PATENT DOCUMENT

Publication Number: US-10281630-B2
Application Number: US-201615351212-A
Country: US
Kind Code: B2

Title: Optical films for electronic device displays

Abstract:
A display may include an optical film to promote sunglass-friendly viewing of the display. Displays may include linear polarizers. For example, a liquid crystal display may have a linear polarizer above a liquid crystal layer, whereas an organic light-emitting diode display may have a linear polarizer that forms a portion of a circular polarizer to reduce reflections in the display. Displays that emit linearly polarized light may not be compatible with polarized sunglasses. To ensure an optimal user experience for users wearing sunglasses, displays may include sunglass-friendly optical films. A sunglass-friendly optical film may be a film formed from a birefringent material such as a polymer or liquid crystal. The sunglass-friendly optical film may have an optical axis that is at a 45° angle relative to the optical axis of the underlying linear polarizer. The sunglass-friendly optical film may be patterned to have reduced thickness regions.

Claims:
What is claimed is: 
     
       1. A display comprising:
 display layers; 
 a linear polarizer that receives light from the display layers and that has a first optical axis; and 
 an optical film positioned above the linear polarizer, wherein the entire optical film is formed from a single birefringent material, wherein the optical film is patterned into first regions with a first thickness and second regions with a second thickness that is different than the first thickness, and wherein the entire optical film has a second optical axis that is at a given angle relative to the first optical axis. 
 
     
     
       2. The display defined in  claim 1 , wherein the display layers comprise a liquid crystal layer that is interposed between a color filter layer and a thin-film transistor layer, wherein the linear polarizer is an upper polarizer formed above the liquid crystal layer, and wherein the display further comprises a lower polarizer formed below the liquid crystal layer. 
     
     
       3. The display defined in  claim 1 , wherein the display layers comprise an organic emissive layer that is interposed between an anode and a cathode. 
     
     
       4. The display defined in  claim 3 , wherein the linear polarizer is formed above a quarter wave plate. 
     
     
       5. The display defined in  claim 1 , wherein the optical film is attached to the linear polarizer with a layer of adhesive. 
     
     
       6. The display defined in  claim 1 , wherein the optical film is laminated directly to the linear polarizer. 
     
     
       7. The display defined in  claim 1 , wherein the optical film is attached to a touch sensor layer. 
     
     
       8. The display defined in  claim 1 , wherein the first thickness and the second thickness are both thicknesses between 30 and 50 microns and wherein a difference between the first thickness and the second thickness is between 0.5 and 5 microns. 
     
     
       9. The display defined in  claim 1 , wherein the first and second regions are arranged in alternating horizontal, vertical, or slanted stripes. 
     
     
       10. The display defined in  claim 1 , wherein the first and second regions are arranged in a checkerboard pattern. 
     
     
       11. The display defined in  claim 1 , wherein the given angle is a 45° angle. 
     
     
       12. The display defined in  claim 1 , wherein the first regions make up between 30% and 70% of the optical film. 
     
     
       13. A display comprising:
 display layers; 
 a linear polarizer that receives light from the display layers; and 
 an optical film positioned above the linear polarizer, wherein the optical film comprises a base film and a layer of birefringent material, wherein the layer of birefringent material has three quarter wave plate regions and quarter wave plate regions, and wherein the three quarter wave plate regions make up between 25% and 35% of the layer of birefringent material. 
 
     
     
       14. The display defined in  claim 13 , wherein the layer of birefringent material is a liquid crystal layer, wherein the three quarter wave plate regions have a first thickness, wherein the quarter wave plate regions have a second thickness, and wherein the first thickness is greater than the second thickness. 
     
     
       15. The display defined in  claim 13 , wherein the layer of birefringent material is a liquid crystal layer, wherein the three quarter wave plate regions have a first thickness and a first birefringence, wherein the quarter wave plate regions have a second thickness and a second birefringence, wherein the first thickness is the same as the second thickness, and wherein the first birefringence is greater than the second birefringence. 
     
     
       16. The display defined in  claim 1 , wherein the entire optical film has a given birefringence. 
     
     
       17. A display comprising:
 display layers; 
 a linear polarizer that receives light from the display layers; and 
 an optical film positioned above the linear polarizer, wherein the optical film is formed from a birefringent material and wherein the optical film is patterned to have a plurality of recesses defined by curved surfaces, wherein the linear polarizer has a first optical axis and the entire optical film has a second optical axis that is at a given angle relative to the first optical axis. 
 
     
     
       18. The display defined in  claim 17 , wherein the curved surfaces comprise concave surfaces. 
     
     
       19. The display defined in  claim 17 , wherein the curved surface curve towards a planar lower surface of the optical film.

