PATENT DOCUMENT

Publication Number: US-10094963-B2
Application Number: US-201715483974-A
Country: US
Kind Code: B2

Title: Infrared-transparent window coatings for electronic device sensors

Abstract:
An electronic device may be provided with a display. The display may have a display cover layer. The display may have an active area with pixels and an inactive area without pixels. An opaque masking layer such as a layer of black ink may be formed on the underside of the display cover layer in the inactive area. Windows may be formed from openings in the opaque masking layer. Optical components such as infrared-light-based optical components may be aligned with the windows. The windows may include coatings in the openings that block visible light while transmitting infrared light. The window coatings may be formed from polymer layers containing pigments, polymer layers containing dyes that are coated with antireflection layers, thin-film interference filters formed from stacks of thin-film layers, or other coating structures.

Claims:
What is claimed is: 
     
       1. An electronic device, comprising:
 a transparent layer; 
 an opaque masking layer on at least a portion of the transparent layer, wherein the opaque masking layer has an opening; and 
 at least one optical component aligned with a window formed from the opening, wherein the window includes a visible-light-blocking-and-infrared-light-transmitting coating in the opening and wherein the coating is configured to exhibit a haze of less than 5% and a transmission of 75-95% at near-infrared wavelengths of 900-1000 nm. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the coating includes a polymer layer on the transparent layer. 
     
     
       3. The electronic device defined in  claim 2  further comprising a visible-light-absorbing-and-infrared-light-transmitting dye in the polymer layer. 
     
     
       4. The electronic device defined in  claim 3  wherein the polymer layer is free of pigment and wherein the coating further comprises an infrared-light antireflection coating on the polymer layer. 
     
     
       5. The electronic device defined in  claim 4  wherein the antireflection coating comprises a stack of 2-10 thin-film layers on the polymer layer. 
     
     
       6. The electronic device defined in  claim 5  wherein the thin-film layers include at least one silicon oxide layer. 
     
     
       7. The electronic device defined in  claim 5  wherein the optical component comprises a light-emitting component. 
     
     
       8. The electronic device defined in  claim 5  wherein the optical component comprises a light-detecting component. 
     
     
       9. The electronic device defined in  claim 5  wherein the optical component comprises an array of infrared lasers. 
     
     
       10. The electronic device defined in  claim 5  wherein the optical component comprises an infrared image sensor. 
     
     
       11. The electronic device defined in  claim 5  wherein the transparent layer comprises a display cover layer in a display, wherein the display has a pixel array in an active area of the display that displays images, and wherein the display has an inactive area that does not display images and that includes the opaque masking layer. 
     
     
       12. An electronic device, comprising:
 a housing; 
 a display in the housing having an active area with an array of pixels and having an inactive area without pixels, wherein the display has a display cover layer and has an opaque masking layer on the display cover layer in the inactive area; 
 at least one optical component; and 
 a window in the inactive area that is aligned with the at least one optical component, wherein the window includes an opening in the opaque masking layer and a coating in the opening, wherein the coating includes a polymer that contains dye and that contains an infrared-light antireflection layer on the polymer, and wherein the coating is configured to block light at visible wavelengths while transmitting light at near-infrared wavelengths and exhibiting a haze of less than 5% at the near-infrared wavelengths. 
 
     
     
       13. The electronic device defined in  claim 12  wherein the visible wavelengths are wavelengths of 400-700 nm and wherein the coating is configured to transmit less than 15% of the light at the visible wavelengths. 
     
     
       14. The electronic device defined in  claim 13  wherein the near-infrared wavelengths are wavelengths of 900-1000 nm, and wherein the coating is configured to transmit 75-90% of the near-infrared light at the wavelengths of 900-1000 nm while exhibiting a haze of less than 4% at 900-1000 nm. 
     
     
       15. The electronic device defined in  claim 14  wherein the antireflection layer comprises 2-10 thin-film layers. 
     
     
       16. The electronic device defined in  claim 15  wherein the thin-film layers include at least one inorganic layer. 
     
     
       17. The electronic device defined in  claim 16  wherein the optical component comprises an optical component selected from the group consisting of: a light source having an array of lasers, a time-of-flight proximity sensor, and an infrared camera. 
     
