In a couple of years, supersized smartphones may be available with 4K displays. Nikkei Technology reports that Sharp is demoing a new IGZO prototype that crams a 2560x1600 display resolution into a 4.1" panel. The pixel density works out to an incredible 736 PPI, which is high enough to squeeze a 4K display into a phablet-friendly 6" footprint. For reference, Samsung's Galaxy Note 4 is 515 PPI, Google's Nexus 6 is 493 PPI, and Apple's iPhone 6 Plus is 401 PPI.
Prior to the new prototype, Sharp's highest-density IGZO unit was just under 500 PPI. New, ultra-small pixels enabled the jump to a higher resolution. According to an image posted by Gizmodo, the prototype's RGB clusters are just 11.5 µm wide—less than half the width of the 27-µm pixels found in older 4.7", 720p smartphone displays.
Those 11.5-µm pixels will likely be impossible to see with the naked eye. Higher pixel densities can make images appear sharper and more detailed even when the individual dots are too small to be visible, though. The returns from ever-higher-density displays may not diminish as quickly as one might expect. That said, higher-density displays typically require more power to achieve the same brightness levels.
Sharp's new panel tech is scheduled to start sampling to handset makers next year. Mass production will reportedly begin in 2016.