Foldable substrate and method of manufacturing the same

Abstract

A foldable substrate has a first portion, a second portion, and a central portion therebetween, wherein a first transition region forms a first average angle with respect to a first central surface region of the central portion. In various aspects, the first average angle is about 176.1° to about 179.9° or about 177.0° to about 179.9°. In various aspects, the polymer angle is about 178.3° to about 179.9° or about 179.1° to about 179.9°. The method includes placing an etching mask above a first main surface of the foldable substrate prior to etching the foldable substrate. In various aspects, the etching mask includes a first polymer layer located between a first barrier layer and the first main surface. In various aspects, the etching mask includes a plurality of inkjet-printed shapes. A method for measuring contrast ratio includes illuminating a transparent device with a collimated beam.

Description

Cross-references to related applications

[0001] This application claims priority to U.S. Application Serial No. 18 / 409627, filed January 10, 2024, pursuant to 35 USC § 120, which in turn claims priority to U.S. Provisional Application Serial No. 63 / 545576, filed October 25, 2023, pursuant to 35 USC § 119. The contents of each of these applications are incorporated herein by reference in their entirety. Technical Field

[0002] This disclosure generally relates to foldable substrates and manufacturing methods, and more specifically, to foldable substrates including a first central surface region recessed from a first main surface and methods for manufacturing foldable substrates. Background Technology

[0003] Glass substrates are commonly used in display devices, such as liquid crystal displays (LCDs), electrophoretic displays (EPDs), organic light-emitting diode displays (OLEDs), and plasma display panels (PDPs).

[0004] There is a desire to develop foldable displays and foldable protective covers for mounting on them. Foldable displays and covers should possess good impact and puncture resistance. Simultaneously, they should have a small minimum bending radius (e.g., approximately 10 mm or less). However, plastic displays and covers with small minimum bending radii tend to have poor impact and / or puncture resistance. Furthermore, it is conventionally believed that ultra-thin glass sheets with small minimum bending radii (e.g., approximately 75 micrometers (μm or micron) or thinner) tend to have poor impact and / or puncture resistance. Conversely, thicker glass sheets with good impact and / or puncture resistance (e.g., greater than 125 micrometers) tend to have relatively large minimum bending radii (e.g., approximately 30 mm or greater). Therefore, there is a need to develop foldable devices with small minimum bending radii and good impact and puncture resistance. Summary of the Invention

[0005] This document describes a foldable device including a foldable substrate, a foldable substrate, and a method of manufacturing the foldable device and the foldable substrate including the foldable substrate, said foldable substrate comprising a first portion and a second portion. The portions may include glass-like and / or ceramic portions, which provide good dimensional stability, a reduced rate of mechanical instability, good impact resistance, and / or good puncture resistance. The first and / or second portions may include glass-like and / or ceramic portions, which include one or more compressive stress zones, further improving impact resistance and / or puncture resistance. By providing a substrate comprising a glass-like and / or ceramic substrate, such substrate also improves impact resistance and / or puncture resistance while promoting good folding performance. In all aspects, the substrate thickness may be sufficiently large (e.g., from about 80 micrometers (µm) to about 2 millimeters) to further enhance impact resistance and puncture resistance. A foldable substrate is provided in which the center thickness of its central portion is less than the substrate thickness, thus enabling a smaller parallel plate spacing (e.g., about 10 millimeters or less) while reducing the thickness of the central portion.

[0006] In various aspects, the foldable device and / or foldable substrate may include multiple recesses, such as a first central surface region recessed from a first main surface by a first distance and a second central surface region recessed from a second main surface by a second distance. Providing opposing first and second recesses can provide a central thickness less than the substrate thickness. Furthermore, providing opposing first and second recesses can reduce the maximum bending strain of the foldable device, for example, the bending strain between the central portion and the first and / or second portions, because the central portion, including the central thickness, can be closer to the central axis of the foldable device and / or foldable substrate compared to providing only a single recess. Additionally, making the first distance substantially equal to the second distance can reduce the incidence of mechanical instability in the central portion, for example, because the foldable substrate is symmetrical about a plane that includes the midpoint between the substrate thickness and the central thickness. Moreover, compared to a single recess whose surface is recessed by the sum of the first and second distances, providing opposing first and second recesses can reduce the bending strain of the material located in the first and / or second recesses. Having reduced bending strain in the material located in the first and / or second recesses allows for a wider range of applications for the material due to reduced strain requirements. For example, a harder and / or more rigid material can be located in the first groove, which can improve the impact resistance, puncture resistance, abrasion resistance, and / or scratch resistance of the foldable device. Additionally, controlling the properties of the first material located in the first groove and the second material located in the second groove can control the position of the intermediate 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 a central portion to a first portion and / or a second transition region attaching a central portion to a second portion. Smoothing and / or monotonically decreasing (e.g., continuously decreasing) the thickness of the transition region can reduce stress concentration in the transition region and / or avoid optical distortion. Providing a sufficiently long transition region (e.g., from about 2 mm to about 5 mm, from about 2.2 mm to about 4 mm, or from about 2.5 mm to about 3.5 mm) can reduce the visibility of the transition region (e.g., achieving a lower contrast ratio and / or creating a transition region invisible to the naked eye), for example, measured by contrast ratio as defined herein. A sufficiently long transition region (and / or associated average transition angle) and / or polymer angle (defined herein) can prevent optical distortion that would otherwise be perceptible to the user (which could be caused by abrupt changes in the thickness of the foldable substrate), for example, a contrast ratio of about 0.27 or less, about 0.26 or less, or 0.25 or less. See references... Figure 29 As discussed in Example AE, a contrast ratio of 0.25 or lower may be invisible to the naked eye (e.g., to the user).

[0008] Providing a sufficiently large average transition angle and / or a surface angle of the first transition surface region relative to the first central surface region (e.g., from about 176.1° to about 179.9° or from about 177.0° to about 179.9°) can reduce optical distortion and / or decrease the visibility of the transition region, making it imperceptible to the user. See Examples 1-4 and... Figure 30 As shown, when the foldable substrate includes a first groove and a second groove opposite to the first groove, the average transition angle and / or surface angle can be from about 176.1° to about 179.9° or from about 177.0° to about 179.9° to produce a contrast ratio of 0.25 or lower, which relates to a transition area that is not visible to the naked eye. See Examples 5-8 and... Figure 30 As shown, when the foldable substrate includes a second groove and the second central surface region is flush with the second main surface, the average transition angle can be from about 176.1° to about 179.9° to produce a contrast ratio of 0.25 or lower, which is related to the transition area that is not visible to the naked eye.

[0009] Providing a sufficiently large polymer angle (e.g., from about 178.3° to about 179.9° or from about 179.1° to about 179.9°) can reduce optical distortion and / or decrease the visibility of the transition zone, making it imperceptible to the user. See Examples 1-4 and... Figure 30 As shown, when the foldable substrate includes a first groove and a second groove opposite to the first groove, the polymer angle can be about 178.3° to about 179.9° or about 179.1° to about 179.9° to produce a contrast ratio of 0.25 or lower, which relates to a transition region that is not visible to the naked eye. See Examples 5-8 and... Figure 30 As shown, when the foldable substrate includes a second groove and the second central surface region is flush with the second main surface, the polymer angle can be from about 179.1° to about 179.9° to produce a contrast ratio of 0.25 or lower, which is related to the transition region that is not visible to the naked eye.

[0010] Furthermore, providing a polymeric material with a refractive index close to (e.g., within 0.1 or less, within 0.05 or less, within 0.02 or less, or within 0.01 or less) that of the foldable substrate within the groove can further reduce the visibility of the transition region (e.g., achieving a lower contrast ratio and / or creating a transition region invisible to the naked eye), as illustrated in Comparative Examples 3-4 or Examples 7-8. When the polymeric material does not extend beyond the groove, providing a distance of approximately 5 µm or less (e.g., approximately 2 µm or less) between the contact surface of the polymeric portion and the corresponding main surface of the foldable substrate contributes to a low contrast ratio (e.g., low visibility) in the transition region. Alternatively, a portion of the polymeric portion may be located within the groove, while another portion (e.g., a continuous portion) of the polymeric portion may further contact the main surface of the foldable substrate, which can reduce optical distortion.

[0011] The methods of various aspects of this disclosure can use an etching mask and an etchant to form a transition region. An etching mask providing a polymer layer at the peripheral portion of the etching mask can form a transition width (e.g., about 1.5 mm or wider, about 1.5 mm to about 5 mm, about 2 mm to about 4 mm), an average transition angle (e.g., about 178.3° to about 179.9° or about 179.1° to about 179.9°), and / or a surface angle (e.g., about 178.3° to about 179.9° or about 179.1° to about 179.9°) that is greater than the transition region of a comparative etching mask (see Examples 10-12). Not wishing to be bound by theory, during etching, the polymer layer can be deflected away from the foldable substrate, allowing the etchant to approach other portions of the foldable substrate that would otherwise have been in contact with the polymer layer. While the etchant can contact other portions of the foldable substrate through the deflection of the polymer layer, the diffusion of the etchant to these other portions is limited, which restricts the degree of etching of those other portions, thus creating a transition region.

[0012] Alternatively, the method may include inkjet printing multiple shapes (e.g., on an existing first central surface region and / or an existing first main surface), which can be etched to form a central portion (e.g., a first transition region, a second transition region, a central region). Having one or more of the multiple shapes have a width of about 500 nm to about 50 μm allows the underlying foldable substrate to be etched, resulting in a substantially continuous and / or smooth surface (e.g., ...). Figure 2-5The first transition surface region 215, the third transition surface region 217, and / or the first central surface region 213 are shown in the diagram. In each respect, the fractional area distribution (of the corresponding predetermined pattern) can be proportional to the amount of material removed by etching to produce predetermined first transition regions and predetermined second transition regions in the etching of step 1207. It is not intended to be theoretically constrained, but it is believed that the shape of this disclosure is small enough that the undercut of the etchant (e.g., an isotropic etchant) can produce a relatively smooth surface (e.g., without identifiable flat points corresponding to the predetermined pattern). Simultaneously, it is believed that the shape of this disclosure is large enough to confine etching (e.g., etchant diffusion) to regions with a higher fractional area, thereby producing the predetermined distribution.

[0013] The following describes some example aspects of this disclosure. It should be understood that any of the features of each aspect may be used alone or in combination with each other.

[0014] Aspect 1. A foldable device including a foldable substrate, said foldable substrate comprising:

[0015] The substrate thickness is in the range of about 80 micrometers to about 5 millimeters, the substrate thickness being defined between a first main surface and a second main surface opposite to the first main surface, and the foldable substrate includes glass-like materials or ceramic materials;

[0016] The first part includes the substrate thickness between a first surface region of the first main surface and a second surface region of the second main surface;

[0017] The second part includes the substrate thickness between the third surface region of the first main surface and the fourth surface region of the second main surface; and

[0018] The central portion includes:

[0019] The center thickness is less than the substrate thickness and is in the range of about 20 micrometers to about 200 micrometers. The center thickness is defined between a first center surface region and a second center surface region opposite to the first center surface region, and the first center surface region is recessed from the first main surface by a first distance and defines a first groove.

[0020] A first transition region, comprising a first transition surface region extending at a first average angle relative to the first central surface region between the first surface region and the first central surface region, and the thickness of the first transition region smoothly and monotonically decreasing between the substrate thickness of the first portion and the central thickness of the central portion; and

[0021] The second transition region includes a third transition surface region that extends at a third average angle relative to the first central surface region between the third surface region and the first central surface region, and the thickness of the second transition region smoothly and monotonically decreases between the substrate thickness of the second portion and the center thickness of the central portion.

[0022] The first average angle is in the range of approximately 178.3° to approximately 179.9°.

[0023] Aspect 2. The foldable device according to aspect 1, wherein the first average angle is in the range of about 178.5° to about 179.0°.

[0024] Aspect 3. The foldable device according to any one of Aspects 1 to 2, wherein the first transition width of the first transition region is in the range of about 2.0 mm to about 6.0 mm.

[0025] Aspect 4. The foldable device according to any one of Aspects 1 to 3, wherein the second central surface region is flush with the second surface region and the fourth surface region.

[0026] Aspect 5. The foldable device according to any one of Aspects 1 to 4, further comprising a polymeric portion located in the first recess, wherein the absolute value of the difference between the first refractive index of the foldable substrate and the second refractive index of the polymeric portion is about 0.1 or less.

[0027] Aspect 6. The foldable device according to aspect 5, wherein the absolute value of the difference between the first refractive index and the second refractive index of the foldable substrate is about 0.01 or less.

[0028] Aspect 7. The foldable device according to any one of Aspects 5 to 6, wherein the polymer portion includes a first contact surface facing the first central surface region and a second contact surface opposite to the first contact surface, wherein the distance between the first main surface and the second contact surface in the substrate thickness direction is about 5 micrometers or less.

[0029] Aspect 8. The foldable device according to any one of Aspects 5 to 6, wherein the polymeric portion further extends beyond the plane defined by the first main surface.

[0030] Aspect 9. The foldable device according to any one of Aspects 5 to 8, wherein the foldable device comprises a contrast ratio of about 0.25 or less, and the contrast ratio is defined as the difference between the maximum fractional intensity and the minimum fractional intensity measured using a contrast test, divided by the sum of the maximum fractional intensity and the minimum fractional intensity.

[0031] Aspect 10. The foldable device according to any one of Aspects 1 to 9, wherein the first distance, expressed as a percentage of the thickness of the substrate, is in the range of about 50% to about 80%.

[0032] Aspect 11. The foldable device according to any one of Aspects 1 to 10, wherein the substrate thickness is in the range of about 100 micrometers to about 400 micrometers, and the center thickness is in the range of about 25 micrometers to about 80 micrometers.

[0033] Aspect 12. The foldable device according to any one of aspects 1 to 11, wherein the third average angle is substantially equal to the first average angle.

[0034] Aspect 13. The foldable device according to any one of Aspects 1 to 12, wherein the foldable substrate achieves a parallel plate spacing of 10 mm.

[0035] Aspect 14. The foldable device according to any one of Aspects 1 to 13, wherein the foldable substrate includes a minimum parallel plate spacing in the range of about 0.5 mm to about 10 mm.

[0036] Aspect 15. The foldable device according to any one of Aspects 1 to 14, wherein the second central surface region is recessed from the second main surface by a second distance and defines a second groove, the first transition region further includes a second transition surface region extending at a second average angle relative to the second central surface region between the second surface region and the second central surface region, and the second transition region further includes a fourth transition surface region extending at a fourth average angle relative to the second central surface region between the fourth surface region and the second central surface region.

[0037] Aspect 16. A foldable device including a foldable substrate, the foldable substrate comprising:

[0038] The substrate thickness is in the range of about 80 micrometers to about 5 millimeters, the substrate thickness being defined between a first main surface and a second main surface opposite to the first main surface, and the foldable substrate includes glass-like materials or ceramic materials;

[0039] The first part includes the substrate thickness between a first surface region of the first main surface and a second surface region of the second main surface;

[0040] The second part includes the substrate thickness between the third surface region of the first main surface and the fourth surface region of the second main surface; and

[0041] The central portion includes:

[0042] The center thickness is less than the substrate thickness and is in the range of about 20 micrometers to about 200 micrometers. The center thickness is defined between a first center surface region and a second center surface region opposite to the first center surface region. The first center surface region is recessed from the first main surface by a first distance and defines a first distance. The second center surface region is recessed from the second main surface by a second distance and defines a second groove.

[0043] A first transition region, comprising a first transition surface region and a second transition surface region, wherein the first transition surface region extends at a first average angle relative to the first central surface region between the first surface region and the first central surface region, and the second transition surface region extends at a second average angle relative to the second central surface region between the second surface region and the second central surface region, and the thickness of the first transition region smoothly and monotonically decreases between the substrate thickness of the first portion and the central thickness of the central portion; and

[0044] The second transition region includes a third transition surface region and a fourth transition surface region. The third transition surface region extends at a third average angle relative to the first central surface region between the third surface region and the first central surface region. The fourth transition surface region extends at a fourth average angle relative to the second central surface region between the fourth surface region and the second central surface region. The thickness of the second transition region smoothly and monotonically decreases between the substrate thickness of the second portion and the center thickness of the central portion.

[0045] The first average angle is in the range of about 179.1° to about 179.9°.

[0046] Aspect 17. The foldable device according to any one of Aspects 15 to 16, wherein the first average angle is in the range of about 179.2° to about 179.5°.

[0047] Aspect 18. The foldable device according to any one of aspects 15 to 17, wherein the second average angle is in the range of about 179.1° to about 179.9°.

[0048] Aspect 19. The foldable device according to any one of aspects 15 to 18, wherein the first average angle is substantially equal to the third average angle.

[0049] Aspect 20. The foldable device according to any one of aspects 15 to 19, wherein the first average angle is substantially equal to the second average angle.

[0050] Aspect 21. The foldable base device according to any one of Aspects 15 to 20, wherein the first transition width of the first transition region is in the range of about 2.0 mm to about 6.0 mm.

[0051] Aspect 22. The foldable device according to any one of aspects 15 to 21, further comprising:

[0052] The first polymeric portion located in the first groove, wherein the absolute value of the difference between the first refractive index of the foldable substrate and the second refractive index of the first polymeric portion is about 0.1 or less; and

[0053] The second polymer portion located in the second groove has an absolute value of the difference between the first refractive index of the foldable substrate and the third refractive index of the second polymer portion of about 0.1 or less.

[0054] Aspect 23. The foldable device according to aspect 22, wherein the absolute value of the difference between the first refractive index and the second refractive index of the foldable substrate is about 0.01 or less.

[0055] Aspect 24. The foldable device according to any one of Aspects 22 to 23, wherein the absolute value of the difference between the first refractive index and the third refractive index of the foldable substrate is about 0.01 or less.

[0056] Aspect 25. The foldable device according to any one of Aspects 22 to 24, wherein the first polymeric portion includes a first contact surface facing the first central surface region and a second contact surface opposite to the first contact surface, wherein the distance between the first main surface and the second contact surface in the substrate thickness direction is about 5 micrometers or less.

[0057] Aspect 26. The foldable device according to any one of aspects 22 to 25, wherein the first polymeric portion further extends beyond the first plane defined by the first main surface.

[0058] Aspect 27. The foldable device according to any one of Aspects 22 to 25, wherein the second polymeric portion includes a fourth contact surface facing the second central surface region and a third contact surface opposite the fourth contact surface, wherein the distance between the second main surface and the third contact surface in the substrate thickness direction is about 5 micrometers or less.

[0059] Aspect 28. The foldable device according to any one of aspects 22 to 27, wherein the second polymeric portion further extends beyond the second plane defined by the second main surface.

[0060] Aspect 29. The foldable device according to any one of Aspects 22 to 27, wherein the foldable device comprises a contrast ratio of about 0.25 or less, and the contrast ratio is defined as the difference between the maximum fractional intensity and the minimum fractional intensity measured using a contrast test, divided by the sum of the maximum fractional intensity and the minimum fractional intensity.

[0061] Aspect 30. The foldable device according to any one of aspects 15 to 29, wherein the first distance, expressed as a percentage of the thickness of the substrate, is in the range of about 20% to about 50%, and the second distance, expressed as a percentage of the thickness of the substrate, is in the range of about 20% to about 50%.

[0062] Aspect 31. The foldable device according to aspect 30, wherein the first distance is substantially equal to the second distance.

[0063] Aspect 32. The foldable device according to any one of aspects 15 to 31, wherein the substrate thickness is in the range of about 100 micrometers to about 400 micrometers, and the center thickness is in the range of about 25 micrometers to about 80 micrometers.

[0064] Aspect 33. The foldable device according to any one of Aspects 15 to 32, wherein the foldable substrate achieves a parallel plate spacing of 10 mm.

[0065] Aspect 34. The foldable device according to any one of Aspects 15 to 33, wherein the foldable substrate includes a minimum parallel plate spacing in the range of about 0.5 mm to about 10 mm.

[0066] Aspect 35. A consumer electronic device comprising:

[0067] The housing includes a front surface, a rear surface, and side surfaces;

[0068] An electrical component, at least partially located within the housing, the electrical component including a controller, a memory, and a display, the display being located at or adjacent to the front surface of the housing; and

[0069] A cover plate substrate, which is disposed above the display.

[0070] The portion of the housing or at least one of the cover plate substrates comprises a foldable device according to any one of aspects 1 to 34.

[0071] Aspect 36. A method for measuring the contrast ratio of a transparent device, said transparent device comprising a substrate having at least one groove;

[0072] Position the transparent device on the sample holder;

[0073] Generate a collimated beam from the light source;

[0074] The collimated beam is used to illuminate the transparent device to form a measurement beam;

[0075] The measurement beam is focused onto the surface of the optical detector;

[0076] Transmit a signal corresponding to the measurement beam detected by the optical detector;

[0077] Process the signal to determine the position associated with the at least one groove; and

[0078] The contrast ratio is calculated and is defined as the difference between the maximum and minimum fractional intensities divided by the sum of the maximum and minimum fractional intensities, which are measured at that location.

[0079] Aspect 37. The method according to aspect 36, wherein generating a collimated beam from the light source comprises:

[0080] A first beam is emitted from the light source toward the sample holder;

[0081] The first beam is transmitted through the pinhole aperture to form a second beam; and

[0082] The second beam is transmitted through the optical aperture of the spatial filter to form a collimated beam.

[0083] Aspect 38. The method according to any one of Aspects 36 to 37, wherein the light source is configured to emit substantially monochromatic light.

[0084] Aspect 39. The method according to aspect 38, wherein the basic monochromatic light comprises light wavelengths in the range of about 300 nanometers to about 700 nanometers.

[0085] Aspect 40. The method according to any one of Aspects 36 to 39, wherein the optical detector comprises a plurality of pixels.

[0086] Aspect 41. The method according to any one of aspects 36 to 40, wherein the processing signal further comprises:

[0087] Rotate the image associated with the signal such that a portion of the signal associated with the at least one groove is aligned along the axis; and

[0088] Determining the position associated with the at least one groove involves averaging the signal along the direction of the axis.

[0089] Aspect 42. The method according to any one of Aspects 36 to 41, wherein the processing signal further comprises removing background noise based on a signal detected when the transparent device is not in the sample holder.

[0090] Aspect 43. A method for manufacturing a foldable substrate including a substrate thickness, the method comprising:

[0091] An etching mask is disposed above the first main surface of the foldable substrate, the etching mask comprising:

[0092] The first portion includes a first barrier layer at least partially adhered to the first main surface, a first polymer layer located at a first peripheral portion of the first portion between the first barrier layer and the first main surface, a first contact surface of the first polymer layer adhered to the first barrier layer, and a second contact surface of the first polymer layer facing the first main surface; and

[0093] The second part includes a second barrier layer at least partially adhered to the first main surface, a second polymer layer located between the second barrier layer and the first main surface at a second peripheral portion of the second part, a third contact surface of the second polymer layer adhered to the second barrier layer, and a fourth contact surface of the second polymer layer facing the first main surface, and the minimum distance between the first peripheral portion and the second peripheral portion is in the range of about 1 mm to about 50 mm.

[0094] The foldable substrate is etched by contacting the central region of the central portion of the foldable substrate between the first portion and the second portion of the etching mask. The etching removes a portion of the foldable substrate to form a first central surface region recessed from the first main surface by a first distance and defining a first groove; the etching removes a portion of the foldable substrate to form a first transition surface region of a first transition region; and the etching removes a portion of the foldable substrate to form a third transition surface region of a second transition region.

[0095] Remove the etch mask.

[0096] The first transition width of the first transition region is greater than or equal to the first width of the first polymer layer, the second transition width of the second transition region is greater than or equal to the second width of the second polymer layer, the central portion includes the first transition region, the central region and the second transition region, and the first width is in the range of about 1.5 mm to about 4 mm, and the second width is in the range of about 1.5 mm to about 4 mm.

[0097] Aspect 44. The method according to aspect 43, wherein the method produces a foldable substrate of a foldable device according to any one of aspects 1 to 34.

[0098] Aspect 45. The method according to aspect 43, wherein the first transition surface region extends at a first average angle relative to the first central surface region between a first surface of the first main surface and the first central surface region, the third transition surface region extends at a third average angle relative to the first central surface region between a third surface region of the first main surface and the first central surface region, and the first average angle is in the range of about 178.3° to about 179.9°.

[0099] Aspect 46. The method according to aspect 45, wherein the first average angle is in the range of about 178.5° to about 179.0°.

[0100] Aspect 47. The method according to any one of Aspects 43 to 46, wherein the central portion includes a second central surface region opposite to the first central surface region, the foldable substrate further includes a second main surface opposite to the first main surface, and the second central surface region is flush with the second main surface.

[0101] Aspect 48. The method according to aspect 43, further comprising, prior to the etching, placing a second etching mask on a second main surface of the foldable substrate, the second etching mask comprising:

[0102] The third part includes a third barrier layer at least partially adhered to the second main surface, a third polymer layer located at a third peripheral portion of the third part between the third barrier layer and the second main surface, a fifth contact surface of the third polymer layer adhered to the third barrier layer, and a sixth contact surface of the third polymer layer facing the second main surface; and

[0103] The fourth part includes a fourth barrier layer at least partially adhered to the second main surface, a fourth polymer layer located between the fourth barrier layer and the second main surface at a fourth peripheral portion of the fourth part, a seventh contact surface of the fourth polymer layer adhered to the fourth barrier layer, and an eighth contact surface of the fourth polymer layer facing the second main surface, and the minimum distance between the third peripheral portion and the fourth peripheral portion is in the range of about 1 mm to about 50 mm;

[0104] The etching further includes a central region of the central portion of the foldable substrate between the third portion and the fourth portion of the second etching mask, the etching removing a portion of the foldable substrate to form a second central surface region recessed from the second main surface by a second distance and defining a second groove, the etching removing a portion of the foldable substrate to form a second transition surface region of the first transition region, and the etching removing a portion of the foldable substrate to form a fourth transition surface region of the second transition region; and

[0105] After the etching, the second etch mask is removed.

[0106] The third width of the third polymer layer is in the range of about 1.5 mm to about 4 mm, and the fourth width of the fourth polymer layer is in the range of about 1.5 mm to about 4 mm.

[0107] Aspect 49. The method according to aspect 48, wherein the first transition surface region extends at a first average angle relative to the first central surface region between a first surface of the first main surface and the first central surface region, the third transition surface region extends at a third average angle relative to the first central surface region between a third surface region of the first main surface and the first central surface region, and the first average angle is in the range of about 179.1° to about 179.9°.

[0108] Aspect 50. The method according to aspect 48, wherein the first average angle is in the range of about 179.2° to about 179.5°.

[0109] Aspect 51. A method of manufacturing a foldable substrate, the foldable substrate including a substrate thickness, a predetermined first transition region, and a predetermined second transition region, the method comprising:

[0110] Multiple shapes are inkjet printed on a first main surface including the central portion of the foldable substrate, wherein the multiple shapes are unevenly distributed on the first main surface in a predetermined pattern; and

[0111] The foldable substrate is etched by contacting the central portion and the plurality of shapes with an etchant. The etching removes a portion of the foldable substrate to form a first central surface region that is recessed from the first main surface by a first distance and defines a first groove. The etching removes a portion of the foldable substrate to form a first transition surface region of the predetermined first transition region. The etching removes a portion of the foldable substrate to form a third transition surface region of the predetermined second transition region.

[0112] Aspect 52. The method according to aspect 51, wherein the predetermined pattern generates a fractional area distribution of a portion of a first main surface covered by the plurality of shapes, the fractional area distribution being averaged in both a direction perpendicular to the thickness of the substrate and a direction extending from the first transition surface to the third transition surface region, and the fractional area distribution being proportional to the amount of material removed by the etching to generate the predetermined first transition region and the predetermined second transition region.

[0113] Aspect 53. The method according to any one of aspects 51 to 52, wherein the plurality of shapes correspond to a plurality of curved shapes.

[0114] Aspect 54. The method according to any one of aspects 51 to 52, wherein the plurality of shapes comprises a plurality of elongated shapes having an aspect ratio of about 10 or greater.

[0115] Aspect 55. The method according to any one of aspects 51 to 54, wherein the shape of the plurality of shapes includes a shape width in the range of about 500 nanometers to about 50 micrometers, and the shape width is in a direction extending from the first transition surface to the third transition surface region.

[0116] Aspect 56. The method according to any one of aspects 51 to 55, wherein the method produces a foldable substrate of a foldable device according to any one of aspects 1 to 34.

[0117] Aspect 57. The method according to any one of Aspects 51 to 55, wherein the first transition surface region extends at a first average angle relative to the first central surface region between a first surface of the first main surface and the first central surface region, the third transition surface region extends at a third average angle relative to the first central surface region between a third surface region of the first main surface and the first central surface region, and the first average angle is in the range of about 178.3° to about 179.9°.

[0118] Aspect 58. The method according to aspect 57, wherein the first average angle is in the range of about 178.5° to about 179.0°.

