PATENT DOCUMENT

Publication Number: US-12206061-B2
Application Number: US-202016915629-A
Country: US
Kind Code: B2

Title: Electronic device having display with internal light reflection suppression

Abstract:
An electronic device may have a display. The display has pixels configured to display an image. The display is mounted in a housing. The housing may include head-mounted support structures configured to support the display for viewing through lenses. The pixels of the display may be covered by a layer of thin-film encapsulation. The thin-film encapsulation may be covered with a cover layer such as a glass cover layer that is attached to the thin-film encapsulation layer by a layer of adhesive. To suppress internal light reflections, the display may include reflection suppression structures. The reflection suppression structures may include an antireflection layer and/or polarizer and waveplate layers. The reflection suppression structures may be formed on an outwardly facing surface of the cover layer and/or between the thin-film encapsulation layer and the cover layer.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 pixels configured to form a display; 
 a support structure configured to support the display; 
 an encapsulation layer on the pixels; 
 a first quarter wave plate; 
 a first linear polarizer between the first quarter wave plate and the pixels; 
 a second quarter wave plate; and 
 a second linear polarizer between the first linear polarizer and the encapsulation layer. 
 
     
     
       2. The electronic device of  claim 1  wherein the pixels have a pixel density of at least  1000  pixels per inch. 
     
     
       3. The electronic device of  claim 1  wherein the pixels have a pixel density of at least  1500  pixels per inch. 
     
     
       4. The electronic device of  claim 1  further comprising a cover layer between the first linear polarizer and the pixels. 
     
     
       5. The electronic device of  claim 1  further comprising:
 a lens overlapping the pixels, wherein the pixels are viewable through the lens. 
 
     
     
       6. The electronic device of  claim 5  wherein the pixels have a pixel density of at least 1000 pixels per inch. 
     
     
       7. The electronic device of  claim 1  further comprising a layer of adhesive between a cover layer and the encapsulation layer. 
     
     
       8. The electronic device of  claim 1  further comprising:
 a lens, wherein the support structure comprises a head-mounted support structure configured to support the display for viewing through the lens. 
 
     
     
       9. An electronic device, comprising:
 a display that has pixels configured to display light, wherein the pixels include a light-emitting device, wherein the display has a quarter wave plate and has a linear polarizer, and wherein the linear polarizer is between the quarter wave plate and the pixels; and 
 a lens configured to receive the light from the display. 
 
     
     
       10. The electronic device of  claim 9  wherein the pixels have a pixel density of at least 1500 pixels per inch. 
     
     
       11. The electronic device of  claim 9  wherein the light-emitting device in each pixel is an organic light-emitting diode. 
     
     
       12. The electronic device of  claim 11  wherein the pixels are covered with a thin-film encapsulation layer. 
     
     
       13. The electronic device of  claim 12  further comprising a glass layer, wherein the glass layer is between the linear polarizer and the thin-film encapsulation layer. 
     
     
       14. The electronic device of  claim 13  wherein the linear polarizer is attached to an outwardly facing surface of the glass layer. 
     
     
       15. The electronic device of  claim 9  wherein the lens is configured to transmit the light from the display towards an eye box. 
     
     
       16. An electronic device, comprising:
 a display, wherein the display comprises:
 pixels; 
 a quarter wave plate overlapping the pixels; 
 a linear polarizer overlapping the pixels; 
 an encapsulation layer; and 
 a glass cover layer between the linear polarizer and the encapsulation layer. 
 
 
     
     
       17. The electronic device of  claim 16  wherein the pixels comprise organic light-emitting diode pixels. 
     
     
       18. The electronic device of  claim 17  further comprising an anti-scratch layer on the quarter wave plate. 
     
     
       19. The electronic device of  claim 18  further comprising an adhesive layer, wherein the adhesive layer is between the glass cover layer and the encapsulation layer. 
     
     
       20. The electronic device of  claim 18 , wherein the pixels are configured to display an image, the electronic device further comprises a lens, and the image is viewable through the lens.

