Technical evolution of liquid crystal displays

Liquid crystal displays (LCDs) have evolved rapidly as a result of fierce competition among the various LCD technologies, and now occupy the largest proportion of the entire display market. The evolution of LCDs continues, with new technologies and new materials in development to replace current devices. This review summarizes the key technologies used in commercially successful LCD products, focusing on the requirements for high-end displays and the benefits of the in-plane switching and multi-domain vertical alignment modes. As in past advances, the development of new materials will play an important role in the continued technical evolution of LCDs.open252

Wide Viewing Angle Liquid Crystal Displays

In this dissertation, novel phase compensation technologies are applied to the designs of wide viewing angle and high transmittance liquid crystal displays. First, a design of wide viewing angle liquid crystal displays utilizing crossed linear polarizers is proposed. The designed multi-domain vertical-alignment liquid crystal display predicts superb contrast ratio over wide viewing angles. Next, to increase the bright state transmittance while maintain the high contrast. Finally, to reduce the cost and improve the applicability of the broadband and wide-view circular polarizer, the device configuration of the broadband and wide-view circular polarizer is significantly simplified by the application of biaxial compensation films. The produced states of polarization remain close to the ideal circular polarization over a wide range of incident angles within the visual spectrum. With this circular polarizer, the presented wide-view liquid crystal display predicts high contrast ratio as well as high and uniform transmittance over wide viewing angles within the visual spectrum. ratio, wide viewing angle circular polarizers are developed. The produced states of polarization are very close to the ideal circular state of polarization over a wide range of incident angles within the visual spectrum. This guarantees not only high contrast ratio but also high and uniform transmittance

Fast Response in-plane-switching pi-cell liquid crystal displays

Transmissive liquid crystal displays having response time that can be approximately 2 to approximately 3 times faster than conventional displays. The displays adjust the rubbing angles to above approximately 20 degrees and preferably between approximately 30 and approximately 40 degrees. The displays have fast response times, enhanced brightness and increased gray scale linearity while maintaining wide viewing angle

Flower Shaped Vertical Alignment Liquid Crystal Display with Wide Viewing Angle and Fast response time

A novel vertical alignment liquid crystal display with a structure having a flower-shaped vertical alignment (FVA) has the properties of fast response, high contrast ratio and a wide view angle. The method for making the device and structure of the FVA comprises the arrangement of: a first substrate with a protrusion shaped electrode as the pixel electrode; and a second substrate as the common electrode; aligning layers formed on said first and second substrates providing liquid crystal vertical alignment; liquid crystal materials filling a space between said first and second substrates as a liquid crystal cell; a linear polarizer and wide band quarter-wave film forming a circular polarizer; and, said circular polarizer disposed on exterior surfaces of said liquid crystal cell. When voltage is applied to the device, the liquid crystal (LC) director distribution looks like a flower blossom

