PATENT DOCUMENT

Publication Number: US-10845925-B2
Application Number: US-201816212488-A
Country: US
Kind Code: B2

Title: Electronic device having force sensor air flow promotion structures

Abstract:
An electronic device such as a device with a display may have a force sensor. The force sensor may include capacitive electrodes separated by a deformable layer such as a layer of an elastomeric polymer. The display or other layers in the electronic device may deform inwardly under applied force from a finger of a user or other external object. As the deformed layers contact the deformable layer, the deformable layer is compressed and the spacing between the capacitive electrodes of the force sensor decreases. This causes a measurable rise in the capacitance signal and therefore the force signal output of the force sensor. To prevent the deformable layer from sticking to the inner surface of the display layers, air flow promotion structures may be interposed between the deformable layer and the inner surface of the display. The air flow promotion structures may include spacer pads with anti-stick surfaces.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 first and second capacitive sensor electrodes separated by a deformable layer, wherein a distance between the first and second capacitive sensor electrodes changes when a force is applied by an external object; 
 a layer that is separated from the first capacitive sensor electrode by an air gap and that deforms towards the first capacitive sensor electrode when the force is applied by the external object, wherein the first capacitive sensor electrode is interposed between the second capacitive sensor electrode and the layer; and 
 air flow promotion structures interposed between the layer and the first capacitive sensor electrode to enhance air flow in the air gap when the force has been removed from the layer and the layer is moving away from the first capacitive sensor electrode. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the air flow promotion structures include at least one spacer pad. 
     
     
       3. The electronic device defined in  claim 2  wherein the spacer pad has a textured anti-stick surface. 
     
     
       4. The electronic device defined in  claim 2  wherein the spacer pad has a hydrophobic coating. 
     
     
       5. The electronic device defined in  claim 2  wherein the spacer pad has an elastic modulus of at least 1 GPa and a height of 10-100 microns. 
     
     
       6. The electronic device defined in  claim 2  wherein the spacer pad comprises a layer of polymer. 
     
     
       7. The electronic device defined in  claim 6  further comprising a layer of adhesive that attaches the layer of polymer to the deformable layer. 
     
     
       8. The electronic device defined in  claim 2  wherein the air flow promotion structures include a plurality of spacer pads including the at least one spacer pad. 
     
     
       9. The electronic device defined in  claim 8  wherein the plurality of spacer pads include first spacer pads having a first height and second spacer pads having a second height that is different than the first height. 
     
     
       10. The electronic device defined in  claim 1  wherein the deformable layer comprises an elastomeric polymer layer. 
     
     
       11. The electronic device defined in  claim 10  wherein the first capacitive sensor electrode comprises one of a plurality of electrodes on the elastomeric polymer layer. 
     
     
       12. The electronic device defined in  claim 1  further comprising a display, wherein the layer that is separated from the first capacitive sensor electrode by the air gap comprises part of the display. 
     
     
       13. The electronic device defined in  claim 12  wherein the display includes a backlight unit and wherein the layer that is separated from the first capacitive sensor electrode by the air gap comprises part of the backlight unit. 
     
     
       14. An electronic device operable by a user with an external object, comprising:
 a housing; 
 a display mounted in the housing, wherein the display has display layers that deform inwardly in response to pressure from the external object; 
 a capacitive force sensor that measures force levels applied by the external object to the display layers by making capacitance measurements using first and second electrodes separated by an elastomeric layer, wherein a distance between the first and second electrodes changes in response to the pressure from the external object, and wherein the first electrode is located between the display layers and the second electrode; and 
 an array of spacer pads covering the elastomeric layer, wherein the array of spacer pads is interposed between the display layers and the first electrode, wherein the display layers press against the array of spacer pads, and wherein the display layers compress the elastomeric layer when the display layers are bent inwardly. 
 
     
     
       15. The electronic device defined in  claim 14  wherein the spacer pads include first spacer pads having a first height and second spacer pads having a second height that is different than the first height. 
     
     
       16. The electronic device defined in  claim 15  wherein the first and second spacer pads are arranged in a checkerboard pattern on the elastomeric layer. 
     
     
       17. The electronic device defined in  claim 14  further comprising touch sensor circuitry that makes position measurements on the external object. 
     
     
       18. An electronic device, comprising:
 a display that deforms inwardly when pressed with a force by an external object; 
 an array of first capacitive electrodes on a first surface of an elastomeric layer; 
 a second capacitive electrode on an opposing second surface of the elastomeric layer, wherein a distance between the array of first capacitive electrodes and the second capacitive electrode changes in response to the force, and wherein the array of first capacitive electrodes is located between the display and the second capacitive electrode; 
 force sensing circuitry that measures the force by measuring capacitances between the first capacitive electrodes and the second capacitive electrode; and 
 an array of spacer pads on the first surface of the elastomeric layer that are contacted by an inner surface of the display when the display deforms inwardly and thereby deforms the elastomeric layer and increases the measured capacitances, wherein the array of spacer pads is interposed between the display and the array of first capacitive electrodes. 
 
     
     
       19. The electronic device defined in  claim 18  wherein the spacer pads include polymer layers. 
     
     
       20. The electronic device defined in  claim 19  wherein the spacer pads have anti-stick surfaces. 
     
     
       21. An electronic device having an outer surface, comprising:
 first and second capacitive sensor electrodes separated by a deformable layer that is overlapped by the outer surface, wherein a distance between the first and second capacitive sensor electrodes changes when a force is applied to the outer surface by an external object; 
 a layer that is separated from the deformable layer by an air gap, wherein the first capacitive sensor electrode is interposed between the layer and the second capacitive sensor electrode, wherein the air gap is interposed between the layer and the first capacitive sensor electrode, wherein the deformable layer and the layer that is separated from the deformable layer contact each other across the air gap when the force is applied to the outer surface by the external object; and 
 air flow promotion structures that enhance air flow in the air gap when the force has been removed from the layer and the layer is moving away from the first capacitive sensor electrode. 
 
