TW202208302A - Foldable substrates and methods of making - Google Patents

Abstract

In some embodiments, 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. In further embodiments, the core layer comprising 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. In some embodiments, foldable substrates comprise a first portion comprising a first depth of compression, a first depth of layer, and a first average concentration. In further embodiments, the central portion comprises a first central depth of compression, a first central depth of layer, and a central average concentration. Methods comprise chemically strengthening a foldable substrate. In some embodiments, methods comprise etching the foldable substrate and then further chemically strengthening the foldable substrate.

Description

Foldable substrate and method of making the same

The present disclosure generally relates to foldable substrates and methods of making them, and more particularly, to foldable substrates comprising multiple parts and methods of making foldable substrates.

Glass-based substrates are commonly used, for example, in display devices such as liquid crystal displays (LCDs), electrophoretic displays (EPDs), organic light emitting diode displays (OLEDs), Plasma display panel (PDP) or the like.

There is a need to develop foldable versions of displays, as well as foldable protective covers for mounting on foldable displays. Foldable displays and covers should have good impact resistance and puncture resistance. At the same time, the foldable display and cover should have a small minimum bend radius (eg, 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 flakes with small minimum bend radii (eg, about 75 micrometers (µm or micron) thick) or less tend to have poor impact resistance and/or puncture resistance. Furthermore, thicker glass-based flakes (eg, greater than 125 microns) that have good impact and/or puncture resistance tend to have relatively large minimum bend radii (eg, about 30 microns or greater). Therefore, there is a need to develop foldable devices with a low minimum bend radius and good impact and puncture resistance.

Described herein are foldable devices including foldable substrates, foldable substrates, and methods of making foldable devices and foldable substrates, the foldable substrates including a foldable substrate including a first portion and a second portion. Such portions may include glass-based portions and/or ceramic-based portions, which may provide good dimensional stability, reduced occurrence of mechanical instability, good impact resistance, and/or good puncture resistance. The first portion and/or the second portion may comprise a glass-based portion and/or a ceramic-based portion comprising one or more regions of compressive stress, which may further provide increased impact resistance and/or increased Puncture resistance. By providing a substrate comprising a glass-based substrate and/or a ceramic-based substrate, the substrate may also provide increased impact resistance and/or puncture resistance while contributing to good folding performance. In some embodiments, the substrate thickness may be sufficiently large (eg, from about 80 micrometers (microns or μm) to about 2 millimeters) to further enhance impact and puncture resistance. Providing a foldable substrate comprising a central portion comprising a central thickness less than a substrate thickness (eg, the first thickness of the first portion and/or the second thickness of the second portion) can be based on a reduction in the central portion. The thickness enables a small effective minimum bend radius (eg, about 10 mm or less).

In some embodiments, the foldable device and/or foldable substrate may include a plurality of recesses, eg, a first central surface area recessed a first distance from a first major surface and from a second major surface A second central surface area is recessed a second distance. Providing a first recess opposite a second recess can provide a center thickness less than a substrate thickness. Additionally, providing a first recess opposite a second recess may reduce a maximum bending-induced strain of the foldable device, eg, between the central portion and the first and/or second portion, which is Since the central portion including the central thickness can be closer to a neutral axis of the foldable device and/or foldable substrate than if only a single recess were provided. Additionally, providing the first distance substantially equal to the second distance may reduce the occurrence of mechanical instabilities in the central portion, eg, because the foldable substrate is symmetric about a plane including a midpoint of the substrate thickness and the central thickness. Furthermore, providing a first recess opposite a second recess may reduce positioning at the first recess compared to a single recess having a surface recessed by the sum of the first and second distances Bending induced strain in the seat and/or the material in the second recess. Providing a reduced bending induced strain of the material positioned in the first pocket and/or the second pocket enables use of a wider range of materials due to reduced strain requirements on the material. For example, a harder and/or more rigid material may be positioned in the first recess, which may improve impact resistance, puncture resistance, abrasion resistance, and/or scratch resistance of the foldable device. Additionally, controlling the properties of the first material positioned in the first pocket and the second material positioned in the second pocket can control the position of the neutral axis of the foldable device and/or foldable substrate, which can reduce ( For example, reduce, eliminate) the occurrence of mechanical instability, equipment fatigue and/or equipment failure.

In some embodiments, the foldable device and/or foldable substrate may include a first transition portion attaching the central portion to a first portion and/or a second transition portion attaching the central portion to a second portion. Providing a transition region with a continuously increasing thickness can reduce stress concentrations in the transition region and/or avoid optical distortion. Providing transition regions of sufficient length (eg, about 1 mm or more) can avoid optical distortions that could otherwise arise from sudden, stepped changes in the thickness of the foldable substrate. Providing transition regions of sufficiently small length (eg, about 5 mm or less) can reduce the amount of foldable devices and/or foldable substrates having intermediate thicknesses that can have reduced Small impact resistance and/or reduced puncture resistance. Additionally, providing the first transition region and/or the second transition region with regions of tensile stress may counteract the strain between the first or second portion and the first and/or second transition portion during folding, the tension The stress region contains a maximum tensile stress greater than the maximum tensile stress of the central tensile stress region of the central portion. Additionally, providing the first transition region and/or the second transition region with a region of tensile stress can counteract the strain between the central portion and the first and/or second transition portion during folding, the region of tensile stress comprising greater than The maximum tensile stress of the maximum tensile stress of the first tensile stress region of the first portion and/or the second tensile stress region of the second portion.

The devices and methods of embodiments of the present disclosure can be achieved by controlling (eg, limiting, reducing, equalizing) the difference between the expansion of different portions of the foldable device and/or foldable substrate as a result of chemical strengthening, to reduce (eg, mitigate, eliminate) the occurrence of mechanical instability, equipment fatigue and/or equipment failure. Controlling the difference between the expansions of the different parts can reduce chemical strengthening induced strains between parts of the foldable device and/or foldable substrate, which can help to achieve critical buckling at the foldable device and/or foldable substrate Greater folding induces strain prior to strain (eg, the onset of mechanical instability). Additionally, reducing mechanical instabilities and/or the difference between the core layer and the first outer layer and/or the first outer layer or the difference between the central portion and the first portion and/or the second portion may reduce optical distortion, eg, Caused by the (etc.) difference in strain within the foldable device and/or the foldable substrate.

In some embodiments, providing a foldable device and/or foldable substrate comprising a laminate may enable control of the differential expansion between the first portion, the second portion, and the center portion in a single chemical strengthening process. For example, the properties of the core layer relative to the first outer layer and/or the second outer layer may enable substantially uniform expansion of the foldable device and/or foldable substrate. In some embodiments, the density of the core layer may be greater than the density of the first outer layer and/or the second outer layer. In some embodiments, the thermal expansion coefficient of the core layer may be greater than the thermal expansion coefficient of the first outer layer and/or the second outer layer. In some embodiments, the network expansion coefficient of the core layer may be smaller than the network expansion coefficient of the first outer layer and/or the second outer layer. Additionally, providing a core layer in relationship to the first outer layer and/or the second outer layer may reduce (eg, minimize) the force of folding the foldable device and/or the foldable substrate.

As a result of chemical strengthening, providing one or more compounds comprising a concentration of one or more alkali metals near (eg, within 100 ppm, 10 ppm on an oxide basis) of the central portion compared to the central portion A first portion and/or a second portion of the average concentration of alkali metal can minimize the differential expansion of the first portion and/or the second portion. Substantially uniform expansion reduces the occurrence of mechanical deformation and/or mechanical instability as a result of chemical strengthening.

As a result of chemical strengthening, providing a corresponding ratio of depth of layer to the first and/or second portion near (eg, within 0.5%, within 0.1%, within 0.01%) of the center portion compared to the center portion A ratio of thicknesses may minimize the difference in near-surface expansion of the first portion and/or the second portion. Minimizing the difference in near-surface expansion can reduce stress and/or strain in one of the planes of the first major surface, the second major surface, the first central surface region, and/or the second central surface region, which can further reduce as a chemical The occurrence of mechanical deformation and/or mechanical instability as a result of strengthening.

Providing a ratio of the depth of compression to the thickness of the first portion and/or the second portion near (eg, within 1%, within 0.5%, within 0.1%) of the corresponding ratio of the central portion can minimize the first portion and/or The difference between the chemical strengthening induced strain of the second part relative to the central part. Minimizing the difference in chemical strengthening induced strain can reduce the occurrence of mechanical deformation and/or mechanical instability as a result of chemical strengthening.

Minimizing stress and/or strain in the first major surface, the second major surface, the first central surface region, and/or the second central surface region can reduce stress-induced optical distortion. Again, minimizing these stresses may increase puncture resistance and/or impact resistance. Also, minimizing these stresses can be associated with low optical retardation differences (eg, about 2 nanometers or less) along a centerline. Additionally, minimizing these stresses may reduce the occurrence of mechanical deformation and/or mechanical instability as a result of chemical strengthening.

The methods of the present disclosure may enable the fabrication of foldable substrates that include one or more of the above-mentioned benefits. In some embodiments, the methods of the present disclosure can achieve the above-mentioned benefits in a single chemical strengthening step, eg, fabricating a foldable substrate comprising a laminate, which can reduce the labor associated with producing the foldable substrate Time, equipment, space and labor costs. In some embodiments, existing recesses may be provided or formed prior to any chemical strengthening of the foldable substrate (eg, existing first central surface region recessed from the first major surface, existing second two central surface areas), which may provide the above benefits for foldable devices with deeper pockets (eg, greater first distance, greater second distance) than pockets that could otherwise be achieved. In some embodiments, the above benefits may be provided by chemically strengthening the foldable substrate, etching a central portion of the foldable substrate (eg, etching an existing first central surface region to form a new first central surface region) , etching an existing second central surface region to form a new second central surface region), and then further chemically strengthening the foldable substrate. In further embodiments, the above benefits may be provided by controlling a time period of the chemical strengthening relative to a second time period of the further chemical strengthening and/or a thickness etched from the central portion. Providing the further chemical strengthening of the foldable substrate can achieve greater compressive stress without encountering mechanical deformation and/or mechanical instability, and the greater compressive stress can further increase the impact resistance of the foldable substrate and/or Puncture resistance.

Some example embodiments of the present disclosure are described below, with the understanding that any of the features of the various embodiments may be used alone or in combination with each other.

Embodiment 1. A foldable substrate comprising 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 microns to about 2 millimeters. The foldable substrate includes a first outer layer including the first main surface and a first inner surface opposite the first main surface. A first outer thickness is defined between the first major surface and the first inner surface. The first outer layer includes a first portion and a second portion separated by a first minimum distance. The first portion includes the first main surface and the first inner surface. The second portion includes the first main surface and the first inner surface. The foldable substrate includes a second outer layer including the second main surface and a second inner surface opposite the second main surface. The second outer layer includes a second outer thickness defined between the second major surface and the second inner surface. The second outer layer includes a third portion and a fourth portion separated by a second minimum distance. The third portion includes the second main surface and the second inner surface. The fourth portion includes the second main surface and the second inner surface. The foldable substrate includes a core layer including a third inner surface and a fourth inner surface opposite the third inner surface. A central thickness is defined between the third inner surface and the fourth inner surface. The center thickness is in a range from about 25 microns to about 80 microns. The core layer is positioned between the first outer layer and the second outer layer. The third inner surface contacts the first inner surface of the first portion and the first inner surface of the second portion. A first central surface region is positioned between the first portion of the first outer layer and the second portion of the first outer layer. The fourth inner surface contacts the second inner surface of the third portion and the second inner surface of the fourth portion. A second central surface region is positioned between the third portion of the second outer layer and the fourth portion of the second outer layer. The first central surface region is recessed a first distance from the first major surface. The second central surface region is recessed a second distance from the second major surface.

Embodiment 2. The foldable substrate of Embodiment 1, wherein the core layer comprises a core thermal expansion coefficient greater than a first thermal expansion coefficient of the first outer layer. The core thermal expansion coefficient is greater than a second thermal expansion coefficient of the second outer layer.

Embodiment 3. The foldable substrate of Embodiment 2, wherein the first coefficient of thermal expansion is substantially equal to the second coefficient of thermal expansion.

Embodiment 4. The foldable substrate of any one of embodiments 2 to 3, wherein the core thermal expansion coefficient is greater than the first thermal expansion coefficient from about 10×10 ⁻⁷ °C ⁻¹ to about 70 × 10 ⁻⁷ °C ^-1 .

Embodiment 5. The foldable substrate of any one of Embodiments 1-4, wherein a core density of the core layer is greater than a first density of the first outer layer. The core density is greater than a second density of the second outer layer.

Embodiment 6. The foldable substrate of Embodiment 5, wherein the core density is greater than the first density by from about 0.01 grams per cubic centimeter to about 0.05 grams per cubic centimeter (g/cm ³ ).

Embodiment 7. The foldable substrate of any one of Embodiments 5-6, wherein the first density is substantially equal to the second density.

Embodiment 8. The foldable substrate of any one of Embodiments 1 to 7, wherein a core network expansion coefficient of the core layer is smaller than a first network expansion coefficient of the first outer layer. The core network expansion factor is smaller than a second network expansion factor of the second outer layer.

Embodiment 9. The foldable substrate of Embodiment 8, wherein the first network expansion coefficient is substantially equal to the second network expansion coefficient.

Embodiment 10. The foldable substrate of any one of Embodiments 1-9, wherein the first minimum distance is in a range from about 5 millimeters to about 50 millimeters.

Embodiment 11. The foldable substrate of any one of Embodiments 1-10, wherein the first minimum distance is substantially equal to the second minimum distance.

Embodiment 12. The foldable substrate of any one of Embodiments 1-11, wherein the first outer thickness is substantially equal to the second outer thickness.

Embodiment 13. The foldable substrate of any one of Embodiments 1-12, wherein the substrate thickness is in a range from about 125 microns to about 200 microns.

Embodiment 14. The foldable substrate of any one of Embodiments 1-13, wherein the center thickness is in a range from about 25 microns to about 60 microns.

Embodiment 15. The foldable substrate of any one of Embodiments 1-14, wherein the first outer layer comprises a glass-based substrate.

Embodiment 16. The foldable substrate of any one of Embodiments 1-14, wherein the first outer layer comprises a ceramic-based substrate.

Embodiment 17. The foldable substrate of any one of Embodiments 1-16, wherein the core layer comprises a glass-based substrate.

Embodiment 18. The foldable substrate of any one of Embodiments 1-16, wherein the core layer comprises a ceramic-based substrate.

Embodiment 19. The foldable substrate of any one of Embodiments 1-17, further comprising a coating disposed on the first major surface and filling the region defined by the first central surface and formed by The first major surface defines a recess between a first plane.

Embodiment 20. The foldable substrate of any one of embodiments 1-19, wherein the first outer layer comprises a first oxide-based average potassium concentration and the second outer layer comprises an oxide-based and a central portion of the core layer positioned between the first central surface region and the second central surface region comprises a central average potassium concentration on an oxide basis. An absolute difference between the first average potassium concentration and the central average potassium concentration is about 100 parts per million or less.

Embodiment 21. The foldable substrate of Embodiment 20, wherein an absolute difference between the second average potassium concentration and the central average potassium concentration is about 100 parts per million or less.

Embodiment 22. The foldable substrate of any one of Embodiments 1-21, further comprising a first region of compressive stress extending from the first portion of the first outer layer at the first major surface to a The first compression depth. The foldable substrate includes a second region of compressive stress extending from the third portion of the second outer layer at the second major surface to a second depth of compression. The foldable substrate includes a third region of compressive stress extending from the second portion of the first outer layer at the first major surface to a third depth of compression. The foldable substrate includes a fourth region of compressive stress extending from the fourth portion of the second outer layer at the second major surface to a fourth depth of compression. The foldable substrate includes a first central compressive stress region extending from the first central surface region to a first central compressive depth. The foldable substrate includes a second central compressive stress region extending to a second central compressive depth extending from the second central surface region.

Embodiment 23. The foldable substrate of Embodiment 22, wherein an absolute difference between the first compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the center thickness is about 1% or less.

Embodiment 24. The foldable substrate of any one of Embodiments 22-23, wherein the third depth of compression as a percentage of the thickness of the substrate and the first depth of compression as a percentage of the center thickness An absolute difference between is about 1% or less.

Embodiment 25. The foldable substrate of any one of Embodiments 22-24, wherein the second depth of compression as a percentage of the thickness of the substrate and the second depth of compression as a percentage of the center thickness An absolute difference between is about 1% or less.

Embodiment 26. The foldable substrate of any one of Embodiments 22-25, wherein the fourth depth of compression as a percentage of the thickness of the substrate and the second depth of compression as a percentage of the center thickness An absolute difference between is about 1% or less.

Embodiment 27. The foldable substrate of any one of Embodiments 22-26, wherein the first portion comprises a first layer depth of one or more alkali metal ions associated with the first compression depth. The third portion includes a second layer depth of one or more alkali metal ions associated with the second compression depth. The second portion includes a third layer depth of one or more alkali metal ions associated with the third compression depth. The fourth portion includes a fourth layer depth of one or more alkali metal ions associated with the fourth compression depth. The central portion includes a first central layer depth of one or more alkali metal ions associated with the first central compression depth. The central portion includes a second central layer depth of one or more alkali metal ions associated with the second central compression depth. An absolute difference between the first layer depth as a percentage of the substrate thickness and a first center layer depth as a percentage of the center thickness is about 0.5% or less.

Embodiment 28. The foldable substrate of Embodiment 27, wherein an absolute difference between the depth of the third layer as a percentage of the substrate thickness and the depth of the first center layer as a percentage of the center thickness is about 0.5% or less.

Embodiment 29. The foldable substrate of any one of Embodiments 27-28, wherein the second layer depth as a percentage of the substrate thickness and the second center layer depth as a percentage of the center thickness An absolute difference between is about 0.5% or less.

Embodiment 30. The foldable substrate of any one of Embodiments 27-29, wherein the fourth layer depth as a percentage of the substrate thickness and the second center layer depth as a percentage of the center thickness An absolute difference between is about 0.5% or less.

Embodiment 31. The foldable substrate of any one of Embodiments 1-30, wherein the second central surface region is recessed a second distance from the second major surface region. The second distance is from about 5% to about 20% of the thickness of the substrate.

Embodiment 32. The foldable substrate of Embodiment 31, wherein the first distance is substantially equal to the second distance.

Embodiment 33. A foldable substrate comprising 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 microns to about 2 millimeters. The foldable substrate includes a first portion comprising a thickness of the substrate. The first portion includes a first region of compressive stress extending from the first major surface to a first compressive depth. The first portion includes a second region of compressive stress extending from the second major surface to a second depth of compression. The first portion includes a first layer depth of one or more alkali metal ions associated with the first compression depth. The first portion includes a second layer depth of one or more alkali metal ions associated with the second compression depth. The foldable substrate includes a second portion comprising the thickness of the substrate. The second portion includes a third region of compressive stress extending from the first major surface to a third depth of compression. The second portion includes a fourth region of compressive stress extending from the second major surface to a fourth depth of compression. The second portion includes a third layer depth of one or more alkali metal ions associated with the third compression depth. The second portion includes a fourth layer depth of one or more alkali metal ions associated with the fourth compression depth. The foldable substrate includes a central portion positioned between the first portion and the second portion. The central portion includes a central thickness defined between a first central surface region and a second central surface region opposite the first central surface region. The central portion includes a first central compressive stress region extending from the first central surface region to a first central compressive depth. The central portion includes a second central compressive stress region extending from the second central surface region to a second central compressive depth. The central portion includes a first central layer depth of one or more alkali metal ions associated with the first central compression depth. The central portion includes a second central layer depth of one of the one or more alkali metal ions associated with the second central compression depth. The center thickness is in a range from about 25 microns to about 80 microns. The first central surface region is recessed a first distance from the first major surface. An absolute difference between the first layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is about 0.5% or less.

Embodiment 34. The foldable substrate of Embodiment 33, wherein an absolute difference between the depth of the third layer as a percentage of the substrate thickness and the depth of the first center layer as a percentage of the center thickness is about 0.5% or less.

Embodiment 35. The foldable substrate of any one of Embodiments 33-34, wherein the second layer depth as a percentage of the substrate thickness and the second center layer depth as a percentage of the center thickness An absolute difference between is about 0.5% or less.

Embodiment 36. The foldable substrate of any one of Embodiments 33-35, wherein the fourth layer depth as a percentage of the substrate thickness and the second center layer depth as a percentage of the center thickness An absolute difference between is about 0.5% or less.

Embodiment 37. The foldable substrate of any one of Embodiments 33-36, wherein the first portion comprises a first average potassium concentration based on oxide and the second portion comprises oxide based A second average potassium concentration, and the central portion contains a central average potassium concentration on an oxide basis. An absolute difference between the first average potassium concentration and the central average potassium concentration is about 100 parts per million or less.

Embodiment 38. A foldable substrate comprising 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 microns to about 2 millimeters. The foldable substrate includes a first portion comprising a thickness of the substrate. The first portion contains a first average potassium concentration on an oxide basis. The first portion includes a first region of compressive stress extending from the first major surface to a first compressive depth. The first portion includes a second region of compressive stress extending from the second major surface to a second depth of compression. The foldable substrate includes a second portion comprising the thickness of the substrate. The second portion contains a second average potassium concentration on an oxide basis. The second portion includes a third region of compressive stress extending from the first major surface to a third depth of compression. The second portion includes a fourth region of compressive stress extending from the second major surface to a fourth depth of compression. The foldable substrate includes a central portion positioned between the first portion and the second portion. The central portion includes a central thickness defined between a first central surface region and a second central surface region opposite the first central surface region. The central portion contains a central average potassium concentration on an oxide basis. The central portion includes a first central compressive stress region extending from the first central surface region to a first central compressive depth. The central portion includes a second central compressive stress region extending from the second central surface region to a second central compressive depth. The center thickness is in a range from about 25 microns to about 80 microns. The first central surface region is recessed a first distance from the first major surface. An absolute difference between the first average potassium concentration and the central average potassium concentration is about 100 parts per million or less.

Embodiment 39. The foldable substrate of any one of embodiments 37-38, wherein an absolute difference between the second average potassium concentration and the central average potassium concentration is about 100 parts per million or less .

Embodiment 40. The foldable substrate of any one of Embodiments 33-39, wherein the first depth of compression as a percentage of the thickness of the substrate and the first depth of compression as a percentage of the center thickness An absolute difference between is about 1% or less.

Embodiment 41. A foldable substrate comprising 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 microns to about 2 millimeters. The foldable substrate includes a first portion comprising a thickness of the substrate. The first portion includes a first region of compressive stress extending from the first major surface to a first compressive depth. The first portion includes a second region of compressive stress extending from the second major surface to a second depth of compression. The foldable substrate includes a second portion comprising the thickness of the substrate. The second portion includes a third region of compressive stress extending from the first major surface to a third depth of compression. The second portion includes a fourth region of compressive stress extending from the second major surface to a fourth depth of compression. The foldable substrate includes a central portion including a central thickness defined between a first central surface region and a second central surface region opposite the first central surface region. The central portion includes a first central compressive stress region extending from the first central surface region to a first central compressive depth. The central portion includes a second central compressive stress region extending from the second central surface region to a second central compressive depth. The center thickness is in a range from about 25 microns to about 80 microns. The first central surface region is recessed a first distance from the first major surface. The central portion is positioned between the first portion and the second portion. An absolute difference between the first compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the center thickness is about 1% or less.

Embodiment 42. The foldable substrate of any one of Embodiments 40-41, wherein the third depth of compression as a percentage of the thickness of the substrate and the first depth of compression as a percentage of the center thickness An absolute difference between is about 1% or less.

Embodiment 43. The foldable substrate of any one of Embodiments 40-42, wherein the second depth of compression as a percentage of the thickness of the substrate and the second depth of compression as a percentage of the center thickness An absolute difference between is about 1% or less.

Embodiment 44. The foldable substrate of any one of Embodiments 40-43, wherein the fourth depth of compression as a percentage of the thickness of the substrate and the second depth of compression as a percentage of the center thickness An absolute difference between is about 1% or less.

Embodiment 45. The foldable substrate of any one of Embodiments 33-44, wherein the substrate thickness is in a range from about 125 microns to about 200 microns.

Embodiment 46. The foldable substrate of any one of Embodiments 33-45, wherein the center thickness is in a range from about 25 microns to about 60 microns.

Embodiment 47. The foldable substrate of any one of Embodiments 33-46, wherein the foldable substrate comprises a glass-based substrate.

Embodiment 48. The foldable substrate of any one of Embodiments 33-46, wherein the foldable substrate comprises a ceramic-based substrate.

Embodiment 49. The foldable substrate of any one of Embodiments 33-48, wherein the second central surface region is recessed a second distance from the second major surface.

Embodiment 50. The foldable substrate of Embodiment 49, wherein the second distance is from about 5% to about 20% of the thickness of the substrate.

Embodiment 51. The foldable substrate of any one of Embodiments 49-50, wherein the first distance is substantially equal to the second distance.

Embodiment 52. The foldable substrate of any one of Embodiments 49-51, wherein the second major surface includes the second central surface region.

Embodiment 53. The foldable substrate of any one of Embodiments 22-52, wherein the first region of compressive stress comprises a first maximum compressive stress of about 700 megapascals or greater. The second region of compressive stress includes a second maximum compressive stress. The third region of compressive stress contains a third maximum compressive stress of about 700 megapascals or greater. The fourth region of compressive stress includes a fourth maximum compressive stress. The first central compressive stress region contains a first central maximum compressive stress of about 700 megapascals or greater. The second central compressive stress region includes a second central maximum compressive stress.

Embodiment 54. The foldable substrate of Embodiment 53, wherein the second maximum compressive stress is about 700 megapascals or greater. The fourth maximum compressive stress is about 700 megapascals or more. The second central maximum compressive stress is about 700 megapascals or more.

Embodiment 55. The foldable substrate of any one of Embodiments 22-53, further comprising a first stretch of a first portion of the first portion positioned between the first region of compressive stress and the second region of compressive stress stress area. The first tensile stress region includes a first maximum tensile stress. The foldable substrate includes 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 includes a second maximum tensile stress. The foldable substrate includes 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 contains 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.

Embodiment 56. The foldable substrate of Embodiment 55, wherein an absolute difference between the central maximum tensile stress and the second maximum tensile stress is about 10 megapascals or less.

Embodiment 57. The foldable substrate of any one of Embodiments 55-56, wherein the first maximum tensile stress is substantially equal to the second maximum tensile stress.

Embodiment 58. The foldable substrate of any one of Embodiments 22-57, wherein the central portion further comprises the center portion positioned between a portion of the first central surface area and a portion of the second central surface area A central tensile stress region in one of the central sections. The central tensile stress region contains a central maximum tensile stress. The central portion includes a first transition portion attaching the first central major surface to the first portion. The first transition portion includes a first transition tensile stress region, and the first transition tensile stress region includes a first transition maximum tensile stress. The central portion includes a second transition portion attaching the first central major surface to the second portion. The second transition portion includes a second transition tensile stress region, the second transition tensile stress region includes a second transition maximum tensile stress. The first transition maximum tensile stress is greater than the central maximum tensile stress.

Embodiment 59. The foldable substrate of Embodiment 58, wherein the second transition maximum tensile stress is greater than the central maximum tensile stress.

Embodiment 60. The foldable substrate of any one of Embodiments 58-59, further comprising a first stretch of a first portion of the first portion positioned between the first region of compressive stress and the second region of compressive stress stress area. The first tensile stress region includes a first maximum tensile stress. The first transition maximum tensile stress is greater than the first maximum tensile stress.

Embodiment 61. The foldable substrate of any one of Embodiments 58-60, further comprising a second tensile force of the second portion positioned between the third region of compressive stress and the fourth region of compressive stress tensile stress region. The foldable substrate includes the second tensile stress region including a second maximum tensile stress. The second transition maximum tensile stress is greater than the second maximum tensile stress.

Embodiment 62. The foldable substrate of any one of Embodiments 1-61, wherein the first distance is from about 20% to about 45% of the thickness of the substrate.

Embodiment 63. The foldable substrate of any one of Embodiments 1-62, wherein the substrate thickness is at least 71 microns greater than about 4 times the center thickness.

Embodiment 64. The foldable substrate of any one of Embodiments 1-63, wherein the substrate achieves an effective bend radius of 5 millimeters.

Embodiment 65. A foldable device comprising the foldable substrate of any one of Embodiments 1-64. The foldable device includes an adhesive including a first contact surface and a second contact surface opposite the first contact surface. At least a portion of the adhesive is positioned in a pocket defined between the second central surface region and a second plane defined by the second major surface.

Embodiment 66. A foldable device comprising the foldable substrate of any one of Embodiments 1-64. The foldable device includes a polymer-based portion positioned in a recess defined between the second central surface region and a second plane defined by the second major surface. The foldable device includes an adhesive including a first contact surface and a second contact surface opposite the first contact surface.

Embodiment 67. The foldable device of Embodiment 66, wherein the polymer-based portion comprises a strain at yield in a range from about 5% to about 10%.

Embodiment 68. The foldable device of any one of Embodiments 66-67, 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.

Embodiment 69. The foldable device of any one of embodiments 65-68, wherein a magnitude of a difference between a refractive index of the substrate and a refractive index of the adhesive is about 0.1 or more Small.

Embodiment 70. The foldable device of any one of Embodiments 65-69, further comprising a display device attached to the second contact surface of the adhesive.

Embodiment 71. A consumer electronic product comprising a housing comprising a front surface, a rear surface and side surfaces. The consumer electronic product includes electrical components at least partially within the housing. The electrical components include a controller, a memory and a display. The display is at or adjacent to the front surface of the housing. The consumer electronic product includes a cover substrate disposed on the display. At least one of a portion of the housing or the cover substrate includes the foldable substrate of any one of Embodiments 1-64.

Embodiment 72. A method of making a foldable substrate comprising a core layer positioned between a first outer layer and a second outer layer and in contact with the first outer layer and the second outer layer. A substrate thickness is defined between a first major surface and a second major surface. The first outer layer defines the first major surface, and the second outer layer defines the second major surface opposite the first major surface. The method includes etching a portion of the first major surface to form a first central surface region of the core layer. The method includes etching a portion of the second major surface to form a second central surface region of the core layer. A central portion includes a central thickness defined between the first central surface region and the second central surface region. The first central surface region of the core layer in the central portion is positioned between a first portion of a first outer layer and a second portion of the first outer layer. The second central surface region of the core layer in the central portion is positioned between a third portion of the second outer layer and a fourth portion of the second outer layer.

Embodiment 73. A method of making a foldable substrate comprising drawing to form a core layer. The method includes drawing to form a first outer layer and a second outer layer. The method includes laminating the first outer layer to a third inner surface of the core layer, and laminating the second outer layer to a fourth inner surface of the core layer. The first outer layer defines a first major surface, and the second outer layer defines a second major surface opposite the first major surface. A substrate thickness is defined between the first major surface and the second major surface. During the lamination, the first outer layer contains a first temperature above a softening point of the first outer layer, the second outer layer contains a second temperature above a softening point of the second outer layer, the core The layer includes a third temperature above a softening point of the core layer. Next, the method includes etching a portion of the first major surface to form a first central surface region of the core layer. The method includes etching a portion of the second major surface to form a second central surface region of the core layer. The foldable substrate includes a central portion that includes a central thickness defined between the first central surface region and the second central surface region. The first central surface region is positioned between a first portion of the first outer layer and a third portion of the first outer layer. The second central surface region is positioned between a second portion of the second outer layer and a fourth portion of the second outer layer.

Embodiment 74. The method of any one of Embodiments 72-73, wherein the first outer layer comprises a first existing average potassium concentration based on the oxide. The core layer contains a core existing average potassium concentration on an oxide basis. The core existing average potassium concentration is about 10 parts per million, or greater than the first existing average potassium concentration.

Embodiment 75. The method of embodiment 74, wherein the second outer layer comprises a second existing average potassium concentration based on the oxide, and the core existing average potassium concentration is about 10 parts per million, or greater than The second existing average potassium concentration.

Embodiment 76. The method of any one of Embodiments 72-75, wherein the first outer layer comprises a first existing average lithium concentration based on oxide and the core layer comprises a The core has an existing average lithium concentration, and the first existing average lithium concentration is about 10 parts per million, or greater than the core existing average lithium concentration.

Embodiment 77. The method of any one of Embodiments 72-76, further comprising chemically strengthening the foldable substrate after the etching the portion of the first major surface and after the etching the portion of the second major surface .

Embodiment 78. A method of making a foldable substrate comprising a core layer positioned between a first outer layer and a second outer layer and in contact with the first outer layer and the second outer layer. A substrate thickness is defined between a first major surface of the first outer layer and a second major surface of the second outer layer. The core layer includes a central portion that includes a central thickness defined between a first central surface region and a second central surface region. The first central surface region of the core layer in the central portion is positioned between a first portion of a first outer layer and a second portion of the first outer layer. The second central surface region of the core layer in the central portion is positioned between a third portion of the second outer layer and a fourth portion of the second outer layer. The method includes chemically strengthening the foldable substrate.

Embodiment 79. The method of any one of Embodiments 77-78, wherein, prior to the chemical strengthening, the first outer layer comprises a first diffusivity of one or more alkali metal ions. The core layer includes a core diffusivity of one or more alkali metal ions, and the first diffusivity is greater than the core diffusivity.

Embodiment 80. The method of Embodiment 79, wherein a first ratio comprises the square root of the first diffusivity divided by the difference defined between the first major surface and a first inner surface of the first outer layer a first thickness. A core ratio comprises the square root of the core diffusivity divided by the center thickness, and an absolute difference between the first ratio and the core ratio is about 0.01 s ^-0.5 or less.

Embodiment 81. The method of Embodiment 80, wherein a second ratio comprises the square root of a second diffusivity of one or more alkali metal ions of the second outer layer divided by the first A second thickness between the two main surfaces and a second inner surface. An absolute difference between the second ratio and the core ratio is about 0.01 s ^{- 0.5} or less.

Embodiment 82. The method of any one of Embodiments 77-81, wherein, after the chemical strengthening, the first outer layer comprises a first average potassium concentration based on the oxide. The second outer layer contains a second average potassium concentration based on the oxide. The central portion positioned between the first central surface region and the second central surface region contains a central average potassium concentration on an oxide basis. An absolute difference between the first average potassium concentration and the central average potassium concentration is about 100 parts per million or less.

Embodiment 83. The method of any one of Embodiments 77-82, wherein the chemical strengthening comprises forming a first region of compressive stress from the first outer layer at the first major surface The first portion extends to a first compression depth. The method includes forming a second region of compressive stress extending from the third portion of the second outer layer at the second major surface to a second depth of compression. The method includes forming a third region of compressive stress extending from the second portion of the first outer layer at the first major surface to a third depth of compression. The method includes forming a fourth region of compressive stress extending from the fourth portion of the second outer layer at the second major surface to a fourth depth of compression. The method includes forming a first central compressive stress region extending from the first central surface region to a first central compressive depth. The method includes forming a second central compressive stress region extending to a second central compressive depth extending from the second central surface region.

Embodiment 84. The method of Embodiment 83, wherein an absolute difference between the first compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the center thickness is about 1% or less.

Embodiment 85. The method of any one of Embodiments 83-84, wherein the third depth of compression as a percentage of the substrate thickness is between the first depth of compression as a percentage of the center thickness An absolute difference of about 1% or less.

Embodiment 86. The method of any one of Embodiments 83-85, wherein the second depth of compression as a percentage of the substrate thickness is between the second depth of compression as a percentage of the center thickness An absolute difference of about 1% or less.

Embodiment 87. The method of any one of Embodiments 83-86, wherein the fourth depth of compression as a percentage of the substrate thickness is between the second depth of compression as a percentage of the center thickness An absolute difference of about 1% or less.

Embodiment 88. The method of any one of Embodiments 83-87, wherein the first portion comprises a first layer depth of one or more alkali metal ions associated with the first compression depth. The third portion includes a second layer depth of one or more alkali metal ions associated with the second compression depth. The second portion includes a third layer depth of one or more alkali metal ions associated with the third compression depth. The fourth portion includes a fourth layer depth of one or more alkali metal ions associated with the fourth compression depth. The central portion includes a first central layer depth of one or more alkali metal ions associated with the first central compression depth. The central portion includes a second central layer depth of one or more alkali metal ions associated with the second central compression depth. An absolute difference between the first layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is about 0.5% or less.

Embodiment 89. The method of Embodiment 88, wherein an absolute difference between the depth of the third layer as a percentage of the substrate thickness and the depth of the first center layer as a percentage of the center thickness is about 0.5% or less.

Embodiment 90. The method of any one of Embodiments 88-89, wherein the second layer depth as a percentage of the substrate thickness is between the second center layer depth as a percentage of the center thickness An absolute difference of about 0.5% or less.

Embodiment 91. The method of any one of Embodiments 88-89, wherein the fourth layer depth as a percentage of the substrate thickness is between the second center layer depth as a percentage of the center thickness An absolute difference of about 0.5% or less.

Embodiment 92. The method of any one of Embodiments 72-91, wherein the core layer comprises a core thermal expansion coefficient that is greater than a first thermal expansion coefficient of the first outer layer. The core thermal expansion coefficient is greater than a second thermal expansion coefficient of the second outer layer.

Embodiment 93. The method of any one of Embodiments 72-92, wherein a core density of the core layer is greater than a first density of the first outer layer. The core density is greater than a second density of the second outer layer.

Embodiment 94. The method of any one of Embodiments 72-93, wherein a core network expansion factor of the core layer is less than a first network expansion factor of the first outer layer. The core network expansion factor is smaller than a second network expansion factor of the second outer layer.

Embodiment 95. A method of making a foldable substrate comprising a substrate thickness defined between a first major surface and a second major surface opposite the first major surface. The method includes chemically strengthening the foldable substrate for a first period of time. Next, the method includes etching a portion of the first major surface to form a first central surface region. The method includes etching a portion of the second major surface to form a second central surface region. The method then further includes further chemically strengthening the foldable substrate for a second period of time. A central portion includes a central thickness defined between the first central surface region and the second central surface region. The central portion is positioned between a first portion and a second portion. The first central surface region is recessed a first distance from the first major surface. The second central surface region is recessed a second distance from the second major surface. After the further chemical strengthening, the foldable substrate includes a first compressive stress region of the first portion extending from the first major surface to a first compressive depth. The foldable substrate includes a second compressive stress region of the third portion extending from the second major surface to a second compressive depth. The foldable substrate includes a third region of compressive stress in the second portion extending from the first major surface to a third depth of compression. The foldable substrate includes a fourth region of compressive stress of the fourth portion extending from the second major surface to a fourth depth of compression. The foldable substrate includes a first central compressive stress region of the central portion extending from the first central surface region to a first central compressive depth. The foldable substrate includes a second central compressive stress region of the central portion extending from the second central surface region to a second central compressive depth.

Embodiment 96. A method of making a foldable substrate comprising a substrate thickness defined between a first major surface and a second major surface opposite the first major surface. The method includes chemically strengthening the foldable substrate for a first period of time. Next, the method includes etching an existing first central surface region to form a first central surface region. The existing first central surface region is not coplanar with the first major surface. The method includes etching an existing second central surface region to form a second central surface region. Next, the method further includes further chemically strengthening the foldable substrate for a second period of time. A central portion includes a central thickness defined between the first central surface region and the second central surface region. The central portion is positioned between a first portion and a second portion. The first central surface region is recessed a first distance from the first major surface. After the further chemical strengthening, the foldable substrate includes a first compressive stress region of the first portion extending from the first major surface to a first compressive depth. The foldable substrate includes a second compressive stress region of the third portion extending from the second major surface to a second compressive depth. The foldable substrate includes a third region of compressive stress in the second portion extending from the first major surface to a third depth of compression. The foldable substrate includes a fourth region of compressive stress of the fourth portion extending from the second major surface to a fourth depth of compression. The foldable substrate includes a first central compressive stress region of the central portion extending from the first central surface region to a first central compressive depth. The foldable substrate includes a second central compressive stress region of the central portion extending from the second central surface region to a second central compressive depth.

Embodiment 97. The method of Embodiment 96, wherein prior to the etching the first central surface region, the existing first central surface region is recessed from the first major surface a first existing distance, the first existing The distance ranges from about 10% to about 75% of the thickness of the substrate.

Embodiment 98. The method of any one of Embodiments 96-97, wherein prior to the etching of the existing second central surface region, the existing second central surface region is substantially coplanar with the second major surface.

Embodiment 99. The method of any one of Embodiments 96-97, wherein prior to the etching the existing second central surface region, the existing second central surface region is recessed from the second major surface by an extent of approximately 1% to about 50% of a second existing distance.

Embodiment 100. The method of any of Embodiments 96-99, wherein the second central surface region is recessed a second distance from the second major surface.

Embodiment 101. The method of any of Embodiments 97-98, wherein prior to the etching the existing second central surface region, the existing second central surface region protrudes from the second major surface.

Embodiment 102. The method of Embodiment 101, wherein after the etching the existing second central surface region, the second central surface region is substantially coplanar with the second major surface.

Embodiment 103. The method of embodiment 95 or embodiment 100, wherein the first distance is substantially equal to the second distance.

Embodiment 104. The method of embodiment 95 or embodiment 100, wherein the second distance is from about 5% to about 20% of the thickness of the substrate.

Embodiment 105. The method of any one of Embodiments 95-104, wherein the first distance is from about 20% to about 45% of the thickness of the substrate.

Embodiment 106. The method of any one of Embodiments 95-105, wherein a square root of a ratio of a ratio of the second time period to the first time period is the difference between the center thickness and the substrate thickness and the center thickness. Divide the difference by 10%.

Embodiment 107. The method of Embodiment 106, wherein the square root of the ratio of the second time period to the first time period is substantially equal to the center thickness divided by the ratio between the substrate thickness and the center thickness Difference.

Embodiment 108. The method of any one of Embodiments 95-107, wherein the second time period is from about 2% to about 50% of the first time period.

Embodiment 109. The method of any one of Embodiments 95-108, wherein, after the chemical strengthening, but before the further chemical strengthening, the first portion comprises a first portion extending to a first intermediate compression depth An intermediate compressive stress region. The first intermediate compression depth is divided by the substrate thickness in a range from about 10% to about 20%.

Embodiment 110. The method of any one of Embodiments 95-108, wherein after the chemical strengthening, but before the further chemical strengthening, the first portion comprises a first intermediate compressive stress region and A first interlayer depth from the first major surface of one or more alkali metal ions introduced during strengthening. The first interlayer depth divided by the substrate thickness is in a range from about 10% to about 20%.

Embodiment 111. The method of any one of Embodiments 95-110, wherein, after the further chemically strengthening the foldable substrate, the first portion is included during the chemical strengthening and/or the further chemical strengthening The first portion of the one or more alkali metal ions is at a first layer depth from the first major surface. The central portion comprises a first central layer depth from the first central surface region of one or more alkali metal ions introduced into the central portion during the further chemical strengthening. An absolute difference between the first layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is about 0.5% or less.

Embodiment 112. The method of Embodiment 111, wherein, after the further chemically strengthening the foldable substrate, the foldable substrate further comprises introducing into the second portion during the chemical strengthening and/or the further chemical strengthening The one or more alkali metal ions are a third depth from the first major surface. An absolute difference between the third layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is about 0.5% or less.

Embodiment 113. The method of any one of Embodiments 111-112, wherein the one or more alkali metal ions comprise potassium ions.

Embodiment 114. The method of any one of Embodiments 95-113, wherein after the further chemically strengthening the foldable substrate, the first portion comprises a first average potassium concentration based on the oxide. The central portion contains a central average potassium concentration on an oxide basis. An absolute difference between the first average potassium concentration and the central average potassium concentration is about 100 parts per million or less.

Embodiment 115. The method of Embodiment 114, wherein after the further chemically strengthening the foldable substrate, the second portion comprises a second average potassium concentration based on the oxide. An absolute difference between the second average potassium concentration and the central average potassium concentration is about 100 parts per million or less.

Embodiment 116. The method of any one of Embodiments 95-115, wherein after the further chemically strengthening the foldable substrate, the first compression depth as a percentage of the substrate thickness and as the center thickness An absolute difference between the first central compression depths of a percentage is about 1% or less.

Embodiment 117. The method of Embodiment 116, wherein after the further chemically strengthening the foldable substrate. An absolute difference between the third compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the center thickness is about 1% or less.

Embodiment 118. The method of any one of Embodiments 95-117, wherein after the chemical strengthening, the foldable substrate further comprises a A first tensile stress region of one of the first portions. The first tensile stress region includes a first maximum tensile stress. The foldable substrate further includes 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 includes a second maximum tensile stress. The foldable substrate further includes 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 contains 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.

