LC Technology

Session 1B: LC Technology
Monday, Feb. 13, 2017  14:20-15:40
15:10 - 15:25 Paper No.  2017-MON-S0301-O001
Tae-Hoon Choi
Fast Switching of a Homogeneously Aligned Liquid Crystal Cell by Two-Dimensional Virtual Confinement

We demonstrate that we can increase the switching speed by several times through two-dimensional virtual confinement in an IPS cell and an FFS cell. In addition to a very short response time, the device exhibits several outstanding features, such as a wide viewing angle, small color shift, simple drive scheme, etc.

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15:25 - 15:40 Paper No.  2017-MON-S0301-O002
Chih-Hsuan Lin
Broad and highly reflective photonic bandgap structure in the infrared region in an enantiomorphic template with a longitudinal pitch gradient

For fabricating an Infrared (IR) reflector with high-quality, this study employs the washing-out/refilling technique. To fabricate a CLC template film which can reflect an IR wide-band with right- or left-circular polarization, several steps including injecting a curable left- or right-handed CLC mixture into a CLC template with a longitudinal pitch gradient in the refilling stage and then curingusing UV light irradiation, removing the unreacted meogens, and refilling with NLCs are performed [3,4]. Stacking these two refilled CLC template with opposite chiralities(enantiomorphic template) results in an IR reflector which can reflect both right-handed and left-handed circularly polarized light (CPL) in a wide IR range, as shown in Fig. 1.The IR reflector reported in this study can reflect more than 70% of solar IR energy and the reflective IR bandwidth are broaden up to 750 nm which almost covers the primary IR region of the solar radiation.

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LC Technology

Session 4B: LC Technology
Tuesday, Feb. 14, 2017  10:40-12:05
11:05 - 11:20 Paper No.  2017-TUE-S0304-O001
Ray Chou
Cutting-edge LC materials enabling performance upgrade for TV applications

PS-VA (Polymer-Stabilized VA) is one of the mainstream technologies for TV display application. The market trend was once pursuing fast switching time to cope with 3D fever. However, during recent years, the demand of 3D is shrinking while the trend of high resolution is more and more prominent. Transmittance of the display is one of the key properties which is directly impacted so that the demand of high transmittance display and corresponding materials becomes stronger and stronger. We will present Merck’s latest LC materials and RMs development status for the advanced TV applications.

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11:20 - 11:35 Paper No.  2017-TUE-S0304-O002
Da-Som Yoon
A fabrication of polymer stabilized cholesteric liquid crystal displays with good contrast ratio and color properties

Cholesteric liquid crystal displays are suitable for color e-papers because of low power consumption and good color characteristics. To stabilize the cell gap of flexible cholesteric LCD based on plastic substrate, polymer wall formation in the LC layer using PIPS (polymerization induced phase separation) method has been developed. Planar state is in general more stable than focal conic state in cholesteric LCDs. If an electrically uncontrollable LC area with absence of electrodes in passive matrix cholesteric LCDs has planar texture, it causes decrease of contrast ratio. We tried to make the cholesteric LCD with more stable focal conic state than planar state by formulating an appropriate monomer-liquid crystal mixture.

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11:35 - 11:50 Paper No.  2017-TUE-S0304-O003
Rijeesh Kizhakidathazhath
Weak anchoring interface inducing acrylate copolymer designs for high-performance polymer stabilized blue phase liquid crystal displays

Weak anchoring of Liquid crystal is highly desired in liquid crystal display devices because it decreases the switching voltage and improves display performances. The creation of such liquid crystal systems is an important goal for the next generation displays including polymer-stabilized blue phases (PSBPs). However, achieving weak anchoring in practice is proved to be difficult. Here, we report a new method of weak anchoring for LCs in contact with uniquely designed non-liquid crystalline side-chain copolymers, featuring both mesogenic and non-mesogenic units. The mesogenic pendant of polymers enhances the compatibility with the LC molecules, while the non-mesogenic part reduces the possible azimuthal anchoring energy of the mesogenic side-chain on LCs. LCs in a glass plate cell coated with these side-chain non-liquid crystalline copolymers showed anchoring transitions and weak anchoring interface formation at precise temperatures. The weak anchoring nature of LCs on copolymer surfaces was confirmed by their easy response to an applied magnetic field. Interestingly, significant decrease of operating voltage was achieved (~ 25 %) with this method in PSBPs while preserving the electro-optic performance of LCs at the same time. We therefore suggest that this unique method of producing weak anchoring might find application in the next generation liquid crystal displays.

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11:50 - 12:05 Paper No.  2017-TUE-S0304-O004
Jin-Wei Lin
Fiber-optic random laser based on Liquid crystal

Random lasers are featured with low spatial coherence duo to multiple scattering in resonant. We used partially ordered liquid crystal as scattering medium and fabricated a liquid crystal based fiber random laser. The speckle contrast from random laser was below 0.04.As a result, we fabricated a speckle-free light source.

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LC Technology

Poster Session
Tuesday, Feb. 14, 2017  16:10-18:10
Paper No.  2017-TUE-P0301-P001
Sin-An Lin
Tunable reflective filter in full visible spectrum based on liquid crystal cladded guided-mode resonant

This work proposes a tunable reflective guided-mode resonant (GMR) filter that incorporates a 90o twisted nematic liquid crystal (TNLC). The GMR grating acts as an optical resonator that reflects strongly at the resonance wavelength and as an alignment layer for LC. The 90o TNLC functions as an achromic polarization rotator that alters the polarization of incident light. The resonance wavelength and reflectance of such a filter can be controlled by setting the angle of incidence and driving the 90o TNLC, respectively. The designed filter exhibits a very large spectral shift in resonance wavelength from 710 to 430 nm, which covers the entire visible spectrum. The transmittance can be tuned to within 10 V at various resonance wavelengths. The hybrid GMR - LC filter is compact, has a simple design, and is easy to fabricated. It can therefore be used in practical applications.

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Paper No.  2017-TUE-P0301-P002
Moon Jong Han
Fabrication of ordered conducting polymer by evaporation method

The advantages of organic semiconductor are simple, solution-based processing which allows for unconventional deposition methods such as inkjet, screen, and micro-contact printing. For Poly(3-hexylthiophene) (P3HT), it is self-assembled in trichloro-benzene (TCB) solution and exhibits liquid crystal. In such systems, highly ordered and oriented films are important to electronic applications in which direction of electron transfer is favor of π-π stacking direction. Here, the MIMIC-based on technique is demonstrated, in which we can produce highly ordered large-area semiconducting polymer films assisted by poly(dimethylsiloxane) (PDMS) stamps. The Polarized optical microscopy (POM) exhibits development of birefringence and long-range ordering with mono domain, which induces efficient charge transport through π-π interactions. The desired molecular ordering for organic electronics is investigated by fabrication of organic thin film transistors (OTFTs) under different angles between orientation of conducting polymer and source/drain channel direction, which exhibits relation between charge carrier mobility and π-π stacking direction. The results show that the nucleation and growth of conducting polymer can be controlled by spontaneous swelling method using stamps, which allows the control of orientation, packing density. It suggests insight of the conjugated polymer solution process to generate highly ordered and oriented thin films for high-performance organic electronic devices.

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Paper No.  2017-TUE-P0301-P003
Yun Jeong Cha
Alignment control of lyotropic chromonic liquid crystals by varying shear rates and its application

Lyotropic chromonic liquid crystals (LCLCs) have unique structural characteristics organizing linear aggregation of their plank-shaped molecules in aqueous solution and the structural features produce various potential applications such as electro-optical devices.[1] For the practical applications, a fabrication of well-aligned LCLC film is very important. In present work, we firstly report a simple method to control the orientation of LCLCs in a multi-directional array and its application as an orthogonally patterned alignment layer. To make well-oriented LCLC structures, we adopt a generally used mechanical shearing method such as doctor blade coating[2] but shearing rates was finely regulated. In our system, the aggregation of LCLCs was aligned parallel and perpendicular to the shear direction at a fast and slow shear rate, respectively, which induced by a competition between hydrodynamic effects and self-assembly of molecules. Based on this result, orthogonally patterned LCLC film was formed and it can be used as an alignment layer to guide other guest molecules. Our result can provide a facile way to make multi-directional orientation of soft- and bio-materials in a process of evaporation, which bring potential patterning applications due to their fine structural characteristics.