     
       18. An electronic device, comprising:
 a housing; 
 a display in the housing having an active area with an array of pixels and having an inactive area without pixels, wherein the display has a display cover layer and has an opaque masking layer on the display cover layer in the inactive area; 
 at least one optical component, wherein the at least one optical component comprises an optical component selected from the group consisting of: an array of lasers, a time-of-flight proximity sensor, and an infrared camera; and 
 a window in the opaque masking layer in the inactive area that is aligned with the at least one optical component, wherein the window includes an opening in the opaque masking layer and a thin-film interference filter formed from a plurality of thin-film layers in the opening, wherein the thin-film interference filter is configured to block light at visible wavelengths while transmitting light at near-infrared wavelengths. 
 
     
     
       19. The electronic device defined in  claim 18  wherein the visible wavelengths are wavelengths of 400-700 nm, wherein the coating is configured to transmit less than 20% of the light at the visible wavelengths, wherein the near-infrared wavelengths are wavelengths of 900-1000 nm, and wherein the coating is configured to transmit 75-90% of the near-infrared light at the wavelengths of 900-1000 nm while exhibiting a haze of less than 4% at 900-1000 nm. 
     
     
       20. The electronic device defined in  claim 19  wherein the thin-film layers include hydrogenated amorphous silicon layers and include silica layers.

