Comparison of organic and inorganic alignment layers for low‐power liquid‐crystal devices using low‐frequency applied‐voltage waveforms

Abstract— Bistable displays are known to have low‐power consumption, but they usually lack the ability to display full‐color video‐rate images. Operating active‐matrix liquid‐crystal displays (AMLCDs) with an ultra‐wide refresh‐rate range, down to ～1 Hz, can lower the power consumption to that of bistable devices and offer video rates as well. A SiO^x‐layer‐based liquid‐crystal (LC) alignment technique is studied here to overcome the ion problems typically encountered with low‐refresh‐rate devices. The effect of ions on the voltage‐holding ratio (VHR) and residual DC voltage (RDC) with SiO^x‐based LC alignment is compared with those for polyimide‐based LC alignment. It is found that only SiO^x alignment provides high VHR and small RDC, with good stability over time. Therefore, it is shown that SiO^x alignment is an excellent candidate for low‐power AMLCDs operated with an ultra‐wide refresh‐rate range.     

Analysis of image sticking on a real MVA Cell

Abstract— Image‐sticking phenomenon is one of the most important issues affecting LCDs, especially LCD TV. It is known that image sticking is caused by residual DC voltage. An analysis of the cause that induces image sticking on a real LCD cell is very difficult to perform and is rarely reported. In this paper, the impurities that cause boundary image sticking on a real MVA cell was analyzed by examining a cross section of a cell, the bulk LC layer, the vicinity of the LC layer, the LC layer/PI alignment film interface using microanalysis methods such as infrared micro‐spectroscopy (μ‐IR) and micro‐sampling mass spectrometry (μ‐MS). It is clarified that there is quite a bit of aromatic acid at the boundary of the image‐sticking area than in the normal area at the LC/PI alignment film interface on the color‐filter side, not the TFT side, and it is assumed that aromatic carboxylic acid, a negative charged material, is condensed at the LC/PI alignment film interface on the color filter side by an electrically driven DC component inducing an electric‐condenser residual DC voltage.     

Decidability of a Hybrid Duration Calculus

We present a logic which we call Hybrid Duration Calculus (HDC). HDC is obtained by adding the following hybrid logical machinery to the Restricted Duration Calculus (RDC): nominals, satisfaction operators, down-arrow binder, and the global modality. RDC is known to be decidable, and in this paper we show that decidability is retained when adding the hybrid logical machinery. Decidability of HDC is shown by reducing the satisfiability problem to satisfiability of Monadic Second-Order Theory of Order. We illustrate the increased expressive power obtained in hybridizing RDC by showing that HDC, in contrast to RDC, can express all of the 13 possible relations between intervals.     

A study on reducing image‐sticking artifacts in wide‐screen TFT‐LCD monitors

Abstract— In order to improve the image quality of flat‐panel displays, the image retention of a display has to be reduced. But at the same time, display devices also have to produce durable images while they are used for long periods of time in a single session. To achieve high‐quality images with reduced image sticking in TFT‐LCD devices, we have increased their voltage‐holding ratio (VHR). This technology ensures the achievement of durable images over long periods of time and also reduces the image‐sticking problem. There are many ways to achieve increased VHR. In terms of the characteristics of the TFT devices, reducing the leakage‐current effects is the most frequently applied method in the display industry.     

Nano‐domains formation on photoalignment thin film by self‐organized dewetting

A novel discontinuous photoalignment surface with nano‐domains for liquid crystal is developed. The formation of the discontinuous structure is created by self‐organized dewetting, which is regarded as one of the most promising bottom‐up approaches to fabricate nano‐structure. Different dewetting conditions, such as surface roughness, thickness and viscosity, have been investigated. Such discontinuous photoalignment layer can be fabricated on top of another continuous alignment layer to form a new kind of heterogeneous nano‐structured alignment surface – stacked alignment layers. This heterogeneous alignment surface can be used to produce arbitrary pretilt angles for the liquid crystal display. Simulation model has been built to understand the dewetting mechanism. Experiments using photo‐aligned and photo‐polymerisable polymer have been done to verify the dewetting theory. The produced stacked alignment layers are proved to be robust. Moreover, the dewetting processing is a fully controllable process and is compatible with existing manufacturing techniques.     

Homeotropic alignment of liquid crystals on ITO surface using LBL assembly

In this work, the very thin layer‐by‐layer (LBL) film that was constructed by dip coating method on indium tin oxide surface can be used in liquid crystal (LC) displays devices. The obtained results indicate that the ultrathin LBL film shows the homeotropic alignment layer, and a uniform vertical alignment of LC molecules was gained very easily. The progress of vertical‐aligned LC cells with a LBL layer was evaluated. The obtained threshold voltage and response time of the LC cell were 2.472 V and 12.5 ms, respectively. So, the competitive performance of the LC cell could allow new sign at a low‐cost budget with rubbing process in LC display technology.     

