Foldable device, foldable substrate and method for manufacturing the same

Abstract

A foldable device comprising a foldable substrate foldable about an axis and a substrate thickness defined between a first major surface and a second major surface. The foldable substrate comprises a center portion between a first portion and a second portion. The first portion comprises a substrate thickness. The center portion comprises a center thickness that is less than the substrate thickness. In some embodiments, the width of the center portion is less than or equal to about 45 mm. A method of manufacturing a foldable device comprising forming a depression in a first major surface of the foldable substrate. In some embodiments, the method comprises chemically strengthening the foldable substrate.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority under 35 U.S.C. §119 to U.S. Provisional Application Serial No. 63 / 022,748, filed on May 11, 2020; U.S. Provisional Application Serial No. 62 / 914,720, filed on October 14, 2019, and U.S. Provisional Application Serial No. 62 / 893,291, filed on August 29, 2019, the contents of each of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure generally relates to foldable devices, foldable substrates and methods of manufacturing the same, and more particularly, to foldable devices and foldable substrates including parts and methods of manufacturing the foldable devices and foldable substrates. Background Art

[0004] Glass-based substrates are commonly used, for example, in display devices such as liquid crystal displays (LCDs), electrophoretic displays (EPDs), organic light emitting diode displays (OLEDs), plasma display panels (PDPs), and the like.

[0005] It is desirable to develop a display in a foldable form and a foldable protective cover mounted on the foldable display. The foldable display and cover should have excellent impact resistance and puncture resistance. At the same time, the foldable display and cover should have a small minimum bending radius [e.g., about 10 millimeters (mm) or less]. However, plastic displays and covers with a small minimum bending radius tend to have poor impact resistance and / or puncture resistance. In addition, conventional wisdom suggests that ultra-thin glass-based sheets with a small minimum bending radius [e.g., a thickness of less than or equal to about 75 microns (μm or micron)] tend to have poor impact resistance and / or puncture resistance. Furthermore, thicker glass-based sheets (e.g., greater than 125 microns) with excellent impact resistance and / or puncture resistance tend to have a relatively large minimum bending radius (e.g., greater than or equal to about 30 mm). As a result, it is necessary to develop a foldable device with a low minimum bending radius and excellent impact resistance and puncture resistance. Summary of the invention

[0006] The present invention describes a foldable device, a foldable substrate, and a method for manufacturing a foldable device and a foldable substrate, wherein the foldable substrate includes a first portion and a second portion. Each portion may include a glass-based and / or ceramic-based portion, which may provide excellent dimensional stability, a reduced incidence of mechanical instability, excellent impact resistance, and / or excellent puncture resistance. The first portion and / or the second portion may include a glass-based and / or ceramic-based portion, wherein the glass-based and / or ceramic-based portion includes one or more compressive stress zones, which may further increase the impact resistance and / or puncture resistance. By providing a substrate including a glass-based and / or ceramic-based substrate, the substrate may also provide increased impact resistance and / or increased puncture resistance, while at the same time contributing to excellent folding performance. In some embodiments, the substrate thickness may be sufficiently large [e.g., about 80 microns (micron or μm) to about 2 millimeters] to provide excellent impact resistance and excellent puncture resistance. A foldable substrate is provided that includes a central portion, the central portion including a central thickness that is less than the substrate thickness of the first portion and / or the second portion, thereby enabling a small effective minimum bending radius [e.g., about 10 millimeters (mm) or less] based on the reduced thickness of the central portion. In some embodiments, the central thickness can be sufficiently small (e.g., about 10 microns to about 125 microns) in a bending region (e.g., the central portion) of the foldable device to provide a low effective bending radius (e.g., less than or equal to about 10 mm, less than or equal to about 9 mm, less than or equal to about 8 mm, less than or equal to about 7 mm, less than or equal to about 6 mm, less than or equal to about 5 mm, less than or equal to about 4 mm, less than or equal to about 3 mm, less than or equal to about 2 mm, or about 1 mm).

[0007] In some embodiments, the foldable substrate may include a first transition portion attaching the central portion to the first portion, and / or a second transition region attaching the central portion to the second portion. Providing a transition region with increasing thickness can reduce stress concentration in the transition region and / or avoid optical distortion. Providing a transition region of sufficient length (e.g., about 1 mm or greater) can avoid optical distortion that may otherwise exist due to a sudden step change in the thickness of the foldable substrate. Providing a transition region of sufficiently small length (e.g., less than or equal to about 5 mm) can reduce the amount of foldable substrates with medium thickness, which can have reduced impact resistance and / or reduced puncture resistance.

[0008] Providing a first portion and / or a second portion, and including an average concentration of one or more alkali metals that is close to (e.g., within 100 parts per million, within 10 parts per million, on an oxide basis) the concentration of one or more alkali metals in the central portion, can minimize differential expansion of the first portion and / or the second portion compared to the central portion due to chemical strengthening. Substantially uniform expansion can reduce the incidence of mechanical deformation and / or mechanical instability due to chemical strengthening.

[0009] Providing a ratio of the layer depth to the thickness of the first portion and / or the second portion that is close to (e.g., within 0.1%, within 0.01%) the corresponding ratio of the central portion can minimize the difference in near-surface expansion of the first portion and / or the second portion compared to the central portion due to chemical strengthening. Minimizing the difference in near-surface expansion can reduce stress and / or strain in the plane of the first major surface, the second major surface, the first central surface region, and / or the second central surface region, which can further reduce the incidence of mechanical deformation and / or mechanical instability due to chemical strengthening.

[0010] Providing a ratio of the compression depth to the thickness of the first portion and / or the second portion that is close to (e.g., within 1%, within 0.1%) the corresponding ratio of the central portion can minimize the chemical strengthening-induced strain difference of the first portion and / or the second portion relative to the central portion. Minimizing the chemical strengthening-induced strain difference can reduce the incidence of mechanical deformation and / or mechanical instability due to chemical strengthening.

[0011] Minimizing stress and / or strain on the first major surface, the second major surface, the first central surface region, and / or the second central surface region can reduce stress-induced optical distortion. Moreover, minimizing such stress can increase puncture resistance and / or impact resistance. Moreover, minimizing such stress can be associated with a low difference in optical retardation along the centerline (e.g., about 2 nanometers or less). Further, minimizing such stress can reduce the incidence of mechanical deformation and / or mechanical instability due to chemical strengthening.

[0012] The central maximum tensile stress of the central tensile stress zone of the central portion is provided to be greater than the first maximum tensile stress of the first tensile stress zone of the first portion and / or the second maximum tensile stress of the second tensile stress zone of the second portion, thereby making the fracture caused by impact in the first portion and / or the second portion a low-energy fracture, while providing excellent folding performance. In some embodiments, the low-energy fracture can be the result of a reduction in the thickness of the central portion, and for a given maximum tensile stress, the central portion with reduced thickness stores less energy than the thicker glass portion. In some embodiments, the low-energy fracture can be the result of a fracture of the first portion and / or the second portion away from the central portion that undergoes bending, wherein the first portion and / or the second portion comprises a lower maximum tensile stress than the central portion. Further, in some embodiments, providing a substantially uniform compression depth associated with the compressive stress zone of the foldable substrate can simplify the manufacture of the article by avoiding the use of shielding or another non-uniform ion exchange method.

[0013] Providing a neutral stress configuration when the foldable device is in a bent configuration can reduce the force that causes the foldable device to bend to a predetermined parallel plate distance. Further, providing a neutral stress configuration when the foldable device is in a bent state can reduce the maximum stress and / or strain experienced by the foldable substrate, adhesive layer and / or polymer-based portion during normal use conditions, which can, for example, increase the durability of the foldable device and / or reduce fatigue of the foldable device. In some embodiments, the polymer-based portion may include a low (e.g., negative) coefficient of thermal expansion, which can mitigate warping caused by volume change during curing of the polymer-based portion. In some embodiments, the neutral stress configuration can be generated by providing a polymer-based portion that expands due to curing. In some embodiments, the neutral stress configuration can be generated by curing the polymer-based portion in a bent configuration. In some embodiments, the neutral stress configuration can be generated by bending the foldable substrate at an elevated temperature (e.g., when the foldable substrate comprises about 10 4 Pascal-seconds to about 10 7 (Pascal-second viscosity).

[0014] The methods of the present disclosure can produce a foldable substrate that includes one or more of the benefits mentioned above. For example, providing a diffusion barrier above the first central surface area and / or the second central surface area can adjust the rate of chemical strengthening of the central portion relative to the first portion and / or the second portion. For example, providing a paste containing alkali metal ions above the surface area of ​​the first portion and / or the second portion can achieve the above benefits by promoting one or more of the above ratios and / or concentrations of the balancing central portion relative to the first portion and / or the second portion. In some embodiments, the foldable substrate can further undergo chemical strengthening to achieve greater compressive stresses without encountering mechanical deformation and / or mechanical instability, and the greater compressive stress can further increase the impact resistance and / or puncture resistance of the foldable substrate.

[0015] Further, the method of the embodiments of the present disclosure can achieve the above benefits in a single chemical strengthening step (e.g., heating a paste containing alkali metal ions, immersing the foldable substrate in a solution containing alkali metal ions), which can reduce the time, equipment, space and labor costs associated with producing foldable substrates. For example, the diffusion barrier disposed on the two surfaces of the central portion may include a thickness that can produce a foldable substrate after a single chemical strengthening step. For example, a paste containing alkali metal ions different from the paste containing alkali metal ions applied to the first portion and / or the second portion can be applied to the central portion to produce a foldable substrate after a single chemical strengthening step. In some embodiments, the concentration of one or more alkali metal ions in the alkali metal ion-containing paste applied to the first portion and / or the second portion can be greater than the concentration in the different alkali metal-containing pastes applied to the central portion. In some embodiments, the different alkali metal-containing pastes applied to the central portion may include one or more alkaline earth metal ions, which can reduce the rate of chemical strengthening of the central portion.

[0016] Some exemplary embodiments of the present disclosure are described below, while it should be understood that any features of the various embodiments may be used alone or in combination with each other.

[0017] Embodiment 1: A foldable device includes a foldable substrate that can be folded around an axis extending along the width direction of the foldable substrate. The foldable substrate also includes a substrate thickness, which is defined between a first major surface and a second major surface opposite the first major surface. The foldable substrate also includes a first portion, the first portion including the substrate thickness, a first surface area of ​​the first major surface, and a first tensile stress zone including a first maximum tensile stress. The foldable substrate also includes a second portion, the second portion including the substrate thickness, a third surface area of ​​the first major surface, and a second tensile stress zone including a second maximum tensile stress. The foldable substrate also includes a center portion, the center portion including a center thickness defined between the first center surface area and the second major surface opposite the first center surface area. The first center surface area attaches the first surface area to the third surface area. The center thickness is less than the substrate thickness. The center tensile stress zone includes a center maximum tensile stress. The center portion is located between the first portion and the second portion in a length direction of the foldable substrate, the length direction being perpendicular to the width direction of the foldable substrate. The first maximum tensile stress and the second maximum tensile stress are less than the center maximum tensile stress.

[0018] Embodiment 2: The foldable device of embodiment 1, wherein the first maximum tensile stress is less than or equal to about 100 MPa. The second maximum tensile stress is less than or equal to about 100 MPa. The central maximum tensile stress is in a range from about 125 MPa to about 375 MPa.

[0019] Embodiment 3: The foldable device of any one of Embodiments 1-2, wherein the first maximum tensile stress is in a range from 10 megapascals to about 100 megapascals. The second maximum central tensile stress is in a range from about 10 megapascals to about 100 megapascals.

[0020] Embodiment 4: The foldable device of any of Embodiments 1-3, wherein the central portion further comprises a first transition portion attaching the first portion to the central portion. The first transition portion comprises a thickness that continuously increases from the central portion to the first portion. The central portion further comprises a second transition portion attaching the second portion to the central portion. The second transition portion comprises a thickness that continuously increases from the central portion to the second portion.

[0021] Embodiment 5: The foldable device of any one of Embodiments 1-4, wherein the width of the central portion is in a range from about 3 mm to about 45 mm.

[0022] Embodiment 6: A foldable device comprising a foldable substrate comprising a first major surface extending along a first plane, a second major surface extending along a second plane, the second plane being parallel to the first plane. The foldable device comprises a substrate thickness defined between the first plane and the second plane. The foldable substrate further comprises a first portion comprising a first surface area of ​​the first major surface. The foldable substrate further comprises a second portion comprising a third surface area of ​​the first major surface. The foldable substrate further comprises a center portion attaching the first portion of the foldable substrate to the second portion of the foldable substrate. The center portion comprises a first center surface area between the first surface area and the third surface area. The center portion comprises a center thickness of the foldable substrate defined between the second plane and the first center surface area. The center thickness is less than the substrate thickness. The center portion comprises a first transition portion attaching the first portion to the center portion. The first transition portion comprises a thickness that increases continuously from the center portion to the first portion. The center portion comprises a second transition portion attaching the second portion to the center portion. The second transition portion comprises a thickness that increases continuously from the center portion to the second portion. The width of the central portion is in the range of about 3 mm to about 45 mm. A recess is defined between the first central surface area of ​​the central portion and the first plane. The adhesive fills the recess.

[0023] Embodiment 7: The foldable device of embodiment 6, wherein the first central surface area of ​​the central portion includes a central major surface of the central portion that extends along a third plane parallel to the second plane.

[0024] Embodiment 8: The foldable device of any one of Embodiments 4-7, wherein a width of the first transition portion and / or a width of the second transition portion is in a range from about 1 mm to about 5 mm.

[0025] Embodiment 9: The foldable device of any one of Embodiments 4-8, wherein the thickness of the first transition portion increases at a constant rate from the central portion to the first portion.

[0026] Embodiment 10: The foldable device of any one of Embodiments 4-9, wherein the thickness of the second transition portion increases at a constant rate from the central portion to the second portion.

[0027] Embodiment 11: The foldable device of any one of Embodiments 1-10, wherein the foldable device comprises a neutral stress configuration when the foldable device is in a bent configuration.

[0028] Embodiment 12: A foldable device comprising a foldable substrate that is foldable about an axis extending in a width direction of the foldable substrate. The foldable substrate also includes a substrate thickness, which is defined between a first major surface and a second major surface opposite the first major surface. The foldable substrate also includes a first portion, the first portion including the substrate thickness and a first surface area of ​​the first major surface. The foldable substrate also includes a second portion, the second portion including the substrate thickness and a third surface area of ​​the first major surface. The foldable substrate also includes a center portion, the center portion including a center thickness defined between a first center surface area and a second major surface opposite the first center surface area. The first center surface area attaches the first surface area to the third surface area. The width of the center portion is less than or equal to about 45 mm. The center thickness is less than the substrate thickness. The center portion is located between the first portion and the second portion in a length direction of the foldable substrate, the length direction being perpendicular to the width direction of the foldable substrate. When the foldable device is in a bent configuration, the foldable device includes a neutral stress configuration.

[0029] Embodiment 13: The foldable device of any of embodiments 11-12, wherein the foldable device includes a polymer-based portion located in a recess defined between a first central surface area of ​​the central portion and a first plane along which the first major surface extends. The movement of the foldable device from the flat configuration to the neutral stress configuration corresponds to a maximum magnitude of the deflection strain of the polymer-based portion in the range of about 1% to about 8%.

[0030] Embodiment 14: The foldable device of embodiment 13, wherein the maximum magnitude of the deviation strain is in the range of about 2% to about 6%.

[0031] Embodiment 15: The foldable device of any of Embodiments 5-14, wherein the foldable substrate of the foldable device comprises an effective minimum bend radius in the range of about 1 mm to about 10 mm.

[0032] Embodiment 16: The foldable device of embodiment 15, wherein the foldable substrate achieves an effective minimum bending radius of 10 mm.

[0033] Embodiment 17: The foldable device of embodiment 15, wherein the foldable substrate achieves an effective minimum bending radius of 5 mm.

[0034] Embodiment 18: The foldable device of embodiment 15, wherein the foldable substrate achieves an effective bending radius of 2 mm.

[0035] Embodiment 19: The foldable device of any of Embodiments 15-18, wherein a width of the central portion is in a range from about 2.8 times the effective minimum bending radius to about 6 times the effective minimum bending radius.

[0036] Embodiment 20: The foldable device of any of Embodiments 15-18, wherein the width of the central portion is 4.4 times or greater than the effective minimum bend radius.

[0037] Embodiment 21: The foldable device of any one of Embodiments 15-18, wherein the width of the central portion is in a range from about 2.8 mm to about 40 mm.

[0038] Embodiment 22: The foldable device of any of Embodiments 1-21, wherein the substrate thickness is in a range from about 80 microns to about 2 millimeters.

[0039] Embodiment 23: The foldable device of embodiment 22, wherein the substrate thickness is in the range of about 125 microns to about 200 microns.

[0040] Embodiment 24: The foldable device of any of Embodiments 1-23, wherein the center thickness is in a range from about 10 microns to about 125 microns.

[0041] Embodiment 25: The foldable device of embodiment 24, wherein the center thickness ranges from about 10 microns to about 50 microns.

[0042] Embodiment 26: The foldable device of any of Embodiments 1-25, wherein the center thickness is about 0.5% to about 13% of the thickness of the substrate.

[0043] Embodiment 27: The foldable device of any of Embodiments 1-26, wherein the substrate thickness is at least 71 microns greater than about 4 times the center thickness.

[0044] Embodiment 28: The foldable device of any of Embodiments 1-27, wherein the first portion further comprises a first compressive stress zone and a second compressive stress zone, the first compressive stress zone extending from a first surface area of ​​the first major surface to a first compression depth, and the second compressive stress zone extending from a second surface area of ​​the second major surface to a second compression depth. The second portion further comprises a third compressive stress zone and a fourth compressive stress zone, the third compressive stress zone extending from a third surface area of ​​the first major surface to a third compression depth, and the fourth compressive stress zone extending from a fourth surface area of ​​the second major surface to a fourth compression depth. The central portion further comprises a first central compressive stress zone and a second central compressive stress zone, the first central compressive stress zone extending from a first central surface area to a first central compression depth, and the second central compressive stress zone extending from a second central surface area of ​​the second major surface to a second central compression depth.

[0045] Embodiment 29: The foldable device of Embodiment 28, wherein the absolute difference between the first compression depth as a percentage of the substrate thickness and the first center compression depth as a percentage of the center thickness is less than or equal to about 1%.

[0046] Embodiment 30: The foldable device of any of Embodiments 28-29, wherein the absolute difference between the third compression depth as a percentage of the substrate thickness and the first center compression depth as a percentage of the center thickness is less than or equal to about 1%.

[0047] Embodiment 31: The foldable device of any of Embodiments 28-30, wherein the absolute difference between the second compression depth as a percentage of the substrate thickness and the second center compression depth as a percentage of the center thickness is less than or equal to about 1%.

[0048] Embodiment 32: The foldable device of any of Embodiments 28-31, wherein the absolute difference between the fourth compression depth as a percentage of the substrate thickness and the second center compression depth as a percentage of the center thickness is less than or equal to about 1%.

[0049] Embodiment 33: The foldable device of any of Embodiments 28-32, wherein the first center compression depth is about 10% to about 30% of the center thickness. The second center compression depth is about 10% to about 30% of the center thickness.

[0050] Embodiment 34: The foldable device of any of Embodiments 28-33, wherein the first compression depth is about 1% to about 10% of the thickness of the substrate. The second compression depth is about 1% to about 10% of the thickness of the substrate.

[0051] Embodiment 35: The foldable device of any of Embodiments 28-34, wherein the third compression depth is about 1% to about 10% of the thickness of the substrate. The fourth compression depth is about 1% to about 10% of the thickness of the substrate.

[0052] Embodiment 36: The foldable device of any of Embodiments 28-35, wherein the first compression depth is substantially equal to the first central compression depth. The third compression depth is substantially equal to the first central compression depth.

[0053] Embodiment 37: The foldable device of any of Embodiments 28-36, wherein the second compression depth is substantially equal to the second central compression depth. The fourth compression depth is substantially equal to the second central compression depth.

[0054] Embodiment 38: The foldable device of any of Embodiments 28-35, wherein the first central compression depth of the central portion is less than the first compression depth of the first portion of the first surface area from the first major surface. The first central compression depth of the central portion is less than the third compression depth of the second portion of the second surface area from the first major surface.

[0055] Embodiment 39: The foldable device of any of Embodiments 28-38, wherein the first compressive stress region comprises a first maximum compressive stress greater than or equal to about 700 MPa. The second compressive stress region comprises a second maximum compressive stress, and the third compressive stress region comprises a third maximum compressive stress greater than or equal to about 700 MPa. The fourth compressive stress region comprises a fourth maximum compressive stress. The first central compressive stress region comprises a first central maximum compressive stress greater than or equal to 700 MPa. The second central compressive stress region comprises a second central maximum compressive stress.

[0056] Embodiment 40: The foldable device of embodiment 39, wherein the second maximum compressive stress is greater than or equal to about 700 MPa. The fourth maximum compressive stress is greater than or equal to about 700 MPa. The second center maximum compressive stress is greater than or equal to about 700 MPa.

[0057] Embodiment 41: The foldable device of any of Embodiments 28-40, wherein the first portion comprises a first average concentration of potassium based on oxide. The second portion comprises a second average concentration of potassium based on oxide. The central portion comprises a central average concentration of potassium based on oxide. The absolute difference between the first average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0058] Embodiment 42: The foldable device of Embodiment 41, wherein the absolute difference between the second average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0059] Embodiment 43: A foldable device of any of Embodiments 28-42, wherein the first portion includes a first layer depth of one or more alkali metal ions associated with a first compression depth, and a second layer depth of one or more alkali metal ions associated with a second compression depth. The second portion includes a third layer depth of one or more alkali metal ions associated with a third compression depth, and a fourth layer depth of one or more alkali metal ions associated with a fourth compression depth. The center portion includes a first center layer depth of one or more alkali metal ions associated with a first center compression depth, and a second center layer depth of one or more alkali metal ions associated with a second center compression depth. The absolute difference between the first layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is less than or equal to about 0.1%.

[0060] Embodiment 44: The foldable device of embodiment 43, wherein the absolute difference between the third layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is less than or equal to about 0.1%.

[0061] Embodiment 45: The foldable device of any of Embodiments 43-44, wherein the absolute difference between the second layer depth as a percentage of the substrate thickness and the second center layer depth as a percentage of the center thickness is less than or equal to about 0.1%.

[0062] Embodiment 46: The foldable device of any of Embodiments 43-45, wherein the absolute difference between the fourth layer depth as a percentage of the substrate thickness and the second center layer depth as a percentage of the center thickness is less than or equal to about 0.1%.

[0063] Embodiment 47: The foldable device of any one of Embodiments 28-46, further comprising an optical retardation in a central portion along a centerline exactly halfway between the first portion and the second portion, wherein an absolute difference between a maximum value of the optical retardation along the centerline and a minimum value of the optical retardation along the centerline is less than or equal to about 2 nanometers.

[0064] Embodiment 48: The foldable device of any one of Embodiments 1-47, wherein the foldable substrate is a glass-based substrate.

[0065] Embodiment 49: The foldable device of any one of Embodiments 1-47, wherein the foldable substrate is a ceramic-based substrate.

[0066] Embodiment 50: The foldable device of any of Embodiments 1-5, wherein a recess defined between the first central surface area of ​​the central portion and the first plane defined by the first major surface is filled with an adhesive.

[0067] Embodiment 51: The foldable device of embodiment 6 or embodiment 50, wherein the adhesive includes a first contact surface that contacts a first surface area of ​​the first major surface, a second surface area of ​​the first major surface opposite the first surface area, and a first central surface area of ​​the central portion, the adhesive including a second contact surface spaced apart from the first contact surface of the adhesive.

[0068] Embodiment 52: The foldable device of any of Embodiments 50-51, wherein the magnitude of the difference between the refractive index of the foldable substrate and the refractive index of the adhesive is less than or equal to about 0.1.

[0069] Embodiment 53: The foldable device of any one of Embodiments 50-52, further comprising a display device attached to the second contact surface of the adhesive.

[0070] Embodiment 54: The foldable device of any of Embodiments 50-52, further comprising a release liner attached to the second contact surface of the adhesive.

[0071] Embodiment 55: A consumer electronic product comprising a housing, the housing comprising a front surface, a rear surface, and a side surface. An electrical component is at least partially located within the housing. The electrical component comprises a controller, a memory, and a display. The display is located at or adjacent to the front surface of the housing. The consumer electronic device comprises a cover substrate disposed above the display. At least one of a portion of the housing or the cover substrate comprises a foldable device as in any one of Embodiments 1-54.

[0072] Embodiment 56: A method of manufacturing a foldable device, the method comprising: forming a depression in a first major surface of a foldable substrate, the depression providing a first central surface area, the first central surface area attaching a first portion of the foldable substrate and a second portion of the foldable substrate. The central portion includes a first transition portion attaching the first portion to the central portion. The thickness of the first transition portion increases continuously from the central portion to the first portion. The central portion includes a second transition portion attaching the second portion to the central portion. The thickness of the second transition portion increases continuously from the central portion to the second portion. The method comprises: chemically strengthening a first central surface area of ​​the central portion of the foldable substrate, a first surface area of ​​the first portion of the first major surface, a third surface area of ​​the second portion of the first major surface, and a second major surface of the foldable substrate. The method comprises: applying an adhesive to contact the first surface area of ​​the first major surface, the third surface area of ​​the first major surface, and the first central surface area of ​​the central portion. The adhesive fills the depression.

[0073] Embodiment 57: The method of Embodiment 56, wherein the depression is mechanically formed in the first major surface of the foldable substrate.

[0074] Embodiment 58: The method of any of Embodiments 56-57, further comprising: reducing the thickness of the foldable substrate prior to chemical strengthening.

[0075] Embodiment 59: The method of Embodiment 58, wherein reducing the thickness occurs after forming the recess.

[0076] Embodiment 60: The method of any of Embodiments 58-59, wherein reducing the thickness comprises removing a layer of the second major surface of the foldable substrate.

[0077] Embodiment 61: The method of any of Embodiments 58-60, further comprising: etching the foldable substrate after chemically strengthening and before applying the adhesive.

[0078] Embodiment 62: The method of any of Embodiments 56-61, wherein the chemical strengthening comprises chemically strengthening the first portion to a first compression depth from a first surface region of the first major surface. The chemical strengthening comprises chemically strengthening the second portion to a third compression depth from a third surface region of the first major surface. The chemical strengthening comprises chemically strengthening the center portion to a first center compression depth from a first center surface region of the center portion. The first center compression depth is less than the first compression depth. The first center compression depth is less than the third compression depth.

[0079] Embodiment 63: The method of any of Embodiments 56-62, wherein the chemical strengthening comprises chemically strengthening the first portion to a second compression depth from a second surface region of the second major surface. The chemical strengthening comprises chemically strengthening the second portion to a fourth compression depth from a fourth surface region of the second major surface. The chemical strengthening comprises chemically strengthening the center portion to a second center compression depth from a second center surface region of the second major surface. The second center surface region is between the second surface region and the fourth surface region. The second center compression depth is less than the second compression depth. The second center compression depth is less than the fourth compression depth.

[0080] Embodiment 64: A method of manufacturing a foldable device, the method comprising: forming a depression in a first major surface of a foldable substrate, the depression forming a first central surface area of ​​a central portion, the first central surface area attaching the first portion to the second portion. The first portion includes a first surface area and a second surface area opposite the first surface area. The second portion includes a third surface area and a fourth surface area opposite the third surface area. The foldable substrate includes a second major surface, the second major surface including the second surface area and the fourth surface area. The foldable substrate includes a first major surface opposite the second major surface. The first major surface includes the first surface area and the third surface area. The method comprises: curing a polymer base portion disposed between the first portion and the second portion. During curing, the foldable device is in a bent configuration, wherein the movement of the foldable device from the flat configuration to the neutral stress configuration corresponds to a maximum amplitude of a deviation strain of the polymer base portion in the range of about 1% to about 8%.

[0081] Embodiment 65: The method of embodiment 64, further comprising: chemically strengthening the first central surface region, the first surface region, the third surface region, and the second major surface of the central portion.

[0082] Embodiment 66: A method of manufacturing a foldable device, the method comprising: forming a foldable substrate including about 10 4 Pascal-seconds to about 10 7 The method includes solidifying the liquid to form a polymer-based portion between a first portion of the foldable substrate and a second portion of the foldable substrate.

[0083] Embodiment 67: The method of embodiment 66, further comprising: forming a recess in the foldable substrate, the recess forming a first central surface area of ​​the central portion of the foldable substrate, the first central surface area attaching the first portion of the foldable substrate to the second portion of the foldable substrate.

[0084] Embodiment 68: The method of any of Embodiments 66-67, further comprising: chemically strengthening the foldable substrate.

[0085] Embodiment 69: The method of any of Embodiments 66-68, wherein the movement of the foldable device from the flat configuration to the neutral stress configuration corresponds to a maximum magnitude of the deflection strain of the polymer base portion in a range from about 1% to about 8%.

[0086] Embodiment 70: The method of Embodiment 64, Embodiment 65, or Embodiment 69, wherein the maximum amplitude of the deviation strain is in the range of about 2% to about 6%.

[0087] Embodiment 71: The method of any of Embodiments 64-70, wherein the polymer-based portion expands upon curing.