Embodiment 119. The method of Embodiment 118, wherein an absolute difference between the central maximum tensile stress and the second maximum tensile stress is about 10 megapascals or less.

Embodiment 120. The method of any of Embodiments 118-119, wherein the first maximum tensile stress is substantially equal to the second maximum tensile stress.

Embodiment 121. The method of any one of Embodiments 95-120, wherein after the chemical strengthening, the central portion further comprises a portion positioned in the first central surface region and a portion of the second central surface region A central tensile stress region between one of the central parts. The central tensile stress region contains a central maximum tensile stress. The central portion includes a first transition portion attaching the first central surface region to the first portion. The first transition portion includes a first transition tensile stress region, and the first transition tensile stress region includes a first transition maximum tensile stress. The central portion includes a second transition portion attaching the first central surface region to the second portion. The second transition portion includes a second transition tensile stress region, the second transition tensile stress region includes a second transition maximum tensile stress. The first transition maximum tensile stress is greater than the central maximum tensile stress.

Embodiment 122. The method of Embodiment 121, wherein the second transition maximum tensile stress is greater than the central maximum tensile stress.

Embodiment 123. The method of any one of Embodiments 121-122, wherein after the chemical strengthening, the foldable substrate further comprises a A first tensile stress region of one of the first portions. The first tensile stress region includes a first maximum tensile stress. The first transition maximum tensile stress is greater than the first maximum tensile stress.

Embodiment 124. The method of any one of Embodiments 121-123, wherein after the chemical strengthening, the foldable substrate further comprises a A second tensile stress region of the second portion. The second tensile stress region includes a second maximum tensile stress. The second transition maximum tensile stress is greater than the second maximum tensile stress.

Embodiment 125. The method of any one of Embodiments 78-124, further comprising disposing a coating on the first major surface, the coating filling defined in the first central surface region and formed by the first The major surface defines a recess between a first plane.

Embodiment 126. The method of any of Embodiments 78-125, further comprising disposing an adhesive on the second major surface of the foldable substrate. The adhesive includes a first contact surface and a second contact surface opposite the first contact surface.

Embodiment 127. The method of Embodiment 126, wherein at least a portion of the adhesive is positioned in a recess defined between the second central surface region and a second plane defined by the second major surface .

Embodiment 128. The method of any one of Embodiments 126-127, wherein a magnitude of a difference between an index of refraction of the substrate and an index of refraction of the adhesive is about 0.1 or less.

Embodiment 129. The method of any of Embodiments 126-128, further comprising attaching a display device to the second contact surface of the adhesive.

Embodiments will now be described more fully hereinafter with reference to the accompanying drawings that illustrate example embodiments. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. However, the claimed scope may encompass many different aspects of various embodiments and should not be construed as limited to the embodiments set forth herein.

FIGS. 1-9 and 11-12 illustrate foldable devices 101 , 301 , 401 , 501 , 601 , 701 including a foldable substrate 206 , 407 or 807 according to embodiments of the present disclosure , 801 and 1201 and/or views of the test foldable device 1102. Unless otherwise indicated, discussions of features of one embodiment of a foldable device are equally applicable to corresponding features of any embodiment of the present disclosure. For example, the same part numbers throughout this disclosure may indicate that, in some embodiments, the identified features are identical to each other, and unless otherwise indicated, a discussion of the identified features of one embodiment is equally applicable to this disclosure Characteristics of identification of any of the other embodiments of the content.

Figures 2-3 and 6 schematically illustrate foldable devices 101 , 301 and 601 including a foldable substrate 206 according to an embodiment of the present disclosure in an unfolded (eg, flat) configuration Example embodiments, and FIG. 11 illustrates an example embodiment of a test foldable device 1102 including a foldable substrate 206 in accordance with an embodiment of the present disclosure included in a folded configuration. The foldable substrate 206 includes a laminate including a core layer 207 positioned between a first outer layer 213 and a second outer layer 215 . Figures 4-5 and 7 schematically illustrate foldable devices 401 , 501 and 701 including a foldable substrate 407 according to an embodiment of the present disclosure in an unfolded (eg, flat) configuration Example embodiments, and FIG. 12 includes a folded foldable device 1201 including a foldable substrate 407 in accordance with an embodiment of the present disclosure in a folded configuration. Figure 8 schematically illustrates a foldable device 801 including a foldable substrate 807 in accordance with an embodiment of the present disclosure in an unfolded (eg, flat) configuration.

The foldable devices 101, 301, 401, 501, 601, 701, 801 and 1201 include a first part 221, 421 or 821, a second part 231, 431 or 831, and are positioned between the first part 221, 421 or 821 and the first part 221, 421 or 821. A central portion 281 , 481 or 881 between the two portions 231 , 431 or 831 . In some embodiments, as shown in FIGS. 2 and 4, foldable device 101 or 401 may include a release liner 271, although other substrates may be used in other embodiments (eg, as discussed throughout this application). glass-based substrates and/or ceramic-based substrates) instead of the release liner 271 shown. In some embodiments, as shown in FIGS. 1-5 and 11-12, foldable devices 101 , 301 , 401 , 501 and 1201 or test foldable device 1102 may include a coating 251 . In some embodiments, as shown in FIGS. 1-5 and 12, foldable devices 101 , 301 , 401 , 501 , and 1201 may include an adhesive layer 261 . In some embodiments, as shown in Figures 2, 5, and 12, foldable devices 101, 501, and 1201 may include a polymer-based portion 241. In some embodiments, as shown in FIGS. 1-12 , the foldable substrates 206 , 407 and 807 may include a first recess 234 , 434 or 834 . In other embodiments, as shown in FIGS. 1-7 and 10-12, the foldable substrate 206 or 407 may further include a second recess 244 or 444 . It should be understood that any of the foldable devices of the present disclosure may include a second substrate (eg, a glass-based substrate and/or a ceramic-based substrate), a release liner 271, a display device 307, A coating 251 , an adhesion layer 261 and/or a polymer-based portion 241 .

Throughout this disclosure, referring to Figure 1, the width 103 of the foldable device 101, 301, 401, 501, 601, 701, and/or 801 is considered to be foldable in one direction 104 of the folding axis 102 of the foldable device The dimensions of the foldable device taken between opposing edges of the device, where direction 104 also includes the direction of width 103 . Furthermore, throughout this disclosure, the length 105 of the foldable devices 101, 301, 401, 501, 601, 701 and/or 801 is considered to be perpendicular to the foldable devices 101, 301, 401, 501, 601, 701 and/or or 801 in one direction 106 of the folding axis 102 of the foldable device 101, 301, 401, 501, 601, 701 and/or 801 taken between the opposing edges of the foldable device 101, 301, 401, 501, 601, 701 and/or 801 dimensions. In some embodiments, as shown in FIGS. 1-5, the foldable device of any embodiment of the present disclosure may include a folding plane 109 including a folding axis 102, and when the foldable device is in a flat configuration (for example, see FIG. 1 ), it includes one direction of the substrate thickness 211 , 411 or 811 . In some embodiments, the plane 109 may include a central axis 107 of the foldable device. In some embodiments, the foldable device is foldable in direction 111 (eg, see FIG. 1 ) about a folding axis 102 extending in direction 104 of width 103 to form a folded configuration (eg, see FIG. 9 ) and Figures 11 to 12). As shown, the foldable device can include a single folding axis to allow the foldable device to contain a bifold, wherein, for example, the foldable device can be folded in half. In further embodiments, the foldable device may include two or more folding axes, wherein each folding axis includes a corresponding central portion similar or identical to central portion 281 , 481 or 881 discussed herein. For example, providing two folding axes may allow the foldable device to include a trifold, wherein, for example, the foldable device can be folded, wherein the first portion 221, 421 or 821, the second portion 231, 431 or 831 and the third a portion similar to a first portion having a central portion 281, 481 or 881 and another central portion (similar or identical to the central portion positioned between the first and second portions and between the second and third portions, respectively) or the second part.

The foldable device 101 , 301 or 601 that includes the foldable device 206 may include a core layer 207 positioned between the first outer layer 213 and the second outer layer 215 . The foldable device 401 , 501 , 701 or 801 may include a foldable substrate 407 or 807 . In some embodiments, the foldable substrate 407 or 807, the first outer layer 213, the second outer layer 215, and/or the core layer 207 may comprise a glass-based glass having a pencil hardness of 8H or greater (eg, 9H or greater) substrate and/or a ceramic-based substrate.

In some embodiments, the foldable substrate 407 or 807, the first outer layer 213, the second outer layer 215, and/or the core layer 207 may comprise a glass-based substrate. As used herein, "glass-based" includes glasses and glass-ceramics, wherein the glass-ceramic has one or more crystalline phases and an amorphous residual glass phase. A glass-based material (eg, a glass-based substrate) can include an amorphous material (eg, glass), and optionally, one or more crystalline materials (eg, ceramic). Amorphous materials and glass-based materials can be strengthened. As used herein, the term "strengthened" may refer to a material that has been chemically strengthened, eg, by ion-exchange of larger ions for smaller ions in the surface of the substrate, as discussed below. However, other strengthening methods, such as thermal tempering, or utilizing mismatches in thermal expansion coefficients between portions of the substrate to create compressive stress and a central tensile region, can be utilized to form the strengthened substrate. Exemplary glass-based materials that may be without or with lithium oxide include soda lime glass, alkali aluminosilicate glass, alkali borosilicate glass, alkali aluminoborosilicate glass, alkali phosphosilicate glass, and Alkali-aluminophosphosilicate glass. In one or more embodiments, on a molar percent (mol%) basis, the glass-based material may comprise: _SiO2 in a range from about 40 mol% to about 80%, in a range from about 5 mol% Al ₂ O ₃ in a range from about 0 mol % to about 30 mol %, B ₂ O ₃ in a range from about 0 mol % to about 10 mol %, in a range from about 0 mol % to about 10 mol % ZrO ₂ in a range from about 5 mol %, P ₂ O ₅ in a range from about 0 mol % to about 15 mol %, in a range from about 0 mol % to about 2 mol % _TiO2 in a range, R2O in a range from about 0 mol% to about 20 mol%, and RO in a range from about ₀ mol% to about 15 mol%. As used herein, R ₂ O may refer to alkali metal oxides, eg, Li ₂ O, Na ₂ O, K ₂ O, Rb ₂ O, and Cs ₂ O. As used herein, RO may refer to MgO, CaO, SrO, BaO, and ZnO. In some embodiments, the glass-based substrate may optionally further comprise each of the following in a range from about 0 mol% to about 2 mol%: _Na2SO4 , NaCl, _NaF , NaBr, K ₂ SO ₄ , KCl, KF, KBr, As ₂ O ₃ , Sb ₂ O ₃ , SnO ₂ , Fe ₂ O ₃ , MnO, MnO ₂ , MnO ₃ , Mn ₂ O ₃ , Mn ₃ O ₄ , Mn ₂ O ₇ . "Glass-ceramic" includes materials produced by controlled crystallization of glass. In some embodiments, the glass-ceramic has about 1% to about 99% crystallinity. Examples of suitable glass-ceramics may include _Li2O - _Al2O3 - _SiO2 system (ie, LAS system) glass-ceramic, MgO _{- Al2O3 - SiO2} system (ie, MAS system) glass-ceramic, ZnO x Al ₂ O ₃ x nSiO ₂ (ie, ZAS systems) and/or glass-ceramics including a predominant crystalline phase (including β-quartz solid solution, β-spodumene, cordierite, hectorite, and/or bismuth) Lithium Silicate). These glass-ceramic substrates can be strengthened using chemical strengthening processes. In one or more embodiments, the MAS system glass-ceramic substrate can be strengthened in a _Li2SO4 molten salt, whereby the exchange of 2Li ₊ for ^{Mg2 +} can occur.

In some embodiments, the foldable substrate 407 or 807, the first outer layer 213, the second outer layer 215, and/or the core layer 207 may comprise a ceramic-based substrate. As used herein, "ceramic-based" includes ceramics and glass-ceramics, wherein the glass-ceramic has one or more crystalline phases and an amorphous residual glass phase. Ceramic-based materials can be strengthened (eg, chemically strengthened). In some embodiments, the ceramic-based material may be formed by heating the glass-based material to form a ceramic (eg, crystalline) portion. In further embodiments, the ceramic-based material can include one or more nucleating agents that can aid in the formation of a crystalline phase. In some embodiments, the ceramic-based material may include one or more oxides, nitrides, oxynitrides, carbides, borides, and/or silicides. Illustrative examples of ceramic oxides include zirconia (ZrO ₂ ), zirconia zirconium silicate (ZrSiO ₄ ), alkali metal oxides (eg, sodium oxide (Na ₂ O)), alkaline earth metal oxides (eg, oxide magnesium (MgO)), titanium oxide (TiO ₂ ), hafnium oxide (Hf ₂ O), yttrium oxide (Y ₂ O ₃ ), iron oxide, beryllium oxide, vanadium oxide (VO ₂ ), fused silica, mullite (ore containing a combination of alumina and silica) and spinel (MgAl ₂ O ₄ ). Exemplary embodiments of ceramic nitrides include silicon nitride (Si ₃ N ₄ ), aluminum nitride (AlN), gallium nitride (GaN), beryllium nitride (Be ₃ N ₂ ), boron nitride (BN), Tungsten nitride (WN), vanadium nitride, alkaline earth metal nitrides (eg, magnesium _nitride ( _Mg3N2 )), nickel nitride, and tantalum nitride. Exemplary embodiments of oxynitride ceramics include silicon oxynitride, aluminum oxynitride, and SiAlON (a combination of aluminum oxide and silicon oxynitride, and can have, for example, Si12 _{-mn Alm +} nOnN16 _{-n , Si6 -n} Al _n On N _8-n or the chemical formula of Si _2-n Al _n O _{1+n N 2-n} , where m, n and the resulting subscripts are all non-negative integers). Exemplary embodiments of carbides and carbon-containing ceramics include silicon carbide (SiC), tungsten carbide (WC), iron carbide, boron carbide (B4C), alkali metal carbides (eg, lithium carbide _{( Li4C3 )} ), alkaline earth metal carbides (eg, magnesium carbide (Mg ₂ C ₃ )), and graphite. Exemplary examples of borides include chromium boride (CrB ₂ ), molybdenum boride (Mo ₂ B ₅ ), tungsten boride (W ₂ B ₅ ), iron boride, titanium boride, zirconium boride (ZrB _{2 )} ), hafnium boride (HfB ₂ ), vanadium boride (VB ₂ ), niobium boride (NbB ₂ ) and lanthanum boride (LaB ₆ ). Example embodiments of silicides include molybdenum disilicide (MoSi2), tungsten disilicide ( _WSi2 ), titanium disilicide ( _{TiSi2 )} , nickel silicide (NiSi), alkaline earth silicides (eg, sodium silicide (NaSi)), Alkali metal silicides (eg, magnesium silicide (Mg ₂ Si)), hafnium disilicide (HfSi ₂ ), and platinum silicide (PtSi).

Throughout this disclosure, polymeric materials (eg, adhesion properties) were determined using ASTM D638 using a tensile testing machine (eg, Instron 3400 or Instron 6800) with Type I dogbone specimens at 23°C and 50% relative humidity of the polymer-based portion), ultimate elongation (eg, strain at failure), and yield point. Throughout this disclosure, ISO 527-1:2019 is used to measure elastic modulus (eg, Young's modulus) and/or Poisson's ratio. In some embodiments, foldable substrate 206, 407 or 807, first outer layer 213, second outer layer 215, and/or core layer 207 may comprise about 1 gigapascal (GPa) or more, about 3 GPa or more, One of elastic modulus of about 5 GPa or more, about 10 GPa or more, about 100 GPa or less, about 80 GPa or less, about 60 GPa or less, or about 20 GPa or less. In some embodiments, the foldable substrate 206, 407, or 807 can be comprised in from about 1 GPa to about 100 GPa, from about 1 GPa to about 80 GPa, from about 3 GPa to about 80 GPa, from about 3 GPa to about An elastic modulus in a range of 60 GPa, from about 5 GPa to about 60 GPa, from about 5 GPa to about 20 GPa, from about 10 GPa to about 20 GPa, or in any range or sub-range therebetween. In further embodiments, the foldable substrate 206, 407 or 807, the first outer layer 213, the second outer layer 215, and/or the core layer 207 may comprise a glass-based portion or a ceramic-based portion that is included in a self-contained 10 GPa to about 100 GPa, from about 40 GPa to about 100 GPa, from about 60 GPa to about 100 GPa, from about 60 GPa to about 80 GPa, from about 80 GPa to about 100 GPa, or any range therebetween A modulus of elasticity in a range or subrange.

In some embodiments, the foldable substrate 206, 407, or 807, the first outer layer 213, the second outer layer 215, and/or the core layer 207 may be optically transparent. As used herein, "optically clear" or "optically clear" means an average transmittance of 70% or greater in the wavelength range of 400 nm to 700 nm through a 1.0 mm thick piece of material. In some embodiments, an "optically clear material" or "optically clear material" may have 75% or more, 80% or more in the wavelength range of 400 nm to 700 nm when passing through a 1.0 mm thick piece of material One of greater, 85% or greater, or 90% or greater, 92% or greater, 94% or greater, 96% or greater average transmittance. The average transmittance in wavelengths from 400 nm to 700 nm is calculated by measuring the transmittance from all wavelengths from about 400 nm to about 700 nm and averaging the measurements.

As shown in FIGS. 2-3 , 6 and 11 , foldable devices 101 , 301 and 601 and test foldable device 1102 include foldable substrate 206 . The foldable substrate includes a first main surface 203 and a second main surface 205 opposite to the first main surface 203 . As shown in FIGS. 2-3 and 6, the first major surface 203 may extend along the first plane 204a. The second major surface 205 may extend along a second plane 204b. In some embodiments, as shown, the second plane 204b may be parallel to the first plane 204a. As used herein, substrate thickness 211 may be defined between first major surface 203 and second major surface 205 as the distance between first plane 204a and second plane 204b.

As shown in FIGS. 2-3 , 6 , and 11 , the foldable substrate 206 may include a first outer layer 213 . As shown, the first outer layer 213 can include the first major surface 203 and a first inner surface 214 opposite the first major surface 203 . In some embodiments, the first inner surface 214 may extend along the third plane 204c when the foldable device 101, 301 and/or 601 is in a flat configuration. As used herein, the first outer thickness 217 of the first outer layer 213 may be defined between the first major surface 203 and the first inner surface 214 as the distance between the first plane 204a and the third plane 204c. In some embodiments, the substrate thickness 211 may be about 10 micrometers (μm) or greater, about 25 μm or greater, about 40 μm or greater, about 60 μm or greater, about 80 μm or greater, about 100 μm or more, about 125 μm or more, about 150 μm or more, about 2 millimeters (mm) or less, about 1 mm or less, about 800 μm or less, about 500 μm or less , about 300 μm or less, about 200 μm or less, about 180 μm or less, or about 160 μm or less. In some embodiments, the substrate thickness 211 may be from about 10 μm to about 2 mm, from about 25 μm to about 2 mm, from about 40 μm to about 2 mm, from about 60 μm to about 2 mm, from about 80 μm to about 2 mm μm to about 2 mm, from about 100 μm to about 2 mm, from about 100 μm to about 1 mm, from about 100 μm to about 800 μm, from about 100 μm to about 500 μm, from about 125 μm to about 500 μm , from about 125 μm to about 300 μm, from about 125 μm to about 200 μm, from about 150 μm to about 200 μm, from about 150 μm to about 160 μm, or in any range or sub-range therebetween.

The first outer layer 213 will now be described with reference to the foldable device 101 of FIG. 2, with the understanding that unless otherwise stated, this description of the first outer layer 213 may also apply to any embodiment of the present disclosure, for example, in FIG. 3 Foldable device 301 and/or 601 , test foldable device 1102 and/or foldable substrate 206 illustrated in FIGS. 6 and 11 . As shown in Figure 2, the first outer layer 213 may include a first portion 213a and a second portion 213b. A first minimum distance 210 may be defined between the first portion 213a of the first outer layer 213 and the second portion 213b of the first outer layer 213 . In some embodiments, the first portion 213a of the first outer layer 213 may include a first surface region 223 of the first major surface 203 , and a first inner surface region 214a of the first inner surface 214 opposite the first surface region 223 . In some embodiments, the second portion 213b of the first outer layer 213 may include a third surface region 233 of the first major surface 203 and a second inner surface region 214b of the first inner surface 214 opposite the third surface region 233 . In some embodiments, as shown, the first surface region 223 and the third surface region 233 may extend along the first plane 204a. In some embodiments, as shown, the first inner surface region 214a and the second inner surface region 214b may extend along the third plane 204c. In some embodiments, the first portion 213a of the first outer layer 213 may include a first outer thickness 217 . In further embodiments, the first outer thickness 217 may span its corresponding length (ie, in the direction 106 of the length 105 of the foldable device) and/or its corresponding width (ie, in the width of the foldable device) 104 in the direction 103) is substantially uniform between the first surface region 223 and the first inner surface region 214a. In some embodiments, the second portion 213b of the first outer layer 213 may include the first outer thickness 217 . In further embodiments, the first outer thickness 217 may span its corresponding length (ie, in the direction 106 of the length 105 of the foldable device) and/or its corresponding width (ie, in the width of the foldable device) 104 in the direction 103) is substantially uniform between the third surface region 233 and the second inner surface region 214b.

As shown in FIGS. 2-3 , 6 and 11 , the foldable substrate 206 may include a second outer layer 215 . As shown, the second outer layer 215 can include the second major surface 205 and a second inner surface 216 opposite the second major surface 205 . In some embodiments, the second inner surface 216 may extend along the fourth plane 204d when the foldable devices 101, 301 and/or 601 are in a flat configuration. As used herein, the second outer thickness 237 of the second outer layer 215 may be defined between the second major surface 205 and the second inner surface 216 as the distance between the second plane 204b and the fourth plane 204d.

The second outer layer 215 will now be described with reference to the foldable device 101 of FIG. 2, with the understanding that unless otherwise stated, this description of the second outer layer 215 may also apply to any embodiment of the present disclosure, eg, in FIG. 3 Foldable device 301 and/or 601 , test foldable device 1102 and/or foldable substrate 206 illustrated in FIGS. 6 and 11 . As shown in Figure 2, the second outer layer 215 may include a first portion 215a and a second portion 215b. A second minimum distance 220 may be defined between the first portion 215a of the second outer layer 215 and the second portion 215b of the second outer layer 215 . In some embodiments, the first portion 215a of the second outer layer 215 may include a second surface region 225 of the second major surface 205 and a third inner surface region 216a of the second inner surface 216 opposite the second surface region 225 . In some embodiments, the second portion 215b of the second outer layer 215 may include a fourth surface region 235 of the second major surface 205 and a fourth inner surface region 216b of the second inner surface 216 opposite the fourth surface region 235 . In some embodiments, as shown, the second surface region 225 and the fourth surface region 235 may extend along the second plane 204b. In some embodiments, as shown, the third inner surface region 216a and the fourth inner surface region 216b may extend along the fourth plane 204d. In some embodiments, the first portion 215a of the second outer layer 215 may include a second outer thickness 237 . In further embodiments, the second outer thickness 237 may span its corresponding length (ie, in the direction 106 of the length 105 of the foldable device) and/or its corresponding width (ie, in the width of the foldable device) 104 in direction 103) is substantially uniform between the second surface region 225 and the third inner surface region 216a. In some embodiments, the second portion 215b of the second outer layer 215 may include a second outer thickness 237 . In further embodiments, the second outer thickness 237 may span its corresponding length (ie, in the direction 106 of the length 105 of the foldable device) and/or its corresponding width (ie, in the width of the foldable device) 104 in direction 103) is substantially uniform between the fourth surface region 235 and the fourth inner surface region 216b.

As shown in FIGS. 2-3 , 6 and 11 , the foldable substrate 206 may include a core layer 207 . As shown, the core layer 207 may include a third inner surface 208 and a fourth inner surface 218 opposite the third inner surface 208 . In some embodiments, the third inner surface 208 may extend along the third plane 204c. In some embodiments, the fourth inner surface 218 may extend along the fourth plane 204d. As used herein, the center thickness 227 of the core layer 207 may be defined between the third inner surface 208 and the fourth inner surface 218 as the distance between the third plane 204c and the fourth plane 204d.

In some embodiments, the first outer thickness 217, the second outer thickness 237, and/or the center thickness 227 may be about 1 μm or more, about 5 μm or more, about 10 μm or more, about 25 μm or more larger, about 40 μm or larger, about 80 μm or larger, about 100 μm or larger, about 125 μm or larger, about 150 μm or larger, about 1 mm or smaller, about 800 μm or larger Small, about 500 μm or less, about 300 μm or less, about 200 μm or less, about 180 μm or less, or about 160 μm or less. In some embodiments, the first outer thickness 217, the second outer thickness 237, and/or the center thickness 227 may range from about 1 μm to about 1 mm, from about 1 μm to about 800 μm, from about 5 μm to about 800 μm μm, from about 5 μm to about 500 μm, from about 10 μm to about 500 μm, from about 10 μm to about 300 μm, from about 25 μm to about 300 μm, from about 25 μm to about 200 μm, from about 40 μm μm to about 200 μm, from about 80 μm to about 200 μm, from about 80 μm to about 200 μm, from about 100 μm to about 200 μm, from about 125 μm to about 200 μm, from about 125 μm to about 180 μm , in a range from about 125 μm to about 160 μm, from about 125 μm to about 150 μm, or any range or sub-range therebetween. In further embodiments, the center thickness 227 may be about 1 μm or greater, about 5 μm or greater, about 10 μm or greater, about 25 μm or greater, about 40 μm or greater, about 100 μm or greater, or smaller, about 80 μm or less, about 60 μm or less, or about 50 μm or less. In further embodiments, the center thickness 227 may range from about 1 μm to about 100 μm, from about 5 μm to about 100 μm, from about 10 μm to about 100 μm, from about 10 μm to about 80 μm, from about 25 μm to about 100 μm In one of the range of µm to about 80 µm, from about 25 µm to about 60 µm, from about 40 µm to about 60 µm, or any range or sub-range therebetween. In some embodiments, the first outer thickness 217 may be substantially equal to the second outer thickness 237 . In some embodiments, the first outer thickness 217 may be greater than the second outer thickness 237 . In some embodiments, the second outer thickness 237 may be greater than the first outer thickness 217 .

The core layer 207 will now be described with reference to the foldable device 101 of FIG. 2, with the understanding that unless otherwise stated, this description of the core layer 207 is also applicable to any embodiment of the present disclosure, eg, in FIG. 3, Foldable device 301 and/or 601 , test foldable device 1102 and/or foldable substrate 206 are illustrated in FIGS. 6 and 11 . As shown in FIG. 2 , the core layer 207 may be positioned between the first outer layer 213 and the second outer layer 215 . In some embodiments, as shown, the third inner surface 208 of the core layer 207 can contact the first inner surface region 214a of the first inner surface 214 of the first portion 213a of the first outer layer 213 . In some embodiments, as shown, the third inner surface 208 of the core layer 207 can contact the second inner surface region 214b of the first inner surface 214 of the second portion 213b of the first outer layer 213 . In some embodiments, as shown, the fourth inner surface 218 of the core layer 207 can contact the third inner surface region 216a of the second inner surface 216 of the first portion 215a of the second outer layer 215 . In some embodiments, as shown, the fourth inner surface 218 of the core layer 207 may contact the fourth inner surface region 216b of the second portion 215b of the second outer layer 215 .

As shown in FIG. 2 , the third inner surface 208 may comprise a first inner surface region 214a of the first inner surface 214 of the first portion 213a of the first outer layer 213 and a first portion of the second portion 213b of the first outer layer 213 A first central surface region 209 between the inner surface 214 and the second inner surface region 214b. In some embodiments, as shown, the first central surface region 209 of the core layer 207 can be recessed from the first major surface 203 a first distance, which can be substantially equal to or greater than the first outer thickness 217 . The first recess 234 may be defined between the first plane 204a and the first central surface region 209 .

As shown in FIG. 2, the fourth inner surface 218 may be included in the third inner surface region 216a of the second inner surface 216 of the first portion 215a of the second outer layer 215 and the second portion 231 of the second outer layer 215 A second central surface region 219 between the fourth inner surface regions 216b of the inner surface 216 . In some embodiments, as shown, the second central surface region 219 of the core layer 207 can be recessed from the second major surface 205 a second distance, which can be substantially equal to or greater than the second outer thickness 237 . The second recess 244 may be defined between the second plane 204b and the second central surface region 219 .

The width of the first central surface region 209 may be substantially equal to the first minimum distance 210 , and the width of the second central surface region 219 may be substantially equal to the second minimum distance 220 . In some embodiments, the first minimum distance 210 and/or the second minimum distance 220 may be about 1 mm or more, about 3 mm or more, about 5 mm or more, about 8 mm or more, about 10 mm or more, about 15 mm or more, about 20 mm or more, about 100 mm or less, about 60 mm or less, about 50 mm or less, about 40 mm or less, about 35 mm or less, about 30 mm or less, or about 25 mm or less. In some embodiments, the first minimum distance 210 and/or the second minimum distance 220 may range from about 1 mm to about 100 mm, from about 3 mm to about 100 mm, from about 3 mm to about 60 mm, from about 5 mm to approx. 60 mm, from approx. 5 mm to approx. 50 mm, from approx. 8 mm to approx. 50 mm, from approx. 8 mm to approx. 40 mm, from approx. 10 mm to approx. 40 mm, from approx. 10 mm to approx. 35 mm mm, from about 15 mm to about 35 mm, from about 15 mm to about 30 mm, from about 20 mm to about 30 mm, from about 20 mm to about 25 mm, or in any range or sub-range therebetween . In some embodiments, the first minimum distance 210 may be substantially equal to the second minimum distance 220 . In some embodiments, the first minimum distance 210 may be greater than the second minimum distance 220 . In some embodiments, the second minimum distance 220 may be greater than the first minimum distance 210 .

In some embodiments, the first distance by which the first central surface area 209 is recessed from the first plane 204a (eg, the first outer thickness 217 ) as a percentage of the substrate thickness 211 and/or as a percentage of the substrate thickness 211 The second distance (eg, the second outer thickness 237) of the second central surface region 219 recessed from the second plane 204b may be about 1% or more, about 5% or more, about 10% or more, about 15% or more, about 20% or more, about 25% or more, about 75% or less, about 60% or less, about 50% or less, about 40% or less, about 35% or less or about 30% or less. In some embodiments, the first distance and/or the second distance as a percentage of the substrate thickness 211 may be from about 1% to about 75%, from about 1% to about 60%, from about 5% to about 60% %, from about 5% to about 50%, from about 10% to about 50%, from about 10% to about 40%, from about 15% to about 40%, from about 15% to about 35%, from about 20% % to about 35%, from about 20% to about 30%, from about 25% to about 30%, or any range or subrange therebetween. In some embodiments, the first distance may be substantially equal to the second distance. Providing the first distance substantially equal to the second distance can further reduce the occurrence of mechanical instabilities in the central portion, eg, because the foldable substrate is symmetric about a plane including a midpoint of the substrate thickness and the central thickness. In some embodiments, the second distance may be greater than the first distance. In some embodiments, the first distance may be greater than the second distance. In further embodiments, the second distance that the second central surface region 219 is recessed from the second plane 204b as a percentage of the substrate thickness 211 (eg, the second outer thickness 237 ) may be about 1% or greater, about 2% or more, about 5% or more, about 10% or more, about 12% or more, about 30% or less, about 25% or less, about 20% or less, about 18% % or less or about 15% or less. In further embodiments, the second distance by which the second central surface region 219 is recessed from the second plane 204b (eg, the second outer thickness 237 ) as a percentage of the substrate thickness 211 may be from about 1% to about 30% , from about 1% to about 25%, from about 2% to about 25%, from about 5% to about 25%, from about 5% to about 20%, from about 10% to about 20%, from about 10% to about 18%, from about 12% to about 18%, from about 12% to about 15%, or any range or sub-range therebetween.

In some embodiments, the center thickness 227 as a percentage of the substrate thickness 211 can be about 0.5% or more, about 1% or more, about 2% or more, about 5% or more, about 6% or greater, about 20% or less, about 13% or less, about 10% or less, or about 8% or less. In some embodiments, the center thickness 227 as a percentage of the substrate thickness 211 may range from about 0.5% to about 20%, from about 0.5% to about 13%, from about 1% to about 13%, from about 1% to about 10%, from about 2% to about 10%, from about 2% to about 8%, from about 5% to about 8%, from about 6% to about 8%, or any range therebetween or in the subrange.

The first outer layer 213 may include a first coefficient of thermal expansion, the second outer layer 215 may include a second coefficient of thermal expansion, and the core layer 207 may include a core coefficient of thermal expansion. Throughout this disclosure, the coefficient of thermal expansion of a foldable substrate or a layer of a foldable substrate refers to the linear expansion rate based on temperature, and is measured according to ASTM E228-17 at 25°C. In some embodiments, the first coefficient of thermal expansion, the second coefficient of thermal expansion, and/or the core thermal expansion coefficient may be about 5×10 ⁻⁷ °C ⁻¹ or more, about 10×10 ⁻⁷ °C ⁻¹ or more, about 20 × 10 ^-7 °C ^-1 or more, about 30 × 10 ^-7 °C ^-1 or more, about 40 × 10 ^-7 °C ^-1 or more, about 50 × 10 ^-7 °C ^-1 or more , about 60 × 10 ^-7 °C ^-1 or more, about 500 × 10 ^-7 °C ^-1 or less, about 300 × 10 ^-7 °C ^-1 or less, about 200 × 10 ^-7 °C ^-1 or less Smaller, about 150 × 10 ^-7 °C ^-1 or less, about 100 × 10 ^-7 °C ^-1 or less, about 90 × 10 ^-7 °C ^-1 or less, about 80 × 10 ^-7 °C ^{- 1} or less or about 70×10 ^-7 °C ^-1 or less. In some embodiments, the first coefficient of thermal expansion, the second coefficient of thermal expansion, and/or the core thermal expansion coefficient may range from about 5×10 ⁻⁷ °C ⁻¹ to about 500×10 ⁻⁷ °C ⁻¹ , ^from about 5×10 −1 ⁷ ℃ ^-1 to about 300× ^10-7 ℃ ^-1 , from about 10× ^10-7 ℃ ^-1 to about 300× ^10-7 ℃ ^-1 , from about 10× ^10-7 ℃ ^-1 to about 200× ^10-7 ℃ ^-1 , from about 20× ^10-7 ℃ ^-1 to about 200× ^10-7 ℃ ^-1 , from about 20× ^10-7 ℃ ^-1 to about 100× ^10-7 ℃ ^-1 , from about About 30×10 ^-7 °C ^-1 to about 100×10 ^-7 °C ^-1 , from about 30×10 ^-7 °C ^-1 to about 90×10 ^-7 °C ^-1 , from about 40×10 ^-7 °C ^{- 1} to about 90× ^10-7 °C ^-1 , from about 40× ^10-7 °C ^-1 to about 80× ^10-7 °C ^-1 , from about 50× ^10-7 °C ^-1 to about 80× ^10-7 °C ^-1 , from about 50 x 10 ^-7 °C ^-1 to about 70 x 10 ^-7 °C ^-1 , from about 60 x 10 ^-7 °C ^-1 to about 70 x 10 ^-7 °C ^-1 or in a range between in any range or sub-range. In some embodiments, the first coefficient of thermal expansion may be substantially equal to the second coefficient of thermal expansion. In some embodiments, the core thermal expansion coefficient may be greater than the first thermal expansion coefficient and/or the second thermal expansion coefficient. In further embodiments, the core thermal expansion coefficient may be about 5×10 ⁻⁷ °C ⁻¹ or greater, about 10×10 ⁻⁷ °C ⁻¹ or greater, or about 20× greater than the first thermal expansion coefficient and/or the second thermal expansion coefficient. ^10-7 °C ^-1 or greater, about 30× ^10-7 °C ^-1 or greater, about 40× ^10-7 °C ^-1 or greater, about 50× ^10-7 °C ^-1 or greater, or About 100× ^10-7 °C ^-1 or less, about 80× ^10-7 °C ^-1 or less, or about 70× ^10-7 °C ^-1 or less, or about 60× ^10-7 °C ^-1 or larger. In further embodiments, the core thermal expansion coefficient may be greater than the first thermal expansion coefficient and/or the second thermal expansion coefficient by an amount from about 5×10 ⁻⁷ °C ⁻¹ to about 100×10 ⁻⁷ °C ⁻¹ , from about 5 × ^10-7 ℃ ^-1 to about 80× ^10-7 ℃ ^-1 , from about 10× ^10-7 ℃ ^-1 to about 80× ^10-7 ℃ ^-1 , from about 10× ^10-7 ℃ ^-1 to Approx. 70×10 ^-7 ℃ ^-1 , from about 20×10 ^-7 ℃ ^-1 to about 70×10 ^-7 ℃ ^-1 , from about 20×10 ^-7 ℃ ^-1 to about 60×10 ^-7 ℃ ^{- 1.} From about 30× ^10-7 ℃ ^-1 to about 60× ^10-7 ℃ ^-1 , from about 30× ^10-7 ℃ ^-1 to about 50× ^10-7 ℃ ^-1 , ^from about 40×10- In a range of ⁷ °C ^-1 to about 60× ^10-7 °C ^-1 , from about 40× ^10-7 °C ^-1 to about 50× ^10-7 °C ^-1 , or any range or sub-range therebetween. As discussed herein, controlling the difference between the coefficients of thermal expansion of the core layer relative to the first outer layer and/or the second outer layer or the central portion relative to the first portion and/or the second portion can reduce the foldable device and/or can Chemical strengthening between layers and/or portions of the folded substrate induces expansion and/or strain, which can help to reach critical buckling strains (eg, onset of mechanical instability) in the foldable device and/or foldable substrate The larger folding before the induced strain, and reduce the occurrence of optical distortion.

The first outer layer 213 may include a first density, the second outer layer 215 may include a second density, and the core layer 207 may include a core density. Throughout this disclosure, density is measured according to ASTM C693-93 (2019) at 25°C. In some embodiments, the first density, the second density, and/or the core density may be about 2 grams per cubic centimeter (g/cm ³ ) or greater, about 2.2 g/cm ³ or greater, about 2.3 g/cm cm ³ or more, about 2.4 g/cm ³ or more, about 2.42 g/cm ³ or more, about 2.45 g/cm ³ or more, about 2.47 g/cm ³ or more, about 3 g/ cm ³ or less, about 2.8 g/cm ³ or less, about 2.7 g/cm ³ or less, about 2.65 g/cm ³ or less, about 2.6 g/cm ³ or less, or about 2.58 g/cm cm ³ or less, about 2.55 g/cm ³ or less, about 2.52 g/cm ³ or less, or about 2.5 g/cm ³ or less. In some embodiments, the first density, the second density, and/or the core density can range from about 2 g/cm ³ to about 3 g/cm ³ , from about 2 g/cm ³ to about 2.8 g/cm ³ , from about 2.2 g/cm ³ to about 2.8 g/cm ³ , from about 2.2 g/cm ³ to about 2.7 g/cm ³ , from about 2.3 g/cm ³ to about 2.7 g/cm ³ , from about 2.4 g/cm cm ³ to about 2.7 g/cm ³ , from about 2.42 g/cm ³ to about 2.7 g/cm ³ , from about 2.42 g/cm ³ to about 2.68 g/cm ³ , from about 2.45 g/cm ³ to about 2.68 g/cm ³ , from about 2.45 g/cm ³ to about 2.65 g/cm ³ , from about 2.48 g/cm ³ to about 2.65 g/cm ³ , from about 2.48 g/cm ³ to about 2.52 g/cm ³ , In a range from about 2.48 g/cm ³ to about 2.5 g/cm ³ or any range or sub-range therebetween. In some embodiments, the first density may be substantially equal to the second density. In some embodiments, the core density may be greater than the first density and/or the second density. ^In further embodiments, the core density may be about 0.005 g/cm or greater, about 0.01 g/cm or greater, about 0.015 g/cm or greater, about 0.02 g ^/ cm or greater ^than the first density and/or the second density g/cm ³ or more, about 0.025 g/cm ³ or more, about 0.055 g/cm ³ or less, about 0.05 g/cm ³ or less, about 0.045 g/cm ³ or less, about 0.04 g/cm ³ or less, about 0.35 g/cm ³ or less, or about 0.3 g/cm ³ or less. In further embodiments, the core density may be greater than the first density and/or the second density by an amount from about 0.005 g/cm ³ to about 0.055 g/cm ³ , from about 0.005 g/cm ³ to about 0.05 g/cm 3 cm ³ , from about 0.01 g/cm ³ to about 0.05 g/cm ³ , from about 0.01 g/cm ³ to about 0.045 g/cm ³ , from about 0.015 g/cm ³ to about 0.045 g/cm ³ , from about 0.015 g/cm ³ to about 0.04 g/cm ³ , from about 0.02 g/cm ³ to about 0.04 g/cm ³ , from about 0.02 g/cm ³ to about 0.035 g/cm ³ , from about 0.025 g/cm ³ In one range to about 0.035 g/cm ³ , from about 0.025 g/cm ³ to about 0.03 g/cm ³ , or any range or sub-range therebetween. As discussed herein, controlling the difference between the density of the core layer relative to the first outer layer and/or the second outer layer or the central portion relative to the first portion and/or the second portion can reduce the foldable device and/or foldable Chemical strengthening between layers and/or portions of the substrate induces expansion and/or strain, which can help before the foldable device and/or foldable substrate reach critical buckling strain (eg, the onset of mechanical instability) The larger folding induced strain, and the reduction of the occurrence of optical distortion.

The first outer layer 213 may include a first network expansion factor, the second outer layer 215 may include a second network expansion factor, and the core layer 207 may include a core network expansion factor. Throughout this disclosure, a network expansion coefficient (eg, lattice expansion coefficient) refers to the increase in volume of a material (eg, glass-based material, ceramic-based material) per mole % of alkali metal ions as the alkali metal ion increases. Exchange into the material and increase. In some embodiments, the network expansion factor may be for oxide-based potassium. In some embodiments, the network expansion coefficient may be for oxide-based sodium. In some embodiments, the first network expansion factor, the second network expansion factor, and/or the core network expansion factor may be about 300 × 10 ^-6 /mol% or greater, about 500 × 10 ^-6 / mol % or more, about 700 × 10 ^-6 /mol % or more, about 800 × 10 ^-6 /mol % or more, about 900 × 10 ^-6 /mol % or more, about 200 × 10 ^-6 /mol % or less, about 1500 × 10 ^-6 /mol % or less, about 1200 × 10 ^-6 /mol % or less, about 1100 × 10 ^-6 /mol % % or less or about 1000 × 10 ^-6 /mol% or less. In some embodiments, the first network expansion factor, the second network expansion factor, and/or the core network expansion factor may be in the range from about 300×10 ⁻⁶ /mol% to about 2000×10 ⁻⁶ /mol% %, from about 300 × 10 ^-6 /mol % to about 1500 × 10 ^-6 /mol %, from about 500 × 10 ^-6 /mol % to about 1500 × 10 ^-6 /mol %, from about 500 × 10 ^-6 /mol % to about 1200 × 10 ^-6 /mol %, from about 700 × 10 ^-6 /mol % to about 1200 × 10 ^-6 /mol %, from about 700 × 10 ^{- 6} /mol % to about 1100 × 10 ^-6 /mol %, from about 800 × 10 ^-6 /mol % to about 1100 × 10 ^-6 /mol %, from about 800 × 10 ^-6 /mol % % to about 1000 x 10" ⁶ /mol%, in a range from about 900 x 10" ⁶ /mol% to about 1000 x 10" ⁶ /mol%, or any range or subrange therebetween. In some embodiments, the first network expansion factor may be substantially equal to the second network expansion factor. In some embodiments, the core network expansion factor may be smaller than the first network expansion factor and/or the second network expansion factor. As discussed above, controlling the difference between the network expansion coefficients of the core layer relative to the first outer layer and/or the second outer layer or the center portion relative to the first portion and/or the second portion may reduce the foldable device and/or may Chemical strengthening between layers and/or portions of the folded substrate induces expansion and/or strain, which can help to reach critical buckling strains (eg, onset of mechanical instability) in the foldable device and/or foldable substrate The larger folding before the induced strain, and reduce the occurrence of optical distortion.