Arbitrary pretilt and azimuth angles generation by stacked photoalignment layers

We report a method of fabricating a nano‐sized stack alignment layer. The stacked alignment layer consists of nano‐domains of vertical and planar alignment materials. Experiments reveal that photoalignment thin film can undergo dewetting and form discrete nano‐sized domains. Such self‐organized structure creates a discontinuous layer stacked on top of a continuous layer and hence produces an inhomogeneous alignment surface. With two or more different principle alignment directions, this new alignment layer is capable of producing multiple pretilt and azimuth angle domains on a single substrate.     

FFS‐mode OS‐LCD for reducing eye strain

In order to reduce eye strain, a driving method for reducing flickers of liquid crystal display (LCD) is devised. For this driving, an oxide semiconductor (OS) is used in a backplane, liquid crystal and alignment layer materials are optimized, and a fringe field switching (FFS) mode with a structurally formed storage capacitor is used. This work reveals that suitable usages of positive and negative liquid crystals differ from each other according to their characteristics. This work also describes an OS‐LCD with a touch sensor we fabricated for mobile devices, which proves the possibility of reducing‐eye‐strain technology (REST) with reduced flickers.     

Optical rewritable liquid‐crystal‐alignment technology

Abstract— A new optical rewritable (ORW) liquid‐crystal‐alignment technology has been developed to create a display and to demonstrate its maturity and potential. ORW displays have no electrodes and use polarizers as substrates. The display requires no photolithography on plastic. Its simple construction secures durability and low cost for mass production. The on‐screen information is optically changed in a writing unit that consists of an LCD mask and an exposure source that is based on LEDs, low power, and low cost in comparison with Hg lamps or lasers. A high contrast image can be easily written, viewed, and rewritten through a polarizer, while the multi‐stable gray‐level image requires zero power to maintain the image. Reconfigurable LC alignment using ORW technology best suits plastic‐card displays as well as for LC photonics and various one‐mask processes of patterned LC‐alignment applications.     

Photoalignment of LCoS LCDs

Because the pixel area of liquid‐crystal‐on‐silicon (LCoS) microdisplays is about 100 times smaller than that of direct‐view liquid‐crystal displays (LCDs), the limitations of the conventional alignment by brushing are obvious: Scratches and particle contamination caused by brushing become visible due to the strong optical magnification required for LCoS LCDs both in front or rear projection. As an alternative, photoalignment with the linear photo‐polymerization (LPP) technology avoids the generation of defects, thus increasing production yields considerably. For application in LCoS LCDs, alignment layer materials must match the high‐voltage holding ratio (VHR) specifications of TFT‐LCDs. The VHR performance of the newly developed second‐generation LPP materials is shown to be similar to standard TFT polyimides used for conventional brushed alignment. We report investigations of pretilt‐angle generation by photoalignment on reflective CMOS substrates. UV light reflected from the CMOS surface during LPP exposure affects the resulting pretilt angle. Compared to pretilt angles on transmissive substrates, the reflected UV light can induce lower, higher, or identical pretilt angles, depending on LPP material properties. In any case, the pretilt angles are well defined, which results in perfect LCD alignment.     

Evaluating the Quality of Face Alignment without Ground Truth

The study of face alignment has been an area of intense research in computer vision, with its achievements widely used in computer graphics applications. The performance of various face alignment methods is often image‐dependent or somewhat random because of their own strategy. This study aims to develop a method that can select an input image with good face alignment results from many results produced by a single method or multiple ones. The task is challenging because different face alignment results need to be evaluated without any ground truth. This study addresses this problem by designing a feasible feature extraction scheme to measure the quality of face alignment results. The feature is then used in various machine learning algorithms to rank different face alignment results. Our experiments show that our method is promising for ranking face alignment results and is able to pick good face alignment results, which can enhance the overall performance of a face alignment method with a random strategy. We demonstrate the usefulness of our ranking‐enhanced face alignment algorithm in two practical applications: face cartoon stylization and digital face makeup.     

Flexible LCDs fabricated with a slit coater: Not requiring an alignment film

A homogeneously aligned liquid crystal layer on a substrate film on which it is not necessary to form a liquid crystal alignment film can be assembled by a slit coater. Types of twisted nematic and in‐plane switching flexible liquid crystal displays were demonstrated. The production time can be considerably shortened because of the lack of need for an alignment film. The slit coater method is also applicable to the roll‐to‐roll process.     

Second wind of the oblique deposition method of liquid‐crystal alignment: Ion‐beam sputtering technique

Abstract— Liquid‐crystal (LC) alignment on SiO_x films produced by ion‐beam sputtering deposition was comprehensively studied. The conditions for planar, tilted planar, homeotropic, and tilted homeotropic LC alignment of high uniformity were determined. The alignment photostability and aging issue are discussed. An original sputtering system based on the anode‐layer source excelling in high reliability and quality of sputtered coatings were used. Because this system can be easily scaled up, the alignment treatment of the large‐area alignment substrates, including those used in modern LCD manufacturing, can be realized. The advantages of the sputtering LC alignment technique, in comparison with its vapor‐deposition predecessor, are described.     

