PATENT DOCUMENT

Publication Number: US-9195108-B2
Application Number: US-201213591095-A
Country: US
Kind Code: B2

Title: Displays with bent signal lines

Abstract:
A display may be provided with an active central region and a peripheral inactive region. The display may have one or more flexible edges in the peripheral inactive region. Conductive lines may pass between components in the active central region such as display pixels and touch sensor electrodes and components in the inactive peripheral region such as gate driver circuitry and patterned interconnect lines. Each conductive line may have an unbent segment on a portion of a display layer in the active central region and may have a segment on the bent edge of the display layer. The display layer may be formed from a polymer or other flexible material. The bent segments may be configured to be less susceptible to increases in resistance from bending than the unbent segments.

Claims:
What is claimed is: 
     
       1. A display, comprising:
 display layers having a planar central active region and a peripheral inactive region, wherein the peripheral inactive region includes a bent region in which the display layers form a bend; 
 at least one conductive line that passes from the planar central region to the peripheral inactive region, wherein the conductive line includes a first segment in the planar central active region and includes a second segment that passes through the bent region over the bend and wherein the second segment is more resistant to damage when bent than the first segment; and 
 gate driver circuitry in the peripheral inactive region, wherein the bent region is between the gate driver circuitry and the planar central active region. 
 
     
     
       2. The display defined in  claim 1  wherein the second segment includes multiple parallel lines. 
     
     
       3. The display defined in  claim 1  wherein the second segment includes a metal line that follows a meandering path. 
     
     
       4. The display defined in  claim 1  wherein the second segment includes a different material than the first segment. 
     
     
       5. The display defined in  claim 4  wherein the first segment includes aluminum and wherein the second segment includes copper. 
     
     
       6. The display defined in  claim 1  wherein the second segment is wider than the first segment. 
     
     
       7. The display defined in  claim 1  wherein the second segment comprises a metal mesh. 
     
     
       8. The display defined in  claim 7  wherein the metal mesh has holes, the second segment further comprising conductive particles in the holes. 
     
     
       9. The display defined in  claim 1  wherein the second segment includes a lower metal line segment and an upper metal line segment that is coupled to the first metal line segment by vias. 
     
     
       10. The display defined in  claim 9  further comprising an inorganic passivation layer that covers the first segment, wherein the vias are formed from openings in the inorganic passivation layer. 
     
     
       11. The display defined in  claim 1  wherein the first segment includes a given number of metal layers and wherein the second segment includes more metal layers than the given number of metal layers. 
     
     
       12. The display defined in  claim 11  wherein the second segment includes copper. 
     
     
       13. The display defined in  claim 1  wherein the second segment includes a metal line with an undulating surface. 
     
     
       14. The display defined in  claim 1  wherein the first segment includes a line of metal and wherein the second segment includes the line of metal and an overlapping conductive material containing conductive particles. 
     
     
       15. The display defined in  claim 1  wherein the display layers comprise at least one rigid substrate in the active region and at least one flexible polymer layer in the inactive region. 
     
     
       16. The display defined in  claim 15  further comprising gate lines and data lines in the active region, wherein the second segment includes part of one of the data lines. 
     
     
       17. The display defined in  claim 1  wherein the display layers include organic light-emitting diode structures. 
     
     
       18. A display having an active area surrounded by a peripheral border, comprising:
 display structures having a planar portion in the active area and at least one flexible edge at the peripheral border with a bend; and 
 conductive lines on the display structures, wherein each conductive line has an unbent segment on the planar portion and a bent segment that runs across the bend and wherein each bent segment is configured to be less susceptible to increases in resistance from bending than each unbent segment. 
 
     
     
       19. The display defined in  claim 18  wherein each bent segment comprises a conductive structure selected from the group consisting of: a path having multiple parallel conductive lines, a path having a meandering conductive line, a path having a conductive mesh, a path having a lower line coupled to an upper line by a plurality of vias, a path having a conductive layer with an undulating surface, and a path having a layer of conductive particles. 
     
     
       20. The display defined in  claim 19  wherein the display structures comprise display pixels in the planar portion. 
     
     
       21. The display defined in  claim 19  wherein the display structures include capacitive touch sensor electrodes in the planar portion. 
     
     
       22. A display, comprising:
 a color filter layer; 
 a flexible layer having an array of display pixels, thin-film-transistor gate driver circuitry, and conductive lines including gate lines that distribute signals between the thin-film-transistor gate driver circuitry to the display pixels and including data lines, wherein the flexible layer has at least one bent edge region, and wherein the thin-film transistor gate driver circuitry is located in the bent edge region; and 
 a layer of liquid crystal material interposed between the color filter layer and the flexible layer, wherein each conductive line has an unbent segment on the flexible layer and has a bent segment on the bent edge region of the flexible layer, and wherein each bent segment comprises a conductive structure selected from the group consisting of: a path having multiple parallel conductive lines, a path having a meandering conductive line, a path having a conductive mesh, a path having a lower line coupled to an upper line by a plurality of vias, a path having a conductive layer with an undulating surface, and a path having a layer of conductive particles. 
 
     
     
       23. The display defined in  claim 22  wherein the flexible layer comprises a dielectric with an undulating surface and wherein the conductive structure comprises a path having a conductive layer on the undulating surface of the dielectric.

