PATENT DOCUMENT

Publication Number: US-11448801-B2
Application Number: US-202016848732-A
Country: US
Kind Code: B2

Title: Textured glass layers in electronic devices

Abstract:
An electronic device may have a housing surrounding an interior in which electrical components are mounted. A display may be mounted to housing structures in the device. The housing may have a rear wall. The display cover layer and rear wall of the housing may be formed from transparent glass layers. Coatings may be formed on inwardly facing surfaces of the transparent glass layers. A coating on a transparent glass layer may be formed from a thin-film interference filter having a stack of dielectric layers. The coating may include an ink layer on the thin-film interference filter. The transparent glass layers may have one or more textured surfaces that allow light at high angles to enter the transparent layers and reflect off the coatings at high angles, thereby adjusting optical properties of the coatings.

Claims:
What is claimed is: 
     
       1. An electronic device having opposing front and rear faces and an interior, the electronic device comprising:
 a display on the front face; 
 a transparent layer that forms a housing wall on the rear face, wherein the transparent layer has an inner surface facing the interior and an opposing outer surface with surface texture; and 
 a coating on the inner surface comprising a thin-film interference filter, wherein the coating is neutral at on-axis viewing angles and non-neutral at off-axis viewing angles. 
 
     
     
       2. The electronic device defined in  claim 1  wherein the thin-film interference filter is a coating layer on the inner surface of the transparent layer. 
     
     
       3. The electronic device defined in  claim 1  wherein the coating further comprises a buffer layer on the inner surface of the transparent layer and wherein the thin-film interference filter is on the buffer layer. 
     
     
       4. The electronic device defined in  claim 1  wherein the thin-film interference filter is formed on a polymer film and attached to the transparent layer. 
     
     
       5. The electronic device defined in  claim 1  wherein the surface texture is formed from protrusions selected from the group consisting of: semi-spherical bumps and semi-cylindrical bumps. 
     
     
       6. The electronic device defined in  claim 1  wherein the surface texture comprises randomly distributed protrusions and recesses on the outer surface of the transparent layer. 
     
     
       7. The electronic device defined in  claim 1  wherein the on-axis neutral coating exhibits first a and b color coordinates in LAB color space, and wherein a root sum squared of the first a and b color coordinates is less than two in magnitude at a viewing angle of 0°. 
     
     
       8. The electronic device defined in  claim 7  wherein the off-axis non-neutral coating exhibits second a and b color coordinates in LAB color space, and wherein a root sum squared of the second a and b color coordinates is greater than three in magnitude at a viewing angle of 80°. 
     
     
       9. The electronic device defined in  claim 8  wherein the thin-film interference filter has a reflectivity of at least 80% from 400 nm to 700 nm. 
     
     
       10. The electronic device defined in  claim 8  wherein the thin-film interference filter has an L luminance coordinate in LAB color space that changes less than 25% when viewed at viewing angles between 0° and 75°. 
     
     
       11. An electronic device having an interior and an exterior, the electronic device comprising:
 a housing having a rear glass layer that has a textured surface that faces the exterior and an inner surface that faces the interior; and 
 a coating on the inner surface, wherein the coating comprises a thin-film interference filter and wherein the coating is neutral when viewed on-axis and non-neutral when viewed off-axis. 
 
     
     
       12. The electronic device defined in  claim 11  wherein the thin-film interference filter is a band stop filter with a stop band at infrared wavelengths when viewed on-axis. 
     
     
       13. The electronic device defined in  claim 12  wherein the stop band is at visible wavelengths when viewed off-axis. 
     
     
       14. The electronic device defined in  claim 11  wherein the textured surface is a first textured surface and is a first distance from the inner surface of the rear glass layer, and wherein the rear glass layer comprises a second textured surface at a second distance from the inner surface that is different from the first distance and a tapered surface between the first textured surface and the second textured surface.

Description:
This application claims the benefit of provisional patent application No. 62/880,597, which is hereby incorporated by reference herein in its entirety. 
    