[0088] Embodiment 72: A method of manufacturing a foldable device, the method comprising: forming a recess in a first major surface of a foldable substrate, the recess forming a first central surface area of ​​a central portion, the first central surface area attaching the first portion to the second portion. The first portion includes a first surface area and a second surface area opposite the first surface area. The second portion includes a third surface area and a fourth surface area opposite the third surface area. The foldable substrate includes a second major surface, the second major surface including the second surface area and the fourth surface area. The foldable substrate includes a first major surface opposite the second major surface, the first major surface including the first surface area and the third surface area. The method comprises: curing a polymer base portion disposed in the recess. The polymer base portion expands due to curing.

[0089] Embodiment 73: The method of embodiment 72, further comprising: chemically strengthening the first central surface region, the first surface region, the third surface region, and the second major surface of the central portion.

[0090] Embodiment 74: The method of any of Embodiments 72-73, wherein the polymer-based portion comprises a negative coefficient of thermal expansion.

[0091] Embodiment 75: The method of Embodiment 74, wherein the polymer-based portion comprises particles of one or more of copper oxide, beta-quartz, tungstates, vanadates, pyrophosphates, and / or nickel titanium alloys.

[0092] Embodiment 76: The method of any of Embodiments 72-75, wherein curing the polymer-based portion comprises ring-opening disproportionation polymerization.

[0093] Embodiment 77: A method of manufacturing a foldable device, the method comprising: forming a depression in a first major surface of a foldable substrate, the depression forming a first central surface area of ​​a central portion, the first central surface area attaching the first portion to the second portion. The first portion includes a first surface area and a second surface area opposite the first surface area. The second portion includes a third surface area and a fourth surface area opposite the third surface area. The foldable substrate includes a second major surface, the second major surface including a second surface area and a fourth surface area. The foldable substrate includes a first major surface opposite the second major surface. The first major surface includes a first surface area and a third surface area. The method comprises: curing a polymer base portion disposed between the first portion and the second portion. During curing, the foldable device is in a bent configuration. The movement of the foldable device from a flat configuration to a neutral stress configuration corresponds to a maximum amplitude of a deviation strain of the polymer base portion in a range of about 1% to about 8%.

[0094] Embodiment 78: The method of embodiment 77, further comprising: chemically strengthening the first central surface region, the first surface region, the third surface region, and the second major surface of the central portion.

[0095] Embodiment 79: The method of any of Embodiments 77-78, wherein the maximum magnitude of the deviation strain is in a range from about 2% to about 6%.

[0096] Embodiment 80: A method of manufacturing a foldable device, the method comprising: forming a foldable substrate including about 10 4 Pascal-seconds to about 10 7 The method includes solidifying the liquid to form a polymer-based portion between a first portion of the foldable substrate and a second portion of the foldable substrate.

[0097] Embodiment 81: The method of embodiment 80, further comprising: forming a recess in the foldable substrate, the recess forming a first central surface area of ​​the central portion of the foldable substrate, the first central surface area attaching the first portion of the foldable substrate to the second portion of the foldable substrate.

[0098] Embodiment 82: The method of any of Embodiments 80-81, further comprising: chemically strengthening the foldable substrate.

[0099] Embodiment 83: The method of any of Embodiments 80-82, wherein the movement of the foldable device from the flat configuration to the neutral stress configuration corresponds to a maximum magnitude of the deflection strain of the polymer base portion in a range from about 1% to about 8%.

[0100] Embodiment 84: The method of embodiment 83, wherein the maximum amplitude of the deviation strain is in the range of about 2% to about 6%.

[0101] Embodiment 86: A method of manufacturing a foldable substrate, the foldable substrate comprising a foldable substrate comprising a substrate thickness defined between a first major surface and a second major surface. The foldable substrate comprises a first portion, the first portion comprising a substrate thickness. The foldable substrate comprises a second portion, the second portion comprising a substrate thickness. The foldable substrate comprises a center portion, the center portion comprising a center thickness defined between a first center surface region and a second center surface region. The center thickness is less than the substrate thickness. The center portion is located between the first portion and the second portion. The method comprises: disposing a first layer above one or more of the first center surface region or the second center surface region. The method comprises: after disposing the first layer, chemically strengthening the foldable substrate for a first period of time. The method comprises: after chemically strengthening the foldable substrate, removing the first layer.

[0102] As in embodiment 86: the method of embodiment 85, wherein the first layer comprises a thickness of about 10 nanometers to about 200 nanometers.

[0103] Embodiment 87: The method of any of Embodiments 85-86, wherein providing the first layer comprises providing SiO2 using physical vapor deposition.

[0104] Embodiment 88: The method of any of Embodiments 85-87, further comprising: before disposing the first layer, forming a recess in the first major surface of the glass-based substrate to provide a first central surface region.

[0105] Embodiment 89: The method of any of Embodiments 85-88, wherein after chemically strengthening the foldable substrate, the first portion comprises a first layer depth from the first major surface of one or more alkali metal ions introduced into the first portion during chemical strengthening. After chemically strengthening the foldable substrate, the center portion comprises a first center layer depth from the first center surface region of one or more alkali metal ions introduced into the center portion during chemical strengthening. The absolute difference between the first layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is less than or equal to about 1%.

[0106] Embodiment 90: The method of Embodiment 89, wherein after chemically strengthening the foldable substrate, the second portion comprises a third layer depth from the first major surface of the one or more alkali metal ions introduced into the second portion during chemical strengthening, and the absolute difference between the third layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is less than or equal to about 1%.

[0107] Embodiment 91: The method of any of Embodiments 89-90, wherein the one or more alkali metal ions comprise potassium ions.

[0108] Embodiment 92: The method of any of Embodiments 85-91, wherein after chemically strengthening the foldable substrate, the first portion comprises a first average concentration of potassium on an oxide basis. After chemically strengthening the foldable substrate, the central portion comprises a central average concentration of potassium on an oxide basis. The absolute difference between the first average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0109] Embodiment 93: The method of Embodiment 92, wherein after chemically strengthening the foldable substrate, the second portion comprises a second average concentration of potassium on an oxide basis, wherein the absolute difference between the second average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0110] Embodiment 94: The method of any of Embodiments 85-93, wherein after chemically strengthening the foldable substrate, the first portion comprises a first compressive stress region extending from the first major surface to a first compression depth. After chemically strengthening the foldable substrate, the central portion comprises a first central compressive stress region extending to the first central compression depth. The absolute difference between the first compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the central thickness is less than or equal to about 1%.

[0111] Embodiment 95: The method of Embodiment 94, wherein after chemically strengthening the foldable substrate, the second portion comprises a third compressive stress region extending from the first major surface to a third compression depth. The absolute difference between the third compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the central thickness is less than or equal to about 1%.

[0112] Embodiment 96: The method of any of Embodiments 85-88, further comprising: after removing the first layer, further chemically strengthening the foldable substrate for a second period of time.

[0113] Embodiment 97: The method of embodiment 96, wherein the second time period is greater than the first time period.

[0114] Embodiment 98: The method of Embodiment 97, wherein the second time period is in a range of about 103% to about 175% as a percentage of the first time period.

[0115] Embodiment 99: The method of any of Embodiments 96-98, wherein after further chemical strengthening of the foldable substrate, the first portion comprises a first layer depth from the first major surface of one or more alkali metal ions introduced into the first portion during chemical strengthening or further chemical strengthening. After further chemical strengthening of the foldable substrate, the center portion comprises a first center layer depth from the first center surface region of one or more alkali metal ions introduced into the center portion during chemical strengthening or further chemical strengthening. The absolute difference between the first layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is less than or equal to about 0.1%.

[0116] Embodiment 100: The method of Embodiment 99, wherein after further chemical strengthening of the foldable substrate, the one or more alkali metal ions introduced into the second portion during chemical strengthening or further chemical strengthening have a third layer depth from the first major surface, wherein the absolute difference between the third layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is less than or equal to about 0.1%.

[0117] Embodiment 101: The method of any of Embodiments 99-100, wherein the one or more alkali metal ions include potassium ions.

[0118] Embodiment 102: The method of any of Embodiments 96-101, wherein after further chemical strengthening of the foldable substrate, the first portion comprises a first average concentration of potassium on an oxide basis. After further chemical strengthening of the foldable substrate, the central portion comprises a central average concentration of potassium on an oxide basis. The absolute difference between the first average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0119] Embodiment 103: The method of Embodiment 102, wherein after further chemically strengthening the foldable substrate, the second portion comprises a second average concentration of potassium on an oxide basis, wherein the absolute difference between the second average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0120] Embodiment 104: The method of any of Embodiments 96-103, wherein after further chemical strengthening of the foldable substrate, the first portion comprises a first compressive stress region extending from the first major surface to a first compression depth. After further chemical strengthening of the foldable substrate, the central portion comprises a first central compressive stress region extending to the first central compression depth. The absolute difference between the first compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the central thickness is less than or equal to about 1%.

[0121] Embodiment 105: The method of Embodiment 104, wherein after further chemically strengthening the foldable substrate, the second portion comprises a third compressive stress region extending from the first major surface to a third compression depth. The absolute difference between the third compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the central thickness is less than or equal to about 1%.

[0122] Embodiment 106: A method of manufacturing a foldable substrate, the foldable substrate comprising a foldable substrate including a substrate thickness defined between a first major surface and a second major surface. The foldable substrate includes a first portion, the first portion including the substrate thickness. The foldable substrate includes a second portion, the second portion including the substrate thickness. The foldable substrate includes a central portion, the central portion including a central thickness defined between a first central surface area and a second central surface area. The central thickness is less than the substrate thickness. The central portion is located between the first portion and the second portion. The method includes applying a paste comprising alkali metal ions to the first portion and the second portion. The method includes heating the foldable substrate after applying the paste. The method includes removing the paste after heating the foldable substrate. The method includes chemically strengthening the foldable substrate after removing the paste.

[0123] Embodiment 107: The method of Embodiment 106, wherein after chemically strengthening the foldable substrate, the first portion comprises a first layer depth from the first major surface of one or more alkali metal ions introduced into the first portion during heating or chemical strengthening. After chemically strengthening the foldable substrate, the central portion comprises a first central layer depth from the first central surface region of one or more alkali metal ions introduced into the central portion during chemical strengthening. The absolute difference between the first layer depth as a percentage of the substrate thickness and the first central layer depth as a percentage of the central thickness is less than or equal to about 0.1%.

[0124] Embodiment 108: The method of Embodiment 107, wherein after chemically strengthening the foldable substrate, the second portion comprises a third layer depth from the first major surface of one or more alkali metal ions introduced into the second portion during heating or chemical strengthening, and the absolute difference between the third layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is less than or equal to about 0.1%.

[0125] Embodiment 109: The method of any of Embodiments 107-108, wherein the one or more alkali metal ions include potassium ions.

[0126] Embodiment 110: The method of any of Embodiments 106-109, wherein after chemically strengthening the foldable substrate, the first portion comprises a first average concentration of potassium on an oxide basis. After chemically strengthening the foldable substrate, the central portion comprises a central average concentration of potassium on an oxide basis. The absolute difference between the first average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0127] Embodiment 111: The method of Embodiment 110, wherein after chemically strengthening the foldable substrate, the second portion comprises a second average concentration of potassium on an oxide basis, wherein the absolute difference between the second average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0128] Embodiment 112: The method of any of Embodiments 106-111, wherein after chemically strengthening the foldable substrate, the first portion includes a first compressive stress region extending from the first major surface to a first compression depth. After chemically strengthening the foldable substrate, the central portion includes a first central compressive stress region extending to the first central compression depth. The absolute difference between the first compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the central thickness is less than or equal to about 1%.

[0129] Embodiment 113: The method of Embodiment 112, wherein after chemically strengthening the foldable substrate, the second portion comprises a third compressive stress region extending from the first major surface to a third compression depth. The absolute difference between the third compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the central thickness is less than or equal to about 1%.

[0130] Embodiment 114: A method for manufacturing a foldable substrate, the foldable substrate comprising a foldable substrate including a substrate thickness defined between a first major surface and a second major surface. The foldable substrate includes a first portion, the first portion including the substrate thickness. The foldable substrate includes a second portion, the second portion including the substrate thickness. The foldable substrate includes a central portion, the central portion including a central thickness defined between a first central surface area and a second central surface area. The central thickness is less than the substrate thickness. The central portion is located between the first portion and the second portion. The method includes: applying a first paste comprising alkali metal ions to the first portion. The method includes: applying a second paste comprising alkali metal ions to the central portion. The method includes: heating the foldable substrate after applying the first paste and the second paste. The method includes: removing the first paste from the first portion after heating the foldable substrate. The method includes: removing the second paste from the central portion after heating the foldable substrate.

[0131] Embodiment 115: The method of Embodiment 114, wherein the potassium ion concentration in the first paste is greater than the potassium ion concentration in the second paste.

[0132] Embodiment 116: The method of any of Embodiments 114-115, wherein the second paste further comprises one or more alkaline earth metal ions at a concentration greater than or equal to about 5 parts per million on an oxide basis.

[0133] Embodiment 117: The method of Embodiment 116, wherein the one or more alkaline earth metal ions include calcium at a concentration in a range from about 10 parts per million to about 1000 parts per million on an oxide basis.

[0134] Embodiment 118: The method of any of Embodiments 114-117, wherein after heating the foldable substrate, the first portion comprises a first layer depth from the first major surface of the one or more alkali metal ions introduced into the first portion during heating. After heating the foldable substrate, the center portion comprises a first center layer depth from the first center surface region of the one or more alkali metal ions introduced into the center portion during heating. The absolute difference between the first layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is less than or equal to about 0.1%.

[0135] Embodiment 119: The method of any of Embodiments 114-118, wherein after heating the foldable substrate, the first portion comprises a first average concentration of potassium on an oxide basis. After heating the foldable substrate, the central portion comprises a central average concentration of potassium on an oxide basis. The absolute difference between the first average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0136] Embodiment 120: The method of Embodiment 119, wherein after further chemically strengthening the foldable substrate, the second portion comprises a second average concentration of potassium on an oxide basis, wherein the absolute difference between the second average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0137] Embodiment 121: The method of any of Embodiments 114-120, wherein after heating the foldable substrate, the first portion includes a first compressive stress region extending from the first major surface to a first compression depth. After heating the foldable substrate, the central portion includes a first central compressive stress region extending to the first central compression depth. The absolute difference between the first compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the central thickness is less than or equal to about 1%.

[0138] Embodiment 122: The method of Embodiment 121, further comprising: applying a first paste comprising alkali metal ions to the second portion before heating the foldable substrate. The method further comprises: removing the first paste from the second portion after heating the foldable substrate.

[0139] Embodiment 123: The method of Embodiment 122, wherein after heating the foldable substrate, the second portion comprises a third layer depth from the first major surface of one or more alkali metal ions introduced into the second portion during heating. After chemically strengthening the foldable substrate, the center portion comprises a first center layer depth from the first center surface region of one or more alkali metal ions introduced into the center portion during heating. The absolute difference between the third layer depth as a percentage of the substrate thickness and the first center layer depth as a percentage of the center thickness is less than or equal to about 0.1%.

[0140] Embodiment 124: The method of Embodiments 122-123, wherein after chemically strengthening the foldable substrate, the second portion comprises a second average concentration of potassium on an oxide basis. After chemically strengthening the foldable substrate, the central portion comprises a central average concentration of potassium on an oxide basis. The absolute difference between the first average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0141] Embodiment 125: The method of Embodiment 124, wherein after further chemically strengthening the foldable substrate, the second portion comprises a second average concentration of potassium on an oxide basis, wherein the absolute difference between the second average concentration of potassium and the central average concentration of potassium is about 100 parts per million or less.

[0142] Embodiment 126: The method of any of Embodiments 122-125, wherein after heating the foldable substrate, the second portion includes a third compressive stress region extending from the first major surface to a third compression depth. After heating the foldable substrate, the central portion includes a first central compressive stress region extending from the first central surface to the first compression depth. The absolute difference between the third compression depth as a percentage of the substrate thickness and the first central compression depth as a percentage of the central thickness is less than or equal to about 1%. BRIEF DESCRIPTION OF THE DRAWINGS

[0143] The above features and advantages and other features and advantages of the embodiments of the present disclosure may be better understood by reading the following detailed description with reference to the accompanying drawings, in which:

[0144] Figure 1 is a schematic diagram of an exemplary foldable device in a flat configuration according to some embodiments, wherein the schematic diagram of the folded configuration may be as shown in FIG. Figure 4 As shown;

[0145] Figure 2-3 According to some other embodiments, the foldable device is arranged along Figure 1 A cross-sectional view along line 2-2 of ;

[0146] Figure 4 is a schematic diagram of an exemplary foldable device of an embodiment of the present disclosure in a folded configuration, wherein a schematic diagram of a flat configuration may be as shown in FIG. Figure 1 As shown;

[0147] Figure 5 is a schematic diagram of an exemplary foldable substrate according to an embodiment of the present disclosure in a folded configuration for failure mode testing;

[0148] Figure 6 is a test device for determining the effective minimum bending radius of an exemplary modified foldable device along Figure 4 A cross-sectional view taken along line 6-6;

[0149] Figure 7 According to some embodiments, another exemplary foldable device is along Figure 4 A cross-sectional view taken along line 6-6;

[0150] Figure 8 is a schematic plan view of an exemplary consumer electronic device according to some embodiments;

[0151] Fig. 9 yes Figure 8 A perspective schematic diagram of an exemplary consumer electronic device;

[0152] Figure 10-11 is a flow chart illustrating an exemplary method of manufacturing a foldable substrate and / or a foldable device according to an embodiment of the present disclosure;

[0153] Figure 12-26 Schematically illustrating steps in a method of making a foldable substrate and / or a foldable device;

[0154] Fig. 27 is a flow chart illustrating an exemplary method of manufacturing a foldable substrate and / or a foldable device according to an embodiment of the present disclosure;

[0155] Figure 28-37 Schematically illustrating steps in a method of making a foldable substrate and / or a foldable device;

[0156] Fig.38 Schematically illustrates a similar Figure 3 A foldable device and a foldable device in a neutral stress configuration;

[0157] Fig.39schematically illustrating a polymer base portion when the foldable device is in a flat configuration;

[0158] Fig.40 Schematic illustration of a polymer-based portion when the foldable device is in a neutral stress configuration.

[0159] Fig.41 is a perspective schematic diagram of a pen-drop device;

[0160] Fig.42 shows the results of a pen drop test of a glass-based substrate, which shows the maximum principal stress on the major surface of the glass-based substrate as a function of the thickness of the glass-based substrate;

[0161] Fig.43 showing the types of mechanical instabilities observed for foldable devices as a function of substrate thickness and center thickness; and

[0162] Fig.44 Optical hysteresis measurements of a foldable substrate according to an embodiment of the present disclosure are schematically shown.

[0163] In the present disclosure, the drawings are used to emphasize certain aspects. Therefore, unless otherwise explicitly stated, the relative sizes of different regions, parts and substrates shown in the drawings should not be considered to be proportional to their actual relative sizes. DETAILED DESCRIPTION

[0164] The various embodiments will be described more fully herein with reference to the accompanying drawings, in which exemplary embodiments are shown. Whenever possible, the same reference numerals are used throughout the drawings to represent the same or similar parts. However, the claims may include many different aspects of the various embodiments and should not be construed as being limited to the embodiments set forth herein.

[0165] Figure 1-4 6-7 illustrate views of foldable devices 101 and 301 and / or test foldable devices 602 including foldable substrates 201 according to embodiments of the present disclosure. Unless otherwise noted, the discussion of features of an embodiment of a foldable device may be equally applicable to corresponding features of any embodiment of the present disclosure. For example, throughout the present disclosure, the same part number may indicate that the identified features are the same as each other in some embodiments, and the discussion of the identified features of one embodiment may be equally applicable to the identified features of any other embodiment of the present disclosure, unless otherwise noted.

[0166] Figure 2-3 Schematically illustrates exemplary embodiments of foldable devices 101 and 301 including foldable substrates 201 according to embodiments of the present disclosure in a non-folded (eg, flat) configuration, while Figure 6-7A test foldable device 602 and a foldable device 301 of an embodiment of the present disclosure comprising a foldable substrate 201 are shown in a folded configuration, respectively. The foldable devices 101 and 301 include a first portion 221, a second portion 231, and a central portion 251 located between the first portion 221 and the second portion 231. In some embodiments, as Figure 2-3 As shown, the foldable device 101, 301 may include a foldable substrate 201. In some embodiments, as Figure 2 As shown, the foldable device 101 may include a release liner 271, but in other embodiments, other substrates (e.g., glass-based substrates and / or ceramic-based substrates described in the present application) may be used instead of the illustrated release liner 271. In some embodiments, as Figure 3 As shown, the foldable device 301 may include a display device 307. It should be understood that any foldable device of the present disclosure may include an additional substrate (e.g., a glass-based substrate and / or a ceramic-based substrate), a release liner 271, and / or a display device 307. In some embodiments, as Figure 2-3 As shown in FIGS. 6-7 , an adhesive layer 261 (eg, an optically clear adhesive (OCA)) may be disposed over the first major surface 203 of the foldable substrate 201. In another embodiment, as shown in FIG. Figure 3 and 6 As shown in FIG. 7 , a polymer base portion (e.g., Figure 3 As shown, it is arranged above the first central surface area 209).

[0167] Throughout this disclosure, reference is made to Figure 1 , the width 103 of the foldable device 101 and / or 301 is considered to be 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. In addition, throughout this disclosure, the length 105 of the foldable device 101 and / or 301 is considered to be the dimension of the foldable device 101 and / or 301 obtained between opposite edges of the foldable device 101 and / or 301 in the direction 106 perpendicular to the folding axis 102 of the foldable device 101 and / or 301. In some embodiments, such as Figure 1-3 As shown, the foldable device of any embodiment of the present disclosure may include a folding plane 109, which includes the folding axis 102 and the folding device in a flat configuration (e.g., see Figure 1 ) in the direction 202 of the substrate thickness 227 (e.g., the first thickness of the first portion 221). In some embodiments, the plane 109 may include the central axis 107 of the foldable device, which may be located at the second major surface 205, such as Figure 2-3In some embodiments, the foldable device can be folded about a folding axis 102 extending in a direction 104 of width 103, along a direction 111 (e.g., see Figure 1 ) to form a folded structure (see, for example, Figure 4 and 6 -7). As shown, the foldable device may include a single folding axis to allow the foldable device to include a bifold, wherein, for example, the foldable device can be folded in half. In other embodiments, the foldable device may include two or more folding axes, wherein each folding axis includes a corresponding central portion that is the same or similar to the central portion 251 described herein. For example, providing two folding axes may allow the foldable device to include a trifold, wherein, for example, the foldable device can be folded to have a first portion 221, a second portion 231, and a third portion that is similar or identical to the first portion or the second portion, and having a central portion 251 located between the first portion and the second portion, and another central portion that is similar or identical to the central portion and located between the second portion and the third portion.

[0168] The foldable devices 101 and 301 of the present disclosure may include a foldable substrate 201. In some embodiments, the foldable substrate 201 may include a glass-based substrate and / or a ceramic-based substrate having a pencil hardness greater than or equal to 8H, for example, greater than or equal to 9H.

[0169] In some embodiments, the foldable substrate 201 may include a glass-based substrate. As used herein, "glass-based" includes both glass and glass ceramics, wherein the glass ceramics have one or more crystalline phases and an amorphous residual glass phase. Glass-based materials (e.g., glass-based substrates) may include amorphous materials (e.g., glass) and optionally one or more crystalline materials (e.g., ceramics). Amorphous materials and glass-based materials may be strengthened. As used herein, the term "strengthened" may refer to materials that have been chemically strengthened, for example, by exchanging smaller ions in the substrate surface with larger ions, as described below. However, other strengthening methods may also be used to form a strengthened substrate, such as thermal tempering, or to generate a compressive stress zone and a central tension zone using a mismatch in the thermal expansion coefficient between the various parts of the substrate. Exemplary glass substrates that do not contain or contain lithium oxide include soda-lime glass, alkali aluminosilicate glass, alkali-containing borosilicate glass, alkali-containing aluminoborosilicate glass, alkali-containing phosphosilicate glass, and alkali-containing aluminophosphosilicate glass. In one or more embodiments, the glass-based material may include, by mole percent (mol%), about 40 mol% to about 80 mol% SiO2, about 5 mol% to about 30 mol% Al2O3, 0 mol% to about 10 mol% B2O3, 0 mol% to about 5 mol% ZrO2, 0 mol% to about 15 mol% P2O5, 0 mol% to about 2 mol% TiO2, 0 mol% to about 20 mol% R2O, and 0 mol% to about 15 mol% RO. As used herein, R2O may refer to alkali metal oxides, for example, Li2O, Na2O, K2O, Rb2O, and Cs2O. As used herein, RO may refer to MgO, CaO, SrO, BaO, and ZnO. In some embodiments, the glass-based substrate may optionally further include 0 mol % to about 2 mol % of each of the following: Na2SO4, NaCl, NaF, NaBr, K2SO4, KCl, KF, KBr, As2O3, Sb2O3, SnO2, Fe2O3, MnO, MnO2, MnO3, Mn2O3, Mn3O4, Mn2O7. "Glass-ceramics" include materials produced by controlled crystallization of glass. In some embodiments, the glass-ceramics have a crystallinity of about 1% to about 99%. Examples of suitable glass ceramics may include Li2O-Al2O3-SiO2 system (i.e., LAS system) glass ceramics, MgO-Al2O3-SiO2 system (i.e., MAS system) glass ceramics, ZnO×Al2O3×nSiO2 (i.e., ZAS system) and / or glass ceramics containing a main crystalline phase, the main crystalline phase comprising β-quartz solid solution, β-spodumene, cordierite, petalite and / or lithium disilicate. The glass ceramic substrate may be strengthened using a chemical strengthening process.In one or more embodiments, the glass-ceramic substrate of the MAS system may be strengthened in a Li2SO4 molten salt, whereby 2Li may be generated. + Mg 2+ exchange.

[0170] In some embodiments, the foldable substrate 201 may include a ceramic-based substrate. As used herein, "ceramic-based" includes both ceramics and glass-ceramics, wherein the glass-ceramics have one or more crystalline phases and an amorphous residual glass phase. The ceramic-based material may be strengthened (e.g., chemically strengthened). In some embodiments, the ceramic-based material may be formed by heating the glass-based material to form a ceramic (e.g., crystalline) portion. In other embodiments, the ceramic-based material may include one or more nucleating agents that may promote the formation of a crystalline phase. In some embodiments, the ceramic-based material may include one or more oxides, nitrides, oxynitrides, carbides, borides, and / or silicides. Exemplary embodiments of ceramic oxides include zirconium oxide (ZrO2), zircon zirconium oxide (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 quartz, mullite (a mineral containing a combination of aluminum oxide and silicon dioxide), and spinel (MgAl2O4). Exemplary embodiments 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)). Exemplary embodiments of oxynitride ceramics include silicon oxynitride, aluminum oxynitride, and SiAlON (eg, a combination of aluminum oxide and silicon nitride, and which may have the following chemical formula, 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-n, wherein m, n and resulting subscripts are all non-negative integers). Exemplary embodiments of carbides and carbon-containing ceramics include silicon carbide (SiC), tungsten carbide (WC), iron carbide, boron carbide (B4C), alkali metal carbides (e.g., lithium carbide (Li4C3)), alkaline earth metal carbides (e.g., magnesium carbide (Mg2C3)), and graphite. Exemplary embodiments of borides include chromium boride (CrB2), molybdenum boride (Mo2B5), tungsten boride (W2B5), iron boride, titanium boride, zirconium boride (ZrB2), hafnium boride (HfB2), vanadium boride (VB2), niobium boride (NbB2), and lanthanum boride (LaB6). Exemplary embodiments of silicides include molybdenum disilicide (MoSi2), tungsten disilicide (WSi2), titanium disilicide (TiSi2), nickel silicide (NiSi), alkaline earth metal silicides (e.g., sodium silicide (NaSi)), alkali metal silicides (e.g., magnesium silicide (Mg2Si), hafnium disilicide (HfSi2), and platinum silicide (PtSi).

[0171] Throughout this disclosure, the tensile strength, ultimate elongation (e.g., failure strain), and yield point of polymeric materials (e.g., adhesives, polymer-based portions) are determined using ASTM D638 using a tensile testing machine [e.g., Instron 3400 or Instron 6800] at 23° C. and 50% relative humidity using a Type I dog-bone specimen. Throughout this disclosure, elastic modulus (e.g., Young's modulus) and / or Poisson's ratio are measured using ISO 527-1:2019. In some embodiments, the foldable substrate 201 may include an elastic modulus of greater than or equal to about 1 gigapascal (GPa), greater than or equal to about 3 GPa, greater than or equal to 5 GPa, greater than or equal to 10 GPa, less than or equal to about 100 GPa, less than or equal to about 80 GPa, less than or equal to about 60 GPa, or less than or equal to about 20 GPa. In some embodiments, 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 sub-range therebetween. In further embodiments, the foldable substrate 201 may include a glass-based portion and / or a ceramic-based portion comprising an elastic modulus in the range of about 10 GPa to about 100 GPa, about 40 GPa to about 100 GPa, about 60 GPa to about 100 GPa, about 60 GPa to about 80 GPa, about 80 GPa to about 100 GPa, or any range or sub-range therebetween.

