Generally, the screen of a smartphone has three layers: one LCD display layer, one touch screen layer and the protected glass layer. And sometimes the whole cover will be made of glass for a better view. At first, the smartphone shells, both front shell and back cover, are commonly used plastic materials for low cost and best budget. But, as the mobile phone manufacturing technology developed and the massive consumers’ need for high quality smartphones, some high end or medium range smartphones will use other materials, like glass for a better hand feeling and appearance. So more and more smartphone OEMs started to design double-sided glass smartphones with both front shell and back cover using glass, not plastic, not metal.