Description:
This application claims the benefit of provisional patent application No. 62/880,220, filed Jul. 30, 2019, 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 
     Displays such as organic light-emitting diode displays may be used in electronic devices such as head-mounted devices. During operation, the pixels in a display emit light. The light passes through overlapping transparent structures for viewing by a user. 
     It can be challenging to form emissive displays for electronic devices such as head-mounted devices. The transparent structures that overlap an emissive display may help protect the display, but serve as a potential high-refractive-index layer that can trap and guide off-axis emitted light rays in accordance with the principal of total internal reflection. Particularly in a display with a high pixel density such as a display in a head-mounted device, there are numerous surface imperfections that can scatter this trapped light outwardly, thereby reducing the contrast of the display. 
     SUMMARY 
     An electronic device may have a display. The display has pixels configured to display an image. The display is mounted in a housing. The housing may include head-mounted support structures configured to support the display for viewing through lenses. 
     The pixels of the display may be thin-film organic light-emitting diode pixels or other pixels covered by a layer of thin-film encapsulation. The thin-film encapsulation may be covered with a cover layer such as a glass cover layer that is attached to the thin-film encapsulation layer by a layer of adhesive. 
     To suppress internal light reflections within the transparent layer of the display such as the thin-film encapsulation layer and cover layer, the display may include reflection suppression structures. The reflection suppression structures may include an antireflection layer and/or polarizer and waveplate layers. Antireflection layers may be formed form moth-eye structures, thin-film interference filters, microlenses, and/or other antireflection structures. In configurations in which the reflection suppression structures include polarizer and waveplate structures, the reflection suppression structures may include a quarter waveplate and a linear polarizer between the quarter wave plate and the display cover layer. A coating containing an anti-scratch layer and/or other layers may be formed on an outwardly facing surface of the quarter wave plate. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a side view of an illustrative electronic device in accordance with an embodiment. 
         FIG.  2    is a side view of an illustrative display in accordance with an embodiment. 
         FIG.  3    is a cross-sectional side view of an illustrative display without reflection suppression structures showing how off-axis emitted light may be trapped and spread outwardly before being scattered out of the display. 
         FIG.  4    is a cross-sectional side view of an illustrative display with an antireflection layer in accordance with an embodiment. 
         FIG.  5    is a cross-sectional side view of an illustrative antireflection layer formed from a thin-film interference filter structure having a stack of dielectric layers of different refractive index values in accordance with an embodiment. 
         FIG.  6    is a cross-sectional side view of an illustrative antireflection layer formed from microstructures such as microlenses in accordance with an embodiment. 
         FIG.  7    is a cross-sectional side view of an illustrative antireflection layer formed from microstructures such as moth-eye structures in accordance with an embodiment. 
         FIG.  8    is a graph showing how an antireflection layer may be formed from a graded-index layer in accordance with an embodiment. 
         FIG.  9    is a cross-sectional side view of an illustrative display with reflection suppression structures formed from a linear polarizer and quarter wave plate in accordance with an embodiment. 
         FIG.  10    is a cross-sectional side view of an illustrative display with one or more layers of reflection suppression structures in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An electronic device may have a display. The display may present images for a user during operation of the device. In some configurations, the display may be an emissive display having pixels formed from light-emitting devices such as light-emitting diodes. The display may include reflection suppression structures to help enhance display contrast. 
     A diagram of an illustrative electronic device with a display is shown in  FIG.  1   . Device  10  may be a head-mounted device such as a pair of glasses, goggles, a helmet, a head-mounted device based on a hat or headband structure, or other equipment that is worn on a user&#39;s head. Other types of electronic equipment may be used in forming electronic devices such as device  10  if desired. For example, device  10  may be a wristwatch device or other device that is worn on a portion of a user&#39;s body other than the user&#39;s head, may be a stand-alone device that rests on a desktop or that is built into a kiosk or vehicle, may be a cellular telephone, tablet computer, laptop computer, or other portable electronic device, or may be other suitable electronic equipment. Illustrative configurations in which device  10  is a head-mounted device may sometimes be described herein as an example. 