[0172] In some embodiments, the foldable substrate 201 can be optically transparent. As used herein, "optically transparent" or "optically clear" means that the average transmittance through a 1.0 mm thick sheet of material is 70% or greater in the wavelength range of 400 nm to 700 nm. In some embodiments, the average transmittance of an "optically transparent material" or "optically clear material" through a 1.0 mm thick sheet of material in the wavelength range of 400 nm to 700 nm can be 75% or greater, 80% or greater, 85% or greater, or 90% or greater, 92% or greater, 94% or greater, 96% or greater. The average transmittance in the wavelength range of 400 nm to 700 nm is calculated by measuring the transmittance of all integer wavelengths from about 400 nm to about 700 nm and averaging the measured values.

[0173] like Figure 2-3 As shown in FIGS. 6-7 , the foldable substrate 201 may include a first major surface 203 and a second major surface 205 opposite to the first major surface 203. Figure 2-3 As shown, the first major surface 203 may extend along the first plane 204a. The second major surface 205 may extend along the second plane 204b. In some embodiments, as shown, the second plane 204b may be parallel to the first plane 204a. As used herein, the substrate thickness may be defined between the first major surface 203 and the second major surface 205, and it is defined as the distance between the first plane 204a and the second plane 204b. In some embodiments, the substrate thickness can be greater than or equal to about 10 micrometers (μm), greater than or equal to about 25 μm, greater than or equal to about 40 μm, greater than or equal to about 60 μm, greater than or equal to about 80 μm, greater than or equal to about 100 μm, greater than or equal to about 125 μm, greater than or equal to about 150 μm, less than or equal to about 2 millimeters (mm), less than or equal to about 1 mm, less than or equal to about 800 μm, less than or equal to about 500 μm, less than or equal to about 300 μm, less than or equal to about 200 μm, less than or equal to about 180 μm, or less than or equal to about 160 μm. In some embodiments, the substrate thickness can be in the range of about 10 μm to about 2 mm, about 25 μm to about 2 mm, about 40 μm to about 2 mm, about 60 μm to about 2 mm, about 80 μm to about 2 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 125 μm to about 500 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, and any ranges and sub-ranges therebetween. Based on the Pen Drop Test (hereinafter referred to as Fig.42As a result of the above (discussed above), increased puncture resistance can be achieved by selecting a foldable substrate thickness greater than about 80 micrometers (μm). In some embodiments, the puncture resistance of the foldable substrate can be increased when the substrate thickness 227 is greater than or equal to about 80 μm, greater than or equal to about 200 μm, greater than or equal to about 500 μm, less than or equal to about 2 mm, less than or equal to about 1 mm, less than or equal to about 500 μm, or less than or equal to about 300 μm. In some embodiments, the substrate thickness 227 can be in the range of about 80 μm to about 2 mm, about 80 μm to about 1 mm, about 80 μm to about 500 μm, about 80 μm to about 300 μm, about 200 μm to about 2 mm, about 200 μm to about 1 mm, about 200 μm to about 500 μm, about 500 μm to about 2 mm, about 500 μm to about 1 mm, or any range or sub-range therebetween.

[0174] Now refer to Figure 2 The first part 221 is described with reference to the foldable device 101. It should be understood that, unless otherwise specified, such description of the first part 221 may also be applicable to any embodiment of the present disclosure, for example, Figure 3 and 6 -7 shows a foldable device 301 and / or a foldable substrate 201. Figure 2As shown, the first portion 221 may include a first surface area 223 and a second surface area 225 opposite to the first surface area. In some embodiments, as shown, the second surface area 225 of the first portion 221 may include a planar surface. In other embodiments, as shown, the second surface area 225 may be parallel to the first surface area 223. In some embodiments, as shown, the first major surface 203 may include the first surface area 223, and the second major surface 205 may include the second surface area 225. In other embodiments, the first surface area 223 may extend along the first plane 204a. In other embodiments, the second surface area 225 may extend along the second plane 204b. A substrate thickness 227 may be defined between the first plane 204a and the second plane 204b. In some embodiments, the substrate thickness 227 may correspond to the distance between the first surface area 223 of the first portion 221 and the second surface area 225 of the first portion 221. In some embodiments, the substrate thickness 227 may be substantially uniform throughout the first surface area 223. In some embodiments, the first thickness defined between the first surface area 223 and the second surface area 225 can be within one or more of the ranges described above for substrate thickness. In other embodiments, the first thickness can constitute substrate thickness 227. In other embodiments, the first thickness of the first portion 221 can be substantially uniform between the first surface area 223 and the second surface area 225 over the entire corresponding length of the foldable device (i.e., in the direction 106 of the length 105 of the foldable device) and / or over the entire corresponding width of the foldable device (i.e., in the direction 104 of the width 103 of the foldable device).

[0175] like Figure 2-3 As shown in FIGS. 6-7 , the foldable substrate 201 may further include a second portion 231, wherein the second portion 231 includes a third surface area 233 and a fourth surface area 235 opposite to the third surface area 233. Figure 2 The second part 231 is described with reference to the foldable device 101. It should be understood that, unless otherwise specified, the description of the second part 231 may also be applicable to any embodiment of the present disclosure, for example, Figure 3 and 6-7. In some embodiments, as shown, the third surface area 233 of the second portion 231 may include a planar surface. In other embodiments, the third surface area 233 of the second surface portion 231 may be coplanar with the first surface area 223 of the first portion 221. In some embodiments, as shown, the fourth surface area 235 of the second portion 231 may include a planar surface. In other embodiments, as shown, the fourth surface area 235 may be parallel to the third surface area 233. In other embodiments, the fourth surface area 235 of the second portion 231 may be coplanar with the second surface area 225 of the first portion 221.

[0176] A second thickness 237 may be defined between the third surface area 233 of the second portion 231 and the fourth surface area 235 of the second portion 231. In some embodiments, the second thickness 237 may be within the range described above with respect to the substrate thickness. In other embodiments, the second thickness 237 may constitute the substrate thickness. In other embodiments, as shown in the figure, the second thickness 237 may be substantially equal to the first thickness (e.g., substrate thickness 227). In some embodiments, the second thickness 237 of the second portion 231 may be substantially uniform between the third surface area 233 and the fourth surface area 235.

[0177] like Figure 2-3 As shown in FIGS. 6-7 , the foldable substrate 201 may include a central portion 251 located between the first portion 221 and the second portion 231. In some embodiments, the central portion 251 may include a first central surface area 209 and a second central surface area 213 opposite the first central surface area 209. In other embodiments, the central portion 251 may include a first central surface area 209 located between the first surface area 223 and the third surface area 233. In other embodiments, as shown, the first central surface area 209 may be recessed from the first major surface 203. In other embodiments, the central portion 251 may include a second central surface area 213 located between the second surface area 225 and the fourth surface area 235. In other embodiments, as shown, the second major surface 205 may include the second central surface area 213.

[0178] A central thickness 217 of the central portion 251 may be defined between the first central surface region 209 and the second central surface region 213. In some embodiments, the first central surface region 209 may include a central major surface 211 that may extend along the third plane 204c when the foldable device 101, 301 is in a flat configuration, but in other embodiments, the first central surface region 209 may be provided as a non-planar region. In other embodiments, the third plane 204c may be substantially parallel to the first plane 204a and / or the second plane 204b. By providing a central major surface 211 of the central portion 251 extending along the third plane 204c parallel to the second plane 204b, a uniform central thickness 217 may extend throughout the central portion 251, which may provide enhanced folding performance at a predetermined thickness of the central thickness 217. The uniform central thickness 217 over the entire central portion 251 may improve folding performance by preventing stress concentration, which may occur if a portion of the central portion 251 is thinner than the remaining central portion 251.

[0179] In some embodiments, Figure 2-3As shown in Figures 6-7, the center thickness 217 may be less than the substrate thickness 227 (e.g., the first thickness of the first portion 221, the second thickness 237 of the second portion 231). In some embodiments, the center thickness 217 may be about 0.5% or more, about 1% or more, about 2% or more, about 5% or more, about 13% or less, about 10% or less, or about 5% or less of the substrate thickness 227 (e.g., the first thickness, the second thickness 237). In some embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness, the second thickness 237), the center thickness 217 may be in the following ranges: about 0.5% to about 13%, about 0.5% to about 10%, about 0.5% to about 5%, about 1% to about 13%, about 1% to about 10%, about 1% to about 5%, about 2% to about 13%, about 2% to about 10%, about 2% to about 5%, about 5% to about 13%, about 5% to about 10%, or any range or sub-range therebetween. In other embodiments, the center thickness 217 can be within one or more ranges of the substrate thickness 227 (e.g., the first thickness, the second thickness 237) while being less than the substrate thickness. In other embodiments, the center thickness 217 can be greater than or equal to about 10 μm, greater than or equal to about 25 μm, greater than or equal to about 50 μm, greater than or equal to about 80 μm, less than or equal to about 220 μm, less than or equal to about 125 μm, less than or equal to about 100 μm, less than or equal to about 80 μm, less than or equal to about 60 μm, or less than or equal to about 40 μm. In other embodiments, the center thickness 217 can be within the following ranges: about 10 μm to about 220 μm, about 10 μm to about 125 μm, about 10 μm to about 100 μm, about 10 μm to about 80 μm, about 25 μm to about 80 μm, about 25 μm to about 60 μm, about 50 μm to about 60 μm, or any range or sub-range therebetween. Based on the following reference Fig.42The results of the pen drop test described above show that increased puncture resistance can be achieved by selecting a center thickness 217 of less than about 50 micrometers (μm) or greater than about 80 μm. In other embodiments, the center thickness 217 can be greater than about 80 μm, for example, greater than or equal to about 80 μm, greater than or equal to about 100 μm, greater than or equal to about 125 μm, less than or equal to about 220 μm, less than or equal to about 175 μm, or less than or equal to about 150 μm. In other embodiments, the center thickness 217 can be in the following ranges: about 80 μm to about 220 μm, about 80 μm to about 175 μm, about 80 μm to about 150 μm, about 100 μm to about 150 μm, about 125 μm to about 150 μm, or any range or sub-range therebetween. In other embodiments, the center thickness 217 may be less than about 80 μm, for example, within the range of about 10 μm to about 80 μm, about 25 μm to about 60 μm, about 10 μm to about 50 μm, about 25 μm to about 50 μm, about 10 μm to about 40 μm, about 25 μm to about 40 μm, or any range or sub-range therebetween.

[0180] like Figure 2 As shown, the central portion 251 may include a first transition portion 253. The first transition portion 253 may attach the first portion 221 to an area of ​​the central portion 251 that includes the central thickness 217 (e.g., an area that includes the central major surface 211). The thickness of the first transition portion 253 may be defined between the second plane 204b and the first central surface area 209. Figure 2 As shown, the thickness of the first transition portion 253 can increase continuously from the central major surface 221 (e.g., from the central thickness 217) to the first portion 221 (e.g., to the first thickness, substrate thickness 227). In some embodiments, as shown, the thickness of the first transition portion 253 can increase at a constant rate from the central major surface 211 to the first portion 221. Although not shown, in some embodiments, the thickness of the first transition portion 253 can increase more slowly at the location where the central major surface 211 meets the first transition portion 253 than at the middle of the first transition portion 253. Although not shown, in some embodiments, the thickness of the first transition portion 253 can increase more slowly at the location where the first portion 221 meets the first transition portion 253 than at the middle of the first transition portion 253. In some embodiments, as Figure 3 As shown, the central portion 251 may not include the first transition portion.

[0181] The central portion 251 may include a second transition portion 255. Figure 2As shown, the second transition portion 255 can attach the second portion 231 to an area of ​​the central portion 251 that includes the central thickness 217 (e.g., an area that includes the central major surface 211). The thickness of the second transition portion 255 can be defined between the second plane 204b and the first central surface area 209. Figure 2 As shown, the thickness of the second transition portion 255 can increase continuously from the central major surface 211 (e.g., from the central thickness 217) to the second portion 231 (e.g., to the first thickness). In some embodiments, as shown, the thickness of the second transition portion 255 can increase at a constant rate from the central major surface 211 to the second portion 231. Although not shown, in some embodiments, the thickness of the second transition portion 255 can increase more slowly at the location where the central major surface 211 meets the second transition portion 255 than at the middle of the second transition portion 255. Although not shown, in some embodiments, the thickness of the second transition portion 255 can increase more slowly at the location where the second portion 231 meets the second transition portion 255 than at the middle of the second transition portion 255. In some embodiments, as Figure 3 As shown, the central portion 251 may not include the second transition portion.

[0182] like Figure 2 As shown, in the direction 106 of the length 105 of the foldable device 101, a width 254a of the first transition portion 253 may be defined between the central main surface 211 and the first portion 221. In the direction 106 of the length 105 of the foldable device 101, a width 254b of the second transition portion 255 may be defined between the central main surface 211 and the second portion 231. In some embodiments, the width 254a of the first transition portion 253 and / or the width 254b of the second transition portion 255 may be sufficiently large (e.g., greater than or equal to 1 mm) to avoid optical distortion that may otherwise occur with a stepped transition width or a small transition width (e.g., less than 1 mm) between the first thickness and the central thickness. Based on the following reference Fig.42The pen drop test described above, providing a transition region with a sufficiently small length (e.g., less than or equal to about 5 mm) reduces the amount of foldable substrates with medium thickness, for example, in the range of about 50 μm to about 80 μm, foldable substrates with medium thickness may have reduced impact resistance and / or puncture resistance. In some embodiments, in order to enhance the puncture resistance of the foldable substrate while avoiding optical distortion, the width 254a of the first transition portion 253 and / or the width 254b of the second transition portion 255 may be greater than or equal to about 1 mm, greater than or equal to about 2 mm, greater than or equal to about 3 mm, less than or equal to about 5 mm, less than or equal to about 4 mm, or less than or equal to about 3 mm. In some embodiments, the width of the first transition portion 253 and / or the width 254b of the second transition portion 255 may be in the range of about 1 mm to about 5 mm, about 1 mm to about 4 mm, about 1 mm to about 3 mm, about 2 mm to about 5 mm, about 2 mm to about 4 mm, about 2 mm to about 3 mm, about 3 mm to about 5 mm, about 3 mm to about 4 mm, or any range or sub-range therebetween.

[0183] If a first layer and / or component is described as being "disposed above a second layer and / or component," other layers may or may not exist between the first layer and / or component and the second layer and / or component. In addition, as used herein, "disposed above" does not refer to a relative position with reference to gravity. For example, when the first layer and / or component is located below, above, or to one side of the second layer and / or component, the first layer and / or component may be considered to be "disposed above the second layer and / or component." As used herein, a first layer and / or component described as "a first layer and / or component combined with a second layer and / or component" means that the layers and / or components are combined with each other, which is achieved by direct contact and / or combination between the two layers and / or components or by combination through an adhesive layer. As used herein, a first layer and / or component described as "contacting a second layer and / or component" or "contacting a second layer and / or component" refers to direct contact and includes situations where the layers and / or components are combined with each other.

[0184] like Figure 2-3As shown in Figures 6-7, the foldable device 101 and / or 301 and / or the test foldable device 602 may include an adhesive layer 261. As shown, the adhesive layer 261 may include a first contact surface 263 and a second contact surface 265 that may be opposite to the first contact surface 263. In some embodiments, as shown, the second contact surface 265 of the adhesive layer 261 may include a planar surface. An adhesive thickness 267 of the adhesive layer 261 may be defined between the first contact surface 263 and the second contact surface 265. In some embodiments, the adhesive thickness 267 of the adhesive layer 261 may be greater than or equal to about 1 μm, greater than or equal to about 5 μm, greater than or equal to about 10 μm, less than or equal to about 100 μm, less than or equal to about 60 μm, less than or equal to about 30 μm, or less than or equal to about 20 μm. In some embodiments, 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 sub-range therebetween.

[0185] In some embodiments, Figure 2 As shown, the first contact surface 263 of the adhesive layer 261 can face the first major surface 273 of the release liner 271 (described below). In other embodiments, as shown, the first contact surface 263 of the adhesive layer 261 can contact the first major surface 273 of the release liner 271. In some embodiments, as shown Figure 3 and 6 -7, the first contact surface 263 of the adhesive layer 261 may face the first major surface 303 of the display device 307. In another embodiment, as shown in the figure, the first contact surface 263 of the adhesive layer 261 may contact the first major surface 303 of the display device 307.

[0186] Now refer to Figure 2 The foldable device 101 is used to describe the adhesive layer 261, and it should be understood that this description of the adhesive layer 261 can also be applied to Figure 3 and 6 -7 shows a foldable device 301 and / or a foldable substrate 201. In some embodiments, as Figure 2As shown, the second contact surface 265 of the adhesive layer 261 can face the first surface area 223 of the first portion 221. In other embodiments, as shown, the second contact surface 265 of the adhesive layer 261 can contact the first surface area 223 of the first portion 221. In some embodiments, as shown, the second contact surface 265 of the adhesive layer 261 can face the third surface area 233 of the second portion 231. In other embodiments, as shown, the second contact surface 265 of the adhesive layer 261 can contact the third surface area 233 of the second portion 231.

[0187] In some embodiments, adhesive layer 261 may include one or more of the following: polyolefins, polyamides, halogenide-containing polymers (e.g., polyvinyl chloride or fluoropolymers), elastomers, urethanes, phenolic resins, polyparaxylene, polyethylene terephthalate (PET), and polyetheretherketone (PEEK). Exemplary embodiments of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), and polypropylene (PP). Exemplary embodiments of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP) polymers, and ethylene tetrafluoroethylene (ETFE) polymers. Exemplary embodiments 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 embodiments, adhesive layer 261 may include an optically clear adhesive. In other embodiments, the optically clear adhesive may include one or more optically clear polymers: acrylics (e.g., polymethyl methacrylate (PMMA)), epoxies, silicones, and / or polyurethanes. Examples of epoxy materials include: bisphenol-based epoxy resins, phenolic resin varnish-based epoxy materials, cycloaliphatic-based epoxy materials, and glycidylamine-based epoxy materials. In other embodiments, 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 adhesives. Exemplary embodiments of optically clear adhesives include transparent acrylics, epoxies, silicones, and polyurethanes. For example, the optically clear liquid adhesive may include one or more of the following: LOCTITE AD 8650, LOCTITE AA 3922, LOCTITE EA E-05MR, LOCTITE UK U-09LV, all available from Henkel.

[0188] like Figure 2 As shown, at least a portion of the adhesive layer 261 of the foldable device 101 may be located between the first portion 221 and the second portion 231. In some embodiments, as shown, a recess 219 may be defined between the first central surface area 209 and the first plane 204a. In some embodiments, the recess 219 may be defined between the third plane 204c and the first plane 204a. In some embodiments, as shown, the adhesive layer 261 may be at least partially located in the recess 219. In other embodiments, as shown, the polymer base portion 241 may fill the recess 219. In some embodiments, although not shown, the recess may not be completely filled, for example, leaving space for electronic devices and / or mechanical devices.

[0189] like Figure 3 and 6 -7, the polymer base portion 241 of the foldable device 301 and / or the test foldable device 602 may be located between the first portion 221 and the second portion 231. In some embodiments, as shown, a recess 219 may be defined between the first central surface area 209 and the first plane 204a. In some embodiments, the recess 219 may be defined between the third plane 204c and the first plane 204a. In some embodiments, as shown, the polymer base portion 241 may be at least partially located in the recess 219. In other embodiments, as shown, the polymer base portion 241 may fill the recess 219. In other embodiments, the polymer base portion 241 may include the same material as the adhesive layer 261 so that the adhesive layer 261 may fill the recess. Although not shown, in some embodiments, the adhesive layer 261 may extend into the recess to replace the polymer base portion 241, and / or the adhesive layer 261 may fill the recess. Although not shown, in some embodiments, the recess may not be completely filled, for example, leaving space for electronic devices and / or mechanical devices.

[0190] like Figure 3As shown, the polymer base portion 241 may include a fourth contact surface 247 opposite to the third contact surface 245. In some embodiments, as shown, the fourth contact surface 247 may include a planar surface. In other embodiments, the fourth contact surface 247 may be substantially coplanar with the first surface area 223 and the third surface area 233 (e.g., extending along the common planar first plane 204a). In some embodiments, the third contact surface 245 may include a planar surface. In some embodiments, in addition to the fourth contact surface 247 being substantially coplanar with the first surface area 223 and the third surface area 233, the third contact surface 245 may also be substantially coplanar with the first central surface area 209 (e.g., the central main surface 211) (e.g., extending along the common planar third plane 204c). The polymer base portion 241 may extend in the direction 202 of the substrate thickness 227 (e.g., the first thickness of the first portion 221), and the extension is substantially equal to the difference between the substrate thickness 227 (e.g., the first thickness of the first portion 221) and the central thickness 217.

[0191] In some embodiments, the second contact surface 265 of the adhesive layer 261 may face the fourth contact surface 247 of the polymer base portion 241. In other embodiments, as shown, the second contact surface 265 of the adhesive layer 261 may contact the fourth contact surface 247 of the polymer base portion 241. In other embodiments, as shown, Figure 2 As shown, adhesive layer 261, but not polymer base portion 241, may occupy recess 219. In some embodiments, although not shown, adhesive layer 261 may not be present, and instead, polymer base portion 241 may occupy the area occupied by adhesive layer 261.

[0192] In some embodiments, the polymer base portion 241 includes a polymer (e.g., an optically transparent polymer). In other embodiments, the polymer base portion 241 may include one or more optically transparent polymers: acrylics (e.g., polymethyl methacrylate (PMMA)), epoxies, silicones, and / or polyurethanes. Examples of epoxy materials include: bisphenol-based epoxies, novolac-based epoxies, cycloaliphatic-based epoxies, and glycidylamine-based epoxies. In other embodiments, the polymer base portion 241 may include one or more of the following: polyolefins, polyamides, halogenated polymers (e.g., polyvinyl chloride or fluoropolymers), elastomers, urethanes, phenolic resins, polyparaxylene, polyethylene terephthalate (PET), and polyetheretherketone (PEEK). Exemplary embodiments of polyolefins include low molecular weight polyethylene (LDPE), high molecular weight polyethylene (HDPE), ultra-high molecular weight polyethylene (UHMWPE), and polypropylene (PP). Exemplary embodiments of fluoropolymers include polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), perfluoropolyether (PFPE), perfluorosulfonic acid (PFSA), perfluoroalkoxy polymer (PFA), fluorinated ethylene propylene (FEP) polymer and ethylene tetrafluoroethylene (ETFE) polymer. Exemplary embodiments of elastomers include rubber (e.g., polybutadiene, polyisoprene, chloroprene rubber, butyl rubber, nitrile rubber) and block copolymers (e.g., styrene-butadiene, high-impact polystyrene, poly(dichlorophosphazene)), for example, including one or more of polystyrene, polydichlorophosphazene and poly(5-ethylidene-2-norbornene). In some embodiments, the polymer base portion may include a sol-gel material. Exemplary embodiments of polyurethane include thermosetting polyurethanes (e.g., Dispurez 102 purchased from Incorez) and thermoplastic polyurethanes (e.g., KrystalFlex PE505 purchased from Huntsman). In other embodiments, the second portion may include ethylene acid copolymers. An exemplary embodiment of the ethylene acid copolymer includes SURLYN (e.g., Surlyn PC-2000, Surlyn 8940, Surlyn 8150) purchased from Dow. Another exemplary embodiment of the second part includes Eleglass w802-GL044 purchased from Axalta, which has 1 wt % to 2 wt % of a crosslinking agent. In some embodiments, the polymer base portion 241 may also include nanoparticles, such as carbon black, carbon nanotubes, silica nanoparticles, or nanoparticles containing polymers. In some embodiments, the polymer base portion may also include fibers to form a polymer-fiber composite.

[0193] In some embodiments, the polymer base portion 241 may include a coefficient of thermal expansion (CTE). As used herein, the coefficient of thermal expansion is measured between -20°C and 40°C using a PICOSCAL Michelson Interferometer according to ASTM E289-17. In some embodiments, the polymer base portion 241 may include particles of one or more of copper oxide, β-quartz, tungstate, vanadate, pyrophosphate, and / or nickel titanium alloy. In some embodiments, the polymer base portion 241 may include a CTE greater than or equal to about -20x10 -7 1 / ℃, greater than or equal to about -10x10 -7 1 / ℃, greater than or equal to about -5x10 -7 1 / ℃, greater than or equal to about -2x10 -7 1 / ℃, less than or equal to about 10x10 -7 1 / ℃, less than or equal to about 5x10 -7 1 / ℃, less than or equal to about 2x10 -7 1 / ℃, less than or equal to about 1x10 -7 1 / °C, or a CTE less than or equal to 0 1 / °C. In some embodiments, the polymer base portion 241 may include a CTE in the following ranges: about -20x10 -7 1 / ℃ to about 10x10 -7 1 / ℃, about -20x10 -7 1 / ℃ to about 5x10 -7 1 / ℃, about -10x10 -7 1 / ℃ to about -5x10 -7 1 / ℃, about -10x10 -7 1 / ℃ to about 2x10 -7 1 / ℃, about -10x10 -7 1 / ℃ to 0 1 / ℃, about -5x10 -7 1 / ℃ to 01 / ℃, about -2x10 -7 1 / °C to about 0 1 / °C, or any range or sub-range therebetween. By providing a polymer-based portion comprising a low (eg, negative) coefficient of thermal expansion, warping due to volume change during curing of the polymer-based portion can be mitigated.

[0194] In some embodiments, the polymer base portion 241 may include an elastic modulus of greater than or equal to about 0.01 megapascals (MP), greater than or equal to about 1 MPa, greater than or equal to about 10 MPa, greater than or equal to about 20 MPa, greater than or equal to about 100 MPa, greater than or equal to about 200 MPa, greater than or equal to about 1,000 MPa, less than or equal to about 5,000 MPa, less than or equal to about 3,000 MPa, less than or equal to about 1,000 MPa, less than or equal to about 500 MPa, or less than or equal to about 200 MPa. In some embodiments, the polymer base portion 241 may include an elastic modulus in the following ranges: 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 5,000 MPa, about 1 MPa to about 1,000 MPa, about 1 MPa to about 1,000 MPa, about 1 MPa to about 200 MPa, about 10 MPa to about 5,000 MPa. , about 10 MPa to about 1,000 MPa, about 10 MPa to about 200 MPa, about 20 MPa to about 3,000 MPa, about 20 MPa to about 1,000 MPa, about 20 MPa to about 200 MPa, about 100 MPa to about 3,000 MPa, about 100 MPa to about 1,000 MPa, about 100 MPa to about 200 MPa, about 200 MPa to about 5,000 MPa, about 200 MPa to about 3,000 MPa, about 200 MPa to about 1,000 MPa, or any range or sub-range therebetween. In some embodiments, the elastic modulus of the polymer base portion 241 may be in the range of about 1 GPa to about 20 GPa, about 1 GPa to about 18 GPa, about 1 GPa to about 10 GPa, about 1 GPa to about 5 GPa, about 1 GPa to about 3 GPa, or any range or sub-range therebetween. By providing a polymer base portion 241 having an elastic modulus in the range of about 0.01 MPa to about 3,000 MPa (e.g., in the range of about 20 MPa to about 3 GPa), folding of the foldable device without failure can be facilitated. In some embodiments, the adhesive layer 261 includes an elastic modulus greater than the elastic modulus of the polymer base portion 241, and this arrangement provides improved performance in puncture resistance. In some embodiments, the elastic modulus of the polymer base portion 241 may be less than the elastic modulus of the foldable substrate 201. In some embodiments, the adhesive layer 261 may include an elastic modulus within the range listed previously in this paragraph. In other embodiments, the adhesive layer 261 may include an elastic modulus substantially the same as the elastic modulus of the polymer base portion 241.In other embodiments, 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 sub-range therebetween. In some embodiments, the elastic modulus of the polymer base portion 241 may be less than the elastic modulus of the first portion 221. In some embodiments, the elastic modulus of the polymer base portion 241 may be less than the elastic modulus of the second portion 231.

[0195] In some embodiments, adhesive layer 261 may include an elastic modulus of greater than or equal to about 0.001 megapascals (MPa), greater than or equal to about 0.01 MPa, greater than or equal to about 0.1 MPa, less than or equal to about 1 MPa, less than or equal to about 0.5 MPa, less than or equal to about 0.1 MPa, or less than or equal to about 0.05 MPa. In some embodiments, adhesive layer 261 may include an elastic modulus in the following ranges: about 0.001 MPa to about 1 MPa, about 0.01 MPa to about 1 MPa, about 0.01 MPa to about 0.5 MPa, about 0.05 MPa to about 0.5 MPa, about 0.1 MPa to about 0.5 MPa, about 0.001 MPa to about 0.5 MPa, about 0.001 MPa to about 0.01 MPa, or any range or sub-range therebetween. In some embodiments, adhesive layer 261 can include an elastic modulus within one or more of the ranges described above with respect to the elastic modulus of polymer base portion 241 .

