Patent Publication Number: US-2022225523-A1

Title: Electronic Devices With Durable Folding Displays

Description:
This application claims the benefit of provisional patent application No. 63/136,981, filed Jan. 13, 2021, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices, and, more particularly, to electronic devices with displays. 
     BACKGROUND 
     Electronic devices often have displays. Portability may be a concern for some devices, which tends to limit available real estate for displays. 
     SUMMARY 
     An electronic device may be provided with a foldable housing. The housing may have first and second portions that are coupled by a hinge for rotation about a bend axis. 
     A foldable display may be mounted to the foldable housing. The foldable display may have a display cover layer and a flexible display panel. The foldable display may bend around a bend axis. The display panel may have an array of pixels configured to display an image through the display cover layer. 
     The display cover layer may be formed from a layer of glass. A recess may be formed in the layer of glass that extends along the bend axis. The recess may form a flexible locally thinned portion in the layer of glass that allows the glass layer to bend about the bend axis. To ensure that the display cover layer exhibits satisfactory impact resistance during drop events, corner portions and other edge portions of the display cover layer may have increased thickness relative to other portions of the display cover layer outside of the locally thinned portion. 
     The hinge and/or other structures in the display may be configured to help hold the display flat when unfolded during normal use, while causing the display to slightly fold about the bend axis when the electronic device is jolted during a drop event. This helps prevent the display from impacting a hard surface while fully opened. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative electronic device with a display in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of an illustrative display having a cover layer with a locally thinned hinge region in accordance with an embodiment. 
         FIG. 5  is a top view of an illustrative display cover layer having a locally thinned portion that is aligned with a bend axis for a flexible display in accordance with an embodiment. 
         FIGS. 6 and 7  are cross-sectional end views of illustrative display cover layers with locally thinned portions in accordance with embodiments. 
         FIG. 8  is a cross-sectional side view of an illustrative display cover layer with a locally thinned portion that runs along a bend axis and end edge portions of enhanced thickness in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of another illustrative display cover layer with a locally thinned portion that runs along a bend axis and edge portions of enhanced thickness in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of an illustrative display cover layer with a locally thinned portion characterized by an elongated recess having a cross-sectional profile with curved edges in accordance with an embodiment. 
         FIGS. 11 and 12  are cross-sectional side views of illustrative flexible displays in accordance with embodiments. 
         FIGS. 13 and 14  are graphs showing illustrative relationships between stored energy and display bending angle for electronic devices in accordance with embodiments. 
         FIG. 15  is a cross-sectional side view of an illustrative hinge for a foldable electronic device in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of an illustrative display cover layer with a locally thinned portion formed by attaching layers of glass or other clear material together in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may be provided with displays. Displays may be used for displaying images for users. Displays may be formed from arrays of light-emitting diode pixels or other pixels. For example, a device may have an organic light-emitting diode display or a display formed from an array of micro-light-emitting diodes (e.g., light-emitting diodes formed from crystalline semiconductor dies). 
     A schematic diagram of an illustrative electronic device having a display is shown in  FIG. 1 . Device  10  may be a cellular telephone, tablet computer, laptop computer, wristwatch device or other wearable device, a television, a stand-alone computer display or other monitor, a computer display with an embedded computer (e.g., a desktop computer), a system embedded in a vehicle, kiosk, or other embedded electronic device, a media player, or other electronic equipment. Configurations in which device  10  is a cellular telephone, tablet computer, or other portable electronic device may sometimes be described herein as an example. This is illustrative. Device  10  may, in general, be any suitable electronic device with a display. 
     Device  10  may include control circuitry  20 . Control circuitry  20  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  20  may be used to gather input from sensors and other input devices and may be used to control output devices. The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors and other wireless communications circuits, power management units, audio chips, application specific integrated circuits, etc. During operation, control circuitry  20  may use a display and other output devices in providing a user with visual output and other output. 
     To support communications between device  10  and external equipment, control circuitry  20  may communicate using communications circuitry  22 . Circuitry  22  may include antennas, radio-frequency transceiver circuitry (wireless transceiver circuitry), and other wireless communications circuitry and/or wired communications circuitry. Circuitry  22 , which may sometimes be referred to as control circuitry and/or control and communications circuitry, may support bidirectional wireless communications between device  10  and external equipment over a wireless link (e.g., circuitry  22  may include radio-frequency transceiver circuitry such as wireless local area network transceiver circuitry configured to support communications over a wireless local area network link, near-field communications transceiver circuitry configured to support communications over a near-field communications link, cellular telephone transceiver circuitry configured to support communications over a cellular telephone link, or transceiver circuitry configured to support communications over any other suitable wired or wireless communications link). Wireless communications may, for example, be supported over a Bluetooth® link, a WiFi® link, a wireless link operating at a frequency between 6 GHz and 300 GHz, a 60 GHz link, or other millimeter wave link, cellular telephone link, wireless local area network link, personal area network communications link, or other wireless communications link. Device  10  may, if desired, include power circuits for transmitting and/or receiving wired and/or wireless power and may include batteries or other energy storage devices. For example, device  10  may include a coil and rectifier to receive wireless power that is provided to circuitry in device  10 . 
