Why my sprites are pixelated?

Hi! I’m a newbie in Unity3D, I’m making a 2D game, but, I’m making the menu, and I’ts all pixelated!
Im my PC Looks fine, but when I run it on my iPhone, It pixelates.
I have the compress assets on import turn off, and the image original size is bigger than the size that have in Unity!.

PS: All Of the components are buttons with PNG Images, I dont know if it affects, but i’ts good to know.

Unity has some filters that it applies to imported sprites. By default the filter is Bilinear, this causes a blurred effect on the sprites, which is not desirable in sprites being used for UI.

On a side note, you might want to use bilinear on texture when applying to a 3D model.

So select your sprite in the project window.
Look over to your inspector and change the filter mode to Point (No filter).
You might have to reassign the sprite in your Image component again.

This will most probably fix your problem.

Read more about the filter modes in Unity here.