US Patent 9429999 Foldable display device

A foldable display device is disclosed. In one aspect, the foldable display device includes a display panel and a window panel on the display panel. The window panel includes a folding area and a flat area adjacent to at least one side of the folding area. The flat area is less flexible than the folding area. An elastic modulus of the folding area is less than an elastic modulus of the flat area. The window panel includes a plurality of layers including a first layer, wherein a first thickness of the first layer in the folding area is different from a second thickness of the first layer in the flat area.