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Paper No.  2017-TUE-P0301-P004
Seung-Won Oh
Smart window fabricated using liquid crystals doped with push-pull azobenzene

We propose a smart window using polymer-networked liquid crystal doped with push-pull azobenzene. The proposed smart window is switchable between the translucent and transparent states by application of an electric field or by UV irradiation. Switching by UV irradiation is based on the change of the liquid crystal (LC) clearing point by the photo-isomerization effect of push-pull azobenzene. Under sunlight, the smart window can be switched from the translucent to the transparent state by the nematic-isotropic phase transition of the LC domains triggered by trans-cis photo-isomerization of the push-pull azobenzene molecules. When the amount of sunlight is low because of cloud cover or when there is no sunlight at sunset, the smart window rapidly relaxes from its transparent state back to its initial translucent state by the isotropic-nematic phase transition induced by cis-trans back-isomerization of the push-pull azobenzene molecules.

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Paper No.  2017-TUE-P0301-P005
Yu-Jen Wang
An optical image stabilization by manipulating a droplet on a liquid crystal and polymer composite film

We proposed and demonstrated a compensator for optical path variation induced by vibration using a movable liquid lens on liquid crystal and polymer composite film (LCPCF). The optical path variation can be compensated by changing the position of the liquid lens (water droplet). The liquid lens moves because of the distribution of surface wettability of LCPCF induced by electric fields. The changes of surface properties result from electrically tunable orientations of liquid crystal molecules on its surface. The deviation of light in the image system under a handshake vibration can be compensated based on the mechanism of the droplet movement on LCPCF. As a result, the image system under handshake vibrations could keep a clear image. Such a system is so-called optical image stabilization (OIS). The operating principles are introduced and the experiments are performed and discussed. The concept in this paper can also be extended to design other optical components for beam steering function, which modulates the direction of light.

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Paper No.  2017-TUE-P0301-P006
Junji Kobashi
Hologram generation using patterned cholesteric liquid crystals

Cholesteric liquid crystals (ChLCs) show a circular polarization selective reflection band over a wavelength range determined by the ordinary and extraordinary refractive indices (n_o, n_e) and helix pitch (p). Conventionally, research on ChLCs had focused on the control of reflection band, however, the recent discovery that reflected wavefront control is possible has led to research of ChLCs as phase modulators. The geometric phase, or helix phase of ChLCs, is defined by the orientation direction of the LC director on the substrate, and causes a shift in the reflected optical that is twice the change in helix phase. Because 0–2pi modulation of phase is possible, various planar optical elements such as deflectors, lenses, and optical vortex generators have been reported based on this approach. Here, we report a pseudo color hologram using a patterned ChLC. Using the 0–2pi controllability of the optical phase, a hologram can be implemented in ChLCs by appropriately designing the helix phase distribution. Also, the circular polarization selectivity of Bragg reflection is retained regardless of the helix phase; therefore, semi-transparent holograms, that generates an image only when illuminated with circularly polarized light, can be fabricated.

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Paper No.  2017-TUE-P0301-P007
Chao-Ping Pai
Surface plasmon resonance from a nanoantenna array regulated by a high-birefringence liquid crystal

In this study, we demonstrate a hybrid structure consisting of a gold nanoantenna array covered with high-birefringence LC. Based on transmission measurements in the spectrum ranging from the visible to the near-infrared wavelengths, our results suggest that he hybrid plasmonic–photonic resonances in the proposed device can considerably be modified through the refractive index as well as polarization changes upon the application of external voltages to the LC bulk. Noticeably, the hybrid structure enables the control of the spectrum with a large shift in resonance wavelength of the metallic nanoantennas actively by an applied electric field. Our modeling supports the observed results, by assuming that the nanoantenna array leads to two orthogonal easy axes with a finite anchoring energy. In combination of the nanostructured surface with birefringent LC, tunability up to 90 nm is achieved in the visible wavelengths, opening the door towards nanoscale displays or nano-optical switches [1].

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Paper No.  2017-TUE-P0301-P008
Jyun-Cong Lai
Electro-opto-thermal addressing bistable and rewritable display device based on gelator-doped liquid crystal in poly(N-vinylcarbazole) film-coated liquid crystal cell

This paper reports electro-opto- thermal addressing bistable and rewritable display devices based on gelator-doped liquid crystals (LCs) in a poly(N-vinylcarbazole) film-coated LC cell. The bistability and rewritability of the devices are achieved through the formation of the rubbery LC/gel mixture at room temperature. The desired patterns can be addressed, erased, and re-addressed by controlling the temperature, applied voltage, and UV light illumination. Grayscales can be obtained by adjusting UV light intensity.

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Paper No.  2017-TUE-P0301-P009
Bo-Kai Tseng
Fast-Response VA-FFS liquid crystal mode using 3D electrode design

A new 3D electrode design is proposed for a fast-response VA-FFS liquid crystal mode. A VA-FFS (or Dual-FFS) mode is known for its intrinsic sub-millisecond fast response time without the use of a thin liquid crystal cell gap or other liquid crystal phases. In this paper, we report and discuss the results obtained for this liquid crystal mode using a new 3D electrode design (instead of 2D in previous designs). We found that, by using this new 3D electrode design, it is possible to improve the maximum possible transmission (without using a dual electrode design) by reducing the disclinations along the transverse direction and also improve the potential response speed of this liquid crystal mode by having “smaller liquid crystal domains” in the liquid crystal bulk.

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Paper No.  2017-TUE-P0301-P010
L.-Y. Ke
Gelator-doped liquid crystal device switchable between reflective and transmissive mode

Transflective liquid crystal displays (LCD) are commonly known that each pixel is divided into reflective (R) and transmissive (T) subpixels. The R mode uses ambient light, while the T mode utilizes a backlight to display images. However, the division of the pixel results in lower light efficiency and resolution than a transmissive or reflective LCD. This study demonstrates a gelator (12-hydroxystearic acid; HSA)-doped liquid crystal (LC) devices, that is switchable between R and T modes, without sub-pixel division. The R and T modes are designed to have bend configurations with phase retardation of π/2 and π, respectively, as shown in Fig. 1. The phase retardation of a LC device can be varied and fixed by the thermoreversible association and dissociation of the gelator molecules. It is believed that the proposed device is a potential candidate for portable information systems.

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Paper No.  2017-TUE-P0301-P011
Hee Sang Yang
Electro-optical properties of hybrid type black PDLCs

Emulsion type PDLCs, which are able to yield high transmittance and blocking of light due to accurate control of LC droplet size, have been developed for transmittance variable devices. To provide a black background, a dichroic dye needs to be added into the PDLCs. But in that case, dye molecules existing in the polymer matrix of the emulsion type PDLCs could not be reoriented by an applied electric field, so that the dye-doped emulsion type PDLCs could not give sufficiently high transmittance in voltage on-state. Coacervation type PDLCs might be a good candidate for black background PDLCs because dye molecules existed in LC capsules, where the dye molecules can be reoriented by an applied electric field, but not in polymer matrix. It was hard to make dye-doped coacervation type LC capsules with small size of 1~2m, suitable for providing high scattering effect. In this paper, we proposed a hybrid type black PDLC, where the small size emulsion type LC capsules without dye and coacervation type LC capsules with dye were mixed. The electro-optical properties of the hybrid type Black PDLCs will be discussed.