     
     
       22. The electronic device defined in  claim 21  wherein the air flow promotion structures comprise openings in the deformable layer. 
     
     
       23. The electronic device defined in  claim 21  wherein the air flow promotion structures comprise recesses in the deformable layer. 
     
     
       24. The electronic device defined in  claim 23  wherein the recesses comprise deformations in the deformable layer. 
     
     
       25. The electronic device defined in  claim 21  wherein the air flow promotion structures comprise deformations in the layer that is separated from the deformable layer by the air gap. 
     
     
       26. The electronic device defined in  claim 21  further comprising a display, wherein the deformable layer is attached to the display. 
     
     
       27. The electronic device defined in  claim 26  wherein the air flow promotion structures comprise an array of spacer pads on the deformable layer. 
     
     
       28. The electronic device defined in  claim 21  further comprising a display, wherein the layer that is separated from the deformable layer is attached to the display. 
     
     
       29. The electronic device defined in  claim 21  wherein the air flow promotion structures include at least one hole that passes through the first capacitive sensor electrode.

Description:
This application is a continuation of patent application Ser. No. 15/175,536, filed Jun. 7, 2016, which claims the benefit of provisional patent application No. 62/206,428, filed Aug. 18, 2015, both of which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     This relates generally to electronic devices and, more particularly, to electronic devices with force sensors. 
     Electronic devices such as laptop computers may be provided with displays to provide visual output and track pads and other devices to gather touch and force input from a user. In some electronic devices such as tablet computers and cellular telephones, touch screens are used to display visual information and gather touch input. 
     There are challenges associated with implementing sensors such as force and touch sensors in an electronic device. If care is not taken, sensor measurements may be less accurate than desired or devices may be more bulky than desired. 
     It would therefore be desirable to be able to provide improved sensor arrangements for electronic devices. 
     SUMMARY 
     An electronic device such as a device with a display may have a force sensor. The force sensor may include capacitive electrodes separated by a deformable layer such as a layer of an elastomeric polymer. The electrodes may include an upper set of electrodes formed in an array pattern and a lower electrode on an opposing surface of the elastomeric polymer layer. Force sensor circuitry may make capacitance measurements between the capacitor electrode structures on the opposing surfaces of the elastomeric layer. 
     The display may have a backlight unit and a display module that is backlit by the backlight unit or may have other display layers. The display layers or other layers in the electronic device may bend inwardly under force from a finger of a user or other external object applied to the surface of the display or other external surface of the electronic device. These layers may be separated from the deformable layer by an air gap. When bent inwardly, the bent layers may come into contact with the deformable layer. 
     As the bent layers contact the deformable layer, the deformable layer becomes compressed and the spacing between the capacitive electrodes of the force sensor decreases. This causes a measurable rise in the capacitance associated with the electrodes and therefore a rise in the force signal output of the force sensor. When the user&#39;s finger is released from the bent layers or the applied external force is otherwise removed, the bent layers will experience a restoring force that moves the bent layers outwardly toward their original (unbent) position. 
     To prevent the deformable layer from sticking to the contacting surface of the display layers as a result of smooth-surface-to-smooth-surface contact and/or due to adhesion of the contacting layers to each other, air flow promotion structures may be interposed between the deformable layer and the contacting surface of the display layer. The air flow promotion structures may include spacer pads and anti-stick surfaces. The spacer pads may create air flow channels to help ensure adequate air flow into the air gap between the display layers and deformable layer as the display layers spring back to their original (unbent) position. The anti-stick surfaces may include textured surface structures and hydrophobic coatings to reduce adhesion to the display layers. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of an illustrative electronic device in accordance with an embodiment. 
         FIG. 3  is a top view of an illustrative touch sensor in accordance with an embodiment. 
         FIG. 4  is a top view of an illustrative touch sensor electrode pattern in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative force sensor in a configuration in which a user&#39;s finger has not contacted the sensor in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of the illustrative force sensor of  FIG. 5  following depression of the surface of the force sensor with the user&#39;s finger in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of an illustrative device with a force sensor that is not being contacted by an external object such as a user&#39;s finger in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of the illustrative device of  FIG. 7  following application of pressure on the force sensor with the finger of the user or other external object in accordance with an embodiment. 
         FIG. 9  is a graph showing how an output signal from a force sensor may be affected by the presence of air-flow promotion structures and other structures that promote the release of adjacent layers within a force sensor in accordance with an embodiment. 
         FIGS. 10 and 11  are cross-sectional side views of illustrative air flow promotion structures to promote air flow within a force sensor and thereby enhance force sensor responsiveness in accordance with an embodiment. 
         FIGS. 12-17  are top views of illustrative spacer pad patterns of the type that may be used in air flow promotion structures in an electronic device with a force sensor in accordance with an embodiment. 
         FIGS. 18-21  are top views of illustrative air flow promotion structures showing possible relationships between the size of spacer pads in the air flow promotion structures and electrodes on a deformable layer in a force sensor in accordance with an embodiment. 
