• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.05a
• /
• pp.206-209
• /
• 2004

We investigated response characteristics of liquid crystal display(LCD) with different operating mode of nematic liquid crystals (NLCs) such as $45^{\circ}$twist nematic (TN), $67.3^{\circ}$TN and ECB(electrical controlled birefringence) on a rubbed polyimide (PI) surface. The three kinds of LCD operating mode obtain stable EO performance. Low transmittances of the $45^{\circ}$TN and $67.3^{\circ}$TN cell on the rubbed PI surface were achieved by using low cell gap d. The fast response time of ECB cell among the three kinds of LCD operating mode was measured.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.571-574
• /
• 2003

Three ring type liquid crystalline compounds having 4-alklycyclohexyl group, 1,2-difluorobenzene and phenylisothiocyanate moieties as main skeleton were designed to have negative dielectricity. However, the compounds with 2,3,2'-trifluoro-3'-isothiocyanated biphenylcyclohexane core did not exhibit the nematic liquid crystalline phase because of two conformers by interaction of isothiocyanate and adjacent fluorine atoms. Also, 4-alkyl-2,2',3'-trifluoro-3-isothiocyanated biphenylcyclohexane core was designed expecting to have uniform conformers of isothiocyanate group. In the course of developing polyimides for VA mode LCD, we synthesized alkyl-3,5-diaminobenzene efficiently with various length of alkyl chains from commercially available di-t-butyl malonate and 3,5-dinitrobenzoyl chloride as starting material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2004.11a
• /
• pp.563-566
• /
• 2004

We have studied a electrically controlled birefringence (ECB) mode for field sequential liquid crystal display (FSLCD). We measured response time of the ECB mode. The ECB mode exhibiting fast response time, high transmittance, low operating voltage and adequate viewing angle. The positive liquid crystal (LC) is better than negative LC on dielectric anisotropy, birefringence and rotational viscosity. So that, the ECB mode is one of strongest candidate for FSLCD application.

• Journal of Information Display
• /
• v.11 no.3
• /
• pp.119-122
• /
• 2010

This paper proposes a transflective liquid crystal display (LCD) in a whole-pixel switchable configuration with a high aperture ratio using an electrophoretic particle layer (EPL). The switchable transflective LCD consisted of the liquid crystal layer as a display unit, and the EPL as a switchable mirror. The switching of the EPL between the mirror for the reflective mode and the transparency for the transmissive mode was performed by controlling electrophoretic nanoparticles with an applied voltage in a three-electrode structure. The single pixel was used as the whole transmissive or reflective mode that corresponded to the switchable EPL mirror. Thus, a transflective LCD with a high aperture ratio was obtained.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.312-313
• /
• 2008

A transflective liquid crystal displays associated with fringe field switching (FFS) mode of new concept is proposed. The device utilizes unique characteristic of the FFS mode in which the rotation angle of LC director is strongly dependent on electrode position in on state. We use the liquid crystal with negative dielectric anisotropy. Also we are look for optimized electrode size and the optimization of pixel electrode width and distance between them, the LC director could rotate about $22.5^{\circ}$ and $45^{\circ}$ depending on electrode positions. Consequently, we get high transmittance and high reflection on the optimized electrode condition. Respectively, a high image quality transflective display with single gap and single gamma characteristics realized.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.05a
• /
• pp.181-184
• /
• 2005

In this paper, we have improved a novel fast response time liquid crystal operating mode using tilt angle in the unique condition by hot-plate equipment. The new control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by Hot-plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. Especially, the low LC tilt angle of positive type NLC (${\Delta}n$>0) on the rubbed homeotropic PI surface by increasing temperature and time was measured. The EO characteristics of the high tilted OCB(HTOCB) mode using control of tilt angle on the homeotropic surface than that of conventional OCB cell can be improved. We suggest that the developed the HTOCB cell using control of tilt angle on the homeotropic surface is a promising technique for the achievement of a fast response time and a high contrast ratio.

• Journal of Information Display
• /
• v.1 no.1
• /
• pp.9-13
• /
• 2000

In liquid crystal displays, the display mode that represents initial liquid crystal alignment and method of applying voltage, mainly determines the image quality of display. Recently we have developed the fringe-field switching (FFS) mode exhibiting high image quality. In this paper, a pixel concept, manufacturing process, materials, and electro-optic characteristics of the FFS mode comparing with conventional in-plane switching mode, and its possible application to reflective type are discussed.

• Journal of the Optical Society of Korea
• /
• v.20 no.1
• /
• pp.156-164
• /
• 2016

We demonstrated the pretilt angle effect on the viewing angle properties of a single-domain fringe-field switching (FFS) liquid crystal (LC) mode. By performing the Póincare sphere analysis, we investigated, in detail, the origin of the viewing angle asymmetry that exists in the single-domain FFS LC mode both in the field-on and field-off states. Using this analysis, we confirmed that the pretilt angle reduces the viewing angle symmetry in the single-domain FFS LC mode. Finally, we examined the effect of a zero pretilt angle on the viewing angle symmetry by evaluating real single-domain FFS LC cells.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.5
• /
• pp.530-535
• /
• 2004

We have studied 90$^{\circ}$ twisted nematic mode switching by fringe electric field(F-TN mode) using a liquid crystal (LC) with negative dielectric anisotropy. In the device, two polarizers are parallel each other, electrodes exist only on bottom substrate, and one of rubbing direction is coincident with polarizer axis. Therefore, the cell shows a black state before a voltage is applied. With a bias voltage generating fringe-electric field, the LC twists perpendicular to fringe electric field such that the LCs are almost homogeneously aligned except near the bottom surface since the negative type of the LC is used. Consequently, the new device exhibits much wider viewing angle than that of the conventional TN mode due to in-plane switching and relatively high transmittance since the LC director above whole electrode area aligns parallel to the polarizer axis.

• Journal of Information Display
• /
• v.6 no.2
• /
• pp.1-6
• /
• 2005

We demonstrated stability-enhanced liquid crystal (LC) displays using pixel-isolated LC mode in which LC molecules are isolated in pixel by horizontal polymer layer and vertical polymer wall. The device shows good electro-optic properties against external point or bending pressure due to the polymer structures. The polymer wall acts as supporting structure from mechanical pressure and prevents the cell gap from bending. Moreover, the polymer layer acts as an adhesive to ensure a tight attachment of the two substrates. We present herein various methods for producing polymer structures by using an anisotropic phase separation from LC and polymer composites or patterned micro-structures for stable flexible liquid crystal displays.