in switching devices for active-matrix liquid crystal displays(AM-LCDs). High quality Ta$_2$O$\sub$5/ thin films have been obtained from anodizing method. We fabricated a TFD element using Ta$_2$O$\sub$5/ films which had perfect current-voltage symmetry characteristics. We applied novel process technologies which were postannealed whole TFD element instead of conventional annealing to the fabrication. One-Time Post-Annealing(OPTA) heat treatment process was introduced to reduce the asymmetry and shift of the I-V characteristics, respectively. OPTA means that the whole layers of lower metal, insulator, and upper metal are annealed at one time. Futhermore, in this paper, we discussed the effects of top-electrode metals and annealing conditions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.6
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• pp.501-509
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• 2003

We have designed transflective liquid crystal display(LCD) associated with in-plane switching of a LC director driven by fringe-field, unlike other LCD mode. Reflective area consists of a λ/2 compensation film and a LC cell with retardation value(dΔn) of λ/4 with their optic axes making an angle of 15$^{\circ}$ and 75$^{\circ}$ against polarizer, respectively. In the transmissive area, top and bottom polarizers are parallel each other, an LC has a dΔn of λ/2, and another λ/2 compensation film is inserted between the LC cell and bottom polarizer. With the configuration, both devices show dark state initially. When an incident light is 550nm, the device shows wide-viewing-angle characteristics such that in the reflective area the contrast ratio target than 5 exists up to 55$^{\circ}$ of polar angle in all directions and in transmissive area it exists about 100$^{\circ}$ in vortical direction and 110$^{\circ}$ in horizontal direction.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.241.2-241.2
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• 2014

We present highly transparent liquid crystal displays (LCDs) using hybrid films based on carbon nanomaterials, metal grid, and indium-tin-oxide (ITO) grid. Carbon based nanomaterials are used as transparent electrodes because of high transmittance. Despite of their high transmittance they have relatively high sheet resistance. To solve this problem, we applied grid and made hybrid conductive films based on carbon nanomaterials. Conventional photolithography processes were used to make a grid pattern of metal and ITO. To fabricate transparent conductive films, carbon nanotube (CNT) ink was spin coated on the grid pattern. The transparency of the conductive film was controlled by shape and size of the grid pattern and the thickness of CNT films. The optical transmittance of CNT-based hybrid films is 92.2% and sheet resistance is also reduced to $168{\Omega}/square$. These substrates were used for the fabrication of typical twisted nematic (TN) LCD cells. From the characteristics of LCD devices such as transmittance, operating voltage, voltage holding ratio our devices were comparable to those of pristine ITO substrates. The result shows that the hybrid conductive films based on carbon nanomaterials could be alternative of ITO for the highly transparent LCDs.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1220-1222
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• 2004

We developed a new device structure using anisotropic phase separation from liquid crystal (LC) and polymer composite materials using UV intensity variation and polymer wetting properties. In the device, the LC molecules are isolated in pixels where LCs are surrounded by the inter-pixel vertical polymer walls and the horizontal polymer films on the upper substrate. These devices show very good mechanical stability against external pressure. The electro-optic characteristics and the mechanical stability of the devices are discussed in view of the flexible display applications.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.300-300
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• 2008

In this study, the advanced DuoPIGatron-type ion beam (IB) system was applied to inorganic thin film for aligning liquid crystal (LC). LC alignment on $Ta_2O_5$ via IB irradiation was embodied. As a result of IB irradiation, the homogeneously aligned liquid crystal display (LCD) on $Ta_2O_5$ was observed with low pretilt angles. The $Ta_2O_5$ were deposited on indium-tin-oxide coated Coming 1737 glass substrates by rf magnetron sputtering at $200^{\circ}C$. The deposition process resulted in forming very uniform thin film on glass substrates without any defects. To confirm the application of the inorganic alignment on modem display optical devices, we fabricated twisted nematic LCD and measured optical property and response time. As a result of the experiment, the electro optical characteristics of the LCD fabricated by using IB irradiation on $Ta_2O_5$ alignment layer were similar with the other LCD fabricated by using rubbing process.

• Korean Journal of Optics and Photonics
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• v.20 no.4
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• pp.241-248
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• 2009

We suggest a new method to determine the off-alignment error of the composite film, together with in-plane($R_{in}$) and out-of-plane retardation($R_{th}$) of the compensation film, simultaneously. The composite film consists of a polarizing film and a compensation film for improvement of viewing angle of a liquid crystal display. We regarded the compensation film as o-plate with its optic axis along an arbitrary direction. By using an extended Jones matrix method, the polarization characteristics of the composite film are examined. The calculated Fourier constants, ($\alpha$, $\beta$) curves of the composite film as the azimuth angle is varied at the incident angles of $0^{\circ}$ and $50^{\circ}$, respectively, are used to determine the axis misalignment, the tilt angle and the azimuth angle of the compensation film by adopting the linear regressional analysis technique. Since this method can be applied for the inspection of the composite film even after laminating the polarizing film and the compensation film, it will be useful for simplifying the manufacturing process and reducing the production cost of liquid crystal display panels.

• Current Optics and Photonics
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• v.3 no.1
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• pp.66-71
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• 2019

Application of liquid crystal (LC) materials to a flexible device is challenging because the bending of LC displays easily causes change in thickness of the LC layer and orientation of LCs, resulting in deterioration in a displayed image quality. In this work, we demonstrate a prototype device combining a flexible polymer substrate and an optically isotropic LC-polymer composite in which the device consists of interdigitated in-plane switching electrodes deposited on a flexible colorless polyimide substrate and the composite consisting of nano-sized LC droplets in a polymer matrix. The device can keep good electro-optic characteristics even when it is in a bending state because the LC orientation is not disturbed in both voltage-off and -on states. The proposed device shows a high potential to be applicable for future flexible LC devices.

• Proceedings of the KIEE Conference
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• 1999.07d
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• pp.1809-1811
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• 1999

In recent years, attempts have been made to greatly improve the display quality of active-matrix liquid crystal display devices, and many techniques have been proposed to solve such problems as gate delay, feed-through voltage and image sticking. Gate delay is one of the biggest limiting factors for large-screen-size, high-resolution thin-film transistor liquid crystal display (TFT/LCD) design. Many driving method proposed for TFT/LCD progress. Thus we developed gate driving signal generator. Since Pixel-Design Array Simulation Tool (PDAST) can simulate the gate, data and pixel voltages of a certain pixel on TFT array at any time and at any location on an array, the effect of the driving signals of gate lines on the pixel operations can be effectively analyzed.