Micro LEDs big time
Seamless transitions are required when tiny LEDs light up in large displays. Micro LEDs for video walls or instrument displays in cars are tiled.
At Display Week, tiny diodes for pixel sizes from a few micrometers to 100 micrometers can be seen in high-resolution large displays, including at BOE, Innolux, Samsung and TCL. Micro-LEDs are also interesting for cars because they can withstand high temperatures as well as sub-zero temperatures.
Large LED screens are made up of several tiles, which in turn contain the small micro-LEDs. This means that you are not completely free to choose the resolution, as this depends on the display size or the number of tiles joined; the latter have a fixed resolution.
(Bild: Ulrike Kuhlmann, c't)
In the 106-inch micro LED display from Innolux, for example, there are 96 tiles made up of 12.3-inch panels, which are fitted with 20 × 40 micrometer LEDs for each RGB sub-pixel. These are blue LEDs that generate red and green light with color-converting quantum dots. The trick here is to combine the 96 image tiles in such a way that no transitions are visible in video mode. To achieve this, the tiles must be very precisely color-coordinated, shine with the same brightness and there must be no delays in the control. Innolux has achieved this very well with the screen shown at Display Week. Innolux achieves the stated contrast of 8000:1 in bright surroundings with a matt tile surface that reflects little ambient light and thus ensures good black; the super-bright micro-LEDs are simply switched off for dark picture content in a similar way to OLEDs
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The Chinese display manufacturer Visionox assembles its LED video walls from 14.5-inch LED tiles that reflect less than 5 percent of the ambient light. This also achieves very good black levels in the bright exhibition. The tiles contain 25 micrometer light-emitting diodes and the modules are intended for cinema screens or museums.
(Bild: Ulrike Kuhlmann, c't)
In the car
Display specialist BOE demonstrates the art of seamlessly joining micro LED tiles on a display for a car console. The enormous brightness of the tiny LEDs can be put to particularly good use there. As the inorganic LEDs are also quite insensitive to temperature fluctuations, they are ideal for cars: In the automotive sector, all components must be able to withstand temperature fluctuations of at least -40 to 85 degrees Celsius. This is no problem for micro-LEDs.
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Expensive transfer
The production of the tiny LEDs still poses problems: it is expensive, especially the transfer of the tiny LEDs from the sapphire wafers to the display substrate. After all, at least 24 million LEDs have to be transferred for a 4K display, often significantly more if the manufacturers allow for reserves per pixel. This is why the step of tiling is also used – if pixels on a tile fail, the entire display is not lost.
(uk)