Description:
BACKGROUND 
     This relates generally to electronic devices, and more particularly, to electronic devices with displays. 
     Electronic devices often include displays. For example, cellular telephones and portable computers often include displays for presenting information to a user. An electronic device may have a housing such as a housing formed from plastic or metal. Components for the electronic device such as display components may be mounted in the housing. 
     It can be challenging to incorporate a display into the housing of an electronic device. Size and weight are often important considerations in designing electronic devices. If care is not taken, displays may be bulky or may be surrounded by overly large borders. 
     It would therefore be desirable to be able to provide improved displays for electronic devices. 
     SUMMARY 
     A display may be provided with an active central region and a peripheral inactive region. The active central region may include planar structures such as color filter layer substrates, thin-film-transistor substrates, and planar touch sensor structures. The peripheral inactive region may be provided with thin-film-transistor gate driver circuitry and other structures. 
     The display may have one or more flexible edges in the peripheral inactive region. The flexible edges may be bent at an angle with respect to the planar central active portion of the display. Conductive lines may pass between components in the active central region such as display pixels and touch sensor electrodes and components in the inactive peripheral region such as gate driver circuitry and patterned interconnect lines. Each conductive line may include an unbent segment on a portion of a display layer in the active central region and may have a bent segment that traverses the bend on the flexible edge of the display layer. 
     Display layers may be formed from polymers and other flexible materials. Each bent segment may be configured to be less susceptible to increases in resistance from bending than each unbent segment. 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a laptop computer with a display in accordance with an embodiment of the present invention. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a handheld electronic device with a display in accordance with an embodiment of the present invention. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer with a display in accordance with an embodiment of the present invention. 
         FIG. 4  is a schematic diagram of an illustrative electronic device with a display in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional side view of an illustrative display in accordance with an embodiment of the present invention. 
         FIG. 6  is a cross-sectional side view of an illustrative structure such as a display or touch sensor having a rigid central area and flexible edge portions in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side view of an illustrative flexible structure such as a flexible display or flexible touch sensor having bent edge portions in accordance with an embodiment of the present invention. 
         FIG. 8  is a top view of an illustrative display in accordance with an embodiment of the present invention. 
         FIG. 9  is a top view of an illustrative touch sensor in accordance with an embodiment of the present invention. 
         FIG. 10  is a perspective view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a bent edge portion with a signal path that is formed as an integral extension of a conductive line on unbent portions of the structure in accordance with an embodiment of the present invention. 
         FIG. 11  is a perspective view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a conductive path with an unbent segment and a bent segment that is less susceptible to increases in resistance from bending than the unbent segment in accordance with an embodiment of the present invention. 
         FIG. 12  is a perspective view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a signal path on a bent surface that is formed from parallel conductive lines in accordance with an embodiment of the present invention. 
         FIG. 13  is a top view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a signal path on a bent surface that is formed from a meandering line with right angle bends in accordance with an embodiment of the present invention. 
         FIG. 14  is a top view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a signal path on a bent surface that is formed from a meandering line with angled bends in accordance with an embodiment of the present invention. 
         FIG. 15  is a top view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a signal path on a bent surface that is formed from a flexible conductive material in accordance with an embodiment of the present invention. 
         FIG. 16  is a top view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a signal path on a bent surface that is formed from a locally widened conductive line in accordance with an embodiment of the present invention. 
         FIG. 17  is a top view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a signal path on a bent surface that is formed from a conductive mesh in accordance with an embodiment of the present invention. 
         FIG. 18  is a cross-sectional side view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a signal path on a bent surface that is formed from a conductive mesh with a conductive paint or other material with conductive particles in accordance with an embodiment of the present invention. 
         FIG. 19  is a cross-sectional end view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a signal path on a bent surface that is formed from multiple conductive layers in accordance with an embodiment of the present invention. 
         FIG. 20  is a cross-sectional side view of an illustrative structure such as a display pixel substrate or touch sensor structure that has a signal path on a bent surface that is formed from a lower conductive line and an upper conductive line that is coupled to the lower conductive line by vias through an interposed dielectric layer in accordance with an embodiment of the present invention. 
         FIG. 21  is a side view of half-tone mask equipment being used to expose a photoimageable polymer layer in accordance with an embodiment of the present invention. 
         FIG. 22  is a cross-sectional side view of a conductive line with an undulating surface of the type that may be produced using the equipment of  FIG. 21  in accordance with an embodiment of the present invention. 
         FIG. 23  is a cross-sectional side view of a conductive line with a corrugated shape of the type shown in  FIG. 22  that is being used to form a signal path on a bent surface of a display layer such as a display pixel substrate or touch sensor substrate in accordance with an embodiment of the present invention. 
