Blur behind

Is there any way to apply blur, in all that is behind an object?
I’m using 2d, and i made a simple example to explain.
I try to use the Blur (Optimized) but this apply to the image.

English is not my main language, feel free to ask if you don’t understood my question.

Just assign a blur shader to a new material and assign that material to the object you desire.

I’m not very familiar with materials, could explain a little better?
The part to apply blur on material.
Thanks