     Electronic device  10  may have a display such as display  14 . Display  14  may be any suitable type of display. As an example, display  14  may be an emissive display having an array of pixels P that emit light such as organic light-emitting diode pixels or light-emitting diode pixels formed from crystalline semiconductor dies. Pixels P in display  14  may be formed on a rigid or flexible substrate and may have a planar shape or a curved shape with a curved cross-sectional profile. 
     Electronic device  10  may have a housing such as housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or support structure, may be configured to be worn on a user&#39;s head (e.g., device  10  may be a head-mounted device and housing  12  may serve as a head-mounted support structure). In this type of illustrative arrangement, images from display  14  may pass through lens  16  for viewing by a user&#39;s eye located in eye box  18 . There may be multiple lenses  16  and multiple sets of display pixels P for displaying images for the user&#39;s eyes (e.g., a pair of lenses  16  and a pair of pixel groups for left and right eye boxes associated with the user&#39;s left and right eyes).  FIG.  1    shows a single eye box  18  to avoid over-complicating the drawing. 
     During operation, pixels P in device  14  (e.g., a layer of pixels in an array or other pattern) may be used to display images. Image light  24  is emitted by display  14  and is received by lens  16 . Light  24  passes through lens  16  and is provided to eye box  18  as image light  26  so that a user may view the displayed images. In some configurations, light  24  may be polarized (e.g., circularly polarized) and lens  16  may be a reflective lens such as a catadioptric lens that receives and uses polarized light (e.g., circularly polarized light). 
     Housing  12  may be formed from polymer, metal, glass, crystalline material such as sapphire, ceramic, fabric, fibers, fiber composite material, natural materials such as wood and cotton, other materials, and/or combinations of such materials. Housing  12  may be configured to form housing walls. The housing walls may enclose an interior region within device  10  and may separate the interior region from an exterior region surrounding device  10 . Housing structures for device  10  may, if desired, include head straps and other support structures that allow device  10  to be worn by a user. 
     Electrical components  22  may be mounted in the interior of device  10  (e.g., within an interior region of housing  12 . Components  22  may include integrated circuits, discrete components, light-emitting components, sensors, and/or other circuits. Electrical components  22  may include control circuitry. The control circuitry 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 the control circuitry may be used to control the operation of device  10 . For example, the processing circuitry may use sensors and other input-output circuitry to gather input and to provide output, to transmit signals to external equipment, to adjust display  14 , and/or to perform other tasks. 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. The control circuitry may include wired and/or wireless communications circuitry (e.g., antennas and associated radio-frequency transceiver circuitry such as cellular telephone communications circuitry, wireless local area network communications circuitry, etc.). The communications circuitry of the control circuitry may allow device  10  to communicate with other electronic devices. For example, the control circuitry (e.g., communications circuitry in the control circuitry) may be used to allow wired and/or wireless control commands and other communications to be conveyed between devices such as cellular telephones, tablet computers, laptop computers, desktop computers, head-mounted devices, handheld controllers, wristwatch devices, other wearable devices, keyboards, computer mice, remote controls, speakers, accessory displays, accessory cameras, and/or other electronic devices. Wireless communications circuitry may, for example, wirelessly transmit control signals and other information to external equipment in response to receiving user input or other input from sensors or other devices in components  22 . 
     Input-output circuitry in components  22  of device  10  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. The input-output circuitry may include input devices that gather user input and other input and may include output devices that supply visual output, audible output, or other output. 
