Patent Publication Number: US-2022232698-A1

Title: Patterned Glass Layers in Electronic Devices

Description:
This application is a continuation of U.S. patent application Ser. No. 16/922,871, filed Jul. 7, 2020, which is a continuation of U.S. patent application Ser. No. 16/680,312, filed Nov. 11, 2019, now U.S. Pat. No. 10,757,805, which is a continuation of U.S. patent application Ser. No. 16/375,635, filed Apr. 4, 2019, now U.S. Pat. No. 10,537,023, which is a continuation of U.S. patent application Ser. No. 15/841,117, filed Dec. 13, 2017, now U.S. Pat. No. 10,292,286, which claims the benefit of provisional patent application No. 62/539,454, filed Jul. 31, 2017, each of which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND 
     This relates generally to electronic devices, and, more particularly, to forming visually distinguishable regions in glass structures in electronic devices. 
     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. 
     SUMMARY 
     An electronic device may include electrical components and other components mounted within an interior of a housing. The device may have a display on a front face of the device and may have a glass layer that forms a rear housing wall on an opposing rear face of the device. 
     The rear housing wall may be provided with regions having different appearances. The regions may be selectively textured, may be selectively provided with coatings such as thin-film interference filter coatings formed from stacks of dielectric material having alternating indices of refraction, metal coating layers, and/or ink coating layers, and/or may be provided with other structures that visually distinguish regions from each other. 
     A region of the rear housing wall may have a matte appearance formed from a textured surface. Textured surfaces may be formed directly on the glass layer and/or textured surfaces may be formed on thin glass layers and polymer films that are coupled to the glass layer. 
     A glass layer may be formed form a pair of coupled glass layers. The coupled layers may have one or more recesses or other structures to visually distinguish different regions of the glass layer. 
    
    
     
       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 in accordance with an embodiment. 
         FIG. 3  is a rear view of an illustrative electronic device in accordance with an embodiment. 
         FIG. 4  is a cross-sectional side view of an illustrative glass layer with a textured region and a smooth region overlapped by a coating on an outer surface of the glass layer in accordance with an embodiment. 
         FIG. 5  is a cross-sectional side view of an illustrative glass layer with an outer surface having a textured region and a smooth region and having an inner surface with a coating that overlaps the smooth region in accordance with an embodiment. 
         FIG. 6  is a cross-sectional side view of an illustrative glass layer with an inner film with textured regions in accordance with an embodiment. 
         FIG. 7  is a cross-sectional side view of an illustrative glass layer covered with a textured thin glass layer and multiple coatings interposed between the thin glass layer and an outer surface of the glass layer in accordance with an embodiment. 
         FIG. 8  is a cross-sectional side view of an illustrative glass layer with an outer surface covered with a layer such as a thin glass layer and an interposed coating in accordance with an embodiment. 
         FIG. 9  is a cross-sectional side view of an illustrative glass layer coated with multiple selectively textured layers in accordance with an embodiment. 
         FIG. 10  is a cross-sectional side view of an illustrative glass layer with a textured coated film attached to the glass layer with an interposed layer of adhesive in accordance with an embodiment. 
         FIG. 11  is a cross-sectional side view of an illustrative glass layer with textured regions formed directly on an outer surface of the glass in accordance with an embodiment. 
         FIG. 12  is a cross-sectional side view of an illustrative glass layer with textured regions formed directly on an inner surface of the glass in accordance with an embodiment. 
         FIG. 13  is a cross-sectional side view of an illustrative glass layer having a textured surface and having a recess with a tapered cross-sectional profile in accordance with an embodiment. 
         FIG. 14  is a cross-sectional side view of an illustrative glass layer formed from a pair of coupled sublayers having overlapping recesses that define a cavity within the glass layer in accordance with an embodiment. 
         FIG. 15  is a cross-sectional side view of an illustrative glass layer with visible internal structures such as laser-damaged regions embedded within the glass layer in accordance with an embodiment. 
