PATENT DOCUMENT

Publication Number: US-12087187-B2
Application Number: US-202217580080-A
Country: US
Kind Code: B2

Title: Electronic devices with deformation-resistant displays

Abstract:
A flexible display in a foldable electronic device may have a display cover layer and display panel that 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 pixels may be formed from thin-film display circuitry that is supported by a flexible display panel substrate. The flexible substrate may be supported by a display support plate that bends about the bend axis. The display may be configured to allow attachment of the display panel substrate to the display support plate while helping to prevent undesired localized deformation of the thin-film display circuitry.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a foldable housing that is configured to bend about a bend axis; 
 a flexible display panel that overlaps the bend axis, wherein the flexible display panel comprises thin-film display circuitry on a substrate; 
 a display support plate configured to bend about the bend axis; and 
 a polymer layer that attaches the substrate to the display support plate, wherein the polymer layer has first and second opposing sides, wherein the polymer layer is bonded to the substrate on the first side, wherein the display support plate has openings that extend along the bend axis, wherein the polymer layer has protruding portions on the second side that protrude into the openings and attach the flexible display panel to the display support plate, and wherein the protruding portions of the polymer layer only partially fill the openings. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the substrate comprises thermoplastic polymer. 
     
     
       3. The electronic device defined in  claim 1  wherein the thin-film display circuitry is configured to form light-emitting diodes. 
     
     
       4. The electronic device defined in  claim 1  wherein the display support plate comprises a layer selected from the group consisting of: a metal layer and a glass layer. 
     
     
       5. The electronic device defined in  claim 1  further comprising gaps between the protruding portions and adjacent sidewalls of the openings. 
     
     
       6. The electronic device defined in  claim 1  wherein the substrate has an elastic modulus of at least 1 GPa. 
     
     
       7. The electronic device defined in  claim 6  wherein the display support plate comprises metal. 
     
     
       8. The electronic device defined in  claim 7  further comprising:
 a display cover layer; and 
 a polarizer between the display cover layer and the thin-film display circuitry. 
 
     
     
       9. An electronic device, comprising:
 a foldable housing that is configured to bend about a bend axis; 
 a flexible display panel that overlaps the bend axis, wherein the flexible display panel has a layer of thin-film display circuitry on a substrate; 
 a display support plate configured to bend about the bend axis, wherein the display support plate has flexibility enhancing openings and wherein the display support plate includes a linkage structure that bridges a given opening of the flexibility enhancing openings; and 
 a polymer adhesive layer that attaches the substrate to the display support plate, wherein a portion of the polymer adhesive layer protrudes into the given opening and extends to the linkage structure. 
 
     
     
       10. The electronic device defined in  claim 9  wherein the display support plate comprises a metal display support plate or a glass display support plate. 
     
     
       11. The electronic device defined in  claim 10  wherein the portion of the polymer adhesive layer extends between the substrate and the linkage structure. 
     
     
       12. The electronic device defined in  claim 11  wherein the given opening is defined by sidewalls of the display support plate and wherein the linkage structure is coupled between the sidewalls. 
     
     
       13. The electronic device defined in  claim 11  wherein the given opening is defined by sidewalls of the display support plate and wherein the portion of the polymer adhesive layer extends between the sidewalls. 
     
     
       14. The electronic device defined in  claim 10  wherein the polymer adhesive layer comprises an additional planar portion between the substrate and the display support layer and wherein the portion of the polymer adhesive layer protrudes into the given opening from the additional planar portion of the polymer adhesive layer. 
     
     
       15. An electronic device, comprising:
 a foldable housing that is configured to bend about a bend axis; 
 a flexible display panel that overlaps the bend axis, wherein the flexible display panel has a layer of thin-film display circuitry on a display panel substrate; and 
 a display support plate configured to bend about the bend axis, wherein the display panel substrate has an inwardly facing surface, wherein the display support plate has an opposing outwardly facing display support plate surface that is directly attached to the inwardly facing surface using a polymer layer, and wherein the polymer layer comprises a planar polymer layer having a modulus of elasticity of at least 1 GPa and having first and second opposing surfaces, the first surface contacting the inwardly facing surface of the display panel substrate and the second surface contacting the outwardly facing display support plate surface. 
 
