Journal of the Society for Information Display最新文献

In 2022, we presented a high-efficiency improvement for blue fluorescent OLEDs through Dual emitting layer (BH1/BH2 EML) technology to enhance performance. In this study, the light extraction efficiency was improved by controlling the molecular orientation and the spectral shape of the blue dopant (BD) in the blue host (BH) on the anode side. Additionally, through mechanism analysis, we confirmed that the clear functional separation of the two layers enhanced the Triplet-Triplet Fusion (TTF) efficiency and each BHs deuteration impact resulting in a multiplicative extension of lifetime. Furthermore, by applying a dual-hole transporting layer (HTL) that contributes to light extraction improvement, the bottom-emission (BE) device achieved external quantum efficiency (EQE) = 16.3%, and top-emission (TE) device reached BI = 350, LT95@50 mA/cm² > 200 h.

Stretchable displays, characterized by their flexibility and deformability, are gaining attention as next-generation display technologies. While various studies have been conducted on hardware aspects of stretchable displays, the software aspects have received comparatively less focus. When displays are stretched, empty pixels inevitably lead to a decrease in overall luminance, which significantly degrades visual quality and user experience. To address this issue from a software aspect, we propose a novel luminance compensation method that leverages deep learning through a Learned Perceptual Image Patch Similarity (LPIPS)-based pre-optimization technique combined with Gaussian-weighted kernels. The proposed method applies relatively higher values to areas near empty pixels, where luminance loss is most significant while preserving the original luminance in unaffected areas. This design minimizes color distortion and enhances brightness effectively. Specifically, the optimal brightness increase rates (BIRs) are pre-optimized using an LPIPS-based loss function, tailored to various stretching scenarios, such as stretching types, directions, and rates. Based on the optimized BIRs, Gaussian-weighted kernels are generated for efficient luminance adjustment. Our method flexibly supports diverse stretching conditions, including linear/non-linear stretching and uni-directional/bi-directional stretching, with stretching ratios ranging from 10% to 30%. Through simulations, we qualitatively and quantitatively compared the proposed method with existing approaches, demonstrating superior performance across a wide range of scenarios.

Phototherapy is a safe, non-invasive, and effective treatment that can be widely applied to treat various diseases. Conventional LED and laser-based phototherapy have two major drawbacks: (1) they have low uniformity and stability due to local heat and light concentration, and (2) they have spatiotemporal constraints. On the other hand, OLEDs can be treated uniformly with a thin and light surface light source, and it is suitable for wearable and skin-attached platforms due to its excellent expandability and process compatibility. With such characteristics as OLEDs, it is possible to provide users with a comfortable and convenient treatment environment. To overcome the limitation that the existing phototherapy platform simply served as a light source for light therapy, this study proposed a user-friendly OLED phototherapy platform using bifacial OLEDs (Bi-OLEDs) which can be vertical-stacked and parallel-connected. The vertical-stacking process demonstrated a facile fabrication process, and the parallel connection structure ensured individual driving capability, flexibility, driving reliability, and thermal stability. Notably, the red light emitted from OLEDs was observed to enhance wound healing in in vivo tests, achieving 85% wound closure. Therefore, OLED-based phototherapy can be utilized as an innovative platform with both effective light therapy and user interaction.

We propose an active-switching light-field (LF) camera system that significantly extends the measurable depth range over conventional passive-optics-based LF systems by integrating a stacked geometric phase lens (GPL) module in a compact design. During elemental image acquisition and LF rendering, chromatic aberration in the focus-tunable GPL is compensated by adjusting the reconstruction depth and magnification for each color channel. Additionally, the optimal GPL operation sets are selected based on color-dependent depth-of-focus conditions. These optimizations enable the proposed GPL-based LF system to achieve full-color, depth-enhanced LF imaging while mitigating the typical trade-off between spatial resolution and depth of field limitations.

We have successfully developed a coating polarizer with an order parameter of over 0.97, transmittance of 42.3%, and polarization degree of 99.9%, in addition to outstanding heat resistance. These were achieved by crystallizing dye aligned along the liquid crystals, at a nano-sized scale. The polarizer does not require elongation, preventing shrinkage from temperature or humidity and ensuring dimensional stability. These properties make it ideal for large and flexible displays in applications such as automotive displays.