Description:
This application claims the benefit of provisional patent application No. 62/383,268, filed on Sep. 2, 2016, which is hereby incorporated by reference herein its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to coating layers for infrared-transparent sensor windows in electronic devices. 
     Electronic devices such as laptop computers, cellular telephones, and other equipment are sometimes provided with light sensors. For example, cellular telephones may sometimes include infrared proximity sensors. An infrared proximity sensor may include a light-emitting diode that emits infrared light and may include a light detector that measures the infrared light after the infrared light has been reflected off of the head of a user or other external object. The amount of light that is detected by the light detector is indicative of whether external objects are in the vicinity of the light sensor. 
     Sensors such as proximity sensors may be mounted behind an inactive area of a display. The display may have a protective layer of clear glass that serves as a display cover layer. The underside of the display cover layer may be coated with a black ink layer to hide internal components from view by a user. Windows may be formed in the black ink layer to accommodate components. Some windows, such as windows for visible-light cameras, may be transparent at visible light wavelengths. Other windows, such as those associated with infrared proximity sensors, may be provided with an ink (sometimes referred to as infrared ink) that is transparent at infrared wavelengths. The infrared ink may be opaque at visible wavelengths so that the infrared ink has a dark appearance that matches the black ink layer. 
     Infrared ink windows that are suitably opaque at visible wavelengths to match the appearance of nearby black ink in the black ink layer may scatter more light than desired at infrared wavelengths. This can make it difficult or impossible to achieve desired levels of sensor performance. 
     It would therefore be desirable to be able to provide enhanced visible-light-blocking-and-infrared-light-transparent window coatings to accommodate components such as sensors in an electronic device. 
     SUMMARY 
     An electronic device may be provided with a display mounted in a housing. The display may have an array of pixels that form an active area and may have an inactive area that runs along an edge of the active area and that is free of pixels. The display may have a display cover layer that overlaps that array of pixels in the active area. An opaque masking layer such as a layer of black ink may be formed on the underside of the display cover layer in the inactive area. Opaque masking layers may also be formed on other transparent members. 
     Windows may be formed from openings in the opaque masking layer. Optical components such as infrared-light-based optical components may be aligned with the windows. The infrared-light-based optical components may include proximity sensors and other light-based components. 
     The windows may include coatings in the openings that block visible light while transmitting infrared light. The window coatings may be formed from polymer layers containing pigments, polymer layers containing dyes that are coated with antireflection layers, thin-film interference filters formed from stacks of thin-film layers, or other coating structures. The coatings may exhibit low haze at infrared wavelengths to reduce light scatter and noise for the infrared-light-based optical components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic diagram of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a perspective view of a portion of an electronic device display with a sensor window in accordance with an embodiment. 
         FIGS. 3, 4, and 5  are cross-sectional side views of illustrative light-based devices aligned with infrared-transparent windows on a transparent structure in an electronic device such as a transparent display cover layer in accordance with an embodiment. 
         FIG. 6  is a diagram of an illustrative infrared-transparent window in accordance with an embodiment. 
         FIG. 7  is a graph in which light transmission has been plotted as a function of wavelength for an illustrative visible-light-blocking-and-infrared-light-transmitting window coating in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of a portion of a display cover layer with an illustrative infrared-transparent coating having pigments in accordance with an embodiment. 
         FIG. 9  is a diagram of an illustrative pigment in accordance with an embodiment. 
         FIG. 10  is a graph in which haze has been plotted as a function of wavelength for an illustrative coating in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of an illustrative window coating having a polymer layer with visible-light-absorbing dye and a stack of inorganic dielectric layers that form an antireflection coating on the polymer layer in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of an illustrative window coating formed from a thin-film interference filter in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     An illustrative electronic device of the type that may be provided with one or more light sensors 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, a pendant device, a headphone or earpiece device, a device embedded in eyeglasses or other equipment worn on a user&#39;s head, or other wearable or miniature device, a television, a computer display that does not contain an embedded computer, a gaming device, a navigation device, an embedded system such as a system in which electronic equipment with a display is mounted in a kiosk or automobile, equipment that implements the functionality of two or more of these devices, or other electronic equipment. 