    
     FIELD 
     This relates generally to electronic devices and, more particularly, to textured transparent layers and associated coatings that provide color-shifting optical properties in electronic devices. 
     BACKGROUND 
     Electronic devices such as cellular telephones, computers, watches, and other devices may contain glass structures. For example, electronic devices may have displays in which an array of pixels is covered with a transparent layer of glass. In some devices, a rear housing wall may be covered with a layer of glass. A decorative layer may be applied to the layer of glass to help improve the appearance of the rear housing wall or may be applied to an inactive portion of the transparent layer of glass that covers the display. 
     It may be desirable to improve the outward appearance of the display cover layer in the inactive area or the output appearance of a glass housing layer. 
     SUMMARY 
     An electronic device may have a housing in which a display is mounted. The housing may be formed from housing structures that surround an interior region in the electronic device. Electrical components may be mounted in the electronic device interior. 
     The display may be coupled to the housing structures on a front face of the electronic device. The housing structures may include a rear wall on an opposing rear face of the electronic device. 
     A display cover layer for the display may have a surface that faces the interior of the housing. The rear wall may also have a surface that faces the interior of the housing. Structures in the electronic device such as the display cover layer and rear housing wall may be formed from transparent glass layers. Coatings may be formed on the inwardly facing surfaces of the transparent glass layers. The transparent glass layers may have textured surfaces opposite the inwardly facing surfaces that allow light at high viewing angles to pass into the glass layers and be reflected by the underlying coatings. In this way, optical properties of the housing may change when viewed by a user at different viewing angles. 
     A coating on a transparent glass layer may be formed from a thin-film interference filter having a stack of dielectric layers. The coating may also include an ink layer on the thin-film interference filter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 2  is a cross-sectional side view of an illustrative electronic device having transparent layers forming housing walls in accordance with an embodiment. 
         FIG. 3  is a cross-sectional side view of a smooth glass layer having a reflective coating in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of a textured glass layer having a reflective coating in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of a textured glass layer having a coating formed from a plurality of layers in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of a thin-film interference filter formed from a plurality of dielectric layers in accordance with an embodiment. 
         FIG. 7  is a graph of reflectivity profiles for illustrative coating layers at different viewing angles in accordance with an embodiment. 
         FIG. 8  is a graph of reflectivity profiles for illustrative coating layers that form band stop filters in accordance with an embodiment. 
         FIG. 9  is a graph of reflectivity profiles for illustrative coating layers that form band pass filters in accordance with an embodiment. 
         FIG. 10  is a graph of reflectivity profiles for illustrative coating layers that form partially reflective filters across a set of wavelengths in accordance with an embodiment. 
         FIG. 11  is a graph of reflectivity profiles for illustrative neutral ink coatings in accordance with an embodiment. 
         FIG. 12  is a graph of reflectivity profiles for illustrative non-neutral ink coatings in accordance with an embodiment. 
         FIG. 13  is a graph of reflectivity profiles for illustrative non-neutral ink coatings that have multiple reflectivity peaks in accordance with an embodiment. 
         FIG. 14  is a graph of reflectivity profiles for illustrative coatings on textured glass layers with thin-film interference filters that form band pass filters and ink that has absorptivity peaks at different viewing angles in accordance with an embodiment. 
         FIG. 15  is a graph of reflectivity profiles for illustrative thin-film interference filters at different viewing angles that have decreasing reflectivity across the visible spectrum. 
         FIG. 16  is a graph of reflectivity profiles for illustrative coatings that form band stop filters on a textured glass layer at different viewing angles in accordance with an embodiment. 
         FIG. 17  is a graph of reflectivity profiles for illustrative coatings having thin-film interference filters and ink layers with varying reflectivity peaks in accordance with an embodiment. 
         FIG. 18  is a cross-sectional side view of a glass surface that forms a portion of an electronic device housing and has edge surfaces exposed to an exterior of the device in accordance with an embodiment. 
         FIG. 19  is a cross-sectional side view of a textured glass layer having textured surfaces of different heights and having a coating formed from a plurality of layers in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices such as cellular telephones often include glass members such as display cover glass layers and glass housing members. These layers are traditionally coated with materials such as ink. The ink may be opaque to hide internal device components from view, but may not always have a desired appearance. The appearance of glass layers in an electronic device can be altered by depositing inorganic layers such as physical vapor deposition (PVD) inorganic layers onto the glass layers. Alternatively or additionally, coatings that include thin-film interference filters and ink layers may be applied to the glass layers. In these coatings, thin-film interference filter layers may be arranged to produce non-neutral colors or to produce neutral colors. The thin-film interference filter layers may be coated with ink such as neutrally colored ink or ink with a non-neutral color. Optional buffer layer material may be included in the coatings. In some configurations, thin-film interference layers may be supported by a polymer film and attached to a transparent glass layer using a layer of adhesive. 
     Challenges arise, however, in ensuring that the deposited layers produce desired optical effects (e.g., desired transmission, opacity, and reflection values at various viewing angles). In some embodiments, it may be desirable to form coatings on transparent layers that shift color at different viewing angles. To ensure that the coatings are viewable at large viewing angles, a surface of the transparent layers may be textured. In this way, light may be transmitted through the transparent layer and reflect off of the coatings at large viewing angles, which may result in a color shift in the reflected light. 
