The patent number is 6,410,940. It is titled “Micro-size LED and detector arrays for mini-displays, hyperbright light emitting diodes, lighting and UV detector and imaging sensor,” and it disclosed a tiny LED with a size around 20 microns (one micron equals one-millionth of a meter), or micro-LED, as well as micro-LED arrays.
The patent was filed more than 17 years ago with several applications imagined by its inventors, Hongxing Jiang and Jingyu Lin. They thought the best use for micro-LEDs would be for small displays and wearable displays that could be used anywhere and would eventually revolutionize the traditional displays and projectors.
“We thought it was interesting to see what kind of new properties would come out of this very small size LED,” Jiang said. “As soon as we started talking about this, then the questions came as to what kind of things you can use from this. We thought about microdisplays and micro-size projectors, we thought about wearable displays and their related applications.”
Shortly after developing micro-LED technology at Kansas State University, Jiang and Lin were recruited by Texas Tech University to occupy the inaugural Edward E. Whitacre Jr. endowed chair and Linda F. Whitacre Endowed Chair, respectively, established by the AT&T Foundation.
They moved their research group, which included research professors, postdoctoral researchers, graduate students and others, along with truckloads of equipment, to Lubbock thanks to the Emerging Technology Fund created in 2005 at the urging of then-Gov. Rick Perry. Today they also are Horn professors in the Edward E. Whitacre College of Engineering and direct the Texas Tech Nanophotonics Center.
Today, micro-LED is one of the fastest-growing technologies in the world as companies utilize it on everything from large-screen televisions to heads-up displays. Even with the upcoming release of the iPhone 8, which is reported to utilize Organic LED (OLED) technology, companies are already moving past that toward micro-LED technology, using it in the next generation of smart phones and televisions.
It just took a couple of decades.
“People are starting to recognize this technology,” Lin said. “They are trying to get it into the smartphones, big and small screens by putting more pixels per area to try to get a higher resolution and higher brightness, while saving power consumption and extending the battery lifetimes of smart phones because micro-LED displays have the advantages of being self-emissive, high efficiency, high brightness and high turn-on/off speed.”
The beginning of LED, or Light Emitting Diode, can be traced back to the mid-1960s. LED uses semiconducting materials to produce a diode that emits light when activated by a suitable voltage source. Until the early-1990s, though, LEDs came in just two colors – red and yellow. It wasn’t until about 1993 that blue and green colors were produced, and that enabled the possibility of combining primary colors to produce a white light. That led to the development of LED lightbulbs that are more efficient and use less electricity to produce the same amount of light as an incandescent bulb.
Most televisions that claim to be LED TVs, the researchers said, actually still use the Liquid Crystal Display, or LCD, that is backlit by white LEDs. What that means is that the background light from a big-screen TV comes from an LED but the display is still LCD. LED light is emitted or blocked to create the dark spots on a screen, or certain colors of LED can be blocked or transmitted to produce color images on the screen.
The technology works the same on smartphone screens. The background is lit by white LEDs and colors are blocked or transmitted in LCD to produce text or color images on the screen.
“In terms of TV applications, all of the commercial LED TVs are using LEDs as backlight,” Lin said. “The display is still LCD. They’re not using micro-LEDs yet.”
But it’s coming.
While the iPhone 8 is expected to be the first Apple device to incorporate an OLED display, the company already has made moves to advance past OLED to micro-LED.
Jiang and Lin can see a time, eventually, when micro-LED technology could shrink and eliminate a computer or phone screen altogether.
“We demonstrated the principle of micro-LED technology 17 years ago that you can use them to make microdisplays, where you can wear them,” Jiang said. “We were also developing this technology for projection. You can display all the information on a wall, on a window, on a car windshield. In principle, you can also make something like this where the applications allow you to wear something like a Goggle Glass for the projection, or you can have a very small device, like a pen, that can project the images.”
As for what the future holds, both speculated emerging three-dimensional (3-D) and AR, or augmented reality, micro-LEDs, with their outstanding properties, especially high turn on/off speed, could be the next to become part of the mainstream. They also feel the surface of micro-LED technology has just been scratched.
Hongxing Jiang, Edward E. Whitacre Jr. Chair, Department of Electrical and Computer Engineering, Whitacre College of Engineering, Texas Tech University, (806) 834-5739 or firstname.lastname@example.org; or Jingyu Lin, Linda F. Whitacre Chair, Department of Electrical and Computer Engineering, Whitacre College of Engineering, Texas Tech University, (806) 834-5383 or email@example.com
(News release from Texas Tech University)