PATENT DOCUMENT

Publication Number: US-10649248-B1
Application Number: US-201715839195-A
Country: US
Kind Code: B1

Title: Displays with adjustable privacy levels

Abstract:
A display may have display layers such as liquid crystal display layers having a liquid crystal layer interposed between a color filter layer and a thin-film transistor layer or organic light-emitting diode layers having organic light-emitting diodes formed from thin-film transistor circuitry. The display layers may be configured to form an array of pixels that display images and may include a polarizer. An angle-of-view adjustment layer may overlap the display layers. The angle-of-view adjustment layer may include one or more liquid crystal layers. A first polarizer may be interposed between first and second liquid crystal layers and the second liquid crystal layer may be overlapped by a second polarizer. The first and second polarizers may have pass axes that are aligned with a pass axis of the polarizer in the display layers. One or more liquid crystal layers in the angle-of-view adjustment layer may include dichroic dye.

Claims:
What is claimed is: 
     
       1. An apparatus, comprising:
 a pixel array configured to display an image; and 
 an angle-of-view adjustment layer overlapping the pixel array that contains a liquid crystal layer with liquid crystal molecules and dichroic dye molecules; and 
 a backlight that provides backlight illumination to the pixel array, wherein the pixel array is interposed between the backlight and the angle-of-view adjustment layer and wherein the backlight comprises:
 a first light guide layer; 
 a second light guide layer that overlaps the first light guide layer; and 
 a light source that is electrically adjustable between a first operating mode in which the backlight illumination is provided to an edge of the first light guide layer and a second operating mode in which the backlight illumination is provided to an edge of the second light guide layer. 
 
 
     
     
       2. The apparatus defined in  claim 1  wherein the pixel array has liquid crystal molecules and is free of dichroic dye molecules and has a polarizer interposed between the liquid crystal molecules and the angle-of-view adjustment layer. 
     
     
       3. The apparatus defined in  claim 1  wherein the angle-of-view adjustment layer comprises at least one additional liquid crystal layer and a polarizer interposed between the liquid crystal layer and the additional liquid crystal layer. 
     
     
       4. The apparatus defined in  claim 3  wherein the additional liquid crystal layer includes additional dichroic dye molecules. 
     
     
       5. The apparatus defined in  claim 1  wherein the angle-of-view adjustment layer comprises:
 a first liquid crystal layer interposed between first and second electrodes; and 
 a second liquid crystal layer interposed between third and fourth electrodes. 
 
     
     
       6. The apparatus defined in  claim 5  wherein the pixel array has first and second polarizers, the apparatus further comprising:
 a third polarizer interposed between the first and second liquid crystal layers; and 
 a fourth polarizer, wherein the second liquid crystal layer is interposed between the third polarizer and the fourth polarizer. 
 
     
     
       7. The apparatus defined in  claim 1  further comprising:
 control circuitry configured to control the angle-of-view adjustment layer to place the display in a selected one of: 1) a normal operating mode and 2) a privacy mode. 
 
     
     
       8. The apparatus defined in  claim 7  wherein the angle-of-view adjustment layer comprises at least one additional liquid crystal layer and a polarizer interposed between the liquid crystal layer and the additional liquid crystal layer. 
     
     
       9. The apparatus defined in  claim 7  wherein the angle-of-view adjustment layer includes first and second additional liquid crystal layers and first and second pairs of electrodes with which the control circuitry controls the angle-of-view adjustment layer wherein the first additional liquid crystal layer is interposed between the first pair of electrodes, and wherein the second additional liquid crystal layer is interposed between the second pair of electrodes. 
     
     
       10. The apparatus defined in  claim 1 , wherein the first light guide layer has first light scattering features configured to scatter the backlight illumination over a first angular spread and wherein the second light guide layer has second light scattering features configured to scatter the backlight illumination over a second angular spread that is different than the first angular spread.