     Output may be provided using light-emitting diodes (e.g., crystalline semiconductor light-emitting diodes for status indicators and/or displays such as display  14 , organic light-emitting diodes in displays and other components), lasers, and other light-emitting devices, audio output devices (e.g., tone generators and/or speakers), haptic output devices (e.g., vibrators, electromagnetic actuators, piezoelectric actuators, and/or other equipment that supplies a user with haptic output), and other output devices. 
     The input-output circuitry of device  10  (e.g., the input-output circuitry of components  22 ) may include sensors. Sensors for device  10  may include force sensors (e.g., strain gauges, capacitive force sensors, resistive force sensors, etc.), audio sensors such as microphones, touch and/or proximity sensors such as capacitive sensors (e.g., a two-dimensional capacitive touch sensor integrated into a display, a two-dimensional capacitive touch sensor and/or a two-dimensional force sensor overlapping a display, and/or a touch sensor or force sensor that forms a button, trackpad, or other input device not associated with a display), and other sensors. Touch sensors for a display or for other touch components may be based on an array of capacitive touch sensor electrodes, acoustic touch sensor structures, resistive touch components, force-based touch sensor structures, a light-based touch sensor, or other suitable touch sensor arrangements. If desired, a display may have a force sensor for gathering force input (e.g., a two-dimensional force sensor may be used in gathering force input on a display). 
     If desired, the sensors may include optical sensors such as optical sensors that emit and detect light, ultrasonic sensors, optical touch sensors, optical proximity sensors, and/or other touch sensors and/or proximity sensors, monochromatic and color ambient light sensors, image sensors, fingerprint sensors, temperature sensors, sensors for measuring three-dimensional non-contact gestures (“air gestures”), pressure sensors, sensors for detecting position, orientation, and/or motion (e.g., accelerometers, magnetic sensors such as compass sensors, gyroscopes, and/or inertial measurement units that contain some or all of these sensors), health sensors, radio-frequency sensors (e.g., sensors that gather position information, three-dimensional radio-frequency images, and/or other information using radar principals or other radio-frequency sensing), depth sensors (e.g., structured light sensors and/or depth sensors based on stereo imaging devices), optical sensors such as self-mixing sensors and light detection and ranging (lidar) sensors that gather time-of-flight measurements, humidity sensors, moisture sensors, gaze tracking sensors, three-dimensional sensors (e.g., time-of-flight image sensors, pairs of two-dimensional image sensors that gather three-dimensional images using binocular vision, three-dimensional structured light sensors that emit an array of infrared light beams or other structured light using arrays of lasers or other light emitters and associated optical components and that capture images of the spots created as the beams illuminate target objects, and/or other three-dimensional image sensors), facial recognition sensors based on three-dimensional image sensors, and/or other sensors. 
     In some configurations, components  22  may include mechanical devices for gathering input (e.g., buttons, joysticks, scrolling wheels, key pads with movable keys, keyboards with movable keys, and other devices for gathering user input). During operation, device  10  may use sensors and/or other input-output devices in components  22  to gather user input (e.g., buttons may be used to gather button press input, touch and/or force sensors overlapping displays can be used for gathering user touch screen input and/or force input, touch pads and/or force sensors may be used in gathering touch and/or force input, microphones may be used for gathering audio input, etc.). The control circuitry of device  10  can then take action based on this gathered information (e.g., by transmitting the information over a wired or wireless path to external equipment, by supplying a user with output using a haptic output device, visual output device, an audio component, or other input-output device in housing  12 , etc.). 
     If desired, electronic device  10  may include a battery or other energy storage device, connector ports for supporting wired communications with ancillary equipment and for receiving wired power, and other circuitry. In some configurations, device  10  may serve as an accessory and/or may include a wired and/or wireless accessory (e.g., a keyboard, computer mouse, remote control, trackpad, etc.). 
     A cross-sectional side view of an illustrative display for device  10  is shown in  FIG.  2   . As shown in  FIG.  2   , display  14  may have a substrate such as substrate  30 . Substrate  30  may be, for example, a flexible polymer substrate such as a layer of polyimide or may be a rigid substrate. Substrate  30  may be planar or may have a curved cross-sectional profile. Pixels P may be formed form respective light-emitting diodes  34  and pixel circuits formed from transistors  32 . In an organic light-emitting diode display, diodes  34  are thin-film organic light-emitting diodes and transistors  32  are thin-film transistors formed in a layer of thin-film circuitry on substrate  30  such as thin-film circuitry layer  36 . Thin-film circuitry layer  36  may have structures that create a non-smooth surface such as anodes, cathodes, pixel definition layers, routing, and other thin-film structures. 