Description:
This application claims the benefit of provisional patent application No. 62/396,713, filed Sep. 19, 2016, which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to displays for electronic devices, and more particularly, to displays with optical films that ensure sunglass-friendly viewing. 
     Electronic devices often include displays. For example, an electronic device may have an organic light-emitting diode display based on organic-light-emitting diode pixels or a liquid crystal display based on liquid crystal pixels. 
     Conventional liquid crystal displays and light-emitting diode displays may emit linearly polarized light. This may cause problems for users that view the display while wearing polarized sunglasses. Polarized sunglasses may only pass light of a given orientation. Depending on the orientation of display, the light emitted by the display may therefore not be visible to a user wearing sunglasses. 
     Optical films are sometimes included in displays to promote sunglass-friendly viewing. However, conventional optical films may undesirably reduce the intensity of light emitted from the display and lead to color differences in the display depending on the orientation of the display. 
     It would therefore be desirable to be able to provide improved displays for sunglass-friendly viewing. 
     SUMMARY 
     A display for an electronic device may include an optical film to promote sunglass-friendly viewing of the display. Displays may include linear polarizers that cause emitted light to be linearly polarized. For example, a liquid crystal display may have a linear polarizer above a liquid crystal layer, whereas an organic light-emitting diode display may have a linear polarizer that forms a portion of a circular polarizer to reduce reflections in the display. 
     Displays that emit linearly polarized light may not be compatible with polarized sunglasses. Polarized sunglasses may only pass light of a certain orientation. Depending on the orientation of display, the light emitted by the display may therefore not be visible to a user wearing polarized sunglasses. To ensure an optimal user experience for users wearing sunglasses, displays may include sunglass-friendly optical films. 
     A sunglass-friendly optical film may be a film formed from a birefringent material such as a polymer or liquid crystal. The sunglass-friendly optical film may have an optical axis that is at a 45° angle relative to the optical axis of the underlying linear polarizer. The sunglass-friendly optical film may be patterned to have reduced thickness regions. 
     The sunglass-friendly optical film may include a liquid crystal layer formed over an underlying base layer. The reduced thickness regions may be quarter wave plate regions and the liquid crystal layer may also have three quarter wave plate regions. Instead of varying the thickness of the sunglass-friendly optical film, the birefringence of the sunglass-friendly optical film may be varied to vary the retardation of the sunglass-friendly optical film. In some embodiments, both the thickness and the birefringence of the sunglass-friendly optical film may vary. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device such as a laptop computer that has a display with a sunglass-friendly optical film in accordance with an embodiment. 
         FIG. 2  is a perspective view of an illustrative electronic device such as a handheld electronic device that has a display with a sunglass-friendly optical film in accordance with an embodiment. 
         FIG. 3  is a perspective view of an illustrative electronic device such as a tablet computer that has a display with a sunglass-friendly optical film in accordance with an embodiment. 
         FIG. 4  is a perspective view of an illustrative electronic device such as a computer or television that has a display with a sunglass-friendly optical film in accordance with an embodiment. 
         FIG. 5  is a perspective view of an illustrative electronic device that has a display with a sunglass-friendly optical film in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative liquid crystal display with a sunglass-friendly optical film on the upper polarizer layer in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of an illustrative liquid crystal display with a sunglass-friendly optical film on the lower surface of an additional electronic device layer in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of an illustrative liquid crystal display with a sunglass-friendly optical film on the upper surface of an additional electronic device layer in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of an illustrative organic light-emitting diode display in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of illustrative functional layers including a sunglass-friendly optical film that may be included in an organic light-emitting diode display in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of illustrative functional layers for an organic light-emitting diode display including a sunglass-friendly optical film on a touch sensor layer in accordance with an embodiment. 
         FIGS. 12 and 13  are cross-sectional side views of an illustrative sunglass-friendly optical film with reduced thickness areas in accordance with an embodiment. 
         FIGS. 14A-14E  are top views of illustrative sunglass-friendly optical films with reduced thickness areas in accordance with an embodiment. 
         FIGS. 15 and 16  are cross-sectional side views of illustrative sunglass-friendly films with liquid crystal layers in accordance with an embodiment. 
         FIG. 17  is a cross-sectional side view of an illustrative sunglass-friendly film with varied birefringence in accordance with an embodiment. 