     An illustrative electronic device of the type that may have one or more textured glass structures 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 wristwatch 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, an accessory (e.g., earbuds, a remote control, a wireless trackpad, etc.), or other electronic equipment. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a cellular telephone, media player, tablet computer, or other portable computing device. Other configurations may be used for device  10  if desired. The example of  FIG. 1  is merely illustrative. 
     In the example of  FIG. 1 , device  10  includes a display such as display  14  mounted in housing  12 . Housing  12 , which may sometimes be referred to as an enclosure or case, may be formed of plastic, glass, ceramics, fiber composites, metal (e.g., stainless steel, aluminum, titanium, gold, 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 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 include an array of pixels formed from liquid crystal display (LCD) components, an array of electrophoretic pixels, an array of plasma pixels, an array of organic light-emitting diode pixels or other light-emitting diodes, an array of electrowetting pixels, or pixels based on other display technologies. 
     Display  14  may include one or more layers of glass. For example, the outermost layer of display  14 , which may sometimes be referred to as a display cover layer, may be formed from a hard transparent material such as glass to help protect display  14  from damage. Other portions of device  10  such as portions of housing  12  and/or other structures may also be formed from glass. For example, walls in housing  12  such as a rear housing wall may be formed from glass. 
     A cross-sectional side view of device  10  is shown in  FIG. 2 . As shown in  FIG. 2 , device  10  may have an interior  24  in which electrical components  22  are housed. Electrical components  22  may include integrated circuits, sensors, and other circuitry. As examples, electrical components  22  may form wireless communications circuitry, wireless charging circuitry, processing circuitry, and/or display circuitry, as examples. In general, any desired circuitry may be formed in device  10 . Components  22  may be mounted on one or more printed circuits such as printed circuit  20 . 
     As shown in  FIG. 2 , device  10  may have opposing front and rear faces. Display  14  may be formed on the front face of device  10  and may be covered by a front housing wall  12 FW. Housing  12  may have a rear housing wall  12 RW on the opposing rear face of device  10 . Portions of housing  12  may also form sidewalls  12 SW for device  10 . These sidewall portions of housing  12  may be formed from a material such metal, may be formed from a glass substrate layer, may be formed from the same layer as rear housing wall  12 RW, and/or may be formed from the same layer as front housing wall  12 FW, as examples. 
     Display  14  may include a display cover layer (e.g., a layer of glass) that forms front wall  12 FW of housing  12  and may include display module  18  (e.g., display layers that form an array of pixels that present images for a user on the front face of device  10 ). Display module  18  may be a liquid crystal display structure, an organic light-emitting diode display structure, or other suitable display. During operation, module  18  may present images that are viewable through front housing wall  12 FW. The rear of the housing for device  10  may be formed from a glass structure (e.g., rear housing wall  12 RW may formed from a glass layer). The thickness of rear housing wall  12 RW may be 0.2-5 mm, at least 0.05 mm, at least 0.1 mm, at least 0.2 mm, at least 0.5 mm, at least 0.75 mm, less than 1 mm, less than 2 mm, or other suitable thickness. If desired, a metal plate or other strengthening structures may be laminated to portions of the inner surface of rear housing wall  12 RW and/or sidewalls  12 SW to enhance strength. 
     Inactive border areas in front housing wall  12 FW and portions of other glass structures in device  10  such as some or all of rear housing wall  12 RW and/or sidewalls  12 SW may be covered with coatings and other structures. In some arrangements, a coating may be used primarily to block light (e.g., to hide internal device structures from view). For example, a coating may be formed on the inner surface of rear housing wall  12 RW to hide internal components from view from a user. In other arrangements, a patterned coating may be used to form text, logos, trim, and/or other visible patterns. Coatings that are unpatterned and that coat all of rear housing wall  12 RW and/or sidewalls  12 SW may also be used to block internal structures from view and/or to provide device  10  with a desired appearance. Patterned coatings may create visible elements and may also block internal structures from view. 
     Coatings for glass structures in device  10  may be black or other neutral colors or may have non-black (non-neutral) colors (e.g., blue, red, yellow, gold, rose gold, red-violet, pink, etc.). In some configurations, some or all of the coatings for glass structures in device  10  may be shiny (e.g., exhibiting a mirror-like reflective surface with a reflectance of at least 50%, at less 80%, at least 95%, less than 99.99%, or other suitable reflectance). 
     If desired, a coating may be formed on one or more layers that have textured regions. In particular, glass forming rear housing wall  12 RW, sidewalls  12 SW, and/or front wall  12 FW may be have surfaces facing exterior  26  that are completely textured, partially textured, or untextured. If desired, these layers may have internal surfaces that are coated with inks, physical vapor deposition (PVD) layers, and/or thin-film interference filter coatings. These coatings and the texture on the glass layers may be tuned to appear neutral (e.g., exhibit a neutral color) at low viewing angles (e.g., head-on viewing angles) and non-neutral (e.g., exhibit a non-neutral color) at high viewing angles (e.g. grazing angles). In this way, a combination of texture on glass housing surfaces and underlying coating layers may be used to provide color-shifting properties on an electronic device housing. 
     Coatings on rear housing wall  12 RW and/or other glass structures in device  10  may be formed from metals, semiconductors, and/or dielectrics. Dielectric materials for the coatings may include organic materials such as polymer layers and/or inorganic materials such as oxide layers, nitride layers, and/or other inorganic dielectric materials. In arrangements in which a shiny surface is desired, a metal coating with a high reflectivity or a thin-film interference filter with dielectric layers (e.g., a stack of dielectric layers of alternating higher and lower refractive index values) may be configured to serve as a mirror coating (reflective coating). Ink coatings may also be incorporated onto the glass structures, if desired. 