[0196] In some embodiments, Figure 2As shown, a coating 281 may be disposed over the second major surface 205 of the foldable substrate 201. In other embodiments, the coating 281 may be disposed over the first portion 221, the second portion 231, and the central portion 251. In some embodiments, the coating 281 may include a third major surface 283 and a fourth major surface 285 opposite the third major surface 283. In other embodiments, the coating 281 (e.g., the third major surface 283) may contact the foldable substrate 201 (e.g., the second major surface 205). In other embodiments, the coating 281 may include a coating thickness 287 defined between the third major surface 283 and the fourth major surface 285. In other embodiments, the coating thickness 287 can be greater than or equal to about 0.1 μm, greater than or equal to about 1 μm, greater than or equal to about 5 μm, greater than or equal to about 10 μm, greater than or equal to about 15 μm, greater than or equal to about 20 μm, greater than or equal to about 25 μm, greater than or equal to about 40 μm, greater than or equal to about 50 μm, greater than or equal to about 60 μm, greater than or equal to about 70 μm, greater than or equal to about 80 μm, greater than or equal to about 90 μm, less than or equal to about 200 μm, less than or equal to about 100 μm, or about 50 μm, less than or equal to about 30 μm, less than or equal to about 25 μm, less than or equal to about 20 μm, less than or equal to about 20 μm, less than or equal to about 15 μm, or less than or equal to about 10 μm. In some embodiments, the coating thickness 287 may be in the range of about 0.1 μm to about 200 μm, about 1 μm to about 200 μm, about 10 μm to about 200 μm, about 50 μm to about 200 μm, about 0.1 μm to about 100 μm, about 1 μm to about 100 μm, about 10 μm to about 100 μm, about 20 μm to about 100 μm, about 30 μm to about 100 μm, about 40 μm to about 100 μm, about 50 μm to about 100 μm, about 60 μm to about 100 μm, about 70 μm to about 100 μm, about 80 μm to about 100 μm, about 90 μm to about 100 μm, about 0.1 μm to about 50 μm, about 1 μm to about 50 μm, about 10 μm to about 50 μm, or any range or sub-range therebetween.In other embodiments, the coating thickness 287 may be in the range of about 0.1 μm to about 50 μm, about 0.1 μm to about 30 μm, about 0.1 μm to about 25 μm, about 0.1 μm to about 20 μm, about 0.1 μm to about 15 μm, about 0.1 μm to about 10 μm, about 1 μm to about 30 μm, about 1 μm to about 25 μm, about 1 μm to about 20 μm, about 1 μm to about 15 μm, about 1 μm to about 10 μm, about 5 μm to about 30 μm. m, about 5 μm to about 25 μm, about 5 μm to about 20 μm, about 5 μm to about 15 μm, about 5 μm to about 10 μm, about 10 μm to about 30 μm, about 10 μm to about 25 μm, about 10 μm to about 20 μm, about 10 μm to about 15 μm, about 15 μm to about 30 μm, about 15 μm to about 25 μm, about 15 μm to about 20 μm, about 20 μm to about 30 μm, about 20 μm to about 25 μm, or any ranges and sub-ranges therebetween.

[0197] In some embodiments, coating 281 may include a polymer hard coat. In other embodiments, the polymer hard coat may include one or more of ethylene-acid copolymers, polyurethane-based polymers, acrylate resins, and mercaptoester resins. Exemplary embodiments of ethylene-acid copolymers include ethylene-acrylic acid copolymers, ethylene-methacrylic acid copolymers, and ethylene-acrylic acid-methacrylic acid terpolymers [e.g., Nucrel manufactured by DuPont], ionomers of ethylene acid copolymers (e.g., Surlyn manufactured by DuPont), and ethylene-acrylic acid copolymer amine dispersions (e.g., Aquacer manufactured by BYK). Exemplary embodiments of polyurethane-based polymers include modified polyurethane aqueous dispersions (e.g., ). Exemplary embodiments of UV-curable acrylate resins include acrylate resins (e.g., resins), cyanoacrylate adhesives (e.g., manufactured by Krayden UV620) and UV free radical acrylic resins (e.g., Ultrabond windshield repair resins, such as Ultrabond (45CPS)). Exemplary embodiments of mercapto ester resins include mercapto ester triallyl isocyanuates (e.g., Norland's optical adhesive NOA 61). In other embodiments, the polymer hard coating may include ethylene-acrylic acid copolymers and ethylene-methacrylic acid copolymers, which may be ionomerized by neutralizing carboxylic acid residues to form ionomer resins, typically using alkali metal ions, such as sodium and potassium, and zinc. Such ethylene-acrylic acid and ethylene-methacrylic acid ionomers may be dispersed in water and applied to a substrate to form an ionomer coating. Alternatively, such acid copolymers may be neutralized with ammonia, which, after coating and drying, releases the ammonia to reform the acid copolymer as a coating. By providing a coating comprising a polymer coating, the foldable device may include low energy fracture.

[0198] In some embodiments, coating may include polymer hard coating, which includes optically transparent polymer hard coating. Materials suitable for optically transparent polymer hard coating include, but are not limited to, cured acrylic resin materials, inorganic-organic hybrid polymer materials, aliphatic or aromatic hexafunctional urethane acrylates, hybrid materials based on siloxanes, and nanocomposites, such as epoxy materials and urethane materials with nano silicates. In some embodiments, optically transparent polymer hard coating may be mainly composed of one or more of these materials. In some embodiments, optically transparent polymer hard coating may be composed of one or more of these materials. As used herein, "inorganic-organic hybrid polymer material" means a polymer material comprising a monomer and having inorganic and organic components. Inorganic-organic hybrid polymers are obtained by polymerization reaction between monomers having inorganic groups and organic groups. Inorganic-organic hybrid polymers are not nanocomposites comprising separated inorganic and organic components or phases (e.g., inorganic particles are dispersed in an organic matrix). More specifically, materials suitable for optically transparent polymer (OTP) hard coatings include, but are not limited to, polyimide, polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), organic polymer materials, inorganic-organic hybrid polymer materials, and aliphatic or aromatic hexafunctional urethane acrylates. In some embodiments, the OTP hard coating may be substantially composed of organic polymer materials, inorganic-organic hybrid polymer materials, or aliphatic or aromatic hexafunctional urethane acrylates. In some embodiments, the OTP hard coating may be composed of polyimide, organic polymer materials, inorganic-organic hybrid polymer materials, or aliphatic or aromatic hexafunctional urethane acrylates. In some embodiments, the OTP hard coating may include a nanocomposite material. In some embodiments, the OTP hard coating may include at least one of nano-silicate, epoxy material, and urethane material. Suitable compositions for 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 and the monomers have only organic components. In some embodiments, the OTP hard coating may include an organic polymer material manufactured by Gunze Co., Ltd. and having a hardness of 9H, for example, Gunze's "High Durability Transparent Film". As used herein, "inorganic-organic hybrid polymer material" means a polymer material comprising monomers and having inorganic and organic components. Inorganic-organic hybrid polymers are obtained by polymerization reactions between monomers having inorganic groups and organic groups. Inorganic-organic hybrid polymers are not nanocomposites comprising separated inorganic and organic components or phases (e.g., inorganic particles are dispersed in an organic matrix).In some embodiments, the inorganic-organic hybrid polymer material may include a polymerized monomer containing an inorganic silicon-based group, for example, a silsesquioxane polymer. The silsesquioxane polymer may have, for example, the following chemical structure: (RSiO. 1.5 ) nAlkyl-silsesquioxane, aryl-silsesquioxane, or arylalkyl-silsesquioxane, wherein R is an organic group, such as but not limited to methyl or phenyl. In some embodiments, the OTP hard coating may include a silsesquioxane polymer combined with an organic matrix, such as SILPLUS manufactured by Nippon Steel Chemical Co., Ltd. In some embodiments, 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], and a hardness of 8H or greater. In some embodiments, an OTP hard coating layer composed of an aliphatic or aromatic hexafunctional urethane acrylate can be formed as a separate layer by spin coating the layer on a polyethylene terephthalate (PET) substrate, curing the urethane acrylate, and removing the urethane acrylate layer from the PET substrate. The coating thickness (e.g., coating thickness 287) of the OTP hard coating layer can be in the range of 1 μm to 150 μm, including sub-ranges. For example, the coating thickness (e.g., coating thickness 287) can be in the range of 10 μm to 140 μm, 20 μm to 130 μm, 30 μm to 120 μm, 40 μm to 110 μm, 50 μm to 100 μm, 60 μm to 90 μm, 70 μm, 80 μm, 2 μm to 140 μm, 4 μm to 130 μm, 6 μm to 120 μm, 8 μm to 110 μm, 10 μm to 100 μm, 10 μm to 90 μm, 10 μm, 80 μm, 10 μm, 70 μm, 10 μm, 60 μm, 10 μm, 50 μm, or in the range of any two of these values ​​as endpoints. In some embodiments, the OTP hard coating can be a single integral layer. In some embodiments, the OTP hard coating layer may be an inorganic-organic hybrid polymer material layer or an organic polymer material layer having a thickness in the range of 80 μm to 120 μm (including sub-ranges). For example, the thickness of the OTP hard coating layer comprising an inorganic-organic hybrid polymer material or an organic polymer material may be 80 μm to 110 μm, 90 μm to 100 μm, or in a range with any two of these values ​​as endpoints. In some embodiments, the OTP hard coating layer may be an aliphatic or aromatic hexafunctional urethane acrylate material layer having a thickness in the range of 10 μm to 60 μm (including sub-ranges).For example, the thickness of the OTP hard coating comprising an aliphatic or aromatic hexafunctional urethane acrylate material can be 10 μm to 55 μm, 10 μm to 50 μm, 10 μm to 40 μm, 10 μm to 45 μm, 10 μm to 40 μm, 10 μm to 35 μm, 10 μm to 30 μm, 10 μm to 25 μm, 10 μm to 20 μm, or in any range with any two of these values ​​as endpoints.

[0199] In some embodiments, if provided, the surface coating 281 may also include one or more of an easy-to-clean coating, a low-friction coating, an oleophobic coating, a diamond-like coating, a scratch-resistant coating, or a wear-resistant coating. The scratch-resistant coating may include a nitrogen oxide, such as aluminum oxynitride or silicon oxynitride, and have a thickness of about 500 microns or more. In such an embodiment, the wear-resistant layer may include the same material as the scratch-resistant layer. In some embodiments, the low-friction coating may include a highly fluorinated silane coupling agent, such as an alkylfluorosilane, in which an oxymethyl group is attached to the silicon atom. In such an embodiment, the easy-to-clean coating may include the same material as the low-friction coating. In other embodiments, the easy-to-clean coating may include a protonatable group, such as an amine, such as an alkylaminosilane, in which an oxymethyl group is attached to the silicon atom. In such an embodiment, the oleophobic coating may include the same material as the easy-to-clean coating. In some embodiments, the diamond-like coating includes carbon and may be produced by applying a high voltage potential in the presence of a hydrocarbon plasma.

[0200] In some embodiments, Figure 2As shown, the foldable device 101 may include a release liner 271, but in other embodiments, other substrates (e.g., glass-based substrates and / or ceramic-based substrates described in the present application) may be used instead of the illustrated release liner 271. In other embodiments, as shown, the release liner 271 or another substrate may be disposed above the adhesive layer 261. In other embodiments, as shown, the release liner 271 or another substrate may directly contact the first contact surface 263 of the adhesive layer 261. The release liner 271 or another substrate may include a first major surface 273 and a second major surface 275 opposite to the first major surface 273. As shown, the release liner 271 or another substrate may be disposed on the adhesive layer 261 by attaching the first contact surface 263 of the adhesive layer 261 to the second major surface 275 of the release liner 271 or another substrate. In some embodiments, as shown, the first major surface 273 of the release liner 271 or another substrate may include a planar surface. In some embodiments, as shown, the second major surface 275 of the release liner 271 or another substrate may include a planar surface. The release liner 271 may include paper and / or polymers. Exemplary embodiments of paper include kraft paper, machine-made paper, polymer-coated paper (e.g., polymer-coated glass paper, siliconized paper), or clay-coated paper. Exemplary embodiments of polymers include polyesters (e.g., polyethylene terephthalate (PET)) and polyolefins (e.g., low-density polyethylene (LDPE), high-density polyethylene (HDPE), polypropylene (PP)).

[0201] In some embodiments, Figure 3 and 7 As shown, the foldable device 301 may include a display device 307. In other embodiments, as shown, the display device 307 may be disposed above the adhesive layer 261. In other embodiments, as shown, the display device 307 may contact the first contact surface 263 of the adhesive layer 261. In some embodiments, by removing Figure 2The foldable device 301 can be produced by attaching the release liner 271 of the foldable device 101 and attaching the display device 307 to the first contact surface 263 of the adhesive layer 261. Alternatively, the foldable device 301 can be produced without the step of removing the release liner before attaching the display device 307 to the first contact surface 263 of the adhesive layer 261, for example, when the release liner 271 is not applied to the first contact surface 263 of the adhesive layer 261. The display device 307 may include a first major surface 303 and a second major surface 305 opposite to the first major surface 303. As shown in the figure, the display device 307 can be disposed on the adhesive layer 261 by attaching the first contact surface 263 of the adhesive layer 261 to the second major surface 305 of the display device 307. In some embodiments, as shown in the figure, the first major surface 303 of the display device 307 may include a planar surface. In some embodiments, as shown in the figure, the second major surface 305 of the display device 307 may include a planar surface. Display device 307 may include a liquid crystal display (LCD), an electrophoretic display (EPD), an organic light emitting diode display (OLED), or a plasma display panel (PDP). In some embodiments, display device 307 may be part of a portable electronic device such as a consumer electronic product, a smartphone, a tablet computer, a wearable device, or a laptop computer.

[0202] Embodiments of the present disclosure may include a consumer electronic product. The consumer electronic product may include a front surface, a rear surface, and a side surface. The consumer electronic product may also include an electrical component at least partially within a housing. The electrical component may include a controller, a memory, and a display. The display may be at the front surface of the housing or adjacent to the front surface of the housing. The consumer electronic product may include a cover substrate disposed above the display. In some embodiments, at least one of a portion of the housing or the cover substrate includes a foldable device described in the present disclosure.

[0203] The foldable device disclosed herein can be incorporated into another article, such as an article with a display (or display article) [such as consumer electronic devices, including mobile phones, tablets, computers, navigation systems, wearable devices (such as watches), etc.]; architectural products; transportation products (such as cars, trains, aircraft, ships, etc.), equipment products, or any article that can benefit from a certain degree of transparency, scratch resistance, wear resistance, or a combination of the above properties. Figure 8-9 An exemplary article of manufacture comprising any of the foldable devices disclosed herein is shown. Specifically, Figure 8-9A consumer electronic device 800 is shown, which includes a housing 802 having a front surface 804, a rear surface 806, and a side surface 808; electrical components (not shown) at least partially or completely located within the housing and including at least a controller, a memory, and a display 810, the display 810 being at or adjacent to the front surface of the housing; and a cover substrate 812 at or above the front surface of the housing so that the cover substrate is above the display. In some embodiments, at least one of the cover substrate 812 or a portion of the housing 802 can include any of the foldable devices disclosed herein, for example, a foldable substrate.

[0204] In some embodiments, the foldable devices 101 and 301 and / or the test foldable device 602 can be arranged around a flat surface (e.g., Figure 1-3 In some embodiments, plane 109 may include a central axis 107 of the foldable device, which may be located at the second major surface 205 of the foldable substrate 201. As further illustrated, in some embodiments, plane 109 may include a pivot axis 102 of the foldable device. In some embodiments, the foldable device may be pivoted about the pivot axis 102 along a direction 111 (e.g., see Figure 1 ) to form a folded structure (see, for example, Figure 6-7 ). As shown, the foldable device can include a single pivot axis to allow the foldable device to include a bifold, wherein, for example, the foldable device can be folded in half. In other embodiments, the foldable device can include two or more pivot axes, wherein each pivot axis includes a corresponding intermediate portion similar or identical to the center portion 251 described above. For example, providing two pivot axes can allow the foldable device to include a trifold, wherein, for example, the foldable device can be folded to have three portions, including a first portion 221, a second portion 231, and a third portion similar or identical to the first portion or the second portion.

[0205] In some embodiments, the foldable substrate 201 may include a glass-based substrate and / or a ceramic-based substrate, and the first portion 221, the second portion 231, and / or the central portion 251 may include one or more compressive stress regions. In some embodiments, the compressive stress region may be established by chemical strengthening. Chemical strengthening may include an ion exchange process in which ions in the surface layer are replaced (or exchanged with) larger ions having the same valence or oxidation state. The method of chemical strengthening will be discussed below. Without being limited to theory, chemical strengthening of the first portion 221, the second portion 231, and / or the central portion 251 can achieve excellent impact resistance and / or puncture resistance (e.g., resistance to failure at a pen drop height of greater than or equal to about 15 centimeters (cm), greater than or equal to about 20 cm, or greater than or equal to 50 cm). Without wishing to be bound by theory, chemical strengthening of the first portion 221, the second portion 231, and / or the central portion 251 can achieve a small (e.g., less than about 10 mm or less) bending radius because the compressive stress from the chemical strengthening can offset the bending-induced tensile stress on the outermost surface of the substrate. The compressive stress zone can extend into a portion of the first portion and / or the second portion, extending to a certain depth, which is called the compression depth. As used herein, the compression depth means the depth at which the stress in the chemically strengthened substrate and / or portion described herein changes from compressive stress to tensile stress. Depending on the ion exchange treatment and the thickness of the article being measured, the compression depth can be measured by a surface stress meter or a scattered light polarizer (SCALP, wherein the values ​​reported herein are performed using a SCALP-5 manufactured by Glasstress Co., Estonia). If the stress in the substrate and / or portion is generated by exchanging potassium ions into the substrate, the compression depth is measured using, for example, 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 Corporation. Surface stress measurements rely on accurate measurement of the stress optical coefficient (SOC), which is related to the birefringence of the glass. Unless otherwise specified, SOC is measured according to Protocol C (Glass Disk Method) described in ASTM Standard C770-16, entitled "Standard Test Method for Measurement of Glass Stress-Optical Coefficient", which is incorporated herein by reference in its entirety. If the stress is generated by exchanging sodium ions into the substrate and the thickness of the article being measured exceeds about 400 μm, SCALP is used to measure the depth of compression and the central tension (CT).If the stress in the substrate and / or portion is generated by exchanging both potassium and sodium ions into the substrate and / or portion, and the thickness of the article being measured exceeds about 400 μm, the depth of compression and CT are measured by SCALP. Without wishing to be bound by theory, the depth of exchange of sodium can indicate the depth of compression, while the depth of exchange of potassium ions can indicate a change in the magnitude of the compressive stress (but not a change in stress from compressive stress to tensile stress). Refractive near field (RNF; the RNF method is described in U.S. Pat. No. 8,854,623, entitled "Systems and methods for measuring a profile characteristic of a glass sample", which is incorporated herein by reference in its entirety) methods can also be used to obtain a graphical representation of the stress distribution. When the RNF method is used to obtain a graphical representation of the stress distribution, the maximum central tension value provided by SCALP is used in the RNF method. The graphical representation of the stress distribution obtained by RNF is force balanced and calibrated to the maximum central tension value provided by the SCALP measurement. As used herein, "depth of layer" (DOL) means the depth of ions (e.g., sodium, potassium) exchanged into a substrate and / or part. In the present disclosure, when the maximum central tension cannot be measured directly by SCALP (such as when the article being measured is thinner than about 400 μm), the maximum central tension can be approximated by the product of the maximum compressive stress and the compression depth divided by the difference between the substrate thickness and twice the compression depth, where the compressive stress and the compression depth are measured by FSM.

[0206] In some embodiments, the first portion 221 including a glass-based portion and / or a ceramic-based portion may include a first compressive stress region at a first surface region 223, which may extend from the first surface region 223 to a first compression depth. In some embodiments, the first portion 221 including a first glass-based portion and / or a ceramic-based portion may include a second compressive stress region at a second surface region 225, which may extend from the second surface region 225 to a second compression depth. In some embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness), the first compression depth and / or the second compression depth may be greater than or equal to about 1%, greater than or equal to about 5%, greater than or equal to about 10%, less than or equal to about 30%, less than or equal to about 25%, or less than or equal to about 20%. In some embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness), the first compression depth and / or the second compression depth may be in the following ranges: 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 sub-range therebetween. In other embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness), the first compression depth and / or the second compression depth may be less than or equal to about 10%, 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 sub-range therebetween.

[0207] In other embodiments, the first compression depth may be substantially equal to the second compression depth. In some embodiments, the first compression depth and / or the second compression depth may be greater than or equal to about 1 μm, greater than or equal to about 10 μm, greater than or equal to about 30 μm, greater than or equal to about 50 μm, less than or equal to about 200 μm, less than or equal to about 150 μm, less than or equal to about 100 μm, or less than or equal to about 60 μm. In some embodiments, the first compression depth and / or the second compression depth may be in the range of about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 10 μm to about 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 sub-range therebetween. Excellent impact resistance and / or puncture resistance may be achieved by providing a first portion comprising a first glass-based and / or ceramic-based portion and comprising a first compression depth and / or a second compression depth of about 1% to about 30% of the first thickness.

[0208] In some embodiments, the first compressive stress region may include a first maximum compressive stress. In some embodiments, the second compressive stress region may include a second maximum compressive stress. In other embodiments, the first maximum compressive stress and / or the second maximum compressive stress may be greater than or equal to about 100 megapascals (MPa), greater than or equal to about 300 MPa, greater than or equal to about 500 MPa, greater than or equal to about 600 MPa, greater than or equal to about 700 MPa, less than or equal to about 1,500 MPa, less than or equal to about 1,200 MPa, less than or equal to about 1,000 MPa, or less than or equal to about 800 MPa. In other embodiments, the first maximum compressive stress and / or the second maximum compressive stress may be in the range of about 100 MPa to about 1,500 MPa, about 100 MPa to about 1,200 MPa, about 300 MPa to about 1,200 MPa, about 300 MPa to about 1,000 MPa, about 500 MPa to about 1,000 MPa, about 600 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, or any range or sub-range therebetween. By providing a first maximum compressive stress and / or a second maximum compressive stress of about 100 MPa to about 1,500 MPa, excellent impact resistance and / or puncture resistance may be achieved.

[0209] In some embodiments, the first portion 221 may include a first layer depth of one or more alkali metal ions, the one or more alkali metal ions being associated with the first compressive stress region and the first layer depth. In some embodiments, the first portion 221 may include a second layer depth of one or more alkali metal ions, the one or more alkali metal ions being associated with the second compressive stress region and the second layer depth. As used herein, the one or more alkali metal ions in the layer depth of one or more alkali metal ions may include sodium, potassium, rubidium, cesium, and / or francium. In some embodiments, the one or more alkali metal ions in the first layer depth of the one or more alkali metal ions and / or the one or more alkali metal ions in the second layer depth of the one or more alkali metal ions include potassium. In some embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness), the first layer depth and / or the second layer depth may be greater than or equal to about 1%, greater than or equal to about 5%, greater than or equal to about 10%, less than or equal to about 40%, less than or equal to about 35%, less than or equal to about 30%, less than or equal to about 25%, or less than or equal to about 20%. In some embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness), the first layer depth and / or the second layer depth can be in the following ranges: 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 sub-range therebetween. In other embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness), the first layer depth of the one or more alkali metal ions and / or the second layer depth of the one or more alkali metal ions can be less than or equal to about 10%, 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 sub-range therebetween. In some embodiments, the first layer depth of the one or more alkali metal ions and / or the second layer depth of the one or more alkali metal ions may be greater than or equal to about 1 μm, greater than or equal to about 10 μm, greater than or equal to about 30 μm, greater than or equal to about 50 μm, less than or equal to about 200 μm, less than or equal to about 150 μm, less than or equal to about 100 μm, or less than or equal to about 60 μm. In some embodiments, the first layer depth of the one or more alkali metal ions and / or the second layer depth of the one or more alkali metal ions may be in the range of about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 10 μm to about 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 sub-range therebetween.

[0210] In some embodiments, the first portion 221 may include a first tensile stress region. In some embodiments, the first tensile stress region may be located between the first compressive stress region and the second compressive stress region. In some embodiments, the first tensile stress region may include a first maximum tensile stress. In other embodiments, the first maximum tensile stress may be greater than or equal to about 10 MPa, greater than or equal to about 20 MPa, greater than or equal to about 30 MPa, less than or equal to about 100 MPa, less than or equal to about 80 MPa, or less than or equal to about 60 MPa. In other embodiments, the first maximum tensile stress may be in the range of about 10 MPa to about 100 MPa, about 10 MPa to about 80 MPa, about 10 MPa to about 60 MPa, about 20 MPa to about 100 MPa, about 20 MPa to about 80 MPa, about 20 MPa to about 60 MPa, about 30 MPa to about 100 MPa, about 30 MPa to about 80 MPa, about 30 MPa to about 60 MPa, or any range or sub-range therebetween. By providing a first maximum tensile stress of about 10 MPa to about 100 MPa, excellent impact resistance and / or puncture resistance can be achieved while providing low energy to fracture, as described below.

[0211] In some embodiments, the first portion 221 may include a first average concentration of potassium based on an oxide. As used herein, "based on an oxide" means that the measurement of a component is calculated as if the non-oxygen component in the compound is converted into a specified oxide form or, if a specified oxide is not specified, into a fully oxidized oxide. For example, sodium (Na) based on an oxide refers to the amount in terms of sodium oxide (Na2O), while potassium based on an oxide refers to the amount in terms of potassium oxide (K2O). In this way, the component does not need to actually be in the specified oxide form or the fully oxidized oxide form in order for the component to be measured "based on an oxide". Thus, the "based on an oxide" measurement of a specified component includes conceptually converting a substance containing a non-oxygen element of a specified component into a specified oxide form, or, if a specified oxide form is not specified, into a fully oxidized oxide, and then calculating the concentration based on the oxide. In some embodiments, the first average concentration of potassium on an oxide basis can be greater than or equal to about 10 parts per million (10 ppm), greater than or equal to about 50 ppm, greater than or equal to about 200 ppm, greater than or equal to about 500 ppm, greater than or equal to about 1,000 ppm, greater than or equal to about 2,000 ppm, less than or equal to about 300,000, less than or equal to about 100,000 ppm, less than or equal to about 50,000 ppm, less than or equal to about 20,000 ppm, less than or equal to about 10,000 ppm, or less than or equal to about 5,000 ppm. In some embodiments, the first average concentration of potassium on an oxide basis can be in the range of about 10 ppm to about 300,000 ppm, about 50 ppm to about 300,000, about 50 ppm to about 100,000, about 200 ppm to about 100,000, about 200 ppm to about 50,000 ppm, about 500 ppm to about 50,000, about 500 ppm to about 20,000 ppm, about 1,000 ppm to about 20,000 ppm, about 2,000 ppm to about 10,000 ppm, about 2,000 ppm to about 5,000 ppm, or any range or sub-range therebetween. Without wishing to be bound by theory, the average concentration of potassium includes potassium introduced by chemical strengthening and potassium in the foldable substrate as it is formed.

[0212] In some embodiments, the second portion 231 including the second glass-based and / or ceramic-based portion may include a third compressive stress region at a third surface region 233, which may extend from the third surface region 233 to a third compression depth. In some embodiments, the second portion 231 including the second glass-based and / or ceramic-based portion may include a fourth compressive stress region at a fourth surface region 235, which may extend from the fourth surface region 235 to a fourth compression depth. In some embodiments, as a percentage of the substrate thickness 227 (e.g., the second thickness 237), the third compression depth and / or the fourth compression depth may be greater than or equal to about 1%, greater than or equal to about 5%, greater than or equal to about 10%, less than or equal to about 30%, less than or equal to about 25%, or less than or equal to about 20%. In some embodiments, as a percentage of the substrate thickness 227 (e.g., the second thickness 237), the third compression depth and / or the fourth 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 sub-range therebetween. In other embodiments, the third compression depth may be substantially equal to the fourth compression depth. In some embodiments, the third compression depth and / or the fourth compression depth may be greater than or equal to about 1 μm, greater than or equal to about 10 μm, greater than or equal to about 30 μm, greater than or equal to about 50 μm, less than or equal to about 200 μm, less than or equal to about 150 μm, less than or equal to about 100 μm, or less than or equal to about 60 μm. In some embodiments, the third compression depth and / or the fourth compression depth may be in the range of about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 10 μm to about 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 sub-range therebetween. Excellent impact resistance and / or puncture resistance may be obtained by providing a second portion comprising a glass-based and / or ceramic-based portion, and the second portion comprising a third compression depth and / or a fourth compression depth of about 1% to about 30% of the thickness of the substrate.

[0213] In some embodiments, the third compressive stress region may include a third maximum compressive stress. In some embodiments, the fourth compressive stress region may include a fourth maximum compressive stress. In other embodiments, the third maximum compressive stress and / or the fourth maximum compressive stress may be greater than or equal to about 100 megapascals (MPa), greater than or equal to about 300 MPa, greater than or equal to about 500 MPa, greater than or equal to about 600 MPa, greater than or equal to about 700 MPa, less than or equal to about 1,500 MPa, less than or equal to about 1,200 MPa, less than or equal to about 1,000 MPa, or less than or equal to about 800 MPa. In other embodiments, the third maximum compressive stress and / or the fourth maximum compressive stress may be in the range of about 100 MPa to about 1,500 MPa, about 100 MPa to about 1,200 MPa, about 300 MPa to about 1,200 MPa, about 300 MPa to about 1,000 MPa, about 500 MPa to about 1,000 MPa, about 600 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, or any range or sub-range therebetween. By providing a third maximum compressive stress and / or a fourth maximum compressive stress of about 100 MPa to about 1,500 MPa, excellent impact resistance and / or puncture resistance may be achieved.