     As shown in  FIG. 1 , electronic device  10  may have control circuitry  16 . Control circuitry  16  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  16  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  12  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  12  may include buttons, joysticks, scrolling wheels, touch pads, key pads, keyboards, microphones, speakers, tone generators, vibrators, light-emitting diodes for components such as status indicators, data ports, etc. A user can control the operation of device  10  by supplying commands through input-output devices  12  and may receive status information and other output from device  10  using the output resources of input-output devices  12 . 
     Input-output devices  12  may include one or more displays such as display  14 . Display  14  may be a touch screen display that includes a touch sensor for gathering touch input from a user or display  14  may be insensitive to touch. A touch sensor for display  14  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. 
     Input-output devices  12  may also include sensors  18 . Sensors  18  may include a capacitive proximity sensor, a light-based proximity sensor, an ambient light sensor, a light-based fingerprint sensor, a fingerprint sensor based on a capacitive touch sensor, a magnetic sensor, an accelerometer, a force sensor, a touch sensor for a button or track pad, a temperature sensor, a pressure sensor, a compass, a microphone or other sound sensor, a visible digital image sensor (visible-light camera), an infrared digital image sensor (infrared-light camera), and other sensors. Sensors  18  may be used to gather user commands (e.g., commands that direct control circuitry  16  to take action), may be used to gather information on the environment surrounding device  10  (e.g., information on ambient light levels, ambient temperature, ambient atmospheric pressure, etc.), and may be used in performing biometric authentication operations (e.g., using a fingerprint sensor, using visible and/or infrared cameras, using voice recognition, etc.). After a user has been authenticated using biometric authentication operations and/or after entering a password or supplying other information to device  10 , control circuitry  16  may provide the user with access to the features of device  10  (e.g., circuitry  16  may allow the user to make telephone calls, access stored information in storage in device  10 , send text messages or email messages, etc.). 
     A perspective view of a portion of an illustrative electronic device is shown in  FIG. 2 . In the example of  FIG. 2 , device  10  includes a display such as display  14  mounted in housing  22 . Housing  22 , 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  22  may be formed using a unibody configuration in which some or all of housing  22  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, clear plastic, sapphire, or other clear layer. 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, a speaker port, or other components. Openings may be formed in housing  22  to form communications ports (e.g., an audio jack port, a digital data port, etc.), to form openings for buttons, etc. 
     Display  14  may be a liquid crystal display, may be an electrophoretic display, may be an organic light-emitting diode display or other display with an array of light-emitting diodes, may be a plasma display, may be an electrowetting display, may be a display based on microelectromechanical systems (MEMs) pixels, or may be any other suitable display. Display  14  may have an array of pixels in active area AA. The pixels of active area AA may display images for a user of device  10 . Active area AA may be rectangular or may have other suitable shapes. 
     Inactive border area IA may run along one or more edges of active area AA and may be free of pixels. Inactive border area IA may contain circuits, signal lines, and other structures that do not emit light for forming images. To hide circuitry and other components in border area IA from view by a user of device  10 , the underside of the outermost layer of display  14  (e.g., the display cover layer or other display layer) may be coated with an opaque masking material. The opaque masking material may have a dark color (e.g., the opaque masking material may be black, dark blue, dark gray, or other dark colors) or may have other opaque colors (e.g., opaque white, opaque silver, etc.). Configurations in which the opaque masking layer in inactive area IA of display  14  is formed from a dark material such as black ink (e.g., a polymer containing visible-light-absorbing dye and/or pigment that imparts a black color to the polymer) may sometimes be described herein as an example. This is merely illustrative. The opaque masking layer may be formed from opaque inks or other materials of other colors if desired. 
     Optical components (sometimes referred to as light-based components, light-based devices, optical devices, etc.) may be mounted under inactive border area IA. One or more windows may be formed from openings in the opaque masking layer of inactive area IA to accommodate the optical components. For example, one or more light component windows such as illustrative window  20  of  FIG. 2  may be formed in a peripheral portion of display  14  such as inactive border area IA to accommodate one or more associated optical components. During operation, light-emitting components in device  10  can emit light through windows such as window  20  and light-sensitive components in device  10  can receive light through widows such as window  20 . If desired, other portions of device  10  may be provided with openings to accommodate optical components (e.g., openings may be formed in housing  12 , etc.). 
     If desired, camera window covering layers (e.g., thin sapphire members or transparent members formed from glass, plastic, or other materials) may be provided with opaque masking layer material having openings and coatings for forming windows  20 . Windows  20  may also be formed from visible-light-blocking-and-infrared-light-transmitting coatings on other transparent structures in device  10  (e.g., a planar rectangular rear housing member formed from glass, sapphire, plastic, other transparent structures, or combinations of such structures, transparent button members, or other transparent structures in device  10 ). These coatings may be formed in window openings in opaque masking layer material that is deposited on the planar rectangular rear housing members (rear housing walls) or other transparent structures. The example of  FIG. 2  in which window  20  has been formed in inactive area IA of display  14  is merely illustrative. 