         FIG. 18  is a cross-sectional side view of an illustrative sunglass-friendly film with varied birefringence and thickness in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as cellular telephones, tablet computers, laptop computers, desktop computers, computers integrated into computer monitors, televisions, media players, portable devices, and other electronic equipment may include displays. The displays of these electronic devices may include sunglass-friendly optical films that modify the light emitted by the display for sunglass-friendly viewing. The optical films may modify the light such that a user wearing sunglasses will be able to operate the electronic device in any orientation with minimal color change and intensity loss. 
     Illustrative electronic devices of the types that may be provided with sunglass-friendly displays are shown in  FIGS. 1, 2, 3, 4, and 5 . 
     Electronic device  10  of  FIG. 1  has the shape of a laptop computer and has upper housing  12 A and lower housing  12 B with components such as keyboard  16  and touchpad  18 . Device  10  has hinge structures  20  (sometimes referred to as a clutch barrel) to allow upper housing  12 A to rotate in directions  22  about rotational axis  24  relative to lower housing  12 B. Display  14  is mounted in housing  12 A. Upper housing  12 A, which may sometimes be referred to as a display housing or lid, is placed in a closed position by rotating upper housing  12 A towards lower housing  12 B about rotational axis  24 . 
       FIG. 2  shows an illustrative configuration for electronic device  10  based on 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  has opposing front and rear surfaces. Display  14  is mounted on a front face of 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.). Display  14  may be protected using a display cover layer such as a layer of transparent glass or clear plastic. Openings may be formed in the display cover layer. For example, an opening may be formed in the display cover layer to accommodate a button such as button  26 . An opening may also be formed in the display cover layer to accommodate ports such as speaker port  28 . Openings may be formed in housing  12  to form communications ports, holes for buttons, and other structures. 
     In the example of  FIG. 3 , electronic device  10  is a tablet computer. In electronic device  10  of  FIG. 3 , housing  12  has opposing planar front and rear surfaces. Display  14  is mounted on the front surface of housing  12 . As shown in  FIG. 3 , display  14  has an opening to accommodate button  26 . 
       FIG. 4  shows an illustrative configuration for electronic device  10  in which device  10  is a computer display, a computer that has an integrated computer display, or a television. Display  14  is mounted on a front face of housing  12 . With this type of arrangement, housing  12  for device  10  may be mounted on a wall or may have an optional structure such as support stand  27  to support device  10  on a flat surface such as a table top or desk. 
       FIG. 5  shows an illustrative configuration for electronic device  10  in which device  10  is a wrist-watch device. Display  14  is mounted on a front face of housing  12 . Electronic device  10  may have straps  19  for securing electronic device  10  to a user&#39;s wrist. 
     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. 
     Display  14  may be a liquid crystal display, an organic light-emitting diode display, a plasma display, an electrophoretic display, an electrowetting display, a display using other types of display technology, or a display that includes display structures formed using more than one of these display technologies. 
     A cross-sectional side view of an illustrative configuration for display  14  of device  10  (e.g., for display  14  of the devices of  FIG. 1 ,  FIG. 2 ,  FIG. 3 ,  FIG. 4 ,  FIG. 5  or other suitable electronic devices) is shown in  FIG. 6 . As shown in  FIG. 6 , 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. 6 ) and passes through display pixel structures in display layers  46 . This illuminates any images that are being produced by the display pixels for viewing by a user. For example, backlight  44  may illuminate images on display layers  46  that are being viewed by viewer  48  in direction  50 . 
     Display layers  46  may be mounted in chassis structures such as a plastic chassis structure and/or a metal chassis structure to form a display module for mounting in housing  12  or display layers  46  may be mounted directly in housing  12  (e.g., by stacking display layers  46  into a recessed portion in housing  12 ). Display layers  46  may form a liquid crystal display or may be used in forming displays of other types. 
     In a configuration in which display layers  46  are used in forming a liquid crystal display, display layers  46  may include a liquid crystal layer such a liquid crystal layer  52 . Liquid crystal layer  52  may be sandwiched between display layers such as display layers  58  and  56 . Layers  56  and  58  may be interposed between lower polarizer layer  60  and upper polarizer layer  54 . 
     Layers  58  and  56  may be formed from transparent substrate layers such as clear layers of glass or plastic. Layers  56  and  58  may be layers such as a thin-film transistor layer and/or a color filter layer. Conductive traces, color filter elements, transistors, and other circuits and structures may be formed on the substrates of layers  58  and  56  (e.g., to form a thin-film transistor layer and/or a color filter layer). Touch sensor electrodes may also be incorporated into layers such as layers  58  and  56  and/or touch sensor electrodes may be formed on other substrates. 
     With one illustrative configuration, layer  58  may be a thin-film transistor layer that includes an array of thin-film transistors and associated electrodes (display pixel electrodes) for applying electric fields to liquid crystal layer  52  and thereby displaying images on display  14 . Layer  56  may be a color filter layer that includes an array of color filter elements for providing display  14  with the ability to display color images. If desired, layer  58  may be a color filter layer and layer  56  may be a thin-film transistor layer. 