[0214] In some embodiments, the second portion 231 may include a third layer depth of one or more alkali metal ions, the one or more alkali metal ions being associated with a third compressive stress region and the third layer depth. In some embodiments, the second portion 231 may include a fourth layer depth of one or more alkali metal ions, the one or more alkali metal ions being associated with a fourth compressive stress region and a fourth compression depth. In some embodiments, the one or more alkali metal ions in the third layer depth of the one or more alkali metal ions and / or the one or more alkali metal ions in the fourth layer depth include potassium. In some embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness, the second thickness 237), the third layer depth and / or the fourth layer depth may be greater than or equal to about 1%, greater than or equal to about 5%, greater than or equal to about 10%, less than or equal to about 40%, less than or equal to about 35%, less than or equal to about 30%, less than or equal to about 25%, or less than or equal to about 20%. In some embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness, the second thickness 237), the third compression depth and / or the fourth compression depth may be in the following ranges: 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 sub-range therebetween. In other embodiments, as a percentage of the substrate thickness 227 (e.g., the first thickness, the second thickness 237), the third layer depth of the one or more alkali metal ions and / or the fourth layer depth of the one or more alkali metal ions may be less than or equal to about 10%, 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 sub-range therebetween. In some embodiments, the third layer depth of the one or more alkali metal ions and / or the fourth layer depth of the one or more alkali metal ions may be greater than or equal to about 1 μm, greater than or equal to about 10 μm, greater than or equal to about 30 μm, greater than or equal to about 50 μm, less than or equal to about 200 μm, less than or equal to about 150 μm, less than or equal to about 100 μm, or less than or equal to about 60 μm. In some embodiments, the third layer depth of the one or more alkali metal ions and / or the fourth layer depth of the one or more alkali metal ions may be in the following ranges: 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 sub-range therebetween.

[0215] In some embodiments, the second portion 231 may include a second tensile stress region. In some embodiments, the second tensile stress region may be located between the third compressive stress region and the fourth compressive stress region. In some embodiments, the second compressive stress region may include a second maximum tensile stress. In other embodiments, the second maximum tensile stress may be greater than or equal to about 10 MPa, greater than or equal to about 20 MPa, greater than or equal to about 30 MPa, less than or equal to about 100 MPa, less than or equal to about 80 MPa, or less than or equal to about 60 MPa. In other embodiments, the second maximum tensile stress may be in the range of about 10 MPa to about 100 MPa, about 10 MPa to about 80 MPa, about 10 MPa to about 60 MPa, about 20 MPa to about 100 MPa, about 20 MPa to about 80 MPa, about 20 MPa to about 60 MPa, about 30 MPa to about 100 MPa, about 30 MPa to about 80 MPa, about 30 MPa to about 60 MPa, or any range or sub-range therebetween. Providing a second maximum tensile stress of about 10 MPa to about 100 MPa can achieve excellent impact resistance and / or puncture resistance while providing low energy to fracture, as described below.

[0216] In some embodiments, the second portion 231 can include a second average concentration of potassium on an oxide basis. In some embodiments, the second average concentration of potassium on an oxide basis can be greater than or equal to about 10 parts per million (10 ppm), greater than or equal to about 50 ppm, greater than or equal to about 200 ppm, greater than or equal to about 500 ppm, greater than or equal to about 1,000 ppm, greater than or equal to about 2,000 ppm, less than or equal to about 300,000, less than or equal to about 100,000 ppm, less than or equal to about 50,000 ppm, less than or equal to about 20,000 ppm, less than or equal to about 10,000 ppm, or less than or equal to about 5,000 ppm. In some embodiments, the second average concentration of potassium on an oxide basis may be in the range of about 10 ppm to about 300,000 ppm, about 50 ppm to about 300,000, about 50 ppm to about 100,000, about 200 ppm to about 100,000, about 200 ppm to about 50,000 ppm, about 500 ppm to about 50,000, about 500 ppm to about 20,000 ppm, about 1,000 ppm to about 20,000 ppm, about 2,000 ppm to about 10,000 ppm, about 2,000 ppm to about 5,000 ppm, or any range or sub-range therebetween.

[0217] In some embodiments, the first compression depth may be substantially equal to the third compression depth. In some embodiments, the second compression depth may be substantially equal to the fourth compression depth. In some embodiments, the first maximum compressive stress may be substantially equal to the third maximum compressive stress. In some embodiments, the second maximum compressive stress may be substantially equal to the fourth maximum compressive stress. In some embodiments, the first layer depth of one or more alkali metal ions may be substantially equal to the third layer depth of one or more alkali metal ions. In some embodiments, the second layer depth of one or more alkali metal ions may be substantially equal to the fourth layer depth of one or more alkali metal ions. In some embodiments, the first average concentration of potassium may be substantially equal to the second average concentration of potassium.

[0218] In some embodiments, the central portion 251 including a glass-based portion and / or a ceramic-based portion may include a first central compressive stress region at a first central surface region 209, which may extend from the first central surface region 209 to a first central compressive depth. In some embodiments, the central portion 251 including a glass-based portion and / or a ceramic-based portion may include a second central compressive stress region at a second central surface region 213, which may extend from the second central surface region 213 to a second central compressive depth. In some embodiments, as a percentage of the central thickness 217, the first central compressive depth and / or the second central compressive depth may be greater than or equal to about 1%, greater than or equal to about 5%, greater than or equal to about 10%, less than or equal to about 30%, less than or equal to about 25%, or less than or equal to about 20%. In some embodiments, the first central compression depth and / or the second central 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 sub-range therebetween, as a percentage of the central thickness 217. In other embodiments, the first central compression depth and / or the second central compression depth may be greater than or equal to about 10%, 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 sub-range therebetween, as a percentage of the central thickness 217.

[0219] In other embodiments, the first central compression depth may be substantially equal to the second central compression depth. In some embodiments, the first central compression depth and / or the second central compression depth may be greater than or equal to about 1 μm, greater than or equal to about 10 μm, greater than or equal to about 30 μm, greater than or equal to about 50 μm, less than or equal to about 200 μm, less than or equal to about 150 μm, less than or equal to about 100 μm, or less than or equal to about 60 μm. In some embodiments, the first central compression depth and / or the second central compression depth may be in the range of about 1 μm to about 200 μm, about 1 μm to about 150 μm, about 10 μm to about 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 sub-range therebetween. Excellent impact resistance and / or puncture resistance can be achieved by providing a center portion comprising a glass-based and / or ceramic-based portion, and the center portion includes a first center compression depth and / or a second center compression depth of about 1% to about 30% of the center thickness.

[0220] In some embodiments, the first central compressive stress region may include a first central maximum compressive stress. In some embodiments, the second central compressive stress region may include a second central maximum compressive stress. In other embodiments, the first central maximum compressive stress and / or the second central maximum compressive stress may be greater than or equal to about 100 megapascals (MPa), greater than or equal to about 300 MPa, greater than or equal to about 500 MPa, greater than or equal to about 600 MPa, greater than or equal to about 700 MPa, less than or equal to about 1,500 MPa, less than or equal to about 1,200 MPa, less than or equal to about 1,000 MPa, or less than or equal to about 800 MPa. In other embodiments, the first central maximum compressive stress and / or the second central maximum compressive stress may be in the range of about 100 MPa to about 1,500 MPa, about 100 MPa to about 1,200 MPa, about 300 MPa to about 1,200 MPa, about 300 MPa to about 1,000 MPa, about 500 MPa to about 1,000 MPa, about 600 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, or any range or sub-range therebetween. By providing a first central maximum compressive stress and / or a second central maximum compressive stress of about 100 MPa to about 1,500 MPa, excellent impact resistance and / or puncture resistance may be achieved.

[0221] In some embodiments, the center portion 251 may include a first center layer depth of one or more alkali metal ions, the one or more alkali metal ions being associated with the first center compressive stress region and the first center layer depth. In some embodiments, the center portion 251 may include a second center layer depth of one or more alkali metal ions, the one or more alkali metal ions being associated with the second center compressive stress region and the second center layer depth. In some embodiments, the one or more alkali metal ions in the first center layer depth of the one or more alkali metal ions and / or the second center layer depth of the one or more alkali metal ions include potassium. In some embodiments, as a percentage of the center thickness 217, the first center layer depth and / or the second center layer depth may be greater than or equal to about 1%, greater than or equal to about 5%, greater than or equal to about 10%, less than or equal to about 40%, less than or equal to about 35%, less than or equal to about 30%, less than or equal to about 25%, or less than or equal to about 20%. In some embodiments, as a percentage of the center thickness 217, the first center layer depth and / or the second center layer depth may be in the following ranges: 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 sub-range therebetween. In other embodiments, as a percentage of the center thickness 217, the first center layer depth of the one or more alkali metal ions and / or the second center layer depth of the one or more alkali metal ions may be less than or equal to about 10%, 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 sub-range therebetween. In some embodiments, the first center layer depth of the one or more alkali metal ions and / or the second center layer depth of the one or more alkali metal ions may be greater than or equal to about 1 μm, greater than or equal to about 10 μm, greater than or equal to about 30 μm, greater than or equal to about 50 μm, less than or equal to about 200 μm, less than or equal to about 150 μm, less than or equal to about 100 μm, or less than or equal to about 60 μm. In some embodiments, the first center layer depth of the one or more alkali metal ions and / or the second center layer depth of the one or more alkali metal ions may be in the following ranges: 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 sub-range therebetween.

[0222] In some embodiments, the first compression depth and / or the third compression depth can be greater than the first central compression depth. In some embodiments, the second compression depth and / or the fourth compression depth can be greater than the second central compression depth. In some embodiments, the first layer depth and / or the third layer depth can be greater than the first central layer depth. In some embodiments, the second layer depth and / or the fourth layer depth can be greater than the second central compression depth.

[0223] In some embodiments, the central portion 251 may include a central tensile stress region. In some embodiments, the central tensile stress region may be located between the first central compressive stress region and the second central compressive stress region. In some embodiments, the central tensile stress region may include a central maximum tensile stress. In other embodiments, the central maximum tensile stress may be greater than or equal to about 125 MPa, greater than or equal to about 150 MPa, greater than or equal to about 200 MPa, less than or equal to about 375 MPa, less than or equal to about 300 MPa, or less than or equal to about 250 MPa. In other embodiments, the center maximum tensile stress can be in the range of about 125 MPa to about 375 MPa, about 125 MPa to about 300 MPa, about 125 MPa to about 250 MPa, about 150 MPa to about 375 MPa, about 150 MPa to about 300 MPa, about 150 MPa to about 250 MPa, about 200 MPa to about 375 MPa, about 200 MPa to about 300 MPa, about 200 MPa to about 250 MPa, or any range or sub-range therebetween. Providing a center maximum tensile stress of about 125 MPa to about 375 MPa enables a low minimum bend radius to be achieved.

[0224] In some embodiments, the first maximum tensile stress and the second maximum tensile stress may be less than the center maximum tensile stress. Providing a first maximum tensile stress and a second maximum tensile stress that are less than the center maximum tensile stress in the center portion can achieve low energy fracture while achieving a lower minimum bending radius. In other embodiments, the first compression depth can be substantially equal to the first center compression depth. In other embodiments, the third compression depth can be substantially equal to the first center compression depth. In other embodiments, the second compression depth can be substantially equal to the second center compression depth. In other embodiments, the fourth compression depth can be substantially equal to the second center compression depth. As described above, the center thickness can be less than the substrate thickness (e.g., in the range of about 0.5% to about 13%), which can make the center maximum center tension greater than the first maximum center tension and the second maximum center tension, even if the compression depths of the first portion, the second portion, and the center portion can be substantially the same.

[0225] In some embodiments, the second portion 251 can include a central average concentration of potassium on an oxide basis. In some embodiments, the central average concentration of potassium on an oxide basis can be greater than or equal to about 10 parts per million (10 ppm), greater than or equal to about 50 ppm, greater than or equal to about 200 ppm, greater than or equal to about 500 ppm, greater than or equal to about 1,000 ppm, greater than or equal to about 2,000 ppm, less than or equal to about 300,000, less than or equal to about 100,000 ppm, less than or equal to about 50,000 ppm, less than or equal to about 20,000 ppm, less than or equal to about 10,000 ppm, or less than or equal to about 5,000 ppm. In some embodiments, the center average concentration of potassium on an oxide basis may be in the range of about 10 ppm to about 300,000 ppm, about 50 ppm to about 300,000, about 50 ppm to about 100,000, about 200 ppm to about 100,000, about 200 ppm to about 50,000 ppm, about 500 ppm to about 50,000, about 500 ppm to about 20,000 ppm, about 1,000 ppm to about 20,000 ppm, about 2,000 ppm to about 10,000 ppm, about 2,000 ppm to about 5,000 ppm, or any range or sub-range therebetween.

[0226] A foldable substrate (e.g., foldable substrate 201) may be subject to various types of mechanical instabilities. Throughout this disclosure, mechanical instabilities include local mechanical instabilities and systemic mechanical instabilities. As used herein, local mechanical instabilities refer to deviations (e.g., multiple deviations) from the plane of a surface (e.g., a first central surface area), but the surface as a whole is not distorted, such as buckling and / or wrinkling. As used herein, systemic mechanical instabilities refer to distortions of the entire surface from a plane, such as warping. Fig.43 As shown, a central axis 4301 (eg, x-axis) includes a central thickness (eg, central thickness 217 ), and a vertical axis 4303 (eg, y-axis) includes substrate thicknesses (eg, first thickness, second thickness 237 ). Fig.43The shapes plotted correspond to the type of mechanical instability observed for the center thickness and substrate thickness at that location. Diamond 4309 corresponds to buckling. Circle 4307 corresponds to buckling and wrinkling. Triangle 4313 corresponds to warping and wrinkling. Square 4311 corresponds to warping. Curves 4304 and 4305 distinguish combinations of center thickness and substrate thickness for which only widespread instability (e.g., warping) occurs from combinations for which localized instability occurs. Curve 4305 is a line indicating localized instability that may be observed when the substrate thickness is greater than about 4 times the center thickness minus 71 microns. More specifically, curve 4305 is a line indicating localized instability that may be observed when the substrate thickness is greater than about 4.1 times the center thickness minus 71.37 microns. Curves 4304 and 4305 indicate that some instabilities (e.g., local mechanical instabilities) encountered by thinner foldable substrates (e.g., above curves 4304 and / or 4305) may be different from instabilities encountered by thicker foldable substrates (e.g., below curves 4304 and / or 4305).

[0227] When a critical strain (e.g., a critical buckling strain) of a portion (e.g., a central portion) of the foldable substrate is exceeded, the onset of mechanical instability (e.g., a local mechanical instability) may occur. Figure 3 For the foldable substrate 201 shown in FIG. 20, where the width 252 of the central portion 251 is 20 mm, the critical buckling strain of the central portion can be approximately 10 times the square of the central thickness. 6 times the center thickness minus 23 times the center thickness plus 0.0006. For example, without wishing to be bound by theory, something like Figure 3 For a foldable substrate 201 with a central thickness 217 of 30 μm, the critical buckling strain of the central portion can be approximately 3x10 -7 Divided by the square of the width 252 of the central portion 251 .

[0228] The chemical strengthening induced compressive strain of the central portion of the foldable substrate obtained by chemically strengthening the foldable substrate can be proportional to the product of the network expansion coefficient (B), the concentration difference (C), and the difference between the layer depth of the central portion divided by the central thickness and the layer depth of the first portion (or the second portion) divided by the substrate thickness. In some embodiments, the compressive strain of the chemical strengthening induced compressive strain of the central portion can be reduced (e.g., reduced to a level below the critical buckling strain) by minimizing the concentration difference and / or minimizing the difference between the layer depth of the central portion divided by the central thickness and the layer depth of the first portion (or the second portion) divided by the substrate thickness. As used herein, the network expansion coefficient refers to how much the volume of the foldable substrate (e.g., the first portion, the second portion, the central portion) expands due to an increase in the concentration of one or more alkali metal ions (e.g., due to chemical strengthening). In some embodiments, the network expansion constant of the first portion and / or the network expansion constant of the second portion can be substantially equal to the network expansion constant of the central portion, for example, if the first portion and / or the second portion and the central portion all include the same material before chemical strengthening.

[0229] As used herein, the concentration difference of a portion refers to the difference between the concentration at the surface of the portion and the concentration in the body of the portion. Unless otherwise indicated, the concentration and concentration difference refer to the concentration of one or more alkali metal ions associated with chemical strengthening and / or compressive stress zones. In some embodiments, the concentration and / or concentration difference may refer to the concentration of potassium based on oxide. In some embodiments, the concentration of the body of the first portion and / or the concentration of the body of the second portion may be substantially equal to the concentration of the body of the central portion, for example, if the first portion and / or the second portion and the central portion include the same material before chemical strengthening, and / or if the layer depth of a portion is less than about 45% of the thickness of the corresponding portion. In some embodiments, the first average concentration of potassium in oxides of the first portion may be greater than the potassium concentration in oxides in the body of the first portion. In some embodiments, the second average concentration of potassium in oxides of the second portion may be greater than the potassium concentration in oxides in the body of the second portion. In some embodiments, the central average concentration of potassium in oxides of the central portion may be greater than the potassium concentration in oxides in the body of the central portion.

[0230] As used herein, the concentration difference between the portions means the difference between an average concentration and another average concentration. Unless otherwise indicated, concentrations and concentration differences refer to the concentration of one or more alkali metal ions associated with chemical strengthening and / or compressive stress zones. In some embodiments, concentrations and / or concentration differences may refer to the concentration of potassium based on oxides. In some embodiments, the absolute difference between the first average concentration of potassium based on oxides and the central average concentration of potassium based on oxides may be greater than or equal to about 1 ppm, greater than or equal to about 10 ppm, greater than or equal to about 20 ppm, greater than or equal to about 50 ppm, about 70 ppm, less than or equal to about 500 ppm, less than or equal to about 200 ppm, less than or equal to about 100 ppm, or less than or equal to about 85 ppm. In some embodiments, the absolute difference between the first average concentration of potassium on an oxide basis and the central average concentration of potassium on an oxide basis can be in the range of about 1 ppm to about 500 ppm, about 10 ppm to about 500 ppm, about 10 ppm to about 200 ppm, about 20 ppm to about 200 ppm, about 20 ppm to about 100 ppm, about 50 ppm to about 100 ppm, about 70 ppm to about 100 ppm, about 70 ppm to about 85 ppm, or any range or sub-range therebetween. In some embodiments, the absolute difference between the second average concentration of potassium on an oxide basis and the central average concentration of potassium on an oxide basis can be greater than or equal to about 1 ppm, greater than or equal to about 10 ppm, greater than or equal to about 20 ppm, greater than or equal to about 50 ppm, about 70 ppm, less than or equal to about 500 ppm, less than or equal to about 200 ppm, less than or equal to about 100 ppm, or less than or equal to about 85 ppm. In some embodiments, the absolute difference between the second average concentration of potassium on an oxide basis and the central average concentration of potassium on an oxide basis can be in the range of about 1 ppm to about 500 ppm, about 10 ppm to about 500 ppm, about 10 ppm to about 200 ppm, about 20 ppm to about 200 ppm, about 20 ppm to about 100 ppm, about 50 ppm to about 100 ppm, about 70 ppm to about 100 ppm, about 70 ppm to about 85 ppm, or any range or sub-range therebetween. For example, for a foldable substrate comprising a central thickness of 30 μm and a central width of 20 mm, the chemical strengthening-induced strain can be less than the critical buckling strain when the absolute difference in the average concentration difference is less than or equal to about 75 ppm.In some embodiments, the absolute difference between the first average concentration of potassium based on oxide and the central average concentration of potassium based on oxide may be less than 70 ppm, for example, in the range of about 0.1 ppm to about 50 ppm, about 0.1 ppm to about 20 ppm, about 0.5 ppm to about 20 ppm, about 0.5 ppm to about 10 ppm, about 1 ppm to about 10 ppm, about 5 ppm to about 10 ppm, or any range or sub-range therebetween. In some embodiments, the absolute difference between the second average concentration of potassium based on oxide and the central average concentration of potassium based on oxide may be less than 70 ppm, for example, in the range of about 0.1 ppm to about 60 ppm, about 0.1 ppm to about 50 ppm, about 0.1 ppm to about 40 ppm, about 0.1 ppm to about 30 ppm, about 0.1 ppm to about 20 ppm, about 0.5 ppm to about 20 ppm, about 0.5 ppm to about 10 ppm, about 1 ppm to about 10 ppm, about 5 ppm to about 10 ppm, or any range or sub-range therebetween. Providing an absolute difference between the first average concentration and / or the second average concentration of potassium as oxide and the central average concentration can provide reduced chemical strengthening induced strain (e.g., below the critical buckling strain) and / or reduce the occurrence of mechanical instability in the foldable substrate and / or foldable device.

[0231] In some embodiments, the absolute difference between the first layer depth divided by the substrate thickness and the first center layer depth divided by the center thickness may be greater than or equal to about 0.001%, greater than or equal to about 0.002%, greater than or equal to about 0.005%, less than or equal to about 1%, less than or equal to about 0.2%, less than or equal to about 0.1%, or less than or equal to about 0.05%, less than or equal to about 0.01%, or less than or equal to about 0.008%. In some embodiments, the absolute difference between the first layer depth divided by the substrate thickness and the center layer depth divided by the center thickness can be in the range of about 0.001% to about 1%, about 0.002% to about 1%, about 0.002% to about 0.2%, about 0.005% to about 0.2%, about 0.005% to about 0.1%, about 0.005% to about 0.1%, about 0.005% to about 0.05%, about 0.005% to about 0.01%, about 0.005% to about 0.008%, or any range or sub-range therebetween. In some embodiments, the absolute difference between the third layer depth divided by the substrate thickness and the first center layer depth divided by the center thickness may be greater than or equal to about 0.001%, greater than or equal to about 0.002%, greater than or equal to about 0.005%, less than or equal to about 1%, less than or equal to about 0.2%, less than or equal to about 0.1%, or less than or equal to about 0.05%, less than or equal to about 0.01%, or less than or equal to about 0.008%. In some embodiments, the absolute difference between the third layer depth divided by the substrate thickness and the first center layer depth divided by the center thickness can be in the following range: about 0.001% to about 1%, about 0.002% to about 1%, about 0.002% to about 0.2%, about 0.005% to about 0.2%, about 0.005% to about 0.1%, about 0.005% to about 0.1%, about 0.005% to about 0.05%, about 0.005% to about 0.01%, about 0.005% to about 0.008%, or any range or sub-range therebetween.

[0232] In some embodiments, the absolute difference between the second layer depth divided by the substrate thickness and the second center layer depth divided by the center thickness may be greater than or equal to about 0.001%, greater than or equal to about 0.002%, greater than or equal to about 0.005%, less than or equal to about 1%, less than or equal to about 0.2%, less than or equal to about 0.1%, or less than or equal to about 0.05%, less than or equal to about 0.01%, or less than or equal to about 0.008%. In some embodiments, the absolute difference between the second layer depth divided by the substrate thickness and the second center layer depth divided by the center thickness can be in the range of about 0.001% to about 1%, about 0.002% to about 1%, about 0.002% to about 0.2%, about 0.005% to about 0.2%, about 0.005% to about 0.1%, about 0.005% to about 0.1%, about 0.005% to about 0.05%, about 0.005% to about 0.01%, about 0.005% to about 0.008%, or any range or sub-range therebetween. In some embodiments, the absolute difference between the fourth layer depth divided by the substrate thickness and the second center layer depth divided by the center thickness may be greater than or equal to about 0.001%, greater than or equal to about 0.002%, greater than or equal to about 0.005%, less than or equal to about 1%, less than or equal to about 0.2%, less than or equal to about 0.1%, or less than or equal to about 0.05%, less than or equal to about 0.01%, or less than or equal to about 0.008%. In some embodiments, the absolute difference between the fourth layer depth divided by the substrate thickness and the second center layer depth divided by the center thickness can be in the range of about 0.001% to about 1%, about 0.002% to about 1%, about 0.002% to about 0.2%, about 0.005% to about 0.2%, about 0.005% to about 0.1%, about 0.005% to about 0.1%, about 0.005% to about 0.05%, about 0.005% to about 0.01%, about 0.005% to about 0.008%, or any range or sub-range therebetween. For example, for a foldable substrate comprising a center thickness of 30 μm and a center width of 20 mm, the chemical strengthening induced strain can be less than the critical buckling strain when the absolute difference between the layer depth associated with the first portion or the second portion divided by the substrate thickness and the layer depth associated with the center portion divided by the center thickness is less than or equal to about 0.075%. In some embodiments, the absolute difference between one of the first layer depth, the second layer depth, the third layer depth, or the fourth layer depth divided by the substrate thickness and the first center layer depth or the second center layer depth divided by the center thickness may be less than 0.07%, for example, within the following ranges: about 0.001% to about 0.07%, about 0.01% to about 0.07%, about 0.01% to about 0.05%, about 0.01% to about 0.02%, or any range or sub-range therebetween.Providing an absolute difference between the first layer depth, the second layer depth, the third layer depth and / or the fourth layer depth divided by the substrate thickness and the first center layer depth and / or the second center layer depth divided by the center thickness (e.g., the layer depth of potassium) can provide reduced chemical strengthening induced strain (e.g., below the critical buckling strain) and / or reduce the occurrence of mechanical instability in a foldable substrate and / or foldable device.

[0233] The compression depth may be proportional to the corresponding layer depth. In some embodiments, the absolute difference between the first compression depth divided by the substrate thickness and the first center compression depth divided by the center thickness may be greater than or equal to about 0.001%, greater than or equal to about 0.002%, greater than or equal to about 0.005%, less than or equal to about 1%, less than or equal to about 0.2%, less than or equal to about 0.1%, or less than or equal to about 0.05%, less than or equal to about 0.01%, or less than or equal to about 0.008%. In some embodiments, the absolute difference between the first compression depth divided by the substrate thickness and the first center compression depth divided by the center thickness can be in the range of about 0.001% to about 1%, about 0.002% to about 1%, about 0.002% to about 0.2%, about 0.005% to about 0.2%, about 0.005% to about 0.1%, about 0.005% to about 0.1%, about 0.005% to about 0.05%, about 0.005% to about 0.01%, about 0.005% to about 0.008%, or any range or sub-range therebetween. In some embodiments, the absolute difference between the third compression depth divided by the substrate thickness and the first center compression depth divided by the center thickness may be greater than or equal to about 0.001%, greater than or equal to about 0.002%, greater than or equal to about 0.005%, less than or equal to about 1%, less than or equal to about 0.2%, less than or equal to about 0.1%, or less than or equal to about 0.05%, less than or equal to about 0.01%, or less than or equal to about 0.008%. In some embodiments, the absolute difference between the third compression depth divided by the substrate thickness and the first center compression depth divided by the center thickness can be in the range of about 0.001% to about 1%, about 0.002% to about 1%, about 0.002% to about 0.2%, about 0.005% to about 0.2%, about 0.005% to about 0.1%, about 0.005% to about 0.1%, about 0.005% to about 0.05%, about 0.005% to about 0.01%, about 0.005% to about 0.008%, or any range or sub-range therebetween.

[0234] In some embodiments, the absolute difference between the second compression depth divided by the substrate thickness and the second center compression depth divided by the center thickness may be greater than or equal to about 0.001%, greater than or equal to about 0.002%, greater than or equal to about 0.005%, less than or equal to about 1%, less than or equal to about 0.2%, less than or equal to about 0.1%, or less than or equal to about 0.05%, less than or equal to about 0.01%, or less than or equal to about 0.008%. In some embodiments, the absolute difference between the second compression depth divided by the substrate thickness and the second center compression depth divided by the center thickness can be in the range of about 0.001% to about 1%, about 0.002% to about 1%, about 0.002% to about 0.2%, about 0.005% to about 0.2%, about 0.005% to about 0.1%, about 0.005% to about 0.1%, about 0.005% to about 0.05%, about 0.005% to about 0.01%, about 0.005% to about 0.008%, or any range or sub-range therebetween. In some embodiments, the absolute difference between the fourth compression depth divided by the substrate thickness and the second center compression depth divided by the center thickness may be greater than or equal to about 0.001%, greater than or equal to about 0.002%, greater than or equal to about 0.005%, less than or equal to about 1%, less than or equal to about 0.2%, less than or equal to about 0.1%, or less than or equal to about 0.05%, less than or equal to about 0.01%, or less than or equal to about 0.008%. In some embodiments, the absolute difference between the fourth compression depth divided by the substrate thickness and the second center compression depth divided by the center thickness can be in the range of about 0.001% to about 1%, about 0.002% to about 1%, about 0.002% to about 0.2%, about 0.005% to about 0.2%, about 0.005% to about 0.1%, about 0.005% to about 0.1%, about 0.005% to about 0.05%, about 0.005% to about 0.01%, about 0.005% to about 0.008%, or any range or sub-range therebetween. For example, for a foldable substrate comprising a center thickness of 30 μm and a center width of 20 mm, the chemical strengthening induced strain can be less than the critical buckling strain when the absolute difference between the compression depth divided by the substrate thickness associated with the first portion or the second portion and the compression depth divided by the center thickness associated with the center portion is less than or equal to about 0.075%. In some embodiments, the absolute difference between one of the first compression depth, the second compression depth, the third compression depth, or the fourth compression depth divided by the substrate thickness and the first center compression depth or the second center compression depth divided by the center thickness may be less than 0.07%, for example, in the following ranges: about 0.001% to about 0.07%, about 0.01% to about 0.07%, about 0.01% to about 0.05%, about 0.01% to about 0.02%, or any range or sub-range therebetween.Providing an absolute difference between the first compression depth, the second compression depth, the third compression depth, and / or the fourth compression depth divided by the substrate thickness and the first center compression depth and / or the second center compression depth divided by the center thickness can provide reduced chemical strengthening induced strain (e.g., below the critical buckling strain) and / or reduce the occurrence of mechanical instability in the foldable substrate and / or foldable device.

