Improvement of the flexoelectric coefficients estimating procedure by means of the transmission phase difference measurement was demonstrated. It was found that the sign of the sum of two flexoelectric coefficients for splay and bend deformation can be determined from the DC applied voltage dependence curve of the phase difference for obliquely incident light. The value of the sum of two flexoelectric coefficient was evaluated by means of symmetric oblique incident transmission ellipsometry (SOITE), and the several pC/m are recognizable by numerical fitting. Subtraction of two flexoelectric coefficients was also estimated with normal incidence measurement under DC applied voltage. From these three step evaluations, two flexoelectric coefficient with accuracy of several pC/m was confirmed for seven of nematic liquid crystals.
In this paper, we report the resettable functionality of helix pitch length in the mixture composed of cholesteric liquid crystal and self-assembly dendrimer with lysine groups. Cholesteric-phase liquid crystal was obtained by doping a tiny amount of dendrimer less than 0.01 wt% concentration. The mixture showed not only thermal stability of helix pitch length but also resettability of that by temperature control process based on sol-gel transition characteristics in the dendrimer with lysine group. We discuss the temperature effect of the proposed cholesteric liquid crystal on such unique functionality.
For photosynthesis promotion in the field of agriculture, we report on solution-processed molecular alignment control of organic fluorescent dye using guest-host effect and photo-polymerization reaction in this paper. We investigated the relation between molecular conformation and polarized photoluminescence characteristics in dye/polymer blend films. As the result, we observed polarized photoluminescence with reduction of concentration quenching effect and disordered region of dye molecules. We discussed the solution process and materials for highly-ordered solid-state films using liquid crystalline monomer and fluorescent dye.
We examined anisotropic light-diffusing films for reflective displays to realize a wide viewing angle for a rotating screen such as a tablet. By orthogonally laminating 60-μm-thick anisotropic light diffusing films having bent columnar structure, we were able to demonstrate uniform diffuse reflection characteristics for a point light source polar angle of 30° from various azimuth angles. Then, we showed that image blur could be suppressed by narrowing the gap between the reflector and the diffusing layer, such as by grinding the top cell glass.
Barrier films are key components of organic electronics devices such as OLEDs, OPVs, OTFTs, etc. Novel barrier films with high temperature tolerance were developed by applying the alternatingly stacked barrier layers with Si3N4 deposited by sputtering and Al2O3 deposited by ALD (Atomic Layer Deposition) to simultaneously biaxially stretched polyetheretherketone (EXPEEK) films. The WVTR (Water Vapor Transmission Rate) values of single and various stacking barrier layers on EXPEEK were investigated by Ca corrosion method. While the single barrier layers with Si3N4 or Al2O3 showed poor barrier abilities, the several alternatingly stacked layers with Si3N4 and Al2O3 achieved high gas barrier ability with WVTR values of the order of 10-5g/m2/day. The results implies that defects and pinholes of Si3N4 layer deposited by sputtering are effectively covered by Al2O3 layer deposited by ALD, which has excellent defect coverage. In addition, flexible OLED devices were fabricated using the developed barrier films.
Quantum-dot light-emitting diodes (QD-LEDs) that exhibit green emission were fabricated using Ag-In-Ga-S/GaSx (AIGS) core/shell QDs as low-toxicity QDs. Although multi-element QDs such as AIGS are prone to broad-wavelength defect-induced emission, the core/shell structure enables sharp emission from band-edge transitions. The electroluminescence (EL) spectra were found to include a large defect emission component compared with the photoluminescence spectra of the QD films because of the difference in the excitation process of the QDs. The defect emission was attributed to the electrons injected into the emitting layer (EML) being easily trapped at the defect sites in the QDs. The addition of an electron transporting material to the EML effectively blocked the direct injection route and reduced the electron trapping at the defect sites. Consequently, the color purity of the EL emission was enhanced and the QD-LEDs exhibited green EL emission.
Metallo-supramolecular polymers (MSPs) are a novel type of electrochromic (EC) materials. Ru(II)-based MSP (polyRu) composed of Ru(II) and bis(terpyridyl)benzene showed reversible color changes between orange and pale green. The orange color was caused by the metal-to-ligand charge transfer (MLCT) absorption in polyRu and disappeared by the electrochemical oxidation of Ru(II) to Ru(III). The pale green was returned to the original orange by the electrochemical reduction of Ru(III) to Ru(II). EC devices with polyRu were fabricated by the combination of an electrolyte solution, counter material, and two ITO glasses. The character images were displayed on the EC devices using insulating films. The insulating films prevented the electron transfer between the ITO glass and the polyRu layer and made the image stand out in the device. The fabricated EC display devices were presented at a science museum of Japan as experience-based exhibits.
