Foldable substrate and method of manufacturing the same

Abstract

The foldable substrate includes a first portion, a second portion, and a central portion positioned therebetween. The first portion includes a substrate thickness and a first depth of compression. The central portion includes a central thickness and a first central compression depth. In aspects, the ratio of the first depth of compression to the substrate thickness is greater than the ratio of the first center depth of compression to the center thickness. In aspects, a ratio of a first depth of a layer associated with the first depth of compression to the substrate thickness is greater than a ratio of a first center depth of a layer associated with the first center compressive stress zone to the center thickness. The method includes chemically strengthening the foldable substrate; etching a portion of the first major surface to form a first central surface region; and further chemically strengthening the foldable substrate.

Description

Technical Field

[0001] This application claims the priority benefit of U.S. Provisional Application Serial No. 63 / 436948 filed on January 4, 2023 and U.S. Provisional Application Serial No. 63 / 353993 filed on June 21, 2022 under the Patent Law, and the contents of each of these applications are relied upon and incorporated herein by reference in their entirety.

[0002] The present disclosure relates generally to foldable substrates and methods of making the same, and more particularly, to foldable substrates including a first central surface region recessed from a first major surface and methods of making the foldable substrates including etching. Background Art

[0003] Glass-based substrates are generally used in, for example, display devices such as liquid crystal displays (LCD), electrophoretic displays (EPD), organic light-emitting diode displays (OLED), plasma display panels (PDP), and the like.

[0004] It is desirable to develop a foldable version of a display and a foldable protective cover mounted on the foldable display. The foldable display and cover should have good impact resistance and puncture resistance. At the same time, the foldable display and cover should have a small minimum bending radius (e.g., about 10 millimeters (mm) or less). However, plastic displays and covers with a small minimum bending radius tend to have poor impact resistance and / or puncture resistance. In addition, conventional concepts suggest that ultra-thin glass-based sheets (e.g., about 75 microns (μm or microns) or thinner) with a small minimum bending radius tend to have poor impact resistance and / or puncture resistance. In addition, thicker glass-based sheets (e.g., greater than 125 microns) with good impact resistance and / or puncture resistance tend to have a relatively large minimum bending radius (e.g., about 30 mm or more). Therefore, it is necessary to develop a foldable device with a low minimum bending radius and good impact resistance and puncture resistance. Summary of the invention

[0005] The present invention describes a foldable device including a foldable substrate, a foldable substrate, and a method for manufacturing a foldable device and a foldable substrate including a foldable substrate, wherein the foldable substrate includes a first portion, a second portion, and a central portion positioned therebetween. The substrate and / or portion may include a glass-based and / or ceramic-based portion, which may provide good dimensional stability, a reduced incidence of mechanical instability, good impact resistance, and / or good puncture resistance. The portions may include a glass-based and / or ceramic-based portion, which may include one or more compressive stress regions, which may further provide increased impact resistance and / or increased puncture resistance. By providing a substrate including a glass-based and / or ceramic-based substrate, the substrate may also provide increased impact resistance and / or puncture resistance while facilitating good folding performance. In various aspects, the substrate thickness may be large enough (e.g., from about 50 microns (micrometers or μm) to about 2 millimeters) to further enhance impact resistance and puncture resistance. Providing a foldable substrate including a central portion (which includes a central thickness that is less than the thickness of the substrate (e.g., the first thickness of the first portion and / or the second thickness of the second portion) (e.g., about 10 μm or greater)) can achieve a small parallel plate distance (e.g., about 10 mm or less) based on the reduced thickness of the central portion, which can achieve foldability and / or rollability of the foldable substrate and / or foldable device.

[0006] In various aspects, the foldable device and / or the foldable substrate may include one or more recesses, for example, a first central surface area recessed a first distance from the first major surface and / or a second central surface area recessed a second distance from the second major surface. Providing a first recess opposite to the second recess may provide a central thickness that is less than the thickness of the substrate. In addition, providing a first recess opposite to the second recess may reduce the strain induced by the maximum bending of the foldable device, for example between the central portion and the first portion and / or the second portion, because the central portion including the central thickness may be closer to the neutral axis of the foldable device and / or the foldable substrate than when only a single recess is provided. In addition, providing a first distance that is substantially equal to the second distance may reduce the incidence of mechanical instability in the central portion, for example, because the foldable substrate is symmetrical about a plane including the midpoint of the substrate thickness and the central thickness. In addition, providing a first recess opposite to the second recess may reduce the strain induced by bending of the material positioned in the first recess and / or the second recess compared to a single recess having a surface recessed the sum of the first distance and the second distance. Providing reduced bending-induced strain of the material positioned in the first recess and / or the second recess can enable 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 the impact resistance, puncture resistance, abrasion resistance, and / or scratch resistance of the foldable device. In addition, controlling the properties of the first material positioned in the first recess and the second material positioned in the second recess can control the position of the neutral axis of the foldable device and / or the foldable substrate, which can reduce (e.g., mitigate, eliminate) the incidence of mechanical instability, device fatigue, and / or device failure.

[0007] In various aspects, the foldable device and / or foldable substrate may include a first transition region attaching the center portion to the first portion and / or a second transition region attaching the center portion to the second portion. Providing a transition region with a smoothly and / or monotonically decreasing (e.g., continuously decreasing) thickness can reduce stress concentration in the transition region and / or avoid optical distortion. Providing a transition region of sufficient length (e.g., about 0.15 mm or more or about 0.3 mm or more) can avoid optical distortion that may otherwise exist due to a sharp change in the thickness of the foldable substrate. Providing a sufficiently large average transition angle of the first transition surface area of ​​the first transition region relative to the first center surface area (e.g., about 167° or more or about 170° or more) can avoid optical distortion and / or reduce the visibility of the transition region. Providing a sufficiently small average transition angle (e.g., about 179° or less or about 176° or less) can reduce the amount of foldable devices and / or foldable substrates having intermediate thicknesses, which can have reduced impact resistance and / or reduced puncture resistance.

[0008] As discussed below, it was unexpectedly discovered that providing a ratio of the first compression depth to the substrate thickness that is greater than the ratio of the first central compression depth to the central thickness (even when the difference is greater than 0.01) can reduce the incidence of buckling, while the inverse relationship (i.e., a relationship where the ratio of the first central compression depth to the central thickness is greater than the ratio of the first compression depth to the substrate thickness) does not hold. Unexpectedly, as described below, it has been determined that providing a ratio of the first depth of the layer to the substrate thickness that is greater than the ratio of the first central depth to the central thickness of the layer (even when the difference is greater than 0.001) can reduce the incidence of buckling, while the inverse relationship (i.e., a relationship where the ratio of the first central depth to the central thickness of the layer is greater than the ratio of the first depth of the layer to the substrate thickness) does not hold. Such configurations can impart a stabilizing force on the central portion that suppresses fluctuations in the surface profile that could otherwise lead to the onset of mechanical instability (e.g., buckling), which can enable the central portion to withstand a critical buckling strain, wherein the critical buckling strain is calculated for a sample comprising a substrate material having a uniform thickness. This is unexpected because, by definition, exceeding the critical buckling strain is expected to result in the onset of mechanical instability (e.g., buckling). In addition, providing such configurations can improve manufacturing yields because a larger portion of the foldable substrate will be free of mechanical instability (e.g., buckling) (e.g., compared to a case where the ratio of the first compression depth or first depth of the layer to the substrate thickness is less than or equal to the ratio of the first central compression depth or first central depth of the layer to the central thickness).

[0009] The foldable substrate may be used as a rollable substrate having a central width greater than the second width. Providing a second width of the second portion of about 15 mm or less (e.g., about 2 mm to about 6 mm) and / or about 15% or less (e.g., about 2% to about 6%) of the length of the foldable substrate may provide sufficient width to handle the ends of the foldable substrate during processing to secure the foldable substrate and / or the foldable device as part of an electronic device, and / or to maximize the amount of the foldable substrate and / or the foldable device that may be part of a display portion visible to a user. Providing a central portion of about 15% to about 50% (e.g., about 40% to about 48%) of the length of the foldable substrate may enable adjustment of the display portion of the foldable device because a portion of the rollable substrate is moved into and / or out of the user's field of view when in a fully rolled-up configuration without having to enlarge the size of the corresponding device. Providing a first width of the first portion that is approximately 35% or greater (e.g., approximately 40% to approximately 70%) of the length of the foldable substrate can provide a large display portion visible to a user while ensuring that substantially all of the remaining foldable substrate (e.g., the center portion and the second portion) can be within the footprint of the first portion.

[0010] Methods of various aspects of the present disclosure can use an etching mask and an etchant to manufacture a foldable substrate and / or a foldable device having a center thickness that is less than the substrate thickness (e.g., about 10 μm or greater). In various aspects, using a barrier layer when initially chemically strengthening the foldable substrate before etching the foldable substrate to form a first recessed portion can enable a first compression depth or a ratio of the first depth of the layer to the substrate thickness to be greater than a first center compression depth or a ratio of the first depth of the layer to the center thickness. In various aspects, initially chemically strengthening the foldable substrate before etching the foldable substrate to form a first recessed portion and a second recessed portion can enable a first compression depth or a ratio of the first depth of the layer to the substrate thickness to be greater than a first center compression depth or a ratio of the first depth of the layer to the center thickness. In various aspects, the design of the etching mask can tune the first transition width and / or the second transition width. Placing the etching mask in a vacuum can dissipate bubbles between the barrier layer and the foldable substrate and / or increase the adhesion between the barrier layer and the foldable substrate, which can increase the uniformity of the resulting foldable substrate.

[0011] Some exemplary aspects of the present disclosure are described below and it should be understood that any features of the various aspects may be used alone or in combination with each other.

[0012] Aspect 1. A foldable substrate comprising:

[0013] a substrate thickness defined between a first major surface and a second major surface opposite the first major surface;

[0014] a first portion including the substrate thickness, a first compressive stress region extending from the first major surface to a first compressive depth, and a second compressive stress region extending from the second major surface to a second compressive depth;

[0015] a second portion including the substrate thickness, a third compressive stress region extending from the first major surface to a third compressive depth, and a fourth compressive stress region extending from the second major surface to a fourth compressive depth; and

[0016] a central portion, the central portion being positioned between the first portion and the second portion, the 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, a first central compressive stress region extending from the first central surface region to a first central compressive depth, a second central compressive stress region extending from the second central surface region to a second central compressive depth, and the central thickness being less than the substrate thickness,

[0017] The foldable substrate comprises a glass-based material or a ceramic-based material, the first central surface area is recessed a first distance from the first main surface, and a ratio of the first compression depth to the substrate thickness is greater than a ratio of the first central compression depth to the central thickness.

[0018] Aspect 2. The foldable substrate of Aspect 1, wherein the ratio of the first compression depth to the substrate thickness is about 0.01 to about 0.2 greater than the ratio of the first center compression depth to the center thickness.

[0019] Aspect 3. A foldable substrate as described in any of Aspects 1-2, wherein the ratio of the first compression depth to the substrate thickness is about 0.015 to about 0.15 greater than the ratio of the first center compression depth to the center thickness.

[0020] Aspect 4. A foldable substrate as described in any of Aspects 1-3, wherein the ratio of the first compression depth to the substrate thickness is about 0.02 to about 0.12 greater than the ratio of the first center compression depth to the center thickness.

[0021] Aspect 5. The foldable substrate of any of Aspects 1-4, wherein a ratio of the second compression depth to the substrate thickness is about 0.01 to about 0.2 greater than a ratio of the second center compression depth to the center thickness.

[0022] Aspect 6. The foldable substrate of aspect 5, wherein the ratio of the second compression depth to the substrate thickness is about 0.015 to about 0.15 greater than the ratio of the second center compression depth to the center thickness.

[0023] Aspect 7. The foldable substrate of any of Aspects 5-6, wherein the ratio of the second compression depth to the substrate thickness is about 0.02 to about 0.12 greater than the ratio of the second central compression depth.

[0024] Aspect 8. The foldable substrate of any one of Aspects 1-7, wherein the first compression depth is substantially equal to the third compression depth.

[0025] Aspect 9. The foldable substrate of any one of Aspects 1-8, wherein the second compression depth is substantially equal to the fourth compression depth.

[0026] Aspect 10. The foldable substrate of any one of Aspects 1-9, wherein the first central compression depth is substantially equal to the second central compression depth.

[0027] Aspect 11. The foldable substrate according to any one of aspects 1 to 10, wherein:

[0028] The first portion further comprises: a first depth of one or more alkali metal ion layers associated with the first compression depth and a second depth of one or more alkali metal ion layers associated with the second compression depth;

[0029] The second portion further comprises: a third depth of one or more alkali metal ion layers associated with the third compression depth and a fourth depth of one or more alkali metal ion layers associated with the fourth compression depth,

[0030] The central portion further comprises: a first central depth of one or more alkali metal ion layers associated with the first central compression depth, a second central depth of one or more alkali metal ion layers associated with the second central compression depth, and

[0031] A ratio of the first depth of the layer to the substrate thickness is greater than a ratio of the first center depth of the layer to the center thickness.

[0032] Aspect 12. A foldable substrate comprising:

[0033] a substrate thickness defined between a first major surface and a second major surface opposite the first major surface;

[0034] a first portion comprising the substrate thickness, a first compressive stress region extending from the first major surface to a first compressive depth, a second compressive stress region extending from the second major surface to a second compressive depth, a first depth of one or more alkali metal ion layers associated with the first compressive depth, and a second depth of one or more alkali metal ion layers associated with the second compressive depth;

[0035] a second portion comprising the substrate thickness, a third compressive stress region extending from the first major surface to a third compressive depth, a fourth compressive stress region extending from the second major surface to a fourth compressive depth, a third depth of one or more alkali metal ion layers associated with the third compressive depth, and a fourth depth of one or more alkali metal ion layers associated with the fourth compressive depth; and

[0036] a central portion, the central portion being positioned between the first portion and the second portion, the central portion comprising a central thickness defined between a first central surface region and a second central surface region opposite the first central surface region, a first central compressive stress region extending from the first central surface region to a first central compressive depth, a second central compressive stress region extending from the second central surface region to a second central compressive depth, a first central depth of one or more alkali metal ion layers associated with the first central compressive depth, a second central depth of one or more alkali metal ion layers associated with the second central compressive depth, and the central thickness being less than the substrate thickness,

[0037] The foldable substrate comprises a glass-based material or a ceramic-based material, the first central surface area is recessed a first distance from the first main surface, the foldable substrate comprises a ratio of the first compression depth to the substrate thickness, and a ratio of the first depth of the layer to the substrate thickness is greater than a ratio of the first central depth of the layer to the central thickness.

[0038] Aspect 13. The foldable substrate of any of Aspects 11-12, wherein the ratio of the first depth of the layer to the substrate thickness is about 0.001 to about 0.2 greater than the ratio of the first center depth of the layer to the center thickness.

[0039] Aspect 14. A foldable substrate as described in any of Aspects 11-13, wherein the ratio of the first depth of the layer to the substrate thickness is about 0.01 to about 0.15 greater than the ratio of the first center depth of the layer to the center thickness.

[0040] Aspect 15. A foldable substrate as described in any of Aspects 11-14, wherein the ratio of the first depth of the layer to the substrate thickness is about 0.02 to about 0.12 greater than the ratio of the first center depth of the layer to the center thickness.

[0041] Aspect 16. A foldable substrate as described in any of Aspects 11-15, wherein a ratio of the second depth of the layer to the substrate thickness is about 0.001 to about 0.2 greater than a ratio of the second center depth of the layer to the center thickness.

[0042] Aspect 17. The foldable substrate of aspect 16, wherein the ratio of the second depth of the layer to the substrate thickness is about 0.01 to about 0.15 greater than the ratio of the second center depth of the layer to the center thickness.

[0043] Aspect 18. A foldable substrate as described in any of Aspects 16-17, wherein the ratio of the second depth of the layer to the substrate thickness is about 0.02 to about 0.12 greater than the ratio of the second center depth of the layer.

[0044] Aspect 19. The foldable substrate of any one of Aspects 11-18, wherein the first depth of the layer is substantially equal to the third depth of the layer.

[0045] Aspect 20. The foldable substrate of any one of Aspects 11-19, wherein the second depth of the layer is substantially equal to the fourth depth of the layer.

[0046] Aspect 21. The foldable substrate of any of Aspects 11-20, wherein the first central depth of the layer is substantially equal to the second central depth of the layer.

[0047] Aspect 22. The foldable substrate of any of Aspects 11-21, wherein the ratio of the first depth of the layer to the thickness of the substrate is in a range of about 0.10 to about 0.22.

[0048] Aspect 23. The foldable substrate of aspect 22, wherein the ratio of the first depth of the layer to the thickness of the substrate is in the range of about 0.12 to about 0.17.

[0049] Aspect 24. The foldable substrate of any one of aspects 11-23, wherein the one or more alkali metal ions comprise potassium ions.

[0050] Aspect 25. The foldable substrate of any of Aspects 1-24, wherein the ratio of the first compression depth to the substrate thickness is in a range of about 0.10 to about 0.22.

[0051] Aspect 26. The foldable substrate of any of Aspects 1-25, wherein the ratio of the first compression depth to the substrate thickness is in a range of about 0.12 to about 0.17.

[0052] Aspect 27. A foldable substrate as described in any of Aspects 1-26, wherein a width of the second portion is approximately 15 mm or less, a width of the first portion is greater than a width of the center portion, a width of the center portion is greater than the width of the second portion, and a sum of the width of the first portion, the width of the center portion, and the width of the second portion corresponds to a size of the foldable substrate.

[0053] Aspect 28. The foldable substrate of Aspect 27, wherein the width of the second portion is about 2 mm to about 6 mm.

[0054] Aspect 29. A foldable substrate comprising:

[0055] a substrate thickness defined between a first major surface and a second major surface opposite the first major surface;

[0056] a first portion including the substrate thickness, a first compressive stress region extending from the first major surface to a first compressive depth, and a second compressive stress region extending from the second major surface to a second compressive depth;

[0057] a second portion including the substrate thickness, a third compressive stress region extending from the first major surface to a third compressive depth, and a fourth compressive stress region extending from the second major surface to a fourth compressive depth; and

[0058] a central portion, the central portion being positioned between the first portion and the second portion, the 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, a first central compressive stress region extending from the first central surface region to a first central compressive depth, a second central compressive stress region extending from the second central surface region to a second central compressive depth, and the central thickness being less than the substrate thickness,

[0059] The foldable substrate comprises a glass-based material or a ceramic-based material, the first central surface area is recessed a first distance from the first main surface, and a width of the first portion, a width of the central portion, and a width of the second portion are measured in a direction corresponding to a dimension of the foldable substrate, the width of the second portion accounts for a percentage of the dimension of the foldable substrate that is less than 15%, and the width of the first portion accounts for a percentage of the dimension of the foldable substrate that is approximately 35% or greater.

[0060] Aspect 30. A foldable substrate as described in any of Aspects 1-28, wherein a width of the first portion, a width of the center portion, and a width of the second portion are measured in a direction corresponding to a dimension of the foldable substrate, the width of the second portion accounts for a percentage of the dimension of the foldable substrate that is less than 15%, and the width of the first portion accounts for a percentage of the dimension of the foldable substrate that is approximately 35% or greater.

[0061] Aspect 31. The foldable substrate of any of Aspects 29-30, wherein the width of the second portion accounts for a percentage of about 2% to about 6% of the dimension of the foldable substrate.

[0062] Aspect 32. The foldable substrate of any one of Aspects 29-31, wherein the width of the first portion accounts for a percentage of about 40% to about 70% of the foldable substrate.

[0063] Aspect 33. The foldable substrate of any one of Aspects 29-32, wherein the width of the central portion accounts for a percentage of about 15% to about 50% of the foldable substrate.

[0064] Aspect 34. The foldable substrate of Aspect 33, wherein the width of the central portion accounts for a percentage of about 40% to about 48% of the foldable substrate.

[0065] Aspect 35. A foldable substrate as described in any of Aspects 1-34, wherein a deflectometer profile of the first central surface region taken along a centerline of the central portion equally spaced from the first portion and the second portion comprises a substantially parabolic shape.

[0066] Aspect 36. The foldable substrate of any one of Aspects 1-35, wherein the second central surface region is recessed a second distance from the second major surface.

[0067] Aspect 37. The foldable substrate of aspect 36, wherein the second distance is about 5% to about 20% of the thickness of the substrate.

[0068] Aspect 38. The foldable substrate of any one of Aspects 36-37, wherein the first distance is substantially equal to the second distance.

[0069] Aspect 39. The foldable substrate of any of Aspects 1-38, wherein the second major surface includes the second central surface area.

[0070] Aspect 40. The foldable substrate of any of Aspects 1-39, wherein the first distance is about 20% to about 45% of the thickness of the substrate.

[0071] Aspect 41. The foldable substrate of any one of aspects 1-40, wherein the central portion further comprises:

[0072] a first transition portion, the first transition portion comprising a first transition surface region and a second transition surface region opposite the first transition surface region, the first transition surface region attaching the first central surface region to the first portion, a thickness of the first transition portion decreasing smoothly and monotonically between the substrate thickness of the first portion and the central thickness of the central portion; and

[0073] a second transition portion, the second transition portion comprising a third transition surface region and a fourth transition surface region opposite the third transition surface region, the third transition surface region attaching the first central surface region to the second portion, a thickness of the second transition portion decreasing smoothly and monotonically between the substrate thickness of the second portion and the central thickness of the central portion.

[0074] Aspect 42. The foldable substrate of aspect 41, wherein the first transition surface region extends at a first average angle of about 167° to about 179° relative to the first central surface region.

[0075] Aspect 43. The foldable substrate of aspect 42, wherein the first average angle is in a range from about 170° to about 176°.

[0076] Aspect 44. The foldable substrate of any one of Aspects 41-43, wherein a first transition width of the first transition zone is in a range from about 150 microns to about 700 microns.

[0077] Aspect 45. The foldable substrate of aspect 44, wherein the first transition width is in a range from about 200 microns to about 500 microns.

[0078] Aspect 46. A foldable substrate as described in any of Aspects 1-45, wherein the first compressive stress zone comprises a first maximum compressive stress of about 400 MPa or greater, the second compressive stress zone comprises a second maximum compressive stress, the third compressive stress zone comprises a third maximum compressive stress of about 400 MPa or greater, the fourth compressive stress zone comprises a fourth maximum compressive stress, the first central compressive stress zone comprises a first central maximum compressive stress of about 400 MPa or greater, and the second central compressive stress zone comprises a second central maximum compressive stress.

[0079] Aspect 47. The foldable substrate of Aspect 46, wherein the second maximum compressive stress is about 400 MPa or greater, the fourth maximum compressive stress is about 400 MPa or greater, and the second central maximum compressive stress is about 400 MPa or greater.

[0080] Aspect 48. The foldable substrate of any one of Aspects 1-47, wherein the substrate thickness is in a range from about 50 microns to about 2 millimeters.

[0081] Aspect 49. The foldable substrate of any of Aspects 1-48, wherein the substrate thickness is in a range from about 100 microns to about 200 microns.

[0082] Aspect 50. The foldable substrate of any one of Aspects 1-49, wherein the center thickness is in a range of about 25 microns to about 120 microns,

[0083] Aspect 51. The foldable substrate of any of Aspects 1-50, wherein the center thickness is in a range from about 25 microns to about 60 microns.

[0084] Aspect 52. The foldable substrate of any one of Aspects 1-51, wherein the foldable substrate comprises a glass-based substrate.

[0085] Aspect 53. The foldable substrate of any one of Aspects 1-51, wherein the foldable substrate comprises a ceramic-based substrate.

[0086] Aspect 54. The foldable substrate of any one of Aspects 1-53, wherein the foldable substrate achieves a parallel plate distance of 1 mm to 10 mm.

[0087] Aspect 55. The foldable substrate of any one of Aspects 1-54, wherein the foldable substrate achieves a parallel plate distance of 5 mm.

[0088] Aspect 56. A consumer electronic product comprising:

[0089] A housing comprising a front surface, a rear surface and side surfaces;

[0090] electronic components located at least partially within the housing, the electronic components including a controller, a memory, and a display located at or adjacent to the front surface of the housing; and

[0091] a cover substrate, the cover substrate is arranged on the display,

[0092] Wherein at least one of a portion of the housing or the cover substrate comprises a foldable substrate as described in any one of claims 1-55.

[0093] Aspect 57. A method of manufacturing a foldable substrate, the foldable substrate comprising a substrate thickness defined between a first major surface and a second major surface opposite the first major surface, the method comprising:

[0094] chemically strengthening the foldable substrate for a first period of time; then

[0095] etching a portion of the first major surface to form a first central surface region;

[0096] etching a portion of the second major surface to form a second central surface region; and then

[0097] further chemically strengthening the foldable substrate for a second period of time,

[0098] wherein a central portion comprises 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, and after further chemical strengthening, the foldable substrate comprises:

[0099] a first compressive stress region of the first portion extending from the first major surface to a first compression depth;

[0100] a second compressive stress region of the third portion extending from the second major surface to a second compression depth;

[0101] a third compressive stress region of the second portion extending from the first major surface to a third compression depth;

[0102] a fourth compressive stress region of the fourth portion extending from the second major surface to a fourth compression depth;

[0103] a first central compressive stress zone of the central portion extending from the first central surface area to a first central compressive depth;

[0104] a second central compressive stress zone of the central portion extending from the second central surface area to a second central compressive depth; and

[0105] A ratio of the first compression depth to the substrate thickness is greater than a ratio of the first central compression depth to the central thickness, and the foldable substrate comprises a glass-based material or a ceramic-based material.

[0106] Aspect 58. A method of manufacturing a foldable substrate, the foldable substrate comprising a substrate thickness defined between a first major surface and a second major surface opposite the first major surface, the method comprising:

[0107] masking an existing second central surface region that is coplanar with the second major surface; and then

[0108] chemically strengthening the foldable substrate for a first period of time;

[0109] etching an existing first central surface region to form a first central surface region, the existing first central surface region being coplanar with the first major surface;

[0110] removing the mask from the existing second central surface area; and

[0111] further chemically strengthening the foldable substrate for a second period of time,

[0112] wherein a central portion comprises 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, and after further chemical strengthening, the foldable substrate comprises:

[0113] a first compressive stress region of the first portion extending from the first major surface to a first compression depth;

[0114] a second compressive stress region of the third portion extending from the second major surface to a second compression depth;

[0115] a third compressive stress region of the second portion extending from the first major surface to a third compression depth;

[0116] a fourth compressive stress region of the fourth portion extending from the second major surface to a fourth compression depth;

[0117] a first central compressive stress zone of the central portion extending from the first central surface area to a first central compressive depth;

[0118] a second central compressive stress zone of the central portion extending from the second central surface area to a second central compressive depth; and

[0119] A ratio of the first compression depth to the substrate thickness is greater than a ratio of the first central compression depth to the central thickness, and the foldable substrate comprises a glass-based material or a ceramic-based material.

[0120] Aspect 59. The method of any one of Aspects 57-58, further comprising: after the further chemical strengthening, substantially uniformly etching from about 0.1 microns to about 5 microns from the foldable substrate.

[0121] Aspect 60. The method of aspect 59, wherein the etching substantially uniformly removes about 0.2 microns to about 1 micron from the foldable substrate.

[0122] Aspect 61. The method of any of Aspects 57-60, wherein the ratio of the first compression depth to the substrate thickness is approximately 0.01 to approximately 0.2 greater than the ratio of the first center compression depth to the center thickness.

[0123] Aspect 62. The method of any one of Aspects 57-61, wherein the ratio of the first compression depth to the substrate thickness is approximately 0.015 to approximately 0.15 greater than the ratio of the first center compression depth to the center thickness.

[0124] Aspect 63. The method of any of Aspects 57-62, wherein the ratio of the first compression depth to the substrate thickness is approximately 0.02 to approximately 0.12 greater than the ratio of the first center compression depth to the center thickness.

[0125] Aspect 64. The method of any of Aspects 57-63, wherein a ratio of the second compression depth to the substrate thickness is about 0.01 to about 0.2 greater than a ratio of the second center compression depth to the center thickness.

[0126] Aspect 65. The method of aspect 64, wherein the ratio of the second compression depth to the substrate thickness is about 0.015 to about 0.15 greater than the ratio of the second center compression depth to the center thickness.

[0127] Aspect 66. The method of any of Aspects 64-65, wherein the ratio of the second compression depth to the substrate thickness is about 0.02 to about 0.12 greater than the ratio of the second center compression depth.

[0128] Aspect 67. A method as described in any of Aspects 57-66, wherein a width of the second portion is approximately 15 mm or less, a width of the first portion is greater than a width of the center portion, a width of the center portion is greater than the width of the second portion, and a sum of the width of the first portion, the width of the center portion, and the width of the second portion corresponds to a size of the foldable substrate.

[0129] Aspect 68. The method of aspect 67, wherein the width of the second portion is about 2 mm to about 6 mm.

[0130] Aspect 69. A method as described in any of Aspects 57-66, wherein a width of the first portion, a width of the center portion, and a width of the second portion are measured in a direction corresponding to a dimension of the foldable substrate, the width of the second portion accounts for a percentage of the dimension of the foldable substrate that is less than 15%, and the width of the first portion accounts for a percentage of the dimension of the foldable substrate that is approximately 35% or greater.

[0131] Aspect 70. The method of aspect 69, wherein the width of the second portion as a percentage of the dimension of the foldable substrate is about 2% to about 6%.

[0132] Aspect 71. The method of any of Aspects 69-70, wherein the width of the first portion as a percentage of the foldable substrate is about 40% to about 70%.

[0133] Aspect 72. The method of any one of Aspects 69-71, wherein the width of the central portion as a percentage of the foldable substrate is about 15% to about 50%.

[0134] Aspect 73. The method of aspect 72, wherein the width of the central portion as a percentage of the foldable substrate is about 40% to about 48%.

[0135] Aspect 74. The method of any one of Aspects 57-73, wherein the first compression depth is substantially equal to the third compression depth.

[0136] Aspect 75. The method of any one of Aspects 57-74, wherein the second compression depth is substantially equal to the fourth compression depth.

[0137] Aspect 76. The method of any one of Aspects 57-75, wherein the first central compression depth is substantially equal to the second central compression depth.

