[Interview conducted by Sony.net] In March 2009, Tetsuo Urabe of Sony’s Display Device Development Group and three others received the 55th Okochi Memorial Award. These awards are presented to individual researchers and business organizations that have made major contributions to the field of production engineering, including the development of production technology, and the implementation of advanced production methods. The award received by Urabe and his colleagues was in recognition of their work relating to the development and mass-production of the world’s first OLED television.
Sony has earned widespread acclaim for its success in the development and mass-production of the world’s first OLED television, which follows earlier development successes—the Super Top Emission structure for OLED panels, and the active matrix OLED display.
Creating an OLED Display Suitable for Television Use
Sony first became involved in OLED research around 1994. A growing number of organizations had established OLED R&D projects after the publication of a paper in 1987 describing a thin-film OLED device fabricated using vapor deposition. In this sense, Sony was a latecomer to this field. At the time, Trinitron was still Sony’s core technology for display devices. Of course, the Company was also working on the development of next-generation flat-panel display devices and had established parallel projects focusing on various types of devices, including the Plasmatron (plasma addressed liquid crystal) and field emission display (FED) systems.
“Various systems were being tried at that time. It was as if they were in competition with each other. There was extensive debate on which technology would be the winner.”
Not everyone thought that OLED was likely to become a major future display technology, and the development of display devices based on OLED technology did not begin in earnest until 1998. Tetsuo Urabe was a member of the OLED display development team established that year.
Technology had already been developed to create light using OLED. However, Sony wanted to develop an OLED display for TV use. This achievement would necessitate the creation of a screen made up of large numbers of picture elements. Sony decided to use an active matrix system based on thin-film transistor (TFT) technology, which is also used in LCD panels. The consensus view at the time was that it would be very difficult to apply this technology to the development of an OLED display. However, Urabe and his colleagues began to develop an active matrix driver for an OLED-based system.
“There was growing interest in the concept of an OLED system with an active matrix driver. It was seen as a technology for the future. Sony was a latecomer to OLED R&D, but we were among the first to start developing the technology for use as a television display device.”
Successful Development of 13-inch OLED Display in 2001
The first problem in using an active matrix system to drive an OLED display was variation in pixel brightness. This variation results from differences in the characteristics of the TFTs positioned in each pixel.
“In an OLED display, the TFTs drive the luminescence themselves. This means that any variation in TFT characteristics end up as variations in the brightness of individual pixels.”
Since creating TFTs with identical characteristics is virtually impossible, Urabe’s team decided to focus instead on the development of a method to compensate for this. After studying several possible solutions, they decided to use current mirror circuits.
Current mirror circuits consist of two circuits that are mirror images of each other. When a current flows in one of the circuits, the same exact current will flow through the other one. These circuits were attached to neighboring pixels. Provided both pixels in each pair have the same TFT characteristics, there will be no variation in pixel brightness between them. Using this concept, Urabe’s team was able to overcome the brightness variation problem by arranging large numbers of pixels symmetrically. In 2001, they succeeded in developing the world’s first 13-inch active matrix OLED display. At the time, it was the largest in the world.
Challenges in Establishing Mass-production Technology
Sony had developed a 13-inch OLED display, but it was still only a prototype. The first challenge on the path to commercialization would be to extend the life of the product. When first developed, the display was completely useless as a commercial product since its brightness declined dramatically in just two or three days. There were countless additional challenges, including the choice of organic materials and drive system and the method used to stack thin organic layers. The development team also had to consider the structure of the organic layers, and the method used to isolate the materials from the external environment. Urabe and his team solved each of these problems in turn by conducting a massive program of testing and evaluation. The work was so intense that team members sometimes fought over access to larger pieces of testing equipment.
The next challenge was the establishment of production technology. Before OLED products could be launched commercially, Sony needed a production technology able to mass-produce panels without any loss of quality. One of the most difficult tasks was reducing the number of defective pixels. The organic film in an OLED panel is only a few hundred nanometers thick. This extremely thin layer is sandwiched between electrodes, and the presence of even a minute particle of dust can prevent the current from flowing to the organic film, resulting in a dead pixel. To prevent dead pixels, it’s necessary to eliminate dust, so the team began to remove all possible sources of dust from the production line. They also sought to minimize the effects of dust by increasing the thickness of the film as much as possible without compromising its characteristics. Another solution involved the use of lasers to repair any dead pixels discovered after production.
This process culminated in 2004 with the launch of the Courier PEG-VZ90, the first PDA with an OLED panel.
A Letter to the Families of Development Team Members
In 2007, Sony decided to use its years of experience and mass-production technology in developing another commercial product, the XEL-1 OLED television. However, there was another challenge ahead.
“We couldn’t increase yield and product life to the degree we initially anticipated. We were under pressure due to a tight schedule and the knowledge that we must not fail in coming up with a commercialized product. It was hell.” [Laughs]
The development team worked relentlessly to create the world’s first OLED television. The three team leaders, including Urabe, sent letters to the families of development team members apologizing to them for the relentless work schedule and asking them to understand the importance of the project to Sony.
Enhancing Japan’s Competitiveness with OLED
The XEL-1, the world’s first OLED television, was launched on schedule in December 2007. Urabe recalls the supreme happiness he felt at the shipment ceremony at Sony EMCS Corporation’s Inazawa TEC, where the XEL-1 is manufactured.
“People from various departments were involved in the XEL-1 project. They were all at the facility for the shipment ceremony. That was our greatest moment, because all of us felt the satisfaction of having created a new product that was a world’s first.”
This is the first time in 12 years that Sony has won an Okochi Memorial Award. According to Urabe, the real significance of the award will only become apparent when OLED technology matures into a key product category for Sony and a driving force for Japan’s competitiveness.
Sony is still developing OLED technology. Current goals are to create large-screen OLED televisions at a commercially viable cost.
The Okochi Memorial Award was established in April 1954 in memorializing the achievements of the late Dr. Masatoshi Okochi, who served as Director of the Riken Institute. In addition to general and technology awards for individuals or groups, there is also a production award for business organizations. Sony won the 1973 technology award for the development of Trinitron, the 1984 production award for its UHIC circuit mounting technology, the 1989 technology award for the development of mass-production technology for alloy optical recording discs, the 1990 production award for development and mass-production of compound semiconductors using the MOCVD method, the 1992 production award for the development and implementation of a vapor deposition method for video tape production, the 1995 technology award for the development of lithium ion storage batteries, and the 1997 technology award for the development and mass-production of Digital Betacam, a commercial VTR. This latest award was Sony’s eighth.
The winners of the 55th Okochi Memorial Technology Award were as follows.
- Tetsuo Urabe
- Senior Vice President, Display Device Development Group, Sony
- Yoshito Shiraishi
- E Business Development Department, FTV Business Division, TV Business Group, Sony
- Akihiko Yoshida
- Advanced Display (AD) Business Development Department, AD Business Development, Sony
- Masaya Yamauchi
- FPD Manufacturing Engineering Development Group, Manufacturing Engineering Development Division, Production Group, Sony
* Titles and entities appearing throughout this article are as of March 2009.