Smartphone manufacturers are always looking to pack more pixels-per-inch than their competitors, with Samsung already hinting that a smartphone with a 4K display could arrive as early as this year. Now Sharp has unveiled its own 5.5-inch IGZO 4K display that has a ridiculous pixel density of 806ppi, this is compared to the 577ppi that the Galaxy S6 packs and the 441ppi that the One M9 has.