PATENT DOCUMENT

Publication Number: US-9140927-B2
Application Number: US-201213631153-A
Country: US
Kind Code: B2

Title: Display with liquid crystal shutters for minimizing display borders

Abstract:
An electronic device may be provided with a display mounted in a housing. The display may have an array of display pixels that provide image light to a user. The array of display pixels may form active display structures with a rectangular shape. The rectangular active display structures may be surrounded by an inactive border region. Liquid crystal light distribution structures may be used to distribute light that is emitted from peripheral portions of the active display structures to a portion of the display overlapping the inactive border region, thereby increasing the apparent area of the display. The light distribution structures may include a liquid crystal cell, a reflecting polarizer, and a reflector that reflects light from the peripheral portions of the active display structures vertically upwards after the light has passed through the liquid crystal cell and has reflected off of the reflecting polarizer.

Claims:
What is claimed is: 
     
       1. A display for displaying content with an apparent size to a user, the display comprising:
 active display structures having an area, having a central region of display pixels, and having a peripheral edge region of display pixels; and 
 adjustable liquid crystal light distribution structures formed separately from the active display structures that distribute light from the display pixels in the peripheral edge region to make the apparent size of the display larger than the area of the active display structures, wherein the adjustable liquid crystal light distribution structures include a reflecting polarizer, and wherein the adjustable liquid crystal light distribution structures include a liquid crystal cell having a layer of liquid crystal material interposed between a pair of transparent electrodes. 
 
     
     
       2. The display defined in  claim 1  wherein the active display structures include an array of display pixels with a rectangular periphery and wherein the adjustable liquid crystal light distribution structures are located along at least part of the rectangular periphery. 
     
     
       3. The display defined in  claim 2  wherein the adjustable liquid crystal light distribution structures include a reflector that receives reflected light from the reflecting polarizer. 
     
     
       4. The display defined in  claim 3  wherein the reflector includes non-planar surfaces. 
     
     
       5. The display defined in  claim 3  wherein the reflector is configured to reflect the light from the display pixels in the peripheral edge region that has passed through the liquid crystal cell and that has reflected from the reflecting polarizer. 
     
     
       6. A display for viewing by a viewer, comprising:
 display structures having a first set of active display pixels and a second set of active pixels; and 
 liquid crystal light distribution structures that are operable in a first state in which light from the second set of active display pixels is passed vertically upwards towards the viewer and has a linear polarization with a first orientation and a second state in which the light from the second set of active display pixels is reflected horizontally and has a linear polarization with a second orientation that is different than the first orientation. 
 
     
     
       7. The display defined in  claim 6  further comprising a reflector that reflects the light that is reflected horizontally in a vertical direction towards the viewer. 
     
     
       8. The display defined in  claim 7  wherein the display structures include a color filter layer, a thin-film-transistor layer, a liquid crystal layer interposed between the color filter layer and the thin-film transistor layer, an upper polarizer on the color filter layer, and a lower polarizer on a lower surface of the thin-film transistor layer. 
     
     
       9. The display defined in  claim 6  wherein the display structures include a display pixel array, wherein the first set of display pixels forms a central portion of the display pixels in the display pixel array, wherein the second set of display pixels forms peripheral display pixels that surround the central portion of the display, and wherein the liquid crystal light distribution structures are configured to distribute light from the peripheral display pixels. 
     
     
       10. The display defined in  claim 9  wherein the liquid crystal light distribution structures include a liquid crystal cell having a layer of liquid crystal material. 
     
     
       11. The display defined in  claim 10  wherein the liquid crystal light distribution structures include a reflecting polarizer that receives light from the peripheral display pixels that has passed through the layer of liquid crystal material in the liquid crystal cell. 
     
     
       12. The display defined in  claim 11  wherein the liquid crystal light distribution structures include a reflector that reflects light that has reflected from the reflecting polarizer. 
     
     
       13. The display defined in  claim 12  wherein the display structures include a color filter layer, a thin-film-transistor layer, and a liquid crystal layer interposed between the color filter layer and the thin-film transistor layer. 
     
