PATENT DOCUMENT

Publication Number: US-9423897-B2
Application Number: US-201313854376-A
Country: US
Kind Code: B2

Title: Electronic device display with shielding layer

Abstract:
A display may have a color filter layer and a thin-film transistor layer. A layer of liquid crystal material may be located between the color filter layer and the thin-film transistor layer. A transparent conductive shielding layer may be formed on the lower surface of the thin-film transistor layer. Grounding structures may ground the transparent conductive shielding layer to a ground. The ground may be formed form metal traces on a flexible printed circuit. The display may have a backlight unit. Light-emitting diodes may be used to provide backlight for the backlight unit. The light-emitting diodes may be mounted on the flexible printed circuit. The grounding structures may be formed from a rectangular ring-shaped conductive tape or other conductive structures.

Claims:
What is claimed is: 
     
       1. A display, comprising:
 display layers configured to display images, wherein the display layers include a transparent thin-film transistor layer having a glass substrate; 
 a conductive transparent shielding layer on the glass substrate; 
 a backlight unit; 
 a metal trace on a first surface of a dielectric, wherein the dielectric has a second surface opposite the first surface; 
 signal lines on the second surface that provide signals to the backlight unit; and 
 a grounding structure having first and second opposing surfaces that grounds the conductive transparent shielding layer to the metal trace, wherein the grounding structure is interposed between the transparent thin-film transistor layer and the dielectric such that the first surface contacts the conductive transparent shielding layer and the second surface contacts the metal trace. 
 
     
     
       2. The display defined in  claim 1 , wherein the backlight unit comprises light-emitting diodes. 
     
     
       3. The display defined in  claim 1  wherein the dielectric comprises a flexible polymer layer. 
     
     
       4. The display defined in  claim 1  wherein the grounding structure comprises conductive tape having a conductive metal layer sandwiched between opposing conductive adhesive layers. 
     
     
       5. The display defined in  claim 1  wherein the display layers include a touch sensor array. 
     
     
       6. The display defined in  claim 5  wherein the touch sensor array comprises an array of capacitive touch sensor electrodes. 
     
     
       7. The display defined in  claim 6  wherein the grounding structure comprises a rectangular ring-shaped structure that runs along a peripheral edge of the thin-film transistor layer. 
     
     
       8. The display defined in  claim 1  wherein the glass substrate has opposing first and second surfaces, wherein the thin-film transistor layer comprises thin-film transistor circuitry on the first surface, wherein the conductive transparent shielding layer is formed on the second surface, and wherein the display further comprises a polarizer layer on the conductive transparent shielding layer. 
     
     
       9. The display defined in  claim 8  wherein the grounding structure has a rectangular opening in which the polarizer layer is located and wherein the metal trace and the dielectric form portions of a flexible printed circuit backlight unit cable. 
     
     
       10. The apparatus defined in  claim 1  wherein the second surface directly contacts the metal trace. 
     
     
       11. A display, comprising:
 a color filter layer; 
 a thin-film transistor layer having a thin-film transistor substrate; 
 a layer of liquid crystal material between the color filter layer and the thin-film transistor layer; 
 a backlight; 
 an upper polarizer and a lower polarizer, wherein the color filter layer, the thin-film transistor layer, and the layer of liquid crystal material are located between the upper polarizer and the lower polarizer, and wherein the lower polarizer is interposed between the backlight and the thin-film transistor layer; 
 a conductive transparent shielding layer interposed between the thin-film transistor substrate and the lower polarizer; 
 a ground trace on a first surface of a dielectric substrate; 
 patterned metal traces on a second surface of the dielectric substrate opposite the first surface, wherein the patterned metal traces supply signals to the backlight; and 
 grounding structures that couple the conductive transparent shielding layer to the ground trace. 
 
     
     
       12. The display defined in  claim 11  wherein the backlight comprises light-emitting diodes mounted to the flexible printed circuit. 
     
     
       13. The apparatus defined in  claim 11 , wherein the color filter layer is interposed between the thin-film transistor layer and the upper polarizer. 
     
