Postcard Size Display — Optimal Solution Finally Achieved through a Long Way of Relentless Effort in Development
July 17, 2020
Extremely bright and vivid image, with stability which is unique to inorganic materials. In order to take full advantage of these LED characteristics, the Crystal LED Display System employs fine light sources and a scalable display system, realizing an unimaginable visual presentation that astonishes even filmmaking professionals. However, the path to achieve this successful outcome was not an easy one — a long rough road of development over more than 20 years. We talked to Masato Doi, who was in charge of research and development, and Jun Yasuda, who contributed to the commercialization of the product, to share their story.
Tokyo Laboratory 04
Display Device Business Division
Sony Semiconductor Solutions Corporation
20 Years of Facing the Risk of Discontinuing the Development
──I heard that the development of Crystal LED Display System started about 20 years ago. How did the project start?
Doi Masato：It started in 1999 when an engineer who worked in the same department suggested his idea of laying out tiny LEDs to make an ultimate display. He's already retired now, but his idea sounded very interesting and challenging, so I joined him and started the project together.
──In 1999, what kind of use and potential was expected in LEDs?
Doi：The blue LED was invented in 1993, and since the RGB (red, green and blue) primary colors of light were all made available, people started to explore various possibilities using them. I think the traffic lights were beginning to be replaced by LEDs at that time. And as for the displays that use typical-size LEDs, sports stadiums started to use a large screen based on them, but there was no product using tiny LEDs for a display that is a TV size or little larger than that.
──When did you join the project, Yasuda-san?
Yasuda：I joined Sony in 1996, and since then, I have been involved in the development of display devices such as TVs and PC monitors. At first, I was in the CRT (Cathode Ray Tube) department, but there had already been movement within the company considering there was no future in CRT and exploring new technology for display devices. As the company went through reorganizations, I moved from one department to another, working on the next-generation devices or LED backlight technology. In 2009, I finally joined the department where Doi-san was working.
──I hear that there had been some skeptical opinions about the idea of placing tiny LEDs to create an ultimate display.
Doi：Well, we were almost forced to suspend the development several times. In the first few years, there was no prospect at all, so we always felt the pressure from around us. We didn't know what the right answer was, and we couldn't even tell whether there was a right answer in the first place. It was very hard for us to work in that situation. But we believe it is important to continue in any way, so we solely continued our work.
When we finally achieved creating a 2.3-inch QVGA panel in 2003 and exhibited a prototype of micro LEDs at Sony Technology Exchange Fair (STEF), which is Sony's internal technology exhibition, we received a great response from many people. In those days, no one in the world had achieved what we were trying to do and it was often said that it can't be possible, so I was very happy to see people's excitement.
Yasuda：In 2012, a few years after I joined the team, I took a 55-inch, 2 million pixel full HD consumer TV over to the U.S. and showcased our technology at CES held in Las Vegas. When I explained our panel in the midst of the crowded people, I received a lot of praise and felt great expectations from visitors, which made me feel confident in our technology. However, when I got back to Japan, I was told that commercialization for consumers would be stopped. It was so sudden and I felt like the earth crumbled under my feet.
Doi：We had been conducting research and development in a strictly confidential environment for a long time, and we thought we were finally able to show it to the public, so we really faced a tough time then.
──How did you recover from that situation?
Yasuda：We talked and argued very heatedly among the members. In the end, we reached the concept of "creating smaller to produce bigger" in order to create a large display based on the technology designed for consumers. Whether it's LCD or OLED (organic LED), mass-producing large panels involves a large-scale equipment industry, and building a single factory requires money of as much as 100 billion yen. So, we decided to focus on a device of post card size in order to increase efficiency of capital investment and yield. After various proof-of-principle experiments, we found that it was possible to combine small devices to form a single large display.
LEDs make a scalable display system possible
──Please tell me the advantages of using LEDs as pixels of the display.
Yasuda：LEDs are a technology that produces light when an electric current is passed through a semiconductor. Compared to OLEDs, LEDs are very stable because they are inorganic. They also have a characteristic of being very bright. Because LEDs can produce the three primary colors of light, which are red, green, and blue, they can create a deep and wide range of colors. So, with LEDs, we can have high brightness, vivid colors, and stability—if we use such devices as pixels, we should be able to create an ultimate display. That's our basic concept of using LEDs.