     To protect thin-film circuitry in layer  36 , display  14  may include a layer of thin-film encapsulation such as thin-film encapsulation layer  40 . Thin-film encapsulation layer  40  may be formed from thin-film layers such as silicon nitride layers and/or other inorganic layers interspersed with optional polymer layers. Thin-film encapsulation layer  40  may help prevent moisture from damaging underlying structures in thin-film circuitry layer  36 . The thickness of layer  40  may be less than 10 microns, less than 3 microns, less than 2 microns, at least 0.05 microns, at least 0.3 microns, or other suitable thickness. 
     Thin-film layer  38  (e.g., thin-film circuitry layer  36  and thin-film encapsulation layer  40 ) may be provided with additional protection. For example, additional protection may be provided by attaching cover layer  44  to display  14  (e.g., to the outer surface of thin-film encapsulation layer  40 ) using adhesive such as optically clear adhesive layer  42 . Cover layer  44  may be formed from glass or other transparent material to help protect thin-film circuitry layer  36  from moisture and/or scratches. The thickness of layer  44  may be, as an example, 0.1 microns to 100 microns, at least 10 microns, at least 100 microns, at least 400 microns, less than 1000 microns, less than 500 microns, or other suitable thickness. 
     As shown in  FIG.  3   , some light emitted from a pixel P in layer  36  such as illustrative light ray  50  may be emitted parallel or nearly parallel to surface normal n of display  14 . This light passes through surface  48  of display  14  and is received by lens  16 . Off-axis light such as light ray  52  strikes surface  48  of display  14  at an angle that is sufficiently large to support total internal reflection. Accordingly, there is a risk that off-axis light rays such as ray  52  will be reflected internally at surface  48  and guided laterally (e.g., in the X-Y plane) away from pixel P within the transparent material (layer) of display  14  such as layer  44 , layer  42 , and layer  40  in accordance with the principal of total internal reflection. Eventually, these guided rays could be scattered out of the transparent layer of display  14  due to surface irregularities on the surface of layer  36 . Because the scattered light would no longer be located at the source of light ray  52  (e.g., pixels P in this scenario), this scattered light is a potential cause of reduced display contrast. To prevent such loss of display contrast, display  14  may be provided with reflection suppression structures. 
     In general, display  14  may have any suitable pixel density (e.g., 400-800 pixels per inch, at least 350 pixels per inch, at least 2000 pixels per inch, less than 4000 pixels per inch, less than 2000 pixels per inch, etc.). In displays with pixel arrays configured in operating in head-mounted displays, pixels P may, in some embodiments, have a density of at least 1000 pixels per inch or at least 1500 pixels per inch, which may increase the risk for light scattering and contrast reduction due to internal reflections. 
     To help suppress light scattering, internal reflections of rays such as ray  52  from surface  48  may be minimized using reflection suppression structures. With one illustrative configuration, which is shown in  FIG.  4   , display  14  may have an antireflection layer such as antireflection layer  54  on surface  48 . As shown in  FIG.  4   , in the presence of antireflection layer  54 , off-axis light rays such as light ray  52  may pass out of display  14  and are not trapped within the transparent layers of display  14 . 
     Antireflection layer  54  may be formed from a stack of dielectric layers with different refractive index values (e.g., alternating high and low refractive index values). This type of arrangement is shown in  FIG.  5   . As shown in  FIG.  5   , antireflection layer  54  may be formed from a thin-film interference filter formed from a stack of dielectric thin-film layers  56 . The thin-film interference filter may be tuned to enhance light transmission out of display  14  at the wavelengths of light emitted by pixels P (e.g., red, green, and blue visible light wavelengths). 
     In the example of  FIG.  6   , antireflection layer  54  has been formed from an array of microstructures such as microlenses  58 . Microlenses  58  may have lateral dimension on the order of a pixel size (e.g., 10 microns or less, 20 microns or less, at least 3 microns, or other suitable size). 