     
       14. Apparatus, comprising:
 a color filter layer; 
 a thin-film transistor layer having a surface with a layer of thin-film circuitry and an opposing surface with a conductive transparent shielding layer; 
 a layer of liquid crystal material between the color filter layer and the thin-film transistor layer; 
 a dielectric substrate that is separate from the thin-film transistor layer and that has first and second opposing surfaces; 
 a metal trace on the first surface of the dielectric substrate; 
 at least one signal line on the second surface of the dielectric substrate; 
 grounding structures that ground the conductive transparent shielding layer to the metal trace on the first surface of the dielectric substrate, wherein the grounding structures are interposed between the thin-film transistor layer and the dielectric substrate; and 
 a display backlight unit having light-emitting diodes, wherein the at least one signal line on the second surface of the dielectric substrate comprises patterned metal traces that supply signals to the light-emitting diodes. 
 
     
     
       15. The apparatus defined in  claim 14  wherein the dielectric substrate comprises a flexible polymer. 
     
     
       16. The apparatus defined in  claim 14  wherein the grounding structures include a layer of metal. 
     
     
       17. The apparatus defined in  claim 16  wherein the layer of metal has a rectangular ring shape that runs along a peripheral edge of the thin-film transistor layer. 
     
     
       18. The apparatus defined in  claim 16  wherein the layer of metal has opposing upper and lower surfaces and wherein the grounding structures include a first layer of conductive adhesive on the upper surface and a second layer of conductive adhesive on the lower surface. 
     
     
       19. The apparatus defined in  claim 14  wherein the grounding structures comprise:
 a rectangular ring-shaped conductive layer that is adjacent to the conductive transparent shielding layer and that runs along a peripheral edge of the conductive transparent shielding layer; and 
 a conductive structure that is separate from the rectangular ring-shaped conductive layer and that grounds the rectangular ring-shaped conductive layer to the metal trace.