     During operation of display  14  in device  10 , control circuitry (e.g., one or more integrated circuits on a printed circuit) may be used to generate information to be displayed on display  14  (e.g., display data). The information to be displayed may be conveyed to a display driver integrated circuit such as circuit  62 A or  62 B using a signal path such as a signal path formed from conductive metal traces in a rigid or flexible printed circuit such as printed circuit  64  (as an example). 
     Backlight structures  42  may include a light guide plate such as light guide plate  78  (sometimes referred to herein as a light guide layer). Light guide layer  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 layer  78  and may be distributed in dimensions X and Y throughout light guide layer  78  due to the principal of total internal reflection. Light guide layer  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 layer  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 layer  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. 
     Lower polarizer layer  60  and upper polarizer layer  54  may be linear polarizers with optical axes that are offset by 90°. The linear polarizers may (in combination with liquid crystal layer  52 ) allow per-pixel control of the magnitude of emitted light. After the light passes through upper polarizer  54 , the light may be linearly polarized. Linearly polarized light may not be suitable for easy viewing by a user wearing sunglasses. Since polarized sunglasses only pass incoming light of one orientation, the linearly polarized light from upper polarizer  54  will not be viewable by the sunglasses in either the landscape orientation or the portrait orientation of the display. In order to ensure that display  14  may be operated in any orientation by a user wearing sunglasses, sunglass-friendly optical film  82  may be included in display  14 . 
     Sunglass-friendly optical film  82  (sometimes referred to as sunglass-friendly film  82 , optical film  82 , film  82 , or layer  82 ) may be included directly above upper polarizer  54  (sometimes referred to as linear polarizer  54  or polarizer  54 ). Optical film  82  may modify the light emitted from display  14  so that the light is perceived as uniform to a user wearing sunglasses regardless of the orientation of the display. Optical film  82  may include more than one film or layer if desired. Optical film  82  may be attached to polarizer  54  with an adhesive layer or optical film  82  may be laminated directly to polarizer  54 . In general, optical film  82  may be attached to polarizer  54  using any desired method. 
     Optical film  82  may be a waveplate (sometimes referred to as a retarder) that has an optical axis that is at an angle of 45° with respect to the optical axis of polarizer  54 . The retarder may delay the phase of incoming light such that the emitted light has minimal variance to a user with sunglasses regardless of display orientation. 
       FIG. 6  shows optical film  82  positioned directly adjacent to polarizer  54 . This example is merely illustrative, and optical film  82  may be positioned in any desired location within electronic device  10 . For example, as shown in  FIG. 7 , display  14  may include an additional layer  84 . The additional layer  84  may be, for example, a touch sensor layer, a cover glass, or any other desired layer. Sunglass-friendly film  82  may be positioned on the lower surface of the additional layer, as shown in  FIG. 7 . Alternatively, as shown in  FIG. 8 , sunglass-friendly film  82  may be positioned on the upper surface of additional layer  84 . In general sunglass-friendly film  82  may be positioned anywhere above upper polarizer  54  that allows the emitted light to pass through optical film  82  after passing through polarizer  54 . Additionally, the examples above of a sunglass-friendly film being incorporated into a liquid crystal display are merely illustrative, and a sunglass-friendly film may be incorporated into other types of displays such as organic light-emitting diode displays if desired. 
     A cross-sectional side view of a portion of an illustrative organic light-emitting diode display is shown in  FIG. 9 . As shown in  FIG. 9 , display  14  may include a substrate layer such as substrate layer  128 . Substrate  128  may be formed from a polymer or other suitable materials. 
     Thin-film transistor circuitry  144  (sometimes referred to as display layers  144 ) may be formed on substrate  128 . Thin film transistor circuitry  144  may include layers  132 . Layers  132  may include inorganic layers such as inorganic buffer layers, barrier layers (e.g., barrier layers to block moisture and impurities), gate insulator, passivation, interlayer dielectric, and other inorganic dielectric layers. Layers  132  may also include organic dielectric layers such as a polymer planarization layer. Metal layers and semiconductor layers may also be included within layers  132 . For example, semiconductors such as silicon, semiconducting-oxide semiconductors, or other semiconductor materials may be used in forming semiconductor channel regions for thin-film transistors. Metal in layers  132  such as metal traces  174  may be used in forming transistor gate terminals, transistor source-drain terminals, capacitor electrodes, and metal interconnects. 
     As shown in  FIG. 9 , display layers  144  may include diode anode structures such as anode  136 . Anode  136  may be formed from a layer of conductive material such as metal on the surface of layers  132  (e.g., on the surface of a planarization layer that covers underlying thin-film transistor structures). Light-emitting diode  126  may be formed within an opening in pixel definition layer  160 . Pixel definition layer  160  may be formed from a patterned photoimageable polymer such as polyimide and/or may be formed from one or more inorganic layers such as silicon nitride, silicon dioxide, or other suitable materials. 
