ionic-framework/ionic/components/button/test/clear/main.html

<ion-toolbar>
  <ion-title>Clear Buttons</ion-title>
</ion-toolbar>

<ion-content class="padding" style="text-align:center">

  <p>
    <button clear>D</button>
    <button clear class="hover">D.hover</button>
    <button clear class="activated">D.activated</button>
  </p>

  <p>
    <button clear secondary>S</button>
    <button clear secondary class="hover">S.hover</button>
    <button clear secondary class="activated">S.activated</button>
  </p>

  <p>
    <button clear danger>D</button>
    <button clear danger class="hover">D.hover</button>
    <button clear danger class="activated">D.activated</button>
  </p>

  <p>
    <button clear light>L</button>
    <button clear light class="hover">L.hover</button>
    <button clear light class="activated">L.activated</button>
  </p>

  <p>
    <button clear dark>D</button>
    <button clear dark class="hover">D.hover</button>
    <button clear dark class="activated">D.activated</button>
  </p>

</ion-content>