     Device  10  may include input-output devices such as devices  24 . Input-output devices  24  may be used in gathering user input, in gathering information on the environment surrounding the user, and/or in providing a user with output. Devices  24  may include one or more displays such as display  14 . Display  14  may be an organic light-emitting diode display, a liquid crystal display, an electrophoretic display, an electrowetting display, a plasma display, a microelectromechanical systems display, a display having a pixel array formed from crystalline semiconductor light-emitting diode dies (sometimes referred to as microLEDs), and/or other display. Configurations in which display  14  is an organic light-emitting diode display or microLED display are sometimes described herein as an example. 
     Display  14  may have an array of pixels configured to display images for a user. The pixels may be formed as part of a display panel that is bendable. This allows device  10  to be folded and unfolded about a bend axis. For example, a flexible (bendable) display in device  10  may be folded so that device  10  may be placed in a compact shape for storage and may be unfolded when it is desired to view images on the display. 
     Sensors  16  in input-output devices  24  may include force sensors (e.g., strain gauges, capacitive force sensors, resistive force sensors, etc.), audio sensors such as microphones, touch and/or proximity sensors such as capacitive sensors (e.g., a two-dimensional capacitive touch sensor integrated into display  14 , a two-dimensional capacitive touch sensor overlapping display  14 , and/or a touch sensor that forms a button, trackpad, or other input device not associated with a display), and other sensors. If desired, sensors  16  may include optical sensors such as optical sensors that emit and detect light, ultrasonic sensors, optical touch sensors, optical proximity sensors, and/or other touch sensors and/or proximity sensors, monochromatic and color ambient light sensors, image sensors, fingerprint sensors, temperature sensors, sensors for measuring three-dimensional non-contact gestures (“air gestures”), pressure sensors, sensors for detecting position, orientation, and/or motion (e.g., accelerometers, magnetic sensors such as compass sensors, gyroscopes, and/or inertial measurement units that contain some or all of these sensors), health sensors, radio-frequency sensors, depth sensors (e.g., structured light sensors and/or depth sensors based on stereo imaging devices that capture three-dimensional images), optical sensors such as self-mixing sensors and light detection and ranging (lidar) sensors that gather time-of-flight measurements, humidity sensors, moisture sensors, gaze tracking sensors, and/or other sensors. In some arrangements, device  10  may use sensors  16  and/or other input-output devices to gather user input. For example, buttons may be used to gather button press input, touch sensors overlapping displays can be used for gathering user touch screen input, touch pads may be used in gathering touch input, microphones may be used for gathering audio input, accelerometers may be used in monitoring when a finger contacts an input surface and may therefore be used to gather finger press input, etc. 
     If desired, electronic device  10  may include additional components (see, e.g., other devices  18  in input-output devices  24 ). The additional components may include haptic output devices, audio output devices such as speakers, light-emitting diodes for status indicators, light sources such as light-emitting diodes that illuminate portions of a housing and/or display structure, other optical output devices, and/or other circuitry for gathering input and/or providing output. Device  10  may also include a battery or other energy storage device, connector ports for supporting wired communication with ancillary equipment and for receiving wired power, and other circuitry. 
       FIG. 2  is a perspective view of electronic device  10  in an illustrative configuration in which device  10  is a portable electronic device such as a cellular telephone or tablet computer. As shown in  FIG. 2 , device  10  may have a display such as display  14 . Display  14  may cover some or all of the front face of device  10 . Touch sensor circuitry such as two-dimensional capacitive touch sensor circuitry may be incorporated into display  14 . 
     Display  14  may be mounted in housing  12 . Housing  12  may form front and rear housing walls, sidewall structures, and/or internal supporting structures (e.g., a frame, an optional midplate member, etc.) for device  10 . Glass structures, transparent polymer structures, and/or other transparent structures that cover display  14  and other portions of device  10  may provide structural support for device  10  and may sometimes be referred to as housing structures. For example, a transparent housing portion such as a glass or polymer housing structure that covers and protects a pixel array in display  14  may serve as a display cover layer for the pixel array while also serving as a housing wall on the front face of device  10 . In configurations in which a display cover layer is formed from glass, the display cover layer may sometime be referred to as a display cover glass or display cover glass layer. The portions of housing  12  on the sidewalls and rear wall of device  10  may be formed from glass or other transparent structures and/or opaque structures. Sidewalls and rear wall structures may be formed as extensions to the front portion of housing  12  (e.g., as integral portions of the display cover layer) and/or may include separate housing wall structures. 
