A scalable manufacturing process for flexible active‐matrix e‐paper displays

Abstract— A scalable manufacturing process for fabricating active‐matrix backplanes on low‐cost flexible substrates, a key enabler for electronic‐paper displays, is presented. This process is based on solution processing, ink‐jet printing, and laser patterning. A multilayer architecture is employed to enable high aperture ratio and array performance. These backplanes were combined with E Ink electrophoretic media to create high‐performance displays that have high contrast, are bistable, and can be flexed repeatedly to a radius of curvature of 5 mm.     

Flexible electrophoretic display driven by solution‐processed organic thin‐film transistors

Abstract— An organic thin‐film‐transistor (OTFT) backplane has been fabricated by using a solution‐processed organic semiconductor (OSC) and organic insulators. The OSC, a peri‐xanthenoxanthene derivative, provides a mobility of 0.5 cm²/V‐sec. These organic materials enhance the mechanical flexibility of the backplane. The developed backplane successfully drives a 13.3‐in. flexible UXGA electrophoretic display that can operate when bent at a radius of 5 mm.     

A flexible,organic QVGA display with gray‐scale capability

Abstract— A flexible 4.7‐in. QVGA active‐matrix display was demonstrated, containing 76,800 solution‐processed organic transistors. The combination of our plastic active‐matrix backplane with electrophoretic‐ink display material developed by E‐Ink resulted in a reflective low‐power display with paper‐like appearance. By using high‐performance organic transistors, it was possible to generate 2‐bit images on the display. The display can be bent to a radius below 2 cm.     

A rollable,organic electrophoretic QVGA display with field‐shielded pixel architecture

Abstract— A 100‐μm thin QVGA display was made by combining a 25‐μm thin organic transistor active‐matrix backplane with an electrophoretic display film. High contrast and low crosstalk was achieved by the addition of a field shield to the backplane. The display can be bent repeatedly to a radius of 2 mm without any performance loss. Extended mechanical tests at a radius of curvature of 7.5 mm show that the display can be rolled at least 30,000 times without noticeable degradation.     

A portable driving system for high‐resolution active matrix electrowetting display based on FPGA

How to display pictures and even videos on electrowetting displays (EWDs) still needs improvement. Therefore, we seek to develop a robust, portable and scalable system for the realization of high‐resolution EWDs. In this paper, a driving system for an 8 inch active matrix electrowetting display (AM‐EWD) based on a Field‐Programmable‐Gate‐Array (FPGA) is proposed, where the key components are an active matrix backplane, an FPGA driving waveform and driver integrated circuits (ICs). We successfully demonstrate an AM‐EWD with 1024×768 resolution and 16‐level gray‐scale realized by unique dynamic and asymmetric sub‐frame of FPGA. The whole system is just powered by a 3.7V 1100mAH lithium battery. Such a system has not been reported before, also well‐suited for transferring to a higher performance portable EWD in the future.     

Improvement in image quality of a 5.8‐in. OTFT‐driven flexible AMOLED display

Abstract— The image quality of an OTFT‐driven flexible AMOLED display has been improved by enhancing the performance of OTFTs and OLEDs. To reduce the operating voltage of OTFTs on a plastic film, Ta²O⁵ with a high dielectric constant was used as a gate insulator. The organic semiconductor layer of the OTFT was successfully patterned by a polymer separator, which is an isolating wall structure using an organic material. The OTFT performance, such as its current on/off ratio, carrier mobility, and spatial uniformity on the backplane, was enhanced. A highly efficient phosphorescent OLED was used as a light‐emission device. A very thin molybdenum oxide film was introduced as a carrier‐injection layer on a pixel electrode to reduce the operating voltage of the OLED. After an OTFT‐driven flexible AMOLED display was fabricated, the luminance and uniformity on the display was improved. The fabricated display also showed clear moving images, even when it was bent at a low operating voltage.     

A 5‐in. flexible ferroelectric liquid‐crystal display driven by organic thin‐film transistors

Abstract— An organic thin‐film‐transistor (OTFT) driven color flexible ferroelectric‐liquid‐crystal (FLC) display with 160 × 120 pixels and a resolution of 50 ppi has been developed. The flexible FLC was fabricated on a pentacene‐OTFT array using printing and lamination techniques. To drive the display at a fast driving speed, an OTFT was developed with a short channel length having a large current output. The fabricated OTFT array with a channel length of 5 μm exhibits a carrier mobility of 0.3 cm²/V‐sec and an ON/OFF ratio of over 10⁷ at a low drain voltage of ?6 V. A field‐sequential‐color system with a flexible backlight unit was also developed and used to drive the display. Color moving images were successively shown on the 5‐in. display using an active‐matrix driving technique of the OTFT.     

