Journal of the Society for Information Display最新文献

Tiling with a variety of panel units is a promising approach to customizing displays in terms of size, shape, and aspect ratio. However, tiled displays with conventional panel units have a major drawback in that they suffer from noticeable seams due to the bezels of the panel units. Here, we demonstrate a flexible bezel-less thin-film transistor (TFT) backplane for seamless tiling. By using through-plastic-vias (TPVs) that penetrate an ultrathin polyimide (PI) film substrate, a bezel-less backplane with an ultra-narrow bezel width of 8 μm was realized, in which oxide TFTs in pixel circuits on the backplane are driven from the back side of the PI film substrate using three-dimensional signal wires, which go through the TPVs. The resistance of a TPV was evaluated with a TPV chain with 1000 TPVs connected in series and was found to be as small as 1.3 Ω. Furthermore, the transfer characteristics of an oxide TFT in a test element group for a pixel circuit were evaluated from the back side of the PI film substrate. The TFT exhibited clear switching behavior with an on/off current ratio of more than 10⁸ and a high mobility of 25 cm²/Vs, which are sufficient to drive light-emitting devices.

High-power blue-emitting laser diodes have been used in projectors and lighting systems as excitation sources for yellow-emitting phosphors. These phosphors must be robust and should not exhibit thermal quenching. In this work, we developed a durable eutectic phosphor consisting of single-crystal Ce-doped yttrium aluminum garnet (Ce:YAG) phosphor and Al₂O₃ (sapphire), with a thermal conductivity greater than 20 W/(m·K). This eutectic phosphor is named EPOCH-Neo. EPOCH-Neo specimens were cut from a large crystal substrate prepared by an edge-defined film-fed growth method. We evaluated the optical properties of EPOCH-Neo specimens and the optical uniformity of an EPOCH-Neo substrate. In addition, to control the chromaticity, the Y-sites of Ce:YAG were doped with Gd at concentrations as high as 50% and the chromaticity and thermal characteristics of the resultant phosphors were evaluated. Moreover, the characteristics of a device composed of EPOCH-Neo on a heatsink under blue laser excitation were examined. The results showed that EPOCH-Neo is a durable phosphor suitable for use in high-power-excitation applications.

Quantum dots (QDs) are important luminescent structures with applications in wide-color-gamut displays requiring exceptional color reproducibility. Multinary semiconductor QDs are expected to serve as eco-friendly materials to replace conventional QDs owing to the narrow spectral widths and tunable bandgaps of these QDs. However, the application of multinary QDs, which tend to exhibit defect-related emissions, to QD light-emitting diode (QLED) displays will require electroluminescence to be obtained from QLEDs incorporating inkjet-printed emitting layers. The present work examines QLEDs exhibiting vibrant color emissions based on blue-emitting Zn–Se–Te QDs, green-emitting Ag–In–Ga–S QDs, and red-emitting Ag–Cu–In–Ga–S QDs. Each such QLED contains QD emitting layers comprising a mixture of charge transport materials. The spectra obtained from these RGB QLEDs fabricated by spin-coating show very high color purity. Passive matrix QLED displays incorporating these QDs are also fabricated by inkjet printing to demonstrate the high color purity that can be obtained from multinary QDs in displays. In conjunction with passive matrix driving, these displays produce clear moving images with vibrant electroluminescence originating from the multinary QDs. The present results indicate that these QDs have significant potential for utilization in wide-color-gamut displays.

Electrophoretic displays (EPDs) are popular in consumer electronics, like e-readers and tags, for their paper-like visuals and minimal power consumption. However, EPDs struggle to rapidly switch to target grayscales due to the inherent limitations in the response speed of their display particles. Video halftoning technology achieves a smoother video grayscale display, but it also inevitably reduces the image quality and affects the viewing experience. Therefore, this paper proposes an EPD driving method based on image semantic segmentation. The method could distinguish the dynamic region and the static region accurately. For static areas, high-definition driving waveforms were used to ensure the image display accuracy. For the dynamic area, dynamic target and dynamic text were processed by different algorithms, respectively, and the speed-driving waveforms were used to maintain the fluency and clarity of the video display. With the method we proposed, the display quality for EPD in complex video playback was optimized significantly. Compared to DBS refresh techniques, the SSIM had increased from 4% to 82% and the PSNR had increased from 2.56 dB to 10.89 dB with our method, significantly enhancing the video playback performance of EPDs.

In this paper, we proposed a new optical Mura compensation method that requires only a few Mura detections for all gray levels. We analyzed the characteristics of Mura resulting from process variations in the thin film transistor (TFT) of each pixel and developed a new model using a logarithmic function. The proposed compensation algorithm has been verified with simulation and experimental results. We found that the uniformity of the proposed compensation algorithm at 7G, 24G, 75G, 100G, 150G, and 255G, which required only two image captures, was comparable to those that required five captures. The model improved uniformity from 41.32% to 68.60% at 0.18 nit brightness, demonstrating its effectiveness. Additionally, the method significantly reduces the number of image captures needed from five to two and decreases the image capturing process time from 2183 to 150 ms, saving over 14 times in process efficiency. The proposed methodology demonstrates significant advancements in achieving luminance uniformity in OLED displays, addressing mass production constraints.

