unit – Why the user interface of Unity3D 2018 is bad and very sharp?

I update my project from Unity 2017.1.1 to 2018.3.9 and everything is ok except the user interfaces.
All user interfaces like images, buttons, text, mesh text, sprites and more seem very sharp and pixels pixel …

please see the attached picture:

Unity3D 2017 before the update:

enter the description of the image here

Unity3D 2018 after the update:

enter the description of the image here

why does this happen? and how can I solve this problem?