US 12,240,781 B2
Foldable substrates, foldable apparatus, and methods of making
Gabriel Pierce Agnello, Corning, NY (US); Joy Banerjee, Corning, NY (US); Vitor Marino Schneider, Painted Post, NY (US); and Ian David Tracy, Hampstead, NC (US)
Assigned to CORNING INCORPORATED, Corning, NY (US)
Filed by CORNING INCORPORATED, Corning, NY (US)
Filed on Jan. 9, 2024, as Appl. No. 18/408,113.
Application 18/408,113 is a continuation of application No. PCT/US2023/036084, filed on Oct. 27, 2023.
Claims priority of provisional application 63/443,846, filed on Feb. 7, 2023.
Claims priority of provisional application 63/421,241, filed on Nov. 1, 2022.
Prior Publication US 2024/0182359 A1, Jun. 6, 2024
Int. Cl. C03C 21/00 (2006.01); G02F 1/1333 (2006.01); G06F 1/16 (2006.01)
CPC C03C 21/002 (2013.01) [G02F 1/133305 (2013.01); G02F 1/133331 (2021.01); G06F 1/1652 (2013.01)] 17 Claims
OG exemplary drawing
 
1. A foldable apparatus comprising a substrate comprising:
a substrate thickness defined between a first major surface and a second major surface opposite the first major surface;
a first portion comprising the substrate thickness, a first compressive stress region extending to a first depth of compression from the first major surface, a second compressive stress region extending to a second depth of compression from the second major surface;
a second portion comprising the substrate thickness, a third compressive stress region extending to a third depth of compression from the first major surface, a fourth compressive stress region extending to a fourth depth of compression from the second major surface;
a central portion positioned between the first portion and the second portion, the central portion comprising a central thickness defined between a first central surface area and a second central surface area opposite the first central surface area, a first central compressive stress region extending to a first central depth of compression from the first central surface area, a second central compressive stress region extending to a second central depth of compression from the second central surface area, the first central surface area is recessed from the first major surface by a first distance, the second central surface area is recessed from the second major surface by a second distance, and the central thickness is less than the substrate thickness; and
a concentration of lithium oxide at the first central surface area is greater than a concentration of lithium oxide at a central midpoint by from 0.2 mol % to 2 mol %,
wherein the first portion comprises:
a midpoint midway between the first major surface and the second major surface;
a concentration of lithium oxide at the first major surface;
a total concentration of potassium oxide, rubidium oxide, cesium oxide, and francium oxide at the first major surface;
a concentration of lithium oxide at the midpoint; and
a total concentration of potassium oxide, rubidium oxide, cesium oxide, and francium oxide at the midpoint, and
wherein the substrate is a glass-based substrate or a ceramic-based substrate, and the central midpoint is midway between the first central surface area and the second central surface area, the central portion comprises:
a total concentration of potassium oxide, rubidium oxide, cesium oxide, and francium oxide at the first central surface area; and
a total concentration of potassium oxide, rubidium oxide, cesium oxide, and francium oxide at the central midpoint.
 
15. A foldable apparatus comprising a substrate comprising:
a substrate thickness defined between a first major surface and a second major surface opposite the first major surface;
a first portion comprising the substrate thickness, a first compressive stress region extending to a first depth of compression from the first major surface, a second compressive stress region extending to a second depth of compression from the second major surface;
a second portion comprising the substrate thickness, a third compressive stress region extending to a third depth of compression from the first major surface, a fourth compressive stress region extending to a fourth depth of compression from the second major surface;
a central portion positioned between the first portion and the second portion, the central portion comprising a central thickness defined between a first central surface area and a second central surface area opposite the first central surface area, a first central compressive stress region extending to a first central depth of compression from the first central surface area, a second central compressive stress region extending to a second central depth of compression from the second central surface area, the first central surface area is recessed from the first major surface by a first distance, and the central thickness is less than the substrate thickness; and
a concentration of lithium oxide at the first central surface area is greater than a concentration of lithium oxide at a central midpoint by from 0.2 mol % to 2 mol %,
wherein the first portion comprises:
a midpoint midway between the first major surface and the second major surface;
a concentration of lithium oxide at the first major surface;
a total concentration of potassium oxide, rubidium oxide, cesium oxide, and francium oxide at the first major surface;
a concentration of lithium oxide at the midpoint; and
a total concentration of potassium oxide, rubidium oxide, cesium oxide, and francium oxide at the midpoint, and
wherein the substrate is a glass-based substrate or a ceramic-based substrate, and the central midpoint is midway between the first central surface area and the second central surface area, the central portion comprises:
a total concentration of potassium oxide, rubidium oxide, cesium oxide, and francium oxide at the first central surface area; and
a total concentration of potassium oxide, rubidium oxide, cesium oxide, and francium oxide at the central midpoint,
wherein a surface profile of the first central surface area has an average gradient of 0.015 mm/mm or less.