[0138] Aspect 77. The method of any one of Aspects 57-76, wherein a square root of a ratio of the second time period to the first time period is less than the center thickness divided by a difference between the substrate thickness and the center thickness.

[0139] Aspect 78. The method of any one of aspects 57-77, wherein the second period of time is from about 1 minute to about 10 minutes.

[0140] Aspect 79. The method of any one of aspects 57-77, wherein the first period of time is from about 45 minutes to about 8 hours.

[0141] Aspect 80. The method of any of aspects 57-79, wherein the second time period is about 2% to about 20% of the first time period.

[0142] Aspect 81. A method as described in any of Aspects 57-80, wherein after the chemical strengthening but before the further chemical strengthening, the first portion includes a first intermediate compressive stress region extending to a first intermediate compressive depth, and the first intermediate compressive depth divided by the thickness of the substrate is in the range of about 10% to about 20%.

[0143] Aspect 82. The method of any one of Aspects 57-81, wherein at least one of the chemical strengthening or the further chemical strengthening comprises contacting the foldable substrate with potassium ions.

[0144] Aspect 83. The method according to any one of aspects 57-82, further comprising: before the etching:

[0145] disposing an etching mask over the first major surface of the foldable substrate; and

[0146] The etch mask is degassed in a vacuum.

[0147] Aspect 84. The method of any one of claims 57-82, further comprising: before the etching:

[0148] An etching mask is disposed on the first major surface of the foldable substrate, the etching mask comprising:

[0149] a first portion, the first portion comprising a first barrier layer, the first barrier layer at least partially adhered to the first major surface; a first polymer layer, the first polymer layer positioned between the first barrier layer and the first major surface at a first peripheral portion of the first portion, the first polymer layer comprising a first width; a first contact surface of the first polymer layer, the first contact surface adhered to the first barrier layer; and a second contact surface of the first polymer layer, the second contact surface facing the first major surface; and

[0150] a second portion, the second portion comprising a second barrier layer, the second barrier layer at least partially adhered to the first major surface; a second polymer layer, the second polymer layer positioned between the second barrier layer and the first major surface at a second peripheral portion of the second portion, the second polymer layer comprising a second width; a third contact surface of the second polymer layer, the third contact surface adhered to the second barrier layer; and a fourth contact surface of the second polymer layer, the fourth contact surface facing the first major surface, and a minimum distance between the first peripheral portion and the second peripheral portion is in the range of about 1 mm to about 50 mm; and

[0151] The etch mask is degassed in a vacuum.

[0152] Aspect 85. The method of any one of Aspects 83-84, wherein degassing the etch mask in the vacuum occurs for 1 minute to 15 minutes.

[0153] Aspect 86. A method as described in any of Aspects 83-85, wherein a first transition width of the first transition zone is greater than or equal to a first width of the first polymer layer, a second transition width of the second transition zone is greater than or equal to a second width of the second polymer layer, the central portion includes the first transition zone, the central zone and the second transition zone, and the first width is in the range of about 100 microns to about 3 millimeters, and the second width is in the range of about 100 microns to about 3 millimeters.

[0154] Aspect 87. The method of any one of Aspects 83-86, wherein a thickness of the first transition zone decreases smoothly and monotonically between the substrate thickness of the first portion and a central thickness of the central portion.

[0155] Aspect 88. A method as described in any of Aspects 83-87, wherein the first compressive stress zone comprises a first maximum compressive stress of about 400 MPa or greater, the second compressive stress zone comprises a second maximum compressive stress, the third compressive stress zone comprises a third maximum compressive stress of about 400 MPa or greater, the fourth compressive stress zone comprises a fourth maximum compressive stress, the first central compressive stress zone comprises a first central maximum compressive stress of about 400 MPa or greater, and the second central compressive stress zone comprises a second central maximum compressive stress.

[0156] Aspect 89. The method of aspect 88, wherein the second maximum compressive stress is about 400 MPa or greater, the fourth maximum compressive stress is about 400 MPa or greater, and the second central maximum compressive stress is about 400 MPa or greater.

[0157] Aspect 90. The method of any one of aspects 57-89, wherein the substrate thickness is in a range from about 50 microns to about 2 millimeters.

[0158] Aspect 91. The method of any of Aspects 57-90, wherein the substrate thickness is in a range from about 100 microns to about 200 microns.

[0159] Aspect 92. The method of any of Aspects 57-91, wherein the center thickness is in a range from about 25 microns to about 120 microns.

[0160] Aspect 93. The method of any of Aspects 57-92, wherein the center thickness is in a range from about 25 microns to about 60 microns. BRIEF DESCRIPTION OF THE DRAWINGS

[0161] The above and other features and advantages of various aspects of the present disclosure may be better understood when the following detailed description is read with reference to the accompanying drawings, in which:

[0162] Figure 1 is a schematic diagram of an exemplary foldable device in a flat configuration according to various aspects, wherein the schematic diagram of the folded configuration can be as shown in FIG. Figure 5 As shown;

[0163] Figures 2 to 4 According to various aspects Figure 1 A cross-sectional view of a foldable device including a foldable substrate along line 2-2;

[0164] Figure 5 is a schematic diagram of an exemplary foldable device of various aspects of the present disclosure in a folded configuration, wherein a schematic diagram of a flat configuration may be as shown in FIG. Figure 1 As shown;

[0165] Figure 6is used to determine the exemplary foldable substrate along Figure 5 A cross-sectional view of the test device with the minimum parallel plate distance at line 7-7;

[0166] Figure 7 is used to determine the exemplary modified foldable device along Figure 5 A cross-sectional view of another test device with a minimum parallel plate distance along line 7-7;

[0167] Figure 8 is used to determine the exemplary foldable substrate along Figure 5 A cross-sectional view of the test device with the minimum parallel plate distance at line 7-7;

[0168] Fig. 9 is used to determine the exemplary modified foldable device along Figure 5 A cross-sectional view of the test device with the minimum parallel plate distance at line 7-7;

[0169] Fig.10 is a schematic plan view of an exemplary consumer electronic device according to various aspects;

[0170] Fig.11 yes Fig.10 A schematic perspective view of an exemplary consumer electronic device of ;

[0171] Figure 12 to Figure 13 is a flow chart illustrating an exemplary method of manufacturing a foldable substrate and / or a foldable device according to aspects of the present disclosure;

[0172] Figure 14 to Figure 15 Schematically illustrating steps in a method of manufacturing a foldable substrate and / or a foldable device;

[0173] Fig.16 The foldable substrate Fig.15 or Fig.17 After the steps shown and / or Fig.18 a cross-sectional view prior to the step shown;

[0174] Figure 17 to Figure 18 Schematically illustrating steps in a method of manufacturing a foldable substrate and / or a foldable device;

[0175] Fig.19 The foldable substrate Fig.18 After the steps shown and / or Fig. 20 a cross-sectional view prior to the step shown;

[0176] Fig. 20 Schematically illustrating steps in a method of manufacturing a foldable substrate and / or a foldable device;

[0177] Fig.21 The foldable substrate Fig. 20 After the steps shown and / or Fig. 22 a cross-sectional view prior to the step shown;

[0178] Figure 22 to Figure 26 Schematically illustrating steps in a method of manufacturing a foldable substrate and / or a foldable device;

[0179] Fig. 27 The foldable substrate Fig.26 After the steps shown and / or Fig.28 a cross-sectional view prior to the step shown;

[0180] Figures 28 to 30 Schematically illustrating steps in a method of manufacturing a foldable substrate and / or a foldable device;

[0181] Fig.31 The foldable substrate Fig.30 After the steps shown and / or Fig.32 a cross-sectional view prior to the step shown;

[0182] Figure 32 to Figure 35 Schematically illustrating steps in a method of manufacturing a foldable substrate and / or a foldable device;

[0183] Fig.36 Example surface profile;

[0184] Fig.37 schematically illustrating a plan view of a foldable substrate; and

[0185] Figure 38 to Figure 39 A cross-sectional view of a foldable device including a rollable foldable substrate is schematically illustrated.

[0186] Throughout the disclosure, the drawings are used to emphasize certain aspects. Therefore, unless otherwise explicitly stated, the relative sizes of different regions, parts, and substrates shown in the drawings should not be assumed to be proportional to their actual relative sizes. DETAILED DESCRIPTION

[0187] Various aspects are described more fully hereinafter with reference to the accompanying drawings, in which exemplary aspects are shown. Whenever possible, the same reference numerals are used throughout the drawings to refer to the same or similar parts.

[0188] Figures 1 to 4 , Figures 6 to 9 and Figure 38 to Figure 39Views illustrating foldable devices 101, 301, 401, 501, 701, 801, 901, 3801, and 3901 including a foldable substrate 201 according to various aspects of the present disclosure. Unless otherwise noted, a discussion of features of various aspects of a foldable device may be equally applicable to corresponding features of any aspect of the present disclosure. For example, the same part number throughout the present disclosure may indicate that in some aspects, the identified features are identical to each other, and unless otherwise noted, a discussion of identified features of one aspect may be equally applicable to identified features of any of the other aspects of the present disclosure.

[0189] Figures 2 to 4 Schematically illustrating exemplary aspects of foldable devices 101, 301, and 401 including a foldable substrate 201 in an unfolded (eg, flat) configuration according to various aspects of the present disclosure, and Figures 6 to 9 Exemplary aspects of foldable devices 501 , 701 , 801 , and 901 including a foldable substrate 201 in a folded configuration according to aspects of the present disclosure are illustrated. Figure 3 Exemplary aspects of a foldable device 301 composed of a foldable substrate 201 in an unfolded (eg, flat) configuration according to aspects of the present disclosure are schematically illustrated. Figure 38 to Figure 39 Exemplary aspects of foldable devices 3801 and 3901 as rollable devices including a foldable substrate 201 as a rollable substrate are schematically illustrated. The foldable devices 101, 301, and 401 and the foldable substrate 201 include a first portion 221, a second portion 231, and a center portion 281 positioned between the first portion 221 and the second portion 231. In various aspects, as Figure 2 and Figure 4 As shown, the foldable devices 101 and 401 may include a release liner 271, but in other aspects other substrates (e.g., glass-based substrates and / or ceramic-based substrates discussed throughout this application) may be used instead of having the illustrated release liner 271. In various aspects, as Figure 2 and Figure 7 As shown, the foldable device 101 and 701 may include a coating 251. In various aspects, as Figure 2 and Figure 4 As shown, the foldable device 101 may include an adhesive layer 261. In various aspects, as Figure 2 and Figure 7 As shown, the foldable devices 101 and 701 may include polymer base portions 289 and / or 299. Figures 2 to 4 As shown, the foldable substrate 201 may include a first recessed portion 211. In various aspects, as Figures 2 to 3As shown, the foldable substrate 201 may further include a second recessed portion 241. It should be understood that any of the foldable devices of the present disclosure may include a second substrate (e.g., a glass-based substrate and / or a ceramic-based substrate), a release liner 271, a display device, a coating 251, an adhesive layer 261, and / or a polymer-based portion 289 and / or 299.

[0190] Throughout this disclosure, reference is made to Figure 1 , the width 103 of the foldable device 101, 301, 401, 501, 701, 801, 901, 3801 and / or 3901 is considered to be the dimension of the foldable device taken in the direction 104 of the folding axis 102 of the foldable device between opposite edges of the foldable device, where the direction 104 also includes the direction of the width 103. Furthermore, throughout this disclosure, the length 105 of the foldable device 101, 301, 401, 501, 701, 801, 901, 3801, and / or 3901 is considered to be a dimension of the foldable device 101, 301, 401, 501, 701, 801, 901, 3801, and / or 3901 taken between opposite edges of the foldable device 101, 301, 401, 501, 701, 801, 901, 3801, and / or 3901 in a direction 106 perpendicular to the folding axis 102 of the foldable device 101, 301, 401, 501, 701, 801, 901, 3801, and / or 3901. It should be understood that the direction 104 of the width 103 and / or the direction 106 of the length 105 may correspond to corresponding directions in the foldable substrate 201. In various aspects, as Figure 1 to Figure 2 As shown, the foldable device of any aspect of the present disclosure can be in a flat configuration (e.g., see Figure 2 ) includes a folding plane 109 including the folding axis 102. In another aspect, as Figure 2 As shown, the folding plane 109 can be in a flat configuration (see, for example, Figure 2 ) along the folding axis 102 and in the direction of the substrate thickness 207. The folding plane 109 can include the central axis 107 of the foldable device. In various aspects, the foldable device can be folded in the direction 111 (e.g., see Figure 1 ) is folded about a folding axis 102 extending in a direction 104 of width 103 to form a folded configuration (see, for example, Figure 5 , Figure 7 and Fig. 9 ). Similarly, folding the foldable substrate 201 around the folding axis (see, for example, Figure 3 ) can form a folded configuration (see, for example, Figure 6 and Figure 8). As shown, the foldable device and / or the foldable substrate may include a single folding axis to allow the foldable device and / or the foldable substrate to include a double fold, wherein, for example, the foldable device and / or the foldable substrate can be folded in half. In other aspects, the foldable device and / or the foldable substrate may include two or more folding axes, each folding axis including a corresponding central portion similar or identical to the central portion 281 discussed herein. For example, providing two folding axes may allow the foldable device and / or the foldable substrate to include a trifold, wherein, for example, the foldable device and / or the foldable substrate can be folded together with the first portion 221, the second portion 231 and the third portion are similar or identical to the first portion or the second portion and the central portion 281 and the other central portion are similar or identical to the central portions positioned between the first portion and the second portion and between the second portion and the third portion, respectively.

[0191] The foldable substrate 201 may include a glass-based substrate and / or a ceramic-based substrate having a pencil hardness of 8H or greater (e.g., 9H or greater). As used herein, pencil hardness is measured using a standard lead-grade pencil using ASTM D 3363-20. Providing a glass-based foldable substrate and / or a ceramic-based foldable substrate may enhance puncture resistance and / or impact resistance.

[0192] In various aspects, the foldable substrate 201 may include a glass-based substrate. As used herein, "glass-based" includes both glass and glass-ceramics, wherein the glass-ceramics have one or more crystalline phases and an amorphous residual glass phase. Glass-based materials (e.g., glass-based substrates) may include amorphous materials (e.g., glass) and, as appropriate, one or more crystalline materials (e.g., ceramics). Amorphous materials and glass-based materials may be strengthened. As used herein, the term "strengthened" may refer to a material that has been chemically strengthened by, for example, ion-exchanging larger ions for smaller ions in the surface of the substrate as discussed below. However, other strengthening methods, such as thermal tempering or utilizing the mismatch of thermal expansion coefficients between portions of the substrate to generate compressive stress and a central tension zone, may be utilized to form a strengthened substrate. Exemplary glass-based materials that may or may not contain lithium include soda-lime glass, alkali aluminosilicate glass, alkali-containing borosilicate glass, alkali-containing aluminoborosilicate glass, alkali-containing phosphosilicate glass, and alkali-containing aluminophosphosilicate glass. In various aspects, the glass-based material may include an alkali-containing glass or an alkali-free glass, either of which may or may not contain lithium. In various aspects, the glass material may be alkali-free and / or include a low content of alkali metals (e.g., about 10 mol% or less of R2O, wherein R2O includes Li2O Na2O, KO, or the more extensive list provided below). In one or more aspects, the glass-based material may include, in molar percentage (mol%): SiO2 in a range of about 40 mol% to about 80%, Al2O3 in a range of about 5 mol% to about 30 mol%, B2O3 in a range of 0 mol% to about 10 mol%, ZrO2 in a range of 0 mol% to about 5 mol%, P2O5 in a range of 0 mol% to about 15 mol%, TiO2 in a range of 0 mol% to about 2 mol%, R2O in a range of 0 mol% to about 20 mol%, and RO in a range of 0 mol% to about 15 mol%. As used herein, R2O may refer to alkali metal oxides, such as Li2O, Na2O, K2O, Rb2O, and Cs2O. As used herein, RO may refer to MgO, CaO, SrO, BaO, and ZnO. In various aspects, the glass-based substrate may further include 0 mol% to about 2 mol% of each of Na2SO4, NaCl, NaF, NaBr, K2SO4, KCl, KF, KBr, As2O3, Sb2O3, SnO2, Fe2O3, MnO, MnO2, MnO3, Mn2O3, Mn3O4, Mn2O7. "Glass ceramics" include materials produced by controlling glass crystallization. In various aspects, the glass ceramic has a crystallinity of about 1% to about 99%.Examples of suitable glass ceramics may include Li2O-Al2O3-SiO2 (i.e., LAS) glass ceramics, MgO-Al2O3-SiO2 (i.e., MAS) glass ceramics, ZnO×Al2O3×nSiO2 (i.e., ZAS), glass ceramics including a main crystalline phase (including β-quartz solid solution), β spodumene, cordierite, petalite and / or lithium disilicate. A chemical strengthening process may be used to strengthen the glass ceramic substrate. In one or more aspects, the MAS glass ceramic substrate may be strengthened in a Li2SO4 molten salt, thereby 2Li. + Exchanged to Mg 2+ Can happen.

[0193] In various aspects, the foldable substrate 201 may include a ceramic-based substrate. As used herein, "ceramic-based" includes both glass-based and ceramic-based, wherein the glass-ceramic has one or more crystalline phases and an amorphous residual glass phase. The ceramic-based material can be strengthened (e.g., chemically strengthened). In various aspects, the ceramic-based material can be formed by heating the glass-based material to form a ceramic (e.g., crystalline) portion. In other aspects, the ceramic-based material may include one or more nucleating agents that may be conducive to the formation of a crystalline phase. In various aspects, the ceramic-based material may include one or more oxides, nitrides, oxynitrides, carbides, borides, and / or silicides. Exemplary aspects of ceramic oxides include zirconium oxide (ZrO2), zircon (ZrSiO4), alkali metal oxides such as sodium oxide (Na2O), alkaline earth metal oxides such as magnesium oxide (MgO), titanium dioxide (TiO2), hafnium oxide (Hf2O), yttrium oxide (Y2O3), iron oxide, beryllium oxide, vanadium oxide (VO2), fused silica, mullite (a mineral comprising a combination of aluminum oxide and silicon dioxide), and spinel (MgAl2O4). Exemplary aspects of ceramic nitrides include silicon nitride (Si3N4), aluminum nitride (AlN), gallium nitride (GaN), beryllium nitride (Be3N2), boron nitride (BN), tungsten nitride (WN), vanadium nitride, alkaline earth metal nitrides such as magnesium nitride (Mg3N2), nickel nitride, and tantalum nitride. Exemplary aspects of oxynitride ceramics include silicon oxynitride, aluminum oxynitride, and SiAlON (a combination of aluminum oxide and silicon nitride and may have a chemical formula such as Si 12-m-n Al m+n O n N 16-n 、Si 6-n Al n O n N 8-n or Si 2-n Al n O 1+n N 2-n, where m, n, and resulting subscripts are all non-negative integers). Exemplary aspects of carbides and carbon-containing ceramics include silicon carbide (SiC), tungsten carbide (WC), iron carbide, boron carbide (B4C), alkali metal carbides such as lithium carbide (Li4C3), alkaline earth metal carbides such as magnesium carbide (Mg2C3), and graphite. Examples of borides include chromium boride (CrB2), molybdenum boride (Mo2B5), tungsten boride (W2B5), iron boride, titanium boride, zirconium boride (ZrB2), hafnium boride (HfB2), vanadium boride (VB2), niobium boride (NbB2), and lanthanum boride (LaB6). Exemplary aspects of silicides include molybdenum disilicide (MoSi2), tungsten disilicide (WSi2), titanium disilicide (TiSi2), nickel silicide (NiSi), alkaline earth metal silicides such as sodium silicide (NaSi), alkali metal silicides such as magnesium silicide (Mg2Si), hafnium disilicide (HfSi2), and platinum silicide (PtSi).

[0194] Throughout this disclosure, elastic modulus (e.g., Young's modulus) and / or Poisson's ratio are measured using ISO 527-1: 2019. In various aspects, the foldable substrate 201 can include an elastic modulus in the range of about 10 GPa to about 100 GPa, about 40 GPa to about 100 GPa, about 60 GPa to about 100 GPa, about 60 GPa to about 80 GPa, about 80 GPa to about 100 GPa, or any range or sub-range therebetween.

[0195] In various aspects, the foldable substrate 201 can be optically transparent. As used herein, "optically transparent" or "optically clear" means an average transmittance of 70% or more through a 1.0 mm thick sheet of material in the wavelength range of 400 nm to 700 nm. In various aspects, an "optically transparent material" or "optically clear material" can have an average transmittance of 75% or more, 80% or more, 85% or more, or 90% or more, 92% or more, 94% or more, 96% or more through a 1.0 mm thick sheet of material in the wavelength range of 400 nm to 700 nm. The average transmittance in the wavelength range of 400 nm to 700 nm is calculated by measuring the transmittance of all wavelengths from about 400 nm to about 700 nm and averaging the measurements.

[0196] like Figures 2 to 4 As shown, the foldable devices 101, 301 and 401 include a foldable substrate 201, which includes a first main surface 203 and a second main surface 205 opposite to the first main surface 203. Figures 2 to 4As shown, the first major surface 203 may extend along the first plane 204a. The second major surface 205 may extend along the second plane 206a. In various aspects, as shown, the second plane 206a may be parallel to the first plane 204a. As used herein, the substrate thickness 207 may be defined between the first major surface 203 and the second major surface 205 as the distance between the first plane 204a and the second plane 206a. In various aspects, the substrate thickness 207 can be about 10 micrometers (μm) or more, about 25 μm or more, about 40 μm or more, about 50 μm or more, about 60 μm or more, about 70 μm or more, about 80 μm or more, about 90 μm or more, about 100 μm or more, about 125 μm or more, about 150 μm or more, about 200 μm or more, about 300 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 various aspects, the substrate thickness 207 may be in a range of about 10 μm to about 2 mm, about 25 μm to about 2 mm, about 40 μm to about 2 mm, about 50 μm to about 2 mm, about 60 μm to about 2 mm, about 70 μm to about 2 mm, about 70 μm to about 1 mm, about 70 μm to about 800 μm, about 80 μm to about 500 μm, about 90 μm to about 500 μm, about 100 μm to about 200 μm, about 125 μm to about 200 μm, about 150 μm to about 200 μm, about 150 μm to about 160 μm, or any range or sub-range therebetween.

[0197] like Figures 2 to 4 As shown, the first portion 221 of the foldable substrate 201 may include a first surface area 223 and a second surface area 225 opposite to the first surface area 223. The first portion 221 will now be referred to as Figure 2 The foldable device 101 is described, and it is understood that unless otherwise stated, such description of the first portion 221 can apply to any aspect of the present disclosure, such as Figure 3 to Figure 4 , Figures 6 to 9 and Figure 38 to Figure 39The illustrated foldable device 301, 401, 501, 701, 801, 901, 3801 and / or 3901. In various aspects, as shown, the first surface area 223 may include a planar surface, and / or the second surface area 225 of the first portion 221 may include a planar surface. In other aspects, as shown, the second surface area 225 may be parallel to the first surface area 223. In various aspects, as shown, the first major surface 203 may include the first surface area 223, and the second major surface 205 may include the second surface area 225. In other aspects, the first surface area 223 may extend along the first plane 204a. In other aspects, the second surface area 225 may extend along the second plane 206a. In various aspects, the substrate thickness 207 may correspond to the distance between the first surface area 223 of the first portion 221 and the second surface area 225 of the first portion 221. In various aspects, the substrate thickness 207 may be substantially uniform across the first surface area 223. In various aspects, the first thickness defined between the first surface area 223 and the second surface area 225 can be within one or more of the ranges discussed above with respect to the substrate thickness 207. In further aspects, the first thickness can include the substrate thickness 207. In further aspects, the first thickness of the first portion 221 can be substantially uniform between the first surface area 223 and the second surface area 225 across its corresponding length (i.e., in the direction 106 of the length 105 of the foldable device) and / or its corresponding width (i.e., in the direction 104 of the width 103 of the foldable device).

[0198] like Figures 2 to 4 As shown, the second portion 231 of the foldable substrate 201 may include a third surface area 233 and a fourth surface area 235 opposite to the third surface area 233. The second portion 231 will now be referred to as Figure 2 The foldable device 101 is described, and it is understood that unless otherwise stated, such description of the second portion 231 can apply to any aspect of the present disclosure, such as Figure 3 to Figure 4 , Figures 6 to 9 and Figure 38 to Figure 39The illustrated foldable device 301, 401, 501, 701, 801, 901, 3801 and / or 3901. In various aspects, as shown, the third surface area 233 of the second portion 231 may include a planar surface, and / or the fourth surface area 235 of the second portion 231 may include a planar surface. In other aspects, the third surface area 233 of the second portion 231 may be in a shared plane with the first surface area 223 of the first portion 221. In other aspects, as shown, the fourth surface area 235 may be parallel to the third surface area 233. In other aspects, the fourth surface area 235 of the second portion 231 may be in a shared plane with the second surface area 225 of the first portion 221. The second thickness may be defined between the third surface area 233 of the second portion 231 and the fourth surface area 235 of the second portion 231. In various aspects, the second thickness may be within the range discussed above with respect to the substrate thickness 207. In further aspects, the second thickness can include the substrate thickness 207. In further aspects, as shown, the second thickness can be substantially equal to the substrate thickness 207 (e.g., the first thickness). In various aspects, the second thickness of the second portion 231 can be substantially uniform between the third surface region 233 and the fourth surface region 235.

[0199] like Figures 2 to 4 As shown, the foldable substrate 201 may include a central portion 281 positioned between the first portion 221 and the second portion 231. In various aspects, the central portion 281 may include a first central surface area 213 and a second central surface area 243 opposite the first central surface area 213. As shown, the first central surface area 213 of the central portion 281 may be positioned between the first surface area 223 and the third surface area 233. In further aspects, the first central surface area 213 may correspond to the central area 248 of the central portion 281. In further aspects, as shown, when the foldable device 101, 301 and / or 401 is in a flat configuration, the first central surface area 213 may extend along the third plane 204b. The first recessed portion 211 may be defined between the first central surface area 213 (e.g., the third plane 204b) and the first plane 204a.

[0200] In various aspects, the third plane 204b can be substantially parallel to the first plane 204a and / or the second plane 206a. Figures 2 to 3As shown, the first central surface region 213 can be recessed a first distance 219 from the first major surface 203. In further aspects, the first distance 219 where the first central surface region 213 is recessed from the first plane 204a can be about 1 μm or more, about 5 μm or more, about 10 μm or more, about 25 μm or more, about 40 μm or more, about 80 μm or more, about 100 μm or more, about 125 μm or more, about 150 μm or more, 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 further aspects, the first distance 219 may be in a range of about 1 μm to about 1 mm, about 1 μm to about 800 μm, about 5 μm to about 800 μm, about 5 μm to about 500 μm, about 10 μm to about 500 μm, about 10 μm to about 300 μm, about 25 μm to about 300 μm, about 25 μm to about 200 μm, about 40 μm to about 200 μm, about 80 μm to about 200 μm, about 80 μm to about 200 μm, about 100 μm to about 200 μm, about 125 μm to about 200 μm, about 125 μm to about 180 μm, about 125 μm to about 160 μm, about 125 μm to about 150 μm, or any range or sub-range therebetween. In further aspects, the first distance 219 by which the first central surface region 213 is recessed from the first plane 204a can 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 of the substrate thickness 207. In further aspects, the first distance 219 as a percentage of the substrate thickness 207 can be in a range of about 1% to about 75%, about 1% to about 60%, about 5% to about 60%, about 5% to about 50%, about 10% to about 50%, about 10% to about 45%, about 15% to about 45%, about 20% to about 45%, about 20% to about 35%, about 20% to about 30%, about 25% to about 30%, or any range or sub-range therebetween.

[0201] like Figures 2 to 4 As shown, the second central surface area 243 of the central portion 281 can be positioned between the second surface area 225 and the fourth surface area 235. In another aspect, as Figures 2 to 3 As shown, when the foldable device 101 and / or 301 is in a flat configuration, the second central surface area 243 can extend along the fourth plane 206b. Figures 2 to 3As shown, the second recessed portion 241 can be defined between the second central surface area 243 (eg, the fourth plane 206b) and the second plane 206a. Figure 4 As shown, the second central surface region 243 may extend along the second plane 206a.

[0202] In another aspect, Figures 2 to 3 As shown, the second central surface area 243 can be recessed from the second major surface 205 by a second distance 249. In further aspects, the second distance 249 can be within one or more of the ranges discussed above for the first distance 219. In further aspects, the first distance can be greater than the second distance. In even further aspects, the second central surface area 243 can be recessed from the second plane 206a by a second distance 249 as a percentage of the substrate thickness 207 by about 1% or more, about 2% or more, about 5% or more, about 10% or more, about 12% or more, about 30% or more, about 25% or less, about 20% or less, about 18% or less, or about 15% or less. In even further aspects, the second distance 249 as a percentage of the substrate thickness 207 can be in a range of about 1% to about 30%, about 1% to about 25%, about 2% to about 25%, about 5% to about 25%, about 5% to about 20%, about 10% to about 20%, about 10% to about 18%, about 12% to about 18%, about 12% to about 15%, or any range or sub-range therebetween. In further aspects, as Figure 2 As shown, the first distance 219 can be substantially equal to the second distance 249. Providing a first distance substantially equal to the second distance can further reduce the incidence of mechanical instability in the central portion, for example, because the foldable substrate is symmetrical about a plane including the midpoint of the substrate thickness and the central thickness. In further aspects, as Figure 4 As shown, the second central surface region 243 can be coplanar with the second surface region 225 and / or the fourth surface region 235, for example, thereby forming a planar second major surface 205 extending along the second plane 206a.