     
       14. The display defined in  claim 13  further comprising a polarizer on the color filter layer through which the light from the peripheral display pixels passes. 
     
     
       15. The display defined in  claim 14  further comprising a backlight unit having a light guide plate, wherein the light guide plate has light scattering structures that are configured to scatter brighter backlight through the peripheral display pixels than through the central portion of the display pixels. 
     
     
       16. The display defined in  claim 6 , wherein all of the light passed vertically upwards towards the viewer in the first state has the linear polarization with the first orientation, and wherein all of the light reflected horizontally in the second state has the linear polarization with the second orientation. 
     
     
       17. An electronic device, comprising:
 liquid crystal display structures including central display pixels and peripheral display pixels that surround the central display pixels; 
 liquid crystal light distribution structures that distribute light from the peripheral display pixels, wherein the liquid crystal light distribution structures comprise a liquid crystal cell formed above the peripheral display pixels; and 
 control circuitry that synchronously controls the peripheral display pixels and the liquid crystal light distribution structures. 
 
     
     
       18. The electronic device defined in  claim 17  wherein the liquid crystal light distribution structures include a reflecting polarizer. 
     
     
       19. The electronic device defined in  claim 17  wherein the light crystal display structures include an upper polarizer and wherein liquid crystal cell has a layer of liquid crystal material that receives light from the peripheral display pixels that has passed through the upper polarizer.