         FIG. 16  is a cross-sectional side view of an illustrative glass layer with a coating having particles such as glass particles in accordance with an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Electronic devices and other items may be provided with structures that are formed from transparent materials. For example, an electronic device may include a display. The display may have an array of pixels for displaying images for a user. To protect the pixel array from damage, the display may be covered with a layer of transparent material that serves as a display cover layer. The transparent material may be ceramic, polymer, crystalline material such as sapphire, or other suitable transparent material. Configurations in which such layers are formed from glass are sometimes described herein as an example. Portions of electronic devices such as optical windows, buttons, housing walls (e.g., rear housing walls), and other structures other than display cover layers may also be formed from ceramic, polymer, crystalline material such as sapphire, and/or glass and may be clear or may be colored. For example, the rear face of an electronic device may be covered with a layer of glass that forms a rear housing wall. 
     It may be desirable to locally and/or globally modify the appearance of a layer of glass (or other layer of material) in an electronic device. For example, it may be desirable to create attractive trim around a display, around the periphery of a camera window or button, or other suitable location. In some arrangements it may be desirable to selectively modify the appearance of a glass layer or other structure to form text, graphical patterns such as icons, logos, and/or other patterns visible to a user. 
     When creating structures such as these, there is a potential for unattractive features to develop on the glass layer. For example, if care is not taken, undesired shadowing may occur or surfaces may appear to sparkle excessively. 
     These concerns can be addressed by forming visually distinguishable areas on the glass layer (e.g., visually distinguishable regions for forming logos, text, etc.) using textured areas, neutrally colored or non-neutrally colored reflective coatings formed from a stack of alternating high and low index-of-refraction dielectric layers or other thin-film interference filter coatings (sometimes called dichroic layers or decoration layers), ink layers, adhesive layers, and/or other structures that selectively and/or globally impart visible changes to glass layers and other layers in an electronic device. 
     An illustrative electronic device of the type that may include 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 (e.g., a watch with a wrist strap), 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. In the illustrative configuration of  FIG. 1 , device  10  is a portable device such as a cellular telephone, media player, tablet computer, wrist device, 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. 
       FIG. 2  is a cross-sectional side view of an illustrative device that contains glass structures such as device  10  of  FIG. 1 . 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 . Housing  12  may have a rear housing wall formed from layer  24  on the opposing rear face of device  10 . Portions of housing  12  may also form sidewalls for device  10 . These sidewall portions of housing  12  may be formed from a material such metal (as an example). 
     Display  14  may include display cover layer  16  (e.g., a layer of glass) and 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 display cover layer  16 . The rear of the housing for device  10  may be formed from a glass structure (e.g., layer  24  may be a glass layer). The thickness of layer  24  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 the inner surface of layer  24  to enhance strength. Internal components in device  10  such as components  22  (e.g., electrical components such as integrated circuits, sensors, etc.) may be mounted on one or more substrates such as printed circuit  20 . 
     Inactive border areas in layer  16  and portions of other glass structures in device  10  such as some or all of glass layer  24  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 layer  24  to hide internal components from view from a user such as viewer  26  who is viewing device  10  in direction  28 . 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 glass layer  24  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). Textured features may also be formed. 
     If desired, a coating may include one or more layers that define textured regions on a layer such as glass layer  24  that are interspersed with smooth and shiny regions that are not textured. As an example, a logo may be formed form a shiny region and may be surrounded by a matte textured region. Textured and shiny regions may be formed from textured and/or reflective surfaces on glass layer  24  and/or on one or more layers coupled to glass layer  24 . For example, textured and/or shiny regions may be formed from textured and/or shiny films that are adhered to glass layer  24 . Textured and shiny regions may also be defined by texturing selected portions of glass layer  24  directly. 
     Coatings on glass layer  24  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. 
