High brightness and low power among the benefits with the up-and-coming display tech
TOKYO — The Apple Watch Series 4 surprised observers at Apple’s annual iPhone event last week by stealing the show from the latest iPhone generation. With rounded corners, a larger display, and built-in EKG scanner, the new Apple watch was billed in some media reports as “the most sought-after gadget in the aftermath of Apple’s fall hardware refresh.”
Patrick Moorhead, founder and president of Moor Insights & Strategy, said, “With Watch Series 4, Apple continued its differentiated approach of creating a ‘computer on the wrist’ that runs real apps, not just applets.” He called the Series 4’s 30% bigger viewable image area as key to new uses. He added that users might prefer to “rely more on their Watch than their iPhones.”
Meanwhile display technology watchers are watching the Watch for an entirely different reason. They want to know when Apple will be ready to incorporate in the Watch screen microLED instead of OLED. If Apple pulls that off, the Cupertino giant, which has never been a display provider, would be nailing a technology nobody else in the world has yet mastered.
To be clear, the Watch Series 4 doesn’t do microLED.
There is “no surprise” there, Eric Virey, senior market and technology analyst at Yole Développement told us. “We know that Apple is still very active and committed to its microLED display development, but even if they were close to deliver the ‘perfect display’ they need for their products, it will still take time to set up the supply chain, ramp manufacturing and qualify the displays.”
Virey predicted last year that microLED could arrive in the wearable device market, such as Apple Watch, in late 2019. When we caught up with him last week, he acknowledged pushing back his prediction for the arrival of high-volume consumer microLED products by at least two years — to 2021.
What changed? Where is Apple today with its microLED technology? Who else in the industry has joined the microLED rush? And what’s the big delay in the microLED rollout?
We sat down with Virey and asked about what now appears to be an elusive breakthrough to microLED.
MicroLED displays consist of an array of microscopic LEDs forming individual pixel elements. Unlike OLED, microLED uses conventional gallium-nitride LED technology. MicroLED offers many promises, ranging from high brightness, high dynamic range and a wide color gamut to fast refresh rates, wide viewing angles and low power drain. MicroLED proponents claim total brightness can outshine OLED products by a factor of 30 while offering higher efficiency in lux per watt.
So, how would microLED change the user’ Watch experience? The biggest factor is the microLED’s lower power consumption, which Virey said, “would translate into extended battery life.”
Equally important is the microLED’s brightness. “That means excellent readability at any angle and in any condition, even direct bright sunlight,” Virey stressed. “This is a valuable feature for many use cases when people don't want to have to fiddle with the position of the watch or cover it with their hand, so they can read the display.”
Despite his own prediction of a two-year delay in the microLED rollout, Virey believes the major roadblocks that have hindered microLED development for more than a year are beginning to fall away.
Among the problems were refining a methodology to transfer very tiny individual LED chips to a display, while getting better yields and energy efficiency out of LED.
One cannot overemphasize how genuinely small those microLED chips are. In order to build a 4K display based on microLED, for example, one must assemple 25 million LED chips — each individual chip is the size of "grains of pollen," according to Virey — with a positioning accuracy of ~1 µm, without a single error, noted Yole. That's no cakewalk.
Virey quickly added, “We are not there yet when it comes to volume manufacturing" necessary for commercial displays. The level of microLED technology, however, has improved to a level that allows the industry to deliver prototypes, he explained.
By “prototypes,” Virey means microLED displays in which most pixels light up. This assumes a tolerable number of defects. Also, in general, cost and yield are no object in the development of prototypes.
In contrast, consumer-grade microLED demands zero-pixel defects, while offering higher performance and better efficiency compared to LCD and OLED. While the requirement for “impeccable color and brightness homogeneity” is a given, microLED is expected to offer “stability of more than1000 hours” and “no visible stitching/placement errors at any angle,” according to Yole.
In short, microLED has already passed such phases as early-stage feasibility, technology development and technology demonstration. But as with display technologies in the past, like LCD and OLED, the last mile — system/equipment development and manufacturing for microLED — is harder, explained Virey.
Samsung’s microLED entry
What has become clear over the last year is that Samsung is very serious about staking its claim on the microLED market.
The South Korean giant displayed at the Consumer Electronics Show earlier this year what the company calls “The Wall,” a 146-inch screen with microLED technology. In its announcement, Samsung boasted that the microLED technology in The Wall “eliminates the need for color filters or backlight, and yet allows the screen to offer consumers the ultimate viewing experience.” Samsung added that the microLED screen “excels in durability and effectiveness, including luminous efficiency, the light source lifetime and power consumption, setting the standard for future screen technology.”