We have developed an integration process for LED microdisplays toward augmented reality (AR) applications and present the first demonstration of a blue mono-color active-matrix LED microdisplay fabricated with this process methodology. One of the primary manufacturing challenges in realizing LED microdisplays is to develop a process that provides pixel-level heterogeneous connections between III-V compound LEDs and Si CMOS circuits at a fine pixel pitch. In this work, a die-to-silicon process is employed, in which GaN on Si chips are reconstituted on a larger-diameter support Si wafer (referred to as GaN/Si wafer), allowing the use of Si CMOS wafer processes, including novel Cu-Cu hybridization. After the Cu-Cu hybridization process to bond a die-to-silicon transferred GaN/Si wafer and a Si CMOS backplane wafer, LED mesas and on-chip lenses (OCLs) are fabricated. We achieved high yields of pixel-level connections at 3.8-μm and 4.5-μm pitches through the Cu-Cu hybridization. Finely tapered 1.2-μm LED mesas with OCLs exhibited a 4.2-fold enhancement in light extraction efficiency (LEE) compared with a Lambertian emitter within the emission angle of ±20°. Also, we introduce the key features and results of the prototyped 0.26-in., 5,644-ppi LED microdisplay.

In this study, we designed and fabricated a crystal InO_x (crystal IO)-based field-effect transistor (FET) on a 3.5th generation glass (600 mm × 720 mm) substrate line. The FET exhibits high field-effect mobility exceeding 90 cm²/Vs, an on-state current higher than that of a low-temperature polysilicon (LTPS)-based FET, normally-off characteristics, an extremely low off-state current, a high breakdown voltage, and high reliability. The synthesized crystal IO is less susceptible to grain boundary scattering and exhibits a small variation in grain size on the substrate plane. The crystal IO-based FET exhibits a small variation in electrical characteristics. Combining our organic light-emitting diode (OLED) patterning technology with a display backplane based on crystal IO, we obtained an 8.3-in. 8K4K OLED display with high luminance and low power consumption. These results demonstrate that crystal IO can replace LTPS and low-temperature polycrystalline oxide, which have been mainly used in the backplanes of small- and medium-sized displays, and that backplanes of displays of all sizes can be completely oxide based.

Polarization-dependent bifocal Pancharatnam-Berry phase lenses are proposed to integrate designable bifocal functionality into a single compact device. These lenses are fabricated using photoalignment techniques with a patterned light field generated by a spatial light modulator and are designed in both longitudinal and transverse configurations to address critical challenges in AR displays. The longitudinal configuration resolves the vergence-accommodation conflict by enabling multi-plane displays, while the transverse configuration extends the field-of-view (FOV) through dual horizontal FOVs. A key innovation in this system is the incorporation of an electrically suppressed helix ferroelectric liquid crystal (ESHFLC) polarization rotator, which enables rapid switching between dual depths or FOVs with a response time of 35 μs. The performance of the designed flat lenses and ESHFLC polarization rotator is thoroughly characterized. As a proof of concept, the integrated system is successfully demonstrated for AR display applications, showcasing dual-depth imaging and extended FOV capabilities. This compact and efficient solution addresses key challenges in AR displays, enabling true 3D multi-plane displays and extending the FOV for next-generation AR systems.

This study introduces recent innovative progress in white organic light emitting diode (WOLED) technology for premium OLED TV and IT displays. By fabricating a four-stack tandem device consisting of red, first blue, green, and second blue devices in sequence from the anode, we could achieve a current efficiency of the WOLED up to 134 cd/A at 10 mA/cm², resulting in enhanced efficiency for red, green, and blue subpixels after transmitting color filters. The new OLED TV implementing the four-stack WOLED technology reached luminance levels of 2,900, 1,000, and 400 nit at the average picture level (APL) of 3%, 25%, and 100%, respectively, and a flash peak luminance of 4,000 nit. Since the four-stack device uses red, green, and blue dopants of saturated color, eliminating yellow green (YG) dopant used for our previous WOLEDs, its color gamut in the Broadcasting service Television (BT)-2020 standard was widen up to 83%. We will explain how to enhance the efficiency and the lifetime in terms of device structure and materials.

The impact of pixel leakage current and liquid crystal flexoelectric effect on flicker were studied with simulation and measurement methods. The impact rule of pixel architecture, TFT voltage, electrode design, liquid crystal material, driving signal, and other factors is obtained, and the key factors under different conditions are identified. The pixel design and liquid crystal mixture development scheme under different conditions are proposed, and a strategy of data voltage modulation at the blanking period combined with frequency-wise ACC brightness compensation is established to reduce flicker. Based on the proposed total flicker optimization scheme, flicker lower than -50 dB is achieved on 55/65/75 in. products when swapping between 48/120 Hz every 200 ms, meeting the G-Sync flicker standard.