How to move a UI Image in the z axis? 2D

Hi I have 2 pictures in front of each other and only one is visible on the camera(because the other on is behind it), and i have a button. when you press this button the other Image should be shown (come closer to the camera) but i can't do it, when i change the other pic's z axis and move it closer to the camera it just don't render it by some reason, its like being a bit transparent, idk how to describe it. conclusion: what i need is when you press the button the other image(the one behind) becomes visible without using SetActive() - (i need them both turned on). Hope you understand, also my game is 2D Thanks