Reflective Liquid Crystal Display Research Articles

87‐2: Study on Optical Performances of New Structure Reflective Liquid Crystal Display with Advanced Polarizer Film†

Reflective liquid crystal displays (RLCDs), which use ambient light as their light source, have been extensively explored as people pay more attention to eye care displays. In this work, a novel variety of normal white mode RLCD with improved high contrast ratio (CR) performance is studied. The reflection function is achieved by cleverly designing the angle of the advanced polarizer film (APF). The CR of the RLCD is enhanced by over 90% when compared to the conventional metal RLCD, significantly enhancing its performance. The study demonstrates that by adjusting the angle of polarizer PVA, Chroma can be optimized and adjusted. The new RLCD's customizable Chroma on bright state makes it suited for a variety of application scenarios. The results show that the new RLCD has a high CR, a flexible Chroma design, and a wide range of application scenarios.

35‐2: A kind of Front Light Source Module Adapted to Reflective LCD

Reflective Liquid Crystal display (RLCD) has the advantage s of low power and lightweight relying on the metal layer in TFT glass to reflect the environment light, developing rapidly in the outdoor display, e‐books, price tag, and sports watch market. However, when the ambient light weaker, RLCD requires an additional light source. Therefore the development of the front light source has become a new research direction. This paper designed a thin front light source adapted to Reflective LCD by using the microstructure to control light angle. Optimize microstructure parameters to improve contrast ratio and light efficiency utilization. The density arrangement of microstructures to achieve the higher uniformity and no moire.

P‐12.7: Front Light Guide Plates for Reflective LCDs

Reflective liquid crystal display has the advantages of energy saving and environmental protection. When the ambient light is low, the front light source is required to provide illumination rays. The front light guide plate has a great influence on display luminance, contrast, etc. Based on Comprehensive considerations on luminance, uniformity, stray light, an analysis and evaluation method for front light guide source is proposed. Taking spherical dots as an example, the influence of dot radius and height on the comprehensive performance of the front light source is analyzed. The simulation results show that when the R:H is 3:1, the comprehensive evaluation parameters of the spherical structure are high, and the signal‐to‐noise ratio is increased by 240%, which can greatly improve the display performance. The analysis and evaluation method proposed in this paper can effectively guide the development of front light guide plates, shorten the development time and reduce the development cost.

P‐3.2: Research on the Structure and Optical Performance of Reflective Liquid Crystal Display

P‐3.2: Research on the Structure and Optical Performance of Reflective Liquid Crystal Display

Reflectance-enhanced liquid crystal displays and thermochromic multi-color patterning

This paper presents a reflective liquid crystal display (LCD) combined with thermochromic liquid crystal microcapsules to enhance the electro-optical performance of the LCD and to empower new driving modes. The prepared reflectance-enhanced liquid crystal display (Re-LCD) possesses a bilayer structure, with the upper layer being a polymer-stabilized liquid crystal layer prepared by UV-induced phase separation and the lower layer being a thermochromic layer prepared by coating with thermochromic liquid crystal microcapsules. The effect of chiral compound content on the reflection wavelength of liquid crystal center was investigated. After that, the effects of monomer ratio, polymerization time and spin coating speed on the electro-optical properties and morphology of Re-LCD were investigated comprehensively by three sets of experiments. The results show that the combination of LCD and thermochromic materials has a synergistic effect in display, and the prepared Re-LCD shows more than 51% reflectance compared with typical LCD. The multi-field driving function allows the Re-LCD to rapidly switch optical states by force, electric, and temperature fields and obtain multi-color patterns during the driving process. This provides new application possibilities for LCD.

P‐111: Research on the Structure and Optical Performance of Reflective Liquid Crystal Display

In this article, we designed two different Reflective liquid‐crystal displays (RLCD) structures using PDLC with high haze and high transparency, and discussed the influence of dye of liquid crystal and reflective particles in different structures on the display effect. Dye liquid crystals have a bright future in reflective display, but the influence of dye concentration on color gamut still needs further verification. When the TiO2 reflective particles are added to the color film (CF) to increase the reflectivity, because the reflection occurs on the surface of the film, adding higher concentration of TiO2 in a thin film shows the best display effect.