[0119] Aspect 59. The method according to any one of Aspects 51 to 55 and 57 to 58 (inclusive), wherein the central portion includes a second central surface region opposite to the first central surface region, the foldable substrate further includes a second main surface opposite to the first main surface, and the second central surface region is flush with the second main surface.

[0120] Aspect 60. The method according to aspect 57, wherein the first average angle is in the range of about 179.1° to about 179.9°.

[0121] Aspect 61. The method according to aspect 60, wherein the foldable substrate includes a second central surface region opposite to the first central surface region, the second central surface region being recessed from a second main surface opposite to the second main surface by a second distance and defining a second groove.

[0122] Aspect 62. The method according to any one of Aspects 43 to 61, wherein the foldable substrate exhibits a contrast ratio of about 0.25 or less, and the contrast ratio is defined as the difference between the maximum fractional intensity and the minimum fractional intensity measured using a contrast test when the first groove is filled with a material having a refractive index substantially the same as that of the foldable substrate, divided by the sum of the maximum fractional intensity and the minimum fractional intensity.

[0123] Aspect 63. A method of forming a foldable device, the method comprising:

[0124] A method for manufacturing a foldable substrate according to any one of aspects 43 to 61; and

[0125] The first polymeric portion is disposed in at least the first groove, and the absolute value of the difference between the first refractive index of the foldable substrate and the second refractive index of the first polymeric portion is about 0.1 or less.

[0126] The foldable substrate exhibits a contrast ratio of about 0.25 or less, and the contrast ratio is defined as the difference between the maximum and minimum fractional intensities measured using a contrast test, divided by the sum of the maximum and minimum fractional intensities.

[0127] Aspect 64. A method of forming a foldable device, the method comprising:

[0128] A method for manufacturing a foldable substrate according to aspect 47 or aspect 61;

[0129] The first polymeric portion is disposed in at least the first groove, and the absolute value of the difference between the first refractive index of the foldable substrate and the second refractive index of the first polymeric portion is about 0.1 or less; and

[0130] The second polymeric portion is disposed in at least the second groove, and the absolute value of the difference between the first refractive index of the foldable substrate and the third refractive index of the second polymeric portion is about 0.1 or less.

[0131] The foldable substrate exhibits a contrast ratio of about 0.25 or less, and the contrast ratio is defined as the difference between the maximum and minimum fractional intensities measured using a contrast test, divided by the sum of the maximum and minimum fractional intensities.

[0132] Aspect 65. The method according to aspect 64, wherein the absolute value of the difference between the first refractive index and the third refractive index of the foldable substrate is about 0.01 or less.

[0133] Aspect 66. The method according to any one of Aspects 63 to 65, wherein the absolute value of the difference between the first refractive index and the second refractive index of the foldable substrate is about 0.01 or less.

[0134] Aspect 67. A foldable device including a foldable substrate, said foldable substrate comprising:

[0135] The substrate thickness is in the range of about 80 micrometers to about 5 millimeters, the substrate thickness being defined between a first main surface and a second main surface opposite to the first main surface, and the foldable substrate includes glass-like materials or ceramic materials;

[0136] The first part includes the substrate thickness between a first surface region of the first main surface and a second surface region of the second main surface;

[0137] The second part includes the substrate thickness between the third surface region of the first main surface and the fourth surface region of the second main surface;

[0138] A central portion, the central portion including a central thickness less than the substrate thickness and ranging from about 20 micrometers to about 200 micrometers, the central thickness defining a first central surface region and a second central surface region opposite the first central surface region, and the first central surface region being recessed from the first main surface by a first distance and defining a first groove; and

[0139] A first polymeric portion disposed in the first groove, the first polymeric portion including a first contact surface facing the first central surface region and a second contact surface opposite to the second contact surface, and the absolute value of the difference between the first refractive index of the foldable substrate and the second refractive index of the first polymeric portion is about 0.1 or less.

[0140] The first polymer angle is defined as the interior angle between the first main surface of the foldable substrate and the second contact surface of the polymer portion, which is in the range of about 178.3° to about 179.9°.

[0141] Aspect 68. The foldable device according to aspect 67, wherein the first polymer angle is in the range of about 178.5° to about 179.0°.

[0142] Aspect 69. The foldable device according to any one of Aspects 67 to 68, wherein the distance between the first main surface and the second contact surface in the thickness direction of the substrate is about 5 micrometers or less.

[0143] Aspect 70. The foldable device according to any one of Aspects 67 to 69, wherein the foldable device comprises a contrast ratio of about 0.25 or less, and the contrast ratio is defined as the difference between the maximum fractional intensity and the minimum fractional intensity measured using a contrast test, divided by the sum of the maximum fractional intensity and the minimum fractional intensity.

[0144] Aspect 71. The foldable device according to any one of Aspects 67 to 70, wherein the substrate thickness is in the range of about 100 micrometers to about 400 micrometers, and the center thickness is in the range of about 25 micrometers to about 80 micrometers.

[0145] Aspect 72. The foldable device according to any one of aspects 67 to 71, wherein the second central surface region is flush with the second surface region and the fourth surface region.

[0146] Aspect 73. The foldable device according to any one of aspects 67 to 71, wherein the second central surface region is recessed from the second main surface by a second distance and defines a second groove, and the first polymer angle is in the range of about 179.2° to 179.5°.

[0147] Aspect 74. The foldable device according to any one of aspects 67 to 73, wherein the central portion further comprises:

[0148] A first transition region, comprising a first transition surface region extending at a first average angle relative to the first central surface region between the first surface region and the first central surface region, and the thickness of the first transition region smoothly and monotonically decreasing between the substrate thickness of the first portion and the central thickness of the central portion; and

[0149] The second transition region includes a third transition surface region that extends at a third average angle relative to the first central surface region between the third surface region and the first central surface region, and the thickness of the second transition region smoothly and monotonically decreases between the substrate thickness of the second portion and the center thickness of the central portion.

[0150] The first average angle is in the range of about 176.1° to about 179.9°.

[0151] Aspect 75. The foldable device according to any one of aspects 67 to 74, wherein the first average angle is in the range of about 177.0° to about 179.0°.

[0152] Aspect 76. The foldable device according to any one of Aspects 74 to 75, wherein the first transition width of the first transition region is in the range of about 2.0 mm to about 6.0 mm.

[0153] Aspect 77. The foldable device according to any one of aspects 67 to 76, wherein the foldable substrate achieves a parallel plate spacing of 10 mm.

[0154] Aspect 78. The foldable device according to any one of Aspects 67 to 77, wherein the foldable substrate includes a minimum parallel plate spacing in the range of about 0.5 mm to about 10 mm.

[0155] Aspect 79. A consumer electronic device comprising:

[0156] The housing includes a front surface, a rear surface, and side surfaces;

[0157] An electrical component, at least partially located within the housing, the electrical component including a controller, a memory, and a display, the display being located at or adjacent to the front surface of the housing; and

[0158] A cover plate substrate, which is disposed above the display.

[0159] The portion of the housing or at least one of the cover plate substrates comprises a foldable device according to any one of aspects 67 to 78.

[0160] Aspect 80. A foldable device including a foldable substrate, the foldable substrate comprising:

[0161] The substrate thickness is in the range of about 80 micrometers to about 5 millimeters, the substrate thickness being defined between a first main surface and a second main surface opposite to the first main surface, and the foldable substrate includes glass-like materials or ceramic materials;

[0162] The first part includes the substrate thickness between a first surface region of the first main surface and a second surface region of the second main surface;

[0163] The second part includes the substrate thickness between the third surface region of the first main surface and the fourth surface region of the second main surface; and

[0164] The central portion includes:

[0165] The center thickness is less than the substrate thickness and is in the range of about 20 micrometers to about 200 micrometers. The center thickness is defined between a first center surface region and a second center surface region opposite to the first center surface region, and the first center surface region is recessed from the first main surface by a first distance and defines a first groove.

[0166] A first transition region, comprising a first transition surface region extending at a first average angle relative to the first central surface region between the first surface region and the first central surface region, and the thickness of the first transition region smoothly and monotonically decreasing between the substrate thickness of the first portion and the central thickness of the central portion; and

[0167] The second transition region includes a third transition surface region that extends at a third average angle relative to the first central surface region between the third surface region and the first central surface region, and the thickness of the second transition region smoothly and monotonically decreases between the substrate thickness of the second portion and the center thickness of the central portion.

[0168] The first average angle is in the range of about 176.1° to about 179.9°.

[0169] Aspect 81. The foldable device according to aspect 80, wherein the first average angle is in the range of about 177.0° to about 179.0°.

[0170] Aspect 82. The foldable device according to any one of Aspects 80 to 81, wherein the first transition width of the first transition region is in the range of about 0.6 mm to about 5.0 mm.

[0171] Aspect 83. The foldable device according to aspect 82, wherein the first transition width is in the range of about 1.0 mm to about 5.0 mm.

[0172] Aspect 84. The foldable device according to aspect 82, wherein the first transition width is in the range of about 2.0 mm to about 5.0 mm.

[0173] Aspect 85. The foldable device according to any one of aspects 80 to 84, wherein the second central surface region is flush with the second surface region and the fourth surface region.

[0174] Aspect 86. The foldable device according to any one of aspects 80 to 85, further comprising a polymeric portion located in the first recess, wherein the absolute value of the difference between the first refractive index of the foldable substrate and the second refractive index of the polymeric portion is about 0.1 or less.

[0175] Aspect 87. The foldable device according to aspect 86, wherein the absolute value of the difference between the first refractive index and the second refractive index of the foldable substrate is about 0.01 or less.

[0176] Aspect 88. The foldable device according to any one of Aspects 86 to 87, wherein the polymeric portion includes a first contact surface facing the first central surface region and a second contact surface opposite to the first contact surface, wherein the distance between the first main surface and the second contact surface in the substrate thickness direction is about 5 micrometers or less.

[0177] Aspect 89. The foldable device according to any one of Aspects 86 to 88, wherein the first polymer angle is defined as the interior angle between the first main surface of the foldable substrate and the second contact surface of the polymer portion, which is in the range of about 178.3° to about 179.9°.

[0178] Aspect 90. The foldable device according to aspect 89, wherein the first polymer angle is in the range of about 178.5° to about 179.0°.

[0179] Aspect 91. The foldable device according to aspect 89, wherein the first polymer angle is in the range of about 179.1° to about 179.9°.

[0180] Aspect 92. The foldable device according to aspect 91, wherein the first polymer angle is in the range of about 179.2° to about 179.5°.

[0181] Aspect 93. The foldable device according to any one of aspects 86 to 87, wherein the polymeric portion further extends beyond the plane defined by the first main surface.

[0182] Aspect 94. The foldable device according to any one of Aspects 86 to 93, wherein the foldable device comprises a contrast ratio of about 0.25 or less, and the contrast ratio is defined as the difference between the maximum fractional intensity and the minimum fractional intensity measured using a contrast test, divided by the sum of the maximum fractional intensity and the minimum fractional intensity.

[0183] Aspect 95. The foldable device according to any one of aspects 80 to 94, wherein the first distance, expressed as a percentage of the thickness of the substrate, is in the range of about 50% to about 80%.

[0184] Aspect 96. The foldable device according to any one of aspects 80 to 95, wherein the substrate thickness is in the range of about 100 micrometers to about 400 micrometers, and the center thickness is in the range of about 25 micrometers to about 80 micrometers.

[0185] Aspect 97. The foldable device according to any one of Aspects 80 to 96, wherein the foldable substrate achieves a parallel plate spacing of 10 mm.

[0186] Aspect 98. The foldable device according to any one of Aspects 80 to 97, wherein the foldable substrate includes a minimum parallel plate spacing in the range of about 0.5 mm to about 10 mm.

[0187] Aspect 99. The foldable device according to any one of Aspects 80 to 83, wherein the second central surface region is recessed from the second main surface by a second distance and defines a second groove, the first transition region further includes a second transition surface region extending at a second average angle relative to the second central surface region between the second surface region and the second central surface region, and the second transition region further includes a fourth transition surface region extending at a fourth average angle relative to the second central surface region between the fourth surface region and the second central surface region.

[0188] Aspect 100. A foldable device including a foldable substrate, the foldable substrate comprising:

[0189] The substrate thickness is in the range of about 80 micrometers to about 5 millimeters, the substrate thickness being defined between a first main surface and a second main surface opposite to the first main surface, and the foldable substrate includes glass-like materials or ceramic materials;

[0190] The first part includes the substrate thickness between a first surface region of the first main surface and a second surface region of the second main surface;

[0191] The second part includes the substrate thickness between the third surface region of the first main surface and the fourth surface region of the second main surface; and

[0192] The central portion includes:

[0193] The center thickness is less than the substrate thickness and is in the range of about 20 micrometers to about 200 micrometers. The center thickness is defined between a first center surface region and a second center surface region opposite to the first center surface region. The first center surface region is recessed from the first main surface by a first distance and defines a first distance. The second center surface region is recessed from the second main surface by a second distance and defines a second groove.

[0194] A first transition region, comprising a first transition surface region and a second transition surface region, wherein the first transition surface region extends at a first average angle relative to the first central surface region between the first surface region and the first central surface region, and the second transition surface region extends at a second average angle relative to the second central surface region between the second surface region and the second central surface region, and the thickness of the first transition region smoothly and monotonically decreases between the substrate thickness of the first portion and the central thickness of the central portion; and

[0195] The second transition region includes a third transition surface region and a fourth transition surface region. The third transition surface region extends at a third average angle relative to the first central surface region between the third surface region and the first central surface region. The fourth transition surface region extends at a fourth average angle relative to the second central surface region between the fourth surface region and the second central surface region. The thickness of the second transition region smoothly and monotonically decreases between the substrate thickness of the second portion and the center thickness of the central portion.

[0196] The first average angle is in the range of about 177.0° to about 179.9°.

[0197] Aspect 101. The foldable device according to aspect 100, wherein the first transition width of the first transition region is in the range of about 1.0 mm to about 5.0 mm.

[0198] Aspect 102. The foldable device according to aspect 101, wherein the first transition width is in the range of about 2.0 mm to about 5.0 mm.

[0199] Aspect 103. The foldable device according to any one of aspects 100 to 102, further comprising:

[0200] The first polymeric portion located in the first groove, wherein the absolute value of the difference between the first refractive index of the foldable substrate and the second refractive index of the first polymeric portion is about 0.1 or less; and

[0201] The second polymer portion located in the second groove has an absolute value of the difference between the first refractive index of the foldable substrate and the third refractive index of the second polymer portion of about 0.1 or less.

[0202] Aspect 104. The foldable device according to aspect 103, wherein the absolute value of the difference between the first refractive index and the second refractive index of the foldable substrate is about 0.01 or less.

[0203] Aspect 105. The foldable device according to any one of Aspects 103 to 104, wherein the absolute value of the difference between the first refractive index and the third refractive index of the foldable substrate is about 0.01 or less.

[0204] Aspect 106. The foldable device according to any one of Aspects 103 to 105, wherein the first polymeric portion includes a first contact surface facing the first central surface region and a second contact surface opposite to the first contact surface, wherein the distance between the first main surface and the second contact surface in the substrate thickness direction is about 5 micrometers or less.

[0205] Aspect 107. The foldable device according to any one of aspects 103 to 106, wherein the first polymer angle is defined as the interior angle between the first main surface of the foldable substrate and the second contact surface of the polymer portion, which is in the range of about 179.1° to about 179.9°.

[0206] Aspect 108. The foldable device according to aspect 107, wherein the first polymer angle is in the range of about 179.2° to about 179.5°.

[0207] Aspect 109. The foldable device according to any one of aspects 103 to 105, wherein the first polymeric portion further extends beyond the first plane defined by the first main surface.

[0208] Aspect 110. The foldable device according to any one of Aspects 100 to 109, wherein the second polymeric portion includes a fourth contact surface facing the second central surface region and a third contact surface opposite the fourth contact surface, wherein the distance between the second main surface and the third contact surface in the substrate thickness direction is about 5 micrometers or less.

[0209] Aspect 111. The foldable device according to any one of aspects 101 to 109, wherein the second polymeric portion further extends beyond the second plane defined by the second main surface.

[0210] Aspect 112. The foldable device according to any one of Aspects 100 to 111, wherein the foldable device comprises a contrast ratio of about 0.25 or less, and the contrast ratio is defined as the difference between the maximum fractional intensity and the minimum fractional intensity measured using a contrast test, divided by the sum of the maximum fractional intensity and the minimum fractional intensity.

[0211] Aspect 113. The foldable device according to any one of aspects 100 to 112, wherein the first distance, expressed as a percentage of the thickness of the substrate, is in the range of about 20% to about 50%, and the second distance, expressed as a percentage of the thickness of the substrate, is in the range of about 20% to about 50%.

[0212] Aspect 114. The foldable device according to aspect 113, wherein the first distance is substantially equal to the second distance.

[0213] Aspect 115. The foldable device according to any one of aspects 100 to 114, wherein the substrate thickness is in the range of about 100 micrometers to about 400 micrometers, and the center thickness is in the range of about 25 micrometers to about 80 micrometers.

[0214] Aspect 116. The foldable device according to any one of aspects 100 to 115, wherein the foldable substrate achieves a parallel plate spacing of 10 mm.

[0215] Aspect 117. The foldable device according to any one of Aspects 100 to 116, wherein the foldable substrate includes a minimum parallel plate spacing in the range of about 0.5 mm to about 10 mm.

[0216] Aspect 118. A consumer electronic device comprising:

[0217] The housing includes a front surface, a rear surface, and side surfaces;

[0218] An electrical component, at least partially located within the housing, the electrical component including a controller, a memory, and a display, the display being located at or adjacent to the front surface of the housing; and

[0219] A cover plate substrate, which is disposed above the display.

[0220] The portion of the housing or at least one of the cover plate substrates comprises a foldable device according to any one of aspects 80 to 117. Attached Figure Description

[0221] The above and other features and advantages of various aspects of this disclosure will be better understood when the following detailed description is read with reference to the accompanying drawings, in which:

[0222] Figure 1 These are schematic diagrams of example foldable devices in a planar configuration, as shown in the diagram. Figure 6 As shown;

[0223] Figure 2-5 It is based on various aspects of foldable devices along Figure 1 Cross-sectional view of line 2-2;

[0224] Figure 6 These are schematic diagrams of example foldable devices of various aspects of this disclosure in a folded configuration, wherein a schematic diagram of a planar configuration may be as follows: Figure 1 As shown;

[0225] Figure 7-8 It is a test device used to determine the minimum parallel plate spacing of an example foldable device. Figure 5 The cross-sectional view of line 7-7;

[0226] Figure 9 It is a schematic plan view based on various examples of consumer electronic devices;

[0227] Figure 10 yes Figure 9 A schematic perspective view of an example consumer electronics device;

[0228] Figure 11-12 This is a flowchart illustrating an example method of manufacturing a foldable device according to various aspects of this disclosure;

[0229] Figure 13-25 The steps in a method of manufacturing a foldable substrate and / or a foldable device are illustrated schematically.

[0230] Figure 26The measuring equipment used in the method for determining the contrast ratio is shown schematically.

[0231] Figure 27 The illustration schematically shows ray tracing, demonstrating how the central portion of a foldable device distorts light passing through it;

[0232] Figure 28 A method for measuring the contrast ratio of foldable devices is illustrated schematically.

[0233] Figure 29 Experimental measurements used to determine the contrast ratio of instance AE are shown;

[0234] Figure 30 This illustrates the method for calculating the contrast ratio based on experimental measurements from Example A;

[0235] Figure 31 The relationship between polymer angle and contrast ratio is shown in Examples 1-8;

[0236] Figure 32 The relationship between the distance and the contrast ratio between the first main surface and the surface of the first polymeric portion in Examples 1-8 is shown.

[0237] Figure 33 A schematic diagram of an example foldable device is shown; and

[0238] Figure 34 The relationship between the angle and contrast ratio of the transition zone in Examples 1-8 is shown.

[0239] Throughout this disclosure, the accompanying drawings are used to emphasize certain aspects. Therefore, unless otherwise explicitly stated, the relative sizes of the different areas, portions, and substrates shown in the drawings should not be assumed to be proportional to their actual relative sizes. Detailed Implementation

[0240] The aspects will now be described more fully below with reference to the accompanying drawings, which show example aspects. Where possible, the same reference numerals are used throughout the drawings to refer to the same or similar parts.

[0241] Figure 1-5 Views 7-8 and 33 show views of foldable devices 101, 301, 401, 501, 601, and 801 including a foldable substrate 201 according to various aspects of this disclosure. Unless otherwise indicated, descriptions of features of various aspects of a foldable device are equally applicable to corresponding features of any aspect of this disclosure. For example, the same part numbers throughout this disclosure may indicate that, in some aspects, identified features are identical to each other, and unless otherwise indicated, descriptions of identified features of one aspect are equally applicable to identified features of any other aspect of this disclosure.

[0242] Figure 2-5 Figures 3 and 33 schematically illustrate example aspects of foldable devices 101, 301, 401, 501, and 3301, comprising a foldable substrate 201, in an undisturbed (e.g., flat) configuration according to various aspects of this disclosure. Figure 7-8 Example aspects of foldable devices 601 and 801, including a foldable substrate 201, in a foldable configuration according to various aspects of this disclosure are shown.

[0243] Foldable devices 101, 301, 401, 501, and 3301 include a first portion 221, a second portion 231, and a central portion 281 located between the first portion 221 and the second portion 231. In various aspects, such as Figure 2 and 4 As shown in Figure 5, the foldable device 101 may include a release liner 271, but in other respects other substrates may be used (e.g., glass substrates and / or ceramic substrates discussed throughout the application, see, for example, see...). Figure 3 Instead of the release liner 271 shown. In all aspects, such as Figure 2 and 8 As shown, foldable devices 101 and 801 may include a coating 251. In various aspects, such as Figure 3 As shown, the foldable device 301 may include a cover plate substrate 351. In various aspects, such as Figure 2 and 4 As shown, the foldable device 101 may include an adhesive layer 261. In various aspects, such as Figure 2-5 As shown in Figures 7-8, foldable devices 101, 301, 401, 601, and 801 may include polymeric portions 289 and / or 299. Figure 2-5 As shown, the foldable substrate 201 may include a first groove 211. In various aspects, such as Figure 2-3 As shown, the foldable substrate 201 may further include a second groove 241. It should be understood that any foldable device of this disclosure may include a second substrate (e.g., a glass substrate and / or a ceramic substrate), a release liner 271, a display device, a coating 251, an adhesive layer 261, and / or polymeric portions 289 and / or 299.

[0244] See throughout this publication. Figure 1The width 103 of the foldable devices 101, 301, 401, 501, 601, and / or 801 is considered as the dimension of the foldable device obtained between opposite edges of the foldable device in the direction 104 of the folding axis 102 of the foldable device, wherein the direction 104 also includes the direction of the width 103. Furthermore, throughout this disclosure, the length 105 of the foldable devices 101, 301, 401, 501, 601, and / or 801 is considered as the dimension of the foldable devices 101, 301, 401, 501, 601, and / or 801 obtained between opposite edges of the foldable devices 101, 301, 401, 501, 601, and / or 801 in the direction 106 perpendicular to the folding axis 102 of the folding axis 102 of the foldable devices 101, 301, 401, 501, 601, and / or 801. In various aspects, such as Figure 1 As shown, any foldable device according to any aspect of this disclosure may include a folding plane 109 when the foldable device is in a planar configuration (see, for example, see...). Figure 2 and 4 When ), the folding plane includes a folding axis 102. The folding plane 109 may include the central axis 107 of the foldable device. In other aspects, such as Figure 2 As shown, when the foldable device is in a planar configuration, the folding plane 109 may extend along the central axis 107 (and / or the folding axis) and in the direction of the substrate thickness 207. In various aspects, the foldable device may be positioned about the folding axis 102 extending in the direction 104 of the width 103 in the direction 111 (see, for example, [reference needed]). Figure 1 Fold up to form a folded configuration (see, for example, see...) Figure 6-8 As shown in the figure, the foldable device may include a single folding axis to allow the foldable device to include a double fold, such as a foldable device that can be folded in half. In other aspects, the foldable device may include two or more folding axes, wherein each folding axis includes a central portion similar to or identical to the central portion 281 discussed herein. For example, providing two folding axes may allow the foldable device to include a triple fold, such as a foldable device that can be folded to have a first portion 221, a second portion 231, and a third portion similar to or identical to the first or second portion, with the central portion 281 and another central portion similar to or identical to the central portion located between the first and second portions and between the second and third portions, respectively.

[0245] The foldable substrate 201 may include a glass substrate and / or a ceramic substrate with a pencil hardness of 8H or higher, such as 9H or higher. As used herein, pencil hardness is measured using ASTM D 3363-20 with standard lead-grade pencils. Providing a glass substrate and / or a ceramic substrate can enhance puncture resistance and / or impact resistance.

[0246] In various aspects, the foldable substrate 201 may include a glass-like substrate. As used herein, "glass-like" includes glass and glass-ceramics, wherein the glass-ceramics have one or more crystalline phases and an amorphous residual glass phase. Glass-like materials (e.g., glass-like substrates) may include amorphous materials (e.g., glass) and optionally one or more crystalline materials (e.g., ceramics). The crystalline material and the glass-like material may be strengthened. As used herein, the term "strengthened" may refer to a material that has been chemically strengthened, for example, by exchanging smaller ions with larger ions in the substrate surface, as discussed below. However, other strengthening methods may also be used, such as thermal tempering, or by utilizing the mismatch in the coefficients of thermal expansion between different portions of the substrate to create compressive stress and a central tension zone, thereby forming a strengthened substrate. Exemplary glass-like materials that may be lithium-free or lithium-oxide-free include soda-lime glass, alkali aluminosilicate glass, alkali borosilicate glass, alkali aluminosilicate glass, alkali phosphosilicate glass, and alkali aluminosilicate glass. In various aspects, the glass-like material may include alkali glass or alkali-free glass, either of which may be lithium-free or contain lithium oxide. In all aspects, the glass material may be alkali-free and / or include low contents of alkali metals (e.g., about 10 mol% or less of R2O, where R2O includes Li2O, Na2O, K2O, or a broader list provided below). In one or more aspects, the glass material may include, in molar percentage (mol%): SiO2 in the range of about 40 mol% to about 80 mol%, Al2O3 in the range of about 5 mol% to about 30 mol%, B2O3 in the range of 0 mol% to about 10 mol%, ZrO2 in the range of 0 mol% to about 5 mol%, P2O5 in the range of 0 mol% to about 15 mol%, TiO2 in the range of 0 mol% to about 2 mol%, R2O in the range of 0 mol% to about 20 mol%, and RO in the range of 0 mol% to about 15 mol%. As used herein, R₂O can refer to alkali metal oxides, such as Li₂O, Na₂O, K₂O, Rb₂O, and Cs₂O. As used herein, RO can refer to MgO, CaO, SrO, BaO, and ZnO. In all respects, glass substrates may optionally include each of the following in the range of 0 mol% to 2 mol%: Na₂SO₄, NaCl, NaF, NaBr, K₂SO₄, KCl, KF, KBr, As₂O₃, Sb₂O₃, SnO₂, Fe₂O₃, MnO, MnO₂, MnO₃, Mn₂O₃, Mn₃O₄, and Mn₂O₇. “Glass ceramics” includes materials produced by controlled crystallization of glass. In all respects, glass ceramics have a crystallinity of about 1% to about 99%.Suitable examples of glass-ceramics may include Li₂O-Al₂O₃-SiO₂-based (i.e., LAS-based) glass-ceramics, MgO-Al₂O₃-SiO₂-based (i.e., MAS-based) glass-ceramics, ZnO × Al₂O₃ × nSiO₂ (i.e., ZAS-based) glass-ceramics and / or glass-ceramics comprising a major crystalline phase comprising β-quartz solid solution, β-spodumene, cordierite, petalite, and / or lithium disilicate. The glass-ceramic substrate can be strengthened using chemical strengthening processes. In one or more aspects, the MAS-based glass-ceramic substrate can be strengthened in a Li₂SO₄ molten salt, wherein 2Li can be incorporated. + With Mg 2+ The exchange.

[0247] In various aspects, the foldable substrate 201 may include a ceramic substrate. As used herein, "ceramic" includes both ceramics and glass-ceramics, wherein the glass-ceramic has one or more crystalline phases and an amorphous residual glass phase. Ceramic materials may be strengthened (e.g., chemically strengthened). In various aspects, ceramic materials may be formed by heating a glass-ceramic material to form ceramic (e.g., crystalline) portions. In other aspects, ceramic materials may include one or more nucleating agents that can promote the formation of the crystalline phase. In various aspects, ceramic materials may include one or more oxides, nitrides, oxynitrides, carbides, borides, and / or silicides. Examples of ceramic oxides include zirconium oxide (ZrO2), zirconium (ZrSiO4), alkali metal oxides (e.g., sodium oxide (Na2O)), alkaline earth metal oxides (e.g., 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 alumina and silicon dioxide), and spinel (MgAl2O4). Examples 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 (e.g., magnesium nitride (Mg3N2)), nickel nitride, and tantalum nitride. Examples of nitride ceramics include silicon oxynitride, aluminum oxynitride, and SiAlON (a composition of alumina and silicon nitride, and may contain, for example, 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-nChemical formulas, where m, n, and the resulting subscripts are all non-negative integers. Examples of carbides and carbon-containing ceramics include silicon carbide (SiC), tungsten carbide (WC), iron carbide, boron carbide (B4C), alkali metal carbides (e.g., lithium carbide (Li4C3)), alkaline earth metal carbides (e.g., 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). Examples of silicides include molybdenum disilicide (MoSi2), tungsten disilicide (WSi2), titanium disilicide (TiSi2), nickel disilicide (NiSi), alkaline earth metal silicides (e.g., sodium silicide (NaSi)), alkali metal silicides (e.g., magnesium silicide (Mg2Si)), hafnium disilicide (HfSi2), and platinum disilicide (PtSi).