Fabrication of flexible organic light‐emitting‐diode display with a flexible color filter driven by In—Ga—Zn—Oxide TFTs

Abstract— A novel flexible active‐matrix organic light‐emitting‐diode (OLED) display fabricated on planarized stainless—used‐steel substrates with a resolution of 85 dpi in a 4.7‐in. active area has been demonstrated. Amorphous indium—gallium—zinc—oxide thin‐film transistors were used as the backplane for the OLED display with high device performance, high electrical stability, and long lifetime. A full‐color moving image at a frame frequency of 60 Hz was also realized by using a flexible color filter directly patterned on a plastic substrate with a white OLED as the light source.     

An LTPS active‐matrix process with PECVD doped N+ drain/source areas

Abstract— A low‐temperature polysilicon active‐matrix process without the need for ion implantation to dope drain and source areas of TFTs has been developed. A doped silicon layer is deposited by PECVD and structured prior to the deposition of the intrinsic silicon for the channel. The dopant is diffused and activated during the excimer‐laser crystallization step. N‐channel test TFTs with different geometries were realized. The TFT properties (mobility, on/off ratio, saturation, etc.) are suitable to realize AMLCDs and AMOLED displays and to integrate driver electronics on the displays. In addition to simple TFTs, a full‐color 4‐in. quarter‐VGA AMLCD was realized. The complete display (including photolithographic masks, active‐matrix backplane, and color‐filter/black‐matrix frontplane), and an addressing system were developed and manufactured at the Chair of Display Technology, University of Stuttgart, Germany. The substitution of ion doping by PECVD deposition overcomes a major limitation for panel sizes in poly‐Si technology and avoids large investment costs for ion‐implantation equipment.     

Development of 8‐in. oxide‐TFT‐driven flexible AMOLED display using high‐performance red phosphorescent OLED

An 8‐in. flexible active‐matrix organic light‐emitting diode (AMOLED) display driven by oxide thin‐film transistors (TFTs) has been developed. In‐Ga‐Zn‐O (IGZO)‐TFTs used as driving devices were fabricated directly on a plastic film at a low temperature below 200 °C. To form a SiO_x layer for use as the gate insulator of the TFTs, direct current pulse sputtering was used for the deposition at a low temperature. The fabricated TFT shows a good transfer characteristic and enough carrier mobility to drive OLED displays with Video Graphic Array pixels. A solution‐processable photo‐sensitive polymer was also used as a passivation layer of the TFTs. Furthermore, a high‐performance phosphorescent OLED was developed as a red‐light‐emitting device. Both lower power consumption and longer lifetime were achieved in the OLED, which used an efficient energy transfer from the host material to the guest material in the emission layer. By assembling these technologies, a flexible AMOLED display was fabricated on the plastic film. We obtained a clear and uniform moving color image on the display.     

High‐resolution autostereoscopic 3‐D projection display with a space‐dividing iris‐plane shutter

Abstract— A high‐resolution autostereoscopic 3‐D projection display with a polarization‐control space dividing the iris‐plane liquid‐crystal shutter is proposed. The polarization‐control iris‐plane shutter can control the direction of stereo images without reducing the image quality of the microdis‐play. This autostereoscopic 3‐D projection display is 2‐D/3‐D switchable and has a high resolution and high luminance. In addition, it has no cross‐talk between the left and right viewing zones, a simple structure, and the capability to show multi‐view images.     

Discharge efficiency of a 25‐in. high‐resolution SMPDP

Abstract— A novel round subpixel and triangle‐arrangement shadow‐mask plasma‐display panel (SMPDP) suitable for high‐resolution displays has been investigated. The discharge efficiency of this high‐resolution SMPDP and the AC coplanar PDP (ACCPDP) has been calculated separately. The variance of the discharge efficiency with pressure and xenon content will be reported. Results indicate that the SMPDP can reach a higher efficiency for high‐resolution displays than conventional ACCPDPs.     

Fabrication and characteristics of ZnO thin films deposited by RF sputtering on plastic substrates for flexible display

ZnO thin films were successfully grown on flexible plastic substrates using radio-frequency mag-netron sputtering method at room temperature.The effects of the sputtering power on the quality of the ZnO films have been investigated.The results show that thin films were polycrystalline,with wurtzite structure and a strong preferred c-axis orientation (002).The root-mean-square (rms) surface roughness of the ZnO thin films is 22.1 nm.The ZnO thin films fabricated by sputtering with 70 W sputtering power have a high mobility of 34.33 cm 2 /V·s.The ZnO films are shown to be compatible with flexible display on plastic substrates.     