         FIG. 22  is a cross-sectional side view of an illustrative spacer pad in a configuration in which the surface of the spacer pad has been provided with a texture to minimize sticking to adjacent layers in accordance with an embodiment. 
         FIG. 23  is a top view of an illustrative spacer pad with textured anti-stick structures to prevent sticking in accordance with an embodiment. 
         FIG. 24  shows how a spacer pad may have an undulating surface texture to prevent sticking in accordance with an embodiment. 
         FIG. 25  is a cross-sectional side view of an illustrative spacer pad with an anti-stick surface coating to help prevent sticking in accordance with an embodiment. 
         FIG. 26  is a cross-sectional side view of an illustrative display with air flow promotion structures formed from recesses in structures below an air gap in accordance with an embodiment. 
         FIG. 27  is a cross-sectional side view of an illustrative display with air flow promotion structures formed from surface deformations on structures above an air gap in accordance with an embodiment. 
         FIG. 28  is a cross-sectional side view of an illustrative display with air flow promotion structures formed from surface deformations on structures below an air gap in accordance with an embodiment. 
         FIG. 29  is a cross-sectional side view of an illustrative layer that has air flow promotion structures formed from holes that pass through sensor electrodes in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device such as electronic device  10  of  FIG. 1  may have sensors such as force and touch sensors and a display such as display  14 . The sensors of device  10  may be integrated with display  14  (e.g., display  14  may include a touch sensor and force sensor that overlaps the pixels of display  14 ) and/or device  10  may have a trackpad or other structure that gathers force and/or touch sensor input on a portion of device  10  that is separate from display  14 . Illustrative configurations for device  10  in which touch and/or force input is gathered by touching and pressing against display  14  are sometimes described herein as an example. 
     Device  10  may be a handheld electronic device such as a cellular telephone, media player, gaming device, or other device, may be a laptop computer, tablet computer, or other portable computer, may be a desktop computer, may be a computer display, may be a display containing an embedded computer, may be a television or set top box, may be a tablet computer that is attached to a detachable cover with a keyboard or other accessory, or may be other electronic equipment. 
     As shown in the example of  FIG. 1 , device  10  may have a housing such as housing  12 . Housing  12  may be formed from plastic, metal (e.g., aluminum), fiber composites such as carbon fiber, glass, ceramic, other materials, and combinations of these materials. Housing  12  or parts of housing  12  may be formed using a unibody construction in which housing structures are formed from an integrated piece of material. Multipart housing constructions may also be used in which housing  12  or parts of housing  12  are formed from frame structures, housing walls, and other components that are attached to each other using fasteners, adhesive, and other attachment mechanisms. 
     Device  10  may have a display such as display  14  mounted in housing  12 . Display  14  may be formed using any suitable display technology. For example, display  14  may be liquid crystal display (LCD), a plasma display, an organic light-emitting diode (OLED) display, an electrophoretic display, a microelectromechanical systems (MEMs) shutter display, or a display implemented using other display technologies. 
     A touch sensor and a force sensor may be incorporated into display  14 . Touch sensors for display  14  may be resistive touch sensors, capacitive touch sensors, acoustic touch sensors, light-based touch sensors, force-based touch sensors, or touch sensors implemented using other touch technologies. As an example, device  10  may include a capacitive touch sensor with an array of capacitive touch sensor electrodes that allows measurement of the position of an external objected such as finger  20 . The touch sensor may determine where an external object such as a user&#39;s finger (e.g., finger  20 ) is contacting the surface of device  10  and display  14  (i.e., the touch sensor may measure the location at which an external finger contacts the surface of display  14  in lateral dimensions  18 ). Display  14  lies within the X-Y plane of  FIG. 1 , so the touch sensor output from the touch sensor of display  14  produces information on the position of the user&#39;s finger (or other external object) in lateral dimensions X and Y. 
     When an external object such as finger  20  presses downwards on display  14  (or other external surface of device  10 ) in direction  22 , force is imparted on the surface of display  14  (or other device structure). Display  14  may include force sensor structures that detect force on display  14  in direction  22  (i.e., in the −Z direction of  FIG. 1 ). With one suitable arrangement, display  14  includes an outer transparent layer (sometimes referred to as a display cover layer). The display cover layer may be formed from a material such as glass, plastic, sapphire, or other transparent material. The display cover layer is clear, so that display  14  may display images for a user using an array of pixels overlapped by the display cover layer. The display cover layer or other planar member in device  10  (e.g., a trackpad member) may deform out of the X-Y plane when force is exerted in direction  22 . 
     A force sensor may be implemented using capacitive sensor electrodes within device  10 . The force sensor may be formed on the underside of display  14  or may be formed on layers of material that are separated from display  14  by an air gap. 
     Capacitances associated with the electrodes in the force sensor may vary as a function of separation between the electrodes, which can be influenced by the amount of force applied to the force sensor by pressing on display  14  or other structures in device  10 . Force measurements may therefore be gathered by making capacitance measurements between appropriate capacitor electrodes. If desired, these capacitance measurements may also be processed to determine the position at which a force is being applied to device  10  (i.e., to covert force data into touch location data). In this way, force data may be used to implement a touch sensor. 