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Paper No.  2017-TUE-P0301-P012
Yi-Jun Liu
Floating-ring-electrode liquid crystal lens with polymer stabilization

We constructed hole-patterned liquid crystal lens (H LC lenses) with structure of floating ring electrode (FRE LC lens), which can preserve large lens power, low driving voltage and aberration, and fast driving response. Unfortunately, the disclination defects still occurs under the fringing field, and the recovery time is still insufficient fast. Take into account these, we construct the FRE LC lens combined the approach of polymer stabilization (FRE PSLC lens). The addition of low concentration of reactive monomer (RM 257) will preserve original lens functions. The FRE PSLC lens keeps similar interference fringe number as the FRE LC lens, and furthermore, the disclination defects are avoided when voltages are addressed. Also, the faster recovery time will be expected due to the strong anchoring force provided by the formed polymer networks.

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Paper No.  2017-TUE-P0301-P013
Bo-Hao Song
Fabrications of tunable coaxially bifocal liquid crystal lens array via photo-polymerization processes

Liquid crystal (LC) lenses with hole-patterned electrodes possess the excellent capabilities of tunable focal lengths. In this study, tunable coaxially bifocus(CB) liquid crystal (LC) lens array via photo-polymerization processes are demonstrated. The characteristics of tunable CB are clearly exhibited when the voltage applied is continuously increased,the inner ring interference patterns will produce. When no operating voltage is provided,the interference pattern of outer ring was fixed and continued the lens function.

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Paper No.  2017-TUE-P0301-P014
Yu-Kuan Chang
Fast-response LCs for Multi-ring Electrodes LC Lens

The 3 mm diameter multi-ring electrodes were patterned into concentric shape for lens application. The gradient voltage distribution from edge electrode to centre electrode was controlled by thin PEDOT:PSS line which printed by aerosol jet printing system. Three different high birefringence LCs, named PCI-03, PCI-04, and PCI-05, were evaluated for their EO properties in lens cell. In particular, the total response time (rising + falling time) is 0.7s (0.058s + 0.65s) with 22.5 pi modulations in a 29.45um PCI-05 lens cell. The total response can be suppressed to 0.3s (0.025s+0.28s) with 15 pi modulations in a 19.93 μm PCI-05 lens cell.

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Paper No.  2017-TUE-P0301-P015
Yi-Lin Tsai
Generation of multi-beam interference with helical wave fronts based on Spatial Light Modulator

A simple method for producing multi helical beam interferences based on Spatial Light Modulator (SLM) with digital program of phase masks is presented. Firstly, we generated the phase mask corresponding to the symmetrical multi-facet pyramid lens [1],[2] in SLM (Fig. 1) to spatially modulate an incident laser beam to form desired two-dimensional (2D) multi-beam interference patterns. Then, we realized multi helical beam interferences by superposing a multi-facet pyramid lenses phase with a helical phase [3]. Figure 2 presents the simulated intensity distributions formed by various facet pyramid lens phase masks, and the simulated results of multi helical beam interferences. Notably, this method is simple, flexible and low-cost.

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Paper No.  2017-TUE-P0301-P016
Kai-Hsiang Chan
Long period fiber grating based on blue phase liquid crystal and polymer composite layers

Recently, blue phase liquid crystal (BPLC) materials have received intense interest due to its several attractive features including fast response time, alignment-free fabrication, and optical isotropy at voltage off state. Therefore, BPLC serves as a good candidate for polarization-independent switchable lens with potentially fast response time and easy processing. In this work, a simple method for fabricating a polarization independent blue phase liquid crystal fiber grating (BPLCFG) is demonstrated by utilizing the photo-polymerization induced phase separation (PIPS). The BPLC/polymer binary zones is obtained well by periodic UV illumination with phase separation of the BPLC molecules and UV-curable pre-polymer mixture. Figure 1 shown the optical microscopic photograph of BPLC fiber grating formed after PIPS process. The spectral properties of BPLCFGs with different grating periods were measured by the optic spectrum analyzer. As indicated in the experimental results, the resonant wavelength of the transmission spectrum can be observed as a function of the grating period and the environmental temperature. This temperature-induced LC refractive index variation will notably alter the optical properties of the MZI. Thus, such a fiber could work as a thermally tunable photonic device or temperature sensor from the viewpoint of applications.

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Paper No.  2017-TUE-P0301-P017
Chun-Ying Yang
Enhanced Electro-Optical Performance of In-Plane Switching Vertical Alignment Liquid Crystal Devices Using the Vertical Field and Polymers

In this paper, to produce the good electro-optical properties of IPS-VA LC devices, we proposed a simple alignment method by employing the vertical electric field and polymers with the concentration of 2 wt.% in the IPS-VA LC (E7) cell during the photo-curing process, and the effects of the pretilt angle on the device performance are investigated in detail.

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Paper No.  2017-TUE-P0301-P018
Jae-Hyeon Woo
Accelerated In-plane Switching of Vertically-Aligned Liquid Crystals by Two-Dimensional Confinement

In this presentation, we report a simple method for achieving a short response time in a VA-IPS cell, based on two-dimensional (2-D) confinement effect.

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Paper No.  2017-TUE-P0301-P019
Yan Lu
Tunable Tamm Plasmon Devices

A tunable Tamm plasmon device is proposed by filling liquid crystal (LC) molecules in the cell gap between the metal film and one-dimension photonic crystal as shown in Fig. 1. The resonance wavelength of Tamm plasmon device can be tuned by changing the temperature and thickness of liquid LC layer as shown in Fig. 2. Experimental results show that the resonance wavelength shows a redshift when the thickness or refractive index of LC layer is increased. When the cell gap of LC layer is ~150 nm, the resonance wavelength can shift ~1.2 nm while the refractive index is changed by 0.01.

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Paper No.  2017-TUE-P0301-P020
Ching-Min Lin
Applications of blue-phase liquid crystals for biodetection and quantitation

Blue phase liquid crystals (BPLCs) as mesophases are unique due to their three-dimensional helical structure with distinct lattice parameters and thus the spectral features. To date, BPLCs have been studied extensively in the field of display technology, whereas their applications for LC-based biosensing have not been explored. In this study, we employ BPLCs as sensing platforms for the detection of bovine serum albumin (BSA) and develop a quantitative method through the change in transmission spectrum as a function of the BSA concentration. The spectral approach proposed in this study for BPLC-based biosensing of protein concentrations can be extended to practically clinical applications, such as the specific detection of antigen–antibody immunoassay, to promote the applicability of BPLC-based biosensing in the biomedical field.

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Paper No.  2017-TUE-P0301-P021
Yi-Lun Chiang
Quantitative biosensing methods based on measurements of phase retardation and capacitance of liquid-crystal cells

Biomolecular detection with conventional liquid crystal (LC)-based biosensing relies on textural observations, the quantitative analysis is impossible due to the difficulty in determining the change in textural brightness. In this study, we consider two alternative LC-based biosensing approaches and establish two quantitative assay methods according to the unique electro-optical and electric capacitance properties of LCs. By applying an increasing AC voltage across the LC samples to reorient LC molecules in the homeotropic state, the voltage-dependent optical transmittance (VT) and electric capacitance (VC) were correlated with the amount of BSA immobilized on DMOAP-coated glass substrates. Accordingly, two parameters designated N (reduced refractive index) and ΔC/Cmax (normalized capacitance change) are proposed to quantitatively estimate the influence of BSA concentration on the disrupted vertical orientation of LC molecules based on VT and VC measurements. The results are shown in Fig. 1. It clearly reveals positive correlation of N and ΔC/Cmax with the BSA concentration, suggesting that quantitation in LC-based biosensing with high sensitivity and accuracy can be achieved by utilizing the properties of LC cells. We believe that this is the first study to demonstrate quantitative LC-based biosensing through electro-optical and electric capacitance measurements, which are extensively employed in LCD research and development.