       FIG. 3  is a cross-sectional side view of an illustrative transparent layer  30 , such as a glass layer, with a polished front surface  32  and a coating  34  on an opposing rear surface. As an example, transparent layer  30  may form one or more of rear housing wall  12 RW, sidewalls  12 SW, or front housing wall  12 FW of  FIG. 2 . In general, coating  34  may be any desired coating and may include one or more of ink layers, film layers, dielectric layers, thin-film interference filter layers, or other desired layers. 
     As shown in  FIG. 3 , a user  36  may view glass layer  30  from the exterior  26  of device  10 . User  36  may see light  42  that has been emitted from light source  38 , refracted by polished surface  32 , reflected by coating  34  at angle  46 , and been refracted by polished surface  32  to an eye of user  36 . Angle  46  may be measured from normal axis  40  and may be less than 5°, less than 10°, less than 15°, or may be less than 20°, as examples. The refraction of light  42  may be due to a difference in the index of refraction between the air at exterior  26  and glass layer  30 . Air may have a refractive index of approximately 1.0, and layer  30  may have a refractive index of approximately 1.5 or 1.6. However, layer  30  may be formed from different materials and therefore may have a different refractive index. In general, any difference in refractive index between the air and layer  30  may cause refraction when light enters and exits layer  30 . 
     In some cases, it may be desired for a user to view glass layer  30  from a larger angle (e.g., a greater angle when measured from an axis normal to surface  32 ). For example, user  36 ′ may see light  44  that has been emitted from light source  38 ′, refracted by polished surface  32 , reflected by coating  34  at angle  48 , and been reflected by polished surface  32  to an eye of user  36 ′. As shown in  FIG. 3 , angle  48  may be greater than angle  46 , and may be less than 40°, less than 43°, or less than 45°, as examples. Because user  36 ′ is viewing layer  30  at such a large angle, user  36 ′ will receive light that has entered layer  30  at a grazing angle (e.g., a very large angle when measured from an axis normal to surface  32 ). As examples, the grazing angle may be greater than 50°, greater than 55°, greater than 60°, greater than 70°, greater than 80°, or less than 90°. 
     In general, angle  48  may be the maximum angle at which light viewed by a user may be viewed due to polished surface  32  refracting light  44  into layer  30 . The maximum angle may be approximately 43°, for example. In some embodiments, however, it may be desirable to allow light to reflect at larger angles off of coating  34  and be visible to user  36 . An arrangement that allows light to reflect off of coating  34  at larger angles is shown in  FIG. 4 . 
     As shown in  FIG. 4 , transparent layer  30 , which may be a glass layer, for example, may be provided with a textured exterior surface, such as textured surface  54 . User  36  may view glass layer  30  from a grazing angle, such as the grazing angle described above in connection with  FIG. 3 . Due to the textured surface, however, light  44  that is emitted by light source  38  may be scattered by textured surface  54 , which is illustrated by scattered light  50 . Some of the scattered light will enter layer  30  as refracted light  51 , which will be reflected off of coating  34  at angle  52 . Angle  52  may be larger than angle  48  of  FIG. 3 . For example, angle  52  may be greater than 45°, greater than 50°, or greater than 60°. Light reflected by coating  34  may then be scattered by textured layer  54  and be viewed by user  36 . In this way, having a textured surface on layer  30  may allow light reflected by coating  34  at larger angles to be viewed by user  36 . 
     An illustrative coating  34  on layer  30  having textured surface  54  is shown in  FIG. 5 . Textured surface  54  may be defined by semi-spherical or semi-cylindrical bumps, randomly distributed recesses and protrusions (e.g., recesses and protrusions formed through a process such as sand blasting), or may be defined by any other desired texture. Textured surface  54  may have protruding surface structures that are 100 s of nm to 1 micron in height (e.g., at least 100 nm, at least 500 nm, less than 5 microns, less than 1 micron). Surface  54  may have an RMS surface roughness of 100 nm to 2 microns or other suitable value that provides a desired appearance (e.g., a matte appearance). This may be in contrast with polished surfaces or other smooth surfaces, which may have protruding surface features that are less than 5 nm in height, surfaces with features that are less than 50 nm in height, etc.). Smooth surfaces may have an RMS surface roughness of less the RMS surface roughness of the textured surfaces (e.g., an RMS surface roughness of less than 25 nm or other suitable value that provides a desired appearance such as a smooth and potentially reflective appearance). 
     In general, layer  30  may be glass, sapphire, ceramic, or any other desired material. In general, layer  30  may be a transparent layer having any desired haze value. For example, layer  30  may exhibit at least 5% haze, at least 10% haze, at least 20% haze, at least 30% haze, or less than 60% haze. 
     Layer  30  may be coated with coating  34 , which may include optional buffer layer  56 , dielectric layer  58 , optional ink layer  60 , and optional additional layer  64 . Optional buffer layer  56  may be polymer, such as epoxy, polyester, etc. In some embodiments, buffer layer  56  may be formed from a polymer binder with embedded particles, such as silica spheres that control the index of refraction of buffer layer  56  and provide improved adhesion between layers  56  and  30 . However, this is merely illustrative. In general, buffer layer may be formed from any desired material to reduce the stresses applied to layer  30  by underlying layers. 
     Buffer layer  56  may have any desired thickness, such as 1-3 microns, at least 0.5 microns, at least 1 micron, less than 4 microns, or other suitable thickness. In some embodiments, optional buffer layer  56  may be formed to provide protection for layer  30  when underlying layer  58  is applied. 
     Thin-film interference filter  58  may be formed on optional buffer layer  56 , or in the absence of buffer layer  56 , directly on glass layer  30  (e.g., through PVD operations). In some cases, thin-film interference filter  58  may be formed on a polymer layer and attached to glass layer  30 . Thin-film interference filter  58  may include multiple thin-film dielectric layers of alternating high and low indices of refraction. In this way, thin-film interference filter  58  may produce interference effects when light passes into filter  58  from layer  30 . 