Description:
This application claims the benefit of provisional patent application No. 62/447,267, filed Jan. 17, 2017, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices and, more particularly, to electronic devices with displays. 
     BACKGROUND 
     Electronic devices often include displays. For example, laptop computers have displays. Displays are typically designed to display images over a relatively wide angle of view to accommodate movements in the position of a viewer relative to the display. In some situations, such as when a user of a laptop or other device with a display is using the device in public, the wide viewing angle is undesirable as it compromises privacy. 
     SUMMARY 
     A display may have display layers such as liquid crystal display layers having a liquid crystal layer interposed between a color filter layer and a thin-film transistor layer, organic light-emitting diode layers having organic light-emitting diodes formed from thin-film transistor circuitry, or structures formed from an array of crystalline semiconductor light-emitting diode dies. The display layers may be configured to form an array of pixels that display images and may include a polarizer. 
     An angle-of-view adjustment layer may overlap the display layers. The angle-of-view adjustment layer may include one or more liquid crystal layers. A first polarizer may be interposed between first and second liquid crystal layers. The second liquid crystal layer may be interposed between the first polarizer and a second polarizer. The first and second polarizers may have pass axes that are aligned with a pass axis of the polarizer in the display layers. One or more liquid crystal layers in the angle-of-view adjustment layer may include dichroic dye. 
     An electronic device may include a display with display layers overlapped by an angle-of-view adjustment layer. Control circuitry in the electronic device may be used to supply electric fields to the liquid crystal layers in the angle-of-view adjustment layer. The control circuitry may place the angle-of-view adjustment layer in a wide angle transparency mode that allows images on the pixel array to be viewed over a wide angle of view and may place the angle-of-view adjustment layer in one or more narrower angle transparency modes (privacy modes) in which the angle of view for images on the pixel array is reduced to enhance privacy. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG. 2  is a schematic diagram of an illustrative electronic device having a display in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of an illustrative display in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of an illustrative light-emitting diode pixel array of the type that may be used in the display of  FIG. 3  in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative an angle-of-view adjustment layer formed from a pair of stacked liquid crystal cells in accordance with an embodiment. 
         FIG. 6  is a graph showing how the angular spread of light transmission through an angle-of-view adjustment layer may be narrowed when multiple liquid crystal cells are stacked in the angle-of-view adjustment layer in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with a display is shown in  FIG. 1 . Electronic device  10  may be a computing device such as 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, or other wearable or miniature device, a computer display that does not contain an embedded computer, a computer display that includes 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. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a laptop computer. Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     As shown in  FIG. 1 , device  10  includes a display such as display  14  mounted in housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, etc.), other suitable materials, or a combination of any two or more of these materials. Housing  12  may be formed using a unibody configuration in which some or all of housing  12  is machined or molded as a single structure or may be formed using multiple structures (e.g., an internal frame structure, one or more structures that form exterior housing surfaces, etc.). 
     Housing portions  12 A and  12 B of housing  12  may be connected to each other using hinge structures located along the upper edge of lower housing  12 B and the lower edge of upper housing  12 A. Hinges may allow upper housing  12 A to rotate about axis  22  in directions  24  relative to lower housing  12 B. 
     Display  14  may be mounted in upper housing  12 A. Display  14  may be a touch screen display that incorporates a layer of conductive capacitive touch sensor electrodes or other touch sensor components (e.g., resistive touch sensor components, acoustic touch sensor components, force-based touch sensor components, light-based touch sensor components, etc.) or may be a display that is not touch-sensitive. Capacitive touch screen electrodes may be formed from an array of indium tin oxide pads or other transparent conductive structures. A touch sensor may be formed using electrodes or other structures on a display layer that contains a pixel array or on a separate touch panel layer that is attached to the pixel array (e.g., using adhesive). 