     Illustrative configurations for the force and touch sensing structures of device  10  may sometimes be described herein in the context of touch and force sensors integrated into display  14 . This is, however, merely illustrative. Touch and/or force sensors may be incorporated into other portions of device  10  (e.g., portions of device  10  that do not include display structures), if desired. 
     A schematic diagram of an illustrative electronic device such as device  10  of  FIG. 1  is shown in  FIG. 2 . As shown in  FIG. 2 , electronic device  10  may have control circuitry  24 . Control circuitry  24  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, 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  24  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  26  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  26  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors, light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  26  and may receive status information and other output from device  10  using the output resources of input-output devices  26 . Input-output devices  26  may include one or more displays such as displays  14 . 
     Control circuitry  24  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  24  may display images on display  14  (e.g., video, still images such as text, alphanumeric labels, photographs, icons, other graphics, etc.) using arrays of pixels in display  14 . 
     Display  14  may have a rectangular shape or other suitable shape. For example, display  14  may have a rectangular footprint and a rectangular peripheral edge that runs around the rectangular footprint. Display  14  may be planar or may have a curved profile. 
     Touch sensor  28  may be implemented using an array of capacitive electrodes (e.g., electrodes that extend across the surface of device  10  in dimensions X and Y. The touch sensor may be formed as part of a track pad or other structure that is independent from display  14  or may be incorporated into one of the layers of display  14 . In configurations in which touch sensor  28  is incorporated into the structures of display  14 , capacitive touch sensor electrodes for sensor  28  may be formed from a transparent material such as indium tin oxide. 
     Force sensor  30  may be implemented in an opaque structure such as a track pad in display  14  and/or may be implemented as part of display  14 . Force sensor  30  may be formed from capacitive electrodes that produce a capacitance output that is indicative of applied force or may be implemented using other force sensor technologies. If desired, some of the capacitive electrodes that are used in forming force sensor  30  may be shared with some of the capacitive electrodes that are used in forming touch sensor  28 . Configurations in which the sensor electrodes for measuring touch sensor input and force sensor input are separate may also be used. 
     In some configurations, force sensor signals from an array of force sensor electrodes may be processed provide information on the location at which finger  20  is applying force, thereby allowing force sensor  30  to serve as a touch sensor (in addition to serving as a force sensor that produces force output data proportional to the amount of force applied by finger  20  in inward direction  22 ). 
     Configurations in which touch sensor  28  and force sensor  30  are implemented using transparent capacitive touch sensor electrodes that overlap display  14  are sometimes described here as an example. Other touch sensor and force sensor arrangements may be used in device  10 , if desired. 
       FIG. 3  is a top view of an illustrative capacitive touch sensor. As shown in  FIG. 3 , touch sensor  28  may have overlapping electrodes such as electrodes  36  and electrodes  38 . Electrodes  36  and  38  may be coupled to touch sensor circuitry such as touch sensor controller  34 . Controller  34  may apply drive signals to electrodes  36  while gathering corresponding sense signals from electrodes  38 . In the presence of an external object such as finger  20  at an intersection between a particular one of electrodes  36  and a particular one of electrodes  38 , the capacitance sensed between the intersecting electrodes will change. By processing the drive and sense signals, controller  34  can monitor the capacitances between each of the intersecting electrodes in sensor  38  and thereby determine whether or not those electrodes are being touched by finger  20 . This allows the position of finger  20  to be determined by controller  34 . 
     In the example of  FIG. 3 , electrodes  36  and  38  have the shape of elongated strips of conductive material (e.g., indium tin oxide, etc.). Other electrode shapes may be used if desired (e.g., blanket films, patterns of diamond-shaped or rectangular electrodes, etc.). In the illustrative electrode pattern of  FIG. 4 , electrode  36  is a blanket conductive layer (e.g., an electrode that overlaps all of display  14 ) and electrodes  38  are patterned to from an array of rectangular pads. Other electrode patterns may be used, if desired. The illustrative capacitive touch sensor electrode patterns of  FIGS. 3 and 4  are merely examples. 
       FIGS. 5 and 6  show how force sensor  30  may use a capacitive sensor arrangement. In the example of  FIG. 5 , sensor  30  has upper (outer) force sensor capacitive electrode  40  and lower (inner) force sensor capacitive electrode  44 . Dielectric material  42  (e.g., an elastomeric polymer or other deformable layer) may be interposed between electrodes  40  and  44 . Controller  46  may measure the capacitance between electrodes  40  and  44 . Capacitance is at a minimum when the separation between electrodes  40  and  44  is a maximum, as shown in  FIG. 5 . After a user has pressed finger  20  inwards in direction  22  as shown in  FIG. 6 , upper electrode  40  deforms towards electrode  44 , thereby increasing the amount of capacitance measured by controller  46 . With this type of arrangement, the capacitance output of sensor  30  is proportion to force. Capacitance is low when applied force is low and is high when applied force is high. 
     It may be desirable to form a touch sensor such as touch sensor  28  and a force sensor such as force sensor  30  from structures in display  14 . Consider, as an example, the cross-sectional side view of the portion of device  10  that is shown in  FIG. 7 . As shown in  FIG. 7 , display  14  may include an outer layer such as display cover layer  50 . Display structures  52  may be attached to the lower surface of display cover layer  50 . Display structures  52  may include, for example, an organic light-emitting diode layer, a liquid crystal display layer, and/or other types of display structures for producing images for a user. A touch sensor may be formed within layers  52  or may be formed elsewhere in device  10 . With one illustrative configuration, display structures  52  include liquid crystal display layers (module)  52 A and backlight unit  52 B. 