       FIG. 3  is a cross-sectional side view of display  14  of  FIG. 2  taken along line  24  and viewed in direction  26  of  FIG. 2 . In the illustrative example of  FIG. 3 , window  20  has been formed in inactive area IA of display  14 . In active area AA, display  14  includes a pixel array (sometimes referred to as a display module or display) such as pixel array  30 . Pixel array  30  may have an array of pixels P for displaying images for a user of device  10 . Pixels P may be organic light-emitting diode pixels, liquid crystal display pixels, or other suitable display pixels. The underside of display cover layer  32  in active area AA is free of opaque masking material  34 , so that images on pixel array  30  can be viewed through display cover layer  32 . 
     In inactive area IA, the underside of display cover layer  32  may be covered with opaque masking material such as opaque masking layer  34 . Opaque masking layer  34  may be a layer of ink (e.g., a layer of polymer that contains visible-light-absorbing substances such as dyes and/or pigments that block visible light) and/or may contain thin-film layers for forming a light-blocking thin-film interference filter that blocks visible light. As an example, opaque masking layer  34  may be a layer of black ink formed from polymer that includes black pigment (e.g., carbon black). Other types of opaque masking layer material may be used to form layer  34  if desired. 
     Due to the presence of opaque masking layer  34 , internal device components (e.g., inactive display structures, integrated circuits, printed circuit board structures, etc.) may be hidden from view from a user of device  10 . Opaque masking layer  34  is generally at least somewhat opaque at infrared wavelengths, so one or more infrared-transparent regions such as window  20  may be formed to accommodate optical components that operate at infrared wavelengths. Windows such as window  20  may be covered with window structures (sometimes referred to as coatings or filter layers) that transmit infrared light while blocking visible light. In the example of  FIG. 3 , infrared-transparent layer  36  overlaps window  20 . Layer  36  is preferably opaque at visible wavelengths and has an appearance (color, reflectivity, etc.) that matches that of layer  34  when viewed by a user. This helps make the presence of window  20  undetectable or nearly undetectable to a user. 
     One or more optical components (e.g., infrared optical components) may be aligned with windows such as window  20 , as shown by illustrative optical component  38  of  FIG. 3 . During operation, visible light will be blocked by layer  36  of window  20 , so that component  38  will be hidden from view. Infrared light will pass through layer  36  of window  20 . Optical component  38  may emit and/or receive infrared light passing through layer  36 . The infrared light may be, for example, near infrared light (e.g., near light at wavelengths of 700 to 2500 nm, light at 900-1000 nm, light at 940 nm, light at wavelengths longer than 800 nm or less than 3000 nm, etc.). 
     Components such as component  38  may include light-emitting components (e.g., infrared light-emitting diodes or infrared lasers for providing infrared illumination for an infrared camera, infrared output light for an amplitude proximity sensor, infrared output light for a time-of-flight proximity sensor, etc.), may include light sensors (e.g., discrete silicon photodetectors that measure infrared light at one or more infrared wavelengths, two-dimensional light sensor arrays that form infrared digital image sensors), infrared light sensors such as silicon photodetectors in infrared amplitude or time-of-flight proximity sensors, or other suitable light-emitting and/or light-detecting infrared optical components. 
     In the example of  FIG. 3 , optical component  38  is an infrared proximity sensor. Component  38  may include a light-emitting device such as light-emitting component  40  (e.g., an infrared light-emitting diode or infrared laser) that emits infrared light  42 . Infrared light  42  that has been emitted by light-emitting component  40  may be reflected off of an external object in the vicinity of device  10  such as external object  44 . Reflected light  42  may be detected by infrared light detector  46 . Light detector  46  may be, for example, a silicon photodiode. Light  42  that has been emitted by component  40  may pass through visible-light-blocking-and-infrared-light-transmitting layer  36  and, following reflection from object  44 , light  42  may pass through visible-light-blocking-and-infrared-light-transmitting layer  36  before being received by light detector (light sensor)  46 . Component  38  may measure the amplitude of reflected light  42  and/or may make time-of-flight measurements on pulses of emitted light  42  (e.g., component  38  may be an amplitude proximity sensor or may be a time-of-flight infrared proximity sensor). As shown in  FIG. 4 , components such as light-emitting component  40  and light-detecting component  46  may be mounted under separate windows  20  or may be mounted under separation portions of a single infrared-transparent window region that is divided into two separate regions using an intervening strip of visible-light-blocking-and-infrared-light-blocking material such as opaque masking material  34 . 
       FIG. 5  is a cross-sectional side view of a portion of display  14  in a configuration in which light-detecting component  46  is an infrared camera. As shown in  FIG. 5 , light-emitting component  40  may emit light  42  that serves as camera illumination for component  46 . Emitted light  42  that has passed through layer  36  in a first window  20  may illuminate external object  44  (e.g., a user&#39;s face, a user&#39;s eye, etc.). Light  42  that has reflected off of object  44  may pass through layer  36  in a second window  20  to component  46 . 