[0248] Throughout this disclosure, the tensile strength, ultimate elongation (e.g., strain at failure), and yield point of polymeric materials (e.g., adhesives, polymeric parts) are determined using ASTM D638, at 23°C and 50% relative humidity, with a Type I dog-bone specimen, using a tensile testing machine such as an Instron 3400 or Instron 6800; and the elastic modulus (e.g., Young's modulus) and / or Poisson's ratio are measured from them using ISO 527-1:2019. Throughout this disclosure, the Young's modulus of glassy and ceramic materials is measured using the ultrasonic resonance spectroscopy technique, described in ASTM E2001-13, entitled "Standard Guide for Resonant Ultrasound Spectroscopy for Defect Detection in Both Metallic and Non-metallic Parts". In various aspects, the foldable substrate 201 may include an elastic modulus of about 1 gigapascal (GPa) or greater, about 3 GPa or greater, about 5 GPa or greater, about 10 GPa or greater, about 100 GPa or less, about 80 GPa or less, about 60 GPa or less, or about 20 GPa or less. In various aspects, the foldable substrate 201 may include an elastic modulus in the range of about 1 GPa to about 100 GPa, about 1 GPa to about 80 GPa, about 3 GPa to about 80 GPa, about 3 GPa to about 60 GPa, about 5 GPa to about 60 GPa, about 5 GPa to about 20 GPa, about 10 GPa to about 20 GPa, or any range or subrange thereof. In other respects, the foldable substrate 201 may include glassy or ceramic materials with 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 subrange thereof.

[0249] In all respects, the foldable substrate 201 may be optically transparent. As used herein, “transparent,” “optically transparent,” or “optically clear” means an average transmittance of 70% or higher through a 1.0 mm thick sheet of material in the wavelength range of 400 nm to 700 nm. In all respects, “optically transparent material” or “optically clear material” may have an average transmittance of 75% or higher, 80% or higher, 85% or higher, or 90% or higher, 92% or higher, 94% or higher, or 96% or higher 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 at integer wavelengths from about 400 nm to about 700 nm and averaging the measured values.

[0250] like Figure 2-5 As shown in Figures 3 and 33, foldable devices 101, 301, 401, 501, and 3301 include a foldable substrate 201, the foldable substrate including a first main surface 203 and a second main surface 205 opposite to the first main surface 203. Figure 2-5As shown in Figure 33, the first main surface 203 may extend along the first plane 204a. The second main surface 205 may extend along the second plane 206a. In various respects, 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 main surface 203 and the second main surface 205, i.e., the distance between the first plane 204a and the second plane 206a. In all respects, the substrate thickness 207 may be about 10 µm or greater, about 25 µm or greater, about 40 µm or greater, about 60 µm or greater, about 80 µm or greater, about 100 µm or greater, about 125 µm or greater, about 150 µm or greater, about 5 mm or less, about 3 mm or less, about 2 mm or less, about 1 mm or less, about 800 µm or less, about 500 µm or less, about 400 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 can be in the range of about 10 µm to about 5 mm, about 25 µm to about 5 mm, about 40 µm to about 5 mm, about 60 µm to about 5 mm, about 80 µm to about 5 mm, about 100 µm to about 3 mm, about 100 µm to about 2 mm, about 100 µm to about 1 mm, about 100 µm to about 800 µm, about 100 µm to about 500 µm, about 100 µm to about 400 µm, about 125 µm to about 300 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. In an exemplary aspect, the substrate thickness 207 can be in the range of about 80 µm to about 5 mm or about 100 µm to about 400 µm.

[0251] like Figure 2-5 As shown in Figure 33, the first portion 221 of the foldable substrate 201 may include a first surface region 223 and a second surface region 225 opposite to the first surface region 223. Reference will now be made to... Figure 2 The foldable device 101 describes a first part 221, wherein it should be understood that, unless otherwise stated, this description of the first part 221 may also be applied to any aspect of this disclosure, for example... Figure 3-5The foldable devices 301, 401, 501, 601, 801, and / or 3301 shown in Figures 7-8 and 33. In various aspects, as shown, the first surface region 223 may include a flat surface, and / or the second surface region 225 of the first portion 221 may include a flat surface. In other aspects, as shown, the second surface region 225 may be parallel to the first surface region 223. In various aspects, as shown, the first main surface 203 may include the first surface region 223, and the second main surface 205 may include the second surface region 225. In other aspects, the first surface region 223 may extend along a first plane 204a. In other aspects, the second surface region 225 may extend along a second plane 206a. In various aspects, the substrate thickness 207 may correspond to the distance between the first surface region 223 and the second surface region 225 of the first portion 221. In various aspects, the substrate thickness 207 may be substantially uniform throughout the first surface region 223. In various aspects, the first thickness defined between the first surface region 223 and the second surface region 225 may be within one or more of the ranges discussed above regarding the substrate thickness 207. In other aspects, the first thickness may include the substrate thickness 207. In other aspects, the first thickness of the first portion 221 between the first surface region 223 and the second surface region 225 may be substantially uniform in 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). In other aspects, such as Figure 2-5 As shown in Figure 33, the first thickness and the second thickness can be substantially equal to the substrate thickness 207.

[0252] like Figure 2-5 As shown in Figure 33, the second portion 231 of the foldable substrate 201 may include a third surface region 233 and a fourth surface region 235 opposite to the third surface region 233. Reference will now be made to... Figure 2 The second part 231 of the description of the foldable device 101 should be understood, unless otherwise stated, that this description of the second part 231 may also be applied to any aspect of this disclosure, for example... Figure 3-5The foldable devices 301, 401, 501, 601, 801, and / or 3301 shown in Figures 7-8 and 33. In various aspects, as shown, the third surface region 233 of the second portion 231 may include a flat surface, and / or the fourth surface region 235 of the second portion 231 may include a flat surface. In other aspects, the third surface region 233 of the second portion 231 may be in a coplanar with the first surface region 223 of the first portion 221. In other aspects, as shown, the fourth surface region 235 may be parallel to the third surface region 233. In other aspects, the fourth surface region 235 of the second portion 231 may be in a coplanar with the second surface region 225 of the first portion 221. A second thickness may be defined between the third surface region 233 and the fourth surface region 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 other aspects, the second thickness may include the substrate thickness 207. In other respects, as shown in the figure, the second thickness may be substantially equal to the substrate thickness 207 (e.g., the first thickness). In various respects, the second thickness of the second portion 231 may be substantially uniform between the third surface region 233 and the fourth surface region 235.

[0253] like Figure 2-5 As shown in Figures 33 and 43, the foldable substrate 201 may include a central portion 281 located between the first portion 221 and the second portion 231. In various aspects, the central portion 281 may include a first central surface region 213 and a second central surface region 243 opposite to the first central surface region 213. As shown, the first central surface region 213 of the central portion 281 may be located between the first surface region 223 and the third surface region 233. In other aspects, the first central surface region 213 may correspond to a central region 248 of the central portion 281. In other aspects, as shown, when the foldable devices 101, 301, and / or 401 are in a planar configuration, the first central surface region 213 may extend along a third plane 204b. A first groove 211 may be defined between the first central surface region 213 (e.g., the third plane 204b) and the first plane 204a.

[0254] In various aspects, the third plane 204b may be substantially parallel to the first plane 204a and / or the second plane 206a. In other aspects, such as Figure 2-3As shown, the first central surface region 213 may be recessed from the first main surface 203 by a first distance 219 and define a first groove 211. In other aspects, the first distance 219 in which the first central surface region 213 is recessed from the first plane 204a may be about 5 µm or greater, about 10 µm or greater, about 20 µm or greater, about 25 µm or greater, about 40 µm or greater, about 80 µm or greater, about 100 µm or greater, about 125 µm or greater, about 150 µm or greater, about 2 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 160 µm or less, about 120 µm or less, or about 80 µm or less. In other respects, the first distance 219 may be within the range of about 5 µm to about 2 mm, about 5 µm to about 1 mm, about 10 µm to about 800 µm, about 20 µm to about 500 µm, about 25 µm to about 300 µm, about 40 µm to about 200 µm, about 80 µm to about 160 µm, about 100 µm to about 120 µm, or any range or subrange thereof. In other respects, expressed as a percentage of the substrate thickness 207, the first distance 219 indented from the first plane 204a by the first central surface region 213 may be about 1% or greater, about 5% or greater, about 10% or greater, about 15% or greater, about 20% or greater, about 25% or greater, about 30% or greater, about 35% or greater, about 40% or greater, about 45% or greater, about 50% or greater, about 55% or greater, about 60% or greater, about 65% or greater, about 70% or greater, about 90% or less, about 85% or less, about 80% or less, about 75% or less, about 70% or less, about 65% or less, about 60% or less, about 55% or less, about 50% or less, about 40% or less, about 35% or less, or about 30% or less. In other respects, expressed as a percentage of the substrate thickness 207, the first distance 219 may be in the range of about 1% to about 90%, about 5% to about 90%, about 10% to about 90%, about 15% to about 85%, about 20% to about 85%, about 25% to about 85%, about 30% to about 85%, about 40% to about 80%, about 45% to about 80%, about 50% to about 80%, about 55% to about 75%, about 60% to about 70%, about 65% to about 70%, or any range or subrange thereof. In other respects, expressed as a percentage of the substrate thickness 207, the first distance 219 may be in the range of about 1% to about 50%, about 5% to about 45%, about 10% to about 40%, about 15% to about 35%, about 20% to about 30%, or any range or subrange thereof.In a preferred embodiment, the first distance 219 can be expressed as a percentage of the substrate thickness 207 in the range of 1% to 90%, 20% to 85%, or 50% to 80%.

[0255] like Figure 2-5 As shown in Figure 33, the second central surface region 243 of the central portion 281 may be located between the second surface region 225 and the fourth surface region 235. In other aspects, such as... Figure 2-3 As shown, when the foldable devices 101 and / or 301 are in a planar configuration, the second central surface region 243 can extend along the fourth plane 206b. In other aspects, such as Figure 2-3 As shown, the second groove 241 may be defined between the second central surface region 243 (e.g., the fourth plane 206b) and the second plane 206a. Alternatively, in various aspects, as Figure 4 As shown, the second central surface region 243 may extend along the second plane 206a, and / or the second central surface region 243 may be flush with the second main surface 205 (e.g., the second surface region 225 and / or the fourth surface region 235).

[0256] In all aspects, such as Figure 2-3As shown in Figure 33, the second central surface region 243 may be recessed from the second main surface 205 by a second distance 249 and define a second groove 241. In other aspects, the second distance 249 may be within one or more ranges discussed above with respect to the first distance 219. In other aspects, the first distance may be greater than the second distance. In other respects, the second distance 249 in which the second central surface region 243 is recessed from the second plane 206a, expressed as a percentage of the substrate thickness 207, may be about 1% or greater, about 5% or greater, about 10% or greater, about 12% or greater, about 15% or greater, about 18% or greater, about 20% or greater, about 22% or greater, about 25% or greater, about 27% or greater, about 30% or greater, about 32% or greater, about 35% or greater, about 37% or greater, about 40% or greater, about 50% or less, about 47% or less, about 45% or less, about 42% or less, about 40% or less, about 37% or less, about 35% or less, about 33% or less, about 30% or less, about 25% or less, about 20% or less, about 18% or less, or about 15% or less. In still other aspects, expressed as a percentage of the substrate thickness 207, the second distance 249 may be in the range of about 1% to about 50%, about 5% to about 50%, about 10% to about 45%, about 12% to about 45%, about 15% to about 45%, about 18% to about 40%, about 20% to about 40%, about 22% to about 37%, about 25% to about 35%, about 27% to about 32%, or any range or sub-range therebetween. In still other aspects, expressed as a percentage of the substrate thickness 207, the second distance 249 may be in the 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 a preferred embodiment, the second distance 249 in which the second central surface region 243 is recessed from the second plane 206a, expressed as a percentage of the substrate thickness 207, can be approximately 1% to approximately 50%, approximately 20% to approximately 50%, or approximately 30% to approximately 45%. In other embodiments, such as Figure 2 As shown, the first distance 219 can be substantially equal to the second distance 249. Making the 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 that includes the midpoint between the substrate thickness and the center thickness. Alternatively, in other aspects, such as... Figure 4-5 As shown, the second central surface region 243 may be coplanar with the second surface region 225 and / or the fourth surface region 235, for example, forming a flat second main surface 205 extending along the second plane 206a.

[0257] The center thickness 209 can be defined between the first center surface region 213 and the second center surface region 243, and can be measured as the distance between the third plane 204b and the fourth plane 206b. In various aspects, the center thickness 209 can be about 1 µm or more, about 5 µm or more, about 10 µm or more, about 20 µm or more, about 25 µm or more, about 40 µm or more, about 60 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 160 µm or less, about 120 µm or less, 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 1 mm, about 5 µm to about 1 mm, about 10 µm to about 800 µm, about 10 µm to about 500 µm, about 20 µm to about 300 µm, about 20 µm to about 200 µm, about 25 µm to about 160 µm, about 25 µm to about 120 µm, about 25 µm to about 100 µm, about 25 µm to about 80 µm, about 40 µm to about 60 µm, or any range or sub-range thereof. In a preferred aspect, the center thickness 209 can be in the range of about 10 µm to about 1 mm, about 20 µm to about 200 µm, or about 25 µm to about 80 µm. In all aspects, the center thickness 209, expressed as a percentage of 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 35% or less, about 30% or less, about 25% or less, about 20% or less, about 15% or less, about 13% or less, about 10% or less, or about 8% or less. In all aspects, expressed as a percentage of the substrate thickness 207, the center thickness 209 can be in the range of about 0.1% to about 40%, about 0.5% to about 40%, about 1% to about 35%, about 2% to about 35%, about 5% to about 35%, about 10% to about 30%, about 13% to about 25%, about 15% to about 20%, or any range or subrange thereof. In various aspects, expressed as a percentage of the substrate thickness 207, the center thickness 209 can be about 15% or less, for example, in the range of about 0.1% to about 20%, about 0.5% to about 15%, 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 a preferred aspect, expressed as a percentage of the substrate thickness 207, the center thickness 209 can be in the range of about 0.5% to about 40%, about 10% to about 35%, or about 13% to about 30%.In various respects, the central region 248 of the central portion 281 may correspond to the region including the central thickness 209. By making the first central surface region 213 of the central portion 281 extending along the third plane 204b parallel to the second central surface region 243 of the central portion 281 extending along the fourth plane 206b, a uniform central thickness 209 can be extended throughout the entire central portion 281, thereby providing enhanced folding performance at a predetermined thickness of central thickness 209. The uniform central thickness 209 throughout the central portion 281 can improve folding performance by preventing stress concentration that would occur if a portion of the central portion 281 were thinner than the rest of the central portion 281.

[0258] In all aspects, such as Figure 2-5 As shown, the central portion 281 of the foldable substrate 201 may include a first transition region 212, which includes a first transition surface region 215 extending between the first surface region 223 and the first central surface region 213. In other aspects, as shown, the width of the first transition region 212 (e.g., a first transition width 214) can be measured as a distance 106 along a length 105 between a portion of the first central surface region 213 extending along the third plane 204b and a portion of the first surface region 223 (see Figure 106). Figure 1The minimum distance on the first transition region 212. In other aspects, the first transition width 214 of the first transition region 212 may be about 1.7 mm or greater, 2.0 mm or greater (e.g., about 2 mm or greater), about 2.2 mm or greater, about 2.5 mm or greater, about 2.7 mm or greater, about 3.0 mm or greater (e.g., about 3 mm or greater), about 3.2 mm or greater, about 3.5 mm or greater, about 6.0 mm or less (e.g., about 6 mm or less), about 5.5 mm or less, about 5.0 mm or less (e.g., about 5 mm or less), about 4.5 mm or less, about 4.0 mm or less (e.g., about 4 mm or less), about 3.8 mm or less, about 3.5 mm or less, about 3.2 mm or less, about 3.0 mm or less (e.g., about 3 mm or less), about 2.8 mm or less, or about 2.5 mm or less. In other respects, the first transition width 214 of the first transition region 212 may be in the range of about 1.7 mm to about 6.0 mm, about 2.0 mm to about 6.0 mm (e.g. about 2 mm to about 6 mm), about 2.0 mm to about 5.5 mm, about 2.0 mm to about 5.0 mm (e.g. about 2 mm to about 5 mm), about 2.0 mm to about 4.5 mm, about 2.2 mm to about 4.0 mm, about 2.2 mm to about 3.8 mm, about 2.5 mm to about 3.5 mm, about 2.5 mm to about 3.2 mm, about 2.7 mm to about 3.0 mm, or any range or sub-range thereof. In other aspects, the first transition width 214 of the first transition region 212 may be in the range of about 2.5 mm to about 6.0 mm, about 2.5 mm to about 5.5 mm, about 2.5 mm to about 5.0 mm, about 2.7 mm to about 4.5 mm, about 3.0 mm to about 4.0 mm, about 3.0 mm to about 3.7 mm, about 3.2 mm to about 3.5 mm, or any range or sub-range therebetween. In a preferred aspect, the first transition width 214 of the first transition region 212 may be in the range of about 2 mm to about 6 mm, about 2.2 mm to about 4 mm, or about 2.5 mm to about 3.5 mm. Providing a transition width of about 2 mm to about 6 mm (e.g., about 2.2 mm to about 4 mm or about 2.5 mm to about 3.5 mm) for the first transition region and / or the second transition region may reduce the visibility of the transition region (e.g., resulting in a lower contrast ratio and / or creating a transition region that is not visible to the naked eye).

[0259] In all aspects, such as Figure 2-3As shown in Figure 33, the first transition region 212 may include a second transition surface region 245 extending between the second surface region 225 and the second central surface region 243. In other aspects, the width of the second transition surface region 245 may be measured as a distance 106 along a length 105 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 (see Figure 33). Figure 1 The minimum distance on the surface. In other respects, the width of the second transition surface region 245 may be substantially equal to (e.g., equal to) the first transition width 214 of the first transition region 212. In other respects, such 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 two surface regions.

[0260] In all aspects, such as Figure 2-5 As shown in Figure 33, the thickness of the first transition region 212 may decrease between the substrate thickness 207 of the first portion 221 and the center thickness 209 of the central portion 281. In other aspects, as shown, the thickness of the first transition region 212 may 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 central portion 281. As used herein, a smooth decrease in thickness means that the change in cross-sectional area is smooth (e.g., gradual) rather than a sudden change in thickness (e.g., stepwise). As used herein, a monotonically decreasing thickness in one direction means that the thickness decreases for a portion of the time and remains constant, decreases, or both for the remainder of the time (i.e., the thickness decreases in this direction but never increases). The smooth shape of the first transition region and / or the second transition region can reduce optical distortion. A monotonically decreasing thickness of the first transition region and / or the second transition region can reduce the incidence of mechanical instability and / or reduce the visibility of the transition region.

[0261] In all aspects, such as Figure 2-5As shown in Figures 3 and 33, the first transition surface region 215 may include a linearly inclined surface extending between the first central surface region 213 and the first surface region 223. In various aspects, although not shown, the first transition surface region may include a concave shape, for example, wherein a local slope of the first transition surface region smoothly transitions to the slope of the first central surface region 213, and the local slope of the first transition surface region is substantially different from the slope of the first surface region 223. In various aspects, although not shown, the first transition surface region may include an S-shaped shape. In various aspects, although not shown, the local slope of the first transition surface region at the midpoint of the first transition surface region may be greater than the slope at the locations where the first transition surface region meets the first central surface region 213 and the locations where the first transition surface region meets the first surface region 223. In various aspects, although not shown, the first transition surface region may include a concave shape, for example, wherein a local slope of the first transition surface region smoothly transitions to the slope of the first surface region 223, and the local slope of the first transition surface region is substantially different from the slope of the first central surface region 213. In various respects, the second transition surface region may include one of the shapes or characteristics discussed above with respect to the first transition surface region. For example, as Figure 2 As shown, the second transition surface region 245 may include a linear inclined surface extending between the second central surface region 243 and the second surface region 225.

[0262] In all aspects, such as Figure 2-5 As shown in Figure 33, the thickness of the first transition region 212 can decrease from the substrate thickness 207 to the center thickness 209 at a constant rate (e.g., linearly). In various aspects, although not shown, the rate of decrease of the thickness of the first transition region at the location where the first transition surface region meets the first center surface region 213 can be slower than at the midpoint of the first transition region and / or slower than at the location where the first transition surface region meets the first surface region 223 (e.g., the first portion 221). In various aspects, although not shown, the rate of decrease of the thickness of the first transition region at the location where the first transition surface region meets the first center surface region 213 can be faster than at the midpoint of the first transition region and / or faster than at the location where the first transition surface region meets the first surface region 223. Making the surface regions of the first transition region and / or the second transition region non-uniform in slope can reduce the number of corresponding transition regions, the intermediate thickness of which includes, for example, the expansion strain caused by chemical strengthening, is smaller than a portion of the corresponding transition region closer to the first center surface region and / or the second center surface region and / or smaller than the first center surface region and / or the second center surface region.

[0263] 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 “average angle” is calculated with respect to a position on the corresponding transition surface region relative to the corresponding central surface region, where the position of the corresponding central surface region approximates a plane fitted by measurements at 20 locations evenly spaced along a direction 106 of length 105 on the corresponding central surface region. The measured “average angle” is the exterior angle of the foldable substrate, meaning it extends from the plane fitted to the corresponding central surface region to the position of the corresponding transition surface region without penetrating the material of the foldable substrate, except for accidental amounts at the endpoints. The average angle is calculated based on 10 locations on the corresponding transition surface region located in an area comprising 80% of the distance the corresponding central surface region is recessed from the corresponding main surface, wherein the region is centered at the midpoint of the direction 202 of thickness (e.g., substrate thickness 207, central thickness 209) between the corresponding central surface region and the corresponding main surface.

[0264] In all aspects, such as Figure 2-5As shown in Figure 33, the first transition surface region 215 of the first transition region 212 extends between the first surface region 223 and the first central surface region 213 at a first average angle 282 relative to the first central surface region 213. As described above, the first average angle 282 is an exterior angle because, except for accidental amounts at the endpoints, it does not penetrate the material of the foldable substrate 201. In other aspects, the first average angle 282 may be about 176.0° or greater, about 176.1° or greater, about 176.3° or greater, about 176.5° or greater, about 176.7° or greater, about 177.0° or greater, about 177.1° or greater, 177.2° or greater, about 177.3° or greater, about 177.4° or greater, about 177.5° or greater, about 177.6° or greater, or 177.7° or greater. Larger, approximately 177.8° or larger, approximately 179.9° or smaller, approximately 179.7° or smaller, approximately 179.5° or smaller, approximately 179.3° or smaller, approximately 179.0° or smaller, approximately 178.7° or smaller, approximately 178.5° or smaller, approximately 178.3° or smaller, approximately 178.0° or smaller, approximately 177.7° or smaller, approximately 177.5° or smaller, approximately 177.3° or smaller, or approximately 177.0° or smaller. In other respects, the first average angle 282 may be within the range of about 176.0° to about 179.9°, about 176.1° to about 179.9°, about 176.3° to about 179.7°, about 176.5° to about 179.7°, about 176.7° to about 179.5°, about 177.0° to about 179.5°, about 177.1° to about 179.3°, about 177.2° to about 179.3°, about 177.3° to about 179.0°, about 177.4° to about 178.7°, about 177.5° to about 178.5°, about 177.6° to about 178.3°, about 177.7° to about 178.0°, or any range or subrange thereof. In other respects, the first average angle 282 may be about 177.0° or greater, for example, within the range of about 177.0° to about 179.9°, about 177.1° to about 179.7°, about 177.2° to about 179.5°, about 177.3° to about 179.3°, about 177.4° to about 179.0°, about 177.5° to about 178.7°, about 177.6° to about 178.5°, about 177.7° to about 178.3°, or any range or subrange thereof. For example, a first transition surface including a linear (e.g., flat) surface region has a first transition width of 1.0 mm and a height of 70 µm (i.e., the difference between the first central surface region 213 and the first main surface 203, corresponding to the first distance 219), corresponding to a first average angle of about 176.1°.In other respects, when the foldable substrate 201 includes a first groove 211 and a second groove 241 opposite to the first groove 211 (see). Figure 2-3 and Figure 33 When the first average angle 282 is within the range of about 177.0° to about 179.9°, about 177.1° to 179.5°, or about 177.2° to about 179.3°, the first average angle 282 can be within the range of about 177.0° to about 179.9°, about 177.1° to 179.5°, or about 177.2° to about 179.3°. In other aspects, when the foldable substrate 201 includes the first recess 211 and the second central surface region 243 is flush with the second main surface 205 (see...), Figure 4-5 The first average angle 282 may be in the range of about 176.1° to about 179.9°, about 176.3° to 179.7°, or about 176.5° to about 179.5°. As discussed herein, providing a first average angle from about 176.1° to about 179.9° or from about 177.0° to about 179.9° may reduce the visibility of the transition zone (e.g., resulting in a lower contrast ratio and / or creating a transition zone that is not visible to the naked eye).

[0265] In all aspects, such as Figure 2-3 As shown in Figure 33, the third transition surface region 217 of the second transition region 218 extends between the third surface region 233 and the first central surface region 213 at a third average angle 286 relative to the first central surface region 213. In other aspects, the third average angle 286 may be within one or more ranges discussed above with respect to the first average angle 282. In other aspects, the first average angle 282 may be substantially equal to the third average angle 286.

[0266] In all aspects, such as Figure 2-5 As shown in Figure 33, the central portion 281 of the foldable substrate 201 may include a second transition region 218, which includes a third transition surface region 217 extending between the third surface region 233 and the first central surface region 213. In other aspects, as shown, the width of the second transition region 218 (e.g., a second transition width 216) may be such that, between a portion of the first central surface region 213 extending along the third plane 204b and a portion of the third surface region 233, in a direction 106 of length 105 (see Figure 33). Figure 1 The minimum distance measurement on the second transition region 218. In other aspects, the second transition width 216 of the second transition region 218 may be within one or more of the ranges discussed above with respect to the first transition width 214. In other aspects, the second transition width 216 of the second transition region 218 may be substantially equal to (e.g., equal to) the first transition width 214.

[0267] In all aspects, such as Figure 2-3As shown in Figure 33, the second transition region 218 may include a fourth transition surface region 247 extending between the fourth surface region 235 and the second central surface region 243. In other aspects, the width of the fourth transition surface region 247 may be such that a portion of the second central surface region 243 extending along the fourth plane 206b and a portion of the fourth surface region 235 lie in the direction 106 of length 105 (see Figure 33). Figure 1 The minimum distance measurement on ). In other respects, the width of the fourth transition surface region 247 can be substantially equal to (e.g., equal to) the second transition width 216. In various respects, such as Figure 2-3 As shown in Figure 33, 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, such as Figure 4 As shown, the portion of the second transition region 218 extending between the fourth surface region 235 and the second central surface region 243 may be coplanar with one or two surface regions.

[0268] In all aspects, such as Figure 2-5 As shown in Figure 33, the third transition surface region 217 may include a linearly 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 respect 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 respect to the first transition surface region. For example, as... Figure 2-5 As shown in Figure 33, 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, such as Figure 2-5 As shown in Figure 33, the thickness of the second transition region 218 can decrease at a constant rate (e.g., linearly) from the substrate thickness 207 to the center thickness 209. In some aspects, although not shown, the rate of decrease in the thickness of the second transition region at the location where the third transition surface region meets the first center surface region 213 can be slower than at the midpoint of the second transition region and / or slower than at the location where the third transition surface region meets the third surface region 233 (e.g., the first portion 221). In some aspects, although not shown, the rate of decrease in the thickness of the second transition region at the location where the third transition surface region meets the first center surface region 213 can be faster than at the midpoint of the second transition region and / or at the location where the third transition surface region meets the third surface region 233.

[0269] In all aspects, such as Figure 2-3 As shown in Figure 33, the second transition surface region 245 of the first transition region 212 extends between the second surface region 225 and the second central surface region 243 at a second average angle 284 relative to the second central surface region 243. In other aspects, the second average angle 284 may be within one or more ranges discussed above with respect to the first average angle 282. In other aspects, the first average angle 282 may be substantially equal to the second average angle 284. Placing the average angle within one of the ranges mentioned above can reduce the visibility of the transition region.