     Another illustrative configuration for antireflection layer  54  is shown in  FIG.  7   . In the example of  FIG.  7   , antireflection layer  54  has been formed from a moth-eye structure in which multiple protrusions  60  with small lateral dimensions (e.g. sub-wavelengths sizes, less than 1 micron, less than 0.5 microns, less than 0.3 microns, or other suitable sizes). Microstructures such as the moth-eye structures of  FIG.  7    and the microlens structures of  FIG.  6    may be formed by etching, sandblasting, nano-imprinting, attachment of laminated textured films, photolithography followed by reflow operations, self-assembled growth techniques (e.g., crystal growth techniques), and/or other suitable fabrication techniques. 
     In another illustrative configuration, antireflection layer  54  may be formed from a graded index material. The graded index material may have an index of refraction n that varies smoothly and continuously from a first (higher) value at outwardly facing surface  48  of layer  44  to a second (lower) value at the outwardly facing surface of the graded index material. An illustrative index profile for the graded index material is illustrated by curve  62  of the graph of  FIG.  8   . The distance from surface  48  through the graded index material is given by h. At h=0, the graded index material forms an interface with surface  48  on the top of display  14 . At h=H, the graded index material is exposed to air. At intermediate values of h, the value of the refractive index n of the graded index material gradually changes. 
     If desired, antireflection coatings may also be formed using a single layer of material (e.g., a thin-film layer of material with a refractive index that lies between the refractive index of layer  44  and the refractive index of air). 
     In addition to or instead of using antireflection structures to reduce internal reflections of off-axis light rays such as ray  52 , display  14  may include polarizer structures to help reduce reflections. Polarizer-based reflection reduction structures may, for example, be formed from circular polarizers or other polarizer structures having a linear polarizer and a wave plate. 
     Consider, as an example, the arrangement of  FIG.  9   . As shown in  FIG.  9   , pixels such as pixel P may emit light rays such as light ray  80  (on-axis rays and off-axis rays) and these light rays may propagate outwardly toward surface  48  of layer  44 . 
     Reflection suppression layer  70  may be formed on the transparent layers of display  14  (e.g., on the transparent layer of display  14  formed form thin-film encapsulation layer  40 , adhesive layer  42 , and cover layer  44 ). Layer  70  may include polarizer and retarder structures. Optional layer  76  on quarter wave plate  74  of layer  70  may include a thin-film hard coat layer (e.g., a dielectric anti-scratch film formed form a transparent dielectric layer such as silicon nitride, an anti-scratch formed from other inorganic materials such as metal nitride, silicon oxide, metal oxide, diamond-like coating material, other transparent material with abrasion resistance, and/or other hard coat materials), an adhesive layer, and/or other layer(s). The refractive index of layer  70  may be matched or close to the refractive index of layers  46 ,  44 , and  42 , so that internal reflections at surface  48  of layer  46  may be minimized. Upper surface  48 T is exposed to air and may therefore give rise to a potential for internal reflections of on-axis and off-axis light. 
     To help suppress internal reflections from surface  48 T and thereby prevent contrast loss due to scattered light, layer  70  may include a circular polarizer. In particular, layer  70  may include linear polarizer  72  on surface  48  and a retarder such as quarter wave plate  74  on linear polarizer  72 . Linear polarizer  72  and quarter wave plate  74  may be formed on surface  48  and may be covered by optional layer(s)  76 . Additional optical layers may also be included in layer  70 . For example, one or more birefringent layers may be provided between linear polarizer  72  and to help enhance off-axis viewing performance, a hard coat layer may be included between linear polarizer  72  and layer  44 , etc. 
     When pixel P emits light  80 , light  80  is initially unpolarized. Layers  40 ,  42 , and  44  are transparent, so unpolarized light  80  travels outwardly from pixel P to linear polarizer  72 . Linear polarizer  72 , which may sometimes be referred to as a linear polarizer layer, linearly polarizes light  80  to form linearly polarized light  82 . Light  82  passes through quarter wave plate  74  and becomes circularly polarized light  84 . To help suppress reflections from the outermost surface of display  14 , optional quarter wave plate  74  may include an antireflection coating (e.g., an antireflection layer may be provided on an anti-scratch layer on quarter wave plate  74 ). Nevertheless, due to the refractive index mismatch between the layers of display  14  and surrounding air, some of circularly polarized light  84  may reflect internally from the outermost surface of the layers on display  14 . In the example of  FIG.  9   , circularly polarized light  84  reflects internally from surface  48 T of optional layer  76  as downwardly directed circularly polarized light  86 . As light  86  travels downward through quarter wave plate  74 , light  86  retraces the path taken by outwardly directed circularly polarized light  82  and becomes linearly polarized with a polarization axis that is perpendicular to the polarization axis of linearly polarized light  82 . 