       FIG. 3  is a top view of an illustrative configuration for the rear face of device  10  in which one region (region  24 - 1 ) has a first appearance (textured, shiny, a particular color, etc.) and has a first shape (e.g., text, a logo, a trim pattern, or other patterned shape) and in which another region (background region  24 - 2  in this example) has a second appearance (e.g., textured, shiny, a particular color, etc.). In order to ensure that region  24 - 1  is visible to a user of device  10 , the appearances of regions  24 - 1  and  24 - 2  may contrast with each other. For example, in a scenario in which region  24 - 1  is reflective (e.g., in which region  24 - 1  is a shiny silver or gold region associated with a logo, text, etc.), region  24 - 2  may have a matte finish. 
     Glass layer  24  may have any suitable number of separately patterned regions such as regions  24 - 1  and  24 - 2 , each of which may potentially have a different separate appearance. Configurations in which glass layer  24  has one or more patterned layers that provide textured and shiny regions may sometimes be described herein as an example. The regions of device  10  that have different appearances may be formed by selectively patterning glass layer  24  and associated coatings, films, and other structures. For example, these regions may be selectively formed by depositing coatings using physical vapor deposition, chemical vapor deposition, or other deposition techniques followed by photolithography and etching, using shadow-masking or other selective deposition techniques such as printing techniques, by using selective surface treatment such as selective laser treatment, selective roughening or polishing using mechanical or chemical-mechanical polishing equipment, selective treatment with machining equipment, sand-blasting equipment or blasting equipment using other particles, by roughening or otherwise processing the surfaces of polymer films using embossing tools, presses, and/or by using other equipment for selectively processing particular areas of coatings, films, and/or surfaces (e.g., glass layer surfaces). 
     Textured surfaces in layer  24  and/or in coatings, films, and/or other layers coupled to layer  24  may provide a matte finish. These textured surfaces may have protruding surface structures that are 100s 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). Such textured surfaces 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). Smooth surfaces (e.g., polished surfaces or other smooth surfaces) 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.). Such 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 potentially reflective appearance). If desired, regions of the rear housing wall of device  10  or other glass-layer structures may have other roughness values (e.g., values intermediate to those associated with strongly textured matte finishes and smooth reflective finishes). The use of textured and smooth surfaces to form visually distinct regions of glass layer  24  is merely illustrative. 
       FIGS. 4-16  set forth various examples of patterned regions on a structure in device  10  such as a rear housing wall (e.g., glass layer  24 ) that have potentially different visual appearances. These regions may be used in forming logos, text, trim, and/or other patterns. There may be any suitable number of patterned regions on layer  24  and these layers may include textured backgrounds and smooth backgrounds, textured foregrounds and smooth backgrounds, background and foreground elements of different colors, reflectivity values, etc. Coatings may be provided on the outer surface of these illustrative patterned regions (e.g., antismudge coatings, antiscratch coatings, etc.) or, if desired, these external coating layers may be omitted and/or incorporated into the coatings, films, and surfaces forming layer  24 . The examples of  FIGS. 4-16  are merely illustrative. 
       FIG. 4  is a cross-sectional side view of glass layer  24  in an illustrative configuration in which the outer surface of layer  24  has a textured region and a coated region such as a smooth shiny region. The textured region is visually distinguishable from the smooth region because the surface roughness of the textured region is larger than that of the smooth region and therefore may provide the textured region with a matte appearance. Glass layer  24  may have opposing inner and outer surfaces such as inner surface  32  and outer surface  30 . Inner surface  32  may face internal device components such as components  22  of  FIG. 1  in the interior of housing  12  and device  10 . Outer surface  30  may face a user of device  10  such as viewer  42  who is viewing device  10  in direction  44  from the exterior of device  10 . 