         FIG. 24  is a top view of a conductive line with a corrugated shape of the type shown in  FIG. 22  that is being used to form a signal path on a bent surface of a display layer such as a display pixel substrate or touch sensor substrate in accordance with an embodiment of the present invention. 
         FIG. 25  is a cross-sectional end view of a conductive line with an additional conductive layer that is being used to form a signal path on a bent surface of a display layer such as a display pixel substrate or touch sensor substrate in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices may include displays. The displays may be used to display images to a user. Illustrative electronic devices that may be provided with displays are shown in  FIGS. 1 ,  2 , and  3 . 
       FIG. 1  shows how electronic device  10  may have the shape of a laptop computer having upper housing  12 A and lower housing  12 B with components such as keyboard  16  and touchpad  18 . Device  10  may have hinge structures  20  that allow upper housing  12 A to rotate in directions  22  about rotational axis  24  relative to lower housing  12 B. Display  14  may be mounted in upper housing  12 A. Upper housing  12 A, which may sometimes referred to as a display housing or lid, may be placed in a closed position by rotating upper housing  12 A towards lower housing  12 B about rotational axis  24 . 
       FIG. 2  shows how electronic device  10  may be a handheld device such as a cellular telephone, music player, gaming device, navigation unit, or other compact device. In this type of configuration for device  10 , housing  12  may have opposing front and rear surfaces. Display  14  may be mounted on a front face of housing  12 . Display  14  may, if desired, have a display cover layer or other exterior layer that includes openings for components such as button  26 . Openings may also be formed in a display cover layer or other display layer to accommodate a speaker port (see, e.g., speaker port  28  of  FIG. 2 ). 
       FIG. 3  shows how electronic device  10  may be a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  may have opposing planar front and rear surfaces. Display  14  may be mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  may have a cover layer or other external layer (e.g., a color filter layer or thin-film-transistor layer) with an opening to accommodate button  26  (as an example). 
     The illustrative configurations for device  10  that are shown in  FIGS. 1 ,  2 , and  3  are merely illustrative. In general, electronic device  10  may be a laptop computer, a computer monitor containing an embedded computer, a tablet computer, a cellular telephone, a media player, or other handheld or portable electronic device, a smaller device such as a wrist-watch device, a pendant device, a headphone or earpiece device, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     Housing  12  of device  10 , which is sometimes referred to as a case, may be formed of materials such as plastic, glass, ceramics, carbon-fiber composites and other fiber-based composites, metal (e.g., machined aluminum, stainless steel, or other metals), other materials, or a combination of these materials. Device  10  may be formed using a unibody construction in which most or all of housing  12  is formed from a single structural element (e.g., a piece of machined metal or a piece of molded plastic) or may be formed from multiple housing structures (e.g., outer housing structures that have been mounted to internal frame elements or other internal housing structures). 
     Display  14  may be a touch sensitive display that includes a touch sensor or may be insensitive to touch. Touch sensors for display  14  may be formed from an array of capacitive touch sensor electrodes, a resistive touch array, touch sensor structures based on acoustic touch, optical touch, or force-based touch technologies, or other suitable touch sensor components. 
     Displays for device  10  may, in general, include image pixels formed from light-emitting diodes (LEDs), organic LEDs (OLEDs), plasma cells, electrowetting pixels, electrophoretic pixels, liquid crystal display (LCD) components, or other suitable image pixel structures. In some situations, it may be desirable to use LCD components to form display  14 , so configurations for display  14  in which display  14  is a liquid crystal display are sometimes described herein as an example. It may also be desirable to provide displays such as display  14  with backlight structures, so configurations for display  14  that include a backlight unit may sometimes be described herein as an example. Other types of display technology may be used in device  10  if desired. The use of liquid crystal display structures and backlight structures in device  10  is merely illustrative. 
     A display cover layer may cover the surface of display  14  or a display layer such as a color filter layer, thin-film transistor layer or other portion of a display may be used as the outermost (or nearly outermost) layer in display  14 . For example, a color filter layer or thin-film transistor layer that is covered by a polarizer layer may form the outermost layer for device  10 . A display cover layer or other outer display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member. 
     Touch sensor components such as an array of capacitive touch sensor electrodes formed from transparent materials such as indium tin oxide may be formed on the underside of a display cover layer, may be formed on a separate display layer such as a glass or polymer touch sensor substrate, or may be integrated into other display layers (e.g., substrate layers such as a thin-film transistor layer). 
     A schematic diagram of an illustrative configuration that may be used for electronic device  10  is shown in  FIG. 4 . As shown in  FIG. 4 , electronic device  10  may include control circuitry  28 . Control circuitry  28  may include storage and processing circuitry for controlling the operation of device  10 . Control circuitry  28  may, for example, 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. Control circuitry  28  may include processing circuitry based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio codec chips, application specific integrated circuits, etc. 
     Control circuitry  28  may be used to run software on device  10 , such as operating system software and application software. Using this software, control circuitry  28  may present information to a user of electronic device  10  on display  14 . When presenting information to a user on display  14 , sensor signals and other information may be used by control circuitry  28  in making adjustments to the strength of backlight illumination that is used for display  14 . 