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. 
     Displays contain arrays of display pixels for generating images. The display pixels are controlled using display driver circuitry. Touch screen displays include touch sensor arrays. Touch sensor arrays such as capacitive touch sensor arrays can be incorporated into a display to provide the display with the ability to accept touch commands from a user. 
     If care is not taken, a display can generate interference signals that can disrupt operation of sensitive components in a device. For example, wireless radio-frequency transceiver circuitry may be susceptible to interference from a display. Touch sensor arrays in displays may also be susceptible to interference. For example, signal sources such as integrated circuits within a device may generate signals that can disrupt touch sensor operation. 
     It would therefore be desirable to be able to provide electronic devices that are less susceptible to disruption from these types of interference. 
     SUMMARY 
     A display may have a color filter layer and a thin-film transistor layer. A layer of liquid crystal material may be located between the color filter layer and the thin-film transistor layer. A transparent conductive shielding layer may be formed on the lower surface of the thin-film transistor layer. The display may include a touch sensor array. The shielding layer may prevent display interference from disrupting operation of internal components in an electronic device and may prevent interference from the internal components from interfering with the touch sensor array. 
     Grounding structures may ground the transparent conductive shielding layer to a ground. The ground may include metal traces on a flexible printed circuit. The display may have a backlight unit. Light-emitting diodes may be used to provide backlight for the backlight unit. The light-emitting diodes may be mounted on the flexible printed circuit. The grounding structures may be formed from a rectangular ring-shaped conductive tape or other conductive structures. 
     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 perspective view of an illustrative electronic device such as a computer display with display structures 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 a portion of a display showing how the display may be provided with a shielding layer in accordance with an embodiment of the present invention. 
         FIG. 7  is a top view of an illustrative rectangular ring-shaped grounding structure that may be used to electrically connect a shielding layer in a display to ground in accordance with an embodiment of the present invention. 
         FIG. 8  is a top view of an illustrative grounding structure having the shape of a strip of conductor that runs along the edge of a display that may be used to electrically connect a shielding layer in a display to ground in accordance with an embodiment of the present invention. 
         FIG. 9  is a top view of an illustrative U-shaped grounding structure that may be used to electrically connect a shielding layer in a display to ground in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional side view of a portion of an illustrative grounding structure having a layer of metal or other conductor sandwiched between upper and lower layers of conductive adhesive in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional side view of a portion of an illustrative grounding structure such as a conductive paint grounding structure in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of an illustrative grounding structure formed on the lower surface of a shielding layer in accordance with an embodiment of the present invention. 
         FIG. 13  is a cross-sectional side view of an illustrative grounding structure formed from raised ridge structures or other protruding portions of a transparent conductive shielding structure in accordance with an embodiment of the present invention. 
         FIG. 14  is a cross-sectional side view of a portion of a display in which a two-part grounding structure is being used to electrically couple a shielding layer on the display to ground in accordance with an embodiment of the present invention. 
         FIG. 15  is a flow chart of illustrative steps involved in forming an electronic device with a grounded display shielding structure 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, 3, and 4 . 
       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 openings for components such as button  26 . Openings may also be formed in display  14  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 an opening to accommodate button  26  (as an example). 
       FIG. 4  shows how electronic device  10  may be a computer display or a computer that has been integrated into a computer display. With this type of arrangement, housing  12  for device  10  may be mounted on a support structure such as stand  27 . Display  14  may be mounted on a front face of housing  12 . 
     The illustrative configurations for device  10  that are shown in  FIGS. 1, 2, 3, and 4  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. 
     Touch sensor components such as capacitive touch sensor electrodes may be incorporated into display  14  using a substrate that is separate from other substrate layers in the display or may be formed from conductive structures that are patterned onto the same substrate in display  14  as display pixel structures. For example, a substrate layer such as a layer of glass or plastic may have a pattern of transparent conductive touch sensor electrodes such as indium tin oxide electrodes. This substrate layer may be attached to other display layers to form a touch sensitive display. If desired, a display layer such as a thin-film transistor layer in a liquid crystal display may be provided with indium tin oxide electrodes for a capacitive touch sensor. With this type of arrangement, both display pixel electrodes for the liquid crystal display and capacitor electrodes for the touch sensor may be formed on a common display layer substrate (e.g., a shared glass substrate layer). 
     Display  14  for device  10  may include display pixels formed from liquid crystal display (LCD) components or other suitable image pixel structures. 