As shown in FIGS. 4-5 and 7 , the foldable substrate 407 may include a first major surface 403 and a second major surface 405 opposite the first major surface 403 . As shown in FIGS. 4-5 and 7, the first major surface 403 may extend along the first plane 404a. The second major surface 405 may extend along a second plane 404b. In some embodiments, as shown, the second plane 404b may be parallel to the first plane 404a. As used herein, substrate thickness 411 may be defined between first major surface 403 and second major surface 405 as the distance between first plane 404a and second plane 404b. Substrate thickness 411 may be within one or more of the ranges discussed above with reference to substrate thickness 211 .

As shown in FIGS. 4-5 and 7, the foldable substrate 407 can include a first portion 421 that includes a first surface area 423 and a second surface area 425 opposite the first surface area 423 . The first portion 421 will now be described with reference to the foldable device 401 of Fig. 4, with the understanding that unless otherwise stated, this description of the first portion 421 may also apply to any embodiment of the present disclosure, eg, in Figs. 5 and 5 Foldable devices 501 and 701 and/or foldable substrate 407 are illustrated in FIG. 7 . As shown in FIG. 4 , the first portion 421 may include a first surface region 423 and a second surface region 425 opposite the first surface region 423 . In some embodiments, as shown, the second surface region 425 of the first portion 421 may comprise a flat surface. In further embodiments, the second surface region 425 may be parallel to the first surface region 423 as shown. In further embodiments, as shown, the first major surface 403 may include a first surface region 423 and the second major surface 405 may include a second surface region 425 . In further embodiments, the first surface region 423 may extend along the first plane 404a. In further embodiments, the second surface region 425 may extend along the second plane 404b. In some embodiments, the substrate thickness 411 may correspond to the distance between the first surface region 423 of the first portion 421 and the second surface region 425 of the first portion 421 . In some embodiments, the substrate thickness 411 may be substantially uniform across the first surface region 423 . In some embodiments, the first thickness defined between first surface region 423 and second surface region 425 may be within one or more of the ranges discussed above with respect to substrate thickness 211 or 411 . In further embodiments, the first thickness may include the substrate thickness 411 . In further embodiments, the first thickness of the first portion 421 may span its corresponding length (ie, in the direction 106 of the length 105 of the foldable device) and/or its corresponding width (ie, in the direction 106 of the foldable device) (in the direction 104 of the width 103 ) is substantially uniform between the first surface region 423 and the second surface region 425 .

As shown in FIGS. 4-5 and 7, the foldable substrate 407 may also include a second portion 431 that includes a third surface area 433 and a fourth surface opposite the third surface area 433 District 435. The second portion 431 will now be described with reference to the foldable device 401 of FIG. 4, with the understanding that unless otherwise stated, this description of the second portion 431 may also apply to any embodiment of the present disclosure, for example, in Section 5 Foldable device 501 and/or 701 and/or foldable substrate 407 illustrated in Figure 7 and Figure 7 . In some embodiments, as shown, the third surface region 433 of the second portion 431 may comprise a flat surface. In further embodiments, the third surface region 433 of the second portion 431 may be in a common plane with the first surface region 423 of the first portion 421 . In some embodiments, as shown, the fourth surface region 435 of the second portion 431 may comprise a flat surface. In further embodiments, the fourth surface region 435 may be parallel to the third surface region 433 as shown. In further embodiments, the fourth surface region 435 of the second portion 431 may be in a common plane with the second surface region 425 of the first portion 421 . A second thickness may be defined between the third surface region 433 of the second portion 431 and the fourth surface region 435 of the second portion 431 . In some embodiments, the second thickness may be within the range discussed above with respect to substrate thickness 211 or 411 . In further embodiments, the second thickness may include the substrate thickness 411 . In further embodiments, as shown, the second thickness may be substantially equal to the substrate thickness 411 (eg, the first thickness). In some embodiments, the second thickness of the second portion 431 may be substantially uniform between the third surface region 433 and the fourth surface region 435 .

As shown in FIGS. 4-5 and 7 , the foldable substrate 407 may include a central portion 481 positioned between the first portion 421 and the second portion 431 . In some embodiments, the central portion 481 may include a first central surface region 409 and a second central surface region 419 opposite the first central surface region 409 . In further embodiments, the central portion 481 may include a first central surface region 409 positioned between the first surface region 423 and the third surface region 433 . In still further embodiments, as shown, the first central surface region 409 may be recessed from the first major surface 403 a first distance 417 . The first distance 417 may be within one or more of the ranges discussed above with reference to the foldable substrate 206 for the first distance (eg, the first outer thickness 217 ). In still further embodiments, the first central surface region 409 may extend along the third plane 404c when the foldable devices 401, 501 and/or 701 are in a flat configuration as shown, but in further embodiments may The first central surface region 409 is provided as a non-planar region. The first recess 434 may be defined between the first central surface region 409 (eg, the third plane 404c) and the first plane 404a. In other embodiments, the third plane 404c may be substantially parallel to the first plane 404a and/or the second plane 404b.

In some embodiments, central portion 481 may include second central surface region 419 positioned between second surface region 425 and fourth surface region 435 . In further embodiments, as shown, the second central surface region 419 may be recessed a second distance 437 from the second major surface 405 . The second distance 437 may be within one or more of the ranges discussed above with reference to the foldable substrate 206 for the second distance (eg, the second outer thickness 237 ). In still further embodiments, the second central surface region 419 may extend along the fourth plane 404d when the foldable devices 401, 501 and/or 701 are in a flat configuration as shown, but in further embodiments may The second central surface region 419 is provided as a non-planar region. The second recess 444 may be defined between the second central surface region 419 (eg, the fourth plane 404d) and the second plane 404b. As discussed above, providing a first distance that the first central surface region is recessed from the first major surface that is substantially equal to a second distance that the second central surface region is recessed from the second major surface can reduce the occurrence of mechanical instability in the central portion , for example, because the foldable substrate is symmetric about a plane containing the midpoint between the thickness of the substrate and the thickness of the center.

A central thickness 427 can be defined between the first central surface region 409 and the second central surface region 419, and this thickness can be measured as the distance between the third plane 404c and the fourth plane 404d. In some embodiments, the center thickness 427 may be within one or more of the ranges discussed above for the center thickness 227 of the foldable substrate 206 . In some embodiments, the center thickness 427 as a percentage of the substrate thickness 411 may be within one or more of the ranges discussed above for the center thickness 227 as a percentage of the substrate thickness 211 of the foldable substrate 206 . By providing a first central surface region 409 of the central portion 481 extending along the third plane 404c parallel to the second central surface region 419 of the central portion 481 extending along the fourth plane 404d, the uniform central thickness 427 can span the center Portion 481 extends, which can provide enhanced folding performance at a predetermined thickness of center thickness 427 . Uniform center thickness 427 across center portion 481 may improve folding performance by preventing stress concentrations that would occur if one portion of center portion 481 were thinner than the rest of center portion 481 .

In some embodiments, as shown in Figures 4-5, the transition between the first central surface region 409 and the first surface region 423 and/or the third surface region 433 may be substantially abrupt (eg, sufficient narrow to resemble a straight edge perpendicular to the first plane 404a and/or the third plane 404c). In some embodiments, as shown in FIGS. 4-5, the transition between the second central surface region 419 and the second surface region 425 and/or the fourth surface region 435 may be substantially abrupt (eg, sufficient narrow to resemble a straight edge perpendicular to the second plane 404b and/or the fourth plane 404d). In some embodiments, although not shown, the foldable substrate 407 can include a first transition between the first surface region and the first central surface and/or between the second surface region and the second central surface region, which It may be similar to the first transition portion 853 in FIG. 8, for example. In some embodiments, although not shown, the foldable substrate 407 can include a second transition between the third surface region and the first central surface and/or between the fourth surface region and the second central surface region, which It may be similar to the second transition portion 855 in FIG. 8, for example.

In some embodiments, as shown in FIG. 7 , foldable device 701 can include a foldable substrate 707 that can include a first portion 421 and/or a second portion that are similar or identical to corresponding portions of foldable substrate 407 431. In some embodiments, the foldable substrate 707 may include a first transition portion 753 positioned between the first portion 421 and a portion of the central portion 781 including the third plane 404c (eg, the first central surface region 709). In another embodiment, the first transition portion 753 includes a portion of the first transition portion 753 extending from the first portion 421 with a continuously varying thickness of the first transition portion and a portion extending from the third plane 404c that can change abruptly. In still further embodiments, the abruptly changed transition depth 727 may be about 1 μm or more, about 5 μm or more, about 10 μm or more, about 12 μm or more, about 50 μm or less, About 30 μm or less, about 25 μm or less, about 20 μm or less, about 18 μm or less, or about 15 μm or less. In still further embodiments, the abruptly changed transition depth 727 may range from about 1 μm to about 50 μm, from about 1 μm to about 30 μm, from about 2 μm to about 30 μm, from about 2 μm to about 25 μm , from about 5 µm to about 25 µm, from about 5 µm to about 20 µm, from about 10 µm to about 20 µm, from about 10 µm to about 18 µm, from about 12 µm to about 18 µm, from about 12 µm in a range to about 15 µm or any range or sub-range therebetween. In some embodiments, as shown in Figure 7, the foldable substrate 707 can include a portion (eg, the first central surface region 709) positioned between the second portion 431 and a central portion 781 that includes the third plane 404c a second transition portion 755. In another embodiment, the second transition portion 755 includes a portion of the second transition portion 755 extending from the second portion 431 with a continuously varying thickness of the second transition portion and a portion extending from the third plane 404c that can change abruptly. In still further embodiments, a transition depth 727 of the abrupt change of the second transition portion may be within one or more of the ranges discussed above for the abrupt change of the transition depth 727 of the first transition portion. In still further embodiments, a transition depth 727 of the abrupt change of the second transition portion may be substantially equal to the transition depth 727 of the abrupt change of the first transition portion.

As shown in FIG. 8 , foldable device 801 may include a foldable substrate 807 . The foldable substrate may include a first main surface 803 and a second main surface 805 opposite the first main surface 803 . As shown in Figure 8, the first major surface 803 may extend along a first plane 804a. The second major surface 805 may extend along a second plane 804b. In some embodiments, as shown, the second plane 804b may be parallel to the first plane 404a. As used herein, substrate thickness 811 may be defined between first major surface 803 and second major surface 805 as the distance between first plane 804a and second plane 804b. Substrate thickness 811 may be within one or more of the ranges discussed above with reference to substrate thickness 211 or 411 .

As shown in FIG. 8 , the foldable substrate 807 can include a first portion 821 that includes a first surface area 823 and a second surface area 825 opposite the first surface area 823 . In some embodiments, as shown, the second surface region 825 of the first portion 821 may comprise a flat surface. In further embodiments, the second surface region 825 may be parallel to the first surface region 823 as shown. In further embodiments, the first major surface 803 may include a first surface region 823 and the second major surface 805 may include a second surface region 825, as shown. In further embodiments, the first surface region 823 may extend along the first plane 804a. In further embodiments, the second surface region 825 may extend along the second plane 804b. In some embodiments, the substrate thickness 811 may correspond to the distance between the first surface region 823 of the first portion 821 and the second surface region 825 of the first portion 821 . In some embodiments, the substrate thickness 811 may be substantially uniform across the first surface region 823 . In some embodiments, the first thickness defined between the first surface region 823 and the second surface region 825 may be within one or more of the ranges discussed above with respect to substrate thicknesses 211 , 411 or 811 . In further embodiments, the first thickness may include the substrate thickness 811 . In further embodiments, the first thickness of the first portion 821 may span its corresponding length (ie, in the direction 106 of the length 105 of the foldable device) and/or its corresponding width (ie, in the direction 106 of the foldable device) (in the direction 104 of the width 103 ) is substantially uniform between the first surface region 823 and the second surface region 825 .

As shown in FIG. 8 , the foldable substrate 807 may also include a second portion 831 that includes a third surface area 833 and a fourth surface area 835 opposite the third surface area 833 . In some embodiments, as shown, the third surface region 833 of the second portion 831 may comprise a flat surface. In further embodiments, the third surface region 833 of the second portion 831 may be in a common plane with the first surface region 823 of the first portion 821 . In some embodiments, as shown, the fourth surface region 835 of the second portion 831 may comprise a flat surface. In further embodiments, the fourth surface region 835 may be parallel to the third surface region 833 as shown. In further embodiments, the fourth surface region 835 of the second portion 831 may be in a common plane with the second surface region 825 of the first portion 821 . A second thickness may be defined between the third surface region 833 of the second portion 831 and the fourth surface region 835 of the second portion 831 . In some embodiments, the second thickness may be within the range discussed above with respect to substrate thickness 211 , 411 or 811 . In further embodiments, the second thickness may include the substrate thickness 811 . In further embodiments, as shown, the second thickness may be substantially equal to the substrate thickness 811 (eg, the first thickness). In some embodiments, the second thickness of the second portion 831 may be substantially uniform between the third surface region 833 and the fourth surface region 835 .

As shown in FIG. 8 , the foldable substrate 807 can include a central portion 881 positioned between the first portion 821 and the second portion 831 . In some embodiments, the central portion 881 may include a first central surface region 809 and a second central surface region 819 opposite the first central surface region 809 . In further embodiments, the central portion 881 may include a first central surface region 809 positioned between the first surface region 823 and the third surface region 833 . In still further embodiments, as shown, the first central surface region 809 may be recessed from the first major surface 803 a first distance 817 . The first distance 817 may be within one or more of the ranges discussed above with reference to the foldable substrate 206 for the first distance (eg, the first outer thickness 217 ). In still further embodiments, the first central surface area 809 may extend along the third plane 804c when the foldable device 801 is in the flat configuration as shown, but in further embodiments the first central surface area may be 809 is provided as a non-flat area. The first recess 834 may be defined between the first central surface region 809 (eg, the third plane 804c) and the first plane 804a. In other embodiments, the third plane 804c may be substantially parallel to the first plane 804a and/or the second plane 804b. In further embodiments, the central portion 881 may include a second central surface region 819 positioned between the second surface region 825 and the fourth surface region 835 . In still further embodiments, the second major surface 805 may include a second central surface region 819 as shown. In still further embodiments, although not shown, a portion of the second central surface region may be recessed from the second plane. In still further embodiments, although not shown, the foldable substrate may include another recess in the second major surface of the foldable substrate that exposes the second central surface area.

A central thickness 827 of central portion 881 may be defined between the first central surface region 809 and the second central surface region 819 . In some embodiments, the first central surface area 809 may extend along the third plane 804c when the foldable device 801 is in a flat configuration, but in other embodiments the first central surface area 809 may be provided as non-planar Area. In other embodiments, the third plane 804c may be substantially parallel to the first plane 804a and/or the second plane 804b. In some embodiments, the center thickness 827 may be within one or more of the ranges discussed above for the center thickness 227 of the foldable substrate 206 . In some embodiments, center thickness 827 as a percentage of substrate thickness 811 may be within one or more of the ranges discussed above for center thickness 227 as a percentage of substrate thickness 211 of foldable substrate 206 . Uniform center thickness 827 may extend across center portion 881 by providing first central surface region 809 along center portion 881 extending parallel to third plane 804c of second plane 804b, which may provide a predetermined thickness at center thickness 827 Enhanced folding performance at Uniform center thickness 827 across center portion 881 may improve folding performance by preventing stress concentrations that would occur if one portion of center portion 881 were thinner than the rest of center portion 881 .

As shown in FIG. 8 , the central portion 881 may include a first transition portion 853 . The first transition portion 853 may attach the first portion 821 to an area of the central portion 881 that includes the central thickness 827 . The thickness of the first transition portion 853 may be defined between the second plane 804b and the first central surface region 809 . As shown in Figure 8, the thickness of the first transition portion 853 may increase continuously from the first central surface region 809 (eg, central thickness 827) to the first portion 821 (eg, substrate thickness 811). In some embodiments, as shown, the thickness of the first transition portion 853 may increase at a constant rate from the first central surface region 809 to the first portion 821 . In some embodiments, although not shown, where the first central surface region 809 meets the first transition portion 853 , the thickness of the first transition portion 853 may increase more slowly than in the middle of the first transition portion 853 . In some embodiments, although not shown, where the first portion 821 and the first transition portion 853 meet, the thickness of the first transition portion 853 may increase more slowly than in the middle of the first transition portion 853 . In some embodiments, although not shown in Figure 8, the central portion may be similar to the central portion 481 of Figure 4, which may not include the first transition portion. In some embodiments, although not shown, the first transition portion 853 may transition from the second surface region to the second central surface region, eg, if the second central surface region is recessed from the second plane. In some embodiments, although not shown, the first transition portion may include a portion extending from the first portion where a thickness of the first transition portion continuously changes and a portion extending from the third plane 804c that may change abruptly in thickness ( For example, see Figure 7).

The central portion 881 may include a second transition portion 855 . As shown in FIG. 8 , the second transition portion 855 may attach the second portion 831 to an area of the central portion 881 that includes the central thickness 827 (eg, the area that includes the first central surface region 809 ). The thickness of the second transition portion 855 may be defined between the second plane 804b and the first central surface region 809 . As shown in Figure 8, the thickness of the second transition portion 855 may increase continuously from the first central surface region 809 (eg, central thickness 827) to the second portion 831 (eg, substrate thickness 811). In some embodiments, as shown, the thickness of the second transition portion 855 may increase at a constant rate from the first central surface region 809 to the second portion 831 . In some embodiments, although not shown, where the first central surface region 809 meets the second transition portion 855 , the thickness of the second transition portion 855 may increase more slowly than in the middle of the second transition portion 855 . In some embodiments, although not shown, where the second portion 831 and the second transition portion 855 meet, the thickness of the second transition portion 855 may increase more slowly than in the middle of the second transition portion 855 . In some embodiments, as shown in FIG. 8, the central portion 881 may include a second transition portion. In some embodiments, although not shown in Figure 8, the central portion may be similar to the central portion 481 of Figure 4, which may not include the second transition portion. In some embodiments, although not shown, the second transition portion 855 may transition from the fourth surface region to the second central surface region, eg, if the second central surface region is recessed from the second plane. In some embodiments, although not shown, the second transition portion may include a portion extending from the second portion in which a thickness of the second transition portion continuously changes and a portion extending from the third plane 804c that may change abruptly in thickness , for example, similar to that shown in Figure 7.

As shown in FIG. 8, the width of the first transition portion 853 may be defined in the direction 106 of the length 105 of the foldable device 801 at a portion of the center portion 881 including the center thickness 827 (eg, the third plane 804c) and the Between the first part 821. The width of second transition portion 855 may be defined between a portion of central portion 881 including central thickness 827 (eg, third plane 804c ) and second portion 831 in direction 106 of length 105 of foldable device 101 . In some embodiments, the width of the first transition portion 853 and/or the width of the second transition portion 855 may be large enough (eg, 1 mm or greater) to avoid any additional thicknesses that may otherwise be between the first thickness and the center thickness. Optical distortion that occurs at stepped transitions or at small transition widths (eg, less than 1 mm). In some embodiments, in order to enhance the puncture resistance of the foldable substrate while avoiding optical distortion, the width of the first transition portion 853 and/or the width of the second transition portion 855 may be about 1 mm or more, about 2 mm or more, about 3 mm or more, about 5 mm or less, about 4 mm or less, or about 3 mm or less. In some embodiments, the width of the first transition portion 853 and/or the width of the second transition portion 855 may range from about 1 mm to about 5 mm, from about 1 mm to about 4 mm, from about 1 mm to about 3 mm mm, from about 2 mm to about 5 mm, from about 2 mm to about 4 mm, from about 2 mm to about 3 mm, from about 3 mm to about 5 mm, from about 3 mm to about 4 mm, or in any range or subrange in between.

As used herein, if a first layer and/or component is described as being "disposed on a second layer and/or component," it is between the first layer and/or component and the second layer and/or component Other layers may or may not be present. Furthermore, as used herein, "positioned on" does not refer to a relative position with reference to gravity. For example, a first layer and/or component may be considered "disposed on a second layer and/or component," eg, when the first layer and/or component is positioned on a second layer and/or component down, above, or to one side. As used herein, a first layer and/or component described as "bonded to" a second layer and/or component means that the layers and/or components are in direct contact and/or by direct contact between the two layers and/or components. /or bonded or bonded to each other via an adhesive layer. As used herein, a first layer and/or component described as "in contact with the second layer and/or component" or "in contact with the second layer and/or component" refers to direct contact and includes such layers and/or components situation of mutual combination.

As shown in FIGS. 2-5 and 12, foldable devices 101 , 301 , 401 , 501 and/or 1201 may include an adhesive layer 261 . As shown, the adhesion layer 261 can include a first contact surface 263 and a second contact surface 265 that can be opposite the first contact surface 263 . In some embodiments, as shown in FIGS. 2-5, the second contact surface 265 of the adhesive layer 261 may comprise a flat surface. In some embodiments, as shown in FIGS. 2 and 5, the first contact surface 263 of the adhesive layer 261 may comprise a flat surface. The adhesive thickness 267 of the adhesive layer 261 can be defined as the minimum distance between the first contact surface 263 and the second contact surface 265 . In some embodiments, the adhesive thickness 267 of the adhesive layer 261 may be about 1 μm or more, about 5 μm or more, about 10 μm or more, about 100 μm or less, about 60 μm or less , about 30 μm or less, or about 20 μm or less. In some embodiments, the adhesive thickness 267 of the adhesive layer 261 may range from about 1 μm to about 100 μm, from about 5 μm to about 100 μm, from about 5 μm to about 60 μm, from about 5 μm to about 30 μm µm, one of the range from about 10 µm to about 30 µm, from about 10 µm to about 20 µm, or any range or sub-range therebetween.

In some embodiments, as shown in Figures 2 and 4, the second contact surface 265 of the adhesive layer 261 may face the first major surface 273 of the release liner 271 (described below). In further embodiments, as shown, the second contact surface 265 of the adhesive layer 261 may contact the first major surface 273 of the release liner 271 . In some embodiments, as shown in FIGS. 3 , 5 and 12 , the second contact surface 265 of the adhesive layer 261 may face the first main surface 303 of the display device 307 . In further embodiments, as shown, the second contact surface 265 of the adhesive layer 261 may contact the first major surface 303 of the display device 307 .

In some embodiments, as shown in FIGS. 2-5 and 12 , the first contact surface 263 of the adhesive layer 261 may face the second surface region 225 or 425 of the first portion 221 or 421 . In further embodiments, as shown, the first contact surface 263 of the adhesive layer 261 may contact the second surface region 225 or 425 of the first portion 221 or 421 . In some embodiments, as shown in FIGS. 2-5 and 12 , the first contact surface 263 of the adhesive layer 261 may face the fourth surface region 235 or 435 of the second portion 231 or 431 . In further embodiments, as shown, the first contact surface 263 of the adhesive layer 261 may contact the fourth surface region 235 or 435 of the second portion 231 or 431 . In some embodiments, as shown in FIGS. 2-5 and 12 , the first contact surface 263 of the adhesive layer 261 may face the second central surface region 219 or 419 of the central portion 281 or 481 . In further embodiments, as shown in FIGS. 3-4 , the first contact surface 263 of the adhesive layer 261 may contact the second central surface region 219 or 419 of the central portion 281 or 481 . In other embodiments, as shown in FIGS. 3-4 , the adhesive layer 261 may extend into the second recess 244 or 444 . In some embodiments, although not shown, the second recess may not be fully filled, eg, to make room for electronic and/or mechanical devices. In some embodiments, although not shown, another adhesive layer (eg, similar to adhesive layer 261 ) may be disposed on and/or contact the first major surface (eg, first surface region, third surface region) The first major surface, and/or extends into the first recess, but the first recess may not be fully filled, eg, to make room for electronic and/or mechanical devices.

In some embodiments, the adhesive layer 261 may comprise polyolefins, polyamides, halogen-containing polymers (eg, polyvinyl chloride or fluoropolymers), elastomers, urethanes, phenolic resins, parylenes , one or more of polyethylene terephthalate (polyethylene terephthalate; PET) and polyether ether ketone (PEEK). Example embodiments of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultrahigh molecular weight polyethylene (UHMWPE), and polypropylene ( polypropylene; PP). Example embodiments of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), Perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers and ethylene tetrafluoroethylene (ETFE) polymers. Example embodiments of elastomers include rubbers (eg, polybutadiene, polyisoprene, neoprene, butyl rubber, nitrile rubber) and block copolymers (eg, styrene-butadiene, high impact polystyrene, polydichlorophosphazene). In another embodiment, the adhesive layer 261 may include a light-transmitting adhesive. In yet other embodiments, the light-transmitting adhesive may comprise one or more optically clear polymers: acrylic (eg, polymethylmethacrylate (PMMA)), epoxy, silicone, and/or polyamine based formate. Examples of epoxy resins include bisphenol-based epoxy resins, novolac-based epoxy resins, cycloaliphatic compound-based epoxy resins, and glycidylamine-based epoxy resins. In still further embodiments, the light transmissive adhesive may include, but is not limited to, an acrylic adhesive (eg, 3M 8212 adhesive), or an optically clear liquid adhesive (eg, LOCTITE optically clear liquid adhesive). Exemplary examples of clear adhesives include clear acrylics, epoxies, silicones, and polyurethanes. For example, the optically clear liquid adhesive may comprise one or more of LOCTITE AD 8650, LOCTITE AA 3922, LOCTITE EA E-05MR, LOCTITE UK U-09LV, all available from Henkel.

In some embodiments, the adhesion layer 261 may comprise about 0.001 megapascals (MPa) or more, about 0.01 MPa or more, about 0.1 MPa or more, about 1 MPa or less, about 0.5 MPa or less, A modulus of elasticity of about 0.1 MPa or less or about 0.05 MPa or less. In some embodiments, the adhesion layer 261 may be included at from about 0.001 MPa to about 1 MPa, from about 0.01 MPa to about 1 MPa, from about 0.01 MPa to about 0.5 MPa, from about 0.05 MPa to about 0.5 MPa, from about A modulus of elasticity in a range of 0.1 MPa to about 0.5 MPa, from about 0.001 MPa to about 0.5 MPa, from about 0.001 MPa to about 0.01 MPa, or in any range or sub-range therebetween. In some embodiments, the adhesive layer may comprise an elastic modulus within one or more of the ranges discussed below for the elastic modulus of the polymer-based portion 241 .

As shown in Figures 2, 5 and 12, the polymer-based portion 241 of the foldable device 101, 401 and/or 1201 may be positioned between the first portion 221 or 421 and the second portion 231 or 431 . In some embodiments, the polymer-based portion 241 can be positioned at least partially in the second recess 244 or 444 as shown. In further embodiments, the polymer-based portion 241 may fill the second recess 244 or 444 as shown. In some embodiments, although not shown, the second recess may not be fully filled, eg, to make room for electronic and/or mechanical devices. In some embodiments, although not shown, another polymer-based portion (eg, similar to polymer-based portion 241 ) may extend into and/or fill the first recess. As shown in FIGS. 2 , 5 and 12 , the polymer-based portion 241 may include a fourth contact surface 247 opposite the third contact surface 245 . In some embodiments, as shown, the fourth contact surface 247 may comprise a flat surface. In further embodiments, the fourth contact surface 247 may be substantially coplanar with the second surface region 225 or 425 and the fourth surface region 235 or 435 (eg, extending along a common plane (the second plane 204b or 404b )) . In some embodiments, the third contact surface 245 may comprise a flat surface. In some embodiments, the third contact surface 245 may be substantially coplanar with the second central surface region 219 except that the fourth contact surface 247 is substantially coplanar with the second surface region 225 or 425 and the fourth surface region 235 or 435 or 419 are coplanar (eg, extending along a common plane (fourth plane 204d )). In some embodiments, as shown in FIGS. 2 and 5 , the first contact surface 263 of the adhesive layer 261 may face the fourth contact surface 247 of the polymer-based portion 241 . In further embodiments, as shown, the first contact surface 263 of the adhesive layer 261 may contact the fourth contact surface 247 of the polymer-based portion 241 .

In some embodiments, the polymer-based portion 241 comprises a polymer (eg, an optically clear polymer). In further embodiments, the polymer-based portion 241 may comprise one or more of optically transparent: acrylic (eg, polymethylmethacrylate (PMMA)), epoxy, silicone, and/or poly Urethane. Examples of epoxy resins include bisphenol-based epoxy resins, novolac-based epoxy resins, cycloaliphatic compound-based epoxy resins, and glycidylamine-based epoxy resins. In further embodiments, the polymer-based portion 241 may comprise polyolefins, polyamides, halogen-containing polymers (eg, polyvinyl chloride or fluoropolymers), elastomers, urethanes, phenolic resins, poly One or more of p-xylene, polyethylene terephthalate (PET) and polyether ether ketone (PEEK). Example embodiments of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultrahigh molecular weight polyethylene (UHMWPE), and polypropylene ( polypropylene; PP). Example embodiments of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinylfluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), Perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers and ethylene tetrafluoroethylene (ETFE) polymers. Example embodiments of elastomers include rubbers (eg, polybutadiene, polyisoprene, neoprene, butyl rubber, nitrile rubber) and block copolymers (eg, styrene-butadiene, High impact polystyrene, polydichlorophosphazene), for example, comprising one or more of polystyrene, polydichlorophosphazene, and poly(5-ethylene-2-norbornene). In some embodiments, the polymer-based portion may comprise a sol-gel material. Example embodiments of polyurethanes include thermoset polyurethanes, such as Dispurez 102, available from Incorez, and thermoplastic polyurethanes, such as KrystalFlex PE505, available from Huntsman. In still further embodiments, the second part may comprise an ethylene acid copolymer. An illustrative example of an ethylene acid copolymer includes SURLYN commercially available from Dow (eg, Surlyn PC-2000, Surlyn 8940, Surlyn 8150). An additional exemplary embodiment of the second section comprises Eleglass w802-GL044, available from Axalta, with from 1 wt% to 2 wt% crosslinker. In some embodiments, the polymer-based portion 241 may further comprise nanoparticles, eg, carbon black, carbon nanotubes, silica nanoparticles, or nanoparticles comprising polymers. In some embodiments, the polymer-based portion may further comprise fibers to form a polymer-fiber composite.

In some embodiments, the polymer-based portion 241 may include a coefficient of thermal expansion (CTE). As used herein, coefficient of thermal expansion is measured using a Picoscale Michelson interferometer between -20°C and 40°C according to ASTM E289-17. In some embodiments, the polymer-based portion 241 may comprise particles of one or more of copper oxide, beta quartz, tungstate, vanadate, pyrophosphate, and/or nickel-titanium alloys. In some embodiments, the polymer-based portion 241 may comprise about -20 x 10" ⁷ 1/°C or greater, about -10 x 10" ⁷ 1/°C or greater, about -5 x 10 ^"7 1 /°C or more, about -2 × 10 ^-7 1/°C or more, about 10 × 10 ^-7 1/°C or less, about 5 × 10 ^-7 1/°C or less, about 2 × 10 A CTE of ^-7 1/°C or less, about 1 x 10 ^-7 1/°C or less, or 01/°C or less. In some embodiments, the polymer-based moiety 241 can be included at from about -20 x 10 ^-7 1/°C to about 10 x 10 ^-7 1/°C, from about -20 x 10 ^-7 1/°C to about 5 × 10 ^-7 1/°C, from about -10 × 10 ^-7 1/°C to about -5 × 10 ^-7 1/°C, from about -10 × 10 ^-7 1/°C to about 2 × 10 ^-7 1/°C, from about -10 × 10 ^-7 1/°C to 0 1/°C, from about -5 × 10 ^-7 1/°C to 0 1/°C, from about -2 × 10 ^-7 1/°C to A CTE in a range of about 0 1/°C or any range or sub-range therebetween. By providing a polymer-based portion comprising a low (eg, negative) coefficient of thermal expansion, warpage caused by volume changes during curing of the polymer-based portion can be mitigated.

In some embodiments, the polymer-based portion 241 may comprise about 0.01 megapascals (MPa) or greater, about 1 MPa or greater, about 10 MPa or greater, about 20 MPa or greater, about 100 MPa or greater, or Greater, about 200 MPa or more, about 1,000 MPa or more, about 5,000 MPa or less, about 3,000 MPa or less, about 1,000 MPa or less, about 500 MPa or less, or about 200 MPa or less One of the smaller elastic modulus. In some embodiments, the polymer-based portion 241 can be included in a range from about 0.001 MPa to about 5,000 MPa, from about 0.01 MPa to about 3,000 MPa, from about 0.01 MPa to about 1,000 MPa, from about 0.01 MPa to about 500 MPa , from about 0.01 MPa to about 200 MPa, from about 1 MPa to about 5,000 MPa, from about 1 MPa to about 1,000 MPa, from about 1 MPa to about 1,000 MPa, from about 1 MPa to about 200 MPa, from about 10 MPa to about 5,000 MPa, from about 10 MPa to about 1,000 MPa, from about 10 MPa to about 200 MPa, from about 20 MPa to about 3,000 MPa, from about 20 MPa to about 1,000 MPa, from about 20 MPa to about 200 MPa, from about 100 MPa to about 3,000 MPa, from about 100 MPa to about 1,000 MPa, from about 100 MPa to about 200 MPa, from about 200 MPa to about 5,000 MPa, from about 200 MPa to about 3,000 MPa, from about 200 MPa to A modulus of elasticity in a range of about 1,000 MPa and all ranges and subranges therebetween. In some embodiments, the elastic modulus of the polymer-based moiety 241 can range from about 1 GPa to about 20 GPa, from about 1 GPa to about 18 GPa, from about 1 GPa to about 10 GPa, from about 1 GPa to about 1 GPa to An elastic modulus of about 5 GPa, a range from about 1 GPa to about 3 GPa, or any range or subrange therebetween. By providing the polymer-based portion 241 having an elastic modulus in a range from about 0.01 MPa to about 3,000 MPa (eg, in a range from about 20 MPa to about 3 GPa), it may be helpful to Fold the foldable device without trouble. In some embodiments, the adhesive layer 261 comprises a modulus of elasticity that is greater than the modulus of elasticity of the polymer-based portion 241, a configuration that provides improved performance in puncture resistance. In some embodiments, the elastic modulus of the polymer-based portion 241 may be less than the elastic modulus of the foldable substrate 206 , 407 or 807 . In some embodiments, the adhesive layer 261 may comprise an elastic modulus within the ranges recited above in this paragraph. In further embodiments, the adhesive layer 261 may comprise substantially the same elastic modulus as the elastic modulus of the polymer-based portion 241 . In further embodiments, the elastic modulus of the adhesive layer 261 may be from about 1 GPa to about 20 GPa, from about 1 GPa to about 18 GPa, from about 1 GPa to about 10 GPa, from about 1 GPa to about 5 GPa , an elastic modulus in a range from about 1 GPa to about 3 GPa, or in any range or subrange therebetween. In some embodiments, the elastic modulus of the polymer-based portion 241 may be less than the elastic modulus of the first portion 221 , 421 , or 821 . In some embodiments, the elastic modulus of the polymer-based portion 241 may be less than the elastic modulus of the second portion 231 , 431 , or 831 .

In some embodiments, as shown in FIGS. 2-5 and 11-12 , the coating 251 may be disposed on the first major surface 203 of the foldable substrate 206 or 407 . In further embodiments, the coating 251 may be disposed on the first portion 221 or 421 , the second portion 231 or 431 and the central portion 281 or 481 . In some embodiments, the coating 251 may include a third major surface 253 and a fourth major surface 255 opposite the third major surface 253 . In further embodiments, coating 251 (eg, fourth major surface 255 ) may contact foldable substrate 206 or 407 (eg, first major surface 203 or 403 ). In further embodiments, at least a portion of the coating 251 may be positioned in the first recess 234 or 434 . In still further embodiments, the coating 251 may fill the first recess 234 or 434 . In further embodiments, coating 251 may include a coating thickness 257 defined between third major surface 253 and fourth major surface 255 . In further embodiments, the coating thickness 257 may be about 0.1 μm or greater, about 1 μm or greater, about 5 μm or greater, about 10 μm or greater, about 15 μm or greater, about 20 μm or larger, about 25 μm or larger, about 40 μm or larger, about 50 μm or larger, about 60 μm or larger, about 70 μm or larger, about 80 μm or larger, about 90 μm or larger, or larger, about 200 µm or less, about 100 µm or less, or about 50 µm or less, about 30 µm or less, about 25 µm or less, about 20 µm or less, about 20 µm or less Small, about 15 μm or less, or about 10 μm or less. In some embodiments, the coating thickness 257 can range from about 0.1 μm to about 200 μm, from about 1 μm to about 200 μm, from about 10 μm to about 200 μm, from about 50 μm to about 200 μm, from about 0.1 μm to about 100 μm, from about 1 μm to about 100 μm, from about 10 μm to about 100 μm, from about 20 μm to about 100 μm, from about 30 μm to about 100 μm, from about 40 μm to about 100 μm μm, from about 50 μm to about 100 μm, from about 60 μm to about 100 μm, from about 70 μm to about 100 μm, from about 80 μm to about 100 μm, from about 90 μm to about 100 μm, from about 0.1 In one of the range of μm to about 50 μm, from about 1 μm to about 50 μm, from about 10 μm to about 50 μm, or any range or sub-range therebetween. In further embodiments, the coating thickness 257 may range from about 0.1 μm to about 50 μm, from about 0.1 μm to about 30 μm, from about 0.1 μm to about 25 μm, from about 0.1 μm to about 20 μm, from about 0.1 μm to about 15 μm, from about 0.1 μm to about 10 μm, from about 1 μm to about 30 μm, from about 1 μm to about 25 μm, from about 1 μm to about 20 μm, from about 1 μm to about 15 μm μm, from about 1 μm to about 10 μm, from about 5 μm to about 30 μm, from about 5 μm to about 25 μm, from about 5 μm to about 20 μm, from about 5 μm to about 15 μm, from about 5 μm to about 5 μm μm to about 10 μm, from about 10 μm to about 30 μm, from about 10 μm to about 25 μm, from about 10 μm to about 20 μm, from about 10 μm to about 15 μm, from about 15 μm to about 30 μm , from about 15 μm to about 25 μm, from about 15 μm to about 20 μm, from about 20 μm to about 30 μm, from about 20 μm to about 25 μm, or in any range or subrange therebetween.

In some embodiments, the polymer-based portion and/or the adhesive layer may include a yield strain. Providing a first pocket opposite the second pocket reduces the strain (eg, from 0% to 50%) encountered by the polymer-based portion or other material (eg, adhesive layer) in the pocket ). Thus, the requirement for yield strain of the polymer-based part can be relaxed. In some embodiments, the polymer-based portion and/or the adhesive layer may have a yield strain of about 3% or greater, about 4% or greater, about 5% or greater, about 6% or greater, about 7% or more, about 500% or less, about 100% or less, about 50% or less, about 20% or less, about 15% or less, about 10% or less, about 9% % or less or about 8% or less. In some embodiments, the yield strain of the polymer-based portion and/or the adhesive layer may be from about 1% to about 500%, from about 1% to about 100%, from about 2% to about 100%, from about 2% to about 50%, from about 3% to about 50%, from about 3% to about 20%, from about 4% to about 20%, from about 4% to about 15%, from about 5% to about 15% %, from about 5% to about 10%, from about 5% to about 9%, from about 6% to about 9%, from about 6% to about 8%, from about 7% to about 8%, or in any range or subrange in between.

In some embodiments, coating 251 may comprise a polymeric hard coat. In further embodiments, the polymeric hard coat layer may comprise one or more of ethylene-acid copolymers, polyurethane-based polymers, acrylate resins, and mercapto-ester resins. Illustrative examples of ethylene-acid copolymers include ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and ethylene-acrylic acid-methacrylic acid terpolymers (eg, Nucrel manufactured by DuPont), ethylene acid copolymers ionic polymers (eg, Surlyn manufactured by DuPont) and ethylene-acrylic acid copolymer amine dispersions (eg, Aquacer manufactured by BYK). Illustrative examples of polyurethane-based polymers include aqueous modified polyurethane dispersions (eg, Eleglas® manufactured by Axalta). Illustrative examples of acrylate resins that may be UV curable include acrylate resins (eg, Uvekol® resins manufactured by Allinex), cyanoacrylate adhesives (eg, Permabond® UV620 manufactured by Krayden), and UV free based acrylic resin (eg, Ultrabond windshield repair resin, eg, Ultrabond (45CPS)). Illustrative examples of mercapto-ester resins include mercapto-ester triallyl isocyanate (eg, Norland Optical Adhesive NOA 61). In further embodiments, the polymeric hard coat layer can include ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, which can be ionically polymerized to react via carboxylic acid residues with typical basic metal ions (eg, sodium and potassium, and also zinc) to form ionomer resins. The ethylene-acrylic acid copolymer and ethylene-methacrylic acid ionomer can be dispersed in water and coated onto a substrate to form an ionomer coating. Alternatively, these acid copolymers can be neutralized with ammonia, which liberates ammonia after coating and drying to reconstitute the acid copolymer into a coating. By providing a coating comprising a polymeric coating, the foldable device can contain low energy rupture.

In some embodiments, the coating may comprise a polymeric hardcoat comprising an optically clear polymeric hardcoat. Suitable materials for optically clear polymeric hardcoat layers include, but are not limited to: cured acrylic resin materials, inorganic-organic hybrid polymeric materials, aliphatic or aromatic hexafunctional urethane acrylates, siloxane-based Hybrid materials and nanocomposites, eg, epoxy resins and urethane materials with nanosilicates. In some embodiments, the optically clear polymeric hardcoat layer may consist essentially of one or more of these materials. In some embodiments, the optically clear polymeric hardcoat layer may be composed of one or more of these materials. As used herein, "inorganic-organic hybrid polymeric material" means a polymeric material comprising monomers having inorganic and organic components. Inorganic-organic hybrid polymers are obtained by polymerization between monomers having inorganic and organic groups. Inorganic-organic hybrid polymers are not nanocomposites comprising separate inorganic and organic components or phases, eg, inorganic particles dispersed within an organic matrix. More specifically, suitable materials for optically transparent polymeric (OTP) hard coat layers include, but are not limited to, polyimide, polyethylene terephthalate (PET), polycarbonate Ester (polycarbonate; PC), poly methyl methacrylate (poly methyl methacrylate; PMMA), organic polymer materials, inorganic-organic hybrid polymer materials and aliphatic or aromatic hexafunctional urethane acrylates. In some embodiments, the OTP hard coat layer may consist essentially of organic polymeric materials, inorganic-organic hybrid polymeric materials, or aliphatic or aromatic hexafunctional urethane acrylates. In some embodiments, the OTP hard coat layer may be composed of polyimide, organic polymeric materials, inorganic-organic hybrid polymeric materials, or aliphatic or aromatic hexafunctional urethane acrylates. In some embodiments, the OTP hard coat layer may include nanocomposites. In some embodiments, the OTP hard coat layer may include at least one of nanosilicate, epoxy, and urethane materials. Suitable compositions for this OTP hardcoat layer are described in US Patent Publication No. 2015/0110990, which is hereby incorporated by reference in its entirety. As used herein, "organic polymeric material" means a polymeric material comprising monomers having only organic components. In some embodiments, the OTP hard coat layer may comprise an organic polymer material manufactured by Gunze Limited and having a hardness of 9H, eg, Gunze's "Highly Durable Transparent Film". As used herein, "inorganic-organic hybrid polymeric material" means a polymeric material comprising monomers having inorganic and organic components. Inorganic-organic hybrid polymers are obtained by polymerization between monomers having inorganic and organic groups. Inorganic-organic hybrid polymers are not nanocomposites comprising separate inorganic and organic components or phases, eg, inorganic particles dispersed within an organic matrix. In some embodiments, the inorganic-organic hybrid polymeric material may include polymerized monomers comprising inorganic silicon-based groups, eg, silsesquioxane polymers. The silsesquioxane polymer can be, for example, an alkylsilsesquioxane, an arylsilsesquioxane, or an arylalkylsilsesquioxane having the following chemical structure: (RSiO _1.5 ) _n , where R is Organic groups such as, but not limited to, methyl or phenyl. In some embodiments, the OTP hard coat layer may comprise a silsesquioxane polymer, eg, SILPLUS manufactured by Nippon Steel Chemical Co., Ltd., in combination with an organic matrix. In some embodiments, the OTP hard coat layer may comprise 90% to 95% by weight of an aromatic hexafunctional urethane acrylate (eg, PU662NT (aromatic hexafunctional urethane) manufactured by Miwon Specialty Chemical Company acrylate)), and 10% to 5% by weight of a photoinitiator having a hardness of 8H or greater (eg, Darocur 1173 manufactured by Ciba Specialty Chemicals). In some embodiments, an OTP hard coat layer composed of aliphatic or aromatic hexafunctional urethane acrylates can be formed by spin coating the polyethylene terephthalate (PET) substrate. layer, curing the urethane acrylate and removing the urethane acrylate layer from the PET substrate to form a separate layer. The OTP hard coat layer may have a coating thickness (eg, coating thickness 257) in one of the ranges of 1 μm to 150 μm, including sub-ranges. For example, coating thicknesses (eg, coating thickness 257) can range from 10 µm to 140 µm, from 20 µm to 130 µm, from 30 µm to 120 µm, from 40 µm to 110 µm, from 50 µm to 100 µm µm, from 60 µm to 90 µm, 70 µm, 80 µm, 2 µm to 140 µm, from 4 µm to 130 µm, 6 µm to 120 µm, from 8 µm to 110 µm, from 10 µm to 100 µm, from 10 µm µm to one of 90 µm, 10 µm, 80 µm, 10 µm, 70 µm, 10 µm, 60 µm, 10 µm, 50 µm or within a range with any two of these values as one of the endpoints . In some embodiments, the OTP hard coat layer may be a single integral layer. In some embodiments, the OTP hard coat layer may be an inorganic-organic hybrid polymeric material layer or an organic polymeric material layer having a thickness in a range of 80 μm to 120 μm, including sub-ranges. For example, an OTP hard coat layer comprising an inorganic-organic hybrid polymeric material or an organic polymeric material can have from 80 μm to 110 μm, 90 μm to 100 μm, or any two of these values as endpoints a thickness within a range. In some embodiments, the OTP hard coat layer may be a layer of aliphatic or aromatic hexafunctional urethane acrylate material having a thickness in the range of 10 μm to 60 μm, including sub-ranges. For example, OTP hard coat layers comprising aliphatic or aromatic hexafunctional urethane acrylate materials can have 10 µm to 55 µm, 10 µm to 50 µm, 10 µm to 40 µm, 10 µm to 45 µm , 10 µm to 40 µm, 10 µm to 35 µm, 10 µm to 30 µm, 10 µm to 25 µm, 10 µm to 20 µm, or a thickness within a range having either of these values as one of the endpoints .