[0235] In some embodiments, chemical strengthening induced strain and / or stress may be observed in the optical hysteresis distribution of the foldable substrate. As used herein, the optical hysteresis distribution is measured using a gray-field polarimeter that detects light emitted by a green LED and passed through the foldable substrate, the light comprising a wavelength of light of about 553 nm. Without wishing to be bound by theory, spatial differences in optical hysteresis may correspond to differences in stress (e.g., in-plane strain) in the foldable substrate, for example, stress-induced birefringence. In some embodiments, the optical hysteresis of the central portion along a center line exactly halfway between the first portion and the second portion, the absolute difference between the maximum value of the optical hysteresis along the center line and the minimum value of the optical hysteresis along the center line may be greater than or equal to about 0.1 nm, greater than or equal to about 0.5 nm, greater than or equal to about 1 nm, less than or equal to about 3 nm, less than or equal to about 2 nanometers, or less than or equal to about 1.5 nm. In some embodiments, the absolute difference between the maximum value of the optical retardation along the center line and the minimum value of the optical retardation along the center line can be in the range of about 0.1 nm to about 3 nm, about 0.1 nm to about 2 nm, about 0.5 nm to about 2 nm, about 0.5 to about 1.5 nm, about 1 nm to about 1.5 nm, or any range or sub-range therebetween.

[0236] In some embodiments, the maximum difference between the optical retardation of the central portion 251 and the minimum optical retardation of the first portion 221 and / or the second portion 231 can be greater than or equal to about 0.1 nm, greater than or equal to about 0.5 nm, greater than or equal to about 1 nm, greater than or equal to about 2 nm, greater than or equal to about 3 nm, less than or equal to about 8 nm, less than or equal to about 6 nm, less than or equal to about 5 nm, or less than or equal to about 4 nm. In some embodiments, the maximum difference between the optical retardation of the central portion 251 and the minimum optical retardation of the first portion 221 and / or the second portion 231 can be in the range of about 0.1 nm to about 8 nm, about 0.1 nm to about 6 nm, about 0.5 nm to about 6 nm, about 0.5 nm to about 5 nm, about 1 nm to about 5 nm, about 2 nm to about 5 nm, about 2 nm to about 5 nm, about 2 nm to about 4 nm, or any range or sub-range therebetween. For example, when the maximum difference between the optical retardation of the central portion 251 and the minimum optical retardation of the first portion 221 and / or the second portion 231 is less than or equal to about 4.6 nm, a foldable substrate including a central thickness of about 30 μm can avoid mechanical instability. For example, when the maximum difference between the optical retardation of the central portion 251 and the minimum optical retardation of the first portion 221 and / or the second portion 231 is less than or equal to about 5.9 nm, a foldable substrate including a central thickness of about 40 μm can avoid mechanical instability.

[0237] Fig.44 Schematic diagram showing the optical hysteresis measurement results of a foldable substrate without adhesive, polymer-based portion, release liner, display device and PET sheet. Fig.44, a horizontal axis 4401 (e.g., an x-axis) is a position along a direction 106 of a length 105, and a vertical axis 4403 (e.g., a y-axis) is a position along a direction 104 of a width 103. A region 4411 corresponding to a maximum optical retardation is located in the central portion 251 along an interface between the central portion 251 and the first portion 221 and / or the second portion 231. A region 4409 is adjacent to the region 4411 in the central portion and corresponds to a slightly smaller optical retardation. The central portion 251 between the regions 4411 includes alternating portions of regions 4405 and 4407, wherein the region 4405 includes the lowest optical retardation in the central portion 251, and the region 4407 includes an optical retardation between the optical retardations of the regions 4405 and 4411. The center line will roughly bisect regions 4405 and 4407 (parallel to the vertical axis 2903), and region 4405 includes an optical hysteresis minimum along the center line, while region 4407 includes an optical hysteresis maximum along the center line. Without wishing to be bound by theory, local instabilities may occur when the alternating pattern along the center line is too large. Outside the central portion 251, region 4413 includes a series of portions that roughly correspond to the alternating pattern between regions 4405 and 4407. Region 4413 includes an optical hysteresis similar to that of region 4409. In the first portion 221 and the second portion 231, region 4417 includes the lowest optical hysteresis in the first portion 221 and the second portion 231. Region 4415 includes an optical hysteresis value between the optical hysteresis of regions 4413 and 4417.

[0238] In some embodiments, the polymer base portion 241 can be optically transparent. The polymer base portion 241 may include a first refractive index. The first refractive index can be a function of the wavelength of light passing through the optically transparent adhesive. For light of a first wavelength, the refractive index of a material is defined as the ratio between the speed of light in a vacuum and the speed of light in a corresponding material. Without being limited by theory, the refractive index of an optically transparent adhesive can be determined using the ratio of the sine of a first angle to the sine of a second angle, wherein light of a first wavelength is incident on the surface of the optically transparent adhesive from air at a first angle and refracted at the surface of the optically transparent adhesive, thereby causing the light to propagate within the optically transparent adhesive at a second angle. Both the first angle and the second angle are measured relative to the normal to the surface of the optically transparent adhesive. As used herein, the refractive index is measured according to ASTM E1967-19, wherein the first wavelength includes 589nm. In some embodiments, the first refractive index of the polymer base portion 241 can be greater than or equal to about 1, greater than or equal to about 1.3, greater than or equal to about 1.4, greater than or equal to about 1.45, greater than or equal to about 1.49, less than or equal to about 3, less than or equal to about 2, or less than or equal to about 1.7, less than or equal to about 1.6, or less than or equal to about 1.55. In some embodiments, the first refractive index of the polymer base portion 241 can be in the range of about 1 to about 2, about 1 to about 1.7, about 1.3 to about 1.7, about 1.4 to about 1.7, about 1.4 to about 1.6, about 1.45 to about 1.55, about 1.49 to about 1.55, or any range or sub-range therebetween.

[0239] In some embodiments, the foldable substrate 201 can include a second refractive index. In some embodiments, the second refractive index of the foldable substrate 201 can be greater than or equal to about 1, greater than or equal to about 1.3, greater than or equal to about 1.4, greater than or equal to about 1.45, greater than or equal to about 1.49, less than or equal to about 3, less than or equal to about 2, or less than or equal to about 1.7, less than or equal to about 1.6, or less than or equal to about 1.55. In some embodiments, the second refractive index of the foldable substrate 201 can be in the following range: about 1 to about 3, about 1 to about 2, about 1 to about 1.7, about 1.3 to about 1.7, about 1.4 to about 1.7, about 1.4 to about 1.6, about 1.45 to about 1.55, about 1.49 to about 1.55, or any range or sub-range therebetween. In some embodiments, the difference in the absolute value of the difference between the second refractive index of the foldable substrate 201 and the first refractive index of the polymer base portion 241 can be less than or equal to about 0.1, less than or equal to about 0.07, less than or equal to about 0.05, greater than or equal to about 0.001, greater than or equal to about 0.01, or greater than or equal to about 0.02. In some embodiments, the difference is in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween. In some embodiments, the second refractive index of the foldable substrate 201 can be greater than the first refractive index of the polymer base portion 241. In some embodiments, the second refractive index of foldable substrate 201 can be less than the first refractive index of polymer base portion 241 .

[0240] In some embodiments, adhesive layer 261 may include a third refractive index. In some embodiments, the third refractive index of adhesive layer 261 may be within one or more ranges described above with respect to the first refractive index of polymer base portion 241. In some embodiments, 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 polymer base portion 241 may be less than or equal to about 0.1, less than or equal to about 0.07, less than or equal to about 0.05, greater than or equal to about 0.001, greater than or equal to about 0.01, or greater than or equal to about 0.02. In some embodiments, the difference is in the range of about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween. In some embodiments, the third refractive index of adhesive layer 261 can be greater than the first refractive index of polymer base portion 241. In some embodiments, the third refractive index of adhesive layer 261 can be less than the first refractive index of polymer base portion 241.

[0241] In some embodiments, the difference in absolute value of the difference between the third refractive index of adhesive layer 261 and the second refractive index of foldable substrate 201 can be less than or equal to about 0.1, less than or equal to about 0.07, less than or equal to about 0.05, greater than or equal to about 0.001, greater than or equal to about 0.01, or greater than or equal to about 0.02. In some embodiments, the difference is in the following range: about 0.001 to about 0.1, about 0.001 to about 0.07, about 0.001 to about 0.05, about 0.01 to about 0.1, about 0.01 to about 0.07, about 0.01 to about 0.05, about 0.02 to about 0.1, about 0.02 to about 0.07, about 0.02 to about 0.05, or any range or sub-range therebetween. In some embodiments, the third refractive index of adhesive layer 261 can be greater than the second refractive index of foldable substrate 201. In some embodiments, the third refractive index of adhesive layer 261 can be less than the second refractive index of foldable substrate 201 .

[0242] The foldable device and / or foldable substrate may have a failure mode that can be described as a low energy failure or a high energy failure. Figure 5The failure mode of the foldable substrate is measured using a parallel plate device 501 of the invention. As described below with respect to the effective minimum bending radius, the parallel rigid stainless steel plates 503, 505 are moved together at a rate of 50 μm / second until a target parallel plate distance 507 is achieved. The target parallel plate distance 507 is the greater of twice the effective minimum bending radius of the foldable device and / or the foldable substrate or 4 mm. Next, a tungsten carbide sharp contact probe impacts the foldable substrate 201 at an impact position 511, which is a distance 509 of 30 mm from the outermost periphery of the foldable substrate 201. As used herein, if during the fracture, particles are ejected from the foldable substrate 201 at a speed greater than or equal to 1 meter / second (m / s), and the fracture results in more than 2 crack branches, the fracture is high energy. As used herein, if the fracture results in less than or equal to 2 crack branches, or during the fracture, particles are not ejected from the foldable substrate 201 at a speed greater than or equal to 1 m / s, the fracture is low energy. The average velocity of the ejected particles can be measured by capturing a high-speed video of the foldable device from the time a sharp contact probe touches the impact location until 5,000 microseconds later.

[0243] Figure 4 and 6 -7 schematically illustrates some embodiments of the test folding device 602 and / or the foldable devices 101 and 301 in a folded configuration according to embodiments of the present disclosure. Figure 6 As shown, the test device 602 is folded so that the second major surface 205 of the foldable substrate 201 is on the inner side of the folded test foldable device 602. Figure 6 In the folded configuration shown, the user will view the display device 307 through the foldable substrate 201 instead of the PET sheet 607, and therefore, the user will be on one side of the second major surface 205. Figure 7 As shown, the foldable device 301 is folded such that the second major surface 205 of the foldable substrate 201 is on the outside of the folded foldable device 301. Figure 7 In the folded configuration, the user will view the display device 307 through the foldable substrate 201, and therefore, the user will be on the side of the second major surface 205. In some embodiments, although not shown in the folded configuration, the foldable device may include a coating 281 disposed over the polymer base portion 241 (see Figure 2 ). In other embodiments, the polymer-based portion 241 can be disposed over another substrate (e.g., a glass-based substrate and / or a ceramic-based substrate, rather than over the release liner 271), and the other substrate can be disposed over the display device 307. In other embodiments, the user will view the display device 307 through the coating 281.

[0244] As defined herein, "foldable" includes full folding, partial folding, bending, flexing, and multiple folding capabilities. As used herein, the terms "failure," "failed," and the like refer to breakage, destruction, delamination, or crack propagation. When a foldable device is maintained at an "X" radius at about 85°C and a relative humidity of about 85% for at least 24 hours, if it resists failure, the foldable device achieves an effective bending radius of "X," or has an effective bending radius of "X," or includes an effective bending radius of "X." Similarly, when a foldable device is maintained at a parallel plate distance of "X" at about 85°C and a relative humidity of about 85% for 24 hours, if it resists failure, the foldable device achieves a parallel plate distance of "X," or has a parallel plate distance of "X," or includes a parallel plate distance of "X."

[0245] As used herein, the "effective minimum bending radius" and "parallel plate distance" of a foldable device are described using the parallel plate device 601 (see Figure 6 ) is measured by the following test configuration and process, wherein the parallel plate device 601 includes a pair of parallel rigid stainless steel plates 603, 605, the pair of parallel rigid stainless steel plates 603, 605 including a first rigid stainless steel plate 603 and a second rigid stainless steel plate 605. When measuring the "effective minimum bending radius" or "parallel plate distance", the test adhesive layer 609 includes a thickness of 50 μm (for example, instead of Figure 2-3 When measuring the "effective minimum bending radius" or "parallel plate distance", a 100 μm thick polyethylene terephthalate (PET) sheet 607 is used instead of Figure 2 Release liner 271 or Figure 3 The measurements were made using the display device 307 shown. Therefore, during the test for determining the "effective minimum bend radius" or "parallel plate distance" of the foldable device configuration, the 100 μm thick sheet of polyethylene terephthalate (PET) 607 was used instead of the 100 μm thick sheet of polyethylene terephthalate (PET) 607. Figure 2 Release liner 271 or Figure 3 The display device 307 shown in the figure is used to produce a test foldable device 602. When preparing the test foldable device 602, Figure 2 The release liner 271 is attached to the first contact surface 263 of the adhesive layer 261 or to the Figure 3 In the same manner as the display device 307 is attached to the first contact surface 263 of the adhesive layer 261, a 100 μm thick sheet of polyethylene terephthalate (PET) 607 is attached to the test adhesive layer 609. To test Figure 3-4 The foldable device 101 and / or 301 may be provided with a test adhesive layer 609 and a sheet 607, which is similar in construction to Figure 6The configuration shown is tested on a test foldable device 602. The test foldable device 602 is placed between the pair of parallel rigid stainless steel plates 603, 605 so that it is similar to Figure 6 In the configuration shown, the foldable substrate 201 will be on the inside of the bend. To determine the "parallel plate distance", reduce the distance between the parallel plates at a rate of 50 μm / second until the parallel plate distance 611 is equal to the "parallel plate distance" to be tested. Next, keep the parallel plates at the "parallel plate distance" to be tested for 24 hours at about 85°C and about 85% relative humidity. As used herein, the "minimum parallel plate distance" is the minimum parallel plate distance that the foldable device can withstand testing without failure under the above conditions and configurations. To determine the "effective minimum bending radius", reduce the distance between the parallel plates at a rate of 50 μm / second until the parallel plate distance 611 is equal to twice the "effective minimum bending radius" to be tested. Next, keep the parallel plates at about 85°C and about 85% relative humidity for 24 hours at twice the effective minimum bending radius to be tested. As used herein, the "effective minimum bending radius" is the minimum effective bending radius that the foldable device can withstand testing without failure under the above conditions and configurations.

[0246] In some embodiments, the foldable device 101 and / or 301 and / or the test foldable device 602 can achieve a parallel plate distance of less than or equal to 200 mm, less than or equal to 100 mm, less than or equal to 50 mm, less than or equal to 20 mm, less than or equal to 10 mm, less than or equal to 5 mm, or less than or equal to 3 mm. In other embodiments, the foldable device 101 and / or 301 and / or the test foldable device 602 can achieve a parallel plate distance of 50 millimeters (mm), or 20 mm, or 10 mm, or 5 mm, or 3 mm. In some embodiments, the foldable device 101 and / or 301 and / or the test foldable device 602 can include a minimum parallel plate distance of less than or equal to about 40 mm, less than or equal to about 20 mm, less than or equal to about 10 mm, less than or equal to about 5 mm, less than or equal to about 3 mm, less than or equal to about 1 mm, greater than or equal to about 1 mm, greater than or equal to about 3 mm, greater than or equal to about 5 mm, or greater than or equal to about 10 mm. In some embodiments, the foldable device 101 and / or 301, the test foldable device 602, and / or the foldable substrate 201 can achieve a parallel plate distance of 20 mm, 18 mm, 15 mm, 4 mm, 12 mm, 10 mm, 8 mm, 6 mm, 5 mm, 4 mm, and / or 3 mm. In some embodiments, the foldable device 101 and / or 301 and / or the test foldable device 602 can include an effective minimum bend radius within the range of about 1 mm to about 100 mm, about 1 mm to about 60 mm, about 1 mm to about 40 mm, about 1 mm to about 20 mm, about 1 mm to about 10 mm, about 1 mm to about 5 mm, about 1 mm to about 3 mm, about 3 mm to about 40 mm, about 3 mm to about 40 mm, about 3 mm to about 20 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 sub-range therebetween. In some embodiments, the foldable device 101 and / or 301, the test foldable device 602, and / or the foldable substrate 201 can achieve an effective bend radius of 10 mm, 9 mm, 8 mm, 7 mm, 6 mm, 5 mm, 4 mm, 3 mm, 2 mm, and / or 1 mm.

[0247] In some embodiments, a width 252 of a central portion 251 of the foldable substrate 201 is defined between the first portion 221 and the second portion 231 in the direction 106 of the length 105. In some embodiments, the width 252 of the central portion 251 of the foldable substrate 201 can extend from the first portion 221 to the second portion 231. Figure 2As shown, if present, the width 252 of the central portion 251 may include the width 254a of the first transition portion 253 and / or the width 254b of the second transition portion 255. In some embodiments, the width 252 of the central portion 251 of the foldable substrate 201 defined between the first portion 221 and the second portion 231 in the direction 106 of the length 105 may be about 2.8 times or more, about 3 times or more, about 4 times or more, about 6 times or less, about 5 times or less, or about 4 times or less of the effective minimum bending radius. In some embodiments, as a multiple of the effective minimum bending radius, the width 252 of the central portion 251 may be in the following ranges: about 2.8 times to about 6 times, about 2.8 times to about 5 times, about 2.8 times to about 4 times, about 3 times to about 6 times, about 3 times to about 5 times, about 3 times to about 4 times, about 4 times to about 6 times, about 4 times to about 5 times, or any range or sub-range therebetween. It should be understood that in some embodiments, the central major surface 211 of the central portion 251 extending along a third plane 204c parallel to the second plane 204b can include a width of about 3 times or greater (e.g., about 3.2 times or greater, about 4.4 times or greater) the effective minimum bending radius (e.g., bending length) to provide reduced stress concentration and damage in the bending area of ​​the foldable device.

[0248] Without wishing to be bound by theory, the length of the curved portion in the circular configuration between the parallel plates can be about 1.6 times the parallel plate distance 507 or 601 (e.g., about 3 times the effective minimum bend radius, about 3.2 times the effective minimum bend radius). In some embodiments, the width 252 of the central portion 251 of the foldable substrate 201. In some embodiments, the width 252 of the central portion 251 of the foldable substrate 201 can be greater than or equal to about 2.8 mm, greater than or equal to about 6 mm, greater than or equal to about 9 mm, less than or equal to about 60 mm, less than or equal to about 40 mm, or less than or equal to about 24 mm. In some embodiments, the width 252 of the central portion 251 of the foldable substrate 201 can be in the range of about 2.8 mm to about 60 mm, about 2.8 mm to about 40 mm, about 2.8 mm to about 24 mm, about 6 mm to about 60 mm, about 6 mm to about 40 mm, about 6 mm to about 24 mm, about 9 mm to about 60 mm, about 9 mm to about 40 mm, about 9 mm to about 24 mm, or any range or sub-range therebetween. By providing a width of the central portion between the first portion and the second portion, folding of the foldable device without failure can be facilitated.

[0249] Without wishing to be bound by theory, the length of the curved portion in the elliptical configuration between the parallel plates can be about 2.2 times the parallel plate distance 507 or 601 (e.g., about 4.4 times the effective minimum bend radius). In some embodiments, the width 232 of the central portion 251 of the foldable substrate 201 can be substantially equal to or greater than the curved length of the foldable substrate or foldable device when it is at the effective minimum bend radius. In some embodiments, the width 252 of the central portion 251 of the foldable substrate 201 can be greater than or equal to about 4 mm, greater than or equal to about 10 mm, greater than or equal to about 20 mm, less than or equal to about 45 mm, less than or equal to about 40 mm, or less than or equal to about 30 mm. In some embodiments, the width 252 of the central portion 251 of the foldable substrate 201 can be in the range of about 4 mm to about 45 mm, about 4 mm to about 40 mm, about 4 mm to about 30 mm, about 4 mm to about 20 mm, about 4 mm to about 10 mm, about 10 mm to about 45 mm, about 10 mm to about 40 mm, about 10 mm to about 30 mm, about 10 mm to about 20 mm, about 20 mm to about 45 mm, about 20 mm to about 40 mm, about 20 mm to about 30 mm, about 30 mm to about 45 mm, about 30 mm to about 40 mm, about 40 mm to about 45 mm, or any range or sub-range therebetween.

[0250] The foldable device can have impact resistance, which is measured by the ability of a region of the foldable device (e.g., a region including the first portion 221, a region including the second portion 231, a region including the polymer base portion 241 and / or the central portion 251) to avoid failure at a pen drop height (e.g., 5 centimeters (cm) or greater, 10 centimeters or greater, 20 cm or greater) when measured according to a "pen drop test". As used herein, the "pen drop test" is performed so that the foldable device is tested under a load (i.e., from a pen dropped from a certain height) imparted to a major surface (e.g., the second major surface 205 or the first major surface 203 of the foldable substrate 201), and its configuration is as in the parallel plate test, and a 100 μm thick PET sheet 607 is placed instead of Figure 3 The display device 307 is shown attached to a 50 μm thick test adhesive layer 609. Thus, 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, the foldable device combined with the PET layer was placed on an aluminum plate (6063 aluminum alloy, which was polished to a certain surface roughness with 400 paper) with the PET layer in contact with the aluminum plate. No tape was used on the sample side that rested on the aluminum plate.

[0251] like Fig.41As shown, the pen drop device 4101 includes a ballpoint pen 4103. The pen used for the pen drop test is a BIC Easy Glide Pen, a fine pen, which includes a tungsten carbide bead point tip 4105 with a diameter of 0.7 mm (0.68 mm) and a weight of 5.73 grams (g) including the pen cap (the weight without the pen cap is 4.68 g). The ballpoint pen 4103 is held at a predetermined height 4109 from the first major surface 203 of the foldable substrate 201. In the pen drop test, the ballpoint pen 4103 is guided to the first major surface 203 of the foldable substrate 201 using a tube (not shown for clarity), and the tube is placed in contact with the first major surface 203 of the foldable substrate 201 so that the longitudinal axis of the tube is substantially perpendicular to the first major surface 203 of the foldable substrate 201. The tube had 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 was used to hold the ballpoint pen 4103 at a predetermined height 4109. After each drop, the tube was repositioned relative to the foldable substrate 201 to direct the ballpoint pen 4103 to a different impact location on the foldable substrate 201. Although not shown, it should be understood that the pen drop test can be used to Figure 1-4 Or any foldable substrate shown in 6-7.

[0252] The tube is used for pen drop testing to guide the pen to the outer surface of the foldable device. Figure 2-3 6-7, the pen is guided to the second major surface 205 of the foldable substrate 201, and the tube is placed in contact with the second major surface 205 of the foldable substrate 201 so that the longitudinal axis of the tube is substantially perpendicular to the second major surface 205 and the longitudinal axis of the tube extends in the direction of gravity. The tube has an outer diameter of 1 inch (2.54 cm), an inner diameter of nine-sixteenths of an inch (1.4 cm), and a length of 90 cm. 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 a different impact location on the sample. The pen used for the pen drop test was a BIC Easy Glide Pen, a fine pen including a tungsten carbide bead point tip having a diameter of 0.7 mm (0.68 mm) and a weight including the cap of 5.73 grams (4.68 g without the cap).

[0253] For the pen drop test, the ballpoint pen 4103 is dropped with the pen cap attached to the top end (i.e., the end opposite the tip) so that the ballpoint tip 4105 can interact with the first major surface 203 of the foldable substrate 201. In the drop procedure according to the pen drop test, a pen drop is performed at an initial height of 1 cm, followed by sequential drops in 0.5 cm increments until a height of 20 cm is reached, and then, after 20 cm, drops are performed in 2 cm increments until the foldable substrate 201 fails. After each drop, the presence of any observed fracture, failure, or other evidence of damage to the foldable substrate 201 and the specific predetermined height 4109 of the pen drop are recorded. When using the pen drop test, multiple foldable substrates (e.g., samples) can be tested according to the same drop procedure to produce a population with improved statistical accuracy. For the pen drop test, the ballpoint pen 4103 is replaced with a new pen after every 5 drops, and for each new foldable substrate 201. Furthermore, all pen drops are performed at or near the center of the foldable substrate 201 , at random locations on the foldable substrate 201 , and the pen does not drop near or on the edge of the foldable substrate 201 .

[0254] For the purpose of the pen drop test, "failure" means the formation of a visible mechanical defect in the laminate. The mechanical defect can be a crack or plastic deformation (e.g., a surface dent). The crack can be a surface crack or a through crack. The crack can form on the interior or exterior surface of the laminate. The crack can extend through all or a portion of the foldable substrate 201 and / or the coating 281. The minimum size of a visible mechanical defect is 0.2 mm or larger.

[0255] Fig.42 A curve 4205 is shown of the maximum principal stress 4203 in megapascals (MPa) on the first major surface of the glass-based substrate as a function of the thickness 4201 of the glass-based substrate in micrometers based on a pen drop height of 2 cm on the second major surface of the glass-based substrate. Fig.42 As shown, the maximum principal stress on the first major surface of the glass-based substrate is greatest at about 65 μm. This suggests that the pen-down performance can be improved by avoiding a thickness of about 65 μm, for example, making the thickness less than about 50 μm or greater than about 80 μm.

[0256] In some embodiments, the foldable device can resist pen drop failure at a pen drop height of 10 centimeters (cm), 12 cm, 14 cm, 16 cm, or 20 cm in an area including the first portion 221 and / or the second portion 231. In some embodiments, the maximum pen drop height that the foldable device can withstand without failure in the area including the first portion 221 or the second portion 231 can be greater than or equal to about 10 cm, greater than or equal to about 12 cm, greater than or equal to about 14 cm, greater than or equal to about 16 cm, less than or equal to about 40 cm, or less than or equal to about 30 cm, less than or equal to about 20 cm, less than or equal to about 18 cm. In some embodiments, the maximum pen drop height that the foldable device can withstand without failure of the area including the first portion 221 or the second portion 231 can be in the following range: about 10 cm to about 40 cm, about 12 cm to about 40 cm, about 12 cm to about 30 cm, about 14 cm to about 30 cm, about 14 cm to about 20 cm, about 16 cm to about 20 cm, about 18 cm to about 20 cm, or any range or sub-range therebetween.

[0257] In some embodiments, the region including the polymer base portion 241 between the first portion 221 and the second portion 231 (eg, the central portion 251, see Figure 3 ), the foldable device can resist pen drop failure at a pen drop height of 1 cm, 2 cm, 3 cm, 4 cm, 5 cm or more. In some embodiments, the maximum pen drop height that the foldable device can withstand without failure in the area containing the polymer base portion 241 between the first portion 221 and the second portion 231 can be greater than or equal to about 1 cm, greater than or equal to about 2 cm, greater than or equal to about 3 cm, greater than or equal to about 4 cm, less than or equal to about 20 cm, less than or equal to about 10 cm, less than or equal to about 8 cm, or less than or equal to about 6 cm. In some embodiments, the maximum pen drop height that the foldable device can withstand without failure in the area containing the polymer base portion 241 between the first portion 221 and the second portion 231 can be in the following range: about 1 cm to about 20 cm, about 2 cm to about 20 cm, about 2 cm to about 10 cm, about 3 cm to about 10 cm, about 3 cm to about 8 cm, about 4 cm to about 8 cm, about 4 cm to about 6 cm, or any range or sub-range therebetween. In some embodiments, the maximum pen drop height that the foldable device can withstand without failure in the area including the polymer base portion 241 between the first portion 221 and the second portion 231 may be in the range of about 1 cm to about 10 cm, about 1 cm to about 8 cm, about 1 cm to about 5 cm, about 2 cm to about 5 cm, about 3 cm to about 5 cm, about 4 cm to about 5 cm, or any range or sub-range therebetween.

[0258] The predetermined parallel plate distance for a foldable device can be achieved using minimal force. As described above, Figure 6 The parallel plate device 601 is used to measure the "closing force" of the foldable device of the present disclosure embodiment. The measurement is made from a flat configuration (e.g., see Figure 1 ) into a curved (e.g., folded) configuration comprising a predetermined parallel plate distance (e.g., see Figure 6-7 ). In some embodiments, the force to bend the foldable device from a flat configuration to a parallel plate distance of 10 mm can be less than or equal to about 20 Newtons (N), less than or equal to 15N, less than or equal to about 12N, less than or equal to about 10N, greater than or equal to about 0.1N, greater than or equal to about 0.5N, greater than or equal to about 1N, greater than or equal to about 2N, greater than or equal to about 5N. In some embodiments, the force to bend the foldable device from a flat configuration to a parallel plate distance of 10 mm can be in the following range: about 0.1N to about 20N, about 0.5N to about 20N, about 0.5N to about 15N, about 1N to about 15N, about 1N to about 12N, about 2N to about 12N, about 2N to about 10N, about 5N to about 10N, or any range or sub-range therebetween. In some embodiments, the force to bend the foldable device from a flat configuration to a parallel plate distance of 3 mm can be less than or equal to about 10 N, less than or equal to about 8 N, less than or equal to about 6 N, less than or equal to about 4 N, less than or equal to about 3 N, greater than or equal to about 0.05 N, greater than or equal to about 0.1 N, greater than or equal to about 0.5 N, greater than or equal to about 1 N, greater than or equal to about 2 N, greater than or equal to about 3 N. In some embodiments, the force to bend the foldable device from a flat configuration to a parallel plate distance of 3 mm can be in the range of about 0.05 N to about 10 N, about 0.1 N to about 10 N, about 0.1 N to about 8 N, about 0.5 N to about 8 N, about 0.5 N to about 6 N, about 1 N to about 6 N, about 1 N to about 4 N, about 2 N to about 4 N, about 2 N to about 3 N, or any range or sub-range therebetween.