     Light-emitting component  40  may include a housing such as housing  54 . A light source such as light source  50  may be mounted in housing  54 . Light source  50  may include one or more light-emitting diodes or lasers. For example, light source  50  may include an array of lasers  52  (e.g., vertical-cavity surface-emitting lasers). Lasers  52  may operate at a near infrared wavelength (e.g., a wavelength of 700-2500 nm, more than 800 nm, more than 900 nm, less than 3000 nm, less than 2000 nm, less than 1000 nm, 940 nm, 900-1000 nm, 800-1100 nm, or other suitable wavelength). Component  40  may have a light diffuser such as diffuser  56  that diffuses light that has been emitted by lasers  52 . Diffuser  56  may be mounted to housing  54  (as an example). 
     Component  46  may have a digital image sensor such as infrared digital image sensor  62 . Sensor  62  may be formed from a silicon die or other semiconductor structures. Sensor  62  may include an array of photosensitive pixels (image sensor pixels)  64 . An optical system such as one or more lenses (see, e.g., illustrative lens  66 ) may be used to focus reflected light  42  from object  44  for imaging by image sensor  62 . Image sensor  62  and lens  66  may be mounted in housing  60  (as an example). 
     Optical components such as infrared time-of-flight proximity sensors may be used to measure the distance separating a user&#39;s head from display  14  (e.g., to allow control circuitry  16  to ignore inadvertent touch screen input when device  10  is being held adjacent to a user&#39;s head and to allow control circuitry  16  to process intentional touch screen input when device  10  is not adjacent to the user&#39;s head). Infrared images captured with component  46  may be used by control circuitry  16  to implement biometric security controls. For example, control circuitry  16  may use component  46  to gather infrared images of a user&#39;s face, a user&#39;s eye (e.g., a user&#39;s iris), or other portion of a user and may process these images using facial recognition algorithms, iris recognition algorithms, or other biometric recognition algorithms implemented on control circuitry  16 . Biometric recognition processes such as these may be used by control circuitry  16  to securely control access to device  10 . If biometric authentication is successful, control circuitry  16  can unlock device  10 . If biometric authentication is unsuccessful (e.g., if an infrared image of a user&#39;s face or iris pattern does not match a previously registered face or iris pattern), control circuitry  16  can prevent access to device  10  (e.g., control circuitry  16  can maintain device  10  in a locked state if biometric authentication operations indicate that access is being attempted by an unauthorized individual). 
     Windows such as windows  20  of  FIGS. 2, 3, 4, and 5 , may have any suitable shape (outline when viewed from above). For example, windows  20  may have circular footprints, oval footprints, rectangular footprints, shapes with straight and curved edges, or other suitable outlines. Light-emitting and light-detecting components may be mounted behind a common infrared-transparent window or a separate windows may be formed for light-emitting and light-detecting components. As shown in the illustrative configuration of  FIG. 6 , window  20  may be divided into first and second regions (windows) by depositing a single circular region of material  36  in a circular opening (or an opening of another suitable shape) in opaque masking layer  34  and by dividing material  36  into left and right halves using an additional strip of opaque masking material (see, e.g., opaque masking layer strip  34 ′). This type of arrangement may be used, for example, to accommodate a component such as component  38  of  FIG. 3 . For example, light-emitting device  40  may be aligned with the left-hand portion of layer  36  and light-detecting device  46  may be aligned with the right-hand portion of layer  36 . 
     For satisfactory performance of components  40  and  46 , it may be desirable for layer  36  to exhibit low visible-light transmission, high infrared-light transmission, and low infrared-light scattering (low haze). These attributes may help ensure that components  40  and  46  operate satisfactorily. For example, providing layer  36  with a low visible-light transmission (e.g., light transmission at 400-700 nm that is less than 20%, less than 15%, less than 10%, less than 5%, less than 2%, less than 1%, 1-15%, more than 0.1%, or other suitable amount) may help window  20  obscure internal components such as components  40  and  46  from view from the exterior of device  10 . High infrared light transmission (e.g., infrared light transmission at near infrared wavelengths such as 940 nm or 900-1000 nm or other suitable wavelengths that is more than 50%, more than 75%, more than 80%, more than 90%, more than 95%, more than 98%, 75-95%, 80-90%, 80-99%, less than 99.9%, or other suitable amount) may help ensure that sufficient emitted infrared light  42  from component  40  passes through layer  36  to external object  44  and may help ensure that sufficient reflected infrared light  42  from object  44  passes through layer  36  to component  46 . 
     An illustrative light transmission characteristic is shown in  FIG. 7 . As shown by curve  68  of  FIG. 7 , layer  36  may exhibit low light transmission T at visible wavelengths of 400-700 nm and may exhibit high light transmission T at near infrared wavelengths. For example, T may be less than 20%, less than 15%, less than 10%, less than 5%, less than 2%, or less than 1% at visible wavelengths from 400-700 nm and may be greater than 80%, greater than 90%, greater than 95%, or greater than 98% at 900-1000 nm (e.g., at 940 nm) or other near infrared wavelengths. 
     The performance of an infrared proximity sensor (e.g., a time-of-flight proximity sensor) and/or an infrared camera (e.g., a camera used for gathering biometric information) may be adversely affected by excessive light scattering in layer  36 . It may therefore be desirable to form layer  36  from one or more layers of low-light-scattering materials. Low scattering may help to minimize or eliminate undesired scattered light noise in a time-of-flight proximity sensor or other infrared light-based proximity sensor and may minimize or eliminate undesired noise and image distortion in an infrared biometric image. 