     Input-output circuitry  30  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 circuitry  30  may include communications circuitry  32 . Communications circuitry  32  may include wired communications circuitry for supporting communications using data ports in device  10 . Communications circuitry  32  may also include wireless communications circuits (e.g., circuitry for transmitting and receiving wireless radio-frequency signals using antennas). 
     Input-output circuitry  30  may also include input-output devices  34 . A user can control the operation of device  10  by supplying commands through input-output devices  34  and may receive status information and other output from device  10  using the output resources of input-output devices  34 . 
     Input-output devices  34  may include sensors and status indicators  36  such as an ambient light sensor, a proximity sensor, a temperature sensor, a pressure sensor, a magnetic sensor, an accelerometer, and light-emitting diodes and other components for gathering information about the environment in which device  10  is operating and providing information to a user of device  10  about the status of device  10 . 
     Audio components  38  may include speakers and tone generators for presenting sound to a user of device  10  and microphones for gathering user audio input. 
     Display  14  may be used to present images for a user such as text, video, and still images. Sensors  36  may include a touch sensor array that is formed as one of the layers in display  14 . 
     User input may be gathered using buttons and other input-output components  40  such as touch pad sensors, buttons, joysticks, click wheels, scrolling wheels, touch sensors such as sensors  36  in display  14 , key pads, keyboards, vibrators, cameras, and other input-output components. 
     A cross-sectional side view of an illustrative configuration that may be used for display  14  of device  10  (e.g., for display  14  of the devices of  FIG. 1 ,  FIG. 2 , or  FIG. 3  or other suitable electronic devices) is shown in  FIG. 5 . As shown in  FIG. 5 , display  14  may include backlight structures such as backlight unit  42  for producing backlight  44 . During operation, backlight  44  travels outwards (vertically upwards in the orientation of  FIG. 5 ) and passes through display pixel structures in display layers  46 . This illuminates any images that are being produced by the display pixels for viewing by a user. For example, backlight  44  may illuminate images on display layers  46  that are being viewed by viewer  48  in direction  50 . 
     Display layers  46  may be mounted in chassis structures such as a plastic chassis structure and/or a metal chassis structure to form a display module for mounting in housing  12  or display layers  46  may be mounted directly in housing  12  (e.g., by stacking display layers  46  into a recessed portion in housing  12 ). Display layers  46  may form a liquid crystal display or may be used in forming displays of other types. 
     In a configuration in which display layers  46  are used in forming a liquid crystal display, display layers  46  may include a liquid crystal layer such a liquid crystal layer  52 . Liquid crystal layer  52  may be sandwiched between display layers such as display layers  58  and  56 . Layers  56  and  58  may be interposed between lower polarizer layer  60  and upper polarizer layer  54 . 
     Layers  58  and  56  may be formed from transparent substrate layers such as clear layers of glass or plastic. Layers  56  and  58  may be layers such as a thin-film transistor layer and/or a color filter layer. Conductive traces, color filter elements, transistors, and other circuits and structures may be formed on the substrates of layers  58  and  56  (e.g., to form a thin-film transistor layer and/or a color filter layer). Touch sensor electrodes may also be incorporated into layers such as layers  58  and  56  and/or touch sensor electrodes may be formed on other substrates in the layers of a display. 
     With one illustrative configuration, layer  58  may be a thin-film transistor layer that includes an array of thin-film transistors and associated electrodes (display pixel electrodes) for applying electric fields to liquid crystal layer  52  and thereby displaying images on display  14 . Layer  56  may be a color filter layer that includes an array of color filter elements for providing display  14  with the ability to display color images. If desired, the positions of color filter layer  56  and thin-film-transistor layer  58  may be inverted so that the thin-film-transistor layer is located above the color filter layer. 
     During operation of display  14  in device  10 , control circuitry  28  (e.g., one or more integrated circuits such as components  68  on printed circuit  66  of  FIG. 5 ) may be used to generate information to be displayed on display  14  (e.g., display data). The information to be displayed may be conveyed from circuitry  68  to display driver integrated circuit  62  using a signal path such as a signal path formed from conductive metal traces in flexible printed circuit  64  (as an example). 
     Display driver integrated circuit  62  may be mounted on thin-film-transistor layer driver ledge  82  or elsewhere in device  10 . A flexible printed circuit cable such as flexible printed circuit  64  may be used in routing signals between printed circuit  66  and thin-film-transistor layer  60 . If desired, display driver integrated circuit  62  may be mounted on printed circuit  66  or flexible printed circuit  64 . Printed circuit  66  may be formed from a rigid printed circuit board (e.g., a layer of fiberglass-filled epoxy) or a flexible printed circuit (e.g., a flexible sheet of polyimide or other flexible polymer layer). 
     Backlight structures  42  may include a light guide plate such as light guide plate  78 . Light guide plate  78  may be formed from a transparent material such as clear glass or plastic. During operation of backlight structures  42 , a light source such as light source  72  may generate light  74 . Light source  72  may be, for example, an array of light-emitting diodes. 
     Light  74  from light source  72  may be coupled into edge surface  76  of light guide plate  78  and may be distributed laterally throughout light guide plate  78  due to the principal of total internal reflection. Light guide plate  78  may include light-scattering features such as pits or bumps. The light-scattering features may be located on an upper surface and/or on an opposing lower surface of light guide plate  78 . 
     Light  74  that scatters upwards from light guide plate  78  may serve as backlight  44  for display  14 . Light  74  that scatters downwards may be reflected back in the upwards direction by reflector  80 . Reflector  80  may be formed from a reflective material such as a layer of white plastic or other shiny materials. 
