Response Time Of Liquid Crystal Research Articles

56‐1: Invited Paper: Ultra‐high Frame Rate ADS LCDs

In recent years, LCD end‐users are putting forward higher and higher requirements for dynamic picture display realism. With the increase of display panel refresh rate, dynamic picture fidelity has a significant improvement. The extremely high refresh rate has become one of the most important indicators of high‐end display panels, especially for video game usage scenarios. However, the increase in refresh rate is a challenge to the drive capability of LCD semiconductor TFTs (Thin Film Transistor), the response time of liquid crystal, and the transmission of high‐frequency signals, resulting in the maximum refresh rate of high‐refresh‐rate displays currently on the market still at 240 ~ 300 Hz. In this paper, we solve the display distortion due to low charging ratio at ultra‐high refresh rate by improving GOA（Gate Driver on Array） driver circuit and applying high stability and high mobility bilayer oxide semiconductor technology. At the same time, the 1ms GTG (Gray to Gray) response time is achieved by testing and optimizing the pixel slit angle and cell gap of ADS (Advanced Super Dimension Switch) LCD, ensuring no image trailing at refresh rates up to 600 Hz. Then the anti‐electromagnetic interference ability of high‐speed signal is improved by high‐speed signal transmission quality enhancement technology. Through the application of the above technologies, we have developed the ultra‐high refresh rate IT display panel products such as 600Hz frame rate FHD NB LCD and 500 Hz FHD MNT LCD. And the 16.0” WUXGA 600Hz ADS LCD achieves the highest CMR 9000 rating in VESA latest dynamic picture CMR certification.

64‐4: Invited Paper: High Contrast Ratio ADS LCD Using Negative Liquid Crystal Material

Mini‐LED technology is becoming a mainly driving force in the development of LCD industry. Only using excellent spatial viewing angle characteristics, high picture quality and high contrast ratio LCD panel, Mini‐LED can maximize its effectiveness in improving image quality and has the strength to challenge the dominance of OLED in the high‐end market. As we known, ADS technology belongs to plane field switching display mode, taking into account the excellent wide‐angle characteristics and excellent image quality, has been widely used in mobile phone, tablet, notebook, monitor and TV, the only shortcoming is the low contrast ratio (CR), just at 1000‐1200:1. This paper aims to introduce the development of ultra‐high contrast ADS LCD panel and its implementation method. By using low scattering coefficient negative liquid crystal, fine rubbing alignment process, and fine calibrated POL attachment process, an ultra‐high contrast ratio of CR 3000‐3500:1 is achieved for the first time on ADS panel. The slow response time of negative liquid crystal is improved by balancing the operating voltage (Vop) and adjusting the Cell gap, while the decrease in transmittance caused by lower Cell gap can be overcome by the spectral aperture pixel (SAP) design. All the techniques described in this paper are applicable to various types of plane field switching panels. The paper also concludes with a discussion and outlook on how to further improve the contrast ratio of ADS‐like panel.

Improved electro-optical and dielectric properties of polymer dispersed liquid crystal doped with disperse dye red 1 and carbon nanoparticles

ABSTRACT Disperse dye red 1 (DR1) and carbon nanoparticles (CNPs) were doped separately to form polymer dispersed liquid crystal films, namely, DPDLC & CPDLC. Nematic liquid crystal (LC) and photopolymer NOA-65 were used to prepare these composite films using polymerisation-induced phase separation (PIPS) technique. In this research work, it is demonstrated that the minute concentration (0.05% wt./wt.) of DR1 and CNPs controls the LC droplet alignment and LC droplet size in polymer dispersed liquid crystal (PDLC) film. The effect of DR1 and CNPs on PDLC film has been investigated in terms of LC droplet size, transition temperature, voltage-transmittance characteristic, contrast ratio, response time, haze, and dielectric measurements. The obtained results reveal that the threshold voltage values of the composite film get reduced from 34.87 V (undoped) to 10.19 and 9.26 V, for 0.05% of DR1 and CNPs doping, respectively. The DR1 (0.05%) doped film shows improved contrast of the undoped film as compared to CNPs (0.05%) film, whereas CNPs (0.05%) doped film shows a faster response time of 2.81 ms as compared to DR1 (0.05%) doped film (3.14 ms). Dielectric analysis of undoped, DPDLC, and CPDLC films represents Debye type relaxation mode.