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. The housing of an electronic device can be adjusted to accommodate a bulky display with large borders, but this can lead to undesirable enlargement of the size and weight of the housing and unappealing device aesthetics. 
     It would therefore be desirable to be able to provide improved displays for electronic devices. 
     SUMMARY 
     An electronic device may be provided with a display mounted in a housing. The display may have an array of display pixels that provide image light to a user. The array of display pixels may form active display structures with a rectangular shape. The rectangular active display structures may be surrounded by an inactive border region. Liquid crystal light distribution structures may be used to distribute light that is emitted from peripheral portions of the active display structures to a portion of the display overlapping the inactive border region, thereby providing the display with an apparent active area that is larger than the area of the active display structures. 
     The liquid crystal light distribution structures may include a liquid crystal cell that receives light from display pixels in the peripheral portions of the active display structures. The liquid crystal cell may be controlled by control circuitry to adjust the orientation of linearly polarized light received from the display pixels. Light that has passed through the liquid crystal call may be received by a reflecting polarizer, which reflects or transmits the light based on the polarization state of the light. A reflector may be used to reflect light from the peripheral portions of the active display structures vertically upwards towards a viewer after the light has passed through the liquid crystal cell and has reflected off of the reflecting polarizer. 
     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 top view of illustrative display layers in a display having an active region with an array of display pixels and an inactive border region in accordance with an embodiment of the present invention. 
         FIG. 7  is a perspective view of a liquid crystal cell in a state that does not rotate the polarization of incoming light in accordance with an embodiment of the present invention. 
         FIG. 8  is a perspective view of the liquid crystal cell of  FIG. 7  in a state that rotates the polarization of incoming light by 90° in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional side view of an illustrative electronic device with liquid crystal light distribution structures to distribute light from a pixel on the edge of a display to minimize display borders in accordance with an embodiment of the present invention. 
         FIG. 10  is a cross-sectional side view of an illustrative electronic device with liquid crystal light distribution structures to distribute light from multiple pixels on the edge of a display to minimize display borders in accordance with an embodiment of the present invention. 
         FIG. 11  is a cross-sectional side view of an illustrative liquid crystal shutter structure with an associated reflector having non-planar surfaces in accordance with an embodiment of the present invention. 
         FIG. 12  is a cross-sectional side view of a display having a light guide plate with a locally increased scattering feature density to enhance light intensity for a peripheral display pixel producing light that is distributed using liquid crystal light distribution structures 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 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 or other portion of a display may be used as the outermost (or nearly outermost) layer in display  14 . A display cover layer or other outer display layer may be formed from a transparent glass sheet, a clear plastic layer, or other transparent structures. 
     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  29 . Control circuitry  29  may include storage and processing circuitry for controlling the operation of device  10 . Control circuitry  29  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  29  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  29  may be used to run software on device  10 , such as operating system software and application software. Using this software, control circuitry  29  may present information to a user of electronic device  10  on display  14 . Display  14  may contain an array of display pixels (e.g., liquid crystal display pixels) that are organized in rows and columns. Control circuitry  29  may be used to display content for a user of device  10  on the array of display pixels in display  14 . 
     Control circuitry  29  may include display driver circuitry and other circuitry for controlling the rate at which display pixels are refreshed and for controlling which pixel data is displayed by each display pixel. Display driver circuitry may be formed using thin-film-transistor circuitry on display  14  and/or integrated circuits mounted on a layer in display  14  or on a printed circuit. In addition to controlling the display of pixel data using the display pixels of display  14 , control circuitry  29  may perform control operations within device  10  such as controlling the states of liquid crystal light distribution structures (sometimes referred to as liquid crystal shutter structures) and other controllable electronic components. Control circuitry  29  may, for example, issue control commands that place liquid crystal light distribution structures in a desired state. Adjustments to liquid crystal light distribution structures such as these may be synchronized with display control operations. For example, control circuitry  29  can ensure that light passing through the liquid crystal light distribution structures is distributed as desired while simultaneously controlling the operation of peripheral display pixels in display  14  so that those pixels display desired pixel data for distribution by the liquid crystal light distribution structures. 