     Display  14  may include an array of pixels formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of electrowetting pixels, an array of organic light-emitting diode pixels, or pixels based on other display technologies. 
     As shown in  FIG. 1 , device  10  may have input-output devices such as track pad  18  and keyboard  16 . Device  10  may also have components such as cameras, microphones, speakers, buttons, status indicator lights, buzzers, sensors, and other input-output devices. These devices may be used to gather input for device  10  and may be used to supply a user of device  10  with output. Connector ports in device  10  may receive mating connectors (e.g., an audio plug, a connector associated with a data cable such as a Universal Serial Bus cable, a data cable that handles video and audio data such as a cable that connects device  10  to a computer display, television, or other monitor, etc.). 
       FIG. 2  is a schematic diagram of device  10 . As shown in  FIG. 2 , electronic device  10  may have control circuitry  26 . Control circuitry  26  may include storage and processing circuitry for supporting the operation of device  10 . The storage and processing circuitry may include storage such as hard disk drive storage, nonvolatile memory (e.g., flash memory or other electrically-programmable-read-only memory configured to form a solid state drive), volatile memory (e.g., static or dynamic random-access-memory), etc. Processing circuitry in control circuitry  26  may be used to control the operation of device  10 . The processing circuitry may be based on one or more microprocessors, microcontrollers, digital signal processors, baseband processors, power management units, audio chips, application specific integrated circuits, etc. 
     Input-output circuitry in device  10  such as input-output devices  28  may be used to allow data to be supplied to device  10  and to allow data to be provided from device  10  to external devices. Input-output devices  28  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, cameras, sensors (e.g., ambient light sensors, proximity sensors, orientation sensors, magnetic sensors, force sensors, touch sensors, etc.), light-emitting diodes and other status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  28  and may receive status information and other output from device  10  using the output resources of input-output devices  28 . Input-output devices  28  may include one or more displays such as display  14 . 
     Control circuitry  26  may be used to run software on device  10  such as operating system code and applications. During operation of device  10 , the software running on control circuitry  26  may display images on display  14  using an array of pixels in display  14 . Display  14  may include adjustable viewing angle control structures such as an adjustable angle-of-view adjustment layer that overlaps the pixels and/or an adjustable backlight. The angle-of-view adjustment layer can be operated in a wide viewing angle mode when privacy is not needed and can be operated in one or more narrow viewing angle modes when privacy is desired. 
     When operated in the restricted angle-of-view mode (sometimes referred to as privacy mode), the angle of view of display  14  is restricted. When the angle of view of display  14  is restricted, it is difficult or impossible for viewers that are located at off-axis positions relative to display  14  to view images on display  14  (e.g., a viewer seated next to the user on an airplane will not be able to view images on display  14 ). At the same time, the user of device  10  who is located in an on-axis position will be able to use display  14  to view images. When operated in an unrestricted angle-of-view mode (sometimes referred to as wide viewing angle mode or normal operation), both on-axis and off-axis viewers will be able to view content on display  14  (i.e., content will not generally be private). 
     Changes in the operating mode of display  14  to implement angle-of-view restrictions (i.e., adjustments to display  14  to place display  14  in normal viewing mode or a reduced-angle-of-view privacy mode) may be made based on user input to input-output devices  28  or may be made automatically by control circuitry  26 . Control circuitry  26  may, for example, use information such as content sensitivity information to determine whether or not content that is being display on display  14  should be displayed in normal mode or privacy mode. If, for example, a user is viewing a movie, the movie may be displayed in normal mode. In the event that a private message such as an incoming text message is detected, display  14  may be placed in privacy mode, thereby ensuring that the content of the text message will not be inadvertently revealed to unauthorized parties. If desired, the angle-of-view adjustment layer for display  14  may be segmented (e.g., using individually adjustable segmented electrodes), so that only a part of display  14  may be placed in privacy mode (e.g., to ensure the privacy of a text message) while the remainder of display  14  is operated normally (e.g. to display a movie). 