     Module  52 A may have upper (outer) and lower (inner polarizers) and interposed layers such as a color filter layer, liquid crystal layer, and thin-film transistor layer. Capacitor electrode  56  may be located on the inner surface of the inner polarizer layer and may overlap display  14 . 
     Backlight unit  52 B may be located below electrode  56 . Backlight unit  52 B may be formed from a light guide layer that receives light from edge-mounted light-emitting diodes. The light guide layer distributes the light laterally throughout display  14 . Light that is scattered outwards through module  52 A may serve as backlight illumination for display  14 . Light that is scattered inwards may be reflected upwards by a reflector located on the bottom surface of backlight unit  52 B. 
     Capacitive electrodes  60  may be formed in an array (e.g., a two-dimensional array) that covers display  14 . Elastomeric layer  62  may support electrodes  60 . An air gap such as air gap  64  may lie between electrodes  60  and backlight unit  52 B. Elastomeric layer  62  may separate lower capacitive electrode  66  from electrodes  60  by a distance D 1  when finger  20  is not pressing inwardly on display cover layer  50 . Dielectric layers  68  (e.g., polymer layer(s)) may separate ground layer  70  from lower electrode  66 . Additional structures such as structures  72  may serve as support structures for the layers of material mounted above structures  72 . Structures  72  may include, for example, pressure sensitive adhesive, battery structures, housing structures, etc. 
     During operation of the force sensor, control circuitry such as circuitry  46  of  FIGS. 5 and 6  may measure capacitances using the capacitive electrodes of device  10 . As an example, force sensor circuitry such as circuitry  46  may monitor capacitances between electrodes  60  on the upper surface of deformable elastomeric layer  62  and electrode  66  on the lower surface of deformable elastomeric layer  62 . 
     When finger  20  presses downward in direction  22 , display cover layer  50  may deform inwardly so that backlight unit  52 B and other display structures  52  press against the upper surface of elastomeric layer  62  and thereby deform elastomeric layer  62  inwardly, as shown in  FIG. 8 . This reduces the distance separating electrodes  60  from lower electrode  66  from D 1  in  FIG. 7  to a value D 2  that is less than D 1  in  FIG. 8 . As the separation between electrodes  60  and electrode  66  decreases, controller  46  may measure correspondingly increased capacitance(s) between each displaced electrode  60  and electrode  66 , thereby producing an output that is proportional to force. The output can be obtained independently for each deflected electrode  60  or the maximum output of electrodes  60  or other collective output signal may be gathered. In configurations in which a force signal is gathered from each electrode  60  force data may be converted to position information (e.g., the force sensor structures may be used in producing position data that can complement or replace the position data produced using touch sensor  28 ). If desired, controller  46  may measure other capacitance values (e.g., the capacitance between upper electrode  56  and electrodes  60  may be measured, which is also indicative of applied force levels). 
     Touch sensor structures for display  14  may be formed from an array of touch sensor electrodes in display structures  52  (e.g., electrodes in display module  52 A), from an array of touch sensor electrodes interposed between display module  52 A and the inner surface of display cover layer  50 , or other capacitive touch sensor electrodes that are separate from the force sensor electrodes and/or force sensor electrodes such as electrode  56 , electrodes  60 , and/or electrode  66  may be used in forming a capacitive touch sensor. 
     As shown in  FIG. 8 , the lower portion of display  14  (i.e., inner surface  76  of backlight unit  52 B) may press inwardly against layer  62  and electrodes  60  when finger  20  presses inwards in direction  22  and deforms (i.e., bends) display  14 . This forces the air from air gap  64  to move outwards from under display  14  in directions  78 . When finger  20  is released from display cover layer  50  in direction  74 , the depressed portion of display cover layer  50  will move in direction  74  to return to its original shape (e.g., a planar shape). Display cover layer  50  will move in direction  74  to relieve the stress that was imparted to layer  50  when layer  50  was bent due to the pressure of finger  20  in direction  22 . Elastomeric layer  62  may also exert a restoring force on display layer  50  in direction  74  and will restore electrodes  60  to their initial position. The spring-back force imparted in direction  74  by display cover layer  50  will pull the lower surface of display  14  (e.g., backlight  52 B) away from electrodes  60  and layer  62 . As a result, the air that was displaced from under display cover layer  50  to air gap regions  64 ′ will be drawn back under display cover layer  50  in directions  80 . 
     The air flow in directions  80  that is created by the release of finger  20  from display cover layer  50  is impeded by the small separation between the lower surface of display  14  (e.g., the lower surface of backlight  52 B) and the upper surface of the adjacent portions of the structures of  FIG. 8  such as electrodes  60  and elastomeric layer  62 . Particularly in configurations in which these two mating surfaces are smooth, there is a risk that the gap size (the height of adjacent air gap portions  64 ′ and the air gap directly under the primary deformed portion of display cover layer  50 ) will be so small that air cannot readily return to fill air gap  64 . This blocks airflow and slows down the process of returning display  14  and air gap  64  to their normal states. 
