Mesh artifacts only on render I am making my phone in Blender and my mesh has weird artifacts on rounded corners only on render, not in viewport. Removing doubles and flipping normals doesn't help. I thought it's releated to non-quads on rounded surface but connecting verticles with knife tool also doesn't help. 

What is this and how to resolve my problem?
You have a big and ugly n-gon (a polygon of more than 4 vertices) trying to bend as that curve.


You need to subdivide it into more faces.
Here's what you get when you delete that n-gon and do grid fill:



The curvature is better but far from ideal (plus you get terrible topology).

Try to create a curve that has the same number of vertices for both sides (and try to keep the rest of the topology as quads)