Asymmetric chemical strengthening

A method, comprising:

• asymmetrically strengthening a glass article to include an asymmetric distribution of compressive stress comprising:
• chemically strengthening a peripheral portion of the glass article including chemically strengthening a first zone including a bend located along the peripheral portion of the glass article and defining a curved front surface and a curved back surface, thereby creating a first stress pattern extending through a first thickness of the glass article at the bend;
• and
• chemically strengthening a central portion of the glass article including chemically strengthening a second zone corresponding to the central portion of the glass article, thereby creating a second stress pattern extending through a second thickness of the glass article in the second zone, the second stress pattern defining a front compressive stress layer having a uniform depth across the second zone, a back compressive stress layer, and an imbalance of compressive stress between the front compressive stress layer and the back compressive stress layer;
• wherein:
• the first stress pattern is asymmetric along the first thickness and the second stress pattern is asymmetric along the second thickness;
• the back compressive stress layer has a depth less than the uniform depth of the front compressive stress layer;
• the first stress pattern and the second stress pattern differ;
• the chemically strengthened peripheral portion counteracts the imbalance of compressive stress in the second zone and front and rear surfaces of the second zone are substantially flat;
• and
• the glass article is for use in a portable electronic device.

A cover glass, comprising:

• a first chemically strengthened zone within a chemically strengthened peripheral portion of the cover glass, the peripheral portion including a bend formed in the cover glass and the first chemically strengthened zone having a first stress pattern extending through a first thickness of the cover glass from a curved first front surface to a curved first rear surface, the first stress pattern asymmetric along the first thickness;
• and
• a second chemically strengthened zone within a chemically strengthened central portion of the cover glass, the second chemically strengthened zone having a second stress pattern extending through a second thickness of the cover glass from a substantially flat second front surface to a substantially flat second rear surface, the second stress pattern asymmetric along the second thickness, and defining:
• a front compressive stress layer having a uniform depth across the second chemically strengthened zone and a rear compressive stress layer having a depth less than the uniform depths;
• and
• an imbalance of compressive stress between the front compressive stress layer and the rear compressive stress layer, the imbalance of compressive stress counteracted by the chemically strengthened peripheral portion to produce the substantially flat second front surface and the substantially flat second rear surface;
• wherein the first stress pattern and the second stress pattern differ.