     In addition to slowing movement of the bent display layers of display  14 , stiction arising from the small air gap can produce force sensor hysteresis. In particular, upward movement of display  14  as display  14  is springing back to its original position may create suction that momentarily pulls upon layer  62  and electrodes  60 . This upward pull on layer  62  tends to separate electrodes  60  from electrode  66 , thereby creating an overshoot condition characterized by an overly small output capacitance measured across electrodes  66  and  60 . One of the consequences of inadequate airflow in regions  64 ′ (and/or stickiness of the bent display layers with respect to layer  62 ) is therefore an overshoot in the force signal. 
     To minimize or eliminate force sensor signal overshoot, air flow promotion structures may be formed on electrodes  60  and the upper surface of layer  62 . By promoting air flow and reducing sticking between layer  62  and the lower surface of display  14 , display cover layer  50  may return upwards to its planar configuration rapidly after finger  20  is removed. The air flow promotion structures may be reduce or eliminate upwards suction on electrodes  60  during this process. The air flow promotion structures may include rectangular spacers (sometimes referred to as shims, pads, or spacer pads) that prevent uninterrupted intimate contact between large smooth portions of display  14  and layer  62  when display  14  is bent inwardly to compress layer  62 . Anti-stick coatings, textures, and other features may be incorporated into the air flow promotion structures to enhance performance. 
     The impact of incorporating air flow promotion structures between electrodes  60  and the lower surface of display  14  is illustrated in the graph of  FIG. 9 . In the graph of  FIG. 9 , force sensor output F (e.g., the capacitance between one or more of electrodes  60  and electrode  66 ) has been plotted as a function of time for two different illustrative force sensor configurations. Dashed line  84  corresponds to a force sensor configuration of the type shown in  FIG. 8  without any air flow promotion structures interposed between display  14  and electrodes  60 . Solid line  86  corresponds to a force sensor configuration in which air flow promotion structures have been incorporated onto the lower surface of display  14  and/or the opposing upper surface of electrodes  60  and layer  62 . 
     At time t 1 , a user of device  10  presses inwards in direction  22 . This causes display  14  to bridge air gap  64  and press electrodes  60  inwardly towards electrode  66 . The output of the force sensor (i.e., the capacitance between electrode(s)  60  and electrode  66  therefore increases from low level FL to high level FH. The magnitude of force sensor output signal (capacitance) FH is proportional to the force exerted on display  14  (i.e., FH is inversely proportional to the distance separating electrodes  60  from electrode  66 ). 
     At time t 1 , the user releases finger  20  and display  14  springs upwards in direction  74 . Air flows under the released portion of display  14  in directions  80 . In the presence of air flow promotion structures, display  14  quickly returns to its normal planar state (or other resting state) and force signal F (i.e., the capacitance between electrodes  60  and electrode  66 ) drops quickly to low level FL, as illustrated by solid line  86  of  FIG. 9 . In the absence of air flow promotion structures, in contrast, the narrow size of gap  64 ′ and the smooth and intimate contact between display  14  and electrodes  60  slows air flow and creates upwards suction on electrodes  60  and surface stickiness, momentarily pulling electrodes  60  away from electrode  66  and creating an abnormally low force output signal F (see, e.g., overshoot  84 ′ in line  84  of  FIG. 9 ). 
     Illustrative air flow promotion structures are shown in  FIG. 10 . In the example of  FIG. 10 , air flow promotion structures  90  have been formed on lower layer  62  (e.g., an elastomeric support for electrodes  60 , which are not shown in  FIG. 10 ). If desired, air flow promotion structures  90  may be formed on the opposing lower surface of backlight unit  52 B or air flow promotion structures  90  may be formed on both of the opposing surfaces facing air gap  64  (i.e., the lower surface of backlight unit  52 B and the opposing upper surface of electrode support structures such as layer  62 ). Configurations in which air flow promotion structures  90  are formed on layer  62  are sometimes described herein as an example. 
     In the illustrative configuration of  FIG. 10 , air flow promotion structures  90  include an array of pads (sometimes referred to as spacers, spacer pads, or shims) separated by interposed air flow channels  96 . The spacer pads may all have the same height, may have three or more different heights, or, as shown in  FIG. 10  structures  90  may include pads of two different heights (i.e., two different thicknesses) such as tall pads  90 - 1  and short pads  90 - 2 . Configurations with multiple different heights may help promote quick release of the lower surface of display  14  from layer  62  and satisfactory air flow. 
     Pads  90 - 1  and  90 - 2  may be formed from layers of polymer or other materials (layers  92 ) that have been attached to layer  62  using adhesive  94 . In this type of arrangement, pads  90 - 1  and  90 - 2  may be attached to layer  62  from a tape (as an example). If desired, pads such as pads  90 - 1  and  90 - 2  (or other spacer structures that promote air flow) may be deposited using screen printing, blanket deposition of a layer or layers of material followed by photolithographic patterning (e.g., a layer of photoimageable polymer exposed and developed to form a desired pad pattern), blanket deposition followed by etching, shadow-mask deposition, electroplating, or other techniques for forming pads  90 - 1  and  90 - 2  from a single material or layers of material. Configurations for air flow promotion structures  90  that are formed from three or more different materials (e.g., an adhesive layer, a stiff polymer shim pad layer, and a non-stick coating) may also be used. 
     Air flow promotion structure pads  90 - 1  and  90 - 2  may be organized in a rectangular array having rows and columns or may be arranged in other patterns. A top view of air flow promotion structures  90  of  FIGS. 10 and 11  is shown in  FIG. 12 . As shown in  FIG. 12 , air flow promotion structures  90  may include pads  90 - 1  and  90 - 2 . The heights of pads  90 - 1  and  90 - 2  causes pads  90 - 1  and  90 - 2  to protrude upwards away from layer  62  and prevents the lower surface of backlight unit  52 B from contacting layer  62 . When display cover layer  50  is released and is springing back towards its planar configuration, air may flow through structures  90  in air flow channels such as channels  96  of  FIG. 12  and over the pads (particularly shorter pads  90 - 2 , as illustrated by arrow  98  of  FIG. 12 ). Because of the uneven surface formed by air flow promotion structures  90  (and the reduced amount of area where the display layers and layer  62  contact each other), display cover layer  50  and layer  62  will be able to pull apart from each other without excessive resistance (i.e., air will be able to flow quickly in directions  80 , thereby avoiding overshoot in force output signal F). 