     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  (e.g., the array of display pixels in 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 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  14  may, if desired, have one or more optical structures that are located above display layers  46 . For example, display  14  may have a display cover layer such as display cover layer  84 . Display cover layer  84  may be formed from a layer of clear glass, a transparent sheet of plastic, or other transparent structure. Display cover layer  84  may be mounted in housing  12  (e.g., using housing sidewalls). During operation, light  44  may pass through the array of display pixels formed from display layers  46  and display cover layer  84  for viewing by user  48 . 
     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. Display layers  46  may sometimes be referred to as a display module, a display, or an array of display pixels. The image light (light  44 ) that passes through the array of display pixels is used in displaying content on display  14  for user  48 . 
     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  29  (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 (e.g., display data). The information to be displayed may be conveyed from circuitry  68  to display control circuitry such as 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 . During operation of display  14 , display driver circuitry  62  and/or other display control circuitry such as gate driver circuitry formed on substrate  58  or coupled to substrate  58  may be used in controlling the array of display pixels in layers  46  (e.g., using a grid of vertical data lines and horizontal gate lines). 
     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  58 . 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 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 layers  46  and the other display structures of  FIG. 5  typically have rectangular shapes with four peripheral edges, but display configurations with other shapes may be used in forming display  14  if desired. 
     As shown in  FIG. 6 , display structures  46  of display  14  may include a plurality of display pixels  86 . Display pixels  86  may be organized in rows and columns. Display control circuitry may be used in controlling the operation of display pixels  86  using signal lines such as data lines  88  and gate lines  90 . In liquid crystal displays, display pixels  86  may each contain an electrode for applying an electric field to an associated portion of liquid crystal layer  52  ( FIG. 5 ) and a thin-film (amorphous silicon or polysilicon) transistor for controlling the magnitude of the signal applied to the electrode and therefore the magnitude of the electric field. In other types of displays, display pixels  86  may be formed from other types of structures (e.g., organic light-emitting diodes, etc.). 
     Lines  90  may be coupled to the gates of the thin-film transistors and may sometimes be referred to as gate lines. Lines  88  may be coupled to the sources of the thin-film transistors and may sometimes be referred to as source lines or data lines. Gate driver circuitry (e.g., thin-film transistor gate driver circuitry) may be coupled to gate lines  90 . Display driver circuitry that produces data signals for lines  88  (e.g., a display driver integrated circuit) may be coupled to data lines  88 . 
     Gate driver circuitry, one or more display driver integrated circuits, traces for distributing gate and data signals and other display control signals, and other display control circuitry may be formed in inactive region  46 I of display  14  and display structures  46 . As an example, a display driver integrated circuit may be mounted along the upper segment of inactive region  46 I, whereas gate driver thin-film circuitry may be formed along the left and right segments of inactive region  46 I. During operation of display  14 , display pixels  86  may display images for a user, so the portion of display structures  46  containing display pixels  86  may sometimes be referred to as active display structures or the active area of display  14 . The metal traces and other display control circuit structures in inactive region  46 I do not display any images, so this portion of structures  46  may sometimes be referred to as inactive display structures. 
     Inactive region  46 I may form a border that surrounds some or all of active area  46 A. For example, inactive region  46 I may have a rectangular ring shape of the type shown in  FIG. 6  having opposing upper and lower border segments and left and right border segments. 
     To provide display  14  with a borderless appearance, display  14  may be provided with light distribution structures that distribute light from peripheral display pixels near the edge of active area  46 A into a portion of the display overlapping inactive area  46 I. In this way, image content can be displayed over inactive area  46 I, effectively increasing the lateral dimensions of display  14  and the apparent size of the display sufficiently to eliminate inactive area  46 I from view by a user (i.e., making the apparent size of the display to the viewer larger than the area of structures  46  and active area  46 A). 
     The light distribution structures that are used for distributing edge light in display  14  may be based on liquid crystal light distribution structures. As an example, a liquid crystal cell may be mounted over a peripheral display pixel. The liquid crystal cell can be controlled by control circuitry  29  to adjust the polarization of the light from the peripheral display pixel. A reflective polarizer may receive light exiting the liquid crystal cell. When the liquid crystal cell is placed in a first of two states, the light will pass vertically upwards. When the liquid crystal cell is placed in a second of the two states, the light will be deflected to the side. A secondary mirror or other reflector may then reflect the deflected light vertically upwards. If desired, other types of light distribution components may be used in distributing light near the edge of display  14  to minimize visible borders. Configurations for display  14  in which light distribution structures based on liquid crystal structures are used in distributing light near the edge of display  14  may sometimes be described herein as an example. 