[0203] A central thickness 209 can be defined between the first central surface region 213 and the second central surface region 243, which can be measured as the distance between the third plane 204b and the fourth plane 206b. In various aspects, the central thickness 209 can be about 1 μm or more, about 5 μm or more, about 10 μm or more, about 25 μm or more, about 40 μm or more, about 120 μm or more, about 100 μm or less, about 80 μm or less, about 60 μm or less, or about 50 μm or less. In various aspects, the center thickness 209 can be in the range of about 1 μm to about 120 μm, about 5 μm to about 120 μm, about 10 μm to about 120 μm, about 10 μm to about 120 μm, about 25 μm to about 120 μm, about 25 μm to about 100 μm, about 25 μm to about 80 μm, about 25 μm to about 60 μm, about 40 μm to about 60 μm, or any range or sub-range therebetween. In various aspects, the center thickness 209 can be less than the substrate thickness 207 by about 10 μm or more, about 20 μm or more, about 30 μm or more, about 40 μm or more, about 50 μm or more, or about 60 μm or more. In various aspects, the percentage of the central thickness 209 to the substrate thickness 207 can be about 0.5% or more, about 1% or more, about 2% or more, about 5% or more, about 6% or more, about 40% or less, about 30% or less, about 20% or less, about 13% or less, about 10% or less, or about 8% or less. In various aspects, the percentage of the central thickness 209 to the substrate thickness 207 can be in the range of about 0.5% to about 40%, about 0.5% to about 30%, about 0.5% to about 20%, about 0.5% to about 13%, about 1% to about 13%, about 1% to about 10%, about 2% to about 10%, about 2% to about 8%, about 5% to about 8%, about 6% to about 8%, or any range or sub-range therebetween. In various aspects, the central region 248 of the central portion 281 can correspond to the region containing the central thickness 209. By providing a first central surface area 213 of the central portion 281 extending along the third plane 204b parallel to the second central surface area 243 of the central portion 281 extending along the fourth plane 206b, a uniform central thickness 209 may extend across the central portion 281 which may provide enhanced folding performance at a predetermined thickness of the central thickness 209. The uniform central thickness 209 across the central portion 281 may improve folding performance by preventing stress concentration that would occur if a portion of the central portion 281 were thinner than the remainder of the central portion 281.

[0204] In various aspects, such as Figures 2 to 4As shown, the central portion 281 of the foldable substrate 201 can include a first transition region 212, which includes a first transition surface area 215 extending between the first surface area 223 and the first central surface area 213. In other aspects, as shown, the width of the first transition region 212 (e.g., the first transition width 214) can be measured in the direction 106 of the length 105 (see Figure 1) between a portion of the first central surface area 213 extending along the third plane 204b and a portion of the first surface area 223. In even further aspects, the first transition width 214 of the first transition zone 212 can be about 0.15 mm or more, about 0.2 mm or more, about 0.3 mm or more, about 0.4 mm or more, about 0.5 mm or more, about 0.6 mm or more, about 0.7 mm or more, about 0.8 mm or more, about 0.9 mm or more, about 2 mm or less, about 1.8 mm or less, about 1.5 mm or less, about 1.2 mm or less, about 1 mm or less, about 0.8 mm or less, about 0.7 mm or less, or about 0.5 mm or less. In even further aspects, the first transition width 214 of the first transition zone 212 can be within a range of about 0.15 mm to about 2 mm, about 0.2 mm to about 2 mm, about 0.3 mm to about 2 mm, about 0.4 mm to about 2 mm, about 0.5 mm to about 2 mm, about 0.5 mm to about 1.8 mm, about 0.6 mm to about 1.8 mm, about 0.6 mm to about 1.5 mm, about 0.7 mm to about 1.5 mm, about 0.7 mm to about 1.2 mm, about 0.8 mm to about 1.2 mm, about 0.8 mm to about 1 mm, about 0.9 mm to about 1 mm, or any range or sub-range therebetween. In even further aspects, the first transition width 214 of the first transition region 212 can be in the range of about 0.5 mm to about 1.8 mm, about 0.5 mm to about 1.5 mm, about 0.5 mm to about 1.2 mm, about 0.5 mm to about 1 mm, about 0.6 mm to about 1 mm, about 0.7 mm to about 1 mm, or any range or sub-range therebetween. In even further aspects, the first transition width 214 of the first transition region 212 can be in the range of about 0.15 mm to about 1.8 mm, about 0.15 mm to about 1.5 mm, about 0.15 mm to about 1.2 mm, about 0.15 mm to about 1 mm, about 0.15 mm to about 0.7 mm, about 0.15 mm to about 0.7 mm, about 0.2 mm to about 0.5 mm, about 0.3 mm to about 0.5 mm, about 0.4 mm to about 0.5 mm, or any range or sub-range therebetween. Reducing the width of the first transition zone and / or the second transition zone can reduce the stress induced by the total chemical strengthening exerted on the central portion by the corresponding transition zone, so that the strain of the first central surface area and / or the second central surface area is less than the critical buckling strain (e.g., the onset of mechanical instability).

[0205] In various aspects, such as Figures 2 to 3 As shown, the first transition zone 212 can include a second transition surface region 245 extending between the second surface region 225 and the second central surface region 243. In another aspect, the width of the second transition surface region 245 can be measured in the direction 106 of the length 105 (see Figure 1 ) between a portion of the second central surface region 243 extending along the fourth plane 206b and a portion of the second surface region 225. In even further aspects, the width of the second transition surface region 245 can be substantially equal to (e.g., equal to) the first transition width 214 of the first transition region 212. In various aspects, as Figure 4 As shown, the portion of the first transition region 212 extending between the second surface region 225 and the second central surface region 243 may be coplanar with one or both surface regions.

[0206] In various aspects, such as Figures 2 to 4 As shown, the thickness of the first transition zone 212 can decrease between the substrate thickness 207 of the first portion 221 and the center thickness 209 of the center portion 281. In other aspects, as shown, the thickness of the first transition zone 212 can decrease smoothly, monotonically, and / or smoothly and monotonically between the substrate thickness 207 of the first portion 221 and the center thickness 209 of the center portion 281. As used herein, if the change in cross-sectional area is smooth (e.g., gradual) rather than an abrupt (e.g., step-like) change in thickness, the thickness decreases smoothly. As used herein, if the thickness decreases for a portion of the time and remains the same, decreases, or a combination thereof for the rest of the time, the thickness decreases monotonically in a direction (i.e., the thickness decreases in that direction but never increases). Providing a smooth shape for the first transition zone and / or the second transition zone can reduce optical distortion. Providing a monotonically decreasing thickness of the first transition zone and / or the second transition zone can reduce the incidence of mechanical instability and / or reduce the visibility of the transition zone.

[0207] In various aspects, such as Figures 2 to 4As shown, the first transition surface area 215 may include a linear inclined surface extending between the first central surface area 213 and the first surface area 223. In various aspects, although not shown, the first transition surface area may include, for example, an upward concave shape, and the local slope of the first transition surface area smoothly transitions to the slope of the first central surface area 213, while the local slope of the first transition surface area is substantially different from the slope of the first surface area 223. In various aspects, although not shown, the first transition surface area may include an S-shaped shape. In various aspects, although not shown, the local slope of the first transition surface area may be greater at the midpoint of the first transition surface area than at the position where the first transition surface area intersects the first central surface area 213 and the position where the first transition surface area intersects the first surface area 223. In various aspects, although not shown, the first transition surface area may include, for example, an upward convex shape, and the local slope of the first transition surface area smoothly transitions to the slope of the first surface area 223, while the local slope of the first transition surface area is substantially different from the slope of the first central surface area 213. In various aspects, the second transition surface region may include one of the shapes or characteristics discussed above for the first transition surface region in this paragraph. Figure 2 As shown, the second transition surface region 245 may include a linearly inclined surface extending between the second central surface region 243 and the second surface region 225 .

[0208] In various aspects, such as Figures 2 to 4 As shown, the thickness of the first transition region 212 can decrease at a constant rate (e.g., linearly) from the substrate thickness 207 to the central thickness 209. In various aspects, although not shown, the thickness of the first transition region can decrease more slowly at the location where the first transition surface region intersects the first central surface region 213 than at the midpoint of the first transition region and / or at the location where the first transition surface region intersects the first surface region 223 (e.g., the first portion 221). In various aspects, although not shown, the thickness of the first transition region can decrease faster at the location where the first transition surface region intersects the first central surface region 213 than at the midpoint of the first transition region and / or at the location where the first transition surface region intersects the first surface region 223. Providing a non-uniform slope of the surface area of ​​the first transition zone and / or the second transition zone can reduce the amount of the corresponding transition zone that includes an intermediate thickness (e.g., includes a chemical strengthening-induced expansion strain), and the chemical strengthening-induced expansion strain is smaller than that of a portion of the corresponding transition zone closer to the first central surface region and / or the second central surface region and / or compared to the first central surface region and / or the second central surface region.

[0209] Throughout this disclosure, the average angle of the transition surface region relative to the central surface region is measured as the angle between the transition surface region and the central surface region. The angle of a position on the corresponding transition surface region relative to the corresponding central surface region is calculated, where the position of the corresponding central surface region is approximated by a plane fitted from measurements at 20 positions evenly spaced above the corresponding central surface region in the direction 106 of length 105. The measured angle is an external angle of the foldable substrate, meaning that it extends from the plane fitted to the corresponding central surface region to the position on the corresponding transition surface region without passing through the material of the foldable substrate except for occasional amounts at the endpoints. The average angle is calculated from 10 positions on the corresponding transition surface region, which are located in a region that includes 80% of the distance that the corresponding central surface region is recessed from the corresponding major surface, where the region is centered at the midpoint between the corresponding central surface region and the corresponding major surface in the direction 202 of thickness (e.g., substrate thickness 207, center thickness 209).

[0210] In various aspects, such as Figures 2 to 4 As shown, the first transition surface area 215 of the first transition zone 212 extends between the first surface area 223 and the first central surface area 213 at a first average angle 282 relative to the first central surface area 213. As described above, the first average angle 282 is an external angle because it does not pass through the material of the foldable substrate 201 except for an occasional amount at the end point. In further aspects, the first average angle 282 can be about 167° or greater, about 170° or greater, about 171° or greater, about 172° or greater, about 179° or less, about 176° or less, about 175° or less, about 174° or less, or about 173° or less. In further aspects, first average angle 282 can be in a range of about 167° to about 179°, about 167° to about 176°, about 170° to about 176°, about 170° to about 175°, about 171° to about 175°, about 171° to about 174°, about 172° to about 174°, about 172° to about 173°, or any range or sub-range therebetween. For example, a first transition surface corresponds to a first average angle of about 176.6°, the first transition surface comprising a first transition width of 500 μm and a height of 30 μm (i.e., the difference between first central surface region 213 and first major surface 203 corresponding to first distance 219).

[0211] In various aspects, such as Figures 2 to 4As shown, the third transition surface area 217 of the second transition zone 218 extends between the third surface area 233 and the first central surface area 213 at a third average angle 286 relative to the first central surface area 213. In further aspects, the third average angle 286 can be within one or more of the ranges discussed above for the first average angle 282. In further aspects, the first average angle 282 can be substantially equal to the third average angle 286.

[0212] In various aspects, such as Figures 2 to 4 As shown, the central portion 281 of the foldable substrate 201 can include a second transition region 218, which includes a third transition surface area 217 extending between the third surface area 233 and the first central surface area 213. In another aspect, as shown, the width of the second transition region 218 (e.g., the second transition width 216) can be measured in the direction 106 of the length 105 (see Figure 1 ) between a portion of the first central surface area 213 extending along the third plane 204b and a portion of the third surface area 233. In even further aspects, the second transition width 216 of the second transition zone 218 can be within one or more of the ranges discussed above for the first transition zone width 214. In yet further aspects, the second transition width 216 of the second transition zone 218 can be substantially equal to (e.g., equal to) the first transition zone width 214.

[0213] In various aspects, such as Figures 2 to 3 As shown, the second transition zone 218 can include a fourth transition surface region 247 extending between the fourth surface region 235 and the second central surface region 243. In another aspect, the width of the fourth transition surface region 247 can be measured in the direction 106 of the length 105 (see Figure 1 ) between a portion of the second central surface region 243 extending along the fourth plane 206b and a portion of the fourth surface region 235. In even further aspects, the width of the fourth transition surface region 247 can be substantially equal to (e.g., equal to) the second transition region width 216. In various aspects, as Figures 2 to 3 As shown, the thickness of the second transition region 218 can decrease between the substrate thickness 207 of the second portion 231 and the center thickness 209 of the center portion 281. In other aspects, as shown, the thickness of the first transition region 212 can decrease smoothly, monotonically, or smoothly and monotonically between the substrate thickness 207 of the second portion 231 and the center thickness 209 of the center portion 281. In various aspects, as shown Figure 4 As shown, the portion of the second transition zone 218 extending between the fourth surface region 235 and the second central surface region 243 may be coplanar with one or both surface regions.

[0214] In various aspects, such as Figures 2 to 4 As shown, the third transition surface region 217 may include a linear inclined surface extending between the first central surface region 213 and the third surface region 233. In various aspects, the third transition surface region 217 and / or the fourth transition surface region 247 may include one of the shapes or characteristics discussed above with reference to the first transition surface region. In various aspects, the fourth transition surface region 247 may include one of the shapes or characteristics discussed above with reference to the first transition surface region in this paragraph. For example, Figures 2 to 4 As shown, the fourth transition surface region 247 may include a linearly inclined surface extending between the second central surface region 243 and the fourth surface region 235. In various aspects, as Figures 2 to 4 As shown, the thickness of the second transition region 218 can decrease at a constant rate from the substrate thickness 207 to the central thickness 209 (e.g., linearly). In various aspects, although not shown, the thickness of the second transition region can decrease more slowly at the location where the third transition surface region intersects the first central surface region 213 than at the midpoint of the second transition region and / or than at the location where the third transition surface region intersects the third surface region 233 (e.g., the first portion 221). In various aspects, although not shown, the thickness of the first transition region can decrease faster at the location where the third transition surface region intersects the first central surface region 213 than at the midpoint of the second transition region and / or than at the location where the third transition surface region intersects the third surface region 233.

[0215] In various aspects, such as Figures 2 to 3 As shown, the second transition surface area 245 of the first transition zone 212 extends between the second surface area 225 and the second central surface area 243 at a second average angle 284 relative to the second central surface area 243. In other aspects, the second average angle 284 can be about 167° or more, about 170° or more, about 171° or more, about 172° or more, about 179° or less, about 176° or less, about 175° or less, about 174° or less, or about 173° or less. In other aspects, the second average angle 284 can be in the range of about 167° to about 179°, about 167° to about 176°, about 170° to about 176°, about 170° to about 175°, about 171° to about 175°, about 171° to about 174°, about 172° to about 174°, about 172° to about 173°, or any range or sub-range therebetween. In further aspects, the first average angle 282 can be substantially equal to the second average angle 284. Providing an average angle within one of the above ranges can provide reduced visibility of the transition zone.

[0216] In various aspects, such as Figures 2 to 324. As shown, the fourth transition surface area 247 of the second transition zone 218 extends between the fourth surface area 235 and the second central surface area 243 at a fourth average angle 288 relative to the second central surface area 243. In further aspects, the fourth average angle 288 can be within one or more of the ranges discussed above for the second average angle 284. In further aspects, the second average angle 284 can be substantially equal to the fourth average angle 288. In further aspects, the first average angle 282 and / or the third average angle 286 can be substantially equal to the fourth average angle 288.

[0217] As used herein, if a first layer and / or component is described as being "disposed on" a second layer and / or component, other layers may or may not be present between the first layer and / or component and the second layer and / or component. In addition, as used herein, "disposed on..." does not refer to a relative position relative to gravity. For example, when a first layer and / or component is positioned below, above, or to one side of a second layer and / or component, the first layer and / or component may be considered to be "disposed on" a second layer and / or component. As used herein, a first layer and / or component is described as being "bonded to" a second layer and / or component, meaning that the layers and / or components are bonded to each other by direct contact and / or bonding between the two layers and / or components or by an adhesive layer. As used herein, a first layer and / or component described as being "in contact with" or "in contact with" a second layer and / or component refers to direct contact and includes situations where the layers and / or components are bonded to each other.

[0218] like Figure 2 and Figure 4 As shown, the foldable device 101 may include an adhesive layer 261. As shown, the adhesive layer 261 may include a first contact surface 263 and a second contact surface 265 that may be opposite to the first contact surface 263. In various aspects, as shown in FIG. Figure 2 and Figure 4 As shown, the second contact surface 265 of the adhesive layer 261 may include a planar surface. Figure 2 and Figure 4As shown, the first contact surface 263 of the adhesive layer 261 may include a planar surface. The adhesive thickness 267 of the adhesive layer 261 may be defined as the minimum distance between the first contact surface 263 and the second contact surface 265. In various aspects, 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, about 20 μm or less. In various aspects, the adhesive thickness 267 of the adhesive layer 261 may be about 1 μm to about 100 μm, about 5 μm to about 100 μm, about 5 μm to about 60 μm, about 5 μm to about 30 μm, about 10 μm to about 30 μm, about 10 μm to about 20 μm, or any range or sub-range therebetween.

[0219] In various aspects, such as Figure 2 and Figure 4 As shown, the second contact surface 265 of the adhesive layer 261 can face and / or contact the first major surface 273 of the release liner 271 (described below). Figure 2 As shown, the first contact surface 263 of the adhesive layer 261 can face and / or contact the second surface area 225 of the first portion 221. In various aspects, as Figure 2 As shown, the first contact surface 263 of the adhesive layer 261 can face and / or contact the fourth surface area 235 of the second portion 231. In various aspects, as Figure 2 As shown, the first contact surface 263 of the adhesive layer 261 can face the second central surface area 243 of the central portion 281. In various aspects, as Figure 4 As shown, the first contact surface 263 of the adhesive layer 261 can face and / or contact the first surface area 223 of the first portion 221. In various aspects, as Figure 4 As shown, the first contact surface 263 of the adhesive layer 261 can face and / or contact the third surface area 233 of the second portion 231. In various aspects, as Figure 4 As shown, the first contact surface 263 of the adhesive layer 261 can face the first central surface area 213 of the central portion 281. In various aspects, as Figure 2 As shown, the first contact surface 263 of the adhesive layer 261 may face the second central surface area 243 of the central portion 281. In another aspect, although not shown, the first contact surface 263 of the adhesive layer 261 may be indicated by, for example, filling Figure 2The area occupied by the second polymer base portion 299 in the center (e.g., the second recessed portion 241) contacts the second central surface area 243 of the center portion 281. In various aspects, although not shown, the second recessed portion may not be completely filled, for example, to leave room for electronic devices and / or mechanical devices. In various aspects, although not shown, Figure 4 The foldable substrate 201 may be assembled with an adhesive layer 261 contacting the second major surface 205 instead of the first major surface 203, and the polymer base portion 299 or the coating 251 replacing the polymer base portion 299 may be at least partially positioned in the first recess 211.

[0220] In various aspects, the adhesive layer 261 may include one or more of polyolefins, polyamides, halogenide-containing polymers (e.g., polyvinyl chloride or fluoropolymers), elastomers, polyurethanes, phenolic resins, polyparaxylene, polyethylene terephthalate (PET), and polyetheretherketone (PEEK). Exemplary aspects of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), and polypropylene (PP). Exemplary aspects of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers, and ethylene tetrafluoroethylene (ETFE) polymers. Exemplary aspects of elastomers include rubbers (e.g., polybutadiene, polyisoprene, chloroprene rubber, butyl rubber, nitrile rubber) and block copolymers (e.g., styrene-butadiene, high impact polystyrene, poly(dichlorophosphazene). In further aspects, the adhesive layer 261 may include an optically clear adhesive. In even further aspects, the optically clear adhesive may include one or more optically transparent polymers: acrylic (e.g., polymethyl methacrylate (PMMA)), epoxy resin, silicone and / or polyurethane. Examples of epoxy resins include bisphenol-based epoxy resins, novolac-based epoxy resins, alicyclic-based epoxy resins, and glycidylamine-based epoxy resins. In even further aspects, the optically clear adhesive may include, but is not limited to, acrylic adhesives such as 3M 8212 adhesive, or an optically clear liquid adhesive, such as LOCTITE optically clear liquid adhesive. Exemplary aspects of optically clear adhesives include clear acrylics, epoxies, silicones, and polyurethanes. For example, the optically clear liquid adhesive may include one or more of LOCTITE AD 8650, LOCTITE AA3922, LOCTITE EAE-05MR, LOCTITE UKU-09LV, all of which are available from Henkel.

[0221] Throughout the present disclosure, the tensile strength, ultimate elongation (e.g., strain at failure), and yield point of polymeric materials (e.g., adhesives, polymer-based portions) are determined using ASTM D638 using a tensile testing machine (e.g., Instron 3400 or Instron 6800) at 23° C. and 50% relative humidity using a Type I dog-bone specimen. In various aspects, the adhesive layer 261 may include an elastic modulus of about 0.001 megapascals (MPa) or greater, about 0.01 MPa or greater, about 0.1 MPa or greater, about 1 MPa or less, about 0.5 MPa or less, about 0.1 MPa or less, about 0.05 MPa or less. In various aspects, the adhesive layer 261 may include an elastic modulus within the range of about 0.001 MPa to about 1 MPa, about 0.01 MPa to about 1 MPa, about 0.01 MPa to about 0.5 MPa, about 0.05 MPa to about 0.5 MPa, about 0.1 MPa to about 0.5 MPa, about 0.001 MPa to about 0.5 MPa, about 0.001 MPa to about 0.01 MPa, or any range or sub-range therebetween. In various aspects, the adhesive layer may be included in one or more of the ranges discussed below for the elastic modulus of the polymer base portion 289 and / or 299.

[0222] like Figure 2 and Figure 4 As shown, the polymer base portion 289 and / or 299 of the foldable device 101 can be positioned between the first portion 221 and the second portion 231. In various aspects, as shown, the polymer base portion can include a first polymer base portion 289 at least partially positioned in the first recess 211 and / or filling the first recess. In various aspects, as shown, Figure 2 As shown, the polymer-based portion may include a second polymer-based portion 299 at least partially positioned in the second recess 241 and / or filling the second recess. Figure 4 As shown, the polymer base portion may include a second polymer base portion 299 at least partially positioned in and / or filling the first recess 211. In various aspects, although not shown, the second recess may not be completely filled, for example to leave room for electronic and / or mechanical devices.

[0223] like Figure 2 As shown, the first polymer-based portion 289 can include a fourth contact surface 285 opposite the third contact surface 283. In various aspects, as shown, the third contact surface 283 can include, for example, a planar surface that is substantially coplanar with the first surface region 223 and the third surface region 233 (e.g., extending along a shared plane, the first plane 204a). In various aspects, as shown, Figure 2As shown, the fourth major surface 255 of the coating 251 can face and / or contact the third contact surface 283 of the polymer base portion 289. In various aspects, the fourth contact surface 285 can include, for example, a planar surface that is substantially coplanar with the first central surface region 213 (e.g., extending along a shared plane, the third plane 204b). In further aspects, the fourth contact surface 285 can contact the first central surface region 213, the first transition surface region 215, and / or the third transition surface region 217.

[0224] like Figure 2 and Figure 4 As shown, the second polymer-based portion 299 may include a fourth contact surface 295 opposite to the third contact surface 293. In another aspect, as Figure 2 As shown, the third contact surface 293 can contact the second central surface area 243, the second transition surface area 245 and / or the fourth transition surface area 247. In various aspects, as Figure 2 As shown, the third contact surface 293 may include, for example, a planar surface that is substantially coplanar with the second central surface area 243 (e.g., extending along a shared plane with the fourth plane 206b). Figure 2 As shown, the fourth contact surface 295 can include, for example, a planar surface that is substantially coplanar with the second surface region 225 and the fourth surface region 235 (eg, extending along a shared plane with the second plane 206a).

[0225] In various aspects, such as Figure 4 As shown, the third contact surface 293 can contact the first central surface area 213, the first transition surface area 215 and / or the third transition surface area 217. In various aspects, as Figure 4 As shown, the third contact surface 293 may include, for example, a planar surface that is substantially coplanar with the first central surface area 213 (e.g., extending along a shared plane with the third plane 204b). In various aspects, as shown, the third contact surface 293 may include, for example, a planar surface that is substantially coplanar with the first central surface area 213 (e.g., extending along a shared plane with the third plane 204b). In various aspects, as shown, the third contact surface 293 may include, for example, a planar surface that is substantially coplanar with the first central surface area 213 (e.g., extending along a shared plane with the third plane 204b). Figure 4 As shown, the fourth contact surface 295 can be coplanar with the first surface area 223 and the third surface area 233 (e.g., extending along a shared plane with the first plane 204a). Figure 2 and Figure 4 As shown, the first contact surface 263 of the adhesive layer 261 may face and / or contact the fourth contact surface 295 of the polymer base portion 299 .

[0226] In various aspects, the polymer base portion 289 and / or 299 comprises a polymer (e.g., an optically transparent polymer). In further aspects, the polymer base portion 289 and / or 299 may comprise one or more of the following optically transparent: acrylic (e.g., polymethyl methacrylate (PMMA)), epoxy resin, silicone and / or polyurethane. Examples of epoxy resins include bisphenol-based epoxy resins, novolac-based epoxy resins, alicyclic-based epoxy resins, and glycidylamine-based epoxy resins. In further aspects, the polymer base portion 289 and / or 299 comprises one or more of polyolefins, polyamides, halide-containing polymers (e.g., polyvinyl chloride or fluoropolymers), elastomers, polyurethanes, phenolic resins, polyparaxylene, polyethylene terephthalate (PET), and polyetheretherketone (PEEK). Exemplary aspects of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), and polypropylene (PP). Exemplary aspects of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers, and ethylene tetrafluoroethylene (ETFE) polymers. Exemplary aspects of elastomers include rubbers (e.g., polybutadiene, polyisoprene, chloroprene, butyl rubber, nitrile rubber) and block copolymers (e.g., styrene-butadiene, high impact polystyrene, poly(dichlorophosphazene), such as polystyrene, polydichlorophosphazene, and poly(5-ethylene-2-norbornene). In various aspects, the polymer-based portion may include a sol-gel material. Exemplary aspects of polyurethanes include thermosetting polyurethanes such as Dispurez 102 from Incorez and thermoplastic polyurethanes such as KrystalFlexPE505 from Huntsman. In even further aspects, the second portion may include ethylene acid copolymers. Exemplary aspects of ethylene acid copolymers include SURLYN (e.g., Surlyn PC-2000, Surlyn 8940, Surlyn 8150) from Dow. Additional exemplary aspects of the second portion include Eleglass from Axalta. w802-GL044, which has 1 wt% to 2 wt% crosslinker. In various aspects, the polymer base portion 289 and / or 299 may further include nanoparticles, such as carbon black, carbon nanotubes, silica nanoparticles, or nanoparticles comprising a polymer. In various aspects, the polymer base portion may further include fibers to form a polymer-fiber composite.

[0227] In various aspects, the polymer base portion 289 and / or 299 may include a coefficient of thermal expansion (CTE). As used herein, the coefficient of thermal expansion is measured between -20°C and 40°C using a picoscale Michaelis interferometer according to ASTM E289-17. In some aspects, the polymer base portion 289 and / or 299 may include particles of one or more of copper oxide, β-quartz, tungstate, vanadate, pyrophosphate, and / or nickel titanium alloy. In various aspects, the polymer base portion 289 and / or 299 may include about -20x10 -7 1 / ℃ or greater, about -10x10 -7 1 / ℃ or greater, about -5x10 -7 1 / ℃ or greater, about -2x10 -7 1 / ℃ or greater, about 10x10 -7 1 / ℃ or less, about 5x10 -7 1 / ℃ or less, about 2x10 -7 1 / ℃ or less, about 1x10 -7 1 / °C or less, or 0 1 / °C or less. In various aspects, the polymer base portion 289 and / or 299 may include a CTE of about -20x10 -7 1 / ℃ to about 10x10 -7 1 / ℃, about -20x10 -7 1 / ℃ to about 5x10 -7 1 / ℃, about -10x10 -7 1 / ℃ to about -5x10 -7 1 / ℃, about -10x10 -7 1 / ℃ to about 2x10 -7 1 / ℃, about -10x10 -7 1 / ℃ to 0 1 / ℃, about -5x10 -7 1 / ℃ to 0 1 / ℃, about -2x10 -7 A CTE in the range of about 1 / °C to 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, warping caused by volume changes during curing of the polymer-based portion can be mitigated.

[0228] In various aspects, the polymer-based portions 289 and / or 299 may include an elastic modulus of about 0.001 megapascals (MPa) or greater, about 0.001 MPa or greater, about 1 MPa or greater, about 10 MPa or greater, about 20 MPa or greater, about 100 MPa or greater, about 200 MPa or greater, about 1,000 MPa or greater, 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. In various aspects, the polymer base portion 289 and / or 299 may include an elastic modulus in the range of about 0.001 MPa to about 5,000 MPa, about 0.01 MPa to about 3,000 MPa, about 0.01 MPa to about 1,000 MPa, about 0.01 MPa to about 500 MPa, about 0.01 MPa to about 200 MPa, about 1 MPa to about 200 MPa, about 10 MPa to about 200 MPa, about 100 MPa to about 200 MPa, or any range or sub-range therebetween. In various aspects, the polymer base portion 289 and / or 299 may include an elastic modulus in the range of about 1 MPa to about 5,000 MPa, about 10 MPa to about 5,000 MPa, about 10 MPa to about 1,000 MPa, about 20 MPa to about 1,000 MPa, about 20 MPa to about 200 MPa, or any range or sub-range therebetween. In various aspects, the elastic modulus of the polymer base portion 289 and / or 299 may be in the range of about 1 GPa to about 20 GPa, about 1 GPa to about 18 GPa, about 1 GPa to about 10 GPa, about 1 GPa to about 5 GPa, about 1 GPa to about 3 GPa, or any range or sub-range therebetween. By providing the polymer base portion 289 and / or 299 with an elastic modulus in the range of about 0.001 MPa to about 5,000 MPa (e.g., in the range of about 10 MPa to about 3 GPa), the foldable device may be facilitated to fold without failure. In various aspects, the elastic modulus included in the adhesive layer 261 is greater than the elastic modulus of the polymer base portion 289 and / or 299, and the arrangement provides improved anti-puncture performance. In various aspects, the elastic modulus of the polymer base portion 289 and / or 299 may be less than the elastic modulus of the foldable substrate 201. In various aspects, the adhesive layer 261 may include an elastic modulus in the range listed above in this paragraph. In further aspects, the adhesive layer 261 can include an elastic modulus that is substantially the same as the elastic modulus of the polymer base portion 289 and / or 299. In further aspects, the elastic modulus of the adhesive layer 261 can be in a range of about 1 GPa to about 20 GPa, about 1 GPa to about 18 GPa, about 1 GPa to about 10 GPa, about 1 GPa to about 5 GPa, about 1 GPa to about 3 GPa, or any range or sub-range therebetween.In various aspects, the elastic modulus of the polymer base portions 289 and / or 299 can be less than the elastic modulus of the foldable substrate 201 .