     To enhance backlight performance for backlight structures  42 , backlight structures  42  may include optical films  70 . Optical films  70  may include diffuser layers for helping to homogenize backlight  44  and thereby reduce hotspots, compensation films for enhancing off-axis viewing, and brightness enhancement films (also sometimes referred to as turning films) for collimating backlight  44 . Optical films  70  may overlap the other structures in backlight unit  42  such as light guide plate  78  and reflector  80 . For example, if light guide plate  78  has a rectangular footprint when viewed in direction  50  of  FIG. 5  (i.e., when viewed as a top view), optical films  70  and reflector  80  may have a matching rectangular footprint. 
     Display  14  may include a touch sensor (i.e., display  14  may be a touch screen display). The touch sensor may be implemented using an array of capacitive touch sensor electrodes such as transparent conductive electrodes formed from indium tin oxide or may be implemented using other touch technologies (e.g., resistive touch, acoustic touch, light-based touch, etc.). Capacitive touch sensor electrodes and other touch structures may be formed on a clear polymer substrate, a transparent glass substrate, or other substrates. The substrate on which the touch sensor structures are formed may be separate from the layers of display  14  of  FIG. 5  (e.g., by forming a touch sensor above upper polarizer  54 ) or may be combined with one or more of the layers of display  14  of  FIG. 5  (e.g., layers such as color filter layer  56  and/or thin-film-transistor layer  58 ). 
     To form narrow borders for display  14 , it may be desirable to bend display layers along the edges of display  14 . For example, it may be desirable to bend a flexible portion of a substrate so that inactive display structures such as the structures associated with gate driver circuitry in a liquid crystal display or the structures associated with distributing and gathering signals from capacitive touch sensor electrodes in a touch sensor are bent out of the way and are not visible to a viewer of display  14 . As an example, it may be desirable to bend flexible tail portions of a liquid crystal display or inactive edge portions of an organic light-emitting diode display downwards at a right angle with respect to a planar active display region. It may also be desirable to bend flexible inactive edge portions of a flexible touch sensor downwards at right angles to the active portion of the touch sensor. 
     When bending flexible substrates in a display, care should be taken to avoid creating stress cracks in the conductive lines on the substrates. Conductive lines that are formed exclusively from thin layers of relatively stiff metals such as aluminum may be prone to cracking if bent excessively. 
     The layers of a display with bent edges may be formed from flexible planar sheets of material with bent edges or from rigid structures that have flexible edge portions that are bent. 
       FIG. 6  is a cross-sectional side view of display structures for display  14  in a configuration in which the display structures have a rigid central region formed by rigid substrates  102  and a flexible edge portion formed by laterally protruding flexible display layers  104 . Display layers  104  may include structures such as thin flexible sheets of polymer, liquid crystal material, indium tin oxide touch sensor structures, or other flexible structures. Substrates  102  may be formed from layers of glass, plastic, or other materials that are generally harder and more rigid than flexible display layers  104 . 
     In the portion of display structures  100  in which flexible display layers  104  are sandwiched between substrate layers  102 , display structures  100  will be relatively rigid. In edge portions running along one or more, two or more, three or more, or four or more of the edges of display structures  100 , portions of flexible display layers  104  that are uncovered by rigid substrate layers  102  may be flexible to allow these edge portions of layers  104  to be bent at an angle with respect to the planar rigid portion of structures  100  that is formed by substrate layers  102 . 
     As shown in  FIG. 7 , display structures  100  may include a flexible layer with bent edges such as flexible display layer  104  in a configuration in which no rigid substrate layers are present. 
     Flexible display layers  104  of  FIG. 6  and  FIG. 7  may be touch sensor layers and/or display layers that include active display pixels for presenting images to a user (e.g., a flexible organic light-emitting diode layer). As shown in  FIG. 7 , flexible display layer  104  may, if desired, include one or more sublayers of material such as sublayers  104 A,  104 B, and  104 C. Sublayers  104 A,  104 B, and  104 C may include emissive organic layers, encapsulation layers, substrate layers, touch sensor electrode layers, thin-film-transistor layer substrates or other display pixel substrates, or other touch and display structure layers. 
     Display  14  may have a rectangular shape with a periphery having four edges. The flexible edge portions of display structures  100  in configurations of the type shown in  FIGS. 6 and 7  may be bent along one or more of the four peripheral edges, along two or more of the four peripheral edges, along three or more of the four peripheral edges, or along four or more of the four peripheral edges. The bent edges may be formed by bending flexible structures such as protruding flexible layer  104  of  FIG. 6  and the edges of flexible layer  104  of  FIG. 7  along a fold line (sometimes referred to as a bend axis). A minimum bend radius R may be maintained during bending to prevent damage to the display structures. The value of bend radius R may be, for example, less than 2 mm, less than 1 mm, less than 0.5 mm, or less than 0.25 mm (as examples). 
       FIG. 8  is a top view of an illustrative display of the type having edge structures that may be folded out of the way to minimize the display border. The structures of  FIG. 8  may be, for example, display structures that include pixels for producing images for a viewer. As shown in  FIG. 8 , display  14  may include a substrate such as thin-film-transistor layer  58 . A display driver integrated circuit may be mounted on thin-film-transistor layer  58  or may be mounted on a separate substrate such as a flexible printed circuit that is attached to layer  58 . Display  14  may include a central rectangular active area AA containing rows and columns of display pixels  106  (e.g., an array of display pixels). Each display pixel may contain electrodes for applying an electric field to an associated portion of liquid crystal layer  52  and a thin-film transistor for controlling the electric field. 
     Data pixels  106  may be controlled by signals that are applied to data pixels  106  via signal lines such as data lines D and gate lines G. Gate driver circuitry  108  may be used to assert gate control signals on gate lines G. Gate driver circuitry  108  may include thin-film transistors. Thin-film transistor gate driver circuitry  108  and the thin-film transistors of display pixels  106  may be formed from thin-film semiconductor materials such as silicon (e.g., polysilicon or amorphous silicon) or compound semiconductors (e.g., indium gallium zinc oxide). 
