material unexpected mask

Hello,
I was making a deform material on a texture like the screen. but seeing the texture preview there’s like a strange diagonal mask. the UV don’t go in the right up corner and left bottom corner. I would like the noise coming up into all preview. how can i do this? the panner has a speed by -0.2 and 0.2 so the right up corner DOES show something actually.

I’m a beginner and don’t really know how resolve this.

thank you!