[0229] In various aspects, such as Figure 2As shown, the coating 251 may be disposed on the first major surface 203 of the foldable substrate 201. In further aspects, the coating 251 may be disposed on the first portion 221, the second portion 231, and the central portion 281. In various aspects, the coating 251 may include a third major surface 253 and a fourth major surface 255 opposite to the third major surface 253. In further aspects, the coating 251 (e.g., the fourth major surface 255) may contact the foldable substrate 201 (e.g., the first major surface 203). In further aspects, at least a portion of the coating 251 may be positioned in the first recessed portion 211. In even further aspects, the coating 251 may fill the first recessed portion 211. In further aspects, the coating 251 may include a coating thickness 257 defined between the third major surface 253 and the fourth major surface 255. In further aspects, the coating thickness 257 can 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 greater, about 25 μm or greater, about 40 μm or greater, about 50 μm or greater, about 60 μm or greater, about 70 μm or greater, about 80 μm or greater, about 90 μm or greater, 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, about 15 μm or less, about 10 μm or less. In various aspects, the coating thickness 257 may be in the range of about 0.1 μm to about 200 μm, about 1 μm to about 200 μm, about 10 μm to about 200 μm, about 50 μm to about 200 μm, about 0.1 μm to about 100 μm, about 1 μm to about 100 μm, about 10 μm to about 100 μm, about 20 μm to about 100 μm, about 30 μm to about 100 μm, about 40 μm to about 100 μm, about 50 μm to about 100 μm, about 60 μm to about 100 μm, about 70 μm to about 100 μm, about 80 μm to about 100 μm, about 90 μm to about 100 μm, about 0.1 μm to about 50 μm, about 1 μm to about 50 μm, about 10 μm to about 50 μm, or any range or sub-range therebetween.In further aspects, the coating thickness 257 can be between about 0.1 μm and about 50 μm, about 0.1 μm and about 30 μm, about 0.1 μm and about 25 μm, about 0.1 μm and about 20 μm, about 0.1 μm and about 15 μm, about 0.1 μm and about 10 μm, about 1 μm and about 30 μm, about 1 μm and about 25 μm, about 1 μm and about 20 μm, about 1 μm and about 15 μm, about 1 μm and about 10 μm, about 5 μm and about 30 μm, about 5 μm and about 5 μm. m to about 25 μm, about 5 μm to about 20 μm, about 5 μm to about 15 μm, about 5 μm to about 10 μm, about 10 μm to about 30 μm, about 10 μm to about 25 μm, about 10 μm to about 20 μm, about 10 μm to about 15 μm, about 15 μm to about 30 μm, about 15 μm to about 25 μm, about 15 μm to about 20 μm, about 20 μm to about 30 μm, about 20 μm to about 25 μm, or any range or sub-range therebetween.

[0230] In various aspects, coating 251 may include a polymer hard coat. In other aspects, the polymer hard coat may include one or more of ethylene-acid copolymers, polyurethane-based polymers, acrylate resins, and mercaptoester resins. Exemplary aspects of ethylene-acid copolymers include ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and ethylene-acrylic acid-methacrylic acid terpolymers (e.g., Nucrel manufactured by DuPont), ionic polymers of ethylene acid copolymers (e.g., Surlyn manufactured by DuPont), and ethylene-acrylic acid copolymer amine dispersions (e.g., Aquacer manufactured by BYK). Exemplary aspects of polyurethane-based polymers include water-based modified polyurethane dispersions (e.g., ). Exemplary aspects of UV-curable acrylate resins include acrylate resins (e.g., resins), cyanoacrylate adhesives (e.g., manufactured by Krayden UV620) and UV free radical acrylic resins (e.g., Ultrabond windshield repair resins, such as Ultrabond (45CPS)). Exemplary aspects of mercapto ester resins include mercapto ester triallyl isocyanurate (e.g., Norland optical adhesive NOA61). In other aspects, the polymer hard coating may include ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, which can be ionically polymerized through neutralization of carboxylic acid residues with typical alkali metal ions (e.g., sodium and potassium and also zinc) to form ionomer resins. Such ethylene-acrylic acid and ethylene-methacrylic acid ionomers can be dispersed in water and applied to a substrate to form an ionomer coating. Alternatively, such acid copolymers can be neutralized with ammonia, which after coating and drying, releases the ammonia to reform the acid copolymer into a coating. By providing a coating comprising a polymer coating, the foldable device can include low energy fracture.

[0231] In various aspects, coating can include polymer hard coating, and this polymer hard coating includes optically transparent polymer hard coating. Suitable materials for optically transparent polymer hard coating include but are not limited to cured acrylate resin materials, inorganic-organic hybrid polymer materials, aliphatic or aromatic hexafunctional urethane acrylates, siloxane-based hybrid materials and nanocomposite materials such as epoxy resins and polyurethane materials with nano silicates. In various aspects, optically transparent polymer hard coating can be basically composed of one or more of these materials. In various aspects, optically transparent polymer hard coating can be composed of one or more of these materials. As used herein, "inorganic-organic hybrid polymer material" means a polymer material comprising a monomer with inorganic and organic components. Inorganic-organic hybrid polymers are obtained by polymerization reaction between monomers with inorganic groups and organic groups. Inorganic-organic hybrid polymers are not nanocomposite materials comprising separate inorganic and organic components or phases (e.g., inorganic particles dispersed in an organic matrix). More specifically, suitable materials for optically transparent polymer (OTP) hard coatings include, but are not limited to, polyimide, polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), organic polymer materials, inorganic-organic hybrid polymer materials, and aliphatic or aromatic hexafunctional urethane acrylates. In various aspects, the OTP hard coating may be substantially composed of organic polymer materials, inorganic-organic hybrid polymer materials, or aliphatic or aromatic hexafunctional urethane acrylates. In various aspects, the OTP hard coating may be composed of polyimide, organic polymer materials, inorganic-organic hybrid polymer materials, or aliphatic or aromatic hexafunctional urethane acrylates. In various aspects, the OTP hard coating may include nanocomposite materials. In various aspects, the OTP hard coating may include at least one of nanosilicate epoxy resin materials and nanosilicate polyurethane materials. Suitable compositions for such OTP hard coatings are described in U.S. Patent Publication No. 2015 / 0110990, which is hereby incorporated by reference in its entirety. As used herein, "organic polymer material" means a polymer material comprising monomers having only organic components. In various aspects, the OTP hard coating may include an organic polymer material manufactured by Gunze Limited and having a hardness of 9H, such as Gunze's "Highly Durable Transparent Film". As used herein, "inorganic-organic hybrid polymer material" means a polymer material comprising monomers having inorganic and organic components. Inorganic-organic hybrid polymers are obtained by polymerization reactions between monomers having inorganic groups and organic groups. Inorganic-organic hybrid polymers are not nanocomposites comprising separate inorganic and organic components or phases (e.g., inorganic particles dispersed in an organic matrix). In various aspects, inorganic-organic hybrid polymer materials may include polymerized monomers comprising inorganic silicon-based groups, such as silsesquioxane polymers.The silsesquioxane polymer may be, for example, an alkyl-silsesquioxane, an aryl-silsesquioxane, or an arylalkyl-silsesquioxane having the following chemical structure: (RSiO. 1.5 ) n , wherein R is an organic group, such as but not limited to methyl or phenyl. In various aspects, the OTP hard coating may include a silsesquioxane polymer combined with an organic matrix, such as SILPLUS manufactured by Nippon Steel Chemical Co., Ltd. In various aspects, the OTP hard coating may include 90% to 95% by weight of an aromatic hexafunctional urethane acrylate (e.g., PU662NT (aromatic hexafunctional urethane acrylate) manufactured by Miwon Specialty Chemical) and 10% to 5% by weight of a photoinitiator (e.g., Darocur 1173 manufactured by Ciba Specialty Chemicals Corporation), and a hardness of 8H or greater. In various aspects, the OTP hard coating composed of an aliphatic or aromatic hexafunctional urethane acrylate can be formed as a separate layer by spin coating the layer on a polyethylene terephthalate (PET) substrate, curing the urethane acrylate, and removing the urethane acrylate layer from the PET substrate. In various aspects, the OTP hard coating can be a layer of an aliphatic or aromatic hexafunctional urethane acrylate material having a thickness within one or more of the thickness ranges discussed above for coating thickness 257 .

[0232] In various aspects, coating 251 (if provided) may also include one or more of an easy-to-clean coating, a low-friction coating, an oil-averse coating, a diamond-like coating, a scratch-resistant coating, or a wear-resistant coating. The scratch-resistant coating may include a nitride oxide having a thickness of about 500 microns or more, such as aluminum oxynitride or silicon oxynitride. In this aspect, the wear-resistant layer may include the same material as the scratch-resistant layer. In various aspects, the low-friction coating may include a highly fluorinated silane coupling agent, such as an alkylfluorosilane with methoxy groups suspended from silicon atoms. In this aspect, the easy-to-clean coating may include the same material as the low-friction coating. In other aspects, the easy-to-clean coating may include a protonatable group, such as an amine, such as an alkylaminosilane with hydroxymethyl groups suspended from silicon atoms. In this aspect, the oil-averse coating may include the same material as the easy-to-clean coating. In various aspects, the diamond-like coating includes carbon and may be produced by applying a high voltage potential in the presence of a hydrocarbon plasma.

[0233] Providing a first recess opposite to a second recess can reduce bending-induced strain of a material positioned in the first recess and / or the second recess compared to a single recess having a surface recessed by the sum of a first distance and a second distance. Providing reduced bending-induced strain of a material positioned in the first recess and / or the second recess can enable the use of a wider range of materials due to the reduced strain requirements on the material. For example, a harder and / or more rigid material (e.g., coating 251, first polymer-based portion 289) can be positioned in the first recess, which can improve the impact resistance, puncture resistance, wear resistance, and / or scratch resistance of the foldable device. In addition, controlling the properties of the first material (e.g., coating 251, first polymer-based portion 289) positioned in the first recess and the second material positioned in the second recess can control the position of the neutral axis of the foldable device and / or the foldable substrate, which can reduce (e.g., mitigate, eliminate) the incidence of mechanical instability, device fatigue, and / or device failure. Providing a first recessed portion opposite to the second recessed portion can reduce the strain (e.g., from 0% to 50%) encountered by the polymer base portion or other materials (e.g., adhesive layer) in the recessed portion. Therefore, the requirements for the yield strain of the polymer base portion can be relaxed. In various aspects, the yield strain of the polymer base portion and / or the adhesive layer can be about 3% or greater, about 4% or greater, about 5% or greater, about 6% or greater, about 7% or greater, 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, about 8% or less. In various aspects, the yield strain of the polymer base portion and / or the adhesive layer may be in the range of about 1% to about 500%, about 1% to about 100%, about 2% to about 100%, about 2% to about 50%, about 3% to about 50%, about 3% to about 20%, about 4% to about 20%, about 4% to about 15%, about 5% to about 15%, about 5% to about 10%, about 5% to about 9%, about 6% to about 9%, about 6% to about 8%, about 7% to about 8%, or any range or sub-range therebetween.

[0234] In various aspects, such as Figure 2 and Figure 4As shown, the foldable device 101 may include a release liner 271, but other substrates (e.g., glass-based substrates and / or ceramic-based substrates discussed throughout this application) may be used instead of the illustrated release liner 271 in other aspects. In other aspects, as shown, the release liner 271 or another substrate may be disposed on the adhesive layer 261. In even further aspects, 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 to 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 various aspects, as shown, the first major surface 273 of the release liner 271 or another substrate may include a planar surface. In various aspects, as shown, the second major surface 275 of the release liner 271 or another substrate may include a planar surface. The substrate including the release liner 271 may include paper and / or a polymer. Exemplary aspects of paper include kraft paper, machine glossy paper, polymer coated paper (e.g., polymer coated paper, glassine paper, siliconized paper), or clay coated paper. Exemplary aspects of polymers include polyesters (e.g., polyethylene terephthalate (PET)) and polyolefins (e.g., low density polyethylene (LDPE), high density polyethylene (HDPE), polypropylene (PP)).

[0235] Aspects of the present disclosure may include consumer electronic products. The consumer electronic product may include a front surface, a rear surface, and a side surface. The consumer electronic product may further include an electronic component at least partially within the housing. The electronic component may include a controller, a memory, and a display. The display may be located at or adjacent to the front surface of the housing. The display may include a liquid crystal display (LCD), an electrophoretic display (EPD), an organic light-emitting diode (OLED) display, or a plasma display panel (PDP). The consumer electronic product may include a cover substrate disposed above the display. In various aspects, at least one of a portion of the housing or the cover substrate includes a foldable device discussed throughout the present disclosure. The consumer electronic product may include a portable electronic device, such as a smartphone, a tablet computer, a wearable device, or a notebook computer.

[0236] The foldable devices disclosed herein may be incorporated into another article, such as an article with a display (or display article) (e.g., consumer electronics, including mobile phones, tablet computers, computers, navigation systems, wearable devices (e.g., watches), and the like), an architectural article, a transportation article (e.g., a car, a train, an airplane, a ship, etc.), an appliance article, or any article that may benefit from a certain degree of transparency, scratch resistance, abrasion resistance, or a combination thereof. An exemplary article incorporating any of the foldable devices disclosed herein is shown in Figure 10 to Figure 11 . Specifically, Figure 10 to Figure 11 1000 is shown, which includes a housing 1002 having a front surface 1004, a rear surface 1006, and a side surface 1008. Although not shown, the consumer electronic device may include electronic components at least partially located inside the housing or completely located inside it. For example, the electronic components include at least a controller, a memory, and a display. Figure 10 to Figure 11 As shown, display 1010 can be located at or adjacent to the front surface of housing 1002. The consumer electronic device can include a cover substrate 1012 located at or on the front surface of housing 1002 such that it is located above display 1010. In various aspects, at least one of cover substrate 1012 or a portion of housing 1002 can include any of the foldable devices disclosed herein, such as a foldable substrate.

[0237] In various aspects, the foldable substrate 201 including a glass-based substrate and / or a ceramic-based substrate, and a first portion 221, a second portion 231, and / or a central portion 281 may include one or more compressive stress regions. In various aspects, the compressive stress region may be generated by chemical strengthening. Chemical strengthening may include an ion exchange process in which ions in the surface layer are replaced or exchanged with larger ions having the same valence or oxidation state. The method of chemical strengthening will be discussed later. Without being bound by theory, the chemically strengthened first portion 221, the second portion 231, and / or the central portion 281 may achieve good impact resistance and / or puncture resistance (e.g., resistance to failure at a pen drop height of about 15 centimeters (cm) or greater, about 20 cm or greater, about 50 cm or greater). Without being bound by theory, the chemically strengthened first portion 221, the second portion 231, and / or the central portion 281 may achieve a small (e.g., less than about 10 mm or less) bending radius because the compressive stress from chemical strengthening may offset the tensile strain induced by bending on the outermost surface of the substrate. The compressive stress zone may extend into a portion of the first portion and / or the second portion to a depth called the depth of compression (DOC). As used herein, the depth of compression means the depth at which the stress in the chemically strengthened substrate and / or portion described herein changes from compressive stress to tensile stress. The depth of compression can be measured by a surface stress meter or a scattered light polariscope (SCALP, wherein the values ​​reported herein are made using a SCALP-5 made by Glasstress, Estonia), depending on the ion exchange treatment being measured and the thickness of the article. When stress in the substrate and / or portion is generated by exchanging potassium ions into the substrate, the depth of compression is measured using a surface stress meter such as FSM-6000 (Orihara Industrial Co., Ltd. (Japan)). Unless otherwise stated, compressive stress (including surface CS) is measured by a surface stress meter (surface stress meter; FSM) using a commercially available instrument such as FSM-6000 manufactured by Orihara. Surface stress measurements rely on accurate measurement of the stress optical coefficient (SOC), which is related to the birefringence of the glass. Unless otherwise specified, SOC is measured according to Procedure C (Glass Disc 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 their entirety.Where stress is generated by exchanging sodium ions into the substrate, and the article being measured is thicker than about 400 μm, SCALP is used to measure the depth of compression and central tension (CT). Where stress is generated in the substrate and / or portion by exchanging both potassium and sodium ions into the substrate and / or portion, and the article being measured is thicker than about 400 μm, the depth of compression and CT are measured by SCALP. Without being bound by theory, the depth of exchange of sodium may indicate the depth of compression, while the depth of exchange of potassium ions may indicate a change in the magnitude of the compressive stress (but not a change in stress from compression to tension). A refracted near-field (RNF; the RNF method is described in U.S. Pat. No. 8,854,623, entitled "Systems and methods forming a profile characteristic of a glass sample," which is incorporated herein by reference in its entirety) method may also be used to derive a graphical representation of the stress profile. When the RNF method is used to derive a graphical representation of the stress profile, the maximum central tension value provided by SCALP is used in the RNF method. The graphical representation of the stress contour derived by the RNF is force balanced and calibrated to 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 the substrate and / or part (e.g., sodium, potassium). Throughout this disclosure, the DOL is measured according to ASTM C-1422. Without being bound by theory, the DOL is generally greater than or equal to the corresponding DOC. Throughout this disclosure, when the maximum central tension cannot be measured directly by SCALP (such as when the article being measured is thinner than about 400 μm), the maximum central tension can be approximated by the product of the maximum compressive stress and the compression depth divided by the difference between the substrate thickness and twice the compression depth, where the compressive stress and the compression depth are measured by the FSM.

[0238] In various aspects, the first portion 221 including the glass-based and / or ceramic-based portion may include a first compressive stress region at the first surface region 223, and the first compressive stress region may extend from the first surface region 223 to a first compression depth. In various aspects, the first portion 221 including the first glass-based and / or ceramic-based portion may include a second compressive stress region at the second surface region 225, and the second compressive stress region may extend from the second surface region 225 to a second compression depth. In various aspects, the first compression depth and / or the second compression depth as a percentage of the substrate thickness 207 may be about 5% or more, about 10% or more, about 12% or more, about 15% or more, about 30% or less, about 25% or less, about 22% or less, about 20% or less, about 17% or less, or about 15% or less. In various aspects, the first compression depth and / or the second compression depth as a percentage of the substrate thickness 207 may be in a range of about 5% to about 30%, about 10% to about 25%, about 10% to about 22%, about 12% to about 20%, about 12% to about 17%, about 15% to about 17%, or any range or sub-range therebetween. In various aspects, the first compression depth and / or the second compression depth may be about 1 μm or more, about 10 μm or more, about 15 μm or more, about 20 μm or more, about 25 μm or more, about 30 μm or more, about 200 μm or less, about 150 μm or less, about 100 μm or less, about 60 μm or less, about 45 μm or less, about 30 μm or less, or about 20 μm or less. In various aspects, the first compression depth and / or the second compression depth may be in the range of about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 10 μm to about 100 μm, about 15 μm to about 600 μm, about 20 μm to about 45 μm, about 20 μm to about 30 μm, or any range or sub-range therebetween. By providing a first portion comprising a first glass-based and / or ceramic-based portion, the first portion comprising a first compression depth and / or a second compression depth in the range of about 1% to about 30% of the first thickness, good impact resistance and / or puncture resistance may be achieved.

[0239] In various aspects, the first compressive stress region can include a maximum first compressive stress. In various aspects, the second compressive stress region can include a maximum second compressive stress. In further aspects, the maximum first compressive stress and / or the maximum second compressive stress can be about 100 megapascals (MPa) or greater, about 300 MPa or greater, 400 MPa or greater, about 500 MPa or greater, about 600 MPa or greater, about 700 MPa or greater, about 1,500 or less, about 1,200 MPa or less, about 1,000 MPa or less, or about 800 MPa or less. In further aspects, the maximum first compressive stress and / or the maximum second compressive stress can be in the range of about 100 MPa to about 1,500 MPa, about 100 MPa to about 1,200 MPa, about 300 MPa to about 1,200 MPa, about 300 MPa to about 1,000 MPa, about 400 MPa to about 1,000 MPa, about 500 MPa to about 1,000 MPa, about 600 MPa to about 900 MPa, about 700 MPa to about 800 MPa, or any range or sub-range therebetween. By providing a maximum first compressive stress and / or a maximum second compressive stress in the range of about 100 MPa to about 1,500 MPa, good impact resistance and / or puncture resistance can be achieved.

[0240] In various aspects, the first portion 221 may include a first depth of one or more alkali metal ion layers associated with the first compressive stress region. In various aspects, the first portion 221 may include a second depth of one or more alkali metal ion layers associated with the second compressive stress region and the second compressive depth. As used herein, the one or more alkali metal ions of the depth of the one or more alkali metal ion layers may include sodium, potassium, rubidium, cesium, and / or francium. In various aspects, the first depth of the one or more alkali ion layers and / or the one or more alkali ions of the second depth of the one or more alkali ion layers include potassium. In various aspects, the first depth of the layer and / or the second depth of the layer as a percentage of the substrate thickness 207 may be about 5% or more, about 10% or more, about 12% or more, about 15% or more, about 30% or less, about 25% or less, about 22% or less, about 20% or less, about 17% or less, or about 15% or less. In various aspects, the first depth of the layer and / or the second depth of the layer as a percentage of the substrate thickness 207 can be in the range of about 5% to about 30%, about 10% to about 25%, about 10% to about 22%, about 12% to about 20%, about 12% to about 17%, about 15% to about 17%, or any range or sub-range therebetween. In various aspects, the first depth of the one or more alkali ion layers and / or the second depth of the one or more alkali ion layers can be about 1 μm or more, about 10 μm or more, about 15 μm or more, about 20 μm or more, about 25 μm or more, about 30 μm or more, about 200 μm or less, about 150 μm or less, about 100 μm or less, about 60 μm or less, about 45 μm or less, about 30 μm or less, or about 20 μm or less. In various aspects, the first depth of the one or more alkali ion layers and / or the second depth of the one or more alkali ion layers may be in the range of about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 10 μm to about 100 μm, about 15 μm to about 600 μm, about 20 μm to about 45 μm, about 20 μm to about 30 μm, or any range or sub-range therebetween.

[0241] In various aspects, the first portion 221 may include a first tensile stress region. In various aspects, the first tensile stress region may be positioned between the first compressive stress region and the second compressive stress region. In various aspects, the first tensile stress region may include a maximum first tensile stress. In other aspects, the maximum first 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 other aspects, the maximum first tensile stress may be in the range of about 10 MPa to about 100 MPa, about 10 MPa to about 80 MPa, about 10 MPa to about 60 MPa, about 20 MPa to about 100 MPa, about 20 MPa to about 80 MPa, about 20 MPa to about 60 MPa, about 30 MPa to about 100 MPa, about 30 MPa to about 80 MPa, about 30 MPa to about 60 MPa, or any range or sub-range therebetween. Providing a maximum first tensile stress in the range of about 10 MPa to about 100 MPa can achieve good impact resistance and / or puncture resistance while providing low energy to fracture, as discussed below.

[0242] In various aspects, the second portion 231 including the second glass-based and / or ceramic-based portion may include a third compressive stress region at the third surface region 233, and the third compressive stress region may extend from the third surface region 233 to a third compression depth. In various aspects, the second portion 231 including the second glass-based and / or ceramic-based portion may include a fourth compressive stress region at the fourth surface region 235, and the fourth compressive stress region may extend from the fourth surface region 235 to a fourth compression depth. In various aspects, the third compression depth and / or the fourth compression depth as a percentage of the substrate thickness 207 may be within one or more of the ranges discussed above for the first compression depth and / or the second compression depth. In further aspects, the third compression depth may be substantially equal to the fourth compression depth. In various aspects, the third compression depth and / or the fourth compression depth may be within one or more of the ranges discussed above for the first compression depth and / or the second compression depth. By providing a second portion comprising a glass-based and / or ceramic-based portion comprising a third compression depth and / or a fourth compression depth in the range of about 1% to about 30% of the substrate thickness, good impact resistance and / or puncture resistance may be achieved.

[0243] In various aspects, the third compressive stress region may include a maximum third compressive stress. In various aspects, the fourth compressive stress region may include a maximum fourth compressive stress. In further aspects, the maximum third compressive stress and / or the maximum fourth compressive stress may be within one or more of the ranges discussed above for the maximum first compressive stress and / or the maximum second compressive stress. By providing a maximum third compressive stress and / or a maximum fourth compressive stress in the range of about 100 MPa to about 1,500 MPa, good impact resistance and / or puncture resistance may be achieved.

[0244] In various aspects, the second portion 231 may include a third depth of one or more alkali metal ion layers associated with a third compressive stress region and a third compression depth. In various aspects, the second portion 231 may include a fourth depth of one or more alkali metal ion layers associated with a fourth compressive stress region and a fourth compression depth. In various aspects, the third depth of the one or more alkali metal ion layers and / or the one or more alkali ions of the fourth depth of the one or more alkali metal ion layers include potassium. In various aspects, the third depth of the layer and / or the fourth depth of the layer as a percentage of the substrate thickness 207 may be within one or more of the ranges discussed above for the first depth of the layer and / or the second depth of the layer as a percentage of the substrate thickness 207. In various aspects, the third depth of the one or more alkali metal ion layers and / or the fourth depth of the one or more alkali metal ion layers may be the first depth of the layer and / or the second depth of the layer.

[0245] In various aspects, the second portion 231 may include a second tensile stress region. In various aspects, the second tensile stress region may be positioned between the third compressive stress region and the fourth compressive stress region. In various aspects, the second tensile stress region may include a maximum second tensile stress. In further aspects, the maximum second tensile stress may be within one or more of the ranges discussed above for the maximum first tensile stress. In various aspects, the maximum first tensile stress may be substantially equal to the maximum second tensile stress. Providing a maximum second tensile stress in the range of about 10 MPa to about 100 MPa may achieve good impact resistance and / or puncture resistance while providing low energy fracture, as discussed below.

[0246] In various aspects, the first compression depth may be substantially equal to the third compression depth. In various aspects, the second compression depth may be substantially equal to the fourth compression depth. In various aspects, the maximum first tensile stress may be substantially equal to the maximum third compressive stress. In various aspects, the maximum second compressive stress may be substantially equal to the maximum fourth compressive stress. In various aspects, the first depth of the one or more alkali metal ion layer may be substantially equal to the third depth of the one or more alkali metal ion layer. In various aspects, the second depth of the one or more alkali metal ion layer may be substantially equal to the fourth depth of the one or more alkali metal ion layer.

[0247] In various aspects, the central portion 281 can include a first central compressive stress zone at the first central surface region 213, which can extend from the first central surface region 213 to a first central compression depth. In various aspects, the central portion 281 can include a second central compressive stress zone at the second central surface region 243, which can extend from the second central surface region 243 to a second central compression depth. In further aspects, the first central compressive stress zone and / or the second compressive stress zone can be within the central region 248 of the central portion 281 (e.g., coextensive with the first central surface region 213 and / or the second central surface region 243). In further aspects, the first central compression depth and / or the second central compression depth as a percentage of the central thickness 209 can be within one or more of the ranges discussed above for the first compression depth and / or the second compression depth as a percentage of the substrate thickness 207. In further aspects, the first central compression depth and / or the second central compression depth as a percentage of the central thickness 209 can be about 1% or more, about 2% or more, about 5% or more, about 8% or more, about 10% or more, about 12% or more, about 20% or less, about 17% or less, about 15% or less, about 12% or less, about 10% or less, about 7% or less, or about 5% or less. For example, the first central compression depth and / or the second central compression depth as a percentage of the central thickness 209 can be in the range of about 1% to about 20%, about 2% to about 17%, about 5% to about 15%, about 7% to about 10%, or any range or sub-range therebetween. In further aspects, the first central compression depth can be substantially equal to the second central compression depth. In further aspects, the first central compression depth and / or the second central compression depth can be within one or more of the ranges discussed above for the first compression depth and / or the second compression depth. In further aspects, the first center compression depth and / or the second center compression depth may be about 1 μm or more, about 2 μm or more, about 4 μm or more, about 6 μm or more, about 20 μm or less, about 15 μm or less, about 10 μm or less, or about 8 μm or less. For example, the first center compression depth and / or the second center compression depth may be in the range of about 1 μm to about 20 μm, about 2 μm to about 15 μm, about 4 μm to about 10 μm, about 6 μm to about 8 μm, or any range or sub-range therebetween. Good impact resistance and / or puncture resistance may be achieved by providing a center portion comprising a glass-based and / or ceramic-based portion, the center portion comprising a center compression depth and / or a second center compression depth in the range of about 1% to about 30% (e.g., about 1% to about 20%) of the center thickness.

[0248] In various aspects, the first central compressive stress region may include a maximum first central compressive stress. In various aspects, the second central compressive stress region may include a maximum second central compressive stress. In further aspects, the maximum first central compressive stress and / or the maximum second central compressive stress may be within one or more of the ranges discussed above for the maximum first compressive stress and / or the maximum second compressive stress. By providing a maximum first central compressive stress and / or a maximum second central compressive stress in the range of about 100 MPa to about 1,500 MPa, good impact resistance and / or puncture resistance may be achieved.

[0249] In various aspects, central portion 281 can include a first central depth of one or more alkali metal ion layers associated with a first central compressive stress region and a first central compressive depth. In various aspects, central portion 281 can include a second central depth of one or more alkali metal ion layers associated with a second central compressive stress region and a second central compressive depth. In various aspects, the first central depth of the one or more alkali ion layers and / or the one or more alkali ions of the second central depth of the one or more alkali ion layers include potassium. In various aspects, the first central depth of the layer and / or the second central depth of the layer as a percentage of central thickness 209 can be within one or more of the ranges discussed above for the first depth of the layer and / or the second depth of the layer as a percentage of substrate thickness 207.