Development of a 10.4‐in. UXGA display using low‐temperature poly‐Si technology

A new 10.4‐in.‐diagonal display with UXGA resolution (1600 H × 1200 V pixels) using low‐temperature polysilicon (poly‐Si) TFTs has been developed for notebook‐PC applications. The source drive technique uses integrated selector switches, which decreases the number of tape carrier packages (TCPs) for a poly‐Si TFT‐LCD and increases the connection pitch of the TCPs to the glass substrate. In this paper, we present a new display configuration and fabrication process.     

Demonstration of a technological prototype of an active‐matrix BiNem liquid‐crystal display

Abstract— The first implementation of active‐matrix addressing on a BiNem bistable nematic liquid‐crystal display has been demonstrated. Compared to previous passive‐matrix addressing, major improvements have been made for the bistable mode: a smoother image refreshment, shorter refreshing frame time compatible with that of high‐resolution e‐book displays, the use of a touch screen for interactive functions such as hand‐writing, a virtual keyboard, improved functionality for scrolling menus, partial refreshment, etc. On the same display but in the monostable mode, by using electrically controlled birefringence (ECB), the potential of displaying moving pictures at a rate of 25 images/sec, at an extended room temperature, has been demonstrated. In the ECB monostable mode, static images can be displayed down to ?20°C. A new transflective single‐polarizer optical mode has been developed to optimize the indoor and outdoor readability of the display. By lowering the surface reflection and enhancing the panel transmission, a contrast ratio of 94:1 and a transmittance of 17% have been achieved.     

A 470 × 235‐ppi poly‐Si TFT‐LCD for high‐resolution 2‐D and 3‐D autostereoscopic displays

Abstract— We have developed a 470 × 235‐ppi poly‐Si TFT‐LCD with a novel pixel arrangement, called HDDP (horizontally double‐density pixels), for high‐resolution 2‐D and 3‐D autostereoscopic displays. 3‐D image quality is especially high in a lenticular‐lens‐equipped 3‐D mode because both the horizontal and vertical resolutions are high, and because these resolutions are equal. 3‐D and 2‐D images can be displayed simultaneously in the same picture. In addition, 3‐D images can be displayed anywhere and 2‐D characters can be made to appear at different depths with perfect legibility. No switching of 2‐D/3‐D modes is necessary, and the design's thin and uncomplicated structure makes it especially suitable for mobile terminals.     

Flexible active‐matrix OLED displays: Challenges and progress

Abstract— Organic light‐emitting‐device (OLED) devices are very promising candidates for flexible‐display applications because of their organic thin‐film configuration and excellent optical and video performance. Recent progress of flexible‐OLED technologies for high‐performance full‐color active‐matrix OLED (AMOLED) displays will be presented and future challenges will be discussed. Specific focus is placed on technology components, including high‐efficiency phosphorescent OLED technology, substrates and backplanes for flexible displays, transparent compound cathode technology, conformal packaging, and the flexibility testing of these devices. Finally, the latest prototype in collaboration with LG. Phillips LCD, a flexible 4‐in. QVGA full‐color AMOLED built on amorphous‐silicon backplane, will be described.     

A novel low‐power‐consumption all‐digital system‐on‐glass display with serial interface

Abstract— A new conceptual ultra‐compact LCD panel, which features a simple interface and lower‐power consumption by using low‐temperature polysilicon thin‐film transistor (LTPS‐TFT) technology has been developed. This panel is capable of switching operation modes based on an input command, and all the data are directly communicated with the circuit inside the panel through a Serial Peripheral Interface (SPI) protocol. The integration of the serial‐data‐receiver function on glass substrate has enabled the achievement of a significant reduction in the number of interface pins. Moreover, a low power consumption of 15 μW for a 2.26‐in. reflective LCD panel in combination with the technique of integrating a memory circuit in each pixel has been achieved.     

A 550‐PPI LCD using 1.5 µm channel width LTPS TFTs with low frame rate driving

A 550 PPI low‐temperature polycrystalline silicon thin‐film transistor liquid‐crystal display has been developed. Shrinkage of the channel width of pixel thin‐film transistor together with thinner insulator for the storage capacitor allows high display quality in terms of vertical cross‐talk and flicker. Thirty hertz frame rate driving is implemented to offer low power while keeping high display quality.