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Paper No.  2017-TUE-P0301-P022
Wen-Yi Yang
Driving scheme of a tristable dual-frequency cholesteric liquid crystal and its electro-optical applications

This study demonstrates an electrically switchable and optically tristable dual-frequency cholesteric liquid crystal device. The three stable states exhibited in the DFCLC are the planar, the focal conic, and the uniformly lying helix textures, respectively. According to the mechanism of electrohydrodynamically induced ULH alignment and the material characteristic of the DFLC, two frequencies designated f1 and f2 as determined by means of dielectric spectroscopy in this study are critical to accomplish the tristable switching in the DFCLC cell. It is suggested that the frequency f1 should be selected in a proper frequency regime to induce the P-to-ULH and the FC-to-ULH switching via the electrodydrodynamic effect. To reversibly switch the ULH state back to the P or the FC state, the frequencycf2 is designed to be higher than the crossover frequency of the DFLC to change its sign of dielectric anisotropy from positive to negative. Based on the aforementioned concepts, a driving scheme to execute the direct and reversible tristable switching for the DFCLC cell is illustrated. Furthermore, in considering the spectral features of the three stable states, potential applications as a light shutter and a switchable waveplate will be demonstrated accordingly by using DFCLCs with designated helical pitches.

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Paper No.  2017-TUE-P0301-P023
Chun-Yu Chien
Holographic exposure processed liquid crystal cells as an infrared phase modulator with characteristics of scattering-free and fast response

In this study, we investigate performance of processed LC cells as an infrared phase modulator. It shows that fabricated phase modulators possess characteristics of fast response time (~ sub-ms) and scattering-free for the incident wavelength of 1550 nm. In addition, 2wt% NVP dopant for purpose of reduction of applied voltages also maintain same performance of phase modulators as well as LC cells without NVP dopant except for response time.

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Paper No.  2017-TUE-P0301-P024
Jong-Min Baek
Optically-switchable light shutter using cholesteric liquid crystals

Technologies for a light shutter, by which we can control the optical transparency, has been studied extensively for use as curtain-free smart windows. In addition to electrically-controllable light shutters, optically-controllable light shutter using photosensitive materials, especially azobenzene materials, has been one of the subjects of interest. In this presentation, we propose a light shutter using cholesteric liquid crystal (ChLC) doped with push-pull azobenzene. We proposed sunlight-switchable light shutter using ChLCs doped with push-pull azobenzene. In the initial translucent state, the incident light is scattered by liquid crystals (LCs) in the focal conic state. Under sunlight irradiation, the proposed light shutter can be switched from the translucent to transparent state by nematic-isotropic phase transition of the LC domains triggered by trans-cis photo-isomerization of push-pull azobenzene molecules. When sunlight is weakened by the cloud or disappears by sunset, the proposed light shutter rapidly relaxes from the transparent isotropic to translucent nematic state by cis-trans back-isomerization of push-pull azobenzene molecules. It can be switched from the translucent to transparent state by applying a vertical electric field, too. Under an applied vertical electric field, the focal conic state is switched to the homeotropic state and the light shutter becomes transparent.

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Paper No.  2017-TUE-P0301-P025
You-Jin Lee
Linearly polarized electroluminescence in a liquid crystalline conjugated polymer onto an alignment layer

Liquid crystalline conjugated polymer (LCCP) has attracted much attention in recent years since the optoelectronic performance could be easily enhanced by improving the molecular ordering of the LCCP. Especially, the linearly polarized electroluminescence (EL) is strongly affected by the orientational ordering of the LCCP, which is generally produced by a rubbing process of the alignment layer for the LC. In general, the order parameters of the LCCP is gradually decreased along the bulk LCCP from the alignment surface. As a result, the polarization ratio of the emitting light is strongly governed by the emitting zone within the LCCP in the EL process. In our work, to investigate the effect of the LCCP ordering on the polarization ratio of the light emission, we varied a thickness of the alignment layer acting as a burden of a hole transportation. The polarization ratio of the EL was gradually increased with increasing the thickness of the alignment layer. Since the alignment layer acts as a burden of a hole transportation, the emitting zone in the EL process moves toward an anode within the LCCP. As a consequence, the order parameters of the LCCP is gradually increased and thus the polarization ratio is also increased.

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Paper No.  2017-TUE-P0301-P026
Shang-Ho Wang
Optically switchable tristability in a chiral-tilted homeotropic nematic liquid crystal

Based on the trans–cis isomerization of an azo-chiral compound, optically generated tristable chiral-tilted homeotropic nematic liquid crystal (T-CTHN) is demonstrated. Compared with the conventional bistable chiral-tilted homeotropic nematic liquid crystals (BHN), whose host material is limited to dual-frequency liquid crystal [1], the proposed T-CTHN can readily be created using typical nematic materials (e.g. E7 in this study). Moreover, the T-CTHN is attractive because it enables direct and reversible switching among the three stable states—the tilted-twisted, tilted-homeotropic, and the fingerprint state, by controlling its exposure to green and ultraviolet light [2]. In this study, we firstly proposed a polarizer-free energy-conservative light modulator using dye-doped T-CTHN. A hybrid photonic structure with the T-CTHN as the defect layer, sandwiched between two one-dimensional (1D) PC multilayers, is also suggested for applications as wavelength modulators, controllable attenuators, and multichannel filters for optical communications. Our results indicate that the dichroic-dye-doped T-CTHN reveals the ability for gray-level tuning and each of them can be regarded as a stable state. Moreover, the contrast ratio of the dye-doped T-CTHN can be promoted to 12:1 with the augmentation of a phase-compensating homogeneous cell.

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Paper No.  2017-TUE-P0301-P027
Guan-Wei Wu
Dielectric heating-induced Bragg bandgap shifts in a chiral nematic cell

Based on the thermo-sensitive spectral properties of cholesteric liquid crystal (CLC) and the voltage induction of the dielectric heating effect, in this study, we demonstrate some unique features of electrically controllable bandgap shifts in a CLC cell upon the application of high-frequency voltage pulses. In contrast to other works, in which the voltage-induced dielectric heating effect and its applications are obtained mostly in dual-frequency LCs, the proposed CLC device is made using commercially available nematic LC with negative dielectric anisotropy as the host material [1,2], capable of reduction in the material dependency. By doping a proper amount of the chiral additive S-811 into the negative nematic, the spectrum of the resulting CLC exhibits blueshift with elevating temperature [3].

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Paper No.  2017-TUE-P0301-P028
Cheng-Yu Chi
Effects of the Cell Gap on the Kerr Constant of Blue Phase Liquid Crystals

In this study, the Kerr constant of pure blue phase liquid crystal (BPLC) without polymer doping at room temperature, and the optoelectronic properties dependent on the cell thickness are explored. The relation between the phase and the voltage in oblique incident light was measured via a reasonable vertical electric field for different thicknesses of BPLC cells. It was found that the Kerr constant formula can be amended with the functions related to the cell-gap. This study demonstrates a method to estimate the Kerr constant, especially for cells within a small electrical field, which will benefit optoelectronic applications.

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Paper No.  2017-TUE-P0301-P029
Min-Cheng Tsai
Optically controllable linear-polarization rotator using chiral azobenzene-doped cholesteric liquid crystals

Nowadays, cholesteric liquid crystals (CLCs), also known as chiral nematic LCs, have been studied by many scientists . Polarization rotation of linearly polarized light from one orientation to another via exposure UV light based on chiral azobenzene-doped cholesteric liquid crystals (CLCs) is demonstrated. The effects of UV-illumination duration, polarization direction of incident light, wavelength, cell gap, on the performance of such a polarization rotator are examined.

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Paper No.  2017-TUE-P0301-P030
Hao-Shiun Yang
Electro-opto induced binary liquid crystal alignment using the mixture of ionic material and nematic liquid crystals

The ions inside the ionic material has affinity with ITO. It could also be induced by electric field when there is alignment layer onto the substrate surface. After applying an electric field onto the LC cell, the nematic LCs (NLCs) aligned by the original alignment layer can be changed to be aligned vertically by ionic materials.