[0270] In all aspects, such as Figure 2-3 As shown in Figure 33, the fourth transition surface region 247 of the second transition region 218 extends between the fourth surface region 235 and the second central surface region 243 at a fourth average angle 288 relative to the second central surface region 243. In other aspects, the fourth average angle 288 may be within one or more ranges discussed above with respect to the second average angle 284. In other aspects, the second average angle 284 may be substantially equal to the fourth average angle 288. In other aspects, the first average angle 282 and / or the third average angle 286 may be substantially equal to the fourth average angle 288.

[0271] Throughout this disclosure, the “surface angle” of the transition surface region relative to the main surface is measured as the angle between the transition surface region and the central surface region. The “surface angle” is calculated with respect to a position on the corresponding transition surface region relative to the corresponding main surface, where the position of the corresponding main surface approximates a plane fitted by measurements at 20 evenly spaced positions along a length 105 direction 106 on the corresponding main surface. The measured “surface angle” is an interior angle of the foldable substrate, meaning it extends from the plane fitted to the corresponding main surface to the position of the corresponding transition surface region without leaving the material of the foldable substrate, except for accidental amounts at the endpoints. The average angle is calculated based on 10 positions on the corresponding transition surface region located in an area comprising 80% of the distance the corresponding central surface region is recessed from the corresponding main surface, wherein this area is centered at the midpoint of the direction 202 between the corresponding central surface region and the corresponding main surface in terms of thickness (e.g., substrate thickness 207, central thickness 209).

[0272] In all aspects, such as Figure 33 As shown, the first surface angle 3302 is defined between the first transition surface region 215 of the first transition region 212 and the first main surface 203 (e.g., the first surface region 223, the first plane 204a). In various aspects, such as Figure 33As shown, the third surface angle 3306 is defined between the third transition surface region 217 of the second transition region 218 and the first main surface 203 (e.g., the third surface region 233, the first plane 204a). In various aspects, the first surface angle 3302 and / or the third surface angle 3306 may be within one or more of the ranges discussed above with respect to the first average angle 282. In various aspects, the first surface angle 3302 may be substantially equal to the first average angle 282. In various aspects, the first surface angle 3302 may be substantially equal to the third surface angle 3306.

[0273] In all aspects, such as Figure 33 As shown, the second surface angle 3304 is defined between the second transition surface region 245 of the first transition region 212 and the second main surface 205 (e.g., the second surface region 225, the second plane 206a). In various aspects, such as Figure 33 As shown, the fourth surface angle 3308 is defined between the fourth transition surface region 247 of the second transition region 218 and the second main surface 205 (e.g., the fourth surface region 235, the second plane 206a). In various aspects, the second surface angle 3304 and / or the fourth surface angle 3308 may be within one or more of the ranges discussed above with respect to the first average angle 282. In various aspects, the second surface angle 3304 may be substantially equal to the first average angle 282. In various aspects, the second surface angle 3304 may be substantially equal to the first surface angle 3302. In various aspects, the second surface angle 3304 may be substantially equal to the second average angle 284. In various aspects, the second surface angle 3304 may be substantially equal to the fourth surface angle 3308.

[0274] As used herein, if a first layer and / or component is described as “positioned above a second layer and / or component,” then there may or may not be other layers between the first layer and / or component and the second layer and / or component. Furthermore, as used herein, “positioned above” does not refer to a relative position with respect to gravity. For example, the first layer and / or component can be considered “positioned above the second layer and / or component” when it is located below, above, or to the side of the second layer and / or component. As used herein, describing a first layer and / or component as “bonded to” a second layer and / or component means that the layers and / or components are bonded to each other through direct contact and / or bonding or via an adhesive layer. As used herein, describing a first layer and / or component as “in contact” with or “with” a second layer and / or component means direct contact and includes cases where the layers and / or components are bonded to each other.

[0275] like Figure 2 and 4As shown, the foldable device 101 may include an adhesive layer 261. As illustrated, the adhesive layer 261 may include a first contact surface 263 and a second contact surface 265 that may oppose the first contact surface 263. In various aspects, such as Figure 2 and 4 As shown, the second contact surface 265 of the adhesive layer 261 may include a flat surface. In various aspects, such as Figure 2 and 4 As shown, the first contact surface 263 of the adhesive layer 261 may include a flat 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, or about 20 µm or less. In various aspects, the adhesive thickness 267 of the adhesive layer 261 may be in the range of 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 subrange thereof.

[0276] In all aspects, such as Figure 2 and 4 As shown, the second contact surface 265 of the adhesive layer 261 may face and / or contact the first main surface 273 of the release liner 271 (described below). In various aspects, as Figure 2 As shown, the first contact surface 263 of the adhesive layer 261 can face and / or contact the second surface region 225 of the first portion 221. In various aspects, such as Figure 2 As shown, the first contact surface 263 of the adhesive layer 261 may face and / or contact the fourth surface region 235 of the second portion 231. In various aspects, such as Figure 2 As shown, the first contact surface 263 of the adhesive layer 261 can face the second central surface region 243 of the central portion 281. In various aspects, such as Figure 4 As shown, the first contact surface 263 of the adhesive layer 261 may face and / or contact the first surface region 223 of the first portion 221. In various aspects, such as Figure 4 As shown, the first contact surface 263 of the adhesive layer 261 may face and / or contact the third surface region 233 of the second portion 231. In various aspects, such as Figure 4 As shown, the first contact surface 263 of the adhesive layer 261 may face the first central surface region 213 of the central portion 281. In various aspects, such as Figure 2As shown, the first contact surface 263 of the adhesive layer 261 may face the second central surface region 243 of the central portion 281. In other aspects, although not shown, the first contact surface 263 of the adhesive layer 261 may contact the second central surface region 243 of the central portion 281, for example, by filling... Figure 2 The area indicated is occupied by the second polymer portion 299 (e.g., the second recess 241). In various aspects, although not shown, the second recess may not be completely filled, for example, leaving space for electronic and / or mechanical devices. In various aspects, although not shown, Figure 4 The foldable substrate 201 can be configured such that the adhesive layer 261 contacts the second main surface 205 instead of the first main surface 203, while the second polymer portion 299 or the coating 251 replacing the second polymer portion 299 can be at least partially positioned in the first groove 211.

[0277] In various aspects, adhesive layer 261 may include one or more of polyolefins, polyamides, halogenated polymers (e.g., polyvinyl chloride or fluoropolymers), elastomers, urethanes, phenolic resins, parylene, polyethylene terephthalate (PET), and polyether ether ketone (PEEK). Examples of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), and polypropylene (PP). Examples of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers, and ethylene tetrafluoroethylene (ETFE) polymers. Examples 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 other aspects, adhesive layer 261 may include an optically clear adhesive. In yet another aspect, the optically clear adhesive may include one or more optically transparent polymers: acrylics (e.g., polymethyl methacrylate (PMMA)), epoxy resins, silicones, and / or polyurethanes. Examples of epoxy resins include bisphenol epoxy resins, phenolic epoxy resins, alicyclic epoxy resins, and glycidylamine epoxy resins. In yet another aspect, the optically clear adhesive may include, but is not limited to, acrylic adhesives, such as 3M 8212 adhesive, or optically clear liquid adhesives, such as LOCTITE optically clear liquid adhesive. Exemplary aspects of optically clear adhesives include transparent acrylics, epoxy resins, silicones, and polyurethanes. For example, optically transparent liquid adhesives may include one or more of LOCTITE AD 8650, LOCTITE AA 3922, LOCTITE EA E-05MR, and LOCTITE UK U-09LV, all of which are available from Henkel.

[0278] In various aspects, adhesive layer 261 may include an elastic modulus of about 0.001 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, or about 0.05 MPa or less. In various aspects, adhesive layer 261 may include an elastic modulus in 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 subrange thereof. In various aspects, the elastic modulus included in the adhesive layer may be within one or more of the ranges discussed below with respect to the elastic modulus of polymeric portions 289 and / or 299.

[0279] like Figure 2-5 As shown in Figures 33 and 4, polymeric portions 289 and / or 299 of the foldable device 101 may be located between the first portion 221 and the second portion 231. In various aspects, as shown, the polymeric portion may include a first polymeric portion 289 that is at least partially located in and / or fills the first recess 211. In various aspects, as... Figure 2-3 As shown in Figures 33 and 4, the polymeric portion may include a second polymeric portion 299 that is at least partially located in and / or fills the second groove 241. In various aspects, as... Figure 4-5 As shown, the polymeric portion may include a second polymeric portion 299 that is at least partially located in and / or fills the first recess 211. In various aspects, although not shown, the second recess may not be completely filled, for example, leaving space for electronic and / or mechanical devices. In various aspects, such as Figure 3 or Figure 5 As shown, a portion of the second polymer portion 299 may be located in the corresponding groove (e.g., Figure 5 The first groove 211 or Figure 3 In the second groove 241), and another continuous portion of the second polymer portion 299 may extend beyond the corresponding groove (e.g., in Figure 5 The second polymer portion 299 further extends beyond the first plane 204a or... Figure 3 (extending beyond the second plane 206a), wherein the additional thickness 399 or 589 is disposed on the corresponding main surface (e.g., in Figure 5 The additional thickness 589 is placed on the first main surface 203 or... Figure 3An additional thickness of 399 is placed on the second main surface 205. In various aspects, such as Figure 3 As shown, a portion of the first polymeric portion 289 may be located in the first groove 211, and another continuous portion of the first polymeric portion 289 may extend beyond the groove (e.g., the first polymeric portion 289 further extends beyond the first plane 204a), wherein an additional thickness 389 (discussed below) is disposed on the first main surface 203.

[0280] like Figure 2-3 As shown in Figures 33, the first polymeric portion 289 may include a fourth contact surface 285 opposite to the third contact surface 283. In various aspects, as shown, the third contact surface 283 may include a flat surface, for example, substantially coplanar with the first surface region 223 and the third surface region 233 (e.g., extending along a common plane, i.e., the first plane 204a). In various aspects, as... Figure 2 As shown, the third contact surface 283 may be substantially flush with the first main surface 203 (e.g., the first surface region 223, the third surface region 233, and / or the first plane 204a). In various aspects, such as Figure 33 As shown, the distance 3323 (measured in direction 202) between the third contact surface 283 of the first polymeric portion 289 and the first main surface 203 (e.g., the first surface region 223, the third surface region 233, and / or the first plane 204a) can be about 5 µm or less, about 4 µm or less, about 3 µm or less, about 2 µm or less, or about 1 µm or less. As discussed herein, the distance between the contact surface of the polymeric portion and the corresponding main surface of the foldable substrate helps to reduce the contrast ratio of the transition region (e.g., reduce visibility). In various aspects, such as Figure 2 As shown, the fourth primary surface 255 of the coating 251 may face and / or contact the third contact surface 283 of the first polymer-like portion 289. In various aspects, such as Figure 3 As shown, the fourth main surface 355 of the cover plate substrate 351 can face and / or contact the third contact surface 283 of the first polymeric portion 289. In various aspects, such as Figure 2-3 As shown, the fourth contact surface 285 may include a flat surface, for example, substantially coplanar with the first central surface region 213 (e.g., extending along a common plane, i.e., the third plane 204b). In other aspects, the fourth contact surface 285 may contact the first central surface region 213, the first transition surface region 215, and / or the third transition surface region 217. In other aspects, such as Figure 3As shown, the portion of the first polymeric portion 289 extending beyond the first groove 211 (e.g., extending beyond the first plane 204a) may include an additional thickness 389 of about 1 µm or greater, about 5 µm or greater, about 10 µm or greater, about 100 µm or less, about 60 µm or less, about 30 µm or less, or about 20 µm or less. In all aspects, the additional thickness 389 may be in the range of 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 subrange thereof.

[0281] like Figure 2-5 As shown in Figure 33, the second polymeric portion 299 may include a fourth contact surface 295 opposite to the third contact surface 293. In other aspects, such as... Figure 2-3 As shown in Figure 33, the third contact surface 293 can contact the second central surface region 243, the second transition surface region 245, and / or the fourth transition surface region 247. In various aspects, such as Figure 2-3 As shown, the third contact surface 293 may include a flat surface, for example, substantially coplanar with the second central surface region 243 (e.g., extending along a plane common to the fourth plane 206b). In various aspects, such as Figure 33 As shown, the distance 3325 (measured in direction 202) between the fourth contact surface 295 of the second polymer portion 299 and the second main surface 205 (e.g., the second surface region 225, the fourth surface region 235 and / or the second plane 206a) can be about 5 µm or less, about 4 µm or less, about 3 µm or less, about 2 µm or less, or about 1 µm or less.

[0282] In all aspects, such as Figure 2 and 4 As shown, the third contact surface 283 can be substantially flush with the corresponding main surface of the foldable substrate 201, that is... Figure 2 The second main surface 205 of the foldable device 101 shown (e.g., second surface region 225, fourth surface region 235, and / or second plane 206a), or Figure 4The first main surface 203 of the foldable device 401 shown (e.g., first surface region 223, third surface region 233, and / or first plane 204a). For example, the distance (measured in direction 202) between the third contact surface 283 of the first polymeric portion 289 and the corresponding main surface of the foldable substrate can be about 5 µm or less, about 4 µm or less, about 3 µm or less, about 2 µm or less, or about 1 µm or less. As discussed herein, the distance between the contact surface of the polymeric portion and the corresponding main surface of the foldable substrate helps to reduce the contrast ratio of the transition region (e.g., reduce visibility). In various aspects, such as Figure 2 As shown, the fourth contact surface 295 may include a flat surface, for example, substantially coplanar with the second surface region 225 and the fourth surface region 235 (e.g., extending along a plane common to the second plane 206a).

[0283] Throughout this disclosure, the average angle of the contact surface of the polymer portion relative to the main surface is measured as the angle between the contact surface of the polymer portion and the main surface of the foldable substrate. The angle is calculated with respect to a position on the corresponding contact surface relative to a corresponding central surface region, where the position on the corresponding main surface approximates a plane fitted by measurements from 20 locations evenly spaced along a length 105 direction 106 on the corresponding main surface. The measured angle is an interior angle of the foldable substrate, meaning it extends from the plane fitted to the corresponding main surface to the position on the corresponding contact surface without leaving the foldable device, except for accidental values ​​at the endpoints. The average angle is calculated based on 10 positions on the corresponding contact surface located within a region comprising 33% of the width 287 of the central portion 281 closest to the corresponding main surface.

[0284] In all aspects, such as Figure 33As shown, the third contact surface 283 of the first polymeric portion 289 may be non-planar (e.g., including portions not parallel to the first plane 204a). For example, as shown, the shape of the third contact surface 283 (e.g., relative to the first plane 204a) may be proportional to the shape of the first transition surface region 215, the first central surface region 213, and the third transition surface region 217 relative to a common reference (e.g., relative to the first plane 204a). In various aspects, the third contact surface 283 of the first polymeric portion 289 may form a first polymer angle 3312 with the first main surface 203 of the foldable substrate 201 (e.g., the first plane 204a and / or the first surface region 223), and / or the third contact surface 283 of the first polymeric portion 289 may form a third polymer angle 3316 with the first main surface 203 of the foldable substrate 201 (e.g., the first plane 204a and / or the third surface region 233). In various aspects, the third contact surface 283 of the first polymeric portion 289 may form a first polymer angle 3312 with the first main surface 203 of the foldable substrate 201 (e.g., the first plane 204a and / or the first surface region 223), and / or the third contact surface 283 of the first polymeric portion 289 may form a third polymer angle 3316 with the first main surface 203 of the foldable substrate 201 (e.g., the first plane 204a and / or the third surface region 233). Without being bound by theory, the shape of the third contact surface of the polymeric portion may reflect the degree of shrinkage of the polymeric portion due to curing. Polymers with deeper grooves, steeper transition angles (e.g., the first average angle discussed above), and greater shrinkage due to curing exhibit more pronounced deviations from the first main surface 203 (e.g., the first plane 204a) (e.g., distance 3323 and / or the first polymer angle 3312). As described above, the first polymer angle 3312 is an interior angle because it does not depart from the combined region of the foldable substrate 201 and the first polymer portion 289, except for accidental amounts at the endpoints. In other aspects, the first polymer angle 3312 may be approximately 178° or greater, approximately 178.3° or greater, approximately 178.4° or greater, approximately 178.5° or greater, approximately 178.6° or greater, approximately 178.7° or greater, approximately 178.8° or greater, 178.9° or greater, approximately 179.0° or greater, approximately 179.1° or greater, approximately 179.2° or greater, approximately 179.3° or greater. Larger, 179.4° or larger, about 179.5° or larger, about 179.9° or smaller, about 179.8° or smaller, about 179.7° or smaller, about 179.6° or smaller, about 179.5° or smaller, about 179.4° or smaller, about 179.3° or smaller, about 179.2° or smaller, about 179.1° or smaller, about 179.0° or smaller, or about 178.9° or smaller.In other respects, the first polymer angle 3312 may be within the range of about 178.0° to about 179.9°, about 178.3° to about 179.9°, about 178.3° to about 179.8°, about 178.4° to about 179.7°, about 178.4° to about 179.6°, about 178.5° to about 179.5°, about 178.5° to about 179.4°, about 178.6° to about 179.3°, about 178.6° to about 179.2°, about 178.7° to about 179.2°, about 178.7° to about 179.1°, about 178.8° to about 179.0°, about 179.8° to about 178.9°, or any range or subrange thereof. In other aspects, the first polymer angle 3312 may be about 179.0° or greater, for example, within the range of about 179.0° to about 179.9°, about 179.1° to about 179.9°, about 179.1° to about 179.8°, about 179.2° to about 179.7°, about 179.2° to about 179.6°, about 179.3° to about 179.5°, about 179.4° to about 179.5°, or any range or subrange thereof. In other aspects, the foldable substrate 201 may include a first recess 211 and a second recess 241 opposite to the first recess 211 (see [reference]). Figure 2-3 And 33), the first polymer angle 3312 may be in the range of about 178.3° to about 179.9°, about 178.5° to 179.5°, or about 179.1° to about 179.4°. In other aspects, when the foldable substrate 201 includes the first groove 211 and the second central surface region 243 is flush with the second main surface 205 (see 33), Figure 4-5 The first polymer angle 3312 may range from about 179.1° to about 179.9°, from about 179.2° to about 179.7°, or from about 179.3° to about 179.5°. As discussed herein, providing a first average angle from about 178.3° to about 179.9° or from about 179.1° to about 179.9° may reduce the visibility of the transition region (e.g., resulting in a lower contrast ratio and / or creating a transition region that is not visible to the naked eye). In other aspects, the third polymer angle 3316 may be within one or more of the ranges discussed above with respect to the first polymer angle 3312. In other aspects, the first polymer angle 3312 may be substantially equal to the third polymer angle 3316.

[0285] In all aspects, such as Figure 33As shown, the fourth contact surface 295 of the second polymeric portion 299 may be non-planar (e.g., including portions not parallel to the second plane 206a). For example, as shown, the shape of the fourth contact surface 295 (e.g., relative to the second plane 206a) may be proportional to the shape of the second transition surface region 245, the second central surface region 243, and the fourth transition surface region 247 relative to a common reference (e.g., relative to the second plane 206a). In various aspects, the fourth contact surface 295 of the second polymeric portion 299 may form a second polymer angle 3314 with the second main surface 205 of the foldable substrate 201 (e.g., the second plane 206a and / or the second surface region 225), and / or the fourth contact surface 295 of the second polymeric portion 299 may form a fourth polymer angle 3318 with the second main surface 205 of the foldable substrate 201 (e.g., the second plane 206a and / or the fourth surface region 235). In other aspects, the second polymer angle 3314 may fall within one or more of the ranges discussed above with respect to the first polymer angle 3312. In other aspects, the first polymer angle 3312 may be substantially equal to the second polymer angle 3314. In other aspects, the fourth polymer angle 3318 may fall within one or more of the ranges discussed above with respect to the first polymer angle 3312. In other aspects, the first polymer angle 3312 and / or the second polymer angle 3314 may be substantially equal to the fourth polymer angle 3318.

[0286] In all aspects, such as Figure 4-5 As shown, the third contact surface 293 can contact the first central surface region 213, the first transition surface region 215, and / or the third transition surface region 217. In various aspects, such as Figure 4-5 As shown, the third contact surface 293 may include a flat surface, for example, substantially coplanar with the first central surface region 213 (e.g., extending along a plane common to the third plane 204b). In various aspects, as shown, the third contact surface 293 may include a flat surface, for example, substantially coplanar with the first central surface region 213 (e.g., extending along a plane common to the third plane 204b). In various aspects, as... Figure 4-5 As shown, the fourth contact surface 295 may be coplanar with the first surface region 223 and the third surface region 233 (e.g., extending along a plane common to the first plane 204a). In various aspects, such as Figure 2 and 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 second polymeric portion 299.

[0287] In other aspects, such as Figure 3 and 5As shown, the second polymer portion 299 may be included in the corresponding groove (e.g., Figure 3 The second groove 241 or Figure 5 The portion within the first groove 211, and another portion extending further beyond the corresponding plane with an additional thickness of 399 or 589. In other aspects, such as Figure 3 As shown, the portion of the second polymeric portion 299 extending beyond the second groove 241 (e.g., beyond the second plane 206a) may include an additional thickness 399, which may be within one or more ranges discussed above with reference to the additional thickness 389. In other aspects, such as Figure 5 As shown, the portion of the first polymeric portion 289 extending beyond the first groove 211 (e.g., beyond the first plane 204a) may include an additional thickness 589, which may be within one or more ranges discussed above with reference to the additional thickness 389.

[0288] In various aspects, polymer portions 289 and / or 299 include polymers (e.g., optically transparent polymers). In other aspects, polymer portions 289 and / or 299 may include one or more optically transparent polymers: acrylics (e.g., polymethyl methacrylate (PMMA)), epoxy resins, silicones, and / or polyurethanes. Examples of epoxy resins include bisphenol epoxy resins, phenolic epoxy resins, alicyclic epoxy resins, and glycidyl amine epoxy resins. In other aspects, polymer portions 289 and / or 299 include one or more of polyolefins, polyamides, halogenated polymers (e.g., polyvinyl chloride or fluoropolymers), elastomers, urethanes, phenolic resins, parylene, polyethylene terephthalate (PET), and polyetheretherketone (PEEK). Examples of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), and polypropylene (PP). Examples of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers, and ethylene tetrafluoroethylene (ETFE) polymers. Examples 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)), such as one or more of polystyrene, polydichlorophosphazene, and poly(5-ethylidene-2-norbornene). In each aspect, the polymer portion may include sol-gel materials. Examples of polyurethanes include thermosetting polyurethanes, such as Dispurez 102 available from Incorez, and thermoplastic polyurethanes, such as KrystalFlex PE505 available from Huntsman. In other aspects, the second portion may include an ethylene glycol copolymer. Exemplary aspects of the ethylene glycol copolymer include SURLYN (e.g., Surlyn PC-2000, Surlyn 8940, Surlyn 8150) available from Dow Chemical Company. Additional exemplary aspects of the second portion include Eleglass w802-GL044 available from Axalta, wherein the crosslinking agent is 1 wt% to 2 wt%. In various aspects, polymeric portions 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 polymeric portion may further include fibers to form a polymer-fiber composite.

[0289] In all respects, polymeric portions 289 and / or 299 may include an elastic modulus of about 0.001 MPa or greater, about 0.01 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, polymeric portions 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, or any range or subrange thereof. In various aspects, polymeric portions 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 subrange thereof. In various aspects, the elastic modulus of polymeric portions 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 subrange thereof. By providing polymeric portions 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), non-destructive folding of the foldable device can be facilitated. In various aspects, the elastic modulus of adhesive layer 261 is greater than that of polymeric portions 289 and / or 299, and this arrangement improves puncture resistance. In various aspects, the elastic modulus of polymeric portions 289 and / or 299 may be less than that of the foldable substrate 201. In various aspects, adhesive layer 261 may include an elastic modulus in the range listed above in this paragraph. In other respects, the elastic modulus of the adhesive layer 261 may be substantially the same as that of the polymeric portions 289 and / or 299.In other respects, the elastic modulus of the adhesive layer 261 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 subrange thereof. In other respects, the elastic modulus of the polymeric portions 289 and / or 299 may be less than the elastic modulus of the foldable substrate 201.

[0290] In all aspects, such as Figure 2-3 As shown, coating 251 can be disposed over a first main surface 203 of the foldable substrate 201. In other aspects, coating 251 can be disposed over a first portion 221, a second portion 231, and a central portion 281. In various aspects, coating 251 may include a third main surface 253 and a fourth main surface 255 opposite to the third main surface 253. In other aspects, such as Figure 2As shown, coating 251 (e.g., fourth main surface 255) may contact foldable substrate 201 (e.g., first main surface 203). In other aspects, at least a portion of coating 251 may be located in the first recess 211. In other aspects, coating 251 may include a coating thickness 257 defined between the third main surface 253 and the fourth main surface 255. In other respects, 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, or about 10 µm or less. In all respects, 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 subrange thereof.In other aspects, the coating thickness 257 can be from about 0.1 µm to about 50 µm, from about 0.1 µm to about 30 µm, from about 0.1 µm to about 25 µm, from about 0.1 µm to about 20 µm, from about 0.1 µm to about 15 µm, from about 0.1 µm to about 10 µm, from about 1 µm to about 30 µm, from about 1 µm to about 25 µm, from about 1 µm to about 20 µm, from about 1 µm to about 15 µm, from about 1 µm to about 10 µm, from about 5 µm to about 30 µm, from about 5 µm to about 25 µm, from about 10 µm to about 20 µm, from about 10 µm to about 15 µm, from about 15 µm to about 30 µm, from about 15 µm to about 25 µm. The range of 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 subrange thereof.

[0291] In various aspects, coating 251 may include a polymeric hard coating. In other aspects, the polymeric hard coating may include one or more of ethylene-acid copolymers, polyurethane polymers, acrylate resins, and mercapto-ester resins. Examples of ethylene-acid copolymers include ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and ethylene-acrylic acid-methacrylic acid trimers (e.g., Nucrel, manufactured by DuPont), ionomers of ethylene-acid copolymers (e.g., Surlyn, manufactured by DuPont), and amine dispersions of ethylene-acrylic acid copolymers (e.g., Aquacer, manufactured by BYK). Examples of polyurethane polymers include water-modified polyurethane dispersions (e.g., Eleglas®, manufactured by Axalta). Examples of UV-curable acrylate resins include acrylate resins (e.g., Uvekol® resin, manufactured by Allinex), cyanoacrylate adhesives (e.g., Permabond® UV620, manufactured by Krayden), and UV-radical acrylate resins (e.g., Ultrabond windshield repair resins, such as Ultrabond (45CPS)). Examples of mercapto-ester resins include mercapto-ester triallyl isocyanurate (e.g., Norland optical adhesive NOA 61). In other aspects, polymeric hard coatings can include ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, which can be ionized by neutralizing carboxylic acid residues with typical alkali metal ions (e.g., sodium and potassium) and zinc to form ionomer resins. These ethylene-acrylic acid and ethylene-methacrylic acid ionomers can be dispersed in water and coated onto a substrate to form an ionomer coating. Alternatively, these acid copolymers can be neutralized with ammonia, which is released after coating and drying, reforming the acid copolymer as a coating. By providing coatings that include polymeric coatings, foldable devices can achieve low-energy breakage.

[0292] In various aspects, the coating may include a polymeric hard coating, including optically transparent polymeric hard coatings. Materials suitable for optically transparent polymeric hard coatings include, but are not limited to, cured acrylate resins, inorganic-organic hybrid polymers, aliphatic or aromatic hexafunctional urethane acrylates, siloxane hybrids, and nanocomposites, such as epoxy resins and urethane materials containing nanosilicates. In various aspects, the optically transparent polymeric hard coating may consist substantially of one or more of these materials. As used herein, "inorganic-organic hybrid polymer" means a polymeric material comprising monomers containing both inorganic and organic components. Inorganic-organic hybrid polymers are obtained through polymerization reactions between monomers having inorganic and organic groups. Inorganic-organic hybrid polymers are not nanocomposites comprising separate inorganic and organic components or phases, such as inorganic particles dispersed in an organic matrix. More specifically, materials suitable for use in 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 consist substantially of an organic polymer material, an inorganic-organic hybrid polymer material, or an aliphatic or aromatic hexafunctional urethane acrylate. In various aspects, the OTP hard coating may consist of polyimide, an organic polymer material, an inorganic-organic hybrid polymer material, or an aliphatic or aromatic hexafunctional urethane acrylate. In various aspects, the OTP hard coating may include nanocomposite materials. In various aspects, the OTP hard coating may include at least one of nanosilicates, epoxy resins, and / or urethane materials. Compositions suitable for use in such OTP hard coatings are described in U.S. Patent Publication No. 2015 / 0110990, which is incorporated herein by reference in its entirety. As used herein, “organic polymer material” means a polymer material comprising monomers containing only organic components. In various respects, OTP hard coatings may include organic polymer materials manufactured by Gunze Limited with 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 containing both inorganic and organic components. Inorganic-organic hybrid polymers are obtained through polymerization reactions between monomers having both inorganic and organic groups. Inorganic-organic hybrid polymers are not nanocomposites comprising separate inorganic and organic components or phases, such as inorganic particles dispersed in an organic matrix.In various aspects, inorganic-organic hybrid polymer materials may contain polymeric monomers including inorganic silicon groups (e.g., silsesquioxane polymers). For example, silsesquioxane polymers may be alkyl-silsesquioxanes, aryl-silsesquioxanes, or arylalkyl-silsesquioxanes having the following chemical structure: (RSiO). 1.5 ) n Where 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 bonded to an organic matrix, such as SILPLUS manufactured by Nippon Steel Chemical Co., Ltd. In various aspects, the OTP hard coating may include 90 wt% to 95 wt% of an aromatic hexafunctional urethane acrylate (e.g., PU662NT (aromatic hexafunctional urethane acrylate) manufactured by Miwon Specialty Chemical Co.) and 10 wt% to 5 wt% of a photoinitiator (e.g., Darocur 1173 manufactured by Ciba Specialty Chemicals Corporation) having a hardness of 8H or higher. In various aspects, an OTP hard coating composed of aliphatic or aromatic hexafunctional urethane acrylate can be formed as a separate layer by spin-coating the layer onto 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 aliphatic or aromatic hexafunctional urethane acrylate material with a thickness within one or more of the thickness ranges discussed above for coating thickness 257.

