US-12622164-B2 - Foldable substrates and methods of making

US12622164B2US 12622164 B2US12622164 B2US 12622164B2US-12622164-B2

Abstract

Foldable substrates comprise a first outer layer comprising a first major surface, a second outer layer comprising a second major surface, and a core layer positioned therebetween. The core layer may comprise a first central surface area positioned between a first portion and a second portion of the first outer layer, and the core layer comprising a second central surface area positioned between a third portion and fourth portion of the second outer layer. Some foldable substrates comprise a first portion comprising a first depth of compression, a first depth of layer, and a first average concentration. The central portion may comprise a first central depth of compression, a first central depth of layer, and a central average concentration. Methods comprise chemically strengthening a foldable substrate. Some methods comprise etching the foldable substrate and then further chemically strengthening the foldable substrate.

Inventors

Douglas Clippinger Allan
Matthew John Dejneka
Yuhui Jin
Xinghua Li
Yousef Kayed Qaroush
Tingge XU

Assignees

CORNING INCORPORATED

Dates

Publication Date: 20260505
Application Date: 20200828

Claims (15)

1 . A foldable substrate comprises: a substrate thickness defined between a first major surface and a second major surface opposite the first major surface, the substrate thickness is in a range from about 100 micrometers to about 2 millimeters; a first portion comprising the substrate thickness, the first portion comprises a first average concentration of potassium on an oxide basis, 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, the second portion comprises a second average concentration of potassium on an oxide basis, 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 comprises a central thickness defined between a first central surface area and a second central surface area opposite the first central surface area, a central average concentration of potassium on an oxide basis, a first central compressive stress region extending to a first central depth of compression from the first central surface area, the central portion further comprises a second central compressive stress region extending to a second central depth of compression from the second central surface area, wherein the central thickness is in a range from about 25 micrometers to about 80 micrometers, wherein the first central surface area is recessed from the first major surface by a first distance, and an absolute difference between the first average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.
2 . The foldable substrate of claim 1 , wherein an absolute difference between the first depth of compression as a percentage of the substrate thickness and the first central depth of compression as a percentage of the central thickness is about 1% or less.
3 . The foldable substrate of claim 1 , wherein the substrate thickness is in a range from about 125 micrometers to about 200 micrometers.
4 . The foldable substrate of claim 1 , wherein the second central surface area is recessed from the second major surface by a second distance.
5 . The foldable substrate of claim 4 , wherein the second distance is from about 5% to about 20% of the substrate thickness.
6 . The foldable substrate of claim 4 , wherein the first distance is substantially equal to the second distance.
7 . The foldable substrate of any one of claim 1 , wherein the first compressive stress region comprises a first maximum compressive stress of about 700 MegaPascals or more; the second compressive stress region comprises a second maximum compressive stress; the third compressive stress region comprises a third maximum compressive stress of about 700 MegaPascals or more; the fourth compressive stress region comprises a fourth maximum compressive stress; the first central compressive stress region comprises a first central maximum compressive stress of about 700 MegaPascals or more; the second central compressive stress region comprises a second central maximum compressive stress.
8 . The foldable substrate of claim 1 , further comprising a first tensile stress region of the first portion positioned between the first compressive stress region and the second compressive stress region; the first tensile stress region comprises a first maximum tensile stress; the foldable substrate comprises a second tensile stress region of the second portion positioned between the third compressive stress region and the fourth compressive stress region; the second tensile stress region comprises a second maximum tensile stress; the foldable substrate comprises a central tensile stress region of the central portion positioned between the first central compressive stress region and a second central compressive stress region; the central tensile stress region comprises a central maximum tensile stress; an absolute difference between the central maximum tensile stress and the first maximum tensile stress is about 10 MegaPascals or less.
9 . The foldable substrate of claim 1 , wherein the central portion further comprises a central tensile stress region of the central portion positioned between a portion of the first central surface area and a portion of the second central surface area; the central tensile stress region comprising a central maximum tensile stress; the central portion comprises a first transition portion attaching the first central major surface to the first portion; the first transition portion comprising a first transition tensile stress region comprising a first transition maximum tensile stress; the central portion comprises a second transition portion attaching the first central major surface to the second portion; the second transition portion comprising a second transition tensile stress region comprising a second transition maximum tensile stress; the first transition maximum tensile stress is greater than the central maximum tensile stress.
10 . The foldable substrate of claim 9 , wherein the second transition maximum tensile stress is greater than the central maximum tensile stress.
11 . The foldable substrate of any one of claims 1-10 , wherein the first distance is about 20% to about 45% of the substrate thickness.