     The rectangular array of display pixels  106  in display  14  is used in displaying images for a user and is therefore sometimes referred to as the active area (area AA) of display  14 . Inactive region IA may surround active area AA on thin-film-transistor layer  58 . Inactive region IA may form a rectangular ring that surrounds the periphery of active area AA (as an example). Circuitry such as gate driver circuitry  108  and associated conductive paths (metal lines) may be formed in inactive regions. To minimize the visibility of the inactive border regions of display  14 , display  14  may be provided with flexible edges (e.g., by forming the circuitry of  FIG. 8  on a flexible display layer such as layer  104  of  FIGS. 6 and 7 ). With this type of arrangement, inactive display regions IA may be bent out of the way by folding the flexible display layer along bend lines in the inactive regions such as illustrative bend lines  110  and  112  of  FIG. 8 . 
     When forming folds in the layers of display  14  in this way, care should be taken not to damage the conductive paths on the display such as the data lines D and gate lines G and the other conductive lines that are used in routing signals for display  14 . The process of bending a flexible layer in a display such as a display layer with display pixels or a flexible touch sensor layer may bend conductive paths on the flexile layer sufficiently to create stress cracks in metal lines in the bent area. Premature failures, increased line resistance, and other issues with metal that has stress cracks can be avoided by providing the flexible layers of display  14  with structures that are configure to resist damage during bending and to be less susceptible to increases in resistance from bending than unbent structures. 
       FIG. 9  is a top view of an illustrative touch sensor. Touch sensor  114  may be formed on a flexible substrate such as substrate  130 . Substrate  130  may be formed from a layer of polyimide or a sheet of other flexible polymeric material. Substrate  130  may be integrated with display pixels and other active area display circuitry (e.g., substrate  130  may be integrated with a color filter layer, thin-film transistor layer, or other liquid crystal display substrate layer) or may be formed form a separate substrate that is mounted on top of a color filter layer other display layer. 
     Capacitive touch sensor electrodes such as electrodes  116  and  118  may be formed on substrate  130 . Electrodes  116  and  118  may be formed on the same side of substrate  130  and may be separated by an interposed dielectric layer or may be formed on opposing sides of substrate  130  (as examples). Configurations for sensor  114  that use electrodes of other shapes and sizes (e.g., square pads, thin columns or rows of electrodes), or other capacitive electrode structures may be used if desired. The illustrative configuration of  FIG. 9  is merely illustrative. 
     Capacitive touch sensor electrodes  116  and  118  may be formed from transparent conductive materials such as indium tin oxide. Conductive lines  120  may be used to connect electrodes  116  and  118  to connection areas  122 . A flexible printed circuit cable may be used to couple touch sensor  114  to touch sensor processing circuitry. The conductive traces in the flexible printed circuit cable may be connected to conductive lines  120  using conductive adhesive (e.g., anisotropic conductive film), solder, welds, connectors, or other connecting structures. 
     The conductive paths of the thin-film transistor circuitry such as lines D and G and the lines interconnecting display driver integrated circuit  62  and gate driver circuitry  108  with display pixels in  FIG. 8  and the conductive paths of display layers such as touch sensor layer  114  of  FIG. 9  may be formed from conductive materials such as one or more layers of metal. 
     In displays such as liquid crystal displays in which the thin-film-transistor circuitry is formed from silicon, conductive lines such as lines D and G and the other conductive lines on thin-film-transistor substrate  58  may, as an example, be formed from materials such as aluminum (e.g., solid aluminum or a multi-layer stack formed from a layer of aluminum sandwiched between layers of a metal such as molybdenum). In displays such as liquid crystal displays in which the thin-film-transistor circuitry is formed from a compound semiconductor, the conductive structures such as lines D and G and the other conductive lines on thin-film-transistor substrate  58  may be formed from a metal such as copper (as an example). In touch sensors, conductive lines may be formed from aluminum, copper, or other metals. 
     Copper lines or lines formed from other relatively soft and flexible metals may be sufficiently flexible to withstand damage during bending. Displays that have copper lines (e.g., for forming data and gate lines in the active area of the display) may therefore use copper lines in the bent inactive edge portions of the display. These lines may be, for example, integrally formed extended portions of the data lines or other lines in the active area of the display. Aluminum tends to be more susceptible to stress cracking than copper, so in displays with aluminum lines it may be desirable to use different materials and/or structures in the bent regions from the aluminum line structures being used in the active area. In this way, the conductive paths in the inactive region may be configured to resist cracking. As an example, the bent portions of the conductive paths may be provided with a segment of a soft metal such as copper or may be formed using other materials and/or structures that enhance the ability of the lines to flex without damage and without exhibiting undesired increase in resistance). 
       FIG. 10  is a perspective view of display structures with a bent edge portion. Display structures  140  of  FIG. 10  may include one or more layers that include an array of display pixels for producing images for a user and/or one or more touch sensor layers. Display structures  140  may have flexible bent edge portions  144  in inactive area IA. Inactive area IA may also include portions such as portions  146  on which components  154  are formed. Components  154  may include, for example, thin-film-transistor gate driver circuitry, circuitry associated with thin-film-transistor signal demultiplexing circuits, circuitry for routing and otherwise processing touch sensor signals, an integrated circuit such as display driver integrated circuit  62 , or other display circuits associated with displaying images and/or processing touch sensor signals. Display structures  140  may be formed using a rigid central region with flexible tails of the type described in connection with  FIG. 6  or may be formed using a flexible layer as described in connection with  FIG. 7  (as examples). 