Electro-optical synaptic characteristics of ferroelectric liquid crystals for artificial intelligence.

We propose electro-optical synaptic devices using surface-stabilized ferroelectric liquid crystals. Typical synaptic characteristics were observed for varying pulse time intervals, numbers of pulses, and signal voltages. Plasticity only occurred when pulses were applied at intervals shorter than the response time of the ferroelectric liquid crystal. Moreover, the plasticity increased with a higher pulse voltage and number of pulses. This demonstrates the importance of repeated learning. The synaptic weights required to make connections through learning in an artificial neural network can be determined by tuning the pulse signal. We discuss the high-speed computational potential of optical neuromorphic devices using liquid crystals.

Greenly synthesized porous carbon nanoparticle (bio‐waste‐based)‐doped nematic liquid crystal composite with optimized electric and electro‐optical properties for devices

AbstractThe present investigation on the impact of porous carbon nanoparticles (PCNPs) on a room temperature nematic liquid crystalline compound (TP‐188‐01) reports extensive electro‐optical analysis of composite followed by dielectric and luminescence study as well. The pure nematic compound has been doped with 0.1%, 0.25%, and 0.5% of PCNPs (spherical), which have been synthesized by green synthesis technique without use of any activating agents. Low‐frequency dielectric analysis (50 Hz to 1 kHz) has been done to confirm ion generation with increase in PCNS concentration. The dielectric data also indicate preferential orientation of molecules from homogeneous to homeotropic alignment, which can be used in performance optimization of electro‐optical devices. The analysis of dielectric data also illustrates the application of PCNS‐doped systems in circuits operating at high voltages. Diffusion coefficient, mobility, and DC conductivity have been further examined to support the above observations. A significant decrease (of about 47%) in the response time of porous carbon nanoparticle liquid crystal (NP‐LC) composites has also been observed. The photoluminescence spectrum of NP‐LC composites as a function of carbon nanosphere (CNS) concentration has shown Quenching (following the Stern–Volmer quenching mechanism) in the luminescence intensity with increasing CNS concentration. The highly improved response time and quenching in the luminescence intensity further make the PCNS‐doped LC composites as ideal materials to be used in devices, encouraging LC‐aided green nanotechnology.

Robust marker-based projector–camera synchronization

Recording clean pictures of projected images requires the projector and camera to be synchronized. This task usually requires additional hardware or imposes major restrictions on the devices with software-based approaches, e.g., a specific frame rate of the camera. We present a novel software-based synchronization technique that supports projectors and cameras with different frame rates and at the same time tolerates camera frame drops. We focus on the special needs of LCD projectors and the effect of their liquid crystal response time on the projected image. By relying on visible marker detection we entirely refrain from taking time measurements, allowing for a robust and fast synchronization.

Synthesis of β-cyclodextrin Functionalized silica nanoparticles and their effects on the dielectric, optical and electro-optic properties of nematic liquid crystal

ABSTRACT The present work reported the synthesis and characterisation of β-cyclodextrin (βCD) grafted into silica (SiO2@βCD) nanoparticles (NPs). Morphology analysis shows that the prepared NPs have a spherical shape with 170 nm of size. The electro-optic, dielectric and viscoelastic properties of SiO2@βCD doped nematic 5CB were examined in different concentrations of the NPs. A decrease in clearing temperature, birefringence and the order of the nanocomposite systems as compared to the pure system was observed. Dielectric parameters of pure and doped samples were measured in the frequency range of 1–2 MHz. Ionic conductivity and dielectric anisotropy increase significantly with NPs concentration due to the strong dipole moment and polarisability of SiO2@βCD. The advantage of dopedSiO2@βCDnematic 5CB is attributed to the significant decrements in threshold voltage by 32% and strong additional coupling of the electrical dipole moments in the spherical NPs with the nematic director field. On the other hand, it is found that the NPs exhibit a decreasing effect on the response time of the nematic liquid crystal, which is demonstrated by the decrement in the viscosity. The results indicate that doping SiO2@βCD is appropriate to fabricate a fast response LC device.