[0250] In further aspects, the first center depth of the layer and / or the second center depth of the layer as a percentage of the center thickness 209 can be about 1% or more, about 2% or more, about 5% or more, about 8% or more, about 10% or more, about 12% or more, about 20% or less, about 17% or less, about 15% or less, about 12% or less, about 10% or less, about 7% or less, or about 5% or less. For example, the first center depth of the layer and / or the second center depth of the layer as a percentage of the center thickness 209 can be in the range of about 1% to about 20%, about 2% to about 17%, about 5% to about 15%, about 7% to about 10%, or any range or sub-range therebetween. In further aspects, the first center depth of the layer can be substantially equal to the second center depth of the layer. In further aspects, the first center depth of the layer and / or the second center depth of the layer can be within one or more of the ranges discussed above for the first depth of the layer and / or the second depth of the layer. In other aspects, the first center depth of the layer and / or the second center depth of the layer can be about 1 μm or more, about 2 μm or more, about 4 μm or more, about 6 μm or more, about 20 μm or less, about 15 μm or less, about 10 μm or less, or about 8 μm or less. For example, the first center depth of the layer and / or the second center depth of the layer can be in the range of about 1 μm to about 20 μm, about 2 μm to about 15 μm, about 4 μm to about 10 μm, about 6 μm to about 8 μm, or any range or sub-range therebetween.

[0251] In various aspects, the central portion 281 may include a central tensile stress region. In various aspects, the central tensile stress region may be positioned between the first central compressive stress region and the second central compressive stress region. In various aspects, the central tensile stress region may include a maximum central tensile stress. In further aspects, the maximum central tensile stress may be about 125 MPa or greater, about 150 MPa or greater, about 200 MPa or greater, about 375 MPa or less, about 300 MPa or less, or about 250 MPa or less. In further aspects, the maximum central tensile stress can be in the range of about 125 MPa to about 375 MPa, about 125 MPa to about 300 MPa, about 125 MPa to about 250 MPa, about 150 MPa to about 375 MPa, about 150 MPa to about 300 MPa, about 150 MPa to about 250 MPa, about 200 MPa to about 375 MPa, about 200 MPa to about 300 MPa, about 200 MPa to about 250 MPa, or any range or sub-range therebetween. Providing a maximum central tensile stress in the range of about 125 MPa to about 375 MPa can achieve a low minimum bend radius.

[0252] In various aspects, the ratio of the first compression depth to the substrate thickness is greater than the ratio of the first central compression depth to the central thickness. In further aspects, the ratio of the first compression depth to the substrate thickness is about 0.01 or more, about 0.015 or more, about 0.02 or more, about 0.05 or more, about 0.07 or more, about 0.10 or more, about 0.20 or less, about 0.17 or less, about 0.15 or less, about 0.12 or less, about 0.11 or less, about 0.10 or less, or about 0.08 or less than the ratio of the first central compression depth to the central thickness. In further aspects, the ratio of the first compression depth to the substrate thickness is about 0.01 to about 0.20, about 0.015 to about 0.17, about 0.015 to about 0.15, about 0.02 to about 0.12, about 0.05 to about 0.11 or less, about 0.05 to about 0.08, or any range or sub-range therebetween, than the ratio of the first central compression depth to the central thickness. In further aspects, the ratio of the first compression depth to the substrate thickness is about 0.05 to about 0.22, about 0.07 to about 0.22, about 0.10 to about 0.22, about 0.12 to about 0.17, about 0.12 to about 0.15, or any range or sub-range therebetween, than the ratio of the first central compression depth to the central thickness. In various aspects, the ratio of the third compression depth to the substrate thickness, the ratio of the second compression depth to the substrate thickness, and / or the ratio of the fourth compression depth to the substrate thickness may be within one or more of the ranges discussed above. In further aspects, the third compression depth to substrate thickness ratio, the second compression depth to substrate thickness ratio, and / or the fourth compression depth to substrate thickness ratio can be substantially equal to the first compression depth to substrate thickness ratio.

[0253] In various aspects, the ratio of the first depth of the layer to the substrate thickness is greater than the ratio of the first center depth of the layer to the center thickness. In further aspects, the ratio of the first depth of the layer to the substrate thickness is about 0.001 or more, about 0.01 or more, about 0.015 or more, about 0.02 or more, about 0.05 or more, about 0.07 or more, about 0.10 or more, about 0.20 or more, about 0.17 or less, about 0.15 or less, about 0.12 or less, about 0.11 or less, or about 0.10 or less than the ratio of the first center depth of the layer to the center thickness. In further aspects, the ratio of the first depth of the layer to the substrate thickness is greater than the ratio of the first center depth of the layer to the center thickness in the range of about 0.001 to about 0.20, about 0.01 to about 0.20, about 0.01 to about 0.17, about 0.01 to about 0.15, about 0.015 to about 0.15, about 0.02 to about 0.12, about 0.05 to about 0.11 or less, about 0.07 to about 0.11, or any range or sub-range therebetween. In further aspects, the ratio of the first depth of the layer to the substrate thickness is greater than the ratio of the first center depth of the layer to the center thickness in the range of about 0.05 to about 0.22, about 0.07 to about 0.22, about 0.10 to about 0.22, about 0.12 to about 0.17, about 0.12 to about 0.15, or any range or sub-range therebetween. In various aspects, the ratio of the third depth of the layer to the substrate thickness, the ratio of the second depth of the layer to the substrate thickness, and / or the ratio of the fourth depth of the layer to the substrate thickness can be within one or more of the ranges discussed above. In further aspects, the ratio of the third depth of the layer to the substrate thickness, the ratio of the second depth of the layer to the substrate thickness, and / or the ratio of the fourth depth of the layer to the substrate thickness can be substantially equal to the ratio of the first depth of the layer to the substrate thickness.

[0254] Throughout this disclosure, the "brittleness limit" for a given substrate thickness is defined as the maximum amount of chemical strengthening (e.g., compression depth, depth of layer) without breaking into five (5) or more fragments with two or more branch points in a "brittleness test". The "brittleness test" uses a 5 centimeter (cm) (2 inch) x 5 cm (2 inch) square of material containing the substrate thickness and degree of chemical strengthening to be tested, where the midpoint of the first major surface is struck with a sharp probe using minimal force. As used herein, a branch point is a location with through cracks extending in at least three (3) different directions (i.e., extending through the thickness of the substrate), for example, a line including a through crack that strikes the branch point and at least one more through crack that strikes the branch point. In various aspects, the ratio of the first compression depth to the substrate thickness may be less than the brittleness limit expressed as the ratio of the compression depth to the substrate thickness by about 0.05 or less, about 0.03 or less, about 0.02 or less, about 0.005 or more, or about 0.01 or more. In various aspects, the ratio of the first depth of compression to the thickness of the substrate may be less than the brittle limit expressed as the ratio of the depth of compression to the thickness of the substrate may be in the range of about 0.005 to about 0.05 or less, about 0.005 to about 0.03 or less, about 0.001 to about 0.02 or less, or any range or sub-range therebetween. In various aspects, the ratio of the first depth of the layer to the thickness of the substrate may be less than the brittle limit expressed as the ratio of the depth of the layer to the thickness of the substrate by about 0.05 or less, about 0.03 or less, about 0.02 or less, about 0.005 or more, or about 0.01 or more. In various aspects, the ratio of the first depth of the layer to the thickness of the substrate may be less than the brittle limit expressed as the ratio of the depth of the layer to the thickness of the substrate may be in the range of about 0.005 to about 0.05 or less, about 0.005 to about 0.03 or less, about 0.001 to about 0.02 or less, or any range or sub-range therebetween. Providing a first compressive depth to substrate thickness ratio and / or a first depth to substrate thickness ratio of a layer that is less than the brittle limit (e.g., within about 0.05 or less) can achieve a large difference between the corresponding ratios of the first compressive stress region and the first central compressive stress region.

[0255] In various aspects, the foldable device 101, 301, 401, 501, 701, 801 and / or 901 and / or the foldable substrate 201 may not buckle in the central portion 281 and / or the central region 248. Throughout this disclosure, when a deflectometer profile of the first central surface area taken along a centerline of the central portion equally spaced from the first portion and the second portion includes a non-parabolic shape, the foldable substrate and / or the foldable device includes buckling. As used herein, the deflectometer profile is measured using SpecGAGE3D from IrsaVision. For example, refer to Figure 2 and Figure 4, the folding plane 109 is shown as extending along the centerline of the central portion 281. Fig.36 The deflection in mm on the vertical axis 3603 is shown as a function of the distance in mm along the centerline on the horizontal axis 3601. Fig.36 As shown, curve 3605 is substantially parabolic, which means that the foldable substrate corresponding to curve 3605 does not buckle in the central portion. In contrast, curves 3607 and 3609 are non-monotonic and non-parabolic because these curves change direction multiple times, indicating that the foldable substrates corresponding to these curves exhibit buckling.

[0256] Previously, for example, as discussed in WO 2022 / 046080, it was believed that if the center portion was not centered between the first and second major surfaces (e.g., symmetric about a plane containing the midpoints of the substrate thickness and the center thickness), the first center compression depth as a percentage of the substrate thickness must be closely matched (e.g., about 1% or less) to the first center compression depth as a percentage of the center thickness (and / or have a similar relationship for corresponding depths of layers that differ by about 0.1% or less) to reduce the incidence of buckling by subjecting the center portion to less than a critical buckling strain (e.g., due to chemical strengthening-induced expansion). Unexpectedly, as described below, it has been determined that a ratio of the first compression depth to the substrate thickness that provides a greater ratio than the first center compression depth to the center thickness (even when the difference is greater than 0.01) can reduce the incidence of buckling, while the reverse relationship is not true. Unexpectedly, as described herein, it has been determined that providing a ratio of the first depth of the layer to the substrate thickness that is greater than the ratio of the first center depth of the layer to the center thickness (even when the difference is greater than 0.001) can reduce the incidence of buckling, while the inverse relationship is not true. Without being bound by theory, it is believed that when the first portion and / or the second portion undergoes a greater chemical strengthening-induced expansion than the center portion, the first portion and / or the second portion in the direction 104 (i.e., perpendicular to the center portion) may be subjected to a greater chemical strengthening-induced expansion. Figures 2 to 4The greater linear expansion in the direction 104 of the center portion (i.e., the cross-section shown) exerts a stabilizing force on the center portion (i.e., a tensile force in the direction 104) that suppresses fluctuations in the surface profile that could otherwise lead to the onset of mechanical instability (e.g., buckling). As noted, it has been observed that the stabilizing force can enable the center portion to withstand a critical buckling strain, where the critical buckling strain is calculated for a sample comprising a substrate material having a uniform thickness. This is unexpected because, by definition, exceeding the critical buckling strain is expected to lead to the onset of mechanical instability (e.g., buckling). Without being bound by theory, it is currently believed that when the first portion and / or the second portion undergoes less chemical strengthening-induced expansion than the center portion, the less linear expansion in the direction 104 of the first portion and / or the second portion destabilizes the center portion by compressing the center portion (i.e., in the direction 104), which can amplify fluctuations in the surface profile that could lead to the onset of mechanical instability (e.g., buckling).

[0257] In various aspects, the polymer base portion 289 and / or 299 can be optically clear. The polymer base portion 289 and / or 299 can include a first refractive index. The first refractive index can be a function of the wavelength of light passing through the optically clear adhesive. For light of a first wavelength, the refractive index of a material is defined as the ratio between the speed of light in a vacuum and the speed of light in a corresponding material. Without being bound by theory, the refractive index of an optically clear adhesive can be determined using the ratio of the sine of a first angle to the sine of a second angle, wherein light of a first wavelength is incident on the surface of the optically clear adhesive from air at a first angle, and refracted at a second angle at the surface of the optically clear adhesive to propagate light within the optically clear adhesive. Both the first angle and the second angle are measured relative to a direction orthogonal to the surface of the optically clear adhesive. As used herein, the refractive index is measured according to ASTM E1967-19, wherein the first wavelength includes 589nm. In various aspects, the first refractive index of the polymer base portion 289 and / or 299 can be about 1 or more, about 1.3 or more, about 1.4 or more, about 1.45 or more, about 1.49 or more, 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 various aspects, the first refractive index of the polymer base portion 289 and / or 299 can be in the range of about 1 to about 3, about 1 to about 2, about 1 to about 1.7, about 1.3 to about 1.7, about 1.4 to about 1.7, about 1.4 to about 1.6, about 1.45 to about 1.55, about 1.49 to about 1.55, or any range or sub-range therebetween.

[0258] In various aspects, the foldable substrate 201 may include a second refractive index. In various aspects, the second refractive index of the foldable substrate 201 may be about 1 or more, about 1.3 or more, about 1.4 or more, about 1.45 or more, about 1.49 or more, 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 various aspects, the second refractive index of the foldable substrate 201 may be in the range of about 1 to about 3, about 1 to about 2, about 1 to about 1.7, about 1.3 to about 1.7, about 1.4 to about 1.7, about 1.4 to about 1.6, about 1.45 to about 1.55, about 1.49 to about 1.55, or any range or sub-range therebetween. In various aspects, the differential equal to the absolute value of the difference between the second refractive index of the foldable substrate 201 and the first refractive index of the polymer base portion 289 and / or 299 can 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 various aspects, the differential is in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween. In various aspects, the second refractive index of the foldable substrate 201 can be greater than the first refractive index of the polymer base portion 289 and / or 299. In various aspects, the second refractive index of foldable substrate 201 can be less than the first refractive index of polymer base portions 289 and / or 299 .

[0259] In various aspects, the adhesive layer 261 may include a third refractive index. In various aspects, the third refractive index of the adhesive layer 261 may be within one or more of the ranges discussed above with respect to the first refractive index of the polymer base portion 289 and / or 299. In various aspects, 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 base portion 289 and / or 299 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 various aspects, the differential is in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween. In various aspects, the third refractive index of the adhesive layer 261 may be greater than the first refractive index of the polymer base portion 289 and / or 299. In various aspects, the third refractive index of the adhesive layer 261 may be less than the first refractive index of the polymer base portion 289 and / or 299.

[0260] In various aspects, 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 201 can 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 various aspects, the differential is in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween. In various aspects, the third refractive index of the adhesive layer 261 can be greater than the second refractive index of the foldable substrate 201. In various aspects, the third refractive index of the adhesive layer 261 may be less than the second refractive index of the foldable substrate 201 .

[0261] In various aspects, coating 251 can include a fourth refractive index. In various aspects, the fourth refractive index of coating 251 can be within one or more of the ranges discussed above with respect to the first refractive index of polymer base portions 289 and / or 299. In various aspects, the differential equal to the absolute value of the difference between the fourth refractive index of coating 251 and the first refractive index of polymer base portions 289 and / or 299 can 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 various aspects, the differential is in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween. In various aspects, the fourth refractive index of the coating 251 can be greater than the first refractive index of the polymer base portion 289 and / or 299. In various aspects, the fourth refractive index of the coating 251 can be less than the first refractive index of the polymer base portion 289 and / or 299.

[0262] In various aspects, the differential equal to the absolute value of the difference between the fourth refractive index of the coating 251 and the second refractive index of the foldable substrate 201 can 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 various aspects, the differential is in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween. In various aspects, the fourth refractive index of the coating 251 can be greater than the second refractive index of the foldable substrate 201. In various aspects, the fourth refractive index of the coating 251 can be less than the second refractive index of the foldable substrate 201.

[0263] In various aspects, the differential equal to the absolute value of the difference between the fourth refractive index of the coating 251 and the third refractive index of the adhesive layer 261 can 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 various aspects, the differential is in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween. In various aspects, the fourth refractive index of the coating 251 can be greater than the third refractive index of the adhesive layer 261. In various aspects, the fourth refractive index of the coating layer 251 can be less than the third refractive index of the adhesive layer 261 .

[0264] Figures 6 to 9 Schematically illustrating aspects of a foldable device 501, 701, 801, and / or 901 in a folded configuration according to aspects of the present disclosure. Figure 6 As shown, the foldable device 501 is folded so that the second major surface 205 of the foldable substrate 201 is located on the inner side of the folded foldable device 501, for example, the foldable device 301 can be folded to form the foldable device 501. For example, the display can be located on one side of the second major surface 205, and the viewer will view the display from the side of the first major surface 203. Alternatively, the display can be located on one side of the first major surface 203, and the viewer will view the display from the side of the second major surface 205. Figure 8 As shown, the foldable device 801 is folded so that the second major surface 205 of the foldable substrate 201 is located on the inner side of the folded foldable device 501. For example, the display may be located on one side of the second major surface 205, and the viewer will view the display from the side of the first major surface 203. Alternatively, the display may be located on one side of the first major surface 203, and the viewer will view the display from the side of the second major surface 205.

[0265] like Figure 7 As shown, (modified as described in the parallel plate test below) Figure 1 The foldable device 101 shown in FIG. 1 is folded to form a folded foldable device 701 such that the first major surface 203 of the foldable substrate 201 is located on the inner side of the folded foldable device 701. Figure 7 In the embodiment, instead of the PET sheet 707, the user will view the display device through the foldable substrate 201, and therefore, the display device will be positioned on one side of the first major surface 203. In various aspects, as Figure 7As shown, the foldable device 701 may include a coating 251 disposed on the foldable device 701 (e.g., the second major surface 205). In other aspects, instead of the PET sheet 707, the user will view the display device through the coating 251. In various aspects, as Figure 7 As shown, the polymer-based portion 289 and / or 299 may be disposed on the foldable substrate 201. In another aspect, although an additional substrate (e.g., a glass-based substrate and / or a ceramic-based substrate instead of the release liner 271 or the PET sheet 707) is not shown, the additional substrate may be disposed on the display device. Fig. 9 As shown, (modified as described in the parallel plate test below) Figure 4 The foldable device 401 shown in FIG. 4 is folded to form a folded foldable device 901 such that the first major surface 203 of the foldable substrate 201 is located on the inner side of the folded foldable device 901. Fig. 9 In the embodiment, instead of the PET sheet 707, the user will view the display device through the foldable substrate 201, and therefore, the display device will be positioned on one side of the first major surface 203. In various aspects, as Fig. 9 As shown, the polymer-based portion 299 may be disposed on the foldable substrate 201 (e.g., in the first recessed portion 211). In further aspects, although an additional substrate (e.g., a glass-based substrate and / or a ceramic-based substrate instead of the release liner 271 or the PET sheet 707) is not shown, the additional substrate may be disposed on the display device. It should be understood that the foldable device may be designed to be folded so that the display device is located on the inside of the bend, on the outside of the bend, or so that the foldable device can be folded in either direction.

[0266] As used herein, "foldable" includes fully foldable, partially foldable, bendable, flexible, or multiple capabilities. As used herein, the terms "failure," "malfunction," and the like refer to breakage, destruction, delamination, or crack propagation. Likewise, a foldable device achieves a parallel plate distance of "X," or has a parallel plate distance of "X," or includes a parallel plate distance of "X" if the foldable device resists failure when the foldable device is maintained at a parallel plate distance of "X" at about 85° C. and about 85% relative humidity for 24 hours.

[0267] As used herein, the "parallel plate distance" of a foldable device and / or a foldable substrate is referred to as a parallel plate device 601 (see Figures 6 to 9 ) is measured using the following test configuration and process. The parallel plate device includes a pair of parallel rigid stainless steel plates 603 and 605. The pair of parallel rigid stainless steel plates includes a first rigid stainless steel plate 603 and a second rigid stainless steel plate 605. When measuring Figure 6 and Figure 8The foldable substrate 201 shown (eg, composed of the foldable substrate 201) Figure 3 When the “parallel plate distance” of the foldable device 301 shown in FIG. 1 is measured, the foldable substrate 201 is placed between a pair of plates 603 and 605 so that the first major surface 203 is in contact with the pair of plates 603 and 605. Figure 2 and Figure 4 When the "parallel plate distance" of the foldable devices 101 and 401 is shown, the adhesive layer 261 is removed and replaced by a test adhesive layer 709 comprising a thickness of 50 μm. In addition, the test utilizes a 100 μm thick polyethylene terephthalate (PET) sheet 707 instead of Figure 2 and Figure 4 Therefore, during the test of determining the "parallel plate distance" of the configuration of the foldable device, the foldable device 701 was tested by using a 100 μm thick polyethylene terephthalate (PET) sheet 707 instead of Figure 2 and Figure 4 A release liner 271 is produced.

[0268] When preparing the foldable device 701, a 100 μm thick polyethylene terephthalate (PET) sheet 707 is attached to the test adhesive layer 709 in the same manner as follows: a release liner 271 is attached to the second contact surface 265 of the adhesive layer 261, as shown in FIG. Figure 2 For testing Figure 7 The foldable device 701, the test adhesive layer 709 and the PET sheet 707 can also be as shown in Figure 7 The foldable device 701 is installed in a configuration to test the foldable device 701. The foldable device 701 is placed between a pair of parallel rigid stainless steel plates 603 and 605 so that the foldable substrate 201 will be located on the inside of the bend, similar to Figure 7 Similarly, when preparing the foldable device 901, a test adhesive layer 709 and a 100 μm thick PET sheet 707 are used to replace the adhesive layer 261 and the release liner 271 to prepare the foldable device 901. Figure 4 The foldable device 401 shown is used for testing. To determine the "parallel plate distance", the distance between the parallel plates is reduced at a rate of 50 μm / second until the parallel plate distance 611 or 711 is equal to the "parallel plate distance" to be tested. Then, the parallel plates are kept at the "parallel plate distance" for testing at about 85°C and about 85% relative humidity for 24 hours. As used herein, the "minimum parallel plate distance" is the minimum parallel plate distance that the foldable device can withstand under the above conditions and configurations without failure.

[0269] In various aspects, the foldable device 101, 301, 401, 501, 701, 801, 901, 3801 and / or 3901 and / or the foldable substrate 201 can achieve a parallel plate distance of 100 mm or less, 50 mm or less, 20 mm or less, 10 mm or less, 5 mm or less, or 3 mm or less. In further aspects, the foldable device 101, 301, 401, 501, 701, 801, 901, 3801 and / or 3901 and / or the foldable substrate 201 can achieve a parallel plate distance of 50 millimeters (mm), or 20 mm, or 10 mm, or 5 mm, or 3 mm. In various aspects, the foldable device 101, 301, 401, 501, 701, 801, 901, 3801 and / or 3901 and / or the foldable substrate 201 may include a minimum parallel plate distance of 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 10 mm or more. In various aspects, the foldable device 101, 301, 401, 501, 701, 801, 901, 3801 and / or 3901 and / or the foldable substrate 201 may include a minimum parallel plate distance in the range of about 1 mm to about 40 mm, about 1 mm to about 20 mm, about 1 mm to about 10 mm, about 1 mm to about 5 mm, about 1 mm to about 3 mm. In various aspects, the foldable device 101, 301, 401, 501, 701, 801, 901, 3801 and / or 3901 and / or the foldable substrate 201 can achieve a minimum parallel plate distance within the following ranges or any range or sub-range therebetween: about 2 mm to about 40 mm, about 2 mm to about 20 mm, about 2 mm to about 10 mm, about 3 mm to about 10 mm, about 3 mm to about 5 mm, about 5 mm to about 10 mm.

[0270] A central width 287 of the central portion 281 of the foldable substrate 201 is defined between the first portion 221 and the second portion 231 in the direction 106 of the length 105. In various aspects, the central width 287 of the central portion 281 of the foldable substrate 201 can extend from the first portion 221 to the second portion 231. A width 210 of the first central surface region 213 and the second central surface region 243 of the foldable substrate 201 is defined between the first transition region 212 and the second transition region 218 in the direction 106 of the length 105, for example as a portion including the central thickness 209. In various aspects, the width 287 of the central portion 281 of the foldable substrate 201 and / or the width 210 of the first central surface region 213 of the foldable substrate 201 can be about 1.4 times or more, about 1.6 times or more, about 2 times or more, about 2.2 times or more, about 3 times or less, or about 2.5 times or less of the minimum parallel plate distance. In various aspects, the width 287 of the central portion 281 of the foldable substrate 201 and / or the width 210 of the first central surface area 213 of the foldable substrate 201 as a multiple of the minimum parallel plate distance can be in the range of about 1.4 times to about 3 times, about 1.6 times to about 3 times, about 1.6 times to about 2.5 times, about 2 times to about 2.5 times, about 2.2 times to about 2.5 times, about 2.2 times to about 3 times, or any range or sub-range therebetween. Without being bound by theory, the length of the curved portion in the circular configuration between the parallel plates can be about 1.6 times the parallel plate distance 611 or 711. Without being bound by theory, the length of the curved portion in the elliptical configuration between the parallel plates can be about 2.2 times the parallel plate distance 611 or 711. In various aspects, the central width 287 of the central portion 281 of the foldable substrate 201 and / or the width 210 of the first central surface area 213 of the foldable substrate 201 can be about 1 mm or greater, about 3 mm or greater, about 5 mm or greater, about 8 mm or greater, about 10 mm or greater, about 15 mm or greater, about 20 mm or greater, 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 various aspects, the central width 287 of the central portion 281 of the foldable substrate 201 and / or the width 210 of the first central surface area 213 of the foldable substrate 201 may be within a range of about 1 mm to about 100 mm, about 3 mm to about 100 mm, about 3 mm to about 60 mm, about 5 mm to about 60 mm, about 5 mm to about 50 mm, about 8 mm to about 50 mm, about 8 mm to about 40 mm, about 10 mm to about 40 mm, about 10 mm to about 35 mm, about 15 mm to about 35 mm, about 15 mm to about 30 mm, about 20 mm to about 30 mm, about 20 mm to about 25 mm, or any sub-range therebetween.In various aspects, the central width 287 of the central portion 281 of the foldable substrate 201 and / or the width 210 of the first central surface area 213 of the foldable substrate 201 can 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 various aspects, the central width 287 of the central portion 281 of the foldable substrate 201 and / or the width 210 of the first central surface area 213 of the foldable substrate 201 can be in the range of about 2.8 mm to about 60 mm, about 2.8 mm to about 40 mm, about 2.8 mm to about 24 mm, about 6 mm to about 60 mm, about 6 mm to about 40 mm, about 6 mm to about 24 mm, about 9 mm to about 60 mm, about 9 mm to about 40 mm, about 9 mm to about 24 mm, or any range or sub-range therebetween. In various aspects, the first central surface area 213, the central portion 281 (e.g., the centerline of the central portion 281), and / or the folding plane 109 may correspond to a midpoint between opposite ends of the foldable substrate and / or the foldable device in the direction 106 of the length 105. By providing the central portion (e.g., between the first portion and the second portion) with a width within the above range, trouble-free folding of the foldable device may be facilitated.

[0271] In various aspects, the central width 287 of the central portion 281 and / or the width 210 of the first central surface area 213 as a percentage of the length 105 of the foldable device can be about 30% or more, about 35% or more, about 40% or more, about 45% or more, about 70% or less, about 60% or less, about 55% or less, or about 50% or less. In various aspects, the central width 287 of the central portion 281 and / or the width 210 of the first central surface area 213 as a percentage of the length 105 of the foldable device can be in the range of about 30% to about 70%, about 35% to about 60%, from about 40% to about 55%, about 45% to about 50%, or any range or sub-range therebetween. In various aspects, the central width 287 of the central portion 281 and / or the width 210 of the first central surface area 213 can be about 30 mm or more, about 35 mm or more, about 40 mm or more, about 45 mm or more, about 50 mm or more, about 100 mm or less, about 80 mm or less, about 70 mm or less, or about 60 mm or less. In various aspects, the central width 287 of the central portion 281 and / or the width 210 of the first central surface area 213 can be in the range of about 30 mm to about 100 mm, about 35 mm to about 80 mm, about 40 mm to about 70 mm, about 45 mm to about 60 mm, about 50 mm to about 60 mm, or any range or sub-range therebetween. In various aspects, the centerline of the central portion 281 can be displaced from a midpoint between opposite ends of the foldable substrate and / or the foldable device in the direction 106 of the length 105 by about 5% or more, about 10% or more, about 15% or less, about 20% or less, about 40% or less, about 35% or less, or about 30% or less of the length 105, such as in a range of about 5% to about 40%, about 10% to about 40%, about 15% to about 35%, about 20% to about 35%, about 20% to about 30%, or any range or sub-range therebetween. Alternatively, in various aspects, the first central surface area 213, the central portion 281 (e.g., the centerline of the central portion 281), and / or the folding plane 109 can correspond to a midpoint between opposite ends of the foldable substrate and / or the foldable device in the direction 106 of the length 105. Alternatively, in various aspects, the first central surface area 213, the central portion 281 and / or the folding plane 109 may correspond to a midpoint between opposite ends of the foldable substrate and / or the foldable device in the direction 106 of the length 105.

[0272] In various aspects, the foldable substrate and / or foldable device may be rollable. As used herein, a foldable substrate or foldable device is "rollable" if it can achieve a threshold parallel plate distance of 10 mm or 10% of the length of the corresponding foldable substrate and / or foldable device over the length of the corresponding foldable substrate and / or foldable device, whichever is greater. For example, Fig.37 As shown, when the central width 287 of the central portion 281 is greater than 10% of the length 105 extending in the direction 106 of the length 105 (see Figure 1 ), the foldable substrate 201 is considered to be "rollable". In various aspects, such as Fig.37 As shown, the foldable substrate 201 may include a first width 3727, a center width 287, and a second width 3737 in the direction 106 of the length 105. The sum of the first width 3727, the center width 287, and the second width 3737 may be substantially equal to and / or equal to the length of the foldable substrate 201 (e.g., Figure 1 The foldable device 101 is shown with a length 105).