       FIG. 7  is a perspective view of a liquid crystal cell of the type that may be used in forming liquid crystal light distribution structures for display  14 . As shown in  FIG. 7 , liquid crystal cell  300  may, during operation of the light distribution structures, receive polarized light such as linearly polarized light  308 . Light  308  may, for example, be vertically polarized light having an electric field that runs vertically (in the orientation of  FIG. 7 ). Light  308  may propagate through liquid crystal cell  300  along axis  310 . 
     Liquid crystal cell  300  may include a layer of liquid crystal material such as liquid crystal material  304 . Liquid crystal material  304  may be sandwiched between a pair of transparent electrodes such as electrodes  302  and  306 . Electrodes  302  and  306  may be formed from transparent conductive material such as indium tin oxide. If desired, other electrode configuration may be used for liquid crystal cell  300 . The configuration of  FIG. 7  is merely illustrative. 
     Using electrodes  302  and  306 , control circuitry  29  may provide control signals (e.g., a control voltage) across liquid crystal material  304 . The control signals may be adjusted in real time to adjust the orientation of liquid crystals within liquid crystal material  304 . The orientation of the liquid crystals determines the amount of polarization rotation that will be imposed on incoming polarized light  308 . When placed in a first state, such as the state of  FIG. 7 , liquid crystal cell  300  will not rotate vertically polarized light, so light  308  at the exit of liquid crystal cell  300  will not be rotated with respect to incoming light  308  and will have the same vertically polarized state as incoming light  308 . When placed in a second state, such as the state of  FIG. 8 , however, liquid crystal cell  300  will rotate incoming vertically polarized light  308  by 90° to produce horizontally polarized light  308  at the exit of cell  300 . 
     Liquid crystal polarization rotating structures such as cell  300  of  FIGS. 7 and 8  may be combined with polarizer structures such as a reflecting polarizer (i.e., a linear reflecting polarizer) to form a liquid crystal shutter that can be used as a light distribution structure along the peripheral edge of display  14 . 
       FIG. 9  is a cross-sectional side view of display  14  in device  10  showing how light distribution structures based on liquid crystal shutter structures may be used to enhance the apparent size of display  14  and thereby reduce or eliminate the size of visible inactive border regions in display  14 . As shown in  FIG. 9 , display  14  may include a display cover layer such as display cover layer  84 . Display cover layer  84  may be mounted in housing  12  of device  10  so as to cover and protect display structures  46 . Display structures  46  may include active structures  46 A containing display pixels and inactive structures  46 I that are devoid of display pixels. Display structures  46  may include central pixels such as display pixels  86 . Display pixels  86  may produce light  112  that travels vertically upwards to viewer  48  in region  114  of display  14 . Display structures  46  may also include a rectangular ring of peripheral display pixels such as peripheral display pixel  86 ′ that surround central display pixels  86 . During operation of display  14 , light distribution structures  216  may be used to distribute light from peripheral pixels such as display pixel  86 ′ alternately into portions  116 - 1  and  116 - 2  of region  116  of display  14 . Because region  116  overlaps inactive portion  46 I of display structures  46  (when viewed from the position of viewer  48 ), the use of light distribution structures  216  to distribute pixel data from peripheral display pixel  86 ′ into region  116  increases the apparent size of display  14  and minimizes or eliminates visible inactive border regions in display  14 . 
     Control circuitry  29  can control which content is displayed on display pixels  86  of display structures  46  at a given time. Control circuitry  29  may, for example, supply display pixel data and control signals to display pixels  86  using signal paths such as signal path  110 . Synchronously, control circuitry  29  may supply control signals on path  108  to adjust liquid crystal cell  300 . By adjusting liquid crystal cell  300 , control circuitry  29  can adjust the polarization of light from display pixel  86 ′. 
     Light exiting display pixel  86 ′ is linearly polarized, because this light has passed through upper linear polarizer  54  ( FIG. 5 ). In response to control signals from control circuitry  29 , cell  300  may be used to maintain the initial linear polarization orientation of the light exiting display pixel  86 ′ or may be used to rotate the polarization of this light by 90°, as described in connection with  FIGS. 7 and 8 . 
     Upon exiting cell  300 , light from display pixel  86 ′ will either be linearly polarized with an electric field that is oriented within the page of  FIG. 9  (as illustrated by light ray  210 ) or will be linearly polarized with an electric field that is oriented perpendicular to the page of  FIG. 9  (as illustrate by light ray  212 ). 
     Reflective polarizer  208  may be mounted on a support structure such as support structure  206  at a 45° angle relative to display structures  46 . Light rays such as light rays  210  will be produced when display pixel  86 ′ is producing light and cell  300  has been placed in a first of its two polarization rotating states. Light rays such as light rays  212  will be produced by display pixel  86 ′ when display pixel  86 ′ is producing light and cell  300  has been placed in a second of its two polarization rotating states. Reflective polarizer  208  is oriented to allow light  210  to pass vertically through reflective polarizer  208  to portion  116 - 2  of region  116  while reflecting light  212  horizontally onto reflector  214 . Reflector  214  is configured to reflect light  212  from reflective polarizer  208  vertically upward into portion  116 - 1  of region  116 . 