Although Samsung calls it microLED, the Samsung CES prototype used LED chips of 120μm x 200μm. Virey observed that Samsung’s Wall more accurately falls into the category of “miniLED,” too big to be “micro.” Yole estimated the cost for Samsung’s 146-inch Wall between $200,000 and $250,000.
However, Samsung is promising to deliver in 2019 a newly designed, cost-down version of a “consumer 4K TV” based on microLED. That new version will contain 30μm x 50μm LED chips. In Yole’s opinion, this is another Samsung PR effort to herald its involvement in microLED. If Samsung is indeed gunning for the consumer market, its microLED-based TV should use LED chips tinier than 10μm, said Virey.
According to Knowmade, a Yole group company specializing in patent analysis, IP activities in the microLED field have proliferated in the last five years. Patent publication between 2012 1017 has jumped at a compound annual growth of 53%. An increase in patents, however, doesn’t necessarily indicate a sudden surge in microLED breakthroughs, observed Virey. Instead, as interest in microLED has heated up, traditional display companies with LCD and OLED technologies have rushed to file patents — any patents — in case their technologies might someday prove relevant to microLED production, for example.
Virey, however, added that traditional display companies are getting into the microLED field, “because they can’t afford not to look at the microLED.”
Noting that microLED is “a global trend,” Virey said the number of microLED patent publications has reached 1,495, filed by more than 120 organizations. Of these, 628 patents have been granted and 780 are pending.
Notable here is the number of organizations now involved in microLED patents. To build microLED, a company needs technologies that range from chips to transfer and assembly technologies, Virey explained. “Very few companies have such broad horizontal patents,” he said, although Apple appears to have major key patents covering various aspects of microLED.
Among the IP holders, X-Celeprint (Cork, Ireland) has “a fairy broad patent portfolio,” said Virey, ranging from transfer technology (X-Celeprint calls it “micro-transfer printing") to technologies to improve microLED manufacturing. X-Celeprint covers both upstream and downstream microLED, he added.
PlayNitride, a Taiwan startup, has two main technologies covering both mass transfer process and pixel repair technology. Earlier this year, rumors were flying about an Apple-PlayNitride collaboration. Other speculation had Samsung possibly acquiring PlayNitride. However, Virey last week confirmed Samsung’s recent 30% ownership investment in PlayNitride.
Obviously, Samsung, a late comer to microLED technology, has been “scrambling to find companies to acquire or license technologies from,” said Virey. In addition to PlayNitride, Samsung sealed a deal with Chinese LED behemoth San’an Optoelectronics earlier this year with plans to co-develop microLED displays. San’an today leads the LED market with the largest manufacturing capacity. For Samsung, the partnership with San’an is vital to securing a stable source of LED chips.
After all is said and done, however, Apple is believed to retain the lead in microLED development. Apple’s 2014 acquisition of startup Luxvue, a developer of low-power, microLED-based displays for consumer electronics, allowed Apple to have “by far the broadest patent portfolio in microLED,” said Virey.
A good example is the Silicon Valley wafer fab that Apple acquired from Maxim Integrated in December 2015. Since Apple’s Luxvue has MEMS-based printing technology to place tiny LED chips precisely onto backplanes, Virey suspsects that what used to be Maxim's small MEMS fab is now used by the Luxvue team to do test runs to perfect the technology of those “transfer heads."
Among many microLED applications, Virey regards smartwatches as “low-hanging fruit,” largely because microLED’s advantages used in smartwatches are clearer compared to applications such as TVs or smartphones.
However, Apple is still no cinch to become the first to use microLED, cautioned Virey. If Apple intends to use microLED in its Watch, it must ensure massive high-volume availability from Day 1, said Virey — because the market for Apple Watch itself is huge. In contrast, smaller OEMs, such as Xiaomi or Huawei, will need only a few million microLED units, he speculated.
Either way, it is hard to imagine that Apple would risk rolling out microLED half-cocked. Typically, Apple wants not only to perfect the technology but also “to further increase the gap with competition and bring on some unique and disruptive features enabled by microLED,” Virey said.
For example, by taking advantage of the larger real-estate available on a microLED display after full pixels are integrated, Virey speculated that Apple might add various “sensors in pixels.”
This could be 3D sensing, including gesture and position, he added.
Looking ahead, microLED’s applications are expected to spread further and broader as its process matures, according to Yole. Calling the period between 2021 and 2023 “Phase 1,” microLED is expected to go into smartwatches and “the very high-end large size TVs (85-110 inches) where cost is not a concern.
Asked about other Phase 1 possibilities, Virey noted that microLED’s early killer apps might be “AR (augmented reality)” and “HUD (heads-up display)” for automotive. “Small devices… they don’t need huge volume.”
— Junko Yoshida, Global Co-Editor-In-Chief, AspenCore Media, Chief International Correspondent, EE Times