In some embodiments, the coating 251 (if provided) may also comprise one of an easy-to-clean coating, a low friction coating, an oleophobic coating, a diamond-like coating, a scratch-resistant coating, or a wear-resistant coating, or many. The scratch resistant coating may comprise oxynitride, eg, aluminum oxynitride or silicon oxynitride, having a thickness of about 500 microns or greater. In such embodiments, the abrasion resistant layer may comprise the same material as the scratch resistant coating. In some embodiments, the low friction coating may include a highly fluorinated silane coupling agent, eg, an alkyl fluorosilane with methoxy groups pendant on the silicon atom. In such embodiments, the easy-to-clean coating may comprise the same materials as the low friction coating. In other embodiments, the easy-to-clean coating may contain protonatable groups, eg, amines, eg, alkylaminosilanes with methoxy groups pendant on the silicon atom. In such embodiments, the oleophobic coating may comprise the same material as the easy-to-clean coating. In some embodiments, the diamond-like coating comprises carbon and can be produced by applying a high voltage potential in the presence of a hydrocarbon plasma.

Providing a first recess opposite a second recess reduces positioning of the first recess and the /or bending induced strain of the material in the second recess. Providing a reduced bending induced strain of the material positioned in the first pocket and/or the second pocket enables the use of a wider range of materials due to the reduced strain requirements on the material. For example, a harder and/or rigid material (eg, coating 251 ) can be positioned in the first recess, which can improve impact resistance, puncture resistance, abrasion resistance, and/or the foldable device Scratch resistance. Additionally, controlling the properties of the first material (eg, coating 251 ) positioned in the first pocket and the second material positioned in the second pocket can control the neutral axis of the foldable device and/or foldable substrate location, which may reduce (eg, mitigate, eliminate) the occurrence of mechanical instability, equipment fatigue, and/or equipment failure.

In some embodiments, as shown in Figures 2 and 4, foldable devices 101 and 401 may include release liners 271, although other substrates may be used in other embodiments (eg, based on the glass substrates and/or ceramic-based substrates) instead of the release liner 271 shown. In further embodiments, as shown, a release liner 271 or another substrate may be disposed on the adhesive layer 261 . In still further embodiments, as shown, the release liner 271 or another substrate may directly contact the second contact surface 265 of the adhesive layer 261 . The release liner 271 or another substrate may include a first major surface 273 and a second major surface 275 opposite the first major surface 273 . As shown, the release liner 271 or another substrate may be disposed on the adhesive layer 261 by attaching the second contact surface 265 of the adhesive layer 261 to the first major surface 273 of the release liner 271 or another substrate. In some embodiments, as shown, the first major surface 273 of the release liner 271 or another substrate may include a flat surface. In some embodiments, as shown, the second major surface 275 of the release liner 271 or another substrate includes a flat surface. The substrate including the release liner 271 may include paper and/or polymer. Exemplary examples of paper include kraft paper, machine-finished paper, poly-coated paper (eg, polymer-coated paper, cellophane, silicone-treated paper), or clay-coated paper. Exemplary examples of polymers include polyesters (eg, polyethylene terephthalate (PET)) and polyolefins (eg, low-density polyethylene (LDPE), high density polyethylene Ethylene (high-density polyethylene; HDPE), polypropylene (polypropylene; PP)).

In some embodiments, as shown in FIGS. 3 , 5 , and 12 , foldable devices 301 , 501 , and 1201 may include a display device 307 . In further embodiments, the display device 307 may be disposed on the adhesive layer 261 as shown. In further embodiments, as shown, the display device 307 may contact the second contact surface 265 of the adhesive layer 261 . In some embodiments, a foldable device similar to foldable device 301, 501 or 1201 can be produced by removing the release liner 271 of the foldable device 101 or 401 of FIGS. 2 and 4 and placing the display device This is achieved by attaching 307 to the second contact surface 265 of the adhesive layer 261 . Alternatively, the foldable device 301 may be produced without the additional step of removing the release liner 271 prior to attaching the display device 307 to the second contact surface 265 of the adhesive layer 261, eg, when the release liner is not 271 is applied to the second contact surface 265 of the adhesive layer 261 . The display device 307 may include a first main surface 303 and a second main surface 305 opposite to the first main surface 303 . As shown, the display device 307 may be disposed on the adhesive layer 261 by attaching the second contact surface 265 of the adhesive layer 261 to the second major surface 305 of the display device 307 . In some embodiments, as shown, the first major surface 303 of the display device 307 may comprise a flat surface. In some embodiments, as shown, the first major surface 303 of the display device 307 may comprise a flat surface. The display device 307 may include a liquid crystal display (LCD), an electrophoretic display (EPD), an organic light emitting diode display (OLED), or a plasma display panel (PDP) ). In some embodiments, the display device 307 may be part of a portable electronic device, such as a consumer electronic product, a smart phone, a tablet, a wearable device, or a laptop.

Embodiments of the present disclosure may include a consumer electronic product. The consumer electronic product may include a front surface, a rear surface and side surfaces. The consumer electronic product may further include electrical components at least partially within the housing. The electrical components may include a controller, a memory, and a display. The display may be at or adjacent to the front surface of the housing. The consumer electronic product may include a cover substrate disposed over the display. In some embodiments, at least one of a portion of the housing or the cover substrate includes a foldable device as discussed throughout this disclosure.

The foldable devices disclosed herein can be incorporated into another article, such as an article (or display article) having a display (eg, consumer electronics including mobile phones, tablets, computers, navigation systems, wearables devices (eg, watches, and the like), building items, transportation items (eg, cars, trains, airplanes, marine vessels, etc.), electrical items, or that may benefit from a certain degree of transparency, scratch resistance, abrasion resistance, or any of its combinations. An exemplary item in conjunction with any of the foldable devices disclosed herein is shown in FIGS. 13-14. Specifically, FIGS. 13-14 show a consumer electronic device 1300 including: a housing 1302 having a front surface 1304, a rear surface 1306 and a side surface 1308; electrical components (not shown) , which is at least partially or wholly within the housing and includes at least a controller, a memory, and a display 1310 at or adjacent to the front surface of the housing; and a cover substrate 1312 on the front surface of the housing at or on so that it is on the display. In some embodiments, at least one of the cover substrate 1312 or a portion of the housing 1302 can include any of the foldable devices disclosed herein, eg, a foldable substrate.

In some embodiments, the foldable substrate 206, 407, or 807 may comprise a glass-based substrate and/or a ceramic-based substrate, and the first portion 221, 421, or 821, the second portion 231, 431, or 831, and/or The central portion 281, 481 or 881 may contain one or more regions of compressive stress. In some embodiments, a region of compressive stress can be created by chemical strengthening. Chemical strengthening may include an ion exchange process in which ions in a surface layer are replaced by, or exchanged with, larger ions of the same valence or oxidation state. Methods of chemical strengthening will be discussed later. Without wishing to be bound by theory, chemically strengthening the first portion 221 , 421 or 821 , the second portion 231 , 431 or 831 and/or the central portion 281 , 481 or 881 may achieve good impact and/or puncture resistance (eg , resistant to damage to a drop height of about 15 centimeters (cm) or more, about 20 cm or more, and about 50 cm or more). Without wishing to be bound by theory, chemically strengthening the first portion 221 , 421 or 821 , the second portion 231 , 431 or 831 and/or the central portion 281 , 481 or 881 can achieve small (eg, less than about 10 mm or less) bends radius, since compressive stress from chemical strengthening can counteract the bending-induced tensile stress on the outermost surface of the substrate. The region of compressive stress may extend into a portion of the first portion and/or the second portion to a depth known as the compressive depth. As used herein, compressive depth means the depth at which the stress in the chemically strengthened substrates and/or portions described herein changes from compressive stress to tensile stress. Depending on the ion-exchange treatment and the thickness of the object being measured, the compression depth can be measured by means of a surface stress meter or a scattered light polariscope (SCALP, where the values reported in this paper are using a SCALP- 5) to the amount is. In cases where stress in the substrate and/or portion is generated by exchanging potassium ions into the substrate, a surface stress meter (eg, FSM-6000 (Orihara Industries, Ltd. (Japan))) is used to measure the compression depth. Unless otherwise specified, compressive stress (including surface CS) was measured by a surface stress meter (FSM) using a commercially available instrument manufactured by Orihara (eg, FSM-6000). Surface stress measurements rely on accurate measurements of the stress optical coefficient (SOC) related to the birefringence of the glass. Unless otherwise specified, SOC is measured according to Procedure C (Glass Disk Method) described in ASTM Standard C770-16 entitled "Standard Test Method for Measurement of Glass Stress-Optical Coefficient", the contents of which are Incorporated herein by reference in its entirety. SCALP was used to measure compression depth and central tension (CT) with stress generated by the exchange of sodium ions into the substrate and the object being measured was thicker than about 400 µm. Where the stress in the substrate and/or section is generated by exchanging both potassium and sodium ions into the substrate and/or section and the object being measured is thicker than about 400 µm, the compression depth and CT are determined by SCALP Measure. Without wishing to be bound by theory, the exchange depth of sodium may indicate the depth of compression, while the depth of exchange of potassium ions may indicate a change in the magnitude of compressive stress (rather than a change in stress from compression to tension). The refracted near-field (RNF; RNF method is described in US Pat. No. 8,854,623, entitled "Systems and methods for measuring a profile characteristic of a glass sample," which is incorporated herein by reference in its entirety ) method can also be used to derive a graphical representation of the stress distribution. When using the RNF method to derive a graphical representation of the stress distribution, the maximum central tension value provided by SCALP is used in the RNF method. The graphical representation of the stress distribution derived by the RNF is force balanced and calibrated with the maximum central tension value provided by the SCALP measurement. As used herein, "depth of layer" (DOL) means the depth to which ions have been exchanged into a substrate and/or moiety (eg, sodium, potassium). Through the present disclosure, when the maximum central tension cannot be directly measured by SCALP (such as when the object being measured is thinner than about 400 µm), the maximum compressive stress can be measured by the difference between the thickness of the substrate and twice the depth of compression. The maximum central tension is estimated by dividing the difference between compressive stress and the compression depth by the product of the compression depth measured by the FSM.

In some embodiments, the first portion 221 , 421 or 821 including the glass-based portion and/or the ceramic-based portion may include a first region of compressive stress at the first surface region 223 , 423 or 823 , which may be free from The first surface region 223, 432 or 823 extends to the first compression depth. In some embodiments, the first portion 221 , 421 or 821 including the first glass-based and/or ceramic-based portion can include a second compressive stress region at the second surface region 225 , 425 or 825 , which can be obtained from The second surface region 225, 425 or 825 extends to the second compression depth. In some embodiments, the first depth of compression and/or the second depth of compression as a percentage of substrate thickness 211 , 411 or 811 may be about 1% or more, about 5% or more, about 10% or more greater, about 30% or less, about 25% or less, or about 20% or less. In some embodiments, the first depth of compression and/or the second depth of compression, as a percentage of substrate thickness 211, 411 or 811, may range from about 1% to about 30%, from about 5% to about 30%, from A range from about 5% to about 25%, from about 5% to about 20%, from about 10% to about 30%, from about 10% to about 25%, from about 10% to about 20%, or any between in a range or sub-range. In further embodiments, the first depth of compression and/or the second depth of compression as a percentage of substrate thickness 211, 411 or 811 may be about 10% or less, eg, from about 1% to about 10%, from about 1% to about 10%. From about 1% to about 8%, from about 3% to about 8%, from about 5% to about 8%, or any range or subrange therebetween.

In further embodiments, the first compression depth may be substantially equal to the second compression depth. In some embodiments, the first compression depth and/or the second compression depth can be about 1 μm or more, about 10 μm or more, about 30 μm or more, about 50 μm or more, about 200 μm or less, about 150 μm or less, about 100 μm or less, or about 60 μm or less. In some embodiments, the first compression depth and/or the second compression depth may range from about 1 μm to about 200 μm, from about 1 μm to about 150 μm, from about 10 μm to about 150 μm, from about 10 μm to about 100 µm, from about 30 µm to about 100 µm, from about 30 µm to about 60 µm, from about 50 µm to about 60 µm, or any range or sub-range therebetween. by providing a first depth of compression and/or a second depth of compression comprising the first glass-based and/or ceramic-based portion including a first depth of compression and/or a second depth of compression in a range from about 1% to about 30% of the A first part that achieves good impact resistance and/or puncture resistance.

In some embodiments, the first region of compressive stress may include a first maximum compressive stress. In some embodiments, the second region of compressive stress may include a second maximum compressive stress. In further embodiments, the first maximum compressive stress and/or the second maximum compressive stress may be about 100 megapascals (MPa) or more, about 300 MPa or more, about 500 MPa or more, about 600 MPa or more Greater, about 700 MPa or more, about 1,500 MPa or less, about 1,200 MPa or less, about 1,000 MPa or less, or about 800 MPa or less. In further embodiments, the first maximum compressive stress and/or the second maximum compressive stress may range from about 100 MPa to about 1,500 MPa, from about 100 MPa to about 1,200 MPa, from about 300 MPa to about 1,200 MPa, from about 300 MPa to about 1,000 MPa, from about 500 MPa to about 1,000 MPa, from about 600 MPa to about 1,000 MPa, from about 600 MPa to about 1,000 MPa, from about 700 MPa to about 1,000 MPa, from about 700 MPa to about 800 MPa in one range or any range or sub-range therebetween. Good impact resistance and/or puncture resistance may be achieved by providing a first maximum compressive stress and/or a second maximum compressive stress in a range from about 100 MPa to about 1,500 MPa.

In some embodiments, the first portion 221, 421, or 821 may include a first layer depth of one or more alkali metal ions associated with the first compressive stress region and the first layer depth. In some embodiments, the first portion 221, 421 or 821 may include a second layer depth of one or more alkali metal ions associated with the second compressive stress region and the second layer depth. As used herein, the layer depth of the one or more alkali metal ions can include sodium, potassium, rubidium, cesium, and/or francium. In some embodiments, the one or more alkali ions of the first layer depth of the one or more alkali ions and/or the one or more alkali ions of the second layer depth of the one or more alkali ions comprise potassium. In some embodiments, the depth of the first layer and/or the depth of the second layer as a percentage of the substrate thickness 211 , 411 or 811 may be about 1% or more, about 5% or more, about 10% or more greater, about 40% or less, about 35% or less, about 30% or less, about 25% or less, or about 20% or less. In some embodiments, the depth of the first layer and/or the depth of the second layer as a percentage of the substrate thickness 211, 411 or 811 may be from about 1% to about 40%, from about 1% to about 35%, from from about 1% to about 30%, from about 1% to about 25%, from about 1% to about 20%, from about 5% to about 30%, from about 5% to about 25%, from about 5% to about 20%, from about 10% to about 30%, from about 10% to about 25%, from about 10% to about 20%, or any range or sub-range therebetween. In further embodiments, the depth of the first layer of the one or more alkali metal ions and/or the depth of the second layer of the one or more alkali metal ions as a percentage of the substrate thickness 211, 411 or 811 may be about 10% or more Small, for example, from about 1% to about 10%, from about 1% to about 8%, from about 3% to about 8%, from about 5% to about 8%, or any range or subrange therebetween. In some embodiments, the depth of the first layer of the one or more alkali metal ions and/or the depth of the second layer of the one or more alkali metal ions may be about 1 μm or more, about 10 μm or more, about 30 μm or larger, about 50 μm or larger, about 200 μm or smaller, about 150 μm or smaller, about 100 μm or smaller, or about 60 μm or smaller. In some embodiments, the depth of the first layer of the one or more alkali metal ions and/or the depth of the second layer of the one or more alkali metal ions may be from about 1 μm to about 200 μm, from about 1 μm to about 150 μm , from about 10 µm to about 150 µm, from about 10 µm to about 100 µm, from about 30 µm to about 100 µm, from about 30 µm to about 60 µm, from about 50 µm to about 60 µm, or a range therebetween in any range or sub-range.

In some embodiments, the first portion 221, 421 or 821 may include a first tensile stress region. In some embodiments, the first region of tensile stress may be positioned between the first region of compressive stress and the second region of compressive stress. In some embodiments, the first tensile stress region may include a first maximum tensile stress. In further embodiments, the first maximum tensile stress can be about 10 MPa or more, about 20 MPa or more, about 30 MPa or more, about 100 MPa or less, about 80 MPa or less or about 60 MPa or less. In further embodiments, the first maximum tensile stress may be in the range from about 10 MPa to about 100 MPa, from about 10 MPa to about 80 MPa, from about 10 MPa to about 60 MPa, from about 20 MPa to about 100 MPa, One range from about 20 MPa to about 80 MPa, from about 20 MPa to about 60 MPa, from about 30 MPa to about 100 MPa, from about 30 MPa to about 80 MPa, from about 30 MPa to about 60 MPa, or therebetween in any range or subrange. Providing a first maximum tensile stress in a range from about 10 MPa to about 100 MPa can achieve good impact and/or puncture resistance while providing low energy rupture, as discussed below.

In some embodiments, the first portion 221, 421 or 821 may comprise a first average potassium concentration on an oxide basis. As used herein, "oxide-based" means that a component is measured as if a non-oxygen component of the compound was converted to the specified oxide form or to a fully oxidized oxide if the specific oxide form is not specified. For example, oxide-based sodium (Na) refers to the amount in terms of sodium _oxide (Na2O), and oxide-based potassium refers to the amount in terms of potassium _oxide (K2O). Thus, the components need not actually be in the designated oxide form or in the fully oxidized oxide form in order to count the components on an "oxide-based" measure. Thus, an "oxide-based" measurement for a specific component involves the conceptual conversion of a material containing a specific component's non-oxygen element into the specified oxide form or fully oxidized oxide (if the oxide is used as the The specific oxide form is not specified before the base calculated concentration). In some embodiments, the first average potassium concentration on an oxide basis may be about 10 parts per million (ppm) or greater, about 50 ppm or greater, about 200 ppm or greater, about 500 ppm or greater. Greater, about 1,000 ppm or more, about 2,000 ppm or more, about 300,000 ppm or less, about 100,000 ppm or less, about 50,000 ppm or less, about 20,000 ppm or less, about 10,000 ppm or less or about 5,000 ppm or less. In some embodiments, the first average potassium concentration on an oxide basis may be from about 10 ppm to about 300,000 ppm, from about 50 ppm to about 300,000 ppm, from about 50 ppm to about 100,000 ppm, from about 200 ppm to about 100,000 ppm, from about 200 ppm to about 50,000 ppm, from about 500 ppm to about 50,000 ppm, from about 500 ppm to about 20,000 ppm, from about 1,000 ppm to about 20,000 ppm, from about 2,000 ppm to about 10,000 ppm, In a range from about 2,000 ppm to about 5,000 ppm or any range or sub-range therebetween. Without wishing to be bound by theory, the average potassium concentration included potassium introduced via chemical strengthening and potassium in the prototype foldable substrate.

In some embodiments, the second portion 231 , 431 or 831 including the second glass-based and/or ceramic-based portion may include a third region of compressive stress at the third surface region 233 , 433 or 833 , which may Extends from the third surface region 233, 433 or 833 to a third depth of compression. In some embodiments, the second portion 231 , 431 or 831 including the second glass-based and/or ceramic-based portion may include a fourth region of compressive stress at the fourth surface region 235 , 435 or 835 , which may Extends from the fourth surface region 235 to a fourth compression depth. In some embodiments, the third depth of compression and/or the fourth depth of compression as a percentage of substrate thickness 211 , 411 or 811 may be about 1% or more, about 5% or more, about 10% or more greater, about 30% or less, about 25% or less, or about 20% or less. In some embodiments, the third depth of compression and/or the fourth depth of compression as a percentage of the substrate thickness 211, 411 or 811 may be from about 1% to about 30%, from about 5% to about 30%, from A range from about 5% to about 25%, from about 5% to about 20%, from about 10% to about 30%, from about 10% to about 25%, from about 10% to about 20%, or any between in a range or sub-range. In further embodiments, the third compression depth may be substantially equal to the fourth compression depth. In some embodiments, the third compression depth and/or the fourth compression depth can be about 1 μm or more, about 10 μm or more, about 30 μm or more, about 50 μm or more, about 200 μm or less, about 150 μm or less, about 100 μm or less, or about 60 μm or less. In some embodiments, the third compression depth and/or the fourth compression depth may be from about 1 μm to about 200 μm, from about 1 μm to about 150 μm, from about 10 μm to about 150 μm, from about 10 μm to about 100 µm, from about 30 µm to about 100 µm, from about 30 µm to about 60 µm, from about 50 µm to about 60 µm, or any range or sub-range therebetween. By providing a second depth of compression comprising glass-based and/or ceramic-based portions including a third depth of compression and/or a fourth depth of compression in a range from about 1% to about 30% of the thickness of the substrate In part, good impact resistance and/or puncture resistance can be achieved.

In some embodiments, the third region of compressive stress may include a third maximum compressive stress. In some embodiments, the fourth region of compressive stress may include a fourth maximum compressive stress. In further embodiments, the third maximum compressive stress and/or the fourth maximum compressive stress may be about 100 megapascals (MPa) or more, about 300 MPa or more, about 500 MPa or more, about 600 MPa or more Greater, about 700 MPa or more, about 1,500 MPa or less, about 1,200 MPa or less, about 1,000 MPa or less, or about 800 MPa or less. In further embodiments, the third maximum compressive stress and/or the fourth maximum compressive stress may range from about 100 MPa to about 1,500 MPa, from about 100 MPa to about 1,200 MPa, from about 300 MPa to about 1,200 MPa, from about 300 MPa to about 1,000 MPa, from about 500 MPa to about 1,000 MPa, from about 600 MPa to about 1,000 MPa, from about 600 MPa to about 1,000 MPa, from about 700 MPa to about 1,000 MPa, from about 700 MPa to about 800 MPa in one range or any range or sub-range therebetween. Good impact resistance and/or puncture resistance may be achieved by providing a third maximum compressive stress and/or a fourth maximum compressive stress in a range from about 100 MPa to about 1,500 MPa.

In some embodiments, the second portion 231, 431 or 831 may include a third layer depth of one or more alkali metal ions associated with the third compressive stress region and the third layer depth. In some embodiments, the second portion 231 may include a fourth layer depth of one or more alkali metal ions associated with a fourth region of compressive stress and a fourth depth of compression. In some embodiments, the one or more alkali ions at the third layer depth and/or the one or more alkali ions at the fourth layer depth comprise potassium. In some embodiments, the depth of the third layer and/or the depth of the fourth layer as a percentage of the substrate thickness 211 , 411 or 811 may be about 1% or more, about 5% or more, about 10% or more greater, about 40% or less, about 35% or less, about 30% or less, about 25% or less, or about 20% or less. In some embodiments, the third depth of compression and/or the fourth depth of compression as a percentage of the substrate thickness 211, 411 or 811 may be from about 1% to about 40%, from about 1% to about 35%, from from about 1% to about 30%, from about 1% to about 25%, from about 1% to about 20%, from about 5% to about 30%, from about 5% to about 25%, from about 5% to about 20%, from about 10% to about 30%, from about 10% to about 25%, from about 10% to about 20%, or any range or sub-range therebetween. In further embodiments, the depth of the third layer of the one or more alkali metal ions and/or the depth of the fourth layer of the one or more alkali metal ions as a percentage of the substrate thickness 211, 411 or 811 may be about 10% or more Small, for example, from about 1% to about 10%, from about 1% to about 8%, from about 3% to about 8%, from about 5% to about 8%, or any range or subrange therebetween. In some embodiments, the depth of the third layer of the one or more alkali metal ions and/or the depth of the fourth layer of the one or more alkali metal ions may be about 1 μm or more, about 10 μm or more, about 30 μm or larger, about 50 μm or larger, about 200 μm or smaller, about 150 μm or smaller, about 100 μm or smaller, or about 60 μm or smaller. In some embodiments, the depth of the third layer of the one or more alkali metal ions and/or the depth of the fourth layer of the one or more alkali metal ions may be from about 1 μm to about 200 μm, from about 1 μm to about 150 μm , from about 10 µm to about 150 µm, from about 10 µm to about 100 µm, from about 30 µm to about 100 µm, from about 30 µm to about 60 µm, from about 50 µm to about 60 µm, or a range therebetween in any range or sub-range.

In some embodiments, the second portion 231, 431 or 831 may include a second tensile stress region. In some embodiments, the second region of tensile stress may be positioned between the third region of compressive stress and the fourth region of compressive stress. In some embodiments, the second tensile stress region may include a second maximum tensile stress. In further embodiments, the second maximum tensile stress may be about 10 MPa or more, about 20 MPa or more, about 30 MPa or more, about 100 MPa or less, about 80 MPa or less or about 60 MPa or less. In further embodiments, the second maximum tensile stress may be in the range from about 10 MPa to about 100 MPa, from about 10 MPa to about 80 MPa, from about 10 MPa to about 60 MPa, from about 20 MPa to about 100 MPa, One range from about 20 MPa to about 80 MPa, from about 20 MPa to about 60 MPa, from about 30 MPa to about 100 MPa, from about 30 MPa to about 80 MPa, from about 30 MPa to about 60 MPa, or therebetween in any range or subrange. Providing a second maximum tensile stress in a range from about 10 MPa to about 100 MPa can achieve good impact and/or puncture resistance while providing low energy rupture, as discussed below.

In some embodiments, the second portion 231, 431 or 831 may comprise a second average potassium concentration on an oxide basis. In some embodiments, the second average potassium concentration on an oxide basis can be about 10 parts per million (ppm) or greater, about 50 ppm or greater, about 200 ppm or greater, about 500 ppm or greater. Greater, about 1,000 ppm or more, about 2,000 ppm or more, about 300,000 ppm or less, about 100,000 ppm or less, about 50,000 ppm or less, about 20,000 ppm or less, about 10,000 ppm or less or about 5,000 ppm or less. In some embodiments, the second average potassium concentration on an oxide basis may be from about 10 ppm to about 300,000 ppm, from about 50 ppm to about 300,000 ppm, from about 50 ppm to about 100,000 ppm, from about 200 ppm to about 100,000 ppm, from about 200 ppm to about 50,000 ppm, from about 500 ppm to about 50,000 ppm, from about 500 ppm to about 20,000 ppm, from about 1,000 ppm to about 20,000 ppm, from about 2,000 ppm to about 10,000 ppm, In a range from about 2,000 ppm to about 5,000 ppm, or any range or sub-range therebetween.

In some embodiments, the first compression depth may be substantially equal to the third compression depth. In some embodiments, the second compression depth may be substantially equal to the fourth compression depth. In some embodiments, the first maximum compressive stress may be substantially equal to the third maximum compressive stress. In some embodiments, the second maximum compressive stress may be substantially equal to the fourth maximum compressive stress. In some embodiments, the depth of the first layer of the one or more alkali metal ions may be substantially equal to the depth of the third layer of the one or more alkali metal ions. In some embodiments, the depth of the second layer of the one or more alkali metal ions may be substantially equal to the depth of the fourth layer of the one or more alkali metal ions. In some embodiments, the first average potassium concentration may be substantially equal to the second average potassium concentration.

In some embodiments, the central portion 281 , 481 or 881 including the glass-based portion and/or the ceramic-based portion may include a first central compressive stress region at the first central surface region 209 , 409 or 809 , which Can extend from the first central surface region 209, 409 or 809 to a first central compression depth. In some embodiments, the central portion 281 , 481 or 881 including the glass-based and/or ceramic-based portion can include a second central compressive stress region at the second central surface region 219 , 419 or 819 , which can be The second central surface region 219, 419 or 819 extends to a second central compression depth. In some embodiments, the first central compression depth and/or the second central compression depth as a percentage of the central thickness 227, 427 or 827 may be about 1% or more, about 5% or more, about 10% or greater, about 30% or less, about 25% or less, or about 20% or less. In some embodiments, the first central compression depth and/or the second central compression depth as a percentage of the central thickness 227, 427 or 827 may be from about 1% to about 30%, from about 5% to about 30% , from about 5% to about 25%, from about 5% to about 20%, from about 10% to about 30%, from about 10% to about 25%, from about 10% to about 20% in a range or therebetween in any range or sub-range. In further embodiments, the first central compression depth and/or the second central compression depth as a percentage of the central thickness 227, 427 or 827 may be about 10% or greater, eg, from about 10% to about 30% , from about 10% to about 25%, from about 15% to about 25%, from about 15% to about 20%, or any range or subrange therebetween.

In further embodiments, the first central compression depth may be substantially equal to the second central compression depth. In some embodiments, the first central compression depth and/or the second central compression depth may be about 1 μm or more, about 10 μm or more, about 30 μm or more, about 50 μm or more, about 200 μm or less, about 150 μm or less, about 100 μm or less, or about 60 μm or less. In some embodiments, the first central compression depth and/or the second central compression depth may range from about 1 μm to about 200 μm, from about 1 μm to about 150 μm, from about 10 μm to about 150 μm, from about In a range of 10 µm to about 100 µm, from about 30 µm to about 100 µm, from about 30 µm to about 60 µm, from about 50 µm to about 60 µm, or any range or sub-range therebetween. By providing a glass-based and/or ceramic-based portion comprising a first central compression depth and/or a second central compression depth in a range from about 1% to about 30% of the thickness of the center Center section for good impact and/or puncture resistance.

In some embodiments, the first central compressive stress region may include a first central maximum compressive stress. In some embodiments, the second central compressive stress region may include a second central maximum compressive stress. In further embodiments, the first central maximum compressive stress and/or the second central maximum compressive stress may be about 100 megapascals (MPa) or greater, about 300 MPa or greater, about 500 MPa or greater, about 600 MPa or greater MPa or more, about 700 MPa or more, about 1,500 MPa or less, about 1,200 MPa or less, about 1,000 MPa or less, or about 800 MPa or less. In further embodiments, the first central maximum compressive stress and/or the second central maximum compressive stress may range from about 100 MPa to about 1,500 MPa, from about 100 MPa to about 1,200 MPa, from about 300 MPa to about 1,200 MPa, from about 300 MPa to about 1,000 MPa, from about 500 MPa to about 1,000 MPa, from about 600 MPa to about 1,000 MPa, from about 600 MPa to about 1,000 MPa, from about 700 MPa to about 1,000 MPa, from about 700 MPa to In a range of about 800 MPa or any range or sub-range therebetween. Good impact resistance and/or puncture resistance can be achieved by providing a first central maximum compressive stress and/or a second central maximum compressive stress in one of from about 100 MPa to about 1,500 MPa.

In some embodiments, the central portion 281, 481 or 881 may comprise a first central layer depth of one or more alkali metal ions associated with the first central compressive stress region and the first central layer depth. In some embodiments, the central portion 281, 481, or 881 may include a second central layer depth of one or more alkali metal ions associated with the second central compressive stress region and the second central layer depth. In some embodiments, the one or more alkali ions of the first central layer depth of the one or more alkali ions and/or the second central layer depth of the one or more alkali ions comprise potassium. In some embodiments, the first center layer depth and/or the second center layer depth as a percentage of the center thickness 227, 427, 827 may be about 1% or more, about 5% or more, about 10% or greater, about 40% or less, about 35% or less, about 30% or less, about 25% or less, or about 20% or less. In some embodiments, the first center layer depth and/or the second center layer depth as a percentage of the center thickness 227, 427, or 827 may be from about 1% to about 40%, from about 1% to about 35% , from about 1% to about 30%, from about 1% to about 25%, from about 1% to about 20%, from about 5% to about 30%, from about 5% to about 25%, from about 5% to about 20%, from about 10% to about 30%, from about 10% to about 25%, from about 10% to about 20%, or any range or sub-range therebetween. In further embodiments, the first center layer depth of the one or more alkali metal ions and/or the second center layer depth of the one or more alkali metal ions as a percentage of the center thickness 227, 427 or 827 may be about 10% or less, for example, from about 1% to about 10%, from about 1% to about 8%, from about 3% to about 8%, from about 5% to about 8%, or any range or sub- scope. In some embodiments, the first central layer depth of the one or more alkali metal ions and/or the second central layer depth of the one or more alkali metal ions may be about 1 μm or more, about 10 μm or more, about 30 μm or more, about 50 μm or more, about 200 μm or less, about 150 μm or less, about 100 μm or less, or about 60 μm or less. In some embodiments, the first central layer depth of the one or more alkali metal ions and/or the second central layer depth of the one or more alkali metal ions may be from about 1 μm to about 200 μm, from about 1 μm to about A range of 150 µm, from about 10 µm to about 150 µm, from about 10 µm to about 100 µm, from about 30 µm to about 100 µm, from about 30 µm to about 60 µm, from about 50 µm to about 60 µm or any range or subrange therebetween.

In some embodiments, the first compression depth and/or the third compression depth may be greater than the first central compression depth. In some embodiments, the second compression depth and/or the fourth compression depth may be greater than the second central compression depth. In some embodiments, the first layer depth and/or the third layer depth may be greater than the first center layer depth. In some embodiments, the second layer depth and/or the fourth layer depth may be greater than the second center layer depth.

In some embodiments, the central portion 281, 481 or 881 may comprise a central tensile stress region. In some embodiments, a central tensile stress region may be positioned between the first central compressive stress region and the second central compressive stress region. In some embodiments, the central tensile stress region may contain a central maximum tensile stress. In further embodiments, the central maximum tensile stress can be about 125 MPa or more, about 150 MPa or more, about 200 MPa or more, about 375 MPa or less, about 300 MPa or less, or about 250 MPa or more MPa or less. In further embodiments, the central maximum tensile stress may range from about 125 MPa to about 375 MPa, from about 125 MPa to about 300 MPa, from about 125 MPa to about 250 MPa, from about 150 MPa to about 375 MPa, from A range from about 150 MPa to about 300 MPa, from about 150 MPa to about 250 MPa, from about 200 MPa to about 375 MPa, from about 200 MPa to about 300 MPa, from about 200 MPa to about 250 MPa, or any one therebetween in a range or sub-range. Providing a central maximum tensile stress in a range from about 125 MPa to about 375 MPa can achieve a low minimum bend radius.

In some embodiments, the first maximum tensile stress may be substantially equal to the second maximum tensile stress. In some embodiments, the first maximum tensile stress and the second maximum tensile stress may be less than the central maximum tensile stress. Providing a first maximum tensile stress and a second maximum tensile stress in the central portion that is less than the central maximum tensile stress enables low energy rupture while achieving a low minimum bend radius. In some embodiments, the absolute difference between the central maximum tensile stress and the first maximum tensile stress and/or the second maximum tensile stress may be about 0 MPa or more, about 1 MPa or more, about 5 MPa or more, about 50 MPa or less, about 20 MPa or less, about 10 MPa or less, or about 8 MPa or less. In some embodiments, the absolute difference between the central maximum tensile stress and the first maximum tensile stress and/or the second maximum tensile stress may be from about 0 MPa to about 50 MPa, from about 1 MPa to about 50 MPa, from about 1 MPa to about 20 MPa, from about 5 MPa to about 20 MPa, from about 5 MPa to about 10 MPa, from about 5 MPa to about 8 MPa, or in any range or sub-range therebetween .

In some embodiments, the first compression depth may be substantially equal to the first central compression depth. In still further embodiments, the third compression depth may be substantially equal to the first central compression depth. In some embodiments, the second compression depth may be substantially equal to the second central compression depth. In further embodiments, the fourth compression depth may be substantially equal to the second central compression depth. As discussed above, the center thickness can be less than the substrate thickness (eg, in a range from about 0.5% to about 13%), which can make the center maximum center tension greater than the first and second maximum center tensions, even if the first The compression depths of one portion, the second portion and the central portion may be substantially the same.

In some embodiments, the first transition portion (eg, first transition portion 853 ) and/or the second transition portion may include a region of transitional tensile stress. The transitional tensile stress region may contain a transitional maximum tensile stress. In further embodiments, the transitional maximum tensile stress may be about 125 MPa or more, about 150 MPa or more, about 200 MPa or more, about 500 MPa or more, about 375 MPa or less, about 300 MPa or more MPa or less or about 250 MPa or less. In further embodiments, the transitional maximum tensile stress may range from about 125 MPa to about 500 MPa, from about 125 MPa to about 375 MPa, from about 125 MPa to about 300 MPa, from about 125 MPa to about 250 MPa, from about 150 MPa to about 375 MPa, from about 150 MPa to about 300 MPa, from about 150 MPa to about 250 MPa, from about 200 MPa to about 375 MPa, from about 200 MPa to about 300 MPa, from about 200 MPa to about 250 MPa in one range or any range or sub-range therebetween. In further embodiments, the transition maximum tensile stress may be greater than the central maximum tensile stress. In further embodiments, the transition maximum tensile stress may be greater than the first maximum tensile stress and/or the second maximum tensile stress. Providing a transition maximum tensile stress greater than the central maximum tensile stress may counteract the strain between the first or second portion and the first and/or second transition portion during folding. Providing a transition maximum tensile stress greater than the first maximum tensile stress and/or the second maximum tensile stress may counteract the strain between the central portion and the first transition portion and/or the second transition portion during folding.

In some embodiments, the central portion 281, 481, or 881 may comprise an oxide-based central average potassium concentration. In some embodiments, the central average potassium concentration on an oxide basis may be about 10 parts per million (ppm) or greater, about 50 ppm or greater, about 200 ppm or greater, about 500 ppm or greater Greater, about 1,000 ppm or more, about 2,000 ppm or more, about 300,000 ppm or less, about 100,000 ppm or less, about 50,000 ppm or less, about 20,000 ppm or less, about 10,000 ppm or less, or About 5,000 ppm or less. In some embodiments, the central average potassium concentration on an oxide basis can range from about 10 ppm to about 300,000 ppm, from about 50 ppm to about 300,000 ppm, from about 50 ppm to about 100,000 ppm, from about 200 ppm to about 200 ppm to about 100,000 ppm, from about 200 ppm to about 50,000 ppm, from about 500 ppm to about 50,000 ppm, from about 500 ppm to about 20,000 ppm, from about 1,000 ppm to about 20,000 ppm, from about 2,000 ppm to about 10,000 ppm, from In a range of about 2,000 ppm to about 5,000 ppm or any range or sub-range therebetween.

Foldable substrates (eg, foldable substrates 206, 407, or 807) can experience various types of mechanical instabilities. Throughout this disclosure, mechanical instability includes localized mechanical instability, as well as systemic mechanical instability. As used herein, localized mechanical instability manifests as a deviation (eg, a plurality of deviations) from a plane of a surface (eg, a first central surface region) without generally distorting the surface, eg, buckling and/or wrinkling. As used herein, systemic mechanical instability manifests as the distortion of all surfaces from a plane, eg, warping. As shown in Figure 54, the horizontal axis 5401 (eg, the x-axis) includes the center thickness (eg, the center thickness 227, 427, or 827), and the vertical axis 5403 (eg, the y-axis) includes the substrate thickness 211, 411, or 811 . The shape represented by the curve in Figure 54 corresponds to the type (or types) of mechanical instability observed for the combination of center thickness and substrate thickness at that location. Diamond 5409 corresponds to buckling. Circles 5407 correspond to buckling and wrinkling. Triangles 5413 correspond to warping and wrinkling. Square 5411 corresponds to warping. Curves 5404 and 5405 separate the combination of center thickness and substrate thickness, where only broad instability (eg, warpage) occurs, as opposed to the combination where localized instability occurs. Curve 5405 is a line indicating the observed localized instability when the substrate thickness is greater than about 4 times the center thickness minus 71 microns. More specifically, curve 5405 is a line indicating that localized instabilities are observed when the substrate thickness is greater than about 4.1 times the center thickness minus 71.37 microns. Curves 5404 and 5405 indicate that some instabilities (eg, localized mechanical instability) encountered with thinner foldable substrates (eg, above curves 5404 and/or 5405 ) may be encountered with thicker foldable substrates. The resulting instability (eg, below curves 2804 and/or 2805) is different.

The onset of mechanical instability (eg, localized mechanical instability) can occur when the critical strain (eg, critical buckling strain) of a portion (eg, the central portion) of the foldable substrate is exceeded. For example, the critical buckling strain for a center portion of a foldable substrate 807 similar to that of Figure 8 (including a width of a center portion 881 of 20 mm) can be calculated by multiplying ¹⁰ times the square of the center thickness minus 23 times the center thickness Add the sum of 0.0006 to estimate. For example, without wishing to be bound by theory, the critical buckling strain of a central portion of a foldable substrate 807 similar to Figure 8 (including a central thickness 827 of 30 µm) can be divided by 3 x ^10-7 by the central portion The square of the width of 281 is estimated.

The chemical strengthening induced compressive strain in the central portion of the foldable substrate produced from the chemically strengthened foldable substrate can be proportional to the product of: the network expansion coefficient (B), the concentration difference (C), and the layer depth at the central portion Divide by the difference between the center thickness and the layer depth of the first portion (or second portion) divided by the substrate thickness. In some embodiments, the concentration difference can be minimized by minimizing the difference in concentration and/or by minimizing the difference between the layer depth of the central portion divided by the central thickness and the layer depth of the first portion (or second portion) divided by the substrate thickness Reduce the compressive strain (eg, to a level below the critical buckling strain) of the chemical strengthening induced compressive strain in the central portion. As used herein, network expansion coefficient refers to a foldable substrate (eg, first portion, second portion, as a result of an increase in the concentration of one or more alkali ions exchanged into the substrate (eg, as a result of chemical strengthening) , the central part) of the volume expansion. In some embodiments, the network expansion constant of the first portion and/or the network expansion constant of the second portion may be substantially equal to the network expansion constant of the central portion, eg, if prior to chemical strengthening, the network expansion constant of the first portion and/or the second portion Both parts and the central part consist of the same material.

As used herein, the concentration difference of a portion refers to the difference between the concentration at the surface of the portion and the concentration in the bulk of the portion. Unless otherwise indicated, concentrations and concentration differences refer to the concentration of one or more alkali metal ions associated with chemical strengthening and/or compressive stress regions. In some embodiments, the concentration and/or concentration difference may refer to the concentration of the oxide-based potassium. In some embodiments, the concentration in the bulk of the first portion and/or the concentration in the bulk of the second portion may be substantially equal to the concentration in the bulk of the central portion, eg, if the first portion and/or The second portion and the central portion comprise the same material prior to chemical strengthening, and/or if the layer depth of one portion is less than about 45% of the thickness of the corresponding portion. In some embodiments, the first oxide-based average potassium concentration of the first portion may be greater than the oxide-based potassium concentration in the bulk of the first portion. In some embodiments, the second average oxide-based potassium concentration of the second portion may be greater than the oxide-based potassium concentration in the bulk of the second portion. In some embodiments, the oxide-based central average potassium concentration of the central portion may be greater than the oxide-based potassium concentration in the bulk of the central portion.