     In each light-emitting diode, layers of organic material  138  may be interposed between a respective anode  136  and cathode  142 . Anodes  136  may be patterned from a layer of metal (e.g., silver) and/or one or more other conductive layers such as a layer of indium tin oxide or other transparent conductive material. Cathode  142  may be formed from a common conductive layer that is deposited on top of pixel definition layer  160 . Cathode  142  may be formed from a thin metal layer (e.g., a layer of metal such as a magnesium silver layer) and/or indium tin oxide or other transparent conductive material. Cathode  142  is preferably sufficiently transparent to allow light to exit light emitting diode  126 . 
     If desired, the anode of diode  126  may be formed from a blanket conductive layer and the cathode of diode  126  may be formed from a patterned conductive layer. The illustrative configuration of display  14  in which a transparent blanket cathode layer  142  covers diodes that have individually patterned anodes  136  allows light to be emitted from the top of display  14  (i.e., display  14  in the example of  FIG. 9  is a “top emission” organic light-emitting diode display). Display  14  may be implemented using a bottom emission configuration if desired. Layers such as layers  136 ,  138 , and  142  are used in forming organic light-emitting diodes such as diode  126  of  FIG. 9 , so this portion of display  14  is sometimes referred to as an organic light-emitting diode layer (see, e.g., layer  130  of  FIG. 9 ). 
     If desired, display  14  may have a protective outer display layer such as cover layer  170 . The outer display layer may be formed from a material such as sapphire, glass, plastic, clear ceramic, or other transparent material. Protective layer  146  may cover cathode  142 . Layer  146 , which may sometimes be referred to as an encapsulation layer may include moisture barrier structures, encapsulant materials such as polymers, adhesive, and/or other materials to help protect thin-film transistor circuitry. 
     Functional layers  168  may be interposed between layer  146  and cover layer  170 . Functional layers  168  may include a touch sensor layer, a circular polarizer layer, a sunglass-friendly optical film, and other layers. A circular polarizer layer may help reduce light reflections from reflective structures such as anodes  136 . A touch sensor layer may be formed from an array of capacitive touch sensor electrodes on a flexible polymer substrate. The touch sensor layer may be used to gather touch input from the fingers of a user, from a stylus, or from other external objects. Layers of optically clear adhesive may be used to attach cover glass layer  170  and functional layers  168  to underlying display layers such as layer  146 , thin-film transistor circuitry  144 , and substrate  128 . 
     Organic layer  138  may include an organic emissive layer (e.g., a red emissive layer in red diodes that emits red light, a green emissive layer in green diodes that emits green light, and a blue emissive layer in blue diodes that emits blue light, etc.). The emissive material may be a material such as a phosphorescent material or fluorescent material that emits light during diode operation. The emissive material in layer  138  may be sandwiched between additional diode layers such as hole injection layers, hole transport layers, electron injection layers, and electron transport layers. 
     As shown in  FIGS. 10 and 11 , a sunglass-friendly film may be incorporated into the functional layers of an organic light-emitting diode display such as display  14  in  FIG. 9 . In  FIG. 10 , functional layers  168  include touch sensor layer  182 , sunglass-friendly film  82 , and circular polarizer  188 . Touch sensor layer  182  may be formed from an array of capacitive touch sensor electrodes on a flexible polymer substrate. The touch sensor layer may be used to gather touch input from the fingers of a user, from a stylus, or from other external objects. Circular polarizer layer  188  may help reduce light reflections from reflective structures such as anodes  136  in  FIG. 9 . Circular polarizer  188  may include quarter wave plate (QWP)  186  and linear polarizer  184 . As shown in  FIG. 10 , a sunglass-friendly film  82  may be interposed between polarizer  184  of circular polarizer  188  and touch sensor layer  182 . 
     Optical film  82  may modify the light emitted from display  14  so that the light is perceived as uniform to a user wearing sunglasses regardless of the orientation of the display. Optical film  82  may include more than one film or layer if desired. Optical film  82  may be attached to polarizer  184  with an adhesive layer or optical film  82  may be laminated directly to polarizer  184 . In general, optical film  82  may be attached to polarizer  184  using any desired method. 
     Optical film  82  may be a waveplate (sometimes referred to as a retarder) that has an optical axis that is at an angle of 45° with respect to the optical axis of polarizer  184 . The retarder may delay the phase of incoming light such that the emitted light has minimal variance to a user with sunglasses regardless of display orientation. 
       FIG. 10  shows optical film  82  positioned directly adjacent to polarizer  184 . This example is merely illustrative, and optical film  82  may be positioned in any desired location within electronic device  10 . As shown in  FIG. 11 , for example, optical film  82  may be formed on an upper surface of touch sensor layer  182  (instead of on a lower surface of touch sensor layer  182  as shown in  FIG. 10 ). In general, optical film  82  may be positioned at any desired location above polarizer  184  of circular polarizer  188 . 