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Paper No.  2017-TUE-P0301-P031
Jin-Hun Kim
Ion-doped liquid crystal cell for control of haze and transmittance

Recently, liquid crystal (LC) devices have been studied for various applications, such as display, light shutter and LC lens, etc. Especially, LC device for light shutter application which can control the haze and transmittance simultaneously have been studied actively. To control the haze and transmittance simultaneously, an LC device requires the light scattering to hide the objects behind it and light absorption to control the transmittance. In this work, we demonstrate a LC cell doped with ionic dopant and dichroic-dye. The ionic dopant is used to realize electro-hydrodynamic effect for light scattering and dichroic-dye is doped for light absorption. The proposed LC cell can pass most of the incident light in the transparent state and block the incident light in the opaque state.

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Paper No.  2017-TUE-P0301-P032
Shang-Yi Chih
Smart window based on polymer-stabilized liquid crystal device with a light dependent resistor

In this study, we design a smart window [1, 2] based on a polymer-stabilized liquid crystal (PSLC) with a light dependent resistor (LDR) (Fig. 1). It presents a stable highly transparent state at low ambient light, and can be switched to multi-gray transmission states under a biased applied voltage (~20 V) controlled by the ambient light intensity (Fig. 2). The mechanism can be understood as follows. Under the biased voltage, the voltage across the LDR is reduced under exposing it with a higher ambient light intensity. Thus, the voltage across the LC cell becomes higher, and then causes the transmission of the PSLC lower. It should be noted that the design of the proposed device is simple to fabricate, and low-cost.

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Paper No.  2017-TUE-P0301-P033
Hsiu-Ling Chen
Polarization-independent electrically tunable microlens array based on polymer dispersed nano-liquid crystal droplets

Liquid crystal (LC) lens arrays possess electrically tunable focal lengths by spatial LC gradient distribution under the application of external electrical field. The LC lens array has the advantages of light weight, simple operation and fabrication. However, many drawbacks of LC lens arrays are still needed to be improved, such as slow response time, low tolerance of thickness variation, and low optical efficiency. Learning from these, we fabricate the LC microlens arrays with a thin and simple optical structure by polymer dispersed LC (PDLC) material consisting of nano-LC droplets dispersed in the polymer matrix. In this study, the used PDLC mixture comprises of nematic LCs, prepolymer (NOA65), and a small amount of photo-initiator. The mixture is then injected into the empty cell with a hole-patterned array electrode, and then irradiated with UV light to form nano-scale LC droplets in the polymer matrix. The fabricated PDLC microlens array has polarization-independent properties [Fig. 1] and fast response time [Table. 1], because of random LC orientations and nano-scale LC droplets. The method to build LC microlens array is potential for applications in light field imaging systems, 3D integrating imaging systems and augment reality.

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Paper No.  2017-TUE-P0301-P034
Mao-Kun Huang
Effects of hollow silica nanoparticles on ionic and electro-optical properties of the liquid crystal cells

Liquid crystal (LC) displays are intensively investigated owing to their low operating voltage, low power consumption, and compact size. However, image degradation, which is caused primarily by impurity ions in LC cells, is a significant obstacle to practical applications. Researches on LC-nanoparticle dispersions have indicated that inorganic nano-additives suppress the mobile ions and faster the response time of the LC cells. In this study, we investigate the low-frequency permittivity spectra and electro-optical properties of the hollow silica nanoparticles (HSNs)-doped LC in 5 different concentrations of 0, 0.5, 1, 2, 3, 5wt %, respectively. The HSN-LC mixtures were filled in the homogeneous aligned (HA) and vertical aligned (VA) cells separated with 5- and 9-μm-thick spacers. The addition of HSN alters the ionic characteristics, such as ion density, conductivity; the doped HSNs also alter the electro-optical properties of the cell, such as response time, viscosity. Furthermore, the doped HSNs are found to be mixed well with the LC host. The obtained results and possible mechanisms will be discussed in this paper.

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Paper No.  2017-TUE-P0301-P035
Cheng-Hau Li
Electrically tunable liquid crystal lenses to achieve characteristics of varied aperture bifocuses and unique aperture focuses

In this study, electrically tunable liquid crystal (LC) lenses with characteristics of bifocuses and focuses are demonstrated. In addition, shorter focal lengths are achieved in this proposed structure than focal lengths in convenient LC lenses with hole-patterned electrodes.

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Paper No.  2017-TUE-P0301-P036
Cheng-Yu Chi
Effects of the Vertically Switching Electric Field on the Electro-Optical Properties of Blue Phase Liquid Crystals

This study uses the director model to analyze the optoelectronic properties of polymer-stabilized blue phase liquid crystal (PS-BPLC). The director model revealed a linear relationship of refractive index change and the cosine squared of the angle between the LCs and the direction of the electric field. Moreover, we employed the simulations based on the Kerr effect and compared the results with those of the director model. The simulation results also show the high consistency with real circumstances. Consequently, it can be of great help to design BPLC displays and can be applied to make better strategies in developing the next generation LCD devices.

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Paper No.  2017-TUE-P0301-P037
Akpeko Gasonoo
Direct visualization of graphene domains and boundaries by optical birefringency of Nematic Liquid Crystals

The phenomenal properties of graphene have made it one of the most widely studied two-dimensional materials. These properties are strongly influenced by the sizes and boundaries of its domains and defect distribution. Therefore the direct observation of the domain size and defect distribution in graphene is very important for the development of electronic applications involving graphene. Conventional approaches for domain visualization, which are based on microscopy and spectroscopy, are only effective for domains that are less than a few micrometers in size; hence require sophisticated optical systems and complex sample preparation procedures. In this letter, we report a simple and cheap fabrication process in direct visualization of domain sizes, boundaries and defect distribution of arbitrarily large graphene surface covered with nematic liquid crystals. We found out that the liquid crystal molecules align anisotropically with respect to the graphene domains and exhibit distinct birefringence properties that can be used to image the graphene domains by using the polarized optical microscopy (POM). The method relies on a correspondence between the orientation of the liquid crystals and that of the underlying graphene, which we use to determine the boundaries of macroscopic domains.

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Paper No.  2017-TUE-P0301-P038
Yi-Xuan Chen
Effect of ZnO nanoparticles on switching voltage of Polymer Dispersed Liquid Crystal film

When using Polymer Dispersed Liquid Crystal (PDLC) in the smart window, the high power consumption is a big drawback for the environmental friendly world. We have investigated the effect of pure ethanol and ZnO/ethanol mixtures on the threshold and driving voltages (Vth and Vd) of the PDLC films. The cell gaps are 15 μm. We dissolved ZnO nanoparticles (22.2 wt%) in ethanol. The Vth and Vd of the pure PDLC films are 7.8 V and 19.0 V, respectively, and contrast ratio (CR) is 19. As the concentration of pure ethanol increased, the Vth and Vd of doped PDLC films reduced dramatically, but CR decreased. For example, CR reduced to 11, Vth and Vd decreased to 4.7 and 11.3 V, respectively, when the concentration of ethanol was 6.56 wt%. On the other hand, the concentration of ZnO/ethanol mixture increased, the Vth and Vd of the doped PDLC films decreased and the CR raised. Our lowest Vth and Vd are 1.9 V and 4.6 V, respectively, and the corresponding CR is 26 for the 2.44 wt% concentration of ZnO nanoparticles.

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Paper No.  2017-TUE-P0301-P039
Yeongyu Choi
Fast Turn-off Switching of Vertically-Aligned Negative Liquid Crystals by Fine Patterning of Pixel Electrodes

We demonstrate that the turn-off time of a VA cell can be reduced significantly by fine patterning of pixel electrodes. We confirmed that the turn-off time of a VA cell is dependent on the pitch of pixel electrodes as well as the cell gap; therefore, as the pitch of pixel electrodes is reduced, the turn-off time is significantly reduced. For an example, the turn-off time of a conventional VA cell was 6.3 ms whereas that of VA cell with fine patterned pixel electrodes was 3.9 ms, as shown in Fig. 1. The turn-off time of the VA cell can be further reduced though fine patterning of pixel electrodes.

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Paper No.  2017-TUE-P0301-P040
Ko-Ting Cheng
Bistable scattering mode light shutters using mesoporous-doped dual frequency liquid crystals

This study reports a bistable scattering mode light shutter with the advantages of simple fabrication processes based on mesoporous-doped dual frequency liquid crystals. The effective refractive index of LCs can be electrically tuned to be matched (transparency) and mismatched (scattering) with that of the doped mesoporous.