Reflective blue phase liquid crystal display with triangular dielectric layer

ABSTRACT We propose a reflective blue-phase liquid-crystal display (LCD) with triangular dielectric layers and a diffuse reflector electrode. The triangular dielectric layers with a high dielectric coefficient on the top and bottom indium tin oxide glass substrates are equivalent to the conductive plates, forming a corrugated electrode structure. This type of reflective blue-phase LCD based on planar electrode and diffuse mirror electrode can offer relatively high reflectance (~74.5%) and low operation voltage (9.2 Vrms) compared to most other devices due to its fairly strong and uniform horizontal electric field component along the whole blue-phase liquid crystal bulk. This design has the advantages of fast response time, easy manufacturing process, a high resolution and full-colour capability. It is a promising future high-quality reflective full-colour microdisplay.

Reflective liquid crystal display with fast response time and wide viewing angle

A reflective liquid crystal display (RLCD) with fast response time and wide viewing angle is proposed. Both the top and the bottom substrates are deposited with a whole planar common electrode, the bottom substrate is additionally involved square pixel electrodes arranged at uniformly-spaced, and a bumpy reflector is coated under the bottom substrate. The square pixel electrodes and planar common electrode generate a strong vertical electric field above the pixel electrodes and a fringe field between the pixel electrodes, which helps to reduce the reflection dead zone. The simulation results verify that this device can achieve wide viewing angle, high contrast ratio, small gamma shift, fast response time, while keep low operating voltage and high reflectance. What is more, the fabrication process and driving mode of the proposed structure is relatively simple.

35.1: Invited Paper: Measurement and Standardization of Display Lighting Units

Display lighting unit has always been the focus for optimization when comes into display engineering to improve its electrical, optical, and electro‐optical performance. In recent years, with the development of reflective LCD (liquid crystal display), electronic paper display, laser projection display, etc., the measurement of display lighting unit has received more attention. The IEC TC110 "Electronic Display" established the standardization team PT62595 to develop international standards. Currently, the project team has worked a variety of lighting technologies, including back light unit (BLU) and front light unit (FLU), light module and engine, light bar, and light components. In this paper, we reviewed the roadmap of this group and key items that involve in the measurement methods to give an overview of the documents.In the previous year, the IEC released two new standards, IEC62595‐2‐2 “Measuring methods of LED light bars used in LCD BLUs” and IEC62595‐2‐3 “Electro‐optical measuring methods of LED frontlight unit”. Both documents have now been put into the implementation in the display industry.In IEC 6595‐2‐2, spatial luminance uniformity and angular luminance, color uniformity and color angular uniformity were addressed. In Figure 1, it shows an example of a typical light bar luminance distribution profile to indicate the luminance uniformity by quantifying the information along axis.Example of the luminance distribution profiles along the x‐axis, Lv(x, o)figureIn addition, in order to achieve these characteristics, the optical coupling analysis and optimization between the light bar and the light guide plate (LGP) was discussed. Furthermore, this work introduced the specifications on the requirements for test environment, the architecture of the test equipment, the reference diffuser settings, and the coordinate system.In IEC 62595‐2‐3, the standard specifies the measurement conditions and measuring methods for determining electrical, optical, and electro‐optical properties of LED FLUs for reflective displays. In FLU, the light ray of the FLU with a reflective LC display can be sensitive to the testing position and viewing direction. As shown in Figure 2, light rays are introduced to the LGP (light guide plate) from the coupling side. The rays are reflected on the inner surfaces of the micro‐structures (on the front surface) due to TIR (total internal reflection). The FLU is served as a transparent medium that has reflection property on both surfaces. We explained some of the factors that were covered in the standard document for the measurement and evaluation of both surfaces, including angular luminance distribution, luminance uniformity, spectral power distribution, chromaticity uniformity and angular color uniformity in CIE 1976 system, as well as FLU‐polarization characteristics and optical noise (undesired luminance) along the zenith angle in any azimuth angle.Light rays of FLU with a reflective LC displayfigure

P‐79: Research and Development of Reflective Display Technology

This article mainly presents the R&D of the innovative technique about RLCD (Reflective Liquid Crystal Display). By means of fully independent innovation, products without backlight have been successfully developed. The reflectance of the reflecting films can reach 88.9%. The RLCD technology has been applied to current production lines without equipment investment. Meanwhile, by successfully solving key technical difficulty such as reflecting film structure, shared mask process and reflective metal layer corrosion, the best condition has been adopted in the products.

Expanding color gamut of reflective liquid crystal displays from filtering undesirable wavelengths of a light source by an embedded etalon.