     Depending on the incoming light received by optical film  82  in  FIGS. 6-8, 10, and 11 , a high retardation may be required to produce an emitted light that will be perceived the same by a user wearing sunglasses regardless of the orientation of the display. The light received by optical film  82  may have particular wavelength in the display output spectrum that has a narrow and strong peak (e.g., 600-650 nm or approximately 620 nm) that looks different to the user depending on the orientation of the display. One way to correct this issue is to increase the retardation of the optical film while maintain a uniform thickness in the entire film. Retardation of a layer is calculated with the equation Re=Δn×d, where Re is the retardation of the layer, d is the thickness of the layer, and Δn (which may optionally be written as (n e −n o )) is the birefringence of the layer. Accordingly, increasing the retardation of optical film  82  to ensure uniform light regardless of display orientation may require increasing the thickness of the optical film (since retardation is directly proportional to thickness). For example, if the film has a uniform thickness a retardation of 30,000 may be required to ensure uniform output of light. Achieving this level of retardation may necessitate a thick film that takes up an undesirably large amount of z-height in the electronic device. 
     Instead of increasing the thickness of the optical film to increase the retardation of the film and ensure uniform output at all wavelengths (including the particular wavelength (e.g., 620 nm as mentioned above)), the optical film may have a non-uniform thickness. For example, the optical film may have some regions with a first thickness and other regions with a second thickness that is different than the first thickness. The regions of the optical film may be referred to as first thickness regions and second thickness regions or normal thickness regions and reduced thickness regions. The thickness of the reduced thickness regions may be reduced so that the reduced thickness regions have a reduced retardation. The retardation of the reduced thickness regions may have a retardation of Re reduced =Re normal −(λ/2+m*λ), where Re reduced  is the retardation of the reduced thickness regions, Re normal  is the retardation of the normal thickness regions, λ is the particular wavelength (e.g., 620 nm), and m is an offset factor (e.g., 0, ±1, ±2, ±3, etc.). The reduced retardation of the reduced thickness regions may result in light emitted from the optical film that is perceived the same by the user regardless of the orientation of the display. 
       FIGS. 12 and 13  are cross-sectional side views of an optical film with reduced thickness regions. As shown, sunglass-friendly optical film  82  may be attached to a polarizer  202  by adhesive  204 . Polarizer  202  may be a polarizer such as polarizer  54  in  FIG. 6  or polarizer  184  in  FIGS. 10 and 11 . Sunglass-friendly film  82  may be attached to polarizer  202  using adhesive  204 , as shown in  FIGS. 12 and 13 . However, these examples are merely illustrative. If desired, sunglass-friendly film  82  may be laminated directly to polarizer  202  or attached to polarizer  202  using other methods. Adhesive  204  may be an optically clear adhesive or any other desired type of adhesive. 
     As shown in  FIG. 12 , optical film  82  may be patterned into normal thickness regions  82 - 1  and reduced thickness regions  82 - 2 . The normal thickness regions  82 - 1  may have a thickness  208  while the reduced thickness regions  82 - 2  may have a thickness  206 . Thicknesses  208  and  206  may be any desired thicknesses (e.g., less than 5 microns, less than 10 microns, greater than 5 microns, greater than 20 microns, greater than 40 microns, between 30 and 50 microns, greater than 100 microns, less than 100 microns, greater than 1000 microns, etc.). The difference in thicknesses  206  and  208  is step size  210 . Step size  210  may be any desired length (e.g., less than 1 microns, between 1 and 2 microns, between 0.5 and 5 microns, less than 5 microns, less than 10 microns, greater than 5 microns, greater than 50 microns, etc.). 
     To achieve the desired output from display  14 , the reduced thickness portions of optical film  82  may be combined with the normal thickness portions of optical film  82  at a desired ratio. As shown in  FIG. 12 , the normal thickness portions may have a width  222  and the reduced thickness portions may have a width  224 . Widths  222  and  224  may be any desired widths (e.g., less than 50 microns, less than 100 microns, between 50 and 100 microns, between 75 and 80 microns, approximately 78 microns, less than 1000 microns, greater than 75 microns, etc.). In some embodiments, the widths  222  and  224  may be the same. This means that the ratio of normal thickness area to reduced thickness area is 1:1. The ratio of normal thickness area to reduced thickness area may be any ratio: (e.g., 1:1, 1:2, 1:3, 2:1, 3:1, between 1:2 and 2:1, between 1:3 and 3:1, greater than 3:1, less than 1:3, etc.). Said another way, the reduced thickness area may make up 50% of the entire optical film or another desired percentage of the entire optical film (e.g., 50%, 40%, 45%, 60%, between 45% and 55%, between 40% and 60%, between 30% and 70%, etc.). 
       FIG. 12  shows recessed portions  82 - 2  with planar surfaces. However, the recesses that form reduced thickness portions  82 - 2  may instead by formed by curved surfaces.  FIG. 13  shows an illustrative example of reduced thickness portions  82 - 2  of optical film  82  formed by concave surfaces  212  in optical film  82 . The peak thickness of the normal thickness regions may still be thickness  208 , and the lowest thickness of the reduced thickness regions may still be thickness  206 . However, instead of an instant change between thickness  206  and thickness  208  as shown in  FIG. 12 , the film in  FIG. 13  may have a smooth and gradual change between thickness  206  and thickness  208 . 