Doi：If I can add to it, in the case of LCDs and OLEDs, we need a "frame" as a sealing structure to prevent liquid crystals from flowing out, but LEDs do not need it. Since LEDs are stable, a sealing technique is also simple.
──Among such beneficial LEDs, what are the special advantages of the Crystal LED Display System?
Yasuda：Crystal LED Display System uses ultrafine LED light sources, which are processed and mounted at high speed on a postcard-size panel, which is called a "cell." Cells are combined into one unit, and units are shipped to the field where they are assembled to form a scalable display of any size. This display has no visible bezels or seams, looking like one giant screen.
Since the ultrafine LED we've developed is smaller (about 0.003 mm2) than the thickness of a human hair, the area except for the LEDs can be made all black, which can provide a higher contrast ratio. That means no reflection occurs even in a bright room, so the images look brighter and more vivid.
When it comes to driving pixels, we've tried to make the light emission time a little longer in order to make the image look brighter with small light emitters. We developed a new driving circuit to achieve a frame rate of up to 120 fps (frames per second), compared to the usual 60 fps with 4K. Because LEDs have good response characteristics, there is almost no time loss to drive the signal from 0 to 100%. In other words, it can continue producing 120 images per second without any blur. Since it additionally requires some specific mechanism on the input side, we hope that the world will catch up with this system soon.
Doi：Furthermore, it can achieve a frame rate of 120 fps in 10-bit RGB format (8-bit RGB is common), which can provide a wider color range to reproduce. A typical LCD TV has a brightness of 500 cd/m2, but this display can produce a brightness of 1000 cd/m2 across the screen. When the whole wall glows at 1000 cd/m2, it's so bright that it's difficult to keep your eyes open. At the same time, our display can produce a lowest brightness of less than 0.01 cd/m2 when it is the cinema model. By devising the driving circuit, it is possible to reproduce colors accurately from light to dark.
Yasuda：0.01 cd/m2 is virtually totally dark. In an SF movie, for example, even when a pitch-black spaceship is moving through a very dark space, our display can show the unevenness on the surface of the spaceship very clearly. In fact, when I showed it to the people in Hollywood, they were extremely surprised with high capabilities of our display.
Doi：A wide viewing angle of nearly 180 degrees is another important feature. RGB lights are emitted individually and uniformly in all directions, so there is no disruption in the image when viewing from any angle.
Yasuda：Crystal LED Display System is assumed to offer a large screen viewing experience by combining units, so we thought it was very important that everyone can experience the same picture from any viewpoint.
With a large screen, there is a case in which the edges of the image cannot be seen, color shift occurs, or the image may be too dark depending on where the viewer stands.
There is a similar case in the LCD TV as well—the image suddenly gets invisible from a certain angle. Crystal LED Display System, on the other hand, gives consistent image even if the viewer is standing right next to the display. In a place like public viewing where many people see the same picture from various angles, the capability to let everyone experience the same image will be a great advantage.
Even professionals are stunned by the visual presentation
──So, high contrast ratio, high frame rate, rich color gradation, outstanding reproduction of colors, and wide viewing angle of virtually 180 degrees. Even the state-of-the-art professionals were stunned by these qualities.
Yasuda：One creator who watched a demonstration video at an exhibition said to me, "This footage shows the defect of the camera that actually shot the video." And he went on by saying, "What kind of camera did you use to take this, and how did you process the video to make it visible?" Although he asked me enthusiastically, I had no choice but to reply that we're just demonstrating a display monitor. But this story tells me how much he felt the difference from other videos he had ever seen, through our display.
There was also a computer graphic artist who said, "The light shining on the car is strange, and I know it is a simulation problem, but this is the first time I've ever seen a display that shows it." Putting aside whether it's intentional or not, its high level of visual presentation seems amazing, and even more so when people with professional eyes see it.
──It's something of Sony to influence creativity and entertainment through technology.
Doi：That's right. It is one of the happiest things for us engineers to stimulate creators.
──How do you expect Crystal LED Display System to be used in the future, including indoors and outdoors?
Yasuda：As I mentioned a little earlier, public viewing will the most possible usage in Japan.
Offering opportunities to enjoy sports and live performances while sharing the same space with the highest image quality should be an important step for us to promote the Crystal LED Display System widely.
However, if it is targeted at home use, the price needs to be reasonable enough to be put on the house wall. Otherwise, it cannot be spread widely in homes. I think the technology of showing images right there can be applied into various forms, such as eyeglass-type displays, and we have to see for a while before deciding how we should make it evolve.
