• Journal of the Korean Vacuum Society
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• v.17 no.4
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• pp.365-373
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• 2008

We have succeeded in synthesizing vertically aligned thin multi-walled carbon nanotubes (VA thin-MWCNTs) by a catalytic chemical vapor deposition (CCVD) method onto Fe/Al thin film deposited on a Si wafers using an optimum amount of hydrogen sulfide ($H_2S$) additive. Scanning electron microscope (SEM) images revealed that the as-synthesized CNT arrays were vertically well-oriented perpendicular to the substrate with relatively uniform length. Transmission electron microscope (TEM) observations indicated that the as-grown CNTs were nearly catalyst-free thin-MWCNTs with small outer diameters of less than 10nm. The average wall number is about 5. We suggested a possible growth mechanism of the VA thin-MWCNT arrays. The VA thin-MWCNTs showed a low turn-on electric field of about $1.1\;V/{\mu}m$ at a current density of $0.1\;{\mu}A/cm^2$ and a high emission current density about $2.5\;mA/cm^2$ at a bias field of $2.7\;V/{\mu}m$. Moreover, the VA thin-MWCNTs presented better field emission stability without degradation over 20 hours (h) at the emission current density of about $1\;mA/cm^2$.

• 한국정보디스플레이학회:학술대회논문집
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• 2005.07b
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• pp.1067-1070
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• 2005

A large size flat panel LCD-TV must fulfill different requirements than a desktop LCD-monitor: The contrast must be much larger, the viewing angle should be as wide as possible and the switching times must be shorter to allow moving pictures to be displayed naturally. The "Vertically Aligned" technology is most promising to realize such a product. LC-material development for this technology began at Merck about 10 years ago. New materials based on the 1,1,6,7-tetrafluoroindane skeleton were recently synthesized via ortho-metallation and intramolecular Heck cyclization followed by an oxidative fluorination procedure. The materials offer improved properties over liquid crystals currently employed in flat panel LCD-TVs.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.11 no.6
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• pp.671-677
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• 2018

In this paper, we investigated the vertical alignment characteristics of liquid crystals (LCs) on fluorinated self-assembled monolayers (FSAMs). For comparison, a commercialized homeotropic polyimide (PI) layer was used as an LC alignment layer. We confirmed the successful deposition of FSAMs and the change of FSAMs before and after rubbing treatment through contact angle measurement and atomic force microscopy. The optical transmittance spectrum of the FSAMs is similar to that of the homeotropic PI layer, which is a superior optical characteristic applicable to LC devices. When FSAMs were applied to the vertically aligned (VA) LC cell, uniform and vertical LC alignments were achieved. In addition, the voltage-transmittance characteristic of VA LC cell with FSAMs was superior to that of VA LC cell with the conventional homeotropic PI layers. These results indicate that the FSAMs are suitable as the homeotropic LC alignment layer for enhanced LC devices.

• Journal of the Optical Society of Korea
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• v.20 no.4
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• pp.510-514
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• 2016

The conventional liquid crystal displays (LCDs) have been using optically uniaxial liquid crystal (LC) medium and this often causes a significant image change at oblique viewing angles. We simulated the viewing angle properties of the biaxial nematic (N_b) phase of a bent-core liquid crystal (BLC) and compared the results with the vertically aligned (VA)- and the in-plane switching (IPS)-LCDs. The N_b phase of the BLC showed a smaller transmittance at the dark state as well as a greater contrast ratio at wide viewing angle. The viewing angle property of the N_b-mode without any compensation film was slightly superior to the IPS-mode with the compensation films eliminating the decross of the polarizers at oblique viewing angle.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.186-186
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• 2009

Most liquid crystal display modes, including the twisted nematic (TN) $mode^1$, the in-plane switching (IPS) $mode^2$, the fringe field switching (FFS) $mode^3$, and the vertically aligned (VA) $mode^4$ are based on either a horizontal or a vertical alignment. However, for some applications, such as no-bias-bend (NBB) pi cell or bistable bend-splay display, an intermediate pretilt angle is essential$^5$. NBB pi cells have been a focus of interest because of their fast response time; however, the reliable control of the intermediate pretilt angle of liquid crystals that is required for the fabrication of NBB pi cells is challenging. The controllable pre-tilt angle of liquid crystals was investigated using a blend of horizontal and vertical polyimide prepared by a rubbing method. Various pretilt angles in the range from 0^{\circ}$ to 90^{\circ}$ were achieved as a function of the vertical polyimide content. We observed uniform liquid crystal alignment on the rubbing-treated blended polyimide layer. A NBB pi cell with an intermediate pretilt angle of 47.8^{\circ}$ was manufactured. This cell had no initial bias voltage and a low threshold voltage, which indicates that it has low power consumption. In addition, the response time of the NBB pi cell was rapid.