     The embodiments of  FIGS. 12 and 13  where optical film  82  is positioned on polarizer  202  are merely illustrative. As discussed in connection with  FIGS. 6-11 , optical film  82  may be positioned in any desired location in the display. 
     There are a number of possible arrangements for the reduced thickness portions of optical film  82 .  FIGS. 14A-14E  are top views of optical film  82  showing different arrangements for normal thickness portions  82 - 1  and reduced thickness portions  82 - 2 . As shown in  FIG. 14A , the reduced thickness portions and normal thickness portions may be arranged in alternating horizontal stripes. Alternatively, as shown in  FIG. 14B , the reduced thickness portions and normal thickness portions may be arranged in alternating vertical stripes.  FIG. 14C  shows yet another arrangement where the reduced thickness portions and normal thickness portions are arranged in alternating slanted stripes. The slanted stripes may be positioned at an angle  226  relative to the bottom surface of the film. Angle  226  may be any angle between 0° (i.e., horizontal stripes) and 90° (i.e., vertical stripes). The slanted stripes may also run from the upper left of the optical film to the lower right of the optical film (i.e., angle  226  may also be between 180° and 90°). 
     Instead of the reduced thickness portions and normal thickness portions of optical film  82  being arranged in stripes (as shown in  FIGS. 14A-14C ), the reduced thickness portions and normal thickness portions of optical film  82  may be arranged in a checkerboard pattern. An arrangement of this type is shown in  FIG. 14D , with a checkerboard pattern of the normal thickness portions and reduced thickness portions. The checkerboard pattern may be formed by squares or rectangles of any desired size. Similar to the slanted stripes discussed in connection with  FIG. 14C , the checkerboard pattern of  FIG. 14D  may be positioned at any desired angle relative to the bottom of the film. An illustrative example of the checkerboard pattern being angled is shown in  FIG. 14E . 
     Optical film  82  may be formed from any desired material. For example, optical film  82  may be formed from cyclic olefin polymers (COP), anti-static polyethylene terephthalate (AS-PET), polyethylene naphthalate (PEN), or any other desired polymer or crystal material. In general, optical film  82  may be formed from any material that is birefringent. In some embodiments, optical film  82  may be formed from liquid crystal material. 
       FIG. 15  shows an illustrative embodiment where sunglass-friendly optical film  82  is formed from a liquid crystal layer  232  on a base film  234 . The base film may have a retardation of 0 (i.e., base film  234  may be formed from a material that is not birefringent such as polyimide). Base film  234  may sometimes be referred to as an alignment film. Base film  234  may be patterned to form regions that have a thickness  236  and regions that have a thickness  238 . Thicknesses  236  and  238  may be any desired thicknesses (e.g., less than 40 microns, less than 20 microns, less than 10 microns, greater than 5 microns, greater than 30 microns, between 30 and 50 microns, between 25 and 35 microns, greater than 50 microns, greater than 100 microns, greater than 1000 microns, etc.). Liquid crystal layer  232  may have regions with a thickness  242  and regions with a thickness  244 . The regions of liquid crystal layer  232  with thickness  242  (i.e., regions  232 - 1 ) may be quarter wave plates (QWPs). Regions  232 - 1  of liquid crystal layer  232  may have any desired thickness  242  (e.g., between 1.5 and 2 microns, between 1 and 2.5 microns, between 1 and 2 microns, less than 1 microns, greater than 0.5 microns, greater than 5 microns, etc.). The regions of liquid crystal layer  232  with thickness  244  (i.e., regions  232 - 2 ) may be three quarter wave plates (3QWPs). Regions  232 - 2  of liquid crystal layer  232  may have any desired thickness  244  (e.g., between 4 and 6 microns, between 1 and 8 microns, greater than 1 microns, less than 2 microns, greater than 10 microns, etc.). 
     As shown in  FIG. 15 , the three quarter wave plate portions of liquid crystal layer  232  may have a width  252  and the quarter wave plate portions may have a width  254 . Widths  252  and  254  may be any desired widths (e.g., less than 50 microns, greater than 25 microns, between 25 and 50 microns, less than 100 microns, between 50 and 100 microns, between 75 and 80 microns, approximately 78 microns, less than 1000 microns, greater than 75 microns, etc.). The three quarter wave plate portions may make up 30% of the entire liquid crystal layer or any other desired percentage (e.g., between 25% and 35%, between 20% and 40%, between 10% and 50%, greater than 10%, less than 60%, etc.). 
     An additional layer may sometimes be formed between base film  234  and liquid crystal layer  232 . An embodiment of this type is shown in  FIG. 16 . As shown, polyimide layer  262  is formed between base film  234  and liquid crystal layer  232 . Polyimide layer  262  may sometimes be referred to as an alignment film. 
     The three quarter wave plate regions and quarter wave plate regions may be arranged in vertical, horizontal or slanted stripes, a checkerboard pattern, an offset checkerboard pattern, or any other desired pattern (similar to as shown in  FIGS. 14A-E ). 
     In the embodiments of  FIGS. 12, 13, 15, and 16 , the thickness of a birefringent material is selectively reduced to improve the output of the display for users wearing sunglasses. The thickness of the birefringent material is adjusted in order to adjust the retardation of the optical film in those regions. However, instead of selectively adjusting the thickness of the film to alter retardation, the birefringence of the film may be selectively adjusted to alter retardation. An embodiment of this type is shown in  FIG. 17 . 