     In the example of  FIG. 4 , inner surface  32  is smooth and is coated by inner coating layer  34 . Coating layer  34  may be a global layer that covers all of the inner surface of layer  24  (as an example). Outer coating layer  36  may be formed on region  40  of outer surface  30 . Region  38  of outer surface  30  may be textured and may, if desired, surround region  40 . Coatings  36  and  34  may include one or more sublayers (see, e.g., illustrative sublayers  46  of coating  34 ) or may each be formed of only a single layer of material. 
     Coatings  36  and  34  may be shiny. For example, a stack of multiple dielectric sublayers in coating  36  and/or  34  may have alternating index of refraction values to form a thin-film interference filter or coating  36  and/or coating  34  may include a reflective material such as metal. The texture of outer surface  30  in region  38  may provide glass layer  24  with a pleasing feeling to the touch. Coating  36  in region  40 , which may be a physical vapor deposition coating deposited through a shadow mask or other patterned layer, may be shaped to form text, a logo, or other visual element and may have a different appearance than textured outer surface  30  in region  38 . Coating  34  may help hide internal components from view by blocking light transmission into the interior of device  10 . If desired, coating  34  may be formed from an opaque material such as neutrally colored (white, black, or gray) or non-neutrally colored (red, blue, yellow, etc.) ink. 
     In the illustrative configuration of  FIG. 5 , coating  36  in region  40  has been formed on inner surface  32  of glass layer  24 . Outer surface  30  is smooth in region  40  and textured in region  38 . This approach protects coating  36  under glass layer  24 . 
       FIG. 6  is a cross-sectional side view of an illustrative glass layer to which a layer of film with textured regions has been attached. As shown in  FIG. 6 , film  48  (e.g., a flexible polymer sheet) may have a smooth surface that is attached to inner surface  32  of glass layer  24 . Film  48  may be attached directly to surface  32  or may be attached to surface  32  with an intervening layer of adhesive. Film  48  may have an inner surface that is textured in region  38  and that is smooth in region  40 , so that regions  38  and  40  have respective matte and shiny appearances. Film  48  may be covered with polymer layer  50 . Polymer layer  50  may have a lower index of refraction than film  48  and may be covered with coating  52 . Coating  52  may be formed from ink or a shiny material such as metal. If desired, coating  52  may be a shiny coating formed from a thin-film interference filter with high reflectively. 
     In the example of  FIG. 7 , layer  54  may be a polymer film or may be a thin glass layer that is thinner than glass layer  24  (e.g., at least 3 times thinner, at least 7 times thinner, at least 10 times thinner, at least 20 times thinner, etc.). The use of glass as an outer layer on top of glass layer  24  may help reduce scratches. In configurations in which glass is used, the thickness of layer  54  may be relatively thin to enhance the appearance of the logo or other pattern formed by region  40 . Layer  54  may, if desired, be a thin glass layer with at thickness of 20-250 microns, at least 30 microns, at least 100 microns, at least 150 microns, less than 200 microns, less than 500 microns, or less than 800 microns. Thin glass layer  54  may have an outer surface that is textured in region  38  to provide region  38  with a matte appearance that is smooth in region  40  or textured region  38  may be formed from a textured surface on the inner surface of layer  54 . 
     As shown in  FIG. 7 , the inner surface of layer  54  may be selectively coated with first coating layer  56  in region  40  (e.g., a patterned coating layer). A second coating layer such as blanket coating layer  58  may be used to cover coating layer  56 . Coatings  56  and  58  may provide an attractive appearance (e.g., a shiny appearance with a desired color, reflectivity, etc.). Coatings  56  and  58  may be formed from dielectric thin-film interference filters (e.g., stacks of alternating high and low index-of-refraction materials), may be formed from metal, and/or may be formed from other materials (e.g., ink). Because coating layer  56  is present only in region  40  and not in region  38 , the presence of coating layer  56  will help to visually distinguish regions  38  and  40 . If desired coating  56  may be omitted and/or coating  58  may be omitted or coating  58  may be selectively omitted from region  40  and not region  38 . Optically clear adhesive  60  may be used in attaching film  54  and coatings  56  and  58  to outer surface  30  of layer  24 . If desired, coating  56  (e.g., a thin-film interference filter, metal coating layer, and/or ink layer) may be formed on inner surface  32  of glass layer  24  instead of on the inner surface of film  54 , as illustrated by coating  56 ′. In other configurations, both coatings  56  and  56 ′ may be used. 