     A cross-sectional side view of display  14  is shown in  FIG. 3 . Display  14  may have a rectangular shape (i.e., display  14  may have a rectangular footprint and a rectangular peripheral edge that runs around the rectangular footprint) or may have other suitable shapes. Display  14  may be planar, as shown in  FIG. 3 , or may have a curved profile. An adjustable angle-of-view control layer such as angle-of-view adjustment layer  90  may overlap the footprint of display  14 . Angle-of-view adjustment layer  90  may have one or more electrically adjustable structures that control circuitry  26  can control dynamically to place display  14  in a normal viewing mode or a private viewing mode. Layer  90  may, for example, have one or more liquid crystal layers that can be adjusted to produce a variable amount of viewing angle restriction (adjustable privacy) based on user input, input from sensors, information on the nature of which content is being presented on display  14 , etc. 
     As shown in  FIG. 3 , display  14  may include backlight structures such as backlight unit  42  for producing backlight illumination such as backlight illumination (backlight)  44 . During operation, backlight illumination  44  travels outwards (vertically upwards in dimension Z in the orientation of  FIG. 3 ) and passes through an array of pixels in display layers  46 . This illuminates any images that are being produced by the 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 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  58  and  56  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 pixel circuits based on thin-film transistors and associated electrodes (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. Configurations in which color filter elements are combined with thin-film transistor structures on a common substrate layer in the upper or lower portion of display  14  may also be used. Layers  46  may form any suitable type of liquid crystal display (e.g., a fringe-field switching display, a vertical alignment liquid crystal display, a twisted nematic liquid crystal display, an in-plane switching liquid crystal display, an electrically controlled birefringence liquid crystal display, etc.). 
     During operation of display  14  in device  10 , control circuitry  26  (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 one or more display driver integrated circuits. The display driver circuits may supply data and control signals to an array of pixels in display layers  46  (e.g., pixel circuits in layer  58 , etc.). 
     Backlight structures  42  may include a light guide layer such as light guide layer  78  (sometimes referred to as a light guide structure or light guide). Light guide layer  78  may be formed from one or more stacked layers of transparent material such as clear glass or plastic (e.g., molded plastic that forms a light guide plate, a thin flexible plastic film, etc.). During operation of backlight structures  42 , light sources such as light source  72  may generate light that creates backlight  44 . Light source  72  may be an array of light-emitting diodes that runs along one or more edges of light guide layer  78  such as edge  76  of light guide layer  78  (i.e., into the page along the X axis in the orientation of  FIG. 3 ). Light-source  72  may emit light  74  into edge  76  of light guide layer  78 . 
     Light  74  may be distributed throughout light guide layer  78  due to the principal of total internal reflection. Scattering features (protrusions, recesses, etc.) may be incorporated into light guide layer  78  (e.g., on the upper and/or lower surface of layer  78 ) to scatter light from layer  78 . Light that is scattered upwards in direction Z from light guide layer  78  may serve as backlight  44  for display  14 . Light 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 plastic covered with a dielectric mirror thin-film coating. 