Low Voltage Blue Phase Liquid Crystal Displays

From cell phones, laptops, desktops, TVs, to projectors, high reliability LCDs have become indispensable in our daily life. Tremendous progress in liquid crystal displays (LCDs) has been made after decades of extensive research and development in materials, device configurations and manufacturing technology. Nowadays, the most critical issue on viewing angle has been solved using multidomain structures and optical film compensation. Slow response time has been improved to 2-5 ms with low viscosity LC material, overdrive and undershoot voltage, and thin cell gap approach. Moving image blur has been significantly reduced by impulse driving and frame insertion. Contrast ratio in excess of one million-to-1 has been achieved through local dimming of the segmented LED backlight. The color gamut would exceed 100% of the NTSC (National Television System Committee), if RGB LEDs are used. Besides these technological advances, the cost has been reduced dramatically by investing in advanced manufacturing technologies. Polymer-stabilized blue phase liquid crystal displays (BPLCDs) based on Kerr effect is emerging as a potential next-generation display technology. In comparison to conventional nematic devices, the polymer-stabilized BPLCDs exhibit following attractive features: (1) submillisecond response time, (2) no need for molecular alignment layers, (3) optically isotropic dark state when sandwiched between crossed polarizers, and (4) transmittance is insensitive to cell gap when the in-plane electrodes are employed. However, aside from these great potentials, there are still some tough technical issues remain to be addressed. The major challenges are: 1) the operating voltage is still too high (~50 Volts vs. 5 Volts for conventional nematic LCDs), and the transmittance is relatively low (~65% iv vs. 85% for nematic LCDs), 2) the hysteresis effect and residual birefringence effect are still noticeable, 3) the mesogenic temperature range is still not wide enough for practical applications (40 oC to 80 oC), and 4) the ionic impurities in these polymer-stabilized nano-structured LC composites could degrade the voltage holding ratio, which causes image sticking. In this dissertation, the BPLC materials are studied and the new BPLC device structures are designed to optimize display performances. From material aspect, the electro-optical properties of blue phase liquid crystals are studied based on Kerr effect. Temperature effects on polymer-stabilized blue phase or optically isotropic liquid crystal displays are investigated through the measurement of voltage dependent transmittance under different temperatures. The physical models for the temperature dependency of Kerr constant, induced birefringence and response time in BPLCs are first proposed and experimentally validated. In addition, we have demonstrated a polymer-stabilized BPLC mixture with a large Kerr constant K~13.7 nm/V2 at 20 oC and =633 nm. These models would set useful guidelines for optimizing material performances. From devices side, the basic operation principle of blue phase LCD is introduced. A numerical model is developed to simulate the electro-optic properties of blue phase LCDs based on in-plane-switching (IPS) structure. Detailed electrode dimension effect, distribution of induced birefringence, cell gap effect, correlation between operation voltage and Kerr constant, and wavelength dispersion are investigated. Viewing angle is another important parameter. We have optimized the device configurations according to the device physics studied. With proper new device designs, the operating voltage is decreased dramatically from around 50 Volts to below 10 Volts with a reasonably high transmittance (~70%) which enables the BPLCDs to be addressed by amorphous silicon thin-film transistors (TFTs). Moreover, weak wavelength v dispersion, samll color shift, and low hysteresis BPLCDs are achieved after their root causes being unveiled. Optimization of device configurations plays a critical role to the widespread applications of BPLCDs. In addition to displays, blue phase liquid crystals can also be used for photonic applications, such as light modulator, phase grating, adaptive lens and photonic crystals. We will introduce the application of blue phase liquid crystal as a modulator to realize a viewing angle controllable display. The viewing angle can be tuned continuously and precisely with a fast response time. The detailed design and performance are also presented in this dissertation

JTEC panel on display technologies in Japan

This report is one in a series of reports that describes research and development efforts in Japan in the area of display technologies. The following are included in this report: flat panel displays (technical findings, liquid crystal display development and production, large flat panel displays (FPD's), electroluminescent displays and plasma panels, infrastructure in Japan's FPD industry, market and projected sales, and new a-Si active matrix liquid crystal display (AMLCD) factory); materials for flat panel displays (liquid crystal materials, and light-emissive display materials); manufacturing and infrastructure of active matrix liquid crystal displays (manufacturing logistics and equipment); passive matrix liquid crystal displays (LCD basics, twisted nematics LCD's, supertwisted nematic LCD's, ferroelectric LCD's, and a comparison of passive matrix LCD technology); active matrix technology (basic active matrix technology, investment environment, amorphous silicon, polysilicon, and commercial products and prototypes); and projection displays (comparison of Japanese and U.S. display research, and technical evaluation of work)

