Sharp has begun production on 1080p displays for smartphones. The company has announced that the LCD panel type 5 will be 5-inch full HD (1920 x 1080) displays with a rather large 443 PPI. The screen will go into full production this month and will be shown in Japan at CETEC this week. It is not yet known what smartphones will make use of the display.
It has been observed that a human eye can generally not differentiate detail past 300 PPI, however it does depend on the distance. Being that these displays are for smartphones, it's really not likely users will be able to see a whole lot of difference with such a large pixel density.
Sharp has been unprofitable lately, seeing losses across the board. Sharp presented its banks with a revival plan that included cutting more than 10,000 jobs, and selling overseas factories, as well as Recurrent Energy, which they are rumored to be selling for 25 billion yen. So who knows if this push in display technology can help Sharp return to profitability.