[0293] In various aspects, coating 251 (if provided) may also include one or more of an easy-clean coating, a low-friction coating, an oleophobic coating, a diamond-like carbon (DLC) coating, a scratch-resistant coating, or a wear-resistant coating. The scratch-resistant coating may include oxynitrides with a thickness of about 500 micrometers or greater, such as aluminum oxynitride or silicon oxynitride. In these aspects, 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 an oxymethyl group attached to the silicon atom. In these aspects, the easy-clean coating may include the same material as the low-friction coating. In other aspects, the easy-clean coating may include a protonable group, such as an amine, such as an alkylaminosilane with an oxymethyl group attached to the silicon atom. In these aspects, the oleophobic coating may include the same material as the easy-clean coating. In various aspects, the diamond-like carbon (DLC) coating includes carbon and can be produced by applying a high-voltage potential in the presence of a hydrocarbon plasma.

[0294] In all aspects, such as Figure 3 As shown, the foldable device 301 may include a cover substrate 351 instead of the coating 251 discussed above, but in other aspects, both a coating and a cover substrate may be provided. In other aspects, the cover substrate 371 may include a glass-like material, a ceramic-like material, and / or sapphire. In other aspects, as shown, the cover substrate 351 may include a third main surface 353 and a fourth main surface 355 opposite to the third main surface 353. In other aspects, as shown, the coverage thickness 359 of the cover substrate 351 is defined between the third main surface 353 and the fourth main surface 355. In yet another aspect, the coverage thickness 359 may be within one or more of the ranges discussed above with respect to the coating thickness 257. In other aspects, as shown, the fourth main surface 356 may face the first main surface 203, the first central surface region 213, and / or the first polymeric portion 239 and / or be disposed above them. In other respects, as shown in the figure, the fourth main surface 355 may contact the third contact surface 283 of the first polymeric portion 289, but an adhesive layer (e.g., similar to or the same as adhesive layer 261) may be located between them.

[0295] Compared to a single groove whose surface is recessed by the sum of a first distance and a second distance, providing opposing first and second grooves can reduce the bending strain of the material located in the first and / or second grooves. This reduced bending strain in the material located in the first and / or second grooves broadens the material's applicability due to reduced strain requirements. For example, a harder and / or more rigid material (e.g., coating 251, first polymeric portion 289) can be located in the first groove, which can improve the impact resistance, puncture resistance, abrasion resistance, and / or scratch resistance of the foldable device. Furthermore, controlling the characteristics of the first material (e.g., coating 251, first polymeric portion 289) located in the first groove and the second material located in the second groove can control the position of the central axis of the foldable device and / or foldable substrate, which can reduce (e.g., mitigate, eliminate) the incidence of mechanical instability, device fatigue, and / or device failure. Providing opposing first and second grooves can reduce the strain encountered by the polymeric portion or other materials (e.g., adhesive layers) in the grooves (e.g., a reduction of 0% to 50%). Therefore, the yield strain requirement for the polymeric portion can be relaxed. In all aspects, the yield strain of the polymeric portion and / or 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, or about 8% or less. In all aspects, the yield strain of the polymeric portion and / or adhesive layer can 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 subrange thereof.

[0296] In all aspects, such as Figure 2 and 4 As shown in Figure 5, the foldable device 101, 401, or 501 may include a release liner 271, but in other respects other substrates (e.g., glass-like substrates and / or ceramic-like substrates discussed throughout the application) may be used instead of the shown release liner 271. In other respects, such as Figure 2 and 4 As shown, release liner 271 or another substrate can be disposed above adhesive layer 261. In other aspects, as shown, release liner 271 or another substrate can directly contact the second contact surface 265 of adhesive layer 261. In other aspects, such as... Figure 5As shown, release liner 271 or another substrate may be disposed over and / or in contact with a corresponding polymeric portion (e.g., the fourth contact surface 295 of the second polymeric portion 299). Release liner 271 or another substrate may include a first main surface 273 and a second main surface 275 opposite to the first main surface 273. As shown, release liner 271 or another substrate may be disposed on adhesive layer 261 by attaching the second contact surface 265 of adhesive layer 261 to the first main surface 273 of release liner 271 or another substrate. In various aspects, as shown, the first main surface 273 of release liner 271 or another substrate may include a flat surface. In various aspects, as shown, the second main surface 275 of release liner 271 or another substrate may include a flat surface. The substrate including release liner 271 may include paper and / or polymer. Exemplary aspects of paper include kraft paper, machine-made paper, polymer-coated paper (e.g., polymer-coated paper, cellophane, 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)).

[0297] In all aspects, such as Figure 3 As shown, the foldable device 301 may include an additional substrate 371 instead of the release liner 271 discussed above. In other aspects, the additional substrate 371 may include a glass-like material, a ceramic-like material, a rigid polymer portion (e.g., PET, PMMA, PI), a display device, and / or a touch sensor. In other aspects, as shown, the additional substrate 371 may include a third main surface 373 and a fourth main surface 375 opposite to the third main surface 373. In other aspects, as shown, the third main surface 373 may face the second main surface 205, the second central surface region 243, and / or the second polymer portion 299 and / or be disposed above them. In yet another aspect, as shown, the third main surface 373 may contact the fourth contact surface 295 of the second polymer portion 299, but an adhesive layer (e.g., similar to or the same as adhesive layer 261) may be located between them.

[0298] Various aspects of this disclosure may include consumer electronic products. Consumer electronic products may include a front surface, a rear surface, and side surfaces. Consumer electronic products may further include electrical components at least partially located within a housing. Electrical components may include a controller, memory, and a display. The display may be located on 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). Consumer electronic products may include a cover plate substrate disposed above the display. In various aspects, a portion of the housing or at least one of the cover plate substrates includes the foldable devices discussed throughout this disclosure. Consumer electronic products may include portable electronic devices such as smartphones, tablets, wearable devices, or laptops.

[0299] The foldable devices disclosed herein can be incorporated into another article, such as articles with a display (or display articles) (e.g., consumer electronics devices, including mobile phones, tablets, computers, navigation systems, wearable devices (e.g., watches), etc.), architectural articles, transportation articles (e.g., automobiles, trains, airplanes, ships, etc.), electrical articles, or any article that may benefit from some degree of transparency, scratch resistance, abrasion resistance, or a combination thereof. Exemplary articles with any of the foldable devices disclosed herein are shown in [the document / document]. Figure 9-10 middle. Specifically, Figure 9-10 A consumer electronic device 900 is shown, comprising a housing 902 having a front surface 904, a rear surface 906, and side surfaces 908. Although not shown, the consumer electronic device may include electrical components at least partially or entirely within the housing. For example, the electrical components include at least a controller, memory, and a display. Figure 9-10 As shown, the display 910 may be located on or adjacent to the front surface of the housing 902. The consumer electronic device may include a cover plate substrate 912 located on or above the front surface of the housing 902, such that it is above the display 910. In various aspects, at least one of the cover plate substrate 912 or a portion of the housing 902 may contain any foldable device disclosed herein, such as a foldable substrate.

[0300] In various aspects, the foldable substrate 201 may include a glass substrate and / or a ceramic substrate, and the first portion 221, the second portion 231, and / or the central portion 281 may include one or more compressive stress zones. In various aspects, the compressive stress zones may be generated by chemical strengthening. Chemical strengthening may include an ion exchange process, wherein ions in the surface layer are replaced or exchanged by larger ions having the same valence or oxidation state. Methods of chemical strengthening will be discussed later. Without being bound by theory, chemical strengthening of the first portion 221, the second portion 231, and / or the central portion 281 can achieve good impact resistance and / or puncture resistance (e.g., it will not be damaged when a pen is dropped from a height of about 15 cm or higher, about 20 cm or higher, or about 50 cm or higher). Without being bound by theory, chemical strengthening of the first portion 221, the second portion 231, and / or the central portion 281 can achieve a smaller (e.g., less than about 10 mm or less) bending radius, because the compressive stress generated by chemical strengthening can offset the tensile stress caused by bending on the outermost surface of the substrate. The compressive stress zone can extend into the first and / or part of the second portion to a certain depth, referred to as the compressive depth. As used herein, compressive depth means the depth to which the stress in the chemically strengthened substrate and / or portion described herein changes from compressive stress to tensile stress. The compressive depth can be measured by a surface stress meter or a scattered light polarizer (SCALP, where the value reported here is obtained using a SCALP-5 manufactured by Glassstress, Estonia), depending on the ion exchange treatment and the thickness of the article being measured. If the stress in the substrate and / or portion is generated by potassium ion exchange into the substrate, the compressive depth is measured using a surface stress meter, such as the FSM-6000 (Orihara Industrial Co., Ltd. (Japan)). Unless otherwise specified, compressive stress (including surface CS) is measured by a surface stress meter (FSM) using a commercially available instrument, such as the FSM-6000 manufactured by Orihara. Surface stress measurement relies on the accurate measurement of the stress optical coefficient (SOC), which is related to the birefringence of the glass. Unless otherwise specified, SOC shall be measured according to Procedure C (glass disc method) of 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. If the stress is generated by sodium ion exchange into the substrate and the thickness of the article under test is greater than approximately 400 µm, the depth of compression and center tension (CT) shall be measured using SCALP.If the stress in the substrate and / or portion is generated by the exchange of potassium and sodium ions into the substrate and / or portion, and the thickness of the article under test exceeds approximately 400 µm, the depth of compression and CT are measured by SCALP. To avoid being bound by theory, the depth of sodium ion exchange may indicate the depth of compression, while the depth of potassium ion exchange may indicate a change in compressive stress value (rather than a change in stress from compression to tension). A graphical representation of the stress distribution can also be derived using the refractive near-field (RNF) method; the RNF method is described in U.S. Patent No. 8,854,623 entitled "Systems and methods for measuring a profile characteristic of a glass sample," which is incorporated herein by reference in its entirety. When deriving a graphical representation of the stress distribution using the RNF method, the maximum center tension value provided by SCALP is utilized in the RNF method. The graphical representation of the stress distribution derived from the RNF is force-balanced and calibrated based on the maximum center tension value provided by the SCALP measurement. As used herein, “layer depth” (DOL) refers to the depth to which ions (e.g., sodium, potassium) have been exchanged into the substrate and / or portions thereof. Throughout this disclosure, when the maximum center tension cannot be directly measured by SCALP (e.g., when the thickness of the article under test is less than about 400 µm), the maximum center tension can be approximated by dividing the product of the maximum compressive stress and the compression depth by the difference between the substrate thickness and twice the compression depth, wherein the compressive stress and compression depth are measured by FSM.

[0301] In various aspects, the first portion 221, including the glass and / or ceramic portion, may include a first compressive stress region at a first surface region 223, the first compressive stress region extending from the first surface region 223 to a first compression depth. In various aspects, the first portion 221, including the first glass and / or ceramic portion, may include a second compressive stress region at a second surface region 225, the second compressive stress region extending from the second surface region 225 to a second compression depth. In various aspects, expressed as a percentage of the substrate thickness 207, the first compression depth and / or the second compression depth may be about 1% or greater, about 5% or greater, about 10% or greater, about 30% or less, about 25% or less, or about 20% or less. In various aspects, expressed as a percentage of the substrate thickness 207, the first compression depth and / or the second compression depth may be in the range of about 1% to about 30%, about 5% to about 30%, about 5% to about 25%, about 5% to about 20%, about 10% to about 30%, about 10% to about 25%, about 10% to about 20%, or any range or subrange therebetween. In other aspects, expressed as a percentage of the substrate thickness 207, the first compression depth and / or the second compression depth may be about 10% or less, for example, about 1% to about 10%, about 1% to about 8%, about 3% to about 8%, about 5% to about 8%, or any range or subrange therebetween. In other aspects, the first compression depth may be substantially equal to the second compression depth. In all aspects, the first compression depth and / or the second compression depth can be about 1 µm or greater, about 10 µm or greater, about 30 µm or greater, about 50 µm or greater, about 200 µm or less, about 150 µm or less, about 100 µm or less, or about 60 µm or less. In all aspects, the first compression depth and / or the second compression depth can be in the range of about 1 µm to about 200 µm, about 1 µm to about 150 µm, about 10 µm to about 150 µm, about 10 µm to about 100 µm, about 30 µm to about 100 µm, about 30 µm to about 60 µm, about 50 µm to about 60 µm, or any range or subrange thereof. Good impact resistance and / or puncture resistance can be achieved by including the first portion, including the first glassy and / or ceramic portion, within the range of about 1% to about 30% of the first thickness (e.g., substrate thickness) of the first compression depth and / or the second compression depth.

[0302] In all aspects, the first compressive stress zone may include a maximum first compressive stress. In all aspects, the second compressive stress zone may include a maximum second compressive stress. In other aspects, the maximum first compressive stress and / or the maximum second compressive stress may be about 100 MPa or greater, about 300 MPa or greater, about 500 MPa or greater, about 600 MPa or greater, about 700 MPa or greater, about 1,500 MPa or less, about 1,200 MPa or less, about 1,000 MPa or less, or about 800 MPa or less. In other respects, the maximum first compressive stress and / or the maximum second compressive stress can be within 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 500 MPa to about 1,000 MPa, about 600 MPa to about 1,000 MPa, about 700 MPa to about 1,000 MPa, about 700 MPa to about 800 MPa, about 500 MPa to about 800 MPa, or any range or subrange thereof. By keeping the first maximum compressive stress and / or the second maximum compressive stress within the range of about 100 MPa to about 1,500 MPa, good impact resistance and / or puncture resistance can be achieved.

[0303] In various aspects, the first portion 221 may include one or more alkali metal ions at a first layer depth associated with the first compressive stress region. In various aspects, the first portion 221 may include one or more alkali metal ions at a second layer depth associated with the second compressive stress region and the second compression depth. As used herein, one or more alkali metal ions at a certain layer depth may include sodium, potassium, rubidium, cesium, and / or francium. In various aspects, one or more alkali metal ions at the first layer depth and / or one or more alkali metal ions at the second layer depth include potassium. In various aspects, expressed as a percentage of the substrate thickness 207, the first layer depth and / or the second layer depth may be about 1% or more, about 5% or more, about 10% or more, about 40% or less, about 35% or less, about 30% or less, about 25% or less, or about 20% or less. In all aspects, expressed as a percentage of the substrate thickness 207, the depth of the first layer and / or the depth of the second layer may be in the range of about 1% to about 40%, about 1% to about 35%, about 1% to about 30%, about 1% to about 25%, about 1% to about 20%, about 5% to about 30%, about 5% to about 25%, about 5% to about 20%, about 10% to about 30%, about 10% to about 25%, about 10% to about 20%, or any range or subrange thereof. In other aspects, expressed as a percentage of the substrate thickness 207, the depth of the first layer of one or more alkali metal ions and / or the depth of the second layer of one or more alkali metal ions may be about 10% or less, for example, about 1% to about 10%, about 1% to about 8%, about 3% to about 8%, about 5% to about 8%, or any range or subrange thereof. In all aspects, the depth of the first layer of one or more alkali metal ions and / or the depth of the second layer of one or more alkali metal ions can be about 1 µm or greater, about 10 µm or greater, about 30 µm or greater, about 50 µm or greater, about 200 µm or less, about 150 µm or less, about 100 µm or less, or about 60 µm or less. In all aspects, the depth of the first layer of one or more alkali metal ions and / or the depth of the second layer of one or more alkali metal ions can be in the range of about 1 µm to about 200 µm, about 1 µm to about 150 µm, about 10 µm to about 150 µm, about 10 µm to about 100 µm, about 30 µm to about 100 µm, about 30 µm to about 60 µm, about 50 µm to about 60 µm, or any range or subrange thereof.

[0304] In various aspects, the first portion 221 may include a first tensile stress region. In various aspects, the first tensile stress region may be located between a first compressive stress region and a 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 greater, about 20 MPa or greater, about 30 MPa or greater, 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 within 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 subrange thereof. Good impact and / or puncture resistance can be achieved in the range of approximately 10 MPa to approximately 100 MPa, while providing low-energy fracture, as discussed below.

[0305] In various aspects, the second portion 231, including the second glass-like and / or ceramic portion, may include a third compressive stress region at a third surface region 233, the third compressive stress region extending from the third surface region 233 to a third compression depth. In various aspects, the second portion 231, including the second glass-like and / or ceramic portion, may include a fourth compressive stress region at a fourth surface region 235, the fourth compressive stress region extending from the fourth surface region 235 to a fourth compression depth. In various aspects, expressed as a percentage of the substrate thickness 207, the third compression depth and / or the fourth compression depth may be about 1% or greater, about 5% or greater, about 10% or greater, about 30% or less, about 25% or less, or about 20% or less. In various aspects, expressed as a percentage of the substrate thickness 207, the third compression depth and / or the fourth compression depth may be within one or more of the ranges discussed above with respect to the first compression depth and / or the second compression depth expressed as a percentage of the substrate thickness 207. In other aspects, the third compression depth may be substantially equal to the fourth compression depth. In all respects, the third and / or fourth compression depths may fall within one or more of the ranges discussed above with respect to the first and / or second compression depths. Good impact resistance and / or puncture resistance can be achieved by including the second portion, which includes glassy and / or ceramic portions, within a third and / or fourth compression depth ranging from about 1% to about 30% of the substrate thickness.

[0306] In various aspects, the third compressive stress zone may include the maximum third compressive stress. In various aspects, the fourth compressive stress zone may include the maximum fourth compressive stress. In other aspects, the maximum third compressive stress and / or the maximum fourth compressive stress may be within one or more ranges discussed above with respect to the maximum first compressive stress and / or the maximum second compressive stress. By keeping the maximum third compressive stress and / or the maximum fourth compressive stress in the range of about 100 MPa to about 1,500 MPa, good impact resistance and / or puncture resistance can be achieved.

[0307] In various aspects, the second portion 231 may include one or more alkali metal ions at a third layer depth associated with the third compressive stress region and the third compressive depth. In various aspects, the second portion 231 may include one or more alkali metal ions at a fourth layer depth associated with the fourth compressive stress region and the fourth compressive depth. In various aspects, one or more alkali ions at the third layer depth and / or at the fourth layer depth include potassium. In various aspects, expressed as a percentage of the substrate thickness 207, the third layer depth and / or the fourth layer depth may be within one or more ranges discussed above with respect to the first layer depth and / or the second layer depth expressed as a percentage of the substrate thickness 207. In various aspects, the third layer depth and / or the fourth layer depth of one or more alkali metal ions may be the first layer depth and / or the second layer depth.

[0308] In various aspects, part 231 may include a second tensile stress zone. In various aspects, the second tensile stress zone may be located between the third and fourth compressive stress zones. In various aspects, the second tensile stress zone may include a maximum second tensile stress. In other aspects, the maximum second tensile stress may be within one or more ranges discussed above with respect to the maximum first tensile stress. In various aspects, the maximum first tensile stress may be substantially equal to the maximum second tensile stress. Achieving good impact and / or puncture resistance while providing low-energy fracture, as discussed below, can be achieved by placing the maximum second tensile stress in the range of about 10 MPa to about 100 MPa.

[0309] In all aspects, the first compression depth can be substantially equal to the third compression depth. In all aspects, the second compression depth can be substantially equal to the fourth compression depth. In all aspects, the maximum first compressive stress can be substantially equal to the maximum third compressive stress. In all aspects, the maximum second compressive stress can be substantially equal to the maximum fourth compressive stress. In all aspects, the first layer depth of one or more alkali metal ions can be substantially equal to the third layer depth of one or more alkali metal ions. In all aspects, the second layer depth of one or more alkali metal ions can be substantially equal to the fourth layer depth of one or more alkali metal ions.

[0310] In various aspects, the central portion 281 may include a first central compressive stress region at a first central surface region 213, the first central compressive stress region extending from the first central surface region 213 to a first central compressive depth. In various aspects, the central portion 281 may include a second central compressive stress region at a second central surface region 243, the second central compressive stress region extending from the second central surface region 243 to the first central compressive depth. In other aspects, the first central compressive stress region and / or the second compressive stress region may be within a central region 248 of the central portion 281 (e.g., extending together with the first central surface region 213 and / or the second central surface region 243). In other aspects, the first central compressive depth and / or the second central compressive depth, expressed as a percentage of the central thickness 209, may be within one or more of the ranges discussed above with respect to the first compressive depth and / or the second compressive depth expressed as a percentage of the substrate thickness 207. In other respects, expressed as a percentage of the center thickness 209, the first center compression depth and / or the second center compression depth can be about 10% or greater, for example, about 10% to about 30%, about 10% to about 25%, about 15% to about 25%, about 15% to about 20%, or any range or subrange therebetween. In other respects, the first center compression depth can be substantially equal to the second center compression depth. In all respects, the first center compression depth and / or the second center compression depth can be within one or more ranges discussed above with respect to the first compression depth and / or the second compression depth. Good impact resistance and / or puncture resistance can be achieved by including the center portion, including glassy and / or ceramic portions, within the range of a first center compression depth and / or a second center compression depth in the range of about 1% to about 30% of the center thickness.

[0311] In various aspects, the first central compressive stress zone may include the maximum first central compressive stress. In various aspects, the second central compressive stress zone may include the maximum second central compressive stress. In other aspects, the maximum first central compressive stress and / or the maximum second central compressive stress may be within one or more ranges discussed above with respect to the maximum first compressive stress and / or the maximum second compressive stress. By keeping the maximum first central compressive stress and / or the maximum second central compressive stress in the range of about 100 MPa to about 1,500 MPa, good impact resistance and / or puncture resistance can be achieved.

[0312] In various aspects, the central portion 281 may include one or more alkali metal ions at a first central layer depth associated with the first central compressive stress region and the first central compressive depth. In various aspects, the central portion 281 may include one or more alkali metal ions at a second central layer depth associated with the second central compressive stress region and the second central compressive depth. In various aspects, one or more alkali metal ions at the first central layer depth and / or at the second central layer depth include potassium. In various aspects, the first central layer depth and / or the second central layer depth, expressed as a percentage of the central thickness 209, may be within one or more ranges discussed above with respect to the first layer depth and / or the second layer depth, expressed as a percentage of the substrate thickness 207. In various aspects, the first central layer depth and / or the second central layer depth of one or more alkali metal ions may be within one or more ranges discussed above with respect to the first layer depth and / or the second layer depth. In various aspects, the first compression depth and / or the third compression depth may be greater than the first central compressive depth. In various aspects, the second compression depth and / or the fourth compression depth may be greater than the second central compressive depth. In all respects, the depth of the first layer and / or the depth of the third layer may be greater than the depth of the first central layer. In all respects, the depth of the second layer and / or the depth of the fourth layer may be greater than the depth of the second central layer.

[0313] In various aspects, the central portion 281 may include a central tensile stress region. In various aspects, the central tensile stress region may be located between a first central compressive stress region and a second central compressive stress region. In various aspects, the central tensile stress region may include a maximum central tensile stress. In other 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 other respects, 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 subrange thereof. A low minimum bending radius can be achieved by keeping the maximum central tensile stress in the range of about 125 MPa to about 375 MPa.

[0314] Throughout this disclosure, the refractive index is measured using light with an optical wavelength of 589 nm, in accordance with ASTM E1967-19. In all aspects, the substrate refractive index of the foldable substrate 201 may be about 1.4 or greater, about 1.45 or greater, about 1.47 or greater, about 1.49 or greater, about 1.5 or greater, about 1.53 or greater, about 1.55 or greater, about 1.6 or less, about 1.58 or less, about 1.56 or less, about 1.55 or less, about 1.54 or less, about 1.53 or less, about 1.52 or less, or about 1.51 or less. In all aspects, the substrate refractive index of the foldable substrate 201 may be in the range of about 1.4 to about 1.6, about 1.45 to about 1.58, about 1.47 to about 1.56, about 1.49 to about 1.55, about 1.5 to about 1.54, about 1.51 to about 1.53, or any range or subrange thereof. In all aspects, the foldable substrate 201 may be optically clear.

[0315] In all respects, polymeric portions 289 and / or 299 may be optically clear. In all respects, the first refractive index of polymeric portions 289 and / or 299 may be about 1.3 or greater, about 1.4 or greater, about 1.45 or greater, about 1.47 or greater, about 1.49 or greater, about 1.5 or greater, about 1.53 or greater, about 1.55 or greater, about 1.7 or less, about 1.6 or less, about 1.58 or less, about 1.56 or less, about 1.55 or less, about 1.54 or less, about 1.53 or less, about 1.52 or less, about 1.51 or less, or about 1.5 or less. In all respects, the first refractive index of polymer portions 289 and / or 299 may be in the range of about 1.3 to about 2, about 1.4 to about 1.6, about 1.45 to about 1.58, about 1.45 to about 1.56, about 1.47 to about 1.55, about 1.47 to about 1.54, about 1.49 to about 1.53, about 1.5 to about 1.52, about 1.5 to about 1.51, or any range or subrange thereof.

[0316] In all aspects, the difference equal to the absolute value of the difference between the substrate refractive index of the foldable substrate 201 and the first refractive index of the polymeric portions 289 and / or 299 can be about 0.1 or less, about 0.07 or less, about 0.05 or less, about 0.02 or less, about 0.01 or less, about 0.001 or more, about 0.005 or more, about 0.01 or more, or about 0.02 or more. In all aspects, the difference can be in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.005 to about 0.05, about 0.005 to about 0.02, about 0.005 to about 0.01, or any range or subrange thereof. In all aspects, the difference can be in the range of about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.02 to about 0.05, or any range or subrange thereof. In all aspects, the substrate refractive index of the foldable substrate 201 may be greater than the first refractive index of the polymeric portions 289 and / or 299. In all aspects, the substrate refractive index of the foldable substrate 201 may be less than the first refractive index of the polymeric portions 289 and / or 299.

[0317] In various aspects, adhesive layer 261 may include a third refractive index, which may be within one or more ranges discussed above with respect to the first refractive index of polymeric portions 289 and / or 299. In various aspects, the difference equal to the absolute value of the difference between the third refractive index of adhesive layer 261 and the first refractive index of polymeric portions 289 and / or 299 may be about 0.1 or less, about 0.07 or less, about 0.05 or less, about 0.02 or less, about 0.01 or less, about 0.001 or greater, about 0.005 or greater, about 0.01 or greater, or about 0.02 or greater. In various aspects, the difference may be within the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.005 to about 0.05, about 0.005 to about 0.02, about 0.005 to about 0.01, or any range or subrange thereof. In all aspects, the difference may be in the range of about 0.01 to about 0.1, about 0.01 to about 0.05, about 0.02 to about 0.05, or any range or subrange thereof. In all aspects, the third refractive index of adhesive layer 261 may be greater than the first refractive index of polymeric portions 289 and / or 299. In all aspects, the third refractive index of adhesive layer 261 may be less than the first refractive index of polymeric portions 289 and / or 299.

[0318] In all aspects, the difference equal to the absolute value of the difference between the third refractive index of the adhesive layer 261 and the substrate 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 0.02 or less, about 0.01 or less, about 0.001 or more, about 0.005 or more, about 0.01 or more, or about 0.02 or more. In all aspects, the difference can be in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.005 to about 0.05, about 0.005 to about 0.02, about 0.005 to about 0.01, or any range or subrange thereof. In all aspects, the difference can be in the range of about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.02 to about 0.05, or any range or subrange thereof. In all aspects, the third refractive index of the adhesive layer 261 can be greater than the substrate refractive index of the foldable substrate 201. In all aspects, the third refractive index of the adhesive layer 261 can be less than the substrate refractive index of the foldable substrate 201.