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Paper No.  2017-TUE-P0301-P041
Rui-Wen Wang
Characteristics of liquid crystal fiber grating based on polymer-stabilization

In this paper, a liquid crystal fiber grating (LCFG) element was fabricated by using the unique optical properties of the liquid crystal and the UV monomer of the hollow fiber. The mixture of liquid crystal and UV monomer was filled in the hollow core fiber, and the polymer stabilization technique was used to control the alignment of liquid crystal molecules in a hollow core fiber to a periodic structure. By carefully adjusting the UV exposure conditions, a periodic LCFG is successfully formed.

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Paper No.  2017-TUE-P0301-P042
You-Jin Lee
Effect of thermal annealing on the order parameter of an aligned liquid crystalline conjugated polymer

The orientational ordering in liquid crystalline conjugated polymer (LCCP) has been interest in photonic and electronic applications such as organic light emitting diodes (OLEDs) and thin-film transistors [1,2] since their order parameter strongly affects the polarization ratio of the electroluminescence (EL). The rubbing process used in the conventional LC devices is a candidate to achieve the high order parameter in the LCCP [3]. In this work, we investigated effect of thermal annealing with different cooling rate on the orientational ordering of the LCCP. Poly(9,9-di-n-octylfluorenyl-2,7-diyl) was used as an emitting layer for the linearly polarized EL devices. The PFO film dissolved in toluene was spin-coated onto the rubbed AL22636 as an alignment layer for PFO. For nematic ordering of the PFO, the sample was annealed at 210 C for 20 min. After thermal annealing, we cooled down the substrate with different cooling rates. As shown in Fig. 1, the quenched sample exhibited lower optical retardation than the sample cooled down with -20 C/min, which is originated from the high crystallinity at low temperature. Also, the corresponding polarization ratio, defined by a ratio of EL intensities polarized parallel and perpendicular to the rubbed direction, showed the similar behavior.

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Paper No.  2017-TUE-P0301-P043
Tsu-Chun Chang
Fast response liquid crystal microlens array by polymer stabilization

Electrically tunable liquid crystal (LC) microlens had attractive attentions owing to their advantages of tunable focus, light weight, low power consumption, simple fabrication, and good stability. Japanese scientist Sato was the first one who fabricated the LC lens with hole-array patterned electrode structure [1]. However, the hole-array patterned LC microlens had a shortcoming of slow response time due to the thick LC layer used to provide enough phase retardations. Learning from this shortcoming, we construct a fast response LC microlens array with polymer stabilization. A mixture comprises of monomer (RM257) and nematic LC is injected into the hole-patterned microlens cell, where the monomer concentration is 1 wt%. The hole-patterned microlens is then UV cured with intensity of 120 mW/cm-2 for 1 minute under -10 °C to form the micro LC domains, which significantly faster the response time of the hole-patterned LC microlens array, as shown in Table 1. Because of the addition of small amounts of monomers, the electro-optic properties of the proposed LC microlens array can be preserved as that of the traditional LC microlens array, and light scattering can be negligible.

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Paper No.  2017-TUE-P0301-P044
Li-Jyuan Lin
Electro-optic effect of Au nanoparticles on liquid crystal cell

Doping nanoparticles (NPs) into liquid crystals (LCs) is a simple process and can be easily adopted to the conventional LC display fabrication process. Many kinds of NPs in LCs have been investigated, such as Au [1] or Ag [2] NP dopant changes the elastic constant and the rotational viscosity of LCs, the ferroelectric NP dopant enhance the LC dielectric anisotropy [3,4]. The LCs with doped NPs also demonstrate new properties, such as memory effects, fast response, and low addressing voltage. Overall, NPs result in slight change of the physical and chemical properties of LCs. In the study, we investigate the electro-optic properties of nematic LCs doped with Au NPs. In comparison to the pristine LC cell, Au NPs in LC cell strengthen the electric fields and the van der Waals forces between the LC molecules and polyimide alignment layer, and thus decrease the addressing voltage and fall time of LC cell. As shown in Figs. (a) and (b), the 0.07 wt% Au NP dopant significantly decreases the threshold voltage and fall time of the LC cell. The excess dopants will interfere the reorientation of LC molecules, and hence slows down the response time of the cell.

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Paper No.  2017-TUE-P0301-P045
Huang-Kai Peng
Improving Electro-Optical Properties of a Two-Domain Fringe-Field Switching Display by Adjusting Oblique Angle for Electrode Structure.

Recently, liquid crystal displays (LCDs) have widely used in various applications, for example: smart phone, televisions, tablet PCs, etc. because they have several advantage, such as low power consumption, high resolution and low cost. In these LCDs, fringe-field switching (FFS) is excellent in wide viewing angle, low color shift, high transmittance and high contrast ratio. In the conventional FFS mode two-domain (2D) chevron electrode structure as shown in Fig. 1(a) has been proposed to enhance the wide-viewing angle and the color shift. In this paper, to further improve the FFS, we propose a method, which reduces the oblique angle of pixel electrode in an FFS mode with 2D-chevron electrodes as shown in Fig.1 (b). The improved FFS LCD exhibits wide-viewing angle and low color shift.

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Paper No.  2017-TUE-P0301-P046
Chia-Chun Liu
Non-contact Liquid Crystal Alignment by Using ZnO Films

Applications of inorganic ZnO films for aligning liquid crystals (LCs) are very promising for LCD systems operated in severe conditions, where a highly durable material is needed. In this work, the process of dip-coating was applied to form the ZnO films for liquid crystal alignment. A solution of zinc acetate dihydrate (0.2854 g, 1.3 mmol) in 130 mL of isopropanol was stirred vigorously at 120 °C for 10 minutes. 2-(Dimethylamino)ethanol (0.1158 g, 1.3mmol) was slowly added to the above solution and stirred at the same temperature for an additional 2 hours to form a homogeneous precursor solution. The ITO glass substrate was withdraw vertically from the prepared-solution. The as-prepared film was annealed at 200℃ in air for 90 minutes to form a ZnO thin film. The antiparallel LC cells were fabricated with a ~5 m mylar spacer and filled with LC molecules. The photographs of the vertically-aligned LCD observed by POM with the crossed polarizers are shown in Fig. 1. The voltage-dependent optical transmittance of the VA-LCD is shown in Fig. 2. The comparison of electro-optical properties between polyimide and ZnO alignment films will be conducted in the near future.

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Paper No.  2017-TUE-P0301-P047
Seong Jun Lee
Electro-optical properties of dye-doped emulsion type PDLCs

Emulsion type PDLCs, which are able to yield high transmittance and blocking of light due to accurate control of LC droplet size, have been much studied for an application to a transmittance variable device. In order to apply PDLC to transparent displays with high contrast ratio as a light shutter, it is needed to be black in off-state. To achieve black background in the PDLC cells, we added a dichroic dye in the emulsion. We fabricated the black background PDLCs by doping dichroic dye into the LC layer, and investigated LC droplet size dependent electro-optical properties of the dye-doped emulsion PDLCs.

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Paper No.  2017-TUE-P0301-P048
Jing-Ren Hu
Electro-optical properties of a blue phase liquid crystal cell affected by its elastic constants

We propose a double high-pretilted-twist-nematic (DHPTN) director model to describe and analyze the electro-optical characteristics of a polymer-stabilized blue phase liquid crystal (PSBPLC) cell. By means of substituting the PSBPLC cell by a number of DHPTN layers, we simulated the experimental result. The number of stacked DHPTN layers in the simulation is obtained by comparing the experimental result to the simulation result. In this study, we considered the elastic constants, splay, twist and bend, and use two different methods to simulate the PSBPLC cell. One is one-constant-approximation and the other is directly using the material elastic constants. According to the simulated results, both methods are fit of the experiment very well. Besides, we found that the refractive index change of PSBPLC is linearly proportional to the cosine of the averaged angle of the director with respect to the direction of electric field. Furthermore, we consider difference of the three elastic constants. When the difference to the averaged value is small, the result of the simulate curve fits the experiment very well, but if the difference to the averaged value is large, the result of simulate curve will be changed.

