Chinese telecom and smartphone giant ZTE will launch the “world’s first” under display camera (UDC) 5G smartphone called ZTE Axon 20 5G on Tuesday.
UDC is considered a higher tier technology compared to punch-in-hole cameras. Much like in hole displays, the cameras for UDC is under the display but there isn’t a hole and instead there is a transparent display atop the camera.
Users of UDC will be able to see the camera when taking photos, but it will disappear when not used. The transparent display area atop the camera has reduced number of pixels, and the pixels are fixed wider apart compared to remaining areas of the screen. The widen width between the pixels is made to absorb light more, which is crucial for the concept to work.
Cathode is the main challenge in realizing UDC. Samsung Display, the world leader in organic light emitting diode (OLED) technology, uses lasers to punch holes tightly together on the cathode to increase light transmittance.
In its production, there are laser equipment dubbed Hole in Active Area 2 (HIAA2) for this task. Wonik IPS and Philoptics provides the laser system for the equipment.
Samsung Display was hoping to launch a UDC display within the year but is facing difficulty in technology development, people familiar with the matter said. The issue is the particles that form when the cathode is cut with lasers. Samsung Display uses Mg-Ag as the cathode materials.
UDC made in the lab
Visionox, which provided the display for ZTE Axon 20 5G, used fine metal mask deposition to realize UDC. Cathode are placed sparsely. Previous OLED panels used open metal mask deposition to place the cathode. Cathode is placed thinly on the display. Mg-Ag is an opaque material but is super thin and can be semitransparent on an OLED structure. Still, the area where the camera hole will be needs to have higher light transmittance.
Visionox was producing UDC display in a lab-level production line rather than a conventional production line, people knowledgeable on the matter said.
The company makes thin film transistors on a 5.5th generation (1300mm x 1500mm) substrate and cut it by four (650mm x 750mm), then deposit the organic materials. So far the process is similar to those in conventional production lines.
But for the cathode placement, the substrate is further cut to 200mm x 200mm ones. It uses a deposition method that spins the substrate __ called the “revolver method” __ that is difficult in conventional production lines as substrates are too big to spin around.
Visionox used various technology besides fine metal mask cathode to achieve UDC, one of the people said, but it is only achievable in lab-like environments and will be difficult to produce massively in conventional production lines.
Chinese start-up Royole launched the “world’s first” foldable smartphone FlexPai in late 2018. But the company is yet to launch a successor.
Samsung launched its first foldable smartphone the Galaxy Fold last year, followed by Galaxy Z Flip earlier this year. It has launched the Galaxy Z Fold 2 on September 1.