As used herein, the difference in concentration between parts means the difference between one average concentration and another average concentration. Unless otherwise indicated, concentrations and concentration differences refer to the concentration of one or more alkali metal ions associated with chemical strengthening and/or compressive stress regions. In some embodiments, the concentration and/or concentration difference may refer to the concentration of the oxide-based potassium. In some embodiments, the absolute difference between the oxide-based first average potassium concentration and the oxide-based central average potassium concentration may be about 1 ppm or greater, about 10 ppm or greater, about 20 ppm or more, about 50 ppm or more, about 70 ppm, about 500 ppm or less, about 200 ppm or less, about 100 ppm or less, or about 85 ppm or less. In some embodiments, the absolute difference between the oxide-based first average potassium concentration and the oxide-based central average potassium concentration may be from about 1 ppm to about 500 ppm, from about 10 ppm to about 500 ppm, from about 10 ppm to about 200 ppm, from about 20 ppm to about 200 ppm, from about 20 ppm to about 100 ppm, from about 50 ppm to about 100 ppm, from about 70 ppm to about 100 ppm, from about In a range of 70 ppm to about 85 ppm or any range or sub-range therebetween. In some embodiments, the absolute difference between the oxide-based second average potassium concentration and the oxide-based central average potassium concentration can be about 1 ppm or greater, about 10 ppm or greater, about 20 ppm or more, about 50 ppm or more, about 70 ppm, about 500 ppm or less, about 200 ppm or less, about 100 ppm or less, or about 85 ppm or less. In some embodiments, the absolute difference between the oxide-based second average potassium concentration and the oxide-based central average potassium concentration can be from about 1 ppm to about 500 ppm, from about 10 ppm to about 500 ppm, from about 10 ppm to about 200 ppm, from about 20 ppm to about 200 ppm, from about 20 ppm to about 100 ppm, from about 50 ppm to about 100 ppm, from about 70 ppm to about 100 ppm, from about In a range of 70 ppm to about 85 ppm or any range or sub-range therebetween. For example, the chemical strengthening induced strain can be less than the critical buckling strain for a foldable substrate comprising a center thickness of 30 μm and a center width of 20 mm when the absolute difference between the mean concentrations is about 75 ppm or less. In some embodiments, the absolute difference between the oxide-based first average potassium concentration and the oxide-based central average potassium concentration may be less than 70 ppm, eg, at from about 0.1 ppm to about 60 ppm, from about 0.1 ppm to about 50 ppm, from about 0.1 ppm to about 40 ppm, from about 0.1 ppm to about 30 ppm, from about 0.1 ppm to about 20 ppm, from about 0.5 ppm to about 20 ppm, from about 0.5 ppm to about In a range of about 10 ppm, from about 1 ppm to about 10 ppm, from about 5 ppm to about 10 ppm, or any range or sub-range therebetween. In some embodiments, the absolute difference between the oxide-based second average potassium concentration and the oxide-based central average potassium concentration can be less than 70 ppm, for example, at from about 0.1 ppm to about 50 ppm, one of from about 0.1 ppm to about 20 ppm, from about 0.5 ppm to about 20 ppm, from about 0.5 ppm to about 10 ppm, from about 1 ppm to about 10 ppm, from about 5 ppm to about 10 ppm, or therebetween in any range or subrange. Providing the absolute difference between the first average concentration and/or the second average concentration of oxide-based potassium and the central average concentration can provide reduced chemical strengthening induced strain (eg, below a critical buckling strain) and/or Or reduce the occurrence of mechanical instability in foldable substrates and/or foldable devices.

In some embodiments, the absolute difference between the depth of the first layer divided by the thickness of the substrate and the depth of the first center layer divided by the thickness of the center may be about 0.001% or more, about 0.002% or more, about 0.005%, or greater, about 1% or less, about 0.2% or less, about 0.1% or less, about 0.05% or less, about 0.01% or less, or about 0.008% or less. In some embodiments, the absolute difference between the depth of the first layer divided by the thickness of the substrate and the depth of the first center layer divided by the thickness of the center may be from about 0.001% to about 1%, from about 0.002% to about 1%, from about 0.002% to about 0.2%, from about 0.005% to about 0.2%, from about 0.005% to about 0.1%, from about 0.005% to about 0.1%, from about 0.005% to about 0.05%, from about 0.005% to In a range of about 0.01%, from about 0.005% to about 0.008%, or any range or subrange therebetween. In some embodiments, the absolute difference between the depth of the third layer divided by the thickness of the substrate and the depth of the first center layer divided by the thickness of the center may be about 0.001% or more, about 0.002% or more, about 0.005%, or greater, about 1% or less, about 0.2% or less, about 0.1% or less, about 0.05% or less, about 0.01% or less, or about 0.008% or less. In some embodiments, the absolute difference between the depth of the third layer divided by the thickness of the substrate and the depth of the first center layer divided by the thickness of the center may be from about 0.001% to about 1%, from about 0.002% to about 1%, from about 0.002% to about 0.2%, from about 0.005% to about 0.2%, from about 0.005% to about 0.1%, from about 0.005% to about 0.1%, from about 0.005% to about 0.05%, from about 0.005% to In a range of about 0.01%, from about 0.005% to about 0.008%, or any range or subrange therebetween.

In some embodiments, the absolute difference between the depth of the second layer divided by the thickness of the substrate and the depth of the second center layer divided by the thickness of the center may be about 0.001% or more, about 0.002% or more, about 0.005%, or greater, about 1% or less, about 0.2% or less, about 0.1% or less, or about 0.05% or less, about 0.01% or less, or about 0.008% or less. In some embodiments, the absolute difference between the depth of the second layer divided by the thickness of the substrate and the depth of the second center layer divided by the thickness of the center may be from about 0.001% to about 1%, from about 0.002% to about 1%, from about 0.002% to about 0.2%, from about 0.005% to about 0.2%, from about 0.005% to about 0.1%, from about 0.005% to about 0.1%, from about 0.005% to about 0.05%, from about 0.005% to In a range of about 0.01%, from about 0.005% to about 0.008%, or any range or subrange therebetween. In some embodiments, the absolute difference between the depth of the fourth layer divided by the thickness of the substrate and the depth of the second center layer divided by the thickness of the center may be about 0.001% or more, about 0.002% or more, about 0.005%, or greater, about 1% or less, about 0.2% or less, about 0.1% or less, or about 0.05% or less, about 0.01% or less, or about 0.008% or less. In some embodiments, the absolute difference between the depth of the fourth layer divided by the thickness of the substrate and the depth of the second center layer divided by the thickness of the center may be from about 0.001% to about 1%, from about 0.002% to about 1%, from about 0.002% to about 0.2%, from about 0.005% to about 0.2%, from about 0.005% to about 0.1%, from about 0.005% to about 0.1%, from about 0.005% to about 0.05%, from about 0.005% to In a range of about 0.01%, from about 0.005% to about 0.008%, or any range or subrange therebetween. For example, when the absolute value between the depth of the layer associated with the first portion or the second portion divided by the thickness of the substrate and the depth of the layer associated with the central portion divided by the central thickness is about 0.075% or less, for a For a foldable substrate with a center thickness of 30 µm and a center width of 20 mm, the chemical strengthening induced strain can be less than the critical buckling strain. In some embodiments, one of the first layer depth, the second layer depth, the third layer depth, or the fourth layer depth is divided by the substrate thickness and the first center layer depth or the second center layer depth divided by the center thickness The absolute difference between can be less than 0.07%, for example, in a range from about 0.001% to about 0.07%, from about 0.01% to about 0.07%, from about 0.01% to about 0.05%, from about 0.01% to about 0.02% or any range or subrange therebetween. Provide the first layer depth, second layer depth, third layer depth, and/or fourth layer depth divided by substrate thickness and first center layer depth and/or second center layer depth divided by center thickness (e.g., a layer of potassium The absolute difference between depths) may provide reduced chemical strengthening induced strain (eg, below a critical buckling strain) and/or reduce the occurrence of mechanical instability in foldable substrates and/or foldable devices.

The compression depth may be proportional to the corresponding layer depth. In some embodiments, the absolute difference between the first depth of compression divided by the thickness of the substrate and the first depth of compression divided by the center thickness may be about 0.001% or more, about 0.002% or more, about 0.005%, or greater, about 1% or less, about 0.2% or less, about 0.1% or less, about 0.05% or less, about 0.01% or less, or about 0.008% or less. In some embodiments, the absolute difference between the first compression depth divided by the substrate thickness and the first center compression depth divided by the center thickness may be from about 0.001% to about 1%, from about 0.002% to about 1%, from about 0.002% to about 0.2%, from about 0.005% to about 0.2%, from about 0.005% to about 0.1%, from about 0.005% to about 0.1%, from about 0.005% to about 0.05%, from about 0.005% to In a range of about 0.01%, from about 0.005% to about 0.008%, or any range or subrange therebetween. In some embodiments, the absolute difference between the third depth of compression divided by the thickness of the substrate and the first depth of compression divided by the thickness of the center may be about 0.001% or more, about 0.002% or more, about 0.005%, or greater, about 1% or less, about 0.2% or less, about 0.1% or less, about 0.05% or less, about 0.01% or less, or about 0.008% or less. In some embodiments, the absolute difference between the third compression depth divided by the substrate thickness and the first center compression depth divided by the center thickness may be from about 0.001% to about 1%, from about 0.002% to about 1%, from about 0.002% to about 0.2%, from about 0.005% to about 0.2%, from about 0.005% to about 0.1%, from about 0.005% to about 0.1%, from about 0.005% to about 0.05%, from about 0.005% to In a range of about 0.01%, from about 0.005% to about 0.008%, or any range or subrange therebetween.

In some embodiments, the absolute difference between the second depth of compression divided by the thickness of the substrate and the second depth of compression divided by the thickness of the center may be about 0.001% or more, about 0.002% or more, about 0.005%, or greater, about 1% or less, about 0.2% or less, about 0.1% or less, about 0.05% or less, about 0.01% or less, or about 0.008% or less. In some embodiments, the absolute difference between the second compression depth divided by the substrate thickness and the second central compression depth divided by the central thickness may be from about 0.001% to about 1%, from about 0.002% to about 1%, from about 0.002% to about 0.2%, from about 0.005% to about 0.2%, from about 0.005% to about 0.1%, from about 0.005% to about 0.1%, from about 0.005% to about 0.05%, from about 0.005% to In a range of about 0.01%, from about 0.005% to about 0.008%, or any range or subrange therebetween. In some embodiments, the absolute difference between the fourth depth of compression divided by the thickness of the substrate and the second depth of compression divided by the center thickness may be about 0.001% or more, about 0.002% or more, about 0.005%, or greater, about 1% or less, about 0.2% or less, about 0.1% or less, about 0.05% or less, about 0.01% or less, or about 0.008% or less. In some embodiments, the absolute difference between the fourth compression depth divided by the substrate thickness and the second center compression depth divided by the center thickness may be from about 0.001% to about 1%, from about 0.002% to about 1%, from about 0.002% to about 0.2%, from about 0.005% to about 0.2%, from about 0.005% to about 0.1%, from about 0.005% to about 0.1%, from about 0.005% to about 0.05%, from about 0.005% to In a range of about 0.01%, from about 0.005% to about 0.008%, or any range or subrange therebetween. For example, when the absolute value between the depth of compression associated with the first portion or the second portion divided by the thickness of the substrate and the depth of compression associated with the central portion divided by the central thickness is about 0.075% or less, for a composition comprising For a foldable substrate with a center thickness of 30 µm and a center width of 20 mm, the chemical strengthening induced strain can be less than the critical buckling strain. In some embodiments, one of the first compression depth, the second compression depth, the third compression depth, or the fourth compression depth is divided by the thickness of the substrate and the first central compression depth or the second central compression depth divided by the central thickness The absolute difference between can be less than 0.07%, for example, in a range from about 0.001% to about 0.07%, from about 0.01% to about 0.07%, from about 0.01% to about 0.05%, from about 0.01% to about 0.02% or any range or subrange therebetween. Provide the first compression depth, the second compression depth, the third compression depth, and/or the fourth compression depth divided by the substrate thickness and the first central compression depth and/or the second central compression depth divided by the central thickness (eg, a layer of potassium The absolute difference between depths) may provide reduced chemical strengthening induced strain (eg, below a critical buckling strain) and/or reduce the occurrence of mechanical instability in foldable substrates and/or foldable devices.

In some embodiments, chemical strengthening-induced strain and/or stress may be observed in the optical retardation profile of the foldable substrate. As used herein, the optical retardation distribution is measured using a grayscale field polarimeter that detects light emitted from a green LED comprising an optical wavelength of about 553 nm, passing through the foldable substrate. Without wishing to be bound by theory, the spatial difference in optical retardation may correspond to the difference in stress (eg, in-plane strain) in the foldable substrate, eg, as stress-induced birefringence. In some embodiments, the optical retardation along the center portion of the centerline halfway between the first portion and the second portion, the maximum value of the optical retardation along the centerline and the optical retardation along the centerline The absolute difference between the minimum values can be about 0.1 nm or more, about 0.5 nm or more, about 1 nm or more, about 3 nm or less, about 2 nm or less, or about 1.5 nm or smaller. In some embodiments, the absolute difference between the maximum value of the optical retardation along the centerline and the minimum value of the optical retardation along the centerline may be from about 0.1 nm to about 3 nm, from about 0.1 nm to In a range of about 2 nm, from about 0.5 nm to about 2 nm, from about 0.5 nm to about 1.5 nm, from about 1 nm to about 1.5 nm, or any range or sub-range therebetween.

In some embodiments, the maximum difference between the optical retardation of the central portion 281 , 481 or 881 and the minimum optical retardation of the first portion 221 , 421 or 821 and/or the second portion 231 , 431 or 831 may be about 0.1 nm or more, about 0.5 nm or more, about 1 nm or more, about 2 nm or more, about 3 nm or more, about 8 nm or less, about 6 nm or less, about 5 nm or less or about 4 nm or less. In some embodiments, the maximum difference between the optical retardation of the central portion 281 , 481 or 881 and the minimum optical retardation of the first portion 221 , 421 or 821 and/or the second portion 231 , 431 or 831 may be determined at 0.1 nm to about 8 nm, from about 0.1 nm to about 6 nm, from about 0.5 nm to about 6 nm, from about 0.5 nm to about 5 nm, from about 1 nm to about 5 nm, from about 2 nm to about 5 nm nm, one range from about 2 nm to about 5 nm, from about 2 nm to about 4 nm, or any range or subrange therebetween. For example, when the maximum difference between the optical retardation of the central portion 281, 481 or 881 and the minimum optical retardation of the first portion 221, 421 or 821 and/or the second portion 231, 431 or 831 is about 4.6 nm or Even smaller, a foldable substrate comprising a central thickness of about 30 µm avoids mechanical instability. For example, when the maximum difference between the optical retardation of the central portion 281, 481 or 881 and the minimum optical retardation of the first portion 221, 421 or 821 and/or the second portion 231, 431 or 831 is about 5.9 nm or Even smaller, a foldable substrate comprising a central thickness of about 40 µm avoids mechanical instability.

In some embodiments, the polymer-based portion 241 is light transmissive. The polymer-based portion 241 may include a first index of refraction. The first index of refraction can be a function of the wavelength of light passing through the clear adhesive. For light of the first wavelength, the refractive index of a material is defined as the ratio between the speed of light in vacuum and the speed of light in the corresponding material. Without wishing to be bound by theory, the ratio of the sine of the first angle to the sine of the second angle can be used to determine the index of refraction of a light-transmitting adhesive, wherein light of a first wavelength presses the first wavelength on a surface of the light-transmitting adhesive. The angle is incident from air and is refracted at the surface of the clear adhesive to propagate light within the clear adhesive at a second angle. Both the first angle and the second angle are measured relative to the normal of the surface of the light-transmitting adhesive. As used herein, the refractive index is measured according to ASTM E1967-19, wherein the first wavelength comprises 589 nm. In some embodiments, the first refractive index of the polymer-based portion 241 can be about 1 or greater, about 1.3 or greater, about 1.4 or greater, about 1.45 or greater, about 1.49 or greater, about 3 or less, about 2 or less, or about 1.7 or less, about 1.6 or less, or about 1.55 or less. In some embodiments, the first index of refraction of the polymer-based portion 241 may range from about 1 to about 3, from about 1 to about 2, from about 1 to about 1.7, from about 1.3 to about 1.7, from about 1.4 In a range of to about 1.7, from about 1.4 to about 1.6, from about 1.45 to about 1.55, from about 1.49 to about 1.55, or any range or sub-range therebetween.

In some embodiments, the foldable substrate 206, 407 or 807 may include a second index of refraction. In some embodiments, the second index of refraction of the foldable substrate 206, 407 or 807 may be about 1 or greater, about 1.3 or greater, about 1.4 or greater, about 1.45 or greater, about 1.49 or greater , about 3 or less, about 2 or less, or about 1.7 or less, about 1.6 or less, or about 1.55 or less. In some embodiments, the second index of refraction of the foldable substrate 206, 407 or 807 may be from about 1 to about 3, from about 1 to about 2, from about 1 to about 1.7, from about 1.3 to about 1.7, from In a range of about 1.4 to about 1.7, from about 1.4 to about 1.6, from about 1.45 to about 1.55, from about 1.49 to about 1.55, or any range or sub-range therebetween. In some embodiments, the differential equal to the absolute value of the difference between the second index of refraction of the foldable substrate 206, 407 or 807 and the first index of refraction of the polymer-based portion 241 may be about 0.1 or less, about 0.07 or less, about 0.05 or less, about 0.001 or more, about 0.01 or more, or about 0.02 or more. In some embodiments, the differential is from about 0.001 to about 0.1, from about 0.001 to about 0.07, from about 0.001 to about 0.05, from about 0.01 to about 0.1, from about 0.01 to about 0.07, from about 0.01 to about 0.05 , from about 0.02 to about 0.1, from about 0.02 to about 0.07, from about 0.02 to about 0.05, or in any range or sub-range therebetween. In some embodiments, the second index of refraction of the foldable substrate 206 , 407 or 807 may be greater than the first index of refraction of the polymer-based portion 241 . In some embodiments, the second index of refraction of the foldable substrate 206 , 407 or 807 may be less than the first index of refraction of the polymer-based portion 241 .

In some embodiments, the adhesive layer 261 may include a third index of refraction. In some embodiments, the third index of refraction of adhesion layer 261 may be within one or more of the ranges discussed above with respect to the first index of refraction of polymer-based portion 241 . In some embodiments, the differential equal to the absolute value of the difference between the third refractive index of the adhesive layer 261 and the first refractive index of the polymer-based portion 241 may be about 0.1 or less, about 0.07 or less, About 0.05 or less, about 0.001 or more, about 0.01 or more, or about 0.02 or more. In some embodiments, the differential is from about 0.001 to about 0.1, from about 0.001 to about 0.07, from about 0.001 to about 0.05, from about 0.01 to about 0.1, from about 0.01 to about 0.07, from about 0.01 to about 0.05 , from about 0.02 to about 0.1, from about 0.02 to about 0.07, from about 0.02 to about 0.05, or in any range or subrange therebetween. In some embodiments, the third index of refraction of the adhesion layer 261 may be greater than the first index of refraction of the polymer-based portion 241 . In some embodiments, the third index of refraction of the adhesion layer 261 may be less than the first index of refraction of the polymer-based portion 241 .

In some embodiments, the differential equal to the absolute value of the difference between the third refractive index of the adhesive layer 261 and the second refractive index of the foldable substrate 206, 407 or 807 may be about 0.1 or less, about 0.07 or more Small, about 0.05 or less, about 0.001 or more, about 0.01 or more, or about 0.02 or more. In some embodiments, the differential is from about 0.001 to about 0.1, from about 0.001 to about 0.07, from about 0.001 to about 0.05, from about 0.01 to about 0.1, from about 0.01 to about 0.07, from about 0.01 to about 0.05 , from about 0.02 to about 0.1, from about 0.02 to about 0.07, from about 0.02 to about 0.05, or in any range or sub-range therebetween. In some embodiments, the third index of refraction of the adhesive layer 261 may be greater than the second index of refraction of the foldable substrate 206 , 407 or 807 . In some embodiments, the third index of refraction of the adhesive layer 261 may be smaller than the second index of refraction of the foldable substrate 206 , 407 or 807 .

In some embodiments, coating 251 may include a fourth index of refraction. In some embodiments, the fourth index of refraction of coating 251 may be within one or more of the ranges discussed above with respect to the first index of refraction of polymer-based portion 241 . In some embodiments, the differential equal to the absolute value of the difference between the fourth index of refraction of coating 251 and the first index of refraction of polymer-based portion 241 may be about 0.1 or less, about 0.07 or less, About 0.05 or less, about 0.001 or more, about 0.01 or more, or about 0.02 or more. In some embodiments, the differential is from about 0.001 to about 0.1, from about 0.001 to about 0.07, from about 0.001 to about 0.05, from about 0.01 to about 0.1, from about 0.01 to about 0.07, from about 0.01 to about 0.05 , from about 0.02 to about 0.1, from about 0.02 to about 0.07, from about 0.02 to about 0.05, or in any range or sub-range therebetween. In some embodiments, the fourth index of refraction of coating 251 may be greater than the first index of refraction of polymer-based portion 241 . In some embodiments, the fourth index of refraction of the coating 251 may be less than the first index of refraction of the polymer-based portion 241 .

In some embodiments, the differential of the absolute value of the difference between the fourth index of refraction of coating 251 and the second index of refraction of foldable substrate 206, 407 or 807 may be about 0.1 or less, about 0.07 or less , about 0.05 or less, about 0.001 or more, about 0.01 or more, or about 0.02 or more. In some embodiments, the differential is from about 0.001 to about 0.1, from about 0.001 to about 0.07, from about 0.001 to about 0.05, from about 0.01 to about 0.1, from about 0.01 to about 0.07, from about 0.01 to about 0.05 , from about 0.02 to about 0.1, from about 0.02 to about 0.07, from about 0.02 to about 0.05, or in any range or sub-range therebetween. In some embodiments, the fourth index of refraction of coating 251 may be greater than the second index of refraction of foldable substrate 206 , 407 or 807 . In some embodiments, the fourth index of refraction of coating 251 may be less than the second index of refraction of foldable substrate 206 , 407 or 807 .

In some embodiments, the differential equal to the absolute value of the difference between the fourth index of refraction of coating 251 and the third index of refraction of adhesion layer 261 may be about 0.1 or less, about 0.07 or less, about 0.05 or less, about 0.001 or more, about 0.01 or more, or about 0.02 or more. In some embodiments, the differential is from about 0.001 to about 0.1, from about 0.001 to about 0.07, from about 0.001 to about 0.05, from about 0.01 to about 0.1, from about 0.01 to about 0.07, from about 0.01 to about 0.05 , from about 0.02 to about 0.1, from about 0.02 to about 0.07, from about 0.02 to about 0.05, or in any range or sub-range therebetween. In some embodiments, the fourth index of refraction of the coating layer 251 may be greater than the third index of refraction of the adhesive layer 261 . In some embodiments, the fourth index of refraction of the coating layer 251 may be smaller than the third index of refraction of the adhesive layer 261 .

The foldable device and/or the foldable substrate can have one failure mode that can be described as a low energy failure or a high energy failure. The failure mode of the foldable substrate can be measured using the parallel plate apparatus 1001 in Figure 10. As described below for the effective minimum bend radius, the parallel rigid stainless steel plates 1003, 1005 are moved together at a rate of 50 μm/sec until the target parallel plate distance 1007 is reached. The target parallel plate distance 1007 is the greater of 4 mm or twice the effective minimum bend radius of the foldable device and/or the foldable substrate. Next, the tungsten carbide tip contact probe strikes the foldable substrate 206 at an impact position 1011 that is a distance 1009 of 30 mm from the outermost periphery of the foldable substrate 206 . As used herein, if particles are ejected from the foldable substrate 206 at 1 meter per second (m/s) during rupture, the rupture is high energy and the rupture results in more than 2 crack branches. As used herein, a rupture is low energy if it results in 2 or fewer crack branches or does not result in ejection of particles from the foldable substrate 206 at 1 m/s or greater during rupture. The average velocity of the ejected particles can be measured by capturing high-speed video of the foldable device from when the tip contacts the probe contacting the impact location to 5,000 microseconds thereafter.

Figures 9 and 11-12 schematically illustrate some embodiments of a test foldable device 1102 and/or foldable device 1201 in accordance with embodiments of the present disclosure in a folded configuration. As shown in FIG. 11 , the test foldable device 1102 is folded such that the second major surface 205 of the foldable substrate 206 is on the interior of the folded test foldable device 1102 . In the folded configuration shown in Figure 11, the user would view the display device 307 via the foldable substrate 206, instead of the PET sheet 1107, and would therefore be positioned on the side of the second major surface 205. As shown in FIG. 12 , foldable device 401 is folded to form folded device 1201 such that second major surface 405 of foldable substrate 407 is on the outside of folded foldable device 1201 . In Figure 12, the user will view the display device 307 through the foldable substrate 407 and will therefore be positioned on the side of the second major surface 205. In some embodiments, as shown in FIGS. 11-12, a foldable device may include a test foldable device 1102 or foldable device 1201 mounted on a test foldable device 1102 or 1201 (eg, first major surface 203 or 403, first center A coating 251 on the surface region 209 or 409). In other embodiments, the user would view the display device 307 through the coating. In some embodiments, although not shown, the polymer-based portion 241 and/or the adhesion layer 261 may be disposed on an additional substrate (eg, a glass-based substrate and/or a ceramic-based substrate in place of the release liner 271 or PET sheet 1107 ), and the additional substrate can be placed on the display device 307 .

As used herein, "foldable" includes the ability to fully fold, partially fold, bend, flex, or multiple. As used herein, the terms "failure", "failure" and the like refer to damage, destruction, delamination or propagation of cracks. When the foldable device is maintained at about 85°C and about 85% relative humidity at an "X" radius for 24 hours, the foldable device achieves an effective bend radius of "X", or has an "X" if it resists failure The effective bending radius of , or the effective bending radius including "X". Likewise, when the foldable device is maintained at the "X" parallel plate distance at about 85°C and about 85% relative humidity for 24 hours, the foldable device achieves the "X" parallel plate distance if it resists failure , or a parallel-to-plate distance with an "X", or a parallel-to-plate distance that includes an "X".

As used herein, a parallel plate apparatus 1101 (see FIG. 11 ) comprising a pair of parallel rigid stainless steel plates 1103, 1105 (including a first rigid stainless steel plate 1103 and a second rigid stainless steel plate 1105) is used, by the following Test configuration and process measurement of "effective minimum bending radius" and "parallel board distance" of foldable devices. When measuring the "effective minimum bend radius" or "parallel distance", the test adhesive layer 1109 includes a thickness of 50 µm (eg, in place of the adhesive layer 261 in Figures 2-5). When measuring the "effective minimum bending radius" or "parallel distance", the test is carried out with a 100 µm thick sheet 1107 of polyethylene terephthalate (PET), not Fig. 2 and Fig. 2. The release liner 271 in Figure 4 or the display device 307 shown in Figures 3 and 5. Therefore, during testing to determine the "effective minimum bend radius" or "parallel distance" of one configuration of foldable devices, by using a 100 µm thick sheet of polyethylene terephthalate (PET) 1107 , instead of the release liner 271 shown in Figures 2 and 4 or the display device 307 shown in Figures 3 and 5, the foldable device 1102 was produced and tested. When ready to test the foldable device 1102 , to attach the release liner 271 to the second contact surface 265 of the adhesive layer 261 (as shown in FIGS. 2 and 4 ) or to attach the display device 307 to the adhesive layer 261 The second contact surface 265 (as shown in Figures 3 and 5) of the 100 µm thick sheet 1107 of polyethylene terephthalate (PET) was attached to the test adhesive layer 1109 in the same manner . To test the foldable devices 601, 701 and/or 801 of FIGS. 6-8, the test adhesive layer 609 and sheet 607 may likewise be installed as shown in the configuration of FIG. 12 to test the foldable device 1102 carry out testing. The test foldable device 1102 was placed between the pair of parallel rigid stainless steel plates 1103, 1105 such that similar to the configuration shown in Figure 11, the foldable substrate 206, 407 or 807 would be on the inside of the bend. To determine the "parallel distance", the distance between the parallel plates is decreased at a rate of 50 µm/sec until the parallel plate distance 1111 is equal to the "parallel distance" to be tested. Next, the parallel plates were held for testing at about 85°C and about 85% relative humidity for 24 hours at a "parallel plate distance". As used herein, "minimum parallel plate distance" is the minimum parallel plate distance that a foldable device can withstand without failure under the conditions and configurations described above. To determine the "effective minimum bend radius", the distance between the parallel plates is reduced at a rate of 50 µm/sec until the parallel plate distance 11 is equal to twice the "effective minimum bend radius" to be tested. The parallel plates were then held for testing at about twice the effective minimum bend radius at about 85°C and about 85% relative humidity for 24 hours. As used herein, "effective minimum bend radius" is the smallest effective bend radius that a foldable device can withstand without failure under the conditions and configurations described above.

In some embodiments, foldable devices 101, 301, 401, 501, 601, 701, 801, and/or 1201 and/or test foldable devices 1102 can achieve 100 mm or less, 50 mm or less, 20 mm One of the parallel plate distances of 10 mm or less, 5 mm or less, or 3 mm or less. In further embodiments, foldable devices 101 , 301 , 401 , 501 , 601 , 701 , 801 and/or 1201 and/or test foldable device 1102 may achieve 50 millimeters (mm) or 20 mm or 10 mm or 5 mm or one of the parallel plate distances of 3 mm. In some embodiments, foldable devices 101, 301, 401, 501, 601, 701, 801, and/or 1201 and/or test foldable device 1102 may comprise about 40 mm or less, about 20 mm or less, about 10 mm or less, about 5 mm or less, about 3 mm or less, about 1 mm or less, about 1 mm or more, about 3 mm or more, about 5 mm or more or about A minimum parallel plate distance of 10 mm or greater. In some embodiments, the foldable devices 101, 301, 401, 501, 601, 701, 801, and/or 1201 and/or the test foldable device 1102 can be included in a range from about 1 mm to about 40 mm, from about 1 mm to about 20 mm, from about 1 mm to about 10 mm, from about 1 mm to about 5 mm, from about 1 mm to about 3 mm, from about 3 mm to about 40 mm, from about 3 mm to about 40 mm, One of a range from about 3 mm to about 20 mm, from about 3 mm to about 10 mm, from about 3 mm to about 5 mm, from about 5 mm to about 10 mm, or any range or sub-range therebetween Effective minimum bend radius.

In some embodiments, a width of the central portion 281 , 481 and/or 881 of the foldable substrate 206 , 407 or 807 is defined in the direction 106 of the length 105 between the first portion 221 , 421 or 821 and the second portion 231 , 431 or between 831. In some embodiments, the width of the central portion 281 , 481 and/or 881 of the foldable substrate 206 , 407 or 807 may extend from the first portion 221 , 421 or 821 to the second portion 231 , 431 or 831 . In some embodiments, the central portion 281 , 481 or 881 of the foldable substrate 206 , 407 or 807 is defined between the first portion 221 , 421 or 821 and the second portion 231 , 431 or 831 in the direction 106 of the length 105 The width can be about 2.8 times or more, about 3 times or more, about 4 times or more, about 6 times or less, about 5 times or less, or about 4 times or less the effective minimum bend radius . In some embodiments, the width of the central portion 281, 481, and/or 881, which is a multiple of the effective minimum bend radius, can range from about 2.8 times to about 6 times, from about 2.8 times to about 5 times, from about 2.8 times to One of about 4 times, from about 3 times to about 6 times, from about 3 times to about 5 times, from about 3 times to about 4 times, from about 4 times to about 6 times, from about 4 times to about 5 times range or any range or subrange therebetween. Without wishing to be bound by theory, the length of a curved portion in a circular configuration between parallel plates can be about 1.6 times the parallel plate distance 1111 (eg, about 3 times the effective minimum bend radius, about 3.2 times the effective minimum bend radius ). In some embodiments, the width of the central portion 281 , 481 and/or 881 of the substrate 206 , 407 or 807 can be folded. In some embodiments, the width of the central portion 281 , 481 and/or 881 of the foldable substrate 206 , 407 or 807 may be about 2.8 mm or more, about 6 mm or more, about 9 mm or more, about 60 mm or less, about 40 mm or less, or about 24 mm or less. In some embodiments, the width of the central portion 281 , 481 and/or 881 of the foldable substrate 206 , 407 or 807 may range from about 2.8 mm to about 60 mm, from about 2.8 mm to about 40 mm, from about 2.8 mm to about 24 mm, from about 6 mm to about 60 mm, from about 6 mm to about 40 mm, from about 6 mm to about 24 mm, from about 9 mm to about 60 mm, from about 9 mm to about 40 mm, In a range from about 9 mm to about 24 mm, or any range or sub-range therebetween. By providing a width for the central portion (eg, between the first portion and the second portion) within the range indicated above, folding of the foldable device without failure may be facilitated.

The foldable devices 101, 301, 401, 501, 601, 701, 801, and 1201 may have an area composed of a foldable device (eg, an area including the first portion 221, 421, or 821, an area including the second portion 231, 431, or Impact resistance defined by the ability of an area of 831, including an area of the polymer-based portion 241 and/or the central portion 281, 481 or 881) to avoid falling of the pen when measured according to the "Pen Drop Test" Failures at drop heights (eg, 5 centimeters (cm) or more, 10 centimeters or more, 20 cm or more). As used herein, a "pen drop test" is performed by applying a load (ie, from a A pen dropped from a certain height) to test samples of foldable devices, the major surface was configured as a 100 µm thick sheet 1107 of PET in the parallel plate test attached to a test adhesive layer having a thickness of 50 µm 1109 instead of the display device 307 shown in Figures 3 and 5 or the release liner 271 of Figures 2 and 4. Thus, the PET layer in the pen drop test is intended to simulate a foldable electronic display device (eg, an OLED device). During the test, the foldable device bonded to the PET layer was placed on an aluminum plate (6063 aluminum alloy, eg polished to a surface roughness by 400 sandpaper) with the PET layer in contact with the aluminum plate. No tape was used on the side of the sample that rested on the aluminum panel.

The tube was used in a pen drop test to guide the pen to the outer surface of the foldable device. For foldable devices 101, 301, 401, 501, 601, 701, 801, and 1201 and/or test foldable device 1102 in Figures 2-8 and 11-12, direct the pen to The second major surface 205, 405 or 805 of the foldable base plate 206, 407 or 807 is folded and the tube is placed in contact with the second major surface 205, 405 or 805 of the foldable base plate 206, 407 or 807 such that the longitudinal direction of the tube is The axis is substantially perpendicular to the second major surface 205, 405 or 805, wherein the longitudinal axis of the tube extends in the direction of gravity. The tube has an outer diameter of 1 inch (2.54 cm), an inner diameter of nine sixteenths of an inch (1.4 cm), and a length of 90 cm. For each test, an acrylonitrile butadiene (ABS) spacer was used to hold the pen at a predetermined height. After each drop, the tube was repositioned relative to the sample to guide the pen to a different impact location on the sample. The pen used in the pen drop test was a BIC Easy Glide pen, thin, with a 0.7 mm (0.68 mm) diameter tungsten carbide bead point, and 5.73 grams (g) including cap (4.68 g without cap) weight.

For the pen drop test, the pen is dropped with a cap attached to the tip (ie, the end opposite the tip) so that the ball point can interact with the test sample. In the drop sequence according to the pen drop test, a pen drop was performed at an initial height of 1 cm, followed by successive drops in 0.5 cm increments up to 20 cm, and then after 20 cm, in 2 cm increments amount until the test sample fails. After each drop was made, record any observable breakage, failure, or other evidence of sample damage along with the specific pen drop height. Using the pen drop test, multiple samples can be tested against the same drop sequence to generate a population with improved statistical precision. For the pen drop test, the pen should be changed to a new pen after every 5 drops and for each new sample tested. In addition, all pen drops were performed at random locations on the sample at or near the center of the sample, with no pen drops near or on the edges of the sample.

For the purposes of the pen drop test, "failure" means the formation of mechanical defects visible in the laminate. Mechanical defects can be cracks or plastic deformations (eg surface dents). The cracks can be surface cracks or through cracks. Cracks can be formed in the laminate or on the outer surface. The cracks may extend through all or a portion of the foldable substrate 206, 407 or 807 and/or the coating. Visible mechanical defects have a minimum dimension of 0.2 mm or greater.

Figure 53 shows a curve 5305 of the maximum principal stress in megapascals (MPa) 5303 on the first major surface of the glass-based substrate as a function of the thickness 5301 in microns of the glass-based substrate, which is Based on a 2 cm pen drop height onto the second major surface of the glass-based substrate. As shown in Figure 53, the maximum principal stress on the first major surface of the glass-based sheet is greatest around 65 μm. This shows that pen drop performance can be improved by avoiding thicknesses of about 65 μm, eg, less than about 50 μm or greater than about 80 μm.

In some embodiments, the foldable device is resistant to a pen drop height of 10 centimeters (cm), 12 cm, 14 cm, 16 cm, or 20 cm, including the first portion 221, 421 or 821 or the second portion 231, Failed to drop the pen in one of the 431 or 831 areas. In some embodiments, the maximum pen drop height that the foldable device can withstand without failure over one of the areas including the first portion 221 , 421 or 821 or the second portion 231 , 431 or 831 can be about 10 cm or more, about 12 cm or more, about 14 cm or more, about 16 cm or more, about 40 cm or less or about 30 cm or less, about 20 cm or less, about 18 cm or smaller. In some embodiments, the maximum pen drop height that the foldable device can withstand without failure on one of the areas including the first portion 221 , 421 or 821 or the second portion 231 , 431 or 821 may be from about 10 cm to about 40 cm, from about 12 cm to about 40 cm, from about 12 cm to about 30 cm, from about 14 cm to about 30 cm, from about 14 cm to about 20 cm, from about 16 cm to about 20 cm , in a range from about 18 cm to about 20 cm, or any range or subrange therebetween.

In some embodiments, the foldable device is resistant to a pen drop height of 1 cm, 2 cm, 3 cm, 4 cm, 5 cm, or greater comprising the first portion 221, 421 or 821 and the second portion 231, Pen drop failure in one of the regions of the polymer-based portion 241 between 431 or 831 (eg, central portion 281, 481 or 881). In some embodiments, the foldable device can withstand without failure on an area of the polymer-based portion 241 comprised between the first portion 221 , 421 or 821 and the second portion 231 , 431 or 831 The maximum pen drop height can be about 1 cm or more, about 2 cm or more, about 3 cm or more, about 4 cm or more, about 20 cm or less, about 10 cm or less, about 8 cm or less or about 6 cm or less. In some embodiments, the foldable device can withstand without failure on an area of the polymer-based portion 241 comprised between the first portion 221 , 421 or 821 and the second portion 231 , 431 or 831 The maximum pen drop height can be from about 1 cm to about 20 cm, from about 2 cm to about 20 cm, from about 2 cm to about 10 cm, from about 3 cm to about 10 cm, from about 3 cm to about 8 cm cm, in a range of from about 4 cm to about 8 cm, from about 4 cm to about 6 cm, or in any range or sub-range therebetween. In some embodiments, the foldable device can withstand without failure on an area of the polymer-based portion 241 comprised between the first portion 221 , 421 or 821 and the second portion 231 , 431 or 831 The maximum pen drop height can be from about 1 cm to about 10 cm, from about 1 cm to about 8 cm, from about 1 cm to about 5 cm, from about 2 cm to about 5 cm, from about 3 cm to about 5 cm cm, in a range from about 4 cm to about 5 cm, or any range or subrange therebetween.

The predetermined parallel plate distance can be achieved by the foldable device using minimal force. The parallel-plate apparatus 1101 of FIG. 11 described above is used to measure the "closing force" of the foldable apparatus of the embodiments of the present disclosure. The force was measured from a flat configuration (eg, see Figure 1) to a curved (eg, folded) configuration (eg, see Figures 9 and 11-12) that includes a predetermined parallel-plate distance. In some embodiments, the force to bend the foldable device from a flat configuration to a parallel-plate distance of 10 mm may be about 20 Newtons (N) or less, 15 N or less, about 12 N or less, about 10 N or less, about 0.1 N or more, about 0.5 N or more, about 1 N or more, about 2 N or more, about 5 N or more. In some embodiments, the force to bend the foldable device from a flat configuration to a parallel-panel distance of 10 mm may range from about 0.1 N to about 20 N, from about 0.5 N to about 20 N, from about 0.5 N to about 15 N N, a range from about 1 N to about 15 N, from about 1 N to about 12 N, from about 2 N to about 12 N, from about 2 N to about 10 N, from about 5 N to about 10 N, or in any range or subrange in between. In some embodiments, the force to bend the foldable device from a flat configuration to a parallel-panel distance of 3 mm can be about 10 N or less, about 8 N or less, 6 N or less, about 4 N or less Small, about 3 N or less, about 0.05 N or more, about 0.1 N or more, about 0.5 N or more, about 1 N or more, about 2 N or more, about 3 N or more . In some embodiments, the force to bend the foldable device from a flat configuration to a parallel-panel distance of 3 mm can range from about 0.05 N to about 10 N, from about 0.1 N to about 10 N, from about 0.1 N to about 8 N, from about 0.5 N to about 8 N, from about 0.5 N to about 6 N, from about 1 N to about 6 N, from about 1 N to about 4 N, from about 2 N to about 4 N, from about 2 In a range of N to about 3 N or any range or subrange therebetween.

In some embodiments, the force per width 103 of the foldable device bending the foldable device from a flat configuration to a parallel-panel distance of 10 mm may be about 20 Newtons per millimeter (N/mm) or less, 0.15 N/ mm or less, about 0.12 N/mm or less, about 0.10 N/mm or less, about 0.001 N/mm or more, about 0.005 N/mm or more, about 0.01 N/mm or more, About 0.02 N/mm or more, about 0.05 N/mm or more. In some embodiments, the force per width 103 of the foldable device to bend the foldable device from a flat configuration to a parallel-panel distance of 0.10/mm can range from about 0.001 N/mm to about 0.20 N/mm, from about 0.005 N/mm to about 0.20 N/mm, from about 0.005 N/mm to about 0.15 N/mm, from about 0.01 N/mm to about 0.15 N/mm, from about 0.01 N/mm to about 0.12 N/mm, from In a range from about 0.02 N/mm to about 0.12 N/mm, from about 0.02 N/mm to about 0.10 N/mm, from about 0.05 N/mm to about 0.10 N/mm, or in any range or sub-range therebetween . In some embodiments, the force per width 103 of the foldable device to bend the foldable device from a flat configuration to a parallel-panel distance of 3 mm may be about 0.10 N/mm or less, about 0.08 N/mm or less , about 0.06 N/mm or less, about 0.04 N/mm or less, about 0.03 N/mm or less, about 0.0005 N/mm or more, about 0.001 N/mm or more, about 0.005 N/mm mm or more, about 0.01 N/mm or more, about 0.02 N/mm or more, about 0.03 N/mm or more. In some embodiments, the force per width 103 of the foldable device to bend the foldable device from a flat configuration to a parallel-panel distance of 3 mm can range from about 0.0005 N/mm to about 0.10 N/mm, from about 0.001 N /mm to about 0.10 N/mm, from about 0.001 N/mm to about 0.08 N/mm, from about 0.005 N/mm to about 0.08 N/mm, from about 0.005 N/mm to about 0.06 N/mm, from about 0.01 N/mm to about 0.06 N/mm, from about 0.01 N/mm to about 0.04 N/mm, from about 0.02 N/mm to about 0.04 N/mm, from about 0.02 N/mm to about 0.03 N/mm in a range or any range or sub-range therebetween.

Providing a coating enables low forces to achieve small parallel plate distances. Without wishing to be bound by theory, a coating comprising a modulus less than that of a foldable substrate may result in a coating that is farther away from the coating (eg, user-facing the neutral axis of the displaced foldable substrate. Without wishing to be bound by theory, providing a coating with a thickness of about 200 µm or less can result in a foldable substrate that is displaced away from the coating (eg, the user-facing surface) than would be the case with a thicker substrate neutral axis. Without wishing to be bound by theory, the neutral axis of the foldable substrate portion displaced away from the coating (eg, the user-facing surface) enables low forces to achieve small parallel plate distances because it reduces pull The concentration of tensile stress and the resulting deformation of a portion of the foldable substrate (due to the spread of the tensile stress over a larger portion of the foldable substrate).

Embodiments of methods of making foldable devices and/or foldable substrates according to embodiments of the present disclosure will refer to the flowcharts in FIGS. 15-18 and the examples illustrated in FIGS. 19-52 method steps are discussed.