[0259] In some embodiments, the force per width 103 to bend the foldable device from a flat configuration to a parallel-plate distance of 10 mm can be less than or equal to 20 Newtons per millimeter (N / mm), less than or equal to 0.15 N / mm, less than or equal to about 0.12 N / mm, less than or equal to about 0.10 N / mm, greater than or equal to about 0.001 N / mm, greater than or equal to about 0.005 N / mm, greater than or equal to about 0.01 N / mm, greater than or equal to about 0.02 N / mm, greater than or equal to about 0.05 N / mm. In some embodiments, the force per width 103 to bend the foldable device from a flat configuration to a parallel plate distance of 0.10 / mm can be in the range of about 0.001 N / mm to about 0.20 N / mm, about 0.005 N / mm to about 0.20 N / mm, about 0.005 N / mm to about 0.15 N / mm, about 0.01 N / mm to about 0.15 N / mm, about 0.01 N / mm to about 0.12 N / mm, about 0.02 N / mm to about 0.12 N / mm, about 0.02 N / mm to about 0.10 N / mm, about 0.05 N / mm to about 0.10 N / mm, or any range or sub-range therebetween. In some embodiments, the force per width 103 to bend the foldable device from a flat configuration to a parallel plate distance of 3 mm can be less than or equal to about 0.10 N / mm, less than or equal to about 0.08 N / mm, less than or equal to about 0.06 N / mm, less than or equal to about 0.04 N / mm, less than or equal to about 0.03 N / mm, greater than or equal to about 0.0005 N / mm, greater than or equal to about 0.001 N / mm, greater than or equal to about 0.005 N / mm, greater than or equal to about 0.01 N / mm, greater than or equal to about 0.02 N / mm, greater than or equal to about 0.03 N / mm. In some embodiments, the force per width 103 to bend the foldable device from a flat configuration to a parallel plate distance of 3 mm can be in the range of about 0.0005 N / mm to about 0.10 N / mm, about 0.001 N / mm to about 0.10 N / mm, about 0.001 N / mm to about 0.08 N / mm, about 0.005 N / mm to about 0.08 N / mm, about 0.005 N / mm to about 0.06 N / mm, about 0.01 N / mm to about 0.06 N / mm, about 0.01 N / mm to about 0.04 N / mm, about 0.02 N / mm to about 0.04 N / mm, about 0.02 N / mm to about 0.03 N / mm, or any range or sub-range therebetween.

[0260] Providing a coating enables a small parallel plate distance to be achieved with low force. Without wishing to be bound by theory, a coating comprising a modulus that is less than the modulus of the foldable substrate can deviate the neutral axis of the foldable substrate from the coating (e.g., the surface facing the user) compared to if a glass-based substrate and / or a ceramic-based substrate is used. Without wishing to be bound by theory, providing a coating having a thickness of less than or equal to about 200 μm can deviate the neutral axis of the foldable substrate from the coating (e.g., the surface facing the user) compared to if a thicker substrate material is used. Without wishing to be bound by theory, a neutral axis of the foldable substrate that deviates from the coating (e.g., the surface facing the user) can achieve a small parallel plate distance with low force because this reduces the concentration of tensile stresses, and because the tensile stresses are distributed over a larger portion of the foldable substrate, deformation of a portion of the foldable substrate due to tensile stress concentration is reduced.

[0261] The foldable device 101 or 301 and / or the test foldable device 602 may include a neutral stress configuration. Throughout this disclosure, the "neutral stress configuration" is measured by the following test configuration and process. When measuring the "neutral stress configuration", Fig.38 The test foldable device 3801 shown includes a test adhesive layer 609 including a thickness of 50 μm between a fifth contact surface 613 of the test adhesive layer 609 and a sixth contact surface 615 of the test adhesive layer 609, and a 100 μm thick sheet 607 of polyethylene terephthalate (PET), without including Figure 2 Release liner 271 or Figure 3 and 7 The display device 307 shown. For example, a foldable device including a foldable substrate 201 - such as Fig.38 The test foldable device 3801 shown may be similar to Figure 6 The parallel plate device 601 shown is used to measure the "effective bending radius". Fig.38 As shown, when the test adhesive layer 609 is disposed over the first major surface 203 of the foldable substrate 201, the material (e.g., the polymer base portion 241) located in the recess 219 of the foldable substrate 201 can be held in place. To test the test foldable device 3801, the test foldable device 3801 is placed on its side so that the cross section perpendicular to the direction of gravity is similar to Fig.38 The test foldable device 3801 is placed on a surface comprising SAE grade 304 (e.g., ISO A2) stainless steel and having an arithmetic mean deviation (surface roughness (Ra)) of less than or equal to 3 μm (e.g., 2.40 μm, gloss number 3). As shown, a plane that primarily includes a direction 202 of the substrate thickness 227 and a direction 106 of the length 105 of the foldable substrate 201 is substantially perpendicular to the direction of gravity, and a direction 104 of the folding axis 102 (see Figure 1 ) is also the direction of gravity. Next, the test foldable device is allowed to relax for 1 hour to achieve a balanced configuration, such as Fig.38 shown.

[0262] In some embodiments, Fig.38 As shown, the neutral stress configuration may include a curved configuration. As used herein, a curved configuration is a non-planar configuration (with Figure 1-3 In another embodiment, as Fig.38 As shown, first major surface 203 and / or second major surface 205 of foldable substrate 201 may deviate significantly from a planar shape.

[0263] In some embodiments, the magnitude of the maximum deviation strain can be used to quantify the deviation of the neutral stress configuration from the flat configuration. As used herein, "deviation strain" means the shape change component of the strain tensor (e.g., the strain tensor minus the average of the diagonal components of the strain tensor as isostatic strain). The strain tensor can be measured by using digital image recognition and / or topological comparison of the shape and size between the flat configuration and the neutral stress configuration of a portion of the folding device (e.g., the polymer base portion). For example, Fig.39 , which shows an exemplary polymer base portion 241 in a flat configuration. In the flat configuration, the length 3901 of the polymer base portion (e.g., measured in the direction 106 of the length of the foldable device) is substantially equal when measured at the third contact surface 245 and the fourth contact surface 247. Fig.38 and 40 , which shows an exemplary polymer base portion 241 in a neutral stress configuration. For ease of understanding, Figure 39-40 The volumes of the polymer base portions 241 in the configuration are equal, which would be the case after removing the isostatic strain from the digitally captured shape and dimensions of the neutral stress configuration. Fig.40 As shown, the first length 4003 measured along the third contact surface 245 is different from (e.g., greater than) the second length 4001 measured along the fourth contact surface 247. As used herein, strain means the difference in length of a portion between a flat configuration and a neutral stress configuration divided by a reference length from the flat configuration. For example, the strain measured at the third contact surface 245 is Figure 39-40 The strain between (e.g., the deviation strain when the isostatic strain is removed as described above) will be equal to the difference between the first length 4003 in the neutral stress configuration and the length 3901 in the flat configuration divided by the length 3901 in the flat configuration. For example, the measured length at the fourth contact surface 247 is Figure 39-40The strain between (e.g., the deviation strain when the isostatic strain is removed as described above) will be equal to the difference between the second length 4001 in the neutral stress configuration and the length 3901 in the flat configuration divided by the length 3901 of the flat configuration. As used herein, the magnitude of a numerical value (e.g., a scalar value) is the absolute value of the numerical value. As used herein, the maximum amplitude of a tensor (e.g., a strain tensor, a deviation strain tensor) means the component of the tensor (e.g., a deviation strain tensor) having the largest value (e.g., a maximum value). As used herein, the maximum amplitude of the deviation strain of the polymer base portion 241 means the larger value of the maximum amplitude of the deviation strain calculated at the third contact surface 245 and the fourth contact surface 247 of the polymer base portion. In some embodiments, the maximum amplitude of the deviation strain of the polymer base portion 241 may be greater than or equal to about 1%, greater than or equal to about 2%, greater than or equal to about 3%, greater than or equal to about 4%, less than or equal to about 10%, less than or equal to about 8%, less than or equal to about 7%, less than or equal to about 6%, or less than or equal to about 5%. In some embodiments, the maximum amplitude of the deflection strain of the polymer base portion 241 may be in the range of about 1% to about 10%, about 1% to about 8%, about 1% to about 7%, about 2% to about 7%, about 2% to about 6%, about 2% to about 5%, about 3% to about 5%, about 3% to about 4%, about 2% to about 10%, about 2% to about 8%, about 3% to about 8%, about 4% to about 8%, about 4% to about 7%, about 4% to about 6%, or any range or sub-range therebetween.

[0264] In some embodiments, the deviation of the neutral stress configuration from the flat configuration can be quantified using an angle "B" measured between a first line extending from the length of the first portion and a second line extending from the length of the second portion. Fig.38 , angle "B" is measured between first line 3802 and second line 3804. First line 3802 is in the length direction 106 of the test foldable device 3801 (e.g., the length direction 106 of the foldable device 301), at and extending from the first portion 221 (e.g., the first surface area 223) of the foldable substrate 201. In some embodiments, as Fig.38 As shown, the first line 3802 can extend along a plane along which the first surface area 223 can extend. The second line 3804 extends from the second portion 231 (e.g., the third surface area 233) of the foldable substrate 201 in the length direction 106 of the test foldable device 3801 (e.g., the length direction 106 of the foldable device 301). In some embodiments, as Fig.38As shown, second line 3804 can extend along a plane along which third surface region 233 can extend. In some embodiments, the magnitude of the difference between angle "B" in the neutral stress configuration and angle "B" in the flat configuration (e.g., 180°) can be greater than or equal to about 1°, greater than or equal to about 2°, greater than or equal to about 5°, greater than or equal to about 10°, less than or equal to about 40°, less than or equal to about 20°, less than or equal to about 15°, or less than or equal to about 8°. In some embodiments, the magnitude of the difference between the angle "B" in the neutral stress configuration and the angle "B" in the flat configuration (e.g., 180°) may be in the range of about 1° to about 40°, about 1° to about 20°, about 2° to about 20°, about 5° to about 20°, about 5° to about 15°, about 10° to about 15°, about 2° to about 15°, about 5° to about 15°, about 5° to about 8°, about 1° to about 8°, about 2° to about 8°, or any range or sub-range therebetween.

[0265] By providing a neutral stress configuration when the foldable device is in a bent configuration, the force that bends the foldable device to a predetermined parallel plate distance can be reduced. Further, providing a neutral stress configuration when the foldable device is in a bent state can reduce the maximum stress and / or strain experienced by the polymer base portion during normal use conditions, which can, for example, increase the durability of the foldable device and / or reduce fatigue of the foldable device. In some embodiments, the neutral stress configuration can be generated by providing a polymer base portion that expands due to curing. In some embodiments, the neutral stress configuration can be generated by curing the polymer base portion in a bent configuration. In some embodiments, the neutral stress configuration can be generated by bending the foldable substrate at an elevated temperature (e.g., when the foldable substrate comprises about 10 4 Pascal-seconds to about 10 7 (Pascal-second viscosity).

[0266] Will refer to Figure 10-11 and the flowchart of 27 and Figure 12-26 Embodiments of methods of manufacturing a foldable device and / or foldable substrate of the present disclosure are discussed using the exemplary method steps illustrated in FIGS. 28-37.

[0267] Now refer to Figure 12-18 , 24-26 and 32-34 and Fig.10Flowchart of the present disclosure is used to discuss exemplary embodiments of manufacturing a foldable device 101 and / or 301, a test foldable device 602, and / or a foldable substrate 201. In the first step 1001 of the method of the present disclosure, the method may begin by providing a foldable substrate 201. In some embodiments, the foldable substrate 201 may be provided by purchasing, or otherwise obtaining a substrate, or by forming a foldable substrate. In some embodiments, the foldable substrate 201 may include a glass-based substrate and / or a ceramic-based substrate. In other embodiments, the glass-based substrate and / or the glass-ceramic-based substrate may be provided by forming them using various tape forming processes, such as slit drawing, down-drawing, fusion down-drawing, up-drawing, pressing rollers, redrawing, or floating. In other embodiments, the ceramic-based substrate may be provided by heating a glass-based substrate to crystallize one or more ceramic crystals. The foldable substrate 201 may include a second major surface 205 (see Fig.12 ), which may extend along a plane. The second major surface 205 may be opposite to the first major surface 203. In some embodiments, as Fig.34 As shown, the foldable substrate 201 can be bent (e.g., include a curved structure). In another embodiment, as a result of bending the foldable substrate 201 into the curved structure, the foldable substrate 201 can include a curved structure, and the foldable substrate 201 includes about 10 4 Pascal-seconds to about 10 7 The viscosity is in Pascal-seconds (eg, within the processing range of the foldable substrate 201, between the softening point of the foldable substrate 201 and the processing point of the foldable substrate 201).

[0268] In some embodiments, the foldable substrate 201 may include a recess 219 in the first major surface 203 of the foldable substrate 201, which exposes the first central surface area 209. In other embodiments, the recess 219 can be formed by etching, laser ablation, or machining the first major surface 203. For example, the first major surface 203 can be machined by diamond engraving, thereby creating extremely precise patterns in a glass-based substrate and / or a ceramic-based substrate. Fig.12As shown, a recess 219 may be produced in the first major surface 203 of the foldable substrate 201 using diamond engraving, wherein a computer numerical control (CNC) machine 1203 may be used to control the diamond tip probe 1201. Materials other than diamond may also be used for engraving using a CNC machine. Additionally, other methods of forming the recess include photolithography, etching, and laser ablation. For example, etching may include: setting a mask above the first surface region 223 and the third surface region 233, exposing the first major surface 203 of the foldable substrate 201 to an etchant to form the recess 219, and then removing the mask. Forming the recess 219 in the first major surface 203 may provide a center portion 251 between the first portion 221 and the second portion 231 of the foldable substrate 201. The center portion 251 may include a first center surface region 209, wherein the recess 219 may be defined between the first center surface region 209 and a first plane 204a, which is Fig.12 The plane along which the first major surface 203 extends in the flat configuration shown. The first central surface area 209 can attach the first portion 221 to the second portion 231. Figure 2 As shown, the central portion 251 may further include: a first transition portion 253 attaching the first portion 221 to the central main surface 211 and a second transition portion 255 attaching the second portion 231 to the central main surface 211. In some embodiments, the thickness of the first transition portion 253 may increase continuously from the central main surface 211 to the first portion 221. In other embodiments, the thickness of the second transition portion 255 may increase continuously from the central main surface 211 to the second portion 231. Fig.12 As shown, in some embodiments, the first central surface region 209 may include a central major surface 211 of the central portion 251, which may be planar as shown, but in other embodiments, a non-planar configuration may be provided. In addition, the central major surface 211 may be parallel relative to the first plane 204a and / or the second major surface 205, such as Fig.12 shown.

[0269] Although about Fig.12 The apparatus is not shown, but in some embodiments, step 1001 may further include reducing the thickness of the foldable substrate 201. In other embodiments, the thickness of the foldable substrate 201 may be reduced by mechanical processing (e.g., grinding). In other embodiments, chemical etching may be used to reduce the thickness of the foldable substrate 201. In other embodiments, chemical etching may include: contacting the foldable substrate 201 with an etching solution contained in an etching bath. In other embodiments, the etching solution may include one or more inorganic acids (e.g., HCl, HF, H2SO4, HNO3). For example, referring to Fig.29The foldable substrate 201 shown can be reduced in thickness by chemical etching, which can include contacting the foldable substrate 201 with an etching solution 2903 containing one or more inorganic acids (e.g., HCl, HF, H2SO4, HNO3) contained in an etching bath 2901. In some embodiments, the thickness of the foldable substrate 201 can be reduced by removing a layer from the first major surface 203 of the foldable substrate 201 to expose a new first major surface, which can be formed as shown in FIG. Figure 2-3 Additionally or alternatively, the thickness of foldable substrate 201 may be reduced by removing a layer from second major surface 205 of foldable substrate 201 to expose a new second major surface, which may be formed as shown in FIG. Figure 2-3 and the second major surface 205 shown in 5-7.

[0270] In some embodiments, the second major surface 205 (eg, the entire second major surface 205) can be covered with an optional mask (eg, Fig.29 The mask 2905 in FIG. 2 is used to prevent the second main surface 205 from being etched and can be used as described above with respect to Figure 2-3 and the second major surface 205 described in 5-7 to provide the second major surface 205. Preventing the second major surface 205 from being etched can be beneficial in preserving the original properties of the second major surface 205, which may exist with some processing techniques (e.g., pulling up or pulling down, for example, by overflow or fusion). Maintaining the original surface can allow the second major surface 205 to present a particularly smooth surface, which second major surface can form the outermost surface of the foldable device, and the outermost surface can be viewed and / or touched by a user of the foldable device. Alternatively, the thickness of the foldable substrate 201 can be reduced by removing layers from the second major surface 205, for example, removing a surface layer to expose a center layer with more consistent optical properties over the length of the foldable substrate 201 (e.g., a glass-based substrate and / or a ceramic-based substrate), as described above. In some embodiments, layers can be removed from the first major surface 203 to expose a new first major surface, which can constitute Figure 2-3 and the first major surface 203 shown in 5-7, and the layer can be removed from the second major surface 205 to expose a new second major surface, which can constitute Figure 2-35-7. Removing layers from both the first major surface and the second major surface can remove an outer layer of the foldable substrate 201 (e.g., a glass-based substrate and / or a ceramic-based substrate) that may have inconsistent optical properties compared to the underlying inner portion of the foldable substrate 201 (e.g., a glass-based substrate and / or a ceramic-based substrate). As a result, the entire thickness of the foldable substrate 201 over the entire length and width can have more consistent optical properties to provide consistent optical performance with little distortion across the entire foldable substrate 201 (e.g., a glass-based substrate and / or a ceramic-based substrate).

[0271] In some embodiments, removing a layer from the first major surface 203 can be beneficial in removing surface defects created during the formation of the recess 219. For example, mechanical processing (e.g., with a diamond tip probe) of the first major surface 203 to create the recess 219 may create microcrack surface flaws or other defects, which may present a weak point at which catastrophic failure of the foldable substrate 201 may occur when folded. Therefore, by removing a layer from the first major surface 203, surface defects created in the layer during the formation of the recess 219 can be removed, wherein a new first major surface 203 with fewer surface defects can be presented. Due to the presence of fewer surface defects, a smaller bending radius can be achieved without the foldable substrate failing. For example, certain processing of the foldable substrate may present different glass-based material properties and / or ceramic-based material properties at the first and second major surfaces of the foldable substrate than at the central portion of the foldable substrate. For example, during the down-draw process, the properties of the glass-based material and / or ceramic-based material at the major surfaces may be different from the central portion. Thus, by removing layers from the first major surface 203 at the first portion 221 and the second portion 231, the new first major surface 203 of these portions can have the same properties as the first central surface area 209 to provide consistent optical properties over the length of the foldable substrate 201, for example, if the foldable substrate 201 includes a glass-based substrate and / or a ceramic-based substrate.

[0272] After step 1001, if Fig.13As shown, the method may proceed to step 1003, which includes chemically strengthening the foldable substrate 201. When a first cation within the surface depth of the foldable substrate 201 is exchanged with a second cation (which has a larger radius than the first cation) within the molten salt or salt solution 1303, chemical strengthening of the foldable substrate 201 (e.g., a glass-based substrate, a ceramic-based substrate) may occur through ion exchange. For example, lithium cations within the depth of the surface of the foldable substrate 201 may be exchanged with sodium cations or potassium cations in the salt solution 1303. As a result, since the radius of the lithium cation is smaller than the radius of the exchanged sodium cation or potassium cation in the salt solution 1303, the surface of the foldable substrate 201 is in a compressed state, and is thereby chemically strengthened through the ion exchange process. Chemically strengthening the foldable substrate 201 may include contacting at least a portion of the foldable substrate 201 including lithium cations and / or sodium cations with a salt bath 1301 including a salt solution 1303, wherein the salt solution 1303 includes potassium nitrate, potassium phosphate, potassium chloride, potassium sulfate, sodium chloride, sodium sulfate, sodium nitrate, and / or sodium phosphate, whereby the lithium cations and / or sodium cations diffuse from the foldable substrate 201 to the salt solution 1303 contained in the salt bath 1301. In some embodiments, the temperature of the salt solution 1303 may be greater than or equal to about 300° C., greater than or equal to about 360° C., greater than or equal to about 400° C., less than or equal to about 500° C., less than or equal to about 460° C., or less than or equal to about 400° C. In some embodiments, the temperature of the salt solution 1303 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 300° C. to about 400° C., about 360° C. to about 400° C., or any range or sub-range therebetween. In some embodiments, the foldable substrate 201 can be in contact with the salt solution 1303 for greater than or equal to about 15 minutes, greater than or equal to about 1 hour, greater than or equal to about 3 hours, less than or equal to about 48 hours, less than or equal to about 24 hours, or less than or equal to about 8 hours. In some embodiments, the foldable substrate 201 is contacted with the saline solution 1303 for a time in the range of about 15 minutes to about 48 hours, about 1 hour to about 48 hours, about 3 hours to about 48 hours, about 15 minutes to about 24 hours, about 1 hour to about 24 hours, about 3 hours to about 48 hours, about 3 hours to about 24 hours, about 3 hours to about 8 hours, or any range or sub-range therebetween.

[0273] Chemically strengthening foldable substrate 201 may include chemically strengthening first central surface region 209, chemically strengthening first surface region 223 of first portion 221 of first major surface 203, chemically strengthening third surface region 233 of second portion 231 of first major surface 203, and chemically strengthening second major surface 205 of foldable substrate 201. In some embodiments, chemical strengthening may include chemically strengthening first portion 221 to an initial first compression depth from first surface region 223 of first major surface 203, chemically strengthening second portion 231 to an initial third compression depth from third surface region 233 of first major surface 203, and chemically strengthening central portion 251 to an initial first central compression depth from first central surface region 209. In some embodiments, chemically strengthening second major surface 205 of foldable substrate 201 may include chemically strengthening second surface region 225 of first portion 221 of second major surface 205, chemically strengthening fourth surface region 235 of second portion 231 of second major surface 205, and chemically strengthening second central surface region 213 of central portion 251 of second major surface 205. In some embodiments, chemically strengthening second major surface 205 may include chemically strengthening first portion 221 to an initial second compression depth from second surface region 225 of second major surface 205, chemically strengthening second portion 231 to an initial fourth compression depth from fourth surface region 235 of second major surface 205, and chemically strengthening central portion 251 to an initial second central compression depth from second central surface region 213 of second major surface 205.

[0274] After step 1003, if Figure 14-15As shown, the method may proceed to step 1005, which includes disposing a layer over the central portion 251. In some embodiments, the layer may include: disposing a material using chemical vapor deposition (CVD) (e.g., low pressure CVD, plasma enhanced CVD), physical vapor deposition (PVD) (e.g., evaporation, molecular beam epitaxy, ion plating), atomic layer deposition (ALD), sputtering, spray pyrolysis, chemical bath deposition, and / or sol-gel deposition. In some embodiments, the layer may include a material that has a diffusivity of one or more alkali metal ions. In other embodiments, the diffusivity of the layer may be less than or equal to the corresponding diffusivity of the foldable substrate. Without wishing to be bound by theory, a layer having a reduced diffusivity relative to the foldable substrate may limit (e.g., reduce) the extent of chemical strengthening of a portion of the foldable substrate over which the layer is disposed, for example, by reducing the concentration of the one or more alkali metal ions at the surface of the foldable substrate relative to another portion of the foldable substrate over which the layer is not disposed. In other embodiments, the diffusivity of the layer relative to the diffusivity of the foldable substrate may be greater than or equal to about 5%, greater than or equal to about 10%, greater than or equal to about 20%, greater than or equal to about 25%, less than or equal to about 80%, less than or equal to about 60%, less than or equal to about 50%, less than or equal to about 40%, or less than or equal to about 30%. In other embodiments, the diffusivity of the layer relative to the diffusivity of the foldable substrate may be in the following range: about 5% to about 80%, about 5% to about 60%, about 10% to about 60%, about 10% to about 50%, about 20% to about 50%, about 25% to about 50%, about 25% to about 40%, about 25% to about 30%, or any range or sub-range therebetween. In some embodiments, the layer includes titanium dioxide (TiO2), zirconium oxide (ZrO2), tin oxide (SnO2), aluminum oxide (Al2O3), silicon dioxide (SiO2), silicon nitride (Si3N4), and / or combinations thereof. Exemplary embodiments include using PVD to deposit a SiO2 layer. Providing a layer with a reduced (but still significant) diffusivity relative to the foldable substrate can reduce chemical strengthening induced instabilities while keeping the number of required chemical strengthening steps low, keeping processing costs and processing time down.

[0275] In some embodiments, as shown, the first layer 1401 or 1501 can be disposed over the first central surface region 209. In other embodiments, the first layer 1401 or 1501 can contact the first central surface region 209. In other embodiments, as shown, the first layer 1401 or 1501 can be disposed over the first central surface region 209 but not over the first surface region 223 and / or the third surface region 233. In other embodiments, the first layer 1401 or 1501 can cover substantially the entire first central surface region 209. In other embodiments, the first layer 1401 or 1501 can include a first layer thickness 1402 or 1502, which is defined as the average depth of the first layer 1401 or 1501 disposed over the first central surface region 209, the average depth from the first central surface region 209 in the direction shown (e.g., Figure 2-3 The first layer thickness 1402 and 1502 are measured at 5 (five) points equally spaced along the first central surface area 209 in the direction 106 in the middle. In other embodiments, the first layer thickness 1402 and 1502 can be greater than or equal to about 0.5 nm, greater than or equal to about 1 nm, greater than or equal to about 5 nm, greater than or equal to about 10 nm, greater than or equal to about 20 nm, less than or equal to about 250 nm, less than or equal to about 200 nm, less than or equal to about 150 nm, less than or equal to about 100 nm, or less than or equal to about 50 nm. In other embodiments, the first layer thickness 1402 and 1502 can be in the range of about 0.5 nm to about 250 nm, about 0.5 nm to about 200 nm, about 1 nm to about 200 nm, about 1 nm to about 150 nm, about 5 nm to about 150 nm, about 5 nm to about 100 nm, about 10 nm to about 100 nm, about 10 nm to about 50 nm, about 20 nm to about 50 nm, or any range or sub-range therebetween. In other embodiments, as Fig.14 As shown, the first layer 1401 may include a substantially constant thickness over the first central surface area 209 (e.g., in the direction 106 of the length 105 of the foldable device and / or in the direction 104 of the width 103 of the foldable device). In other embodiments, as Fig.15 As shown, the first layer 1501 may include a thickness that varies across the first central surface region 209 (e.g., in the direction 106 of the length 105 of the foldable device and / or in the direction 104 of the width 103 of the foldable device). In further embodiments, as shown, the thickness of the first layer 1501 near the interface between the central portion 251 and the first portion 221 and / or the second portion 231 may be less than the thickness away from the corresponding interface. Providing a reduced thickness near the interface may reduce stress concentration at the interface due to chemical strengthening.

[0276] In some embodiments, Figure 14-15 As shown, the second layer 1403 or 1503 may be disposed above the second central surface area 213. In other embodiments, the second layer 1403 or 1503 may contact the second central surface area 213. In other embodiments, as shown, the second layer 1403 or 1503 may be disposed above the second central surface area 213 but not disposed above the second surface area 225 and / or the fourth surface area 235. In other embodiments, the second layer 1403 or 1503 may cover substantially the entire second central surface area 213. In other embodiments, the second layer 1403 or 1503 may include a second layer thickness, which is defined as the average depth of the second layer 1403 or 1503 disposed above the second central surface area 213. In other embodiments, the second layer thickness may be within one or more of the ranges described above with respect to the first layer thicknesses 1402 and 1502. In other embodiments, the second layer thickness may be substantially equal to the first layer thicknesses 1402 and 1502. In other embodiments, as Fig.14 As shown, the second layer 1403 may include a substantially constant thickness across the second central surface region 213 (e.g., in the direction 106 of the length 105 of the foldable device and / or in the direction 104 of the width 103 of the foldable device). In other embodiments, as Fig.15 As shown, the second layer 1503 may include a thickness that varies across the second central surface region 213 (e.g., in the direction 106 of the length 105 of the foldable device and / or in the direction 104 of the width 103 of the foldable device). In other embodiments, as shown, the thickness of the second layer 1503 near the interface between the central portion 251 and the first portion 221 and / or the second portion 231 may be less than the thickness away from the corresponding interface. Providing a reduced thickness near the interface can reduce stress concentration at the interface due to chemical strengthening. Further discussion of the method of the disclosed embodiments will be provided by Fig.14 The first layer 1401 and the second layer 1403 are shown, wherein it should be understood that the method can be applied in a similar or identical manner to Fig.15 A first layer 1501 and a second layer 1503 are shown.