     If desired, backlight structures  42  may emit backlight  44  over an adjustable range of angles. For example, backlight structures  42  may include multiple light guide layers (e.g., layer  78  may be a multilayer stack having a first layer such as layer  78 - 1  and a second layer such as layer  78 - 2 ) and each light guide layer may receive light  74  from a respective set of light-emitting didoes or other light producing components in light source  72 . Each light guide layer in the stack (e.g., layer  78 - 1  and  78 - 2  in a two-layer configuration) may have light scattering features that are configured to scatter light over a different range of angles. As an example, light guide layer  78  may include a first sublayer such as layer  78 - 1  that scatters light  72  to form highly collimated backlight  44  (backlight illumination with a narrow range of angles relative to the surface normal of layer  78 ) and may include a second sublayer  78 - 2  that scatters light  72  over a wider ranges of angles. When it is desired to operate display  14  in a normal operating mode, light source  72  can be directed to emit light into second sublayer  78 - 2 , so that the pixel array of layers  46  is illuminated over a wide range of angles. When it is desired to operate display  14  in a privacy mode, light source  72  can be directed to emit light into first sublayer  78 - 1 , so that the pixel array of layers  46  is illuminated over a narrow range of angles (e.g., so that backlight  44  is collimated, thereby reducing the visibility of images from off-axis angles). Any suitable variable adjustable-backlight-angle backlight structures may be used in forming backlight structures  42  if desired. The use of multiple overlapping light guide layers with different light scattering properties is illustrative. If desired, backlight structures  42  may be configured to only emit collimated light (or light over a relatively narrow range of angles) or may be configured to only emit wide-angle light. 
     To enhance display performance, optical films  70  may be incorporated between backlight structures  42  and layers  46 . Optical films  70  may include diffuser layers for helping to homogenize backlight  44  and thereby reduce hotspots, light collimating films such as prism films (sometimes referred to as brightness enhancement films) and turning films for directing backlight  44  towards direction Z, and compensation films for enhancing off-axis viewing. Optical films  70  may overlap the other structures in backlight unit  42  such as light guide layer  78  and reflector  80 . For example, if light guide layer  78  has a rectangular footprint in the X-Y plane of  FIG. 3 , optical films  70  and reflector  80  may have a matching rectangular footprint. If desired, films such as compensation films may be incorporated into other layers of display  14  (e.g., a polarizer layer). 
     Angle-of-view adjustment layer  90  may be operated in multiple viewing modes such as a normal angle-of-view mode and one or more reduced angle-of-view modes. When operated in a normal angle-of-view mode, viewer  48  can view images on display  14  over a relatively wide range of angles A. When privacy is desired, display  14  can be operated in the reduced angle-of-view mode. In this mode, viewer  48  can view images on display  14  over a more restricted range of angles (see, e.g., reduced angle-of-view range B, where B&lt;A, B&lt;60% of A, where B&lt;40% of A, etc.). 
     As shown in  FIG. 3 , layer  90  may include one or more liquid crystal layers such as liquid crystal layer  92 . Liquid crystal layer  92  may include liquid crystal molecules  94  and may optionally include light-absorbing dichroic dye molecules  96 . In configurations in which layer  92  includes only liquid crystal molecules  94 , layer  92  may be configured to serve as an electrically controllable birefringence layer (sometimes referred to as an ECB liquid crystal layer). In configurations in which layer  92  includes dichroic dye  96 , liquid crystal molecules  94  may serve as host molecules and dichroic dye molecules  96  may serve as guest molecules (e.g., layer  92  may form a dichroic dye guest-host liquid crystal layer). Guest dye molecules  96  may exhibit maximum light absorption when the electric field of a light ray is oriented with a first orientation relative to molecules  96  (e.g., parallel to the longitudinal axis of molecules  96 ) and may exhibit minimum light absorption when the electric field of a light ray is oriented with a second orientation relative to molecules  96  (e.g., perpendicular to the longitudinal axis of molecules  96 ). The orientation of dye molecules  96  is aligned with the orientation of elongated liquid crystal molecules  94 , so molecules  96  can be rotated by rotating liquid crystal molecules  94 . 
     Layer  90  may have two or more liquid crystal layers such as layer  92 . In the illustrative configuration of  FIG. 3 , layer  90  contains a single liquid crystal layer. Liquid crystal layer  92  may be interposed between transparent electrodes  98 . Control circuitry  26  may control the operation of layer  90  by applying controlled amounts of electric field to layer  92  using electrodes  98 . Electrodes  98  may be formed from transparent conductive material such as indium tin oxide and may be supported by transparent planar members such as clear substrates  100  (e.g., glass, plastic, etc.). Polarizer layers and/or other layers in display  14  may also serve as substrates for electrodes  98 . The use of substrates  100  to support electrodes  98  in  FIG. 3  is merely illustrative. 