[0319] In various aspects, coating 251, cover plate substrate 351, and / or additional substrate 371 may include a fourth refractive index, which may be within one or more ranges discussed above with respect to the first refractive index of polymeric portions 289 and / or 299. In various aspects, the difference equal to the absolute value of the difference between the fourth refractive index of coating 251 and the first refractive index of polymeric portions 289 and / or 299 may be about 0.1 or less, about 0.07 or less, about 0.05 or less, about 0.02 or less, about 0.01 or less, about 0.001 or more, about 0.005 or more, about 0.01 or more, or about 0.02 or more. In various aspects, the difference may be within the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.005 to about 0.05, about 0.005 to about 0.02, about 0.005 to about 0.01, or any range or subrange thereof. In all aspects, the difference may be in the range of about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.02 to about 0.05, or any range or subrange thereof. In all aspects, the fourth refractive index of coating 251 may be greater than the first refractive index of polymeric portions 289 and / or 299. In all aspects, the fourth refractive index of coating 251 may be less than the first refractive index of polymeric portions 289 and / or 299.

[0320] Figure 7-8 Aspects of foldable devices 601 and / or 801 according to aspects of this disclosure are schematically shown in a folded configuration. Figure 7As shown, when the foldable device 601 is folded, the second main surface 205 of the foldable substrate 201 is located inside the folded foldable device 501. In this case, for example, the display can be located on the side of the second main surface 205, and a viewer can view the display from the side of the first main surface 203. Figure 8 As shown, Figure 1 The foldable device 101 shown (described below) is modified and folded to form a folded foldable device 801, such that the first main surface 203 of the foldable substrate 201 is located inside the folded foldable device 801. Figure 8 In this configuration, the user can view the display device through the foldable substrate 201, rather than the PET sheet 707, thus the display device will be located on the side of the first main surface 203. In various aspects, such as... Figure 8 As shown, the foldable device 801 may include a coating 251 disposed above the foldable device 801 (e.g., the first main surface 203). In other aspects, the user will view the display device through the coating 251, rather than the PET sheet 707. In various aspects, such as Figure 8 As shown, polymer portions 289 and / or 299 may be disposed above the foldable substrate 201. In other aspects, although not shown, additional substrates (e.g., glass substrates and / or ceramic substrates, in place of release liner 271 or PET sheet 707) may be present, and these additional substrates may be disposed on the display device.

[0321] As used herein, “foldable” includes the ability to fold completely, partially, bend, flex, or a combination thereof. As used herein, the terms “fail”, “damage,” etc., refer to breakage, damage, delamination, or crack propagation. Similarly, if a foldable device maintains a parallel plate spacing “X” for 24 hours at approximately 85°C and approximately 85% relative humidity without being damaged, then the foldable device achieves, has, or includes a parallel plate spacing “X.”

[0322] As used in this article, the "parallel plate spacing" of the foldable device is defined using parallel plate device 701 (see [link]). Figure 7-8 The parallel plate device comprises a pair of parallel rigid stainless steel plates 703 and 705, measured by the following test configuration and method. This pair of parallel rigid stainless steel plates includes a first rigid stainless steel plate 703 and a second rigid stainless steel plate 705. When measured with... Figure 2 When testing the "parallel plate spacing" of a foldable device similar to the foldable device 101 shown, the adhesive layer 261 was removed and replaced with a test adhesive layer 709 with a thickness of 50 µm. Furthermore, the test was conducted using a 100 µm thick polyethylene terephthalate (PET) sheet 707 instead of [previous material]. Figure 2 The release liner 271 was used. Therefore, during the testing to determine the “parallel plate spacing” of the foldable device configuration, a 100 µm thick polyethylene terephthalate (PET) sheet 707 was used instead of Figure 2 The release liner 271 is used to manufacture the foldable device 601. Therefore, it is possible to... Figure 1 The foldable device 101 shown is modified (as described herein) and folded to form Figure 8 The foldable device 801 shown is folded as shown.

[0323] When measuring the "parallel plate spacing" of a foldable substrate, the foldable device 601 is formed by placing a 50 μm thick test adhesive layer 709 and a 100 μm thick polyethylene terephthalate (PET) sheet 707, the sheet 707 being positioned such that... Figure 2 As shown, the release liner 271 is attached to the second contact surface 265 of the adhesive layer 261 in the same manner as the test adhesive layer 709. For testing... Figure 7 The foldable device 601, testing the adhesive layer 709 and PET sheet 707 can also be performed according to... Figure 7 The foldable device 601 is configured and installed for testing on the foldable device 601. The foldable device 601 is placed between the pair of parallel rigid stainless steel plates 703 and 705, such that the foldable substrate 201 is located inside the bend, and... Figure 7 The configuration shown is similar. Similarly, this is achieved by replacing adhesive layer 261 and release liner 271 with test adhesive layer 709 and a 100 µm thick PET sheet 707. Figure 4 The foldable device 401 shown is ready for testing. In determining the "parallel plate spacing," the distance between the parallel plates is decreased at a rate of 50 µm / s until the parallel plate spacing 711 equals the "parallel plate spacing" to be tested. Then, the parallel plates are held at the "parallel plate spacing" to be tested for 24 hours at approximately 85°C and approximately 85% relative humidity. As used herein, the "minimum parallel plate spacing" is the minimum parallel plate spacing that the foldable device can withstand without damage under the conditions and configuration described above.

[0324] In various aspects, the foldable devices 101, 301, 401, 501, 601, 801 and / or 3301 and / or the foldable substrate 201 can achieve parallel plate spacing 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 other aspects, the foldable devices 101, 301, 401, 501, 601, 801 and / or 3301 and / or the foldable substrate 201 can achieve parallel plate spacing of 50 mm, or 20 mm, or 10 mm, 5 mm, or 3 mm. In various aspects, the foldable devices 101, 301, 401, 501, 601, 801 and / or 3301 and / or the foldable substrate 201 may include a minimum parallel plate spacing 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 devices 101, 301, 401, 501, 601, 801 and / or 3301 and / or the foldable substrate 201 may include a minimum parallel plate spacing 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, and about 1 mm to about 3 mm. In all respects, the foldable devices 101, 301, 401, 501, 601, 801 and / or 3301 and / or the foldable substrate 201 can achieve a minimum parallel plate spacing in the range of 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 or any range or subrange thereof.

[0325] The width 287 of the central portion 281 of the foldable substrate 201 is defined along a direction 106 of length 105 between the first portion 221 and the second portion 231. In various aspects, the width 287 of the central portion 281 of the foldable substrate 201 may extend from the first portion 221 to the second portion 231. The width 210 of the first central surface region 213 and the second central surface region 243 of the foldable substrate 201 is defined along a direction 106 of length 105 between the first transition region 212 and the second transition region 218, for example including a portion of 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 may 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 spacing. In all respects, the width 287 of the central portion 281 of the foldable substrate 201, expressed as a multiple of the minimum parallel plate spacing, and / or the width 210 of the first central surface region 213 of the foldable substrate 201, can be in the range of approximately 1.4 times to approximately 3 times, approximately 1.6 times to approximately 3 times, approximately 1.6 times to approximately 2.5 times, approximately 2 times to approximately 2.5 times, approximately 2.2 times to approximately 2.5 times, approximately 2.2 times to approximately 3 times, or any range or subrange thereof. Not wishing to be bound by theory, the length of the curved portion arranged in a circular configuration between the parallel plates can be approximately 1.6 times the parallel plate spacing 711. Not wishing to be bound by theory, the length of the curved portion arranged in an elliptical configuration between the parallel plates can be approximately 2.2 times the parallel plate spacing 711. In all respects, 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 may be about 1 mm or more, about 3 mm or more, about 5 mm or more, about 8 mm or more, about 10 mm or more, about 15 mm or more, about 20 mm or more, about 100 mm or less, about 60 mm or less, about 50 mm or less, about 40 mm or less, about 35 mm or less, about 30 mm or less, or about 25 mm or less.In all 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 within any 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 subrange thereof. In all 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 2.8 mm or greater, about 6 mm or greater, about 9 mm or greater, about 60 mm or less, about 40 mm or less, or about 24 mm or less. In all respects, 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 within any 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 subranges thereof. By making the width within the ranges proposed above for the central portion (e.g., between the first and second portions), folding of the foldable device can be facilitated without damage.

[0326] Foldable devices 101, 301, 401, 501, 601, 801, and / or 3301 may have impact resistance, defined as the ability of a region of the foldable device (e.g., the region including the first portion 221, the region including the second portion 231, the region including the polymeric portions 289 and / or 299 and / or the central portion 281) to remain undamaged at a certain pen drop height (e.g., 5 cm or higher, 10 cm or higher, 20 cm or higher) when measured according to a "pen drop test". As used herein, a "pen drop test" is performed to ensure that the pen is dropped to the external main surface (e.g., Figure 2-3 The first main surface 203 of the foldable substrate 201 of the foldable device 101 or 301 shown, Figure 3-5The foldable device 301, 401, or 501 shown is tested under a load (i.e., a pen dropped from a certain height) applied to the second main surface 205 of the foldable substrate 201. The foldable device is configured as in a parallel plate test, i.e., a 100 µm thick PET sheet 707 is attached to a 50 µm thick test adhesive layer 709, instead of... Figure 2 The release liner 271 is shown. Therefore, the PET layer in the pen drop test is intended to simulate a foldable electronic display device (e.g., an OLED device). During the test, a foldable device bonded to the PET layer is placed on an aluminum plate (6063 aluminum alloy, polished to a surface roughness with 400-grit sandpaper), with the PET layer in contact with the aluminum plate. No tape is used to support the sample resting on one side of the aluminum plate.

[0327] The pen drop test uses a tube to guide the pen onto the outer surface of the foldable device. For Figure 2-5 In the foldable devices 101, 301, 401, 501, 601, 801 and / or 3301 in 7-8 and 33, the pen is guided to the external main surface (e.g., Figure 2-3 The first main surface 203 of the foldable substrate 201 of the foldable device 101 or 301 shown, Figure 3-5 The foldable substrate 201 of the foldable device 301, 401, or 501 shown has a second main surface 205, and the tube is positioned to contact the second main surface 205 of the foldable substrate 201 such that the longitudinal axis of the tube is substantially perpendicular to the outer main surface, wherein the longitudinal axis of the tube extends in the direction of gravity. The tube has an outer diameter of 1 inch (2.54 cm), an inner diameter of nine-sixteenths of an inch (1.4 cm), and a length of 90 cm. For each test, an acrylonitrile-butadiene (ABS) pad is used to hold the pen at a predetermined height. After each drop, the tube is repositioned relative to the sample to guide the pen to different impact points on the sample. The pen used in the pen drop test is a BIC Easy Glide pen, fine type, with a 0.7 mm (0.68 mm) diameter tungsten carbide ballpoint tip, weighing 5.73 grams (g) including the cap (4.68 g without the cap).

[0328] In the pen drop test, the pen cap is attached to the tip of the pen (i.e., the end opposite the pen tip), and the pen is dropped, allowing the ballpoint pen to interact with the test sample. Following the drop sequence, the pen is dropped once from an initial height of 1 cm, then in increments of 0.5 cm up to 20 cm, and then in increments of 2 cm after 20 cm, until the test sample is damaged. After each drop, the presence of any observable breakage, damage, or other signs of damage, as well as the specific drop height, are recorded. Using the pen drop test allows for testing multiple samples in the same drop sequence, generating a population with improved statistical accuracy. During the pen drop test, a new pen is used every 5 drops, and for each new sample tested. Furthermore, all pens land at random locations on or near the center of the sample; no pens land near or on the edges of the sample.

[0329] In the pen drop test, "damage" refers to the formation of visible mechanical defects in the laminate. Mechanical defects may be cracks or plastic deformations (such as surface indentations). Cracks may be surface cracks or penetrating cracks. Cracks may form on the inner or outer surface of the laminate. Cracks may extend through all or part of the foldable substrate 201 and / or coating. The minimum size of a visible mechanical defect is 0.2 mm or greater.

[0330] In all aspects, the foldable device is capable of resisting damage caused by a pen falling from a height of 10 cm, 12 cm, 14 cm, 16 cm, or 20 cm onto the area including the first portion 221 or the second portion 231. In all aspects, the maximum pen drop height that the foldable device can withstand without damaging the area including the first portion 221 or the second portion 231 can be approximately 10 cm or greater, approximately 12 cm or greater, approximately 14 cm or greater, approximately 16 cm or greater, approximately 40 cm or less, approximately 30 cm or less, approximately 20 cm or less, or approximately 18 cm or less. In all aspects, the maximum pen drop height that the foldable device can withstand without damaging the area including the first portion 221 or the second portion 231 can be within the range of approximately 10 cm to approximately 40 cm, approximately 12 cm to approximately 40 cm, approximately 12 cm to approximately 30 cm, approximately 14 cm to approximately 30 cm, approximately 14 cm to approximately 20 cm, approximately 16 cm to approximately 20 cm, approximately 18 cm to approximately 20 cm, or any range or subrange thereof.

[0331] In all respects, the foldable device is capable of resisting damage caused by a pen falling from a height of 1 cm, 2 cm, 3 cm, 4 cm, 5 cm or greater into the area (e.g., the center portion 281) comprising the polymeric portions 289 and / or 299 between the first portion 221 and the second portion 231. In all respects, the maximum pen drop height that the foldable device can withstand without damaging the area comprising the polymeric portions 289 and / or 299 between the first portion 221 and the second portion 231 can be about 1 cm or greater, about 2 cm or greater, about 3 cm or greater, about 4 cm or greater, about 20 cm or less, about 10 cm or less, about 8 cm or less, or about 6 cm or less. In all aspects, the maximum pen drop height that the foldable device can withstand without damaging the area including the polymeric portions 289 and / or 299 between the first portion 221 and the second portion 231 can be within 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 subrange thereof. In all aspects, the maximum pen drop height that the foldable device can withstand without damaging the area including the polymeric portions 289 and / or 299 between the first portion 221 and the second portion 231 can be within 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 subrange thereof.

[0332] In various aspects, the foldable substrate 201 and / or the foldable devices 101, 301, 401, 501, 601, 801 and / or 3301 may include a contrast ratio as determined in a contrast test as defined herein (see reference below). Figure 26 and 28 (The discussion continues). Throughout this disclosure, the "contrast ratio" (C) is defined as the difference between the maximum fractional intensity (max) and the minimum fractional intensity (min) divided by the sum of the maximum and minimum fractional intensities (i.e., C = (max - min) / (max + min)). As described below, the maximum and minimum fractional intensities are determined by processing the signals (e.g., images) obtained from imaging a foldable substrate and / or a foldable device under bright-field transmission conditions. Not wishing to be bound by theory, the contrast ratio may be related to the visibility (e.g., optical distortion) of the transition region to the naked eye (e.g., a user); a lower contrast ratio indicates lower visibility. (See reference...) Figure 29As discussed in the examples, contrast ratios of about 0.27 or less, about 0.26 or less, or about 0.25 or less are not visible to the naked eye (e.g., to a user). In all aspects, the contrast ratios of the foldable substrate 201 and / or the foldable devices 101, 301, 401, 501, 601, 801 and / or 3301 may be about 0.25 or less, about 0.24 or less, about 0.23 or less, about 0.22 or less, about 0.21 or less, about 0.20 or less, about 0.18 or less, about 0.15 or less, about 0.12 or less, or about 0.10 or less. In all respects, the contrast ratios of the foldable substrate 201 and / or the foldable devices 101, 301, 401, 501, 601, 801 and / or 3301 may be in the range of about 0.01 to about 0.27, about 0.01 to about 0.26, about 0.01 to about 0.25, about 0.03 to about 0.24, about 0.05 to about 0.23, about 0.07 to about 0.22, about 0.10 to about 0.21, about 0.12 to about 0.20, about 0.15 to about 0.18 or any range or subrange thereof.

[0333] Reference Figure 26-28 Section 30 discusses methods for determining contrast ratios (e.g., using contrast testing) and contrast devices that can be used therein. In various aspects, such as Figure 26 As shown, the contrast device 2601 includes a sample holder 2641 (e.g., clamps 2643a and 2643b) that defines a cavity 2651 configured to accommodate a transparent device to be measured (e.g., a foldable substrate 201 and / or foldable devices 101, 301, 401, 501, 601 and / or 801). In various aspects, as shown, the contrast device 2601 includes a light source 2611 configured to emit a light beam (e.g., a first beam 2605a) along an optical axis 2603 in a direction 2602. In various aspects, as shown in the figures, for example, by directing a light beam (e.g., a first beam 2605a) onto a pinhole aperture (e.g., an optical device 2621 having a pinhole aperture 2623), and subsequently directing a light beam (e.g., a second beam 2605b) onto a spatial filter optical aperture (e.g., an optical device 2631), the light beam traveling along the optical axis 2603 can be collimated to produce a collimated beam 2605c. As shown in the figures, the collimated beam 2605c traveling along the optical axis 2603 is configured to irradiate the central portion 281 of the sample located in the cavity 2651 of the sample holder 2641 (e.g., including the above reference). Figure 2-5 The transition region discussed. After irradiating the sample and / or cavity 2651, the collimated beam 2605c becomes the measurement beam 2605d, which has optical distortion information related to the sample transition region (see below). Figure 27(To be discussed further). In various aspects, the measurement beam 2605d can be focused, for example, using optical devices 2661 and / or 2671 onto the detector 2683 (e.g., the detection surface and / or pixel) of the optical detector 2681. The optical detector 2681 can be configured to generate a signal corresponding to an image associated with optical distortions produced in the sample (e.g., the central portion 281 and / or the transition region), which can be processed to determine the contrast ratio.

[0334] refer to Figure 27 Ray tracing (left) will be used to explain optical distortions (right) that may be associated with transition regions (e.g., first transition region 212 and / or second transition region 218). For simplicity, Figure 2-3 The foldable substrate 201 is shown separately; it should be understood that additional materials (e.g., a first polymeric portion, a second polymeric portion) may be present, but this would complicate the interpretation. The incident beam is represented by multiple rays 2703, which will be discussed based on the portion of the foldable substrate that is irradiated. Figure 27 In the first portion 2713, light rays (e.g., light ray 2727) pass through the first portion of the foldable substrate 201 without modification. Figure 2-3 The first portion 221 (e.g., when light is incident at an angle perpendicular to the first principal surface 203). Similarly, light in the second portion 2715 (e.g., light ray 2721) also passes through the second portion (e.g., without modification). Figure 2-3 The same applies to the light rays (e.g., ray 2724) illuminating the central region 248 (e.g., the first central surface region 213), as shown in the second part 231 of the first transition region 212. However, as shown, the light rays 2725 and 2726 illuminating the third part 2717 of the first transition region 212 and / or the light rays 2722 and 2723 illuminating the fourth part 2719 of the second transition region 218 are distorted relative to other light rays. As shown by the normals 2732, 2733, 2735, and 2736 extending in a direction perpendicular to (e.g., the first transition region 212 or the second transition region 218) of the corresponding transition surface region, the light rays 2722, 2723, 2725, and 2726 illuminate the corresponding transition surface at non-zero incident angles relative to the corresponding normals 2732, 2733, 2735, and 2736, respectively. This non-perpendicular incident causes the corresponding light rays to refract, and due to the tilt of the corresponding transition regions, the light rays deviate from the central region 248. At the other end of the transition zone, the light rays remain at non-zero angles of incidence relative to the normals 2742, 2743, 2745, and 2746. For example... Figure 27As shown, the paths of rays 2722, 2723, 2725, and 2726 after illuminating (and passing through) the transition regions (e.g., the first transition region 212 and / or the second transition region 218) assume that another material is disposed thereon, the refractive index of which closely matches the refractive index of the foldable substrate 201. This is why the corresponding rays are essentially unmodified when leaving the transition regions. However, even if no refractive index-matching material is disposed on the second main surface 205 and / or the second central surface region 243, the positions of rays 2722, 2723, 2725, and 2726 will still be offset relative to rays 2721, 2724, and 2727 based on the refraction and propagation of rays 2722, 2723, 2725, and 2726 in the transition regions (e.g., the first transition region 212 and / or the second transition region 218). Figure 27 As shown, distortion occurs in the vertical direction. Therefore, rays 2725 and 2726 are distorted toward the first portion 2713, and rays 2722 and 2723 are offset toward the second portion 2715 (e.g., distorted).

[0335] Figure 27 The right side schematically depicts how the deflection of light rays in sections 2717 and 2719 affects the intensity of light incident on observation screen 2741, which may be a substitute for detector 2683 or the user's eye. As shown, sections 2751a, 2751b, and 2753 have substantially the same intensity. Due to the deflection (e.g., distortion) of light rays 2725 and 2726 towards section 2715 (and possibly into section 2715), the relatively bright section 2757a has a higher intensity than section 2751a. Therefore, the deflection of light rays 2725 and 2726 from the central section 248 (and the light rays in the central section 248 are not correspondingly deflected) produces a relatively dark section 2755a with a lower intensity than sections 2751a, 2751b, and 2753. Similarly, because light rays 2722 and 2723 are deflected (e.g., distorted) towards the first portion 2713 (and may enter the first portion 2713), the relatively bright region 2757b has a higher intensity than region 2751b. Therefore, the deflection of light rays 2722 and 2723 from the central region 248 (and the lack of a corresponding deflection of light rays from the central region 248) produces a relatively dark region 2755b with a lower intensity than regions 2751a, 2751b, and 2753. In summary, each transition region produces a pair of relatively bright (e.g., high intensity) and relatively dark (e.g., low intensity) regions. The visibility of this optical distortion (e.g., the user's ability to distinguish it) depends on the difference between the relatively bright regions 2757a and 2757b and their adjacent relatively dark regions 2755a and 2755b. See below for reference. Figure 30 The discussion and processing Figure 30 Image (a) to obtain Figure 30 The graph shown in (b) extracts the minimum values ​​3021 and 3023 and the maximum values ​​3025 and 3027 and uses them to calculate the contrast ratio. Not wanting to be bound by theory, there is a threshold for intensity differences below which the human eye cannot detect (e.g., distinguish). If the intensity difference (quantified by the contrast ratio) is below this threshold, the presence of a transition region cannot be detected (e.g., the central portion 281 – see below). Figure 2-5 Furthermore, it appears to be invisible. As discussed in this article, a contrast ratio of 0.25 or lower is essentially invisible to the human eye.

[0336] Figure 28 The general conditions for imaging the central portion 281 to measure contrast ratio are schematically illustrated. As shown, the central portion 281 (e.g., the first transition region 212 and / or the second transition region 218) is imaged using bright-field transmission, wherein a beam 2803 is incident at 0° relative to the direction perpendicular to the third contact surface 2823 of the first polymeric portion 2821 of the test sample or the first main surface 203 of the foldable substrate 201 of the reference sample. The test sample is positioned such that the beam width 2805 of the beam 2803 from the beam source covers the width 287 of the central portion 281. The first beam spacing 2807 between the collimated position of the beam 2803 and the third contact surface 2823 of the first polymeric portion 2821 of the test sample or the first main surface 203 of the foldable substrate 201 is at least 1 mm. The test sample may include a portion of a first polymeric portion 2821 extending a first distance 2827 beyond the first main surface 203 of the foldable substrate 201, and / or the test sample may include a portion of a second polymeric portion 2831 extending a second distance 2837 beyond the second main surface 205 of the foldable substrate 201. The optical detector 2813 is positioned such that the second beam spacing 3817 includes a distance of at least 400 μm (measured in a direction of 0° relative to the direction perpendicular to the second main surface 205) from the fourth contact surface 2833 of the second polymeric portion 2831 of the test sample to the corresponding surface of the detection surface 2815 of the optical detector 2813. The light intensity measured by the optical detector 2813 is a function of direction 106. Then, as discussed herein (in the preceding paragraph and the following paragraphs), the fractional intensity as a function of distance along direction 106 is processed to determine the contrast ratio.

[0337] See Figure 26 Measuring transparent devices having at least one groove (e.g., first groove 211 and / or second groove 241) Figure 28The method for comparing the test samples and / or foldable devices 101, 301, 401 and / or 501 in the sample holder 2641 includes positioning the transparent device in the sample holder 2641 (e.g., in the cavity 2651 between clamps 2643a and 2643b). The method further includes generating a collimated beam 2605c from a light source 2611. In various aspects, generating the collimated beam may include emitting a beam (e.g., a first beam 2605a) toward the sample holder 2641 (e.g., along the optical axis 2603 in direction 2602), which is then transmitted through a pinhole aperture 2623 to form a second beam 2605b, which in turn is transmitted through a spatial filter optical aperture (e.g., an optical device 2631) to form the collimated beam 2605c. In various aspects, the light source 2611 may be configured to emit the first beam 2605a and / or the collimated beam 2605c, which comprises substantially monochromatic light. In other aspects, substantially monochromatic light can include optical wavelengths of about 300 nm or larger, about 350 nm or larger, about 400 nm or larger, about 450 nm or larger, about 500 nm or larger, about 550 nm or larger, about 600 nm or larger, about 650 nm or larger, about 700 nm or smaller, about 650 nm or smaller, about 600 nm or smaller, about 550 nm or smaller, about 500 nm or smaller, about 450 nm or smaller, about 400 nm or smaller, or about 350 nm or smaller. In other aspects, substantially monochromatic light can include optical wavelengths in the range of about 300 nm to about 700 nm, about 350 nm to about 650 nm, about 400 nm to about 650 nm, about 450 nm to about 600 nm, about 500 nm to about 550 nm, or any range or subrange thereof. For example, the light source 2611 can be configured to emit substantially monochromatic light including optical wavelengths of about 450 nm, about 510 nm, about 590 nm (e.g., 589 nm), about 620 nm, or about 640 nm. Providing a substantially monochromatic beam (e.g., a collimated beam) compared to non-monochromatic light can make the test sample image clearer, thereby determining the contrast ratio (e.g., unaffected by chromatic aberration).

[0338] In addition, see Figure 26 The method for measuring the contrast ratio may include irradiating a transparent device located in the cavity 2651 with a collimated beam 2605c (e.g., Figure 28 The test sample and / or foldable device 101, 301, 401 and / or 501 are used to form a measurement beam 2605d, which may contain information related to the above reference. Figure 27The central part 281 discusses optical distortion information. The method may further include focusing a measurement beam 2605d onto a surface (e.g., a detector 2683) of an optical detector 2681. In various aspects, focusing the measurement beam 2605d may include transmitting the measurement beam 2605d through an optical device 2661 (e.g., a converging optics) to form a converging beam 2605e, which may in turn be transmitted through an optical device 2671 (e.g., a focusing optics) to focus the resulting beam onto a surface (e.g., detector 2683) of the optical detector 2681. In various aspects, the surface of the detector 2683 may include multiple pixels. The optical detector 2681 may be configured to generate and transmit a signal corresponding to the measurement beam detected by the optical detector 2681.

[0339] In addition, see Figure 30 The method may include processing a signal (from optical detector 2681) to determine a position associated with at least one recess in the central portion 281. In various aspects, the method may include removing background noise based on a reference symbol detected (by optical detector 2681) when the cavity 2651 of sample holder 2641 is empty (e.g., the transparent device is not in sample holder 2641). In various aspects, processing may include rotating an image associated with the signal (see...). Figure 30 (a)) such that portions of the signal associated with at least one groove are aligned along the axis. For example, as Figure 30 As shown in (a), the signal (e.g., an image) can be rotated by an angle 3024 such that dark areas 3011 and 3013 (e.g., lines) are rotated along axis 3022 (e.g., ...). Figure 30 (a) Alignment in the vertical direction. In various aspects, determining the position associated with at least one groove may include averaging the signal (e.g., a rotation signal or a rotation image) in a direction (e.g., perpendicular to the axis). For example, as Figure 30 As shown in (b), the signal (e.g., a rotated image in terms of grayscale values) can be averaged along the direction of axis 3022 (e.g., by averaging all values ​​at a given distance in the horizontal distance to fold). Figure 30 (a) The image in the image is used to determine curve 3005. Figure 30 In (b), the horizontal axis 3001 corresponds to a position perpendicular to axis 3022 (e.g., corresponding to a pixel of an optical detector), and the vertical axis 3003 corresponds to the average intensity (e.g., a grayscale value between 0 and 255). Figure 30 In curve 3005 shown in (b), Figure 30 In (a), dark areas 3011 and 3013 correspond to respectively... Figure 30 (b) shows the minimum values ​​of curve 3005, 3021 and 3023. Between the dark areas 3011 and 3013, Figure 30The bright areas 3015 and 3017 in (a) correspond to Figure 30 The maximum values ​​3025 and 3027 of curve 3005 in (b). The paired minimum values ​​3021 and 3023, and the maximum values ​​3025 and 3027, are used to determine the location of the groove (e.g., the transition zone surrounding the central region 248) and to calculate the contrast ratio. As defined above, the “contrast ratio” (C) is defined as the difference between the maximum fractional intensity (max) and the minimum fractional intensity (min) divided by the sum of the maximum and minimum fractional intensities (i.e., C = (max - min) / (max + min)). See also Figure 30 (b) Take the average of the minimum values ​​3021 and 3023 to determine the minimum value (min), and take the average of the maximum values ​​3025 and 3027 to determine the maximum value (max).