     In general, thin-film interference filter  58  may be formed using any desired process. For example, one or more layers of thin-film interference filter  58  may be applied using physical vapor deposition (PVD). It may be desirable to include buffer layer  56  to reduce stress applied to glass layer  30  when thin-film interference filter  58  is applied using PVD techniques. 
     Optional layer  60  may be applied to a lower surface of thin-film interference filter  58 . Layer  60  may be include any suitable coating materials. With one illustrative configuration, layer  60  may include one or more ink layers. The one or more ink layers in layer  60  may be formed from polymer containing colorant such as dye and/or pigment. The colorant may have a neutral color such as white, gray, or black, may have a non-neutral color such as red, blue, green, yellow, gold, or may have another suitable color. 
     Additional optional layers  64  may include support layers, additional thin-film interference layers, or any other desired coating layers. For example, optional layers  64  may include a metal support layer, a dielectric support layer, and/or a metal oxide support layer. 
     The thin-film interference filter layer of  FIG. 5  may be formed from individual layers. As shown in  FIG. 6 , thin-film interference filter  58  may be formed from individual thin-film dielectric layer  62 . Layers  62  may have thicknesses of 0.01-1 micron, at least 0.05 microns, at least 0.1 microns, at least 0.15 microns, less than 1.5 microns, less than 1 micron, etc. Layers  62  may be inorganic dielectric layers (e.g. oxides such as silicon oxide, niobium oxide, titanium oxide, tantalum oxide, zirconium oxide, magnesium oxide, etc., nitrides such as silicon nitride, oxynitrides, and/or other inorganic dielectric materials). Organic dielectric layers (e.g., clear polymer layers) and/or other materials (thin metal films, semiconductor layers, etc.) may also be included in the thin-film stack, if desired. In general, thin-film stack  58  may be formed from any desired number of layers  62  that have any desired individual thicknesses. In this way, thin-film stack  58  may be tuned to have desirable optical properties. 
     In the example of  FIG. 6 , the thin-film stack formed from layers  62  forms thin-film interference filter  58 . Filter  58  may be formed form dielectric materials such as inorganic dielectric layers deposited with physical vapor deposition techniques and may therefore sometimes be referred to as a physical vapor deposition layer, physical vapor deposition coating, or physical vapor deposition stack. Other techniques for forming filter  58  may be used, if desired. 
     Filter  58  may be configured to exhibit high reflectivity (e.g., filter  58  may be configured to form a dielectric mirror that reflects a relatively large amount of light), may be configured to exhibit low reflectivity, may be configured to form a colored (tinted) layer (e.g., by reflecting one or more selected colors of light such as when configuring filter  58  to serve as a bandpass filter, band-stop filter, low pass filter, or high pass filter), and/or may be configured to from a light-blocking layer (e.g., by exhibiting a high opacity). Layers  62  may also be configured to adjust the optical properties (transmission, reflection, absorption) of filter  58  at multiple different values of angle A (e.g., an angle A with respect to surface normal n for filter  58  that is associated with an incident angle of incoming light). For example, filter  58  may be configured to adjust the optical properties of layer  30  and coating  34  at different angles  52  relative to normal axis  40  of  FIG. 4 . 
     Layers  62  may include inorganic materials such as oxides. For example, layers  62  may include one or more silicon oxide layers and one or more niobium oxide layers. Niobium oxide can be deposited consistently using sputtering and may allow filter  58  to exhibit good color control. Other oxides may be used (e.g., one or more tantalum oxide layers  62  may be interspersed with one or more silicon oxide layers in filter  62 , one or more titanium oxide layers  62  may be interspersed with one or more silicon oxide layers, etc.). In some arrangements, higher and lower refractive index materials alternate in the stack of layers forming filter  58 . For example, filter  58  may include alternating niobium oxide layers and silicon oxide layers, may include alternating titanium oxide and silicon oxide layers, or may include alternating tantalum oxide layers and silicon oxide layers. 
       FIG. 7  is a graph containing curves  65 ,  66 , and  68  for respective illustrative reflectivity profiles for filter  58  at a 0° viewing angle (e.g., an angle along normal axis  40  of  FIGS. 3 and 4 ), at a maximum reflection angle for a polished glass layer (e.g., angle  48  of  FIG. 3 ), and at a maximum reflection angle for a textured glass layer (e.g., angle  52  of  FIG. 4 ). 
     The optical characteristics of filter  58  can be tuned (at one or more values of angle A) by adjusting the attributes of layers  62  (e.g., index of refraction, thickness, etc.). The optical properties of filter  58  may also be adjusted by adjusting the number of layers  62  in filter  58 . With one illustrative configuration, the overall thickness of filter  58  is maintained at a relatively low value (e.g., 80-300 nm, less than 3 microns, less than 2 microns, less than 1 micron, at least 0.1 micron) by limiting the thicknesses of each of layers  62  (e.g., to less than 1.5 microns, less than 1 micron, less than 0.5 microns, less than 0.4 microns, etc.) and by limiting the number of layers  62  in filter  58  (e.g., to 2-6, at least 2, at least 3, at least 4, at least 5, fewer than 20, fewer than 14, fewer than 10, fewer than 7, etc.). In general, filter  58  need not be restricted to these configurations and may contain any suitable types of layers  58  and/or may include layers  58  of any suitable thickness, index of refraction, etc. 
     As shown by curve  65 , filter  58  may be tuned such that coating  34  has peak reflectivity at a range of wavelengths. The peak relativity may be at least 60%, at least 70%, at least 80%, or less than 99%, as examples. This range of wavelengths may encompass the entire spectrum of visible wavelengths (e.g., 400-700 nm), may encompass a portion of visible wavelengths, may include infrared wavelengths (e.g., 700-900 nm), and/or may include ultraviolet wavelengths (e.g., 300-400 nm), as examples. 
