May 28, 2018
At SID Display Week, Micro LEDs were all over the place and X-Celeprint showed, behind closed doors, a demonstration of a 5.1-inch microLED Display. AUO showed an 8-inch microLED display but didn’t say whether it was transfer printed. AUO says its display uses color convergence technology, so, presumably all of the micro LEDs are blue and the red and green are created by quantum dots or phosphors.
AUO does not have a specific roadmap or a schedule for volume production of micro LED display products currently. AUO's micro LED technology employs LTPS-TFT backplane, high dynamic range and power-saving strengths, according to company data. Each micro LED in size of less than 30-micron can achieve a pixel density of up to 169ppi and is able to yield accurate colors when integrated with other color conversion technologies, according to AUO.
According to Ken Werner, the X-Celelprint display has 70 RGB pixels per inch, active-matrix switching using single crystal Si transistors, pixel level compensation, high contrast, and highly saturated colors including a very red red. X-Celelprint has accumulated an extensive IP portfolio on micro transfer printing, including the transfer of LED chips to make microLED displays and the transfer of microcircuits and other small objects. The backplane of the display is created by transfer printing of the micro-IC pixel switches (transistors). X-Celeprint and Corning tried this approach to build backplanes for LCDs, at least 5-years ago but it never took hold. The company uses a proprietary polymer transfer printing head that is able to pick the LED chips and micro-ICs off the wafers on which they were fabricated using a sacrificial technology that frees the active layers from the bulk wafer. The printing head then prints the LEDs on the substrate. It is possible to design a head such that it picks up every tenth, hundredth, or nth LED. Then, when the LEDs are printed on their new substrate, the pixel pitch can be appropriate for a direct-view display, such as the 5.1-inch shown by X-Celeprint. X-Celeprint intends to spin off a new company devoted exclusively to displays within the next 12 months.