In May 2019, Apple was granted a pair of micro-LED patents based on Quantum Dot technologies.  Then in April Apple won a third patent for micro-LED displays that could be used in future iMacs, MacBooks, iDevices and even a TV. In late July a rumor surfaced claiming that two Taiwanese micro-LED suppliers had been chosen to produce a future Apple Watch with high-end micro-LED displays.

Yesterday Patently Apple discovered a new micro-LED display patent published in Europe on August 1, 2019. Apple begins their application stating that the "State of the art displays for portable electronics, computers, and televisions commonly utilize glass substrates with thin film transistors (TFTs) to control transmission of backlight through pixels based on liquid crystals. More recently emissive displays such as those based on organic light emitting diodes (OLEDs) have been introduced.

Even more recently, it has been proposed to integrate emissive inorganic semiconductor-based micro LEDs into displays. More specifically, it has been proposed to transfer individual micro LEDs from carrier substrates to a display substrate utilizing an array of electrostatic transfer heads.

Apple's invention covers embodiments that describe light emitting structures and methods of forming light emitting structures. In an embodiment, a method of forming a light emitting structure includes forming one or more pluralities of LED coupons on one or more corresponding temporary substrates, transferring the one or more pluralities of LED coupons to a carrier substrate, patterning the one or more pluralities of LED coupons into LED mesa structures, and transferring the LED mesa structures to a display substrate.

In some embodiments, well structures may also be formed around the LED mesa structures prior to transferring to the display substrate. Additionally, hybrid bonding may be utilized for bonding to the display substrate. The processing sequences in accordance with embodiments may be used to form both monochromatic and full color displays.

In accordance with some embodiments, the processing sequence may facilitate the integration scaling of the LEDs to small micro dimensions, and integration of optical structures around and over the LEDs with mitigated alignment challenges. Additionally, the integration of reflective well structures, and micro-optic elements may additionally bolster on-axis light extraction efficiency.

Apple's patent FIG. 1 below covers a process flow and corresponding cross-sectional side view illustrations of a method of forming a light emitting structure.

Apple's patent FIG. 12A above is a schematic cross-sectional side view illustration of a transparent half-ball high-index lens over an LED; FIG. 12B is a schematic cross-sectional side view illustration of a transparent cone-shaped high-index lens over an LED; FIG. 18 is a schematic top view illustration of a micro LED in a well structure; FIGS. 19-20 are schematic cross-sectional side view illustrations of a micro LED in a well structure.

Apple's patent application WO2019147589 was published in Europe on August 1, 2019. It was filed on January 22, 2019. Some of the original work on this dates back to 2018.  Considering that this is a patent application, the timing of such a product to market is unknown at this time.

While it's not an easy read for general Apple fans, it may be of interest to industry experts and display engineers. To review the deeper details, check out the full filing titled "Micro LED based Display Panel," here.

Some of the Inventors

Dmitry Sizov: Senior Hardware Engineer. He came to Apple via Corning.

John T. Leonard, Ph.D.: Display Technologist

Jonathan Steckel: Lead Technologist

Xiaobin Xin: Technologist

Ranojoy Bose: Technologist

I've never seen so many "Technologists" listed on a single patent application before.  

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