In this paper, we propose a novel scan driver combined with a logic circuit using amorphous indium-gallium-zinc-oxide (a-InGaZnO) thin-film transistors (TFTs) in order to enhance the electrical stability and reduce power consumption in display panels. The latest mobile displays with high resolution and refresh rates consume more battery power, which inevitably limits portability and usability. The proposed scan driver can mask the signal by combining the output stage with a logic circuit, thereby blocking the output pulse for static images. This allows the display panel to operate in a partial driving mode depending on the display content. Due to the masking of the scan driver's output pulses, the connected pixel circuits are consistently maintained in the same state as the previous frame, leading to a lower refresh rate and reduced power consumption. Furthermore, by constructing additional control signals, the proposed scan driver can operate stably in depletion mode under a ∆V_TH = −3 V.

(In)GaN microLEDs have reached a high degree of maturity due to their development in the lighting industry. Their robustness and high efficiency make them ideal candidates for high-brightness, high-resolution micro-displays. Beyond display applications, microLEDs are being explored for non-display uses, including wireless Visible Light Communication (VLC) and parallel communication via multicore fiber. This study investigates short-range chip-to-chip optical communication using InGaN/GaN microLEDs and micro Photodiodes (microPDs). Leveraging processes developed for micro-displays, we address the challenges of integrating GaN microLEDs and microPDs on ASICs. We outline the main figures of merit, including expected energy efficiency, optical coupling to multicore fibers or waveguides, and the spectral efficiency of InGaN/GaN microPDs correlated with TCAD simulation and experimental transmission results. Our study highlights the potential of GaN microLEDs and microPDs for massively parallel, energy-efficient data transmission, paving the way for innovative short-range and energy-efficient optical communication solutions.

The most significant challenge associated with micro-light-emitting-diode (micro-LED) displays, which are anticipated to be the next generation of display technology, is the high manufacturing cost. In order to reduce manufacturing costs, it is essential to improve yield. Improving the manufacturing yield of them necessitates the evaluation of micro-LED chips prior to their installation onto substrates. However, the microsize and large quantity of these chips renders inspection difficult with conventional inspection methods. Herein, we propose a method for inspecting micro-LED chips by measuring the voltage generated between the anode and cathode due to the photovoltaic effect using a developed proximity capacitance image sensor. As this inspection method does not require the use of probe pins to contact LED electrodes, it enables simultaneous inspection of multiple chips in a short time without causing any damage to the electrodes. In this paper, an experimental system equipped with this sensor was developed to demonstrate the basic measurement principle. Moreover, we demonstrated that more than 50,000 micro-LED chips with a size of 60 μm × 34 μm can be simultaneously inspected in approximately 2 s.

Perovskite light-emitting diodes (PeLEDs) have recently emerged as a potential next-generation display technology due to their wide color gamut, high external quantum efficiency (EQE), and low fabrication cost. The thermal evaporation process with no solvent involvement and offers low substrate selectivity and high compatibility with production lines has attracted significant academic interest. However, in thermal evaporation processes, the shadow effect greatly affects the deposition size and positioning accuracy of the patterns, consequently impacting the effective device area and process repeatability of PeLEDs. In this study, we calculated the shadow distance during the dual-source thermal evaporation and analyzed the issues of misalignment and size deviation caused by shadow effects. Based on the calculation of shadow distance, we increased the substrate height from 33 to 38 cm to enhance the deposition angle. This adjustment led to an improvement in the characteristic parameter W₁/W_dot from 0.178 to 0.365 during perovskite deposition. As a result, we successfully obtained a high-resolution perovskite array with uniform morphology and photofluorescence (PL) emission at 600 pixels per inch (ppi). This demonstrated the reliable calculation and analysis of shadow distance, which is effective for fine deposition of high-resolution perovskite patterns and PeLEDs.

We proposed a linear grooves 3D display that can display 360° viewable 3D images by creating linear grooves that correspond to the viewpoint positions. In the conventional method, arc-shaped grooves are drawn on a flat substrate of transparent film. However, depending on the viewing position, the image may be distorted. In addition, when a flat substrate is bent into a curved shape, the image is more affected than one observed in a flat shape. Furthermore, the conventional method of arc 3D display method cannot display a 3D image that corresponds to the viewpoint position. In this paper, we propose design and fabrication methods that reduce the image distortion for both flat and curved shapes. A 3D image displayed by the proposed method can change depending on the viewpoint position, and a natural 3D image with motion parallax can be observed. In the experiment, our proposed method fabricated a 360° 3D display by calculating the linear grooves and presented natural 3D images with smooth motion parallax.