This paper proposes two methods for improving uniformity in the low luminance region of an organic light-emitting diode (OLED) display. To supply a stable current to subpixels in the low luminance region, the time-division method produces long-term and short-term subframes for the frame period. On the other hand, the area-division method produces non-emitting and amplified emitting regions of grouped pixels. These methods assume that the effective use of a high current improves spatial uniformity, as it becomes worse in low luminance regions. In experiments involving an actual display, the spatial distribution of luminance was measured while applying each of the proposed methods and evaluated based on the root mean square (RMS) value of the luminous deviation. When the results of the experiments with or without application of the proposed methods were compared, the proposed methods were shown to produce a decrease in the RMS value.
We compare the diffraction characteristics of ferroelectric (FLC) and nematic liquid crystal (NLC) devices with one-dimensional stripe patterns of 1-10 µm pixel pitches. The polarizing micrographs show pixel boundaries of black/white pixels blur as the pixel pitch becomes smaller. The blur of NLC is more remarkable than that of FLC. The first-order diffraction efficiency of NLC remains constant for the pixel pitch of 4-10 µm and sharply decreases for the pixel pitch of < 2 µm. By contrast, the FLC efficiency decreases with the pixel pitch decrease from 10 to 4 µm and remains constant for the pixel pitch of < 3 µm. The FLC efficiency (5.5%) is four times larger than that of NLC (1.4%) with a 1 µm pixel pitch. The Fourier transform calculation shows the efficiency degradation of FLC is caused by the blur at the pixel boundary, whereas that of NLC caused by the blur and contrast deterioration.
In this paper, we propose a quality improvement method of a real-time free viewpoint video (FVV) synthesis. Two functions, adaptive silhouette dilation and view-dependent shape refinement, are applied to obtain a 3D model with accurate shapes in the real-time FVV. The adaptive dilation reduces the missing part of a reconstructed 3D model caused by a camera calibration error. In addition, the excessively expanded part of a 3D model caused by the silhouette dilation is corrected by the view-dependent refinement algorithm on a screen rendering. A part of the model outlines becomes transparently displayed to refine the model shape by comparing the camera image used for texture mapping with a background model. In the experiments, the proposed method achieved the best quality compared with conventional real-time FVV methods. Furthermore, the processing was executed in real-time because the computation cost of the proposed functions was extremely small.
Exploring brands that customers are likely to purchase jointly has a profound effect on marketing. This study proposes a new way to measure, or estimate the similarity between brands using social media. The proposed algorithm analyzes the daily photos and hashtags posted by each brand's followers. By clustering them and converting them into histogram-based features, we can calculate the similarity between brands. We evaluate our proposed algorithm by comparing it with the purchase logs of point/credit card companies, and answers to the questionnaires. The results show that purchase logs can predict the co-purchase behaviors in the questionnaires very well, but cannot predict customers' potential interest or willingness to buy products from new brands. On the other hand, our method can predict the users’ interest in brands with a correlation coefficient of over 0.53, which is high considering that such interest in brands is highly subjective and individual dependent.
In this paper, we propose a method for estimating stress levels using multibiological information obtained from red-green-blue (RGB) facial videos. The most popular method for estimating stress is by questionnaire, which is not highly objective or accurate. To estimate stress levels more accurately, it is desirable to establish the method which can estimate with objective and accurate information. In recent years, many methods for using biological information have been proposed. In this study, we used three types of biological information to estimate stress: pulse rate variability, blink rate, and pupil size, which were captured using an RGB camera. Results showed that the use of these biological signals improved the accuracy of stress estimation. Moreover, using biological information in a multimodal manner enabled the most accurate and detailed stress estimation.
A method for color reproduction of old glass dry plates digitized by a linear sensor camera is proposed. A high-resolution scanner based on linear sensor camera was developed for digitizing glass plates, which is beneficial for high-quality color reproduction. The color reproduction uses filter coefficient calculated from color information of multiband filters. An approach for the calculation of filter coefficient used for color reproduction is addressed in detail. The method was applied to the digitization and color reproduction of a wall painting belonging to World Cultural Heritage Horyuji Kondo, Japan. A verification experiment is conducted to evaluate the accuracy of color reproduction results. Experimental results show that the proposed method is capable of high-quality color reproduction of image details, and there is merit to using this high-resolution digitization techniques for cultural heritage.