• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.430-430
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• 2007

In this study, the nematic liquid crystal (NLC) alignment effects treated on the ZnO thin film layers using ion beam irradiation were successfully studied for the first time. The ZnO thin films were deposited on indium-tin-oxide (ITO) coated glass substrates by rf-sputter and The ZnO thin films were deposited at the three kinds of rf power. The used DuoPIGatron type ion beam system, which can be advantageous in a large area with high density plasma generation. The ion beam parameters were as follows: energy of 1800 eV, exposure time of 1 min and ion beam current of $4\;mA/cm^2$ at exposure angles of $15^{\circ}$, $30^{\circ}$, $45^{\circ}$, and $60^{\circ}$. The homogeneous and homeotropic LC aligning capabilities treated on the ZnO thin film surface with ion beam exposure of $45^{\circ}$ for 1 min can be achieved. The low pretilt angle for a NLC treated on the ZnO thin film surface with ion beam irradiation for all incident angles was measured. The good LC alignment treated on the ZnO thin film with ion beam exposure at rf power of 150 W can be measure. For identifying surfaces topography of the ZnO thin films, atomic force microscopy (AFM) was introduced. After ion beam irradiation, test samples were fabricated in an anti-parallel configuration with a cell gap of $60{\mu}m$.

• Polymer(Korea)
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• v.34 no.1
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• pp.32-37
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• 2010

Photo-alignment property of groove patterned surface prepared from blend of poly (vinyl cinnamate) (PVCi) and oligomeric dicinnamate was investigated for the application for alignment layer of liquid crystal display. The study of the photoreaction kinetics using UV-vis spectrum with the irradiation time showed that the reaction rate of oligomeric cinnamate was enhanced compared to that of PVCi. Blend where PVCi was main component showed a slight improvement on the photoreaction rate. It was unable to obtain groove patterned surface only using oligomeric cinnamate itself owing to the high crystalline character. However, blending of PVCi made it possible to obtain clear surface pattern. Molecular orientation could be confirmed from the polar plot data. It can be suggested that blend of oligomeric cinnamate and polymeric cinnamate is promising material for the photoalignment layer.

• Polymer(Korea)
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• v.33 no.5
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• pp.496-500
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• 2009

Optically compensated bend liquid crystal display (OCB-LCD) has many application fields owing to its fast response time and wide viewing angle. However, in order to operate the OCB-LCD in bend state, this device needs quick transitions from the initial splay state to bend state. Unlike conventional approach using transient high voltage for the transition, the OCB-LCD with high surface tilt angle, which was achieved by polymerization of UV curable reactive mesogen monomer under certain voltage, was manufactured and the cell showed bend state initially. Electro-optic and electrical characteristics of the cell were analyzed. The cell shows a fast response time owing to high surface pretilt angle and very low residual DC less than 0.1 V although another polymer layer is formed above polymer alignment layers.

• 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