19 to 24 and 50 to 52 and 15, the flow charts produced in Figures 2 to 3, 6 and 11 to 12 will now be discussed Example embodiments of foldable devices 101 , 301 , 601 and/or 1201 , test foldable device 1102 and/or foldable substrate 206 are illustrated. In a first step 1501 of the method of the present disclosure, the method may begin by providing a foldable substrate 206 . In some embodiments, the foldable substrate 206 may be provided by purchasing or otherwise obtaining the substrate or by forming a foldable substrate. As discussed above, the foldable substrate 206 can include a core layer 207 positioned between a first outer layer 213 and a second outer layer 215 . In some embodiments, the core layer 207, the first outer layer 213, and/or the second outer layer 215 of the foldable substrate 206 may comprise a glass-based substrate and/or a ceramic-based substrate. In further embodiments, glass-based substrates and/or ceramic-based substrates may be formed by various strip-forming processes (eg, slot draw, draw down, fusion draw, pull up, roll, redraw, or float) it is provided. In further embodiments, the ceramic-based substrate may be provided by heating the glass-based substrate to crystallize one or more ceramic crystals. The foldable substrate 206 can include a second major surface 205 that can extend along a plane (see FIGS. 20-21 ). The second major surface 205 may be opposite to the first major surface 203 .

For example, as shown in Figure 19, a lamination melt draw apparatus 1901 may be used to produce foldable substrate 206. As shown, the lamination melt draw apparatus 1901 can include an upper forming device 1902 positioned on a lower forming device 1904 . In some embodiments, as shown, upper forming device 1902 can include one of first slots 1910 configured to receive first molten material 1906 and lower forming device 1904 can include one of second molten material 1908 configured to receive The second slot 1912. In some embodiments, the second molten material 1908 can overflow the second groove 1912 and flow over the corresponding outer forming surfaces 1916 and 1918 of the lower forming device 1904 . In further embodiments, as shown, outer forming surfaces 1916 and 1918 may converge at root 1920 of lower forming device 1904 to form a core melt layer 1932 that may be cooled to form core layer 207 . In some embodiments, the first molten material 1906 can overflow the first groove 1910 and flow over the corresponding outer surfaces 1922 and 1924 of the upper forming device 1902 . In further embodiments, the first molten material 1906 may be deflected by the upper forming device 1902 such that the first molten material 1906 flows around the lower forming device 1904 and contacts the second molten material 1908 as the second molten material is between the lower forming device 1904 Flow on corresponding outer forming surfaces 1916 and 1918. In still further embodiments, the first molten material 1906 can form a first molten outer layer 1934 that can be cooled to form the first outer layer 213 and the first molten material 1906 can form a second molten material 1906 that can be cooled to form the second outer layer 215 Melt the outer layer 1936. In still further embodiments, as shown, the core molten layer 1932 may be positioned below the root 1920, between the first molten outer layer 1934 and the second molten outer layer 1936. In yet other embodiments, the temperature of the first molten material 1906 comprising the first molten outer layer 1934 and the second molten outer layer 1936 at the root 1920 may be higher than the temperature of the first molten material comprising the first molten outer layer 1903 and the second molten outer layer 1936 Softening point of material 1906. In yet other embodiments, the temperature of the second molten material 1908 comprising the core melt layer 1932 at the root 1920 may be higher than the softening point of the second melt material 1908 comprising the core melt layer 1932. In yet other embodiments, the first fused outer layer 1934 can be laminated to the core fused layer 1932 (eg, the first outer layer 213 can be laminated to between the core layers 207 in FIGS. 2-3 and 6 third inner surface 208 ), and/or second outer fused layer 1936 may be laminated to core fused layer 1932 (eg, second outer layer 215 may be laminated to the core of FIGS. 2-3 and 6 the fourth inner surface 218 of layer 207) to form the foldable substrate 206 shown in FIGS. 20-21.

In some embodiments, the density of the core layer 207 may be greater than the first density of the first outer layer 213 and/or the second density of the second outer layer 215 . In some embodiments, the network expansion factor of the core layer 207 may be smaller than the network expansion factor of the first outer layer 213 and/or the network expansion factor of the second outer layer 215 . In some embodiments, the thermal expansion coefficient of the core layer 207 may be greater than the thermal expansion coefficient of the first outer layer 213 and/or the thermal expansion coefficient of the second outer layer 215 .

In some embodiments, in step 1501, the foldable substrate 206 can have a first recess 234 in the first major surface 203 of the foldable substrate 206 exposing the first central surface region 209 of the core layer 207, and /or a second recess 244 in the second major surface 205 of the foldable substrate 206 that exposes the second central surface region 219 of the core layer 207 . In further embodiments, the recess(s) (eg, first recess 234, second recess 244) may be processed by etching, laser ablation, or machining of first major surface 203 and/or second major surface surface 205 to form. For example, the etching process may be similar to steps 1503, 1505, and 1507 discussed below. For example, machining the foldable substrate 206 may be similar to step 1517 discussed below.

After step 1501, in some embodiments, the core layer 207 may comprise an oxide-based core existing average potassium concentration and/or an oxide-based core existing average lithium concentration. In some embodiments, the first outer layer 213 may comprise a first existing average potassium concentration on an oxide basis and/or a first existing average lithium concentration on an oxide basis. In some embodiments, the second outer layer 215 may comprise a second existing average potassium concentration based on oxide and/or a second average lithium concentration based on oxide. In some embodiments, the core existing average potassium concentration is about 10 parts per million, or greater than the first existing average potassium concentration and/or the second existing average potassium concentration. In some embodiments, the first existing average lithium concentration and/or the second existing average lithium concentration may be about 10 parts per million, or greater than the core existing average lithium concentration. Without wishing to be bound by theory, providing a larger existing average potassium concentration in the core layer will reduce the expansion of the core layer as a result of the chemical strengthening process, and/or reduce the core layer relative to the first outer layer and/or the second The extent of chemical strengthening of the outer layer. Without wishing to be bound by theory, providing a larger existing average lithium concentration in the first outer layer and/or the second outer layer will reduce the range of chemical strengthening, and/or increase the corresponding layer relative to the core as a result of the chemical strengthening process Expansion of layers.

In some embodiments, after step 1501 (eg, before step 1509 including chemically strengthening the foldable substrate 206 ), the core layer may include the core diffusivity of one or more alkali metal ions. In some embodiments, the first outer layer may comprise a first diffusivity of one or more alkali metal ions. In some embodiments, the second outer layer may comprise a second diffusivity of one or more alkali metal ions. In some embodiments, the first diffusivity and/or the second diffusivity may be greater than the core diffusivity. In some embodiments, the diffusivities may relate to sodium ions. In some embodiments, the diffusivities may relate to potassium ions. Without wishing to be bound by theory, providing a first outer layer and/or a second outer layer having a diffusivity of one or more alkali metal ions that is less than the associated diffusivity in the core layer can increase the first outer layer and/or the second outer layer The extent of chemical strengthening in the outer layer relative to the core layer. In further embodiments, the first ratio may be defined as the square root of the first diffusivity divided by the first thickness of the first outer layer 213 (eg, the first outer thickness 217). In further embodiments, the second ratio may be defined as the square root of the second diffusivity divided by the second thickness of the second outer layer 215 (eg, the second outer thickness 237 ). In further embodiments, the core ratio may be defined as the square root of the core diffusivity divided by the central thickness of the core layer 207 (eg, the central thickness 227). In further embodiments, the difference between the first ratio and the core ratio may be about 0.01 s ^{- 0.5} or less. In still further embodiments, the first ratio may be substantially equal to the core ratio. In further embodiments, the difference between the second ratio and the core ratio may be about 0.01 s ^{- 0.5} or less. In still further embodiments, the second ratio may be substantially equal to the core ratio. In further embodiments, the difference between the first ratio and/or the second ratio and the core ratio can be about 0.00001 s ^{- 0.5} or more, about 0.0001 s ^{- 0.5} or more, about 0.001 s ^{- 0.5} or more , about 0.003 s ^{- 0.5} or more, about 0.1 s ^{- 0.5} or less, about 0.05 s ^{- 0.5} or less, about 0.02 s ^{- 0.5} or less, about 0.01 s ^{- 0.5} or less, or about 0.008 s ^{- 0.5} or less. In further embodiments, the difference between the first ratio and/or the second ratio and the core ratio may be from about 0.00001 s- ^0.5 to about 0.1 s- ^0.5 , from about 0.0001 s- ^0.5 to about 0.05 s- ^0.5 , from about 0.001 s- ^0.5 to about 0.02 s- ^0.5 , from about 0.001 s- ^0.5 to about 0.01 s- ^0.5 , from about 0.003 s- ^0.5 to about 0.01 s- ^0.5 , from about 0.003 s ^{- 0.5} to about 0.005 s- ^0.5 or any range or sub-range therebetween. Without wishing to be bound by theory, the depth of the layer from chemical strengthening is proportional to the square root of the diffusivity divided by the corresponding thickness. Providing the first ratio, the second ratio, and/or the core ratio can provide substantially equal layer depths as a percentage of the corresponding thicknesses, which can reduce chemical strengthening induced strain in the foldable substrate.

At step 1501 , in some embodiments, the method may proceed to step 1517 including forming the first recess 234 and/or by machining the first major surface 203 and/or the second major surface 205 of the foldable substrate 206 or the second recess 244 . A first recess 234 may be formed in the first major surface 203 of the foldable substrate 206 that exposes the first central surface region 209 of the core layer 207 . A second recess 244 may be formed in the second major surface 205 of the foldable substrate 206 that exposes the second central surface region 219 of the core layer 207 . For example, the first major surface 203 and/or the second major surface 205 can be machined by diamond engraving to create very precise patterns in glass-based substrates and/or ceramic-based substrates. As shown in Figure 20, diamond engraving can be used to create first pockets 234 in the first major surface 203 of the foldable substrate 206, wherein the diamond can be controlled using a computer numerical control (CNC) machine 2003 Sharp probe 2001. Materials other than diamond can be used for engraving by CNC machines. In some embodiments, although not shown, a similar process may be used to form the second recess 244 , which may be opposite the first recess 234 . It should be understood that other methods of forming the recess(s) may be used, such as lithography and laser ablation.

After step 1501 , in some embodiments, the method may proceed to step 1503 including disposing a mask on one or more portions of the foldable substrate 206 . In some embodiments, as shown in FIG. 21 , step 1503 may include disposing a first liquid 2107 on one or more portions of the foldable substrate 206 . In further embodiments, as shown, a container 2101 (eg, tubing, flexible tubing, micropipette, or syringe) may be used to place the first liquid 2107 on one or more portions of the foldable substrate 206 . In further embodiments, as shown, the first liquid 2107 may be disposed on the first surface region 223 as the first liquid deposit 2103 and on the third surface region 233 as the second liquid deposit 2105. Although not shown, it should be understood that similar liquid deposits may be formed on the second surface region and/or the fourth surface region. In further embodiments, the liquid deposits (eg, the first liquid deposit 2103 and the second liquid deposit 2105 shown in FIG. 21 ) may be cured to form a mask (eg, the first liquid deposit shown in FIG. 22 ) mask 2205 and third mask 2209). Curing the first liquid can include heating the first liquid 2107, irradiating the first liquid 2107 with ultraviolet (UV) radiation, and/or waiting a predetermined amount of time (eg, from about 30 minutes to 24 hours, from about 1 hour to about 8 hours). In some embodiments, another method (eg, chemical vapor deposition (CVD) (eg, low pressure CVD, plasma enhanced CVD), physical vapor deposition (PVD) ( For example, evaporation, molecular beam epitaxy, ion plating), atomic layer deposition (ALD), sputtering, spray pyrolysis, chemical bath deposition, sol-gel deposition) to form the mask(s) Masks (eg, masks 2205, 2207, 2209, and 2211). As shown in FIG. 22, the result of step 1503 may include a first mask 2205 disposed on the first surface area 223, a second mask 2207 disposed on the second surface area 225, a second mask 2207 disposed on the third surface area 233 A third mask 2209 disposed on top and/or a fourth mask 2211 disposed on the fourth surface area 235. In some embodiments, the material of the mask may include titanium dioxide (TiO ₂ ), zirconium oxide (ZrO ₂ ), tin oxide (SnO ₂ ), aluminum oxide (Al ₂ O ₃ ), silica (SiO ₂ ), nitride Silicon (Si ₃ N ₄ ) and/or combinations thereof, although other materials may be used for the mask in other embodiments.

After step 1503 , as shown in FIG. 22 , the method may continue to step 1505 , including etching the foldable substrate 206 . In some embodiments, etching can include exposing the foldable substrate 206 to an etchant 2203, as shown. In further embodiments, as shown, the etchant 2203 may be a liquid etchant contained in the etchant bath 2201 . In still further embodiments, the etching solution may include one or more inorganic acids (eg, HCl, _HF , _H2SO4 , _HNO3 ). In some embodiments, as shown, etching can include etching a central portion 281 of the first major surface 203 to form a first central surface region 209 . In further embodiments, as shown, the first central surface region 209 may include a portion of the third inner surface 208 . In further embodiments, as shown, the etching may form a first recess 234 between the first plane 204a and the first central surface region 209 . In some embodiments, the depth of the first recess 234 may be substantially equal to the first outer thickness 217 of the first outer layer 213 (see FIGS. 2-3 and 5). In some embodiments, although not shown, the depth of the first recess may be greater than the first thickness of the first outer layer. In some embodiments, as shown, the etching can include etching the central portion 281 of the second major surface 205 to form a second central surface region 219 . In further embodiments, as shown, the second central surface region 219 may include a portion of the fourth inner surface 218 . In further embodiments, the etching may form a second recess 244 between the second plane 204b and the second central surface region 219, as shown. In some embodiments, the depth of the second recess 244 may be substantially equal to the second outer thickness 237 of the first outer layer 213 (see FIGS. 2-3 and 5). In some embodiments, although not shown, the depth of the second recess may be greater than the second thickness of the second outer layer.

After step 1505, as shown in FIG. 23, the method may proceed to step 1507, including removing the mask(s). In some embodiments as shown, removing the mask(s) (eg, masks 2205, 2207, 2209, and 2211) may include in a direction 2302 across the surface (eg, third surface region 233) Move the grinding tool 2301. In still further embodiments, using the tool may include sweeping, scraping, grinding, pushing, and the like. In further embodiments, the mask(s) (eg, masks 2205, 2207, 2209, and 2211) may be prepared by washing the surfaces (eg, first surface region 223, second surface region 225, third surface) with a solvent area 233, fourth surface area 235) to remove. In some embodiments, removing the mask(s) may include removing the masks 2205, 2207, 2209 from the first surface region 223, the second surface region 225, the third surface region 233, the fourth surface region 235, respectively and 2211.

Additionally or alternatively, steps 1501 , 1507 or 1517 may include exposing the sub-layer by removing the sub-layer from the second major surface 205 of the foldable substrate 206 to expose the A new second major surface of second major surface 205 (eg, by machining, by etching, by lithography, by ablation) reduces the thickness of foldable substrate 206 . Removing sub-layers from both the first and second major surfaces may remove the outer sub-layers of the foldable substrate 206 , which outer sub-layers may have non-uniform interior portions of the foldable substrate 206 underlying corresponding layers optical properties. Accordingly, the entire thickness of the length and width of the corresponding layers of the foldable substrate 206 may have more consistent optical properties to provide consistent optical performance across the entire foldable substrate 206 with little or no distortion. Removing the sub-layer from the first major surface 203 and/or from the second major surface 205 may be beneficial for removing surface imperfections that were created during the formation of the first recess 234 and/or the second recess 244 . For example, machining the first major surface 203 and/or the second major surface 205 (eg, with a diamond-tipped probe) to create the first recess 234 and/or the second recess 244 may create a Microcracked surface cracks or other imperfections where, after folding, catastrophic failure of the foldable substrate 206 can occur. Thus, by removing the sub-layer from the first major surface 203 and the sub-layer from the second major surface 205, the removal of the sub-layer during the formation of the first recess 234 and/or the second recess 244 can be removed The resulting surface imperfections, wherein a new first major surface and/or a new second major surface with fewer surface imperfections can be present. Because there are fewer surface defects, smaller bend radii can be achieved without failure of the folded substrate. For example, a certain processing of the foldable substrate may exhibit glass-based material properties and/or ceramic-based material properties at the first and second major surfaces of the foldable substrate and at the central portion of the foldable substrate difference. For example, the properties of the glass-based material and/or ceramic-based material at the major surfaces may differ from the central portion during the down-draw process.

After steps 1501 , 1507 or 1517 , as shown in FIG. 24 , the method may continue to step 1509 including chemically strengthening the foldable substrate 206 . Chemical chemistry by ion exchange can occur when a first cation within the depth of the surface of the foldable substrate 206 exchanges with a second cation within the molten salt or salt solution 2403 having a radius larger than the first cation The foldable substrate 206 is strengthened (eg, glass-based substrate and/or ceramic-based substrate of the first outer layer, second outer layer, and/or core layer). For example, lithium cations within the depth of the surface of the foldable substrate 206 can be exchanged with sodium or potassium cations within the salt solution 2403. Thus, the surface of the foldable substrate 206 is compressed and thereby chemically strengthened by the ion exchange process, since the lithium cations have a smaller radius than the exchanged sodium or potassium cations in the salt solution 2403. Chemically strengthening the foldable substrate 206 may include mixing at least a portion of the foldable substrate 206 containing lithium cations and/or sodium cations with a salt solution 2403 (containing potassium nitrate, potassium phosphate, potassium chloride, potassium sulfate, sodium chloride, sulfuric acid) A salt bath 2401 of sodium, sodium nitrate and/or sodium phosphate) contacts, whereby lithium cations and/or sodium cations diffuse from the foldable substrate 206 to the salt solution 2403 contained in the salt bath 2401. In some embodiments, the temperature of the salt solution 2403 can be about 300°C or greater, about 360°C or greater, about 400°C or greater, about 500°C or less, about 460°C or less, or about 400°C °C or less. In some embodiments, the temperature of the salt solution 2403 can range from about 300°C to about 500°C, from about 360°C to about 500°C, from about 400°C to about 500°C, from about 300°C to about 460°C, from In a range of about 360°C to about 460°C, from about 400°C to about 460°C, from about 300°C to about 400°C, from about 360°C to about 400°C, or any range or sub-range therebetween. In some embodiments, foldable substrate 206 can be contacted with saline solution 2403 for about 15 minutes or more, about 1 hour or more, about 3 hours or more, about 48 hours or less, about 24 hours or more Less or about 8 hours or less. In some embodiments, the foldable substrate 206 can be contacted with the saline solution 2403 for from about 15 minutes to about 48 hours, from about 1 hour to about 48 hours, from about 3 hours to about 48 hours, from about 15 hours to about 24 hours, from about 1 hour to about 24 hours, from about 3 hours to about 48 hours, from about 3 hours to about 24 hours, from about 3 hours to about 8 hours, or any range or sub-range therebetween a time in the range.

The chemically strengthened foldable substrate 206 can include a chemically strengthened first central surface region 209, a chemically strengthened first surface region 223, a chemically strengthened third surface region 233, a chemically strengthened second surface region 225, a chemically strengthened fourth surface region 235, and The second central surface region 219 is chemically strengthened. In some embodiments, chemical strengthening may include chemically strengthening the first portion 221 to a first compression depth from the first surface region 223 of the first major surface 203 , and chemically strengthening the first portion 221 to a second depth from the second major surface 205 . A second compression depth of the surface region 225 chemically strengthens the second portion 231 to a third compression depth of the third surface region 233 from the first main surface 203 and chemically strengthens the second portion 231 to a distance from the second main surface 205 a fourth depth of compression of fourth surface region 235, chemically strengthened central portion 281 to a first central compression depth of first central surface region 209, and/or chemically strengthened central portion 281 to a distance of chemically strengthened central portion 281 to second central surface region 219 A second central compression depth.

At step 1509, the foldable substrate 206 may include one or more regions of compressive stress (eg, first, second, third, fourth, first central, and/or second central compressive stress regions), which are included above A compression depth and/or an associated layer depth within one or more ranges is discussed with respect to the corresponding compressive stress region. In another embodiment, one of the first layer depth, the second layer depth, the third layer depth, or the fourth layer depth is divided by the thickness of the substrate and the depth of the first center layer or the depth of the second center layer divided by the center thickness The absolute difference between can be within one or more of the ranges discussed above. In further embodiments, one of the first compression depth, the second compression depth, the third compression depth, or the fourth compression depth is divided by the thickness of the substrate and the first central compression depth or the second central compression depth divided by the central thickness The absolute difference between can be within one or more of the ranges discussed above. In further embodiments, the absolute difference between the first average potassium concentration or the second average potassium concentration and the central average potassium concentration may be within one or more of the ranges discussed above.

After step 1509 , as shown in FIG. 50 , the method of the present disclosure may proceed to step 1511 including disposing a coating 251 on the first major surface 203 and/or in the first recess 234 . In some embodiments, the second liquid 4703 may be disposed on the first major surface 203 as shown. In other embodiments, the second liquid 4703 may be disposed on the first surface region 223 of the first portion 221 and the third surface region 233 of the second portion 231 . In further embodiments, the second liquid 4703 may be disposed on the first central surface region 209 and/or fill the first recess 234 . In further embodiments, as shown, a container 4701 (eg, tubing, flexible tubing, micropipette, or syringe) may be used to accommodate the second liquid 4703. In some embodiments, the second liquid 4703 may include coating precursors, solvents, particles, nanoparticles, and/or fibers. In some embodiments, the coating precursor may include, without limitation, one or more of monomers, accelerators, curing agents, epoxy resins, and/or acrylates. In some embodiments, the solvent used for the adhesive precursor may comprise a polar solvent (eg, water, ethanol, acetate, acetone, formic acid, dimethylformamide, acetonitrile, dimethylamine phenylsulfinic acid) , nitromethane, propylene carbonate, poly(ether ether ketone)) and/or non-polar solvents (e.g., pentane, 1,4-dioxane, chloroform, dichloromethane, diethyl ether, hexane, heptane , benzene, toluene, xylene). The second liquid 4703 can be cured to form a coating 251, as shown in FIG. Curing the second liquid 4703 can include heating the second liquid 4703, irradiating the second liquid 4703 with ultraviolet (UV) radiation, and/or waiting a predetermined amount of time (eg, from about 30 minutes to 24 hours, from about 1 hour to about 8 hours). In some embodiments, another method (eg, chemical vapor deposition (CVD) (eg, low pressure CVD, plasma enhanced CVD), physical vapor deposition (PVD) ( For example, evaporation, molecular beam epitaxy, ion plating), atomic layer deposition (ALD), sputtering, spray pyrolysis, chemical bath deposition, sol-gel deposition) to form the coating 251 . In some embodiments, although not shown, coating 251 may be disposed in first recess 234 (eg, fill first recess 234 ) without contacting first major surface 203 (eg, first surface region 223 ) , the third surface area 233).

After step 1509 or 1511 , as shown in FIG. 51 , the method of the present disclosure may proceed to step 1513 , including placing material in the second recess 244 . In some embodiments, the third liquid 4803 can be seated in the second recess 244 as shown. In some embodiments, the third liquid 4803 may include precursors, solvents, particles, nanoparticles, and/or fibers. In further embodiments, as shown, the third liquid 4803 may be disposed in the second recess 244 from the container 4801, although other methods may be used to deposit the third liquid or other material in the second recess, as described above with respect to the first The dimples and/or the second liquid are discussed. In some embodiments, the third liquid 4803 can be cured (eg, heat the third liquid, irradiate the third liquid, wait a specified amount of time) to form the polymer-based portion 241 in the second recess 244, as in Shown in Figure 52. In some embodiments, although not shown, the third liquid may be cured to form an adhesive layer disposed in the second recess 244 , eg, similar to the adhesive layer 261 .

After step 1511 or 1513, the method of the present disclosure may proceed to step 1515, including using the foldable substrate 206 to assemble a foldable device. As shown in FIG. 52 , step 1515 may include applying an adhesive layer 261 to bring the second surface region 225 of the second major surface 205 into contact with the fourth surface region 235 of the second major surface 205 . For example, in some embodiments, the adhesive layer 261 may comprise one or more sheets of adhesive material. In some embodiments, there may be an integral interface between one or more sheets comprising the adhesive layer 261 and/or material disposed in the second recess (eg, the polymer-based portion 241 ), which may reduce ( For example, avoid) optical diffraction and/or optical discontinuities as light travels between the flakes, since in some embodiments one or more flakes may comprise substantially the same refractive index. In some embodiments, although not shown, at least a portion of the adhesive layer may be disposed in the second recess. In some embodiments, a release liner (eg, see release liner 271 in Figures 2 and 4) or a display device (eg, see display device 307 in Figures 3 and 5) can be Disposed on the adhesive layer 261 (eg, the first contact surface 263 ). At step 1515 , the method of the present disclosure according to the flowchart in FIG. 15 of making a foldable device may be completed at step 1519 .

In some embodiments, a method of making a foldable device according to embodiments of the present disclosure may follow steps 1501 , 1503 , 1505 , 1507 , 1509 , 1511 , 1513 , 1515 and 1519 of the flowchart in FIG. 15 This is done sequentially, as discussed above. In some embodiments, as shown in FIG. 15, arrow 1502 may follow step 1501 and step 1503 may be omitted, eg, when one or more pockets are to be folded by machining the foldable substrate (eg, not chemically strengthened) The recess(s) are formed in the foldable substrate 206 by folding the substrate to form the recess(s). In some embodiments, arrow 1506 may follow step 1501 to step 1509 of including a chemically strengthened foldable substrate, eg, if at the end of step 1501, the foldable device includes a recess. In some embodiments, arrow 1508 may follow step 1509 to step 1513 which includes placing material in the second recess. In further embodiments, the method may include disposing a coating 251 on the first major surface and/or in the first recess 234 along arrow 1512 from step 1513 to step 1511 . In further embodiments, the method may follow arrow 1518 from step 1513 to step 1519, eg, if the foldable device is fully assembled at the end of step 1513, or if another material is to be placed in the first recess, the first on the major surface and/or on the second major surface. In some embodiments, the method may follow arrow 1510 from step 1509 to step 1519, eg, if the foldable substrate 206 is the desired product (eg, no material in the first pocket or the second pocket). Any of the above options can be combined to make a foldable device according to embodiments of the present disclosure.

25 to 34 and 47 to 49 and the flow charts in 16 will now be discussed to discuss the possibility of making those illustrated in Figures 4 to 5, 7 and 12. Example embodiments of folding apparatuses 401 , 501 and/or 1201 and/or foldable substrate 407 . In a first step 1601 of the method of the present disclosure, the method may begin by providing a foldable substrate 407 and/or foldable substrate 2505 (see FIGS. 25-27). In some embodiments, foldable substrate 407 and/or foldable substrate 2505 may be provided by purchasing or otherwise obtaining the substrates or by forming foldable substrates. In some embodiments, foldable substrate 407 and/or foldable substrate 2505 may comprise a glass-based substrate and/or a ceramic-based substrate. In further embodiments, glass-based substrates and/or ceramic-based substrates may be formed by various strip-forming processes (eg, slot draw, draw down, fusion draw, pull up, roll, redraw, or float) it is provided. In further embodiments, the ceramic-based substrate may be provided by heating the glass-based substrate to crystallize one or more ceramic crystals. Foldable substrate 407 and/or foldable substrate 2505 may include a second major surface 405 (see FIG. 27 ) that may extend along a plane. The second major surface 405 may be opposite to the first major surface 403 .

In some embodiments, in step 1601 , foldable substrate 407 may be provided with a first recess 434 in foldable substrate 407 and/or first major surface 403 of foldable substrate 2505 exposed at central portion 481 The first central surface area 409 of the foldable substrate 407 and/or the foldable substrate 2505 in . In some embodiments, in step 1601 , foldable substrate 407 may be provided with a second recess 444 in foldable substrate 407 and/or second major surface 405 of foldable substrate 2505 exposed at central portion 481 The second central surface area 419 of the foldable substrate 407 and/or the foldable substrate 2505 in . In further embodiments, although not shown, the first central surface region 409 and/or the second central surface region 419 may include a transition region (eg, similar to transition regions 853 and/or 855). In further embodiments, the recess(s) (eg, first recess 434, second recess 444) may be processed by etching, laser ablation, or machining of first major surface 403 and/or second major surface surface 405 is formed. For example, machining foldable substrate 407 and/or foldable substrate 2505 may be similar to step 1603 discussed below. In some embodiments, in step 1601 , the foldable substrate 407 may be provided with one or more regions of initial compressive stress, eg, having one or more of the properties discussed below with reference to step 1605 .

After step 1601 , in some embodiments, the method may proceed to step 1603 , including forming the first recess 434 and/or the second recess 444 . In some embodiments, the recess(s) may be formed by machining the first major surface 403 and/or the second major surface 405 of the foldable substrate 407 and/or the foldable substrate 2505. A first recess 434 may be formed in the first major surface 403 of the foldable substrate 407 and/or the foldable substrate 2505 that exposes the first central surface region 409 of the central portion 481 . A second recess 444 may be formed in the second major surface 405 of the foldable substrate 407 and/or the foldable substrate 2505 that exposes the second central surface region 419 of the central portion 481 . For example, the first major surface 403 and/or the second major surface 405 can be machined by diamond engraving to create very precise patterns in glass-based substrates and/or ceramic-based substrates. As shown in Figure 26, diamond engraving can be used to create first recesses 434 in the first major surface 403 of the foldable substrate 407 and/or the foldable substrate 2505, where computer numerical control can be used; CNC) machine 2003 to control the diamond tip probe 2001. Materials other than diamond can be used for engraving by CNC machines. In some embodiments, although not shown, a similar process may be used to form the second recess 444 , which may be opposite the first recess 434 . It should be understood that other methods of forming the recess(s) may be used, such as lithography and laser ablation. After step 1603 , in some embodiments, the foldable substrate 2505 can include the foldable substrate 407 including the first recess 434 and/or the second recess 444 .

In some embodiments, step 1603 may include an etching process to form the first recess and/or the second recess (eg, masking, etching, and removing the mask, similar to steps 1503, 1505, and 1507 discussed above) . In further embodiments, as shown in FIG. 27, step 1603 may include disposing a mask on one or more portions of foldable substrate 407 and/or foldable substrate 2505. In further embodiments, step 1603 may include disposing a first liquid 2107 on one or more portions of foldable substrate 407 and/or foldable substrate 2505, as shown. In further embodiments, as shown and discussed above with reference to step 1503, a container 2101 may be used to place the first liquid 2107 on the foldable substrate 407 and/or one or more portions of the foldable substrate 2505. In further embodiments, as shown, the first liquid 2107 may be disposed on the first surface region 423 as the first liquid deposit 2103 and on the third surface region 433 as the second liquid deposit 2105. Although not shown, it should be understood that similar liquid deposits may be formed on the second surface region and/or the fourth surface region. In further embodiments, the liquid deposits (eg, the first liquid deposit 2103 and the second liquid deposit 2105 shown in FIG. 27 ) can be cured to form a mask (eg, the first liquid deposit shown in FIG. 28 ) mask 2205 and third mask 2209). Curing the first liquid may include heating the first liquid 2107, irradiating the first liquid 2107 with ultraviolet (UV) radiation, and/or waiting a predetermined amount of time. In further embodiments, the masks (eg, masks 2205, 2207, 2209, and 2211) may be formed using another method as discussed above. As shown in FIG. 28, the first mask 2205 may be disposed on the first surface area 423, the second mask 2207 may be disposed on the second surface area 425, and the third mask 2209 may be disposed on the third surface area 433 and/or the fourth mask 2211 may be disposed on the fourth surface area 435 . In further embodiments, as shown in FIG. 28, step 1603 may further include etching foldable substrate 407 and/or foldable substrate 2505. In further embodiments, as shown, etching may include exposing foldable substrate 407 and/or foldable substrate 2505 to an etchant 2203 (eg, one or more inorganic acids). In further embodiments, as shown, the etchant 2203 may be a liquid etchant contained in the etchant bath 2201 . In further embodiments, as shown, the etching may include etching the central portion 481 of the first major surface 403 to form a first central surface region 409 . In further embodiments, the etching may form a first recess 434 between the first plane 404a and the first central surface region 409, as shown. In still other embodiments, the first recess 434 may be recessed a first distance 417 from the first plane 404a and/or the first major surface 403 . In further embodiments, as shown, the etching may include etching the central portion 481 of the second major surface 405 to form a second central surface region 419 . In further embodiments, the etching may form a second recess 444 between the second plane 404b and the second central surface region 419, as shown. In still other embodiments, the second recess 444 may be recessed a second distance 437 from the second plane 404b and/or the second major surface 405 . In still further embodiments, step 1603 may further include removing the mask(s). In some embodiments, as shown in FIG. 29, removing the mask(s) (eg, masks 2205, 2207, 2209, and 2211) may be included in a spanning surface (eg, third surface region 433) Move the grinding tool 2301 in a direction 2302. In still further embodiments, using the tool may include sweeping, scraping, grinding, pushing, and the like. In further embodiments, the mask(s) (eg, masks 2205, 2207, 2209, and 2211) may be prepared by washing the surfaces (eg, first surface region 423, second surface region 425, third surface) with a solvent area 433, fourth surface area 435) to remove. In some embodiments, removing the mask(s) may include removing the masks 2205, 2207, 2209 from the first surface region 423, the second surface region 425, the third surface region 433, the fourth surface region 435, respectively and 2211. After step 1603 , in some embodiments, the foldable substrate 2505 may include the foldable substrate 407 including the first recess 434 and/or the second recess 444 .

Additionally or alternatively, steps 1601 and/or 1603 may include exposing the sub-layer by removing the sub-layer from the second major surface 205 of the foldable substrate 407 and/or the foldable substrate 2505 which may be included in FIGS. 4-5 and A new second major surface of second major surface 405 illustrated in Figure 7 (eg, by machining, by etching, by lithography, by ablation) to reduce foldable substrate 407 and/or Or the thickness of the foldable substrate 2505. As discussed above, removing sub-layers from both the first and second major surfaces can remove the outer sub-layers of foldable substrate 407 and/or foldable substrate 2505, which outer sub-layers may have the same 407 and/or the corresponding layers of foldable substrate 2505 with inconsistent optical properties of underlying interior portions, eg, having more consistent optical properties to provide across all foldable substrates 407 and/or foldable substrates 2505 407 and/or foldable substrates The 2505 has consistent optical performance with little or no distortion, thereby removing surface imperfections created during the formation of the mask(s).

After step 1601 or 1603 , as shown in FIGS. 25 and 30 , the method may continue to step 1605 including chemically strengthening the foldable substrate 407 . In some embodiments, as shown, chemically strengthening the foldable substrate 407 can include contacting at least a portion of the foldable substrate 407 comprising lithium cations and/or sodium cations with a salt bath 2401 comprising a salt solution 2403, the salt solution One or more of the components discussed above with respect to step 1509 for saline solution 2403 may be included. In some embodiments, the temperature of the salt solution 2403 and/or the time for which the foldable substrate 407 can contact the salt solution 2403 may be within one or more of the ranges discussed above with reference to step 1509 . In some embodiments, chemically strengthened foldable substrate 407 in step 1605 may include chemically strengthened first central surface region 409 to form an initial first central compression extending from first central surface region 409 to an initial first central compression depth Stressed region, chemically strengthened first surface region 423 to form an initial first compressive stress region extending from first surface region 423 to an initial first compression depth, chemically strengthened third surface region 433 to form extending from third surface region 433 to an initial third depth of compression to an initial third depth of compression, chemically strengthening the second surface region 425 to form an initial second depth of compression extending from the second surface region 425 to an initial second depth of compression, chemically strengthening the fourth surface region 435 to form an initial fourth compressive stress region extending from the fourth surface region 435 to an initial fourth depth of compression, and chemically strengthening the second central surface region 419 to form an initial second central compression extending from the second central surface region 419 One of the depths The initial second center compression depth.

After step 1601 or 1605, the foldable substrate 206 may include one or more initial compressive stress regions (eg, first, second, third, fourth, first central, and/or second central compressive stress regions), It includes an initial compression depth and/or an associated initial layer depth. In some embodiments, the initial first depth of compression, the initial second depth of compression, the initial third depth of compression, and/or the initial fourth depth of compression as a percentage of substrate thickness 411 may be about 5% or more, 10% or greater, about 12% or greater, about 14% or greater, about 25% or less, about 20% or less, about 18% or less, or about 16% or less. In some embodiments, the initial first depth of compression, the initial second depth of compression, the initial third depth of compression, and/or the initial fourth depth of compression as a percentage of substrate thickness 411 may be from about 5% to about 25%, from about 8% to about 25%, from about 8% to about 20%, from about 10% to about 20%, from about 10% to about 18%, from about 12% to about 18%, from about 12% to In a range of about 16%, from about 14% to about 16%, or any range or subrange therebetween. In some embodiments, the initial first compression depth, the initial second compression depth, the initial third compression depth, and/or the initial fourth compression depth as a percentage of the corresponding compression depth of the finished foldable substrate 407 may be about 50% or more, 60% or more, about 65% or more, about 68% or more, about 80% or less, about 75% or less, or about 72% or less, or about 70% or less. In some embodiments, the initial first compression depth, the initial second compression depth, the initial third compression depth, and/or the initial fourth compression depth as a percentage of the corresponding compression depth of the finished foldable substrate 407 may be from about 50% to about 80%, from about 60% to about 80%, from about 60% to about 75%, from about 65% to about 75%, from about 65% to about 72%, from about 68% to about 72%, a range from about 68% to about 70%, or any range or subrange therebetween. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of substrate thickness 411 may be about 5% or greater, 10% or greater, about 12% or greater, about 14% or greater, about 25% or less, about 20% or less, about 18% or less, or about 16% or less. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of substrate thickness 411 may be from about 5% to about 25%, from about 8% to about 25%, from about 8% to about 20%, from about 10% to about 20%, from about 10% to about 18%, from about 12% to about 18%, from about 12% to In a range of about 16%, from about 14% to about 16%, or any range or subrange therebetween. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of the corresponding layer depths of the finished foldable substrate 407 may be about 50% or more, 60% or more, about 65% or more, about 68% or more, about 80% or less, about 75% or less, or about 72% or less, or about 70% or less. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of the corresponding compression depth of the finished foldable substrate 407 may be about 50% to about 80%, from about 60% to about 80%, from about 60% to about 75%, from about 65% to about 75%, from about 65% to about 72%, from about 68% to about 72%, a range from about 68% to about 70%, or any range or subrange therebetween.

After step 1605, although not shown, the method may continue to step 1607, including etching the foldable substrate to remove the sub-layers from the existing first central surface region and/or the existing second central surface region. In some embodiments, as discussed above with reference to steps 1503, 1505, and 1507 or discussed below with reference to steps 1707, 1709, and 1711, step 1605 may include placing the foldable substrate 407 (eg, the existing first central surface region and/or A mask is placed over the first surface region 423, the second surface region 425, the third surface region 433, and/or the fourth surface region 435 prior to exposure to an etchant (eg, etchant 2203) , after which the mask(s) can be removed. In further embodiments, the depth removed from the central portion 481 (eg, the first central surface region, the second central surface region) may be substantially equal to the corresponding layer depth and/or compression of the corresponding compressive stress region extending from the corresponding surface depth. In further embodiments, the depth of removal from the central portion 481 (eg, first central surface region, second central surface region) may be greater than the corresponding layer depth and/or compressive depth at which the corresponding compressive stress region extends from the corresponding surface. In further embodiments, the depth removed from the central portion 481 (eg, first central surface region, second central surface region) may be less than the corresponding layer depth and/or compressive depth at which the corresponding compressive stress region extends from the corresponding surface.

After steps 1601 , 1603 , 1605 or 1607 , as shown in FIG. 31 , the method may continue to step 1609 including applying a paste comprising alkali metal ions to the first portion 421 and the second portion 431 . In some embodiments, as shown, step 1609 may include placing a first salt paste 3103 from a source 3101 on the first portion 421 and placing the first salt paste 3105 on the second portion 431 . In further embodiments, as shown, the first salt paste 3103 may be applied to the first surface region 423 of the first portion 421 and the first salt paste 3105 may be applied to the third portion of the second portion 431 Surface area 433. In further embodiments, although not shown, a first salt paste (eg, first salt paste 3103 and/or 3105 ) may be applied to the second surface region 425 of the first portion 421 and the second portion 231 the fourth surface area 435. In some embodiments, the source 3101 may include tubing (eg, flexible tubing, micropipettes, or syringes), nozzles, or vessels (eg, beakers). The first salt paste 3103 can be disposed on the first portion 421 and the second portion 431 and can be cured to form the first salt deposits 3205, 3207, 3209 and/or 3211, as in FIGS. 32-33 exhibit.

As used herein, a salt paste contains potassium and/or sodium. In some embodiments, the first salt pastes 3103 and 3105 may include one or more of potassium nitrate, potassium phosphate, potassium chloride, potassium sulfate, sodium chloride, sodium sulfate, sodium nitrate, and/or sodium phosphate . In further embodiments, the first salt paste may comprise potassium nitrate and potassium phosphate. In further embodiments, the first salt paste may be substantially free of alkaline earth metals (eg, alkaline earth metal ions, alkaline earth metal-containing compounds). As used herein, alkaline earth metals include beryllium, magnesium, calcium, strontium, barium, and radium. In further embodiments, the first salt paste can contain about 1,000 ppm or more, about 5,000 ppm or more, about 10,000 ppm or more, about 25,000 ppm or more, about 500,000 ppm or less, about An oxide-based potassium and/or sodium concentration of 200,000 ppm or less, about 100,000 ppm or less, or about 50,000 ppm or less. In further embodiments, the first salt paste may contain from about 1,000 ppm to about 500,000 ppm, from about 5,000 ppm to about 500,000 ppm, from about 5,000 ppm to about 200,000 ppm, from about 10,000 ppm to about 200,000 ppm , from about 10,000 ppm to about 100,000 ppm, from about 25,000 ppm to about 100,000 ppm, from about 25,000 ppm to about 50,000 ppm, or any range or sub-range therebetween, oxide-based potassium and/or or sodium concentration.

In some embodiments, the first salt pastes 3103 and 3105 may contain an organic binder or solvent. The organic binder may include cellulose, cellulose derivatives, hydrophobically modified ethylene oxide urethane modifier (HUER), and ethylene acrylic acid. Examples of cellulose derivatives include ethyl cellulose, methyl cellulose, and AQUAZOL (poly2ethyl-2oxazine). Solvents can include polar solvents (eg, water, ethanol, acetate, acetone, formic acid, dimethylformamide, acetonitrile, dimethylamine phenylsulfinic acid, nitromethane, propylene carbonate, poly(ether ether) ketone)) and/or non-polar solvents (eg, pentane, 1,4-dioxane, chloroform, dichloromethane, diethyl ether, hexane, heptane, benzene, toluene, xylene). In some embodiments, the first salt paste can be cured to form first salt deposits 3205, 3207, 2109, and/or 3211 by removing solvent and/or organic binder. In further embodiments, the solvent and/or organic can be removed by drying the first salt pastes 3103 and 3105 at room temperature (eg, from about 20°C to about 30°C) for eight hours or more adhesive. In further embodiments, the first salt pastes 3103 and 3105 may be dried at a temperature in a range of from about 100°C to about 140°C or from about 100°C to about 120°C. The solvent and/or organic binder is removed for a time period in the range of about 8 minutes to about 30 minutes, or from about 8 minutes to about 20 minutes, or from about 8 minutes to about 15 minutes.

In some embodiments, as shown in FIG. 32 , step 1609 may include applying a paste comprising alkali metal ions to the central portion 281 . In some embodiments, as shown, step 1609 may include disposing a second salt paste 3203 from a container 3201 on the first central surface region 409 of the central portion 481 . In further embodiments, although not shown, a second salt paste (eg, second salt deposit 3303 ) may be applied to the second central surface region 419 of the central portion 481 . In some embodiments, source 3101 may include any of the structures described above with respect to source 3101 . A second salt paste 3203 can be disposed on the central portion 481 and can be cured to form a second salt deposit 3303 and/or 3305, as shown in FIG. 33 . In further embodiments, as shown in FIGS. 32-33 , the second salt paste 3203 may be used in conjunction with the first salt paste 3103 and/or 3105 to form a second salt paste disposed on the foldable substrate 407 . A salt deposit 3205, 3207, 3209 and/or 3211 and a second salt deposit 3303 and/or 3305. In further embodiments, although not shown, the second salt deposit may be disposed on the foldable substrate without disposing the first salt deposit.