     Housing  12  may have flexible structures (e.g., bendable housing wall structures) and/or hinge structures such as hinge  30 . Hinge  30  may have a hinge axis aligned with device bend axis  28 . Hinge  30  and/or flexible housing structures that overlap bend axis  28  may allow housing  12  to bend about bend axis  28 . For example, housing  12  may have a first portion on one side of bend axis  28  and a second portion on an opposing side of bend axis  28  and these two housing portions may be coupled by hinge  30  for rotational motion about axis  28 . 
     As housing  12  is bent about bend axis  28 , the flexibility of display  14  allows display  14  to bend about axis  28 . In an illustrative configuration, housing  12  and display  14  may bend by 180°. This allows display  14  to be folded back on itself (with first and second outwardly-facing portions of display  14  facing each other). The ability to place device  10  in a folded configuration in this way may help make device  10  compact so that device  10  can be stored efficiently. When it is desired to view images on display  14 , device  10  may be unfolded about axis  28  to place device  10  in the unfolded configuration of  FIG. 2 . This allows display  14  to lie flat and allows a user to view flat images on display  14 . The ability to fold display  14  onto itself allows device  10  to exhibit an inwardly folding behavior. Display  14  may be sufficiently flexible to allow device  10  to be folded outwardly and/or inwardly. 
     Device  10  of  FIG. 2  has a rectangular outline (rectangular periphery) with four corners. As shown in  FIG. 2 , a first pair of parallel edges (e.g., the left and right edges of device  10  in the example of  FIG. 2 ) may be longer than a second pair of parallel edges (e.g., the upper and lower edges of device  10  of  FIG. 2 ) that are oriented at right angles to the first pair of parallel edges. In this type of configuration, housing  12  is elongated along a longitudinal axis that is perpendicular to bend axis  28 . Housing  12  may have other shapes, if desired (e.g., shapes in which housing  12  has a longitudinal axis that extends parallel to bend axis  28 ). With an arrangement of the type shown in  FIG. 2 , the length of device  10  along its longitudinal axis may be reduced by folding device  10  about axis  28 . 
       FIG. 3  is a cross-sectional side view of an illustrative foldable electronic device. Device  10  of  FIG. 3  may bend about bend axis  28 . Bend axis  28  may be aligned with display cover layer  14 CG or other structures in device  10 . For example, bend axis  28  may pass through a portion of display cover layer  14 CG or may be located above or below layer  14 CG. 
     As shown in  FIG. 3 , display  14  includes an array of pixels P forming display panel  14 P under an inwardly facing surface of display cover layer  14 CG. Display panel  14 P may be, for example, a flexible organic light-emitting diode display or a microLED display in which light-emitting pixels are formed on a flexible substrate layer (e.g., a flexible layer of polyimide or a sheet of other flexible polymer). Flexible support layer(s) for display  14  may also be formed from flexible glass, flexible metal, and/or other flexible structures. 
     Display cover layer  14 CG may be formed from polymer, glass, crystalline materials such as sapphire, other materials, and/or combinations of these materials. To locally increase flexibility, a portion of layer  14 CG that overlaps and extends along bend axis  28  may be locally thinned (e.g., this portion may be thinned relative to portions of layer  14 CG that do not overlap bend axis  28 ). The thickness of layer  14 CG (e.g., the non-thinned portions of layer  14 CG) may be 50-200 microns, 70-150 microns, 100-200 microns, 100-600 microns, at least 100 microns, at least 200 microns, less than 600 microns, less than 400 microns, less than 250 microns, less than 150 microns, less than 100 microns, at least 50 microns, or other suitable thickness. 
     In the example of  FIG. 3 , housing  12  has a portion on rear face R that forms a rear housing wall and has side portions forming sidewalls  12 W. The rear housing wall of housing  12  may form a support layer for components in device  10 . Housing  12  may also have one or more interior supporting layers (e.g., frame structures such as an optional midplate, etc.). These interior supporting layers and the rear housing wall may have first and second portions that are coupled to opposing sides of a hinge that is aligned with bend axis  28  (see, e.g., hinge  30  of  FIG. 2 ) or may be sufficiently flexible to bend around bend axis  28 . 