     
     
       16. The electronic device defined in  claim 15  wherein the display support plate comprises flexibility enhancing openings. 
     
     
       17. The electronic device defined in  claim 16  wherein the polymer layer comprises polymer adhesive, wherein portions of the polymer adhesive are in portions of the flexibility enhancing openings, and wherein the polymer adhesive is attached to sidewalls of the flexibility enhancing openings and is attached to portions of the inwardly facing surface. 
     
     
       18. The electronic device defined in  claim 15  wherein the display panel substrate has a thickness of 20-50 microns. 
     
     
       19. The electronic device defined in  claim 15  wherein the display panel substrate has a modulus of elasticity of 9-20 GPa. 
     
     
       20. The electronic device defined in  claim 15  wherein the display support plate comprises glass, wherein the display support plate comprises flexibility enhancing openings, and wherein the flexibility enhancing openings extend along a strip-shaped region that overlaps the bend axis. 
     
     
       21. An electronic device, comprising:
 a housing; 
 a display panel that overlaps a bend axis, wherein the display panel has a layer of thin-film display circuitry on a substrate; 
 a display support plate having a plurality of openings that extend along the bend axis; and 
 a polymer layer that attaches the substrate to the display support plate, wherein the polymer layer comprises a planar layer having first and second opposing surfaces, wherein the first surface is bonded to the substrate, wherein the second surface is bonded to the display support plate, wherein a distance separating the substrate and the display support layer across the planar layer is less than 15 microns, wherein the planar layer has a portion that overlaps the plurality of openings, wherein the plurality of openings pass partly through the display support plate, and wherein a portion of the display support plate separates the plurality of openings from the portion of the planar layer. 
 
     
     
       22. The electronic device defined in  claim 21  wherein the polymer layer is a polymer adhesive layer. 
     
     
       23. The electronic device defined in  claim 22  further comprising a display cover layer overlapping the display panel, wherein the display cover layer has a thickness of less than 300 microns.

Description:
This application claims the benefit of provisional patent application No. 63/153,824, filed Feb. 25, 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. Displays may include sensing circuitry such as circuitry that detects input from a finger or stylus. During operation, a display may gather input from a user with the sensing circuitry while presenting the user with images for viewing. 
     SUMMARY 
     An electronic device may have a display that is resistant to deformation-induced damage due to contact by a finger, stylus, or other external object. The electronic device may be a foldable electronic device having a foldable display. The foldable display may have a display cover layer and display panel that 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 pixels may be formed from thin-film display circuitry that is supported by a flexible substrate. The flexible substrate may be supported by a display support plate that bends about the bend axis. If desired, the flexible substrate may be supported by a display support plate that bends about multiple axes (e.g., in a tri-fold device). Arrangements in which a flexible or rigid display are supported by a rigid support plate may also be used (e.g., in a device where the display is covered with a thin and/or soft cover layer). 
     The display support plate may be formed from a stiff layer that resists deformation when pressure is applied to the display from an external object such as a computer stylus. Thermoplastic polymer bonding, polymer adhesive bonding, and/or other attachment techniques may be used in attaching the display substrate to the display support plate. In an illustrative arrangement, the excessive use of soft material between the support plate and substrate is avoided to help prevent undesired localized deformation of the thin-film display circuitry. 
    
    
     
       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 display in accordance with an embodiment. 
         FIG.  4    is a cross-sectional side view of an illustrative display cover layer with a locally thinned hinge region in accordance with an embodiment. 
         FIG.  5    is a top view of an illustrative display support plate with flexibility enhancement openings in accordance with an embodiment. 
         FIG.  6    is a cross-sectional side view of a portion of a display in accordance with an embodiment. 
         FIG.  7    is a cross-sectional side view of illustrative display structures in which a thin adhesive layer has been used to attach a display panel substrate to a display support plate in accordance with an embodiment. 
         FIGS.  8 ,  9 ,  10 ,  11 ,  12 ,  13 ,  14 ,  15 ,  16 ,  17 , and  18    are cross-sectional side views of illustrative display structures with adhesive for attaching display panel substrates to display support plates in accordance with embodiments. 
         FIGS.  19 ,  20 ,  21 ,  22 , and  23    are cross-sectional side views of illustrative display structures with thermoplastic attachment mechanisms for attaching display panels to support plates in accordance with embodiments. 
     