     In the illustrative arrangement of  FIG. 12 , tall spacer pads  90 - 1  and short spacer pads  90 - 2  are arranged in a checkerboard pattern (alternating across both rows and columns of the array of pads).  FIG. 13  shows how pads  90 - 1  and pads  90 - 2  may be arranged in alternating columns. In the configuration of  FIG. 14 , pads  90 - 1  and pads  90 - 2  are arranged in a checkerboard pattern and have different shapes. Pads  90 - 1  are rectangular. Pads  90 - 2  are diamond shaped. In the illustrative checkerboard pattern of  FIG. 15 , pads  90 - 1  and pads  90 - 2  are circular.  FIG. 16  shows how pads  90 - 1  and  90 - 2  may be elliptical. In the example of  FIG. 17 , pads  90 - 1  and  90 - 2  are triangular. The shape of the channels  96  surrounding each cluster of six pads  90 - 1  and  90 - 2  of the type shown in  FIG. 17  is hexagonal. In general, the pads of air flow promotion structures  90  may be triangular, rectangular, circular, elliptical, square, hexagonal, may have shapes with curved sides, shapes with straight sides, and shapes with combinations of straight and curved sides, may form grooves, may form recesses, may form arrays and have other regular patterns, may be arranged in pseudorandom patterns, or may have other suitable configurations. The configurations of  FIGS. 10-17  are merely illustrative. 
     As shown in  FIG. 18 , air flow promotion pads  90 P in air flow promotion structures  90  may be smaller than electrodes  60  and may be overlapped by electrodes  60 . Electrodes  60  may be formed from an array of rectangular pads (e.g., metal pads) or other suitable electrode structures. In the example of  FIG. 19 , air flow promotion structure pad  90 P has the same rectangular shape and same size as electrode  60 .  FIG. 20  shows how air flow promotion structure pad  90 P may be larger than electrode  60 . In the  FIG. 21  example, there are four pads  90 P on a single corresponding electrode  60 . Configurations in which pads  90 P partly overlap electrodes  60  and/or are spaced unevenly with respect to electrodes  60  may also be used. 
     It may be desirable to texture pads  90 P, as shown in  FIG. 22 . In the example of  FIG. 22 , upper surface  90 P′ of spacer pad  90 P has been provided with protruding portions  100  that are separated by recessed portions  102 . The surface texture associated with upper surface  90 P′ may help prevent sticking between the lower surface of display  14  and the upper surface of the air flow promotion structures on layer  62  and may therefore be referred to as an anti-stick surface, anti-stick structures, or anti-stick texture. 
       FIG. 23  is a top view of the illustrative anti-stick structures of  FIG. 22  showing how protrusions  100  may have rectangular shapes and may be arranged in an array with rows and columns. Other configurations may be used for protrusions  100  (e.g., triangular shapes, rectangular shapes, protrusions with different heights, circular shapes, elliptical shapes, shapes with straight edges, curved edges, or combinations of strait and curved edges, shapes in pseudorandom patterns, etc.). The cross-sectional side view of  FIG. 24  shows how protrusions  100  may have a wavy profile. Protrusions  100  may be formed using embossing, etching, molding, photolithography, or other techniques. 
     A non-stick coating layer such as a layer of polytetrafluoroethylene or other non-stick coating may be formed on the upper surface of a textured or smooth spacer pad, as shown by illustrative non-stick coating  104  on pad  90 P of air flow promotion structures  90  of  FIG. 25 . 
     To prevent air flow promotion structures  90  from deforming excessively and thereby tending to stick when contacted by display cover layer  50  or other surfaces, it may be desirable to form air flow promotion structures  90  (e.g., spacer pads, etc.) from stiff materials (e.g., materials such as plastic, metal, glass, ceramic, or other materials having an elastic modulus of 0.5 GPa or more, 1 GPa or more, 1-100 GPa, more than 2 GPa, less than 200 GPa, or other suitable value). When air flow prevention structures  90  are formed from stiff materials such as these, downwards force from display cover layer  50  may be transferred to deformable elastomeric layer  62 , so that electrodes  60  and layer  62  are deformed downwards without expending downwards force from finger  20  compressing the material of structures  90 . Stiff air flow prevention structures are therefore able to efficiently transfer force from finger  20  to electrodes  60 . 
     The height of air flow prevention structures  90  (e.g., the heights of tall and short spacer pads) may be about 20-50 microns, more than 5 microns, more than 10 microns, more than 20 microns, 10-150 microns, less than 200 microns, more than 30 microns, less than 75 microns, or other suitable height. This helps allow sufficient air to flow without creating excess thickness in the layers of device  10 . 
     The ratio of the area consumed by the spacer pads to the air flow channels surrounding the spacer pads may be 1:1, 1-100 to 1, more than 1 to 1, more than 2 to 1, more than 100 to 1, less than 100 to 1, less than 2 to 1, less than 1 to 1, 1 to 1-100, 1 to 2-20, 1 to more than 1, 1 to more than 10, 1 to more than 100, or 1 to less than 50 (as examples). When relatively more area is consumed by spacer pads, force transfer is enhanced, but air flow can become restricted. When relatively more area is consumed by air flow channels, air flow is enhanced, but excessively small spacer pad areas should be avoided to ensure that there is sufficient contact area to deflect electrodes  60  satisfactorily. 
     The surface characteristics of the spacer pads in air flow promotion structures  90  can be selected to reduce sticking and thereby help avoid sensor overshoot. Stickiness can be reduced by creating a texture on the upper surface of the spacer pads and/or by applying a non-stick coating to the spacer pads. Textured surfaces are illustrated in the examples of  FIGS. 22-24 . A non-stick coating is illustrated by coating  104  of  FIG. 25 . Non-stick coatings for structure  90  may by hydrophobic. Examples of non-stick (hydrophobic) coating materials for structures  90  include polytetrafluoroethylene and fluorinated ethylene propylene. Hydrophobic coating materials for use in coating air flow promotion structures  90  may be characterized by relatively large contact angles A (e.g., contact angle A may be greater than 90°, contact angle A may be greater than 130°, or contact angle A may be greater than 170°). Non-stick coatings may be formed on spacer pads with smooth or textured surfaces. 