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Paper No.  2017-TUE-P0301-P049
Aboozar Nasrollahi
In Situ Control of Continuous Pre-tilt Angle of Nematic Liquid Crystals Doped by Photochromic Azo-Dye

Control of pre-tilt angle of liquid crystal is a crucial factor to enhance the performance of display devices. Mixing homeotropic and homogenous polyimide (PI) at different proportion is one of the main methods to control the pre-tilt angle of LC which has been shown by several reports [1-4]. In this case, an anchoring competition of LCs with horizontal and vertical PIs leads to a generation of intermediate pre-tilt angles. In all methods that have been achieved to control the pre-tilt angles, a pretreatment of substrate for LC alignment is required. A recent study depicts in situ creation of homeotropic alignment based on the photochromic azo-dye without using pretreated alignment layer [5]. In this report, we demonstrate how UV-irradiation at regular intervals induces anchoring transition from homogenous to homeotropic state with continuous variation of pre-tilt angle. To achieve in situ creation of homeotropic alignment, photo-responsive azo-dye has been doped in LC host and subsequently UV treatment has been performed. Approximately 0.3 wt% of azo-dye has been mixed with nematic liquid crystal (NLC) with negative dielectric anisotropy. Electro optic (E.O.) cells with electrically controlled birefringence (ECB) configuration have been fabricated by using the rubbed ITO (Indium-Tin-Oxide) glass plates with no alignment layer

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Paper No.  2017-TUE-P0301-P050
Po-Chang Wu
Electrically induced bistability in a dual-frequency SmA liquid crystal cell

In this study, a new type of memory-enabling smectic-A (SmA) liquid crystal (LC) cell, enabling the direct and reversible bistable switching between the planar (P) and the homeotropic (H) states by external voltages, is demonstrated. Here, the SmA LC phase showing frequency-revertible dielectric anisotropy is made possible by incorporating a proper concentration of a chiral agent into a commercial dual-frequency (DF)LC. The crossover frequency (fc) determining the sign of dielectric anisotropy of the DF-SmA phase was examined by means of dielectric spectroscopy. According to the mechanism of field-induced layer reorientation and the DFLC property of frequency-revertible dielectric anisotropy, the direct two-way switching between the P and H states with uniform alignment in the cell is realized by manipulating the frequency of applied voltage pules with fixed amplitude of 100 V between 1 kHz and 40 kHz. High contrast ratio of P as the bright state to H as the dark state can thus be obtained by placing the cell between crossed polarizers. Consequently, the proposed DF-SmA cell is potentially applicable for the development of energy-efficient electro-optical devices, such as optical switches, displays, and smart windows. Further discussions on the electro-optical responses of the DF-SmA cell will explicitly be presented.

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Paper No.  2017-TUE-P0301-P051
Vineet Kumar
In-situ Alignment Control and Stabilization for Planar Aligned Nematic Liquid Crystals

Photo-alignment is one of the promising non-contact methods of achieving liquid crystal alignment which has been widely explored since last two decades [1]. In an attempt to explore this area further, we have designed a photo-responsive polymer material which upon coating at ITO substrate and by irradiation of polarized visible light gives homogeneously aligned cell. Synthesis of photo-responsive polymer is an extended analog of conventional polyimide material where side chain contains Methyl Red modified azo dye molecules. Designing of photo-responsive polymer has been done by keeping in mind the advantage of Methyl Red dye absorption peak in the visible range. As an advantage of this designed polymer, we have an extra window of UV- light irradiation. To confirm the hypothesis of dual irradiation approach, the empty cell fabricated by polymer coated ITO substrates has been irradiated at elevated temperature of 110 C for 10 minutes by linearly polarized visible light with the metal halide light source. Further filling the cell with liquid crystal MLC 15600-100 at isotropic temperature and slowly cooling to room temperature yields in well planar aligned cell. Thus alignment has been achieved by reorientation of azo dye molecules as a result of continuous cis-trans isomerization phenomenon.

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Paper No.  2017-TUE-P0301-P052
Yi -Liang Chen
Study of electro-optical properties of dual-domain fringe-field-switching liquid crystal with the electrodes tilt small angle

Fringe-field-switching (FFS) and in-plane-switching (IPS) liquid crystal displays (LCD) have been widely used in smart phones and flat panel displays because of their wide viewing angle and the advantages of pressure-resistance for touch screen. Notably, FFS mode has much better transmittance and viewing angle than IPS mode. In the FFS mode, the use of wedge-shaped pixel electrode structure of the dual-domain can reduce the color shift and enhance the viewing angle. In the previous study, we know that Byung-June Mun et al. used a double-exposed UV alignment method to give a FFS display a small pretilt angle to increase the transmittance and viewing angle. In this study, we follow the idea as mentioned above, but change the electrode tilt angle (2°) which is smaller than Jun-Hee Park et al.’s model. Therefore, we propose a dual-domain FFS structure that is not quite the same as before. The structure is shown in Figure 1. According to the simulation results, the driving voltage is slightly increased after the angle becomes smaller, but the transmittance is also increased, and the contrast ratio and iso-luminance are also improved.

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Paper No.  2017-TUE-P0301-P053
Chu-Hung Lu
The investigation of nonlinear optical properties of diacrylates

In this study, the nonlinear optical properties of the diacrylate mesogens were investigated.The polymerization of the diacrylate masogens can be initiated using 632.8nm wavelength emitted from a He-Ne laser.It is thought that the radicals required for the polymerization are produced during a TPA process.

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Paper No.  2017-TUE-P0301-P054
Chih-Chin Chang
A study of the soft conducting film of the polymer dispersed liquid crystal devices

Energy saving become a trend in recent years. It is much more important that using thermal insulation building windows with adjustable light transmittance function. However, optical devices made by the polymer and the liquid crystal materials have been widely researched and used. Especially, polymer dispersed liquid crystal (PDLC) is the light adjustable device most extensively used without polarizer. In this plan, we mainly use the series of non-ITO (Indium Tin Oxide) conductive PEDOT (poly (3, 4-ethylenedioxythiophene) with soft substrate which is processed at low temperature. It collocates with the high efficient soft smart film of the polymer dispersed nematic liquid crystal. By using special optical design, it has several properties including nice light transmittance, good UV/infrared ray effect. It can not only reduce the cost of air-condition but also achieve photoelectric function. User could control the surface of the substrate to be transparent or matted by using switch. Whereby, it could satisfy people to protect privacy. We utilize the weather ability of the PDLC liquid crystal mixing with photo-curable monomer and combine with soft substrate PEDOT-PET. Then, the energy saving, thermal insulation, light adjustable device of the soft substrate PDLC with ultra-violet light induced photo-polymerization process.

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Paper No.  2017-TUE-P0301-P055
Yi-Hsin Chen
Develop a photoelectric detection system by using the optoelectronic transformation characteristic of liquid crystal

It is getting future trend for the healthcare and biotech markets to develop the advanced medical display panels with specially designed multi-features. It has won recognition for its high resolution, high brightness, high contrast medical display panels, clearly demonstrates the maturity of advanced technology for the development of medical display panels. A photoelectric detection system has been widely used and it provides thin film transistor array flaw and defect detection capability with optoelectronic transformation characteristic of liquid crystal. This paper reports detected a critical small-pixel sized defects and report correct position of a 4K 65” 4096(RGB) x2560 thin film transistor array panel with ultra-high-definition medical display application. The system is using to detect a small sized pixel defect and shown efficiency thin film transistor array flaw detection of ultra-high-definition oxide-based thin-film-transistor array medical displays panel. Moreover, it requests a good solution for defects detection with thin-film-transistor array panel design configuration.