    
    
     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, liquid crystal display pixels, or other pixels. For example, a device may have an organic light-emitting diode display, a display formed from an array of micro-light-emitting diodes (e.g., diodes formed from crystalline semiconductor dies), or a liquid crystal display. These displays may, if desired, be flexible. Flexible displays may be used in folding devices and other devices in which display panel structures are configured to bend about a bend axis. 
     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 may 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 rigid or bendable. Configurations in which the display panel is bendable allow device  10  to be folded and unfolded about a bend axis or about multiple bend axes. 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. In a tri-fold device configuration, display  10  may bend about first and second parallel bend axes. Arrangements in which device  10  bends about a single bend axis may sometimes be described herein as an example. 
     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  (e.g., to gather input from a finger, computer stylus, or other external object). 
     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 and/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 . 
     Display  14  may be flexible so that 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 flexible display panel for display  14 . Display panel  14 P of  FIG.  3    may have a flexible substrate such as display panel substrate  40 . Substrate  40  may be formed from a flexible material such as polymer (e.g., a polyimide substrate layer or other sheet of flexible polymer material), glass (e.g., a layer of glass that is sufficiently thin to allow panel  14 P to be bent), and/or other layer(s) and/or combinations of these layers. Pixels P may be formed on top of substrate  40  to form panel  14 P. In some embodiments, each pixel P may contain a respective light-emitting diode. 
     In an illustrative configuration, pixels P are formed from a layer of thin-film display circuitry such as thin-film circuitry  42 . Thin-film circuitry  42  includes thin-film layers  44  on substrate  40  (e.g., patterned thin-film layers for forming thin-film transistors, thin-film capacitors, thin-film light-emitting didoes such as organic light-emitting diodes, thin-film layers for forming buffer layers, routing layers that are patterned to form interconnects, encapsulation layers, and/or other display layers). Layers  44  may include organic materials (e.g., polymer buffer layers, organic materials for encapsulation structures, etc.) and/or may include inorganic dielectric (e.g., silicon nitride, silicon oxide, metal oxide layers, etc.). Inorganic dielectric layers may, as an example, form interlayer dielectric for a routing stack, may form portions of an encapsulation layer and/or buffer layer, may form gate oxide structures, etc. In some displays, a polarizer layer such as polarizer  46  (e.g., a flexible circular polarizer having a linear polarizer and quarter wave plate) may be used on the outwardly facing side of panel  14 P to suppress ambient light reflections. Polarizing layers may be provided as stand-alone layers and/or may be embedded into thin-film layers and/or embedded into cover layers. To protect display panel  14 P, display panel  14 P of display  14  may be overlapped by a display cover layer. Display  14  may be provided with a touch sensor. For example, a touch sensor layer such as a two-dimensional capacitive touch sensor for gathering touch input from a finger, stylus, or other external object may be formed from a flexible substrate that is attached between panel  14 P and the display cover layer, a touch sensor may be integrated into panel  14 P (e.g., by forming capacitive touch sensor electrodes on a common substrate with thin-film display pixel circuitry), or a touch sensor may be integrated into any other layer of display  14 . If desired, a touch sensor (and/or other sensor(s) such as force sensors, etc.) may be formed using ultrasonic devices, optical touch sensor circuitry, pressure sensing components, etc. The use of a two-dimensional capacitive touch sensor to provide display  14  with touch sensing capabilities is illustrative. 
