• 한국정보디스플레이학회:학술대회논문집
• /
• 2003.07a
• /
• pp.500-503
• /
• 2003

We studied the nematic liquid crystal (NLC) aligning capabilities by the UV alignment method on a a-C:H thin film surface. A good LC alignment by UV exposure on the a-C.H thin film surface at 200 ${\AA}$ of layer thickness was achieved. Also, a good LC alignment by the UV alignment method on the a-C:H thin film surface was observed at annealing temperature of 180 $^{\circ}C$. However, the alignment defect of the NLC was observed above annealing temperature of 200 $^{\circ}C$. Consequently, the good thermal stability of LC alignment by the UV alignment method on the a-C:H thin film surface can be achieved.

• Journal of Information Display
• /
• v.6 no.1
• /
• pp.1-7
• /
• 2005

We propose new fabrication methods of a pixel-isolated liquid crystal (LC) structure for flexible display applications. In the LC structure fabricated through the proposed method, the patterned interpixel walls for sustaining the cell thickness are supported by the solidified polymer layer through anisotropic phase separation of LC/polymer composite, causing the alignment of the LC molecules to have very good mechanical stability against external pressure. In addition, we show that such pixel-isolating walls can be made by the stamping method which can be applied to fabricate large size plastic LCDs by roll-to-roll processing.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2000.01a
• /
• pp.9-10
• /
• 2000

The wide viewing angle and fast response time characteristics of negative dielectric anisotropy nematic liquid crystal (NLC) using a novel vertical-alignment (VA) - 1/4 ${\pi}$ cell mode on a homeotropic alignment layer were investigated. Good voltage-transmittance curves and low driving voltage using the novel VA - 1/4 ${\pi}$ cell mode without a negative compensation film were obtained. The iso-viewing angle characteristics of NLC using the novel VA - 1/4 ${\pi}$ cell mode without a negative compensation film can be achieved. The fast response time of 24.4 ms in NLC was successfully measured. The iso-viewing angle, fast response time, and low driving voltage characteristics using the novel VA - 1/4 ${\pi}$ cell mode can be achieved.

• Transactions on Electrical and Electronic Materials
• /
• v.7 no.6
• /
• pp.297-300
• /
• 2006

The response surface modeling of the pretilt angle control using ion-beam (IB) alignment on nitrogen doped diamond-like carbon (NDLC) thin film layer is investigated. This modeling is used to analyze the variation of the pretilt angle under various process conditions. IB exposure angle and IB exposure time are considered as input factors. The analysis of variance technique is settled to analyze the statistical significance, and effect plots are also investigated to examine the relationships between the process parameters and the response. The model can allow us to reliably predict the pretilt angle with respect to the varying process conditions.

• Journal of the Optical Society of Korea
• /
• v.19 no.4
• /
• pp.346-350
• /
• 2015

We report a measurement of the effective refractive index of a nematic liquid crystal (NLC) inside a Fabry-Perot (FP) etalon according to the applied electric fields. The effective refractive index of the NLC depends on the intensity of the applied electric field. A wavelength-swept laser with a polygon-scanner-based wavelength filter is used as a wide-band optical source to measure the effective refractive index of the NLC. The bandwidth of the optical source is greater than 90 nm around 1300 nm. The fabricated NLC FP etalon consists of glass substrates, gold layers as the electrodes with highly reflective surfaces, polyimide layers as the planar alignment layers, and an LC layer. Furthermore, we measured the Freedericksz transition voltages for three types of NLC FP etalons having thicknesses of $30.6{\mu}m$, $55.4{\mu}m$, and $108.8{\mu}m$. The Freedericksz transition voltages in the three cases are nearly equal. The measured effective refractive indices in the three cases decreased from 1.67 to 1.51 as the applied electric field intensity was increased. Beyond the threshold electric field, the effective refractive indices quickly decreased and eventually saturated at a value of 1.51 for all cases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.04a
• /
• pp.42-42
• /
• 2008

Considerable attention has been focused on the applications of flexible liquid crystal (LC)-based displays because of their many potential advantages, such as portability, durability, light weight, thin packaging, flexibility, and low power consumption. To develop flexible LCDs that are capable of delivering high-quality moving images, like conventional glass-substrate LCDs, the LC device structure must have a stable alignment layer of LC molecules, concurrently support uniform cell gaps, and tightly bind two flexible substrates under external tension. However, stable LC molecular alignment has not been achieved because of the layerless LC alignment, and consequently high-quality images cannot be guaranteed. To solve these critical problems, we have proposed a PDMS pixel-wall based bonding method via the IB irradiation was developed for fasten the two substrates together strongly and maintain uniform cell gaps. The effect of the IB irradiation on PDMS with PI surface was also evaluated by side structure configuration and a result of x-ray photoelectron spectroscopic analysis of PDMS interlayer as a function of binder with substrates. large number of PDMS pixel-walls are tightly fastened to the surface of each flexible substrate and could maintain a constant cell gap between the LC molecules without using any other epoxy or polymer. To enhance the electro-optical performance of the LC device, we applied an alignment method that creates pretilt angle on the PI surface via ion beam irradiation. Using this approach, our flexible LCDs have a contrast ratio of 132:1 and a response time of about 15 ms, resulting in highly reliable electro-optical performance in the bent state, comparable to that of glass-substrate LCDs.

• Polymer(Korea)
• /
• v.28 no.4
• /
• pp.298-304
• /
• 2004

We fabricated a polymer dispersed liquid crystal (PDLC) cell using LC with negative dielectric anisotropy and UV curable monomer exhibiting transparent state initially (called normally transparent (NT)) and studied the electro-optic characteristics. The NT PDLC cell made with the ratio of LC : monomer = 70/30 wt%, curing temperature of 20 $^{\circ}C$ and strong UV intensity of 198 ㎽/$\textrm{cm}^2$ had high contrast ratio and showed good electro-optic characteristics. In this condition, LC is aligned vertically on the substrate due to the vertical alignment layer and the polymer made with the UV exposure does not influence the alignment of the LC much. Therefore, the transmittance at the zero voltage is very high and the scattering state of the cell is good after applying the voltage because LC with negative dielectric anisotropy tries to align perpendicular to the field. And also, the NT PDLC cell showed better viewing angle characteristics than that in the normally scattering (NS) PDLC.

• Proceedings of the KIEE Conference
• /
• 2001.11a
• /
• pp.182-185
• /
• 2001

A photoalignment material based N-(phenyl)maileimide were synthesized and the liquid crystal (LC) aligning capabilities on the photopolymer layer were studied. A goof LC alignment with UV exposure on the PM15CA(N-(phenyl)maileimide with 5-carbon chain cinnamoyl group) can be obtained However, the LC alignment defects were observed on the PM13CA (N-(phenyl)maileimide with 3-carbon cam cinnamoyl group) and PMIF (N-(Phenyl)maileimide including fluoro cinnamoyl group). Also, the good LC alignment with UV exposure on the PM15CA surface was observed at until $150^{\circ}C$ of annealing temperature. The LC aliging ability on the photopolymer layer based N-(phenyl)maleimide depends on the side chin length of photopolymer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2009.04a
• /
• pp.59-60
• /
• 2009

The conventional in-plane field driven-vertical alignment display (VA-IPS) shows fast response time but transmittance shows very low and operating voltage is very high. In this paper, we studies electro-optical properties of the novel in-plane field driven vertical alignment device which has two transistors on array part and common electrode on CF substrate with dielectric layer. The device shows fast response time and high transmittance.

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