This work demonstrates a method to reduce the intensity of the undesirable wavelengths of blue (B-) and green (G-) ambient lights to expand the color gamut of reflective liquid crystal displays (LCDs) by an embedded etalon. The built-in reflector of the reflective LCDs is replaced by the blue-green overlapping wavelengths filtering etalon, which is used to reduce the intensity of undesirable B- and G-primaries, thereby decreasing the color cross talk of B- and G-color filters. After etalon adoption, the color gamut can be expanded from 105.96% to 121.81% of National Television System Committee (NTSC) in International Commission on Illumination (CIE) 1976 color space. Compared with the color gamut of the display without the blue-green overlapping wavelength etalon, the maximum expansion of color gamut is ∼15.85%. Moreover, the balance between light loss and color gamut expansion should be taken into consideration.

7-2: Transmissive OLED and Reflective LC Hybrid (TR-Hybrid) Display

In our newly developed display with low power consumption, circuits for a reflective liquid crystal display (LCD) and an organic light-emitting diode (OLED) display are formed in the same field-effect transistor layer to control these two types of display devices. This display has high visibility in both a bright and a dark environment with use of the reflective LCD and the OLED display, respectively.

Reflective LCD with high reflectance and color reproducibility for reduced eye strain

AbstractWe fabricated a prototype of a 434‐ppi 5.9‐in reflective liquid crystal display for use as an e‐book reader. With high‐level optical characteristics with a reflectance of 28.7% and an NTSC ratio of 37%, we achieved eye‐friendly reflective liquid crystal display.

Circularly Polarized Luminescence and a Reflective Photoluminescent Chiral Nematic Liquid Crystal Display Based on an Aggregation‐Induced Emission Luminogen

Circularly Polarized Luminescence and a Reflective Photoluminescent Chiral Nematic Liquid Crystal Display Based on an Aggregation‐Induced Emission Luminogen

High contrast reflective liquid crystal display using a thermochromic reflector

This paper presents a reflective liquid crystal display (LCD) with a high contrast ratio (CR) combined with mono-type thermochromic materials to solve the low CR of reflective type LCDs. Here, reflective, wide-band, electrically controlled birefringence mode was used as the optical liquid crystal (LC) mode, and a thermochromic material was used as the reflector for the white state and an absorber for the dark state. The combination of LCD and thermochromic material can have a synergistic effect in achieving a better display. By controlling the reflectance of the thermochromic reflector using Joule heating, the proposed reflective LC cell exhibited a high CR of approximately 70:1. The figure was extremely high compared to the approximately 10:1 of a typical reflective LC cell with an optically wide band design. The proposed LC cell configuration is expected to find many outdoor applications which can admit slow response speed.

Reflective liquid crystal display without flicker for reducing eye strain

AbstractWe fabricated two types of 6.05‐in. active matrix reflective liquid crystal displays (LCD) using a c‐axis‐aligned crystalline oxide semiconductor (CAAC‐OS) for the driver circuit and field‐effect transistors in pixels: one is of the high‐reflectance type, and the other is of the wide‐gamut type. Because of the small off‐state current of the CAAC‐OS and the improved liquid crystal material, low‐frequency driving at 1/60 fps or lower was achieved without memory in a pixel. Consequently, the still image display does not require data writing, except in turning pages; thus, it is flicker‐free in still image display. We also examined the page‐turning operation for less eye strain.The study shows that a reflective color LCD using a CAAC‐OS results in eye‐friendly still image display without flicker similar to an electrophoretic display (EPD); however, it is capable of moving image display, color display, and eye‐friendly page‐turning operation, which are difficult to achieve with an EPD.

P‐135: Reflective LCD without Flicker for Reduced Eye Strain

AbstractWe fabricated a 6.05‐inch reflective liquid crystal display (LCD) using a CAAC‐OS for a driving transistor. We achieved low frequency driving at 1/60 fps or lower and flicker reduction. With our LCD, eye strain can be reduced more than with an electrophoretic display.

Novel write-erasable input display with memory circuits and photosensors

We have developed a new conceptual liquid crystal display (LCD) with a memory circuit and a photosensor in each pixel to realize excellent handwriting performance. Direct writing and erasing a character in the LCD are available because their direct processing only in the pixel are performed without calculating coordinates by using a light pen and integrated pixel circuits. In addition, this LCD enables to display still image data stored in the pixel memory circuit at a low liquid crystal (LC) driving frequency of 1.0 Hz. In the result, we have achieved faster handwriting response time of 0.5 ms and lower power consumption of 0.7 mW in 7.0-in. QVGA reflective LCD panel.