     A cross-sectional side view of an illustrative display cover layer that may be used to cover display panel  14 P is shown in  FIG.  4   . As shown in  FIG.  4   , display cover layer  48  may be formed from a transparent protective layer such as layer  50 . Layer  50  may have a thickness of less than 700 microns, less than 300 microns, at least 100 microns, at least 400 microns, or other suitable thickness. Layer  50  may be a transparent layer of polymer and/or glass that allows viewing of display images by a user of device  10 . For example, layer  50  may be formed from a layer of glass or polymer that is sufficiently thin to be flexible and/or a layer of glass or polymer having a locally thinned portion such as portion  52  (e.g., a locally thinned strip formed from a recess that runs across the width of layer  50 , which is into the page in the orientation of  FIG.  4   ). The presence of optional locally thinned portion  52  and/or the use of flexible material may help layer  48  bend about bend axis  28  during folding of device  10 . If desired, there may be multiple locally thinned portions such as portion  52  (e.g., multiple parallel locally thinned regions). Arrangements in which layer  50  is locally softened in one or more regions (e.g., one or more parallel strips) by etching a strip-shaped array of holes into layer  50  may also be used. Flexibility for layer  50  may also be provided by forming layer  50  from multiple stacked layers and ensuring that only a subset of these layers span the locally thinned portion. 
     As shown in  FIG.  4   , an optional polymer filler layer such as layer  54  may fill the recess under locally thinned portion  52  and may extend over some or all of the inner surface of layer  50 . Optional additional layers such as layer  56  may be included in cover layer  48 , if desired. Layers such as layer  56  may include oleophobic layers to prevent fingerprints, hard coats to help prevent scratching, and/or other organic layers, inorganic layers, polymer films, etc. The maximum thickness of layer  50  may be at least 50 microns, at least 150 microns, at least 250 microns, at least 300 microns, 200-400 microns, less than 1000 microns, less than 500 microns, or other suitable maximum thickness value. The minimum thickness of layer  50  may be at least 20 microns, at least 50 microns, at least 150 microns, at least 250 microns, at least 300 microns, 200-400 microns, less than 1000 microns, less than 500 microns, or other suitable minimum thickness value. 
     Display panel  14 P may be supported on one or more supporting structures (e.g., structures formed from polymer, metal, ceramic, glass, and/or other materials that form one or more display panel supporting members). In an illustrative configuration, the support structures for display  14  may include a display support plate formed from metal, glass, and/or other material that is sufficiently rigid to resist deformation when external pressure is applied. The support plate, which may sometimes be referred to as a support member, support structure, backplate, or back film, may, as an example, have a modulus of elasticity of at least 1 GPa. 
     To allow the metal layer, glass layer, and/or other rigid layer(s) that form the display support plate to bend about bend axis  28 , a strip-shaped portion of the display support plate that overlaps and runs along bend axis  28  (and, if desired, other portions of the plate) may be provided with flexibility enhancement openings such as through-hole openings and/or openings that pass partially through the plate. This type of arrangement is shown in the top view of illustrative display support plate  58  of  FIG.  5   , which has openings  60  in a strip that extends along bend axis  28  to enhance the flexibility of display support plate  58  about bend axis  28 . Openings  60  may be circular, oval, rectangular, hexagonal, slot-shaped, and/or may have other shapes. Openings  60  may have lateral dimensions of at least 100 microns, 150-200 microns, less than 300 microns, less than 100 microns, less than 75 microns, or other suitable size. The fill ratio (ratio of opening area to non-opening area in the portion of plate  58  that contains openings  60 ) may be 40-60%, at least 35%, less than 70%, or other suitable fill ratio value. The thickness of layer  58  may be 75-250 microns, at least 20 microns, at least 50 microns, at least 75 microns, less than 800 microns, less than 500 microns, or less than 250 microns (as examples). Plate  58  may also be provided with a desired amount of flexibility about bend axis  28  by providing plate  58  with a strip-shaped locally thinned region formed from a recess in plate  58  that runs along bend axis  28 . This locally thinned plate portion may or may not include openings  60 . 