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Paper No.  2017-TUE-P0301-P056
Jia-Lun Hsieh
New design for Transflective Polymer Stabilized Blue Phase Liquid Crystal Display with low operation voltage and high transmission

We propose a new Transflective Polymer Stabilized Blue-Phase Liquid Crystal Display which has a square S-shaped electrode structure that is coated with the Aluminum reflective electrode. Due to the strong horizontal electric field that can be generated by the wall-like reflective electrode, this new proposed new design can help minimize the dead-zone that often exists above the electrode and also lower the operation voltage. This new design can thus help achieve relatively low operation voltage and high transmission. After adjusting the protrusion height and the electrode width, the transmission and reflection curves can match very well in a single cell gap. The transmittance T and reflectance R can reach 92.4% and 92.1% respectively at 8V operating in optimized structure.

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Paper No.  2017-TUE-P0301-P057
VanBao Bui
Study on Response Time Improvement in Polymer Stabilized Nematic Liquid Crystal Loaded Microwave and Miliwave Phase Shifter

As the development of cell phone and satellite communications, liquid crystal material have attracted considerable attention for realizing these electrically controllable microwave and milliwave components because they have a large dielectric anisotropy in the microwave and milliwave region. As usual, nematic liquid crystal is mainly used for microstrip line (MSL) phase shifter, but has one serious problem, that is, the response time when the driving voltage is removed, is very long as the order of 10 s, because the thickness of the liquid crystal layer is typically more than 50 μm. In this study, we report the improvement of response time and phase shift in microwave and milliwave phase shifter with using polymer stabilized nematic liquid crystal (PSNLC), which is performed by adding mesogenic monomer to nematic liquid crystal and irradiating UV light to polymerize.

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Paper No.  2017-TUE-P0301-P058
Chi-Yu Hsieh
Polymer-Stabilized Blue-Phase Liquid Crystal Display using 3-level voltage design without protrusions

We propose new designs for Polymer-Stabilized Blue-Phase Liquid Crystal Displays (PS-BP LCD) using three-level voltage design. These new designs can potentially increase the transmission and lower the operation voltage of PS-BP LCDs without using protrusions. Although protrusions can be an effective way to lower the voltage and increase the transmission of PS-BP LCD, the fabrication of protrusions can sometimes be demanding. In this paper, we report the results we have obtained by using the three-level voltage design for PS-BP LCD. PS-BP LCD has attractive features of fast response time, no need of alignment layers and good dark state with good viewing angle and thus has potential to become the next-generation LCDs.

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Paper No.  2017-TUE-P0301-P059
Fei-Hung Tsai
Study and analysis of ITO films under different AR flow by RF magnetron sputtering

The RF magnetron sputtering was used to deposit the ITO films on glass substrates. The experimental parameters from Table 1 will be applied to the magnetron sputter deposition system, and we investigated the influence of ITO films on the crystallinity, electrical and optical properties under different Ar flow. As shown in Fig.1, the more Ar flow we have, the more effect on the crystallinity for the ITO films we will get. As shown in Fig.2, even though we used the different Ar flow to deposit the ITO films, all the ITO films have abrupt absorption edge in the ultraviolet region. It proves the theory of Burstein-Moss effect. [1] According to the experiment, the average transmittance of ITO films is about 86% in the visible light region which is 400nm to 800nm. As shown in Fig.3, we can get the best electrical and optical properties of ITO film under 30sccm, and the sheet resistance of 22.75 Ω/sq is obtained.

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LC Technology

Session 7B: LC Technology
Wednesday, Feb. 15, 2017  10:40-12:05
11:05 - 11:20 Paper No.  2017-WED-S0307-O001
Seong Ho Ryu
1D Nanoconfined liquid crystal as an active medium for photonic crystal

The porous anodic aluminum oxide (AAO) was used as a nano-confined geometry where the molecules orientation was successfully controlled by treating inner surface of the AAO with self-assembled monolayers. We systemically investigated the molecular orientation in the AAOs with varied pore diameter and surface anchoring condition by using grazing incidence X-ray diffraction technique. The porous structure of the AAO can be engineered by pulse anodization with alternating constant current, which produces a modulated AAO that selectively reflects a particular wavelength called a photonic crystal (PC). A spectral range of the reflection, photonic bandgap (PBG), is determined by effective refractive index consisted of air and Al2O3 (corresponding to pore wall) and can be shifted by filling other functional materials. We demonstrated the switchable 1D AAO PC using nematic LC doped with an azo LC material. In the N phase, the LC molecules are aligned parallel to the inner surface of the AAO owing to nanoconfinement, which make the LC medium induces ordinary refractive index. Phase transition from N to isotropic phases can be induced by irradiating UV light that triggers photoisomerization of the azo compound. The refractive index is changed from no to isotropic refractive index, which shifts the PBG.

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11:20 - 11:35 Paper No.  2017-WED-S0307-O002
Jae-Won Huh
Dye-doped Cholesteric Liquid Crystal Cell for a Bistable Light Shutter

Recently, see-through displays using organic light emitting diodes (OLEDs) have been considered as one of the next generation displays [1]. However, a see-through display shows poor image quality because each pixel includes transparent window area. Objects behind a display panel are always overlapped with displayed images. Moreover, a see-through OLED display cannot provide black color. This inevitable problem can be solved by placing a light shutter at the backside of a see-through display. In this work, we demonstrate a bistable light shutter using dye-doped ChLCs. For dye-doped ChLCs, we used positive liquid crystal (p-LC) and dual-frequency liquid crystal (DFLC). To realize a bistable light shutter using p-LC, we employed patterned electrodes on both the top and bottom substrates. To improve the electro-optic characteristics in the focal-conic (opaque) state, we used a crossed electrode structure where the top and bottom interdigitated electrodes are crossed to each other. However, a bistable light shutter using p-LC requires complicated electrode structure for switching. To avoid the complicated electrode structure, we can use DFLC. These light shutters can provide black color and hide the objects behind a display panel completely in focal-conic state.

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11:35 - 11:50 Paper No.  2017-WED-S0307-O003
Mao-Chou Tai
Multi-directional Bendable Chiral Nematic Liquid Crystal Polymer Based on Photo Responsive Azobenzene Mesogenic

Stimuli Polymetric liquid crystals hasn’t shown great potential in leagues of neither biomedical, mechanics, nor photonic applications during the past decades. This work is in the lead to demonstrate a multi-directional bending circularly polarizing reflector based on photo-mechanical and meanwhile reacts as a filter by the nature properties of cholesteric liquid crystal polymers. With the help of azobenzene mesogenics of CLCPs, the reflector would be able to select bending angles from 15° to 58° after trans-cis isomerization. Since CLC has the characteristics of reflecting single handedness circularly polarizing light which the photonic band gap is angle-dependent. Therefore, the reflected wavelength could be shifted between 570nm to 670nm with a ~60nm bandwidth. The transitions between trans and cis states could be achieved in ~6s and ~30s. The times are proportional to the intensity of pump lasers. The tunable angle for beam steering is ~54° as the transmittance is below 8% under He-Ne laser. Furthermore, the tunable range is believed to be enhanced by the bandwidth and different wavelength of probe beam after theoretical analyzing. Additionally, the tunable range is independent with the initial angle, proving it flexibility for practical use.

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11:50 - 12:05 Paper No.  2017-WED-S0307-O004
Jia-Heng Dai
Circular-polarization selective gratings based on refilled cholesteric liquid crystal template

In this work, we fabricated optical gratings based on planar CLCs, instead of fingerprint CLCs conventionally. The gratings presented in this work are fabricated on the basis of the CLC template (washing out/refilling) technique. By refilling left- or right-handed CLCs into a right handed CLCs template grating, the refilled CLC template grating can diffract light with specific wavelength in reflection mode. In addition, the refilled CLC template grating shows different diffraction efficiencies for left- and right-handed circularly polarizations (L- and RCP), as shown in Fig. 1. This beam steering element has the features of circularly polarization selectivity and dual operation modes. Therefore, this CLC-based device can be potentially used for applied diffraction elements in optics.

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