[0277] After step 1005, if Fig.16 As shown, the method may proceed to step 1007, which includes chemically strengthening the foldable substrate 201 for a first period of time. As used herein, the first period of time is the time when at least a portion of the foldable substrate 201 is in contact with one or more alkali metals (e.g., sodium ions, potassium ions) described with respect to the salt solution 1303. In some embodiments, as Fig.16As shown, the chemical strengthening in step 1007 may include contacting the foldable substrate 201, the first layer 1401, and / or the second layer 1403, which includes at least a portion of lithium cations and / or sodium cations, with a salt bath 1601 including a salt solution 1603, which is similar or identical to the salt solution 1303 described above. In some embodiments, the salt solution 1603 may include a certain temperature, which is within one or more ranges of the temperature of the above-mentioned salt solution 1303. In other embodiments, the temperature of the salt solution 1603 may be substantially the same as the temperature of the salt solution 1303. In some embodiments, the first time period of the chemical strengthening in step 1007 may be within one or more ranges described above for the time of contact with the salt solution 1303 in step 1007. The relationship between the first time period in step 1007 and the time of contact with the alkali metal (e.g., salt solution) in step 1003 and / or step 1011 will be discussed below.

[0278] After step 1007, if Fig.17 As shown, the method may proceed to step 1009, which includes removing a layer disposed over the central portion 251. In some embodiments, removing the layer may include removing the first layer 1401 disposed over the first central surface region 209 of the central portion 251. In other embodiments, removing the layer may include removing the second layer 1403 disposed over the second central surface region 213 of the central portion 251. In other embodiments, as shown, removing the first layer 1401 and / or the second layer 1403 may include moving an abrasive tool 1701 in a direction 1702 over the surface (e.g., the first central surface region 209, the second central surface region 213). In other embodiments, using the tool may include sweeping, scraping, grinding, pushing, etc. In other embodiments, the first layer 1401 and / or the second layer 1403 may be removed by washing the surface (e.g., the first central surface region 209, the second central surface region 213) with a solvent.

[0279] In some embodiments, after step 1009, Fig.18As shown, the method may proceed to step 1011, which includes further chemically strengthening the foldable substrate 201. As described herein, this further chemical strengthening of the foldable substrate 201 may continue for a second time period. As used herein, the second time period may be the sum of the time of steps 1003 and 1013 (if present in the method), which is the time that at least a portion of the foldable substrate 201 is in contact with the one or more alkali metals (e.g., sodium ions, potassium ions) described with respect to the salt solution 1303. Therefore, the time period for which the foldable substrate 201 is in contact with the one or more alkali metals (e.g., sodium ions, potassium ions) in step 1013 may be less than or equal to the second time period. In some embodiments, the time period for which the foldable substrate 201 is in contact with the one or more alkali metals (e.g., sodium ions, potassium ions) in step 1013 may be within one or more of the ranges described above with respect to step 1003. In some embodiments, the second time period may be greater than the first time period. In other embodiments, as a percentage of the first time period, the second time period can be greater than or equal to about 103%, greater than or equal to about 110%, greater than or equal to about 120%, greater than or equal to about 135%, less than or equal to about 200%, less than or equal to about 175%, less than or equal to about 160%, or less than or equal to about 150%. In other embodiments, as a percentage of the first time period, the second time period can be in the range of about 103% to about 200%, about 103% to about 175%, about 110% to about 175%, about 110% to about 160%, about 120% to about 160%, about 120% to about 150%, about 135% to about 150%, or any range or sub-range therebetween.

[0280] In some embodiments, Fig.18As shown, further chemically strengthening the foldable substrate 201 in step 1011 may include contacting at least a portion of the foldable substrate 201 including lithium cations and / or sodium cations with a salt bath 1801 including a salt solution 1803, wherein the salt solution 1803 includes one or more of the alkali metal ions and / or alkali metal-containing compounds described above with respect to steps 1003 and 1007. In some embodiments, the salt solution 1803 may include a certain temperature, and the temperature is within one or more ranges described above with respect to step 1003. After step 1011, the foldable substrate may include one or more compressive stress regions (e.g., 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), wherein the compressive stress region includes a compression depth and / or an associated layer depth, which ranges within one or more ranges described above with respect to the corresponding compressive stress region. In some embodiments where step 1011 is omitted (e.g., following arrows 1004 or 1006), after step 1009, the foldable substrate may include one or more compressive stress regions (e.g., 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) comprising a compression depth and / or an associated layer depth within one or more of the ranges described above for the corresponding compressive stress region. In further embodiments, the absolute difference between the layer depth of one of the first layer depth, the second layer depth, the third layer depth, or the fourth layer depth divided by the substrate thickness and the first central layer depth or the second central layer depth divided by the central thickness may be within one or more of the above ranges. In further embodiments, the absolute difference between the compression depth of one of the first compression depth, the second compression depth, the third compression depth, or the fourth compression depth divided by the substrate thickness and the first central compression depth or the second central compression depth divided by the central thickness may be within one or more of the above ranges. In further embodiments, the absolute difference between the first average concentration of potassium or the second average concentration of potassium and the central average concentration of potassium may be within one or more of the above ranges.

[0281] In some embodiments, step 1011 may further include: chemically etching the foldable substrate 201 after chemically strengthening the foldable substrate 201 (e.g., after chemical strengthening in steps 1007 and / or 1011). In some embodiments, as described below, step 1013 may include: chemically etching the foldable substrate 201 in step 1013 after chemically strengthening the foldable substrate 201 (e.g., after chemical strengthening in steps 1007 and / or 1011) before assembling the foldable device. As described above, chemical etching may include: contacting the foldable substrate 201 with an etching solution contained in an etching bath. In some embodiments, the first major surface 203 and the first central surface region 209 are etched. In some embodiments, the second major surface 205 is etched. In other embodiments, the first major surface 203, the first central surface region 209, the second major surface 205, and / or the second central surface region 213 are etched. If present in steps 1011 and / or 1013, the chemical etching may be designed to remove surface defects that may remain as a result of chemically strengthening the foldable substrate 201. In fact, chemical strengthening may result in some surface defects that may affect the strength and / or optical quality of the foldable substrate 201. By etching during steps 1011 and / or 1013, surface defects generated during chemical strengthening may be removed. In some embodiments, such etching may be designed to remove a portion of a layer that includes a depth of about 1 nm or more, about 5 nm or more, about 2 μm or less, about 1 μm or less, about 500 nm or less, about 100 nm or less, about 50 nm or less, or about 10 nm or less. In some embodiments, such etching can be designed to remove a portion of a layer that includes a depth in the range of about 1 nm to about 2 μm, about 1 nm to about 1 μm, about 5 nm to about 1 μm, about 5 nm to about 500 nm, about 5 nm to about 100 nm, about 5 nm to about 50 nm, about 5 nm to about 10 nm, or any range or sub-range therebetween. Such etching can avoid significantly changing the thickness of the foldable substrate 201 or the surface compression achieved during chemical strengthening.

[0282] After step 1011, the method of the present disclosure may proceed to step 1013, which includes: assembling a foldable device using the foldable substrate 201. Fig.24 and 26 As shown, step 1013 may include applying adhesive layer 261 to contact first surface region 223 of first major surface 203 and third surface region 233 of first major surface 203. As shown, second contact surface 265 of adhesive layer 261 may contact first surface region 223 and third surface region 233. In some embodiments, as shown Fig.24 As shown, adhesive layer 261 may include one or more layers of adhesive material. For example, there may be an integral interface between the one or more layers that make up adhesive layer 261, which may reduce (e.g., avoid) optical refraction and / or optical discontinuity when light is transmitted between the layers because the one or more layers may include substantially the same refractive index in some embodiments. In some embodiments, as Fig.24 As shown, adhesive layer 261 may further fill recess 219. In another embodiment, as shown in FIG. Fig.24 As shown, the second contact surface 265 of the adhesive layer 261 can contact the first central surface area 209. In some embodiments, as shown in FIG. Fig.26 As shown, step 1013 may include: disposing a polymer base portion 241 in the recess 219. In other embodiments, the polymer base portion 241 may include a third contact surface 245, which may contact the first central surface area 209. In other embodiments, as Fig.26 As shown, polymer base portion 241 may include fourth contact surface 247 that may contact second contact surface 265 of adhesive layer 261. Although not shown, in some embodiments, the recess may not be completely filled, for example, leaving space for electronic devices and / or mechanical devices.

[0283] In some embodiments, Fig.25 and 32 As shown in FIG. 33 , step 1013 may include: disposing a second liquid 2503 in the recess 219. The second liquid 2503 may then be cured to form a polymer-based portion. In some embodiments, Fig.25 As shown, step 1013 may further include: when the foldable substrate 201 is in a flat configuration, curing the second liquid 2503 to form the polymer base portion 241. In some embodiments, as Figure 32-33 As shown, step 1013 may further include: when the foldable substrate 201 is in the bent configuration, curing the second liquid 2503 to form the polymer base portion 241. In another embodiment, as Fig.32 As shown, in step 1013, the foldable substrate 201 can be in a curved configuration such that the first major surface 203 and the first central surface area 209 are on the outside of the curve. Fig.33 As shown, in step 1013, foldable substrate 201 can be in a bent configuration such that second major surface 205 is on the outside of the bend.

[0284] In step 1013, curing the second liquid 2503 may form the polymer base portion 241. In some embodiments, as Fig.25 and 32As shown in FIG. 33 , step 1013 may include: disposing a liquid 2503 in the recess 219. In another embodiment, a conduit (e.g., a flexible tube, a micropipette, or a syringe) may be used to dispose the second liquid 2503 into the recess 219. In another embodiment, as Fig.25 and 32 -33, by dispensing the second liquid 2503 from the container 2501 into the recess 219, the second liquid 2503 can be set in the recess 219. In some embodiments, the second liquid 2503 set in the recess 219 can at least partially (e.g., substantially completely) fill the recess 219. In some embodiments, as shown in the figure, the second liquid 2503 set in the recess 219 can set the second liquid 2503 between the first part 221 and the second part 231. In some embodiments, the second liquid 2503 can include one or more precursors and solvents of the polymer-based part. In some embodiments, the precursor of the polymer-based part may include, but is not limited to, one or more of the following: monomers, oligomers, accelerators, curing agents, epoxides, polyurethanes (e.g., isocyanates, esters, polyols), mercaptoesters, acrylates, particles (e.g., one or more of copper oxides, β-quartz, tungstates, vanadates, pyrophosphates, nickel-titanium alloys) and / or fibers. In some embodiments, the solvent of the precursor may include a polar solvent (e.g., water, alcohol, acetate, acetone, formic acid, dimethylformamide, acetonitrile, dimethyl sulfoxide, nitromethane, propylene carbonate, poly(ether ether ketone)) and / or a non-polar solvent (e.g., pentane, 1,4-dioxane, chloroform, dichloromethane, ethyl ether, hexane, heptane, benzene, toluene, xylene). The second liquid 2503 may be solidified to form a Fig.26 The polymer base portion 241 shown. In other embodiments, curing the second liquid 2503 to form the polymer base portion 241 may include: heating the second liquid 2503. In other embodiments, curing the second liquid 2503 to form the polymer base portion 241 may include: irradiating the second liquid 2503 with ultraviolet (UV) radiation. In other embodiments, curing the second liquid 2503 to form the polymer base portion 241 may include: waiting for a predetermined time (e.g., about 30 minutes to 24 hours, about 1 hour to about 8 hours). In some embodiments, the polymer base portion 241 may include a negative thermal expansion coefficient, as described above. In some embodiments, the precursor may include a cyclic monomer (e.g., norbornene, cyclopentene), wherein curing the precursor includes ring-opening disproportionation polymerization, which may increase the volume from the second liquid 2503 to the polymer base portion 241. In some embodiments, curing the second liquid 2503 may form a polymer base portion located between the first portion 221 and the second portion 231 of the foldable substrate 201.

[0285] In some embodiments, after steps 1013 and / or 1015, a foldable device comprising a foldable substrate may include a neutral stress configuration when in a bent configuration. In other embodiments, in the neutral stress configuration, the foldable device may include a maximum magnitude of the deflection strain of the polymer base portion, the maximum magnitude being within one or more of the ranges described above (e.g., within a range of about 1% to about 8%, within a range of about 2% to about 6%). In other embodiments, in the neutral stress configuration, the foldable device may include an angle within one or more of the ranges described above. In some embodiments, the neutral stress configuration may correspond to a bent configuration resulting from bending the foldable substrate 201. In some embodiments, the neutral stress configuration may correspond to a bent configuration resulting from curing the second liquid 2503 to form the polymer base portion 241 when the foldable substrate 201 is bent. In some embodiments, the neutral stress configuration may correspond to a bent configuration resulting from an increase in volume when curing the second liquid 2503 to form the polymer base portion 241. In some embodiments, the neutral stress configuration can correspond to a curved configuration resulting from the polymer base portion 241 including a negative coefficient of thermal expansion.

[0286] In some embodiments, a release liner (eg, see Figure 2 Release liner 271) or display device (see, for example, Figure 3 In some embodiments, a coating may be provided on the second major surface of the foldable substrate 201 (eg, see Figure 2 Coating 281). Fig.10 At the end point 1015 of the flowchart, the foldable device is completed.

[0287] In some embodiments, the method for manufacturing a foldable device according to an embodiment of the present disclosure may be as follows: Fig.10 Steps 1001, 1003, 1005, 1007, 1009, 1011, 1013, and 1015 of the flowchart of proceed in sequence as described above. In some embodiments, when it is possible to Fig.10 As shown, step 1003 may be omitted by following arrow 1002 from step 1001, for example, when the folded substrate 201 is not chemically strengthened before step 1007. In some embodiments, step 1011 may be omitted by following arrow 1004 from step 1009 to step 1013, for example, if the foldable substrate 201 already includes a compressive stress region of the finished foldable substrate. In some embodiments, step 1015 may be omitted by following arrow 1006 from step 1009, for example, if the method produces a foldable substrate 201 (e.g., see Figure 5), and the foldable substrate 201 already includes a compressive stress region of the finished foldable substrate. In some embodiments, arrow 1008 can be followed from step 1011 to step 1015, for example, if the method produces a foldable substrate 201 (e.g., see Figure 5 ). In some embodiments, the method may include a single chemical strengthening step in step 1007, for example, by following arrow 1002 and following one of arrows 1004 or 1006, while omitting additional chemical strengthening steps. In some embodiments, the method may include two chemical strengthening steps, including step 1007 and one of steps 1003 or 1011, for example, by following arrow 1002 or one of arrows 1004 or 1006, respectively, while omitting additional chemical strengthening steps. Any of the above options can be combined to manufacture a foldable device according to embodiments of the present disclosure.

[0288] Now refer to Fig.12 , 18 -26 and 32-34 and Fig.11 A flowchart to illustrate the manufacturing Figure 2-3 and 5-7 illustrate exemplary embodiments of the foldable device 101 and / or 301, the test foldable device 602, and / or the foldable substrate 201. In the first step 1101 of the method of the present disclosure, the method may begin by providing a foldable substrate 201. In some embodiments, the foldable substrate 201 may be provided by purchasing, or otherwise obtaining a substrate, or by forming a foldable substrate. In some embodiments, the foldable substrate 201 may include a glass-based substrate and / or a ceramic-based substrate. In other embodiments, the glass-based substrate and / or the glass-ceramic-based substrate may be provided by forming them using various tape forming processes, such as slit drawing, down-drawing, fusion down-drawing, up-drawing, pressing rollers, redrawing, or floating. In other embodiments, the ceramic-based substrate may be provided by heating a glass-based substrate to crystallize one or more ceramic crystals. The foldable substrate 201 may include a second major surface 205 (see Fig.12 ), which may extend along a plane. The second major surface 205 may be opposite to the first major surface 203. In some embodiments, as Fig.34 As shown, the foldable substrate 201 is bendable (eg, includes a curved configuration). In another embodiment, as a result of bending the foldable substrate 201 into the curved configuration, the foldable substrate 201 includes about 10 4 Pascal-seconds to about 10 7 When the viscosity is less than 0.05 Pascal-seconds (eg, within the working range of the foldable substrate 201, between the softening point of the foldable substrate 201 and the working point of the foldable substrate 201), the foldable substrate 201 may include a curved configuration.

[0289] In some embodiments, the foldable substrate 201 may include a recess 219 in the first major surface 203 of the foldable substrate 201, which exposes the first central surface area 209. In other embodiments, the recess 219 can be formed by etching, laser ablation, or machining the first major surface 203. For example, the first major surface 203 can be machined by diamond engraving, thereby creating extremely precise patterns in a glass-based substrate and / or a ceramic-based substrate. Fig.12 As shown, a recess 219 may be produced in the first major surface 203 of the foldable substrate 201 using diamond engraving, wherein a computer numerical control (CNC) machine 1203 may be used to control the diamond tip probe 1201. Materials other than diamond may also be used for engraving using a CNC machine. Additionally, other methods of forming the recess include photolithography, etching, and laser ablation. For example, etching may include: setting a mask above the first surface region 223 and the third surface region 233, exposing the first major surface 203 of the foldable substrate 201 to an etchant to form the recess 219, and then removing the mask. Forming the recess 219 in the first major surface 203 may provide a center portion 251 between the first portion 221 and the second portion 231 of the foldable substrate 201. The center portion 251 may include a first center surface region 209, wherein the recess 219 may be defined between the first center surface region 209 and a first plane 204a, which is Fig.12 The plane along which the first major surface 203 extends in the flat configuration shown. The first central surface area 209 can attach the first portion 221 to the second portion 231. Figure 2 As shown, the central portion 251 may further include: a first transition portion 253 attaching the first portion 221 to the central main surface 211 and a second transition portion 255 attaching the second portion 231 to the central main surface 211. In some embodiments, the thickness of the first transition portion 253 may increase continuously from the central main surface 211 to the first portion 221. In other embodiments, the thickness of the second transition portion 255 may increase continuously from the central main surface 211 to the second portion 231. Fig.12 As shown, in some embodiments, the first central surface region 209 may include a central major surface 211 of the central portion 251, which may be planar as shown, but in other embodiments, a non-planar configuration may be provided. In addition, the central major surface 211 may be parallel relative to the first plane 204a and / or the second major surface 205, such as Fig.12 shown.

[0290] Although about Fig.12The apparatus is not shown, but in some embodiments, step 1101 may further include reducing the thickness of the foldable substrate 201. In other embodiments, the thickness of the foldable substrate 201 may be reduced by mechanical processing (e.g., grinding). In other embodiments, chemical etching may be used to reduce the thickness of the foldable substrate 201. In other embodiments, chemical etching may include: contacting the foldable substrate 201 with an etching solution contained in an etching bath. In other embodiments, the etching solution may include one or more inorganic acids (e.g., HCl, HF, H2SO4, HNO3). For example, referring to Fig.29 The foldable substrate 201 shown can be reduced in thickness by chemical etching, which can include contacting the foldable substrate 201 with an etching solution 2903 containing one or more inorganic acids (e.g., HCl, HF, H2SO4, HNO3) contained in an etching bath 2901. In some embodiments, the thickness of the foldable substrate 201 can be reduced by removing a layer from the first major surface 203 of the foldable substrate 201 to expose a new first major surface, which can be formed as shown in FIG. Figure 2-3 Additionally or alternatively, the thickness of foldable substrate 201 may be reduced by removing a layer from second major surface 205 of foldable substrate 201 to expose a new second major surface, which may be formed as shown in FIG. Figure 2-3 and the second major surface 205 shown in 5-7.

[0291] In some embodiments, the second major surface 205 (eg, the entire second major surface 205) can be covered with an optional mask (eg, Fig.29 The mask 2905 in FIG. 2 is used to prevent the second main surface 205 from being etched and can be used as described above with respect to Figure 2-3 and the second major surface 205 described in 5-7 to provide the second major surface 205. Preventing the second major surface 205 from being etched can be beneficial in preserving the original properties of the second major surface 205, which may exist following some processing techniques (e.g., pulling up or pulling down, for example, by overflow or fusion). Maintaining the original surface can allow the second major surface 205 to present a particularly smooth surface, which second major surface 205 can form the outermost surface of the foldable device, and the outermost surface can be viewed and / or touched by a user of the foldable device. Alternatively, the thickness of the foldable substrate 201 can be reduced by removing layers from the second major surface 205, for example, removing a surface layer to expose a center layer with more consistent optical properties over the length of the foldable substrate 201 (e.g., a glass-based substrate and / or a ceramic-based substrate), as described above. In some embodiments, layers can be removed from the first major surface 203 to expose a new first major surface, which can constitute Figure 2-3and the first major surface 203 shown in 5-7, and the layer can be removed from the second major surface 205 to expose a new second major surface, which can constitute Figure 2-3 5-7. Removing layers from both the first major surface and the second major surface can remove an outer layer of the foldable substrate 201 (e.g., a glass-based substrate and / or a ceramic-based substrate) that may have inconsistent optical properties compared to the underlying inner portion of the foldable substrate 201 (e.g., a glass-based substrate and / or a ceramic-based substrate). As a result, the entire thickness of the foldable substrate 201 over the entire length and width can have more consistent optical properties to provide consistent optical performance with little distortion across the entire foldable substrate 201 (e.g., a glass-based substrate and / or a ceramic-based substrate).

[0292] In some embodiments, removing a layer from the first major surface 203 can be beneficial in removing surface defects created during the formation of the recess 219. For example, mechanical processing (e.g., with a diamond tip probe) of the first major surface 203 to create the recess 219 may create microcrack surface flaws or other defects, which may present a weak point at which catastrophic failure of the foldable substrate 201 may occur when folded. Therefore, by removing a layer from the first major surface 203, surface defects created in the layer during the formation of the recess 219 may be removed, wherein a new first major surface 203 with fewer surface defects may be presented. Due to the presence of fewer surface defects, a smaller bending radius may be achieved without the foldable substrate failing. For example, certain processing of the ribbon may present different glass-based material properties and / or ceramic-based material properties at the first and second major surfaces of the foldable substrate than at the central portion of the foldable substrate. For example, during the down-draw process, the properties of the glass-based material and / or ceramic-based material at the major surfaces may be different from the central portion. Thus, by removing layers from the first major surface 203 at the first portion 221 and the second portion 231, the new first major surface 203 of these portions can have the same properties as the first central surface area 209 to provide consistent optical properties over the length of the foldable substrate 201, for example, if the foldable substrate 201 includes a glass-based substrate and / or a ceramic-based substrate.

[0293] After step 1101, if Fig.19 As shown, the method of the present disclosure may proceed to step 1103, which includes applying a paste containing alkali metal ions to the first portion 221 and the second portion 231. In some embodiments, as Fig.19As shown, step 1103 may include: disposing a first salt paste 1903 on the first portion 221 and a first salt paste 1905 on the second portion 231, wherein the first salt pastes 1903 and 1905 are from a source 1901. In other embodiments, as shown, the first salt paste 1903 may be applied to a first surface area 223 of the first portion 221, and the first salt paste 1905 may be applied to a third surface area 233 of the second portion 231. In other embodiments, although not shown, the first salt paste (e.g., the first salt paste 1903 and / or 1905) may be applied to a second surface area 225 of the first portion 221 and a fourth surface area 235 of the second portion 231. In some embodiments, the source 1901 may include a conduit (e.g., a flexible tube, a micropipette, or a syringe), a nozzle, or a container (e.g., a beaker). The first salt paste 1903 , which may be disposed on the first portion 221 and the second portion 231 , may be cured to form first salt deposits 2005 , 2007 , 2009 , and / or 2011 .

[0294] As used herein, the salt paste comprises potassium and / or sodium. In some embodiments, the first salt pastes 1903 and 1905 may comprise one or more of potassium nitrate, potassium phosphate, potassium chloride, potassium sulfate, sodium chloride, sodium sulfate, sodium nitrate and / or sodium phosphate. In other embodiments, the first salt paste may comprise potassium nitrate and potassium phosphate. In other embodiments, the first salt paste may be substantially free of alkaline earth metals (e.g., alkaline earth metal ions, compounds comprising alkaline earth metals). As used herein, alkaline earth metals include beryllium, magnesium, calcium, strontium, barium and radium. In further embodiments, the first salt paste may comprise a concentration of potassium and / or sodium, calculated as oxide, of greater than or equal to about 1,000 ppm, greater than or equal to about 5,000 ppm, greater than or equal to about 10,000 ppm, greater than or equal to about 25,000 ppm, less than or equal to about 500,000 ppm, less than or equal to about 200,000 ppm, less than or equal to about 100,000 ppm, or less than or equal to about 50,000 ppm. In further embodiments, the first salt paste may comprise a concentration of potassium and / or sodium, calculated as oxide, in the range of about 1,000 ppm to about 500,000 ppm, about 5,000 ppm to about 500,000, about 5,000 ppm to about 200,000 ppm, about 10,000 ppm to about 200,000 ppm, about 10,000 ppm to about 100,000, about 25,000 ppm to about 100,000 ppm, about 25,000 ppm to about 100,000 ppm, about 25,000 ppm to about 50,000 ppm, or any range or sub-range therebetween....

Claims

1. A foldable device comprising a foldable substrate capable of being folded about an axis extending in a width direction of the foldable substrate, the foldable substrate further comprising: a substrate thickness defined between a first major surface and a second major surface opposite the first major surface; a first portion including a substrate thickness and a first surface area of ​​a first major surface; a second portion including the thickness of the substrate and a third surface area of ​​the first major surface; a central portion including a central thickness defined between a first central surface region and a second major surface opposite the first central surface region, the first central surface region attaching the first surface region to the third surface region, the central portion having a width less than or equal to about 45 mm, and a central thickness less than a thickness of the substrate, wherein the central portion is located between the first portion and the second portion in a length direction of the foldable substrate, the length direction being perpendicular to a width direction of the foldable substrate, and when the foldable device is in a bent configuration, the foldable device comprises a neutral stress configuration, wherein the thickness of the central portion is less than or equal to 50 μm, and The thickness of the substrate is in the range of 80 micrometers to 2 millimeters.

2. The foldable device of claim 1, wherein: The foldable device includes a polymer base portion located in a recess between a first central surface area defined in the central portion and a first plane, the first major surface extending along the first plane, and the foldable device moving from a flat configuration to a neutral stress configuration corresponds to a maximum amplitude of a deviation strain of the polymer base portion in a range of about 1% to about 8%.

3. The foldable device of claim 2, wherein: The maximum magnitude of the deflection strain is in the range of about 2% to about 6%.

4. The foldable device of claim 1, wherein: The foldable substrate of the foldable device includes an effective minimum bending radius in the range of about 1 mm to about 10 mm.

5. The foldable device of claim 4, wherein: The foldable substrate achieves an effective bending radius of 5 mm.

6. The foldable device of claim 4, wherein: The width of the central portion is in a range from about 2.8 times the effective minimum bend radius to about 6 times the effective minimum bend radius.

7. The foldable device of claim 4, wherein: The width of the central portion is in the range of about 2.8 mm to about 40 mm.

8. The foldable device of claim 1, wherein: The substrate thickness ranges from about 125 microns to about 200 microns.

9. The foldable device according to any one of claims 1 to 7, wherein: The core thickness ranges from about 10 microns to about 50 microns.

10. The foldable device according to any one of claims 1 to 7, wherein: The core thickness is in the range of about 0.5% to about 13% of the substrate thickness.

11. The foldable device according to any one of claims 1 to 7, wherein: The substrate thickness is at least 71 microns greater than about 4 times the center thickness.

12. A method for preparing a foldable device, the method comprising: forming a depression in a first major surface of the foldable substrate, the depression forming a first central surface area of ​​the central portion, the first central surface area attaching the first portion to the second portion, wherein the first portion includes a first surface area and a second surface area opposite the first surface area, the second portion includes a third surface area and a fourth surface area opposite the third surface area, the foldable substrate includes a second major surface including the second surface area and the fourth surface area, and the foldable substrate includes a first major surface opposite the second major surface, the first major surface including the first surface area and the third surface area; and curing a polymer-based portion disposed between the first portion and the second portion, wherein during the curing, the foldable device is in a bent configuration, wherein movement of the foldable device from the flat configuration to the neutral stress configuration corresponds to a maximum magnitude of a deflection strain of the polymer-based portion in a range of about 1% to about 8%, and wherein when the foldable device is in the bent configuration, the foldable device comprises a neutral stress configuration, wherein the thickness of the central portion is less than or equal to 50 μm, and The thickness of the substrate is in the range of 80 micrometers to 2 millimeters.

13. The method of claim 12, further comprising: The first central surface region, the first surface region, the third surface region, and the second major surface of the central portion are chemically strengthened.

14. The method of claim 12, wherein: The maximum magnitude of the deflection strain is in the range of about 2% to about 6%.

15. The method according to any one of claims 12 to 14, wherein: The polymer-based portion expands due to curing.

16. The method according to any one of claims 12 to 14, wherein: The polymer-based portion includes a negative coefficient of thermal expansion.

17. The method of claim 16, wherein: The polymer-based portion includes particles of one or more of copper oxide, beta-quartz, tungstate, vanadate, pyrophosphate, or nickel titanium alloy.

18. The method according to any one of claims 12 to 14, wherein: Curing the polymer base portion includes ring-opening disproportionation polymerization.

19. The method according to any one of claims 12 to 14, wherein: Foldable substrates include glass-based substrates.

20. The method of any one of claims 12 to 14, wherein: The width of the central portion is in the range of 3 mm to 45 mm.

21. The foldable device according to any one of claims 1 to 7, wherein: The width of the central portion is in the range of 3 mm to 45 mm.

22. The foldable device of any one of claims 1 to 7, wherein: The foldable substrate is a glass-based substrate.

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