     Consider, an example, a scenario in which linear polarizer  72  has a pass axis aligned with the X axis of  FIG.  9   . In this scenario, linearly polarized light  82  at the upper surface of linear polarizer  72  and the lower surface of quarter wave plate  74  will have a polarization axis aligned with the X axis. In this configuration, the downward passage of circularly polarized light  86  through quarter wave plate  74  will produce linearly polarized light  88  at the lower surface of quarter wave plate  74  having a polarization axis that is rotated by 90° about the Z axis with respect to light  82 . As a result, light  88  has a polarization axis that is aligned with the Y axis of  FIG.  9    and that is orthogonal to the polarization axis of linear polarizer  72 . With this rotated polarization state, linearly polarized light  88  is absorbed by linear polarizer  72  and is thereby blocked from returning to layer  44 . The presence of the circular polarizer formed from linear polarizer  72  and quarter wave plate  74  thereby suppresses internal reflection of light  80  and helps enhance the contrast of display  14 . 
     If desired, one or more layers such as layer  70  and/or one or more layers such as antireflection layer  54  may be used in display  14 . For example, an antireflection layer may be formed on the outermost surface of quarter wave plate  74  (e.g., directly on quarter wave plate  74  or on one or more coating layers on quarter wave plate  74  such as an anti-scratch coating). As another example, a polarizer-based reflection absorption layer such as reflection suppression layer  70  and/or an antireflection layer may be formed between layer  40  and layer  44 . There is a potential for internal reflections between layer  40  and layer  44  due to refractive index mismatch between layer  40  and layer  44 , so incorporating a polarizer-based reflection suppression layer and/or an antireflection layer between layers  40  and  44  can help suppress reflected light. Illustrative locations  81  and  82  for forming antireflection layer  54  and/or reflection suppression layer  70  are shown in display  14  of  FIG.  10   . Location (layer)  81  may contain antireflection layer  54  and/or reflection suppression layer  70 , location (layer)  82  may contain antireflection layer  54  and/or reflection suppression layer  70 , and/or locations  81  and  82  may contain layers such as antireflection layer  54  and/or reflection suppression layer  70 . 
     Wave plates, antireflection layers, linear polarizers, and other structures may be formed by laminating flexible films to display  14  (e.g., using pressure sensitive adhesive, optically clear liquid adhesive, etc.). For example, linear polarizer  72  may be attached to surface  48  of layer  44  using adhesive, an antireflection layer, anti-scratch layer, and/or other layers may be attached to quarter wave plate  74  using adhesive, etc. If desired, some or all of the adhesive layers in display  14  can be omitted. For example, one or more adhesive layers may be omitted when optical films such as a wave plate or other layers are deposited as coatings other layers in display  14  using thin-film deposition techniques. 
     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: 20200629
Publication Date: 20250121
Grant Date: 20250121
Priority Date: 20190730
Inventors: FLEISCHMAN, Dagny
CHUNG, CHI-JUI
DORJGOTOV, ENKHAMGALAN
CARBONE, GIOVANNI
MYHRE, GRAHAM B.
SLOOTSKY, MICHAEL
Assignee: APPLE INC
CPC Classifications: [{"code": "H10K2102/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K50/868", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/844", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133331", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133528", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/879", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/8793", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K59/8792", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/873", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B1/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/3083", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B5/3033", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02B27/0172", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/865", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B27/0018", "inventive": true, "first": true, "tree": "[]"}, {"code": "H10K2102/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K50/868", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133528", "inventive": false, "first": false, "tree": "[]"}, {"code": "G02F1/133331", "inventive": false, "first": false, "tree": "[]"}, {"code": "H10K59/12", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/844", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10K50/865", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 72047112