Sharp announced it started production of a 5" screen with a resolution of 1920 x 1080 pixels, offering a pixel density of 443ppi. Exact details about the screen are unknown, but it's world's first 5-inch screen with a Full HD resolution.
Right now, most of the super-sized smartphones on the market offer display resolutions around 720p range. The smaller iPhone 5 has a resolution of 1136x640, making Sharp's new panel a big step up. Of course, just because there are more pixels doesn't mean the display looks better than what's out there right now. There are important factors other than pixel density, and the PPI scale offers diminishing returns the higher you climb.