     Portion  146  of display structures  140  may, if desired, have a planar shape and may contain conductive lines such as lines  152 . 
     With a configuration of the type shown in  FIG. 10 , active area conductive lines  148  (e.g., unbent lines that lie in a planar active portion of the display), conductive lines  150  that traverse bend  144  (e.g., bent lines), and conductive lines  152  (e.g., unbent lines or lines that are bent less than line segments  150 ) may all be formed as integral portions of the same patterned conductive lines on the same layer of material. As an example, in a compound semiconductor thin-film-transistor display structure or a touch sensor, line segments such as segments  148 ,  150 , and  152  may each form a portion of a unitary copper line. 
     As shown by illustrative display structures  140 ′ of  FIG. 11 , line segments such as line segment  150  in bent region  144  of inactive area IA may, if desired, be fully or partly formed from structures that are different than the structures used in forming line segments  148  and  152 . In particular, line segment  150  may be formed from materials such as copper that are more flexible and less prone to resistance increases upon bending than the materials of segments  148  and  152  and/or may be formed from structures such as parallel lines, mesh structures, structures using supplemental layers of bendable conductor, meandering line structures, structures with undulating surfaces, or other structures that allow segment  150  to be more flexible and more resistant to damage and resistance increases when bent than unbent segments  148  and  152 . Configurations of the type shown in  FIG. 11  may be used where it is desired to form segments such as segment  148  (and, if desired, segments such as segment  152 ) from materials such as aluminum that can be prone to stress-induced cracking for compatibility with other display fabrication operations). 
       FIG. 12  is a top view of an illustrative structure that may be used for forming segment  150 . In the illustrative configuration of  FIG. 12 , conductive signal path segment  150  has been formed from a conductive line that has been divided into multiple parallel lines  150 - 1 ,  150 - 2 ,  150 - 3 , and  150 - 4 . Due to the presence of multiple redundant parallel signal paths, line segment arrangements of the type shown in  FIG. 12  are less likely to fail due to stress cracks (which, when present, tend to propagate across the entire width of a given line). There are four parallel line segments in the illustrative configuration of  FIG. 12 , but, in general, line segment  150  may be provided with any suitable number of parallel lines (e.g., two or more, three or more, four or more, 10 or more, etc.). 
     In the illustrative configuration of line segment  150  of  FIG. 13 , line segment  150  has a meandering path. The use of the meandering path allows line segment  150  to stretch slightly when bent due the presence of the bend of region  144 . The illustrative meandering path of  FIG. 13  has bends such as bends  156  at angles A of 90°.  FIG. 14  shows an illustrative meandering path configuration for segment  150  that has bends  158  at angles B of about 30-150°. Other types of meandering path shapes may be used if desired (e.g., paths with curved shapes, paths with combinations of curved and straight segments, etc.). 
       FIG. 15  shows how segment  150  may be formed from a more flexible conductive material than the materials used in segments  148  and  152 . For example, segments  148  and  152  may be formed from aluminum (with or without thin upper and lower layers of molybdenum) and segments  150  may be fully or partly formed from copper, which is softer and more resistant to cracking when bent than aluminum. The respective widths W 1 , W 2 , and W 3  of lines  148 ,  150 , and  152  may, if desired, be substantially equal.  FIG. 16  shows how the respective widths W 1 ′, W 2 ′, and W 3 ′ of line segments  148 ,  150 , and  152  may, if desired, be configured so that the conductive line is locally widened in the portion where the line is bent (i.e., W 2 ′ may be greater than W 1 ′ and/or W 3 ′). The material used to form widened segment portion  150  may be formed from the same material as segments  148  and  152  or may be formed from a different material (e.g., a softer more flexible material such as copper). 
     If desired, line segments such as line segment  150  may be formed from conductive mesh structures. This type of arrangement is shown in  FIG. 17 . As shown in  FIG. 17 , line segments  148  and  152  may be formed from solid lines. Line segment portion  150  may be formed from a mesh having a conductive grid layout with an array of openings (e.g., conductive metal grid  162  with openings  160 ). 
     If desired, a material containing conductive particles such as silver paint or other metal paint, conductive paint filled with conductive nanostructures, a conductive material containing conductive fibers such as carbon nanofibers or metal nanofibers, or other bendable conductive material may be used in coating mesh  162 .  FIG. 18  is a cross-sectional view of line segment  150  taken along line  164  and viewed in direction  166  in a configuration in which grid  162  has been filled with a material containing conductive particles such as conductive paint  168 . As shown in  FIG. 18 , conductive material  168  may fill some or all of openings  160  in the mesh  162 . 
     As shown in the cross-sectional side view of  FIG. 19 , conductive lines such as line  174  may be formed form one or more layers of conductive material (e.g., metal or other material in layers such as layers  170 ,  172 , etc.). Conductive lines such as line  174  may be used in forming line segments such as segments  148 ,  150 , and/or  152 . If desired, conductive display lines may be formed from aluminum (or aluminum sandwiched between upper and lower layers of molybdenum) in segments  148  and  152  while in segment  150 , one or more layers of flexible metal (e.g., an upper layer such as layer  172 ) may be formed on top of the aluminum (or aluminum sandwiched between upper and lower layers of molybdenum). In this type of configuration, the presence of a softer more flexible upper layer such as layer  172  on a less flexible layer such as layer  170  may help the conductive line withstand damage and increases in resistance in bent segment  150 . 