In some embodiments, the second salt paste 3203 can include one or more of the potassium- and/or sodium-containing compounds discussed above with respect to the first salt pastes 3103 and/or 3105. In some embodiments, the second salt paste 3203 may comprise the same composition as the first salt paste 3103 and/or 3105 . In some embodiments, the second salt paste 3203 may comprise an organic binder or solvent, including the organic binders or solvents discussed above with respect to the first salt pastes 3103 and 3105. In some embodiments, the second salt paste can be cured to form second salt deposits 3303 and/or 3305 by removing solvent and/or organic binder, eg, by drying at room temperature The second salt paste 3203 (eg, for about 8 hours or more) or is dried at high temperature (eg, in one of the range from about 100°C to about 140°C or from about 100°C to about 120°C) Di-salt paste 3203 for a period of time (eg, in a range from about 8 minutes to about 30 minutes, or from about 8 minutes to about 20 minutes, or from about 8 minutes to about 15 minutes).

In some embodiments, the second salt paste 3203 may comprise an oxide-based potassium and/or sodium concentration that is less than the corresponding concentration of the first salt paste. In further embodiments, the oxide-based potassium and/or sodium concentration as a percentage of the corresponding concentration of the first salt paste may be about 10% or more, about 20% or more, about 25% % or more, about 80% or less, about 60% or less, about 50% or less, about 40% or less, or about 30% or less. In further embodiments, the oxide-based potassium and/or sodium concentration as a percentage of the corresponding concentration of the first salt paste may be from about 10% to about 80%, from about 10% to about 60% %, a range from about 20% to about 60%, from about 20% to about 50%, from about 25% to about 50%, from about 25% to about 40%, from about 25% to about 30%, or in any range or subrange in between.

In some embodiments, the second salt paste 3203 may include one or more alkaline earth metals (eg, alkaline earth metal ions, alkaline earth metal-containing compounds). In further embodiments, the one or more alkaline earth metals in the second salt paste may comprise calcium (eg, calcium ions, calcium chloride, calcium nitrate, potassium carbonate). Without wishing to be bound by theory, providing one or more alkaline earth metals in the salt paste can reduce the range of chemical strengthening, eg, by competing with the alkali metals in the salt paste, which reduces the The rate of exchange between ions and alkali metal ions in the salt paste. Without wishing to be bound by theory, providing calcium as one or more alkaline earth metals in a salt paste can compete with potassium more effectively than other alkaline earth metals due to the similarities in ionic radius and mass between potassium and calcium ions. In further embodiments, the concentration of one or more alkaline earth metals (eg, calcium) may be about 10 ppm or greater, about 50 ppm or greater, about 100 ppm or greater, about 200 ppm or greater, about 400 ppm or greater ppm or more, about 10,000 ppm or less, about 5,000 ppm or less, about 2,000 ppm or less, about 1,000 ppm or less, about 750 ppm or less, or about 500 ppm or less. In further embodiments, the concentration of the one or more alkaline earth metals (eg, calcium) may be from about 10 ppm to about 10,000 ppm, from about 10 ppm to about 5,000 ppm, from about 50 ppm to about 5,000 ppm, from about 50 ppm to about 5,000 ppm ppm to about 2,000 ppm, from about 100 ppm to about 2,000 ppm, from about 100 ppm to about 1,000 ppm, from about 200 ppm to about 1,000 ppm, from about 200 ppm to about 750 ppm, from about 400 ppm to about 750 ppm , in a range from about 400 ppm to about 500 ppm, or any range or sub-range therebetween.

After step 1609 , as shown in FIG. 33 , the method of the present disclosure may proceed to step 1611 , including heating the foldable substrate 407 . In some embodiments, foldable substrate 407 may be placed in oven 3301 as shown. In further embodiments, as shown, the foldable substrate 407 may include a plurality of first salt deposits 3205, 3207, 3209 and/or 3211, and one or more second salt deposits 3303 and/or 3305. In some embodiments, although not shown, the foldable substrate 407 heated in step 1609 (eg, in the oven 3304) may include the first salt deposits 3205, 3207, 3209, and/or 3211, but not any The second salt deposits 3303 and/or 3305, or vice versa. In some embodiments, the foldable substrate 407 can be at about 300°C or greater, about 360°C or greater, about 400°C or greater, about 500°C or less, about 460°C or less, or about 400°C or lower temperature. In some embodiments, the foldable substrate 407 can be heated from about 300°C to about 500°C, from about 360°C to about 500°C, from about 400°C to about 500°C, from about 300°C to about 460°C, from about at a temperature in a range of 360°C to about 460°C, from about 400°C to about 460°C, from about 300°C to about 400°C, from about 360°C to about 400°C, or any range or sub-range therebetween heating. In some embodiments, the foldable substrate 407 can be heated for about 15 minutes or more, about 1 hour or more, about 3 hours or more, about 48 hours or less, about 24 hours or less or about 8 hours or less. In some embodiments, the foldable substrate 407 can be heated for from about 15 minutes to about 48 hours, from about 1 hour to about 48 hours, from about 3 hours to about 48 hours, from about 15 hours to about 24 hours , from about 1 hour to about 24 hours, from about 3 hours to about 48 hours, from about 3 hours to about 24 hours, from about 3 hours to about 8 hours, or any range or sub-range therebetween a time. After the foldable substrate 407 has been heated, the foldable substrate 407 may include chemically strengthened first portion 421, second portion 431, and/or central portion 481, which portions may include as discussed above with associated compression depths and/or or compressive stress regions for layer depths, which depths may further include any and/or all of the relationships discussed above (e.g., distance from the first surface region, second surface region, third surface region, and/or as a percentage of substrate thickness) or the absolute difference between the compression depth and/or layer depth of the fourth surface region and the corresponding depth from the first and/or second central surface region as a percentage of the central thickness).

After step 1611, as shown in FIG. 34, the method of the present disclosure may proceed to step 1613, including removing salt paste (eg, salt deposits). In some embodiments, as shown, removing the paste (eg, the first salt deposit 3209 ) can include moving the abrasive tool 3401 in a direction 3402 across the surface (eg, the third surface region 433 ). In still further embodiments, using the tool may include sweeping, scraping, grinding, pushing, and the like. In further embodiments, the paste (eg, first salt deposits 3205, 3207, 3209, and/or 3211) may be prepared by washing the surfaces (eg, first surface region 223, second surface region 225, The third surface area 233, the fourth surface area 235) are removed. In some embodiments, as shown, removing the paste (eg, the second salt deposit 3303 ) can include moving the abrasive tool 3403 in a direction 3404 across the surface (eg, the first central surface region 409 ). In still further embodiments, using the tool may include sweeping, scraping, grinding, pushing, and the like. In further embodiments, the paste (eg, second salt deposits 3303 and/or 3305) may be obtained by washing the surface (eg, first central surface region 409 and/or second central surface region 419) with a solvent to remove.

After step 1613 , the method of the present disclosure may proceed to step 1615 , including further chemically strengthening the foldable substrate 407 . In some embodiments, as shown in FIG. 30, further chemical strengthening of the foldable substrate 407 in step 1615 may be similar or identical to the chemical strengthening in step 1605 discussed above. In some embodiments, as shown in FIG. 30, step 1615 may include contacting at least a portion of the foldable substrate 407 comprising lithium cations and/or sodium cations with a salt bath 2401 comprising a salt solution 2403, the salt solution Include one or more of the alkali metal ions and/or alkali metal-containing compounds discussed above with respect to steps 1615 or 1509. In some embodiments, the salt solution 2403 may comprise a temperature within one or more of the ranges discussed above with respect to steps 1615 or 1509. After step 1615, the foldable substrate 407 may include one or more regions of compressive stress (eg, first, second, third, fourth, first central, and/or second central regions of compressive stress) included in the A compression depth and/or an associated layer depth within one or more ranges is discussed above with respect to corresponding regions of compressive stress.

In some embodiments, steps 1613 or 1615 may further comprise chemically etching the foldable substrate 407 . As described above, chemically etching the foldable substrate 407 may include contacting the foldable substrate 407 with an etching solution contained in an etching bath. In some embodiments, the first major surface 403 and the first central surface region 409 are etched. In some embodiments, the second major surface 405 and the second central surface region 419 are etched. In further embodiments, the first major surface 403, the first central surface region 409, the second major surface 405, and/or the second central surface region 419 are etched. Chemical etching, if present in steps 1613 or 1615 , may be designed to remove surface imperfections that may be left from chemically strengthened foldable substrate 407 . In fact, chemical strengthening can result in surface imperfections that can affect the strength and/or optical quality of the foldable substrate 407 . By etching during steps 1613 or 1615, surface defects created during chemical strengthening can be removed. In some embodiments, this etch can be designed to remove about 1 nm or more, about 5 nm or more, about 2 μm or less, about 1 μm or less, about 500 nm or less, A portion of the layer to a depth of about 100 nm or less, about 50 nm or less, or about 10 nm or less. In some embodiments, this etch can be designed to remove particles ranging from about 1 nm to about 2 μm, from about 1 nm to about 1 μm, from about 5 nm to about 1 μm, from about 5 nm to about 500 μm nm, from about 5 nm to about 100 nm, from about 5 nm to about 50 nm, from about 5 nm to about 10 nm, a range of depths, or a portion of the layer in any range or subrange therebetween. This etching can avoid substantially changing the thickness of the foldable substrate 407 or the surface compression achieved during chemical strengthening.

After step 1613 or 1615, the method of the present disclosure may proceed to step 1617, including using the foldable substrate 407 to assemble the foldable device. In some embodiments, as shown in FIG. 47 , step 1617 may include disposing a coating 251 on the first major surface 403 and/or in the first recess 434 . In some embodiments, the second liquid 4703 may be disposed on the first major surface 403 as shown. In other embodiments, the second liquid 4703 may be disposed on the first surface area 423 of the first portion 421 and the third surface area 433 of the second portion 431 . In further embodiments, the second liquid 4703 may be disposed on the first central surface region 409 and/or fill the first recess 434 . In further embodiments, as shown, a container 4701 (eg, tubing, flexible tubing, micropipette, or syringe) may be used to accommodate the second liquid 4703. In some embodiments, the second liquid 4703 may include coating precursors, solvents, particles, nanoparticles, and/or fibers. In some embodiments, the coating precursor may include, without limitation, one or more of the monomers, accelerators, curing agents, epoxy resins, and/or acrylates discussed above with reference to step 1511 . The second liquid 4703 can be cured to form a coating 251, as shown in FIG. Curing the second liquid 4703 can include heating the second liquid 4703, irradiating the second liquid 4703 with ultraviolet (UV) radiation, and/or waiting a predetermined amount of time (eg, from about 30 minutes to 24 hours, from about 1 hour to about 8 hours). In some embodiments, as discussed above with reference to step 1511, another method may be used to form coating 251. In some embodiments, although not shown, coating 251 may be disposed in first recess 434 (eg, fill first recess 434 ) without contacting first major surface 403 (eg, first surface region 423 ) , the third surface area 433).

In some embodiments, as shown in FIG. 48 , step 1617 may include placing a material in the second recess 444 . In some embodiments, the third liquid 4803 can be seated in the second recess 444 as shown. In some embodiments, the third liquid 4803 may include precursors, solvents, particles, nanoparticles, and/or fibers. In further embodiments, as shown, the third liquid 4803 may be disposed in the second recess 444 from the container 4801, although other methods may be used to deposit the third liquid or other material in the second recess, as described above with reference to step 1511 Discussed with respect to the first recess and/or the second liquid. In some embodiments, the third liquid 4803 may be cured (eg, heating the third liquid, irradiating the third liquid, waiting a specified amount of time) to form the polymer-based portion 241 in the second recess 444, as in Shown in Figure 49. In some embodiments, although not shown, the third liquid may be cured to form an adhesive layer disposed in the second recess 444 , eg, similar to the adhesive layer 261 .

After step 1613 or 1615, as shown in FIG. 49, the method may proceed to step 1619, including using the foldable substrate 407 to assemble the foldable device. As shown in FIG. 49 , step 1617 may include applying the adhesive layer 261 to bring the second surface region 425 of the second major surface 405 into contact with the fourth surface region 435 of the second major surface 405 . For example, in some embodiments, the adhesive layer 261 may comprise one or more sheets of adhesive material. In some embodiments, there may be an integral interface between one or more sheets including the adhesive layer 261 and/or material disposed in the second recess (eg, the polymer-based portion 241 ), which may reduce ( For example, avoid optical diffraction and/or optical discontinuities as light travels between the flakes, since in some embodiments one or more flakes may comprise substantially the same index of refraction. In some embodiments, although not shown, at least a portion of the adhesive layer may be disposed in the second recess. In some embodiments, a release liner (eg, see release liner 271 in Figures 2 and 4) or a display device (eg, see display device 307 in Figures 3 and 5) can be Disposed on the adhesive layer 261 (eg, the first contact surface 263 ). At step 1617 , the method of the present disclosure according to the flowchart in FIG. 16 of making a foldable device may be completed at step 1619 .

In some embodiments, a method of making a foldable device according to embodiments of the present disclosure may follow steps 1601 , 1603 , 1605 , 1607 , 1609 , 1611 , 1613 , 1615 , 1617 of the flowchart in FIG. 16 and 1619 in sequence, as discussed above. In some embodiments, as shown in FIG. 16, arrow 1602 may follow step 1601, omitting step 1603, eg, when foldable substrate 407 already includes one or more recesses. In some embodiments, arrow 1604 may follow step 1601 to step 1609 that includes placing a mask on the foldable substrate, eg, if the foldable device includes a recess at the end of step 1501, and the foldable substrate 407 already contains areas of initial compressive stress, or the foldable substrate 407 will be chemically strengthened until after step 1609. In some embodiments, arrow 1608 may follow step 1603 to step 1609 that includes placing a mask on foldable substrate 407, eg, if foldable substrate 407 already includes an area of initial compressive stress, or foldable substrate 407 Chemical strengthening is applied until after step 1609. In further embodiments, the method may follow arrow 1612 from step 1613 to step 1617 comprising assembling the foldable device, eg, if coating 251 is not to be seated in first recess 434 and/or first major surface 403 , and the polymer-based portion 241 will not be seated in the second recess 444 . In some embodiments, the method may follow arrow 1614 from step 1613 to step 1619, eg, if the foldable substrate 407 is the desired product (eg, no material in the first pocket or the second pocket). In some embodiments, the method may follow arrow 1618 from step 1615 to step 1619 , eg, if the foldable device would not include a release liner 271 , display device 307 and/or adhesive layer 261 . Any of the above options can be combined to make a foldable device according to embodiments of the present disclosure.

Making a foldable device similar to the foldable device 701 illustrated in Figure 8 and/or the flow charts in Figures 35-39 and 47-49 and 17 will now be discussed An example embodiment of a foldable substrate similar to foldable substrate 707 . In a first step 1701 of the method of the present disclosure, the method may begin by providing a foldable substrate 707 . In some embodiments, the foldable substrate 707 may be provided by purchasing or otherwise obtaining the substrate or by forming a foldable substrate. In some embodiments, the foldable substrate 707 may include a glass-based substrate and/or a ceramic-based substrate. In further embodiments, glass-based substrates and/or ceramic-based substrates may be formed by various strip-forming processes (eg, slot draw, draw down, fusion draw, pull up, roll, redraw, or float) it is provided. In further embodiments, the ceramic-based substrate may be provided by heating the glass-based substrate to crystallize one or more ceramic crystals. The foldable substrate 707 can include a second major surface 405 (see FIG. 35 ) that can extend along a plane, and/or a second major surface opposite the first major surface 403 that can also extend along a plane 405. In other embodiments, the first recess 3534 may be formed by etching, laser ablation, or machining the first major surface 403 . For example, machining the foldable substrate 707 may be similar to step 1603 discussed above. In some embodiments, in step 1701 , the foldable substrate 707 may be provided with one or more regions of initial compressive stress, eg, having one or more of the properties discussed above with reference to step 1605 .

In some embodiments, in step 1701 , the foldable substrate 707 may be provided with a first recess 3534 in the first major surface 403 of the foldable substrate 707 that is exposed between the foldable substrate 707 in the central portion 781 There is a first central surface region 3609, as shown in FIG. In other embodiments, a portion of the existing first central surface region 3609 may extend along a first central plane 3704a. In some embodiments, although not shown, the foldable substrate can be provided with a second recess in a second major surface of the foldable substrate that exposes a second central surface area of the foldable substrate in the central portion . In some embodiments, as shown in Figure 35, the existing first central surface region 3609 may include a first transition portion 3553 (eg, similar to the first transition portion 853 in Figure 8) and/or a first transition portion 3553 Two transition portions 3555 (eg, similar to the second transition portion 855 in Figure 8). In further embodiments, as shown, the thickness of the first transition portion 3553 may increase continuously from a portion of the existing first central surface region 3609 that includes the first central plane 3704a to the first portion 421 . In further embodiments, as shown, the thickness of the second transition portion 3555 may increase continuously from a portion of the existing first central surface region 3609 that includes the first central plane 3704a to the second portion 431 .

After step 1701 , as shown in FIG. 35 , the method may proceed to step 1703 including chemically strengthening the foldable substrate 707 . In some embodiments, as shown, chemically strengthening the foldable substrate 707 can include contacting at least a portion of the foldable substrate 707 comprising lithium cations and/or sodium cations with a salt bath 2401 comprising a salt solution 2403, the salt solution One or more of the components discussed above with respect to step 1713 for saline solution 2403 may be included. In some embodiments, the temperature of the salt solution 2403 and/or the time for which the foldable substrate 707 can contact the salt solution 2403 may be within one or more of the ranges discussed above with reference to step 1509 . In some embodiments, chemically strengthened foldable substrate 707 in step 1703 may include chemically strengthened first major surface 403 to form an initial first compression extending from first major surface 403 of first portion 421 to an initial first compression depth Stressed region, chemically strengthened first major surface 403 to form an initial third compressive stress region extending from first major surface 403 of second portion 431 to an initial third compression depth, chemically strengthened second major surface 405 to form from the first The second major surface 405 in the portion 421 extends to an initial second compressive stress region at the initial second compression depth, and the second major surface 405 is chemically strengthened to form extending from the second major surface 405 in the second portion 431 to the initial second An initial fourth compressive stress region at one of the four compression depths, chemically strengthening the existing first central surface region 3609 to form an initial first central compressive stress region extending from the existing first central surface region 3609 to the initial first central compression depth, and The second major surface 405 is chemically strengthened to form an initial second central compressive stress region extending from the second major surface 405 in the central portion 781 to the initial second central compressive depth. In some embodiments, the initial first depth of compression, the initial second depth of compression, the initial third depth of compression, and/or the initial fourth depth of compression as a percentage of substrate thickness 411 may be about 5% or greater, 10% or greater, about 12% or greater, about 14% or greater, about 25% or less, about 20% or less, about 18% or less, or about 16% or less. In some embodiments, the initial first depth of compression, the initial second depth of compression, the initial third depth of compression, and/or the initial fourth depth of compression as a percentage of substrate thickness 411 may be from about 5% to about 25%, from about 8% to about 25%, from about 8% to about 20%, from about 10% to about 20%, from about 10% to about 18%, from about 12% to about 18%, from about 12% to In a range of about 16%, from about 14% to about 16%, or any range or subrange therebetween. In some embodiments, the initial first compression depth, the initial second compression depth, the initial third compression depth, and/or the initial fourth compression depth as a percentage of the corresponding compression depth of the finished foldable substrate 407 may be about 50% or more, 60% or more, about 65% or more, about 68% or more, about 80% or less, about 75% or less, or about 72% or less, or about 70% or less. In some embodiments, the initial first compression depth, the initial second compression depth, the initial third compression depth, and/or the initial fourth compression depth as a percentage of the corresponding compression depth of the finished foldable substrate 407 may be from about 50% to about 80%, from about 60% to about 80%, from about 60% to about 75%, from about 65% to about 75%, from about 65% to about 72%, from about 68% to about 72%, a range from about 68% to about 70%, or any range or subrange therebetween. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of substrate thickness 411 may be about 5% or greater, 10% or greater, about 12% or greater, about 14% or greater, about 25% or less, about 20% or less, about 18% or less, or about 16% or less. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of substrate thickness 411 may be from about 5% to about 25%, from about 8% to about 25%, from about 8% to about 20%, from about 10% to about 20%, from about 10% to about 18%, from about 12% to about 18%, from about 12% to In a range of about 16%, from about 14% to about 16%, or any range or subrange therebetween. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of the corresponding layer depths of the finished foldable substrate 407 may be about 50% or more, 60% or more, about 65% or more, about 68% or more, about 80% or less, about 75% or less, or about 72% or less, or about 70% or less. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of the corresponding compression depth of the finished foldable substrate 407 may be from about 50% to about 80%, from about 60% to about 80%, from about 60% to about 75%, from about 65% to about 75%, from about 65% to about 72%, from about 68% to about 72%, a range from about 68% to about 70%, or any range or subrange therebetween.

After step 1701 or 1703 , as shown in FIG. 36 , the method may proceed to step 1707 including disposing a mask on one or more portions of the foldable substrate 707 . In some embodiments, step 1707 may include disposing the first liquid 2107 on one or more portions of the foldable substrate 407, as shown. In further embodiments, as shown and discussed above with reference to step 1503, a container 2101 may be used to place the first liquid 2107 on one or more portions of the foldable substrate 707. In further embodiments, as shown, the first liquid 2107 may be disposed on the first major surface 403 of the first portion 421 and the first transition portion 3553 of the existing first central surface region 3609 as the first liquid deposit 3603, And on the first main surface 403 of the second portion 431 and the second transition portion 3555 of the existing first central surface region 3609, as the second liquid deposit 3605. Although not shown, it should be understood that similar liquid deposits may form on the second major surface of the first portion and/or the second major surface of the second portion. In further embodiments, the liquid deposits (eg, the first liquid deposit 3603 and the second liquid deposit 3605 shown in FIG. 36 ) can be cured to form a mask (eg, the first liquid deposit 3605 shown in FIG. 37 ) mask 3705 and third mask 3709). Curing the first liquid may include heating the first liquid 2107, irradiating the first liquid 2107 with ultraviolet (UV) radiation, and/or waiting a predetermined amount of time. In further embodiments, the masks (eg, masks 3705, 3707, 3709, and 3711) may be formed using another method as discussed above. As shown in FIG. 30, the first mask 3705 may be disposed on the first major surface 403 of the first portion 421 and the first transition portion 3553 of the existing first central surface area 3609, and the second mask 3707 may be disposed on the first On the first main surface 403 of the two parts 431 and the second transition part 3555 of the existing first central surface area 3609, the third mask 3709 may be disposed on the second main surface 405 of the first part 421, and/or the fourth mask The cover 3711 may be disposed on the second major surface 405 of the second portion 431 .

After step 1707 , as shown in FIG. 37 , the method may proceed to step 1709 including etching the foldable substrate 707 . In some embodiments, as shown, etching can include exposing the foldable substrate 707 to an etchant 2203 (eg, one or more inorganic acids). In further embodiments, as shown, the etchant 2203 may be a liquid etchant contained in the etchant bath 2201 . In further embodiments, as shown, etching may include etching a portion of central portion 781 (eg, an unmasked portion of existing first central surface region 3609 ) to form a first central surface region 709 . In further embodiments, as shown, the first central surface region 709 formed by etching may be recessed by a transition depth 727 from the first central plane 3704a. In further embodiments, the first central surface region 709 formed by etching may include a first transition portion 753 and/or a second transition portion 755 that include abrupt changes in the thickness of the corresponding transition portion including the transition depth 727 Change. In further embodiments, as shown, the etching may form a second recess 444 between the second major surface 405 and the second central surface region 719 .

After step 1709, as shown in FIG. 38, the method may proceed to step 1711, including removing the mask(s). In some embodiments, as shown in FIG. 38, removing the mask(s) (eg, masks 3705, 3707, 3709, and 3711) may be included in the spanning surface (eg, third surface region 433) Move the grinding tool 3801 in a direction 3802. In still further embodiments, using the tool may include sweeping, scraping, grinding, pushing, and the like. In further embodiments, the mask(s) (eg, masks 3705, 3707, 3709, and 3711) may be prepared by washing the surfaces (eg, first surface region 423, second surface region 425, third surface) with a solvent area 433, fourth surface area 435) to remove. In some embodiments, removing the mask(s) may include removing the masks 3705, 3707, 3709 from the first surface region 423, the second surface region 425, the third surface region 433, the fourth surface region 435, respectively and 3711.

After step 1703 , the method may continue to step 1705 including machining the foldable substrate 707 . Similar to the effect of step 1707, step 1705 may remove material from the existing first central surface region 3609 including the first central plane 3704a and/or the central portion 781 of the second major surface 405. Machining the foldable substrate 707 may include any of the techniques discussed above with reference to step 1517 .

After step 1711 or 1705 , as shown in FIG. 39 , the method may proceed to step 1713 including chemically strengthening the foldable substrate 707 . In some embodiments, as shown, chemically strengthening the foldable substrate 707 can include contacting at least a portion of the foldable substrate 707 comprising lithium cations and/or sodium cations with a salt bath 2401 comprising a salt solution 2403, the salt solution One or more of the components discussed above with respect to step 1509 for saline solution 2403 may be included. In some embodiments, the temperature of the salt solution 2403 and/or the time for which the foldable substrate 707 can contact the salt solution 2403 may be within one or more of the ranges discussed above with reference to step 1509 . In some embodiments, chemically strengthening the foldable substrate 707 in step 1713 may include chemically strengthening the first surface region 423 to form a first compressive stress region extending from the first surface region 423 to the first compression depth, the chemically strengthening the first compressive stress region. Two surface regions 425 to form a second compressive stress region extending from the second surface region 425 to a second compression depth, and chemically strengthening the third surface region 433 to form a first region extending from the third surface region 433 to the third compression depth Three compressive stress regions, chemically strengthened fourth surface region 435 to form a fourth compressive stress region extending from fourth surface region 435 to a fourth compression depth, chemically strengthened first central surface region 709 to form from the first central surface region 709 a first central compressive stress region extending to the first central compression depth, and chemically strengthening the second central surface region 719 to form a second central compressive stress region extending from the second central surface region 719 to the second central compression depth . After step 1713, the foldable substrate may include one or more regions of compressive stress (eg, first, second, third, fourth, first central, and/or second central compressive stress regions), which are included above A compression depth and/or an associated layer depth within one or more ranges is discussed with respect to the corresponding compressive stress region. In another embodiment, one of the first layer depth, the second layer depth, the third layer depth, or the fourth layer depth is divided by the thickness of the substrate and the depth of the first center layer or the depth of the second center layer divided by the center thickness The absolute difference between can be within one or more of the ranges discussed above. In further embodiments, one of the first compression depth, the second compression depth, the third compression depth or the fourth compression depth is divided by the thickness of the substrate and the first central compression depth or the second central compression depth divided by the central thickness The absolute difference between can be within one or more of the ranges discussed above. In further embodiments, the absolute difference between the first average potassium concentration or the second average potassium concentration and the central average potassium concentration may be within one or more of the ranges discussed above.

After step 1713, the first transition portion and/or the second transition portion may include a transitional tensile stress region that includes a transitional maximum tensile stress. In some embodiments, the first portion can include a first region of tensile stress that includes a first maximum tensile stress, the second portion can include a second region of tensile stress that includes the first maximum tensile stress, and the center portion can include The central tensile stress region containing the central maximum tensile stress region. In further embodiments, the transition maximum tensile stress may be greater than the central maximum tensile stress. In further embodiments, the transition maximum tensile stress may be greater than the first maximum tensile stress and/or the second maximum tensile stress. For example, masking the first transition portion and/or the second transition portion in steps 1705 and 1707 may prevent removal of the corresponding initial compressive stress region, which may enable the first transition portion and/or the second transition portion to be After step 1713 a maximum tensile stress is included that is greater than the central portion. Likewise, the initial compressive stress region of the first transition portion and/or the second transition portion maintained through steps 1705 and 1707 is combined with the first transition portion and/or the second transition portion relative to the first portion and/or the second portion. The reduced thickness enables the transition maximum tensile stress to be greater than the first maximum tensile stress and/or the second maximum tensile stress. Providing a transition maximum tensile stress greater than the central maximum tensile stress may counteract the strain between the first or second portion and the first and/or second transition portion during folding. Providing a transition maximum tensile stress greater than the first maximum tensile stress and/or the second maximum tensile stress may counteract the strain between the central portion and the first transition portion and/or the second transition portion during folding.

After step 1713 , the method of the present disclosure may proceed to step 1715 including disposing a coating 251 on the first major surface 403 and/or in the first recess 434 . In some embodiments, as shown in FIG. 47 for the foldable substrate 407 , the second liquid 4703 may be disposed on the first major surface 403 . In other embodiments, the second liquid 4703 may be disposed on the first surface region 423 of the first portion 421 and the third surface region 433 of the second portion 431 . In other embodiments, the second liquid 4703 may be disposed on the first central surface region 709 and/or fill the first recess 434 . In further embodiments, as shown, a container 4701 (eg, tubing, flexible tubing, micropipette, or syringe) may be used to accommodate the second liquid 4703. In some embodiments, the second liquid 4703 may include coating precursors, solvents, particles, nanoparticles, and/or fibers. In some embodiments, the coating precursor may include, without limitation, one or more of monomers, accelerators, curing agents, epoxy resins, and/or acrylates. In some embodiments, the solvent used for the adhesive precursor may comprise a polar solvent (eg, water, ethanol, acetate, acetone, formic acid, dimethylformamide, acetonitrile, dimethylamine phenylsulfinic acid) , nitromethane, propylene carbonate, poly(ether ether ketone)) and/or non-polar solvents (e.g., pentane, 1,4-dioxane, chloroform, dichloromethane, diethyl ether, hexane, heptane , benzene, toluene, xylene). The second liquid 4703 can be cured to form a coating 251, as shown in FIGS. 48-49. Curing the second liquid 4703 can include heating the second liquid 4703, irradiating the second liquid 4703 with ultraviolet (UV) radiation, and/or waiting a predetermined amount of time (eg, from about 30 minutes to 24 hours, from about 1 hour to about 8 hours). In some embodiments, another method (eg, chemical vapor deposition (CVD) (eg, low pressure CVD, plasma enhanced CVD), physical vapor deposition (PVD) ( For example, evaporation, molecular beam epitaxy, ion plating), atomic layer deposition (ALD), sputtering, spray pyrolysis, chemical bath deposition, sol-gel deposition) to form the coating 251 . In some embodiments, although not shown, coating 251 may be disposed in first recess 434 (eg, fill first recess 434 ) without contacting first major surface 403 (eg, first surface region 423 ) , the third surface area 433).

After step 1713 or 1715 , the method of the present disclosure may proceed to step 1719 , including placing material in the second recess 444 . In some embodiments, as shown in FIG. 48 for the foldable substrate 407 , the third liquid 4803 may be seated in the second recess 444 . In some embodiments, the third liquid 4803 may include precursors, solvents, particles, nanoparticles, and/or fibers. In further embodiments, as shown, the third liquid 4803 may be disposed in the second recess 444 from the container 4801, although other methods may be used to deposit the third liquid or other material in the second recess, as described above with respect to the first The dimples and/or the second liquid are discussed. In some embodiments, the third liquid 4803 can be cured (eg, heating the third liquid, irradiating the third liquid, waiting a specified amount of time) to form the polymer-based portion 241 in the second recess 444, as in Shown in Figure 49. In some embodiments, although not shown, the third liquid may be cured to form an adhesive layer disposed in the second recess 244 , eg, similar to the adhesive layer 261 .

After step 1715 or 1717, the method of the present disclosure may proceed to step 1719, including using the foldable substrate 707 to assemble a foldable device. As shown in FIG. 49 with reference to the foldable substrate 407 , step 1719 may include applying the adhesive layer 261 to bring the second surface region 425 of the second major surface 405 into contact with the fourth surface region 435 of the second major surface 405 . For example, in some embodiments, the adhesive layer 261 may comprise one or more sheets of adhesive material. In some embodiments, there may be an integral interface between one or more sheets comprising the adhesive layer 261 and/or material disposed in the second recess (eg, the polymer-based portion 241 ), which may reduce ( For example, avoid) optical diffraction and/or optical discontinuities as light travels between the flakes, since in some embodiments one or more flakes may comprise substantially the same refractive index. In some embodiments, although not shown, at least a portion of the adhesive layer may be disposed in the second recess. In some embodiments, a release liner (eg, see release liner 271 in Figures 2 and 4) or a display device (eg, see display device 307 in Figures 3 and 5) can be Disposed on the adhesive layer 261 (eg, the first contact surface 263 ). After step 1719 , the method of the present disclosure according to the flowchart of FIG. 17 of making a foldable device may be completed at step 1721 .

In some embodiments, a method of making a foldable device according to embodiments of the present disclosure may follow steps 1701 , 1703 , 1707 , 1709 , 1711 , 1713 , 1715 , 1717 , 1719 of the flowchart in FIG. 17 and 1721 in sequence, as discussed above. In some embodiments, as shown in FIG. 17, arrow 1702 may follow step 1701, omitting step 1703, eg, when foldable substrate 707 includes one or more regions of compressive stress after step 1701. In another embodiment, arrow 1708 may follow step 1703 to step 1705 that includes machining the foldable substrate 707, rather than chemically etching the foldable substrate through steps 1707, 1709, and 1711. In some embodiments, arrow 1704 may follow step 1701 to step 1707 , eg, when the foldable substrate 707 includes one or more regions of compressive stress after step 1701 . In some embodiments, arrow 1706 may follow step 1701 to step 1713 of including chemically strengthened foldable substrate, eg, when foldable substrate 707 already includes the desired recesses. In some embodiments, the method may include placing material in the second recess 444 along arrow 1714 from step 1713 to step 1717 . In further embodiments, the method may include disposing a coating 251 on the first major surface and/or in the first recess 434 along arrow 1716 from step 1717 to step 1715 . In still further embodiments, the method may include assembling the foldable device, along arrow 1718 from step 1715 to step 1719, eg, if the foldable device already includes coating 251 or a polymer-based portion 241, or another The material is to be seated in one or more pockets. In some embodiments, the method may follow arrow 1720 from step 1715 to step 1721, eg, if the foldable device is fully assembled at the end of step 1715, or if another material is to be placed in the first recess and/or on the first major surface, and/or on the second major surface. In some embodiments, the method may follow arrow 1722 from step 1717 to step 1721, eg, if the foldable device is fully assembled at the end of step 1717, or if another material is to be placed in the second recess and/or on the second major surface. In some embodiments, the method may follow arrow 1712 from step 1713 to step 1721, eg, if the foldable substrate 707 is the desired product (eg, no material in the first pocket or the second pocket). Any of the above options can be combined to make a foldable device according to embodiments of the present disclosure.

An example embodiment of making a foldable device similar to the foldable device 801 illustrated in FIG. 8 will now be discussed with reference to the flowcharts in FIGS. 40-49 and 18 . In a first step 1801 of the method of the present disclosure, the method may begin by providing a foldable substrate 4007 . In some embodiments, the foldable substrate 4007 may be provided by purchasing or otherwise obtaining the substrate or by forming a foldable substrate. In some embodiments, the foldable substrate 4007 may comprise a glass-based substrate and/or a ceramic-based substrate. In further embodiments, glass-based substrates and/or ceramic-based substrates may be formed by various strip-forming processes (eg, slot draw, draw down, fusion draw, pull up, roll, redraw, or float) it is provided. In further embodiments, the ceramic-based substrate may be provided by heating the glass-based substrate to crystallize one or more ceramic crystals. The foldable substrate 4007 can include an existing second major surface 4005 (see FIG. 40 ) that can extend along a plane. The existing second main surface 4005 may be opposite to the first main surface 4003 .

In some embodiments, in step 1801 , the foldable substrate 407 may be provided with a first recess 834 in the first major surface 4003 of the foldable substrate 4007 that is exposed between the foldable substrate 4007 in the central portion 4081 There is a first central surface area 4009. In further embodiments, although not shown, the existing first central surface region 4009 may include a transition region (eg, similar to transition regions 853 and/or 855). In other embodiments, the first recess 834 may be formed by etching, laser ablation, or machining the first major surface 4003 . For example, machining the foldable substrate 4007 can be similar to step 1603 discussed above. In some embodiments, in step 1801 , the foldable substrate 4007 may be provided with one or more regions of initial compressive stress, eg, having one or more of the properties discussed above with reference to step 1605 .

After step 1801, in some embodiments, the method may proceed to step 1803, including machining the existing second major surface 4005 (see FIG. 41). In some embodiments, step 1803 may include removing the first portion 821 of the existing second major surface 4005 to reveal the second surface region 825 of the first portion 821 . In some embodiments, step 1803 may include removing the second portion 831 of the existing second major surface 4005 to reveal the fourth surface region 835 of the second portion 831 . As shown in FIG. 41 , the second surface region 825 and/or the fourth surface region may include a second major surface 805 . As shown in FIG. 41 , the existing second major surface 4005 extending along a plane 4104 may be modified to reveal the second surface region 825 and/or the fourth surface region 835 . For example, as shown in Figure 26 with reference to the foldable substrate 404, diamond engraving may be used, wherein a computer numerical control (CNC) machine 2003 may be used to control the diamond tip probe 2001. Materials other than diamond can be used for engraving by CNC machines. It should be understood that other methods of forming the recess(s) may be used, such as lithography and laser ablation.

After step 1801 , as shown in FIG. 40 , the method may continue to step 1805 including disposing a mask on one or more portions of the foldable substrate 4007 . In further embodiments, as shown, step 1805 may include disposing the first liquid deposit 4011 on the existing second major surface 4005 in the central portion 4081 . In further embodiments, as shown, a container 3201 may be used to house the first liquid deposit 4011. In further embodiments, the first liquid deposit 4011 may comprise the first liquid 2107 discussed above. In further embodiments, the liquid deposit (eg, the first liquid deposit 4011 shown in FIG. 40 ) may be cured to form a mask (eg, the first mask 4103 shown in FIG. 41 ). Curing the first liquid may include heating it, irradiating it with ultraviolet (UV) radiation, and/or waiting a predetermined amount of time. In further embodiments, the mask may be formed using another method as discussed above.

After step 1805 , the method may continue to step 1807 including etching at least the existing second major surface 4005 of the foldable substrate 4007 . In further embodiments, etching can include exposing the foldable substrate 4007 to an etchant (eg, one or more inorganic acids). In further embodiments, as shown in FIG. 41 , the etching may include etching the first portion 821 of the existing second major surface 4005 extending along the plane 4104 to reveal the second surface region 825 of the first portion 821 . In further embodiments, as shown in FIG. 41 , the etching may include etching the second portion 831 of the existing second major surface 4005 extending along the plane 4104 to reveal the fourth surface region 835 of the second portion 831 . In further embodiments, as shown in FIG. 41 , the second surface region 825 and/or the fourth surface region 835 exposed by etching may include a second major surface 805 .

After step 1807 , as shown in FIG. 41 , the method may proceed to step 1809 , including removing mask 4103 . In some embodiments, as shown, removing the mask 4103 can include moving the abrasive tool 4101 in a direction 4102 across a surface (eg, the existing second major surface 4005 in the central portion 4081). In still further embodiments, using the tool may include sweeping, scraping, grinding, pushing, and the like. In further embodiments, the mask 4103 may be removed by washing the surface (eg, the existing second major surface 4005 in the central portion 4081) with a solvent. In some embodiments, removing the mask can include removing the mask 4103 from the existing second major surface 4005 in the central portion 4081 .

After step 1803 or 1809 , as shown in FIG. 42 , the method may proceed to step 1811 including chemically strengthening the foldable substrate 4007 . In some embodiments, as shown, chemically strengthening the foldable substrate 407 can include contacting at least a portion of the foldable substrate 4007 comprising lithium cations and/or sodium cations with a salt bath 4201 comprising a salt solution 4203, the salt solution One or more of the components discussed above with reference to step 1509 for saline solution 2403 may be included. In some embodiments, the temperature of saline solution 4203 and/or the time for which foldable substrate 4007 can contact saline solution 100 may be within one or more of the ranges discussed above with reference to step 1509. In some embodiments, chemically strengthening the foldable substrate 4007 in step 1811 may include chemically strengthening the existing first central surface region 4009 to form an initial first one extending from the existing first central surface region 4009 to the initial first central compression depth Central compressive stress region, chemically strengthened first surface region 823 to form an initial first compressive stress region extending from first surface region 823 to an initial first compression depth, chemically strengthened third surface region 833 to form from third surface region 833 an initial third compressive stress region extending to an initial third compression depth, chemically strengthening the second surface region 825 to form an initial second compressive stress region extending from the second surface region 825 to an initial second compression depth, chemically strengthening the fourth surface region 835 to form an initial fourth compressive stress region extending from the fourth surface region 835 to the initial fourth compression depth, and chemically strengthening the existing second major surface 4005 to form an initial fourth compressive stress region extending from the existing second major surface 4005 to the initial An initial second central compressive stress region of the second central compressive depth.

After step 1811, the foldable substrate 4007 may include one or more initial compressive stress regions (eg, first, second, third, fourth, first central, and/or second central compressive stress regions) including An initial compression depth and/or an associated initial layer depth. In some embodiments, the initial first depth of compression, the initial second depth of compression, the initial third depth of compression, and/or the initial fourth depth of compression as a percentage of substrate thickness 811 may be about 5% or more, 10% or greater, about 12% or greater, about 14% or greater, about 25% or less, about 20% or less, about 18% or less, or about 16% or less. In some embodiments, the initial first depth of compression, the initial second depth of compression, the initial third depth of compression, and/or the initial fourth depth of compression as a percentage of substrate thickness 811 may be from about 5% to about 25%, from about 8% to about 25%, from about 8% to about 20%, from about 10% to about 20%, from about 10% to about 18%, from about 12% to about 18%, from about 12% to In a range of about 16%, from about 14% to about 16%, or any range or subrange therebetween. In some embodiments, the initial first compression depth, the initial second compression depth, the initial third compression depth, and/or the initial fourth compression depth as a percentage of the corresponding compression depth of the finished foldable substrate 4007 may be about 50% or more, 60% or more, about 65% or more, about 68% or more, about 80% or less, about 75% or less, or about 72% or less, or about 70% or less. In some embodiments, the initial first compression depth, the initial second compression depth, the initial third compression depth, and/or the initial fourth compression depth as a percentage of the corresponding compression depth of the finished foldable substrate 4007 may be about 50% to about 80%, from about 60% to about 80%, from about 60% to about 75%, from about 65% to about 75%, from about 65% to about 72%, from about 68% to about 72%, a range from about 68% to about 70%, or any range or subrange therebetween. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of substrate thickness 811 may be about 5% or greater, 10% or greater, about 12% or greater, about 14% or greater, about 25% or less, about 20% or less, about 18% or less, or about 16% or less. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of substrate thickness 811 may be from about 5% to about 25%, from about 8% to about 25%, from about 8% to about 20%, from about 10% to about 20%, from about 10% to about 18%, from about 12% to about 18%, from about 12% to In a range of about 16%, from about 14% to about 16%, or any range or subrange therebetween. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of the corresponding layer depths of the finished foldable substrate 4007 may be about 50% or more, 60% or more, about 65% or more, about 68% or more, about 80% or less, about 75% or less, or about 72% or less, or about 70% or less. In some embodiments, the initial first layer depth, initial second layer depth, initial third layer depth, and/or initial fourth layer depth as a percentage of the corresponding compression depth of the finished foldable substrate 4007 may be about 50% to about 80%, from about 60% to about 80%, from about 60% to about 75%, from about 65% to about 75%, from about 65% to about 72%, from about 68% to about 72%, a range from about 68% to about 70%, or any range or subrange therebetween.

In some embodiments, as shown in FIG. 42, after step 1811 (eg, before etching the foldable substrate 4007 in step 1815), the existing second central surface region including the existing second major surface 4005 may be free from The second main surface 805 protrudes. As discussed above, the second surface region 825 and the fourth surface region 835 may include the second major surface 805 . In further embodiments, the distance by which the existing second central surface region including the existing second major surface 4005 protrudes from the second major surface 805 may be substantially equal to or greater than the initial second central compression depth produced in step 1811 .

After step 1811 , as shown in FIGS. 43-44 , the method may continue to step 1813 including disposing a mask on the foldable substrate 4007 . In some embodiments, as shown in FIG. 43 , step 1813 may include disposing the first liquid deposit 4303 on the second surface area 825 and disposing the second liquid deposit 4305 on the fourth surface area 835 . In further embodiments, as shown, a container 3201 (eg, a tube, flexible tube, micropipette, or syringe) may be used to house the liquid comprising the first liquid deposit 4303 and the second liquid deposit 4305. In further embodiments, although not shown, a third liquid deposit can be disposed on the first surface region 823 and/or a fourth liquid deposit can be disposed on the second surface region 825 . In further embodiments, the liquid deposits (eg, first liquid deposit 4303, second liquid deposit 4305) may be cured to form a mask (eg, second mask 4405 shown in FIG. 44 and/or fourth mask 4409). Curing the liquid deposit may include heating it, irradiating it with ultraviolet (UV) radiation, and/or waiting a predetermined amount of time. In further embodiments, the mask may be formed using another method as discussed above. As shown in FIG. 44, step 1813 may result in a first mask 4407 disposed over the first surface region 823, a second mask 4405 disposed over the second surface region 825, a second mask 4405 disposed over the third surface region 833 The third mask 4411 and the fourth mask 4409 disposed on the fourth surface area 835.

