Backplane

Semiconductor Energy Laboratory (SEL) demonstrated two new OLED display prototypes, both based on the company's proprietary CAAC-IGZO (c-axis aligned crystalline In-Ga-Zn-O) backplane material.

First up is the world's smallest 8K display, a 8.3" OLED (1058 PPI) with a resolution of 7680x4320. The panel is based on a white OLED with color filter architecture.

Apple recently launched its latest smartwatch - the Watch Series 4. It seems that at least some customers are complaining about a strong blue off-angle blue tint on the new OLED display. Some of these customers say that the tint is stronger compared to previous generation Watch devices - and also stronger than the tint on the iPhone X and LG OLED TVs.

It's not clear whether this is a real issue or not at this stage - we only have heard of a few customers complaining so far. But this is interesting as Apple has adopted its new LTPO backplane technology in the Watch 4, which could be responsible for the stronger tint (Is this the beginning of LTPO-gate?). All previous Watch devices used flexible AMOLED displays made by LG Display. We do not know yet whether LGD is still the exclusive supplier, or whether Apple added Samsung Display as its second source (or even exclusive).

IHS posted an interesting article which details a new backplane technology that Apple is developing. So-called Low-Temperature Polycrystalline Oxide (LTPO) combines both LTPS TFTs and Oxide TFTs (IGZO, Indium Gallium Zinc Oxide). LTPO is applicable for both OLED and LCD displays.

In LTPO, the switching circuits are using LTPS while the driving TFTs will use IGZO materials. This could lead to a power saving of around 5-15% compared to the currently-used LTPS backplanes. The main drawback of LTPO, however, is that the IGZO TFTs are larger and so the display density may be compromised. IHS says that Apple may introduce this into future iPhones - but it also says that LTPO will be limited to low-density displays at first which is a bit confusing.

Taiwan's AU Optronics (AUO) developed a 13-inch 100 PPI transparent OLED display, specifically for AR applications. This is a highly-transparent display - with 68% transmittance.

AUO 6" transparent OLED prototype (2011)

To achieve such high transparency, AUO optimized the TFT array layer stack, the OLED cathode pattern and the encapsulation. This is the first transparent OLED AUO has developed since 2011. It will discuss this new display at SID Display 2018 - and will hopefully demonstrate it as well.