     A display cover layer may cover the surface of display  14  or a display layer such as a color filter layer or other portion of a display may be used as the outermost (or nearly outermost) layer in display  14 . The outermost display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent member. 
     A cross-sectional side view of an illustrative configuration for display  14  of device  10  (e.g., for display  14  of the devices of  FIG. 1 ,  FIG. 2 ,  FIG. 3 ,  FIG. 4  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 dimension Z 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. 
     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, layer  58  may be a color filter layer and layer  56  may be a thin-film transistor layer. 
     During operation of display  14  in device  10 , control circuitry (e.g., one or more integrated circuits on a printed circuit) may be used to generate information to be displayed on display  14  (e.g., display data). The information to be displayed may be conveyed to a display driver integrated circuit such as circuit  62 A or  62 B using a signal path such as a signal path formed from conductive metal traces in a rigid or flexible printed circuit such as printed circuit  64  (as an example). 
     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 in dimensions X and Y 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 in direction Z 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 in the X-Y plane of  FIG. 5 , optical films  70  and reflector  80  may have a matching rectangular footprint. 
     Display driver circuitry  62 A and/or  62 B may drive data and control signals into the thin-film transistor circuitry of display layer  58  during operation. Touch sensor signals may be routed from electrodes in display  14  to touch sensor processing circuitry. Internal device components such as integrated circuits in device housing  12  may produce interference signals and/or may be susceptible to interference signals. As a result, it may be desirable to shield display  14  from other components in device  10 . It may, for example, be desirable to incorporate a transparent conductive electrode such as a layer of indium tin oxide onto a display layer in display  14  to serve as an electromagnetic interference shield. The shield may prevent interference signals such as signals produced when operating display  14  from reaching internal device components such as wireless transceiver circuits or other sensitive device circuits. The shield may also prevent interference signals that are generated by clocks, processors, transmitters, and other integrated circuits and circuitry in device  10  from reaching display  14 . This can help ensure that touch sensor circuitry in display  14  is not disrupted due to interference from within device  10 . 
     A cross-sectional side view of a portion of display  14  showing how display  14  may be provided with electromagnetic signal interference shielding is shown in  FIG. 6 . In the example of  FIG. 6 , display  14  is a liquid crystal display of the type shown in  FIG. 5 . Thin-film transistor layer  58  includes a substrate such as thin-film transistor substrate  58 - 2  (e.g., a clear layer of glass). Thin-film transistor circuitry  58 - 3  may be formed on the upper surface of thin-film transistor substrate  58 - 2 . Thin-film transistor circuitry  58 - 3  may include polysilicon thin-film transistors, amorphous silicon thin-film transistors, oxide thin-film transistors, or other thin-film transistors. Thin-film transistor circuitry  58 - 3  may also include structures such as electrodes for applying electric fields to the liquid crystal material associated with an array of display pixels, thin-film transistors for controlling the application of the electric fields by the electrodes, capacitors, etc. Thin-film transistor circuitry  58 - 3  may, if desired, also include touch sensor circuitry such as capacitive touch sensor electrodes (e.g., indium tin oxide electrodes in the form of an array of rectangular pads, electrode patterns with pads and lines, etc.). 
     As shown in  FIG. 6 , the lowermost (innermost) layer of thin-film transistor layer  58  (i.e., the lower surface of layer  58  opposing the upper surface of layer  58  on which the thin-film transistor circuitry and optional touch sensor electrodes are formed) may be coated with shielding layer  58 - 1 . Lower polarizer layer  60  may be attached to the lower surface of shielding layer  58 - 1  (e.g., using adhesive). Lower polarizer  60  may, for example, be formed in a central rectangular portion of layer  58 . 
     Shielding layer  58 - 1  may be a layer of conductive transparent material such as indium tin oxide. Shielding layer  58 - 1  may be deposited using physical vapor deposition or other deposition techniques. The presence of a conductive layer on the lower surface of thin-film transistor layer  58  may help block interference that is present in layer  58 - 2  from reaching sensitive integrated circuits and other internal components  90  in device  10  and may help block interference signals that are generated by internal components  90  from reaching touch sensor circuitry on layer  58  or other substrates in display  14 . 
     Components  90  may include sensitive circuitry such as wireless transceiver circuitry, may include processors, may include application-specific integrated circuits, etc. Components  90  may be mounted on one or more substrates such as substrate  88  (e.g., a printed circuit such as a rigid printed circuit board formed from a material such as fiberglass-filled epoxy and/or a flexible printed circuit substrate material such as a sheet of polyimide or a layer of other flexible polymer). Components  90  have the potential to emit interference that could interfere with a touch sensor in display  14  such as an array of indium tin oxide capacitor electrodes. The presence of shielding layer  58 - 1  may help block these interference signals and may help block signals generated in layer  58 - 3  from reaching components  90  or other sensitive circuitry in device  10 . If desired, shielding layer  58 - 1  may be formed on substrates other than thin-film transistor substrate  58 - 2 . The configuration of  FIG. 6  is merely illustrative. 