[0273] In further aspects, the second width 3737 as a percentage of the length of the foldable substrate 201 and / or the foldable device 101 can be about 15% or less, about 12% or less, about 10% or less, about 8% or less, about 6% or less, about 5% or less, about 4.5% or less, about 4% or less, about 1% or more, about 1.5% or more, about 2% or more, about 2.5% or more, about 3% or more, or about 3.5% or more. In further aspects, the second width 3737 as a percentage of the length of the foldable substrate 201 and / or the foldable device 101 can be in the range of about 1% to about 15%, about 1% to about 12%, about 1.5% to about 10%, about 1.5% to about 8%, about 2% to about 6%, about 2.5% to about 5%, about 3% to about 4.5%, about 3.5% to about 4%, or any range or sub-range therebetween. In further aspects, the second width 3737 can be about 15 mm or less, about 12 mm or less, about 10 mm or less, about 8 mm or less, about 6 mm or less, about 5 mm or less, about 4.5 mm or less, about 4 mm or less, about 1 mm or more, about 1.5 mm or more, about 2 mm or more, about 2.5 mm or more, about 3 mm or more, or about 3.5 mm or more. In further aspects, the second width 3737 can be in the range of about 1 mm to about 15 mm, about 1 mm to about 12 mm, about 1.5 mm to about 10 mm, about 1.5 mm to about 8 mm, about 2 mm to about 6 mm, about 2.5 mm to about 5 mm, about 3 mm to about 4.5 mm, about 3.5 mm to about 4 mm, or any range or sub-range therebetween. Providing a second width within one or more of the above-mentioned ranges in this paragraph may provide sufficient width to handle the end of the foldable substrate during processing to secure the foldable substrate and / or the foldable device as part of an electronic device and / or maximize the amount of the foldable substrate and / or the foldable device that may be part of a display portion visible to a user (e.g., as described below with reference to Figure 38 to Figure 39 As used herein, "display portion" refers to the portion of the foldable device corresponding to the location where an image can be displayed by the display device and viewed by a viewer through the foldable substrate (e.g., a rollable substrate).

[0274] In further aspects, the first width 3727 as a percentage of the length of the foldable substrate 201 and / or the foldable device 101 can be 35% or more, about 40% or more, about 45% or more, about 50% or more, about 75% or less, about 70% or less, about 65% or less, about 60% or less, or about 55% or less. In further aspects, the first width 3727 as a percentage of the length of the foldable substrate 201 and / or the foldable device 101 can be in the range of about 35% to about 75%, about 40% to about 70%, about 45% to about 65%, about 50% to about 60%, about 50% to about 55%, or any range or sub-range therebetween. In further aspects, the first width 3727 can be about 35 mm or more, about 40 mm or more, about 45 mm or more, about 50 mm or more, about 75 mm or less, about 70 mm or less, about 65 mm or less, about 60 mm or less, or about 55 or less. In various aspects, the first width 3727 can be in the range of about 35 mm to about 75 mm, about 40 mm to about 70 mm, about 45 mm to about 65 mm, about 50 mm to about 60 mm, about 50 mm to about 55 mm, or any range or sub-range therebetween. Providing a first width within one or more of the above-mentioned ranges in this paragraph can provide a large display portion visible to the user while ensuring that substantially all of the remaining portions of the foldable substrate (e.g., the center portion and the second portion) can be within the coverage of the first portion (e.g., except for the referenced portions below). Figure 38 to Figure 39 outside the part surrounding the rollers discussed).

[0275] Additionally or alternatively, the center width 287 may be greater than the second width 3737. In various aspects, the center width 287 as a percentage of the length of the foldable substrate 201 and / or the foldable device 101 may be about 15% or more, about 20% or more, about 25% or more, about 30% or more, about 35% or more, about 40% or more, about 42% or more, about 44% or more, about 45% or more, about 50% or less, about 49% or less, about 48% or less, about 47% or less, about 46% or less, about 45% or less, about 38% or less, or about 32% or less. In various aspects, the percentage of the center width 287 as a percentage of the length of the foldable substrate 201 and / or the foldable device 101 can be in the range of about 15% to about 50%, about 20% to about 50%, about 25% to about 49%, about 30% to about 49%, about 35% to about 48%, about 40% to about 48%, about 42% to about 47%, about 43% to about 46%, about 44% to about 45%, or any range or sub-range therebetween. Providing a center width within one or more of the above-mentioned ranges in this paragraph can enable adjustment of the display portion of the foldable device as a portion of the rollable substrate is moved into and / or out of the user's field of view when in the fully rolled configuration without having to enlarge the size of the corresponding device.

[0276] Figure 38 to Figure 39Foldable devices 3801 and 3901 are shown as being configured to include a foldable substrate 201 as a rollable substrate. As shown, the foldable substrate 201 (e.g., a rollable substrate) is configured to be rolled around a winder 3805 (e.g., corresponding to a folding axis, wherein when the rollable substrate is moved in a direction 3821 or in a direction opposite to the direction 3821, the rollable substrate is configured to fold within a series of axes corresponding to the winder). For example, the foldable substrate 201 (e.g., a rollable substrate) can be rolled in the direction 3821 to expand the display portion of the foldable devices 3801 and 3901. Similarly, the foldable substrate 201 (e.g., a rollable substrate) can be rolled in a direction opposite to the direction 3821 to reduce the display portion of the foldable devices 3801 and 3901. The foldable devices 3801 and 3901 can be configured to adjust the size of the display portion from substantially equal to the first width 3727 (for example, where the center portion and the second portion 231 are within the footprint of the first portion 221 or around the winder) to approximately 1.6 to 3 times the sum of the first width 3727 and the center width 287 minus the diameter 3807 of the winder 3805. In various aspects, the diameter 3807 of the winder 3805 can be about 1 mm or greater, about 1.5 mm or greater, about 2 mm or greater, about 2.5 mm or greater, about 3 mm or greater, about 4 mm or greater, about 5 mm or greater, about 6 mm or greater, about 7 mm or greater, about 8 mm or greater, about 9 mm or greater, about 10 mm or greater, about 50 mm or less, about 30 mm or less, about 20 mm or less, about 18 mm or less, about 16 mm or less, about 14 mm or less, about 12 mm or less, about 10 mm or less, about 8 mm or less, about 6 mm or less, about 5 mm or less, or about 4 mm or less. In various aspects, the diameter 3807 of the winder 3805 can be in the range of about 1 mm to about 50 mm, about 1.5 mm to about 30 mm, about 2 mm to about 20 mm, about 2.5 mm to about 18 mm, about 3 mm to about 16 mm, about 4 mm to about 14 mm, about 5 mm to about 12 mm, about 6 mm to about 10 mm, about 6 mm to about 8 mm, or any range or sub-range therebetween. In various aspects, the diameter 3807 of the winder 3805 can be about 6 mm or less, for example, about 1 mm to about 6 mm, about 1.5 mm to about 5 mm, about 2 mm to about 4 mm, about 2.5 mm to about 4 mm, about 3 mm to about 4 mm, or any range or sub-range therebetween.

[0277] like Figure 38 to Figure 39 As shown, the foldable substrate 201 (eg, a rollable substrate) may include one or more recessed portions. Fig.38 The foldable substrate 201 (eg, a rollable substrate) shown may include a single recessed portion. Fig.39The foldable substrate 201 (eg, rollable substrate) shown may include two recessed portions. In various aspects, the polymer base portion (eg, the second polymer base portion 299) and / or the adhesive layer 261 may be positioned in the first recessed portion (eg, in the Fig.38 , defined by a first central surface area 213), a second recessed portion (e.g., Fig.39 The area between the first central surface area 213 and the sixth surface area 3815 of the display device 3811 may correspond to the area between the first central surface area 213 and the first major surface 273 of the release liner 271, although in other aspects the adhesive layer 261 may extend into the recess, the second polymer base portion 299 may extend beyond the recess, the corresponding area may not include the adhesive layer 261, or the corresponding area may not include the second polymer base portion 299. Figure 4 The configuration shown, wherein the second polymer base portion 299 is positioned in the first recess 211 and the adhesive layer 261 is disposed thereon. Fig.38 In the configuration shown, the fifth surface area 3813 of the display device 3811 (opposite to the sixth surface area 3815) can be configured to contact the outer periphery of the winder 3805 and / or move along the periphery; and / or an observer can be positioned on one side of the second major surface 205 of the foldable substrate 201 (e.g., a rollable substrate) to view an image emitted from the display device 3811 through the foldable substrate 201. In various aspects, the display device 3811 can include a liquid crystal display (LCD), an electrophoretic display (EPD), an organic light emitting diode (OLED) display, or a plasma display panel (PDP). It should be understood that the coating (e.g., coating 251) can be provided on Fig.38 On the second major surface 205 of the foldable substrate 201 shown.

[0278] like Fig.39 As shown, although in other aspects the adhesive layer 261 may extend into the recessed portion, the second polymer base portion 299 may extend beyond the recessed portion, the corresponding area may not include the adhesive layer 261, or the corresponding area may not include the second polymer base portion 299, but the area between the second central surface area 243 and the sixth surface area 3815 of the display device 3811 may correspond to the area between the second central surface area 243 and the first major surface 273 of the release liner 271. Figure 2The configuration shown, wherein the first polymer base portion 289 (instead of the second polymer base portion 299) is positioned in the second recess 241 and the adhesive layer 261 is disposed thereon; or between the first central surface area 213 and the coating 251 Figure 2 The configuration shown in FIG. 1 , wherein the second polymer base portion 299 is positioned in the first recess 211. In various aspects, as Fig.39 As shown, the material disposed on the first central surface region 213 may include the first polymer-based portion 289 and the coating 251, but in other aspects (e.g., similar or identical to the adhesive layer 261) another adhesive layer may be positioned therebetween or in place of the first polymer-based portion. Fig.39 In the configuration shown, the fifth surface area 3813 (opposite the sixth surface area 3815) of the display device 3811 can be configured to contact the outer periphery of the winder 3805 and / or move along the periphery; and / or an observer can be positioned on one side of the second major surface 205 of the foldable substrate 201 (e.g., a rollable substrate) and / or the third major surface 253 of the coating 251 to view the image emitted from the display device 3811 through the foldable substrate 201.

[0279] The foldable device 101, 301, 401, 501, 701, 801, 901, 3801, and / or 3901 may have an impact resistance defined by the ability of a region of the foldable device (e.g., a region including the first portion 221, a region including the second portion 231, a region including the polymer base portion 289 and / or 299, and / or the center portion 281) to avoid failure at a pen drop height (e.g., 5 centimeters (cm) or more, 10 centimeters or more, 20 cm or more) when measured according to a "pen drop test". As used herein, a "pen drop test" is performed such that a sample of the foldable device is subjected to an impact with a pen drop applied to an outer major surface (e.g., for Figures 2 to 3 The first major surface 203 of the foldable substrate 201 of the foldable device 101 or 301 shown can be used Figure 3 to Figure 4 The foldable device 301 or 401 shown was tested under load (i.e., from a pen dropped from a certain height), wherein the foldable device was assembled in a parallel plate test, wherein a 100 μm thick PET sheet 707 was attached to a test adhesive layer 709 having a thickness of 50 μm instead of Figure 2 The release liner 271 is shown. Thus, the PET layer in the pen drop test is meant to simulate a foldable electronic display device (e.g., an OLED device). During the test, the foldable device bonded to the PET layer was placed on an aluminum plate (e.g., 6063 aluminum alloy polished to a surface roughness with 400 grit sandpaper) with the PET layer in contact with the aluminum plate. No tape was used on one side of the sample that was stationary on the aluminum plate.

[0280] The tube is used in the pen drop test to guide the pen to the outer surface of the foldable device. Figures 2 to 4 , Figures 6 to 9 , Figure 38 to Figure 39 In the foldable device 101, 301, 401, 501, 701, 801, 901, 3801 and / or 3901, the pen is guided to the outer main surface (e.g., for Figures 2 to 3 The first main surface 203 of the foldable substrate 201 of the foldable device 101 or 301 is used Figure 3 to Figure 4 The foldable device 301 or 401 shown is placed on the second major surface 205 of the foldable substrate 201, and the tube is placed in contact with the second major surface 205 of the foldable substrate 201, so that the longitudinal axis of the tube is substantially perpendicular to the outer major surface, and 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. Each test uses an acrylonitrile butadiene (ABS) pad to hold the pen at a predetermined height. After each drop, the tube is 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 is Fine's BIC Easy Glide pen, which has a 0.7 mm (0.68 mm) diameter tungsten carbide ballpoint pen tip and a weight of 5.73 grams (g) including the cap.

[0281] For the pen drop test, the pen is dropped with the cap attached to the top end (i.e., the end opposite the pen tip) so that the ball can interact with the test sample. In the drop sequence according to the pen drop test, one pen drop is performed at an initial height of 1 cm, followed by continuous drops in 0.5 cm increments up to 20 cm, and then after 20 cm, drops in 2 cm increments until the test sample fails. After each drop is performed, the presence of any observable breakage, failure, or other evidence of damage to the sample is recorded as well as the specific pen drop height. Using the pen drop test, multiple samples can be tested according to the same drop sequence to produce a population with improved statistical accuracy. For the pen drop test, the pen will be changed to a new pen after every 5 drops and for each new sample tested. In addition, all pen drops are performed at a random location on the sample at or near the center of the sample, and no pen is dropped near or on the edge of the sample.

[0282] For the purpose of the pen drop test, "failure" means a visible mechanical defect is formed in the laminate. The mechanical defect may be a crack or a plastic deformation (e.g., a surface indentation). The crack may be a surface crack or a through crack. The crack may be formed on the interior surface or the exterior surface of the laminate. The crack may extend through all or a portion of the foldable substrate 201 and / or the coating. Visible mechanical defects have a minimum dimension of 0.2 mm or greater.

[0283] In various aspects, the foldable device can resist pen drop failure at a pen drop height of 10 centimeters (cm), 12 cm, 14 cm, 16 cm, or 20 cm in an area including the first portion 221 or the second portion 231. In various aspects, the maximum pen drop height that the foldable device can withstand without failure on an area including the first portion 221 or the second portion 231 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 less. In various aspects, the maximum pen drop height that the foldable device can withstand without failure on an area including the first portion 221 or the second portion 231 may be in the range of about 10 cm to about 40 cm, about 12 cm to about 40 cm, about 12 cm to about 30 cm, about 14 cm to about 30 cm, about 14 cm to about 20 cm, about 16 cm to about 20 cm, about 18 cm to about 20 cm, or any range or sub-range therebetween.

[0284] In various aspects, the foldable device can resist pen drop failure at a height of 1 cm, 2 cm, 3 cm, 4 cm, 5 cm or more in an area (e.g., central portion 281) including polymer base portions 289 and / or 299 located between the first portion 221 and the second portion 231. In various aspects, the maximum pen drop height that the foldable device can withstand without failure on the area including polymer base portions 289 and / or 299 located between the first portion 221 and the second portion 231 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 various aspects, the maximum pen drop height that the foldable device can withstand without failure on the area including the polymer base portion 289 and / or 299 located between the first portion 221 and the second portion 231 can be in the range of about 1 cm to about 20 cm, about 2 cm to about 20 cm, about 2 cm to about 10 cm, about 3 cm to about 10 cm, about 3 cm to about 8 cm, about 4 cm to about 8 cm, about 4 cm to about 6 cm, or any range or sub-range therebetween. In various aspects, the maximum pen drop height that the foldable device can withstand without failure on the area including the polymer base portion 289 and / or 299 located between the first portion 221 and the second portion 231 can be in the range of about 1 cm to about 10 cm, about 1 cm to about 8 cm, about 1 cm to about 5 cm, about 2 cm to about 5 cm, about 3 cm to about 5 cm, about 4 cm to about 5 cm, or any range or sub-range therebetween.

[0285] Various aspects of the method of manufacturing a foldable device and / or a foldable substrate according to various aspects of the present disclosure will refer to Figure 12 to Figure 13 The flowchart and Figure 14 to Figure 15 , Figure 17 to Figure 18 , Fig. 20 , Figure 22 to Figure 26 , Figures 28 to 30 and Figure 32 to Figure 35 The exemplary method steps and Fig.16 , Fig.19 , Fig.21 , Fig. 27 , Fig.31 The discussion is based on the cross-sectional diagram illustrated in FIG.

[0286] manufacture Figure 4 and Figures 8 to 9 Exemplary aspects of the illustrated foldable device 401, 801 and / or 901 and / or the foldable substrate 201 will now be referred to. Figures 14 to 25 and Fig.12 In the first step 1201 of the method of the present disclosure, the method can obtain a foldable substrate 1401 (see Figure 14 to Figure 15 ). In various aspects, the foldable substrate 1401 may be provided by purchasing or otherwise obtaining a substrate or by forming a foldable substrate. In various aspects, the foldable substrate 1401 may include a glass-based substrate and / or a ceramic-based substrate. In other aspects, the glass-based substrate and / or the ceramic-based substrate may be provided by forming them using various strip forming processes, such as slot drawing, down-drawing, fusion down-drawing, up-drawing, roller pressing, redrawing or floating. In other aspects, the ceramic-based substrate may be provided by heating a glass-based substrate to crystallize one or more ceramic crystals. The foldable substrate 1401 may include an existing first major surface 1403 that may extend along a first plane 1404. The foldable substrate 1401 may include an existing second major surface 1405 that may extend along a second plane 1406. The existing second major surface 1405 may be opposite to the existing first major surface 1403, and / or the first plane 1404 may be parallel to the second plane 1406. In various aspects, as Fig.14 As shown, in step 1201, the foldable substrate 1401 may include an existing first central surface area 1413 coplanar with the existing first major surface 1403, for example, the existing first major surface 1403 includes the existing first central surface area 1413. In various aspects, as Fig.14 As shown, in step 1201, the foldable substrate 1401 may include an existing second central surface area 1443 coplanar with the existing second major surface 1405, for example, the existing second major surface 1405 includes the existing second central surface area 1443. The central portion 281 includes the existing first central surface area 1413 and the existing second central surface area 1443.

[0287] After step 1201, if Fig.14 As shown, the method may proceed to step 1203, which includes covering the existing second central surface area 1443, for example, by disposing a second barrier layer 1433 on the existing second central surface area 1443. In various aspects, as shown, the second barrier layer 1433 may be disposed on and cover the entire existing second central surface area 1443. In various aspects, as shown, Fig.16 As shown, step 1203 may optionally include disposing a first barrier layer 1435 on the existing first central surface region 1413. In various aspects, as shown, the first barrier layer 1435 may be disposed on and cover the entire existing first central surface region 1413. In various aspects, the first barrier layer 1435 and / or the second barrier layer 1433 may reduce the diffusion of alkali metal ions therethrough during the chemical strengthening in step 1205 (discussed below). In further aspects, the first barrier layer 1435 and / or the second barrier layer 1433 may prevent the diffusion of alkali metal ions therethrough during the chemical strengthening in step 1205 (discussed below). In further aspects, the first barrier layer 1435 and / or the second barrier layer 1433 may include a covalent solid as compared to an ionic solid. Without being bound by theory, the covalent solid may reduce (e.g., prevent, block) the diffusion of alkali metal ions therethrough. In further aspects, the first barrier layer 1435 and / or the second barrier layer 1433 may include one of aluminum nitride (AlN), aluminum oxynitride (AlON, as described above), sputtered silicon nitride (Si3N4), or a combination thereof. In various aspects, the second barrier layer 1433 may include the same material as the first barrier layer 1435. In various aspects, disposing the first barrier layer 1435 and / or the second barrier layer 1433 may include sputtering, chemical vapor deposition, thermal evaporation, or electron beam deposition. Exemplary aspects of disposing the first barrier layer 1435 and / or the second barrier layer 1433 include sputtering. In various aspects, the first barrier layer 1435 and / or the second barrier layer 1433 may include an average thickness of about 5 nanometers (nm) or more, about 10 nm or more, about 20 nm or more, about 50 nm or more, about 100 nm or more, about 10 μm or less, about 2 μm or less, about 1 μm or less, about 500 nm or less, or about 200 nm or less. In various aspects, the first barrier layer 1435 and / or the second barrier layer 1433 may include an average thickness in the range of about 5 nm to about 10 μm, about 5 nm to about 2 μm, about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 20 nm to about 1 μm, about 20 nm to about 500 nm, about 50 nm to about 500 nm, about 50 nm to about 200 nm, about 100 nm to about 200 nm, or any range or sub-range therebetween.

[0288] After step 1201 or 1203, if Fig.15 As shown, the method may proceed to step 1205, which includes initially chemically strengthening the foldable substrate 1401. In various aspects, the foldable substrate 1401 may be substantially unstrengthened prior to the chemical strengthening step of step 1205. As used herein, substantially unstrengthened refers to a substrate comprising: no layer depth, no compression depth, a layer depth in the range of 0% to about 5% of the substrate thickness, or a compression depth in the range of 0% to about 5% of the substrate thickness. In various aspects, as Fig.15 As shown, chemically strengthening the foldable substrate 1401 may include contacting at least a portion of the foldable substrate 1401 including lithium cations and / or sodium cations with a salt bath 1501 including a salt solution 1503. When a first cation within the surface depth of the foldable substrate 1401 is exchanged with a second cation having a larger radius than the first cation within the molten salt or salt solution 1503, chemically strengthening the foldable substrate 1401 (e.g., a glass-based substrate, a ceramic-based substrate) by ion exchange may occur. For example, lithium cations within the surface depth of the foldable substrate 1401 may be exchanged with sodium cations or potassium cations within the salt solution 1503. Therefore, since the lithium cations have a radius that is smaller than the radius of the sodium cations or potassium cations exchanged within the salt solution 1503, the surface of the foldable substrate 1401 is placed in a compressed state and is thereby chemically strengthened by the ion exchange process. Chemically strengthening the foldable substrate 1401 may include contacting at least a portion of the foldable substrate 1401 including lithium cations and / or sodium cations with a salt bath 1501 having a salt solution 1503 including potassium nitrate, potassium phosphate, potassium chloride, potassium sulfate, sodium chloride, sodium sulfate, sodium nitrate, and / or sodium phosphate, whereby the lithium cations and / or sodium cations diffuse from the foldable substrate 1401 into the salt solution 1503 contained in the salt bath 1501. In various aspects, the temperature of the salt solution 1503 may be about 300° C. or more, about 360° C. or more, about 400° C. or more, about 500° C. or less, about 460° C. or less, or about 420° C. or less. In various aspects, the temperature of the salt solution 1503 may be in the range of about 300° C. to about 500° C., about 360° C. to about 460° C., about 400° C. to about 420° C., or any range or sub-range therebetween. In various aspects, the foldable substrate 1401 can be in contact with the saline solution 1503 for about 30 minutes or more, about 45 minutes or more, about 1 hour or more, about 8 hours or less, about 4 hours or less, about 2 hours or less, or about 1.5 hours or less. In various aspects, the foldable substrate 1401 can be in contact with the saline solution 1503 for a time in the range of about 30 minutes to about 8 hours, about 45 minutes to about 4 hours, about 1 hour to about 2 hours, about 1 hour to about 1.5 hours, or any range or sub-range therebetween.

[0289] In various aspects, such as Fig.16 As shown, initially chemically strengthening the foldable substrate 1401 in step 1205 may include chemically strengthening the existing first major surface 1403 in the first portion 1421 and the second portion 1431 to form an initial first compressive stress region extending from the existing first major surface 1403 to an initial first depth 1613 (e.g., a compression depth, a depth of a layer). In various aspects, as Fig.16 As shown, chemically strengthening the foldable substrate 1401 in step 1205 may include chemically strengthening the existing second major surface 1405 in the first portion 1421 and the second portion 1431 to form an initial second compressive stress region extending from the existing second major surface 1405 to an initial second depth 1615 (e.g., a compression depth, a depth of a layer). In various aspects, as described by Fig.16 As indicated by the lack of dots (or open circles 1617) in FIG. 16, the center portion 281 may not be chemically strengthened as a result of step 1205. In various aspects, as indicated by Fig.16 As indicated by the open circle 1617, when the first barrier layer 1435 is not present during step 1205, the existing first central surface region 1413 may be chemically strengthened during step 1205 without chemically strengthening the existing second central surface region 1443. Fig.16 As indicated, since the first distance 1629 of the recess will be greater than the initial first depth 1613, any chemical strengthening at the existing first central surface region 1413 will be removed when the first recess (indicated by dashed line 1619) is formed in step 1211 (discussed below). In various aspects, the initial first depth 1613 and / or the initial second depth 1615 as a percentage of the initial substrate thickness 1409 can be about 10% or more, about 11% or more, about 12% or more, about 13% or more, about 20% or less, about 18% or less, about 16% or less, or about 14% or less. In various aspects, the initial first depth 1613 and / or the initial second depth 1615 as a percentage of the initial substrate thickness 1409 can be in the range of about 10% to about 20%, about 11% to about 18%, about 12% to about 16%, about 13% to about 14%, or any range or sub-range therebetween.

[0290] After step 1205, if Fig.16As shown, the method can proceed to step 1207, which includes removing the first barrier layer 1435 (if present) and / or the second barrier layer 1433. In various aspects, step 1207 can include contacting the first barrier layer 1435 (if present) and / or the second barrier layer 1433 with an alkaline solution. In other aspects, the alkaline solution can include about 20°C or more, about 30°C or more, about 40°C or more, about 50°C or more, about 60°C or more, about 70°C or more, about 120°C or less, about 100°C or less, about 90°C or less, or about 80°C or less. In further aspects, the alkaline solution may comprise a temperature in the range of about 20°C to about 120°C, about 20°C to about 100°C, about 30°C to about 100°C, about 40°C to about 100°C, about 40°C to about 90°C, about 50°C to about 90°C, about 50°C to about 80°C, about 60°C to about 80°C, about 70°C to about 80°C, or any range or sub-range therebetween. In further aspects, the alkaline solution may comprise an alkaline detergent solution, for example, and the concentration of the alkaline detergent is about 1 wt % to about 4 wt %, or about 2 wt % to about 3 wt %. An exemplary aspect of the alkaline detergent solution is Semiclean KG available from Yokohama Oils & Fats Industry Co., Ltd.

[0291] After step 1201 or 1207, if Figure 17 to Figure 18 As shown, the method may proceed to step 1209, which includes providing an etching mask on the foldable substrate 1401 without covering the entire existing first central surface area 1413. In various aspects, as Fig.18 As shown, the first portion 1703b can be disposed on the first portion 221 (eg, the first surface region 1707b of the first portion 1703b can contact the existing first major surface 1403 in the first portion 221). In another aspect, as shown in FIG. Figure 17 to Figure 18 As shown, the second portion 1703a can extend into the central portion 281 by a certain length 1719 (relative to the size of the resulting foldable substrate), for example by accounting for the undercut during step 1211, which can allow for a predetermined size of the resulting foldable substrate. Fig.18 As shown, the second portion 1703a can be disposed on the second portion 231 (eg, the second surface region 1707a of the second portion 1703a can contact the existing first major surface 1403 in the second portion 231). In another aspect, as shown in FIG. Figure 17 to Figure 18 As shown, the second portion 1703a can extend into the central portion 281, for example, by a length equal to the length 1719. In various aspects, as shown in FIG. Figure 17 to Figure 18As shown, the third portion 1705 can be disposed on the existing second main surface 1405 (e.g., including the existing second central surface area 1443) (e.g., the third surface area 1709 of the third portion 1705 contacts the existing second main surface 1405), for example, covering the entire existing second main surface 1405. In various aspects, the etching mask (e.g., the first portion 1703b, the second portion 1703a, the third portion 1705) can include a polymer (e.g., an acid-resistant polymer) or an inorganic material. Exemplary aspects of polymers include polyolefins, polyamides, halogenide-containing polymers (e.g., polyvinyl chloride or fluoropolymers), elastomers, polyurethanes, phenolic resins, polyparaxylene, polyethylene terephthalate (PET) and polyetheretherketone (PEEK) One or more. Exemplary aspects of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE) and polypropylene (PP). Exemplary aspects of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers, and ethylene tetrafluoroethylene (ETFE) polymers. Exemplary aspects of elastomers include rubbers (e.g., polybutadiene, polyisoprene, chloroprene rubber, butyl rubber, nitrile rubber) and block copolymers (e.g., styrene-butadiene, high impact polystyrene, poly(dichlorophosphazene). Exemplary aspects of inorganic materials for the etch mask include titanium dioxide (TiO2), zirconium oxide (ZrO2), tin oxide (SnO2), aluminum oxide (Al2O3), silicon dioxide (SiO2), silicon nitride (Si3N4), and / or combinations thereof, but other materials for the mask may be used in other aspects. In various aspects, the etch mask may be provided by curing a precursor dispensed from a container onto a foldable substrate or by attaching a tape comprising an acid-resistant polymer and an adhesive. Alternatively, another method (e.g., chemical vapor deposition (CVD) (e.g., low pressure CVD, plasma enhanced CVD), physical vapor deposition (PVD) (e.g., evaporation, molecular beam epitaxy, ion plating), atomic layer deposition (ALD)) may be used. deposition; ALD), sputtering, spray pyrolysis, chemical bath deposition, sol-gel deposition) can be used to form the etch mask. Alternatively, as Fig.28 As shown, and discussed below with reference to step 1307, the etching mask may be similar to an etching mask (e.g., first portion 2851) disposed on the polymer layer and the existing first major surface 1403 and comprising a polymer layer (e.g., first polymer layer 2856) and a barrier layer (e.g., first barrier layer 2853).

[0292] After step 1201 or 1209, by comparing Figure 16 to Figure 17 and Fig.18 As shown, the method may proceed to step 1211, which includes etching the existing first central surface region 1413 (see Figure 16 to Figure 17 ) to form a first central surface region 1813. In various aspects, as shown, step 1211 may include contacting at least the existing first central surface region 1413 with an etchant 1803, for example by immersing the foldable substrate 201 in an etchant bath 1801 containing the etchant 1803. In further aspects, the etchant 1803 may include one or more acids (e.g., HCl, HF, H2SO4, HNO3). In various aspects, the etchant 1803 may undercut the first portion 1703b and / or the second portion 1703a of the etch mask, for example, by a length 1719. Step 1211 may form a first central surface region 1813 that may be recessed from the first plane 1704 by a first distance 1629, which may be substantially equal to the difference between the substrate thickness 207 and the central thickness 209 (see Figure 4 ). In various aspects, such as Figure 18 to Figure 19 As shown, step 1211 may further form a first transition zone 212 including a first transition surface region 1815 and / or a second transition zone 218 including a third transition surface region 1817. In further aspects, as shown, the angle between the first transition surface region 1815 and the first central surface region 1813 may be substantially equal to the first average angle 282, and / or the angle between the third transition surface region 1817 and the first central surface region 1813 may be substantially equal to the third average angle 286.

[0293] After step 1211, Fig.19 As shown, the method may proceed to step 1213, which includes removing one or more etching masks. In various aspects, step 1213 may include removing the etching mask using a tool (e.g., grinding, sweeping, scraping, pushing, etc.), cleaning the foldable substrate (e.g., using a detergent solution, using an alkaline solution), or a combination thereof.

