Foldable window, display device including the same, and a method of manufacturing the window

A display device comprising:

• a display module configured to fold and un-fold;
• and
• a window disposed on the display module and configured to fold and un-fold, wherein the window includes:
• a substrate comprising a folding area, a non-folding area, an upper surface, and a lower surface, wherein the folding area is configured to fold about a folding axis;
• and
• a plurality of groove patterns arranged in the folding area along one direction crossing the folding axis, wherein each of the plurality of groove patterns comprises:
• a bottom surface recessed from the upper surface of the substrate and substantially parallel to the upper surface of the substrate;
• and
• a side surface, wherein each side surface of the plurality of groove patterns connects each bottom surface of the plurality of groove patterns to the upper surface of the substrate, and wherein the side surface comprises at least one curved surface.

A method of manufacturing a window, comprising:

• providing a mother substrate in which a first line extending in a first direction is for forming a first groove pattern;
• and
• forming the first groove pattern in areas of the mother substrate, wherein the forming of the first groove pattern comprises:
• irradiating, with a first laser beam, first portions, of the mother substrate, overlapping the first line;
• and
• providing an alkaline solution onto the first portions of the mother substrate to etch the first portions, and
• wherein a refractive index of the first portions irradiated with the first laser beam is different from a refractive index of the mother substrate before being irradiated by the first laser beam, and the first portions irradiated with the first laser beam have a thickness smaller than a thickness of a second portion of the mother substrate not irradiated by the first laser beam.