     Backlight unit  42  may include a light source such as light source  72 . Light source  72  may emit light  74  into light guide plate  78 . Reflector  80  may help reflect light that has escaped downwards from light guide plate  78  in an upwards direction through the layers of display  14  to serve as backlight. Optical films  70  may be interposed between thin-film transistor layer  58  and light guide plate  78 . 
     Light source  72  may include components such as light-emitting diodes. The light emitting diodes may be provided with power through a backlight power supply cable such as cable  84 . Cable  84  may be formed from a flexible printed circuit (sometimes referred to as a “flex circuit”). As shown in  FIG. 6 , backlight cable  84  may include a flexible printed circuit substrate such as polymer layer  84 - 2  (e.g., a layer of polyimide or other flexible dielectric) and metal traces such as upper metal traces  84 - 1  and lower metal traces  84 - 3 . Metal traces  84 - 1  and  84 - 3  may be patterned by photolithography, may be patterned by shadow masking during physical vapor deposition, may be pattered by screen printing, may be patterned using ink-jet printing, may be patterned by pad printing, or may be patterned using other metal deposition and patterning techniques. Examples of metals that may be used in forming metal traces  84 - 1  and  84 - 3  include copper, gold, aluminum, other metals, metal layers that include two or more metals, etc. The metal traces may be thinner than 20 microns, thinner than 2 microns, or other suitable thickness. 
     Metal traces  84 - 3  may include metal lines for conveying power to solder joints  86  that are connected to respective terminals on light-emitting diodes  72 . There may be, for example, a positive power supply trace in metal traces  84 - 3  that is coupled to a positive power supply terminal on each light-emitting diode  72  and a negative power supply trace in metal traces  84 - 3  that is coupled to a negative power supply terminal on each light-emitting diode. During operation of display  14 , a battery or other source of power may be used in providing light-emitting diodes  72  with power supply signals over metal traces  84 - 3 . The power supply signals (e.g., current signals) may turn on the light-emitting diodes and cause the light-emitting diodes to emit light  74 . 
     Metal traces  84 - 1  may be ground traces that are coupled to a source of ground potential such as ground  91  (e.g., metal traces  84 - 1  may be considered to form part of a ground in device  10  and may be coupled to a ground terminal such as ground  91  through traces such as traces  93  within printed circuit substrates such as substrate  88 ). Ground  91  may be formed from portions of housing  12 , from a ground plane on printed circuit substrate  88 , from metal housing structures in the interior of device  10 , or from other ground structures. 
     Shielding layer  58 - 1  may provide effective shielding when grounded to ground  91 . With one suitable arrangement, grounding structures such as grounding structures  82  may be used to couple shielding layer  58 - 1  to ground traces  84 - 1  and thereby couple shielding layer  58 - 1  to ground. As shown in  FIG. 6 , the upper surface of grounding structures  82  may contact and bear against the lower surface of shielding layer  58 - 1  and the lower surface of grounding structures  82  may contact and bear against the upper surface of ground traces  84 - 1  in backlight unit power supply cable  84 . Shorting shielding layer  58 - 1  to ground in this way helps ensure that shielding layer  58 - 1  can effectively prevent interference from display  14  from reaching internal device components under shielding layer  58 - 1  such as components  90 . 
     Grounding structures  82  may be formed from metal tape, conductive adhesive, metal tape that is coated on its upper and/or lower surfaces by conductive adhesive, conductive paint (e.g., silver paint or other metal paint), solder, weld structures, conductive fabric, conductive foam, other conductive materials and/or combinations of two or more of these structures. Grounding structures  82  preferably run along some or all of the peripheral edges of shielding layer  58 - 1  and display  14  (e.g., grounding structures  82  may have a rectangular ring shape that surrounds lower polarizer  60 ). This allows a satisfactory low-resistance path to be formed between shielding layer  58 - 1  and ground  91  without blocking light from travelling through display  14 . 
     As shown in the top view of illustrative grounding structures  82  of  FIG. 7 , grounding structures  82  may have the shape of a rectangular ring that runs around the rectangular periphery of thin-film transistor layer  58  and the other rectangular display layers in display  14 . The rectangular opening in the center of the rectangular ring may be sized to accommodate lower polarizer  60  (e.g., lower polarizer  60  may be located within the opening in the rectangular ring-shaped grounding structures). Backlight unit flexible printed circuit cable  84  may be attached along one edge of the rectangular ring formed by grounding structures  82 . As shown in the top view of illustrative grounding structures  82  of  FIG. 8 , grounding structures  82  may have the shape of a strip of metal having an elongated footprint running along one of the edges of shielding layer  58 - 1  and display  14 .  FIG. 9  is a top view of illustrative grounding structures  82  in a configuration in which grounding structures  82  have a U-shape that runs along three of the four edges of shielding layer  58 - 1  and display  14 . Other layouts may be used for grounding structures  82  if desired. The configurations of  FIGS. 7, 8, and 9  are merely illustrative. 
     As shown in the cross-sectional side view of  FIG. 10 , grounding structures  82  may be formed from multiple layers of material. For example, grounding structures  82  may be formed from a central layer such as layer  82 - 2  that is sandwiched between lower layer  82 - 3  and upper layer  82 - 1 . Layers  82 - 1 ,  82 - 2 , and  82 - 3  may be formed from conductive materials. As an example, layers  82 - 1  and  82 - 3  may be conductive adhesive layers and layer  82 - 2  may be a metal layer (e.g., a layer of metal foil) that is interposed between layers  82 - 1  and  82 - 3 . 