LEDs have already been used in electronic advertising for stores for many years. If the ad is just meant to give information, a high resolution or image quality is not so much required, but if the ad is used indoors, and if it is aimed to convey important messages such as the company's concept or profile in the entrance lobby to customers through video, a high resolution and image quality immediately play an important role. In China and the United States, LED displays are already everywhere in towns and cities, and I think there is a great possibility that Crystal LED Display System can useful in such areas.
──How about you, Doi-san?
Doi：I don't know how big the market is, but I think it's interesting if it will be used as something in the amusement area, such as omnidirectional display or cubic display, because it is good at creating a highly immersive experience.
──Is it possible to make Crystal LED Display System into a sphere instead of a plane?
Doi：It is not possible now, but it's possible in principle. Since it uses small LEDs, it is strong against bending.
Great potential brought by high-precision mounting technology
──Do you think this experience and know-how will produce by-products?
Doi：No one else has achieved the technology of implementing chips of only a few tens of microns at high speed and with high accuracy.
I think this technology is worth more than just using it for displays. It can be applied to various composite devices and integrated devices, and I would really like to expand it.
For example, when we need a combination of a sensor and a light emitting device, we have the technology that allows various devices to be integrated on a chip. In fact, each LED is a separate device whose color is individually red, blue, or green, and we integrate those LEDs on a chip. We can integrate devices with various functions onto a very small space. We can make it two-dimensional, or cut into pieces and sell them individually at a lower price. There are many applications.
And if we continue to refine our technology to reduce the size of an LED or a chip, we'll be able to provide smaller displays, like watches and wearable devices, in addition to the current large displays.
──Were there any difficulties in commercialization?
Yasuda：As development goes and when we enter the commercialization phase, we need to examine how to design the architecture, what the level of completion is, how to maintain reliability, and what is the margin of error. We call each of these processes a "gate."
For better or worse, our company is based on vertical integration, and basically we do everything from making LED devices to commercializing them in-house. So, we always face a variety of challenges as we work on each gate. For example, I spent time hearing about the LED problem first in the morning, and an hour after that, I heard about a signal processing problem occurring on the main body. When I got back to my desk, I received a report about the problem caused by some dust particles discovered on a postcard-size unit. It looks like many issues were happening in a synchronized way.
Since we did not have an existing production line, we had to check the yield and quality by installing equipment on each site and starting it up for producing products. We examined with our own eyes to see manufacturing variations and make production stable. In fact, each site combined their efforts and worked very hard. I believe we were able to receive the Okochi Memorial Production Prize not only for the excellent performance of our product, but also for the achievement of such manufacturing efforts.
I think it's a good idea to have a unified thinking or intention within the project, but the project manager needs to know the full scope. If left alone, some engineers tend to optimize their assigned responsibilities, which may cause a lot of trouble to other people. Since each area has its own leader, the project leader closely communicates with them to coordinate the whole project. We were able to do this because we worked on the project through collaboration across the Sony Group as one team.
──What kind of role do you like to play in the future?
Yasuda：As I am working in the business division, I would like to put out products that sell well. Since I joined Sony, I have been involved in video devices and display devices. And I don't think display devices will disappear from the world, although I don't know what they look like in the future. I'm not sure if I can make as much impact as the Crystal LED Display System, but I would like to continue to deliver products by seeking what people think is the best thing for their life.
Doi：I would like to pursue my research and give something to Yasuda-san and his team as soon as possible so that they can create a new business. But this micro LED display is full of great technologies, so I'm having an ambition to further expand this technology into various forms and make it spread widely in the world.
──Do you see the path to that?
Doi：Well, I haven't seen it before, and that's why I'm in R&D. It's fun without knowing the answer.
Yasuda：It's like Doi-san is making a road on a desert island. In this interview, we talked a lot about the Crystal LED Display System, but seeing is believing. Please experience it. I've worked on a variety of video devices for a long time, but when Doi-san first showed it to me, I was really amazed. That was the only time I'd ever experienced having goosebumps looking at the display. Maybe I won't have the same experience, either.
The demonstration video was wonderful and it was a loop of about three minutes, but I watched it almost two hours. Although I'm involved in the development, I simply admire this device, which makes me feel shocked and deeply impressed with its enormous quality.
Crystal LED Display System official movie
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