     Layer  90  may include a polarizer such as polarizer  102 . Liquid crystal alignment layers (e.g., polyimide alignment layers or other suitable alignment layers) may be formed on the surfaces of electrodes  98  facing layer  92 . These layers provide liquid crystals  94  with a default alignment in the absence of an applied electric field. When an electric field is applied to liquid crystals  94 , the orientation of liquid crystal molecules  94  (and dye molecules  96 , if present) will change in proportion to the strength of the applied field. The polarization of backlight illumination  44  is affected by the orientations of liquid crystal molecules  96 . By changing in the orientation of liquid crystal molecules  94  with an adjustable electric field, the polarization state of rays of backlight illumination  44  that are passing through layer  92  can be adjusted. 
     In configurations in which no dye molecules  96  are included in layer  92 , off-axis light absorption can be selectively enhanced during privacy mode by adjusting the orientations of liquid crystal molecules  94  to alter the birefringence in layer  92 . The changes in birefringence affect the polarization state of light  44  passing through layer  92  and therefore the amount of light  44  that is transmitted through polarizer  102 . 
     In configurations for layer  90  in which dye molecules  96  are included in layer  92 , changes in orientation for dye molecules  96  affect light absorption in layer  92 . As an example, a positive dichroic dye will exhibit maximum light absorption and minimum light transmission when the dye molecules are oriented parallel to the electric field of light  44  and will exhibit minimum light absorption and maximum light transmission when the dye molecules are oriented perpendicular to the electric field of light  44 . This effect can be exploited in addition to electrically controlled birefringence effects to selectively enhance off-axis light absorption in privacy mode. 
     With one illustrative configuration, polarizer  60  may have a pass axis aligned with the X axis of  FIG. 3 . Polarizer  54  may have a pass axis aligned with the Y axis of  FIG. 3 . Polarizer  102  may have a pass axis that is aligned with the Y axis and that is therefore aligned with the pass axis of polarizer  54 . The alignment layers on surface of electrodes  98  may be configured to align liquid crystal molecules  94  with the Y axis (parallel to the pass axis of polarizer  54 ) in the absence of an applied electric field. With this configuration, backlight illumination  44  will become linearly polarized along the Y axis when passing through polarizer  54 . In the absence of applied electric fields to layer  92 , liquid crystal molecules  94  will not rotate, off-axis light  44  will remain predominantly linearly polarized, and off-axis light transmission will be relatively high. In the presence of applied electric fields to layer  92 , liquid crystal molecules  94  will rotate upwardly and birefringence will be induced in layer  92  accordingly. This will cause off-axis light  44  to become elliptically polarized at polarizer  102  and will reduce off-axis light transmission through polarizer  102  (and therefore layer  90 ). In configurations in which dye  96  is present, off-axis light absorption will be enhanced when liquid crystal molecules  94  are rotated by applying electric fields to layer  92  to rotate molecules  94  and  96 . 
     In the example of  FIG. 3 , display layers  46  are liquid crystal display layers and include a liquid crystal layer such as layer  52  (e.g., a layer of liquid crystal molecules sandwiched between a pair of conductive transparent electrodes and polyimide alignment layers). If desired, display layers  46  may be formed from other types of display structures. As an example, display layers  46  may be based on light-emitting diode display structures. As shown in  FIG. 4 , for example, display layers  46  may include a substrate such as substrate  112  (e.g., glass, plastic, one or more inorganic buffer layers, etc.). Thin-film circuitry  108  may be formed on substrate  112 . Thin-film circuitry  108  may include thin-film transistors, thin-film capacitors, and organic light-emitting diodes that form pixels  110 . Each pixel  110  may, for example, include a pixel circuit that controls the light output from a respective organic light-emitting diode. Pixels  110  may be arranged in an array for displaying images for viewer  48  of  FIG. 3  in a configuration for display  14  of  FIG. 3  in which display layers  46  of  FIG. 4  have been used in place of display layers  46  of  FIG. 3 . If desired, pixels  110  in display layers  46  of  FIG. 3  or other display layers for display  14  may be formed from micro-LEDs (e.g., an array of discrete light-emitting diodes each of which is formed from a crystalline semiconductor die). In general, display layers  46  may be formed from any suitable type of display (e.g., an electrophoretic display, a plasma display, a display formed from microelectromechanical systems pixels, etc.). 