       FIG. 11  is a cross-sectional side view of grounding structures  82  in a configuration in which grounding structures  82  have been formed from conductive particles  82 ′ in a carrier material  82 ″. Conductive particles  82 ′ may be metal particles and carrier material  82 ″ may be a solvent-based binder that at least partly evaporates after being applied between shielding layer  58 - 1  and ground  91  (e.g., layer  82  of  FIG. 11  may be a layer of conductive paint such as metal paint). 
     In the example of  FIG. 12 , grounding structures  82  have been formed from a solid layer of material that is located adjacent to shield layer  58 - 1  (e.g., a layer of material that is formed on the underside of shield layer  58 - 1  or that is otherwise attached to the underside of shield layer  58 - 1 ). Layer  58 - 1  may be a layer of conductive foam, a layer of metal, a layer of conductive adhesive, a layer of conductive fabric, or other conductive layer. 
       FIG. 13  shows how grounding structures  82  may be formed from a portion of material that is part of shielding layer  58 - 1 . Shielding layer  58 - 1  may, for example, be formed from a layer of transparent conductive material such as indium tin oxide. Grounding structures  82  may be formed from a raised area of shielding layer  58 - 1  such as protruding portion  58 - 1 ′ (e.g., a raised rectangular ring-shaped ridge). Protrusion  58 - 1 ′ may protrude downwards away from the lower surface of thin-film layer  58  to help short shielding layer  58 - 1  to ground trace  84 - 1  in backlight unit flexible printed circuit cable  84 . Techniques such as grinding (polishing), laser processing, physical vapor deposition (e.g., with shadow masking), etching, and other techniques may be used in forming a shielding layer such as shielding layer  58 - 1  of  FIG. 13  in which grounding structures  82  form an integral portion of shielding layer  58 - 1 . 
     If desired, more than one layer of structures may be interposed between shield layer  58 - 1  and ground traces  84 - 1  on flexible printed circuit cable  84 . This type of configuration is shown in  FIG. 14 . As shown in  FIG. 14 , grounding structures  82  may form an electrical connection with the lower surface of shielding layer  58 - 1 . 
     Grounding structures  82  may, for example, be formed on the lower surface of shielding layer  58 - 1  (e.g., using physical vapor deposition or other deposition techniques), may be attached to the lower surface of shielding layer  58 - 1  (e.g., using conductive adhesive, solder, welds, etc.), or may otherwise be mounted in display  14  adjacent to shielding layer  58 - 1  and in electrical contact with shielding layer  58 - 1 . 
     Grounding structures  92  may be interposed between the lower surface of a portion of grounding structures  82  and ground traces  84 - 1  in backlight unit flexible printed circuit power supply cable  84 . Grounding structures  92  may have an upper surface that is in contact with the lower surface of grounding structures  82  and may have a lower surface that is in contact with metal ground traces  84 - 1  on flexible printed circuit cable  84 . Grounding structures  92  and/or grounding structures  82  may be formed from multilayer structures of the type described in connection with  FIG. 10 , from metal paint or other structures of the type described in connection with  FIG. 11 , from a layer of material of the type described in connection with  FIG. 12 , from an integral protrusion of another layer as described in connection with protrusion  58 - 1 ′ of shielding layer  58 - 1 , from solder, welds, conductive adhesive, conductive fabric, conductive tape, conductive metal foil, or other conductive materials. 
     There are two layers of grounding structures (grounding structures  82  and grounding structures  92 ) that are interposed between the lower surface of shielding layer  58 - 1  and the upper surface of the signal line formed from ground traces  84 - 1  on backlight unit cable  84  in the example of  FIG. 14 . This is merely illustrative. Any suitable number of different conductive structures may be coupled in series between shielding layer  58 - 1  and ground traces  84 - 1  or other source of ground potential if desired. 
       FIG. 15  is a flow chart of illustrative steps involved in forming an electronic device with a grounded display shielding structure. At step  94 , display layers for display  14  may be formed such as color filter layer  56  and thin-film transistor layer  58 . Thin-film transistor layer  58  may include a layer of thin-film transistor circuitry such as thin-film transistor circuit layer  58 - 3 , a substrate layer such as substrate layer  58 - 2  (e.g., a layer of transparent glass or plastic), and a shielding layer such as shielding layer  58 - 1  (e.g., a conductive transparent layer such as a layer of indium tin oxide or other transparent conductor). 
     At step  96 , the layers of display  14  may be assembled (e.g., a display or display module for device  10  may be formed) and during the operations of step  98 , the display layers (e.g. an assembled display module and/or individual layers of display  14 ) may be mounted in housing  12  with other device components such as components  90  to form electronic device  10 . During the assembly operations of steps  96  and/or  98 , grounding structures such as grounding structures  82  and, if desired, grounding structures  92 , may be interposed between the lower surface of shielding layer  58 - 1  and the upper surface of a ground such as ground traces  84 - 1  on flexible printed circuit backlight unit cable  84  or other conductor coupled to a source of ground potential. 
     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: 20130401
Publication Date: 20160823
Grant Date: 20160823
Priority Date: 20130401
Inventors: BAE HOPIL
Assignee: APPLE INC
CPC Classifications: [{"code": "G06F3/041", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F3/041", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": true, "tree": "[]"}, {"code": "G06F2203/04103", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G06F2203/04107", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/13452", "inventive": true, "first": false, "tree": "[]"}, {"code": "G06F3/0412", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 51620499