12 . The foldable substrate of claim 1 , wherein the substrate achieves an effective bend radius of 5 millimeters.
13 . A foldable apparatus comprising the foldable substrate of claim 1 , the foldable apparatus further comprises an adhesive comprising a first contact surface and a second contact surface opposite the first contact surface, wherein at least a portion of the adhesive is positioned in a recess defined between the second central surface area and a second plane defined by the second major surface.
14 . A foldable apparatus comprises the foldable substrate of claim 1 , the foldable apparatus further comprises a polymer-based portion positioned in a recess defined between the second central surface area and a second plane defined by the second major surface, wherein the foldable apparatus comprises an adhesive comprising a first contact surface and a second contact surface opposite the first contact surface.
15 . The foldable apparatus of claim 14 , wherein the polymer-based portion comprises a strain at yield in a range from about 5% to about 10%, and wherein a magnitude of a difference between an index of refraction of the foldable substrate and an index of refraction of the polymer-based portion is about 0.1 or less.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a national stage entry of International Patent Application Serial No. PCT/US2020/048492, filed on Aug. 28, 2020, the content of which is relied upon and incorporated herein by reference in its entirety. FIELD The present disclosure relates generally to foldable substrates and methods of making and, more particularly, to foldable substrates comprising portions and methods of making foldable substrates. BACKGROUND Glass-based substrates are commonly used, for example, in display devices, for example, liquid crystal displays (LCDs), electrophoretic displays (EPD), organic light emitting diode displays (OLEDs), plasma display panels (PDPs), or the like. There is a desire to develop foldable versions of displays as well as foldable protective covers to mount on foldable displays. Foldable displays and covers should have good impact and puncture resistance. At the same time, foldable displays and covers should have small minimum bend radii (e.g., about 10 millimeters (mm) or less). However, plastic displays and covers with small minimum bend radii tend to have poor impact and/or puncture resistance. Furthermore, conventional wisdom suggests that ultra-thin glass-based sheets (e.g., about 75 micrometers (μm or microns) or less thick) with small minimum bend radii tend to have poor impact and/or puncture resistance. Furthermore, thicker glass-based sheets (e.g., greater than 125 micrometers) with good impact and/or puncture resistance tend to have relatively large minimum bend radii (e.g., about 30 millimeters or more). Consequently, there is a need to develop foldable apparatus that have low minimum bend radii and good impact and puncture resistance. SUMMARY There are set forth herein foldable apparatus comprising foldable substrates, foldable substrates, and methods of making foldable apparatus and foldable substrates comprising foldable substrates that comprise a first portion and a second portion. The portions can comprise glass-based and/or ceramic-based portions, which can provide good dimensional stability, reduced incidence of mechanical instabilities, good impact resistance, and/or good puncture resistance. The first portion and/or the second portion can comprise glass-based and/or ceramic-based portions comprising one or more compressive stress regions, which can further provide increased impact resistance and/or increased puncture resistance. By providing a substrate comprising a glass-based and/or ceramic-based substrate, the substrate can also provide increased impact resistance and/or puncture resistance while simultaneously facilitating good folding performance. In some embodiments, the substrate thickness can be sufficiently large (e.g., from about 80 micrometers (microns or μm) to about 2 millimeters) to further enhance impact resistance and puncture resistance. Providing foldable substrates comprising a central portion comprising a central thickness that is less than a substrate thickness (e.g., first thickness of the first portion and/or second thickness of the second portion) can enable small effective minimum bend radii (e.g., about 10 millimeters or less) based on the reduced thickness in the central portion. In some embodiments, the foldable apparatus and/or foldable substrates can comprise a plurality of recesses, for example, a first central surface area recessed from a first major surface by a first distance and a second central surface area recessed from a second major surface by a second distance. Providing a first recess opposite a second recess can provide the central thickness that is less than a substrate thickness. Further, providing a first recess opposite a second recess can reduce a maximum bend-induced strain of the foldable apparatus, for example, between a central portion and a first portion and/or second portion since the central portion comprising the central thickness can be closer to a neutral axis of the foldable apparatus and/or foldable substrates than if only single recess was provided. Additionally, providing the first distance substantially equal to the second distance can reduce the incidence of mechanical instabilities in the central portion, for example, because the foldable substrate is symmetric about a plane comprising a midpoint in the substrate thickness and the central thickness. Moreover, providing a first recess opposite a second recess can reduce a bend-induced strain of a material positioned in the first recess and/or second recess compared to a single recess with a surface recessed by the sum of the first distance and the second distance. Providing a reduced bend-induced strain of a material positioned in the first recess and/or the second recess can enable the use of a wider range of materials because of the reduced strain requirements for the material. For example, stiffer and/or more rigid materials can be positioned in the first recess, which can improve impact resistance, puncture resistan