Government-sponsored Industrial Technology Research Institute (ITRI) of Taipei, Taiwan is reportedly developing micro LED technology for various sized displays, according to a DigiTimes article. For small displays, ITRI created a 0.55-inch display made from single-light micro LED chips of just 10-micron in size on a silicon substrate at a pixel pitch of 12.8-micron. ITRI intends to use this small display technology in AR (augmented reality) and VR (virtual reality) devices.
For this demonstration project, ITRI combined innovative ultra–fine pitch LED digital signage with high throughput and wire bonding–free micro LED packaging. They reportedly combined this technology with highly–uniform LED epitaxy wafers, PCBs with fine pitch, and micro laser–drilled pores with mass transfer bonding equipment, driving chips, and system integration that aids connection and integration among domestic LED, PCB, and driving components.
Head-Mounted Displays Require Fast Response
Since AR and VR devices are head-mounted, displays with short sight distance require fast response. Based on what they know about small, head-mounted displays currently using AMOLED technology with 800-1000 pixels per inch (ppi), ITRI estimates that an optimal pixel density would be about twice that at 2,000 ppi. Display experts expect that such a small display is feasible with micro LED technology.
For much larger displays with much greater viewing distance, such minuscule pixel pitch is not needed. ITRI focuses its efforts on producing displays over 130 inches diagonal, which are made from blue and green micro LEDs with each pixel about five times to ten times as large (25-100x the area) of the single light LED chips of the demonstration model small display. These larger micro LEDs are mass transferred onto PCB substrates.
ITRI speculates that it would be relatively easy to mass transfer red-, blue-, and green-light micro LED chips onto glass substrates instead of PCB to make a panchromatic display, and even one that is 70% transparent.