     During operation of device  10 , a user may press a finger, computer stylus, or other external object inwardly against the outermost surface of display  14  or may inadvertently drop an object with sharp curvature onto display  14 . For example, a computer stylus may be used to select on-screen items, draw lines, and otherwise control the operation of device  10 . A cross-sectional side view of device  10  in an illustrative configuration in which an external object is pressing against display  14  is shown in  FIG.  6   . 
     As shown in  FIG.  6   , device  10  may have a housing such as housing  12  to which display  14  may be coupled. The walls of housing  12  and display  14  may separate exterior region  86 , which surrounds device  10 , from interior region  80 . Electrical components  82  (see, e.g., the circuitry of  FIG.  1   ) may be mounted in interior region  80  (e.g., using printed circuits such as printed circuit  84 ). 
     During operation, display  14  may be used to present images viewable from exterior region  86 . A user may interact with device  10  by providing input to device  10  while viewing images displayed on display  14 . As shown in the example of  FIG.  6   , tip  64  of external object  66  (e.g., a tip with a radius of curvature of 0.5-1 mm or other tip  64  of an object such as a computer stylus) may be used to provide stylus input to a two-dimensional capacitive sensor and/or other sensor in device  10  that overlaps display  14 . When an object with sharp curvature is inadvertently dropped onto display  14  or during use of object  66  in supplying device  10  with input, a sharply curved structure such as tip  64  may press inwardly in direction  68 , thereby locally deforming display cover layer  48  as shown by dashed line  48 D. This, in turn, can result in local deformation of underlying soft layers in display  14  such as touch sensor layers and/or polarizer layers (see, e.g., layer  46 , which may deform as shown by dashed line  46 D). 
     Display panel  14 P and/or display support plate  58  may be configured to help avoid deformation of the potentially brittle inorganic layers and/or other structures of thin-film circuitry  42  due to the deformation of cover layer  48  and layer  46  from tip  64  of object  66 . For example, the amount of polymer adhesive or other soft material between layer  42  and support plate  58  may be maintained at a suitably low level. This ensures that the lower surface of circuitry  42  will be stiffly supported to help avoid excessive localized deformation of the thin-film layers in circuitry  42 . In this way, cracking and other damage to circuitry  42  can be avoided. 
     Consider, as an example, the cross-sectional side view of display  14  in  FIG.  7   . As shown in  FIG.  7   , substrate  40  of display panel  14 P may be attached to support plate  58  using polymer adhesive layer  90 . In some arrangements, the polymer used in forming the adhesive of layer  90  may be relatively soft (e.g., the adhesive may have a modulus of elasticity of less than 1 GPa, less than 500 MPa, etc.) and therefore subject to deformation under applied pressure on the surface of display  14  from external object  66 . To prevent excessive deformation in layer  14 , the total thickness T of layer  90  may be less than 20 microns, less than 15 microns, 10 microns, or less than 5 microns (as examples). Because use of a relatively small value of thickness T for layer  90  helps to reduce deformation of circuitry  42 , this arrangement may help prevent cracking and other damage to the thin-film layers in circuitry  42  from external object  66 . 
     If desired, substrate  40  may also have a thickness that helps prevent excessive localized deformation of substrate  40  from object  66 . As an example, the thickness of substrate  40  may be 10-50 microns. In some configurations, increased thickness for substrate  40  will help reduce localized deformation. 
     In an illustrative configuration, adhesive layer  90  may be relatively stiff (e.g., layer  90  may have a modulus of elasticity of 1-2 GPa, at least 0.8 GPa, at least 1 GPa, etc.). The use of stiff material for layer  90  (and, if desired, a small value of T) may help prevent deformation of layer  90  that could lead to deformation of circuitry  42 . 