     Layer  36  may be formed from a polymer binder that includes light-absorbing substances such as dyes and/or pigments that exhibit bulk visible light absorption and infrared transparency and/or may be formed from one or more thin-film layers that form a thin-film interference filter with desired optical properties (e.g., visible light blocking, infrared transparency, infrared antireflection properties, etc.). 
     Consider, as an example, a scenario in which layer  36  include pigment in a polymer binder. This type of approach may be used, for example, when it is desired to provide layer  36  with enhance stability when exposed to ultraviolet light. As shown in  FIG. 8 , window  20  may include a visible-light-blocking-and-infrared-light-transmitting layer such as layer  36  that is formed from a polymer binder material (polymer  70 ) that includes embedded pigment  72 . Polymer  70  may be, for example, a low viscosity acrylic or other suitable polymer. The use of low viscosity for polymer  70  (e.g., a viscosity of 20-50 centipoise, less than 40 centipoise, more than 5 centipoise, or other suitable viscosity) may help reduce surface roughness in layer  36  and thereby reduce light scattering. As shown in  FIG. 8 , the exposed surface of layer  36  may have a root-mean-square (RMS) surface roughness R. The value of R may be less than 500 nm, less than 250 nm, less than 100 nm, less than 20 nm, more than 1 nm, or other suitable value that helps reduce light scattering. The thickness of layer  36  may be 4 microns, 2-7 microns, more than 1 micron, more than 3 microns, less than 8 microns, less than 10 microns, or other suitable thickness. 
     Pigment  72  may be a black pigment such as carbon black, may be a blue pigment, may include a mixture of black and blue pigment, or may be any other suitable pigment. As shown in  FIG. 9 , pigment  72  may include aggregates of nanoparticles (subparticles)  72 ′. With one suitable arrangement, layer  36  includes carbon black pigment or other pigment  72  that is characterized by relatively small aggregates and nanoparticles to help reduce light scattering. As shown in  FIG. 9 , carbon pigment  72  may have a particle size (nanoparticle size) of D1 (e.g., a particle diameter of 20 nm, 15-25 microns, less than 20 nm, less than 30 nm, 10-30 nm, less than 40 nm, less than 25 nm, less than 15 nm, 5-35 nm, more than 5 nm, or other suitable size) and may have an aggregate size of D2 (e.g., an aggregate particle diameter of 200 nm, 50-300 nm, 100-300 nm, 50-250 nm, less than 5 microns, less than 1000 nm, less than 500 nm, less than 300 nm, less than 250 nm, less than 200 nm, 150-250 nm, more than 50 nm, or other suitable aggregate size). Pigment with relatively small values of D1 and D2 may be characterized by enhanced dispersion of the pigment and closer packing at the surface of layer  36 , which may help minimize light scatter and reflection while enhancing uniformity. 
     The haze of layer  36  (e.g., layer  36  of  FIG. 8 ) may be, for example, less than 10% or, more preferably, less than 5%, less than 4%, less than 3.5%, less than 3%, less than 2.5%, or less than 2% (as measured using the ASTM D1003 haze standard) at wavelengths of 900-1000 nm when the transmission T of layer  36  is 75-95%, 80-90%, 85%, or has other suitable transmission values at 900-1000 nm. A graph in which haze has been plotted as a function of wavelength for an illustrative visible-light-blocking-and-infrared-light-transmitting layer such as layer  36  of  FIG. 8  is shown in  FIG. 10 . As shown in  FIG. 10 , when transmission at 900-1000 nm is 80-90% (or 75-95%, less than 95%, or other suitable value), the haze of layer  36  at 900-1000 nm (e.g., at 940 nm) may be less than 2% (or 1-4%, less than 3%, less than 5%, less than 4%, or other suitable value) as measured using the ASTM D1003 haze standard. 
     If desired, a low haze configuration for the visible-light-blocking-and-infrared-light-transmitting layer of window  20  may be formed from a polymer that contains dye (e.g., a coating formed from a polymer layer that contains visible-light-absorbing-and-infrared-light-transmitting dye and that is free of pigment). This type of configuration is shown in  FIG. 11 . In the example of  FIG. 11 , window  20  has been formed from an opening in opaque masking layer  34 . The opening for window  20  has been filled with polymer layer  80  and thin-film layers  82 . Layer  80  may be formed from an acrylic polymer, polyester, or other suitable polymer material on the exposed inner surface of display cover layer  32  in window  20 . Visible-light-absorbing dye may be incorporated into layer  80 . The dye may be transparent at infrared wavelengths. For example, the light transmission of layer  80  may be at least 80%, at least 85%, at least 90%, 80-90%, 75-95%, or other suitable transmission value at wavelengths of 900-1000 nm (e.g., 940 nm) or other suitable near infrared wavelengths. The dye of layer  80  in  FIG. 11  may cause layer  80  to absorb visible light. For example, layer  80  (and therefore window  20  of  FIG. 11 ) may have a visible light transmission at wavelengths of 400-700 nm of less than 20%, less than 15%, less than 10%, less than 5%, less than 2%, more than 0.1%, or other suitable transmission value. 
     Layers  82  on layer  80  of  FIG. 11  may be thin-film layers that form an infrared-light antireflection coating at 900-1000 nm or other near infrared wavelengths. The presence of layers  82  on layer  80  may enhance transmission by 1-6%, 2-5%, 3-4%, more than 1%, more than 2%, more than 3%, less than 10%, or other suitable amount at 900-1000 nm or other near infrared wavelengths. There may be any suitable number of layers in the antireflection coating on layer  82  (e.g., 2-5 layers, more than 2 layers, more than 3 layers, more than 4 layers, 2-10 layers, fewer than 10 layers, etc.). Layers  82  may be formed from organic materials (e.g., polymers), inorganic materials (e.g., dielectrics such as silicon oxide, metal oxides such as titanium oxide or aluminum oxide, other metal oxides, silicon nitride or other nitrides, silicon oxynitride or other oxynitrides, other dielectric materials), semiconductors (e.g., silicon such as hydrogenated amorphous silicon, indium tin oxide, copper oxide, etc.), or other thin-film layers. For example, layers  82  may include three layers or 2-10 layers such as alternating silicon oxide and silicon nitride layers or such as alternating silicon oxide and titanium oxide layers. 