Intrinsic Decompositions for Image Editing

Intrinsic images are a mid‐level representation of an image that decompose the image into reflectance and illumination layers. The reflectance layer captures the color/texture of surfaces in the scene, while the illumination layer captures shading effects caused by interactions between scene illumination and surface geometry. Intrinsic images have a long history in computer vision and recently in computer graphics, and have been shown to be a useful representation for tasks ranging from scene understanding and reconstruction to image editing. In this report, we review and evaluate past work on this problem. Specifically, we discuss each work in terms of the priors they impose on the intrinsic image problem. We introduce a new synthetic ground‐truth dataset that we use to evaluate the validity of these priors and the performance of the methods. Finally, we evaluate the performance of the different methods in the context of image‐editing applications.     

Nano‐structured liquid‐crystal alignment layers (Invited Paper)

Abstract— The alignment of liquid crystal by nano‐structured surfaces is investigated. It is shown that reliable pretilt angles of any value between 0° and 90° can be produced with these surfaces. The physics and properties of such alignment layers are studied using a variety of techniques. The anchoring energy and temperature stability of the alignment are also measured. Dependence on various processing conditions is also characterized. It is shown that these nano‐structured alignment layers are useful for the production of high pretilt angles needed for a variety of applications.     

基于ARM的直流电机位置伺服系统设计

针对图像跟踪中对转台响应快、定位精度高的要求,设计了以ARM和轴角转换芯片组成的位置伺服控制系统。系统使用轴角转换芯片采集旋转变压器反馈的位置信息,通过IR2130驱动MOSFET功率管构成的H桥电机驱动电路,采用带有速度前馈加速度前馈的PID调节算法实现了直流电机位置伺服控制。试验结果表明该控制系统能够满足图像跟踪中对转台快速性和准确性的要求。     

Fluorinated indium‐gallium‐zinc oxide thin‐film transistor with reduced vulnerability to hydrogen‐induced degradation

Thin‐film transistors (TFTs) based on amorphous indium‐gallium‐zinc oxide channels with or without fluorination were fabricated. The sensitivity of their electrical characteristics to hydrogen exposure was compared. It is shown that TFTs built with fluorinated channels exhibit significantly improved intrinsic resistance against hydrogen‐induced degradation; hence, they are potentially better suited for integration with hydrogen‐containing devices such as photo‐diodes based on amorphous hydrogenated silicon and TFTs based on low‐temperature polycrystalline silicon. The observed improvement correlates well with a reduced population of oxygen‐related defects and reduced hydrogen incorporation in the fluorinated channels.     

Tailored liquid‐crystal switching on ferroelectric polymer films

Abstract— The development of voltage‐controlled visible‐wavelength progression in displays and optical data storage devices using ferroelectric polymers and liquid crystals is described. Ferroelectric polymers are materials that have a ready distribution of dipoles which can be oriented by manipulating material composition and external fields. Utilizing the charge polarization distribution, their performance as an alignment layer for inducing liquid‐crystal alignment is presented. The switching response of the devices was tailored by changing the material composition through copolymers and nanoclay doping.     

Power saving through state retention in IGZO‐TFT AMOLED displays for wearable applications

We present a qHD (960 × 540 with three sub‐pixels) top‐emitting active‐matrix organic light‐emitting diode display with a 340‐ppi resolution using a self‐aligned IGZO thin‐film transistor backplane on polyimide foil with a humidity barrier. The back plane process flow is based on a seven‐layer photolithography process with a CD = 4 μm. We implement a 2T1C pixel engine and use a commercial source driver IC made for low‐temperature polycrystalline silicon. By using an IGZO thin‐film transistor and leveraging the extremely low off current, we can switch off the power to the source and gate driver while maintaining the image unchanged for several minutes. We demonstrate that, depending on the image content, low‐refresh operation yields reduction in power consumption of up to 50% compared with normal (continuous) operation. We show that with the further increase in resolution, the power saving through state retention will be even more significant.     

Effect of gas pressure on permanent dark image sticking on a bright screen in AC plasma‐display panels

Abstract— The permanent dark‐image‐sticking phenomenon on a bright screen was examined under various gas pressures in a 42‐in. ACPDP with an He(35%)‐Xe(11%)‐Ne gas composition. Infrared‐emission observations reveal that the discharge characteristics related to the MgO surface are almost the same in both the discharge and non‐discharge cells, whereas luminance observations show a deterioration in the visible‐conversion characteristics related to the phosphor layer in both the discharge and non‐discharge cells. Consequently, the permanent dark‐image‐sticking phenomenon on a bright screen is found to be strongly related to the deposition on the phosphor layer to the Mg species sputtered from the MgO surface due to a repetitive strong sustain discharge. For a decrease in gas pressure, the permanent dark image sticking on a bright screen became worse due to a severe degradation of the visible‐conversion characteristics of the phosphor layer caused by the deposition of higher amounts of sputtered Mg species on the phosphor layer, as confirmed by various measurements, such as V_t closed curves, time‐of‐flight secondary‐ion mass spectrometry, photoluminescence, and atomic‐force‐microscope analyses.