Naruhiko Kasai

15.2: Development of an UXGA Display System by a Digital Packet Video Link

In this paper, we describe the development an UXGA Display system by using a trial Digital Packet Video(PV) Link for a next-generation interface(I/F). We already presented the basic idea and performance about this system. Then, we can apply this system for a QUXGA display, and then we can decrease the data transfer rate from PC to LCD. So we can solve the problem of I/F by this system, we propose the Digital PV Link as a standard for the next generation I/F of high density displays.

9.1: A 3.5-inch OLED Display using a 4-TFT Pixel Circuit with an Innovative Pixel Driving Scheme

A new pixel circuit for the “clamped inverter driving method” reported previously is developed. The pixel circuit is composed of four TFTs, one capacitor and five signal lines including power supply. A 3.5-inch OLED display with the proposed new pixel circuit has been fabricated by LTPS processing and COG of an existing LCD driver chip. A vertical scanning circuit and selector switches are integrated in the panel. The proposed driving scheme is confirmed as OLED display to produce 6-bit gray-scale, gamma correction, and peak luminance with clear full-color images.

51.1: A 2.5‐inch OLED Display with a Three‐TFT Pixel Circuit for Clamped Inverter Driving

A new pixel circuit for “clamped inverter driving” was developed. Since a PMOS inverter is applied instead of the conventional CMOS for the pixel circuit, the circuit is simplified and is composed of only three TFTs. A simulation of gray-scale characteristics verified that this pixel circuit can compensate variation in Vth and carrier mobility. A 2.5-inch OLED display based on the new pixel circuit was fabricated by LTPS processing and achieves 6-bit gray-scale and good uniformity.

High-Speed Programming Architecture and Image-Sticking Cancellation Technology for High-Resolution Low-Voltage AMOLEDs

We have developed a high-speed programming architecture and an image-sticking cancellation technology that utilize a pixel circuit with only four TFTs for LTPS active-matrix organic light-emitting-diode (OLED) displays. High-speed programming is realized through controlled-amplitude precharging. The gate voltage of the drive TFT in data programming converges the fixed voltage on very low voltage and very short programming time by controlled-amplitude precharging. This means that an image-lag-free picture can be achieved on a low-power high-resolution display. Image-sticking cancellation is realized by detecting the OLED anode voltage difference between neighboring pixels. When there is a large amount of OLED characteristic shading over an entire panel, it is difficult to detect the absolute value of the OLED characteristic to judge image sticking. Therefore, detecting the OLED difference between neighboring pixels is useful. A 3.0-in 202 × 267 ppi full-color panel was developed. This panel could produce image-lag-free pictures at low-voltage (4-V) operation because of high-speed programming, and we confirmed that image sticking could be detected and canceled by the proposed cancellation technology.

49.4: Two TFT Pixel Circuit with Non-Uniformity Suppress-Function for Voltage Programming Active Matrix OLED Displays

We proposed the worlds first two TFT pixel circuit with an inter-pixel non-uniformity suppress-function for the analog voltage programming to assist in the realization of small pixel bottom emission OLED displays. The pixel circuit provides larger OLED fill factor. We fabricated a 2.5 inch 240 (V) × 960 (H) pixel monochrome bottom emission display.

LTPS AM-OLED Display Consisting of Two-TFTs/One-Capacitor Pixel Circuits for Producing High-Uniformity Images

A method for generating threshold voltage (Vth) of thin-film transistors (TFTs) is proposed. This method is applied to the simplest pixel circuit, namely, one composed of two TFTs, a drive TFT and an address TFT, and one capacitor [i.e., two TFTs and one capacitor configuration], of active-matrix organic light-emitting diode (AM-OLED) displays. It involves two steps. First, source voltage of the drive TFT is quickly and precisely detected under the condition that carriers, namely holes, in the drive TFT are detrapped. Second, a simple subtraction and bit-shift operation are executed using the detected source voltage of the drive TFT. A prototype 3.8-in 480 × 320-pixel AM-OLED display was developed to confirm that a Vth-distribution image produced by this method corresponds to nonuniform images of AM-OLED displays. Furthermore, the AM-OLED display produced high-uniformity images when the Vth distribution was compensated by the proposed method.

40.3: A 2.5-inch Low-Power LTPS AMOLED Display—Using Clamped-Inverter Driving—For Mobile Applications

We developed a 2.5-inch low-power LTPS AMOLED display, in which data driver and scan driver are integrated. The developed low-power pixel circuit of this display contributes to panel power consumption of 350 mW at a luminance of 100 cd/m2 through a circular polarizer. We confirmed that the panel only suffers a slight temperature increase.

Clamped-inverter circuit architecture for luminescent-period-control driving of active-matrix OLED displays

— An innovative pixel-driving technology for high-performance active-matrix OLED flat-panel displays is described. Called “clamped-inverter circuit architecture,” it uses luminescent-period-control driving to reduce the inter-pixel non-uniformity caused by the device-to-device variability of low-temperature poly-Si TFTs. A prototype full-color display shows a luminous deviation of less than 1.6%, which corresponds to only the LSB-error in 6-bit gray-scale.

L-1: Late-News Paper: 3.0-inch High-resolution Low-voltage LTPS AM-OLED Display with Novel Voltage-programmed Driving Architecture

A new voltage-programmed driving architecture with controlled-amplitude precharge for lower-power LTPS AM-OLED displays with very-low-voltage-driven OLED is presented. with this new architecture, a 3.0-inch 202 × 267-ppi full-color panel was developed. We confirmed that these panels produce image-lag-free high-quality pictures at low-voltage (4 V) operation.

44.4L: Late-News Paper: A Color Balance Control System for OLED with Clamped Inverter Method

In order to product active matrix Organic light emitting Diode (OLED) displays, it is necessary to solve the problem of the image uniformity, so we had proposed the driving scheme named “Clamped Inverter (C.I) Driving”. For the display applied C.I method, we have developed an external driving circuit that has realized keeping color balance for a long time, peak luminance, power consumption control, and so on.