[0340] Throughout this disclosure, the contrast test used to determine the contrast ratio of a transparent device including at least one groove involves placing the transparent device into the aforementioned reference. Figure 26 The contrast device 2601 is described in cavity 2651. A light source 2611 emits a monochromatic light beam with an optical wavelength of 450 nm. This beam is collimated using a pinhole aperture 2623 and a spatial filter optical aperture (such as optical device 2631) such that the width of the collimated beam is greater than the width 287 of the central portion 281 of the transparent device (see...). Figure 2 , Figure 4-5 and Figure 28 Unless otherwise instructed, see [link to relevant documentation]. Figure 28 The first distance 2827 (and the second distance 2837 when the foldable substrate 201 includes a second groove 241 opposite to the first groove) is essentially 0 (e.g., within 5 µm, including from 5 µm to -5 µm, where -5 µm means that the fourth contact surface 2833 is closer to the second central surface region 243 by 5 µm than the second plane 206a of the reference second polymeric portion 2831), which is achieved by curing the precursor liquid disposed in the respective groove to form the respective polymeric portion.

[0341] As discussed in the examples below, Figure 29 It shows the method for determining Figure 29 Experimental measurement images of the contrast ratio of examples AE in (a)-29(e). Figure 29 As shown in (a)-29(c), the optical distortion associated with the groove (e.g., the transition region) is visible at high contrast ratios, specifically 0.87, 0.60 and 0.48, respectively. Figure 29 The optical distortion shown in (d) is not Figure 29 (a)-29(c) are so obvious, Figure 29 The image shown in (d) has a contrast ratio of 0.28. Figure 29 The optical distortion shown in (e) is not readily discernible (note) Figure 29 (The scales in (a)-29(e) are the same), making it impossible for the viewer to notice the optical distortions that are particularly relevant to the central parts (e.g., the transition zone), and Figure 29 The image shown in (e) has a contrast ratio of 0.21. Based on these measurements and other work, it is assumed that a contrast ratio of about 0.25 or less is not visible to the naked eye (e.g., to the user), although in other respects the contrast ratio may be about 0.27 or less, about 0.26 or less, about 0.24 or less, about 0.23 or less, or 0.22 or less.

[0342] Reference Figure 11-12 Flowcharts and Figure 13-25 The example method steps shown illustrate aspects of methods for manufacturing foldable devices and / or foldable substrates according to aspects of this disclosure.

[0343] Reference Figure 13-21 and Figure 11 The flowchart in the discussion of manufacturing Figure 2-5 Examples of foldable devices 101, 301, 401, 501, 601 and / or 801 and / or foldable substrate 201 shown in 7-8. In the first step 1101 of the method of this disclosure, the method may begin by providing foldable substrate 1305 (see example 7-8). Figure 13 and 16 -17). In various aspects, the foldable substrate 1305 can be provided by purchasing or otherwise obtaining the substrate or by forming the foldable substrate. In various aspects, the foldable substrate 1305 may include a glass substrate and / or a ceramic substrate. In other aspects, the glass substrate and / or the ceramic substrate can be provided by forming it using various strip forming processes, such as slot stretching, down stretching, melt down stretching, up stretching, pressure roll stretching, re-stretching, or float stretching. In other aspects, the ceramic substrate can be provided by heating the glass substrate to crystallize one or more ceramic crystals. The foldable substrate 1305 may include an initial second primary surface 1315 (see...). Figure 13 and 17 This surface can extend along a plane. The initial second primary surface 1315 can be opposite to the initial first primary surface 1313. In various aspects, such as Figure 16 As shown, in step 1101, the foldable substrate 1305 may include an existing first central surface region 1343 coplanar with the first surface region 1323 and / or the third surface region 1333. For example, the initial first main surface 1313 may include the existing first central surface region 1343, the first surface region 1323, and the third surface region 1333. In various aspects, such as Figure 17As shown, in step 1101, the foldable substrate 1305 may include an existing second central surface region 1345 that is coplanar with the second surface region 1325 and / or the fourth surface region 1335. For example, the initial second main surface 1315 may include the existing second central surface region 1345, the second surface region 1325 and the fourth surface region 1335.

[0344] After step 1101, as Figure 13As shown, the method can proceed to step 1103, which includes initial chemical strengthening of the foldable substrate 1305. In various aspects, the foldable substrate 1305 may be substantially unstrengthened prior to the chemical strengthening in step 1103. In various aspects, as shown, chemical strengthening of the foldable substrate 1305 may include contacting at least a portion of the foldable substrate 1305, including lithium cations and / or sodium cations, in a salt solution 1302 (e.g., contained in a salt bath 1301). Chemical strengthening of the foldable substrate 1305 (e.g., a glass substrate, a ceramic substrate) can be achieved by ion exchange when a first cation within a depth of the surface of the foldable substrate 1305 exchanges with a second cation with a radius larger than the first cation within the molten salt or salt solution 1302. For example, lithium cations within this depth of the surface of the foldable substrate 1305 may exchange with sodium or potassium cations in the salt solution 1302. Therefore, the surface of the foldable substrate 1305 is compressed, thereby undergoing chemical strengthening through an ion exchange process, since the radius of the lithium cation is smaller than the radius of the sodium or potassium cations exchanged in the salt solution 1302. Chemical strengthening of the foldable substrate 1305 may include contacting at least a portion of the foldable substrate 1305 comprising lithium cations and / or sodium cations with a salt bath 1301 comprising a salt solution 1302, which includes potassium nitrate, potassium phosphate, potassium chloride, potassium sulfate, sodium chloride, sodium sulfate, sodium nitrate, and / or sodium phosphate, wherein lithium cations and / or sodium cations diffuse from the foldable substrate 1305 into the salt solution 1302 contained in the salt bath 1301. In various aspects, the temperature of the salt solution 1302 may be about 300°C or higher, about 360°C or higher, about 400°C or higher, about 500°C or lower, about 460°C or lower, or about 420°C or lower. In all aspects, the temperature of the salt solution 1302 can be in the range of about 300°C to about 500°C, about 360°C to about 500°C, about 400°C to about 500°C, about 300°C to about 460°C, about 360°C to about 460°C, about 400°C to about 460°C, about 400°C to about 420°C, about 300°C to about 400°C, about 360°C to about 420°C, or any range or subrange thereof. In all aspects, the foldable substrate 1305 can be in contact with the salt solution 1302 for about 5 minutes or longer, about 30 minutes or longer, about 1 hour or longer, about 3 hours or longer, about 48 hours or less, about 24 hours or less, or about 8 hours or less. In all respects, the foldable substrate 1305 may be in contact with the salt solution 1302 for a period of time ranging from about 5 minutes to about 48 hours, from about 30 minutes to about 48 hours, from about 30 minutes to about 24 hours, from about 1 hour to about 24 hours, from about 3 hours to about 24 hours, from about 3 hours to about 8 hours, or any range or subrange thereof.In all respects, the foldable substrate 1305 may be in contact with the salt solution 1302 for a period of time ranging from about 5 minutes to about 8 hours, from about 30 minutes to about 8 hours, from about 1 hour to about 8 hours, or any range or subrange thereof.

[0345] In various aspects, chemically strengthening the foldable substrate 1305 in step 1103 may include chemically strengthening the initial first main surface 1313 to form an initial first compressive stress region extending from the initial first main surface 1313 to an initial first compression depth. In various aspects, chemically strengthening the foldable substrate 1305 in step 1103 may include chemically strengthening the initial second main surface 1315 to form an initial second compressive stress region extending from the initial second main surface 1315 to an initial second compression depth. The initial first compressive stress region and / or the initial second compressive stress region may extend through portions of the foldable substrate 1305 corresponding to the first portion, the second portion, and the central portion. For example, the initial first compressive stress region may extend from the first surface region 1323 and / or the third surface region 1333, and / or the initial second compressive stress region may extend from the second surface region 1325 and / or the fourth surface region 1335. In various aspects, with a substrate thickness of 207 (see...), Figure 2-5 The initial first compression depth and / or the initial second compression depth can be expressed as a percentage of approximately 5% or greater, 10% or greater, approximately 12% or greater, approximately 14% or greater, approximately 25% or less, approximately 20% or less, approximately 18% or less, or approximately 16% or less. In all aspects, with a substrate thickness of 207 (see...), Figure 2-5 The initial first compression depth and / or the initial second compression depth can be expressed as a percentage of about 5% to about 25%, about 8% to about 25%, about 8% to about 20%, about 10% to about 20%, about 10% to about 18%, about 12% to about 18%, about 12% to about 16%, about 14% to about 16%, or any range or subrange thereof. In all aspects, the substrate thickness is 207 (see...). Figure 2-5 The percentages represent the initial first layer depth of one or more alkali metal ions associated with the initial first compressive stress region and / or the initial second layer depth of one or more alkali metal ions associated with the initial second compressive stress region, which may be about 5% or more, 10% or more, about 12% or more, about 14% or more, about 25% or less, about 20% or less, about 18% or less, or about 16% or less. In all aspects, with a substrate thickness of 207 (see...) Figure 2-5The percentages represent the initial first layer depth of one or more alkali metal ions associated with the initial first compressive stress region and / or the initial second layer depth of one or more alkali metal ions associated with the initial second compressive stress region, which can be in the range of about 5% to about 25%, about 8% to about 25%, about 8% to about 20%, about 10% to about 20%, about 10% to about 18%, about 12% to about 18%, about 12% to about 16%, about 14% to about 16%, or any range or subrange thereof. In each aspect, the initial first compression depth can be less than the first distance 219 of the resulting foldable substrate 201 and / or the initial second compression depth can be less than the second distance 249 of the resulting foldable substrate 201, which allows the entire initial first compression depth and / or second compression depth to be removed from the central portion 281 (e.g., central region 248) of the foldable substrate 1305 during the etching process in step 1107 (see [link to etch diagram]). Figure 18 In all respects, prior to step 1103, the foldable substrate 1305 may be substantially unstrengthened (e.g., unstressed, unchemically strengthened, unthermally strengthened). As used herein, substantially unstrengthened means that the substrate does not include layer depth, or that the layer depth is in the range of 0% to about 5% of the substrate thickness.

[0346] After step 1101 or 1103, as Figure 16-17 As shown, the method can proceed to step 1105, which includes placing an etching mask on the initial first main surface 1313 of the foldable substrate 1305. In various aspects, such as Figure 16-17 As shown, the etching mask may include a first portion 1641 and a second portion 1651, the first portion 1641 including a first polymer layer 1401 and the second portion 1651 including a second polymer layer 1411. In various aspects, as Figure 16-17 As shown, step 1105 may include disposing a first polymer layer 1401 on an initial first main surface 1313 and disposing a second polymer layer 1411 on the initial first main surface 1313. In other aspects, as shown, the first polymer layer 1401 may include a second contact surface 1405 facing the initial first main surface 1313. In still other aspects, as shown, the first polymer layer 1401 may include a first width 1417. In still other aspects, as shown, the second polymer layer 1411 may include a fourth contact surface 1415 facing the initial first main surface 1313. In still other aspects, as shown, the second polymer layer 1411 may include a second width 1419.

[0347] In all aspects, such as Figure 15As shown, when the polymer layer is disposed on the initial first main surface 1313, the first polymer layer 1401 and the second polymer layer 1411 may respectively include a first width 1417 and a second width 1419. In other respects, the first width 1417 and / or the second width 1419 may be approximately 1.5 mm or greater, approximately 1.6 mm or greater, approximately 1.7 mm or greater, approximately 1.8 mm or greater, approximately 1.9 mm or greater, approximately 2.0 mm or greater (e.g., approximately 3 mm or greater), 2.1 mm or greater, 2.2 mm or greater, 2.3 mm or greater, 2.4 mm or greater, 2.5 mm or greater, 2.7 mm or greater, 3.0 mm or greater (e.g., approximately 3 mm or greater), 3.2 mm or greater, 3.5 mm or greater, approximately 4.0 mm or less (e.g., approximately 4 mm or less), approximately 3.8 mm or less, approximately 3.6 mm or less, approximately 3.4 mm or less, approximately 3.2 mm or less, approximately 3.0 mm or less (e.g., approximately 3 mm or less), approximately 2.8 mm or less, approximately 2.6 mm or less, approximately 2.5 mm or less, approximately 2.4 mm or less, approximately 2.3 mm or less. The width is approximately 2.5 mm or less, about 2.2 mm or less, about 2.1 mm or less, or about 2.0 mm or less (about 2 mm or less). In other aspects, the first width 1417 and / or the second width 1419 may be in the range of about 1.5 mm to about 4.0 mm, about 1.6 mm to about 3.8 mm, about 1.7 mm to about 3.6 mm, about 1.8 mm to about 3.4 mm, about 1.9 mm to about 3.2 mm, about 2.0 mm to about 3.0 mm (e.g., about 2 mm to about 3 mm), about 2.1 mm to about 2.8 mm, about 2.2 mm to about 2.6 mm, about 2.3 mm to about 2.5 mm, or any range or sub-range therebetween. In a preferred aspect, the first width 1417 and / or the second width 1419 may be in the range of about 1.5 mm to about 4 mm, about 1.7 mm to about 3 mm, or about 2 mm to about 2.8 mm. In other aspects, the first width 1417 may be substantially equal to the second width 1419. Providing a polymer layer width of 1.5 mm or greater can produce a first transition width and / or a first average angle within one or more ranges discussed herein, which helps reduce visibility in the central region (e.g., optical distortion associated with the transition region). In other aspects, the first width 1417 can be equal to or less than the first transition width 214 of the resulting first transition region 212 of the foldable device (see [link to documentation]). Figure 2-5 In other respects, the second width 1419 may be equal to or less than the second transition width 216 of the resulting second transition zone 218 of the foldable device (see...). Figure 2-5Providing a first width and / or a second width within one of the aforementioned ranges can form a transition region by controlling the etchant's proximity to portions of the foldable substrate corresponding to the first and / or second widths of the first and / or second polymer portions, for example, by restricting etchant diffusion to the corresponding portions. It is not desirable to be bound by theory; a gap allows the etchant to contact a portion of the foldable substrate, but restricts the diffusion of the etchant to other portions, thus limiting the etching extent of those other portions and creating a transition region. During etching, the first and / or second polymer layers can be deflected away from the foldable substrate, allowing the etchant to approach other portions of the foldable substrate that the polymer layers might otherwise contact, which further reduces etchant diffusion and achieves a longer transition region.

[0348] In various aspects, although not shown, in step 1105, the first polymer layer 1401 and the second polymer layer 1411 can be positioned on the initial first main surface 1313 by trimming the polymer sheet. In other aspects, although now shown, step 1105 may include placing tape on the initial first main surface 1313, removing a first portion including a first width 1417 to create a space (e.g., corresponding to the location of the first polymer layer 1401), and removing a second portion including a second width 1419 to create a second space (e.g., corresponding to the location of the second polymer layer 1411). Thus, the tape can be divided into three parts, and a polymer sheet can be placed on it and cut flush with the tape to form the first polymer layer 1401 and / or the second polymer layer 1411. The tape can then be removed, leaving the first polymer layer 1401 and / or the second polymer layer 1411. A first barrier layer 1601 and / or a second barrier layer 1603 can be positioned thereon to form Figure 16-17 The first portion 1641 and / or the second portion 1651 are shown. Therefore, as shown, a portion of the first barrier layer 1601 and / or the second barrier layer 1603 may contact the initial first main surface 1313, and the first barrier layer 1601 and / or the second barrier layer 1603 may adhere at least partially to the initial first main surface 1313. As used herein, if a portion of the first layer adheres to the second layer but the entire surface of the first layer does not necessarily adhere to the second layer, then the first layer is partially adhered to the second layer. For example, a first surface region 1605 of the first barrier layer 1601 may contact and / or adhere to a portion of the initial first main surface 1313 including a first surface region 1323, and / or a second surface region 1607 of the second barrier layer 1603 may contact and / or adhere to a portion of the initial first main surface 1313 including a third surface region 1333.

[0349] In other aspects, such as Figure 16-17As shown, the first portion 1641 may include a first polymer layer 1401 located between the first barrier layer 1601 and the initial first main surface 1313. In yet another aspect, a first surface region 1403 of the first polymer layer 1401 may contact and / or adhere to the first barrier layer 1601 (e.g., a first surface region 1605). In yet another aspect, the first polymer layer 1401 may be located at a first peripheral portion 1631 of the first barrier layer 1601. For example, as shown, the inner peripheral surface of the first polymer layer 1401 may be flush with the first peripheral portion 1631 of the first barrier layer 1601. For example, as shown, the first peripheral portion 1631 of the first barrier layer 1601 may be the portion of the first barrier layer 1601 closest to the second barrier layer 1603. In other aspects, such as Figure 16-17 As shown, the second portion 1651 may include a second polymer layer 1411 located between the second barrier layer 1603 and the first main surface. In yet another aspect, a third contact surface 1413 of the second polymer layer 1411 may contact and / or adhere to the second barrier layer 1603 (e.g., the second surface region 1607). In yet another aspect, the second polymer layer 1411 may be located at a second peripheral portion 1633 of the second barrier layer 1603. For example, as shown, the inner peripheral surface of the second polymer layer 1411 may be flush with the second peripheral portion 1633 of the second barrier layer 1603. For example, as shown, the second peripheral portion 1633 of the second barrier layer 1603 may be the portion of the second barrier layer 1603 closest to the first barrier layer 1601 (e.g., the first peripheral portion 1631).

[0350] In all aspects, such as Figure 16-17As shown, the minimum distance 1407 between the first peripheral portion 1631 and the second peripheral portion 1633 can be defined as the minimum distance between the first polymer layer 1401 and the second polymer layer 1411. In other aspects, the minimum distance 1407 can be about 1 mm or more, about 2 mm or more, about 5 mm or more, about 10 mm or more, about 15 mm or more, about 20 mm or more, about 50 mm or less, about 40 mm or less, about 35 mm or less, about 30 mm or less, about 25 mm or less, or about 20 mm or less. In other aspects, the minimum distance 1407 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 35 mm, about 10 mm to about 30 mm, about 15 mm to about 25 mm, about 15 mm to about 20 mm, or any range or subrange thereof. In other respects, the minimum distance 1407 may be within one or more of the ranges discussed above with respect to the width 287 of the center portion 281, for example, based on a multiple of the absolute distance and / or the minimum parallel plate spacing. In other respects, the minimum distance 1407 may be less than the width 287 of the center portion 281 of the resulting foldable device (see...). Figure 2 and Figure 4 In other respects, the minimum distance 1407 may be substantially equal to the width 210 of the first central surface region 213 (e.g., central region 248).

[0351] In various aspects, the first polymer layer 1401 and / or the second polymer layer 1411 may comprise one or more of polyolefins, polyamides, halogenated polymers (e.g., polyvinyl chloride or fluoropolymers), elastomers, urethanes, phenolic resins, parylene, polyethylene terephthalate (PET), and polyether ether ketone (PEEK). Examples of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), and polypropylene (PP). Examples of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers, and ethylene tetrafluoroethylene (ETFE) polymers. Examples 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 1401 and / or the second polymer layer 1411 is poly(ethylene terephthalate). In all aspects, the adhesive layer of the first polymer layer 1401 and / or the second polymer layer 1411 may not be in contact with the initial first primary surface 1313 of the foldable substrate 1305.

[0352] In various aspects, the first barrier layer 1601 and / or the second barrier layer 1603 may include polymeric tapes, for example, including polymeric films and adhesive films. In other aspects, the polymeric film may include one or more materials discussed above with respect to the first polymeric layer 1401. An exemplary aspect of the polymeric film is polyimide. In other aspects, the adhesive film may include pressure-sensitive adhesives. In other aspects, the adhesive film may include silicone polymers, acrylate polymers, epoxy polymers, polyimide materials, or polyurethanes. In yet another aspect, the adhesive film may include vinyl acetate copolymers. An exemplary aspect of vinyl acetate copolymers includes SURLYN (e.g., Surlyn PC-2000, Surlyn 8940, Surlyn 8150) available from Dow Chemical. Examples of epoxy resins include bisphenol epoxy resins, phenolic epoxy resins, alicyclic epoxy resins, and glycidylamine epoxy resins. An exemplary aspect of the adhesive film is a silicone polymer (e.g., silicone). Therefore, an exemplary aspect of the first barrier layer 1601 and / or the second barrier layer 1603 is a polymer tape comprising a polymer film containing polyimide and an adhesive film containing silicone. The first barrier layer 1601 and the second barrier layer 1603 are resistant to etchants (e.g., acids) that can be used to etch the foldable substrate. In various aspects, although not shown, the barrier layers (e.g., the first barrier layer 1601, the second barrier layer 1603) can be adhered to the foldable substrate 1305 (e.g., the initial first main surface 1313) via the adhesive layer of the corresponding barrier layer. In various aspects, although not shown, the barrier layers (e.g., the first barrier layer 1601, the second barrier layer 1603) can be adhered to the corresponding polymer layers (e.g., the first polymer layer 1401, the second polymer layer 1411) via the adhesive layer of the corresponding barrier layer and / or the adhesive layer of the corresponding polymer layer, such as Maxi 689BL-003 (Maxi Adhesive Products) or JVCC EGPF-01 (JV Converting Company).

[0353] In all aspects, such as Figure 17 As shown (e.g., relative to) Figure 16Step 1105 may further include placing a third portion 1741 and / or a fourth portion 1751 of the etching mask over the initial second primary surface 1315. In other aspects, as shown, the third portion 1741 may include a third polymer layer 1701 having a third width. In yet another aspect, the third width may be within one or more ranges discussed above with respect to the first width 1417 of the first polymer layer 1401. In still another aspect, the third width may be substantially equal to the first width 1417. In yet another aspect, the third polymer layer 1701 may include the third width before it is placed on the initial second primary surface 1315. In yet another aspect, the third polymer layer 1701 may be formed of a polymer sheet similar to or the same as the portion discussed above with respect to the first polymer layer 1401 in step 1105. In yet another aspect, a sixth contact surface 1705 of the third polymer layer 1701 may contact a portion of the initial second primary surface 1315 including the second surface region 1325. In another aspect, as shown, the third portion 1741 may include a third barrier layer 1721 disposed on the initial second main surface 1315. In yet another aspect, a third polymer layer 1701 may be located between the third barrier layer 1721 and the initial second main surface 1315. In yet another aspect, at least a portion of the third surface region 1725 of the third barrier layer 1721 may contact and / or adhere to the initial second main surface 1315 including the second surface region 1325. In yet another aspect, a fifth contact surface 1703 of the third polymer layer 1701 may contact and / or adhere to the third barrier layer 1721 (e.g., the third surface region 1725). In yet another aspect, the third polymer layer 1701 may be located at the third peripheral portion 1731 of the third barrier layer 1721. For example, as shown, the inner peripheral surface of the third polymer layer 1701 may be flush with the third peripheral portion 1731 of the third barrier layer 1721. In other respects, as shown in the figure, the third part 1741 can be a mirror image of the first part 1641.

[0354] In other aspects, such as Figure 17As shown, the fourth portion 1751 may include a fourth polymer layer 1711 having a fourth width. In yet another aspect, the fourth width may be within one or more ranges discussed above with respect to the first width 1417 of the first polymer layer 1401. In still another aspect, the third width may be substantially equal to the first width 1417 and / or the second width 1419. In yet another aspect, the fourth polymer layer 1711 may include the fourth width before it is disposed on the initial second main surface 1315. In yet another aspect, the fourth polymer layer 1711 may be formed of a polymer sheet similar to or the same as the portion discussed in step 1105 above. In yet another aspect, the eighth contact surface 1715 of the fourth polymer layer 1711 may contact a portion of the initial second main surface 1315 including the fourth surface region 1727. In yet another aspect, as shown, the fourth portion 1751 may include a fourth barrier layer 1723 disposed on the initial second main surface 1315. In other aspects, the fourth polymer layer 1711 may be located between the fourth barrier layer 1723 and the initial second main surface 1315. In yet another aspect, at least a portion of the fourth surface region 1727 of the fourth barrier layer 1723 may contact and / or adhere to the initial second main surface 1315, including the fourth surface region 1335. In yet another aspect, the seventh contact surface 1713 of the fourth polymer layer 1711 may contact and / or adhere to the fourth barrier layer 1723 (e.g., the fourth surface region 1727). In yet another aspect, the fourth polymer layer 1711 may be located at the fourth peripheral portion 1733 of the fourth barrier layer 1723. For example, as shown, the inner peripheral surface of the fourth polymer layer 1711 may be flush with the fourth peripheral portion 1733 of the fourth barrier layer 1723. In yet another aspect, as shown, the fourth portion 1751 may be a mirror image of the second portion 1651. In other respects, the minimum distance between the third part 1741 and the fourth part 1751 may be within one or more of the ranges discussed above with respect to the minimum distance 1407. In still other respects, the minimum distance between the third part 1741 and the fourth part 1751 may be substantially equal to the minimum distance 1407. Alternatively, although not shown, it may be... Figure 16 The structure shown is on the entire initial second primary surface 1315 (e.g., including the existing second central surface region 1345) instead of on the entire initial second primary surface 1315. Figure 17 A uniform layer (e.g., the material of the first barrier layer 1601) is disposed on the third portion 1741 and the fourth portion 1751, for example, to produce Figure 4-5 The foldable substrate 201 shown is illustrated.

[0355] After step 1105, as Figure 18As shown, the method can proceed to step 1107, which includes etching the foldable substrate 1305 by contacting the central region 248 of the central portion 281 of the foldable substrate 1305 between the first portion 1641 and the second portion 1651 of the etching mask to form the foldable substrate 201. As used herein, if the surface is laterally positioned between the two portions, the surface is positioned between the two portions, which allows for displacement of the surface in a direction perpendicular to the minimum distance between the two portions. For example, as... Figure 18 As shown, even though the central region 248 is displaced from the first portion 1641 and the second portion 1651 of the etching mask in the thickness direction 202, because the thickness direction 202 is perpendicular to the direction of the minimum distance 1407 between the first portion 1641 and the second portion 1651 of the etching mask (e.g., direction 106), and the central region 248 is laterally located (e.g., in direction 106) between the first portion 1641 and the second portion 1651 of the etching mask, the central region 248 of the foldable substrate 201 can be entirely located between the first portion 1641 and the second portion 1651 of the etching mask. In some aspects, etching may remove a portion of the foldable substrate to form a first central surface region 213 recessed from the first main surface 203 (e.g., the first plane 204a) by a first distance 219. In other aspects, etching may remove a portion of the foldable substrate to form a first transition surface region 215 of the first transition region 212. In other aspects, etching may remove a portion of the foldable substrate to form a third transition surface region 217 of the second transition region 218. In other aspects, the first transition width 214 of the first transition region 212 may be greater than or equal to the first width 1417 of the first polymer layer 1401. In other aspects, the second transition width 216 of the second transition region 218 may be greater than or equal to the second width 1419 of the second polymer layer 1411.

[0356] In all aspects, such as Figure 18 As shown, step 1107 may further include etching the foldable substrate 1305 by contacting the central region 248 of the central portion 281 of the foldable substrate 1305 between the third portion 1741 and the fourth portion 1751 of the etching mask to form the foldable substrate 201. In various aspects, etching may remove a portion of the foldable substrate to form a second central surface region 243 recessed from the second main surface 205 (e.g., the second plane 206a) by a second distance 249. In other aspects, etching may remove a portion of the foldable substrate to form a second transition surface region 245 of the first transition region 212. In other aspects, etching may remove a portion of the foldable substrate to form a fourth transition surface region 247 of the second transition region 218. Although Figure 18The diagram illustrates etching an existing first central surface region 1343 to form a first central surface region 213 and etching an existing second central surface region 1345 to form a second central surface region 243 (e.g., to form...). Figure 2-3 (and the foldable substrate 201 shown in 15), but step 1107 may include etching the existing first central surface region 1343 to form the first central surface region 213, without etching the existing second central surface region 1345 relative to the initial second main surface 1315, for example to produce Figure 4-5 and Figure 14 The foldable substrate 201 shown is illustrated.

[0357] In all aspects, such as Figure 18 As shown, the etching in step 1107 may include contacting the central portion 281 (e.g., central region 248) of the foldable substrate 1305 with an etchant 1803 to form the foldable substrate 201. In other aspects, as shown, the etchant 1803 may be a liquid etchant contained in an etchant bath 1801. In yet other aspects, the etchant may include one or more acids (e.g., HCl, HF, H2SO4, HNO3). Not wishing to be bound by theory, during etching, the polymer layer may be deflected away from the foldable substrate, allowing the etchant to approach other portions of the foldable substrate that the polymer layer might otherwise have contacted. While the etchant can contact other portions of the foldable substrate through the deflection of the polymer layer, the diffusion of the etchant to these other portions is limited, which restricts the degree of etching in those portions, thus creating a transition zone.

[0358] In various aspects, step 1107 may further include removing the etch mask (e.g., first portion 1641, second portion 1651, third portion 1741, fourth portion 1751). In other aspects, removing the etch mask may include lifting and / or peeling the etch mask from the foldable substrate. In still other aspects, removing the etch mask may include rinsing the foldable substrate with deionized water, a neutral detergent, an alkaline detergent, and / or an alkaline solution. Rinsing the foldable substrate may remove any residue of material that has adhered the etch mask to the foldable substrate.