[0294] After step 1211 or 1213, if Fig. 20As shown, the method may proceed to step 1215, which includes further chemically strengthening the foldable substrate 201. In various aspects, as shown, step 1215 may include contacting the foldable substrate 201 with the salt solution 2003 for a second time period. In further aspects, as shown, step 1215 may include immersing the foldable substrate 201 in a salt bath 2001 containing the salt solution 2003. In various aspects, the salt solution 2003 may be the same as the salt solution 1503 in step 1205, but the salt solution may be different in other aspects. In further aspects, the salt solution 2003 may include potassium ions. In various aspects, the salt solution 2003 may be maintained at a temperature within one or more of the ranges discussed above for the temperature of the salt solution 1503. In various aspects, the second time period that the salt solution 2003 contacts the foldable substrate 201 may be less than the first time period. In other aspects, the percentage of the second time period to the first time period can be about 2% or more, about 5% or more, about 8% or more, about 10% or more, about 20% or less, about 18% or less, about 15% or less, or about 12% or less. In other aspects, the percentage of the second time period to the first time period can be in the range of about 2% to about 20%, about 5% to about 18%, about 8% to about 15%, about 10% to about 12%, or any range or sub-range therebetween. In various aspects, the second time period can be about 1 minute or longer, about 2 minutes or longer, about 4 minutes or longer, about 10 minutes or shorter, about 8 minutes or shorter, or about 6 minutes or shorter. In various aspects, the second time period can be in the range of about 1 minute to about 10 minutes, about 2 minutes to about 8 minutes, about 4 minutes to about 6 minutes, or any range or sub-range therebetween. In various aspects, the square root of the ratio of the second time period to the first time period may be less than the center thickness divided by the difference between the substrate thickness and the center thickness, which can provide the above-mentioned relationship between the ratio of the first compression depth to the substrate thickness and the ratio of the first center compression depth to the center thickness and / or the ratio of the first depth of the layer to the substrate thickness and the ratio of the first center depth of the layer to the center thickness.

[0295] At the end of step 1215, if Fig.21 As shown, the compressive stress zone extending from the existing first major surface 1403 can increase from an initial first depth (as indicated by open circles 2103) to about a first depth 2109 (as indicated by solid dots 2105). At the end of step 1215 or at the end of step 1217 (discussed below), the first compressive stress zone in the first portion 221 can extend to the first depth 2109 (e.g., the first compression depth, the first depth of the layer) and / or the third compressive stress zone in the second portion 231 can extend to the first depth 2109 (e.g., the third compression depth, the third depth of the layer). At the end of step 1215, as Fig.21As shown, the compressive stress zone extending from the existing second major surface 1405 can increase from the initial second depth (as indicated by open circle 2113) to about second depth 2119 (as indicated by solid dot 2115). At the end of step 1215 or at the end of step 1217 (discussed below), the second compressive stress zone in the first portion 221 can extend to the second depth 2119 (e.g., the second compression depth, the second depth of the layer) and / or the fourth compressive stress zone in the second portion 231 can extend to the second depth 2119 (e.g., the fourth compression depth, the fourth depth of the layer). At the end of step 1215, as Fig.21 As shown, a first central compressive stress zone in the central portion 281 extending from the first central surface area 1813 (as indicated by solid dot 2107) may extend to a first central depth 2129 (e.g., a first central compression depth, a first central depth of the layer) and / or a second central compressive stress zone in the central portion 281 extending from the second central surface area 1843 (as indicated by solid dot 2117) may extend to a second central depth 2139 (e.g., a second central compression depth, a second central depth of the layer). The relationship between these compression depths and / or depths of the layers may correspond to those described above (e.g., the ratio of the first compression depth to the substrate thickness is greater than the amount by which the first central compression depth to the central thickness is greater).

[0296] like Fig.21 As shown, the first surface layer 2101 and / or the second surface layer 2111 may be removed in step 1217 (discussed below). In various aspects, the first surface layer 2101 may be substantially uniform across the existing first major surface 1403, the first transition surface area 1815, the third transition surface area 1817, and / or the first central surface area 1813. In various aspects, the second surface layer 2111 may be substantially uniform across the existing second major surface 1405 (e.g., including the existing second central surface area 1443). In other aspects, the second surface layer 2111 may be substantially equal to the first surface layer 2101. After step 1217, the foldable substrate may correspond to Figure 4 The foldable substrate shown.

[0297] After step 1215, if Fig. 22As shown, the method may proceed to step 1217, which includes substantially uniformly etching a uniform thickness from the foldable substrate 201. In various aspects, as shown, step 1217 may include contacting the foldable substrate 201 with an etchant 2203. In further aspects, as shown, step 1217 may include immersing the foldable substrate 201 in an etchant bath 2201 containing the etchant 2203. In various aspects, the etchant 2203 may be the same as the etchant 1803 discussed above with reference to step 1211. In various aspects, the etchant 2203 may include a lower concentration (e.g., molar concentration) than the etchant 1803. In various aspects, the thickness substantially uniformly removed from the foldable substrate 201 in step 1217 may be about 0.1 μm or more, about 0.2 μm or more, about 0.5 μm or more, about 5 μm or less, about 2 μm or less, about 1 μm or less, or about 0.8 μm or less. In various aspects, the thickness substantially uniformly removed from the foldable substrate 201 in step 1217 may be in the range of about 0.1 μm to about 5 μm, about 0.1 μm to about 2 μm, about 0.2 μm to about 1 μm, about 0.5 μm to about 0.8 μm, or any range or sub-range therebetween. Etching the substrate in step 1217 (after further chemically strengthening the foldable substrate in step 1215) may remove cracks near or at the surface of the foldable substrate 201, which may increase the strength (e.g., pen drop height) and / or flexibility (e.g., the ability to achieve a particular parallel plate distance) of the foldable substrate 201. In various aspects, as shown, at the end of step 1217, etching may produce a foldable substrate having a substrate thickness 207 and a center thickness 209. In various aspects, as shown, at the end of step 1217, etching may form a foldable substrate having the thickness 207 and the center thickness 209 described above with reference to Figure 4 The first surface area 223, the second surface area 225, the third surface area 233, the fourth surface area 235, the first central surface area 213 and / or the second central surface area 243 of the discussed characteristics.

[0298] After step 1215 or 1217, if Figure 23 to Figure 25 As shown, the method can proceed to step 1219, which includes assembling a foldable device from the foldable substrate 201. For example, step 1219 can include disposing one or more adhesive layers, disposing one or more polymer-based portions, disposing one or more coatings, disposing a release liner or display device, and / or a combination thereof on the foldable substrate. In various aspects, one or more materials can at least partially fill the first recessed portion 211, although not shown, the recessed portion may not be completely filled, for example to leave room for electronic devices and / or mechanical devices. In various aspects, as shown Fig.23As shown, one or more adhesive layers 2301 may be at least partially disposed in the first recess 211. In other aspects, as shown, the first layer 2301 may be disposed in the first recess 211 (e.g., contacting the first central surface area 213), and the second layer 2303 may be disposed thereon and / or disposed to contact the first major surface 203 (e.g., the first surface area 223, the third surface area 233). As shown, the one or more layers 2301 may form an adhesive layer 261, which includes a first contact surface 263 facing and / or contacting the first major surface 203 (e.g., the first surface area 223, the third surface area 233) and / or the first central surface area 213. Alternatively, although not shown, the adhesive layer may be formed by dispensing a precursor liquid that is cured to form the adhesive layer 261 (e.g., similar to the method for forming the polymer-based portion discussed in the next sentence). In various aspects, as Fig.24 As shown, the precursor liquid 2403 can be dispensed from a container 2401 (e.g., a catheter, a flexible tube, a micropipette, or a syringe) to at least partially fill the first recess 211. The precursor liquid 2403 can be cured (e.g., heated, irradiated, and / or waited) to form Fig.25 The polymer base portion 299 is shown. In another aspect, as Fig.26 As shown, the adhesive layer 261 (e.g., one or more layers as described above) can be disposed on the polymer base portion 299 and / or the first major surface 203 (e.g., using the first contact surface 263 to contact the polymer base portion and the first major surface 203). In another aspect, the isolation liner 271 can be disposed on the second contact surface 265 of the adhesive layer 261 to form Figure 4 The foldable device 401 is shown. In various aspects, the foldable substrate 201 can be a rollable substrate, and / or the foldable substrate 201 can be replaced by a display device 3811, for example. Figure 4 The release liner 271 is shown assembled with Fig.38 The foldable device 3801 shown is similar or identical to the foldable device.

[0299] After step 1215, 1217 or 1219, the method may proceed to step 1221, where the method of manufacturing a foldable substrate and / or a foldable device may be completed. In various aspects, the method of manufacturing a foldable substrate and / or a foldable device according to various aspects of the present disclosure may be performed as described above. Fig.121201, 1203, 1205, 1207, 1209, 1211, 1213, 1215, 1217, and 1219 of the flowchart in . In various aspects, the method can follow arrow 1202 from step 1201 to step 1205, for example, in the case where a barrier layer is already disposed on the foldable substrate at the end of step 1201. In various aspects, the method can follow arrow 1204 from step 1201 to step 1204, for example, in the case where the foldable substrate already includes an initial compressive stress region at the end of step 1201. In various aspects, the method can follow arrow 1206 from step 1201 to step 1211, for example, in the case where the foldable substrate already includes an initial compressive stress region and has an etching mask disposed thereon at the end of step 1201. In various aspects, the method may follow arrow 1210 from step 1211 to step 1215, for example, in the case where the etching mask is permeable to ions in the salt solution, will be removed by the salt solution, or has been removed at the end of step 1211. In various aspects, the method may follow arrow 1212 from step 1215 to step 1217, for example, in the case where the foldable substrate is not uniformly etched before being assembled in the foldable device. In various aspects, the method may follow arrow 1214 from step 1215 to step 1221, for example, in the case where the method is complete at the end of step 1215. In various aspects, the method may follow arrow 1216 from step 1217 to step 1221, for example, in the case where the method is complete at the end of step 1217. Any of the above options can be combined to manufacture a foldable device according to an embodiment of the present disclosure.

[0300] manufacture Figures 2 to 3 and Figure 6 to Figure 7 Exemplary aspects of the illustrated foldable device 101, 301, 501 and / or 701 and / or the foldable substrate 201 will now be referred to. Figure 26 to Figure 35 and Fig.13 In the first step 1301 of the method of the present disclosure, the method can obtain a foldable substrate 1401 (see Fig.26 ) starts. Step 1301 may include any one (one or more) of the aspects discussed above with reference to step 1201.

[0301] After step 1301, Fig.26 As shown, the method may proceed to step 1303, which includes initially chemically strengthening the foldable substrate 1401. In various aspects, the foldable substrate 1401 may be substantially unstrengthened prior to the chemical strengthening step of step 1303. In various aspects, as Fig.26As shown, chemically strengthening the foldable substrate 1401 can include contacting at least a portion of the foldable substrate 1401 including lithium cations and / or sodium cations with a salt bath 1501 including a salt solution 1503. The salt solution 1503 can include any one or more of the materials discussed above with reference to step 1205. The salt solution 1503 can be maintained at a temperature within one or more of the ranges discussed above with reference to step 1205. The foldable substrate 1401 can be contacted with the salt solution 1503 for a first period of time, which can be within one or more of the ranges discussed above with reference to step 1205.

[0302] like Fig. 27 As shown, initially chemically strengthening the foldable substrate 1401 in step 1303 may include chemically strengthening the existing first major surface 1403 and / or the central portion 281 in the first portion 1421 and the second portion 1431 to form an initial first compressive stress region extending from the existing first major surface 1403 to an initial first depth 2713 (e.g., a compression depth, a depth of a layer). In various aspects, as Fig. 27 As shown, chemically strengthening the foldable substrate 1401 in step 1303 may include chemically strengthening the existing second major surface 1405 and / or the central portion 281 in the first portion 1421 and the second portion 1431 to form an initial second compressive stress region extending from the existing second major surface 1405 to an initial second depth 2715 (e.g., compression depth, depth of the layer). The percentage of the initial first depth 2713 and / or the initial second depth 2715 to the initial substrate thickness may be as described above with respect to reference Fig.16 Although the central portion is initially chemically strengthened at the end of step 1303, since the first recessed portion first distance 2727 will be greater than the initial first depth 2713, the chemical strengthening at the existing first central surface region 1413 will be removed when the first recessed portion (as indicated by dashed line 2717) is formed in step 1307 (discussed below), and since the second recessed portion second distance 2729 will be greater than the initial second depth 2715, the chemical strengthening at the existing second central surface region 1443 will be removed when the second recessed portion (as indicated by dashed line 2719) is formed in step 1307 (discussed below).

[0303] After step 1303, if Fig.28As shown, the method can proceed to step 1305, which includes disposing an etch mask on the foldable substrate. In various aspects, the etch mask can be similar to and / or include any (one or more) of the aspects discussed above with respect to portions 1703a, 1703b, and / or 1705 discussed above with reference to step 1209, but with spaces between portions of the etch mask corresponding to a portion of the first central surface area and a portion of the second central surface area. Alternatively, in various aspects, as Fig.28 As shown, the etching mask may include a first portion 2851 including a first barrier layer 2853 disposed on a first polymer layer 2856, and / or the etching mask may include a second portion 2861 including a second barrier layer 2863 disposed on a second polymer layer 2866. In further aspects, the first polymer layer 2856 may be disposed on the first barrier layer 2853, and then the first portion 2851 is disposed on the foldable substrate 1401. Alternatively, in further aspects, the first polymer layer 2856 may be disposed on the foldable substrate 1401, and then the first barrier layer 2853 is disposed on the first polymer layer 2856. In further aspects, as shown, the first portion 2851 and / or the second portion 2861 can be disposed on and / or at least partially adhered to the existing first major surface 1403 (e.g., by an adhesive layer not shown), for example, where the first contact surface 2855 of the first barrier layer 2853 and / or the second contact surface 2865 of the second barrier layer 2863 are disposed on and / or at least partially adhered to the existing first major surface 1403. As used herein, a first layer is partially adhered to a second layer if a portion of the first layer is adhered to the second layer, but the entire surface of the first layer is not necessarily adhered to the second layer. In even further aspects, as shown, the first contact surface 2855 of the first barrier layer 2853 can be disposed on and / or attached to the sixth contact surface 2859 of the first polymer layer 2856, and / or the second contact surface 2865 of the second barrier layer 2863 can be disposed on and / or attached to the eighth contact surface 2869 of the second polymer layer 2866. In even further aspects, as shown, the fifth contact surface 2857 of the first polymer layer 2856 can be disposed on (e.g., not directly adhered to) the existing first major surface 1403, and / or the seventh contact surface 2867 of the second polymer layer 2866 can be disposed on (e.g., not directly adhered to) the existing first major surface 1403.

[0304] In various aspects, such as Fig.28As shown, the first polymer layer 2856 may include a first width 2847 and / or the second polymer layer 2866 may include a second width 2849. In further aspects, the first width 2847 and / or the second width 2849 may be about 100 μm or more, about 150 μm or more, about 200 μm or more, about 300 μm or more, about 400 μm or more, about 3 mm or less, about 1 mm or less, about 700 μm or less, or about 500 μm or less. In further aspects, the first width 2847 and / or the second width 2849 may be in the range of about 100 μm to about 3 mm, about 150 μm to about 1 mm, about 200 μm to about 700 μm, about 300 μm to about 500 μm, or any range or sub-range therebetween. The resulting first transition width 214 of the first transition zone 212 can be greater than the first width 2847 and / or the resulting second transition width 216 of the second transition zone 218 can be greater than the second width 2849. Providing the first polymer layer 2856 and / or the second polymer layer 2866 can achieve longer widths of the transition zones than otherwise achievable.

[0305] In various aspects, such as Fig.28 As shown, the first polymer layer 2856 can be positioned at the first inner peripheral portion 2858 of the first portion 2851 (e.g., flush with the first barrier layer 2853), and / or the second polymer layer 2866 can be positioned at the second inner peripheral portion 2868 of the second portion 2861 (e.g., flush with the second barrier layer 2863). In various aspects, as Fig.28 As shown, the minimum distance 2841 can be defined between the first inner peripheral portion 2858 and the second inner peripheral portion 2868. In other aspects, the minimum distance 2841 can be about 1 mm or more, about 2 mm or more, about 5 mm or more, about 10 mm or more, about 50 mm or less, about 40 mm or less, about 30 mm or less, or about 20 mm or less. In various aspects, the minimum distance 2841 can be in the range of about 1 mm to about 50 mm, about 1 mm to about 40 mm, about 2 mm to about 40 mm, about 5 mm to about 30 mm, about 10 mm to about 20 mm, or any range or sub-range therebetween. In other aspects, the minimum distance 2841 can be within one or more of the ranges discussed above for the width 287 of the center portion 281, for example in terms of absolute distance and / or as a multiple of the minimum parallel plate distance. In other aspects, the minimum distance 2841 can be less than the width 287 of the center portion 281 of the resulting foldable device (see Figure 2 and Figure 4 ). In further aspects, the minimum distance 2841 can be substantially equal to the width 210 of the first central surface region 213 (eg, the central region 248).

[0306] In various aspects, the first polymer layer 2856 and / or the second polymer layer 2866 may include one or more of a polyolefin, a polyamide, a halide-containing polymer (e.g., polyvinyl chloride or a fluoropolymer), an elastomer, a polyurethane, a phenolic resin, polyparaxylene, polyethylene terephthalate (PET), and polyetheretherketone (PEEK). Exemplary aspects of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), and polypropylene (PP). Exemplary aspects of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymer, and ethylene tetrafluoroethylene (ETFE) polymer. Exemplary aspects of elastomers include rubbers (e.g., polybutadiene, polyisoprene, chloroprene rubber, butyl rubber, nitrile rubber) and block copolymers (e.g., styrene-butadiene, high impact polystyrene, poly(dichlorophosphazene). An exemplary aspect of the polymer used for the first polymer layer 2856 and / or the second polymer layer 2866 is poly(ethylene terephthalate). In various aspects, there may be no adhesive layer of the first polymer layer 2856 and / or the second polymer layer 2866 contacting the existing first major surface 1403 of the foldable substrate 1401.

[0307] In various aspects, the first barrier layer 2853 and / or the second barrier layer 2863 may include, for example, a polymer tape including a polymer film and an adhesive film. In other aspects, the polymer film may include one or more of the materials discussed above for the first polymer layer 2856. An exemplary aspect of the polymer film is a polyimide. In other aspects, the adhesive film may include a pressure-sensitive adhesive. In other aspects, the adhesive film may include a silicone-based polymer, an acrylate-based polymer, an epoxy-based polymer, a polyimide-based material or a polyurethane. In even other aspects, the adhesive film may include an ethylene acid copolymer. Exemplary aspects of ethylene acid copolymers include SURLYN (e.g., Surlyn PC-2000, Surlyn 8940, Surlyn 8150) from Dow. Examples of epoxy resins include bisphenol-based epoxy resins, novolac-based epoxy resins, alicyclic-based epoxy resins, and glycidylamine-based epoxy resins. An exemplary aspect of the adhesive film is an organosilicon-based polymer (e.g., organosilicon). Thus, an exemplary aspect of the first barrier layer 2853 and / or the second barrier layer 2863 is a polymer tape having a polymer film comprising polyimide and an adhesive film comprising organosilicon. The first barrier layer 2853 and the second barrier layer 2863 are resistant to an etchant (e.g., acid) that can be used to etch the foldable substrate. In various aspects, although not shown, the barrier layer (e.g., the first barrier layer 2853, the second barrier layer 2863) can be adhered to the foldable substrate 1401 (e.g., the existing first main surface 1403) through the adhesive layer of the corresponding barrier layer. In various aspects, although not shown, the barrier layers (e.g., the first barrier layer 2853, the second barrier layer 2863) may be adhered to the corresponding polymer layers (e.g., the first polymer layer 2856, the second polymer layer 2866) via adhesive layers of the corresponding barrier layers and / or adhesive layers of the corresponding polymer layers (e.g., Maxi 689BL-003 (Maxi Adhesive Products, Inc.) or JVCC EGPF-01 (JVConverting Company, Inc.)).

[0308] In various aspects, such as Fig.28As shown, the etching mask may further include a third portion 2871 including a third barrier layer 2873 disposed on a third polymer layer 2876, and / or the etching mask may further include a fourth portion 2881 including a fourth barrier layer 2883 disposed on a fourth polymer layer 2886. In further aspects, the third polymer layer 2876 may be disposed on the third barrier layer 2873, and then the third portion 2871 is disposed on the foldable substrate 1401. Alternatively, in further aspects, the third polymer layer 2876 may be disposed on the foldable substrate 1401, and then the third barrier layer 2873 is disposed on the third polymer layer 2876. In further aspects, as shown, the third portion 2871 and / or the fourth portion 2881 may be disposed on the existing second major surface 1405 and / or at least partially adhered to the existing second major surface (e.g., by an adhesive layer not shown), for example, wherein the third contact surface 2875 of the third barrier layer 2873 and / or the fourth contact surface 2885 of the fourth barrier layer 2883 are disposed on and / or at least partially adhered to the existing second major surface 1405. In even further aspects, as shown, the third contact surface 2875 of the third barrier layer 2873 may be disposed on and / or attached to the tenth contact surface 2879 of the third polymer layer 2876, and / or the fourth contact surface 2885 of the fourth barrier layer 2883 may be disposed on and / or attached to the twelfth contact surface 2889 of the fourth polymer layer 2886. In even further aspects, as shown, the ninth contact surface 2877 of the third polymer layer 2876 can be disposed on (e.g., not directly adhered to) the existing second major surface 1405, and / or the eleventh contact surface 2887 of the fourth polymer layer 2886 can be disposed on (e.g., not directly adhered to) the existing second major surface 1405. In various aspects, the third polymer layer 2876 can include a third width that can be substantially equal to the first width 2847, and / or the fourth polymer layer 2886 can include a fourth width that can be substantially equal to the second width 2849. In various aspects, as Fig.28 As shown, the third polymer layer 2876 can be positioned at the third inner peripheral portion 2878 of the third portion 2871 (e.g., flush with the third barrier layer 2873), and / or the fourth polymer layer 2886 can be positioned at the fourth inner peripheral portion 2888 of the fourth portion 2881 (e.g., flush with the fourth barrier layer 2883). In various aspects, as Fig.28 As shown, the minimum distance between the third inner peripheral portion 2878 and the fourth inner peripheral portion 2888 can be substantially equal to the minimum distance 2841.

[0309] In various aspects, step 1305 may further include degassing the etch mask by placing the foldable substrate in a vacuum. As used herein, vacuum refers to an absolute pressure of 1,000 Pascals or less. Placing the etch mask in a vacuum can dissipate bubbles between the barrier layer and the foldable substrate and / or increase the adhesion between the barrier layer and the foldable substrate, which can increase the uniformity of the resulting foldable substrate. In other aspects, the etch mask can be degassed in a vacuum for about 1 minute or more, about 2 minutes or more, about 5 minutes or more, about 15 minutes or less, about 12 minutes or less, or about 10 minutes or less. In other aspects, the etch mask can be degassed in a vacuum for about 1 minute to about 15 minutes, about 2 minutes to about 12 minutes, about 5 minutes to about 10 minutes, or any range or sub-range therebetween.

[0310] After step 1301 or 1305, if Fig.29 As shown, the method may proceed to step 1307, which includes etching the existing first central surface region 1413 (see Figure 27 to Figure 28 ) to form the first central surface region 1813, and / or to etch the existing second central surface region 1443 (see, for example, Figure 27 to Figure 28) to form the second central surface region 1843. In various aspects, as shown, step 1307 can include contacting at least the existing first central surface region 1413 and / or the existing second central surface region 1443 with an etchant 1803, for example, by immersing the foldable substrate 201 in an etchant bath 1801 containing the etchant 1803. In further aspects, the etchant 1803 can include one or more acids (e.g., HCl, HF, H2SO4, HNO3). In various aspects, the etchant 1803 can undercut the first polymer layer 2856, the second polymer layer 2866, the third polymer layer 2876, and / or the fourth polymer layer 2886, for example, by a corresponding width of the polymer layer. Step 1307 can form the first central surface region 1813 that can be recessed a first distance 2727 from the existing first major surface 1403. Step 1307 may form a second central surface region 1843 that may be recessed a second distance 2729 from the existing second major surface 1405. The central region 248 including the first central surface region 1813 and the second central surface region 1843 may include a width 2920 that may be substantially equal to the width 210. Step 1307 may form the first transition surface region 215 and / or the second transition surface region 245 including the first transition region 212 with a width 2924 that may be substantially equal to the first transition width 214. Step 1309 may form the third transition surface region 217 and / or the fourth transition surface region 247 including the third transition region 218 with a width 2926 that may be substantially equal to the second transition width 216. In various aspects, as shown in the figures, the angle between the first transition surface area 215 and the first center surface area 1813 may be substantially equal to the first average angle 282, the angle between the second transition surface area 245 and the second center surface area 1843 may be substantially equal to the second average angle 284, the angle between the third transition surface area 217 and the first center surface area 1813 may be substantially equal to the third average angle 286, and / or the angle between the fourth transition surface area 247 and the second center surface area 1843 may be substantially equal to the fourth average angle 288.

[0311] After step 1301 or 1307, if Fig.30 As shown, the method may proceed to step 1309, which includes removing the etch mask. Step 1309 may include any one (one or more) of the aspects discussed above with reference to step 1213.

[0312] After step 1307 or 1309, if Fig.30 As shown, the method may proceed to step 1311, which includes further chemically strengthening the foldable substrate. Step 1311 may include any one or more of the aspects discussed above with reference to step 1215.

[0313] At the end of step 1311, if Fig.31 As shown, the compressive stress zone extending from the existing first major surface 1403 can increase from an initial first depth (as indicated by open circles 3103) to about a first depth 3109 (as indicated by solid dots 3105). At the end of step 1311 or at the end of step 1313 (discussed below), the first compressive stress zone in the first portion 221 can extend to the first depth 3109 (e.g., the first compression depth, the first depth of the layer) and / or the third compressive stress zone in the second portion 231 can extend to the first depth 3109 (e.g., the third compression depth, the third depth of the layer). At the end of step 1311, as Fig.31 As shown, the compressive stress zone extending from the existing second major surface 1405 can increase from the initial second depth (as indicated by the open circle 3113) to about the second depth 3119 (as indicated by the solid point 3115). At the end of step 1311 or at the end of step 1313 (discussed below), the second compressive stress zone in the first portion 221 can extend to the second depth 3119 (e.g., the second compression depth, the second depth of the layer) and / or the fourth compressive stress zone in the second portion 231 can extend to the second depth 3119 (e.g., the fourth compression depth, the fourth depth of the layer). At the end of step 1311, as Fig.21 As shown, a first central compressive stress zone in the central portion 281 extending from the first central surface area 1813 (as indicated by solid dot 3107) may extend to a first central depth 3129 (e.g., a first central compression depth, a first central depth of the layer) and / or a second central compressive stress zone in the central portion 281 extending from the second central surface area 1843 (as indicated by solid dot 3117) may extend to a second central depth 3139 (e.g., a second central compression depth, a second central depth of the layer). The relationship between these compression depths and / or depths of the layers may correspond to those described above (e.g., the ratio of the first compression depth to the substrate thickness is greater than the amount by which the first central compression depth to the central thickness is greater).

[0314] like Fig.31 As shown, the first surface layer 3101 and / or the second surface layer 3111 may be removed in step 1313 (discussed below). In various aspects, the first surface layer 3101 may be substantially uniform across the existing first major surface 1403, the first transition surface area 215, the third transition surface area 217, and / or the first central surface area 1813. In various aspects, the second surface layer 3111 may be substantially uniform across the existing second major surface 1405, the second transition surface area 245, the fourth transition surface area 247, and / or the second central surface area 1843. In other aspects, the second surface layer 3111 may be substantially equal to the first surface layer 3101. After step 1315, the foldable substrate may correspond to Figures 2 to 3 The foldable substrate shown.

[0315] After step 1311, if Fig.32 As shown, the method can proceed to step 1313, which includes substantially uniformly etching a uniform thickness from the foldable substrate 201. In various aspects, as shown, step 1313 can include contacting the foldable substrate 201 with an etchant 2203. In further aspects, as shown, step 1313 can include immersing the foldable substrate 201 in an etchant bath 2201 containing the etchant 2203. In various aspects, the etchant 2203 can be the same as the etchant 1803 discussed above with reference to steps 1211 and 1307. In various aspects, the etchant 2203 can include a lower concentration (e.g., molar concentration) than the etchant 1803. In various aspects, the thickness substantially uniformly removed from the foldable substrate 201 in step 1313 may be about 0.1 μm or more, about 0.2 μm or more, about 0.5 μm or more, about 5 μm or less, about 2 μm or less, about 1 μm or less, or about 0.8 μm or less. In various aspects, the thickness substantially uniformly removed from the foldable substrate 201 in step 1313 may be in the range of about 0.1 μm to about 5 μm, about 0.1 μm to about 2 μm, about 0.2 μm to about 1 μm, about 0.5 μm to about 0.8 μm, or any range or sub-range therebetween. Etching the substrate in step 1313 (after further chemically strengthening the foldable substrate in step 1311) may remove cracks near or at the surface of the foldable substrate 201, which may increase the strength (e.g., pen drop height) and / or flexibility (e.g., ability to achieve a particular parallel plate distance) of the foldable substrate 201. In various aspects, as shown, at the end of step 1217, etching can produce a foldable substrate having a substrate thickness 207 and a center thickness 209. In various aspects, as shown, at the end of step 1313, etching can form a foldable substrate having the above reference Figures 2 to 3 The first surface area 223, the second surface area 225, the third surface area 233, the fourth surface area 235, the first central surface area 213 and / or the second central surface area 243 of the discussed characteristics.