     Electrical components  32  may be mounted in the interior of device  10  (e.g., between display  14  and the rear of housing  12 . Components  32  may include circuitry of the type shown in  FIG. 1  (e.g., control circuitry  20 , communications circuitry  22 , input-output devices  24 , batteries, etc.). Display  14  may be mounted on front face F of device  10 . When device  10  is folded about axis  28 , display cover layer  14 CG, display panel  14 P, and the other structures of device  10  that overlap bend axis  28  may flex and bend to accommodate folding. 
     The outer and/or inner surfaces of display cover layer  14 GC may be provided with coatings. These coatings may include, for example, antireflection coatings, anti-scratch coatings, anti-smudge coatings, and/or other coating layers. Consider, as an example, the cross-sectional side view of display cover layer  14 CG of  FIG. 4 . As shown in  FIG. 4 , display cover layer may have an outer surface (outwardly facing surface) such as surface  40  and an opposing inner surface (inwardly facing surface) such as surface  42 . A strip-shaped region of display cover layer  14 CG that overlaps and runs parallel to bend axis  28  may be locally thinned (e.g., a groove or other recess that runs parallel to bend axis  28  may be formed in layer  14 CG to form locally thinned portion  44  of layer  14 CG). Locally thinned portion  44  of layer  14 CG may be thinner than other portions of layer  14 CG such as non-thinned portions  46  (which may be, for example, planar glass layer portions of layer  14 CG). The presence of portion  44  in display cover layer  14 CG may facilitate bending of display cover layer  14 CG about bend axis  28 . 
     To help planarize inner surface  42  and thereby facilitate mounting of display panel  14 P against inner surface  42  (e.g., with a layer of adhesive), the elongated recess (groove) in the inner surface of layer  14 CG that forms thinned portion  44  may be filled with polymer  50 . Polymer  50  may be sufficiently flexible to bend about bend axis  28  when device  10  is opened and closed. The refractive index of polymer  50  may be matched to that of display cover layer  14 CG to help minimize light reflections (e.g., by incorporating inorganic nanoparticles in polymer  50 ). For example, at a wavelength of 500 nm, the refractive index of polymer  50  may differ from that of layer  14 CG by less than 0.15, less than 0.1, or less than 0.05 (as examples). 
     Coating layers  52  may be formed on outer surface  40 . Coating layers  52  may include, for example, anti-scratch layers (sometimes referred to as hard coats), protective polymer layers, anti-smudge layers, anti-fog layers, antireflection layers, anti-static layers, adhesion layers, and/or other coatings. In some configurations, each of these functions may be implemented using a separate respective coating layer. In other configurations, a single layer may serve multiple functions. In general, coatings such as coatings  52  may be formed on outer surface  40  and/or inner surface  42 . In the illustrative configuration of  FIG. 4 , coatings  52  are formed on outer surface  40 . 
     Coatings  52  may be provided in any suitable order. As one example, the lowermost coating of coatings  52  (e.g., a coating layer formed directly on surface  40  of  FIG. 4 ) may be a hard coat or other anti-scratch layer that helps prevent scratches that could damage layer  14 CG. An antireflection coating may be formed on top of the anti-scratch layer. The antireflection layer may be a thin-film interference filter antireflection coating containing a stack of thin-film layers such as dielectric sublayers of alternating refractive index. One of the thin-film layers may be a conductive layer such as a transparent semiconductor layer (e.g., an indium tin oxide layer) that serves as an antistatic layer. An anti-smudge coating or anti-fog coating may be formed on top of the antireflection layer. Anti-smudge coatings (e.g., hydrophobic polymer coatings) may help reduce fingerprints and other undesired marks on the surfaces of display  14 . An example of an anti-smudge coating is a fluoropolymer coating (e.g., a fluoropolymer formed from evaporated perfluoropolyether) that serves as an oleophobic layer. Fluoropolymers can be adhered to underlying coating layers using an intervening adhesion layer. 
       FIG. 5  is a top view of an illustrative display cover layer with a locally thinned portion. As shown in  FIG. 5 , thinned portion  44  may have an elongated shape formed by a groove that extends across the underside of display cover layer  14 CG. Thinned portion  44  overlaps and extends along bend axis  28  and helps allow display cover layer  14 CG to flex about axis  28 . 
     During use of device  10 , it is possible for device  10  to be exposed to stress. For example, during a drop event, display cover layer  14 CG may strike a hard surface such as a floor. During such undesired drop events, the corners and edges of display cover layer  14 CG typically make contact with the hard surface, while interior areas of the surface of display cover layer  14 CG do not directly strike the hard surface or only strike the hard surface incidentally after the brunt of the impact has been borne by the edges. As a result, it is less likely for excessive impact-induced stress to display cover layer  14 CG to occur in the central area of layer  14 CG away from the four edges of layer  14 CG than near the edges (e.g., the corners). 
