Semiconductor Energy Laboratory (SEL) has developed a high density OLED display (5,291 PPI) based on its proprietary CAAC-IGZO (C-Axis aligned crystalline In-Ga-Zn-O) backplane. SEL will discuss this new achievement at SID 2019.
We do not have more information, but SEL has shown some high resolution CAAC OLEDs before. In 2014 it demonstrated a 2.8" 2560x1440 (1,058 PPI) WRGB OLED display. If SEL indeed developed a 5,291 PPI OLED display on glass it is very impressive.
SEL also developed a 2,351 PPI OLED with Stacked OS-FETs. This too will be discussed at SID.