Gradient ramp problem

Hi, I want to create a dark gradient for background in Ae. I have used the gradient ramp option, in the viewport the gradient is perfect, but even if i render in lossless the result is terrible:

Is there any solution to resolve this problem?

I got the best result if i rendered in Quictime - animation mode, but then 10 seconds is more than 700MB, and these rings are also visible.