       FIG. 8  is a cross-sectional side view of glass layer  24  in an illustrative configuration in which a thin glass layer with a textured inner surface has been coupled to outer surface  30 . As shown in  FIG. 8 , thin glass layer  66  (e.g., a glass layer with at thickness of at least 30 microns, at least 100 microns, at least 150 microns, less than 200 microns, less than 500 microns, or less than 800 microns that is at least 3 times thinner, 7 times thinner, 10 times thinner, 20 times thinner, etc. than layer  24 ) may have a textured inner surface in region  38  to provide region  38  with a matte appearance. The inner surface of thin glass layer  66  may be smooth in region  40 . Coating layer  64  (e.g., a dielectric thin-film interference coating, a metal thin-film coating, or other material such as ink) may be formed on the inner surface of layer  66 . If desired, other patterned coatings such as coating  64  may be provided, as described in connection with the multiple coatings on layer  54  of  FIG. 7  (e.g., only in region  38 , only in region  40 , or overlapping both regions  38  and  40 ). Optically clear adhesive  62  may be used to attach layer  66  and coating layer  64  to outer surface  30  of layer  24 . 
     If desired, chemical strengthening may be used to strengthen thin-glass layers such as layer  54  of  FIG. 7  or layer  66  of  FIG. 8 . In other configurations, thin-glass layers such as layer  54  and layer  66  may be replaced by a layer of polymer with textured regions and smooth regions. 
     In the example of  FIG. 9 , layer  72  has an outer surface with texture in region  38 . The inner surface of layer  72  may be textured in region  38  and region  38 ′. As a result, textured region  38  will have an appearance that is more matte than the appearance of textured region  38 ′. Layer  72  may be formed from a thin glass layer (see, e.g., layer  54  of  FIG. 7  and layer  66  of  FIG. 8 ) or a sheet of polymer. Coating layer  70  may be formed on the inner surface of layer  72  and optically clear adhesive layer  68  may be used in attaching layer  72  and coating  70  on layer  72  to outer surface  30 . Coating layer  70  may be a thin-film interference filter, metal layer, or ink layer. There is no texture on layer  72  or coating  70  in region  40 , so region  40  will not have a matte appearance. Because region  38  and region  38 ′ have different appearances, regions  38  and/or  38 ′ may be provided with the shapes of text, logos, trim patterns, and/or other patterns and may be visually distinguished by viewer  42 . 
     Another illustrative arrangement is shown in  FIG. 10 . As shown in  FIG. 10 , inner surface  32  of glass layer  24  may be textured to provide an overall matte appearance to layer  24 . Coating layer  74  (e.g., a thin-film interference filter coating, metal coating, and/or ink coating) may be used to help block internal components from view by user  42 . Layer  80  (e.g., a polymer film or a thin glass layer) may have an outer surface that is textured in region  38  to enhance the matte appearance of glass layer  24  in region  38 . In region  40 , the outer surface of layer  80  may be smooth. Coating layer  78  may be selectively formed in region  38  on the inner surface of layer  80  to adjust color, reflectivity, and/or other optical characteristics in region  38  relative to region  40 . Optically clear adhesive  76  may be used in attaching layer  80  to outer surface  30  of layer  24 . 
     In the illustrative configuration of  FIGS. 11 and 12 , a first texture is formed in region  38  and a second texture (e.g., a texture for a logo, text, or other pattern) or no texture is formed in region  40 . Coating layer  82  (e.g., a thin-film interference filter coating, metal coating, and/or ink coating) may be formed on inner surface  32 . In the example of  FIG. 11 , outer surface  30  of glass layer  24  is textured (e.g., with a first texture in region  38  and a different second texture or no texture in region  40 ). In the example of  FIG. 12 , inner surface  32  of glass layer  24  is selectively textured in this way. 