Simple, rapid and sensitive detection of Parkinson's disease related alpha-synuclein using a DNA aptamer assisted liquid crystal biosensor.

Alpha-synuclein (αS) has been proposed as a potential biomarker for the diagnosis of Parkinson's disease (PD). However, the detection of αS using a simple, rapid and sensitive approach is still challenging. Herein, we construct a new type of biosensor for the detection of αS, combining the stimuli-responsiveness of liquid crystals (LCs) and the specific interaction of a DNA aptamer with proteins. In principle, the positively charged surfactant hexadecyltrimethylammonium bromide (CTAB) binds with the negatively charged DNA aptamer via electrostatic interactions; in the presence of αS, the DNA aptamer specifically binds with αS and releases CTAB, which is an amphiphilic molecule and subsequently assembles at the LC-aqueous interface, resulting in a homeotropic alignment of LCs with a dark optical signal. In the absence of αS, CTAB binds with the DNA aptamer without affecting the alignment of LCs, which shows planar anchoring with a bright optical signal. The response time of LCs towards αS is rapid and can be down to minutes. The LC biosensor established here has a good specificity for αS and can recognize αS even from a mixture of proteins. The LC biosensor also exhibits high sensitivity with a limit of detection of αS as low as 10 pM, which is comparable to that of the enzyme-linked immunosorbent assay. This work provides a new strategy for the detection of αS in a simple, rapid and sensitive manner, possessing promising potentials towards early diagnosis and clinical applications.

Seventeen‐inch laser backlight in‐plane switching liquid crystal display with 8K, 120‐Hz driving, and BT.2020 color gamut

AbstractWe have developed a 17‐inch laser backlight in‐plane switching liquid crystal display satisfying the main BT.2020 specifications, which are 8K, 120‐Hz driving, and a BT.2020 wide color gamut. The color gamut of the developed in‐plane switching liquid crystal display covers 98% of the BT.2020 wide color gamut, thanks to a laser backlight and appropriate color filters. The liquid crystal response time of 5 ms, which is sufficient for 120‐Hz driving, is achieved by adapting a faster in‐plane switching liquid crystal display, namely, the short‐range lurch control in‐plane switching liquid crystal display.

Influence of Human Visual Perception and Eye Tracking Motion on the Quality of Moving Image in LCD

There is a very important index in the influence of human visual perception, that is, the degree of the motion blur about the moving image on display device. In this paper, a new kind of improved method is proposed to calculate the response time of liquid crystal under the new backlight driving and modulation, which is more accurate than the traditional moving window integration method. This paper also discusses the eye tracking movement of the human visual system, including studying the influence of image content, size, motion speed and motion direction, based on the human vision property study and the analyzes of the simulation model of image motion artifacts perceived by human eyes. Experiments are performed, using the human eye vision perception measurement system. The experiment data shows that the edge blur time can be reduced to 10.5 ms, compared with the 16.5 ms in traditional drive, reduced by 36.4%, and the human perception of motion blur can be markedly reduced. Also, the results show that the simulation results are in good agreement with the actual measurement data by modifying the proportion coefficient of the eye tracking object model to 0.9. At the same time, through the improved human eye tracking model of smooth moving objects, the actual motion blur phenomenon perceived by the human eye can be calculated more accurately, and the results can be used in image processing algorithms to improve the quality of the moving image on the display.