     In some arrangements, the modulus of elasticity of substrate  40  (e.g., a polyimide substrate layer) may be larger than the modulus of elasticity of layer  90 . In an illustrative configuration, layer  90  may be formed from a polymer having a modulus of elasticity of less than 0.5 GPa (as an example) and substrate  40  may be formed from a polymer having a larger modulus (e.g., 9-20 GPa, at least 6 GPa, at least 8 GPa, at least 9 GPa, etc.). If desired, substrate  40  may be formed from a material such as glass (e.g., a layer of glass with a thickness of less than 100 microns or other suitable thickness to allow bending about bend axis  28 ). 
       FIG.  8    is a cross-sectional side view in which polymer adhesive layer  90  has been used to attach substrate  40  to support plate  58 . One side of layer  90  is bonded to substrate  40  and the opposing side of layer  90  is bonded to plate  58 . 
     As described in connection with  FIG.  5   , at least the portion of plate  58  that overlaps bend axis  28  may be provided with flexibility enhancing openings such as opening  60 . Openings such as opening  60  of  FIG.  8    may, as an example, be through-hole openings. Air, liquid, soft polymer, and/or other materials (e.g., materials with elastic modulus values of less than 1 GPa, less than 200 MPa, etc.) may be present in openings  60 . Openings  60  may be evenly or unevenly spaced from each other across plate  58 . For example, the density of openings  60  may be enhanced over axis  28  relative to other portions of plate  58 . Openings  60  may be formed by laser drilling, machining, wet and/or dry etching (one-sided or two-sided), stamping, and/or other fabrication techniques. If desired, plate  58  may be formed from multiple layers of material (e.g., a first layer with an array of openings  60  to which a second layer with no openings is attached by welds, adhesive, etc.). 
     The illustrative configuration of  FIG.  8    has openings  60  with straight vertical sidewalls. If desired, openings  60  may have different profiles as shown in the examples of  FIGS.  9  and  10   . 
       FIG.  11    shows how openings  60  may pass only partway through plate  58  (which may be formed from a single structure or multiple structures attached with welds and/or other attachment mechanisms). With configurations of the type shown in  FIG.  11   , the portion of plate  58  that overlaps each opening  60  may help provide vertical support for layer  90  and thereby help to prevent excess deformation of substrate  40 . Openings  60  in this type of arrangement may have any suitable cross-sectional shape. In the example of  FIG.  12   , opening  60  has a narrowed middle portion. In the example of  FIG.  13   , opening  60  has curved sidewalls forming a downwardly facing dome. 
     As shown in the example of  FIG.  14   , the upper portions of openings  60  may be partly or completely bridged by flexible linkage structures such as linkage  92 . Linkage  92  may be, for example, a thinned portion of plate  58  with a curved (e.g., bowed) cross-sectional profile that helps hold adjacent portions of plate  58  together while allowing plate  58  to flex. The adhesive of layer  90  may lie in a single layer (e.g., without penetrating into opening  60 ) or may, as shown in  FIG.  14   , at least partly penetrate into opening  60  (e.g., the portion of opening  60  above linkage  92  may be filled with adhesive). 
     If desired, the soft polymer adhesive material of layer  90  may be eliminated between the inwardly facing surface of substrate  40  and the opposing outwardly facing surface of support plate  58 . In this type of arrangement, which is shown in  FIG.  15   , the inwardly facing surface of substrate  40  directly contacts the outwardly facing surface of plate  58 . The adhesive of layer  90  may be located only in the upper portions of openings  60 . Adhesive bonds at the sides of openings  60  and on the portions of the inwardly facing surface of substrate  40  that overlap openings  60  can be used to attach substrate  40  to plate  58 . This type of arrangement may be used with openings of any suitable shape (see, e.g., the illustrative cross-sectional profiles of openings  60  of  FIGS.  16  and  17   ).  FIG.  18    shows how the polymer adhesive of layer  90  may be formed in openings  60  over linkages such as linkage  92 . Although openings  60  of  FIGS.  15 ,  16 ,  17 , and  18    are only partly filled with adhesive, adhesive and/or other soft materials (e.g., polymer) may fill most or all of openings  60 , if desired. The approach of  FIGS.  15 ,  16 ,  17   , and  18  in which a plug of adhesive is formed only at the top of each opening  60  is illustrative. 