     As shown in  FIG. 17 , optical film  82  may include a liquid crystal layer  232  with uniform thickness across the liquid crystal layer. Instead of a varied thickness, liquid crystal layer  232  may have regions with different birefringence. Regions  232 - 1  may have a lower birefringence and form quarter wave plates, while regions  232 - 2  may have a higher birefringence and form three quarter wave plates. The birefringence of liquid crystal layer  232  may be selectively altered by different exposure to ultraviolet (UV) light. Ultraviolet light  272  may be emitted through half-tone mask  274 . Half-tone mask  274  may allow certain amounts of light through different portions of the mask. In  FIG. 17 , mask  274  includes regions  274 - 1  that allow less light to pass than regions  274 - 2 . The liquid crystal regions that are exposed to more light (i.e., regions  232 - 2 ) have a higher resulting birefringence than the liquid crystal regions that are exposed to less light (i.e., regions  232 - 1 ). This example is merely illustrative. In other embodiments (depending on the liquid crystal material used), the liquid crystal material that is exposed to more UV light may have a lower birefringence than the liquid crystal material that is exposed to less UV light. 
     If desired, both the thickness and the birefringence of the birefringence material may be selectively altered. An embodiment of this type is shown in  FIG. 18 . As shown, regions  232 - 2  of liquid crystal layer  232  may have a larger thickness and greater birefringence than regions  232 - 1  of liquid crystal layer  232 . In general, the retardation of the optical film may be selectively altered using any combination of thickness and birefringence variation. 
     In various embodiments, a display may include display layers, a linear polarizer that receives light from the display layers, and an optical film positioned above the linear polarizer. The optical film may be formed from a birefringent material and the optical film may be patterned into first regions with a first thickness and second regions with a second thickness that is different than the first thickness. The display layers may include a liquid crystal layer that is interposed between a color filter layer and a thin-film transistor layer. The linear polarizer may be an upper polarizer formed above the liquid crystal layer, and the display may also include a lower polarizer formed below the liquid crystal layer. The display layers may include an organic emissive layer that is interposed between an anode and a cathode. The linear polarizer may be formed above a quarter wave plate. 
     The optical film may be attached to the linear polarizer with a layer of adhesive. The optical film may be laminated directly to the linear polarizer. The optical film may be attached to an additional layer in the display. The additional layer may be a touch sensor layer. The first thickness and the second thickness may both be thicknesses between 30 and 50 microns. A difference between the first thickness and the second thickness may be between 0.5 and 5 microns. The first and second regions may be arranged in alternating horizontal, vertical, or slanted stripes. The first and second regions may be arranged in a checkerboard pattern. The linear polarizer may have a first optical axis, the optical film may have a second optical axis, and the second optical axis may be at a 45° angle relative to the first optical axis. The first regions may make up between 30% and 70% of the optical film. 
     In various embodiments, a display may include display layers, a linear polarizer that receives light from the display layers, and an optical film positioned above the linear polarizer. The optical film may include a base film and a layer of birefringent material and the layer of birefringent material may have three quarter wave plate regions and quarter wave plate regions. The layer of birefringent material may be a liquid crystal layer, the three quarter wave plate regions may have a first thickness, the quarter wave plate regions may have a second thickness, and the first thickness may be greater than the second thickness. The three quarter wave plate regions may have a first birefringence, the quarter wave plate regions may have a second birefringence, the first thickness may be the same as the second thickness, and the first birefringence may be greater than the second birefringence. The three quarter wave plate regions may make up between 10% and 50% of the layer of birefringent material. 
     In various embodiments, a display may include a color filter layer, a thin-film transistor layer, a first liquid crystal layer that is interposed between the color filter layer and the thin-film transistor layer and that has first and second opposing sides, a lower polarizer layer on the first side of the first liquid crystal layer, an upper polarizer layer on the second side of the first liquid crystal layer that has a first optical axis, and an optical film above the upper polarizer layer. The optical film may include a base film and a second liquid crystal layer, the second liquid crystal layer may have first regions with a first thickness and second regions with a second thickness that is different than the first thickness, and the second liquid crystal layer may have a second optical axis that is at a 45° angle relative to the first optical axis. 
     The foregoing is merely illustrative and various modifications can be made by those skilled in the art without departing from the scope and spirit of the described embodiments. The foregoing embodiments may be implemented individually or in any combination.

Metadata:
Filing Date: 20161114
Publication Date: 20190507
Grant Date: 20190507
Priority Date: 20160919
Inventors: CHEN, YUAN
NEMATI, HOSSEIN
TAI, CHIA HSUAN
YAN, Jin
YANG, YOUNG CHEOL
GE, ZHIBING
Assignee: APPLE INC
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Family ID: 61621035