     Curve  65  may correspond to the wavelengths of light viewed through layer  30  (e.g., light that has entered layer  30 , been reflected by coating  34 , and been refracted out of layer  30 ) at a 0° angle (e.g., along an axis normal to layer  30 ). At higher viewing angles, different wavelengths of light may be reflected. As shown by curve  66 , at a viewing angle such as angle  48  of  FIG. 3 , the reflected light may shift in wavelength toward lower wavelengths. Curve  66  may correspond to light viewed at a maximum reflectivity angle for a glass layer with a polished outer surface, such as glass layer  30  with polished surface  32  in  FIG. 3 . In some embodiments, it may be desired to have a larger maximum shift of reflected wavelengths through layer  30 . For example, it may be desired to have a rear surface of an electronic device appear neutral (e.g., reflect a neutral color) at low angles of view and appear non-neutral (e.g., reflect a non-neutral color) at high angles of view. 
     Curve  68  may correspond to light viewed at a maximum reflectivity angle for a glass layer with a textured outer surface, such as glass layer  30  with textured surface  54  of  FIGS. 4 and 5 . As shown by curve  68 , light reflected through a coated, textured glass layer may shift more toward lower wavelengths at higher angles of view than the maximum shift allowed by a coated, polished glass layer. In this way, coating  34  may appear neutral at a 0° viewing angle, and may appear non-neutral at a grazing viewing angle through a textured glass layer. In the example of  FIG. 7 , coating  34  may appear neutral on-axis and blue off-axis, as examples. However, this is merely illustrative. The texture of surface  54  may be adjusted to change the maximum angle of reflectance at filter  58 , and the composition of filter  58  (and other layers in coating  34 , if desired) may be adjusted to change the optical properties of the light reflected by the coating at different viewing angles, thereby adjusting its appearance to a user. 
     In some arrangements, it may be desirable for filter  58  to be configured to exhibit a color tint at 0° viewing angles (rather than being neutral at on-axis viewing angles). For example, it may be desirable for filter  58  to reflect red light so that the coated, textured glass layer appears pink or to reflect light that provides filter  58  with a gold appearance in reflection. 
     The apparent color of filter  58  (e.g., light reflected off of filter  58 ) may be characterized by a color in CIELAB color space (also referred to as LAB color space herein). With one illustrative configuration, thin-film interference filter  58 , operates as a partially reflective mirror (e.g., a mirror of 10-20% reflectivity, or a reflectivity of at least 5%, at least 15%, at least 20%, less than 85%, less than 60%, less than 50%, less than 35%, or other suitable value) and exhibits a neutral color in reflection at on-axis viewing angles (e.g., viewing angles less than 45°, less than 42°, or less than 43°) and a non-neutral color at off-axis viewing angles (e.g., viewing angles less than 45°, less than 42°, or less than 43°. In this configuration, for example, the color of reflected light may be characterized by LAB color coordinates a* and b* (also referred to as color coordinates a and b herein). The square-root of the sum of the squares of color coordinates a and b (e.g., the root sum squared of color coordinates a and b) may be less than 3, less than 2, or less than 1 at on-axis viewing angles, and may be greater than 3, greater than 2, or greater than 1 at off-axis viewing angles. In this way, the reflected light may appear neutral (e.g., reflect a neutral color) on-axis and non-neutral (e.g., reflect a non-neutral color) off-axis. Moreover, the luminance (L coordinate in LAB color space), may change less than 5%, less than 15%, less than 25%, or more than 10% over viewing angles between 0° and 75°. 
     Although illustrated in  FIG. 7  to be reflective of a range of wavelengths (e.g., a range of visible light wavelengths, infrared light wavelengths, and/or other desired wavelengths), filter  58  may have any desired reflectivity profile. 
     As shown in  FIG. 8 , coating  34  and/or filter  58  may have a reflectivity profile (or a portion of a reflectivity profile) corresponding to curve  70 . In an embodiment, curve  70  may represent filter  58  being a band stop filter (e.g., reflecting light at a desired range of wavelengths). Band stop filter  58  may exhibit a band-width  72  defined as a full-width half-max band-width, a 10%-90% band-width, or any other desired band-width of at least 5 nm, at least 10 nm, at least 15 nm, at least 25 nm, at least 50 nm, at least 100 nm, of less than 500 nm, or less than 400 nm, as examples. In general, band stop filter  58  may be configured to have any desired band-width  72 . As discussed above in connection with  FIG. 7 , band  70  may cover (e.g., exhibit high reflectivity in) the entire spectrum of visible wavelengths, may cover a portion of visible wavelengths, may cover some or all infrared wavelengths, and/or may cover some or all ultraviolet wavelengths. Additionally, although band stop filter  58  has been illustrated with a single reflectivity peak (e.g., band), band stop filter  58  may include more than one reflectivity peak, if desired. 
     As shown in  FIG. 9 , coating  34  and/or filter  58  may have a reflectivity profile (or a portion of a reflectivity profile) corresponding to curve  74 . In an embodiment, curve  74  may represent filter  58  being a band pass filter (e.g., passing/transmitting light at a desired range of wavelengths). Band pass filter  58  may exhibit a band-width  76  defined as a full-width half-max band-width, a 10%-90% band-width, or any other desired band-width of at least 5 nm, at least 10 nm, at least 15 nm, at least 25 nm, at least 50 nm, at least 100 nm, of less than 500 nm, or less than 400 nm, as examples. In general, band pass filter  58  may be configured to have any desired band-width. Band  74  may cover (e.g., exhibit low reflectivity/high transmission in) the entire spectrum of visible wavelengths, may cover a portion of visible wavelengths, may cover some or all infrared wavelengths, and/or may cover some or all infrared wavelengths. Additionally, although band pass filter  58  has been illustrated with a single transmission peak (e.g., band), band pass filter  58  may include more than one transmission peak, if desired. 
     Although the reflectivity profiles of filter  58  have been shown as band pass and band stop filters with sharp changes in reflectivity in  FIGS. 8 and 9 , this is merely illustrative. As shown in  FIG. 10 , filter  58  may exhibit a reflectivity profile illustrated by curve  78 . As shown, filter  58  may have a peak reflectivity profile similar to a band stop filter, but may have a more gradual transition than the one shown in  FIG. 8 . The reflectivity of filter  58  may have a width  80  defined as a full-width half-max width, a 10%-90% band-width, or any other desired band-width of at least 5 nm, at least 10 nm, at least 15 nm, at least 25 nm, at least 50 nm, at least 100 nm, of less than 500 nm, or less than 400 nm, as examples, and may cover the entire spectrum of visible wavelengths, may cover a portion of visible wavelengths, may cover some or all infrared wavelengths, and/or may cover some or all infrared wavelengths. 