액정기반 발광형 디스플레이를 위한 용액공정 내재형 편광판에 관한 연구

학위논문 (석사) -- 서울대학교 대학원 : 공과대학 전기·정보공학부, 2020. 8. 이신두.Recently, the advancement of the liquid crystal display (LCD) technology has greatly focused on the clear image quality together with the natural color. According to the demand for the image quality, the in-cell polarizers have been attracted much attention owing to the advantages of improving the contrast ratio and reducing the thickness of LCD. In this work, we proposed the QD-based emissive LCD with the in-cell polarizer composed of dichroic dyes. The in-cell polarizer was fabricated through the solution-processing of a dichroic dye solution. The QD layer was constructed on the inner surface of the top substrate, and the in-cell polarizer was subsequently prepared on the QD layer to prevent the depolarization of the emission light and the degradation of the QDs. The intensity of the incident light for exciting QDs was modulated by the phase retardation through the LC layer, depending on the magnitude of the applied voltage. This leads directly to the modulation of the emission spectra of QDs with the color gamut extended to about 80 % of the BT.2020 standard. The architecture based on the in-cell polarizer will provide a simple and viable method of constructing the QD-based emissive LCD with high color purity in a cost-effective manner.최근 액정 디스플레이(LCD) 기술들은 자연스러운 색상과 더불어 선명한 화질을 중심으로 크게 발전했다. 고화질 영상에 대한 수요와 함께, 내재형 편광판 (in-cell polarizer)는 대조율 향상과 LCD 두께 감소라는 다양한 장점들로 인해 더 많은 관심을 끌었다. 본 연구에서는 이색성 염료로 구성된, 내재형 편광판를 적용한 양자점 기반 광 발광 액정 디스플레이를 제안하였다. 양자점 층은 상단 기판의 내부 표면에 구성되었고, 이후 양자점 층에 내재형 편광판를 도입하여 입사광의 편광상태를 유지하고 양자점의 성능 저하를 방지하였다. 내재형 편광판은 용액 공정을 통해 이색성 염료를 정렬하여 제작되었다. 양자점 광 발광을 위한 입사광의 세기는 적용된 전압의 세기에 따라 액정 셀을 통한 위상 지연에 의해 변조되었다. 이는 색 영역이 BT.2020 표준의 약 80%까지 확장된 높은 색 순도를 보여준다. 내재형 편광판에 기반한 액정 디스플레이 구조는 비용-효율적인 방법으로 높은 색 순도를 가진 양자점 기반 광 발광 액정 디스플레이를 구성하는 간단하고 실행가능한 방법을 제공할 것이다.1. Introduction 1 1.1. Overview of liquid crystal-based displays 1 1.1.1. Main LCD Modes 3 1.1.2. Types of backlight unit for LCDs 9 1.2. Outline of thesis 15 2. LCD with QD color filters 16 2.1. Types of polarizers 16 2.2. Architecture of QD-LCD with in-cell polarizer 19 3. Experiments 24 3.1. Fabrication of photoluminescence QD patterns 24 3.2. Dichroic dye-based in-cell polarizer 26 3.3. Solution-processed in-cell polarizer with QD-based LC cell 29 3.4. Measurements of optical and photoluminescence characteristics 30 4. Results and Discussion 31 4.1. Analysis of polarizing characteristics of in-cell polarizer 31 4.2. Photoluminescence characteristics of QD-based LC cell with in-cell polarizer 34 4.3. Microscopic images of QD-based LC cell with in-cell polarizer 35 5. Conclusion 38 Bibliography 39 국문 초록 43Maste

Fast Response Liquid Crystal Mode. DIV.B

A novel nematic liquid crystal (LC) mode is based on the Fringing-Field-Switching of Vertically-Aligned liquid crystals. The VA-FFS mode is capable of generating very fast optical modulation without the use of very thin cell gap. IA major feature of this LC mode is that it has unusual fast relaxation time compared with the conventional nematic LC modes that require a thin cell gap. This fast relaxation occurs even at very low applied voltages and the operation is very stable. The fast-response mechanism of this LC mode involves the confinement of liquid crystal molecular switching within self-imposed thin LC layers. The present invention provides a novel approach to overcome the fundamental problem of the long relaxation time of the conventional nematic liquid crystal modes