How to make a completely transparent button in Flash Builder

I am making a mobile application, and I am wondering how to make a completely transparent button. I've tried using

<s:Button x="-5" y="0" width="410" height="1504"

                                skinClass="spark.skins.mobile.TransparentNavigationButtonSkin" click="navigator.pushView(Sun)"/>

But it still has one line on the side. I need a way to make it completely transparent.

Thanks,

     8th grade student