       FIG. 26  is a cross-sectional side view of display  14  in an illustrative configuration in which air flow promotion structures have been formed by forming openings  202 R in layer  202 . Layer  202  may include some or all of the layers below air gap  64  such as the layers forming electrodes  60  and/or  66  and/or layers  62 ,  68 ,  70 , and  72  of  FIGS. 7 and 8  and may be separated from display structures  52  (e.g., layer  200 ) by air gap  64 . Openings  202 R may pass through all of layer  202  as shown by illustrative openings  202 R′ or may protrude only partway through layer  202  as shown by illustrative recesses  202 R″. Openings  202 R may be formed through electrodes such as electrodes  60  and/or  66 , may be formed in gaps between electrodes, and/or may be formed in other portions of layer  202 . 
     Protruding portions  202 P of layer  202  are formed between respective openings  202 R and may form spacer pads, texture on a spacer pad, or other air flow promotion structures. Recesses  202 R in layer  202  may be formed by punching, laser drilling, machining, photolithography, or other suitable fabrication techniques. Openings  202 R may be patterned to form circular openings, square openings, grooves, slots, air channels, and/or other air flow promotion shapes of the type described in connection with 10-23. Openings  202 R may be formed in non-sensing portions of layer  202  or other portions of layer  202 . Openings such as openings  202 R in lower layer  202  may be formed in one or more of the layers of material above air gap  64  (see, e.g., display structures  52 ). The example of  FIG. 26  in which openings  202 R have been formed in lower layer  202  is merely illustrative. 
       FIG. 27  is a cross-sectional side view of a layer of material  200  above air gap  64  that has been provided with recesses  200 R and corresponding protrusions  200 P to form air flow promotion structures for display  14 . Layer  200  may include one or more of display layers  52 . Recesses  200 R and protrusions  200 P may be formed by deforming display layers (structures  52 ) under heat and/or pressure in a press with patterned raised portions and depressions, using laser drilling, using photolithography, using machining equipment, by building layers of material such as protrusions onto the lower surface of structures  52  using adhesive and additional layer(s) of material, or other suitable techniques.  FIG. 28  shows how surface deformation techniques (e.g., compressing some or all of the layers of material in layer  202  with a press, etc.) can be used to create depressions such as recessed portions  202 R and protrusions  202 P in layer  202 . Arrangements of the type shown in  FIG. 27  may be used alone, arrangements of the type shown in  FIG. 28  may be used alone, or arrangements of the type shown in  FIGS. 27 and 28  may be used together. The recesses in the opposing surfaces above and/or below air gap  62  may serve as air flow promotion channels or other air flow promotion structures and may, if desired, form anti-stick surfaces for such structures, as described in connection with the structures of  FIGS. 7-25 . Protrusions  200 P and/or  202 P may form spacer pads, may form anti-stick textures, and/or may form other air flow promotion structures. 
     If desired, sensor structures such as electrodes  60  and  66 , deformable layer  62 , etc. (see, e.g., some or all of layer  202  of  FIG. 28 ) may be formed on the lower surface of display structures  52  and may be deformed (e.g., bent inwardly) under pressure from a finger or other external object. In this situation, layer  202  of  FIG. 28  may be located above air gap  64  and other structures (e.g., a battery, internal housing structures, and/or one or more other layers of material) may be located below air gap. When the outer sensor layers are bent inwardly by pressure from the user&#39;s finger, deformable layer  62  of the outer sensor layers will contact the battery or other internal layer, thereby deforming a portion of layer  62  and decreasing the spacing between electrodes  60  and  66  to produce a force signal. To promote airflow and to combat stiction effects, air flow promotion structures (e.g., shims, deformations, etc.) may be formed on the lower surface of the structures above air gap  64  (e.g., the lower surface of the sensor layers) and/or on the opposing upper surface of the battery or other layer(s) under air gap  64 . 
     As shown in  FIG. 29 , the recesses or other openings formed in the layers above or below air gap  64  may pass through sensor electrodes. In the example of  FIG. 29 , an array of capacitive force sensor electrodes  302  has been formed on layer  300 . Layer  300  may be formed above or below air gap  64  and may include structures such as some or all of the structures of layers  200  and  202 . In response to an applied external force, display structures or structures in device  10  may deform. This deformation may cause display structures or other structures to contact surface  308  of layer  300 . Air flow promotion structures may be formed from openings that pass through some or all of layer  300 , as illustrated by holes  306  and may include openings that pass through electrodes  302 , as illustrated by holes  304 . There may be any suitable number of holes such as holes  304  and  306  (e.g., one or more holes may be formed per electrode) and these holes may be circular, rectangular, or may have other suitable shapes. The illustrative configuration of  FIG. 29  is shown as an example. 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20181206
Publication Date: 20201124
Grant Date: 20201124
Priority Date: 20150818
Inventors: LIN, WEI
Herman, III, Henry E.
CHEN, PO-JUI
RUMFORD, ROBERT W.
TERRY, STEVE L.
CHUO, YINDAR
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/0445", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0445", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F3/0447", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/0447", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04105", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/044", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 58157511