     To help reduce the risk of impact-induced damage from drop events, it may be desirable to provide the portions of display cover layer  14 CG at the corners and other edge locations with increased thickness (e.g., a thickness that is greater than the thickness of display cover layer in the central area adjacent to locally thinned portion  44 ). As shown in  FIG. 5 , for example, it may be desirable for the thickness of display cover layer  14 CG to be greater at corner areas  48  and/or other edge areas such as end edge areas  51  and side edge areas  53  than in some or all of central area  54 . In some illustrative arrangements, non-thinned portions  46  of display cover layer may have a thickness that increases as a function of increasing distance away from locally thinned portion  44  towards the ends of display cover layer  14 CG. By selectively enhancing the thickness of display cover layer  14 CG in non-thinned regions  46 , the edges and corners of layer  14 CG can be made thicker and more robust than other non-thinned portions of layer  14 CG, thereby helping to increase the ability of display cover layer  14 CG to resist impact damage. 
       FIGS. 6 and 7  are cross-sectional end views of display cover layer  14 CG in illustrative configurations in which the edge thickness of layer  14 CG has been locally increased to help resist impact damage.  FIG. 6  is a cross-sectional end view of layer  14 CG taken along line  60  of  FIG. 5  and viewed in direction  62 . As shown in  FIG. 6 , the thickness T 2  of display cover layer  14 CG is uniform across the width of display cover layer  14 CG and is greater than the thickness T 1  of the thinned portion  44  of layer  14 CG. In the illustrative configuration of  FIG. 6 , thickness T 2  is also thicker than the thickness of display cover layer  14 CG in the area of non-thinned portion  46  between end edge area  51  and the area of portion  46  that is immediately adjacent to portion  44 . As shown in  FIG. 7 , which is a cross-sectional end view of another illustrative layer  14 CG taken along line  60  and viewed in direction  62 , layer  14 CG may, if desired, have an increased edge thickness that is not uniform across the width of layer  14 CG. In the example of  FIG. 7 , layer  14 CG has thickness T 2  at the left and right edges of layer  14 CG (e.g., in the corners of layer  14 CG) but has a smaller thickness T 3  in the middle of layer  14 CG (e.g., the thickness of layer  14 CG is greater in corners  48  than in the center of end edge area  51 ). The outermost end edge of layer  14 CG (e.g., the edge of layer  14 CG viewed end on, rather than in cross section) may have a variable-thickness profile of the type shown in  FIG. 7 , may have a uniform-thickness profile of the type shown in  FIG. 6 , or other suitable thickness profile. 
       FIG. 8  is a cross-sectional profile of layer  14 CG of  FIG. 8  taken along line  64  of  FIG. 5  and viewed in direction  66 . In the illustrative configuration of  FIG. 8 , locally thinned portion  44  has a thickness that is reduced relative to non-thinned portions  46 . Non-thinned portions  46  of  FIG. 8  have a tapered cross-sectional profile and exhibit a thickness that increases from a minimum value near locally thinned portion  44  to a maximum value at the outermost end edge areas  51  of layer  14 CG. This configuration enhances the end edge thickness of display cover layer  14 CG (including, if desired, the corners of layer  14 CG) relative to other portions of non-thinned portions  46  to help layer  14 CG resist impact stress from a drop event. 
     In the example of  FIG. 8 , non-thinned portions  46  have tapered thickness profiles and increase in thickness linearly (or nearly linearly) as a function of distance from bend axis  28  towards the ends and end edges of layer  14 CG. If desired, the thickness profile of layer  14 CG may exhibit one or more different slopes along the length of layer  14 CG. As shown in  FIG. 9 , for example, non-thickened portions  46  may have greater-thickness edge portions  46 - 1  along edge areas  51  and may have constant-thickness portions  46 - 2  that extend between the edge portions  46 - 1  and locally thinned portion  44 . The thickness of layer  14 CG of  FIG. 9  may be constant across the width of layer  14 CG (as described in connection with  FIG. 6 ) or may vary across the width of layer  14 CG (see, e.g., the illustrative configuration of  FIG. 7 ). Using a thickness profile of the type shown in  FIG. 9 , the corners of layer  14 CG and the edges of layer  14 CG (particularly the end edges such as edge areas  51 ) may be provided with greater thickness relative to other non-thinned portions of layer  14 CG (e.g., relative to non-thinned portions  46 - 2 ). Display panel  14 P may overlap portions  46 - 1 , portions  46 - 2 , and portion  44  or may overlap only portions  46 - 2  and portion  44  (as examples). Polymer  50  may fill the recess under portion  44  and, if desired, may extend outwardly over portions  46 - 2  (and, if desired, portions  46 - 1 ) to planarize the entire inner surface of layer  14 CG that is overlapped by panel  14 P. 
