Your computer might come with an ePrivacy screen. It can reduce screen visibility from side angles to protect screen content against visual hacking.
This function is disabled
by default. You can press F12 or Fn+D
to enable it. You will be prompted by the on-screen icon 
or 
every time the function is enabled
or disabled.
You can press 
to increase
the privacy level or 
to decrease the privacy level.
Note:The
privacy level of this function varies depending on the
screen brightness level, the contrast ratio, and the physical environment
where you are using this function. The recommended range of the screen
brightness level is 50-60.