UI button are sliced after exporting

Hi, sorry for the following mistakes and the time you will loose by answering my question.

I have one Menu scene where i have a text and three buttons. The problem is that my buttons are sliced when i make them bigger or just when they are bigger than approximatly 41px.

Bigger the buttons are, bigger the number of slice is. In my computer, everything is working perfectly, but when i export it to my phone, it's sliced. I've tried everything, so as you can see in the following screenshot, nothing is working (i've made more buttons to make more tests)

I don't have this problem with unity remote, but it's totaly different sure. Basicaly, my canvas is like that : and my buttons : http://tinyurl.com/gq5d6cd

But when i try to make them bigger, they are sliced like on the first screenshot.

If you couldn't help finding the source of this problem, maybe you could help me to find a way to do the same thing (button + img) without using something that will make me have this sliced button.

Thank you a lot in advance !