US Patent 11048295 Flexible window for foldable display

A cover window for a display device comprising a substrate, a joining layer and an outer cover, wherein the cover window has at least one folding region and at least one non-folding region. The substrate in the folding region has openings filled with at least a first filler material and a second filler material, wherein a stiffness of the first filler material is less than a stiffness of the second filler material, and the stiffness of the second filler material is less than a stiffness of the substrate.