     If desired, transitions between areas of different slope in the cross-sectional profile of layer  14 CG may be provided with curved cross-sectional profiles. These curved profile shapes may help avoid stress concentrations due to abrupt thickness changes and can therefore help enhance the strength of display cover layer  14 CG. Consider, as an example, the illustrative cross-sectional profile of display cover layer  14 CG that is shown in  FIG. 10 . As shown in this illustrative configuration, the cross-sectional profile of layer  14 CG may be provided with curved portions such as portions  70  at the transition between the centermost (thinnest) section of locally thinned portion  44  and the remainder of locally thinned portion  44  and such as portions  72  at the transition between locally thinned portion  44  and non-thinned portions  46 . Smoothing out the thickness changes in layer  14 CG at the transitions between areas of different slope (change in thickness per distance) may help increase the durability of layer  14 CG. As shown in  FIG. 10 , portions  46  may also have tapered shapes or other shapes with increased edge thickness to help increase the resistance of layer  14 CG to damage during drop events. 
       FIGS. 11 and 12  are cross-sectional side views of illustrative flexible displays showing how the recess in display cover layer  14 CG may be filled with polymer  50  ( FIG. 11 ) or air  74  ( FIG. 12 ). As shown in  FIGS. 11 and 12 , display cover layer  14 CG may have a groove the runs along bend axis  28  and forms locally thinned portion  44 . Non-thinned portions  46  of  FIGS. 11 and 12  have increased edge (and corner) thickness. Flexible display panel  14 P has been attached to inner surface  42  of display cover layer overlapping bend axis  28 . 
     In the example of  FIG. 11 , polymer  50  has been formed in the groove under locally thinned portion  44  to help smooth out the inner surface of display cover layer  14 CG. Polymer  50  may be index matched to display cover layer  14 CG. A layer of polymer (e.g., polymer  50 ′) may be used in attaching display panel  14 P to the inner surface of display cover layer  14 CG. Polymer  50 ′ may be an extended portion of polymer  50  or may be a separate polymer layer. Polymer  50 ′ may conform to the taper or other profile of non-thinned portions  46  (as shown in  FIG. 11 ) or may have an opposing taper or other profile that is configured to counteract the taper or other profile of non-thinned portions  46  so that the inner surface of polymer  50 ′ lies in a single plane across all of display  14 . Arrangements in which polymer  50 ′ has a relatively uniform thickness so that the inner surface of polymer  50 ′ follows the tapered profile of portions  46  are sometimes described herein as an example. 
     In the example of  FIG. 12 , the groove in display cover layer  14 CG has been filled with air  74 . A layer of polymer (e.g., polymer  76 ) may be used to attach the portions of display panel  14 P that do not overlap air  74  to inner surface  42  of display cover layer  14 CG. 
     To help display  14  avoid impact damage during an unexpected drop event, it may be desirable for device  10  and display  14  to fold slightly upon experiencing the forces associated with a drop. In a typical drop scenario, device  10  is jolted out of a user&#39;s hands or experiences other jolting forces just prior to impact with a floor or other hard surface. The attributes of display  14  and hinge  30  can be configured so that the folding behavior of device  10  in response to a sudden jolt helps to avoid a scenario in which device  10  strikes the ground while display  14  is fully deployed and flat. For example, device  10  can be configured to normally exert a slight opening force that helps hold device  10  and display  14  in a flat state during normal use (i.e., so that the angle between the left and right halves of device  10  is equal to 180°) while device  10  is resting in a user&#39;s hands. Device  10  can also be configured so that this slight opening force will be overcome by the jolting force that results when device  10  is knocked from a user&#39;s hands. When the slight opening force is overcome, the properties of display  14  and hinge  30  make it energetically favorable for device  10  and display  14  to fold inwardly. This folding action causes the angle A between the left and right halves of the device housing to take on a value of less than 180° (e.g., a value of A between 179° and 135°, a value less than 179°, or other suitable value) because device  10  is at least partly folded in on itself rather than being completely open. When device  10  finally strikes the ground, device  10  and display  14  will be partly folded, which helps ensure that only edge portions of display  14  and device  10  will be impacted. By configuring hinge  30  and/or the structures of display  14  (e.g., the air, polymer, or other substances in the groove of display cover layer  14 CG and other display attributes) to help display  14  and device  10  fold in this way upon being jolted during a drop event, display  14  will be protected from scenarios in which display  14  is fully deployed (completely open and flat) and therefore more vulnerable to impact-induced damage. 