Effects of electrode structure and dielectric anisotropy on the performance of VA-FFS LC mode.

Vertically-Aligned Fringe-Field Switching (VA-FFS) liquid crystal (LC) mode is known for its intrinsic submillisecond fast response time due to existence of self-imposed boundaries of virtual walls. In this paper, we investigate the effects of electrode structure and LC dielectric anisotropy. The performance of VA-FFS with conventional 2D and 3D electrode designs are compared. By using the 3D electrode design, higher transmission and faster response time are found possible as a result of having less dark states and at the same time having more virtual walls surrounding a 3D pixel. In the second part, we investigate the difference between VA-FFS LC mode employing LC materials with positive and negative dielectric anisotropy, while keeping all other factors the same. We found that, in general, positive LC materials can provide faster response time whereas negative LC materials can provide higher transmission. In the case of 2D design, however, negative LC is found to have rather unexpected slow response times due to i) existence of a 2-step switching process and ii) disappearance of virtual wall, which have never been reported or published before for VA-FFS. In this paper, we will show that, by using a 3D design, both of these problems for negative LC can be improved such that 3D design can help maintain the stability of virtual walls and also help bring the response time of negative LC closer to that of positive LC. VA-FFS LC has been actively researched for VR/AR application in recent years.

49‐1: Invited Paper: Analog LCOS SLM Devices for Display Applications

Liquid‐crystal‐on‐silicon (LCOS) device is a potential candidate for spatial light modulators (SLMs) due to its high resolution and the wide range of tunable phase retardation. Besides the telecom applications, SLM is also very promising for display applications, especially for the augmented reality (AR) displays. In this paper, we will discuss the advantages of analog LCOS SLM compared with the digital one. A 0.6” short‐loop sample test result with precise cell gap controlled is introduced. Some CGH images are demonstrated using different algorithms. Finally, the liquid crystal response time performances are also discussed.

Color-switchable liquid crystal smart window with multi-layered light guiding structures.

We propose here a novel multi-layered waveguide liquid crystal (LC) smart window with full color rendering based on a polymer-network liquid crystal system. The inserted position of three-primary-color LED light bars is specially designed, which is parallel to the LC alignment to obtain a higher difference between transparent and scattering states. The optimal matching of polymer-network LC system is experimentally achieved by comparing several groups of LC and reactive mesogen materials. The prepared smart window is measured and analyzed in detail including optical/chromatic test, morphology characterization, and actual application effect. The proposed architecture opens up new prospects of flexible color switchable ability and synchronized full-color display for smart windows without limitations of slow LC response time and complicated field sequential driving scheme.

Performance enhancement of low viscosity nematic liquid crystal dichroic dye mixtures by addition of chiral dopants

This work investigates the improvement of transmittance dynamic and response time of low viscosity nematic liquid crystals, combined with neutral dichroic dyes, by the addition of chiral dopants, while maintaining a low Haze value. We present some experimental results showing the impact of the addition of these chiral dopants on both dichroic efficiency, switching time, and scattering, obtained from a benchmark of various commercially available liquid crystal mixtures.

Pursuing High Quality Phase-Only Liquid Crystal on Silicon (LCoS) Devices

Fine pixel size and high-resolution liquid crystal on silicon (LCoS) backplanes have been developed by various companies and research groups since 1973. The development of LCoS is not only beneficial for full high definition displays but also to spatial light modulation. The high-quality and well-calibrated panels can project computer generated hologram (CGH) designs faithfully for phase-only holography, which can be widely utilized in 2D/3D holographic video projectors and components for optical telecommunications. As a result, we start by summarizing the current status of high-resolution panels, followed by addressing issues related to the driving frequency (i.e., liquid crystal response time and hardware interface). LCoS panel qualities were evaluated based on the following four characteristics: phase linearity control, phase precision, phase stability, and phase accuracy.