     Antireflection coatings and/or other coatings on layer  80  (e.g., thin-film interference filters formed from stacks of layers  82  that are configured to block visible light while transmitting infrared light) may be formed by depositing layers  82  on layer  80  by physical vapor deposition (e.g., evaporation or sputtering), chemical vapor deposition (e.g., plasma enhanced chemical vapor deposition, atomic layer deposition, low-pressure chemical vapor deposition, or other suitable chemical vapor deposition technique), and/or other thin-film deposition processes. If desired, infrared-light antireflection coatings may be deposited on polymer layers with pigments (see, e.g., polymer  70  of  FIG. 8 ). 
       FIG. 12  shows how polymer layer  80  may be omitted from the visible-light-blocking-and-infrared-light-transmitting layer in window  20 . In this type of configuration, window  20  includes only thin-film layers  82 . Layers  82  may be deposited on the inner surface of display cover layer  32  that is exposed in the window opening formed in opaque masking layer  34 . Layers  82  in window  20  may be thin-film layers that form a visible-light-blocking-and-infrared-light-transmitting thin-film interference filter (sometimes referred to as a dichroic filter) having a transmission of 80-90%, 75-95%, at least 80%, at least 85%, at least 90%, at least 95%, less than 99.9%, more than 70%, or other suitable light transmission value at 900-1000 nm (e.g., 940 nm) or other near-infrared wavelengths while exhibiting a transmission of less than 30%, less than 20%, less than 15%, less than 10%, less than 5%, less than 2%, less than 1%, or more than 0.01% at visible light wavelengths of 400-700 nm. There may be any suitable number of layers in the thin-film interference filter formed by layers  82  in  FIG. 12 . (e.g., 20 layers, 10-30 layers, at least 5 layers, at least 10 layers, at least 15 layers, fewer than 40 layers, fewer than 30 layers, etc.). As with thin-film layers  82  of  FIG. 11 , layers  82  of window  20  of  FIG. 12  may be formed from organic materials (e.g., polymers), inorganic materials (e.g., dielectrics such as silicon oxide, metal oxides such as titanium oxide or aluminum oxide, other metal oxides, silicon nitride or other nitrides, silicon oxynitride or other oxynitrides, other dielectric materials), semiconductors (e.g., silicon, indium tin oxide, copper oxide, etc.), and/or other thin-film layers and may be deposited using physical vapor deposition (e.g., evaporation or sputtering), chemical vapor deposition (e.g., plasma enhanced chemical vapor deposition, atomic layer deposition, low-pressure chemical vapor deposition, or other suitable chemical vapor deposition technique), or other thin-film deposition techniques. The thin-film interference filter formed from layers  82  of  FIG. 12  may, as an example, be formed from materials with different indices of refraction (e.g., alternating higher and lower refractive index materials) such as silica (silicon oxide) and hydrogenated amorphous silicon. Other materials, other patterns of alternating higher and lower refractive index materials, and/or other stacks of thin-film interference layers may be used, if desired. The use of layers of silica and silicon to form an infrared transparent coating for window  20  that blocks visible light is merely illustrative. 
     Window coating arrangements of the type shown in  FIGS. 11 and 12  may be characterized by low haze due to the absence of pigments. For example, the haze of layer  80  and the antireflection coating formed from layers  82  in  FIG. 11  and the haze of the thin-film interference filter formed by layers  82  in  FIG. 12  may be less than 10% or, more preferably, less than 5%, less than 4%, less than 3.5%, less than 3%, less than 2%, less than 1%, or less than 0.5% (as measured using the ASTM D1003 haze standard) at wavelengths of 900-1000 nm when the transmission T of window  20  (e.g., the coating in window  20 ) is 80-90% at 900-1000 nm (e.g., at 940 nm). 
     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: 20170410
Publication Date: 20181009
Grant Date: 20181009
Priority Date: 20160902
Inventors: GIACHINO, MARTA M.
MATSUYUKI, NAOTO
ROGERS, MATTHEW S.
ZHAO, Xianwei
WANG, LIGANG
Assignee: APPLE INC
CPC Classifications: [{"code": "G02B5/285", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/14649", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01L27/1462", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B1/115", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/281", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01S5/4025", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F39/805", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F39/184", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F39/184", "inventive": true, "first": false, "tree": "[]"}, {"code": "H10F39/805", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/281", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B5/281", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J2003/2806", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J1/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B1/115", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/285", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B1/115", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/285", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01S5/4025", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/4204", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J1/0418", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J2003/2806", "inventive": false, "first": false, "tree": "[]"}]
Family ID: 61280615