     Thermoplastic bonding may be used to attach substrate  40  to plate  58 . For example, substrate  40  may be formed from a stiff thermoplastic polymer that can be softened under application of heat and pressure. Under these conditions, substrate  40  may be bonded directly to plate  58 , without an intervening soft adhesive layer. The modulus of elasticity of the thermoplastic material (e.g., substrate  40 ) in this type of arrangement may be, as an example, at least 1 GPa or at least 2 GPa. To ensure compatibility with thin-film circuitry  42 , it may be desirable to form substrate  40  from a material such as polyimide or glass. In this type of configuration, a stiff layer of the thermoplastic polymer that is separate from substrate  40  may be interposed between substrate  40  and plate  58  and may form a bonding layer. The thermoplastic polymer that is used to form this type of bonding layer to attach display panel  14 P to support plate  58  may soften and/or liquify under application of heat and pressure and may resolidify and bond to adjacent surfaces when cooled. Configurations in which substrate  40  is bonded to plate  58  using a separate thermoplastic polymer layer may be described herein as an example. 
     In the example of  FIG.  19   , substrate  40  of display panel  14 P is bonded to the surface of plate  58  with thermoplastic polymer layer  90 ′.  FIG.  20    shows how openings  60  may have narrowed upper portions to help engage portions of thermoplastic polymer layer  90 ′ that have flowed into the upper regions of openings  60 . Once resolidified, the portions of layer  90 ′ that protrude into the narrowed upper portions of openings  60  will help lock layer  90 ′ and substrate  40  to plate  58 .  FIGS.  21  and  22    show different illustrative cross-sectional profiles that may be used in forming openings  60 . 
     If desired, lateral gaps may be formed between the sides of the inwardly protruding portions of bonding layer  90 ′ and adjacent sidewalls of openings  60 . This type of arrangement is shown in  FIG.  23   . As shown in  FIG.  23   , circuitry  42  may be formed on substrate  40  and bonded to plate  58  using thermoplastic layer  90 ′. Layer  90 ′ may be formed from thermoplastic polymer that protrudes inwardly through the narrowed upper portion of each opening  60  to form protruding portions  90 P. Portions  90 P may have shapes configured to hold layer  90 ′ and substrate  40  to the surface of support plate  58 . Due to shrinkage following cooling, selective material removal, and/or other fabrication operations, gaps  100  (e.g., gaps filled with air, liquid, low modulus polymer, etc.) may be formed between the sides of each protruding portion  90 P and adjacent sidewalls of openings  60 . These gaps allow portions  90 P (and therefore layer  90 ′ and substrate  40 ) to slide slightly (e.g., to shift laterally, parallel to the surface of plate  58 ) as display  14  is folded and unfolded. The sides of openings  60  may be straight (tapered, vertical, etc.) and/or may be locally narrowed (see, e.g., profile lines  102 ) and/or curved in profile (see, e.g., profile lines  104 ). 
     Although sometimes described in the context of folding devices, the use of structures that help resist damage to thin-film circuitry in display  14  from pressure from objects with sharp curvature can be used in any suitable electronic device  10 . Device  10  may, as an example, be a cellular telephone, tablet computer, wristwatch, laptop computer or other device with a display that does not fold. Device  10  may also be provided with a foldable housing that folds about two or more bend axes (e.g., device  10  may have a tri-fold device housing). 
     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.

Metadata:
Filing Date: 20220120
Publication Date: 20240910
Grant Date: 20240910
Priority Date: 20210225
Inventors: AFSAR, YASMIN F.
HIGHTOWER, BEN
LALGUDI VISWESWARAN, BHADRINARAYANA
HUANG, CHANG-CHIA
KIM, HOON SIK
DRZAIC, PAUL S.
MANDLIK, PRASHANT
Lam, Terry C.
HSIEH, WEN-I
SHAO, ZHICHUN
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F1/1652", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/3025", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B1/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/3025", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F1/1652", "inventive": true, "first": false, "tree": "[]"}, {"code": "G09F9/33", "inventive": true, "first": true, "tree": "[]"}, {"code": "G09F9/301", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F1/1652", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/3025", "inventive": false, "first": false, "tree": "[]"}, {"code": "G09F9/33", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 82900870