The influence of cyano compound on liquid crystal blue phase range

Liquid crystal blue phase (BP) is interesting for fast light modulators and tunable photonic crystals. In this study the influence of mixture composition on the thermal stability of BP was investigated, especially the influence of cyano compound addition. The relationship between polymer stabilization possibility and cyano dopant was examined, too. It was shown that the cyano compound is not necessary to create blue phase and has no effect on polymer stabilization of blue phase. Full Text: PDF References H. Kikuchi, M. Yokota, Y. Hisakado, H. Yang, T. Kajiyama, "Polymer-stabilized liquid crystal blue phases", Nature Materials 1, 64 (2002) CrossRef H. Yoshida, Y. Tanaka, K. Kawamoto, H. Kubo, T. Tsuda, A. Fuji, S. Kuwabata, H. Kikuchi, M. Ozaki, "Optical and Thermal Characteristics of Nd:LuVO 4 Grown by Floating Zone Method", Appl. Phys. Express, 2, 12501 (2009) CrossRef K. Z. Zheng, D. Shen, P. Huang, "Wide blue phase range of chiral nematic liquid crystal doped with bent-shaped molecules", New J. Phys., 12, 113018 (2010). CrossRef H. Kikuchi, H. Higuchi, "Fast Electro-Optical Switching in Polymer-Stabilized Liquid Crystalline Blue Phases for Display Application", SID07 Digest, 38, 1737-1740 (2007) CrossRef J. P. Sethna, in Theory and Applications of Liquid Crystals (edited by J. L. Ericksen and D. Kinderlehrer) (Springer-Verlag,1987), p. 305 CrossRef P.P. Crooker, in Chirality in Liquid Crystals (edited by H.S. Kitzerow and C. Bahr)186-222 (Springer, New York, 2001) CrossRef P. R. Gerber, "Electro-Optical Effects of a Small-Pitch Blue-Phase System", Mol. Cryst. Liq. Cryst., 116, 197 (1985) CrossRef K. M. Chen, S. Gauza, H. Xianyu, S. T. Wu, "Submillisecond Gray-Level Response Time of a Polymer-Stabilized Blue-Phase Liquid Crystal", J. Display Technol., 6, 49 (2010) CrossRef S. T. Wu, D. K. Yang, Reflective Liquid Crystal Displays, New York: Wiley (2001) S. K. Hong, G. L. Lim, H. Kikuchi, "Thickness Dependence of Blue Phase Transition Behavior of Chiral Nematic Liquid Crystal", Mol. Cryst. Liq. Cryst., 511, 248 (2009). CrossRef S. K. Hong, H. S. Choi, S. Shibayama, H. Higuchi, H. Kikuchi, "Blue Phase Temperature Range at n-Cyanobiphenyl Homologue Chiral Nematic Liquid-Crystal Mixtures", Mol. Cryst. Liq. Cryst., 528, 32 (2010) CrossRef P. Kula, Synthesis and properties of terphenyl and quaterphenyl based chiral diesters; Liquid Crystals, in press. W. Rejmer, K. Czupryński, W. Drzewiński, "An Influence of Nematic Medium on Helical Twisting Power of Chiral Compounds", Mol. Cryst. Liq. Cryst., 547, 33 (2011). CrossRef H. Kaczmarek, P. Gałka, "Active Thermitic Material Discovered in Dust from the 9/11 World Trade Center Catastrophe", The Open Process Chemistry Journal, 1, 8 (2008). CrossRef

Reflective dual-mode liquid crystal display possessing low power consumption and high contrast ratio under ambient light

We propose a reflective dual-mode liquid crystal display (RD-LCD) which has advantages of long memory retention time and high contrast ratio. The proposed device adopts ideal bistable characteristics, a cell thickness over pitch (d/p) of 0.25. It can realize long memory retention time, thereby reducing power consumption. In addition, an optical configuration for the RD-LCD makes low light leakages at dark state and shows good dispersion characteristics in both dark and bright states over the entire visible ranges. We experimentally confirmed retention time over 6 months in memory mode and memory and dynamic contrast ratios of 47:1 and 43:1 under ambient light, respectively. As a result, the proposed RD-LCD demonstrates convincingly that it is a candidate for green display.