Galaxy Note 9: Why Light seems to Reflect from Phone's Corner ?
Leak light phenomenon from window outline sides which happen on Galaxy Note9 is the unique characteristics of devices that have flexible display window.
It usually appears when using at dark place and it’s not device faulty but normal phenomenon.
Flexible display has unique characteristics which light go spreading to around along the window due to window panel’s structure.
Same phenomenon may also appear on previous devices with similar concept of curved display. This phenomenon appears to not only white color model but also other colors. But, since white color model reflects the more light than other colors, leak light phenomenon is recognized more strongly on white color model.