Algorithm and Architecture Design of a Hardware-Efficient Frame Rate Upconversion Engine

Owing to the limited response time of liquid crystal displays (LCDs), the motion-blurring effect is a critical problem to overcome for LCD applications. Among the available motion-blurring reduction methods, frame-rate upconversion (FRUC) presents an outstanding performance; however, it also yields a high computational load, which causes a design challenge for a hardware-efficient FRUC engine running advanced specifications. In this paper, a hardware-efficient FRUC algorithm and architecture were proposed, comprising three core techniques: bidirectional 3-D recursive search (BD-3DRS), spatial and temporal motion vector refinement (ST-MVR), and spatial and temporal overlapped-block motion compensation (ST-OBMC). BD-3DRS provides an initial MV with minor computational overhead. Subsequently, ST-MVR refines the initial MV to generate a more accurate final MV. With this final MV, ST-OBMC has finely processed the interpolated block, especially for the textural smoothness across block boundaries. The experiment results indicated that compared with other sophisticated FRUC methods, computation was reduced by 80% with a minor degradation in a peak signal-to-noise ratio of less than 2%. The hardware architecture was realized using the CMOS technology, and the chip size was $1.20 \times 1.20$ mm2. The working frequency was 270 MHz with a power consumption of 128.08 mW. The maximum throughput was as high as 508 Mpixels/s, which can support a resolution of $3840 \times 2160$ from 60 to 120 Hz. Compared with other FRUC architectures, this paper has demonstrated superior hardware efficiencies in terms of area usage and energy consumption.

51‐5: Late-News Paper: Fast Motion Picture Response Color Filter LCOS for Wearable Applications

The display for augmented reality (AR) applications has to update image promptly in order to cope with the user's head movement or any environment change. It makes image blur become noticeable if the motion picture response time of the AR display is longer than 1.5ms. We propose an image blur free Color Filter LCOS (CFLCOS) which equipped with 1.9ms liquid crystal response time; analog frame buffer and 480fps refreshing rate. It is found that the MPRT of such device can be as fast as <1.5ms.

16.3: Zero Seamless LCD Splice Wall Design System

LCD splice wall can achieve excellent display result with large area and low cost. The main technology of splice wall include seam width, brightness, contrast, visual angle, chromaticity consistency, liquid crystal response time and so on. Among these factors, the seam width is the most important key affecting the user experience, Now there are three kinds of technology to optimize the seam width: Design more narrow border module, weaken the gap with optical components, weaken the gap with LED. The results of the survey show weaken the gap with LED is the best solution, Filling the gap of LCD splice wall with LED, Through N-Scalar image processing technology, LCD and LED can display the same video at the same time, which can get better display effect. This article focuses on the technical scheme of using LED to weaken the seam, and implemented in one FPGA chip.

Improved response time of thick liquid crystal device by using electrospun nanofiber

In this study, we report the improved response time of a thick nematic liquid crystal (LC) device by using an electrospun nanofiber (NF). We investigated the influence of NF characteristics including polymer material, NF volume ratio, and diameter, on the electrical characteristic of the NF/LC composite. A conventional LC device and a polymer-stabilized liquid crystal (PSLC) device were fabricated to compare their electrical characteristics with those of the NF/LC composite. The rise time, decay time, and threshold voltage of these LC devices are determined by measuring the dielectric permittivity. In comparison with the conventional LC device, the decay time of the NF/LC device is significantly improved. Compared with the PSLC device with the same thickness, the NF/LC device shows a lower threshold voltage while exhibiting the same decay time. Finally, we demonstrated the markedly improved response time of a THz phase shifter by using an NF/LC composite.

47‐4: Invited Paper: Development of Fast Response, Low Latency Real‐time Camera and Display System for Automotive Applications

We have newly developed a Camera Monitoring System (CMS) for automotive side and back mirrors. With improved liquid crystal response time, display brightness, refresh rate and system latency, developed CMS will greatly enhance the safety of driving, compared to the conventional CMS.