Method and apparatus for separation of strengthened glass and articles produced thereby

A method, comprising:

• providing a substrate having a first main surface, a second main surface opposite the first main surface, an edge surface extending from the first main surface to the second main surface, a tension region within an interior of the substrate and a compression region between the first main surface and the tension region, wherein a portion of the substrate has a preliminary stress;
• contacting at least the one of the first main surface and the second main surface with a support member configured to support the substrate, wherein a portion of the at least one of the first main surface and the second main surface adjoining the edge surface is spaced apart from the support member;
• forming a vent crack in the first main surface, wherein the vent crack is aligned with a guide path extending to the edge surface;
• and
• after forming the vent crack, forming a modified stress zone extending along the guide path within the substrate such that the portion of the substrate is within the modified stress zone, wherein the portion of the substrate within the modified stress zone has a modified stress different from the preliminary stress,
• wherein the vent crack and the modified stress zone are configured such that the substrate is separable along the guide path upon forming the modified stress zone.

An apparatus for separating a substrate having a first main surface, a tension region within an interior of the substrate and a compression region between the first main surface and the tension region, wherein a portion of the substrate has a preliminary stress, the apparatus comprising:

• a stress modification system configured to form a modified stress zone extending along a guide path within the substrate such that the portion of the substrate is within the modified stress zone and has a modified stress different from the preliminary stress;
• a vent crack initiator system configured to form a vent crack in the first main surface;
• and
• a controller coupled to the stress modification system and the vent crack initiator system, the controller comprising:
• a processor configured to execute instructions to control the stress modification system and the vent crack initiator system to:
• form the modified stress zone extending along the guide path and form the vent crack in the first main surface such that the substrate is separable along the guide path;
• and
• a memory configured to store the instructions.