     If desired, one or more additional layers of metal may be added to bent segment  150  by using vias that pass through a dielectric layer to couple one or more upper layers of conductive material to a conductive line. This type of configuration for line segment  150  is shown in  FIG. 20 . As shown in  FIG. 20 , a conductive display line may have segments such as segments  148  and  152  that are coupled by bent line segment  150 . Line segments  148 ,  150 , and  152  may include a conductive line such as conductive line  174  on display layers  104  (e.g., on a dielectric substrate with a flexible edge region that is bent). Line  174  may be formed from metal. For example, line  174  may be formed from aluminum or copper. A dielectric layer such as passivation layer  182  (e.g., one or more inorganic layers of material such as silicon oxide or silicon nitride) may be used to cover structures such as line  174 . 
     To provide line segment  150  with an enhanced ability to resist damage when bent as shown in  FIG. 20 , a line segment such as line segment  178  may be formed on top of line  174 . Line segment  178  may be formed form a material such as copper or other flexible metal (as an example). Vias  180  (e.g., through holes in dielectric layer  182  that have been filled with a conductive material such as metal) may be used to electrically connect metal line segment  178  to metal lines  174  within bent line segment  150 . In the illustrative configuration of  FIG. 20 , one additional layer of conductive material has been added to line  174  in forming line segment  150 . This is merely illustrative. If desired, two or more additional line layers may be added to line  174  to form bent line segment  150 . 
       FIG. 21  is a diagram of a system that may be used to form a corrugated line that is resistant to damage when bent. Light source  188  may produce line  190 . Light  190  may be passed through half-tone photomask  192  before exposing photoimageable polymer  194  on substrate  196 . Following development of photoimageable polymer  194  to produce a corrugated dielectric substrate, a deposition tool and photolithographic equipment may be used to deposit and pattern a conductive line such as metal line  198  of  FIG. 22 . 
     Metal line  198  may be used in forming segment  150  and, if desired, some or all of segments  148  and  152 . The vertically undulating surface of metal line  198  may be used in forming line segment  150 . When the metal line is bent as shown in  FIG. 23 , the waviness of metal line  198  in segment  150  may allow line  198  to stretch when bent, thereby avoiding stress-induced cracking. 
       FIG. 24  is a top view of a conductive display line (line  200 ) in a configuration in which conductive display line  200  has been provided with a conductive layer such as conductive layer  202  in line segment  150 . Conductive layer  202  may be formed from a material that contains conductive particles such as metal paint, carbon nanotubes, gold nanotubes, other metal nanotubes, other conductive nanofibers, metal particles, or other conductive particles such as particles  208 . The conductive particles of conductive layer  202  may be applied in a resin or solvent. 
     Conductive layer  202  may be patterned to form a rectangular patch that overlaps line  200  in line segment  150 , a line that overlaps line  200  within line segment  150 , or a patch of other shapes. Photolithographic patterning or other patterning techniques (e.g., pad printing, screen printing, ink-jet printing, etc.) may be used in forming conductive layer  202 . 
       FIG. 25  is a cross-sectional side view of line segment  150  of  FIG. 24  taken along line  204  and viewed in direction  206 . As shown in  FIG. 25 , conductive line  200  may be formed on flexible display layers  104  (e.g., layers including a dielectric layer on which conductive line  200  is formed). Dielectric layer  210  (e.g., a passivation layer such as one or more layers of silicon oxide and/or silicon nitride) may have an opening such as an elongated trench-shaped opening that overlaps line  200  within line segment  150 . Conductive material  202  may be deposited within the trench in contact with line  200 . Conductive material may be more resistant to damage and resistance increases when bent than unbent and uncovered portions of line  200 , thereby enhancing the ability of the display line to flex in bent segment  150  without sustaining damage. 
     The foregoing illustrative configurations for forming display lines with structures and/or materials that allow the display lines to bend without damage and undesired increases in resistance within segments such as segments  150  may be used separately on in any combination. As an example, segment  150  may be implemented using parallel paths, single layer of conductive material, multiple layers of conductive material, lines with corrugated surfaces, lines with meandering paths, lines with locally soft metals, lines with locally widened metals, lines that have been formed using overlapping lines coupled with vias, lines that have been coated with conductive particles such as carbon nanotubes or metal nanotubes or metal particles associated with a metal paint, lines with mesh conductors, and/or lines that been coated with other conductive material. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20120821
Publication Date: 20151124
Grant Date: 20151124
Priority Date: 20120821
Inventors: PARK YOUNG BAE
ZHONG JOHN Z.
CHANG SHIH-CHANG
CHEN WEI
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/13452", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133305", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/136286", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/136286", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13306", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1333", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/441", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/411", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10D86/60", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/5203", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/52", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L2251/5338", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/136286", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/1333", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L51/524", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/323", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K2102/311", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K2102/311", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K50/841", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/805", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K77/111", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K50/80", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K77/111", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/131", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/1315", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/40", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/131", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 50147698