[0316] After step 1311 or 1315, if Figure 33 to Figure 35 As shown, the method may proceed to step 1315, which includes assembling a foldable device including a foldable substrate. In various aspects, as Figure 33 to Figure 35 As shown, step 1317 may include assembling the foldable device by disposing a polymer base portion (e.g., first polymer base portion 289, second polymer base portion 299), adhesive layer 261 and / or coating 251 on foldable substrate 201. In another aspect, as Fig.33As shown, the first polymer-based portion 289 can be disposed within the first recess 211 and / or on the first central surface region 213. In another aspect, as shown in FIG. Figure 33 to Figure 34 As shown, the coating 251 can be disposed on the first major surface 203 (e.g., the first surface area 223 and the third surface area 233), for example, by dispensing a first liquid 3303 from a container 3301 (e.g., a catheter, a flexible tube, a micropipette, or a syringe) onto the first major surface 203, and the first liquid can be cured to form the coating 251. In even further aspects, the first liquid 3303 can include a coating precursor, a solvent, particles, nanoparticles, and / or fibers. In still further aspects, the coating precursor can include, but is not limited to, one or more of a monomer, an accelerator, a curing agent, an epoxy resin, and / or an acrylate. Curing the first liquid 3303 can include heating the first liquid 3303, irradiating the first liquid 3303 with ultraviolet (UV) radiation, and / or waiting a predetermined amount of time (e.g., about 30 minutes to 24 hours, about 1 hour to about 8 hours). In various aspects, although not shown, for example, instead of Figure 33 to Figure 35 In the first polymer base portion 289, the coating 251 can be disposed within the first recess 211 (e.g., fills the first recess 211) without contacting the first major surface 203 (e.g., the first surface region 223, the third surface region 233). In another aspect, as Figure 33 to Figure 35 As shown, the second polymer-based portion 299 can be disposed in the second recess 241, for example, by dispensing a second liquid 2403 from a container 2401 (e.g., a catheter, a flexible tube, a micropipette, or a syringe) onto the second central surface area 243, and the second liquid can be cured to form the second polymer-based portion 299. Curing the second liquid 2403 can include heating the second liquid 2403, irradiating the second liquid 2403 with ultraviolet (UV) radiation, and / or waiting a predetermined amount of time (e.g., about 30 minutes to 24 hours, about 1 hour to about 8 hours). In another aspect, as Fig.35 As shown, the adhesive layer 261 can contact the second major surface 205 (e.g., the second surface area 225 and the fourth surface area 235). For example, the adhesive layer 261 can include one or more sheets of adhesive material. In various aspects, there can be an integrated interface between the one or more sheets comprising the adhesive layer 261, which can reduce (e.g., avoid) optical diffraction and / or optical discontinuity when light travels between the sheets because the one or more sheets can include substantially the same refractive index. In various aspects, although not shown, at least a portion of the adhesive layer can be disposed in the second recessed portion. In various aspects, a release liner (e.g., see Figure 2The release liner 271 in the adhesive layer 261 or the display device may be disposed on the adhesive layer 261 (eg, the second contact surface 265). In various aspects, the foldable substrate 201 may be a rollable substrate, and / or the foldable substrate 201 may be replaced by, for example, a display device 3811. Figure 2 The release liner 271 is shown assembled with Fig.39 The foldable device 3901 shown is similar or identical to the foldable device.

[0317] After step 1311, 1313 or 1315, the method may proceed to step 1317, where the method of manufacturing a foldable substrate and / or a foldable device may be completed. In various aspects, the method of manufacturing a foldable substrate and / or a foldable device according to various aspects of the present disclosure may be performed as described above. Fig.13 1309, 1311, 1313, 1315, and 1317 of the flowchart in FIG. 1301. In various aspects, the method may follow arrow 1302 from step 1301 to step 1305, for example, in the case where the foldable substrate already includes an initial compressive stress region at the end of step 1301. In various aspects, the method may follow arrow 1301 to step 1304, for example, in the case where the foldable substrate already includes an initial compressive stress region at the end of step 1301 and has an etch mask disposed thereon at the end of step 1301. In various aspects, the method may follow arrow 1306 from step 1307 to step 1311, for example, in the case where the etch mask is permeable to ions in the salt solution, will be removed by the salt solution, or has been removed at the end of step 1307. In various aspects, the method may follow arrow 1308 from step 1311 to step 1315, for example, in the case where the foldable substrate is not uniformly etched before being assembled in the foldable device. In various aspects, the method may follow arrow 1310 from step 1311 to step 1317, for example, in the case where the method is complete at the end of step 1311. In various aspects, the method may follow arrow 1312 from step 1313 to step 1317, for example, in the case where the method is complete at the end of step 1313. Any of the above options can be combined to manufacture a foldable device according to an embodiment of the present disclosure.

[0318] Examples

[0319] Various aspects will be further illustrated by the following examples. Examples AG and AA-BB comprised glass-based substrates (Composition 1 having the following nominal compositions expressed in mol %: 63.6 SiO2; 15.7 Al2O3; 10.8 Na2O; 6.2 Li2O; 1.16 ZnO; 0.04 SnO2; and 2.5 P2O5) having dimensions of 100 mm x 160 mm in a direction perpendicular to the thickness of the substrate. Examples AG and Examples AA-BB were prepared according to the method discussed above. Fig.13 The flowchart in is processed to form Figure 3 The foldable substrate shown is similar to the foldable substrate 201. Unless otherwise stated, the properties reported in Table 1 are based on at least 5 samples of each example.

[0320] Table 1 presents the processing conditions and characteristics of Examples AG and Examples AA-BB. A monolithic substrate (substantially comprising the substrate thickness described in Table 1) is initially chemically strengthened in a salt solution containing 100 wt % KNO3 maintained at 410°C for the time described in Table 1 (IOX#1). The monolithic substrate is then masked and etched to form a first recess and a second recess, and the distance therebetween is substantially equal to the center thickness described in Table 1. The etched substrate is then further chemically strengthened in a salt solution containing 100 wt % KNO3 maintained at 410°C for the time described in Table 1 (IOX#2). Example B is then etched to remove approximately 0.5 μm from the thickness of the foldable substrate (i.e., approximately 0.25 μm from each surface) to form the substrate thickness and center thickness described in Table 1. Examples A, CG, and AA-BB are not subjected to etching after the foldable substrate is further chemically strengthened. Cases AG and AA-BB include a first depth of compression (as a ratio to substrate thickness) (1st DOC) and a first center depth of compression (as a ratio to center thickness) (1st center DOC).

[0321] Example A and Example AA include a center width of the center portion described in Table 1, which is centered in the foldable substrate (at the midpoint of the foldable substrate) (e.g., about 73 mm on each side of the center portion). The substrate thickness and center thickness in Example A and Example AA are 102 μm and 32 μm, respectively. Example A and Example AA include a transition width of 0.3 mm. The first center compression depth (expressed in μm and as a ratio to the center thickness) is 5.4 μm (0.169) in Example A and AA. Example A includes a first compression depth of 19.3 μm, corresponding to a ratio of the first compression depth to the substrate thickness of 0.189. Therefore, the ratio of the first compression depth to the substrate thickness is 0.02 greater than the first center compression depth to the center thickness. As shown in Table 1, none of the samples of Example A buckled.

[0322] In contrast, Example AA includes a first compression depth of 17.2 μm, corresponding to a ratio of the first compression depth to the substrate thickness of 0.169. Therefore, the ratio of the first compression depth to the substrate thickness is equal to (i.e., not greater than) the first center compression depth to the center thickness. As shown in Table 1, 20% of the samples of Example AA buckled. In addition, 20% of the samples of Example AA exhibited corrugations. Comparing Example A to Example AA, a ratio of the first compression depth to the substrate thickness greater than the first center compression depth to the center thickness can reduce the incidence of buckling (or other mechanical instabilities). As discussed above, this result is unexpected because the conditions of Example A were expected to exceed the critical buckling strain of the center portion (calculated for samples comprising a substrate material having a uniform thickness), which would be expected to result in the onset of mechanical instability (e.g., buckling).

[0323] Example B includes a center width as described in Table 1, which is offset from the midpoint of the foldable substrate by 30 μm (18.7% of the substrate thickness) (e.g., 73 mm on one side of the center portion and 10 mm on the other side of the center portion). As shown in Table 1, the substrate thickness is 150 μm and the center thickness is 56 μm. Examples A and AA include a transition width of 0.3 mm. The first compression depth is 18 μm, and the ratio of the first compression depth to the substrate thickness is 0.12. The first center compression depth is 5.5 μm, and the ratio of the first center compression depth to the center thickness is 0.10. Similar to Example A, in Example B, the ratio of the first compression depth to the substrate thickness is 0.02 greater than the first center compression depth to the center thickness. As shown in Table 1, none of the samples of Example B buckled. Examples A and Example B demonstrate that the principle is applicable to foldable substrates in which the center portion is centered on the midpoint of the foldable substrate and when the center portion is displaced from the midpoint of the foldable substrate.

[0324] Example C is the same as Example AA, except that for Example C, the second chemical strengthening step is 10 minutes longer. The first center compression depth (in μm and as a ratio to center thickness) is 6.75 μm (0.21) in Example C, and the first compression depth is 17.2 μm, corresponding to a first compression depth to substrate thickness ratio of 0.169. Therefore, the ratio of the first compression depth to substrate thickness is 0.04 greater than the first center compression depth to center thickness. As shown in Table 1, none of the samples of Example C buckled.

[0325] Table 1: Characteristics of instances AG and AA-BB

[0326]

[0327]

[0328] Examples DG and BB include a center width of the center portion described in Table 1, which is centered in the foldable substrate (at the midpoint of the foldable substrate) (e.g., about 73 mm on each side of the center portion). The substrate thickness and center thickness in Examples DG and BB are 102 μm and 32 μm, respectively. Examples A and AA include a transition width of 1.0 mm.

[0329] For Example BB, the first center compression depth (in μm and as a ratio to the center thickness) was 5.45 μm (0.169), and the first compression depth was 17.2 μm (0.169). The ratio of the first compression depth to the substrate thickness was designed to be equal to the first center compression depth to the center thickness. As shown in Table 1, 94% of the samples of Example BB buckled. The increased center width (and the associated increase in transition width) made Example CC more susceptible to buckling (when the difference in the ratio of DOC to the corresponding thickness was 0) compared to Example AA. The larger center width increases the amount of foldable substrates with lower critical buckling strains (associated with the center thickness).

[0330] Example D includes the same dimensions as Example BB, but the first compression depth is increased from 17.2 μm (0.169) to 19.3 μm (0.189). Therefore, the ratio of the first compression depth to the substrate thickness in Example D is designed to be 0.02 greater than the first center compression depth to the center thickness (instead of 0 in Example BB). As shown in Table 1, 73% of the samples of Example D buckled. Compared to Example BB, the increased ratio of the first compression depth to the substrate thickness in Example D relative to the ratio of the first center compression depth to the center thickness reduces the fraction of buckled samples. Compared to Example B, the increased center thickness of Example B increases the critical buckling strain that the sample can withstand without buckling, which (in addition to the smaller center width) explains the reason why the fraction of buckled samples of Example B is lower than that of Example D.

[0331] Example E includes the same dimensions as Example D, but the first center compression depth is reduced from 5.4 μm (0.169) to 5.0 μm (0.156). Therefore, the ratio of the first compression depth to the substrate thickness in Example E is designed to be 0.033 greater than the first center compression depth to the center thickness (instead of 0.02 in Example D). As shown in Table 1, 57% of the samples of Example E buckled. Compared to Example D, the increased ratio of the first compression depth to the substrate thickness in Example E relative to the ratio of the first center compression depth to the center thickness reduces the fraction of samples that buckle. This continues the trend from Example BB to Example D described above.

[0332] Example F includes the same dimensions as Example DE, but the first center compression depth is reduced to 4.0 μm (0.125) (from 5.4 μm (0.169) in Example D and from 5.0 μm (0.156) in Example E). Therefore, the ratio of the first compression depth to the substrate thickness in Example F is designed to be 0.064 greater than the first center compression depth to the center thickness (instead of 0.02 in Example D and 0.033 in Example E). As shown in Table 1, 0% of the samples of Example F buckle. Compared to Example DE, the increased ratio of the first compression depth to the substrate thickness in Example E relative to the ratio of the first center compression depth to the center thickness reduces the fraction of samples that buckle (to 0%).

[0333] Example G includes the same dimensions as Example DF, but the first center compression depth (from 5.4 μm (0.169) in Example D and from 5.0 μm (0.156) in Example E and from 4.0 μm (0.125) in Example F) is reduced to 3.0 μm (0.094). Therefore, the ratio of the first compression depth to the substrate thickness in Example G is designed to be 0.095 greater than the first center compression depth to the center thickness (instead of 0.02 in Example D, 0.033 in Example E and 0.064 in Example F). As shown in Table 1, the 0% buckling of the sample of Example G.

[0334] Table 2 presents the distribution of the difference between the ratio of the first center DOC to the center thickness and the ratio of the first DOC to the substrate thickness for Example A, Example CG, and Example BB. As shown, most of the samples of Example A have a difference in DOC ratio of 0.02 to 0.03, which is consistent with the average value of about 0.02 for Example A. 10% to 20% of the samples in Example A have a difference in DOC ratio of 0.01 to 0.02 and 0.03 to 0.04. A smaller fraction of the samples of Example A have a difference in DOC ratio of 0 to 0.01. About 30% of the samples in Example C have a difference in DOC ratio of 0.03 to 0.04 and 0.04 to 0.05, which is consistent with the average difference in DOC ratio of about 0.04 for Example C. The distribution of Example C is skewed to the right (higher values), while the distribution of Example A is relatively symmetrical. Given the natural variation in the DOC ratio differences corresponding to the distributions shown in Table 2, providing a DOC ratio difference of 0.01 to 0.20 (eg, 0.02 to 0.12) may reduce the incidence of buckling.

[0335] Table 2: Distribution of Instance A, Instance CG and Instance BB

[0336]

[0337] Most samples of Example BB included a difference in DOC ratio of less than 0.01. The distribution of the difference in DOC ratio of Example D was extended from 0 to 0.03. Most samples of Example E included a difference in DOC ratio of 0.02 to 0.03. In Example FG, most samples included a difference in DOC ratio of greater than 0.05, and (as described above for Table 1) Example FG did not have any sample curvature.

[0338] Example BB and Example DG include larger center widths (20 mm) compared to Example A and Example C (14 mm). As discussed above with reference to Table 1, larger center widths are associated with higher buckling rates at comparable DOC ratio differences (e.g., compare Example AA with Example BB, or compare Example A with Example D). In fact, samples of Example A with a DOC ratio difference of 0.01 to 0.02 (and with higher DOC ratio differences) did not buckle. In contrast, all samples of Example DE with a DOC ratio difference of 0.01 to 0.02 buckled. For Example E, some (not all) of the samples with a DOC ratio of 0.02 to 0.03 buckled, while other samples with the same DOC ratio did not buckle. For Example DG, all samples with a DOC ratio greater than 0.03 (e.g., 0.03 to 0.04, 0.04 to 0.05, and 0.05 to 0.08) did not buckle.

[0339] The above observations can be combined to provide a foldable substrate comprising a low minimum parallel plate distance, high impact resistance, increased durability, reduced fatigue, and reduced incidence of mechanical instability. The substrate and / or portion can include a glass-based and / or ceramic-based portion that can provide good dimensional stability, reduced incidence of mechanical instability, good impact resistance, and / or good puncture resistance. The portions can include a glass-based and / or ceramic-based portion that includes one or more compressive stress regions that can further provide increased impact resistance and / or increased puncture resistance. By providing a substrate comprising a glass-based and / or ceramic-based substrate, the substrate can also provide increased impact resistance and / or puncture resistance while facilitating good folding performance. In various aspects, the substrate thickness can be large enough (e.g., from about 50 microns (micrometers or μm) to about 2 millimeters) to further enhance impact resistance and puncture resistance. Providing a foldable substrate including a central portion (the central thickness of the central portion being less than the thickness of the substrate (e.g., the first thickness of the first portion and / or the second thickness of the second portion) (e.g., about 10 μm or greater)) can achieve a small parallel plate distance (e.g., about 10 mm or less) based on the reduced thickness in the central portion, which can achieve foldability and / or rollability of the foldable substrate and / or foldable device.

[0340] In various aspects, the foldable device and / or the foldable substrate may include one or more recesses, for example, a first central surface area recessed a first distance from the first major surface and / or a second central surface area recessed a second distance from the second major surface. Providing a first recess opposite to the second recess may provide a central thickness that is less than the thickness of the substrate. In addition, providing a first recess opposite to the second recess may reduce the strain induced by the maximum bending of the foldable device, for example between the central portion and the first portion and / or the second portion, because the central portion including the central thickness may be closer to the neutral axis of the foldable device and / or the foldable substrate than when only a single recess is provided. In addition, providing a first distance that is substantially equal to the second distance may reduce the incidence of mechanical instability in the central portion, for example, because the foldable substrate is symmetrical about a plane including the midpoint of the substrate thickness and the central thickness. In addition, providing a first recess opposite to the second recess may reduce the strain induced by bending of the material positioned in the first recess and / or the second recess compared to a single recess having a surface recessed the sum of the first distance and the second distance. Providing reduced bending-induced strain of the material positioned in the first recess and / or the second recess can enable 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 the impact resistance, puncture resistance, abrasion resistance, and / or scratch resistance of the foldable device. In addition, controlling the properties of the first material positioned in the first recess and the second material positioned in the second recess can control the position of the neutral axis of the foldable device and / or the foldable substrate, which can reduce (e.g., mitigate, eliminate) the incidence of mechanical instability, device fatigue, and / or device failure.

[0341] In various aspects, the foldable device and / or foldable substrate may include a first transition region attaching the center portion to the first portion and / or a second transition region attaching the center portion to the second portion. Providing a transition region with a smoothly and / or monotonically decreasing (e.g., continuously decreasing) thickness can reduce stress concentration in the transition region and / or avoid optical distortion. Providing a transition region of sufficient length (e.g., about 0.15 mm or more or about 0.3 mm or more) can avoid optical distortion that may otherwise exist due to a sharp change in the thickness of the foldable substrate. Providing a sufficiently large average transition angle of the first transition surface area of ​​the first transition region relative to the first center surface area (e.g., about 167° or more or about 170° or more) can avoid optical distortion and / or reduce the visibility of the transition region. Providing a sufficiently small average transition angle (e.g., about 179° or less or about 176° or less) can reduce the amount of foldable devices and / or foldable substrates having intermediate thicknesses, which can have reduced impact resistance and / or reduced puncture resistance.

[0342] As discussed above, it was unexpectedly discovered that providing a ratio of the first compression depth to the substrate thickness that is greater than the ratio of the first central compression depth to the central thickness (even when the difference is greater than 0.01) can reduce the incidence of buckling, while the opposite relationship (i.e., a relationship where the ratio of the first central compression depth to the central thickness is greater than the ratio of the first compression depth to the substrate thickness) does not hold. Unexpectedly, as described below, it has been determined that providing a ratio of the first depth of the layer to the substrate thickness that is greater than the ratio of the first central depth to the central thickness of the layer (even when the difference is greater than 0.001) can reduce the incidence of buckling, while the opposite relationship (i.e., a relationship where the ratio of the first central depth to the central thickness of the layer is greater than the ratio of the first depth of the layer to the substrate thickness) does not hold. Such configurations can impart a stabilizing force on the central portion that suppresses fluctuations in the surface profile that could otherwise lead to the onset of mechanical instability (e.g., buckling), which can enable the central portion to withstand a critical buckling strain, wherein the critical buckling strain is calculated for a sample comprising a substrate material having a uniform thickness. This is unexpected because, by definition, exceeding the critical buckling strain is expected to result in the onset of mechanical instability (e.g., buckling). In addition, providing such configurations can improve manufacturing yields because a larger portion of the foldable substrate will be free of mechanical instability (e.g., buckling) (e.g., compared to a case where the ratio of the first compression depth or first depth of the layer to the substrate thickness is less than or equal to the ratio of the first central compression depth or first central depth of the layer to the central thickness).

[0343] The foldable substrate may be used as a rollable substrate having a central width greater than a second width. Providing a second width of about 15 mm or less (e.g., about 2 mm to about 6 mm) and / or about 15% or less (e.g., about 2% to about 6%) of the length of the foldable substrate may provide sufficient width to handle the ends of the foldable substrate during processing to secure the foldable substrate and / or the foldable device as part of an electronic device, and / or to maximize the amount of the foldable substrate and / or the foldable device that may be part of a display portion visible to a user. Providing a central portion of about 15% to about 50% (e.g., about 40% to about 48%) of the length of the foldable substrate may enable adjustment of the display portion of the foldable device because a portion of the rollable substrate is moved into and / or out of the user's field of view when in a fully rolled-up configuration without having to enlarge the size of the corresponding device. Providing a first width of the first portion that is approximately 35% or greater (e.g., approximately 40% to approximately 70%) of the length of the foldable substrate can provide a large display portion visible to a user while ensuring that substantially all of the remaining foldable substrate (e.g., the center portion and the second portion) can be within the footprint of the first portion.

[0344] The methods of various aspects of the present disclosure can use an etching mask and an etchant to manufacture a foldable substrate and / or a foldable device including a center thickness that is less than the substrate thickness (e.g., about 10 μm or greater). In various aspects, using a barrier layer when initially chemically strengthening the foldable substrate before etching the foldable substrate to form a first recessed portion can enable a ratio of a first compression depth or a first depth of a layer to a substrate thickness that is greater than a ratio of a first center compression depth or a first depth of a layer to a center thickness. In various aspects, initially chemically strengthening the foldable substrate before etching the foldable substrate to form a first recessed portion and a second recessed portion can enable a ratio of a first compression depth or a first depth of a layer to a substrate thickness that is greater than a ratio of a first center compression depth or a first depth of a layer to a center thickness. In various aspects, the design of the etching mask can tune the first transition width and / or the second transition width. Placing the etching mask in a vacuum can dissipate bubbles between the barrier layer and the foldable substrate and / or increase adhesion between the barrier layer and the foldable substrate, which can increase the uniformity of the resulting foldable substrate.

[0345] Directional terms used herein—eg, up, down, right, left, front, back, top, bottom—are made with reference only to the drawings depicted and are not intended to imply an absolute orientation.

[0346] It will be understood that the various aspects disclosed may relate to features, elements or steps described in conjunction with that aspect. It will also be understood that features, elements or steps, although described with respect to one aspect, may be interchanged or combined with alternative aspects in various combinations or arrangements not illustrated.

[0347] It should also be understood that the terms "the," "a," or "an" as used herein mean "at least one," and should not be limited to "only one," unless clearly indicated to the contrary. For example, reference to "a" component includes aspects having two or more such components unless the context clearly indicates otherwise. Likewise, "plurality" is intended to mean "more than one."

[0348] As used herein, the term "about" means that the amount, size, formula, parameter and other quantity and characteristics are not and need not be exact, but may be approximate and / or larger or smaller as needed, reflecting tolerances, conversion factors, truncation, measurement errors, etc., and other factors known to those skilled in the art. Ranges may be expressed herein as from "about" or "approximately" a particular value and / or to "about" or "approximately" another particular value. When such a range is expressed, aspects include from one particular value and / or to another particular value. Similarly, when a value is expressed as an approximate value by means of the antecedent "about", it will be understood that the particular value forms another aspect. Whether or not the numerical value or endpoint of a range in the specification states "about", the numerical value or endpoint of the range is intended to include two aspects: one modified by "about" and one not modified by "about". It will be further understood that the endpoints of each of the ranges are important in relation to and independent of the other endpoint.

[0349] As used herein, the terms "substantial," "substantially," and variations thereof are intended to indicate that the feature being described is equal to or approximately equal to a value or description. For example, a "substantially planar" surface is intended to mean a planar or approximately planar surface. Additionally, as defined above, "substantially similar" is intended to mean that two values ​​are equal or approximately equal. In various aspects, "substantially similar" may mean values ​​that are within about 10% of each other, such as within about 5% of each other, or within about 2% of each other.

[0350] Unless explicitly stated otherwise, it is not intended that any method described herein be construed as requiring that its steps be performed in a specific order. Therefore, if a method claim does not actually recite the order in which its steps are to be followed or if it is not otherwise specifically stated in the claims or description that such steps are to be limited to a specific order, it is not intended that any specific order be inferred.

[0351] Although the transition phrase "comprising" may be used to disclose various features, elements, or steps of a particular aspect, it should be understood that alternative aspects, including those aspects that may be described using the transition phrases "consisting of" or "consisting essentially of," are implied. Thus, for example, implicit alternative aspects of a device comprising A+B+C include aspects wherein the device consists of A+B+C and aspects wherein the device consists essentially of A+B+C. Unless otherwise noted, as used herein, the terms "comprising" and "including" and variations thereof should b...

Claims

1. A foldable substrate, comprising: a substrate thickness defined between a first major surface and a second major surface opposite the first major surface; a first portion, the first portion comprising the substrate thickness, a first compressive stress region extending from the first major surface to a first compressive depth, and a second compressive stress region extending from the second major surface to a second compressive depth; a second portion, the second portion comprising the substrate thickness, a third compressive stress region extending from the first major surface to a third compressive depth, and a fourth compressive stress region extending from the second major surface to a fourth compressive depth; and a central portion, the central portion being positioned between the first portion and the second portion, the central portion comprising a central thickness defined between a first central surface region and a second central surface region opposite the first central surface region, a first central compressive stress region extending from the first central surface region to a first central compressive depth, a second central compressive stress region extending from the second central surface region to a second central compressive depth, and the central thickness being less than the substrate thickness, The foldable substrate comprises a glass-based material or a ceramic-based material, the first central surface region is recessed a first distance from the first major surface, and a ratio of the first compression depth to the substrate thickness is greater than a ratio of the first central compression depth to the central thickness.

2. The foldable substrate of claim 1, wherein the ratio of the first compression depth to the substrate thickness is about 0.01 to about 0.2 greater than the ratio of the first center compression depth to the center thickness.

3. The foldable substrate of any one of claims 1-2, wherein the ratio of the first compression depth to the substrate thickness is about 0.015 to about 0.15 greater than the ratio of the first center compression depth to the center thickness.

4. The foldable substrate of any one of claims 1-3, wherein the ratio of the first compression depth to the substrate thickness is about 0.02 to about 0.12 greater than the ratio of the first center compression depth to the center thickness.

5. The foldable substrate according to any one of claims 1 to 4, wherein: The first portion further comprises: a first depth of one or more alkali metal ion layers associated with the first compression depth and a second depth of one or more alkali metal ion layers associated with the second compression depth; The second portion further includes: a third depth of one or more alkali metal ion layers associated with the third compression depth and a fourth depth of one or more alkali metal ion layers associated with the fourth compression depth, The central portion further comprises: a first central depth of one or more alkali metal ion layers associated with the first central compression depth, a second central depth of one or more alkali metal ion layers associated with the second central compression depth, and A ratio of a first depth of the layer to a thickness of the substrate is greater than a ratio of a first center depth of the layer to the center thickness.

6. A foldable substrate as described in any one of claims 1-5, wherein the width of the second portion is approximately 15 mm or less, the width of the first portion is greater than the width of the center portion, the width of the center portion is greater than the width of the second portion, and the sum of the width of the first portion, the width of the center portion, and the width of the second portion corresponds to the size of the foldable substrate.

7. The foldable substrate of claim 6, wherein the width of the second portion is about 2 mm to about 6 mm.

8. A foldable substrate, comprising: a substrate thickness defined between a first major surface and a second major surface opposite the first major surface; a first portion, the first portion comprising the substrate thickness, a first compressive stress region extending from the first major surface to a first compressive depth, and a second compressive stress region extending from the second major surface to a second compressive depth; a second portion, the second portion comprising the substrate thickness, a third compressive stress region extending from the first major surface to a third compressive depth, and a fourth compressive stress region extending from the second major surface to a fourth compressive depth; and a central portion, the central portion being positioned between the first portion and the second portion, the central portion comprising a central thickness defined between a first central surface region and a second central surface region opposite the first central surface region, a first central compressive stress region extending from the first central surface region to a first central compressive depth, a second central compressive stress region extending from the second central surface region to a second central compressive depth, and the central thickness being less than the substrate thickness, wherein the foldable substrate comprises a glass-based material or a ceramic-based material, the first central surface area is recessed a first distance from the first major surface, and the width of the first portion, the width of the central portion, and the width of the second portion are measured in a direction corresponding to the size of the foldable substrate, the width of the second portion accounts for less than 15% of the size of the foldable substrate, and the width of the first portion accounts for approximately 35% or more of the size of the foldable substrate.

9. A foldable substrate as described in any one of claims 1-7, wherein the width of the first portion, the width of the central portion and the width of the second portion are measured in a direction corresponding to the size of the foldable substrate, the width of the second portion accounts for less than 15% of the size of the foldable substrate, and the width of the first portion accounts for about 35% or more of the size of the foldable substrate.

10. The foldable substrate of any one of claims 8-9, wherein the width of the second portion accounts for about 2% to about 6% of the dimension of the foldable substrate.

11. The foldable substrate of any one of claims 8-10, wherein the width of the first portion accounts for about 40% to about 70% of the foldable substrate.

12. The foldable substrate of any one of claims 8-11, wherein the width of the central portion accounts for about 15% to about 50% of the foldable substrate.

13. The foldable substrate of any one of claims 1-12, wherein the second central surface region is recessed a second distance from the second major surface.

14. The foldable substrate of any one of claims 1-12, wherein the second major surface includes the second central surface area.

15. The foldable substrate of any one of claims 1-14, wherein the first distance is about 20% to about 45% of the thickness of the substrate.

16. A foldable substrate as described in any one of claims 1-15, wherein the first compressive stress region comprises a first maximum compressive stress of about 400 MPa or greater, the second compressive stress region comprises a second maximum compressive stress, the third compressive stress region comprises a third maximum compressive stress of about 400 MPa or greater, the fourth compressive stress region comprises a fourth maximum compressive stress, the first central compressive stress region comprises a first central maximum compressive stress of about 400 MPa or greater, and the second central compressive stress region comprises a second central maximum compressive stress.

17. The foldable substrate of any one of claims 1-16, wherein the substrate thickness is in the range of about 50 microns to about 2 millimeters.

18. The foldable substrate of any one of claims 1-17, wherein the center thickness is in a range of about 25 microns to about 120 microns.

19. The foldable substrate of any one of claims 1-18, wherein the foldable substrate achieves a parallel plate distance of 1 mm to 10 mm.

20. The foldable substrate of any one of claims 1-18, wherein the foldable substrate achieves a parallel plate distance of 5 mm.

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