     Control circuitry  29  may direct pixels  86  to display pixel data such as pixel data P 2 , P 3 , . . . in the central portion of display structures  46 . Control circuitry  29  may change the state of display pixel  86 ′ at twice the rate of display pixels  86 . For example, while displaying pixel data P 2  in the leftmost display pixel  86 , control circuitry  29  may direct pixel  86 ′ to display pixel data P 1  (while placing cell  300  is its first state) and then to display pixel data P 1 ′ (while placing cell  300  in its second state). 
     Control circuitry  29  can therefore alter the pixel data that is being presented by display pixel  86 ′ while synchronously adjusting the state of cell  300  in liquid crystal light distribution structures  216  so as to ensure that the light from display pixel  86 ′ is distributed across portion  116  of display  14 . Taken together, display portion  116 , which receives light from light distribution structures  216 , and display portion  114 , which is associated with light  112  from central display pixels  86 , have a size that is larger than display structures  46  (and that is larger than active structures  46 A). By alternating the state of cell  300  while simultaneously controlling the pixel data that is displayed by display pixel  86 ′, control circuitry  29  can distribute display light over inactive border region  46 I, increasing the apparent size of the active region in display  14  and ensuring that display  14  appears borderless. 
     Light distribution structures such as light distribution structures  216  of  FIG. 9  that are formed from liquid crystal cell  300 , reflective polarizer  208  and reflector  214  may be formed in linear arrays along the left and right borders of display  14  (and, if desired, along the upper and lower borders of display  14  in addition to along the left and right borders of display  14 ). This allows one or more, two or more, three or more, or four or more of the edges of display  14  to be provided with distributed pixel data in regions such as region  116  of  FIG. 9 . 
     If desired, the components of light distribution structures  216  such as reflective polarizer  208  may be used to distribute light from multiple peripheral display pixels in parallel. This type of configuration is shown in  FIG. 10 . As shown in  FIG. 10 , a set of peripheral display pixels  86 ′ such as a strip of display pixels  86 ′ of width N may run along the peripheral edge of display structures  46  (into the page in the orientation of  FIG. 10 ). Liquid-crystal cell  300  may distribute light  210  from display pixels  86 ′ into portion  116 - 2  of peripheral display region  116  and may, after control circuitry  29  has changed the data being displayed by display pixels  86 ′, distribute light  210  from display pixels  86 ′ into portion  116 - 1  of display region  116 . 
       FIG. 11  shows how reflector  214  may, if desired, have a non-planar surface. In the example of  FIG. 11 , reflector  214  has three curved surface regions each of which has a radius of curvature R. The use of curved surfaces in reflector  214  may help distribute reflected light  210 . 
     Because light distribution structures  216  spread out the light from display pixels  86 ′ over multiple regions such as regions  116 - 1  and  116 - 2 , whereas light  212  from display pixels  86  passes directly through display cover layer  86  to viewer  48  in region  114 , the intensity of light in region  116  has the potential for being lower than the intensity of light in region  114 . For example, when spreading light from a peripheral display pixel over two regions such as regions  116 - 1  and  116 - 2 , the intensity of light in each pixel location in region  116  will be half of the intensity of light in each pixel location in region  114 , because pixel regions  116 - 1  and  116 - 2  are each illuminated for half of the time as the pixel regions in region  116 . 
     To compensate for the decreased light intensity in region  116  relative to region  114 , backlight unit  42  may be configured to provide backlight  44  with a greater intensity under peripheral pixels such as pixel  86 ′ than under central pixels such as pixels  86 . The backlight for pixel  86 ′ of  FIG. 9  may be, for example, twice as bright as the backlight for each of pixels  86 . 
     As shown in  FIG. 12 , locally increased backlight intensity may be produced by configuring light scattering features  220  (e.g., bumps, pits, and/or the type of bumps or pits used) in light guide plate  78  to ensure that the amount of backlight  44  that is scattered upwards through pixel  86 ′ is twice as much (or other suitable ratio) as the amount of backlight  44  that is scattered upwards through pixels  86 ′. For example, in a light guide plate configuration that uses pits to scatter backlight, the pits that are formed on the portion of light guide plate  78  that lies under pixels  86 ′ may be twice the density of pits that are formed on the portion of light guide plate  78  that lies under pixels  86  (or other suitable ratio). 
     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: 20120928
Publication Date: 20150922
Grant Date: 20150922
Priority Date: 20120928
Inventors: MEMERING DALE N.
YANG TSENG-MAU
PREST CHRISTOPHER D.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F2001/133388", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133536", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13362", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/13362", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133388", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133536", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133536", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133388", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 50384845