     While the reflectivity profile of  FIG. 10  has been shown as having a single reflectivity peak, this is merely illustrative. In general, the reflectivity profile may have two or more, three or more, or fewer than 5 peaks at any desired wavelengths. Moreover, filter  58  may also have more gradually changing reflectivity profiles that transmit selected wavelengths (e.g., similar to the band stop filter of  FIG. 9 , but with more gradually changing reflectivity), and may have both reflectivity peaks and transmission peaks, if desired. 
     In embodiments in which coating  34  is provided with ink layer  60 , the reflectivity of ink layer  60  may also be adjusted to change a color reflected through a transparent layer, such as layer  30  of  FIGS. 3-5  to a viewer  36 . In general, ink  60  may have any desired reflectivity profile. 
     As shown in  FIG. 11 , ink  60  may exhibit reflectivity profile  82 , which may correspond to a neutral reflectivity profile. In particular, ink  60  may reflect a constant (or nearly constant) amount of light across visible wavelengths, and may appear black, gray, white, or other neutral color. 
     As shown in  FIG. 12 , ink  60  may exhibit reflectivity profile  84 , which may correspond to an ink that reflects a desired color (e.g., a color that corresponds to wavelength λ M ). For example, if λ M  is approximately 540 nm, the ink may be a green ink. However, in general, λ M  may be any desired wavelength. As shown in  FIG. 12 , reflectivity profile  84  may cover a range of wavelengths, and may have a width  86  defined as a full-width half-max width, a 10%-90% band-width, or any other desired band-width of at least 5 nm, at least 10 nm, at least 15 nm, at least 25 nm, at least 50 nm, at least 100 nm, of less than 500 nm, or less than 400 nm, as examples. 
     Although reflectivity profile  84  of ink  60  has been illustrated as having a single reflectivity peak in  FIG. 12 , this is merely illustrative. As shown in  FIG. 13 , for example, ink  60  may exhibit reflectivity profile  88  and have multiple reflectivity peaks (e.g., reflect light at multiple wavelengths). Each peak of reflectivity profile  88  (as well as each transmission peak in the regions between the reflectivity peaks) may be defined by a width as described above in connection with  FIG. 12 . 
     In general, the peak reflectivity and width  86  of reflectivity profile  84  may be selected to tune the optical properties of ink  60 , and thereby adjust the optical properties of coating  34 , as desired. For example, if ink layer  60  is formed from white material or other brightly colored material, ink layer  60  may help reflect light that has been transmitted through transparent layer  30  outwardly towards viewer  36 . When ink layer  60  is black, light transmitted through layer  30  may be absorbed, so that the color of the light reflected from filter  58  towards viewer  36  dominates. Gray ink reflects some but not all of the light that has been transmitted through layer  30 . In configurations in which ink  60  has a non-neutral color (e.g., red, green, blue, yellow, gold, etc.), the color of coating  34  will be tinted accordingly. In this way, thin-film interference filter  58  and ink layer  60  may be selected to provide desired coloring of light that passes through layer  30 . However, these examples are merely illustrative. In general, any desired ink  60  may be used in combination with any desired filter  58  to produce desired optical effects. 
     An example of using filter  58  and ink  60  in combination to produce desired optical effects is shown in  FIG. 14 . As shown in  FIG. 14 , filter  58  may be a band pass filter with reflectivity profile  88  when viewed on-axis (e.g, at a 0° viewing angle or other on-axis angle). The pass band of reflectivity profile  88  may be aligned with a peak of reflectivity profile  90  of ink  60  when viewed on-axis. As a result, the overall coating  34  (e.g., filter  58  and ink  60 ) may reflect a neutral color and appear neutral when viewed on-axis. 
     When viewed off-axis (e.g., at a grazing angle such as 80° or other desired angle as shown in  FIGS. 3 and 4 ), the reflectivity profile of ink  60  may shift, as shown by reflectivity profile  92 . When the pass band shifts to lower wavelengths, it may no longer be aligned with the peak reflectivity of ink  90 , thereby allowing wavelengths aligned with the pass band to pass through filter  58 , and reflecting a non-neutral complementary color to a viewer of coating  34 . For example, reflectivity profile  92  may shift to blue wavelengths at high viewing angles, allowing blue light to pass through filter  58 , and coating  34  may therefore appear red to a viewer. However, these colors are merely illustrative. In general, any the pass band of reflectivity profile  92  may be allow any desired light to pass through filter  58 . 
     Alternatively, filter  58  may have a reflectivity profile corresponding to curve  94  when viewed on-axis. Curve  94  may have a pass band that is not aligned with the reflectivity peak of ink  60  at on-axis viewing angles. For example, the pass band may be aligned with red wavelengths, thereby allowing red light to pass through filter  58 , and coating  34  may therefore appear blue to a viewer. When viewed at high angles, however, the pass band may shift to curve  88  and be aligned with the reflectivity peak of ink  60 , and coating  34  may therefore appear neutral to a viewer. Alternatively, the pass band may shift to curve  92  at high viewing angles, and coating  34  may therefore appear red to a user. In one embodiment, filter  58  may be configured to shift from reflectivity profile  94  when viewed on-axis, to reflectivity profile  88  when viewed at moderate angles, and to reflectivity profile  92  when viewed at higher angles. In this way, coating  34  may be designed to appear blue on-axis, neutral at moderate angles, and red off-axis. However, the colors mentioned in these examples are merely illustrative. In general, reflectivity profiles  90 ,  92 , and  94  may be aligned with any desired wavelengths, and ink  60  may have absorptivity peaks at any desired wavelengths, to provide coating  34  with desired color-shifting properties. 
     While  FIG. 14  shows ink  60  having an absorptivity peak aligned with a pass band of filter  58 , this is merely illustrative. In some embodiments, a filter may be provided that reduces reflectivity at all wavelengths when viewed at high angles. 