       FIGS. 13 and 14  illustrate two possible characteristics for the folding behavior of device  10  that result from configuring hinge  30  and the layers of display  14  to promote folding of device  10  when jolted during a drop event. In the graphs of  FIGS. 13 and 14 , the amount of stored (potential) energy E in the springs and/or other structures of hinge  30  and display  14  is plotted as a function of folding angle A, where A=180° corresponds to a completely unfolded configuration and A=0° corresponds to a completely folded configuration in which the left and right halves of display  14  are folded to face one another. 
     In the example of  FIG. 13 , there is a small rise in stored energy E at angle A 1 . When device  10  is resting in a user&#39;s hands in an open state, the rise in energy E at angle A 1  creates a slight restoring force that helps hold device  10  flat and completely open (with an angle A of) 180°. In the event of a jolt due to a drop event, the two halves of device  10  will fold by more than angle A 1  and, in this example, will continue to fold towards each other during the drop. By the time device  10  strikes the ground, device  10  will have folded sufficiently to help avoid a flat impact between display  14  and the ground that could potentially damage display  14 . 
     In the example of  FIG. 14 , there is also a small rise in stored energy E at angle A 1 , followed by a dip in stored energy at angle A 2  (when device  10  is slightly folded) and then a subsequent rise in stored energy for larger angles (e.g., angles greater than A 3 ). There may be a dip in stored energy near the fully closed position (A=0°) that helps hold the two halves of device  10  in a position facing each other when device  10  is closed. When fully opened, the rise in stored energy exhibit at angle A 1  helps hold device  10  in its fully opened position for normal use. The dip in stored energy at angle A 2  (e.g., relative to the larger amount of stored energy E at angles A 1  and A 3 ) creates a detent that helps cause device  10  to remain in this slightly folded orientation (A=A 2 ) when jolted past angle A 1  during a drop event. The slightly folded shape associated with folding angle A 2  helps device  10  avoid excessive damage during a drop event. When a user desires to close device  10 , the user can fold the left and right halves of device  10  together, overcoming the slight resistance to closing as angle A moves from A 2  past angle A 3 . 
     The detent behavior of  FIG. 14  may be implemented using any suitable display and hinge mechanisms.  FIG. 15  is a side view of an illustrative configuration for hinge  30  based on a spring-loaded cam mechanism. As shown in  FIG. 15 , hinge  30  includes cam wheel  30 - 1  and spring-loaded pin  30 - 2 . Wheel  30 - 1  is mounted on hinge shaft  82  and rotates relative to pin  30 - 2  as device  10  is folded and unfolded. Wheel  30 - 1  has a recessed portion corresponding to A=180° (the fully unfolded state of device  10 ), a protruding portion corresponding to angle A=A 1 , a recess corresponding to the detent at A=A 2 , a protruding portion corresponding to angles greater than A 3 , and a recess corresponding to the completely folded state (A=0°). When pin  30 - 2  is pressed outwards by the protruding portions of wheel  30 - 1 , stored energy E rises and when pin  30 - 2  is allowed to move inwards by the recessed portions of wheel  30 - 1 , the spring associated with pin  30 - 2  relaxes and stored energy E decreases. In this way, hinge  30  of  FIG. 15  exhibits a behavior of the type shown in  FIG. 14 . If desired, other cam mechanisms and/or hinge and/or display structures of other configurations may be used to impart a folding device behavior of the type shown in  FIG. 14  (or  FIG. 13 , etc.). The arrangement of  FIG. 15  is illustrative. 
     In the example of  FIGS. 8 and 9 , the increased thickness of the edge portions of display cover layer  14 CG was created using a single layer of glass or other cover layer material. If desired, two or more layers of glass or other transparent material may be laminated together in a configuration that forms a locally thinned bending region and enhanced-thickness edges. Consider, as an example, the arrangement of  FIG. 16 . As shown in  FIG. 16 , display cover layer  14 CG can be formed by laminating three layers of glass (or other transparent materials) together (e.g., glass layers  14 CG- 1 ,  14 CG- 2 , and  14 CG- 3 ). Upper layer  14 CG- 1  may be attached to left and right halves of middle layer  14 CG- 2  by an interposed layer of polymer  90 . The left and right halves of middle layer  14 CG- 2  may, in turn, be attached to first and second portions (e.g., left and right halves) of lower layer  14 CG- 3  by an interposed layer of polymer  92 . Polymer layers  90  and/or  92  may be integral portions of polymer  50 , which is used in filling the groove under locally thinned portion  44  that is formed by creating a gap between the left and right halves of layer  14 CG- 2  or layers  90  and/or  92  may be separate polymer layer(s) from polymer  50 . If desired, layer  90  and/or layer  92  may be omitted (e.g., in configurations in which the layers of display cover layer  14 CG are fused together without intervening polymer layers). Layer  14 CG- 3  may be patterned to enhance the thickness of only the end edges  50  of layer  14 CG or parts of edge-thickness enhancement layer(s) such as layer  14 CG- 3  may extend along some of the side edges of layer  14 CG (see, e.g., side edge areas  53  of  FIG. 5 ). If desired, layers such as layers  14 CG- 2  and/or  14 CG- 3  may have tapered cross-sectional shapes or other profiles that help enhance side and/or end edge thickness relative to the thickness of other areas of non-thinned portion  46 . The arrangement of  FIG. 16  is illustrative. 