       FIG. 13  shows how inner surface  32  of glass layer  24  may have a recess (e.g., a recess with sloped sidewalls, vertical sidewalls, or other sidewall profile). Protruding layer  88  (e.g., a glass or polymer layer with a thickness T of about 50-150 microns, at least 75 microns, fewer than 500 microns, etc.) may have a protrusion that is placed in the recess in inner surface  32  and that has a shape that mates with this recess. An optional layer such as layer  91  (e.g., a thin-film interference filter coating, metal coating, and/or ink coating and/or a layer of adhesive) may be interposed between layer  88  and layer  24 . 
     In the example of  FIG. 14 , glass layer  24  has been formed from mating first and second layers such as outer layer  24 A and inner layer  24 B. Inner surface  32 ′ of outer layer  24 A and/or outer surface  30 ′ of inner layer  24 B may be provided with recesses, protrusions, and/or other non-planar portions to create visual contrast between regions  38  and  40 . For example, inner surface  32 ′ may have recess  90  and outer surface  30 ′ may have a fully or partly overlapping recess such as recess  92  (e.g., a mating recess). The inner surfaces of recesses  90  and  92  may, if desired, be provided with respective coating layers  94  and  96  (e.g., thin-film interference filter coatings, metal coatings, and/or ink coatings). Recesses  90  and  92  may be filled with air, a liquid, a polymer, a glass insert or an insert formed from other material, and/or other material. Outer layer  24 A and inner layer  24 B may be coupled using adhesive  98 . In some configurations, recess  90  or recess  92  may be omitted. Glass layer  24  may also be formed only from layer  24 A and not layer  24 B, if desired. 
     If desired, laser processing techniques may be used to form visible structures on glass layer  24 . For example, high power laser beams may be focused into interior portions of glass layer  24 . This may create laser-damaged regions that are embedded within layer  24 , as shown by laser-damaged portions  100  of  FIG. 15 . Laser processing to form these visible laser-processed structures may take place in region  40  but not region  38  (or vice versa) to provide regions  38  and  40  of glass layer  24  with a visually distinguishable appearance. Optional coating layer  102  (e.g., a thin-film interference filter coating, metal coating, and/or ink coating) may be formed on inner surface  32  of layer  24 . 
     As shown in  FIG. 16 , inner surface  32  of glass layer  24  may be coated with a polymer layer such as layer  106 . Layer  106  may contain particles such as particles  108 . Particles  108  may have a different refractive index than the polymer binder that makes up layer  106  and may have a diameter that is sufficient to give rise to light ray reflection. Particles  108  may, for example, be glass particles having diameters of 20-100 microns, at least 10 microns, at least 30 microns, fewer than 200 microns, etc. and may provide glass layer  24  with a pearlescent appearance. 
     If desired, one or more of the polymer layers of  FIGS. 4-16  coupled to glass layer  24  may be formed from glass rather than polymer and/or one or more of the glass layers coupled to glass layer  24  may optionally be formed from a polymer coating or polymer film. Glass layer  24  may be replaced with a polymer layer or a layer of other material (sapphire or other crystalline material, ceramic, etc.). The illustrative structures of  FIGS. 4-16  may be formed on a glass layer  24  that forms part of a rear housing wall, a window structure for an optical component, a display cover layer, a button member, a keyboard key, a trackpad surface, or any other suitable structure in device  10 . The examples of  FIGS. 4-16  are merely illustrative and the coatings, glass layers, films, textures, and other structures of these examples may be used together, if desired (e.g., by stacking the layers of one configuration on top of those of another, in laterally spacing the structures from different configurations across a common glass layer, etc.). 
     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.