     As shown in  FIG. 15 , filter  58  may have an absorptivity profile  96  when viewed on-axis, which may shift to absorptivity profile  98  when viewed off-axis. While absorptivity profile  96  reflects light across the visible spectrum (e.g., from 400-700 nm) to some degree, absorptivity profile  98  reflects less light at all visible wavelengths. In this way, any ink  60  provided behind filter  58  may be more visible when viewed at high angles, causing a color associated with ink  60  to become more noticeable at higher angles. Therefore, any color may be used for ink  60  to impart that color to a user at high angles. 
     In some embodiments, it may be desired to form filter  58  as a band stop filter. As shown in  FIG. 16 , filter  58  may exhibit reflectivity profile  100  when viewed on-axis. Reflectivity profile  100  may have a stop band at desired wavelengths (e.g., wavelengths greater than λ x ). In some embodiments, the stop band of reflectivity profile  100  may be in the infrared range (e.g, in the range of 700-900 nm). In this case, filter  58  may not reflect light when viewed on-axis and therefore appear neutral. However, when viewed off-axis, filter  58  may exhibit reflectivity profile  102 , which may reflect light in the visible spectrum. For example, reflectivity profile  102  may have a stop band in red wavelengths, thereby appearing red to a viewer. However, this is merely illustrative. In general, band stop filters may be used at any desired wavelengths to provide any desired color-shift. 
     Although the embodiment of  FIG. 16  does not show an absorptivity profile for ink  60 , coating  34  may be provided with or without ink when filter  58  has a stop band at infrared wavelengths. For example, in some embodiments, ink  60  may be used to impart a color on coating  34  at on-axis viewing angles and to impart a different color at off-axis viewing angles when filter  58  reflects an additional color. 
     An example of reflectivity profiles of coating  34  having a filter  58  having multiple reflectivity peaks (e.g., stop bands) and ink  60  with multiple reflectivity peaks is show in  FIG. 17 . 
     As shown in  FIG. 17 , filter  58  may have a reflectivity profile with peaks (e.g., stop bands)  104 ,  106 , and  108  when viewed on-axis. Each of these peaks may correspond to different reflectivity values, as illustrated in  FIG. 17 , or at least some of the peaks may have the same reflectivity values. Although peak  104  has a greater reflectivity than peak  106 , which in turn has a greater reflectivity than peak  108 , this is merely illustrative. In general, the reflectivity profile of filter  58  may have any number of reflectivity peaks that correspond to any desired reflectivity values. 
     Ink  60  may have multiple reflectivity peaks when viewed on-axis, as well. As shown in  FIG. 17 , ink  60  may have stop bands  110 ,  114 , and  118 . Some stop bands such as stop bands  110  and  118  may be aligned with peaks in the reflectivity profile of filter  58 , such as peaks  104  and  108 . Other reflectivity peaks of ink  60 , such as peak  114 , may be aligned with portions of the filter absorptivity profile having higher transmission (e.g., pass bands). As a result, filter stop bands, such as stop band  106  may align with highly transmissive portions of the ink profile, such as portion  112 . Alternatively or additionally, transmissive ink portions, such as portion  106  may overlap with a pass band of the filter. However, the examples shown in  FIG. 17  are merely illustrative. In general, the stop bands and pass bands corresponding to filter  58  may align with reflectivity peaks and/or transmission peaks of ink  60  in any desired manner to provide desired optical properties of coating  34 . 
     Layer  30  having coating  34  may form a portion of housing  12 , as shown in  FIGS. 2 and 3 . In particular, as shown in  FIG. 18 , layer  30  may have a top portion that forms an exterior portion of housing  12  (e.g., the outer surface of layer  30 , which may be textured, faces exterior  26 ). Additionally, layer  30  may have an opposing inner surface to which coating  34  may be applied. Between the outer surface and inner surface, layer  30  may have an edge surface  120  that is exposed to exterior  26  of device  10 . In particular, it may be desirable to leave edge surface uncovered and viewable to a user. In some cases, the texture of layer  30  (e.g., textured surface  54 ) and coating  34  may be tuned such that high angle light exits layer  30  through edge surface  120 , and may therefore create a glowing effect at the edge surface. 
     Although not shown, the outer surface of layer  30  (e.g., textured surface  54 ) may be coated with any desired layers. These layers may be protective layers, oleophobic layers, and/or antireflection layers, as examples. 
     In some embodiments, portions of layer  30  may have different thicknesses. As shown in  FIG. 19 , for example, layer  30  may have a first portion with thickness H 1  and a second portion with thickness H 2  that is greater than thickness H 1 . As a result, layer  30  may have outer surfaces  122 ,  124 , and  126 , as well as edge surface  120 . In one embodiment, surfaces  124  and  126  (e.g., the planar outer surfaces) may be textured, while surface  122  (e.g., the tapered outer surface) may be polished. These surfaces, combined with coating  34 , may result in glowing effects at edge surface  120  and surface  122  when viewed at high angles. However, this arrangement is merely illustrative. In general, layer  130  may have any number of surfaces that are fully textured, partially textured, untextured, or polished to provide desired optical effects. 
     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: 20200414
Publication Date: 20220920
Grant Date: 20220920
Priority Date: 20190730
Inventors: WILSON, JAMES R.
ROGERS, MATTHEW S.
Assignee: APPLE INC
CPC Classifications: [{"code": "G02F1/133504", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/0268", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/0221", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02F1/133331", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/288", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/0221", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B5/288", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/288", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/0268", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02F1/133314", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/28", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B5/281", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/0268", "inventive": true, "first": false, "tree": "[]"}, {"code": "G02B5/0221", "inventive": true, "first": true, "tree": "[]"}, {"code": "G02B5/288", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 74260299