     As described above, one aspect of the present technology is the gathering and use of information such as information from input-output devices. The present disclosure contemplates that in some instances, data may be gathered that includes personal information data that uniquely identifies or can be used to contact or locate a specific person. Such personal information data can include demographic data, location-based data, telephone numbers, email addresses, twitter ID&#39;s, home addresses, data or records relating to a user&#39;s health or level of fitness (e.g., vital signs measurements, medication information, exercise information), date of birth, username, password, biometric information, or any other identifying or personal information. 
     The present disclosure recognizes that the use of such personal information, in the present technology, can be used to the benefit of users. For example, the personal information data can be used to deliver targeted content that is of greater interest to the user. Accordingly, use of such personal information data enables users to calculated control of the delivered content. Further, other uses for personal information data that benefit the user are also contemplated by the present disclosure. For instance, health and fitness data may be used to provide insights into a user&#39;s general wellness, or may be used as positive feedback to individuals using technology to pursue wellness goals. 
     The present disclosure contemplates that the entities responsible for the collection, analysis, disclosure, transfer, storage, or other use of such personal information data will comply with well-established privacy policies and/or privacy practices. In particular, such entities should implement and consistently use privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining personal information data private and secure. Such policies should be easily accessible by users, and should be updated as the collection and/or use of data changes. Personal information from users should be collected for legitimate and reasonable uses of the entity and not shared or sold outside of those legitimate uses. Further, such collection/sharing should occur after receiving the informed consent of the users. Additionally, such entities should consider taking any needed steps for safeguarding and securing access to such personal information data and ensuring that others with access to the personal information data adhere to their privacy policies and procedures. Further, such entities can subject themselves to evaluation by third parties to certify their adherence to widely accepted privacy policies and practices. In addition, policies and practices should be adapted for the particular types of personal information data being collected and/or accessed and adapted to applicable laws and standards, including jurisdiction-specific considerations. For instance, in the United States, collection of or access to certain health data may be governed by federal and/or state laws, such as the Health Insurance Portability and Accountability Act (HIPAA), whereas health data in other countries may be subject to other regulations and policies and should be handled accordingly. Hence different privacy practices should be maintained for different personal data types in each country. 
     Despite the foregoing, the present disclosure also contemplates embodiments in which users selectively block the use of, or access to, personal information data. That is, the present disclosure contemplates that hardware and/or software elements can be provided to prevent or block access to such personal information data. For example, the present technology can be configured to allow users to select to “opt in” or “opt out” of participation in the collection of personal information data during registration for services or anytime thereafter. In another example, users can select not to provide certain types of user data. In yet another example, users can select to limit the length of time user-specific data is maintained. In addition to providing “opt in” and “opt out” options, the present disclosure contemplates providing notifications relating to the access or use of personal information. For instance, a user may be notified upon downloading an application (“app”) that their personal information data will be accessed and then reminded again just before personal information data is accessed by the app. 
     Moreover, it is the intent of the present disclosure that personal information data should be managed and handled in a way to minimize risks of unintentional or unauthorized access or use. Risk can be minimized by limiting the collection of data and deleting data once it is no longer needed. In addition, and when applicable, including in certain health related applications, data de-identification can be used to protect a user&#39;s privacy. De-identification may be facilitated, when appropriate, by removing specific identifiers (e.g., date of birth, etc.), controlling the amount or specificity of data stored (e.g., collecting location data at a city level rather than at an address level), controlling how data is stored (e.g., aggregating data across users), and/or other methods. 
     Therefore, although the present disclosure broadly covers use of information that may include personal information data to implement one or more various disclosed embodiments, the present disclosure also contemplates that the various embodiments can also be implemented without the need for accessing personal information data. That is, the various embodiments of the present technology are not rendered inoperable due to the lack of all or a portion of such personal information data. 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.