After step 1813 , as shown in FIG. 44 , the method may proceed to step 1815 , including etching the foldable substrate 4007 . In further embodiments, as shown, etching solution 4403 may be a liquid etchant contained in etchant bath 4401 . In still further embodiments, the etching solution 4403 may include one or more inorganic acids (eg, HCl, _HF , _H2SO4 , _HNO3 ). In some embodiments, as shown, etching can include etching a central portion 4081 of the existing second major surface 4005 extending along plane 4104 to form a second central surface region 819 . In further embodiments, as shown, the second central surface region 819 may be coplanar with the second major surface 825 and/or the fourth major surface 835 . In some embodiments, as shown, the etching can include etching a central portion 881 including the existing first central surface region 4009 (see FIG. 42 ) (eg, extending along another plane 4406 ) to reveal a second central surface District 4509. In some embodiments, the depth of material removed to reveal the first central surface region may be substantially equal to, less than, or greater than the original first central compression depth. In some embodiments, the depth of material removed to reveal the second central surface region may be substantially equal to, less than, or greater than the original second central compression depth.

After step 1815, as shown in FIG. 45, the method of the present disclosure may proceed to step 1817, including removing the mask(s). In some embodiments, as shown, removing the mask(s) (eg, fourth mask 4409 ) may include moving abrasive tool 4501 in a direction 4502 across the surface (eg, fourth surface region 835 ) . In still further embodiments, using the tool may include sweeping, scraping, grinding, pushing, and the like. In further embodiments, the mask(s) can be removed by washing the surface of the foldable substrate with a solvent. In some embodiments, as shown, removing the mask(s) may include removing the first mask 4407 from the first surface region 823, removing the second mask 4405 from the second surface region 825, removing the second mask 4405 from the second surface region 825, The third mask 4411 is removed from the three surface regions 833 and/or the fourth mask 4409 is removed from the fourth surface region (eg, by the grinding tool 4501).

After step 1817 , the method of the present disclosure may proceed to step 1819 , including further chemically strengthening the foldable substrate 807 . In some embodiments, as shown in Figure 46, further chemical strengthening of the foldable substrate 4007 in step 1817 may be similar or identical to the chemical strengthening in steps 1605, 1615, or 1811 discussed above. In some embodiments, as shown in FIG. 46, step 1817 may include contacting at least a portion of the foldable substrate 4007 comprising lithium cations and/or sodium cations with a salt bath 4601 comprising a salt solution 4603, the salt solution Include one or more of the alkali metal ions and/or alkali metal containing compounds discussed above with respect to steps 1811, 1615 or 1509. In some embodiments, the salt solution 4603 may comprise a temperature within one or more of the ranges discussed above with respect to steps 1811 , 1615 or 1509 . After step 1819, the foldable substrate 4007 may include one or more regions of compressive stress (eg, first, second, third, fourth, first central, and/or second central regions of compressive stress) that compress Stress regions include compression depths and/or associated layer depths within one or more of the ranges discussed above with respect to corresponding compressive stress regions, which depths may further include any and/or all relationships discussed above (eg, as Compression depth and/or layer depth from the first surface region, second surface region, third surface region and/or fourth surface region as a percentage of the substrate thickness and from the first central surface region as a percentage of the center thickness and/or the absolute difference between the corresponding depths of the second central surface area).

After step 1819 , the methods of the present disclosure may proceed to step 1821 , including disposing material (eg, coating 251 , polymer-based portion 241 , on first major surface 803 and/or in first recess 834 ) , adhesive layer 261). In some embodiments, placing the coating may be the same as or substantially similar to steps 1713 or 1715 discussed above.

After step 1817 or 1819, the method of the present disclosure may proceed to step 1821, including using the foldable substrate 4007 to assemble the foldable device. Step 1821 may include applying an adhesive layer to contact the first major surface or the second major surface of the foldable substrate. Additionally, step 1821 may include disposing a release liner (eg, see release liner 271 in Figures 2 and 4) or a display device (eg, see Figures 3 and 5) on the adhesive layer display device 307). Following step 1821 , the method of the present disclosure according to the flowchart in FIG. 18 of making a foldable device may be completed at step 1823 .

In some embodiments, a method of making a foldable device according to embodiments of the present disclosure may follow steps 1801 , 1805 , 1807 , 1809 , 1811 , 1813 , 1815 , 1817 , 1819 of the flowchart in FIG. 18 , 1821, 1823, and 1825 are performed sequentially, as discussed above. In some embodiments, as shown in Figure 18, arrow 1802 may follow step 1801, to step 1803, including machining the foldable substrate to remove material from the central portion of the first major surface. In some embodiments, arrow 1804 may follow step 1801 to step 1804 , eg, if the foldable substrate already includes a first recess at the end of step 1801 . In some embodiments, the method may follow arrow 1812 from step 1821 to step 1821, eg, if the foldable device is fully assembled at the end of step 1821, or if another material is to be placed in the second recess and/or on the second major surface. In some embodiments, the method may follow arrow 1808 from step 1819 to step 1825, eg, if foldable substrate 4007 is the desired product (eg, no material in first or second recess). Any of the above options can be combined to make a foldable device according to embodiments of the present disclosure. example

The various embodiments will be further clarified by the following examples. Examples A-C demonstrate a method of the present disclosure for forming a foldable device 401 , 501 , 701 or 801 including a foldable substrate 407 or 801 shown in FIGS. 4-5 and 7-8 Example Methods of Embodiments. The strain of the material in the first pocket of Examples D-E, the strain at the first central surface region of Examples D-E, and the force of folding Examples D-E are shown in FIGS. 55-57. Out-of-plane warping based on numerical simulations is shown schematically in Figures 58-59 for Examples F-G.

In Table 1, the thickness of the first part and the second part, the thickness of the central part, the average depth of layer (DOL) of the first part and the second part, and the average depth of layer of the central part; DOL) are presented at different stages of the illustrated method for Examples A-C. Table 1: Properties of Examples A to C example initial first chemical strengthening Etch the center part Second chemical strengthening First second center First second center First second center First second center A t (µm) 100 58 100 58 100 30 100 30 DOL (µm) 0 0 14 14 14 0 20 6 B t (µm) 150 78 150 78 150 30 150 30 DOL (µm) 0 0 twenty four twenty four twenty four 0 30 6 C t (µm) 200 98 200 98 200 30 200 30 DOL (µm) 0 0 34 34 34 0 40 6

Example A initially included a glass-based substrate comprising a substrate thickness (eg, first thickness, second thickness) of 100 μm and a center thickness of 58 μm. In the first chemical strengthening process, a substantially uniform depth of layer (DOL) of 14 μm was produced from all surfaces. Next, the central portion was etched to remove 14 µm from the existing first central surface region and 14 µm from the second existing second surface region, which essentially removed the entire DOL from those surfaces to yield a central thickness of 30 µm, while Leave the first and second parts as they are. In the second chemical strengthening process, all surfaces were sufficiently strengthened to produce 6 µm DOL for the first and second central surface regions, which also increased the DOL of the surfaces in the first and second portions 6 µm. Overall, this process produces a first and second portion comprising a DOL of 20 µm (20% of a 100 µm substrate thickness), and a center portion comprising a DOL of 6 µm (20% of a 30 µm center thickness).

Example B initially included a glass-based substrate comprising a substrate thickness (eg, first thickness, second thickness) of 100 μm and a center thickness of 78 μm. In the first chemical strengthening process, a substantially uniform depth of layer (DOL) of 24 μm was produced from all surfaces. Next, the central portion was etched to remove 24 µm from the existing first central surface region and 24 µm from the second existing second surface region, which essentially removed the entire DOL from those surfaces to yield a central thickness of 30 µm, while Leave the first and second parts as they are. In the second chemical strengthening process, all surfaces were sufficiently strengthened to produce 6 µm DOL for the first and second central surface regions, which also increased the DOL of the surfaces in the first and second portions 6 µm. Overall, this process produces a first and second portion comprising a DOL of 30 µm (20% of the 150 µm substrate thickness), and a center portion comprising a DOL of 6 µm (20% of the 30 µm center thickness).

Example C initially included a glass-based substrate comprising a substrate thickness (eg, first thickness, second thickness) of 200 μm and a center thickness of 98 μm. In the first chemical strengthening process, a substantially uniform depth of layer (DOL) of 34 μm was produced from all surfaces. Next, the central portion was etched to remove 34 µm from the existing first central surface region and 34 µm from the second existing second surface region, which essentially removed the entire DOL from those surfaces to yield a central thickness of 30 µm, while Leave the first and second parts as they are. In the second chemical strengthening process, all surfaces were sufficiently strengthened to produce 6 µm DOL for the first and second central surface regions, which also increased the DOL of the surfaces in the first and second portions 6 µm. Overall, this process produces a first and second portion comprising a DOL of 40 µm (20% of the 200 µm substrate thickness), and a center portion comprising a DOL of 6 µm (20% of the 30 µm center thickness).

Examples A-C demonstrate achieving the average layer depth of the first portion (eg, the first layer depth, the second layer depth) and/or the average layer depth of the second portion as a percentage of the substrate thickness (eg, the third layer depth, fourth layer depth), which may be substantially equal to the average layer depth of the center portion as a percentage of the center thickness for different substrate thicknesses (eg, first center layer depth, second center layer depth). In Examples A-C, a first chemical strengthening process achieves a DOL of 14% of the substrate thickness (70% of the final DOL), then the DOL is etched from each surface of the central portion, and finally another chemically strengthened process is used to achieve Final DOL. It should be understood that similar methods can be used to generate foldable substrates of different substrate thicknesses, different center thicknesses, and different DOLs as a percentage of the corresponding thicknesses.

Examples D-E included a glass-based substrate (Composition 1 had a nominal composition in mol% of: 63.6 _SiO2 ; 15.7 _Al2O3 ; 10.8 Na2O; _{6.2 Li2O ;} 1.16 ZnO; 0.04 SnO ₂ ; and 2.5 P ₂ O ₅ ), substrate thickness of 150 µm, center thickness of 30 µm and width of center section of 20 mm, without any transitions. Example D includes a first recess having a first central surface area recessed 120 μm from the first major surface and no second recess opposite the first recess. Example E includes a first recess having a first central surface region recessed 60 μm from the first major surface and a second recess opposite the first recess, wherein the second central surface region is The main surface is recessed by 60 µm.

In Figure 55, the horizontal axis 5501 (eg, the x-axis) is the parallel plate distance (in mm), and the vertical axis 5503 (eg, the y-axis) is the material positioned in the first pocket (eg, based on polymer parts, adhesive materials, coatings). The results of Example D are shown by curve 5505 and the results of Example E are shown by curve 5507. As shown, for all parallel plate distances shown, Example D, which includes a single first pocket, has a higher percentage of material positioned in the first pocket than Example E, which includes both the first pocket and the second pocket. which corresponds to a large strain of the material. In fact, the strain of Example E was about half of the strain of Example D.

In Figure 56, the horizontal axis 5601 (eg, the x-axis) is the parallel plate distance (in mm), and the vertical axis 5603 (eg, the y-axis) is the strain on the first central surface region. The results of Example D are shown by curve 5605 and the results of Example E are shown by curve 5607. As shown, for all parallel plate distances shown, Example D including a single first recess has a greater first center on the first central surface area than Example E including both the first and second recesses Large strains in the surface area. In fact, the strain of Example E was about half that of Example D for parallel plate distances greater than at least 12 mm.

In Figure 57, the horizontal axis 5701 (eg, the x-axis) is the parallel-panel distance (in mm), and the vertical axis 5703 (eg, the y-axis) is the force to fold the foldable substrate to a given parallel-panel distance ( in Newtons (N). The results of Example D are shown by curve 5705 and the results of Example E are shown by curve 5707. As shown, the force to fold Example D to a parallel plate of about 10 mm or less is greater than the corresponding stress to fold Example E to the same parallel plate distance.

Figures 55-57 demonstrate that the use of two pockets opposite each other, rather than a single pocket, reduces the strain on the material positioned in the pockets by about half, reducing the foldable substrate (eg, the first The strain on the central surface area) is reduced by about half and the force to bend the foldable substrate is reduced.

Figures 58-59 schematically show out-of-plane deformations of foldable devices based on the numerical simulations of Examples F-G. Examples F to G all included a substrate thickness of 150 μm, a center thickness of 30 μm, and the width of the center portion included 20 mm. In Example F, the second central surface region is coplanar with the second major surface, and the first central surface region is recessed 120 μm from the first major surface. In contrast, in Example G, the first central surface region was recessed 65 μm from the first major surface, and the second central surface region was recessed 65 μm from the second major surface. In Examples F to G, the first part and the second part include an artificial thermal expansion coefficient of 21520 × 10 ^-7 °C ^-1 , and the center section includes an artificial thermal expansion coefficient of 4300 × 10 ^-7 °C ^-1 , and the foldable substrate is The first part, the second part and the center part were heated 1°C to the temperature containing the stated dimensions. As used herein, the artificial thermal expansion coefficient is equal to 0.461, the network expansion coefficient, the difference between the concentration of one or more alkali metal ions at a surface and in the bulk, and the layer depth from the compressive stress region from the surface divided by Corresponds to the product of thickness.

Without wishing to be bound by theory, the mechanical instabilities encountered from the differences in artificial thermal expansion coefficients in Examples F to G may correspond to different compression depths and/or layers in different sections based on self-chemically strengthened foldable substrates Mechanical instability due to differential expansion of depth. For example, the difference in artificial thermal expansion coefficients in Examples F-G may correspond to the layer depths of the first and/or second portions as a percentage of the substrate thickness (eg, first layer depth, second layer depth, The third layer depth, the fourth layer depth) and about 23% (for a network expansion coefficient of 700 × 10 ^-6 /mol % and a concentration difference of 20 mol % between the surface of each part and the block, 933 × A net expansion coefficient of 10 ^-6 /mol % and a concentration difference of 15 mol % between the surface of each section and the block or a net expansion coefficient of 1400 × 10 ^-6 /mol % and the surface of each section The difference between the layer depths (eg, first center layer depth, second center layer depth) of the center portion as a percentage of the center thickness from the 10 mol% concentration difference between the blocks. For example, the difference in artificial thermal expansion coefficients in Examples F-G may correspond to the difference between the first maximum tensile stress and/or the second maximum tensile stress and the central maximum tensile stress of about 140 MPa (when each Some include a Poisson's ratio of 0.22 and an elastic modulus of 71 GPa). For example, the difference in artificial thermal expansion coefficients in Examples F-G may correspond to the maximum compressive stress of the first portion and/or the second portion (eg, first maximum compressive stress, second maximum compressive stress, third maximum compressive stress , the fourth maximum compressive stress) and the maximum compressive stress of the central portion of approximately 140 MPa (eg, the first central maximum compressive stress, the second maximum compressive stress), each portion containing a Poisson's ratio of 0.22 and 71 GPa modulus of elasticity.

In Figure 58, which shows Example F, the central portion is centered and includes a width that generally corresponds to the widest portion of region 5811. Region 5805 corresponds to the largest positive deformation (eg, about 80 μm) and is located primarily at the top and bottom edges of the foldable substrate in the central portion and adjacent portions. At the top and bottom, region 5807 is adjacent to region 5805, and region 5807 corresponds to a slightly smaller positive deformation than region 5805. Region 5809 is adjacent to region 5807, and region 5809 corresponds to a negative deformation (eg, about -450 µm).

In contrast, region 5821 corresponds to the largest negative deformation (eg, about -850 µm) and is located along the centerline of the central portion. Region 5823 is adjacent to region 5815 containing a more moderate negative deformation (eg, about -350 μm). The central portion includes a generally ribbon-like section, including regions 5805, 5815, 5811, 5813, 5815, 5823, 5815, 5823, 5815, 5813, 5815, 5815, and 5805 from top to bottom. In effect, these bands alternate with every other band of region 5815, with the remaining bands toward the middle of Figure 58 containing region 5823. Region 5813 corresponds to the negative deformation intermediate the negative deformations of region 5809 and region 5815. Region 5817 is adjacent to the center of the banded regions (eg, regions 5815 and 5823) and corresponds to negative deformations (eg, about -700 μm) with a limit less than region 5823. Regions 5819 located at the right and left edges correspond to negative deformations with a limit less than region 5817 (eg, about -600 μm).

In Figure 59, which shows Example G, the central portion is centered and includes a width that corresponds approximately to the widest portion of region 5905. Region 5907 corresponds to the largest positive deformation (eg, less than 1 picometer), which is at least 6 orders of magnitude smaller than the positive deformation encountered in Figure 58 of Example F. Region 5905 is adjacent to region 5909 that corresponds to a smaller positive deformation than region 5905. Region 5909 is adjacent to region 5911 which corresponds to substantially no deformation. Region 5905 located along the centerline of the central portion corresponds to the deformation intermediate region 5911 and region 5909. Regions 5917 located at the left and right edges correspond to the largest negative deformation (eg, less than -1 picometer), which is at least 6 orders of magnitude smaller than the negative deformation encountered in Figure 58 of Example F. Region 5917 is adjacent to region 5915 that corresponds to a less negative deformation than region 5917. Region 5913 is positioned between regions 5911 and 5915, and region 5913 corresponds to a deformation intermediate the deformations of regions 5911 and 5915.

Based on the results of Examples F-G presented in Figures 58-59, Example G, which includes a central portion recessed from both the first and second major surfaces, exhibits deformations greater than those encountered for Example F A deformation that is at least 10 orders of magnitude smaller. Additionally, the central portion is positioned such that the first distance that the first central surface region is recessed from the first major surface is substantially equal to the second distance that the second central surface region is recessed from the second major surface (as in Example G) further minus small deformation.

The above observations can be combined to provide a foldable substrate that includes a low effective minimum bend radius, high impact resistance, low closing force, increased durability, and reduced fatigue. Such portions may include glass-based portions and/or ceramic-based portions, which may provide good dimensional stability, reduced occurrence of mechanical instability, good impact resistance, and/or good puncture resistance. The first portion and/or the second portion may include a glass-based portion and/or a ceramic-based portion that includes one or more regions of compressive stress, which may further provide increased impact resistance and/or increased Puncture resistance. By providing a substrate comprising a glass-based substrate and/or a ceramic-based substrate, the substrate may also provide increased impact resistance and/or puncture resistance while contributing to good folding performance. In some embodiments, the substrate thickness may be sufficiently large (eg, from about 80 micrometers (microns or μm) to about 2 millimeters) to further enhance impact and puncture resistance. Providing a foldable substrate that includes a central portion including a central thickness that is less than a substrate thickness (eg, the first thickness of the first portion and/or the second thickness of the second portion) can be based on a reduction in the central portion. The thickness enables a small effective minimum bend radius (eg, about 10 mm or less).

In some embodiments, the foldable device and/or foldable substrate may include a plurality of recesses, eg, a first central surface area recessed a first distance from a first major surface and from a second major surface A second central surface area is recessed a second distance. Providing a first recess opposite a second recess can provide a center thickness less than a substrate thickness. Additionally, providing a first recess opposite a second recess may reduce a maximum bending-induced strain of the foldable device, eg, between the central portion and the first and/or second portion, which is Since the central portion including the central thickness can be closer to a neutral axis of the foldable device and/or foldable substrate than if only a single recess were provided. Additionally, providing the first distance substantially equal to the second distance can reduce the occurrence of mechanical instabilities in the central portion, eg, because the foldable substrate is symmetric about a plane that includes a midpoint of the substrate thickness and the central thickness. Furthermore, providing a first recess opposite a second recess may reduce positioning at the first recess compared to a single recess having a surface recessed by the sum of the first and second distances Bending induced strain in the seat and/or the material in the second recess. Providing a reduced bending induced strain of the material positioned in the first pocket and/or the second pocket enables the use of a wider range of materials due to the reduced strain requirements on the material. For example, a harder and/or more rigid material can be positioned in the first recess, which can improve impact resistance, puncture resistance, abrasion resistance, and/or scratch resistance of the foldable device. Additionally, controlling the properties of the first material positioned in the first pocket and the second material positioned in the second pocket can control the position of the neutral axis of the foldable device and/or foldable substrate, which can reduce ( For example, reduce, eliminate) the occurrence of mechanical instability, equipment fatigue and/or equipment failure. In some embodiments, the foldable device and/or foldable substrate may include a first transition portion attaching the central portion to a first portion and/or a second transition portion attaching the central portion to a second portion. Providing a transition region with a continuously increasing thickness can reduce stress concentrations in the transition region, and/or avoid optical distortion. Providing transition regions of sufficient length (eg, about 1 mm or more) can avoid optical distortions that might otherwise exist from abrupt, stepped changes in the thickness of the foldable substrate. Providing transition regions of sufficiently small length (eg, about 5 mm or less) can reduce the amount of foldable devices and/or foldable substrates having intermediate thicknesses that can have reduced Small impact resistance and/or reduced puncture resistance. Additionally, providing the first transition region and/or the second transition region with regions of tensile stress may counteract the strain between the first or second portion and the first and/or second transition portion during folding, the tension The stress region contains a maximum tensile stress greater than the maximum tensile stress of the central tensile stress region of the central portion. Additionally, providing the first transition region and/or the second transition region with a region of tensile stress may counteract the strain between the central portion and the first transition portion and/or the second transition portion during folding, the region of tensile stress comprising greater than The maximum tensile stress of the maximum tensile stress of the first tensile stress region of the first portion and/or the second tensile stress region of the second portion.

The devices and methods of embodiments of the present disclosure may be achieved by controlling (eg, limiting, reducing, equalizing) the difference between the expansion of different portions of the foldable device and/or foldable substrate as a result of chemical strengthening Reduce (eg, mitigate, eliminate) the occurrence of mechanical instability, equipment fatigue and/or equipment failure. Controlling the difference between the expansions of the different parts can reduce chemical strengthening induced strains between parts of the foldable device and/or foldable substrate, which can help to reach critical buckling at the foldable device and/or foldable substrate Greater folding induces strain prior to strain (eg, the onset of mechanical instability). Additionally, reducing mechanical instabilities and/or the difference between the core layer and the first outer layer and/or the first outer layer or the difference between the central portion and the first portion and/or the second portion may reduce optical distortion, eg, Caused by the (etc.) difference in strain within the foldable device and/or the foldable substrate.

In some embodiments, providing a foldable device and/or foldable substrate comprising a laminate may enable control of the differential expansion between the first portion, the second portion and the central portion in a single chemical strengthening process. For example, the properties of the core layer relative to the first outer layer and/or the second outer layer may enable substantially uniform expansion of the foldable device and/or foldable substrate. In some embodiments, the density of the core layer may be greater than the density of the first outer layer and/or the second outer layer. In some embodiments, the thermal expansion coefficient of the core layer may be greater than the thermal expansion coefficient of the first outer layer and/or the second outer layer. In some embodiments, the network expansion coefficient of the core layer may be smaller than the network expansion coefficient of the first outer layer and/or the second outer layer. Additionally, providing a core layer in relationship to the first outer layer and/or the second outer layer may reduce (eg, minimize) the force of folding the foldable device and/or the foldable substrate.

As a result of chemical strengthening, providing one or more compounds comprising a concentration of one or more alkali metals near (eg, within 100 ppm, 10 ppm on an oxide basis) of the central portion compared to the central portion A first portion and/or a second portion of the average concentration of alkali metal can minimize the differential expansion of the first portion and/or the second portion. Substantially uniform expansion reduces the occurrence of mechanical deformation and/or mechanical instability as a result of chemical strengthening. As a result of chemical strengthening, providing a corresponding ratio of depth of layer to the first and/or second portion close to (eg, within 0.5%, within 0.1%, within 0.01%) of the center portion compared to the center portion A ratio of thicknesses can minimize the difference in near-surface expansion of the first portion and/or the second portion. Minimizing the difference in near-surface expansion can reduce stress and/or strain in one of the planes of the first major surface, the second major surface, the first central surface region, and/or the second central surface region, which can further reduce as a chemical The occurrence of mechanical deformation and/or mechanical instability as a result of strengthening. Providing a ratio of the depth of compression to the thickness of the first portion and/or the second portion near (eg, within 1%, within 0.5%, within 0.1%) of the corresponding ratio of the central portion can minimize the first portion and/or The difference between the chemical strengthening induced strain of the second part relative to the central part. Minimizing the difference in chemical strengthening induced strain can reduce the occurrence of mechanical deformation and/or mechanical instability as a result of chemical strengthening. Minimizing stress and/or strain in the first major surface, the second major surface, the first central surface region, and/or the second central surface region can reduce stress-induced optical distortion. Also, minimizing these stresses may increase puncture resistance and/or impact resistance. Also, minimizing these stresses can be associated with low optical retardation differences (eg, about 2 nanometers or less) along a centerline. Additionally, minimizing these stresses may reduce the occurrence of mechanical deformation and/or mechanical instability as a result of chemical strengthening.

The methods of the present disclosure may enable the fabrication of foldable substrates that include one or more of the above-mentioned benefits. In some embodiments, the methods of the present disclosure can achieve the above-mentioned benefits in a single chemical strengthening step, eg, fabricating a foldable substrate comprising a laminate, which can reduce the labor associated with producing the foldable substrate Time, equipment, space and labor costs. In some embodiments, existing recesses may be provided or formed prior to any chemical strengthening of the foldable substrate (eg, existing first central surface region recessed from the first major surface, existing first central surface region recessed from the second major surface two central surface areas), which may provide the above benefits for foldable devices with deeper pockets (eg, larger first distance, larger second distance) than pockets that could otherwise be achieved. In some embodiments, the above benefits may be provided by chemically strengthening the foldable substrate, etching a central portion of the foldable substrate (eg, etching an existing first central surface region to form a new first central surface region) , etching an existing second central surface region to form a new second central surface region), and then further chemically strengthening the foldable substrate. In further embodiments, the above benefits may be provided by controlling a time period of the chemical strengthening relative to a second time period of the further chemical strengthening and/or a thickness etched from the central portion. Providing the further chemical strengthening of the foldable substrate can achieve greater compressive stress without encountering mechanical deformation and/or mechanical instability, and the greater compressive stress can further increase the impact resistance of the foldable substrate and/or Puncture resistance.

Directional terms (eg, top, bottom, right, left, front, back, top, bottom) as used herein are made only with reference to the figures as drawn, and are not intended to imply absolute orientation.

It should be understood that various disclosed embodiments may involve the features, elements or steps described in connection with that embodiment. It should also be understood that a feature, element or step, although described in relation to one embodiment, may be interchanged or combined with alternative embodiments in various combinations or permutations not shown.

It will also be understood that, as used herein, the terms "the", "an (a or an)" mean "at least one" and should not be limited to "only one" unless expressly indicated to the contrary. For example, reference to "an element" includes embodiments having two or more of such elements, unless the context clearly dictates otherwise. Likewise, "plurality" is intended to mean "more than one".

As used herein, the term "about" means that quantities, sizes, formulations, parameters and other quantities and characteristics are not and need not be exact, but can be approximate and/or greater or lesser as desired, reflecting tolerances, conversions Factors, rounding, measurement errors and the like and other factors known to those skilled in the art. Ranges can be expressed herein as from "about" one particular value and/or to "about" another particular value. When expressing such ranges, embodiments include from that one particular value and/or to another particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. Whether or not a value or endpoint in a range is stated as "about" in the specification, the value or endpoint of a range is intended to include two embodiments: the embodiment modified by "about" and the embodiment not modified by "about" Modified Example. It will be further understood that the endpoint of each of these ranges is valid with respect to and independent of the other endpoint.

As used herein, the terms "substantial, substantially" and variations thereof are intended to indicate that a described feature is equal to or approximately equal to a value or description. For example, a "substantially flat" surface is intended to mean a surface that is flat or substantially flat. Also, as defined above, "substantially similar" is intended to mean that two values are equal or approximately equal. In some embodiments, "substantially similar" can mean values within about 10% of each other, eg, within about 5% of each other, or within about 2% of each other.

Unless expressly stated otherwise, any method set forth herein is in no way intended to be construed as requiring a specific order for performing its steps. Thus, where a method claim does not actually recite an order of steps followed or otherwise specifically state in the claims or description that the steps should be limited to a specific order, no particular order is intended in any way.

Although various features, elements, or steps of particular embodiments may be disclosed using the transitional phrase "comprising", it should be understood that alternative embodiments are implied, including the use of the transitional phrase "consisting of" or "consisting essentially of." described embodiment. Thus, for example, alternative embodiments implying an apparatus comprising A+B+C include embodiments in which the apparatus consists of A+B+C and embodiments in which the apparatus consists essentially of A+B+C. As used herein, the terms "comprising" and "including" and variations thereof should be construed as synonymous and open ended, unless otherwise indicated.

The above embodiments and features of their embodiments are exemplary and may be used alone or in combination with other embodiments provided herein without departing from the scope of this disclosure. Any one or more of the features are provided in any combination.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the spirit and scope of the disclosure. Accordingly, it is intended that this disclosure covers such modifications and variations of the embodiments herein, subject to the proviso that they are within the scope of the appended claims and their equivalents.

101, 301, 401, 501, 601, 701, 801, 1201: foldable devices 102: Folding axis 103: width 104: Direction of width 105: length 106: The direction of the length 107: Center shaft 109: Folding Plane 111: Parallel plate distance 203, 403, 803, 4003: First major surface 204a, 404a, 804a: first plane 204b, 404b, 804b: Second plane 204c, 404c, 804c: Third Plane 204d, 404d: Fourth plane 205, 405, 805, 4005: Second major surface 206, 407, 707, 807, 2505, 4007: Foldable substrates 207: Core Layer 208: Third inner surface 209,409,709,809,3609,4009: First central surface area 210: First Minimum Distance 211,411,811: Substrate thickness 213: First outer layer 213a: The first part of the first outer layer 213b: Second part of the first outer layer 214: First inner surface 214a: first inner surface area 214b: second inner surface area 215: Second outer layer 215a: The first part of the second outer layer 215b: The second part of the second outer layer 216: Second inner surface 216a: third inner surface area 216b: Fourth inner surface area 217: First outer thickness 218: Fourth inner surface 219,419,719,819,4509: Second Central Surface Area 220: Second minimum distance 221,421,821: Part 1 223: the first surface area of the first main surface 225: the second surface area of the second main surface 227,427,827: Center Thickness 231,431,831: Part II 233: the third surface area of the first main surface 234,434,834,3534: First Recess 235: the fourth surface area of the second main surface 237: Second outer thickness 241: Polymer-Based Parts 244,444: Second Recess 245: Third contact surface 247: Fourth Contact Surface 251: Coating 253: Third main surface 255: Fourth main surface 257: Coating Thickness 261: Adhesive layer 263: First Contact Surface 265: Second Contact Surface 267: Adhesive Thickness 271: Release liner 273: The first major surface of the release liner 275: Second main surface of release liner 281, 481, 781, 881, 4081: Center Section 303: the first main surface of the display device 305: the second main surface of the display device 307: Display device 417,817: First distance 423,823: First surface area 425,825: Second surface area 433,833: Third surface area 435,835: Fourth surface area 437: Second Distance 727: Transition Depth 753,853,3553: First Transition Section 755, 855, 3555: Second Transition Section 1001, 1101: Parallel Plate Equipment 1003, 1005, 1103, 1105: Parallel Rigid Stainless Steel Plates 1007, 1111: Parallel Plate Distance 1009: Distance 1011: Impact position 1102: Testing foldable devices 1107: Flakes 1109: Test Adhesion 1300: Consumer Electronics Devices 1302: Shell 1304: Front Surface 1306: Back Surface 1308: Side Surface 1310: Display 1312: Cover substrate 1501, 1503, 1505, 1507, 1509, 1511, 1513, 1515, 1517, 1519, 1601, 1603, 1605, 1607, 1609, 1611, 1613, 1615, 1617, 1619, 1701, 1703, 1705, 1707, 1709 1711,1713,1715,1717,1719,1721,1801,1803,1805,1807,1809,1811,1813,1815,1817,1819,1821,1823,1825: Steps 1502,1506,1508,1510,1512,1514,1516,1518,1602,1604,1608,1610,1612,1614,1618,1702,1704,1706,1708,1710,1714,1716,1718,1720,1722, 1802, 1804, 1808, 1812, 1814: Arrow 1901: Laminate melt drawing equipment 1902: Upper forming device 1904: Lower forming device 1906: First molten material 1908: Second molten material 1910: The first slot 1912: Second slot 1916, 1918: Externally formed surfaces 1920: Roots 1922, 1924: External Surfaces 1932: Core Fusion Layer 1934: First molten outer layer 1936: Second Molten Outer Layer 2001: Diamond Tip Probe 2003: Computer Numerical Control (CNC) Machines 2101, 3201, 4701, 4801: Containers 2103, 3603, 4011, 4303: First liquid deposits 2105, 3605, 4305: Second liquid deposits 2107: First Liquid 2201, 4401: Etchant baths 2203: Etchant 2205, 3705, 4103, 4407: first mask 2207, 3707, 4405: Second mask 2209, 3709, 4411: Third mask 2211, 3711, 4409: Fourth mask 2301, 3401, 3403, 3801, 4101, 4501: Grinding tools 2302, 3402, 3404, 3802, 4102, 4502: Directions 2401, 4201, 4601: Salt baths 2403, 4203, 4603: Salt solutions 3101: Source 3103, 3105: First salt paste 3203: Second Salt Paste 3205, 3207, 3209, 3211: First salt deposits 3301: Furnace 3303, 3305: Second Salt Deposit 3704a: First center plane 4104, 4406: Plane 4403: Etching Solution 4703: Second Liquid 4803: Third Liquid 5301: Thickness 5303: Maximum principal stress 5305, 5404, 5405, 5505, 5507, 5605, 5607, 5705, 5707: Curve 5401, 5501, 5601, 5701: Horizontal axis 5403, 5503, 5603, 5703: Vertical axis 5407: Circle 5409: Rhombus 5411: Square 5413: Triangle 5805, 5807, 5809, 5811, 5813, 5815, 5817, 5819, 5821, 5823, 5905, 5907, 5909, 5911, 5913, 5915, 5917: Area

The above and other features and advantages of embodiments of the present disclosure are better understood when reading the following detailed description with reference to the accompanying drawings, wherein:

FIG. 1 is a schematic diagram of an example foldable device in a flat configuration, wherein the schematic diagram of the folded configuration may appear as shown in FIG. 9, according to some embodiments;

Figures 2-8 are cross-sectional views of the foldable device along line 2-2 of Figure 1, according to some embodiments;

9 is a schematic diagram of an example foldable device of an embodiment of the present disclosure in a folded configuration, wherein the schematic diagram of the flat configuration may appear as shown in FIG. 1;

Figures 10 to 11 are cross-sectional views of a test device for determining the effective minimum bending radius of an example modified foldable device;

12 is a schematic diagram of an example foldable device of an embodiment of the present disclosure in a folded configuration;

13 is a schematic plan view of an example consumer electronic device in accordance with some embodiments;

FIG. 14 is a schematic perspective view of the example consumer electronic device of FIG. 13;

FIGS. 15-18 are flowcharts illustrating an example method of making a foldable device according to embodiments of the present disclosure;

Figures 19 to 52 schematically illustrate steps in a method of making a foldable substrate and/or a foldable device;

Figure 53 shows the experimental results of a pen drop test of a glass-based substrate showing the maximum principal stress on a major surface of a glass-based substrate as a function of thickness of the glass-based substrate;

Figure 54 shows the type of mechanical instability observed for foldable devices as a function of substrate thickness and center thickness;

FIGS. 55-57 are graphs illustrating results for some embodiments of the present disclosure; and

Figures 58-59 schematically show optical retardation measurements for a foldable substrate of an embodiment of the present disclosure.

Throughout this disclosure, these figures are used to emphasize certain aspects. Thus, the relative sizes of the various regions, portions and substrates shown in the figures should not be assumed to be proportional to their actual relative sizes unless expressly indicated otherwise.

Domestic storage information (please note in the order of storage institution, date and number) without Foreign deposit information (please note in the order of deposit country, institution, date and number) without

101: Foldable Devices

107: Center shaft

109: Folding Plane

203: First main surface

204a: First plane

204b: Second plane

204c: Third Plane

204d: Fourth plane

205: Second main surface

206: Foldable Substrate

207: Core Layer

208: Third inner surface

209: First central surface area

210: First Minimum Distance

211: Substrate thickness

213: First outer layer

213a: The first part of the first outer layer

213b: Second part of the first outer layer

214: First inner surface

214a: first inner surface area

214b: second inner surface area

215: Second outer layer

215b: The second part of the second outer layer

216: Second inner surface

216a: third inner surface area

216b: Fourth inner surface area

217: First outer thickness

218: Fourth inner surface

219: Second central surface area

220: Second minimum distance

221: Part One

223: the first surface area of the first main surface

225: the second surface area of the second main surface

227: Center Thickness

231: Part II

233: the third surface area of the first main surface

234: First Recess

235: the fourth surface area of the second main surface

237: Second outer thickness

241: Polymer-Based Parts

244: Second recess

245: Third contact surface

247: Fourth Contact Surface

251: Coating

253: Third main surface

255: Fourth main surface

257: Coating Thickness

261: Adhesive layer

263: First Contact Surface

265: Second Contact Surface

267: Adhesive Thickness

271: Release liner

273: The first major surface of the release liner

275: Second main surface of release liner

281: Center Section

Claims (20)

A foldable substrate comprising: a substrate thickness defined between a first major surface and a second major surface opposite the first major surface, the substrate thickness in a range from about 100 microns to about 2 millimeters; a first outer layer comprising the first main surface and a first inner surface opposite the first main surface, a first outer thickness defined between the first main surface and the first inner surface, the first outer layer An outer layer includes a first portion and a second portion separated by a first minimum distance, the first portion including the first major surface and the first inner surface, and the second portion including the first major surface and the first major surface an inner surface; a second outer layer including the second major surface and a second inner surface opposite the second major surface, the second outer layer including a first defined between the second major surface and the second inner surface two outer thicknesses, and the second outer layer includes a third portion and a fourth portion separated by a second minimum distance, the third portion includes the second major surface and the second inner surface, and the fourth portion includes the second major surface and the second inner surface; and a core layer comprising a third inner surface and a fourth inner surface opposite to the third inner surface, a central thickness defined between the third inner surface and the fourth inner surface, the central thickness from In a range of about 25 microns to about 80 microns, the core layer is positioned between the first outer layer and the second outer layer, and the third inner surface contacts the first inner surface of the first portion and the second portion. The first inner surface, a first central surface area is between the first portion of the first outer layer and the second portion of the first outer layer, the fourth inner surface contacts the second inner surface of the third portion and the second inner surface of the fourth portion, a second central surface area between the third portion of the second outer layer and the fourth portion of the second outer layer, the first central surface area from the first A major surface is recessed a first distance, and the second central surface region is recessed a second distance from the second major surface. The foldable substrate of claim 1, wherein the core layer includes a core thermal expansion coefficient greater than a first thermal expansion coefficient of the first outer layer, and the core thermal expansion coefficient is greater than a second thermal expansion coefficient of the second outer layer. The foldable substrate of claim 1, wherein a core density of the core layer is greater than a first density of the first outer layer, and the core density is greater than a second density of the second outer layer. The foldable substrate of claim 1, wherein a core network expansion coefficient of the core layer is smaller than a first network expansion coefficient of the first outer layer, and the core network expansion coefficient is smaller than one of the second outer layers The second network expansion factor. The foldable substrate of claim 1, wherein the first outer thickness is substantially equal to the second outer thickness. The foldable substrate of claim 1, wherein the substrate thickness is in a range from about 125 microns to about 200 microns. The foldable substrate of claim 1, wherein the central thickness is in a range from about 25 microns to about 60 microns. The foldable substrate of any one of claims 1 to 7, further comprising a coating disposed on the first major surface and filling the region defined by the first central surface and defined by the first major surface The surfaces define a recess between a first plane. The foldable substrate of any one of claims 1 to 7, wherein the first outer layer comprises a first oxide-based average potassium concentration and the second outer layer comprises a second oxide-based Average potassium concentration, a central portion of the core layer positioned between the first central surface region and the second central surface region comprises a central average potassium concentration based on oxide, and the first average potassium concentration is the same as An absolute difference between the mean potassium concentrations at the centers is about 100 parts per million or less. The foldable substrate of any one of claims 1 to 7, further comprising: a first region of compressive stress extending from the first portion of the first outer layer at the first major surface to a first compression depth; a second region of compressive stress extending from the third portion of the second outer layer at the second major surface to a second depth of compression; a third region of compressive stress extending from the second portion of the first outer layer at the first major surface to a third depth of compression; a fourth region of compressive stress extending from the fourth portion of the second outer layer at the second major surface to a fourth depth of compression; a first central compressive stress region extending from the first central surface region to a first central compressive depth; and A second central compressive stress region extending to a second central compressive depth extending from the second central surface region. The foldable substrate of claim 10, wherein an absolute difference between the first compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the center thickness is about 1% or smaller. The foldable substrate of claim 10, wherein the first portion includes a first layer depth of one or more alkali metal ions associated with the first compression depth, and the third portion includes a first layer depth associated with the second compression depth a second depth of layers associated with one or more alkali metal ions, the second portion comprising a third depth of layers of one or more alkali metal ions associated with the third compression depth, the fourth portion comprising a fourth depth of layers of one or more alkali metal ions associated with the fourth depth of compression, the central portion comprising a first central layer of one or more alkali metal ions associated with the first depth of compression Depth, the central portion contains a second central layer depth of one or more alkali metal ions associated with the second central compression depth, the first layer depth as a percentage of the substrate thickness and as the central thickness An absolute difference between a percentage of a first center layer depth is about 0.5% or less. The foldable substrate of any one of claims 1-7, wherein the second distance is from about 5% to about 20% of the thickness of the substrate. The foldable substrate of any one of claims 1 to 7, wherein the first distance is substantially equal to the second distance. A method of making a foldable substrate comprising a core layer positioned between a first outer layer and a second outer layer and in contact with the first outer layer and the second outer layer, defined on a first major surface A substrate thickness between a second major surface, the first outer layer defining the first major surface and the second outer layer defining the second major surface opposite the first major surface, the method comprising the steps of: etching a portion of the first major surface to form a first central surface region of the core layer; and etching a portion of the second major surface to form a second central surface region of the core layer, wherein a central portion includes a central thickness defined between the first central surface region and the second central surface region, the first central surface region of the core layer in the central portion is positioned on one of the first outer layers Between the first portion and a second portion of a first outer layer, the second central surface area of the core layer in the central portion is positioned between a third portion of the second outer layer and a fourth portion of the second outer layer between parts. The method of claim 15, wherein the first outer layer comprises a first oxide-based average potassium concentration, the core layer comprises a core oxide-based average potassium concentration, and the core has The average potassium concentration is about 10 parts per million, or greater than the first existing average potassium concentration. The method of claim 15, further comprising the step of chemically strengthening the foldable substrate after the step of etching the portion of the first major surface and the step of etching the portion of the second major surface. The method of claim 17, wherein, prior to the step of chemical strengthening, the first outer layer comprises a first diffusivity of one or more alkali metal ions and the core layer comprises a core of one or more alkali metal ions diffusivity, and the first diffusivity is greater than the core diffusivity. 18. The method of any one of claims 17 to 18, wherein, after the step of chemical strengthening, the first outer layer comprises a first average potassium concentration based on an oxide, and the second outer layer comprises an oxide based a second average potassium concentration based on an oxide, the central portion is positioned between the first central surface region and the second central surface region, comprising a central average potassium concentration based on an oxide, and the first average An absolute difference between the potassium concentration and the average potassium concentration at the center is about 100 parts per million or less. The method of any one of claims 17 to 18, further comprising the steps of: forming a first region of compressive stress extending from the first portion of the first outer layer at the first major surface to a first compression depth; forming a second region of compressive stress extending from the third portion of the second outer layer at the second major surface to a second depth of compression; forming a third region of compressive stress extending from the second portion of the first outer layer at the first major surface to a third depth of compression; forming a fourth region of compressive stress extending from the fourth portion of the second outer layer at the second major surface to a fourth depth of compression; forming a first central compressive stress region extending from the first central surface region to a first central compressive depth; and forming a second central compressive stress region extending to a second central compressive depth extending from the second central surface region, wherein an absolute difference between the first compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the center thickness is about 1% or less.

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