[0359] After step 1107, as Figure 14-15As shown, the method can proceed to step 1109, which includes chemically strengthening the foldable substrate 201. In various aspects, as shown, chemically strengthening the foldable substrate 201 may include contacting at least a portion of the foldable substrate 201 with a salt solution 1402 or 1502 comprising potassium cations and / or sodium cations in a salt bath 1441 or 1551. In other aspects, the composition of the salt solution 1402 or 1502 may include one or more materials discussed above when referring to salt solution 1302. In other aspects, the composition of the salt solution 1402 or 1502 may be the same as that of salt solution 1302 discussed above. In other aspects, the temperature of the salt solution 1402 or 1502 may be within one or more ranges discussed above when referring to the temperature of salt solution 1302. In other aspects, the contact time of the salt solution 1402 or 1502 with the foldable substrate 201 may be within one or more ranges discussed above when referring to the contact time of salt solution 1302 with the foldable substrate 1305. At the end of step 1109, the foldable substrate 201 may include a first compressive stress region, a second compressive stress region, a third compressive stress region, a fourth compressive stress region, a first central compressive stress region, and / or a second central compressive stress region. These regions may include the corresponding maximum compressive stress within one or more ranges discussed above for the corresponding maximum compressive stress of the corresponding compressive stress region, and / or the corresponding compression depth may be within one or more ranges discussed above for the corresponding compression depth of the corresponding compressive stress region.

[0360] After step 1109, as Figure 19-21 As shown, the method can proceed to step 1111, which includes assembling the foldable device. In various aspects, such as Figure 19-21 As shown, step 1111 may include assembling the foldable device by placing polymeric portions (e.g., first polymeric portion 289, second polymeric portion 299), adhesive layer 261, and / or coating 251 on the foldable substrate 201. In other aspects, such as Figure 19 As shown, the first polymeric portion 289 may be disposed in the first recess 211 and / or on the first central surface region 213. In other aspects, such as Figures 19-20As shown, coating 251 can be applied to a first main surface 203 (e.g., first surface region 223 and third surface region 233), for example, by dispensing a first liquid 1903 from a container 1901 (e.g., a catheter, flexible tube, micropipette, or syringe) onto the first main surface 203, which can then cure to form coating 251. In yet another aspect, the first liquid 1903 may include a coating precursor, solvent, particles, nanoparticles, and / or fibers. In still other aspects, the coating precursor may include, but is not limited to, one or more of monomers, accelerators, curing agents, epoxy resins, and / or acrylates. Curing the first liquid 1903 may include heating the first liquid 1903, irradiating the first liquid 1903 with ultraviolet (UV) radiation, and / or waiting for a predetermined amount of time (e.g., from about 30 minutes to 24 hours, from about 1 hour to about 8 hours). In various respects, although not shown, coating 251 may be disposed in the first groove 211 (e.g., filling the first groove 211) without contacting the first main surface 203 (e.g., the first surface region 223, the third surface region 233), for example instead of Figure 19-21 The first polymer class section 289. In other aspects, such as Figure 20-21 As shown, the second polymeric portion 299 can be disposed in the second recess 241, for example, by dispensing the second liquid 2003 from the container 2001 (e.g., a catheter, flexible tube, micropipette, or syringe) over the second central surface region 243, which can solidify to form the second polymeric portion 299. Solidifying the second liquid 2003 may include heating the second liquid 2003, irradiating the second liquid 2003 with ultraviolet (UV) radiation, and / or waiting for a predetermined amount of time (e.g., about 30 minutes to 24 hours, about 1 hour to about 8 hours). In other aspects, such as Figure 21 As shown, adhesive layer 261 may contact the second primary surface 205 (e.g., the second surface region 225 and the fourth surface region 235). For example, adhesive layer 261 may comprise one or more sheets of adhesive material. In various aspects, there may be an integral interface between the one or more sheets including adhesive layer 261, which can reduce (e.g., avoid) optical diffraction and / or optical discontinuities as light propagates between the sheets, since the one or more sheets may contain substantially the same refractive index. In various aspects, although not shown, at least a portion of the adhesive layer may be disposed in the second groove. In various aspects, as... Figure 3 As shown, the cover plate substrate 351 may be disposed on the polymeric portion (e.g., the first polymeric portion 289) instead of the coating 251, but in other respects both the coating 251 and the cover plate substrate 351 may be provided. In various respects, the release liner (e.g., see...) Figure 2The release liner 271 or display device can be mounted on the adhesive layer 261 (e.g., the second contact surface 265). Following steps 1107, 1109, or 1111, the process according to [the instructions] can be completed at step 1113. Figure 11 The flowchart in this disclosure describes a method for manufacturing foldable substrates and / or foldable devices.

[0361] In all aspects, through Figure 11 The foldable substrate 201 produced by the method outlined in the flowchart may include a first average angle 282, a second average angle 284, a third average angle 286, and / or a fourth average angle 288, which may be within one or more ranges discussed above with respect to the corresponding average angles. In various aspects, through Figure 11 The foldable substrate 201 produced by the method outlined in the flowchart may include a first transition width 214 and / or a second transition width 216, which may be within one or more ranges discussed above with respect to the corresponding transition widths. In various aspects, through Figure 11 The foldable substrate 201 produced by the method outlined in the flowchart may include a first distance 219, a second distance 249, a substrate thickness 207, and / or a center thickness 209, these distances or thicknesses being within one or more ranges discussed above with respect to the corresponding distances or thicknesses. In various aspects, through Figure 11 The foldable substrate 201 produced by the method outlined in the flowchart may include a contrast ratio (e.g., about 0.25 or less) within one or more ranges discussed above for corresponding values.

[0362] In various aspects, the methods for manufacturing foldable devices according to various aspects of this disclosure can follow... Figure 11 Steps 1101, 1103, 1105, 1107, 1109, 1111, and 1113 in the flowchart are performed sequentially as described above. In various aspects, for example, when the foldable substrate 1305 includes one or more compressive stress zones after step 1101 and / or is not chemically strengthened before etching in step 1107, the method may follow arrow 1102 from step 1101 to step 1105. In various aspects, for example, when the method of manufacturing the foldable substrate 201 is completed at the end of step 1107, it may follow arrow 1104 from step 1107 to step 1113. In various aspects, for example, when the method of manufacturing the foldable substrate 201 is completed at the end of step 1109, it may follow arrow 1106 from step 1109 to step 1113. According to various aspects of this disclosure, any of the above options may be combined to manufacture a foldable device.

[0363] Reference Figure 13-15 and 19-25 and Figure 12The flowchart in the discussion of manufacturing Figure 2-5 Examples of foldable devices 101, 301, 401, 501, 601 and / or 801 and / or foldable substrate 201 shown in 7-8. In the first step 1201 of the method of this disclosure, the method may begin by providing foldable substrate 1305 (see example 7-8). Figure 13 and 22 -23). ​​In step 1201, the foldable substrate 1305 may be provided by any of the methods discussed in step 1101 above, and the foldable substrate may include the characteristics discussed for the foldable substrate 1305 in step 1101 above.

[0364] After step 1201, as Figure 13 As shown, the method may proceed to step 1203, which includes initial chemical strengthening of the foldable substrate 1305. In various aspects, prior to the chemical strengthening in step 1203, the foldable substrate 1305 may exist in a substantially unstrengthened state (i.e., substantially unstrengthened). In various aspects, as shown, chemical strengthening of the foldable substrate 1305 may include contacting at least a portion of the foldable substrate 1305 comprising lithium cations and / or sodium cations with a salt bath 1301 comprising a salt solution 1302. In other aspects, the salt solution 1302 may include any of the components discussed above in step 1103. In other aspects, the temperature of the salt solution 1302 and / or the duration for which the foldable substrate 1305 may be in contact with the salt solution 1302 may be within one or more of the ranges discussed above for the corresponding characteristics. Step 1103 may generate an initial first compressive stress region extending from the initial first main surface 1313 to the initial first compression depth and / or an initial second compressive stress region extending from the initial second main surface 1315 to the initial second compression depth, wherein the corresponding initial compression depth, expressed as a percentage of the substrate thickness 207, may be within one or more ranges discussed in step 1103 above. In various aspects, the initial first compression depth may be less than a first distance 219 of the resulting foldable substrate 201 and / or the initial second compression depth may be less than a second distance 249 of the resulting foldable substrate 201, which may enable the entire initial first compression depth and / or second compression depth to be removed from the central portion 281 (e.g., central region 248) of the foldable substrate 1305 during the etching process in step 1107. In various aspects, prior to step 1103, the foldable substrate 201 may be in a substantially unstrengthened state (i.e., substantially unstrengthened) (e.g., unstressed, unchemically strengthened, unthermally strengthened). As used herein, “substantially unstrengthened” and “substantially unstrengthened state” refer to a substrate excluding layer depth or a layer depth ranging from 0% to approximately 5% of the substrate thickness.

[0365] After step 1201 or 1203, as Figure 22-25 As shown, the method can proceed to step 1205, which includes placing an etching mask 2205 or 2305 over the initial first primary surface 1313 of the foldable substrate 1305 (e.g., including the existing first central surface region 1343). In various aspects, such as Figure 22-23 As shown, the etching mask 2205 or 2305 may include a first portion disposed on the foldable substrate 1305 (e.g., see...). Figure 2-5 The first portion 2203a or 2303a above the first portion 221) and the second portion disposed on the foldable substrate 1305 (e.g., see...) Figure 2-5 The second part 231) above the second part 2203b or 2303b. Additionally, as... Figure 22-25 As shown, the etching mask may further include multiple shapes (e.g., multiple features 2201 or 2301) disposed on the foldable substrate 1305 (e.g., the existing first central surface region 1343). Although not shown, it should be understood that in step 1205, a pattern similar to or identical to the multiple shapes (e.g., multiple features 2201 and / or 2301) may be disposed on the existing second central surface region (e.g., to produce...). Figure 2-3 and Figure 15 The foldable substrate 201 shown), or a uniform mask placed on the existing second central surface region and second main surface (e.g., to produce Figure 4-5 and Figure 14 The foldable substrate 201 shown.

[0366] In various aspects, multiple shapes (e.g., multiple features 2201 and / or 2301) are arranged as part of an etching mask 2205 or 2305 (see [reference]). Figure 22-23 This can include inkjet printing multiple shapes on an initial first main surface 1313 that includes a central portion of a foldable substrate 1305 (e.g., including an existing first central surface region 1343). Figure 24-25 They were presented respectively Figure 22-23 Enlarged view of the multiple features 2201 and 2301 shown. The multiple features 2201 and 2301 can be curved, curved, and / or polygonal. In other aspects, such as Figure 24 As shown, multiple shapes (e.g., multiple features 2201) may include (e.g., corresponding to) multiple curved shapes (e.g., ellipses 2401a-2401c and / or circles 2403a-2403c). For example, multiple shapes (e.g., multiple features 2201) may include curved shapes of ellipses 2401a-2401c and / or circles 2403a-2403c. Or, or additionally, in other aspects, such as Figure 25As shown, the multiple shapes 2501, 2503, 2505, 2507, 2509, and / or 2511 may include elongated shapes (e.g., having an aspect ratio of about 10 or greater). For example, as Figure 25 As shown, multiple shapes 2501, 2503, 2505, 2507, 2509 and / or 2511 can extend substantially from one end of the existing first central surface region 1343 to the other end opposite to that end, but in other respects shorter but still elongated shapes are possible. In other respects, the aspect ratio of the elongated shapes of the plurality of shapes may be 10 or greater, 15 or greater, 20 or greater, 25 or greater, 30 or greater, 40 or greater, 50 or greater, 60 or greater, 80 or greater, or 100 or greater, for example, in the range of about 10 to about 100,000, about 15 to about 10,000, about 20 to about 5,000, about 25 to about 2,000, about 30 to about 1,000, about 40 to about 800, about 50 to about 600, about 60 to about 400, about 80 to about 300, about 100 to about 200, or any range or subrange thereof.

[0367] Throughout this disclosure, the width of a shape among multiple shapes is defined in direction 106 (see...). Figure 1-5 The transition region extends from the first transition region 212 (e.g., the first transition surface region 215) to the second transition region 218 (e.g., the third transition surface region 217) (see also...) Figure 2-5 The maximum distance. For example, such as Figure 24 As shown, the width 2402 of the ellipse 2401c is measured as the maximum distance in direction 106, where the maximum dimension is the longest line segment (excluding endpoints) completely within the shape. In various aspects, as Figure 24 As shown, the width 2402 of the ellipse 2401c of one or more of the multiple shapes can be greater than the corresponding dimension perpendicular to direction 106 (and perpendicular to direction 202 of substrate thickness 207). Or, additionally, as Figure 24 As shown, the width 2404 of the circle 2403c of one or more of the multiple shapes can be substantially equal to the corresponding dimension perpendicular to direction 106 (and perpendicular to direction 202 of substrate thickness 207). Or, alternatively, as Figure 25As shown, the width 2502 of shape 2501 of one or more of the plurality of shapes can be significantly smaller than the corresponding dimension perpendicular to direction 106 (and perpendicular to direction 202 of substrate thickness 207). In all aspects, the width of one or more of the plurality of shapes can be about 500 nm or greater, about 800 nm or greater, about 1 µm or greater, about 2 µm or greater, about 5 µm or greater, about 8 µm or greater, about 10 µm or greater, about 15 µm or greater, about 20 µm or greater, about 25 µm or greater, about 50 µm or greater, about 40 µm or greater, about 30 µm or greater, about 25 µm or less, about 20 µm or less, about 15 µm or less, about 10 µm or less, about 8 µm or less, about 5 µm or less, about 2 µm or less, or about 1 µm or less. In all respects, the width of one or more of the plurality of shapes may be in the range of about 500 nm to about 50 µm, about 500 nm to about 40 µm, about 800 nm to about 30 µm, about 800 nm to about 25 µm, about 1 µm to about 20 µm, about 1 µm to about 15 µm, about 2 µm to about 10 µm, about 5 µm to about 8 µm, or any range or subrange thereof. Providing a width of one or more of the plurality of shapes of about 500 nm to about 50 µm allows the underlying foldable substrate to be etched to produce a substantially continuous and / or smooth surface of the resulting surface (e.g., Figure 2-5 The first transition surface region 215, the third transition surface region 217, and / or the first central surface region 213 shown in the figure.

[0368] like Figure 22-25 As shown, multiple shapes can be unevenly distributed in a predetermined pattern on the initial first main surface 1313 (e.g., including the existing first central surface region 1343). Throughout this disclosure, "fractional area" (or "fractional area distribution") refers to the ratio of the area of ​​the first main surface (including the existing first central surface region) covered by the multiple shapes to the total area of ​​the first main surface (including the existing first central surface region), wherein this ratio can be calculated for segments of the first main surface (including the existing first central surface region) in a direction (e.g., the average of the width of one of the multiple shapes in a direction perpendicular to the substrate thickness and the direction extending from the first transition surface region to the third transition surface region). For example, see... Figure 25 , Figure 25 The right third fraction of the area will be the area of ​​shapes 2509 and 2511 covering the existing first central surface region 1343 divided by Figure 25 The total area of ​​the existing first central surface region 1343 in the right third. In various aspects, such as Figure 22-23As shown, the predetermined pattern can produce a fractional area distribution that increases (e.g., monotonically increases) with increasing distance from the center of the central portion 281. For example, as... Figure 25 As shown, from right to left (corresponding to) Figure 23 The area occupied by shapes 2511, 2509, 2507, 2505, 2503, and 2501 (to the left of the central portion 281) increases, for example, by increasing the width of the corresponding shapes, which causes the fractional area distribution to also increase from right to left. In various aspects, such as Figure 22 As shown, the fractional area distribution of the edges of the central portion 281 (corresponding to the first transition portion and / or the second transition portion) may change more rapidly relative to the center of the central portion 281. In various aspects, the fractional area distribution (of the corresponding predetermined pattern) may be proportional to the amount of material removed by etching to produce predetermined first transition regions and predetermined second transition regions in the etching of step 1207.

[0369] After step 1205, the method may proceed to step 1207, which includes etching the foldable substrate by bringing the central portion of the foldable substrate into contact with a plurality of shapes, for example, similar to those described above. Figure 18 Step 1107, as described above, should be understood as follows: Figure 18 The etching mask in the middle is Figure 22-23 The etch masks 2205 and / or 2305 shown are used instead. Therefore, in various aspects, the etchant can be a liquid etchant contained in an etchant bath, etching can include immersing the foldable substrate in which the etch mask is disposed into the etchant bath, and / or the etchant can include one or more inorganic acids (e.g., HCl, HF, H2SO4, HNO3). Additionally, step 1207 can further include removing the remaining portion of the etch mask after etching. In various aspects, one or more (e.g., most) of the multiple shapes in the central portion of the foldable substrate can be removed in the etching itself, while other portions disposed on the first and / or second portions can remain on the foldable substrate throughout the etching process for subsequent removal. As discussed above, the fractional area distribution and / or predetermined pattern of the etch mask can be proportional to the amount of material removed by the etching to create predetermined first transition regions and predetermined second transition regions during etching. It is not intended to be theoretically constrained, but it is believed that the shapes of this disclosure are small enough that the undercut of the etchant (e.g., an isotropic etchant) can produce a relatively smooth surface (e.g., without identifiable flat points corresponding to the predetermined pattern). At the same time, it is believed that the shape of this disclosure is large enough to confine etching (e.g., diffusion of etchant) to a region with a high fractional area, thereby producing a predetermined distribution.

[0370] After step 1207, as Figure 14-15As shown, the method may proceed to step 1209, which includes chemically strengthening the foldable substrate 201. In various aspects, step 1209 may include any and / or all aspects discussed when referring to step 1109 above.

[0371] After step 1209, as Figure 19-21 As shown, the method can proceed to step 1211, which includes assembling the foldable device. In various aspects, step 1211 may include any and / or all of the aspects discussed above in reference to step 1111. For example, a first polymeric portion 289 may be disposed in a first recess 211 and / or a second polymeric portion 299 may be disposed in a recess (e.g., the first recess 211 and / or the second recess 241). Furthermore, a coating 251, a cover plate substrate 351, an adhesive layer 261, a release liner 271, and / or a display device may be disposed thereon to assemble the foldable device. After steps 1207, 1209, or 1211, the method may be completed upon reaching step 1213.

[0372] In all aspects, through Figure 12 The foldable substrate 201 produced by the method outlined in the flowchart may include a first average angle 282, a second average angle 284, a third average angle 286, and / or a fourth average angle 288, which may be within one or more ranges discussed above with respect to the corresponding average angles. In various aspects, through Figure 12 The foldable substrate 201 produced by the method outlined in the flowchart may include a first transition width 214 and / or a second transition width 216, which may be within one or more ranges discussed above with respect to the corresponding transition widths. In various aspects, through Figure 12 The foldable substrate 201 produced by the method outlined in the flowchart may include a first distance 219, a second distance 249, a substrate thickness 207, and / or a center thickness 209, these distances or thicknesses being within one or more ranges discussed above with respect to the corresponding distances or thicknesses. In various aspects, through Figure 12 The foldable substrate 201 produced by the method outlined in the flowchart may include a contrast ratio (e.g., about 0.25 or less) within one or more ranges discussed above for corresponding values.

[0373] In various aspects, the methods for manufacturing foldable devices according to various aspects of this disclosure can follow... Figure 12Steps 1201, 1203, 1205, 1207, 1209, 1211, and 1213 in the flowchart are performed sequentially as discussed above. In various aspects, for example, when the foldable substrate 1305 includes one or more compressive stress zones after step 1201 and / or is not chemically strengthened before etching in step 1207, the method may follow arrow 1202 from step 1201 to step 1205. In various aspects, for example, when the method of manufacturing the foldable substrate 201 is completed at the end of step 1207, it may follow arrow 1204 from step 1207 to step 1213. In various aspects, for example, when the method of manufacturing the foldable substrate 201 is completed at the end of step 1209, it may follow arrow 1206 from step 1209 to step 1213. According to various aspects of this disclosure, any of the above options may be combined to manufacture a foldable device.

[0374] Example

[0375] The various aspects will be further illustrated by the following examples. Examples 1-8, 10-14, and AE comprise a glass substrate (composition 1, with the following nominal composition (mol%): 63.6 SiO2; 15.7 Al2O3; 10.8 Na2O; 6.2 Li2O; 1.16 ZnO; 0.04 SnO2; and 2.5 P2O5), with a substrate thickness 207 of 100 µm. In Examples 1-4, 9-14, and AE, the glass substrate is etched to form a center thickness 209 of 30 μm, and a first groove 211 and a second groove 241 opposite to the first groove 211 (e.g., the first distance 219 and the second distance 249 are substantially equal to 35 μm; see [link to relevant documentation]). Figure 2-3 The foldable substrate 201 in the example. Examples 5-8 include a center thickness of 35 μm and a first groove 211 (e.g., a first distance 219 is substantially equal to about 65 μm; see also...). Figure 4-5 The foldable substrate 201 in the middle) and a second central surface region flush with the second main surface. In Examples 1-8 and Example AE, the groove is filled with a polymeric material, wherein the polymeric material is formed by curing a precursor liquid flush with the corresponding main surface (e.g., the first main surface, the second main surface), on the outer surface of the corresponding main surface (e.g., the first main surface, the second main surface) and the polymeric portion (e.g., Figure 2-3 The differences between the third contact surface 283 and / or the fourth contact surface 295 are presented in Tables 1-2 and 4 as “polymer-surface height difference” in micrometers (see Table 1-2). Figure 33(Distances 3323 and 3325 in the original text). In Examples 1-3, 5-7, and AE, the polymeric material is polymer X, whose refractive index is within 1.501 of the refractive index of the foldable substrate. In Examples 4 and 8, the polymeric material is polymer Y with a refractive index of 1.505.

[0376] Table 1 presents the characteristics of Examples 1-4 (having a first groove opposite to the second groove), which are also respectively in Figures 31-32 Points 1-4 are presented in 34. The “average transition angle” in Table 1-2 is measured as the “surface angle” as defined above, although the “average angle” defined above is essentially equal to the “surface angle.” As shown, from Example 1 to Example 3, the contrast ratio decreases as the average transition angle (e.g., the first average angle) and / or polymer angle increase. It is worth noting that, as... Figure 31 As shown in Table 1, Example 3, with a polymer angle of 178.5°, has a contrast ratio of 0.14, lower than that shown in the reference here. Figure 29 The proposed visibility threshold is approximately 0.25. This is based on modeling and additional sampling (not shown, but...). Figure 31 (Line 3107 in the example is representative) determines that when the polymer angle is 178.3° or greater, the dual-groove foldable substrate (with the thickness and center thickness of Examples 1-4) can achieve a contrast ratio of 0.25 or less.

[0377] like Figure 34 As shown in Table 1, the average transition angle of Example 3 was 178.9° (corresponding to a transition width of 1.96 mm), which is below the visibility threshold of approximately 0.25. This is based on modeling and additional sampling (not shown, but...). Figure 34 Line 3407 in the example is representative. It is determined that when the average transition angle is 177.0° or greater (corresponding to a transition width of 0.67 mm), the dual-groove foldable substrate (with the thickness and center thickness of Examples 1-4) can achieve a contrast ratio of 0.25 or less.

[0378] Table 1: Characteristics of Examples 1-4 ...

Claims

1. A foldable device comprising a foldable substrate, the foldable substrate comprising: a substrate thickness in a range from about 80 microns to about 5 millimeters, the substrate thickness being defined between a first major surface and a second major surface opposite the first major surface, the foldable substrate comprising a glass-like material or a ceramic-like material; a first portion comprising the substrate thickness between a first surface area of the first major surface and a second surface area of the second major surface; a second portion comprising the substrate thickness between a third surface area of the first major surface and a fourth surface area of the second major surface; a central portion comprising a central thickness less than the substrate thickness and in a range from about 20 microns to about 200 microns, the central thickness being defined between a first central surface area and a second central surface area opposite the first central surface area, and the first central surface area being recessed from the first major surface by a first distance and defining a first recess; and a first polymer-like portion disposed in the first recess, the first polymer-like portion comprising a first contact surface facing the first central surface area and a second contact surface opposite the second contact surface, and an absolute value of a difference between a first refractive index of the foldable substrate and a second refractive index of the first polymer-like portion being about 0.1 or less, wherein a first polymer angle is defined as an interior angle between the first major surface of the foldable substrate and the second contact surface of the polymer-like portion, which is in a range from about 178.3° to about 179.9°.

2. The foldable device of claim 1, wherein the first polymer angle is in a range from 178.5° to about 179.0°.

3. The foldable device of claim 1, wherein a distance between the first major surface and the second contact surface in a direction of the substrate thickness is about 5 microns or less.

4. The foldable device of claim 1, wherein the foldable device comprises a contrast ratio of about 0.25 or less, and the contrast ratio is defined as a difference between a maximum fractional intensity and a minimum fractional intensity divided by a sum of the maximum fractional intensity and the minimum fractional intensity, measured using a contrast test.

5. The foldable device of claim 1, wherein the substrate thickness is in a range from about 100 microns to about 400 microns, and the central thickness is in a range from about 25 microns to about 80 microns.

6. The foldable device of claim 1, wherein the second central surface area is flush with the second surface area and the fourth surface area.

7. The foldable device of claim 1, wherein the second central surface area is recessed from the second major surface by a second distance and defines a second recess, and the first polymer angle is in a range from 179.2° to about 179.5°.

8. The foldable device of claim 1, wherein the central portion further comprises: A first transition region, the first transition region including a first transition surface region, the first transition surface region extending at a first average angle relative to the first central surface region between the first surface region and the first central surface region, and the thickness of the first transition region smoothly and monotonically decreasing between the substrate thickness of the first portion and the central thickness of the central portion. as well as The second transition region includes a third transition surface region that extends at a third average angle relative to the first central surface region between the third surface region and the first central surface region, and the thickness of the second transition region smoothly and monotonically decreases between the substrate thickness of the second portion and the center thickness of the central portion. The first average angle is in the range of about 176.1° to about 179.9°.

9. The foldable device of claim 1, wherein the first average angle is in the range of about 177.0° to about 179.0°.

10. The foldable device of claim 8, wherein the first transition width of the first transition region is in the range of about 2.0 mm to about 6.0 mm.

11. The foldable device of claim 1, wherein the foldable substrate achieves a parallel plate spacing of 10 mm.

12. The foldable device of claim 1, wherein the foldable substrate comprises a minimum parallel plate spacing in the range of about 0.5 mm to about 10 mm.

13. A consumer electronic device comprising: The housing includes a front surface, a rear surface, and side surfaces; An electrical component, at least partially located within the housing, the electrical component including a controller, a memory, and a display, the display being located at or adjacent to the front surface of the housing; as well as A cover plate substrate, which is disposed above the display. The portion of the housing or at least one of the cover plate substrates comprises the foldable device according to claim 1.

14. A method of manufacturing a foldable substrate, the foldable substrate comprising a substrate thickness, a predetermined first transition region, and a predetermined second transition region, the method comprising: Multiple shapes are inkjet printed on a first main surface including the central portion of the foldable substrate, wherein the multiple shapes are unevenly distributed on the first main surface in a predetermined pattern. as well as The foldable substrate is etched by contacting the central portion and the plurality of shapes with an etchant. The etching removes a portion of the foldable substrate to form a first central surface region that is recessed from the first main surface by a first distance and defines a first groove. The etching removes a portion of the foldable substrate to form a first transition surface region of the predetermined first transition region. The etching removes a portion of the foldable substrate to form a third transition surface region of the predetermined second transition region.

15. The method of claim 14, wherein the predetermined pattern generates a fractional area distribution of a portion of a first main surface covered by the plurality of shapes, the fractional area distribution being averaged in both a direction perpendicular to the substrate thickness and a direction extending from the first transition surface region to the third transition surface region, and the fractional area distribution being proportional to the amount of material removed by the etching to generate the predetermined first transition region and the predetermined second transition region.

16. The method of claim 14, wherein the plurality of shapes comprises a plurality of elongated shapes having an aspect ratio of about 10 or greater.

17. The method of claim 14, wherein the shape of the plurality of shapes includes a shape width in the range of about 500 nanometers to about 50 micrometers, and the shape width is in a direction extending from the first transition surface region to the third transition surface region.

18. The method of claim 14, wherein the first transition surface region extends at a first average angle relative to the first central surface region between a first surface of the first main surface and the first central surface region, the third transition surface region extends at a third average angle relative to the first central surface region between a third surface region of the first main surface and the first central surface region, and the first average angle is in the range of about 176.1° to about 179.9°.

19. The method of claim 14, wherein the central portion includes a second central surface region opposite to the first central surface region, the foldable substrate further includes a second main surface opposite to the first main surface, the second central surface region being flush with the second main surface, and the first average angle being in the range of about 177.0° to about 179.0°.

20. The method of claim 14, wherein the foldable substrate exhibits a contrast ratio of about 0.25 or less, and the contrast ratio is defined as the difference between the maximum and minimum fractional intensities measured using a contrast test when the first groove is filled with a material having a refractive index substantially the same as that of the foldable substrate, divided by the sum of the maximum and minimum fractional intensities.

Images