     The pixel array of display layers (layer)  46  of  FIG. 4  may be overlapped by layer  104 . Layer  104  may include linear polarizer  54  (e.g., a polarizer with a pass axis aligned with the Y axis of  FIGS. 3 and 4 ). Layer  104  may, if desired, include a wave plate such as circular wave plate  106  (e.g., wave plate  106  may be included so that layer  104  forms a circular polarizer that helps suppress ambient light reflections from reflective structures in thin-film circuitry  108 ). 
     As shown in  FIG. 5 , angle-of-view adjustment layer  90  may include sublayers such as first layer  90 - 1  and second layer  90 - 2 . Layer  90 - 1  may be formed from first liquid crystal layer  92 - 1 , which is interposed between polarizer  54  and polarizer  102 - 1 . Layer  90 - 2  may be formed from second liquid crystal layer  92 - 2 , which is interposed between polarizer  102 - 1  and polarizer  102 - 2 . Polarizers  54 ,  92 - 1 , and  92 - 2  may have pass axes aligned with the Y axis of  FIG. 5  (as an example). The use of multiple stacked liquid crystal cells in layer  90  may enhance privacy. In particular, light transmission through layer  90  may be reduced more for light at off-axis angles θ (e.g., light rays such as off-axis light ray  44 R at non-zero angles θ with respect to surface normal n of layer  90  and display  14 ) than for on-axis light (e.g., light rays such as on-axis light ray  44 A, which is oriented at an angle θ=0° with respect to surface normal n and is therefore parallel to surface normal n). 
     As shown in  FIG. 6 , transmission T of light  44  passing through a single angle-of-view adjustment layer such as layer  90 - 1  (see, e.g., layer  90  of  FIG. 3 ) when layer  90 - 1  is in its privacy mode of operation may be characterized by a curve such as light transmission curve  120  of  FIG. 6 , whereas transmission T of light  44  passing through multiple angle-of-view adjustment layers such as layers  90 - 1  and  90 - 2  in their privacy mode of operation may be characterized by a narrower (more collimated) curve such as light transmission curve  122  of  FIG. 6 . Liquid crystal layers  92 - 1  and  92 - 2  of layer  90  of  FIG. 5  may both be liquid crystal layers without guest dye molecules  96 , may both be liquid crystal layers that contain liquid crystal molecules  94  and dye molecules  96 , or may include a single liquid crystal layer without dye and a single liquid crystal layer with dye. Configurations with three or more stacked angle-of-view adjustment layers (with or without dye  96 ) may also be used, if desired. 
     Any suitable dichroic dye  96  may be used in the liquid crystal material of layer  90  (e.g., black dye, blue dye, purple dye, etc.). The concentration of dye may be at least 0.1%, at least 0.5%, 0.1% to 3%, less than 5%, or other suitable concentration. There may be one liquid crystal layer in layer  90  or layer  90  may contain a stack of two or more liquid crystal layers separated by interposed polarizers. The transmission axis of each polarizer may be parallel to the transmission axis of the top polarizer in display layers  46  (e.g., polarizer  54 ) or may have other suitable orientation(s). The liquid crystal alignment directions of liquid crystal layer(s)  92  of layer  90  may be parallel or perpendicular to the liquid crystal alignment direction of liquid crystal layer  52 . Positive or negative liquid crystal material may be used for the liquid crystal layers of display  14 . For effective privacy mode switching, it may be desirable for the electrically induced retardation And of layer  90  to be at least 500 nm, 600-900 nm, or less than 900 nm, where Δn is the birefringence induced in the electrically adjustable liquid crystal layer of layer  90  and d is the liquid crystal layer thickness). 
     The foregoing is merely illustrative and various modifications can be made to the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20171212
Publication Date: 20200512
Grant Date: 20200512
Priority Date: 20170117
Inventors: FAN JIANG, SHIH-CHYUAN
CHANG, SHIH-WEI
CHEN, YUAN
GE, ZHIBING
CHEN, CHENG
Assignee: APPLE INC
CPC Classifications: [{"code": "H04N7/141", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1323", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133606", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N7/141", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/1323", "inventive": true, "first": true, "tree": "[]"}, {"code": "H04N5/23219", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133606", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N5/2256", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N23/611", "inventive": true, "first": false, "tree": "[]"}, {"code": "H04N23/56", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133626", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/1323", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/13725", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 70612644